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, dividing Earth's history into eons, eras, periods, epochs, and ages.

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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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Which supereon covers 88% of Earth's history?

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Precambrian.

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What are fossils?

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Preserved remains or traces of ancient organisms, providing evidence of past life.

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What does the law of crosscutting state?

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Any geological feature that cuts across another is younger than the feature it cuts.

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What is the youngest rock layer called?

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The most recent layer of sedimentary rock, which is typically found at the top of a sequence.

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What are sedimentary rocks?

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Rocks formed by the accumulation and compaction of mineral and organic particles, often containing fossils.

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What is radioactive dating?

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A method used to determine the age of rocks and fossils by measuring the decay of radioactive isotopes.

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What is the Paleozoic Era known for?

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The era characterized by the emergence of fish, amphibians, and the first land plants.

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What significant event marks the end of the Mesozoic Era?

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The mass extinction event that wiped out the dinosaurs.