Coastal Processes Flashcards
What are destructive waves and their features?
They are created from big, strong waves when the wind is powerful and has been blowing for a long time.
They occur when wave energy is high and the wave has travelled over a long fetch.
They have a stronger backwash than swash, which is why they tend to erode the coast.
What are constructive waves and their features?
They are created in calm weather and are less powerful than destructive waves.
They have a long wavelength, and are low in height.
They break on the shore and deposit material, building up beaches, because they have a swash that is stronger than the backwash.
What are the 3 main coastal processes?
Erosion - Waves can erode the coastline in a similar way to the water in rivers.
This usually occurs when the sea takes lots of energy from the power of destructive waves.
There are 4 key factors that affect the erosion of a coastline.
Transportation - The movement of eroded material up and down, and along the coast.
There are 4 stages of transportation
Deposition - When the sea loses energy, it drops the sand, rock particles and pebbles that it has been carrying, depositing them.
There are 2 causes of deposition.
What are the 4 processes of erosion?
Hydraulic action- Air becomes trapped in joints and cracks in the cliff face.
When a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion.
Abrasion- Bits of rock and sand in waves are flung against the cliff face.
Over time they grind down cliff surfaces like sandpaper.
Attrition- Waves smash rocks and pebbles on the shore into each other, and they break and become smaller and smoother.
Solution- Weak acids contained in sea water will dissolve some types of rock such as chalk or limestone.
What are the 4 stages that lead to transportation?
Solution- Minerals are dissolved in sea water and carried in solution.
The load is not visible. Load can come from cliffs made from chalk or limestone, and calcium carbonate is carried along in solution.
Suspension- Small particles are carried in water, e.g: silts and clays, which can make the water look cloudy. Currents pick up large amounts of sediment in suspension during a storm, when strong winds generate high energy waves.
Saltation- Load is bounced along the sea bed, e.g: small pieces of shingle or large sand grains.
Currents cannot keep the larger and heavier sediment afloat for long periods.
Traction- Pebbles and larger sediment are rolled along the sea bed.
What is longshore drift and what does it do?
Longshore drift is a process responsible for moving significant amounts of sediment along the coast.
This usually occurs in one direction as dictated by the prevailing wind.
As the result waves break on to the beach obliquely at an angle of around 45 degrees.
The swash moves beach material along the beach and the backwash, under gravity, pulls the material back down the beach at right angles to the coastline.
Over time this creates a net shift of material along the coast.
