Thus hath the Lord GOD shewed unto me: and, behold, the Lord GOD called to contend by fire, and it devoured the great deep, and did eat up a part.(Amos 7:4) KJV
When Noah’s flood took place the waters of the great deep burst forth and flooded the Earth. If we know the volume of water and the radius of the Earth at this time, then we may calculate how deep the water was.
The water of the great deep has a volume of a sphere of radius 6,371 km minus the core, a sphere of radius 1,800 km
|Volume of present day Earth||p||1.08E+12 m3|
|Volume of the core||c||2.44E+10 m3|
|Volume of the great deep||p-c||1.06E+12 m3|
As hell expanded and heated the waters of the great deep the pressure built up. God’s instruction to Noah to build the ark was timed perfectly so that Noah would be ready when the waters in contact with the core reached boiling point and the system exploded, flooding the Earth. The waters of the great deep burst forth out of the fountains of the great deep.
The fountains of the great deep are channels through the crust and mantle of the original Earth through which water drained into the great deep. They were later used to flood the Earth in the time of Noah.– Fountains of the Great Deep, definition
All of the waters of the great deep were available to flood the Earth, as were waters from above the firmament.