I have the impression that something is wrong - when Luffy fell into the water and we thought he would die, it did not happen - and now everyone announces victory, although something extraordinary is happening (eruption) - Kado and Big Mom (especially Kaido) control all the elements, (fire) - just a moment ago his body was melting everything around and now i'm to believe it's over because they fell into a magma pool ?!?
A little investigation:
In chapter 1048, Kaido melted one of Onigashim's horns with his body temperature.
In order for the fire to burn the bone, it must be around 1200 °C.
Depending on its chemical composition and the content of gases dissolved in it, the magma temperature usually ranges from approx. +650 to approx. +1250 ° C.
Why the eruption took place at all - if the pressure increased, does it mean that Kaido used the form of a fire dragon?