Glarus Overthrust (KEYSTONE)

Geologist David Imper unrolls a map of the Swiss Tectonic Arena Sardona. Here among the mountains of the Glarus Alps, a clearly visible line separates older, darker rock on top from the younger, lighter rock below. 

IMPER: The younger rocks are 35-50 million years old. But the Verrucano rocks are much older. They are 250-300 million years old. And the layer between, the lubricant, where the gliding took place, mainly arose during the overthrust.

This phenomenon of older rocks lying above younger ones happens in other parts of the world. But none can match the Glarus Overthrust, says Adrian Pfiffner, professor of geology at Bern University.

PFIFFNER: The area is special because there are a number of structures which are of unique importance in understanding mountain-building and also they are outcropping in this Sardona area in a way which is not seen anywhere else in mountain ranges throughout the world.

The UNESCO site covers more than 300 square kilometres around Piz Sardona. It straddles the borders of the cantons of St Gallen, Glarus and Graubünden. UNESCO listing is both an honour and a commitment, says Imper.

IMPER: The educational aspects are very important. The UNESCO label is a magnet. That will bring us visitors but you have to offer something. And that will be the big task in coming years to present it in the right way and to get people here.

For years scientists puzzled over the geology of the Glarus Alps. Eventually they were forced to conclude that the gigantic layers of rock folded and pushed on top of each other. Today, you don‘t even need to be a geologist to see how the Alps were formed.