Coasts 2 - Coastal processes Flashcards
What are the 6 types of erosion
- Corrasion (Abrasion)
- Hydraulic action
- Cavitation
- Wave quarrying
- Solution (Corrosion)
- Attrition
What is corrosion (Abrasion)
Bits of sediment transported by the waves, small and grind against rocks and cliffs, breaking bits off and smoothing surfaces
What is hydraulic action
Air in cracks in cliffs are compressed when waves crash. The pressure exerted by the compressed air breaks off rock pieces
What is cavitation?
As waves recede the compressed air expands exerting pressure on the rock and causing bits to break off
What is wave quarrying
The energy of a wave as it breaks against a cliff enough to attack bits of rock222222
What is solution (Corrosion)?
Soluble rocks gradually dissolve In seawater
What is attrition?
Bits of rock in the water smash against each other and break into smaller pieces
What Is transportation
The process of eroded material being moved
What are 4 transportation processes?
- Solution
- Suspension
- Saltation
- Traction
What is solution?
Substances that dissolve are carried along the water eg.- limestone is dissolved into slightly acidic water
What is suspension>
Very fine material, like slit and clay particles is whipped up by turbulence and carried along the water causing them to BOUNCE along the seas bed
What is saltation?
Larger particles like gravel and pebbles are too heavy to be carried along in water. Most eroded material is transported like this
What is traction?
Very large particles like boulders are pushed along the seabed by the force of water
How does longshore drift work?
Swash carries sediment up the beach, parallel to the prevailing wind. Backwash carries sediment back down the beach at right angles to the shoreline.
When there’s an angle between the prevailing wind and shoreline, a few rounds of swash and backwash move the sediment along shoreline
What is deposition
The material Being transported and dropped at the coast
What are the 2 types of deposition
- Marine
- Aeolian
What’s marine deposition?
Sediment carried by seawater that’s deposited
What is aeolian deposition?
Sediment carried by wind is deposited
When does deposition occur?
When sediment load exceeds the ability of wind or water to carry it
Why does this happen?
Because sediment load increases or wind or water flow slows down
Why do wind and water slow down?
Friction increases and flow becomes turbulent
How does friction increase?
Waves enter shallow water or wind reaches land, friction between water / wind and the ground increases, slowingg down the water or wind
How do flows become turbulent
If water or wind encounters an obstacle the flows become rougher and overall speed decreases
What happens if the wind drops?
Wave height, speed and energy absorption decrease
What is sub-aerial weathering?
The gradual breakdown of rocks by agents like ice, salt, roots and acids
What does weathering do?
Weakens cliffs and makes them more vulnerable to erosion
What 4 types of weathering affect the coast
- Salt Weathering
- Freeze - thaw weathering
- Wetting and drying
- Chemical weathering
What is salt weathering caused by?
Saline (salty) water
How does saline water enter the rocks?
Through pores or cracks at high tide
What happens as the tide goes out?
Rocks dry and water evaporates forming salt crystals/ As they form, they expand, exerting pressure on rocks causing pieces to fall off
When does freeze-thaw weathering occur?
In areas where temperature fluctuates above and below freezing
How does water enter the rocks?
In the joints and crevices
What happens as the temperature freezes?
Water in cracks freeze and expand. Over time, repeated freeze-thaw weakens the rocks meaning pieces fall off
What happens when rock containing clay gets wet?
Expand and the pressure caused by this breaks off fragments of the rock
What is chemical weathering?
The breakdown of rock by changing its chemical composition
Give an example of chemical weathering
CO2 in the atmosphere dissolves in rainwater, forming weak carbonic acid. The acid reacts with rock that contains calcium carbonate
what is mass movement
The shifting of material downhill due to gravity
When is mass movement more likely in coast areas
When cliffs are undercut by wave action - causing an unsupported overhang which is likely to collapse
What are the 4 types of mass movement
- Landslides
- Slumping
- Rockfalls
- Mudflows
How can material move gradually downwards?
By soil creep
What are slides?
Material shifts in a straight line
What are slumps?
material shifts with a rotation
What are rockfalls?
Material breaks up and falls
What are mudflows
Material flows downslope
What’s an example of an unconsolidated rock?
clay
What’s likely to happen to unconsolidated rock?
They’re prone to collapse as there’s little friction between particles to hold them together
What happens when there’s heavy rain on unconsolidated rock?
It can saturate the rock and reduces the friction making it more likely to collapse
What is runoff
The flow of water over the land
What can runoff do?
Erodes fine particles and transport them downslope
