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The Coastal Zone
How Waves Form

Waves are formed by the wind blowing over the sea.
Friction with the surface of the water causes ripples to form and these develop into
waves.
They can also be formed when volcanic eruptions shake the seabed. These
waves are called tsunamis .

Beach…

Page 2

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As the water become shallower , the friction with the seabed distorts the circular
motion and becomes more elliptical . This causes the crest of the wave to rise up




and then eventually topple onto the beach.







Constructive Waves


Constructive waves are waves that surge up on the beach with…

Page 3

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Destructive Waves

Destructive waves have a weak swash and strong backwash, which means
material is removed from the coast.
They are formed by local storms close to the coast.
They are closely spaced and often interfere with each other, producing a chaotic
swirling mass of water.
They rear up to…

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It is




effective if the rock is porous or permeable .






Exfoliation (onion skin weathering): The heat makes the rock expand during the
day. As it cools at night, it contracts. Repeated cycles of this leads to the outer
layer peeling away from the rest of the rock. Water weakens…

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Chemical weathering: A chemical change occurs during weathering. Rainwater,
being slightly acidic can slowly dissolve certain rocks and minerals. The parts
which are unaffected by chemical weathering form a fine clay deposit .

Solution : The process of rocks (e.g. rock salt) dissolving in rainwater.

Carbonation : The rainwater picks…

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Processes of Coastal Erosion

Coastal erosion: The wearing away of land by the sea.
Hydraulic power : The force of the water hitting the cliff and squeezing air into
cracks in the rock, causing rocks to break apart (captivation).
Abrasion : The effect of pebbles grinding over a rocky platform…

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Longshore drift: Transportation of sediment along the coastline caused by waves
approaching at an angle, making the sediment move along the beach in a
zigzag pattern .








1) The waves follow the direction of the prevailing (most common) wind.
2) They hit the coast an oblique angle (any angle that…

Page 8

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Headlands are most vulnerable to power of the waves, which explains the
presence of cliff and wavecut platforms.
Bay : a broad coastal inlet often with a beach.
Bays are sheltered from the full fury of the sea, which means that the waves are
less powerful and deposition dominates. This…

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Destructive waves remove the beach once again and expose the wavecut
platform.

Caves, Arches, Stacks and Stumps

Cave : a hollowedout feature at the base of an eroding cliff.
Arch : a headland that has been partly broken through by the sea to form a
thinroofed arch.
Stack : An…

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Common characteristics on beaches are berms and ridges (small ridges which
represent different tides).


Spits

Spit: A long narrow finger of sand or shingle jutting out into the sea from the
coast.
As sediment is moved along the shore by longshore drift , it is deposited when
there is a…

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