Why do nations rise and fall?   Historians and anthropologists can usually make an educated hypothesis but some instances are nothing more than guesses.   Here are 10 that disappeared and maybe it was due to global warming or global cooling or famine or flood, but no one knows, including the Minoans, the Anasazi, the Indus, the Nabateans and six more.

Top 10 Civilizations That Mysteriously Disappeared