Cascade Range Current Update

Mount St. Helens Notice of Volcano Alert, October 2, 2004

A notice of Volcano Alert (Alert Level 3) was issued today at 2:00 p.m. PDT

Immediately after the small steam emission at 12:15, seismic activity changed from principally rock breakage events to continuous low-frequency tremor, which is indicative of magma movement. We are increasing the alert level to Volcano Alert the highest alert level indicating that an eruption could be imminent.

The cause and outcome of the accelerating unrest is uncertain. Explosions from the vent 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 to tens of thousands of feet above the crater rim and drift downwind. Currently wind forecasts from the National Weather Service, combined with eruption models, show that ash clouds will move to the northwest. If ash emissions are large, drifting ash could affect downwind communities. Minor melting of the glacier could trigger debris flows from the crater that are large enough to reach the Pumice Plain. There is very low probability that downstream communities would be impacted by these hydrologic events. .

We continue to monitor the situation very closely and will issue additional updates as warranted, whether activity escalates or returns to background levels.



Past Updates

News and Current Events