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Geological Time

TermDefinition
fossil the preserved remains of an organism, or traces of an organism such as a mark or print left by an animal
carbon films a thin film coatings which consist predominantly of the chemical element carbon
mold a fossil that forms when the remains of an organism leave an imprint in the sediment after the organic material has been completely replaced
casts a type of fossil formed when sediment fills a mold of an organic object such as a fossil shell, creating a replica of that object made of sediment
trace fossils fossilized evidence of plant existence or animal movements such as root channels, footprints, and burrows
paleontologist scientist who studies fossils and the fossil record
relative age the dating of events based solely upon the order in which they occurred
absolute age the age given in years, of a fossil, a rock, a feature, or an event; usually determined through radiometric dating
superposition the ordering of sedimentary layers of rock with the oldest on the bottom and the youngest on top
index fossils fossils of organisms belonging to species that existed in large numbers for a relatively short amount of geologic time; used to date the rocks in which they are found
radioactive decay a process by which an unstable atom loses energy by emitting ionized particles over a period of time
half-life the time in which half the atoms of a radioactive material disintegrate
eon the longest division of time in the geologic time scale
era the second-longest division in the geologic time scale, measured in tens- to hundreds-of-millions of years
epoch a division of the geologic time scale that is smaller than a period and measured in hundreds of thousands to millions of years
mass extinction the loss of many species throughout the world in a short period of time
Paleozoic era the earliest of three geologic eras
Mesozoic era includes the Triassic, Jurassic, and Cretaceous Periods and is characterized by the development of flying reptiles, birds, and flowering plants and by the appearance and extinction of dinosaurs.
Cenozoic era pertaining to the present era, beginning 65 million years ago and characterized by the ascendancy of mammals.
Created by: FriedChicken#1