Hey you. Do you know what "God" means? The people around here, you see, don't really believe in God. Instead, do you know what it is they believe in? It's this place. The Abyss itself. Because the bottom of the Abyss/Netherworld is unknown, and since they're afraid of it, it replaces their god.
Relevant quote from Ozen the Immovable in Made in Abyss.
Also casts doubt on markers discovered showing possible life on other planets. We missed a source of oxygen creation on our own planet. Who's to say there aren't other ways that both methane and carbon dioxide are present on other planets.
(I'm certain there's life on other planets. This just makes it less likely that a planets with all the signs is one of those planets)
If this is coming from metals in these rocks forming electrochmical cells, they should've corroded away long time ago. Maybe there's some unknown process that recovers metallic elements back from salts? Maybe some bacteria? Even if, then why? It costs a lot of energy to do this.
Usually putting together metal and water you get metal-oxide and hydrogen gas.
m + H2O → mO + H2
What they discover is a unusual zone where they have both oxygen (dissolved) and metal. So, i guess they have the reverse process :
mxOy + energy → (x)m + (y/2)O2
They should measure electrical field intensity in the water near the sea floor to evaluate electrical current going through the sea floor from the ocean.