Cascade Range Current Update

MOUNT ST. HELENS UPDATE
Sunday, February 20, 2005 10:15 a.m. PST (1815 UTC)

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, 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.

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 in variable directions with time and altitude. Early clouds would drift lazily northward at low elevation, but east-northeastward at higher altitudes. Later, low-level clouds would drift lazily north-northwestward, but more southeastward at higher altitudes.

Potential ash hazards to aviation: Under current eruptive conditions, any ash clouds produced are unlikely to exceed 15,000 feet in altitude. Ashfall from such events rarely reaches more than 20 miles downwind. If the lava dome continues to grow over the next several months, it will become able to produce larger ash clouds that reach higher altitudes and extend farther downwind.

Recent observations: The crater is partly obscured by clouds this morning. A minor ash emission, much smaller than that of Friday afternoon, occurred yesterday morning. On the basis of seismicity, a similar event may have occurred early this morning. Further analysis of recent aerial photos reveals that as of February 1, the whaleback-shaped extrusion is about 1,550 feet long and 500 feet wide. The new dome and uplifted welt of crater floor and deformed glacier ice have grown to a combined volume of about 50 million cubic yards, almost one-half the volume of the old lava dome.

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/

For seismic information: http://www.pnsn.org/HELENS/welcome.html

For a definition of alert levels: http://vulcan.wr.usgs.gov/Volcanoes/Cascades/CurrentActivity/volcano_warning_scheme.html

For a webcam view of the volcano: http://www.fs.fed.us/gpnf/volcanocams/msh/

Telephone recordings with the latest update on Mount St. Helens and phone contacts for additional information can be heard by calling:

Media (360) 891-5180

General public (360) 891-5202

OTHER CASCADE VOLCANOES

All other volcanoes in the Cascade Range are all at normal levels of background seismicity. These include Mount Baker, Glacier Peak, Mount Rainier, and Mount Adams in Washington State; Mount Hood, Mount Jefferson, Three Sisters, Newberry, and Crater Lake, in Oregon; and Medicine Lake, Mount Shasta, and Lassen Peak in northern California.

USGS Cascades Volcano Observatory, the Pacific Northwest Seismograph Network at the University of Washington, and the USGS Northern California Seismic Network and Volcano Hazards Team in Menlo Park, California, monitor the major volcanoes in the Cascade Range of northern California, Oregon, and Washington.



Past Updates

News - Mount St. Helens Current Eruption Menu