Editing Hadean (section)

==Plate tectonics==
[[File:Hadean and Archean continents.gif|thumb|upright=1.75|Evolution of continental crust and ocean depths (from Korenaga, 2021)<ref name=Korenaga2021/>]]
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).<ref>{{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}}</ref> However, some geologists suggest that the zircons could have been formed by meteorite impacts.<ref>{{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}}</ref> The direct evidence of Hadean geology from zircons is limited, because the zircons are largely gathered in one locality in Australia.<ref name=Korenaga2021/><ref name=Harrison2020/> Geophysical models are underconstrained, but can paint a general picture of the state of Earth in the Hadean.<ref name=Korenaga2021/><ref>{{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}}</ref>

[[Mantle convection]] in the Hadean was likely vigorous, due to lower [[viscosity]].<ref name=Korenaga2021/> 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.<ref name=Korenaga2021a>{{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}}</ref> Whether the vigorous convection led to plate tectonics in the Hadean or was confined under a rigid lid is still a matter of debate.<ref name=Korenaga2021/><ref name=Windley2021>{{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}}</ref><ref name=Harrison2020>{{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 }}</ref><ref name=Tang2016>{{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 }}</ref> The presence of Hadean oceans is thought to have triggered plate tectonics.<ref name=Regenauer2001>{{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}}</ref>

[[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.<ref name=Sleep2014>{{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 }}</ref>

If plate tectonics occurred in the Hadean, it would have formed [[continental crust]].<ref name=Guo2020>{{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}}</ref> Different models predict different amounts of continental crust during the Hadean.<ref name=Harrison2009>{{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 }}</ref> The work of Dhiume ''et al.'' predicts that by the end of the Hadean, the continental crust had only 25% of today's area.<ref name=Dhuime2012>{{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}}</ref> The models of Korenaga, ''et al.'' predict that the continental crust grew to present-day volume sometime between 4.2 and 4.0 [[Gya (unit)|Gya]].<ref name=Guo2020/><ref>{{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 }}</ref>