Sunday, September 11, 2005

Could This Be the Next Lower 48 Volcano to Blow?



South Sister (left) is about 25 miles from our house as the crow flies. It is a popular mountain for climbing because the south approach to its 10,358-foot summit is a steep but non-technical hike. South Sister is surrounded by some of the most beautiful backpacking country you'll ever find.

It is starting to look like it could be the next volcano in the Cascade Mountain Range to go off:

A recent survey of a bulge that covers about 100 square miles near the South Sister indicates the area is still growing, suggesting it could be another volcano in the making or a major shift of molten rock under the center of the Cascade Range. * * *

The likely cause of the bulge is a pool of magma that, according to Deschutes National Forest geologist Larry Chitwood, is equal in size to a lake 1 mile across and 65 feet deep.

The magma lake is rising 10 feet each year, under tremendous pressure, and it deforms the Earth's surface as it expands, causing the bulge.

Although the city of Bend is very close to this mountain, Bend is on the east side of South Sister and the slowly-growing bulge is on the west side. If it erupts, Bend will likely get hit by a lot of ash but would probably not be affected by any pyroclastic flows or mudflows.

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