GEOLOGICAL KNOWLEDGE



Geology is the science of Earth. It covers the science of earth origin and history, internal and external structures and processes of earth materials, mineral and other internal resources.
To study the details of earth, one should have to learn about the physics and chemistry of Earth. Naturally occuring deposits of the earth's crust are classified by engineers into 'soil' and 'rock'. They are further divided with an arbitrary division based on strength, related physical properties and use.

SOIL

Soil is the relatively loose mass of minerals and organic materials and sediments found above the bedrock. Geologically, soil is the natural products of weathering of rocks and decomposition of organic matter. Again, soil mass is an accumulation of individual particles that are bonded together by mechanical means. These particles may range from colloidal to small boulders size(>300 mm).

ROCK

Rock is the natural aggregate of mineral grains bonded together with rigid internal strength. This rock forms the earth's crust which provides the 'bedrock'. Rock is generally used in engineering purpose to mean 'bedrock' or large and hard fragments of 'bedrock'. The exposed bedrock is called the 'outcrops'. Loose deposits on the bedrock are called surface deposits. These surface deposits essentially constitute 'Soil' in the engineering sense.

Soil Forming Processes(Weathering)

Weathering and erosion of rocks and minerals are considered to be the main processes for soil formation. There are three types of weathering processes:mechanical, chemical and biological.

Mechanical processes:

This process means the disintegration or breakdown of rock masses into smaller fragments and subordinate sizes of particles. Spliting action of frost, roots and fire, expansion and contraction due to temperature changes and abrasion are the different mechanical processes.

Chemical processes :

Chemical weathering means the decomposion of minerals and rocks into new compounds. This leads to the formation of finer grained materials such as clay particles, silica, carbonates and iron oxides. This process depends on the presence of water and other solution with temperature. Other solution includes HCl, sulphuric acid, carbolic acid, sodium hydroxide etc. Oxidation, hydration, hydrolysis, carbonation and leaching are the main chemical processes for soil formation.

Biological processes:

In the suitable environment, Bacteria and other microorganisms produce chemical changes to the mineral materials, sometimes by contributing digestive fluids or organic acids.

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