I thought the juxtaposition of sandstone and sand and the sharp demarcation between them was a perfect illustration of the cycle of geologic change that has occurred on the Colorado Plateau over the eons. What was once a vast desert like the Sahara was transformed into amazing sandstone formations and today you can see the process reversing itself as the stone is worn down back to the sand from whence it came. This was taken near Paria canyon in southern Utah.