USGS Update 2005-Aug-19 09:40

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 north-northwesterly in the early part of the day, transitioning to east-northeasterly by this evening.

Recent observations: Observers at Coldwater reported seeing an intense glow and vertical column over the space of several minutes at ~9:20 pm PDT last night, corresponding with two rockfall signals recorded by seismometers at 9:20 and 9:27 pm. Another rockfall was associated with a M 2.9 earthquake at 10:49pm PDT. Pictures from the Sugarbowl camera show that the new lava spine continues to grow and steepen with the formerly active spine continuing to sag and collapse, a scenario ripe for continued production of rockfalls and associated ash plumes and (at night) light shows. Seismic and ground-deformation data indicate that no significant changes have occurred in the level of activity over the last 24 hours. Yesterday field crews installed several temporary seismic instruments on the flanks and north end of the crater floor, repositioned several GPS stations, and did geologic mapping along the flanks. Weather permitting crews today will install more temporary seismometers, continue geologic mapping efforts, attempt to move several GPS spiders, and acquire rock samples from the new lava spine.

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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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