Publication Citation

USGS Series Fact Sheet
Report Number 2005-3036
Title Mount St. Helens Erupts Again: Activity from September 2004 through March 2005
Edition -
Language ENGLISH
Author(s) Major, Jon J.; Scott, William E.; Driedger, Carolyn; Dzurisin, Dan
Year 2005
Originating office USGS Cascades Volcano Observatory
USGS Library Call Number
Physical description 4 p.
ISBN

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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-years long 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.