When drought hit Chaco Canyon in the 800-900 A.D. period, it resulted in a large sand dune that blocked the canyon, creating a lake and delta behind it, that offered a wonderful farming environment. When the dune dam disappeared around 900 A.D., so did the inhabitants for more than a century, returning when they figured out new farming techniques, according to geo-archeologist Eric Force, in a talk to the Arizona Geological Society tonight [above, Chaco Culture National Historical Park, NPS].
Eric then postulated, "Could modern climate change lead to drought that will similarly increase eolian conditions across Arizona, blocking more canyons and washes and producing swampy playas behind them and locally rising water tables?"