Fossils

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Fossils

• When, What, Where
• and Why!
• By Peggy Patterson

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Some Definitions

• Absolute Dating A measure of Time
• Tells how long something has existed by using
  special measurement techniques using
  radioactivity.
• Three Radiometric Tracers
• Uranium-Lead
• Potassium-Argon
• Carbon-14

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• Relative Dating Determining if an object is
  older or younger than another object.
• Compares an unknown object to a known object to
  set its place on a time scale.
• For fossils looks at placement in strata

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• Superposition Oldest at the bottom Youngest at
  the top
• For fossils The older the fossil, the deeper it
  should be.
• Geologic events bring fossils to the surface.

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Types of Fossils

• Fossils in Rocks
• Hard portion of organism buried quickly in
  Sediments and preserved.
• Found in Sedimentary Rocks

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• Fossils in Amber Organism is trapped by tree sap
  that hardens.
• Best Insect fossils occur in this form.

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• Mummification Organism that die in dry places
  can dry out fast enough that bacteria cant cause
  decay.
• Some cultures could preserve humans this way.
• Preserves soft tissue.

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• Frozen Fossils Organisms that get trapped in ice
  or snow.
• Some of the best preserved specimens were from
  glacial melting.
• Similar to Frozen are the organisms sometimes
  found preserved in bogs.
• Specimens of Wooly Mammoth and Man have been
  discovered.

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• Fossils in Tar Organisms that have been
  preserved in sticky ponds of tar that occur
  naturally.
• La Brea Tar Pits in California is one of the most
  studied.
• Saber-toothed cats and other mammals have been
  located there.

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• Trace Fossils Not of organisms themselves but of
  an activity of an organism.
• A footprint could leave a trace that could become
  a fossil.
• Burrows could fill in rapidly and become
  fossilized

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Why Do We Study Fossils?

• Fossils give us clues to changes in the
  environment.
• Finding sea life fossils in the dessert.

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• Changes in Life The older the rock that is
  surveyed contain different organisms than those
  that are younger. (Remember that term
  superposition!)
• Fish fossils are found below amphibians and
  reptiles.

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Using Fossils to Date Rocks

• The Index Fossil A fossil that existed for a
  short well-defined span of geologic time.
• Allows geologists to relatively date rocks found
  in the same strata.
• Allows geologists to compare strata from
  different parts of the world.

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Now You Know The What, When, Where and WhyOf
Fossils!