mass movement

Question 1

define ‘mass movement’:

Answer 1

• the downward movement of material under the force of gravity
• once rocks are weakened by weathering/erosion, they can fall into the sea/beaches through mass movement to be eroded even more

Question 2

what is mass movement caused by?

Answer 2

• weathering
• erosion
• gravity
• small changes over time mean that the centre of gravity of a cliff can hang over the sea instead of over land, making the cliff unstable and prone to mass movement.

Question 3

describe rockfall:

Answer 3

• pieces of rock are continually degraded by weathering and erosion (weathering from above, erosion from below)
• erosion may weaken the rock from below
• the cliff’s rock fragments will break away and fall, now weakened

Question 4

describe landslides:

Answer 4

• large area of land moving down a slope in a straight line
• it occurs after heavy rai
• soil and rock take a straight slip movement
• the slide is lubricated by the water between the soil and the wet bedrock below.
• mudslides are literally the same, apart from the fact that it occurs with mud instead of rock.

Question 5

describe rotational slip (slumping):

Answer 5

• large area of land moving down a curved slip plane
• it occurs when rainfall has moved through a permeable layer, and has reached an impermeable layer
• the permeable layer is saturated and heavy, and the cliff will slump downwards and forwards.
• only happens in areas with alternating layers of rock (permeable and impermeable)

Question 6

what is the outcome of mass movement?

Answer 6

• causes the cliff to retreat.
• provides an input to the coastal system. material is eroded and transported away by waves.
• cliff-top property can be damaged and infrastructure can be lost.
• tourism can suffer.