Across
- 3. an impression made in sediments by the hard parts of an organism
- 5. unit of geologic time smaller than an era
- 8. a mold filled with sediment and hardened to create a replica of the original fossil
- 10. a piece of an older rock that is stuck in a newer rock
- 11. are the longest unit of geologic time
- 12. the extinction of many species over of short period of time
- 14. the use of the age of rocks and geologic features compared with other rocks and features nearby or organize layers of rocks in chronological order
- 15. unit of geologic time smaller than a period
- 16. the numerical age, in years, or a rock or fossil
- 18. any process by which remains or traces of once-living organisms become fossils
Down
- 1. scientists who study fossils
- 2. process using fossil to match rock layers from different locations
- 4. the preserved remains or evidence of ancient living things
- 6. elements that emit radiation
- 7. the amount of time it takes for half of a radioactive element to decay
- 9. fossil: fossil of a species that was widespread but short-lived and can be used to determine the age of rock layers in different areas
- 13. unit of geologic time smaller than an eon
- 17. scientists who study rocks
- 19. of superposition: the oldest rocks are found at the bottom of undisturbed sedimentary rock layers