Yes, if he'd be deep enough he could remain at one place, which explains why in Zeal you see he's underwater and 12,000 years later, viola, he's underground.
Besides, look at the scene where he erupts. See where I marked Medina? Remember how that area looks like, then look at the eruption scene. Same place. Then go to 1000's Medina. Then go to 600 AD at where Medina is. Magus' Castle. Then go to 12,000 BC. Open Sea. Then go to 65,000,000 BC. Tyran lair. Then go to 2,300 AD. Keeper's Dome. See what I mean?