What are sub-aerial processes?

Use this Power Point to make notes about the different types of weathering

& mass movement

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.

What is weathering?

What has caused the cracks to appear?

Biological weathering

How do you think these rocks have become weathered?

Chemical weathering

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.

What are the different types of weathering?

Mechanical weathering

Frost shattering• Daily

temperatures fluctuate around 0oC

• Ice occupies 9% more volume

• Freeze-thaw process widens joints

Mechanical weathering

Exfoliation• Outer layers of

rock warm faster and cool more rapidly

• Outer layers peel like an onion (onion skin weathering)

Mechanical weathering

Pressure release• Rocks developed under great pressure.• Later exposure releases pressure and

exposure to atmosphere.• Cracks develop and sheeting occurs

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

Biological Weathering

Biological weathering

• Plant / tree roots expand along joints and bedding planes

• Blocks of rock become detached

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

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

Chemical weathering

Hydrolysis• Hydrogen in water reacts with minerals• E.g. Breakdown of feldspar (mineral in

igneous rock) to granite

Chemical weathering

Carbonation• Rainwater contains

carbon dioxide, which produces carbonic acid.

• Dissolves limestone in to solution (calcium bicarbonate (soluble)).

Chemical weathering

Solution• Minerals which

are soluble dissolve, with increasing acidity in the water

Chemical weathering

Acid rain• Human activity increasing carbon dioxide,

sulphur dioxide and nitrogen oxide• Increases rate of carbonation of limestone

What is mass movement?

What are the different types of mass movement?

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