How is coal formed?
Coal was formed as massive amounts of vegetation died and fell into the swamp-like surfaces that existed in the heavily vegetated Earth of the Carboniferous Period. Huge mats of waterlogged plant material were formed that resisted decay. Over millions of years, as the climatic and geologic conditions changed, these plant sediments were covered and compacted by other sediments, resulting in their lithification.
Coal is formed in several steps. First dead organic matter falls to the ground and is covered with sediment ( a low oxygen environment). Then peat is formed. This can be burned but produces very little heat and a lot of smoke. During the potato famine in Ireland, peat blocks from the peat bogs were the main source of fuel for much of the population. More heat and pressure are applied by more sediment and Lignite is formed. Lignite will, with more heat and pressure, metamorphose into Bituminous coal. Even more heat and pressure metamorphose the bituminous coal into a nice hard shiny Anthracite. Coal is usually classified into three grades: Lignite, brown coal; Bituminous coal, soft coal; and Anthracite, hard coal. Anthracite is dense, nice and hard, and shiny. It produces the most heat with the least amount of smoke. As a side note, much of the world’s coal deposits were formed during the Carboniferous Period which occurred from about 354 to 290 million years ago during the late Paleozo
