Why does the land often crack in the continuous dry weather?

The deep soil contains a lot of water and there is no direct sunlight, so the temperature change is relatively small. The surface layer of soil is short of water, and the temperature regulation function of water is lost. When it is irradiated by the sun, the temperature will be very high, and then it will make the soil surface expand and compact. At night, the temperature will suddenly decrease and shrink, resulting in cracking. Drought in summer is more likely to cause land cracking than drought in winter because of the large temperature difference in summer.