Across
- 2. dating that gives a rocks age in actual years
- 3. an intrusive rock body is younger than the rocks it intrudes
- 5. 3.8-2.5 billion years ago
- 7. 3.5 million years ago to today
- 9. new layers of rock will be on top of older layers
- 10. 4.5-3.8 billion years ago
Down
- 1. 251-65.5 million years ago
- 4. comparison of one rock or fossil to another to determine which one is older or younger
- 6. evidence of past species
- 8. amount of time it takes for half of a remaining isotope to decay