The Loess Plateau , also known as the Huangtu Plateau, is a plateau that covers an area of some 640,000 km² in the upper and middle reaches of China's Yellow River. Loess is the name for the silty sediment that has been deposited by wind storms on the plateau over the ages. Loess is a highly erosion-prone soil that is susceptible to the forces of wind and water; in fact, the soil of this region has been called the "most highly erodible soil on earth". The Loess Plateau and its dusty soil cover almost all of Shanxi and Shaanxi provinces, as well as parts of Gansu province, the Ningxia Hui Autonomous Region, and the Inner Mongolia Autonomous Region.