Transcript Year 8 Coasts Revision PowerPoint 2014

Revision PowerPoint
Use this PowerPoint to help you revise some of the
key ideas from this model to help you get ready for
your test.
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presentations and animations!
What is the Coast?
What do we use it for?
 The
Coast is where the land meets
the sea.
 The next slide some of the many
things we use the coast for.
 Many people visit the coast for
leisure and holidays.
 People live and work there.
 Could any of these activities conflict?
Could any
of these
conflict?
The Power of the waves
 Waves
are changing the coast every
day, they do this by following a
master plan
Erode
Waves at Work
Transport
Deposit
Waves change the coast in 3 ways
Erode
Transport
Deposit
What do these keywords mean?
 Waves
erode (wear down) the coast.
 Waves transport (move) the eroded
material.
 Waves deposit (drop) this material
in sheltered areas where they lose
their energy.
There are 4 types of Erosion By Waves
Waves smash against the rock, breaking the rock up over time.
Hydraulic
action
solution
erosion
attrition
Abrasion
How do these types of erosion work?
Hydraulic Action
 Waves
force water into cracks under
pressure. This helps break up the
rock.
Solution
 Water
dissolves soluble material
from the rock.
Abrasion

Waves fling sand,pebbles and large
stones against the rock. This acts as
sand paper wearing away the rock.
Attrition
 Waves
knock together the pieces of
rock broken off by erosion. These
wear down into smaller and smaller
pieces.
 The rock wears down into shingle
(Pebbles) and sand.
The waves don’t have all the
power!
 Erosion
of the cliffs also occur from
weathering
 What are the different types of
weathering ?
Water trickles into cracks.In icy
weather it freezes, forcing the
cracks wider until the rock breaks
up.
In hot places, Like deserts,
the rock heats up during the
day and expands. At night it
cools and contracts this
weakens the rock. The outer
layers of he rock break uprather like an onion skin.
Plant and tree roots grow
in cracks and widen them,
causing the rock to break
up
Remember Science?
Water reacts with Carbon dioxide in
the air. The water becomes slightly
acidic. (Carbonic acid). This
dissolves the rock.
Erosion of a Headland
Caves Arches Stacks Stumps
The video link below will help
you reacp these land forms:
http://www.bbc.co.uk/learningzone/clips/coastlines-cavesarches-and-stacks/8432.html
Make sure you can describe and explain how these land
forms are created.
Remember your P2L, the big picture activity and your
diagram?
Geog 2 describes the process of a headland being eroded
as shown below:
Erosion of a Headland
Crack
Stack
Arch
Cave
Stump
Waves transport the material
they erode from the land.
Much of the material is
transported by
Longshore drift
What happen when the waves reach the land?
 When
the waves reach the beach,
they break and cause a swash and
backwash.
When the water
rushes up the
beach with lots
of energy this is
called the swash
When the water
rushes down the
beach with a lot
less energy this
is called the
backwash
Longshore Drift
How the eroded rock moves around
SEA
Direction of longshore drift
Many seaside towns build groynes to stop
their beaches being washed away
The groyne disrupts longshore drift
How do groynes work?
Direction of
longshore drift
Wave
direction
Pebbles and sand carried by
longshore drift are stopped by the
groyne, so the beach builds up on
this side
On this side longshore drift carries
on . It moves pebbles and sand away
in the direction of the longshore drift,
so there is less beach material.
.
Watch this video clip to see
longshore drift in action.
http://www.bbc.co.uk/learningzone/clips/thecoastline-longshore-drift-and-spits/3086.html
Cliff Collapse

Wave erosion, Weathering and rain
combine to weaken cliffs. This can
cause them to collapse.
Holbeck Hall Hotel in
Scarborough
Weathering
Chemical: rain soaks in and dissolves minerals
Freeze- thaw: In winter water freezes in the cracks
making them larger
If we can reduce
the effects of
these processes,
we can prevent
cliffs falling into
the sea.
Cliff Collapse
Make sure you can
describe, explain and
evaluate the
advantages and
disadvantages of the
different methods we
use to prevent cliff
collapse.
Rain
Wave Erosion
Soaks into the cracks.
It makes clay cliffs
very slippery. The clay
can just slide away.
Waves attack the cliff
through Hydraulic
Action, Abrasion,
Solution and Attrition.
Rock Armour








Heavy rocks cemented in front of the cliff.
Absorbs energy from the waves.
Creates a barrier protecting the land from attcak by
wave erosion.
Difficult to transport heavy stones
Interferes with Longshore Drift
Ugly, spoils the view and some of the beach is
covered.
Heavy lorries need to transport the rocks causing
traffic problems, noise and pollution.
Needs to be replaced when it has been eroded.
Drainage Pipes






Pipes that are dug into the cliff.
Drains away water from the cliff, so it is less
slippery.
It doesn’t spoil the view.
Very Effective, especially to protect soft clay cliffs
that become very slippery when they are saturated
with water.
Very expensive to install.
Noise, pollution and disruption while trenches are
dug to install the pipes.
Salt resistant vegetation







Plants that can survive in salty conditions near the
coast are planted on the cliff.
They draw out some of the water from the cliff.
Their roots bind the soil together, stabilising it and
making it less likely to slip.
Quite cheap and low maintenance.
Looks natural and could create habitats.
Loss of agricultural (Farm) land.
Changes the natural habitat of animals and plants
Wave Barriers/Granite Reefs



Break the waves away from the coast
Doesn’t stop Longshore Drift completely
Extremely expensive
Groynes
Stops Longshore drift causing sand to
build up.
 Ugly and costly to maintain

Beach Replenishment
Replacing the material moved by waves.
 Natural effect against erosion
 Needs constant “Topping up”
(replenishment)

There is always a downside…
Knock on Effects
If we stop erosion and cliff collapses in one
place, longshore drift will not be able to
transport the eroded material along the coast to
another place.
The beach there will not be replenished, but it
will be transported away by longshore drift.
This means erosion will be worse there as there
is less beach to protect the coast
However we protect the
coast or try to prevent cliffs
collapsing there will be a
disadvantage.