geologic timescale

The table and timeline of geologic periods presented here is in accordance with the dates and nomenclature proposed by the International Commission on Stratigraphy. When used in formal writing, specific geological and historical periods and events are capitalized. Some examples: the Silurian Period, the Ice Age, the Neolithic, the Archean; however, when not specific, some historical events remain uncapitalized, as in ice ages. The Earth is thought by geologists to be 4570 million years old. The geologic or "deep" time of Earth's past has been organized into various periods according to events which took place in each period.

Table of geologic periods

style="background:#efefef;" \| Million Years Ago^3,6	style="background:#efefef;" \| Epoch	style="background:#efefef;" colspan="2" \| Period⁴	style="background:#efefef;" \| Era	style="background:#efefef;" \| Eon	style="background:#efefef;" \| Major Events
Present day	Holocene	colspan="2" rowspan="4" \| Neogene⁵	rowspan="7" \| Cenozoic	rowspan="17" \| Phanerozoic	End of ice age and rise of modern civilization
0.011430 0.00013	Pleistocene	Extinction of many large mammals; Evolution of fully modern humans
1.806 0.005 ^*	Pliocene	rowspan="3" \|
5.332 0.005 ^*	Miocene
23.03 0.05 ^*	Oligocene	rowspan="3" colspan="2" \| Paleogene⁵
33.9 0.1 ^*	Eocene	Appearance of first "modern" mammals
55.8 0.2 ^*	Paleocene
65.5 0.3 ^*	rowspan="25" \|	colspan="2" \| Cretaceous	rowspan="3" \| Mesozoic	Dinosaurs reach peak, become extinct. Primitive placental mammals
145.5 4.0	colspan="2" \| Jurassic	Marsupial mammals, first birds, first flowering plants
199.6 0.6	colspan="2" \| Triassic	First dinosaurs, egg-laying mammals, breakup of Pangea into Gondwana and Laurasia
251.0 0.4 ^*	colspan="2" \| Permian	rowspan="7" \| Paleozoic	Permian extinction event- 95% of life on Earth becomes extinct
299.0 0.8 ^*	rowspan="2" \| Carboniferous¹	Pennsylvanian	Abundant insects, first reptiles, coal forests
318.1 1.3 ^*	Mississippian	Large primitive trees, first land vertebrates
359.2 2.5 ^*	colspan="2" \| Devonian	First amphibians, clubmosses and horsetails appear, progymnosperms (first seed bearing plants) appear
416.0 2.8 ^*	colspan="2" \| Silurian	First vascular land plants, first jawed fish
443.7 1.5 ^*	colspan="2" \| Ordovician	Invertebrates dominant; first land plants
488.3 1.7 ^*	colspan="2" \| Cambrian	Major diversification of life in the Cambrian explosion
542.0 1.0 ^*	colspan="2" \| Ediacaran	rowspan="3" \| Neoproterozoic	rowspan="10" \| Proterozoic²	First multi-celled animals
630 +5/-30 ^*,8	colspan="2" \| Cryogenian	Possible snowball Earth period, Rodinia begins to break up
850 0 ⁹	colspan="2" \| Tonian	First acritarch radiation
1000 0 ⁹	colspan="2" \| Stennian	rowspan="3" \| Mesoproterozoic	Formation of Rodinia
1200 0 ⁹	colspan="2" \| Ectasian	rowspan ="2" \|
1400 0 ⁹	colspan="2" \| Calymmian
1600 0 ⁹	colspan="2" \| Statherian	rowspan="4" \| Paleoproterozoic	First complex single-celled life
1800 0 ⁹	colspan="2" \| Orosirian	Transition to oxygen atmosphere
2050 0 ⁹	colspan="2" \| Rhyacian	rowspan="2" \|
2300 0 ⁹	colspan="2" \| Siderian
2500 0 ⁹	colspan="2" rowspan="5" \|	Neoarchean	rowspan="4" \| Archaean²	Stabilization of most modern cratons, possible mantle overturn event
2800 0 ⁹	Mesoarchean
3200 0 ⁹	Paleoarchean	First known oxygen producing bacteria
3600 0 ⁹	Eoarchean	Simple single-celled life
3800		Hadean^2,7	4100 MYA - Oldest known rock; 4400 MYA - Oldest known mineral; 4570 MYA - Formation of Earth

In North America, the Carboniferous is subdivided into Mississippian and Pennsylvanian Periods.
The Proterozoic, Archean and Hadean are often collectively referred to as Precambrian Time, and sometimes also as the Cryptozoic.
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 interval in question.
Paleontologists often refer to faunal stages rather than geologic Periods. The Stage Nomenclature is quite complex. See Harland for an excellent time ordered list of faunal stages. Also see the article on GSSPs.
Historically, the Cenozoic has been divided up into the Quaternary and Tertiary sub-eras, as well as the Neogene and Paleogene periods. However, the International Commission on Stratigraphy has recently decided to stop using the terms Quaternary and Tertiary as part of the formal nomenclature.
The time shown in the "Years Ago" column is that of the end of the interval named beside it.
Hadean is not a formal eon. It was sometimes called Priscoan.
The GSSP for the base of the Ediacaran, ratified in 2004, is a climatic/geochemical marker rather than biostratigraphic. It represents the end of a widespread glaciation event.
Defined by absolute age (Global Standard Stratigraphic Age).

Geologic Timescale

Table of geologic periods

Graphical timeline

References

See also