Earth History

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Across
  1. 3. geological processes explained by geological processes
  2. 5. trace remains of organisms in rocks
  3. 7. determine the absolute age of an object
  4. 9. weather conditions over a period of time
  5. 10. divide Earth´s history
  6. 12. a break in geologic record
  7. 13. ordered arrangement of rock layers
  8. 15. time required for radioactive isotope to break down
Down
  1. 1. radioactive isotope
  2. 2. younger rocks lay above older rocks
  3. 4. whether a object is older or younger than other objects
  4. 6. measuring the age of an event or object in years
  5. 8. fossilized structure in sedimentary rock
  6. 11. study of history and structure of Earth
  7. 14. long cylinder of ice