Theories of Coal Formation - In Situ and Drift

Coal may be defined as a compact stratified mass of plant debris which has been modified chemically and physically by natural agencies, interspersed with smaller amounts of inorganic matter. Coal can also be said as an organic sedimentary rock, the physical, chemical and technological properties of which depend on its composition and degree of metamorphism. There are two major theories of coal formation, (1) In situ Theory of coal Formation, (2) Drift Theory of Coal formation.