I visited Mesa Verde in Colorado near the Four Corners. This was my first encounter with the "ruins" of the ancestral Puebloan people, progenitors of the Pueblo and Hopi nations. I had heard about Mesa Verde since I was a kid, but nothing could prepare me for the awesome reality. Despite the influx of tourists, there is a peaceful and spiritual quality that persists.
The most famous aspect of what was left behind there are the cliff dwellings, which are certainly magnificent. These finely crafted rock structures emerge from huge alcoves within the cliff faces, and from a distance resemble swallows' nests, fitting into the surrounding rock just as naturally. Actually the cliff houses represent the culmination of about seven centuries of habitation at Mesa Verde. Then around 1300 AD the people abruptly abandoned their homes and moved south and southeast to establish other communities. There is much speculation about why they moved, but the most likely cause was a prolonged period of at least 12 years of drought.
The cliffs were only occupied for the last two centuries at Mesa Verde; before that, all habitation was on the mesa above. At first the people made rectangular pit houses that were dug partially into the ground and then built up with poles and sticks plastered with mud. The entrance was via a hole in the roof with a ladder descending to the floor below. Archeologists believe that from this simple pit house both the freestanding masonry pueblo and the underground circular kiva evolved. The cliff dwellings combined both interconnected pueblo "apartments" and kivas, which were used for ceremonial and community functions. Some of the larger cliff dwellings may have housed over a hundred people. Most of the Mesa Verdeans lived in this communal way, but there were also many smaller housing units scattered throughout the area. It is obvious that they were a very cooperative society.
Little did they know that their style of architecture would become so enormously popular many centuries later. "Pueblo" or "Santa Fe" style building can be linked directly to them. The Spanish introduced modular adobe blocks that make the construction go faster, but the simple stacked rectangular shapes with protruding vigas is native American.
These people were primarily farmers, growing squash, corn and beans in terraced garden plots on the mesa tops. They carefully guided water to their gardens. The mesa itself slopes gently toward the south, which improves the solar gain for gardening, and the colder air slides down the canyons and off the mesa, which increases the growing season.
There is a lot of speculation about why they decided to start building communities within the cliff faces. Some think it was for defensive purposes, although there is little evidence of violence to support this. My sense is that they moved to the cliffs for comfort. Some enterprising individual or family probably tried building a stone house on one of the many cliff ledges that faces south and soon realized that there were many advantages, which were pointed out to the others. Sealing off a cave or cliff alcove with rock walls effectively makes the room a part of the cliff itself. It's like digging into the ground to take advantage of the cool in the summer and the warmth in the winter, but under the rock ledge they were also protected from the rain and snow and had much more thermal mass to buffer temperature extremes. Facing south, or southwest, as many of the cliff dwellings do, would allow the sun to enter the openings into the interior and also warm the stones, which would give off heat at night. During the summer, when the sun is high in the sky, much less sun would reach the buildings and they would remain cooler.
I got an indication of how well solid rock can modulate temperatures at another stop. On the outskirts of Moab, Utah is a 5,000 square foot dwelling blasted out of solid monolithic rock, called Hole-in-the-Rock. It is open for tours, so I checked it out and was informed that the temperature stays about 65 degrees F. all year round. Moab is at about 4,000 feet elevation, so it is a warmer climate than Mesa Verde, but even so the cliff dwellings must have been fairly comfortable most of the time.
I couldn't help but compare what the ancestral Puebloans have achieved with what I have been advocating about sustainable architecture. They score remarkably high! The rooms are very compact, often sharing walls with each other (which makes for less transportation of building materials and the adjacent rooms help keep each other warm.) The rooms are often stacked on top of each other (I saw as many as four stories), which again conserves space, materials, and heating energy. There is very little wasted space; even the tops of the pueblos and kivas were used for community activity.
Most of the cliff dwellings were oriented to collect solar energy. Even though they didn't have glass to keep the rooms cozy, they compensated by using quite small entrances and ventilation holes, which could be sealed with slabs of rock or hides when they wanted. Being built into the cliff face, they did not overheat in the summer. Because of these factors they were relatively energy efficient, requiring less wood for heating.
The materials they used to build with were definitely local and natural, being just the sandstone and adobe found in the area. Very little wood was used, just small vigas to support the floors of the various stories or the kiva roofs. What wood they did use was obviously not milled. Deforestation was likely an issue for these people, as it is for us.
I'm sure they recycled building materials as there is much evidence of remodeling over time. They most certainly built to last, as much of their work has survived some seven centuries without any maintenance. The Park Service has stabilized some of the structures, but they say only about 10% of what is there now has been done since the natives left. In fact you can usually tell which work was done in modern times because it is much cruder than the original work, which was carefully carved with stone tools and then plastered to make very smooth, colorful walls. Most of the original colored plasters have not lasted.
They did not have enclosed greenhouses, for obvious reasons, but they did grow all of their food nearby, basically on the mesa top that was their roof. They also had domesticated turkeys (the feathers were used for making blankets) and dogs (which provided hair that was woven into belts, etc.)
With all of this sustainability, why were they unable to sustain their culture at Mesa Verde? As I mentioned earlier, the likely cause was a prolonged drought that made it very difficult to provide food for the thousands of people living there. This could be the final message from these ancestors: ultimately we live at the mercy of mother nature. They were able to move on to other places where streams provided water for their gardens. Where could we move if our climate becomes inhospitable or we have polluted the waters or poisoned the air or our great machines cease to run?