Geological time scale
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  • 1. I. What is the Geologic Time Scale? a. Based on their interpretations of the rock record, geologists have divided Earth’s 4.56-billion-year history into units that represent specific amounts of time. Taken together, these time spans make up the geologic time scale.
  • 2. I. What is The Geologic Time Scale b. The geologic time scale is divided into sections based on fossil evidence. c. Organisms have become more complex over time. d. Geologic time divisions represent changes in the fossil evidence.
  • 3. Extra Why do Geologists have the time scale? It helps break it up into manageable parts!
  • 4. II.Measuring Geologic Time A. Eras (largest divisions) 1. Precambrian – earliest, 4 billion years 2. Paleozoic – 345 million years 3. Mesozoic – 160 million years 4. Cenozoic – current, so far 65 million years
  • 5. B. Eras are divided into periods (except for Precambrian) C. Cenozoic periods are divided into epochs
  • 6. III. Geologic Eras A. Precambrian 1. Earth forms including seas & mountains 2. Few fossils of jellyfish, worms, bacteria, algae, & fungi
  • 7. Extra How do you date rocks that don’t have organisms in it? URANIUM’s-Lead’s Half-Life Any rock/fossil that is over 50,000 years!
  • 8. B. Paleozoic – 6 periods 1. Invertebrates most common a. Trilobites b. Brachiopods 2. Vertebrates – fish and amphibians 3. Plants – ferns and trees in swampy areas
  • 9. Trilobite
  • 10. Trilobite
  • 11. Trilobite
  • 12. Brachiopods
  • 13. Brachiopods
  • 14. Brachiopods
  • 15. Eryops Eryops
  • 16. Eryops
  • 17. Eryops
  • 18. C. Mesozoic – 3 periods 1. Pangaea began to break apart 2. Cycads & conifers evolved 3. “Age of the Reptiles” 4. Dinosaurs became extinct
  • 19. Tyrannosaurus rex
  • 20. Cycads
  • 21. D. Cenozoic – 2 periods 1. “Age of Mammals” 2. At least 4 ice ages
  • 22. Question of the Day How would a new era start?!?!
  • 23. Science Attack