The Coastal Zone Flashcards
What is mechanical weathering?
The breakdown of rock without changing its chemical composition.
What is chemical weathering?
The breakdown of rock by changing its chemical composition
What happens during freeze thaw weathering?
- Water gets into cracks in the rock
- It freezes and expands, putting pressure on the rock
- The water thaws and contracts, releasing the pressure
- The process repeats and widens the cracks
What is carbonation weathering?
- Rainwater has carbon dioxide dissolved in it which makes weak carbonic acid
- Carbonic acid reacts with rock that contains calcium carbonate
What is mass movement?
When material shifts down a slope as one, under the force of gravity
What are slides?
Material shifting in a straight line
What are slumps?
Material shifts with a rotation
Mass movement causes coasts to…
…retreat rapidly
When is mass movement more likely to happen?
When the material is full of water, as it acts as a lubricant
What are the 4 processes of erosion?
Hydraulic action, abrasion, attrition and solution
What is Hydraulic action?
Waves crash against the rock and compress the air in the cracks. This puts pressure on the rock. Repeated compression widens the cracks and bits of rock break off
What is abrasion?
Eroded particles in the water scrape and rub against the rock, removing small pieces
What is attrition?
Eroded particles in the water smash into each other, and break into smaller fragments. Their edges also get rounded off.
What is solution?
Weak carbonic acid in seawater dissolves rock like chalk and limestone
What are the features of a destructive wave?
- High frequency (10-14 a minute)
- They’re high and steep
- Their backwash is more powerful than their swash
- They remove material from the coast
Waves erode cliffs to form…
…wave cut platforms
How are wave cut platforms formed?
- Waves cause most erosion at the foot of a cliff.
- This forms a wave cut notch, which is enlarged as erosion continues
- Undercutting occurs
- The rock above becomes unstable and collapses
- Repeated collapsing causes the cliff to retreat
- A wave cut platform is left behind
How are Headlands and Bays formed?
- Headlands and bays form where there are alternating bands of hard and soft rock along a coast
- The less resistant rock is eroded quickly and this forms a bay
- The resistant rock is eroded more slowly so is left protruding into the sea, forming a headland