The Dust Bowl, or the irty thirties, was a period of severe dust storms causing major ecological and agricultural damage to American and Canadian prairie lands from 1930 to 1936 (in some areas until 1940), caused by severe drought coupled with decades of extensive farming without crop rotation or other techniques to prevent erosion. It was a mostly man-made disaster caused when virgin top soil of the Great Plains was exposed to deep plowing, killing the natural grasses - the grasses normally kept the soil in place and moisture trapped, even during periods of drought and high winds. However, during the drought of the 1930s, with the grasses destroyed, the soil dried, turned to dust, and blew away eastwards and southwards in large dark clouds. At times the clouds blackened the sky, reaching all the way to East Coast cities like New York and Washington D.C., with much of the soil deposited in the Atlantic Ocean. The Dust Bowl consisted of 100 million acres, centered on the panhandles of Texas, Oklahoma, New Mexico, Colorado, and Kansas.