A major component of our research is to explore the processes that created Chacoan outlier communities in the Montezuma Valley. A recognized pattern of development repeats throughout the region. It is clear that not every old community in the valley was suited to ascend to this role. In nearly every such case, population levels in the host community were relatively high and leadership structures and land use permissions were well established and recognized. Agricultural production potential appears to have been a major contributing factor insofar as where great houses formed (link below)
Some archaeologists over the last 25 years have explored the economic and social aspects and implications of moving from a small-time production system consisting of cooperating households toward a community based production system focused on creating greater quantities of food and public works projects. For about 150 years, the climate was favorable for such a development but a shift in rainfall patterns and quantities in the second quarter of the 12th Century may have added a level of stress to the system that could not be mitigated with better water collection techniques. When rain doesn't fall, there is no water to harvest or distribute.
Production within communities with a greathouse may have transitioned from simple production methods by households or extended households to communal farming that developed enhanced water collection/distribution, mulching, terracing, check dam mini-fields, and other technologies including frost protection. These methods required far more individuals, maintenance, and managers, than a simple production economy.
As part of this research, investigations of the exposed portions of the tri-wall and Pueblo A has led to some new and interesting discoveries. In 1988 and 1989, tests of the tri-wall revealed an unusual architectural configuration that was somewhat different than what can be gleaned from the 8 or 10 tri-walls that are known to exist. Vivian's 1959 article on tri-walls describes the only published work that I know of that involved excavation. He and his associates used relatively modern excavation and recording techniques for this work. Vivian tried to rebuild the record from earlier tri-wall excavations that had been performed at Pueblo del Arroyo in Chaco Canyon and Mound F and the Hubbard Mound at Aztec. Most known tri-wall's consist of three concentric walls; the innermost being the smallest circumference and the outer, the greatest. The chambers created by the concentric walls were often further divided by cross-walls creating compartments that are generally featureless. It is likely that these chambers held perishable products however, all excavations were performed before pollen and flotation techniques were developed so at this point, no proof has been detected to confirm this. However, it is known that whatever may have been stored in the chambers was gone by the time excavators examined the deposits.
Vivian concluded that the innermost concentric walls of both Mound F and the Hubbard Mound at Aztec as well as the del Arroyo tri-wall contained a building similar to a kiva. During our 1988-89 studies at Mitchell Springs, limited testing in the tri-wall led us to believe that the inner chamber was used as a platform for burning fires. Later tests exposed a single-wythe scabled-masonry tower that appears to have lost its Type I masonry veneer. .Later, a Chaco-style kiva was built inside of the tower. The bench of this kiva was coated with multiple coatings of red, white and gray plaster.
This part of the Mitchell Springs community was occupied continuously or-nearly-continuously for almost six centuries. Construction appears to have begun in the middle AD 600s and it ended before 1230-1240. During this time, two Pueblo I era (circa AD 825) curvilinear roomblocks were built and within 150 years, a small multi-story great house with an appended tri-wall developed over the top of the decommissioned PI houses.
Another interesting recent discovery that also involves ritualized decommissioning was documented in Pit Structure 25 which is located near the southeast corner of Pueblo A. It contained approximately 30 sq meters of floor space and may have been used by a larger segment of the community rather than by a few interrelated or cooperating families from the proximal house. Regular domestic activities were conducted inside this structure although the evidence for food processing is somewhat confusing. On the south side of the wingwall, the grinding of maize and other items was performed. Although 22 manos and 8 pecking stones were documented, only two incomplete metates were present. Almost no de-facto trash was present. Two sets containing 3 bone awls of various sizes, were nested together in the ceiling immediately to the north of the wingwall and another set was clustered in the northeast quarter of the structure along with two large Moccasin Gray jars, and four small gray ware cups, sandals, and mats. A hafted axe hammer, a large core, 2-hand polishing stone and a small abrading stone were also stored in the area south of the wingwall. Fragments of mats and fabric were collected from the floor just north of the ventilator opening and in the east section of space just south of the wingwall. More than 400 tree-ring samples of conifer or juniper were processed from the burned roof. It is clear that tools and other implements were deliberately left in the building when it was burned and was likely related to the ceremonial closing of the building. A very similar closing occurred in Pitstructure 2, located about 60 m to the northwest. It also was deliberately burned along with its complement of attendant tools and weavings. Thirty five pottery vessels and other items were left inside the building when it was set ablaze. Another example of this closing ritual was found during test excavations in the south and west ends of the great kiva where beneath its floor, the burned remains of over-sized Pitstructure 6 was identified. It contained approximately 65 square meters of floor space and was also closed by burning immediately after abandonment. As om Pitstructure 25 and 2, a large assemblage of usable tools, fabric, human hair twine, mats, baskets, ceramic vessels and ornaments were left on the floor when the building was intentionally burned in the late 700s. In the mid to late 900's, the great kiva was built over it and subsequently rebuilt at least two more times before being abandoned in the 1130's or 40's.
In Pueblo A , an effort to emulate a construction style which had roots in Chaco is apparent in the pre-planned footprint of the pueblo as well as some masonry style characteristics incorporated into some of the rooms. The front two rows of storage rooms on the south end of the pueblo and the two storage rooms on the east side of Pueblo A were single story rooms. In one event, the burning pueblo's southern wall fell southward and because it was still articulated, it was measurable; once standing a little over 3 meters tall. Another interesting item in regard to the pre-planned footprint of Pueblo A is that only two of the 22 ground floor rooms were habitation rooms. They are the only square-shaped rooms in the pueblo, a trait that was also noted at Salmon Ruins in Bloomfield NM. The second-story rooms above these two rooms may have been used for domestic activities such as cooking and sleeping but they were evidently not used for grinding operations.
Chaco-style Kiva A, built into the center of the greathouse, utilized masonry of a finer style than was the norm at Mitchell Springs. Like Room 18, it also burned in the fire that ended the occupation of Pueblo A and possibly the entire Mitchell Springs community. It contained an under-floor ventilator feature that brought fresh air down into the kiva chamber from either the floor of the room above it or from atop Pueblo A. The pressure differential between the dark spaces in Kiva A in the belly of the pueblo, to the sunlit intake point 20 feet above (on the roof of Pueblo A), would have created a natural circulating cooling effect in the summer months. Regulating the airflow into the ventilator would prevent too much cold air from entering during cold nights. On one of the masonry stones that was used to create the elaborated ventilator feature (see photo below Left), an interesting petroglyph was carved (See Mitchell Springs Tab for more information on this work).