Out in the plaza, during the latter part of this first occupation, work started on the Great Kiva, for this was the center of the ceremonial life of the entire pueblo. Here would be performed the ceremonies which would insure the inhabitants that theirs would be a long and happy life and that everything would prosper for the new community.
For roofing the rooms, main stringers of pine or juniper were used, and over these were laid splits of juniper or long poles of cottonwood. Next came a layer of rush or reed mattings and then a layer of dirt and adobe which formed the top of the roof, or the floor of the room above if there was more than one story.
The pine logs used for the main stringers are good-sized, many being 1 foot to 1½ feet in diameter and up to 10 or 12 feet long. Although juniper is still fairly abundant in the nearby country, good stands of pine today are many miles away. At the time the first parts of this pueblo were constructed, the pine forest may have been much closer. Perhaps extensive cutting hastened soil erosion and thus caused the forest growth to retreat.
Prehistorically it still was a long haul to bring in such big logs. Many people have assumed that the logs were floated down the Animas River. This would have been the easy way of doing it, but the logs found in situ in the ruins were obviously fresh cut, peeled while green, and show no scars. They must therefore have been carried overland from their source, no matter how far away, for it would have been impossible to float them downstream without being scarred and bruised in transit.
Through the growth of tree rings on pine logs, it is possible to date the time at which they were cut. If a tree is cut today, the outermost ring constitutes its growth for the year in which it is cut. Counting toward the center of the tree ring by ring, you will arrive at the date at which the tree was a young sapling. Climatic factors, dry and wet spells, are reflected in the width of the rings. Dry years usually show small, odd-shaped or stunted rings; normal years show regular well-shaped rings, and extremely wet years may result in excessively large rings. These various rings, which are arranged into patterns, can be matched with similar tree-ring patterns from still older trees, and a chart of patterns can be prepared which will extend as far back in time as you can find specimens with overlapping patterns. Against this master chart the ring pattern of any particular tree can be compared and the specimen dated. Today archeologists have such a tree-ring master chart which extends back to the time of Christ for the San Juan area.
At Aztec, samples of tree rings were secured from some of the beams that still existed at the time this dating process was discovered. Such samples fall into two groups of dates. One group (with numerous samples) was placed between A.D. 1110 and 1124; the second group (with only six samples) between 1225 and 1252. The tree-ring dates indicate that the great pueblo at Aztec had undergone at least two major periods of construction. Since a large number of dates range from 1111 and 1115, this would appear to have been the first peak of building activity.
It is possible that earlier samples have rotted away or have been destroyed by later Indians or by the early white settlers. Moreover, all building activity probably did not suddenly cease in A.D. 1124; it may well have continued for another 10 years, but the beams representative of this later period have since been destroyed. We can safely say that the first construction period at Aztec pueblo occurred sometime between 1110 and 1130, with most of the development occurring around 1111 and 1115. Likewise, a second major construction period at Aztec occurred sometime between 1220 and 1260, with major development in the 25-year span between 1225 and 1250.
The two construction periods at Aztec, as indicated by the tree-ring dates, are corroborated nicely by other evidence found by Morris that Aztec actually was built by one group of people, abandoned, and then reoccupied at a later date by a slightly different group of people. Throughout all the rooms he dug, he found sterile layers of windblown sand and ruined debris from falling walls and ceilings. In this debris and under the sand he found Chaco-like pottery and artifacts. In addition there were surprisingly few burials. The last point might seem strange, except for the fact that even today, 40 years after Morris’ work and despite endless searching, archeologists have located few Chaco-type burials in Chaco Canyon itself. Whatever the burial customs of the Chaco people may have been, they have eluded archeologists for many years. The absence of burials of this period at Aztec is a clue that probably a group of Chaco-like people, bearing the distinctive Chaco culture, may actually have moved into the Aztec area.
Morris wrote that he found many rooms built in typical Chaco-style architecture. Granting that the local sandstone was not quite as easily worked as that at Chaco, the large-size rooms, the high ceilings, the banded-veneer masonry walls, the large doorways, and other techniques used were very similar to the architectural techniques of the Chaco area.
Overlying the Chaco debris and sterile sand layers, Morris found pottery, household utensils, and burials characteristic of the classic Mesa Verde Period—a period which occurred later than the great Chaco Period. In addition, there were obvious architectural signs of rebuilding and remodeling within the pueblo. Large Chaco-type rooms had been made smaller by wattle-and-daub partition walls, while doorways had been shortened and narrowed more like the ones at Mesa Verde.