The colored bands in the rock layers of Rainbow Valley were created during a much wetter time in the history of this very dry region.

Heavy rains would cause the reddish,iron-rich sandstone to dissolve and the subsequent dry seasons would cement those dissolved minerals on the surface, staining them a deeper red.

The dark red caprock contains the most iron and is more resistant to erosion than the lighter colored sandstone layers, which delays the eventual collapse and disintegration of the formations