Coal is basically a sedimentary rock made of various
amounts of decaying organic matter. The origins of coal require a swampy
area that has abundant plant life. This occurred mainly in swamps and in
lagoons producing a spongy, brown material called peat.
Geologic forces buried the peat under the Earth's surface and layers
of peat were further compacted by heat and pressure. The compressed peat
was eventually converted to coal. The greater the heat and pressure, the
harder the coal.
There are times in geologic history where coal formation was
dominate. The Carboniferous Period, named for abundance of carbon
derived from plants (280 to 345 million years ago). Vast regions in
North America and Eurasia produced large coal fields which are still
mined.
