Geologic timescale
A timeline of geologic periods.(not shown to scale)
| Years Ago3,6 | Epoch | Period/Age4,5 | Era | Eon | Major Events | |
|---|---|---|---|---|---|---|
| Present day | Holocene | Quaternary | Cenozoic | Phanerozoic | ||
| 11,430 | Pleistocene | Extinction of many large mammals. Evolution of fully modern humans | ||||
| 1.81 million | Pliocene | Tertiary | Neogene | |||
| 5.33 million | Miocene | |||||
| 23.0 million | Oligocene | Paleogene | ||||
| 37.2 million | Eocene | |||||
| 55.8 million | Paleocene | |||||
| 65.5 million* | Cretaceous | Mesozoic | Dinosaurs reach peak, become extinct. Primitive placental mammals | |||
| 146 million | Jurassic | Marsupial mammals, first birds, first flowering plants | ||||
| 200 million | Triassic | First dinosaurs, Egg-laying mammals | ||||
| 251 million* | Permian | Paleozoic | Permian extinction event- 95% of life on Earth becomes extinct | |||
| 299 million | Carboniferous1 | Pennsylvanian | Abundant insects, first reptiles, coal forests | |||
| 318 million | Mississippian | Large primitive trees | ||||
| 359 million | Devonian | First amphibians, clubmosses and horsetails appear, progymnosperms (first seed bearing plants) appear | ||||
| 416 million* | Silurian | First land plant fossils | ||||
| 443 million* | Ordovician | Invertebrates dominant | ||||
| 488 million* | Cambrian | Major diversification of life in the Cambrian explosion | ||||
| 542 million* | Neoproterozoic2 | Proterozoic | Precambrian7 | First multi-celled animals | ||
| 1.0 billion | Mesoproterozoic | |||||
| 1.6 billion | Paleoproterozoic | First Complex single-celled life | ||||
| 2.5 billion | Archaean | Simple single-celled life | ||||
| 3.8 billion | Hadean8 | 4.1 billion- Oldest known rock;
4.4 billion- Oldest known mineral; 4.57 billion- Formation of Earth |
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1) In North America, the Carboniferous is subdivided into Mississippian and Pennsylvanian Periods.
2) Discoveries in the past quarter century have substantially changed the view of geologic and paleontologic events immediately prior to the Cambrian. The nomenclature has not stabilized. The term Neoproterozoic is used here, but other writers might equally well have used one or more of the terms 'Ediacarian', 'Vendian', 'Varangian', 'Precambrian', 'Protocambrian', 'Eocambrian', or might have extended the Cambrian further back in time. All of these terms are usually treated as a subset of the Proterozoic rather than a period between the Paleozoic and the Proterozoic.
3) Dates are slightly uncertain with differences of a few percent between various sources being common. This is largely due to uncertainties in radiometric dating and the problem that deposits suitable for radiometric dating seldom occur exactly at the places in the geologic column where we would most like to have them. Dates with an * are radiometrically determined based on internationally agreed to GSSPs. The dates quoted above are according to the International Commission on Stratigraphy 2004 time scale. All dates given are for the end of the epoch in question.
4) Paleontologists often refer to faunal stages rather than geologic Periods. The Stage Nomenclature is quite complex. See http://flatpebble.nceas.ucsb.edu/public/harland.html for an excellent time ordered list of faunal stages. Also see the article on GSSPs.
5) In common usage the Tertiary-Quaternary and Paleogene-Neogene-Quaternary Periods are treated as equivalents to the Mesozoic and Paleozoic Periods. The term 'Period|Age' (e.g. 'Neogene Period|Age') is sometimes used instead of 'Period'.
6) The time shown in the "Years Ago" column is that of the end of the Epoch in the "Epoch" column.
7) Precambrian was sometimes called Cryptozoic.
8) Hadean was sometimes called Priscoan.
