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Weathering

Weathering- disintegration or decay of rocks in situ (original place) at or close to the ground surface.

Types of Weathering

  • mechanical weathering/ Physical weathering- Involves the disintegration of rocks without any chemical changes taking place, It often resuilts in piles of angular rock fragments called scree found at the foot of bare rocky outcrops
  • Chemical weathering- a chemical change occurs when weathering takes place. Rainwater, being slightly acidic, can slowly dissolve certain rocks and minerals (calcium carbonate). Those minerals or particals unaffeted by chemical weathering are usually left behind to form a fine clay deposit.
  • Biological Weathering- involves the actions of flora and fana. plant roots are effective at growing and expanding in cracks in the rocks.

Solution- dissolving of minerals by rainwater

Carbonation- weathering of limestone and chalk by the rainwater

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Mechanical Weathering

Freeze- thaw Weathering

The action of water freezing and thawing in a crack or hole in a rock. It is common in places with temperature fluctuation above and beneath freezing point and where water is plentiful.

1. Water seeps into pores/ cracks in the rock 

2. Water freezes in the rock to form ice- it expands by around 9%

3. The expansion causes stresses in rock and cracks are enlarged

4. Repeated freezing and thawing

5. Eventually rock fragment breaks off and collects as scree at the foot of the rockface

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