USGS Fact Sheet 2005–3036: Mount St. Helens Erupts Again: Activity from September 2004 through March 2005

Mount St. Helens Erupts Again: Activity from September 2004 through March 2005

By Jon J. Major, William E. Scott, Carolyn Driedger, and Dan Dzurisin

Abstract

Eruptive activity at Mount St. Helens captured the world’s attention in 1980 when the largest historical landslide on Earth and a powerful explosion reshaped the volcano, created its distinctive crater, and dramatically modified the surrounding landscape. Over the next 6 years, episodic extrusions of lava built a large dome in the crater. From 1987 to 2004, Mount St. Helens returned to a period of relative quiet, interrupted by occasional, short-lived seismic swarms that lasted minutes to days, by months-to-yearslong increases in background seismicity that probably reflected replenishment of magma deep underground, and by minor steam explosions as late as 1991. During this period a new glacier grew in the crater and wrapped around and partly buried the lava dome. Although the volcano was relatively quiet, scientists with the U.S. Geological Survey and University of Washington’s Pacific Northwest Seismograph Network continued to closely monitor it for signs of renewed activity.

First posted April 15, 2005

This report is available only on the Web

For additional information, contact:
CVO, Volcano Science Center,
Cascades Volcano Observatory
U.S. Geological Survey
1300 SE Cardinal Court, Building 10, Suite 100
Vancouver, WA 98683-9589
http://vulcan.wr.usgs.gov/

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Suggested citation:

Major, J.J., Scott, W.E., Driedger, C., and Dzurisin, D., 2005, Mount St. Helens Erupts Again: Activity from September 2004 through March 2005: U.S. Geological Survey Fact Sheet 3005–3036, 4 pp., https://pubs.usgs.gov/fs/2005/3036/.