I know a few things about geology from college but I really don't care about the 'realism' of geology in a fantasy game setting.
When there are magical, titanic, reality-warping forces around, you can't really expect everything to necessarily be nice and tidy realistic in its geography and suchlike. I don't need to know how the heck a mountain range is shaped just so, or why there's a lone mountain over here, or why there's an arid desert adjacent to a humid marsh (as there is in my Rhunaria homebrew, where magic and spirits shaped the landscape).
It's friggin' magic. And gods. And spirits. And the rampages of psychotic wizards, deranged cultists, angry dragons, demonic hordes, Far Realmsian invaders mucking up reality, and that slaadi over there who just thought it would be cute to have a shiny, crystalline mountain range in the middle of the bayou that happens to be shaped like a grinning slaadi's face. Or whatever.
Geological forces do not a D&D world make. Gods and mystical, unknowable, fey forces of Nature shape the world in a D&D setting, generally. They might build some geological forces into the world when they do so, but those're still at the mercy of gods and strange Nature.