A huge doline, 70 meters deep and 100 meters wide, has been discovered on (Mount Shangfang) in Beijing's (Fangshan District).
Dolines are special geolo-gical landscape formations found in karst regions, form-ed by repeated cave-ins of the tops of underground caves.
They are common in China, Mexico and Papua New Guinea, Xinhua news agency reported.
This is the first time that a doline has been found in north China, said Song Linhua, a research fellow with the Geoscience and Resources Research Institute of the Chinese Academy of Sciences, who discovered the doline.
Song said Mount Shang-fang is made of limestone formed more than 600 million years ago. Water erosion and dissolution have turned the mountain's surface into a karst land-scape, from which dolines easily take shape.
It was learned that a group of dolines, discovered in Leye in southern Guangxi Zhuang Autonomous Region, is the largest in the world, Xinhua said.
Song said the dolines found in Guangxi are located in a low-lying area, several hundred meters deep and with underground rivers.
( Eastday.com.cn 10/12/2001)
