International Glaciospeleological Survey

U.S. Geological Survey, Vancouver, Washington University of Washington,  Pacific Northwest Seismograph Network, Seattle, Washington Mount St. Helens Notice of Volcano Alert, October 2, 2004 A notice of Volcano Alert (Alert Level 3) was issued today at 2:00 p.m.  PDT Immediately after the small steam emission at 12:15, seismic activity changed  from principally rock breakage events to continuous low-frequency tremor, which is indicative of magma movement. We are increasing the alert level to Volcano Alert the highest alert level indicating that an eruption could be imminent. The cause and outcome of the accelerating unrest is uncertain. Explosions  from the vent could occur suddenly and without further warning. During such  explosions the dome and crater floor are at greatest risk from ballistic  projectiles, but the rim of the crater and flanks of the volcano could also be  at risk. Explosions would also be expected to produce ash clouds that rise  several to tens of thousands of feet above the crater rim and drift downwind.  Currently wind forecasts from the National Weather Service, combined with eruption models, show that ash clouds will move to the northwest. If ash  emissions are large, drifting ash could affect downwind communities. Minor melting of the glacier could trigger debris flows from the crater that are large  enough to reach the Pumice Plain. There is very low probability that downstream communities would be impacted by these hydrologic events. . We continue to monitor the situation very closely and will issue additional  updates as warranted, whether activity escalates or returns to background levels.

U.S. Geological Survey, Vancouver, Washington University of Washington,  Pacific Northwest Seismograph Network, Seattle, Washington Mount St. Helens Update, October 2, 2004, 7:00 P.M. Current status is Volcano Alert (Alert Level 3); aviation color code RED At 2 pm today, we increased the alert level to Volcano Alert due to a change in the character of seismic signals (50-minute-long tremor) that occurred  immediately after the small steam emission at 12:15. Since the tremor stopped, seismic character has changed back to the type of earthquakes we have detected  since the beginning of the volcanic unrest. Earthquakes are occurring at a rate  of 1-2 per minute with maximum earthquake magnitues of about M3. All earthquake locations remain shallow. Today field crews took additional thermal images of the dome and crater. Deformation crews were in the field retrieving data from GPS instruments.  Results are not yet available from today's late gas flight . Currently wind forecasts from the National Oceanic and Atmospheric Administration (NOAA), combined with eruption models, show winds this evening will be from the east and southeast and any ash clouds will drift to the west  and northwest. We continue to monitor the situation very closely and will issue additional  updates as warranted. Press conferences will be held tomorrow at the Supervisor's Office of the  Gifford Pinchot National Forest. The morning press conference is at 9:30 am.

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