Soil Formation - Introduction of Soil Mechanics | Soil Mechanics Notes- Agricultural Engineering PDF Download

Soil Formation

Based on the formation, soil can be divided into two groups:
i) soils which are formed due to physical and chemical weathering of the parent rocks
ii) soil which are of organic origin. The causes of the physical weathering of parent rocks are the impact and grinding action of flowing water, wind, ice and splitting action of ice, plants and animals. Gravel and sand are the soil those are formed due to physical weathering of parent rocks. The causes of the chemical weathering of the parent rocks are oxidation, hydration, carbonation and leaching by organic acids and water. Clay and some extent silt are the soils those are formed due to chemical weathering of parent rocks. Figure 1.1 shows the various types of soils based on their formation.

Figure 1.2 shows the various types of soils formed due to weathering of parent rocks. The soils those are formed due to the weathering of parent rocks can be divided into two groups:
 i) Transported soil and
ii) Residual soil.
The soil is called Transported soil if the products of rock weathering are transported from the place where they originated and re-deposited to any other place. The soil is called Residual soil if the products of rock weathering are still located at the place where they originated.

Depending upon the way of formation, the transported soil can be divided into five types: i) Alluvial deposit
ii) Aeolian deposit
iii) Glacial deposit
iv) Lacustrine deposit
v) Marine deposit.
The Alluvial soils are deposited from the suspension of flowing water. The soils are called Aeolian if they have been transported by wind. If the soils have been transported by ice are called Glacial deposit. Lacustrine soils have been deposited from the suspension in still and fresh water of lakes. Marine soils have been deposited from the suspension in sea water.