coal geology

Coal is a combustible black or brown sedimentary rock, primarily composed of carbon, formed from ancient plant matter. The process of coal formation, known as coalification, involves the compaction and hardening of peat deposits over geological time. This transformation is influenced by increasing temperature and pressure as the organic material is buried deeper within the Earth's crust.123

The stages of coalification progress from peat to lignite, then to subbituminous, bituminous, and finally to anthracite coal. These stages are determined by the degree of transformation, or rank, and the amount of carbon present. Coal deposits are often found in stratified layers called seams, and their formation is linked to ancient swamp environments, particularly during the Carboniferous Period when global climates were warm and humid.324