User:ZeinabFashwal/sandbox

My topic: Coal

 Coal Coal

 Formation: 

(My edits) Coal is mainly formed by the decay of a big amount of plant material that died and got buried deep down in the sedimentary layer. Once the plant material get buried, it forms into peat. The peat when compacted, losses it water and gas content forming into coal.

One theory states that about 360 million years ago, some plants evolved the ability to produce lignin, a complex polymer that made their cellulose stems much harder and more woody. Thus, the first trees evolved. But bacteria and fungus did not immediately evolve the ability to decompose lignin, so the wood did not fully decay but became buried under sediment, eventually turning into coal. About 300 million years ago, mushrooms and other fungi developed this ability, ending the main coal-formation period of earth's history.

At various times in the geologic past, the Earth had dense forests in low-lying wetland areas. Due to natural processes such as flooding, these forests were buried underneath soil. As more and more soil deposited over them, they were compressed. The temperature also rose as they sank deeper and deeper. As the process continued the plant matter was protected from biodegradation and oxidation, usually by mud or acidic water. This trapped the carbon in immense peat bogs that were eventually covered and deeply buried by sediments. Under high pressure and high temperature, dead vegetation was slowly converted to coal. The conversion of dead vegetation into coal is called coalification. Coalification starts with dead plant matter decaying into peat. Then over millions of years the heat and pressure of deep burial causes the loss of water, methane and carbon dioxide and an increase in the proportion of carbon. Thus first lignite (also called "brown coal"), then sub-bituminous coal, bituminous coal, and lastly anthracite (also called "hard coal" or "black coal") may be formed.

The wide, shallow seas of the Carboniferous Period provided ideal conditions for coal formation, although coal is known from most geological periods. The exception is the coal gap in the Permian–Triassic extinction event, where coal is rare. Coal is known from Precambrian strata, which predate land plants—this coal is presumed to have originated from residues of algae.

Sometimes coal seams (also known as coal beds) are interbedded with other sediments in a cyclothem.

(My edits) Coal formation causes the release of gases that escape from coal as it gets compacted. The more compacted the coal is, the more gasses it will release. This phenomena is seen in the sandstones of China.

Type of Coal:

(My edits) Coal is classified by its water, carbon dioxide, and sulphate content. The less the water and sulphate content and the higher the carbon dioxide content is, the higher the quality of coal gets.

Hess’s law (i will add it under Hilts)

(My edits)Hess's law calculates the amount of heat enthalpy that is produced during the formation of coal underground. Coal releases a lot of heat in its formation process.

(My edits) References: 


 * 1) Keller, E. 2011. Environmental Geology. 9th Ed. Pearson Prentice Hall, 596 p.
 * 2) Shuichang, Z., Jingkui, M., Liuhong, L., & Shizhen, T. (2009). Geological features and formation of coal-formed tight sandstone gas pools in China: Cases from Upper Paleozoic gas pools, Ordos Basin and Xujiahe Formation gas pools, Sichuan Basin. Petroleum Exploration and Development Online, 36(3), 320–330. https://doi.org/10.1016/S1876-3804(09)60129-4
 * 3) Heats (enthalpies) of formation of coals and the thermodynamic evaluation of the coal formation process.(Report). (2011). Solid Fuel Chemistry, 45(4), 254–260.