tag:theconversation.com,2011:/institutions/us-geological-survey-2092/articlesUS Geological Survey2022-02-17T05:11:47Ztag:theconversation.com,2011:article/1772492022-02-17T05:11:47Z2022-02-17T05:11:47ZMengapa kita tidak buang saja semua sampah kita ke gunung berapi dan membakarnya?<p><a href="https://theconversation.com/id/topics/curious-kids-83797"><img src="https://images.theconversation.com/files/386375/original/file-20210225-21-1xfs1le.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=90&fit=crop&dpr=2" width="100%"></a></p>
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<blockquote>
<p><strong>Mengapa kita tidak buang saja semua sampah kita ke gunung berapi dan membakarnya? – Georgine T.</strong></p>
</blockquote>
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<p>Memang benar, lahar panas (lava) cukup panas untuk membakar sampah-sampah kita.</p>
<p>Saat gunung berapi Kilauea meletus di Hawaii pada tahun 2018, lava yang mengalir panasnya <a href="https://www.usgs.gov/media/images/lava-temperatures-were-about-2000-degrees-fahrenheit">lebih dari 1.100 Celsius</a>. Ini lebih panas dari <a href="https://solarsystem.nasa.gov/planets/venus/overview/">permukaan Planet Venus</a>, dan bisa melelehkan bebatuan. Lava tersebut juga sepanas alat di fasilitas pembakaran sampah yang biasanya <a href="https://www3.epa.gov/ttnchie1/mkb/documents/fthermal.pdf">mencapai 1.000-1.200 C</a>.</p>
<p>Tapi tidak semua lava punya suhu yang sama.</p>
<p>Letusan di Hawaii menghasilkan suatu jenis lava bernama <a href="https://volcanoes.usgs.gov/vsc/glossary/basalt.html">basal</a>. Jenis lava ini jauh lebih panas dan encer daripada lava yang biasanya mengalir dari letusan gunung berapi lainnya, seperti lava jenis <a href="https://volcanoes.usgs.gov/vsc/glossary/dacite.html">dasit</a> yang tumpah dari Gunung St. Helens di Washington, Amerika Serikat (AS). Misalnya, letusan Gunung St. Helens selama tahun 2004-2008 mengasilkan kubah lava dengan suhu permukaan yang kurang dari 704 C.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Infographic on number and location of U.S. volcanoes" src="https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?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>
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<span class="caption">Ilmuwan mengawasi gunung berapi dan memberikan peringatan pada masyarakat sekitar jika mereka melihat tanda-tanda meletus.</span>
<span class="attribution"><a class="source" href="https://www.usgs.gov/media/images/us-one-earths-most-volcanically-active-countries">USGS</a></span>
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<p>Selain suhu, ada alasan lain mengapa membuang sampah ke gunung berapi bukanlah ide yang bagus.</p>
<p>Pertama, meski lava yang bersuhu 1.000 C bisa saja melelehkan banyak benda di tempat sampah kita – termasuk sisa makanan, kertas, plastik, serta beberapa jenis kaca dan logam – suhunya tidak cukup panas untuk melelehkan banyak material lainnya yang cukup umum, termasuk <a href="https://www.americanelements.com/meltingpoint.html">baja, nikel, dan besi</a>.</p>
<p>Kedua, tidak banyak gunung berapi di bumi ini yang memiliki danau lava, atau semacam kawah berbentuk mangkuk berisi lava, yang bisa jadi tempat pembuangan sampah.</p>
<p>Dari ribuan gunung berapi di bumi, ilmuwan hanya mengenali <a href="https://www.bbc.co.uk/newsround/48856373">delapan danau lava aktif</a>. Di antaranya ada <a href="https://www.usgs.gov/media/images/new-usgs-video-about-k-laueas-summit-eruption-now-online">Gunung Kilauea</a>, <a href="https://volcano.si.edu/volcano.cfm?vn=390020">Gunung Erebus</a> di Antartika, dan <a href="https://volcano.si.edu/volcano.cfm?vn=223030">Gunung Nyiragongo</a> di Kongo. Sebagian besar gunung berapi aktif memiliki kawah yang berisi bebatuan dan lava dingin, seperti <a href="https://www.usgs.gov/volcanoes/mount-st-helens/lava-flows-mount-st-helens">Gunung St. Helens</a>, atau berisi air, seperti <a href="https://www.usgs.gov/media/images/crater-lake-caldera-wizard-island-cinder-cone-and-lava-flows">Danau Crater</a> di Oregon, AS.</p>
<p>Ketiga, membuang sampah ke delapan danau lava aktif tersebut pun adalah hal yang tidak mudah dan sangat berbahaya.</p>
<p>Danau lava diselimuti oleh kerak lava yang sudah mendingin, namun tepat di bawahnya terdapat lapisan yang masih berbentuk lelehan panas. Jika bebatuan atau material lain jatuh ke permukaan suatu danau lava, maka keraknya akan hancur, mengusik lava di bawahnya dan kemudian menyebabkan ledakan.</p>
<p>Hal ini terjadi di Kilauea pada tahun 2015. Bongkahan batu dari pinggiran kawah jatuh ke danau lava dan menyebabkan ledakan besar yang <a href="https://www.usgs.gov/media/videos/rockfall-and-explosion-halemaumau-crater">melontarkan bebatuan dan lava</a> keluar dari kawah. Siapapun yang melempar sampah ke danau lava harus berlari menjadi dengan sangat cepat sembari menghindari lontaran lava dan sampah yang terbakar.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/w8IaG2U65Is?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Suatu letusan dari Gunung Cumbre Vieja di Pulau La Palma, Spanyol pada tahun 2021 menghasilkan awan gas beracun.</span></figcaption>
</figure>
<p>Mari kita berandai-andai: jika memungkinkan untuk membuang sampah secara aman ke suatu danau lava, apa yang akan terjadi pada sampah tersebut? </p>
<p>Saat plastik, sampah, dan logam terbakar, mereka menghasilkan banyak sekali gas beracun. Pada, gunung berapi sudah menghasilkan ribuan kilogram gas beracun, termasuk sulfur, klorin, dan karbon dioksida.</p>
<p>Gas sulfur dapat menciptakan kabut asam, atau sering disebut “<em>vog</em>” (<em>volcanic fog</em> atau kabut vulkanis). Kabut ini dapat <a href="https://www.usgs.gov/observatories/hawaiian-volcano-observatory/volcanic-gas">membunuh tumbuhan dan menyebabkan penyakit pernapasan</a> bagi masyarakat sekitar. Bercampurnya gas vulkanis yang sudah berbahaya ini dengan gas lain dari pembakaran sampah akan menghasilkan gas yang jauh lebih berbahaya lagi bagi <a href="https://www.usgs.gov/media/images/lava-breakouts-access_roa">orang dan tumbuhan</a> di sekitar gunung berapi.</p>
<p>Terakhir, banyak komunitas adat menganggap gunung berapi sebagai kawasan yang sakral.</p>
<p>Misalnya, Kawah Halema’uma’u di Gunung Kilauea dianggap sebagai rumah dari Pele, Dewi Api di Hawaii, dan kawasan di sekitar kawah tersebut <a href="https://www.hawaii.com/discover/culture/pele/">sangat sakral bagi penduduk asli Hawaii</a>. Membuang sampah ke gunung berapi bisa jadi suatu hinaan bagi budaya-budaya tersebut.</p>
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<p class="fine-print"><em><span>Emily Johnson menerima dana dari U.S. Geological Survey.</span></em></p>Lava dari gunung berapi punya suhu yang sangat panas. Tapi menjadikannya tempat pembuangan sampah tak hanya berbahaya tapi juga tak menghargai masyarakat adat yang menganggapnya sebagai situs sakral.Emily Johnson, Research Geologist, US Geological SurveyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1709192022-01-03T13:42:00Z2022-01-03T13:42:00ZWhy can’t we throw all our trash into a volcano and burn it up?<figure><img src="https://images.theconversation.com/files/435952/original/file-20211206-141213-f6fuq.jpg?ixlib=rb-1.1.0&rect=49%2C0%2C5472%2C3645&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lava flows from a fissure in the aftermath of eruptions from the Kilauea volcano on Hawaii's Big Island, May 22, 2018. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/lava-flows-from-a-fissure-in-the-aftermath-of-eruptions-news-photo/962057980">Andrew Richard Hara/Ena Media Hawaii 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>
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<blockquote>
<p><strong>Why can’t we throw all our trash into a volcano and burn it up? – Georgine T.</strong></p>
</blockquote>
<hr>
<p>It’s true that lava is hot enough to burn up some of our trash. When Kilauea erupted on the Big island of Hawaii in 2018, the lava flows were <a href="https://www.usgs.gov/media/images/lava-temperatures-were-about-2000-degrees-fahrenheit">hotter than 2,000 degrees Fahrenheit (1,100 Celsius)</a>. That’s hotter than <a href="https://solarsystem.nasa.gov/planets/venus/overview/">the surface of the planet Venus</a>, and hot enough to melt many rocks. It’s also as hot as waste incinerators, which usually burn garbage at <a href="https://www3.epa.gov/ttnchie1/mkb/documents/fthermal.pdf">1,800 to 2,200 F</a> (1,000-1,200 C). </p>
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<p>But not all lavas are the same temperature. The eruptions in Hawaii produce a type of lava called <a href="https://volcanoes.usgs.gov/vsc/glossary/basalt.html">basalt</a>. Basalt is much hotter and more fluid than the lavas that erupt at other volcanoes, like the thicker <a href="https://volcanoes.usgs.gov/vsc/glossary/dacite.html">dacite lava</a> that erupts at Mount St. Helens in Washington state. For example, the 2004-2008 eruption at Mount St. Helens produced a lava dome with surface temperatures less than about 1,300 F (704 C). </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Infographic on number and location of U.S. volcanoes" src="https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/435957/original/file-20211206-21-16nxx9j.jpeg?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">There are 161 volcanoes in 14 U.S. states and territories. Scientists monitor them and warn nearby communities if they see signs that a volcano may erupt.</span>
<span class="attribution"><a class="source" href="https://www.usgs.gov/media/images/us-one-earths-most-volcanically-active-countries">USGS</a></span>
</figcaption>
</figure>
<p>Beyond temperature, there are other good reasons not to burn our trash in volcanoes. First, although lava at 2,000 degrees F can melt many materials in our trash – including food scraps, paper, plastics, glass and some metals – it’s not hot enough to melt many other common materials, including <a href="https://www.americanelements.com/meltingpoint.html">steel, nickel and iron</a>. </p>
<p>Second, there aren’t many volcanoes on Earth that have lava lakes, or bowl-like craters full of lava, that we could dump trash into. Of all of the thousands of volcanoes on Earth, scientists know of only <a href="https://www.bbc.co.uk/newsround/48856373">eight with active lava lakes</a>. They include <a href="https://www.usgs.gov/media/images/new-usgs-video-about-k-laueas-summit-eruption-now-online">Kilauea</a>, <a href="https://volcano.si.edu/volcano.cfm?vn=390020">Mount Erebus in Antarctica</a> and <a href="https://volcano.si.edu/volcano.cfm?vn=223030">Nyiragongo in the Democratic Republic of the Congo</a>. Most active volcanoes have craters filled with rocks and cooled lava, like <a href="https://www.usgs.gov/volcanoes/mount-st-helens/lava-flows-mount-st-helens">Mount St. Helens</a>, or with water, like <a href="https://www.usgs.gov/media/images/crater-lake-caldera-wizard-island-cinder-cone-and-lava-flows">Crater Lake in Oregon</a>. </p>
<p>The third problem is that dumping trash into those eight active lava lakes would be a very dangerous job. Lava lakes are covered with a crust of cooling lava, but just below that crust they are molten and intensely hot. If rocks or other materials fall onto the surface of a lava lake, they will break the crust, disrupt the underlying lava and cause an explosion. </p>
<p>This happened at Kilauea in 2015: Blocks of rock from the crater rim fell into the lava lake and caused a big explosion that <a href="https://www.usgs.gov/media/videos/rockfall-and-explosion-halemaumau-crater">ejected rocks and lava up and out of the crater</a>. Anyone who threw garbage into a lava lake would have to run away and dodge flaming garbage and lava.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/w8IaG2U65Is?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">An eruption from the Cumbre Vieja volcano on the Spanish island of La Palma on Sept. 30, 2021, produced clouds of toxic gas.</span></figcaption>
</figure>
<p>Suppose it was possible to dump trash safely into a lava lake: What would happen to the trash? When plastics, garbage and metals burn, they release a lot of toxic gases. Volcanoes already give off tons of toxic gases, including sulfur, chlorine and carbon dioxide. </p>
<p>Sulfur gases can create acidic fog, which we call “vog,” for “volcanic fog.” It can <a href="https://www.usgs.gov/observatories/hawaiian-volcano-observatory/volcanic-gas">kill plants and cause breathing problems for people nearby</a>. Mixing these already-dangerous volcanic gases with other gases from burning our trash would make the resulting fumes even more harmful for <a href="https://www.usgs.gov/media/images/lava-breakouts-access_road">people and plants near the volcano</a>. </p>
<p>Finally, many indigenous communities view nearby volcanoes as sacred places. For example, Halema’uma’u crater at Kilauea is considered the home of Pele, the native Hawaiian goddess of fire, and the area around the crater is <a href="https://www.hawaii.com/discover/culture/pele/">sacred to native Hawaiians</a>. Throwing trash into volcanoes would be a huge insult to those cultures.</p>
<hr>
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<p class="fine-print"><em><span>Emily Johnson receives funding from the U.S. Geological Survey </span></em></p>Volcanoes might seem like nature’s incinerators, but using them to burn up trash would be dangerous and disrespectful to indigenous people who view them as sacred.Emily Johnson, Research Geologist, US Geological SurveyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1653522021-08-19T12:08:34Z2021-08-19T12:08:34ZWhen hotter and drier means more – but eventually less – wildfire<figure><img src="https://images.theconversation.com/files/415783/original/file-20210812-19-75kq61.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6038%2C4010&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Creek Fire burns near Shaver Lake, Calif., in the Sierra Nevada in September 2020.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/CaliforniaWildfires/fadd01e1646740c7ba63f68efdba0dc8/photo">AP Photo/Noah Berger</a></span></figcaption></figure><p>There is abundant evidence that changes in the climate, both <a href="https://www.pnas.org/content/113/42/11770">increased temperature</a> and <a href="https://www.pnas.org/content/115/36/E8349">reduced precipitation</a>, are making wildfires worse in the western U.S. The relationship between climate and wildfire seems obvious and universal: hotter + drier = more and worse wildfire.</p>
<p>Yet the diversity of wildland areas in the western U.S. means that <a href="https://doi.org/10.1002/eap.1420">not all ecosystems respond in the same way</a> to a hotter and drier climate. Understanding how and why climate change has different effects on wildfire is essential for effective management of our natural areas. </p>
<figure class="align-center ">
<img alt="A satellite-view map showing fire area with Yellowstone, the Sierra Nevada and the Sonoran Desert ecoregions marked" src="https://images.theconversation.com/files/414006/original/file-20210730-25-14i23th.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/414006/original/file-20210730-25-14i23th.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=812&fit=crop&dpr=1 600w, https://images.theconversation.com/files/414006/original/file-20210730-25-14i23th.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=812&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/414006/original/file-20210730-25-14i23th.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=812&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/414006/original/file-20210730-25-14i23th.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1020&fit=crop&dpr=1 754w, https://images.theconversation.com/files/414006/original/file-20210730-25-14i23th.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1020&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/414006/original/file-20210730-25-14i23th.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1020&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">All wildfires over about 12 acres in size from 1984-2019. Red indicates fires from 2010-2019.</span>
<span class="attribution"><a class="source" href="https://mtbs.gov/viewer/index.html">Jeremy Littell</a></span>
</figcaption>
</figure>
<h2>Why do areas respond differently?</h2>
<p>Similar to campfires, wildfires require fuel to burn: parts of trees and shrubs, the leaves, twigs and branches. Dried grasses, too, will work. The growth of this vegetation depends on water, and water availability depends on the climate.</p>
<p>How hot and dry the climate is in an area influences the amount of fuel that is available to burn and the strength of the relationship between wildfire and climate. <a href="http://scholar.google.com/citations?user=36K8XrUAAAAJ&hl=en">Ecologists</a> <a href="https://scholar.google.com/citations?user=VEf_brUAAAAJ&hl=en">such as</a> <a href="https://scholar.google.com/citations?hl=en&user=-lHGpDIAAAAJ">us</a> calculate how closely related wildfire area burned is to how hot and dry it is during the summer, and we have found that the relationship does indeed vary.</p>
<p>Areas that are historically cool and wet have a lot of fuel, but the fuel has to be dry enough to burn, so the relationship in these areas between wildfire and climate is very strong. Areas that are historically warm and dry have less fuel, often not enough fuel for a large wildfire even if it is very dry.</p>
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<p>Let’s consider one extreme. The Sonoran Desert in Arizona is persistently hot and dry, and vegetation is sparse. The dryness of the summer, what we call the “summer water deficit,” does not control the extent and severity of wildfires. Summer is almost always hot and dry enough to burn, and how much it burns depends on the amount of fuel. No matter how much hotter and drier the climate becomes, wildfire is not going to increase unless more fuel appears on the landscape. Unfortunately, <a href="https://doi.org/10.2111/REM-D-09-00151.1">exotic grasses that are adapted to wildfire</a> are invading much of the American Southwest, including the Sonoran Desert, providing that extra fuel.</p>
<p>At the other extreme are mountain forests, such as Yellowstone National Park and the surrounding area, that have abundant vegetation and fuel and are cooler and wetter. There, the amount of land that burns is strongly related to the summer water deficit. Hotter and drier summers are likely to increase wildfire activity.</p>
<p>What about areas in between these two extremes?</p>
<h2>Where hotter and drier can eventually mean less fire</h2>
<p>In California, wildfires in the dry forests of the Sierra Nevada are partly controlled by summer water deficit. For a while, hotter and drier summers are likely to increase the amount of land burned each year. </p>
<p>We ran <a href="http://doi.org/10.1002/ecs2.3657">computer simulations</a> of the interactions among climate, plant growth and wildfire for one area within the Sierra Nevada. In the first decade of the simulations, an initial burst of large areas burned each year. This first pulse of wildfire burned more area in a scenario with increased drought and temperature than in the historical climate, just as we are seeing in the recent extreme fire seasons in the Sierra Nevada. </p>
<p>Over time, however, climate change will modify how plants grow. Persistently hotter and drier climate over decades will increase <a href="https://doi.org/10.1126/science.1165000">the number of dead and dying trees</a> and <a href="https://doi.org/10.1038/ngeo1571">decrease new growth</a>. Eventually less fuel is available to burn as the dead trees decompose and fewer live ones replace them. </p>
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<p>The same computer simulations show that the initial pulse of wildfires removes a lot of dense vegetation, and subsequent fires become smaller compared with fires in historical climate conditions and with increased drought and temperature. Furthermore, because hotter and drier conditions can eventually lead to less fuel development, the wildfire area burned over 60 years <a href="https://doi.org/10.1002/ecs2.3657">may be smaller</a> with increased drought and temperature than in the historical climate. </p>
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<p>Less wildfire due to climate change may sound like good news, but how it occurs is not necessarily a desirable outcome for these forests. In the simulations, reduced wildfire is a consequence of extreme water limitation that results in reduced forest biomass. This means less tree growth and more dying trees that eventually result in a thinner and less productive forest. If the climate changes enough, the trees may even be replaced by shrubs, which have their own unique relationship between climate and wildfire.</p>
<h2>The problem with quickly putting out every fire</h2>
<p>Human actions, in particular <a href="https://academic.oup.com/jof/article-abstract/92/1/39/4635874">putting out every fire</a>, have changed how dry forests burn. </p>
<p>Some fires are started by lightning, but Indigenous peoples burned the landscape frequently, reducing fuels, so the spread and intensity of subsequent wildfires was more limited. After European colonization, the U.S. government spent more than a century actively suppressing wildfires. As a result, many forests became choked with excess fuels. Even without climate change, excess fuels <a href="https://onlinelibrary.wiley.com/doi/toc/10.1002/(ISSN)1939-5582.climate-change-and-westernwildfires">increase the wildfire hazard</a>. </p>
<p>The effect of that fire suppression on current wildfire hazards can also vary from region to region. </p>
<p>In cooler and wetter areas, <a href="https://doi.org/10.1088/1748-9326/abd78e">climate change can have a stronger effect</a> on wildfires than fire suppression. These are the areas with naturally abundant fuel and strong relationships between climate and wildfire. In drier systems, where fuels were historically low and had limited wildfire spread, suppression over the past century can have a stronger effect on current wildfire hazard than in wetter areas. It is important to consider climate change, regional characteristics and land management, all of which affect the fuels that are available to burn in a wildfire.</p>
<h2>What to do about wildfire</h2>
<p>There is no single solution to the increasing wildfire activity and declining health of forests.</p>
<p>The global solution would be to slow and eventually reverse climate change. More locally, combining prescribed fires, which are intentionally set in relatively mild weather conditions, with mechanical removal of small trees and ground fuels is the best way to <a href="https://doi.org/10.1016/j.foreco.2016.05.021">prevent more severe wildfires</a>.</p>
<p><a href="https://theconversation.com/how-years-of-fighting-every-wildfire-helped-fuel-the-western-megafires-of-today-163165">Increasing the use of prescribed fire or allowing wildfires to burn</a> under safe conditions can restore some forests to be more resilient – those that have excess fuel from fire suppression – and reduce the hazards that the western U.S. is seeing now. Past wildfires can limit the spread of new wildfires by reducing the amount of vegetation and fuel available to burn.</p>
<p><img src="https://cdn.theconversation.com/static_files/files/1737/AnnualFiresCumulate.gif?1627675461" width="100%"> </p><figure><figcaption><span class="caption">Wildfire burn perimeters near Yosemite National Park, Calif., 2000-2019. The largest is the 2013 Rim Fire. <a href="https://www.mtbs.gov/">MTBS</a></span></figcaption></figure><p></p>
<p>Over the past five years, wildfires in the U.S. burned an <a href="https://www.nifc.gov/sites/default/files/document-media/SuppCosts.pdf">average of 7.8 million acres annually</a>, which cost an average of US$2.4 billion per year to fight. </p>
<p>Managing forests in the face of the threat of larger, more severe wildfires in a warming climate presents a huge challenge to fire managers, given the costs of treatments and the <a href="https://doi.org/10.5849/jof.16-067">millions of acres that could benefit from them</a>. Plenty of wildland is still <a href="https://doi.org/10.1890/ES15-00294.1">primed to burn</a>, and understanding the intricate relationship among climate, fuels and wildfire can help managers prioritize areas where more fire will be beneficial and areas where different approaches may be preferred.</p>
<p>[<em>Understand new developments in science, health and technology, each week.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-understand">Subscribe to The Conversation’s science newsletter</a>.]</p><img src="https://counter.theconversation.com/content/165352/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Maureen C Kennedy receives funding from the National Science Foundation and the US Forest Service. </span></em></p><p class="fine-print"><em><span>Don McKenzie received funding from the US Forest Service. </span></em></p><p class="fine-print"><em><span>Jeremy Littell receives funding from the United States Geological Survey. </span></em></p>Not all forests respond to hotter and drier conditions in the same way.Maureen C Kennedy, Assistant Professor of Quantitative Fire Ecology, University of WashingtonDon McKenzie, Professor of Environmental and Forest Sciences, University of WashingtonJeremy Littell, Research Ecologist - Climate Impacts, US Geological SurveyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/860432017-10-27T10:19:19Z2017-10-27T10:19:19ZWhy were California’s wine country fires so destructive?<figure><img src="https://images.theconversation.com/files/191970/original/file-20171026-28071-hc4dhy.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Burned area in Santa Rosa, California, Oct. 11, 2017.</span> <span class="attribution"><a class="source" href="https://www.defense.gov/Photos/Essay-View/CollectionId/17453/">US Department of Defense</a></span></figcaption></figure><p>As of late October more than a <a href="http://google.org/crisismap/google.com/2017-tubbs-fire">dozen wildfires</a> north of San Francisco had <a href="http://www.latimes.com/local/lanow/la-me-ln-fires-20171018-story.html">killed more than 40 people</a>, burned approximately 160,000 acres and <a href="http://calfire.ca.gov/communications/communications_StatewideFireSummary">destroyed more than 7,000 structures</a>. </p>
<p>This tragic loss of life and property is unprecedented in California. However, the fires are not anomalous events in terms of their size, intensity or the speed with which they spread. Indeed, the path of the destructive <a href="http://www.fire.ca.gov/current_incidents/incidentdetails/Index/1867">Tubbs fire</a> in Napa and Sonoma counties mirrors that of the <a href="http://www.sfchronicle.com/thetake/article/Wine-Country-fire-of-1964-Eerie-similarities-to-12267643.php">Hanley fire of 1964</a>. This extreme wind-driven fire burned under similar conditions, across much of the same landscape and covered an area substantially greater than the recent Tubbs fire. </p>
<p>Strikingly, though, no lives were lost during the Hanley fire and only 29 structures were destroyed. Why did these two fires, 50 years apart, burn on the same general landscape, under similar extreme winds, with such different human impacts? Fire scientists will study these events intensively to parse out the relative importance of various factors. But it is clear that two factors probably were major contributors: wind and population growth.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/191961/original/file-20171026-28030-1j42pgu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/191961/original/file-20171026-28030-1j42pgu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/191961/original/file-20171026-28030-1j42pgu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=444&fit=crop&dpr=1 600w, https://images.theconversation.com/files/191961/original/file-20171026-28030-1j42pgu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=444&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/191961/original/file-20171026-28030-1j42pgu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=444&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/191961/original/file-20171026-28030-1j42pgu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=558&fit=crop&dpr=1 754w, https://images.theconversation.com/files/191961/original/file-20171026-28030-1j42pgu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=558&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/191961/original/file-20171026-28030-1j42pgu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=558&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">California wildfires photographed from space on October 9, 2017.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/image-feature/goddard/2017/wildfires-running-amok-in-california">NASA Earth Observatory</a></span>
</figcaption>
</figure>
<h2>Driven by Diablo winds</h2>
<p>The Tubbs fire began on the night of Oct. 8 near Calistoga in Sonoma County under extreme fire weather conditions, with high winds and low relative humidity. Normally, winds in this region flow from the west, carrying cool, humid air from the ocean onshore. These winds reversed that pattern: They blew out of the northeast at 40 miles per hour, with gusts up to 75 miles per hour. Such winds are common in California during the autumn, and are known as Diablo, Mono or North winds in Northern California and Santa Ana winds in Southern California. </p>
<p>These hot, dry winds develop from an unusual pattern of high and low pressure cells, and are most prominent in autumn. They follow the normal summer and fall drought that occurs in this Mediterranean-type climate, leading to severe fire weather conditions. Such winds are associated with some of the most catastrophic fires in California’s history. In the San Francisco Bay area, they played a role in the <a href="http://ggweather.com/firestorm/1991OESreport.pdf">1991 Tunnel fire</a>, where wind gusts of 60 miles per hour were responsible for 25 deaths, even though the fire measured only slightly over 1,000 acres. The speed of these fires is a major factor leading to the loss of human lives. </p>
<p>Since fires in Northern California do not appear to have changed in this 50-year period, what accounts for the difference in impact? Certainly one critically important factor is demography. California’s population has <a href="https://www.statista.com/statistics/206097/resident-population-in-california/">more than doubled</a> in the past 50 years, but Santa Rosa, which was hit hard by the Tubbs fire, has five times as many people as it did in 1964.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/191457/original/file-20171023-1698-7xwnvr.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/191457/original/file-20171023-1698-7xwnvr.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/191457/original/file-20171023-1698-7xwnvr.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=253&fit=crop&dpr=1 600w, https://images.theconversation.com/files/191457/original/file-20171023-1698-7xwnvr.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=253&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/191457/original/file-20171023-1698-7xwnvr.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=253&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/191457/original/file-20171023-1698-7xwnvr.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=317&fit=crop&dpr=1 754w, https://images.theconversation.com/files/191457/original/file-20171023-1698-7xwnvr.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=317&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/191457/original/file-20171023-1698-7xwnvr.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=317&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Population growth in Santa Rosa, California.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Santa_Rosa,_California#cite_note-DoF-28">CA Dept of Finance</a></span>
</figcaption>
</figure>
<h2>Population growth</h2>
<p>This dramatic growth can affect fire losses in several ways. Nearly all fires in Sonoma County are caused directly or indirectly by people, such as intentional ignitions or power lines igniting fires. Population growth raises the probability of fire igniting under severe weather conditions. More frequent human-caused fires also convert woody vegetation to more abundant herbaceous vegetation, which <a href="https://d2k78bk4kdhbpr.cloudfront.net/media/publications/files/Halsey_and_Syphard_High_Severity_Fire_in_Chaparral_20151.pdf">increases ignition probability and the rate of fire spread</a>. </p>
<p>Population growth also spurs urban expansion. Development has spread outward, positioning <a href="https://theconversation.com/dont-blame-california-wildfires-on-a-perfect-storm-of-weather-events-86128">people closer to watersheds of dangerous fuels</a>. These fires burned through grasslands, oak woodlands and dense stands of <a href="http://www.californiachaparral.org/">chaparral</a> shrublands that last burned 50 years ago. Diablo winds are often funneled by <a href="http://onlinelibrary.wiley.com/doi/10.1029/2009GL041735/full">particular topographic features</a>, such as low-lying passes in mountains. This makes some parts of the landscape, which fire experts refer to as wind corridors, more vulnerable than others. </p>
<p>The so-called wildland-urban interface, or intermix, where development and wildland vegetation meet, is <a href="http://silvis.forest.wisc.edu/maps/housing">where most homes are destroyed by fires</a>. Data presented at a <a href="https://vimeo.com/238751761">recent Senate Science Forum</a> show that both high- and low-density development in the areas where the California wine country fires occurred have expanded dramatically in the last several decades.</p>
<h2>What about climate change?</h2>
<p>Many accounts increasingly see climate change as a <a href="http://www.laweekly.com/news/study-probes-connection-between-climate-change-fires-8766855">contributing factor</a> in big fire events. There is good evidence that climate change will increase fires in some western forests, but there is little evidence that it will play a similar role in coastal California. </p>
<p>In a <a href="http://www.publish.csiro.au/WF/WF16102?jid=WFv26n4&xhtml=BE6E3DBA-8037-4C1E-BB01-C05C107B0578">recent study</a>, we examined over 100 years of California climate records and examined the extent to which higher temperatures in different seasons might have contributed to enhanced fire activity, and found that there was very little correlation in coastal California. We hypothesized that this was likely because in lower elevations, temperatures are sufficient to lead to large fire events in most years, and fires are more strongly controlled by the timing of human ignitions in association with extreme winds. </p>
<p>Some reports have suggested that widespread tree deaths helped fuel the recent firestorm. The <a href="http://dx.doi.org/10.1002/2015GL064924">extreme drought of 2012-2014</a> caused extensive tree deaths, but most mortalities occurred farther east, in California’s Sierra Nevada mountains. In coastal counties, in contrast, many trees have been killed by <a href="http://www.sfgate.com/bayarea/article/Sudden-oak-death-likely-exacerbated-deadly-12292099.php">sudden oak death syndrome</a>, a disease spread by an exotic fungal pathogen. </p>
<p>However, according to the California State Tree Mortality Database, there were <a href="http://egis.fire.ca.gov/TreeMortalityViewer/">few dead trees within the fire perimeters</a> in wine country. And in some instances fierce winds carried the fire to communities that were a mile or more away from dangerous wildland fuels such as dead trees. These facts imply that tree mortality played a minimal role in the destruction caused by this firestorm. </p>
<p>Still another potential factor is above-normal rainfall during 2017. High rainfall increases plant growth in grasslands, which leads to increased fire incidence and spread. In all likelihood this did play some role. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/191967/original/file-20171026-28033-pksy5c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/191967/original/file-20171026-28033-pksy5c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/191967/original/file-20171026-28033-pksy5c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=379&fit=crop&dpr=1 600w, https://images.theconversation.com/files/191967/original/file-20171026-28033-pksy5c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=379&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/191967/original/file-20171026-28033-pksy5c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=379&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/191967/original/file-20171026-28033-pksy5c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=477&fit=crop&dpr=1 754w, https://images.theconversation.com/files/191967/original/file-20171026-28033-pksy5c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=477&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/191967/original/file-20171026-28033-pksy5c.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"></a>
<figcaption>
<span class="caption">Sign at a residence in the hills above Sonoma, California alerts people to an available pool if needed to shelter from wildfires, Friday, Oct. 13, 2017.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/California-Wildfires-One-Day/ef8f429cd73c49cf94083e2f26fdd189/240/0">AP Photo/Ellen Knickmeyer</a></span>
</figcaption>
</figure>
<h2>Human factors</h2>
<p>Looking to the future, <a href="https://doi.org/10.1071/WF16102">fire-climate studies in coastal California</a> have concluded that in this coastal region, direct human impacts are likely bigger concerns than indirect impacts from climate change. </p>
<p>On the plus side, this suggests that there is great potential for altering fire outcomes by reducing fire ignitions. We do not yet know what ignited this year’s Northern California fires, but extensive experience within the state points to several likely culprits: downed power lines, arson, debris burning and equipment such as generators. </p>
<p>Since these fires started at night, debris burning and equipment seem to be less likely causes. However, there were <a href="http://www.mercurynews.com/2017/10/12/california-fires-pge-power-lines-fell-in-winds-that-werent-hurricane-strength/">reports</a> of extreme winds blowing down power lines, and historically such events have started some of California’s worst fires. </p>
<p>Current U.S. Geological Survey research indicates that during the last several decades there has been a significant decline in arson-ignited fires in California and a decline in area burned due to arson. In all likelihood, increased fire prevention strategies have played a role in this decline. On the other hand, power line fires have not declined in number or area burned in the last several decades, and ignitions from power lines remain a statewide problem. Actions that can reduce the risk of this ignition source can include <a href="https://www.werc.usgs.gov/ProductDetails.aspx?ID=3987">placing power lines underground</a>.</p>
<p>Drought and warmer climates have made wildfires <a href="https://ca.water.usgs.gov/wildfires/index.html">a year-round hazard</a> in California. Expanded urban development, in tandem with hot winds, seems to be the primary reason for the destruction this year. Once we better understand what factors made the 2017 fires so damaging, <a href="https://theconversation.com/california-needs-to-rethink-urban-fire-risk-after-wine-country-tragedy-85966">communities can prepare</a> for future outbreaks in this increasingly fire-prone landscape.</p><img src="https://counter.theconversation.com/content/86043/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jon Keeley is affiliated with the U.S. Geological Survey and the University of California, Los Angeles</span></em></p>Fire is part of the ecology in much of California, but recent wildfires have caused much more damage than past burns of similar size. A fire ecologist points to two key factors: winds and population growth.Jon Keeley, Research Ecologist, US Geological SurveyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/539172016-03-04T11:17:24Z2016-03-04T11:17:24ZHow we used a century of data to create a modern, digital geologic map of Alaska<figure><img src="https://images.theconversation.com/files/113756/original/image-20160303-9486-14d0nj9.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The biggest state has a brand new map.</span> <span class="attribution"><span class="source">Geologic Map of Alaska</span></span></figcaption></figure><p>Since <a href="http://www.simonwinchester.com/map">William Smith’s publication</a> of the first geologic map of England in 1815, geologists have used maps to show the distribution and character of rocks at the Earth’s surface, and display their interpretations of the underlying geology. These maps help guide exploration for natural resources and help users understand natural hazards and ecosystems.</p>
<p>When my colleagues and I began working on a new geologic map of Alaska in the late 1990s, we decided to structure it quite differently from the previous version, published back in 1980. This time around, we’d tap into Geographic Information Systems (GIS) technology. Though what we recently released is called the <a href="http://dx.doi.org/10.3133/sim3340">Geologic Map of Alaska</a>, it’s really a database from which many different maps can be created. </p>
<p>The advent of digital methods has revolutionized mapping. Printed maps are limited in how much they can show before the amount of detail obscures meaning. They’re also restricted to a single view of the information. Digital maps can store and display a variety of information, allowing users to focus on the characteristics of interest. Using GIS and digital data, many different maps can be created and displayed, allowing users of our new Alaska database to choose which aspects to display.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/113622/original/image-20160302-25881-1xc2g61.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/113622/original/image-20160302-25881-1xc2g61.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/113622/original/image-20160302-25881-1xc2g61.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=487&fit=crop&dpr=1 600w, https://images.theconversation.com/files/113622/original/image-20160302-25881-1xc2g61.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=487&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/113622/original/image-20160302-25881-1xc2g61.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=487&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/113622/original/image-20160302-25881-1xc2g61.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=612&fit=crop&dpr=1 754w, https://images.theconversation.com/files/113622/original/image-20160302-25881-1xc2g61.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=612&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/113622/original/image-20160302-25881-1xc2g61.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=612&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 U.S. Geological Survey party in the moraines of the Malaspina Glacier in Alaska, circa 1890.</span>
<span class="attribution"><a class="source" href="http://library.usgs.gov/photo/#/item/51ddacc4e4b0f72b4471ee15">U.S. Geological Survey</a></span>
</figcaption>
</figure>
<h2>New compilation of more than a century of data</h2>
<p>The United States is divided into quadrangles for mapping purposes; in Alaska, each measures one degree of latitude by two or three degrees of longitude – about 70 by 100 miles. Alaska is composed of 153 of these quadrangles. We started compiling a database and digitizing 1:250,000-scale quadrangle geologic maps, for which about two-thirds of the 153 quadrangles had been published. Many of these geologic maps had been completed after release of the 1980 map. We also found unpublished compilations for some additional quadrangles. </p>
<p>Then we added data from other available sources – maps published at other scales, journal articles, original field notes, aerial photos, Google Earth and new fieldwork. We scoured any sources we could think of that might have geological data about Alaska for inclusion in our new map, even going back to some of the Russian writings from prior to the <a href="https://history.state.gov/milestones/1866-1898/alaska-purchase">Alaska purchase in 1867</a>.</p>
<p>Having worked in Alaska for many years, I understand how little we know about the geology of Alaska compared to the conterminous U.S., due to factors including its vast size, its low population and limited infrastructure, and the complexity of its geology. Yet I was surprised how much we <em>do</em> know, just hidden away in forgotten or obscure documents.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/113759/original/image-20160303-9507-3499ug.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/113759/original/image-20160303-9507-3499ug.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/113759/original/image-20160303-9507-3499ug.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=776&fit=crop&dpr=1 600w, https://images.theconversation.com/files/113759/original/image-20160303-9507-3499ug.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=776&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/113759/original/image-20160303-9507-3499ug.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=776&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/113759/original/image-20160303-9507-3499ug.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=976&fit=crop&dpr=1 754w, https://images.theconversation.com/files/113759/original/image-20160303-9507-3499ug.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=976&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/113759/original/image-20160303-9507-3499ug.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">The back cover of the new Geologic Map of Alaska’s pamphlet gives a sense of some of the earlier maps it’s updating.</span>
<span class="attribution"><span class="source">U.S. Geological Survey</span></span>
</figcaption>
</figure>
<p>Our sources span more than 100 years of data collection by a large number of geologists, each with a particular perspective. Many of the early geologic expeditions were limited in what they could see as they traveled; in general, there was no going back if you saw something today that made you want to take another look at something you saw two days ago. Often early expeditions were also producing the topographic maps as they went.</p>
<p>Each geologist was influenced by personal experience and the paradigms of the time. Prior to the advent of radioactive dating techniques, determining the age of rock units was dependent on finding fossils and understanding the geologic structures and stratigraphy. For instance, Father Hubbard, the “<a href="http://www.marywood.edu/archives/archival-exhibits/father-bernard-hubbard.html">Glacier Priest</a>,” <a href="https://books.google.com/books?q=editions:OCLC560491739&id=w7ygnQEACAAJ">studied the geology along the Alaska Peninsula</a> in the 1930s. Noting the coal beds, he thought the chain of volcanoes along the peninsula were due to the burning of coal deep underground. The advent of plate tectonic theory explains the volcanoes as a result of subduction and fits them into larger framework. While the presence of the volcanoes hasn’t changed, how we explain them has. I had to try to get into each geologist’s head, to attempt to understand what they saw and how the clues in the data they collected in the past could be interpreted within a modern plate tectonic paradigm.</p>
<p>Other challenges included determining precise locations from hand-drawn or reconnaissance maps. These early maps might not have complete contour lines; one map area I worked on had some mountains in the wrong spots and others were even missing. Essentially sketches, they were the best that could be done at the time.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/113791/original/image-20160303-13754-qseibx.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/113791/original/image-20160303-13754-qseibx.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/113791/original/image-20160303-13754-qseibx.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=553&fit=crop&dpr=1 600w, https://images.theconversation.com/files/113791/original/image-20160303-13754-qseibx.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=553&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/113791/original/image-20160303-13754-qseibx.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=553&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/113791/original/image-20160303-13754-qseibx.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=695&fit=crop&dpr=1 754w, https://images.theconversation.com/files/113791/original/image-20160303-13754-qseibx.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=695&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/113791/original/image-20160303-13754-qseibx.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=695&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 1959 map of the Ruby quadrangle that served as source material for the new map.</span>
<span class="attribution"><span class="source">U.S. Geological Survey</span></span>
</figcaption>
</figure>
<p>We also had to deal with reconciling the many different styles of geologic maps produced over the decades, along with poorly registered illustrations and lack of sample location information in published literature. For example, an early map of the Ruby quadrangle in west central Alaska was based on a crude, exploratory-quality topographic map; we had to redraw it, trying to more accurately locate geologic features, before we could digitize it.</p>
<p>Based on local geology, we compiled over 15,000 map units from the source maps. Each map unit was defined by distinctive rock units, using characteristics such as age, rock type and environment of formation – beach deposit versus deep ocean, for instance, or lava flow versus granite. By grouping similar map units together, we were able to reduce these to 1,350 unique map units. Further reduction resulted in about 450 map units for the detailed digital release and a generalized 220 units for the eventual print version. The resulting map divides the state along geologic characteristics rather than divided into units based on longitude and latitude.</p>
<p>The published digital map allows the user to zoom from the generalized version to the detailed version. The associated database contains more than a dozen interrelated tables that make this release special; and unlike previous print-only releases, the database is designed to be updated.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/113783/original/image-20160303-9490-rnpqv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/113783/original/image-20160303-9490-rnpqv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/113783/original/image-20160303-9490-rnpqv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/113783/original/image-20160303-9490-rnpqv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/113783/original/image-20160303-9490-rnpqv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/113783/original/image-20160303-9490-rnpqv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/113783/original/image-20160303-9490-rnpqv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/113783/original/image-20160303-9490-rnpqv.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">Warren Coonrad of the USGS working in southwest Alaska in 1975.</span>
<span class="attribution"><span class="source">U.S. Geological Survey</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Though I drove the effort, I stood on the shoulders of giants. Current USGS staff and volunteers and nearly a dozen retired USGS staff (Emeritus) contributed to the effort. Digital support came from many, as we had to capture data, design the spatial databases and package the data for release.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/113788/original/image-20160303-9463-1vo02bz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/113788/original/image-20160303-9463-1vo02bz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/113788/original/image-20160303-9463-1vo02bz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=468&fit=crop&dpr=1 600w, https://images.theconversation.com/files/113788/original/image-20160303-9463-1vo02bz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=468&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/113788/original/image-20160303-9463-1vo02bz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=468&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/113788/original/image-20160303-9463-1vo02bz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=588&fit=crop&dpr=1 754w, https://images.theconversation.com/files/113788/original/image-20160303-9463-1vo02bz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=588&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/113788/original/image-20160303-9463-1vo02bz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=588&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 Anchorage area, in the new map.</span>
<span class="attribution"><span class="source">Geologic Map of Alaska</span></span>
</figcaption>
</figure>
<h2>A geologic map for the 21st century</h2>
<p>Previous generations commonly used hand-drawn overlays to display different types of map data. To discover relationships between data types, geologists had to mentally visualize these relationships or draw new maps.</p>
<p>Today, with GIS, this process can be computer-aided. Choosing the data to display, GIS-capable users can generate derivative maps, or query the map and database for a variety of characteristics. GIS allows the user to explore relationships between data sets, test theories and otherwise use this geologic database of Alaska as an analysis tool. Users can incorporate additional data – for example, geochemical analyses – to characterize geologic units. Alternatively, a user could compare plant distributions with underlying geology to evaluate potential relationships.</p>
<p>The map and database are analogous to a map that shows the roads, but not the route. It doesn’t tell you which path to take until you figure out where you’re going. Like a spreadsheet, this map allows the user to ask questions.</p>
<p>As designed, the map is intended for a wide audience, from Alaska Native Corporations and land management agencies to academic institutions and mining and energy companies. This map provides a broad overview, as well as detailed information, which enhance a user’s ability to search for patterns and trends otherwise not apparent, and its digital form aids users in incorporating other data sets.</p><img src="https://counter.theconversation.com/content/53917/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Frederic Wilson receives funding from the U.S. Geological Survey and the National Park Service. He is a Fellow of the Geological Society of America and a member of the Alaska Geological Society</span></em></p>On printed maps, piling on the detail risks obscuring the meaning. This new digital map is really more of a database from which users can create different versions that match their own interests.Frederic Wilson, Research Geologist, US Geological SurveyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/437662015-10-01T08:23:51Z2015-10-01T08:23:51ZMining for metals in society’s waste<figure><img src="https://images.theconversation.com/files/95239/original/image-20150917-7545-p49ghv.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Could municipal biosolids be a trove of tiny treasure?</span> <span class="attribution"><span class="source">Heather Lowers, USGS Denver Microbeam Laboratory</span></span></figcaption></figure><p>Metals are crucial to society and enable our modern standard of living. Look around and you can’t help but see <a href="http://www.nma.org/index.php/minerals-publications/40-common-minerals-and-their-uses">products made of metals</a>. For instance, a typical gasoline-powered <a href="http://minerals.usgs.gov/granted.html">automobile contains</a> over a ton of iron and steel, 240 pounds of aluminum, 42 pounds of copper, 41 pounds of silicon, 22 pounds of zinc and more than 30 other mineral commodities including titanium, platinum and gold.</p>
<p>Metals and minerals are natural resources that human beings have been mining <a href="https://en.wikipedia.org/wiki/Mining">for thousands of years</a>. Contemporary <a href="https://www.icmm.com/trends-in-the-mining-and-metals-industry">metal mining</a> is dominated by iron ore, copper and gold, with 2 billion tons of iron ore, nearly 20 million tons of copper and 2,000 tons of gold produced every year. Tens to hundreds of tons of other metals that are essential components for electronics, <a href="http://pubs.usgs.gov/circ/1365/">green energy production</a>, and high-technology products are produced annually.</p>
<p>But metals are a nonrenewable resource; while advances in technology allow us to mine lower-grade mineral deposits, there’s ultimately a finite supply of what metals we can economically and technologically mine out of the Earth. So we and our colleagues at the US Geological Survey (USGS) are hunting for gold and other metals in some unconventional places, including in sewage sludge and the waste rock from old inactive metal mines.</p>
<p>We’ve hit scientific pay dirt, so to speak, in our initial attempts. The next step will be figuring out how to economically recover metals from these underutilized sources. So far we’re just determining which metals are present and don’t yet know the scale of what might be out there in waste, waiting to be mined.</p>
<h2>Waste as a sustainable resource?</h2>
<p>We can obtain the metals modern society needs in two ways: by mining them from mineral deposits in the Earth’s crust or by reusing society’s discarded metals. Metals are finite and do not decompose in the environment. The main issues related to mining them from the Earth’s crust include <a href="http://www.usgs.gov/blogs/features/usgs_top_story/going-critical-being-strategic-with-our-mineral-resources/">supply, scarcity</a> and the costs of extraction, concentration and purification. Moreover, there are <a href="http://dx.doi.org/10.1002/2015GL063345">potential environmental consequences</a> related to their extraction, processing, use and disposal.</p>
<p>The General Assembly of the United Nations Environment Programme says <a href="http://www.unep.org/Documents.multilingual/Default.asp?DocumentID=71&ArticleID=932&l=en">sustainable development</a> </p>
<blockquote>
<p>meets the needs of the present without compromising the ability of future generations to meet their own needs and does not imply in any way encroachment upon national sovereignty.</p>
</blockquote>
<p>Finding sources of metals that might be “mined” from society’s wastes can reduce our need for primary resources, reduce our need to import some metals, offset waste disposal costs and conserve space in landfills, reduce dissemination of potentially harmful metals into the environment, and contribute to a sustainable society.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/94554/original/image-20150911-1572-188sbh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/94554/original/image-20150911-1572-188sbh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/94554/original/image-20150911-1572-188sbh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=352&fit=crop&dpr=1 600w, https://images.theconversation.com/files/94554/original/image-20150911-1572-188sbh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=352&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/94554/original/image-20150911-1572-188sbh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=352&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/94554/original/image-20150911-1572-188sbh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=442&fit=crop&dpr=1 754w, https://images.theconversation.com/files/94554/original/image-20150911-1572-188sbh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=442&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/94554/original/image-20150911-1572-188sbh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=442&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’s gold in them… sewage treatment pools?</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/sawater/15978748831">SA Water</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<h2>Prospecting in sewage</h2>
<p>Municipal <a href="http://water.epa.gov/polwaste/wastewater/treatment/biosolids/">biosolids</a> are a mixture of a lot of stuff sent down the drain by homes and businesses that wastewater treatment plants then turn into <a href="http://www.wef.org/Biosolids/page.aspx?id=7513">treated sewage sludge</a>. Currently a little more than half of the biosolids generated in the US are used as fertilizer, with the balance disposed of in landfills or by <a href="http://water.epa.gov/polwaste/wastewater/treatment/biosolids/genqa.cfm">incineration</a>.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/95237/original/image-20150917-7512-130bo9a.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/95237/original/image-20150917-7512-130bo9a.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/95237/original/image-20150917-7512-130bo9a.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=828&fit=crop&dpr=1 600w, https://images.theconversation.com/files/95237/original/image-20150917-7512-130bo9a.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=828&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/95237/original/image-20150917-7512-130bo9a.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=828&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/95237/original/image-20150917-7512-130bo9a.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1041&fit=crop&dpr=1 754w, https://images.theconversation.com/files/95237/original/image-20150917-7512-130bo9a.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1041&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/95237/original/image-20150917-7512-130bo9a.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1041&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Preparing a biosolids sample back in the lab.</span>
<span class="attribution"><span class="source">USGS</span></span>
</figcaption>
</figure>
<p>But beyond human waste – ok, poop – we knew there was other useful stuff in these municipal biosolids. We and our colleagues at the USGS <a href="http://www.acs.org/content/acs/en/pressroom/newsreleases/2015/march/sewage-yes-poop-could-be-a-source-of-valuable-metals-and-critical-elements.html">have measured</a> gold, silver, platinum, copper, zinc and other precious and industrial metals in biosolids. Scientists at <a href="http://ssebe.engineering.asu.edu/">Arizona State University</a> also report finding <a href="http://dx.doi.org/10.1021/es505329q">numerous metals in biosolids</a>. </p>
<p>We are still trying to determine the ultimate sources of many of these metals in biosolids. For example, gold could be coming from <a href="http://www.food.gov.uk/science/additives/enumberlist">food products</a> (both eaten and disposed down the drain) that include it as an additive, dental fixtures or perhaps <a href="http://www.gold.org/technology/gold-medicine">medical facilities</a>. (Gold is used to treat arthritis and cancer as well as in some surgical and diagnostic procedures.) Silver could be coming from some of those same sources. Also, microscopic silver particles are used in a <a href="https://www.silverinstitute.org/site/silver-in-technology/">variety of consumer products</a> due to their <a href="http://articles.chicagotribune.com/2014-02-16/health/ct-nanosilver-met-20140216_1_consumer-products-other-antibiotic-drugs-germs">antibacterial properties</a>, and so could go down the drain with laundry water.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/tTkz_dTgGAc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">One of the authors describes their work.</span></figcaption>
</figure>
<p>It’s not like we’re modern-day <a href="http://www.luckypanner.com/history-of-california-gold-rush-and-the-forty-niners/">“forty-niners”</a> finding visible gold flakes and nuggets at wastewater treatment plants. But we are able to measure concentrations of some metals in the biosolids material – about one part per million of gold, for example – that greatly exceed naturally occurring <a href="http://pubs.usgs.gov/ds/801/">soil metal concentrations</a>. If this gold were in rock instead of biosolids, the amounts we’re finding would be similar to the concentrations measured in low-grade, currently subeconomic <a href="http://pubs.usgs.gov/gip/prospect2/prospectgip.html">gold deposits</a>. We’ve even identified a few very tiny, microscopic gold particles we call “nanonuggets.” </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/94555/original/image-20150911-1551-ee0es.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/94555/original/image-20150911-1551-ee0es.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/94555/original/image-20150911-1551-ee0es.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=372&fit=crop&dpr=1 600w, https://images.theconversation.com/files/94555/original/image-20150911-1551-ee0es.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=372&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/94555/original/image-20150911-1551-ee0es.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=372&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/94555/original/image-20150911-1551-ee0es.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=467&fit=crop&dpr=1 754w, https://images.theconversation.com/files/94555/original/image-20150911-1551-ee0es.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=467&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/94555/original/image-20150911-1551-ee0es.png?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">Historical mining waste-rock piles could be potential sources of mineable ores containing metals.</span>
<span class="attribution"><span class="source">USGS</span></span>
</figcaption>
</figure>
<h2>Recycling historical metal mining waste-rock piles</h2>
<p>Old, inactive hardrock mines in the western US are a result of the California gold rush of the mid-1800s and the other mining booms that followed. Hardrock miners focused on certain metals – including gold, silver, copper, lead and zinc – that were essential for the industrial revolution in the eastern US, and later for war efforts such as the Civil War and World Wars I and II. Near mining sites, piles of waste rock were often left behind.</p>
<p>This waste rock could contain metals with concentrations that were too low to be economically recoverable at the time or metals that weren’t of interest then, but that now have new high-tech applications. At many old inactive mining sites, waste-rock piles and tunnels driven into the hills can be sources of mine drainage waters that may contain high levels of environmentally detrimental, but potentially useful, metals.</p>
<p>There are potential environmental and safety issues and costs associated with any kind of work at these historical mining sites, as demonstrated by the recent <a href="http://www2.epa.gov/goldkingmine">Gold King mine spill</a> into the Animas River in Colorado. From 1997 to 2008, federal agencies spent <a href="http://www.gao.gov/products/GAO-11-834T">at least US$2.6 billion</a> to clean up abandoned hardrock mines on federal, state, private and Indian lands. And there are many more abandoned mining sites on federal lands that <a href="http://www.gao.gov/products/GAO-15-830T">remain to be inventoried and assessed</a>. Metal recovery from waste and drainage waters at some of these abandoned hardrock mining sites might help offset clean-up costs.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/95234/original/image-20150917-7534-xaqyge.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/95234/original/image-20150917-7534-xaqyge.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/95234/original/image-20150917-7534-xaqyge.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/95234/original/image-20150917-7534-xaqyge.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/95234/original/image-20150917-7534-xaqyge.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/95234/original/image-20150917-7534-xaqyge.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/95234/original/image-20150917-7534-xaqyge.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/95234/original/image-20150917-7534-xaqyge.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">Sampling at an historical mining waste pile with associated drainage.</span>
<span class="attribution"><span class="source">USGS</span></span>
</figcaption>
</figure>
<p>We have measured in samples from waste-rock piles some metals – such as indium, tellurium and some rare earth elements – that are needed for industrial, green industry and high-tech applications. Not all mining waste-rock piles are the same, because they come from different geological sources and contain various combinations of different minerals and metals. We’re investigating whether, by knowing about the geology and mining history of these sites, it may be possible to predict which ones will have elevated levels of useful metals. We have also looked at whether waters draining from mines and mining wastes with appropriate geological characteristics can be targeted for <a href="https://www.imwa.info/docs/imwa_2013/IMWA2013_Smith_470.pdf">economic recovery</a> of useful metals.</p>
<p>Recovering and reusing metals from these sites could possibly offset the need for some new mining. There’d be less metal that we’d need to mine from virgin sources and a decrease in the associated environmental costs. That could increase sustainability by offsetting reclamation costs and reducing the amount of waste material that needs to be reclaimed.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/94556/original/image-20150911-1547-ol0f5j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/94556/original/image-20150911-1547-ol0f5j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=434&fit=crop&dpr=1 600w, https://images.theconversation.com/files/94556/original/image-20150911-1547-ol0f5j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=434&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/94556/original/image-20150911-1547-ol0f5j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=434&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/94556/original/image-20150911-1547-ol0f5j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=545&fit=crop&dpr=1 754w, https://images.theconversation.com/files/94556/original/image-20150911-1547-ol0f5j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=545&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/94556/original/image-20150911-1547-ol0f5j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=545&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sampling at a historical mining waste pile with associated drainage.</span>
<span class="attribution"><span class="source">USGS</span></span>
</figcaption>
</figure>
<h2>Can we scale up this kind of recovery?</h2>
<p>Knowing that metals are present in waste is just the first step. Next we need to investigate whether the metals can be extracted from the waste and recovered in a usable form. </p>
<p>We are currently leaching samples of biosolids and mining wastes in the laboratory using chemical solutions that are similar to extractants used by the mining industry to recover metals from hardrock ores. For example, dilute sulfuric acid is used by the mining industry to leach copper ore, and thiosulfate is sometimes used to leach gold ore.</p>
<p>We mix our ground-up samples with these chemical solutions in a container for different amounts of time (from minutes to several hours), pour off or filter the leachate solutions and then analyze the solutions to see which metals have been dissolved. Our results so far show some promise. For biosolids, leaching may provide the additional benefit of extracting some metals, such as copper and zinc, that presently limit the use of some biosolids as a fertilizer.</p>
<p>Thus far, we’ve shown what’s possible at a very small scale in the lab. We hope our work will spark additional interest in metal recovery from wastes on the part of experts in metal and mineral processing. Potential liability concerns have hampered re-mining and metal-recovery activities at historical mining sites. To reduce these liability obstacles, successful projects will likely need to involve partnerships between federal and state regulatory agencies, private entities, and the mining and mineral processing industries.</p><img src="https://counter.theconversation.com/content/43766/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kathleen Smith receives funding from the US Geological Survey, Mineral Resources Program.</span></em></p><p class="fine-print"><em><span>Geoffrey Plumlee received funding for this paper and related work from the US Geological Survey's Mineral Resources Program.</span></em></p><p class="fine-print"><em><span>Philip L Hageman received funding from the US Geological Survey Mineral Resources Program for this research.</span></em></p>Mining waste rock from historic mines or even treated sewage to find useful metals and minerals could be a sustainable way to meet demand for these finite resources.Kathleen S Smith, Research Geologist, US Geological SurveyGeoffrey Plumlee, Research Geochemist—Environment, disasters, and health, US Geological SurveyPhilip L Hageman, Research Physical Scientist, US Geological SurveyLicensed as Creative Commons – attribution, no derivatives.