Wave , Fluvial and Aeolian Processes Flashcards
Wave processes
- Breaking waves erode the coastline through a range of processes.
- They also supply material to the system in the form of sediment which is either deposited or transported
Abrasion / corrasion
Sand, shingle and boulders picked up by the sea and hurled against a cliff.
Attrition
The wearing down of rocks and pebbled as they rub against each other , making them smaller and rounder.
Hydraulic action
Occurs when waves break against a cliff and air and water become trapped in cracks and become COMPRESSED.
As the wave recedes, the pressure is released and the water and air suddenly EXPAND and the crack is widened.
Wave pounding
Occurs when the mass of a breaking wave exerts pressure on the rock causing it to weaken.
High energy waves ~ exert a force of up to 30 tonnes per m^2.
Solution / corrosion
Involves dissolving minerals.
When fresh water and salty water mix , acidity may increase and carbon- based rocks will be broken down.
Solution ( transportation)
Dissolved material which is carried by the water.
This type of load is invisible .
The minerals remain in solution until the water is evaporated and they precipitate out of the solution.
Suspension
very small particles carried in moving water.
Accounts for the muddy appearance of some sea water.
Larger particles can be suspended in storm events.
Saltation
Small stones bounce along the sea bed.
This occurs when material can not be carried continuously through suspension, but picked up for a short distance only to be dropped again.
Traction
Large boulders are rolled along the sea bed by the force of the flow.
may undergo a partial rotation before coming to rest again.
Longshore drift
- Waves approach the coast at an OBLIQUE ANGLE due to the direction of the dominant wind.
- The SWASH carries material up the beach in the same direction as the wave.
- The BACKWASH moves the material PERPENDICULARLY back down the beach where it is picked up by the next incoming wave.
Types of Erosion
- Abrasion / corrasion
- Attrition
- Hydraulic action
- Wave pounding
- solution
Types of transportation
- Traction
- Saltation
- Suspension
- Solution
- Longshore drift
Deposition
Occurs when velocity and / or volume of water decreases and energy is reduced.
Takes place in coastal environments when:
- sediment accumulation exceeds removal
- waves slow after breaking
- backwash percolates into beach material
- there is a sheltered area such as an estuary.
Fluvial processes
The physical interaction of flowing water and the natural channels of rivers and streams.
Occurs in river mouths which have low energy.
Fluvial erosion
- The main sources of a rivers sediment load is the upper catchment.
- Most channel erosion occurs during high-flow , high energy events.
- Sediment is also supplied by weathering and mass movement that result in material moving into river channels.
Fluvial transportation
Rivers transport material in the same way as waves:
- traction
- suspension
- saltation
- solution
Fluvial deposition
Material is deposited when:
- river enters the sea as there is a reduction in velocity as the flowing water enters the static body of sea water.
- tides and currents moving in the opposite direction create a major resistance.
Largest particles are deposited first and the finest particles are carried out further to sea.
FLOCCULATION of clay particles occurs when fresh water meets salt water, material clumps together due to electrical charges between them in saline conditions.
Aeolian processes
Relating to or arising from the action of the WIND.
Coastal landscapes are exposed to open sea surfaces and heavily influenced by winds.
Aeolian erosion
- Erosive forces increase exponentially with an increase in wind velocity.
- ATTRITION on land is more effective than in water as the material is carried for greater distances and the material is not protected from collisions by the film of water that surround material in rivers or sea.
Aeolian transportation
DEFLATION ~ the removal of material as wind picks up sand particles and moves them.
- Dry sand is much easier for wind to pick up as wetter sand has more moisture which increases cohesion of sand particles making them stick together and become heavier.
- Exception of SOLUTION
Aeolian deposition
- Wind speed slows down
- Usually due to surface friction
- occurs more inland as subject to surface irregularities for friction to occur compared to open water.
- Material carried by the wind is deposited.
