Yellowstone Supervolcano Swelling Mysteriously

Nov. 8, 2007 -- The turmoil beneath Yellowstone's "supervolcano" is raising the land as much as 2.8 inches per year, new ground measurements show. But the inflating land is not about to erupt, assured geologists, despite the caldera's ancient history of massive explosions.

The "supervolcano" is really a caldera, a basin-shaped volcanic feature formed in the wake of a large eruption. Spanning roughly 925 square miles in the northwest corner of Wyoming, the Yellowstone Caldera is thought to erupt every few hundred thousand years, but its exact origins remain a mystery.

What can be said is that the recent swell of the land there fits into a larger history of rises and falls that have been underway for a lot longer than geologists have been around to make sense of them, explained geologist Robert Smith of the University of Utah in Salt Lake City. He, Wu-Lung Chang and other colleagues report on the most recent changes at the famous volcanic park in the Nov. 9 issue of the journal Science.

The latest episode began in mid-2004 in the Sour Creek area of the Yellowstone Caldera, just north of Yellowstone Lake. There the swelling is the sharpest yet recorded. The previous six years had seen the land sinking at 1/3 inch per year, the team reported.

"What we know is that we have some intrusion of melt," said Smith, referring to the upward movement of hot, melted rock from around 6 miles underground. That melt is coming out of a large, cooling blob of magma that Smith and his colleagues spotted directly under the geyser-rich caldera using 3-D seismic imaging techniques.