Yellowstone's magma chambers are much larger than ever imagined, but the good news is that they contain too little molten rock to cause Yellowstone to erupt soon.
A huge reservoir of magma and hot rock beneath the Yellowstone supervolcano has been found. The newly found reservoir is about 12-28 miles below the surface, and is 4.5 times larger than the shallower, hot melted rock zone that powers current Yellowstone geysers and caused Yellowstone's last eruption 70,000 years ago.
The volume of the newly discovered, deeper chamber is 11,000 cubic-miles, which is about the volume of Long Island with 9 miles of hot rock piled on it.
“It's existence has been suspected for a while,” said University of Utah geophysicist Hsin-Hua Huang.
Far more carbon dioxide was being released from the ground at Yellowstone, previous research suggested, than could be explained by the smaller, shallower magma reservoir. That smaller reservoir was found using data from a local seismic array.
To see deeper,, scientists used a wider array to record how seismic waves from more distant earthquakes behaved as they passed through the unexplored zone under Yellowstone, Huang said. Seismic waves reveal a lot about the crust because they travel slower through hot rocks than through colder rocks. That wider seismic network came in the form of the USArray, a seismic network that's been crossing the continental United States since 2004.
“Until now we hadn't combined this data,” Huang said. It's the blending of that data that allowed Huang and his colleagues to see the giant hot, partially melted zone.
The data also revealed that the shallower magma chamber is about 9 percent melted rock, and the newly found lower chamber is 2 percent melted. Neither is a giant chamber of magma and neither is in any danger of erupting -- contrary to popular misconceptions -- say the researchers.
The actual image Huang and his colleagues produced was created by what's called seismic tomography.