coal formation

Coal is formed when the remainder of a plant in a swamp goes beneath the surface and oxygen is cut off. the plant does not rot but forms peat.Then as the plant turns from peat to lignite. this happens when the absence of oxygen and more carbon is present. then after it forms lignite it turns into one of the many types of coal: Bituminous, anthracite, then coke. This is the way coal is formed.