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Mount Rainier, the highest peak in the Cascade Range at 4,392m (14,410 ft), forms a dramatic backdrop to the Puget Sound region.


Summary

During an eruption 5,600 years ago the once-higher edifice of Mount Rainier collapsed to form a large crater open to the northeast much like that at Mount St. Helens after 1980. Ensuing eruptions rebuilt the summit, filling the large collapse crater. Large lahars (volcanic mudflows) from eruptions and from collapses of this massive, heavily glaciated andesitic volcano have reached as far as the Puget Sound lowlands. Since the last ice age, several dozen explosive eruptions spread tephra (ash, pumice) across parts of Washington. The last magmatic eruption was about 1,000 years ago. Extensive hydrothermal alteration of the upper portion of the volcano has contributed to its structural weakness promoting collapse. An active thermal system driven by magma deep under the volcano has melted out a labyrinth of steam caves beneath the summit icecap.

News

Date published: October 19, 2020

Trump Administration Officials Tour New Mt. Rainier Lahar Detection Stations

TACOMA, Wash. — Deputy Secretary of the Interior Katharine MacGregor, U.S. Geological Survey Director Jim Reilly, and Counselor to the Secretary Margaret Everson, Exercising the Delegated Authority of the Director of the National Park Service, today visited Mount Rainier National Park to announce the successful permitting and ongoing installation of five new lahar monitoring stations.

Date published: October 16, 2020

Media Advisory: Exclusive Interview Opportunities with Interior Officials to Learn about New Mt. Rainier Lahar Detection Stations

TACOMA, Wash. — What is a lahar and why are they a threat to those who live below Mount Rainier? Journalists are invited to learn about the  threat potential posed by lahars from Mount Rainier to local communities and how  new  USGS lahar monitoring stations will integrate into emergency preparedness and response.    

Date published: October 16, 2020

New station enhances Mount Rainier’s lahar detection network

New station expands scientists' capabilities to detect unrest and provide rapid notification of hazards to emergency officials and the public.

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