Fossils and rock layers

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Fossils and rock layers

  1. 1. Relative Time Fossils and rock layers
  2. 2. Remind me again… What is the difference between a timeLINE and a timeSCALE?
  3. 3. Remind me again… What is the difference between relative-age dating and absolute-age dating?
  4. 4. What is a fossil? Fossil: The trace or remains of an organism that lived long ago.  Are all organisms preserved as fossils?  There are three types of rocks, do you remember their names?  Which type of rock do you think most fossils are preserved in? Why?
  5. 5. If fossils are organisms of the past, how can they help us tell about the history of the earth?
  6. 6. Index Fossils  A fossil that is found in the rock layers of only one geologic age  They are found in rock layers around the world
  7. 7. For example: Which fossil is a good index fossil?
  8. 8. Rock Layers
  9. 9. Almost one half (approximately 2 billion years) of earth’s history can be seen at the Grand Canyons National Parks through the different rock layers found there It is one of the best places in America to see this much history
  10. 10. If you’re looking at a rock sample, which layer would be the oldest?
  11. 11. This is the law of SUPERPOSITION: in sedimentary rock layers, the rocks are laid out fairly flat, where the oldest is on the bottom and the youngest is on the top.
  12. 12. If nothing disturbs the rock layers they will remain the same. If the rock layers are disturbed, they may end up like this:
  13. 13. What things that can disturb rock layers? •Folding or tilting from shifting plate tectonics •Volcanic intrusions •Faults
  14. 14. Volcanic Intrusions
  15. 15. Faults and plate tectonics
  16. 16. UNCONFORMITY An unconformity is a gap in the geologic record. How could this happen?
  17. 17. Lets practice…
  18. 18. Lets practice…
  19. 19. How about a harder one?

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