Description: Submarine hydrothermal systems along active volcanic ridges and arcs are highly dynamic, responding to both oceanographic (e.g., currents, tides) and deep-seated geological forcing (e.g., magma eruption, seismicity, hydrothermalism, and crustal deformation, etc.). In particular, volcanic and hydrothermal activity may also pose profoundly negative societal impacts (tsunamis, the release of climate-relevant gases and toxic metal(loid)s). These risks are particularly significant in shallow (〈1000m) coastal environments, as demonstrated by the January 2022 submarine paroxysmal eruption by the Hunga Tonga-Hunga Ha’apai Volcano that destroyed part of the island, and the October 2011 submarine eruption of El Hierro (Canary Islands) that caused vigorous upwelling, floating lava bombs, and natural seawater acidification. Volcanic hazards may be posed by the Kolumbo submarine volcano, which is part of the subduction-related Hellenic Volcanic Arc at the intersection between the Eurasian and African tectonic plates. There, the Kolumbo submarine volcano, 7 km NE of Santorini and part of Santorini’s volcanic complex, hosts an active hydrothermal vent field (HVF) on its crater floor (~500m b.s.l.), which degasses boiling CO 2 –dominated fluids at high temperatures (~265°C) with a clear mantle signature. Kolumbo’s HVF hosts actively forming seafloor massive sulfide deposits with high contents of potentially toxic, volatile metal(loid)s (As, Sb, Pb, Ag, Hg, and Tl). The proximity to highly populated/tourist areas at Santorini poses significant risks. However, we have limited knowledge of the potential impacts of this type of magmatic and hydrothermal activity, including those from magmatic gases and seismicity. To better evaluate such risks the activity of the submarine system must be continuously monitored with multidisciplinary and high resolution instrumentation as part of an in-situ observatory supported by discrete sampling and measurements. This paper is a design study that describes a new long-term seafloor observatory that will be installed within the Kolumbo volcano, including cutting-edge and innovative marine-technology that integrates hyperspectral imaging, temperature sensors, a radiation spectrometer, fluid/gas samplers, and pressure gauges. These instruments will be integrated into a hazard monitoring platform aimed at identifying the precursors of potentially disastrous explosive volcanic eruptions, earthquakes, landslides of the hydrothermally weakened volcanic edifice and the release of potentially toxic elements into the water column.

Description: Geochemical investigations carried out on submarine hydrothermal fluids vented offshore the Pontine Islands (Tyrrhenian Sea) revealed the existence of gas vents to the W of Zannone Island and SW of Ventotene Island. The geochemical features of the CO2-rich gas samples show a clear mantle-derived signature with 3He/4He of 3.72-3.75 Ra and 1.33 Ra at Zannone and Ventotene, respectively. Gas geochemistry denotes how CO2-rich gases undergo fractionation processes due to CO2 dissolution to a variable extent favoring enrichment in the less soluble gas species, i.e., CH4, N2, and He. The carbon isotope composition of CO2, expressed as δ13C vs. V-PDB, ranges from -0.71 and -6.16‰ at Zannone to 1.93‰ at Ventotene. Preliminary geothermometric and geobarometric estimations indicate equilibrium temperatures in the range of 150-200°C at Zannone and 〉200°C at Ventotene besides H2O pressures in the range of 5 bar and 20 bar at Zannone and Ventotene, respectively. Although the latest volcanic activity at the Pontine Archipelago is dated Middle Pleistocene, the combination of the new geochemical information along with geothermometric estimations indicates that cooling magmas are likely releasing enough thermal energy to form an efficient hydrothermal system.

Description: Published

Description: id 8759609

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal

Description: Geohazards associated to submarine hydrothermal systems still represent a tricky enigma to face and solve for the scientific community. The poor knowledge of a submarine environment, the rare and scarce monitoring activities, and the expensive and sometimes complicated logistics are the main problems to deal with. The submarine low-energy explosion, which occurred last November 3, 2002, off the volcanic island of Panarea, highlighted the absence of any hazard scenario to be used to manage the volcanic crisis. The “unrest” of the volcanic activity was triggered by a sudden input of deep magmatic fluids, which caused boiling water at the sea surface with a massive CO2 release besides changes in the fluids’ geochemistry. That event dramatically pushed scientists to develop new methods to monitor the seafloor venting activity. Coupling the information from geochemical investigations and data collected during the unrest of volcanic activity, we were able to (a) develop theoretical models to gain a better insight on the submarine hydrothermal system and its relationships with the local volcanic and tectonic structures and (b) to develop a preliminary submarine volcanic hazard assessment connected to the Panarea system (Aeolian Islands). In order to mitigate the potential submarine volcanic hazard, three different scenarios are described here: (1) ordinary hydrothermal venting, (2) gas burst, and (3) volcanic eruption. The experience carried out at Panarea demonstrates that the best way to face any submarine volcanic-hydrothermal hazard is to improve the collection of data in near real-time mode by multidisciplinary seafloor observatories and to combine it with periodical sampling activity.

Description: Published

Description: id 8728720

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal

Description: The Ionian Sea in southern Italy is at the center of active interaction and convergence between the Eurasian and African–Adriatic plates in the Mediterranean. This area is seismically active with instrumentally and/or historically recorded Mw 〉 7:0 earthquakes, and it is affected by recently discovered long strike-slip faults across the active Calabrian accretionary wedge. Many mud volcanoes occur on top of the wedge. A recently discovered one (called the Bortoluzzi Mud Volcano or BMV) was surveyed during the Seismofaults 2017 cruise (May 2017). Bathymetric backscatter surveys, seismic reflection profiles, geochemical and earthquake data, and a gravity core are used here to geologically, geochemically, and geophysically characterize this structure. The BMV is a circular feature ' 22m high and ' 1100m in diameter with steep slopes (up to a dip of 22 ). It sits atop the Calabrian accretionary wedge and a system of flowerlike oblique-slip faults that are probably seismically active as demonstrated by earthquake hypocentral and focal data. Geochemistry of water samples from the seawater column on top of the BMV shows a significant contamination of the bottom waters from saline (evaporite-type) CH4-dominated crustalderived fluids similar to the fluids collected from a mud volcano located on the Calabria mainland over the same accretionary wedge. These results attest to the occurrence of open crustal pathways for fluids through the BMV down to at least the Messinian evaporites at about 􀀀3000 m. This evidence is also substantiated by helium isotope ratios and by comparison and contrast with different geochemical data from three seawater columns located over other active faults in the Ionian Sea area. One conclusion is that the BMV may be useful for tracking the seismic cycle of active faults through geochemical monitoring. Due to the widespread diffusion of mud volcanoes in seismically active settings, this study contributes to indicating a future path for the use of mud volcanoes in the monitoring and mitigation of natural hazards.

Description: Published

Description: 1-23

Description: 3SR TERREMOTI - Attività dei Centri

Description: JCR Journal

Description: We report on original geochemical data, which combine the rainfall trace metal contents from three different areas of Mt. Etna, variably fumigated by the volcanic plume, and those from soils, collected over the whole volcano. Trace element contents in rainfall appear mostly related to acidic ash leaching, while only for the most volatile elements (Cu, Zn, Cd, Pb, As, Sb, Tl, Se). We analyzed separately the labile fraction of soil samples, considered the fraction bioavailable to plants and soil organisms living in. The complexing medium used to extract the bioavailable fraction simulates the growth environment of plant roots.The contents of trace elements in the bioavailable fraction from soil samples showed peculiar patterns, apparently unrelated to the plume fumigation. The transition metal contents in the bioavailable fraction account for less than 15 % of the pseudo-total fraction and the highest contents were measured in the less acidic soil samples and farthest from the summit craters. In particular, high Fe, Mn, Co, Ni, Pb, Zn, Cd contents were paralleled by high soil organic carbon concentrations, which increased in the samples collected downwind the summit vents. Concerning immobile elements, their abundance in the bioavailable fraction was related to the degree of alteration of soils. Two elements, Se and Tl, were enriched in soil samples collected at closer distance from the summit vents. Their origin is probably related to the plume deposition.The study highlighted that the accessibility of plants to potentially harmful trace elements present in the soil is not simply related to the exposure to pollutants, but also to their fate in the pedogenetic environment.

Description: Published

Description: 57-78

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal

Description: The time series of geochemical data available for the network ofwells and drainage galleries atMt. Etna has been analyzed to identify the changes in water chemistry related to the input of volcanic CO2 and those related to hydrogeological dynamics. The dynamics of hydrological systems is mainly affected by changes in the rainfall, since this influences the yields of both springs and drainage galleries and the height of thewater table of unconfined aquifers. In addition, the characteristics of hydrological systems can change with the fluid pressure. These mechanisms are probably enhanced by changes in the crustal strain,which can cause interbasin transfer ofwater. The changes in water circulation are paralleled by variations in physicochemical characteristics of groundwater, since water transfer probably occurs among water bodies with different temperatures and compositions. Based on the abovemechanisms, the contribution of different water types has been estimated according to their chemical composition: it has been assumed that water circulating in the volcanic pile has a typical HCO3 −-rich composition,whereas Cl−, SO4 =, andNO3 − could be contributed by rainfall, anthropogenic pollution, and sedimentary fluids rich in Na+ and Cl−. The compositionally different endmembers have been identified based on the results of factor analysis,which allowed those chemicals accounted for by a singlewater endmember to be grouped within the same factor. In some cases the SO4 = enrichment is related to the dissolution of SO4 =-bearing alteration minerals contained in volcanic sequences, and in such cases this is associated with HCO3 −. We hypothesize a binary mixing between the HCO3 −-rich volcanic end member and an end member pollutedwith Cl−, SO4 =, andNO3 − related to water circulation at shallow levels. These two end members are identified by their HCO3 −/(Cl−+SO4 = +NO3 −) ratio and Cl−, SO4 =, and NO3 − contents measured at each sampling site. The extent of mixing between these different water types changes over time, probably due to changes in their circulation patterns, with water being transferred from/towater bodieswith different compositions. Once the proportion of the HCO3 − content related to the binary mixing is determined, we can compute the amount of HCO3 − related to the variable input of CO2 over time into the aquifer. The obtained temporal trends are—over a long time period—synchronous in the two sectors of the volcanowhere themaximal CO2 degassing occurs, namely the Paternò-Belpasso area on the southwestern flank and the Zafferana-S. Venerina area on the eastern flank. This provides evidence for a common deepmechanism underlying the CO2 variations that is related to the dynamics of the volcano. Some inconsistent trends are observed in the two sectors during specific periods, such as in 2012, which is probably due to the marked dynamics affecting the eastern flank compared to the more stable southwestern one.

Description: Published

Description: 71-84

Description: 4V. Dinamica dei processi pre-eruttivi

Description: 5V. Dinamica dei processi eruttivi e post-eruttivi

Description: JCR Journal

Description: The sudden unrest of submarine volcanic activity occurred off the island of Panarea (Aeolian arc) on November 2002 induced a submarine low-energy explosion that opened a “crater” of 20 by 10 meters wide and 7 meters deep. That event dramatically changed the geochemical features and the degassing rate of the submarine hydrothermal vents of the area and pushed the scientists to develop new methods to monitor the sea-floor venting activity. During the unrest period, the huge degassing activity increased the CO2 flow rate by some orders of magnitude. Apart from the former venting areas, degassing occurred from many new fractures opened at the seafloor along a N40°E trend and from the crater. Estimations before the event gave a degassing rate in the range of 107 litres/day of CO2, in contrast with the gas vented only by the crater, estimated to be in the order of 1-2 x109 l/d CO2. Such a large amount of toxic gas released to the atmosphere increased the volcanic risk due to the gas hazard. Coupling the information from geochemical investigations and data collected during the unrest of volcanic activity we were able to: a) provide the necessary information to the National Department of Civil Protection to manage the volcanic crisis and b) to develop theoretical models to gain a better insight on the submarine hydrothermal system and its relationships with the local tectonic structures. The measured helium isotopic ratios close to 4.3Ra (Ra = atmospheric 3He/4He ratio), in the range of the values given for the local magmatic signature, did not allow distinguishing if a fresh degassing magma or a cooling crystallized body was feeding the submarine emissions, however the recorded data were the same as measured on the island of Stromboli and underwent synchronous changes with the time. Besides the sampling activity (gases and hot waters collection by diving activity), a continuous monitoring has been carried out by a new sea-floor observatory developed to perform real-time data transmission from a sea-floor multidisciplinary observatory. Among the other sensors, the acoustic probe (hydrophone), installed for a long-term recording of the noise of the bubbling gases in a frequency range of 0.5-3 kHz, gave useful information for a tight link between the submarine volcanic activity of Panarea Island and the crater explosions of the nearby active volcanic island of Stromboli. The continuous monitoring of the submarine hydrothermal vents showing contemporaneous modifications of the vented fluids and the seismic activity of the nearby Stromboli, besides the contemporary variation of the 3He/4He ratios at both volcanoes, bear testimony to interconnections between the two volcanic islands. The almost contemporary start of the volcanic crisis at Panarea and Stromboli in 2002, together with the large number of submarine crater-shaped structures at Panarea, supports the above outcome too. As a matter of fact, our geochemical approach allowed us: 1) to gain a deeper insight for the management of such an unrest of the submarine volcanic activity results and 2) to recognize that the observed changes in the fluids geochemistry were caused by a magmatic input, as such, the nearby active volcanic system of Stromboli Island is somewhat involved in feeding magmatic fluids to Panarea, probably through the normal N40°E fault linking the two edifices.

Description: European Union, Gobierno de Canarias, Universitad de la Laguna, Universitad de Las PalmasInstituto Volcanoilogico de Canarias

Description: Unpublished

Description: El Hierro, Canary Islands, Spain

Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive

Description: restricted

Description: Twenty gas samples have been collected from the natural gas manifestations of Milos Island, the majority of which is found underwater along its coast. Furthermore, three anomalous degassing fumarolic areas (Kalamos, Paleochori and Adamas) have been recognized on-land. Almost all the gases are CO2-dominated with CO2 ranging from 88 to 99% vol for the samples taken underwater, while the on-land manifestations show a wider range (15–98%) due to air contamination. Methane reaches up to 1.0% vol, H2 up to 3.2% vol and H2S up to 3.5% vol indicating a hydrothermal origin of the gases. The isotope composition of He points out to mantle contributions up to 45%, while the C-isotope composition of CO2 (from−1.9 to +1.3‰vs. V-PDB with most of the values around −0.5‰) suggests a prevailing limestone origin. Isotope composition of CH4, ranging from−18.4 to−5.0‰vs. VPDB for C and from−295 to+7‰vs. V-SMOWfor H, points to a geothermal origin with sometimes evident secondary oxidation processes. Additionally, CO2-flux measurements showed high values in the three fumarolic areas (up to 1100, 1500 and 8000 g/m2/d at Kalamos, Paleochori and Adamas respectively) with the highest CO2-flux values (up to about 23,000 g/m2/d) being measured in the sea at Kanavas with a floating chamber. The south-western part of the island was covered with a lower density prospection revealing only few anomalous CO2 flux values (up to 650 g/m2/d). The total output of the island (30.5 t/d) is typical of quiescent closed-conduit volcanoes and comparable to the other volcanic/geothermal systems of the south Aegean active volcanic arc (Nisyros, Kos, Nea Kameni, Methana and Sousaki).

Description: Published

Description: 13-22

Description: 4V. Processi pre-eruttivi

Description: JCR Journal

Description: We present soil temperature data from a peripheral fumarole emission of Mt Etna at the top end of a radial fracture called Bottoniera. This area lies in the northern flank of the volcano (2,500m a.s.l.), and was interested by fissure eruption during 2002/2003. In the steam heated soil lying around the fumarole release, a shallow vertical profile has been monitored from October 2009 to September 2012. We estimated the local surface heat flux and compared its time variations to the eruptive activity occurred during the monitoring period. The eruptive vents were located on the opposite flank, (〉3200m a.s.l.), far about 4km. The heat flux from this peripheral emission has been highly influenced by the eruptive activity. Its time variations are correlated to the variable rates of products emitted from January 2011 to April 2012. Different ranges of heat flux values have been associated to the pre-eruptive phase, to the productive eruption period and to the end of this eruptive cycle. The decrease of heat flux was registered before the end of the eruptive cycle. The continuous thermal monitoring revealed in real time that ascending magma through the active conduits is the heating bottom source of the heat flux dispersed by a complex network of active fractures present in this area. The recorded data suggest the steam heated soil around fumaroles vents as a possible new investigation field for a low cost monitoring of the local variation in the structural weakness of the apparatus. Extending this thermal monitoring to the other steaming grounds of this complex volcanic system we could also follow variations of the fluid circulation paths and obtain direct information about local pore pressure changes. A multivariate analysis of recorded data could suggest, which part of this complex apparatus is being involved, time by time, with the ongoing evolution. It would contribute to the evaluation of flank instability caused by physical changes occurring on the network of active fractures, and inferred by multidisciplinary investigations (such as deformation patterns, tectonic lineaments and geochemical features of underground waters and diffuse gas emissions).

Description: Published

Description: Yokohama, Japan

Description: 4V. Dinamica dei processi pre-eruttivi

Description: 5V. Dinamica dei processi eruttivi e post-eruttivi

Description: In the period July 2005–October 2006 several soil gas prospections were performed on the island of Pantelleria, an active volcanic/geothermal system at present in a quiescent state. Measured parameters were CO2 concentrations and 220Rn and 222Rn activities at 50 cm depth and CO2 fluxes from the soil. The whole island was covered with a measurement density of 3.5 points/km2 for CO2 (flux and concentration) and 1.6 points/km2 for Rn. Further three main and seven minor areas of previously ascertained or expected exhalative activity were covered with a measurement density up to 100 points/km2. The obtained results ranged from 0.038 to 95%vol for CO2 concentration, from 10 Bq/m3 to 164,000 Bq/m3 from 10 Bq/m3 to 750,000 Bq/m3 for 220Rn and 222Rn activities, respectively and from 〈0.1 to 4700 g/m2 day for CO2 fluxes. Probability plots evidenced for all measured parameters the presence of three populations (background, mixed and hydrothermal). All anomalous values were found in the central part of the island within the youngest caldera. Flux data allowed us to estimate a total CO2 output of the volcanic/geothermal system of Pantelleria in 24.2 tons per day. Some new exhaling area, significantly contributing to the total output and characterised by stunted or absent vegetation, were evidenced on the southern flank of Mt. Grande. At one of these areas the relationships between the measured parameters and vegetation cover were studied in detail along a 140 m long transect of 15 points. Finally, a first evaluation of the gas hazard related to the geogenic degassing evidenced some high risk area at the mofette along the shores of the Lake Specchio di Venere (CO2) and in the village of Rekale (CO2 and Rn).

Description: Published

Description: 49-63

Description: 2V. Struttura e sistema di alimentazione dei vulcani

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal