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Mt. Saint Helens Update

ash. During such eruptions, changes in the level of activity can occur over days to months. The eruption could 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.

Potenial Ash Hazards: Wind forecasts from the National Oceanic and Atmospheric Administration (NOAA), coupled with eruption models, show that ash clouds rising above the crater this morning would drift NE throughout the day.

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.

Recent observations: Cloud cover is down to about the level of the crater floor this morning, obscuring views of the new dome, but clouds are expected to lift and field crews will fly to the crater today to maintain and test instruments and make new observations of dome growth. No significant rockfalls have occurred in the past day, though occasional small rockfalls are likely to continue as they have in recent weeks, occasionally sending dust plumes above the crater rim.

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.

For additional information, background, images, and other graphics: http://vulcan.wr.usgs.gov/Volcanoes/MSH/Eruption04

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