Mangerite is a rock type that was first made famous in a treatise by the Bergen geologist Carl Fredrik Kolderup in 1903. The rock type got its name from the place where it was found, and has made the Mangerud name well known around the world, at least among geologists.
The oceanic crust of the North Sea was subjected to a lot of stretching both in Permian and Triassic times, and later in the Jurassic. This stretching resulted in the North Sea collapsing in and also to large faults forming west of Hordaland and on the mainland. Austefjorden in Sund follows one of these faults.
220 million years ago, glowing hot molten rock masses intruded into fractures in the earth's crust in the outer parts of Hordaland. Some of these are believed to have reached the surface and formed lava flows, which since have been eroded away by wind and weather. But, most of these flows solidified into diabase sills before they got to the surface.