2.8 - Mass Movement (Barton on Sea)

Question 1

What is mass movement?

Answer 1

The downslope movement of material such as soil, rock, mud or snow, under the influence of gravity

Question 2

What is a rockfall?

Answer 2

Rockfalls, or blockfalls, are a rapid form of mass movement.
On coasts blocks of rock can be dislodged by mechanical weathering or by hydraulic action erosion.
Undercutting of cliffs by the creation of wave-cut notches can lead to large falls.

Question 3

What is topple?

Answer 3

It is where rock strata have a very steep seaward dip, undercutting by erosion will quickly lead to instability and blocks of material topping seaward. Geological structure influences topple.

Question 4

What is translational slide?

Answer 4

It is when material will tend to slide down the dipslope towards the sea. A very low angle seaward dip in strata prevents falls.

Question 5

What is rotational slide/slumping?

Answer 5

Rotational slide/slumping is when huge masses of material can slowly rotate downslope over periods lasting from days to years. Mass movements can occur along a curved failure surface.

Question 6

What is flow?

Answer 6

Flows are common in weak rocks such as clay or unconsolidated sands. These materials can become saturated, lose their cohesion and slow downslope. Heavy rainfall combined with high tides can contribute to saturation.

Question 7

Give case study examples of where there has been rotational slumping, flows or mudflows

Answer 7

Holderness coast, the North Norfolk coast and Lyme Bay in Dorset.