Contrary to the oxygen-rich atmosphere that prevails today, early Earth was characterized by the absence of Oxygen both in the atmosphere and in the ocean. This early Earth possessed blood red oceans (due to the massive amounts of suspended iron in the water), harsh ultraviolet radiation (due to its lack of an ozone), large amounts of Methane, Nitrogen, and Carbon-Dioxide in the atmosphere (caused by continuous volcanic activity), and a thriving single-celled anaerobic population. This persisted until the Great Oxidation Event, which was the period of time from roughly 2.2 to 2.5 billion years ago (although opinions of this vary), when Oxygen levels a dramatically increased to a never-before-reached amount.
Evidence of this event is most obvious when looking at the primordial ocean. In the primordial ocean, the small amounts of Oxygen present in the atmosphere would be absorbed by decomposing organisms or bind with iron in the water to produce iron-oxide, otherwise known as rust, that would sink to the ocean floor. But, around 2.3 billion years ago there is evidence of a highly unusual amount of rust being distributed onto the ocean floor providing evidence that Oxygen levels on Earth were rising because, as we learned earlier, the only way rust could form was if the iron in the ocean was binding with Oxygen (Arizona State University 2015). Once all the iron in the ocean ran out/became too saturated with Oxygen, the Oxygen had nowhere else to go but into the atmosphere.
Additionally, fossils containing Cyanobacteria, blue-green algae that were the first organisms capable of obtaining energy through photosynthesis- most scientists believe them to be the cause of the Great Oxidation Event, didn't start to appear till after the Great Oxidation Event (Schirrmeister 2015). Even though there is some evidence of Cyanobacteria some 3.5 billion years ago, there is no significant reflection of there influence in the atmosphere during that time. This suggests that another event could not have led to Oxygen increase like that of the Great Oxidation Event because there were no other significant oxygen-producing organisms to carry out the process, like Cyanobacteria.
Oxygen is a highly reactive substance, so its entrance into the atmosphere would have left some distinct geographical or chemical markers. Another example of this can be found in the isotopic ratio of sulfur altered about 2.45 billion years ago showing evidence of an oxygen increase (Biello 2009). "Mass-independent isotopic signatures for δ33S, δ34S, and δ36S from sulfide and sulfate in Precambrian rocks indicate that a change occurred in the sulfur cycle between 2090 and 2450 million years ago (Ma). Before 2450 Ma, the cycle was influenced by gas-phase atmospheric reactions" (Farquhar, et al. 2000).
“The Oxygenation Catastrophe.” The Origins Project, Arizona State University, 22 July 2015, origins.asu.edu/blog/oxygenation-catastrophe.
“Evolution: Precambrian Eon: (4,550-543 Mya).” PBS, Public Broadcasting Service, 2001, www.pbs.org/wgbh/evolution/change/deeptime/protero.html.
Richard A. KerrApr. 16, 2009, 12:00 AM, et al. “How Early Was Oxygen's Rise?” Science | AAAS, 26 July 2017, www.sciencemag.org/news/2009/04/how-early-was-oxygens-rise.
Monday, 16 March 2009 Heather Catchpole ABC. “Early Oceans Had Oxygen-Loving Life.”ABC - Australian Broadcasting Corporation, 16 Mar. 2009, www.abc.net.au/science/articles/2009/03/16/2517425.htm.
Schirrmeister, Bettina E., et al. “Cyanobacteria and the Great Oxidation Event: Evidence from Genes and Fossils.” Palaeontology, John Wiley and Sons Inc., Sept. 2015, www.ncbi.nlm.nih.gov/pmc/articles/PMC4755140/.
Biello, David. “The Origin of Oxygen in Earth's Atmosphere.” Scientific American, 19 Aug. 2009, www.scientificamerican.com/article/origin-of-oxygen-in-atmosphere/.
Farquhar, James, et al. “Atmospheric Influence of Earth's Earliest Sulfur Cycle.” Science, American Association for the Advancement of Science, 4 Aug. 2000, science.sciencemag.org/content/289/5480/756.
“The Proterozoic Eon.” The Proterozoic Eon, University of California Museum of Paleontology, 2011, www.ucmp.berkeley.edu/precambrian/proterozoic.php.
Photos:
“Banded Iron Formation.” Wikipedia, Wikimedia Foundation, 21 Oct. 2017, en.wikipedia.org/wiki/Banded_iron_formation.
“Great Oxygenation Event.” Wikipedia, Wikimedia Foundation, 4 Sept. 2017, simple.wikipedia.org/wiki/Great_Oxygenation_Event.
Video:
TEDEducation. “How a Single-Celled Organism Almost Wiped out Life on Earth - Anusuya Willis.” YouTube, YouTube, 11 Aug. 2016, www.youtube.com/watch?v=dO2xx-aeZ4w&feature=youtu.be
Evidence of this event is most obvious when looking at the primordial ocean. In the primordial ocean, the small amounts of Oxygen present in the atmosphere would be absorbed by decomposing organisms or bind with iron in the water to produce iron-oxide, otherwise known as rust, that would sink to the ocean floor. But, around 2.3 billion years ago there is evidence of a highly unusual amount of rust being distributed onto the ocean floor providing evidence that Oxygen levels on Earth were rising because, as we learned earlier, the only way rust could form was if the iron in the ocean was binding with Oxygen (Arizona State University 2015). Once all the iron in the ocean ran out/became too saturated with Oxygen, the Oxygen had nowhere else to go but into the atmosphere.
Figure 1 shows banded iron formations. These formations are important because each level shows what was happening to Earth's atmosphere during that time. The larger sections show larger amounts of iron oxide showing there was more oxygen in the atmosphere.
Additionally, fossils containing Cyanobacteria, blue-green algae that were the first organisms capable of obtaining energy through photosynthesis- most scientists believe them to be the cause of the Great Oxidation Event, didn't start to appear till after the Great Oxidation Event (Schirrmeister 2015). Even though there is some evidence of Cyanobacteria some 3.5 billion years ago, there is no significant reflection of there influence in the atmosphere during that time. This suggests that another event could not have led to Oxygen increase like that of the Great Oxidation Event because there were no other significant oxygen-producing organisms to carry out the process, like Cyanobacteria.
Oxygen is a highly reactive substance, so its entrance into the atmosphere would have left some distinct geographical or chemical markers. Another example of this can be found in the isotopic ratio of sulfur altered about 2.45 billion years ago showing evidence of an oxygen increase (Biello 2009). "Mass-independent isotopic signatures for δ33S, δ34S, and δ36S from sulfide and sulfate in Precambrian rocks indicate that a change occurred in the sulfur cycle between 2090 and 2450 million years ago (Ma). Before 2450 Ma, the cycle was influenced by gas-phase atmospheric reactions" (Farquhar, et al. 2000).
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| Increased levels of Oxygen during the GOE |
Figure 2 shows the Oxygen build up in Earth's atmosphere. The red and green lines show the range of estimates for Oxygen levels. Time is measured in billions of years ago (Ga).
Works Cited
“The Oxygenation Catastrophe.” The Origins Project, Arizona State University, 22 July 2015, origins.asu.edu/blog/oxygenation-catastrophe.
“Evolution: Precambrian Eon: (4,550-543 Mya).” PBS, Public Broadcasting Service, 2001, www.pbs.org/wgbh/evolution/change/deeptime/protero.html.
Richard A. KerrApr. 16, 2009, 12:00 AM, et al. “How Early Was Oxygen's Rise?” Science | AAAS, 26 July 2017, www.sciencemag.org/news/2009/04/how-early-was-oxygens-rise.
Monday, 16 March 2009 Heather Catchpole ABC. “Early Oceans Had Oxygen-Loving Life.”ABC - Australian Broadcasting Corporation, 16 Mar. 2009, www.abc.net.au/science/articles/2009/03/16/2517425.htm.
Schirrmeister, Bettina E., et al. “Cyanobacteria and the Great Oxidation Event: Evidence from Genes and Fossils.” Palaeontology, John Wiley and Sons Inc., Sept. 2015, www.ncbi.nlm.nih.gov/pmc/articles/PMC4755140/.
Biello, David. “The Origin of Oxygen in Earth's Atmosphere.” Scientific American, 19 Aug. 2009, www.scientificamerican.com/article/origin-of-oxygen-in-atmosphere/.
Farquhar, James, et al. “Atmospheric Influence of Earth's Earliest Sulfur Cycle.” Science, American Association for the Advancement of Science, 4 Aug. 2000, science.sciencemag.org/content/289/5480/756.
“The Proterozoic Eon.” The Proterozoic Eon, University of California Museum of Paleontology, 2011, www.ucmp.berkeley.edu/precambrian/proterozoic.php.
Photos:
“Banded Iron Formation.” Wikipedia, Wikimedia Foundation, 21 Oct. 2017, en.wikipedia.org/wiki/Banded_iron_formation.
“Great Oxygenation Event.” Wikipedia, Wikimedia Foundation, 4 Sept. 2017, simple.wikipedia.org/wiki/Great_Oxygenation_Event.
Video:
TEDEducation. “How a Single-Celled Organism Almost Wiped out Life on Earth - Anusuya Willis.” YouTube, YouTube, 11 Aug. 2016, www.youtube.com/watch?v=dO2xx-aeZ4w&feature=youtu.be
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