Mass Movement

The Pull of Gravity is stronger than you think

What is Mass Movement

  • Is the Movement of a large mass of rock, soil and debris downward due to the pull of gravity
  • Mass movement is a type of erosion capable of making huge changes to the side of a mountain
  • can happen quickly or slowly
  • the term landslide is often used but does not fully cover the different triggers and types of erosion of this scale.

Causes of Mass Movement

  • Gravity is constantly trying o pull rock and debris down the slope of a mountain, at the same time the mountains resistive force/ sheer strength is pulling against the gravity
  • Causes of mass movement occur when gravitational force overcomes the resisitive forces of the mountain.
  • Increased slope steepness in a mountain increases the chance of mass movement
  • increased water is another factor, as water can wash away particles that keep the mountain side intact.
  • Vegetation also impacts mass movement as the roots anchor the soil particles.
  • Earthquakes plays a role in mass movement as the violent shaking can break off sections of mountains, causing them to slide down the slope
Mass Movement

Slumps and Rockslides

SLUMPS

  • One of the types of mass movement that is an example of the slope failing is a slump, the sliding of coherent rock material along a curved surface, for example water might erode the base of a cliff. Without the base the outer sections of the mountains slumps down as a unit


ROCKSLIDES

  • A rockslide is the sliding of rock material down a mountain, it is similiar to a slump, but a rockslide does not move along a curved surface. In a rockslide we see rocks sliding down a pre existing surface as a result we will see a collection of fallen rocks at the base of a rockslide.

Landslides-What they are & their causes

Debris flow and Earthflow

  • Other types of mass movement involve the downward movement of unconsolidated materials (weak materials)
  • They are known as Debris flow and Earthflow as the material flows like liquid down a slope


Debris flow

  • Movement of water-laden mass of loose mud, sand, soil, rock and debris down a slope
  • Some debris can fall slowly and others reach 100km/h sweeping anything in their, effectively making more debris

Earth Flow

  • Flow of fine grained material that typically develops at the lower end of a slope.
  • When fine grained materials (clay, silt) become exposed to water they become prone to earthflows
  • More water= More speed

Geomorphology 5: Mass Movements