Craters of the Moon National Monument and Preserve
Region of volcanic cones and craters, south-central Idaho, U.S. Established in 1924 as a national monument, it has more than 35 craters, probably extinct only a few millennia. Some are nearly a half-mile across and several hundred feet deep and reach a height of more than 6,000 ft (1,800 m). Tunnels formed by fissure eruptions feature stalactites and stalagmites in red and blue. In 2000 the monument was expanded from 83 to 1,117 sq mi (215 to 2,893 sq km); in 2002 part of it was designated a national preserve.
This entry comes from Encyclopædia Britannica Concise.
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