Cascade Range Current Update

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 11, 2004, 5:30 p.m, PDT

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

Seismic activity remained at a low level today. Currently small earthquakes (maximum about magnitude 1) are occurring at a rate of about 1 per 5 to 10 minutes. Visual observations and thermal imaging of the crater, the 1980-86 lava dome, and the intensely deforming and uplifting area on the south side of the dome were made during the afternoon. The western part of the uplifting area appears to be the most actively deforming site and was the source of a brief steam and emission about 16:00 that drifted southeastward. A dusting of ash on new snow in that sector suggests that similar minor ash emissions also occurred last night. A steam plume originating on the deforming area continues to rise above the crater rim and drift to the southeast. Scientists also conducted a gas-sensing flight. Results will be available tomorrow as will results of thermal imaging.

As a result of the intense unrest of the past two weeks, 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 this evening will remain northwesterly. Any ash clouds will drift south-southeastwardly to southeastwardly.

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



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