Cascade Range Current Update

Mount St. Helens Update, October 2, 2004, 7:30 A.M.

Current status is Alert-Level 2-Volcano Advisory

Yesterday the increasingly energetic seismic swarm of the past week culminated in a small 25-miunute-long eruption around noon from a vent just south of the lava dome. Seismicity dropped to a low level for several hours after the eruption, but quickly increased with earthquakes reaching a peak around 11 pm last night. Currently earthquakes are occurring at a rate of 1-2 per minute with maximum earthquake magnitudes about M3. All earthquake locations remain shallow. The current level of seismic energy release is slightly above where it was prior to the eruption yesterday. We infer that the system has repressurized. As a result, additional steam-and-ash eruptions similar to yesterdays’s could occur at any time.

Yesterday field crews in a helicopter took thermal images of the dome and crater both during and several hours after the eruption. Temperatures were consistent with those expected from the steam explosion and well below magmatic temperatures. Another flight for thermal imagery will occur this morning. A deformation crew will be in the field today to collect data. Yesterday's gas flight detected no magmatic gases in the area of the eruptive vent, but did detect some carbon dioxide (CO2) from a small fumarole on the NW face of the dome. The amount of CO2 will probably be too small to quantify. At times the flight crew thought they smelled a weak sulfurous odor in the vicinity of this fumarole, but the sensors did not detect any SO2 or H2S.

Updated wind forecasts from the National Oceanic and Atmospheric Administration coupled with an eruption model indicate that the wind direction are from the east so that any ash clouds produced today will drift westwardly.

There will be a press conference at CVO this morning at 9:30 am.



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