Also cool that for a period of like 60 million years, nothing decomposed dead trees. As they would die or fall over, they'd just stay there, piling up. This is where most oil came from. The massive amounts of trees stacking up before bacteria and fungus evolved to decomposed them. Imagine 60 million years worth of trees just lying around.
*Thought I'd add an edit, since this post got quite a few eyes on it: It was mostly coal that all those trees turned into. Not oil.