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Longstreet Highroad Guide to the California Sierra Nevada

By Mark Grossi

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California Sierra Nevada > Sidebars > Long Valley Caldera

Long Valley Caldera

In the Owens Valley, against the steep escarpment of the Sierra, the Long Valley Caldera is a huge depression caused by a massive volcanic blast more than 700,000 years ago. The blast sent out 140 to 150 cubic miles of lava, buried everything for more than 300 square miles, and left the 19-mile-long and 10-mile-wide depression that is still visible today. Why was this blast so big? Chemistry played a big part, scientists say. The rhyolite found in the Bishop Tuff is almost three-fourths silica, which is dense and does not flow easily. This thick magma has the capacity to capture more gases. The gases build in the magma. In the case of Long Valley Caldera, their release was an epic explosion.

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Published (print): 2000, Published (Web): September 2000, Revised (Web): November 2002, ISBN: 1-56352-592-5
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