Did Fossil Fuels Create Earth’s Oxygen Supply?

Coal, natural gas and oil likely created the Earth’s oxygen supply, according to new research published Monday by scientists at the University of Wisconsin–Madison.

Rapid increases in the amount of oxygen on Earth may have been due to fossil fuels like coal, natural gas and oil sequestering large amounts of carbon-rich organic matter underground about 500 million years ago. The sequestration of this carbon in fossil fuels prevented it from bonding with oxygen to form carbon dioxide. This greatly increased the amount of oxygen on Earth, triggering the development of complex animal life.

Oxygen enables the chemical reactions that animals use to get energy from stored carbohydrates from plants and one another for food. Researchers suspect it isn’t a coincidence that animals appeared and evolved following a spike in atmospheric oxygen likely caused by fossil fuels roughly 500 million years ago.

“It’s a correlation, but our argument is that there are mechanistic connections between geology and the history of atmospheric oxygen,” Jon Husson, a postdoctoral fellow at the University of Wisconsin–Madison who was involved in the research, said in a press statement. “When you store sediment, it contains organic matter that was formed by photosynthesis, which converted carbon dioxide into biomass and released oxygen into the atmosphere. Burial removes the carbon from Earth’s surface, preventing it from bonding molecular oxygen pulled from the atmosphere.”

Photosynthesis from plants created most of the oxygen on Earth, and much of it likely formed carbon dioxide. This is obvious to researchers as photosynthesis had already been around for at least 2.5 billion years before the spike in atmospheric oxygen.

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