Across
- 4. small events within periods
- 5. widely distributed and around for a short period of time
- 7. atoms of one element breakdown to form another
- 9. a gap in the geologic record
- 10. evidence of activities of ancient organisms
- 12. type of fossil where minerals have replaced organic material
- 16. described as older or younger
- 17. preserves delicate features on rocks
- 18. preserved remains
Down
- 1. division of eras
- 2. solid fossil created by a mold
- 3. hollow area shaped like an organism
- 6. large units of time
- 8. how long an item has been around
- 11. magma that reaches the surface and cools
- 13. magma that cools within the crust
- 14. a break in the earths's crust
- 15. time it takes for half the radioactive material to decay into stable material