We all depend on oxygen to survive, but about 3 billion years ago, there was barely any oxygen at all. When was the last time you thought about where all the oxygen on Earth came from?

A research team from the University of Tokyo’s Department of Earth and Planetary Science thinks about this question all of the time. In a newly published study in Communications Earth & Environment, the team reveals that we may have volcanoes to thank for the abundance of air that we breathe. 

A Volcanic Discovery

During this study, scientists were looking into what kind of events happened on Earth in order to allow oxygenation to occur 2.5 billion years ago. Their findings suggest that volcanic activity helped create the perfect conditions for the oxygen-rich atmosphere needed to sustain all life on our planet.

Focusing on the late Archean eon (3 billion years to 2.5 billion years ago), Professor Eiichi Tajika and his team simulated crucial aspects of Earth’s biological, chemical, and geological history. Creating the right kind of numerical model to simulate the complex cycles and behavior of the late Archean was difficult, but researchers succeeded and were able to gain invaluable insights into Earth’s geologic history.

The simulations revealed the likely process through which volcanic activity modified biogeochemical conditions enough to accelerate oxygenation. 

Initially, large-scale volcanic activity increased the levels of carbon dioxide in the atmosphere. This increase in carbon dioxide warmed the climate, and a warmer climate meant a rise in the amount of nutrients supplied to the ocean. More nutrients in the ocean led to more marine life, which then led to a temporary increase in atmospheric oxygen.

Read More: Chronostratigraphy: How Scientists Unlock Deep Time

A Whiff of Evolution

These increases, however, were extremely unsteady and unreliable, leading the research team to call them “whiffs.” The existence of these whiffs allows scientists to help track the timing of these atmospheric changes and tie them to evidence of volcanic activity at or around the same time.

“Understanding the whiffs is critical for constraining the timing of the emergence of photosynthetic microorganisms,” said visiting research associate Yasuto Watanabe in a press release. “The occurrences are inferred from concentrations of elements sensitive to atmospheric oxygen levels in the geologic record.”

The History of Air

Earth’s atmosphere has had an abundance of oxygen for about 2.5 billion years. But what was Earth like before that, and what process created all of that air?

Photosynthesis is at the heart of our oxygen-rich atmosphere. Thanks to a multitude of occurrences, like whiffs and mass extinction events, microorganisms capable of performing photosynthesis had the necessary atmosphere to grow rapidly and increase their oxygen output. 

This explosion of microorganisms is known as the Great Oxygenation Event (GOE) and took place around 2.5 billion years ago. The microorganisms’ ability to successfully multiply depended on a lack of competition and favorable conditions, likely created by volcanic activity.

As microorganisms capable of photosynthesis became more prevalent, the rate at which carbon dioxide was converted into oxygen also increased. This new abundance of oxygen paved the way for complex life on Earth to occur, and the rest is history.

Read More: 5 Things You Might Not Know About Volcanoes

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As the marketing coordinator at Discover Magazine, Stephanie Edwards interacts with readers across Discover’s social media channels and writes digital content. Offline, she is a contract lecturer in English & Cultural Studies at Lakehead University, teaching courses on everything from professional communication to Taylor Swift, and received her graduate degrees in the same department from McMaster University. You can find more of her science writing in Lab Manager and her short fiction in anthologies and literary magazine across the horror genre.