Process Of Marnie and aeolian deposition Flashcards
Marnie deposition often takes place when?
Where waves are low energy or where rapid coastal erosion provides an abundant supply of material.
The sea lays down what?
Material when there is a reduction in energy resulting from a decrease in velocity or volume or water.
Situations where deposition occurs include?
When sand and shingle accumulate faster than they are removed.
As waves slow following breaking.
As water pauses at the top of the swash before backwash begins.
When water percolates into the beach material as backwash takes it back down the beach.
What’s are aeolian processes?
They refer to the entertainment,transport, and deposition of sediment by wind.
Why does wind play an important role in shaping the coastline.
It drives the prevailing winds that drives most waves. During the day the wind on the coastal fringe is generally from the sea.
Air moves in response to the small pressure differentials set up by the warmer land and colder air.
What happens when there is a large tidal range?
Large amounts of sand may be exposed at low tide thus providing a supply of sediment to be entrained by the wind.
What type of sediment is the most significant in terms of depositional features at the coast?
Sand-sized sediment
Once entrained the sand is what?
Is generally transported close to the ground and over relatively short distances.
Sand is transported by what?
By wind in two ways, which are depended on the wind speed and how dry or moist the source of sand is.
What is soil creep?
A process similar to traction, where wind rolls or slides sand grains along the surface.
What is saltation?
Where the wind is strong enough to temporarily lift the grains into the airflow to heights of up to one metre for distances up to 20 to 30m
What are sub-aerial processes?
Land based processes which shape the coastline.
These come under heading of weathering and mass movement.
What is sub-aerial weathering ?
Sub-aerial weathering included processes that slowly breakdown the coastline, weaken the underlying rocks and allow sudden movements or erosion to happen more easily.
Material is broken down in what?
In situ, remaining in or near its original position.
Weathering processes are common at the coast due to the presence of air and water and cycles of wetting and drying, and can be categories as what?
Mechanical/physical weathering
Biological weathering
Chemical weathering
Mechanical/ physical weathering is what?
Processes that occur at coasts depend on the nature of the climate.
What is biological weathering ?
Includes processes that lead to the breakdown of rocks by the action of vegetation and coastal organisms.
What is chemical weathering ?
Is common on coastlines as it occurs where rocks are exposed to air and moisture so chemical processes can breakdown rocks.
What is the main chemical process in chemical weathering ?
Solution is the main chemical process and was included in the above as it combines with erosion to produce many distinctive features.
What is oxidation ?
Causes rocks to disintegrate when the oxygen dissolved in water reacts with some rock minerals, forming oxides and hydroxides.
What does oxidation affect ?
Ferrous, iron-rich rocks, and is evident by a brownish or yellowish staining of the rock surface.
What is hydration?
It makes rocks more susceptible to further chemical weathering, although it involves the physical addition of water to minerals in the rock.
Hydration- what does the physical addition of water to minerals in he rock cause it do?
Causes rock to expand, creating stress, which can itself cause the rock to disintegrate. The process weakens the rock and can create cracks, or widen joints allowing further chemical weathering to occur.
What is hydrolysis ?
Mildly acidic water reacts or combines with minerals in the rock to create clays and dissolvable salts; this itself degraded the rocks but both are likely to be weaker than the parent rock, thus making it more susceptible to further degradation.
What is carbonation ?
Occurs where carbon dioxide dissolved in rainwater makes a weak carbonic acid. This reacts with the calcium carbonate in rocks like limestone and chalk to create calcium bicarbonate, which then easily dissolves in water.
