Geologic Time Scale Concepts

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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 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 can fossils reveal about Earth?

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Fossils can reveal how life has changed over time, how Earth's climate has changed, and how Earth's features have changed.

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How do most fossils form?

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Most fossils form when a living thing dies and is buried under sediment.

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What is extinction?

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The disappearance of a species from Earth.

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In which era did mammals become the dominant group?

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Cenozoic Era.

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What is a fossil?

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A preserved remains or traces of a once-living organism.

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What is the difference between relative dating and absolute dating?

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Relative dating determines the age of a rock or fossil in relation to other rocks or fossils, while absolute dating provides a specific age or date.

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What is a mass extinction event?

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A period in Earth's history when a significant number of species died out in a relatively short period of time.

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What is the significance of the Cambrian Explosion?

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A rapid diversification of life forms that occurred approximately 541 million years ago, marking the beginning of the Paleozoic Era.