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, 7:45 a.m, PDT

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

Seismicity overnight remained at a low level similar to October 10. Small earthquakes (about magnitude 1) have continued at a rate of about 1 per 5 to 10 minutes.

Viewing conditions were very clear most of October 10, and fresh snow had fallen to the level of the crater floor north of the dome. A USGS field crew noticed a thin ash deposit on the snow in the crater and just beyond the crater rim, trending southeast from the active area.

A steam plume rose to crater rim level or slightly above all day on October 10, heading to the southeast. USGS field workers described the plume as “lazy”—no gas thrust or notably vigorous convection was observed. The plume was clean, with no noticeable ash or blue/orange haze. The odor of H2S was noted at the crater breach, but not elsewhere.

Helicopter field crews were at work on Sunday October 10. A telemetered webcam was placed at Sugarbowl and GPS data were downloaded.

The thermal imaging crew made an excellent video of the uplifted area of the south crater floor. The western portion of the the uplift was steaming over a large diffuse area. Maximum measured surface temperatures were 200-300 deg. C. The thermal imaging crew judged the uplifted area to have grown since it was last seen on the 7th.

No gas observations were made on October 10.

Rockfall deposits were not seen on or around the uplifted area, perhaps indicating a lull in its growth or deformation.

As a result of the intense unrest of the past 18 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, oreven 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.

The weather forecast for the next several days is favorable for fieldwork and observations. Wind forecasts from the National Oceanic and Atmospheric Administration (NOAA), combined with eruption models, show winds today will remain north-northwesterly. Any ash clouds will drift south- southeastwardly to southeastwardly.

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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