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Geologic Time Geologic Time. A method of ordering and measuring past events. How Old is this Photograph?. How can you tell? What are some clues?.

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Geologic Time

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  1. Geologic Time A method of ordering and measuring past events

  2. How Old is this Photograph? • How can you tell? • What are some clues?



  5. Eon • Longest unit of geological time • Measured in billions of years • Present eon: Phanerozoic

  6. Era • Second longest geological time measurement • Hundreds of millions of years • Present era: Cenozoic

  7. Period • Third longest geological time measurement • Measured in tens of millions to hundreds of millions of years • Defined by the life forms that were abundant or became extinct • Present: Quaternary

  8. Epoch • Fourth geological time measurement • Measured in million to tens of million of years • Present epoch: Holocene




  12. Relative Dating • Determines the order in which geological events occurred based on stratigraphic principles, fossils and bands of rock

  13. Absolute Dating • Provides a numerical age for the material tested

  14. Relative Dating Techniques

  15. The Principle of Superposition

  16. The Principle of Original Horizontality

  17. The Principle of Lateral Continuity

  18. The Principle of Cross-cuttining

  19. The Principle of Intrusion/Inclusion

  20. Principle of Deformation/Unconformity

  21. Correlation: Similar Rock Patterns

  22. Correlation: Fossils


  24. Absolute Dating Techniques

  25. Geological Records with Strong Annual Cyclicity • Tree growth rings • Coral growth rings • Varves (annual clay sediment layers)


  27. Coral Annual Ring Growth

  28. Varves

  29. Radiometric Dating • Methods relying on the decay of naturally occurring radioisotopes

  30. Most Common Radioisotope Decay • Carbon-14 -> Nitrogen-14 • Potassium-40 -> Argon-40 • Uranium-235 -> Lead-207 • Uranium-238 -> Lead-206 • Thorium-232 -> Lead-208 • Rubidium-87 -> Strontium-87

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