Please note: this is, like everything else, a series of opinions – both informed and not at all so. So the feeling that I am full of crap and have no idea what I am talking about is ALWAYS a viable feeling about this article.
I think Fantasy writers have an easier time of things. First of all, any unexplained phenomena can be explained with two words: it’s magic.
Second of all, magic can do anything. Whatever the author requires, magic can fill in.
Third of all, when in doubt, emulate Tolkien.
This is, of course, to reduce a difficult genre into ridiculous simplicity.