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Dinosaurs and Fossils

Dinosaurs and Fossils

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Dinosaurs and Fossils

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  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, doesn’t 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. 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

  7. Half Life • The time it takes for an element to go to a 50:50 proportion of parent and daughter isotopes • With measurements on very large numbers of elements we can determine their half lives