Travelers to Southwest USA are usually amazed by the regions many natural sights and national parks such as the Grand Canyon. But among these natural wonders are also plenty of historic sites and ruins. These ruins tell fascinating stories of the people who lived in the region before the arrival of Europeans. Among these is the story of the Ancestral Puebloans who inhabited the region that is today known as the Four Corners, including parts of modern-day Colorado, New Mexico, Arizona and Utah.
For centuries the Ancestral Puebloans lived on mesa tops, mesa referring to flat-topped mountains that are common in the region. But by the end of the 12th century the people started moving, first to cliff dwellings in natural alcoves along the mesa rim, and later further south. What caused these changes is not known for sure, but drought and other environmental factors probably played a role. As the villages moved, the architecture also changed, adapting to new environments and lifestyles.
From nomads to farmers and masonry architects
The earliest Ancestral Puebloans – known as Basketmakers – were nomadic hunter-gatherers that camped out in the open or in caves. After 1200 BCE the Basketmakers started relying more and more on agriculture, and with agriculture came more permanent houses and villages. Around 50 to 500 CE the people started building pit houses, a type of subterranean home built with wood and mud. The ground surrounding the house would help keep the interior warm during winter and night, and cool during summer and day.
After 750 CE Ancestral Puebloans started building more permanent villages of stone masonry. The culture was advancing and the villages started to include round subterranean ceremonial structures known as kivas. Kivas probably evolved from the early pit houses, and both had a ventilation system that provided fresh air into the underground space. Kivas are a prominent feature of all Ancestral Puebloan villages and they are still used by their modern descendants today.
The finest examples of this stone masonry architecture are found at Chaco Canyon in New Mexico. This is where the Ancestral Puebloans built their Great Houses, referring to large sites with planned layouts, multi-story masonry construction with large rooms, plazas and huge kivas. The greatest was Pueblo Bonito, built in stages between 850 and 1150 CE. The buildings were several stories high, and the lower levels had thicker walls which shows that the higher levels were planned when the first story was built.
The area provided plenty of sandstone and the Chacoans were master masons. They built core-and-veneer walls with roughly shaped sandstone and mortar in the middle and carefully selected and shaped stones on the outside. Plaster was then applied to cover the stone walls and to protect the mortar from rain. Wooden beams were used with primary and secondary beams, and the timber was hauled from a great distance.
Cliff dwellings of Mesa Verde
At Mesa Verde Ancestral Puebloans also started building masonry houses. A big change happened by the end of the 12th century when people moved from the mesa into the alcoves below cliffs. This is where the cliff dwellings were built in the 13th century. The cliff dwellings included plazas and courtyards for social gatherings and other outdoor spaces for working. Buildings had multiple stories and reached the cliff which provided a natural ceiling.
The cliff dwellings were built with sandstone blocks and mud mortar. The sandstone was likely harvested locally from the under the cliff and then shaped, sometimes more finely and sometimes more roughly. Wood was used for roof construction and there is evidence that old wood from the pit houses was recycled and used again. This can be a sign that resources were getting to be scarce. Archeologists have even found traces of urine in the mortar which could also have been a way to save resources.
The big question is why the people decided to move below the cliffs. The cliff provides protection from rain, snow and sun, but is this reason enough to go through all the trouble? Construction was certainly technically more difficult than on the mesa, even if stones were readily available below the cliff. Accessing the cliff dwellings was also difficult, requiring rock climbing using narrow foot and handholds – and since farming was still done on the mesa tops this commute had to be done every day.
One popular theory is that the cliff dwellings were built for a defense purpose. It would certainly be difficult to attack a the cliff dwellings. In order to access Balcony House at Mesa Verde for example, people had to crawl through a 3-meter-long tight tunnel. But the theory makes less sense when you consider that all the food and resources were on top of the mesa. Attackers would simply have to block the exit and wait for the people to starve! In addition to this, archeologists have found very little evidence of actual warfare.
Another theory is that people were driven to the alcoves due to drought. Mesa Verde receives little rain and the canyons and rivers only have flowing water after storms. Ancestral Puebloans realized the need for water management in order to grow their crops, and they built dams and reservoirs to catch as much rainwater as possible. Summer rains were unpredictable and often came in storms which made melting snow an important source of water .
But in the 12th century a 50-year drought hit. This meant that people had to rely more and more on groundwater and springs, including seep springs. Seep springs are formed when rain and melting snow on the mesa top passes through the porous sandstone. When the water hits an impermeable layer of rock, the water starts seeping out, washing away the sandstone and slowly forming the cliff and alcove. The alcoves were thus sources of water and building cliff dwellings made it easier to access and protect this valuable resource.
From Ancestral Puebloans to Modern Puebloans
Despite their advanced design, both Chaco Canyon and Mesa Verde were abandoned by 1300 CE. Why did the people leave and what happened to them? Why did the people at Mesa Verde build their grand cliff dwellings, only to abandon them 100 years later?
Again, there is no certain answer and one reason could have been conflicts with other tribes. But environmental issues, climatic changes and and overuse of resources probably played a role. There is evidence that populations had been growing, and this could have put too much pressure on the environment and the agricultural lands. Another major drought hit in the late 13th century and this would have made it even more difficult to grow enough food for the growing population. The people decided to leave and migrated south towards the Rio Grande river.
What’s known is that the people didn’t disappear. The descendants of the Ancestral Puebloans are still living in Arizona and New Mexico, where they continue to keep up their traditions. When the Ancestral Puebloans reached the Rio Grande, they started building new villages. After contact with the Spanish the Ancestral Puebloans started building with sun dried adobe bricks, a material that is well suited to the local climate to provide comfort in both summer and winter.
One of these villages is Taos Pueblo – one of the oldest continuously inhabited places in North America – that is kept alive by the modern Puebloans living there today. The architecture of the village has grown and developed organically over the centuries into multi-story adobe blocks. Today the site is protected as a UNESCO World Heritage Site, which prevents the installation of running water or electricity for fear of damaging the structures. In a way this is a shame, and what I would like to see instead is continued development of the village and adaptation of its adobe houses to 21st century life. What I would like to see is a continuation of 3000 years of architectural development.