Geological Time Scale and Fossils

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What is the Geological Time Scale?

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A system used by geologists and paleontologists to describe the timing and relationships of events in Earth's history.

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What are fossils?

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Remains or traces of ancient organisms preserved in rock.

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What is Amber?

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Hardened resin of ancient trees.

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What does Precambrian time refer to?

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An informal unit of geologic time consisting of the first three eons during which Earth formed and became habitable.

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What can the presence of marine fossils on mountaintops indicate?

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That these rocks were once below the surface of an ocean.

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What is a mold in geology?

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A cavity in rock that is formed when an organism is buried and then decays.

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What is a cast fossil?

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A fossil that forms when minerals fill a mold and create a replica of the original organism.

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What are index fossils?

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Fossils of organisms that were widespread but only existed for a short period, used to date rock layers.

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What is sedimentary rock?

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Rock formed from the accumulation of sediment, often containing fossils.

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What is the Law of Superposition?

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In undisturbed sedimentary rock layers, the oldest layers are at the bottom and the youngest are at the top.