When? The Collapse of the Bronze Age

The collapse of the Bronze Age has many historians coming up with theories on why it happened. Some people think that a chain of 6.5 or higher earthquakes caused it, others there were migration changes and raids. Changes in weather, causing droughts were also blamed, along with the ability to move past bronze weopons and to iron. A natural disaster of any proportion could have had a domino effect on people's livelihoods and crops.

http://en.wikipedia.org/wiki/Bronze_Age_collapse

http://www.worldagesarchive.com/Reference_Links/Empires_in_the_Dust.htm