Geologic Time

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Geologic Time

• How is Earths geologic history classified?

We find no vestige of a beginning,no prospect of
an end. - James Hutton
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Geologic Time Scale

• Record of Earths history from its origin to the
  present
• Based on fossils found in rocks
• Used to correlate geologic events, environmental
  changes and development of life forms that are
  preserved in rocks

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Geologic Time

• Eon
• Longest time unit
• Measured in billion of years
• Archean Eon, Proterozoic Eon, and Phanerozoic Eon
  (Current)

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Geologic Time

• Eras
• Measured in hundreds of millions to billions of
  years
• Paleozoic Era Wide variety of plants and
  animals
• Mesozoic Era Dinosaurs
• Cenozoic Era Mammals, Humans develop

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Geologic Time

• Periods
• Defined by the life forms that were abundant or
  became extinct during the time in which specific
  rocks were deposited
• Measured in terms of tens of millions of years
• Some are named for the geographic region in which
  the rocks of that age were first observed

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Jurassic Period
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Geologic Time

• Epoch
• Measured in millions of years to tens of millions
  of years
• Groups of organisms used to distinguish
• Ex Holocene Epoch, Pleistocene Epoch

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Why study fossils?

• Interpret Earths history
• Determine patterns and cycles to help predict
  future events such as climatic changes
• Locate energy resources (Petroleum geologists
  locate oil)

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Answer in NB

• Why do you think scientists know more about the
  Cenozoic Era than they do about the other eras?
  (Hint Look at their time frames)
• What eon, era, period, and epoch do we live in?