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20971118
COASTS
Description
Year 10 Geography Mind Map on COASTS, created by Amy Taylor on 22/02/2020.
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geography
year 10
Mind Map by
Amy Taylor
, updated more than 1 year ago
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Created by
Amy Taylor
over 4 years ago
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Resource summary
COASTS
Erosion
Weathering
Freeze thaw - water gets in cracks and freezes, expanding the crack
The breaking down of man made things by weather
Mass Movement
The downhill movement of material under the influence of gravity
Impacting factors:
Undercutting the cliff
Building on the cliff top increases the weight
Rain saturates the rock which increases the weight
Weaker rocks (eg. clay) are more likely to collapse than srong rocks (eg. granite)
Coastal erosion
Hydraulic action - waves trap air in rock forcing it apart
Abrasion - rocks thrown at cliff face by waves scraping it away
Attrition - rocks bump into each other and get smaller
Solution - sea water dissolves the rocks
Erosional landforms
Headlands and bays
Soft rock (eg. clay) erodes quickly to make bays
Swanage bay - Dorset
Hard rocks (eg. limestone) erodes slowly to make headlands
The Foreland - Dorset
Caves, arches, stacks and stumps
1. A crack in the headland is expanded by hydraulic action
2. The crack becomes a cave
3. The cave is opened up to form an arch
Durdle door - Dorset
4. The top of the arch collapses to form a stack
Old Harry -Dorset
5. The stack is eroded to form a stump
Old Harry's wife - Dorset
Wave cut notches and platforms
Waves undercut a cliff to leave an overhanging platform above a wave cut notch.
The platform eventually collapses and the process happens again
Transportation
Transportation of different rocks
Traction - big rocks roll along the sea bed
Saltation - pebbles bounce along the sea bed
Suspension - sediment is small enough to be carried along by the water
Solution - tiny particles dissolve in the water and move with it
Longshore drift
Direction depends on the prevailing wind
Constructive waves have a strong swash
Destructive waves have a strong backwash
Sediment is moved along the shore by a diagonal swash and a straight backwash
Swash - a wave moving inland
Backwash - a wave moving back towards the sea
Beaches
Sand beaches
Formed by constructive waves
Can have sand dunes
Shallow gradient, almost flat
Pebble beaches
Formed by destructive waves
Steep gradient, often has berms
Large pebbles at the back of the beach
Depositional landforms
Spit
A finger of sand formed by longshore drift
Hook
A spit with a marsh behind it curves due to the low energy of the marsh to create a hook
Bar
A spit grows between headlands to create a bar
Sand dunes
1. Embryo dune
Small dune closest to the water
Plant found: Couch grass
2. Fore dune/yellow dune
Plant found: Marram grass
3. Grey dune
Plant found: Willow
4. Dune slack
A big dip between high dunes where water can get trapped
Plant found: Common sallow
5. Mature dune
Big dune furthest from the water
Plant found: Pine
Coastal management
Hard engineering - building defenses
Sea wall
Absorbs energy from waves and can redirect them (if curved at the top)
Advantage: Strong and effective
Disadvantage: Expensive - £6000 per meter
Rip rap
Absorbs energy from waves
Advantage: Simple to maintain
Disadvantage: Expensive - £1000 per meter, can look messy, can be dangerous
Groynes
Traps sediment from longshore drift and absorbs energy from waves
Advantage: Helps to build up a natural defence
Disadvantage: Expensive - £10000
Soft engineering - in line with the natural environment
Cliff regrading
Makes a cliff less steep
Advantage: Cheap
Disadvantage: Loss of some cliff
Dune stabalisation
Planting marram grass to hold dunes together
Advantage: Cheap, sustainable, looks natural
Disadvantage: Doesn't always work
Managed retreat
Allowing an area to become flooded by removing costal protection
Aims
Improve costal stability
Protect areas further inland
Rely on natural defences
Creates saltmarsh - a low energy environment
Northen Island, Essex - River Blackwater flooded in 1991, 8000sq metres, nature reserve
Advantages
Earth banks develop
Maintinence costs are low
Saltmarsh and vegitation provide protection from storms
Beaches can naturally replenish
Disadvantages
Land will be lost
Settlements will be destroyed
Not socially acceptable and compensasion will be needed for land owners
Schemes are unpredictable
Case study
Minehead
A coastal town on the Bristol channel and the north-west coast of Somerset
Coastal management strategies used
A 0.6m high seawall with a curve to deflect waves
Expensive but the walkway build beside it is popular with tourists
Rock armour
Expensive but low maintenance and asthentically pleasing
Wildlife can benefit by creating new habitats in it
More sand put on the beach (beach nourishment)
Forces waves to break further out to sea
Attracts tourists
Four rock groynes
Helps to stop sand movement from longshore drift
Provides wind shelter for tourists
Can increas erosion further down the coast
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