Time Marches on!

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Across
  1. 6. this eon was 242 million years ago to the present time
  2. 7. is a person who studies fossils
  3. 8. in this time period the Earths continents began to drift together making giant land masses called Pangaeu
  4. 9. a unit of geologic time that includes two or more periods
  5. 11. this made the extinction of the dinosaurs
  6. 12. exists between tow horizontal rock layers and rock layers that are tilted or folded
  7. 16. this time period was the evolution of mammals
  8. 18. the largest division of geologic time
  9. 19. the death of every member of a species
  10. 22. this is a place where Hutton observed results of a geologic processes that would lead him to form his principle or uniformitarianism
  11. 23. the standard method used to divide the Earth's long natural history into manageable
  12. 26. in this time period the Earths landscape began to turn green
  13. 29. a type of fossil that forms when sediments fill in the cavity left from a decomposed organism
Down
  1. 1. this person was a 20th-century vertebrate paleontologist who made important contributions to the study of dinosaurs
  2. 2. a principle that states that geologic change occurs suddenly
  3. 3. this eon was around 4.6 billion years ago to 3.8 billion years ago
  4. 4. any method of determining whether an event or object is older or younger than other events or objects
  5. 5. a subdivision of a geologic time period
  6. 6. this process in which minerals replace an organism's tissues
  7. 8. this eon was around 2.5 billion years ago to 542 million years ago
  8. 10. a mark or cavity made in a sedimentary surface by a shell or other body
  9. 13. a principle that states that geologic processes that occurred in the past can be explained by current geological processes
  10. 14. these are the traces or remains of a living organism that died a long time ago
  11. 15. what time period did the dinosaurs dominate the Earth
  12. 17. this exists where sedimentary rock layers lie on top of an eroded surface of nonlayered igneous or metamorphic rock
  13. 20. this exists where part of a sequence of a parallel rock layers is missing
  14. 21. the time needed for half of a sample of a radioactive substance to undergo radioactive decay
  15. 24. this burial mound at this place resembles the features of a snake
  16. 25. a fossilized mark that is formed in a soft sediment by the movement of an animal
  17. 27. this eon was around 3.8 billion years ago to 2.5 billion years ago
  18. 28. photos are like a __________ the younger ones lie above and the older ones lie underneath