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USGS/Cascades Volcano Observatory, Vancouver, Washington

Cascade Range Current Update

U.S. Geological Survey, Vancouver, Washington
University of Washington, Pacific Northwest Seismograph Network, Seattle, Washington

Volcanoes in the Cascade Range are all at normal levels of background seismicity except for Mount St. Helens. See Mount St. Helens update below.

Other volcanoes 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.

Mount St. Helens Update, October 10, 2004, 7:00 a.m, PDT

Current status is Volcano Advisory (Alert Level 2); aviation color code ORANGE

Seismic activity has decreased slightly over the past 20 hours to low levels, similar to those observed during the evening hours of October 7. Earthquakes continue to occur at a rate of about 1 per minute, but most have magnitudes of 1.0 or less. With the improving weather, a gas measuring flight is planned within the next two days.

Additional analysis of lidar and photographs of the intensely uplifting area on the south side of the lava dome suggests that the total volume change represented by the deformation between late September and October 6 is about 16 million cubic meters (21 million cubic yards). The average rate of change is about 2 million cubic meters per day (2.6 million cubic yards per day). If this figure represents the rate of intrusion of magma into shallow levels of the dome and(or) underlying crater floor, it is an intrusion rate about twice that measured during dome-building eruptions at Mount St. Helens in the 1980s. Cartographers with the USGS office in Denver are working to develop precise volume change estimates for the uplifted area from stereo airphotos acquired between 1 and 5 October.

As a result of the intense unrest of the past 11 days, we infer that magma is at a very shallow level. During times of unrest, Mount St. Helens and similar volcanoes elsewhere typically go through episodic changes in level of unrest over periods of days to weeks, or even months. Such changes are in part driven by variations in the rate of magma movement. We expect fluctuations in the level of unrest to continue during coming days. Escalation in the degree of unrest and perhaps an eruption could occur suddenly or with very little warning. There may be little time to raise the alert level before a hazardous event occurs. Therefore, we continue to monitor the situation closely and will issue additional updates and changes in alert level as warranted.

Wind forecasts from the National Oceanic and Atmospheric Administration (NOAA), combined with eruption models, show winds early this morning will be from the north-northwest. Any ash clouds will drift to the south-southeast.

Today's media briefing will be held at the Headquarters of the Gifford Pinchot National Forest at 10:30 a.m.



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10/10/04, Lyn Topinka