Roughly 550 million years ago, what is now Finse lay at the bottom of the sea - the remains of mud and clay that were deposited in this sea have ended up on the roofs of Norway. Also the thrust sheet from the continental collision has found its way to Finse, after a several hundred kilometre-long, trek through the mountains, that took several tens of millions of years to complete.
The gneiss landscape west and north of Bergen viewed in profile can remind us of a saw blade of the kind that has long, slanted sides that get broken off shorter transverse sides. It has taken several hundred million years to file this saw blade, an enduring interplay between various geological processes.
There are coal bits hidden in the sand under Vatlestraumen. These remains from a geological layer from the Jurassic Period were discovered when the undersea Bjorøy Tunnel was built in 1994. Oil- and gas reservoirs in the Troll Field in the sea west of Hordaland are from the same time. It is, nonetheless, quite surprising to find bedrock from dinosaur time inside of the outer islands of western Norway. On the Scandinavian mainland north of Denmark, there are only a very few places where one f inds rock from this time in earth history.
Holmengrå is the only place in Hordaland where we find traces of the abrasion that is supposed to have transformed Western Norway from a Himalaya-like high mountain landscape during the earth's Paleozoic Era, to a flat lowlands terrain during the Mezosoic Era. Just 400 million years ago, large and small stones plummeted down from the high mountains. Some of these stones became incorporated into the conglomerate bedrock on Holmengrå.
The Bergen Arcs have an unusually sharp boundary to the bedrock in the east. Geologists think that this was caused by movements in the earth's crust during the Devonian Period. Then, the Bergen Arcs on the Lindås peninsula sank a whole 10 kilometres in relation to the Precambrian basement gneisses on the east side of Fens Fjord and Aust Fjord.