Archean

or Ar·chae·an

[ ahr-kee-uhn ]

/ ɑrˈki ən /

adjective Geology.

noting or pertaining to rocks of the Archeozoic portion of the Precambrian Era.

Origin of Archean

1870–75; <Greek archaî(os) ancient (see archaeo-) + -an

Words nearby Archean

archduchess, archduchy, archduke, archdukedom, arche-, Archean, archebanc, arched, arched truss, archegoniophore, archegonium

Dictionary.com UnabridgedBased on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Example sentences from the Web for Archean

Yet either is inconsiderable against the total lapse of time even from the Archean's close till now.
The Book of the National Parks|Robert Sterling Yard
At one time these rocks were regarded as Archean gneisses of a special type.
Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 3|Various
Two important ones, however—namely, Archean and Algonkian—are of American birth.
North America|Israel C. Russell
A theory held by many refers the ultimate source of the iron to the igneous rocks of the Archean.
The Elements of Geology|William Harmon Norton

We are looking now at the close of the era which geologists call Archean, because it is ancient beyond knowledge.
The Book of the National Parks|Robert Sterling Yard

British Dictionary definitions for Archean

Archean

/ (ɑːˈkiːən) /

adjective

a variant spelling (esp US) of Archaean

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for Archean

Archean

[ 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 a reducing atmosphere consisting primarily of methane, ammonia, and other gases that would be toxic to most modern life forms. There was little free oxygen. Rocks from the earliest part of the Archean are predominantly volcanic and are similar to pillow basalts, suggesting that they formed underwater. Rocks from the later part of the Archean appear to have formed on continents. It is believed that about 70% of the continental masses formed during this time. Fossils preserved in rocks from this period of time include remains of cyanobacteria, the first single-celled forms of life. These organisms are preserved in the form of stromatolites and oncolites. See Chart at geologic time.

单词	archean
释义	Archean or Ar·chae·an [ ahr-kee-uhn ] / ɑrˈki ən / adjective Geology. noting or pertaining to rocks of the Archeozoic portion of the Precambrian Era. Origin of Archean 1870–75; <Greek archaî(os) ancient (see archaeo-) + -an Words nearby Archean archduchess, archduchy, archduke, archdukedom, arche-, Archean, archebanc, arched, arched truss, archegoniophore, archegonium Dictionary.com UnabridgedBased on the Random House Unabridged Dictionary, © Random House, Inc. 2020 Example sentences from the Web for Archean Yet either is inconsiderable against the total lapse of time even from the Archean's close till now. The Book of the National Parks\|Robert Sterling Yard At one time these rocks were regarded as Archean gneisses of a special type. Encyclopaedia Britannica, 11th Edition, Volume 12, Slice 3\|Various Two important ones, however—namely, Archean and Algonkian—are of American birth. North America\|Israel C. Russell A theory held by many refers the ultimate source of the iron to the igneous rocks of the Archean. The Elements of Geology\|William Harmon Norton We are looking now at the close of the era which geologists call Archean, because it is ancient beyond knowledge. The Book of the National Parks\|Robert Sterling Yard British Dictionary definitions for Archean Archean / (ɑːˈkiːən) / adjective a variant spelling (esp US) of Archaean Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Scientific definitions for Archean Archean [ 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 a reducing atmosphere consisting primarily of methane, ammonia, and other gases that would be toxic to most modern life forms. There was little free oxygen. Rocks from the earliest part of the Archean are predominantly volcanic and are similar to pillow basalts, suggesting that they formed underwater. Rocks from the later part of the Archean appear to have formed on continents. It is believed that about 70% of the continental masses formed during this time. Fossils preserved in rocks from this period of time include remains of cyanobacteria, the first single-celled forms of life. These organisms are preserved in the form of stromatolites and oncolites. See Chart at geologic time. The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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