| Comparison aspect | Main idea | Example | Keywords |
|---|---|---|---|
| Geologic time scale |
| — | eonserasperiodsepochs |
| • | Rock and fossil records reveal events | mountain building and volcanic activity | Rockfossilrecordsreveal |
| Relative age |
| — | superpositionindexfossils |
| Absolute age |
| — | radioactiveisotopeshalflife |
| • | Earth is about 4.6 billion years old | — | Earthbillionyears |