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Definition: St Helens, Mount from Philip's Encyclopedia

Volcanic peak in the Cascade Range, SW Washington state. Dormant since 1857, it erupted on May 18, 1980, killing 60 people. The 2,950m (9,578ft) summit was reduced to 2,560m (8,312ft) with a deep horseshoe crater. Two more eruptions occurred in the following two weeks, and it is predicted to erupt again in the early 21st century.

Summary Article: Saint Helens, Mount
from The Columbia Encyclopedia

volcanic peak, 8,363 ft (2,549 m; 9,677 ft/2,950 m before its 1980 eruption) high, SW Wash., historically the most active volcano in the Cascade Range. Dormant since 1857, Mt. St. Helens erupted on May 18, 1980, in one of the largest volcanic explosions in North American history; prior to that event there were a series of earth tremors and steam explosions beginning on Mar. 20, 1980. During the eruption a great portion of the rock facing on north side of the mountain fell, followed by a lateral blast of stone, ash, and poisonous gas that carried debris 17 mi (27 km) and flattened and buried surrounding forest. The disaster took some 65 lives, wiped out substantial populations of elk, deer, bear, and coyote, and destroyed 230 sq mi (600 sq km) of vegetation. A volcanic plume rose 80,000 ft (24,400 m) into the air, blanketing a large area of the NW United States with volcanic ash. The symmetrical summit of Mt. St. Helens was replaced by a horseshoe-shaped crater 2,460 ft (750 m) deep. A number of smaller eruptions, beginning on May 25 and continuing into 1986, resulted in lava flows that built up a dome in the crater; a new, dome-building eruption began in 2004. The volcano and surrounding area are now part of Mt. St. Helens National Volcanic Monument and have provided biologists with a unique opportunity to observe ecological succession and the reestablishment of natural habitats.

  • See Kellar, S. A. , ed., Mount St. Helens (1982);.
  • Olson, S. , Eruption (2016).
The Columbia Encyclopedia, © Columbia University Press 2018

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Full text Article St Helens, Mount
The Macmillan Encyclopedia

46 12N 122 11W A volcano in SW Washington, in the S Cascade Range, S of Seattle. Dormant since 1857, the mountain erupted in May, 1980,...

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