Causes
The massive drought that hit the United States in the 1930s caused a lack of rainfall, snowfall, and moisture in the air, drying out the top soil in most of the country's farming regions. In addition, over-farming had left the soil dehydrated and overused.
The lack of natural grass and shrubs to anchor the soil exacerbated the problem. Cattle farming and sheep ranching had left the ground free of natural vegetation.
Read more about this topic: Black Sunday (storm)