Formation of Coal & Theories associated with coal formation

Formation of Coal

Prepared by: Izhar Mithal Jiskani – 09 MN 98

Formation of Coal Coal is non-renewable fossil fuel formed in ecosystem where plant remain were preserved by water and mud from oxidizatio oxidization n and biodegradation. biodegradation. It can also be described described as “Coal is the compacted and preserved remains of plant matter and it is called a fossil fuel because it was formed from the remains of vegetation that grew as long as 400 million years ago”. It is readily combustible black or brownish-black rock and along with oil and natural gas it is one of the three most important fossil fuels. Coal is formed when accumulated plant debris is altered physically and chemically. The plant debris such as leaves, barks, spores etc settled to the bottom of the swamp and decomposing  begins under the bacterial action. The decomposition is not complete because the stagnant water in the swamps stops the decaying process due to the lack of oxygen. This partially decomposed mate materi rial al is know known n as peat peat.. Peat Peat is the the begi beginni nning ng of coal coal form formin ing g proc proces esss and and is call called ed Coalification.

There are four stages in coal formation: peat, lignite, bituminous and anthracite. The stage depends upon the conditions to which the plant remains are subjected after they were buried - the greater  the pressure and heat, the higher the rank of coal. Higher-ranking coal is denser and contains less moisture and gases and has a higher heat value than lower-ranking coal.

Coal is a sedimentary rock but the forms such as anthracite coal can be regarded as metamorphic rocks because of later exposure to elevated temperature and pressure. It has a wide range of uses; the most important use is for the generation of electricity.

Society of Mining Engineers, Department of Mining Engineers Mehran University of Engineering & Technology, Jamshoro

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Formation of Coal

Prepared by: Izhar Mithal Jiskani – 09 MN 98

Theories associated with coal formation

1. The In-sit In-situ u theory theory (Autoch (Autochtha thanou nous) s) The organic material from which the coal was formed; belongs to the site of deposition. Many researchers researchers have a strong strong objection objection on this theory as this specifies specifies a reverse reverse geological geological cycle but the presence of plant roots under the floor of coal seam signifies the importance of this theory.

2. Drift Theory (Allochthanous) The original vegetation material from which the coal deposit had been formed does not belong to the site of deposition but transported by water to the present site. The supporters of this theory have valid reasons to sustain; the most important one is that the coal is sedimentary rock, its sediments brought down by erosion and deposited to low-lying areas of large water bodies and covered with the other inorganic sediments.