Geography- Coastal Zone Flashcards
How are waves formed?
Friction between the wind and the surface of the water causes ripples to form.
These develop into waves
What is fetch?
The stretch of open water over which the wind blows
The longer the fetch the ………… powerful a wave can become
More
What is swash?
The water that rushes up the beach
What is backwash?
The water that flows back towards the sea
What happens to waves as the water becomes shallower?
The top of the wave (the crest) begins to move faster, which causes the crest of the wave to rise up and eventually topple onto the beach .
What are constructive waves?
powerful waves that surge up the beach with a powerful swash
How do constructive waves change a beach?
They carry large amounts of sediment and construct the beach, making it more extensive.
How are constructive waves formed?
By distant storms, which can be hundreds of kilometres away.
What are the characteristics of constructive waves?
Well spaced apart
Powerful when they reach the coast
What are destructive waves?
Waves that destroy the beach as they have little swash when the wave breaks (as they rear up to form towering waves before crashing down into the beach) but a powerful backwash. Therefore this explains the removal of sediment and the destruction of the beach
How are destructive waves formed?
By local storms close to the coast
What are the characteristics of destructive waves?
Closely spaced, often interference with each other producing a chaotic, swirling mass of water.
What is a cliff?
A steep or vertical face of rock often found at the coast
What is mechanical weathering?
Involves the disintegration of rocks without any chemical changes taking place
What is rockfall?
The collapse of a cliff face or the fall of individual rocks from a cliff, often due to freeze thaw.
What is freeze thaw weathering?
Involves water collecting in cracks or holes in the rock. At night the water freezes and expands. This expansion creates stress within the rock, widening any cracks that already exists. When the temperature rises the water seeps deeper into the rock and the process repeats.
What type of rock is freeze thaw weathering particularly effective in?
Porous (contains holes)
Permeable (allows water to pass through it)
What is exfoliation?
Where the heating and cooling of a rock causes it to expand and contract, eventually leading to the outer layer of the rock flaking off.
What is chemical weathering?
Slight acidic rain dissolves the calcium carbonate slightly to form calcium hydrogen carbonate which is soluble, and over time this process dissolves the rock away.
What is biological weathering?
Plant roots are effective at growing and expanding in cracks in the rocks. Animals such as rabbits can be effective at burrowing into weak rocks such as sands.
What is mass movement?
The downhill movement of material under the influence of gravity
What is a landslide?
Block of rock slide downhill
What is mudflow?
Saturated soil and weak rock flows down a slope
What is rotational slip?
Slump of saturated soil and and weak rock along a curved surface.
Where does most of the materials go from cliff erosion?
Carried away by the waves to be deposited somewhere along the coast
What is hydraulic power (in terms of cliffs)?
This involves the sheer power of the waves as they smash onto a cliff. Trapped air is blasted into holes and cracks in the rock, eventually causing the rock to break apart. This explosive force of the trapped air operations in a crack is called cavitation
What is corrosion (in terms of cliffs)?
Involves fragments of rock being picked up and hurled by the sea at a cliff. The rocks act like erosive tools by scraping and gouging the rock.
What is abrasion (in terms of cliffs)?
The sand papering effect of pebbles grinding over a rocky platform, often causing it to become smooth
What is solution (in terms of cliffs)?
Some rocks are particularly vulnerable to being dissolved by seawater. This is particularly true of limestone and chalk which form cliffs in many parts of the U.K.
What is attrition (in terms of cliffs)?
This is where rock fragments carried by the sea knock against one another, causing them to become smaller and more rounded.
What is longshore drift?
The transport of sediment along a stretch of coastline caused by prevailing winds causing the waves to approach the beach at an angle
How does long shore drift occur?
When waves approach the coastline at an angle, they bring their swash pushed sediment up the beach at the same angle. The back wash then drags the material down the beach at a 90 degrees angle, due to the force of gravity. This produces a zig-zag movement of sediment along the beach. The smaller sediment will be carried furthest.
Where does coastal deposition take place?
Areas where the flow of water slows down as sediment can no longer be carried or rolled along and has to be deposited. This most commonly happens in bays as the energy of the waves is reduced when entering the bay.
What is a bay?
A broad coastal inlet often with a beach
Why is there a lack of beaches at headlands?
The wave energy is much greater
What is a headland?
A point of usually high land jutting out into the sea
How are headlands formed?
They are sections of cliff that are particularly resistant to erosion (e.g sandstone, chalk or limestone)
How are bays formed?
They are weaker sections of coastline the are more easily eroded (e.g clay)
Are bays or headlands more vulnerable to cliffs and wave cut platforms from powerful waves?
Headlands
What is a concordant coast?
If the layers of rock are parallel to the coastline
What is a discordant coast?
Where the layers of rock are perpendicular to the coast
Are headlands and bays formed on discordant or concordant coasts?
Discordant coasts
What is a wave cut notch?
A small indentation (or notch) cut into a cliff by coastal erosion roughly at the level of high tide.
What happens to a wave cut notch over time?
Over a long period of time (usually hundreds of years) the notch gets deeper until the overlying cliff can no longer support its own weight and collapses.