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Bonasia, R.
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Bonasia, R.
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- PublicationRestrictedThe Pomici di Avellino eruption of Somma–Vesuvius (3.9 ka BP). Part II: sedimentology and physical volcanology of pyroclastic density current deposits(2010-02-23)
; ; ; ; ; ; ;Sulpizio, R.; CIRISIVU, c/o Dipartimento Geomineralogico, Bari, Italy ;Bonasia, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Dellino, P.; CIRISIVU, c/o Dipartimento Geomineralogico, Bari, Italy ;Di Vito, M. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Mele, D.; CIRISIVU, c/o Dipartimento Geomineralogico, Bari, Italy ;La Volpe, I.; CIRISIVU, c/o Dipartimento Geomineralogico, Bari, Italy; ; ; ; ; Pyroclastic density currents (PDCs) generated during the Plinian eruption of the Pomici di Avellino (PdA) of Somma–Vesuvius were investigated through field and laboratory studies, which allowed the detailed reconstruction of their eruptive and transportation dynamics and the calculation of key physical parameters of the currents. PDCs were generated during all the three phases that characterised the eruption, with eruptive dynamics driven by both magmatic and phreatomagmatic fragmentation. Flows generated during phases 1 and 2 (EU1 and EU3pf, magmatic fragmentation) have small dispersal areas and affected only part of the volcano slopes. Lithofacies analysis demonstrates that the flow-boundary zones were dominated by granular-flow regimes, which sometimes show transitions to traction regimes. PDCs generated during eruptive phase 3 (EU5, phreatomagmatic fragmentation) were the most voluminous and widespread in the whole of Somma–Vesuvius’ eruptive history, and affected a wide area around the volcano with deposit thicknesses of a few centimetres up to more than 25 km from source. Lithofacies analysis shows that the flowboundary zones of EU5 PDCs were dominated by granular flows and traction regimes. Deposits of EU5 PDC show strong lithofacies variation northwards, from proximally thick, massive to stratified beds towards dominantly alternating beds of coarse and fine ash in distal reaches. The EU5 lithofacies also show strong lateral variability in proximal areas, passing fromthe western and northern to the eastern and southern volcano slopes, where the deposits are stacked beds of massive, accretionary lapilli-bearing fine ash. The sedimentological model developed for the PDCs of the PdA eruption explains these strong lithofacies variations in the light of the volcano’s morphology at the time of the eruption. In particular, the EU5 PDCs survived to pass over the break in slope between the volcano sides and the surrounding volcaniclastic apron–alluvial plain, with development of new flows from the previously suspended load. Pulses were developed within individual currents, leading to stepwise deposition on both the volcano slopes and the surrounding volcaniclastic apron and alluvial plain. Physical parameters including velocity, density and concentration profile with height were calculated for a flow of the phreatomagmatic phase of the eruption by applying a sedimentological method, and the values of the dynamic pressure were derived. Some hazard considerations are summarised on the assumption that, although not very probable, similar PDCs could develop during future eruptions of Somma–Vesuvius234 34 - PublicationRestrictedNumerical inversion and analysis of tephra fallout deposits fromthe 472 ADsub-Plinian eruption at Vesuvius (Italy) through a new best-fit procedure(2010)
; ; ; ; ; ;Bonasia, R.; Corresponding author. Istituto Nazionale di Geofisica e Vulcanologia, Sezione Osservatorio Vesuviano”, Via Diocleziano, 328, Napoli, Italy. ;Macedonio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Costa, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Mele, D.; CIRISIVU, Dipartimento Geomineralogico, Università degli Studi di Bari, Bari, Italy ;Sulpizio, R.; CIRISIVU, Dipartimento Geomineralogico, Università degli Studi di Bari, Bari, Italy; ; ; ; A simple semi-analytical model for ash-fall deposit was applied to reconstruct the tephra deposits of the sub- Plinian 472 AD eruption of Vesuvius, Italy, which is of the scale of the reference eruptive scenario for the emergency planning, at Vesuvius. Applying a novel least-squares method, the bulk grain-size distribution, the total mass, and the eruption column height were obtained by fitting the computed ground load and granulometries with the observed ones. The analysis of the effect of three different weighting factors in the minimization procedure was also performed. Results showed that the statistical weighting factor produced the minimum bias. The best correlation between calculated and measured deposit was found, even though the quantity of the input data was not very high, as it commonly occurs for several ancient eruptions. Model results were also in agreement with estimations provided by other independent methods.153 27 - PublicationOpen AccessDiscriminating the-long distance dispersal of fine ash from sustained columns or near ground ash clouds: the example of the Pomici di Avellino eruption (Somma-Vesuvius, Italy).(2007)
; ; ; ; ; ; ; ; ;Sulpizio, R.; CIRISIVU, c/o Dipartimento Geomineralogico, Bari, Italy ;Bonasia, R.; CIRISIVU, c/o Dipartimento Geomineralogico, Bari, Italy ;Dellino, P.; CIRISIVU, c/o Dipartimento Geomineralogico, Bari, Italy ;Di Vito, M. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;La Volpe, L.; CIRISIVU, c/o Dipartimento Geomineralogico, Bari, Italy ;Mele, D.; CIRISIVU, c/o Dipartimento Geomineralogico, Bari, Italy ;Zanchetta, G.; Dipartimento di Scienze della Terra, Pisa, Italy ;Sadori, L.; Dipartimento di Biologia Vegetale, Università La Sapienza, Roma, Italy; ; ; ; ; ; ; Ash samples from tephra layers correlated with the Pomici di Avellino (Avellino Pumice) eruption of Somma-Vesuvius were collected in distal archives and their composition and particle morphology investigated in order to infer their behaviour of transportation and deposition. Differences in composition and particle morphologies were recognised for ash particles belonging to the magmatic Plinian and final phreatomagmatic phases of the eruption. The ash particles were dispersed in opposite directions during the two different phases of the eruption, and these directions are also different from that of coarse-grained fallout deposits. In particular, ash generated during magmatic phase and injected in the atmosphere to form a sustained column shows a prevailing SE dispersion, while ash particles generated during the final phreatomagmatic phase and carried by pyroclastic density currents show a general NW dispersion. These opposite dispersions indicate an ash dispersal influenced by both high and low atmosphere dynamics. In particular, the magmatic ash dispersal was first driven by stratospheric wind towards NE and then the falling particles encountered a variable wind field during their settling, which produced the observed preferential SE dispersal. The wind field encountered by the rising ash clouds that accompanied the pyroclastic density currents of the final phreatomagmatic phase was different with respect to that encountered by the magmatic ash, and produced a NW dispersal. These data demonstrate how ash transportation and deposition are greatly influenced by both high and low atmosphere dynamics. In particular, fine-grained particles transported in ash clouds of small-scale pyroclastic density currents may be dispersed over distances and cover areas comparable with those injected into the stratosphere by Plinian, sustained columns. This is a point not completely addressed by present day mitigation plans in case of renewal of activity at Somma-Vesuvius, and can yield important information also for other volcanoes potentially characterised by explosive activity.272 689 - PublicationRestrictedThe Pomici di Avellino eruption of Somma-Vesuvius (3.9 ka BP). Part I: stratigraphy, compositional variability and eruptive dynamics(2010)
; ; ; ; ; ; ;Sulpizio, R.; Dipartimento Geomineralogico, CIRISIVU, Bari, Italy ;Cioni, R.; Dipartimento di Scienze della Terra,Cagliari, Italy ;Di Vito, M. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Mele, D.; Dipartimento Geomineralogico, CIRISIVU, Bari, Italy ;Bonasia, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Dellino, P.; Dipartimento Geomineralogico, CIRISIVU, Bari, Italy; ; ; ; ; The stratigraphic succession of the Pomici di Avellino Plinian eruption from Somma-Vesuvius has been studied through field and laboratory data in order to reconstruct the eruption dynamics. This eruption is particularly important in the Somma-Vesuvius eruptive history because (1) its vent was offset with respect to the present day Vesuvius cone; (2) it was characterised by a distinct opening phase; (3) breccia-like very proximal fall deposits are preserved close to the vent and (4) the pyroclastic density currents generated during the final phreatomagmatic phase are among the most widespread and voluminous in the entire history of the volcano. The stratigraphic succession is, here, divided into deposits of three main eruptive phases (opening, magmatic Plinian and phreatomagmatic), which contain five eruption units. Short-lived sustained columns occurred twice during the opening phase (Ht of 13 and 21.5 km, respectively) and dispersed thin fall deposits and small pyroclastic density currents onto the volcano slopes. The magmatic Plinian phase produced the main volume of erupted deposits, emplacing white and grey fall deposits which were dispersed to the northeast. Peak column heights reached 23 and 31 km during the withdrawal of the white and the grey magmas, respectively. Only one small pyroclastic density current was emplaced during the main Plinian phase. In contrast, the final phreatomagmatic phase was characterised by extensive generation of pyroclastic density currents, with fallout deposits very subordinate and limited to the volcano slopes. Assessed bulk erupted volumes are 21×106 m3 for the opening phase, 1.3– 1.5 km3 for the main Plinian phase and about 1 km3 for the final phreatomagmatic phase, yielding a total volume of about 2.5 km3. Pumice fragments are porphyritic with sanidine and clinopyroxene as the main mineral phases but also contain peculiar mineral phases like scapolite, nepheline and garnet. Bulk composition varies from phonolite (white magma) to tephri-phonolite (grey magma).377 48 - PublicationRestrictedNumerical simulation of tephra transport and deposition of the 1982 El Chichón eruption and implications for hazard assessment(2012)
; ; ; ; ; ;Bonasia, R.; Centro de Geociencias, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, 76230 Queretaro, Mexico ;Costa, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Folch, A.; Barcelona Supercomputing Center-Centro Nacional de Supercomputación, Barcelona, Spain ;Macedonio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Capra, L.; Centro de Geociencias, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, 76230 Queretaro, Mexico; ; ; ; El Chichón volcano, Chiapas, Mexico, erupted explosively on March 29th, 1982, after a repose period of about 550 years. Amongst ten eruptive episodes documented between March 29th and April 4th, only the three that occurred on March 29th and April 4th produced significant pyroclastic tephra deposits. Here we use analytical (HAZMAP) and numerical (FALL3D) tephra transport models to reconstruct the deposits and the atmospheric plume dispersal associated with the three main fallout units of the 1982 eruption. On the basis of such a reconstruction, we produce hazard maps of tephra fallout associated to a Plinian eruption and discuss the implications of such a severe eruption scenario.313 20 - PublicationRestrictedTephra fallout hazard assessment for a Plinian eruption scenario at Volcán de Colima (Mexico)(2011)
; ; ; ; ; ;Bonasia, R.; Centro de Geociencias, Universidad Nacional Autonoma de México, Campus Juriquilla, 76230 Queretaro, Mexico ;Capra, L.; Centro de Geociencias, Universidad Nacional Autonoma de México, Campus Juriquilla, 76230 Queretaro, Mexico ;Costa, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Macedonio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Saucedo, R.; Universidad Autónoma de San Luis Potosí, Instituto de Geología/Fac. Ingenieria, San Luis Potosí, Mexico; ; ; ; Volcanic ash fallout associated with renewal of explosive activity at Colima, represents a serious threat to the surrounding urbanized area. Here we assess the tephra fallout hazard associated with a Plinian eruption scenario. The eruptive history of Volcán de Colima shows that Plinian eruptions occur approximately every 100 years and the last eruption, the 1913, represents the largest historic eruption of this volcano. We used the last eruption as a reference to discuss volcanic hazard and risk scenarios connected with ash fallout. Tephra fallout deposits are modeled using HAZMAP, a model based on a semi-analytical solution of the advection– diffusion–sedimentation equation for volcanic particles. Based on a statistical study of wind profiles at Colima region, we first reconstructed ash loading maps and then computed ground load probability maps for different seasons. The obtained results show that a Plinian eruptive scenario at Volcán de Colima, could seriously damage more than 10 small towns and ranches, and potentially affect big cities located at tens of kilometers from the eruptive center. The probability maps obtained are aimed to give support to the risk mitigation strategies.201 17 - PublicationRestrictedConduit flow experiments help constraining the regime of explosive eruptions(2010)
; ; ; ; ; ; ; ; ; ; ; ; ;Dellino, P. ;Dioguardi, F. ;Zimanowski, B. ;Buttner, R. ;Mele, D. ;La Volpe, L. ;Sulpizio, R. ;Doronzo, D.M. ;Sonder, I. ;Bonasia, R. ;Calvari, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Marotta, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ; ; ; ; ; ; ; ; ; ;; It is currently impractical to measure what happens in a volcano during an explosive eruption, and up to now much of our knowledge depends on theoretical models. Here we show, by means of large‐scale experiments, that the regime of explosive events can be constrained on the basis of the characteristics of magma at the point of fragmentation and conduit geometry. Our model, whose results are consistent with the literature, is a simple tool for defining the conditions at conduit exit that control the most hazardous volcanic regimes. Besides the well‐known convective plume regime, which generates pyroclastic fallout, and the vertically collapsing column regime, which leads to pyroclastic flows, we introduce an additional regime of radially expanding columns, which form when the eruptive gas‐particle mixture exits from the vent at overpressure with respect to atmosphere. As a consequence of the radial expansion, a dilute collapse occurs, which favors the formation of density currents resembling natural base surges. We conclude that a quantitative knowledge of magma fragmentation, i.e., particle size, fragmentation energy, and fragmentation speed, is critical for determining the eruption regime.332 25