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Geologic Time

Geology

TermDefinition
Geologic Time Scale Contains information about important events in earth's history. Divisions of time are determined by when major changes happened on earth.
Eon Largest unit of geologic time.
Era Second largest unit of geologic time.
Period Second smallest unit of geologic time.
Epoch Smallest unit of geologic time.
Absolute Age The approximate age of a rock or fossil in years.
Relative Age The age of a rock or fossil compared to other rocks or fossils (older / younger)
Half Life The time it takes for half of the radioactive, parent atoms to decay (change) to stable daughter atoms.
Relative Dating Using the law of superposition, the law of cross cutting, and index fossils in order to compare the age of rocks or fossils (older / younger)
Absolute Dating Using radiometric dating (half life) to determine the approximate age of a rock or fossil in years
Law of Superposition In undisturbed layers of sedimentary rock, the oldest rocks are at the bottom
Law of Crosscutting When a geologic feature (intrusion, erosion, fault) cuts through a rock layer, it is younger than the rock layer it cuts through
Index Fossil Fossil of an organism that lived for a relatively short time, but was widespread.
Trilobite An example of an index fossil
Created by: cyclonescience