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Geologie: Piz Beverin & Heinzenberg

Geologie: Piz Beverin & Heinzenberg
Geologie: Piz Beverin & Heinzenberg
Prof. Adrian Pfiffner, geologist, University of Bern:

Description

"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 slate lies on the eastern flank of the Hoch Büel parallel to the slope, whereby the slope slips in some places. For example, the underground of the village of Massügg slipped to the east. The summit of Beverin consists of a 100 meter 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."

The Alps were formed during 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 Glasergrat as limestones, sandstones and claystones. They reach up to a depth of 10 km into the 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 also consist of Graubünden slate.

The sandstone-claystone sequences of the Graubünden slate are easily eroded, which gives the Heinzenberg its gentle shape. The summit of Beverin, on the other hand, is made of hard, erosion-resistant quartzite, which was formed by transforming the sandstone. As a result, the rugged forms of beverin are formed.

The Nolla claystone, which occurs mainly between Glaspass and Thusis, is a layer within the Grisons 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 notch a deep furrow. How quickly such a notch can happen was shown 400 years ago when the Nolla transported huge mudslides of claystone in the direction of 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. In addition, these landslides are favored by the collapse of the layers to the east. Today, landslides cover the entire eastern slope of the Heinzenberg. They cause an actual mountain tearing, impressively indicated by the double bones on the Glasergrat and Lüschgrat. By draining the top layers, an attempt was made to give the slope more stability.

Map

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