wathering and erosion

freze thaw activity

1. the water penetrates the joints, bedding planes, cleavages, faults and pore spaces 

2. the temperature fals below 0*C and turnes to ice 

3. the ioce occupies 9% greater volume than water

4. this means that immence internal stresses are set up within the rock

5. this process is thenm repeated many times, causing the rock to fracure.

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insulation/exfoliation

1. common in areas with large diternal temerature ranges (over 24 hours)

2. the outer layers of the rock heat up and expand more rapidly than the layers at depth during the day.

3. at night the layers cool more quickly and contract more rapidly than those at depth 

4. a series of concentric fractures are initiated and the rock peals off in  layers like an onion 

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hydrolysis

silicate minerals react with water. clay minerals and ions are produced .

orthoclase feldspar decomposes to form Kaolinite(china clay) and releases ions of potassium and silicone into the solution.

2KAlSi3O8+2H+ + H2O = 2K+ + Al2Si2O5(OH)4+4SiO2

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carbonation

1. rainwater falls through the atmosphere and picks up carbondioxide from week carbonic acid (pH6)

2. the water infiltrating into the soil picks up more carbondioxide from the soilair.

3. the week carbonic acid (pH5.5) is capable of disolving carbonate minerals 

4. limestones, made of calcite(calcium carbonate) are most susceptable to this process

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solution

there are few minerales that are redily soluble in water with a pHof 7

Halite and Gypsum are the3 most soluble minerales that occure at the earth's surface, but have limmmited occurance

the important role of solution is in transporting away the the other chemical prosesses such as hydrolosis.

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oxidation

oxidatio is the ability for minerals to incorporate oxygen atoms into their atomic structure 

thisswill mainly affect iron rich minerals readily

biotite mica, hornblende, augite and olivine result in red, brown, orange and yellow coloured soil

the brown staing on granite is due to Fe ions being oxidised follopwing hydrolosis of biotite mica 

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