Giant karst sinkholes discovered in S China

A cave exploration team has discovered two giant karst sinkholes, and over a dozen smaller limestone caves in the mountainous Donglan County, south China's Guangxi Zhuang Autonomous Region after a week of expedition.

The 30-membered team, which consisted of speleologists and cavers from China, France and Belgium, went through field measurements and found one of the two giant sinkholes, measuring over 300m in depth, 250m in width and 120m in length at the bottom, is one of the world's 50 largest karst sinkholes.

They also confirmed the size of a nearby sinkhole called "Nongqiu Tiankeng" by the locals. It measures 295m in depth, 50m in width and 100m in length at the bottom, and can be categorized as a large sinkhole.

French caver Jean Bottazzi, also a foreign expert at the Leye-Fengshan Global Geopark in Guangxi, said the dimensions of three other caves with similar form to that of sinkholes need to be further investigated.

Giant sinkholes, also known as Tiankeng in Chinese, are dolines, or giant pits, with special geological features found in karst regions formed by repeated cave-ins. They are mainly found in China, Mexico and Papua New Guinea.

In 2001, geologist Zhu Xuewen proposed the Chinese name "Tiankeng" for dolines over 100 meters in depth, as there was no special term yet to define this unique geological feature.