Tolkien made a comment about that in one of his letters, admitting that the map was designed mostly for story purposes and regretting that he didn't research mo

Tolkien made a comment about that in one of his letters, admitting that the map was designed mostly for story purposes and regretting that he didn't research more realistic geology and such. On the other hand, with how much trouble Tolkien had in general with finishing projects, if we waited for him to learn geology too, who knows if we would have gotten any books at all...