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Hang Vom System Overview
The Hang Vom System (HVS) is probably the greatest caving system in Vietnam and perhaps the world in terms of size and splendour. At over 35km
long the HVS has never been traversed as a single caving trip from top to bottom. This is one of the aims of the 2009 expedition. The uppermost sink for the HVS is Ruc Caroon. Access to the sink is via road 20 from Son Trach to Lao. The village of Ban Ban is a minority village of the Ruc people. This small group of people, until very recently lived in cave entrances and hunted food in the jungle nearby. These people are therefore excellent guides for the upper reaches of the HVS. The walk down to Ruc Caroon from Ban Ban takes about 1 hour until the river is reached.
The boulder strewn entrance of Ruc Caroon gives no impression of the caves that lie ahead. Once inside the cave enlarges dramatically and the typical grey solid limestone is encountered which is seen throughout the system. Huge gours and stal deposits are present in large numbers throughout the majority of the HVS in this quality limestone. The first section of Ruc Caroon is only 1km long and ends at the huge exit passage around 100m wide and 80m high in a large depression. In this depression the large river disappears in the boulder floor. Crossing this enclosed depression you finally reach the main river of Ruc Caroon. This major river cave can be followed initially passing many side entrances before finally all coming together as a large single river passage. This section of Ruc Caroon is 2.8km long and ends in a huge sump pool 40m across. The water is not seen again until it reappears again in the final cave of the HVS around 8km away.
In the wet season the river is up to the roof of the initial Ruc Caroon passage and therefore over 50m high and 80m wide and according to the locals flowing very fast. This enormous river at this time cannot be all swallowed up in the downstream cave and thus the entrance backs up and the river joins the rest of the HVS as a flood overflow. We have only explored these caves in the dry season but it must be an incredible sight to see in the wet season around August and September.
There are a number of high level dry caves above the active system such as Hang Cung ,Hang Klung and Hang A Cu. These large now abandoned caves
are around 50m above the now existing river level. Once however the river must have flowed through these caves. All the high level caves explored in
this area are relatively short(around 1km) and all end in stal blockages. The main cave that is regarded as the start of the HVS traverse is Hang En or
Hang Pygmy as we call it to distinguish it from another Hang En in the Phong Nha system.
Translated it means Swift cave due to the large numbers living in the roofs of the huge passage. Vines are seen near the entrance where local are able to
climb up to the roof arch over 100m high and collect the birds for eating. This cave is really huge and in fact daylight can just be seen throughout its 1km
length. During the American war the local people lived here and a school was set up near the entrance in a huge gour. The cave has been attacked from the air but we were told no one was killed during any attack.
Vegetation is seen for the first 300m in the cave due to its enormous size allowing daylight in. In the dry season, only small amounts of water are found
in the lower reaches of the huge main passage, but is believed that this fills up dramatically in the rainy season. Passing through Hang Pygmy is achieved by climbing up large gours and boulders to emerge in a steep doline .Sections of the cave have been measured at over135m wide.
The local people have forced a difficult path out of this doline not knowing that a cave is present at the base. This cave Hang Over is 3.3km long and the
small entrance is very misleading considering its huge dimensions inside. One passage just inside the cave is over 130m wide. Hang Over is very easy going and the flat floored passage with very little water in the dry season makes for very pleasant caving in passage mainly 40m wide and high. This exits deep in the jungle but only 100m away is another huge entrance called Hang Ho (Tiger Cave). The short jungle section between the 2 caves is very bad for leeches.
Hang Ho entrance is 80m wide and slopes down on boulders to reach a small stream .Just before reaching the stream and a number of swims a passage on the right leads to more fine caving and another exit in a streambed. This streambed leads to another cave Hang About which is an upstream feeder into Hang Ho. Downstream in Hang Ho is excellent caving in beautiful smooth polished limestone. A number of swims are passed until the exit of Hang Ho is seen. At this entrance, huge trees around 60m high grow at 45 degrees due to the draught that emits from the cave. Following the stream bed downstream from Hang Ho is very difficult due to the incredibly slippy nature of the rocks.
Around 500m from the exit of Hang Ho the water sinks in a cave which has not been pushed to a conclusion. A little further down the valley a huge boulder slope is come across and a small entrance can be found into the main continuation of the HVS called Pitch Cave. This entrance is difficult to find and a much larger one can be found by climbing up and around to the left facing downstream. This large dry entrance leads into Pitch Cave which is a huge rift over 60m high for most of its length. A stream is then reached which can be followed down a few climbs to a sump. Just before the stream is reached a 30m pitch up leads to a high level passage and an exit over the sump. However it is not possible to climb this pitch without rigging from the top. A difficult bypass in dense jungle can miss out most of Pitch Cave and if one can find the small entrance to Pitch Cave in the Col (Vandal’s entrance) it is possible to bypass the pitch. After Pitch cave a very steep descent where a rope is useful leads to another stream bed where the water from Pitch Cave exits. This water sinks in boulders but on the right of the streambed and 10m above the water is one of the many entrances to Hang Duat.
This fantastic Cave is very complex with many levels of development. At just under 4km long Hang Duat is a truly fabulous Cave with sections of active
streamway and higher levels which give the name to this cave which translates as Maze Cave. There are a number of exits to Hang Duat but if the
main downstream passage is followed a huge chamber is reached where an exit to the left can be taken. In low water conditions a short duck can be
passed to lead back to the streambed and the main exit to Hang Duat. The next section of streambed is again very slippy and after another 500m an inlet
on the right is picked up which is fed from another important cave called Hang Dai Cao. This section of the HVS has many tiger prints around the cave
entrance which adds to the excitement of caving in this area.
Hang Dai Cao is the cave we used as a base camp to explore most of the upstream HVS. It can be reached from road 20 in around a 4 hour walk which
many of the jungle guides know and use the entrance a camp for there excursions in the jungle. Hang Dai Cao is another splendid cave and is
another feeder into the main HVS. The water in Hang Dai Cao comes from an unknown source and the upstream exits have not been fully checked out for
further prospects. Hang Dai Cao is an excellent cave for camping in and we have used it as a base on many expeditions.
Downstream of both Hang Duat and Hang Dai Cao is 2km of streambed which is again slippy but leads to the impressive entrance of Hang Ba. This is an extremely large bit of passage typical of the HVS. At 1km long Hang Ba so named because of its 3 large entrances on the downstream exits. Much of the cave can be done by climbing on boulders above the water and taking the largest exit. However swimming is easier and it is very spectacular to exit from the middle entrance with daylight entering from high level avens. This amazing place exits in a huge enclosed doline with large cliffs surrounding a
large lake with a nice beach. After another short section of cave called Arch Cave which is only 100m long the main downstream entrance to Hang Vom called Panthers entrance is seen. A 500m swim is the easiest way to reach this quite spectacular place.
The next section and the final and longest in the HVS is without doubt one of the great sections of cave anywhere in the world. At over 15km long this
section has both huge river passage often over 50m high and wide as well as huge high level passage with enormous stal formations. After around 200m from the Panthers entrance a large fast flowing river is met which powers out from a sump. This is thought to be from Ruc Caroon and around 8km away. Much cave awaits to be discovered in this missing section and a diving expedition is planned for 2009.
Downstream the cave increases in size with the roof and walls often out of sight. After just over 1km using a large shelf to traverse the passage a huge
left hand bend is reached where due to the immense size of the cave passage the way on is very confusing. This area has not been fully checked out and a return may yield further passage. After another 500m the passage suddenly changes character and a 10m wide canal with a 350m swim called the hall of bright carvings is followed until again daylight can be seen. Only 100m separates this exit from the next entrance. This leads into the main upper river
gallery. After around 2km an inlet on the right is reached called Pretentious inlet which was used as a camp in the initial exploration of the system.
Downstream of this inlet the cave is generally 50m wide and high at least and is followed for around 4km of splendid passage involving many swims and
cascades to emerge at the Daylight Beckons.
This is where an enormous shaft around 240m high enters and is a splendidlocation. Because of the daylight entering here it was possible to see the walls and roof of the huge cave and high on the right hand wall downstream a large high level passage can be entered by climbing on a shelf. This passage isvery large with excellent formations. As it is around 50 to 100m above the river passage it is mainly dry but in the wet season water does flow in this passage which is quite a sobering thought. This continues for around 6km in huge passage before exiting at the base of a cliff. Nearby the exit to this section of cave another cave called Hang Me Bon Con can be found which has over 800m of high level passage with excellent formations which must connect with the rest of the high level passage in Hang Vom but has not yet been connected.
Back at the daylight shaft the main river passage continues in fine style for another 2km to finally reach the immense exit of Hang Vom (Arch Cave) This exit has an enormous lake the 4th largest underground lake in the world and the sight of the jungle and the huge entrance which is around 80m high and over 100m wide is without doubt one of the greatest locations I have ever had the pleasure to see.
Hang Vom is a truly a remarkable cave system and it is hoped that with further expeditions planned more of this amazing cave will be discovered in the near future.