AZTEC RUINS Excavation of a Portion of the East Ruins, Aztec Ruins National Monument, New Mexico

Architecture

In spite of some disturbance, very few construction details have been lost in the 13-1/2 rooms excavated. Masonry and architecture are analogous to and contemporaneous with the Montezuma Phase at Mesa Verde National Park, and are synchronous at least in part with the reoccupied portions of the West Ruin at Aztec. Uniformity of construction displayed in the 12 upper and lower Rooms 8-14 almost bespeaks a preconceived building plan; certainly they were built as a unit, and exemplify a very high order of Pueblo architecture. These rooms also display unique construction of doorways in the use of pole sills and lintels which may be a secular adaptation of a feature sometimes found in a religious structure, the Great Kiva.

Although not enough of the ruin has been excavated to outline the building sequence or mechanics of growth, it is thought that the north section was the highest, with lower rooms terraced down toward the south. At least walls of the north tier are thickest. No outside entrances have been found but they are believed to exist at the south, probably in the form of either a vestibule or hallway entry to ground-floor rooms. Both halves of the East Ruin appear to be rectangular houseblocks with incorporated kivas, an estimated 200 to 300 rooms. During the span of occupation in the area tested, there is a hint that the interior was modified. The unexcavated kiva adjacent to Rooms 8, 9, and 11 probably came into use at this time.

We found conclusive evidence that building materials such as face stones, shakes and poles were reused, probably salvaged from the West Ruin. Tree-ring dates, when compared with pottery dates and architectural remains, point to similar reuse of main beams. Therefore, the tree-ring dates, and those which may be obtained in the future, should be viewed with considerable caution and their association carefully noted.

It is significant that in the seven rooms containing original ceilings, nearly all of the main beams and secondary roofing materials are juniper. This suggests either a drier climate in the 13th century or, more probably, an imposed choice whereby the people resorted to the use of wood growing in the Aztec vicinity.

A rebuilding spurt by Mesa Verdeans in the West Ruin is noted for the period 1225-1252 when the supply of reusable pine and fir was apparently exhausted and new timbers were cut. Apparently, after usable beams from the West Ruin were no longer easily available, juniper was used exclusively for main beams in the East Ruin during the final years of construction there.

At this point, an admittedly speculative synthesis of 86 tree-ring dates obtained thus far at Aztec temptingly suggests that the period 1225-1252 witnessed the following more or less contemporary events: (1) the movement of Mesa Verde people in considerable number to Aztec, (2) their rehabilitation and/or salvage of portions of the West Ruin, and (3) their inauguration of an ambitious building program consisting of the East Ruin, the West Ruin Annex, and the two tri-wall socio-religious structures.

Obviously, the answer is not quite this simple, because there are four or five additional mounds within the area whose study might alter this interpretation. Mound F, the second tri-wall building, has been merely tested. It should be noted that the wood found on the pilasters of the central kiva, partially uncovered in 1953, was juniper. Surface sherds here are mostly Mesa Verde Black-on-white and the exposed masonry is identical to that in the East Ruin.

In support of the foregoing, it has been shown by Morris (1939), Martin (1936), and O'Bryan (1950) that Chaco Branch characteristics dominated both to the south and northwest of Mesa Verde at A.D. 1121, when the West Ruin was built, and in the decades immediately preceding that date. By A.D. 1225, the resurgence by the Mesa Verde Branch at Aztec occurred, involving the construction of the East Ruin and at this time also the La Plata and Animas Valley sites possessed the same traits as their Mesa Verde cave-dwelling neighbors on the north side of Mancos Canyon.

Pottery

Evaluation of room deposits shows that out of 13-1/2 rooms excavated, there are 6 lower rooms which were abandoned and left vacant in which the fill was largely secondary, the result of natural agencies. Out of six upper rooms, one had been previously excavated and backfilled; contents of only two were not appreciably disturbed, while the remaining three were disturbed in varying degrees, either in prehistoric or modern times. Deposits in the kiva over Room 1 were valid for the three successive floors which were laid in a relatively short time. Collapsed material in the remaining one-half of Room 24 was likewise valid and undisturbed.

Simultaneous trade contacts with the Little Colorado and Kayenta areas are indicated by intrusive sherds.

The preponderance of Mesa Verde pottery is in agreement with the architectural data, indicating that occupation followed the initial abandonment of the West Ruin and the Hubbard Site. From this it may be inferred that either in the late 1100's or early 1200's there was a migration to the Aztec vicinity from the Mesa Verde. Presumably this was slow and intermittent, since the Mesa Verde not only remained populated but was also flourishing with the inhabitants mainly concentrated in the large cliff dwellings. This movement out of Mesa Verde may have been the result of overcrowded living conditions or, more probably, lack of arable land for the expanding population. While the Mesa Verde area apparently suited the people's predilection for caves, unquestionably the well watered and fertile Animas Valley was equally favorable.

In seeking causes for this gradual movement southward, there is also the possibility that by A.D. 1200 or shortly thereafter, people in the Mesa Verde either had heard rumors of nomadic tribes operating in the vicinity, or may have actually encountered them in brief, outlying skirmishes, which, singly or combined, touched off their large-scale movement from the mesa tops to the caves (Lancaster et al. 1954: 106). If this motivated a southward migration it is difficult to see how these newcomers proposed to defend themselves in open valleys like the Animas, unless by construction of massive-walled pueblos such as the East Ruin.

There is still another possibility. Lacking tangible evidence for enemy peoples, it is quite possible that climate was the controlling factor. Admittedly difficult of proof in the light of present knowledge, it is not inconceivable that several cold and dry or cold and moist, unseasonable years, drove the Mesa Verde people to the shelters provided by the caves. Obviously, tree-rings record in sequence only in a relative manner the dry, normal, and moist years, but do not reveal how cold the climate was. Crop shortages or partial failures could have resulted from too short a growing season due to extremely cold and wet weather.

As for the general abandonment of the San Juan area at the end of Pueblo III times, there is now a tendency to seek multiple causes or combinations thereof, citing factors such as drought, arroyo cutting, inter- and intra-village feuds, guerilla raids by hostile tribes, disease, dietary deficiency, and land shortages (see Jett 1964: 295-297), for an excellent and comprehensive discussion).

A clear-cut case cannot yet be made for Aztec. However, according to Schulman (1956: 65) "the average annual [tree] ring growth and, perhaps, . . . rainfall and runoff during the 85-year drought of 1215-1299 seems to have been about half that during the drought since 1930 in this basin [in the Southwest; in the Colorado River Basin]." Therefore, the intensely dry 24-year period of 1276-1299, which apparently exceeded disastrous droughts in our times, could well have tipped the scales against farming, particularly corn, which is not an especially drought resistant annual, and would be unable either to germinate or mature properly.

The fact that exceptional rainfall occurred in 1300 and subsequent years (Schulman 1956: 65) could mean that the abandoned pueblos were not reoccupied with the return of favorable farming conditions on grounds of either superstition or dispersal of the original population.

On the other hand there is a suggestion that Aztec was untenable during at least part of the 14th century for another reason. Schulman (1956: 65) further points out that the interval 1300-1396 was the wettest during the past eight centuries. Aztec is not particularly well drained and it is quite possible that former fields were flooded during the planting or growing season. Thus, there is some evidence that flood stages of the Animas River destroyed a section of the East Ruin at the southeast side.

At present, however, there is only indirect and negative evidence from which it is not yet possible to make a more precise assessment of the question concerning abandonment.

Definitive answers to this and other questions may be forthcoming as result of the studies of the National Park Service-National Geographic Society in their jointly sponsored archeological project on Wetherill Mesa in Mesa Verde National Park.

Lastly, we may ask ourselves: is this study based on a sufficient number of specimens and examples for the site thus far exposed, and will the largely unexcavated remainder of the site yield approximately the same correlation? It is the writer's considered opinion that the first question may he confidently answered in the affirmative, while the second must be relegated to the now somewhat overworked phrase "more spadework and intensive research is needed" in both mounds of the East Ruin.

Morris tentatively concluded that the East Ruin is a large open Mesa Verde Pueblo. The work reported herein does nothing to detract from his conclusion but tends, I believe, to confirm it.

PLATE 39—A general view of the partially excavated northwest corner of the East Ruin