Unit 2: GEOLOGICAL TIME

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Across
  1. 3. Type of fossil created through tree sap.
  2. 5. Fragments in a rock layer must be older than the rock layer that contains them.
  3. 7. When an unusually large amount of organisms disappear
  4. 8. Timescale unit that is smaller than a period.
  5. 9. fossil formed when an earlier fossil of a plant or animal leaves a cavity and then it fills up with sediment and minerals.
  6. 10. A type of fossil evidence of an organism that consist of footprints, claw marks, poopoo, tunnels.
  7. 15. period of time it takes for radioactive isotopes to decay one-half it's original amount.
  8. 17. Gap in the rock record caused my weathering and erosion.
  9. 18. theory that geological processes have been occurring since the Earth has formed.
  10. 19. The Age of Mammals
  11. 20. Second-longest time unit, measured to tens to millions of years and defined by the different life forms.
  12. 21. principle that an intrusion or fault is younger than the rock layer it cuts through.
  13. 23. Third longest time unit on the GTS. Tens to millions of years.
Down
  1. 1. A principle that states that oldest rock you will find at the bottom and youngest towards the top.
  2. 2. A record of Earth's History from its origin 4.6 BYA
  3. 4. method that enables scientist to determine the actual age of a certain rock or object.
  4. 6. Dominance of aquatic life in this Era
  5. 11. establishing an order of past geological events by studying just the rock layers.
  6. 12. Informal unit of time consisting of early Earth and first 3 Eons.
  7. 13. The Age of Reptiles
  8. 14. Longest time unit in the geological time scale
  9. 16. The change in species over time.
  10. 22. A fossil of an organism that was widely abundant and distributed. Existed briefly and used by geologist to identify rock layers.