Dinosaurs and Fossils

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Dinosaurs and Fossils

• Determining the age of dinosaur fossils

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Dino Domination

• Dinosaurs ruled the earth for 165 million years
• Mass extinction at the end of the Cretaceous
  period, 65 million years ago

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How do we know?

• Fossils of every shape and size have been found
  on 6 continents
• Limited fossil record but we continue to discover
  more
• We can tell the age of fossils using 2 dating
  techniques

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Dating Techniques

• Relative Dating Dating using rock layers,
  doesnt determine an exact age
• Radiometric Dating ages can be determined using
  radioactive decay of elements

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Relative Dating

• Only technique available in the 18th and 19th
  century
• Relative ages of fossils can be found based on
  the rock layers they are found in
• Principle of Superposition Younger sedimentary
  rocks are deposited on top of older sedimentary
  rocks

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Radiometric Dating

• Ages of rocks and fossils can be more closely
  determined
• Some elements have isotopes that are unstable
  (parent isotope)
• These isotopes have a natural tendency to change,
  or decay (form daughter isotope)
• If we know the proportion of parent and daughter
  isotope present, and its half life, we can find
  the age of the fossil

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Half Life

• The time it takes for an element to go to a 5050
  proportion of parent and daughter isotopes
• With measurements on very large numbers of
  elements we can determine their half lives