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.)
Did You Know?
Yellowstone contains approximately one-half of the world’s hydrothermal features. There are over 10,000 hydrothermal features, including over 300 geysers, in the park.