The low plain became an ext ensive sand sea environment under the actions of the cold and dry winter monsoon , the sand sea environment was called the shelf sand sea and constituted the eas t margin of the North Hemisphere desert belt.

• 该低平原在寒冷而又干燥的冬季风作用之下 ,出现了大面积的沙海环境 ,或者称为陆架沙海 ,并构成北半球沙漠带的最东缘