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Coastal processes and landforms
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The sea is constantly eroding, moving and dropping material. These processes create the features you see at the coast.
Erosion processes
Hydraulic action: waves force air into cracks, breaking the rock.
Abrasion: waves throw rocks against the cliff, wearing it away.
Attrition: rocks knock against each other and become smaller and rounder.
Solution: seawater dissolves some rocks, such as chalk and limestone.
Abrasion: waves throw rocks against the cliff, wearing it away.
Attrition: rocks knock against each other and become smaller and rounder.
Solution: seawater dissolves some rocks, such as chalk and limestone.
Erosional landforms
Where hard and soft rock alternate, the soft rock erodes into bays and the hard rock forms headlands.
On a headland: a crack becomes a cave, then an arch, then a stack when the arch collapses, then a stump.
Wave erosion at the foot of a cliff forms a wave-cut notch; when the cliff collapses and retreats it leaves a wave-cut platform.
On a headland: a crack becomes a cave, then an arch, then a stack when the arch collapses, then a stump.
Wave erosion at the foot of a cliff forms a wave-cut notch; when the cliff collapses and retreats it leaves a wave-cut platform.
Transport and deposition
Longshore drift: waves hit the beach at an angle (swash) and drain straight back (backwash), zigzagging material along the coast.
Where the coast changes direction, material builds out into the sea as a spit.
Destructive waves erode; constructive waves build beaches.
Where the coast changes direction, material builds out into the sea as a spit.
Destructive waves erode; constructive waves build beaches.
Explain how a stack forms.
- Hydraulic action and abrasion widen a crack in a headland into a cave.
- The cave erodes through the headland to form an arch.
- The arch roof is weakened and collapses, leaving a tall column of rock: a stack.
Answer: Crack, cave, arch, then the arch collapses to leave a stack.
Erosion by hydraulic action, abrasion, attrition and solution. Headland sequence: crack, cave, arch, stack, stump. Longshore drift moves material along the coast and builds spits.
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