2) Salt Crystallisation
3) Insolation
4) Wetting and Drying
5) Hydration
1. Freeze-thaw
- Only possible where temperatures fluctuate above and below freezing.
- Possible in semi-arid/mid-latitude environments.
1) Water enters cracks in the rocks because of rain or moisture.
2) Overnight it freezes, expanding causing the cracks to grow.
3) Eventually after repeating this process many times the cracks join causing chunks of rock to fall.
2. Salt Crystallisation
- Would not happen in more humid environments as the salt would be dissolved by rainwater and washed away in rivers or lakes
1) The sun (high insolation) causes the salt in solution to crystallise out of solution.
2) This causes stresses on the rock.
3) This causes disintegration in a similar way to freeze-thaw.
3. Insolation
- Temperatures range from 80°C in daytime to below freezing in hot deserts.
1) These temperature ranges cause rock minerals to expand at different rates.
2) At night the rock minerals contract causing stresses/fractures in the surface rock layers.
3) The surface rock layers disintegrate peeling away from the boulder (known as exfoliation)
4. Wetting and Drying
Occurs when:
- flash floods
- seasonal rains
- coastal fog
- dew
Moisture encourages clay minerals in rocks to swell. Repeated expansion on wetting and contraction on drying causes the rock to disintegrate.
5. Hydration
Minerals absorb water which causes stress and granular disintegration.
e.g. ANHYDRITE was turned into GYPSUM (makes it more susceptible to weathering processes such as carbonation)
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