Ground deformation and gravimetric monitoring at Somma-Vesuvius and in the Campanian volcanic area (Italy)

This paper describes an integrated ground deformation and gravity network aimed at monitoring volcano-tectonic movements in the Campanian area (Southern Italy). It covers an area of more than 3000 km², including the volcanic centres of Somma-Vesuvius, Campi Flegrei caldera and Ischia island. Levelling, EDM and gravity networks, as well as periodic and continuous GPS measurements are carried out. The aim of the network is twofold: monitoring ground deformations in the above mentioned volcanic areas, and studying the complex tectonics of the Campania Plain, a graben-like structure in which the Neapolitan volcanism is concentrated, in relation to the tectonics of the Southern Apennines and of the Tyrrhenian Basin. The monitoring network consists of larger-scale levelling, EDM and GPS networks covering the whole Campania Plain, connected to the relatively stable areas of Apennines, together with smaller scale networks aimed at accurately monitoring the Somma-Vesuvius volcano, one of the most dangerous over the World due to the high degree of urban development. The Somma-Vesuvius is monitored by levelling network, over 200 km long, by periodic EDM and GPS measurements and by a small network of continuously recording GPS receivers. Moreover, high precision gravimetry is also employed to deep the knowledge of the dynamic framework of the area. The main results indicate that Mt. Vesuvius and the island of Ischia are currently quiescent, while Campi Flegrei are subject to significant slow vertical ground movements, known as “bradyseism”. Recently, two large uplifts, both of about 1.8 m, affected the area respectively in 1970–72 and 1982–84.     

Sr isotopic evidence for a multi-source origin of the potassic magmas in the neapolitan area (S. Italy)

New Sr isotopic data on lavas and xenoliths from Somma-Vesuvius and other nearby volcanic areas (Phlegrean Fields and Ischia) are presented. Chemical and isotopic evidences show that not all the Phlegrean Fields rocks belong to the low K series, but some of them may be interpreted as low pressure differentiates of Somma magmas, i.e. as a part of the high K series. Two rock groups are defined in the Ischia low K series, which are well identified both in time and in chemical and isotopic features, and cannot be derived from the same magma source. The low K series in the studied area generally has lower Sr isotopic values than the high K series.Historical Vesuvian lavas show two distinct linear trends with negative slopes when⁸⁷Sr/⁸⁶Sr ratios are plotted against their ages of eruption. Such trends are interpreted to result from mixing of magmas in two separate reservoirs. Evidence from the Vesuvian ejecta shows that Somma-Vesuvius magmas underwent high or low pressure fractionation, in connection with different events of the Vesuvian activity. Distinct magma reservoirs developed episodically at different depths. Isotopic and geochemical evidences do not favour large scale assimilation of crustal materials by Somma-Vesuvius magmas, but instead appear to reflect mantle characteristics.A minimum of three different (inhomogeneous) source regions is necessary to account for the isotopic features of the studied rocks.     

Mineral control of arsenic content in thermal waters from volcano-hosted hydrothermal systems: Insights from island of Ischia and Phlegrean Fields (Campanian Volcanic Province, Italy)

This paper documents arsenic concentrations in 157 groundwater samples from the island of Ischia and the Phlegrean Fields, two of the most active volcano-hosted hydrothermal systems from the Campanian Volcanic Province (Southern Italy), in an attempt to identify the environmental conditions and mineral-solution reactions governing arsenic aqueous cycling. On Ischia and in the Phlegrean Fields, groundwaters range in composition from NaCl brines, which we interpret as the surface discharge of deep reservoir fluids, to shallow-depth circulating fluids, the latter ranging from acid-sulphate steam-heated to hypothermal, cold, bicarbonate groundwaters. Arsenic concentrations range from 1.6 to 6900 μg·l^− 1 and from 2.6 to 3800 μg·l^− 1 in the Phlegrean Fields and on Ischia, respectively. They increase with increasing water temperature and chlorine contents, and in the sequence bicarbonate groundwaters < steam-heated groundwaters < NaCl brines. According to thermochemical modeling, we propose that high As concentrations in NaCl brines form after prolonged water-rock interactions at reservoir T, fO₂ and fH₂S conditions, and under the buffering action of an arsenopyrite + pyrite + pyrrhotite rock assemblage. On their ascent toward the surface, NaCl brines become diluted by As-depleted meteoric-derived bicarbonate groundwaters, giving rise to hybrid water types with intermediate to low As contents. Steam-heated groundwaters give their intermediate to high As concentrations to extensive rock leaching promoted by interaction with As-bearing hydrothermal steam.     

Clinopyroxene–liquid thermometers and barometers specific to alkaline differentiated magmas

We present new thermometers and barometers based on clinopyroxene–liquid equilibria specific to alkaline differentiated magmas. The new models were calibrated through the regression analyses of experimental datasets obtained by merging phase equilibria experiments from the literature with new experiments performed by using trachytic and phonolitic starting compositions. The regression strategy was twofold: (1) we have tested previous thermometric and barometric equations and recalibrated these models using the new datasets; (2) we have calibrated a new thermometer and a new barometer including only regression parameters that closely describe the compositional variability of the datasets. The new models yield more precise estimates than previous thermometers and barometers when used to predict temperatures and pressures of alkaline differentiated magmas. We have tested the reliability of the new equations by using clinopyroxene–liquid pairs from trachytes and phonolites erupted during major explosive eruptions at the Phlegrean Fields and Mt. Vesuvius (central Italy). The test yielded crystallization conditions comparable to those determined by means of melt and fluid inclusion analyses and phase equilibria studies; this validates the use of the proposed models for precise estimates of crystallization temperatures and pressures in differentiated alkaline magmas. Because these magmas feed some of the most voluminous, explosive, and threatening volcanic eruptions in the world, a better understanding of the environmental conditions of their reservoirs is mandatory and this is now possible with the new models provided here.     

The Ischia debris avalanche: first clear submarine evidence in the Mediterranean of a volcanic island prehistorical collapse

Sector or flank collapse with related debris avalanches is increasingly recognized as a relatively common volcanic behaviour, in particular, for large, hot‐spot related oceanic islands. Here, we report the case of a catastrophic collapse that occurred at Ischia volcanic island in prehistorical times and was driven by the volcano‐tectonic uplift of Mt Epomeo, the major relief of the island. The collapse left a subaerial to submarine horseshoe scar on the southern flank of the island and generated a debris avalanche incorporating thousands of giant blocks dispersed as far as 50 km from the island. During the emplacement, part of the debris avalanche evolved into a debris flow covering an area of 250–300 km². This constitutes the first, clear evidence of a submarine debris avalanche in the Mediterranean Sea. The major collapse was followed, and probably also preceded, by recurrent, less catastrophic terrestrial and underwater failures. Two other undersea hummocky deposits are found north and west of the island and might tentatively be correlated to the major southern collapse. Such volcanic behaviour, previously unknown for Ischia Volcano, has likely triggered tsunami waves over the entire Bay of Naples raising the question of their impact on prehistorical/historical communities.     

The Somma–Vesuvius volcano (Southern Italy): Structure,dynamics and hazard evaluation

We review the main results, with several new analyses, obtained in recent times about the structure, present dynamics and hazard evaluation at Somma–Vesuvius volcanic complex. We present a global review and interpretation of structural features, both at local and regional scale, constrained both by seismic and petrological data. The local structure of Somma–Vesuvius is reviewed in three depth ranges, shallow, intermediate and deep. The shallow velocity structure is inferred by the joint inversion of shot and local earthquake arrival time data. The main feature pointed out at shallow depth is a high velocity anomaly at the crater axis, extending down to about 5 km of depth. Such an anomaly, first observed at Vesuvius, seems to be common to many other volcanoes. It can be interpreted in terms of the presence of solidified residual magma in the shallow conduits, accumulated in last eruptive cycles. The local seismicity is strongly clustered around this anomaly, due to the focusing effect of the rigidity contrast. The seismic occurrence appears as a result of the superposition of a background level, mainly due to gravitational instability of the Vesuvius cone, and of intense activity episodes, which possibly reflect episodic internal activity. Two main zones of magma accumulation in the upper crust are evidenced by the joint interpretation of seismic and petrological data. The first one, located in the depth range 4–6 km, is mainly constrained by the crystallisation depth of phonolitic magmas which fed Plinian and sub-Plinian eruptions; the second one, around 11–15 km of depth, is mainly constrained by reflected–converted seismic waves, and in agreement with crystallization depths inferred for the moderate eruptions. The study of the deep structure, performed by regional tomography with teleseisms, further points out magma roots at higher depths (15–30 km). An additional result for the deep structure, studied at regional scale and very important for geodynamic interpretations of the Tyrrhenian volcanisms, has been the evidence for a subducting slab under the Apennines, in an area where previous models hypothesised a slab window.New original studies of crystal growth (phenocrystals and microlites) on the eruptive products allow to infer typical times of magma rising from such reservoirs, which appear very low, on the order of minutes to tens of minutes. Static deformation at this volcano, in the last 30 yr, has been detected by the joint use of levelling, GPS and DIFSAR techniques. It indicates subsidence, very concentrated in the crater area and in a narrow strip all around the volcanic edifice, with maximum rates less than 0.01 m/yr. Static deformation in the crater area appears in agreement with the mechanism of gravitational instability generating local volcano-tectonic seismicity, while the peculiar pattern around the volcanic edifice is probably due to the combination of extensional stress and volcanic loading, generating a ring normal fault-like structure. While the key results about structure and dynamics help to define pre-eruptive scenarios, a new probabilistic procedure to combine volcanological data and computer simulations has been used, in this paper, to build hazard maps giving the probability, at each location in the area, to be hit by a pyroclastic flow or to experience a destructive fall-out deposit. The review and new results of this work give then the first complete picture of the state of the art in our knowledge about Somma–Vesuvius volcano.     

The rheological evolution of alkaline Vesuvius magmas and comparison with alkaline series from the Phlegrean Fields, Etna, Stromboli and Teide

Somma-Vesuvius is considered one of the highest-risk volcanic systems in the world due to its high population density and record of highly destructive explosive activity. Eruptive style at Vesuvius varies greatly, alternating between effusive and explosive activities, and is likely strongly controlled by the evolution of the physical and chemical properties of the magma. Nevertheless, with the exception of the 1631 eruption, the rheological properties of Vesuvius magmas remain largely unconstrained. Here, we investigate the Newtonian shear viscosity (η) of dry and hydrous melts from the Mercato (plinian) and 1906 (violent strombolian) eruptions. These eruptions differ in size, eruptive style and magma chemistry (from phonolite to phono-tephrite). To evaluate the dry liquid viscosity variation covered by the eruptive products of the recent activity at Vesuvius, we measured the melt viscosities of bulk rock compositions and, for highly crystalline samples, of the separated groundmasses of tephras from the Pollena and 1906 eruptions. Hydrated samples with up to 4.24 wt% dissolved water were synthesised in a piston cylinder apparatus at confining pressure up to 10 kbar. The dry high temperature and the dry and hydrous low-temperature viscosities were obtained by combining the concentric cylinder and micropenetration techniques. The measured viscosities were parameterized by a modified Vogel-Fulcher-Tammann equation, accounting for the effect of water content, and were compared with previous measurements and models. At magmatic temperatures, the viscosities of Mercato samples are about four orders of magnitude higher than that of the least viscous investigated products from the 1906 eruption. Complex numerical models to forecast eruptive scenarios and their environmental impact are extremely sensitive to the accuracy of the input parameters and constitutive equations of magma properties. As a consequence, the numerical expressions obtained here are of particular relevance in the context of hazard assessment related to the different possible eruptive scenarios at Vesuvius through numerical simulation tools. The effect of composition on the liquid viscosities is compared to other high-Na (e.g., samples from Teide and Etna) and high-K (e.g., samples from Stromboli and Phlegrean Fields) alkaline magmas.     

Continuous gravity record at Mount Vesuvius: A tool to monitor its dynamics

The results of more than three years of continuous gravity record on Mt. Vesuvius (Southern Italy) are presented and discussed.The goal of this research is to determine whether continuous gravity records can improve the overall monitoring efforts at the volcano specifically by detecting a gravity signal of “non-tidal” origin.The ocean and atmospheric effects have been taken into account for the computation of the tidal parameters and gravity residuals. Tidal analyses have been carried out by means of classical and recent methodologies and the results compared.The time dependent behaviour of the main tidal parameters and of the gravity residuals have been compared with features of the vesuvian dynamics, namely with the seismic activity and the temporal gravity changes detected by absolute and relative gravimetry.     

Volcanic Risk Assessment and Mapping in the Vesuvian Area Using GIS

This paper assesses the risk to people and property from lava flow hazard in the Vesuvian area of Italy using a Geographical Information System (GIS). The intense urbanisation and dense population near Mt. Vesuvius make the area very hazardous. Due to the large amount of available data, GIS is an essential tool to facilitate risk evaluation and constant monitoring of the zone. This analysis is based mainly on a lava flow hazard map of Mt. Vesuvius, determined from volcanic activity between 1631 and 1944. A land-use zonation map of the area was created in order to show areal distribution of the resources, built-up centres and population. For each of the 17 municipalities in the area, demographic and urban data were entered into the GIS database and linked to each appropriate geographic unit in order to create a set of reference maps at the 1:50 000 scale. The lava flow hazard map was overlain on the land use map, and spatial and numerical information of risk were extracted from the resulting maps.     

Geochemical similarities between the Vesuvius, Phlegraean Fields and Stromboli Volcanoes: petrogenetic, geodynamic and volcanological implications

Summary Vesuvius and Stromboli are two active and extensively studied volcanoes that traditionally have been considered as having different styles of eruption, rock composition and tectonic setting. Data reveal close compositional affinities between these two volcanoes. The abundant 13–15 Ka old Stromboli leucite-tephritic rocks have radiogenic isotope signatures, and abundances and ratios of incompatible elements with the exception of Rb and K, which are identical to those of Vesuvius. The Phlegraean Fields also show close affinities to these volcanoes. The similarity between Stromboli leucite-tephrites and Vesuvius rocks cannot be the result of low pressure processes, given the differences between the two volcanoes in terms of structural features, eruptive behaviour and type of basement rocks. Instead, the observed geochemical signatures are likely to represent a primary magma composition and reveal a common homogeneous source for the two suites. The higher K and Rb contents in the Vesuvius rocks suggest either selective enrichment during magma ascent or a role for phlogopite melting during mantle anatexis. The most primitive rocks from Vesuvius, Phlegraean Fields and Stromboli reveal intermediate compositions between arc and intraplate volcanics. It is suggested that the mantle sources beneath these volcanoes consist of a mixture of intraplate- and slab-derived components. Intraplate material was probably provided by inflow of asthenosheric mantle into the wedge above the subducting Ionian Sea plate, either from the Apulian plate and/or from the Tyrrhenian Sea region. Fluids or melts released from the sinking slab and associated sediments generated metasomatic modification of the intraplate material, whose melting gave rise to the Stromboli, Vesuvius and Phlegraean Fields magmas. The present study demonstrates how comparative investigations of various volcanic centres from southern Italy allow clarification of a number of problems involving magma genesis and evolution, composition of mantle sources and geodynamic significance, which have been long debated and are difficult to solve if individual volcanoes are considered in isolation. Received July 20, 2000; revised version accepted March 19, 2001     

Multi-parametric approach to the analysis of soil radon gas for its validation as geoindicator in two sites of the Phlegrean Fields caldera (Italy)

Radon is considered one of the short- and immediate-term earthquake precursors by International Association of Seismology and Physics of the Earth’s Interior. For this reason, the accurate and reliable measurement of its specific activity in soil gas is mandatory. Since its presence is influenced by many environmental factors, in order to eliminate this influence on the radon activity measurement a multi-parametric and multi-site analysis is necessary. Following this approach, a continuous radon monitoring was carried out in two sites of the Phlegrean Fields caldera (Campania, Italy) using the RaMonA system, which also allows for the measurement of temperature, relative humidity and pressure. In particular, the dependence of measured radon specific activity on the meteorological conditions was studied using the multiple linear regression method. The analysis was implemented also by testing data averages on different timescales. In this paper, the results of a preliminary analysis performed on data collected throughout 2012 are presented; the outcomes obtained allow to emphasize site-specific behavior and to discriminate apparent radon “anomalies” of climatic origin from those tied to the phenomena occurring in the earth’s crust. The method employed showed its usefulness by removing the effects of meteorological conditions and thus to better identify the possible radon anomalies caused by seismo-volcanic activity. The peculiarities of the different sites and some correlations with earthquakes are discussed.     

Landscape response to the deposition of airfall pyroclastics from large explosive eruptions: An example from the campanian area (Southern Italy)

We present in this work data about a peculiar type of alluvial fans formed exclusively by volcaniclastic material from large explosive eruptions. Each alluvial fan results formed by the superimposition of several sedimentary bodies, each of them formed by quite homogeneous volcaniclastic material. Lithological analyses allow us to correlate each sedimentary body with the emplacement of pyroclastics from Phlegrean Fields or Somma-Vesuvius. The development of these alluvial fans is controlled by three main factors: area of dispersion of pyroclastics, morphological features of the supplying basin (i.e. mean slopes and area) and climate. Finally, we present an assessment of the minimum time needed for the complete remobilization of pyroclastics of Pomici di Base and Greenish eruptions.     

The roots of Mt. Vesuvius deduced from gravity anomalies

Summary The structures of the Somma-Vesuvius volcanic complex are modelled on the basis of the interpretation of gravity anomalies obtained from data available in the literature and acquired along a new profile along the coastline from Naples to Castellammare di Stabia. In order to highlight the contribution of shallow crustal structures, the residual anomalies were considered. A marked gravity low was recognised in the eastern sector of Vesuvius. Furthermore data interpretation was carried out along two profiles centred on the low gravity region in question: a first profile crossing the Vesuvius crater in direction WNW-ESE, and a second one in NNE-SSW direction. The 2 ? D model obtained reveals a crustal structure characterised by sediments of 2.3 Mg/m³ density, overlying bedrock with a density of 2.6 Mg/m³. Near the volcanic system the model becomes more complex due to the presence of light sediments with a density of 2.1 Mg/m³ overlying a body with a density of 2.4 Mg/m³ which extends into depth. The latter is thought to be closely related to the zone of magma ascent developed along the volcanic axis. Along the coast the volcanic component is reduced and the model shows that the layer with a density of 2.3 Mg/m³ ranges in thickness from 0 to about 3500 m. An additional body between 1500 and 3000 m with a density of 2.4 Mg/m³ was considered in order to account for the slight rise in the residual anomaly in the area in the vicinity of Mt. Vesuvius. The analysis of the gravity anomaly pattern coincides with the complex system of faults and fractures intersecting the carbonate basement and the volcanic area in question, which developed as a consequence of extensional processes at the continental edge of the Italian Peninsula due to the opening of the Tyrrhenian basin. This extensional tectonics has created favourable conditions for the collapse of the south-western slope of Mt. Vesuvius and the development of eruptive vents and cracks on its flanks. Received May 18, 2000; revised version accepted March 6, 2001     

The aquatic geochemistry of arsenic in volcanic groundwaters from southern Italy

This paper discusses the abundance, speciation and mobility of As in groundwater systems from active volcanic areas in Italy. Using literature data and new additional determinations, the main geochemical processes controlling the fate of As during gas–water–rock interaction in these systems are examined. Arsenic concentrations in the fluids range from 0.1 to 6940 μg/l, with wide differences observed among the different volcanoes and within each area. The dependence of As content on water temperature, pH, redox potential and major ions is investigated. Results demonstrate that As concentrations are highest where active hydrothermal circulation takes place at shallow levels, i.e. at Vulcano Island and the Phlegrean Fields. In both areas the dissolution of As-bearing sulphides is likely to be the main source of As. Mature Cl-rich groundwaters, representative of the discharge from the deep thermal reservoirs, are typically enriched in As with respect to SO₄-rich “steam heated groundwaters”. In the HCO₃⁻ groundwaters recovered at Vesuvius and Etna, aqueous As cycling is limited by the absence of high-temperature interactions and by high-Fe content of the host rocks, resulting in oxidative As adsorption. Thermodynamic modelling suggests that reducing H₂S-rich groundwaters are in equilibrium with realgar, whereas in oxidising environments over-saturation with respect to Fe oxy-hydroxides is indicated. Under these oxidising conditions, As solubility decreases controlled by As co-precipitation with, or adsorption on, Fe oxy-hydroxides. Consistent with thermodynamic considerations, As mobility in the studied areas is enhanced in intermediate redox environments, where both sulphides and Fe hydroxides are unstable.     

Subsidence due to crack closure and depressurization of hydrothermal systems: a case study from Mt Epomeo (Ischia Island,Italy)

Levelling surveys carried out between 1990 and 2003 on the Mt Epomeo resurgent block (Ischia Island) record negative dislocations on its northern and southern flanks with a maximum subsidence rate of 1.27 cm yr⁻¹. This deformation is not associated with the cooling, crystallization or lateral drainage of magma and cannot be explained by a pressure point or prolate ellipsoid source. Results from dislocation models and the available structural and geochemical information indicate that the subsidence is due to crack closure processes along two main ENE–WSW and E–W preexisting faults, which represent the preferred pathway of CO₂ degassing from the hydrothermal system located beneath Mt Epomeo. The monitoring of the dislocations and CO₂ flux along these faults could give useful information on the dynamics of the hydrothermal system.     

Natural background levels for some ions in groundwater of the Campania region (southern Italy)

The aim of the study was the determination of the natural background levels (NBLs) for the ions Na⁺, Cl^?, SO₄ ^2?, As³⁺, F^?, Fe²⁺, and Mn²⁺, in some groundwater bodies of the Campania region (southern Italy). The ??Protocol to evaluate the natural background concentrations?? proposed in 2009 by ISPRA (Italian Institute for Environmental Protection and Research) has been applied to the chemical data set of groundwater of the examined groundwater bodies. These analyses have also been examined following the guidelines of the BRIDGE project (Background cRiteria for the IDentification of Groundwater thrEshold). These approaches to evaluate the Threshold Values (TVs) and the NBLs, based on probability distribution functions, have been applied in many countries by various authors during the last 5?years. Changes applied to ISPRA Protocol in this study concern mainly the preselection criteria, in particular threshold values of specific ions, deriving from the aquifers geochemical features. The preselection criteria of the ISPRA Protocol have been merged with those of the BRIDGE Project in order to define a procedure suitable for the definition of the NBLs in the examined aquifers. The NBL of fluoride for the ??Phlegrean Fields?? and the ??eastern Plain of Naples?? groundwater bodies shows values deeply exceeding the reference value (REF) of 1,500???g/L, ranging between 3,600 and 15,000???g/L. The cause of this very high fluoride content is in the natural features of the aquifers constituted by volcanic and pyroclastic rocks. The volcanic origin of the aquifers is also the reason for the high arsenic content in ??Phlegrean Fields?? groundwater. Here the NBL calculated was about 47???g/L against the drinking water standard value of 10???g/L. The widespread high content of manganese and iron for the groundwater body of the ??eastern Plain of Naples?? is due to the reducing conditions related to the extensive marshlands present in the past. The very high NBL of all the examined ions for the groundwater body of ??Ischia Island?? depends on the existence of a geothermal system.     

Chemical composition of precipitation at Mt. Vesuvius and Vulcano Island,Italy: volcanological and environmental implications

Natural precipitation and water samples from passive devices were collected at Mt. Vesuvius and Vulcano Island, Italy, during the period 2004–2006, in order to investigate its possible interactions with fumarolic gases. Evidence of chemical reactions between fumarolic fluids and rain samples before and after its deposition into the sampling devices was found at Vulcano Island. Very low pH values (down to 2.5) and significant amounts of chlorine and sulfate (up to 22 mEq/l) were measured at sampling points located close to the fumarolic field. In contrast, anthropogenic contributions and/or dissolution of aerosols (both maritime and continental) influence the chemistry of rainwaters at Mt. Vesuvius, which show inter-annual variations that are highly consistent with those recorded at the coastal site at Vulcano Island. Chemistry of waters directly exposed to fumarolic fluids may then give useful information about its temporal evolution, holding the signal of the “maximum” chemical event occurred in the meanwhile. In addition, the observation of the health status of vegetation colonizing the immediate surroundings of the fumarolic fields, due to its strong dependence on the interactions with these fluids, may work as a possible biomarker of volcanic activity.     

Constraining the onset of the Holocene “Neoglacial” over the central Italy using tephra layers

A study of six tephra layers discovered in different deposits between 1600 and 2700 m a.s.l. in the Apennine chain in central Italy allowed precise stratigraphic constraints on environmental and climatic changes between ca. 4.5 and 3.8 cal ka BP. Chemical analyses allowed the correlation of these tephra layers with the eruptions of Agnano Mt Spina (AMST) from Phlegrean Field and Avellino (AVT) from Somma–Vesuvius. Major environmental changes in the high mountains of the Central Apennines occurred just after the deposition of the AMST and predate the deposition of the AVT. At this time, renewed growth of the Calderone Glacier occurred, marking the onset of the Apennine “Neoglacial”. The presence of the AMST and AVT enabled us to make a precise, physical correlation with other archives in central Italy. Synchronization of records between sites showed that the period intervening the deposition of the AMST and AVT layers coincided with environmental changes that were not always exactly in phase. This highlights the fact that stratigraphic correlations using only radiocarbon chronologies (the most common method used for dating archives during the Holocene) could produce erroneous correlation of events, giving rise to oversimplified paleoclimatic reconstructions.     

Distribution of arsenic and other minor trace elements in the groundwater of Ischia Island (southern Italy)

The island of Ischia belongs to the active volcanic area of Naples. It is formed from Quaternary volcanic rocks and exhibits intense hydrothermal activity, which is manifested through numerous springs, fumaroles and sporadic geysers. The content of minor and trace elements in groundwater has been analyzed, including some elements that are considered toxic for humans. Mean concentrations of As, B, Fe, Mn, Sb, and Se in samples from 43 aquifer points exceed the WHO recommended values and the limits set by European and Italian legislation (98/83/CE and DM 471, respectively). In general, the spatial distribution of the elements follows a common pattern: it is governed by a marked structural control, which favors hydrochemical processes that liberate the elements into the water.     

Chemistry versus time in the volcanic complex of Ischia (Gulf of Naples,Italy): evidence of successive magmatic cycles

An extensive petrochemical and geochronological study of the volcanic complex of the island of Ischia has been made in order to assess the variation of the magmatic characteristics through time. The major and trace element chemistry and the mineralogy of more than 40 samples, coupled with their K/Ar ages, reveal four phases of volcanic activity: (1) prior to 150000 years B.P. — alkali-trachyte pyroclastic products; (2) 150000–75000 years B.P. — alkali-trachytic to phonolitic lava domes and minor pyroclastics; (3) 55000–20000 years B.P. — great pyroclastic emissions of trachytic and alkali-trachytic composition; (4) 10000 years B.P.-1302 A.D. — mainly lava flows, ranging from alkali-trachytes to magmas between basalt and latite. In spite of a relatively monotonous major element chemistry, the trace element contents of the rocks show a large variation (up to a factor of 9). Comparison of glass compositions with the modal phases permits us to distinguish at least four clearly established supplies of new magma to a shallow chamber. After the first three events, the magmas possibly evolved in a closed system controlled by fractional crystallization with at least one single eutectic crystallization occurring afterwards (sodalite, nepheline and alkali feldspar+aegirine and salite). During the fourth event, increasing proportions of a less evolved liquid, suddenly charged with mafic xenocrysts, contaminated the residual liquid in the chamber and generated through time more and more basic products. Their high Th/Ta and Th/Hf ratios and Ta, Nb and Ti negative anomalies suggest an orogenic tendency of the recent volcanic activity on the island of Ischia.