Levi's actions caused the end of the world happen outside the cave.

They continue to another long hallway. Once again, all sound has vanished and the telepathically sound of the whale has also stopped.

It actually takes several hours to travel in the hallway and the cold, dampness makes a return. They encounter another crossroads. Go straight, which is an uphill slope, or go right which continues the same.

Visuals to demonstrate.