Mass Movements Flashcards Preview

A2 Geography - Earth Hazards > Mass Movements > Flashcards

Flashcards in Mass Movements Deck (14)
Loading flashcards...
1
Q

Define a mass movement

A

the downhill transfer of slope materials as a coherent body

2
Q

When do mass movements occur?

A

when the downslope forces exceed the upslope forces.

3
Q

What are the ultimate causes of mass movements?

A
  1. A reduction in the internal resistance (shear strength) of the slope
  2. An increase inshear stress(i.e. the forces acting on a slope that may lead to MM)
4
Q

Name 2 trigger mechanisms of mass movements?

A
  1. Precipitation

2. Seismic activity

5
Q

What are the 5 physical factors contributing to slope instability?

A
  1. Steep gradient
  2. Rock type
  3. Geological structure
  4. Water content and permeability
  5. Slope undercutting
6
Q

Physical factors contributing to slope instability

steep gradient

A

Steeper the slope, the more effective the downward pull of gravity

7
Q

Physical factors contributing to slope instability

geology - rock type

A
  • Granite and limestone vs sandstone and clay / unconsolidated vs consolidated
  • Rock juxtaposition – weaker on top of stronger may be prone to sliding over underlying strata
8
Q

Physical factors contributing to slope instability

geology - geological structure

A

Heavily fractured / jointed rocks more prone to weathering processes e.g. freeze thaw

9
Q

Physical factors contributing to slope instability

geology - water content and permeability

A

water decreases friction and lubricates the slope

10
Q

Physical factors contributing to slope instability

slope undercutting

A

By natural processes e.g. fluvial / marine erosion

11
Q

Name 2 human factors contributing to slope instability

A
  1. Removal of vegetation

2. Human actions/ development

12
Q

How does removal of vegetation contribute to slope instability?

A

Vegetation intercepts rainfall and binds soil and rock particles together. Removal decreases shear strength of slope.

13
Q

Give 3 examples of human actions/ developments and explain how they contribute to slope instability

A
  1. Settlement
  2. Mining
  3. Infrastructure (roads)
  • increases weight on slopes ( increases shear stress acting on slope)
  • digging of foundations mades material more unconsolidated, this reduces the shear strength of the slope
  • interference of natural drainage systems results in higher water content in slopes which acts as a lubricant
  • road building steepens slope
14
Q

What are the 3 geographical issues associated with mass movements?

A
  1. Impact on human activities
  2. Human activities causing slope destabilisation
  3. Physical geography causing landslides