Hang Va Cave Formations
Hang Va is home to some fascinating cave formations including the tower cones, spread across an entire passage that reaches a width of about 85m. There are more than a hundred calcite cones rising from the Earth in some mysterious way.
These Hang Va Tower Cones are all very steep, and they reach heights of around 2m each. 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 millimetres 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, making them incredibly unique and worth visiting if you have chance.
The cones of Hang Va have many similar features of Raft Cones – these calcite rafts usually 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.