COASTS: Coastal Processes Flashcards
What are the processes of erosion?
- Abrasion (corrasion)
- Hydraulic action
- Cavitation
- Wave quarrying
- Solution (corrosion)
- Attrition
Abrasion (corrasion)
Rock and sediment transported by the waves smash against he rocks and cliffs, breaking bits off and smoothing the surfaces.
Hydraulic action
Air in cracks in cliffs is compressed when waves crash in.
Pressure exerted by the compressed air breaks off rock pieces.
Cavitation
As waves recede, the compressed air expands violently, again exerting pressure on the rock and causing pieces to break off.
Wave quarrying
The energy of a wave as it breaks against a cliff is enough to detach rock.
Solution (corrosion)
Soluble rocks get gradually dissolved by the seawater.
Attrition
Rock and sediment in the water smash against each other and breaks into smaller pieces.
Rock and sediment transported by the waves smash against he rocks and cliffs, breaking bits off and smoothing the surfaces.
Abrasion (corrasion)
Air in cracks in cliffs is compressed when waves crash in.
Pressure exerted by the compressed air breaks off rock pieces.
Hydraulic action
As waves recede, the compressed air expands violently, again exerting pressure on the rock and causing pieces to break off.
Cavitation
The energy of a wave as it breaks against a cliff is enough to detach rock.
Wave quarrying
Soluble rocks get gradually dissolved by the seawater.
Solution (corrosion)
Rock and sediment in the water smash against each other and breaks into smaller pieces.
Attrition
What are the processes of transportation?
- Solution
- Saltation
- Suspension
- Traction
Solution
Substances dissolve and are carried along in the water.
Eg. limestone dissolved in acidic water.
Saltation
The force of the water causes larger particles to bounce along the sea bed.
Suspension
Very fine material is whipped by turbulence and carried in the water.
Most common transportation in coastal systems.
Traction
Large particles are pushed along the sea bed by the force of water.
Substances dissolve and are carried along in the water.
Eg. limestone dissolved in acidic water.
Solution
The force of the water causes larger particles to bounce along the sea bed.
Saltation
Very fine material is whipped by turbulence and carried in the water.
Most common transportation in coastal systems.
Suspension
Large particles are pushed along the sea bed by the force of water.
Traction
Marine deposition
Sediment carred by seawater is deposited.
Aeolion depostion
Sediment carried by the wind is deposited.
Give two reasons why wind or water might slow down:
- Friction increases
- Flows becomes turbulent
Sub-aerial weathering
The gradual break down or rock by agents such as ice, salt, plants roots and acids.
What are the different types of weathering?
Chemical
Mechanical
Biological
What are the different types of chemical weathering?
Carbonation
Oxidation
What are the different type of mechanical weathering?
Freeze-thaw
Salt crystallisation
Wetting and drying
Exfoliation
Biological weathering
Growing plant roots widen cracks.
Sub-aerial processes
Land based processes that consist of weathering and mass movement.
Carbonation
Sea and rain absorb carbon dioxide forming carbonic acid which then dissolves the calcium carbonate in rocks, such as limestone or chalk, into calcium bicarbonate.
Oxidation
Rocks containing iron (ferrous) compounds experience this when turned into a ferric state when oxygen and water are available, leading to disintergration.
Salt crystallisation
- Saline (salty) water enters pores or cracks in rocks at high tide.
- As the tide goes out the rocks dry and water evaporates.
- Salt crystals form and expand.
- Puts pressure on the rock causing pieces to break off.
Chemical weathering
The breakdown of rock by changing its chemical composition.
Freeze-thaw
- Water enters the joints and crevices in rocks.
- When temperature drops below 0oC, this water freezes and expands.
- Overtime, repeated freeze-thaw action weakend the rocks and causes pieces to fall off.
Wetting and drying
- Clay/shale expands when wet and contracts when dry.
- Creates cracks that are vulnerable.
- Fragments break off.
Exfoliation
- Rock under considerable heat will expand.
- Sea cools this rock causing rapid contraction.
- This repeated process causes the outer layer to crack and peel off.
Mass movement
The shifting of material downhill due to gravity.
When is freeze-thaw weathering likely to occur?
In areas where temperatures fluctuate above and below freezing.
When is mass movement most likely to occur in coastal areas?
When the cliffs are undercut by wave action causing an unsupported overhang.
Give some examples of mass movement:
Soil creep
Rotational slumping
Rock falls
Landslides
Mudflows
Runoff
Soil creep
Slow, gradual movement of material downhill.
Rotational slumping
Material shifts down with a rotation.
What is rotational slumping caused by?
- Heavy rain infiltrates unconsolidated soil.
- Impermeable soil layer traps water - adds weight.
- Undercutting causes collapse on slip plane.
What type of rocks are prone to collapse?
Why?
Unconsolidated rocks.
There is little friction between particles to hold them together.
