coalforming

Coalforming, or coal formation, is the geological process by which plant material deposited in ancient wetlands is transformed into coal through burial, diagenesis, and coalification. The process begins with the accumulation of vegetation in an anoxic swamp, producing peat. As sediment covers the peat, pressure and temperature rise, and chemical reactions remove moisture and volatiles, slowly converting peat into coal over millions of years.

Coalification proceeds through a series of ranks: peat, lignite, sub-bituminous coal, bituminous coal, and anthracite. Each rank represents increasing carbon content and energy density and generally requires greater burial depth and longer heat exposure. The exact path depends on local burial conditions, heat flow, and tectonics. In general, peat is the precursor stage; lignite is the lowest-grade coal; anthracite is the highest grade formed under higher metamorphic conditions.

Coal has been a major energy resource since the Carboniferous period, with vast deposits formed in swamps across what are now Europe, North America, and Asia. Modern coal is mined by surface or underground methods, then processed for use in electricity generation, cement production, and steelmaking (notably coke in iron and steel production).

Environmental considerations include greenhouse gas emissions from burning coal, mining impacts, and land and water disturbances. The study of coalforming helps paleogeographers reconstruct ancient ecosystems and burial histories.