| Term | Definition |
|---|---|
| fossil | the remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock. |
| original remains | the unchanged fossilized remains of animals and plants. |
| ice core | a core removed form an ice sheet |
| relative age | The geologic age of a fossil organism, rock, or geologic feature or event defined relative to other organisms, rocks, or features or events rather than in terms of years. |
| index fossil | a fossil that is useful for dating and correlating the strata in which it is found. |
| absolute age | the true age of a rock or fossil. |
| half-life | the time taken for the radioactivity of a specified isotope to fall to half its original value. |
| uniformitarianism | the theory that changes in the earth's crust during geological history have resulted from the action of continuous and uniform processes. |
| geological time scale | a system of chronological measurement that relates stratigraphy to time, |
