The past is the key to the present

Coal is mostly the remains of fossil plant material buried in swamps with so little oxygen that even bacteria couldn’t survive to feed on it. This implies that climate at the time was warm and wet.

It took twenty million years for the low-lying wetland forests and peat bogs of the late Carboniferous times to build up most of the world's coal supplies. It's taken humans only 200 years to burn up most of them.

How'd the world get to be the way it is? Scientists can answer that question because the landscape is full of clues.

By carefully documenting types of rocks, their composition, and the fossils found within them, scientists can attempt to reconstruct a regional history of events. And regional events fit into the larger geologic history of our planet through correlation. Bits and pieces of evidence overlap, and by putting them together, scientists can build up a picture of how the Earth has changed over time.