A huge collapse ditch about 200 m deep shelters a century-old forest which could harbor species never seen before.
A team of Chinese researchers recently made a striking and interesting discovery. They have found a gigantic collapse ditch lost in the middle of a lush forest in the autonomous region of Guangxi Zhuang, known for its breathtaking landscapes studded with spectacular geological formations.
These huge ditches that geologists call sinkholes occur in a particular geological environment; the latter is called karst by analogy with the Slovenian-Croatian massif which gave it its name, but it is also found in France, for example in the Vercors. The karst is characterized by a set of carbonate rocks, mainly limestone, which have the particularity of being relatively soluble.
A karstic terrain suitable for sinkholes
Rainwater, on the other hand, is slightly acidic, and therefore capable of dissolving these rocks over the long term. Over the centuries, the water therefore tends to seep deep into the rock. It therefore attacks the overall structure by causing increasingly large cracks. These then allow the liquid to infiltrate even deeper, and so on. Eventually, the passage of water can end up digging a complex network of underground cavities typical of karsts.
But this process cannot continue indefinitely. When the subsoil has been attacked too much, the rock tends to collapse on itself; we then witness a sudden and sometimes very spectacular collapse. It results in the appearance of a circular pit which can be very deep. This can cause significant damage when such an event occurs in town, sometimes due to an unscrupulous town planning policy.
But in this case, we are talking about a remote region; the water has had plenty of time to circulate freely for centuries. Many successive collapses therefore ended up causing this spectacular subsidence 200 meters deep – enough to stack four Arcs de Triomphe there!
A century-old forest landlocked 200 meters below the surface
The geological structure is certainly impressive, but what is more interesting is what cavers have found below. They unearthed a century-old forest made up of spectacular trees; by dint of growing to get closer to the light, some individuals have cheerfully exceeded 40 meters in height.
In addition to these trees, the pit is also home to extremely dense vegetation that is of particular interest to naturalists. Indeed, this very particular geological enclave could well be an ecological niche in its own right, with its own unique biodiversity. And researchers are already hoping to make great finds in this underground world.
“I wouldn’t be surprised if there were species that have never been described or even discovered by science until now”explains Chen Lixin, the Chinese caver and biologist who led the expedition.