The calcareous rocks of the Karst plateau were formed between 120 and 40 million years ago on the seabed of an ancient, warm, tropical sea. The marine origin of these rocks is clearly proven by the types of fossils that can be found inside, such as the common presence of Rudists, a type of mollusk that went extinct together with the dinosaurs towards the end of the cretaceous period (approx. 65 million years ago). The museum showcases various fossil findings coming from the Trieste province, amongst fossilized fish such as an ichthyolite from Trebiciano (Turonian stage, 90-75 Mya), a gastropod of the plesioptygmatis species and a bivalve of the neithea species, both from Monrupino (Albian/Cenomanian stage 110-90 Mya).
The museum exhibits various examples of principal speleothems that characterize the underground environment of the Trieste Karst, amongst which the characteristic pisolites or “cave pearls”, spheric or elliptic concretions made out of layers of carbonate laminae around a single grain. Furthermore, the cross section of a 140cm high stalagmite allows you to observe the accretionary layers of calcite deposition, narrating a formative process that started 55.000 years ago. A special place within the showcases is dedicated to calcite crystals, a mineral that frequently forms in cave environments as part of the calcium carbonate precipitation process.
The discipline of modern speleology was born in the 19th century, thanks to the curiosity and the courage of the first pioneers. Rudimentarily equipped and exposed to the dangers of underground exploration, they were the first to venture into the holes, caves and abysses under the Trieste Karst. Our museum seeks to narrate this story through exhibiting of material and equipment, starting from the early days of the discipline through to modern times.
It was an Austro-Hungarian speleologist named Anton Frederick Lindner who wrote history for the modern-day discipline on the Trieste Karst: Engineer by profession, he tried to resolve one of the most pressing issues affecting the rapidly expanding city of Trieste in the 19th century – the lack of drinking water. Following his own intuition, Lindner would take to elaborating a plan to look for the underground course of the Timavo river, which can still be found under the Karst, and use its waters to supply the city. He started searching the many caves of the Karst plateau, hoping to intercept the underground river somewhere in the bowels of the Karst. Finally, after many tries, he managed to reach the Timavo by descending deep down into the Abyss of Trebiciano, where the river water flows in a depth of 320 meters under the surface, too deep to bring up to the surface, unfortunately condemning Lindner`s great plan to failure.
“Waste not want not” may have been the principal motto of speleologists from the 19th century through to the 1970s! In order to make do with limited budget and restrictive technological means improvising solutions became a necessity, and much of the equipment used was recuperated from other sources. In this sense, amongst our exhibits, we can also admire WW1 helmets “converted” to speleological helmets with candle holders, or WW2 helmets fitted with bicycle lamps amongst other “homemade” equipment.
Quaternary fauna has left many traces in various sites across the Trieste Karst, delineating the presence of a vast array of different species. The museum exhibits numerous bone findings from megafauna species such as Ursus spelaeus (Cave Bear), Panthera spelaea (Cave Lion), Megaloceros sp. (Giant Elk), Palaeoloxodon antiquus (Straight-tusked Elephant), Hippopotamus sp. (Hippopotamus), Cervus elaphus (Red Deer), Stephanorhinus cf. hundsheimensis (Rhinoceros), Bison priscus (Steppe Bison), Equus cf. ferus (Wild Horse) and Pachycrocuta brevirostris (Cave Hyena). The most documented of these species is undoubtedly the Cave bear, a plantigrade species widespread in Europe during the Pleistocene period. The exhibited artefacts come straight from some of the principal Pleistocene archeological sites on the Trieste Karst, such as the ossiferous breccia of Slivia, the “Grotta del Bue” and the “Piccola Pocala”, while the complete skeleton of Ursus Ingressus, a formerly common species of central Europe, was acquired from the Ural Mountains.
Cave bears were once very common on the Trieste Karst. Appearing around 600.000 years ago until their extinction around 30.000 years ago, they were of similar size to the largest present-day bears, and in some cases even bigger! Their molarized teeth and strongly developed sagittal crest for accommodating chewing muscles indicate a diet that was mostly plant based. These bears would spend the winters hibernating inside caves and would often also die here during their sleep if they did not manage to accumulate sufficient fat reserves during the summer. In fact, numerous bone findings stem from inside caves of the Trieste Karst, such as the “Grotta del Orso”, “Grotta Pocala”, “piccolo Pocala”, “Grotta dell’Alce”, “Grotta Cosmini”, Grotta Gigante, “Grotta degli Orsi” and the Sistiana Quarry. The Cave bear’s extinction may possibly be due to climatic cooling and a consequence decline of vegetation productivity.
The dawn of the human genus, the Paleolithic, is characterized by the exclusive use of stone tools. Scarce findings of artefacts from this period in the Karst caves may point to a merely sporadic human presence, possibly connected to hunting expeditions. The exhibition displays materials from the “Grotta San Leonardo” where few instruments of splintered stones (scrapers) where found, and from the “Riparo di Visogliano”, where the most ancient human traces of the Trieste province were discovered, dating back to Homo heidelbergensis (400.000-220.000 years ago).
During the Mesolithic period split stone tools gradually start to evolve into more complex forms (microlites) reflecting new ways of human behavior and way of living as a consequence of improving climatic conditions. The production of arrowheads and tips to mount onto shafts indicate a greater selectiveness of species being hunted meaning that also smaller species than in the past could be targeted, while the presence of numerous gastropod shells (Osilinus turbinatus, Ostrea edulis) suggest that these microlites might have also been used to open shellfish. The Mesolithic period is documented in about 15 caves on the Trieste Karst, and the museum’s exhibits stem from the “Grotta della Tartaruga” close to the Grotta Gigante.
A decisive improvement in climatic conditions over the millennia following the end of the Ice Age lead to the so-called Neolithic Revolution which marks the gradual abandoning of nomadic and semi-nomadic lifestyles towards a productive economy based on agriculture and animal husbandry. This period is especially characterized by the introduction of ceramics: Ollas, vases, hand-modeled cups and bowls used for the preparation and conservation of food. During the Neolithic, human population of the Karst caves was at its greatest, and many caverns were used as proper houses, testified by the common presence of ceramics. The showcases exhibit findings from Grotta Gigante, “Grotta dei Ciclamini”, and “Grotta della Tartaruga”.
The human conquest of metalworking is conventionally viewed as the passage from prehistory to protohistory in which social structures passed from clan-based societies (parental groups) to chiefdoms (communities with chiefs/leaders) and finally to the first states (societies with political and juridical bases). From the Copper Age (4.000 BC) all the way through to the late Iron age (300 – 200 years BC) the “Castellieri” appeared on the Trieste Karst, hilltop fortifications with one or more circular defense walls. The communities of the Castellieri cultures were farmers and herders and used to live inside their fortifications in huts of which few traces remain. During this time the Karst caves, now no longer serving as primary habitations, became used mainly as pastoral shelters for livestock, which is testified by archeological findings of organic remains from goats and sheep together with ceramics and some metal artefacts.
In the 2nd century BC, the Roman Empire expanded towards the Istrian peninsula which brought on a radical transformation from the culture of the Castellieri to a new order centered urban centers and the foundations of new Civitas and colonies as well as more rustic Villae, or farmhouses. In this way, according to the principles of the Centurion, the Trieste Karst began to be populated by numerous roman farms. Artefacts from this period indicate that the frequentation of Karst caves was now intermittent, being used as livestock shelter and also as sources of water and clay. Findings often include ceramic objects associated with terracotta Ollas, oil lamps, coins, metal tools and bones from domestic animals stemming from periods between the 1st and 4th century AD. The museum hosts some of the numerous Roman findings from the “Grotta del Mitreo”.
“Deep in the face of that Euboean crag A cavern vast is hollowed out amain, With hundred openings, a hundred mouths (…) Virgil, Aeneid, VI, 42-53. This is how Virgil imagines the entrance to the underworld, the Kingdom of the dead, a cave on the flanks of a mountain. Caves since ancient times in fact have captured the awe and imagination of people leading to mistic and esoteric interpretations by strongly superstitious ancient societies. In this way we often find them as places used for burials (such as the “Grotta Preistorica di Duino Aurisino), places for offerings to the gods of the Underworld (“Antro delle Sorgenti di Bagnoli”), or, as in the case of the “Grotta del Mitreo” near Sezana, sanctuaries dedicated to the Roman cult of Mitra.
From the 3rd century AD, the territory of Roman Trieste (Tergeste) became subject to various raids and incursions. Quadi, Marcomanni, Goths, and other Germanic tribes wreaked havoc across the Roman provinces of Venetia and Histria, forcing the inhabitants to occasionally seek refuge inside the caves. The findings of various small treasures and groupings of voluntarily hidden coins dating from the 4th and 5th century AD testify these insecure and unstable times.
The enormous devastation and consequent famines caused by the Gothic war (535-553 AD) radically transformed the italic landscape leading to a depopulation and decline of the cities. The centuries old Roman roads and agricultural facilities, now without maintenance, where gradually replaced by the advance of swamps, woodlands, and uncultivated areas. The decidedly rural high medieval period did not leave many traces inside the Karst caves, even if an intermittent use as livestock shelters seems possible. During the late medieval (12th-15th centuries AD) however findings in terracotta however suggest an increased human presence, possibly due to the need of protection during Hungarian and Turkish raids.
Grotta Gigante’s pendula were installed at the beginning of the 1960s under the supervision of professor of Geophysics A. Marussi with the aim to measure all the deformations of rock affecting the cave, and since 1960 it has been delivering uninterrupted data. Le station is owned and managed by the Department of Geosciences of the University of Trieste under the scientific responsibility of prof. C. Braitenberg, and it also receives subvention from the Italian Institute of Geophysics and Volcanology. The data collected represents the horizontal offset movement between two fixed points, on the ceiling and on the floor of the cave. After having been processed, this data is able to deliver precious information about the movement of our Earth’s crust. To the human experience the Earth’s crust, apart from occasional earthquakes, seems static and immobile. This however is not the case: In reality the crust is subject to a multitude of movements with many varying causes and effects. These deformations are slow and happen over long timescales need to be studied over many years by using instruments of extreme sensibility that are able to measure such small movements. Unlike seismometers which are made specifically for observing seismic waves that travel fast through the terrain, geodetic pendula instead measure the slow but constant permanent deformations of the Earth’s crust which are caused by mechanisms such as plate tectonics, tide effects, filling up the Karst aquifers after periods of precipitation as well as faster movements induced by earthquakes. Various types of movements on the pendula can be subdivided into various components: Variation of inclination, shear deformation, rotation of the entire cave as well as horizontal oscillations caused by seismic waves. Placing the geodetic pendula inside such a vast underground cavity revealed itself as a good choice owing to the geomorphologic properties of the great hall that allow for amplification leading to a resolution of up to ½ nanoradian*. To the visitor’s eyes, the geodetic pendula present themselves as two long plastic tubes suspended from the ceiling that end in the roof of a little house located on the bottom of the cave. In reality, the actual horizontal pendula are hidden inside this building, while the two plastic tubes are merely for protecting the fine cables against water etc. The technical principle of the pendula’s instillation is known as “Zöllner bifilar suspension”, and each pendulum consists of 1.5 meters long horizontal metal rod attached both to the ceiling and to the bottom of the cave with metal wires. Each pendulum can swing freely around an imaginary center point located in a vertical axis between top and bottom attachments. The two pendula are fixed in a 90° angle to each other (One oriented N-S and the other E-W) as to measure both components of rock deformation. Each deformation of the caves therefore corresponds to a small rotation around the axis of both pendula which is an amplification of the movement undergone by the deforming rock. Two charge-coupled devices (CCDs) measure the angle of rotation by shooting a laser beam that is reflected by a small mirror fixed to the horizontal pendulum. The received digital signal is thereafter transmitted to the surface by cable to be processed and analyzed by the researchers.
Data obtained by Grotta Gigante’s geodetic pendula have been used to study some of the biggest earthquake events that have been registered such as the Chile earthquake of 1960 (magnitude 9.5), the 2004 Indian Ocean Earthquake (magnitude 9.3) and the 2010 Chile Earthquake (magnitude 8.8). Though terrible and destructive, these events have allowed for greater insight into studying the Earth’s crust free oscillations – the instrumentation inside the Grotta Gigante for example is the only station worldwide that is able to directly confront modern seismic events to the 1960 Chile Earthquake, one of the strongest ever. Having measurements that date back over such a long timespan furthermore allows for the study of the secular trend (indicating a general crust movement constant over various decades) of crust deformation: Measurements from the Grotta Gigante indicate a general inclination towards Northwest, corresponding to the crust movement caused by the colliding of the Adriatic plate with the Eurasian plate. Furthermore, it has also been determined that the cave undergoes a seasonal variation of inclination, with a maximum leaning of the cave towards the Southwest in November and towards the Northeast in March. The geodetic pendula have also been able to capture altered crust oscillations proceeding strong Earthquakes: On the 6th of May 1976 a disastrous Earthquake hit the town of Gemona del Friuli and surrounding regions (circa 100km from Grotta Gigante) killing almost 1000 people. In the 3 years before the event, Grotta Gigante’s instrumentation showed anomalous oscillation readings which immediately ceased after the Earthquake happened. These readings were afterwards interpreted as precursory events, and similar readings in future could supply an early warning. Apart from Grotta Gigante, similar geodetic stations of large dimension can be found in Japan, California, and Belgium.
The first seismographic registrations in Trieste began at the “Osservatorio Marittimo” in the city at the beginning of the 20th century but were interrupted at the end of the First World War. A new seismographic station run by the Geophysical Institute (OGS), situated first at Campo Marzio in the city centre, started operating in 1931 and was shifted to Grotta Gigante in the year 1963: The site was perfect due to its position inside solid calcareous rock and relative protection from outside noise and disturbance. The new seismometers were installed by United States Geological Survey (USGS) as part of a network of 120 stations forming the World Wide Seismographic Station Network (WWSSN). These instruments consisted of 3 seismographs (components E-W, N-S, and vertical) of the Benioff type for close by earthquakes and 3 Ewing-Press type seismographs for seismic events further afield. In 1996 the WWSSN instruments were replaced by 3 wideband digital sensors of the Streckeisen type which permit an accurate detection of seismic events both near and far. All data, both of the older WWSSN instruments as well as the newer wideband sensor is transferred and archived by the OGS.
Caves represent extreme environments for animals as well as plants, the main limiting factor being the absence of light, which permits plants to colonize only in the vicinity of cave openings and renders the life of animals very particular.
Proceeding from the cave entrances to the deeper and darker zones of the cave plants gradually become smaller and simpler until vanishing completely to the absolute absence of light and the impossibility of photosynthesis. We can therefore distinguish between four different vegetation growth zones: 1. Liminal: Zones that are well illuminated and subject to variations of temperature and humidity, here we can find superior plant species such as common ivy. 2. Subliminal: With less available light, ferns predominate. 3. Sub obscure: Going towards the darkness, ferns are gradually substituted by mosses and finally by microscopic algae (cyanophytes). 4. Obscure: Temperature and humidity become constant, and a total absence of light makes plant life impossible. In this way only fungi and other microorganisms remain. However, artificial illumination of the cave can favor the growth of photosynthetic organisms (typically referred to as “lampenflora”) also in deeper parts of the cave. Seeds and spores can be transported into the cave by air and water but also on the clothing of visitors. In order to prevent excessive alteration of the cave’s delicate ecosystem, special ultraviolet lights are switched on at night: This low frequency light is able to naturally limit the proliferation of these plants.
The darkness and the consequent absence of plant life inside the cave mean that nutriments inside the cave must be introduced from the outside by air, water or other animals. Some life forms have managed to adapt to these special conditions, and a patient observer may stumble across several interesting species. More than 30 different species have been discovered, most of them invertebrates, excluding a few higher species such as various different bats and the redstart, a bird that often choses niches inside the cave to nest in. Not all species are therefore connected to the cave in the same mode, in fact, various categories can be distinguished: Trogloxenes: Species that often make use of caves but are not strictly dependant on them for survival. Troglophiles: Species that depend on caves during some part their life cycles, such as bats etc. Troglobites: Species whose livelihoods strictly play out inside caves. They present evolutionary characteristics such as the absence of eyes and pigmentation (no longer necessary in dark environments), elongation of limbs and appendices (e.g., antennae and tactile instruments), and loss of daily or seasonal behavioural rhythms. The only strictly troglobial vertebrate on the Trieste Karst is the cave olm (Proteus anguinus) that lives in underground waterways, whose limited area of habitat extends from the Gorizia Karst down the Dinaric ranges to Montenegro.