Karst Sinkholes in Western Guangxi

It was during my home visit to southern Sichuan Province more than 10 years ago that I heard of a karst tiankeng situated in Wenxing County in neighboring Yunnan Province. So I journeyed there and took a look. The tiankeng took the shape of a funnel. It was so deep and so broad that it looked much larger than the Jiangwan Stadium in Shanghai that I had seen in my student years decades ago. I longed in vain to explore the huge funnel.

The memory of that huge tiankeng haunted me all these years. So when I heard of the discovery of a cluster of even bigger sinkholes in the west of Guangxi Autonomous Region in southwestern China， my heart throbbed. I had to go and take a look.

Shortly after I reach Nanning， the capital of Guangxi， I change to a coach. The coach travels westward for two hours before it treks into mountains. The coach roars， shakes， swings from side to side， slows down and powers itself again and again along the zigzagging road. I pray my trip should be rewarding.

Around the midnight， the coach reaches Leye， a mountainous county at the highest elevation in Guangxi and home to 10 ethnic groups. In the following days， I travel and enjoy looking around at huge tiankengs， underground karst caves， and underground rivers. I am deeply impressed by the outlandish splendors of the local scenery， and people’s warmness and unique lifestyles.

The first sinkhole I visit is Barking Deer Cave. I learn from Zhu Xuewen， an old friend and geologist， that relatively small sinkholes are now called funnels whereas larger ones， more than 100 meters in diameter， are called Tiankeng (heavenly pit). The Barking Deer Cave measures 170 to 320 meters in diameter11 and the area of its mouth is 51，700 square meters. The most outstanding feature of the pit is its primitive forest on the bottom and along the edge of the huge pit. There is a newly installed walkway along the upper edge of the pit. We walk around， peeping down now and then through thick foliage. We are able to see just some tiny corners of the bottom here and there. Walking around among towering trees is a quiet delight. Though it is late November， a mass of orchids are in furious bloom， swinging elegantly. To be a little bit more accurate， there are more than 100 species of orchids in bloom. Breathing the rich aroma and absorbing the blooming extravagancy， my fellow travelers and I become excited and all cheer. Some begin to sing aloud while some even make a few whooping noises at the top of their voice trying to make an echo or two.

Then we come to a platform， which presents us a spectacular view of a cliff-like rock. The cliff spreads like a huge scroll of traditional Chinese landscape painting hanging there. The stand-alone cliff looks as if it grew up from the bottom that is 170 meters deep. The guide tells us that the strange rock has served as the venue for a few international rock-climbing competitions， and that international players agree that it is the best rock for the sport in the world.

The Barking Deer Cave was found accidentally by some forest rangers on their regular patrol through the primitive forests in the late 1990s. They tumbled onto the pit and， to their surprise， they spotted a herd of wild deer roaming through the forest on the bottom. Pretty soon， a string of similar caves were discovered in close neighborhood. Zhu Xuewen， a professor with China Karst Geology Research Institute， and his colleagues were invited to do a field study. Professor Zhu confirmed the value of this sinkhole for both scientific research and tourism. The huge sinkhole was named Barking Deer Cave and tourism started， bringing opportunities to the mountainous area. The cave put the county on the map of national tourism.

The second sinkhole I visit is called “Walking-Through Cave.” I stroll into a spacious hall inside a karst cave. From the hall I can see a tunnel through which light comes in. I negotiate an earth bank and climb up a few dozen meters and reach the middle point of the cave. Then I follow a walkway zigzagging downward toward the bottom. Everyone needs to go through a tunnel before reaching the large sinkhole. That’s why it is called walking-through cave.

Like other sinkholes in the neighborhood， this sinkhole has a thick primitive forest at the bottom. The bottom is 30，000 square meters large and 300 meters deep from the upper edge of the sinkhole. Like a huge botanic garden， the bottom abounds with thousands of trees and flowers; the air is crisp and soothing. Some trees have huge trunks. In order to get sunlight， these trees are tall and straight. Masses of vines climb everywhere to find a way skyward. The walkway on the bottom goes through the thick vines. In several places I need to lower myself in order to go under some overreaching vines. The guide tells me what these vines are known locally. The names all suggest the tenacity and courage of these plants for survival and for a better life. The names also reflect local people's tenacity to lead a meaningful life in this mass of mountains. Terraced fields stretch along steep slopes， small houses perch on small lots， and numerous cisterns stand to keep water. It is a hard life.

Another big attraction I visit is a large stone-walled pithead of a spectacular tiankeng. It has the highest elevation: nearly 1500 meters above sea level. The upper edge of the funnel is on the mountain top. The deep funnel looks like a huge well， three sides being sheer cliffs dropping down to a 613-meter-deep bottom. The sinkhole is huge: the bottom measures 108，000 square meters and the mouth 148，800 square meters. It is actually the world’s second largest sinkhole. The bottom is almost fully covered by a primitive forest. Some threes trunks there measure nearly 2 meters in diameter. The sinkhole formed about 2.5 million years ago. Looking down， I see a large forest， rags of clouds flowing there. It is here that I am deeply impressed by the spectacular view and I feel that all the trouble I have taken in traveling pays off here.

During my stay in Leye County， I also visit some more karst caves and see some underground rivers， but the sinkholes are most amazing. I learn that 28 of the 87 sinkholes in the world are in Leye County and that 9 of the 28 are of large size and that all the 28 are scattered in an area of 110 square kilometers. Moreover， seven sinkholes are found in the neighboring Fengshan County. The seven rank side by side as if they are stringed together. The cluster of these sinkholes is really a geological wonder. It is said that it won’t take long before these sinkholes become a world geopark and it gets inscribed on the list of the world’s natural heritage. □