Petrified sand dunes — a fine-grain record built over 60 million years

Sand dunes in a desert pass like ocean waves, but at a glacial pace. Over a 5,000 year period, a single-sand-grain layer accumulates at the base. Over 100,000 years, an inch of compressed sand has grown, with striations capturing the history, frozen in time. This beauty would be lost underground were it not for a number of subsequent factors. First, the desert flooded with a great inflowing of the sea, burying the formation under water to slowly mineralize into sandstone. Then a sedimentary layer of relatively tougher rock accumulated on top, which becomes the capstone you see at the top (more on that later). Then, the movement of tectonic plates lifts the sandstone vertically, rather than at an angle, preserving the tougher capstone on top. If not for each of those factors, cracks and erosion would wash the beauty away, but the capstone protects the beauty below like an umbrella to the elements.

The iron bridge across the hoodoos is part of the rock climbing adventure. More history below.