Sand Turned to Stone

Those slanting lines in the rock are old sand dunes, turned to stone mid-slope. This is the Navajo Sandstone, the remains of the largest sand desert we know of in the planet's history, laid down about a hundred and eighty million years ago. Zion is where it reaches its greatest thickness, over two thousand feet. Each set of lines is a cross-bed, the leaning face of a dune, and they dip the way the wind was blowing. So what you're looking at is a fossil wind, mostly out of the north-northwest. Some of that sand came a long way. Trace grains of zircon show that at least part of it began in the ancient Appalachians, rode rivers across most of the continent, then blew in on the desert wind. Part of this Utah rock used to be eastern mountains. The white tops weren't always white. They were pinkish-red until, long after burial, ancient groundwater or hydrocarbons moved through and stripped out the iron. Watch the slickrock streams for stacked potholes. Many sit in plain sight of this highway. Your best odds of spotting bighorn in the park are on this stretch, between the tunnel and the East Entrance, so watch the ledges. If you pull over, stay on the pavement or a trail, and leave the crust on the sand alone. It's a living skin of cyanobacteria, algae, mosses and fungi, and one step can destroy it. It may take several decades to mature again. Anything over nineteen feet can't use the pullouts on this side, except the Checkerboard Mesa viewpoint. Come back after dark if you can. You can see the Milky Way anywhere in Zion, but the park says the darkest skies are on this east side.