Hell wasn't part of the six days of creation, it's a direct consequence of sin. At the fall of man in the garden of Eden God cursed the Earth. This was the beginning of nuclear decay.
Hell is Expanding in the Old Testament
The Bars of the Pit
"The bars of the pit" is a synonym for "the pillars of the earth." They're in the great gulf or "mega chasm" which is the region of Earth's interior which popular science (SciPop) calls the "liquid outer core."
Sheol
Sheol refers to life beyond the grave, quite literally an underworld realm of the dead. It's also modified in a variety of ways which can be grouped to correspond to the main regions of the interior of the Earth.
Tehom became Sheol
The region between Earth's core and mantle, referred to by Jesus as a mega chasm or great gulf, has to transition from water filled to open space due to the expansion of hell.
The Volume of the Great Deep
When Noah's flood took place all of 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.
It Devoured the Great Deep
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
August 31st
After Noah's flood the region in the interior of the Earth, formerly occupied by the great deep (tehom), is now a great gulf or mega chasm of open space that Jesus spoke of in Luke 16:26 (sheol).
March 25th
A major transition in the condition of planet Earth, like its interior changing from Tehom to Sheol, has to be in the Bible somewhere. We (me and the Holy spirit) found it in Amos 7:4.