Across
- 2. The amount of time it takes for half an isotope to decay.
- 5. Fossils used to determine another fossils age.
- 6. Layers of rock.
- 9. Era where Pangaea was formed.
- 10. Outline of the major rocky divisions in earths history.
Down
- 1. An estimate of how old a fossil is by using index fossils.
- 3. The top-most layer is youngest, and the bottom-most layer is oldest.
- 4. Era with only single celled organisms
- 7. The exact age of a fossil found by radiometric dating.
- 8. remains or traces of an organism that lived long ago