8

This is only a partial answer as it doesn't explain why the excess of O2 stayed but one thing you have to appreciate is the fact that aerobic respiration appeared almost half a billion years after photosynthesis, so we can't really say that photosynthesis and respiration have always balanced each other. Cyanobacteria (and with them photosynthesis) are ...


7

Because Al and Si were already oxidised to begin with. When the Earth formed, it had some amount of metals (Fe, Si, Mg, Al, Ca, etc) and a fixed amount of oxygen to bond with those metals. Certain metals with bond with oxygen preferentially. Mg and Ca are usually the first to take up oxygen, followed by Al, Si, and then Fe comes last (out of the short list ...


6

Photosynthesis has not stopped. It happens all the time, splitting water and carbon dioxide, and producing oxygen and carbohydrates. Likewise, organic matter rots and decomposes all the time, requiring oxygen and releasing carbon dioxide. The Keeling curve actually illustrates this quite nicely: most of the land mass where this happens lies in the north, and ...


5

First, let me clarify this again: Al2O3 is not clay. Now, back to topic. You are mixing apples and oranges here. The geological section you are referring it was deposited 2 billion years after the GOE. This was long after all surface iron was oxidised, and abundant oxygen was present in Earth's atmosphere. Nowhere you will see the (oxidized) Ferrum in ...


4

the great oxygenation event was caused by the evolution of photosynthesis, photosynthesis turns CO2 and water in to sugar and oxygen. so the oxygen came from CO2 and water. keep in mind CO2 levels were many many times higher (~20X) than today. Hydrogen was not released it was combined with carbon and oxygen to make sugars


4

If I understand it right, you are assuming that in the beginning we had CO2, which was then split to organic carbon and O2 via photosynthesis. And now you are asking if it's possible to reverse all of that by burning all organic carbon, so that it consumes the O2. Your assumption is not quite right. Oxygen is the most abundant element in Earth's crust and ...


3

I'd like to add to the other answers. Yes, it is correct that photosynthesis by cyanobacteria caused the rise of atmospheric oxygen. Some important points to talk about: Estimated fossil fuels are around 5 times as much as existing carbon biomass. If these estimates are appropriate, then probably before the oxygen was released it was not locked up in ...


2

My answer goes a little beyond the evidence -- there isn't much evidence. The question There's a lot of free oxygen now. This oxygen did not suddenly come from underground or from space. So it used to be attached to something. The question is, what was it attached to, and what happened to what it was attached to? Background First off, there's every ...


1

What I have learned from this is that things were very different before the Great Oxygenation Event; more than just the same elements rearranged. If all of the free oxygen came from water (and the hydrogen escaped to outer space), that isn't very different. That's around 10^18 liters of water lost from the oceans. The surface of the earth is about 5x10^14 ...


1

Actually quite interesting. Oxygen is made by the splitting of water, either by photosynthesis or by UV-based photo-dissociation in the upper atmosphere. In the case of photosynthesis, the reduced-carbon products must be buried in order for a net accumulation of oxygen to happen. In this case the oxygen effectively comes from water: (1) 2H2O + vis. light. ...


1

The earliest photosynthetic marine organisms (cyanobacteria) are known to have been established by 3.8 billion years ago from the isotopic composition of sedimentary rocks. The earliest microfossils of such organisms are dated at 3.5 billion years. Therefore these photosynthetic micro-organisms were pumping oxygen into the ocean and into the atmosphere at ...


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