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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.

EonEraPeriodTime of Period
PhanerozoicCenozoicQuaternary  1.8 million years ago - Present
Tertiary        65 - 1.8 million years ago
MesozoicCretaceous145 - 65 million years ago
Jurassic213 - 145 million years ago
Triassic248 - 213 million years ago
PaleozoicPermian286 - 248 million years ago
CarboniferousPennsylvanian325 - 286 million years ago
Mississippian360 - 325 million years ago
Devonian410 - 360 million years ago
Silurian440 - 410 million years ago
Ordovician505 - 440 million years ago
Cambrian544 - 505 million years ago
PrecambrianProterozoic 3.0 billion - 544 million years ago
Archean 4.6 - 3.0 billion years ago

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