TSR Wiki > Study Help > Subjects and Revision > Revision Notes > Geography > Coastal Erosion Landforms
Headlands & Bays
- These are alternating bands of more and less resistant rock and are exaggerated and destroyed by wave action (may not be a large difference but will show after a long period of time).
- Hard Rock erodes slowly = headland.
- Soft Rock erodes faster = bay.
Due to wave refraction energy will be less concentrated on the hard rock (headlands) and this will slow down the erosion of the bay.
Case Study - Wilworth Cove, South coast of England.
It has a narrow entrance due to hard rock been resistant to erosion (Portland Beds). Also featured is a circular bay due to the Wealdon Beds that are soft and easily eroded. Chalk is relatively more resistant to erosion and this is slowing down the northward erosion movement. The bay will enlarge in the east and west directions due to this been soft rock (Warbarrow Bay).
Wave Cut Platforms
- Waves erode the base of cliffs by hydraulic action, abrasion and solution. This results in a Wave Cut Notch at the high tide line. The cliff is undercut by stress and tension on the cliff so therefore it will crack and collapse. This is repeated and the cliff retreats landwards leaving a gentle sloping wave cut platform. The platform cuts across no matter what type or structure the cliffs have. Some pools may form where solution occurs on dissolvable and if there’s a crack in the rock. The wave cut platform is covered in debris. As the platform widens the waves break further out to sea so they have to travel over a wider area and so the energy is dissipated therefore erosion at the headland is reduced.
- There is a hypothesis that wave cut platforms can’t exceed over 0.5km in width. Instead wave energy is used for attrition to reduce the size of debris on the platform. Abrasion lowers the platform level and erosion of the headland continues again.
The Erosion of the Headland
- The headland is made of resistant rock (chalk / granite). The base of the cliff is eroded to form a wave cut notch or an abrasion notch. A Geo may form if the sea cuts inland along a joint by hydraulic acts and abrasion. A Geo is a narrow steep sided inlet. A cave is formed by a wave cut notch eroded backwards and side wards to form a cave by hydraulic action and abrasion. These are best formed in a macrotidal environment with storm waves and resistant rock.
- Caves - will not form in weak and unconsolidated rock, E.g. Bolderclay because the land will slide down. In resistant rock with vertical faults blowholes may form. A blowhole is when the sea enters the cave and water and air are shot up the vertical joint.
- Arches - Arches are formed as the cave wears backwards along a fault by hydraulic action and abrasion right through the headland.
- Stacks - These continue to erode at the arch and weathering at the top, it cracks and falls into the sea and this leaves the tip of the headland.
- Cave E.g. Flambrough, Swanage (Chalk).
- Arch E.g. Flambrough (Chalk).
- Stack E.g. Old Harry needles, Flambrough (Chalk), Old man hoy (Old red sandstone).
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