The story, they say, may have begun with the fusion of an early “supercontinent” (think Pangaea) called Columbia. With sufficient amounts of land above sea level, erosion can deliver enough nutrients into the oceans to support large quantities of photosynthetic cyanobacteria. We can see evidence of this in marine sedimentary rocks rich in organic carbon.
Colombia’s rupture aligns with the first signs of declining low temperatures. This would allow more of this organic carbon and carbonates stored in the shallow waters around Colombia to flow deeper into the mantle.
This is followed by the Boring Billion, when mantle convection and tectonic plate movement also appear to be sluggish. But after that, the formation and breakup of the supercontinents Gondwana and Pangea leads us to a map of tectonic plate boundaries that looks a lot like our current world, with much lower temperatures than subduction.
For example, the “Ring of Fire” around the Pacific Ocean today marks a vast zone of subduction that continuously transports carbon and sulfur-rich sediments deep into the mantle. Once this type of subduction became common, Earth’s oxygen balance became able to tilt more toward the atmosphere.
There is certainly a lot to the story, both in terms of biology and geology. Our oxygen-rich atmosphere is the product of a rich set of interactions. But, the researchers write, “All of these processes operate on top of a baseline defined by the net flow of carbon (and sulfur) between Earth’s interior and exterior, which we argue was controlled by the evolved efficiency of cold subduction on a cold Earth.”
PNAS, 2026. doi:10.1073/pnas.2534056123 (About DOI).
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