Recently I had an opportunity to have on board my aircraft 4 officers from the Department of Natural Resources. Although the mission on that day was not the sand dunes tour the flight took us overhead and one of the officers had never seen them before, and neither had I. So, I dropped down a few thousand feet to take a closer look. The first photo we are approaching at 3500ft and I start my descent to 1500 ft.
The sand dunes constantly change shape from the wind and you can actually see where on this photo a small river flowage is overtaken and blocked.
Below the top photo I added a link to some of the history about the sand dunes and should you ever have an opportunity to see them, don't miss it, there is some real natural beauty which never remains the same for long.