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Geologic Times Vocab
| Term | Definition |
|---|---|
| fossils | the preserved remains of an organism, or traces of an organism such as a mark or print left by an animal |
| carbon films | 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 |
| paleontologists | 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 of the Phanerozoic Eon, spanning from 541 to 252.17 million years ago. |
| Mesozoic era | an interval of geological time from about 252 to 66 million years ago. |
| Cenozoic era | the current and most recent of the three Phanerozoic geological eras, following the Mesozoic Era and covering the period from 66 million years ago to present day. |
Created by:
LovelyyBRJ
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