GCSE COASTS
COASTAL EROSION
Erosion Processes
1.Corrasion / Abrasion
2.Scouring
3.Hydraulic Action
4.Solution
5.Attrition
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.
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.
DISCORDANT COASTLINE
HEADLAND
HARD ROCK
SOFT ROCK
BAY
HEADLAND
HARD
SOFT
Discordant Coastline
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.
Concordant Coastline
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.
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.
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.
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 subaerial 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.
OLD HARRY
COASTAL
TRANSPORTATION
COASTAL
DEPOSITION
MANAGING
COASTLINES
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.
BEACH
NOURISHMENT
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.
Holderness Coast
Weak
Boulder
Clay