Chapter 9 Vocab "A View at Earth's Past"
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10 terms
Terms | Definitions |
|---|---|
 Geologic Column | an ordered arrangement of rocks layers that is based on the relative ages of the rocks and in which the oldest rocks are at the bottom |
| Era | a unit of geologic time that includes two or more periods |
| Period | a unit of geologic time that is longer than an epoch but shorter than an era |
| Epoch | a subdivision of geologic time that is longer than an age but shorter then a period |
| Evolution | a heritable change in the characteristics within a population from one generation to the next; the development of new types of organisms from preexisting types of organisms over time |
| Precambrian Time | the interval of time in geologic time scale from Earth's formation to the beginning of the Paleozoic era, from 4.6 billion to 542 million year ago |
| Paleozoic Era | the geologic era that followed Precambrian time and that lasted from 542 million to 251 million years ago |
| Mass extinction | an episode during which large numbers of species become extinct |
| Mesozoic Era | the geologic era that last from 251 million to 65.5 million years ago; also called the "Age of Reptiles" |
| Cenozoic Era | the current geologic era, which began 65.5 million years ago; called the "the Age of Mammals" |
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