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 floods In addition, some Yadan are formed by the simultaneous action of wind and running water, such as Longcheng Yadan