2005-02-18

 

USGS Update 2005-Feb-18 10:10


Aerial views taken on 2005-Feb-16

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 westward early in the day and northwestward later.

Potential ash hazards to aviation: Under current eruptive conditions, any ash clouds produced are unlikely to exceed 15,000 feet in altitude. Ashfall from such events rarely reaches more than 20 miles downwind. If the lava dome continues to grow over the next several months, it will become able to produce larger ash clouds that reach higher altitudes and extend farther downwind.

Recent observations: The GPS unit deployed on the east arm of the crater glacier on Wednesday is moving northward at about 4 feet per day. This rapid rate of flow is consistent with the thickening of the glacier that has resulted from its compression between the growing lava dome and east crater wall. Results of Wednesday’s thermal-imaging flight suggest that a longitudinal crack is developing along the top of the new lava dome. Similar to what happened in mid-December, the long smooth whaleback-shaped dome may be starting to crack apart. During such a process, the probability of rock avalanches increases and with that an increased chance of more ash clouds rising above the crater rim than we’ve witnessed in recent weeks.





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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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