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High mountain relief in marble in Pirin Mountains, Bulgaria: structure, specifics and evolution

The present article is focused on high mountain relief in marble, which combines glacial, periglacial and karstic morphology. High mountain karst is found in Northern Pirin (Vihren and Sinanitsa area) and central Pirin (Orelek area), the latter lacking traces of glaciation due to its low altitude. In the most representative area, Vihren part, several vast and deep cirques-uvalas were formed, which comprise a large diversity of landforms. Main factor for the specifics of relief in marble is the structure of the rock, which combines carbonate mineral content and crystalline properties; they favour both the occurrence of karstification and frost weathering. The high elevation of Northern Pirin (up to 2914 m a.s.l.), and the resulting extensive former glaciation enhanced the karst processes by weathering of the morphological surface. At present, surface karst is most developed on elevated sections of cirque bottoms, which were ice free before the beginning of the Holocene and are away from rockfall creep accumulation. A special element of glaciokarstic relief in Pirin are the summer lasting snow/ice features (glacierets and snow patches), two of which are considered centuries old, and still survive despite the temperature warming. In general, karst processes in the high mountain areas of Pirin are less developed than in the western part of the Balkan Peninsula (the Dinarides), due to the greater susceptibility of marble to physical weathering compared to limestone, which leads to a more intensive formation of regolith on the surface, and in result of the generally colder and dryer climate.