Coasts Flashcards
What are the two types of waves?
Constructive and Destructive
What are the features of a constructive wave?
Long wavelength Shallow gradient waves Strong swash Weak backwash Beach built up by deposition of material bought up in swash
What are the features of a destructive wave?
Tall waves with short wavelengths Steep gradient waves Weak swash Strong backwash that erodes beach Takes more than it leaves
Name the four types of coastal erosion
Hydraulic action
Abrasion
Attrition
Corrosion
What is hydraulic action?
The force of the water hitting the cliffs often forces pockets of air into cracks and crevices in a cliff face.
What it abrasion?
Abrasion is caused by the waves picking up stones and hurling them at the cliffs and so wearing the cliff away.
What is attrition?
Any material carried by the waves will become rounder and smaller over time as it collides with other particles and all the edges get knocked off.
What is corrosion?
The dissolving of rocks and minerals by sea water.
How is a stump formed?
CRACKS form in cliff faces where less resistant rocks are eroded. The waves continue to erode the cliff and the material in the sea can turn the crack into a CAVE. If the cave is formed in a headland then it will eventually break through and become an ARCH. This will become bigger until it erodes through and becomes a STACK. Due to hydraulic action and corrosion this will eventually become a STUMP.
What is physical weathering?
The disintegration of rock into smaller pieces by physical processes without any chemical change in the rock.
E.G. salt crystal growth and freeze-thaw weathering
What is chemical weathering?
The decomposition of rocks caused by a chemical change within the rock.
E.G acid rain
What is biological weathering?
The action of plants and animals on the land
E.G. where burrowing animals and plant roots breakdown the rocks.
Name the main forms of mass movement
Rockfall and Slumping
What is rockfall
Rockfalls occur when fragments of rock weathered from a cliff face fall under gravity and collect at the base, it happens suddenly.
What is slumping?
It happens when the bottom of a cliff is eroded by waves. The slope becomes steeper and the cliff can slide downwards. Usually triggered by saturation due to rain, which lubricates the rock and makes it heavier.
Explain Salt crystal growth
The spray from sea water lands on rock, the water evaporates, leaving salt behind . The salt crystals grow and create stress on rock, causing it to break down into smaller fragments.
Give an example of where coastal erosion has occured
Old harry rocks - Dorset
Durdle door
What does fetch mean?
The distance the wind has blown over the sea.
How does fetch affect the coast?
Coasts that face a major ocean (e.g southwest coast, England) have a long fetch. This produces destructive waves with high energy. These waves can erode cliffs at rapid rates.
How is a wave cut platform formed?
> the waves carve wave cut notches into headlands
they get deeper until the rock above collapses
the sea carries the debris away
this leaves a wave cut platform
What is longshore drift?
Sediment is carried straight down the shore by backwash and gravity. It is then carried up the beach at an angle by the swash of another wave. This will continue down the beach.
Which direction is sediment carried in longshore drift?
The direction of the prevailing winds.
What is prevailing wind?
The main/strong wind on a particular area; the average direction of the wind.
How is a bar formed?
When longshore drift blocks off a bay. Sand is moved along the coast and eventually in goes across a bay joining the land on both ends.
How is a spit formed?
Longshore drift carries sediment down a coast. When the shape changes the sand continues in the same direction. There are weak currents and the sediment gets deposited. This extends out from the coast. This is called a spit.
