for National Geographic News
Yellowstone National Park is rising. Its central region, called the Yellowstone caldera, has been moving upward since mid-2004 at a rate of up to three inches (seven centimeters) a year—more than three times faster than has ever been measured.
The surface is inflating like a bellows due to an infusion of magma about 6 miles (10 kilometers) underground, according to a new study published in tomorrow's issue of the journal Science.
But that doesn't mean Yellowstone is about to go the way of Mount St. Helens.
"There's no evidence of an imminent eruption or hydrothermal explosion," said Robert Smith, a geophysics professor at the University of Utah who co-authored the study.
"Supervolcano" Under Yellowstone
Yellowstone is situated on a giant, geologically active feature known as a supervolcano.
"It's hundreds of times bigger than Mount St. Helens," Smith said, referring to the active volcano in Washington State.
(Read related story: "Supervolcano Raises Yellowstone, Fuels Geysers, Study Says" [March 1, 2006].)
Much of the park sits in a caldera, or crater, some 40 miles (70 kilometers) across, which formed when the cone of the massive volcano collapsed in a titanic eruption 640,000 years ago.
The supervolcano has produced three similarly large blasts in the past two million years, with 30 smaller eruptions since the caldera formed.
The volcano's most recent flare-up was 70,000 years ago, and volcanic heat continues to fuel the park's famous geysers and hot springs.
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