Little information exists regarding the geomorphologic characteristics, spatial distribution and genesis and activity of rock glaciers in the Balkan Peninsula. A total of 224 rock glaciers were identified in four major mountainous regions (Dinaric Alps, Rila and Pirin, North Macedonia, Pindus and Parnassus), covering a total of 16.74 km². Most of the rock glaciers are considered relict and have fronts between 1412 and 2645 m. In the Balkan Peninsula, rock glaciers are not uniformly distributed, but rather concentrate in several mountain ranges (e.g. Pirin, Rila, Prokletije and Śar). Climate, elevation, aspect and lithology are the key factors controlling rock glaciers’ distribution in the study area. The vast majority of the rock glaciers (73%) are concentrated in the northern quadrant. Statistical analysis revealed that the size of the rock glaciers can be explained to a certain degree by the characteristics of the contributing area (e.g. its extent and elevation range), climate, aspect, altitude and slope. In Pirin Mountains the density of the rock glaciers and the mean specific area are considerably higher than in the other mountain ranges. Based on palaeoclimate reconstructions and climatological records we infer that at least three generations of rock glaciers developed in the Balkan Peninsula. It is hypothesized that above the 0°C isotherm of mean annual air temperature in the Rila and Pirin Mountains, intact rock glaciers may survive to present-day climatic conditions. https://www.tandfonline.com/eprint/TCEBXHSSXJCJVK4JKBIY/full?target=10.1080/04353676.2020.1809905
The proposed research addresses the problem of permafrost occurrence for the first time in the highest mountains of the Balkan Peninsula. The likely/unlikely presence of ice-rich permafrost in 13 rock glaciers in the Rila and Pirin Mountains was investigated using thermal measurements (e.g., ground surface temperature monitoring, measurements of the bottom temperature of snow cover and late summer alpine spring water temperature measurements) and ground penetrating radar surveys. Based on the thermal records, intact rock glaciers appear likely above 2450m on north-facing slopes, where incoming solar radiation is small and the pronounced shadow effect of the ridges allow an extended duration of snow cover. Thermal results revealed that the coarse blocks influence the near-surface energy exchange fluxes, confirming the significant influence of the cooling effect of high-porosity unconsolidated debris deposits. The intense ground overcooling during the early winter is mainly the result of temperature-driven air convection, whereas in late winter, the low thermal conductivity of the porous boulder mantle below a thick snow cover can cause ground cooling. Furthermore, the reduced insolation below the late-lying snow patches prevents the ground from heating up during the warm season. At most of the sites, the winter equilibrium temperatures are lower than −3 °C and the mean annual ground surface temperatures are negative or close to 0 °C. Ground penetrating radar (GPR) measurements detected permafrost occurrence in three rock glaciers underneath a thick active layer (4–10 m). Forthcoming research on this topic is needed to evaluate more carefully the importance of local conditions for permafrost preservation.