| A | B |
|---|
| prehistoric | before the written history of man on earth |
| fossil | anything left behind by prehistoric life |
| impression | a shape left in something by an object |
| mold | a hardened impression left by an object |
| cast | a mold that has filled up with minerals |
| mammoth | an ancient woolly elephant |
| preserve | keep something as it is |
| extinct | something that once lived on the earth but is no longer found alive |
| saber-toothed tiger | an extinct animal |
| amber | hardened pine sap |
| adapt | change in order to adapt to changes in the enviroment |
| trilobites | animals that lived in the oceans about 600 million years ago |
| geologic time scale | a history of the earth based on observations of rocks and fossils |
| eras | five periods of time that the geologic time scale is divided into |
| period | smaller intervals of time that some eras of the geologic time scale are divided into |
| epochs | still smaller intervals of time that recent periods of geologic time scale are divided into |
| natural gas | a gas found in the earth's crust |
| fuel | a material that gives off heat when it is burned |
| petroleum | a liquid fossil fuel: crude oil |
| swamp | an area of shallow water where a lot of plant life grows |
