User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-3315689-20130728153935/@comment-6050823-20130728190851

Actually the area is said to be made by an underwater volcano(Which I'm guessing is the same volcano on the island). Raviente was said to be awakened by the volcano after being dormant/sleep underwater for so long and so I'm guessing it attacked the island when it saw multiple food sources on the island(Which that benchmark pretty much helped explained why Raviente awakened). The Violent Period Raviente is an Raviente that has gone crazy from extreme hunger so, its possible that after it awakened was extremely hungry and went on a hunger rampage.

Anyway, volcanoes are said to change the shape of an island from the volcanic rock and forming more land around an area so, after the eruption it could've just made more land and changed the shape of the island.