From Washington To You
Snow-covered Mount Rainier reflected in the still water of Bench Lake in early September.
Photograph by Steve Redman, National Park Service. Public domain.

From Washington to you

Mount Rainier

Mount Rainier · Pierce County · last eruption about 1,000 years ago

The highest Cascade peak is also the most threatening volcano in the range — not for lava, but for mud.

Mount Rainier is the highest peak in the Cascade Range: 4,392 meters, or 14,410 feet. USGS places it in Pierce County at 46.853° N, 121.76° W. It is a stratovolcano of andesite to dacite. The last magmatic eruption was about 1,000 years ago.

The National Volcano Early Warning System rates its threat potential as Very High. USGS calls it the most threatening volcano in the Cascades because of its height, hydrothermal alteration, icecap, glacier-fed valleys, and the suburbs of Seattle and Tacoma downstream.

The greatest risk is lahars — volcanic mudflows. They can start in an eruption or when weakened rock collapses, even without an eruption. Past lahars have reached the Puget Sound lowlands. The last large one, the Electron Mudflow, came off the west flank about 500 years ago with no known triggering eruption. The sources below are the public USGS record of the mountain and its hazards.

  • Geography & Geology
  • Science / Strange Washington

Sources (3)

Last reviewed: September 20, 2026

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Mount Rainier · From Washington To You