Professor Zhu Xuewen, director of the China Cave Study Association, suggested that international geological circles consider using the technical term to refer to natural karst dolines of over 100 meters in depth.
China has the world's largest group of karst dolines.
They are located in Leye County, in southwest China's Guangxi Zhuang Autonomous Region. The largest doline is in Chongqing Municipality, also in southwest China. Dolines are special geological features found in karst regions, formed by repeated cave-ins. They are mainly found in China, Mexico and Papua New Guinea. Sino-foreign teams have conducted five surveys of dolines in Leye, to help collect data on this phenomenon and gauge the tourism prospects of the local caves.