The Dust Bowl , also known as the Dirty Thirties , was a period of severe dust storms that greatly damaged the ecology and agriculture of the American and Canadian prairies during the 1930s ; severe drought and a failure to apply dryland farming methods to prevent wind erosion ( the Aeolian processes ) caused the phenomenon . The drought came in three waves , 1934 , 1936 , and 1939 -- 1940 , but some regions of the high plains experienced drought conditions for as many as eight years . With insufficient understanding of the ecology of the plains , farmers had conducted extensive deep plowing of the virgin topsoil of the Great Plains during the previous decade ; this had displaced the native , deep - rooted grasses that normally trapped soil and moisture even during periods of drought and high winds . The rapid mechanization of farm equipment , especially small gasoline tractors , and widespread use of the combine harvester contributed to farmers ' decisions to convert arid grassland ( much of which received no more than 10 inches ( 250 mm ) of precipitation per year ) to cultivated cropland .

Question: what were the two causes of the dust bowl
Answer: severe drought