- Created by: :) PurpleJaguar (: - Team GR
- Created on: 29-04-12 15:24
Types of erosion
Hydraulic action: Constant force of the waves against the rock causes pressure and weakness so the cliff face wears away.
Abrasion: Small rocks and other materials smash against the cliff face removing small particles off the rock.
Attrition: Rocks and other materials carried by the water collide and break into smaller pieces.
Corrosion: Salts and acids in the water gradually erode the coastline.
What is deposition?
Eroded material is transported along the coastline, once the material gets too heavy for the wave to carry (the wave is losing energy) it is dropped or deposited onto the floor. This is depostion.
Concordant and Discordant
Concordant coasts cantain usually one rock type, the layers of the rock are parallel to the coastline.
Discordant coasts contain many types of rock and the layers are perpendicular to the coastline. (I didn't draw this by the way :))
Wind blows across the sea the friction caused makes a wave.
The size of a wave depends on the distance the wind has travelled (fetch), it's strenght and speed and the the length of time it has blown for.
When a wave breaks on the shore it is called swash.
When it goes back out to sea it is called backwash.
Constructive waves happen when the swash is stronger than the backwash. (forming a gentle sloping beach)
Destructive waves happen when the backwash is stronger than the swash. (forming a steep beach)
This next card shows you a constructive beach ------------------------------>>>>>
This next card shows you a destructive beach ------------------------------------->
Long shore drift
This is basically how long shore drift happens ( where it says waves that is also the direction of the prevailing winds )
Spits are formed when deposition deposits sand in a river estuary. This is one;
This is Barmouth spit in North Wales
A tombolo is a spit connecting an island to a mainland.
A sand bar is a ridge of sand formed underwater in a river or along a shore by the action of waves.
A sand dune forms when sand is blown onto the mainland by prevailing winds.
I hope my notes help you with your revision :)
If i have made a mistake or need to add something plz comment below and i will make changes
P.S I'm going to add notes on coastal defences soon, I haven't forgotten about them :)
I have now added the sea defences section :P
Coastal sea defenses- Groynes
Groynes prevent long shore drift, they interupt water flow and limit the movement of sediment (so no spits form). They can be made from wood, like these, or rock.
Gabions / Rip Rap
These are wire mesh baskets filled with rocks / pebbles. They are flexible so absorb wave and wind energy. You can just about see them here...
It is basically a big wall, they protect houses and any other thing behind the sand that the sea will erode. The sea wall stays still and conflicts the changing coast.
Revetments break the force of the wave but also trap sediment and other beach material behind them. they are like big fences and can also be made out of concrete.
This is when the beach / coast has been left to let nature take its cause, because overtime the coast will probably go back to how it was before a defence system was put in place.
This is where sand from another source is replaces the sand that was lost due to long shore drift. It produces a wider beach which can also protect from storms.
Steel barriers and drains put into a cliff to intercept the water movement through the cliff which causes mass movement. The drains help remove water quicker.
Hard and Soft
- Sea Walls
- Managed retreat
- Beach nourishment
Hard engineering is more expensive than soft.