Mount St. Helens Update, October 10, 2004

International Glaciospeleological Survey

Mount St. Helens Update, October 10, 2004

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

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

Mount St. Helens Update, October 10, 2004, 5:00 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 (about magnitude 1) are occurring at a rate of about 1 per 5 to 10 minutes. Very small earthquakes are occurring at a rate of about 1 per minute. 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 early afternoon. The deforming area has increased in area by about 10 percent since last seen on 7 October. Estimate of change in height awaits further analysis. A steam plume originating at vents on the deforming area is rising above the crater rim and drifting to the southeast. A dusting of ash on new snow high on the volcano suggests that minor ash emission may be occurring intermittently. Installation of a remotely controlled video camera provided by the USGS Hawaiian Volcano Observatory began late in the day at Sugar Bowl, which lies at the eastern side of The Breach, the open north end of the 1980 Crater.

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 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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