Where does coal come from?
A reddit user writes:
Most coal comes from the Carboniferous [period].
Plants with a structural polymer called lignin in their wood evolved [during that period], and completely dominated the planet. There were forests of woody club moss relatives called lycopsids that looked like Dr. Seuss trees all over the place.
These days we have organisms like termites with symbiotic bacteria in their stomachs to break down lignin and eat wood, but it took millions of years for decomposers and detritivores to figure out how to eat it fast enough to keep up with the supply of dead trees. For ancient life all this wood might as well have been plastic. Vast, vast amounts of lignin-bearing wood piled up and was buried and we have named lignite coal for it. Carboniferous means carbon-bearing.
Fascinating. I did not know this.