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What is the Principle of Original Horizontality?

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It states that rock-forming materials are deposited in horizontal layers.

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What does the Principle of Uniformitarianism state?

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It states that geologic processes that occur today are similar to those that have occurred in the past.

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Who studies fossils?

Back

Paleontologists are scientists who study fossils.

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What is a Half-life?

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The time required for half of the parent isotope to decay into daughter isotopes.

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What does the Principle of Superposition explain?

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In undisturbed rock layers, the oldest rocks are on the bottom.

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What is Absolute Age?

Back

The actual age of a rock or fossil, determined by methods such as radioactive dating.

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What is Relative Age?

Back

The age of a rock or fossil in comparison to other rocks or fossils.

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What are Index Fossils?

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Fossils of organisms that were widespread but only existed for a short period, used to date rock layers.

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What are Unconformities?

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Gaps in the geological record that occur when rock layers are eroded or not deposited for a period of time.

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What is Radiometric Dating?

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A method used to date materials by comparing the abundance of a radioactive isotope to its decay products.