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Robert B. Smith and Lee J. Siegel/University of Utah

Yellowstone supervolcano keeps getting bigger, new U. study finds

By Amy Joi O'Donoghue  |  Posted Apr 24th, 2015 @ 8:54am


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SALT LAKE CITY — New research by University of Utah seismologists maps the hot molten rock material deep beneath the Yellowstone supervolcano more extensively than ever before, revealing that it would fill the Grand Canyon more than 11 times over.

The hot rock in this newly discovered magma reservoir is as far down as 28 miles and significantly eclipses what scientists had previously concluded about the components of the chamber.

“For the first time, we have imaged the continuous volcanic plumbing system under Yellowstone,” said first author Hsin-Hua Huang, a postdoctoral researcher in geology and geophysics. “That includes the upper crustal magma chamber we have seen previously, plus a lower crustal magma reservoir that has never been imaged before and that connects the upper chamber to the Yellowstone hotspot plume below.”

The seismologists discovered and made images of a reservoir of hot, partly molten rock 12 to 28 miles beneath the Yellowstone supervolcano, and it is 4.4 times larger than the shallower, long-known magma chamber.

While the hot rock in the newly discovered reservoir would fill the 1,000-cubic-mile Grand Canyon 11.2 times, the other mapped magma chamber would fill the Grand Canyon 2.5 times, according to postdoctoral researcher Jamie Farrell, a co-author of the study published online Thursday in the journal Science.

The discovery does not mean there is any more risk and does not point to increased chances for eruption, researchers stress.

“The actual hazard is the same, but now we have a much better understanding of the complete crustal magma system,” said study co-author Robert B. Smith, a research and emeritus professor of geology and geophysics at the University of Utah.

Smith pointed out that the earthquake hazard is much more of a threat — with the most recent one occurring in 1959 that killed 28 people. By comparison, the last volcanic eruption happened 700,000 years ago.

"The actual hazard is the same, but now we have a much better understanding of the complete crustal magma system." -Study co-author Robert B. Smith

Farrell added that even though the large reservoir of magma has always been there, grasping the scope of its size can be a bit daunting.

"Yellowstone is a really big volcano," he said. "Some of these things are on scales that we have not seen before."

The nature of the volcanic hazard that exists has not altered because it is based on an evidentiary record that includes the manner and extent of previous volcanic eruptions, Farrell said.

Fan-Chi-Lin, a study co-author and an assistant professor of geology and geophysics, said the research gives a better understanding of the plumbing under Yellowstone and a more comprehensive ability to estimate potential seismic and volcanic hazards.

The three supervolcano eruptions at Yellowstone — on the Wyoming-Idaho-Montana border — covered much of North America in volcanic ash. A supervolcano eruption today would be cataclysmic, but Smith says the annual chance is 1 in 700,000.

The study in Science is titled “The Yellowstone Magmatic System from the Mantle Plume to the Upper Crust.” Huang, Lin, Farrell and Smith conducted the research with Brandon Schmandt at the University of New Mexico and Victor Tsai at the California Institute of Technology. Funding came from the University of Utah, National Science Foundation, Brinson Foundation and William Carrico.

Yellowstone is among the world’s largest supervolcanoes, with frequent earthquakes and Earth’s most vigorous continental geothermal system.

Previous research indicates the Yellowstone plume emerges from a depth of at least 440 miles in Earth’s mantle. Some researchers suspect it originates 1,800 miles deep at Earth’s core.

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