Station 9 Geologiepfad Malbun: Gipsgestein näher betrachtet

In a shallow basin at the edge of the sea, salt water evaporated. In the process, the substances dissolved in the water remained at the bottom. At regular intervals, water flowed into the basin from the nearby mainland and broke fine dust and mud with it, which settled over the gypsum. The gypsum rock therefore shows a banding of alternating light and dark stripes. The plaster is light, the washed in material is dark. The regularity of the stripe pattern suggests an even alternation of evaporation and wash-in. The reason for this was probably the change of seasons in the Triassic period over 200 million years ago. Dry and rainy seasons followed one another and today in the areas on the edges of the deserts.

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How do you fold rocks?

The banding in the gypsum rock shows wrinkles in some places. These were formed when the rock came under pressure due to tectonic movements. But not only soft gypsum rock is foldable. Rock-hard limestone and many other rocks were also folded during mountain formation. Rock can only be folded under very high pressure, high temperatures and usually in the presence of water. Wrinkles take thousands of years to form. Folds, such as in the limestone of the Fläscherberg near Balzers, did not form on the surface of the earth. Such folds were formed deep in the seabed when the seabed was still under water and was already compressed by continental drift. The conditions for the folding of limestone are only given almost one kilometre below the earth's surface. When the mountains were finally lifted out of the sea, the folds had already formed.