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Coastal Landforms and Processes

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Coastal Landforms and Processes Powered By Docstoc
					Coastal Landforms and
      Processes


         GCSE 1F/3H
      The Physical World
                                                   Back to:
                                                   Title, Waves, Cliffs,
                                                   Arches, LSD, Spits


 Waves are created as the wind
     blows over the sea
Constructive waves      Destructive waves erode
build the coastline     the coastline




Short fetch/gentle winds Long fetch/strong winds

Strong swash and gentle Weak swash and strong
backwash                backwash
                                                                               Back to:
                                                                               Title, Waves, Cliffs,
                                                                               Arches, LSD, Spits


  Cliffs and wave cut platforms
                                                         4. Eventually the
1. Destructive waves break                               cliff will not be
on the cliff between the high                            able to support
and low tide marks. The                                  itself and will
force of the wave hitting the                            collapse and so
cliff compresses air in                                  retreat. A wave cut
cracks which then expands                                platform is a flat
explosively when the wave                                area of rock left
retreats (hydraulic action).                             behind as the cliff
This breaks bits off and                                 retreats
helps to create a wave cut
notch. The waves then throw
these broken rocks back at
the cliff and break even
more bits off (abrasion).

                                          3. Biological weathering
                     2. The notch         will weaken the cliff as
                     steadily grows       plant roots grow into the
                     until the cliff is   cracks widening them
                     overhanging          further
                                                                    Back to:
                                                                    Title, Waves, Cliffs,
                                                                    Arches, LSD, Spits


     Arches, stacks and stumps
1. Waves refract
                                               3. Biological
around a headland
                                               weathering will
and their energy is
                                               weaken the top of
focussed on either
                                               the arch whilst
side. Destructive
                                               destructive waves
waves crash into the
                                               will continue to
rock and their force
                                               cause bits of rock
compresses air in
                                               to break off and
cracks which then
                                               the arch will get
expands explosively
                                               wider and taller.
when the wave retreats
                                               Eventually the top
(hydraulic action).
                                               of the arch will
The waves then throw
                                               become too weak
these broken rocks
                                               to support its own
back at the cliff and    2. The caves          weight and will
break even more bits     continue to deepen    collapse leaving
off (abrasion).A cave    until they meet and   behind an isolated
is slowly formed on      an arch is formed     stack.
either side on the       through the
headland.                headland.
                                                              Back to:
                                                              Title, Waves, Cliffs,


  The process of Longshore Drift                              Arches, LSD, Spits




(LSD) transports sediment along the
             coastline
             LDS occurs when the prevailing wind blows in
             at an angle to the coastline. When this
             happens,the waves will also approach the
             coastline at an angle. The swash will move the
             sediment up the beach at the same angle as the
             wave approached but the backwash will move
             the sediment straight back down the beach
             under the influence of gravity.
             The zig-zag movement will continue and
             sediment will slowly be moved along a beach.
                                                                                           Back to:
                                                                                           Title, Waves, Cliffs,

Spits are features of coastal deposition                                                   Arches, LSD, Spits




and are formed by constructive waves
                                 A spit is a finger of beach
                                 sediment attached to the land at
                                 one end and sticking out into the
                                 sea at the other.
                                                                     3. The water
 They are formed in                                                  behind a spit is
 shallow, calm                                                       protected from the
 waters where the                                                    waves. It is called
 coastline changes                                                   a lagoon. Fine
 direction.                                                          sediment will be
                                                                     deposited in the
                 1. LSD will move
                                                                     still waters and a
                 sediment off the
                                                                     salt marsh may
                 ‘corner’ of the
                                               2. A spit may get a   develop.
                 coastline and deposit it
                 in the shallow sea.           curved end if the
                 Slowly the sediment           direction of the
                 will build up to make         prevailing wind
                 new land and the              (and hence LSD)
                 process continues             changes
                                                           Back to:
                                                           Title, Waves, Cliffs,


                   Dictionary                              Arches, LSD, Spits




 Abrasion – broken pieces of rock are thrown back
  against the cliff by destructive waves breaking even
  more off
 Attrition – pieces of rock are bashed together by the
  waves and made smaller and rounder
 Backwash – the movement of the wave back down the
  beach
 Fetch – the distance over which the wind blows to
  produce the waves
 Corrosion/solution – water is able to dissolve some
  rocks, such as chalk
 Hydraulic action – as waves break against a cliff they
  compress the air in cracks, when they retreat the air
  expands explosively and breaks bits of rock off
 Swash – the movement of the breaking wave up the
  beach
                                                            Back to:
                                                            Title, Waves, Cliffs,
                                                            Arches, LSD, Spits


              Dictionary (cont)
 Wave refraction – this occurs when waves approach the
  shore at an angle and is common on coastlines with
  headlands and bays. The part of the wave nearest the
  shore is slowed down by contact the the sea floor while
  the rest of the wave continues as normal. The wave then
  bends. The result is that wave energy is focussed on
  headlands and spreads out in the bays.

				
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posted:1/30/2012
language:English
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