Forest Turned To Coal

The air was hot and damp. The ground was soft and marshy. Centipedes as long as your arm crawled around the forest floor. Cockroaches as big as your fist scurried about. And growing thickly everywhere were strange, towering trees and other plants. Huge lizards crept through the plants, snapping up insects with their long tongue. That's what a forest was like during the Carboniferous Period, about 300 million years ago.

(from: Childcraft volume 4)