403 research outputs found
Mud volcanoes in onshore Sicily: a short overview
A short overview on Sicilian mud volcanoes is given. A total of 8 sites are presently known and studied in Sicily, mainly
located in centralâsouthern Sicily (Caltanissetta basin). All of these are of small dimension and sometimes associated to
water pools. Methane is the main emitted gaseous phase, with the exception of the PaternĂČ site, dominated by CO2 due
to its proximity to Mt. Etna.
Emitted waters are of the chlorideâsulphateâalkaline type, due to the dominance of NaCl as the main dissolved salt.
Sicilian mud volcanoes represent a potential threat for humans but, at the same time, they are threatened by anthropic
activities. The main risks are related to the damages produced by paroxysmal events, while their survival is threatened
by illegal discharge of wastes, consumption of rural land and agricultural activities
Possible Micrometeorological Anomalies Induced by Volcanic Activity Recorded at Stromboli Island (Aeolian Archipelago, Italy)
Hourly values of atmospheric pressure and air temperature have been acquired at the top of two volcanic islands, Stromboli and
Salina in the Aeolian Archipelago (Italy), very similar in height and morphology but completely different with regard to their
volcanic activity state: the former is permanently active, whereas the latter is extinguished. During the last four years Stromboli
experienced normal activity, volcanic unrests, and an effusive eruption (AugustâNovember 2014).The comparative analysis of the
recorded data, both in the time and frequency domains, evidenced a peculiar micrometeorological regime at Stromboli, more
turbulent during unrests with respect to the quieter periods, but showing an apparent paradox during eruptions, characterized
by a lower atmospheric turbulence. These observations suggest that the studied volcanic-micrometeorological system is chaotic,
due to contemporary opposite transients generated in the atmosphere by volcanic activity changes, and that micrometeorological
conditions in volcanic areas are controlled both by exogenous processes and volcanic activity
Geomorphological and geochemical characterization of the 11 August 2008 mud volcano eruption at S. Barbara village (Sicily, Italy) and its possible relationship with seismic activity
On 11 August 2008 a paroxysmal eruption occurred at Santa Barbara mud volcano (MV), located close to Caltanissetta, one of the most densely populated cities of Sicily (Italy). An associated minor event took place on August 2009. Both the events caused severe damage to civil infrastructures located within a range of about 2 km from the eruptive vent. Geomorphological, geochemical, and seismological investigations were carried out for framing the events in the appropriate geodynamic context. Geomorphological surveys recognized, in the immediate surrounding of the main emission point, two different families of processes and landforms: (i) ground deformations and (ii) changes in morphology and number of the fluid emitting vents. These processes were associated to a wider network of fractures, seemingly generated by the shock wave produced by the gas blast that occurred at the main paroxysm. Geochemical characterization allowed an estimation of the source of the fluids, or at least their last standing, at about 3 km depth. Finally, the close time relationships observed between anomalous increments of seismic activity and the two main paroxysmal events accounted for a possible common trigger for both the phenomena, even with different timing due to the very different initial conditions and characteristics of the two processes, i.e. seismogenesis and gas overloading
The use of non-invasive field techniques in the study of small topographically closed lakes: two case studies in Sicily (Italy)
Small endhoreic (topografically closed) lakes represent a little percentage
of continental waters but, in arid or sub-arid regions, they develop special
ecosystems potentially prone to ecological involution due to climatic
changes. The mandatory use of light, non-invasive field techniques is
often required, especially in protected areas. In the present work the use
of non-invasive techniques like GPSâbased bathymetric and photographic
surveys have been applied to the study of two lakes, Specchio di
Venere and Sfondato (Sicily, southern Italy), both natural reserves. The
comparison between historical surveys and modern GPSâbased bathymetries
highlighted the difficulty of using the former for the reconstruction
of climatic-induced variations due to the low number of
measurements (spatial aliasing). In particular, at the intracaldera Lake
Specchio di Venere, a high resolution survey gave new insights into a peculiar
geo-ecosystem whose evolution is driven by both volcanic phenomena
and biomineralization processes. On the contrary, the morphology
of Lake Sfondato floor is much more simple and driven only by the superimposition
of a detrital sedimentation on the initial collapse that generated
the lake. The comparison betweem direct measurements and
estimated changes of lake level, carried out between February 2008 and
October 2009 variations, allowed us to test different hypotheses of hydrological
balances, leading to opposite conclusions with respect to previous
studies and remarking the fundamental importance of direct
measurements in the validation of theoretical hydrological models
Geomorphological and geochemical characterization of the August 11, 2008 mud volcano eruption at S. Barbara village (Sicily, Italy) and its possible relationship with seismic activity
On August 11, 2008 a paroxysmal eruption occurred at Santa Barbara mud volcano (MV), located close to Caltanissetta, one of the most densely populated cities of Sicily (Italy). An associated minor event took place on August, 2009. Both the events caused severe damages to civil infrastructures located within a range of about 2 km from the eruptive vent. Geomorphological, geochemical and seismological investigations were carried out for framing the events in the appropriate geodynamic context. Geomorphological surveys recognized, in the immediate surrounding of the main emission point, two different families of processes and landforms: ground deformations and changes in morphology and number of the fluid emitting vents. These processes were associated to a wider network of fractures, seemingly generated by the shock wave produced by the gas blast occurred at the main paroxysm. Geochemical characterization allowed to estimate the source of the fluids, or at least their last standing, at about 3 km depth. Finally, the close time relationships observed between anomalous increments of seismic activity and the two main paroxysmal events, accounted for a common possible trigger for both the phenomena, even if with a different timing due to the very different initial conditions and characteristics of the two processes, i.e. seismogenesis and gas overloading
Relationship between surface temperatures and seismic activity at Vulcano, Aeolian Island (Italy)
Time-series acquired during last years by surface monitoring parameters are compared, and the results are discussed, following a theoretical approach. Surface parameters are fluid temperature, soil temperatures and seismic activity at La Fossa of Vulcano. Discussed periods are 1998 and from 2004 to 2007, when time relationship between changes of the heat flow from the ground and seismic activity, resulted worth noting. Earthquakes originating in the area of Vulcano are associated with both fracturing and degassing mechanisms. The formers are related to the activity of tectonic structures; while the latter are connected to fluid dynamics within the interior of the volcanic apparatus. In November 1998 seismic activity at La Fossa sharply increased: Five events were registered, with seismic signals of typical faulting earthquakes, triggered by mechanism of shear fracturing and focal depths ranging 1-4 km. Fumaroles temperatures, recorded by continuous monitoring system of INGV - Palermo, showed a growing trend since October to November 1998, highlighting a big increase of heat transfer during the period, and also the soil temperature, out of the fumaroles field showed a marked increase. Fumaroles temperatures heralded the increase of heat and energy flow during a pre-seismic period of about 1 month. The transient variation of surface release reflect an excited state of the system and may have many different causes, not directly related to the magma. Indeed, stress drops generated by small fracturing earthquakes, introduce a significant perturbation in the system resulting in a relevant production of mass and energy flow. Until these flows counteract every stress gradient, they support stationary state of the system. The observed time relationships only allow a qualitative discussion about cause and effects, but doesnât allow any quantitative evaluation. Pressure transients generate anomalies (flows of matter, differential in heat flows, chemical reaction rates) whose time frame is specific, depending on many possible processes and path-ways. Fluid phases, along fumarolic conduits, reach the surface faster than the co-genetic earthquake, as the earthquake is embedded in a strain transient that broadly exceeds the time-space frame of the seismic transient (Lomnitz, 1994). On the other hand, in a volcano-tectonic context, different energy flows can either be a cause, either an effect of perturbation, depending on depth of their primary source. Thus, in some instances the strain transient related to local earthquakes produces anomalous chemical flows, while, in other instances the local seismic activity may be produced by chemical flows from the magmatic source. Following a period of lower energy release, other 3 anomalous periods were observed from November 2004, either in the seismic release and in the surface heat flow, even out from fumaroles. So far, the monitored sites resulted very sensitive to minor perturbations of the system. The comparative analysis of different time-series supplies information related to perturbations of the state variables, useful to verify conceptual framework and to better define âclassicalâ and ânewâ monitoring techniques for volcanic, as well as seismic surveillance
Anthropogenic sinkholes in the Marsala area (western Sicily) linked to underground quarries
Marsala territory (western Sicily) is characterized by the presence of a Lower Pleistocene (Calabrian) calcarenite
succession (Marsala Calcarenite Fm). It can be divided into three lithofacies that show the regressive evolution
of the depositional system: a) coarse to fine yellow bio- and lithoclastic calcarenites, b) sands, and c) gray sandy
clays. At least 80 m-thick, this succession gently dips (5-10) towards the south and the south-west. At some
locations the Marsala Calcarenite is covered by Middle and Upper Pleistocene marine terraced deposits.
Since the Roman period, due to the great abundance of calcarenite rocks, and to the facility of extraction, the
Marsala area has been characterized by a high number of quarries for the extraction of this building materials.
Many of them were excavated underground, at depth varying from a few meters to about 25 m, and are arranged
in one or two levels, following the galleries and pillars excavation technique. With time, the underground quarries
have been progressively abandoned for the decay of the physical and mechanical properties of the calcarenite
rock mass, the interaction with the groundwater, the high costs of extraction, and the dangers and difficulties
encountered in working underground.
Since the 1960âs the quarries have been affected by instability processes, visible through collapses and deformations
of vaults and pillars. These phenomena often propagate upward reaching the topographic surface and
forming sinkholes which affect and severely damage the built-up area.
In particular, two case studies of sinkholes related to different underground quarries will be analyzed in this paper.
The aim is to provide a description of the most significant processes and factors responsible of the instability
processes based on field surveys, as well as to understand the generation mechanisms of these anthropogenic
sinkholes by means of numerical modeling, based on rock laboratory testing data, that represents in these cases
a remarkable tool for the investigation of the cause-effect relationships, as already performed in other areas of Italy
Discrimination between effects induced by microbial activity and water-rock interactions under hydrothermal conditions according to REE behaviour
Rare earth elements (REE) were investigated in siliceous stromatolites forming in the Specchio di Venere Lake on Pantelleria Island. Chondrite-normalised patterns show significant La enrichments and Eu depletions suggesting that fluids involved in stromatolite growth experienced strong rock-water interactions under hydrothermal conditions. At the same time, enrichments in heavy REE (HREE) with respect to intermediate REE (MREE) suggest that hydrothermal fluids interacted with microbial mats during deposition of the stromatolites. The above-mentioned features suggest that rock-water interactions and bacterial activity were simultaneously recorded in the REE patterns of stromatolites, and can be discriminated in terms of amplitudes of the La anomaly, and the HREE/MREE ratio
A landscape approach in the isotopic modeling of natural precipitations: two cases in Mediterranean mountain areas
The present paper proposes a method to simplify the very complex isotopic fractionation processes occurring during the water cycle. The method is constrained by a relatively small number of variables, with the precision needed in hydrological applications. After a theoretical
introduction on the adopted interpolation criteria, two cases in the Mediterranean are presented.
In both cases the evaluation of the âgeometric
complexityâ of the systems appears to be the
best tool to produce reliable isotopic models. If
the complexity is low, it is apparently easier to
fit different models; on the contrary the higher
the complexity is, more difficult it is to find a
reliable model but, at the same time, more difficult it is to find effective alternative models
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