Coastal Landforms (Erosional)

Caves, Arches, Stacks and Stumps

Wave energy is concentrated at headlands, leading to erosion
Joints are eroded first to form a cave
Over time, caves are eroded through the headland to form an arch
The unsupported rock above the arch collapses to form a stack
Over time, weathering and erosion causes the stack to become a stump

Beaches

A depositional landforms that stretches from roughly the low tide to the high tide line. Beach accretion occurs due to constructive waves during the summer. Beach excavation occurs due to to destructive waves in winter.

Spits

Long, narrow ridge of sand that extends from the land into the sea.
Longshore drift transports sediment along the coast.
Where the coastline changes direction, material is deposited into open water.
Over time, the sediment builds up to form a spit.
The end may curve due to wind and wave changes.
Salt marshes may form in sheltered areas behind the spit.

Corrasion

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. This undercuts the cliff, creating a wave cut notch.

Hydraulic Action

Some rocks have lines of weakness within them or cracks
Water enters these cracks and compresses the air within
The compressed air forces the crack to widen (as water leaves there is a pop)
As a result rock is weakened over time

Solution

The mildly acidic seawater can cause alkaline rock such as limestone to be eroded.

Attrition

Rocks and particles carried by water collide with each other, causing them to break into smaller, rounder fragments.

Factors affecting coastal erosion - Waves

The rate/type of erosion experienced on a particular stretch of coast is influenced by size/type of waves. Most erosion occurs during winter when destructive waves are most powerful.

Factors affecting coastal erosion - Rock type (lithology)

A rocks’ physical strength and chemical composition is important. For example:
Tough and resistant rocks (e.g granite) erode at very slow rates, forming steep cliffs.
Soft, weak rocks (clay, sandstone) erode quickly, forming gentle slopes and are prone to mass movement.
Highly fractured or permeable rocks erode faster due to increased water infiltration and wave attack.

Wave Cut Notch

• A hollowed-out indentation at the base of a cliff.
• Formed by hydraulic action and abrasion as waves erode the rock.
• Undercuts the cliff, making it unstable.
• Leads to cliff collapse and retreat over time.

Wave Cut Platform

• A flat, gently sloping rocky surface left behind after cliff retreat.
• Formed as waves continue eroding the base of a cliff.
• Exposed at low tide, covered at high tide.
• Often has rock pools, cracks, and uneven surfaces due to erosion