Editing Precambrian (section)

==Planetary environment and the oxygen catastrophe==

[[File:Temagami greenstone belt pillow lava.jpg|thumb|Weathered Precambrian [[pillow lava]] in the [[Temagami Greenstone Belt]] of the [[Canadian Shield]]]]
Evidence of the details of [[plate tectonics|plate motions]] and other [[tectonic]] activity in the Precambrian is difficult to interpret. It is generally believed that small proto-continents existed before 4280 Ma, and that most of the Earth's landmasses collected into a single [[supercontinent]] around 1130 Ma. The supercontinent, known as [[Rodinia]], broke up around 750 Ma. A number of [[glaciation|glacial periods]] have been identified going as far back as the [[Huronian]] epoch, roughly 2400–2100 Ma. One of the best studied is the [[Sturtian-Varangian]] glaciation, around 850–635 Ma, which may have brought glacial conditions all the way to the equator, resulting in a "[[Snowball Earth]]".<ref>{{Cite journal |last1=Hoffman |first1=Paul F. |last2=Abbot |first2=Dorian S. |last3=Ashkenazy |first3=Yosef |last4=Benn |first4=Douglas I. |last5=Brocks |first5=Jochen J. |last6=Cohen |first6=Phoebe A. |last7=Cox |first7=Grant M. |last8=Creveling |first8=Jessica R. |last9=Donnadieu |first9=Yannick |last10=Erwin |first10=Douglas H. |last11=Fairchild |first11=Ian J. |last12=Ferreira |first12=David |last13=Goodman |first13=Jason C. |last14=Halverson |first14=Galen P. |last15=Jansen |first15=Malte F. |display-authors=8 |date=2017-11-08 |title=Snowball Earth climate dynamics and Cryogenian geology-geobiology |journal=Science Advances |volume=3 |issue=11 |pages=e1600983 |doi=10.1126/sciadv.1600983 |pmc=5677351 |pmid=29134193|bibcode=2017SciA....3E0983H }}</ref><ref>{{Cite journal |last=Parnell |first=John |date=2022-06-01 |title=Snowball Earth to Global Warming: Coupled vanadium-carbonaceous deposits in the Cryogenian-Cambrian |url=https://www.sciencedirect.com/science/article/pii/S0169136822001846 |journal=Ore Geology Reviews |volume=145 |pages=104876 |doi=10.1016/j.oregeorev.2022.104876 |bibcode=2022OGRv..14504876P |issn=0169-1368|hdl=2164/18433 |hdl-access=free }}</ref>

It is believed that [[molecular]] oxygen was not a significant fraction of Earth's atmosphere until after [[photosynthesis|photosynthetic]] life forms evolved and began to produce it in large quantities as a byproduct of their [[metabolism]]. This radical shift from a chemically inert to an oxidizing atmosphere caused an [[ecological crisis]], sometimes called the [[Great Oxygenation Event|oxygen catastrophe]]. At first, [[oxygen]] would have quickly combined with other elements in Earth's crust, primarily iron, removing it from the atmosphere. After the supply of oxidizable surfaces ran out, oxygen would have begun to accumulate in the atmosphere, and the modern high-oxygen atmosphere would have developed. Evidence for this lies in older rocks that contain massive [[banded iron formation]]s that were laid down as iron oxides.<ref>{{Citation |last1=Kump |first1=Lee R. |title=8.1 The Great Oxidation Event |date=2013 |work=Reading the Archive of Earth’s Oxygenation: Volume 3: Global Events and the Fennoscandian Arctic Russia - Drilling Early Earth Project |pages=1517–1533 |editor-last=Melezhik |editor-first=Victor A. |url=https://link.springer.com/chapter/10.1007/978-3-642-29670-3_11 |access-date=2025-01-27 |place=Berlin, Heidelberg |publisher=Springer |language=en |doi=10.1007/978-3-642-29670-3_11 |isbn=978-3-642-29670-3 |last2=Fallick |first2=Anthony E. |last3=Melezhik |first3=Victor A. |last4=Strauss |first4=Harald |last5=Lepland |first5=Aivo |editor2-last=Prave |editor2-first=Anthony R. |editor3-last=Hanski |editor3-first=Eero J. |editor4-last=Fallick |editor4-first=Anthony E.}}</ref><ref>{{Cite journal |last1=Konhauser |first1=Kurt O. |last2=Pecoits |first2=Ernesto |last3=Lalonde |first3=Stefan V. |last4=Papineau |first4=Dominic |last5=Nisbet |first5=Euan G. |last6=Barley |first6=Mark E. |last7=Arndt |first7=Nicholas T. |last8=Zahnle |first8=Kevin |last9=Kamber |first9=Balz S. |date=2009 |title=Oceanic nickel depletion and a methanogen famine before the Great Oxidation Event |url=https://www.nature.com/articles/nature07858 |journal=Nature |language=en |volume=458 |issue=7239 |pages=750–753 |doi=10.1038/nature07858 |pmid=19360085 |bibcode=2009Natur.458..750K |issn=1476-4687}}</ref>