Perhaps it will hard to believe that several millions years ago, the vast area of the Tengger Desert is a great clear and blue lake, warm, humid and good vegetation were the landscpe at that time. Through the research of the playa, ancient lakeshore line, lake sediment and paleontological fossils that near the Tengger Desert by scientists, they presumed that here has existed a huge fresh water with at least an area of 16200km² and water depth 25m(Zhang Hucai, 1997). Especially in 35000—22000 years ago, it formed “Great Tengger Lake Period” (Figure 4-44) (Zhang Hucai, 1997, 2002).

Figrue 4-45 The estimated distribution of ancient lakes in Great Tengger Lake

(After Zhang Hucai, et.al., 2002)

Later, there were scientists decetced the ancient water system in Alxa through space imaging radar(Guo Huadong, 2000), which corroborated the former presumption to a large extent.

In late Paleogene, the Qinghai-Tibet Plateau became uplifting, the following kunlun-yellow river tectonic motion and gonghe movement have changed the terrain of Alxa. The uplifting of Qinghai-Tibet Plateau leads to the change of global atmospheric circulation, and then the climatic deterioration(Shi Yafeng, et al. 1998), drought turned up, ancient river(lake) disappeared, and desert and gobi appeared. At the same time, a lot salt lake has formed, such as Jilantai salt lake, residual lake, the lake basin in the Tengger Desert and many grass lakes.