Great Oxidation Event 2.5 Billion Years Ago Lasted for Over 200 Million Years, Longer Than Previously Thought [Study]

The Great Oxidation Event, also known as the Oxygen Catastrophe and Oxygen Revolution, took place on Earth more than 2 billion years ago. This ancient natural phenomenon involved the rise of molecular oxygen and its escape into the atmosphere, replacing methane and becoming a major component of the biosphere. While it occurred long before complex life existed, it caused a mass extinction among anaerobic life.

Unlike aerobic creatures which rely on oxygen to survive, anaerobic organisms can live and grow even without oxygen. An oxygenated environment has been proven to be fatal for anaerobic lifeforms, as seen during the Great Oxygenation Event starting 2.5 billion years ago. The dominance of anaerobic life ended following the evolution of cyanobacteria living in the oceans.

According to scientists, marine cyanobacteria started producing large amounts of oxygen via photosynthesis, a process also used by plants to create the chemical element essential to life. The entire duration of the Oxygen Catastrophe remains unclear for decades. However, a study revealed in June 2024 that the Oxygen Revolution occurred for at least 200 million years, based on geochemical discoveries.

Great Oxidation Event

The Great Oxidation Event took place after almost half of Earth's lifespan was devoid of oxygen, since the planet formed approximately 4.5 billion years ago. Coinciding with the evolution of cyanobacteria, the said event involving the mass accumulation of oxygen served as a "poison" that paved the way for the eradication of most anaerobic life, according to the American Society for Microbiology (ASM).

A group of microbes called cyanobacteria evolved around 2.7 billion years ago. Scientists in the past have discovered that these living organisms can use water and oxidize it through photosynthesis. Prior to this event, it was theorized that life on Earth was dominated by anaerobic organisms since the earliest onset of life date back 3.8 billion years ago, according to biochemist Leslie Orgel, as cited by the ASM.

Anaerobic Life Extinction

Although biologists have considered the anaerobic life extinction as a catastrophe, it also led to the development of complex flora and fauna later on in Earth's biological history. Despite the said extinction, the majority of surviving anaerobic organisms retreated deep on the planet's subsurface where oxygen is absent, according to a 2016 report by the Imperial College London.

It is evident that the Great Oxidation Event did not occur overnight, yet the scientific community are still in the dark when it comes to the exact termination of the phenomenon. However, a new study published in the journal Nature on Wednesday, June 12, revealed the planet's atmosphere-ocean oxygenation started 2.3 billion years ago and lasted for at least 200 million years.

The research paper's lead author, professor Chadlin Ostrander, explains that the oxygenation process is not linear and involves fluctuating trends of the initial increase of oxygen in Earth's atmosphere.