What is a coast?
A part of land that joins the sea.
What causes waves to form?
Wind blowing over the sea
What does the size and strength of waves depend on?
- How strong the wind is
- How long it blows for
- How far it travels
Water rushing up the beach
Water draining back down the beach
The distance a wave has travelled
What are constructive waves?
Waves that have a very strong swash and a weak backwash.
They build up the beach.
How do constructive waves build beaches?
They deposit material with the swash as the backwash is weak and leave sand and pebbles behind
What are destructive waves?
Waves that have a weak swash and a strong backwash.
They pull pebbles and sand back down the beach as the water retreats
Name the features of constructive waves?
- Wave crests far apart
- Gentle sloping wave front
- 6 - 8 per minute
- Gentle beach created
Name the features of destructive waves?
- Steep beach created
- Break close together
- Up to 15 per minute
What are marine processes?
The base of cliffs being eroded by hydraulic action and abrasion
Which waves are associated with coastal erosion?
Weathering is the breakdown of rock at or near the surface by the weather
List the 2 main types of weathering?
1. Mechanical weathering
2. Chemical weathering
What is mechanical weathering?
Mechanical weathering is caused by physical changes such as changes in temperature, freezing and thawing.
Water gets into cracks in rocks, freezes when the temperature drops below 0'c, prising the rock apart. When the water melts, a larger crack develops. Overtime this causes rocks to break apart.
What is chemical weathering?
The weathering of rocks by chemicals is called chemical weathering. Rainwater is naturally slightly acidic because carbon dioxide from the air dissolves in it. Minerals in rocks may react with the rainwater, causing the rock to be weathered
Wearing away of rocks by water, weather or ice
List the 4 main types of erosion
- Hydraulic action
Define 'hydraulic action'
Water being forced into cracks in the rock and breaking it up.
Loose rocks (sediment) are thrown against the cliff by waves. This wears away at the cliff and chips bits of rock off.
Loose sediment that has been knocked off the cliff is swirled around by waves, colliding with other pieces wearing them into smaller smoother pieces.
Seawater dissolves material from the rock.
What is mass movement?
When rocks loosened by weathering move down slope under gravity. They can slide or slump
What is slumping?
This is common where cliffs are made of clay. The clay becomes saturated during heavy rain and oozes down towards the sea.
What is sliding?
This is when large chunks slide down slope quickly without any warning
What is 'rock fall'?
A type of mass movement where material breaks off the cliff and falls down the slope.
How is sediment transported along the coastline?
Describe how longshore drift
1. Waves approach the beach at an angle
2. As waves break the swash carries material up the beach at the same angle
3. The backwash carries material straight back down the beach under gravity
4. This causes the material to move along the beach in a zig-zag pattern
What is deposition?
When the sea loses energy, it drops the sand, rock particles and pebbles it has been carrying. This is called deposition.
Deposition happens when the swash is stronger than the backwash and is associated with constructive waves.