AREA 2: Nam Khum

Initially, the exploration of this area indicated a complex aquatic system, with, most probably, the cave of Tham Ta Tong as exsurgence. On the second expedition, the area between Nam Khum and the polje of Ban Tham was explored extensively, in order to unveil the missing trajectory of the 'Jan River' by finding new accesses to it. Some were found indeed, but turned out to be impenetrable or were ending at a sump. Two kilometres to the North, another main drain was found, emerging , in the village of Phieng Ngua, which unfortunately soon ends at a sump. It is clear that further exploration of these systems cannot be done without diving some of the many sumps that were encountered.

NK03 Hang Ran (Snake Cave)

This important cave was explored in 1993 and 1717m was surveyed. We returned to investigate some points which were marked as possible continuations.Using one 100m rope to descend the pitches gived rapid access to the mainstream of the river. Upstream the water-level was similar to that found in the previous explorations; the cave ends at a sump at the same location as found before. Downstream, the inlet coming from the north (which joins the river at 500m from the pitches) was explored and surveyed. A short climb over collapsed boulders emerges in a long gallery, perfectly straight and horizontal (2m wide, 3m high), in which one can easily progress upright. The bottom is covered by cobbles and dried-up mud. At the end the gallery becomes very muddy, till a small lake is reached, where the passage becomes submerged. This sump cannot be passed without the appropriate gear. It is obvious that this gallery becomes an important water-supply to the mainstream in the rainy season.

NK11 Tham ta Tong , Part II (the revenge)

This part had been surveyed during the previous expedition, but the data of the part after the first sump had been lost. After this sump, the cave widens and continues in the same way. The South side is particularly beautifully decorated with flowstone. Close to the terminal sump the cave widens. There is a large muddy 'beach' in which one sinks up to the waist! This is very close to the sump of Nam Long.

NK15 Cop Pop 2

In the valley leading from Son La to Kau Pha, near the village of Phieng Ngua, there is an important resurgence. This resurgence is impenetrable, but the people of the village showed us a small entrance, some 150m to the NW and 40m up a hill. It was New Year 1996. Hot steam came out of a squeezy passage between blocks. The squeeze is at the top of a 40m pitch! After some difficulties in getting through with full SRT gear, we descended this pitch, and entered a nice streamway at the bottom. It is definitely this water that comes out at the resurgence. We could follow the river some 200m upstream, through a very regular tubular gallery, to a sump. In some parts, there are large mud banks, testifying to the erosion on the surface. Downstream the river could be followed about 100m to a sump which is probably close to the resurgence. It would certainly be interesting to dive the upstream sump, which is rather large. It has all the aspects of a main drain and it is heading West, which is straight into the mountain.

NK18 Chien Le

Located behind the hotel up the mountain on a steep path. Where the path turns to the right, continue climbing. The entrance is a porch of about 4m high, followed by a little chamber (5m wide, 7m long). The roof is a fissure of 12m high, where daylight comes through. Climbing down between blocks (3m) brings you to a little chamber where a meander starts (inclination of 40). We followed it for over 13m, descending to -8m. The meander becomes too small. No continuation.

NK28 Tham Hoa

The local kids who lead us to the cave were really not exaggerating when they told us about 'chambers as large as fields' in this cave, on the ascending side of the steep shortcut track to Ban Tham. A small boulder slope brings you into the entrance chamber, from which there are three ways on. The right one, which goes down about 12m below the entrance chamber, might be an access to a lower level (At this point, we’re not far away from the downstream sump of Hang Ran...). Only the middle way on has a development of interest, heading towards the valley of Ban Tham (Snake Cave). It enters a very old, large fossil cave with white-grey coloured walls in which some passages are equipped with bamboo. After the 'Grande Diaclase' (oriented south-west, as usual) a natural bridge over a pitch brings you into a decorated chamber with small, white 're-activated' child stalagmites hanging onto their old, large, brownish bases. From here, the river probably followed its way through a narrowing gallery which is choked with mud at the end. A way up brings one to a narrow passage which is followed by an old cascade. From here the aspect of the cave changes; the gallery is more streamlined and the walls have a rusty brown colour. There are some relatively young stalagmites on the floor, underneath a drip of water. This small area is the only wet part of this very dry cave. The passage now follows the magnificent fossil river, sometimes more than 20m wide. After about 100m, the gallery narrows and goes downhill to the last big chamber, with a mud-covered floor and huge old concretions. The way on narrows and suddenly stops in a passage which is covered with mud. No way on was found here. Several pitches were encountered and might lead to a lower level. The ones near the narrow passage deserve attention.

NK30 Missing link

We found this cave when looking for entrances on the line between Hang Ran (Snake Cave) and Nam Khum. The entrance lies about 10m above the small, choked resurgence, which the villagers use as a shower. According to local people the water comes from Ban Tham and the cave would be 'very long'. The discharge is small, compared to the Jan river in Snake Cave, so this might be a side-branch of the main stream. The comfortable entrance gives way to a remarkable turn in the river; downstream, the river splits into different branches and flows between rocks and concretions. At the end (20m from the entrance) the river disappears between boulders (the inner side of the 'shower'). Upstream one can follow the shallow water with many deposits on both banks. As the ceiling lowers, the water becomes deeper and stagnant till a sump is reached, where the water seems to come out of a mud-hill.

NK36 Lan Chon

Leaving Highway 6 to Ban Tham, take a right as soon as you reach the polje, in the direction of the house at the south-eastern end. From there, follow the path to the North, which goes over the hill after about 600 m. The cave is located in a large doline, filled with blocks and overgrown by vegetation. The first drop descends over a series of blocks, and one arrives in the entrance pitch (P10), which leads to a squeeze on the left side between two blocks. Next is a P45, which is highly fractured and beautifully decorated. A last descent from a natural bridge takes you to the bottom, where you can follow a large gallery. On the left side, there are several cracks, which lead to a lower level. We went down the last one, which takes you down two little steps (5 m) to the muddy lowest level, which is choked. We had to leave the cave quickly because of CO2; the two blocks on top of the pit prevent ventilation.

NK 41 Hay La Pho 2
NK 42 Hay La Pho 1

Follow Route No 6 from Son La up to the village of Dong Huy. Take a steep path to the north, about 300m further, that brings you to the polje of Ban Mot. At the southern end of the valley there are two dolines in which both entrances are located. It is clear that they drain the water during the rainy season. Hay La Pho 1 starts with a boulder slope and develops against the direction of the layers, towards the main valley, in which Route No 6 is located. The cave stops at a very small passage, which is choked. Hay La Pho 2 also starts in a doline, and has the same depth. After a short boulder slope there is a short but beautiful pitch. Each time the cave goes through a softer layer, it widens, indicating that the cave is being formed by heavy water flows, during the rainy season. The cave also ends at a choked narrow passage.

NK 43 Tham Hiem

The cave is located in the same valley as the Hay La Pho caves. Tham Hiem is a fossil chamber, with a flowstone cascade at the end, which we did not climb due to lack of equipment. There is no doubt that the cave continues there, but since the cave is located quite high up the hill, it won't be very long. Graffiti of people with helmets show that the army sheltered in this easy and accessible cave during the war.

NK 38 Rung Ma (Phantom Forest)

The entrance is located near the top of a cone, just above the local school and town hall of the village of Ban Hun. The entrance (2 by 2m) is followed by a horizontal gallery which runs gently upwards (80m estimated). From there on the roof becomes low; we followed a crawl for 40m further. It stops, no interest.

NK40 Phieng Phe

Next to the road the cave opens with a small conduit (0.75 m to 1 m width and 2 m high) which slopes down at 50 for about 50 m to -20 m. A draft comes out. We stopped at a little pit (5 m) where nasty animals made continuation unpleasant. It might be interesting to go back.