It's too dry to grow crops. People in these regions have become nomadic herders and they must move their herds to find water and grass. The people also might have to adjust to find ways to get water such as developing an irrigation system.
The belief generally led to bills that supported people who decided to
move out west. Thus, many people moved out west, which led directly to
Indians loosing land, Mexico loosing lands, and indirectly the
California Gold rush, and many many other things.
The first event that took place out of these options was the Spanish Conquest that destroyed the Aztec Civilization which was in 1519. Therefore the correct sequence is 3,1,2,4.
