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COPYRIGHT 2002 Gale, COPYRIGHT 2005 Thomson Gale, a part of The Thomson Corporation
MASS WASTING
Mass wasting, or mass movement, is the process that moves Earth materials down a slope, under the influence of gravity. Mass wasting processes range from violent landslides to imperceptibly slow creep. Mass wasting decreases the steepness of slopes, leaving them more stable. While ice formation or water infiltration in sediments or rocks may aid mass wasting, the driving force is gravity. All mass wasting is a product of one or more of the following mass wasting processes: flow, fall, slide, or slump.
The four processes of mass wasting are distinguished based on the nature of the movement that they produce. Flow involves the rapid downslope movement of a chaotic mass of material. Varying amounts of water may be involved. Amud flow, for example, contains a large amount of water and involves the movement of very fine-grained Earth materials. Fall involves very rapid downslope movement of Earth materials as they descend (free fall) from a cliff. Ignoring wind resistance, falling materials accelerate at 32 ft/sec2 (9.8 m/sec2)—the average gravitational force of the earth. Slides result when a mass of material moves downslope, as a fairly coherent mass, along a planar surface. Slumps are similar to slides, but occur along a curved (concave-upward) surface and move somewhat more slowly.
Consider a chunk of rock currently attached to a jagged outcrop high on a mountain. It will move to the sea as a result of three processes: weathering, mass wasting, and erosion.
On warm days, water from melting snow trickles into a crack which...
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