Siggjo is a cone-shaped, volcano-like mountaintop in the part of Hordaland where one finds the best preserved volcanic rocks. The rock types originate from one or several volcanoes that spewed out glowing lava and ash. But, the shape of the mountain, as it appears today, formed later and by completely different forces.
In 1868 the first stone workers came to Rubbestadneset to take out the granite for the Skoltegrunns Pier, predecessor of the Skoltegrunns wharf in Bergen. Later granite was also taken out from the area, around Innværs Fjord and UransvågenN. The activity probably peaked around 1900, with over 40 men at work. 15 years later, it was finished.
The different bedrock types that got shoved in over Hordaland in Cambro-Silurian times still remain, layer by layer, almost like a cake. But at Kvamskogen the cake has been turned upside down.
Folds are to be found everywhere in the remains of the Caledonian mountain chain. Some were formed during the collision with Greenland, others stem from the time when the mountain chain collapsed. Few can compare with the giant fold that remains in the mountain area around Tørvikenuten, Vesoldo and Hellefjellet.
At Flintaneset by Finnåsvika, in the centre of the municipality, we find the most beautiful and best preserved igneous rocks in western Norway. We must go to Hawaii or Island to find as fine structures as at Bømlo.