China’s amazing “heavenly craters” (also called Tianqing) are the result of carbonate rocks being dissolved over time by groundwater. As these underground rivers carved out large caverns, they eventually collapsed, creating vertical chasms, or giant dolines, 500 to 600 meters deep.
These areas resemble giant greenhouses, trapping heat and moisture so that the climate is stable and humid. The absence of external winds, combined with extreme temperature changes from day to night, provides an ideal environment for ancient forests, as well as a unique type of biodiversity. According to the scientific community and UNESCO, the deep karst landscape provides a “thermal buffer,” allowing many rare species to thrive in distinct pristine ecosystems that serve as prehistoric biological refuges.
How China’s deepest crater shaped its own microclimates
According to the paper published on ResearchGate, with such great depth and verticality, “sky craters” like Xiaozhai Tiankeng create an almost insulated physical barrier that maintains a “thermal insulator” due to the constant temperature difference between the cooler summer/warmer winter bottom and the outside air. Furthermore, the massive depressions also retain moisture generated by the underground river systems that run through them.
Their deep, enclosed structure allows them to function like naturally occurring, self-sustaining greenhouses with stable environments, regardless of what happens in the atmosphere outside them.Tianqing is formed by “collapse-type” karst formation through the slow dissolution of carbonate rocks (mostly limestone) by powerful underground rivers that have passed through the area over thousands of years, creating enormous underground voids.
When the roof of one of these voids loses its structural integrity due to prolonged erosion or tectonic uplift, it collapses, resulting in a vertical cave more than 500 meters deep, as listed in the UNESCO World Heritage Centre.
How craters protect ancient life
Streamways are also known as “evolutionary islands” or biological refuges because they are isolated from other habitats by sheer vertical cliffs and great depth. More than 1,200 species of animal and plant life have been found in the sinkholes, including more primitive forms such as ginkgo trees and some rare animal species, including the Chinese giant salamander.
Protecting the world’s lost species
According to the Karst Mountain Sinkhole, many of the species found in the sinkholes are either extinct or have changed significantly in the outside world due to the effects of climate change or human activity. These unique ecosystems preserve species that have been destroyed by climate change or have been significantly modified to meet human needs or desires.
How trapped air feeds giant forests
The air quality inside Tiankeng is very different from the air above it. The dense vegetation and the fact that each hole contains a large source of moisture (usually from inland waterfalls and rivers) creates an atmosphere with a large amount of negative oxygen ions and a very high level of humidity from the constant presence of moisture. This stable microatmosphere prevents soil erosion and allows the growth of huge trees (some over 40 meters tall) which are protected from the damaging winds found on the plateau surrounding Tianqing.
