[Answer] What process produces Earth's atmospheric oxygen?

Answer: photosynthesis

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What process produces Earth's atmospheric oxygen? Great Oxidation Event - Wikipedia Geological history of oxygen - Wikipedia Oxygen cycle - Wikipedia Atmosphere of Earth - Wikipedia The three major constituents of Earth's atmosphere are nitrogen oxygen and argon. Water vapor accounts for roughly 0.25% of the atmosphere by mass. The concentration of water vapor (a greenhouse gas) varies significantly from around 10 ppm by volume in the coldest portions of the atmosphere to as much as 5% by volume in hot humid air masses and concentrations of other atmospheric gases are typically quoted in terms of dry air (without water vapor). The remaining gases are often referred to as trace gas… While there are many abiotic sources and sinks for O2 the presence of the profuse concentration of free oxygen in modern Earth's atmosphere and ocean is attributed to O2 production from the biological process of oxygenic photosynthesis in conjunction with a biological sink known as the biological pump and a geologic process of carbon burial involving plate tectonics. Biology is the main driver of O2 flux on modern Earth and the evolution of oxygenic photosynthesis by bacteria which is discussed as part of The Great Oxygenation Event is thought to be directly responsible for the conditions permitting t… While there are many abiotic sources and sinks for O2 the presence of the profuse concentration of free oxygen in modern Earth's atmosphere and ocean is attributed to O2 production from the biological process of oxygenic photosynthesis in conjunction with a biological sink known as the biological pump and a geologic process of carbon burial involving plate tectonics. Biology is the main driver of O2 flux on modern Earth and the evolution of oxygenic photosynthesis by bacteria which is discussed as part of The...

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