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The Hadean
Hadean
( /ˈheɪdiən/) is a geologic eon of the Earth
Earth
predating the Archean. It began with the formation of the Earth
Earth
about 4.6 billion years ago and ended, as defined by the ICS, 4 billion years ago.[1] As of 2016[update], the ICS describes its status as informal.[2] The geologist Preston Cloud coined the term in 1972, originally to label the period before the earliest-known rocks on Earth. W. Brian Harland later coined an almost synonymous term: the "Priscoan period". Other, older texts simply refer to the eon as the Pre-Archean.

Artist's impression of a Hadean
Hadean
landscape.

Contents

1 Etymology 2 Subdivisions 3 Hadean
Hadean
rocks 4 Atmosphere and oceans 5 See also 6 References 7 Further reading 8 External links

Etymology[edit]

Life timeline

view • discuss • edit

-4500 — – -4000 — – -3500 — – -3000 — – -2500 — – -2000 — – -1500 — – -1000 — – -500 — – 0 —

water

Single-celled life

photosynthesis

Eukaryotes

Multicellular life

Land life

Dinosaurs    

Mammals

Flowers

 

Earliest Earth
Earth
(−4540)

Earliest water

Earliest life

LHB meteorites

Earliest oxygen

Atmospheric oxygen

Oxygen crisis

Earliest sexual reproduction

Ediacara biota

Cambrian
Cambrian
explosion

Earliest humans

P h a n e r o z o i c

P r o t e r o z o i c

A r c h e a n

H a d e a n

Pongola

Huronian

Cryogenian

Andean

Karoo

Quaternary

Axis scale: million years Orange labels: ice ages. Also see: Human
Human
timeline and Nature timeline

"Hadean" (from Hades, the Greek god of the underworld) describes the hellish conditions then prevailing on Earth: the planet had just formed and was still very hot owing to its recent accretion, the abundance of short-lived radioactive elements, and frequent collisions with other Solar System bodies. Subdivisions[edit] Since few geological traces of this eon remain on Earth, there is no official subdivision. However, the Lunar geologic timescale
Lunar geologic timescale
embraces several major divisions relating to the Hadean, so these are sometimes used in an informal sense to refer to the same periods of time on Earth. The Lunar divisions are:

Pre-Nectarian, from the formation of the Moon's crust (4,533 million years ago) up to about 3,920 million years ago Nectarian ranging from 3,920 million years ago up to about 3,850 million years ago, in a time when the Late Heavy Bombardment, according to that theory, was in a stage of decline.

In 2010, an alternative scale was proposed that includes the addition of the Chaotian and Prenephelean Eons preceding the Hadean, and divides the Hadean
Hadean
into three eras with two periods each. The Paleohadean era consists of the Hephaestean (4.5-4.4 Ga) and the Jacobian periods (4.4-4.3 Ga). The Mesohadean is divided into the Canadian (4.3-4.2 Ga) and the Procrustean periods (4.2-4.1 Ga). The Neohadean is divided into the Acastan (4.1-4.0 Ga) and the Promethean periods (4.0-3.9 Ga).[3] As of February 2017[update], this has not been adopted by the IUGS. Hadean
Hadean
rocks[edit] Further information: Oldest dated rocks In the last decades of the 20th century geologists identified a few Hadean
Hadean
rocks from Western Greenland, Northwestern Canada, and Western Australia. In 2015, traces of carbon minerals interpreted as "remains of biotic life" were found in 4.1-billion-year-old rocks in Western Australia.[4][5] The oldest dated zircon crystals, enclosed in a metamorphosed sandstone conglomerate in the Jack Hills
Jack Hills
of the Narryer Gneiss Terrane of Western Australia, date to 4.404 ± 0.008 Ga.[6] This zircon is a slight outlier, with the oldest consistently-dated zircon falling closer to 4.35 Ga[6]—around 200 million years after the hypothesized time of the Earth's formation. In many other areas xenocryst, or relict Hadean
Hadean
zircons enclosed in older rocks indicate that younger rocks have formed on older terranes and have incorporated some of the older material. One example occurs in the Guiana shield from the Iwokrama Formation of southern Guyana where zircon cores have been dated at 4.22GA[7]. Atmosphere and oceans[edit]

Early Earth, Hadean
Hadean
Eon

volcanism

A sizeable quantity of water would have been in the material that formed the Earth.[8] Water
Water
molecules would have escaped Earth's gravity more easily when it was less massive during its formation. Hydrogen
Hydrogen
and helium are expected to continually escape (even to the present day) due to atmospheric escape. Part of the ancient planet is theorized to have been disrupted by the impact that created the Moon, which should have caused melting of one or two large regions of the Earth. Earth's present composition suggests that there was not complete remelting as it is difficult to completely melt and mix huge rock masses.[9] However, a fair fraction of material should have been vaporized by this impact, creating a rock vapor atmosphere around the young planet. The rock vapor would have condensed within two thousand years, leaving behind hot volatiles which probably resulted in a heavy CO 2 atmosphere with hydrogen and water vapor. Liquid water oceans existed despite the surface temperature of 230 °C (446 °F) because at an atmospheric pressure of above 27 atmospheres, caused by the heavy CO 2 atmosphere, water is still liquid. As cooling continued, subduction and dissolving in ocean water removed most CO 2 from the atmosphere but levels oscillated wildly as new surface and mantle cycles appeared.[10] Studies of zircons have found that liquid water must have existed as long ago as 4.4 billion years ago, very soon after the formation of the Earth.[11][12][13] This requires the presence of an atmosphere. The Cool Early Earth
Earth
theory covers a range from about 4.4–4.0 billion years. A September 2008 study of zircons found that Australian Hadean
Hadean
rock holds minerals pointing to the existence of plate tectonics as early as 4 billion years.[14][15] If this is true, the time when Earth finished its transition from having a hot, molten surface and atmosphere full of carbon dioxide, to being very much like it is today, can be roughly dated to about 4.0 billion years ago. The actions of plate tectonics and the oceans trapped vast amounts of carbon dioxide, thereby eliminating the greenhouse effect and leading to a much cooler surface temperature and the formation of solid rock, and possibly even life.[14][15]

See also[edit]

Chaotian (geology) Formation and evolution of the Solar System Hadean
Hadean
zircon History of Earth – the first sections describe the formation of the Earth Oldest dated rocks Precambrian Timeline of natural history

References[edit]

^ "International Chronostratigraphic Chart 2015" (PDF). ICS. Retrieved 23 January 2016.  ^ Ogg, J.G.; Ogg, G.; Gradstein, F.M. (2016). A Concise Geologic Time Scale: 2016. Elsevier. p. 20. ISBN 978-0-444-63771-0.  ^ "The Eons of Chaos and Hades" (PDF). Solid Earth. January 26, 2010.  ^ Borenstein, Seth (19 October 2015). "Hints of life on what was thought to be desolate early Earth". Excite. Yonkers, NY: Mindspark Interactive Network. Associated Press. Retrieved 2015-10-20.  ^ Bell, Elizabeth A.; Boehnike, Patrick; Harrison, T. Mark; et al. (19 October 2015). "Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon" (PDF). Proc. Natl. Acad. Sci. U.S.A. Washington, D.C.: National Academy of Sciences. 112: 14518–21. Bibcode:2015PNAS..11214518B. doi:10.1073/pnas.1517557112. ISSN 1091-6490. PMC 4664351 . PMID 26483481. Retrieved 2015-10-20.  Early edition, published online before print. ^ a b Wilde, Simon A.; Valley, John W.; Peck, William H.; Graham, Colin M. (2001). "Evidence from detrital zircons for the existence of continental crust and oceans on the Earth
Earth
4.4 Gyr ago". Nature. 409 (6817): 175–178. doi:10.1038/35051550.  ^ Nadeau, Serge; Chen, Wei; Reece, Jimmy; Lachhman, Deokumar; Ault, Randy; Faraco, Maria; Fraga, Leda; Reis, Nelson; Betiollo, Leandro (2013-12-01). "Guyana: the Lost Hadean
Hadean
crust of South America?". Brazilian Journal of Geology. 43: 601–606. doi:10.5327/Z2317-48892013000400002.  ^ Drake, Michael J. (2005), "Origin of water in the terrestrial planets" (PDF), Meteoritics & Planetary Science, 40 (4): 515–656, Bibcode:2005M&PS...40..515J, doi:10.1111/j.1945-5100.2005.tb00958.x, archived from the original (PDF) on 2011-10-09 . ^ Solar System Exploration: Science & Technology: Science Features: View Feature ^ Sleep, N. H.; Zahnle, K.; Neuhoff, P. S. (2001), "Initiation of clement surface conditions on the earliest Earth", PNAS, 98 (7): 3666–3672, Bibcode:2001PNAS...98.3666S, doi:10.1073/pnas.071045698, PMC 31109 , PMID 11259665 . ^ ANU - Research School of Earth
Earth
Sciences - ANU College of Science - Harrison Archived 2006-06-21 at Archive.is ^ ANU - OVC - MEDIA - MEDIA RELEASES - 2005 - NOVEMBER - 181105HARRISONCONTINENTS ^ A Cool Early Earth ^ a b Chang, Kenneth (December 2, 2008). "A New Picture of the Early Earth". The New York Times.  ^ a b Abramov, Oleg; Mojzsis, Stephen J. (December 2008). "Thermal State of the Lithosphere During Late Heavy Bombardment: Implications for Early Life". AGU Fall Meeting Abstracts. Fall Meeting 2008: American Geophysical Union. 1 (2008 Fall Meeting). Bibcode:2008AGUFM.V11E..08A. Retrieved 24 May 2015. 

Further reading[edit]

Hopkins, Michelle; Harrison, T. Mark; Manning, Craig E. (2008), "Low heat flow inferred from >4 Gyr zircons suggests Hadean
Hadean
plate boundary interactions", Nature, 456 (7221): 493–496, Bibcode:2008Natur.456..493H, doi:10.1038/nature07465, PMID 19037314 . Valley, John W.; Peck, William H.; King, Elizabeth M. (1999), "Zircons Are Forever", The Outcrop for 1999, University of Wisconsin-Madison, retrieved January 10, 2006  – Evidence from detrital zircons for the existence of continental crust and oceans on the Earth
Earth
4.4 Gyr ago. Wilde, S. A.; Valley, J. W.; Peck, W. H. & Graham, C. M. (2001), "Evidence from detrital zircons for the existence of continental crust and oceans on the Earth
Earth
4.4 Gyr ago", Nature, 409 (6817): 175–178, doi:10.1038/35051550, PMID 11196637 . Wyche, S.; Nelson, D. R. & Riganti, A. (2004), "4350–3130 Ma detrital zircons in the Southern Cross Granite–Greenstone Terrane, Western Australia: implications for the early evolution of the Yilgarn Craton", Australian Journal of Earth
Earth
Sciences, 51 (1): 31–45, Bibcode:2004AuJES..51...31W, doi:10.1046/j.1400-0952.2003.01042.x . Carley, Tamara L.; et al. (2014), "Iceland is not a magmatic analog for the Hadean: Evidence from the zircon record", Earth
Earth
and Planetary Science Letters, 405 (1): 85–97, Bibcode:2014E&PSL.405...85C, doi:10.1016/j.epsl.2014.08.015 .

External links[edit]

Wikimedia Commons has media related to Hadean.

Palaeos.org: Hadean
Hadean
eon Peripatus.nz: Description of the Hadean
Hadean
Era Astronoo.com: Hell of the Hadean

v t e

Hadean
Hadean
Eon

Cryptic Basin Groups Nectarian Lower Imbrian

The Hadean
Hadean
does not have any subdivisions recognized by the International Commission on Stratigraphy. These subdivisions represent one proposal that is loosely based on the lunar geologic time scale.

v t e

Geologic history of Earth

Cenozoic
Cenozoic
era¹ (present–66.0 Mya)

Quaternary
Quaternary
(present–2.588 Mya)

Holocene
Holocene
(present–11.784 kya) Pleistocene
Pleistocene
(11.784 kya–2.588 Mya)

Neogene
Neogene
(2.588–23.03 Mya)

Pliocene
Pliocene
(2.588–5.333 Mya) Miocene
Miocene
(5.333–23.03 Mya)

Paleogene (23.03–66.0 Mya)

Oligocene
Oligocene
(23.03–33.9 Mya) Eocene
Eocene
(33.9–56.0 Mya) Paleocene
Paleocene
(56.0–66.0 Mya)

Mesozoic
Mesozoic
era¹ (66.0–251.902 Mya)

Cretaceous
Cretaceous
(66.0–145.0 Mya)

Late (66.0–100.5 Mya) Early (100.5–145.0 Mya)

Jurassic
Jurassic
(145.0–201.3 Mya)

Late (145.0–163.5 Mya) Middle (163.5–174.1 Mya) Early (174.1–201.3 Mya)

Triassic
Triassic
(201.3–251.902 Mya)

Late (201.3–237 Mya) Middle (237–247.2 Mya) Early (247.2–251.902 Mya)

Paleozoic
Paleozoic
era¹ (251.902–541.0 Mya)

Permian
Permian
(251.902–298.9 Mya)

Lopingian
Lopingian
(251.902–259.8 Mya) Guadalupian
Guadalupian
(259.8–272.3 Mya) Cisuralian
Cisuralian
(272.3–298.9 Mya)

Carboniferous
Carboniferous
(298.9–358.9 Mya)

Pennsylvanian (298.9–323.2 Mya) Mississippian (323.2–358.9 Mya)

Devonian
Devonian
(358.9–419.2 Mya)

Late (358.9–382.7 Mya) Middle (382.7–393.3 Mya) Early (393.3–419.2 Mya)

Silurian
Silurian
(419.2–443.8 Mya)

Pridoli (419.2–423.0 Mya) Ludlow (423.0–427.4 Mya) Wenlock (427.4–433.4 Mya) Llandovery (433.4–443.8 Mya)

Ordovician
Ordovician
(443.8–485.4 Mya)

Late (443.8–458.4 Mya) Middle (458.4–470.0 Mya) Early (470.0–485.4 Mya)

Cambrian
Cambrian
(485.4–541.0 Mya)

Furongian (485.4–497 Mya) Series 3 (497–509 Mya) Series 2 (509–521 Mya) Terreneuvian
Terreneuvian
(521–541.0 Mya)

Proterozoic
Proterozoic
eon² (541.0 Mya–2.5 Gya)

Neoproterozoic era (541.0 Mya–1 Gya)

Ediacaran
Ediacaran
(541.0-~635 Mya) Cryogenian (~635-~720 Mya) Tonian (~720 Mya-1 Gya)

Mesoproterozoic era (1–1.6 Gya)

Stenian (1-1.2 Gya) Ectasian (1.2-1.4 Gya) Calymmian (1.4-1.6 Gya)

Paleoproterozoic era (1.6–2.5 Gya)

Statherian (1.6-1.8 Gya) Orosirian
Orosirian
(1.8-2.05 Gya) Rhyacian (2.05-2.3 Gya) Siderian
Siderian
(2.3-2.5 Gya)

Archean
Archean
eon² (2.5–4 Gya)

Eras

Neoarchean (2.5–2.8 Gya) Mesoarchean (2.8–3.2 Gya) Paleoarchean
Paleoarchean
(3.2–3.6 Gya) Eoarchean
Eoarchean
(3.6–4 Gya)

Hadean
Hadean
eon² (4–4.6 Gya)

 

 

kya = thousands years ago. Mya = millions years ago. Gya = billions years ago.¹ = Phanerozoic
Phanerozoic
eon. ² = Precambrian
Precambrian
supereon. Source: (2017/02). International Commission on Stratigraphy. Retrieved 13 July 2015. Divisions of Geologic Time—Major Chronostratigraphic and Geochronologic Units USGS Retrieved 10 March 2013.

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