What a interesting place to go and see.
I like one, the ridge, ripples all just pull your eyes forward into the frame and the distant view implies openness and remoteness, something deserts are famous for and something to capture. However, its filled the frame up with intereest. Techincally you've shot into the direction of the light, robbing the scene of a little of colour. Overall I'd say its under exposed to try hold that sky in. I'd have shot the other way. The shadows seen give it some depth.
2. This is a starker composition, less interesting. I feel there is too much sky atop the frame not doing much for you, a wider aspect ratio again would help and I think if you were higher, and a little further forward on the dune you'd have a better composition.
IMG_2971.jpg by Lostgear, on Flickr
IMG_2969.jpg by Lostgear, on Flickr