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Yellowstone National Park
Caldera
Yellowstone's caldera
 
At Yellowstone and some other volcanoes, some scientists theorize that the earth's crust fractures and cracks in a concentric or ring-fracture pattern. At some point these cracks reach the magma “reservoir,” release the pressure, and the volcano explodes. The huge amount of material released causes the volcano to collapse into a huge crater—a caldera. (Illustration based on Smith, R. B., and Siegel, L., 2000, Windows into the Earth; New York, Oxford University Press.)

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Summer Crowd at Old Faithful.

Did You Know?
At peak summer levels, 3,500 employees work for Yellowstone National Park concessioners and about 800 work for the National Park Service.
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Last Updated: July 11, 2007 at 16:45 MST