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Isaia, Roberto
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Isaia, Roberto
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roberto.isaia@ingv.it
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- PublicationRestrictedMagmatic reactivation of the Campi Flegrei volcanic system: insights from the Baia–Fondi di Baia eruption(2018)
; ; ; ; ; ; ; ; ; ; ; ; ;; ;; ; ; ;; ;The Baia–Fondi di Baia was a multi-stage, small-scale eruption which occurred in the western part of the Campi Flegrei caldera at 9525–9696 BP, marking the onset of Epoch 2 of post-Neapolitan Yellow Tuff volcanism. The eruption was characterized by a complex series of events related to two distinct eruptive episodes (Baia and Fondi di Baia) separated by a short time interval, and each characterized by several eruptive phases. Mineralogical, geochemical (major, and trace elements on whole rocks, major and volatile elements on matrix glasses, and melt inclusions), and Sr isotope characterization of the tephra material sampled along the entire sequence was carried out in order to constrain magmatic evolution and dynamics of the feeding system. Three main compositional groups were identified in matrix glasses and interpreted as representative of different magma bodies: (i) a trachyte (SiO2 60.3–64.7 wt.%), which is volumetrically predominant; (ii) a tephriphonolite-latite (SiO2: 55.1–57.9 wt.%); and (iii) an intermediate magma group between phonolite and trachyte compositions. This wide compositional heterogeneity contrasts with the narrow variability recognized in the bulk-rock compositions, which are all trachytic. Mineral, melt inclusions, and Sr isotope data suggest that the trachytic magma possibly derived from the Campanian Ignimbrite reservoir located at 6–9 km depth. Volatile content in matrix glass indicates a storage depth of at least 6 km for the tephriphonolite-latitic magma. The intermediate magma is interpreted as being derived from a remelting and assimilation process of a partially crystallized trachytic body (crystal mush) by the hotter tephriphonolite-latitic magma. As the tephriphonolite-latite was erupted together with the trachyte from the beginning of the eruption, we suggest that the ascent of this magma played a fundamental role in triggering the eruption. Upwards through the tephra sequence, we observed a progressive increase of the tephriphonolite-latitic and intermediate phonolite-trachytic components. The presence of banded clasts characterized by different compositions is also indicative of syn-eruptive mingling during the final phases of the eruption.257 6 - PublicationRestrictedCaldera unrest prior to intense volcanism in Campi Flegrei (Italy) at 4.0 ka B.P.: Implications for caldera dynamics and future eruptive scenarios(2009)
; ; ; ;Isaia, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Marianelli, P.; Dipartimento di Scienze della Terra, Universita` degli Studi di Pisa ;Sbrana, A.; Dipartimento di Scienze della Terra, Universita` degli Studi di Pisa; ; The Campi Flegrei caldera is one of the highest risk volcanic areas on the Earth. Our research documents a 150 year-long period of intense volcanism following less than 200 years of repose after the Agnano-Monte Spina Plinian eruption (4.1 ka). The new data show that the renewal of volcanism was preceded by an uplift of a few tens of meters, triggered by mafic refilling of reservoirs at depths of 3 km or less. Our studies also indicate for the first time the occurrence of contemporaneous eruptions from at locations in different sectors of the caldera. These results suggest that a future eruptive crisis will likely be preceded by several meters of caldera-wide uplift in response to magma movements at depth. The trend of uplift of the caldera since 1969 may thus represent the unrest expected before a renewal of volcanism within an interval of decades to centuries.272 46 - PublicationRestrictedHydrothermal alteration of surficial rocks at Solfatara (Campi Flegrei): Petrophysical properties and implications for phreatic eruption processesSolfatara crater is locatedwithin the Campi Flegrei caldera to the west of Naples (Italy). It is one of the largest fumarolic manifestations known, and the rocks hosting the hydrothermal system are affected by intense hydrothermal alteration. Alteration can result in changes of degassing behavior, and in the formation of a cap rock thereby increasing the probability of phreatic eruptions. Here, we investigate the effects of alunitic (solfataric) alteration on the mineralogy, the physical properties (porosity, density, permeability) and the mechanical properties (strength) of the rocks involved, aswell as its influence on fragmentation and ejection behavior. Our results showthat the pristine mineralogy of deposits fromthe vicinity of the Solfatara cryptodome and from Pisciarelli is almost completely replaced by amorphous silica and alunite. The differences in the degree of alteration among the samples series are reflected in the investigated properties and behavior aswell as in the analysis of the experimentally generated particles. Alunitic alteration increases porosity and permeability,whereas it reduces density, elastic wave velocity and strength leading to higher fragmentation and ejection speeds for the sample series examined in this study. Our results also show that alteration results in the generation of a high fraction of fines (particle sizes b10 μm) during fragmentation, mainly composed of alunite crystals. Due to their potential for inducing chronic disease, dispersion of such material should represent a serious health hazard on a local scale and the evaluation of precautions should be considered.
70 4 - PublicationRestrictedThe present state of the magmatic system of the Campi Flegrei caldera based on a reconstruction of its behavior in the past 12 ka(1999)
; ; ; ; ; ; ; ; ; ;D’Antonio, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Civetta, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Orsi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Pappalardo, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Piochi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Carandente, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;de Vita, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Di Vito, M. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Isaia, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; ; ; ; ; ; ; New geochemical and Sr-isotope data have been acquired on samples representative of volcanic units erupted inside the resurgent Campi Flegrei caldera CFc. over the past 12 ka. These data, integrated with previous published petrological, and with newly acquired geochronological, volcanological and geothermal data, shed light on the nature and timing of the processes that controlled the evolution of the Phlegraean magmatic system. In the past 12 ka, three isotopically and geochemically distinct magmatic components were erupted at the CFc as either homogeneous or mixed magma batches. One component, Campanian Ignimbrite component CIc. 87Srr86Srs0.70735–0.70740., is similar to the trachytic magma extruded during the first phase of the Campanian Ignimbrite CI. eruption 37 ka.. A second component, Neapolitan Yellow Tuff component NYTc. 87Srr86Srs0.70750–0.70757., is similar to the latitic–alkali–trachytic magma batches extruded during the course of the Neapolitan Yellow Tuff NYT. eruption 12 ka.. A third component, Minopoli component MIc. 87Srr86Srf0.7086., is similar to the trachybasaltic magma of the Minopoli 2 MI. eruption 9.7 ka.. These components were erupted as either single batches of magma, or mixed CI–NYT or MI–NYT batches of magma, through vents located either along the structural boundary of the NYT caldera or inside the NYT caldera, mainly on portions of the resurgent block under extensional stress. The CI and NYT components represent residual portions of older, large-volume magma reservoirs which have fed eruptions since about 60 and 15 ka, respectively. The least-evolved MI component was erupted only during the 12–9.5 ka and 8.6–8.2 ka epochs of activity, through vents located on a NE–SW regional fault system. This component could represent a deeper reservoir tapped by the NE–SW regional fault system reactivated after the NYT caldera collapse. Deeper MI and shallower CI and NYT magmatic systems interacted by mixing among batches of magma during their rise to surface. Overall, the data suggest that the CFc magmatic system today is characterized by the presence of two larger, independent reservoirs, filled by residual portions of the CI and NYT magmas. These generated many smaller, shallower pockets of evolved magma, that fed most of the eruptions that occurred in the CFc over the past 12 ka. Moreover, a deeper reservoir MI., tapped by the NE–SW regional fault system, provided batches of less-evolved magma that mixed with magma present in the shallower pockets. q1999 Elsevier Science B.V. All rights reserved.181 16 - PublicationRestrictedVolcanic risk perception in the Vesuvius population(2008)
; ; ; ; ; ;Barberi, F.; Dipartimento di Scienze Geologiche, Università di Roma Tre, Italy ;Davis, M. S.; Psychology Department, Dominican University of California, USA ;Isaia, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Nave, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Ricci, T.; Dipartimento di Scienze Geologiche, Università di Roma Tre, Italy; ; ; ; A volcanic risk perception study of the population residing near Vesuvius was carried out between May and July, 2006. A total of 3600 questionnaires with 45 items were distributed to students, their parents and the general population. The largest number of surveys (2812) were distributed in the 18 towns of the Red Zone, the area nearest to the volcano that is exposed to pyroclastic flow hazards and whose 550,000 residents, according to the civil protection emergency plan (in operation since 1995), should be evacuated in case of an eruption crisis. The remaining 788 questionnaires were distributed in 3 additional towns and 3 neighborhoods of Naples, all within the Yellow Zone, which is an area exposed to pyroclastic fallout hazards. A total of 2655 surveys were returned, resulting in a response rate of 73.7%. Results indicated that people have a realistic view of the risk: they think that an eruption is likely, that it will have serious consequences for their towns and for themselves and their families and they are quite worried about the threat. However, several other social, economic, and security-related issues were listed as a problem more often than Vesuvius. The study also demonstrated a widespread lack of knowledge about the emergency plan, a lack of confidence in the plan's success and in public officials and low feelings of self-efficacy. People want to be more deeply involved in public discussions with scientists and civil protection officials on emergency planning and individual preparedness measures. It is clear from the results that a major education-information effort is still needed to improve the public's knowledge, confidence and self-efficacy, thereby improving their collective and individual capability to positively face a future volcanic emergency.275 55 - PublicationOpen AccessAssessing pyroclastic density current hazard in caldera settings: the example of Campi Flegrei caldera (Italy)(2013)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ;; ;; ; ;; ; ;Mapping of pyroclastic density currents (PDCs) hazard in caldera settings is particularly challenging due to the large uncertainty on future vent location and eruption scale as well as the complex dynamics of the flow over the irregular caldera topography. Nevertheless, probabilistic mapping of PDC invasion, able to account for the intrinsic uncertainties affecting the system, is needed for hazard assessment, particularly for highly populated regions. Campi Flegrei (CF) is a vivid example of active and densely populated caldera with a very high risk associated with the occurrence of PDCs produced by explosive events. In this presentation we show the results of new field work and mathematical modelling of past eruptive activity aimed at producing long-term probabilistic vent opening and PDC invasion maps at CF. Field work was focused on the structural and morphological features of the caldera and particularly on the reconstruction of the location of past eruptive vents as well as of the distribution of the main faults and fractures formed in the last 15 kyr of activity. One specific objective of the analysis was to incorporate into the vent opening maps the main uncertainties affecting the system by adopting appropriate density distributions and by relying on expert judgement. We then used these maps to produce, by adopting a Monte Carlo approach, a variety of probabilistic PDC hazard maps of the CF area based on different invasion models and accounting for the uncertainty on vent location and event scale. In particular we developed and adopted a simplified invasion flow model based on the so-called box model approximation and tuned on transient and 2D numerical simulations of the flow dynamics. The new model allowed to describe the exponential decay of the flow energy as well as to account for first-order topographic effects. The developed methodology appears able to provide relatively quick and robust probabilistic assessments of PDC hazard in caldera settings and could be potentially extended to other calderas worldwide.65 13 - PublicationOpen AccessReconciling complex stratigraphic frameworks reveals temporally and geographically variable depositional patterns of the Campanian IgnimbriteThe 39.8-ka Campanian Ignimbrite was emplaced during a large caldera-forming eruption of Campi Flegrei near Naples, Italy. The ignimbrite is found up to 80 km from the caldera, and co-ignimbrite ash-fall deposits occur 3200 km away. The proximal and distal stratigraphy of the Campanian Ignimbrite has not been definitively correlated due to the dissimilar appearance of the proximal and distal deposits, a lack of medial exposures, and the inconsistency and heterogeneity of the proximal stratigraphy. Here, we document the majorelement glass-shard chemistry, matrix componentry, and lithic componentry of the proximal and distal stratigraphic sequences of the ignimbrite to attempt to correlate the units. The results of these disparate observations taken together suggest that the established stratigraphic units cannot be directly and uniquely correlated between the proximal and distal regions and that neither the proximal nor distal stratigraphy provides a record of the entire eruptive sequence. However, the characteristics studied can be used to demarcate eruptive phases that are connected to some of the defined units in the proximal and distal stratigraphy
31 9 - PublicationRestrictedCorrigendum to “Sensitivity test and ensemble hazard assessment for tephra fallout at Campi Flegrei, Italy” [J. Vol. Geotherm. Res. 351(2018) 1–28](2019)
; ; ; ; ; ; ; ; ; ; ; The authors found a mistake in the quantification of the ensemble model evaluated as the weighted mixture distribution of 5 input models, as described in Section 4. The error consisted in an incorrect averaging of the input models in the ensemble. The mistake affected Figs. 10 and 11, as well as the data reported in the Supplementary Electronic Material. The corrected Figs. 10 and 11 are reported here. The new results are consistent with the results already discussed in the original manuscript. More specifically, similar results are found for the central tendency statis- tics of the ensemble (mean and median), with a slight tendency toward a larger hazard especially in the very near field. More significant changes are found for the confidence intervals (16th–84th percentiles), which re- sults wider. These results further strengthen one of the main results of the orig- inal manuscript, that is that the epistemic uncertainty resulting from the ensemble model goes beyond the nominal uncertainty quantified by any single Bayesian model. The complete updated results, in the form of Shapefiles, can be found in the Supplementary Electronic Material.699 4 - PublicationOpen AccessQuantifying volcanic hazard at Campi Flegrei caldera (Italy) with uncertainty assessment: 1. Vent opening maps(2015)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ;; ; ; ;Campi Flegrei is an active volcanic area situated in the Campanian Plain (Italy) and dominated by a resurgent caldera. The great majority of past eruptions have been explosive, variable in magnitude, intensity, and in their vent locations. In this hazard assessment study we present a probabilistic analysis using a variety of volcanological data sets to map the background spatial probability of vent opening conditional on the occurrence of an event in the foreseeable future. The analysis focuses on the reconstruction of the location of past eruptive vents in the last 15 ka, including the distribution of faults and surface fractures as being representative of areas of crustal weakness. One of our key objectives was to incorporate some of the main sources of epistemic uncertainty about the volcanic system through a structured expert elicitation, thereby quantifying uncertainties for certain important model parameters and allowing outcomes from different expert weighting models to be evaluated. Results indicate that past vent locations are the most informative factors governing the probabilities of vent opening, followed by the locations of faults and then fractures. Our vent opening probability maps highlight the presence of a sizeable region in the central eastern part of the caldera where the likelihood of new vent opening per kilometer squared is about 6 times higher than the baseline value for the whole caldera. While these probability values have substantial uncertainties associated with them, our findings provide a rational basis for hazard mapping of the next eruption at Campi Flegrei caldera.566 40 - PublicationRestrictedFractures and faults in volcanic rocks (Campi Flegrei, southern Italy): Insight into volcano-tectonic processesThe present study was focused to analyze fractures and faults in the Campi Flegrei calderas presently hosting several volcanic edifices, such as lava domes, scoria, and tuff cones. A complex network of fractures and faults affects the volcanic rocks, mostly as planar with highly variable density. Frequently faults appearing as conjugate structures showing normal kinematics often associated with ductile deformation such as drag folds and deflexed layers, suggesting a syn-eruption deformation. However, the most of faults, mainly hosted along the caldera/ crater rims, are very steep with dominant normal and secondary reverse movements. The fracture pattern indicates a slight prevalence of NE–SW and NW–SE directions, but N–S and E–W trends also occur. Fractures and faults found in rocks older than 15 ka (Neapolitan Yellow Tuff included), measured in western and eastern sectors of the study area, indicate a rotation of ca. 30° of the main directions among these two sectors. For the faults occurring along the caldera/crater rims, we suggest a kinematic evolution characterized by the reactivation of tensile fractures previously formed in response to both regional extension and locale resurgent dome. Finally, normal faults located in the central sector of caldera, between La Starza and Accademia localities, cutting the youngest volcanic deposits, indicate a constant NNE–SSW extension probably related to the caldera resurgence.
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