Across
- 4. when layers of rock is older than another layer
- 5. first known glaciations occurred
- 9. exact age of someone
- 10. The time era ends when a ___ happens
Down
- 1. is the youngest layer/newest
- 2. the remains or impression of a prehistoric organism
- 3. is the oldest layer
- 6. not an exact number or age
- 7. modern bases of life was in place
- 8. earth's crust cooled during this time