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19 Jan 11- Yellowstone National Park's supervolcano just took a deep "breath," causing miles of ground to rise dramatically, says this article in National Geographic. Yellowstone's caldera, which covers more than two million acres and sprawls across parts of Wyoming, Montana and Idaho, was formed some 640,000 years ago. Since then, about 30 smaller eruptions—including one as recent as 70,000 years ago—have combined to create the relatively flat landscape we see today, says author Brian Handwerk.
"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.'") "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. Fortunately, the surge doesn't seem to herald an imminent catastrophe, Smith said "Once we saw [the magma] was at a depth of ten kilometers, we weren't so concerned," said Smith. "If it had been at depths of two or three kilometers [one or two miles], we'd have been a lot more concerned." "There are many examples where it appears the ground has risen and fallen for thousands of years without an eruption. "These calderas tend to go up and down, up and
down," he said. "But every once in a while they burp, creating hydrothermal
explosions, earthquakes, or—ultimately—they can produce volcanic eruptions."
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