What Happened at Mesa Verde?

Ancient Anasazis: What Really Happened at Mesa Verde? What could have motivated a large, apparently sophisticated culture to just suddenly pick up and walk away from their homes leaving everything, utensils, pottery, toys, even food, still in place? Who were these ancient people that lived in well made, modern for the time, stone structures? And what happened to them? Are the spectacular dwellings, lying silent for centuries, now shouting a warning to us across the centuries? Could the same thing happen to us?