Cascade Range Current Update

CASCADES VOLCANO OBSERVATORY WEEKLY UPDATE
Thursday, July 10, 2008 09:22 PDT (Thursday, July 10, 2008 16:22 UTC)

MOUNT ST. HELENS VOLCANO (CAVW#1201-05-)
46.20°N 122.18°W, Summit Elevation 8363 ft (2549 m)
Volcano Alert Level: NORMAL
Aviation Color Code: GREEN

The more than three-years-long, lava-dome eruption of Mount St. Helens that began in autumn 2004 and paused in late January of this year appears to have ended. Therefore, we are lowering the Volcano-Alert Level from Advisory to NORMAL and the Aviation Color Code from Yellow to GREEN, to indicate that monitoring parameters have returned to background conditions. Since late January, five months have passed with no signs of renewed eruptive activity and earthquakes, volcanic gas emissions, and ground deformation have remained at pre-eruptive background levels. The rate of lava-dome growth had gradually declined throughout the eruption, which accounted for at least 93 million cubic meters (125 million cubic yards) of new lava. That volume would cover seven lanes of interstate highway 3 feet thick from New York City to Portland, Oregon. All lava erupted since 1980 sums to about 7% of the volume removed from the cone by the catastrophic landslide of May 18, 1980, that formed the crater.

Even with the end of lava dome growth, some hazards persist. The new lava dome remains hot in places-capable of producing small hot avalanches or minor explosions that could dust areas with ash up to tens of miles downwind. Rock fall from the crater walls can produce clouds of dust that rise above the crater rim, especially during dry, windy days, as has happened in the past. Also, heavy rainfall or rapid snowmelt can send small debris flows onto the Pumice Plain north of the crater.

The U.S. Geological Survey and the University of Washington continue to monitor the situation closely and will issue additional updates and changes in alert level as warranted.

INFORMATION:

For additional information, background, images, and other graphics:
http://vulcan.wr.usgs.gov/Volcanoes/MSH/Eruption04/

For seismic information:
http://www.pnsn.org/HELENS/welcome.html

For a definition of alert levels:
http://vulcan.wr.usgs.gov/Volcanoes/Cascades/CurrentActivity/volcano_warning_scheme.html

For a webcam view of the volcano:
http://www.fs.fed.us/gpnf/volcanocams/msh/

Telephone recordings with the latest update on Mount St. Helens and phone contacts for additional information can be heard by calling:
Media (360) 891-5180

OTHER CASCADE VOLCANOES

All other volcanoes in the Cascade Range are all at normal levels of background seismicity. These include Mount Baker, Glacier Peak, Mount Rainier, and Mount Adams in Washington State; Mount Hood, Mount Jefferson, Three Sisters, Newberry, and Crater Lake, in Oregon; and Medicine Lake, Mount Shasta, and Lassen Peak in northern California.

USGS Cascades Volcano Observatory, the Pacific Northwest Seismograph Network at the University of Washington, and the USGS Northern California Seismic Network and Volcano Hazards Team in Menlo Park, California, monitor the major volcanoes in the Cascade Range of northern California, Oregon, and Washington.



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