Upper and Lower Cathedral Valley offer exquisite views of sculptured monoliths with intriguing names such as the Walls of Jericho and the Temples of the Sun, Moon, and Stars. The monoliths are composed of the earthy, buff-pink Entrada Sandstone.
Deposited 160 million years ago in the Jurassic period, this fine- grained sandstone formed by the deposition of sand and silt in tidal flats. It crumbles easily to a fine sand which is rapidly removed by water; therefore, talus (debris) slopes do not form and Entrada cliffs tend to rise sheer from their base. Above the Entrada, the grayish-green sandstone and siltstone of the Curtis Sandstone forms a hard cap rock on some of the monoliths and higher cliffs and buttes, protecting them from erosion. Above the Curtis is the thinly-bedded, reddish-brown siltstone of the Summerville Formation.