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Mass wasting, also known as mass movement, [1] is a general term for the movement of rock or soil down slopes under the force of gravity. It differs from other processes of erosion in that the debris transported by mass wasting is not entrained in a moving medium, such as water, wind, or ice.
It is the removal of the slope's physical support which provokes this mass wasting event. Thorough wetting is a common cause, which explains why slumping is often associated with heavy rainfall, storm events and earthflows. Rain provides lubrication for the material to slide, and increases the self-mass of the material.
Solifluction is a collective name for gradual processes in which a mass moves down a slope ("mass wasting") related to freeze-thaw activity. This is the standard modern meaning of solifluction, which differs from the original meaning given to it by Johan Gunnar Andersson in 1906. [1] [2]
A mudflow, also known as mudslide or mud flow, is a form of mass wasting involving fast-moving flow of debris and dirt that has become liquified by the addition of water. [1] Such flows can move at speeds ranging from 3 meters/minute to 5 meters/second. [2]
Debris avalanche deposit of Tata Sabaya in Bolivia Cross-section diagram showing (a) pre-collapse volcano, (b) after collapse, (c) new edifice built on top of collapsed old edifice At volcanoes, the term landslide is commonly used for slope movements with shear and displacement in a relatively narrow zone. [ 7 ]
In traditional usage, the term landslide has at one time or another been used to cover almost all forms of mass movement of rocks and regolith at the Earth's surface. In 1978, geologist David Varnes noted this imprecise usage and proposed a new, much tighter scheme for the classification of mass movements and subsidence processes. [26]
Amongst these erosional properties, water is arguably the most effective geologic agent that causes mass-wasting events to occur. Water aids in the downslope movement of surface material by adding weight to the soil and by filling pores which tends to push apart individual grains, decreasing the resistance of the material to movement. [4]
Mass wasting or mass movement is the downward and outward movement of rock and sediments on a sloped surface, mainly due to the force of gravity. [49] [50] Mass wasting is an important part of the erosional process and is often the first stage in the breakdown and transport of weathered materials in mountainous areas.