New research has found the first evidence that large rivers control desert sands and dust. But how exactly? First we need to know a little bit about loess. Loess is a silt-sized sediment which is formed by the accumulation of wind-blown dust. Loess deposits may be very thick and often blankets areas. One of the largest deposits of loess is in an area right-fully named the Loess Plateau, a 640,00 square kilometer area in the upper and middle China’s Yellow River and China proper. However, there are also large loess deposits in the central United States and central Europe.