2 Coasts Flashcards
How do constructive waves help to create beaches, spits and bars?
Constructive (or ‘spilling’) waves move up the beach (the swash) quite strongly so travel a long distance.
Much of the water soaks into the beach thus the returning water (the backwash) is weaker.
These waves tend to move sand and other material up the beach, towards the land.
How do destructive waves help to create features such as wave cut notches, cracks, caves, arches, stacks, stumps and headlands?
Destructive (or ‘plunging’) waves break with a steep descent and will have little swash so backwash is strong, eroding material.
Plunging waves that are closer together can form a rip current, removing lots of sand.
How is slumping caused?
- During heavy rainfall cliffs become saturated with water. Water flowing inside the cliff exerts extra pressure which weakens the cliff.
- Weak rock layers such as clay can begin to move under this pressure.
- Water often acts as a ‘lubricant’ inside the cliff which helps gravity pull the cliff down.
How can a wave-cut notch and platform be formed?
- Destructive waves attack and undercut the cliff- abrasion and hydraulic action form a wave cut notch.
- Eventually the notch becomes large and the weight of the cliff causes it to collapse.
- As the cliff collapses the rubble is washed away by the waves, forming a wave cut platform.
How are caves, arches and stacks/stumps formed?
- Large crack in the headland opened up by hydraulic action.
- The crack widens and forms a cave by hydraulic action and abrasion.
- The cave becomes larger and eventually the sea breaks through to the other side forming an arch.
- The arch is eroded and eventually collapses.
- This leaves a tall rock called a stack which will erode in time, forming a stump.
Define discordant coastline.
Coastline is made up of both hard and soft rock, usually at right angles to the coast.
Headlands and bays are found in discordant coastlines.
Define concordant coastline.
Coastline is made up of hard and soft rock that runs parallel to the coastline.
This means the rock erodes at different rates. Waves cut the narrow entrance to the cove then rapidly erode the softer rock behind it.
Name 7 rock types from least resistant to most resistant.
Shale➡️Clay➡️Sandstone➡️Chalk➡️Limestone
➡️Granite➡️Basalt.
What is hydraulic action?
The erosion process in which water is forced into cracks in the rocks. This compresses air. When the wave retreats, the air blasts out which can force the rock apart.
What is abrasion?
A process of erosion in which loose rocks are thrown against the cliff by waves. This wears way the cliff and chips bits of rock off the cliff.
What is attrition?
Rocks smash together and break into smaller, smoother and rounder particles.
What is solution?
A process of erosion in which the water itself is slightly acidic and can dissolve minerals such as calcium carbonate, which is chalk and limestone.
For a named hard rock coastline, and a named soft rock coastline describe the differences between their features (6 marks).
At Flamborough Head there are steep cliffs which often have little vegetation, leaving a bare cliff face. There are erosional features such as caves, arches, stacks and stumps. Headlands are dominant and cliffs retreat leaving loose rocks at the base exposing wave cut platforms.
At Holderness Coast the cliffs aren’t as steep and there is evidence of mass moving (slumping). Rapid rates of erosion leading to large bays. Coastline will retreat very quickly meaning there is common use of coastal engineering schemes. Beaches are made of sand and mud.
Explain how a headland/bay is formed.
The main processes are hydraulic action and abrasion.
Bays are formed where destructive waves erode the soft rock more rapidly. Areas where soft rock has eroded are called bays.
Headlands are formed where there is more resistant rock. Over time, a section of land is left jutting out into the sea called a headland.
Explain the process of longshore drift.
Longshore drift is the process by which beach material is transported along the coast by the action of waves (in a zig zag pattern).
When waves break onto a beach at an angle due to prevailing wind, material is pushed up the beach by swash but pulled back down the beach by backwash (due to gravity) at 90o to the coast.
Each wave can move the sediment a little further across the beach.
How are spits formed?
If there is a change in the coastline, material in longshore drift is deposited across the river mouth. Sometimes spits have hooked or recurved ends when wind direction varies. Salt marches may form behind the spit.
How are bars formed?
If there is a bay, material will be deposited across it and eventually it may close off creating a sand bar. This will create a lagoon in the closed off bay.
For Hornsea, give the costs and benefits of their sea wall.
✅Very stong sea defence and long lasting.
✅Reflects waves back out to sea which means the land and buildings behind it are protected.
✅Helps prevent flooding (although may need to be built higher to cope with rising sea levels in future).
❌Many argue the sea wall looks ugly, spoiling the landscape.
❌They suffer from wave scour, where plunging waves erode the beach and attack the wall’s foundations.
❌Can restrict easy access to the beach.
For Hornsea, give the costs and benefits of their wooden groynes.
✅Prevents longshire drift by trapping sand and shingle.
✅Large beach areas attract tourists which brings money.
✅Beaches are a natural defence against erosion and dissipate wave energy.
❌Need to be maintained which can be costly, and even then may only last 10 years.
❌Prevents longshore drift which starves other beaches of sediment further along the coast.
For Mappleton, give the advantages and disadvantages of beach replenishment.
✅Beaches are a natural defence against erosion and coastal flooding.
✅Beaches attract tourism bringing money.
✅Looks natural and doesn’t spoil the landscape.
❌Costs vary depending how far the sand needs to be transported.
❌Requires contant maintenance to replace the beach material as it is washed away.
