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Vocab 2/1

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 daughter isotope--the final stable isotope