What's covered
Key facts
A stack is formed when the roof of a coastal arch becomes unsupported and collapses, leaving an isolated column of rock.
Attrition is the erosion process in which rocks and pebbles knock against each other in the waves, becoming smaller, smoother and rounder over time.
Bays form where softer, less resistant rock is eroded back faster than the surrounding harder rock, leaving a curved inlet between two headlands.
Constructive waves have a strong swash and weaker backwash, building up the beach by deposition; destructive waves have a stronger backwash than swash and remove material, eroding the beach.
A bay is the landform produced by erosion of softer rock between two headlands of harder rock.
Deposition is the laying down of material that was being carried by the sea, occurring when waves no longer have enough energy to keep transporting it.
When a cave on a headland is enlarged by continued wave erosion, it cuts right through the headland to form an arch.
Coastal deposition occurs when waves lose energy (in sheltered bays or where they slow down), causing them to drop the sediment they were carrying.
Headlands and bays form along the same coast when bands of hard and soft rock lie perpendicular to the shore; the softer rock erodes faster, producing alternating headlands and bays.
Hard engineering uses artificial structures such as sea walls, groynes and rock armour to defend the coast, while soft engineering works with natural processes (beach nourishment, dune regeneration, managed retreat).
Sample questions
A taste of the 23 questions in this topic — answers marked. Sign up to practise the full set with spaced repetition.
Why do headlands and bays often form along the same stretch of coastline?
- ✓Alternating hard and soft rock erodes at different rates
- •Coastal flooding fills low-lying areas between headlands creating bays
- •Longshore drift deposits sediment between headlands to create bays
- •Wave refraction erodes the headlands while protecting the bay areas behind
Which type of coastal erosion occurs when waves force air into cracks in rock, causing it to break apart?
- •Coastal abrasion
- ✓Hydraulic action
- •Salt solution
- •Wave attrition
How does a stack form along a coastline?
- •Glaciers carve out a steep-sided pillar during the last Ice Age
- •Tectonic uplift raises a section of seabed above the high-tide line
- ✓Waves erode a crack, then a cave, then an arch which collapses
- •Wind blows sand into a tall pile that hardens over centuries
What is hydraulic action?
- •Rocks carried by the sea grinding against each other
- •Sand and pebbles thrown against the cliff face by waves
- •The chemical weathering of limestone cliffs by slightly acidic seawater
- ✓Water forces air into rock cracks, breaking the rock apart
Which feature comes after a cave is enlarged by erosion?
- ✓Arch
- •Spit
- •Stack
- •Stump
What is attrition?
- •Acid in seawater dissolves the rock face
- ✓Rocks knock together, becoming smaller and rounder
- •Water forces air into cracks, breaking rock
- •Waves drag pebbles along the seabed surface
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