Black roller dust storm is rushing toward Clayton, New Mexico, May 29, 1937. It was one of worst ever to strike that portion of southwestern dust bowl. A moment after this picture was taken the city was in darkness. The storm lasted several hours and was followed by rain. The interiors of houses were coated with dust and the outsides with mud. This picture was taken by an amateur photographer who happened to see the storm coming. The Dust Bowl, or the Dirty 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). The phenomenon was caused by severe drought coupled with decades of extensive farming without crop rotation, fallow fields, cover crops or other techniques to prevent wind erosion. Deep plowing of the virgin topsoil of the Great Plains had displaced the natural deep-rooted grasses that normally kept the soil in place and trapped moisture even during periods of drought and high winds.