The rocks in the canyon walls are formed of three distinct layers – the upper third of Walnut Canyon's walls contain Kaibab Limestone that varies in layers and hardness, where the cliff dwellings are found, which overlies steep, scrub covered slopes of the Toroweap Formation, while the lowest third is the sheer-walled, cross-bedded Coconino Sandstone. Many layers of the limestone eroded, creating alcoves that the Sinagua Indians used as cave-dwellings.
