Nationwide aerial laser scanning reveals relict rock glaciers and protalus ramparts in Slovenia

Abstract. In 2015 the nationwide aerial laser scanning (lidar) of Slovenia became publicly available. These data enable a wide range of detailed geomorphological studies, also in areas that are less accessible or covered with dense vegetation. This makes it possible to identify potential rock glaciers and protalus ramparts in the Slovenian mountains. The laser scanning products, the grey-shaded terrain model and the classified point cloud were used to identify and measure these features. All the mountainous areas at elevations of approximately 1200 m above sea level (a.s.l.) were evaluated. During the Alpine Late Glacial period these were in glacial and periglacial conditions. The mountain ranges of the Julian Alps, Karavanks, Kamnik-Savinja Alps, Pohorje and Dinaric mountains (Trnovski Gozd and Snežnik) were evaluated. Twenty potential rock glaciers and eight potential protalus ramparts were found. They are the most abundant in the Karavanks, followed by the Julian Alps, with one potential rock glacier also on the Snežnik plateau. The majority of the potential rock glaciers are probably relicts, due to the heavy vegetation cover, the low mean elevations (between 1040 m and 1850 m a.s.l.) and because their slopes are directed more towards southern directions (65 % of rock glaciers). The identified rock glaciers rarely exceed 600 m in length. The terminus slope angles of the identified objects are from 20° to 40°. Three of the identified protalus ramparts can be regarded as relict, due to the total vegetation cover; the remaining five can be regarded as intact. The potential protalus ramparts are found at elevations between 1220 m and 1950 m a.s.l. All the identified protalus ramparts are directed towards southern directions, with terminus slope angles from 30° to 40°. The spatial distribution of the discussed permafrost objects in Slovenia with regards to the bedrock composition presented on the geological map of Slovenia (scale 1 : 250 000) reveals that 75 % of all objects can be found in thick-bedded Dachstein limestones with transitions to dolomite, while almost all the remaining objects are found in Triassic dolomite.