An international group of scientists has proposed a new hypothesis for the appearance of oxygen on Earth, an alternative to the hypothesis of the Great Oxidative Event. According to the researchers’ findings published in the journal Geosystems and Geoenvironment, the increase in oxygen concentration was a slow process occurring between 2.8 and 1.8 billion years ago.
According to the hypothesis of the Great Oxidative Event, oxygen content rose rapidly about 2.4 billion years ago, and then plummeted over the next 200 million years. However, an analysis of the chemical composition of minerals formed in rocks and on the seabed showed that the growth of atmospheric oxygen occurred over a billion years, while the peak of the oxygen fraction at about 21 percent occurred about 1.9 billion years ago.
The slow increase in concentration is associated with the collision of continental plates, leading to the formation of supercontinents, and the evolution of cyanobacteria in the oceans. The change in the chemical composition of minerals in the earth’s crust correlates with an increase in oxygen levels due to the presence of new types of oxidized metals that have become available only due to an increase in oxygen levels.
The increase in oxygen content was also accompanied by a decrease in carbon dioxide and methane, which led to the creation of more suitable conditions for life in the ocean and atmosphere. Prior to this, the ancient oceans were enriched with toxic elements such as arsenic and mercury. During the collision of continents, mountain formation occurred, which contributed to the leaching of nutrients into the oceans, stimulating the reproduction of microorganisms and increasing biogenic oxygen production.