Richard Denevan's artistic medium is the earth itself. His "brushes," if you will, are sticks he finds in his chosen locale. Most examples of his art that I've seen in the past were done on the California beaches. These photos of new work that he created in the Nevada desert are from his website.
Robin Reagler 
That’s incredible. It reminds me of Tibetan sand paintings. So fleetingly here, yet so incredibly beautiful.