Source: Encyclopedia of Earth
Bituminous coal. Image: USGS
Bituminous coal. Image: USGS

Coal is a combustible carbon-based rock. Its origins are in prehistoric earth where generations of dead vegetation were deposited in an oxygen-depleted swampy environment to form peat. As geological forces compressed these deposits, the resulting high temperature and pressure converted peat to coal and, occasionally, coal to diamond. Coal is denser than peat, contains less water, and has higher energy content. The elements found in coal are the same found in the vegetation from which it originated, as well as the soils and waters associated with it. Those elements are most notably carbon, hydrogen, nitrogen, sulfur, and oxygen. Silicon, iron, magnesium, potassium, phosphorus, and virtually the entire Periodic Table of elements are generally present in smaller or trace quantities. Coal is ranked as lignite, bituminous, or anthracite, depending upon energy content; with increasing coalification, moisture content decreases and carbon content increases.

Combustion of coal provided warmth that enabled the human population to move into northern latitudes as earth emerged from the most recent ice age. Coal has been used to heat homes, cook food, raise steam, and make hundreds of consumer products – from dyes to pharmaceuticals, synthetic rubber and plastics to fibers, kerosene to solvents and fuels. Mining of coal has provided jobs for people throughout the world, but has also cut short the life of miners due to prevailing safety and health practices. Coal is the stuff of folklore, songs, and stories often spun into the credentials of local and national politicians. A worldwide abundance of coal provides many countries of the world with opportunities for economic development. Today, in North America, coal is the predominant source of energy used to generate electricity. With advances in clean coal technology, coal is expected to serve as a dominant source of energy well into the future and even beyond the 21st Century.

Further Reading
Schobert, Harold H., 1987. Coal – the Energy Source of the Past and Future. The American Chemical Society, Washington, DC.

Perry, Mildred (Lead Author); Cutler J. Cleveland (Topic Editor). 2007. "Coal." In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth August 28, 2006; Last revised January 22, 2007; Retrieved September 16, 2008]. <>


(2008). Coal. Retrieved from


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