These dunes have such dynamic shapes, I really want to see them in black and white so you'll have to excuse my excessive use of that time-honored medium. These are the kind of images that I'll tinker with for a long time before I get them "right".
After the sun came up, I headed out onto the dunes for the approximately 500 foot climb to the top. This first picture is from the bottom, looking up.
Getting closer to the top, I put my tripod in the frame for this picture.
It was a cloudy morning, but clearing. On top of the dunes, I pointed my camera toward the mountains in the North. I think this is Mount Herard at 13,297 feet.
Loking towards the NorthWest, the dunes had some interesting patterns
Later in the afternoon, after a rest, and with the sky now completely clear I headed back out for the long climb onto the top of the dunes.
On top again, the late afternoon sun started casting some long shadows across the tops of the dunes. I was about two hours early for the sunset, so I just sat around taking it all in.
The same location, but with a little more foreground detail.
Once the sun went behind the San Juan mountains, the shadows went out like a light - literally within the span of a few seconds. I was changing lenses when it happened, and took this picture soon afterwards.
There was nothing left to do but to hike back before it turned completely dark (made it with a few minutes to spare). Here's the scene looking towards the South as I was nearly off of the dunes.
I headed for Denver the next morning, and then back home after 2,950 miles of travel.