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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: June 2, 2021

Opportunity to Comment on Mount Rainier Lahar Detection and Seismic Monitoring System

Expansion of the lahar detection system at Mount Rainier will improve the Cascades Volcano Observatory's overall volcano monitoring and lahar detection capacity and provide more rapid notification to the immediate area and surrounding communities.  

Date published: February 18, 2021

Brief earthquake swarm detected beneath Mount Rainier

While the seismicity represents a temporary uptick in activity, Mount Rainier remains at normal, background levels of activity.

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.

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