| A | B |
|---|
| fossil | A preserved clue to life on Earth long ago |
| trace fossil | A fossil that shows changes that long-dead animals made in their surroundings |
| mold | A fossil imprint made by the outside of a dead plant or animal |
| cast | A fossil formed when sediments or minerals fill a mold |
| fossil fuel | Fuel formed from the remains |
| petroleum | A thick brown or black liquid fossil fuel |
| natural gas | A gas, mostly methane, usually found with petroleum |
| peat | The first stage of coal formation |
| lignite | The second stage of coal formation |
| bituminous coal | The third stage of coal formation |
| anthracite | The fourth stage in coal formation |
