Marine erosion processes and erosional coastal landforms

Question 1

What are the four main processes that cause erosion?

Answer 1

Hydraulic action (wave quarrying)
Abrasion
Attrition
Corrosion

Question 2

What is hydraulic action?

Answer 2

Air trapped in cracks and fissures in compressed by the force of waves crashing against the cliff face.
Pressure forces cracks open, meaning more air is trapped and greater force is experienced in the next cycle of compression.
This process dislodges blocks of rock from the cliff face.

Question 3

What is abrasion?

Answer 3

Sediment picked up by breaking waves is thrown against the cliff face.
The sediment acts on the cliff like a tool, chiselling away at the surface and gradually wearing it down.

Question 4

What is attrition?

Answer 4

As sediment is moved around by waves, the numerous collisions between particles slowly chip fragments off the sediment, making it smaller and more rounded over time.

Question 5

What is corrosion?

Answer 5

Carbonate rocks (limestones) are vulnerable to solution by rainwater, spray from the sea and seawater.

Question 6

Example of a sequence of distinctive coastal landform

Answer 6

Cave - arch - stack -stump

Question 7

What is the most fundamental process of landform formation on a coastline?

Answer 7

Creation of a wave-cut notch. This is eroded at the base of a cliff by hydraulic action and abrasion.

Question 8

Process of cliff recession

Answer 8

As the notch becomes deeper, the overhanging rock above becomes unstable and eventually collapses as a rock fall.
Repeated cycles of north-cutting and collapse cause cliffs to recede inland.
The former cliff position is shown by a horizontal rock platform visible at low tide, called a wave-cut platform.

Question 9

What influences the location of caves and therefore arches?

Answer 9

The location of fault lines and major fissures.