Coasts Flashcards
What is mechanical weathering?
Mechanical weathering is the breakdown of rock without changing its chemical composition. Eg: freeze thaw
What is freeze thaw?
It happens when water enters rock that has cracks
When the water freezes it expands which puts pressure on the rock
When the water thaws it contracts which releases the pressure on the rock
Repeated freezing and thawing widens the cracks and causes the rock to break up
What is chemical weathering?
It’s the breakdown of rock by changing its chemical composition.
Eg:carbonation weathering
How does carbonation weathering happen?
Rainwater has co2 dissolved in it which makes it a weak carbonic acid
Carbonic acid reacts with rock that contains calcium carbonate
So the rocks are dissolved by the rainwater
What is mass movement?
It’s the shifting of rocks and lose material down a slope
It happens when the force of gravity acting on a slope is greater than the force supporting it
What are slides?
Slides are when the material shifts in a straight line along a side plane
What are slumps?
Slumps are when material rotates along a curved slip plane
What are rock falls?
Rock falls are when material breaks up and falls down a slope
What is erosion?
Erosion is when rocks are broken down and carried away by something
What is fetch?
Fetch is the distance the wind blows over the sea
What is a storm surge?
Storm surges are temporary sea level rises caused as strong winds push water onshore
What are destructive waves?
Destructive waves erode the coast as their backwash is more powerful than their swash
What are some properties of destructive waves?
They have a high frequency and are high and steep
What is backwash?
Backwash is water moving down the beach
What is swash?
Swash is water moving up the beach
What are some properties of constructive waves?
They have a low frequency and are low and long
What are the 4 erosional processes?
Hydraulic action, abrasion, attrition and solution
What is hydraulic action?
When waves crash against rock they compress air into the cracks and this puts pressure on the rock
Repeated compression widens the cracks and causes bits of rock to break off
What is abrasion?
Eroded particles in the water scrape and rub against rock removing small pieces
What is attrition?
Eroded particles in the water collide, break into smaller pieces and become more rounded
What is longshore drift?
The prevailing wind brings the waves in at an angle
The swash is then carried up the beach in the same direction of the wave
The backwash then carries material down the beach at right angles
Overtime this causes sediment to move in a zig zag along the beach
What are the processes of transportation?
Traction, suspension, slatation and solution
What is traction?
Traction is large particles like boulders being pushed along the sea bed by the force of water
What is suspension?
Suspension is when small particles like silt and clay are carried along in the water
What is saltation?
Saltation is when pebble sized particles ard bounced along the sea bed by the force of water
What is solution?
Solution is when soluble materials dissolve in the water and are carried along
Why does deposition happen?
Deposition occurs when water carrying sediment loses energy and slows down
What are discordant coastlines?
Discordant coastlines are made up of alternating bands of hard and soft rock at right angles to the coast
What are concordant coastlines ?
On a concordant coastlines the alternating bands of hard and soft rock are parallel to the coast
How do headlands and bays form?
Headlands and bays are formed where there are alternating bands of resistant and less resistant rock
The less resistant rock is eroded faster forming a bay with a gentle slope
As the resistant rock erodes more slowly it juts out forming a headland
How do caves form?
The resistant rock makes up headland often weakens and has cracks
Waves then crash into the headland and enlarge the cracks
This erosion causes the cracks to grow bigger and this forms a cave
How do arches form?
Erosion continues to erode the cave until it breaks throught the headland and this forms an arch
How does a stack form?
A stack forms when an arch collapses
How does a stump form?
A stump forms when a stack is eroded down
Where do waves cause the most erosion?
Waves cause most erosion at the foot of a cliff
How does a wave cut notch form?
A wave cut notch is formed when waves erode the bottom of a cliff
How are beaches formed?
Beaches are formed by constructive waves
How are sand beaches created?
Sand beaches are created by low energy waves and are flat and wide
How are shingle beaches formed?
Shingle beaches are created by high energy waves and are steep and narrow
How are bars formed?
A bar forms when a spit joins 2 headlands together
The bay between the headlands gets cut off from the sea
Offshore bars can form if the coast has a gentle slope as friction with the sea bed causes waves to slow down and deposit sediment offshore creating a bar that is not connected to the coast
How are sand dunes formed?
Sand dunes are formed when sand deposited by longshore drift is moved up the beach by the wind
Obstacles decrease wind speed so sand is deposited forming small embryo dunes
What is hard engineering?
Man made structures built to control the flow of the sea and reduce flooding and erosion
What is soft engineering?
Schemes set up using knowledge of the sea and its processes to reduce the effects of flooding and erosion
What is a sea wall?
A wall made out of a hard material like concrete that reflects waves back to sea
What are the benefits of a sea wall?
It prevents erosion of the coast and also acts as a barrier yo prevent flooding
What are the disadvantages of a sea wall?
It creates a strong backwash that erodes under the wall
They are also expensive to build and maintain
What are gabion?
Gabion are a wall of wire cages filled with rocks
What are the benefits of gabion?
Gabion absorb wave energy and so reduce erosion
They are cheap and easy to maintain
What are the disadvantages of gabion?
They are ugly to look at and the wire cages can corrode over time
What is rock armour?
Boulders that are piled up along the coast
What are the benefits of rock armour?
It absorbs wave energy reducing erosion and flooding
It’s a fairly cheap defence
What are the disadvantages of rock armour?
Boulders can be moved around by strong waves so they need to be replaced
What are groynes?
Wooden or stone fences that are built at right angles to the coast
They trap material transported by longshore drift
What are the benefits of groynes?
They create wider beaches which slow waves
This gives greater protection from flooding and erosion
They are a fairly cheap defence
What are the disadvantages of groynes?
They starve beaches further down the coast of sand making them narrower
What is beach reprofiling?
Sand and shingle from elsewhere or from lower down the beach is added to upper parts of the beach
What are the benefits of beach reprofiling?
It creates wider beaches which slow the waves
This gives greater protection from flooding and erosion
What are the disadvantages of beach reprofiling?
Taking material from the sea bed can kill organisms like sponges and corals
Its very expensive and has to be repeated
What is dune regeneration?
Creating or restoring sand dunes by nourishment or by planting vegetation to stabilise the sand
What are the benefits of dune regeneration?
Dunes create a barrier between land and sea and absorb wave energy preventing flooding and erosion
Stabilisation is cheap
What are the disadvantages of dune regeneration?
The protection is limited to a small area
Nourishment is very expensive
What is managed retreat?
It involves removing all current defences and allowing the sea to flood the land behind
What are the benefits of managed retreat?
It’s cheap and easy and it doesn’t need maintaining
The marshland this creates creates a new habitat for plants and animals
What are the disadvantages of managed retreat?
It can cause conflicts as flooding farmland affects the livelihood of farmers and saltwater can have negative affects on the existing ecosystems
