CRATERS OF THE MOON NATIONAL MONUMENT

region of volcanic cones and craters near the foot of White Knob Mountain in south central Idaho, U.S., 20 mi (32 km) southwest of Arco. The more than 35 craters, which have probably been extinct only a few centuries, are located on a tract of 53,545 ac (21,669 ha) set apart as a government reservation in 1924; some are nearly a half mile across and several hundred feet deep. The name was suggested by the terrain's resemblance to the Moon's surface. Although the black lava and cinders support only the scantiest vegetation and quickly absorb the very light rainfall, water is to be found in tunnels formed by fissure eruptions through a partly formed crust. The cones reach a height of more than 6,000 ft (1,800 m). Lava stalactites and stalagmites (mineral deposits resembling icicles) in red and blue are striking features of the tunnels.