Rocks and it's classification

Rocks

Rock is mixture of two or more minerals.

Minerals

minerals are naturally occurring inorganic solids homogeneous substance composed of atoms having an orderly and regular arrangement with definite chemical composition and characteristic geometric form.

Example quartz(SiO2), Orthoclase and Olivine.

Classification of Rocks

On the basis of their genesis and structure.

Rock are generally group into three classes

1. Igneous 
2. sedimentary
3.  metamorphic

Composition of upper 5 kilometre of earth surface.

Igneous Rocks

Solidification of molten magma on  beneath the surface of Earth.

Non laminar massive structure and whole make up 95% of earth crust.

Igneous rocks based on mode of origin composition.

1. Intrusive or plutonic basic
2. Extrusive or volcanic

Intrusive

Solidification at moderate depth of earth surface.

Example granite, and Bassalt

Coarse grained crystals

Extrusive or volcanic

Solidification takes palace surface of Earth.

Example granite.

Fine grain crystals

Igneous rocks based on chemical three types.

1. Acid. (65-75%).    ----sandstone
2.  neutral. (55-65%).    ---Deorite
3.  basic. (40-55%).  ----- Basalt

Sedimentary rocks

Sedimentary is Latin word 'sedimentum' maining settling.

Sediments derived from the breaking down of Pre existing rocks.

sediments are transported to New palace through wind and water action and deposited in new arrangement and cemented to form sedimentary rocks.

stratification is most common feature of these Rock so these are called a stratified rocks.

They are formed through four stage

1. Weathering
2.  transportation
3.  deposition
4.  Diagenesis

Metamorphic rocks

Metamorphic rockspart are those which have undergone some chemical or physical change from its original form.

transformation of igneous and sedimentary rocks under the influence of chemically active liquid and gases and internal heat and pressure.

There are two broad classes of metamorphism

1. Thermal 
2. dynamothermal

Thermal

Change bring about by heat as a dominant factor.

Dynamothermal

Change bring about  heat and pressure of combine effect.

Example marble graphite

Weathering

Process of disintegration and decomposition of Rocks and minerals, by physical ,chemical and biological process leading to the formation of regolith.

Regolith

Unconsolidated residue of the weathering or weather rock on the earth surface or above the solid Rocks.

Regolith is upper part.

Weathering process

Different weathering agent.

1. Physical /mechanical
2. Chemical (decomposition)
3. Biological (disintegration and decomposition)

Physical or mechanical weathering process

1. Physical condition of rocks
2. Change in temperature
3. Action of water (Fragmentation, Transportation, Decomposition , and action of freezing)
4. Alternate wetting and drying
5. Action of glacier
6. Action of wind and sand blast
7. Atmospheric electric phenomena.

Chemical (decomposition)

1. Hydration
2.  hydrolysis
3.  solution
4.  carbonation 
5. oxidation and reduction

Biological (disintegration and decomposition)

1. Man and animal
2. Higher plant 
3. Microorganism

Physical weathering

Broken down of rocks into small pieces by the physical agent is called physical weathering.

Physical condition of rocks

the most important single factor that determine the rate at which the rocks weather.

Change in temperature

alternate expansion and contraction due to diurnal change in temperature is more common in hot and desert region where the surface of rocks weeken

Action of water

Water act as disintegrating, transporting and depositing agent.

Moving water has a great cutting and carrying force.

It forms gallies and ravines.

Action of freezing

Increase in volume due to freezing of subsurface water exerts an enormous outward or side ward pressure which break apart the Rocks.

Alternate wetting and drying

Some minerals expand or increase in volume on wetting and shrink on drying , caused the large number of  crack in rocks and ground.

Action of wind and sand blast

Dost storms which transport of material from one place to another.

Chemical weathering

Weathering of rocks into small pieces by the chemical agent.

• Chemical weathering involve transformation of new products.

Feldspars +water = Clay minerals soluble cation and anions.

• Chemical weathering are more effective increase the surface area of rocks.
• Chemical weathering is most important factor for soil formation.

Chemical weathering are

1. Hydration 
2. hydrolysis
3.  solution 
4. Carbonation
5. oxidation and reduction

Hydration

chemical combination of water or addition of water of crystallization then swelling and  increase in volume ,minerals lose their structure , become soft and break.

Hydrolysis

dissociation of H2O into H plus and OH minus ion chemically combined with minerals and bring about change such as decomposition of crystallization structure and formation of new compound.

Solution

Minerals which are soluble in water are removed by the continuous flowing of water.

Rocks develop holes rill or rough surface and decompose.

Carbonation

Combination of carbon dioxide with base. Decomposing the minerals of the rocks and soil.

These are quite effective in weathering of rocks.

Oxidation and reduction

Oxidation is the absorption of oxygen ions on the surface of rocks.

Water takes oxygen from atmosphere and form solution which creates crevice and fissure of rocks.

Biological weathering

Decomposition and disintegration of rocks by the biological agent.

Fungi are active in warm and humid environment.

Bacteria are active in cool and humid environment.

Soil science

Carbohydrates and its classification

Enzymes