Coasts

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Coast
The frontier between land and sea.
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Fetch
The maximum distance of water over which winds can blow.
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Swash
The movement of waves up the beach. The swash transfers energy diagonally up the beach.
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Backwash
The movement of waves back down the beach, perpendicular to the beach.
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Constructive wave
low and shallow in height; weak backwash so little erosion; strong swash so deposition; limited energy; beach is made steep arrive slowly at 6-8 per minute
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Destructive wave
tall and steep in height strong backwash so high erosion; weak swash so little deposition; high energy; beach is made more shallow; frequent and close together at 13-15 per minute
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Corrasion
Large waves beach material at a cliff
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Attrition
Waves cause boulders and rocks to bump into each other and break up into little particles
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Corrosion
When salts and other acids in the seawater slowly dissolve a cliff
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Hydraulic pressure
The force of the waves compressing air in the cracks in a cliff
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Headlands
Made of resistant rock that doesn't erode as quickly as the soft rock surrounding it so it sticks out
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Bays
Destructive waves erode softer rock areas to form bays
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Wave-cut platform
The gently sloping expanse of rock marking the foot of the retreating cliff
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Wave-cut notch
When the waves undercut the foot of a cliff
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Cave
Abrasion, pounding and hydraulic action of waves widen cracks in the weak areas of a cliff to form a cave.
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Arch
Waves cut through headlands to form an arch which is continually widened at its base
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Stack
An isolated portion of a cliff
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Stump
The stack is undercut and collapsed leaving a stump
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Erosion
The wearing away of rocks by the action of the sea
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Weathering
The breakdown of rocks in situ by either mechanical or chemical processes
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Sub-aerial processes
Processes active on the face and top of rocks
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Geology
To do with how rocks change over time
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Long-shore drift
The movement of material along the coastline by the action of the waves
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Sand dunes
Spits become permanent when sand is blown up the beach by prevailing winds to form sand dunes
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Bar
A spit that connects two parts of the mainland
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Spit
An extended stretch of beach material that projects out to sea and is joined to the mainland at one end
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Tombolo
A spit that joins the mainland onto an island
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Beach
An accumulation of sand and shingles found where deposition occurs at the coast
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Cliff
A vertical, near-vertical or sloping wall of rock or sediment that borders the sea
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Groynes
Wooden or concrete barriers built at right angles to the beach to limit long-shore drift
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Salt marsh
Develops in the sheltered area behind a spit
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Silt
Very fine sediment
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Hard engineering
When man-made structures are built in order to defend coastlines from the sea
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Soft engineering
When the area is adapted to the risk of flooding by using nature
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Managed retreat
Allowing the sea to flood lowland areas
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Beach replenishment
Adding sand to the beach to maintain it
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Sea Wall
A wall built on the edge of the coastline
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Rock armour (rip rap)
Large boulders piled up on the beach
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Gabions
Wire cages filled with rocks that can be built up to support a cliff or to provide a buffer to the sea
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Coastal system
The coastal system is a giant conveyor belt; material is worn away from some places, moved by waves, and deposited in other places
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Depositional landforms
Beaches; spits; bars; barrier beach; salt marshes
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Erosional landforms
Headlands and bays; cliffs; wave-cut notches and wave-cut platforms; caves; arches; stacks
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Physical causes of flooding:
Heavy rainfall/long periods of rain; snow melt; steep slopes; impermeable rock; wet, saturated rock; compacted dry soil
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Human causes of flooding:
Urbanisation (more towns and cities=more impermeable surfaces); deforestation (no trees= less water intercepted and more runoff)
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Why is it important to protect coastlines?
Erosion may be threatening beaches/coastal settlements; declining tourism; risk of flooding; sewage/pollution problems; nearby protected areas at risk
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Advantages of sea walls:
Protects the base of the cliffs, land and buildings from erosion; can also prevent coastal flooding; can have a promenade to help tourism.
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Disadvantages of sea walls:
Expensive to build (£5000-£10,000 per metre); curved tops reflect the energy back to sea meaning the waves keep power; overtime it may erode and maintenance costs are high.
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Advantages of groynes:
Prevents LSD and allows the build up of a beach; beaches are a natural protection and can create tourism.
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Disadvantages of groynes:
Can be seen as unattractive and they are costly to build and maintain; wooden type has relatively short lifespan; £150,000 each (timber - needed every 200m)
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Advantages of rock armour:
Absorb the energy of the waves and allow the beach to be built up; they can provide interest to the coast and can be used to aid fishing.
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Disadvantages of rock armour:
Can be expensive to obtain and transport to the area; around £200,000 per 100m; do not fit in with local geology.
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Advantages of beach replenishment:
The beach is a natural defence and attracts tourism; it looks natural and is relatively inexpensive.
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Disadvantages of beach replenishment:
It needs constant maintenance as it is constantly eroded and transported; therefore this adds to the cost which is around £500,000 per 100 metres.
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Advantages of managed retreat:
It encourages the development of beaches and salt marshes which are natural and is a low cost option.
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Disadvantages of managed retreat:
May need to compensate people for lost land and buildings, and only suitable for low value sites.
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Advantages of gabions:
Relatively cheap to produce and the final design is flexible; the drainage of the cliff base is improved and eventually they become vegetated and merge into the landscape.
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Disadvantages of gabions:
For a while they can look unattractive and may only last 5-10 years before rusting; cost up to £50,000 per 100m.
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What is weathering?
Weathering is a part of a system of processes at work on the coast.
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What is chemical weathering?
Chemical weathering is when rain or seawater mixes with rocks such as chalk and linage on and the calcium carbonate in these rocks dissolves (solution) and is washed away, weakening the rock.
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What is mechanical weathering?
Mechanical weathering includes freeze-thaw. Temperatures can drop below freezing at night, and get warmer throughout the day. Water in rocks freezes and expands, and then thaws out. This happens over and over again and the rock is weakened.
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What happens when weathering works with erosion?
You get mass movement. Waves erode the bass of a cliff and weathering weakens the top. Rain filters through cliffs, and gets trapped on layers of impermeable clay. This destabilises the cliff and causes land slides, rock falls and mud slides.
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What is onion-skin weathering?
Onion-skin weathering is when less resistant rocks like clay get wet and then dry out again; this causes them to expand and contract, weakening the rock.
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What is biological weathering?
Biological weathering is when plants and animals weaken rocks eg. plant roots separate rocks or animals weaken them (eg. limpets scarring rocks).
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Other cards in this set

Card 2

Front

Fetch

Back

The maximum distance of water over which winds can blow.

Card 3

Front

Swash

Back

Preview of the front of card 3

Card 4

Front

Backwash

Back

Preview of the front of card 4

Card 5

Front

Constructive wave

Back

Preview of the front of card 5
View more cards

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