Earth History Vocabulary

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The branch of science involving the physical composition and history of the planet.

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Geology

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The system of time measurement involving the formation of and changes of the Earth.

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Geologic Time Scale

Front

Very large division of geologic time; usually referred to as the longest division of time.

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Eon

Front

Subdivision of an eon (Paleozoic, Mesozoic, Cenozoic)

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Era

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Subdivision of an Era: Era, Eon, Period, Epock

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Period

Front

Subdivision of a period; shortest division of geologic time.

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Epoch

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Occurs when a species( organism) dies out and no longer lives on the planet.

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Extinction

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Method of determining the age based on measuring radioactive elements (radiometric)

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Radioactive Dating

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Determination of the age of a rock based on the surrounding evidence

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Relative Age

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A common fossil found in many areas from a specific time; used to help identify the age of other formations.

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Index Fossil