Qingkou tiankeng and waterfalls

Group of Qingkou tiankengs

More information about tiankengs is in the article about Xiaozhai tiankeng.

Out of 45 – 50 known tiankengs of China (and China has by far the most tiankengs in the world) five belong to the group of Qingkou tiankengs. These are Daluodang, Niubizi, Shiwangdong (Shi Wang), Taipingmiao, and finally – Qingkou tiankeng itself, which is described here.

These tiankengs have formed at the border of Paleozoic sandstone and a thick layer of Lower Ordovician limestone, which is rich with underground streams – tributaries of Muzong River. These underground streams have formed some of the most magnificent caves in the world – such as San Wang Dong and Er Wang Dong caves. In some places, the roof of caves has collapsed, creating sinkholes of gargantuan size – tiankengs.

Erosional tiankengs

Most tiankengs are formed by the collapse of giant cave rooms. But sometimes these giant holes are created by surface water which finds a crack in the limestone and falls down until it reaches the base of the layer. As time goes, the hole is washed out, larger and larger until an enormous hole – tiankeng – is created.

Such tiankengs are called erosional tiankengs. Typically rivers fall IN these tiankengs as spectacular waterfalls and then continue underground, in caves.

Best erosional tiankeng in China

Qingkou tiankeng is a typical erosional tiankeng and most likely – finest one in China. It receives two larger streams – one from the north-west, another – from the east. Both fall down in the sinkhole, each forming some 150 – 200 m tall waterfall. During the rainy periods, the sound of waterfalls in the tiankeng is almost unbearable.

Qingkou tiankeng is 295 – 195 m deep, with almost vertical walls. Area of tiankeng is 40,700 m². It has formed at the area, where sandstone and shale overlay a thick layer of Lower Ordovician limestone. Streams reach here the border where this sandstone ends and starts limestone. In this place has formed Qingkou tiankeng.

It seems that tiankeng was not that deep initially – older caves start from the walls of tiankeng, marking former levels of the bottom of this sinkhole. In total there are dozens of such caves.

Waterfalls form a single stream and disappear in an enormous cave – the giant Er Wang Dong Cave, a section named Tiankeng Express. In the winter the stream almost disappears but in summer, during the rain it can become powerful, with a force of several m³ per second.

History

Most likely local people knew well about this giant hole in the ground – but the scientific world learned about Qingkou tiankeng only on March 25, 2001, when doctor Zhy Xiewen first visited it.

Already in October 2003 Qingkou tiankeng and surrounding landscape – Wulong Karst – were protected as a national geopark. In 2007 it became a part of the UNESCO World Heritage monument – "South China Karst" and since then it is becoming an increasingly popular tourist destination.

Tiankeng and Er Wang Dong cave are explored by Hong Meigui Cave Exploration Society.

References

1. Zhu Xuewen, Chen Weihai, Tiankengs in the karst of China. Speleogenesis and Evolution of Karst Aquifers. The Online Scientific Journal. Accessed in the 31st July 2010
2. Waltham Tony. The 2005 Tiankeng Investigation Project in China. Speleogenesis.Info. Accessed in the 10th October 2013.