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Dinosaurs and Fossils

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Dinosaurs ruled the earth for 165 million years. Mass extinction at the end of the Cretaceous period, 65 million years ago. How do we know? ... – PowerPoint PPT presentation

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Title: Dinosaurs and Fossils


1
Dinosaurs and Fossils
  • Determining the age of dinosaur fossils

2
Dino Domination
  • Dinosaurs ruled the earth for 165 million years
  • Mass extinction at the end of the Cretaceous
    period, 65 million years ago

3
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

4
Dating Techniques
  • Relative Dating Dating using rock layers,
    doesnt determine an exact age
  • Radiometric Dating ages can be determined using
    radioactive decay of elements

5
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

6
(No Transcript)
7
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

8
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
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