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Ar·che·analso Ar·chae·an (är-kē′ən)
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.
The Archean Eon. Also called Archeozoic.
[From Greek arkhaios, ancient; see archaic.]
(Geological Science) a variant spelling (esp US) of Archaean
of or pertaining to rocks of the Archeozoic portion of the Precambrian Era.
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.
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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|
|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"