Earth pyramids are steep forms of erosion in the shape of a tower or cone, which are preserved for a certain period of time due to the presence of overlying rock blocks. They are therefore very unstable forms of relief, with a life span of the single pyramid between 10 and 100 years. The prerequisites for the formation of these earth pyramids are the starting material (presence of relatively fine-grained blocks), the climate (regular rainfall) and a position protected from the wind. Typical starting material for the formation of earth pyramids are glacial deposits (moraine material).
The earth pyramids in the Rio di Fana Valley (Pfanntal) are not as spectacular as those in Perca and often show cone shapes without a top boulder. The reason for this is that the source material is not a typical moraine material, but rather an ancient detrital deposit that formed towards the end of the last ice age. These sediments originated from repeated debris flows, which filled the Pfanntal, when there was a higher base level on the valley floor of the Val Pusteria due to the presence of residual ice masses. In general, the deposits are slightly consolidated, which results in smaller, Badlands-type erosion forms and only rarely do true earth pyramids develop.