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Yellowstone Has Bulged as Magma Pocket Swells

Laatste wijziging: donderdag 20 januari 2011 om 14:38, 2566 keer bekeken Print dit artikel Bekijk alle nieuws feeds van onze site
 
donderdag 20 januari 2011

Some places saw the ground rise by ten inches, experts report.

Steam rising from Castle Geyser in Yellowstone National Park.
Steam rises from Castle Geyser in Yellowstone National Park (file photo).
Photograph by Mark Thiessen, National Geographic

Yellowstone National Park's supervolcano just took a deep "breath," causing miles of ground to rise dramatically, scientists report.

The simmering volcano has produced major eruptions—each a thousand times more powerful than Mount St. Helens's 1980 eruption—three times in the past 2.1 million years. Yellowstone's caldera, which covers a 25- by 37-mile (40- by 60-kilometer) swath of Wyoming, is an ancient crater formed after the last big blast, some 640,000 years ago.

(See "When Yellowstone Explodes" in National Geographic magazine.)

Since then, about 30 smaller eruptions—including one as recent as 70,000 years ago—have filled the caldera with lava and ash, producing the relatively flat landscape we see today.

But beginning in 2004, scientists saw the ground above the caldera rise upward at rates as high as 2.8 inches (7 centimeters) a year. (Related: "Yellowstone Is Rising on Swollen 'Supervolcano.'")

The rate slowed between 2007 and 2010 to a centimeter a year or less. Still, since the start of the swelling, ground levels over the volcano have been raised by as much as 10 inches (25 centimeters) in places.

"It's an extraordinary uplift, because it covers such a large area and the rates are so high," said the University of Utah's Bob Smith, a longtime expert in Yellowstone's volcanism.

Read more / lees verder: nationalgeographic.com



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