GCSE COASTS

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GCSE COASTS
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1a CONSTRUCTIVE DESTRUCTIVE WAVES
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1b COASTAL EROSION
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EG COASTLINE
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• Erosion Processes p63 BP
• Corrasion / Abrasion
• Scouring
• Hydraulic Action
• Solution
• Attrition

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Coastal erosion processes create a number of
significant landforms. There are a number of
factors which affect the rate of this erosion i)
Rock Type A more resistant rock, such as
granite, will be eroded slowly, whilst a less
resistant rock, such as clay or mud, can be
eroded very quickly. ii) Jointing / Faulting
The more faults and joints a rock has the more
susceptible it is to erosion, both from coastal
and sub-aerial processes.
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Coastal Rock Arrangement A coastline with rocks
that run parallel to the coast is called a
concordant or Pacific coastline. One that has
rocks running at right angles to the coast is
called a discordant or Atlantic coastline.
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DISCORDANT COASTLINE Rocks are at right angles to
the sea
HEADLAND
HARD ROCK
BAY
SOFT ROCK
HEADLAND
HARD
SOFT
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Discordant Coastline
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Headlands and Bays - Formed on an Atlantic
(discordant) coastline due to the softer rock
being eroded quicker than the harder rock. -
Beaches form in the bays where the soft rock has
been eroded away. - Headlands of more resistant,
hard rock are left behind.
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Concordant Coastline
ROCKS ARE PARALLEL TO THE SEA
ARD ROCK
BAY
BAY
OFT ROCK
OFT ROCK
ARD ROCK
ARD ROCK
EG Lulworth Cove, Dorset
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Wave Cut Platform Formation Fig 18.4 p301 Add
in the Retreating cliff lines
The sea uses its four erosion methods during high
and low tide to create a notch. This means the
cliff above is unsupported and collapses
retreating inland. This process is called
UNDERCUTTING. The cliff is vertical and steep.
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Cliffs Wave Cut Platforms - Cliffs are formed
when destructive waves attack the bottom of the
rock face between high and low water mark. - The
area under attack is eroded using the major
processes of coastal erosion. - Points of
weakness, such as faults and joints are attacked
most, and eventually a wave-cut notch is gouged
out.
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The rock above overhangs the notch, and as it is
cut deeper into the rock, gravity causes the
overhanging rock to collapse. - The loose rocks
are removed by the sea and transported along the
coast by long shore drift. - The whole process of
undercutting the cliff begins again. - As the
cliff is eroded backwards it leaves behind a
wave-cut platform, at the level of the low water
mark. - This platform is rarely eroded, as the
waves energy is concentrated on eroding the area
between the high and low water mark, and not the
rock that is underneath them.
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Model Answer Erosion Headland Formation A cave is
formed in the rock as various processes of
coastal erosion operate on it. Hydraulic action
(which involved mini explosions of air under
water) eats out the notch to form a cave. A cave
is eroded further by the processes of attrition,
corrosion (solution) abrasion and scouring. This
eventually forms an arch. Over time the arch
weakens and collapses leaving an stack. The stack
erodes over time to form a stump.
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Caves, Arches, Stacks and Stumps - Mainly seen on
headlands. - Waves start by attacking the main
points of weakness in the rock the joints and
faults. - A point of weakness is increased in
size until it becomes a cave. - The waves
continue to attack the cave, which finally
results in an arch being formed through the
headland. - The arch is attacked both by coastal
erosion and sub-aerial erosion and finally the
roof of the arch falls into the sea. - This
leaves behind a stack, which is then slowly
eroded down to become a stump.
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OLD HARRY
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Model Answers Rock Types Sheet 1a) The slate
rock must be harder (more resistant) than the
sandstone as it sticks out on the coastline as
headlands (2) 1b) The limestone must be harder
than the sands and clays because although the
limestone is closer to the sea, and therefore
more easily eroded, the sands and clays have been
eroded BEHIND the limestone to form coves eg
Lulworth cove (2) 2a) Headlands are sections of
rock jutting out into the sea whereas bays are
indentations into the coastline where the sea has
eaten it away (2) 2b) Arches look like headlands
except they have a hole at the base and stumps
are large towers or columns of rock sticking out
of the sea 3a) Erosion occurs in both headlands
and bays. As the headlands are made up of hard
rock they are eroded more slowly. Processes such
as hydraulic action and abrasion will be
important in their formation. Bays will be eroded
more quickly as they are made of softer rock.
Material eroded at the headland cliffs will also
be transported to the bays 3 b) First of all
hydraulic action attacks small notches in the
cliff face. Over time this is enlarged
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..to form an arch. The arch is then eroded until
the top collapses away forming a stack. Erosion
from the sea then leads to the stack collapsing
forming a stump. (6) 4. In Devon DISCORDANT
COASTLINE the rocks lie at right angles to the
sea. This forms headlands (on the resistant rock
- SLATE) and bays (on the weaker rock -
SANDSTONE). In Dorset CONCORDANT COASTLINE
rocks lie parallel to the sea. This forms
isolated parallel rock features in the limestone
and coves behind in the weaker sands and clays.
(9) 5. Devon headlands will get more
PRONOUNCED as the bays will be eroded at a
quicker rate Dorset the weak rock behind the
limestone (sands and clays) will be eaten out
even more to form very large coves. Some of the
coves may join up with each other too. The
limestone (which is more resistant) will slowly
get eaten away and will end up as isolated rock
outcrops in the sea standing alone (5)
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1c COASTAL TRANSPORTATION
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EG COASTLINE
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Groynes are used to stop LSD
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• Q3 Advantages
• It stops the beach from being eroded away eg
  tourist towns such as Bournemouth have
  constructed groyne systems
• By trapping beach material (through groyne
  construction) this protects the cliff from being
  eroded
• Disadvantages of groynes
• Look horrible and costs at lot of money
• Divide the beach up into unnatural sections
• Towns further down the coast may suffer because
  there is no sediment coming along as it has been
  trapped further up by groynes

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1d COASTAL DEPOSITION
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Spurn Head Spit
SEA
LSD
SALT MARSH
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Spits - A long, narrow ridge of sand attached at
one end to the coast. - Built up by long shore
drift transporting material along the coast. - At
a bend or break (for an estuary) in the coastline
the material being carried is dropped. However it
is deposited away from the coastline. - As the
spit builds out to sea the end is affected more
by the wind and by wave currents, causing the end
to curve towards the shore, to create a hook
end. - Material often accumulates in the area of
standing water that occurs behind a spit, and
this can lead to the formation of salt marshes. -
Spits can be areas where large sand dunes build
up, nearer the back of it.
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• Beaches
• Created by constructive waves depositing material
  (sand, shingle and pebbles) that has been
  transported from further along the coast.
• LSD also transports and deposits material from
  and to them
• - They lie between high and low watermark and are
  gently sloping, towards the sea.
• A constantly changing feature, beaches may be
  built up at certain times of the year, and eroded
  away at others, depending on the type of waves
  hitting them at the time. Often this change can
  be seasonal.
• The best natural coastal defence feature

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TOMBOLO
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• Tombolos
• A bar of deposited material linking the mainland
  to an island.
• Draw Fig 1.68 p47

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Bars - A ridge of sand that blocks off a bay or
river mouth. It will create a lagoon behind if it
is across a non-river bay.
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1e OS MAP WORK
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2 COASTAL MANAGEMENT
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Unfortunately, the sea defences stop the erosion,
but this allows mass movement time to takeover.
Rainwater seeps into the porous TILL and causes
ROTATIONAL SLUMPING.
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BEACH NOURISHMENT
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Human Intervention
Humans are affected by the retreat of the cliff
(loss of land, housing, etc.) They erect sea
defences which stop the erosion (groynes,
revetments, gabion cages and anti-tank blocks.
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Holderness Coast
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Weak Boulder Clay
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A(i) Lulworth Cove is a circular shaped hollow in
the coast. It is steeper towards the back and the
gradient drops off towards sea level. It is made
of 3 types of rock limestone at the front,
followed by sand and clay then chalk. The mouth
of the cove is 50m wide and the maximum width of
the cove is 350m. (3) A (ii) This stretch of
coastline is a concordant coastline where the
rocks are lying parallel to the sea. The
limestone is eventually eroded and breached and
the sea attacks the weaker sands and clays until
it hits the resistant layer of chalk at the back
of the cove. (3)
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b) HOLDERNESS COAST Physical environment the
coasts here are made of weak rocks called
boulder clay which have been carried by the
icesheets at the end of the last glacial period
( Devensian 10,000 yrs ago). The cliffs around
Mappleton have been affected eg Mr Cross and
Sue Earles farm, Easington Gas Terminal in
danger of falling into the sea. Human
Environment Groynes have been added to
Mappleton which have prevented LSD from taking
sediment further down the coastline. This has
meant that the coast has been built up at one
point but attacked at other places. Dairies have
been affected and gas terminals as well as
peoples property. (7)
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• c) For
• It protects the coastline and preserves peoples
  property (Mr Cross), businesses (Sue Earle) ,
  industry (gas terminal)
• Groyne encourage a beach to grow which can help
  tourism and bring money to the area
• Against
• Looks very ugly
• Very expensive to build
• No guarantee it will last forever
• Some people suffer if groynes are built and
  sediment is trapped eg Mr Cross (who was
  cross!) (6)
• d) SPIT eg Spurn Head is a hooked shaped
  landform which typically runs along a coastline
  with a hooked shaped end often where a river
  estuary meets the coast. It is formed by the
  process of Longshore Drift bringing material
  along the coastline in a zig-zag fashion. A
  saltmarsh often forms behind the spit as the
  sediment can build up here in shallower waters.
  (6)