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 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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