The karst in the Quang Binh province of central Vietnam is notable for the extensive series of very large cave passages that drain through the blocks of limestone. Many of the caves are part of the Hang Phong Nha system. In March 2012, the British-Vietnamese Caving Expedition was fortunate to be able to explore Hang Va.

HANG VA CAVE INTRODUCTION

The entrance to Hang Va is a collapse in the floor of a small steep valley, with cliffs to the north. A descent of about 15m leads into a stream passage that averages 5m high and wide. The cave passage contains a stream throughout the dry season.

Downstream leads after 400m to a sump, we believe this water flows into Nuoc Nut Cave, though it has not been confirmed scientifically.

A small passage entering the Hang Va streamway can be followed up to another small sump. This is believed to carry water from the flood stream that sinks at the bottom of the Wall of Vietnam in Hang Son Doong, about 900m away.

Upstream Hang Va continues for 350m through areas of rock collapse, until a high-level passage opens about 20m above. The streamway continues underneath for a further 300m to an upstream sump. The water comes from Khe Om, a stream which disappears into rocks on the surface.

Inside Hang Va, the upstream high-level passage above the flowstone climb and traverse is much larger that the streamway beneath; it is 20-30m wide and 10m high. Initially the passage slopes up over mud floors in dry gour pools. Further along the pools are partially filled with water. Within the wet and dry gours are the numerous conical calcite formations that have been named as the Tower Cones.

THE CALCITE CONES OF THE TOWER CONE CHAMBER

The cones are spread across the entire passage where it reaches a width of about 85 meters. There are more than a hundred calcite cones.

They are all very steep, and they reach heights of around 2 meters. Many of the tops are at the same level, which is the same as the water level in the gour pool before it dried out. They are coated in soft mud, but this is generally only a few millimeters thick over the calcite. When washed clean of the mud, the cones reveal a complicated structure.

There is some uncertainty in exactly how these cones have formed. Their characteristics are comparable with some features of cones, recorded in other caves, that are either raft cones or geysermites, but many different processes have created their present structure.

RAFT CONES, TOWER CONES, TUFA TOWERS AND GEYSERMITES

The cones of Hang Va have many features of raft cones. These calcite rafts form as a thin layer on the surface of cave pools. They sink into the pool either under their own weight when they grow too thick, or when hit by a drop of water falling from the cave roof. A repeated drip from the same place sinks a number of rafts that then build up on the pool floor to create a cone, which may reach to the level of the water surface. These are known as raft cones, because they are cones formed from calcite rafts.

Steep sided cones are more often called tower cones. It is not known exactly why some cones form very steeply, and other with a more shallow slope.

A striking feature of the tower cones in Hang Va, and those in many other caves, is the external layer of calcite that gives them a knobbly appearance and also hides any structure remaining from the original piles of rafts.

The knobbly outer surface and very steep profiles of the cones in Hang Va are similar to the features of tufa towers. These form over vents of geothermally warmed water, full of dissolved calcite, that lie in the floors of lakes and cause rapid, underwater precipitation of the calcite. Again they are exposed only when the lake level declines. Those of Lake Abhé in Djibouti are the best known examples (Waltham, 2005). Many of these rise to heights of more than 20m.

Features comparable to tufa towers but formed inside caves are known as geysermites.

The one available cross-section of a cone from Hang Va reveals a porous core with upward-pointing branches, a structure that would be expected in a growing tufa tower, or geysermite.

HANG VA CAVE’S EXPEDITION TOUR

While not physically connected to Son Doong, Hang Nuoc Nut and Hang Va are part of Son Doong cave system based on their shared water flow. Some explorers even commented that the stalactites and stalagmites in Hang Va are even more beautiful and extraordinary than Son Doong cave, but you should see and feel it yourself.

These caves were found recently in 2012. To be one of the people who put early human steps into the caves, you will have to hike, stoop through the entrance, use ropes and cross some rivers including the ones inside the caves.

But don’t worry, the tour provides the very best adventure experiences with every aspects of the trip are carefully planned including delicious meals, the highest safety standards, and friendly and informative adventure guides.

Come and enjoy unique and unforgettable experiences in the caves with our dedicated adventure tours. Although this tour operates 3-4 times per week, the maximum capacity is only 8 people per tour, so please book in advance because available places will be filled very quickly.

For photography enthusiasts and professionals alike, Hang Va Photography tour is another option to conquer this cave for the 2017 season. This tour will be focused on capturing unique images within Hang Va Cave with extra lighting and porters support. Sign up now at Hang Va Photography Challenge.