Relative Age Dating Principles fossil& rocks/ Absolute age rock

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uniformitarianism

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doctrine that Earth's geologic processes have remained constant and uniform throughout history

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Superposition Principle

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determines a relative age of rock layers

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Cross Cutting Principle

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geologic feature or rock body that cuts across or deforms another is the younger of the two

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Unconformities

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contacts between rock units that show a break in the geologic record.

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What are index fossils?

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animal or plant in rock record that characteristics of a certain span of geological time and ennvironment

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Half life

What is it?

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refers to the time it takes for half of a substance to decay or reduce to half its original amount.

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Half life

How do we use it as a clock to determine age?

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is used as a "clock" in radiometric dating to determine the age of rocks, fossils, and other materials.

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Half life

What assumptions do geologists make when using this method?

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radiometric dating, they make several key assumptions to ensure accurate age

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Half life Which rock types can we do this with and why?

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most effective with igneous and metamorphic rocks.