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Tiankeng - A Heavenly Pit on Earth

"Tiankeng," a Chinese term that literally means "heavenly pit," depicts a unique geological feature that largely appears in Southwest China's Guangxi Zhuang Autonomous Region and Chongqing Municipality. The term "Tiankeng" for karst doline was proposed by a senior Chinese geologist since there is no special term to define the natural wonder. Besides its natural rarity, Tiankeng is also characterized for its tourism value and special ecological environment.

Dolines are special geological features found in karst regions formed by repeat cave-ins. They are mainly found in China, Mexico and Papua New Guinea. Professor Zhu Xuewen, director of the China Cave Study Association, said international geological circles use the technical term "Tiankeng" to refer to natural karst dolines of over 100 meters both in depth and diameter.

As a large, steep-walled, pit-like, negative karst landform that opens from beneath towards the surface, Tiankeng develops into a great thickness of continuous soluble rocks within the aquifer vadose zone above the deeply buried water table and connects with an active cave river at its foot.

  Discovery of Tiankengs in China

China has the world's largest group of Tiankengs, which are located in Leye County, Southwest China's Guangxi Zhuang Autonomous Region. The country's largest, the Xiaozhai Tiankeng, with a depth of 660 meters and 119-million-cubic-meter capacity, is located in Chongqing Municipality on the upper reaches of the Yangtze River. Altogether, there are about 50 karst Tiankengs known in China. Of these, three are giant Tiankengs, more than 500 meters deep and 500 meters wide in diameter at the entrance, respectively located in Chongqing and Guangxi.
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