During the Late Cretaceous, the sediments were deposited at sea level. Subsequent uplift due to mountain building processes rose what is now the Colorado Plateau to present day elevations. Between 40,000 and 70,000 years ago, Chaco Canyon was eroded to expose the Menefee Formation. Since that time, the canyon has filled with 38 meters of alluvium, which form the modern valley floor.
The Menefee Formation is less resistant to erosion than the Cliff House Formation and often completely erodes from beneath the younger sandstone. The unsupported sandstone will then break away in large slabs and boulders as the undercutting reaches joints and local weaknesses. This step-wise erosion is responsible for producing the prominent cliff faces in Chaco Canyon as well as the debris mounds or talus slopes piled against them.
When this erosional process continues from several directions, it may actually "sever" a landform into separate segments and produce large, apparently free standing rock masses. Fajada Butte was "severed" from Chacra Mesa over the last 10,000 years by just such a process of gradual erosion.