Paleontology Flashcards
record of earths history from origin to present
geologic time scale
second longest time unit
era
third longest time unit
period
an unusually large number of organisms disappear from the rock record around the same time
mass extinction
theory that geologic processes occurring today have been occurring since the beginning of earth
uniformitarianism
establishing the order of past geologic events
relative age dating
principle that sedimentary rocks are deposited in horizontal layers
original horizontality
the oldest rocks are on the bottom, each layer is younger than the one below it
superposition
an intrusion or fault is younger than the rocks it cuts across
cross-cutting relationship
gap in the rock record caused by weathering or erosion
unconformity
method that determines actual age of certain rocks and objects
absolute age dating
emission of radioactive particles and its resulting change over time into other isotopes
radioactive decay
time it takes for a radioactive isotope to decay one half of its original amount
half life
fossil that can form when a shelled organism decays in sedimentary rock and is removed by weathering or erosion
mold
fossil formed when an earlier fossil of a plant for animal leaves a cavity that becomes filled with minerals or sediment
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