Mass Movements and Their Human Impacts
Mass Movement is defined as the down slope movement of rock and regolith near the Earth's surface mainly due to the force of gravity. Mass movements are an important part of the erosional process, as it moves material from higher elevations to lower elevations where transporting agents like streams and glaciers can then pick up the material and move it to even lower elevations. Mass movement processes are occurring continuously on all slopes; some act very slowly, others occur very suddenly, often with disastrous results. Any perceptible down slope movement of rock or regolith is often referred to in general terms as a landslide. Landslides, however, can be classified in a much more detailed way that reflects the mechanisms responsible for the movement and the velocity at which the movement occurs. Types of Mass Movement Processes
The down-slope movement of material, whether it be bedrock, regolith, or a mixture of these, is commonly referred to as a landslide. All of these processes generally grade into one another, so classification of such processes is somewhat difficult. We will use a classification that divides mass movement processes into two broad categories (note that this classification is somewhat different than that used by your textbook). 1. Slope Failures - a sudden failure of the slope resulting in transport of debris down hill by sliding, rolling, falling, or slumping. 2. Sediment Flows - debris flows down hill mixed with water or air.
Slumps (also called Rotational Slides)-types of slides wherein downward rotation of rock or regolith occurs along a concave-upward curved surface (rotational slides). The upper surface of each slump block remains relatively undisturbed, as do the individual blocks. Slumps leave arcuate scars or depressions on the hill slope. Slumps can be isolated or may occur in large complexes covering thousands of square meters. They often form as a result of...
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