The zones of movement follow these fjords. On land, these zones can be observed in the Ostereid and Bjørsvik Bay areas.
The dramatic changes started about 400 million years ago, when the rocks lay at great depth under the earth's crust. At this depth it was so hot that the rock behaved like a viscous dough during the movements. Such zones of movement are called "shear zones" in geological terms; the name of this zone is the "Bergen Arcs shear zone". When the rock was still pliable, it flowed out over what is now the Lindås peninsula, and it sank downwards over millions of years in relation to the basement bedrock to the east.
Through all this time, layer upon layer was removed by the destructive forces in the area, simultaneously as the movements between the Lindås peninsula and the land to the east continued. Through this process, the rock types that originally lay deep down under the crust, came up to shallower depths, so that the temperatures in these rocks cooled. The bedrock therefore grew steadily harder, and that which had earlier been a broad and ductile shear zone, became a narrow and brittle fault. This is how the Fensfjord Fault was formed; the last phase of movement in the region occurred along this fault. Ground up bedrock, which resulted from the faulting, together with the calcite- and quartz crystals, can be found along the sides of the valley north of Bjørsvik. The fault is clearly visible in the landscape as the narrow depression from Bjørsvik over to Stallbotnen.
