What are drop stones

Formation of the caves and the stalactites

The Rübeland stalactite caves were created over the course of several hundred thousand years. The age of the Baumannshöhle is about 500,000 years and that of the Hermannshöhle about 400,000 years. The underground side arms of the Bode are mainly responsible for the washing out of the cavities. Originally the river bed was about 40 meters higher. For this reason, the uppermost cave rooms are also the oldest.

The cave formation is not yet complete even in our day. The cave brook of the Hermannshöhle continues to work on the creation of new cavities in the mountain. This cave brook represents a tributary of the Bode flowing along the valley outside. Its altitude corresponds to that of this important Harz river.

The first stalactites were probably formed soon after the cave formation began. They are a result of the chemical weathering of the calcareous cover rock above the cavity.

The stalactites still grow in the following way: The precipitation absorbs carbon dioxide from the atmosphere and forms carbonic acid with it. This slightly acidic water seeps into the ground and penetrates through cracks in the rock to the ceiling of the cave. On the way, the liquid reacts with the poorly water-soluble calcium carbonate of the limestone to form calcium hydrogen carbonate. This substance is readily soluble in water.

When it reaches the ceiling of the cave, the solution forms drops on the existing crevices. As air now enters, the carbon dioxide escapes from the liquid. The calcium hydrogen carbonate then converts back into the poorly water-soluble calcium carbonate (lime). This lime is deposited on the cave ceiling or falls to the ground with a drop of water. This creates new limestone, which has formed stalactites over the course of thousands of years.

There are different forms of dripstones. A stalactite growing from the ceiling is called stalactite, a stalactite growing on the floor is called stalagmite. Stalactite columns, which reach from the floor to the ceiling, are called stalagnate. So-called sinter curtains are a special form. The flap-like structures are created on inclined surfaces. The water does not drip to the ground here, but runs along the rock face - over and over again on the same path.

If the water detaches additional metals from the limestone on its way from the surface of the earth to the cave ceiling, the actually gray stalactite is discolored. Copper makes it shimmer green, iron yellow or reddish.

Dripstones grow about an inch per century. The speed depends on the amount of water and the condition of the overburden. Touching the stalactite leaves small amounts of fat and other substances adhering to the skin. This hinders the natural growth of the stone at this point. For this reason, you are not allowed to touch the stalactites during your visit to one of the caves.


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Additional Information:
The Rübeland stalactite caves | The Cave Festival | Opening times and admission prices | Cave maps


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