GEOMORPHOLOGY OF MOUNT BALTO

Mount Baldo is prevalently made up of carbonate sedimentary rocks, formed in marine waters, that were uplifted due to tectonic thrusts exerted on one flank by the Prealps of Brescia and on the other by the Mounts of Lessinia. This determined the great fold convex upward (anticline) that formed the distinctive structural features of the mountain.

However, the anticline of Mount Baldo is not as simple and regular as it seems at first, both because of the “knee-shaped” fold (which partially collapsed or was taken away by erosion at a later stage) that formed towards the eastern slope (which, in fact, exhibits a more complex structure compared to the western slope) and because of the numerous fractures and faults breaking the continuity of the strata, which have largely been dismantled by erosion.

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The current shape of Monte Baldo is the result of the interaction of two apparently contrasting phenomena that have actually been “working together” for millions of years in shaping the mountain: on the one hand, there is a “building” tendency determined by the uplift of the mountain range, a still an ongoing process (endogenous phenomena); and on the other hand, there is a whole range of erosive phenomena that tend to “decay” the mountain (exogenous phenomena). Some of these were important in the past, but they have now ceased their activity, though we can still see unmistakable traces of their action: for example, the erosion of rock surfaces and the formation of debris related to the presence of glaciers during past glacial periods that ended about 10,000 years ago.

The phenomena that are currently most responsible for the changing shape of Monte Baldo are mainly related to the dynamics of water: both surface runoff (which leads to erosion) and water percolating into the rock. However, on the summits the breaking down of rock surfaces as a result of alternate freeze-thaw cycles is still quite strong. The action of erosive phenomena is strongly influenced by the nature of the rocks (softer rock is obviously more subject to the erosive action of water and frost), the structure of rock types and by the pre-existing structure of the mountain, the arrangement of rock layers in particular, which determines the distinctive asymmetry of the two slopes in the summit zone.

All this determined the unique, linear-shaped outline of Monte Baldo (that stretches from north-east to south-west) with its ten peaks rising over 2,000 m above sea level (M. Altissimo -2079-, Cima delle Pozzette -2132-, Cima del Longino -2179-, Cima Val Finestra -2086-, Cima Valdritta -2218-, Cima del Pra’ della Baziva -2207-, Punta Pettorina -2192-, Punta Telegrafo -2200, Punta Sascaga -2152-, Vetta delle Buse -2155-, Coal Santo -2072-), alternating with saddles overlooking deep valleys and distinctive glacial cirques: an exceptional landscape both for its stunning panoramas and naturalistic particularities.

SCHEMA-GEOMORFOLOGIA
erosione

Along the eastern slope is a secondary ridgeline that limits eastwards the longest valley of the Mount Baldo range, called the “Valley of the Great Bear” (also known as the “Valley of Novezza”), which falls almost entirely within the territory of the Municipality of Ferrara di Monte Baldo. The Valley of the Great Bear has a particular morphology: it starts from Brentino Belluno as a narrow, steep gorge, then turns into a river valley from Spiazzi up to Cambrigar where it fans out into a large valley covered by pastures, and finally winds up as a high mountain pass, the Passo Cavallo, literally “Horse Pass” (also known as Cavallo Novezza), right above Novezza, at 1582 meters above sea level.

During the ice age in which the great glaciers of the Adige River Valley and Lake Garda formed, Novezza Valley was the site of an independent glacial tongue fed by local glacial basins: this feature was an important factor in the shaping of the valley, both because of the transport of moraine and for the erosion produced by sub-glacial melt waters. At a later stage, the valley took on a more complex shape owing to the formation of large soft rock surfaces, the obstruction of landslide boulders, and the process of fluvial erosion, connected to the ongoing uplift of the mountain.

The western slope is characterized by a greater structural uniformity (tectonic), since it was shaped by the same inclined layers that form the anticline. Also the western side, however, is not as uniform as it might seem at first glance, because of the intensive dismantling caused by erosion, greatly increased by the high “energy of the mountain” that is generated by the impressive steepness of the slope. Two geomorphological features associated to glacial erosion are located on the western slope of Monte Baldo: the “cirques” and the “flatirons” (or “blades”).

Glacial cirques are vast bowl-shaped hollows carved by the lateral hanging valleys of the large Sarca Glacier (that took up the entire basin of today’s Lake Garda during the Quaternary period). There are seven glacial cirques, two of which are double (Telegraph Cirque and Larga Valle Cirque, located between Punta Telegrafo, Punta Pettorina and Cima Pra’ della Baziva). In the upper section of the “fan” of each cirque, ice erosion exposed the layered structure of the bedrock, while in the lower sections the cirques open up into the valley with their characteristic “windows” (where the action of glacial erosion is clearly visible in the “U” shape of the valley) that extend for a long stretch with a virtually unchanging cross-section, then develop gradually into deep torrential incisions, which are mainly related to the subsequent effect of water flow and erosion.

Flatirons (called blades in Veneto, but also miters because of their similarity to the headdress of bishops) are the result of the fragmentation of a wide extension of rock surface, caused by the formation of a network of cracks (faults) that cut the rock layers into large prisms with a rectangular base; the upper parts of each prism was progressively and intensely eroded by water and ice that molded them into the characteristic pointed shapes (flatiron). The flatirons are aligned, from the bottom upwards, in parallel rows separated by torrential furrows.

Because of its limestone rocks and its caves (hypogeal phenomena), Mount Baldo displays a great variety of landforms related to the corrosive action of surface water (epigeal phenomena): dolines (sinkholes), uvala (compound dolines), karrens (furrowed surfaces) and kamenize (solution pans).

doline

Dolines: dolines are depressions in the ground, extremely variable in shape and size, caused by erosion and by the mainly chemical dissolution process of the rocks. The bottom of a doline is usually covered with red earth, either clay sediment or rubble and in some cases, it has an opening through which water is disposed of. Dolines are sometimes connected to underground vacuums (ponors) that can reach considerable sizes.

Uvala: uvala are asymmetrical and irregular depressions in the ground formed by the coalescence of several dolines. They are much larger in size than individual dolines and are characterized by sinuous and irregular floors, with various different inclines.

campi-solcati

Karrens (“furrowed surfaces”): karrens are rocky surfaces molded by the weathering action of rainwater. Erosion occurs by processes that are both chemical (dissolution of calcium carbonate, which these rocks are composed of) and physical (rainwater or melting snow runoff). Water flows over a rocky surface that is eroded along the lines where dissolution is most intensive. These furrows develop parallel to each other because of the uniformity of the slope.

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Kamenitza (“solution pans”): kamenitza are depressions in the rock surface, measuring a few decimeters wide and a few centimeters deep, that often retain residual water on the bottom. They are formed by the corrosive action of the carbon dioxide contained in stagnant water (and not by running water). Kamenitza start off as small depressions that grow progressively larger.