AREA 19: Lan Nhi Thang

NT1 Hang Doi Nuoc

2000 Expedition

An entrance can be seen from the main road, underneath white cliffs. This is the fossil entrance, close to the actual entrance. The entrance pitch (P15) lies between the vegetation behind some big rocks that are used for rigging. Down this pitch a strong draft is felt. Next two steps, R2 and R4, can be descended without rigging. The lead gets steeper, the sides and the bottom are well polished. The P12 leads to a horizontal part, followed by a narrow step (R4).  A strong draft is again felt above the P8, down this pitch is a pool. A short meander leads to a bell-shaped P5. A sloping step (R2) brings us to the Wind Tunnel, a beautiful straight passage with a lot of draft. Another steep climb (with rope) leads to a round chamber the bottom of which is covered with rounded pebbles. A collapsed zone (maybe once connected with the fossil entrance) is followed by a larger part with few formations. Behind this part we went down a sloping narrow passage between the layers. After having proceeded 60 meters through this sloping crack, the passage (Into the Eagles' Nest) emerges high (P12) into a wide chamber. Where the horizontal gallery starts dipping down, there's a large block that is used for anchoring. Down the slope, there are some remarkable furrows, cut out into the floor. At the end of the passage, there'a long and high block in between two pitches, that is used as natural bridge. This block also divides the stream in two parts running down one of the pitches. The eastern pitch was not yet descended, even it was clear that a lot of water disappears in it and that there were lots of bats down the pitch. Crossing the bridge brings us at the start of the descent of the left pitch (rather a very steep slope). Down the slope, there is a small 'waiting room' on top of a spectacular P46 (a series of a P15, P16 and P15). Down the P16 there is a shallow basin, which offers a place for a break. Down the final P15 is another deeper basin, which can be avoided. We arrive into a narrow meander, interrupted by some deep basins which gives into a large chamber (P10). Going west behind a high mud hill, one arrives into a wide and muddy gallery interrupted by a small meander with gour pools, leading to the
deepest part of the cave. There are different inlets and points where the water disappears. To the east of the mud hill, a meander goes upstream, that gives onto a pitch (estimated 6m, not descended, draft is felt here). Halfway the route water comes down from the roof as if it were raining, maybe it is coming from the pitch that was not descended at -175m. In the chamber, once can also go northwards through a conduit. A low passage through the mud and over a small sump with cave-crabs (Crab's Crawl) brings us to a canyon with a small river flowing through. A little further upstream, this waster comes out of the ceiling along a beautiful cascade (fountain). Further on the passage gets wide and steeper and very muddy. Not fully explored here.

Rigging Sheet:

Entrance: 13m, 2 AN (tape, cable), 1 spit (rebelay)
P12:  25m, 1 AN + 3 spits
P8:  15m, 2 spits
P5:  12m, 1 + 2 spits
R7:  6m, AN
P12:  25m (continues to next AN), 3 spits
Slope: 12m, AN (cable)
MC:  6m, 2 spits
P15:  35m, AN (cable), AN (cable or tape), 1 spit
P46: P15: 35m 2spit + AN
P16:  2spit + AN (cable)
P15: 20m  2spit
P10:  12m, 1 gloch, 1 AN

2001 Expedition:

Development: 1305, Denivelation :  -290

During the 2000 expedition a smaller parallel pitch near –170m was not descended, although it was clear that there was a way on. Despite the heavy rain, we decide to go down the cave. The small stream that flows to the cave, disappeared between the boulders before the entrance pitch. The first team (Peter and Vince) rigs down to this first pitch with freshly brought ropes. Apparently, nearly all ropes of last year were still in place but some of them heavily damaged. A series of two neat pitches (P10, P8) was descended, followed by a series of steps. The passage was quite narrow compared to the other parts, but the way goes on through well-polished rocks. After a narrow and well decorated part, a slope is reached which gives into another 10m pitch with a relatively wide base. From here, a small canyon starts, interrupted by small steps and basins. We stopped on top of a 3m pitch which gives into a small chamber. Next day this 3m pitch was descended by Xtof, Vince and Nam. At the end of the chamber, a little step led to the top of a 17m pitch, in which a small streamlet falls down. Could this be the inlet that was reported last year in the narrow meander? Down the pitch there was indeed two ways on. We followed the part going down to the north west, till Xtof noticed a footprint in the mud, facing the direction we came from. The newly discovered passage enables a round trip into Hang Doi Nuoc and also offer a more easy and direct access to the lower parts of the cave.

They mystery of the strong draft is not resolved yet. Furthermore, whilst going up we could smell smoke in the air. At the exit however, nobody was making fire, meaning that the source of smoke as well as another entrance to this system must be located far away. Further prospection (possibly across the mountain) could be interesting.


NT 2 Si Leng Chai (2000 Expedition)

To the North West of the huge depression where the village of Si Leng Chai is located, a little river disappears in a small entrance blocked by trees. 20m higher, another entrance was found. A climb down between blocks leads to the underground river downstream from the sinkhole. Here the river flows through a nice litlle gallery with a very important gradient. Progess is immediatedly very sporting in and above the meandering water and through canyons. After some hundred meters at the end of a little chamber a small pitch (4m) leads back to the river which can be followed, passing through some nice chambers, for another twohunderd meter to a pseudo-sump. In fact the water disappears between blocks leaving only passages which are too narrow. However, draught is clearly going through. A few meters upstream from the sump a side passage can be entered. Starting with a little pool, followed by a small passage over pebbles into a larger and beautifully shaped gallery. There is a rather strong draught going through this gallery and it is clear that this gallery acts as an overflow during floods. During our visit there was water flowing, but there were many, often deep, basins and pools with cristal clear water. Progression in this nice and quickly desending gallery is often high above the water, always sporting and pleasant. Until it comes back to the main underground river we couldn't see any clay or mud deposits at all. After some 200m meters the gallery widens into a small chamber (climb down of about 10m, rope), which gives way to another chamber with very beautiful white bassins and gourpools. The way on is a steep descent over these bassins and gourpools for about 100m to a nice window overlooking the river about 20m lower. In this bassin, part of the gallery, large side passages could be followed over a long distance (not surveyed). They have not been explored yet, but certainly lead back to the main river (and maybe also elswhere?). Abseiling from the window over huge flowstones leads, back to the river, which at this point flows through a large chamber (30m x 15m). At the far end of the chamber the river enters a rather wide and high gallery which is much bigger than the entrance gallery (2 to 4m width, up to 10m high). The river descents quickly and steamy over blocks and down some steps to a first beautiful waterfall (about 6m). Bolts were placed on the left bank. The passages here and further downstream however are not anymore through pure limestone, but through what we like to call claystone. This claystone is like board paper, making it rather difficult to rig the passages. In fact, most of the bolts and nuts which were placed in the downstream part of Si Leng Chai should be used very carefully. Not one of them is really safe, the safest being the one or two which could be placed in calcite.

The first waterfall, with a traverse on the left bank, leads after a passage over huge blocks, passing an important inlet on the right side, to another litlle waterfall (3m), some pools which can be passed along the left bank to the next waterfall (5m), where the water comes down in a nice pool (10m x 5m). The waterfall can be avoided by traversing down to the left into a chamber. At the end of the chamber the water goes down a fantastic waterfall (15m). The (insecure) bolts are again on the left side. The river continues then superbly down over many other smaller waterfalls and rapids (many need some rigging)  until it reaches a huge chamber at about -280m deep. In this chamber the water disappears between blocks, where again draught  can be felt. Unfortunately we couldn't find any way on. In the chamber a very steep, almost vertical mud wall was climbed to about 30m high, but without success. It is clear that we did not yet came near the water table and that the potential is still large (the entrance being situated at about 950m altitude and the supposed resurgence at about 250m). It is indeed worthwhile to have a second look at several side passages upstream and maybe also to have a more thorough prospection on the surface downstream of the entrance. Together with Hang Doi Nuoc, Si Leng Chai proved to be one of the most sporting caves we have found until now in N.W.Vietnam. It offers a variety of river passages, waterfalls, small pitches and some well decorated and beautifully shaped galleries and walls together with a fantastic passage over superb basins.

NT3  Seven Fields Cave (2001 Expedition)

Development: 251, Denivelation :  -38

The cave can be found on the left of the road nr 40 from Tam Duong to the NE. The entrance porche 6x4m immediately leads to a slope of 15m (rope necessary). At the bottom a small low passage brings you to a muddy sump after 10m, which looks very much as the end of the cave. However climbing up through the boulders leads you in a large gallery higher up, which can be followed for 50m. Suddenly the ceiling becomes very low and soon the cave is too narrow to continue. Going back 15m, a right turn leads to what seems to be a huge mud mountain. On top of the mountain there is a small crack between the cave ceiling and the mud to get down the other side. A small inlet makes the cave a total mud bath and shokes the cave at the bottom of the mud mountain.


NT4 Hong Thu Man 1 (2001 Expedition)

Development: 1010, Denivelation :  -143

The entrance is a small passage under a boulder near the top of a steep slope under road nr 40 near Ban Hong Thu Man. A first pitch (P20) is immediatedly followed by a second drop (P13) between boulders. Landing is in a very nice streamway at the beginning of a large and steeply descending chamber with nice flow and rimstones. Down the chamber to the right side a short steeply ascending gallery can be followed for about 50m over beautiful flowstone with hundreds of cave pearls. In fact a little streamway is coming down here and joins the main stream. In he far left side this main stream flows down a 18m pitch and continues in a very high rift probably formed along a fault. The passage here is between 1 and 4m wide and 7 to 10m high. After some smaller steps which can easily be climbed down, a 6m pitch is descended giving way to a continuation in the same kind of rift passage. Some 100m further there is a 90 degrees turn where the ceiling is rapidly descending to a short duck (about 20cm high and 60cm large) which we had to hammer and dig before being able to pass. Draught can be felt here. Beyond the duck the passage opens up again and becomes similar to the one before the duck: high rift passage which is not very large but descending rather fast. 150m of passage can be followed thus before becoming too narrow at the bottom. The way on is a very muddy meandering passage higher up in the rift. About 30m further a little step (R6) leads back to the streamway and another 5m step. The gallery once again lowers down: a narrow passage (7m long, 30cm high) can be followed to a larger gallery with a small inlet coming from the right. From here varied streamway passage and two more short squeezes lead to a first sump which can bypassed to the right where a small chamber with very beautiful and white flowstones and curtains allows to follow the river beyond the sump unfortunately only for some 10m to a second sump. Upon returning to the main chamber down the pitches at the beginning of the cave we see that the streamway also can be followed upstream through similar high rift passage for some 100m to a boulder choke on a very steep slope. If we look at the plan of this cave we can easily see that the cave developed along faults and rifts which are directed at 90 degrees difference towards each other. This cave is a nice sporting water cave which proves that there exists underground water courses rather near to the surface even high upon the steep karst slopes. If necessary this underground water can be exploited locally. We could also easily feel a big difference in temperature between the first part of the cave (where we had the pitches) and the second part along the underground streamway where it is considerabily warmer indicating that the water is flowing rather slowly but remains long time underground. In short: it is a fine cave with various passages and an intriguing river: where does this water come from and where is it going?


NT5 Hang Thut Nuoi (2001 Expedition)

Development: 129, Denivelation :  -54

From the path take a small track down the slope until you reach the fossil entrance. The cave starts with a small meander on the right hand side of the niche. Climb down a 3m-drop, followed by some flowstone and sinter pools. This brings you to the edge of a small pitch of 10m, which can be descended alongside a nice flowstone leading to a small but beautiful room with more sinter pools. By passing over a big rock the cave continues. First climb down 8 meters from some blocks, followed by again some flowstone until you reach the final part of the cave. A muddy hallway quickly becomes too narrow. The water can still be heard on the other side but there is no way to pass.