Revision:Weathering 2

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Chemical Weathering

- Solution - Minerals dissolve in water and are removed in solution.

- Hydration - Incorporation of water into the crystalline structure of a rock, and it becomes easier to erode.

- Hydrolosis - The hydrogen and hydroxyl ions of water break the rock down.

- Oxidation - The chemical combination of oxygen with a mineral, making it easily eroded.

- Reduction - Chemical removal from a mineral, making it easily eroded.

- Carbonation - Combination of rainwater and carbon dioxide in the atmosphere, forming carbonic acid. This then attacks limestone, to form calcium hydrogen carbonate which will dissolve and be removed.

Mechanical Weathering

- Pressure Release - An overlying rock is removed, and the underlying may expand and fracture.

- Freeze-thaw - Water in pores and cracks in the rock freezes, and expands by approx 10%. When repeating several times, the crack or pore expands and deepens, and the rock fractures.

- Temperature Change - Minerals within rocks may expand and contract at different rates, possibly causing lines of weakness and fracturing.

Boilogical Weathering

- Root action - Roots grow into cracks and weaknesses in rocks, and deepens it and fractures the rock.

- Trampling - Feet of humans and/or animals may damage rocks.

- Humic acids - Carbon dioxide and acids produced by soil organisms chemically attack rocks.

Rock Types

• Igneous

• • Originated from magma

• • Such as Granite, Basalt

• Metamorphic

• • Originated from Igneous and Sedimentary Rocks
  • Such as Marble (from Limestone), and Mudstone (Slate)

• Sedimentary

• • Originated from Mechanical Breakdown, Organic Accumulation, or Chemical Precipitation

• • Such as Conglamerate Sandstone (Mechanical Breakdown), Coal (Organic Accumulation), or Gypsum (Chemical Precipitation)