The Coastal Zone

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What is Mechanical Weathering?
The break up or decay of rocks in their original place or close to the Earth's surface
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Give an example of Mechanical Weathering
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What type of rock is freeze-thaw most effective on?
Porous and permeable rocks such as chalk
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Describe the process of freeze-thaw
1) Water gets into cracks in rocks 2) When the water freezes, it expands, which puts pressure on the rock 3)When the water thaws it contracts, which releases the pressure on the rock 4)Repeated freeze-thaw widens the crack causing the rock to breakup
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What is Chemical Weathering?
The breakdown of rock by changing its chemical composition
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Name a type of chemical weathering
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Describe the carbonation process
1)Rainwater has carbon dioxide dissolved in it, which makes it a weak carbonic acid 2) Carbonic acid reacts with rock that contains calcium carbonate so the rocks are dissolved by rainwater
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What are the 5 types of erosion?
Corrasion, Abrasion, Solution, Hydraulic Power and Attrition
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What is Corrasion?
Fragments of rock are hurled at the cliffs by the sea. They scrape and gouge the cliffs
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What is Abrasion?
Pebbles grind over rocks and make them smooth- a bit like sandpapering
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What is Solution?
Some rocks dissolve very easily in the sea e.g. limestone and chalk
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What is Hydraulic Power?
The force of the waves as they smash against cliffs. Trapped air is blasted into holes and cracks in the rocks, exploding it apart- called 'Cavitation'
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What is Attrition?
Fragments of rock carried in the sea bash into each other and break into smaller ones
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What is Mass Movement?
The downhill movement of material under the influence of gravity.
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What are 3 examples of Sliding?
Rockfalls, landslides and mudflows
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What is one example of Slumping?
Rotational Slip
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What is Rockfall?
Smaller fragments of rocks break away from the cliff face, often due to freeze-thaw weathering
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What is a Lanslide?
Large blocks of rock sliding downhill
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What is Mudflow?
After high amounts of rainfall, saturated soil and weak rock flow down a slope in a fan-shape
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What is Rotational Slip?
Rotational Slip involves a slump of saturated soil and weak rock along a curved surface
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What type of waves attack the bottom of a cliff to create a wave-cut platform?
Destructive waves
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Which processes of erosion are involved to create a wave-cut notch?
Hydraulic Power and Corrasion
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Describe the process in which a wave-cut platform is formed.
1)Attacking waves and erosion create a wave-cut notch 2)The notch gets bigger until the weight of the overhanging rock collapses 3)This process repeats and the cliff retreats inland 4)As the cliff moves back a gently-sloping rock is left (WCP)
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What force causes the overhanging rock above a WCN to collapse?
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Why is a WCP usually smooth?
Because of abrasion
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What 4 features can a headland be eroded into?
Caves, arches, stacks and stumps
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What are lines of weakness in a headland vulnerable to?
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What type of wave and types of erosion erode lines of weaknesses?
Destructive waves, corrasion and hydraulic power
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Describe how caves are formed
Destructive waves erode a line of weakness to form a cave by corrasion and hydraulic power
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Describe how an arch is formed
Over time, erosion may lead to two back-to-back caves breaking through a headland to form an arch. The arch is enlarged by erosion at the base and sides and by weathering processes acting on the roof
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Describe how a stack is formed
Eventually, the roof of an arch is too heavy to be supported and so it collapses. This leaves an isolated pillar of rock called a stack.
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Describe how a stump is formed.
A stack is undercut and collapses to leave a stump which is covered up at high tide.
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Name the four types of transportation
Traction, Saltation, Suspension and Solution
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What is traction?
Larger rocks and boulders are rolled along the sea floor
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What is Saltation?
Smaller rocks and pebbles are bounced along the sea floor.
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What is Suspension?
Tiny fragments and particles are carried by the sea
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What is Solution?
Dissolved material floats in the sea- normally chalk and limestone.
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What is longshore drift?
Waves approach the coastline at an angle, swash carries sediment up the beach, backwash carries sediment back down the slope at right-angles, material is transported along the coastline in a zig-zag pattern
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Name the two types of waves
Constructive and Destructive
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How do constructive waves affect a beach?
They carry large amounts of sediment and build up beaches (deposition)
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How do destructive waves affect a beach?
They remove sediment and destroy beaches
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Describe the swash, backwash and size of a constructive wave
Strong swash, weak backwash, long wave in proportion to length
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Describe the swash, backwash and size of a destructive wave
Weak swash, strong backwash, high wave in proportion to length
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How are Constructive waves formed?
By distant storms 100's of kilometres away
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How are Destructive waves formed?
By local storms close to the coast
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What is deposition?
Where sediment can no longer be carried or rolled along and has to be dropped off
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Name 3 landforms created by coastal deposition
Beaches, spits and bars
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What is a beach?
An accumulation of sand or shingle along the coast
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Where do sandy beaches tend to be found?
In sheltered bays
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Where do pebble beaches tend to be found?
Near to cliffs that are being eroded
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What is a spit?
A long narrow finger of sand and shingle jutting out into the sea from the land
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How are spits formed?
Longshore drift causes sediment to be transported along the coastline where the coastline then changes direction. More sediment is deposited which extends out to the sea over time. The tip of the sediment is affected by wind approaching it
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What can happen behind a spit?
Behind the spit will become colonised by grass and bushes forming a salt marsh
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What is a bar?
A spit which extends across two headlands, joining them together so lagoons can form behind the bar
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What is the main cause of rising sea levels?
Thermal expansion of the seawater as it absorbs heat from the atmosphere
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What is the slight cause of rising sea levels?
Melting land ice e.g. glaciers on Greenland
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What 3 things will the amount of sea-level rise depend on?
1) Rises and falls in the level of the land, 2) The amount of deposition occurring at the coast, 3) The rate of global warming
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What is meant by hard-engineering coastal defences?
Hard-engineering strategies are man-made structures built to control the flow of the sea and reduce flooding and erosion
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What is meant by soft-engineering coastal defences?
Soft engineering strategies are schemes set up using knowledge of the sea and its processes to reduce the effects of flooding and erosion
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Name 3 examples of hard-engineering coastal defences
Sea walls, Rock Armour, Groynes
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What is a Sea Wall?
Walls made out of a hard strong material like concrete that reflects waves back to the sea
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Give 2 advantages and 2 disadvantages of a sea wall
1a) Effective at stopping erosion by the sea 1b) Promenade on top for tourists to walk along 2a) Can look unattractive 2b) Very expensive and high maintenance
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Give 2 advantages and 2 disadvantages of rock armour
1a) Cheap and easy to maintain 1b) Habitats for sea life and for fishing/rock-pooling 2a) Rocks are expensive to transport 2b) Rocks may not geologically blend in
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Give 2 advantages and 2 disadvantages of groynes
1a) Bigger beach 1b) More tourists 2a) Spoils appearance of beach 2b) Erosion increased further down the coast
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Name 3 examples of soft-engineering coastal defences
Beach nourishment, Dune Regeneration, Managed Retreat
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What is rock armour?
This is where boulders are piled up along the coast
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What are groynes?
These are wooden or stone fences that are built at right-angles to the coast. They trap material transported by longshore drift
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What is beach nourishment?
This is when sand and shingle from elsewhere (e.g. the offshore seabed) is added to build up a beach
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What is dune regeneration?
This involves creating or restoring sand dunes by either nourishment, or by planting vegetation to stabilise the sand
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What is managed retreat?
This means allowing land to be flooded and eroded in the hope of creating new more useful land
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Give 2 advantages and 2 disadvantages of beach nourishment
1a) Bigger beach-more tourists 1b) Inexpensive 2a) Beach will always need re-nourishment 2b) Can be expensive over time due to repeated nourishment
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Give 2 advantages and 2 disadvantages of dune regeneration
1a) Cheap 1b) Creates a barrier between the land and sea 2a) Easily damaged because people ignore fenced areas 2b) Protection is limited to a small area
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Give 2 advantages and 2 disadvantages of managed retreat
1a) Virtually free of cost 1b) Creates habitats 2a) Land lost as its flooded 2b) Farmers need compensation
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Card 2


Give an example of Mechanical Weathering



Card 3


What type of rock is freeze-thaw most effective on?


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Card 4


Describe the process of freeze-thaw


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Card 5


What is Chemical Weathering?


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