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EROSIONAL PROCESSES AND FEATURES
WAVES
Waves are the dominant force behind many coastal processes. They may create features
such as beaches, they may erode coastlines and create caves and other coastal features,
and they may inundate coastal areas and cause devastating floods.
How a wave breaks: When a wave approaches the coast, the sea bed causes it to slow
down.…read more

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PROCESSES OF EROSION
(i) Hydraulic Action: A wave breaking against a cliff exerts a considerable
pressure as hundreds of tonnes of water hit the rock face. Shock waves of
up to 20 tonnes per sq metre may be generated.
The high pressure only exists for an instant but it may be sufficient to
loosen blocks by acting along faults, joints and bedding planes, particularly
as 15,000 waves a day may batter a cliff.…read more

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PROCESSES OF WEATHERING
(i) Salt crystallisation: Salt crystals form in the cracks and pore spaces of
rocks when the saline sea water evaporates. As the crystals grow, they
impose stress and cause the rocks to disintegrate.
This process is particularly effective where cliffs are well-jointed as
salt-laden spray will find its way into the cliffs. Pitting or honey-combing of
cliff faces within the spray zone is evidence of this process.
(ii) Solution.…read more

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EROSIONAL FEATURES
WAVE ­CUT PLATFORMS
A wave-cut platform is a gently sloping (normally about 4°) surface of rock that is
exposed between the low and high water marks.
How are they formed? The first stage in their formation is the development of a
wave-cut notch which is created by marine erosion between the low and high water
mark.
As the notch increases in size, the weight of the overhanging rock increases and
eventually collapses.…read more

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CAVES, STACKS AND ARCHES
A cave is formed when waves exploit weaknesses (such as joints, faults and bedding planes) in
the cliff face.
It is by the processes of abrasion, corrosion and hydraulic action that the waves exploit these
weaknesses.
A cave will only form if the rock is relatively hard and resistant (limestone is hard, chalk is
soft), otherwise the cliff face will collapse before the cave forms.…read more

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CASE STUDY - FLAMBOROUGH HEAD
This part of the Holderness coastline is famous for its steep chalk cliffs, stacks and
arches.
The chalk is much harder than the boulder clay that makes up the cliffs to the south of
Flamborough Head. The chalk is well-jointed and caves form where the waves have
exploited weaknesses in the rock. The caves may be eroded to form arches and then
stacks.…read more

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CONCORDANT AND DISCORDANT COASTLINES
A coastline where the rocks run parallel to the coastline is known as a concordant
coastline. The stretch of coastline from Durdle Door to Lulworth Cove is a
well-known example as the four rock types exposed (Portland limestone, Purbeck
limestone, Wealden clay and chalk) run parallel to the coastline. A concordant coastline
forms when alternate layers of hard and soft rock lay in parallel to the coastal direction.…read more

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DEPOSITIONAL PROCESSES AND FEATURES
TRANSPORT OF MATERIAL
Sediment in the sea is transported in the same ways that it is transported in rivers,
namely:
Traction - pebbles roll along the sea bed. This is a slow form of transport
and tends to occur where weak currents are transporting sands or strong
currents pebbles and boulders.
Saltation ­ particles bounce along the sea-bed.…read more

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BEACHES
The beach is the area from the lowest level of a spring low tide to the upper point that
waves can throw material. A cliff, grassy slope or sand dune normally marks the end of
the beach.
They are formed when constructive waves deposit material on them. They are normally
made of either sand or shingle.
SPITS
A spit is a long and narrow ridge of sand.…read more

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