Sognefjord is formed by a combination of exploitation of rock structur
e and subaerial and subglacial processes. The fjord system follows zon
es of rock-structural weakness. Above sea level the landforms are due
mainly to subaerial processes, and somewhat surprisingly not to glacia
l activity. Removal of erosive products and deepening of the fjord bel
ow sea level is due to glacial erosion.