Geography- Coastal Zone Flashcards
How are waves formed?
Friction between the wind and the surface of the water causes ripples to form.
These develop into waves
What is fetch?
The stretch of open water over which the wind blows
The longer the fetch the ………… powerful a wave can become
More
What is swash?
The water that rushes up the beach
What is backwash?
The water that flows back towards the sea
What happens to waves as the water becomes shallower?
The top of the wave (the crest) begins to move faster, which causes the crest of the wave to rise up and eventually topple onto the beach .
What are constructive waves?
powerful waves that surge up the beach with a powerful swash
How do constructive waves change a beach?
They carry large amounts of sediment and construct the beach, making it more extensive.
How are constructive waves formed?
By distant storms, which can be hundreds of kilometres away.
What are the characteristics of constructive waves?
Well spaced apart
Powerful when they reach the coast
What are destructive waves?
Waves that destroy the beach as they have little swash when the wave breaks (as they rear up to form towering waves before crashing down into the beach) but a powerful backwash. Therefore this explains the removal of sediment and the destruction of the beach
How are destructive waves formed?
By local storms close to the coast
What are the characteristics of destructive waves?
Closely spaced, often interference with each other producing a chaotic, swirling mass of water.
What is a cliff?
A steep or vertical face of rock often found at the coast
What is mechanical weathering?
Involves the disintegration of rocks without any chemical changes taking place
What is rockfall?
The collapse of a cliff face or the fall of individual rocks from a cliff, often due to freeze thaw.
What is freeze thaw weathering?
Involves water collecting in cracks or holes in the rock. At night the water freezes and expands. This expansion creates stress within the rock, widening any cracks that already exists. When the temperature rises the water seeps deeper into the rock and the process repeats.
What type of rock is freeze thaw weathering particularly effective in?
Porous (contains holes)
Permeable (allows water to pass through it)
What is exfoliation?
Where the heating and cooling of a rock causes it to expand and contract, eventually leading to the outer layer of the rock flaking off.
What is chemical weathering?
Slight acidic rain dissolves the calcium carbonate slightly to form calcium hydrogen carbonate which is soluble, and over time this process dissolves the rock away.
What is biological weathering?
Plant roots are effective at growing and expanding in cracks in the rocks. Animals such as rabbits can be effective at burrowing into weak rocks such as sands.
What is mass movement?
The downhill movement of material under the influence of gravity
What is a landslide?
Block of rock slide downhill
What is mudflow?
Saturated soil and weak rock flows down a slope
What is rotational slip?
Slump of saturated soil and and weak rock along a curved surface.
Where does most of the materials go from cliff erosion?
Carried away by the waves to be deposited somewhere along the coast
What is hydraulic power (in terms of cliffs)?
This involves the sheer power of the waves as they smash onto a cliff. Trapped air is blasted into holes and cracks in the rock, eventually causing the rock to break apart. This explosive force of the trapped air operations in a crack is called cavitation
What is corrosion (in terms of cliffs)?
Involves fragments of rock being picked up and hurled by the sea at a cliff. The rocks act like erosive tools by scraping and gouging the rock.
What is abrasion (in terms of cliffs)?
The sand papering effect of pebbles grinding over a rocky platform, often causing it to become smooth
What is solution (in terms of cliffs)?
Some rocks are particularly vulnerable to being dissolved by seawater. This is particularly true of limestone and chalk which form cliffs in many parts of the U.K.
What is attrition (in terms of cliffs)?
This is where rock fragments carried by the sea knock against one another, causing them to become smaller and more rounded.
What is longshore drift?
The transport of sediment along a stretch of coastline caused by prevailing winds causing the waves to approach the beach at an angle
How does long shore drift occur?
When waves approach the coastline at an angle, they bring their swash pushed sediment up the beach at the same angle. The back wash then drags the material down the beach at a 90 degrees angle, due to the force of gravity. This produces a zig-zag movement of sediment along the beach. The smaller sediment will be carried furthest.
Where does coastal deposition take place?
Areas where the flow of water slows down as sediment can no longer be carried or rolled along and has to be deposited. This most commonly happens in bays as the energy of the waves is reduced when entering the bay.
What is a bay?
A broad coastal inlet often with a beach
Why is there a lack of beaches at headlands?
The wave energy is much greater
What is a headland?
A point of usually high land jutting out into the sea
How are headlands formed?
They are sections of cliff that are particularly resistant to erosion (e.g sandstone, chalk or limestone)
How are bays formed?
They are weaker sections of coastline the are more easily eroded (e.g clay)
Are bays or headlands more vulnerable to cliffs and wave cut platforms from powerful waves?
Headlands
What is a concordant coast?
If the layers of rock are parallel to the coastline
What is a discordant coast?
Where the layers of rock are perpendicular to the coast
Are headlands and bays formed on discordant or concordant coasts?
Discordant coasts
What is a wave cut notch?
A small indentation (or notch) cut into a cliff by coastal erosion roughly at the level of high tide.
What happens to a wave cut notch over time?
Over a long period of time (usually hundreds of years) the notch gets deeper until the overlying cliff can no longer support its own weight and collapses.
What is a wave cut platform?
A wide gently sloping rocky surface at the foot of a cliff
How are wave cut platforms formed?
Through a continuous sequence of wave-cut notch formation and cliff collapse, the cliff line gradually retreats and in its place will be a gently sloping rocky platform called a wave-cut platform.
What is a cave?
A hollowed out feature at the base of an eroding cliff
How are caves formed?
The energy of the waves gouges out the rock along a line of weakness to form a cave.
What is an arch?
A headland that has been partly broken through by the sea to form a thin-roofed arch.
How is an arch formed?
Over time erosion of a cave may lead to two back to back caves breaking through a headland to form an arch.
What is a stack?
An isolated portion of the cliff.
How is a stack formed?
When the arch is enlarged by erosion at the age and sides and by weathering processes acting on the roof, eventually it becomes too heavy to be supported and collapses
How is a stump formed?
When the stack is undercut and collapses, a stump is left which is covered at high tide.
What is a beach?
A deposit of sand or shingle at the coast, often found at the head of a bay
What causes wave refraction in bays?
The way the water gets shallower as the waves enter the bays
How does wave refraction cause deposition?
Because wave refraction spreads out and reduces the wave energy in a bay, which is why deposition occurs.
What is a spit?
A long, narrow finger of land, made of sand or shingle jutting out into the sea from the coast.
How are spots formed?
- as sediment is transported along the coast by longshore drift, it becomes deposited at a point where the coast line changes direction or where a river mouth/estuary occurs.
- gradually as more and more sediment is deposited the feature extends into the sea. Away from the coast, the tip is affected by waves approaching from different directions and the spit often becomes curved as a result.
- over time the sediment breaks the surface to form new land and a spit is formed .
- it soon becalmed colonised by grass, bushes, and eventually trees.
- on the landward sheltered side of a spit where the water is calm, mudflats and salt marches form.
What is a salt marsh?
Low-lying coastal wetland mostly extending between high and low tide.
What is a bar
A spit that has grown across a bay, trapping a freshwater lake or lagoon behind it.
How will Kings Lynn be affected by rising sea levels?
Valuable agricultural land (the fens) will be at greater risk from flooding.
How will the Norfolk boards be affected by rising sea level?
Sea level rise would flood the broads, destroying the economy of the area (popular tourist destination, bringing £5m + to the local area)
How will coastal settlements such as Happisburgh be affected by rising sea level?
Erosion rates are likely to increase so sea defences will need strengthening, which will be expensive.
How will East Anglia be affected by rising sea levels?
In the past East Anglia have suffered from a severe storm surge, killing 300 people. People are worried that such an event may occur again.
How will Essex be affected by rising sea level?
It is a area of low lying mudflats and marshes which can be easily flooded.
How will the Thames barrier be affected by rising sea level?
The Thames barrier protects buildings worth £80bn. As sea levels rise, large areas of the lower estuary will be at risk of flooding, affecting housing, industry and farmland.
What is the main cause of sea-level rise?
Thermal expansion of sea water.
What is thermal expansion of sea water?
Where the sea absorbs more heat from the atmosphere, which will cause the melting of ice on the land (e.g glaciers on Greenland), which will increase the amount of water in the ocean.
What are Spring tides?
Exceptionally high tides that happen twice a year when the sun and moon are in alignment.
What factors can contribute to cliff collapse?
Weathering processes- such as heavy rainfall that can saturate the land and make it unstable.
Mass movement- such as sliding and slumping, which is more likely if the land is made of soft weak rock types.
The power of the waves continually crashing against the cliffs and undercutting them.
What methods can be used to prevent cliff collapse?
Make the slope where the landslide occurs flatter
Insert drainage pipes into the cliff
Put rock armour at the base of the cliff
Put sheets of strong plastic called Geotextile (lets water through) into clic face and pack with clay from land slip
What is sliding?
A type of mass movement involving material moving downhill on a flat surface (a landslide)
What is slumping?
A type of mass movement involving material moving downhill under its own weight.
What is land slip?
A type of mass movement common at the coast involving material slipping downhill usually along a curved slip surface.
What is the Shoreline Management Plan (SMP)?
An integrated coastal management plan for a stretch of coastline in England and Wales. It details natural processes, environmental considerations and human uses.
What are the four strategies generally used by the council to manage the coast?
Holding the line- using sea defences to keep the coast where it is
Advance the line- use sea defences to move the coast further into the sea
Strategic retreat- let the cliff erode and move people and businesses away from at- risk areas.
Do nothing- take no action.
What does holistic management take into account?
Needs of different groups of people
Economic costs and benefits of different strategies today and in the future
Environment, both on land and in the sea
Name a holistic form of coastal management (ICZM)
Integrated coastal zone management
Name three hard engineering processes for coasts
Sea wall, groynes, rock armour
What is a sea wall?
Concrete barrier built at the foot of cliffs. It has a curved face to reflect the waves back into the sea (usually about 3m-5m high)
How much does a sea wall cost?
Up to £10 million per km
Name two advantages of sea walls
Effective at stopping the sea
Often has a walkway or promenade for people to walk along
Name two disadvantages of sea walls
Can be obtrusive and unnatural to look at.
Very expensive and has high maintenance.
What is a groyne
Timber/rock structures built out to sea from the coast. They trap sediment being moved by longshore drift and broaden the beach. The wider beach acts as a buffer to the incoming waves, reducing wave attack at the coast.
How much do groynes cost?
Up to £5,000 per metre
Name two advantages of groynes
Results in a bigger beach, which can enhance the tourist potential of the coast
Not too expensive
What are the disadvantages of groynes
In interrupting longshore drift they starve beaches down drift, often leading to increased rates of erosion elsewhere.
Groynes are unnatural and can be unattractive
What is rock armour?
Piles of large boulders dumped at the foot of the cliff. The rocks force waves to break, absorbing their energy and protecting the cliffs.
How much does rock armour cost?
Approximately £1000 to £4000 per metre
2 advantages of rock armour
Relatively cheap and easy to maintain
Can provide interest to the coast. Often used for fishing
2 disadvantages of rock armour.
Rocks are usually from other parts of the coastline, so they can be expensive to transport and nit fit in with the local geology
Can be obtrusive
Name three soft engineering strategies
Beach nourishment, dune regeneration and marsh creation (managed retreat)
What is beach nourishment?
The addition of sand or shingle to an existing beach to make it higher or broader. The sediment is usually obtained locally so that it blends in with the existing beach material.
How much does beach nourishment cost?
Approximately £3,000 per metre
3 advantages of beach nourishment
Relatively cheap and easy to maintain
Blends in with existing beach
Increases tourist potential by creating a bigger beach
A disadvantage of beach nourishment
Needs constant maintenance unless structures are built to retain the beach
What is dune regeneration?
Sand dunes are effective buffers to the sea yet they are easily damaged and destroyed, especially by trampling. Marram grass can be planted to stabilise the dunes and help them to develop. Areas can be fenced to keep people off newly planted dunes.
How much does dune regeneration cost?
Approximately £2000 per 100m
2 advantages of dune regeneration
Maintains a natural coastal environment that is popular with people and wildlife
Relatively cheap
3 disadvantages of dune regeneration
Time consuming to plant marram grass and fence off areas
People do not always respond well to being prohibited from accessing certain areas
Can be damaged by storms
What is marsh creation (managed retreat)?
This involves allowing low-lying coastal areas to be flooded by the sea to become salt marshes, e.g poor quality grazing land. This is an example of managed retreat. Salt marshes are effective barriers to the sea.
What is the cost of marsh creation (managed retreat)?
It depends on the value of the land. Arable land costs somewhere in the region of £5000 to £10000 per hectare.
2 advantages of marsh creation (managed retreat)
A cheap option compared with maintaining expensive sea defences that might be protecting relatively low-value land
Creates a much needed habitat for wildlife .
2 disadvantages of marsh creation (managed retreat)
Land will be lost as it is flooded by sea water.
Farmers or landowners will need to be compensated
What is managed retreat?
Allowing controlled flooding of low- lying coastal areas or cliff collapse in areas where the value of land is low
How do salt marshes form?
They start as an accumulation of mud and silt in a sheltered part of the coastline (e.g in the lee of a spit or bar). As more disposition takes place, the mud begins to break the surface to form mudflats. As the level of the mud rises, it is less frequently covered by water.
Give four examples of managed retreat
Carrying out no more repairs to old sea defences
Abandoning the coast to the forces of nature
Allowing the tide to invade low lying land, forming salt marshes
Leaving marshes as wildlife habitats for birds
What is a pioneer plant?
The first plant species to colonise an area that is well adapted to living in a harsh environment.
Where do people get money for sea defences in the UK?
Local councils and maybe the Government or the Environment Agency
How are sand dunes formed?
At low tide the sand dries out allowing onshore winds to transport in inland. Sand may become trapped by sea weed and driftwood at the highest point of the spring tides. Plants begin to colonise the area, stabilising the sand and encouraging further accumalation.
Where are sand dunes usually found?
Exposed locations in the intertidal zones (the area above water at low tide and under water at high tide)
In order of age name the different types of sand dunes, and some of the vegetation found on them
Embryo dune- marram grass For dune- marram grass (a couple more) Yellow dune- dominated by marram grass although 80% covered Grey dune- (less acidic) dune heath (Dune slack)- water Mature dune- trees
What is vegetation succession?
A sequence of vegetation species colonising an environment.
