• Waves cause the most erosion at the foot of a cliff.
• This forms a wave-cut notch, which enlarges as erosion continues.
• The rock above the notch becomes unstable and eventually collapses.
• Collapsed material is washed away and a new wave-cut notch starts to form.
• Repeated collapsing results in the cliff retreating.
• A wave-cut platform is the platform left behind as the cliff retreats.

Headlands and bays form where there are alternating bands of resistant and less resistant rock along a coastline.

1. Cracks

• Cracks are widened in the headland through the erosional processes of hydraulic action and abrasion.

2. Caves

• As waves continue to grind away at the crack, it begins to open up to form a cave.
• The cave becomes larger and eventually breaks through the headland to form an arch.

3. Arches

• The base of the arch is continually widened by further erosion until its roof becomes too heavy and collapses into the sea.
• This leaves a stack (an isolated column of rock).

4. Stacks

• The stack is undercut at the base until it collapses to form a stump.