USGS Update 2005-Jun-17 10:30

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-northwestward to northward. Under these conditions, Johnston Ridge and the east end of Highway 504 could receive ash fall.

Recent observations: Additional analysis of data from Wednesday’s field work shows an interesting pattern. Thermal-sensing data reveal a hot zone around the perimeter of the western part of the new lava dome, an area about 400 meters long by 50 meters wide. In the past few months, such a hot zone has been restricted to the north end of the dome, where lava was being extruded to form a succession of whaleback-shaped domes, which chiefly moved southward. Coupled with the orientation of grooves that form as the dome extrudes from the vent, these new thermal data suggest that much of the western part of the dome is moving upward, as well as southward. We would like to place a GPS spider on this part of the dome to measure its rate of movement, but stable spots are scarce because this part of the dome is also producing a lot of rockfalls.

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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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