Great Sand Dunes Sunset

On a late afternoon in Colorado's Great Sand Dunes, the sun came out from behind the clouds for a brief moment before it went behind the horizon, illuminating the stoss side of an eroding dune. Sand originated from lacustrine deposits in the San Luis Valley-- the Sangre de Cristo mountains, which can be seen in the background, provided a source of some of the sand. This image therefore illustrates a significant part of the rock cycle- uplift, erosion, and redeposition.