User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-5913830-20121106222409

Volcano Swimming Theory
I propose a theory. Since Uragaan and Agnaktor are seen burrowing and swimming respectively in the volcano; however, there's no possible way for them to just "walk" through the solid rock.

So I propose that there is only a foot layer of rock, very strong, and arched in a way, but with a 20+' crawlspace under it. The creatures can make cuts in this rock once one part is broken, hence Agnaktor's Land Swim. Uragaan uses his horns and jaw to bust the rock and bury himself in it. That would be all!