Coasts (4) Flashcards
Name the different types of Weathering processes?
Biological
Mechanical
Chemical
What is Mechanical Weathering?
The breakdown of rock without changing it’s chemical composition
-mainly salt weathering:
-seawater gets into cracks, evaporates, forms crystals, expand and put pressure on the rock, causing the rock to break
What is Chemical Weathering?
The breakdown of rock by changing it’s chemical composition
-mainly carbonation weathering
-seawater has CO2 dissolved in it, which makes them an acid
-carbonic acids react with calcium carbonate, so rocks are dissolved
What is Biological Weathering?
The breakdown of rock by living things eg. plant roots by growing into cracks and pushing it apart
What is Mass Movement?
The shifting of rock and loose material down a slope (cliff)
-happens due to the force of gravity being greater than the supporting force
When is Mass Movement more likely to happen?
When the cliff is saturated / lubricated with water - making the material heavier
3 types of Mass Movement?
Slides
Slumps
Rockfalls
3 types of coastal erosion + explanations
Hydraulic power - waves crash against rock and compress the air in the cracks, putting pressure on the rock. Repeated compressions widen the cracks
Abrasion - eroded particles in the water RUB against ROCK, removing small pieces
Attrition - eroded particles in the water SMASH into EACH OTHER and break into smaller fragments. Their edges become rounded off as they rub against each other
What type of Coastlines are there?
Concordant
Discordant
Describe Concordant coastlines
Alternating bands of soft and hard rock PARALLEL to the coastline
Erosional landforms like headlands are less common as the rock erodes at the same rate
Describe Discordant coastlines
Alternating bands of soft and hard rock perpendicular to the coast
Erosional landforms like headlands and bays are more common as the rock erodes at the same rate
How does the UK climate have an impact on Coastal Erosion?
-Temperature varies with seasons - coldest in winter, hottest in summer
-Storms are more frequent in the winter - strong winds create high energy, destructive waves which increase the rate of erosion on the cliffs
-Intense rainfall can cause cliffs to become more saturated - mass movement is more likely
Characteristics of Destructive waves
-High and steep (larger amplitude)
-High frequency (10-14 waves/minute)
-Backwash is more powerful than swash
-Increased rate of coastal retreat
What is a Wave-cut Platform? (How is it formed)
1) Waves cause erosion at the foot of a cliff, forming a wave-cut notch
2) The rock above becomes unstable and collapses
3) W-c Platform is the land that’s left behind after the cliff retreats
How do Caves, Arches, Stacks and Stumps form?
1) Waves crash into the cracks of the headlands and enlarge the cracks
2) Repeated enlargement causes a cave to form
3) Continued erosion deepens the cave until it breaks through the headland, forming an arch
4) Erosion continues to wear away the rock supporting the arch until it collapses
5) This forms a stack - isolated rock separated from the headland
How is material transported along the coast?
LSD
Longshore Drift
How does LSD work?
1) Waves follow the direction of the prevailing winds along the coast
2) Swash carries material up the beach in the same direction as the waves
3) Backwash carries material down the beach at right angles
4) Sediment zig-zags along the coast
How do Spits form?
1) Spits form at sharp bends in the coastline
2) LSD transports sand and shingle past the bend and deposits into the sea
3) Strong winds and waves can curve the end of the spit - recurved end
4) The sheltered area behind the spit is protected from waves, lots of material accumulates here
How does a Bar form?
1) A bar is formed when a spit joins 2 headlands together
2) The bar cuts off the bay between the headlands from the sea
3) A lagoon can form behind the bar
Human activities having impacts on the coastlines
Agriculture
Development
Industry
Coastal Managment
In what ways is climate change increasing the risk of Coastal flooding?
Rising Sea Levels
Storm Frequency
Describe ‘Rising Sea Levels’ increasing risk of Coastal flooding
-Rising sea levels pose a threat to low-lying coastal areas
-An increase in sea-levels could cause higher tides that would flood areas more often
-Higher tides could remove larger amounts of beach material - increased cliff erosion because there is less sediment to protect the cliffs
-Beaches could become narrower - less sediment
Describe ‘Storm frequency’ in increasing the risk of Coastal flooding
-Climate change is causing storms to become more frequent - melting icebergs leads to an increased sea levels and storm surge
-Storms give the sea more erosional power
Threats to People from Coastal flooding
1) Low-lying coastal areas could be permanently flooded - uninhabitable
2) Coastal industries may be shut down because of damage to equipment and buildings
3) Risk of damage to infrastructure like roads and rail networks
4) Puts people of tourism in these areas - business closure
Threats to the Environment
1) Ecosystems will be affected because seawater has a high salt content
2) The force of floodwater can uproot trees and plants - can drown them
3) Some conservation areas are threatened by coastal erosion - eg. lagoons
Benefits + Costs of Sea Wall
+ Prevents erosion of the coast
+ Acts as a barrier to prevent flooding
- Very expensive to build and maintain
- Doesn’t look nice for many tourists
Benefits + Costs of Groynes
+ Create wider beaches which slow the waves - greater protection from erosion
+ Fairly cheap
- Starve beaches further down the coast of sediment, making them narrower
- This means these areas are more vulnerable to erosion
Benefits + Costs of Beach Replenishment
+ Creates wider beaches which slow the waves
+ Gives greater protection from flooding and erosion
- Taking material from the seabed can kill organisms like corals
- Very expensive
- Must be repeated
Benefits + Costs of Strategic Realignment
+ Over time, land will become marshland, creating new habitats
+ Flooding and erosion are reduced behind the marshland
- People may disagree about what land is allowed to flood
- eg. Flooding farmland will affect the livelihood of farmers
What should Management Strategies be? (Most beneficial)
Sustainable
Benefits + Costs of Slope Stablilisation
+ Prevents mass movement by increasing the strength of the cliff
- Very expensive
- Difficult to install
