While visiting Arches National Park, we had the opportunity to view strata directly overlying those we saw at Zion, including the Navajo Sandstone, Carmel Formation and Entrada Sandstone. Most of the arches are in the Jurassic Entrada Sandstone and result from a combination of jointing (vertical fractures) due to uplift of the Colorado Plateau and water dissolution of cements that lithified the sandstone. Holes develop in weakened regions, erosion of the underlying Carmel Formation ensues, and eventually produce an arch-like opening.
Above we see a series of normal faults that are visible from the visitor center parking lot.
North and South
Group photograph at Delicate Arch. From left, (back row): Darlene Montesanti, Stefanie Burney, Ashley Gentry, Ashley Cuthill, Dr. Phillips, Danielle Powers, (front row) McNeill Lytch, Bryan Chavis, Garrett Adams, and Salyna Dvorovy.