" Renfrew noted the general features of systems collapse, itemizing them as follows: (1) the collapse of the central administrative organization; (2) the disappearance of the traditional elite class; (3) a collapse of the centralized economy; and (4) a settlement shift and population decline. It might take as much as a century for all aspects of the collapse to be completed, he said, and noted that there is no single, obvious cause for the collapse. "

― Eric H. Cline , 1177 B.C.: The Year Civilization Collapsed