Time Scale

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Across
  1. 2. Study of rock layers and layering.
  2. 6. Era that saw the rise of mammals and humans.
  3. 8. Division of time smaller than an eon but larger than a period.
  4. 10. Fossilized tree resin that sometimes preserves insects.
  5. 11. The largest unit of geological time.
  6. 13. A subdivision of a period.
  7. 14. A gap in the geological record caused by erosion or non-deposition.
  8. 18. Period that ended with Earth’s largest mass extinction.
  9. 19. Fossil used to identify and correlate specific geologic periods.
  10. 20. Remains or impressions of ancient life preserved in rock.
Down
  1. 1. Layers of sedimentary rock that record Earth’s history.
  2. 3. Time required for half of a radioactive isotope to decay.
  3. 4. Process of crustal movement shaping Earth’s surface over time.
  4. 5. A time when global temperatures dropped and glaciers expanded.
  5. 7. Type of dating based on radioactive decay.
  6. 9. Science of determining the age of rocks and fossils.
  7. 12. Study of ancient life through fossils.
  8. 15. Period marked by a sudden explosion of life forms.
  9. 16. Era known for the dominance of dinosaurs.
  10. 17. The permanent disappearance of a species.