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
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
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.