AREA 26: Sin Chai

SC1 Cang Ti 1

Development:   159
Denivelation :  -137

In this valley, four shafts were found. The shafts at the beginning of the valley were not very deep, but Cang Ti 2 has already been explored to –90m and Cang Ti 1 to -45m. Both caves continue, but we had to stop the prospection because we needed longer ropes.

Cang Ti 1 is a very beautiful fossil vertical shaft. The problem is that the rock is very soft flowstone so it was very difficult to anchor the ropes. In fact, the traditional bolts didn’t work, so we had a lot of work using stalagmites and traversing to reach natural anchors. We could reach –45m, but throwing rocks into the shaft makes us think that the shaft could be –100m to –200m deep. We will come back in 2001 with longer ropes and special bolts or chemical anchors.    

The cave, along with others in the area, lies along a fault of NE direction. Nearby, the limestone is crust into powder, signifying the fault activity. There is only limestone present, and no other types of rock. The cave starts with a large pitch of 119 meters. At the bottom, one turns south and goes down a 7m drop to enter a chamber. A small opening leads to another 5m drop and a second chamber. The floor consists of hexagonally dried clay. A 5m climb brings one to a third chamber where the cave ends, except for maybe an opening in the ceiling.

SC2 Cang Ti 2

Development:  376
Denivelation :  -254

To the eastern side of the new road going from Ta Xin Thang to Sin Chai, a now dry river can be followed. After a small cascade a flat area is reached where the river falls down a 65m pitch. Here, we started to rig. Down this entrance pitch, we arrive in the wide base of the pitch, covered with non karstic pebbles. A few meters up the pitch, we found the same fossils in the black limestone as in Ta Chinh near -300m. “Upstream” a small passage can be followed a few meters, till a choke. Downstream, one can climb down boulders to a drafting hole where a 10m pitch goes down. Here, a short horizontal part with small basins gives onto a “window” behind which there is another very deep pitch (stone falls 6 seconds, compared to 4.2 seconds for the 65m entrance pitch). Very promising indeed.

Exploration of Cang Ti 2 started in 2000 and ended on top of a deep pitch after the 60m entrance pitch and a P10. After two years of patience, we would finally be able to resume exploration and see what was down this very vertical cave.

Just upon my arrival from a long trip from Europe into Ta Xin Thang on December 24th, Nele, Manuela and Peter left to Cang Ti 2, to continue exploration down the recently discovered 85m pitch. Dorien, Lieven and myself follow shortly afterwards and improve the rigging so that our Vietnamese colleagues would be able to go down as well. Trung, still shaking after his SRT initiation above the P60 the day before stays outside and exercised his Hmong language with the local kids.

The 85m pitch on top of which we halted exploration a year ago was impressive. One descents close to the rock and parallel to a giant calcite column of 60cm wide and tens of meters long. In the middle of the pitch one could see several frogs on small ledges. Down this pitch is a beautiful section of the cylindrical pitch through the inclined layers.  A narrow passage through formations and a series of piches brings you to a spacious little chamber, from which a short meandering passage gave onto a 30m pitch. Down this pitch the passage continued over a series of steps. On top of a pitch exploration was halted that day, on the bottom we could see pebbles; it seemed to be the riverbed of a master cave!

Next day, Peter, Trung and Vince returned to Cang Ti 2, ready to explore the master cave. Trung did not yet recover from his traumatising experience and did not go down. We raced down the pitches and started bolting in the new part. Down the pitch we found a small basin which turned out to be the sump! A climb was initiated from several conducts leading back to the same water level. A small snake was found in these passages, moving very slowly. Also in the pool, a variety of cave fish, crabs, frogs and tadpoles was found. Cang Ti 2 ended at -254m and is one of the most vertical caves explored in Vietnam.


SC3, SC4 Cang Ti 3 & 4

Development:  25 & 20, Denivelation :  -19 & -24

Whereas Cang Ti 1 and 2 start with an enormous entrance pitch, the dimensions of Cang Ti 3 and 4 are much more modest. All are located on the map of Sin Chai. Cang Ti 1 and 2 are near to the village, Can Ty 3 is located a bit down the road and it needs a walk of about half an hour to reach Can Ti 4.

Cang Ti 3 is a fossil pitch of 19m deep. When we got to the bottom, a parallel pitch could be seen of which the top is collapsed. The bottom consists of sand and gravel.

Can Ti 4 is also a fossil cave, very unstable and with sharp edges. A first pitch of 15m deep ends on a small platform and is followed by a second pitch of 9m deep. Down the pitches it is all debris and lots of mud. A few tens of meters from Can Ty 4 there is another pitch that can easily be descended and where the local people sometimes come to get water.

SC5 Sin Chai 1

Development:   342
Denivelation :  -193
Hamong Farm Sin Chai
On December 28 we went back to Sin Chai in order to investigate two points Ke had marked on the map back in 1997. After a quick tea at the ranch of the city’s president, we were walking back the main road towards a large porch that can be seen from the road. The water from a small river that passes underneath the road (just at the place where the road cuts through the limestone/sandstone contact) disappears in this porch. When walking down one of the several paths that lead down towards the porch, one needs to cross another riverbed which heads for the valley. When approaching the porch area, the bottom is very unstable and consists of loose blocks and mud. It took a while to convince the spectators not to follow us further in order not to get hit by rocks tumbling down.

The entrance, a small hole below solid rock face (on which Van practiced his bolting technique) was blocked by two big rocks. After some desobstruction a small hole was opened, leading some 3 meters down over boulders. Vince would go and have a quick look. Behind it lies a small chamber with a disappointing flat and muddy floor, which completely chokes the way on. On the right side and a little higher up however, a small fossil opening (70 x 30 cm) was found with a steep slope behind it. This lead to a wider area between large boulders still going down. The way on needed to be marked with Scotchlite, the delicate squeeze between boulders in particular. Quite suddenly, the aspect of the cave changed; the unstable boulder area gave into genuine canyon-like passage with a small stream running down!  There were some narrow passages, but the cave definitely decided to go on. Vince turned back upon reaching the top of a P4, adding extra reflectors in the boulder choke on his way out. We reached -50 from the entrance and it looked very promising.

The next day, Peter and Vince went back together with Trung. The P4 was quickly rigged and is followed by a series of steps. The six meter pitch behind required some bolting and… a rope that is two meter longer than the one we used. The cascade going down this pitch made sure none of us hesitated too long before going for the final drop. The bottom of this pitch shows a fascinating pattern; the floor is horizontal and flat, but the limestone layers dip down vertically, revealing a fishbone-like pattern. This is accentuated by the contacts being partially eroded away and the river that cut itself through the middle of the floor. A passage with some formations on the ceiling gives way to a meandering part going down steeply. The meander gives into a small chamber via an eight meter pitch. Again we made sure not to waste any rope on this one, but no jumps were required this time. Behind the chamber the passage becomes low and is followed by an Eagles’ Nest giving into the top of a wet 13m pitch! The formations just above the access enabled us to rig down without any bolting and we went down in no time, again stimulated by a cascade trying to soak us. Peter tried to remediate using a deviation, which didn’t help much, but enabled Trung to exercise moving along this type of rigging. Below a narrow part gave into a P7. A bolt and our last rope facilitated the descent. Another steep but narrow passage was found, which could be climbed down and hopefully back up again. We were halted on top of a 5 meter pitch, which should be referred to as a 5m step, since Vince, who was in Vietnam for just one week wanted to do some more virgin passage before returning home, went down without rope. He was however quickly halted by another genuine pitch. This cave went on and seemed to get bigger as well.

We asked Trung, the novice, to go back out whilst we surveyed our way some 140m up in 50 stations. Development was only 250m, damn meanders.

The day after, Peter and Vince, supported by deriggin’ Thang went down for final exploration in Sin Chai Cave; the next day we were supposed to leave the area and join the team in Tam Duong. The aquatic 5m step was rigged and we started bolting above the following 5m Pitch. Another bolt was required to reach the bottom of the following drop (P4) where a meander with some small steps starts. The meander, which is very high, gets quite narrow, at a certain point it is advised to remove part of the gear (meander with a lowercase ‘m’). Higher up, the passage is often a bit wider and more horizontal, but one hits a dead end quite soon when trying to progress at higher level. This narrow passage gives into a P5 which was very hard to rig; no natural anchors available and the passage was so narrow that bolting was impossible due to lack of space for hammering. Thang, who accidentally followed a higher passage that started some 15m back, suddenly reappeared a few meters above Vince who was still figuring out how to get down the pitch. Some stalagmites in the fossil passage allowed fixing a long rope, which could then be grabbed from the actual meander floor. Below this pitch, yet another, wider meander starts; an alteration of perfect S-shaped passage continues for about 25m (estimated) and gives into a large pitch of an estimated 20m which was not descended. We decided to go back since we would need a lot of time to survey the meander (survey started on the bottom of the last 5m pitch) and derig the cave.

We hope to be able to continue the exploration in the future. The newly found pitch looks very promising. The cave is now heading northeast, which is towards the sinkhole of the main river that runs through Sin Chai valley.  The discoveries should motivate the next team to start digging in the unstable entrance area, in case it gets choked in the meantime! We returned with another 92m of passage, resulting in a total development of 342m for a depth of -193m.


SC6 Sin Chai 2

In the afternoon, we checked out the another sinkhole at the far end of the valley where the main river of Sin Chai disappears. Several holes were found, one higher up was rigged and descended without success. The small holes next to the sinkhole look the most promising, but it is quite narrow and definitely wet! But promising indeed.