
In Deutsch


In Deutsch

Salt Mines

Salt is different from other typical mining products, as it is necessary for living, it is an important part of food. Thus salt is probably the first thing which was mined and it has been a sort of money over centuries. The first known salt works are about 8,000 years old, found in the Shanxi province of China. Salt lakes and sea water were the source for salt water which was boiled in clay pots. In some areas of the world, the sun is suficcient to drie the water, at least during some parts of the year. In other areas salt exists on the surface and is mined in shallow open pits. In the Sahara the salt is mined and transported into the south, the subtropic prairies and rain forests with caravans.

But soon mining started. In areas with no salt lakes, remote from the sea, it was important to find salt deposits which could be mined. In the Austrian salt mines around Salzburg (mention the name) Keltic remains like shoes and wooden tool were found, which ar around 3,000 years old. The mining was a little easier than in other mines, as salt is rather soft. Today huge caverns are made, big enough to drive trucks inside.

Still there is a lot of salt cooking, even today. It is easy to pump water into salt bearing layers, wait until it soluted the salt and then pump it back up. To clean the salt it is always improtant to solute it in water and filter it. At last the water is vaporized and pure salt remains.

This is the way the salt deposits all over the world were formed. Salt, contained in small amounts in any rock, is washed into the sea. In the sea the amount of salt rises since million of years. But when parts of the sea are cut off and the weather is dry, the water evaporates and the salt remains. The salt is deposited in a sequence, first the salt types which are hard to dissolve are deposited, then the next and so on. The typical sequence of those evaporites is limestone, gypsum, and salt. If the salt is covered by mud or sand later, the salt deposit has formed.

Other important processes are the halokinetic processes. Salt unde high pressure and high temperature starts to flow very slowly. Although it looks still hard as a rock, it is deformed by the pressure of the rock above. If there are fractures the salt starts to flow upwards forming huge diapirs or salt domes. Often those diapirs are mined, as they are less deep. Sometimes they reach the surface, although the salt layer is three kilometers deeper. (eg Northern Germany)

The mines are of impressive size, and as salt is hygroscopic, they are extremely dry too. This is a big difference to other mines. The air is very pure and full of salt, and many people think this air has healing powers. There are abandoned mines which are now used for Halotherapy, especially in eastern Europe.

Some countries use abandoned mines for the storage of various goods. Because of the size, the chambers are easily accessed by truck, so it is possible to store a lot of things, like documents, valuables, art, and food. Some are used to dump dangerous chemicals or (unfortunately) radioactive waste. Some mines are used for underground bicycle races.

Salt Mines

See also