Karst Phenomena

Let's talk about karst phenomena

The surface manifestations of the karst phenomenon can be easily observed in the Geopark area. Less visible but widespread are deep morphologies such as caves, wells, abysses, and springs. Among the surface karst forms, there are microforms, also called Karren and macro forms, such as dolines.

All forms related to the karst phenomenon are created by water, which, under certain conditions, can "corrode" the rocks, in particular, the carbonate ones, that is those made of calcium carbonate. The "corrosion" activity is more significant when the temperature is low, and the concentration of dissolved carbon dioxide is higher.

As conditions change, the opposite phenomenon can occur, namely the deposition of calcium carbonate. And thus concretions are formed, such as stalactites, stalagmites, columns, flowstones, and curtains.

In addition to corroding rocks, water also plays a mechanical erosive action called modelling, by smoothing and digging rock walls.

Karstificable rocks

In the territory of the Geopark different types of karst rocks emerge.

Limestone emerges widely in the Carnic Alps, where they form, for example, the massif of Monte Coglians, Pizzo di Timau and Zermula, as far as Mount Cavallo in Pontebba.

The karst systems of more significant development and depth, in fact, are found in the area of the Crete of Rio Secco and of Mount Cavallo in Pontebba, with 5 km of development and 700 m of depth.

Other Karst rocks are the gypsum rocks, which can be seen in Val Pesarina, Val Calda and Val Pontaiba: in fact, the first cave in gypsum rock explored in the region is located near Ligosullo.

The Karst phenomena in the Carnic Alps and Prealps: a work in progress

The lithology of the Geopark area is so complex and variable that it displays many karst phenomena’s aspects: not only the most classical phenomena, i.e. those found in carbonate rocks but also those in gypsums and conglomerates. A natural cave developed in travertine was studied in Val Pesarina, and at Forni Avoltri it was possible to date the perennial ice in a cave of the Pic Chiadenis!

On the Italian side, the first speleological exploration of which we have news dates back to August 25, 1875, when the members of the Tolmezzo Branch (that later became the Friulian Alpine Society) of CAI (The Italian Alpine Club) made an excursion to the Fontanon del Riu Neri, in Val Tagliamento, near Caprizzi. It was followed by the explorations of Marinoni, Marinelli, Lazzarini and Coppadoro until the publication in 1915 of "Caves and Chasms of Friuli" by Giovan Battista De Gasperi, which is still a fundamental text for the study of the karst phenomenon in Friuli.

After an isolated study by Anelli in the 1930s on the cavities of Val Pesarina, it is necessary to wait until the 1960s for the explorations to start again, primarily conducted by the Trieste Speleological Group and by the Friulian Hydrological Speleological Circle. In more recent years, the Gortani Group explorers from the CAI Branch of Tolmezzo continued the exploration work.

Inside the caves: minerals and chemical deposits

The water that creates a cave is also the architect of its filling, which occurs not only with the transport of sands and clays but also through a slow chemical accumulation.  In the high mountain karstic areas, the conditions are such to allow mainly the dissolution of rock, while the deposit is scarce. For this reason, in these caves, there are large chambers and conduits, while stalactites and stalagmites are rare.

Karst phenomena in the Geopark area

The most impressive karst phenomena you can see in the Geopark area are:


  Sinkholes and Karrens