Avalanches and mudflows like those described are normal events at Mount Rainier and are expected to happen again in the future. Almost any cliff on the volcano can produce a large rockfall, but which cliff will collapse next, or when, cannot be predicted. Should the volcano again become active, earthquakes and volcanic explosions would trigger avalanches and mudflows that would rush down the mountain. Molten rock would melt snow and ice at the volcano’s summit and send floods of water down the volcano’s flanks. These indirect effects of an eruption would be much more hazardous than lava flows and pumice, if eruptions are on a scale similar to that of the past 10,000 years.
The Volcano’s Future?
An active volcano changes continually. Repeated eruptions build the cone by piling one lava flow on top of others, or on top of other volcanic formations. Simultaneously, the combined processes of erosion wear the volcano down. The relative importance of the two processes—one building, the other destroying—is reflected in the volcano’s shape. The scarred and deeply gouged sides of Rainier’s cone show that erosion has been dominant here for a long time. Is Mount Rainier now doomed to continued piecemeal destruction until the lofty cone is reduced to a featureless mound? Will future eruptions of lava restore some of the volcano’s bulk? Or will the volcano erupt violently some day, and then collapse as did Mount Mazama to form the deep basin of Crater Lake? The answers may not be known for centuries—or they may appear tomorrow.
Further Reading in Geology
Crandell, D. R., 1969, Surficial geology of Mount Rainier National Park, Washington: U.S. Geological Survey Bulletin 1288. A geologic map that shows where glacial deposits, landslides, and mudflows are located in the park is accompanied by an illustrated nontechnical description of these and other surficial deposits.
Crandell, D. R., and Fahnestock, R. K., 1965, Rockfalls and avalanches from Little Tahoma Peak on Mount Rainier, Washington: U.S. Geological Survey Bulletin 1221-A, 30 pages. A description of the seven successive landslides of December 1963 that buried the upper White River valley under thick deposits of rock debris.
Crandell, D. R., and Mullineaux, D. R., 1967, Volcanic hazards at Mount Rainier, Washington: U.S. Geological Survey Bulletin 1238, 26 pages. A discussion of Mount Rainier’s eruptions during the last 10,000 years and the anticipated effects of similar future eruptions.
Fiske, R. S., Hopson, C. A., and Waters, A. C., 1964, Geologic map and section of Mount Rainier National Park, Washington: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-432, with text. A geological map of the park’s bedrock is accompanied by a brief nontechnical discussion of the geological evolution of the park as recorded by the rock formations.
Sigafoos, R. S., and Hendricks, E. L., 1961, Botanical evidence of the modern history of Nisqually Glacier, Washington: U.S. Geological Survey Professional Paper 387-A, 20 pages. A description of the recent moraines of several glaciers and an explanation of how they are dated by counting the growth rings of trees growing on them.
U.S. GOVERNMENT PRINTING OFFICE: 1968 O—353-560