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, they can fall into the sea/beaches to be eroded

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, now weakened, will then give into gravity, and rock fragments will break away and fall.

Question 4

describe landslides:

Answer 4

a large area of land moving down a slope in a straight line. it occurs after heavy rain. 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

a slump is a 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.