During large periods of the ice ages, much of the glacier from Hardanger Fjord flowed over Kvamskogen to Samnanger. On its way further out toward the Norwegian Oceanic Trench, the ice went via Fusa Fjord and Kors Fjord. By Fossen cliff the ice merged together with the glacier from Tveitakvitingen down toward Raunebotnen. Together, they carved out a trough under the ice, such that there arose a step in the valley where the water now flows out from. It helped a lot that the gneiss had a lot of cracks just here; Raunebots valley is carved out along these north-south-trending cracks. In the fracture zones the glacier plucked loose large pieces of the bedrock. These pieces got frozen into the bottom of the glacier and helped to carve away the mountain further down through the valley.
In the mountainside north of the waterfall, one clearly sees an area with tightly packed vertical fractures in the bedrock that run north-south. Along the fractures there are also signs of landslides; one occurred in the winter of 1999.
From the top of the waterfall there is a view to two river fans in the valley below. The trough the glacier carved out is now filled with loose deposits. Here, it is nearly flat, and the river has too little energy to transport the coarsest flood deposits any further. When the big stones get deposited in the river channel during a flood, the nearest part of the river channel will get plugged up, and the river is forced to make a new path. In this way the river is constantly changing its flow direction. The result is a system of active and abandoned river channels that branch out and form river fans.
Along the river, 75 metres above the waterfall, there is a 7 metre-deep pot-hole in the gneiss. Here, there is rare to find big pot-holes in gneiss. If there is little water in the river, we can also study many smaller pot-holes in the coastal rocks just above the big pot-hole.
