4 ms·

Hum, I'd like to read more about this. I find hard to believe that the current atmospheric conditions are completely unrelated to the rise of oxygen attributed

Hum, I'd like to read more about this. I find hard to believe that the current atmospheric conditions are completely unrelated to the rise of oxygen attributed to photosynthesis, and that they can only be explained by anthropic selection (which is always a possible explanation anyway).

pfdietz 5y ago
Oxygen has cycled many times through the crust and back out again since the GOE (or even since the Neoproterozoic Oxygenation Event) so I don't see why you think any sort of "memory" of those ancient events would remain in the system.
- bnegreve 5y ago
  Ok, I'm not saying that the exact same molecules of O2 from the GOE were preserved until today, rather that the presence of O2 in the atmosphere is related to the emergence of plants and photosynthesis. This is what I meant by "O2 comes from prehistoric plants". For the record, the "memory" if you want to call it like this, would be the (unoxidized) carbon buried underground and/or segregated in the plants body.
  - pfdietz 5y ago
    There is unoxidized carbon buried underground, but the bulk of the Earth has vastly more reducing capacity than relatively piddling amounts of buried organic carbon. Fully oxidized, the Earth could consume orders of magnitude more oxygen than exists in the atmosphere. Simply oxidizing all the minerals in the crust down to a couple of hundred meters would use all the atmosphere's O2, and then there's thousands of kilometers of mantle loaded with ferrous iron and sulfides, and then the iron core.
    - bnegreve 5y ago
      I see, it's actually a bit scary. But if oxidation doesn't happen fast enough (no matter why) the O2 surplus can still be explained somewhat indirectly by the emergence of photosynthesis billions years ago. Or maybe by something else. Anyway, I finally got your point, interesting.
      - pfdietz 5y ago
        The atmosphere is like a leaky boat. Oxygen leaks out when rocks are eroded and weathered and when volcanoes release reduced gases, and burial of photosynthesized material pumps it back in. The troubling part is that there's no obvious reason why these two processes have to be balanced over periods much longer than the time constant of the system.
        emmelaich 5y ago
        Yep, I've read somewhere that an enormous amount of oxygen came from rocks, and the Himalayas in particular.
        pfdietz 5y ago
        What? That's not what I said at all. Erosion of mountains should itself be an O2 sink, not a source (although subsequent burial of organic matter as the eroded material reaches the ocean, and fertilization of plankton in the ocean by the material, could be an O2 source).
        emmelaich 5y ago
        Sorry if I misunderstood, but you wrote > Oxygen leaks out when rocks are eroded and weathered.. which is what I reinforced. ?
        pfdietz 5y ago
        It leaks out of the atmosphere. It is pumped back into the atmosphere by photosynthesis + burial of organic material. Perhaps not the best metaphor.
        emmelaich 5y ago
        I was mistaken. It's a sink for CO2. See the work of Ruddiman and Raymo.

pfdietz 5y ago

Oxygen has cycled many times through the crust and back out again since the GOE (or even since the Neoproterozoic Oxygenation Event) so I don't see why you think any sort of "memory" of those ancient events would remain in the system.

bnegreve 5y ago
Ok, I'm not saying that the exact same molecules of O2 from the GOE were preserved until today, rather that the presence of O2 in the atmosphere is related to the emergence of plants and photosynthesis. This is what I meant by "O2 comes from prehistoric plants". For the record, the "memory" if you want to call it like this, would be the (unoxidized) carbon buried underground and/or segregated in the plants body.
- pfdietz 5y ago
  There is unoxidized carbon buried underground, but the bulk of the Earth has vastly more reducing capacity than relatively piddling amounts of buried organic carbon. Fully oxidized, the Earth could consume orders of magnitude more oxygen than exists in the atmosphere. Simply oxidizing all the minerals in the crust down to a couple of hundred meters would use all the atmosphere's O2, and then there's thousands of kilometers of mantle loaded with ferrous iron and sulfides, and then the iron core.
  - bnegreve 5y ago
    I see, it's actually a bit scary. But if oxidation doesn't happen fast enough (no matter why) the O2 surplus can still be explained somewhat indirectly by the emergence of photosynthesis billions years ago. Or maybe by something else. Anyway, I finally got your point, interesting.
    - pfdietz 5y ago
      The atmosphere is like a leaky boat. Oxygen leaks out when rocks are eroded and weathered and when volcanoes release reduced gases, and burial of photosynthesized material pumps it back in. The troubling part is that there's no obvious reason why these two processes have to be balanced over periods much longer than the time constant of the system.
      - emmelaich 5y ago
        Yep, I've read somewhere that an enormous amount of oxygen came from rocks, and the Himalayas in particular.
        pfdietz 5y ago
        What? That's not what I said at all. Erosion of mountains should itself be an O2 sink, not a source (although subsequent burial of organic matter as the eroded material reaches the ocean, and fertilization of plankton in the ocean by the material, could be an O2 source).
        emmelaich 5y ago
        Sorry if I misunderstood, but you wrote > Oxygen leaks out when rocks are eroded and weathered.. which is what I reinforced. ?
        pfdietz 5y ago
        It leaks out of the atmosphere. It is pumped back into the atmosphere by photosynthesis + burial of organic material. Perhaps not the best metaphor.
        emmelaich 5y ago
        I was mistaken. It's a sink for CO2. See the work of Ruddiman and Raymo.