Geological Time Scale

Geologists have given strange names to rocks of different ages. These names, and the ages of the rocks measured in millions of years ago (mya), are given in the following list, as defined by the International Commission on Stratigraphy. Numbers given here are rounded for simplicity.

Note that geologists normally show these dates with the oldest at the bottom, youngest at the top, since that is the order they would be found in geological sediment, but for this history of the Universe it makes more sense to start with the oldest.

Note also that this is not a complete list. It includes only those names most important for this story, plus some others which we do not discuss in any detail.

Precambrian Eon (4600 to 544 mya)

Hadean Era (4600 to 4000 mya)

Archaean Era (4000 to 2500 mya)

  Eoarchean (4000 to 3600 mya)

  Paleoarchean (3600 to 3200 mya)

  Mesoarchean (3200 to 2800 mya)

  Neoarchean (2800 to 2500 mya)

Proterozoic Era (2500 to 542 mya)

  Paleoproterozoic (2500 to 1600 mya)

  Mesoproterozoic (1600 to 1000 mya)

  Neoproterozoic (1000 to 542 mya)

Tonian (1000 to 850 mya)

Cryogenian (850 to 635 mya)

Ediacaran (635 to 542 mya)

Phanerozoic Eon (542 mya to today)

Paleozoic Era (542 to 251 mya)

  Cambrian (542 to 488 mya)

  Ordovician (488 to 444 mya)

  Silurian (444 to 416 mya)

  Devonian (416 to 359 mya)

  Carboniferous (359 to 299 mya)

  Permian (299 to 251 mya)

Mesozoic Era (251 to 66 mya)

  Triassic (251 to 200 mya)

  Jurassic (200 to 146 mya)

  Cretaceous (146 to 66 mya)

Cenozoic Era (66 mya to today)

  Paleogene (66 to 23 mya)

Paleocene (66 to 56 mya)

Eocene (56 to 34 mya)

Oligocene (34 to 23 mya)

  Neogene (23 to 2.6 mya)

  Miocene (23 to 5.3 mya)

Pliocene (5.3 to 2.6 mya)

  Quaternary (2.6 mya to today)

  Pleistocene (2.6 mya to 11,700 yrs)

Holocene (11,700 years to today)