3.1.3.2 Coastal landscapes in the UK Flashcards
How is rock broken down?
By mechanical and chemical weathering
What is chemical weathering?
Breakdown of rock by changing its chemical composition
Give an example of chemical weathering and explain how it works
Carbonation weathering:
- Rainwater has carbon dioxide dissolved in it = makes it weak carbonic acid
- Carbonic acid reacts with rock that contains calcium carbonate e.g. carboniferous limestone = rocks are dissolved by rainwater
Where does carbonation weathering occur?
Happens in warm and wet conditions
What is mechanical weathering?
The breakdown of rock without changing its chemical composition
Give an example of mechanical weathering and explain how it works
Freeze-thaw weathering:
- Happens when temperature alternates above and below 0°C
- Water gets into rock that has cracks e.g. granite
- When water freezes it expands = just pressure on rock
- When water thaws it contacts = releases pressure on rock
- Repeated freezing and thawing widens cracks and curses rock to break up
What does freeze-thaw weathering mainly affect/occur?
Coasts
Name 4 processes of erosion
- Hydraulic Power
- Abrasion
- Attrition
- Solution
What is erosion?
When rocks are broken down and carried away by something e.g. seawater
How does hydraulic power erode rocks?
- Waves crash against rock and compress air in cracks = puts pressure on rock
- Repeated compression widens cracks and makes bits of rock break off
How does abrasion erode rocks?
Eroded particles in water scrape and rub against rock = removing small pieces
How does attrition erode rocks?
Eroded particles in water smash into each other and break into smaller fragments ∴ edges get rounded off as
they rub together
How does solution erode rocks?
Water dissolves some material (rocks)
What waves carry out erosional processes?
DESTRUCTIVE waves
Name 3 features of destructive waves
- Have high frequency (10-14 waves per minute)
- Are high and steep
- Their backwash is more powerful > than their swash ∴ material is removed from coast
What is mass movement?
Shifting of rocks and loose material down a slope e.g. cliff
When does mass movement occur?
Happens when gravity acting on slope is greater than force supporting it
What does mass movement cause coasts to do?
Causes coasts to retreat rapidly
When is mass movement more likely to occur and why?
More likely to happen when material is full of water because it acts as lubricant = makes material heavier
Name 3 types of mass movement
- Slides
- Slumps
- Rockfalls
What are slides (the mass movement)?
When material shifts in a straight line
What are slumps (the mass movement)?
When material shifts with a rotation
What are rockfalls (the mass movement)?
When material breaks up and falls down slope
Name 3 groups of landforms that are caused by erosion
- Wave-Cut Platforms
- Headlands and Bays
- Caves, Arches and Stacks
Explain how wave-cut platforms are formed
- Waves cause most erosion at foot of cliff
- This forms a wave-cut notch - is enlarged as erosion continues
- Rock above notch becomes and unstable and eventually collapses
- Collapsed material is washed away and new wave-cute notch starts to form
- Repeated collapsing results in cliff retreating
- Wave-cut platform is platform that’s left behind as cliff retreats
What are soft rocks or rocks with lots of joints like (resistance wise)?
Have low resistance to erosion
What are hard rocks with a solid structure like (resistance wise)?
Have high resistance to erosion
Where do headlands and bays form?
Where there’s alternating bands of resistant and less resistant rock along coast
How are bays formed?
Less resistant rock (e.g. Clay) along coast is eroded quickly and forms bay
What are bays like (slope wise)?
Bays have gentle slope
How are headlands formed?
Resistant rock (e.g. Chalk) along coast is eroded more slowly and it’s left jutting out, forming headland
What are headlands like (sides)?
Headlands have steep sides
Explain how headlands are eroded to form caves, arches and stacks
- Headlands are made of resistant rocks that have weaknesses like cracks
- Waves crash into headlands and enlarge cracks
- Repeated erosion and enlargement of cracks causes a cave to form
- Continued erosion deepens cave until it breaks though
headland, forming an arch - Erosion continues to wear away rocks supporting arch, until it eventually collapses
- This forms a stack
What is a stack?
An isolated rock that’s separate from headland
What main processes of erosion cause headlands to be eroded to form caves, arches and stacks
Hydraulic action and abrasion
What is transportation?
The movement of material
How is material transported along coasts?
By longshore drift
Explain how material transported along coasts (via longshore drift)
- Waves follow direction of prevailing (most common) wind
- Usually hit coast at an oblique angle
- Swash carries material up beach, in same direction as waves
- Backwash carries material down beach at right angles, back towards sea (due to gravity)
- Over time, material zigzags along coast
Name 4 processes of transportation
- Traction
- Saltation
- Suspension
- Solution
How does traction transport material?
Large particles like boulders are pushed along sea bed by force of water
How does saltation transport material?
Pebble-sized particles are bounced along sea bed by force of water
How does suspension transport material?
Small particles like silt and clay are carried along in water
How does solution transport material?
Soluble materials dissolve in water and are carried along
What is deposition?
When material being carried by seawater is dropped on coast
When does deposition occur?
Occurs when water carrying sediment slows down so that it isn’t moving fast enough to carry so much sediment
When are coasts are built up?
When amount of deposition is greater than amount of erosion
When does the amount of material that’s deposited on coast is increase?
When:
- Lots of erosion elsewhere on coast, lots of material available
- Lots of transportation of material into area
What waves (slow or fast) cause lots of deposition and very little erosion & why?
Low energy waves (i.e. Slow waves) carry material to coast but they’re not strong enough to take a lot of material away
What are consrtcutive waves?
Waves that deposit more material than they erode are called
Give 4 features of consrtcutive waves
- Have low frequency (6-8 waves per minute)
- Are low and long
- Swash is powerful, carries material up coast
- Backwash is weaker and doesn’t take a lot of material back down coast ∴ material is deposited on coast
Name 4 landforms formed by deposition
- Beaches
- Spits
- Bars
- Sand dunes
Where are beaches found?
Beaches are found on coasts between high water mark and the low water mark
How are beaches formed?
They’re formed by constructive waves, depositing material like sand and shingle
Name 3 features of a sand beach
- Flat and wide
- Sand particles are small and weak backwash can move
them back down beach - Creating long, gentle slope
Name 3 features of a shingle beach
- Steep and narrow
- Shingle particles are large and weak backwash can’t move them back down beach
- Shingle particles build up and create steep slope
Describe how a spit (till mud flat or salt marsh) is formed
- Spits form at sharp bends in coastline (e.g. At a river mouth)
- Longshore drift transports sand and shingle past bend
and deposits in sea - Strong winds and waves can curve end of spit (forming recurved end)
- Sheltered area behind spit is protected from waves - lots of material accumulates in this area, means plants can grow
- Over time, sheltered area can become a mud flat or salt marsh
Describe how a sand dune is formed
- Formed when sand deposited by longshore drift is
moved up beach by wind - Obstacles (e.g. driftwood) cause wind speed to decrease = sand is deposited
- Sand is colonised by plants and grasses
- Vegetation stabilises sand & encourages more sand to accumulate = forms small dunes
What are embryo dunes?
Small sand dunes
What happens to the oldest dunes over time and why?
Over time, oldest dunes migrate inland as newer embryos dunes are formed
Describe how a bar is formed
- Formed when a spit joins two headlands together
- Bar cuts off bay between headlands from sea
- Means lagoon can form behind bar
What is hard engineering?
Man-made structures built to control flow of sea and reduce flooding and erosion
What is soft engineering?
Schemes set up using knowledge of sea and its processes to reduce effects of flooding and erosion
What is a sea wall?
Wall made out of hard material like concrete that reflects
waves back to sea
Name 2 benefits of sea walls
- Acts as barrier to prevent flooding
- Prevents erosion of coasts
Name 2 costs of sea walls
- Creates strong backwash which erodes under wall
- Very expensive to build and maintain
What are gabions?
Wall of wire cages filled with rocks, usually built at foot of cliffs
Name 3 benefits of gabions
- Absorb wave energy and so reduce erosion
- Easy to build
- Cheap
Name 2 costs of gabions
- Wire cages can corrode over time
- Ugly
What are groynes?
Wooden or stone fences that are built at right angles to coast. Trap material transported by longshore drift.
Name 2 benefits of groynes
- Create wider beaches with slow the waves = gives greater protection from flooding or erosion
- Fairly cheap
Name a cost of groynes
- They starve beaches further down coast of sand, making them narrower = narrower beaches don’t protect
coast as well, leading to greater erosion and floods
What is rock armour (rip-rap)?
Boulders that are piled up along coast
Name 2 benefits of rock armour
- Absorb wave energy and so reduce erosion and flooding
- Fairly cheap
Name a cost of rock armour
- Boulders can be moved by strong waves so need to be replaced
Name 4 hard engineering strategies
- Gabions
- Sea Wall
- Groynes
- Rock Armour
Name 2 soft engineering strategies
- Beach Nourishment and Reprofiling
- Dune Regeneration
What is beach nourishment and reprofiling?
Sand and shingle from elsewhere (e.g. From seabed) or from lower down the beach that’s added to upper-part of beaches
Name a benefit of beach nourishment and reprofiling
Creates wider beaches which slows waves = gives greater protection from flooding and erosion
Name 3 costs of beach nourishment and reprofiling
- Taking material from seabed can kill organisms like sponges and corals
- Very expensive
- Has to be repeated
What is dune regeneration?
Creating or restoring sand dunes by either nourishment or planting vegetation to stabilise sand
Name 2 benefits of dune regeneration
- Sand dunes provide barrier between land and sea = wave energy is absorbed which prevents flooding and erosion
- Stabilisation is cheap
Name 2 costs of dune regeneration
- Protection is limited to small area
- Nourishment is very expensive
What is managed retreat (aka coastal realignment)?
Involves removing current defences and allowing sea to flood land behind
What is the result of managed retreat (aka coastal realignment)?
Over time, land will become marshland, protects land behind from flooding and erosion
Name 4 benefits of managed retreat
- Marshlands can also creat new habitats for plants and animals
- Doesn’t need maintaining
- Easy strategy
- Cheap
Name 4 benefits of managed retreat
- Because land is lost to sea, choosing areas to flood can cause conflicts
- Saltwater can also have negative effect on existing ecosystems
