USGS Update 2004-Dec-29 10:45

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

Recent observations: Yesterday field crews were able to get good thermal and photographic observations of the growing lava dome. These coupled with views from the DomeCam show clearly that the northern part of the new lava dome is being pushed upward onto the southern part along the prominent fractures created during the past two weeks. Concurrently, the east and west sides of the dome have been moving outward. All these changes are in response to continuing extrusion of lava into the dome. A result of dome expansion toward the east and west is a slight (one inch or less) outward movement of GPS instruments on the outer east and west flanks of the volcano. Similar movements were detected one month ago on the south side when the lava dome reached the base of the south crater wall. All are expectable and are not cause for any alarm. Difficult wind conditions and shifting steam plumes made delivery of new Spiders (portable GPS stations) onto the dome impossible. Deteriorating weather conditions in the afternoon interfered with the planned gas-sensing flight.

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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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