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	Hadean - Wikipedia, the free encyclopedia
		The name Hadean refers to the geologic period before 3800 million years ago (mya).
		In the last decades of the 20th century geologists identified a few Hadean rocks from Western Greenland, Northwestern Canada and Western Australia.
		The etymology of the name "Hadean" is from Hades, Greek for "unseen" and suggesting the underworld.
	en.wikipedia.org /wiki/Hadean (229 words)

	Hadean Era
		The Hadean Era was the first in Earth history, extending from the first formation of continental crust, which began some time around 4,200 Ma (Goodwin 1991, Condie 1997), becoming persistent soon after, to approximately 3,500 Ma.
		The Hadean interval is widely recognised, in Europe and elsewhere, though not by the Precambrian Subcommission.
		The Precambrian Subcommission, however, does not (at least not yet) recognise the Hadean; the oldest unit recognised by the Subcommission is the Archaean, with a lower boundary dated around 3,900 Ma.
	www.peripatus.gen.nz /Paleontology/Hadean.html (2137 words)

	Palaeos Hadean: The Hadean Eon
		The name Hadean was coined by geologist Preston Cloud for the pre-Isuan sequence whose record may not be preserved on Earth but is better known from Moon rocks.
		The Hadean or Pregeologic Eon is the time period during which the Earth was transformed from a gaseous cloud into a solid body.
		The process of solidification is poorly known, however, and the Hadean may have lasted as long as one billion years.
	www.palaeos.com /Hadean/Hadean.htm (1861 words)

	[No title]
		Hadean Ocean Chemistry- Relatively soon (~0.2 Ga) after the Earth formed, it is likely that major oceans appeared in a hot (~100¡C) reducing environment where carbon dioxide was probably the dominant atmospheric gas, with PCO2 values reaching perhaps in excess of 10 atm.
		During the Hadean Eon between 4.3 and 3.8 Ga BP, major changes in the concentration of atmospheric CO2 and associated temperature changes had a profound influence on the carbonate geochemistry of the Hadean Ocean.
		Thus, by the conclusion of the Hadean Eon, if not before, environmental conditions at the EarthÕs surface, including temperature and seawater composition, were sufficiently equable for the evolution of life, including the Archaebacteria: the extreme halophiles and thermophiles and methanogens.
	www-ocean.tamu.edu /News/Waterways/morse_word5.doc (1894 words)

	Geologic Eons
		The first three, the Hadean, Archean, and Proterozoic Eons are frequently lumped together and referred to as the Precambrian.
		The Hadean Eon is the oldest interval of Time and is dated from 4,600 Million Years Ago to 3,900 Million Years Ago.
		No rock record dating from the Hadean Eon is known on Earth with the exception of the 3.96 Billion Year old rocks found in Canada's Northwest Territories.
	imnh.isu.edu /geo_time/geo_time_eons.htm (489 words)

	Did Hades Freeze Over? :: Astrobiology Magazine :: Search for Life in the Universe
		To support the theory that pre-biotic methane may have played an important role in the development of life during the Hadean, Sleep cites the Miller-Urey experiments conducted in the 1950s.
		But even if pre-biotic methane and CO2 were a part of the Hadean atmosphere, their levels were so low that the Earth was probably very cold back then.
		In fact, Sleep and Zahnle suggest a variation on the "Snowball Earth" hypothesis: that at various times, the Earth during the Hadean era was so cold it was almost entirely covered with a crust of ice.
	www.astrobio.net /news/modules.php?op=modload&name=News&file=article&sid=95 (1541 words)

	[No title] (Site not responding. Last check: 2007-10-21)
		Thus the Hadean Eon begins around 4450 Ma ago and extends to between 3900-3650 Ma depending of the age assigned to the ``oldest rock''.
		There is almost no evidence on Earth of the Hadean Eon but the Nectarian (3850-?4200 Ma) and Pre-Nectarian Systems (?4200-?4450 Ma) on the Moon cover this missing period of time in the terrestrial rock record.
		Mantle temperatures during the Hadean were probably significantly higher due both to thermal inputs from impacts of large bodies, and a much higher heat flow.
	wwwrsphysse.anu.edu.au /nuclear/99report/Planetary.html (1183 words)

	Introduction to the Hadean (Site not responding. Last check: 2007-10-21)
		Hadean time is not a geological period as such.
		During Hadean time, the Solar System was forming, probably within a large cloud of gas and dust around the sun, called an accretion disc.
		The relative abundance of heavier elements in the Solar System suggests that this gas and dust was derived from a supernova, or supernovas - the explosion of an old, massive star.
	www.ucmp.berkeley.edu /precambrian/hadean.html (401 words)

	Hadean Eon (Site not responding. Last check: 2007-10-21)
		The Hadean includes the first 800 million years of Earth's history - the time of the formation of the planet from a presumably molten mass.
		The oldest dated rocks found so far are from Canada and are dated at 3.96 billion years old, the end of the Hadean.
		Meteorites and moon rocks date from this ancient time when the Earth's crust was forming and was continually bombarded by meteorites and comets.
	www.watersheds.org /earth/gtime01a.htm (89 words)

	HISTORICAL GEOLOGY
		PDF; JPG) a) processes involved in the formation of the Earth, b) the process responsible for generating the first crust (oceanic), c) the nature of early plate tectonics, d) composition of the first atmosphere and e) processes involved in formation of the first atmosphere.
		b) Know that there is virtually no physical evidence for the Hadean preserved in the rocks on Earth (only a few zircon grains of 4.2-4.3 BY eroded from a Hadean granitic rock and redeposited in a younger Archean sedimentary rock).
		Evidence to reconstruct the Hadean comes from physical constraints of the size and composition of the Earth, the asteroid pitted surface of the moon, lunar samples, and meteorites.
	www.uwosh.edu /faculty_staff/lehrmann/109/tes2studyguidenew.html (1483 words)

	CRYSTALLIZATION TEMPERATURES OF HADEAN ZIRCONS: POSSIBLE PLATE BOUNDARY INTERACTIONS BETWEEN 4.4 AND 4.0 GA (Site not responding. Last check: 2007-10-21)
		A thermometer based on the concentration of Ti in zircon applied to Hadean detrital zircons from Western Australia yields constraints on the nature of magmatism during the first 500 Ma of Earth history.
		Jack Hills zircons ranging from 4.0 to 4.35 Ga yield crystallization temperature peaks at 670 and 710°C, suggesting that a limited range of mechanisms produced zircon-bearing rocks during that period.
		We argue that constraints 1, 3 and 4 imply the existence of liquid water at or near the Earth's surface, constraints 1, 2, 5 and 6 imply the existence of continental crust throughout the Hadean, and we speculate that constraints 1 and 4 reflect Hadean thrust burial.
	gsa.confex.com /gsa/2005AM/finalprogram/abstract_94633.htm (391 words)

	New Scientist Premium- Hadean times - were they really hell on Earth? - Features
		New Scientist Premium- Hadean times - were they really hell on Earth?
		Hadean times - were they really hell on Earth?
		Early Earth was supposed to be a seething inferno of molten magma.
	www.newscientist.com /channel/earth/mg18624991.300 (303 words)

	GeoWhen Database - Hadean
		Hadean Eon (Priscoan, Azoic) From 4567.17 +/- 0.7 To 3800 Ma Start Defined By: Formation of Earth Start Based On: Amelin, Krot, Hutcheon, and Ulyanov, "Lead Isotopic Ages of Chondrules and Calcium-Aluminum-Rich Inclusions", _Science_, Sept. 6, 2002.
		Comment: Start date reflects earliest CAIs formation, at the birth of the solar system.
		The Hadean is not officially recognized ICS nomenclature.
	www.stratigraphy.org /geowhen/stages/Hadean.html (101 words)

	Hadean
		The Hadean Eon represents the time from which the Earth first formed (4.6 Ga) to approximately the oldest dated rocks (3.8-4.0 Ga) on Earth, located in Northwest Canada, Montana,Greenland and Australia.
		Essentially, during the Archean the Earth cooled from a molten state, differentiated into discrete layers and lithified as a layered Earth.
		Note that some geologists do not recognize the Hadean at all (first proposed by Preston Cloud); others consider the Hadean to have ended anywhere from 3.8-3.96 Ga. Science is not simple!
	www.uwsp.edu /geo/faculty/hefferan/Geol106/CLASS3/hadean.htm (330 words)

	PSIgate - Physical Sciences Information Gateway: Search/Browse Results (Site not responding. Last check: 2007-10-21)
		Peripatus Home Page Paleontology Page >> Hadean Era Updated: 18 Oct 2003 Hadean Era Abstract xxx Keywords: xxx Introduction xxx began approx formation of persistent crust approx 3,500 Ma to 2,500 Ma Related Topics Further...
		Hadean time: 4.5 to 3.8 billion years ago Hadean time is not a geological period as such.
		During Hadean time, the Solar System was forming, probably within a large cloud of gas and dust aro...
	www.psigate.ac.uk /roads/cgi-bin/search_webcatalogue.pl?term1=Hadean&limit=0 (238 words)

	Geology, Earth science, geoscience (Site not responding. Last check: 2007-10-21)
		Geological time scale an intro to the Geological Timescale and dating the Earth's past, geology, dating, palaeontology, paleontology, evolution, earth history, stratigraphy, time-scale, timescale
		Three eons: hadean, archean, and proterozoic, paleozoic era (ancient life).
		Geology wing start in the Cenozoic Era (65 million years ago to the present) and work back through time, or start with Hadean time (4.5 to 3.8 billion years ago) and journey forward to the present day, fossil localities, tectonics of the various time periods, click here for Geological time machine
	users.telenet.be /educypedia/education/geology.htm (606 words)

	Tyres: The Thread - Club RSX Message Board
		Oh, and these quotes were for size 205/55R16 so they'd be a little cheaper for the DC2R sizes.
		You probably need to make lots of calls to track down a set of four.
		Perhaps PM Hadean as he has been doing some serious calling and might be able to stear u in the right direction.
	forums.clubrsx.com /showthread.php?referrerid=&t=102746 (1854 words)

	Hadean got their homepage at Neopets.com
		Most pets have long, exciting, heartwarming tales of how they got their petpet.
		Hadean: But he's special and he needs me and I'll take good care of him and I'll never ask for anything else ever again and you're my most favorite ever and...
		As you can see, I own a Gathow.
	www.neopets.com /~Hadean (791 words)

	Use of force to resolve Iran nuclear row 'dangerous': Russia
		Last week Moscow came out in support of a resolution by the UN nuclear watchdog, the International Atomic Energy Agency (IAEA), urging Iran to resume its moratorium on nuclear fuel production.
		1 posted on 08/17/2005 11:04:01 AM PDT by Hadean
		We'll do what needs to be done or Israel will.
	www.freerepublic.com /focus/f-news/1465233/posts (934 words)

	Solar Voyager Forums: Genesis - Hadean Earth
		My aim was to recreate the earth during it's first few hundred millions of years when it was a very hostile place constantly being bombarded with space debris left over from the solar nebula.
		This period of time, when Earth was a place like hell, is called the Hadean Period (4.5 - 3,8 billion years ago)
		Might do well to give it a moving look =)
	www.solarvoyager.com /forum/forum_posts.asp?TID=1714 (1015 words)

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