Fossils

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Fossils
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Todays objectives

• Fossils defined
• Describe five ways fossils form
• Know the three types of fossils
• Explain how fossils can be used to determine past
  history

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Definition of fossil

• The remains or physical evidence of an organism
  preserved by geologic processes.
• Most often preserved in sedimentary rocks
• To be considered a fossil an organism must be at
  least 10,000 years or older

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Five Ways fossils form

• Fossils in rocks
• Fossils in amber
• Petrifaction
• Fossils in Asphalt
• Frozen fossils

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Fossils in Rocks

• When an organism dies , it either immediately
  begins to decay or is consumed by other organisms
• Hard parts of organisms (bones , shells) more
  resistant than soft tissue

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Fossils in Amber

• Amber is hardened tree sap
• Insect fossil remains are usually found here
• Along with some frogs and lizards

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Petrifaction

• Process where organic material (living) C or H is
  converted into stone or a similar substance
• Petrified wood is most common example

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Fossils in Asphalt

• Places on earth where there are thick sticky
  pools of the earth
• The La Brea tar pits is an example

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Frozen fossils

• Cold temperatures slow down decay fossils managed
  to stay preserved in ice and snow
• Wooly mammoth would be an example

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Trace fossils

• A fossilized mark that is formed in soft sediment
  by movement of an animal
• There are three types
• Tracks, burrows and coporolites

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Other types of fossils

• Mold
• Casts