Weathering Processes
• Chemical weathering
– Change in chemical structure/ composition of
minerals
– Examples
– Hydrolysis
KAlSi3O8 + HOH HAlSi3O8 + KOH
(Orthoclase feldspar) Acid-silicate K hydroxide
2 HAlSi3O8 + HOH Al2Si2O5(OH)4 + 4SiO2
Kaolinite
HalSi3O8 + HOH Al(OH)3 + SiO2
Gibbssite

Weathering Processes
• Chemical weathering examples
– Hydration. The combination of solids with water to form hydrates.
2Fe2O3 + 3H2O 2Fe2O3.3H2O
Hematite (reddish) Limonite (yellowish)
– Carbonation and Other Acid Process/Acidification.
CaCO3 + H2CO3 Ca(HCO3)2
Limestone Carbonic acid Soluble bicarbonate
– Oxidation. Removal of one or more electrons from an ion
4FeO + 3O2 2Fe2O3
Ferrous Oxide Hematite (Ferric oxide)
– Solution. Dissolving of simple salts as carbonates or chlorides.
CaCO3 + 2 H H2CO3 + Ca++
– Complexation. Formation of organic matter complexes

Factors Influencing Soil Formation
• Dokuchaev (1846-1903), a Russian Pedologist, first to
publish a soil-forming factor equation :
S= f (cl, o, p) t°
– S = soil; cl= climate; o= the organisms (plants and
animals) p=the geologic substratum; t°= the relative age
of the soil
• Jenny (1961), formulated a soil-forming factor
equation: S= f (cl, o, r, p, t, …)
– Climate. Precipitation and temperature,
– Organisms. Vegetation, microbes and soil animals
– Relief. Slope aspect and landscape position
– Parent Material. Geological or organic
– Time