Mount St. Helens Update October 4, 2004

International Glaciospeleological Survey

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

Mount St. Helens Update 4 October 2004 7:00 A.M.

Current status is Volcano Alert (Alert Level 3); aviation color code RED

Overnight seismic activity increased until a steam (and possibly ash) event occurred about 10:40 P.M. Observers at Coldwater Ridge could see the steam plume, which barely made it to the crater rim, in the moonlight. Since then, the seismicity has been significantly lower as after prior steam-and-ash events. Earthquakes are occurring at a rate of about 1 per minute and the largest since the steam event have been in the magnitude 2s. All locations remain shallow.

Results from GPS measurements indicate no significant deformation of the outer flanks of the volcano. However, visual observations and photographic analysis show large-scale uplift (10’s of meters) of part of the glacier and a nearby segment of the lava dome. Yesterday a field crew installed a new GPS instrument on the dome and also measured the distance from the Johnston Ridge Observatory to the dome.

Yesterday’s gas flight continued to detect carbon dioxide and low levels of hydrogen sulfide.

Two telemetered microphones are now in operation to detect explosions.

Today we will receive a remotely operated video camera that will be installed on the crater rim from the USGS Hawaiian Volcano Observatory. Today field crews will work at installing additional seismometers on the flanks of the volcano and will continue to harden the GPS sites and download data. Time permitting, additional flights to acquire thermal imagery and gas measurements will occur.

Wind forecasts from the NOAA, combined with eruption models show winds today will be from the east and southeast and any ash clouds would drift to the west and northwest.

We continue to be concerned that additional steam-and-ash eruptions could occur at any time. The principal hazard from these types of events is for ash reaching altitudes that could affect aviation. If the current unrest continues there is also an increased probability of larger magnitude and more ash-rich eruptions.

We continue to monitor the situation closely and will issue additional updates and Alert Level changes as warranted.

Press conferences will continue to be held at the Headquarters office of the Gifford Pinchot National Forest. Press conferences are held at 9:30 A.M. and 2:30 P.M.

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

Mount St. Helens Update 4 October 2004 7:00 P.M.

Current status is Volcano Alert (Alert Level 3); aviation color code RED

This morning visitors to Mount St. Helens witnessed a 40-minute-long steam-and-ash emission starting at 9:43 PDT. Steam clouds carrying minor ash billowed out of the crater to an altitude of 10,000 to perhaps 12,000 feet. The event did not generate earthquakes or an explosion signal. We infer that hot rock was pushed up into the glacier, melted ice, and generated the steam. Part of the vent for todayâ€™s and other steam and ash emissions of the past few days is now covered by a boiling lake. The emission occurred during a time of gradually increasing seismicity, which dropped slightly after the emission, but continued to increase gradually through the afternoon. Another period of smaller steam and ash bursts occurred between 2:10 and 2:40 P.M. Visual observations show that the area of uplift, which includes part of the glacier and a nearby segment of the south flank of the lava dome, continues to rise. We infer that magma is at a very shallow level and could soon be extruded into the vent or elsewhere in the deforming area. Additional steam and ash emissions are likely and could occur at any time without warning. Conditions suggest that there is also an increased probability of larger-magnitude and more ash-rich eruptions in coming days.

Yesterday’s gas-sensing flight detected slightly lower concentrations of carbon dioxide in the crater, but for the first time the airborne instruments detected the presence of hydrogen sulfide. Wind conditions during todays flight should permit the first estimation of the rate of gas flux.

Today field crews took additional thermal images of the dome and crater and conducted gas-sensingand geologic-observation flights. Two additional GPS stations were lowered by helicopter onto the 1980-86 lava dome to aid in measuring deformation of the dome.

Wind forecasts from the National Oceanic and Atmospheric Administration (NOAA), combined with eruption models, show winds this evening will be from the west and any ash clouds will drift eastward. By tomorrow morning the wind will shift to the south and any ash clouds will drift northward.

We continue to monitor the situation closely and will issue additional updates and Alert Level changes as warranted.

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.


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