Withrow Moraine and Jameson Lake Drumlin Field erosion resulting from the Missoula Floods, which laid bare many layers of the basalt flows on the edges of the plateau at Grand Coulee and Moses Coulee. Two million years ago the Pleistocene epoch began and Ice age glaciers invaded the area. They scoured the Columbia River Plateau, reaching as far south as the middle of the Waterville Plateau highlands above the Grand Coulee and south to the head of Moses Coulee. In some areas north of the Grand Coulee they were as much as 3 km (10000 feet) thick. Grooves in the exposed granite bedrock are still visible in
Grand Coulee Dam (song) the recommendation of Alan Lomax, the BPA hired Guthrie to write a set of propaganda songs about the federal projects to gain support for federal regulation of hydroelectricity. Although the intended documentary film was not completed until 1949, Guthrie's songs were recorded in Portland, Oregon in May 1941. The tune for "Grand Coulee Dam" is based on that of the traditional song, "The Wabash Cannonball". Guthrie's recording was reissued on the Folkways album "Bound For Glory" in 1956, and subsequently on numerous compilations of Guthrie's songs. The song was later recorded by British skiffle musician Lonnie Donegan, whose version entered