BBC Bitesize coastal landforms
BBC Bitesize coastal landforms video
BBC Coastal processes and landforms video
Landforms resulting from erosion
Headlands and bays
- Headlands and bays form on discordant coastlines where the rock type alternates between more resistant and less resistant rock at right angles to the sea.
- Differential erosion occurs as more resistant (harder) rock erodes slower than the less resistant rock.
- As the less resistant rock is eroded away quicker it creates a bay leaving the more resistant rock jutting out into the sea as headlands.
Caves, arches and stacks
- Headlands are usually made of more resistant rocks that have weaknesses like cracks.
- Waves crash into the headlands due to wave refraction and enlarge the cracks mainly by hydraulic action and abrasion.
- Repeated erosion and enlargement of the cracks causes a cave to form.
- Continued erosion deepens the cave until it breaks through the headland forming an arch.
- Erosion continues to wear away the base of the arch and weathering weakens the roof.
- The arch eventually collapses to form a stack – an isolated rock that seperate from the headland
Landforms resulting from deposition
- Beaches are formed by constructive waves depositing matieral which has often been eroded further along the coast and transported by longshore drift.
- Sand beaches are flat and wide – sand particles are small and the weak backwash can move them back down the beach, creating a long, gentle slope.
- Shingle beaches are steep and narrow – shingle particles are large and the weak backwash can’t move them back down the beach. The shingle partciles build up to create a steep slope.
Spits and bars
Formation of a spit video
Spits from where there is a sharp change in the direction of the coastline e.g. at a river estuary.
Longshore drift transports material along the coastline and past the bend. Then deposits it in the sea as the waves loose energy in the deeper water.
This process repeats and the spit gets bigger over time.
Changes in the direction of the wind can cause the spit to become curved at the end (a hook).
The spit won’t grow across the whole river estuary due to the river current flowing out into the sea.
Behind the spit a saltmarsh is created as the area is protected from the waves and plants start to grow there.