The magma beneath Yellowstone National Park is 2½ times larger than previously thought. Researchers say the biggest risk the park faces is an earthquake, not a volcanic eruption. Researchers have noted swarms of tiny quakes above the magma blob in recent years, repeating every few seconds, and new images show that the molten rock reservoir is about 50 miles long and more than 12 miles wide. "I don't know of any other magma body that's been imaged that's that big," said University of Utah geophysicist Robert Smith.
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