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Geologic Time Scale: Precambrian Time

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This table shows the first nine-tenths of geologic time: Precambrian time. More details beneath the table.

EonEraPeriodDates (m.y.)
Phanerozoic (post-Precambrian time)541-0
ProterozoicNeoproterozoicEdiacaran635-541
Cryogenian850-635
Tonian1000-850
MesoproterozoicStenian1200-1000
Ectasian1400-1200
Calymmian1600-1400
PaleoproterozoicStatherian1800-1600
Orosirian2050-1800
Rhyacian2300-2050
Siderian2500-2300
ArcheanNeoarchean
2800-2500
Mesoarchean
3200-2800
Paleoarchean
3600-3200
Eoarchean
4000-3600
(c) 2009 Andrew Alden, licensed to About.com, Inc. (fair use policy. Data from Geologic Time Scale of 2013.

Back to the top-level geologic time scale

"Precambrian" is a long-established, informal name for the 4 billion years of Earth history before hard-bodied organisms arose at the beginning of the Cambrian Period, earliest division of the Phanerozoic Eon. Aside from the names of the eons and the Ediacaran Period (also called the Vendian), few of the terms in this geologic time scale are yet in wide use. The time before 4000 million years ago (4 billion or 4 Ga) is informally known as Hadean time.

Whereas later geologic history is minutely documented by fossils showing the evolving succession of living things, Precambrian time is almost entirely divided by absolute numerical ages of rocks. Nonetheless, the end of the Archean marks a distinct change in the Earth, roughly at the time atmospheric oxygen first appeared. (Read more about the Archean Eon and the Proterozoic Eon.) Archean and Proterozoic rocks are exposed in the continents' ancient central regions, but they make up a small fraction of Earth's total surface.

The dates shown on this geologic time scale were specified by the International Commission on Stratigraphy in 2013. The colors were specified by the Committee on the Geologic Map of the World in 2009.

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