2005-04-28

 

USGS Update 2005-Apr-28 10:15

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 south-southeastward early in the day and southeastward later.

Recent observations: Many people in the eastern part of the Portland metropolitan area awoke this morning to slightly grimy windshields. We collected samples of the grime and found that it contains some fine ash. Seismic instruments show no evidence of an explosion occurring and there is no evidence of significant new ash on snow in the crater. We think that the large convective storms that built up over the Cascades (including Mount St. Helens) yesterday afternoon and evening and moved southward were the culprits. The storms entrained ash generated by the frequent hot rockfalls from the growing lava dome and kept it in suspension. Some of the ash we see in eastern Clark County appears to have fallen in raindrops. A crew is on the way to the volcano to get a close look at the dome and crater and to collect some ash samples on the volcano’s flank.





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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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