The formation of salt deposits
The secret of the Thetys
Rock salt, or halite, is a rock that was formed naturally from concentrated seawater in the geological past. Apart from minor admixtures of other minerals, it consists exclusively of sodium chloride, the chemical name is NaCl. It is the raw material for around 70 per cent of the table salt produced worldwide, the rest is obtained from sea salt.
The German geologist Carl Ochsenius explained the formation of very thick layers of salt as early as 1877 as part of his barren theory. The formation of the salt deposits goes back several hundred million years. At that time, today's Salzkammergut was located under the Thetys Sea, which was formed by the break-up of the Pangaea continent and extended from the Pyrenees in present-day Spain, across the Alps, Carpathians and Himalayas to New Guinea.
The rising and falling of the seabed formed so-called bars or shoals and pools were created in which salt water was collected. The water evaporated over time and the substances dissolved in it settled in layers. As the separation of the sea area is a slow process and the sea level is subject to fluctuations, water from the neighbouring ocean repeatedly flowed in. This contained more minerals and layers of lime, gypsum, salt and clay were formed. In addition, the entire process was repeated several times. Over time, when these basins were separated from the open sea, the seabed rose, allowing the salt deposits to dry out completely and become covered by sand and clay. In the further course of the earth's history, the sea level rose again to such an extent that the areas were again connected to the oceans for a longer period of time. Today's Salzkammergut was then once again flooded by the sea around 240 million years ago. Huge coral reefs were formed, the limestone of which subsequently covered the existing layers of limestone, gypsum, salt and clay.
Around 60 million years ago, at the end of the Mesozoic Era, the rock layers folded up and the Alps and thus the Hasel Mountains were formed. It forms the base of the Northern Limestone Alps and has a salt content of 20 to 70 per cent, in the mountain core even up to 98 per cent.
Sodium chloride is the most important mineral for humans and animals. The body of an adult human contains around 150 to 200 g of salt and loses up to 20 grams a day, which must be constantly replaced. This is why the history of salt mining goes back more than 7000 years and leads directly to the Salzkammergut, as Hallstatt is home to the oldest salt mine in the world.
