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Mass Movement

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What is a Mass Movement?

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Mass Movement, also known as mass wasting, represents the downhill movement of cliff material under the persuasion of gravity. It depicts the bulk movements occurring in soil and rock residue down slopes in response to rapid or steady sinking of the Earth’s surface in a vertical direction or the pull of gravity. Previously, the word mass wasting was used to reflect different processes by which huge masses of crustal substances are moved by gravity from one place to another.


Terms Used for Mass Movement Geography

More recently, the mass movement meaning or the term mass movement has been used as a replacement to include mass wasting processes and the sinking of constrained areas of the Earth’s ground surface. Mass movements on slopes and sinking mass movements are frequently fed by water and the importance of both types is the part each plays in the remodeling of landforms.


What is Mass Wasting?

Mass wasting, which is identical with slope failure” is the non-fulfillment and downslope movement of rock or unconsolidated substances in response to gravity. If you have heard of the term landslide, it is almost similar to mass wasting, but not totally since some people conserve “landslide” for relatively rapid slope failures, while others do not.


Classification of Mass movements

Mass Movements Can Be Divided into Two Major Classes:

  • Slow movements

  • Rapid movements


Factors Triggering Mass Wasting

Previously, the word mass wasting indicated a variety of processes by which large masses of crustal substances are moved by gravity from one place to another. Latterly, the word mass movement has been substituted to involve mass wasting processes and the sinking of restrained areas of the Earth’s ground surface. That said, Mass movements on slopes and sinking are often sustained by water and the importance of both types is the part each plays in the alteration of landforms.


Features of Mass Movements

  • Mass movement is also known as Mass Wasting, bulk movements of rock and soil

  • Debris down slopes in response to the pull of gravity, or the rapid or steady sinking of the Earth’s surface in a principally vertical direction is influenced with many factors.

  • It is the movement of masses of bodies of mud, soil, rock, bedrock residue, which commonly occurs along steep-sided hills and mountains due to the gravitational pull.

  • Gravity imposes its force on all matter, both bedrock and the elements of weathering. Therefore, weathering is not crucial for mass movement though it aids mass movements.

  • Mass movements that are sliding of massive amounts of rock and soil are observed in landslides, mudslides, and avalanches.

  • These are very active over weathered slopes rather than over unweathered materials.

  • The ice, water or air does not carry debris with them from place to place but conversely, the residue may transport with it ice, water, or air.

  • Mass movements do not appear under erosion though there is a shift of substances from one place to another.

  • Heave, slide and flow are the three forms of movements.


Causes Preceding Mass Movements

There are many activating factors preceding mass movements which are as follows:

  • Elimination of aid from below to substances above through natural or artificial means.

  • Removal of substances or load from over the original slope surfaces.

  • Haphazard elimination of natural vegetation.

  • An upheaval in height of slopes and gradient.

  • Overfilling through the addition of substances naturally or by artificial filling

  • Overburdening because of heavy rainfall, lubrication, saturation of slope materials.

  • Epodes of earthquakes and explosions etc.

  • Tremendous natural seepage.

  • Extreme drawdown of water from reservoirs, rivers, streams, lakes leading to a gradual outflow of water from beneath the slopes or river banks.

FAQ (Frequently Asked Questions)

Q1. How do We Classify Mass Wasting?

Answer: It is very essential to classify slope failures so that we are able to understand what influences them and how to attenuate them. Following are the three criteria that are used to describe slope failures:

  • The kind of material that failed (essentially either bedrock or unconsolidated deposit).

  • The process of the failure (the way the material moved).

  • The rate at which the material moved.

Furthermore, the Type of Motion is a Crucial Characteristic of Slope Failure, and There are 3 Different Types of Motion That are as below:

  • If the material drops via the air, vertically or virtually vertically, it is termed as a fall.

  • If the material moves as a mass alongside a sloping surface (in absence of internal motion within the mass), it is known as a slide.

  • If the material consists of an internal motion, like a fluid, it is known as a flow.

Q2. What are the Different Types of Slope Failure?

Answer: Types of motion, some include all three, while in many cases, it is not easy to have an understanding how the material moved. That said, the different types of slope failure are summarized below.


Failure Type

Kind of Material

Kind of Motion

Rate of Motion

Rock Fall

Rock splinters

Vertical or closely-vertical fall (in addition to bouncing in many cases)        

Very fast ( more than 10s m/s)

Rock Slide

A huge rock body

Motion as a unit alongside a planar surface (translational sliding)

Generally quite slow (mm/y to cm/y), few can be faster

Rock Avalanche

A huge rock body that slides and then collapse into smaller splinters

Flow (at high speeds, the mass of rock splinters is suspended on a pillow of air)

Very fast (more than 10s m/s)

Mudflow

Loose sediment with a substantial component of clay and silt

Flow (a mixture of water and deposits moves down a channel)

Moderate to quick (cm/s to m/s)

Debris Flow

Sand, gravel, and larger broken pieces       

Flow (same as mudflow, but customarily faster)  

Quick (m/s)

Slump       

Thick, unconsolidated sediment

Motion as a unit alongside a curved surface (rotational sliding)   

Slow and steady (cm/y to m/y)

Creep or Solidification

Soil or other load in small cases, mixed with ice

Flow (although sliding motion may also take place)

Super slow (mm/y to cm/y)