What was the main source of oxygen on Earth before photosynthesis?

[Newbie1]

in the middle of the sea where there are no trees around?.

 

[aniketp]

It is the dissolved oxygen.

 

[mgb_phys]

Most of the world's oxygen (70%) is produced by plants (or green stuff depening on how fussy you want to be about the definition of plants) living on the oceans.
It does also blow around quite a lot in the atmosphere.

 

[tiny-tim]

in the middle of the sky where there are no fish around?

 

[mgb_phys]

in the middle of the sky where there are no fish around?

Beause penguins eat them all
https://www.youtube.com/watch?v=nrxmpihCjqw

 

[turbo]

in the middle of the sea where there are no trees around?.

The oceans are teeming with plant-life that can produce oxygen. Oxygen in the air is also entrained into sea-water by wave action.

 

[Newbie1]

Most of the world's oxygen (70%) is produced by plants (or green stuff depening on how fussy you want to be about the definition of plants) living on the oceans.
It does also blow around quite a lot in the atmosphere.

I see... would it be fair to say that there would be more oxygen available where there are trees around?. Or is it fairly distributed?.

Yes i know my questions are weird... lol...

 

[mgb_phys]

I see... would it be fair to say that there would be more oxygen available where there are trees around?. Or is it fairly distributed?.

Trees aren't all that important compared to algae etc they are big and grow slowly so their metabolism is pretty low compared to pond scum.
Depends on the age of the tree and the species of course - the same thing applies to the idea of planting trees to remove CO2.

 

[russ_watters]

I think the OP is asking about oxygen in the atmosphere, not dissolved in the ocean. Oxygen exists everywhere on Earth in similar concentrations because wind spreads it around.

 

[philip041]

I thought the atmosphere is just the atmosphere, any local fluctuations would be just that; local, and due to some insignificant factor, (cows, volcanoes, trees).

 

[mgb_phys]

I think the OP is asking about oxygen in the atmosphere, not dissolved in the ocean. Oxygen exists everywhere on Earth in similar concentrations because wind spreads it around.

Yes, but the OP is assuming that oxygen comes from trees.
The question should really be - why is there oxygen on land if there is no algae around!

 

[philip041]

Yes, but the OP is assuming that oxygen comes from trees.
The question should really be - why is there oxygen on land if there is no algae around!

Does most oxygen come from algae then?

 

[mgb_phys]

Does most oxygen come from algae then?

Most of it comes from stuff growing on the surface of the ocean (not all technically algae)
There is quite a lot of ocean surface area and not a lot of it is desert or covered in concrete so it's a good place to be a plant.

 

[philip041]

If only I were a plant.

 

[JorgeLobo]

Oxygen is an element - it's neither created nor destroyed by plants or anything else. It's just there. The better question is - before evolution of photosynthesis, in what chemical form did much of the oxygen exist?

btw - ever looked at the formula for water? You know - the stuff that covers a lot of the planet?

 

[mgb_phys]

The better question is - before evolution of photosynthesis, in what chemical form did much of the oxygen exist?

The majority of the Oxygen on Earth is in the form of sand.

Before evolution of photosynthesis the atmosphere was mostly carbon dioxide - before plant made global cooling polluted this with toxic chemicals (like molecular oxygen).
Plants continue doing this today, taking our vital CO2 and creating more toxic O2. We are trying to return the atmopshere to it's natural state by burning them, but it's a big job and is taking longer than expected.