Climate regulates soil formation. Soils are more developed in areas with higher rainfall and more warmth. The rate of chemical weathering increases by 2-3 times when the temperature increases by 10 degrees Celsius (18 °F). Climate also affects which organisms are present, affecting the soil chemically and physically (movement of roots).
The organisms living in and on the soil form distinct soil types. Coniferous forests have acidic leaf litter and form what are known as inceptisols. Mixed or deciduous forests leave a larger layer of humus, changing the elements leached and accumulated in the soil, forming alfisols. Prairies have very high humus accumulation, creating a dark, thick A horizon characteristic of mollisols.
The rock from which soil is formed is called parent material. The main types are: eolian, glacial till, glacial outwash, alluvium, lacustrine parent material and residual parent material, or bedrock. Pedologists use the following formula for understanding soil formation:
s = f (cl, o, r, p, t, ...)
where s - soil properties; cl - regional climate; o - potential biota, r - topography; p - parent material; t - time; ... - additional variables.