FORMATION OF SOIL AND THEIR TYPES
On the basis of geological origin of their sediments, soil can be divided into:
a) Physical weathering
b) Chemical weathering
B) Chemical weathering: is the process of chemical decomposition of the original rock. In the case of physical weathering , the rock breaks into smaller smaller pieces with-out a change in its chemical composition.
However , in chemical weathering , the original material may be changed to something entirely different.
For example: the chemical weathering of feldspar Can produce clay minerals.
❖ Most rock weathering is a combination of mechanical and chemical weathering.
Transportation and deposition of soil
a) Transported soils: soil produced by the weathering of rocks can be transported by physical process to other places, such resulting soil deposits are called transported soils.
b) Residual soil: some soils may stay where they are formed and cover the rock surface from which they derive. Such soil deposits are residual soils.
Q) what types of soils are usually produced by the different weathering and transported process?
Transported soils can be sub- divided into five major
categories based on the
transporting agents:
1)gravity transported soil
2) lacustrine (lake) deposits
3) alluvial -soil deposited by running water
4)glacial deposited by glacier
5) aeolian deposited by the wind
examples of transported soil are:
Loess --wind blown deposit with very uniform fine silt
particles
tuff -fine grained slightly cemented volcanic ash
Glacial till –heterogeneous mixture of boulders, gravel,
sand, silt, and clay
Varved clay-alternate layer of silt and clay deposited in fresh water glacial lakes
Marl -vary fine grained soil of marine origin
Peat -a highly aoganic soil consisting almost entirely of vegetable matter in varying stages of decomposition, fibrous, brown to black in colour and highly compressible.
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