Erosional processes attack areas of less resistant rock first forming a bay. The more resistant rock protrudes out to see as a headland. The headlands receive the highest energy waves due to refraction whereas bays experience deposition.
Concordant coats with headlands
When geology runs parallel marine processes can create headlands and bays. Such as San Fransisco Bay in California.
Wave cut notch
When high and steep waves break at the foot of a cliff their energy is concentrated at the foot of the cliff. The cliff begins to undercut into a wave cut notch.
Wave cut platform
After a wave cut notch is formed, the cliff will begin to retreat and after collapsing a gently sloping smooth wave cut platform is formed at the base of the cliff.
Wave cut platform characteristics
If it is continually eroded due to sub-aerial processes, weaknesses can be exploited on the rock face.
Wave cut platform growth
The platform can continually grow, making waves break further out to sea leading to reduced erosion on the cliff.
Along a joint in the cliff, the sea will cut inland exploiting cracks in the joint widening the gap to form a geo.
A cliff is constantly undercut by waves (usually marine processes) leaving an opening into the cliff. Constant weathering of the rock increases the size of the cave.
Vertical erosion upwards on a cliff extended to the top of the cliff then a blowhole forms.
If the cave is on a side of a headland then the continued erosion will go all the way through the headland and form an arch.
As the cliff recedes, the arch will eventually collapse due to gravity due to sub-aerial processes weakening the arch. This leaves an isolated portion of rock known as a stack.
The sea will exploit the base of the stack leading it to collapse with a small amount of the stack being left. This is called a stump.
Twelve apostles in Australia and Sail Rock in the Black sea.
Purbeck in Dorset
Sea has undercut the very famous Old Harry Rocks(stacks) and Durdle Door(arch)