Mount St. Helen is in Danger of Erupting Near Seattle Again

Seattle, Washington (HDW) September 30, 2004 - Earthquake activity beneath Mount St. Helens volcano has increased during the past few days. Scientists of the United States Geological Survey (USGS) Cascades Volcano Observatory (CVO) and the University of Washington described the elevated earthquake activity and indicated that although the outcome of this activity is uncertain, several explosive scenarios are possible. The most recent eruption of the volcano's lava dome occurred in October 1986, and a series of explosions occurred in 1989-91.

Over night, seismic activity at Mount St. Helens has accelerated significantly, which increases USGS concern that current unrest could culminate in an eruption. The USGS is increasing the alert level to the second of three levels, which is similar to the National Weather Service’s hazard watch. Earthquakes are occurring at about four per minute. The largest events are approaching Magnitude 2.5 and they are becoming more frequent. This suggests that the ongoing intense earthquake activity has weakened the dome, increasing the likelihood of explosions or perhaps the extrusion of lava from the dome.

Explosions from the lava dome could occur suddenly and without further warning. During such explosions the dome and crater floor are at greatest risk from ballistic projectiles, but the rim of the crater and flanks of the volcano could also be at risk. Explosions would also be expected to produce ash clouds that rise several thousand feet above the crater rim and drift downwind. On September 29, the USGS reported that, wind forecasts from the National Weather Service, combined with USGS eruption models, show that ash clouds will move in a southeasterly direction and could dust areas tens of miles or more from the volcano with ash. Landslides and debris flows from the crater that are large enough to reach the plain below. The USGS will continue to monitor Mount St. Helens closely and will issue additional updates as warranted.