The Wild Unknown

The Horseshoe Bend of the Colorado River downstream of Glen Canyon and Lake Powell is located near Page in Arizona and marks the spectacular entrance into the Grand Canyon. The wide panoramic view of this canyon and the Paria Plateau and Vermillion Cliffs in the distance with thunderstorm skies above triggers deep feelings of the wild unknown.
The formation of this incised meander, which is a combination of a canyon and a river bend, began about 75 millions of years ago. At this time, in the late Cretaceous era of the dinosaurs, the Colorado Plateau was at sea level. At present it is located about 1300 m (4200 ft) above sea level. The Colorado River cuts through even older sedimentary Navajo Sandstone rocks. These began to form about 180 million years ago in the Jurassic from wind-blown sands of an extended North American desert stretching from Arizona to Wyoming. The rock walls expose diagonal striped layers that are remnants of the dunes layered sand structure. The Navajo sandstone layer is exposed today because younger sediments deposited on top are already weathered away by the uplift of the Colorado Plateau. Through this long-eroded landscape, the ancestral Colorado River was meandering just as any other river. However, when the Colorado Plateau began to rigorously uplift about 5 million years ago, the river incised deep and fast into the uplifting bedrock and created this canyon with the pre-existing 270° bend.
Today, the drop between the rim and the river is about 300 m (1000 ft). The Colorado River continues to cut into the Glen Canyon at a rate of 0.007 inch (0.17 mm) a year. This may sound like a negligible erosion rate, but over the vast time period of 5 million years this makes for a whopping 2800 ft (850 m); about the depth of today’s Grand Canyon. In the far future the river may eventually erode through the narrow neck of rock. This may create a natural bridge. After its collapse a butte will form, like so many others in the Grand Canyon.
The approaching thunderstorm substantially enhances the sublimity of this landscape. Sporadic flash flood events triggered by thunderstorm rain run-off are an important driver of erosion in this arid landscape.

May 2015
Canon 5D MkII, Rokinon 14 mm, f/16, 0.5 to 4 sec, ISO 100, tripod, 180° panoramic composite of 48 images.
Colorado Plateau Gallery » The Wild Unknown