It is believed that, before the ice ages, the mainland extended all the way out to Marsteinen. From Vidden the rivers ran through narrow, "V-shaped" valleys that carved down through an old, weakly undulating landscape. When the climate got colder, and the ice ages began, the first glaciers formed at the top of the valleys. Snow that blew down from Vidden accumulated in depressions in the terrain. The thickness of these snow layers eventually grew so big that those at the bottom were transformed into ice. The ice then began to move slowly but surely down the valley and over time carved trough-shaped depressions, known as "cirques". The ice disappeared and came back again, over and over again. Especially in the beginning of each ice age, the cirques were carved out deeper and deeper. Lake Tarlebøvatnet in the uppermost Våkendalen Valley, Hardbakkadalen and Isdalen valleys up under Ulriken, are areas where the local glaciers carved out cirques.
But, it was not only at the beginning of the individual ice ages that the carving took place. As the ice ages after a time became more extensive, the smaller glaciers merged together. The bigger glacier was stronger than the smaller local glaciers on their own. In this way, a bigger main valley was carved, that was deeper than the side-valleys. Svartediket lies in the main valley. The side valleys became so-called "hanging valleys", with waterfalls and streams down toward the main valley.
