With regard to Morpholithology, the great variety of rock formations generates a series of selective-type relief forms, with steep walls and sheer peaks in marked contrast with milder slopes and forms. In particular, alternances of compact rock types with weaker ones or with rocks of different origin (sedimentary and igneous) or the proximity of rocks with different compositions have all created varied and contrasting morphology, characterised by mild slopes, ledges, steps, steep rock walls and uniform mountain massifs.N-S geological section of the Gardena pass. Legend: CgM, Wg, SC, MB and R - mainly clastic formations; PtS and DP – dolomites. (After Carton & Pelfini, 1988, modified)

This is the case, for example, of arenaceous-marly slopes underlying steep walls of compact dolomite or calcareous shelves, or when marlyclayey beds are interposed between dolomite rocks. A typical example is offered by the ledge of Sella Group, where the Raibl Formation interposed between Dolomia Cassiana at the bottom and Dolomia Principale at the top shows a low slope gradient in comparison with the sub-vertical dolomite walls. The location of some Dolomite passes is also connected to the presence of more easily erodible rocks. This is, for example, the case of the Gardena Pass, Sella Pass, Pordoi Pass and Campolongo Pass, which are shaped on ductile rocks weaker than the surrounding dolomites. In the Dolomite region there are characteristic and spectacular examples of carbonate structural slopes of primary depositional origin which have not been influenced by tectonics. These are the original slopes which connected the top of the Mesozoic shelves with the floors of the proximal basins.

Slope karren on Alpe di Fanes

These Triassic submarine shelf morphologies stand out in the neighbouring landscape, isolated by differential erosion of marly-clayey and pyroclastic rock types in the surrounding basins. Examples of these situations can be observed on the eastern wall of the Sciliar plateau, the eastern slope of Mt. Cernera and the north-western face of Pale di San Lucano. A very particular landscape characterises some mountain groups where rocks have been sculpted, cut and weathered by a series of karst and glacio-karst phenomena. Basically, these phenomena occur in the higher parts of the valleys and are mainly located in high carbonate massifs (1200 to 3000 m). Their developmen is also linked to the variability of calcium carbonate, magnesium and impurities present in the various rock types. In some places, alluvial or solution subsidence dolines are also found. From a morphological standpoint, karst phenomena are prevalent in plateaux, cirque floors or glacial hanging valley floors, on level summit areas, scarps and ridges. The most typical karst landforms in the Dolomites are large glacio-karst depressions, blind valleys, fluvio-karst dry valleys, dolines, glacio-karst karren, landslide scree heaps with karren and slope karren. Numerous other karst landforms are found within the depressions. The most typical examples of glacio-karst depressions are found at Lago Grande di Fosses, Lago Remeda Rossa di Fosses, Tondi di Sorapis, Lago Nero on Monte Popera, at Alpe dei Piani, north of Monte Paterno, in Pale di San Martino near Forc di Sopra, Buse Alte, Sponde Alte, Buse di Coll’Alto, Riviera Manna and near Piani Eterni, in Vette and Feltrine Dolomites. Perennial or temporary lakes are often present inside the depressions. The most typical example of a blind valley is Valle del Piano dell’Antelao: it is a hanging valley, on the floor of which there are several sinkholes near the terminal step. Geomorphological schematic map of the NE Dolomites.

The mountain groups with very spread and typical karst langforms are mainly in the Systems of Pale di San Martino, San Lucano, Dolomiti Bellunesi e Vette Feltrine, of Dolomiti Settentrionali and of Dolomiti di Brenta. In particular, dolines are numerous: in Alpe di Fosses, there are dolines with diameters ranging from 50 to 150 m. However, the forms present in Pale di San Martino are smaller in size, thus creating cylindrical pits with diameters of about 1 to 10 m. The margins of these forms have often been modified by periglacial processes that are particularly effective in these environments. Karren are also very frequent: they occupy wide extensions, mainly on slightly inclined slopes, in highland plains and floors of glacio-karst depressions. On rocks polished by glaciers, other characteristic forms have also been sculpted, including solution runnels of various types (rectilinear ridge runnels, in small steps, meandering), solution pans (kamenitza), solution plains, heel-print karren, grikes several decimetres wide and many metres long, cavernous karren and interstratified layer pits. There is a remarkable group of hundreds of rectilinear furrows on a ridge made up of a very inclined stratum at Alpe di Fosses. Pits are also present in the Dolomite mountain groups and several of them are also very evident. However, generally they are not particularly deep. Their presence is often revealed by local names such as bus, busa, buche and giasère. Among the most developed pits, the Grotta di Franzei (Roccapietore) should be mentioned, with its extent of 472 m and depth of 158 m, almost always blocked by ice, the Meander F2 Alpe di Fosses with its spatial extension of 360 m and depth of 152 m and the F 10/F 11 Meander System at Alpe di Fanes. Other subsurface forms are found also in the mountains of the Systems of Pale di San Martino, San Lucano, Dolomiti Bellunesi e Vette Feltrine and of Dolomiti di Brenta. Apart from the aforementioned geo-structural factors, relief form modelling also depends on morphogenetic agents, such as force of gravity, water, wind etc., and on climate conditions characterising a certain territory. These conditions directly influence morphogenetic agents through changes in temperature, humidity, atmospheric pressure etc. Indeed, relief break-up processes, physical and chemical changes affecting the rocks, accumulation of detritus and so on can either be favoured or hindered. Climate exerts also an indirect influence through vegetation, which can preserve the soil from mechanical erosion phenomena; it can also start biochemical weathering processes and therefore trigger pedogenesis.

Small glacier on Vezzana-C.- Pala_P.S.Martino