Mass movement, also known as mass wasting, refers to the bulk movements of soil and rock debris down slopes in response to the pull of gravity, or the rapid or gradual sinking of the Earths ground surface in a predominantly vertical direction. The term mass movement has been substituted to include mass wasting processes and the sinking of confined areas of the Earths ground surface. Mass movements on slopes and sinking mass movements are often aided by water and the significance of both types is the part each plays in the alteration of landforms.
The variety of downslope mass movements reflects the diversity of factors that are responsible for their origin. Such factors include: weathering or erosional debris cover on slopes, which is usually liable to mass movement; the character and structure of rocks, such as resistant permeable beds prone to sliding because of underlying impermeable rocks; the removal of the vegetation cover, which increases the slopes susceptibility to mass movement by reducing its stability; artificial or natural increases in the slopes steepness, which will usually induce mass movement; earthquake tremors, which affect the slope equilibrium and increase the likelihood of mass movement; and flowing ground water, which exerts pressure on soil particles and impairs slope stability.
The types of mass movements caused by the above factors include: the abrupt movement and free fall of loosened blocks of solid rock, known as rockfalls; several types of almost imperceptible downslope movement of surficial soil particles and rock debris, collectively called creep; the subsurface creep of rock material, known as bulging: the multiplicity of downslope movements of bedrock and other debris caused by the separation of a slope section along a plane of least resistance or slip surface, collectively called landslides; the separation of a mass along a concave head scarp, moving down a curved slip surface and accumulating at the slopes foot, known as a slump; the saturation of debris and weathered material by rainfall in the upper section of a slope or valley, increasing the weight of the debris and causing a slow downslope movement, called an earthflow; a rapidly moving earthflow possessing a higher water content, known as a mudflow; a fast-moving earthflow in a mountainous region, called a debris flow or avalanche; and the downslope movement of moisture-saturated surficial material, known as solifluction, over frozen substratum material, occurring in sub-Arctic regions during seasonal periods of surface thaw.
The study of mass movement is important in understanding the geological processes that shape the Earth’s surface. It is also important in assessing the risks of natural disasters such as landslides, mudflows, and avalanches. The knowledge of mass movement is used in engineering, construction, and urban planning to design structures that can withstand the forces of mass movement. The study of mass movement is also important in the field of environmental science, as it helps in understanding the impact of human activities on the environment and the potential for natural disasters.
In conclusion, mass movement is a geological process that involves the downslope movement of soil and rock debris in response to gravity. The types of mass movements are diverse and are caused by a variety of factors. The study of mass movement is important in understanding the geological processes that shape the Earth’s surface and in assessing the risks of natural disasters. It is also important in engineering, construction, urban planning, and environmental science..
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