Archean
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Ar·che·an
also Ar·chae·an (är-kē′ən)adj.
1. Of, relating to, or being the older of the two divisions of Precambrian time, from about 3.8 to 2.5 billion years ago, marked by an atmosphere with little free oxygen, the formation of the first rocks and oceans, and the development of unicellular life. See Table at geologic time.
2. Of, relating to, or being the oldest known rocks, those of the Precambrian Eon, that are predominantly igneous in composition.
n.
The Archean Eon. Also called Archeozoic.
[From Greek arkhaios, ancient; see archaic.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Archean
(ɑːˈkiːən)adj
(Geological Science) a variant spelling (esp US) of Archaean
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
Ar•che•an
(ɑrˈki ən)adj.
of or pertaining to rocks of the Archeozoic portion of the Precambrian Era.
[1870–75]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
Ar·che·an
(är-kē′ən) The earlier of the two divisions of the Precambrian Eon, from about 3.8 to 2.5 billion years ago. During this time, the Earth had an atmosphere with little free oxygen, and the first single-celled life appeared. See Chart at geologic time.
The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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| Noun | 1. | Archean - the time from 3,800 million years to 2,500 million years ago; earth's crust formed; unicellular organisms are earliest forms of life Precambrian, Precambrian aeon, Precambrian eon, Precambrian period - the eon following the Hadean time and preceding the Phanerozoic eon; from about 3,800 million years ago until 544 million years ago |
| Adj. | 1. | archean - of or relating to the earliest known rocks formed during the Precambrian Eon geology - a science that deals with the history of the earth as recorded in rocks early - at or near the beginning of a period of time or course of events or before the usual or expected time; "early morning"; "an early warning"; "early diagnosis"; "an early death"; "took early retirement"; "an early spring"; "early varieties of peas and tomatoes mature before most standard varieties" |
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