The largest fossil forest known to man is “growing” below Illinois. Coal mining in the Illinois, Kentucky and Indiana border region led to the discovery:

The forests grew just a few million years apart some 300 million years ago; and are now stacked one on top of another.

It appears the ancient land experienced repeated periods of subsidence and flooding which buried the forests in a vertical sequence.

What is it that doomed the old forests and gave us our coal?

The six forests straddle a period in Earth history 306 million years ago that saw a rapid shift from an icehouse climate with big polar ice caps to a greenhouse climate in which the ice caps would have melted.