Earth's oxygen-rich atmosphere may owe its existence to cold subduction

Key Points:

• A new study published in the Proceedings of the National Academy of Sciences suggests that the rise of cold subduction—a process where cool oceanic plates sink into Earth's mantle—was a key driver behind Earth's long-term oxygenation, enabling the buildup of atmospheric oxygen to current levels.
• Geological evidence indicates Earth's atmosphere became oxygen-rich through three major events: the Great Oxygenation Event (2.4-2.0 billion years ago), the Neoproterozoic Oxygenation Event (800-540 million years ago), and the Paleozoic Oxygenation Event (450-250 million years ago), each linked to significant biological and environmental changes.
• The study proposes that cold subduction enhanced the sinking of oxygen-reactive materials like organic carbon and pyrite into the mantle, reducing oxygen sinks and allowing atmospheric oxygen to accumulate over time.
• By analyzing metamorphic temperature-pressure ratios from global rock records over 4 billion years and coupling this data with biogeochemical modeling, researchers found correlations between cold subduction periods and the timing of major oxygenation events.
• Despite limitations such as incomplete geological records and model simplifications, the findings provide important insights into how tectonic processes influenced Earth's atmosphere and the evolution of complex life.