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Vocab
Question | Answer |
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uniformitarianism | the principle that geologic processes that occurred in the past can be explained by current geologic processes. |
relative age | the age of an object in relation to the ages of other objects. |
law of superposition | the principle that a sedimentary rock layer is older than the layers above it, and younger than the layers below it if the layers are not disturbed. |
law of crosscutting relationships | the principle that a fault or body of rock (intrusion) is younger than any other body of rock that it cuts through. |
absolute age | the numeric age of an object or event, often stated in years before the present. |
varve | a pair of sedimentary layers (one coarse, one fine) that is deposited in an annual cycle, commonly in glacial lakes, and that can be used to determine absolute age. |
radiometric dating | a method of determining the absolute age of an object by comparing the relative percentages of a radioactive isotope and a stable isotope. |
half-life | the time required for half of a sample of a radioactive isotope to break down by radioactive decay to form a daughter isotope. |
parent isotope | the original radioactive isotope. |
daughter isotope | the final stable isotope. |