Mount Saint Helens

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Mount St. Helens


On May 18, 1980, Mount St. Helens exploded with a force comparable to 500 Hiroshima-sized atom bombs. David Johnston, a United States Geological Survey (USGS) geologist based at a monitoring station six miles (9.7 km) away announced the eruption with his final words, "Vancouver, Vancouver, this is it." Dramatic photograph's provided the public with an awesome display of nature's power.

Mount St. Helens, in southwestern Washington near Portland, Oregon, is part of the Cascade Range, a chain of subduction volcanoes running from northern California through Washington. The Mount St. Helens eruption was instrumental in the expansion of the USGS Volcano Hazards Program. Research at the new Cascades Volcano Observatory in Vancouver, Washington, has strengthened basic understanding of volcanic processes and the ability to predict eruptions. Highly relevant ecological studies have corrected previous errors and misconceptions, leading to a new theory about nature's ability to recover after such events.

Research has heightened public awareness of the inherent instability of high, snow-covered volcanoes, where even small eruptions can almost instantaneously melt large volumes of snow. A relatively small 1985 eruption at Nevado del Ruiz in central Colombia killed more than 23,000 people. The Mount St. Helens blast and subsequent collapse generated a 0.7 cubic mile (2.8 km3) mud flow which raced 22 miles (35 km) at speeds as high as 157 mph (253 kph). This caused massive problems, even halting traffic on the Columbia River. These flows may also create unstable dams , which may burst years after the intial eruption.

In addition to its awesome power and destructive force, the Mount St. Helens eruption has provided rich material for research. Conductivity studies have located a large rotating block under Mounts Rainier, Adams, and St. Helens, the friction from which is a likely source of eruptions. Geologic mapping and historical research, coupled with field studies of current volcanism, have corrected misconceptions and given clues to hazard frequency. Studies of nature's recovery efforts have produced surprises, notably the early arrival in the eruption zone of predatory insects; elk grazing in open, reforested areas; and the explosive growth of uncommon, dangerous bacteria due to the high temperatures generated by the eruption. Biological legacy has emerged as the unifying theory describing nature's recovery capabilities, an idea with direct applications to forestry practices and reclamation of human-disturbed land. Nature's mess provides valuable nutrients and nurseries; furthermore, old growth areas within managed ecosystems nurture the recovery of biodiversity .

Mount St. Helens has provided a unique laboratory for study of volcano hazards and nature's ability to recover
from the devastation caused by volcanic eruptions.

See also Mount Pinatubo, Philippines; Reclamation; Topography

[Nathan H. Meleen ]


RESOURCES

BOOKS

Bilderback, D. E., ed. Mount St. Helens, 1980: Botanical Consequences of the Explosive Eruptions. Berkeley: University of California Press, 1987.

PERIODICALS

Decker, R., and B. Decker. "Eruption of Mount St. Helens." Scientific American 244 (March 1981): 6880.

OTHER

Tilling, R. I., L. J. Topinka, and D. A. Swanson. Eruptions of Mount St. Helens: Past, Present, and Future. USGS General Interest Publication. Washington, DC: U. S. Government Printing Office, 1990.

Wright, T. L., and T. C. Pierson. Living With Volcanoes: The USGS Volcano Hazards Program. USGS Circular 1073. Washington, DC: U. S. Government Printing Office, 1992.

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Mount Saint Helens, 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 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 S. A. Kellar, ed., Mount St. Helens (1982).

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MOUNT ST. HELENS

MOUNT ST. HELENS is a stratovolcanic peak in southwest Washington State. Dormant since 1857, Mount St. Helens erupted on 18 May 1980, after a series of earthquakes below the volcano's peak. It released a mushroom cloud of gases 63,000 feet high and sent a lavalike mixture of glass, gas, and ash down the mountainside at speeds up to a hundred miles per hour, killing sixty people, decimating several native animal populations, and destroying $500 million worth of timber. Economic losses totaled $3 billion. Subsequent minor eruptions occurred on 25 May 1980 and 11 April 1981. In 1982 Mount St. Helens was declared a national volcano monument.

BIBLIOGRAPHY

Caroline D. Harnly, Caroline D., and David A. Tyckoson. Mount St. Helens: An Annotated Bibliography. Metuchen, N.J.: Scarecrow Press, 1984.

CarolynBronstein/c. w.

See alsoDisasters ; Volcanoes ; Washington, State of ; andpicture (overleaf).

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St Helens, Mount Volcanic peak in the Cascade Range, sw Washington state. Dormant since 1857, it erupted on May 18, 1980, killing 60 people. The 2950m (9578ft) summit was reduced to 2560m (8312ft) 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.

http://www.fs.fed.us/gpnf/mshnvm

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Mount Saint Helens: see Saint Helens, Mount.