1C - 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