The first step in coal formation is accumulation of organic debris in a peat swamp. In most environments, such as the forest floor, plant material decays as fast as it is produced, so it does not accumulate. However, in a peat swamp, stagnant water that does not contain oxygen inhibits the decay of organic material allowing it to accumulate and form peat. Burying the peat with sediment further inhibits the decay of peat.