Cascade Range Current Update

Note: beginning today (October 15, 2004), updates will be posted once a day at approximately 11:00 AM PDT

October 15, 2004 11:00 am PDT (1800 UTC)

MOUNT ST. HELENS VOLCANO

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 southeastward.

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. A gas-sensing flight yesterday found conditions unchanged from Wednesday with a low flux of sulfur dioxide and no detectable carbon dioxide or hydrogen sulfide. Yesterday’s geological observations and thermal imaging of the new lava dome indicate continued slow extrusion of lava. In addition, the surrounding uplifting and intensely deforming area on the south side of the 1980-86 lava dome and adjoining glacier continues to broaden.

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.

We 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, please visit: http://vulcan.wr.usgs.gov/News/framework.html

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

For a definition of alert levels, please see: http://vulcan.wr.usgs.gov/News/framework.html

Telephone recordings with the latest update on Mount St. Helens and phone contacts for additional information can be heard by calling: (360) 891-5180

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 Information