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SALT LAKE CITY — Yellowstone's underground volcanic plumbing is bigger and better connected than scientists thought, researchers reported here today (April 17) at the Seismological Society of America's annual meeting.
"We are getting a much better understanding of the volcanic system of Yellowstone," said Jamie Farrell, a seismology graduate student at the University of Utah. "The magma reservoir is at least 50 percent larger than previously imaged."
Knowing the volume of molten magma beneath Yellowstone is important for estimating the size of future eruptions, Farrell told OurAmazingPlanet.
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Supervolcano trail
Geologists believe Yellowstone sits over a hotspot, a plume of superheated rock rising from Earth's mantle. As North America slowly drifted over the hotspot, the Yellowstone plume punched through the continent's crust, leaving a bread-crumb-like trail of calderas created by massive volcanic eruptions along Idaho's Snake River Plain, leading straight to Yellowstone. The last caldera eruption was 640,000 years ago. Smaller eruptions occurred in between and after the big blasts, most recently about 70,000 years ago. [Infographic: Geology of Yellowstone]
The magma chamber seen in the new study fed these smaller eruptions and is the source of the park's amazing hydrothermal springs and geysers. It also creates the surface uplift seen in the park, said Bob Smith, a seismologist at the University of Utah and author of a related study presented at the meeting.
Scientists have updated this image of Yellowstone volcano's underground magma chamber. Instead of two big yellow blobs, they have a clearer picture that looks like a knobby banana.
(Image credit: Jamie Farrell, University of Utah)
"This crustal magma body is a little dimple that creates the uplift," Smith said. "It's like putting your finger under a rubber membrane and pushing it up and the sides expand."
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Clearer picture
A clearer picture of Yellowstone's shallow magma chamber emerged from earthquakes, whose waves change speed when they travel through molten or solid rock. Farrell analyzed nearby earthquakes to build a picture of the magma chamber.
The underground magma resembles a mutant banana, with a knobby, bulbous end poking up toward the northeast corner of Yellowstone National Park, and the rest of the tubular fruit angling shallowly southwest. It's a single connected chamber, about 37 miles (60 kilometers) long, 18 miles (30 km) wide, and 3 to 7 miles (5 to 12 km) deep.
Previously, researchers had thought the magma beneath Yellowstone was in separate blobs, not a continuous pocket.
The shallowest magma, in the northeast, also matches up with the park's most intense hydrothermal activity, Farrell said. The new study is the best view yet of this zone, which lies outside the youngest caldera rim.
Additional molten rock, not imaged in this study, also exists deeper beneath Yellowstone, scientists think.
Becky Oskin covers Earth science, climate change and space, as well as general science topics. Becky was a science reporter at Live Science and The Pasadena Star-News; she has freelanced for New Scientist and the American Institute of Physics. She earned a master's degree in geology from Caltech, a bachelor's degree from Washington State University, and a graduate certificate in science writing from the University of California, Santa Cruz.
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