The OP said “on Earth,” not IN Earth. I think magma doesn’t count.
I’d guess blood. The average human contains eight pints, or one gallon, of blood. So that’s over six billion gallons right there. If you add in animal blood, that is probably at least another twenty billion. Of course, we hardly ever see all this blood, but it’s out there.
Yes, molten iron would be by far the most abundant liquid component of the Earth. Although only the outer core is liquid (the inner core remains solid due to extreme pressure), it would greatly exceed in volume all the oceans. So water would be the second most abundant liquid on Earth.
I think you would have to exclude all other aqueous solutions, if you want to do a comparison with water. After all, the most abundant liquid is really salt water rather than just “water,” and salt water is more similar in composition to blood than it is to fresh water.
The next most abundant liquid after water (and aqueous solutions) may be petroleum.
Magma and molten iron were both things that occurred to me after I posted the OP, and they’re good answers. But davenportavenger helps me clarify my question – I’m more interested in what’s on the earth’s surface (or above, as with clouds) than in what lies beneath.
Petroleum was my WAG, but that opens up the on vs. in earth question again.
It has to be alcohol, right? I mean given natural fermenation processes plus whatever humans make, I think that EtOH should be the most abundant other liquid on earth.
Maybe this is pulling teeth, but I don’t think that Coca Cola or what have you should count. Because it’s still really just water with a bunch of sugar, some flavor, and coloring in solution. I mean, we aren’t going to distinguish between water, salt water, brackish water, etc. are we? So why does Coca-Cola count seperately?
I think that it should have to be some compound that would be liquid at room temperature and isn’t just a solute in something else.
I’d guess that there are more petroleum distillates on earth than there is alcohol, even just considering the surface (or very near the surface. Underground storage tanks count, right?). Even if you make me pick one, I’d bet there’s more gasoline than there is alcohol. Certainly there is more human-produced gasoline than ethanol, so the question would rest on how much ethanol is produced in natural fermentation and how long it lasts before it’s consumed by something?