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Relative age
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A rock's age compared ti ages of other rocks
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Absolute age
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The number of year's since the rock formed
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Law of superposition
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In horizontal sedimentary rock layers the oldest layer is at the bottom. Each higher layer is younger that the layers below it.
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Extrusion
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Lava that hardens on the surface
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Intrusion
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Magma that cools and hardens into a igneous rock
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Fault
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A break in the Earth's crust
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Unconformity
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The surface where new rock layers meet much older rock layers
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Inclusion
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A piece of rock that is contained in another rock
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Index fossils
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A fossil that is widely distributed and represents a type of organism that only existed briefly
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