Lesson 02: Plate Tectonics in the News

"Odd New Theory Explains How Early Earth Got Its Oxygen"

Cyanobacteria diagram from https://en.wikipedia.org/wiki/Cyanobacteria

Oxygen production on Earth is theorized to have started about 2.5 billion years ago by oceanic cyanobacteria. These cyanobacteria produced oxygen as a product of photosynthesis. At around 2.3 billion years ago, an environmental change occurred, called the Great Oxygenation Event (GOE). At this point, the oxygen sinks on Earth became saturated, so oxygen produced by these cyanobacteria was free to go into the atmosphere.

But what happened during that in between period? There are many theories that explain what happened in that time lag in between the beginning of oxygen production and the GOE. A more recent one is addressed in the news article I found.

Convergent Boundary from https://geomaps.wr.usgs.gov/parks/pltec/converge.html

According to a news article on Live Science, a new study by Megan Duncan and Rajdeep Dasgupta at Rice University in Texas, this might be due to plate tectonics. When organic creatures die, they produce carbon. This new study suggests that carbon from these dead creatures got subducted under Earth's crust. (Subduction occurs when there is a convergent plate boundary and one plate goes underneath the other.) With the carbon out of the picture, the oxygen waste product remained above, in the atmosphere.



The theory was modeled with a computer model of the atmosphere showing what happens when carbon dioxide and water react. They make molecular oxygen and formaldehyde (used in place of more complex organic carbon compounds). Normally, the oxygen cycles back and makes more carbon dioxide and water. However, with plate tectonics in the picture, the formaldehyde element  was pushed underground by the subducting plates, leaving breathable oxygen in the air.

Intro to Plate Tectonics from http://www.bucknell.edu/x17758.xml

However, this theory is only viable if modern plate tectonics have not always existed. While plate tectonics is widely accepted to explain continental drift, volcano and earthquake patterns, and seafloor spreading, it is a point of disagreement to when exactly this mechanism began. Regardless, there is increasing evidence that Earth might not have initially had plate tectonics, such as rock samples found in Canada that contain material created 4.2 billion years ago. These findings indicate that plate tectonics might not have always been in motion.

4.2 Ga Material in Rock from www.sciencenews.org/article/remnants-earths

-original-crust-preserve-time-plate-tectonics

Overall, it seems like an interesting theory that might have environmentally helpful implications for these modern times. If the plates were once able to subduct carbon from the atmosphere, maybe we can use those mechanisms to reduce carbon levels in the atmosphere now. 

Emspak, J. (2017 April 25). Odd New Theory Explains How Early Earth Got Its Oxygen. Retrieved from http://www.livescience.com/58827-how-early-earth-got-its-oxygen.html.
Plait, P. (2014 July 28). Poisoned Planet. Retrieved from http://www.slate.com/blogs/bad_astronomy/2014/07/28/the_great_oxygenation_event_the_earth_s_first_mass_extinction.html.
Sumnet T. (2017 March 16). Remnants of Earth's orginal crust preserve time before plate tectonics. Retrieved from https://www.sciencenews.org/article/remnants-earths-original-crust-preserve-time-plate-tectonics.