Velika and Mala Vetrnica are collapse dolines and karst shafts located on the plateau of Velika planina, where the characteristic geomorphology of a high‑elevation karst landscape meets the influence of periglacial processes. The two dolines are interconnected, and toward the east they continue into a series of unconnected sinkholes that form a distinctive relief pattern of this part of the plateau.

Geographical setting

The dolines lie in the central part of Velika planina, at an elevation of around 1500 metres, in an area where the plateau gently inclines toward the northeast. This is a typical high‑mountain karst environment, characterised by alternating grassy pastures, rocky outcrops, and numerous sinkholes. Velika and Mala Vetrnica are positioned along the edge of a slightly elevated ridge that breaks up eastwards into a chain of smaller depressions and dolines.

Geology and formation

Velika planina is composed primarily of Triassic limestones and dolomites, heavily fractured and permeated by karstic fissures. Due to intense chemical weathering and dissolution of carbonate rocks, the surface has developed into a typical doline‑rich karst relief. Velika and Mala Vetrnica formed as collapse dolines, where the roofs of underlying karst cavities gradually gave way, creating deep depressions.

  • Velika Vetrnica is the larger and more open collapse doline, with a pronounced rocky rim.

  • Mala Vetrnica is narrower and deeper; at its bottom lies a permanent snowfield, preserved year‑round due to the shaded position and the accumulation of cold air. It functions as a true karst shaft, where cold air sinks and remains trapped.

Periglacial processes

The rims and upper walls of both dolines are subject to intense periglacial weathering, caused by repeated freezing and thawing of water within rock fissures. This results in:

  • numerous rockfalls and detached blocks,

  • gradual widening of the dolines,

  • the formation of scree slopes along their inner sides.

These processes are highly active in high‑mountain karst environments and significantly shape the present‑day appearance of both features.

Karst features of Velika planina

Velika and Mala Vetrnica are among the most distinctive karst formations of Velika planina, one of the largest and most developed high‑mountain karst plateaus in Slovenia. Alongside the many sinkholes, shafts, and collapse dolines, they are notable for their unique microclimate, which allows the snowfield in Mala Vetrnica to persist, and for the rich diversity of karst forms in their immediate surroundings.