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La Fossa quiescent volcano and its surrounding area on the Island of Vulcano (Italy) are characterized by intensive, persistent degassing through both fumaroles and diffuse soil emissions. Periodic degassing crises occur, with marked increase in temperature and steam and gas output (mostly CO2) from crater fumaroles and in CO2 soil diffuse emission from the crater area as well as from the volcano flanks and base. The gas hazard of the most inhabited part of the island, Vulcano Porto, was investigated by simulating the CO2 dispersion in the atmosphere under different wind conditions. The DISGAS (DISpersion of GAS) code, an Eulerian model based on advection-diffusion equations, was used together with the mass-consistent Diagnostic Wind Model. Numerical simulations were validated by measurements of air CO2 concentration inside the village and along the crater's rim by means of a Soil CO2 Automatic Station and a Tunable Diode Laser device. The results show that in the village of Vulcano Porto, the CO 2 air concentration is mostly due to local soil degassing, while the contribution from the crater gas emission is negligible at the breathing height for humans and always remains well below the lowest indoor CO2 concentration threshold recommended by the health authorities (1000 ppm). Outdoor excess CO2 maxima up to 200 ppm above local background CO2 air concentration are estimated in the center of the village and up to 100 ppm in other zones. However, in some ground excavations or in basements the health code threshold can be exceeded. In the crater area, because of the combined effect of fumaroles and diffuse soil emissions, CO2 air concentrations can reach 5000-7000 ppm in low-wind conditions and pose a health hazard for visitors. Key Points Volcanogenic carbon dioxide plume dispersion is simulated by a numerical code Air CO2 concentration remains below the recommended threshold in inhabited area In the crater area CO2 air concentration may create breathing difficulties © 2014. American Geophysical Union. All Rights Reserved.

In 2011-2012, Santorini was characterized by seismic-geodetic-geochemical unrest, which was unprecedented since the most-recent eruption occurred in 1950 and led to fear an eruption was imminent. This unrest offered a chance for investigating the processes leading to volcanic reactivation and the compositional characteristics of involved magma. We have thus analyzed the He-Ne-Ar-isotope composition of fluid inclusions in olivines and clinopyroxenes from cumulate mafic enclaves hosted in cogenetic dacitic lavas of the 1570-1573 and 1925-1928 eruptions of Nea Kameni. These unique data on Aegean volcanism were compared with those of gases collected in quiescent periods and during the unrest. The 3He/4He ratios (3.1-4.0 Ra) are significantly lower than the typical arc-volcano values (R/Ra ∼ 7-8), suggesting the occurrence of magma contamination in Santorini plumbing system, which would further modify the 3He/4He ratio of parental magmas generated in the local metasomatized mantle. The 3He/4He values of enclaves (3.1-3.6 Ra) are comparable to those measured in gases during quiescent periods, confirming that enclaves reflect the He-isotope signature of magma residing at shallow depths and feeding passive degassing. A significant increase in soil CO2 flux from Nea Kameni and anomalous compositional variations in the fumaroles were identified during the unrest, accordingly with previous studies. Simultaneously, 3He/4He ratios up to 4.0 Ra were also measured, demonstrating that the unrest was due to the intrusion into the shallow plumbing system of a more-primitive 3He-rich magma, which is even volatile richer and less contaminated than mafic magma erupted as enclaves. This new intrusion did not however trigger an eruption.

Il pianeta Terra rilascia continuamente calore verso la superficie. Questo flusso di calore è particolarmente elevato nelle zone vulcaniche (dorsali oceaniche, cordigliere, archi di isole, punti caldi) dove il magma fuso, con una temperatura di 800-1100°C, può accumularsi in serbatoi a piccola profondità (150°C), media (T=90-150°C) e bassa (T

The Colli Albani volcanic area is affected by huge degassing of likely magmatic or mantle origin, as suggested by the gas He isotopic composition. Gas rising from a buried calcareous aquifer generates several surface emissions and accumulates also in permeable layers at various depths, from 10 to 350 m, beneath impervious formations. When reached by wells, these pressurized gas pockets cause hazardous blowouts of CO 2 and H 2S, often in inhabited zone. Remedy requires the restoration of the drilled cap by cement injections, whose effectiveness can be conveniently assessed by monitoring both CO 2 soil diffuse flux and CO 2 and H 2S air concentration

Although controversy exists about the age of its most recent eruption (either 36 ka or ,23 ka), Colli Albani volcano is unanimously considered to be quiescent and not exinct. During the Holocene, several lahars were generated by overflows from Albano crater lake up to the fourth century BCE, when the Romans excavated a drainage tunnel to keep the lake level below the crater rim. Such recent activity, together with the frequent occurrence of seismic swarms underneath the crater zone, the ongoing uplift of the volcanic edifice and the magmatic affinity of the emitted gas, indicate the presence of an active magma chamber. The most likely site for a new eruption is the deep crater hosted in the southern part of the Lake Albano, where the last eruptive events occurred. Any eruption would have a strong explosive character enhanced by the interaction of magma with the water of the lake and would endanger a densely inhabited area up to the outskirts of Rome. The hazard of a new overflow from Lake Albano is very low because of the present low level of the lake. There is instead a potential for CO2 release from the deep lake water following the occurrence of rollovers, which would threaten the lake shore, a site where thousands of people spend their vacations in the summer. However, the content of dissolved CO2 is presently far from saturation and no Nyos-type events will occur today. Presently, the main hazard is related to strong gas emissions (CO2, H2S and Rn) from fractured zones and gas blowouts from wells reaching shallow gas-pressurized aquifers.

Although controversy exists about the age of its most recent eruption (either 36 ka or ,23 ka), Colli Albani volcano is unanimously considered to be quiescent and not exinct. During the Holocene, several lahars were generated by overflows from Albano crater lake up to the fourth century BCE, when the Romans excavated a drainage tunnel to keep the lake level below the crater rim. Such recent activity, together with the frequent occurrence of seismic swarms underneath the crater zone, the ongoing uplift of the volcanic edifice and the magmatic affinity of the emitted gas, indicate the presence of an active magma chamber. The most likely site for a new eruption is the deep crater hosted in the southern part of the Lake Albano, where the last eruptive events occurred. Any eruption would have a strong explosive character enhanced by the interaction of magma with the water of the lake and would endanger a densely inhabited area up to the outskirts of Rome. The hazard of a new overflow from Lake Albano is very low because of the present low level of the lake. There is instead a potential for CO2 release from the deep lake water following the occurrence of rollovers, which would threaten the lake shore, a site where thousands of people spend their vacations in the summer. However, the content of dissolved CO2 is presently far from saturation and no Nyos-type events will occur today. Presently, the main hazard is related to strong gas emissions (CO2, H2S and Rn) from fractured zones and gas blowouts from wells reaching shallow gas-pressurized aquifers.

Il dominio vulcanico laziale a nord del Fiume Tevere ospita una estesa falda di interesse regionale sostenuta da una potente sequenza di depositi appartenenti alle unità alloctone di facies toscana e tolfetana. Le discontinuità tettoniche connesse con il complesso assetto strutturale dell’area peritirrenica consente la risalita di fluidi endogeni di natura termominerale provenienti dagli acquiferi geotermici ospitati dalle sequenze carbonatiche confinate dalle unità alloctone stesse. Nella fase di risalita i gas endogeni interagiscono con le falde in relazione agli equilibri di fase imposti dalle condizioni di temperatura e pressione. Ciò fa sì che in superficie, in corrispondenza delle principali discontinuità tettoniche, si abbiano manifestazioni gassose più o meno consistenti, associate o meno a sorgenti d’acqua mineralizzata. Questa nota riporta i risultati di una ricerca interdisciplinare mirata a definire come le caratteristiche geometriche della falda delle vulcaniti, l’assetto strutturale e la consistenza dei convogli gassosi possano influenzare le caratteristiche chimico fisiche delle falde e quindi delle sorgenti. La ricerca è stata condotta a scala regionale relativamente ai distretti vulcanici vulsini e cimini e a scala di dettaglio relativamente alle più note aree di manifestazione di acque termali e/o di effusione di gas CO2. Essa si basa su consistenti campagne di rilevamento idrogeologico e chimico-fisico. A queste rilevazioni si è aggiunta quella della determinazione quantitativa delle emissioni gassose in termini di tonnellate-giorno per unità di superficie. Per meglio definire lo schema idrogeologico e geotermico dell’area di studio, sono stati prodotti dagli autori numerosi profili idrogeologici. Numerose carte tematiche, relative alla distribuzione dei valori di conducibilità, pH, temperatura delle acque sotterranee ed entità dell’emissione di CO2 consentono di valutare l’influenza del drenaggio sotterraneo della falda basale sullo specifico parametro. The Latium volcanic domain northern to the Tiber River hosts a wide aquifer of regional interest supported by a powerful sequence of deposits belonging to units of allochthonous facies “toscana” and “tolfetana”. The tectonic discontinuities associated with the complex structural setting of the perithyrrenic area allows the ascent of endogenous thermomineral fluids from the geothermal aquifer hosted by carbonate sequences which are confined by allochthonous units themselves. In the phase of ascent the endogenous gases interact with the groundwater in relation to the equilibrium phase imposed by conditions of temperature and pressure. This causes the surface, in correspondence of the main tectonic discontinuities, you have gaseous manifestations more or less consistent, associated or not to mineralized springs. This note reports the results of an interdisciplinary research aimed at defining how the geometric characteristics of the aquifer of volcanic rocks, the structural setting and the consistency of the convoys may influence the gaseous chemical and physical characteristics of aquifers and springs. The research was conducted on a regional scale in relation to the Vulsini and Cimini Volcanic Districts and at a detailed scale relatively to the most famous areas of thermal waters and / or effusion of CO2 occurrence. It is based on a consistent field hydrogeological and physical-chemical data collecting. Moreover, a quantitative determination of the gas emissions in terms of tons-days per unit of surface area has been carried out. To better define the hydrogeological and geothermal setting of the study area, many hydrogeological cross sections have been produced. Several thematic maps showing the distribution of groundwater conductivity, pH, temperature values and CO2 emission rates allow to assess the influence of the basal aquifer drainage on each single parameter.

Il dominio vulcanico laziale a nord del Fiume Tevere ospita una estesa falda di interesse regionale sostenuta da una potente sequenza di depositi appartenenti alle unità alloctone di facies toscana e tolfetana. Le discontinuità tettoniche connesse con il complesso assetto strutturale dell’area peritirrenica consente la risalita di fluidi endogeni di natura termominerale provenienti dagli acquiferi geotermici ospitati dalle sequenze carbonatiche confinate dalle unità alloctone stesse. Nella fase di risalita i gas endogeni interagiscono con le falde in relazione agli equilibri di fase imposti dalle condizioni di temperatura e pressione. Ciò fa sì che in superficie, in corrispondenza delle principali discontinuità tettoniche, si abbiano manifestazioni gassose più o meno consistenti, associate o meno a sorgenti d’acqua mineralizzata. Questa nota riporta i risultati di una ricerca interdisciplinare mirata a definire come le caratteristiche geometriche della falda delle vulcaniti, l’assetto strutturale e la consistenza dei convogli gassosi possano influenzare le caratteristiche chimico fisiche delle falde e quindi delle sorgenti. La ricerca è stata condotta a scala regionale relativamente ai distretti vulcanici vulsini e cimini e a scala di dettaglio relativamente alle più note aree di manifestazione di acque termali e/o di effusione di gas CO2. Essa si basa su consistenti campagne di rilevamento idrogeologico e chimico-fisico. A queste rilevazioni si è aggiunta quella della determinazione quantitativa delle emissioni gassose in termini di tonnellate-giorno per unità di superficie. Per meglio definire lo schema idrogeologico e geotermico dell’area di studio, sono stati prodotti dagli autori numerosi profili idrogeologici. Numerose carte tematiche, relative alla distribuzione dei valori di conducibilità, pH, temperatura delle acque sotterranee ed entità dell’emissione di CO2 consentono di valutare l’influenza del drenaggio sotterraneo della falda basale sullo specifico parametro. The Latium volcanic domain northern to the Tiber River hosts a wide aquifer of regional interest supported by a powerful sequence of deposits belonging to units of allochthonous facies “toscana” and “tolfetana”. The tectonic discontinuities associated with the complex structural setting of the perithyrrenic area allows the ascent of endogenous thermomineral fluids from the geothermal aquifer hosted by carbonate sequences which are confined by allochthonous units themselves. In the phase of ascent the endogenous gases interact with the groundwater in relation to the equilibrium phase imposed by conditions of temperature and pressure. This causes the surface, in correspondence of the main tectonic discontinuities, you have gaseous manifestations more or less consistent, associated or not to mineralized springs. This note reports the results of an interdisciplinary research aimed at defining how the geometric characteristics of the aquifer of volcanic rocks, the structural setting and the consistency of the convoys may influence the gaseous chemical and physical characteristics of aquifers and springs. The research was conducted on a regional scale in relation to the Vulsini and Cimini Volcanic Districts and at a detailed scale relatively to the most famous areas of thermal waters and / or effusion of CO2 occurrence. It is based on a consistent field hydrogeological and physical-chemical data collecting. Moreover, a quantitative determination of the gas emissions in terms of tons-days per unit of surface area has been carried out. To better define the hydrogeological and geothermal setting of the study area, many hydrogeological cross sections have been produced. Several thematic maps showing the distribution of groundwater conductivity, pH, temperature values and CO2 emission rates allow to assess the influence of the basal aquifer drainage on each single parameter.

Significativi risparmi di combustibili fossili e di elettricità e una forte riduzione dell’inquinamento atmosferico possono essere realizzati utilizzando risorse geotermiche di entalpia molto bassa, con temperature intorno o anche inferiori a 20 °C, per il riscaldamento invernale e il condizionamento estivo di ambienti. I risultati di questo studio mostrano che l’acquifero contenuto nelle ghiaie di base del Tevere rappresenta una importante risorsa geotermica per la città di Roma per questi tipi di impieghi termici. Il processa mento dei dati stratigrafici di 216 pozzi perforati negli anni scorsi nelle alluvioni del Tevere hanno consentito di elaborare mappe del tetto, del letto e quindi dello spessore delle ghiaie di base. L’acquifero si incontra a profondità tra 30 e 60 m dal piano campagna, più alta verso sud, nelle zone dell’Eur e meno a nord di Monte Mario. Questi dati indicano che la risorsa geotermica può essere estratta con pozzi di costo limitato. Lo spessore dell’acquifero di base è in genere intorno a 10 m, ma cresce a 30-40 m nel tratto nord del fiume e vi sono varie zone con spessori di 15-20 m. la continuità è ottima lungo l’asse del fiume e assicura una buona alimentazione longitudinale accresciuta da contributi laterali nelle zone dove le ghiaie vengono a contatto con livelli permeabili, con le ghiaie del Fosso della Crescenza a nord e le vulcaniti dei Colli Albani nella parte centro meridionale. L’acquifero è confinato verso il basso dalle argille dalle argille di Monte Vaticano e verso l’alto dai depositi limosi impermeabili del Tevere che impedendo la percolazione verticale delle piogge e dell’acqua del fiume, lo proteggono da fattori inquinanti e da effetti termici stagionali. I parametri chimico-fisici misurati su 17 pozzi, indicano una temperatura dell’acqua che varia da 16 a 21 °C, ma con una prevalenza di valori intorno a 18-19 °C che appaiono ideali per usi termici sia estivi che invernali. Il pH è per lo più neutro o leggermente acido in alcune zone. La conducibilità elettrica è localmente abbastanza elevata con valori di poco superiori a 5000μS/cm. È stato stimato un fabbisogno intorno a 20 l/s di acqua geotermica con T 17-18 °C per riscaldare e condizionare un grosso condominio di 40.000 m3. L’acquifero di base del Tevere può facilmente fornire tali quantitativi di acqua in vari punti della città, considerato che comunque l’acqua, dopo la sua utilizzazione dovrà essere re iniettata nell’acquifero di provenienza. Significant saving in the fossil fuel and electric energy consumption and a strong reduction of the atmospheric pollution can be obtained by using low enthalpy geothermal resources., with temperature around or even below 20°C for space heating and conditioning. The results of this study indicate that the aquifer contained in the basal gravels of Tiber River represents an important geothermal resource for this kind of direct heat utilization in the city of Rome. Maps describing the variation along the river course of the top, bed and hence thickness of the base gravels have been obtained by processing the stratigraphic data of 216 wells drilled in the past in the Tiber alluvional deposits. The aquifer top is found at 30-60m depth from the ground, higher depths being found in the southern Eur zone and the shallower once in the zone Nord of Monte Mario. This values indicate that the geothermal water can be easily extracted with low-cost wells. The thickness of the base aquifer is usually around 10m, but is rises to 30-40m in the northern river sector and to 15-30m in several other zones. There is an excellent continuity of the aquifer along the river course, that ensures a good longitudinal water recharge, that is increased by lateral contribution from the zones where the gravels are in contact with permeable rocks, such as the Fosso della Crescenza gravels, to the North and the Colli Albano volcanic in the central-southern sector. The aquifer is confined downward by the Monte Vaticano Pleocenic shales and upward by impervious Tiber silt deposit. The latters prevent vertical percolation of rain and river waters protect the base aquifer from both pollution and seasonal thermal effects. Physic-chemical parameters measured in 17 wells indicated a water temperature (T) ranging from 16 to 21,6 °C, but usually around 18-19 °C, values that appear as ideal for direct heat utilization. The pH is mostly neutral and slightly acid in some zones, whereas electrical conductivity is locally rather high with values slightly exceeding 5000µS/cm. it has been stimated that 20 l/s of a geothermal water with a T of 17-18°C are needed for winter heating and summer cooling of a 40,000 m3 space. The base Tiber aquifer can easily provide such a resource in several zone of Rome city considering that the water, after its utilization will have to be reinjected into the provenance aquifer.

The Red Sea and Aden rifts (or propagators) meet in Afar. Here we use remote sensing and field analyses to define the geology and structure of the southern part of the Red Sea propagator, in Central Afar. This consists of the NW-SE trending Tendaho Graben (TG) and the younger and active NW-SE trending Manda Hararo Rift (MHR), partly within TG. Tectonic and volcanic activity within TG developed mostly between ~1.8 to ~0.6 Ma, with a stretching factor ~1.1, an extension rate ~3.6 mm/yr and the fissural eruption of part (~7000 km3/Ma) of the Afar Stratoid sequence (mainly basaltic lava flows and ignimbrites). MHR, before terminating southward, has a ~1.04 and extension rate ~1.2 mm/yr, and is associated with the emission of ~600 km3/Ma of basalts in the last ~0.2 Ma. These data suggest that, after the exceptional amount of magma erupted between ~1.8 to ~0.6 Ma, magmatic and tectonic activity significantly decreased along the southern part of the Red Sea propagator in the last ~0.2 Ma. This decrease coincides with the on-land development and migration of the more active (inferred extension rate in the order of ~10 mm/yr, as proposed in previous studies) Aden propagator, suggesting that spreading in Central Afar mainly occurred along one active propagator at any one time.