AREA 25: Chieu Sai Pin

CS1 Cong Nuoc                            CLICK HERE FOR A SURVEY OF VIETNAM 'S DEEPEST CAVE

Development:   1882
Denivelation :   -600

Cong Nuoc starts in a large and beautiful porche (20m wide, 20m high) high up in the wild forest near the village of Chiêu Sài Pin (about 1h.15m walk from the road). The entrance is located near the border between the sandstone and the limestone. A small river is sinking here during the dry season (some years there is no river at all) which must swell to an important stream during rainy season. Descending between huge blocks at the farest end of the porche and following the strong draught one enters a nice and clean washed gallery (15m wide and 3 to 4 m high) which gives way after 50m to a first very nice and large pitch of 35m (P35). Following the left bank on top of the pitch one can easily traverse to the continuation of the gallery which gives way after 40m to another small pitch (P10) immediatedly followed by a second and larger one of approximatedly 50m. The descent is over flowstones to a freehang of 30m. Landing is in a chamber (20 x 15m) on a flat sandy floor. A gallery leads off, descending rapidly over boulders, via a litlle drop (R3 which can be climbed down) to a small chamber (10 x 10m). In this gallery the alternative route comes in. This route follows the way down the P35. At its bottom the way on is between blocks. A little drop (P10) to a small chamber leads over blocks through a wide rift passage onto the next pitch (P20) which can partly be climbed down. At the bottom a beautiful window with strong draugth opens up into another freehang of 20m (P20). This descent joins in the gallery mentioned above which is supposed to be the main streamway gallery. At this depth huge sandstone blocks coming from outside can still be found. 20m after the descent one arrives at the top of a fantastic 220m pitch: Jo-se-phine pitch (P220). The entire pitch is formed on a fault. The miror of the fault can be observed throughout. From top of the pitch a 160m freehang would be possible. However, in order to avoid problems of water and stonefall we descended via the far south side. A little drop of 5 meters and a passage under a block (-5m) leads down to belays at -18m, -35m and –47m. It goes further down with a first pendulum to –60 and a second one to -78m where the bolts are placed at the backside of an exposed ridge. From here a nice 50m freehang leads to a next belay at –130m. There is large platform some 30 meters lower from which one can imagine the next drop of about 60 meters. However we followed another route to the bottom of the pitch in order to avoid stone fall. 10m above the platform a large gallery (8m wide) can be reached by a pendulum. This gallery turns to the left and descends back into the main shaft via a very beautiful 50m pitch (belay at –10m). At the bottom of Jo-se-phine pitch we find a small lake and sandy beach beneath a superb brexium wall, water is coming in also from the rigth side. Here the cave changes its direction and aspect. A very nice gallery (3 to 5m wide, 4 to 8m high) goes off here to the west and seems to operate as a master cave. It is completely washed, no sign of any deposits, beautifully shaped and descending fast. Throughout spectacular black basalt intrusions can be observed, contrasting with the white limestone and the brexi.(See also geological observations) We followed this gallery for about 100m (with two litlle steps of 4 and 6m- to a wider passage where a 10m pitch can be descended into a chamber filled with blocks. No way on could be found here. In fact the way on is to be found at the top of the pitch where a traverse (5 bolts) gives way to to the continuation of the gallery, however of smaller dimensions (3 to 4m wide, 2 to 3m high). The gallery descends rapidly and gives way after 50m to another 20m pitch (belay at – 6m) at the bottom of witch the way on is in a large rift (P10). A side passage on top of this 20m pitch, where also strong draught can be felt, leads back to the top of the chamber before the traverse. A side passage at the bottom gives way to a small rift which ends after 10m. The descent in the large rift (P10) is followed by another drop of 15m (P15). Landing is in a chamber (5 x 20m), which was used also as place for a camp during the explorations of the lower parts of the cave and is at a depth of - 410m. From the chamber different leads were followed. One is the streamway which came in at the far South West end of the chamber. This streamway can be followed down a 15m rift and another 2m step where the stream disappears under blocks. No draught can be felt here. A second lead is down to the North West side of the chamber, through a small passage into a fossile conduite. This conduite joins the main way on at the first litlle pitch (P5). The main way starts at the North East side of the chamber, where we climbed down into a litlle chamber and further down between blocks to a low but wide passage. After about 50m this passage sudenly turns right to the east and becomes much higher but smaller. Some 30m further a new turn leads through a high rift to a litlle pitch (P5 just mentioned). At the bottom of this pitch one has to crawl through a very narrow passage (with some easy squeezes) for about 30m to the top of the next drop (P13). Descending is in a tide rift, then climbing further down to a small window opening up in a high chamber (10 x 10m). From the window one descends a 20m pitch, landing is between very sharp and chaotic blocks. Between those blocks a passage can be followed down to yet another window opening up in another, much bigger chamber (15 x 25m) with huge boulders. A 15m pitch leads to the bottom of the chamber. It took us some time to find the way on in this chamber (where a whole colony of giant bats was residing indicating maybe that there exists another much faster way). Finally we found the way between the boulders to a large gallery which constitutes a part of the ancient collector or master cave. We called it the Christmas collector (“Le collecteur de Noël”) because we found it right on christmas eve, during the first underground camp.This passage has a typical almost tubular form and is from 4 to 7m wide and 3 to 7m high. It is filled up partly with mud and it is clear that the passage is still in use by the water during the rainy season. There are a many little pools with plenty of white crabs in them and even a beach where some crabs toke there position of defence (with their pincers wide open): the beach of the crabs.  It is also the proof that there really exists a (or maybe more) master cave(s) under the depression along the SE-NW fault which follows approximatedly road nr 40 from Phong Tho to Paso. This master cave lies at a depth of approximatedly 600m, which means only about 160m higher than the supposed resurgence of Hang Doi (altitude 280m) but at a distance of at least 6km (as the crow flies). This is rather remarkable. The passage can be followed downstream for about 100 m to a boulderchoke and upstream for about 80 m, surprisingly, to a nice 8m pitch which gives way to an even lower and more recent collector system. Down the pitch the passage is about 4m high to 6m wide. Downstream the end is about 30m further at a boulder choke, whereas upstream a little streamway can be followed for about 60 m to an upgoing shaft. Here water is flowing, but in the season that we explored it (winter seasson) only a very litlle stream was present here. Remarkably the orientation of the master cave is from West to East, where we supposed it to be directed North West. Of course we only could explore it over a very limited  distance (about 200m in total) which does not allow definite conclusion. 

However, a depth of –600m was reached so that Cong Nuoc constitutes now by far the deepest cave of Vietnam. Moreover, Cong Nuoc is a fantastic sporting and superbely shaped active cave which has offered us a first view on what is probably part of the master cave.

CS2 Vat Cave

Development: 132
Denivelation :  -88

Walking from the village Ban Choi Sao Phin up to the mountain, into the jungle in the direction northwest, you will find the big entrance pitch. There is only one good way two enter the big pitch, but during rainy season these are probably 2 active inlets. On arriving at the bottom of the pitch there are a lot of big dead trees. Go to the lowest point of the chamber and climb down between flowstone formations. You arrive in a small chamber, climb down a squeeze, and use a rope of 5m to step down. You land on a slope with small boulders. Traverse to the top of the next pitch and descend on the left side of the flowstone formation. You can descend one extra small shaft and the cave ends on a boulder choke. We feel that this is a connection to another parallel fossil cave with a large entrance in the middle of a nearby banana tree plantation.

We went up to the village 200m to the northwest and found in the area three more small caves, the first choked at –22m and the second at –40m and the third at –35m. All these caves did not provide us access to the underground system. It is however very clear that all the caves in this area obviously develop on faults.

CS3 Yen Chow Do

<>Development:   699
Denivelation :  -301


Coming from the village of Chau Sai Pin, we take the path which leads to Cong Nuoc cave. We cross the trail leading to the entrance porch of Cong Nuoc and follow the path further on. After about 10 minutes we cross an open field. Another 20 minutes later on the path is going down rather steeply. Here, on the right hand side, completely hidden because of the abundant vegetation, we find the doline leading to the entrance of Yen Chau Do. There are three entrances. We take the lowest (which is the most evident one). We arrive in a small rather chaotic-looking room in which we follow the wall on our right hand side to look for a small diagonal passage which is the start of a P12 (15m). An AN can be used to hang a rope, a spit is present after the diagonal slide. We arrive in a room in which two rather large climb-offs are needed, so one or two slings can be useful here (though not necessary). This leads to a P5 (8m, AN + rope protector). Notice the calcite here which is rather white-ish without any traces of mud. We arrive in a room which we go down by keeping left. In its corner a P16 (20m) starts (spit + AN, go down diagonally for about 6m, spit).


We look for the lowest part in the chamber in which the P16 arrives. A small and short passage can be found which arrives in the Big Gallery. In this gallery we climb off several large boulders (no ropes needed) and arrive in a room in which on its other side a P10 is present, but whitout any continuation. Instead, we perform an easy climb of about 4m (no rope needed) on the right hand side of this room to arrive in a gallery in which some formations can be found near its end. Near the beginning of this gallery however, a small “crack” can be seen in its bottom. This is the start of a P50 (60m). There are several natural belays in this pitch, one or more deviations can also be needed. Note however that at some parts the rock is unstable, so it is safer to wait to go down until your predecessor arrived in the room at the bottom of the pitch.

This chamber leads to a P15 (20m) (AN, horizontal for 3m, spit), immediately followed by a P9 (AN, 4m diagonal, AN). At the bottom of this pitch a small meander can be seen which is heavily ventilated. In this meander a P13 starts (16m). The meander becomes wider and we arrive at the top of the Chaos Chamber. This chamber is split in two halves, separated by a large and steep pile of boulders and mud. To go down 2 spits in Y are present. A rope of 65m is needed. Notice the basalt intrusion layer about halfway this chamber. Because we automatically would arrive at the wrong side of the chamber (it ends in a highly unstable boulder choke in which no continuation has been found), we need to climb up the pile of boulders as soon as possible and go down on the other side of the chamber, where we find the continuation at the lowest part. From there on some short ropes can be needed (but not necessary) for the first few climb-offs. A meander can be followed. In this meander some airflow was present at the beginning, but has been lost further on at the bottom of the meander. Some artificial climbs could be needed to find the draft again