Mesas, Cliffs, and the Ancestral Pueblo

By Luke Carothers

Located in the American Southwest, some of the world’s most impressive early examples of vertical engineering can be found perched on the walls of deep canyons and along the face of steep mesas.  Built by the Ancestral Pueblo, who are also sometimes known as the Anasazi, these structures were complex construction projects that served as apartment-like housing for the population as well as sites for significant religious events.  These dwellings were often multiple stories and, in the largest example, could contain up to 800 individual rooms.

Earlier in their history, the Ancestral Pueblo were a nomadic, hunter-gatherer society, but by 750 CE the culture had shifted towards a focus on agricultural products like cotton.  In turn, larger communities and villages began to form throughout the region.  During this period, the Ancestral Pueblo also developed stone masonry, which allowed them to build community structures, known as pueblos, with dozens of adjoining rooms.  The development of stone masonry also allowed the Ancestral Pueblo to create larger structures both vertically, in the form of great houses, as well as downward in the form of kivas.

By around 1000 CE the Ancestral Pueblo began to build bigger structures to support a growing population.  In this pursuit, they turned their eyes downward from their mesas towards the cliffs high above the canyon floor.  It is believed that this movement was also a form of defense against raiding parties from neighboring Apache and Navajo tribes.  Rather than building defensive structures around their cities, the cliff dwellings relied on a single means of egress, a ladder or rope, that could be pulled up in the event of an attack.  Their agriculture assets would also be protected high on the cliffs.  It is also theorized that this move to the cliffs was done as a way to shelter from wind in the winter and draw heat from the sun.

While their exact reasoning for building settlements on what seems like precarious footing will likely never be known, it is clear that these structures were capable of supporting large populations at one time.  The Ancestral Pueblo cliff dwellings were made primarily with hand cut blocks and plastered with adobe mortar. Built in a stepped fashion with the highest floors built against the stoneface, many of these cliff dwellings were designed to have terraces on each floor.  To create floors and rooms, the Ancestral Pueblo again turned to adobe mortar.  The process began with installing large crossbeams followed by smaller branches to fill in the gaps.  This structure would be repeatedly plastered over with adobe mortar until it was solid enough to serve as a roof.

The largest of these Ancestral Pueblo cliff dwellings is Pueblo Bonito, which is located in modern day New Mexico.  In an area of roughly 3 acres, Ancestral Pueblo were able to construct more than 800 individual rooms.  Another notable site of these cliff dwellings is the Mesa Verde area, which now forms Mesa Verde National Park.  The Ancestral Pueblo inhabited Mesa Verde from around 500 CE to 1300 CE when they were forced out by drought.  During this time, the area’s inhabitants created hundreds of dwellings, from the earliest single story clusters of semi subterranean structures along the mesa’s top to the iconic Cliff Palace, which features 217 individual rooms.

Archaeological evidence suggests that most of the region inhabited by the Ancestral Pueblo experienced a severe drought that lasted several decades at the end of the 13th century.  This in turn made the traditional method of mesa-top farming unsustainable for the Ancestral Pueblo, and they were forced to abandon their cliff dwellings and seek wetter areas elsewhere.  While the Ancestral Pueblo moved to find more suitable living environments and eventually broke into the modern Pueblo tribes, these Ancestral Pueblo left behind an incredible testament to their engineering and architectural prowess, a feat that was not replicated by their descendants following the abandonment of the cliff dwellings.

luke carothers is the Editor for Civil + Structural Engineer Media. If you want us to cover your project or want to feature your own article, he can be reached at lcarothers@zweiggroup.com.