USGS Update 2005-Aug-20 09:45

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 northeasterly.

Recent observations: Early morning pictures from the Sugarbowl camera indicate that dome growth continues, with continued slumping of the middle part of the new dome complex and westwards as well as vertical motion of the latest lava spine located at the western edge of the complex. Over the last week seismicity levels have gradually dropped from an earthquake every 5-10 minutes to one every 10-20 minutes. No other significant changes in seismicity or deformation have occurred over the last 24 hours. A rockfall yesterday evening at 1925 PDT created a small ash cloud that rose over the rim and was briefly visible from the Portland area before it rapidly dissipated to the northeast. Yesterday field crews installed more temporary seismic instruments in the northern part of the crater floor, repositioned several GPS spider stations on the western lobe of the crater glacier, recovered ash samples out of an ash spider placed on the southern side of the old dome, grabbed new rock samples from near the vent, and did geologic mapping along the flanks.

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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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