Mass Wasting at Crater Lake National Park

Rock slides and landslides are a common occurrence at Crater Lake National Park, especially within the caldera rim of Crater Lake. If you wait for long or frequent the rim, you are bound to see one.


A rock slide within the Crater Lake caldera rim wall, Crater Lake National Park, photo by Robert Mutch

Many factors contribute to the downward movement of the rock debris. Most important is melt-water derived from snow that accumulates to great thicknesses on the rock walls. This gives lubricating and hydraulic action for the removal of fine rock particles that support larger debris. Once a slide is started, more material of all sizes is dislodged along the paths. These tumble and bounce from one rock ledge to another, breaking off the edges, filling crevices crossed enroute, cutting their way through snow fields, and only stopping far below. Winds blowing against the walls also loosen fine particles which are supporting more massive material and help to start rock movement. Scurrying movements of small animals and tremblors caused by the rumbles of vehicles passing on the road, by thunder, or by distant slides are other contributing factors. [Active Rock Slides – Nature Notes From Crater Lake, Henry E. Kane, Vol. 16 – 1950]

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 Definition (Mass Wasting):

The process by which soil, regolith, and rock move downslope under the force of gravity. Types of mass wasting include creep, landslides, flows, topples, and falls, each with their own characteristic features, and take place over timescales from seconds to years.

Factors changing the potential of mass wasting include: change in slope angle; weakening of material by weathering; increased water content; changes in vegetation cover; and overloading. — Wikipedia: Mass Wasting

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