tag:theconversation.com,2011:/es/topics/tectonic-plates-40102/articlesTectonic plates – The Conversation2023-12-19T21:59:56Ztag:theconversation.com,2011:article/2201932023-12-19T21:59:56Z2023-12-19T21:59:56ZVolcanic eruption lights up Iceland after weeks of earthquake warnings − a geologist explains what’s happening<p>Lava erupted through a fissure in Iceland’s Reykjanes Peninsula on Dec. 18, 2023, shooting <a href="https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night">almost 100 feet (30 meters)</a> in the air in its early hours.</p>
<p>Icelanders had been anticipating an eruption in the area for weeks, ever since a <a href="https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night">swarm of thousands of small earthquakes</a> began on Oct. 23 northeast of the fishing town of Grindavík, signaling volcanic activity below. </p>
<p>In the days that followed those first rumblings, a series of small rifts opened under the town, breaking streets, rupturing utility lines and tilting houses. GPS stations detected the <a href="https://en.vedur.is/about-imo/news/earthquake-activity-in-fagradalsfjall-area">ground sinking and rising</a> over a large area.</p>
<p>Geologists from the <a href="https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night">Icelandic Met Office</a> interpreted the events as evidence that a basalt dike – pressurized magma that forces its way into a fracture – had intruded under Grindavík. The activity there had tapered off by early December, but 2.5 miles (4 kilometers) north of town, the ground under the <a href="https://www.verkis.com/projects/energy-production/geothermal-energy/nr/936">Svartsengi</a> geothermal power plant was moving.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/566683/original/file-20231219-19-6waspp.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map shows the location of the fissure." src="https://images.theconversation.com/files/566683/original/file-20231219-19-6waspp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566683/original/file-20231219-19-6waspp.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566683/original/file-20231219-19-6waspp.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566683/original/file-20231219-19-6waspp.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566683/original/file-20231219-19-6waspp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566683/original/file-20231219-19-6waspp.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566683/original/file-20231219-19-6waspp.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The location of the fissure where magma erupted starting Dec. 18, 2023, a few miles from the town of Grindavík and just east of Svartsengi power plant and ajacent Blue Lagoon thermal spa.</span>
<span class="attribution"><a class="source" href="https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night">Icelandic Met Office</a></span>
</figcaption>
</figure>
<p>The ground had dropped 10 inches (25 centimeters) as the basalt dike filled, but then it began to rise in a broad dome, indicating that magma was reinflating and repressurizing the magma chamber. The result was the nearby eruption on Dec. 18.</p>
<p>If the fissure continues to propagate to the south, or if a large volume of lava erupts, the evacuated town of Grindavík, with a population of around 3,500, may be in danger. The lava could also spill to the northwest toward the power plant, although the utility built rock walls to try to divert lava flows.</p>
<figure class="align-center ">
<img alt="An aerial photo shows the lights of Grindavík and glow of the eruption very nearby." src="https://images.theconversation.com/files/566707/original/file-20231219-25-zfbj7a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566707/original/file-20231219-25-zfbj7a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566707/original/file-20231219-25-zfbj7a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566707/original/file-20231219-25-zfbj7a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566707/original/file-20231219-25-zfbj7a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=498&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566707/original/file-20231219-25-zfbj7a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=498&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566707/original/file-20231219-25-zfbj7a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=498&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The evacuated town of Grindavík and a nearby geothermal power plant are still at risk.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/the-evacuated-icelandic-town-of-grindavik-is-seen-as-smoke-news-photo/1860420658?adppopup=true">Viken Kantarci/AFP via Getty Images</a></span>
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<p>Iceland is known as “the land of fire and ice” for a reason. Its residents have learned over centuries to live with its overactive geology.</p>
<p>The reason for Iceland’s volcanism has two parts: One has to do with what geologists unimaginatively <a href="https://oceanexplorer.noaa.gov/facts/volcanic-hotspot.html">call a hot spot</a>, and the other involves giant tectonic plates that are pulling apart beneath the island. As <a href="https://scholar.google.com/citations?user=r8FqGBEAAAAJ&hl=en">a geologist</a>, I study both.</p>
<h2>Life on the edge of two tectonic plates</h2>
<p>When <a href="https://www.iris.edu/hq/inclass/animation/plate_tectonic_theorya_brief_history">plate tectonic theory</a> was emerging in the 1960s, geologists realized that many volcanoes are located in zones where tectonic plates meet. Tectonic plates are gigantic chunks of Earth’s rigid outer layer that carry both continents and oceans and are constantly in motion. They <a href="https://www.usgs.gov/media/images/tectonic-plates-earth">cover the planet</a> like large pieces of a spherical jigsaw puzzle.</p>
<p>Many of these volcanoes are in subduction zones, like the Pacific’s <a href="https://education.nationalgeographic.org/resource/plate-tectonics-ring-fire/">Ring of Fire</a>, where thinner oceanic plates slowly sink into <a href="https://education.nationalgeographic.org/resource/mantle/">Earth’s mantle</a>. These are the postcard stratovolcanoes like Mount Fuji, in Japan, or Mount Rainier, outside of Seattle. Because of their high gas content, they tend to erupt catastrophically, shooting ash high into the atmosphere with the energy of nuclear bombs, as <a href="https://www.usgs.gov/volcanoes/mount-st.-helens/science/1980-cataclysmic-eruption">Mount St. Helens did in 1980</a>.</p>
<p>A second, typically quieter kind of volcano forms <a href="https://oceanexplorer.noaa.gov/facts/mid-ocean-ridge.html">where plates pull apart</a>.</p>
<p>The volcanic activity near Grindavík is directly related to this kind of plate tectonic motion. The mid-Atlantic ridge between the Eurasian and North American plates cuts right through that part of the island.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map shows where the earthquakes are taking place in a southwest peninsula and where the tectonic plates meet." src="https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=780&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=780&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=780&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=980&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=980&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=980&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Iceland sits atop the meeting of two tectonic plates, the North American to the west and Eurasian to the east, indicated by the red line crossing the island. The maps show the earthquake swarms on Nov. 12-14, 2023.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/an-infographic-titled-iceland-prepares-for-volcanic-news-photo/1782148842?adppopup=true">Yasin Demirci/Anadolu via Getty Images</a></span>
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</figure>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map shows details of midocean ridges looking like seams on a baseball as they wind through the major oceans." src="https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=330&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=330&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=330&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=415&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=415&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=415&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In the 1950s, cartographer Marie Tharp used echo soundings gathered by ships to develop the first map showing the ocean floor in detail. It clearly revealed the mid-ocean ridges. This hand-painted version of her map includes annotations showing hot spot tracks related to movement of the plates.</span>
<span class="attribution"><a class="source" href="https://www.loc.gov/">Heinrich C. Berann via Library of Congress; annotations by Jaime Toro</a></span>
</figcaption>
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<p>In fact, at <a href="https://guidetoiceland.is/connect-with-locals/jorunnsg/ingvellir-national-park">Thingvellir National Park</a> you can literally walk between the two tectonic plates. You can see the topographic scars of the rift in the long, linear valleys that extend to the northeast from Grindavík. They align with the swarms of earthquakes, the <a href="https://en.vedur.is/about-imo/news/bigimg/4511?ListID=0">ground deformation</a>, and the fissure eruption of 2023.</p>
<p>Where plates pull away from each other, the underlying mantle rises toward the surface to fill the gap, carrying its heat with it and moving into an area of lower pressure. Those <a href="https://www.e-education.psu.edu/rocco/node/1988">two processes</a> cause melting at depth and volcanic activity at the surface.</p>
<p>This is the <a href="https://en.wikipedia.org/wiki/Sheeted_dyke_complex">same process that creates new oceanic crust</a> underwater at mid-ocean ridges. After the magma solidifies as basalt rock, it will look like vertical walls intruded into the surrounding area.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/566733/original/file-20231219-19-4i4dgz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="The uplift is in a large area that includes a nearby power plant and the Blue Lagoon thermal spa." src="https://images.theconversation.com/files/566733/original/file-20231219-19-4i4dgz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/566733/original/file-20231219-19-4i4dgz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=552&fit=crop&dpr=1 600w, https://images.theconversation.com/files/566733/original/file-20231219-19-4i4dgz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=552&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/566733/original/file-20231219-19-4i4dgz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=552&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/566733/original/file-20231219-19-4i4dgz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=694&fit=crop&dpr=1 754w, https://images.theconversation.com/files/566733/original/file-20231219-19-4i4dgz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=694&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/566733/original/file-20231219-19-4i4dgz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=694&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A map shows the uplift of the ground (bright red) north of Grindavík prior to the Dec. 18, 2023, eruption, as well as the extent of the new lava flow (black).</span>
<span class="attribution"><a class="source" href="https://en.vedur.is/">Icelandic Met Office</a></span>
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<h2>Sitting on a hot spot</h2>
<p>In Iceland, the large volcanoes in the interior also <a href="https://doi.org/10.1016/j.epsl.2013.02.022">appear to be over a mantle plume</a>, <a href="https://theconversation.com/where-mauna-loas-lava-is-coming-from-and-why-hawaiis-volcanoes-are-different-from-most-195633">similar to Hawaii</a>.</p>
<p>This kind of volcano typically erupts basalt lava, which melts at very high temperature and tends to flow easily. Eruptions are generally not explosive because the runny lava allows gases to escape. </p>
<p>Exactly what causes hot material to rise at hot spots is still debated, but the most commonly accepted idea is that they are caused by plumes of super-heated rock that originate at the transition <a href="https://doi.org/10.1126/science.349.6252.1032">between Earth’s metallic core and rocky mantle</a>. Hot spots are a mechanism for the Earth to give off some of its <a href="https://www.sciencealert.com/earth-s-insides-are-cooling-faster-than-we-thought-and-it-will-mess-things-up">internal heat</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Hl1gfV-TdU0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">How hot spots develop. Video by Volcano Museum.</span></figcaption>
</figure>
<p>Typically, fissure eruptions are not explosive. However, when lava that is 1,800 degrees Fahrenheit (about 1,000 degrees Celsius) hits water, the flash to steam can cause explosions that can scatter ash over a larger area. </p>
<h2>A silver lining of Iceland’s volcanoes</h2>
<p>Living in an active volcanic area has some advantages, particularly for energy.</p>
<p>Iceland derives 30% of its electricity from geothermal sources that use underground heat to drive turbines and produce power. It’s almost like a controlled version of a lava flow hitting the sea, and it helps make Iceland <a href="https://www.volts.wtf/p/whats-the-deal-with-iceland#details">one of the cleanest economies on earth</a>.</p>
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<a href="https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="People sit in an eggshell-blue lake surrounded by black lava rocks. Steam rises in the background." src="https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=758&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=758&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=758&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=953&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=953&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=953&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Iceland has a lot of natural hot springs, but its Blue Lagoon has an unusual origin linked to geothermal energy.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/people-swimming-on-hot-spring-near-mountain-during-daytime-jTeQavJjBDs">Photo by Jeff Sheldon on Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The <a href="https://www.verkis.com/projects/energy-production/geothermal-energy/nr/936">Svartsengi</a> hydrothermal plant uses the underground heat from the same magma chamber that is now erupting to provide hot water for several thousand homes, plus 75 megawatts of electricity.</p>
<p>That power plant is also part of the reason the <a href="https://www.bluelagoon.com/">Blue Lagoon</a> is so popular. When the power plant was built in 1976, the plan was to discharge its still hot wastewater into an adjacent low area, expecting that it would seep into the ground. However, the geothermal water was loaded with dissolved silica, which became solid minerals when the water cooled, creating an impermeable layer. A small lake began to form.</p>
<p>Because of its high silica content, the water in this lake is a spectacular blue color that inspired the creation of the geothermal spa. The Blue Lagoon is one of the top tourist attractions in the country.</p>
<p>Now the Blue Lagoon is at risk: Sometimes the volcano gives, sometimes it takes away.</p>
<p><em><a href="https://theconversation.com/pourquoi-leruption-volcanique-en-islande-na-rien-dune-surprise-les-explications-dun-geologue-220292">Lire en français</a></em></p>
<p><em>This is an updated version of an <a href="https://theconversation.com/volcanic-iceland-is-rumbling-again-as-magma-rises-a-geologist-explains-eruptions-in-the-land-of-fire-and-ice-217671">article published Nov. 15, 2023</a>.</em></p><img src="https://counter.theconversation.com/content/220193/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jaime Toro works for West Virginia University. In the past, he has received funding from NSF, USGS and DOE.
</span></em></p>Iceland is known as ‘the land of fire and ice’ for a reason.Jaime Toro, Professor of Geology, West Virginia UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2176712023-11-15T19:01:26Z2023-11-15T19:01:26ZVolcanic Iceland is rumbling again as magma rises − a geologist explains eruptions in the land of fire and ice<figure><img src="https://images.theconversation.com/files/559685/original/file-20231115-25-q2cv1s.jpg?ixlib=rb-1.1.0&rect=126%2C247%2C3627%2C2264&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The same region of Iceland saw an eruption in July 2023.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/people-watch-flowing-lava-during-an-volcanic-eruption-near-news-photo/1521694001">Kristinn Magnusson/AFP via Getty Images</a></span></figcaption></figure><p><a href="https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night">Thousands of earthquakes</a> in recent weeks have shaken the Icelandic fishing town of Grindavík, about 30 miles (50 kilometers) southwest of the capital Reykjavik. They have <a href="https://apnews.com/article/iceland-volcano-earthquakes-evacuation-aviation-3bb2f4d18cb7c62967a7ce16cc1b70d3">triggered evacuations</a> and warnings that a volcanic eruption may be imminent.</p>
<p>While the idea of magma rising was no doubt scary for tourists visiting the nearby Blue Lagoon geothermal spa, which was <a href="https://twitter.com/BlueLagoonIS/status/1722551468958294515">closed as a precaution</a>, Iceland’s residents have learned over centuries to live with their island’s overactive geology.</p>
<p>So, why is Iceland so volcanically active?</p>
<p>The answer has two parts: One has to do with what geologists unimaginatively <a href="https://oceanexplorer.noaa.gov/facts/volcanic-hotspot.html">call a hotspot</a>, and the other involves giant tectonic plates that are pulling apart right beneath the island. As <a href="https://scholar.google.com/citations?user=r8FqGBEAAAAJ&hl=en">a geologist</a>, I study both.</p>
<figure class="align-center ">
<img alt="Magma runs downhill in multiple streams over cooled lava." src="https://images.theconversation.com/files/559686/original/file-20231115-19-bcq5zl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559686/original/file-20231115-19-bcq5zl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559686/original/file-20231115-19-bcq5zl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559686/original/file-20231115-19-bcq5zl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559686/original/file-20231115-19-bcq5zl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559686/original/file-20231115-19-bcq5zl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559686/original/file-20231115-19-bcq5zl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Eruptions in this region of Iceland tend to flow rather than being explosive, as residents saw in July 2023 and in 2021-22.</span>
<span class="attribution"><a class="source" href="https://gettyimages.com/detail/news-photo/this-aerial-photograph-taken-on-july-10-2023-shows-flowing-news-photo/1520071527">Kristinn Magnusson/AFP via Getty Images</a></span>
</figcaption>
</figure>
<h2>Life on the edge of two tectonic plates</h2>
<p>When <a href="https://www.iris.edu/hq/inclass/animation/plate_tectonic_theorya_brief_history">plate tectonic theory</a> was emerging in the 1960s, geologists realized that many volcanoes are located in zones where tectonic plates meet. Tectonic plates are gigantic chunks of Earth’s rigid outer layer that carry both continents and oceans and are constantly in motion. They <a href="https://www.usgs.gov/media/images/tectonic-plates-earth">cover the planet</a> like large pieces of a spherical jigsaw puzzle.</p>
<p>Many of these volcanoes are in subduction zones, like the Pacific’s <a href="https://education.nationalgeographic.org/resource/plate-tectonics-ring-fire/">Ring of Fire</a>, where thinner oceanic plates slowly sink into <a href="https://education.nationalgeographic.org/resource/mantle/">Earth’s mantle</a>. These are the postcard stratovolcanoes like Mount Fuji, in Japan, or Mount Rainier, outside of Seattle. Because of their high gas content, they tend to erupt catastrophically, shooting ash high into the atmosphere with the energy of nuclear bombs, as <a href="https://www.usgs.gov/volcanoes/mount-st.-helens/1980-cataclysmic-eruption">Mount St. Helens did in 1980</a>.</p>
<p>A second, typically quieter kind of volcano forms <a href="https://oceanexplorer.noaa.gov/facts/mid-ocean-ridge.html">where plates pull apart</a>.</p>
<p>The volcanic activity near Grindavík is directly related to this kind of plate tectonic motion. The mid-Atlantic ridge between the Eurasian and North American plates cuts right through that part of the island.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map shows where the earthquakes are taking place in a southwest peninsula and where the tectonic plates meet." src="https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=780&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=780&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=780&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=980&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=980&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559688/original/file-20231115-22-mdyae8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=980&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Iceland sits atop the meeting of two tectonic plates, the North American to the west and Eurasian to the east, indicated by the red line crossing the island. The maps show the earthquake swarms on Nov. 12-14, 2023.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/an-infographic-titled-iceland-prepares-for-volcanic-news-photo/1782148842?adppopup=true">Yasin Demirci/Anadolu via Getty Images</a></span>
</figcaption>
</figure>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map shows details of midocean ridges looking like seams on a baseball as they wind through the major oceans." src="https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=330&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=330&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=330&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=415&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=415&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559732/original/file-20231115-27-7uf0ky.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=415&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In the 1950s, cartographer Marie Tharp used echo soundings gathered by ships to develop the first map showing the ocean floor in detail. It clearly revealed the mid-ocean ridges. This hand-painted version of her map includes annotations showing hotspot tracks related to movement of the plates.</span>
<span class="attribution"><a class="source" href="https://www.loc.gov/">Heinrich C. Berann via Library of Congress; annotations by Jaime Toro</a></span>
</figcaption>
</figure>
<p>In fact, at <a href="https://guidetoiceland.is/connect-with-locals/jorunnsg/ingvellir-national-park">Thingvellir National Park</a> you can literally walk between the two tectonic plates. You can see the topographic scars of the rift in the long, linear valleys that extend to the northeast from Grindavík. They align with the recent swarm of earthquakes and the <a href="https://en.vedur.is/about-imo/news/bigimg/4511?ListID=0">ground deformation</a> that is happening. </p>
<p><a href="https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night">Radar satellite data</a> from the Icelandic Meteorological Office show that a broad area around Grindavík sank by about 3 feet (1 meter) over 10 days, and the <a href="https://strokkur.raunvis.hi.is/gps/">GPS station</a> in town moved about 3 feet (1 meter) to the southeast with respect to the North American plate from Oct. 28 to Nov. 9. Large cracks have <a href="https://www.youtube.com/watch?v=p4rkITMtyqU">broken streets and houses</a> in Grindavík.</p>
<figure class="align-center ">
<img alt="A color-coded map shows where an area about 3 miles (5 km) long and about half a mile (1 km) wide depressed by more than 3 feet (1 meter)." src="https://images.theconversation.com/files/559441/original/file-20231114-19-iziwv5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559441/original/file-20231114-19-iziwv5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=610&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559441/original/file-20231114-19-iziwv5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=610&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559441/original/file-20231114-19-iziwv5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=610&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559441/original/file-20231114-19-iziwv5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=767&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559441/original/file-20231114-19-iziwv5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=767&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559441/original/file-20231114-19-iziwv5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=767&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Estimates of how the ground deformed near Grindavík, Iceland, on Nov. 10-11, 2023. The vertical movements of more than 3 feet (dark purple), between Grindavík on the ocean and the Blue Lagoon north of it, were caused by the magma dike’s movement.</span>
<span class="attribution"><a class="source" href="https://en.vedur.is/about-imo/news/bigimg/4511?ListID=0">Icelandic Met Office</a></span>
</figcaption>
</figure>
<p>Where plates pull away from each other, the underlying mantle rises toward the surface to fill the gap, carrying its heat with it and moving into an area of lower pressure. Those <a href="https://www.e-education.psu.edu/rocco/node/1988">two processes</a> cause melting at depth and volcanic activity at the surface.</p>
<p>Starting in October 2023, this pressurized magma began pushing its way along a fissure toward the surface, triggering the earthquake swarms and creating the <a href="https://en.vedur.is/about-imo/news/a-seismic-swarm-started-north-of-grindavik-last-night">possibility of an eruption</a>.</p>
<p>This is the <a href="https://en.wikipedia.org/wiki/Sheeted_dyke_complex">same process that creates new oceanic crust</a> underwater at mid-ocean ridges. After the magma solidifies as basalt rock, it will look like vertical walls intruded into the surrounding area. The Grindavík dike appeared to have reached within about 0.6 miles (1 kilometer) of the surface by Nov. 14 and could soon reach the surface.</p>
<h2>Sitting on a hotspot</h2>
<p>In Iceland, the large volcanoes in the interior also <a href="https://doi.org/10.1016/j.epsl.2013.02.022">appear to be over a mantle plume</a>, <a href="https://theconversation.com/where-mauna-loas-lava-is-coming-from-and-why-hawaiis-volcanoes-are-different-from-most-195633">similar to Hawaii</a>. </p>
<p>This kind of volcano typically erupts basalt lava, which melts at very high temperature and tends to flow easily. Eruptions are generally not explosive because the runny lava allows gases to escape. This is the reason why tourists often <a href="https://youtu.be/GUrIjV82I40?feature=shared">can safely watch lava flows</a> in Hawaii or Iceland.</p>
<p>Exactly what causes hot material to rise at hotspots is still debated, but the most commonly accepted idea is that they are caused by plumes of super-heated rock that originate at the transition <a href="https://doi.org/10.1126/science.349.6252.1032">between Earth’s metallic core and rocky mantle</a>. Hotspots are a mechanism for the Earth to give off some of its <a href="https://www.sciencealert.com/earth-s-insides-are-cooling-faster-than-we-thought-and-it-will-mess-things-up">internal heat</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Hl1gfV-TdU0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">How hotspots develop. Video by Volcano Museum.</span></figcaption>
</figure>
<p>If there is an eruption in Iceland, the basaltic lava will most likely flow relatively peacefully downhill, as it did when Fagradalsfjall volcano erupted in 2021-22 just east of Grindavík, until it reaches the sea. However, when lava that is 1,800 degrees Fahrenheit (about 1,000 Celsius) hits water, it will flash to steam, causing explosions that can scatter ash over a large area. </p>
<h2>A silver lining of Iceland’s volcanoes</h2>
<p>Living in an active volcanic area has some advantages, particularly for energy.</p>
<p>Iceland derives 30% of its electricity from geothermal sources that use underground heat to drive turbines and produce power. It’s almost like a controlled version of a lava flow hitting the sea, and it helps make Iceland <a href="https://www.volts.wtf/p/whats-the-deal-with-iceland#details">one of the cleanest economies on earth</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="People sit in an eggshell-blue lake surrounded by black lava rocks. Steam rises in the background." src="https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=758&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=758&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=758&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=953&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=953&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559465/original/file-20231114-21-f3fk7c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=953&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Iceland has a lot of natural hot springs, but its Blue Lagoon has an unusual origin linked to geothermal energy.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/people-swimming-on-hot-spring-near-mountain-during-daytime-jTeQavJjBDs">Photo by Jeff Sheldon on Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>A hydrothermal plant called <a href="https://www.verkis.com/projects/energy-production/geothermal-energy/nr/936">Svartsengi</a>, near Grindavík, uses the underground heat to provide hot water for several thousand homes plus 75 megawatts of electricity. The plant pumps water through wells drilled into the volcanic field. This water boils to steam, which is then fed to turbines that generate power and to heat exchangers that make hot water for direct heating of homes.</p>
<p>That power plant is also part of the reason the <a href="https://www.bluelagoon.com/">Blue Lagoon</a> is so popular. When the power plant was built in 1976, the plan was to discharge its still hot wastewater into an adjacent low area, expecting that it would seep into the ground. However, the geothermal water was loaded with dissolved silica, which became solid minerals when the water cooled, creating an impermeable layer. A small lake began to form.</p>
<p>Because of its high silica content, the water in this lake is a spectacular blue color that inspired the creation of the geothermal spa. The Blue Lagoon is now one of the top tourist attractions in the country.</p><img src="https://counter.theconversation.com/content/217671/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jaime Toro works for West Virginia University. In the past, he has received funding from NSF, USGS and DOE. </span></em></p>Iceland’s volcanic activity is generally tame compared with explosive eruptions along the Pacific’s Ring of Fire. This time, it’s shaking up a town.Jaime Toro, Professor of Geology, West Virginia UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2132212023-09-11T09:40:18Z2023-09-11T09:40:18ZWhat caused Morocco’s earthquake? A geologist studying the Atlas mountains explains<p><em>The epicentre of Morocco’s <a href="https://www.bbc.com/news/world-africa-66759069">devastating earthquake</a> on 8 September was in the High Atlas Mountains, about 71km south-west of Marrakesh. Moina Spooner, from The Conversation Africa, asked Jesús Galindo-Zaldivar, who has been carrying out research on the formation of the <a href="https://www.researchgate.net/publication/370838816_cGPS_Record_of_Active_Extension_in_Moroccan_Meseta_and_Shortening_in_Atlasic_Chains_under_the_Eurasia-Nubia_Convergence">Atlas mountains</a> and the geology of the area, about the factors which led to this situation.</em></p>
<h2>What research have you been doing in Morocco’s Atlas Mountains?</h2>
<p>The Atlas Mountains are a fascinating range in north-west Africa, spanning Morocco, Algeria and Tunisia. They’re situated south of the main Eurasia and Africa (Nubia) tectonic plate boundary.</p>
<p>This area doesn’t usually have a lot of earthquakes compared to other places near the edges of tectonic plates, where the movements of plates will cause intense seismic activity. But in 1960 the <a href="https://pubmed.ncbi.nlm.nih.gov/29249722/">Agadir earthquake</a> caused a lot of damage and loss of life. </p>
<p>I’m part of a team of geologists, geophysicists and <a href="https://oceanservice.noaa.gov/facts/geodesist.html#:%7E:text=Geodesists%20measure%20and%20monitor%20the,point%20will%20move%20over%20time.">geodesists</a> from various Moroccan universities and Spanish institutions carrying out research in the area. We want to understand this mountain range’s development and its position at the edge of a continental plate boundary. Studies of seismic activity, gravity and other geophysical phenomena allow us to understand the Earth’s deep structure, down to depths exceeding 100km. </p>
<p>Through field geological research, we can detect and analyse faults – fractures or cracks in the Earth’s crust along which there has been movement. These movements can be horizontal, vertical or diagonal, and they occur due to the immense forces acting on the Earth’s tectonic plates.</p>
<p>Finally, using geodetic techniques (GPS recordings) we are able to determine how tectonic plates are moving. This is done by regularly measuring benchmark sites with millimetre accuracy.</p>
<h2>What has your research found?</h2>
<p>Our <a href="https://doi.org/10.3390/s23104846">research</a> shows that the Atlas Mountains were formed during the break-up of the <a href="https://www.usgs.gov/faqs/what-was-pangea#:%7E:text=From%20about%20300%2D200%20million,a%20single%20continent%20called%20Pangea.">Pangea</a> supercontinent. It is now a mountain range that is actively rising, as evidenced by its high peaks and steep slopes. </p>
<p>The steep slopes of the mountains and the straight lines where the Earth’s crust has cracked suggest that there has been recent movement in the Earth beneath this area. It’s surprising that there aren’t more earthquakes here.</p>
<p>The Atlas Mountains are getting pushed together at a rate of <a href="https://doi.org/10.3390/s23104846">about 1 millimetre each year</a>. This happens because the Eurasian and African plates are moving closer to each other. This squeezing action is responsible for creating the tallest mountains in the area, the southern edge of where these two big plates meet.</p>
<h2>What do your findings tell you about this earthquake?</h2>
<p>The catastrophic earthquake took place to the north of the western Atlas mountains, south of Marrakesh. According to estimates by Morocco’s <a href="https://fr.le360.ma/societe/seisme-au-maroc-un-responsable-de-linstitut-national-de-geophysique-livre-les-details-du-tremblement_5JCEYXQBQZCGBAULJBO5SFQSDA/">National Institute of Geophysics</a> and the <a href="https://earthquake.usgs.gov/earthquakes/eventpage/us7000kufc/origin/detail">US geological survey</a>, the depth is between 8km and 26km.</p>
<p>The earthquake resulted from a geological phenomenon called a “reverse fault”. This occurs when tectonic plates collide, causing the Earth’s crust to thicken. The stress along these fault lines can induce earthquakes as rocks abruptly shift to release accumulated stress, which is characteristic of a seismic fault.</p>
<p>The 6.8 magnitude implies that the fault responsible for this earthquake is probably around 30km long. This estimate takes into account the <a href="https://pubs.geoscienceworld.org/ssa/bssa/article/84/4/974/119792/New-empirical-relationships-among-magnitude?casa_token=wI4CsF8HBNYAAAAA:GiDCYkcTUC7_QzF0YQ5xqs-rerR89jeKwMmBef-XYWHRljm5caHPeIhxwrgilBKZN0rCL1E">relationships</a> between active fault length and earthquake magnitudes. </p>
<p>So, why don’t we see many earthquakes in this area, even though it’s a place where the tectonic blocks are moving and the mountains are rising? Earthquakes happen when there’s a sudden shift in rocks along a fault line, caused by the release of stored energy that’s been building up over time. In this region, there haven’t been any major recorded earthquakes before, which suggests that the stress from the plates pushing together has been building up deep underground for a long time. When the stress got too much for the fault to handle, it caused an earthquake.</p>
<p>In this mountain belt faults might not produce earthquakes very often. After the earthquake, the rocks in the area moved and adjusted, but other nearby faults might now be under extra stress, and they could produce smaller earthquakes known as aftershocks that might continue for months or even years.</p>
<h2>What should authorities be doing to prepare?</h2>
<p>Earthquakes are difficult to predict and cannot be avoided. However, we can mitigate their impact. Through integrated studies of the region’s geology, geophysics and geodesy we can find out where there are active earthquake faults. We can also estimate how powerful the earthquakes on these faults could be and how often they might happen again. This helps us understand how strong future earthquakes in a specific area could be. Faults that don’t have earthquakes often but can still produce strong ones are a big concern. In the future, finding and studying these types of faults will be a focus of earthquake research.</p>
<p>The best way to minimise earthquake damage is to improve seismic building design codes to withstand the highest possible seismic activity. This will help buildings and other structures hold up better against strong shaking. In addition, it’s crucial that traditional homes and rock constructions in mountain villages be reinforced to prevent future disasters. New constructions must be tested and designed cheaply and efficiently, respecting new seismic building standards.</p><img src="https://counter.theconversation.com/content/213221/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jesús Galindo-Zaldivar does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The earthquake was caused by the collision of two tectonic plates.Jesús Galindo-Zaldivar, Professor of Geodynamics, Universidad de GranadaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2132202023-09-11T06:40:21Z2023-09-11T06:40:21ZMorocco’s earthquake wasn’t unexpected – building codes must plan for them<p><em>More than 2,000 people <a href="https://www.bbc.com/news/world-africa-66759069">died</a> when a powerful magnitude 6.8 earthquake struck Morocco on 8 September. The epicentre was in the High Atlas Mountains, 71km (44 miles) south-west of Marrakesh. Moina Spooner, from The Conversation Africa, asked José A. Peláez, a professor in geophysics who has carried out <a href="https://www.researchgate.net/publication/306004500_Energetic_and_spatial_characterization_of_seismicity_in_the_Algeria-Morocco_region?_tp=eyJjb250ZXh0Ijp7ImZpcnN0UGFnZSI6InByb2ZpbGUiLCJwYWdlIjoicHJvZmlsZSJ9fQ">research</a> on <a href="https://www.researchgate.net/publication/327542846_Comparative_stochastic_modeling_of_the_Al_Hoceima_Morocco_aftershock_sequences_in_1994_Mw_60_2004_Mw_64_and_2016_Mw_63?_tp=eyJjb250ZXh0Ijp7ImZpcnN0UGFnZSI6InByb2ZpbGUiLCJwYWdlIjoicHJvZmlsZSJ9fQ">seismic activity</a> in Morocco, about what led to this situation.</em></p>
<h2>What geological factors contributed to this earthquake?</h2>
<p>The Earth’s surface is constituted of several <a href="https://www.britannica.com/science/plate-tectonics">tectonic plates</a>, large segments of the planet’s outer layer, which move against each other. This movement is responsible for various geological phenomena, such as earthquakes, volcanoes, and the formation of mountains and ocean basins.</p>
<p>The tectonic activity in Morocco primarily involves the convergence of the Eurasian and the Nubian (African) plates. The Eurasian Plate pushing against the Nubian Plate is what led to the formation of the Atlas Mountains, which run through Morocco, Algeria and Tunisia. The mountains are where the <a href="https://edition.cnn.com/2023/09/10/africa/morocco-earthquake-moulay-brahim-survivors-hnk-intl/index.html">epicentre</a> of this recent earthquake was. </p>
<p>Currently, the collisions between the plates are causing a shortening of the Atlas Mountains, explaining the area’s seismicity. We know this because of data from GPS measurements, which show that they are <a href="https://doi.org/10.3390/s23104846">moving about 1 millimetre</a> closer to each other every year. </p>
<p>This shortening and compression is causing what are known as <a href="https://earthhow.com/types-of-faults/#:%7E:text=Reverse%20faults%20occur%20when%20one,move%20horizontally%20past%20each%20other.">faults</a>, huge friction between plates. These faults are the likely cause of this earthquake. Scientists <a href="https://doi.org/10.1016/S0040-1951(02)00368-2">think</a> that these faults have been active for a long time, going back a few million years.</p>
<p>In addition, <a href="https://doi.org/10.3390/s23104846">as pointed out</a> by various researchers, the High Atlas Mountains have a unique geological feature where the Earth’s outermost and hard layer, called the lithosphere, is thinner than usual, combined with an unusual rise of the mantle. All these features could have influenced the occurrence of this high magnitude earthquake.</p>
<h2>What is Morocco’s history of earthquakes?</h2>
<p>Seismic activity and its phenomena, like earthquakes, are not unusual in Morocco. </p>
<p>Over the last thousand years, earthquakes affecting Morocco have tended to take place mainly in <a href="https://doi.org/10.1785/gssrl.78.6.614">two areas</a>. Offshore, along the Azores-Gibraltar transform fault and the Alboran Sea, and another one onshore, along the Rif mountains in northern Morocco and the Tell Atlas mountain range in north-western Algeria. Earthquakes along the Atlas Belt are smaller in number, but not unusual.</p>
<p>The most significant, recent earthquakes affecting Morocco <a href="https://doi.org/10.3390/app12178744">were in</a> 1994, 2004 and 2016, with magnitudes ranging between 6.0 and 6.3. These occurred in the most seismically active region in Morocco and also in the western Mediterranean region. </p>
<p>A bit further back in history, there was the devastating Agadir earthquake in February 1960, with a magnitude of 6.3. It was located around the boundary between the western High Atlas and the Anti Atlas, to the south. Available data indicates that between 12,000 and 15,000 people died due to this event. In addition, near the location of the recent event, there was another earthquake in 1955, with an estimated magnitude of about 5.8.</p>
<p>Even further back, prior to the establishment of seismometers, several significant events were <a href="https://doi.org/10.1785/gssrl.78.6.614">recorded</a> in Morocco. Among them were the 1624 Fès earthquake, with an estimated magnitude of 6.7, and the 1731 Agadir earthquake, with a magnitude of 6.4. </p>
<h2>Could it have been predicted?</h2>
<p>Earthquakes cannot be predicted, even with the current knowledge in seismology. In fact, many researchers think that it will not be possible to do so in the future either. What seismologists can do is establish the areas in which earthquakes are most likely to occur, even establish the probability of their occurrence and its uncertainty.</p>
<p>This is that we call a long-term prediction, carried out from specific seismic hazard studies in the region. They are based on knowledge of past seismicity in the area, both historical and instrumental, and on the existence and knowledge of active tectonic structures (faults) that could generate earthquakes. The greater the knowledge that one has on these two topics – seismicity and active faults in the region – the more knowledge one will have about the future seismicity that may occur in the area, and the less the uncertainty will be.</p>
<p>Seismic hazard studies also include the study of near-surface soil conditions and the characteristics of buildings. This helps to assess the possible damage from these potential earthquakes.</p>
<h2>What can be done to lessen the impact of future earthquakes in Morocco?</h2>
<p>The best tool we have to mitigate the impact of earthquakes is to conduct reliable seismic hazard studies. The results of these must then be implemented into national building codes. This way engineers can incorporate seismic safety into building designs.</p>
<p>Building codes need to take into account several factors, including the characteristics of the soil, the way seismic waves move and how the soil can amplify its movement during an earthquake. Also the expected shaking of the ground, which influences the behaviour and damage of buildings. These factors vary from one city to another, and in some cases from one district to another.</p>
<p>Seismologists know that earthquakes do not kill people – buildings do. Buildings with lack of regulation and lack of structural support are potential killers in high seismic hazard areas. Building codes must therefore be mandatory, and should be updated periodically. As more is learned about earthquake geology and the impact of earthquakes on buildings, building codes should be updated regularly. This is the best way to protect ourselves against these catastrophic phenomena. Territorial planners and rulers must know this and take it into account.</p><img src="https://counter.theconversation.com/content/213220/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>José A. Peláez Montilla does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Earthquakes cannot be predicted; the best tools to mitigate the impact are seismic hazard studies.José A. Peláez Montilla, Professor of Geophysics, Universidad de JaénLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2090672023-07-06T20:21:18Z2023-07-06T20:21:18ZWhy are there hopping mice in Australia but no kangaroos in Asia? It’s a long story<figure><img src="https://images.theconversation.com/files/535717/original/file-20230705-17-ey6m80.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C4467%2C3136&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The frill-necked lizard is one of many land animals that reached Australia from Southeast Asia.</span> <span class="attribution"><span class="source">Damien Esquerré</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The animals in Australia are super-different to those in Asia. This goes without saying; we know Australia is full of weird and wonderful creatures found nowhere else on Earth, such as the platypus and the koala. </p>
<p>But it may surprise you to know that many of our most iconic critters came from Asia and arrived only recently (in geological terms, at least).</p>
<p>These most recent members of Australia’s characteristic fauna include many lizards, such as goannas and thorny devils, and other animals including hopping mice, flying foxes and the kookaburra. Yet the traffic was largely one way – there are far fewer representatives of Australian fauna in Asia than there are Asian fauna in Australia.</p>
<p>Why is the situation so asymmetrical? In a <a href="https://doi.org/10.1126/science.adf7122">study</a> published today in the journal Science, my colleagues and I analysed information about the distribution and habitat of 20,433 species of land-dwelling vertebrates – as well as climate and plate tectonics over the past 30 million years – to find out.</p>
<h2>Drifting continents on a cooling planet</h2>
<p>The story begins more than 200 million years ago. </p>
<p>Dinosaurs were still a fairly new group walking the Earth, and Australia was part of a supercontinent called Gondwana. This giant landmass included modern Antarctica, South America, Africa, Australia and India. </p>
<p>Gondwana had just broken off from another supercontinent, called Laurasia, which was smooshed together from modern North America, Europe and Asia. The separation of Gondwana and Laurasia removed the last land connection between Australia and Asia.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/535940/original/file-20230705-21-j53okr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map of the globe showing the supercontinents Gondwana and Laurasia." src="https://images.theconversation.com/files/535940/original/file-20230705-21-j53okr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/535940/original/file-20230705-21-j53okr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=463&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535940/original/file-20230705-21-j53okr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=463&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535940/original/file-20230705-21-j53okr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=463&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535940/original/file-20230705-21-j53okr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=581&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535940/original/file-20230705-21-j53okr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=581&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535940/original/file-20230705-21-j53okr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=581&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The supercontinents Gondwana and Laurasia before they separated over 200 million years ago.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Gondwana#/media/File:Laurasia-Gondwana.svg">Lennart Kudling / Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Now, Gondwana itself began to fall part pretty shortly after separating from Laurasia. Each piece of Gondwana gradually became isolated and began its own independent journey. Many of these journeys led them back to Laurasia. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/breaking-new-ground-the-rise-of-plate-tectonics-7514">Breaking new ground – the rise of plate tectonics</a>
</strong>
</em>
</p>
<hr>
<p>India collided with Eurasia and formed the mighty Himalaya; South America crashed into North America, forming the snaking land bridge of Panama; Africa bumped into Eurasia, forming the Mediterranean Sea; and Australia began on a collision course with Asia.</p>
<p>Australia untethered its final Gondwanan connections between 45 and 35 million years ago, when it broke off from Antarctica. </p>
<p>At that time, Australia was much further south than it is today. As it drifted northwards, the increasing space between Australia and Antarctica kick-started the <a href="https://en.wikipedia.org/wiki/Antarctic_Circumpolar_Current">Antarctic circumpolar current</a>, which cooled the planet dramatically.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-how-the-antarctic-circumpolar-current-helps-keep-antarctica-frozen-106164">Explainer: how the Antarctic Circumpolar Current helps keep Antarctica frozen</a>
</strong>
</em>
</p>
<hr>
<p>Australia was isolated, cooling down and drying out. A unique set of animals and plants began to evolve.</p>
<h2>Intercontinental stepping stones</h2>
<p>Meanwhile, the Australian and Eurasian tectonic plates began to collide, forming thousands of islands in the Indonesian archipelago, including today’s Lombok, Sulawesi, Timor, and Lesser Sunda Isles.</p>
<p>These islands don’t belong to either the Australian continental shelf (also known as Sahul), which includes Australia and New Guinea, or to the Asian continental shelf (known as Sunda), which includes Thailand, Malaysia, Singapore, Sumatra, Java, Borneo, and Bali. </p>
<p>This in-between zone is known as Wallacea, after the 19th century British naturalist Alfred Russell Wallace. He first observed a difference in the types of animals found on either side of what is now called Wallace’s line.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/535721/original/file-20230705-2760-7xl4ca.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A map of Indonesia, New Guinea and northern Australia with lines showing regions where different fauna live and climatic zones." src="https://images.theconversation.com/files/535721/original/file-20230705-2760-7xl4ca.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/535721/original/file-20230705-2760-7xl4ca.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=390&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535721/original/file-20230705-2760-7xl4ca.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=390&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535721/original/file-20230705-2760-7xl4ca.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=390&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535721/original/file-20230705-2760-7xl4ca.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=490&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535721/original/file-20230705-2760-7xl4ca.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=490&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535721/original/file-20230705-2760-7xl4ca.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=490&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">More animal species successfully made the crossing from Sunda to Sahul than the other way around.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1126/science.adf7122">Skeels et al. / Science</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The islands became stepping stones between two continents whose groups of species hadn’t seen each other in a very, very long time. But, as our new research shows, only particular kinds of animals were able to make the crossing and establish themselves on the other side.</p>
<h2>Wet and dry</h2>
<p>The first factor determining which animals spread between continents was their ability to cross the ocean. </p>
<p>Of all the groups of animals that moved between Asia and Australia, we found the staggering majority were birds. </p>
<p>But this wasn’t the only key to success. </p>
<figure class="align-center ">
<img alt="A photo of a kookaburra sitting on a wooden post with a beach in the background." src="https://images.theconversation.com/files/535942/original/file-20230706-27-s5muy6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/535942/original/file-20230706-27-s5muy6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535942/original/file-20230706-27-s5muy6.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535942/original/file-20230706-27-s5muy6.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535942/original/file-20230706-27-s5muy6.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535942/original/file-20230706-27-s5muy6.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535942/original/file-20230706-27-s5muy6.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The great majority of animals that spread from Asia to Australia were birds – including the ancestors of the kookaburra.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Animals also needed to be able to thrive in their new location, where the environment may have been quite different. We found animals that could tolerate a broad range of wetter and drier environments were more likely to make the move successfully.</p>
<p>This makes sense. Sunda is wet and Sahul is dry, and if you can tolerate more of that wet–dry spectrum, you are better equipped to move between these regions.</p>
<p>But we still have a big question. Why did more animals move from Sunda to Sahul than in the other direction?</p>
<h2>A lot can change in 30 million years</h2>
<p>The final piece of the puzzle is considering how these crucial factors – the ability for species to disperse and establish themselves in new environments – have changed over time. </p>
<p>We know Sunda has been dominated by lush tropical rainforest since before Australia broke away from Antarctica. Later, when the stepping-stone islands began to pop up, they also had the kind of humid equatorial climate favoured by the rainforest vegetation, and later animals, from Sunda. </p>
<p>In Australia, however, similar rainforests were shrinking and being replaced by grasslands and woodlands in most areas.</p>
<figure class="align-center ">
<img alt="A photo of a kangaroo in the bush." src="https://images.theconversation.com/files/535944/original/file-20230706-25-hte9mu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/535944/original/file-20230706-25-hte9mu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535944/original/file-20230706-25-hte9mu.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535944/original/file-20230706-25-hte9mu.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535944/original/file-20230706-25-hte9mu.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535944/original/file-20230706-25-hte9mu.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535944/original/file-20230706-25-hte9mu.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Marsupials such as the kangaroo spread widely across Sahul, but never made the leap across Wallace’s line to Sunda.</span>
<span class="attribution"><span class="source">Octavio Jiménez Robles</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>What this means is that as animals move from Sunda, through the stepping-stone islands, to New Guinea and the northern tips of Australia in Sahul, they experience a band of similar humid tropical climate. </p>
<p>However, most animals in Sahul evolved on the Australian mainland, most of which was much drier. So moving from mainland Australia, through New Guinea and the stepping stones, to Sunda, requires adaptations to a very different environment. </p>
<p>And Australian animals that did manage to make their way onto the stepping-stone islands would have likely met competition from Sunda groups already happily existing in their preferred tropical climate.</p>
<h2>Answers are a long time in the making</h2>
<p>Climate and geography are some of the most important things that shape evolution and the distributions of different species. Taking the long view, deep into the past, helps us understand the world around us. </p>
<p>Simple questions – like “why are there no kangaroos in Asia but hopping mice in Australia?” – have answers that are hundreds of millions of years in the making.</p><img src="https://counter.theconversation.com/content/209067/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alexander Skeels does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>There’s no single reason many Asian animals spread to Australia but few went the other way – but climate, geography and the slow drift of tectonic plates all played a role.Alexander Skeels, Postdoctoral Researcher, Macroevolution and Macroecology Group, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2076952023-07-06T13:20:25Z2023-07-06T13:20:25ZWhy earthquakes happen all the time in Britain but not in Ireland<figure><img src="https://images.theconversation.com/files/535373/original/file-20230703-197839-tgybq8.jpg?ixlib=rb-1.1.0&rect=10%2C1%2C1126%2C908&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Britain experiences hundreds of earthquakes each year.</span> <span class="attribution"><span class="source">Raffaele Bonadio</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The village of Tean in Staffordshire, England, was <a href="https://www.theguardian.com/world/2023/jun/29/staffordshire-hit-by-3-3-magnitude-earthquake">hit by a 3.3-magnitude earthquake</a> on June 28 2023. The tremors caused windows and doors to rattle in the surrounding area. </p>
<p>Earthquakes of this nature are not uncommon in Britain (the island including England, Scotland and Wales). In fact, hundreds of earthquakes shake Britain every single year. </p>
<p>The majority of these earthquakes are small in magnitude and do not result in any damage. However, there are occasional earthquakes in Britain that have the potential to be destructive. Scientists estimate that the <a href="https://www.bgs.ac.uk/discovering-geology/earth-hazards/earthquakes/where-do-earthquakes-occur/">largest possible earthquake</a> in Britain is around a magnitude 6.5 – surpassing the intensity of the <a href="http://www.earthquakes.bgs.ac.uk/research/events/newZealandFeb2011.html">magnitude 6.3 earthquake</a> that hit Christchurch, New Zealand in 2011 and killed 185 people. </p>
<p>The largest recorded earthquake in Britain so far took place in 1931 near Dogger Bank, 97km off the east coast of England. This earthquake measured <a href="https://en.wikipedia.org/wiki/1931_Dogger_Bank_earthquake">6.1 on the Richter scale</a> and caused damage to buildings along the east coast.</p>
<p>Most earthquakes in Britain are concentrated within a north-to-south band on the west side of the island. Neighbouring Ireland, however, is almost completely free from seismic activity – a phenomenon that has puzzled scientists for hundreds of years.</p>
<p><a href="https://academic.oup.com/gji/article/235/1/431/7157104">Research</a> by my colleagues and I has provided a potential explanation for Ireland’s minimal seismic activity. We found that the lithosphere – Earth’s rigid outer layer that makes up its tectonic plates – is thicker and cooler beneath Ireland than it is under Britain. This makes the tectonic plate under Ireland much less likely to deform – a process that can trigger earthquakes.</p>
<h2>Ireland’s missing earthquakes</h2>
<p>Even before earthquakes were recorded by seismographs as they are today, reports of earthquakes were documented in various towns and monasteries across Britain and Ireland. In the mid-19th century, <a href="https://www.britannica.com/biography/Robert-Mallet">Robert Mallet</a>, an Irish scientist credited with coining the term “seismology”, created earthquake maps based on these reports. He observed that Britain had intermediate seismicity (a term for earthquake activity), while Ireland had low seismicity.</p>
<p>In 1884, Irish seismologist Joseph O’Reilly published the first <a href="https://www.jstor.org/stable/30079053?casa_token=84NU_tDm4dkAAAAA%3AJIEckn73nEm6xP9t25rCa2wtEPlMosx4DxeFs7p_uvTRfI46vtyxx7ejvyp3ey6_CEPqgn-mNrvGIx1BeoNzrVVUAdVYd-1NOvRFKftC6L1kZdBKVQIyKQ">seismicity map of Britain and Ireland</a>, emphasising that Great Britain was “by far more subject to earthquake action than Ireland”.</p>
<p>Understanding the reasons behind this uneven distribution remains important today, especially in terms of how it affects Britain’s growing population. Between 2011 and 2021, the UK population <a href="https://www.ons.gov.uk/peoplepopulationandcommunity/populationandmigration/populationestimates/bulletins/annualmidyearpopulationestimates/mid2021">increased by 6%</a>, to a total of 67 million people.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/535349/original/file-20230703-213178-cfskyu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="O'Reilly's seismicity map of Britain and Ireland" src="https://images.theconversation.com/files/535349/original/file-20230703-213178-cfskyu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/535349/original/file-20230703-213178-cfskyu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=890&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535349/original/file-20230703-213178-cfskyu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=890&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535349/original/file-20230703-213178-cfskyu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=890&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535349/original/file-20230703-213178-cfskyu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1119&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535349/original/file-20230703-213178-cfskyu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1119&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535349/original/file-20230703-213178-cfskyu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1119&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">O’Reilly’s seismicity map of Britain and Ireland.</span>
<span class="attribution"><a class="source" href="https://www.jstor.org/stable/30079053">O'Reilly (1884)</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<h2>Intraplate earthquakes</h2>
<p>Most earthquakes happen at plate boundaries where tectonic plates converge, diverge or slide past each other. Over 80% of the world’s largest quakes occur around the perimeter of the Pacific Ocean – an area known as the <a href="https://www.bgs.ac.uk/discovering-geology/earth-hazards/earthquakes/where-do-earthquakes-occur/">Pacific “Ring of Fire”</a>. </p>
<p>Earthquakes that occur in the interior of the plates are much less common and typically smaller in magnitude. But there are a few notable exceptions. Between 1811 and 1812, the New Madrid Seismic Zone in the central US experienced a <a href="https://www.annualreviews.org/doi/abs/10.1146/annurev.earth.24.1.339">sequence of powerful earthquakes</a>, ranging from magnitude 7 to 8.</p>
<p>Britain and Ireland are geologically very similar. They were formed in the same continental collision around 400 million years ago and are composed of parts of the same continents. The two islands are also equally far from plate boundaries and the tectonic stress (the pressure or tension exerted by other plates or underlying mantle) is similar across them. </p>
<p>Why then is the distribution of earthquakes in Britain and Ireland so uneven?</p>
<h2>Through thick and thin</h2>
<p>Seismic tomography, a technique that uses seismic waves from remote earthquakes to create 3D images of Earth’s interior, has provided valuable insights. Research that I co-authored in 2021 <a href="https://academic.oup.com/gji/article/226/3/2158/6247624">discovered previously unknown variations</a> in the structure of the tectonic plate that both Britain and Ireland sit on.</p>
<p>Tectonic plates are cold and rigid compared to the hot, slowly creeping mantle beneath them. Thicker plates are colder, mechanically stronger and less likely to deform. Conversely, thinner plates are warmer, weaker and more susceptible to deformation. </p>
<p>In our <a href="https://academic.oup.com/gji/article/235/1/431/7157104">more recent research</a>, we found that that the plate thickness below Britain and Ireland ranges from about 75km to as much as 120km. Ireland has a relatively thick lithosphere (around 95-115km beneath most of the island) and very few earthquakes as a result. South-eastern England and eastern Scotland have a similarly thick lithosphere. </p>
<p>By contrast, western Britain has a thinner lithosphere (around 75–85km) and experiences regular earthquakes. Most Irish earthquakes are in the north of the island, the one place where its lithosphere is thinner, warmer and weaker.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/535359/original/file-20230703-262997-k9xj9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two maps showing the location of earthquakes in Britain and Ireland on the left, and variations in lithospheric thickness on the right." src="https://images.theconversation.com/files/535359/original/file-20230703-262997-k9xj9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/535359/original/file-20230703-262997-k9xj9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=407&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535359/original/file-20230703-262997-k9xj9n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=407&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535359/original/file-20230703-262997-k9xj9n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=407&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535359/original/file-20230703-262997-k9xj9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=511&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535359/original/file-20230703-262997-k9xj9n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=511&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535359/original/file-20230703-262997-k9xj9n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=511&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Left: Occurrence of earthquakes in Ireland and Great Britain. Right: Differences in lithosphere thickness.</span>
<span class="attribution"><span class="source">Raffaele Bonadio</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>This discovery solves a longstanding puzzle. Moderate variations in plate thickness, occurring far from plate boundaries, can influence patterns of seismic activity within those regions. </p>
<p>This breakthrough opens up new avenues of research for seismologists. In Britain and Ireland, scientists can now focus on closing the remaining gaps in the coverage of seismic stations (which monitor ground movement at specific locations) and constructing a model of the lithosphere to work out why earthquakes are concentrated where they are. </p>
<p>Earthquake catalogues in other world regions often do not go as far back into the past as in Britain and Ireland. Seismic hazards in these areas can also be much more uncertain. Modelling the thickness and strength of tectonic plates gives scientists the tools to study the puzzling distribution of earthquakes and improve their forecasting ability.</p><img src="https://counter.theconversation.com/content/207695/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sergei Lebedev does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Variations in the thickness of tectonic plates may explain why Britain experiences many more earthquakes than neighbouring Ireland.Sergei Lebedev, Professor of Geophysics, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1957042023-05-01T12:10:20Z2023-05-01T12:10:20ZWhat causes volcanoes to erupt?<figure><img src="https://images.theconversation.com/files/501671/original/file-20221218-11129-2abr3x.jpg?ixlib=rb-1.1.0&rect=7%2C0%2C4985%2C3323&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An aerial view of the Mauna Loa volcano, which erupted on the island of Hawaii in December 2022.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/in-an-aerial-view-lava-erupts-from-the-mauna-loa-volcano-on-news-photo/1245459430?phrase=Mauna%20Loa%20volcano%202022&adppopup=true">Andrew Richard Hara/Getty Images News</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>What causes volcanoes to erupt? – Avery, age 8, Los Angeles</strong></p>
</blockquote>
<hr>
<p>On Nov. 27, 2022, Mauna Loa – the world’s largest active volcano – <a href="https://www.usgs.gov/observatories/hvo/news/volcano-watch-mauna-loa-reawakens-0">erupted on the island of Hawaii</a>. For days, fountains of lava, boiling at more than 2,000 degrees Fahrenheit (1,100 degrees Celsius), spewed upward and flowed down the mountain’s sides. </p>
<p>For tens of millions of people around the world, the videos were a mesmerizing sight. Then, a few weeks later, the eruption ended. Fortunately, there were no known deaths, and no major property damage. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/F0tmu-zaXig?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Mauna Loa is the world’s largest active volcano.</span></figcaption>
</figure>
<p>About a week later, Mount Semeru in East Java, Indonesia, <a href="https://volcano.si.edu/volcano.cfm?vn=263300">erupted a mix of ash, gas and hot rocks</a>. The plumes rose a mile above the mountain’s summit. Thousands <a href="https://www.pbs.org/newshour/world/new-eruption-of-indonesias-mt-semeru-unleashes-lava-river-volcanic-ash">living in the vicinity were evacuated</a>; many wore masks to protect themselves from the ash-filled air. Mount Semeru has continued to erupt for months.</p>
<p>I am a geologist who <a href="https://scholar.google.com/citations?user=4Q8uMqUAAAAJ&hl=en&oi=ao">studies minerals in volcanic rocks</a>. I want to learn more about what causes volcanoes to erupt. Millions of people <a href="https://www.discovery.com/exploration/People-Live-Near-Active-Volcanoes">live near an active volcano</a> – that is, one of the 1,328 volcanoes worldwide that have <a href="https://volcano.si.edu/faq/index.cfm?question=activevolcanoes">erupted over the past 12,000 years</a>. </p>
<p>At any given time, 20 to 50 of these <a href="https://volcano.si.edu/gvp_currenteruptions.cfm">active volcanoes are erupting</a>. The proximity of people and buildings makes it important to study volcanoes and understand the hazards. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/502804/original/file-20230102-22-tpygfq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photograph of the city of Naples, Italy, with Mount Vesuvius in the background." src="https://images.theconversation.com/files/502804/original/file-20230102-22-tpygfq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/502804/original/file-20230102-22-tpygfq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=370&fit=crop&dpr=1 600w, https://images.theconversation.com/files/502804/original/file-20230102-22-tpygfq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=370&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/502804/original/file-20230102-22-tpygfq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=370&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/502804/original/file-20230102-22-tpygfq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=465&fit=crop&dpr=1 754w, https://images.theconversation.com/files/502804/original/file-20230102-22-tpygfq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=465&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/502804/original/file-20230102-22-tpygfq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=465&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Mount Vesuvius, about 6 miles east of Naples, Italy, is still an active volcano. In A.D. 79, Vesuvius erupted and destroyed the city of Pompeii.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/travelling-in-italy-royalty-free-image/906204248?phrase=volcanoes%20mount%20vesuvius&adppopup=true">Antonio Busiello/Moment via Getty Images</a></span>
</figcaption>
</figure>
<h2>How volcanoes blow their stacks</h2>
<p>The center of the Earth is <a href="https://earthhow.com/inside-earth-crust-core-mantle/">called the core</a>; the next layer up is the mantle; the outermost layer is the crust. </p>
<p>Over time, <a href="https://kids.kiddle.co/Magma">magma</a> – which is melted rock mixed with gas and mineral crystals – accumulates in an underground chamber beneath the volcano. The magma at Mauna Loa forms when a <a href="https://www.cbsnews.com/news/where-does-mauna-loa-lava-come-from/">hot mantle plume</a> – think of a conveyor of heat – partly melts rock in the mantle. </p>
<p>The volcano is essentially an <a href="https://www.natgeokids.com/uk/discover/geography/physical-geography/volcano-facts/">opening that lets magma out</a> onto the surface of the Earth. Once released from the volcano, the magma is called lava. </p>
<p>In the months leading to its eruption, scientists noted <a href="https://www.usgs.gov/observatories/hvo">increased earthquakes and a bulging of Mauna Loa</a>, like a balloon being inflated. These signs suggested that more magma was making its way upward, because pressure from rising magma can expand the sides of a volcano and cause rocks to shift and break, which leads to earthquakes.</p>
<p>Typically, for an eruption to occur, enough magma must <a href="https://www.usgs.gov/programs/VHP/about-volcanoes">accumulate in the chamber under the volcano</a>. Then something needs to trigger the eruption. That could be an injection of new magma into the chamber, a buildup of gases within the volcano, or a landslide that removes material from the top of a volcano.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/XLF_lMY2gu8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The eruption on Mount Semeru forced an evacuation of nearly 2,000 nearby residents.</span></figcaption>
</figure>
<h2>Types of volcanoes</h2>
<p>Mauna Loa is a <a href="https://study.com/academy/lesson/shield-volcano-facts-lesson-for-kids.html#:%7E">shield volcano</a>, built up over thousands of years through lava eruptions. Its sides slope gently downward in all directions. </p>
<p>But Mount Semeru is different – it’s a <a href="https://study.com/academy/lesson/composite-volcano-facts-lesson-for-kids.html#:%7E">composite volcano</a>, also known as a stratovolcano, with steep sides that come to a point at the top, like an upside-down sugar cone. </p>
<p>Semeru’s most recent eruption started when heavy rains <a href="https://www.cnn.com/2021/12/08/asia/indonesia-mount-semeru-volcano-eruption-cimate-intl/index.html">washed away rocks near the top of the volcano</a>. That allowed gas to escape – and ash to start erupting. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/517451/original/file-20230324-24-crlmkn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A motorbike, and the ground around it, covered in ash." src="https://images.theconversation.com/files/517451/original/file-20230324-24-crlmkn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517451/original/file-20230324-24-crlmkn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517451/original/file-20230324-24-crlmkn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517451/original/file-20230324-24-crlmkn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517451/original/file-20230324-24-crlmkn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517451/original/file-20230324-24-crlmkn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517451/original/file-20230324-24-crlmkn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">After the eruption at Mount Semeru, nearby villages were covered in volcanic ash.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/motorbike-is-covered-with-volcanic-ashes-after-mount-semeru-news-photo/1237024024?adppopup=true">Bayu Novanta/Xinhua News Agency via Getty Images</a></span>
</figcaption>
</figure>
<h2>The dangers</h2>
<p>Many hazards are associated with erupting volcanoes: lava flows, acidic gases, ash and <a href="https://www.usgs.gov/observatories/cascades-volcano-observatory/lahars-most-threatening-volcanic-hazard-cascades#:%7E">lahars</a>, which are dangerous flows of water, ash and rock that <a href="https://www.usgs.gov/programs/VHP/lahars-move-rapidly-down-valleys-rivers-concrete">run miles down the steep slopes of volcanoes</a>, sometimes <a href="https://www.usgs.gov/programs/VHP/lahars-move-rapidly-down-valleys-rivers-concrete#:%7E">at over 100 miles per hour</a>. The force of lahars can move huge boulders and destroy bridges and buildings. </p>
<p>Mount Semeru’s recent eruption <a href="https://www.usgs.gov/programs/VHP/ashfall-most-widespread-and-frequent-volcanic-hazard">covered nearby villages with ash</a> – tiny particles of rock that can go deep into lungs, causing irritation and making it hard to breathe. </p>
<p>As falling ash accumulates, it can smother crops, contaminate water supplies and trigger the collapse of buildings. Newly fallen dry ash weighs <a href="https://mil.wa.gov/asset/5ba4200a0b533#:%7E:text=Ash%20accumulates%20like%20heavy%20snowfall,Wet%20ash%20is%20slippery.">10 to 20 times more than snow</a>. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/3Jxeh-yAXek?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Below the surface, Earth is always moving and changing.</span></figcaption>
</figure>
<p>Generally, scientists don’t try to stop volcanoes from erupting. They are a natural part of the Earth. But monitoring volcanoes is critical. People need an early warning of an eruption <a href="https://www.usgs.gov/programs/VHP/understanding-volcanic-hazards-can-save-lives">so they can move out of harm’s way</a>. </p>
<p>While we cannot predict the exact time of an eruption, scientists are learning more about what causes them, and how to protect people who live near them. </p>
<p>What’s critical: warning systems for lahars, planned evacuation routes in areas threatened by volcanoes, and excellent communication between the scientists at volcanic monitoring stations and government agencies who can let people know when a volcano is about to go. </p>
<hr>
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<p class="fine-print"><em><span>Rachel Beane receives funding from Bowdoin College and the National Science Foundation. She is affiliated with the Harpswell Heritage Land Trust. </span></em></p>As they shape the Earth, volcanoes inspire and terrify humans.Rachel Beane, Professor of Natural Sciences, Bowdoin CollegeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1996662023-02-15T13:25:59Z2023-02-15T13:25:59ZSeismologists can’t predict an impending earthquake, but longer-term forecasts and brief warnings after one starts are possible<figure><img src="https://images.theconversation.com/files/510218/original/file-20230214-14-uyfac2.jpg?ixlib=rb-1.1.0&rect=589%2C380%2C4203%2C2356&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Seismologists monitor the Earth's activity, but they can't predict a day, time and place for the next 'big one.'</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/technicians-of-the-national-seismological-center-of-the-news-photo/829643960">Christian Miranda/AFP via Getty Images</a></span></figcaption></figure><p><em>Almost like aftershocks, questions about earthquake prediction tend to follow disasters like the one that occurred Sept. 8, 2023, in Morocco. Could advance notice have prevented some of the devastation? Unfortunately, useful predictions are still in the realm of science fiction.</em></p>
<p><em>University of Washington professor of seismology and geohazards <a href="https://scholar.google.com/citations?user=ull69vcAAAAJ&hl=en&oi=ao">Harold Tobin</a> heads the <a href="https://pnsn.org">Pacific Northwest Seismic Network</a>. He explains the differences between predicting and forecasting earthquakes, as well as early warning systems that are currently in place in some areas.</em></p>
<h2>Can scientists predict a particular earthquake?</h2>
<p>In short, no. Science has not yet found a way to make actionable earthquake predictions. A useful prediction would specify a time, a place and a magnitude – and all of these would need to be fairly specific, with enough advance notice to be worthwhile.</p>
<p>For example, if I predict that California will have an earthquake in 2023, that would certainly come true, but it’s not useful because <a href="https://temblor.net/earthquake-insights/overdue-the-future-of-large-earthquakes-in-california-12667/">California has many small earthquakes every day</a>. Or imagine I predict a magnitude 8 or greater earthquake will strike in the Pacific Northwest. That is <a href="https://www.newyorker.com/magazine/2015/07/20/the-really-big-one">almost certainly true</a> but doesn’t specify when, so it’s not helpful new information.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/510220/original/file-20230214-22-a065v2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="rectangular map of Earth with tectonic plates outlined" src="https://images.theconversation.com/files/510220/original/file-20230214-22-a065v2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/510220/original/file-20230214-22-a065v2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=342&fit=crop&dpr=1 600w, https://images.theconversation.com/files/510220/original/file-20230214-22-a065v2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=342&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/510220/original/file-20230214-22-a065v2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=342&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/510220/original/file-20230214-22-a065v2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=429&fit=crop&dpr=1 754w, https://images.theconversation.com/files/510220/original/file-20230214-22-a065v2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=429&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/510220/original/file-20230214-22-a065v2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=429&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tectonic plates fit together like puzzle pieces made of the Earth’s crust.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/tectonic-plates-move-constantly-making-new-areas-of-royalty-free-image/1146522618">Naeblys/iStock via Getty Images Plus</a></span>
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<p>Earthquakes happen because the <a href="https://www.usgs.gov/faqs/what-earthquake-and-what-causes-them-happen">slow and steady motions of tectonic plates</a> cause stresses to build up along faults in the Earth’s crust. Faults are not really lines, but planes extending down miles into the ground. Friction due to the enormous pressure from the weight of all the overlying rock holds these cracks together.</p>
<p>An earthquake starts in some small spot on the fault where the stress overcomes the friction. The two sides slip past each other, with the rupture spreading out at <a href="https://www.usgs.gov/faqs/what-was-duration-earthquake-why-dont-you-report-duration-each-earthquake-how-does-duration">a mile or two per second</a>. The grinding of the two sides against each other on the fault plane sends out waves of motion of the rock in every direction. Like the ripples in a pond after you drop in a stone, it’s those waves that make the ground shake and cause damage. </p>
<p>Most earthquakes strike without warning because the faults are stuck – locked up and stationary despite the strain of the moving plates around them, and therefore silent until that rupture begins. Seismologists have not yet found any reliable signal to measure before that initial break.</p>
<h2>What about the likelihood of a quake in one area?</h2>
<p>On the other hand, earthquake science today has come a long way in what I’ll call forecasting as opposed to prediction.</p>
<p>Seismologists can measure the movement of the plates with <a href="https://www.iris.edu/hq/inclass/animation/measuring_plate_tectonics_with_gps">millimeter-scale precision using GPS technology</a> and other means, and detect the places where stress is building up. Scientists know about the recorded history of past earthquakes and can even infer farther back in time using the <a href="https://www.usgs.gov/programs/earthquake-hazards/introduction-paleoseismology">methods of paleoseismology</a>: the geologically preserved evidence of past quakes.</p>
<p>Putting all this information together allows us to recognize areas where conditions are ripe for a fault to break. These forecasts are expressed as the likelihood of an earthquake of a given size or greater in a region over a period of decades into the future. For example, the <a href="http://pubs.usgs.gov/of/2013/1165/">U.S. Geological Survey estimates the odds</a> of a magnitude <a href="https://www.usgs.gov/faqs/what-probability-earthquake-will-occur-los-angeles-area-san-francisco-bay-area">6.7 or greater quake in the San Francisco Bay Area</a> over the next 30 years is 72%.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/510222/original/file-20230214-30-ka8so1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="collapsing bridge and roadway with black smoke and fire engine" src="https://images.theconversation.com/files/510222/original/file-20230214-30-ka8so1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/510222/original/file-20230214-30-ka8so1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=374&fit=crop&dpr=1 600w, https://images.theconversation.com/files/510222/original/file-20230214-30-ka8so1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=374&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/510222/original/file-20230214-30-ka8so1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=374&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/510222/original/file-20230214-30-ka8so1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=470&fit=crop&dpr=1 754w, https://images.theconversation.com/files/510222/original/file-20230214-30-ka8so1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=470&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/510222/original/file-20230214-30-ka8so1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=470&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The 6.9 magnitude Loma Prieta earthquake in 1989 caused widespread damage around the Bay Area and dozens of deaths.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/oakland-ca-october-17-1989-two-people-lower-right-comfort-news-photo/1172229915">Paul Miller/MediaNews Group/Oakland Tribune via Getty Images</a></span>
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</figure>
<h2>Are there any hints a quake could be coming?</h2>
<p>Only about 1 in 20 damaging earthquakes have foreshocks – <a href="https://www.usgs.gov/faqs/what-probability-earthquake-foreshock-larger-earthquake">smaller quakes that precede a larger one</a> in the same place. By definition they aren’t foreshocks, though, until a bigger one follows. The inability to recognize whether an earthquake in isolation is a foreshock is a big part of why useful prediction still eludes us.</p>
<p>However, in the past decade or so, there have been a number of massive earthquakes of magnitude 8 or more, including the <a href="https://earthquake.usgs.gov/earthquakes/eventpage/official20110311054624120_30/origin/detail?source=us&code=usp000hvnu">2011 magnitude 9.0 Tohoku earthquake and tsunami in Japan</a> and a <a href="https://earthquake.usgs.gov/earthquakes/eventpage/usc000nzvd/executive#summary">2014 magnitude 8.1 in Chile</a>. Interestingly, a larger fraction of those very biggest earthquakes seem to have <a href="https://doi.org/10.1126/science.1256074">exhibited some precursory events</a>, either in the form of <a href="https://doi.org/10.1126/science.1255202">a series of foreshocks detected by seismometers</a> or <a href="https://doi.org/10.1126/science.1215141">sped-up movements of the nearby Earth’s crust</a> detected by GPS stations, called “slow slip events” by earthquake scientists.</p>
<p>These observations suggest perhaps there really are precursory signals for at least some huge quakes. Maybe the sheer size of the ensuing quake made otherwise imperceptible changes in the region of the fault prior to the main event more detectable. We don’t know, because so few of these greater than magnitude 8 earthquakes happen. Scientists don’t have a lot of examples to go on that would let us test hypotheses with statistical methods.</p>
<p>In fact, while earthquake scientists all agree that we can’t predict quakes today, there are <a href="https://press.princeton.edu/books/paperback/9780691173306/predicting-the-unpredictable">now essentially two camps</a>: In one view, earthquakes are the result of complex cascades of tiny effects – a sensitive chain reaction of sorts that starts with the <a href="https://science.howstuffworks.com/math-concepts/butterfly-effect.htm">proverbial butterfly wing flapping</a> deep within a fault – so they’re inherently unpredictable and will always remain so. On the other hand, some geophysicists believe we may one day unlock the key to prediction, if we can just find the right signals to measure and gain enough experience.</p>
<h2>How do early warning systems work?</h2>
<p>One real breakthrough today is that scientists have developed earthquake early warning systems like the <a href="https://pnsn.org/pnsn-data-products/earthquake-early-warning">USGS ShakeAlert now operating</a> in California, Oregon and Washington state. These systems can send out an alert to residents’ mobile devices and to operators of critical machinery, including utilities, hospitals, trains and so on, providing warning of anywhere from a few seconds to more than a minute before shaking begins.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/510224/original/file-20230214-20-m5xy8p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="one person buries something in the ground while another watches" src="https://images.theconversation.com/files/510224/original/file-20230214-20-m5xy8p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/510224/original/file-20230214-20-m5xy8p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/510224/original/file-20230214-20-m5xy8p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/510224/original/file-20230214-20-m5xy8p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/510224/original/file-20230214-20-m5xy8p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/510224/original/file-20230214-20-m5xy8p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/510224/original/file-20230214-20-m5xy8p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A seismologist installs monitoring equipment that will track any earthquake movement.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/seismologist-joao-fontiela-installs-a-seismograph-to-news-photo/1239547561">Patricia De Melo Moreira/AFP via Getty Images</a></span>
</figcaption>
</figure>
<p>This sounds like earthquake prediction, but it is not. Earthquake early warning relies on networks of seismometers that detect the very beginning of an earthquake on a fault and automatically calculate its location and magnitude before the damaging waves have spread very far. The sensing, calculating and data transfer all happen near the speed of light, while the seismic waves move more slowly. That time difference is what allows early warning.</p>
<p>For example, if an earthquake begins off the coast of Washington state beneath the ocean, coastal stations can detect it, and cities like Portland and Seattle could get tens of seconds of warning time. People may well get enough time to take a life safety action like “<a href="https://www.shakeout.org/dropcoverholdon/">Drop, Cover and Hold On</a>” – as long as they are sufficiently far away from the fault itself.</p>
<h2>What complications would predicting bring?</h2>
<p>While earthquake prediction has often been referred to as the “holy grail” of seismology, it actually would present some real dilemmas if ever developed.</p>
<p>First of all, earthquakes are so infrequent that any early methods will inevitably be of uncertain accuracy. In the face of that uncertainty, who will make the call to take a major action, such as evacuating an entire city or region? How long should people stay away if a quake doesn’t materialize? How many times before it’s a boy-who-cried-wolf situation and the public stops heeding the orders? How do officials balance the known risks from the <a href="https://www.chron.com/news/houston-texas/houston/article/Hurricane-Rita-anxiety-leads-to-hellish-fatal-6521994.php">chaos of mass evacuation</a> against the risk from the shaking itself? The idea that prediction technology will emerge fully formed and reliable is a mirage. </p>
<p>It is often said in the field of seismology that <a href="https://theconversation.com/earthquakes-dont-kill-people-buildings-do-and-those-lovely-decorative-bits-are-the-first-to-fall-168476">earthquakes don’t kill people, buildings do</a>. Scientists are already good enough today at forecasting earthquake hazards that the best course of action is to redouble efforts to construct or retrofit buildings, bridges and other infrastructure so they’re safe and resilient in the event of ground shaking in any area known to be at risk from large future quakes. These precautions will pay off in lives and property saved far more than a hoped-for means of earthquake prediction, at least for the foreseeable future.</p>
<p><em>This is an updated version of an article originally published on Feb. 15, 2023.</em></p><img src="https://counter.theconversation.com/content/199666/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Harold Tobin receives funding from the National Science Foundation and the U.S. Geological Survey. </span></em></p>The idea that scientists could warn a region that a big quake was coming at a certain time – with enough advance notice for large-scale preparation and evacuation – remains a dream, not a reality.Harold Tobin, Professor of Seismology and Geohazards, University of WashingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1932772023-01-23T13:24:30Z2023-01-23T13:24:30ZHow has the inside of the Earth stayed as hot as the Sun’s surface for billions of years?<figure><img src="https://images.theconversation.com/files/504323/original/file-20230112-43582-jetsqy.jpg?ixlib=rb-1.1.0&rect=0%2C21%2C4685%2C3672&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The slice you see cut out of the Earth reveals its core, depicted here in bright yellow.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/earth-section-royalty-free-image/174700926">fhm/E+ via Getty Images</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
<hr>
<blockquote>
<p><strong>How does the inside of the Earth stay boiling hot for billions of years? Henry, age 11, Somerville, Massachusetts</strong></p>
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<hr>
<p>Our Earth is structured sort of like an onion – it’s one layer after another. </p>
<p>Starting from the top down, there’s the crust, which includes the surface you walk on; then farther down, the mantle, mostly solid rock; then even deeper, the outer core, made of liquid iron; and finally, the inner core, made of solid iron, and with a radius that’s 70% the size of the Moon’s. The deeper you dive, the hotter it gets – parts of the core are as hot as the surface of the Sun.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/504301/original/file-20230112-52283-32zsaz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An illustration that shows the structure of the Earth: its crust, mantle, inner core and outer core." src="https://images.theconversation.com/files/504301/original/file-20230112-52283-32zsaz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/504301/original/file-20230112-52283-32zsaz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=405&fit=crop&dpr=1 600w, https://images.theconversation.com/files/504301/original/file-20230112-52283-32zsaz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=405&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/504301/original/file-20230112-52283-32zsaz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=405&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/504301/original/file-20230112-52283-32zsaz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=509&fit=crop&dpr=1 754w, https://images.theconversation.com/files/504301/original/file-20230112-52283-32zsaz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=509&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/504301/original/file-20230112-52283-32zsaz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=509&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">This illustration depicts the four sections beneath the Earth’s surface.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/the-structure-of-planet-earth-royalty-free-illustration/1256173927">eliflamra/iStock via Getty Images Plus</a></span>
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<h2>Journey to the center of the Earth</h2>
<p>As a <a href="https://scholar.google.com/citations?user=DpHUpCwAAAAJ&hl=en&oi=ao">professor of earth and planetary sciences</a>, I study the insides of our world. Just as a doctor can use a technique called <a href="https://blog.radiology.virginia.edu/ultrasound-definition-kids-imaging/">sonography</a> to make pictures of the structures inside your body with ultrasound waves, scientists use a similar technique to image the Earth’s internal structures. But instead of ultrasound, geoscientists use <a href="https://easyscienceforkids.com/seismic-waves/">seismic waves</a> – sound waves produced by earthquakes. </p>
<p>At the Earth’s surface, you see dirt, sand, grass and pavement, of course. <a href="https://www.amnh.org/learn-teach/curriculum-collections/earth-inside-and-out/inge-lehmann-discoverer-of-the-earth-s-inner-core">Seismic vibrations reveal what’s below that</a>: rocks, large and small. This is all part of the crust, which may go down as far as 20 miles (30 kilometers); it floats on top of the layer called the mantle. </p>
<p>The upper part of the mantle typically moves together with the crust. Together, they are called <a href="https://education.nationalgeographic.org/resource/lithosphere">the lithosphere</a>, which is about 60 miles (100 kilometers) thick on average, although it can be thicker at some locations. </p>
<p>The lithosphere is divided into several <a href="https://www.kidsdiscover.com/wp-content/uploads/2012/12/KIDS-DISCOVER-Plate-Tectonics.pdf">large blocks called plates</a>. For example, the Pacific plate is beneath the whole Pacific Ocean, and the North American plate covers most of North America. Plates are kind of like puzzle pieces that fit roughly together and cover the surface of the Earth.</p>
<p>The plates are not static; instead, they move. Sometimes it’s the tiniest fraction of inches over a period of years. Other times, there’s more movement, and it’s more sudden. This sort of movement is what triggers earthquakes and volcanic eruptions. </p>
<p>What’s more, plate movement is a critical, and probably essential, factor driving the evolution of life on Earth, because the moving plates change the environment and <a href="https://theconversation.com/plate-tectonics-may-have-driven-the-evolution-of-life-on-earth-44571">force life to adapt to new conditions</a>. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/3FoSAHk7DMA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">You’ll be amazed at all the life happening below your feet.</span></figcaption>
</figure>
<h2>The heat is on</h2>
<p>Plate motion requires a hot mantle. And indeed, as you go deeper into the Earth, the temperature increases. </p>
<p>At the bottom of the plates, around 60 miles (100 kilometers) deep, the temperature is about 2,400 degrees Fahrenheit (1,300 degrees Celsius). </p>
<p>By the time you get to the boundary between the mantle and the outer core, which is 1,800 miles (2,900 kilometers) down, the temperature is nearly 5,000 F (2,700 C). </p>
<p>Then, at the boundary between outer and inner cores, the temperature doubles, to nearly 10,800 F (over 6,000 C). That’s the part that’s <a href="https://www.livescience.com/29054-earth-core-hotter.html">as hot as the surface of the Sun</a>. At that temperature, virtually everything – metals, diamonds, human beings – vaporizes into gas. But because the core is at such high pressure deep within the planet, the iron it’s made up of remains liquid or solid. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/DI6SemRT2iY?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Without plate tectonics, human beings probably would not exist.</span></figcaption>
</figure>
<h2>Collisions in outer space</h2>
<p>Where does all that heat come from? </p>
<p>It is not from the Sun. While it warms us and all the plants and animals on Earth’s surface, sunlight can’t penetrate through miles of the planet’s interior.</p>
<p>Instead, there are two sources. One is the heat that Earth inherited during its formation 4.5 billion years ago. The Earth was made <a href="https://solarsystem.nasa.gov/solar-system/our-solar-system/in-depth/#:%7E">from the solar nebula</a>, a gigantic gaseous cloud, amid endless collisions and mergings between bits of rock and debris <a href="https://www.universetoday.com/35974/planetesimals/">called planetesimals</a>. This process took tens of millions of years.</p>
<p>An enormous amount of heat was produced during those collisions, enough to melt the whole Earth. Although some of that heat was lost in space, the rest of it was locked away inside the Earth, where much of it remains even today. </p>
<p>The other heat source: the decay of radioactive isotopes, distributed everywhere in the Earth. </p>
<p>To understand this, first imagine an element <a href="https://www.ducksters.com/science/chemistry/radiation_and_radioactivity.php">as a family with isotopes as its members</a>. Every atom of a given element has the same number of protons, but different isotope cousins have varying numbers of neutrons. </p>
<p><a href="https://kids.britannica.com/students/article/radioactive-isotope/628328#:%7E">Radioactive isotopes</a> are not stable. They release a steady stream of energy that converts to heat. Potassium-40, thorium-232, uranium-235 and uranium-238 are four of the radioactive isotopes keeping Earth’s interior hot. </p>
<p>Some of those names may sound familiar to you. Uranium-235, for example, is used as a <a href="https://www.eia.gov/energyexplained/nuclear/the-nuclear-fuel-cycle.php#:%7E">fuel in nuclear power plants</a>. Earth is in no danger of running out of these sources of heat: Although most of the <a href="https://www.ducksters.com/science/chemistry/radiation_and_radioactivity.php#:%7E">original uranium-235 and potassium-40 are gone</a>, there’s enough thorium-232 and uranium-238 to last for billions more years. </p>
<p>Along with the hot core and mantle, these energy-releasing isotopes provide the heat to drive the motion of the plates. </p>
<h2>No heat, no plate movement, no life</h2>
<p>Even now, the moving plates keep changing the surface of the Earth, constantly making <a href="https://www.quantamagazine.org/why-earths-cracked-crust-may-be-essential-for-life-20180607/">new lands and new oceans over millions and billions of years</a>. The plates also affect the atmosphere over similarly lengthy time scales. </p>
<p>But without the Earth’s internal heat, the plates would not have been moving. The Earth would have cooled down. Our world would likely have been uninhabitable. You wouldn’t be here.</p>
<p>Think about that, the next time you feel the Earth under your feet.</p>
<hr>
<p><em>Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to <a href="mailto:curiouskidsus@theconversation.com">CuriousKidsUS@theconversation.com</a>. Please tell us your name, age and the city where you live.</em></p><img src="https://counter.theconversation.com/content/193277/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shichun Huang does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Starting at the surface, you would have to dig nearly 2,000 miles before reaching the Earth’s core. No one could survive that trip – and the 10,000-degree F heat once there would vaporize you anyway.Shichun Huang, Associate Professor of Earth and Planetary Sciences, University of TennesseeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1956332022-11-30T13:44:16Z2022-11-30T13:44:16ZWhere Mauna Loa’s lava is coming from – and why Hawaii’s volcanoes are different from most<figure><img src="https://images.theconversation.com/files/498437/original/file-20221201-6346-syova6.jpeg?ixlib=rb-1.1.0&rect=2568%2C1769%2C2083%2C1338&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Magma fountains through a fissure on Mauna Loa, becoming lava, on Nov. 30, 2022.
</span> <span class="attribution"><a class="source" href="https://www.usgs.gov/media/images/november-30-2022-mauna-loa-fissure-3"> K. Mulliken/USGS</a></span></figcaption></figure><p><em>Hawaii’s Mauna Loa, the world’s largest active volcano, began sending up <a href="https://www.usgs.gov/volcanoes/mauna-loa/mauna-loa-eruption-webpage">fountains of glowing rock</a> and spilling lava from fissures as its first eruption in <a href="https://www.usgs.gov/volcanoes/mauna-loa">nearly four decades</a> began on Nov. 27, 2022.</em> </p>
<p><em>Where does that molten rock come from?</em></p>
<p><em>We asked <a href="https://scholar.google.com/citations?user=a7D-WawAAAAJ&hl=en">Gabi Laske</a>, a geophysicist at the University of California-San Diego who led one of the first projects to map the deep plumbing that feeds the Hawaiian Islands’ volcanoes, to explain.</em> </p>
<h2>Where is the magma surfacing at Mauna Loa coming from?</h2>
<p>The magma that comes out of Mauna Loa comes from a series of magma chambers found between about 1 and 25 miles (2 and 40 km) below the surface. These magma chambers are only temporary storage places with magma and gases, and are not where the magma originally came from.</p>
<p>The origin is much deeper in <a href="https://pubs.usgs.gov/gip/dynamic/inside.html">Earth’s mantle</a>, perhaps more than 620 miles (1,000 km) deep. Some scientists even postulate that the magma comes from a <a href="https://www.usgs.gov/observatories/hvo/news/volcano-watch-exploring-deep-source-hawaiian-volcanoes">depth of 1,800 miles (2,900 km)</a>, where the mantle meets Earth’s core.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/498078/original/file-20221129-14-85b5yv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/498078/original/file-20221129-14-85b5yv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/498078/original/file-20221129-14-85b5yv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=318&fit=crop&dpr=1 600w, https://images.theconversation.com/files/498078/original/file-20221129-14-85b5yv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=318&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/498078/original/file-20221129-14-85b5yv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=318&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/498078/original/file-20221129-14-85b5yv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=400&fit=crop&dpr=1 754w, https://images.theconversation.com/files/498078/original/file-20221129-14-85b5yv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=400&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/498078/original/file-20221129-14-85b5yv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=400&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An illustration suggests what Hawaii’s mantle plume might look like.</span>
<span class="attribution"><span class="source">Joel E Robinson/USGS</span></span>
</figcaption>
</figure>
<p>Earth’s crust is made up of tectonic plates that are slowly moving, at about the same speed as a fingernail grows. Volcanoes typically occur where these plates either move away from each other or where one pushes beneath another. But volcanoes can also be in the middle of plates, as Hawaii’s volcanoes are <a href="https://www.usgs.gov/media/images/pacific-plate-boundaries-and-relative-motion">in the Pacific Plate</a>.</p>
<p>The crust and mantle that comprise the Pacific Plate cracks at different places as it moves northwestward. Beneath Hawaii, magma can move upward through the cracks to feed different volcanoes on the surface. The same thing happens at Maui’s Haleakala, <a href="https://www.usgs.gov/volcanoes/haleakal%C4%81">which last erupted</a> about 250 years ago.</p>
<h2>How does molten rock travel from deep in Earth’s mantle, and what exactly is a mantle plume?</h2>
<p>Scientists hypothesize that the mantle is not made of uniform rock. Instead, <a href="https://doi.org/10.1038/s41561-019-0368-9">differences in the type</a> of mantle rock make it melt at <a href="https://openoregon.pressbooks.pub/earthscience/chapter/4-1-magma-and-how-it-forms/">different temperatures</a>. Mantle rock is solid at some places, while it starts to melt at other places.</p>
<p>The partially molten rock becomes buoyant and ascends toward the surface. The ascending mantle rock is what makes a mantle plume. Because the overlying pressure lessens as the rock ascends, it melts more and more, and eventually collects in the magma chamber. If a large enough opening exists at the surface, and enough volcanic gases have collected in the magma chamber, the magma is forced to the surface in a volcanic eruption.</p>
<figure class="align-center ">
<img alt="A cross section of the earth shows two potentially sources for the mantle plume, one starting much deeper and flowing a squiggly route as seismic imaging suggests." src="https://images.theconversation.com/files/498109/original/file-20221129-20-2d4cyv.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/498109/original/file-20221129-20-2d4cyv.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/498109/original/file-20221129-20-2d4cyv.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/498109/original/file-20221129-20-2d4cyv.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/498109/original/file-20221129-20-2d4cyv.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=500&fit=crop&dpr=1 754w, https://images.theconversation.com/files/498109/original/file-20221129-20-2d4cyv.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=500&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/498109/original/file-20221129-20-2d4cyv.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=500&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The origin of the magma may be more than 620 miles deep, and some scientists have suggested it could come from a depth of 1,800 miles, where the mantle meets Earth’s core.</span>
<span class="attribution"><span class="source">Gabi Laske</span></span>
</figcaption>
</figure>
<p>Seismic imaging by research teams I’m involved with has shown that Hawaii’s mantle plume <a href="https://doi.org/10.1126/science.1180165">comes from deep inside the mantle</a>.</p>
<p>But the plume is not a straight pipe as some concept figures suggest. Instead, it has <a href="https://doi.org/10.1038/ngeo1878">twists and turns</a>, originally coming from the southeast, but then turning toward the west of Hawaii as the plume reaches into the shallower mantle. Cracks in the Pacific Plate then channel the magma upward toward the magma chamber beneath the island of Hawaii.</p>
<h2>Why does Hawaii typically see less dramatic eruptions than other locations?</h2>
<p>Hawaii is in the middle of an oceanic plate. In fact, it is the most isolated volcanic hot spot on Earth, far away from any plate boundary.</p>
<p>Oceanic magma is very different from continental magma. It has a different chemical composition and flows much more easily. So, the magma is <a href="https://geowiki.ucsd.edu/sio15/topics/topic09.html">less prone to clog volcanic vents</a> on its ascent, which would ultimately lead to more explosive volcanism.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/9DUexRQfNBA?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Thermal imaging shows the Mauna Loa eruption, which began around 11:30 p.m. local time on Nov. 27, 2022. Temperatures are in Celsius. USGS.</span></figcaption>
</figure>
<h2>How do scientists know what is happening under the surface?</h2>
<p>Volcanic activity is monitored with many different instruments.</p>
<p>The perhaps simplest to understand is GPS. The way scientists use GPS is different from that of everyday life. It can detect minuscule movements of a few centimeters. On volcanoes, any upward movement on the surface detected by GPS indicates that something is pushing from underneath.</p>
<p>Even more sensitive are <a href="https://www.usgs.gov/programs/VHP/tiltmeters-and-strainmeters-measure-subtle-changes-ground-slope-and-shape-volcanoes">tiltmeters</a>, which are in essence the same as bubble levels that people use to hang pictures on a wall. Any change in the tilt on a volcano slope indicates that the volcano is “breathing,” again because of magma moving below.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/498080/original/file-20221129-14-pr28xg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map of the island of Hawaii, showing Mauna Loa and the lava flow paths since the late 1800s. There have been several eruptions and they tend to follow two routes." src="https://images.theconversation.com/files/498080/original/file-20221129-14-pr28xg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/498080/original/file-20221129-14-pr28xg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=776&fit=crop&dpr=1 600w, https://images.theconversation.com/files/498080/original/file-20221129-14-pr28xg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=776&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/498080/original/file-20221129-14-pr28xg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=776&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/498080/original/file-20221129-14-pr28xg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=976&fit=crop&dpr=1 754w, https://images.theconversation.com/files/498080/original/file-20221129-14-pr28xg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=976&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/498080/original/file-20221129-14-pr28xg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=976&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Mauna Loa has a history of eruptions. Here’s where the lava tends to go.</span>
<span class="attribution"><a class="source" href="https://www.usgs.gov/volcanoes/mauna-loa/geology-and-history">USGS</a></span>
</figcaption>
</figure>
<p>A very important tool is watching for seismic activity.</p>
<p>Volcanoes like Hawaii’s are monitored with a large network of seismographs. Any movement of magma below will cause tremors that are picked up by the <a href="https://www.usgs.gov/programs/VHP/networks-multiple-seismometers-are-necessary-adequately-monitor-volcanoes">seismometers</a>. A few weeks before the eruption of Mauna Loa, scientists noticed that the tremors came from ever shallower depths, indicating that magma was rising and an eruption might be imminent. This <a href="https://apnews.com/article/science-hawaii-kilauea-mauna-loa-14f7596e22b08a44600caa5f185b5b18">allowed scientists to warn the public</a>.</p>
<p>Other ways that volcanic activity is monitored includes chemical analysis of gases coming out <a href="https://www.usgs.gov/news/earthword-fumarole">through fumaroles</a> – holes or cracks through which volcanic gases escape. If the composition changes or activity increases, that’s a pretty clear indication that the volcano is changing.</p><img src="https://counter.theconversation.com/content/195633/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gabi Laske receives funding from the National Science Foundation. </span></em></p>A scientist who led one of the first projects to map the Hawaiian Islands’ deep volcanic plumbing explains what’s going on under the surface as Mauna Loa erupts.Gabi Laske, Professor of Geophysics, University of California, San DiegoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1837252022-05-25T20:16:48Z2022-05-25T20:16:48ZHow plate tectonics, mountains and deep-sea sediments have maintained Earth’s ‘Goldilocks’ climate<p>For hundreds of millions of years, Earth’s climate has warmed and cooled with natural fluctuations in the level of carbon dioxide (CO₂) in the atmosphere. Over the past century, <a href="https://theconversation.com/humanity-is-compressing-millions-of-years-of-natural-change-into-just-a-few-centuries-170525">humans have pushed CO₂ levels</a> to their highest in 2 million years – <a href="https://www.sciencedirect.com/science/article/pii/S1674927818300376">overtaking natural emissions</a> – mostly by burning fossil fuels, causing ongoing global warming that may make parts of the globe uninhabitable.</p>
<p>What can be done? As Earth scientists, we look to how natural processes have recycled carbon from atmosphere to Earth and back in the past to find possible answers to this question.</p>
<p>Our <a href="https://www.nature.com/articles/s41586-022-04420-x">new research</a> published in Nature, shows how tectonic plates, volcanoes, eroding mountains and seabed sediment have controlled Earth’s climate in the geological past. Harnessing these processes may play a part in maintaining the “<a href="https://www.abc.net.au/news/science/2016-02-22/goldilocks-zones-habitable-zone-astrobiology-exoplanets/6907836">Goldilocks</a>” climate our planet has enjoyed.</p>
<h2>From hothouse to ice age</h2>
<p><a href="https://theconversation.com/we-are-heading-for-the-warmest-climate-in-half-a-billion-years-says-new-study-73648">Hothouse and icehouse climates</a> have existed in the geological past. The Cretaceous hothouse (which lasted from roughly 145 million to 66 million years ago) had atmospheric CO₂ levels above 1,000 parts per million, compared with around 420 today, and temperatures up to 10°C higher than today. </p>
<p>But Earth’s climate began to <a href="https://www.eurekalert.org/news-releases/911139">cool around 50 million years ago</a> during the <a href="https://www.geosociety.org/GSA/Education_Careers/Geologic_Time_Scale/GSA/timescale/home.aspx">Cenozoic Era</a>, culminating in an <a href="https://theconversation.com/the-last-ice-age-tells-us-why-we-need-to-care-about-a-2-change-in-temperature-126923">icehouse climate</a> in which temperatures dropped to roughly 7°C cooler than today.</p>
<p>What kickstarted this dramatic change in global climate?</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/465011/original/file-20220524-16-e0esr2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/465011/original/file-20220524-16-e0esr2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=196&fit=crop&dpr=1 600w, https://images.theconversation.com/files/465011/original/file-20220524-16-e0esr2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=196&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/465011/original/file-20220524-16-e0esr2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=196&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/465011/original/file-20220524-16-e0esr2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=246&fit=crop&dpr=1 754w, https://images.theconversation.com/files/465011/original/file-20220524-16-e0esr2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=246&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/465011/original/file-20220524-16-e0esr2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=246&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Earth evolved from a hothouse climate in the Cretaceous Period (left) to an icehouse climate in the following Cenozoic Era (right), leading to inland ice sheets.</span>
<span class="attribution"><span class="source">F. Guillén and M. Antón / Wikimedia commons</span></span>
</figcaption>
</figure>
<p>Our suspicion was that Earth’s tectonic plates were the culprit. To better understand how tectonic plates store, move and emit carbon, we built a computer model of the tectonic “carbon conveyor belt”.</p>
<h2>The carbon conveyor belt</h2>
<p>Tectonic processes release carbon into the atmosphere at mid-ocean ridges - where two plates are moving away from each other - allowing magma to rise to the surface and create new ocean crust.</p>
<p>At the same time, at ocean trenches - where two plates converge - plates are pulled down and recycled back into the deep Earth. On their way down they carry carbon back into the Earth’s interior, but also release some CO₂ via volcanic activity. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/465207/original/file-20220525-24-pj1cjh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/465207/original/file-20220525-24-pj1cjh.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=264&fit=crop&dpr=1 600w, https://images.theconversation.com/files/465207/original/file-20220525-24-pj1cjh.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=264&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/465207/original/file-20220525-24-pj1cjh.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=264&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/465207/original/file-20220525-24-pj1cjh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=331&fit=crop&dpr=1 754w, https://images.theconversation.com/files/465207/original/file-20220525-24-pj1cjh.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=331&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/465207/original/file-20220525-24-pj1cjh.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=331&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Earth’s tectonic carbon conveyor belt shifts massive amounts of carbon between the deep Earth and the surface, from mid-ocean ridges to subduction zones, where oceanic plates carrying deep-sea sediments are recycled back into the Earth’s interior. The processes involved play a pivotal role in Earth’s climate and habitability.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<p>Our model shows that the Cretaceous hothouse climate was caused by very fast-moving tectonic plates, which dramatically increased CO₂ emissions from mid-ocean ridges. </p>
<p>In the transition to the Cenozoic icehouse climate tectonic plate movement slowed down and volcanic CO₂ emissions began to fall. But to our surprise, we discovered a more complex mechanism hidden in the conveyor belt system involving mountain building, continental erosion and burial of the remains of miscroscopic organisms on the seafloor.</p>
<h2>The hidden cooling effect of slowing tectonic plates in the Cenozoic</h2>
<p>Tectonic plates slow down due to collisions, which in turn leads to mountain building, such as the Himalayas and the Alps formed over the last 50 million years. This should have reduced volcanic CO₂ emissions but instead our carbon conveyor belt model revealed increased emissions. </p>
<p>We tracked their source to carbon-rich deep-sea sediments being pushed downwards to feed volcanoes, increasing CO₂ emissions and cancelling out the effect of slowing plates. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/waGHSfs_YRg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This video shows plate motions, carbon storage within tectonic plates and carbon degassing along mid-ocean ridges and subduction zones through time. Our carbon model shows these processes alone cannot explain global cooling in the Cenozoic Era. The effects of rock erosion, not shown here, played a key role. Arrows indicate plate motion speed.</span></figcaption>
</figure>
<p>So what exactly was the mechanism responsible for the drop in atmospheric CO₂? </p>
<p>The answer lies in the mountains that were responsible for slowing down the plates in the first place and in carbon storage in the deep sea. </p>
<p>As soon as mountains form, they start being eroded. Rainwater containing CO₂ reacts with a range of mountain rocks, breaking them down. Rivers carry the dissolved minerals into the sea. Marine organisms then use the dissolved products to build their shells, which ultimately become a part of carbon-rich marine sediments. </p>
<p>As new mountain chains formed, more rocks were eroded, speeding up this process. Massive amounts of CO₂ were stored away, and the planet cooled, even though some of these sediments were subducted with their carbon degassing via arc volcanoes.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photographs showing white cliffs rising from the sea." src="https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=353&fit=crop&dpr=1 600w, https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=353&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=353&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=443&fit=crop&dpr=1 754w, https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=443&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/465016/original/file-20220524-21-77qtj5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=443&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The limestone of the White Cliffs of Dover is an example of carbon-rich marine sediment, composed of the remains of tiny calcium carbonate skeletons of marine plankton.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:White_Cliffs_of_Dover_02.JPG">I Giel / Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Rock weathering as a possible carbon dioxide removal technology</h2>
<p>The Intergovernmental Panel on Climate Change (IPCC) <a href="https://www.ipcc.ch/report/sixth-assessment-report-working-group-3/">says</a> large-scale deployment of carbon dioxide removal methods is “unavoidable” if the world is to reach net-zero greenhouse gas emissions.</p>
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Read more:
<a href="https://theconversation.com/on-top-of-drastic-emissions-cuts-ipcc-finds-large-scale-co-removal-from-air-will-be-essential-to-meeting-targets-180663">On top of drastic emissions cuts, IPCC finds large-scale CO₂ removal from air will be "essential" to meeting targets</a>
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<p>The weathering of igneous rocks, especially rocks like basalt containing a mineral called olivine, is very efficient in reducing atmospheric CO₂. Spreading olivine on beaches could <a href="https://www.theguardian.com/environment/2021/jun/23/cloud-spraying-and-hurricane-slaying-could-geoengineering-fix-the-climate-crisis">absorb up to a trillion tonnes of CO₂ from the atmosphere</a>, according to <a href="https://www.vesta.earth/">some estimates</a>. </p>
<p>The speed of current <a href="https://climate.nasa.gov/evidence/">human-induced warming</a> is such that reducing our carbon emissions very quickly is essential to avoid catastrophic global warming. But geological processes, with some human help, may also have their role in maintaining Earth’s “Goldilocks” climate.</p>
<hr>
<p><em>This study was carried out by researchers from the University of Sydney’s <a href="https://www.earthbyte.org/">EarthByte Group</a>, The University of Western Australia, the University of Leeds and the Swiss Federal Institute of Technology, Zurich using <a href="https://www.gplates.org">GPlates</a> open access modelling software. This was enabled by Australia’s National Collaborative Research Infrastructure Strategy (NCRIS) via <a href="https://www.auscope.org.au/">AuScope</a> and The Office of the Chief Scientist and Engineer, NSW Department of Industry.</em></p><img src="https://counter.theconversation.com/content/183725/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dietmar Müller receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Adriana Dutkiewicz receives funding from the Australian Research Council (FT190100829). </span></em></p><p class="fine-print"><em><span>Andrew Merdith receives funding from MSCA-IF project 893615. </span></em></p><p class="fine-print"><em><span>Christopher Gonzalez received funding from Australian Research Council. </span></em></p><p class="fine-print"><em><span>Sabin Zahirovic receives funding from the Australian Research Council (DE210100084). </span></em></p><p class="fine-print"><em><span>Tobias Keller previously received funding from the European Research Council and from the Swiss National Science Foundation.</span></em></p><p class="fine-print"><em><span>Weronika Gorczyk receives funding from Australian Research Council and Minerals Research Institute Of Western Australia</span></em></p><p class="fine-print"><em><span>Jo Condon is affiliated with AuScope, a federally funded and non-profit NCRIS organisation that supports the development of GPlates software used in the research described in this article.</span></em></p><p class="fine-print"><em><span>Ben Mather does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>New modelling shows how tectonic plate movements, carbon-rich deep-sea sediment, and mountain weathering have regulated Earth’s climate.Dietmar Müller, Professor of Geophysics, University of SydneyAdriana Dutkiewicz, ARC Future Fellow, University of SydneyAndrew Merdith, Research fellow, University of LeedsBen Mather, Research fellow, University of SydneyChristopher Gonzalez, Research Fellow, The University of Western AustraliaSabin Zahirovic, Postdoctoral Research Associate, University of SydneyTobias Keller, Senior Scientist in Computational Geosciences, Swiss Federal Institute of Technology ZurichWeronika Gorczyk, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1561042021-02-26T10:56:15Z2021-02-26T10:56:15ZMelting ocean mud helps prevent major earthquakes — and may show where quake risk is highest<figure><img src="https://images.theconversation.com/files/386609/original/file-20210226-19-1rdefw2.jpg?ixlib=rb-1.1.0&rect=0%2C4%2C2731%2C1814&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>The largest and most destructive earthquakes on the planet happen in places where two tectonic plates collide. In our <a href="https://www.nature.com/articles/s41467-021-21657-8">new research</a>, published today in Nature Communications, we have produced new models of where and how rocks melt in these collision zones in the deep Earth. </p>
<p>This improved knowledge about the distribution of melted rock will help us to understand where to expect destructive earthquakes to occur. </p>
<h2>What causes earthquakes?</h2>
<p>Giant earthquakes, such as the magnitude-9.0 quake in 2011 that caused the Fukushima nuclear disaster, or the magnitude-9.1 event in 2004 that caused the Boxing Day tsunami, occur at the collision zones between two tectonic plates. In these so-called subduction zones, one plate slides beneath the other. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-fukushima-quake-may-be-an-echo-of-the-2011-disaster-and-a-warning-for-the-future-155293">The Fukushima quake may be an echo of the 2011 disaster — and a warning for the future</a>
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<p>The sinking plate acts as an enormous conveyor belt, carrying material from the surface down into the deep Earth. Earthquakes occur where the sinking plate gets stuck; strain builds up until it eventually quickly releases. Fluids and molten rocks in the system lubricate the plates, helping them slide past each other and stopping big earthquakes from happening. </p>
<h2>When happens when ocean mud ends up inside Earth?</h2>
<p>My colleague Michael Förster and I were interested in what happens to sediments when they are carried down into the deep Earth at a subduction zone. These sediments start out as thick layers of mud on the ocean floor but get carried down into the deep Earth as part of the sinking plate. </p>
<p>Michael took a sample of mud collected from the ocean floor and heated it up to the high temperatures and pressures it would experience in a subduction zone. He found the sediments melt and then react with the surrounding rocks, forming the mineral phlogopite and also saline fluids. </p>
<h2>A puzzle solved</h2>
<p>Geophysical models of subduction zones allow us to map out exactly where the molten rocks and fluids are. These measurements are like x-rays of Earth’s interior, helping us peer into places we cannot otherwise see. </p>
<p>We were particularly interested in models of the electrical conductivity of subduction zones. This is because the fluids and molten rock we were looking at are more electrically conductive than the surrounding rock. Models of subduction zones have long been enigmatic, because they show Earth is very conductive in regions where people did not expect to see a lot of fluids and molten rock. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/386607/original/file-20210226-17-1qah4kx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/386607/original/file-20210226-17-1qah4kx.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=375&fit=crop&dpr=1 600w, https://images.theconversation.com/files/386607/original/file-20210226-17-1qah4kx.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=375&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/386607/original/file-20210226-17-1qah4kx.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=375&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/386607/original/file-20210226-17-1qah4kx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=471&fit=crop&dpr=1 754w, https://images.theconversation.com/files/386607/original/file-20210226-17-1qah4kx.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=471&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/386607/original/file-20210226-17-1qah4kx.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=471&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Melting sediment from the seafloor helps tectonic plates slide over one another without creating major earthquakes.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1038/s41467-021-21657-8">Selway & Forster</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>I calculated the electrical conductivity of the phlogopite, molten sediments and fluids that were produced in the experiments and found they matched extremely well with the geophysical models. This provides good evidence that what we see in the experiments is happening in the real Earth, and allows us to calculate where the molten rock and fluids are in subduction zones around the world. </p>
<h2>Understanding where big earthquakes are likely to occur</h2>
<p>Giant earthquakes are not likely to occur in the parts of the subduction zone where the sediments melt. All of the products of the melting — the molten rock itself, the saline fluids, and even the mineral phlogopite — help the two plates slide past each other easily without causing large earthquakes. </p>
<p>We compared our models with locations of earthquakes in subduction zones along the west coast of the United States. We found there were no large earthquakes where sediments were melting, but the movement of fluids from the melted sediments could explain some small, non-destructive earthquakes and very faint signals of tremor where the two plates easily slide past each other.</p>
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Read more:
<a href="https://theconversation.com/breaking-new-ground-the-rise-of-plate-tectonics-7514">Breaking new ground – the rise of plate tectonics</a>
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<hr>
<p>Earthquakes are a tangible reminder that we live on an active planet and that, deep beneath our feet, huge forces are making rocks flow and melt and collide. Accurately predicting earthquakes will be an ongoing goal of geoscientists for decades to come. </p>
<p>It requires intricate detective work to weave together all the tiny threads of information we have about processes that occur so deep in the Earth that we will never be able to see or sample them. Our results are one new thread in this puzzle. We hope it will contribute to one day being able to keep people safe from the risk of earthquakes. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/underground-sounds-why-we-should-listen-to-earthquakes-5798">Underground sounds: why we should listen to earthquakes</a>
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<img src="https://counter.theconversation.com/content/156104/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kate Selway receives funding from the Australian Research Council. </span></em></p>When sea sediment melts inside the Earth, it helps tectonic plates slide over one another smoothly.Kate Selway, Macquarie UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1515782020-12-16T19:04:29Z2020-12-16T19:04:29ZEastern Australia has hundreds of enigmatic volcanoes. New research shows how they formed<figure><img src="https://images.theconversation.com/files/375215/original/file-20201215-15-15pzf7a.jpg?ixlib=rb-1.1.0&rect=14%2C0%2C2367%2C1350&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/q9-KwUcNNPQ">Luisa Denu / Unsplash</a></span></figcaption></figure><p>The landscape of eastern Australia is dotted with hundreds of extinct volcanoes. They gave rise to an environment to which Aboriginal people have been connected for <a href="https://theconversation.com/when-the-bullin-shrieked-aboriginal-memories-of-volcanic-eruptions-thousands-of-years-ago-81986">tens of thousands of years</a>, and the rich soils upon which modern Australia has grown in the last <a href="https://maas.museum/inside-the-collection/2016/03/31/industrial-revolution-wool/">few hundred years</a>.</p>
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Read more:
<a href="https://theconversation.com/when-the-bullin-shrieked-aboriginal-memories-of-volcanic-eruptions-thousands-of-years-ago-81986">When the Bullin shrieked: Aboriginal memories of volcanic eruptions thousands of years ago</a>
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<p>Yet until recently, these volcanoes posed a geological mystery. There are two common ways volcanoes form: at the edges of tectonic plates, or on top of blobs of hot material called “mantle plumes”, which rise from the planet’s deep interior. For most of eastern Australia’s volcanoes, however, neither of these explanations fits the bill. </p>
<p>We have now <a href="https://advances.sciencemag.org/content/6/51/eabd0953">solved the puzzle</a>. By studying the history of the eruptions and the chemical makeup of the rocks they spat out, we discovered a previously unknown geological mechanism that links volcanoes from Far North Queensland to the southern tip of Tasmania.</p>
<h2>Australia’s volcanic connection</h2>
<p>You may be surprised to learn that hundreds of volcanoes erupted along the entire eastern side of Australia over the past 100 million years. This volcanism also extended offshore to New Zealand and the <a href="https://www.9news.com.au/national/zealandia-how-the-worlds-hidden-continent-was-formed-near-australia-science/3a06ec96-fd19-421a-8422-e7dc107dd324">submerged continent of Zealandia</a>.</p>
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<strong>
Read more:
<a href="https://theconversation.com/what-are-lost-continents-and-why-are-we-discovering-so-many-126355">What are lost continents, and why are we discovering so many?</a>
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<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/375836/original/file-20201218-17-1p83ap3.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Map showing Australia and Zealandia's volcanoes, mostly located down Australia's east coast" src="https://images.theconversation.com/files/375836/original/file-20201218-17-1p83ap3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/375836/original/file-20201218-17-1p83ap3.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/375836/original/file-20201218-17-1p83ap3.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/375836/original/file-20201218-17-1p83ap3.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/375836/original/file-20201218-17-1p83ap3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/375836/original/file-20201218-17-1p83ap3.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/375836/original/file-20201218-17-1p83ap3.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">There are many volcanoes across Australia and Zealandia. Highlights for volcano spotters include: (A) Sawn Rocks in New South Wales, (B) Glass House Mountains and (C) Undara Lava Tubes in Queensland, (D) Mt Gambier in South Australia, (E) Organ Pipes in Victoria and (F) The Nut in Tasmania.</span>
<span class="attribution"><span class="source">Jo Condon / Mahsa-Chitsaz / Luisa Denu / Jane Farquhar / Charles G / Nick Carson / Around Aus</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Most of the world’s volcanoes form when a process called “subduction” pushes parts of the seafloor down into Earth’s mantle, where it melts and produces volcanism at the surface. The best-known example of this kind of volcanism is the <a href="https://theconversation.com/five-active-volcanoes-on-my-asia-pacific-ring-of-fire-watch-list-right-now-90618">Ring of Fire</a> around the Pacific Ocean.</p>
<p>Alternatively, chains of volcanic islands may be built by hot material rising from the Earth’s deep interior – called “mantle plumes” – in a process that created the likes of Hawaii, Iceland, and the Galapagos Islands. These so-called “hotspot chains” track the movement of tectonic plates as new islands form over a stationary mantle plume.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/375314/original/file-20201216-21-upi7g.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/375314/original/file-20201216-21-upi7g.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/375314/original/file-20201216-21-upi7g.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=264&fit=crop&dpr=1 600w, https://images.theconversation.com/files/375314/original/file-20201216-21-upi7g.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=264&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/375314/original/file-20201216-21-upi7g.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=264&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/375314/original/file-20201216-21-upi7g.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=332&fit=crop&dpr=1 754w, https://images.theconversation.com/files/375314/original/file-20201216-21-upi7g.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=332&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/375314/original/file-20201216-21-upi7g.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=332&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Most volcanoes are clustered near subduction zones, where oceanic crust is recycled into the Earth’s mantle, or above hotspots which create chains of islands in the oceans.</span>
<span class="attribution"><span class="source">University of Saskatchewan</span></span>
</figcaption>
</figure>
<p>However, most of the volcanoes in our backyard are not related to mantle plumes and are not close to plate boundaries. So why are they here?</p>
<h2>Examining Australia’s volcanic pulse</h2>
<p>Our study, <a href="https://advances.sciencemag.org/content/6/51/eabd0953">published today</a> in Science Advances, shows the frequency of volcanic eruptions in eastern Australia and Zealandia depends on what’s happening to the seafloor some 3,000 kilometres further east.</p>
<p>Why does this happen? It’s all to do with how much water and carbon dioxide are trapped in the seafloor, which is recycled down into the mantle. </p>
<p>Over many millions of years, a reservoir of these volatile ingredients has built up in the mantle, more than 410 kilometres below the surface. This reservoir stays dormant beneath the Australian plate, until tectonic forces create bursts of movement.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/australias-volcanic-history-is-a-lot-more-recent-than-you-think-58766">Australia's volcanic history is a lot more recent than you think</a>
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<p>As slabs of seafloor are subducted at the Tonga-Kermadec Trench, which runs from New Zealand all the way to Samoa, the vibrations reach all way to the mantle reservoir beneath eastern Australia and Zealandia. As a result, water and carbon dioxide shake loose from the reservoir and rise up to produce volcanic eruptions at the surface. </p>
<p>We found our first piece of evidence for this driving process in the deep history of volcanic eruptions in the region. There were two gradual increases in volcanism, one between 60 million years ago and 21 million years ago, and the other from 10 million years ago to 2 million years ago. These periods were separated by a brief (in geological terms) lull in eruption frequency. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/ECp63U_8gBs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Reconstruction of volcanism and subduction in eastern Australia and Zealandia since 120 million years ago in map view, visualised in AuScope enabled GPlates software.</span></figcaption>
</figure>
<p>Both episodes were produced by major reorganisations of Earth’s tectonic plates, in which the plates rapidly change speed and direction. These changes led to the subduction of a massive pile of western Pacific seafloor, which in turn caused volcanic activity as water and carbon dioxide were shaken from their reservoir in the mantle.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/375331/original/file-20201216-13-lrijul.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Our model in section view together with a graph of volcanism through time." src="https://images.theconversation.com/files/375331/original/file-20201216-13-lrijul.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/375331/original/file-20201216-13-lrijul.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/375331/original/file-20201216-13-lrijul.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/375331/original/file-20201216-13-lrijul.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/375331/original/file-20201216-13-lrijul.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/375331/original/file-20201216-13-lrijul.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/375331/original/file-20201216-13-lrijul.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Our new model of volcanism shown as a slice through the Earth (sectional view), visualised together with the region’s volcanism over the last 100 million years.</span>
<span class="attribution"><span class="source">Jo Condon / Ben Mather</span></span>
</figcaption>
</figure>
<h2>Fingerprinting Australia’s mystery volcanoes</h2>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/374593/original/file-20201213-15-1qvrg46.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/374593/original/file-20201213-15-1qvrg46.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/374593/original/file-20201213-15-1qvrg46.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/374593/original/file-20201213-15-1qvrg46.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/374593/original/file-20201213-15-1qvrg46.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/374593/original/file-20201213-15-1qvrg46.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/374593/original/file-20201213-15-1qvrg46.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In 2019 we travelled aboard the CSIRO research vessel Investigator to collect rock samples from underwater volcanoes and map thousands of kilometres of seafloor.</span>
<span class="attribution"><span class="source">Supplied</span></span>
</figcaption>
</figure>
<p>This subduction process is not unique to the Australian east coast. What sets the east Australia-Zealandia region apart is that the seafloor being pushed under the continent from the western Pacific is rich in materials that contain water and carbon dioxide. </p>
<p>Not only that, but these materials seem to collect at a shallow depth in the mantle over a long period of time, rather than sink deeper into Earth’s interior. This creates a zone deep in the mantle right under the east coast of Australia that is enriched with volatile materials.</p>
<p>We examined the chemical composition of rocks produced by these ancient eruptions across the region and found the vast majority shared common chemical fingerprints. These fingerprints told us the eruptions across the eastern third of Australia and Zealandia came from a common mantle reservoir, which could only have formed from the subduction of ancient seafloor. This was the final piece of the puzzle that helped us connect seemingly random volcanoes over 100 million years of history.</p>
<h2>New ‘eyes’ to explore abroad and at home</h2>
<p>Combining the perspectives of volcanic history, tectonic plate movements and geochemistry may also help us to unlock other explosive mysteries of our natural world. We hope to test our model further in other enigmatic regions where volcanoes appear in the middle of tectonic plates, such as the western United States, eastern China, and around Bermuda.</p>
<p>In the meantime, we hope our discoveries give you a new way to look at the many beautiful volcanic hills and other features of eastern Australia. If you’re driving around the countryside this summer, here are our top five volcanic highlights for your travelling pleasure:</p>
<ul>
<li><p><a href="https://www.discovertasmania.com.au/attraction/thenut">The Nut</a>, Tasmania</p></li>
<li><p><a href="https://discovermountgambier.com.au/experience/geological-wonders/">Mount Gambier</a>, South Australia</p></li>
<li><p><a href="https://www.parks.vic.gov.au/places-to-see/parks/organ-pipes-national-park">Organ Pipes National Park</a>, Victoria</p></li>
<li><p><a href="https://www.visitnarrabri.com.au/narrabri-directory/sawn-rocks/">Sawn Rocks Narrabri</a>, New South Wales</p></li>
<li><p><a href="https://www.tropicalnorthqueensland.org.au/things-to-do/geological-wonders/lava-tubes/">Undara lava tubes</a>, Queensland</p></li>
</ul>
<hr>
<p><em>This study was carried out by researchers from the University of Sydney, <a href="https://www.monash.edu/science/schools/earth-atmosphere-environment">Monash University</a> and <a href="https://www.gns.cri.nz/">GNS Science</a> in Dunedin, New Zealand. It was enabled by Australia’s National Collaborative Research Infrastructure Strategy (<a href="https://www.education.gov.au/national-collaborative-research-infrastructure-strategy-ncris">NCRIS</a>) via <a href="https://www.auscope.org.au">AuScope</a> and <a href="https://www.chiefscientist.nsw.gov.au">The Office of the Chief Scientist and Engineer</a>, NSW Department of Industry.</em></p>
<p><em>CORRECTION: This article originally referred to Cradle Mountain in Tasmania, which is not in fact volcanic. It should have referred to <a href="https://www.discovertasmania.com.au/attraction/thenut">The Nut</a>, which is. This has been amended.</em></p><img src="https://counter.theconversation.com/content/151578/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ben Mather works for The University of Sydney, supported by funds from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Dietmar Müller receives funding from the Australian Research Council, the AuScope National Collaborative Research Infrastructure and the NSW Department of Industry.</span></em></p><p class="fine-print"><em><span>Jo Condon works for AuScope, a non-profit organisation funded by the Australian Government (NCRIS) that helped to enable this research. </span></em></p><p class="fine-print"><em><span>Maria Seton receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Oliver Nebel receives funding from the Australian Research Council</span></em></p>From far north Queensland to the southern tip of Tasmania, there is a common geological mechanism that links Eastern Australia’s volcanic history.Ben Mather, Computational Geophysicist, University of SydneyDietmar Müller, Professor of Geophysics, University of SydneyJo Condon, Honorary researcher, The University of MelbourneMaria Seton, Senior Lecturer, University of SydneyOliver Nebel, Associate Professor, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1465342020-12-06T10:02:39Z2020-12-06T10:02:39ZThe Atlantic: The driving force behind ocean circulation and our taste for cod<figure><img src="https://images.theconversation.com/files/372503/original/file-20201202-17-1qg6r71.jpg?ixlib=rb-1.1.0&rect=38%2C0%2C4195%2C2818&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Fishing boats coming into Le Guilvinec, Brittany, France, at the end of the day.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/homecoming-tired-fishermans-ships-approaching-after-772649248">Photoneye/Shutterstock</a></span></figcaption></figure><p>“<a href="https://www.abebooks.co.uk/first-edition/Atlantic-Close-Re-Open-Offprint-Nature-Vol/30196723457/bd">Did the Atlantic close and then reopen</a>?” That was the question posed in a 1966 paper by the Canadian geophysicist <a href="https://www.ldeo.columbia.edu/the-vetlesen-prize/past-recipients/john-tuzo-wilson">J. Tuzo Wilson</a>. </p>
<p>The answer? Yes, over millions of years. And it was the breakup of the <a href="https://www.britannica.com/place/Pangea">supercontinent Pangea</a>, starting some 180 million years ago, that began creating the Atlantic Ocean basin as we know it today.</p>
<p>Earth’s surface is made up of <a href="https://www.britannica.com/science/plate-tectonics">intersecting tectonic plates</a>. For much of our planet’s history these plates have been bumping into one another, forming chains of mountains and volcanoes, and then rifting apart, creating oceans. </p>
<p>When Pangea existed it would have been possible to walk from modern Connecticut or Georgia in the U.S. to what is now Morocco in Africa. Geologists don’t know what causes continents to break up, but we know that when rifting occurs, continents thin and pull apart. Magma intrudes into the continental rocks. </p>
<hr>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/369797/original/file-20201117-13-180ibt9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><strong><em>This story is part of <a href="https://theconversation.com/uk/topics/oceans-21-96784">Oceans 21</a></em></strong>
<br><em><a href="https://oceans21.netlify.app/">Five profiles open our series on the global ocean</a>, delving into ancient <a href="https://theconversation.com/exploring-the-indian-ocean-as-a-rich-archive-of-history-above-and-below-the-water-line-133817">Indian Ocean</a> trade networks, <a href="https://theconversation.com/it-might-be-the-worlds-biggest-ocean-but-the-mighty-pacific-is-in-peril-150745">Pacific</a> plastic pollution, <a href="https://theconversation.com/arctic-ocean-climate-change-is-flooding-the-remote-north-with-light-and-new-species-150157">Arctic</a> light and life, <a href="https://theconversation.com/the-atlantic-the-driving-force-behind-ocean-circulation-and-our-taste-for-cod-146534">Atlantic</a> fisheries and the <a href="https://theconversation.com/an-ocean-like-no-other-the-southern-oceans-ecological-richness-and-significance-for-global-climate-151084">Southern Ocean</a>’s impact on global climate. Look out for new articles in the lead up to COP26. Brought to you by The Conversation’s international network.</em></p>
<hr>
<p>The oldest portions of crust in the Atlantic Ocean lie off of North America and Africa, which were adjacent in Pangea. They show that these two continents separated about 180 million years ago, forming the North Atlantic Ocean basin. The rest of Africa and South America rifted apart about 40 million or 50 million years later, creating what is now the South Atlantic Ocean basin. </p>
<p>Magma wells upward from beneath the ocean floor at the Mid-Atlantic Ridge, creating new crust where the plates move apart. Some of this ocean crust is younger than you or me, and more is being created today. The Atlantic is still growing.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/370161/original/file-20201118-17-39dr16.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="World map with colored zones showing age of ocean plates" src="https://images.theconversation.com/files/370161/original/file-20201118-17-39dr16.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/370161/original/file-20201118-17-39dr16.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=330&fit=crop&dpr=1 600w, https://images.theconversation.com/files/370161/original/file-20201118-17-39dr16.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=330&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/370161/original/file-20201118-17-39dr16.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=330&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/370161/original/file-20201118-17-39dr16.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=415&fit=crop&dpr=1 754w, https://images.theconversation.com/files/370161/original/file-20201118-17-39dr16.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=415&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/370161/original/file-20201118-17-39dr16.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=415&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This map shows how ocean crust rises upward at rifts between tectonic plates and spreads outward. In the Atlantic, light blue crust began forming 180 million years ago when North America and Africa rifted apart. Green crust was produced 128 million to 84 million years ago when Africa and South America rifted apart. Dark red crust is the youngest, formed up to 10 million years ago.</span>
<span class="attribution"><a class="source" href="https://www.ngdc.noaa.gov/mgg/ocean_age/data/2008/ngdc-generated_images/whole_world/2008_age_of_oceans_plates.jpg">NOAA NGDC</a></span>
</figcaption>
</figure>
<h2>Winds and currents</h2>
<p>Once the ocean basin formed after Pangea’s breakup, water entered from rain and rivers. Winds began to move the surface water. </p>
<p>Thanks to the <a href="https://www.youtube.com/watch?v=xqM83_og1Fc">unequal heating of Earth’s surface and its rotation</a>, these winds blow in different directions. The Earth is warmer at the equator than near the poles, which puts air in motion. At the equator the planet’s heat causes moist air to warm, expand and rise. At the polar regions cold, dry, heavier air descends. </p>
<p>This motion creates “cells” of rising and descending air that control global wind patterns. Earth’s rotation dictates that different parts of the globe travel at different speeds. At a pole, a molecule of air would just spin around, while a particle of air at the equator in Quito, Ecuador, would travel 7,918 miles (12,742 kilometers) in a single day. </p>
<p>This different movement causes the air cells to break up. For example, in the <a href="https://www.bbc.co.uk/bitesize/guides/zpykxsg/revision/1">Hadley Cell</a>, tropical air, which rose at the equator, cools in the upper atmosphere and descends at about 30 degrees north and south latitude – roughly, near the northern and southern tips of Africa. Earth’s rotation <a href="https://scied.ucar.edu/learning-zone/how-weather-works/global-air-atmospheric-circulation">turns this descending air</a>, creating trade winds that flow from east to west across the Atlantic and back to the equator. At higher latitudes in the North and South Atlantic, the same forces create mid-latitude cells with winds that blow from west to east.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/368418/original/file-20201109-21-1plttsv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Atmospheric circulation diagram" src="https://images.theconversation.com/files/368418/original/file-20201109-21-1plttsv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/368418/original/file-20201109-21-1plttsv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=462&fit=crop&dpr=1 600w, https://images.theconversation.com/files/368418/original/file-20201109-21-1plttsv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=462&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/368418/original/file-20201109-21-1plttsv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=462&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/368418/original/file-20201109-21-1plttsv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=581&fit=crop&dpr=1 754w, https://images.theconversation.com/files/368418/original/file-20201109-21-1plttsv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=581&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/368418/original/file-20201109-21-1plttsv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=581&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Earth’s atmospheric circulation, showing the Hadley, midlatitude and polar cells, and the wind patterns they produce.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:NASA_depiction_of_earth_global_atmospheric_circulation.jpg">NASA/Wikimedia</a></span>
</figcaption>
</figure>
<p>As air flows across the ocean’s surface, it moves water. This creates a circulating system of gyres, or rotating currents, that move clockwise in the North Atlantic and counterclockwise in the South Atlantic. These gyres are part of a <a href="https://svs.gsfc.nasa.gov/vis/a000000/a003600/a003658/">global conveyor belt</a> that transports and redistributes heat and nutrients throughout the global ocean. </p>
<p>The Gulf Stream, which follows the U.S. East Coast before heading east across the North Atlantic, is part of the North Atlantic gyre. Since the current carries warm water north, it is easy to see on false-color <a href="https://visibleearth.nasa.gov/images/54734/temperature-of-the-gulf-stream">infrared satellite images</a> as it transports heat northward. Like a river, it also meanders. </p>
<h2>Moving water masses</h2>
<p>These wind-blown surface currents are important for many reasons, including <a href="https://divediscover.whoi.edu/history-of-oceanography/benjamin-franklin-discovering-the-gulf-stream/">human navigation</a>, but they affect only about 10% of the Atlantic’s volume. Most of the ocean operates in a different system, which is called thermohaline circulation because it is driven by heat (thermo) and salt (saline).</p>
<p>Like many processes in the ocean, salinity is tied to weather and circulation. For example, trade winds blow moist air from the Atlantic across Central America and into the <a href="https://theconversation.com/it-may-be-the-worlds-biggest-deepest-ocean-but-the-mighty-pacific-is-in-peril-150406">Pacific Ocean</a>, which concentrates salinity in the Atlantic waters left behind. As a result, the Atlantic is <a href="https://earthobservatory.nasa.gov/images/78250/a-measure-of-salt">slightly saltier than the Pacific</a>. </p>
<p>This extra salinity makes the Atlantic the driving force in ocean circulation. As currents move surface waters poleward, the water cools and becomes more dense. Eventually at high latitudes this cold, salty water sinks to the ocean floor. From there it flows along the bottom and back toward the the opposite pole, creating density-driven currents with names such as <a href="https://en.wikipedia.org/wiki/North_Atlantic_Deep_Water">North Atlantic Deep Water</a> and <a href="https://en.wikipedia.org/wiki/Antarctic_bottom_water">Antarctic Bottom Water</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/368484/original/file-20201110-22-6dz8ei.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Thermohaline circulation map" src="https://images.theconversation.com/files/368484/original/file-20201110-22-6dz8ei.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/368484/original/file-20201110-22-6dz8ei.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=382&fit=crop&dpr=1 600w, https://images.theconversation.com/files/368484/original/file-20201110-22-6dz8ei.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=382&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/368484/original/file-20201110-22-6dz8ei.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=382&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/368484/original/file-20201110-22-6dz8ei.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=480&fit=crop&dpr=1 754w, https://images.theconversation.com/files/368484/original/file-20201110-22-6dz8ei.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=480&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/368484/original/file-20201110-22-6dz8ei.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=480&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Global thermohaline circulation is driven primarily by the formation and sinking of deep water. It moves heat from the equator toward the poles.</span>
<span class="attribution"><a class="source" href="https://www.grida.no/resources/5228">Hugo Ahlenius, UNEP/GRID-Arendal</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>As these deep currents move, they collect surface organisms that have died and fallen to the bottom. With time, the organisms decompose, filling the deep water with essential nutrients. </p>
<p>In some locations this nutrient-rich water rises back up to the surface, a process called upwelling. When it reaches the ocean’s sunlit zone, within 650 feet (200 meters) of the surface, tiny organisms called phytoplankton feed on the nutrients. In turn, they become food for zooplankton and larger organisms higher up the food chain. Some of the the Atlantic’s richest fishing grounds, such as <a href="https://www.newworldencyclopedia.org/entry/Grand_Banks">the Grand Banks</a> to the southeast of Newfoundland in Canada and the <a href="https://earthobservatory.nasa.gov/features/Malvinas">Falkland/Malvinas Islands</a> in the South Atlantic, are upwelling areas. </p>
<p>Much about the Atlantic remains to be discovered, especially in a changing climate. Will rising carbon dioxide levels and resulting ocean acidification disrupt marine food chains? How will a warmer ocean affect circulation and hurricane intensity? What we do know is that the Atlantic’s winds, currents and sea life are intricately connected, and disrupting them can have far-reaching effects.</p>
<h2>Atlantic cod fishing</h2>
<p>Now, let’s head back up to the surface, and into the wake of the first sailboats that set out to fish for cod along the Canadian coast. These pioneering ships paved the way for greater exploitation of the Atlantic’s wealth of fishery resources – particularly cod. Communities of people greatly benefited from these resources over the following centuries, until the threat of overfishing became impossible to ignore.</p>
<p>The history of fishing in the Atlantic is often said to trace back to the discovery of the cod-rich Canadian waters of Newfoundland, attributed to Italian navigator and explorer John Cabot, who led an English expedition there in 1497. From the 16th to the 20th centuries, cod-fishing mania swept European fleets. Between 1960 to 1976, ships from Spain, Portugal and France were responsible for <a href="https://www.nafo.int/Data/STATLANT">40% of the catch</a>. However, <a href="https://books.google.fr/books/about/Management_of_Marine_Fisheries_in_Canada.html?id=uWOmj-j0jmcC&redir_esc=y">in 1977 Canada extended its territory</a> offshore by 200 miles, taking possession of the Newfoundland cod fisheries, which accounted for 70% of cod production in the Northwest Atlantic.</p>
<figure class="align-center ">
<img alt="Fishermen aboard a boat with a haul of cod" src="https://images.theconversation.com/files/371062/original/file-20201124-15-ud1t75.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/371062/original/file-20201124-15-ud1t75.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/371062/original/file-20201124-15-ud1t75.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/371062/original/file-20201124-15-ud1t75.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/371062/original/file-20201124-15-ud1t75.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/371062/original/file-20201124-15-ud1t75.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/371062/original/file-20201124-15-ud1t75.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Fishermen aboard a boat with a haul of cod.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/fr/image-photo/cod-fishing-lofoten-norway-fisherman-action-1261237213">Georg Kristiansen/Shutterstock</a></span>
</figcaption>
</figure>
<p>For five centuries, the only thing that mattered was the size of the catch. This drove innovations in the design and equipment of fishing boats. The sailboat cod-fishing industry in Newfoundland and Iceland <a href="https://archimer.ifremer.fr/doc/00486/59783/62917.pdf">hit its peak in the late 19th century</a>; from 1800 to 1900, France – the main fishing operator alongside Britain – outfitted more than 30,000 schooners. </p>
<p>At the end of the 19th century, the rowboat was replaced by the dory, a small (two-person) boat from North America, which sharply increased production. A plaque commenting on the new safety of the dory in the French <a href="https://www.ville-fecamp.fr/-Musee-.html">Museum of Fisheries</a>, in Normandy – dedicated to the history of commercial cod fishing – noted that the hazard of losing a man overboard was “built into the mindset of cod-fishing.” But by the early 20th century, steamers had begun to replace these boats.</p>
<p>New <a href="https://doi.org/10.1016/j.marpol.2020.103868">productivity gains</a> came with new techniques, such as <a href="https://www.sciencedirect.com/science/article/abs/pii/S0308597X07000784">using back-trawling</a> instead of side-trawling in the 1950s and 1960s, alongside reduced crew sizes.</p>
<p>The biggest cod catch, at nearly 1.9 million tons, was recorded in 1968. After that, overall production declined year after year, reaching less than a million tons in 1973. Numbers slowly picked up again in the 1980s after European fleets were excluded from the Newfoundland area, but this comeback was short-lived. On July 2, 1992, the Canadian government announced <a href="https://books.google.fr/books/about/Management_of_Marine_Fisheries_in_Canada.html?id=uWOmj-j0jmcC&redir_esc=y">a moratorium</a> on cod fishing, confirming that populations had collapsed. This collapse in the northwestern Atlantic has <a href="https://www.sciencedirect.com/science/article/abs/pii/S0308597X04000600">since become a textbook example of the risks of overfishing</a>.</p>
<h2>The wider catch</h2>
<p>Seafood production in the Atlantic went from an estimated 9 million tons in 1950 to more than 23 million tons in 1980 and 2000, and <a href="http://www.fao.org/fishery/static/Yearbook/YB2018_USBcard/navigation/index_content_capture_e.htm#C">22 million tons in 2018</a>. This overall production has remained stable since 1970. </p>
<p>In the North Atlantic, whiting and herring are the two most fished species by tonnage. Sardine and sardinella hold the top spots in the Central Atlantic. In the South Atlantic, mackerel and Argentine hake dominate the catch.</p>
<p>The Food and Agriculture Organization of the United Nations (FAO) has identified six production areas in the Atlantic Ocean, divided up cardinally, as shown on the map below. In 1950, these various areas accounted for <a href="http://www.fao.org/fishery/static/Yearbook/YB2018_USBcard/navigation/index_content_capture_e.htm#C">52% of the worldwide catch</a>. From 1960 to 1980, this proportion went down to 37% to 43%. Since 1990, one-quarter of global seafood production is caught by fleets operating in the Atlantic.</p>
<p>Nearly <a href="http://www.fao.org/fishery/static/Yearbook/YB2018_USBcard/navigation/index_intro_e.htm">60% of seafood production</a> now comes from fisheries in the Pacific Ocean, and 15% from the Indian Ocean.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/371046/original/file-20201124-17-1waqbvw.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/371046/original/file-20201124-17-1waqbvw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/371046/original/file-20201124-17-1waqbvw.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=763&fit=crop&dpr=1 600w, https://images.theconversation.com/files/371046/original/file-20201124-17-1waqbvw.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=763&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/371046/original/file-20201124-17-1waqbvw.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=763&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/371046/original/file-20201124-17-1waqbvw.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=959&fit=crop&dpr=1 754w, https://images.theconversation.com/files/371046/original/file-20201124-17-1waqbvw.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=959&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/371046/original/file-20201124-17-1waqbvw.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=959&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">FAO has identified six production areas in the Atlantic Ocean.</span>
<span class="attribution"><a class="source" href="http://www.fao.org/fishery/docs/maps/world_2003.gif">Le Floc’h (adapted from FAO's map, 2003)</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p><strong>The northeastern Atlantic</strong> (FAO Area 27) covers fisheries operated by European fleets. This area is, by far, the most bountiful of the entire Atlantic zone, with a total catch of 9.6 million tons in 2018. Norway <a href="http://www.fao.org/fishery/static/Yearbook">took the lead</a> for seafood production by tonnage (2.5 million tons) in 2018, ahead of Spain (just under a million tons). It is also the most diversified zone, with more than 450 commercial species.</p>
<p><strong>The northwestern Atlantic</strong> (FAO Area 21) stretches from the Rhode Island and Gulf of Maine coastlines in the U.S. to the Canadian coasts, including the Gulf of Saint Lawrence and the waters of Newfoundland and Labrador. Cod has dominated the history of fishing in this area since the 16th century. The biggest overall catch was recorded in 1970, at more than 4 million tons. But, after 1990, that number dropped, as a consequence of the 1992 moratorium. Since 2000, the northwest area has accounted for around 10% of the Atlantic catch (1.7 million tons in 2018). There are 220 monitored species in the area.</p>
<p><strong>Eastern Central Atlantic</strong> (FAO Area 34) stretches from the Moroccan to the Zairian coasts. Species caught include sardine, anchovy and herring. In 2018, this area accounted for a quarter of the total seafood production of all six Atlantic areas. That same year, West African fisheries recorded the second biggest catches after the northeastern Atlantic. The high number of commercial species identified by the FAO sets this region apart, at nearly 300.</p>
<p><strong>Western Central Atlantic</strong> (FAO Area 31) stretches from the southern U.S. to the north of Brazil, including the Caribbean. Since 1970, catch size has remained between 1.3 million and 1.8 million tons (5% to 10% of the entire Atlantic catch). Lobster and shrimp are the target species in the Caribbean waters.</p>
<p><strong>Southeast Atlantic</strong> (FAO Area 47) connects the African coastlines of Angola, Namibia and South Africa. Production surpassed 2 million tons in 1970 and 1980, accounting for 10% of the total Atlantic catch. Since 1990, the catch has been stable, with a plateau of 1.5 million tons. It’s the least diversified region in the Atlantic, with 160 species monitored by the FAO. Mackerel, hake and anchovy make up 59% of total production.</p>
<p><strong>Southwest Atlantic</strong> (FAO Area 41), which stretches along the coastlines of Brazil, Uruguay and Argentina in South America, was the lowest-producing of the six areas until 1980. It recorded no more than 5% of the total Atlantic catch. But from 1990, fisheries produced 1.8 million to 2 million tons (8% to 10% of the overall catch). This can be attributed to investment from the Argentinian government into <a href="https://doi.org/10.4000/norois.7300">fishing fleets</a> in the 1980s. Some 225 commercial species are being statistically monitored, with 52% of total production coming from hake, shortfin squid and shrimp.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/371047/original/file-20201124-17-1exliy7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/371047/original/file-20201124-17-1exliy7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/371047/original/file-20201124-17-1exliy7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=287&fit=crop&dpr=1 600w, https://images.theconversation.com/files/371047/original/file-20201124-17-1exliy7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=287&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/371047/original/file-20201124-17-1exliy7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=287&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/371047/original/file-20201124-17-1exliy7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=360&fit=crop&dpr=1 754w, https://images.theconversation.com/files/371047/original/file-20201124-17-1exliy7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=360&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/371047/original/file-20201124-17-1exliy7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=360&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Catches in the Atlantic (1950-2018) according to the FAO areas.</span>
<span class="attribution"><a class="source" href="http://www.fao.org/fishery/statistics/fr">Le Floc’h</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<h2>Protecting the entire ecosystem</h2>
<p>At a time when scientific research predicts that all living marine resources will <a href="https://science.sciencemag.org/content/314/5800/787">be exhausted by 2048</a>, a new fisheries approach is required to avoid new tragedies, like the one that befell the cod populations in the northwestern Atlantic.</p>
<p>In this context, protecting ecosystems has become a priority. This growing acknowledgment of the impacts of fishing is a direct result of the successful work undertaken by ecological and social science researchers since the 1970s, who placed the concept of resilience at the heart of their studies.</p>
<p>This new ecosystem-based management approach, now inscribed in law in <a href="https://ec.europa.eu/environment/marine/eu-coast-and-marine-policy/marine-strategy-framework-directive/index_en.htm">Europe</a> and <a href="https://laws-lois.justice.gc.ca/eng/acts/o-2.4/">Canada</a>, has been positive. A similar <a href="https://obamawhitehouse.archives.gov/administration/eop/oceans/policy">U.S. policy</a> was revoked by President Donald Trump, but likely will be restored by incoming president Joe Biden. However, there is still work to do to tackle the main challenge – making this approach a reality in all Atlantic fisheries.</p><img src="https://counter.theconversation.com/content/146534/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The Atlantic Ocean is still growing physically, but humans are over-harvesting its rich fisheries. The most famous one – North Atlantic cod – has become a textbook example of harmful overfishing.Suzanne OConnell, Professor of Earth and Environmental Sciences, Wesleyan UniversityPascal Le Floc’h, Maître de conférences, économiste, laboratoire Amure (UBO, Ifremer, CNRS), Université de Bretagne occidentale Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1484042020-11-02T20:01:34Z2020-11-02T20:01:34ZMagnetism of Himalayan rocks reveals the mountains’ complex tectonic history<figure><img src="https://images.theconversation.com/files/365671/original/file-20201026-17-199ct3j.jpg?ixlib=rb-1.1.0&rect=155%2C0%2C2993%2C1999&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Himalayan rocks hold magnetic clues about their origins.</span> <span class="attribution"><span class="source">Craig Robert Martin</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Breathing quickly in the thin mountain air, my colleagues and I set down our equipment. We’re at the base of a jagged outcrop that protrudes upwards out of a steep gravel slope.</p>
<p>The muffled soundscape of the spectacular Himalayan wilderness is punctuated by a military convoy roaring along the Khardung-La road below. It’s a reminder how close we are to the long-disputed borders between India, Pakistan and China which lie on the ridgelines just a few miles away.</p>
<iframe src="https://www.google.com/maps/embed?pb=!1m18!1m12!1m3!1d13088582.506864522!2d68.70515675564154!3d34.45999998049693!2m3!1f0!2f0!3f0!3m2!1i1024!2i768!4f13.1!3m3!1m2!1s0x0%3A0x0!2zMzTCsDI3JzM2LjAiTiA3N8KwNDAnMTIuMCJF!5e1!3m2!1sen!2sus!4v1604077003054!5m2!1sen!2sus" width="100%" height="450" frameborder="0" style="border:0;" allowfullscreen="" aria-hidden="false" tabindex="0"></iframe>
<p>This area also contains a different type of boundary, a narrow sinuous geological structure that stretches along the length of the Himalayan mountain range. Known as a suture zone, it’s only a few kilometers wide and consists of slivers of different types of rocks all sliced together by fault zones. It marks the boundary where two tectonic plates fused together and an ancient ocean disappeared.</p>
<p>Our team of geologists traveled here to collect rocks that erupted as lava more than 60 million years ago. By decoding the magnetic records preserved inside them, we hoped to reconstruct the geography of ancient landmasses – and <a href="https://doi.org/10.1073/pnas.2009039117">revise the story of the creation of the Himalayas</a>.</p>
<h2>Sliding plates, growing mountains</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="artist's rendering of two tectonic plates colliding at a subduction zone" src="https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=489&fit=crop&dpr=1 600w, https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=489&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=489&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=614&fit=crop&dpr=1 754w, https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=614&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/366741/original/file-20201030-23-t6znxn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=614&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">At a subduction zone, two tectonic plates collide, with one slowly sliding beneath the other.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/tectonic-plates-world-map-royalty-free-illustration/889618718">VectorMine/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<p>Tectonic plates make up the surface of Earth, and they’re constantly in motion – drifting at the <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/tectonic-plate">imperceptibly slow pace</a> of just a few centimeters each year. Oceanic plates are colder and denser than the mantle beneath them, so they sink downward into it at subduction zones.</p>
<p>The sinking edge of the ocean plate drags the ocean floor along behind it like a conveyor belt, pulling the continents toward each other. When the entire ocean plate disappears into <a href="https://www.nationalgeographic.org/encyclopedia/mantle/">the mantle</a>, the continents on either side plow into each other with enough force to uplift great mountain belts, like the Himalayas.</p>
<p>Geologists generally thought that the Himalayas formed <a href="https://doi.org/10.1130/0016-7606(2000)112%3C324:TOTHAS%3E2.0.CO;2">55 million years ago in a single continental collision</a> – when the Neotethys Ocean plate subducted under the southern edge of Eurasia and the Indian and Eurasian tectonic plates collided. </p>
<p>But by measuring the magnetism of rocks from northwest India’s remote and mountainous Ladakh region, our team has shown that the tectonic collision that formed the world’s largest mountain range was actually a complex, multi-stage process involving at least two subduction zones.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="diagram of interior of Earth and magnetic field stretching from pole to pole" src="https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=646&fit=crop&dpr=1 600w, https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=646&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=646&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=811&fit=crop&dpr=1 754w, https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=811&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/366500/original/file-20201029-13-1784e5k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=811&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Earth’s magnetic field is generated by movement within the planet’s outer core. Magnetic north and south drift and sometimes flip over time.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/illustration/earth-magnetic-field-scientific-vector-royalty-free-illustration/932342344">VectorMine/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<h2>Magnetic messages, preserved for all time</h2>
<p>Constant movement of our planet’s metallic outer core creates electric currents which in turn generate <a href="https://cosmosmagazine.com/geoscience/what-creates-earth-s-magnetic-field/">Earth’s magnetic field</a>. It’s oriented differently depending where in the world you are. The magnetic field always points toward the magnetic north or the south, which is why your compass works, and averaged over thousands of years it points toward the geographic pole. But it also slopes downward into the ground at an angle which varies depending on how far you are from the equator. </p>
<p>When lava erupts and cools to form rock, the magnetic minerals inside lock in the direction of the magnetic field of that location. So <a href="https://doi.org/10.1016/B0-12-369396-9/00106-4">by measuring the magnetization of volcanic rocks</a>, <a href="https://scholar.google.com/citations?hl=en&user=aD8WioMAAAAJ">scientists like me</a> can determine what latitude they came from. Essentially, this method allows us to unwind millions of years of plate tectonic motions and create maps of the world at different times throughout geologic history.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Member of our research team collecting samples in Ladakh." src="https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=884&fit=crop&dpr=1 600w, https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=884&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=884&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1111&fit=crop&dpr=1 754w, https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1111&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/365226/original/file-20201023-20-172l0hn.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1111&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Geologist collects core samples using a water-cooled electric core drill.</span>
<span class="attribution"><span class="source">Craig Robert Martin</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Over multiple expeditions to the Ladakh Himalayas, our team collected hundreds of 1-inch diameter rock core samples. These rocks originally formed on a volcano active between 66 and 61 million years ago, around the time that the first stages of collision began. We used a hand-held electric drill with a specially designed diamond coring bit to drill approximately 10 centimeters down into the bedrock. We then carefully marked these cylindrical cores with their original orientation before chiseling them out of the rock with nonmagnetic tools.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="cylindrical rock core samples with markings" src="https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=431&fit=crop&dpr=1 600w, https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=431&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=431&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=542&fit=crop&dpr=1 754w, https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=542&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/366238/original/file-20201028-15-ujjeor.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=542&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A few rock core samples, with the sample orientation line marked on their sides.</span>
<span class="attribution"><span class="source">Craig Robert Martin</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The aim was to reconstruct where these rocks originally formed, before they were sandwiched between India and Eurasia and uplifted into the high Himalayas. Keeping track of the orientation of the samples as well as the rock layers they came from is essential to calculating which way the ancient magnetic field pointed relative to the surface of the ground as it was over 60 million years ago.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="View of magnetometer equipment at MIT." src="https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/365268/original/file-20201023-19-1igxsu8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The magnetometer sits inside a magnetically shielded room at the MIT Paleomagnetism Laboratory.</span>
<span class="attribution"><span class="source">Craig Robert Martin</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We brought our samples back to the <a href="http://www.benweiss.mit.edu/">MIT Paleomagnetism Laboratory</a> and, inside a special room that’s shielded from the modern-day magnetic field, we heated them in increments up to 1,256 degrees Fahrenheit (680 degrees Celsius) to slowly remove the magnetization.</p>
<p>Different mineral populations acquire their magnetization at different temperatures. Incrementally heating and then measuring the samples in this way enables us to extract the original magnetic direction by removing more recent overprints that might hide it.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="diagrams depicting India colliding with Eurasia either in a single stage or multiple stages" src="https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=239&fit=crop&dpr=1 600w, https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=239&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=239&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=301&fit=crop&dpr=1 754w, https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=301&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/366244/original/file-20201028-17-hpwmb7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=301&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Black lines mark boundaries between tectonic plates. Black lines with triangular tick marks show subduction zones, with the direction of subduction. The Trans-Tethyan Subduction Zone is the additional subduction zone not accounted for in the single-stage collision model. The Trans-Tethyan Subduction Zone is where the volcanic island chain formed before the Indian continent collided into it and pushed it into Eurasia, forming the Himalaya.</span>
<span class="attribution"><a class="source" href="https://doi.org/10.1073/pnas.2009039117">Martin et al 'Paleocene latitude of the Kohistan-Ladakh arc indicates multi-stage India-Eurasia collision,' PNAS 2020</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<h2>Magnetic traces build a map</h2>
<p>Using the average magnetic direction of the whole suite of samples we can calculate their ancient latitude, which we refer to as the paleolatitude.</p>
<p>The original single-stage collision model for the Himalaya predicts that these rocks would have formed close to Eurasia at a latitude of around 20 degrees north, but our data shows that these rocks did not form on either the Indian or the Eurasian continents. Instead, they formed on a chain of volcanic islands, out in the open Neotethys Ocean at a latitude of about 8 degrees north, thousands of kilometers south of where Eurasia was located at the time.</p>
<p>This finding can be explained only if there were <a href="https://doi.org/10.1038/ngeo2418">two subduction zones</a> pulling India rapidly toward Eurasia, rather than just one. </p>
<p>[<em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklysmart">You can get our highlights each weekend</a>.]</p>
<p>During a geologic time period known as the Paleocene, India caught up with the volcanic island chain and collided with it, scraping up the rocks we eventually sampled onto the northern edge of India. India then continued northward before <a href="https://doi.org/10.1016/j.epsl.2013.01.023">ramming into Eurasia around 40 to 45 million years ago</a> – 10 to 15 million years later than was generally thought.</p>
<p>This final continental collision raised the volcanic islands from sea level up over 4,000 meters to their present-day location, where they form jagged outcrops along a spectacular Himalayan mountain pass.</p><img src="https://counter.theconversation.com/content/148404/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Craig Robert Martin receives funding from the National Science Foundation (NSF).</span></em></p>Earth’s magnetic field locks information into lava as it cools into rock. Millions of years later, scientists can decipher this magnetic data to build geologic timelines and maps.Craig Robert Martin, Ph.D. Student in Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology (MIT)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1465762020-09-28T19:59:34Z2020-09-28T19:59:34ZRocky icebergs and deep anchors – new research on how planetary forces shape the Earth’s surface<figure><img src="https://images.theconversation.com/files/360159/original/file-20200927-20-1qx2iju.jpg?ixlib=rb-1.1.0&rect=44%2C187%2C4947%2C2552&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock/Harvepino</span></span></figcaption></figure><p>Have you ever wondered why the Earth’s surface is separated into two distinct worlds – the oceans and large tracts of land? </p>
<p>Why aren’t land and water more mixed up, forming a landscape of lakes? And why is most of the land relatively low and close to sea level, making coastal regions vulnerable to rising seas?</p>
<p>Our new <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GC009150">research</a> uncovers the fundamental forces that control the Earth’s surface. These findings will help scientists calculate how land levels will respond to the melting of ice sheets and rises in sea level, as a consequence of global warming, as well as providing insights into changes in land area throughout our planet’s history.</p>
<figure class="align-center ">
<img alt="View of Mt Cook" src="https://images.theconversation.com/files/360181/original/file-20200928-20-mmciuw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/360181/original/file-20200928-20-mmciuw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=275&fit=crop&dpr=1 600w, https://images.theconversation.com/files/360181/original/file-20200928-20-mmciuw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=275&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/360181/original/file-20200928-20-mmciuw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=275&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/360181/original/file-20200928-20-mmciuw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=345&fit=crop&dpr=1 754w, https://images.theconversation.com/files/360181/original/file-20200928-20-mmciuw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=345&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/360181/original/file-20200928-20-mmciuw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=345&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">View of Mt Cook/Aoraki, rising 3724m above sea level at the head of Lake Pukaki in New Zealand’s South Island. The mountain is underlain by crust about 45km thick.</span>
<span class="attribution"><span class="source">Shutterstock/yong922760</span></span>
</figcaption>
</figure>
<h2>Rocky icebergs</h2>
<p>The research draws on the work by an inspiring early geologist. In 1855, the British Astronomer Royal <a href="https://en.wikipedia.org/wiki/George_Biddell_Airy">George Biddell Airy</a> published what is arguably one of the <a href="https://www.jstor.org/stable/pdf/108511.pdf">most important scientific papers</a> in the earth sciences, setting out the basic understanding of what controls the elevation of the planet’s surface.</p>
<p>Airy was aware the shape of the Earth is very similar to a spinning fluid ball, distorted by the forces of rotation so that it bulges slightly at the equator and flattens at the poles. He concluded the interior of the Earth must be fluid-like.</p>
<p>His <a href="https://www.jstor.org/stable/pdf/108589.pdf">measurements of the force of gravity</a> in mine shafts showed the deep interior of the Earth must be much denser than the shallow parts. </p>
<figure class="align-right ">
<img alt="Ice berg" src="https://images.theconversation.com/files/360173/original/file-20200927-22-m3z7yx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/360173/original/file-20200927-22-m3z7yx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=750&fit=crop&dpr=1 600w, https://images.theconversation.com/files/360173/original/file-20200927-22-m3z7yx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=750&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/360173/original/file-20200927-22-m3z7yx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=750&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/360173/original/file-20200927-22-m3z7yx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=943&fit=crop&dpr=1 754w, https://images.theconversation.com/files/360173/original/file-20200927-22-m3z7yx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=943&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/360173/original/file-20200927-22-m3z7yx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=943&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">Shutterstock/Sergey Nivens</span></span>
</figcaption>
</figure>
<p>Airy then made an extraordinary leap of scientific thinking. He proposed that the outer part of the Earth, which he called the <a href="https://en.wikipedia.org/wiki/Earth%27s_crust">crust</a>, must be floating on underlying “fluid”. </p>
<p>An analogy might be an iceberg floating in water — to rise above the surface, the iceberg must have deep icy roots. </p>
<p>Applying the same principle to the Earth, Airy proposed the Earth’s crust also had iceberg-like roots, and the higher the surface elevation, the deeper these roots must be, creating thicker crust. </p>
<figure class="align-center ">
<img alt="Map of the continents" src="https://images.theconversation.com/files/359204/original/file-20200921-24-trg15b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359204/original/file-20200921-24-trg15b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=499&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359204/original/file-20200921-24-trg15b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=499&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359204/original/file-20200921-24-trg15b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=499&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359204/original/file-20200921-24-trg15b.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=628&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359204/original/file-20200921-24-trg15b.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=628&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359204/original/file-20200921-24-trg15b.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=628&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The continents define large continuous areas of land separated by oceans. The Earth’s crust is much thicker beneath the continents compared to the oceans.</span>
<span class="attribution"><span class="source">Simon Lamb</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Airy’s idea provided a fundamental explanation for continents and oceans. They were regions of thick and thin crust respectively. High mountain ranges, such as the Himalaya or Andes, were underlain by even thicker crust.</p>
<h2>Tectonic plates</h2>
<p>In the 1960s, the new theory of <a href="https://www.livescience.com/37706-what-is-plate-tectonics.html">plate tectonics</a> introduced a complication. It added the concept of tectonic plates, which are colder and denser than the deeper mantle (the geological <a href="https://www.nationalgeographic.org/encyclopedia/mantle/">layer beneath the crust</a>). </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-earths-continents-became-twisted-and-contorted-over-millions-of-years-116168">How Earth's continents became twisted and contorted over millions of years</a>
</strong>
</em>
</p>
<hr>
<p>Over the past two decades, geophysicists have finally put together an accurate picture of the crust in the continents. </p>
<figure class="align-center ">
<img alt="Graphic explaining how tectonic plates add depth to the " src="https://images.theconversation.com/files/359206/original/file-20200921-18-cvgi6k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359206/original/file-20200921-18-cvgi6k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=288&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359206/original/file-20200921-18-cvgi6k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=288&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359206/original/file-20200921-18-cvgi6k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=288&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359206/original/file-20200921-18-cvgi6k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=362&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359206/original/file-20200921-18-cvgi6k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=362&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359206/original/file-20200921-18-cvgi6k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=362&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Airy imagined the crust as a rocky iceberg with buoyant roots holding up the surface. Plate tectonics adds a dense root of the plate that acts as an anchor.</span>
<span class="attribution"><span class="source">Simon Lamb</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We found a surprising result – there seems to be little relation between the average elevations of the continents and the thickness of the underlying crust, except that the crust is much thicker than beneath the oceans. Most of the land area is within a few hundred metres of sea level, yet the thickness of the crust varies by more than 20km.</p>
<p>So why don’t we see the differences in crustal thickness below a continent reflected in its shape above? Our <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GC009150">research</a> shows the underlying thick tectonic plate is acting as an anchor, keeping the elevations relatively low even though the buoyant crust wants to rise higher.</p>
<p>We used measurements of the thickness of the tectonic plates, recently <a href="http://ds.iris.edu/ds/products/emc-cam2016/">determined from the speed of seismic waves</a>. The base of the continental plates reaches up to 250km deep, but most is between 100km and 200km deep. </p>
<p>We also worked out the densities of the different layers from variations in the strength of gravity. It was clear that the dense roots of the plates were capable of pulling down the surface of the Earth in exactly the way needed to explain the actual elevations.</p>
<figure class="align-center ">
<img alt="Graphic showing the relationship between the thickness of the crust and the elevation of a continent." src="https://images.theconversation.com/files/359248/original/file-20200922-24-13a7r5d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/359248/original/file-20200922-24-13a7r5d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=697&fit=crop&dpr=1 600w, https://images.theconversation.com/files/359248/original/file-20200922-24-13a7r5d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=697&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/359248/original/file-20200922-24-13a7r5d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=697&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/359248/original/file-20200922-24-13a7r5d.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=876&fit=crop&dpr=1 754w, https://images.theconversation.com/files/359248/original/file-20200922-24-13a7r5d.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=876&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/359248/original/file-20200922-24-13a7r5d.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=876&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The average elevations of the continents are surprisingly insensitive to their average crustal thicknesses, contrary to Airy’s prediction that they float on the underlying mantle like rocky ‘icebergs’. If the effect of the deep ‘anchor’ of the underlying dense root to the plates is removed, the continents bob up, floating as the iceberg principle would predict, with a straight-line relation between crustal thickness and elevation.</span>
<span class="attribution"><span class="source">Simon Lamb</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>A balance of planetary forces</h2>
<p>Europe and Asia have very similar average elevations of around 175m above sea level. In Asia, both the crust and tectonic plate are thicker than underneath the European continent, but the weight of the extra thickness balances the tendency for the thicker crust to rise up. </p>
<p>But why is there so much land close to sea level? The answer is erosion. Over geological time, major rivers wear away the landscape, carrying rock fragments to the sea. In this way, rivers will always reduce the continents to an elevation close to sea level. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-are-lost-continents-and-why-are-we-discovering-so-many-126355">What are lost continents, and why are we discovering so many?</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="Image of Antarctic landscape" src="https://images.theconversation.com/files/360174/original/file-20200927-24-15xcakm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/360174/original/file-20200927-24-15xcakm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/360174/original/file-20200927-24-15xcakm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/360174/original/file-20200927-24-15xcakm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/360174/original/file-20200927-24-15xcakm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/360174/original/file-20200927-24-15xcakm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/360174/original/file-20200927-24-15xcakm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Antarctica is too cold for rivers to erode the landscape.</span>
<span class="attribution"><span class="source">Shutterstock/Li Hui Chen</span></span>
</figcaption>
</figure>
<p>East Antarctica is the exception that proves the rule. It has been close to the South Pole for hundreds of millions of years, with a climate too cold for large rivers to significantly erode the landscape. </p>
<p>The crust has been “protected” from the forces of erosion and is on average about 5km thicker than all the other southern continents, but it has a similar plate thickness. </p>
<p>The weight of the vast <a href="https://www.nationalgeographic.org/photo/5icesheet-cutaway/?utm_source=BibblioRCM_Row">East Antarctic ice sheet</a> is pushing down the underlying bedrock. But if all the ice melted, the surface of East Antarctica would bounce back over the following 10,000 years or so to form the highest continent of all. </p>
<p>This, of course, is no cause for comfort in our present climate predicament, with much of the world’s population living in coastal areas.</p><img src="https://counter.theconversation.com/content/146576/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Simon Lamb receives funding from New Zealand Marsden Fund, New Zealand Earthquake Commission (EQC), Victoria University of Wellington.</span></em></p>New research uncovers the fundamental factors that control the Earth’s surface, providing insights into how land levels will respond to the melting of ice sheets and sea level rise.Simon Lamb, Associate Professor in Geophysics, Te Herenga Waka — Victoria University of WellingtonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1308602020-02-06T19:02:28Z2020-02-06T19:02:28ZExpedition reveals the violent birth of Earth’s hidden continent Zealandia, forged in a ring of fire<figure><img src="https://images.theconversation.com/files/313190/original/file-20200202-41485-19x7k9a.jpg?ixlib=rb-1.1.0&rect=4%2C59%2C1592%2C708&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">IODP</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Three years ago, the <a href="https://www.geosociety.org/gsatoday/archive/27/3/article/GSATG321A.1.htm">identification of Zealandia as a continent</a> made <a href="https://www.bbc.com/news/world-asia-39000936">global headlines</a>. </p>
<p>Now, newly <a href="https://doi.org/10.1130/G47008.1">published results</a> from our <a href="https://iodp.tamu.edu/scienceops/expeditions/tasman_frontier_subduction_climate.html">scientific drilling expedition</a> reveal the largely submerged Zealandia continent, which stretches across five million square kilometres beneath the southwest Pacific Ocean, was shaped by two tectonic events. </p>
<p>First it was ripped away from Australia and Antarctica, and then it was carved by forces that started the <a href="https://www.nationalgeographic.com/science/earth/ring-of-fire/">Pacific Ring of Fire</a>. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/bk4N6Q7Gc54?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The drilling expedition investigated Zealandia, a continent hidden below the sea.</span></figcaption>
</figure>
<h2>Why Zealandia is so different to other continents</h2>
<p>Zealandia has an unusual geography for a continent. More than half the surface area of Earth’s other six continents are composed of low-lying land and shallow seas, and they have relatively narrow mountain ranges and steep continental slopes in the deep ocean. </p>
<p>In contrast, Zealandia is mostly hidden beneath more than one kilometre of water and could be classified as more than 90% continental slope. This makes it a challenge to explore. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/313188/original/file-20200202-41490-frfdpm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/313188/original/file-20200202-41490-frfdpm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=305&fit=crop&dpr=1 600w, https://images.theconversation.com/files/313188/original/file-20200202-41490-frfdpm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=305&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/313188/original/file-20200202-41490-frfdpm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=305&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/313188/original/file-20200202-41490-frfdpm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=383&fit=crop&dpr=1 754w, https://images.theconversation.com/files/313188/original/file-20200202-41490-frfdpm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=383&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/313188/original/file-20200202-41490-frfdpm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=383&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The world’s continents and Zealandia, at the southern end of the Pacific Ring of Fire.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The first scientific drilling expedition to sample in the area where we now know Zealandia is took place in 1972 between Australia, New Zealand and New Caledonia. The <a href="http://deepseadrilling.org/21/dsdp_toc.htm">results</a> suggested tectonic forces stretched and thinned Zealandia’s crust until it was ripped from the ancient supercontinent Gondwana about 85 million years ago, during the time of dinosaurs. This created a deep ocean: the Tasman Sea. </p>
<p>The evidence remains compelling that this is at least part of the answer to how the geography of Zealandia formed. But detailed surveys during the 1990s and 2000s, carried out to establish sovereignty over the Zealandia continental mass by New Zealand, Australia and France, suggested other contributing factors.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-are-lost-continents-and-why-are-we-discovering-so-many-126355">What are lost continents, and why are we discovering so many?</a>
</strong>
</em>
</p>
<hr>
<h2>How the Pacific Ring of Fire shaped Zealandia</h2>
<p>In 2017, we led a nine-week expedition into the southwest Pacific as part of the International Ocean Discovery Program (<a href="http://www.iodp.org/">IODP</a>), with 32 scientists on board the research vessel <a href="https://joidesresolution.org/">JOIDES Resolution</a>. Our aim was to unravel why Zealandia is so different from the other continents.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/313192/original/file-20200202-41485-cwfyp9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/313192/original/file-20200202-41485-cwfyp9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/313192/original/file-20200202-41485-cwfyp9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/313192/original/file-20200202-41485-cwfyp9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/313192/original/file-20200202-41485-cwfyp9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/313192/original/file-20200202-41485-cwfyp9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/313192/original/file-20200202-41485-cwfyp9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sanny Saito (Japan), Rupert Sutherland (New Zealand), Thomas Westerhold (Germany), and Edo Dallanave (Italy) on the drill floor of the JOIDES Resolution.</span>
<span class="attribution"><span class="source">Michelle Drake</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Our <a href="https://doi.org/10.1130/G47008.1">newly published results</a> have been drawn from that expedition 371, where we collected new samples and sought to test our hypothesis that formation of the Pacific Ring of Fire played a key role in shaping Zealandia.</p>
<p>We collected sediment cores from up to 864 metres beneath the seabed at six sites far away from land or shallow water. At the deepest site, the water was five kilometres deep and our drill weighed 300 tonnes. We used fossils from three of the sites to show northern Zealandia became much shallower and likely even had land areas between 50 and 35 million years ago. At about that time, two other sites became submerged into deeper water, and then the whole region subsided an additional kilometre to its present depth. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/313191/original/file-20200202-41503-tblt6i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/313191/original/file-20200202-41503-tblt6i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=562&fit=crop&dpr=1 600w, https://images.theconversation.com/files/313191/original/file-20200202-41503-tblt6i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=562&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/313191/original/file-20200202-41503-tblt6i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=562&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/313191/original/file-20200202-41503-tblt6i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=706&fit=crop&dpr=1 754w, https://images.theconversation.com/files/313191/original/file-20200202-41503-tblt6i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=706&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/313191/original/file-20200202-41503-tblt6i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=706&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The expedition drilled for samples at six sites, marked on this map with stars.</span>
<span class="attribution"><span class="source">IODP</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>These dramatic changes in northern Zealandia, an area about the size of India, coincided with buckling of rock layers (known as strata) and the formation of underwater volcanoes throughout the western Pacific.</p>
<p>The Pacific Ring of Fire is a zone of volcanoes and earthquakes running along the west coasts of north and south America, past Alaska and Japan, and then through the western Pacific to New Zealand. The violent geological activity in this zone reflects deeper unrest at the boundaries of tectonic plates, caused by “subduction processes” – where one tectonic plate converges on another and sinks back deep into the earth. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/313219/original/file-20200203-41541-1hgzs9h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/313219/original/file-20200203-41541-1hgzs9h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=267&fit=crop&dpr=1 600w, https://images.theconversation.com/files/313219/original/file-20200203-41541-1hgzs9h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=267&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/313219/original/file-20200203-41541-1hgzs9h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=267&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/313219/original/file-20200203-41541-1hgzs9h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=336&fit=crop&dpr=1 754w, https://images.theconversation.com/files/313219/original/file-20200203-41541-1hgzs9h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=336&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/313219/original/file-20200203-41541-1hgzs9h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=336&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Scientists on the expedition identify fossils in sediment cores.</span>
<span class="attribution"><span class="source">IODP</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explorers-probe-hidden-continent-of-zealandia-83406">Explorers probe hidden continent of Zealandia</a>
</strong>
</em>
</p>
<hr>
<p>We know the Pacific Ring of Fire formed about 50 million years ago, but the process remains a mystery. We propose a “subduction rupture event” – a process similar to a massive slow-moving earthquake – spread around the whole of the western Pacific at that time. We suggest this process resurrected ancient subduction faults, which had lain dormant for many millions of years but were primed to start moving again. </p>
<p>This concept of “subduction resurrection” is a new idea and may help explain a range of different geological observations. The subduction rupture event included unique geological phenomena that that have no present-day comparison, and there may have been fewer than 100 such massive events since Earth formed. Our new evidence from Zealandia shows these events can dramatically alter the geography of continents. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/CpCN5W4rV1Q?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>What were the consequences of these geographic changes for plants, animals and regional climate? Can we make a computer model of the geological processes that happened at depth? We are still figuring some of this out, but we do know the event changed the direction and speed of movement of most tectonic plates on Earth. </p>
<p>It was an event of truly global significance – and we now have really good observations and ideas to help us get to the bottom of what happened and why.</p><img src="https://counter.theconversation.com/content/130860/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Our expedition drilled into the recently discovered underwater continent of Zealandia, revealing a new picture of the violent geological forces that created it.Rupert Sutherland, Professor of tectonics and geophysics, Te Herenga Waka — Victoria University of WellingtonGerald Dickens, Professor of Earth, Environmental and Planetary Sciences, Rice UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1234282020-01-06T12:06:32Z2020-01-06T12:06:32ZA new way to identify a rare type of earthquake in time to issue lifesaving tsunami warnings<figure><img src="https://images.theconversation.com/files/308024/original/file-20191219-11946-1t4d9ok.jpg?ixlib=rb-1.1.0&rect=350%2C0%2C5065%2C3700&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">This unusual earthquake type generates an outsized tsunami. </span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/1fEYDfuGli0">camila castillo/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Just a few times in a century, somewhere on the globe, a rare “tsunami earthquake” occurs. These are mysterious because, while they’re just medium-sized as earthquakes go, they cause disproportionately large and devastating tsunamis. This type of midsized earthquake is very different than an event like the <a href="http://www.tectonics.caltech.edu/outreach/highlights/sumatra/what.html">2004 earthquake in Sumatra</a> – a very big magnitude 9.2 event which unsurprisingly produced a huge tsunami.</p>
<p>The most recent tsunami earthquake happened in 2010. <a href="https://doi.org/10.1029/2010GL046552">A magnitude 7.8 earthquake</a> <a href="http://itic.ioc-unesco.org/index.php?option=com_content&view=article&id=1673:301&catid=1444&Itemid=1444">off the Mentawai Islands in Indonesia</a> <a href="https://doi.org/10.1029/2010GL046498">set off a tsunami</a> that was <a href="https://doi.org/10.1029/2012JB009159">over 50 feet in height</a> in some places – much greater than seismologists would predict based just on the earthquake’s size. <a href="https://earthobservatory.sg/outreach/natural-hazard-outreach/west-sumatra-tectonics-and-tsunami-hazard">509 people were killed</a>, and 15,000 more were displaced or left homeless. </p>
<p>Tsunami earthquakes are particularly destructive and dangerous because the massive tsunami waves can hit local coastal communities within just five to 15 minutes – before officials can issue a warning. But <a href="https://doi.org/10.1029/2019GL083989">based on our analysis</a> of previously unavailable closeup observations of the 2010 Mentawai event, my colleagues <a href="https://scholar.google.com/citations?user=8YD_3R8AAAAJ&hl=en&oi=ao">and I</a> think there is a way to determine that an event is a tsunami earthquake in time to warn people that an unexpectedly large wave is on the way.</p>
<h2>Earthquakes under the ocean</h2>
<p>The Earth’s surface is made up of <a href="https://theconversation.com/plate-tectonics-new-findings-fill-out-the-50-year-old-theory-that-explains-earths-landmasses-55424">floating tectonic plates</a> that fit together like a slightly imperfect jigsaw puzzle. These plates are moving next to, under or away from each other.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/308389/original/file-20200102-11904-tusj3g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/308389/original/file-20200102-11904-tusj3g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308389/original/file-20200102-11904-tusj3g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=372&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308389/original/file-20200102-11904-tusj3g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=372&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308389/original/file-20200102-11904-tusj3g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=372&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308389/original/file-20200102-11904-tusj3g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=467&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308389/original/file-20200102-11904-tusj3g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=467&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308389/original/file-20200102-11904-tusj3g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=467&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An earthquake along a subduction zone happens when the leading edge of the overriding plate breaks free and springs seaward, raising the seafloor and the water above it. This uplift starts a tsunami.</span>
<span class="attribution"><a class="source" href="https://www.usgs.gov/media/images/earthquake-starts-tsunami">USGS</a></span>
</figcaption>
</figure>
<p>In <a href="https://www.livescience.com/43220-subduction-zone-definition.html">a subduction zone</a>, one tectonic plate is sinking beneath another. This builds up stresses over time and will eventually create an earthquake. Most typical subduction-zone earthquakes occur roughly 10 to 30 miles down, in an area where the rocks are rigid and strong on the fault between the two tectonic plates.</p>
<p>Meanwhile, the shallowest area of a subduction zone, closest to the seafloor, is made up of soft sediments that are not very strong. Earthquakes rarely occur only here, because stresses mostly don’t build up in these soft, weak rocks.</p>
<p>Geoscientists define an earthquake’s overall size with its magnitude. Earthquake magnitude describes how much “work” is accomplished by the earthquake moving the fault – more work for either more movement, or for moving more rigid rock.</p>
<p>Very large earthquakes, like the magnitude 9 Tohoku earthquake in Japan in 2011, are so big that they break the deeper part of the subduction zone, but also continue upwards to break the shallow part of a subduction zone. This rapid earthquake motion moves the seafloor and <a href="https://www.iris.edu/hq/inclass/animation/subduction_zone_tsunamis_generated_by_megathrust_earthquakes">creates a tsunami</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/293875/original/file-20190924-51434-1ytyrz6.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/293875/original/file-20190924-51434-1ytyrz6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/293875/original/file-20190924-51434-1ytyrz6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=267&fit=crop&dpr=1 600w, https://images.theconversation.com/files/293875/original/file-20190924-51434-1ytyrz6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=267&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/293875/original/file-20190924-51434-1ytyrz6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=267&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/293875/original/file-20190924-51434-1ytyrz6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=336&fit=crop&dpr=1 754w, https://images.theconversation.com/files/293875/original/file-20190924-51434-1ytyrz6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=336&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/293875/original/file-20190924-51434-1ytyrz6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=336&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cartoon depicting the amount of movement in five earthquakes. The 2010 Mentawai tsunami earthquake moved the fault much more – over 65 feet compared to about 15 feet for the others – and the movement occurred much closer to the seafloor than in any of the other earthquakes.</span>
<span class="attribution"><span class="source">Sahakian et al. (2019), GRL</span></span>
</figcaption>
</figure>
<h2>What sets tsunami quakes apart</h2>
<p>“Tsunami earthquakes” are strange in that they happen almost entirely in the soft, weak section of the fault.</p>
<p>Because tsunami earthquakes break such soft rock, they happen slower, and create much more movement on or near the seafloor in comparison to a normal subduction-zone earthquake of the same size that happens in rigid rock. This in turn creates a much larger tsunami than expected. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/306913/original/file-20191214-85412-1b87exs.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/306913/original/file-20191214-85412-1b87exs.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/306913/original/file-20191214-85412-1b87exs.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=314&fit=crop&dpr=1 600w, https://images.theconversation.com/files/306913/original/file-20191214-85412-1b87exs.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=314&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/306913/original/file-20191214-85412-1b87exs.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=314&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/306913/original/file-20191214-85412-1b87exs.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=395&fit=crop&dpr=1 754w, https://images.theconversation.com/files/306913/original/file-20191214-85412-1b87exs.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=395&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/306913/original/file-20191214-85412-1b87exs.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=395&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Seismograms showing how much the ground shook from six similarly sized earthquakes, at seismometers all about the same distance from their earthquake. You’d expect the shaking to be comparable. The 2010 Mentawai earthquake seismogram is at the bottom in orange, and shows significantly less shaking than any of the others.</span>
<span class="attribution"><span class="source">Modified from Sahakian et al. (2019), GRL.</span></span>
</figcaption>
</figure>
<p>A tsunami earthquake might have the same magnitude as an earthquake that occurs in rigid rock but produces much less of what seismologists call high-frequency energy. </p>
<p>Think of breaking a thick slab of concrete – which is strong and would produce an audible bang with both low and high-pitched noise – versus breaking a loaf of bread, which makes almost no sound at all. In the Earth, “sound” is the shaking you feel under your feet. The soft bread break is like a tsunami earthquake that doesn’t release a lot of high-frequency energy, and thus doesn’t create as much shaking as we would expect for its magnitude.</p>
<h2>Sensing quakes in time to warn</h2>
<p>Currently, officials rely on knowing an earthquake’s magnitude and location to issue tsunami warnings within tens of minutes. But this doesn’t work in the case of tsunami earthquakes, because the earthquake’s magnitude doesn’t match up with the size of the tsunami it produces.</p>
<p>Instead, to figure out whether an earthquake is in fact a tsunami earthquake, scientists compare its seismic magnitude measured from afar with the amount of high frequency radiated energy it produced, as recorded by far away stations.</p>
<p>If the ratio of energy to magnitude is very low, it’s a tsunami earthquake – basically, its shaking was far too weak for its magnitude because it was breaking soft rock. Instead, its energy is of the low-frequency type: Rather than strong shaking, its energy goes into large slow movement of the seafloor and the ensuing tsunami.</p>
<p>The problem is that in the past, scientists had never recorded one of these elusive earthquakes closeup in what we call the near-field – within about 180 miles (300 kilometers) or so. Instead, scientists have had to find an earthquake’s energy-to-magnitude ratio using seismic waves that have traveled all the way from the epicenter of the earthquake across the world to where researchers can measure them. This process is relatively slow, so we haven’t been able to identify tsunami earthquakes quickly enough to warn people in time, before the wave hits the coast.</p>
<p>Now my colleagues and I have for the first time analyzed data recorded by seismic stations that happened to be near the epicenter of the 2010 Mentawai earthquake. We think we have figured out a new way to identify the danger of a future tsunami earthquake, faster.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/308439/original/file-20200103-11951-8wlrvt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/308439/original/file-20200103-11951-8wlrvt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/308439/original/file-20200103-11951-8wlrvt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308439/original/file-20200103-11951-8wlrvt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308439/original/file-20200103-11951-8wlrvt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308439/original/file-20200103-11951-8wlrvt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308439/original/file-20200103-11951-8wlrvt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308439/original/file-20200103-11951-8wlrvt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Tsunamis can take a terrible toll, as for this Indonesian family that lost their father and their home in the Mentawai disaster.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Indonesia-Disasters/77a6343c59ee46199456933fc238e848/4/0">AP Photo/Tundra Laksamana</a></span>
</figcaption>
</figure>
<h2>Closer and quicker proxies</h2>
<p>Our new study used the same concept of comparing the energy released by an earthquake to its seismic magnitude – but based on data from geographically close to the event. Instead of looking at energy measurements recorded at a distance, we used two proxies.</p>
<p>To look directly at how much the ground shook, we used seismic stations onshore near the epicenters of 16 earthquakes, including the Mentawai one in 2010. Because the amount the ground accelerates when seismic waves pass through illustrates how much high frequency energy is in the earthquake, this information was a stand-in for the data we would traditionally get from the far-flung teleseismic stations. Low accelerations mean little high frequency energy.</p>
<p>For the normal earthquakes we looked at, the accelerations from near-field seismometers were close to what we’d expect for each earthquake’s magnitude. In comparison, the 2010 Mentawai earthquake’s accelerations were closer to what we would expect for a magnitude 6.3 earthquake – whereas the earthquake was actually a magnitude 7.8, and produced a tsunami we’d expect for an event of greater than magnitude 8.</p>
<p>We also looked at GPS stations close to the earthquakes. They can show us how much the ground actually moved or was displaced, and measure the earthquake magnitude itself.</p>
<p>Using these measurements together allowed us to compare the amount of energy in the earthquake with respect to its magnitude – without waiting for the seismic waves to travel across the globe. Instead, we would have been able to identify a tsunami earthquake immediately by looking at how low the accelerations were on local seismometers in comparison to the magnitude of the earthquake based on GPS readings.</p>
<p>We think our finding is really promising because these near-field measurements are available immediately – even while an earthquake is happening. Seismologists could use this approach in the future, to identify a tsunami earthquake right after it happens, and provide warning to the nearby coast before the tsunami wave arrives.</p>
<p>[ <em>Deep knowledge, daily.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=deepknowledge">Sign up for The Conversation’s newsletter</a>. ]</p><img src="https://counter.theconversation.com/content/123428/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Valerie Sahakian does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A tricky kind of earthquake that happens in the soft rock of the ocean floor causes much larger tsunamis than their magnitude would predict. New research pinpoints a way to identify the danger fast.Valerie Sahakian, Assistant Professor of Geophysics, University of OregonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1279462019-12-02T14:31:09Z2019-12-02T14:31:09ZCan one earthquake cause a cascade of more?<p>Europe isn’t a region well known for intense seismic activity, but large earthquakes do happen. In 1953, a devastating 6.8 magnitude quake struck the Greek Ionian Islands. Though these large events tend to be the exception rather than the rule, a flurry of significant earthquakes struck the Balkans on November 27 2019, with epicentres in Bosnia, Albania and Crete. Geologists are worried that these events might gain momentum, with larger and more destructive events imminent.</p>
<p>Should residents be worried? The Balkans – a region stretching from Croatia to mainland Greece, and the Greek islands to the south – has a very <a href="https://www.researchgate.net/profile/Alexandre_Kounov/publication/272621620_Tectonic_map_of_the_Balkan_Peninsula/data/59615d7c458515a3572441f9/Balkan-map-2017.pdf">complex geology</a>. The whole region is tectonically active due to compression of the Earth’s crust further north and subduction – when one tectonic plate moves under another – to the south. Each process plagues this part of the world with frequent, though usually small, tremors.</p>
<p>Aftershocks are common after large earthquakes, as the region’s geology readjusts to the new tectonic arrangement. This means the recent quakes in south-eastern Europe aren’t unusual, but they may not have released all the pent up seismic energy in the region. Numerous laws of geology say that these shocks gradually subside in magnitude and frequency as time unwinds after the main earthquake. Although poorly understood and believed to be quite rare, earthquakes, instead of petering out into smaller and smaller tremors, can sometimes cause a cascade of further violent quakes. </p>
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Read more:
<a href="https://theconversation.com/nepal-earthquake-such-huge-aftershocks-are-rare-41833">Nepal earthquake: such huge aftershocks are rare</a>
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<p>Perhaps the most extreme episode of cascading earthquakes in recent history happened in New Zealand in 2010. In September that year, New Zealand’s second city, Christchurch, suffered a 7.1 magnitude earthquake, which occurred to the west and shook the city violently. But afterwards, residents and scientists alike felt relieved that they had a lucky escape. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/304685/original/file-20191202-67017-fx6i24.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/304685/original/file-20191202-67017-fx6i24.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/304685/original/file-20191202-67017-fx6i24.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/304685/original/file-20191202-67017-fx6i24.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/304685/original/file-20191202-67017-fx6i24.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/304685/original/file-20191202-67017-fx6i24.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/304685/original/file-20191202-67017-fx6i24.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Medway footbridge in Christchurch was twisted out of shape by the earthquake.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/2010_Canterbury_earthquake#/media/File:Medway_Bridge_76.jpg">Schwede66/Wikipedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Tragically, this was a prelude to a destructive earthquake in February 2011 which struck right beneath the city itself, killing 185 people and causing widespread devastation. The downtown area was largely condemned, along with vast swathes of the city’s suburbs. Following the first event in September 2010, more than 10,000 aftershocks followed. </p>
<p>So while geologists often expect aftershocks to be smaller and less destructive than the first, this isn’t always the case. Aftershocks may bring down buildings that were weakened by the first quake, or hinder rescue attempts of those trapped in buildings by the first one. Anyone responsible for managing the hazards that come with earthquakes must be aware that cascades of further destruction can follow.</p>
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<img alt="" src="https://images.theconversation.com/files/304695/original/file-20191202-67028-1mbvbho.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/304695/original/file-20191202-67028-1mbvbho.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/304695/original/file-20191202-67028-1mbvbho.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/304695/original/file-20191202-67028-1mbvbho.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/304695/original/file-20191202-67028-1mbvbho.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/304695/original/file-20191202-67028-1mbvbho.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/304695/original/file-20191202-67028-1mbvbho.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The Corinth Canal in Greece connects the Gulf of Corinth with the Saronic Gulf in the Aegean Sea.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/passing-through-corinth-canal-by-yacht-1506495587?src=49b2a77a-3838-4680-89c2-112fe08a8d7e-1-12">Victoria Kurylo/Shutterstock</a></span>
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<p>Geologists are particularly worried about the Gulf of Corinth in Greece, an inlet of the Mediterranean that effectively splits the Greek mainland in two. Here, a process called <a href="https://esoexp381corinthactiveriftdevelopment.wordpress.com/2017/11/20/why-are-we-here-plate-tectonics-and-the-gulf-of-corinth/">continental rifting</a> is forcing the Greek mainland apart at an average rate of <a href="https://www.sciencedaily.com/releases/2009/12/091222105215.htm">15mm per year</a>. This rifting process isn’t smooth – stresses can build up and once they reach a certain threshold, rocks can fracture and an earthquake can follow. </p>
<p>Within the Balkans, there have been <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014JB011765">17 earthquakes</a> with magnitudes greater than 6.0 since the 18th century, each with many aftershocks recorded in the days following. Models have suggested that these cycles of earthquakes and shocks are <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014JB011765">set to continue</a>. So it’s not uncommon for one earthquake to cause another, and another, and another. Armed with this knowledge, people should be wary that when an earthquake strikes, it may not be an isolated event.</p><img src="https://counter.theconversation.com/content/127946/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew Blackett does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Post-earthquake aftershocks are often assumed to be less violent, but that’s not always the case.Matthew Blackett, Senior Lecturer in Physical Geography and Natural Hazards, Coventry UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1263552019-11-24T19:05:19Z2019-11-24T19:05:19ZWhat are lost continents, and why are we discovering so many?<figure><img src="https://images.theconversation.com/files/303106/original/file-20191122-74588-1h7i1ci.jpg?ixlib=rb-1.1.0&rect=41%2C137%2C3944%2C2850&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lord Howe Island is one of the few places where the lost continent of Zealandia is exposed above sea level. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/1383726818?src=8cdca944-3b36-41dd-a084-4fbdd2c81e59-1-0&size=huge_jpg">SHUTTERSTOCK</a></span></figcaption></figure><p>For most people, continents are Earth’s seven main large landmasses. </p>
<p>But geoscientists have a different take on this. They look at the type of rock a feature is made of, rather than how much of its surface is above sea level. </p>
<p>In the past few years, we’ve seen an increase in the discovery of lost continents. Most of these have been plateaus or mountains made of <a href="https://en.wikipedia.org/wiki/Continental_crust">continental crust</a> hidden from our view, below sea level. </p>
<p>One example is <a href="https://www.bbc.com/news/world-asia-39000936">Zealandia</a>, the world’s eighth continent that extends underwater from New Zealand. </p>
<p>Several smaller lost continents, called microcontinents, have also recently been discovered submerged in the <a href="http://www.cmar.csiro.au/datacentre/process/data_files/cruise_docs/ss2011_v06_summary.pdf">eastern</a> and <a href="https://www.nationalgeographic.com/news/2013/2/130225-microcontinent-earth-mauritius-geology-science/">western Indian Ocean</a>. </p>
<p>But why, with so much geographical knowledge at our fingertips, are we still discovering lost continents in the 21st century?</p>
<h2>We may have found another</h2>
<p>In August, we undertook a <a href="https://research.csiro.au/educator-on-board/category/in2019_t04/">28-day voyage</a> on the research vessel RV Investigator to explore a possible lost continent in a remote part of the Coral Sea. The area is home to a large underwater plateau off Queensland, called the <a href="https://en.wikipedia.org/wiki/Louisiade_Plateau">Louisiade Plateau</a>, which represents a major gap in our knowledge of Australia’s geology. </p>
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<strong>
Read more:
<a href="https://theconversation.com/explainer-the-rv-investigators-role-in-marine-science-35239">Explainer: the RV Investigator’s role in marine science</a>
</strong>
</em>
</p>
<hr>
<p>On one hand, it could be a lost continent that broke away from Queensland about 60 million years ago. Or it could have formed as a result of a massive volcanic eruption taking place around the same time. We’re not sure, because nobody had recovered rocks from there before - until now. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/300798/original/file-20191107-10940-1ejlfph.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/300798/original/file-20191107-10940-1ejlfph.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/300798/original/file-20191107-10940-1ejlfph.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/300798/original/file-20191107-10940-1ejlfph.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/300798/original/file-20191107-10940-1ejlfph.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/300798/original/file-20191107-10940-1ejlfph.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/300798/original/file-20191107-10940-1ejlfph.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/300798/original/file-20191107-10940-1ejlfph.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An extremely violent eruption formed this volcanic rock we recovered.</span>
<span class="attribution"><span class="source">Author supplied</span></span>
</figcaption>
</figure>
<p>We spent about two weeks collecting rocks from this feature, and recovered a wide variety of rock types from parts of the seafloor as deep as 4,500m. </p>
<p>Most were formed through volcanic eruptions, but some show hints that continental rocks are hiding beneath. Lab work over the next couple of years will give us more certain answers.</p>
<h2>Down to the details</h2>
<p>There are many mountains and plateaus below sea level scattered across the oceans, and these have been mapped from space. They are the lighter blue areas you can see on Google Maps. </p>
<iframe src="https://www.google.com/maps/d/u/0/embed?mid=1-BXL84yHMfY85995MPKhFQf44Ze0z8rb" width="100%" height="480"></iframe>
<hr>
<p>However, not all submerged features qualify as lost continents. Most are made of materials quite distinct from what we traditionally think of as continental rock, and are instead formed by massive outpourings of magma. </p>
<p>A good example is <a href="https://www.youtube.com/watch?v=hLGp6lRaSs0&t=">Iceland</a> which, despite being roughly the size of New Zealand’s North Island, is not considered continental in geological terms. It’s made up mainly of volcanic rocks deposited over the past 18 million years, meaning it’s relatively young in geological terms.</p>
<p>The only foolproof way to tell the difference between massive submarine volcanoes and lost continents is to collect rock samples from the deep ocean.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/300796/original/file-20191107-10905-1of0bqe.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/300796/original/file-20191107-10905-1of0bqe.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/300796/original/file-20191107-10905-1of0bqe.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/300796/original/file-20191107-10905-1of0bqe.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/300796/original/file-20191107-10905-1of0bqe.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/300796/original/file-20191107-10905-1of0bqe.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/300796/original/file-20191107-10905-1of0bqe.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/300796/original/file-20191107-10905-1of0bqe.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Plenty of soft, gloopy sediment covers the bottom of the Coral Sea.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Finding the right samples is challenging, to say the least. Much of the seafloor is covered in soft, gloopy sediment that obscures the solid rock beneath. </p>
<p>We use a sophisticated mapping system to search for steep slopes on the seafloor, that are more likely to be free of sediment. We then send a metal rock-collecting bucket to grab samples.</p>
<p>The more we explore and sample the depths of the oceans, the more likely we’ll be to discover more lost continents.</p>
<h2>The ultimate lost continent</h2>
<p>Perhaps the best known example of a lost continent is <a href="https://www.bbc.com/news/world-asia-39000936">Zealandia</a>. While the geology of New Zealand and New Caledonia have been known for some time, it’s only recently their common heritage as part of a much larger continent (which is 95% underwater) has been accepted. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explorers-probe-hidden-continent-of-zealandia-83406">Explorers probe hidden continent of Zealandia</a>
</strong>
</em>
</p>
<hr>
<p>This acceptance has been the culmination of years of painstaking research, and exploration of the geology of deep oceans through sample collection and geophysical surveys.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/300800/original/file-20191107-10973-1ve9lhc.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/300800/original/file-20191107-10973-1ve9lhc.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/300800/original/file-20191107-10973-1ve9lhc.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/300800/original/file-20191107-10973-1ve9lhc.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/300800/original/file-20191107-10973-1ve9lhc.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/300800/original/file-20191107-10973-1ve9lhc.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/300800/original/file-20191107-10973-1ve9lhc.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/300800/original/file-20191107-10973-1ve9lhc.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Continental rocks recovered from a microcontinent in the Indian Ocean are similar to rocks found in Western Australia.</span>
<span class="attribution"><span class="source">Author supplied</span></span>
</figcaption>
</figure>
<p>New discoveries continue to be made. </p>
<p>During a 2011 expedition, we discovered <a href="https://www.nationalgeographic.com/news/2011/11/111121-dinosaurs-gondwana-ancient-rocks-science/">two lost continental fragments</a> more than 1,000km west of Perth. </p>
<p>The granite lying in the middle of the deep ocean there looked similar to what you would find around Cape Leeuwin, in Western Australia. </p>
<h2>Other lost continents</h2>
<p>However, not all lost continents are found hidden beneath the oceans. </p>
<p>Some existed only in the geological past, millions to billions of years ago, and later collided with other continents as a result of plate tectonic motions. </p>
<p>Their only modern-day remnants are small slivers of rock, usually squished up in mountain chains such as the Himalayas. One example is <a href="https://www.nationalgeographic.com.au/science/lost-continent-revealed-in-new-reconstruction-of-geologic-history.aspx">Greater Adria</a>, an ancient continent now embedded in the mountain ranges across Europe.</p>
<p>Due to the perpetual motion of tectonic plates, it’s the fate of all continents to ultimately reconnect with another, and form a supercontinent. </p>
<p>But the fascinating life and death cycle of continents is the topic of another story.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-earths-continents-became-twisted-and-contorted-over-millions-of-years-116168">How Earth's continents became twisted and contorted over millions of years</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/126355/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Maria Seton receives funding from the Australian Research Council and has received ship time funding through Australia's Marine National Facility.</span></em></p><p class="fine-print"><em><span>Joanne Whittaker receives funding from the Australian Research Council, the Australian Antarctic Division, and ship time through Australia's Marine National Facility. </span></em></p><p class="fine-print"><em><span>Simon Williams is affiliated with the University of Sydney and Northwest University, Xi'an. He receives funding from the Australian Research Council and the Natural Science Foundation of China, and ship time through Australia's Marine National Facility. </span></em></p>We undertook a 28-day voyage to explore a possible lost continent in a remote part of the Coral Sea, in an area off the coast of Queensland. Here’s what we found.Maria Seton, ARC Future Fellow, University of SydneyJoanne Whittaker, Associate Professor, University of TasmaniaSimon Williams, Research Fellow, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1251592019-10-30T16:09:39Z2019-10-30T16:09:39ZHow volcanoes recycle the Earth’s crust to uncover rare metals that are vital to green technology<figure><img src="https://images.theconversation.com/files/299465/original/file-20191030-17914-hioyra.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Motzfeldt deposit in southern Greenland.</span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>To understand the resources of the near future, geologists need to understand the volcanoes of the distant past. Exploration of ancient magma chambers in places such as Greenland has the potential to provide new sources of the rare metals that underpin modern green technologies.</p>
<p>Many rare metals – such as <a href="https://www.rsc.org/periodic-table/element/60/neodymium">neodymium</a>, <a href="https://www.rsc.org/periodic-table/element/41/niobium">niobium</a> and <a href="https://www.rsc.org/periodic-table/element/66/dysprosium">dysprosium</a> – essential to the production of wind turbines and electric cars, are mined from fossil volcanoes.</p>
<p>Volcanoes are nature’s way of bringing material from deep within the earth up to the surface. Melting processes within the <a href="https://www.nationalgeographic.org/encyclopedia/mantle/">mantle</a> – the interior part of the Earth between the super-heated core and the thin outer crust – produce magma which rises up hundreds of kilometres and eventually erupts on to the surface as volcanoes.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/16zt7x1Z9Fs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>The earth’s crust is made up of semi-rigid <a href="https://theconversation.com/how-earths-continents-became-twisted-and-contorted-over-millions-of-years-116168">tectonic plates</a> which move around and collide to form mountains or sink underneath one another at regions called <a href="https://www.universetoday.com/43822/subduction-zone/">subduction zones</a>. The volume of material brought to the Earth’s surface by volcanoes is balanced by similar amounts of material going back into the mantle via sinking tectonic plates. </p>
<p>This points to what we call “element cycles”, where material from depth comes up to the surface via volcanoes and then returns again to the mantle via subduction. One of the big questions in Earth Sciences is what happens to this subducted material and how long it resides in the mantle.</p>
<h2>Fossil volcanoes</h2>
<p>Our recent <a href="https://www.nature.com/articles/s41467-019-12218-1">research</a> studied a group of ancient volcanoes in southern Greenland. Around 1.3 billion years ago, Greenland was a volcanic landscape with deep rift valleys much like modern East Africa. <a href="https://www.sciencedirect.com/science/article/pii/S0012821X1830089X">Substantial volcanoes erupted</a> on to the land surface and major river systems similar to the Nile carried minerals from these volcanoes over huge areas.</p>
<p>The rivers and volcanoes in Greenland are now long eroded, but the <a href="https://www.cambridge.org/core/journals/geological-magazine/article/age-hf-isotope-and-trace-element-signatures-of-detrital-zircons-in-the-mesoproterozoic-eriksfjord-sandstone-southern-greenland-are-detrital-zircons-reliable-guides-to-sedimentary-provenance-and-timing-of-deposition/D0C436D308724096242DDF2E7F89B0C9">sediments</a> that the river transported can still be found, and the volcanic “plumbing systems” that operated beneath these ancient volcanoes have preserved samples of the magmas that erupted.</p>
<p>We wanted to understand how element cycling relates to the concentration of critical metals in these ancient volcanoes in Greenland. While it is useful to study the valuable elements themselves, sometimes we can learn more about Earth’s element cycles by studying other elements associated with them. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/299479/original/file-20191030-17868-v4vrl3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/299479/original/file-20191030-17868-v4vrl3.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=214&fit=crop&dpr=1 600w, https://images.theconversation.com/files/299479/original/file-20191030-17868-v4vrl3.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=214&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/299479/original/file-20191030-17868-v4vrl3.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=214&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/299479/original/file-20191030-17868-v4vrl3.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=269&fit=crop&dpr=1 754w, https://images.theconversation.com/files/299479/original/file-20191030-17868-v4vrl3.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=269&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/299479/original/file-20191030-17868-v4vrl3.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=269&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Fentale volcano in the Ethiopian rift has erupted large volumes of chemically evolved magma similar to Greenland.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Fingerprinting sulphur</h2>
<p>In our study we used the element sulphur of which there are four stable forms (called <a href="https://www.sciencealert.com/explainer-what-is-an-isotope">isotopes</a>). Each has a slightly different mass. This is important because natural processes can selectively separate lighter isotopes from heavier isotopes. Much like snacking on a bag of M&M’s where you prefer the red ones and leave behind the brown M&Ms, geological processes lead to variations in the relative abundances of each element in different materials.</p>
<p>By measuring the amount of isotope in rocks, we can learn about the processes that formed them. Sulphur isotopes are particularly useful because bio- and geochemical processes on the Earth’s surface (at low temperatures) are very efficient at <a href="https://www.nature.com/articles/ngeo1585">modifying</a> sulphur signatures, whereas magmatic processes (at high temperatures) do not create much variation between light and heavy sulphur. </p>
<p>So the variations in sulphur signatures in magmatic rocks allow us to fingerprint traces of recycled crustal material in the mantle source. By choosing volcanoes that were active at different periods of geological time, we reconstruct how the mantle composition and sulphur cycling have varied over Earth’s history.</p>
<p>Geologists have known for a long time that Earth’s surface has changed profoundly over the past 4.5 billion years as life emerged and became progressively more complex. The <a href="https://www.nature.com/articles/ngeo1585">increasing imprint of life on the sulphur cycle</a> has dramatically changed the sulphur isotope ratio of sediments at the surface of the Earth, but this imprint has not previously been documented in rocks from the mantle.</p>
<p>Our work shows for the first time that the sulphur signature of the Earth’s mantle changed in a manner that broadly matches the changes in sulphur on the Earth’s surface. Biological and atmospheric impacts on the surface sulphur signature appear to have been transferred all the way into the Earth’s interior.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/299528/original/file-20191030-17878-6lu3mj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/299528/original/file-20191030-17878-6lu3mj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=380&fit=crop&dpr=1 600w, https://images.theconversation.com/files/299528/original/file-20191030-17878-6lu3mj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=380&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/299528/original/file-20191030-17878-6lu3mj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=380&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/299528/original/file-20191030-17878-6lu3mj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=477&fit=crop&dpr=1 754w, https://images.theconversation.com/files/299528/original/file-20191030-17878-6lu3mj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=477&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/299528/original/file-20191030-17878-6lu3mj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=477&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>This means that the Earth’s surface and mantle are strongly connected – one responding to changes in the other – although timescales of this recycling remain unknown. Our data show that sulphur that was once on the Earth’s surface went back into the mantle through tectonic plate activity and then – 1.3 billion years ago – found itself coming back to the surface in the Greenland volcanoes. It’s like geological <em>déjà-vu</em>.</p>
<h2>One cycle or many?</h2>
<p>How many times has sulphur been recycled between the Earth’s crust and mantle over geological time? We do not currently know the answer to this but our research paints a picture of the Earth as a global element conveyor belt with surface sulphur and mantle closely linked. </p>
<p>The study has many implications. A major question in geology is how rare metal deposits form, particularly the <a href="https://www.worldbank.org/en/topic/extractiveindustries/brief/climate-smart-mining-minerals-for-climate-action">high-tech metals</a> that are essential for the green energy revolution. The story from sulphur seems to be consistent with our work on other isotopes. For example, one of the world’s biggest deposits of the element <a href="https://www.rsc.org/periodic-table/element/73/tantalum">tantalum</a> (used in electronics and also concentrated in one of the ancient volcanoes in Greenland) has isotopic fingerprints that also <a href="https://www.sciencedirect.com/science/article/pii/S0169136819300988">hint at crustal recycling</a>.</p>
<p>It may be that these global cycles have taken elements from surface to mantle and back again many times, effectively concentrating those elements each time. The global cycle that we have documented in sulphur may be an essential precursor to generate the metal deposits that are crucial to modern technologies. By understanding plate tectonics and magmatic processes that took place billions of years ago, we gain insights into how to identify and understand the mineral resources of the future.</p><img src="https://counter.theconversation.com/content/125159/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Adrian Finch receives funding from NERC consortium grant NE/M010856/1 for SoS RARE and the EU Horizon 2020 fund for HiTech AlkCarb grant agreement no. 689909.
In addition to the formal authors in the article, Adrian Finch's research group also includes Nicola Horsburgh and Krzysztof Sokół who also contributed to the backdrop of understanding metal resources on which the article draws. His colleague Eva Stüeken assisted with the sulphur modelling used in the Hutchison et al. (2019) article. </span></em></p><p class="fine-print"><em><span>Anouk Borst receives funding from NERC consortium grant NE/M010856/1 for SoS RARE and Global Challenges Research Funding from the Scottish Funding Council.</span></em></p><p class="fine-print"><em><span>William Hutchison receives funding from the European Union’s Horizon 2020 research and innovation programme and a UKRI Future Leaders Fellowship.</span></em></p>Exploration of ancient magma chambers in fossil volcanoes has the potential to provide new sources of metals that will facilitate environmentally friendly technologies.Adrian Finch, Professor of Geology, School of Earth & Environmental Sciences, University of St AndrewsDr Anouk M Borst, Research Fellow Geology, University of St AndrewsWilliam Hutchison, Research Fellow, University of St AndrewsLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1164292019-06-11T00:20:48Z2019-06-11T00:20:48ZCurious Kids: where do rocks come from?<figure><img src="https://images.theconversation.com/files/276702/original/file-20190528-92790-1ehkdqf.jpg?ixlib=rb-1.1.0&rect=0%2C8%2C5463%2C2506&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Rocks contain a layer-by-layer record of the history of our planet.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/86755183@N04/16485047966/">Fred Moore/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series for children. If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.edu.au You might also like the podcast <a href="http://www.abc.net.au/kidslisten/imagine-this/">Imagine This</a>, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.</em> </p>
<hr>
<blockquote>
<p><strong>Where do rocks come from? - Claire, age 5, Perth, WA.</strong></p>
</blockquote>
<p>Wow, Claire, what a great question. Sitting in a university, I rarely get asked such brilliant questions. So, thank you. </p>
<p>As strange as it sounds, rocks are made from stardust; dust blasted out and made from exploding stars. </p>
<p>In fact, our corner of space has many rocks floating around in it. From really fine dust, to pebbles, boulders and house-sized rocks that can burn up in the night sky to make meteors or “shooting stars”. </p>
<p>The Moon and our local planets – Mars, Venus and Mercury – are just the largest rocks floating around our part of space. These are all made from space dust stuck together over billions of years.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-was-the-earth-made-112067">Curious Kids: how was the Earth made?</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/277790/original/file-20190604-69079-tznyh9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/277790/original/file-20190604-69079-tznyh9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/277790/original/file-20190604-69079-tznyh9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/277790/original/file-20190604-69079-tznyh9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/277790/original/file-20190604-69079-tznyh9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/277790/original/file-20190604-69079-tznyh9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/277790/original/file-20190604-69079-tznyh9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An artist’s impression of early Earth, which was then a molten ball of lava flying through space.</span>
<span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA15808">NASA/JPL-Caltech</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>The ‘light’ rocks are on the Earth’s surface</h2>
<p>Planet Earth is a rock too, but so much has happened since it was formed from dust and small rocks that smashed and stuck together 4.543 billion years ago.</p>
<p>As the space dust hit each other to make the earth, it got super hot and melted. The Earth was, at that time, a spinning ball of red-hot lava flying through space. </p>
<p>In this melted lava planet, heavy bits of the earth sank and the light frothy bits gathered on the surface. </p>
<p>Have you ever looked closely at a glass of milky coffee at a cafe? The dark heavy coffee is at the bottom, whereas the light, frothy milk sits on the top. Well, our planet was a bit like that coffee billions of years ago. </p>
<iframe src="https://giphy.com/embed/fEZ982FPO0jIc" width="100%" height="480" frameborder="0" class="giphy-embed" allowfullscreen=""></iframe>
<p><a href="https://giphy.com/gifs/eastbay-fEZ982FPO0jIc"></a></p>
<p>We don’t see the really heavy rocks these days because they sank deep in the planet very early on. The rocks we see on the surface are like the frothy milk! They were light and rose to the top. Then, as time moved on, the planet cooled and froze to become the solid earth we have now. </p>
<p>I know most rocks are heavy. But in fact some rocks – even really big ones like Uluru – are actually much lighter than the rocks found in the deep Earth.</p>
<h2>Lava and plates</h2>
<p>Those rocks on the Earth’s surface actually <a href="https://theconversation.com/a-map-that-fills-a-500-million-year-gap-in-earths-history-79838">move around</a>. Large chunks the size of continents (called “plates”) jostle each other and this can cause earthquakes. Some of them get forced under other plates and heat up and eventually melt. This forms more lava. The lava erupts from volcanoes, then cools and forms new rocks. </p>
<p>Here are some pictures of lava in the melted state and then after it has cooled down:</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/276748/original/file-20190528-42560-rvs752.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/276748/original/file-20190528-42560-rvs752.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/276748/original/file-20190528-42560-rvs752.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/276748/original/file-20190528-42560-rvs752.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/276748/original/file-20190528-42560-rvs752.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/276748/original/file-20190528-42560-rvs752.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/276748/original/file-20190528-42560-rvs752.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Volcanic lava in Etra Ale Volcano in Ethiopia in 2016. Lava emerges from volcanoes and then cools on the Earth’s surface to form rocks.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/myneur/6900576021/">Petr Meissner/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-do-mountains-form-108246">Curious Kids: how do mountains form?</a>
</strong>
</em>
</p>
<hr>
<h2>Mountains and gems are also rocks</h2>
<p>Mountains form where two plates smash into each other. The rocks that get caught between two of the Earth’s plates get squashed under huge pressures and heat up. These can form really beautiful rocks. Sometimes gems form in these rocks and people try to find them to make jewellery.</p>
<p>Rain and ice break up the rocks in mountains. These form sand and mud that get washed out to form beaches, rivers and swamps. This sand and mud can get buried, squashed and heated, which eventually turns them into rocks.</p>
<p>Rocks contain a record of the history of our planet; what is has been through and what is capable of. We are only just learning how to read it. </p>
<p>So, next time you see a rock, just think what an incredible story it contains.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/273473/original/file-20190509-183086-sm9qf0.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/273473/original/file-20190509-183086-sm9qf0.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/273473/original/file-20190509-183086-sm9qf0.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/273473/original/file-20190509-183086-sm9qf0.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/273473/original/file-20190509-183086-sm9qf0.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/273473/original/file-20190509-183086-sm9qf0.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/273473/original/file-20190509-183086-sm9qf0.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Spectacular layered sedimentary rocks from Tigray, Ethiopia, where each layer represents an ancient sea bed. Rocks of these types contain the history of the surface of the planet.</span>
<span class="attribution"><span class="source">Author provided</span></span>
</figcaption>
</figure>
<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au</em></p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><em>Please tell us your name, age and which city you live in. We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/116429/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alan Collins receives funding from a number of industry and government sources including the Australian Research Council</span></em></p>As strange as it sounds, rocks are made from stardust.Alan Collins, Professor of Geology, University of AdelaideLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1173932019-05-20T10:06:23Z2019-05-20T10:06:23ZWe made a moving tectonic map of the Game of Thrones landscape<figure><img src="https://images.theconversation.com/files/275348/original/file-20190520-69209-xd23xn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Scientists have pieced together Game of Thrones' geology as the show draws last breath on television.</span> <span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/8/87/Game_of_Thrones_-_SEASON_7_Episode_4.jpg">Kal242382 from Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Scientists are among the millions of die-hard Game of Thrones fans digesting the show’s <a href="https://www.abc.net.au/news/2019-05-20/game-of-thrones-seaon-8-finale-viewers-nervous-about-end/11123026">finale today</a>. </p>
<p>The striking landscape of Game of Thrones has led some researchers to build <a href="https://arstechnica.com/science/2017/12/there-is-now-a-climate-model-of-the-world-of-game-of-thrones/">climate simulations</a> that explain the erratic seasons depicted in the show, and others to piece together the <a href="http://www.geologyin.com/2015/04/the-geology-of-game-of-thrones.html">geological history</a>. </p>
<p>Inspired by <a href="http://milestraer.com/the-geology-of-game-of-thrones/">this work</a>, we have built the first plate tectonic reconstruction of the Game of Thrones continents. Tectonic plates are moving slabs that make up the outer layer of our planet, and behave like conveyor belts in the way they carry and drag continents around on the surface. </p>
<p>Even in this fantasy Game of Thrones world, geological processes like tectonic plate movement, earthquakes and volcanic eruptions would have been responsible for building the mountains, carving the rivers and creating vast oceans.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/HB_ky-EAQtU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Plate tectonic reconstructions of Westeros and Essos over 600 million years in GPlates (www.gplates.org). Note the brown regions, mountains, that appear when continents collide. And just like on Earth, the forested regions in Game of Thrones are no older than about 400 million years, when the first plants began colonising the continents.</span></figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-earths-continents-became-twisted-and-contorted-over-millions-of-years-116168">How Earth's continents became twisted and contorted over millions of years</a>
</strong>
</em>
</p>
<hr>
<h2>Why solve tectonic ‘jigsaw puzzles’?</h2>
<p>Firstly, because even scientists are allowed a bit of fun now and then. But we also hope this map will help people better understand the science of plate tectonics, which is key to us knowing our past, present and even future world. </p>
<p>Plate tectonics can help us contextualise climate change and, like in the Game of Thrones world, <a href="https://theconversation.com/how-eurasias-tianshan-mountains-set-a-stage-that-changed-the-world-102772">geological events can influence political and social history</a>.</p>
<p>We built the tectonic maps using free community software, called <a href="http://gplates.org/">GPlates</a>, that we developed for <a href="https://www.earthbyte.org/category/resources/data-models/global-regional-plate-motion-models/">real-world tectonic modelling</a> in the School of Geosciences at the University of Sydney. </p>
<p>The animation first shows our model for Westeros and Essos, but also how we use the same technology to build a detailed representation of Earth’s tectonic evolution. The same technology is also used by <a href="https://astrographer.wordpress.com/2013/08/22/using-gplates-for-realistic-worldbuilding/">hobbyist “planet builders”</a> who create evolving maps that might be used in computer games, movies and TV shows, or other creative pursuits. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/you-know-nothing-about-rehoming-a-pet-jon-snow-116661">You know nothing about rehoming a pet, Jon Snow</a>
</strong>
</em>
</p>
<hr>
<h2>Setting the scene</h2>
<p>There is no doubt <a href="https://arstechnica.com/gaming/2019/04/with-its-latest-battle-game-of-thrones-solidifies-its-seat-on-tvs-vfx-throne/">high-budget visual effects</a>, a gripping storyline and power-plays between characters are key ingredients to the success of Game of Thrones. But so too are the captivating geological settings of the Seven Kingdoms.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"892503644389683200"}"></div></p>
<p>The breathtaking cinematography across sweeping grasslands of the Dothraki steppe to the snow-capped volcanic peaks north of the Wall; each location depicting contrasting topography that has shaped vastly different societies.</p>
<p>The geology also informs the storyline. For example, the all-important Dragonglass (volcanic obsidian rock) and Valyrian steel is extracted from the volcanic cliffs around Dragonstone castle.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1117880018284105728"}"></div></p>
<h2>How we made our map</h2>
<p>In our day-to-day work we use the shapes of continents and the geology they carry to reconstruct how real tectonic plate “puzzle pieces” moved around on Earth over time. </p>
<p>In this project, we worked with “evidence” collected by us and others from the Game of Thrones fictional world. This included evidence of past volcanism and mountain building, which are often the smoking gun for tectonic plate convergence and collision. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/275347/original/file-20190520-69182-gv2ia.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/275347/original/file-20190520-69182-gv2ia.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=538&fit=crop&dpr=1 600w, https://images.theconversation.com/files/275347/original/file-20190520-69182-gv2ia.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=538&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/275347/original/file-20190520-69182-gv2ia.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=538&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/275347/original/file-20190520-69182-gv2ia.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=675&fit=crop&dpr=1 754w, https://images.theconversation.com/files/275347/original/file-20190520-69182-gv2ia.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=675&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/275347/original/file-20190520-69182-gv2ia.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=675&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The geology and tectonics of Westeros and Essos at present-day. Red sawtooth lines represent ‘subduction zones’ where tectonic plates are converging, leading to mountain building and volcanism (like the Andes).</span>
<span class="attribution"><span class="source">Author modified, digital GIS files from cadei at www.cartographersguild.com</span></span>
</figcaption>
</figure>
<p>The easiest part of the tectonic reconstruction takes place by working backwards from seafloor spreading, where continents have been ripped apart by the the churning interior of our planet.</p>
<p>In the case of the Games of Thrones world, we’ve assumed the continents of Westeros and Essos broke apart 25 million years ago to open the Narrow Sea. We mapped this occurring much like the unzipping of the African continent along the East African <a href="https://www.nationalgeographic.org/encyclopedia/rift-valley/">Rift Valley</a> at a similar time. </p>
<p>But as we go deeper in time, we lose a lot of geological evidence. This happens because of erosion, <a href="https://theconversation.com/how-earths-continents-became-twisted-and-contorted-over-millions-of-years-116168">continental collisions that build mountains</a> and subduction, where one tectonic plate sinks beneath another. </p>
<p>In the real world, although India is now part of the Eurasian continent, an ancient seaway called the Tethys once separated them <a href="https://youtu.be/HB_ky-EAQtU?t=71">before the continents collided about 45 million years ago</a>. The continental collision uplifted the Tibetan Plateau and the Himalayas, and in the process crushing and destroying geological evidence and obscuring accurate tectonic models of the region. </p>
<p>Our plate tectonic reconstructions back to the <a href="https://www.livescience.com/38218-facts-about-pangaea.html">Pangea supercontinent</a> at 250 million years ago are fairly accurate by just undoing seafloor spreading, but the restoration of older supercontinents are much more difficult. </p>
<h2>Knowing our planet</h2>
<p>Tectonic plate “jigsaw puzzles” models are vital for explaining the evolution and liveability of our planet. </p>
<p>Plate tectonics controls the arrangement of continents and seaways on geological timescales, rearranging ocean circulation and altering global climate. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/unpacking-the-history-of-how-earth-feeds-life-and-life-changes-earth-103162">Unpacking the history of how Earth feeds life, and life changes Earth</a>
</strong>
</em>
</p>
<hr>
<p>Although much of this geological activity is too slow to be perceptible by humans, the geological past is littered with examples where <a href="https://theconversation.com/unpacking-the-history-of-how-earth-feeds-life-and-life-changes-earth-103162">sudden geological “shocks” to the living creatures on Earth</a> are caused by massive outpourings of volcanic rock and carbon dioxide, sometimes leading to mass extinctions. This may <a href="https://theconversation.com/how-the-dinosaurs-went-extinct-asteroid-collision-triggered-potentially-deadly-volcanic-eruptions-112134">have been a factor</a> in the death of nearly all the dinosaurs. </p>
<p>Tectonic reconstructions can inform climate simulations and help us contextualise current and future climate change. They can also lead us to find <a href="https://www.auscope.org.au/posts/minerals-challenge">mineral deposits</a> that may <a href="https://theconversation.com/how-earths-continents-became-twisted-and-contorted-over-millions-of-years-116168">help create a low-carbon society</a>. </p>
<p>And they’re fun to play with. </p>
<hr>
<p><em>Research assistants Cian Clinton-Gray, Irene Koutsoumbis and Youseph Ibrahim contributed to creating the map and writing this article.</em></p><img src="https://counter.theconversation.com/content/117393/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sabin Zahirovic receives funding from The University of Sydney, the Australian Research Council Industrial Transformation Research Hub for Basin Geodynamics and Evolution of Sedimentary Systems (Basin GENESIS Hub), and the Deep Carbon Observatory (DCO). AuScope is an Australian Government funding initiative that supports the development of GPlates and other critical geoscience infrastructure. </span></em></p><p class="fine-print"><em><span>Jo Condon works for AuScope, an Australian Government (NCRIS) supported organisation that funds critical research infrastructure such as GPlates software for geoscience researchers nationally.</span></em></p>Even in this fantasy world, geological processes like tectonic plate movement, earthquakes and volcanic eruptions would have built the mountains, carved the rivers, and created vast oceans.Sabin Zahirovic, Postdoctoral Research Associate, University of SydneyJo Condon, Honorary researcher, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1161682019-05-08T20:03:25Z2019-05-08T20:03:25ZHow Earth’s continents became twisted and contorted over millions of years<figure><img src="https://images.theconversation.com/files/273240/original/file-20190508-183100-1spavv4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Photographed on Kangaroo Island, this rock – called a ‘zebra schist’ – deformed from flat-lying marine sediments through being stressed by a continental collision over 500 million years ago</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/dietmardownunder/34197272884/in/album-72157681483445374/">Dietmar Muller</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p><a href="https://theconversation.com/breaking-new-ground-the-rise-of-plate-tectonics-7514">Classical plate tectonic theory</a> was developed in the 1960s. </p>
<p>It proposed that the outer layer of our planet is made up of a small number of rigid plates separated by narrow boundaries. The surface of Earth could be viewed as a simple jigsaw puzzle with just nine large plates and a bunch of much smaller ones. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/272932/original/file-20190507-103082-1rob9c6.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/272932/original/file-20190507-103082-1rob9c6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/272932/original/file-20190507-103082-1rob9c6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=322&fit=crop&dpr=1 600w, https://images.theconversation.com/files/272932/original/file-20190507-103082-1rob9c6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=322&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/272932/original/file-20190507-103082-1rob9c6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=322&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/272932/original/file-20190507-103082-1rob9c6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=404&fit=crop&dpr=1 754w, https://images.theconversation.com/files/272932/original/file-20190507-103082-1rob9c6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=404&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/272932/original/file-20190507-103082-1rob9c6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=404&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Map of the Earth’s rigid plates with the major tectonic plates labelled. Narrow plate boundary zones are the thin black lines. Created using plate reconstruction software (www.gplates.org).</span>
<span class="attribution"><span class="source">Maria Seton</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/breaking-new-ground-the-rise-of-plate-tectonics-7514">Breaking new ground – the rise of plate tectonics</a>
</strong>
</em>
</p>
<hr>
<p>But what was glossed over when global plate tectonic models were first developed was the enormous deformation experienced by these seemingly rigid plates. </p>
<p><a href="https://theconversation.com/plate-tectonics-new-findings-fill-out-the-50-year-old-theory-that-explains-earths-landmasses-55424">Fifty years after</a> the plate tectonic revolution, we are pretty sure the continental parts of plates are not uniform, nor are they rigid. The giant forces that slowly move continents across the viscous mantle layer underneath, like biscuits gliding over a warm toffee ocean, stress the continents, and twist and contort the crust. This is a process that has taken place over millions of years. </p>
<p>As part of recent research, we worked with a team of international collaborators to <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018TC005462">build a computer model</a> to show just how much the continents have been deformed since the Triassic Period, about 250 million years ago. The supercontinent Pangea began breaking apart soon after, ripping along the seams between Africa and North America.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/OwBbPa1zqMU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Animation showing the motion of the tectonic plates and the associated evolution of deformation since the breakup of the Pangea supercontinent (Credit: Sabin Zahirovic).</span></figcaption>
</figure>
<p>We detail this new understanding of continent mangling in a paper published this month in the journal <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018TC005462">Tectonics</a>. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Ns-_q_mhjxM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A model of tectonic plates moving over the viscous mantle. Blue material represents plates that are being recycled into the hot interior of the Earth. Red material represents extra hot material rising from the Earth’s core. (Credit: Maelis Arnould, see https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GC007516)</span></figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/plate-tectonics-new-findings-fill-out-the-50-year-old-theory-that-explains-earths-landmasses-55424">Plate tectonics: new findings fill out the 50-year-old theory that explains Earth's landmasses</a>
</strong>
</em>
</p>
<hr>
<h2>Immense forces</h2>
<p>We already knew that that colossal tectonic forces act along plate boundaries. We can see this when continents collide, such as when Africa collided with Eurasia, <a href="https://theconversation.com/curious-kids-how-do-mountains-form-108246">forming mountains</a> like the Alps, or forming basins when continents are torn apart, as <a href="https://www.nationalgeographic.org/encyclopedia/rift-valley/">is happening in East Africa</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/272893/original/file-20190506-103045-19b3cq9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/272893/original/file-20190506-103045-19b3cq9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/272893/original/file-20190506-103045-19b3cq9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/272893/original/file-20190506-103045-19b3cq9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/272893/original/file-20190506-103045-19b3cq9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/272893/original/file-20190506-103045-19b3cq9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/272893/original/file-20190506-103045-19b3cq9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/272893/original/file-20190506-103045-19b3cq9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Folded marine sediments in the Alps (Helvetic Nappes of Switzerland), uplifted and deformed by the collision of the African and Eurasian continents.</span>
<span class="attribution"><a class="source" href="https://imaggeo.egu.eu/">Kurt Stüwe</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Our new research used geological and geophysical data to pinpoint all major zones of continental deformation, built into a global model of plate motions using our <a href="https://www.earthbyte.org/category/gplates/">GPlates software</a>.</p>
<p>We show that at least one third of all continental crust has been massively deformed since Pangea first started breaking up. That’s a whopping 75 million km<sup>2</sup>, roughly the size of North and South America and Africa combined. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/272978/original/file-20190507-103045-vm7pqv.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/272978/original/file-20190507-103045-vm7pqv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/272978/original/file-20190507-103045-vm7pqv.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=373&fit=crop&dpr=1 600w, https://images.theconversation.com/files/272978/original/file-20190507-103045-vm7pqv.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=373&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/272978/original/file-20190507-103045-vm7pqv.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=373&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/272978/original/file-20190507-103045-vm7pqv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=469&fit=crop&dpr=1 754w, https://images.theconversation.com/files/272978/original/file-20190507-103045-vm7pqv.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=469&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/272978/original/file-20190507-103045-vm7pqv.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=469&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Present day map showing the areas that have undergone compression or extension during the past 250 million years.</span>
<span class="attribution"><span class="source">Sabin Zahirovic</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-do-mountains-form-108246">Curious Kids: how do mountains form?</a>
</strong>
</em>
</p>
<hr>
<p>Deformed continental regions include large stretched and submerged continents like <a href="https://theconversation.com/explorers-probe-hidden-continent-of-zealandia-83406">Zealandia</a>, as well as crustal contraction where collisions have occurred, producing mountain belts such as the <a href="https://blogs.egu.eu/divisions/gd/2017/12/20/remarkable-regions-the-india-asia-collision-zone/">Himalayas</a>, the <a href="https://en.wikipedia.org/wiki/Alps">European Alps</a>, Iran’s <a href="https://blogs.egu.eu/geolog/tag/zagros-mountains/">Zagros Mountains</a> and the <a href="https://www.gns.cri.nz/Home/Learning/Science-Topics/Earthquakes/Earthquakes-at-a-Plate-Boundary/Plate-Collision-in-NZ">southern Alps</a> of New Zealand. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/272987/original/file-20190507-103063-e3iwek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/272987/original/file-20190507-103063-e3iwek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/272987/original/file-20190507-103063-e3iwek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/272987/original/file-20190507-103063-e3iwek.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/272987/original/file-20190507-103063-e3iwek.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/272987/original/file-20190507-103063-e3iwek.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/272987/original/file-20190507-103063-e3iwek.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/272987/original/file-20190507-103063-e3iwek.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Folded marine sediments on the Whangaparaoa Peninsula north of Auckland, New Zealand, reflecting the formation of a convergent plate boundary in northern New Zealand in the beginning of the Miocene Period, around 23 million years ago.</span>
<span class="attribution"><span class="source">Adriana Dutkiewicz</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>The cradle of humankind</h2>
<p>When crust is being thinned and stretched, the crustal contortions are usually hidden away from view because they are quickly covered up by sediments. But there are exceptions. </p>
<p>The <a href="https://www.nationalgeographic.org/encyclopedia/rift-valley/">East African Rift valley</a> is one of the most spectacular examples of crustal extension visible at the surface. It has not subsided below sea level because the region is being pushed up by a <a href="https://www.nature.com/articles/s41598-018-33117-3">mantle plume</a>, a large upwelling of hot molten material causing uplift and volcanism. </p>
<p>The rift valley is underlain by a giant fault system that is <a href="https://theconversation.com/africa-is-splitting-in-two-here-is-why-94056">splitting Africa in two</a>. The rift turned a flat landscape into one with 4km high mountains and lake basins with vegetation ranging from desert to cloud forest. This variety of surface environments paved the way for the <a href="https://www.nature.com/articles/d41586-019-00213-x">early evolution and diversification of humans</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/273248/original/file-20190508-183080-zakief.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/273248/original/file-20190508-183080-zakief.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/273248/original/file-20190508-183080-zakief.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/273248/original/file-20190508-183080-zakief.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/273248/original/file-20190508-183080-zakief.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/273248/original/file-20190508-183080-zakief.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/273248/original/file-20190508-183080-zakief.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/273248/original/file-20190508-183080-zakief.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The Rift Valley was an important site for early evolution and diversification of humans.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/beautiful-landscape-rift-valley-photographed-ethiopia-375138130?src=E-ME6PPLXxy6-IIzb-OtvA-1-1">from www.shutterstock.com</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/africa-is-splitting-in-two-here-is-why-94056">Africa is splitting in two – here is why</a>
</strong>
</em>
</p>
<hr>
<h2>The importance of stress</h2>
<p>We may not like stress in our daily lives, but the continuous stress and strain acting on continents provides us with an important record of Earth’s history. </p>
<p>Modelling the patterns of continental deformation through time allows us to explore regional patterns of earthquakes and volcanism and explain dramatic changes in Earth’s climate over time. </p>
<p>It also provides a framework based on tectonic data <a href="https://www.earthbyte.org/earthbyte-group-develops-machine-learning-recipe-to-find-copper-gold-deposits-along-the-andes">to seek mineral resources</a> such as the metals <a href="https://theconversation.com/from-cobalt-to-tungsten-how-electric-cars-and-smartphones-are-sparking-a-new-kind-of-gold-rush-100838">cobalt and tungsten</a>, which are needed for a sustainable energy future.</p><img src="https://counter.theconversation.com/content/116168/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dietmar Müller receives funding from The University of Sydney, the Australian Research Council Industrial Transformation Research Hub for Basin Geodynamics and Evolution of Sedimentary Systems (Basin GENESIS Hub), and the Deep Carbon Observatory (DCO).</span></em></p><p class="fine-print"><em><span>Maria Seton receives funding from the Australian Research Council and has received ship time funding on Australia's Marine National Facility.</span></em></p><p class="fine-print"><em><span>Sabin Zahirovic receives funding from The University of Sydney, the Australian Research Council Industrial Transformation Research Hub for Basin Geodynamics and Evolution of Sedimentary Systems (Basin GENESIS Hub), and the Deep Carbon Observatory (DCO).</span></em></p>Giant forces slowly move continents across a viscous layer of the Earth, like biscuits gliding over a warm toffee ocean. This stresses the continents, and twists and contorts the crust.Dietmar Müller, Professor of Geophysics, University of SydneyMaria Seton, ARC Future Fellow, University of SydneySabin Zahirovic, Postdoctoral Research Associate, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1074542018-11-27T12:13:32Z2018-11-27T12:13:32ZWhat planet Earth might look like when the next supercontinent forms – four scenarios<figure><img src="https://images.theconversation.com/files/247548/original/file-20181127-76752-12xd1ql.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Planet Earth.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/earth-galaxy-elements-this-image-furnished-278864093?src=Z3tU77G_ytYWIdNQI0xdzw-2-85">Triff/Shutterstock</a></span></figcaption></figure><p>The outer layer of the Earth, the solid crust we walk on, is made up of broken pieces, much like the shell of a broken egg. These pieces, the tectontic plates, move around the planet at speeds of a few centimetres per year. Every so often they come together and combine into a supercontinent, which remains for a few hundred million years before breaking up. The plates then disperse or scatter and move away from each other, until they eventually – after another 400-600 million years – come back together again. </p>
<p>The last supercontinent, <a href="http://dinosaurpictures.org/ancient-earth#240">Pangea</a>, formed around 310 million years ago, and started breaking up around 180 million years ago. It has been suggested that the next supercontinent will form in 200-250 million years, so we are currently about halfway through the scattered phase of the current supercontinent cycle. The question is: how will the next supercontinent form, and why?</p>
<p>There are four fundamental scenarios for the <a href="https://www.sciencedirect.com/science/article/pii/S0921818118302054">formation of the next supercontinent</a>: Novopangea, Pangea Ultima, Aurica and Amasia. How each forms depends on different scenarios but ultimately are linked to how Pangea separated, and how the world’s continents are still moving today. </p>
<p>The breakup of Pangea led to the formation of the Atlantic ocean, which is still opening and getting wider today. Consequently, the Pacific ocean is closing and getting narrower. The Pacific is home to a ring of subduction zones along its edges (the “<a href="https://www.nationalgeographic.org/encyclopedia/ring-fire/">ring of fire</a>”), where ocean floor is brought down, or subducted, under continental plates and into the Earth’s interior. There, the old ocean floor is recycled and can go into volcanic plumes. The Atlantic, by contrast, has a large ocean ridge producing new ocean plate, but is only home to two subduction zones: the <a href="https://www.sciencedirect.com/science/article/pii/S0012825299000690?via%3Dihub">Lesser Antilles Arc</a> in the Caribbean and the <a href="http://nora.nerc.ac.uk/id/eprint/507879/1/Global%20relevance%20of%20the%20Scotia%20Arc%20-%20AAM.pdf">Scotia Arc</a> between South America and Antarctica. </p>
<h2>1. Novopangea</h2>
<p>If we assume that present day conditions persist, so that the Atlantic continues to open and the Pacific keeps closing, we have a scenario where the next supercontinent forms in the antipodes of Pangea. The Americas would collide with the northward drifting Antarctica, and then into the already collided Africa-Eurasia. The supercontinent that would then form has been named Novopangea, or Novopangaea. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/247354/original/file-20181126-140540-1toykgt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/247354/original/file-20181126-140540-1toykgt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/247354/original/file-20181126-140540-1toykgt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/247354/original/file-20181126-140540-1toykgt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/247354/original/file-20181126-140540-1toykgt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/247354/original/file-20181126-140540-1toykgt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=369&fit=crop&dpr=1 754w, https://images.theconversation.com/files/247354/original/file-20181126-140540-1toykgt.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=369&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/247354/original/file-20181126-140540-1toykgt.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=369&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Novopangea.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>2. Pangea Ultima</h2>
<p>The Atlantic opening may, however, slow down and actually start closing in the future. The two small arcs of subduction in the Atlantic could potentially spread all along the east coasts of the Americas, leading to a reforming of Pangea as the Americas, Europe and Africa are brought back together into a supercontinent called <a href="https://science.nasa.gov/science-news/science-at-nasa/2000/ast06oct_1">Pangea Ultima</a>. This new supercontinent would be surrounded by a super Pacific Ocean.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/247355/original/file-20181126-140519-oi7eud.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/247355/original/file-20181126-140519-oi7eud.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/247355/original/file-20181126-140519-oi7eud.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/247355/original/file-20181126-140519-oi7eud.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/247355/original/file-20181126-140519-oi7eud.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/247355/original/file-20181126-140519-oi7eud.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=369&fit=crop&dpr=1 754w, https://images.theconversation.com/files/247355/original/file-20181126-140519-oi7eud.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=369&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/247355/original/file-20181126-140519-oi7eud.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=369&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Pangea Ultima, formed by the Atlantic closing.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>3. Aurica</h2>
<p>However, if the Atlantic was to develop new subduction zones – <a href="https://www.cambridge.org/core/journals/geological-magazine/article/future-of-earths-oceans-consequences-of-subduction-initiation-in-the-atlantic-and-implications-for-supercontinent-formation/5F0C1733CB5994BAB1A04979EE59C768">something that may already be happening</a> – both the Pacific and Atlantic oceans may be fated to close. This means that a a new ocean basin would have to form to replace them. </p>
<p>In this scenario the Pan-Asian rift currently cutting through Asia from west of India up to the Arctic opens to form the new ocean. The result is the formation of <a href="https://www.cambridge.org/core/journals/geological-magazine/article/the-future-of-earths-oceans-consequences-of-subduction-initiation-in-the-atlantic-and-implications-for-supercontinent-formation/5F0C1733CB5994BAB1A04979EE59C768">the supercontinent Aurica</a>. Because of <a href="https://www.nytimes.com/2016/09/24/world/what-in-the-world/australia-continental-drift-location-gps.html?_r=1">Australia’s current northwards drift</a> it would be at the centre of the new continent as East Asia and the Americas close the Pacific from either side. The European and African plates would then rejoin the Americas as the Atlantic closes.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/VqjHmtZ9240?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>4. Amasia</h2>
<p>The fourth scenario predicts a completely different fate for future Earth. Several of the tectonic plates are currently moving north, including both Africa and Australia. This drift is <a href="https://www.nature.com/articles/nature10800">believed to be driven</a> by anomalies left by Pangea, deep in the Earth’s interior, in the part called the mantle. Because of this northern drift, one can envisage a scenario where the continents, except Antarctica, keep drifting north. This means that they would eventually gather around the North Pole in a <a href="https://www.sciencemag.org/news/2012/02/meet-amasia-next-supercontinent">supercontinent called Amasia</a>. In this scenario, both the Atlantic and the Pacific would mostly remain open.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/247356/original/file-20181126-140528-r0g50t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/247356/original/file-20181126-140528-r0g50t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/247356/original/file-20181126-140528-r0g50t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/247356/original/file-20181126-140528-r0g50t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/247356/original/file-20181126-140528-r0g50t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/247356/original/file-20181126-140528-r0g50t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=369&fit=crop&dpr=1 754w, https://images.theconversation.com/files/247356/original/file-20181126-140528-r0g50t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=369&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/247356/original/file-20181126-140528-r0g50t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=369&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Amasia, the fourth scenario.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Of these four scenarios we believe that Novopangea is the most likely. It is a logical progression of present day continental plate drift directions, while the other three assume that another process comes into play. There would need to be new Atlantic subduction zones for Aurica, the reversal of the Atlantic opening for Pangea Ultima, or anomalies in the Earth’s interior left by Pangea for Amasia. </p>
<p>Investigating the Earth’s tectonic future forces us to push the boundaries of our knowledge, and to think about the processes that shape our planet over long time scales. It also leads us to think about the Earth system as a whole, and raises a series of other questions – what will the climate of the next supercontinent be? How will the ocean circulation adjust? How will life evolve and adapt? These are the kind of questions that push the boundaries of science further because they push the boundaries of our imagination.</p><img src="https://counter.theconversation.com/content/107454/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mattias Green receives funding from the Natural Environmental Research Council.</span></em></p><p class="fine-print"><em><span>Hannah Davies receives funding from the Portuguese science foundation (FCT)</span></em></p><p class="fine-print"><em><span>Joao C. Duarte receives funding from the Portuguese Science Foundation (FCT)</span></em></p>Scientists have predicted four supercontinent scenarios - but which is the most likely?Mattias Green, Reader in Physical Oceanography, Bangor UniversityHannah Sophia Davies, PhD Researcher, Universidade de Lisboa Joao C. Duarte, Researcher and Coordinator of the Marine Geology and Geophysics Group, Universidade de Lisboa Licensed as Creative Commons – attribution, no derivatives.