What is Great Oxygenation Event?
The '''Great Oxygenation Event''' ('''GOE''')<ref>also called the Oxygen Catastrophe, Oxygen Crisis, or Oxygen Revolution.</ref> was the creation of free [[oxygen]] in our [[atmosphere]]. It was caused by [[cyanobacteria]] doing [[photosynthesis]]. It took a very long time, from three [[billion]] years ago to about one billion years ago.<ref> Zimmer, Carl (3 October 2013). [http://www.nytimes.com/2013/10/03/science/earths-oxygen-a-mystery-easy-to-take-for-granted.html?_r=0 Earth's oxygen: a mystery easy to take for granted]. ''New York Times''. Retrieved 3 October 2013.</ref> Photosynthesis was making oxygen both before and after the GOE. Before the GOE, organic matter and dissolved [[iron]] chemically captured any free oxygen. Earth has much iron, and iron has higher [[solubility]] than its [[Oxide|oxides]], so the oceans had much dissolved iron. It became [[iron oxide]] and made huge deposits of [[Banded iron formation|banded iron]] [[Rock (geology)|rock]] from the [[Archaean]] and [[Proterozoic]] [[era]]s. When not enough iron remained to capture more oxygen, free oxygen accumulated in the atmosphere. This was the GOE.<ref>Canfield, Donald 2014. ''Oxygen: a four billion year history''. Princeton: Princeton University Press. ISBN 978-0-691-14502-0</ref> [[Image:Oxygenation-atm-2.svg|thumb|center|500px|O<sub>2</sub> build-up in the [[Earth's atmosphere]]. Red and green lines represent the range of the estimates while time is measured in billions of years ago (Ga). <br />Stage 1 (3.85–2.45 Ga): Practically no O<sub>2</sub> in the atmosphere. <br />Stage 2 (2.45–1.85 Ga): O<sub>2</sub> produced, but absorbed in oceans & seabed rock. <br />Stage 3 (1.85–0.85 Ga): O<sub>2</sub> starts to gas out of the oceans, but is absorbed by land surfaces. <br />Stages 4 & 5 (0.85–present): O<sub>2</sub> sinks filled and the gas accumulates.<ref>Holland, Heinrich D. 2006.[https://rstb.royalsocietypublishing.org/content/361/1470/903.full.pdf The oxygenation of the atmosphere and oceans.] ''Philosophical Transactions of the Roya