Just south of China’s Tien Shan mountains, in northwestern Xinjiang province, a remarkable series of ridges dominate the landscape. The highest hills rise up to 1,200 meters (3,900 feet) above the adjacent basins, and they are decorated with distinctive red, green and cream-colored sedimentary rock layers. The colors reflect rocks that formed at different times and in different environments.
This part of Xinjiang province has a rich and varied geologic history. About 300 million years ago, the Tien Shan mountains began forming when the Tarim Block—a mass of land that was once part of Australia—collided with Eurasia. During the Mesozoic Era (252 million to 66 million years ago), a series of island arcs (curved chains of volcanic islands) continued to smash into Eurasia, further building the mountain range. About 80 million years ago, the Indian subcontinent started colliding as well, triggering a new phase of mountain building.
Image courtesy of NASA.