How are sandstorms and quicksand formed?

The root of sandstorm is a weather phenomenon in which wind and sand interact, that is, the visibility of the atmosphere drops sharply due to the strong wind blowing the dust on the ground. There are various reasons, both natural and human, such as global greenhouse effect, El Ni? o phenomenon, sharp decline of forests, destruction of vegetation, species extinction, abnormal climate and other factors. Among them, over-exploitation of natural resources, over-logging and over-reclamation caused by population expansion are the main reasons for the formation of sandstorms, which increase the intensity and frequency of sandstorms. As a kind of high-intensity sandstorm disaster, sandstorm can't happen in all windy places, but only in those areas with dry climate and sparse vegetation. Sandstorms mostly occur in April-May every year, taking northwest China as an example. At this time of year, the Hawaiian high is formed in the Pacific Ocean, the Indian low is formed in the Asian continent, and the strong south wind blows from the ocean to the land. The Mongolian high, which controls the mainland, began to move from west to north, where cold and warm air currents met, and the heavy Siberian cold current came quickly from west to east, often forming strong winds. The wind force that forms sandstorms is generally above 8, and the wind speed is about 25 meters per second. In addition, the formation of sandstorms requires sufficient sand sources, and dust can be blown off the ground by the wind. The northwest is deep inland, and the forest coverage rate is not high. Most of the surface is desert and grassland, and there are many sandy wasteland, which provides conditions for the formation of sandstorms. Moreover, poor northwest people also want to make a fortune by digging licorice, holding seaweed and mining. These predatory acts of destruction further aggravated the sandstorm disaster in this area. Exposed land is easily rolled up by strong winds, forming sandstorms or even strong sandstorms.