What is erosion?
The process of wearing away at the earth’s surface and removing material through natural agents.
What are the different erosional landforms found at the coastline?
1) Wave-cut platform
2) Caves, Arches and Stacks
3) Headland and bay’s
What is a wave-cut platform?
A gently sloping rocky surface found at the bottom of a cliff.
How do wave-cut platforms form?
1) They form as the wave erosion and weathering cause the cliff to retreat.
2) Weathering and wave erosion causes a notch to form at the highest wave mark. This eventually develops into a cave.
3) Rocks above the cave become unstable and collapse.
How are headland and bays formed?
1) Headland and bays form in areas where there is alternating bands of resistant rock.
2) The softer rock is eroded quicker due to waves, forming a bay, whilst the harder rock is eroded at a slower pace due to waves refraction forming a headland.
Explain the formation of Caves, arches and stacks
1) At a headland where rock is hard, erosion can be slow, wave refraction concentration wave energy on the headland causing it to erode.
2) Joints in the headland are secepitable to hydraulic action. Over time the joints widen forming a cave enlarged by abrasion and hydraulic action.
3) Eventually erosion cuts through the headland forming an arch. The roof of the cave will eventually collapse due to gravity
4) This leaves a stack which over time will be eroded through abrasion, hydraulic action and weathering to form a stump.
What is deposition?
The process of material being transported and dropped off at the coast
What are the different depositional landforms found at the coastline?
1) Beaches
2) Spits
3) Offshore bars and tombolos
4) Barriers beaches and islands
5) Sand dunes
6) Salt marshes/mudflats.
What are the two ways a beach can be formed?
1) Drift-aligned beach
2) Swash-aligned beach
How does a beach form drift aligned?
Drift-aligned beaches form when longshore drift moves sediment along the beach as waves approach at a right angle.
How does a beach form swash-aligned?
Swash-aligned beaches form where the energy is low. The waves are more parallel to the shore meaning theres very little horizontal and lateral movement of sediment.
How do spits form?
Spits are created due to longshore drift which transports sediment along the coast. When the coastline changes direction the waves deposit the sediment. The build up of deposited sediment out to sea forms a spit.
What causes spits to have curved ends?
How do tombolos form?
Longshore drift connects a offshore island to the mainland, wave refraction causes waves to lose its energy which leads to deposition of sand/shingle to connect the island.
Explain the formation of a offshore bar
Forms due to longshore drift moving sediment along the coast, the sediment is deposited across a bay linking two headlands together. This happens at a bay which has low energy waves and may enclose a lagoon behind the bar.
How do barrier island/beaches form?
Barriers beaches and islands form when rising sea levels flood low-lying coasts and constructive waves deposits large amount of sediment offshore, building long ridges parallel to the coast that become separated from the mainland, trapping lagoons behind them.
How do salt marshes form?
They form in sheltered, low energy environments (behind spits/bars). Here tidal currents and river currents meet and deposit fine sediment. This leads to the formation of mudflats which is then stabilised by salt-tolerant vegetation which can develop into salt marshes. These areas are covered at high tides and exposed at low ones.
How do sand dunes form?
Sand dunes are formed when sand deposited by longshore drift is moved up the beach by the wind. This sand is then trapped by driftwood forming embryo dunes. This is then colonised by Marram grass which traps more sand leading to the growth of dunes through succession.
What is eustatic sea level change?
Eustatic change occurs when there is a change in the volume of water in ocean basins.
What causes eustatic sea level change?
When there is a change in the level of ice as a result of thermal expansion and tectonic movement.
How does tectonics impact eustatic sea level change?
Magma rising to the surface lifts the crust up and reduces the capacity of the oceans causing sea levels to rise.
How does thermal expansion impact eustatic sea level change?
Thermal expansion occurs as water warms causing water fluids to expand to take up a greater volume.
What is isostatic sea level change?
Isostatic change occurs when the height of the land changes relative to the water level.
How does post glacial adjustment lead to isostatic sea level change?
During periods of glaciation extremely heavy ice sheets weight the land down. After the glacier period ends and the ice melts the land will rebound to a higher level, lowering sea level in the process. This is known as isostatic recovery/adjustment.
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