2004-10-16

 

USGS Update 2004-0ct-16 11:00

Current Update

Current status is Volcano Advisory (Alert Level 2); aviation color code ORANGE

Growth of the new lava dome inside the crater of Mount St. Helens continues. As long as this eruption is in progress, episodic changes in the level of activity can occur over days, weeks, or even months. Increase in the intensity of eruption could occur suddenly or with very little warning and may include explosive events that produce hazardous conditions within several miles of the volcano. Under current conditions, small lahars (volcanic debris flows) could suddenly descend the Toutle River valley if they are triggered by heavy rain or by interaction of hot rocks with snow or glacier ice. Such lahars pose negligible hazard below the Sediment Retention Structure (SRS), but could pose a hazard to people working or recreating along the river channel upstream of the SRS. Furthermore, due to weather and stream-flow conditions at this time of year, it is not unusual for rivers draining the volcano to contain high concentrations of sediment that turn the water murky. Although considered less likely at this time, eruptive activity could also evolve into a more explosive phase that affects areas farther from the volcano and sends significant ash thousands of feet above the crater where it could be a hazard to aircraft and to downwind communities.

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 will drift east-southeastward to eastward later in the day.

During the past 24 hours, seismicity has remained at a low level. Global Positioning System (GPS) measurements continue to indicate only minor deformation of the northern part of the 1980-86 lava dome and no deformation of the outer flanks of the volcano. Poor weather yesterday limited geological observations to a few time-lapse pictures from the video camera at Sugar Bowl and brief views from Johnston Ridge Observatory. Parts of the area of uplift and new lava dome visible from those points were higher than when last seen on 14 October.

Our recent observations are consistent with ongoing rise of magma driving the uplift and feeding the surface extrusion of lava. Low rates of seismicity and gas emission suggest that the lava reaching the surface is gas poor.

Today, field crews will continue geologic observations, thermal imaging, and improvements in telemetry systems if weather conditions permit.





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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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