tag:theconversation.com,2011:/id/topics/caldera-14413/articlesCaldera – The Conversation2021-07-21T20:11:21Ztag:theconversation.com,2011:article/1648552021-07-21T20:11:21Z2021-07-21T20:11:21ZWe’ve discovered an undersea volcano near Christmas Island that looks like the Eye of Sauron<figure><img src="https://images.theconversation.com/files/412372/original/file-20210721-19-iqz980.JPG?ixlib=rb-1.1.0&rect=27%2C27%2C4043%2C3124&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Phil Vandenbossche & Nelson Kuna/CSIRO</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Looking like the <a href="https://www.thetolkienforum.com/wiki/Image:eye-of-sauron-by-alex-ortiz">Eye of Sauron</a> from the Lord of the Rings Trilogy, an ancient undersea volcano was slowly revealed by multibeam sonar 3,100 metres below our vessel, 280 kilometres southeast of Christmas Island. This was on day 12 of our <a href="https://mnf.csiro.au/en/Voyages/IN2021_V04">voyage of exploration</a> to Australia’s Indian Ocean Territories, aboard CSIRO’s dedicated ocean research vessel, the <a href="https://mnf.csiro.au/en/RV-Investigator">RV Investigator</a>.</p>
<p>Previously unknown and unimagined, this volcano emerged from our screens as a giant oval-shaped depression called a caldera, 6.2km by 4.8km across. It is surrounded by a 300m-high rim (resembling Sauron’s eyelids), and has a 300 m high cone-shaped peak at its the centre (the “pupil”).</p>
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<a href="https://images.theconversation.com/files/412368/original/file-20210721-19-1c5whs2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Sonar sea bed image" src="https://images.theconversation.com/files/412368/original/file-20210721-19-1c5whs2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412368/original/file-20210721-19-1c5whs2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=272&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412368/original/file-20210721-19-1c5whs2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=272&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412368/original/file-20210721-19-1c5whs2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=272&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412368/original/file-20210721-19-1c5whs2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=341&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412368/original/file-20210721-19-1c5whs2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=341&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412368/original/file-20210721-19-1c5whs2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=341&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">Sonar image of the ‘Eye of Sauron’ volcano and nearby seamounts on the sea bed south-west of Christmas Island.</span>
<span class="attribution"><span class="source">Phil Vandenbossche & Nelson Kuna/CSIRO</span>, <span class="license">Author provided</span></span>
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<p>A caldera is formed when a volcano collapses. The molten magma at the base of the volcano shifts upwards, leaving empty chambers. The thin solid crust on the surface of the dome then collapses, creating a large crater-like structure. Often, a small new peak then begins to form in the centre as the volcano continues spewing magma.</p>
<p>One well-known caldera is the one at <a href="https://www.livescience.com/28186-krakatoa.html">Krakatoa</a> in Indonesia, which exploded in 1883, killing tens of thousands of people and leaving only bits of the mountain rim visible above the waves. By 1927, a small volcano, Anak Krakatoa (“child of Krakatoa”), had grown in its centre. </p>
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Read more:
<a href="https://theconversation.com/krakatoa-is-still-active-and-we-are-not-ready-for-the-tsunamis-another-eruption-would-generate-147250">Krakatoa is still active, and we are not ready for the tsunamis another eruption would generate</a>
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<p>In contrast, we may not even be aware of volcanic eruptions when they happen deep under the ocean. One of the few tell-tale signs is the presence of <a href="https://www.abc.net.au/news/science/2020-06-03/pumice-stone-raft-transporting-marine-life/12278124">rafts of light pumice stone</a> floating on the sea surface after being blown out of a submarine volcano. Eventually, this pumice stone becomes waterlogged and sinks to the ocean floor.</p>
<p>Our volcanic “eye” was not alone. Further mapping to the south revealed a smaller sea mountain covered in numerous volcanic cones, and further still to the south was a larger, flat-topped seamount. Following our Lord of the Rings theme, we have nicknamed them <a href="https://lotr.fandom.com/wiki/Barad-d%C3%BBr">Barad-dûr</a> (“Dark Fortress”) and <a href="https://lotr.fandom.com/wiki/Ash_Mountains">Ered Lithui</a> (“Ash Mountains”), respectively. </p>
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<img alt="" src="https://images.theconversation.com/files/412388/original/file-20210721-21-w24x9u.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/412388/original/file-20210721-21-w24x9u.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=537&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412388/original/file-20210721-21-w24x9u.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=537&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412388/original/file-20210721-21-w24x9u.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=537&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412388/original/file-20210721-21-w24x9u.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=675&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412388/original/file-20210721-21-w24x9u.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=675&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412388/original/file-20210721-21-w24x9u.jpeg?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">
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<span class="caption">The voyage of the RV Investigator around Christmas Island.</span>
<span class="attribution"><span class="source">Tim O'Hara/Museums Victoria</span></span>
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<p>Although author J.R.R. Tolkein’s knowledge of mountain geology <a href="https://www.tor.com/2017/08/01/tolkiens-map-and-the-messed-up-mountains-of-middle-earth">wasn’t perfect</a>, our names are wonderfully appropriate given the jagged nature of the first and the pumice-covered surface of the second.</p>
<p>The Eye of Sauron, Barad-dûr, and Ered Lithui are part of the Karma cluster of seamounts that have been previously estimated by <a href="https://www.livescience.com/17557-christmas-island-seamounts-mystery-solved.html">geologists</a> to be more than 100 million years old, and which formed next to an ancient sea ridge from a time when Australia was situated much further south, near Antarctica. The flat summit of Ered Lithui was formed by wave erosion when the seamount protruded above the sea surface, before the heavy seamount slowly sank back down into the soft ocean seafloor. The summit of Ered Lithui is now 2.6km below sea level.</p>
<p><img width="100%" src="https://cdn.theconversation.com/static_files/files/1720/Karma-fly.gif?1626845098"></p>
<p>But here is the geological conundrum. Our caldera looks surprisingly fresh for a structure that should be more than 100 million years old. Ered Lithui has almost 100m of sand and mud layers draped over its summit, formed by sinking dead organisms over millions of years. This sedimentation rate would have partially smothered the caldera. Instead it is possible that volcanoes have continued to sprout or new ones formed long after the original foundation. Our restless Earth is never still.</p>
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<a href="https://images.theconversation.com/files/412358/original/file-20210721-25-1jei4u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Starfish" src="https://images.theconversation.com/files/412358/original/file-20210721-25-1jei4u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/412358/original/file-20210721-25-1jei4u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412358/original/file-20210721-25-1jei4u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412358/original/file-20210721-25-1jei4u.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412358/original/file-20210721-25-1jei4u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412358/original/file-20210721-25-1jei4u.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412358/original/file-20210721-25-1jei4u.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 large deep-sea predatory seastar Zoroaster.</span>
<span class="attribution"><span class="source">Rob French/Museums Victoria</span>, <span class="license">Author provided</span></span>
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<a href="https://images.theconversation.com/files/412356/original/file-20210721-23-zbhz53.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Batfish" src="https://images.theconversation.com/files/412356/original/file-20210721-23-zbhz53.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/412356/original/file-20210721-23-zbhz53.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412356/original/file-20210721-23-zbhz53.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412356/original/file-20210721-23-zbhz53.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412356/original/file-20210721-23-zbhz53.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412356/original/file-20210721-23-zbhz53.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412356/original/file-20210721-23-zbhz53.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">Small batfish patrol the seamount summits.</span>
<span class="attribution"><span class="source">Rob French/Museums Victoria</span>, <span class="license">Author provided</span></span>
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<a href="https://images.theconversation.com/files/412355/original/file-20210721-25-ax5rh6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Sea pig" src="https://images.theconversation.com/files/412355/original/file-20210721-25-ax5rh6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/412355/original/file-20210721-25-ax5rh6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/412355/original/file-20210721-25-ax5rh6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/412355/original/file-20210721-25-ax5rh6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/412355/original/file-20210721-25-ax5rh6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/412355/original/file-20210721-25-ax5rh6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/412355/original/file-20210721-25-ax5rh6.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">Elasipod sea cucumbers feed on organic detritus on deep sandy seafloors.</span>
<span class="attribution"><span class="source">Rob French/Museums Victoria</span>, <span class="license">Author provided</span></span>
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<p>But life adapts to these geological changes, and Ered Lithui is now covered in seafloor animals. Brittle-stars, sea-stars, crabs and worms burrow into or skate over the sandy surface. Erect black corals, fan-corals, sea-whips, sponges and barnacles grow on exposed rocks. Gelatinous cusk-eels prowl around rock gullies and boulders. Batfish lie in wait for unsuspecting prey.</p>
<p>Our mission is to map the seafloor and survey sea life from these ancient and secluded seascapes. The Australian government recently announced plans to create two massive marine parks across the regions. Our expedition will supply scientific data that will help Parks Australia to manage these areas into the future. </p>
<p>Scientists from museums, universities, CSIRO and Bush Blitz around Australia are participating in the voyage. We are close to completing part one of our journey to the Christmas Island region. Part two of our journey to the Cocos (Keeling) Island region will be scheduled in the next year or so.</p>
<p>No doubt many animals that we find here will be new to science and our first records of their existence will be from this region. We expect many more surprising discoveries.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/this-deep-sea-creature-is-long-armed-bristling-with-teeth-and-the-sole-survivor-of-180-million-years-of-evolution-162842">This deep-sea creature is long-armed, bristling with teeth, and the sole survivor of 180 million years of evolution</a>
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<img src="https://counter.theconversation.com/content/164855/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The voyage of exploration on the RV Investigator was facilitated by a grant of sea time by the CSIRO Marine National Facility, and funding from Parks Australia and Bush Blitz, both part of the Commonwealth Department of Agriculture, Water and Environment. </span></em></p>Sonar scans of the Indian Ocean floor south of Christmas Island have revealed a Tolkeinesque landscape of towering peaks, ashen uplands and ominous volcanic craters.Tim O'Hara, Senior Curator of Marine Invertebrates, Museums Victoria Research InstituteLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1146962019-06-24T12:47:41Z2019-06-24T12:47:41ZWe probed Santorini’s volcano with sound to learn what’s going on beneath the surface<figure><img src="https://images.theconversation.com/files/273695/original/file-20190509-183083-li2utt.jpg?ixlib=rb-1.1.0&rect=0%2C9%2C2285%2C1358&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sound waves let researchers visualize what's happening below the surface.</span> <span class="attribution"><span class="source">Emilie Hooft</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>The island of Santorini in the Mediterranean has attracted people for millennia. Today, it feels magical to watch the sun set from cliffs over the deep bay, surrounded by cobalt blue churches and whitewashed houses. This mystical place attracts about 2 million tourists per year, making it one of the <a href="https://www.planetware.com/tourist-attractions/greece-gr.htm">top destinations in Greece</a>.</p>
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<span class="caption">The Greek islands of Santorini form the perimeter of a volcano whose last major explosion happened about 3,400 years ago. Now the center of the crater-like caldera is filled with seawater.</span>
<span class="attribution"><a class="source" href="https://photojournal.jpl.nasa.gov/catalog/PIA02673">NASA/GSFC/METI/ERSDAC/JAROS and U.S./Japan ASTER Science Team</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>Not all those visitors recognize that Santorini is an active volcano. In 1630 B.C., the volcano exploded and collapsed leaving behind an almost circular hole. This is the caldera – visible today as a bay filled with seawater and lined by cliffs. The large explosion <a href="https://archaeology-travel.com/greece/south-aegean/santorini/akrotiri/">covered a Bronze Age town</a>, burying buildings in volcanic ash two stories deep. </p>
<p>The <a href="https://www.arcgis.com/apps/MapJournal/index.html?appid=007b8ebcbfe34bfabf17c486b2445637">latest lava flows erupted in 1950</a> and <a href="https://www.volcanodiscovery.com/santorini/1950-eruption.html">expanded the islands that have grown at the center of the caldera</a>. Recently, in 2011-2012, the volcano went through a period of unrest. The ground bulged up and out, and many small earthquakes occurred. <a href="https://news.nationalgeographic.com/news/2012/09/120912-magma-balloon-lava-santorini-volcano-science/">Scientists concluded</a> that a small amount of magma was injected about 2.5 miles (4 kilometers) under the northern portion of the caldera.</p>
<p>What attracted me to this iconic place is that most of the volcano is submerged under water. <a href="https://scholar.google.com/citations?user=GoO8Z7oAAAAJ&hl=en&oi=ao">I am a geophysicist</a> interested in how magma moves deep in the Earth. Over the past decade, I’ve been <a href="https://youtu.be/LXh8lZK55VE">using advanced technology</a> to improve how we “see” magma’s otherwise hidden pathways below volcanoes around the world.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/sygEQzn0BP4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Get a glimpse of how researchers conducted their seismic experiment to understand the volcano of Santorini.</span></figcaption>
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<h2>Using sound to see what’s beneath the surface</h2>
<p>In the 1780s, French scientist Ferdinand Fouquet traveled to Santorini to view an ongoing eruption. He was the first to realize how the volcanic <a href="https://www.nationalgeographic.org/encyclopedia/caldera/">surface depression known as a caldera was formed</a>. As magma emptied out of its underground reservoir during the eruption, the roof of rock that had been covering it collapsed. The flanks of the volcano that remained form the ring of islands visible above water today.</p>
<p>My research project aimed to delve deeper, literally, than <a href="https://doi.org/10.1016/j.tecto.2017.06.005">what we can see from the surface</a> to figure out what’s going on within this still active volcano. A blanket of water over everything except the very top of the Santorini volcano meant I could use deep-penetrating marine sound sources to “illuminate” the subsurface structures. My international collaborators and I wanted to find the location and depth where magma was collecting and how much magma there is right now.</p>
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<a href="https://images.theconversation.com/files/273678/original/file-20190509-183086-5rgr4p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/273678/original/file-20190509-183086-5rgr4p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/273678/original/file-20190509-183086-5rgr4p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=268&fit=crop&dpr=1 600w, https://images.theconversation.com/files/273678/original/file-20190509-183086-5rgr4p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=268&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/273678/original/file-20190509-183086-5rgr4p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=268&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/273678/original/file-20190509-183086-5rgr4p.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=337&fit=crop&dpr=1 754w, https://images.theconversation.com/files/273678/original/file-20190509-183086-5rgr4p.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=337&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/273678/original/file-20190509-183086-5rgr4p.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=337&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">R/V Marcus Langseth within the Santorini caldera with an ocean-bottom seismometer floating in front of the ship.</span>
<span class="attribution"><span class="source">Doug Toomey</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We conducted our work from the R/V Marcus Langseth, an American marine seismic ship. It is the only academic ship with a sound source capable of imaging the deep insides of a volcano. This technology is controversial because of the <a href="https://doi.org/10.1038/460939b">potential impact of loud sounds</a> on marine wildlife and its intensive use by oil exploration companies.</p>
<p>We spent months doing environmental permitting and finding the optimal design for the experiment. <a href="https://santorini.uoregon.edu">The ship carried a team</a> of experienced biological observers who surveyed the sea both above and below water for sound-sensitive or endangered species. If any were observed at a distance, we were to follow a prescribed set of actions to ensure they wouldn’t be disturbed. After all this preparation, though, we saw almost no wildlife during the expedition.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/280802/original/file-20190621-61747-175xtok.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/280802/original/file-20190621-61747-175xtok.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/280802/original/file-20190621-61747-175xtok.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=459&fit=crop&dpr=1 600w, https://images.theconversation.com/files/280802/original/file-20190621-61747-175xtok.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=459&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/280802/original/file-20190621-61747-175xtok.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=459&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/280802/original/file-20190621-61747-175xtok.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=577&fit=crop&dpr=1 754w, https://images.theconversation.com/files/280802/original/file-20190621-61747-175xtok.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=577&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/280802/original/file-20190621-61747-175xtok.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=577&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">One of the airguns. It has a volume of 180 cubic inches and is about 18 inches long.</span>
<span class="attribution"><span class="source">Emilie Hooft</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Our “active source seismic imaging” method is like making a CAT-scan picture of the inside of the Earth. Instead of building an image using X-rays, though, we use sound waves generated by 36 heavy, metal canisters – called airguns – that are towed deep in the water behind the ship. When the airguns open, compressed air pushes on the seawater, creating a sound wave that travels through the Earth.</p>
<p>In this instance, the sound travels through the rocks beneath the volcano. Then seismic sensors resting on the seafloor on the other side of the volcano record when the sound reaches them. The team installed 65 of these stations on land, across Santorini and the nearby islands, and dropped another 90 stations to the seafloor. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/273702/original/file-20190509-183109-l65l0a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/273702/original/file-20190509-183109-l65l0a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/273702/original/file-20190509-183109-l65l0a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/273702/original/file-20190509-183109-l65l0a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/273702/original/file-20190509-183109-l65l0a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/273702/original/file-20190509-183109-l65l0a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/273702/original/file-20190509-183109-l65l0a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/273702/original/file-20190509-183109-l65l0a.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">The team installing one of the land seismometers on Anafi.</span>
<span class="attribution"><span class="source">Joanna Morgan, Imperial College London</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We have to use very accurate timing to measure how long it takes the sound energy to go through the different parts of the volcano. The energy from the sound source will travel more slowly through rocks that are broken or that are hot and contain magma. When we probe the structure from many different directions and at many different depths, we can recover a detailed picture of the interior of the Earth.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/273681/original/file-20190509-183106-3expvj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/273681/original/file-20190509-183106-3expvj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/273681/original/file-20190509-183106-3expvj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=311&fit=crop&dpr=1 600w, https://images.theconversation.com/files/273681/original/file-20190509-183106-3expvj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=311&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/273681/original/file-20190509-183106-3expvj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=311&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/273681/original/file-20190509-183106-3expvj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=391&fit=crop&dpr=1 754w, https://images.theconversation.com/files/273681/original/file-20190509-183106-3expvj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=391&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/273681/original/file-20190509-183106-3expvj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=391&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">University of Oregon graduate student Brandon VanderBeek capturing an ocean-bottom seismometer after it resurfaces. The caldera cliffs of Santorini are in the distance. The black fresh lavas of the island inside the caldera are in front, on the left.</span>
<span class="attribution"><span class="source">Emilie Hooft</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>To get the data back from the seafloor, we send a special sound signal to the sensor – like a bird call – that commands the instrument to drop its anchor. Then everyone scans the sea looking for the instrument. During the day we search for a cheerful orange flag, at night a strobe light makes this task easier. Our ship maneuvers alongside the instrument and a crew member leans over the side, hooks the instrument on a long pole and pulls it back on board. The data is in hand. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/273696/original/file-20190509-183112-yzuwdz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/273696/original/file-20190509-183112-yzuwdz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/273696/original/file-20190509-183112-yzuwdz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=371&fit=crop&dpr=1 600w, https://images.theconversation.com/files/273696/original/file-20190509-183112-yzuwdz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=371&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/273696/original/file-20190509-183112-yzuwdz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=371&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/273696/original/file-20190509-183112-yzuwdz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=467&fit=crop&dpr=1 754w, https://images.theconversation.com/files/273696/original/file-20190509-183112-yzuwdz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=467&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/273696/original/file-20190509-183112-yzuwdz.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">Scientists gather around the map table in the R/V Langseth’s main laboratory.</span>
<span class="attribution"><span class="source">PROTEUS Science Team</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Filling out the subsurface picture</h2>
<p>Analysis of the seismic data is an enormous task. It required experienced inspection by Ph.D. student Ben Heath and master’s student Brennah McVey. We then used seismic tomography to make the first detailed “photographs” of Santorini’s subsurface structure. The term tomography comes from the Greek words “tomos” for slice and “graphos” for draw. Basically sophisticated computer code makes a three-dimensional digital model of the object of interest based on the speed sound waves traveled through it.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/280795/original/file-20190621-61733-1wgf0d7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/280795/original/file-20190621-61733-1wgf0d7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/280795/original/file-20190621-61733-1wgf0d7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=329&fit=crop&dpr=1 600w, https://images.theconversation.com/files/280795/original/file-20190621-61733-1wgf0d7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=329&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/280795/original/file-20190621-61733-1wgf0d7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=329&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/280795/original/file-20190621-61733-1wgf0d7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=413&fit=crop&dpr=1 754w, https://images.theconversation.com/files/280795/original/file-20190621-61733-1wgf0d7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=413&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/280795/original/file-20190621-61733-1wgf0d7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=413&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 grey volume is the column of porous rock beneath the northern caldera. This is the zone of the initial collapse during the Bronze age eruption. As the plumbing system refills, magma (red in this schematic) accumulates directly beneath this region.</span>
<span class="attribution"><span class="source">Brennah McVey, University of Oregon</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Surprisingly, <a href="https://doi.org/10.1016/j.epsl.2019.02.033">we found a narrow zone of collapsed rock</a> hiding within the broad caldera at Santorini. <a href="http://elementsmagazine.org/2019/06/11/late-bronze-age-eruption-santorini-volcano-impact-ancient-mediterranean-world/">Geological studies</a> of the eruptions at Santorini hadn’t led us to expect there would be a confined volume of rocks in the northern part of the caldera that sound traveled through more slowly. Rather we thought the entire caldera would be filled with this type of broken rock at shallow depths. Our finding meant that the collapsed portion of the caldera was much narrower and deeper than it appears from the surface. </p>
<p>This column of disrupted rock is less than 2 miles (3 km) across – small compared to the size of the 6-mile-wide (10 km) caldera. The structure goes down into the ground 2 miles (3 km) below the bottom of the bay. These rocks must contain lots of water-filled gaps to have sufficiently slowed the seismic energy we recorded.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/vJqmypD17mU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">3D visualization of Santorini’s caldera and magma plumbing system.</span></figcaption>
</figure>
<p>To figure out how this unique volume of disrupted rock formed, we drew on existing knowledge of <a href="https://nom.maps.arcgis.com/apps/Cascade/index.html?appid=2a6c54875bf743dd8143786a55dcb2b1">Santorini’s most recent large explosion</a>, the Late Bronze Age eruption in 1630 B.C. As magma erupted from the subsurface, it caused the overlying rocks to break up. At the same time, underground explosions fractured the rocks when magma and water came into contact. Then, above this collapsing column, the seafloor depression filled with porous volcanic deposits from the eruption itself. Finally, the entire bay dropped down and <a href="https://doi.org/10.1038/ncomms13332">rapid flooding formed a tsunami wave</a>.</p>
<p>What is particularly interesting about our findings is that magma continues to accumulate directly beneath the column of disrupted rock – thousands of years after the explosion that originally created the caldera. My colleagues and I think the rising magma comes to a halt beneath the reduced weight of the broken rock in the collapsed column.</p>
<p>Our research helps explain how magma systems are reset and regrow after major volcanic episodes.</p><img src="https://counter.theconversation.com/content/114696/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Emilie Hooft receives funding from the U.S. National Science Foundation. The experiment and analysis were supported by National Science Foundation grant number OCE-1459794 to the University of Oregon and Leverhulme Grant RPG-2015-363 to Imperial College London. Data used in this research were provided by instruments from the Ocean Bottom Seismograph Instrument Pool, which is funded by the National Science Foundation. The Geophysical Instrument Pool Potsdam provided 60 land seismometers. The Aristotle University of Thessaloniki contributed 5 land seismometers and the Greek military donated helicopter time for installations on the smaller islands. This work benefited from access to the University of Oregon high performance computer, Talapas. </span></em></p>Geophysicists use sound waves to build a picture of the magma and rock beneath this active volcano, most of which is underwater. It’s like CT scanning the Earth.Emilie Hooft, Associate Professor of Earth Sciences, Volcanology Cluster of Excellence, & Oregon Hazards Lab, University of OregonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/683682016-11-08T16:29:45Z2016-11-08T16:29:45ZSantorini eruption: new theory says ‘pyroclastic flows’ caused devastating Bronze Age tsunamis<figure><img src="https://images.theconversation.com/files/145069/original/image-20161108-16702-1kf4sl6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">All one volcano.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/jurvetson/7449551878/">Steve Jurvetson</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Take the ferry to the beautiful Greek islands of Santorini and you will sail into a truly unique landscape forged by a cataclysm towards the end of the Bronze Age. From either the north or south your ship will leave the brilliant blue seas of the Aegean and enter a natural harbour flanked by majestic cliffs. Ferries pass between the large island of Thira and the smaller island of Thirasia, while straight ahead a small island in the centre of the natural harbour, Nea Kameni, looks like a molehill surrounded by mountains. </p>
<p>It is on Nea Kameni, among hot springs and sulphurous vents, that you can begin to understand the natural history and formation of this island. The harbour, the cliffs, the elegant white houses with blue roofs; all are part of a huge volcano.</p>
<figure> <img src="https://upload.wikimedia.org/wikipedia/commons/f/f1/Santorini_3D_version_1.gif"><figcaption>Santorini in 3D (image: NASA)</figcaption></figure>
<p>Sometime during the mid-second millennium BC, Santorini erupted. It was one of the <a href="http://jgs.lyellcollection.org/content/171/4/583.abstract">biggest volcanic events</a> in human history. In the past 800 years only Mount Tambora in Indonesia has erupted with such force, and Tambora was responsible for a global “year without a summer” in 1816.</p>
<p>The eruption sent devastating tsunamis across the eastern Mediterranean that smashed into the Minoans on Crete, at the time one of the world’s <a href="http://blogs.discovermagazine.com/d-brief/2013/05/14/minoans-first-advanced-european-civilization-originated-from-europe-not-africa/">most advanced civilisations</a>. </p>
<p>The Santorini volcano is a caldera, a type of volcano that erupts so violently that its middle collapses in on itself forming a huge crater. How this crater came to be is the focus of a new paper in <a href="http://nature.com/articles/doi:10.1038/NCOMMS13332">Nature Communications</a> by Paraskevi Nomikou and colleagues. They have published high-resolution seabed maps and combined these with seismic evidence for what rocks the seabed is made of in the caldera to explain how the volcano collapsed, filled with water and might have produced tsunamis.</p>
<p>Prior to the eruption the modern caldera did not exist. Instead a smaller caldera, from a much older eruption, formed a lagoon at the north of the solitary island. Near the modern town of Akrotiri stood a Minoan settlement, a bustling town with three-storey buildings, narrow streets and courtyards, quite different from the palace complexes found in the Minoan homeland of Crete. The prehistoric Akrotiri may have been home to hundreds or thousands of people, and was probably an <a href="http://www.thamesandhudson.com/The_Making_of_the_Middle_Sea/9780500051764">important trading port</a> for the eastern Mediterranean.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/145064/original/image-20161108-16721-15xx7rc.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/145064/original/image-20161108-16721-15xx7rc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/145064/original/image-20161108-16721-15xx7rc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=185&fit=crop&dpr=1 600w, https://images.theconversation.com/files/145064/original/image-20161108-16721-15xx7rc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=185&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/145064/original/image-20161108-16721-15xx7rc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=185&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/145064/original/image-20161108-16721-15xx7rc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=232&fit=crop&dpr=1 754w, https://images.theconversation.com/files/145064/original/image-20161108-16721-15xx7rc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=232&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/145064/original/image-20161108-16721-15xx7rc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=232&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fresco found in ancient Akrotiri. In their heyday the Minoans were among the world’s most advanced civilisations.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:AKROTIRI_SHIP-PROCESSION-FULL_PANO-3.jpg">smial / Luxo</a></span>
</figcaption>
</figure>
<p>The eruption first <a href="http://adsabs.harvard.edu/abs/2001JVGR..109..299T">blasted ash high into the sky</a>, which settled back down onto the settlements and farmland. This terrifying but not immediately catastrophic stage might have given the locals early warning and caused them to abandon the island (no bodies have been found among the archaeology, which implies residents probably fled). </p>
<p>As the ash continued to be thrown into the air, the island would have been eerily dark with fragments falling from the sky – imagine a severe rainstorm, but of ash and dust. As the ash column grew to its full height it entered the stratosphere and began to <a href="http://specialpapers.gsapubs.org/content/345/43.abstract">spread out and drift east</a>. Ash from this eruption has been found in Turkey, the Aegean islands and Crete. </p>
<p>In the <a href="http://link.springer.com/article/10.1007/s00445-014-0794-x">next stage</a> of the eruption pyroclastic flows, hot landslides of volcanic material that travel faster than F1 cars, charged out of the volcanic cone building up large fans that blocked the northwest straits and isolated the caldera from the Mediterranean Sea.</p>
<p>The eruption continued to increase in violence with multiple cones sending out considerable amounts of pyroclastic flows. Deposits of these flows reach 60 metres thick (the height of around 14 double decker buses) and engulfed the Minoan settlement at Akrotiri, creating a Bronze Age Pompeii and a spectacular window into an ancient civilisation in the 1600s BC. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/145055/original/image-20161108-16718-5kpeu2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/145055/original/image-20161108-16718-5kpeu2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/145055/original/image-20161108-16718-5kpeu2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/145055/original/image-20161108-16718-5kpeu2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/145055/original/image-20161108-16718-5kpeu2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/145055/original/image-20161108-16718-5kpeu2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/145055/original/image-20161108-16718-5kpeu2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/145055/original/image-20161108-16718-5kpeu2.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">Akrotiri has been excavated over the past five decades.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/klearchos/7049089631/">Klearchos Kapoutsis</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>It is during this stage that Nomikou and colleagues propose that tsunamis would have been generated. In Crete, 120km away, a nine metre-high wave tore up the northern side of the island leaving devastation and debris in its wake. The waves may have <a href="http://geology.gsapubs.org/content/28/1/59.abstract">reached western Turkey and even Israel</a>.</p>
<p>The seas eventually settled, the eruption ended, and the modern caldera began to form. Erosion by the sea and a catastrophic landslide opened the north-west strait, filling the caldera from the surrounding Mediterranean in a couple of days; further landslides into this full caldera formed the southwestern straits. Completing the modern geography would take several thousand years more as the island of Nea Kameni, an active volcano, gradually erupted above sea-level.</p>
<p>While catastrophic, terrifying and probably life-changing for large numbers of people, the Minoans themselves <a href="http://www.thamesandhudson.com/The_Making_of_the_Middle_Sea/9780500051764">didn’t die out</a>. Though Santorini was not recolonised, evidence from pottery shows civilisation on Crete continued for several generations. However, as a society built on maritime trade the loss of the port of Santorini, which had direct links to the important bronze-producing island of Cyprus, might have diminished their position among the trading powers of the eastern Mediterranean.</p><img src="https://counter.theconversation.com/content/68368/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matthew Pound 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 nine metre-high waves that smashed into Minoan civilisation on Crete weren’t caused by the volcano collapsing.Matthew Pound, Lecturer in Physical Geography, Northumbria University, NewcastleLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/378612015-04-07T05:25:53Z2015-04-07T05:25:53ZDeception Island – the Antarctic volcano that just doesn’t make any sense<figure><img src="https://images.theconversation.com/files/76945/original/image-20150402-9345-1v3ssc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Deception wrong-footed scientists three times in ten years, and remains a mystery</span> <span class="attribution"><a class="source" href="http://onlinelibrary.wiley.com/doi/10.1029/2004JB003046/full">Wikimedia</a></span></figcaption></figure><p>Only two volcanoes in Antarctica are active. There is <a href="http://erebus.nmt.edu">Mount Erebus</a>, which is roughly due south of New Zealand, and Deception Island, which lies about 850km south east of Cape Horn. </p>
<p>Mt Erebus has been erupting continuously over the last few decades. Yet the rather smaller Deception Island, in the South Shetland archipelago, is responsible for the largest known eruption in the Antarctic area.</p>
<p>This horseshoe-shaped cauldron-like structure, or <a href="http://geology.com/articles/caldera/">caldera</a>, was produced more than 10,000 years ago by an explosive eruption that scattered more than 30km³ of molten rock. The result is an enclosed welcoming bay called <a href="http://www.britannica.com/EBchecked/topic/470878/Port-Foster">Port Foster</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/76951/original/image-20150402-9306-mzxjn5.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/76951/original/image-20150402-9306-mzxjn5.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/76951/original/image-20150402-9306-mzxjn5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=560&fit=crop&dpr=1 600w, https://images.theconversation.com/files/76951/original/image-20150402-9306-mzxjn5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=560&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/76951/original/image-20150402-9306-mzxjn5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=560&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/76951/original/image-20150402-9306-mzxjn5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=704&fit=crop&dpr=1 754w, https://images.theconversation.com/files/76951/original/image-20150402-9306-mzxjn5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=704&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/76951/original/image-20150402-9306-mzxjn5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=704&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Deception Island from above.</span>
<span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File:Deception_Island_map.png#/media/File:Deception_Island_map.png">Wikimedia</a></span>
</figcaption>
</figure>
<p>Deception was <a href="http://www.deceptionisland.aq/history.php">officially discovered</a> by the British sealing captain William Smith in 1820 and was subsequently used for purposes such as seal hunting and whaling before finding its modern calling as a site for science and tourism. Maybe because you cannot see most of the volcano above the sea, tourists rarely appreciate its hidden destructive potential.</p>
<h2>The big blunder</h2>
<p>Claimed in the past by the UK, Chile and Argentina, it provides a unique enclosed environment in which to monitor a “volcano under the ice”. All three of those aforementioned countries financed observatories there in the 1960s (Spain added its own in 2000).</p>
<p>Yet two consecutive volcanic eruptions in 1967 and 1969 went unpredicted – remarkable failures in the history of <a href="https://theconversation.com/the-very-useful-art-of-assessing-a-supervolcano-without-making-it-erupt-36277">volcano monitoring</a>. Only the Argentinian and the Spanish observatories still exist.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/76969/original/image-20150402-9309-p9cytk.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/76969/original/image-20150402-9309-p9cytk.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/76969/original/image-20150402-9309-p9cytk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=409&fit=crop&dpr=1 600w, https://images.theconversation.com/files/76969/original/image-20150402-9309-p9cytk.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=409&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/76969/original/image-20150402-9309-p9cytk.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=409&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/76969/original/image-20150402-9309-p9cytk.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=514&fit=crop&dpr=1 754w, https://images.theconversation.com/files/76969/original/image-20150402-9309-p9cytk.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=514&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/76969/original/image-20150402-9309-p9cytk.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=514&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="source" href="https://www.google.co.uk/maps/place/Deception+Island,+Antarctica/@-49.7823323,-59.9212153,3z/data=!4m2!3m1!1s0xbc77305ea493cecb:0x31c3841136415bef">Google Maps</a></span>
</figcaption>
</figure>
<h2>Mud from down below</h2>
<p>The volcanic events at Deception fall into a rare category called subglacial eruptions. The island is situated in a place where there is a glacier on the ocean floor about 100m thick. Scientists would normally expect that if this were hit by lava from below, it would evaporate benignly into steam. </p>
<p>But the lava moving upwards at Deception has several qualities that made things happen differently: it moves slowly and it has high water content. This meant that it turned the glacier into meltwater as well as steam, creating a large overflow of mud to the surface. This was the <a href="http://nora.nerc.ac.uk/17425/">main cause</a> of the destruction of the UK and Chilean stations. </p>
<p>The reason why this melting was unexpected was because in scientific terms the glacier was <a href="http://nora.nerc.ac.uk/17425/">“deceptively thin”</a>. The scientists were not expecting it to produce much more than steam. Ironically, the absence of larger glaciers is what made the island the most hospitable location in Antarctica.</p>
<p>We understand these subglacial eruptions much better now than we did in the 1960s. Nowadays <a href="http://digital.csic.es/bitstream/10261/101780/3/Bartolini_2014_Journal_of_Volcanology_and_geothermal_research_285%20150%20version%20aam.pdf">there are</a> hazard maps to make visitors aware of the higher-risk spots on the island.</p>
<h2>The Deception enigma</h2>
<p>Yet from a volcanic point of view, Deception is a great puzzle. Many volcanoes are caused by <a href="http://www.livescience.com/43220-subduction-zone-definition.html">subduction</a>, which is where two of the Earth’s tectonic plates crash against one another, sending one plate down and pushing the other upwards. A classic example is the <a href="http://www.britannica.com/EBchecked/topic/97772/Cascade-Range">Cascade range</a> in the north-western US, whose most famous volcano is Mt St Helens. The ones that scientists have observed happen on land. </p>
<p>Most volcanoes at sea are like Hawaii and the Azores, which we describe as <a href="http://volcano.oregonstate.edu/what-is-a-hot-spot">hot spots</a>. Instead of taking place near the points between tectonic plates, these are holes in the ocean floor where there is a direct line to the Earth’s mantle. The same goes for submerged calderas in the middle of the ocean, of which there are <a href="https://books.google.co.uk/books?id=V9EsoUOLvYsC&pg=PA40&lpg=PA40&dq=submerged+caldera&source=bl&ots=GRZLEexN-z&sig=lbtiyw3AENU2OA4lPt6zplV2j1Y&hl=en&sa=X&ei=qmYdVYeaDoreaNLngtgD&ved=0CEwQ6AEwCQ#v=onepage&q=submerged%20caldera&f=false">some examples</a> near Japan. </p>
<p>For a time, scientists thought that Deception might be an unusual example of subduction happening in the ocean. But a more recent <a href="http://onlinelibrary.wiley.com/doi/10.1029/2004JB003046/full">hypothesis is that</a> the South Shetlands may be what we call a rift zone. This would mean that it is on a point where plates meet, but instead of colliding, there are gaps from them moving away from each other, creating new oceanic crust in the process. A good example of a rift zone is the <a href="http://www.metoffice.gov.uk/news/releases/latest/volcano/iceland">Iceland</a>, as can be seen in the video eruption below. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/zLOIvrxmbxo?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<h2>The hydrocarbon connection</h2>
<p>Detailed geophysical surveys have been carried out across Deception since 2000, mainly financed by Spanish projects. UK geological research on the island has also been extensive. </p>
<p>You may be wondering why governments have spent so much on research there. Don’t be fooled into thinking that this is some kind of place of virtue where different nations fund research just to understand how our Earth works.</p>
<p>Rifts fill up with the remains of volcanic explosions and other sediment eroded from the margins of the valley. This process is critical for the production of oil. Located at the western edge of the arc, Deception is the ideal place to observe rift processes because of the natural harbour, which shelters scientists from the harsh Antarctic weather.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/76972/original/image-20150402-9306-1t7wmec.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/76972/original/image-20150402-9306-1t7wmec.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/76972/original/image-20150402-9306-1t7wmec.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/76972/original/image-20150402-9306-1t7wmec.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/76972/original/image-20150402-9306-1t7wmec.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/76972/original/image-20150402-9306-1t7wmec.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/76972/original/image-20150402-9306-1t7wmec.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/76972/original/image-20150402-9306-1t7wmec.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">Maybe he can shed light on the situation.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/cmichel67/8400355456/in/photolist-72zRzr-67We48-pL29pu-pLvX8o-6bpsFx-qGG4DT-9wygeN-dNj21L-xBqqu-bnoL9h-9UB8CQ-9wvgKv-abi9EZ-9wvgtZ-bAiDbx-abkX95-abhKCv-9wvjWa-9wyhjj-dNj235-pKGqnt-xBr2Q-abhLzi-abkDTw-9wviet-9wygTh-9wyh49-abkvNm-9wvjmr-9wvdoa-9wvcZR-9wyip5-9wvmne-9wyefs-9wyeCJ-9wycKf-9wydVq-9wyidA-9wvhkX-9wyhLu-9wveiF-9wygwj-ab13g1-9tNUNs-9tKBhZ-9tJuur-9tJt2r-9tJtzK-9tHZRR-9tKYL4">Christopher Michel</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Rifting is the reason for all the oil in the North Sea. The oil is not deposited where the rift is located, but some distance away. In the same way, there is almost no likelihood of an oil discovery on Deception. But understanding the process of rifting there will be a strong indication that there is oil to the north of the South Shetland Islands. It would also confer an exploration advantage worldwide – so Deception without oil is as valuable as Deception with oil.</p>
<p>So Deception could be the key to unveiling how rifts form and where oil is, in places where resources are unexploited. In an era where the political claims to the Antarctic have long since receded, that should ensure that this frozen corner of the world remains important for some time to come.</p><img src="https://counter.theconversation.com/content/37861/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>Deception is the premier tourist destination in the Antarctic. It’s also the volcano that scientists are still not sure why it’s there.Luca De Siena, Lecturer in Geophysics, University of AberdeenDavid Macdonald, Professor of Petroleum Geology, University of AberdeenLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/362772015-01-15T06:03:10Z2015-01-15T06:03:10ZThe very useful art of assessing a supervolcano without making it erupt<figure><img src="https://images.theconversation.com/files/69058/original/image-20150114-3891-fqh8a2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">If Campi Flegrei ever goes off, you won't want to be in Naples - or Europe!</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/emainthecoffee/476237979/in/photolist-J5QXD-drW76x-9fCX6g-8KZKw4-7iK4vz-f7KXLt-9NM1by-pMc4Ky-81Y6a2-qwfeyi-o3hwrZ-gvR4QZ-gME3KC-hycMvd-arFHsZ-pRzJ1H-7J285W-fEn3Lj-6hVsmj-6hVsmh-5ZJLMc-pNzJrG-fDL3Cw-pdQkJK-q3iRV5-a884et-kjcowK-ocz19m-otij4z-q6zDa3-cEZRW1-jvqaXU-cv6e5o-cv6ez9-fDu8na-cYbs7o-obqhor-cKTAUN-gGY9Li-iDkd3Y-b5SiDp-hdTkQe-gRiWPC-c2QDd1-cKUMNS-yrzJf-drWfkS-5XFc6w-jcK847-hJMPg7">Emanuele Nicastro</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Ever heard of <a href="http://www.volcanodiscovery.com/campi-flegrei.html">Campi Flegrei</a>? It is a supervolcano in southern Italy. Literally translating as “fields of fire,” only the <a href="http://io9.com/what-will-really-happen-when-yellowstone-volcano-has-a-508274690">Yellowstone caldera</a> in the United States has more potential to devastate. </p>
<p>The Naples urban area, with its four million inhabitants, extends within this amazing volcanic complex, though it lies mostly beneath the sea. The last time that Campi Flegrei <a href="http://www.geo.mtu.edu/volcanoes/boris/mirror/mirrored_html/Montenuovo.html">erupted was</a> less than 500 years ago, in 1538. It was one of the volcano’s smallest eruptions down the millennia, but it lasted a week and killed 24 people. </p>
<h2>The risks</h2>
<p>You may think that the chance of living in a city where the weather is nice and warm and you smell history at every corner is well worth the volcanic risk. But before buying the tickets, note that Campi Flegrei and <a href="http://www.bbc.co.uk/science/earth/collections/mount_vesuvius">Mt Vesuvius</a>, his more famous and much smaller brother (remember Pompei?) are just the visible scars of a supervolcano whose <a href="http://www.vuelco.net/campi2.php">previous eruptions</a> 35,000 and 15,000 years ago spread volcanic materials over an area of 10,000 sq km. The effects of an eruption of Campi Flegrei could dwarf those of any eruption recorded in human history, and, in the worst-case scenario, challenge human life on the old continent.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/69050/original/image-20150114-3859-13vqcls.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/69050/original/image-20150114-3859-13vqcls.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/69050/original/image-20150114-3859-13vqcls.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=382&fit=crop&dpr=1 600w, https://images.theconversation.com/files/69050/original/image-20150114-3859-13vqcls.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=382&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/69050/original/image-20150114-3859-13vqcls.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=382&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/69050/original/image-20150114-3859-13vqcls.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=480&fit=crop&dpr=1 754w, https://images.theconversation.com/files/69050/original/image-20150114-3859-13vqcls.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=480&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/69050/original/image-20150114-3859-13vqcls.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">Vesuvius: big brother’s little brother.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/glosters/3704149196/in/photolist-5BMQME-cCZXis-8ZASJi-dNfef1-7z1jBX-bp5avf-9LDioy-a3Rswx-a3Ui8Y-ezHgdK-6DjJvj-dXEHk9-2fuJfs-KZ9cg-gMD3zD-8ZE1qf-dYYK36-5Vje4X-9VDe23-5zkK6f-4NUrvD-4y5eLQ-cCZUfG-npkHNg-8bjVu6-7b3Wd4-nBj2ec-98LF9y-823jhT-bXgFip-8NHQEg-buGCFj-f28U3R-5uiYBD-4eZMQz-pNPkBN-bgVpdR-oS68A-4phaG8-pHCTi-49Q4MY-98EBqE-546erG-6TY9j9-98EBV1-pjfVT9-2ra2Sv-5jLZMy-bLgdR6-7t2Jqd">shipscompass</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>This is possibly the moment where you start thinking about what scientists are doing to understand if and when such an eruption will take place. The good news is that the <a href="http://www.ov.ingv.it/ov/en.html">Vesuvius Observatory</a> (OV), monitoring both Mt Vesuvius and Campi Flegrei, is the oldest volcanology observatory in the world. Here geologists, geophysicists, and physicists join forces in a unique environment to understand what’s beneath these volcanoes.</p>
<h2>Drilling and drawbacks</h2>
<p>A good example is the <a href="http://www.icdp-online.org/projects/world/europe/campi-flegrei/">EU deep drilling project</a>, which the OV sponsors. The idea is simple: you drill to a depth of 2.5 miles inside Campi Flegrei caldera to get sensitive scientific data and rock samples, and obtain geothermal energy from the heated volcanic complex. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/69061/original/image-20150114-3874-1y2622y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/69061/original/image-20150114-3874-1y2622y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/69061/original/image-20150114-3874-1y2622y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/69061/original/image-20150114-3874-1y2622y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/69061/original/image-20150114-3874-1y2622y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/69061/original/image-20150114-3874-1y2622y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/69061/original/image-20150114-3874-1y2622y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/69061/original/image-20150114-3874-1y2622y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Ah southern Italy: sun, sea… and lots of boiling lava.</span>
<span class="attribution"><span class="source">Luca de Siena</span></span>
</figcaption>
</figure>
<p>But what happens when you drill an active caldera like this one? As with many simple ideas, this project has been accused of being simplistic and <a href="http://www.popsci.com/science/article/2011-01/what-could-possibly-go-wrong-deep-drilling-supervolcano">somewhat dangerous</a>, due to the fact that the drilling itself may cause changes in the state of the volcanic complex, triggering earthquakes and, possibly, a volcanic eruption.</p>
<p>This is a perfect example of striking the balance between not doing enough to prevent a catastrophe, and doing too much. In the case of Campi Flegrei, the drilling was stopped by the local authority after only a preliminary hole had been drilled. <a href="http://www.icdp-online.org/projects/world/europe/iceland/">In other volcanoes</a>, the drilling caused no problems, but the debate about the safety of the technique rages on – and it has the added disadvantage of being very expensive. </p>
<p>A possible solution may come from another, completely different question: is there another way to “see” inside a volcano without drilling? Using modern technology, we can look at distant stars and inside our own bodies. Can we do the same with a volcano? The answer is that although it is not the same, we can. </p>
<h2>How attenuation tomography works</h2>
<p>You can’t use light to look into the Earth, at least not the “light” we employ to look at the cosmos. And there is no instrument that can scan a volcano like we can do with a human body. But the Earth and, to an even greater extent, volcanoes, talk to us continuously – although our ears are not particularly good at listening. Notice that I say “listening” rather than “looking,” since the sound waves from our voices are in fact the most similar to the Earth’s way of expression: earthquakes, producing elastic waves.</p>
<p>When a strong earthquake happens it is similar to a shout that we record by measuring vibrations on the Earth’s surface. We can use this shout to <a href="http://www.iris.edu/hq/files/programs/education_and_outreach/aotm/7/SeismicTomography_Background.pdf">scan the</a> deep Earth interior, looking at how and where the velocity of the waves is changed by the medium. </p>
<p>Having said that, the voice of a large tectonic earthquake is actually quite plain. A supervolcano like Campi Flegrei speaks in much more interesting and various ways, with magma and hot fluids creating a song of continuous drumbeats and blasts.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/69053/original/image-20150114-3888-m7vizx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/69053/original/image-20150114-3888-m7vizx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/69053/original/image-20150114-3888-m7vizx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=404&fit=crop&dpr=1 600w, https://images.theconversation.com/files/69053/original/image-20150114-3888-m7vizx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=404&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/69053/original/image-20150114-3888-m7vizx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=404&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/69053/original/image-20150114-3888-m7vizx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=508&fit=crop&dpr=1 754w, https://images.theconversation.com/files/69053/original/image-20150114-3888-m7vizx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=508&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/69053/original/image-20150114-3888-m7vizx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=508&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Campi Flegrei’s sulphurous nostrils.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/ekieram/1843803321/in/photolist-3NVYur-dqEhg1-oM7MZH-8Jpqj6-8JnRD4-8Jpk9t-8Jr1XQ-8Jr1wj-8JpkVD-8Jr6RN-8Jss8U-8JpNbX-8JsP2U-8JnQJi-8JnUue-8JsGXJ-8JsxqC-8JqTtS-8JqT1y-8JsPmu-8JnNuB-8Jo4ut-8JssZd-8JpLTH-8JnQg8-8JsL3N-8JsJ95-8JpHKK-8JsJyY-8JpCqM-8Jr2mA-8JsxPY-8Jrft7-8JpDEn-8JnYxz-8JqUR9-8JnN5F-8JnSBe-8Jr181-8Jptqt-8JsCR9-8JpqKP-8JpJXx-8JsBzm-8JqYBY-8JrcMu-8JpBG4-8JsALm-8JsQbm-8Jobn6">EkieraM</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Volcano seismologists use this energy to produce images of what’s inside them. Here’s how this works, in simple terms. Think of loud music coming out of a stereo (the earthquake). If the stereo is in your room, you hear it strong and clear (the louder the nearer you are to it). </p>
<p>Now put a wall between you and the stereo. The volume is lowered as the sound energy is either reflected by the wall or lost inside it. If you are able to measure which notes are lost the most and where “the wall” is you are performing an “attenuation tomography”: only that, instead of the wall, we are talking about a magmatic chamber. </p>
<p>This technique is still relatively new. The Japanese developed it for their volcanoes in the 1990s, but it is only in the past decade that it has reached the West. It has also been applied to Mt St Helen in the north-western US and some South American volcanoes, but not yet to Yellowstone. </p>
<p>In combination with other geophysical and geological observations, we have used this technique to establish that there is <a href="http://onlinelibrary.wiley.com/doi/10.1029/2009JB006938/abstract">no large magmatic chamber</a> under Campi Flegrei between 0km and 4km depth – at least there wasn’t during the last seismic crisis, which <a href="http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CDYQFjAD&url=http%3A%2F%2Felea.unisa.it%3A8080%2Fjspui%2Fbitstream%2F10556%2F1486%2F1%2Ftesi_I_Sabbetta.pdf&ei=Os-2VOz0JYXxaozsgYAE&usg=AFQjCNHbJ398rAyVP8xGLCk7WOLnJarf3Q&sig2=NWa4TTGL3dB39srGwk0Uuw&bvm=bv.83640239,d.ZWU">was between</a> 1980 and 1984. </p>
<p>So if you were thinking about relocating to southern Italy, perhaps this suggests that you would be safe and sound. It probably does mean that there is no immediate risk of an eruption of lava or magma, though you could still see eruptions of gas and fluids (a so-called phreatic eruption). </p>
<p>The volcano is alive and “breathes,” even inside the Naples urban area. You can see it in the way its surface goes <a href="http://whc.unesco.org/en/tentativelists/2030/">up and down</a> each year and you can smell it from the steam produced by the holes that the volcano <a href="http://www.tripadvisor.co.uk/LocationPhotoDirectLink-g187785-i67186179-Naples_Province_of_Naples_Campania.html">has opened</a> on the Earth’s surface. </p>
<p>This “breathing” is a constant reminder to those living in the area, though it is possibly good news. You can think of it like a bottle of champagne continually losing pressure. Having said that, we do not know what’s happening deeper underground – except that there is probably <a href="http://onlinelibrary.wiley.com/doi/10.1029/2008GL034242/full">magma at a depth of 8 km</a>, which is quite a long way down, feeding both Campi Flegrei and Mt. Vesuvius. If magma is recharged and heated continuously, the pressure could grow and the lava could arrive to the surface very quickly – though with clear signs days/weeks before the eruption.</p>
<p>A volcano scientist monitoring Campi Flegrei uses all these senses to understand what he would see if we could actually drill a large hole in the ground. Although we are still not perfect at it, we have at least started listening to Campi Flegrei’s voice.</p><img src="https://counter.theconversation.com/content/36277/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Luca spent four years working for the Vesuvius Observatory, including three at PhD level and one as a post-doc </span></em></p>Ever heard of Campi Flegrei? It is a supervolcano in southern Italy. Literally translating as “fields of fire,” only the Yellowstone caldera in the United States has more potential to devastate. The Naples…Luca De Siena, Lecturer, University of AberdeenLicensed as Creative Commons – attribution, no derivatives.