Coasts Flashcards
What is weathering?
Weathering is the wearing down or breaking of rocks by biological, chemical or physical processes.
What is mechanical weathering?
Breakdown of rocks into smaller pieces without changing their chemical composition.
What occurs in mechanical weathering?
Rocks are broken down by physical processes like freeze-thaw weathering.
At what angle does swash occur and what causes it?
Swash is driven by the prevailing wind, and travels in the same direction
At what angle does backwash occur and what causes it?
At a right angle to the direction of the beach, as it is caused by gravity
Give three characteristics of destructive waves
Wave crest is high, weak swash, strong backwash
Explain why destructive waves cause coastal erosion
Their strong backwash removes sediment from the coast
Give three characteristics of constructive waves
Wave crest is low, strong swash, weak backwash.
Explain why constructive waves can build beaches up
More sediment is deposited through the strong action of the swash than is removed by the weaker action of the backwash.
What occurs in freeze-thaw weathering?
Water enters cracks in rocks. The water freezes and expands. The crack expands. The ice melts and fills up the now larger crack. The process repeats until the rock breaks apart
What effect does mass movement have on a coastline?
Leads to the coast moving further back/retreating as cliffs gradually wear away. Can lead to the formation of beaches, marshes and dunes
What is erosion?
When land or rocks wear away due to action of natural forces like waves
How does erosion occur by hydraulic power?
As waves smash into rocks, they force air into them which causes cracks to form
How does erosion occur by abrasion?
Small particles in the water rub against the rocks, wearing them away
How does longshore drift occur?
Longshore drift occurs when waves approach the beach at an angle. The swash moves material up the beach, while the backwash carries it back down at right angles due to gravity. This process gradually shifts material along the beach and links erosion and deposition. Material is transported through suspension, traction, solution, and saltation.
What occurs in coastal transportation?
Material is moved from one place to another
Explain how the headland and bay have formed.
The coast is made of bands of more and less resistant rock. The waves erodes the less resistant rock faster than the more resistant rock. The eroded area forms a bay. The more resistant area sticks out to form a headland
What is deposition?
When sediment being carried by the water is dropped
Why are sandy beaches likely to form in bays?
Sandy beaches are often found the sheltered bays where waves lose energy, and their capacity to transport material decreases resulting in material being deposited.
What is the zig-zag movement of material along the shore by wave action called?
Longshore Drift
Identify your case study location for landforms of coastal erosion.
The case study location will be identified e.g. Flamborough Head / Durdle Door / Old Harry Rocks
Do headlands form along concordant or discordant coastlines?
Headlands form along discordant coastlines
What is coastal transportation?
The movement of sediment and beach material through wave action.
What is a wave-cut platform?
A wave-cut platform is a wide, gently sloping surface found at the base of the cliff and extends into the sea.
Identify the 4 main processes of coastal transportation.
Solution, suspension, saltation and traction
What is a headland?
A headland is a cliff that sticks out into the sea and is surrounded by water on three sides.
Identify 4 types of mass movement.
Rock fall, landslide, mudslide and slumping
What is traction?
Traction - large pebbles and boulders are rolled along the seafloor.
What is suspension?
Suspension - beach material is suspended and carried by the waves.
Describe the process of slumping
Soft boulder clay retains rainwater, and wave erosion creates a notch at the cliff’s base. When the clay becomes saturated, it forms a slip plane, leading to a slump due to the weight of the saturated material.
Explain the formation of bays and headlands.
The bands of soft rock, such as sand and clay, erode more quickly than those of more resistant rock, such as chalk. This leaves a section of land jutting out into the sea called a headland. The areas where the soft rock has eroded away, next to the headland, are called bays.
Large blocks of rock sliding downhill is which type of mass movement?
Landslide
Which type of mass movement involves saturated soil and weak rock flows down a slope, typically where cliffs are made up of boulder clay?
Mudslide / mudflow
What is a discordant coastline?
A discordant coastline is where the geology alternates between strata (bands) of soft and hard rock.
What is saltation?
Saltation - beach material is bounced along the seafloor.
Which type of mass movement involves fragments of rock breaking away from the cliff face, often due to freeze-thaw weathering?
Rockfall
What is a concordant coastline?
A concordant coastline is where the same rock runs along the length of the coast. Concordant coastlines tend to have fewer bays and headlands.
What is mass movement?
Mass Movement is the downhill movement of cliff material under the influence of gravity.
What is longshore drift also known as?
Littoral drift
Explain the formation of a wave-cut platform.
A wave-cut platform forms when the sea erodes a weakness at the cliff’s base, like a joint in chalk. Erosion creates a wave-cut notch, which destabilizes the cliff, causing it to collapse and retreat inland. The eroded material is transported away, leaving a wave-cut platform. This process continues over time.
What is coastal transportation ?
Coastal transportation involves material being transported by the sea being deposited or dropped.
What is a bay?
A bay is an inlet of the sea where the land curves inwards
What is solution?
Solution - material is dissolved and carried by the water.
Why does coastal deposition occur?
Wave energy reduces leading to material being deposited.
Give three conditions that lead to coastal deposition happening.
Waves enter an area of shallow water / waves enter a sheltered area, e.g. a cove or bay / there is little wind / a river or estuary flows into the sea reducing wave energy / there is a good supply of material and the amount of material being transported is greater than the wave energy can transport.
Describe the landforms that have formed here.
Landforms will include wave cut platforms, headlands, bays, stacks, arches and stumps.
What is a fetch?
How far the wave has travelled.
Rockfall
Bits of rock fall off the cliff face, usually due to freeze-thaw weathering.
Mudflow
Saturated soil (soil filled with water) flows down a slope.
Landslide
Large blocks of rock slide downhill.
Rotational slip
Saturated soil slumps down a curved surface.
What is erosion?
Erosion is the wearing away of rock along the coastline. Destructive waves are responsible for erosion on the coastline. There are four types of erosion - Hydraulic action, abrasion, attrition and solution.
What is the meaning of hydraulic action?
Hydraulic action is the sheer power of the waves as they smash against the cliff. Air becomes trapped in the cracks in the rock and causes the rock to break apart.
What is the meaning of abrasion?
Abrasion is when pebbles grind along a rock platform, much like sandpaper. Over time the rock becomes smooth.
What is the meaning of attrition?
Attrition is when rocks that the sea is carrying knock against each other. They break apart to become smaller and more rounded.
What is the meaning of solution?
Solution is when sea water dissolves certain types of rocks. In the UK, chalk and limestone cliffs are prone to this type of erosion.
Factors leading to deposition include
- waves starting to slow down and lose energy
- shallow water
- sheltered areas, eg bays
- little or no wind
If the roof of an arch collapses, what landform is formed?
When the roof of an arch collapses a sea stack is formed.
How a spit is formed
Longshore drift moves material along the coastline.
A spit forms when the material is deposited.
Over time, the spit grows and develops a hook if wind direction changes further out.
Waves cannot get past a spit, which creates a sheltered area where silt is deposited and mud flats or salt marshes form.
What is a salt marsh?
Salt marshes are coastal wetlands that are flooded and drained by salt water brought in by the tides.
What is the meaning exfoliation?
Exfoliation is when layers of rocks peel off from the surface.
Is solution a type of chemical weathering?
yes
What is the meaning of biological weathering?
Biological weathering is when plants and animals have an effect on the rock.
Constructive wave
A low, gentle wave that builds beaches.
Destructive wave
Tall, high energy waves that erode beach material.
Wave
A disturbance on the surface of the sea in the form of a moving ridge.
Wave energy is determined by
The strength of the wind
The duration of the wind
The distance of open water over which the wind blows (fetch).
Chemical weathering
The break down of rock due to chemical changes.
Landslide
Rapid mass movement of surface material down a slope.
Mass movement
The downhill movement of material under gravity.
Mechanical weathering
The breakdown of rock without chemical changes.
Rockfall
Fragments of rock break away from the cliff face.
Slumping
Cliffs slide down a curved slip plane.
Weathering
The breakdown of rock in situ.
Carbonation
Carbon dioxide, dissolved in rainwater forms a weak carbonic acid. This reacts with calcium carbonate (limestone and chalk) which forms calcium bicarbonate.
Hydrolysis
Acidic rainwater reacts with minerals in granite, causing it to crumble.
Oxidation
Oxygen dissolved in water reacts with iron-rich minerals causing rocks to crumble.
Salt weathering
crystals of salt grow in cracks and expand causing rock fragments to flake away.
Abrasion
Rocks carried along by a wave wear down cliff material.
Attrition
Rocks transported by a wave collide and become smaller and rounded.
Deposition
When material is dropped by constructive waves.
Erosion
The wearing away of land by the sea.
Hydraulic Action
The force of water 1 compressing air in cracks, weakening cliffs.
Longshore Drift
The zig-zag movement of sediment along the coast.
Saltation
Pebbles are bounced along the sea bed.
Solution
Soluble particles are transported by the sea.
Suspension
Lighter sediment is carried within the water.
Traction
Large, heavy pebbles are rolled along the sea bed.
Beach
The area between the lowest tide level and the point reached by storm waves in the highest tides.
Berm
A ridge often found towards the back of a beach.
Lagoon
A shallow body of water protected from a larger body of water.
Deposition
The laying down of sediment.
Dune slack
A trough (dip) that separates sand dunes.
Sand dune
Ridges or hills of sand at the top of a beach.
Salt marsh
A coastal ecosystem found between land and open salt water.
Spit
Stretch of beach material that sticks out to sea and is joined to the mainland at one end.
Bar
A ridge of sand or single that joins two headlands on either side of a bay.
Arch
A wave eroded passage through a headland.
Bay
A broad inlet of the sea where the land curves inwards.
Cave
A large hole in a cliff caused by waves enlarging cracks.
Discordant Coastline
Alternative bands of rock along the coastline.
Headland
Resistant rock that juts out into the sea.
Stack
A column of rock, often the remains of an arch.
Wave-cut Notch
A dent in the cliff usually at the level of high tide.
Wave-cut Platform
A wide, gently sloping surface found at the base of a cliff, extending to the sea.
Deposition occurs when..
- waves enter an area of shallow water
- waves enter a sheltered area, e.g. a cove or bay,
- there is little wind; small wide
- a river or estuary flows into the sea, reducing wave energy; and
there is a good supply of material
Groynes positive impact
They create a wider beach, which can be popular with tourists and boost local economy.
Not too expensive. If well maintained, can last up to 40 years.
Cost £150,000 each but often you only need them every 200m.
Groynes
Groynes look like wooden “fences” that are built down the beach at right angles to the coastline. They are designed to stop material being moved along the beach by longshore drift. They work by building up the amount of sand on the updrift side.
Groynes negative impact
By interrupting longshore drift you are not solving the issue. It just leads to increased rate of erosion somewhere else along the coast - groynes only move the issue.
They require maintenance and repair and speed up erosion down the coast by robbing nearby beaches of sand. The problem is therefore shifted, not solved.
Lyme Regis positive impact
improvement in the attractiveness, due to nourishment and the wide promenade.
Increased visitor numbers, and seafront businesses are thriving.
The defences have withstood recent stormy winters.
The harbour is better protected, benefiting the fishing industry and boat owners.
Lyme Regis negative impacts
Conflicts have increased as visitor numbers
have increased.
Local people have experienced increased traffic congestion and litter due to increased tourism.
Some feel the new coastal defences have spoilt the natural coastal landscape.
The new defences may interfere with natural coastal processes affecting neighbouring stretches of coastline, causing conflicts elsewhere.
Stabilizing cliffs that prevent landslides will reduce the number of fossils found in the area.
Lyme Regis Coast Management
- Nailing and drainage of the cliffs with some reprofiling to stabilise and improve drainage.
- New sea walls
- Widespread beach nourishment.
- Rock armour to protect the harbour wall (the Cobb) and at the eastern end of the town.
Describe how longshore drift transports material.
Longshore drift occurs when waves approach the beach at an angle. The swash moves material up the beach, while the backwash carries it back down at right angles due to gravity. This process gradually shifts material along the beach and links erosion and deposition. Material is transported through suspension, traction, solution, and saltation.
What landforms are mentioned in the study material?
Cliffs, caves, arches, and cracks
How does the sea initially affect the cliff?
The sea attacks the foot of the cliff and erodes areas of weakness
What processes of erosion are involved in the formation of caves?
Hydraulic action, wave pounding, abrasion, and solution
What happens to cracks as erosion continues?
They get larger and develop into small caves
What occurs when two caves erode into the back of each other?
An arch is formed that passes through the headland
What factors contribute to the weakening of the arch structure?
Wave attack at the base and weathering of the roof
What happens to the roof of the arch over time?
It collapses inwards, leaving a stack
What is a stack in geological terms?
A column of rock that stands separate from the rest of the headland
What eventually happens to the stack?
It continues to erode and collapses to form a stump
Beach Nourishment
Beach nourishment is the addition of sand or shingle to an existing beach to make it higher or wider. This sediment is usually obtained offshore locally so that it blends in and then is transported by barge.
Beach Nourishment positives’
It is relatively cheap and easy to maintain and blends in with the existing beach.
It also increases tourist potential by creating a bigger beach-good for local economy.
£500,000 per 100m
Beach Nourishment negative impact
It needs constant maintenance unless structures are built to retain the beach. This replaces beach or cliff material that has been removed by erosion or longshore drift.
It is a relatively cheap option but requires constant maintenance to replace the beach material as it is washed away
Dune Regeneration
Sand dunes are effective buffers to the sea but are easily damaged and destroyed by trampling. Marram grass can be planted to stabilise dunes and help them to develop. Fences can be used to keep people off newly-planted areas.
Dune Regeneration positive impact
This is a relatively cheap and it maintains a natural environment that is popular with people and wildlife.
£200-£2,000 per 100m
Dune Regeneration negative impact
It is time-consuming to plant the grass and fence the dunes off.
People don’t always like being prohibited from certain areas
They can be damaged by storms.
Dune Fencing
Fences are constructed on a sandy beach along the seaward face of existing dunes to encourage new dune formation. These new dunes help to protect the existing dunes
Dune Fencing positive impact
Minimal impact on natural systems.
Can control public access to protect other ecosystems.
£400-£2,000 per 100m
Dune Fencing negative impact
Can be unsightly especially if fences become broken.
Regular maintenance needed especially after storms.
Managed Retreat
Managed retreat (also called coastal realignment) is a deliberate policy of allowing the sea to flood or erode an area of relatively low-value land
Managed Retreat positive impact
In the long term, it is more sustainable than spending lots of money trying to protect the coastline especially as rising sea levels continue.
It can be cheap, as you don’t have to do anything, as long as you aim for low-value land e.g. Farmland all people have to is move inland.
Managed Retreat negative impact
There might be some conflict about where to flood - people will need to be compensated for loss of buildings and farmland.
Sea Walls
Sea walls are concrete or rock barriers against the sea, placed at the foot of cliffs or at the top of a beach. They have a curved face to reflect the waves back into the sea
Sea Walls positive impact
VERY Effective in protecting cliffs from erosion and also act as a barrier to prevent flooding.
Due to the curved sea wall face they deflect wave energy back to sea giving people a sense of security.
Often has a walkway or promenade for people to walk along.
Sea Walls negative impact
They are expensive to construct and require regular repair.
Cost £5,000-£10,000 a metre
They create a strong backwash that can erode the foundations of the sea wall.
Rock Armour
Rock armour consists of massive blocks of natural rock piled up at the base of a cliff. The rocks are dumped on top of each other leaving gaps between them that allow water through. The rocks force the waves to break, absorbing their energy and protecting the cliffs. The rocks are usually brought by barge to the coast.
Rock Armour positive impact
Disperses the energy of the waves and reduces their erosional power.
Structure is quick to build and easy to maintain and they are much cheaper than a sea walls.
Rock Armour negative impact
The rocks are usually from other parts of the coastline or even from abroad, they can be expensive to transport, do not fit in with the local geology and can be very intrusive.
They are expensive to extract, transport and place in position, (although less expensive than sea walls).
£200,000 per 100m
Gabions
Wire cages filled with rocks that can be built up to support a cliff or provide
Gabions positive impact
Cheap to produce and flexible in the final design.
Can improve drainage of cliffs.
Will eventually become vegetated and merge into the landscape.
Gabions negative impact
For a while they look very unattractive.
Cages only last 5-10 years before they rust.
Up to £50,000 per 100m
What causes the formation of headlands and bays on a discordant coastline?
On a discordant coastline, rocks of varying hardness are exposed. Weaker rock erodes faster, forming bays, while more resistant rock erodes slowly, leaving headlands jutting into the sea.
What are Old Harry Rocks and where are they located?
Old Harry Rocks are three chalk formations, including a stack and a stump, located at Handfast Point on the Dorset coast.
Why does Studland Bay have sandy beaches and sand dunes?
Studland Bay is sheltered from strong erosive waves, which allows sand to accumulate, forming sandy beaches and sand dunes.
How was Lulworth Cove formed and what type of coastline is it on?
Lulworth Cove is on a concordant coastline. Waves cut through weaknesses in resistant limestone, creating a narrow entrance. Inside, the cove widens as softer clays are eroded more easily.
How was Durdle Door formed?
Durdle Door is a coastal arch formed in hard limestone standing almost vertically out of the sea. The sea eroded through the limestone and then eroded the softer rock behind, forming the arch.
What is significant about the Dorset Coast?
The Dorset Coast is 142 km long and showcases 185 million years of Earth’s history through its geology and landforms.
Aid
form of help given from one country to another
Formation of Cave, arch, stack, stump and stack
Cracks enlarged by hydraulic action to form a cave.
Cave enlarged by hydraulic action and abrasion.
Arch forms when cave erodes through headland.
Roof of arch weakened by weathering and collapses leaving a stack.
Stump formed when stack collapses due to wave-cut notch.
Formation of wavecut platform
Wave-cut notch forms: Waves erode the cliff, creating a notch at the base. This is due to abrasion, corrosion, and hydraulic action.Waves attack the cliff: Waves hit the base of the cliff between the high and low tide marks.
Notch enlarges: The notch increases in size, causing the cliff to become unstable.
Cliff collapses: The cliff collapses due to weathering and the pressure of the waves.
Wave-cut platform forms: The backwash carries away the eroded material, leaving a wave-cut platform.
Process repeats: The process repeats, and the cliff continues to retreat.
Give two landforms that result from landforms drift
- Spits
- Bars
- Beaches
Difference in sediment size of two locations
Longshore drift carries the lighter material much futher along the spit.
Heaviest material is only carried a short distance.
Greater erosion as sediment is carried futher along the coast.
Suggest one reason why this coastline has suitable conditions for the formation of sand dunes
There are (wide) sandy beaches / sand may be picked up and transported by the wind onshore good supply of sediment. The beaches face westwards where the main winds come from.
What is the crest of a wave?
The highest point at the top of a wave.
What is the trough of a wave?
The lowest point or base of a wave.
What is wave height?
The vertical distance between the crest and the trough.
What is wave length?
The horizontal distance between two wave crests.
What is wave frequency?
The number of waves that break in one minute.
What affects the strength and height of waves?
- The speed of the wind
- The duration the wind blows
- The fetch – the distance the wind travels over the water
What are sea walls and what are their pros and cons?
- Pros:
Very effective in protecting cliffs from erosion.
Reflects wave energy back to the sea, preventing flooding.
Often includes a walkway for public access. - Cons:
Expensive to construct (£5,000-£10,000 per meter).
Requires regular repair.
Creates strong backwash that can erode the sea wall foundations.
Sea walls:
Concrete or rock barriers placed at the foot of cliffs or on beaches to protect against sea erosion and flooding.
Groynes:
Wooden “fences” built at right angles to the coastline to stop material being moved by longshore drift and build up sand on the updrift side.
What are groynes and what are their pros and cons?
- Pros:
Create a wider beach, boosting tourism and the local economy.
Relatively inexpensive (£150,000 each, with installation every 200m).
Can last up to 40 years if well maintained. - Cons:
Do not solve the problem but shift it elsewhere, increasing erosion further along the coast.
Require regular maintenance and repair.
Speed up erosion by robbing nearby beaches of sand.
What is rock armour and what are its pros and cons?
- Pros:
Disperses wave energy, reducing erosional power.
Quick to build and easy to maintain.
Cheaper than sea walls (£200,000 per 100m). - Cons:
Rocks are often sourced from other parts of the coastline or abroad, making them expensive to transport.
Can be intrusive and do not fit well with local geology.
Expensive to extract, transport, and place.
Rock Armour:
Massive blocks of natural rock piled up at the base of cliffs to absorb wave energy and protect the cliffs from erosion.
What are gabions and what are their pros and cons?
- Pros:
Cheap to produce and flexible in design.
Improve drainage of cliffs.
Eventually become vegetated, blending into the landscape. - Cons:
Initially unattractive.
Cages rust after 5-10 years.
Cost up to £50,000 per 100m.
Gabions:
Wire cages filled with rocks, used to support cliffs or provide a buffer against the sea.
What is beach nourishment and what are its pros and cons?
- Pros:
Relatively cheap and easy to maintain.
Blends well with the existing beach.
Increases tourist potential, benefiting the local economy.
Costs around £500,000 per 100m. - Cons:
Requires constant maintenance unless structures are built to retain the beach.
Replaces material lost through erosion or longshore drift.
Needs regular replenishment as material is washed away.
Beach Nourishment:
The addition of sand or shingle to an existing beach to make it higher or wider, typically using local offshore sediment.
What is dune regeneration and what are its pros and cons?
- Pros:
Relatively cheap.
Maintains a natural environment, benefiting both people and wildlife.
Costs between £200-£2,000 per 100m. - Cons:
Can be unsightly, especially if fences become broken.
Requires regular maintenance, particularly after storms.
Dune Regeneration:
The process of stabilizing sand dunes by planting marram grass and using fences to prevent trampling.
What is managed retreat and what are its pros and cons?
- Pros:
Long-term sustainable compared to expensive coastal protection measures.
Cost-effective, as no significant action is required, just relocation of people inland. - Cons:
Potential conflict about which areas to flood.
People may need compensation for the loss of buildings and farmland.
Managed Retreat:
A policy of allowing the sea to flood or erode areas of low-value land, like farmland, without intervention.
Why does Lyme Regis need coastal protection?
- Erosion: Powerful waves from the southwest erode cliffs.
- Landslides and damage: Properties at risk from slumps and waves breaching sea walls.
- Tourism and Economy: Over 500,000 tourists annually, contributing £42 million in 2015.
- Road Threat: 900m of the A3052 road could be lost within 50 years.
Why is Lyme Regis vulnerable to erosion?
Much of the eastern town is built on the edge of cliffs and has been damaged by landslides and wave erosion.
Why is protecting the coastline at Lyme Regis important?
It protects homes, roads, and the tourism industry; around 500,000 tourists visit each year.
What coastal defences are used in Lyme Regis?
Sea walls and rock armour.
When did coastal protection begin in Lyme Regis?
In the 1990s, led by West Dorset District Council.
What was added in Phase 2 in Lyme Regis?
Rock armour, beach nourishment, extended sea walls, and drainage to protect homes.
What are the positive effects of the coastal defences in Lyme Regis?
Powerful waves are slowed down, erosion is reduced, landslides are less frequent, and the area is now more attractive for tourists
What are some conflicts caused by the defences?
Some people feel the defences spoil the natural landscape, disturb fossils, and increase erosion elsewhere.
What type of rock is limestone?
Limestone is a type of sedimentary rock that is formed from the tiny shells and skeletons of dead sea creatures.
Define igneous rock.
Igneous rock is formed when magma from the mantle cools and hardens.
True or False?
Metamorphic rock is a rock which has been changed by heat and pressure.
True.
Metamorphic rock is a rock that has been changed by heat and pressure from an existing rock (igneous, sedimentary or older metamorphic rock).
True or False?
Limestone and chalk are relatively strong and permeable.
True.
What are the main types of sedimentary rocks in the UK?
The main types of sedimentary rocks in the UK are limestone, chalk, clay and shale.
What is meant by the term landscape?
Landscape refers to the character of an area, resulting from the action and interaction of natural and human elements.
Describe the landscape of the UK.
The UK has a varied landscape with uplands, lowlands and important rivers.
True or False?
Most cities in the UK are in upland areas and away from main river courses.
False.
Most cities in the UK are situated in lowland areas and often on main river courses.
What processes created the upland mountain ranges in the UK?
In the past, when tectonic plates collided, it forced the rocks to fold and uplift. This created the mountain ranges of the uplands: Scottish Highlands, Snowdonia, and the Lake District.
True or False?
In the UK, the uplands are mostly sedimentary rock.
False.
In the UK, the uplands are mostly igneous and metamorphic rock, with the softer sedimentary rock found in the lowlands of the south, southeast and central UK.
