Lithified Sand Dunes in Zion National Park
June 13, 2013
Photographer: Ray Boren
Summary Author: Ray Boren
During the Early Jurassic Period, what's now the Colorado Plateau of the southwestern United States was a vast, arid, wind-driven (aeolian) sea of sand comparable to but even sandier than the Sahara, the largest desert on Earth today. That ancient desert’s cross-bedded dunes of Navajo sandstone are spectacularly exposed at places like Zion National Park, as shown above, in what could almost be a panel of minimalist or expressionistic art.
According to the National Park Service’s Geology Resources Division, beginning about 200 million years ago, dry trade winds sifted and built the dunes in a rain shadow of the Western Interior Basin. Over a period of more than 40 million years, granules piled to a depth of 800 to 1100 ft (240 to 340 m). The region’s lithified white-, salmon- and red-tinted sand (now sandstone) is believed by geologists to be the largest example of its kind in the planet’s rock record. Note the light-colored layer at bottom is approximately 10 in (8 cm) thick. Photo taken on April 6, 2013.
Photo details: Camera Model: NIKON D60; Focal Length: 300.0mm; Aperture: f/10.0; Exposure Time: 0.0040 s (1/250); ISO equiv: 180; Software: QuickTime 7.6.4.