|Phanerozoic (post-Precambrian time)||541-0|
|(c) 2009 Andrew Alden, licensed to About.com, Inc. (fair use policy. Data from Geologic Time Scale of 2013.
"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.