Yellowstone volcano bigger than thought!

SALT LAKE CITY, Utah (PNN) - April 18, 2013 - Yellowstone's underground volcanic plumbing is bigger and better connected than scientists thought, researchers reported here today at the Seismological Society of Amerika'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% larger than previously imaged."

Knowing the volume of molten magma beneath Yellowstone is important for estimating the size of future eruptions, said Farrell.

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.

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.

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 long, 18 miles wide, and 3-7 miles 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, said Farrell. The new study is the best view yet of this zone, which lies outside the youngest caldera rim.

Scientists think additional molten rock, not imaged in this study, also exists deeper beneath Yellowstone.