Earth

== Natural history ==
{{Main|History of Earth|Timeline of natural history}}

=== Formation ===
{{Further|Early Earth|Hadean}}
[[File:The Mysterious Case of the Disappearing Dust.jpg|thumb|upright=1.3|A 2012 artistic impression of the early [[Solar System]]'s [[protoplanetary disk]] from which Earth and other Solar System bodies were formed|center]]

The oldest material found in the [[Solar System]] is dated to {{val|4.5682|0.0002|0.0004}} [[Gigaannum|Ga]] (billion years) ago.<ref name=bouvier_wadhwa2010 /> By {{val|4.54|0.04|u=Ga}} the primordial Earth had formed.<ref name="age_earth1" /> The bodies in [[Formation and evolution of the Solar System|the Solar System formed and evolved]] with the Sun. In theory, a [[solar nebula]] partitions a volume out of a [[molecular cloud]] by gravitational collapse, which begins to spin and flatten into a [[circumstellar disk]], and then the planets grow out of that disk with the Sun. A nebula contains gas, ice grains, and [[Cosmic dust|dust]] (including [[primordial nuclide]]s). According to [[nebular theory]], [[planetesimal]]s formed by [[accretion (astrophysics)|accretion]], with the primordial Earth being estimated as likely taking anywhere from 70 to 100 million years to form.<ref>{{cite journal|url=https://ntrs.nasa.gov/citations/20180002991|title=Ag Isotopic Evolution of the Mantle During Accretion: New Constraints from Pd and Ag Metal–Silicate Partitioning|journal=Differentiation: Building the Internal Architecture of Planets|last1=Righter|first1=K.|first2=M.|last2=Schonbachler|date=7 May 2018|volume=2084|page=4034|bibcode=2018LPICo2084.4034R|access-date=25 October 2020}}</ref>

Estimates of the age of the Moon range from 4.5 Ga to significantly younger.<ref>{{Cite journal|last1=Tartèse|first1=Romain|last2=Anand|first2=Mahesh|last3=Gattacceca|first3=Jérôme|last4=Joy|first4=Katherine H.|author-link4=Katherine Joy|last5=Mortimer|first5=James I.|last6=Pernet-Fisher|first6=John F.|last7=Russell|first7=Sara|author7-link=Sara Russell|last8=Snape|first8=Joshua F.|last9=Weiss|first9=Benjamin P.|date=2019|title=Constraining the Evolutionary History of the Moon and the Inner Solar System: A Case for New Returned Lunar Samples|journal=Space Science Reviews|language=en|volume=215|issue=8|page=54|doi=10.1007/s11214-019-0622-x|bibcode=2019SSRv..215...54T|issn=1572-9672|doi-access=free}}</ref> A [[giant impact hypothesis|leading hypothesis]] is that it was formed by accretion from material loosed from Earth after a [[Mars]]-sized object with about 10% of Earth's mass, named [[Theia (planet)|Theia]], collided with Earth.<ref name=reilly20091022 /> It hit Earth with a glancing blow and some of its mass merged with Earth.<ref name="canup_asphaug2001b" /><ref>{{cite journal|title=On the origin and composition of Theia: Constraints from new models of the Giant Impact|journal=Icarus|last1=Meier|first1=M. M. M.|last2=Reufer|first2=A.|last3=Wieler|first3=R.|date=4 August 2014|volume=242|page=5|doi=10.1016/j.icarus.2014.08.003|arxiv=1410.3819|bibcode=2014Icar..242..316M|s2cid=119226112}}</ref> Between approximately 4.1 and {{val|3.8|u=Ga}}, numerous [[Impact event|asteroid impacts]] during the [[Late Heavy Bombardment]] caused significant changes to the greater surface environment of the Moon and, by inference, to that of Earth.<ref>{{cite book|title=Encyclopedia of Astrobiology|first1=Philippe|last1= Claeys|first2=Alessandro|last2=Morbidelli|author-link2=Alessandro Morbidelli (astronomer)|editor-first1=Muriel|editor-last1= Gargaud|editor-first2=Prof Ricardo|editor-last2=Amils|editor-first3= José Cernicharo|editor-last3= Quintanilla|editor-first4= Henderson James (Jim) |editor-last4= Cleaves II|editor-first5=William M.|editor-last5=Irvine|editor-first6= Prof Daniele L.|editor-last6= Pinti|editor-first7= Michel|editor-last7= Viso|year= 2011|publisher=Springer Berlin Heidelberg|pages=909–912|doi=10.1007/978-3-642-11274-4_869|chapter=Late Heavy Bombardment|isbn= 978-3-642-11271-3}}</ref>

=== After formation ===
{{Main|Geological history of Earth}}
[[Atmosphere of Earth|Earth's atmosphere]] and oceans were formed by [[volcanism|volcanic activity]] and [[outgassing]].<ref>{{cite web |url=https://www.lpi.usra.edu/education/timeline/gallery/slide_17.html |title=Earth's Early Atmosphere and Oceans |work=[[Lunar and Planetary Institute]] |publisher=[[Universities Space Research Association]] |access-date=27 June 2019}}</ref> Water vapor from these sources [[Origin of water on Earth|condensed]] into the oceans, augmented by water and ice from asteroids, [[protoplanet]]s, and [[comet]]s.<ref name="watersource" /> Sufficient water to fill the oceans may have been on Earth since it formed.<ref>{{Cite journal|last1=Piani|first1=Laurette|last2=Marrocchi|first2=Yves|last3=Rigaudier|first3=Thomas|last4=Vacher|first4=Lionel G.|last5=Thomassin|first5=Dorian|last6=Marty|first6=Bernard|display-authors=1|date=2020|title=Earth's water may have been inherited from material similar to enstatite chondrite meteorites|url=https://doi.org/10.1126/science.aba1948|journal=Science|language=en|volume=369|issue=6507|pages=1110–1113|doi=10.1126/science.aba1948|issn=0036-8075|pmid=32855337|bibcode=2020Sci...369.1110P|s2cid=221342529}}</ref> In this model, atmospheric [[greenhouse gas]]es kept the oceans from freezing when the newly forming Sun [[Faint young Sun paradox|had only 70%]] of its [[solar luminosity|current luminosity]].<ref name="asp2002" /> By {{val|3.5|u=Ga}}, [[Earth's magnetic field]] was established, which helped prevent the atmosphere from being stripped away by the [[solar wind]].<ref name="physorg20100304" />

[[File:NASA-EarlyEarth-PaleOrangeDot-20190802.jpg|thumb|upright=1.5|''Pale orange dot'', an artist's impression of [[Early Earth]], featuring its tinted orange [[methane]]-rich [[Prebiotic atmosphere|early atmosphere]]<ref name="Trainer Pavlov DeWitt Jimenez pp. 18035–18042">{{cite journal |last1=Trainer |first1=Melissa G. |last2=Pavlov |first2=Alexander A. |last3=DeWitt |first3=H. Langley |last4=Jimenez |first4=Jose L. |last5=McKay |first5=Christopher P. |last6=Toon |first6=Owen B. |last7=Tolbert |first7=Margaret A. |display-authors=1 |date=28 November 2006 |title=Organic haze on Titan and the early Earth |journal=Proceedings of the National Academy of Sciences |volume=103 |issue=48 |pages=18035–18042 |doi=10.1073/pnas.0608561103 |issn=0027-8424 |pmc=1838702 |pmid=17101962 |doi-access=free}}</ref>|center]]

As the molten outer layer of Earth cooled it [[Phase transition|formed]] the first solid [[Earth's crust|crust]], which is thought to have been [[mafic]] in composition. The first [[continental crust]], which was more [[felsic]] in composition, formed by the partial melting of this mafic crust.<ref name="comp">{{cite journal |title=The composition of the Earth |year=1995 |url=https://www.sciencedirect.com/science/article/abs/pii/0009254194001404 |doi=10.1016/0009-2541(94)00140-4 |last1=McDonough |first1=W.F. |last2=Sun |first2=S.-s. |journal=Chemical Geology |volume=120 |issue=3–4 |pages=223–253 |bibcode=1995ChGeo.120..223M }}</ref> The presence of grains of the [[Hadean zircon|mineral zircon of Hadean age]] in [[Eoarchean]] [[sedimentary rock]]s suggests that at least some felsic crust existed as early as {{val|4.4|u=Ga}}, only {{val|140|u=[[Megaannum|Ma]]}} after Earth's formation.<ref name="science310_5756_1947" /> There are two main models of how this initial small volume of continental crust evolved to reach its current abundance:<ref name="williams_santosh2004" /> (1) a relatively steady growth up to the present day,<ref name="science164_1229" /> which is supported by the radiometric dating of continental crust globally and (2) an initial rapid growth in the volume of continental crust during the [[Archean]], forming the bulk of the continental crust that now exists,<ref name="ajes38_613" /><ref name="tp322_19" /> which is supported by isotopic evidence from [[hafnium]] in [[zircon]]s and [[neodymium]] in sedimentary rocks. The two models and the data that support them can be reconciled by large-scale [[crustal recycling|recycling of the continental crust]], particularly during the early stages of Earth's history.<ref name="Dhuime_etal_2018" />

New continental crust forms as a result of [[plate tectonics]], a process ultimately driven by the continuous loss of heat from Earth's interior. Over [[Geologic time scale|the period]] of hundreds of millions of years, tectonic forces have caused areas of continental crust to group together to form [[supercontinent]]s that have subsequently broken apart. At approximately {{val|750|u=Ma}}, one of the earliest known supercontinents, [[Rodinia]], began to break apart. The continents later recombined to form [[Pannotia]] at {{val|600|–|540|u=Ma}}, then finally [[Pangaea]], which also began to break apart at {{val|180|u=Ma}}.<ref name="bradley_2011" />

The most recent pattern of [[ice age]]s began about {{val|40|u=Ma}},<ref>{{cite news |url=https://www.amnh.org/explore/ology/earth/ask-a-scientist-about-our-environment/how-did-the-ice-age-end |title=When and how did the ice age end? Could another one start? |first=Ro |last=Kinzler |access-date=27 June 2019 |website=Ology|publisher=[[American Museum of Natural History]]}}</ref> and then intensified during the [[Pleistocene]] about {{val|3|u=Ma}}.<ref>{{cite journal |title=Causes of ice age intensification across the Mid-Pleistocene Transition |journal=[[Proc Natl Acad Sci U S A]] |date=12 December 2007 |volume=114 |issue=50 |pages=13114–13119 |doi=10.1073/pnas.1702143114 |pmc=5740680 |pmid=29180424 |first1=Thomas B. |last1=Chalk |first2=Mathis P. |last2=Hain |first3=Gavin L. |last3=Foster |first4=Eelco J. |last4=Rohling |first5=Philip F. |last5=Sexton |first6=Marcus P. S. |last6=Badger |first7=Soraya G. |last7=Cherry |first8=Adam P. |last8=Hasenfratz |first9=Gerald H. |last9=Haug |first10=Samuel L. |last10=Jaccard |first11=Alfredo |last11=Martínez-García |first12=Heiko |last12=Pälike |first13=Richard D. |last13=Pancost |first14=Paul A. |last14=Wilson |display-authors=1|doi-access=free }}</ref> [[High latitude|High-]] and [[middle latitude|middle-latitude]] regions have since undergone repeated cycles of glaciation and thaw, repeating about every 21,000, 41,000 and 100,000 years.<ref name="psc" /> The [[Last Glacial Period]], colloquially called the "last ice age", covered large parts of the continents, to the middle latitudes, in ice and ended about 11,700 years ago.<ref>{{cite journal |url=https://www.sciencedirect.com/science/article/abs/pii/S0277379110003197 |title=The potential of New Zealand kauri (Agathis australis) for testing the synchronicity of abrupt climate change during the Last Glacial Interval (60,000–11,700 years ago) |journal=Quaternary Science Reviews |publisher=Elsevier |last1=Turner |first1=Chris S.M. |display-authors=et al |year=2010 |doi=10.1016/j.quascirev.2010.08.017 |volume=29 |issue=27–28 |pages=3677–3682 |bibcode=2010QSRv...29.3677T |access-date=3 November 2020}}</ref>

=== Origin of life and evolution ===
{{Main|Abiogenesis{{!}}Origin of life|Earliest known life forms|History of life}}
[[Chemical reaction]]s led to the first self-replicating molecules about four billion years ago. A half billion years later, the [[last universal common ancestor|last common ancestor of all current life]] arose.<ref name="sa282_6_90" /> The evolution of [[photosynthesis]] allowed the Sun's energy to be harvested directly by life forms. The resultant [[molecular oxygen]] ({{chem2|O2}}) accumulated in the atmosphere and due to interaction with ultraviolet solar radiation, formed a protective [[ozone layer]] ({{chem2|O3}}) in the upper atmosphere.<ref name="NYT-20131003">{{cite news |last=Zimmer |first=Carl |author-link=Carl Zimmer |title=Earth's Oxygen: A Mystery Easy to Take for Granted |url=https://www.nytimes.com/2013/10/03/science/earths-oxygen-a-mystery-easy-to-take-for-granted.html |archive-url=https://web.archive.org/web/20131003121909/http://www.nytimes.com/2013/10/03/science/earths-oxygen-a-mystery-easy-to-take-for-granted.html |archive-date=3 October 2013 |url-access=limited |date=3 October 2013 |work=[[The New York Times]] |access-date=3 October 2013}}</ref> The incorporation of smaller cells within larger ones resulted in the [[endosymbiotic theory|development of complex cells]] called [[eukaryote]]s.<ref name="jas22_3_225" /> True multicellular organisms formed as cells within [[Colony (biology)|colonies]] became increasingly specialized. Aided by the absorption of harmful [[ultraviolet radiation]] by the ozone layer, life colonized Earth's surface.<ref name="burton20021129" /> Among the earliest [[fossil]] evidence for life is [[microbial mat]] fossils found in 3.48&nbsp;billion-year-old [[sandstone]] in [[Western Australia]],<ref>{{cite journal |last1=Noffke |first1=Nora |author-link=Nora Noffke |last2=Christian |first2=Daniel |last3=Wacey |first3=David |last4=Hazen |first4=Robert M. |author4-link=Robert Hazen |title=Microbially Induced Sedimentary Structures Recording an Ancient Ecosystem in the ca. 3.48 Billion-Year-Old Dresser Formation, Pilbara, Western Australia |date=8 November 2013 |journal=[[Astrobiology (journal)|Astrobiology]] |doi=10.1089/ast.2013.1030 |bibcode=2013AsBio..13.1103N |pmid=24205812 |pmc=3870916 |volume=13 |issue=12 |pages=1103–1124}}</ref> [[Biogenic substance|biogenic]] [[graphite]] found in 3.7&nbsp;billion-year-old [[metasediment]]ary rocks in [[Western Greenland]],<ref>{{cite journal |last1=Ohtomo |first1=Yoko |last2=Kakegawa |first2=Takeshi |last3=Ishida |first3=Akizumi |last4=Nagase |first4=Toshiro |last5=Rosing |first5=Minik T. |s2cid=54767854 |display-authors=3 |date=January 2014 |title=Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks |journal=[[Nature Geoscience]] |volume=7 |issue=1 |pages=25–28 |bibcode=2014NatGe...7...25O |doi=10.1038/ngeo2025 |issn=1752-0894}}</ref> and remains of [[biotic material]] found in 4.1&nbsp;billion-year-old rocks in Western Australia.<ref>{{cite news |last=Borenstein |first=Seth |title=Hints of life on what was thought to be desolate early Earth |url=http://apnews.excite.com/article/20151019/us-sci--earliest_life-a400435d0d.html |date=19 October 2015 |work=[[Excite (web portal)|Excite]] |location=Yonkers, NY |publisher=[[Mindspark Interactive Network]] |agency=[[Associated Press]] |access-date=20 October 2015 |archive-url=https://web.archive.org/web/20160818063111/https://apnews.excite.com/article/20151019/us-sci--earliest_life-a400435d0d.html |archive-date=18 August 2016}}</ref><ref>{{cite journal |last1=Bell |first1=Elizabeth A. |last2=Boehnike |first2=Patrick |last3=Harrison |first3=T. Mark |author-link3=T. Mark Harrison |last4=Mao |first4=Wendy L. |author4-link=Wendy Mao |date=19 October 2015 |title=Potentially biogenic carbon preserved in a 4.1&nbsp;billion-year-old zircon |journal=Proc. Natl. Acad. Sci. U.S.A. |doi=10.1073/pnas.1517557112 |issn=1091-6490 |pmid=26483481 |pmc=4664351 |volume=112 |issue=47 |pages=14518–4521 |bibcode=2015PNAS..11214518B |doi-access=free}} Early edition, published online before print.</ref> The [[Earliest known life forms|earliest direct evidence of life]] on Earth is contained in 3.45&nbsp;billion-year-old [[Australia (continent)|Australian]] rocks showing fossils of [[microorganism]]s.<ref>{{cite web |last=Tyrell |first=Kelly April |title=Oldest fossils ever found show life on Earth began before 3.5 billion years ago |url=https://news.wisc.edu/oldest-fossils-ever-found-show-life-on-earth-began-before-3-5-billion-years-ago/ |date=18 December 2017 |publisher=[[University of Wisconsin–Madison]] |access-date=18 December 2017}}</ref><ref>{{cite journal |last1=Schopf |first1=J. William |last2=Kitajima |first2=Kouki |last3=Spicuzza |first3=Michael J. |last4=Kudryavtsev |first4=Anatolly B. |last5=Valley |first5=John W. |title=SIMS analyses of the oldest known assemblage of microfossils document their taxon-correlated carbon isotope compositions |year=2017 |journal=[[Proceedings of the National Academy of Sciences of the United States of America|PNAS]] |volume=115 |issue=1 |pages=53–58 |doi=10.1073/pnas.1718063115 |pmid=29255053 |pmc=5776830 |bibcode=2018PNAS..115...53S |doi-access=free}}</ref>[[File:Archean.png|thumb|An artist's impression of the [[Archean]], the [[Geologic time scale#Divisions of geologic time|eon]] after Earth's formation, featuring round [[stromatolite]]s, which are early oxygen-producing forms of life from billions of years ago. After the [[Late Heavy Bombardment]], [[Earth's crust]] had cooled, its water-rich barren [[planetary surface|surface]] is marked by [[continent]]s and [[volcano]]es, with the Moon still orbiting Earth half as far as it is today, appearing 2.8 times larger and producing strong [[tide]]s.<ref name="Lunar and Planetary Institute">{{cite web |title=Earth-Moon Dynamics |url=https://www.lpi.usra.edu/exploration/training/illustrations/earthMoon/ |access-date=2 September 2022 |website=Lunar and Planetary Institute}}</ref>|center|500x500px]]During the [[Neoproterozoic]], {{val|1000|to|539|u=Ma}}, much of Earth might have been covered in ice. This hypothesis has been termed "[[Snowball Earth]]", and it is of particular interest because it preceded the [[Cambrian explosion]], when multicellular life forms significantly increased in complexity.<ref>{{cite book|page=42|title=Climate Change and the Course of Global History|last1=Brooke|first1=John L.|year= 2014|publisher=Cambridge University Press|isbn=978-0-521-87164-8}}</ref><ref>{{cite book|page=56|title=Epigenetic Mechanisms of the Cambrian Explosion|last1=Cabej|first1=Nelson R.|year=2019|publisher=Elsevier Science|isbn=978-0-12-814312-4}}</ref> Following the Cambrian explosion, {{val|535|u=Ma}}, there have been at least five major [[Extinction event|mass extinctions]] and many minor ones.<ref name="Stanley_2016" /> Apart from the proposed current [[Holocene extinction]] event, the [[Cretaceous–Paleogene extinction event|most recent]] was {{val|66|u=Ma}}, when [[Chicxulub impactor|an asteroid impact]] triggered the extinction of non-avian dinosaurs and other large reptiles, but largely spared small animals such as insects, [[mammal]]s, lizards and birds. Mammalian life has diversified over the past {{val|66|u=Mys}}, and several million years ago, an African [[ape]] species gained the ability to stand upright.<ref name="gould1994" /><ref>{{Cite journal |last=Daver |first=G. |last2=Guy |first2=F. |last3=Mackaye |first3=H. T. |last4=Likius |first4=A. |last5=Boisserie |first5=J.-R. |last6=Moussa |first6=A. |last7=Pallas |first7=L. |last8=Vignaud |first8=P. |last9=Clarisse |first9=N. D. |date=2022 |title=Postcranial evidence of late Miocene hominin bipedalism in Chad |url=https://www.nature.com/articles/s41586-022-04901-z |journal=Nature |language=en |volume=609 |issue=7925 |pages=94–100 |doi=10.1038/s41586-022-04901-z |issn=1476-4687}}</ref> This facilitated tool use and encouraged communication that provided the nutrition and stimulation needed for a larger brain, which led to the [[Human evolution|evolution of humans]]. The [[History of agriculture|development of agriculture]], and then [[List of ancient civilizations|civilization]], led to humans having an [[Human impact on the environment|influence on Earth]] and the nature and quantity of other life forms that continues to this day.<ref name="bgsa119_1_140" />

=== Future ===
{{Main|Future of Earth}}
{{See also|Global catastrophic risk}}
[[File:Red Giant Earth warm.jpg|thumb|upright=1.3|alt=A dark gray and red sphere representing the Earth lies against a black background to the right of an orange circular object representing the Sun|Conjectured illustration of the scorched Earth after the [[Sun]] has entered the [[red giant]] phase, about 5–7&nbsp;billion years from now]]
Earth's expected long-term future is tied to that of the Sun. Over the next {{val|1.1|u=billion years}}, solar luminosity will increase by 10%, and over the next {{val|3.5|u=billion years}} by 40%.<ref name="sun_future" /> Earth's increasing surface temperature will accelerate the [[carbonate–silicate cycle|inorganic carbon cycle]], reducing {{chem2|CO2}} concentration to levels lethally low for plants ({{val|10|ul=ppm}} for [[C4 carbon fixation|C4 photosynthesis]]) in approximately {{val|100|–|900|u=million years}}.<ref name="britt2000" /><ref name="pnas1_24_9576" /> The lack of vegetation will result in the loss of oxygen in the atmosphere, making animal life impossible.<ref name="ward_brownlee2002" /> Due to the increased luminosity, Earth's mean temperature may reach {{convert|100|C|F|0|abbr=}} in 1.5&nbsp;billion years, and all ocean water will evaporate and be lost to space, which may trigger a [[runaway greenhouse effect]], within an estimated 1.6 to 3&nbsp;billion years.<ref name="Mello-2020">{{Cite journal
|last1=Mello |first1=Fernando de Sousa |last2=Friaça |first2=Amâncio César Santos |date=2020 |title=The end of life on Earth is not the end of the world: converging to an estimate of life span of the biosphere? |journal=International Journal of Astrobiology |language=en |volume=19 |issue=1 |pages=25–42 |doi=10.1017/S1473550419000120 |bibcode=2020IJAsB..19...25D |issn=1473-5504 |doi-access=free}}</ref> Even if the Sun were stable, a fraction of the water in the modern oceans will descend to the [[Mantle (geology)|mantle]], due to reduced steam venting from mid-ocean ridges.<ref name="Mello-2020" /><ref name="hess5_4_569" />

The Sun will [[stellar evolution|evolve]] to become a [[red giant]] in about {{val|5|u=billion years}}. Models predict that the Sun will expand to roughly {{convert|1|AU|e6km e6mi|lk=in|abbr=unit}}, about 250 times its present radius.<ref name="sun_future" /><ref name="sun_future_schroder" /> Earth's fate is less clear. As a red giant, the Sun will lose roughly 30% of its mass, so, without tidal effects, Earth will move to an orbit {{convert|1.7|AU|e6km e6mi|lk=off|abbr=unit}} from the Sun when the star reaches its maximum radius, otherwise, with tidal effects, it may enter the Sun's atmosphere and be vaporized.<ref name="sun_future" />