As you walk up the path, the trudge up the sandy hill might seem like a nuisance; but it is actually a walk through cycles of time. About 200 million years ago this sand was part of the largest system of sand dunes the North American continent may have ever seen. These “sand seas” are known as ergs. Our enormous erg was eventually hardened by water and minerals into Navajo Sandstone, an amazing uniform, smooth sandstone layer. It stretches from Arizona to Wyoming, and it can be over two thousand feet thick in some places. When you reach the edge of Horseshoe Bend you will be looking down 1000 feet ( 305 meters) of the sandstone to the river. After the Navajo Sandstone hardened, other layers of sandstone, mudstone, and different sedimentary layers piled on top of it. Then, after a couple of million years, patient water in the form of rain, ice, floods, and streams, worked to erode away the different layers.Today the Navajo Sandstone is once again exposed, and its sand is slowly wearing away. So now, what you are walking upon is sand from the Navajo Sandstone, which was from the giant Jurassic erg – recycled sand!
As you descend, the path is a little bumpier. It alternates between a whitish gravel, more sand, and some pretty solid, sloping rocks, the Navajo Sandstone. Notice how the rock itself has diagonal striped layers. These are the remnants of the layers of the ancient massive sand dunes before they were petrified into stone. The whitish stones tell us how the sandstone was petrified. This rock is calcite, or limestone, the same rock that drips itself into cave formations. Back 180 million years ago, this mineral mixed in with the rain and snow to cement the grains of sand together. The process took about
20 million years, but eventually all of the sand dunes were petrified by the calcite, retaining their beautiful sloping dune shapes. Today, as the grains of sand erode, chunks of the calcite also present themselves. As you get closer to the viewpoint, some of the rocks are covered with hard, sandy bumps. These are concretions of iron. Iron, being heavier than sand grains, was attracted to itself in ball shape while the sandstone was being petrified. Now that the sandstone is eroding away, the iron concretions are coming into view as well. When the little concretion balls break free from the rock, they are known as “Moki Marbles”.
You’ve made it. Worth the walk, wasn’t it? The view of Horseshoe Bend from the rim of the canyon is extraordinary. (You’ll need a wide-angle lens to get the entire scene in your picture!) If you find the height a little daunting, try lying down on the ground and looking over the edge that way. It gives you a much better sense of security. Make sure you keep an eye on your animal companions as well; they can slip as easily as you.
Below you, the Colorado River makes a wide sweep around a sandstone escarpment. Long ago, as the river meandered southward toward the sea, it always chose the steepest downward slope. This downward journey did not always occur in a straight line, and sometimes the river made wide circles and meanders. As the Colorado Plateau uplifted about 5 million years ago, the rivers that meandered across the ancient landscape were trapped in their beds. The rivers cut through the rock, deep and fast, seeking a new natural level. Here at Horseshoe Bend, the Colorado River did just that, and as the river cut down through the layers of sandstone, it created a 270° horseshoe-shaped bend in the canyon.
Conceivably, at some time far in the future, the river could erode through the narrow neck of rock, creating a natural bridge and abandoning the circular channel around the rock. Maybe in a few million years, this will be the site of a brand new natural bridge formed the same way as nearby Rainbow Bridge National Monument.