Mount St. Helens Returns to Slumber
The nearly three and a half years of eruption at Mount St. Helens is over for now and on July 10, 2008, scientists lowered the volcano alert level
from
Advisory to
Normal and the
aviation color code from
Yellow to
Green.
Mount St. Helens reawakened in October 2004 when four explosions blasted steam and ash up to 10,000 feet above the crater. Scientists watched a spine of fresh hot lava pierce the bulging crater floor. Growth of this lava dome continued until late January 2008.
Five months have passed with no signs of renewed eruptive activity. Earthquakes, volcanic gas emissions, and ground deformation are all at levels seen before the eruption began.
Mount St. Helens will erupt again in the future in some mix of renewed dome building and more explosive behavior. However, at this point, scientists can’t forecast when the next eruption will begin.
USGS and the University of Washington’s Pacific Northwest Seismic Network will continue to monitor Mount St. Helens. Scientists expect that days to weeks of warning will herald the next time Mount St. Helens erupts.
From October 2004 to late January 2008, about 125 million cubic yards of lava had erupted onto the crater floor to form a new dome—enough to pave seven highway lanes three feet thick from New York City to Portland, Oregon. A comparable volume had flowed out to form the 1980s lava dome. All lava erupted since 1980 has refilled about 7% of the crater, which was created by the catastrophic landslide and eruption of May 18, 1980.
Even though the eruption has ended, some hazards persist. The new lava dome remains hot in places and capable of producing avalanches or minor explosions that could dust areas with ash up to 50 miles from the volcano. Rock fall from crater walls can produce clouds of dust that rise above the crater rim, especially during dry, windy days. Also, heavy rainfall or rapid snowmelt can send small debris flows onto the Pumice Plain north of the crater.
MSH08_aerial_st_helens_crater_from_north_05-30-08.jpg
Aerial view of Mount St. Helens' crater, as seen from the north. Note the two arms of the Crater Glacier in the crater foreground.
USGS Photograph taken on May 30, 2008, by Steve Schilling.
[large size]
A weekly update of the status of all Cascade volcanoes, including Mount St. Helens, can be seen at
http://volcano.wr.usgs.gov/cvo/current_updates.php.
For more information about the 2004–2008 eruption, visit
http://vulcan.wr.usgs.gov/Volcanoes/MSH/Eruption04/.
Alert level and aviation color code definitions can be found at
http://vulcan.wr.usgs.gov/Volcanoes/Cascades/CurrentActivity/volcano_warning_scheme.html.
Additional information about Mount St. Helens is at the
Cascades Volcano Observatory Website
Additional information about volcanoes and volcano hazards is at the
Volcano Hazards Program Website.
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