Across
- 2. based on major events
- 3. preserved remains of ancient animals
- 6. a layer of rock
- 11. compared to other rocks to find age
- 12. the change in rock layer
- 14. numbers of years since it formed
- 15. one of the period Paleozoic era
Down
- 1. record of events in geoligic history
- 4. the top layer is older than the bottom layer
- 5. one of the period Paleozoic era
- 7. the exact time it happened
- 8. one of the periods of the Mesozoic era
- 9. based on big events not exact
- 10. one of the period Paleozoic era
- 13. one of the period Mesozoic era