What is Yadan landform?

Yadang landform refers to the fragmented ridge and groove terrain formed by wind erosion of lakes or alluvial plains in arid areas. It is called Yadan in Uyghur, which means a hill with steep walls. The raised wind-eroded mounds are in the shape of long strips, arranged parallel to the main wind direction. In recent years, studies have shown that temporary water erosion and lake water erosion are also one of the important reasons for the formation of Yadan. The most typical Yadan landform is near Loulan in the northwest of Lop Nur. (Information provided by the Ministry of Land and Resources)

In China's inland deserts, the landform combination of long rows of long mounds and depressions extending intermittently at intervals is called the Yadan landform. When Chinese and foreign scholars conducted a joint inspection of Lop Nur in the early 20th century, they discovered this peculiar landform near Guloulan in the northwest of Lop Nur. They named it according to the name of the Uighurs, and then translated it back into Chinese as "Yadan".

Yadan can be found in many arid areas around the world, and is not limited to Xinjiang in China. The highway from Yuka in Qinghai to the west to Southern Xinjiang is very desolate. You can see "Yadan" between Nanbaxian and Yiliping Highway. It is the largest "Yadan" distribution area in the northwest inland. . However, Xinjiang has the most Yadan landforms. In addition to the Yadan landforms in Lop Nur and Guloulan, the "Devil City" in Karamay and the "Wind City" in Qitai are also typical Yadan landforms.

The formation mechanism of Yadan landform

There are two key factors in the formation of Yadan. The first is the geological basis for the development of this landform, that is, the lacustrine sedimentary strata; the second is external erosion, that is, the erosion of powerful directional winds and flowing water in the desert.

The formation history of lakes in arid areas often includes repeated inflows and outflows of water, resulting in the development of overlapping layers of mudstone and sand. Wind and flowing water can take away the loose sandy soil layer, but have limited effect on the hard mudstone layer and gypsum cement layer. However, the dense mudstone layer is not indestructible. The expansion and contraction effect caused by the dramatic temperature difference in the desert area will eventually cause the mudstone layer to collapse. The exposed sand layer will be carried away by wind and water and evolve into a groove shape; there are still mudstone layers. The covered part is relatively stable, forming long or small mounds, and the shape of the Yadan landform gradually emerges.

The external factors that form Yadan are generally believed to be the dominant prevailing wind, but this is not the single dominant factor.

For example, the Sanlong Shayadan in the eastern section of the Aqik Valley is south-east, perpendicular to the prevailing northwest wind direction, and consistent with the direction of mountain flood flow. This shows that in this Yadan, the flood is In addition, some Yadan are formed by the simultaneous action of wind and running water, such as Longcheng Yadan