USGS Update 2004-Dec-17 09:50

Potential ash hazards: Wind forecasts from the National Oceanic and Atmospheric Administration (NOAA), coupled with eruption models, show that ash clouds that rise above the crater rim today would drift east-southeastward.

Recent observations: We got clear views of the crater mid-day yesterday during a thermal-imaging flight. The new dome has noticeably broadened and the prominent fracture system along its top continues to widen. Hot cracks emit ash intermittently. During the night of December 15 (Wednesday) ash emitted from the east side of the dome formed a cloud that swept down the east arm of the glacier and over east side of the old lava dome, leaving a dark smear of ash on the snow on its north face. This smear is visible on the USFS VolcanoCam. The flow was relatively cool as it did not melt much snow. We were also able to repair an important radio-telemetry site that was severely damaged during the recent windstorm and do other needed maintenance. Owing to a late start caused by lingering fog in the metro area, we were not able to fit in a gas-sensing flight. That flight will begin shortly today. This morning the volcano is emitting a vapor plume that is drifting over the southeast crater rim. Four earthquakes of about magnitude 3 occurred overnight amidst the ongoing pattern of frequent smaller earthquakes. Swarms of similar-sized events have occurred on several occasions during the past month.

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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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