Definitions
from The American Heritage® Dictionary of the English Language, 5th Edition.
- adjective 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.
- adjective Of, relating to, or being the oldest known rocks, those of the Precambrian Eon, that are predominantly igneous in composition.
- noun The Archean Eon.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adjective of or relating to the earliest known rocks formed during the Precambrian Eon
- noun the time from 3,800 million years to 2,500 million years ago; earth's crust formed; unicellular organisms are earliest forms of life
Etymologies
from The American Heritage® Dictionary of the English Language, 4th Edition
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Examples
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Dial back the clock nearly 4 billion years, to a time called the Archean, and the sun would appear about 30% dimmer than it is now.
Latest Articles ScienceNOW 2010
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The surge of gene births - which the scientists have dubbed the Archean expansion - predate some important changes in Earth's early chemistry, including the appearance of large amounts of oxygen in the atmosphere, say evolutionary biologists Eric Alm and Lawrence David.
Wired Top Stories Tina Hesman Saey 2010
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Actually, during the entire Hadean Eon and part of the Archean Eon the "Earth" was essentially an "all water" planet.
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There is strong geological evidence that the only "dry land" prior to the early Archean was scattered basaltic islands (sitting over mantle plume "hot spots") similar to the Hawaiian islands.
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During the Archean Eon life started and was dominated by one-celled prokaryotic life forms.
Geologic time 2010
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It seems it happened once in the Archean epoch back when the sun was still cool enough that earth didn't loose its ocean and we were all still bacteria.
Scientist Discusses Latest Report of Rising Global Temperatures | Universe Today 2010
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Archean rocks form steeply sloping uplands and lowlands in the Churchill River Upland and Hayes River Upland, while the Archean bedrock of the Lac Seul Upland area forms more broadly sloping uplands and lowlands.
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Massive, crystalline Archean rocks form broad, sloping uplands and lowlands, with numerous small lakes and eskers that drain into Great Slave Lake.
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This basement was formed during different orogenic phases characterized by large and long-lasting tectonic thermal events that occurred repeatedly during Archean and Proterozoic times.
Guyanan savanna 2008
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In the eastern part of the ecoregion, from Lac St. Jean south to the Gulf of St. Lawrence, and as far west as the Labrador coast, the region is underlain by massive Precambrian and Archean granites and gneisses, and lies between sea level and 600 meters (m) above sea level (asl).
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