How Coal is Formed

Coal formation begins when plants die and become stuck in stagnant, oxygen-poor water, such as swamps. The lack of oxygen prevents normal decomposition, preserving the plant matter.

Coal has had a massive and sudden impact, allowing humans to burn ancient organic matter instead of current natural resources like trees for fuel, fundamentally changing history.

Over long periods, layers of sediment are deposited on top of the preserved plants. Under heat and pressure, a process called diagenesis or coalification compresses the plant matter into peat, and eventually, into coal. This entire process is extremely slow, taking millions of years.

Heat and pressure remove hydrogen, nitrogen, and oxygen from the plant matter, leaving behind primarily carbon. The higher the rank of coal, the greater its carbon content, making it shinier, blacker, and more efficient for burning.