Tokyo, Japan – Earth’s atmosphere has gone through significant changes over billions of years, eventually leading to the oxygen-rich air we breathe today. While the presence of photosynthetic microorganisms has long been credited for the oxygenation process, a recent study from the University of Tokyo suggests that volcanic activity may have also played a crucial role in this transformation.
More than 2.5 billion years ago, Earth’s atmosphere was vastly different, with minimal oxygen and a dominance of carbon dioxide and other gases. The prevailing belief was that cyanobacteria slowly began to produce oxygen through photosynthesis, gradually altering the planet’s atmosphere. However, the new research indicates that prior to the Great Oxygenation Event (GOE), brief spikes of oxygenation occurred, potentially triggered by volcanic eruptions.
These volcanic events released large amounts of carbon dioxide into the atmosphere, leading to a greenhouse effect that warmed the climate. This warming, in turn, increased the weathering of rocks, releasing essential nutrients like phosphate into the oceans. According to Professor Eiichi Tajika, the presence of photosynthetic microorganisms alone would not have immediately led to atmospheric oxygenation due to limited nutrient availability in the oceans. Thus, the study suggests that intense volcanic activity was crucial in seeding the oceans with nutrients.
The researchers examined redox-sensitive elements such as molybdenum, rhenium, and selenium to support their theory. One notable oxygen spike around 2.5 billion years ago, as evidenced in geological formations like the Mt. McRae Shale in Australia, aligns with their findings. Lead author Yasuto Watanabe emphasized the difficulties in modeling these ancient events, highlighting the complexity of simulating biogeochemical cycles under late Archean conditions.
While the short-lived oxygen bursts may have seemed insignificant, the study suggests that they played a vital role in shaping the conditions leading up to the GOE. Over millions of years, continuous volcanic activity and these brief oxygen spikes pushed Earth’s atmosphere toward a tipping point, ultimately resulting in a permanent shift in oxygen levels. Understanding these transient oxygenation events is crucial in determining the emergence of photosynthetic microorganisms and the development of oxygen-utilizing enzymes in microorganisms, facilitating life’s adaptation to an oxygen-rich environment.