Those aren't sand dunes, they're just rounded mountains. Their soil might be a little sandy but it's not all loose like a sand dune. And, yes, they're big, probably a few hundred feet tall from their bases at least. This is the desert... click here for more info on where I took the pic from... http://www.nps.gov/jotr
lies in the desert, until they actually
journey into it. Nice shot, Sequoia!