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Flank margin caves form in coastal regions by mixing dissolution. Their development is controlled by the position of the freshsalt water mixing boundary, which in turn, is related to sea-level position. They are characterized by a typical cave pattern and cave-wall morphologies and represent good indicators of past sea levels. This contribution shows the results of recent studies conducted in the Carburangeli Cave, a small sub-horizontal cavity developed in Northern Sicily, close to Palermo. This cave was firstly known for paleontological and archaeological findings and for these reasons, along with its speleological and biological interest, a Nature Reserve has been instituted by the Sicilian government, and the cave was put under the management of “Legambiente Sicilia”. Carburangeli Cave opens on a marine palaeocliff at 22 m a.s.l., roughly 500 m far from the coastline, and is partially developed in Mesozoic limestone and in the overlying Pleistocene calcarenites. Its position, pattern, peculiar morphologies, lack of turbulent-flow wall sculptures and alluvial/colluvial sediments suggest an origin controlled by coastal mixing processes giving also important information on the Upper Pleistocene sea level and coastline position in this Northern sector of Sicily.

Vengono descritti i caratteri geologici e geomorfologici del territorio comunale di Contessa Entellina (PA), i cui risultati sono sintetizzati in una carta geologica, una carta geomorfologica e una carta litologica.

Durante i lavori di ristrutturazione del complesso edilizio di Villa Riso, villa storica ubicata nell’area della Piana dei Colli (Palermo), sono state applicate tecniche di prospezione georadar e di ispezione diretta che hanno permesso di rinvenire un cunicolo drenante di tipo qanat nel sottosuolo della corte antistante la villa. La presenza di cunicoli drenanti al di sotto di antiche ville è frequente in questo settore della città di Palermo, ma la possibilità di accedervi diventa sempre più difficoltosa, a causa del loro cattivo stato di conservazione. Il qanat di Villa Riso presenta la classica struttura dei qanat della Piana dei Colli, dai quali, tuttavia, si differenzia per la presenza di una grande cisterna di raccolta delle acque localizzata nella parte mediana del cunicolo. Nel presente lavoro viene effettuata una descrizione dell’ipogeo, delle sue caratteristiche costruttive, delle peculiarità geologiche della roccia in cui è scavato e delle sue attuali condizioni di conservazione. During the renovation of Villa Riso, a historic complex located in the Piana dei Colli area (Palermo), a qanat-type underground draining tunnel was found. In this sector of Palermo, the presence of qanat below important historical villas is frequent but often their access is hard because of the poor conservation conditions. The qanat of Villa Riso shows the classic structure of the qanat in the Piana dei Colli, from which, however, it differs for the presence of a large water cistern located in the middle part of the tunnel. The detailed description of the qanat, showing its structure and its conservation conditions, and geological features of the rock in which it carved are displayed in this paper.

A totally new corrosion form has been recently observed inside the Natuturingam cave (better known as Puerto Princesa Underground River) in Palawan (Philippines): the guano holes. They consist of perfectly rounded holes, 4–5 cm wide and up to 10–15 cm deep, developing over a flat limestone surfaces covered by a thin layer of fresh guano. In the same cave larger guano-related corrosion forms have also been encountered, but are not presented in detail here (guano pots). A 3D photogrammetric survey has been carried out on a series of guano-holes to make some morphometric measurements. Their development is controlled by the peculiar Palawan climate, which is characterized by short but heavy rainfalls followed by rather long dry periods. During rainfalls each water drip drills a perfectly rounded hole into the fresh guano reaching the limestone surface which is then corroded by the acids produced by guano digestion. The corrosion process on the exposed limestone surface continues during the whole subsequent dry period and causes the deepening of the initial depression with respect to the surrounding area. At the end of the dry period the drilled holes are partially refilled by fresh guano, and the process restarts at the beginning of a new rainstorm. Subsequent cycles of wet and dry periods cause a progressive deepening of each hole. When two or more drops and their splashing areas interfere, their holes coalesce thus giving rise to relatively larger and complex forms. Finally, during the dry periods, capillary rise and evaporation of the solution trapped within the hole may cause the deposition of small aggregates of different minerals (mainly hydroxylapatite, with minor quantities of calcite). During the next rainstorm, sometimes dripping may not be able to wash away all these minerals, so that they progressively accumulate inside thehole developing a layered speleothem.

Caves remain among the most challenging exploration frontiers on planet Earth. They are difficult to access, present a range of unique and unusual environmental characteristics, and can only be mapped through direct human exploration. These challenges and several environmental factors specific to caves mean that speleology shares several analogies with space missions. For humans, cave exploration imposes isolation, confinement, minimal privacy, technical challenges, limited equipment and supplies, a sense of disconnect from the surface and regular life, a lack of diurnal cycles, and the constant presence of risk. As many of the same challenges are imposed on humans during space exploration, in 2005 the European Space Agency (ESA) began examining the possibility of using natural cave systems as a platform for astronaut training. These efforts resulted in a new ESA training programme named CAVES ( C ooperative A dventure for V aluing and E xercising human behaviour and performance S kills) being launched in 2011, involving astronauts from partner space agencies. The primary objective of this training is to enhance astronaut individual and team performance and behavioural competencies by exposing them to the challenges of a real mission into an unknown and dangerous environment. To achieve this, the course's training activities are based around a real scientific and technological programme focused on cave science. Many aspects of the location and course content have been designed by a team of behavioural experts, scientists, trainers, operations engineers and speleologists with the support of caving organizations and schools. CAVES training events leverage cave exploration to create situations that are analogues to spaceflight in terms of safety protocols, perception and management of risk, crew composition and role assignments, group living, isolation, and confinement. In addition, these courses provide an opportunity for astronauts to experience spaceflight-like or relevant operations, science, equipment testing, and exploration, in preparation for future planetary endeavours. The scientific, exploration and equipment testing aspects of the course are real (not simulated). This ensures that these activities provide benefits to the speleological and scientific communities, whilst guaranteeing the realism of these activities for training purposes. During six editions of CAVES, from 2011 to 2019, 34 astronauts from 6 different space agencies (ESA, NASA, JAXA, ROSCOSMOS, CSA and CNSA) have taken part in the training. The CAVES training programme has been recognized by all participant astronauts and, in particular, by those who have travelled to space, as one of the best space analogue training opportunities available on Earth. The learning outcomes are applicable to both current and future orbital missions, as well as surface and subsurface missions to other planetary bodies.

International audience; Guano is a typical deposit found in caves derived from the excretions of bats and in minor cases of birds. These organic deposits decompose and form a series of acid fluids and gases that can interact with the minerals, sediments, and rocks present in the cave. Over sixty phosphates are known and described from caves, but guano decay also often leads to the formation of nitrates and sulfates. In this study twenty-two European caves were investigated for their guano-related secondary minerals. Using various analytical techniques, seventeen phosphates, along with one sulfate (gypsum), were recognized as secondary products of guano decay. Among those minerals, some are very rare and result from the interaction of guano leachates with clays, fluvial deposits, or pyrite. Some of these minerals are even found only in the studied caves (spheniscidite, robertsite). The most common minerals belong to the apatite group. The common mineral association present in fresh decaying guano is brushite-ardealite-gypsum, minerals that usually are not present in older deposits because of their higher solubility. Most minerals are in hydrated form because of the wet cave environment; however, some specific dry conditions may favor the presence of dehydrated minerals, such as berlinite, formed during guano combustion. Investigation on the acidity of guano piles shows pH values as low as 3.5 with an increase of acidity with age and depth. Finally, cave guano deposits should be better studied in the future because of their role in paleoenvironmental and paleoclimatic reconstructions and because it is important to better understand the origin of guano-related minerals, especially the phosphates and sulfates. Among all of the caves studied, Corona ’e sa Craba (Italy) and Domica-Baradla Cave (Slovakia-Hungary) are considered to be outstanding sites with respect to their phosphate mineralogy.

Gypsum (CaSO4∙2H2O) speleothems (i.e. stalactites, stalagmites, etc.) in caves form frequently through dissolution of the gypsum host-rock by seepage water and subsequent secondary mineral re-precipitation from gypsum-saturated solutions [1]. Gypsum takes its structurally-bound hydration water (GHW) from the liquid; the isotopic composition (δ17O, δ18O and δ2H) of GHW reflects that of cave dripwater at the time of mineral crystallization, with insignificant effect of temperature on the liquid-GHW isotope fractionation factors [2]; therefore, GHW may be used to reconstruct the isotopic composition of paleo-dripwater in caves. Here we investigate the triple oxygen and hydrogen isotopic composition of GHW in speleothems from circum-Mediterranean gypsum caves, including the gypsum karsts of Emilia Romagna (NE Italy), Sorbas (SE Spain), Sicily and Mesaoria (Cyprus), all of them hosted in gypsum of Messinian age (ca. 5.5 Ma). The climatic settings of the studied caves range from semiarid (i.e. Sorbas and Mesaoria, -1) to relatively wet (i.e. Emilia Romagna and Sicily >600 mm·yr-1).Our results reveal that most gypsum speleothems in these caves precipitated from unevaporated solutions (e.g. d-excess >8‰ and 17Oexcess >10 per meg), with isotopic compositions similar to those of local meteoric/seepage waters and close to the local meteoric water lines (LMWL) of each region. Gypsum crystallization in absence of evaporation can be explained by the mechanism known as Ostwald ripening [3], a solution-mediated recrystallization under constant temperature by which older crystals (i.e. Messinian gypsum) dissolve to feed new crystals (i.e. gypsum speleothems). Only GHW in speleothems from the Sorbas caves show evidence for solution evaporation prior mineral precipitation. Gypsum speleothems in several caves of Emilia Romagna crystallized from unevaporated waters with significantly different triple oxygen and hydrogen isotopic compositions (e.g. Ca´ Castellina cave: δ18O=-8.3±0.3‰, δ2H=-55.2±1.7‰, 17Oexcess=33±9 per meg; Abisso Bentini cave: δ18O=-10.6±0.3‰, δ2H=-73.4±1.8‰, 17Oexcess=47±13 per meg). In absence of chronological data, this can be interpreted as (1) gypsum speleothems formed in different climatic periods or (2) do at present from waters that seepage into the epikarst during different times of the year. Either way, gypsum records the mean isotopic composition of seepage water under distinct environmental conditions in this region.The δ18O and 17Oexcess values across the entire dataset are negatively correlated, unlike δ18O and d-excess values that are, positively correlated for δ18O18O>-6‰. We suggest that the different behaviors of 17Oexcess and d-excess derive from their distinct sensitivities to environmental parameters (i.e. RH and temperature) during formation of water vapor at the moisture source of rain and local effects during rainfall events in each area. We conclude that gypsum speleothems of known ages may be useful as archives for triple oxygen and hydrogen isotope reconstructions of paleo-rainfall.[1] Gázquez et al. 2017. Chemical Geology, v. 452, p. 34–46; [2] Gázquez et al. 2017. Geochimica et Cosmochimica Acta, v. 198, p. 259–270; [3] Kahlweit, 1975. Advances in Colloid and Interface Science, v. 5, p. 1–35.

Sulfuric acid minerals are important clues to identify the speleogenetic phases of hypogene caves. Italy hosts ~25% of the known worldwide sulfuric acid speleogenetic (SAS) systems, including the famous well-studied Frasassi, Monte Cucco, and Acquasanta Terme caves. Nevertheless, other underground environments have been analyzed, and interesting mineralogical assemblages were found associated with peculiar geomorphological features such as cupolas, replacement pockets, feeders, sulfuric notches, and sub-horizontal levels. In this paper, we focused on 15 cave systems located along the Apennine Chain, in Apulia, in Sicily, and in Sardinia, where copious SAS minerals were observed. Some of the studied systems (e.g., Porretta Terme, Capo Palinuro, Cassano allo Ionio, Cerchiara di Calabria, Santa Cesarea Terme) are still active, and mainly used as spas for human treatments. The most interesting and diversified mineralogical associations have been documented in Monte Cucco (Umbria) and Cavallone-Bove (Abruzzo) caves, in which the common gypsum is associated with alunite-jarosite minerals, but also with baryte, celestine, fluorite, and authigenic rutile-ilmenite-titanite. In addition, the core of alunite and jarosite, from these two systems, results enriched in PO4 3-, clearly suggesting hypogene hydrothermal origin. Santa Cesarea Terme, Capo Palinuro, and Acqua Mintina caves show important native sulfur deposits, which abundantly cover walls, ceilings, and speleothems. Abundant copiapite, pickeringite, tamarugite, hexahydrate assemblages have been observed in the Calabrian systems; their association with pyrite and hematite would suggest they formed in very acidic conditions with pH ranging between 0 and 4.

Over the past 15 years several expeditions by French, American and especially Italian cavers have unveiled over 50 caves in the Cordillera de la Sal (Atacama Desert, Northern Chile). Many of these caves contain a variety of speleothems and minerals, some of which have rarely been observed within karst systems. Most of the secondary deposits in these caves are composed of halite, but also other halide, carbonate, sulphate, nitrate, phosphate, and silicate minerals have been found. Among the sixteen cave mineral species recognized, atacamite, darapskite, blödite, leonite, anhydrite, and especially antarcticite are worth mentioning. In one of the samples an unknown Ca-Sr-bearing chloride mineral has also been discovered, but it has not been possible to carry out detailed mineralogical analyses. These often-rare minerals have formed in this region due to the very extreme hyperarid and salt-rich environment. This research reports the mineralogical results and proposes the genetical mechanisms leading to the formation of antarcticite, powdery anhydrite, and the paragenesis of the halite-darapskite-blödite. This study also shows that Atacama caves may be excellent analogues to study weathering processes and subsurface secondary minerals in hyperarid and hypersaline environments on Mars.

In Italy, especially along the Apennine Chain, numerous active and inactive sulfuric acid speleogenetic (SAS) caves have been documented in the last two decades. Here we present an overview of these peculiar hypogene systems, illustrating their main geomorphological and mineralogical features, and the microbial signatures observed in the active underground environment. SAS caves are widely distributed in the northern and central Apennines, whereas they are less abundant in the southern Apennines, in the Apulian foreland, in Sicily and in Sardinia. Their location is significantly influenced by lithological and structural rock properties, as they occur in carbonate areas where acidic fluids, deriving from the interactions with deep-seated sulfates and/or sulfides, rise through deeply rooted geological structures. Geomorphological observations demonstrated sub-horizontal maze passages to be one of the most favorite arrangements for SAS caves, whereas gypsum, sulfur and alunite supergroup minerals are the most typical sulfuric acid by-products. The δ34 S results demonstrated the deep-seated H2S sources to be mainly related to the interaction between Triassic evaporites and hydrocarbons.

The little known impact of bats and bat guano in the late stages of cave morphogenesis. Bats are considered as symbolic caves inhabitants. The colonies, sometimes huge, may occupy caves through long periods. Large guano deposits were accumulated. Some have been mined for phosphates, either by hand or at the industrial scale. Bats impact is triple: breathing releases CO2, urine is corrosive, and guano mineralization releases acids (carbonic, nitric, sulfuric, and phosphoric). Such aggressive compounds have an effect on carbonate rock and flowstones, either by direct ground corrosion at the contact of the guano, or by condensation-corrosion on walls and ceilings. The speleogenetic impact of these late stages of cave evolution is considerable and may provoke denudation of several meters of rock. The long lasting presence of bat colonies is a major factor of the late speleogenetical stages, making specific morphologies, significant phosphate deposits, and wall reworking ranging from some centimeters to several meters. These corrosion morphologies, sometimes misinterpreted as marks of flooding, are also responsible of the destruction of many prehistoric realizations, which have been preserved only in specific conditions.

Santa Cesarea Terme in Salento is the only area in which hypogenic caves have been recognized in the Apulia region. In this spa area, the rising of sulfidic thermal waters that mix with both recent fresh infiltration waters and coastal salt water has formed four active sulfuric acid speleogenesis (SAS) caves. These caves are characterized by the typical set of sulfuric acid meso- and micromorphologies, and also by the presence of both gypsum and native sulfur. In all caves, biofilms are visible in the sulfidic thermal waters and on the cave walls.

Karst in Sicily develops in both Messinian gypsum and Mesozoic or Tertiary limestone rocks. Caves are also found in the basalts of Mount Etna. Except for some rare cases, until recently most caves developed in limestone were considered to be of epigenetic origin. The discovery of gypsum in some of these caves, and especially detailed morphological studies, have allowed defining a hypogenic origin for a dozen of caves up to now. In some of these, the hypogenic evidences are very clear, while others remain in doubt because of the widespread presence of well-developed condensation-corrosion morphologies not necessarily related to hydrothermal fluids. This paper reports the present knowledge of hypogenic caves in the Island of Sicily.

This paper proposes a morphoevolutionary model for western Sicily. Sicily is a chain–foredeep–foreland system still being built, with tectonic activity involving uplift which tends to create new relief. To reconstruct the morphoevolutionary model, geological, and geomorphological studies were done on the basis of field survey and aerial photographic interpretation. The collected data show large areas characterized by specific geological, geomorphological, and topographical settings with rocks, landforms, and landscapes progressively older from south to north Sicily. The achieved results display: (1) gradual emersion of new areas due to uplift, its interaction with the Quaternary glacio-eustatic oscillations of the sea level, and the following production of a flight of stair-steps of uplifted marine terraces in southern Sicily, which migrates progressively upward and inwards; in response to the uplift (2) triggering of down-cutting processes that gradually dismantle the oldest terraces; (3) competition between uplift and down-cutting processes, which is responsible for the genesis of river valleys and isolated rounded hills in central Sicily; (4) continuous deepening over time that results in the exhumation of older and more resistant rocks in northern Sicily, where the higher heights of Sicily are realized and the older forms are retained; (5) extensional tectonic event in the northern end of Sicily, that produces the collapse of large blocks drowned in the Tyrrhenian Sea and sealed by coastal-marine deposits during the Calabrian stage; (6) trigger of uplift again in the previously subsiding blocks and its interaction with coastal processes and sea level fluctuations, which produce successions of marine terraces during the Middle–Upper Pleistocene stages.

The assessment of stability of man-made underground caves, excavated in the past and later on abandoned, represents a serious challenge for land and urban planning operations, especially for the areas of possible interaction of the caves with overlying structures and infrastructures. Several areas of Southern Italy are characterized by the presence of abandoned underground quarries for the extraction of soft calcarenite rocks, which now threatens the overlying environment due to the risk of collapse and the consequent generation of sinkholes. This work presents a back-analysis of a sinkhole occurred in 2011 in the town of Marsala, caused by the collapse of an underground quarry, as a representative case study of these phenomena. Based on the available geometrical and geological dataset as well as the field observations of the phenomenon, in this article the assumptions and the results about the genesis of the 2011 sinkhole, as derived from a three-dimensional finite element back-analysis aimed at reconstructing the stress-strain evolution that brought to the ground failure collapse, is discussed. In particular, the 3-D numerical analyses have been performed in order to identify the factors responsible of the genetic mechanism of the sinkhole. The finite element analysis has been carried out by accounting for the geotechnical characterization of the Marsala calcarenites derived from both specific laboratory tests performed on samples taken from the site and literature data available on the same rock material; the numerical results have been then validated by means of the comparison with field observations and also compared with those achieved through a 2-D model of the same case study.

none 16 si Although outcropping rarely in Italy, evaporite (gypsum and anhydrite) karst has been described in detail since the early 20th century. Gypsum caves are now known from almost all Italian regions, but are mainly localised along the northern border of the Apennine chain (Emilia Romagna and Marche), Calabria, and Sicily, where the major outcrops occur. Recently, important caves have also been discovered in the underground gypsum mines in Piedmont. During the late 80s and 90s several multidisciplinary studies were carried out in many gypsum areas, resulting in a comprehensive overview, promoting further research in these special karst regions. More recent and detailed studies focused on the gypsum areas of Emilia-Romagna and Sicily. Sinkholes related to Permian-Triassic gypsum have been studied in Friuli Venezia Giulia. This article reviews the state of the art regarding different aspects of evaporite karst in Italy focusing on the main new results. open De Waele, J.; Piccini, L.; Columbu, A.; Madonia, G.; Vattano, M.; Calligaris, C.; D’Angeli, I.M.; Parise, M.; Chiesi, M.; Sivelli, M.; Vigna, B.; Zini, L.; Chiarini, V.; Sauro, F.; Drysdale, R.; Forti, P. De Waele, J.; Piccini, L.; Columbu, A.; Madonia, G.; Vattano, M.; Calligaris, C.; D’Angeli, I.M.; Parise, M.; Chiesi, M.; Sivelli, M.; Vigna, B.; Zini, L.; Chiarini, V.; Sauro, F.; Drysdale, R.; Forti, P.

Caves formed by rising sulfuric waters have been described from all over the world in a wide variety of climate settings, from arid regions to mid-latitude and alpine areas. H2S is generally formed at depth by reduction of sulfates in the presence of hydrocarbons and is transported in solution through the deep aquifers. In tectonically disturbed areas major fractures eventually allow these H2S-bearing fluids to rise to the surface where oxidation processes can become active producing sulfuric acid. This extremely strong acid reacts with the carbonate bedrock creating caves, some of which are among the largest and most spectacular in the world. Production of sulfuric acid mostly occurs at or close to the water table but also in subaerial conditions in moisture films and droplets in the cave environment. These caves are generated at or immediately above the water table, where condensation-corrosion processes are dominant, creating a set of characteristic meso- and micromorphologies. Due to their close connection to the base level, these caves can also precisely record past hydrological and geomorphological settings. Certain authigenic cave minerals, produced during the sulfuric acid speleogenesis (SAS) phase, allow determination of the exact timing of speleogenesis. This paper deals with the morphological, geochemical and mineralogical description of four very typical sulfuric acid water table caves in Europe: the Grotte du Chat in the southern French Alps, the Acqua Fitusa Cave in Sicily (Italy), and the Bad Deutsch Altenburg and Kraushöhle caves in Austria. Caves formed by rising sulfuric waters have been described from all over the world in a wide variety of climate settings, from arid regions to mid-latitude and alpine areas. H2S is generally formed at depth by reduction of sulfates in the presence of hydrocarbons and is transported in solution through the deep aquifers. In tectonically disturbed areas major fractures eventually allow these H2S-bearing fluids to rise to the surface where oxidation processes can become active producing sulfuric acid. This extremely strong acid reacts with the carbonate bedrock creating caves, some of which are among the largest and most spectacular in the world. Production of sulfuric acid mostly occurs at or close to the water table but also in subaerial conditions in moisture films and droplets in the cave environment. These caves are generated at or immediately above the water table, where condensation–corrosion processes are dominant, creating a set of characteristic meso- and micromorphologies. Due to their close connection to the base level, these caves can also precisely record past hydrological and geomorphological settings. Certain authigenic cave minerals, produced during the sulfuric acid speleogenesis (SAS) phase, allow determination of the exact timing of speleogenesis. This paper deals with the morphological, geochemical and mineralogical description of four very typical sulfuric acid water table caves in Europe: the Grotte du Chat in the southern French Alps, the Acqua Fitusa Cave in Sicily (Italy), and the Bad Deutsch Altenburg and Kraushöhle caves in Austria.

A study of deep-seated gravitational slope deformation (DSGSD) phenomena affecting areas of various geological and geomorphological settings in western Sicily is described. Western Sicily is underlain by a thin-skinned imbricate wedge of Meso–Cenozoic carbonate and siliciclastic rocks that formed by the stacking of several thrust nappes over the Iblean foreland. Locally, the original thrust sheets are folded and cut by high-angle faults. Large areas of western Sicily now display high relief energy due to Plio-Pleistocene block-faulting and uplifting, and the Quaternary morphogenetic phases are characterised by incision, thereby triggering widespread DSGSDs. To identify controlling factors and triggering causes and to develop reliable morphoevolutionary models for the DSGSDs of western Sicily, a geomorphological study based on field surveys and aerial-photography interpretations was performed. Previous geomorphological data relating to well-known examples of DSGSDs were reconsidered, leading to remarkable revisions of the interpretative models in certain cases. New data were subsequently collected, enabling recognition of additional DSGSD phenomena. The whole body of data involves a total of 27 DSGSDs affecting areas in two specific geological settings: (1) areas with flat thrust surfaces, where differential settlements, back-tilting, lateral spreads in competent rocks overlying marls and clays, large topples, and/or block-type slope movements may develop; and (2) areas where deep-rooted carbonate units come into lateral contact with clayey–marly units along high-angle faults, where lateral spreads in brittle homogeneous rocks, sinking, and/or rock flows may occur. These DSGSD phenomena are associated with different evolutionary stages, allowing a morphoevolutionary model to be defined for the two geological conditions. For these two different morphoevolutionary models, the following structural features play an important role in the development of DSGSDs: (1) where carbonate bodies overlie clayey–marly rocks, triggering of the DSGSDs traces back to deformation of a ductile substratum that follows the exhumation of the flat thrust planes and the underlying clayey–marly rocks due to block-faulting and/or stream incision; and (2) where homogeneous carbonate rocks hundreds of metres thick crop out, the DSGSDs are triggered by very high relief energy and tensile stress that follow the combined actions of Quaternary block-faulting and stream deepening associated with differential erosion.

Although hypogene cave systems have been described since the beginning of the 20th century, the importance in speleogenesis of ascending fluids that acquired their aggressiveness from in-depth sources has been fully realized only in the last decades. Aggressiveness of waters can be related to carbonic and sulfuric acids and the related corrosion-dissolution processes give rise to different types of caves and underground morphologies. The abundance of hydrothermal springs and associated travertine deposits, and the widespread interaction between volcanic or sub-volcanic phenomena and karst in many sectors of the Italian peninsula are a strong evidence of hypogene speleogenesis. Furthermore, researches on secondary minerals have allowed to discover hypogene caves formed by highly acidic vapors in subaerial environments, also showing that most of these caves have extremely rich mineral associations. Despite this, until the late 1980s the only known important cave systems of clear hypogene origin in Italy were considered to be the ones hosted in the Frasassi Canyon and Monte Cucco, in which important gypsum deposits undoubtedly showed that sulfuric acid played an important role in the creation of voids (Galdenzi, 1990, 2001; Galdenzi & Maruoka, 2003; Menichetti et al., 2007). Afterwards many other caves were categorized as formed by the sulfuric acid speleogenesis throughout the entire Apennines. Following the broad definition of hypogene caves by Palmer in 1991, and the even more general one of Klimchouk in the last decade (Klimchouk, 2007, 2009), the number of caves considered of hypogene origin in Italy has grown rapidly. Figure 1 shows the hypogene karst systems of Italy, including, besides the well-known and published ones, also the known and less studied, and presumed hypogene cave systems (see also Table 1). More recently, in some of these caves detailed studies have been carried out including geomorphology, mineralogy, and geochemistry. Sulfuric acid caves are known from many regions along the Apennine chain (Tuscany, Umbria, Marche, Latium, Campania, Calabria) (Forti, 1985; Forti et al., 1989; Galdenzi and Menichetti, 1989, 1995; Galdenzi, 1997, 2001, 2009; Galdenzi et al., 2010; Piccini, 2000; Menichetti, 2009, 2011; Mecchia, 2012; De Waele et al., 2013b), but also from Piedmont, Apulia, Sicily (Vattano et al., 2013) and Sardinia (De Waele et al., 2013a). In this last region ascending fluids have also formed a hypogene cave in quartzite rock. Oxidation of sulfides can locally create hypogene cave morphologies in dominantly epigenic caves, such as in the Venetian forealps (this cave is not shown in Figure 1, being largely epigenic in origin) (Tisato et al., 2012). Ascending fluids have also created large solution voids in Messinian gypsum beds in Piedmont, and these can be defined hypogene caves according to the definition by Klimchouk (Vigna et al., 2010). Some examples of hypogene cave systems due to the rise of CO2-rich fluids are also known in Liguria and Tuscany (Piccini, 2000). In the Alps and Prealps (Lombardy), some ancient high mountain karst areas exhibit evidences of an early hypogene origin, deeply modified and re-modeled by later epigenic processes. Hypogene morphologies are thus preserved as inactive features, and it is often difficult to distinguish them from epigenic ones. At almost twenty years distance from the first review paper on hypogene cave systems in Central Italy by S. Galdenzi and M. Menichetti (1995), we give a review of the state-of-the-art knowledge on hypogene caves actually known from the whole of Italy.

Although hypogene cave systems have been described since the beginning of the 20th century, the importance in speleogenesis of ascending fluids that acquired their aggressiveness from in-depth sources has been fully realized only in the last decades. Aggressiveness of waters can be related to carbonic and sulfuric acids and the related corrosion-dissolution processes give rise to different types of caves and underground morphologies. The abundance of hydrothermal springs and associated travertine deposits, and the widespread interaction between volcanic or sub-volcanic phenomena and karst in many sectors of the Italian peninsula are a strong evidence of hypogene speleogenesis. Furthermore, researches on secondary minerals have allowed to discover hypogene caves formed by highly acidic vapors in subaerial environments, also showing that most of these caves have extremely rich mineral associations.

A sinkhole, occurred in June 2011 and related to an underground quarry in the eastern sector of Marsala, is described in this paper as a case study (Figure 2). The site was selected for the availability of topographic data of the underground quarry, prior to the formation of the Abstract Anthropogenic sinkholes affect several built-up areas of Sicily (southern Italy) representing a great risk to people, buildings, and infrastructures. These phenomena are generally associated with the presence of ancient underground quarries for the extraction of calcarenite rock, used for building or ornamental materials. These quarries were poorly constructed and abandoned throughout history.