USGS Update 2005-Oct-05 13:00

Potential ash hazards: Wind forecasts from the National Oceanic and Atmospheric Administration (NOAA), coupled with eruption models, show that any ash clouds that rise above the crater rim today would drift broadly east-northeast to east-southeast.

Recent observations: The lava dome’s extrusion continues, as does its inexorable decay by rockfalls and small slope collapses. The past weekend’s storm left snow blanketing most of the volcano. A late afternoon overflight Tuesday found the deposit of a collapse from the north flank of “dome 5.” Number 5 indicates the whaleback-shaped dome that was actively expanding until August. The collapse, which gullied the face of the dome, spun out a fine layer of ash directed northward as a narrow plume for 1 km within the crater. Nothing beyond the crater was affected by this small event. Exact timing of the rockfall is uncertain, occurring possibly Monday night or early Tuesday. Its trigger may have been one of the larger earthquakes (in the magnitude range 2-3) that periodically punctuate the seismic record of smaller earthquakes less than M1.

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Standard USGS Update

Growth of the new lava dome inside the crater of Mount St. Helens continues, accompanied by low rates of seismicity, low emissions of steam and volcanic gases, and minor production of ash. During such eruptions, episodic changes in the level of activity can occur over days to months. The eruption could also intensify suddenly or with little warning and produce explosions that cause hazardous conditions within several miles of the crater and farther downwind. Small lahars could suddenly descend the Toutle River if triggered by heavy rain or by interaction of hot rocks with snow and ice. These lahars pose a negligible hazard below the Sediment Retention Structure (SRS) but could pose a hazard along the river channel upstream.

Potential ash hazards to aviation: Under current eruptive conditions, small, short-lived explosions may produce ash clouds that exceed 30,000 feet in altitude. Ash from such events can travel 100 miles or more downwind.

The U.S. Geological Survey and the University of Washington continue to monitor the situation closely and will issue additional updates and changes in alert level as warranted.

My intent with this page is to provide a clearning house for links to the current activity at Mt.St.Helens. Please send me any links of interest that you may come across, whether for permanent sites or for news reports. I'm not going to be able to do this all alone and all help will be appreciated.

(Disclaimer— I have no association with anyone or any organization, and speak only for myself. Links and quotes are provided for information only.)

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