Eons, Eras, Epochs and Radiometric Dating

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Eons, Eras, Epochs and Radiometric Dating

  1. 1. Eons, Eras, Epochs and Radiometric Dating Meghan Bialk
  2. 2. What is Geologic Time? <ul><li>The geologic time scale is a chronologic model relating rock units to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth </li></ul>
  3. 3. How long is each time period? <ul><li>Eons are half a billion years or more </li></ul><ul><ul><li>There are 4 so far </li></ul></ul><ul><li>Eras are several hundred years </li></ul><ul><ul><li>There are 12 so far </li></ul></ul><ul><li>Epochs are tens of hundreds of years </li></ul><ul><ul><li>There are 37 so far </li></ul></ul>
  4. 4. Geologic Time Scale Author: Richard S. Murphy, Jr.
  5. 5. Radiometric Dating <ul><li>Radiometric dating is a technique used to date materials, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay rate. </li></ul>
  6. 6. Why is it used? <ul><li>Radiometric dating methods are used in geochronology to establish the geological time scale. </li></ul><ul><li>Among the best-known techniques are radiocarbon dating, potassium-argon dating and uranium-lead dating. </li></ul><ul><li>Because it allows the establishment of geological timescales, it provides a significant source of information about the ages of fossils and the deduced rates of evolutionary change. </li></ul>
  7. 7. How is it done? <ul><li>When a fossil is found in a certain type of rock, paleontologists know the approximate date </li></ul><ul><li>To figure out the exact date, they take an element of which they know the half-life and compare it with the fossil they found to get the exact date </li></ul>
  8. 8. An example… <ul><li>Using radiometric dating, paleontologists found that this was from the Pliocene era </li></ul><ul><li>It is a gastropod and attached wormtube </li></ul>

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