Description
The main cavity descends for a total height difference of about 4 metres. The first 9 metres of linear development are open, with the north side sub-vertical and the south side delimited by the lower plane of a large boulder, sloping and forming a sort of "roof" over which some robust plants (fir trees) grow. The last 5 metres of the cave, entirely covered, develop between the landslide boulders, forming a cave with a section varying in width from 4 m to 50 cm, progressively decreasing towards the interior; the height also progressively decreases, from 6 - 7 m to 1 - 1.5 m. The bottom is strewn with detritus and rocky clasts mixed with leaves.
Geology and environment
The north-west flank of Monte Biaena is formed in the upper sector (up to about 1300 m) by a monocline of strata of the Middle and Upper Eocene Nago Limestone Formation. These are grey-yellowish limestones and bio-calcarenites. The significant inclination of the strata caused the formation of a landslide collapse in the postglacial period, generating a considerable accumulation of large boulders at the foot of the slope (Alpine Postglacial Synthema; Upper Pleistocene - Holocene). The not very recent or current age of the landslide is evidenced by the presence of highly developed vegetation, consisting of fir forest and substantial moss and undergrowth cover.
It is in this landslide deposit that the various cavities known as 'Giazzere' open up, and among them the most significant, the Stenone Cave.
From a strictly geomorphological point of view, these cavities are not really included in the speleological cadastre of the Province of Trento. However, in consideration of the relevant historical and scientific importance of Stenone's Cave, due to the fact that it represents one of the first testimonies of the study of a natural cavity in our province by the famous naturalist Niels Stensen (Nicolò Stenone), it is justified that it should be maintained in the cadastre as a cave to all intents and purposes, with the number 313 V.T. assigned in the early decades of the 1900s.
History and Studies of the Giazzera Cave (Stenone Cave) in Val di Gresta
The 'Giazzera' (also known locally as the 'Ice Cave') opens in Gazz at an altitude of 1165 metres, on the western slope of Monte Biaena, just above the village of Ronzo. It is not a true karstic cavity as it was formed between large blocks of landslide from the Quaternary period, a landslide that probably originated after the retreat of the glacier due to the collapse of the calcareous strata, which at this point present a moderate slope. It is not particularly large or deep: the main chamber is a dozen metres long and the entrance, roughly triangular, does not exceed 8 metres on either side. It does, however, have a characteristic that makes it almost unique among the natural phenomena of the region: in summer, in the innermost parts, discrete quantities of ice form and accumulate, which remain until the cold season arrives. It is precisely this peculiarity that has made the cave known since ancient times (it was used as a kind of 'natural refrigerator' almost until the First World War). In the 17th century (in 1671 to be exact), the Danish scientist Niels Stensen (Nicolò Stenone), during one of his many trips to Italy, climbed the Bus de la Giazzéra and completed what can be defined as the first scientific exploration of a cave in Trentino. Having graduated in medicine from the University of Kopenhagen, Stenone (1638-1686) in the second half of the 17th century had begun a long series of research trips across Europe, leading him to meet and get to know the most outstanding scientists of the time. In the early 1770s he arrived in Italy and immediately established relations with Malpighi, Redi and Vincenzo Viviani, Galilei's disciple. He was often a guest of the Medici family in Florence where Ferdinand II appointed him court physician and entrusted him with the mineralogy and palaeontology collections of the Pitti Palace. Florence became the starting point for his excursions along the Peninsula. In 1671, he travelled to the Alps and, in early summer, we find him as a guest of Francesco di Castelbarco in the castle of Gresta. There, he gathers the first information about the Bus de la Giazzéra, under the landslide on the Biavena slope, whose microclimate allows for the formation and preservation of ice in summer. The occasion is the right one to integrate his studies around the long-standing dispute on "Anti-peristalsis" and its applications in the biological and geological fields. He traced the plan of the cavity, carefully studied its fissures, air circulation and ice deposits, communicating his observations to Grand Duke Cosimo III in a long letter in June of the same year: "...The mutation of the weather took away all hope of seeing, before my departure, the freezing of the water in the cave above Gresta, so as not to omit anything that might serve to acquire any possible information, I returned to the cave after sending my last letter to Your Serene Highness and I took a map of it, as the irregularity of its bottom could be reduced to a plane, and I made various profiles, considering the formation of the mountain above it. While for this purpose I researched all parts of the cave, I observed inside a certain wind whence the water of the cave can be said to be chilled partly by the cold air that passes over it, partly by the coldness of the stones that serve as its base ...'. His acute observations precisely reveal the mechanism of summer ice formation: when the temperature outside the cave increases in spring, the humidity of the air circulating between the rockslide boulders also increases. The vapour can condense and freeze even until late summer due to the very cold temperature of the rock and the air currents themselves.
The exploration of the 'Giazzéra' had not yet been completed, and he was already thinking of another, larger cave with a similar phenomenon on the Grigne, in Moncodeno ('I feel that above Lake Como there is a cave of the same nature, and since I am so close to it, I thought it best to take advantage of the situation ...'). Fortunately, the drawings of the Ghiacciaia di Moncodeno remain, whereas the Bus de la Giazzéra in Val di Gresta, the first certain evidence of natural cavity reliefs in Trentino, has been irretrievably lost.
Access route:
Take the Val di Gresta provincial road no. 88, about 800 m after the village of Ronzo, proceeding towards Bordala, at Prà del Lago (altitude 1070), turn south along Via Biaena, which climbs slightly, passing between some houses and arriving, shortly after the last houses, at a car park with a beaten earth surface (altitude 1085). From here, continue southwards along a forest road for about 5 minutes, then take a path that climbs to the left (south-eastwards), on which there is a signpost for the 'Giazzera'. The path initially makes a wide loop to the east along a ridge and then continues true south-west parallel to the slope, passing several cavities between the landslide boulders marked by wooden signposts ("Giazzere"). After about 15 minutes, having passed a short ramp via a few bends in the path, you reach the largest Giazzera, or Stenone Cave, located on a sort of ledge and also marked by a wooden signpost.
Cave main data:
Municipality: Ronzo - Chienis
Location: 995 m E + 21° S from the Church of Ronzo, 850 m W + 32° N from Cima di Monte Biaena (1617.57 m asl)
UTM national system: X= 1652241;Y=5083367
UTM WGS 84 X= 0652212 ; Y=5083344
Long 01° 29' 25.14" W - Lat 45° 53' 10.18"
Altitude 1165 m asl
Bibliography
Corrà, Giuseppe
Steno's itineraries in the Tridentine Pre-Alps (V. di Gresta) and Lombardy (Alpe di Moncodeno) / Giuseppe Corrà, Mario Ferrari. // IN: Dissertations on Steno as geologist / ed. by G. Scherz. - Odense : Odense university press, 1971. - P. 174-203
Corrà, GiuseppeOsservations of Steno on the formation of summer ice in two mountain caves in the Pre-Alps of Trento and Lombardy / Giuseppe Corrà, Mario Ferrari. // IN: Natura alpina. - Trento. - A. 24 (1973), no. 2 ; p. 103-126
Decarli, Riccardo-Ischia, Marco-Zambotto, Paolo
Le origini della speleologia trentina tra uomini illustri e celebri istituti / Riccardo Recarli, Marco Ischia, Paolo Zambotto. // IN: Speleologia. Milan. A.23, no.46 (Jun. 2002); p. 23-31
Ferrari, Mario
The first scientific exploration of a cave in Trentino / Mario Ferrari. // IN: Natura alpina. - Trento. - A. 8 (1957), no. 1; p. 9-16
Scherz, Gustav
To beromte grotter in Alperne. // IN: Naturens verden. - Kobenhavn. - 1950
Scherz, Gustav
Nicolai Stenonis epistolae et epistolae ad eum datae. - Kobenhavn ; Freiburg : [...], 1952.
Scherz, Gustav
Vom Wege Niels Stensen : Beiträge zu seiner naturwissenschaftlichen Entwicklung. - Kobenhavn : Munksgaard, 1956. - 348 p. - (Acta historica scientiarum naturalium et medicinalium / Bibliotheca Universitatis Hauniensis ; 14)
Scherz, Gustav
Nicolaus Steno and his Index. - Kobenhavn : Munksgaard, 1958. - 314 p. - (Acta historica scientiarum naturalium et medicinalium / Bibliotheca Universitatis Hauniensis ; 15)
Scherz, Gustav
Pionier der Wissenschaft : Niels Stensen in seinen Schriften. - Kobenhavn : Munksgaard, 1963. - 348 p. - (Acta historica scientiarum naturalium et medicinalium / Bibliotheca Universitatis Hauniensis ; 18)
Scherz, Gustav-Pollok, Alex J. Steno : geological papers. - Odense : University press, 1969. - (Acta historica scientiarum naturalium et medicinalium / Bibliotheca Universitatis Hauniensis ; 20)
Zambotto, Paolo
The precursors of speleological research in Trentino : from Nicolò Stenone (1671) to Antonio Daldosso (1873). IN: International symposium on the protohistory of speleology : Città di Castello 13-14-15 September 1991. - Città di Castello (PG) : New Prhomos, copyr. 1993. - P. 25-28
