Archean

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Related to Archean eon: Proterozoic eon, Phanerozoic eon

Archean

[är′kē·ən]
(geology)
A term, meaning ancient, which has been applied to the oldest rocks of the Precambrian; as more physical measurements of geologic time are made, the usage is changing; the term Early Precambrian is preferred.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
It wasn't a blue planet by any means." By the end of the Archean Eon some 2.5 billion year ago, oxygen levels rose quickly, creating an explosion of new life on the planet, he said.
The mantle was so hot from its birth and up until about 2.5 billion years ago - during what is known as the Archean Eon - because elements like potassium and uranium were decaying and releasing radioactive heat, according to (http://vtnews.vt.edu/articles/2017/05/science-hottestlavas.html) Virginia Tech .
Two researchers from University of Colorado Boulder say all that may have been required to sustain liquid water and primitive life on Earth during the Archean eon 2.8 billion years ago were reasonable atmospheric carbon dioxide amounts believed to be present at the time and perhaps a dash of methane.
Previously scientists have explained the presence of liquid water in that lowlight time, during the Archean Eon (about 3.8 billion to 2.5 billion years ago), by suggesting that Earth's atmosphere held large amounts of planet-warming greenhouse gases such as carbon dioxide and methane.