Oxygen Triggered Earth’s First Mass Extinction 2.4 Billion Years Ago, Driving a 200-Million-Year Transition
Updated
Updated · spacedaily.com · Jun 3
Oxygen Triggered Earth’s First Mass Extinction 2.4 Billion Years Ago, Driving a 200-Million-Year Transition
3 articles · Updated · spacedaily.com · Jun 3
Summary
Around 2.4 billion years ago, oxygen released by cyanobacteria began accumulating in Earth’s oceans and air, poisoning anaerobic microbes in what is widely described as the planet’s first mass extinction.
Sulfur isotope signals vanish from rocks after that point, marking the rise of free oxygen, while banded iron formations show oxygen reacting with dissolved iron as the atmosphere and seas changed.
Oxygen likely killed in two ways: directly through reactive oxygen damage and indirectly by destroying methane, helping trigger the Huronian glaciation that lasted roughly 2.4 billion to 2.1 billion years ago.
The die-off’s scale remains uncertain because early microbial life left few fossils; researchers can infer a planetary chemical shift far more confidently than they can count which lineages disappeared.
Studies suggest the Great Oxidation Event was not a single moment but an uneven transition, with oxygen levels fluctuating for about 200 million years before becoming a lasting feature of the atmosphere.
Could a similar 'oxygen catastrophe' be a predictable, destructive stage for life evolving on other planets?
If our microbial ancestors had genes to handle oxygen, why did its arrival cause Earth’s first mass extinction?
From Anoxic Beginnings to Oxygen-Rich Skies: Unraveling Earth's Great Oxidation Event and Its Lasting Impact
Overview
This report explores how Earth's atmosphere became rich in oxygen through a long and dynamic process. Although oxygenic photosynthesis by cyanobacteria began hundreds of millions of years before the Great Oxidation Event, low oxygen levels persisted due to complex biogeochemical mechanisms. The growth of cyanobacteria, which formed stromatolites and followed sunlight, was initially limited by a thick atmosphere. Over time, changes in environmental factors allowed these organisms to thrive, leading to significant fluctuations in oxygen levels in both the atmosphere and oceans. This gradual oxygenation set the stage for major shifts in Earth's environment and the evolution of life.