Part 77 (A Scientific Explanation of Chapter 1089 and Kuma's Death Pt. 2)
I will now attempt to explain the "science" based on my source. Once again, this is something that Vegapunk will explain in the future so ignore me if my explanation is... not understandable hahas.
Ok, back to the "new/secondary" seabed level - Please refer to the childish diagram I drew. This secondary seabed is still slightly above the original seabed.
Click to view
Lulusia's original location on the sea surface. 2. When Mother Flame was used to destroy Lulusia, the force of the blast created a cavity/hole beneathe where Lulusia originally was.
Waters from the surrounding flow into this cavity/ hole because of water displacement. However, because of the "artificial" secondary seabed that was sunk and subsequently rested above the original seabed, there are air pockets / airways formed between the secondary seabed and the original seabed. Because the original seabed contains limestone, what this means is that the water flowing down from the sea surface (at Lulusia) towards the original seabed actually travels around/through the airways rather than seeping through the original seabed into the outer/inner cores.
Water continues flowing along the airways and gets pumped out from other side of the globe. This water displacement phenomenon led to earthquakes felt around the world as well as water level rising.
Part 77-2 (A Scientific Explanation of Chapter 1089)
(This is a second follow-up post for Parts 77 and 77-1 as more PMs than expected.)
The mechanics/science of the Mother Flame leading to "earthquakes" and "water falling into an abyss" has actually been drawn.
Please take a look at the last few panels of Chapter 743 and the first few panels of Chapter 744.
In Chapter 743, before Sabo used Dragon's Breath, he mentioned that everything in this world has a core. After blasting the ring floor, the core at the bottom is revealed and he traveled to this bottom core.
This is similar to one of my previous parts where I wrote Luffy in the future will lower the water level around the world, globally, and bring everything and everyone back to the original core at the bottom of the current sea, where people once lived on.
In Chapter 744, after Sabo destroyed the ring floor, water level at the surface fell into the abyss. Fire fist attack was also used by Sabo to reach the bottom core.
This is similar to how the Mother Flame resulted in the destruction of a "landmass" and waterfalling into the abyss core.
Thereafter, in Chapter 744 as well, upon reaching the core, light is finally shone on the darkness down there. Usopp is depicted as creating this "miracle" and hailed as a God.
Similarly, when water level is finally lowered by Luffy in the future and light finally shines upon the original land below that has not seen the sun for 800 years, Luffy will be known throughout the world as a God and bringing (sun)light and miracle to everyone.