SUNSET CRATER VOLCANO NATIONAL MONUMENT

national monument in north-central Arizona, U.S. It lies 15 miles (24 km) northeast of Flagstaff. The monument is centred on a truncated cinder cone, the remnant of an extinct volcano, that rises to an elevation of 1,000 feet (300 m). The cone was dated by means of tree rings found in remains of buried Indian pit houses; it was apparently formed after an eruption that occurred about 1064. The summit crater, 400 feet (120 m) deep and about 1,280 feet (390 m) in diameter, is brilliantly hued, as though illuminated by the setting sun. Established in 1930, the preserve occupies an area of 5 square miles (13 square km). The monument contains numerous lava flows, fumaroles, and lava beds with ice caves.