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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

Mount St. Helens Update, October 6, 2004, 6:00 p.m, PDT

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

The low rate of seismic activity that followed yesterday’s steam and ash emission continued through last night, but rose slowly between about 9 a.m. and 1 p.m., before leveling off at a slightly higher level. Earthquakes are presently occurring at a rate of about one per minute with a maximum magnitude of about 1.0. No thermal observations were possible today owing to low clouds and rain, but late this afternoon scientists were able to get brief views of the vents and the area of intense uplift on the south side of the 1980-86 lava dome. They saw only weak puffs of steam coming from vents. They were able to confirm that the top of the area of intense uplift is at or slightly above the highest point on the lava dome, which suggests that some uplift has occurred during this period of low seismicity. They were also able to observe areas affected by the small lahars that spilled out of the crater and onto the Pumice Plain during last night’s rain storm. Lahars flowed a short distance toward both Spirit Lake and the North Fork Toutle River. Another crew worked on installation of broad-band seismometers on the lower flanks of the volcano.

Information received today indicates that a light dusting of ash from yesterday’s event affected the eastern part of Mount Rainier National Park, about 70 miles north-northeast of Mount St. Helens.

As a result of the intense unrest of the past 10 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 this evening will remain westerly and any ash clouds will drift eastward to northeastward.

Press conferences will continue to be held at the Headquarters office of the Gifford Pinchot National Forest. The morning press conference is at 9:30 AM.



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10/07/04, Lyn Topinka