Geologie: Piz Beverin & Heinzenberg

"The view of the Hoch Büel reveals clear erosion channels that the flowing water has cut into the soft subsoil, the Nolla clay slate. At the top, the gutters show clear funnels. The soft clay slates lie on the eastern flank of the Hoch Büel parallel to the slope inclination, causing the slope to slide in some places. For example, the subsoil of the village of Massügg slid eastwards. The summit of Beverin consists of a 100-metre-thick layer of hard, erosion-resistant quartzite. This shields the underlying softer, more clayey-sandy rocks from erosion. As a result, they form steep rock faces below the summit." Prof. Adrian Pfiffner, geologist, University of Bern

The Alps were formed by the collision of the European and Adriatic plates. Between the two mainland masses there was a sea basin 100 million years ago, in which sand and mud were deposited. At the beginning of the collision, this sea was closed, with the deposits compressed, heated and hardened. Today, they build up the Beverin and the subsoil of the glazier ridge as limestones, sandstones and claystones. They reach a depth of 10 km underground and are referred to as "Graubünden slate". The mountain ranges west of the Safien Valley (Piz Tomül – Piz Fess) and the Stätzerhorn chain east of the Domleschg are also made of Graubünden slate.

The sandstone-claystone sequences of the Graubünden slate are easily eroded, which gives the Heinzenberg its gentle shape. The summit of the Beverin, on the other hand, consists of hard, erosion-resistant quartzite, which was formed by the transformation of the sandstone. This is how the rugged shapes of the Beverin are formed.

The Nolla claystone, which occurs mainly between Glaspass and Thusis, is a layer within the Graubünden slate. It contains a lot of organic carbon, which is why it is so dark. These rocks weather extremely easily and make it easier for the Nolla mountain stream to cut a deep groove. How quickly such a notch can happen was shown 400 years ago, when the Nolla transported huge mudslides of mudstone towards Thusis.

The claystones in the Graubünden slate are also impermeable to water. The rainwater therefore collects in the uppermost layers and causes an unstable surface. As a result, landslides occur. These landslides are additionally favoured by the dipping of the layers to the east. Today, landslides affect the entire eastern slope of the Heinzenberg. They cause an actual mountain tearing, impressively indicated by the double bone on the Glasergrat and Lüschgrat. By draining the uppermost layers, an attempt was made to give the slope more stability.