Some time ago I computed a couple of figures as follows.
To calculate the amount of water needed to cover the earth so that "They rose greatly on the earth, and all the high mountains under the entire heavens were covered. 20 The waters rose and covered the mountains to a depth of more than twenty feet. " (Gen 6:19-20). One need only
1.Calculate the the volume of a sphere (I'm ignoring the oblate shape of the earth (Vs) for simplicity sake) with a radius of the Earth at sea level: Rs.
2.Add to that radius the height of Mt. Everest: Re
3. Calculate that volume Ve
3. Calculate the the difference of the two: Vd
4. Calculate the volume of land land above the sea Vl
5. Subtract Vl from Vd = the amount of water that sat above sea level and reached the top of Mt Everest. (T)otal amount of water
Plugging in the figures. (radius of earth = 6,378 K)
Volume of sphere to sea level
Vs = 4/3 * pi * r cubed
= 4/3 * pi * 6378.4 km cubed
= 1.08698 x 10 to the 12 cubic kilometers
Volume of sphere to top of Mt. Everest.
Ve
V= 4/3 * pi * r cubed
= 4/3 * pi * 6387.248 km cubed
= 1.09151 x 10 to the 12 cubic kilometers
Difference between Ve and Vs = .00453 X 10 to the 12th cubic kilometers, or 4.53 X 10 to the 9th.
Vd
4.525 x 10 to the ninth cubic kilometers (4.525x1009 km3) Or, to put into a more sensible number, 4,525,000,000, cubic kilometers
Volume of dry land above sea level.
1.0217 x 1017 m3 OR 1,039 cubic kilometers.
(
source)
Total amount of water
D - Vl 4,525,000,000, cubic kilometers - 1,039 cubic kilometers = 4,524,998,961.
AND, rounded off =
4,525,000,000, cubic kilometers (note the how extremely little the volume of land above sea level affects the Total volume of water)
Then, dividing this incredible volume of water by the volume of water in the oceans (1, 321, 920,000 cubic kilometers )
we get an idea of how much more water is needed to cover the earth to the top of Mt. Everest. This turns out to be 3.423 times as much!! Almost 3 1/2 times as much water as now exists in all the oceans.
But where did all this water go? If, as some suggest, it seeped into the Earth (where else?) how far down would this 4,525,000,000,cubic kilometers of water extend?
A quick calculation shows it would extend about 10 k, or about 6 miles below the surface of the Earth