Across
- 3. unstable atoms
- 5. oldest layer is on the bottom
- 6. gives years in order they happened
- 7. radioactive elements give actual age
- 11. scientist who studies fossils
- 13. the rock formed around these
- 14. the remains or traces of a dead plant or animal
Down
- 1. scientist who discovered the significance of tree rings.
- 2. vein of rock is younger than rock
- 4. the fossils tell the relative age
- 8. tree ring dating
- 9. has half-life of 4.5 billion yrs
- 10. study of rocks and rock formations
- 12. time for half unstable atoms to decay