Theme 7 – Our Changing Coastline.
There are three main coastal processes:
1.Erosion – the wearing away of land.
Four types of erosion are:
Attrition – when rocks and boulders bump into each other and break
Corrasion (abrasion) – caused by hurling beach materials against the cliffs
Corrosion – when salts and other acids in the sea water dissolve the cliff
Hydraulic Pressure – the force of the waves compressing air in the cracks of the cliffs
Erosion Landforms are:
Headlands and Coves/Bays
Soft rock is eroded by hydraulic action gradually becoming a bay. Hard rock stays and becomes a headland.
Wave Cut Platforms
Sea cuts a notch in the base of a cliff. Overtime the cliff will collapse and a wave cut platform will be created.
Cave, Arches, Stacks and Stumps
1. The seas attacks the foot of the cliff and opens small cracks and weaknesses in the rock.
2. Further wave action widens the crack until a small cave develops.
3. The cave is widened and deepened until it cuts through the headland to form an arch.
4. More erosion will cause the arch to collapse. This leaves a pillar of rock standing called a stack.
5. The stack collapses causing a stump.
2. Transportation – the movement of sand and rocks from one place to another.
The main type of transportation is Longshore Drift – the gradual zig zag movement of sand and sediment along the coast.
The four other types of transportation are:
Traction – rocks roll along the seabed or beach
Saltation – rocks bounce along the seabed
Suspension – sand floating in the water
Solution – dissolved sand
3. Deposition – when sand is dumped or deposited along the coast
1. Sand and shingle are deposited in the water which is sheltered by the headland.
2. Material builds up and outwards forming a pit.
3. A change in wind direction causes the waves to change direction. The end of the spit is made to curve.
4. The shallow sheltered area behind the spit fills with mud, called a salt marsh.
Case Study – Christchurch Bay
Bournemouth, Hurst Castle Spit and Hengistbury Head are nice places and attract tourists because of the coastal landforms…