Entstehung des geologischen Atlas der Schweiz (1:25'000)

The geological maps of Switzerland from the Federal Office of Topography swisstopo are so far the only comprehensive data set on the structure of the subsurface. They thus make an important contribution to the exploration and sustainable use of the subsoil and form an important basis for decisions in areas such as tunnel construction, subsoil investigations, natural hazards and science.

Creation and content

The basis of a geological map is primarily the geological mapping of the earth's surface (e.g. outcrops in stream cuts or construction pits). Geological units are assessed according to their composition, age and storage and presented with various graphic elements on a topographical basis.

The field mapping is supported by modern survey methods such as the evaluation of aerial photographs or digital elevation models and supplemented with other basic data such as drilling or geophysical measurements. Both digital data sets and 3D models of the subsurface are derived from the maps.

After 20 years of mapping, Atlas Sheet No. 173 Elm was published in 2021. On a scale of 1:25,000, it covers a central section of the Geological Map of the Glarus Alps 1:50,000 by J. Oberholzer ("Oberholzer Map") from 1942. In the area of the Elm atlas sheet lies the heart of the UNESCO World Heritage Site Tectonic Arena Sardona: the Glarus main thrust with the Tschingelhörner and the Martinsloch. Here the "magic line" can be seen particularly well.

On a hike over the Segnes Pass from Elm to Flims (stage 6, 73.06 Sardona World Heritage Trail) you can see the Glarus main thrust up close.