How is the soil in the Loess Plateau formed?

Scientists have put forward many hypotheses: there are "wind theory", "water theory" and "feng shui and rain theory", among which "wind theory" has been widely supported, that is, loess material was blown from deserts and Gobi in Central Asia and Mongolia. The evidence is:

1. "The loess is even in thickness" means that the loess is blown from the sky, not rushed by running water.

2. "The particles are getting finer and finer from northwest to southeast" indicates that the trend of loess is from northwest to southeast.

3. "The mineral composition of loess in the Loess Plateau is very different from that of bedrock in the accumulation area, but it is the same as that of Gobi and desert in Central Asia and Mongolia." It shows that loess is not native to China, but may come from Central Asia and Mongolia.

4. "There are many layers of ancient soil in the loess that fluctuate with the terrain" shows that the loess is not gradually formed by the weathering of local rocks, but is foreign.