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Coastal processes and landforms
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The coast is where land meets sea. Waves wear it away in some places and build it up in others.
Waves
Waves are made by wind blowing over the sea. The distance the wind blows over is the fetch: a longer fetch means bigger waves.
Destructive waves are tall and frequent with a strong backwash: they erode beaches.
Constructive waves are low with a strong swash: they build beaches.
Destructive waves are tall and frequent with a strong backwash: they erode beaches.
Constructive waves are low with a strong swash: they build beaches.
Erosion landforms
Waves erode by hydraulic action, abrasion, attrition and solution, like rivers.
Where hard and soft rock meet the sea, soft rock erodes into bays and hard rock is left as headlands.
On a headland, erosion widens a crack into a cave, then an arch (like Durdle Door in Dorset), then the arch collapses to leave a stack, which wears down to a stump (like Old Harry Rocks).
Where hard and soft rock meet the sea, soft rock erodes into bays and hard rock is left as headlands.
On a headland, erosion widens a crack into a cave, then an arch (like Durdle Door in Dorset), then the arch collapses to leave a stack, which wears down to a stump (like Old Harry Rocks).
Longshore drift and deposition
Waves often hit the beach at an angle, following the prevailing wind. The swash carries sand up the beach at an angle; the backwash pulls it straight back down. So sand zigzags along the coast: longshore drift.
Where the coast changes direction, sand is deposited to form a spit, such as Spurn Head in Yorkshire.
Groynes (fences down the beach) trap sand and slow longshore drift.
Where the coast changes direction, sand is deposited to form a spit, such as Spurn Head in Yorkshire.
Groynes (fences down the beach) trap sand and slow longshore drift.
Describe how a stack forms from a headland.
- Waves erode a crack in the headland by hydraulic action and abrasion.
- The crack grows into a cave, then the cave cuts through to form an arch.
- The top of the arch collapses, leaving a stack standing alone.
Answer: Crack, cave, arch, then the arch roof collapses to leave a stack.
Destructive waves erode (strong backwash); constructive waves build (strong swash). Headlands and bays form where hard and soft rock meet. Crack, cave, arch, stack, stump. Longshore drift moves sand along the coast; spits form where the coast changes direction.
The interactive lesson includes the diagrams for this topic.
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