Luglio 2021

PubAIV 2021
(aggiornamento Luglio 2021)

1) Magmi e sistemi di alimentazione (5 articoli)
2) Dinamiche eruttive e di messa in posto (8 articoli)
3) Geologia e struttura dei vulcani (0 articoli)
4) Monitoraggio, pericolosità e rischio vulcanico (1 articolo)

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
Data di pubblicazione: 23/04/2021
PubAIV-ID-00009 - Articolo in Rivista (non-open access)

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.
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
Data di pubblicazione: 22/06/2021
PubAIV-ID-00007 - Articolo in Rivista (open access)

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.
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
Data di pubblicazione: 18/05/2021
PubAIV-ID-00010- Articolo in Rivista (non-open access)

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.
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
Data di pubblicazione: 16/06/2021
PubAIV-ID-00004 - Articolo in Rivista (open access)

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.
Zuccarello F., Schiavi F., Viccaro M. (2021)
Magma dehydration controls the energy of recent eruptions at Mt. Etna volcano.
Terra Nova, 33, 4
Data di pubblicazione: 17/03/2021
PubAIV-ID-00011 - Articolo in Rivista (open access)

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.
Tematica 2: Dinamiche eruttive e di messa in posto
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
Data di pubblicazione: 07/07/2021
PubAIV-ID-00013 - Articolo in Rivista (open access)

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.
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
Data di pubblicazione: 02/03/2021
PubAIV-ID-00014 - Articolo in Rivista (open access)

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.
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.
Data di pubblicazione: 08/07/2021
PubAIV-ID-00001 - Articolo in Rivista (non-open access)

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.
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
Data di pubblicazione: 16/02/2021
PubAIV-ID-00006 - Articolo in Rivista (non-open access)

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.
Galetto F., Bonaccorso A., Acocella V. (2021)
Relating Dike Geometry and Injection Rate in Analogue Flux-Driven Experiments. 
Frontiers in Earth Science 9, 665865.
Data di pubblicazione: 13/05/2021
PubAIV-ID-00012 - Articolo in Rivista (open access)

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.
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
Data di pubblicazione: 21/06/2021
PubAIV-ID-00008 - Articolo in Rivista (non-open access)

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.
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
Data di pubblicazione: 03/03/2021
PubAIV-ID-00005 - Articolo in Rivista (non-open access)

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).
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
Data di pubblicazione: 11/01/2021
PubAIV-ID-00002 - Articolo in Rivista (open access)

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.
Tematica 3: Geologia e struttura dei vulcani
Tematica 4: Monitoraggio, pericolosità e rischio vulcanico
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.
Data di pubblicazione: 11/06/2021
PubAIV-ID-00003 - Articolo in Rivista (open access)

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.
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