Coasts - Processes and landforms Flashcards
What is a wave?
A disturbance on the surface of the sea or ocean.
How do waves form?
Friction created by wind blowing over the surface of the sea.
What happens as waves approach the coast?
Their orbit becomes more elliptical due to friction with the seabed. The crest rises up and breaks on the shore.
What is fetch?
The distance the wind blows over water.
Which factors affect wave size?
The greater the fetch, the larger the wave. Stronger and faster winds create larger waves.
What are the features of constructive waves?
Swash stronger than backwash. Long wavelength. Low height and low frequency. Create beaches with a gently sloping profile.
What are the features of destructive waves?
Backwash stronger than swash. Destroy the beach. High wave frequency. Create a steep beach profile.
Define ‘swash’.
The water flowing towards a beach when a wave breaks.
Define ‘backwash’.
The movement of water down the beach, after a wave has broken.
Define ‘elliptical’.
Oval-shaped or egg-shaped.
What is weathering?
The breakdown of rock, in situ, by biological activity, chemical processes or weather-related factors.
What is mechanical weathering?
The breakdown of rock, without affecting its chemical composition e.g. freeze-thaw weather.
Explain how freeze-thaw weathering works.
Porous rocks hold water/allow it to pass through. The water freezes at night, expanding the cracks. This ice thaws in the daytime when temperatures rise. When ice thaws, water seeps further into the cracks. The crack expands further by water freezing at night. This processes repeats itself, breaking down the rock.
What is chemical weathering?
The breakdown of rock, changing its chemical composition e.g. through carbonation.
How does carbonation happen?
When slightly acidic rainwater comes into contact with limestone or chalk, it causes it to dissolve. A chemical reaction occurs, between the acidic rainwater and calcium carbonate in the limestone/chalk, forming calcium carbonate. Calcium carbonate is soluble and gets carried away.
What is biological weathering?
The breakdown of rock, by the actions of living organisms.
How might biological weathering occur?
Tiny bacteria, algae and lichens all produce chemicals that can help to break down the rocks they live on. Tree roots may prise apart rocks if they grow into the cracks of the rock. If roots grow, they may make cracks bigger and break up the rock.
Define ‘in situ’.
Describes something that remains where it is while being subjected to a process.
Define ‘algae’.
A simple, non-flowering, typically aquatic plant. They lack true stems, roots and leaves.
What is mass movement?
The downhill movement of cliff material, under the influence of gravity.
Which cliff material is susceptible to slumping?
Boulder clay.
How does slumping occur?
Rainfall causes boulder clay to become saturated. This causes the cliff to slump due to its weight (there is additional weight from the water it is holding). The debris from the slump is deposited at the bottom of the cliff. The debris is eroded by the sea, leaving the cliff exposed to coastal marine processes.
How do landslides occur?
Waves breaking at the foot (bottom) of cliffs form a wave-cut notch. Continued erosion increases the size of the notch. The weight of the cliff is too heavy to be supported, resulting in a landslide. The debris is deposited at the bottom of the cliff, providing temporary relief from erosion.
What is a rock fall?
Fragments of rock breaking away from a cliff face, often due to freeze-thaw weathering.
When do mudflows occur?
When saturated soil and weak rock flows down a slope. Mudflows typically affect cliffs made of boulder clay.
Define ‘boulder clay’.
A sort of ‘stony soil’. It is made of rocks, sand and gravel which were deposited by melting glaciers at the end of the ice age.
Define ‘saturated’.
Describes something that is completely full of water, to the extent that it cannot hold any more.
Define ‘slump’.
To fall suddenly.
