Two major drought episodes, A.D. 1000 to 1015 and A.D. 1120 to 1150, contributed to significant change in adaptive strategies of the Virgin Branch Anasazi, a prehistoric population that occupied the southwestern Great Basin between A.D. 100 and A.D. 1150. The first extreme climatic event promoted the adoption of several alternative buffering strategies including intensive agricultural practices, increased reliance on storage, and the organization of large residential labor groups. The second drought, which followed 150 years of favorable climatic conditions and high levels of population growth, had a devastating impact upon the Virgin Branch Anasazi resulting in the complete abandonment of the southwestern Great Basin by that group. These two climatic events required entirely different responses, which suggest that shifts in climate are best viewed as triggering culture change. The preconditions of population growth set the various levels of sensitivity to extreme climatic events and determine the precise nature of the culture changes.
Dynamical mechanisms associated to the occurrence of an extreme climatic event of precipitation in the city of Salvador-BA
