By Lee Siegel
In a study published by the journal “Science,” University of Utah seismologists revealed the discovery of a gargantuan reservoir of hot, partly molten rock 12 to 28 miles under the Yellowstone supervolcano. The reservoir supplies the previously known magma chamber located from 3 to 9 miles beneath the world’s first national park.
The research team included Hsin-Hua Huang, Fan-Chi Lin, Robert. B. Smith and Jamie Farrell in the U’s Department of Geology and Geophysics, along with colleagues at Caltech and the University of New Mexico.
Farrell, a postdoctoral researcher, calculated that the hot rock in the newly discovered, deeper magma reservoir would fill the 1,000-cubic-mile Grand Canyon 11.2 times, while the previously known magma chamber would fill the Grand Canyon 2.5 times.
Huang, the study’s first author and also a postdoc, said the study meant that “for the first time, we have imaged the continuous volcanic plumbing system under Yellowstone. 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.”
Contrary to popular perception, the magma chamber and magma reservoir are not full of molten rock. Instead, the rock is hot, mostly solid and spongelike, with pockets of molten rock within it. Huang says the new study indicates the upper magma chamber averages about 9 percent molten rock and the lower magma reservoir is about 2 percent melt.
The upper magma chamber fueled three cataclysmic supervolcano eruptions at Yellowstone 2 million, 1.2 million and 640,000 years ago. Those eruptions dumped volcanic ash on large portions of North America – something that would be an unprecedented disaster if it happened today. May smaller eruptions also have happened, including lava flows 70,000 years ago.
But the researchers emphasize that Yellowstone’s plumbing system is no larger – nor closer to erupting – than before, only that they now have used advanced seismic imaging techniques to make a complete image of the system that carries hot and partly molten rock upward from the top of the Yellowstone hotspot plume – about 40 miles beneath the surface – to the magma reservoir and the magma chamber above it.
“The actual hazard is the same, but now we have a much better understanding of the complete crustal magma system,” says Smith, a research and emeritus professor, and veteran Yellowstone researcher. He says the annual chance of a Yellowstone supervolcano eruption is 1 in 700,000.
For the full University of Utah news release on the study, click here.
University of Utah seismologists prepared a brief animated video of the Yellowstone supervolcano’s underground plumbing system – including the newly discovered magma reservoir:
National Science Foundation video:
Lee Siegel is a communication specialist at University Marketing and Communications. If you have an interesting story idea, email him at firstname.lastname@example.org.