The Geologic Time Scale
Geologic time is divided into eons, eras, periods, and epochs. This allows geologists to catgorize an expanse of time under a single name. The divisions are largely based upon fossils found in the rocks deposited during a particular time interval. Below is the geologic time scale.| Eon | Era | Period | Time of Period | |
|---|---|---|---|---|
| Phanerozoic | Cenozoic | Quaternary | 1.8 million years ago - Present | |
| Tertiary | 65 - 1.8 million years ago | |||
| Mesozoic | Cretaceous | 145 - 65 million years ago | ||
| Jurassic | 213 - 145 million years ago | |||
| Triassic | 248 - 213 million years ago | |||
| Paleozoic | Permian | 286 - 248 million years ago | ||
| Carboniferous | Pennsylvanian | 325 - 286 million years ago | ||
| Mississippian | 360 - 325 million years ago | |||
| Devonian | 410 - 360 million years ago | |||
| Silurian | 440 - 410 million years ago | |||
| Ordovician | 505 - 440 million years ago | |||
| Cambrian | 544 - 505 million years ago | |||
| Precambrian | Proterozoic | 3.0 billion - 544 million years ago | ||
| Archean | 4.6 - 3.0 billion years ago | |||
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