Geologic Time Scale

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What is the Geologic Time Scale?

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A system of chronological dating that relates geological strata to time, used by geologists and other Earth scientists to describe the timing and relationships of events in Earth's history.

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What is relative age dating?

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A method used to determine the age of rocks and fossils in relation to one another, without determining their exact age.

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What does the Law of Superposition state?

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In an undeformed sequence of sedimentary rocks, the oldest layers are at the bottom and the youngest layers are at the top.

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What is an index fossil?

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A fossil that is used to define and identify a particular time period in the geologic time scale, typically widespread and existed for a short duration.

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Why is fossil 3 not a good index fossil?

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It is found in multiple layers of the same outcrop, which makes it difficult to determine a specific time period.

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Approximately how long ago did Earth form?

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About 4.6 billion years ago (4.6 bya).

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What is the significance of the Law of Superposition in geology?

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It helps geologists determine the relative ages of rock layers and the fossils within them.

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What is a sedimentary rock?

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A type of rock formed by the accumulation and compaction of mineral and organic particles, often containing fossils.

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What is the difference between absolute age dating and relative age dating?

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Absolute age dating provides a specific age or date for a rock or fossil, while relative age dating places events in order without exact dates.

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What are the main divisions of the Geologic Time Scale?

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Eons, Eras, Periods, Epochs.