Perhaps something happened here, and it cracked the skin of the universe in this particular spot. Or perhaps this island is the epicenter of some expanse of natural or magical or mystical power, and they are simply attempting to contain this incursion. Consider - if other realities started bleeding into yours from a crack in the universe, and absolutely anything could come through, wouldn't the authorities in your world try to contain it? There would seem to be nothing to prevent, say, an evil version of Superman from coming through. In a truly infinite multiverse, it's not only inevitable that one exists, but that an infinite number of them exist.

As the laws of physics seem to fluctuate in this world, and there are other worlds where things many of us might have deemed impossible exist, it's difficult to know if this is a localized phenomenon. We have no idea what the rules of this universe are, so we can't even begin to guess what is outside our little bubble. Natural phenomenon tend to be more random in your universe, but if you think about it, there's no guarantee that your logic and common sense transcend your own reality and translate to this one.