soil, development
Soil is the product of two processes: the decomposition of rock and the decay of plant and animal life. Rocks disintegrate or fracture into smaller and smaller particles because of alternate expansion and contraction which result from heating, cooling, freezing, thawing, wetting and drying. Chemical weathering of rocks results from reactions of component minerals with oxygen and water and with carbonic acids of atmospheric and biological origin. Organic materials are usually found in the bottoms of drained swamps or lakes in regions with cold temperate climates. These organic materials were accumulated before drainage, from dead water plants and other organisms. These organisms were only a little decomposed because of rather low temperatures and the absence of oxygen at the bottom of the swamps and lakes. Under the effect of air the organic sediments developed into organic soils. The factors that influence the rate and kind of soil development are: the nature of parent material, climate, biological activity, topography or drainage and the age of the developing soil profile.
