Evolution Of Atmosferic Oxygen. O<sub>2</sub> build-up in <a href="//commons.wikimedia.org/w/index.php?title=Earth%27s_atmosphere&amp;action=edit&amp;redlink=1" class="new" title="Earth's atmosphere (page does not exist)">earth's atmosphere</a>: 1) (3.85–2.45Gyr ago (Ga)) no O<sub>2</sub> produced, 2) (2.45–1.85Ga) O<sub>2</sub> produced, but absorbed in oceans &amp; seabed rock, 3) (1.85–0.85Ga) O<sub>2</sub> starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer, 4) (0.85–0.54Ga) and 5) (0.54Ga–present) O<sub>2</sub> sinks filled and the gas accumulates]]. Redraw from Heinrich D. Holland (2006), <a rel="nofollow" class="external text" href="http://journals.royalsociety.org/content/81v33567p152570m/fulltext.html">The oxygenation of the atmosphere and oceans</a>, <i>Philosophical Transactions of The Royal Society B</i>, Volume 361, Number 1470 / June 29, 2006, pp. 903-915, DOI 10.1098/rstb.2006.1838.
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