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16 Cards in this Set
- Front
- Back
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Eon
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Longest unit of time that is measured in billions of years
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Era
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Next longest unit of time measured in millions to billions of years
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Period
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Unit of time defined by fossils found within specific rock layers
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Epoch
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Smallest division of time usually several million years
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Fossil
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Preserved remains or traces of living organisms
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Relative Dating
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uses geological principles to place events in chronological order
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Principle of Superposition
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Older beds lie under younger beds in any undisturbed geological sequence
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Principle of Horizontality
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Rock beds were originally deposited horizontally
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Principle of Crosscutting
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An intrusion is younger than the rock it cuts across
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Principle of Uniformitarianism
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The present is key to the past
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Absolute Dating
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The actual age of a geological object
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Radiometric Dating
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Process by which scientists determine the ratio of parent to daughter nuclei within
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Daughter Element
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The new element formed after nuclear emission/decay
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Half-life
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The amount of decay over a period of time of a radioactive substance
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Radioactive Isotope
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A radioactive element with a different number of neutrons than the original element
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Radioactive Decay
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An unstable element breaking down to a stable element
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