Peat is plant matter that is partially decomposed under conditions of no oxygen. When dug from the ground peat is about 75 percent water by weight; once dried it is about 60 percent carbon and makes a useful fuel in many regions. Peat forms large and widespread deposits in the northern latitudes, where wet ground (peat bogs and fens) and abundant plant growth favor its preservation.
Peat turns slowly into coal with burial and pressure as gentle heat drives out light hydrocarbons. These volatile compounds become petroleum.
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