Why are Qinghai and Xinjiang linked together?

Xinjiang and Qinghai are adjacent, not directly connected, with Gansu Province in the middle. These three provinces are located in the northwest of China. Xinjiang is the westernmost provincial administrative region in China, located in the border area of China, bordering Kyrgyzstan, Tajikistan, Kazakhstan and other countries in Central Asia in the west. Qinghai, located in the northwest of China, is an inland province of China, adjacent to Gansu and Xinjiang. Qinghai borders Gansu in the east, Xinjiang in the west, Tibet in the south and Inner Mongolia in the north. Geographically, Xinjiang and Qinghai are separated by Gansu and adjacent to Gansu Province respectively. Xinjiang Uygur Autonomous Region (hereinafter referred to as Xin) is a provincial administrative region in People's Republic of China (PRC), one of the five minority autonomous regions in China and the largest provincial administrative region in China. Historically, it was an important passage of the ancient Silk Road, and now it is the only place for the second "Eurasian Continental Bridge".