PubAIV 2021

PubAIV Visite: 2176
PubAIV 2021
(aggiornato a Dicembre 2021)
TEMATICHE GENERALI:

1) Magmi e sistemi di alimentazione (19 articoli)
2) Dinamiche eruttive e di messa in posto (14 articoli)
3) Geologia e struttura dei vulcani (3 articoli)
4) Monitoraggio, pericolosità e rischio vulcanico (8 articoli)

Tematica 1: Magmi e sistemi di alimentazione
Bonechi B., Perinelli C., Gaeta M., Fabbrizio A., Petrelli M., Strnad L. (2021)
High pressure trace element partitioning between clinopyroxene and alkali basaltic melts.
Geochimica et Cosmochimica Acta, 305, 282-305
https://doi.org/10.1016/j.gca.2021.04.023
Data di pubblicazione: 23/04/2021
PubAIV-ID-00009 - Articolo in Rivista (non-open access)
Abstract
We present new experimental data on major and trace element partition coefficients (D) between clinopyroxene and a K-basaltic melt from Procida Island (Campi Flegrei Volcanic District, south Italy). Time-series experiments were conducted at 0.8 GPa and 1080–1250 °C aiming to investigate the role of the crystallization kinetics on trace elements partitioning behaviour at a pressure relevant for deep magmatic reservoirs. Results indicate that large ion lithophile elements (LILE) are incompatible (e.g., DSr ncrease with increasing tetrahedrally-coordinated aluminium content, in agreement with the previous studies. Moreover, we observed the influence of the growth rate on the partition coefficients, with the highest DREE values calculated in the runs with the highest growth rate (~10-7 cm s-1), due to the less efficient rejection of incompatible elements during rapid crystal growth, that in this study is not linked to disequilibrium conditions, but to the presence of pre-existing nuclei. Additionally, the apparent increase in DREE values with time observed in some runs is not referable to a change in time but rather to the different degrees of polymerization, expressed as the ratios NBO/T of these melts, strictly
related to a loss of Fe occurred during the experiments, and thus to a different melt viscosity. Finally, the application of
the experimental clinopyroxene-melt partition coefficients highlights that the deepest step of the magmatic differentiation in the Campi Flegrei Volcanic District is represented by the fractionation of about 20–30% of a clinopyroxenitic mineral assemblage from a basaltic parental magma.
Image
Bonechi B., Perinelli C., Gaeta M., Stagno V., Fabbrizio A., Mollo S., Hrubiak R. (2021)
High pressure experimental investigation of clinopyroxene dissolution in a K-basaltic melt.
Chemical Geology, 584, 120533
https://doi.org/10.1016/j.chemgeo.2021.120533
Data di pubblicazione: 21/09/2021
PubAIV-ID-00028 - Articolo in Rivista (non-open access)
Abstract
Dissolution of clinopyroxene (cpx) in a K-basaltic melt from the Campi Flegrei Volcanic District (Italy) has been investigated through dissolution and dissolution-crystallization experiments at pressure of 0.8 GPa, superliquidus temperature of 1350 °C, and dwell times between 0.5 and 1 h. The obtained dissolution rates range from 7.9·10-6 cm s-1 to 6.1·10-6 cm s-1 as a function of dwell time. In the dissolution-crystallization experiment (1300 °C; 0.8 GPa; 2 h), the formation of overgrowth rims accompanied by new cpx crystals suggests that the injection of recharge magmas in basaltic reservoir may lead to inverse or oscillatory zonation. The interaction between cpx and K-basaltic melt at ~1570 °C was studied by in situ radiography using synchrotron radiation combined with the Paris-Edinburgh press. This resulted in cpx resorption to occur depending on the temperature conditions with respect to the liquidus temperature of the cpx (TcpxL). The calculated cpx dissolution rates are ~5·10-3 cm s-1 at T ≤ TcpxL and ~3·10-2 cm s-1 at T ≥ TcpxL. The role of crystal dissolution in the estimation of magma residence times has been also tested for a natural magmatic system by interpolating the dissolution rates (~10-5-10-6 cm s-1) with the textural data of cpx phenocrysts from the Agnano-Monte Spina pyroclastic deposit at Campi Flegrei caldera (Campanian region, Italy). Results from calculations indicate that the time required for partial or complete resorption of phenocrysts varies from ~0.5 to ~40 h, and that the effect of crystal dissolution may be relevant to estimate magma residence times whether significant dissolution occurs during magma mixing processes.
Image
Caracciolo A., Kahl M., Bali E., Guðfinnsson G.H., Halldórsson S.A., Hartley M.E. (2021)
Timescales of crystal mush mobilization in the Bárðarbunga-Veiðivötn volcanic system based on olivine diffusion chronometry.
American Mineralogist, 106(7), 1083-1096
https://doi.org/10.2138/am-2021-7670
Data di pubblicazione: 01/07/2021
PubAIV-ID-00017 - Articolo in Rivista (non-open access)
Abstract
The timescales of magmatic processes within a volcanic system may be variable over a volcano’s geological history. Crystals reflect environmental perturbations under which they grew, and compositional gradients quenched inside crystals on eruption can be exploited to extract timescales of magmatic processes. Here, we use multi-element diffusion chronometry in olivine macrocrysts to recover their residence time in a melt that ultimately erupted at the surface. The macrocrysts were mobilized by the carrier melt from mushy layers in the magma reservoir, and diffusion timescales likely reflect the time interval between mush disaggregation, ascent, and eruption. To unravel the evolution of mush disaggregation timescales with time, we target early-Holocene, middle-Holocene, and historical magmatic units erupted in the Bárðarbunga-Veiðivötn volcanic system in Iceland’s Eastern Volcanic Zone. Macrocryst contents vary between samples; early-Holocene samples are highly phyric (10–45 vol% macrocrysts) and contain gabbroic nodules, whereas middle-Holocene (5–15 vol%) and historical units (5–10 vol%) tend to be generally less phyric. Early-Holocene olivine macrocrysts have core compositions in the range Fo84–87, while middle-Holocene and historical samples record a wider range in core compositions from Fo80 to Fo86.5. Olivine rims are in chemical equilibrium with their carrier liquid and are slightly more evolved in early-Holocene units (Fo76–81) compared to middle-Holocene (Fo78–80) and historical (Fo81–83) units. Diffusion chronometry reveals that the timescale between mush dis-aggregation and eruption has changed over time, with timescales getting shorter approaching recent times. Early-Holocene olivine macrocrysts dominantly record Fe-Mg diffusion timescales between 200–400 days, while middle-Holocene and historical units typically record timescales of about 70 and 60 days, respectively. Barometric studies suggest that melts and crystals are likely stored and gradually transferred throughout an interconnected multi-tiered system that ultimately culminates in a mid-crustal reservoir(s) at about 6.8–7.5 ± 2.5 km depth, where final disaggregation by the carrier liquid took place. We argue that, as a result of extensional processes enhanced by rifting events, well-mixed melts got drawn into mid-crustal reservoir(s), causing crystal mush loosening and mobilization. In addition, we propose that more energy in the form of heat and/or melt supply was required in the early-Holocene to break up the dense mush fabric and convert it into an eruptible magma. Conversely, as evidenced by the diverse macrocryst content of the historical units and by the lack of gabbroic nodules, the system has become characterized by a less compact mush fabric since at least the middle-Holocene, such that fresh injection of melt would easily loosen and mobilize the mush, resulting in an eruption within a couple of months. This study provides evidence that along axial rift settings, rifting-related processes can help to “pull the mush apart” with no requirement for primitive magma injection as an eruption trigger. Furthermore, we provide evidence that in the Bárðarbunga-Veiðivötn volcanic system specifically, the time between mush disaggregation and eruption has decreased considerably with time, indicating shorter warning times before imminent eruptions.
Image
Coppola D., Laiolo M. , Massimetti F., Hainzl S., Shevchenko A.V., Mania R., Shapiro N.M., Walter T.R.(2021)
Thermal remote sensing reveals communication between volcanoes of the Klyuchevskoy Volcanic Group.
Scientific Reports volume 11, 13090
https://doi.org/10.1038/s41598-021-92542-z
Data di pubblicazione: 22/06/2021
PubAIV-ID-00007 - Articolo in Rivista (open access)
Abstract
Volcanoes are traditionally considered isolated with an activity that is mostly independent of the surrounding, with few eruptions only (multaneously erupt, show unrest, or even shut-down activity. Using infrared satellite data, we detail 20 years of eruptive activity (2000–2020) at Klyuchevskoy, Bezymianny, and Tolbachik, the three active volcanoes of the Klyuchevskoy Volcanic Group (KVG), Kamchatka. We show that the neighboring volcanoes exhibit multiple and reciprocal interactions on different timescales that unravel the magmatic system’s complexity below the KVG. Klyuchevskoy and Bezymianny volcanoes show correlated activity with time-predictable and quasiperiodic behaviors, respectively. This is consistent with magma accumulation and discharge dynamics at both volcanoes, typical of steady-state volcanism. However, Tolbachik volcano can interrupt this steady-state regime and modify the magma output rate of its neighbors for several years. We suggest that below the KVG the transfer of magma at crustal level is modulated by the presence of three distinct but hydraulically connected plumbing systems. Similar complex interactions may occur at other volcanic groups and must be considered to evaluate the hazard of grouped volcanoes.
Image
Costa S., Fulignati P., Campbell I.H., Gioncada A., Carrasco Godoy C.I., Pistolesi M., Masotta M. (2021)
Platinum-group element geochemistry of the shoshonitic igneous suite of Vulcano (Aeolian Arc, Italy): implications for chalcophile element fertility of arc magmas.
Contributions to Mineralogy and Petrology 176, 106.
https://doi.org/10.1007/s00410-021-01865-7
Data di pubblicazione: 29/11/2021
PubAIV-ID-00040 - Articolo in Rivista (non-open access)
Abstract
Platinum-group element (PGE) geochemistry of arc-related magmas can be used to constrain the timing of sulfide saturation, which plays a critical role in the chalcophile element fertility of evolving magmatic systems. In this study, we provide new major and trace elements, PGE, Re and Au data for the shoshonitic suite (from basalt to rhyolite) of the active volcanic system of Vulcano (Aeolian Islands, Italy), an excellent study case for investigating mineralizing processes in arc volcanoes. The most primitive magma erupted at Vulcano is characterized by fractionation of Ir-group PGE (Ir, Os, Ru) relative to the Pd-group PGE (Pd, Pt, Rh), which is attributed to the magma being saturated with a Pt-rich alloy and possibly spinel and Os–Ir alloy. A negative Au anomaly, shown by Vulcano magmas, suggests that the Au was lost to an early exsolved S– (and moderately Cl–) rich fluid phase that, upon migration to higher levels of the feeding system, could have enhanced the mineralizing potential of the magmatic system. The Pd content of Vulcano primitive magmas is high (~ 8 ppb) and comparable to values found in other arc-related mineralized systems. The early Pd depletion, relative to Au and Cu, during evolution towards more evolved magmas, suggests that the magmatic system reached sulfide saturation at about 4 wt.% MgO. Chalcophile element fractionation modeling shows that the immiscible sulfide mass proportion was initially very low (~ 0.0015%), and gradually increased to about 0.1% at about 2 wt.% MgO, causing a late depletion of the less compatible chalcophile elements, including Cu. A significant chalcophile metal depletion in the silicate melt occurred once sulfide saturation was achieved, well before hydrosaline fluid exsolution at 
Image
Costa S., Masotta M., Gioncada A., Pistolesi M. (2021)
A Crystal Mush Perspective Explains Magma Variability at La Fossa Volcano. (Vulcano, Italy)
Minerals, 11(10), 1094
https://doi.org/10.3390/min11101094
Data di pubblicazione: 05/10/2021
PubAIV-ID-00033 - Articolo in Rivista (open access)
Abstract
The eruptive products of the last 1000 years at La Fossa volcano on the island of Vulcano (Italy) are characterized by abrupt changes of chemical composition that span from latite to rhyolite. The wide variety of textural features of these products has given rise to several petrological models dealing with the mingling/mixing processes involving mafic-intermediate and rhyolitic magmas. In this paper, we use published whole-rock data for the erupted products of La Fossa and combine them in geochemical and thermodynamic modelling in order to provide new constrains for the in- terpretations of the dynamics of the active magmatic system. The obtained results allow us to picture a polybaric plumbing system characterized by multiple magma reservoirs and related crystal mushes, formed from time to time during the differentiation of shoshonitic magmas, to produce latites, trachytes and rhyolites. The residing crystal mushes are periodically perturbated by new, fresh magma injections that, on one hand, induce the partial melting of the mush and, on the other hand, favor the extraction of highly differentiated interstitial melts. The subsequent mixing and mingling of mush-derived melts ultimately determine the formation of magmas erupted at La Fossa, whose textural and chemical features are otherwise not explained by simple assimilation and fractional crystallization models. In such a system, the compositional variability of the erupted products reflects the complexity of the physical and chemical interactions among recharging magmas and the crystal mushes.
Di Fiore F., Mollo S., Vona A., MacDonald A., Ubide T., Nazzari M., Romano C., Scarlato P. (2021)
Kinetic partitioning of major and trace cations between clinopyroxene and phonotephritic melt under convective stirring conditions: New insights into clinopyroxene sector zoning and concentric zoning.
Chemical Geology 584 (2021) 120531
https://doi.org/10.1016/j.chemgeo.2021.120531
Data di pubblicazione: 05/12/2021
PubAIV-ID-00029 - Articolo in Rivista (non-open access)
Abstract
Within subvolcanic plumbing systems, along volcanic conduits and post-eruptive emplacement, mineral textures and compositions are governed by complex kinetic (undercooling) and dynamic (convective) processes that deviate from theoretical models and equilibrium criteria. In this perspective, we have investigated the partitioning of major and trace cations between clinopyroxene and phonotephritic melt under convective stirring conditions at high degrees of undercooling (−ΔTnominal = 30–60 °C) and atmospheric pressure. We have integrated this novel data set with conventional static (no physical perturbation) clinopyroxene-melt compositions obtained under interface- and diffusion-controlled growth regimes. Results show that clinopyroxene growth kinetics and diffusion boundary layers caused by melt supersaturation are partly mitigated by the homogenizing effects of stirring. Because of continuous supply of fresh melt to the advancing crystal surface, the partitioning of major and trace cations is governed by local equilibrium effects, which are interpreted as the extension of equilibrium thermodynamic principles to non-equilibrium bulk systems. Major cations are incorporated into the clinopyroxene structure via the coupled substitution [M1Mg, TSi] ↔ [M1Ti, TAl] and in conformity with the thermodynamic mixing properties of CaMgSiO2, CaAl2SiO6, and CaTiAl2O6 components. The complementary relationship between lattice strain (ΔGstrain) and electrostatic (ΔGelectrostatic) energies of heterovalent substitutions is the most appropriate thermodynamic description for the accommodation of trace cations in the clinopyroxene lattice site (i.e., ΔGpartitioning = ΔGstrain + ΔGelectrostatic). The excess energy of partitioning ΔGpartitioning changes principally with Al in tetrahedral coordination and determines the type and number of charge-balanced and -imbalanced configurations taking place in the structural sites of clinopyroxene. An important outcome from dynamic stirring experiments is that superimposition of convective mass transfer on melt supersaturation phenomena causes the formation of Cr-rich concentric zones under closed system crystallization conditions. However, these Cr-rich zones do not correlate with enrichment in other compatible elements and depletion in incompatible elements, as would be expected in natural open systems characterized by input of more primitive magmas. While the convective transport acts to reduce the diffusive length scale of chemical species in the experimental melt, fresh Cr cations are more easily incorporated into the concentric zones due to crystal field effects. Together, our findings reveal that during magma ascent and emplacement, convective stirring may promote clinopyroxene crystallization and minimize kinetic effects on clinopyroxene zoning.
Image
Deb P., Giordano G., Shi X., Lucci F., Clauser C. (2021)
An approach to reconstruct the thermal history in active magmatic systems: Implications for the Los Humeros volcanic complex, Mexico.
Geothermics 96, 102162.
https://doi.org/10.1016/j.geothermics.2021.102162
Data di pubblicazione: 23/06/2021
PubAIV-ID-00032 - Articolo in rivista (non-open access)
Abstract
Reconstructing the thermal history in active volcanic complexes characterized by multiple magmatic events is challenging due to the limited knowledge of the nature and extent of the transient heat sources. Although understanding of the geometry and architecture of a magmatic system is of prime importance for accurate temperature assessments, it is still one of the most uncertain parameters in numerical models. In this work, we presented a methodology for thermal assessment in active volcanic systems, whereby field-based geological, geochemical and petrological data are integrated to define the transient heat sources of a magma plumbing system. This time-varying heat source conceptual model is applied in the Los Humeros Volcanic Complex, an active Quaternary caldera complex in the Trans Mexican Volcanic Belt, for evaluating the thermal footprint related to the major volcanic events. The site is characterized by two caldera-forming eruptions, the Los Humeros (164 000 years ago) and the Los Potreros (69 000 years ago) and numerous episodes of post-caldera bi-modal volcanism during Holocene period (8 000 – 3 000 years old). The transient nature of the heat sources is implemented as time-varying temperature boundary conditions and the complete temporal evolution for a period of 182 000 years is simulated in 13 modeling stages. The thermal impact due to the voluminous caldera-forming events and the later short-lived magma pockets of Holocene ages is simulated by emplacing heat sources in the numerical model distributed heterogeneously in space and active at different instants of time. The depth, volume and age of the magma pockets are constrained from geochemical, petrological, geochronological and thermo-barometric analysis of erupted material. The present temperature state obtained from this approach agrees well with the temperature data recorded in the geothermal wells. The thermal footprint of the individual volcanic events indicates that almost 80 % of the present-day thermal contribution results from the massive caldera-forming events. The post-caldera Holocene magma pockets had additionally increased temperatures locally by 10 % - 20 % depending on the volumes and ages of the magma pockets. The present-day thermal regime of the younger Holocene magma pockets suggests existence of super-hot resources at shallow depths in the southern part of the geothermal field, making it a potential site for future exploration activities.
Fedele L., Cole P.D., Scarpati C., Robertson R.E.A. (2021)
Petrological insights on the last 1000 years of explosive activity at La Soufrière volcano, St. Vincent (Lesser Antilles).
Lithos, 392–393, 106150
https://doi.org/10.1016/j.lithos.2021.106150
Data di pubblicazione: 03/04/2021
PubAIV-ID-00015 - Articolo in Rivista (non-open access)
Abstract
The petrological features of scoria samples and enclosed holocrystalline xenoliths fromthe last ~1000 years of activity of the La Soufrière volcano of St. Vincent (Lesser Antilles) are described in detail here. The products of the investigated prehistoric eruptions (pre-1440, 1440, 1580 CE) are relatively homogeneous basaltic andesites (with a paragenesis consisting of plagioclase, clinopyroxene, orthopyroxene and opaques) commonly hosting gabbroic xenoliths. Scoria samples fromthe historical eruptions (1718–1812 and 1902–03 CE) are mostly similar to the former in terms of whole-rock composition, mineral chemistry and types of xenoliths, but include also a mafic-rich scoria type (plagioclase + clinopyroxene + olivine) in the products of the 1902–03 eruption that is
less evolved in composition and encloses ol-gabbro and ultramafic xenoliths. Both scoria types were likely affected by crystal contamination and accumulation processes, as indicated by their moderately to strongly porphyritic textures and large compositional variation of the crystal populations. Recycling of xenocryst,
protocryst and/or antecryst phases, however, did not significantly modify the original magma composition, as suggested by the overall consistency of whole-rock differentiation trends with petrography, mineral chemistry, xenolith types and glass compositions (within both inclusions and the groundmass) and experimental petrology observations, crystal fractionation therefore still appearing as the main evolutionary process. Most of the gabbro and ol-gabbro xenoliths have mineral compositions in line with that of the coexisting phenocrysts and textural
features consistent with an intrusive origin, i.e., representing fully-crystallised melt aliquots. Conversely, ultramafic, troctolitic and noritic xenoliths (plus some ol-gabbro) are likely representing cumulitic assemblages, i.e., mineral phases removed from the magma by crystal fractionation. The typical association of An-rich plagioclase and relatively Fo-poor olivine of the troctolite (and ol-gabbro) cumulates is ascribed to crystallisation from a hydrous (H2O ~4.5–6 wt%) high-Al2O3 basalt/basaltic andesite magma crystallising at shallow depths (~0.2 GPa,
i.e., at ~7 km). On the other hand, the ultramafic cumulitic xenoliths are thought to derive from a less hydrous basalt magma stalling at deeper levels (~0.4 GPa, ~13 km). The tapping of such magma could mark a major rejuvenation event, which is the process that likely triggered the 1902–03 eruption.
Image
Gaeta M., Bonechi B., Marra F., Perinelli C. (2021)
Uncommon K-foiditic magmas: The case study of Tufo del Palatino (Colli Albani Volcanic District, Italy).
Lithos, 396-397, 106239
https://doi.org/10.1016/j.lithos.2021.106239
Data di pubblicazione: 18/05/2021
PubAIV-ID-00010- Articolo in Rivista (non-open access)
Abstract
Leucititic rocks, K-foiditic in composition are volumetrically important in the Colli Albani (also known as Alban Hills) volcanic district (Central Italy) especially during the most explosive phases of activity (>200 km3). The Colli Albani tephra in distal (>500 km) deposits indicates that K-foiditic magma chambers fed large explosive eruptions (i.e., tens of km3 of pyroclastic rocks). Major oxides, trace elements and Raman spectra were measured on the glasses and minerals occurring in the K-foiditic scoria clasts of the ~530 kyr-old Tufo del Palatino, erupted in the Colli Albani volcanic district. The Colli Albani pre-eruptive magmatic system is characterized by the aH2O < 1 and high CO2 activity in the melt, as testified by the CO3 in the clinopyroxene melt inclusions, by the early crystallization of CO3-bearing apatite and by the high CO2activity in the free volatile phase that led to crystallization of calcium carbonate in the scoria clast vesicles. The K-foiditic magmas plot on the Cpx + Lc + melt divariant surface of the Ol-Cpx-Lc-Mel-H2O-CO2, P ≥ 0.2 GPa and T ≤ 1100 °C. The assimilation of cold carbonate by hot magmas is an important open-system process allowing the establishment of aH20 < 1 condition in the volatile-rich, Colli Albani magma chambers where the stability fields of the olivine and phlogopite are reduced in favor of clinopyroxene and leucite. Trace element modelling indicates large amount of carbonate assimilation (~12.4 wt%) involved in the differentiation process that origins the K-foiditic magmas starting from a K-rich, phonotephritic parental magma. The large amount of assimilate carbonate is consistent with the peculiar distribution of the latent heat across the crystallization interval of the phonotephritic parental magma. The isenthalpic assimilation process is very efficient in the phonotephritic magma because the crystallization of clinopyroxene and leucite in equilibrium with a K-foiditic melt proceeds over a relatively large temperature interval (>200 °C) and the K-foiditic melt shows low viscosity (104Pa·s at 1000 °C). Actually, the low melt viscosity, that increases the growth rate, and the large temperature interval of crystallization are intrinsic factors that increase the release of the latent heat of crystallization from the phonotephritic parental magma. Extrinsic factors enhancing the assimilation process efficiency are the thickness (>4 km) and the depth (down to 5–7 km) of the carbonate substrate in the Colli Albani volcanic district.
Image
Giuffrida M., Scandura M., Costa G., Zuccarello F., Sciotto M., Cannata A., Viccaro M. (2021)
Tracking the summit activity of Mt. Etna volcano between July 2019 and January 2020 by integrating petrological and geophysical data.
Journal of Volcanology and Geothermal Research, 418, 107350
https://doi.org/10.1016/j.jvolgeores.2021.107350
Data di pubblicazione: 18/07/2021
PubAIV-ID-00016 - Articolo in Rivista (non-open access)
Abstract
The evolution of volcanic activity observed at the New South East Crater (NSEC) and Voragine (VOR) between July 2019 and January 2020 has been deciphered by taking into account the changes of textures and chemical zoning of plagioclase and olivine crystals from the erupted lavas and tephra. The petrological observations have been integrated with analyses of the amplitude and source location of volcanic tremor and infrasound data. Characteristics of crystals erupted on July 2019 at the NSEC reflect protracted intrusions of magma into the mid-upper section of the plumbing system, approximately within 290–120 MPa, which acted as the main zone of magma accumulation and crystallization before the beginning of the eruptive activity. Textures and compositions of crystals erupted at VOR emphasize the beginning of volcanic activity driven by recharge/discharge phases that mostly affect the shallowest portion of the Mt. Etna plumbing system (<40 MPa). At the end of 2019, mineral compositions and zoning patterns changed again in accordance with eruption dynamics. The observed changes reflect the transition from an early phase, between November and December 2019, characterized by substantial equilibrium during magma storage and transport toward higher disequilibrium conditions and eruptive frequency, in January 2020. This has been associated to episodes of deep replenishment of mafic magmas displacing the resident one. Diffusion chronometry applied to zoned olivines shows that most of the episodes of magma intrusion correlate temporally with changes in the features of both volcanic tremor and infrasonic events in terms of amplitude and source location, providing evidence that such geophysical signals are directly related to the magma dynamics in the upper plumbing system.
Image
Hughes G.E., Petrone C.M., Downes H., Varley N.R., Hammond S.J. (2021)
Mush remobilisation and mafic recharge: A study of the crystal cargo of the 2013–17 eruption at Volcán de Colima, Mexico.
Journal of Volcanology and Geothermal Research 416, 107296
https://doi.org/10.1016/j.jvolgeores.2021.107296
Data di pubblicazione: 25/05/2021
PubAIV-ID-00035 - Articolo in rivista (non-open access)
Abstract
Volcán de Colima is a highly active stratovolcano at the western end of the Trans-Mexican Volcanic Belt. Present day activity consists of lava dome growth and destruction cycles, lava flows, small explosions, and larger explosive Vulcanian eruptions. It has been postulated that an increased frequency of more mafic eruptions signals the run-up to the end of c. 100-year eruptive ‘cycles’, terminating with a Plinian eruption such as those in 1818 and 1913. It is therefore important to understand the role played by mafic recharge during interplinian activity. We present new petrological and geochemical data for lava and ash from the 2013–17 phase of eruption. The uniform paragenesis and geochemical homogeneity of bulk rocks indicate efficient long-term homogenisation of magmas within the plumbing system, similar to the previous 1998–2005 eruptive products. Mineral chemistry however preserves complex patterns of magma recharge and mixing. Chemical and textural information support the interpretation of two magmatic end-members – an evolved end-member, saturated with respect to Fe–Ti oxides and apatite and crystallising low-An plagioclase and pyroxenes in the Mg# 69–75 range; and a more primitive, mafic end-member, crystallising high-An plagioclase and pyroxenes in the Mg# 77–88 range. Pyroxene textures and zoning patterns suggest mixing of the mafic melts with the evolved magma and remobilisation of the crystal mush. Two-pyroxene geothermometry constrains magmatic temperatures to c. 980–1000 °C for the evolved end-member, and c. 1020–1080 °C for the mafic end-member. Pressure estimates suggest crystallisation at 4–6 kbar, or c. 12–18 km depth.We interpret this to reflect periodic injections of mafic melts and remobilised crystals into evolved reservoirs in a mushy magma storage system in the mid-crust, in agreement with geophysical data suggesting a semi-molten, partially crystallised body at this depth. An increase in reverse zoned crystals, indicative of mafic injection, from mid-2015 onwards suggests that these melts were injected into the system following the large eruption in July 2015. Our findings suggest that the intense July 2015 eruption may be linked to increased input of mafic magmas into the shallow system, indicating that mafic injections may be a key process governing the timing and style of interplinian eruption at Volcán de Colima.
Lucci F., Saki A., Miri M., Rabiee A., White J.C. (2021)
Genesis of trondhjemite by low-pressure low-melt fraction anatexis of hornblende-gabbro at Alvand Plutonic Complex (Hamedan, NW Iran): insights from geochemical modelling.
Arabian Journal of Geosciences 14, 1788.
https://doi.org/10.1007/s12517-021-08104-0
Data di pubblicazione: 16/08/2021
PubAIV-ID-00031 - Articolo in rivista (open access)
Abstract
Amphibole-dominated dehydration melting of gabbro is the primary process responsible for the genesis of adakites, low-K tonalites, modern trondhjemites, and plagiogranites aswell as Archean tonalite-trondhjemite-granodiorite suites that represent the earliest examples of continental crust. Previous literature has mostly focused on the role of Al-rich amphibole during anatexis of a mafic source and many of these studies have investigated this process through experimental melting runs. However, due to experimental boundary conditions, little is known about partial melting of amphibole-bearing mafic rock at temperatures
Image
Nicotra E., Viccaro M., Donato P., Acocella V., De Rosa R. (2021)
Catching the Main Ethiopian Rift evolving towards plate divergence.
Scientific Reports 11, 21821.
https://doi.org/10.1038/s41598-021-01259-6
Data di pubblicazione: 08/11/2021
PubAIV-ID-00039 - Articolo in Rivista (open access)
Abstract
Magmatism accompanies rifting along divergent plate boundaries, although its role before continental breakup remains poorly understood. For example, the magma-assisted Northern Main Ethiopian Rift (NMER) lacks current volcanism and clear tectono-magmatic relationships with its contiguous rift portions. Here we define its magmatic behaviour, identifying the most recent eruptive fissures (EF) whose aphyric basalts have a higher Ti content than those of older monogenetic scoria cones (MSC), which are porphyritic and plagioclase-dominated. Despite these differences, calculations highlight a similar parental melt for EF and MSC products, suggesting only a different evolutionary history after melt generation. While MSC magmas underwent a further step of storage at intermediate crustal levels, EF magmas rose directly from the base of the crust without contamination, even below older polygenetic volcanoes, suggesting rapid propagation of transcrustal dikes across solidified magma chambers. Whether this recent condition in the NMER is stable or transient, it indicates a transition from central polygenetic to linear fissure volcanism, indicative of increased tensile conditions and volcanism directly fed from the base of the crust, suggesting transition towards mature rifting.
Pappalardo L., Buono G. (2021)
Insights Into Processes and Timescales of Magma Storage and Ascent From Textural and Geochemical Investigations.
In Crustal Magmatic System Evolution (eds M. Masotta, C. Beier and S. Mollo), Geophysical Monograph Series AGU.
https://doi.org/10.1002/9781119564485.ch10
Data di pubblicazione: 21/05/2021
PubAIV-ID-00027 - Capitolo di un libro (non-open access)
Abstract
The mechanisms and timescales of magmatic evolution during storage in crustal reservoirs and ascent in the volcanic conduit exert an important control on both the evolution of precursory phenomena recorded during volcanic crises as well as the style and intensity of the impending eruption. Improving our knowledge on this topic is therefore of paramount importance for better assessment of hazard for active high-risk volcanoes. The densely populated Neapolitan volcanic area (Italy) is one of the places most at risk of volcanic disaster in Europe. To reconstruct the magma plumbing system and its evolution toward critical conditions close to eruption, we employed petrological data on past eruptive products representative of the entire volcanic history. Our results are consistent with the possible existence of a long-term magmatic sill-shaped storage zone beneath the whole Neapolitan volcanic area, with its maximum volume under the Campi Flegrei supervolcano, where the largest eruptions occurred in the last 40 ka. Moreover, slow magma transfer, an open degassing regime, and stasis at a shallow level (ephemeral storage zones) characterize magma ascent during small-scale events, whereas fast magma rise and a continuous closed degassing mechanism drive violent large-scale eruptions. These distinctive dynamics could imply different time-depth patterns of precursory unrest.
Image
Petrone C.M., Mangler M. (2021)
Timescales of Magma Dynamics.
Geophysical Monograph Series 264, Chapter 8
https://doi.org/10.1002/9781119564485.ch8
Data di pubblicazione: 21/05/2021
PubAIV-ID-00036 - Capitolo di un Libro (non-open access)
Abstract
Time-related information of pre-eruptive magmatic processes is locked in the chemical profile of compositionally zoned minerals and can be retrieved by means of elemental diffusion chronometry. However, only the timescale of the outermost rim is commonly resolved, limiting our knowledge of timescales to those directly preceding the eruption. A major obstacle is the need to accurately constrain the temperatures at which diffusion occurred. Elemental diffusion chronostratigraphy can be fully resolved for crystals that have spent their lifetime in hot storage. Under this condition, crystals will be kept at the temperature of the eruptible magma(s), and diffusion timescales approximate the storage of the crystal in question in different melt environments. Hot storage conditions are typical of open-conduit systems in steady state and are driven by the regular supply of fresh hot magmas determining the constant presence of eruptible magma. Fe–Mg interdiffusion in pyroxene crystals from Stromboli and Popocatépetl are used to reconstruct elemental diffusion chronostratigraphies of single crystals and to discuss their implications for magma dynamics. Uncertainties introduced by temperature estimates and other input data, including experimentally derived values for the activation energy E and the pre-exponential factor D 0 , have large effects on the accuracy of modeled timescales, which need to be evaluated and mitigated. Elemental diffusion chronostratigraphy is an extremely powerful tool for obtaining time-related temporal information on the dynamics and histories of volcanic plumbing systems, providing in-depth knowledge of the magmatic system far beyond late-stage pre-eruptive processes.
Renzulli A., Taussi M., Brink F.J., Del Moro S., Henley R.W. (2021)
Sulphide Globules in a Porcellanite–Buchite Composite Xenolith from Stromboli Volcano (Aeolian Islands, Southern Italy): Products of Open-System Igneous Pyrometamorphism.
Minerals, 11(6), 639 
https://doi.org/10.3390/min11060639
Data di pubblicazione: 16/06/2021
PubAIV-ID-00004 - Articolo in Rivista (open access)
Abstract
Pyrometamorphism is the highest temperature end-member of the sanidinite facies (high-temperature, low-pressure contact metamorphism) and comprises both subsolidus and partial melting reactions which may locally lead to cryptocrystalline-glassy rocks (i.e., porcellanites and buchites). A wide range of pyrometamorphic ejecta, with different protoliths from Stromboli volcano, have been investigated over the last two decades. Among these, a heterogeneous (composite) glassy sample (B1) containing intimately mingled porcellanite and buchite lithotypes was selected to be studied through new FESEM–EDX and QEMSCAN™ mineral mapping investigations, coupled with the already available bulk rock composition data. This xenolith was chosen because of the unique and intriguing presence of abundant Cu–Fe sulphide globules within the buchite glass in contrast with the well-known general absence of sulphides in Stromboli basalts or their subvolcanic counterparts (dolerites) due to the oxygen fugacity of NNO + 0.5–NNO + 1 (or slightly lower) during magma crystallization. The investigated sample was ejected during the Stromboli paroxysm of 5 April 2003 when low porphyritic (LP) and high porphyritic (HP) basalts were erupted together. Both types of magmas are present as coatings of the porcellanite–buchite sample and were responsible for the last syn-eruptive xenoliths’s rim made of a thin crystalline-glassy selvage. The complex petrogenetic history of the B1 pyrometamorphic xenolith is tentatively explained in the framework of the shallow subvolcanic processes and vent system dynamics occurred shortly before (January–March 2003) the 5 April 2003 paroxysm. A multistep petrogenesis is proposed to account for the unique occurrence of sulphide globules in this composite pyrometamorphic xenolith. The initial stage is the pyrometamorphism of an already hydrothermally leached extrusive/subvolcanic vent system wall rock within the shallow volcano edifice. Successively, fragments of this wall rock were subject to further heating by continuous gas flux and interaction with Stromboli HP basalt at temperatures above 1000 °C to partially melt the xenolith. This is an open system process involving continuous exchange of volatile components between the gas flux and the evolving silicate melt. It is suggested that the reaction of plagioclase and ferromagnesian phenocrysts with SO2 and HCl from the volcanic gas during diffusion into the melt led to the formation of molecular CaCl in the melt, which then was released to the general gas flux. Sulphide formation is the consequence of the reaction of HCl dissolved into the melt from the gas phase, resulting in the release of H2 into the melt and lowering of fO2 driving reduction of the dissolved SO2.
Image
Saki A., Lucci F., Miri M., White J.C. (2021)
Trondhjemite leucosomes generated by partial melting of a hornblende-gabbro (Alvand plutonic complex, Hamedan, NW Iran).
International Geology Reviews, pp.1-34.
https://doi.org/10.1080/00206814.2020.1861554
Data di pubblicazione: 21/01/2021
PubAIV-ID-00030 - Articolo in rivista (non-open access)
Abstract
This work describes the petrogenesis of in situ and in-source trondhjemite leucosomes generated by low-degree partial melting of the Jurassic Cheshmeh-Ghasaban hornblende-gabbros in the northern Alvand batholith (Hamedan, NW Iran). These leucosomes occur in a metatexite migmatite as patches, net-structures, veinlets, and dikes at scales ranging from a few millimetres to a few metres. They have high SiO2 (mean ≈ 78 wt%) and Na2O (4–5 wt%) with low Al2O3 (<15 wt%), K2O (<1.5 wt%), Sr (33–267 ppm), Eu (0.31–0.62 ppm) and heavy REE (<4 ppm) contents similar to typical low-Al2O3 trondhjemites. Batch-melting models indicate these leucosomes are the result of ≈1-2% partial melting of the hornblende-gabbro, whereas thermobarometric modelling constrains their petrogenesis in the field of hornblende hornfels-facies metamorphism (pressure ≈3.0–4.5 kbar and temperature ≈700-750°C). On a wider scale, our results document natural trondhjemites generated in the upper crust by amphibole-dehydration melting of a mafic source at temperature conditions close to the solidus, filling the existing gap of data in low-pressure (P < 5kbar) and low-temperature (T < 800°C) amphibole-dominated partial melting experiments. The genesis of these trondhjemites is then discussed with respect to the Mesozoic evolution of the Alvand plutonic complex.
Image
Zuccarello F., Schiavi F., Viccaro M. (2021)
Magma dehydration controls the energy of recent eruptions at Mt. Etna volcano.
Terra Nova, 33, 4
https://doi.org/10.1111/ter.12527
Data di pubblicazione: 17/03/2021
PubAIV-ID-00011 - Articolo in Rivista (open access)
Abstract
Olivine-hosted melt inclusions (MIs) from tephra of the recent 2013–2018 activity at Mt. Etna were investigated for assessing the chemical evolution of magmas and quantifying their pre-eruptive volatile budget. Microanalyses revealed two types of MIs present in all investigated eruptions; the inclusions, particularly the less evolved ones, appear to have experienced water loss coupled with SiO2 depletion. Restoration of the original SiO2-H2O concentrations provides consistency with the thermodynamic modelling of magma evolution. The two types of MIs developed during crystallization of olivine plus clinopyroxene between 200 and 100 MPa, where magmas also experienced CO2 flushing. Degassing processes at these levels are responsible for water depletion in the melt and diffusive water loss from inclusions. Our data suggest that initial water budget is unchanged all over the last 20 years, reflecting therefore a potential in triggering highly explosive eruptions depending on degassing dynamics under open versus closed system conditions at shallow levels.
Image
Tematica 2: Dinamiche eruttive e di messa in posto
Andronico D., Cannata A., Di Grazia G., Ferrari, F. (2021) 
The 1986–2021 paroxysmal episodes at the summit craters of Mt. Etna: Insights into volcano dynamics and hazard. 
Earth-Science Reviews, 220, 103686
https://doi.org/10.1016/j.earscirev.2021.103686
Data di pubblicazione: 18/05/2021
PubAIV-ID-00018 - Articolo in Rivista (non-open access)
Abstract
Despite Mt. Etna's long-standing reputation as an effusive volcano, since 1986 there has been an evident increase in mid-intensity explosive eruptions from its summit craters, with more than 240 episodes, better known as paroxysms (otherwise called paroxysmal episodes). These are characterized by strong Strombolian to lava fountaining activity that lasts from tens of minutes to a few days, producing some km-high volcanic plumes and tephra fallouts up to hundreds of km on the ground. Most paroxysms give life to sequences which are clustered like “episodic” eruptions for periods of a few days to a few months, their frequent recurrence causing hazard to air traffic and impacting densely inhabited areas. Nonetheless, a list containing the dates and data of these eruptions is lacking. In this paper, we tried to fill this gap by compiling a complete record, including master data (date, crater), eruption style and seismic parameters for identifying, characterizing and quantifying both the individual episodes and the entire period. This information comes from a critical review of surveillance reports, raw-data analysis and scientific literature. A retrieval of homogenous and comparable seismic data was possible only for episodes after 2006 following the renewal of seismic stations. The eruption list provides a complete picture of the 1986–2021 paroxysms, allowing to evaluate their temporal distribution, make a statistical analysis of their time-interval, and undertake a comprehensive investigation of the features of volcanic tremor. The results show a high probability (72%) of having a paroxysmal episode in the 10 days following the previous one. Moreover, a scaling relationship associated with the number-size distribution of the amplitude increases of volcanic tremor accompanying the explosive activities has been constrained. During sequences of paroxysms, combining these outputs can help improve the hazard assessment in terms of frequency of the associated tephra fallouts, and predict the duration of the entire sequence.
Cassetta M., Di Genova D., Zanatta M., Ballaran T.B., Kurnosov A., Giarola M., Mariotto G. (2021) 
Estimating the viscosity of volcanic melts from the vibrational properties of their parental glasses. 
Scientific Reports 11, 13072
https://doi.org/10.1038/s41598-021-92407-5
Data di pubblicazione: 07/07/2021
PubAIV-ID-00013 - Articolo in Rivista (open access)
Abstract
The numerical modelling of magma transport and volcanic eruptions requires accurate knowledge of the viscosity of magmatic liquids as a function of temperature and melt composition. However, there is growing evidence that volcanic melts can be prone to nanoscale modification and crystallization before and during viscosity measurements. This challenges the possibility of being able to quantify the crystal-free melt phase contribution to the measured viscosity. In an effort to establish an alternative route to derive the viscosity of volcanic melts based on the vibrational properties of their parental glasses, we have subjected volcanologically relevant anhydrous glasses to Brillouin and Raman spectroscopic analyses at ambient conditions. Here, we find that the ratio between bulk and shear moduli and the boson peak position embed the melt fragility. We show that these quantities allow an accurate estimation of volcanic melts at eruptive conditions, without the need for viscosity measurements. An extensive review of the literature data confirms that our result also holds for hydrous systems; this study thus provides fertile ground on which to develop new studies of the nanoscale dynamics of natural melts and its impact on the style of volcanic eruptions.
Image
Dellino P., Dioguardi F., Isaia R., Sulpizio R., Mele D. (2021) 
The impact of pyroclastic density currents duration on humans: the case of the AD 79 eruption of Vesuvius. 
Scientific Reports 11, 4959
https://doi.org/10.1038/s41598-021-84456-7
Data di pubblicazione: 02/03/2021
PubAIV-ID-00014 - Articolo in Rivista (open access)
Abstract
Pyroclastic density currents are ground hugging gas-particle flows that originate from the collapse of an eruption column or lava dome. They move away from the volcano at high speed, causing devastation. The impact is generally associated with flow dynamic pressure and temperature. Little emphasis has yet been given to flow duration, although it is emerging that the survival of people engulfed in a current strongly depends on the exposure time. The AD 79 event of Somma-Vesuvius is used here to demonstrate the impact of pyroclastic density currents on humans during an historical eruption. At Herculaneum, at the foot of the volcano, the temperature and strength of the flow were so high that survival was impossible. At Pompeii, in the distal area, we use a new model indicating that the current had low strength and low temperature, which is confirmed by the absence of signs of trauma on corpses. Under such conditions, survival should have been possible if the current lasted a few minutes or less. Instead, our calculations demonstrate a flow duration of 17 min, long enough to make lethal the breathing of ash suspended in the current. We conclude that in distal areas where the mechanical and thermal effects of a pyroclastic density currents are diminished, flow duration is the key for survival.
Image
Dellino P., Dioguardi F., Rinaldi A., Sulpizio R., Mele D. (2021)
Inverting sediment bedforms for evaluating the hazard of dilute pyroclastic density currents in the field.
Scientific reports 11, 2104
https://doi.org/10.1038/s41598-021-00395-3
Data di pubblicazione: 02/11/2021
PubAIV-ID-00038 - Articolo in rivista (open access)
Abstract
Pyroclastic density currents are ground hugging gas-particle flows associated to explosive volcanic eruptions and moving down a volcano's slope, causing devastation and deaths. Because of the hostile nature they cannot be analyzed directly and most of their fluid dynamic behavior is reconstructed by the deposits left in the geological record, which frequently show peculiar structures such as ripples and dune bedforms. Here, a set of equations is simplified to link flow behavior to particle motion and deposition. This allows to construct a phase diagram by which impact parameters of dilute pyroclastic density currents, representing important factors of hazard, can be calculated by inverting bedforms wavelength and grain size, without the need of more complex models that require extensive work in the laboratory.
Image
Di Fiore F., Vona A., Kolzenburg S., Mollo S., Romano C. (2021) 
An extended rheological map of pāhoehoe - ‘a‘ā transition. 
Journal of Geophysical Research: Solid Earth, 126(7), e2021JB022035.
https://doi.org/10.1029/2021JB022035
Data di pubblicazione: 08/07/2021
PubAIV-ID-00001 - Articolo in Rivista (non-open access)
Abstract
The pāhoehoe–‘a‘ā morphological transition involves a change in the rheological response of the magmatic suspension from pure viscous to complex rheological behavior, resulting in the development of tear-apart features. Here, we present a suite of concentric cylinder experiments aimed at studying the effects of cooling and shear rates on the rheology of a phonotephrite melt in response to crystallization. Experiments were conducted at: i) isothermal subliquidus temperatures of 1,167–1,189 °C and shear rates of 1–3 s-1; ii) constant cooling rates of 1–10 °C/min and shear rates of 1–20 s-1. We defined the viscosity-temperature-time window of lava solidification, as well as the transition from coherent flow to shear localization and physical separation (i.e., viscous rupture). Through this approach, we mapped the processes and timescales affecting pāhoehoe–‘a‘ā transition in natural lavas at variable cooling and shear rates. Under disequilibrium conditions, as the cooling rate increases, both crystallization onset and viscous rupture occur at lower temperature and earlier in time. Moreover, the time to reach the crystallization onset and viscous rupture also decreases with increasing shear rate. Both increasing cooling and shear rate reduces the critical crystallinity required for viscous rupture, a consequence of the non-linear interplay between temperature, crystallization kinetics, and melt viscosity. This outcome expands our knowledge on compositional, thermal, and rheological changes in phonotephritic systems. In addition to shear rate and apparent viscosity, comparison with previous measurements on basaltic systems indicates that the pāhoehoe–‘a‘ā transition is sensitive to the composition and cooling path of lavas.
Image
Farina A., Matrone J., Montagna C.P., Rosso F. (2021)
Modeling of a gas slug rising in a cylindrical duct and possible applications to volcanic scenarios. 
Rendiconti Lincei - Matematica e Applicazioni, 31(4), 917-937
https://doi.org/10.4171/RLM/920
Data di pubblicazione: 16/02/2021
PubAIV-ID-00006 - Articolo in Rivista (non-open access)
Abstract
The paper deals with the mathematical modelling of a gas slug rising in a cylindrical duct filled with an incompressible liquid. This research is motivated by a phenomenon commonly observed during Strombolian eruptions at basaltic volcanoes, that is, mildly explosive events driven by a large bubble of magmatic gas (a slug) rising up the conduit and bursting at the surface. The model is compared with the laboratory experiments described in [15] and we prove that the constancy of the slug ascent velocity observed in these experiments is fully justifiable. The model is developed both in the case of a Newtonian fluid and in the case of a non-Newtonian power law fluid, more suitable for magmas, and applied to a volcanic scenario.
Image
Galetto F., Bonaccorso A., Acocella V. (2021)
Relating Dike Geometry and Injection Rate in Analogue Flux-Driven Experiments. 
Frontiers in Earth Science 9, 665865.
https://doi.org/10.3389/feart.2021.665865
Data di pubblicazione: 13/05/2021
PubAIV-ID-00012 - Articolo in Rivista (open access)
Abstract
Dikes feed most eruptions, so understanding their mechanism of propagation is fundamental for volcanic hazard assessment. The variation in geometry of a propagating dike as a function of the injection rate remains poorly studied. Here we use experiments injecting water into gelatin to investigate the variation of the thickness, width and length of a flux-driven dike connected to its source as a function of the injection time and intruded volume. Results show that the thickness of vertically propagating dikes is proportional to the injection rate and remains constant as long as the latter is constant. Neither buoyancy nor injected volume influence the thickness. The along-strike width of the dike is, however, proportional to the injected volume. These results, consistent with the inferred behavior of several dikes observed during emplacement, open new opportunities to better understand how dikes propagate and also to forecast how emplacing dikes may propagate once their geometric features are detected in real-time through monitoring data.
Image
Giordano G., De Astis G. (2021)
The summer 2019 basaltic Vulcanian eruptions (paroxysms) of Stromboli.
Bulletin of Volcanology 83, 1
https://doi.org/10.1007/s00445-020-01423-2
Data di pubblicazione: 10/01/2021
PubAIV-ID-00025 - Articolo in Rivista (open access)
Abstract
Stromboli is an active, open conduit mafic volcano, whose persistent mild Strombolian activity is occasionally punctuated by much stronger explosions, known as paroxysms. During summer 2019, the volcano unexpectedly produced one such paroxysm on July 3, followed by intense explosive and intermittent effusive activity culminating in a second paroxysm on August 28.
Visual observations and the analysis of the fall deposits associated with the two paroxysms allowed us to reconstruct ballistic exit velocities of up to 160 m s−1. Plume heights of ~ 8.4 km and 6.4 km estimated for the two events correspond to mass eruption rates of 1.1 × 106 kg s−1 and 3.6 × 105 kg s−1, respectively. This is certainly an underestimate as directional pyroclastic flows into
which mass was partitioned immediately formed, triggering small tsunamis at the sea entrance. The mass of ballistic spatters and blocks erupted during the July 3 event formed a continuous cover at the summit of the volcano, with a mass calculated at ~ 1.4 × 10^8 kg. The distribution of fall deposits of both the July 3 and August 28 events suggests that pyroclasts characterized by terminal
fall velocities < 10–20 m s−1 remained fully suspended within the convective region of the plume and did not fall at distances closer than ca 1700 m to the vent. Based on the impulsive, blast-like phenomenology of paroxysms as well as the deposit distribution and type, paroxysms are classified as basaltic Vulcanian in style. The evolution of the summer 2019 eruptive events was not properly captured within the framework of the alert level system which is focused on tsunamigenic processes, and this is discussed so as to provide elements for the implementation of the reference scenarios and an upgrade of the system to take into account such events. In particular we find that, although still largely unpredictable, at least at operational time scales, and not necessarily tsunamigenic, Vulcanian eruptions and the subsequent evolution of the eruptive phenomena should be considered for the alert level system. This serves as a warning to the implementation of alert systems where the unexpected needs to be taken into account, even at systems that are believed to be relatively “predictable” as is the case at many persistently active, open vent mafic systems.
Image
Giordano G., Cas R.A.F. (2021)
Classification of ignimbrites and their eruptions.
Earth-Science Reviews 220, 103697
https://doi.org/10.1016/j.earscirev.2021.103697
Data di pubblicazione: 01/06/2021
PubAIV-ID-00026 - Articolo in Rivista (non-open access)
Abstract
The term “ignimbrite” probably encompasses the one of the largest ranges of deposit types on Earth, associated with the partial to total collapse of explosive eruption columns feeding pyroclastic density currents. Surprisingly, there is no quantified classification scheme for ignimbrite types, as there is for fallout deposits, and this is a remarkable deficiency of modern volcanology. This has so far prevented the identification of standardized descriptors for ignimbrites and the improvement of methods for the documentation of their characteristics, such as happened for fallout deposits, building on the classification scheme proposed by Walker in 1973. Despite some earlier attempts, ignimbrite types do not conform to eruption style nomenclature. In this paper, we explore and discuss descriptors for a classification scheme based on the correlation of runout, areal extent, aspect ratio and volume from a compiled database comprising 92 ignimbrites, which then allows current understanding of pyroclastic flow dynamics to be considered. We refer to single ignimbrite outflow units, i.e. emplaced without significant breaks in their sedimentation, in extra-caldera settings and forming individual cooling units, irrespective of internal lithofacies architecture. Our main finding is that ignimbrites show remarkable power-law relationship between dispersal area/equivalent runout and bulk volume. Runout is directly related to increasing mass flow rate feeding the pyroclastic current. Volume is related to the magnitude of the flow event. We therefore propose that by measuring first order field observables such as bulk volume and dispersal area provides the opportunity to evaluate magnitude and intensity of related pyroclastic currents and, for large eruptions dominated by ignimbrites, of the eruption. Based on the relationships identified we propose that ignimbrites that originated from the collapse of single point-source eruption columns, usually smaller than 1 km3, are named “Vulcanian ignimbrites” and “Plinian ignimbrites” depending on the style of the eruption they are associated with. Larger ignimbrites that originated from caldera-forming eruptions along ring-fault fissure vents should be regarded as related to a separate eruption style - with respect to the common Hawaiian-Plinian trend -, where the effect of increased mass flow rate due to ring-fissure vents is dominant and controls the dynamics of the resulting collapsing fountains and pyroclastic flows, irrespective of the kind of eruption style that preceded the onset of the caldera collapse. These are named “caldera-forming ignimbrites” and are further subdivided into small, intermediate, large and super, based on their increasing erupted volume.
Image
Magli A., Branca S., Speranza F., Risica G., Siravo G., Giordano G. (2021)
Paleomagnetic dating of prehistoric lava flows from the urban district of Catania (Etna volcano, Italy). 
Geological Society of America Bulletin
https://doi.org/10.1130/B36026.1
Data di pubblicazione: 21/06/2021
PubAIV-ID-00008 - Articolo in Rivista (non-open access)
Abstract
Determining the ages of past eruptions of active volcanoes whose slopes were historically inhabited is vitally important for investigating the relationships between eruptive phenomena and human settlements. During its almost three-millennia-long history, Catania—the biggest city lying at the toe of Etna volcano—was directly impacted only once by the huge lava flow emplaced during the A.D. 1669 Etna flank eruption. However, other lava flows reached the present-day Catania urban district in prehistoric ages before the founding of the city in Greek times (729/728 B.C., i.e., 2679/2678 yr B.P.). In this work, the Holocene lava flows of Barriera del Bosco, Larmisi, and San Giovanni Galermo, which are exposed in the Catania urban district, were paleomagnetically investigated at 12 sites (120 oriented cores). Paleomagnetic dating was obtained by comparing flow-mean paleomagnetic directions to updated geomagnetic reference models for the Holocene. The Barriera del Bosco flow turns out to represent the oldest eruptive event and is paleomagnetically dated to the 11,234−10,941 yr B.P. and 8395−8236 yr B.P. age intervals. The mean paleomagnetic directions from the San Giovanni Galermo and Larmisi flows overlap when statistical uncertainties are considered. This datum, along with geologic, geochemical, and petrologic evidence, implies that the two lava flows can be considered as parts of a single lava field that erupted in a narrow time window between 5494 yr B.P. and 5387 yr B.P. The emplacement of such a huge lava flow field may have buried several Neolithic settlements, which would thus explain the scarce occurrence of archaeological sites of that age found below the town of Catania.
Image
Spina L., Del Bello E., Ricci T., Taddeucci J., Scarlato P. (2021) 
Multi-parametric characterization of explosive activity at Batu Tara Volcano (Flores Sea, Indonesia)
Journal of Volcanology and Geothermal Research, 413, 107199
https://doi.org/10.1016/j.jvolgeores.2021.107199
Data di pubblicazione: 18/02/2021
PubAIV-ID-00022 - Articolo in Rivista (non-open access)
Abstract
Batu Tara is an active but poorly studied volcano located in the Lesser Sunda Archipelago (Indonesia). Its last known long-lasting eruptive phase, dating 2006–2015, was characterised by frequent short-lived explosions, similar in style and magnitude to those of the well monitored Stromboli volcano (Italy). On September 2014, we collected high-frequency multi-parametric measurements of the ongoing explosive activity to investigate the dynamics of intermediate-size volcanic explosions. We acquired synchronized acoustic, thermal and visible high-speed imaging data, and parameterized different spatial and temporal properties of each explosive event: i) maximum height and ejection velocity of bombs and plumes, ii) duration, iii) amplitude of acoustic and thermal transients, iv) acoustic and thermal energy, v) spectral features of the acoustic signals. The latter ones justify the assumption of a pipe resonance of the uppermost conduit section, likely in response to the arrival of over-pressurized gas at the free magma surface. The variability of the investigated parameters agrees with previous observations of intermediate-size explosions at other volcanoes, reflecting the complexity of the related source processes.
Stabile P., Arzilli F., Carroll M.R. (2021)
Crystallization of peralkaline rhyolitic magmas: pre- and syn-eruptive conditions of the Pantelleria system.
Comptes Rendus. Géoscience, 353, 1-20
https://doi.org/10.5802/crgeos.72
Data di pubblicazione: 05/08/2021
PubAIV-ID-00023 - Articolo in Rivista (open access)
Abstract
Pantelleritic magmas are low-viscosity peralkaline rhyolites which exhibit large differences in eruptive style (explosive to effusive). The processes that promote fragmentation and explosive eruptions of pantelleritic magma remain subject to debate, but undoubtedly variations of magma viscosity during magma ascent and degassing contribute to differences in eruptive style. Because crystallization can significantly influence magma rheology, we present a review of equilibrium and disequilibrium crystallization experiments of pantellerites, focusing on the crystallization of the main phases, alkali feldspar, and (lesser) clinopyroxene. Our analysis of data for several explosive pantelleritic eruptions on Pantelleria suggests pre-eruptive pressures of 50–100 MPa, temperatures of 700–800 °C for water-saturated conditions. Given these conditions, we show that the low pre-eruptive crystal fractions (0.08 to 0.15), temperatures between 700 and 800 °C, and the decrease of melt H2O content during magma ascent/decompression can promote a significant change in viscosity (up to 106–107 Pa·s), leading to magma brittle fragmentation and explosive eruptions. Because of their typical range of viscosity, pantelleritic magmas may show greater variations in eruptive style due to differences in ascent (decompression) rate when compared with metaluminous rhyolites.
Image
Sicola S., Vona A., Ryan A.G., Russell J.K., Romano C. (2021)
The effect of pores (fluid-filled vs. drained) on magma rheology. 
Chemical Geology, 569, 120147
https://doi.org/10.1016/j.chemgeo.2021.120147
Data di pubblicazione: 03/03/2021
PubAIV-ID-00005 - Articolo in Rivista (non-open access)
Abstract
The presence of pore space strongly affects the rheological behavior of magma and thus influences all volcanic processes (pre-, syn- and post- eruptive). The effects of porosity on magma rheology are, however, unresolved and subject to debate. Here, we present new high-temperature experiments designed to constrain the rheological properties of variably porous melts (0.09–0.66 fractional porosity) deforming at high temperature (750–800 °C) and low strain rates (10^−4 — 10^−7 s^−1). The starting materials are cylindrical cores of natural vesicle- and crystal-free rhyolitic obsidian from Krafla (Iceland) initially containing 0.114 wt% of dissolved H2O. Our experiments comprise two steps. First, cores are heated above the glass transition temperature (700 °C) to 900–1050 °C; second, the cores are deformed at lower temperatures (750 or 800 °C) under a constant low load (1.5 N). We have employed two different strategies for the second step: i) samples are deformed in situ directly after foaming (single-stage, SS); or ii) samples are quenched then reheated and deformed at 750 °C after 15 days repose at room conditions (double-stage, DS). Our experiments provide data that inform on the effects of porosity on the viscosity of natural rhyolitic deposits (e.g., ignimbrites, lavas, domes). Discordant results between SS and DS experiments (~0.6 log10 Pa s for 0.5 fractional porosity) suggest that the rheology of porous volcanic materials depends on whether pore spaces are isolated, fluid-filled bubbles (e.g., magmas in the conduit) or are interconnected, drained voids (e.g., domes, lavas, pyroclastic deposits).
Image
Viccaro M., Cannata A., Cannavò F., De Rosa R., Giuffrida M., Nicotra E., Petrelli M., Sacco G. (2021)
Shallow conduit dynamics fuel the unexpected paroxysms of Stromboli volcano during the summer 2019. 
Scientific Reports, 11, 266
https://doi.org/10.1038/s41598-020-79558-7
Data di pubblicazione: 11/01/2021
PubAIV-ID-00002 - Articolo in Rivista (open access)
Abstract
Open conduit basaltic volcanoes can be potentially hazardous as the eruptive activity may turn suddenly from a steady state to highly explosive. Unexpected changes in explosion intensity are recurrent at Stromboli volcano, where major explosions and large-scale paroxysms sometimes break off the ordinary, Strombolian activity with little or no warning. Two powerful paroxysmal eruptions took place at Stromboli volcano during the summer 2019, causing widespread fires, consistent damages across the island, injuries and one fatality. Prediction of similar events is really challenging for the modern volcanology, though models propaedeutic to early-warning monitoring systems are not properly assessed yet in many volcanoes worldwide. Here, we present a multi-parametric study that combines petrological and geophysical data to investigate processes generating the two paroxysms. The time information derived by Li enrichments in plagioclase crystals correlates with tilt time series derived by seismometers installed on the island, highlighting the dominant role of shallow conduit processes in triggering the 2019 paroxysmal activity. Our dataset conceives a mechanism of gas slug formation and fast upward migration that finally triggered the eruptions in very limited times. The proposed model questions our capability to forecast such kind of paroxysms in times that are rapid enough to allow mitigation of the associated risk.
Image
Tematica 3: Geologia e struttura dei vulcani
Cannata A., Iozzia A., Alparone S., Bonforte A., Cannavò F., Cesca S., Gresta S., Rivalta E., Ursino A. (2021) 
Repeating earthquakes and ground deformation reveal the structure and triggering mechanisms of the Pernicana fault, Mt. Etna. 
Communications Earth & Environment 2, 116
https://doi.org/10.1038/s43247-021-00188-6
Data di pubblicazione: 09/06/2021
PubAIV-ID-00019 - Articolo in Rivista (open access)
Abstract
Structure and dynamics of fault systems can be investigated using repeating earthquakes a repeatable seismic sources, alongside ground deformation measurements. Here we utilise a dataset of repeating earthquakes which occurred between 2000 and 2019 along the transtensive Pernicana fault system on the northeast flank of Mount Etna, Italy, to investigate the fault structure, as well as the triggering mechanisms of the seismicity. By grouping the repeating earthquakes into families and integrating the seismic data with GPS measurements of ground deformation, we identify four distinct portions of the fault. Each portion shows a different behaviour in terms of seismicity, repeating earthquakes and ground deformation, which we attribute to structural differences including a segmentation of the fault plane at depth. The recurrence intervals of repeating earthquake families display a low degree of regularity which suggests an episodic triggering mechanism, such as magma intrusion, rather than displacement under a constant stress.
Gambino S., Armienti P., Cannata A., Del Carlo P., Giudice G., Giuffrida G., Liuzzo M., Pompilio M. (2021) 
Chapter 7.3 Mount Melbourne and Mount Rittmann. 
Geological Society, London, Memoirs, 55(1), 741-758.
https://doi.org/10.1144/M55-2018-43
Data di pubblicazione: 01/01/2021
PubAIV-ID-00020 - Capitolo di un libro (non-open access)
Abstract
Mount Melbourne and Mount Rittmann are quiescent, although potentially explosive, alkaline volcanoes located 100 km apart in Northern Victoria Land quite close to three stations (Mario Zucchelli Station, Gondwana and Jang Bogo). The earliest investigations on Mount Melbourne started at the end of the 1960s; Mount Rittmann was discovered during the 1988–89 Italian campaign and knowledge of it is more limited due to the extensive ice cover. The first geophysical observations at Mount Melbourne were set up in 1988 by the Italian National Antarctic Research Programme (PNRA), which has recently funded new volcanological, geochemical and geophysical investigations on both volcanoes. Mount Melbourne and Mount Rittmann are active, and are characterized by fumaroles that are fed by volcanic fluid; their seismicity shows typical volcano signals, such as long-period events and tremor. Slow deformative phases have been recognized in the Mount Melbourne summit area. Future implementation of monitoring systems would help to improve our knowledge and enable near-realtime data to be acquired in order to track the evolution of these volcanoes. This would prove extremely useful in volcanic risk mitigation, considering that both Mount Melbourne and Mount Rittmann are potentially capable of producing major explosive activity with a possible risk to large and distant communities.
Marra F., Cardello G.L., Gaeta M., Jicha B.R., Montone P., Niespolo E.M., Nomade S., Palladino D.M., Pereira A., De Luca G., Florindo F., Frepoli A., Renne P.R., Sottili G. (2021)
The Volsci Volcanic Field (central Italy): eruptive history, magma system and implications on continental subduction processes.
International Journal of Earth Sciences, 110, 689-718.
https://doi.org/10.1007/s00531-021-01981-6
Data di pubblicazione: 12/02/2021
PubAIV-ID-00037 - Articolo in rivista (non-open access)
Abstract
Here, we report on the Quaternary Volsci Volcanic Field (VVF, central Italy). In light of new 40Ar/39Ar geochronological data and compositional characterization of juvenile eruptive products, we refne the history of VVF activity, and outline the
implications on the pre-eruptive magma system and the continental subduction processes involved. Diferent from the nearby volcanic districts of the Roman and Campanian Provinces, the VVF was characterized by small-volume (0.01–0.1 km3) eruptions from a network of monogenetic centers (mostly tuf rings and scoria cones, with subordinate lava occurrences), clustered along high-angle faults of lithospheric depth. Leucite-bearing, high-K (HKS) magmas (for which we report for the frst time the phlogopite phenocryst compositions) mostly fed the early phase of activity (∼761–539 ka), then primitive, plagioclase-bearing (KS) magmas appeared during the climactic phase (∼424–349 ka), partially overlapping with HKS ones, and then prevailed during the late phase of activity (∼300–231 ka). The fast ascent of primitive magma batches is typical of a tectonically controlled volcanic feld, where the very low magma fux is a passive byproduct of regional tectonic strain. We suggest that the dominant compressive stress feld acting at depth was accompanied by an extensional regime in the upper crust, associated with the gravity spreading of the Apennine chain, allowing the fast ascent of magma from the mantle source with limited stationing in shallow reservoirs.
Tematica 4: Monitoraggio, pericolosità e rischio vulcanico

Giacomelli L., Scandone R. (2021)
Pompei sotto il Vesuvio, Cercavano ori hanno trovato Uomini, Volume 2-1.
Amazon.it, 406 pp.
Link editore
Data di pubblicazione: 02/12/2021
PubAIV-ID-00041 - Libro (non-open access)
Abstract
Si è cercato di mettere in luce, quanto più che si poteva, le conseguenze dell’eruzione del Vesuvio del 79 d. C. sulla città e sugli uomini, intersecando, inevitabilmente, anche la lunga storia del recupero dei siti. Tuttavia, per quanto si siano cercate le tracce del disastro di 2000 anni fa, scavi antichi e recenti, ricostruzioni e demolizioni hanno concorso a cancellarne quasi ogni evidenza. Pompei oggi non è più un sito all’ombra del Vesuvio, ma fa ombra lei stessa, con le sue abbaglianti domus, al monte che ne ha involontariamente provocato la fine. Il monumento archeologico nasconde, quasi vergognandosene, gran parte della propria storia.

Giacomelli L., Scandone R. (2021)
Pompei sotto il Vesuvio, Cercavano ori hanno trovato Uomini, Volume 2-2.
Amazon.it, 328 pp.
Link editore
Data di pubblicazione: 02/12/2021
PubAIV-ID-00042 - Libro (non-open access)
Abstract
Il libro cerca di mettere in luce, quanto più possibile, le conseguenze dell’eruzione del Vesuvio del 79 d. C. sulla città di Pompei e sugli uomini, intersecando, inevitabilmente, anche la lunga storia del recupero dei siti. Tuttavia, per quanto si siano cercate le tracce del disastro di 2000 anni fa, scavi antichi e recenti, ricostruzioni e demolizioni hanno concorso a cancellarne quasi ogni evidenza. Pompei oggi non è più un sito all’ombra del Vesuvio, ma fa ombra lei stessa, con le sue abbaglianti domus, al monte che ne ha involontariamente provocato la fine. Il monumento archeologico nasconde, quasi vergognandosene, gran parte della propria storia. Continua nel secondo volume l'esplorazione di Pompei.

Giacomelli L., Scandone R. (2021)
Pompei sotto il Vesuvio, Cercavano ori hanno trovato Uomini, Volume 2-3.
Amazon.it, 240 pp.
Link editore
Data di pubblicazione: 02/12/2021
PubAIV-ID-00043 - Libro (non-open access)
Abstract
Pompei, al momento della distruzione causata dall’eruzione del Vesuvio del 79 d.C., era una città che tentava di risollevarsi dalla precedente catastrofe del 62 d.C. quando un terremoto disastroso aveva raso al suolo tutti gli edifici pubblici e molte case private.
La città era passata attraverso altre drammatiche vicende, fra le quali la conquista nel 89 a.C. di Silla durante la guerra sociale. Conoscendo la ferocia del futuro Dittatore, la deduzione a Colonia Romana popolata dai suoi legionari non sarà stata indolore per gli abitanti sanniti che occupavano la città. Di quegli eventi restano ancora i segni sui muri della città colpiti dai proiettili delle catapulte e baliste degli assedianti e le poche scritte in osco “Eituns” che istruivano gli abitanti quali posizioni occupare in caso di assedio.
L’eruzione venne a cancellare la vita e le speranze di migliaia di persone insieme alle loro proprietà, sepolte sotto una spessa coltre di pomici e ceneri. Tuttavia, preservò la città dalla azione distruttiva del tempo conservando intatte le testimonianze fisiche di quella antica tragedia. La riscoperta e gli scavi iniziati nel 1748 fecero dire a Goethe che nessuna catastrofe aveva reso più felici i posteri per la ricchezza e bellezza dei reperti che affioravano dalla coltre di ceneri a lapilli.
E’ paradossale che il tentativo di portare alla luce l’antica città e di ricostruire in parte le mura abbattute dalla violenza dei flussi piroclastici e i tetti crollati per il peso delle pomici e la violenza dei terremoti, abbia determinato una nuova strisciante distruzione e perdita di testimonianza per l’azione corrosiva degli agenti atmosferici cui si aggiunge negli ultimi anni l’azione di logoramento dei milioni di turisti che ogni anno sciamano in ogni angolo della città. A tutto questo si aggiunsero nel 1943 una serie di rovinosi bombardamenti effettuati dall’aviazione alleata alla ricerca di inesistenti truppe germaniche, quasi un prologo alla distruzione del monastero di Montecassino.
Il grandioso lavoro di ricostruzione iniziato dal grande archeologo Maiuri e poi da tutti i soprintendenti successivi ha cercato di porre rimedio ai guasti della guerra, purtroppo spesso con l’uso di materiali non adeguati, che sarebbero collassati in tempi successivi. Con il bombardamento alleato Pompei perse irrimediabilmente, oltre a molte domus, anche buona parte dei colori sugli intonaci delle facciate delle case che con le molteplici scritte pubblicitarie ed elettorali rendevano ancora viva la città passata attraverso le molteplici distruzioni.
Questi volumi cercano di mettere in luce, quanto più possibile, le conseguenze dell’eruzione sulla città di Pompei e sugli uomini, intersecando, inevitabilmente, anche la lunga storia del recupero dei siti. Tuttavia, per quanto si siano cercate le tracce del disastro di 2000 anni fa, scavi antichi e recenti, ricostruzioni e demolizioni hanno concorso a cancellarne quasi ogni evidenza. Pompei oggi non è più un sito all’ombra del Vesuvio, ma fa ombra lei stessa, con le sue abbaglianti domus, al monte che ne ha involontariamente provocato la fine. Il monumento archeologico nasconde, quasi vergognandosene, gran parte della propria storia.

Giacomelli L., Scandone R. (2021)
Volcanic phenomena between media simplification and the need for a better understanding of human-environment interaction, with particular reference to Italy.
J-Reading 1, 10, 53-70
https://doi.org/10.4458/3945-04
Data di pubblicazione: 02/12/2021
PubAIV-ID-00044 - Articolo in rivista (non-open access)
Abstract
Correct scientific information is particularly necessary when dealing with hazardous phenomena like volcanic eruptions. Many journalists and even popular media divulgators often use incorrect terms, emphasizing dramatic aspects that are not always necessary, in an attempt to raise public awareness to volcanic phenomena. Often the beneficial aspects of volcanoes are overlooked and there is no understanding of the reason of so frequent human settlements around volcanoes. In this paper we discuss the most widely errors made by generalist media and misunderstanding of volcanic phenomena as well as the unknown beneficial aspects of volcanic activity. We discuss in detail also some poorly known aspects of the excavations of Pompeii which could serve as a tool for understanding volcanic hazard. We report the undocumented loss of volcanological data, that could permit a better understanding of the development of an eruption and suggest behaviour of survival during an explosive one.
Lima A., Bodnar R.J., De Vivo B., Spera F. J., Belkin H.E. (2021)
Interpretation of Recent Unrest Events (Bradyseism) at Campi Flegrei, Napoli (Italy): Comparison of Models Based on Cyclical Hydrothermal Events versus Shallow Magmatic Intrusive Events.
Geofluids 2021, 2000255.
https://doi.org/10.1155/2021/2000255
Data di pubblicazione: 15/10/2021
PubAIV-ID-00034 - Articolo in rivista (open access)
Abstract
Several recent models that have been put forth to explain bradyseism at Campi Flegrei (CF), Italy, are discussed. Data obtained during long-term monitoring of the CF volcanic district has led to the development of a model based on lithological-structural and stratigraphic features that produce anisotropic and heterogeneous permeability features showing large variations both horizontally and vertically; these data are inconsistent with a model in which bradyseism is driven exclusively by shallow magmatic intrusions. CF bradyseism events are driven by cyclical magmatic-hydrothermal activity. Bradyseism events are characterized by cyclical, constant invariant signals repeating over time, such as area deformation along with a spatially well-defined seismogenic volume. These similarities have been defined as “bradyseism signatures” that allow us to relate the bradyseism with impending eruption precursors. Bradyseism is governed by an impermeable shallow layer (B-layer), which is the cap of an anticlinal geological structure culminating at Pozzuoli, where maximum uplift is recorded. This B-layer acts as a throttling valve between the upper aquifer and the deeper hydrothermal system that experiences short (1-102 yr) timescale fluctuations between lithostatic/hydrostatic pressure. The hydrothermal system also communicates episodically with a cooling and quasi-steady-state long timescale (103-104 yr) magmatic system enclosed by an impermeable carapace (A layer). Connectivity between hydrostatic and lithostatic reservoirs is episodically turned on and off causing alternatively subsidence (when the systems are connected) or uplift (when the systems are disconnected), depending on whether permeability by fractures is established or not. Earthquake swarms are the manifestation of hydrofracturing which allows fluid expansion; this same process promotes silica precipitation that seals cracks and serves to isolate the two reservoirs. Faults and fractures promote outgassing and reduce the vertical uplift rate depending on fluid pressure gradients and spatial and temporal variations in the permeability field. The miniuplift episodes also show “bradyseism signatures” and are well explained in the context of the short timescale process.
Image
Massaro S., Dioguardi F., Sandri L., Tamburello G., Selva J., Moune S., Jessop D.E., Moretti R., Komorowski J.C., Costa A. (2021)
Testing gas dispersion modelling: A case study at La Soufrière volcano (Guadeloupe, Lesser Antilles)
Journal of Volcanology and Geothermal Research 417, 107312.
https://doi.org/10.1016/j.jvolgeores.2021.107312
Data di pubblicazione: 11/06/2021
PubAIV-ID-00003 - Articolo in Rivista (open access)
Abstract
Volcanic gas dispersal can be a serious threat to people living near active volcanoes since it can have short- and long-term effects on human health, and severely damage crops and agricultural land. In recent decades, reliable computational models have significantly advanced, and now they may represent a valuable tool to make quan- titative and testable predictions, supporting gas dispersal forecasting and hazard assessments for public safety. Before applying a specific modelling tool into hazard quantification, its calibration and its sensitivity to initial and boundary conditions should be carefully tested against available data, in order to produce unbiased hazard quantifications. In this study, we provided a number of prototypical tests aimed to validate the modelling of gas dispersal from a hazard perspective. The tests were carried out at La Soufrière de Guadeloupe volcano, one of the most active gas emitters in the Lesser Antilles.
La Soufrière de Guadeloupe has shown quasi-permanent degassing of a low-temperature hydrothermal nature since its last magmatic eruption in 1530 CE, when the current dome was emplaced. We focused on the distribu- tion of CO2 and H2S discharged from the three main present-day fumarolic sources at the summit, using the mea- surements of continuous gas concentrations collected in the period March–April 2017. We developed a new probabilistic implementation of the Eulerian code DISGAS-2.0 for passive gas dispersion coupled with the mass-consistent Diagnostic Wind Model, using local wind measurements and atmospheric stability information from a local meteorological station and ERA5 reanalysis data. We found that model outputs were not significantly affected by the type of wind data but rather upon the relative positions of fumaroles and measurement stations. Our results reproduced the statistical variability in daily averages of observed data over the investigated period within acceptable ranges, indicating the potential usefulness of DISGAS-2.0 as a tool for reproducing the observed fumarolic degassing and for quantifying gas hazard at La Soufrière. The adopted testing procedure allows for an aware application of simulation tools for quantifying the hazard, and thus we think that this kind of testing should actually be the first logical step to be taken when applying a simulator to assess (gas) hazard in any other volcanic contexts.
Image
Monaco L., Palladino D.M., Gaeta M., Marra F., Sottili G., Leicher N., Mannella G., Nomade S., Pereira A., Regattieri E., Wagner B., Zanchetta G., Albert P.G., Arienzo I., D’Antonio M., Petrosino P., Manning C.J., Giaccio B. (2021)
Mediterranean tephrostratigraphy and peri-Tyrrhenian explosive activity revaluated in light of the 430-365 ka record from Fucino Basin (central Italy).
Earth-Science Review 220, 103706
https://doi.org/10.1016/j.earscirev.2021.103706
Data di pubblicazione: 21/09/2021
PubAIV-ID-00024 - Articolo in Rivista (open access)
Abstract
Accurately reconstructing the scale and timing of dynamic processes, such as Middle-Late Pleistocene explosive volcanism and rapid climatice change, requires rigorous and independent chronological constraints. In this framework, the study of distal volcanic ash layers, or tephra, transported and deposited over wide regions during explosive volcanic eruptions, is increasingly being recognised as a fundamental chronostratigraphic tool for addressing these challenging issues. Here we present a high-resolution distal tephra record preserved in the lacustrine sedimentary succession of the Fucino Basin, central Italy. The investigated record spans the 430-365 ka time interval, covering the entirety of Marine Isotope Stage 11 (MIS 11), and provides important insights into peri-Tyrrhenian potassic explosive volcanism from sources located in central Italy against a backdrop of Mediterranean palaeooclimate records. The succession of ash fall events of this time interval is reconstructed through a detailed lithostratigraphic, geochemical and 40Ar/39Ar geochronological characterization of the deposits preserved as discrete layers in the Fucino F4-F5 sediment core. This work is complemented by similarily detailed characterization of selected proximal pyroclastic units from the peri-Tyrrhenian potassic volcanoes. Geochemical fingerprinting of the tephra deposits by means of their major, minor and trace elements and Sr isotope compositions indicates that all the thirty-two investigated ash layers derived from the peri-Tyrrhenian potassic volcanoes. The stratigraphically continuous succession of the Fucino tephra layers allowed the development of a fully independent, 40Ar/39Ar age-constrained, Bayesian age-depth model for the investigated time interval. The age-model allows us to establish modelled ages for the tephra layers within the succession that are not directly dated. The resulting dated tephra record clearly reveals a highly time resolved and previously unparalelled chronicle of explosive activity from the Vulsini, Vico, Sabatini, Colli Albani and Roccamonfina volcanic complexes. Our study provides a benchmark and valuable geochemical and geochronological dataset to be used as a reference for any future development and application of the tephrostratigraphic methods across the central Mediterranean area both during the investigated 430-365 kyr time interval, and deeper in time. This contribution underlines the importance of integrating proximal and distal sedimentary records to more accurately establish long-term and comprehensive volcanic eruption records.
Image
Re G., Corsaro R.A., D'Oriano C., Pompilio M. (2021)
Petrological monitoring of active volcanoes: A review of existing procedures to achieve best practices and operative protocols during eruptions.
Journal of Volcanology and Geothermal Research, 419, 107365
https://doi.org/10.1016/j.jvolgeores.2021.107365
Data di pubblicazione: 30/07/2021
PubAIV-ID-00021 - Articolo in Rivista (non-open access)
Abstract
A questionnaire to survey the common petrological monitoring procedures adopted by volcano monitoring institutions has been developed, aimed at identifying prevailing techniques and rating their suitability in terms of costs versus benefits. The collected information resulted from a sample of eighteen participating institutions, which include countries with some of the most important active volcanic provinces worldwide. The participating institutions also offer insights into volcanoes with a variety of volcanic activity, providing a comprehensive picture of the state of the art of petrological monitoring. The final purposes are (i) to promote the advancement that petrologic monitoring brings in the comprehension of the eruptive processes, providing the only “signals” (i.e., rock samples) concerning the physico-chemical properties of the magma feeding the eruption; (ii) to design best practices, and (iii) to define the minimum requirements needed to perform an efficient petrological monitoring during ongoing eruptions. The survey also highlighted the main problems to overcome to have a profitable petrological monitoring infrastructure, including (i) the time required to accomplish both field survey and laboratory works (sampling, sample preparation, and analyses), (ii) the lack of onsite analytical facilities, (iii) the shortage of qualified staff.

Starting from the state of the art of petrological monitoring, how it is performed by the different institutions worldwide, and what participants considered as the major problems, we identified the Best Practices in Petrological Monitoring as the best compromise between fast and easy analyses and the relevance of the acquired results.
Image
- editato da A. Vona e F. Di Fiore - per info contattare Questo indirizzo email è protetto dagli spambots. È necessario abilitare JavaScript per vederlo.
Stampa   Email