Thursday, April 16, 2009 - Morrison Center

Climate Change and Cultural Collapse:
The Rise and Fall of the Mississippian Cahokians and the Southwestern Anasazi
Larry Benson, Ph.D., USGS
Between about 1000 A.D. and 1150 A.D., prehistoric Native American cultures in the Midwest and Southwest experienced near-simultaneous political and economic transformation. Great house construction accelerated throughout the San Juan Basin of the Southwest and many earthen mounds were constructed in the Cahokia area of Illinois/Missouri during this time interval. By 1150 both cultures were in decline and by 1300, both the San Juan Basin and the Cahokia areas had been abandoned. Archeologists have long wondered what, if anything caused these distant cultures to rise and fall in a nearly-simultaneous manner. Recent studies, which employ tree-ring-based reconstructions of climate change, indicate that cultural expansion in both areas occurred during an anomalously wet period and that cultural collapse occurred during mega-drought.

Larry Benson joined the USGS in 1982 and is presently Chief of the Arid Regions Climate Project. Prior to USGS he was a professor at the University of Nebraska-Lincoln, Desert Research Institute in Reno, Nevada. He has also been a visiting scientist at the University of California-Berkeley, as well as a principal investigator at the Lawrence Berkeley National Laboratory.