How do you calc sinking feats?

[Abysswalker2126]

A few characters I know have feats involving them sinking things and I wanted to know how exactly you’d calculate them as they’re always listed as Likely higher instead of an estimated AP for it
For example this guy sunk the city of New Orleans and This guy Sunk the continent of Atlantis. It irks me that there’s nobody has a way to calculate sinking feats

 

[Furudo_Erika]

There was a Fire Emblem feat similar to this I believe

Pretty sure it involved GPE:
Area of land x Highest elevation (to completely sink it) x density of the fluid the landmass is being sunk in/submerged under (water in this case) to find mass.

Then:
Mass x Highest elevation x gravity = GPE

As a quick example:
Say a land mass is 1,000km²; 1,000,000,000 m², 1,000m at the highest point, and the planet has 10m/s² of gravity. Gonna say water is 1,000 kg/m³, though if we're talking about ocean water, it's probably closer to like 1,024 kg/m³

1,000,000,000 m² x 1,000m x 1,000 kg/m³ = 1e+15 kg of water

1e+15 kg x 1,000m x 10m/s² = 1e+19 joules, or 2.39 Gigatons of TNT (Large Mountain level/High 7-A)