Divisions of Geological Time
The History of the World at a Glance
Numbers in after a period's or epoch's name indicate how many millions
of years ago that period or epoch began.
"Series" and "Group" names given in the maps indicate particular subcategorizations
of the rock formations from the given period or epoch.
"Upper" and "lower" indicate relative time; for example, the Upper
Cretaceous was more recent than the Lower Cretaceous.
| Eon | Era | Period | Epoch | |
| Phanerozoic | Cenozoic | Neogene* | Holocene* 0.006-0.008 | "Age of Mammals"
Human history spans about the last 130th of the last 1% of this period. |
| Pleistocene* 2 | ||||
| Pliocene 5 | ||||
| Miocene 25 | ||||
| Paleogene* | Oligocene 38 | |||
| Eocene 55 | ||||
| Paleocene 65 | ||||
| Mesozoic | Cretaceous 144 | "Age of Dinosaurs"
Also origins of birds and flowering plants |
||
| Jurassic 213 | ||||
| Triassic 248 | ||||
| Paleozoic | Permian 286 | Colonization of land and beginnings of most "fossil fuels" as swamps (upper Paleozoic) | ||
| Carboniferous 360 | Pennsylvanian** | |||
| Mississippian** | ||||
| Devonian 408 | ||||
| Silurian 438 | First abundant worldwide multicellular macroscopic life in the sea (lower Paleozoic) | |||
| Ordovician 505 | ||||
| Cambrian 590 | ||||
| Precambrian or Cryptozoic*** | Proterozoic | (Vendian) up to 900? | (Ediacarian) 600-700 | Few scattered deposits of multicellular, macroscopic fossils, discovered recently. |
| Origin of life; unicellular, microscopic life only | ||||
| Formation of the Earth; no life |
*This system was preceded by another one. In some cases, a period or epoch in the new system approximates or matches one in the older system, and in these cases sometimes the older name is still used. The Cenozoic Era was divided into the Quarternary and Tertiary Periods. The Tertiary Period included all five of the most ancient Epochs, the Pliocene through the Paleocene. The Quarternary Period included the Holocene and Pleistocene, but they were called "Alluvium" and "Diluvium" respectively.
**These are often considered periods in place of the Carbonifeous Period, rather than epochs within it.
***Due to the scattered, rare, and only recently-discovered nature of such old evidence, the Cryptozoic Eon and especially the fossils of the Proterozoic Era are just beginning to be analyzed. Names in parentheses represent part of one of the more well-known proposed ways to define the smaller divisions of the Cryptozoic and the Proterozoic.