Scopetta

At Scopetta, the fault-related milonites of the Insubric Line are present.

Here we are at the centre of a one-kilometre-wide band of heavily deformed rock, known to geologists as the Insubric Line. The arrangement of the rock’s minerals in thin layers (known as ‘foliation’ because it resembles a stack of sheets) was caused by friction between the two continental plates over the last 30 million years.

On the left bank, the rocks were thrust upwards by the collision of the two continental plates during the formation of the Alps. On the opposite side of the river, the rocks were thrust upwards from a depth of around 30 km and rotated so that, along the Valsesia valley, an almost complete section of them can be seen. In fact, the deepest parts of this crustal section outcrop there, whilst the rocks near Borgosesia were formed at the surface during the supervolcano eruption, some 282 million years ago.