THE TIANKENG CLUS­TER OF HANZHONG

—The Lat­est Ge­o­log­i­cal Dis­cov­ery

China Scenic - - Special Report - By Shui Xiao­jie Pho­to­graphs by Sun Ji­aqi, and as cred­ited

Now with the help of Google Earth and other mod­ern tech­nolo­gies, peo­ple might think that even the most re­mote and un­ex­plored cor­ners of the world con­ceal se­crets no more. Yet the dis­cov­ery of at least 49 karst sink­holes (“Tiankeng” in Chi­nese) in Hanzhong, Shaanxi Prov­ince proves that our planet is far be­yond our imag­i­na­tion.

Now, in the 21st cen­tury even the most re­mote and un­ex­plored cor­ners of the world can be brought to our liv­ing rooms by Google Earth. Mod­ern equip­ment al­lows ama­teur ex­plor­ers to tame a wilder­ness where once only the bravest dared to ven­ture. There are still, how­ever, sur­pris­ing dis­cov­er­ies to made, se­crets that have evaded even the most pry­ing of mod­ern tech­nolo­gies—at the end of 2016 in Hanzhong, Shaanxi Prov­ince, peo­ple dis­cov­ered a group of karst sink­holes of the scale that al­most de­fied imag­i­na­tion—49 in to­tal, of a va­ri­ety of sizes. This ar­ti­cle is a first-hand ac­count of this ge­o­graph­i­cal dis­cov­ery, of a phe­nom­e­non now known as tiankeng or “heav­enly well”.

ly­ing south to north across China in early sum­mer, once your plane clears Daba Moun­tains, mist usu­ally shroud­ing their sum­mits, the squares of pad­dies of Hanzhong Basin start ap­pear­ing un­der the jet’s wings. As the plane de­scends, the land­scape fills with the hus­tle and bus­tle of life— you can start to make out peo­ple and ve­hi­cles hur­ry­ing around the roads on the edges of the pad­dies.

The plane lands at the air­port near Li­ulin Town of Hanzhong. Twenty kilo­me­ters to the north­east of the air­port stands an ir­ri­ga­tion sys­tem, called Wu­menyan (or Wu­men Dam), still op­er­a­tional to­day, which was built at the very start of the first mil­len­nium AD. An­other 20 kilo­me­ters, this time to the north­west, is an an­cient tun­nel named Shi­men Tun­nel with its in­ner wall and sur­round­ing cliffs carved with hun­dreds of in­scrip­tions. What I found strik­ing and con­fused, was that amongst all this hu­man ac­tiv­ity and his­tor­i­cal her­itage, it took peo­ple un­til the year 2016 to dis­cover the lo­cal tiankeng clus­ter, or karst sink­holes, and no fewer than 49 of them!

A Long Story of Dis­cov­er­ies

When I got to the bot­tom of Bo­niu Tiankeng lo­cated in Xiao­nan­hai Town of Nanzheng County, I could not help but feel even more con­fused. My guide told me that back in 1964, a 77-year-old man

called Luo Rongfu had in fact been fre­quent­ing th­ese sink­holes. At that time Luo and a dozen oth­ers would go down the sink­hole to har­vest swal­low drop­pings, which were then used as fer­til­izer, col­lect­ing as much as al­most half a ton per day. Why do we then claim to have “dis­cov­ered” th­ese sink­holes last year when the lo­cals had known about them for decades?

I guess that one of the rea­sons is that tiankeng is a new con­cept in the sci­en­tific cir­cles, whose ex­act def­i­ni­tion and cat­e­go­riza­tions are still be­ing fixed. This nat­u­ral won­der has been around since time im­memo­rial, but it was not un­til 2005 that Zhu Xuewen, a re­searcher at In­sti­tute of Karst Ge­ol­ogy of the Chi­nese Academy of Ge­o­log­i­cal Sciences, put for­ward the term of “karst tiankeng” which was sub­se­quently for­mally ac­cepted by the sci­en­tific cir­cles. Zhu Xuewen, to­gether with Tony Waltham of Not­ting­ham Trent Univer­sity de­fined tiankeng as: “a type of very large col­lapse do­line (“do­line” is an­other term for “sink­hole”) that has evolved by roof col­lapse over a large cave cham­ber where a huge mass of break­down de­bris has been re­moved by a sub­stan­tial cave river”.

How­ever, all this sci­en­tific jar­gon and the fact of the “dis­cov­ery” of tiankeng mean noth­ing to the lo­cals who have for gen­er­a­tions lived side by side with th­ese karst caves. Per­haps that’s why they were not dis­cov­ered un­til re­cently.

The tiankeng, as a mat­ter of fact, could have been “dis­cov­ered” ear­lier, in 2012. In June that year Zhenba County of Hanzhong pro­duced a pro­mo­tional video about the lo­cal sights. Jiang Zongx­i­ang, one of the peo­ple who took part in this project, then posted the video on­line. A tiankeng mo­men­tar­ily ap­pears in the video— this was the first ever record of a Hanzhong tiankeng, but no­body at the time gave it a sec­ond thought.

This lasted un­til 2016 when Chi­nese govern­ment launched a na­tion­wide sur­vey to record ge­o­log­i­cal sites. The sur­vey grad­u­ally gath­ered mo­men­tum,

cap­tur­ing pub­lic at­ten­tion, and the govern­ment of Shaanxi Prov­ince took to the sur­vey in earnest, pour­ing a great deal of re­sources and man­power to search for in­ter­est­ing ge­o­log­i­cal for­ma­tions in the prov­ince. Only then were the tiankeng fi­nally “dis­cov­ered”.

In March 2016, Zhang Yuan­hai, se­nior re­searcher at In­sti­tute of Karst Ge­ol­ogy of the Chi­nese Academy of Ge­o­log­i­cal Sciences filed an ap­pli­ca­tion to China’s Min­istry of Land and Re­sources, to in­vite ex­perts from the Czech Repub­lic to in­spect the karst cave sys­tem in Hanzhong.

Be­fore com­ing to Hanzhong, Zhang Yuan­hai got an ama­teur caver, who goes un­der the nick­name of “Raven”, to find out, us­ing Google Earth, if Hanzhong had tiankeng. Raven is a cu­ri­ous char­ac­ter—his real name is Wu Hongy­ing, he is a na­tive of Guangxi Zhuang Au­ton­o­mous Re­gion whose day­time job is work­ing at a power sta­tion. He is so tanned from spend­ing a lot of time out­side look­ing for caves, that his friends started to call him “Raven”, which he then took as his In­ter­net nick­name. Raven is an ex­pert when it comes to lo­cat­ing karst caves and tiankeng us­ing Google Earth—in his na­tive Guangxi he dis­cov­ered over 200 caves us­ing this method, many of which were then con­firmed by ex­perts in the field. In the cav­ing cir­cles his prodi­gious skills earned him a tongue- in- cheek ti­tle of Mas­ter Raven.

I asked Raven how he got to be this good, but he just laughed it off, say­ing that any­one with an eye for de­tail can learn to do what he does. He men­tioned that you must, first—look at the to­pog­ra­phy, sec­ond—pay close at­ten­tion to edges and depth of shad­ows, third—look at the same place from dif­fer­ent an­gles, fourth—cross-check against old maps. He also said that he hopes to share the ex­pe­ri­ence that he has gained with peo­ple: “In the past, ex­plo­ration re­quired a lot of walk­ing, the progress was, slow, painstak­ing, but now, satel­lites make this job so much eas­ier.”

Zhang Yuan­hai has full trust in Raven’s abil­ity to track down tiankeng us­ing maps, and Raven does not dis­ap­point—he finds that there are tiankeng in two places of Hanzhong! Xiao­nan­hai Town of Nanzheng County, and Luo­ji­aba Town in Xix­i­ang County both have tiankeng and Raven pro­vides co­or­di­nates for both. The team choses one as the first ob­jec­tive, and, hav­ing vis­ited it, they find it worth in­ves­ti­gat­ing—it is a very large tiankeng in­deed. It is no other than Bo­niu Tiankeng men­tioned at the start of the ar­ti­cle— the long­est axis of its open­ing is around 200 me­ters, and the short­est 145 me­ters. The depth of this tiankeng stands at 215 me­ters.

When Zhang Yuan­hai made it to the bot­tom of the Bo­niu Tiankeng for the first time, a car­pet of bright green moss on the ground made him re­luc­tant to tread on it, Zhang re­calls. But what re­ally made an im­pres­sion, was a rhodo­den­dron tree cov­ered by long threads of pine lichen: “Find­ing a rhodo­den­dron in bloom, with red flow­ers, right at the bot­tom of a karst sink­hole, this is not some­thing you can for­get eas­ily!”

Us­ing Raven’s co­or­di­nates and aided by a guide, the team dis­cov­ered many other tiankeng around Bo­niu, reach­ing a con­clu­sion that they have come across a large tiankeng group, or clus­ter. Then more news came from Raven—us­ing Google Earth, he found an even larger tiankeng in Zhenba County. The team headed straight there, wast­ing no time, but an ex­ten­sive search failed to un­cover any ev­i­dence of tiankeng. Dis­ap­pointed, they went on to make en­quiries and came across a lo­cal pho­tog­ra­pher who said that he had pho­tographed a lo­cal tiankeng! Hav­ing looked at his pho­tos, there was no doubt in their minds that it was in­deed a tiankeng. Un­for­tu­nately, a land­slide de­stroyed the road lead­ing to that tiankeng and there was no way to get there to have a look. Zhang Yuan­hai then made a re­port to Dong Ying, the leader of the project doc­u­ment­ing the ge­o­log­i­cal her­itage na­tion­wide. Dong Ying, in his turn, noti-

fied Shaanxi Cen­ter of Ge­o­log­i­cal Sur­veys and the large- scale sur­vey of Hanzhong tiankeng was thus launched.

Di­donghe Tiankeng: A Young and Grow­ing One

In order to col­lect the first-ever data about Hanzhong tiankeng, Chi­nese na­tional ge­og­ra­phy Mag­a­zine sent a team to do a sur­vey. On the 28th of Jan­uary 2017, the team mem­bers as­sem­bled at the house of the pho­tog­ra­pher Sun Ji­aqi and drove off to­wards the Di­donghe Tiankeng in Chan­ji­ayan Town.

The de­ci­sion to come to tiankeng dur­ing the win­ter was done af­ter a lot of care­ful de­lib­er­a­tion. Hanzhong tiankeng are spe­cial in that they are the north­ern­most of the dis­tri­bu­tion range of China’s tiankeng, which was some­thing that Sun Ji­aqi wanted to show in pho­to­graphs. The higher the lat­i­tude, the colder the win­ter, and what can show the cold bet­ter than snow? Sun Ji­aqi hoped to be able to cap­ture the snowy tiankeng land­scape, and in the days be­fore the de­par­ture, he would care­fully scan the weather re­ports, search­ing for the news of in­com­ing snow. To his great dis­ap­point­ment, none such news came.

When we drove into Xi’an, the cap­i­tal of the Shaanxi Prov­ince, to our great ex­cite­ment, a large snow­fall de­scended on Chan­ji­ayan. How­ever, the snow turned the road treach­er­ously slip­pery, and we did not have chains fixed to our tyres. Get­ting to Chan­ji­ayan on the same night was too much of a risk, and so we had to aban­don our orig­i­nal plan and

spend an ex­tra night in Xi’an. By the time we got to Di­donghe Tiankeng, the snow had al­ready melted.

We had too many things to do to feel dis­ap­pointed, a rap­pel sys­tem was rigged up, and a small recce team went down to the bot­tom of the tiankeng to take the first pho­to­graphs. The en­tire team fol­lowed them by the evening, and we all camped out at the bot­tom of the tiankeng. The fol­low­ing morn­ing, hav­ing wrig­gled out of our tents we were left stu­pe­fied by the sight of snowflakes float­ing down from the mouth of the tiankeng. As it only snowed for less than two hours, and with the tem­per­a­ture at the bot­tom of the tiankeng be­ing around 10 °C, the snowflakes melted as they flut­tered down. We could not ob­tain the de­sired ef­fect of a snow-white cover, but at least we man­aged to get those elu­sive shots of snow in a tiankeng.

The gi­gan­tic size of Di­donghe Tiankeng made the sur­vey team gasp in as­ton­ish­ment—the long­est axis of the mouth of the tiankeng turned out to ex­ceed 400 me­ters, with the short­est axis sur­pass­ing 200 me­ters, and the max­i­mum depth of the tiankeng was mea­sured at over 300 me­ters. The walls of the tian-

keng were strat­i­fied into three dif­fer­ent zones, each with its dis­tinct veg­e­ta­tion—the tree-cov­ered zone at the top of the mouth of the tiankeng, and then in the two zones be­low the veg­e­ta­tion tran­si­tioned from shrubs to grasses with very clear bound­aries, cre­at­ing a re­mark­able sight. Even more as­ton­ish­ing was that every one of the three ter­races of each zone had a wa­ter­fall, and the sight of the col­umns of water de­scend­ing down to the bot­tom of the tiankeng left the ob­servers speech­less.

The beauty of the Di­donghe Tiankeng did not just stop there. Af­ter hav­ing passed through the open­ing of the cave we dis­cov­ered a large hid­den cave sys­tem. The team chose one of the tun­nels, go­ing against the cur­rent of a river that was flow­ing through it. It was dry sea­son and parts of the riverbed ran com­pletely dry, leav­ing the riverbed ex­posed, which made walk­ing easy. The riverbed was of large size, wide with high banks, so much so that it seemed that the team was walk­ing through one large cave cham­ber. Af­ter hav­ing walked four kilo­me­ters, the ceil­ing of the cave sud­denly rose and a small moun­tain of de­bris from a col­lapse in the ceil­ing or in the walls of the cave blocked the way. The river de­scended this bar­rier and then its course went up at a slant. An­other kilo­me­ter and the team came across a man-made bam­boo fence, then it was the open­ing of the cave, and a small vil­lage pre­sented it­self the eyes of the team—lu- os­huidong Vil­lage, which means “Vil­lage of Water and Caves”. It was dur­ing the Spring Fes­ti­val and the vil­lage looked re­splen­dent in its dec­o­ra­tions, fes­tooned in lanterns and stream­ers.

The fol­low­ing day, the team went to Di­donghe Tiankeng again, this time from Lu­oshuidong Vil­lage, and ex­plored an­other branch of the cave, dis­cov­er­ing a sta­lac­tite cham­ber on their way. Even though the cham­ber was not large, sud­denly com­ing across such an in­tri­cate nat­u­ral work of art, shel­tered in the bru­tal vast­ness of a cave large enough to har­bour a river, was ex­tra­or­di­nary.

Dr. Zhao Xin­nan of Xi’an Jiao­tong Univer­sity

took a sam­ple of a sta­lag­mite from Di­donghe Tiankeng, send­ing it to be aged at the univer­sity’s iso­tope lab­o­ra­tory. The re­sults re­vealed that the age of the sta­lag­mite, and hence of the cave and of the col­lapse of the cave roof, was less than 340,000 years, a sur­pris­ingly short stretch of time for ge­ol­o­gists!

Ac­cord­ing to Dr. Zhao, the sta­lag­mite sam­ple was col­lected from the mid-sec­tion of the cave wall, about 50 me­ters from the cave en­trance. From the an­gle of the sta­lag­mite Dr. Zhao de­duced that this tiankeng was not formed by a sin­gle col­lapse from the top. She judged it to be more likely that first an an­cient river had eroded out the large cave sys­tem,

which was fol­lowed by the col­lapse of the roof. Then the mod­ern river carved out yet an­other layer in the ex­ist­ing caves. This is the most widely ac­cepted and ap­plied con­sen­sus of tiankeng for­ma­tion, but more ev­i­dence is still re­quired.

The Dis­cov­ery and Frus­tra­tion

Ac­cord­ing to Sun Ji­aqi, the most un­for­get­table tiankeng ex­pe­di­tion that he had done was to Luo­quanya Tiankeng in Hanzhong’s Xix­i­ang County.

On the 5th of April 2017, the team ar­rived in Luo­ji­aba Town in Xix­i­ang, with plans to ex­plore a tiankeng known as Shuangx­u­anwo Tiankeng, which means a tiankeng of two vor­texes. How­ever, the very same evening, they were joined by a team from Xi’an Ge­o­log­i­cal In­ves­ti­ga­tions Cen­ter who gave them three pieces of bad news. First, the 20 kilo­me­ters from Luo­ji­aba Town to Shuangx­u­anwo Tiankeng were not re­ally doable in a day with heavy loads. Sec­ond,

Creeks Run­ning Un­der­ground There is a small cave hid­den be­neath the bot­tom of Bo­niu Tiankeng. Af­ter search­ing step by step for about 800 me­ters, team mem­bers found a pound where three tiny creeks con­verge.

First­hand Pho­tos and Data

At the end of 2016, af­ter the dis­cov­ery of the Hanzhong Tiankeng clus­ter was re­ported, Chi­ne­se­n­a­tion­al­geogra

phy im­me­di­ately or­ga­nized a pro­fes­sional team, con­sist­ing of ex­plor­ers, pho­tog­ra­phers and writ­ers, and sent them deep into the forests of Hanzhong to ob­tain first­hand pho­tos and data. That is how this re­port was cre­ated.

Inside the Bo­niu Tiankeng ➲

The open­ing on the land sur­face is not the only one— there are two other open­ings through the inside walls, just like the win­dows of a house. With head­lamps, team mem­bers are able to check the in­te­rior struc­ture of Bo­niu Tiankeng thor­oughly. ➲

In an­other cave at the bot­tom of Bo­niu Tiankeng, team mem­bers found a nat­u­ral open­ing in its roof. A ray of sun­shine shone through this “sky­light,” shed­ding light into the cave and awak­en­ing the dark un­der­ground world sleep­ing in si­lence.

Photo/ Chen Lixin, Zhao Xin­nan

Ecol­ogy of the Tiankeng Sys­tem Apart from the rich veg­e­ta­tion found in the tiankeng sys­tem, we also found some in­trigu­ing crea­tures liv­ing in th­ese karst en­vi­ron­ments, such as the giant fly­ing squir­rel, a vig­i­lant rodent that is hard to cap­ture with our lens. In the caves at the bot­tom of the tiankeng, we found some al­bino arthro­pods liv­ing in com­plete dark­ness. Some sci­en­tists be­lieve that such iso­lated un­der­ground en­vi­ron­ments are likely to have new species wait­ing for us to dis­cover them. Pe­tau­ris­taal­boru­fus

Lar­vae of ground bee­tle

Al­bino Mille­pede

Al­bino species of Dies­tram­mena

Di­donghe Tiankeng: A Giant Foot­print on the Ground Most tiankeng have open­ings that are round, or nearly round, in shape, but the Di­donghe Tiankeng is an ex­cep­tion. Its open­ing forms a giant foot­print on the ground, with its widest place at over 433 me­ters and a depth of about 340 me­ters. With the help of drones, we see that this tiankeng’s open­ing is sur­rounded by ex­tremely steep cliffs, mak­ing it quite dif­fi­cult to ap­proach.

Com­pli­cated Cave Sys­tem un­der Di­donghe Tiankeng At the bot­tom of Di­donghe Tiankeng, there is a large cave that has an open­ing of 50 me­ters in height and 100 me­ters in width. Yet that is not what sur­prised us the most—af­ter we ex­plored the un­der­ground cave sys­tem thor­oughly, we found that the whole sys­tem is over 9,000 me­ters long with a main cave and more than 40 branch ones. There are grand halls with a height of 70-80 me­ters, as well as nar­row pas­sages that barely al­low one per­son through.

“Farm­lands” and “Pil­lars” In most karst caves, peo­ple of­ten find “side dams”—car­bon­atite sed­i­ments that gather around water bod­ies, form­ing small walls that look like ridges and dams used to hold water in farm­lands. The giant pil­lar was a sta­lag­mite formed by drip­ping water from the cave’s ceil­ing—when the water evap­o­rated, the car­bon­atite it con­tained re­mained on the ground, pre­sent­ing us with this amaz­ing for­ma­tion stand­ing in this un­der­ground world.

The Di­donghe Tiankeng and Its Cave Sys­tem Ponor’s open­ing N Aven con­nect­ing up­per and mid­dle lay­ers Ruin of an­cient salt­peter mine Leg­ends Dry Clay Wet Clay Sta­lac­tite Water Body Scarp Slope Gravel and Scree Water flow Air­flow En­trance Shield-shaped rocky sed­i­ment Scale 0 50 100 200m Di­donghe Tiankeng mite

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