An expedition to explore a giant sinkhole in the forest of Guangxi, China has resulted in the discovery of a tremendous cave hall complex under the ground. From 4 to 8 October, the 19-member team lowered themselves into the sinkhole – using just a single rope. Once inside, they set about mapping the interior.
How big is the cave?
At 6.7 million cubic meters (236 million cubic feet), the cave’s volume is of a rare enormity, making it ‘world class,’ geological experts are reported as saying. The expedition was a joint venture between China and the UK, led by Zhang Yuanhai of the Institute of Karst Geology of the Chinese Academy of Geological Sciences, and British Caving Association chairman Andy Eavis.
This giant cave hall was actually discovered by the Hong Kong expedition last year, so it was named Hong Kong·Haiting Hall. This time we mainly determined its volume and world-class status through three-dimensional scanning.
They discovered that the sinkhole pit is 100 meters (328 ft) wide and nearly 200 meters (656 ft) long, with a maximum depth of 118 meters (387 ft). Towards the southeast end, the slope collapses into a huge cave complex.
What’s inside the cave?
It contains corridors, halls, craters, collapsed rocks, stone pillars and a type of formation called cave pearls – small, round stones polished smooth by water and deposited in cave crannies, where they sit undisturbed.
A shaft in the large cave hall was found to connect to an underground river, which feeds into the nearby Panyang River.
The 3D scanning will also let geologists reconstruct how the sinkhole collapsed.
Three-dimensional scanning found that Hong Kong·Haiting Hall has retained a lot of evidence of the collapse of the crater evolution, especially the traces of rock mechanics produced after the collapse, which are clearly visible, demonstrating the evolutionary characteristics of this sinkhole.
Sinkholes are usually the result of the collapse of an underground cavern, which has slowly been eroded by geological forces, such as water.
These giant caves are natural caves, most of which are caused by collapses and are related to underground rivers. The formation of all caves is not a one-step process. They basically have a history of more than 2 million years.