Geologic time scale

A timeline of geologic periods in accordance with the dates and nomenclature proposed by the International Commission on Stratigraphy.

(not shown to scale)

Years Ago3,6	Epoch	Period/Age4,5		Era	Eon	Major Events
Present day	Holocene	Quaternary		Cenozoic	Phanerozoic	End of ice age and rise of modern civilization
11430	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					Appearance of first "modern" mammals
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, breakup of Pangea into Gondwana and Laurasia
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, first land vertebrates
359 million		Devonian				First amphibians, clubmosses and horsetails appear, progymnosperms (first seed bearing plants) appear
416 million*		Silurian				First vascular land plants, first jawed fish
443 million*		Ordovician				Invertebrates dominant; first land plants
488 million*		Cambrian				Major diversification of life in the Cambrian explosion
542 million*		Ediacaran		Neoproterozoic	Proterozoic2	First multi-celled animals
630 million*,8		Cryogenian				Possible snowball Earth period, Rodinia begins to break up
850 million		Tonian				First acritarch radiation
1.0 billion		Stennian		Mesoproterozoic		Formation of Rodinia
1.2×109		Ectasian
1.4×109		Calymmian
1.6×109		Statherian		Paleoproterozoic		First complex single-celled life
1.8×109		Orosirian				Transition to oxygen atmosphere
2.05×109		Rhyacian
2.3×109		Siderian
2.5×109				Neoarchean	Archaean2
2.8×109				Mesoarchean
3.2×109				Paleoarchean
3.6×109				Eoarchean		Simple single-celled life
3.8×109					Hadean2,7	4.1×109 - Oldest known rock; 4.4×109 - Oldest known mineral; 4.57×109 - Formation of Earth

1) In North America, the Carboniferous is subdivided into Mississippian and Pennsylvanian Periods.

2) The Proterozoic, Archean and Hadean are often collectively referred to as Precambrian Time, and sometimes also as the Cryptozoic.

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 interval in question.

4) 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.

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 interval named beside it.

7) Hadean was sometimes called Priscoan.

8) 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.

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The following five timelines show the geologic time scale to scale. The first shows the entire time from the formation of the Earth to the present, but this gives little space for the most recent eon. The second timeline shows an expanded view of the most recent eon. In a similar way, the most recent era is expanded in the third timeline, the most recent period is expanded in the fourth timeline, and the most recent epoch is expanded in the fifth timeline.

Horizontal scale is Millions of years (above timelines) / Thousands of years (below timeline)

See also

• Fossils and the geological timescale
• Cosmological timeline
• Lunar geologic timescale
• Anthropocene
• Logarithmic timeline

References

• GeoWhen Database
• International Commission on Stratigraphy Time Scale

Capitalization

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.