the study of life in geologic time, as represented by the fossils of animals, plants, and other organisms found in the geologic column

a fossil that regularly appears in certain layers of the geologic column

an organism that scientists consider a step in the evolution from one kind of organism to another higher up on the evolutionary tree of life

the process by which a species, family, or larger group of organisms dies out

a natural energy source that is believed to have formed from fossilized organisms

an organic sedimentary rock formed from fossilized terrestrial plant matter

moderately dense, hard coal; about 70% carbon and dark brown to black in color

dark brown, soft, crumbly coal that is about 30% carbon and includes liquid organic substances

a liquid fossil fuel found underground as crude oil

a gaseous fuel often found with petroleum

the densest and hardest form of coal; very dark in color and more than 90% carbon