Surprising Activity Discovered at Yellowstone Supervolcano

14 March 2007

Supervolcanoes can sleep for centuries or millennia before producing incredibly massive eruptions that can drop ash across an entire continent. One of the largest supervolcanoes in the world lies beneath Yellowstone National Park, which spans parts of Wyoming, Montana and Idaho.

Though the Yellowstone system is active and expected to eventually blow its top, scientists don’t think it will erupt any time soon.

Yet significant activity continues beneath the surface. And the activity has been increasing lately, scientists have discovered. In addition, the nearby Teton Range, in a total surprise, is getting shorter.

For the past 17 years, researchers used Global Positioning System (GPS) satellites to monitor the horizontal and vertical motion of the Yellowstone caldera—a huge volcanic crater formed by a super-eruption more than 600,000 years ago.

The movement of the caldera indicates what’s going on underground where magma, or molten rock, is stored for the next eruption. When magma builds up, some of it starts to rise toward the surface, where it presses against the floor of the caldera. The pressure makes the caldera bulge, while a decrease in pressure makes it sink.

The 45-by-30-mile caldera bulged and deflated significantly during the study period, resulting in a series of small earthquakes that produced 10 times more energy than would occur if the ground were to move suddenly in a large eruption.

“We think it’s a combination of magma being intruded under the caldera and hot water released from the magma being pressurized because it’s trapped,” said lead study author Robert Smith from the University of Utah. “I don’t believe this is evidence for an impending volcanic eruption, but it would be prudent to keep monitoring the volcano.”

[link to www.livescience.com]