| A | B |
|---|
| Fossils | are remains of living things and are found in sedimentary rocks (51) |
| Determining climates | is done by using fossils (52) |
| Geologic time | is estimated with rocks and fossils (53) |
| Relative Age is measured with | Law of superposition, Law of Cross-Cutting Relationships, unconformities, and index fossils (54) |
| Absolute Age is measured with | radioactive isotopes (55) |
| Radioactive isotopes | decays at a known rate (56) |
| Different isotopes | have different rates of decay (57) |
| Half-life | time for half of isotope to decay to stable element (58) |
| Index Fossils | spread over area and are used to find geologic age (59) |
| Uniformitarianism | geologic events that occured today occured in the past (60) |
