The northwest-southeast and north-south ranges,

mainly in the west, include two groups: the Qinlian Mountains between Gansu and Qinghai provinces and the Altay on the border between China and Mongolia and the Soviet Unian

are the Helan and Liapan mountains in Ningxia and other provinces and the Hengduan mountains straddling Sichuan, Yunnan and Tibet. The Himalayas join with the Hengduan and other ranges to form a huge arc-shaped mountain chain.