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Mount St. Helens

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Mount St. Helens
green NORMAL, 2023-10-30 22:53:25 UTC

Prior to 1980, Mt. St. Helens had the shape of a conical volcano sometimes referred to as the Mount Fuji of America. During the 1980 eruption the upper 400 m (1,300 ft) of the summit was removed by a huge debris avalanche, leaving a 2 x 3.5 km horseshoe-shaped crater now partially filled by a lava dome and a glacier. It is primarily an explosive dacite volcano.

Quick Facts

Location: Washington, Skamania County

Latitude: 46.2° N

Longitude: 122.18° W

Elevation: 2,539 (m) 8,330 (f)

Volcano type: Stratovolcano

Composition: Basalt to Rhyodacite

Most recent eruption: 1980, 2004-2008

Nearby towns: Castle Rock, WA; Olympia, WA; Vancouver, WA; Yakima, WA; Portland, OR

Threat Potential: Very High*

*based on the National Volcano Early Warning System

Summary

Mount St. Helens erupted 38 years ago, May 18, 1980
Mount St. Helens.

Mount St. Helens is primarily an explosive dacite volcano with a complex magmatic system. The volcano was formed during four eruptive stages beginning about 275,000 years ago and has been the most active volcano in the Cascade Range during the Holocene. Prior to about 12,800 years ago, tephra, lava domes, and pyroclastic flows were erupted, forming the older St. Helens edifice, but a few lava flows extended beyond the base of the volcano. The bulk of the modern edifice (above the 1980 crater floor) was constructed during the last 3,000 years, when the volcano erupted a wide variety of products from summit and flank vents. Historical eruptions in the 19th century originated from the Goat Rocks area on the north flank, and were witnessed by early settlers. New unpublished data on the timing for Mount St. Helens eruptive activity have been analyzed, which improves some of the eruption dates cited in published literature. This website contains the most up to date information.

Since its 1980 eruption, the summit elevation has decreased. A survey in 1982 gave a measurement of 2549.7 m (8365 ft). However, a lidar survey done in 2009 found the maximum elevation to be 2539 m (8330 ft). The difference in elevation is likely due to erosion and loss of rimrock by crater-wall collapses.

News

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Uptick in earthquake activity at Mount St. Helens remains within background levels (July 15, 2023-Present)

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10 Ways Mount St. Helens Changed Our World

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Volcanoes and USGS Volcano Science: Just the Facts

Publications

2018 update to the U.S. Geological Survey national volcanic threat assessment

When erupting, all volcanoes pose a degree of risk to people and infrastructure, however, the risks are not equivalent from one volcano to another because of differences in eruptive style and geographic location. Assessing the relative threats posed by U.S. volcanoes identifies which volcanoes warrant the greatest risk-mitigation efforts by the U.S. Geological Survey and its partners. This update

Authors
John W. Ewert, Angela K. Diefenbach, David W. Ramsey

Science

Geologic History Summary for Mount St. Helens

Mount St. Helens, located in Washington State, is the most active volcano in the Cascade Range, and it is the most likely of the contiguous U.S. volcanoes to erupt in the future.
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Geologic History Summary for Mount St. Helens

Mount St. Helens, located in Washington State, is the most active volcano in the Cascade Range, and it is the most likely of the contiguous U.S. volcanoes to erupt in the future.
Learn More

Earthquake Monitoring at Mount St. Helens

Due to the eruptions of 1980-86 and 2004-2008, Mount St. Helens has had the best seismic monitoring network of all volcanoes in the Cascade Range. It is also the most seismically active volcanoes in the Washington and Oregon Cascades.
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Earthquake Monitoring at Mount St. Helens

Due to the eruptions of 1980-86 and 2004-2008, Mount St. Helens has had the best seismic monitoring network of all volcanoes in the Cascade Range. It is also the most seismically active volcanoes in the Washington and Oregon Cascades.
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Volcanic Hazards at Mount St. Helens

Mount St. Helens' high frequency of eruptions during the recent geologic past and its two eruptive episodes of the past three decades indicate a high probability of renewed eruptive activity.
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Volcanic Hazards at Mount St. Helens

Mount St. Helens' high frequency of eruptions during the recent geologic past and its two eruptive episodes of the past three decades indicate a high probability of renewed eruptive activity.
Learn More