Geology

Valsabbia can be subdivided into three geological zones: a zone formed by sedimentary rock of the Mesozoic Era, especially during the Triassic Period; a zone, in the centre formed by more ancient rock (sandstone, shale composed by mica and clay, and fossils of the Permian Period); and a third zone in the Northern area formed by eruptive molten rock, pushed upwards from deep-lying magma chambers in the mountains of the Adamello Group.
The zone surrounding Lake Idro to the area north of Bagolino is formed by limestone which originates from the remains of microscopic marine organisms precipitated or deposited on the ocean floor of Thetis, around 230-150 million years ago. The beds of limestone, formed by calcium carbonate mixed with clay or mica, were completely horizontal, but 70 million years ago they were moved by the activity of the African plate and the Eurasian plate. The African plate shifted under the Eurasian plate dragging a part of the sediments from the sea of Thetis which had a thickness of 11-13km. The sediments that didn’t sink under the Earth’s crust were pushed to the Eurasian plate forming vast rocking waves. These waves have an east-west direction, but the movement provoked by the eruption of the Adamello Group bended the waves located at east, where the river Chiese flows. This movement changed the direction towards the axis southwest-northeast shattering the beds of limestone. Also, in the last 70 million years, the atmospheric elements, such as ice, frost, rain, snow and wind have been eroding the superior strata.
In the area of Corna Blacca there is limestone of the middle Triassic Period. On the northern side there is Dolomite while towards south and near the area of Corna Zeno there are other types of limestone (i.e. Liassic limestone).
The area of Valsabbia is formed mainly by rock of the Triassic Period with the exception of the area northwest of Lake Idro where there is Liassic rock which formed 180 million years after the Triassic Period. This type of rock is detectable in the mountains such as Mt Breda, Mt Paghera and by the Rocca d’Anfo.
In the eastern part of Lake Idro, almost all the rock dates back to the last two periods of the Triassic Period (Noric and Rhaetic?).
The Dolomite of the Noric Period characterises mountains such as Mt Carzen, Mt Cingle, Mt Stino and Mt Manos, while the Dolomite of the Rhaetic Period characterises Cima Fobbia and Cima Saline. Moreover, the mountains of Cima Meghè, Corno Zeno, Cima Baremone, Dosso delle Portole, Mt Tombea and Cima Caplone are also formed by Dolomite.
The northern area of Valsabbia is formed by more ancient rock found in the mountains of Dosso Alto, Monti della Corna, Visigno, Ario and Pezzeda.
The most ancient rock of the Triassic Period is constituted by clayey and calcareous schist mixed with beds of limestone and siderite (iron and manganese carbonate).
Mt Carena and Mt Tonolo are formed by porphyry of brown colour. The rock under Mt Colombine is even more ancient and finishes in the area near Bagolino.
The area between Val Camonica and Val del Chiese is characterised by a rock which originates from the Permian Period (230 million years ago). Such a rock has various colours, often reddish, and formed by sandstone and conglomerates that are usually extremely compact and hard. The areas formed with the rock of this constitution are Mt Misa, Dosso dei Galli, Passo Crocedomini, Valle del Caffaro and between Val Dorizzo and Gaver.
By going further north there is the third zone, the area of rock which originated from magma and the massif of Adamello. This rock originated from the magmatic activity deep within the Earth that cooled slowly and assumed a crystalline structure. The elements eliminated the upper strata exposing the granite.
In the formation of the Adamello Group, the eruptions from the deep-lying magma chambers occurred on three occasions: the one at southeast, which is the northern area of Valsabbia, was the most basic and formed Mt Listino, Frerone, Cadino and Blumone. A good example of granitic formation is the rock that forms Mt Bruffione.