Oo982 Mass Wasting Gravity at Work Definition: the spontaneous movement of material down a slope in response to gravity. If a gravitational force acting on a slope exceeds its resisting force, then slope failure (mass wasting) occurs. The slopes shear strength is the result of cohesion and the amount of internal friction between the particles comprising the slope. The steepest angle that particles on a slope can maintain without losing its stability is known as its angle of repose. Fall: Cliff exposure with fractured bedrock. Angular blocks and slabs piled up at the footslope. Scarred and broken trees. Slump: Bank or cliff exposure in soil or bedrock. Movement often back rotational motion. Trees uprooted and tipped back toward slope. Slide: Concave scar on slope. Displaced mass resting anywhere from one meter to a kilmoeter downslope. Broken and bent trees and buried soil. Flow: Lobate forms, trees bent or upright. Buried ground vegetation and soil.