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Geologic Time

Geologic Time. Geologic time. Gigaannus: Ga= Billion years Billion years ago: BYA. Major divisions of geologic time. Paleozoic. Mesozoic. Cenozoic. Precambrian. Early Earth History. Precambrian Longest time unit Biological events Primordial puddle Amino acids formed

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Geologic Time

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  1. Geologic Time

  2. Geologic time • Gigaannus: • Ga= Billion years • Billion years ago: • BYA

  3. Major divisions of geologic time Paleozoic Mesozoic Cenozoic Precambrian

  4. Early Earth History • Precambrian • Longest time unit Biological events • Primordial puddle • Amino acids formed • Invertebrates developed

  5. Precambrian, contd… Geologic events • Very volcanic, many igneous rocks formed • Little is known about this era, because rocks were eroded, heated and pressurized, invertebrates are soft.

  6. Paleozoic Era 544-286 MYA Biological events • Mostly marine life forms: • Trilobites • Brachiopods and Crinoids still exist today • Fish

  7. Clicker • Divisions between ERAS in geologic time is based on? • Mass extinctions • Ice ages • Exfoliation • Volcanic eruptions Times up! Timer

  8. Paleozoic, cont… Appalachian Mountains started forming First vertebrates Plant life moved from ocean to land Then animals moved to land. Pangaea came together and major glaciers formed, caused mass extinctions of animals.

  9. Mesozoic Era 245-66.5 MYA • Divided into three periods: • Triassic • Jurassic • Cretaceous

  10. Mesozoic, contd… • Triassic period • Pangaea separated • Climate dried out • Small dinosaurs appeared • First mammals

  11. Mesozoic, contd… • Jurassic • Reptiles dominated • Big dinosaurs! • Birds appeared

  12. Mesozoic, cont’d • Pangaea breaks up (completely) • Volcanic activity • Dinosaurs become extinct

  13. Cenozoic, 66.4 MYA to present • Ice ages occurred • Himalayan mountains formed • Further evolution of plants and animals. Insects, small animals, Modern Humans appeared 200,000 years ago

  14. Fossil • Evidence such as the remains, imprints or traces of once living organisms preserved in rocks.

  15. Clicker When watching an old movie of Stone Age people battling dinosaurs, you should know the story in the movie is fiction because A. stone age people were intelligent enough to avoid dinosaurs. B. stone age people and dinosaurs were not in competition for the same food. C. stone age people and dinosaurs lived at the same time, but in different environments. D. stone age people and dinosaurs did not exist at the same time. Times up! Timer

  16. Fossil types • Replacement fossil- form when bones, teeth or shells are replaced by minerals dissolved in water. • Carbonization fossil- forms when an animal is compressed, leaving behind a carbon film on the surrounding rock.

  17. Fossil types Cast/Mold • Cast- the part that is the shape of the original object. • Mold- the cavity in the rock.

  18. Fossil types • Original remains- insects can be completely preserved in crystallized tree sap (amber). • Trace fossils- fossilized tracks and other evidence of animal activity. • Footprints • Burrow holes • Coprolites

  19. Michigan’s Geologic History • Precambrian • Metamorphic rock • MI was tectonically active • Copper and Iron • Fossilized algae (stromatolites) • Paleozoic • MI was tropical • Ocean (salt water) • Coral => Petoskey stones • MI basin bowl shaped • Youngest rocks in the center older as you move away

  20. Michigan’s Geologic History • Mesozoic • Jurassic rock the youngest what happened to the rest? • Stolen! • Unconformity • What fossils would you not expect to find? • Sorry no dinosaurs in your backyard • Cenozoic • Glaciers

  21. Clicker Times up! Timer

  22. ABSOLUTE DATING • Absolute dating- Any method used to determine the age, in years, of a rock or other object. • Radiometric Dating • Carbon dating • Uranium dating • Other methods • dendrochronology

  23. RADIOMETRIC DATING • Some isotopes of some elements break down (decay) into other elements over time. These are called radioactive isotopes.

  24. EXAMPLES OF RADIOACTIVE ISOTOPES 238Uranium decays to 206Lead 14Carbon decays to 16Nitrogen Parent product daughter product (Unstable) (stable)

  25. RADIOMETRIC DATING • We know how long it takes uranium to decay to lead. This rate of decay is known as its half-life. This rate is quantifiable.

  26. 1 half life C-14 C-14 N-16 HALF-LIFE • It would take 5,730 years for half of the 14C atoms in an object to decay to 16Nitrogen • The half-life is the time it takes for half of the atoms of the parent product to decay to the daughter product. • 14C = 5,730 years • 238U = 4.5 billion years • 40K = 1.248 billion years

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