Historical reasons for the deterioration of the Loess Plateau

I only know the formation. For a long time, Chinese and foreign scholars have different arguments about the source of loess. Among them, the "wind theory" is more convincing. It is believed that loess comes from the vast arid and desert areas such as Gansu, Ningxia and Mongolian Plateau in the north and northwest, and even Central Asia. The rocks in these areas expand when heated during the day, contract when cooled at night, and gradually weather into stones, sand and clay of different sizes. At the same time, in these areas, whenever the northwest wind prevails in winter and spring, the wind suddenly rises, flying sand and stones, and dust covers the sky. The coarser stones remain in place and become "Gobi", while the finer sand grains fall in the nearby area and gather into deserts, and the tiny silt and clay fly to the southeast one after another. When the wind weakened or was blocked by the winding Qinling Mountains, they stopped accumulating, and after hundreds of thousands of years of accumulation, a vast loess plateau was formed. According to the different loess accumulation environment, the development of Huangshi in China can be divided into three periods: early Pleistocene, equivalent to the first ice age, the climate was drier and colder than Neogene, and loess accumulation occurred in Wucheng; In the Middle Pleistocene, the second glacial period appeared, and the climate dried up further, accumulating a wide range and thick soil layer of Lishi loess; In the third glacial period of late Pleistocene, the climate was drier and colder, and Malan loess was accumulated. Although the thickness is small, it is widely distributed, and it is called Xia Shu Loess in the south. The Holocene climate turned warm and humid, and the loose loess layer was eroded by running water, forming broken surfaces with gullies, beams and headlands alternately.