The Dust Bowl
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 caused the phenomenon.[1] Extensive deep plowing of the virgin topsoil of the Great Plains during the previous decade had displaced the native, deep-rooted grasses that normally trapped soil and moisture even during periods of drought and high winds. Rapid mechanization of farm implements, especially small gasoline tractors and widespread use of the combine harvester, significantly impacted decisions to convert arid grassland (much of which received no more than 10 inches (250 mm) of precipitation per year) to cultivated cropland.
During the drought of the 1930s, the unanchored soil turned to dust that the prevailing winds blew away in clouds that sometimes blackened the sky. These choking billows of dust – named "black blizzards" or "black rollers" – reached such East Coast cities as New York City and Washington, D.C. and often reduced visibility to a meter (about a yard) or less.