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Changes in Earth’s Mantle and Volcanic Activity Might Be Responsible For the Rise of Atmospheric Oxygen

The oxygen accumulated initially in the Earth’s atmosphere almost 2.4 billion years ago. A long-standing theory states that some geologic clues indicate ancient bacteria were photosynthesizing and releasing oxygen hundreds of millions of years before that period. So, where was it all going? Here is what you need to know. 

The Evolution of Atmospheric Oxygen 

It seems that something was holding back oxygen’s rise. A recent examination of billions of years old rocks suggests volcanic gases are the ones to blame. The University of Washington led the research. 

The new rock investigation is based on a 2019 study that discovered the early Earth’s mantle was far less oxidized. And, it also comprised more substances that could react better with oxygen than the actual mantle. The examined rocks were collected from South Africa and Canada sites. 

Furthermore, the recent research combined that data with proof from ancient sedimentary rocks. Scientists wanted to indicate a tipping point approximately 2.5 billion years ago when oxygen made by microbes overcame its waste to volcanic gases and started to accumulate in the atmosphere. 

“As the mantle became more oxidized, fewer oxidizable volcanic gases were released; oxygen flooded the air when there was no longer enough volcanic gas to mop it all up,” explained David Catling, a UW professor. Such a thing has implications for comprehending the evolution of complex life on Earth and the likelihood of life on other planets. 

The chemical structure of Earth’s mantle, or smoother layer of rock underneath the Earth’s crust, controls the types of gases and molten rock emerging from volcanoes. A less-oxidized early mantle would generate more of the gases, such as the hydrogen that combine with free oxygen.

The 2019 study claims that the mantle became progressively more oxidized from 3.5 billion years ago to today. The mantle of a planet, however, cannot be excluded when considering the development of the life and surface of the planet. 



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