Mineral coal is considered a major natural resource in modern times. This mineral has an important place in the industrial development of any country. But for a long time, a question has been arising in the minds of scientists that nature Koyla kaise banta hai? Since 1825, scientists have been convinced that the mineral coal was formed from vegetation. Geologists have expressed two types of views regarding the origin of coal –
- Self-Local (In Situ Theory) and
- The Drift Theory
In the self-local theory, it has been told that in ancient times, a forest at some place got submerged in the ground due to earthquake or any other reason, due to which coal gradually originated. The displacement theory states that the vegetation was moved from one place to another by the flowing water and then deposited in a river, lake or sea, which gradually formed coal.
What is the mineral coal made of?
The study of flaky coal under a microscope reveals that many types of vegetation serve as raw material for the manufacture of mineral coal. More than three thousand types of vegetation have been found in the coal made in the Carboniferous period / Carboniferous period (30-35 million years ago).
Roots and trunks of above mentioned vegetation have been found in the soil level present below the coal level. This confirms the notion of self-local origin of coal. The vegetation found in coal mainly included ferns, lycopods, some flowering plants, angular trees (pine, cedar, pine) and other classes.
Ferns were large trees up to 30 meters in height. Lycopods were also up to 30 meters high. Their knob-like and arch-shaped roots prove that the plants were water-dwellers. There is not a single plant found in coal that grows or grows in salty water.
Different levels and climates of coal
The wide distribution of different coal levels indicates that they were formed in the marshy parts of the delta and the coastal areas whose bottom gradually went downhill. In such areas water would have been stagnating continuously for many years. Stones called lake-deposited carbonaceous cells are found beneath most of the coal-beds.
For coal formation, it is also necessary that there should be low altitude sites around the basin in which coal is being formed, otherwise a large amount of sand will be mixed with coal from the surrounding area.
Freshwater marshes necessary for the development of vegetation useful in coal formation may be separated from the sea by a barrier of sand or may remain separated by a barrier of vegetation, as it has been found that coal and sea-deposited rock Above coal strata are found with anomalous configuration. This type of condition can be found only in submerged sea shores. Depository cycles are found in most of the coalfields.
The rate of vegetation collection depends on the climate and the vegetation cover. J. According to the opinion of a geologist named Votuni Lewis, it takes about 150 years to build a layer of bituminous coal one foot thick. Similarly, one foot thick strata of anthracite is formed in about 200 years.
The temperate climate is considered best for coal formation. Also moderate to heavy rainfall should be received throughout the year. But heavy snowfall should be absent. Intermittent drought also occurs during coal production. This is confirmed by the water accumulators present in the stems and roots of the plants that went to the coal manufacturing site.
conversion of vegetation to coal
The transformation of vegetation into coal occurs due to biochemical activity during which there is partial decay of vegetation. After that there is conservation of further decay of that substance. This is followed by dynamic chemical reactions. The grade and properties of coal depend on the environment, type of vegetation and the time and nature of bacterial activity of that area. The grade of coal depends on the extent to which metamorphosis has occurred.
When a tree falls on dry ground, its decay starts. Its complex components begin to break down. Due to decomposition, carbon dioxide and water are formed, most of which goes into the atmosphere. Because of this coal cannot be manufactured. But when a plant falls into the water, the process of decay proceeds very slowly by the above method.
An essential condition for the formation of coal is that the above decay process should stop after a limit so that the residual part of the vegetation can be stored. This work is accomplished by the decaying bacteria by making the water toxic, which stops the further decay, which stops the further decay and the residual part starts accumulating. Biochemical reactions release oxygen and hydrogen and carbon gets deposited.
The decaying bacteria are more active on the surface of the plant deposit and attack the more decaying and soft components (protoplasm and cellulose) first. Blocked and hard parts such as waxes, resins, cutins and wood fragments tend to settle on the bottom of the marsh. Here the virulence of the water prevents further decay and the residues start to collect.
What components will accumulate in the humus depends on the bacterium and the time of its activity. That part of the vegetation that survives decay, begins to agglomerate as a jelly-like substance. This jelly gradually starts thickening more and more and eventually it is used to bind the whole substance like glue.
Usually in still water, almost all of the wood is preserved except the very delicate part. Where the resin remains hard and heavy, the water solution dilutes, reducing its toxicity and increasing its further decay. When floods occur, the toxicity of water decreases and vegetation is carried away by shedding.
The dry season is also not conducive to coal formation, because in this, the underwater vegetation material can come in contact with the outside atmosphere due to the fall of the water surface and this increases the rate of decay. Thus the surface of the water plays a very crucial role in the formation of coal. Where the surface of the water remains constant, the vitrene is formed. Vitrane is that type of flaky coal in which very thin and shiny layers remain. No woody structure is visible to the naked eye and its fracture is spherical and coking coal is obtained from these varieties.
manufacture of different types of coal
A decrease in the concentration of water results in a thin layer of cutinous material. Due to the flow of vegetation in a flood, duren is formed. Durane is that variety of coal which is without luster, black in color and looks dirty and dirty in appearance. In the end, peat is obtained by collecting the above mentioned substances in the marsh, which is the first stage of coal formation.
There are chemical, physical and other types of changes in the formation of anthracite from peat. After the formation of peat, the role of bacteria becomes almost negligible and most of the changes are chemical which take place due to change in temperature and pressure. The increase in temperature and pressure is due to the accumulation of sediments in the upper part.
As peat is formed, about 10 percent of the oxygen contained in the vegetation gets lost. In the subsequent reactions, the oxygen liberated combines with carbon to form carbon monoxide and carbon dioxide. The carbon monoxide and carbon dioxide thus formed are released from decaying vegetation and enter the atmosphere. Thus changes go on and vegetation forms peat, peat to lignite, lignite to bituminous coal and finally anthracite.
In India, coal is found in rocks of two horizons. One is Gondwana and the other is Tertiary. Coal of Gondwana period is believed to have been formed by transfer method.
In India, tertiary age coal (which includes lignite) is found in Assam, Jammu and Kashmir, Rajasthan, Tamil Nadu and Kutch. Since this coal is very recent, it did not form a higher grade than lignite (except in the Himalayan region). Anthracite has been formed in this coal only in those places where there is more tectonic pressure.