How great was the Great Oxidation Event?

Media and Educational Resources

• Several comments recommend documentaries and series on Earth’s history and the GOE: PBS NOVA “Ancient Earth,” PBS Eons and Space Time episodes on oxygen and mass extinctions, a recent streaming series on extinction events, and various popular-science books and a high-end photobook on impacts and Earth history.

Dynamic Earth, Evolution, and the “Boring Billion”

• Commenters highlight Earth’s high dynamism vs a naive “steady state” view.
• The “boring billion” (mid-Proterozoic) is cited as a long stable interval with slow evolutionary change, flanked by oxygenation events, possibly driving later complexity.
• Others stress this is still speculative and mostly underscores how complex modern cells are.

Sources and Maintenance of Atmospheric Oxygen

• Strong consensus that high atmospheric O₂ is maintained by life, mainly oxygenic photosynthesis.
• One view: without life, O₂ would quickly be locked into oxides; life massively accelerates O₂ production and changes equilibrium concentrations.
• Others discuss abiotic contributions: UV-driven water splitting and oxidation of oceans, metallic nodules at the abyssal seafloor producing “dark oxygen,” and early electrochemical gradients.
• There is debate over whether solar UV alone could ever oxygenate Earth substantially; some argue the UV spectrum and energetics make this unlikely or unclear.

Oxygen as Biomarker and Exoplanets

• Oxygen is described as a strong biosignature because no non-biological cycle seems able to sustain high O₂.
• Some push back: alien life might use different gases (e.g., sulfur), so absence of O₂ would not imply no life, but presence of abundant O₂ would still be notable.

Fire and the Biosphere

• Multiple comments emphasize that familiar terrestrial fire depends on free O₂ and reduced organic matter created by life.
• Rocks and water are already oxidized; life’s reduction of CO₂ provides burnable material.

Life, Entropy, and Philosophy

• Life is framed as decreasing internal entropy by increasing external entropy.
• Discussion touches on definitions of “living vs non-living,” the power of a single ancestral cell over billions of years, and limits of individual control over one’s own cells.

Geological Evidence and Open Questions

• Mention of banded iron formations, tiger’s-eye gemstones, and major iron ore deposits as GOE products, with some iron belts being younger.
• Chromium and molybdenum isotopes are discussed as proxies for reconstructing GOE timing and environments, though details and interpretations remain partly unclear.
• The “Great Unconformity” and Snowball Earth are noted as complicating paleontological records.