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The Formation of Sediments

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Presentation on theme: "The Formation of Sediments"— Presentation transcript:

1 The Formation of Sediments
Mechanical Weathering The alteration of rock by physical action Freeze-thaw Collision/abrasion Exfoliation (expanding ‘onion’ layers of rock) Trends in Mechanical Weathering Big pieces get smaller Angular pieces get rounder Stronger pieces last longer 1

2 The Formation of Sediments
Chemical Weathering The alteration of rock minerals by chemical action Carbonic acid (rainwater and carbon dioxide) Oxidation Organic acids Which minerals would be the most easily attacked by chemical action? The “mafic” minerals (black and green) olivine, pyroxene, amphibole, and biotite 2

3 Chemical Weathering Products
Soluble compounds Get carried away ‘in solution’ by water Insoluble compounds Remain/stain the rock – rust New minerals The clay minerals Individual crystals of clays are very small Residual crystals of the stable minerals Feldspars Quartz 3

4 Working together Mechanical weathering Chemical weathering
Can increase the rate of chemical weathering By increasing the surface area of the rock Chemical weathering Can increase the rate of mechanical weathering By weakening the connections between mineral grains 4


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