:Hadean

The eon's name "Hadean" comes from Hades, the Greek god of the underworld (whose name is also used to describe the underworld itself), referring to the hellish conditions then prevailing on early Earth: the planet had just been formed from recent accretion, and its surface was still molten with superheated lava due to that, the abundance of short-lived radioactive elements, and frequent impact events with other Solar System bodies.

The term was coined by American geologist Preston Cloud, originally to label the period before the earliest known rocks on Earth.{{cite journal |last=Cloud |first=Preston |year=1972 |title=A working model of the primitive Earth |journal=American Journal of Science |volume=272 |issue=6 |pages=537–548 |bibcode=1972AmJS..272..537C |doi=10.2475/ajs.272.6.537}}{{cite book |last=Bleeker |first=W. |year=2004 |chapter=Chapter 10. Toward a 'natural' Precambrian time scale |editor1-last=Gradstein |editor1-first=Felix M. |editor2-last=Ogg |editor2-first=James G. |editor3-last=Smith |editor3-first=Alan G. |title=A Geologic Time Scale |publisher=Cambridge University Press |location=Cambridge, UK |isbn=9780521786737 |page=145 |chapter-url=https://books.google.com/books?id=rse4v1P-f9kC&pg=PA145}} W.B. Harland later coined an almost synonymous term, the Priscoan period, from priscus, a Latin word for 'ancient'.{{cite encyclopedia |title=Priscoan |dictionary=Oxford Living dictionaries |url=https://en.oxforddictionaries.com/definition/priscoan |url-status=dead |archive-url=https://web.archive.org/web/20181129225130/https://en.oxforddictionaries.com/definition/priscoan |archive-date=2018-11-29}} Other, older texts refer to the eon as the Pre-Archean.{{cite conference |last=Shaw |first=D.M. |year=1975 |title=Early history of the Earth |conference=Proceedings of the NATO Advanced Study Institute |publisher=John Wiley |location=Leicester |isbn=0-471-01488-5 |pages=33–53}}{{cite journal |last1=Jarvis |first1=Gary T. |last2=Campbell |first2=Ian H. |date=December 1983 |title=Archean komatiites and geotherms: Solution to an apparent contradiction |journal=Geophysical Research Letters |doi=10.1029/GL010i012p01133 |bibcode=1983GeoRL..10.1133J |volume=10 |issue=12 |pages=1133–1136}}

{{further|Oldest dated rocks}}

Prior to the 1980s and the discovery of Hadean lithic fragments, scientific narratives of the early Earth explanations were almost entirely in the hands of geodynamic modelers.{{cite book |last1=Harrison |first1=T. Mark |title=Hadean earth |date=2020 |publisher=Springer |location=Cham |isbn=978-3030466862 |page=4}}

File:Jack Hills detrital zircons BSE micrographs.jpgs of the Jack Hills, Narryer Gneiss terrane, Western Australia]]

In the last decades of the 20th century, geologists identified a few 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.{{cite news |agency=Associated Press |last=Borenstein |first=Seth |date=19 October 2015 |title=Hints of life on what was thought to be desolate early Earth |work=Excite |publisher=Mindspark Interactive Network |location=Yonkers, NY |url=http://apnews.excite.com/article/20151019/us-sci--earliest_life-a400435d0d.html |access-date=2015-10-20}}{{cite journal |last1=Bell |first1=Elizabeth A. |last2=Boehnike |first2=Patrick |last3=Harrison |first3=T. Mark |last4=Mao |first4=Wendy L. |display-authors=3 |date=19 October 2015 |title=Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon |journal=Proc. Natl. Acad. Sci. U.S.A. |issn=1091-6490 |publisher=National Academy of Sciences |location=Washington, D.C. |doi=10.1073/pnas.1517557112 |doi-access=free |pmid=26483481 |pmc=4664351 |bibcode=2015PNAS..11214518B |volume=112 |issue=47 |pages=14518–21}}

The oldest dated zircon crystals, enclosed in a metamorphosed sandstone conglomerate in the Jack Hills of the Narryer Gneiss terrane of Western Australia, date to 4.404 ± 0.008 Ga.{{cite journal |last1=Wilde |first1=Simon A. |last2=Valley |first2=John W. |last3=Peck |first3=William H. |last4=Graham |first4=Colin M. |date=2001 |title=Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago |journal=Nature |pmid=11196637 |bibcode=2001Natur.409..175W |s2cid=4319774 |doi=10.1038/35051550 |volume=409 |issue=6817 |pages=175–178}} This zircon is a slight outlier, with the oldest consistently dated zircon falling closer to 4.35 Ga—around 200 million years after the hypothesized time of Earth's formation.

In many other areas, xenocryst (or relict) 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 4.22 Ga.{{cite journal |last1=Nadeau |first1=Serge |last2=Chen |first2=Wei |last3=Reece |first3=Jimmy |last4=Lachhman |first4=Deokumar |last5=Ault |first5=Randy |last6=Faraco |first6=Maria |last7=Fraga |first7=Leda |last8=Reis |first8=Nelson |last9=Betiollo |first9=Leandro |date=2013-12-01 |title=Guyana: the Lost Hadean crust of South America? |journal=Brazilian Journal of Geology |doi=10.5327/Z2317-48892013000400002 |doi-access=free |volume=43 |issue=4 |pages=601–606|bibcode=2013BrJG...43..601N }}

A sizable quantity of water would have been in the material that formed Earth.{{cite journal |last=Drake |first=Michael J. |date=April 2005 |title=Origin of water in the terrestrial planets |journal=Meteoritics & Planetary Science |bibcode=2005M&PS...40..515J |doi=10.1111/j.1945-5100.2005.tb00960.x |doi-access=free |volume=40 |number=4 |pages=519–527}} Water molecules would have escaped Earth's gravity more easily when the planet was less massive during its formation. Photodissociation by short-wave ultraviolet in sunlight could split surface water molecules into oxygen and hydrogen, the former of which would readily react to form compounds in the then-reducing atmosphere, while the latter (along with the similarly light helium) would be expected to continually leave the atmosphere (as it does 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 the melting of one or two large regions of Earth. Earth's present composition suggests that there was not complete remelting as it is difficult to completely melt and mix huge rock masses.{{cite web |last=Taylor |first=G. Jeffrey |title=Origin of the Earth and Moon |website=Solar System Exploration |publisher=NASA |url=http://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=446 |url-status=dead |archive-url=https://web.archive.org/web/20150308165917/http://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=446 |archive-date=March 8, 2015}} However, a fair fraction of material should have been vaporized by this impact. The material would have condensed within 2,000 years.{{cite journal |last1=Sleep |first1=NH |last2=Zahnle |first2=K |last3=Neuhoff |first3=PS |year=2001 |title=Initiation of clement surface conditions on the earliest Earth |journal=PNAS |doi=10.1073/pnas.071045698 |doi-access=free |pmid=11259665 |pmc=31109 |bibcode=2001PNAS...98.3666S |volume=98 |issue=7 |pages=3666–3672}} The initial magma ocean solidified within 5 million years,{{cite journal|first=LT|last=Elkins-Tanton|title=Linked magma ocean solidification and atmospheric growth for Earth and Mars|journal=Earth and Planetary Science Letters|volume=271|issue=1–4|year=2008|pages=181–191|doi=10.1016/j.epsl.2008.03.062|bibcode=2008E&PSL.271..181E }} leaving behind hot volatiles which probably resulted in a heavy {{chem|link=carbon dioxide|CO|2}} atmosphere with hydrogen and water vapor. The initial heavy atmosphere had a surface temperature of {{cvt|230|C|F}} and an atmospheric pressure of above 27 standard atmospheres.

{{anchor|Cool early Earth}}

File:Precambrian - Zircon ages.png

Studies of zircons have found that liquid water may have existed between 4.0 and 4.4 billion years ago, very soon after the formation of Earth.{{cite journal |last1=Valley |first1=John W. |last2=Peck |first2=William H. |last3=King |first3=Elizabeth M. |last4=Wilde |first4=Simon A. |date=April 2002 |title=A Cool Early Earth |journal=Geology |doi=10.1130/0091-7613(2002)030<0351:ACEE>2.0.CO;2 |pmid=16196254 |bibcode=2002Geo....30..351V |volume=30 |issue=4 |pages=351–354 |url=http://www.geology.wisc.edu/%7Evalley/zircons/cool_early/cool_early_home.html |access-date=2006-08-22 |url-status=dead |archive-url=https://web.archive.org/web/20130616213221/http://www.geology.wisc.edu/~valley/zircons/cool_early/cool_early_home.html |archive-date=2013-06-16}}{{cite journal|last1=Cavosie|first1=AJ|last2=Valley|first2=JW|last3=Wilde|first3=SA|year=2005|url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X05002773|title=Magmatic d18O in 4400-3900 Ma detrital zircons: A record of the alteration and recycling of crust in the Early Archean|journal=Earth and Planetary Science Letters|volume=235|pages=663–681|doi=10.1016/j.epsl.2005.04.028 }}{{cite journal|first1=EM|last1=Cameron|first2=TB|last2=Blum|last3=Cavosie|first3=AJ|display-authors=et al|year=2024|url=https://www.degruyter.com/document/doi/10.2138/am-2023-9180/html|title=Evidence for oceans pre-4300 Ma confirmed by preserved igneous compositions in Hadean zircon|journal=American Mineralogist|volume=109|issue=10|pages=1670–1681|doi=10.2138/am-2023-9180|bibcode=2024AmMin.109.1670C |doi-access=free}} Liquid water oceans existed despite the high surface temperature, because at an atmospheric pressure of 27 atmospheres, water remains liquid even at those high temperatures.

The most likely source of the water in the Hadean ocean was outgassing from the Earth's mantle.{{cite encyclopedia|title=Encyclopedia of Geology|isbn=9780081029091|year=2020|publisher=Elsevier Science|editor1-first=David|editor1-last=Alderton|editor2-first=Scott|editor2-last=Elias|entry=Precambrian|last1=Reis|first1=HLS|last2=Sanchez|first2=EAM|page=30}} Bombardment origin of a substantial amount of water is unlikely, due to the incompatibility of isotope fractions between the Earth and comets.

Asteroid impacts during the Hadean and into the Archean would have periodically disrupted the ocean. The geological record from 3.2 Gya contains evidence of multiple impacts of objects up to {{convert|100|km}} in diameter.{{cite journal |last1=Lowe |first1=DR |last2=Byerly |first2=GR |year=2015 |title=Geologic record of partial ocean evaporation triggered by giant asteroid impacts, 3.29–3.23 billion years ago |journal=Geology |doi=10.1130/G36665.1 |bibcode=2015Geo....43..535L |volume=43 |issue=6 |pages=535–538}} Each such impact would have boiled off up to {{convert|100|m}} of a global ocean, and temporarily raised the atmospheric temperature to {{convert|500|C|F}}. However, the frequency of meteorite impacts is still under study: the Earth may have gone through long periods when liquid oceans and life were possible.

The liquid water would absorb the carbon dioxide in the early atmosphere; this would not be enough by itself to substantially reduce the amount of {{chem|CO|2}}.

File:Hadean and Archean continents.gif

A 2008 study of zircons found that Australian Hadean rock contains minerals pointing to the existence of plate tectonics as early as 4 billion years ago (approximately 600 million years after Earth's formation).{{cite news |last=Chang |first=Kenneth |date=December 2, 2008 |title=A New Picture of the Early Earth |work=The New York Times |url=https://www.nytimes.com/2008/12/02/science/02eart.html?_r=1}} However, some geologists suggest that the zircons could have been formed by meteorite impacts.{{cite journal |last1=Kenny |first1=GG |last2=Whitehouse |first2=MJ |last3=Kamber |first3=BS |display-authors=etal |date=April 12, 2016 |title=Differentiated impact melt sheets may be a potential source of Hadean detrital zircon |journal=Geology |volume=44 |issue=6 |pages=435–438 |doi=10.1130/G37898.1 |bibcode=2016Geo....44..435K |url=http://geology.geoscienceworld.org/content/44/6/435 |accessdate=March 6, 2017}} The direct evidence of Hadean geology from zircons is limited, because the zircons are largely gathered in one locality in Australia. Geophysical models are underconstrained, but can paint a general picture of the state of Earth in the Hadean.{{cite journal |last1=Korenaga |first1=J |last2=Planavsky |first2=NJ |last3=Evans |first3=DAD |year=2017 |title=Global water cycle and the coevolution of Earth's interior and surface environment. |journal=Phil. Trans. R. Soc. A |doi=10.1098/rsta.2015.0393 |pmid=28416728 |pmc=5394256 |bibcode=2017RSPTA.37550393K |s2cid=2958757 |volume=375 |issue=2094 |page=20150393}}

Mantle convection in the Hadean was likely vigorous, due to lower viscosity. The lower viscosity was due to the high levels of radiogenic heat and the fact that water in the mantle had not yet fully outgassed.{{cite journal |last=Korenaga |first=J |year=2021 |title=Hadean geodynamics and the nature of early continental crust |journal=Precambrian Res |doi=10.1016/j.precamres.2021.106178 |bibcode=2021PreR..35906178K |s2cid=233441822 |volume=359 |page=106178}} Whether the vigorous convection led to plate tectonics in the Hadean or was confined under a rigid lid is still a matter of debate.{{cite journal |last1=Windley |first1=BF |last2=Kusky |first2=T |last3=Polat |first3=A |year=2021 |title=Onset of plate tectonics by the Eoarchean |journal=Precambrian Res |doi=10.1016/j.precamres.2020.105980 |bibcode=2021PreR..35205980W |s2cid=228993361 |volume=352 |page=105980}}{{cite book |last=Harrison |first=T. Mark |year=2020 |title=Hadean Earth |publisher=Springer |location=Cham, Switzerland |isbn=978-3-030-46686-2 |doi=10.1007/978-3-030-46687-9 |page=|bibcode=2020hade.book.....H |s2cid=128932829 }}{{cite journal |last1=Tang |first1=M |last2=Chen |first2=K |last3=Rudnick |first3=RL |year=2016 |title=Archean upper crust transition from mafic to felsic marks the onset of plate tectonics |journal=Science |doi=10.1126/science.aad5513 |pmid=26798012|bibcode=2016Sci...351..372T |s2cid=206643793 |volume=351 |issue=6271 |pages=372–375|doi-access=free }} The presence of Hadean oceans is thought to have triggered plate tectonics.{{cite journal |last1=Regenauer-Lieb |first1=K |last2=Yuen |first2=DA |last3=Branlund |first3=J |year=2001 |title=The initiation of subduction: Criticality by addition of water? |journal=Science |doi=10.1126/science.1063891 |pmid=11641494 |bibcode=2001Sci...294..578R |s2cid=43547982 |volume=294 |issue=5542 |pages=578–580}}

Subduction due to plate tectonics would have removed carbonate from the early oceans, contributing to the removal of the {{chem|CO|2}}-rich early atmosphere. Removal of this early atmosphere is evidence of Hadean plate tectonics.{{cite journal |last1=Sleep |first1=NH |last2=Zahnle |first2=KJ |last3=Lupu |first3=RE |year=2014 |title=Terrestrial aftermath of the Moon-forming impact |journal=Phil. Trans. R. Soc. A |doi=10.1098/rsta.2013.0172 |pmid=25114303 |bibcode=2014RSPTA.37230172S |s2cid=6902632 |volume=372 |issue=2024 |page=20130172|doi-access=free }}

If plate tectonics occurred in the Hadean, it would have formed continental crust.{{cite journal |last1=Guo |first1=M |last2=Korenaga |first2=J |year=2020 |title=Argon constraints on the early growth of felsic continental crust |journal=Science Advances |doi=10.1126/sciadv.aaz6234 |pmid=32671213 |pmc=7314546 |bibcode=2020SciA....6.6234G |volume=6 |issue=21 |page=eaaz6234}} Different models predict different amounts of continental crust during the Hadean.{{cite journal|last=Harrison|first=TM|title=The Hadean crust: evidence from> 4 Ga zircons|journal=Annual Review of Earth and Planetary Sciences|volume=37|year=2009|issue=1 |pages=479–505|doi=10.1146/annurev.earth.031208.100151 |bibcode=2009AREPS..37..479H }} The work of Dhiume et al. predicts that by the end of the Hadean, the continental crust had only 25% of today's area.{{cite journal |last1=Dhuime |first1=B |last2=Hawkesworth |first2=CJ |last3=Cawood |first3=PA |last4=Storey |first4=CD |year=2012 |title=A change in the geodynamics of continental growth 3 billion years ago |journal=Science |doi=10.1126/science.1216066 |pmid=22422979 |bibcode=2012Sci...335.1334D |s2cid=206538532 |volume=335 |issue=6074 |pages=1334–1336}} The models of Korenaga, et al. predict that the continental crust grew to present-day volume sometime between 4.2 and 4.0 Gya.{{cite journal |last1=Rosas |first1=JC |last2=Korenaga |first2=J |year=2018 |title=Rapid crustal growth and efficient crustal recycling in the early Earth: Implications for Hadean and Archean geodynamics |journal=Earth Planet. Sci. Lett. |doi=10.1016/j.epsl.2018.04.051 |bibcode=2018E&PSL.494...42R |s2cid=13666395 |volume=494 |pages=42–49|doi-access=free }}

The amount of exposed land in the Hadean is only loosely dependent on the amount of continental crust: it also depends on the ocean level. In models where plate tectonics started in the Archean, Earth has a global ocean in the Hadean.{{cite journal |last=Russell |first=MJ |year=2021 |title=The "Water Problem", the illusory pond and life's submarine emergence—A review |journal=Life |doi=10.3390/life11050429 |doi-access=free |pmid=34068713 |pmc=8151828 |volume=11 |issue=5 |page=429|bibcode=2021Life...11..429R }}{{cite journal |last=Voosen |first=P |year=2021 |title=Ancient Earth was a water world |journal=Science |doi=10.1126/science.371.6534.1088 |pmid=33707245 |bibcode=2021Sci...371.1088V |s2cid=232206926 |volume=371 |issue=6534 |pages=1088–1089}} The high heat of the mantle may have made it difficult to support high elevations in the Hadean.{{cite journal |last1=Monteux |first1=J |last2=Andrault |first2=D |last3=Guitreau |first3=M |last4=Samuel |first4=H |last5=Demouchy |first5=S |year=2020 |title=A mushy Earth's mantle for more than 500 Myr after the magma ocean solidification |journal=Geophys. J. Int. |doi=10.1093/gji/ggaa064 |volume=221 |issue=2 |pages=1165–1181|doi-access=free }}{{cite journal |last1=Rey |first1=PF |last2=Coltice |first2=N |year=2008 |title=Neoarchean lithospheric strengthening and the coupling of Earth's geochemical reservoirs |journal=Geology |doi=((10.1130/G25031A.1;)) |bibcode=2008Geo....36..635R |volume=36 |issue=8 |pages=635–638}} If continents did form in the Hadean, their growth competed with outgassing of water from the mantle. Continents may have appeared in the mid-Hadean, and then disappeared under a thick ocean by the end of the Hadean.{{cite journal |last1=Bada |first1=JL |last2=Korenaga |first2=J |year=2018 |title=Exposed areas above sea level on Earth >3.5 Gyr ago: Implications for prebiotic and primitive biotic chemistry |journal=Life |doi=10.3390/life8040055 |doi-access=free |pmid=30400350 |pmc=6316429 |volume=8 |issue=4 |page=55|bibcode=2018Life....8...55B }} The limited amount of land has implications for the origin of life.

Abundant Hadean-like geothermal microenvironments were shown by Salditt et al. to have the potential to support the synthesis and replication of RNA and thus possibly the evolution of a primitive life form.{{cite journal|last1=Salditt|first1=A|last2=Karr|first2=L|last3=Salibi|first3=E|last4=Le Vay|first4=K|last5=Braun|first5=D|last6=Mutschler|first6=H|title=Ribozyme-mediated RNA synthesis and replication in a model Hadean microenvironment|journal=Nat. Commun.|date=2023-03-17|volume=14|issue=1|page=1495|doi=10.1038/s41467-023-37206-4|pmid=36932102|pmc=10023712|bibcode=2023NatCo..14.1495S}} Porous rock systems comprising heated air-water interfaces were shown to allow ribozyme-catalyzed RNA replication of sense and antisense strands followed by subsequent strand dissociation, thus enabling combined synthesis, release and folding of active ribozymes.

A study published in 2024 inferred the last common ancestor of all current life to have emerged during the Hadean, between 4.09 and 4.33 Gya.{{cite journal |last1=Moody |first1=Edmund |last2=Álvarez-Carretero |first2=Sandra |last3=Mahendrarajah |first3=Tara |title=The nature of the last universal common ancestor and its impact on the early Earth system |journal=Nat. Ecol. Evol. |date=12 July 2024 |volume=8 |issue=9 |pages=1654–1666 |doi=10.1038/s41559-024-02461-1 |doi-access=free |pmid=38997462 |pmc=11383801 |bibcode=2024NatEE...8.1654M }}

Although the early part of the Late Heavy Bombardment happened during the Hadean, the impacts were frequent only on a cosmic scale, with thousands or even millions of years between each event. As Earth already had oceans, life would have been possible, but vulnerable to extinction events caused by those impacts. The risk would not be on the frequency, but on the size of the impactor, and remains on the Moon suggest impactors bigger than the Chicxulub impactor that caused the extinction of dinosaurs. An impactor big enough may erase all life on the planet, although some models suggest that microscopic life may still survive if underground or in the oceanic depths.{{cite book |last=Bennett |first=Jeffrey |author-link= |date=2017 |title=Life in the universe |url= |location=United States |publisher=Pearson |pages=124–125 |isbn=978-0-13-408908-9}}

• {{annotated link|Chaotian (geology)}}
• {{annotated link|Faint young Sun paradox}}
• Formation and evolution of the Solar System
• {{annotated link|Hadean zircon}}
• {{annotated link|History of Earth}} – the first sections describe the formation of Earth
• {{annotated link|Oldest dated rocks}}
• {{annotated link|Precambrian}}
• {{annotated link|Timeline of natural history}}

{{reflist}}

• {{cite journal |last1=Hopkins |first1=Michelle |last2=Harrison |first2=T. Mark |last3=Manning |first3=Craig E. |year=2008 |title=Low heat flow inferred from >4 Gyr zircons suggests Hadean plate boundary interactions |journal=Nature |doi=10.1038/nature07465 |pmid=19037314 |bibcode=2008Natur.456..493H |s2cid=4417456|volume=456 |issue=7221 |pages=493–496}}
• {{cite journal |last1=Wyche |first1=S. |last2=Nelson |first2=D. R. |last3=Riganti |first3=A. |year=2004 |title=4350–3130 Ma detrital zircons in the Southern Cross Granite–Greenstone Terrane, Western Australia: implications for the early evolution of the Yilgarn Craton |journal=Australian Journal of Earth Sciences |doi=10.1046/j.1400-0952.2003.01042.x |bibcode=2004AuJES..51...31W |volume=51 |issue=1 |pages=31–45}}
• {{cite journal |last1=Carley |first1=Tamara L. |last2=Miller |first2=Calvin F. |last3=Wooden |first3=Joseph L. |last4=Padilla |first4=Abraham J. |last5=Schmitt |first5=Axel K. |last6=Economos |first6=Rita C. |last7=Bindeman |first7=Ilya N. |last8=Jordan |first8=Brennan T. |display-authors=1 |year=2014 |title=Iceland is not a magmatic analog for the Hadean: Evidence from the zircon record |journal=Earth and Planetary Science Letters |doi=10.1016/j.epsl.2014.08.015 |bibcode=2014E&PSL.405...85C |volume=405 |issue=1 |pages=85–97}}
• {{cite journal |last1=Marchi |first1=S. |last2=Bottke |first2=W. F. |last3=Elkins-Tanton |first3=L. T. |last4=Bierhaus |first4=M. |last5=Wuennemann |first5=K. |last6=Morbidelli |first6=A. |last7=Kring |first7=D. A. |display-authors=1 |year=2014 |title=Widespread mixing and burial of Earth's Hadean crust by asteroid impacts |journal=Nature |doi=10.1038/nature13539 |volume=511 |issue=7511 |pages=578–582|pmid=25079556 |bibcode=2014Natur.511..578M |s2cid=205239647 }}

{{Commons}}

• [https://web.archive.org/web/20071103114128/http://www.peripatus.gen.nz/paleontology/Hadean.html Peripatus.nz: Description of the Hadean Era]
• [https://ghkclass.com/ghkC.html?hadean Hadean (chronostratigraphy scale)]

{{Hadean Footer}}

{{Geological history|c}}

{{Authority control}}

Category:Precambrian geochronology