Search

Paleosols (PSs) contain valuable information about the climatic conditions under which they formed and constitute an outstanding archive of past weathering processes. Nevertheless, paleosol dating over most of the Quaternary remains challenging. Volcanic environments are unique sites for such purposes, as precise radiometric age determination can be achieved on volcanic units ‘bracketing’ PSs. Here, we present a combined geochemical and geochronological study of PSs spanning the last Myr in the Central Azores archipelago (Pico, Faial and São Jorge Islands; central North Atlantic). Precise K-Ar dating of lava flows on groundmass separates (unspiked Cassignol-Gillot technique) yield ages with a typical uncertainty of a few kyr, allowing us to tightly constrain PS ages and weathering rates near key paleoclimatic transitions. PS geochemistry further allowed us to reconstruct weathering conditions and estimate Mean Annual Precipitation and Temperature (MAP & MAT) by two proxies previously validated for other volcanic terranes (CIA-K and Clayeyness).Four periods of PSs formation are constrained at 870-845 ka, ~725 ka, 320-280 ka and 130-45 ka. Most PSs formed just after interglacial peaks, with a few exceptions. Our MAP reconstructions are variable (600-1,500 mm/yr), but generally lower than current annual precipitations (~1,000 mm/yr). MAT estimates (14-28°C) are higher than present-day annual temperatures (~17.5°C). MAP & MAT variations are in general agreement with global climatic curves; the highest values (28°C, 1,500 mm/yr) are reached at ~855 ka, coinciding with an interglacial peak. The younger PSs (130-45 ka) indicate more stable MAP & MAT in the ranges 650-1,000 mm/yr and 15-20°C, respectively and seem to show a temperature decrease after the MIS5e interglacial stage.Most paleosols were formed in a few kyr under high MAT (>17°C) and moderate to high MAP (>700 mm/yr), supporting a major influence of temperature on weathering kinetics. Parental material texture also had an important role, as several PSs formed upon pyroclastic deposits over most of their depth, whereas those developed on lava flows were generally restricted to the highly fragmented upper brecciated parts. Minimum vertical soil formation rates are in the range of ~0.3-4.5 cm/kyr, with a mean of ~1.7 cm/kyr and an outlier around ~10 cm/kyr. Those generally high values can be explained by the highly vesicular parental material, and by an exceptionally feldspar-rich (easily weathered) parental rock for the outlier.As current precipitation and temperatures are higher than the threshold values of ~700 mm/yr and ~17°C under which most PSs formed, enhanced soil formation is expected for the near future, especially in the context of global warming and particularly in volcanic contexts. This may have important and fast impacts on local human activities, but also regarding CO2 consumption by rock weathering and geological hazards.

Understanding the pre-eruptive volatile contents in magmas is critical to charactering the magmatic plumbying systems that feed acative volcanoes, and is key to volcano monitoring and volcanic hazard assessment. Silicate melt inclusions (MIs) hosted in primitive minerals are a powerful tool to definite parental melt volatile contents, and to track the volatile degassing path upon magma ascent and decompression.Here, we apply different analyses (Raman Spectroscopy, Nano SIMS, Electron microprobe, Laser Ablation ICPMS) for the characterisation of major and trace elements and volatiles in silicate melt inclusions entrapped in minerals from recently erupted tephra by Fogo Volcano in Cape Verde archipelago, one of the most active intraplate volcanic systems on Earth.Our aims are to (i) characterise the pressure-dependent magma compositional changes taking place during magma storage and ascent, (ii) model magmatic degassing and (iii) constrain the magmatic source, and the rates/modes of magma ascent prior and during eruption.Seventeen MIs hosted in twelve olivine phenocrysts (Fo79-85) were examined from tephra samples of two distinct periods of the last 10 ky of activity of the volcano. In detail, we studied basanitic (SiO2 ~42 wt.%, MgO ~4.8 wt. %) and alkali-rich (Na2O + K2O = 6.9 wt.%) tephra samples of São Jorge (early Holocene activity, ~10 ka) and of the most recent eruptions (1951 and 2014/15).Results reveal high concentrations of incompatible trace elements (e.g.,˜70 ppm Nb) and dissolved volatiles ( ˜2.1 wt.% H2O and ≥1 wt.% CO2) in the parental (un-degassed) magma. We use different H2O-CO2 solubility models to estimate MI entrapment pressures along the magma plumbing system. The deepest entrapment pressures of ˜1000-1400 MPa (corresponding to ˜ 30-46 km) are recorded in Holocene products, while the inclusions from the recent eruptions indicate shallower entrapment pressures of ˜ 350-1100 MPa (˜ 11-35km). These entrapment pressure data, combined with previous independent barometric results, demonstrate a relatively deep (30-40 km) magma source for Fogo eruptions. Our results are the first to unambiguously demonstrate the CO2-rich nature of alkali-rich mafic melts feeding intraplate volcanism at Cape Verde.

To investigate unexplored areas and apply methodologies suitable for monitoring volcanic activity, a pioneer study was undertaken in the crater lagoon of Vila Franca do Campo Islet to identify possible CO2 degassing zones in the marine environment. This study was carried out using a floating accumulation chamber, which to the best of our knowledge, has only been applied to lacustrine environments.A survey was carried out in the crater lagoon in August 2017, resulting in a total of 143 CO2 flux measurements. Other parameters, such as water temperature, pH, electrical conductivity, and depth, were also determined at each measuring point, covering a study area of 0.02 km2. At one of the deepest sites with higher CO2 flux values, water samples were collected at depth for determination of stable isotopic composition.Water temperatures ranged between 21.0 and 27.0 °C, pH from 8.24 to 8.89, and electrical conductivity from 52.5 to 53.9 mS/cm. As expected, due to the marine water composition, sampled waters are of the Na-Cl type. CO2 flux varied between 0.581 and 1.0 g m-2 d-1 (average = 2.967 g m-2 d-1). A single CO2 population, characterized by low CO2 fluxes, points to a biogenic CO2 origin (δ13C = −9.62‰). The estimated value for the total CO2 emitted from the water surface is 0.05 t d-1. CO2 flux measurements were also compared with the structural features that cross the tuff cone, but no clear relation was observed with fractures/faults.This methodology should be applied to other coastal marine areas, especially where anomalous gas emissions have been reported.

This study provides the first micro-thermometric data of fluid inclusions (FIs) in mafic loose (disaggregated) xenocrysts and ultramafic xenoliths in explosive products of the melilitite-carbonatite Mt. Vulture volcano (southern Italy). Pure CO2 late stage FIs hosted in rock-forming minerals of wehrlite xenoliths and clinopyroxene xenocrysts were trapped at the local crust-mantle boundary (32 km). In contrast, trapping pressures within the loose olivine xenocrysts are from 3.2 to 4.5 kbar (8–13 km). Considering the ongoing degassing of mantle-derived CO2 rich gases, together with seismic evidences of the presence of low amount of melts at depth, and the tectonic control of the past volcanic activity, our study opens new perspective about the hazardous nature of the “quiescent” melilitite-carbonatite volcanoes.

Dal 2016 in Veneto ed in particolare a Verona si è registrato un enorme aumento di nigeria-ne vittime di tratta a scopo di sfruttamento sessuale. Come servizio sociale del Comune di Verona, all'interno delle azioni del Progetto NAVe Network Antitratta per il Veneto è emersa l'esigenza di essere più efficaci negli interventi dei vari attori coinvolti nel progetto di aiuto alle ragazze per molte difficoltà nella creazione di relazioni interpersonali di fiducia, con conseguenti esiti fallimentari dei percorsi di assistenza, dovuti sia a limiti dei dispositivi di intervento sia alle sempre più complesse problematiche rilevate (scarsa motivazione, com-portamenti adolescenziali, esiti da traumi, aborti, atti autolesivi, tentati suicidi, ricoveri ospe-dalieri, allontanamenti, comportamenti a rischio e devianti, uso inconsapevole dei social net-work, ecc.). C'era l'esigenza di mettersi in discussione e modificare approcci e modalità di intervento, al fine di essere più efficaci nei percorsi di inclusione individuali, cambiare pro-spettiva e rimettere al centro le vere protagoniste dei percorsi di inclusione. Si è quindi scelto di fare un lavoro di gruppo tra minorenni e neomaggiorenni in carico al servizio sociale. Puntando su accettazione incondizionata e autodeterminazione delle perso-ne, si è avviato un percorso di empowerment di gruppo per accompagnare le giovani nige-riane vittime di tratta seguite in un percorso pedagogico antioppressivo di liberazione. Le attività sono condotte e facilitate da tre assistenti sociali, una mediatrice linguistico cultu-rale nigeriana e da una ragazza nigeriana con funzione di peer educator. Da settembre 2018 si sono organizzati incontri di 4-5 ore ogni sei settimane. Come scelta di conduzione delle attività si è scelto di non dare eccessiva strutturazione agli incontri e di utilizzare delle tecniche di animazione per facilitare un clima informale che age-volasse le relazioni e la libera espressione. L'obiettivo principale non è quello di trasmettere contenuti, ma di stimolare un processo di maturazione e consapevolezza del sé. Il messaggio esplicitato da subito era molto chiaro: «come sistema pubblico di assistenza siamo molto in difficoltà: abbiamo bisogno che siate voi stesse a farci capire come aiutarvi meglio». Le ra-gazze hanno così compreso il ruolo di partecipazione attiva richiesto; contemporaneamente la sfida per il servizio sociale ed i sistemi di accoglienza è stata quella di mettersi maggior-mente in gioco, per ridare fiducia alle ragazze e riconoscere loro competenze e capacità nell'autodeterminarsi. Da loro è inizialmente emersa una propensione a concentrarsi su temi legati al presente ed al futuro (la vita in comunità, la stabilizzazione nel territorio italiano, il lavoro, ecc.) ed una tendenza ad evitare tematiche più dolorose (il passato, il viaggio e l'esperienza di tratta, il rapporto con la Nigeria, ma anche in qualche modo il riconoscimento/consapevolezza di uno status di vittima che necessita di protezione). Si sono coinvolti negli incontri vari soggetti esterni soggetti della rete dei servizi, anche di tipo istituzionali (Questura, servizi specialistici sociosanitari, ecc.), affrontando alcune tematiche scelte dalle ragazze (le regole delle comunità, i documenti, la salute, le emozioni, le relazioni interpersonali, ecc.). Dopo un anno e mezzo, si individuano alcuni iniziali indicatori di esito: continuità della pre-senza e partecipazione attiva agli incontri, clima del gruppo, interazioni tra le ragazze all'interno e fuori dal gruppo, creazione di vicinanza e fiducia verso le istituzioni, tenuta dei percorsi di inclusione, maggiore attenzione, consapevolezza e disponibilità a mettersi mag-giormente in gioco, oltre ad un allargamento e coinvolgimento attivo da parte di servizi so-ciosanitari pubblici.

The Pico do Fogo volcano, in the Cape Verde Archipelago off the western coasts of Africa, has been the most active volcano in the Macaronesia region in the Central Atlantic, with at least 27 eruptions during the last 500 years. Between eruptions fumarolic activity has been persisting in its summit crater, but limited information exists for the chemistry and output of these gas emissions. Here, we use the results acquired during a field survey in February 2019 to quantify the quiescent summit fumaroles' volatile output for the first time. By combining measurements of the fumarole compositions (using both a portable Multi-GAS and direct sampling of the hottest fumarole) and of the SO2 flux (using near-vent UV Camera recording), we quantify a daily output of 1060±340 tons CO2, 780±320 tons H2O, 6.2±2.4 tons H2S, 1.4±0.4 tons SO2 and 0.05±0.022 tons H2. We show that the fumarolic CO2 output from Pico do Fogo exceeds (i) the time-averaged CO2 release during 2015-type recurrent eruptions and (ii) is larger than current diffuse soil degassing of CO2 on Fogo Island. When compared to worldwide volcanoes in quiescent hydrothermal-stage, Pico do Fogo is found to rank among the strongest CO2 emitters. Its substantial CO2 discharge implies a continuous deep supply of magmatic gas from the volcano’s plumbing system (verified by the low but measurable SO2 flux), that becomes partially affected by water condensation and sulphur scrubbing in fumarolic conduits prior to gas exit. Variable removal of magmatic H2O and S accounts for both spatial chemical heterogeneities in the fumarolic field and its CO2- enriched mean composition, that we infer at 64.1±9.2 mol. % H2O, 35.6±9.1 mol. % CO 0.26±0.14 mol. % total Sulfur (S ), and 0.04±0.02 mol. % H2.

The recent eruption from the Cumbre Vieja volcanic system at La Palma Island (19 September to 14 December 2021) occurred through the impulsive emission of various batches of magma. The first emitted magma is a tephrite (clinopyroxene, amphibole and rare olivine phenocrysts). The following pulses erupted basanites (clinopyroxene and olivine phenocrysts).Fluid inclusions and seismicity data of the first 40 days of activity are here merged to provide a snapshot of the magma ascent path.Fluid inclusions form trails through the crystals or are more rarely in isolated clusters. They show evidence of partial density re-equilibration events. At room temperature are single phase (L) or may contain a vapour bubble (V+L).Trapped fluid is pure CO2 (Tm=-56.6 ±0.1 °C). Final inclusion homogenisation occurred to the liquid (ThL) phase in all crystals and to the vapor (Thv) in few olivines. The corresponding density values have been recalculated to account for max 10% water in the trapped fluid.In amphiboles (N=60) ThL=23.3-30.9 °C (ρr=546-768 kg·m3);In clinopyroxenes (N=69) ThL=27.2-31 °C (ρr=514-703 kg·m3);In early olivines (N=241) ThV=30.4-30.9 °C (ρr=382-464kg·m3); ThL=-6.2-31 °C (ρr=492-963 kg·m3);In late october olivines (N=180) ThV=30.9 °C (ρr=464kg·m3); ThL=20.6-30.9 °C (ρr=546-802 kg·m3).The histograms of density data reveals fluid trapping and re-equilibration events. Pressures were obtained from isochore distribution in the P-T space at the trapping temperature of 1075 °C for the tephrite and 1150° C for the basanite.The tephrite ascended from a depth of ~17.2 km (487 MPa) and partially re-equilibrated at ~14.2 km (392 MPa), ~11.5 km (307 MPa), ~10 km (264 MPa) and ~8.2 km (218 MPa).Basanites ascended from (or through) a depth between ~25.8 and ~22.6 km (656-757 MPa). Multiple ponding stages are between ~19 and ~17 km deep (484-543 MPa), at ~12 km (336 MPa) and from ~8.7 to ~6.1 km (162-229 MPa).This picture agrees with the spatial and temporal pattern of the seismicity recorded during the eruption. After a very rapid pre-eruptive phase, lasting about a week, in which hypocentres rapidly ascended from about 10 km depth up to the surface a few hours before the eruption, seismicity waned considerably in just a few days. Since 27 September, a progressive increase of the seismicity in a cluster located at about 8-12 km depth was observed. In the following days, we observed the appearance of another cluster of hypocentres at a depth of about 20-25 km. Seismicity increased progressively during the first weeks of October, with many events having magnitudes higher than 4 in both clusters. The seismicity started waning at the beginning of December, disappearing almost entirely at the end of the eruption. We interpret these syn-eruptive seismicity clusters at the effect of crustal readjustment following the rapid emptying of two magmatic reservoirs located respectively just beneath each seismicity cluster. This model agrees well with the bimodal depth range inferred from fluid inclusion, as well as with the observed variation in the composition during the eruption.

Mafic alkali-rich magmas, such as those which form the Canary Islands, Spain, have been proposed as being CO2-rich due to low-degree partial melting and the presence of recycled oceanic crust in the mantle source region. A CO2-rich mantle source of Canary magmas has been suggested from melt inclusions study of the 2011 submarine El Hierro eruption, but this has not been verified yet by directly measuring magmatic CO2 emissions during a subaerial eruption as the last such event in the archipelago, in 1971, occurred before the advent of modern gas sensing tools. Here we report on the first results for gas emissions from the2021 eruption of Cumbre Vieja on La Palma island. We determined the chemical composition and mass flux of magmatic degassing during both effusive and explosive activities by combining direct plume measurements with MultiGas sensors from the ground, UAV and helicopter, OP-FTIR remote sensing and satellite-based (TROPOMI) SO2 flux quantification based on back-trajectory modelling. Degassing mass budgets and the magma volatile concentrations were then derived from microprobe analysis of olivine-hosted melt inclusions and comparing our gas results with best estimates of the magma extrusion rates during both explosive and effusive activities. Based on this approach we obtain a direct quantification of the initial CO2 content of the magma and of the exsolved pre-eruptive CO2 gas phase that fed the Cumbre Vieja eruption.We find unprecedentedly high CO2 content in the mantle source of La Palma magma, consistent with high volatile contents predicted from petrological analyses. Eruptions of oceanic island alkali-rich magmas produce disproportionately high CO2 emissions, highlighting the key role mantle heterogeneity plays in determining the impact of intraplate volcanism.

The architecture of the magma storage system underneath Fogo Volcano (Cape Verde Archipelago) is characterised using novel fluid inclusion results from fifteen basanites, spanning the last 120 thousand years of volcanic activity, and encompassing a major flank collapse event at -73 ka. Fluid inclusions, hosted in olivine and clinopyroxene, are made of pure CO2, and based on their textural characteristics, are distinguished in early (Type I) and late (Type II) stage. Inclusions homogenize to a liquid phase in the 2.8 to 30.8 degrees C temperature range. Densities values, recalculated assuming an original 10% H2O content at the time of trapping, range from 543 to 952 kg center dot m(-3), and correspond to entrapment or re-equilibration pressure ranges of 500-595 MPa, 700-740 MPa, and 245-610 MPa respectively for pre-collapse, early post-collapse, and Holocene/historical eruptions. These entrapment pressures are interpreted as reflecting the existence of two main magma accumulation zones at similar to 25 km and similar to 13-21 km depth, and a zone of fluid inclusion re-equilibration at 9-12 km depth. There is evidence of a complex temporal evolution of the magma system. Historical eruptions, and especially the three most recent ones (occurred in 1951, 1995 and 2014-25), bring fluid inclusion evidence for transient, pre-eruptive shallow (9-17 km depth) magma ponding. Early post-collapse (60 ka) volcanics, in contrast, document fast magma transport from -25 km, and suggest a reconfiguration of the magma system after the Monte Amarelo collapse event.

Oxygen fugacity (fO2) is a fundamental variable in igneous petrology with utility as a potential tracer of recycled surficial materials in the sources of mantle-derived lavas. It has been postulated that ocean island basalts (OIB) have elevated fO2 relative to mid-ocean ridge basalts (MORB) owing to more oxidized source regions. To clarify this issue, trace-element systematics of olivine grains are reported from OIB lavas with HIMU (high-; Mangaia, Canary Islands), enriched mantle (EM; Samoa; São Miguel, Azores Islands) and depleted MORB mantle (DMM; Pico, Azores) Sr-Nd-Pb-Os isotopic signatures, to constrain the fO2 of each magmatic system. Despite sampling distinct mantle reservoirs based on radiogenic isotope systematics, these OIB suites show similar fO2, ranging from +1.5 to +2.9 FMQ, with an average of 2.0 ± 0.7 FMQ, significantly higher than MORB at +0.6 ± 0.2 FMQ using the same oxybarometer. OIBs show no correlation between fO2 and bulk rock isotopic ratios or parental magma compositions. The lack of correlations with isotopic signatures likely results from radiogenic isotope signatures being hosted in volumetrically minor trace element enriched mantle lithologies, while fO2 reflects the volumetrically dominant mantle component. Higher fO2 in OIB relative to MORB implies a uniformly oxidizing plume source mantle that may be the result of either a common oxidized oceanic crust-rich reservoir parental to all modern plume lavas, or preservation of un-degassed and oxidized mantle domains formed early in Earth history.

A set of springs were sampled along Sao Miguel Island (Azores, Portugal) to proceed to the characterization of the major-ion and radon (222Rn) content. According to the selection criteria a total of 42 discharges were sampled, both during winter and summer periods, along major geological units, namely 3 springs at Sete Cidades Volcano, 4 at Nordeste Volcano, 17 at Fogo Volcano, and 18 at Furnas Volcano. Spring water temperature ranges from 12.8 to 78.1 °C in winter (mean = 23.6 °C), and from 12.6 to 76.7 °C in summer (mean = 23.9 °C), and the dataset comprehends 26 (winter) to 21 (summer) cold springs, 3 to 8 ortothermal springs, as well as 13 thermal discharges. Mean electrical conductivity is equal to 552.9 μS/cm (winter) and 550 μS/cm (summer), suggesting a short residence time, and waters are acidic to slightly basic in character (pHwinter: 4.16–7.16; pHsummer: 4.05–7.35). Groundwater chemistry is manly controlled by silicate leaching, enhanced by the water temperature, seawater spraying and by the active volcanic environment. 222Rn content ranges between 0.99 and 551.64 Bq/L (mean = 47.8 Bq/L) in winter and between 1.42 and 559.67 Bq/L (mean = 49.4 Bq/L) in summer. All the springs with anomalously higher values are located in Fogo Volcano, while the lowest radon concentrations are observed at Furnas Volcano. Groundwater temperature exerts a control over the 222Rn concentration; thus, the lower content corresponds to the most mineralized thermal waters. Springs with the higher radon content show the radiogenic contribution from uranium-rich peralkaline syenite intrusive body. Furthermore, data reveal that besides this lithologic control some waters are influenced by 222Rn migration from a deeper source towards shallower aquifers, carried by a volatile flux of CO2.

New highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundance and Os isotopic compositions, along with major- and trace-element abundance and Sr-Nd-Hf-Pb isotope data are reported for high-MgO (>8–17 wt.%) lavas from the islands of Sao Miguel, Terceira, Pico and Faial in the Azores archipelago. The lavas span the range of Sr-Nd-Hf-Pb isotope and trace-element abundance variability reported previously for the islands. Pico and Faial lavas preserve distinct absolute and relative HSE abundances and 187Os/188Os (ƩHSE = 2 ± 2 ng g−1; 2SD; 187Os/188Os in lavas with > 50 pg g−1 Os = 0.1255 ± 31; 2SD) compared with Sao Miguel and Terceira lavas (ƩHSE = 5 ± 3 ng g−1; 187Os/188Os50pg = 0.1284 ± 48). Although HSE abundance variations in volcanic rocks from individual Azorean islands can be explained by sulfide crystallization, those between Pico and Faial and Sao Miguel and Terceira can only reasonably be attributed to partial melting of distinct mantle sources. Pico and Faial lava compositions are consistent with high degrees of sulfide melting (90–100%) from a sulfide-depleted mantle source ( 0.128). Radiogenic sulfides are not solely linked to the enriched lithophile isotope signature found in eastern Sao Miguel. Instead, Sao Miguel and Terceira magmatism may collectively result from metasomatism associated with the recycling of old subducted oceanic lithosphere. Abundances of sulfide-hosted HSE, and 187Os/188Os, are decoupled from silicate-hosted Sr-Nd-Hf-Pb isotope compositions, in the mantle. Compositional variations of the HSE among global OIB suggest that, while distinct mantle domains are represented by heterogeneous sulfide mineralogy, comprising common metasomatic (enriched) and magmatic (depleted) compositions, these sulfide populations are distinct beneath different OIB due to their origin in different lithospheric materials (e.g., oceanic crust versus pelagic sediment), and to the degree of partial melting caused by variable mantle potential temperature or lithospheric thickness.

Our discovery of moissanite grains in a peralkaline syenite from the Agua de Pau Volcano (Sao Miguel, Azores Islands, Portugal) represents the first report of this mineral in present day oceanic geodynamic settings. Raman spectroscopy and single-crystal X-ray diffraction show the presence of both the 6H and 4H polytypes with the predominance of the first one. The distribution of trace elements is homogeneous, except for Al and V. Azorean moissanite often hosts rounded inclusions of metallic Si and other not yet identified metallic alloys. A process involving a flushing of CH4-H2 ultra-reducing fluids in the alkaline melts might be considered as a possible mechanism leading to the formation of natural SiC, thus calling for strongly reducing conditions that were locally met in the crust-mantle beneath the Sao Miguel Island.

Gaseous elemental mercury (Hg0g or GEM) and CO2 are emitted from active hydrothermal systems in volcanic areas mostly through diffuse degassing. Here, data from about 400 simultaneous measurements of soil GEM and CO2 flux performed within the caldera of Furnas Volcano, Sao Miguel Island (Azores) are discussed for the first time. This survey aimed at providing a new insight into the origin and magnitude of GEM in the investigated hydrothermal/volcanic environment and its relation with CO2 release. The distribution of GEM and CO2 emissions over an area of about 0.04 km2 are correlated with soil temperature, and measurements have provided total CO2 and GEM output of 39 t d−1 and 1.8 × 10−6 t d−1, respectively. These results are similar to the emission from currently active volcanic/hydrothermal areas elsewhere, as well as from important non-volcanic areas, such as Sulphur Bank Mercury Mine (California, USA) and Idrija Mercury Mine (Slovenia, EU), pointing out the relevance of diffuse degassing processes at Furnas Volcano. Atmospheric spot measurements in the most vigorous fumarole vents of the geothermal field have shown that the fumarolic GEM contribution (9.2 × 10−7 t d−1) represents a minor fraction of the total (fumarolic + diffusive) GEM output (2.7 × 10−6 t d−1) for the study area of this volcano. Basing upon the integration of the hydrothermal CO2 released and the H2O/CO2 ratio in the fumarolic gas, we have also estimated the thermal energy release associated with diffuse degassing at Furnas Volcano. Our estimates are ∼7.8 MW and 9.8 MW, respectively for Furnas Lake and Furnas Village fumaroles.

The Lajes Ignimbrite on Terceira Island (Azores) records the last major pyroclastic density current-forming eruption of Pico Alto Volcano that occurred ca. 21 kyrs ago. This comenditic trachyte ignimbrite contains up to 30 vol% of crystals, mostly anorthoclase. Geochemical investigation of the products collected throughout two key outcrops reveals that major element compositions are poorly variable, whereas trace elements show significant variability, pointing to the presence of a zoned magma reservoir. Thermometry and oxygen fugacity estimations yielded pre-eruptive temperatures of 850–900 °C and ∆NNO from − 2.4 to − 1.8. Melt–alkali-feldspar hygrometer indicates magmatic H 2 O contents ranging from 5.8 wt% in the upper part of the reservoir to 3.6 wt% at the bottom, indicating that the magma reservoir (confined at ~ 4 km depth) was mainly water-undersaturated before the eruption, except for the topmost portion. Two types of anorthoclase crystals were identified. Type 1 crystals show reverse to oscillatory zoning with An contents of 0.4–2.1 mol% and Ba of 200–2000 ppm. They formed in the middle/upper portion of the reservoir, where fractional crystallization processes dominated. Type 2 crystals, mainly present in the less evolved products, are characterized by patchy-zoned cores with large dissolution pockets surrounded by thick oscillatory-zoned rims and show a wide compositional range (An of 0.5–4.7 mol% and Ba of 142–4824 ppm). Their zoning patterns, together with whole-rock and glass compositions of the juvenile clasts, are consistent with the involvement of an anorthoclase-bearing cumulate from the bottom of the reservoir that underwent partial melting. Crystal dissolution was likely induced by the presence of a heat source at depth, without any mass transfer to the eruptible magma, as suggested by the lack of petrographic and chemical evidences of mixing between the resident comenditic trachyte and a mafic/intermediate magma. Thermal instability generated convective plumes that were responsible for the admittance of crystals from the cumulate level into the intermediate portions of the magma reservoir and possibly acted as trigger of the explosive eruption.

A multidisciplinary approach combining petrological, geochemical, and fluid-inclusion studies with seismic monitoring data was used to build a model of the magma feeding system of Pico volcano (Azores islands, North Atlantic Ocean). We explore how magma has ascended to the surface in the last 10 ka and how this ascent is associated with the selective activation of the three tectonic systems intersecting the volcano. The deepest and most important ponding level for all ascending magmas is located at 17.3–17.7 km and corresponds to the Moho Transition Zone (MTZ), which marks the transition from mantle rocks to ultramafic cumulates. At shallower depth ascending magmas carry >30 vol% of clinopyroxene and olivine. Each magma ascent followed a distinct path and ponded often for a limited period. Ponding levels common to all feeding systems are present at 16.3–16.7 km, 12.1–14.5 km, 9.4–9.8 km, and 7.7–8.1 km. These depths mark important discontinuities where magmas formed stacked sills and evolved through fractional crystallisation. Dense and un-decrepitated fluid inclusions show rapid ascent from the MTZ along the Lomba do Fogo-Sao Joao fault (N150° system) and along the N120° regional transtensive system, despite multiple intrusions. Magma ponding at 5.6–6.8 km occurs where the N150° and N60° tectonic systems intersect each other. Here magma evolves towards plagioclase-rich and is only erupted at the summit crater and subterminal vents. This region is the source of the frequent microseismicity recorded at 4 to 7 km beneath the southern flank of Pico volcano, which might be associated with the early stages of formation of a more complex magma reservoir. The local and regional tectonics are of paramount importance in the activation of the different magma feeding systems over time. This new information is fundamental to improve the knowledge on the future eruptive behaviour of Pico volcano and can have significant implications on the mitigation of volcanic risk. This multidisciplinary approach can be applied not only to other volcanoes of the Azores but also to poorly monitored oceanic volcanoes, where magma ascent strongly depends on the activation of tectonic systems.

Clinopyroxenes from the Pico Volcano (Pico Island, Azores Archipelago) have been used as a proxy to define the water content of primitive magmas and the volcanological history of the erupted rocks. This very young volcano (53 ± 5 ka) is at a primordial stage of its evolution in comparison with the other volcanoes of the Azores. Clinopyroxenes from Pico Volcano underwent important dehydration processes and after annealing experiments under H2gas flux, a pre-eruptive H2O content between 93 and 182 ppm was recovered. A moderately high cooling rate for the cpx-host lavas expressed by the clinopyroxene closure temperature (Tc = 755–928 °C ± 20 °C) correlates with the dehydration, suggesting that this process may have occurred during magma ponding at the Moho Transition Zone (17.3–17.7 km) and/or after the eruption. By applying anIVAl-dependent partition coefficient to the measured H amount in clinopyroxene, the pre-eruptive water content of the parental magma was calculated to vary between 0.71 and 1.20 (average of 1.0) wt%. Clinopyroxene geobarometry performed by combining X-ray diffraction with mineral chemistry points to a general crystallisation from the mantle lithosphere (~ 8–9 kbar) to the oceanic mantle/crust boundary (~ 4–5 kbar). The similar major and trace chemistry, water content and Fe3+/Fetotratio of clinopyroxene, suggest similar conditions of oxygen fugacity, water content and fractional crystallisation of the magma from which clinopyroxene cores crystallised during the Pico Volcano central eruptions from 40 ka to historical times.

Petrological and geochemical (major element, trace element, Sr–Nd isotope) data for recent (

International audience; The Pico-Faial ridge is a steep WNW-ESE volcanic ridge that has developed within the Nubia-Eurasia diffuse plate boundary, close to the Azores Triple Junction. The ridge comprises two islands, Pico and Faial, separated by a shallow (< 100 m depth) and narrow (< 8 km) channel. Despite some similarities, the two islands show contrasting features still deserving explanation: (1) meaning of GPS data; (2) meaning of palaeomagnetic data; (3) the island-scale Faial Graben does not have a counterpart in Pico; (4) both islands comprise a main central volcano each, but the one in Faial is symmetrical and the one in Pico is asymmetrical; (5) Pico shows evidence of at least two large-scale flank collapses, but none has been recognized so far in Faial. The new data reported here lead to the following probable answers: (1) the GPS data show much larger vertical and horizontal ground motions in Faial, which could be the result of recent volcanism and tectonics; (2) the cyclicity inferred from the paleomagnetic data in Pico could be related to inflation/deflation cycles that could have triggered the inferred flank collapses; (3) the Faial Graben ends abruptly at the eastern edge of the island, which we interpret as inhibited propagation to the east because of the load and stresses imposed by the nearby large Pico Volcano; (4) we attribute the asymmetry of the Pico Volcano to partial flank collapse recognizable in new offshore seismic profiles; (5) either the Faial island is actually gravitationally more stable, or there have been flank collapses not yet recognized. All these processes have concurred to shape the two islands and the ridge to their current morphology, but the current morphologies of Pico and Faial result mainly from three of these processes: volcanism, tectonics and large-scale landslides.

Quantification of the CO2 released by the volcanoes to the atmosphere is relevant for the evaluation of the balance between deep-derived, biogenic and anthropogenic contributions. The current study estimates the CO2 released from Furnas do Enxofre degassing area (Terceira Island, Azores archipelago) by applying an approach that integrates the flux of CO2 from the soil with the δ13C-CO2 values. A deep-derived CO2 output of 2.54 t d−1 is estimated for an area of ~23,715 m2. High biogenic-derived CO2 flux values (~45 g m−2 d−1) associated with light carbon isotopic content (δ13C = −28‰ ± 1.1‰) are detected and explained by the type of vegetation that characterizes the study site. Carbon isotopic compositions of the CO2 (−6.4‰ ± 1.2‰) measured in olivine-hosted fluid inclusions of the Terceira basalts are presented for the first time and contribute to defining the mantle-CO2 signature. Differences between these values and heavier carbon isotope values from gas in fumaroles at Furnas do Enxofre (−4.66‰ to −4.27‰) are explained by the carbon isotopic fractionation occurring when CO2 reacts to form calcite in the geothermal reservoir at temperatures >180 °C. A clear correlation between the soil temperature and deep CO2 fluxes is observed and the integration of the diffuse degassing information with the composition of the fumarolic emissions allows estimating a thermal energy flux of 1.1 MW.

Magmas in the Azores (Portugal) were erupted from both fissure zones and central volcanoes during overlapping periods. Fissure zones follow extensional trends oriented accordingly with the regional tectonics, erupting basalts and hawaiites. Central volcanoes are characterized by transtensive tectonics and erupted basaltic to trachytic magmas. Highly porphyritic magmas, consisting of cumulitic olivines and clinopyroxenes, can be also erupted during flank eruptions. Volcanism occurs because of the different direction of the plate movement at the triple junction where islands are located. Magma production and its ascent occur in response to the stresses of the lithosphere over a geochemically heterogeneous mantle, enriched in incompatible trace elements and water. The variability in the radiogenic isotopes results from the interaction of the differently enriched mantle sources with a ubiquitous and slightly depleted Azores mantle. Finally, a contribution of recycled oceanic crust is evidenced by a progressive east–west variation in Pb isotope ratios across the island of São Miguel. Primitive melts were generated by 1–7% partial melting of a garnet-bearing peridotite. Overall, basalts show relatively high large-ion lithophile element (LILE) abundances and LILE/high-field-strength element ratios that point to chemical heterogeneities in the mantle sources.

Massive fossil shell accumulations require particular conditions to be formed and may provide valuable insights into the sedimentary environments favouring such concentrations. Shallow-water shell beds appear to be particularly rare on reefless volcanic oceanic islands on account of narrow, steep and highly-energetic insular shelves where the potential for preservation is limited. The occurrence of an exceptional coquina (Pedra-que-pica) within the Miocene–Pliocene deposits of Santa Maria Island (Azores), therefore provides a rare opportunity to understand the conditions that led to the formation and preservation of a massive shell bed at mid-ocean insular setting. This study provides a detailed analysis regarding a 10–11-m-thick bivalve-dominated fossil assemblage exposed at Pedra-que-pica on Santa Maria Island in the Azores. Integration of taphonomical, palaeoecological and sedimentological observations are used to reconstruct the genesis of the coquina bed and related events, and to discuss why such exceptional sedimentary bodies are so rare on shelves around reefless volcanic oceanic islands. The sequence at Pedra-que-pica demonstrates a complex succession of sedimentary environments in response to the drowning of an existing coastline during a period of rapid sea-level rise. The Pedra-que-pica shell bed incorporates storm-related materials and possible debris falls that originated nearby in a shallow and highly productive carbonate factory. Deposition took place below fair-weather wave base, at around 50 m depth, as inferred from the overlying volcanic succession. The preservation of this coquina was favoured by deposition on a platform laterally protected by a rocky spur, combined with rapid burial by water-settled volcanic tuffs and subsequent volcanic effusive sequences. The recent exhumation of the deposit is the result of island uplift and subsequent erosion.

The mafic magmatism of the last 50 ka on Terceira Island, Azores archipelago, occurred along three segments of the fissure zone that crosses the island. The two subaerial segments developed with different trends over pre-existing, quiescent or extinct, central volcanoes. The Serreta submarine ridge is the offshore segment of the fissure zone that erupted recently in 1998–2001. The combined study of CO2+H2O fluid inclusions hosted in mafic minerals and rock geochemistry of the magmas, reveals different storage and ascent conditions among the fissure zone segments. The maximum pressure of fluid trapping for all the fissure systems occurred at the Moho Transition Zone, between 498 and 575 MPa (20.3–21 km deep). At this depth interval all magmas stagnated for some time, before ascending toward the surface, experiencing fractional crystallization and degassing. Magmas of the southeastern and Serreta segments of the fissure zone ascended rapidly through the crust without further stops. Those of the central segment experienced a multi-step ascent, with fluid trapping at 406 and 209 MPa (16.5–8.5 km deep) and associated geochemical evolution toward trachybasalt. The magma ascent below the different segments of the fissure zone varies from almost isochoric at the submarine segment, associated with minimum re-equilibration of the inclusions, to polybaric slow ascent at the central segment, associated to almost complete re-equilibration of the inclusions. Variable degrees of re-equilibration and multi-step ascent may be linked to both the presence of pre-existing intracrustal crystallized bodies of more evolved composition and the stress field acting on this area. The latter responds to the local and shallow conditions related to the presence of older central volcanoes and to the main regional spreading direction of the Terceira Rift, which at regional scale, is approximately orthogonal to the fissure zone axis.

Pico, the youngest island of the Azores Archipelago (Portugal), is characterized by a central volcano and a 30-km-long fissure zone. Its eruption rate is the highest of the Azores islands, with more than 35 eruptions in the last 2000 years. Here, we estimate the lava-flow hazard for Pico Island by combining the vent opening probability derived from the spatial distribution of eruptive fissures, the classes of expected eruptions inferred from the physical and chemical characteristics of historical eruptions, and the lava-flow paths simulated by the MAGFLOW model. The most likely area to host new eruptions is along a WNW–ESE trend centred on the central volcano, with the highest hazard affecting the two main residential zones of Lajes do Pico and Madalena. Our analysis is the first attempt to assess the lava-flow hazard for Pico Island, and may have important implications for decision-making in territorial management and future land-use planning.

© 2015 Elsevier B.V. The hazard and risk posed by future effusive eruptions from the Éguas-Carvão fissure system in São Miguel Island (Azores Archipelago) are assessed. This fissure system, located ~. 13. km from the town of Ponta Delgada and its international airport, was the only site in the whole island to be characterized by recurrent basaltic eruptions over the past 5000. yr. Here we report on the stratigraphic record of these Holocene eruptions, with special mention to both areas and volumes of deposits, and eruptive styles and recurrence. These basic data then are used to constrain numerical simulations of lava flow paths using the MAGFLOW model, after which hazard zones of possible future events are proposed. The lava flow risk is evaluated by combining the hazard with the exposed value, referred to the population, infrastructures and land use. These results are shown in two distinct maps, where the areas most prone to lava flow inundation and the extent of damages in case of a future effusive eruption are identified. We find that lava flows issuing from the Éguas-Carvão fissure system may be a threat to the villages of Feteiras, Capelas and Santo Antonio. Although this study was conducted on the Éguas-Carvão fissure system, the approach used can be applied to the whole São Miguel Island., It was partially funded by the Fundação para a Ciência e Tecnologia—Portugal (Project no. PTDC/CTE-GIX/098836/2008). The orthophotos used in this work were kindly provided by the Regional Government of the Azores, through an agreement with the CVARG. V. Zanon was funded by FRCT through grant 03.1.7.2007.1 (FRCT-PROEMPREGO Operational Program and Regional Government of the Azores).

The concept of an 'Azores mantle plume' has been widely debated, and the existence of an Azores hotspot questioned. In an effort to shed new light on this controversy, we present He isotope and major, trace and volatile element compositions for basaltic scoriae from five monogenetic cones emplaced along the fissure zone of Pico Island, the youngest island of the Azores archipelago. The bulk scoriae and lavas are moderately alkaline basalts, and their He isotope ratios, determined on olivine crystals, vary between 10*2 and 11*1 ± 0*1 Ra. In contrast, melt inclusions hosted in olivine (Fo76-83*5) span a large range of compositions (K2O = 0*7-1*7 wt %; Ce = 32-65 ppm; Nb = 21-94 ppm), which extends the compositional field of lavas erupted along the Pico fissure zone. This chemical evolution is predominantly controlled by polybaric fractional crystallization. Most melt inclusions share similar enrichments in large ion lithophile and light rare earth elements, and trace element ratios (La/Sm, La/Yb, Sr/Nd, Ta/Th, Zr/Y) with their bulk-rocks. Only a few of them differ in their lower contents of incompatible elements and La/Sm, Li/Ta and Na/K ratios, a feature that is ascribed to distinct conditions of melting. As a whole, the melt inclusions preserve high and variable volatile contents, and contain up to 1*8-2*0 wt % of H2O and 0*4 wt % of CO2. The total fluid pressures, retrieved from the dissolved CO2 and H2O concentrations, and the PCO2 from fluid inclusions, indicate magma ponding and crystallization at the crust-mantle boundary (ca. 18 km deep). The H2O/Cl and H2O/Ce ratios in the inferred parental undegassed basalts of the Pico fissure zone average 0*036 ± 0*006 and 259 ± 21, respectively. The latter value is significantly higher than that reported for typical mid-ocean ridge basalts from the southern Mid-Atlantic Ridge, but is similar to published ratios for submarine undegassed basalts from the Azores platform. Combining the calculated compositions of Pico primary magmas formed by low degrees of melting with recent geophysical data for the Azores, we propose a model for Azores magma generation involving the decompression melting of a water-enriched mantle domain (H2O = 680-570 ppm) with an estimated temperature excess of ≤120°C with respect to the Mid-Atlantic Ridge.

[1] In the islands of Faial and Pico (the Azores), fluid inclusions are hosted in megacrysts of olivine (Mg#80–88) and clinopyroxene (Mg#79–90) in highly porphyritic lavas and in mineral assemblages of ultramafic xenoliths. Rare inclusions are contained in olivine phenocrysts (Mg#

Oceanic islands – such as the Azores in the mid-North Atlantic – are periodically exposed to large storms that often remobilize and transport marine sediments along coastlines, and into deeper environments. Such disruptive events create deposits – denominated tempestites – whose characteristics reflect the highly dynamic environment in which they were formed. Tempestites from oceanic islands, however, are seldom described in the literature and little is known about storm-related sediment dynamics affecting oceanic island shelves. Therefore, the geological record of tempestite deposits at oceanic islands can provide invaluable information on the processes of sediment remobilization, transport and deposition taking place on insular shelves during and after major storms. In Santa Maria Island (Azores), a sequence of Neogene tempestite deposits was incorporated in the island edifice by the ongoing volcanic activity (thus preserved) and later exposed through uplift and erosion. Because it was overlain by a contemporary coastal lava delta, the water depth at the time of deposition could be inferred, constituting an excellent case-study to gain insight on the still enigmatic processes of insular shelf deposition. Sedimentological, palaeontological, petrographic and palaeo-water depth information allowed the reconstruction of the depositional environment of these sediments. The sequence typifies the characteristics of a tempestite (or successive tempestites) formed at ca 50 m depth, in a steep, energetic open insular shelf, and with evidence for massive sediment remobilization from the nearshore to the middle or outer shelf. The authors claim that cross-shelf transport induced by storm events is the main process of sediment deposition acting on steep and narrow shelves subjected to high-energetic environments, such as the insular shelves of open-sea volcanic islands.

Magmas in Faial Island, Azores (Portugal), were mostly erupted from two fissure zones and the Caldeira central volcano during overlapping periods. The fissure zones follow extensional trends oriented WNW and ESE and erupted nepheline- to hypersthene-normative basalts and hawaiites. The Caldeira central volcano builds the central part of the island, which is cut by the fissure zones. Ne-normative basalts show similar high-field-strength element (HFSE) concentrations but higher large ion lithophile element (LILE) concentrations than hy-normative equivalents. Primitive melts were generated by small (3–5%) degrees of partial melting of garnet-bearing peridotite, variably enriched in incompatible elements. Overall, basalts from Faial show relatively higher LILE abundances and LILE/HFSE ratios than those of the other islands of the Azores and of many other volcanoes in the Atlantic area. This feature indicates the existence of chemical heterogeneities in the mantle sources characterized by variable degrees of metasomatism, both at local and regional scales. Hawaiites evolved from basalts through 30–40% fractional crystallization of mafic phases plus some plagioclase, in deep reservoirs, at about 430–425 MPa (~ 15 km). The Caldeira central volcano rocks range from basalts to trachytes. Basalts, produced under similar conditions as fissure basalts, evolved to trachytes through large degrees of polybaric fractional crystallization (100–760 MPa; i.e. ~ 3.6–26 km), involving olivine, clinopyroxene, feldspar and minor quantities of amphibole, biotite, apatite and oxides. In contrast, mafic magmas from the fissure zones were erupted directly onto the surface from magma reservoirs mainly located at the crust–mantle boundary.

Between December 1998 and April 2001, a submarine basaltic eruption occurred west of Terceira Island, Azores (Portugal) in water depths between 300 and 1,000 m. Physical evidence for the eruption was provided by the periodic occurrence of hot lava “balloons” floating on the sea surface. The balloons consisted of a large gas-filled cavity surrounded by a thin shell (a few centimetres thick). The shells of the collected balloons are composed of two layers, termed the outer layer and the inner layer, defined by different bubble number density, bubble sizes and crystal content. The inner layer is further divided into three sublayers defined by more subtle differences in vesicularity. The outer layer is glassy, golden-coloured and highly porous. It shows signs of fluidal deformation and late-stage extension cracks. Interstitial glass contains 0.29 wt% H2O and CO2 is below detection. Melt inclusions contain up to 1.18 wt% H2O and 1,500 ppm CO2 (from different inclusions). Cooling rates of the outermost glass of the outer layer are found to be as high as 1,259 K/s. During ascent of low viscosity magma to the ocean floor, volatiles, dominated by CO2, exsolved from the magma (melt + crystals). The buoyancy of the vapour phase that accumulated below a thin crust on lava ponded at the vent caused bulging and ultimately cracking of the crust. This allowed large bubbles (central cavity) surrounded by a film of vesicular magma (balloon shell) to leak into the water column. On contact with the seawater, the outermost part of the outer layer of the shell hyperquenched. If an entirely closed shell was produced during detachment, the trapped gas inside allowed buoyant rise. Only balloons with the right balance of physical properties (e.g. size and bulk density) rose all the way to the sea surface.

Twenty eruptive events from the Northeast Crater of Stromboli volcano recorded by a thermal monitoring camera in early 2004 were analysed in order to understand the eruptive dynamics. Selected events were chosen to be typical of explosions that characterize the steady activity of Stromboli in terms of jet height and duration. Most of the explosions consisted of clast-rich single bursts, originating from the same vent inside the Northeast Crater. Conspicuous ash emission was scarce. Eruptions were preceded by the flashing of a perturbation wave characterized by low temperatures and an average propagation velocity of about 35–100 m s−1. This perturbation was thought to be caused by the bursting of the gas slug at the bottom of the crater and is interpreted as an air wave. This was immediately followed by the expansion of a jet of ‘hot’ gas and particles, at a velocity of 35–75 m s−1. Ejecta coarser than 138 cm appeared ~1.6–2 s after the onset of the explosion, moving at a variable velocity (30–60 m s−1). Eruptive events were either vertical or inclined 7–13° towards the NNW. This inclination is thought to be a consequence either of the morphology of the conduit, following modest rock falls that partially obstructed the uppermost part of the crater, or of the displacement of the internal conduit due to the explosive activity of the volcano. The instability of the summit area is a further possible cause of the deformation of the conduit.

The syn-eruptive and post-eruptive history of Sao Roque tuff cone, its geological setting and volcanological features were studied in detail to understand the role played by the different factors that contributed to the morphological evolution of this relatively simple and small volcanic edifice. In addition, attention was also focused on the series of natural changes that affected the tuff cone during the course of the years and that finally led to its structural disassembly. A novel model is proposed to explain this process. The Sao Roque volcanic centre, located on the island of Sao Miguel (Azores), consists of two well-consolidated bodies and numerous small islets that formed more than 4700 years ago during the hydromagmatic activity that took place along an intruding dyke, whose NNW–SSE trend is in agreement with the regional tectonic pattern. The eruptive vents probably migrated progressively from SSE to NNW, forming small edifices through the rapid accumulation of sediments during alternating phases of “dry” and “wet” magmatic emissions. Syn-eruptive partial collapses greatly modified the original morphological structure of these edifices, probably allowing sea water to continuously flow into the vents. The complex interaction of these factors controlled the depth of magma fragmentation, producing different types of deposits, in which the ash-lapilli ratio varies considerably. The high-water saturation degree of these deposits caused syn-eruptive and post-eruptive remobilization which resulted in collapses and some small-scale landslides. Post-eruptive, WNW–ESE trending transtensional and extensional tectonic activities operated during the initial dissection of the cone, generating instability. Furthermore, the rapid accumulation of “wet” tephra, and its following consolidation, caused selective collapses that favoured the fragmentation of the deposit and caused the formation of numerous islets separated by radially-arranged channels. Collapses also involved the lava units emplaced in more recent times around the tuff cone, which show that brittle deformation has been significant in the area for a prolonged period.

The response of environment to ashfall was evaluated aiming at defining the vulnerability in the areas surrounding Mt. Etna volcano, Sicily. The two utilized scenarios assume different thickness of ashfall, over distances comparable with those covered by deposits from realistic eruptions that occurred recently on the volcano. The fall episodes are considered instantaneous or with a duration of 90 days. These models are in agreement with the actual and recent activity of the volcano. The evaluation of vulnerability was performed by a GIS-based method, accordingly with the different themes that constitute the Corine Land Cover inventory of the study area and discovering the potentially damaged elements following the two hypothesized scenarios.

In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009–2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of 50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes.

Rhodoliths are a common producer of carbonates on modern and ancient shelves worldwide, and there is growing evidence that they thrive on volcanic insular shelves. However, little is still known on how rhodoliths cope with the demands of this particularly dynamic environment. In this study, the focus is placed on fossil rhodoliths from a Pliocene sequence at Santa Maria Island, Azores, in order to gain further insight into the life cycle (and death) of rhodoliths living within a mid-ocean active volcanic setting. These rhodoliths occur as a massive accumulation within a larger submarine volcano-sedimentary sequence that was studied from the macro- to the micro-scale in order to reconstruct the paleoenvironmental conditions under which the rhodolith accumulation was deposited and buried. All fossil rhodoliths from this setting are multi-specific and demonstrate robust growth forms with a lumpy morphology. Moreover, taphonomical analyses show the succession of several destructive events during rhodolith growth, suggesting life under a highly dynamic system prior to stabilization and burial. The rhodoliths therefore tell a story of an eventful life, with multiple transport and growth stages, owing to the environment in which they lived. Transport and deposition to their final resting place was storm-associated, as supported by the general sedimentary sequence. In particular, the sequence features an amalgamation of tempestites deposited under increasing water depths, sediment aggradation, and before burial by volcanic activity. This transgressive trend is also attested by the overall characteristics of the volcano-sedimentary succession, which exhibits the transition to subaerial environment in excess of 100 m above the rhodolith bed.

Between 1971 and 2001, the Southeast Crater was the most productive of the four summit craters of Mount Etna, with activity that can be compared, on a global scale, to the opening phases of the Pu‘u ‘Ō‘ō-Kūpaianaha eruption of Kīlauea volcano, Hawai‘i. The period of highest eruptive rate was between 1996 and 2001, when near-continuous activity occurred in five phases. These were characterized by a wide range of eruptive styles and intensities from quiet, non-explosive lava emission to brief, violent lava-fountaining episodes. Much of the cone growth occurred during these fountaining episodes, totaling 105 events. Many showed complex dynamics such as different eruptive styles at multiple vents, and resulted in the growth of minor edifices on the flanks of the Southeast Crater cone. Small pyroclastic flows were produced during some of the eruptive episodes, when oblique tephra jets showered the steep flanks of the cone with hot bombs and scoriae. Fluctuations in the eruptive style and eruption rates were controlled by a complex interplay between changes in the conduit geometry (including the growth of a shallow magma reservoir under the Southeast Crater), magma supply rates, and flank instability. During this period, volume calculations were made with the aid of GIS and image analysis of video footage obtained by a monitoring telecamera. Between 1996 and 2001, the bulk volume of the cone increased by ~36×106 m3, giving a total (1971–2001) volume of ~72×106 m3. At the same time, the cone gained ~105 m in height, reaching an elevation of about 3,300 m. The total DRE volume of the 1996–2001 products was ~90×106m3. This mostly comprised lava flows (72×106 m3) erupted at the summit and onto the flanks of the cone. These values indicate that the productivity of the Southeast Crater increased fourfold during 1996–2001 with respect to the previous 25 years, coinciding with a general increase in the eruptive output rates and eruption intensity at Etna. This phase of intense summit activity has been followed, since the summer of 2001, by a period of increased structural instability of the volcano, marked by a series of important flank eruptions.

The purpose of this paper is to integrate, or even modify where necessary, the geo-volcanological setting outlined by other authors on the history of the small volcanic field of San Venanzo (Umbria, Central Italy). To attain this goal, new accurate field investigations were carried out in that area, coupled with detailed stratigraphic studies and laboratory analyses, to support field evidence with experimental results. The first objective was to stress the importance of a groundwater reservoir whose interaction with magma at various degrees was responsible not only for the explosive character of volcanism in that area, but also for the complex morphology of the volcanic deposits that are widely scattered on the underlying sedimentary basement. Another objective was to clarify the role played by tectonic activity in enhancing the fast and discontinuous ascent of batches of magma from the mantle to the surface, through two different sets of faults, opened by tectonic unrest into the crust, that were also responsible for the morphology and spatial distribution of volcanic centres. This was considered to be very important in consideration of the still-active stress field of the region. Finally, special attention was focused on the presence of a palaeosol between two eruptive sequences, as it most likely denoted a split in the volcanic activity of this site into two separate phases. This observation leads to the conclusion that, in spite of its eruptive characteristics, the small volcano of San Venanzo is not monogenic. For all of these topics, a number of conclusions have been drawn and they are reported with more data in the following sections of this paper.

Following an increase of eruptive activity at Stromboli summit craters in February 2004, we promptly carried out SEM-EDS microanalyses and textural observations on samples of lapilli to check the possible occurrence of Low Porphyritic magma (LP magma), a forerunner of hazardous paroxysmal eruptions. The acquired results suggest that all erupted glasses belong to the High Porphyritic magma (HP magma), which characterizes the typical mild explosive activity of the volcano.