Review#9 earth's history
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Review#9 earth's history

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Review#9 earth's history Review#9 earth's history Presentation Transcript

  • L.O: EARTH’S HISTORY
  • EARTH’S EARLY ATMOSPHEREFORMED FROM OUT GASSING OFVOLCANOES.
  • Geologists have sequenced thegeologic events in past to develop ageologic history of Earth.Scientists use relative age andabsolute age to determine age offossils.
  • Relative age: the age of a fossil, rockor geological event in comparison toanother.
  • absolute age: the real age of afossil.
  • Index fossils: fossils used todetermine relative age of otherfossils, rocks and events.
  • a good Index fossil: wide-spread &lived short time period
  • Volcanic ash also is a good timemarker. Like index fossils wide-spread. Short time period.
  • Now complete page 102-113
  • Radioactivedecay:
  • Radioactive elements:• Radioactive element decay.• The amount of time it takes for half of aradioactive element to decay is half-life.• The half-life of an element cannot be changed.• The half-life of carbon 14 is 5,700 years.• The half-life of uranium 238 is 4.5 billionyears.
  • Carbon 14• Half-life 5,700• Used to date recent fossils-less than 50,000years.
  • Uranium 238• Halflife 4,500,000,000 years.• Uranium’s half life is how we know earth’sage.
  • Complete page 1-7