Principles of Relative-Age Dating

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What is uniformitarianism?

Back

The principle stating that geologic processes that occur today are like those that occurred in the past.

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What does the Law of Superposition state?

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In sedimentary rock layers, the oldest layers are at the bottom and the younger layers are on top.

Front

Which layer represents the oldest layer in a sequence?

Back

The bottom layer is the oldest.

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What is the principle of intrusions in relative age dating?

Back

Intrusions are younger than the rocks they cut through.

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What does the Law of Original Horizontality state?

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Layers of sediment are originally deposited horizontally under the action of gravity.

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What is lateral continuity?

Back

Layers of sediment initially extend laterally in all directions; they may be laterally continuous even if they are separated by a valley.

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What are unconformities?

Back

Unconformities are 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 the significance of cross-cutting relationships?

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If a geological feature cuts through another, the feature that has been cut is older.

Front

What is relative age dating?

Back

Relative age dating is the science of determining the relative order of past events without necessarily determining their absolute age.

Front

What is an example of a geologic process that supports uniformitarianism?

Back

Erosion, sedimentation, and volcanic activity are examples of processes that occur today and have occurred in the past.