Why is Taklimakan Desert the largest mobile desert in the world?

Taklimakan Desert is the largest desert in China and one of the world famous deserts. The desert is dominated by quicksand, accounting for 85% of the whole desert area, and the dunes are tall, generally above 50 ~ 100 meters except the edge.

The modern driving force for shaping the surface landscape of Taklimakan desert is wind, and sand dunes move under the action of wind. According to the moving speed of sand dunes, it can be divided into: ① the value of slow forward movement is less than 1m/ year, such as vast areas in the desert. ② The medium-speed forward movement value is 1 ~ 5m/ year, such as the western and northern deserts. ③ Fast-forward motion value is 6 ~ 10m/ year, such as southwest and southeast direction of desert. ④ The rapid forward movement value is greater than 10m/ year, and the maximum forward movement value can be greater than 40m/ year, such as the sand dunes between Yechengpishan, Qiemoruoqiang and the piedmont gravel plain.

Scholars believe that the wind-blown sand flow is "caused by the wind, and the sand moves into a flow." With the different surface morphology, the transportation height and concentration of sand particles also change. The main descriptive indicators are "wind-sand flow structure", that is, the change of sediment transport capacity with height, and "wind-sand flow sediment transport intensity" (sediment transport rate), which are used to characterize the quantity of sediment-laden substances.

The factors affecting these two indexes, including wind power, sand particle size, sand moisture content, terrain location, vegetation status, air stability, etc., have formed theoretical formulas, but there is still a big gap with the actual situation. It is still necessary to reveal the specific parameters of a specific sand area through the analysis of field observation data.

It is found that the main factors causing the structural difference of wind-sand flow in Taklimakan desert are topography and wind speed. On the horizontal dune chain, vertical sand ridge and flat sand, the logarithm of sediment transport is linear with height, that is, with the increase of height, the percentage of sediment transport by sand flow decreases exponentially. At the height of 10 cm, the sediment discharge accounts for 80% ~ 95% of the total sediment discharge at the observation height (40 cm), and the sediment discharge at the height of 20 cm accounts for more than 98% of the total sediment discharge.

In addition, the sediment transport rate of different landform types and topography is very different, so it is very important to master this characteristic for the design and construction of sandstorm protection system. At the same time, according to the investigation and analysis of the causes, morphological types and distribution characteristics of aeolian landform, the aeolian flow movement of Taklimakan desert-composite transverse dune chain-alluvial plain and tall composite longitudinal sand ridge-inter-ridge lowland is divided into several state characteristic zones, from which the type and intensity of aeolian hazards can be qualitatively judged, thus guiding engineering design.