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USGS/Cascades Volcano Observatory, Vancouver, Washington

Mount St. Helens, Washington
"Plume in the Evening"
March 8, 2005


 
 

A small, short-lived explosive event at Mount St. Helens volcano began at approximately 5:25 p.m. PST, March 8, 2005. Airplane pilot reports indicate that the resulting steam-and-ash plume reached an altitude of about 36,000 feet above sea level within a few minutes and drifted downwind to the northeast. The volcano's rim stands at 8,325 feet.



March 8, 2005

The principal event lasted about 30 minutes, with intensity gradually declining throughout. The resulting plume was mostly white or light colored as viewed in the Pacific Northwest sunset, which is the basis for our preliminary assessment that steam was the predominant component. Even so, light dustings of ash are expected on the flanks of the volcano and are possible as far away as central Washington.

Plume from CVO


The eruption was photographed by many residents in the Portland-Vancouver metropolitan area. Images on a ten-minute sequence were captured by the web cam at the U.S. Forest Service's Johnston Ridge Observatory, 8.5 kilometers (5.2 miles) north of the volcano. We've annotated one of those images from late in the sequence, for the benefit of readers who browse to the U.S. Forest Service website.

Annotated, from USFS JRO camera


Additionally, a research camera about 2.3 kilometers (1.5 miles) from the vent caught the root of the plume as the eruption began. This camera takes an image every 2.5 minutes. Presented here are three images, the first showing the dome on the morning of March 8, 2005, and the next two during the event.

Sugar Bowl DomeCam
Dome from Sugar Bowl Camera, March 8, 2005, 6:56:58 a.m. PST

Sugar Bowl DomeCam
Dome from Sugar Bowl Camera, March 8, 2005, 5:27:42 p.m. PST

Sugar Bowl DomeCam
Dome from Sugar Bowl Camera, March 8, 2005, 5:53:02 p.m. PST


To the best of our knowledge, no lives have been at risk and no injuries sustained as part of the latest steam-and-ash ejection, one of the largest since October 2004. The U.S. Geological Survey had no crews in the field at the time. The area around the volcano is closed to public entry, owing to the hazardous conditions that have been ongoing since the eruption began in late September 2004.

 

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03/08/05, Lyn Topinka