Latest update by USGS
U.S. Geological Survey, Vancouver, Washington
University of Washington, Pacific Northwest Seismograph Network, Seattle, Washington
Saturday, March 12, 2005 10:10 a.m. PST (1810 UTC)
MOUNT ST. HELENS 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, 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: 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 south-southeastward early in the day. Later in the day, low-level clouds would drift south-southwestward but higher-level clouds would drift south-southeastward.
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: The volcano is clear this morning and emitting little steam. Revised analyses of Thursday’s gas measurements indicate that gas emissions are very low and essentially unchanged from those measured in late February. Hence there is no evidence at this time to indicate that a batch of more gas-rich magma has worked its way near the surface. Seismicity remains at a level comparable to that of the days before Tuesday’s explosive event. Next week, crews plan to deploy new seismometers and GPS units to replace those lost to the explosion.