The changing landscapes of the UK : coasts

What are the types of rocks

• igneous

• Sedimentary

• Metamorphic

Describe igneous rocks

• they are formed from molten magma that has cooled down

• They are made of crystals

• Resistant to erosion

• Some are intrusive while others are extrusive

• Examples are granite and basalt

Describe sedimentary rocks

• They are formed when layers of sediments are deposited and compressed over long periods of time

• They form layers called beds

• They contain fossil fuels

• Examples are limestone sandstone and chalk

Describe metamorphic rocks

• they formed from previously existing rocks changed by heat and pressure

• May contain crystals

• They have layers

• Examples are marble slate and schist

What is coastal erosion

This is the action of waves wearing away the rocks along the coastline and removing coastal sediments

What are the four main processes of coastal erosion

• hydraulic action

• Abrasion

• Solution

• Attrition

What is hydraulic action

This is the sheer force of the waves breaking away the rocks. The waves also compresses air in joints causing pressure to build and loose rocks to be dislodged as the waves retreat the air is released explosively loosing the rock

What is abrasion

This is when fragments of rock are picked up by waves and thrown against the cliff face causing pieces of rock to break off

What is solution

This is the chemical action on rocks by seawater

What is attrition

This is when rocks are carried away by waves and are reduced in size as they collide against each other and the cliff face

What is weathering

This is the breakdown of rocks at the surface of the ground

What are the types of weathering

• mechanical ( freeze thaw)

• Chemical

• Biological

What is mechanical weathering

This is cause by repeated freezing and thawing in the crack in a rock

What is chemical weathering

Rainwater is slightly acidic when they fall on limestone or chalk a weak chemical reaction takes place causing the rock to weaken and break down

What is biological weathering

The roots of growing plants can widen cracks in rocks and burrowing animals can cause rocks to decay

What is mass movement

This is the downhill movement of rocks from the cliff due to the action of gravity

What are the types of mass movements

• Rock falls

• Mudflow

• Landslide

• Rotational slip

What is rock fall

This happens suddenly when rocks fall from a weathered cliff fall due to freeze thaw

What is mudflow

This is when saturated soil flows down a slope

What is landslide

This is when large blocks of rock slide downhill

What is rotational slip

This is when saturated soil slumps down a curved surface

What is deposition

This occurs when there’s not enough energy to carry eroded material any further

What determines the height and energy of waves

• wind strength

• Wind duration

• Fetch

What is fetch

This is the distance of open water which a wind blows over

What are the tyoes of waves

• destructive

• Constructive

Describe destructive waves

• they have weak swash and strong backwash

• Short wavelength

• Waves with steep gradient

• Tall waves

Describe constructive waves

• strong swash and weak backwash

• Long wavelength

• Short waves

• Shallow gradient

What are the types of coasts

• concordant

• Discordant

What are concordant coast

This is where bands of hard and soft rock rock run parallel to the coast

What are discordant coasts

This is where band of soft and hard rocks run at a right angle to the coast

How are headlands and bays formed

• they are formed from discordant coastlines

• Alternating bands of hard and soft rock result in the formation of headlands and bays due to differential erosion

• The hard rocks are able to withstand erosion

• But soft rock can’t withstand erosion so they form an inlet of the sea where the land curves inwards

How is a wave cut platform made

• the sea attacks the base of the cliff between the high and low water mark

• A wave cut notch is formed by abrasion- this is a dent in the cliff usually at the level of the high tide

• As the notch increases in size the cliff becomes unstable and collapses l

• The backwash carries away the eroded material leaving a wave cut platform

• The process repeats and the cliff continues to retreat

How are caves arches stacks and stumps made

• cracks are formed in the headland through abrasion and hydraulic action

• As the waves continue to grind at the crack it begins to open up to form a cave

• The cave becomes larger and breaks through the headland to form an arch

• The base of the arch continually becomes wider until its roof becomes too heavy and collapses into the sea this leaves a stack

• The stack is undercut at the base until it collapses to form a stump

What is a beach

These are made up from eroded material that has been transported from elsewhere and then deposited by the sea

How are spits formed

• sediment is carried by longshore drift

• When there is a change in the shape of the coastline deposition occurs. A long thing ridge of material is deep this is the spiy

• A hooked end can form when there is a change in wind direction

• Waves cannot get a spit therefore water behind a spit is very sheltered. Silts are deposited here to form salt marshes or mud flats

What is a bar

This is formed when a spit grows across a bay to join two headlands together

What is hard engineering on the coast

This involves building artificial structures which try to control natural erosionsl processes

What are the type of hard engineering

• sea wall

• Rock armour/rip rap

• Groynes

What is a sea wall

These are concrete walls placed at the foot of a cliff

What are the advantages of sea walls

• effective at protecting the base of the cliff

• Sea walls usually have promenades so people can walk along them

What are the disadvantages of sea wall

• waves are powerful and can still erode sea wall

• Expensive

What is rock armour

Large boulders placed at the foot of a cliff

What are the advantages of rock armour

• Easy to maintain

• Can be used for fishing

What are the disadvantages of rock armour

• they look unnatural

• Rocks are expensive to transport

What are groynes

Wooden structures built at right angles into the sea

What are the advantages of groynes

• builds a beach which encourages tourism

• They trap sediment carried by long shore drift

What are the disadvantages of grounds

• they look unattractive

• By trapping sediment it starves beaches further down the coastline

What are soft engineering strategies

These involves using natural approach to stop erosion

What is beach nourishment

Sand is pumped into an existing beach to build it up

What are the advantages of beach nourishment

• blends in with existing beach

• Large beaches attract tourists

What are the disadvantages of beach nourishment

• needs to be constantly replaced

• The sand has to be brought from somewhere else

What is dune nourishment

Growing of plants on dunes to help trap sand and build them up

What are the advantages of dune nourishment

• relatively cheap

• Maintains a natural looking coastline

What are the disadvantages of dune nourishment

• can be damaged by storm waves

• Areas have to be zoned off from the public

What is reprofiling

This is when sediment is redistributed from lower part of the back to the upper part of the beach

Advantages of reprofiling

• cheap and simple

• Reduces energy of waves

What are the types of transportation

• traction

• Saltation

• Suspension

• Solution

What is traction

Large heavy pebbles are rolled along the sea bed

What is saltation

Pebbles are bounced along the river bed

What is suspension

Lighter sediment is suspended in within the water

What is solution

The transport of dissolved chemicals