What are sub-aerial processes ?
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Transcript of What are sub-aerial processes ?
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What are sub-aerial processes?
Use this Power Point to make notes about the different types of weathering
& mass movement
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What are sub-aerial processes?
The coast is the narrow zone between the land and the sea.
It is worth remembering that the landscape will be influenced by processes on the land as well as the sea.
Sub-aerial processes include weathering and mass movement. These processes operate on the cliff face to weaken it and provide material for coastal erosion.
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What is weathering?
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What has caused the cracks to appear?
Biological weathering
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How do you think these rocks have become weathered?
Chemical weathering
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Can you explain…
Colin forgot to chill the wine so he put it in the freezer to quickly make it cold – but then forgot it was there!Next time he went to the freezer he found it totally shattered. Explain what has happened.
The water expanded as it froze, creating huge forces.
These shattered the glass bottle.
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What are the different types of weathering?
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Mechanical weathering
Frost shattering• Daily
temperatures fluctuate around 0oC
• Ice occupies 9% more volume
• Freeze-thaw process widens joints
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Mechanical weathering
Exfoliation• Outer layers of
rock warm faster and cool more rapidly
• Outer layers peel like an onion (onion skin weathering)
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Mechanical weathering
Pressure release• Rocks developed under great pressure.• Later exposure releases pressure and
exposure to atmosphere.• Cracks develop and sheeting occurs
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Mechanical weathering
Salt crystallisation• Slightly saline water
enters pore spaces• Evaporation leaves
salt crystals which exert stresses on the rock
• This leads to granular disintegration
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Biological Weathering
Biological weathering
• Plant / tree roots expand along joints and bedding planes
• Blocks of rock become detached
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Chemical weathering
Oxidation• Rocks exposed to
oxygen causes rocks to crumble
• E.g. Iron in a ferrous state is changed by oxygen in to a ferric state.
• Rocks change colour from a blue grey to a reddish brown
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Chemical weathering
Hydration• Rocks capable of absorbing
water• E.g. water added to anhydrite,
gypsum results• Active following periods of wet
and dry weather• Also classed as a
physiochemical process – that is, they swell and exert pressure as well as change chemical structure
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Chemical weathering
Hydrolysis• Hydrogen in water reacts with minerals• E.g. Breakdown of feldspar (mineral in
igneous rock) to granite
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Chemical weathering
Carbonation• Rainwater contains
carbon dioxide, which produces carbonic acid.
• Dissolves limestone in to solution (calcium bicarbonate (soluble)).
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Chemical weathering
Solution• Minerals which
are soluble dissolve, with increasing acidity in the water
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Chemical weathering
Acid rain• Human activity increasing carbon dioxide,
sulphur dioxide and nitrogen oxide• Increases rate of carbonation of limestone
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What is mass movement?
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What are the different types of mass movement?
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