The relative age of rocks

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What is an index fossil?

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An index fossil is a fossil that is used by geologists to identify and correlate the age of rock layers. It is typically from a species that was widespread but only existed for a short period of geological time.

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What does unconformity mean in geology?

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Unconformity refers to a gap in the geological record, indicating that sediment was not deposited for a period of time, or that layers were eroded away.

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What is relative age in geology?

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Relative age is the age of a rock or fossil in comparison to other rocks or fossils, rather than an exact age.

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What is the Law of Superposition?

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The Law of Superposition states that in undisturbed sedimentary rock layers, the oldest layers are at the bottom and the youngest layers are at the top.

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What is an intrusion in geology?

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An intrusion is magma that pushes through existing rock layers below the surface, where it cools and solidifies.

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What is absolute age?

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Absolute age is the actual age of a rock or fossil, often determined through radiometric dating methods.

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How do geologists use index fossils?

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Geologists use index fossils to date and correlate the age of rock layers across different geographic locations.

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What is the significance of unconformities?

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Unconformities are significant because they indicate periods of erosion or non-deposition, which can provide insights into the geological history of an area.

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What is the difference between relative age and absolute age?

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Relative age compares the age of rocks or fossils to others, while absolute age provides a specific numerical age.

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What is an example of an index fossil?

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An example of an index fossil is the trilobite, which existed for a relatively short time and is found in many locations.