Below this hole is both a complex and vast underground cave system, which is evaluated by experts at the "world" level.
During the expedition at a recent sinking hole in Guangxi, the geological team suddenly found an extremely complicated underground cave system .
Giant pit in the forest.
The cave has a volume of up to 6.7 million cubic meters - a very rare figure, which makes it an assessment of "world-class geological wonders".
Specifically, the expedition was collaborated by experts from Britain and China, led by Dr. Zhang Yuanhai from the Chinese Academy of Geological Sciences, and chairman of the British Cave Exploration Association Andy Eavis.
From October 4 to October 8, the 19 members of the research team climbed down to Tiankeng (or the heavenly pit - the name of the Chinese for unusually large pits) with a rope. From there, they began exploring and mapping the entire cave.
"The store was actually discovered by an expedition from Hong Kong last year (2017)" - Yuanhai said.
"This time, we want to determine the volume, scale and world scale of the cave, through the 3D scanning system."
According to what was recorded, the mouth of the hole was about 100m wide, 200m long, and at least 118m deep. When facing southeast, the hole gradually slid down and entered an extremely complex cave system. This cave system has all components: from the cave hall, crater, slump, limestone . They connect to an underground river system, flowing into the Panyang River.
Advanced 3D scanning system also allows experts to know the cause of forming this huge hole.
This cave system is connected to an underground river system, which flows into the Panyang River.(Photo: BBC).
"This area has a lot of evidence to show the collapse of a crater, plus many traces of the formation of paradise holes," Yanhai said.
Basically, the tiankeng is often formed due to collapsed underground cave systems - often because of natural causes such as water which cause gradual erosion. For example, the deepest tiankeng in the world - Xiaozhai (626m) was formed by a nearby limestone cave that collapsed because the impact of the underground river was too strong.
Xiaozhai Tiankeng - the largest natural sinkhole in the world.
"They are all natural caves, and the cause of subsidence is due to the impact of the underground river" - quoted Yuanhai.
"But this process is not one-way soon. To form a sinking hole, it usually takes more than 2 million years."