Coastal processes Flashcards
What does weathering mean?
Weathering is the breakdown of rocks in situ (where they are)
What does erosion mean?
Erosion is when rocks are broken down and carried away by something
What is mechanical weathering
Give an example
The breakdown of rock without chnaging its chemical composition
Freeze-thaw weathering
Explain freeze thaw weathering
Water enters the rock that has cracks e.g granite
When the water freezes it expands which puts pressure on the rock
When the water thaws it contracts, which releases the pressure on the rock
Repeated freezing and thawing widens the cracks and causes the rock to break up
When does freeze thaw weathering happen?
It happens when the temperature alternates above and below 0c (freezing point of water)
What is chemical weathering ?
The breakdown of rock by changing its chemical composition
When does carbonaion weathering take place?
A type of chemical weathering that happens in warm and wet conditions
Explain carbonation weathering
Carbon dioxide can dissolve in the rain to create a weak ‘cabonic acid’
Carbonic acid reacts with rock that contains calcium carbonate and dissolves that bit
E.g. carboniferous limestone reacts with the rock and are dissolved
What does fetch mean?
How is a wave more powerful
The distance the wind blows over the sea
The grater the fetch the more powerful wave
Describe constructive waves
- They deposit material
- Not very tall (called calm sea)
- They have a low frequency and are low and long
- Their swash is more powerful then their backwash so the material is deposited
- The wave have longer wavelength than destructive waves
What is swash and backwash
Swash is water moving up the beach
Backwash is water moving down the beach
Describe destructive waves
- They erode the coast
- They have high frequency and are steep
- Their backwash is more powerful than their swash so material is removed
- They are really tall
Abrasion
Process of erosion
Eroded particles in the water scrape and rub against the rock
Hydraulic power
Process of erosion
Waves crash against rack and compress the air in the cracks. This puts pressure on the rock. Repeated compressions widens the cracks and causes bits of rock to fall of
Attrition
Process of erosion
Eroded particles in the water collide break in smaller pieces and become more rounder
What is mass movement?
When material falls down a slope
The shifiting of rock and lose material down a slope e.g. a cliff
Why does mass movement happen ?
It happens when the force of gravity acting on a slope is greater than the force supporting it
What does mass movement do and when is it more likely to happen
It causes coast to retreat rapidly
Its more likely to happen when the material is full of water - water acts as a lubricant and makes the material heavier
When the material shifts it can create a scrap (a steep ‘cut’ in the side of the slope)
How is material transported along the coast
By longshore drift
Explain the process of longshore drift
Waves follow the direction of prevailing (most common) wind
They usually hit the coast at an oblique angle (any angle that isn’t a right angle)
The swash carries that material up the beach in the same direction as the waves
The backwash then carries material up the beach at right angles back towards the see
Overtime material zig zags along the beach
Traction
Large particles like boulders are pushed along the sea bed by the force of the water
Suspension
Small particles like slit and clay are carried along in the water
Solution
Soluble materials (e.g limestone) dissolve in the water and are carried along
Saltation
Pebble sized particles are bounced along the sea bed by the force of the water
What is deposition and when does it occur?
Deposition is the dropping of material
It occurs when water carrying sediment loses energy and slows down
When do coasts build up ?
refer to deposition and erosion
When the amount of deposition is greater than the amount of erosion
The amount of material thats deposited on an area coast is increased when theres lots of erosion elsewhere on the coast (so more material is avaliable)
Lots of material is transported into the sea
Constructive waves drop more material than they remove - theres more deposition than erosion
