Coastal Processes Flashcards
All 13 cards in this deck
Which type of wave has a strong swash and a weak backwash, and what effect does it have on the coast?
Constructive waves — they build up the beach (deposition). They are low, with a long wavelength and low frequency (6–8 per minute).
True or false? Destructive waves are low with a long wavelength.
False. Destructive waves are tall and steep with a short wavelength and high frequency, and a strong backwash that removes beach material.
What are the steps of freeze–thaw (mechanical) weathering on a cliff?
e.g. a cliff with cracks in winter- Water collects in cracks in the rock — rain or spray fills the cracks.
- Temperature falls below 0°C and the water freezes and expands by about 9%, widening the crack.
- Repeated freezing and thawing breaks fragments off the cliff face.
Which chemical weathering process breaks down chalk and limestone cliffs?
Carbonation (solution) — rainwater with dissolved carbon dioxide forms a weak carbonic acid that dissolves the rock.
Which type of mass movement is a rotational movement of saturated soft rock down a curved slip surface?
Slumping — common on soft boulder clay cliffs (e.g. Holderness) after heavy rain.
In sliding (a landslide) at the coast, how does the material move?
Material moves rapidly downslope in a straight line along a flat slip plane, staying largely intact.
Which type of mass movement leaves scree at the base of a steep cliff?
Rock fall — fragments loosened by weathering break off the cliff face and fall to the base.
How does hydraulic power erode a cliff?
Waves trap and compress air in cracks in the rock; the pressure widens the crack and breaks pieces of rock away.
How does abrasion erode the coast?
Sand and pebbles carried by the waves are thrown against the cliff, scraping and wearing it away like sandpaper.
What does attrition wear down at the coast?
The sediment itself — rock fragments carried by the sea collide and knock against each other, becoming smaller, rounder and smoother.
What are the steps of longshore drift?
e.g. a beach with waves driven by a south-westerly prevailing wind- Waves approach the beach at an angle, set by the prevailing wind — from the south-west.
- Swash carries sediment up the beach at that same angle.
- Backwash drags it straight back down under gravity, so sediment zigzags along the coast — towards the north-east.
Why is sediment deposited in coastal areas?
Because the waves lose energy and can no longer transport their load — e.g. in sheltered bays, in shallow water, or where constructive waves dominate.
True or false? Mass movement is a type of coastal erosion.
False. Mass movement is the downhill movement of material under gravity (sliding, slumping, rock falls); erosion is the wearing away of the coast by waves.