The movement of geological materials, usually downslope, in response to the force of gravity is called mass wasting or mass movement. Factors influencing slope stability include slope steepness, moisture, content, plant cover, earthquakes, presence of quick clay or sensitive clay, and human activities. Mass movements are classified on the basis of the type of material moved and the rate of movement. Type of mass movements are decided below.
Most falls are rockfalls.
The lessening of hazards, associated with mass movements can be accomplished by reducing slope angle, using retaining walls, reducing the load on a slope, planting vegetation, placing a supporting material at the base of a slope, using vertical piles or rock bolts to stabilize a slope, and reducing the moisture of the slope material. Areas subject to mass wasting can be recognized by noting missing areas of plant cover on vegetatative slopes, curved or tilted trees, slanted utility poles and other stationary objects, cracked masonry, warped door or window frames, and broken utility lines or pipes. Aerial photography and topographic maps can reveal otherwise obscure mass movements.