Erosional processes

Question 1

Corrasion

Answer 1

Sand and pebbles are picked up by the sea from an offshore sediment sink or
temporal store and hurled against the cliffs at high tide, causing the cliffs to be eroded.
The shape, size, weight and quantity of sediment picked up, as well as the wave speed,
affects the erosive power of this process.

Question 2

Abrasion

Answer 2

This is the process where sediment is moved along the shoreline , causing it to be worn down over time

Question 3

Attrition

Answer 3

Wave action cause rocks and pebbles to hit against each other , wearing each
other down and so becoming round and eventually smaller. Attrition is an erosive process
within the coastal environment, but has little to no effect on erosion of the coastline itself.

Question 4

Hydraulic Action

Answer 4

As a wave crashes onto a rock or cliff face, air is forced into cracks,
joints and faults within the rock. The high pressure causes the cracks to force apart and widen when the wave retreats and the air expands. Over time this causes the rock to fracture. Bubbles found within the water may implode under the high pressure creating tiny jets of water that over time erode the rock. This erosive process is cavitation .

Question 5

Erosion rates are the highest when

Answer 5

-waves are high and have a long fetch (the distance the wind has travelled over the wave)
- waves approach the coast perpendicular to the cliff.
- at high tide - waves travel higher up the cliff so a bigger area of cliff face is able to be
eroded.
- heavy rainfall occurs - water percolates through permeable rock, weakening cliff.
- in winter - destructive waves are the largest and most destructive during winter.

Question 6

How does the resistance of rock increase erosion?

Answer 6

Whether rocks are clastic or crystalline – sedimentary rocks like sandstone are clastic as they
are made up of cemented sediment particles, therefore are vulnerable to erosion, whereas
igneous and metamorphic rocks are made up of interlocking crystals, making them more
resistant to erosion.
▪ The amount of cracks, fractures and fissures – the more weaknesses there are in the rock
the more open it is to erosional processes, especially Hydraulic Action.
▪ The lithology of the rock - as shown in the table below, the type of rocks and the conditions of
the rock’s creation directly affects its vulnerability to erosion:

Question 7

Igneous

Answer 7

Granite, Basalt
Very slow erosion
Interlocking crystals which allow
<0.1cm/year for high resistance