The Cockscomb, Grand Staircase Escalante National Monument, Utah

In this photograph, early-morning light accentuates cross bedding in a layer of Navajo Sandstone high on The Cockscomb above Cottonwood Wash in Grand Staircase Escalante National Monument, Utah. A vast desert of shifting sand dunes reminiscent of todays Sahara blanketed this region approximately 190 million years ago. The cross bedding seen here is typical of sand dune structures as wind deposits layer upon layer of sand down the faces of an active dunes. These layers became frozen in stone when the dunes were subsequently buried beneath thick layers of sediment. Dissolved minerals in groundwater percolated down through the sand and cemented the grains together to form what we now call the Navajo Sandstone.