To what extent do the causes of mass movement hazards depend more on human than on physical factors?

Authors Avatar

To what extent do the causes of mass movement hazards depend more on human than on physical factors?

Both human and physical factors can cause mass movement. Mass movement is the movement down slope of any weathered material (regolith) under the influence of gravity. There are three types of movement; fall, slide and flow. They can be classified according to; speed of movement, type of movement, and amount of moisture present.

There are 6 different types of flow – mudflow, slow earth flow, rapid earth flow, debris flow, rock avalanche and snow avalanche. Mudflows are common on steep unvegetated slopes (clay). Earthflows, (both slow and rapid) contain less water and therefore move slower. Debris flow is much like a debris avalanche, (rapid movement of rock/debris) but with more water. Rock and snow avalanches are the catastrophic movement of snow or rocks.

The actual movement itself can be influenced by both human and physical factors;

  • Amount and type of vegetation – Less vegetation means the land is prone to damage. More vegetation, such as trees and bushes means that they can intercept and help prevent the land from damage. Also, roots from the vegetation make the soil stronger as they bind the soil.
  • Degree of weathering and erosion – Higher amounts of weathering and erosion leads to the actual movement more likely to happen-there is more material available to move. Processes such as frost shattering, wetting & drying and heating & cooling loosen the soil. Removal of material from the base of the slope by marine or fluvial erosion destabilises the slope.
  • Amount of moisture present – If the land is heavily saturated, the material is loosened and therefore more likely to collapse.
  • Human activity – Recreational/leisure activities (walking, golf courses etc) and farming all damage the slope and weaken it. Road, railway and housing construction.
  • Type and structure of rock – Weaker rocks are more liable to collapse, whereas harder rocks retain their structure. Porous rocks allow water into the rock therefore weakening it, whereas impermeable rocks do not.
  • Slope angle – Higher slopes mean quicker/more rapid movement.
  • Climate – More rain leads to heavier saturation, more weathering/erosion equals quicker rates of mass movement. Slopes will become weaker quicker.
Join now!

Triggers of mass movement can also be both physical and human.

  • PHYSICAL – Earthquakes, volcanoes, heavy rain, snow melt, gravity
  • HUMAN – Modification of land, (e.g. urbanisation, building) mining, machinery use, deforestation,      extraction of resources

Physical factors

Causes of mass movement – The most important physical factors that determine movement are gravity, slope angle and pore pressure.

However, natural hazards such as volcanoes and earthquakes exceed the strength of the rock, making it difficult for the slope to retain its structure. Slopes can fail during earthquakes and cause major ...

This is a preview of the whole essay