Cascade Range Current Update

CASCADES VOLCANO OBSERVATORY WEEKLY UPDATE
Friday, July 18, 2008 09:04 PDT (Friday, July 18, 2008 16:04 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

SUMMARY:

The 40-month-long lava-dome eruption of Mount St. Helens that began in autumn 2004 ended in late January of this year. Earthquakes, volcanic gas emissions, and ground deformation are all at pre-eruptive background levels. The alert level and aviation color code were reduced to NORMAL/GREEN on July 10, 2008, following five months with no sign of renewed activity.

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.

RECENT OBSERVATIONS:

Scientists from the Cascades Volcano Observatory made observations July 8, 2008 of Crater Glacier including the co-joined west and east arms of Crater Glacier north of the 1980s dome. They mapped along the northernmost part of the west arm that has advanced about 20 m since May 30, 2008. The advancing glacier ice has moved a bit into the gullies that have been carved by erosion into the Pumice Plain. Calculations from digital elevation data suggests that about 10-11% of the volume of Crater Glacier has been removed over the course of the eruption. Despite incommodious environs at times durning the eruption, Crater Glacier persists, now flanking the 1980s dome on the west, east and north.

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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