1. What are sub-aerial processes?
Use this Power Point to make notes about the different types of weathering & mass movement

2. 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.

3. What is weathering?

4. Biological weathering
What has caused the cracks to appear?

5. How do you think these rocks have become weathered?
Chemical weathering
How do you think these rocks have become weathered?

6. 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.

7. What are the different types of weathering?

8. Mechanical weathering
Freeze thaw
Daily temperatures fluctuate around 0oC
Ice occupies 9% more volume
Freeze-thaw process widens joints

9. Mechanical weathering
Thermal Expansion or Insolation
Outer layers of rock warm faster and cool more rapidly
Outer layers peel like an onion (onion skin weathering)

10. Mechanical weathering
Pressure release
Rocks developed under great pressure.
Later exposure releases pressure and exposure to atmosphere.
Cracks develop and sheeting occurs

11. 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
Sodium sulphate & sodium carbonate expand 300% in temperatures ranging 26-28oC

12. Biological Weathering
Tree roots - Biological weathering
Significant on cliff tops and cliff faces.
Plant / tree roots expand along joints and bedding planes
Blocks of rock become detached
Burrowing animals have similar effect.

13. Biological Weathering
Organic acids Decomposition of plant and animal litter = reaction with some minerals = chelation.
E.g.s:
Blue-green algae = shiny film of iron & manganese oxides on rock
Molluscs secrete acids = hollows on rock surface.

14. 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

15. 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

16. Chemical weathering Hydrolysis
Hydrogen in water reacts with minerals = Silicates combine with water = clays
E.g. Breakdown of feldspar (mineral in granite - igneous rock) to kaolin (china clay)

17. Chemical weathering Carbonation
Rainwater contains carbon dioxide, which produces carbonic acid.
Dissolves limestone in to solution (calcium bicarbonate (soluble)).

18. Chemical weathering Solution
Minerals which are soluble dissolve, with increasing acidity in the water

19. Chemical weathering
Rate of chemical weathering increases with temperature – 10oC increase in temperature = 2.5 times increase in chemical reaction rate.
Climate change & Human activity increasing carbon dioxide, sulphur dioxide and nitrogen oxide = e.g. increased acidity in rainfall = e.g. increases rate of carbonation of limestone

20. What is mass movement?

21. What are the different types of mass movement?
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