Monday, May 24, 2010

Mount Rainier Lahar Hazard Map

With the 30th anniversary of the eruption of Mount Saint Helens in southern Washington our Washington State volcanoes as well as other volcanoes are getting some attention. Mount Rainier gets the most and for good reason. I came across this map of the lahar hazard for Mount Rainier prepared by the United States Geological Survey.

Rainier is a big mountain and mudflows from Rainier have deeply buried the downstream valleys in the past. Crandell and Waldron initially recognized the massive mud deposits from Mt. Rainier in 1956. These deposits had initially been mapped as glacial till. Dragovich, Pringle and Walsh (1994) subsequently used well and geotechnical borings an determined that the mud flows traveled as much as 62 miles and the mudflow combined with post mudflow sedimentation played a major role in filling in an arm of Puget Sound now occupied by Puyallup, Auburn, Sumner, Kent and Fife.

I am used to seeing Mount Baker’s summit rising above the Nooksack and Skagit Valleys in northwest Washington. But the view of Rainier from Orting is awesome looking in more ways than one.


helena.heliotrope said...

Makes you wonder why people keep building casinos and car dealerships in those valleys.
Actually, my parents' house is on a hill overlooking Auburn. Death by lahar was a definitely a childhood concern.

It's good to see another Washingtonian blog!

Ben said...

ive heard that the lahars occur without an eruption taking place leaving people with little warning. im from enumclaw and nobody there would have a clue what to do if a large lahar were to occur in the white river valley

Dan McShane said...

You are correct Ben. Certainly eruption activity increases the mud flow risk, but the internal heat and movement of heated water through the steep volcano slopes will lead to mud flows.