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How Coal Was Formed
Coal is a combustible mineral formed from the remains of trees, ferns and other plants that existed and died before the time of the dinosaurs.
Coal, along with petroleum and natural gas, is a "fossil fuel", energy that can track its beginnings to once-living organic materials. A combustible mineral, coal can trace its ancestry back to the time of the dinosaurs. It developed from the remains of trees, ferns and other plants that existed and died in tropical-like forests between 400 million and 1 million years ago.
Over vast spans of time, many layers of plants were buried under prehistoric forests and seas. Geological processes involving pressure and temperature compressed and altered the plant remains, increasing the amount of carbon present. Millions of years later, the material that once had been living plants was transformed into what we know as coal.
Coal that was formed in swamps covered by sea water contains a higher sulfur content; low sulfur coal was generally formed under freshwater conditions. Coal's complex chemical structure contains other elements as well - primarily carbon, hydrogen and oxygen, but also nitrogen and variable trace quantities of aluminum, zirconium and other minerals.
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