Mount St. Helens Releases More Ash and Steam

Vancouver, Washington (HDW) October 12, 2004 – Mount St. Helens is still in a period of “unrest” according to the U.S. Geological Survey (USGS). The volcano continues to release steam and ash, but a major eruption may not be imminent. Seismic activity remained at a low level yesterday. Small earthquakes around magnitude 1 were occurring at a rate of about 1 per 5 to 10 minutes. Visual observations and thermal imaging of the crater, the 1980-86 lava dome, and the intensely deforming and uplifting area on the south side of the dome were made yesterday afternoon. The western part of the uplifting area appears to be the most actively deforming site and was the source of a brief steam and emission about 16:00 that drifted southeastward. A dusting of ash on new snow in that sector suggests that similar minor ash emissions also occurred recently. A steam plume originating on the deforming area continues to rise above the crater rim and drift to the southeast. Scientists also conducted a gas-sensing flight. Results will be available tomorrow as will results of thermal imaging.

As a result of the intense unrest of the past two weeks, the USGS infers 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. The USGS expects 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, the USGS will 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 may remain northwesterly. Any ash clouds may drift south-southeastwardly to southeastwardly.