Mount St. Helens Update, October 8, 2004

International Glaciospeleological Survey

Mount St. Helens Update, October 8, 2004

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

Mount St. Helens Update, October 8, 2004, 7:00 a.m., PDT

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

Seismic activity continues to be at a low to moderate rate with an overall trend of slightly decreasing energy release over the past 24 hours. Earthquakes are occurring at a rate of 1 to 2 per minute with the largest magnitudes about M1.5. Yesterday field crews reported a new vent near the two that have been present for several days. They also reported that there has not been noticeable additional uplift of the south part of the dome and adjacent glacier in the past 24 hours.

Gas-sensing and thermal imaging flights occurred late yesterday afternoon and we are awaiting those results. There will be limited work in the field today due to the poor weather. Field crews today will mostly work on enhancing data links between field stations and the Cascades Volcano Observatory.

As a result of the intense unrest of the past many 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 that winds during the morning will be from the south-southwest and any ash will drift north-northeast. The National Weather Service is forecasting a weather front that could bring more than 1 inch of rain to the mountains. We anticipate that such intense rain could trigger small to moderate debris flows in the crater that may flow out onto the Pumice Plain.

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

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 8, 2004, 6:30 p.m, PDT

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

Seismic activity has been rising gradually today to a moderate rate of energy release, with earthquakes up to magnitude 2.4 occurring at a rate of about 1 every two minutes. No visual observations of the crater and dome were possible today due to low clouds and rain. AFM data suggest a small lahar flowed out of the crater about midday. Field work was limited to observations of river flows and installation of a satellite dish near Coldwater Visitor Center for telemetry of seismic, GPS, and other data.

Measurements from recent photographs and LIDAR (an acronym for LIght Detection And Ranging) show that the intensely deformed and uplifted area on the south side of the 1980-86 lava dome is about 1300 feet (N-S) by 1600 feet (E-W) with a maximum uplift of about 300-400 feet.

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 this evening will remain westerly and any ash clouds will drift northeastward (tonight) and east-northeastward (early tomorrow morning).

Saturday’s press conferences will be held at the Headquarters office of the Gifford Pinchot National Forest at 10:30 a.m.


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