A Sideways Collision
The formation of the Altun Shan results from the immense geological collision between the Indian and Eurasian tectonic plates. This ongoing continental impact, which began around 55 million years ago, created the Himalayas through direct compression. It also caused huge blocks of the Asian continent to squeeze eastward, out of the way of the advancing Indian plate. This process is known as continental extrusion or "tectonic escape."
The primary engine for this escape is the Altyn Tagh Fault, a massive left-lateral strike-slip fault that runs for approximately 2,000 kilometers along the northern edge of the Tibetan Plateau. This fault is one of the largest active strike-slip structures on Earth. Instead of one plate diving under another, the land on either side of the fault slides past each other horizontally. The movement is immense; since the middle Oligocene epoch, the total displacement along the fault is estimated to be around 475 kilometers. This means a point on the Tarim Basin side of the fault has moved 475 km eastward relative to its counterpart on the Tibetan Plateau.
Building a Mountain Wall
The Altun Shan range itself did not exist in its current form before this process began. Evidence from sedimentary rocks along the Miran River shows a dramatic shift around 15 to 16 million years ago, during the Miocene. Before this time, fine-grained sediments indicate a low-gradient landscape. Afterwards, the geology is dominated by coarse conglomerates (rocks composed of large, rounded fragments) which signal the rapid erosion of a newly rising mountain range.
This uplift was a direct result of the Altyn Tagh Fault's motion. While the primary movement is horizontal (strike-slip), there is also a component of compression, or shortening, across the fault. This compression squeezed, folded, and thrust the crust upwards, creating the Altun Shan range as a topographic barrier. Today, the range separates the extremely arid Tarim Basin to the north from the high-altitude Tibetan Plateau to the south. The peaks in the southwestern section are particularly rugged, with some exceeding 6,100 meters (20,000 feet) in elevation. The highest point, Sulamutag Feng, reaches 6,245 meters (20,489 feet). Modern GPS measurements show the fault is still active, with slip rates estimated between 9 and 14 millimeters per year.
The rise of the Altun Shan had a deep impact on the regional climate. The new mountain wall created a pronounced rain shadow, blocking moisture from reaching the Tarim Basin. This effect intensified the basin's aridity, helping to create the Taklamakan Desert, one of the driest and most barren landscapes on the planet.