Editing Calcium (section)

===Geochemical cycling===
{{Main|Carbonate–silicate cycle}}
[[Calcium cycle|Calcium cycling]] provides a link between [[tectonics]], [[climate]], and the [[carbon cycle]]. In the simplest terms, mountain-building exposes calcium-bearing rocks such as [[basalt]] and [[granodiorite]] to chemical weathering and releases Ca<sup>2+</sup> into surface water. These ions are transported to the ocean where they react with dissolved CO<sub>2</sub> to form [[limestone]] ({{chem|CaCO|3}}), which in turn settles to the sea floor where it is incorporated into new rocks. Dissolved CO<sub>2</sub>, along with [[carbonate]] and [[bicarbonate]] ions, are termed "[[Total inorganic carbon|dissolved inorganic carbon]]" (DIC).<ref name="Berner" />

The actual reaction is more complicated and involves the bicarbonate ion (HCO{{su|b=3|p=−}}) that forms when CO<sub>2</sub> reacts with water at seawater [[pH]]:

:{{chem2 | Ca(2+) + 2 HCO3- -> CaCO3↓ + CO2 + H2O }}

At seawater pH, most of the dissolved CO<sub>2</sub> is immediately converted back into {{chem|HCO|3|-}}. The reaction results in a net transport of one molecule of CO<sub>2</sub> from the ocean/atmosphere into the [[lithosphere]].<ref>{{cite web |author=Zeebe |date=2006 |title=Marine carbonate chemistry |url=https://editors.eol.org/eoearth/wiki/Marine_carbonate_chemistry |access-date=2010-03-13 |publisher=National Council for Science and the Environment}}</ref> The result is that each Ca<sup>2+</sup> ion released by chemical weathering ultimately removes one CO<sub>2</sub> molecule from the surficial system (atmosphere, ocean, soils and living organisms), storing it in carbonate rocks where it is likely to stay for hundreds of millions of years. The weathering of calcium from rocks thus scrubs CO<sub>2</sub> from the ocean and atmosphere, exerting a strong long-term effect on climate.<ref name="Berner">{{Cite journal|last1=Berner|first1=Robert|title= The long-term carbon cycle, fossil fuels and atmospheric composition |journal=Nature|date=2003|volume=426|pages= 323–26|doi=10.1038/nature02131|pmid=14628061|issue=6964|bibcode = 2003Natur.426..323B |s2cid=4420185}}</ref><ref>{{Cite journal|title = A negative feedback mechanism for the long-term stabilization of Earth's surface temperature|journal = Journal of Geophysical Research: Oceans|date = 1981-10-20|pages = 9776–82|volume = 86|issue = C10|doi = 10.1029/JC086iC10p09776|first1 = James C. G.|last1 = Walker|first2 = P. B.|last2 = Hays|first3 = J. F.|last3 = Kasting|bibcode=1981JGR....86.9776W}}</ref>