{"id":13556,"date":"2017-11-07T07:12:00","date_gmt":"2017-11-07T07:12:00","guid":{"rendered":"https:\/\/www.revoscience.com\/en\/?p=13556"},"modified":"2017-11-07T07:12:00","modified_gmt":"2017-11-07T07:12:00","slug":"cool-idea-magma-held-cold-storage-giant-volcano-eruption","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/cool-idea-magma-held-cold-storage-giant-volcano-eruption\/","title":{"rendered":"Cool idea: Magma held in \u2018cold storage\u2019 before giant volcano eruption"},"content":{"rendered":"
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A new study looks at rock from the titanic eruption that formed Long Valley Caldera in California 765,000 years ago. Calderas occur when a volcano collapses after an eruption. The study signals that we don\u2019t fully understand these giant eruptions. PHOTO: U.S. GEOLOGICAL SURVEY<\/figcaption><\/figure>\n

Long Valley, California, has long defined the \u201csuper-eruption.\u201d About 765,000 years ago, a pool of molten rock exploded into the sky. Within one nightmarish week, 650 cubic kilometers of lava and ash spewed out in the kind of volcanic cataclysm we hope never to witness.<\/span><\/p>\n

The ash likely cooled the planet by shielding the sun, before settling across the western half of North America.<\/span><\/p>\n

Here\u2019s a rule of geoscience: The past heralds the future. So it\u2019s not just morbid curiosity that attracts geoscientists to places like Long Valley. It\u2019s an ardent desire to understand why super-eruptions happen, ultimately to understand where and when they are likely to occur again.<\/span><\/p>\n

This week (Nov. 6, 2017), in the\u00a0Proceedings of the National Academy of Sciences<\/a>, a report shows that the giant body of magma \u2014 molten rock \u2014 at Long Valley was much cooler before the eruption than previously thought.<\/span><\/p>\n

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Nathan Andersen, then a UW\u2013Madison graduate student and the first author of the new PNAS study, records data at Laguna del Maule, Chile in 2013. PHOTO: DAVID TENENBAUM<\/figcaption><\/figure>\n

\u201cThe older view is that there\u2019s a long period with a big tank of molten rock in the crust,\u201d says first author\u00a0Nathan Andersen<\/a>, who recently graduated from the University of Wisconsin\u2013Madison with a Ph.D. in geoscience. \u201cBut that idea is falling out of favor.<\/span><\/p>\n

\u201cA new view is that magma is stored for a long period in a state that is locked, cool, crystalline, and unable to produce an eruption. That dormant system would need a huge infusion of heat to erupt.\u201d<\/span><\/p>\n

It\u2019s hard to understand how the rock could be heated from an estimated 400 degrees Celsius to the 700 to 850 degrees needed to erupt, but the main cause must be a quick rise of much hotter rock from deep below.<\/span><\/p>\n

Instead of a long-lasting pool of molten rock, the crystals from solidified rock were incorporated shortly before the eruption, Andersen says. So the molten conditions likely lasted only a few decades, at most a few centuries. \u201cBasically, the picture has evolved from the \u2018big tank\u2019 view to the \u2018mush\u2019 view, and now we propose that there is an underappreciation of the contribution of the truly cold, solidified rock.\u201d<\/span><\/p>\n

The new results are rooted in a detailed analysis of argon isotopes in crystals from the Bishop Tuff \u2014 the high-volume rock released when the Long Valley Caldera formed. Argon, produced by the radioactive decay of potassium, quickly escapes from hot crystals, so if the magma body that contained these crystals was uniformly hot before eruption, argon would not accumulate, and the dates for all 49 crystals should be the same.<\/span><\/p>\n

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Laguna del Maule, whose geology resembles that of Long Valley, is a restive volcanic region in Chile that was the scene of many explosive eruptions over the last million years. It is undergoing the fastest uplift of any known volcanic region on Earth, possibly heralding a major eruption. PANORAMIC IMAGE BY DAVID TENENBAUM<\/figcaption><\/figure>\n

And yet, using a new, high-precision mass spectrometer in the\u00a0Geochronology Lab<\/a>\u00a0at UW\u2013Madison, the research group\u2019s dates spanned a 16,000 year range, indicating the presence of some argon that formed long before the eruption. That points to unexpectedly cool conditions before the giant eruption.<\/span><\/p>\n

Better tools make better science, Andersen says. \u201cThe new instrument is more sensitive than its predecessors, so it can measure a smaller volume of gas with higher precision. When we looked in greater detail at single crystals, it became clear some must have been derived from magma that had completely solidified \u2014 transitioned from a mush to a rock.\u201d<\/span><\/p>\n

\u201cNathan found that about half of the crystals began to crystallize a few thousand years before the eruption, indicating cooler conditions,\u201d says\u00a0Brad Singer<\/a>, a professor of geoscience at UW\u2013Madison and director of the Geochronology Lab. \u201cTo get the true eruption age, you need to see the dispersion of dates. The youngest crystals show the date of eruption.\u201d<\/span><\/p>\n

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Brad Singer<\/figcaption><\/figure>\n

The results have meaning beyond volcanology, however, as ash from Long Valley and other giant eruptions is commonly used for dating.<\/span><\/p>\n

\u201cThese huge eruptions deposit ash all over the place, and that lets you make correlations in the rock record to aid geologic, biologic and climatic studies across the continent,\u201d says Andersen. \u201cThis blanket of ash anchors you in time. The closer we can pin down the eruption age, the better we can study all facets of Earth\u2019s history.\u201d<\/span><\/p>\n

\u201cIt\u2019s controversial, but finding these older crystals means that part of this large magma body was very cool immediately prior to eruption,\u201d says Singer, a volcanologist who was Andersen\u2019s UW advisor. \u201cThis flies in the face of a lot of thermodynamics.\u201d<\/span><\/p>\n

A better understanding of the pre-eruption process could lead to better volcano forecasting \u2014 a highly useful but difficult proposition at present.<\/span><\/p>\n

\u201cThis does not point to prediction in any concrete way,\u201d says Singer, \u201cbut it does point to the fact that we don\u2019t understand what is going on in these systems, in the period of 10 to 1,000 years that precedes a large eruption.\u201d<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

Long Valley, California, has long defined the \u201csuper-eruption.\u201d About 765,000 years ago, a pool of molten rock exploded into the sky. Within one nightmarish week, 650 cubic kilometers of lava and ash spewed out in the kind of volcanic cataclysm we hope never to witness. The ash likely cooled the planet by shielding the sun, […]<\/p>\n","protected":false},"author":6,"featured_media":13557,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-13556","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581.jpg",775,581,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581-300x225.jpg",300,225,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581-768x576.jpg",750,563,true],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581.jpg",750,562,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581.jpg",775,581,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581.jpg",775,581,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581.jpg",775,581,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581.jpg",760,570,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581.jpg",600,450,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581.jpg",600,450,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581.jpg",654,490,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581.jpg",480,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581.jpg",87,65,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581.jpg",640,480,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581.jpg",96,72,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2017\/11\/wes-775x581.jpg",150,112,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/13556","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=13556"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/13556\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/13557"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=13556"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=13556"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=13556"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}