[Fester Chugabrew]

5,140,631,390 cubic kilometers

Please advise as to how you came up with that figure so I can check your math. Thank you.

[Junior]

I assumed the average thickness of the Earth's crust (the geological column) to be ten klicks. I subtracted the volume of a sphere 12,780 km in diameter from the volume of a sphere 12,800 km in diameter.

Dunno, it just seemed the right way to answer such an odd question.