Mt. Rainier (Tahama)
       7 ½’ quadrangles: Mt. Rainier West and Mt. Rainier East, WA
       Pierce County
       Mt. Rainier National Park. Pacific Crest Trail passes on the east side.
       Cascade Range

Igneous Volcanic
14,410 ft (4,392 m)

Mt. Rainier viewed from the north, from along the trail to Mt. Fremont.
Carbon Glacier originates at the foot of Willis Wall and Liberty Cap,
to the right of snowy Columbia Crest in this photo. (1997)

Carbon Glacier's terminus at ~3500 ft elevation north of Mt. Rainier. The
name reflects the fact that the ice is loaded with rock debris. Folded
layers of debris attest to plastic flow within the ice. (1988)

Bedrock: Andesite

Pleistocene and Holocene

Andesitic pumice, ash, cinders and breadcrust bombs, in a steep stratovolcano capped by glacial ice. The summit (Columbia Crest) is the point where the two most recent craters overlap. They were active less than 2500 years ago, within the remnants of a larger, older caldera that collapsed 5700 BP. Ash was ejected in an episode from 1820 to 1854. Steam eruptions happen every so often, most recently in 1879, 1884, 1961, 1963, and 1967, and steam has carved caves into the glacial ice. The biggest danger from an eruption at Rainier is the high likelihood of ash flows and lahars down the valleys into settled areas.

For a discussion of all the volcanic highpoints, see http://www.unh.edu/esci/volcanic_highpoints03.pdf

Surficial Geology: Early Wisconsinan Evans Creek glacial drift and late Wisconsinan drift are found on and around Mt. Rainier, and still younger LaGarda moraines lie in the valleys. The present ice cap feeds numerous valley glaciers: Mowich, Puyallup, and Tahoma to the west; Kautz, Nisqually, Paradise, Cowlitz, and Ingraham to the south; Whitman and Frying Pan to the east; Emmons, Winthrop and Carbon to the north. If the ice were to melt from Mt. Rainier, it would leave behind cirques at the head of each glacial valley and spectacular arêtes between them, for example Cathedral Rocks and Success Cleaver. Little Tahoma Peak would become a horn.

Soil Series: Not applicable for the summit, although steam-altered volcanic rock would form the basis for rich soils in the future.

Selected References:

  • Crandall, Dwight E., 1969a, The geologic story of Mount Rainier: USGS Bulletin 1292, 43p.
  • Crandall, Dwight E., 1969b, Surficial geology of Mount Rainier National Park: USGS Bulletin 1288, 41p.
  • Harris, Stephen L., 1988, Fire Mountains of the West: the Cascades and Mono Lake Volcanoes: Mountain Press, Missoula, MT.

Other suggested sources of information:

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