National Geographic : 1938 May
00 HWANG HO PEASANTS FORTIFY AN OUTPOST THAT BATTLED EROSION TO ASTANDSTILL Many thousands of years ago the dust of the Mongolian plains blew over and settled on North China to form the loess country. Itcovered the original landscape, often to a depth of hundreds of feet. Perhaps this is an original peak, its head covered with the newer soil. Whenthe meandering stream attacked the base, solid rock withstood it; the loess came tumbling down in vertical cleavage, typical of this formation. Or perhaps the cliff wassaved merely bythe vagaries ofthe river.