Wind erosion landforms in arid areas. The ground formed by Xiangtu-like sediments in rivers and lakes is weathered, washed by intermittent running water and eroded by wind, forming a combination of wind erosion hills and wind erosion depressions (troughs) parallel to the prevailing wind direction.

Ya Dan landform is a special landform in Lop Nur, Xinjiang, and a typical wind erosion landform. The word "Ya Dan" was formally put forward by Sven Hed in 1903, and gradually accepted by geoscientists. Since it was studied, it has a history of 100 years.

"Ya Dan" means "a hill with steep walls" in Uyghur. This event was later selected by chinese national geography magazine, and the "Hundred Years of Great Discovery of Chinese Geography" was jointly sponsored by the Chinese Geographical Society.

There are four main methods to study the formation time of Ya Dan:

(1) The modern wind erosion rate was investigated on the spot, and its formation age was indirectly calculated. For example, Xia believes that the wind erosion rate of Loulan ancient city in Lop Nur is 0.24 ~ 0.47 cm/year, and the wind erosion there is the product of nearly a thousand years. Ya Dan, Gutierrez-Eloza and others believe that it was formed on the gypsum waste dumped in the Ya Dan area of HerBraud, Spain less than 65,438,000 years ago.

(2) Obtain the stratigraphic age at the top of Ya Dan landform and calculate the formation age of Ya Dan landform. For example, Clarke et al. dated the small Ya Dan in the Mojave Desert of the United States with infrared luminescence method, and concluded that it was formed less than 250 years ago.

(3) Dating the existing cultural relics in Ya Dan, and inferring the formation age of Ya Dan. Bohlin and Hoerner dated the pottery in the fine sand near Lop Nur and Dunhuang, respectively, and thought that the medium-sized Ya Dan there began to form 1.5 ~ 2.0 thousand years ago.

(4) By analyzing the formation age of the desert around Ya Dan, the climate change in the regional geological history recorded by cave deposits and the previous research results on climate change, the formation age of Ya Dan is indirectly inferred, which is also one of the methods used by scholars.