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How did the Turfan Depression in China form?

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tectonic basins and rift valleys Escarpments of the Great Rift Valley rising above the plain north of Samburu Game Preserve, central Kenya. Beisa oryxes graze in the foreground.

The Turfan Depression in western China was formed by the process of crustal shortening, which classifies it as a ramp valley.

Unlike rift valleys, which are created by crustal extension, a ramp valley develops when blocks of the Earth's crust are thrust toward one another. In the case of the Turfan Depression, these forces thrust crustal blocks up onto an intervening segment of the crust. The weight of this material forces the intervening block downward, creating a deep, flat-floored valley flanked by high mountains—in this instance, the Tien Shan range.1

Because of this tectonic origin, the depression descends to approximately 508 feet (155 meters) below sea level, making it one of the lowest points on Earth. While it shares a similar appearance to rift valleys, its formation is fundamentally driven by the compression and vertical displacement of crustal material.213