Contrasting Coasts Flashcards
What two types of rock do hard rock coasts contain?
Resistant rocks (e.g. granite) and sedimentary rock (e.g. limestone).
Give two examples of hard rock coasts.
Flamborough Head and Lulworth Coast.
What two materials are soft rock coasts made of?
Clay and shale.
What are two examples of soft rock coasts?
Christchurch Bay and the North Norfolk Coast.
Describe how a crack in the coastline can become a stump?
1) Hydraulic action creates a crack in the coast.
2) The crack grows until it becomes a cave.
3) The cave breaks through the headland to form an arch.
4) The arch is eroded until it collapses leaving a stack.
5) The stack is eroded until it leaves a stump.
What are the three ways erosion happens on the coastline?
- Hydraulic Action
- Attrition
- Abrasion
What is hydraulic action?
Air is compressed into cracks in the cliff face by water. When the wave retreats the air explodes out.
What is attrition?
When small pieces of sediment are knocked into each other.
What is abrasion?
When small pieces of sediment are picked up by waves and slammed into the cliff face.
What is a concordant coastline?
A coastline where the strata run parallel to the sea. This means the coastline is made of one type of rock.
What is a discordant coastline?
A coastline where the strata are perpendicular to the sea. This means the coastline is made up of lots of different types of rock.
At what type of coastline are coves formed?
Concodrant
Describe how coves are formed.
1) Erosion breaks through the first layer of rock at a coastline, revealing less resistant rock behind it.
2) The waves erode the softer rock forming a cove.
3) The cove stops widening when it hits harder rock again.
At what type of coastline are headlands and bays made?
Discordant
How are headlands and bays made?
The rocks at discordant coastlines erode at different speeds. The softer rock erodes faster forming bays whereas the harder rocks form headlands.
What coastline is a good example of headlands and bays?
The South-West Irish coast.
How are waves formed?
Wind blows across the sea create friction which becomes waves.
What three factors affect the size of a wave?
- The strength of the wind
- The duration of the wind
- The fetch of the wind
What is the fetch of a wind?
How far the wind has travelled.
What type of waves do we get in the summer?
Constructive waves
What are constructive waves like?
- Strong swash
- Long wavelengths
- Low amplitudes
What effects do constructive waves have on sediment on the beach?
They transport sediment up the beach.
What type of waves do we get in the winter?
Destructive waves
What are destructive waves like?
-•Strong backwash
- Short wavelengths
- Larger amplitudes
What effects do destructive waves have on sediment on beaches?
- They erode and making the beach steeper.
* Some sand is carried offshore and form an offshore bar.
Describe longshore drift.
•The prevailing winds push waves to shore.
2) The swash pushes sediment up the beach in the direction of the prevailing wind.
3) The sediment falls back with the backwash at a 90 degree angle.
How are sand dunes formed?
Onshore winds blow sand inland forming sand dunes parallel to the shore.
How are bars formed?
When there’s a sudden change in the shape of the landscape, longshore drift continues to deposit sediment until it reaches land again.
What do you call the body of water on the other side of a bar?
A lagoon
How is a spit formed?
At a river mouth, longshore drift continues until it is stopped by river flow. The sand continues to build up forming a spit.
How does a spit get a recurved end?
The movement of water during the changing of the tides forces the spit back on itself.
What does the water behind a recurved end become?
A salt marsh?
What three adaptions do plants require to survive in depositional landforms?
- Long roots to stop them being uprooted in strong winds.
- Tough, waxy leaves to stop them being sandblasted.
- They need to be able to survive being sprayed by salt water.
Why are plants useful on depositional landforms?
They help to stabilise it.
How much is the sea level predicted to rise by by 2100?
1m
What could three effects of the sea rising 1m be on global geography?
- 15% of !Bangladesh would flood.
- London and Essex would flood completely.
- Small coral islands like the Maldives could disappear.
What is a storm surge?
When a spring tide combines with an area of low pressure to form huge waves.
What is an example of a storm surge?
Storm Sandy.
When did Storm Sandy happen?
October 2012
Where did Storm Sandy hit?
New York and New Jersey.
How tall were the waves made by Storm Sandy?
4m
How many people lost electricity because of Storm Sandy?
5 million
How many people died in Storm Sandy?
100
What was the total value of damage done to property because of Storm Sandy?
$50 billion
What is a marine reason why cliffs collapse?
The base of the cliff is eroded by hydraulic action and abrasion.
What are three sub-aerial causes of cliffs collapsing?
- Mechanical (i.e. Freeze thaw action) and chemical (i.e. Solution) weathering.
- Rain runs down the cliff face.
- Permeable rock absorbs rain making it heavier.
What is a human cause of cliffs collapsing?
Humans build on top of cliffs.
What is an advantage of hard engineering?
Very effective.
What are two costs of hard engineering?
It is very ugly and expensive.
What do sea walls do?
Reflect waves back into the sea.
What does a sea wall with steps and bullnose do?
It dissipates the waves before throwing it back into the sea.
What do revetments do?
Break up incoming waves.
What are gabions?
Cheaper, permeable sea walls.
What are rip rap?
Large boulders that dissipate sea waves.
What do groynes do?
Trap sediment and dissipate waves.
How much are the cliffs eroded at Christchurch Bay without intervention?
2m a year
Give four effects of rapid cliff erosion at Christchurch Bay.
- Homeowners could lose their homes to the sea. As such insurance is impossible to get.
- Mass movement is dangerous for those above and below the cliffs.
- Roads could be destroyed.
- Erosion makes area less attractive to tourists.
What do the residents and business owners of Christchurch think needs to be done?
They are in favour of doing whatever it takes - although they are mindful that engineering could deter tourists.
What do the councillors and MPs of Christchurch think needs to be done?
They don’t take a stance as to not polarise the public.
What do the residents of towns near Christchurch think needs to be done?
They hunk that it should be a cheap option as they will have to pay for the engineering works with their taxes.
What do the environmentalists of Christchurch think needs to be done?
They think the solution is either to do nothing or use soft engineering.
What do those living downdrift from Christchurch think needs to be done?
They fear that hard engineering will have a knock-on effect on them so prefer soft engineering.
What do the fishermen of Christchurch think needs to be done?
Whatever the solution is, they need easy access to the sea.
Why might the government choose not to save somewhere from coastal erosion?
- The land value could be smaller than the cost of protecting it.
- Protection of the area may increase erosion elsewhere.
What is an ICZM?
Integrated Coastal Zone Management is planning whether or not to protect a shoreline.
What is an SMP?
A Shoreline Management Plan is the type of management chosen for each shoreline. There are four options.
What is meant by “hold the line”?
Use sea defences to keep the shoreline where it is.
What is meant by “advance the line”?
Use sea defences to move the coast further into the sea.
What is meant by “strategic realignment”?
Gradually letting the sea erode the coastline and relocate homes and businesses.
What is meant by “do nothing”?
Letting the sea erode the coastline with no intervention.
What is soft engineering?
Coastline management that is cheap and aims to preserve the coast using natural processes.
What are three examples of soft engineering?
- Planting vegetation.
- Beach nourishment.
- Offshore breakwaters.
What is an offshore breakwater?
A wall of rip rap that breaks up incoming waves.
