in these caves, and not on the mesas or the canyon floors, they were able to use this land towards agricultural production to ensure their success in this high elevation, desert environment. The ruins that make up Navajo National Monument were a large number of rooms used for storage, suggesting that at some point their crop production was successful enough to dedicate a significant amount of their living area towards storage purposes. Dwellings/Architecture The structures contained within this cave site were constructed mainly of sandstone blocks plastered together with mud and mortar. In marked contrast to earlier constructions and villages on top of the mesas, the cliff dwelling of Navajo National Monument reflected a region-wide trend towards the aggregation of growing regional populations into close, highly defensible quarters during the mid to late 13th century. While much of the construction in this site remains similar to common ancestral Pueblo architectural forms, including such features as Kivas, a circular tower (at Keet Seel), and pit-houses, the limited space that this site presented created a much more densely populated living area. At its peak, Keet Seel had more than 150 rooms and 6 kivas, while Betatakin had about 120 rooms and only one kiva. Jacal walls were also found to be used at this site. Jacal walls were made from a screen of upright wooden poles plastered together with mud. The dry conditions and protection from the elements at Keet Seel allowed for preservation of these architectural characteristics. There were also a number of structures believed to be built at the base of the cliff as well. But due to this area not being protected by the over-hanging cliff wall, its exposure to the elements led to its destruction by erosion. At Keet Seel, archaeological excavations have revealed that there were 25 room clusters beneath the overhanging wall, each that included one common living room, with anywhere from one to four storage rooms surrounding a small courtyard. The layout of these dwellings greatly mirrored that of the Pueblo III structures at Mesa Verde, whereas Betatakin had about 20 room clusters. Abandonment Although many archaeologists agree that there is a definitive and sharp exodus from this region in the Southwest, there has been considerable debate on the determining factors that forced people to migrate out of this area. Archaeologists have determined that there was a distinct decrease in the amount of annual precipitation