Soil formation

These are substances which are considered to result from the weathering process. With an exception of nitrates, all salts originate from the mineral. Nitrates originate from the humus.

Mineral matter in the soil are said to be derived from the weathering process breaking of the rocks which form the earth's crust.

This is the process which the parent rocks undergo disintegration (breaking) down to form the fragments or small particles. Weathering process is a combination of disintegration and synthesis (building up process).

It involves series of complex change that alter form of colour, texture, and composition of rock particles. The rock first broken down to smaller fragment and eventually into individually constituent minerals. These fragments can combine with dead organic matter to form a soil layer.

The agents of weathering are the factors that facilitate the weathering process. They include:

1. oxygen
2. water
3. wind
4. temperature
5. plant roots and animal
6. ice
7. human being

1. chemical weathering
2. physical weathering
3. biological weathering

The parent rocks break down into the fragments by the help of animals and plants in this process.

Example: Plant roots, when penetrate through the depression in the rocks, on expanding causing the rock undergo disintegration; finally, the rock gets a fault.

Also, the group of animals when passing in the same area frequently and the burrowing animal they can cause weathering in the soil.

This is the disintegration of rock materials with ought any change in its chemical composition. It is common in area with little vegetation and area with wide temperature range, in this weathering process the parent rocks break to form the fragments due to the physical factor.

These factors are temperature, wind, moving ice, water and earthquakes.

When the earthquake occurs, causes the vibration of the rocks within the soil, which finally collide with each other to form the fragments which combine with other substances then soil is formed.

Moving cold ice on falling on warmed-up rock surface causes the rock to undergo suddenly contraction finally soil particles are formed due to the combination of the weathered materials.

The strong winds may cause the stones /rocks to collide with each other as the result of collision occur which leads to fragmentation.

Ways through which physical weathering takes place:

1. Pressure release
2. Exfoliation
3. Frost sheltering
4. Crystallization

This is the breaking down of rock by chemical alteration of a constitute minerals. The chemical weathering occurs due to the chemical reaction in the soil which destroys the internal structure of a rock. It commonly in warm and wet area, the main agents of chemical weathering is water and acid.

1. Carbonation. This is the process whereby underground rock change its form by weak carbonic acid, which is found in rainwater. The rock such as limestone is changed into calcium bicarbonate, which is weak to physical barrier.
2. Hydrolysis. This is the process in which the substance are broken down by the help of water. When the parent-rocks become into contact with water they disintegrate to form the soil particles.
3. Dissolution. This is the process which the substance dissolves of a solid substance solvent to make a solution. Hence, the large rock they become small particles which combine with organic matter to form soil.
4. Oxidation. This is the gain of oxygen or loss of electrons. This occurs in the rock which is in iron state when they exposed to water and oxygen, oxidation takes place, they change into iron (iii) oxide (rust) form which are weak and easily to be destroyed by any physical barrier.

They include:

1. Nature of the parent rock. The hardest parent rocks cannot undergo disintegration quickly than the soft parent rocks which break down quickly and lead to the formation of fragments which finally combine with the dead organic matter to form the soil. So the soft parent rocks can lead to the formation of soil particles easily than the harder one which delay to form soil particles.
2. Rainfall. The place which there are high rainfall, the rate of the soil formation becomes highest than the regions in which there are low rainfall. The reason is that rainfall, contributes more in the decomposition of the dead organic matter, which finally combine with the other particles to form a soil layer.
3. Temperature. The region with the highest temperature, rate of formation of the soil becomes very high because high temperature on heating the rock-surface causes it to expand but suddenly when the rock surface cools down- contract, these expansion and contraction they led to weathering of that rock. The formed fragment combines with other materials to form the soil.
4. Age of the rocks. Normally the oldest rocks can't undergo disintegration as easy as soft rocks, which disintegrate fastest to form the soil particles.