- Status: Mount Rainier is monitored by the Cascade Volcano Observatory and is at a background level of activity.
- Volcanic History Overview: Mount Rainier, the highest peak in the Cascade Range at 4,392m (14,410 ft.), forms a dramatic backdrop to the Puget Sound region. During an eruption 5,600 years ago the once-higher edifice collapsed. Ensuing eruptions rebuilt the summit, filling the large collapse crater. Large mudflows from eruptions and from collapses of this massive, heavily glaciated andesitic volcano have reached as far as the Puget Sound lowlands. On more than a dozen occasions since the last ice age, 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. There is also a labyrinth of steam caves beneath the summit icecap produced by an active thermal system driven by magma deep beneath the volcano.
- Location: Western US, WA
Elevation: 4392 m
Recent Eruption: Possibly in 1894 and 1840's, larger eruption certain 1,000 years ago
- Hazard Assessments: Hoblitt, et.al., 1998, Volcano Hazards from Mount Rainier, Washington, Revised 1998, USGS Open-File Report 98-428.
- Link to monitoring data: The Pacific Northwest Seismic Network
Volcanic Alert Level: NORMAL Aviation Color Code: GREEN