"After a week of joint scientific research, we confirmed that the recently discovered 'Shenying Tiankeng' and the other three collapse funnels and karst cave groups in Leye, Guangxi, were bred from the Fugui underground river basin and are a brand-new Tiankeng family." Zhangyuanhai, senior engineer of Institute of karst geology, China Geological Survey, Ministry of natural resources (hereinafter referred to as "Institute of Karst"), introduced it to the reporter of science and Technology Daily on June 22. China is very rich in Tiankeng resources. According to the data, 31 Tiankeng groups have been found in China, with more than 270 tiankengs, accounting for nearly 90% of the total known tiankengs in the world, mainly concentrated in Guangxi, Guizhou, Chongqing, Yunnan, Sichuan, Hunan and Hanzhong, Shaanxi. Tiankeng is a precious geological heritage and a deep impression left by the earth. Tiankeng scientific research is of great significance to the study of geological changes, biological changes and vegetation changes of the earth. Tiankeng is distributed in the uplift area of the earth's crust, starting from underground rivers and karst caves, forming from collapse to surface exposure and ending from cliff degradation. It has witnessed the miracle of the evolution of karst landform and hydrogeological conditions, and recorded the history of karst geological evolution. "The discovery of Leye new sinkhole benefited from high-definition satellite images. Shadow analysis was used to find the potential sinkhole location, and then the site was surveyed and confirmed." Zhangyuanhai said that at the beginning of May, after the expedition in Leye County, Guangxi, organized by the karst Institute, a standard Tiankeng, namely "Shenying Tiankeng", was confirmed to have been discovered. At the beginning of June, the karst Institute, together with Guangxi Institute of regional geological survey, Guangxi cave exploration team and Leye County flying cat cave exploration team, formed a joint scientific research team to investigate the negative karst terrain, underground rivers, karst caves and shafts around Tiankeng. "Tiankeng and underground river are closely related." Zhangyuanhai said that the underground river continuously erodes and transports, hollowing out the stratum, forming a karst cave hall, or the erosion and expansion of the sinkhole, coupled with the collapse, finally completely exposes the surface, forming a sinkhole. The "Shenying Tiankeng" is 192 meters deep. It is formed by multiple collapses of the mountain. At the bottom is a well preserved primeval forest system, which breeds rich and unique natural resources. Scientists found fossils of marine organisms on limestone, about 200million years ago. "We also found some animals and plants at the bottom of Tiankeng, including the newly distributed species in Guangxi, chicory moss, the droppings of flying squirrels, rock swallows and eagles on the rock walls, and so on." Zhangyuanhai said. Why are there so many Tiankeng groups in Guangxi? According to zhangyuanhai's analysis, this is closely related to the fact that Guangxi is located in the terrain slope zone transitional from Yunnan Guizhou Plateau to Guangxi, with abundant rainfall, and the dense, hard and thick carbonate rocks. On the other hand, Tiankeng is developed from karst cave halls. "Guangxi has 6 of the top ten karst cave halls in China, 3 of the top ten karst cave halls in the world, and the number of underground rivers in Guangxi is also the largest in China. In this way, it is not surprising that there are many tiankengs in Guangxi." "As a new karst theory, the study of Tiankeng is still in the stage of discovery and investigation." "Although satellite images are becoming clearer and clearer, we still don't know how many sinkholes there are in the world," Zhang said At present, thousands of sinkholes have been found in China through satellite images, but less than 30% of them have been confirmed. A lot of time and energy are needed for on-site certification and measurement. There are still many unsolved mysteries about Tiankeng. For example, how many differences are there between Tiankeng or Tiankeng groups; Although the age of Tiankeng formation has been measured for a few cases, the geological age of Tiankeng formation is still full of unknowns; Although researchers generally know the evolution path of Tiankeng, it is not clear how much the giant collapse of Tiankeng has to do with earthquakes; Although scientists generally know that Tiankeng is a refuge for modern organisms, they do not know whether the uplift of the Qinghai Tibet Plateau and global environmental change have an impact on the ecosystem of Tiankeng, or whether Tiankeng has preserved the information characteristics of global climate change, etc. "All these need us to explore boldly and use a variety of technical means to promote the interdisciplinary and systematic research of Tiankeng." Zhangyuanhai said. (Xinhua News Agency)