That can be explained in a fantasy setting though. Arbitrary shapes of mountains can be attributed to ancient magic. Ancient elves and wizards might have been terraforming the geography for some reasons related to history of Middle-Earth.

The weird unnatural mountains around Sauron's area of the map might have been built by him using spells to create a "natural" protective wall from elves so he has enough time to forge the ring in secret.

If I remember correctly from the books (correct me if I am wrong), there is even a mention in the book about Misty Mountains being "built" by some ancient powerful beings (so that would explain ridiculous geology).

The Wall in Game of Thrones is also not natural, it was build using magic an is held together by the same spell that created it.