Sesia Val Grande Geopark

Geology unique in the world

The area features a combination of rocks from the mantle, deep crust, middle crust and upper crust, constituting an extraordinary geological heritage that has been the subject of study by scientists of various nationalities for many years. These rocks were brought to the surface by the collision between the African and European continents, which, beginning around 65 million years ago, gave rise to the Alpine orogeny. Today, they form one of the most spectacular geological sections in the world. Along the Alps, the suture between the two continents corresponds to the fault system known as the Insubric Line, referred to as the Canavese Line in its western section.

The Fossil Supervolcano

What makes the Geopark’s geological section even more extraordinary is the presence, in its southern part, of the so-called ‘Sesia Supervolcano’. Here, one can identify the rocks belonging to its deep magma chamber and its caldera, formed by an explosive eruption during the Permian period, some 278 million years ago. The Alpine orogeny ‘overturned’ the magmatic system by 90°, allowing it to be fully exposed along the Valsesia.

Monte Rosa

The history of the north-western Alps is well represented by the geological formations exposed on Monte Rosa, with particular regard to the dynamics of the last 200 million years: from the separation of the European and African palaeocontinents, to the formation of the Mesozoic Tethys Ocean, to the subduction and closure of the Ligurian-Piedmont Basin, the collision of the crustal plates, and finally the formation of the gold-bearing veins during the late Mesoalpine phase (around 30 million years ago), which constitute Italy’s largest gold-bearing district.

The Moho

There are few places in the world where one can see with one’s own eyes the boundary between the Earth’s crust and mantle, the so-called Mohorovičić discontinuity (Moho).
In Valsesia and Val d’Ossola, thanks to tectonic processes, this boundary has been exposed at the surface: here, rocks from the mantle (peridotites) can be seen alongside rocks from the deep crust (gneisses and amphibolites).
A unique opportunity to understand the planet’s internal dynamics and the very origin of Europe’s mountains.

The Neanderthal caves

The carbonate massif of Monte Fenera, in Valsesia, contains a complex karst system consisting of caves, shafts and tunnels. More than 80 cavities have developed within it. Some feature a very large chamber, and one of them in particular – the Ciota Ciara – has yielded Neanderthal artefacts dating back almost 300,000 years.