The Coastal Zone

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Physical Geography ­ AQA Spec. A
The Coastal Zone
The Coastal Zone
Coastal Weathering and Erosion
Weathering ­ breakdown of rocks where they are
Erosion ­ rocks are broken down and carried away
Mechanical weathering is the breakdown of rock without changing chemical composition e.g. freeze thaw
weathering. This is when water temperature alternates above and below 0°c. The water gets into cracks in rock, and
when it freezes it expands, putting pressure on the rock. When the water melts it releases the pressure. If this
continues to repeat, the cracks widen and the rocks break up.
Chemical weathering is the breakdown of rock by changing its chemical composition e.g. carbonation weathering.
This happens in warm and wet conditions. Rainwater has carbon dioxide dissolved into it, which makes it a weak
carbonic acid. The reacts with rock containing calcium carbonate so the rocks are dissolved by the rainwater.
Mass movement is the shifting of rocks and loose material down a
slope. It happens when the gravity force is greater than the support.
They cause coasts to retreat rapidly, and they're more likely to occur
when the material is full of water as it acts as a lubricant, making the
movement easier. Slides are material shifts in a straight line, and
slumps are material shifts with a rotation.
Waves wear away the coast by:
Hydraulic Power ­ The force of the water compresses the air in cracks, putting pressure on the rock.
Repeated pressure = bits break off.
Abrasion ­ eroded particles scrape and rub against coast, removing small pieces
Attrition ­ eroded particles in the water hit against each other and break apart/smooth edges
Solution ­ weak carbonic acid in the water dissolves rock such as chalk and limestone
Waves with a small swash and a big backwash are destructive waves, because they take away material.
Waves with a big swash and a little backwash are constructive waves, because they deposit material.

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The Coastal Zone
Coastal Landforms Caused by Erosion
Waves erode cliffs to form wave cut platforms. This happens when a wave makes a wave-cut notch at the base of a
cliff, which becomes enlarged as erosion continues. Eventually the rock above becomes unstable and collapses. The
collapsed material will wash away and another notch will be formed, and the process will repeat.
Headlands and bays form where there are alternating bands of resistant and less resistant rock, horizontal to the
coast edge.…read more

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The Coastal Zone
Bars are spits which connect with another part of a headland. The bar cuts off the
bay between the headlands from the sea, creating a lagoon.
Case Study ­ Chesil Beach
Shingle spit extending 18 miles from the Isle of Portland in the south, to West Bay
in the northwest. Its widest point is 200m. It is made from flint pebbles and churt,
and was formed because of high energy waves and prevailing winds.…read more

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The Coastal Zone
Soft Methods
Groynes ­ natural; encourages natural processes; fairly cheap; not long lasting
Dunes ­ vegetation colonisation; natural; cheap, effective; sustainable; however not immediate protection
Offshore reef ­ reduces energy from waves before hitting sand; reduces fetch; invisible from beach; quick
and fast acting; expensive; could disrupt eco systems
Replenishment ­ natural; enhances natural features; instant; cheap; damaging to environment; gets washed
away again; short term
Case Study ­ Holderness
On average the coastline of Holderness in NW England retreats at a…read more


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