NCERT Notes: Mass Movements [Geography Notes For UPSC]

NCERT notes on important topics for the UPSC civil services exam. These notes will also be useful for other competitive exams like banking PO, SSC, state civil services exams and so on. This article talks about Mass Movements.

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Mass movements
  • Mass movement is also known as mass wasting.
  • It is the movement of masses of bodies of mud, bedrock, soil, and rock debris, which commonly happen along steep-sided hills and mountains because of the gravitational pull.
  • Gravity exerts its force on all matter, both bedrock and the products of weathering.
  • Hence, weathering is not essential for mass movement though it helps mass movements.
  • Mass movements which are sliding of huge amounts of soil and rock are seen in mudslides, landslides, and avalanches.
  • The air, water or ice does not transport debris with them from place to place but on the other hand, the debris may transport with it water, ice or air.
  • These are very active over weathered slopes rather than over unweathered materials.
  • Mass movements do not come under erosion though there is a shift of materials from one place to another.
  • Heave, flow and slide are the three forms of movements.

Causes preceding Mass movements
  • There are many activating causes preceding mass movements. They are :
    • Removal of support from below to materials above through natural or artificial means.
    • An upsurge in height of slopes and gradient.
    • Overfilling through the addition of materials by artificial filling or naturally.
    • Overburdening due to heavy rainfall, saturation, and lubrication of slope materials.
    • Elimination of material or load from over the original slope surfaces.
    • Event of explosions, earthquakes, etc.
    • Extreme natural seepage.
    • Heavy drawdown of water from reservoirs, lakes, and rivers leading to a slow outflow of water from under the slopes or river banks.
    • Indiscriminate removal of natural vegetation.
  • Mass movements can be classified into two major classes:
    • Rapid movements
    • Slow movements

Mass Movements (UPSC Notes):- Download PDF Here

Frequently Asked Questions about Mass movements

What are the examples of Mass movements?

Mass movement is the movement of rock and soil down slope under the influence of gravity. Rock falls, slumps, and debris flows are all examples of mass wasting. Often lubricated by rainfall or agitated by seismic activity, these events may occur very rapidly and move as a flow.

What causes mass movement?

The factors that cause most mass movement events are the undercutting of steep slopes, the removal of vegetation, earthquakes, and heavy prolonged rainfall. Many mass movement disasters are preceded by development, deforestation, and slope steepening, which weakens the slopes.

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