Relative%20Dating%20Notes

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Relative Dating Notes
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Relative Age of Rocks

• Relative Dating Order rocks deposited tells you
  relative age of rocks (order from old to young)
• Geologic Cross-Section Maps show the structure
  of rocks underground.
• Can determine the relative age of rocks by using
  5 geologic principles

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Law of Superposition

• In sedimentary rock, the oldest layer is on
  bottom youngest is on top.

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Canyonlands, Utah
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Law of Original Horizontality
Sediments deposited in flat, horizontal layers.
If rock layers are folded or at an angle, they
were disturbed after originally deposited
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Raplee Monocline, Utah
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Unconformity
Surface where a break in deposition of sediments
occurred or period of erosion.
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Eastern Grand Canyon
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Law of Cross Cutting Relationships
Fault lines or igneous rock intrusions are
younger than the rock it cuts across.
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Hance Rapids, Grand Canyon
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Principle of Inclusion
Rock material trapped inside igneous intrusion
or sedimentary rock layer is older than rock that
surrounds it.
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Lake Pleasant
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