Introduction to Mass Wasting

Mass wasting is a natural result of weathering on slopes. Simply put, gravity pulls loose rock and soil downhill. Mass wasting is the process of erosion whereby rock, soil, and other earth materials move down a slope because of gravitational forces. It proceeds at variable rates of speed and is largely dependent on the water saturation levels and the steepness of the terrain. A destructive, rapid mass‐wasting event is called a landslide; if the movement is slow enough that it cannot be seen in motion, it is called creep.

Three kinds of movement are generally recognized: flow, slip, and fall. A mass‐wasting event is called a flow if the mass moves downslope like a viscous fluid. If the mass moves as a solid unit along a surface or plane, it is called a slip. A slip that moves along a surface parallel to the slope is called a slide. If the movement occurs along a curved surface where the downward movement of the upper part of the mass leaves a steep scarp (cliff) and the bottom part is pushed outward along a more horizontal plane, it is called a slump. Earth material that free‐falls from a steep face or cliff is termed a fall.