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The youngest (last 1500 years) volcanic eruptions of Lipari, within the Aeolian Archipelago, produced the prominent pumice cone of Monte Pilato and the obsidian lava flows of Rocche Rosse and Forgia Vecchia, concentrated in the north-eastern sector of the island as well as highly dispersed white-coloured, fine-grained tephra layers of rhyolitic composition in terrestrial and marine settings on the regional scale. Here we describe in detail the stratigraphy of pyroclastic successions and lava flows erupted by different vents - Monte Pilato, Forgia Vecchia, Lami, and Rocche Rosse - combining field observations, sedimentological characteristics of the tephra deposits, and major and trace element compositions of the volcanic glass. All the pyroclastic materials consist of aphyric pumice lapilli and ash with a largely homogeneous rhyolitic composition. The Monte Pilato and Forgia Vecchia deposits primarily consist of highly vesicular pumice fragments and subordinate obsidian clasts, whilst Rocche Rosse and Lami are characterized by moderately vesicular juvenile fragments with a more significant fraction of obsidian. The Lami tephra also contains peculiar pumice clasts with a fibrous texture and breadcrust bombs. Stratigraphic relationships, and paleomagnetic and 14C ages of the lava and pyroclastic deposits are combined with the archaeological information and historical reports, enabling us to provide an accurate chrono-stratigraphic framework for the youngest eruptions of Lipari. Following the 8th century CE eruption of Monte Pilato, which produced a pumice cone and a obsidian lava flow, activity resumed in the second half of 13th century CE with the explosive eruption of Forgia Vecchia that culminated in the emission of a bilobate obsidian lava flow. This eruption was shortly followed by the explosive eruptions of Lami and Rocche Rosse, the latter concluded with the emission of the widely renowned obsidian lava flow. By integrating stratigraphy and geochemistry of tephra deposits with a new chronological scheme, our work facilitates the refinement of proximal-to-distal correlation of Lipari's rhyolitic tephra in continental marine environments of the central Mediterranean area in the last 1500 years. A fine-grained, rhyolitic ash found on Stromboli (~40 km NE from Lipari) has an origin from the Monte Pilato and thus, constrains tephra dispersion towards the NE. Very similar ash beds dispersed southwards and interlayered within the near-source deposits of La Fossa, Vulcano island (~10 km from Lipari) exhibit features that are consistent with the younger activities of the Rocche Rosse eruption. A possible link between previously identified rhyolitic ash layers identified in marine cores of the Ionian Sea and the Forgia Vecchia eruption are postulated, although the age and textural characteristics of these distal tephra are not univocal in indicating a correlation to either Monte Pilato or Forgia Vecchia.

The timing of the Holocene volcanic activity of Tenerife (Canary Islands) is poorly constrained and the volcanological framework for this area is still incomplete. Most of the eruptions are dated only by a single 14C dating, or the ages are simply stratigraphically determined. We apply palaeomagnetism, increasingly used in the last years to date Holocene volcanism, to improve the knowledge of Tenerife volcanic history. We report on the palaeomagnetic dating, using the SHA.DIF.14K global model, of nine Holocene eruptions that produced scoria cones and major lava flows, and we compare our results with those previously obtained by 14C method. Four of the studied eruptions were previously dated by 14C, four were stratigraphically constrained, and one was never dated so far. Concerning the first group, for Boca Cangrejo and Mna Reventada eruptions, palaeomagnetic and 14C ages agree, while for the others we obtained older or younger ages than radiocarbon data. For the second group, one or more age ranges smaller than stratigraphic intervals were found. Finally, we provided the first dating (790–723 BCE) of the Mna Grande eruption. We confirm that palaeomagnetism can be considered an excellent complement to the radiocarbon method, because it is applicable on volcanics with nearly all compositions and provides higher resolution dating, at least where reliable geomagnetic reference curves are available. The improved framework of the Holocene volcanic activity of Tenerife shows alternating periods characterized by low and high eruptive frequencies, with the last 3 kyr characterized by high eruptive frequency and dominated by basaltic eruptions.

The increasing application of cryptotephra studies is leading the identification of new tephra marker layers the sources of which in many cases may not be known or may be ambiguous. In this contribution, we discuss the controls on tephra geochemistry in the context of establishing the provenance of an unknown tephra layer. We use the RESET database ( https://c14.arch.ox.ac.uk ), which contains major and trace element data for a number of European silicic tephra erupted in the period 100 ka to ca 10 ka, to define new and modify existing tectonic setting discrimination diagrams for use with volcanic glass analyses. Bivariate plots of the elements Rb, Nb, Ta, Y and Th and K 2 O, SiO 2 , FeO and MgO can be used to identify tephra from different tectonic settings. New, detailed glass chemistry shows that tephra from the productive Neapolitan volcanic centres, Somma-Vesuvius (22–4 ka activity), Campi Flegrei (60–15 ka) and Ischia (75–20 ka), can be separated using major elements, CaO–SiO 2 , Na 2 O/K 2 O–CaO and CaO–MgO. In each of these centres, the tephrostratigraphic record is characterized by the repeated occurrence of similar glass compositions, punctuated by significant changes in magma chemistry. The glass compositions of successive eruptions from Campi Flegrei are similar but there is a significant change in the composition following the Campanian Ignimbrite, and there are comparable compositional changes at Ischia following the Monte Epomeo Green Tuff eruption and at Somma-Vesuvius following the Verdoline event. Distinguishing different tephras from a single volcanic centre is more problematic, and in some instances even impossible, without good chronological and stratigraphic control and/or high-resolution trace element glass data. At Somma-Vesuvius certain major elements can be used to separate glasses from the major chronological phases (Group 1 – Pomici di Base and Verdoline; Group 2 – Mercato and Avellino), but separating tephras within a single group on the basis of glass composition can be problematic.

This article presents the UNESCO Creative Cities Network (UCCN) and illustrates the theoretical and practical reasons underpinning its creation, based on the assumption that culture should be a strong component of effective development strategies. It then describes the effective functioning of the Network, and highlights two main tendencies resulting from diverse interpretations of what membership and participation should imply: on one side, the propensity to use the UUCCN membership as a branding tool used in the framework of local communication strategies to attract investors and tourists; on the other side, the tendency to effectively work jointly with the cities of the network to build a stronger identity based of effective results through cooperation activities. The article underlines how the tendency to use the membership as classic branding tool has been so far very strong within the Network, and points out some implications and consequences of this trend. But it also underlines the existence of a strong trend towards more effective collaboration and joint implementation of activities. The article finally shows that an interaction between these two tendencies emerges. The possibility to reinforce the cities’ image and brand through effective joint action and not self-referential communication is then highlighted, as a synthesis that use cooperation to build internationally acknowledged excellence.

The ice-capped Cotopaxi volcano is known worldwide for the large-scale, catastrophic lahars that have occurred in connection with historical explosive eruptions. The most recent large-scale lahar event occurred in 1877 when scoria flows partially melted ice and snow of the summit glacier, generating debris flows that severely impacted all the river valleys originating from the volcano. The 1877 lahars have been considered in the recent years as a maximum expected event to define the hazard associated to lahar generation at Cotopaxi. Conversely, recent field-based studies have shown that such debris flows have occurred several times during the last 800 years of activity at Cotopaxi, and that the scale of lahars has been variable, including events much larger than that of 1877. Despite a rapid retreat of the summit ice cap over the past century, in fact, there are no data clearly suggesting that future events will be smaller than those observed in the deposits of the last 800 years of activity. In addition, geological field data prove that the lahar triggering mechanism also has to be considered as a key input parameter and, under appropriate eruptive mechanisms, a hazard scenario of a lahar with a volume 3-times larger than the 1877 event is likely. In order to analyze the impact scenarios in the southern drainage system of the volcano, simulations of inundation areas were performed with a semi-empirical model (LAHARZ), using input parameters including variable water volume. Results indicate that a lahar 3-times larger than the 1877 event would invade much wider areas than those flooded by the 1877 lahars along the southern valley system, eventually impacting highly-urbanized areas such as the city of Latacunga.

The Island of Vulcano (Aeolian Islands, Southern Italy) consists of several volcanic edifices whose formation overlapped in time and space beginning 120 ka ago. The most recent volcano is the La Fossa cone, a 391 m-high active composite cone that began to erupt 5.5 ka ago. Eruptive activity at the La Fossa cone occurred in several cyclic phases separated by prolonged periods of erosion. The last 1000 years of eruptive activity and morphological variations in the cone and its surrounding area were investigated through a stratigraphic reconstruction. This was based on 139 natural cuts, 26 machine-excavated and 5 hand-dug trenches in the volcaniclastic succession. The revised stratigraphy of the volcanic and volcaniclastic sequence was compared with geological maps based on the Unconformity-bounded Stratigraphic Units criteria compiled in 2006–2010. It was found that the last 1000-year period can be divided into (in hierarchical order) Eruptive Clusters and Units. Several unconformities of different hierarchical order were also identified (erosional surfaces and/or palaeosols). Stratigraphic relationships with the Vulcanello products and with rhyolitic tephras related to the eruptions of Mt. Pilato (the last-formed volcanic edifice of the Island of Lipari) were fundamental in assigning a calendar age to most of the tephra units in the studied sequence. The morphological evolution of the upper part of the cone was also reconstructed in order to assess the average cone growth rate. This work suggests a new stratigraphic and chronological interpretation of the evolution and “cyclic” activity of the La Fossa cone in the last 1000 years. Several eruptions occurred in two main clusters. The stratigraphic record and morphological features reveal that the areas around the cone were affected by the deposition of reworked materials, with large amounts of tephra deposited on the steep slopes and within the major streams.

Textural and mineralogical study of high-temperature, angular blocks erupted during the Stromboli explosion of 15 March 2007 was used to make inferences on the nature and thermal state of rocks forming the subsurface of the volcano' summit crater terrace. The studied ejecta consist of lapilli tuff that formed as a result of the transformation and high temperature induration (sintering) of the basaltic scoriae, lapilli and ash originally accumulated as loose tephra during the current activity of the volcano. The main processes leading to the tephra transformation were investigated through microstructural observations, mineral and glass analyses (SEM-EDS and EMP analyses). Investigations revealed that subsolidus reactions and partial melting of the tephra occurred, at temperatures higher than 600 °C and under variable fO 2 conditions from QFM to HM buffering curves. In some blocks, evidence of high-T reheating and partial melting at the expense of secondary hydrothermal minerals was also observed. In order to track the subsolidus reheating history of the basaltic pyroclasts, a detailed study of the pseudomorphic phases and reactions after olivine, driven by iron oxidation under high-T conditions, was performed. The observed mineralogical transformation suggests that the lapilli tuff material, originating from the burial of tephra routinely accumulated by persistent Strombolian explosions within the crater terrace, were in some cases altered by the circulation of acidic fluids and were in any case reheated due to isotherm rise forced by high heat flux and gas streaming delivered by the underlying magma system. It is worth noting that the ejection of these unusual volcanic lithotypes was possible because a few days before the 15 March 2007 event, the craters were clogged with lapilli tuff material that slid into the crater bottom between 7 and 9 March. Findings of this study suggest that the scattered permanently active vents and shallow conduits of Stromboli are surrounded sideways and underneath the crater terrace, by a fairly large volume of high temperature rocks with variable degree of compaction, sintering up to partially melted. Such a spectrum of rock types is in good agreement with the conceptual model of prominent thermal zoning all around (sideway and upwards) the active magmatic system. We speculate that continuous migration upwards of isotherms led to transformation and partial melting of the normal Strombolian tephra.

Major, minor and trace element analysis of volcanic glass in proximal and distal ( It is evident that correlation of proximal continental and distal marine tephras, at a high level of confidence, requires a full complement of major, minor and trace element data. In conjunction with considerations of the mineralogy and morphology of juvenile deposits these data help define petrological lineages such that precise provenance can be established. Whilst a precise proximal–distal match must be based on identical major, minor and trace element concentrations it is clear that resurgent activity from a single volcano can produce magmas with identical compositions. In such cases stratigraphic relationships must complement any geochemical study. Occasionally proximal stratigraphies may be unrepresentative of the complete eruptive history because of a lack of exposure due to burial by more recent effusive and explosive activity, or sector collapse which can remove vital stratigraphy particularly on volcanic islands.

The determination of eruptive parameters is crucial in volcanology, not only to document past eruptions, but also for tephra fallout hazard assessments. In most tephra fallout studies, eruptive parameters have been determined either by empirical techniques or analytical models, but the uncertainty of such parameters is usually not well described. We have applied both empirical and analytical models to characterize the climactic phase of the 2450 BP Plinian eruption of Pululagua (BF2 layer) and explore the variations in the total erupted mass, column height and total grain size distribution. Both approaches yield comparable results in the total mass of tephra erupted (4.5 ± 1.5 × 1011 kg), while they show some discrepancies for the determination of the column height (36–20 km from empirical techniques and 30–20 km from analytical techniques). The total grain size distribution of the BF2 layers varies with the different techniques used for the calculation and significantly affects the outputs of analytical models. Furthermore, the determination of the total grain size distribution depends strongly on the number and spatial distribution of the sample location. Inverting tephra fallout deposits on the total accumulation (or thickness) gives a good constraint on the total mass erupted but not on the column height. However, inverting on individual grain size classes better constrains the possible range of column heights (but cannot resolve particle release height). Results from the inversion on individual grain size classes show that large diffusion coefficients are necessary to model the BF2 layer and might be required to model proximal tephra deposits in order not to overestimate the total erupted mass. Additionally, we used a statistical method (smoothed bootstrap approach) to quantify the uncertainty in eruptive parameters such as column height and total erupted mass. Our uncertainty analysis yields a mean total erupted mass of 4.5 ± 0.3 × 1011 kg and a mean column height of 30 ± 3 km. Results from the uncertainty analysis compare well with results from other approaches. Finally, although the climactic phase of the 2450 BP Plinian eruption of Pululagua occurred in relatively calm atmospheric conditions, our results show that the dispersion of the BF2 layer was influenced by slight northeasterly wind conditions.

On 27 February 2007, at 12.49 GMT, a new eruption of Stromboli took place with the effusion of a lava flow from a fracture cutting the flank of the NE cone, which rapidly reached the sea. The eruption had been heralded by an increase in the amplitude of tremor and flank movement since at least the 14th of February. Short-term precursors were an increase in the rate of occurrence of small landslides within the “Sciara del Fuoco” scar on the North-western flank of the volcano. A new effusive vent opened at 18.30 GMT on the Sciara del Fuoco at an height of 400 m asl. The new lava emission caused the sudden termination of the summit flow and initiated a period of non-stationary lava outpouring which ended on 2 April, 2007. The eruption has been characterized by a rapid decrease in the eruption rate after the first days and subsequently by episodic pulse increases. On the 15th of March, the increase in lava outpouring, monitored by a thermal camera, heralded by 9 min the occurrence of a violent paroxysmal explosion with the formation of an impulsive eruption column and the emission of small pumices mingled with black scoriae. The pumice had a bulk composition similar to that of the lava and of the black scoriae, but with a distinct lower content of phenocrysts. A similar feature has been repeatedly observed during the major explosive paroxysms of Stromboli. Short term precursors of the paroxysm were recorded by strainmeter and tiltmeter stations. The volcano monitoring activity has been made by a joint team of researchers from the INGV sections of Catania, Napoli, Palermo and Rome, along with researchers from the Universities of Florence, Pisa, Roma Tre, and Palermo. The scientific activity was coordinated by a Synthesis Group made up by scientists responsible for the different monitoring techniques of INGV and Universities and by the volcanic experts of Commissione Nazionale Grandi Rischi of the Prime Minister Office (Civil Protection Department). The group made a daily evaluation of the state of the volcano and transmitted its recommendations to the Civil Protection Department (DPC). Several prevention measures were adopted by DPC, the main of which were the evacuation of the coast zone when strong acceleration of the Sciara del Fuoco slope motion (occurred twice) could led to a dangerous tsunami by flank collapse (as last occurred on 30 December 2002) and four days before the 15 March paroxysm when access was prohibited to the part of the volcano above 290 m asl.

Stromboli, one of the very few tourist volcanic islands in the world in permanent state of activity, has been the site of two important volcanic crises coupled with slope failure episodes in 2002–2003 and 2007. Due to the lucky circumstance that both crises have occurred in winter, the actual consequences on people were moderate. Nevertheless, the first crisis caused a few injuries, threatened the local population and caused relevant economic losses. The emotional impact on public opinion of the 30th December 2002 tsunami acted, in particular, as a trigger for civil protection initiatives aimed at structurally improving the standard volcano safety and preparedness measures to effectively deal with future crises. The main initiatives carried out during the 2003 crisis consisted in the setting up of: 1) new geophysical and geochemical volcano surveillance networks and 2) a local, permanent scientific/civil protection structure (COA, Centro Operativo Avanzato), where signals from volcano monitoring are visualized in real time and eventually used by the personnel of the Department of Civil Protection (DPC) for immediate activation of response procedures. This was followed by the setting up, in 2005, at the (DPC) in Rome, of a centre named “Centro Funzionale Centrale Rischio Vulcanico” (CFCRV), where the most relevant monitoring signals of Italian active volcanoes are visualized in real time and where activities of simple elaboration, for hazard assessment purpose are daily carried out and data sharing within the scientific community is coordinated by civil protection personnel with training in volcanic problems. The response effectiveness of the new system was tested on February–March 2007 when a new volcanic crisis occurred. An internal DPC “state of attention” was declared by the CF 15 days before the eruption onset when seismic and deformation parameters showed an abrupt increase up to values much higher than background. On February 27th the sudden onset of explosive activity outside the main craters and the occurrence of a small landslide down slope of the active craters were detected in real time on the screens of the CFCRV and by monitoring centres of the National Institute of Geophysics and Volcanology (INGV) and University of Florence (UNIFI). This enabled the DPC to immediately activate emergency crisis procedures and start a coordinated management of the crisis between civil protection personnel in Rome and COA. As accelerating slope movements were detected by ground deformation monitoring of UNIFI, a tsunami warning was launched shortly afterward. Warnings were also declared on 8th March and 15th March when slope movements resumed and a large explosion at the central craters occurred, respectively. From the end of February to May 2007 a scientific committee named “Scientific Synthesis Group” (SSG), appointed by the DPC, made daily evaluations of impending hazards in cooperation with CFCRV. During the crisis the DPC coordinated information activities with the media and island residents. The successful managing of the crisis consisted in minimizing risk for people and meanwhile facilitating normal activities and regular access to island.

Probabilistic characterizations of possible future eruptive scenarios at Vesuvius volcano are elaborated and organized within a risk-based framework. In the EXPLORIS project, a wide variety of topics relating to this basic problem have been pursued: updates of historical data, reinterpretation of previous geological field data and the collection of new fieldwork results, the development of novel numerical modelling codes and of risk assessment techniques have all been completed. To achieve coherence, many diverse strands of evidence had to be unified within a formalised structure, and linked together by expert knowledge. For this purpose, a Vesuvius ‘Event Tree’ (ET) was created to summarise in a numerical-graphical form, at different levels of detail, all the relative likelihoods relating to the genesis and style of eruption, development and nature of volcanic hazards, and the probabilities of occurrence of different volcanic risks in the next eruption crisis. The Event Tree formulation provides a logical pathway connecting generic probabilistic hazard assessment to quantitative risk evaluation. In order to achieve a complete parameterization for this all-inclusive approach, exhaustive hazard and risk models were needed, quantified with comprehensive uncertainty distributions for all factors involved, rather than simple ‘best-estimate’ or nominal values. Thus, a structured expert elicitation procedure was implemented to complement more traditional data analysis and interpretative approaches. The structure of the Vesuvius Event Tree is presented, and some of the data analysis findings and elicitation outcomes that have provided initial indicative probability distributions to be associated with each of its branches are summarized. The Event Tree extends from initiating volcanic eruption events and hazards right through to human impact and infrastructure consequences, with the complete tree and its parameterisation forming a quantitative synoptic framework for comprehensive hazard evaluation and mapping of risk impacts. The organization of the Event Tree allows easy updating, as and when new information becomes available.

Impact of large-scale explosive eruptions largely depends on the dynamics of transport, dispersal and deposition of ash by the convective system. In fully convective eruptive columns, ejected gases and particles emitted at the vent are vertically injected into the atmosphere by a narrow, buoyant column and then dispersed by atmosphere dynamics on a regional scale. In fully collapsing explosive eruptions, ash partly generated by secondary fragmentation is carried and dispersed by broad co-ignimbrite columns ascending above pyroclastic currents. In this paper, we investigate the transport and dispersion dynamics of ash and lapillis during a transitional plinian eruption in which both plinian and co-ignimbrite columns coexisted and interacted. The 800 BP eruptive cycle of Quilotoa volcano (Ecuador) produced a well-exposed tephra sequence. Our study shows that the sequence was accumulated by a variety of eruptive dynamics, ranging from early small phreatic explosions, to sustained magmatic plinian eruptions, to late phreatomagmatic explosive pulses. The eruptive style of the main 800 BP plinian eruption (U1) progressively evolved from an early fully convective column (plinian fall bed), to a late fully collapsing fountain (dense density currents) passing through an intermediate transitional eruptive phase (fall + syn-plinian dilute density currents). In the transitional U1 regime, height of the convective plinian column and volume and runout of the contemporaneous pyroclastic density currents generated by partial collapses were inversely correlated. The convective system originated from merging of co-plinian and co-surge contributions. This hybrid column dispersed a bimodal lapilli and ash-fall bed whose grain size markedly differs from that of classic fall deposits accumulated by fully convective plinian columns. Sedimentological analysis suggests that ash dispersion during transitional eruptions is affected by early aggregation of dry particle clusters.

Intrusive degassing and recycling of degassed and dense magma at depth have been proposed for a long time at Stromboli. The brief explosive event that occurred at the summit craters on 9 January 2005 threw out bombs and lapilli that could be good candidates to illustrate recycling of shallow degassed magma at depth. We present an extensive data set on both the textures and the mineral, bulk rock and glassy matrix chemistry of the “9 Jan” products. The latter have the common shoshonitic–basaltic bulk composition of lavas and scoriae issued from typical strombolian activity. In contrast they differ by the heterogeneous chemistry of their matrix glasses and their crystal textures that testify to crystal dissolution event(s) just prior magma crystallization upon ascent and eruption. Comparison between mineral paragenesis of the natural products and experimental phase equilibria suggest water-induced magma re-equilibration. We propose that mineral dissolution is related to water enrichment of the recycled degassed magma, via differential gas bubble transfer and to some extents its physical mixing with volatile-rich magma blobs. However, all these features illustrate transient processes. Even though evidence of mineral dissolution is ubiquitous at Stromboli, its effect on the bulk magma chemistry is minor because of the subtle interplay between mineral dissolution and crystallization in magmas having comparable bulk chemistry.

On April 5, 2003, Stromboli volcano (Italy) produced the most violent explosion of the past 50 years. The event was exceptionally well documented thanks to the presence on the island of several scientists and a large number of instruments deployed over the preceding months to monitor the effusive eruption that began in December 2002. Integration of visual documentation, deposit features and geophysical data allowed an accurate reconstruction of the explosive event and its dynamics. The eruption consisted of a 8-min long explosive event which evolved through four phases whose timing was precisely recorded by an infrared thermometer located about 450 m from the summit crater. Phases 2 and 3 lasted 39 and 42 s, respectively. Both had an impulsive character, were responsible for ejecting almost the entire mass of the pyroclastic products. Phases 1 and 4 represented, respectively, a short-lived precursory event and a waning tale. During Phase 2, meter-sized ballistic blocks were launched with velocities of 170 m/s to altitudes of up to 1400 m above the craters. These fell on the volcano flanks and on the village of Ginostra, about 2 km distant from the vent. A vertical jet rose above the craters which developed to feed a convective plume that reached a height of up to 4 km. The calculated mass of the Phase 2 fallout deposit and mass discharge rate were 1.1–1.4 × 108 kg and 2.8–3.6 × 106 kg/s, respectively. During Phase 3 a scoria flow deposit, with an estimated volume of 0.9–1.1 × 104 m3, was erupted from the same vent that fed the ongoing sustained lava flow. The average mass discharge rate for this phase was 2.5–3.1 × 105 kg/s. Products emitted during Phases 2 and 3 consisted of lithic and fresh magmatic material in similar proportions. The juvenile fraction consisted of a deep-originated, almost aphyric, highly vesicular pumice mingled with a shallow-derived, crystal-rich, moderately vesicular scoria. Similarities with the eruption dynamics of other historical paroxysms at Stromboli makes the April 5, 2003 explosion representative of these highly energetic events that constitute the most hazardous volcanic phenomena at Stromboli volcano.

Correlation of the distal deposits of the Campanian Ignimbrite with their proximal equivalents in the Campi Flegrei caldera is complicated by a lack of medial exposures, complex and limited proximal stratigraphic sections, and large lateral facies changes. Paleomagnetic data from 10 sites in and near the Campi Flegrei yield natural remanent magnetizations (NRM) that are statistically indistinguishable from the distal Campanian Ignimbrite. In addition, their virtual geomagnetic pole (VGP) yields a possible correlation with Lac du Bouchet, France, secular variation data that indicate an age of approximately 32,850 14 C years. The secular variation curve at this age was only briefly at this VGP, and did not return to it for >10,000 years, so the paleomagnetic correlation of proximal and distal deposits is unique and robust. The date is consistent with 14 C dates from the Campanian Ignimbrite, but younger than 39 Ar / 40 Ar dates for the same rocks. This suggests that a better correction factor for cosmic flux for this time period is needed to calibrate older 14 C dates. Anisotropy of magnetic susceptibility (AMS) data show that the proximal deposits have an oblate (disk-shaped), poorly lineated magnetic fabric. The distal deposits are much better lineated. The difference may be due to chaotic depositional currents in the proximal areas, in which particles were not well aligned. With greater distance of travel, and loss of energy, particles within the flow became aligned and developed stronger AMS lineations. Early eruptions of the Piperno Tuff were from a central vent north of Pozzuoli, whereas later tuffs that underlie the Breccia Museo may have been emplaced by flows associated with ring vents located on the northern and southern caldera margins.

Glass inclusions hosted by clinopyroxene and matrix glasses of pumices from the Plinian fall deposit associated with the Campanian Ignimbrite eruption were analysed in order to investigate processes that occurred at various stages of the magmatic evolution and to characterise the magma-withdrawal dynamics during the eruption. Petrographic, SEM–EDS, and electron microprobe analyses were performed on pumice samples, glass inclusions, and host minerals. Primary non-evolved glass inclusions were found both in homogeneous salite and in zoned diopside-salite clinopyroxenes. All the studied glasses are peralkaline alkali-trachytic in composition. The variation trends of glass inclusions and matrix glasses overlap for most elements except for alkalies and Cl. The least evolved compositions, however, are shown by glass inclusions found in salitic clinopyroxene at interfaces with diopside from the early erupted Plinian pumices (Lower Fall), whereas the most evolved compositions were found in the matrix glasses of the late-erupted Plinian pumices (Upper Fall). Excluding the most mafic glass inclusions, the observed compositional range is closely comparable to the range for ignimbrite juvenile clast compositions, indicating that the two eruptive phases drained the same magmatic reservoir. The compositional evolution of the Campanian Ignimbrite magmatic system seems to have resulted from different processes occurring at different stages: pre-eruptive magma mixing, due to an input of mafic magma into the reservoir, and crystal fractionation starting from different hybrid parental magmas to produce the most evolved compositions. These processes could have generated a vertically and laterally zoned magma chamber with multiple layers of variably hybrid magma extending from the input points of mafic magma. This type of zoning seems to better account for all the complex chemical and mineralogical characteristics of the Campanian Ignimbrite magmatic system, instead of a simple vertically zoned magmatic reservoir. A syn-eruptive mingling between the least evolved hybrid magmas and the most evolved melts characterised the first phase of Plinian eruption. This uncommon emptying of the magma chamber could be explained by the particular geometry of the reservoir.

Cotopaxi, the highest active volcano on earth and one of the most dangerous of Ecuador is constituted by a composite cone made up of lava and tephra erupted from the summit crater. The activity of the present volcano begun with large-volume plinian eruptions followed by a succession of small-volume lava emissions and pyroclastic episodes which led to the edification of a symmetrical cone. The growth of the cone was broken by an episode of slope failure, the scar of which is now obliterated by recent and historical products. Volcanic history, eruptive frequency and characteristics of the activity were investigated by studying the stratigraphy of tephra and carrying out fifteen new 14 C dating on paleosols and charcoals. The investigated period is comprised between the slope failure and the present. The deposit of the volcanic landside (dry debris avalanche of Rio Pita), previously believed to be between 13,000 and 25,000 yr B.P., is now considered to have an age slightly older than 5000 yr B.P. The stratigraphy of tephra of the last 2000 years reveals the existence of 22 fallout layers. Seven of them were dated with 14 C whereas three were ascribed to the eruptions of 1534, 1768 and 1877 on the basis of comparison with historical information. Maximum clast size distribution (isopleths) of 9 tephra layers points out that the sustained explosive eruptions of Cotopaxi during the last 2000 years are characterized by very high dispersive power (plinian plumes with column heights between 28 and 39 km) and high intensity (peak mass discharges from 1.1 to 4.1 × 10 8 kg/s). The magnitude (mass) of tephra fallout deposits calculated from distribution of thickness (isopaches) are, however, moderate (from 0.8 to 7.2 × 10 11 kg). The limited volume of magma erupted during each explosive episode is consistent with the lack of caldera collapses. Small-volume pyroclastic flows and surges virtually accompanied all identified tephra fallouts. During such an activity large scale snow/ice melting of the summit glacier produced devastating mudflows comparable in scale to those of 1877 eruption. By assuming a 1:1 correspondence between fallout episodes and generation of large-scale lahar, we have estimated an average recurrence of one explosive, lahartriggering event every 117 years over the last two millennia. This value compares well with that calculated by considering the period since Spanish Conquest. The probability of having an eruption like this in 100 or 200 years is respectively of 0.57 and 0.82. Such an high probability underscores the need for quick actions aimed at the mitigation of Cotopaxi lahar hazard along all the main valleys which originate from the volcano.

The eruption of 1631 A.D. was the most violent and destructive event in the recent history of Vesuvius. More than fifty primary documents, written in either Italian or Latin, were critically examined, with preference given to the authors who eyewitnessed volcanic phenomena. The eruption started at 7 a.m. on December 16 with the formation of an eruptive column and was followed by block and lapilli fallout east and northeast of the volcano until 6 p.m. of the same day. At 10 a.m. on December 17, several nuees ardentes were observed to issue from the central crater, rapidly descending the flanks of the cone and devastating the villages at the foot of Vesuvius. In the night between the 16th and 17th and on the afternoon of the 17th, extensive lahars and floods, resulting from rainstorms, struck the radial valleys of the volcano as well as the plain north and northeast. Deposits of the eruption were identified in about 70 localities on top of an ubiquitous paleosol formed during a long preeruptive volcanic quiescence. The main tephra unit consists of a plinian fallout composed of moderately vesicular dark green lapilli, crystals and lithics. Isopachs of the fallout are elongated eastwards and permit a conservative volume calculation of 0.07 km 3 . The peak mass flux deduced from clast dispersal models is estimated in the range 3–6 × 10 7 kg/s, corresponding to a column height of 17–21 km. East of the volcano the plinian fallout is overlain by ash-rich low-grade ignimbrite, surges, phreatomagmatic ashes and mud flows. Ash flows occur in paleovalleys around the cone of Vesuvius but are lacking on the Somma side, suggesting that pyroclastic flows had not enough energy to overpass the caldera wall of Mt. Somma. Deposits are generally unconsolidated, massive with virtually no ground layer and occasionally bearing sparse rests of charred vegetation. Past interpretations of the products emitted on the morning of December 17 as lava flows are inconsistent with both field observations and historical data. Features of the final phreatomagmatic ashes are suggestive of alternating episodes of wet ash fallout and rainfalls. Lahars interfingered with primary ash fallout confirm episodes of massive remobilization of loose tephra by heavy rainfalls during the final stage of the eruption. Chemical analyses of scoria clasts suggest tapping of magma from a compositionally zoned reservoir. Leucite-bearing, tephritic-phonolite (SiO 2 51.17%) erupted in the early plinian phase was in fact followed by darker and slightly more mafic magma richer in crystals (SiO 2 49.36%). During the nuees ardentes phase the composition returned to that of the early phase of the eruption. The reconstruction of the 1631 eruptive scenario supplies new perspectives on the hazards related to plinian eruptions of Vesuvius.

The active crater of Guagua Pichincha volcano is located only about 10 km west of Quito, the capital city of Ecuador. Archeological and historical records confirm that, in the last few millennia, human communities were repeatedly affected by volcanic eruptions in this region. Tephrostratigraphic studies and 14 C datings indicate that the eruptive history of Pichincha in the last 40,000 years has been characterized mostly be explosive eruptions with an average frequency of one event every few centuries. These eruptions produced relatively small volumes of dacitic pumice fallout and pyroclastic surge and flow. Eruptions of the last 10,000 years has also included lava dome growth and lateral blasts by dome explosions. Based upon the history of the volcano, the explosive eruptions of 970 and 1660 A.D. were selected as those representing, in the case of reactivation, the maximum phenomena to be expected. The eruption behaviour (ash fallout and pyroclastic surge) has been simulated by physical-numerical models on digitized topographic map, and the results have been used to evaluate the harzardous areas.

The pyroclastic products of a poorly-known eruption of Vesuvius (ascribed by a combination of historic and radiocarbon data to A.D. 472) have been investigated from both volcanological and petrological points of view. The eruptive sequence starts with pumice-fall deposits (three units can be recognized) that darken upwards where there are sandwave interbeds. Surge deposits cover the pumice-fall bed and thick pyroclastic-flow deposits represent the uppermost levels of the deposit. Isopach maps of both the pumice-fall and pyroclastic-flow deposits led to an estimate of the total volume of tephra of about 0.32 km3. The eruptive sequence and the distribution of lithic ejecta are similar to those of the major Plinian eruptions of Somma-Vesuvius (although the volume involved is significantly lower) and reflect an increase in the hydromagmatic character of the eruption with time. The products range in composition from phonolites (first-erupted) to phonolitic leucitites with gradual changes upwards. Whole rock chemistry and microprobe mineralogy indicate that the Pollena sequence represents a liquid line of descent towards the phonolitic minimum of petrogeny's residua system. Fractionation occurred within a shallow magma chamber (PH2O probably slightly higher than 1 kb) and was mainly controlled by leucite and clinopyroxene. The basic parental magma approached the composition of the recent period (A.D. 1631–1944), tephritic leucitites of Vesuvius. The phonolitic magma can be derived from a leucititic parent by fractionating about 50% solid phases. A two-stage fractionation model is suggested: the first stage occurred during the rise of magma from the deep source and the second within the shallow magma chamber. The rate of magma introduction during the 150 to 200 year repose time preceeding the eruption probably averaged 1.2 to 1.7 × 10−3 km3-yr−1. These conditions were probably favorable for the occurrence of magma-mixing within the convecting zone of the magma chamber.

Grain-size and component analyses have been carried out on pyroclastic deposits of three well-known explosive eruptions of Vesuvius: those of 79 A.D., 1631 and 1906. These eruptions cover a wide energy spectrum, from Plinian to Strombolian, and each includes a transition from a magmatic to a well-documented and clearly distinguishable phreatomagmatic phase of activity. The chronicles of the eruptions are revisited in light of the granulometric and component data obtained from the study of the deposits and interpretation of the dynamics of the main eruptive episodes is provided for each eruption. The phreatomagmatic products (originated from explosive interaction of magma with groundwater) have characteristic grain-size and component distribution patterns distinct from associated purely magmatic pyroclastic products: in any eruption phreatomagmatic products exhibit: (a) a marked increase in both the lithic/juvenile and the crystal/total juvenile ratios, and (b) a preferential fragmentation of the juvenile fraction. Moreover, eruption energy, degree of evolution of erupted magma, lithic content and depth of provenance are all clearly correlated. The abundance of lithics and crystals in phreatomagmatic deposits can be ascribed to (a) preferential fragmentation of the aquifer-hosting rocks due to explosive vaporization of ground water; (b) vent flaring and craterization possibly related to overpressure conditions following the entrance of large quantities of steam in the conduit; (c) indirect enrichment in both crystal and lithic fractions by removal of juvenile fines from the eruptive cloud. In each eruption some of the deposits with “phreatomagmatic” component distribution patterns also exhibit evidence of steam condensation (accretionary lapilli, vesiculated tuff, mud coating, soft deformations) and some do not: these are therefore to be considered sufficient but not necessary diagnostic features for a hydromagmatic origin of the deposit (“wet” in the sense of Sheridan and Wohletz, 1983). “Dry” phreatomagmatic products correspond to higher energy conditions allowing production and maintenance of overheated steam. The magma/water ratio in terms of heat exchange surface (i.e. the degree of primary fragmentation of the magma) is certainly the main factor controlling the efficiency and the energy balance of the interaction. A series of observations strongly suggest that a primarily fragmented magma is a basic requisite for the explosive magma/water interaction: (a) occurrence of short phreatomagmatic episodes interrupting lava fountains activity (1906 eruption) in connection with drawdown of the magma column in the conduit; (b) parallel increase in depth of magma fragmentation level and magma/water interaction level (as deduced by the nature of lithics), and (c) preferential occurrence of phreatomagmatic activity at the end of explosive eruptions (when juvenile gas pressure declines and water from the confining aquifer more easily enters the conduit).

A systematic petrological and chemical study of the volcanic products of the Phlegraean Fields has been accomplished based on the new stratigraphy described by Rosi et al. (this volume). The majority of Phlegraean rocks belong to the “potassic” series of the Roman province. The compositional spectrum ranges from trachybasalts to latites, trachytes, alkali trachytes, and peralkaline phonolitic trachytes. Trachybasalts are extremely rare and there is a sharp compositional gap between them and the latites. The series between latites and the trachytic varieties is complete. Trachytic rocks are much more voluminous than latites. The order of appearance of the main solid phases is: olivine, clinopyroxene, plagioclase, alkali feldspar, biotite, and oxides. Mineral compositions obtained by microprobe analyases are compatible with the evolution of the rock chemistry. However, primitive compositions of plagioclase (An 80 ) and clinopyroxene (diopside) persist in the cores of phenocrysts, even at the trachytic and alkali trachytic stage. Fractional crystallization within a shallow magma chamber has been the dominant process for the generation of Phlegraean rock series. The volume of the magma chamber is estimated to have been at least 240 km 3 at the moment of the eruption of the Campanian Ignimbrite, nearly 35,000 yr. ago. This event was followed by a large caldera collapse. The depth of the chamber cannot be precisely evaluated. However, its top must have been very shallow, probably at 4–5 km, as suggested by contact metamorphic rocks obtained from deep geothermal wells within the caldera. Volcanological and petrological data favor a model of upward migration of lighter liquids produced mostly by fractionation along the cool walls of the chamber, the deeper part of which is occupied by a convecting trachybasaltic magma. Progressive migration of eruptive vents toward the caldera center and the contemporaneous strong reduction in the volume of the erupted products, suggest that the chamber behaved as a closed system. The volume of magma was progressively reduced by both cooling and extraction to the surface.

The main event within the volcanic history of the Phlegraean Fields was the eruption, about 35,000 years ago, of a huge alkali trachytic ignimbrite (80 km 3 , dre) followed by caldera collapse. The pre-caldera activity (evidence from geothermal wells and surface outcrops) changed from submarine to subaerial shortly before the ignimbrite eruption. The caldera was subsequently invaded by the sea and became progressively filled with tuffites and subordinate submarine flows in its northern half. The last submarine explosive activity dates back to 12000-10500 yr. with the eruption of mostly “hydroplinian” yellow tuffs. Recent, mostly subaerial, activity consists of a series of explosive eruptions whose volume decreases with time, until the last eruption of Mt. Nuovo in 1538 A.D. Two peaks in recent activity occur at 10000-8000 and 4700-3000 years ago. During post-caldera activity, eruptive vents migrated from the caldera rim toward the center where there are two distinct zones of recent vents. Minor collapses occurred within the caldera after the main eruptions; often they are eccentric to the vent and displaced toward the caldera center. Phlegraean explosive activity is characterized by water/magma interaction; eruptive events without a hydromagmatic component are extremely rare. In most cases, the evolved trachytic magmas interacted with surface water (either the sea or intracaldera lakes). However, there is evidence of interaction of magma with deep-seated aquifers for some Plinian events. Explosivity, i.e. the efficiency of the transformation of thermal into kinetic energy during magma/water interaction, is largely controlled by the primary fragmentation of the magmatic melt.