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U.S. Geological Survey, Vancouver, Washington
University of Washington, Pacific Northwest Seismograph Network, Seattle, Washington
Mount St. Helens Update, October 14, 2004, 6:15 p.m, PDT
Current status is Volcano Advisory (Alert Level 2); aviation color code ORANGE
Seismic activity remained at a low level today. Today’s visual observations and thermal imaging of the crater were focused on the intensely deforming and uplifting area on the south side of the 1980-86 lava dome and the new lobe of lava in the western part of that area. The area of both the uplift and the new lobe of lava have increased slightly since yesterday. Yesterday’s gas-sensing flight detected low levels of sulfur dioxide and hydrogen sulfide, but no carbon dioxide. Abundant steam continues to rise from the area of lava extrusion to the crater rim, from which it is being dispersed downwind. Measurements taken yesterday of flow-rate and temperature in streams draining the crater showed no significant change from late September values.
Other field work today included a gas-sensing flight (data not yet reduced), downloading GPS data, and servicing GPS stations.
Wind forecasts from the National Oceanic and Atmospheric Administration (NOAA), combined with eruption models, show that any ash clouds will drift south-southeastward this evening and southeastward tomorrow morning. Magma continues to be at a very shallow level and is extruding onto the surface and forming a new lobe of the lava dome. Small emissions of steam and ash are possible. Reflection onto steam clouds of incandescence or glow from the hot rock and gases will be visible at night from some locations.
Lava-dome growth is a dynamic process and, as we observed in the mid-1980s, Mount St. Helens and similar volcanoes elsewhere typically go through episodic changes in level of activity over periods of days to weeks, or even months. We expect fluctuations in the level of eruptive activity to continue. Escalation could occur suddenly. Therefore, we continue to monitor the situation closely and will issue additional updates and changes in alert level as warranted.
Under current conditions, small lahars (volcanic debris flows) could be triggered if hot material from the new lava extrusion swiftly melts glacier ice. Such lahars pose negligible hazard below the Sediment Retention Structure (SRS), but could pose a hazard to people working or recreating along the river channel upstream of the SRS. Furthermore, due to weather and stream-flow conditions at this time of year, it is not unusual for rivers draining the volcano to contain high concentrations of sediment that turn the water murky.
There will no longer be daily media briefings at the Headquarters of the Gifford Pinchot National Forest. A media briefing will be held tomorrow at 1 p.m. at Castle Lake Viewpoint in the Mount St. Helens National Volcanic Monument. However no additional such briefing are planned until conditions warrant them. Beginning tomorrow, we will release only one daily update, at approximately 11 a.m. Tomorrows update will contain information regarding media contacts with the Joint Information Center.
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