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Geography and geology

Geographically the area is part of the Graian Alps, the northern part of the western Alps. It was possibly named after the mythical Greek hero Ercole Graio (Hercules), who is believed to have passed through Colle del Piccolo San Bernardo while he was completing his famous 12 labours.

Geologically speaking the Gran Paradiso group started out over 230 million years ago as volcanic material, with a fraction of marine sediments. Tectonic activity led, in fits and starts, to the formation of the Alps during the Tertiary period (about 54 to 57 million years ago), the accompanying heat and pressure responsible for the transformation into metamorphic rock. The Gran Paradiso summit, for instance, is made up of a huge dome of augen-gneiss girdled by calcareous rock, mica-schists and greenstone, to mention a few.

View of Valgrisenche mountains during ascent to Col de la Crosatie (AV2 stage 9)

Of great economic significance to man since pre-Roman times have been the immense mineral deposits, first and foremost the magnetite extracted at Cogne up until 1979 and processed at the Aosta steelworks. The original name of the Valle dell'Orco, the main southern valley, was ‘Eva d'or’ (water of gold) because of the precious minerals in its sands.