The karst - Orto botanico 'Pellegrini - Ansaldi'

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The karst of the Apuan Alps

The Apuan Alps represent one of the most important karst areas of Italy; there are almost 1000 caverns. Among the 50 deepest caverns of the peninsula, 17 are Apuan ones, as well as among the 50 largest in length, 8 are Apuan ones. The karst represents one of the most known geological processes for the ability to create spectacular shapes and landscapes. The majority of the karst phenomena is due to the action of the water of meteoric origin on the rocks, especially of the carbonate type (limestone and dolomite). For the calcareous nature of the rocky outcrops, for the permeability due to the strong fracturing and the high rainfall that characterise them, the Apuan Alps present impressive karst phenomena. The rainwater before reaching the rock is enriched by carbon dioxide going through the atmosphere or filtering through a soil, which is rich in substances of animal and vegetal origin (humus). This gives it a weak acidity that causes a dissolving activity of the limestone according to the following chemical reaction:
CaCO3 + H2O + CO2 = Ca(HCO3)2
In this way little existing fractures in the rock become wider over time, giving rise to different forms of karst erosion, like furrowed or grooved fields, sinkholes, wells and caverns. Although high amounts of rain, in the Apuan Alps there are not significant permanent waterways: actually, these mountains are rich in water, but it especially flows in the subsoil, through wide and advanced underground karst systems, and then emerge in correspondence with freshwater springs. These are widespread along the perimeter of the carbonate structures, in correspondence with the contact among the karst rocks and the impermeable underlying substrate, and from here the waters percolated deep return outside. The freshwater spring system is affected by marked seasonal variation.
In the surface, the karst landscape is characterised by the light colour of the limestone rocks and by an uneven morphology caused by the strong fracturing; this determines the infiltration of waters in depth, and as a consequence the aridity of the environment and scarce vegetation. A wide karst area with many sinkholes, fractures and wells is the Carcaraia, on the northern mountainside of the Tambura mount; the sinkhole morphology characterise some areas of the Sagro Mount and of the northern mountainside of the Fiocca Mount.
On the northern mountainside of the group of the Panie, it is possible to observe a typical Apuan karst environment of furrowed soils, represented by the mountain of the Vetricia. Also known with the names of “Karren” or “grooved soils”, it is composed of grooves more or less parallel, deep from some centimetres to some meters and separated by flat and rounded ridges.
The most fascinating shapes due to the karst phenomenon are those underground. In the subsoil there are a set of caves that have different types of development; from those sub-horizontals (caverns and tunnels) to those of inclined axis of elongation (wells and abysses). They have different shapes, dimensions and aspects that mostly depend on the manners of water circulation, which it opens up the road in the limestone mass not only with the chemical action, but often also with the mechanical action due to its movement and with the presence of collapse processes that occur in the vaults of the caves. Wells are frequent, that are up to 50-100 m of deep; two of them over 200 m (The Enrico Revel abyss or Buca della Vetricia, big chasm formed of one well that is deep 316 m).
One of the peculiar features of the karst caverns is that they are adorned with carbonate concretion that form stalactite, stalagmite, rib vaults, columns etc. that make the underground karst landscape wonderful and surreal. Their formation is due to the slow deposit of calcium carbonate from the precarious waters to dripping or thin rib vaults.
In the Corchia Mount (1676 m), it is very remarkable the Corchia Cave (or Eolus Cave), with more than 70 km of total development and 1210 meters of difference in altitude, that is one of the biggest Italian caverns for longitude (1800 m) and even second in the world for deep (805 m).
Speleomantes ambrosii (Lanza, 1955) subsp. Bianchii is an Apuan endemic subspecies that prefer the humid and shaded areas and the karst environment of caverns and ravines is its ideal habitat for its survival.
L'ORTO BOTANICO PIETRO PELLEGRINI, Un giardino alpino nel Parco Regionale delle Alpi Apuane
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