The Eras and Periods of Geologic Time

Subject Outline

APrecambrian time: from the time of formation of the oldest rocks to 540 million years ago
BThe Paleozoic Era: from 540 to 245 million years ago
- 1The Cambrian Period
- 2The Ordovician Period
- 3The Silurian Period
- 4The Devonian Period
- 5The Carboniferous Period
- 6The Permian Period
CThe Mesozoic Era: from 245 to 66.4 million years ago
- 1The Triassic Period
- 2The Jurassic Period
- 3The Cretaceous Period
DThe Cenozoic Era: from 66.4 million years ago to the present
- 1The Tertiary Period
- 2The Quaternary Period [see also 411.C.]
  - aThe Pleistocene Epoch [see also 223.E.6.and 232.C.6.]