Geologic History

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Across
  1. 2. has a half-life of 1.251×10 to the ninth years
  2. 4. buried erosional surface
  3. 8. the oldest geologic time interval of Earth
  4. 9. has a half-life of 4.5 billion years
  5. 11. a form of life that had become extinct 251 million years ago
  6. 13. disintegrate at a predictable rate
  7. 15. have a wide geographic area and existed for a short geologic time
  8. 16. The Acadian Mountains were formed as a result of North America and this
  9. 17. the approximate age of the universe
  10. 18. the event that occurred earliest in geologic history
Down
  1. 1. younger rock layers are on top of older rock layers
  2. 3. the first organism in line for the evolution of life on Earth
  3. 5. the youngest geologic time interval of Earth
  4. 6. what many scientists believe caused the mass extinction of dinosaurs and ammonoids
  5. 7. the last organism in line for the evolution of life on Earth
  6. 10. most often used when determining the age of fossil bones in sediments deposited during the Holocene Epoch
  7. 12. The division of Earth's geological history into eons, eras, periods, and epochs is based on this
  8. 14. group of organisms that existed for the greatest length of time
  9. 19. what living things have undergone in a theory