Coastal Erosion

Coastal Systems

Concordant Coastlines

Soft and hard rock run parallel to the coast

Discordant Coastlines

Soft and hard rock run at right angles to the coast

Erosion

• Process in which the coast is broken down by force of waves

• 4 types: attrition; hydraulic action; abrasion; solution

Attrition

Rocks collide causing them to become smaller, smoother and rounder 

Hydraulic Action

Waves push air into cracks in the rock, exerting pressure

Abrasion

Rocks in waves hit the cliff, wearing it away

Solution

Rocks are completely dissolved

Coves

• Concordant coastlines

• Gaps in the harder, more resistant rocks are breached

• This eventually exposes the softer rocks behind, making it vulnerable to erosional processes such as hydraulic action and abrasion

• Lulworth Cove

Wave-Cut Platforms

• Concordant and discordant coastlines 

• Sea attacks the base of the cliff through hydraulic action and abrasion, forming a wave-cut notch 

• Overtime, as erosion continues, the notch will increase in size 

• Coupled with mechanical weathering, the cliff collapses

• This leaves a wave-cut platform behind which becomes larger as the process repeats and the cliff retreats 

Headlands and Bays

• Headlands: high areas of resistant rock that jut out into the sea

• Bays: low-lying inlets of softer rock that curve inwards

Notch

A curved indentation or hollow that is cut into the base of a cliff or rock face

Cave

• Discordant Coastlines

• Notches / cracks at the base of a cliff become exposed through abrasion and hydraulic action

• The notches widen through weathering and abrasion / hydraulic action, turning them into wave-cut notches and eventually a cave

Arch

• Discordant Coastlines 

• Cave formation

• Wave refraction deepens the cave 

• Wave refraction attacks all the sides of the headland, cutting through the cave to form an arch

Stack

• Discordant Coastlines 

• Arch formation

• Overtime, the arch becomes unstable and collapses, leaving behind a pillar called a stack

Stump

• Discordant coastlines

• Stack formation

• The base of the stack is undercut, crating new wave-cut notches

• Eventually, this collapses and forms a stack