Coasts Flashcards
Abrasion
A type of erosion involving rock particles being scraped against, and wearing away, the surface of other rocks.
Arch
A coastal feature created by the erosion of back-to-back caves
Attrition
A type of erosion involving rock fragments being ground together to become smaller, smoother and rounder.
Backwash
When the water from a wave retreats back into the sea
Bay
An area of sea between two headlands.
Beach
A beach is a narrow, gently sloping strip of land that lies along the edge of an ocean, lake, or river
Solution (Corrosion)
A chemical process involving the dissolving away of rocks e.g. chalk or limestone.
Erosion
The wearing away of material
Estuary
Where freshwater from rivers and streams mixes with salt water from the ocean. Subject to tides.
Headland
A point of land usually high and often with a sheer drop, that extends into a body of water.
It is because the rock is very resistant
Hydraulic Action
Where water enters cracks in the cliff face, compresses air within the cracks and causes pressure to be exerted on the surrounding rock, which weakens and breaks
Longshore Drift
The movement of sand and pebbles along a beach by wave action.
Saltation
Pebbles bounce along the river bed
Solution
The transport of dissolved chemicals
Swash
An incoming coastal wave.
Traction
The transport of boulders in a rolling motion in water.
Weathering
The breakdown of rocks in-situ by mechanical, chemical or biological means.
How are headlands and bays formed?
1) Hard rock and soft rock next to water
2) A wave attack erodes the soft rock, but leaves the hard rock.
3) Differential erosion occurs.
4) The eroded area becomes a bay and the hard rock becomes a headland.
How are wave cut platforms made?
1) The sea attacks a weakness in the base of the cliff.
2) A wave-cut notch is created by erosional processes such as hydraulic action and abrasion.
3) As the notch becomes larger, the cliff becomes unstable and collapses as a result of gravity.
4) The cliff retreats inland.
5) The material from the collapsed cliff face is eroded and transported away.
6) This leaves a wave-cut platform; the process repeats over time.
What is the difference between weathering and erosion?
Weathering is the breakdown of material, but erosion is the wearing away of material.
How are caves, arches, stacks and stumps formed (CASS)?
- Wave attacks form faults in a cliff via hydraulic action and abrasion. The fault is enlarged to become a CAVE.
- The cave is widened and deepened by erosion (HA and abrasion) until it eventually cuts through the headland and becomes an ARCH.
- Undercutting from the waves and a lack of support for the roof of the arch leads the roof to collapse, leaving a STACK.
- Weathering and erosion undercut the back of the stack until it collapses, forming a stump.
How does longshore drift occur?
- The swash moves up the beach at an angle determined by the direction of the prevailing wind and waves.
- When the wave has broken, the backwash returns to the sea at a 90 degrees angle.
- In this way, sediment (sand and pebbles) are moved up the beach, and then they will collect against a groyne.
What are some features of a constructive wave?
- Wave height is small
- Less frequent.
- A strong swash moves sediment up the beach
- A weak backwash carries away little sediment.
- Gives the beach a gentler profile.
What are some features of a destructive wave?
- The wave height is larger
- More frequent
- A weak swash carries less sediment up the beach
- A strong backwash carries away lots of sediment
- This can build steep beaches.
How is a spit formed?
1) Sediment is carried by longshore drift.
2) When there is a change in the shape of the coastline, deposition occurs.
3) A long thin ridge of material is deposited. This is the spit.
4) A hooked end can form if there is a change in wind direction.
What is the difference between hard and soft engineering?
Hard engineering - artificial structures
Soft engineering - sustainable and natural approach
What is beach nourishment?
Beach nourishment is the practice of adding large quantities of sand or sediment to beaches to combat erosion and increase beach width.
What is managed retreat?
- Soft engineering, allows the erosion and flooding to happen
- Retreat further down the coast
- Allows the natural processes of the sea to occur
- Area of low value are allowed to flood, which protects areas of higher importance down the coast.
What is cliff stabilisation?
Soft engineering, cliffs are covered in matting and vegetation planted to help make them more stable and resistant to erosion.
What is a sea wall?
- Extremely effective
- Hard Engineering
- A wall placed at the base of a cliff to reflect the waves energy
- Extremely expensive (£10,000 per km)
- Ugly
What are gabions?
- Hard engineering
- Cages of wire filed with rocks to absorb the waves energy
- Effective
- Cheap
- Environmentally ugly
What are groynes?
- Hard engineering structures
- Used to trap sediment and build up beaches
- Protecting cliffs from erosion
- Causing increased erosion downstream
- Over a 25-30 year period.
What are rip raps?
- Hard engineering
- Large rocks placed at the bottom of the cliff to absorb wave energy
- Effective at dispersing wave energy
- Cheap
- Ugly
Suspension
Lighter sediment is suspended (carried) within the water
