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TheLate Pleistocene-HoloceneDilo-Dukana and Mega volcanic fields (Ririba rift, South Ethiopia) formedthrough monogenetic eruptions of limited volumes of alkaline-basalts, rich in mantle xenoliths. This activity postdated the emplacement of voluminous Pliocene subalkaline basaltic lavas related to the main rifting phase. Both volcanic fields display vent alignments that abruptly cut the rift-related features, suggestive of an emplacement after rift abandonment.We provide new petrological, geochemical and isotopic data on these still poorly studied products aimed at investigating the nature and temporal variation of the mantle source compared to the previous Pliocene activity, and the main differentiation processes.All data discriminate the younger alkaline lavas from the Pliocene products, indicating a variation of the mantle source during the two activities possibly related to the local rifting evolution. The Dilo-Dukana and Mega products overlap both in major, trace elements and radiogenic (Sr-Nd-Pb) isotopes. Well-defined trends, as displayed by incompatible trace elements and by major elements variations, indicate the prominent role of fractional crystallization driving magma differentiation, without evidence of shallow storage levels. No clear geochemical correlation is evident with respect to location, xenoliths content or eruptive style. Light-REEs roughly discriminate between the products erupted at Dilo-Dukana and Mega, pointing to possible variations in the degree of melting and/or crystallization conditions of different magma pulses in the two areas.These data indicate that the volcanic fields are fed by two different systems of deep structures, unrelated to rifting but associated to old inherited fabrics, directly transferring mantle melts to the surface.&nbsp, The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Although volcanic eruptions represent short periods in the whole history of a volcano, the large amount of loose pyroclastic material produced, combined with aeolian processes, can lead to continuous, long-lasting reworking of volcanic products. Driven by wind, these processes significantly influence the geomorphology and prolong the impacts of eruptions on exposed communities and ecosystems. Since such phenomena are of interest to scientists from a range of disciplines (e.g., volcanology, atmospheric and soil sciences), a well-defined, common nomenclature is necessary to optimise the multidisciplinary characterisation of both processes and deposits. We, therefore, first describe ash wind-remobilisation processes and provide definitions for appropriate terms consistent with the World Meteorological Organisation’s (WMO’s) classification of lithometeors. Second, we apply these definitions to investigate aeolian remobilisation of the 2011 Cordón Caulle (Chile) tephra-fallout deposit, which has strongly impacted rural communities in the Argentinian Patagonia steppe. We combine field observations and a physical characterisation of systematically collected ground and airborne material in order to identify the secondary deposits associated with: (i) non-erodible surface roughness elements (e.g., vegetation and rocks) and (ii) pre-existing mounds or similar erodible bedforms. Grainsize analysis shows that wind-remobilised particles have a specific size range, from

Continental rift systems commonly form by progressive growth of isolated rift segments that interact and link, eventually evolving into continuous zones of deformation. Propagation and interaction between adjacent rift segments are important features of rifting, influencing the distribution of volcanoes, seismicity and sedimentary basins. The process also controls the morphology of the rift at breakup with possible implications for the segmentation of mid-ocean ridges. However, how the punctuated, discontinuous zones of extension propagate and interact to form a continuous rift system and how the complex zones of interaction evolve remain poorly documented and understood. The Turkana depression in East Africa is an ideal place where to analyse these processes: within this NW-SE lowland, two major sectors of the East African rift, the Kenyan and Ethiopian rifts, interact giving rise a complex, >300km-wide region of faulting and volcanic activity. In this work, we present geological-structural, geochemical and geochronological data from the poorly documented Ririba rift (South Ethiopia), which is part of the complex, wide region of volcano-tectonic activity in the Turkana depression. This rift is of special interest because it is commonly accepted to represent the southernmost, youngest and less-developed sector of the Ethiopian Rift, having formed from recent southward propagation of this rift into the Turkana depression. Our data confirm the Ririba rift formed from the southward propagation of the Ethiopian rift during the Pliocene but this propagation was short-lived and aborted close to the Pliocene-Pleistocene boundary, when rift-related deformation ceased. Integration of seismicity data with new numerical models indicates that abandonment of laterally offset and overlapping tips of the Ethiopian and Kenyan rifts resulted from progressive focusing of the tectonic and magmatic activity into an oblique, throughgoing rift zone which directly connects the rift sectors. These sectors link by near pure extension without forming the strike-slip transfer faults interpreted as precursors of oceanic transform faults

We present a detailed chronological reconstruction of the 2011 eruption of the Cordón Caulle volcano (Chile) based on information derived from newspapers, scientific reports and satellite images. Chronology of associated volcanic processes and their local and regional effects (i.e. precursory activity, tephra fallout, lahars, pyroclastic density currents, lava flows) are also presented. The eruption had a severe impact on the ecosystem and on various economic sectors, including aviation, tourism, agriculture and fishing industry. Urban areas and critical infrastructures, such as airports, hospitals and roads, were also impacted. The concentration of PM10 (particulate matter ≤ 10 µm) was measured during and after the eruption, showing that maximum safety threshold levels of daily and annual exposures were surpassed in several occasions. Probabilistic analyses suggest that this combination of atmospheric and eruptive conditions has a probability of occurrence of about 1 %. The management of the crisis, including evacuation of people, is discussed, as well as the comparison with the impact associated with other recent eruptions located in similar areas and having similar characteristics (i.e. Quizapu, Hudson and Chaitén volcanoes). This comparison shows that the regions downwind and very close to the erupting volcanoes suffered very similar problems, without a clear relation to the intensity of the eruption (e.g. health problems, damage to vegetation, death of animals, roof collapse, air traffic disruptions, road closure, lahars and flooding). This suggests that a detailed collection of impact data can be largely beneficial for the development of plans for the management of an eruptive crisis and the mitigation of associated risk of the Andean region.

In this study, we combine reconstructions of volcanological data sets and inputs from a structured expert judgment to produce a first long-term probability map for vent opening location for the next Plinian or sub-Plinian eruption of Somma-Vesuvio. In the past, the volcano has exhibited significant spatial variability in vent location; this can exert a significant control on where hazards materialize (particularly of pyroclastic density currents). The new vent opening probability mapping has been performed through (i) development of spatial probability density maps with Gaussian kernel functions for different data sets and (ii) weighted linear combination of these spatial density maps. The epistemic uncertainties affecting these data sets were quantified explicitly with expert judgments and implemented following a doubly stochastic approach. Various elicitation pooling metrics and subgroupings of experts and target questions were tested to evaluate the robustness of outcomes. Our findings indicate that (a) Somma-Vesuvio vent opening probabilities are distributed inside the whole caldera, with a peak corresponding to the area of the present crater, but with more than 50% probability that the next vent could open elsewhere within the caldera; (b) there is a mean probability of about 30% that the next vent will open west of the present edifice; (c) there is a mean probability of about 9.5% that the next medium-large eruption will enlarge the present Somma-Vesuvio caldera, and (d) there is a nonnegligible probability (mean value of 6–10%) that the next Plinian or sub-Plinian eruption will have its initial vent opening outside the present Somma-Vesuvio caldera.

This paper presents a geomorphological map of Mount Ararat/Ağri Daği in Eastern Anatolia (Turkey). Mount Ararat/Ağri Daği is a volcanic complex covered by a unique ice cap in the Near East. The massif is the result of multiple volcanic phases, and present day landforms are the result of subsequent and overlapping glacial, periglacial, and slope processes. The geomorphological mapping of Mount Ararat/Ağri Daği was firstly performed on the basis of desktop studies, by applying remote-sensing investigations using high-resolution satellite imagery (PLEIADES and SPOT images). A preliminary draft of the map was crosschecked and validated in the field as part of an interdisciplinary campaign carried out in the 2014 summer season. All the collected data suggest that the Mount Ararat/Ağri Daği glaciation played a crucial role in the evolution of the landscape and that even today glaciers are significant features in this area. Currently, ice bodies cover 7.28 km2 and include peculiar glacier types. Among these are three well-developed debris-covered glaciers, flowing down along the flanks of the volcano.

This paper introduces the aims and scope of the RESET project (. RESponse of humans to abrupt Environmental Transitions), a programme of research funded by the Natural Environment Research Council (UK) between 2008 and 2013; it also provides the context and rationale for papers included in a special volume of Quaternary Science Reviews that report some of the project's findings. RESET examined the chronological and correlation methods employed to establish causal links between the timing of abrupt environmental transitions (AETs) on the one hand, and of human dispersal and development on the other, with a focus on the Middle and Upper Palaeolithic periods. The period of interest is the Last Glacial cycle and the early Holocene (c. 100-8 ka), during which time a number of pronounced AETs occurred. A long-running topic of debate is the degree to which human history in Europe and the Mediterranean region during the Palaeolithic was shaped by these AETs, but this has proved difficult to assess because of poor dating control. In an attempt to move the science forward, RESET examined the potential that tephra isochrons, and in particular non-visible ash layers (cryptotephras), might offer for synchronising palaeo-records with a greater degree of finesse. New tephrostratigraphical data generated by the project augment previously-established tephra frameworks for the region, and underpin a more evolved tephra 'lattice' that links palaeo-records between Greenland, the European mainland, sub-marine sequences in the Mediterranean and North Africa. The paper also outlines the significance of other contributions to this special volume: collectively, these illustrate how the lattice was constructed, how it links with cognate tephra research in Europe and elsewhere, and how the evidence of tephra isochrons is beginning to challenge long-held views about the impacts of environmental change on humans during the Palaeolithic. © 2015 Elsevier Ltd., RESET was funded through Consortium Grants awarded by the Natural Environment Research Council, UK, to a collaborating team drawn from four institutions: Royal Holloway University of London (grant reference NE/E015905/1), the Natural History Museum, London (NE/E015913/1), Oxford University (NE/E015670/1) and the University of Southampton, including the National Oceanography Centre (NE/01531X/1). The authors also wish to record their deep gratitude to four members of the scientific community who formed a consultative advisory panel during the lifetime of the RESET project: Professor Barbara Wohlfarth (Stockholm University), Professor Jørgen Peder Steffensen (Niels Bohr Institute, Copenhagen), Dr. Martin Street (Romisch-Germanisches Zentralmuseum, Neuwied) and Professor Clive Oppenheimer (Cambridge University). They provided excellent advice at key stages of the work, which we greatly valued. We also thank Jenny Kynaston (Geography Department, Royal Holloway) for construction of several of the figures in this paper, and Debbie Barrett (Elsevier) and Colin Murray Wallace (Editor-in-Chief, QSR) for their considerable assistance in the production of this special volume.

We use PyBox, a new numerical implementation of the box-model approach, to reproduce pyroclastic density current (PDC) deposits from the Somma–Vesuvius volcano (Italy). Our simplified model assumes inertial flow front dynamics and mass deposition equations and axisymmetric conditions inside circular sectors. Tephra volume and density and total grain size distribution of EU3pf and EU4b/c, two well-studied PDC units from different phases of the 79 CE Pompeii eruption, are used as input parameters. Such units correspond to the deposits from variably dilute, turbulent PDCs. We perform a quantitative comparison and uncertainty quantification of numerical model outputs with respect to the observed data of unit thickness, inundation areas and grain size distribution as a function of the radial distance to the source. The simulations consider (i) polydisperse conditions, given by the total grain size distribution of the deposit, or monodisperse conditions, given by the mean Sauter diameter of the deposit; (ii) axisymmetric collapses either covering the whole 360∘ (round angle) or divided into two circular sectors. We obtain a range of plausible initial volume concentrations of solid particles from 2.5 % to 6 %, depending on the unit and the circular sector. Optimal modelling results of flow extent and deposit thickness are reached on the EU4b/c unit in a polydisperse and sectorialized situation, indicating that using total grain size distribution and particle densities as close as possible to the real conditions significantly improves the performance of the PyBox code. The study findings suggest that the simplified box-model approach has promise for applications in constraining the plausible range of the input parameters of more computationally expensive models. This could be done due to the relatively fast computational time of the PyBox code, which allows the exploration of the physical space of the input parameters.

A crucial feature to manage a volcanic crisis is the ability of volcanologists to promptly detect an impending eruption. This is often affected by significant uncertainty, mainly for the difficulty in interpreting the monitoring signals in terms of the exact timing of a possible eruption. Here we contribute to this problem, focusing on the states of active volcanoes with closed conduit, as deduced from monitoring data. Four main states can be identified. In the quiescence state 1) the monitoring data lie on a baseline, suggesting the lack of shallow magma/fluid movement. The unrest state is highlighted by minor 2) to major 3) variations in the intensity and rate of monitoring data; in both cases, radial ground deformation pattern and non-migrating seismicity imply shallow magma and/or fluid accumulation. The state of impending eruption 4) is characterised by non-radial, asymmetric ground deformation pattern and migrating seismicity, which suggest that magma approaches the surface through a propagating dyke. As early recognition of this distinctive state is crucial for timely eruption forecast, monitoring activity should be aimed at its prompt detection. The application of this rationale to two types of active volcanoes in densely inhabited areas, a restless caldera (Campi Flegrei) and a quiescent stratovolcano (Vesuvio), highlights its feasibility and importance in eruption forecasting. This rationale may foster a general reference framework to be adopted in case of unrest, supporting in interpreting the monitoring data, as well as more effective: 1) operationally-oriented, monitoring system; 2) probabilistic forecast; 3) use of volcanic alert levels.

Dissertação (mestrado) — Universidade de Brasília, Instituto de Geociências, Programa de Pós-Graduação em Geologia, 2018. Este trabalho relata o estudo de sequências deposicionais da Formação Onano Superior, referente às fases finais da erupção Onano, na Caldeira de Latera, Província Romana, Distrito Vulcânico Vulsini (0,6-0,13 Ma), Itália. A atividade vulcânica é caracterizada pela alternância entre os estilos eruptivos estrombolianos e freatomagmáticos, diagnosticados pelos depósitos piroclásticos de queda de escórias, púmices, líticos, spatter e depósitos do tipo surge. Os fragmentos juvenis são caracterizados por fenocristais de clinopiroxênio (Mg# = 40,99-89,66), sanidina (Or = 60,74-81,29 mol%), plagioclásio (An = 85,00-94,20 mol%), flogopita e leucita. As fases acessórias incluem magnetita e microcristais de apatita. Dados geoquímicos de rocha total classificam os componentes vulcânicos como alcalinos potássicos e ultrapotássicos insaturados em sílica, indicando um magmatismo bimodal de composição traquibasáltica e tefrítica a fonolítica. Os valores incluem SiO2 = 46,18 a 55,99 wt%, (Na2O + K2O) = 7,21 a 13,21 wt%, Al2O3 = 14,8 a 19,27 wt%, CaO = 4 a 11,87 wt%, Fe2O3 = 4,37 a 8,77 wt% e MgO = 0,89 a 6,66 wt%. A geoquímica dos elementos traço e terras raras é indica composição semelhante às composições de magmatismo em arco vulcânico, com enriquecimento em LILEs e ETR’s leves, juntamente com o empobrecimento em HFSEs e ETR’s pesados. Os padrões multielementares apresentam anomalias positivas em Th, U, K, Pb, Nd e Dy e anomalias negativas em Ba, Nb, Ta, P e Ti. Exibem forte fracionamento nos ETR’s leves em relação aos ETR’s pesados ([La/Yb]N = 21,96 a 31,94) e discreta anomalia negativa em Eu (Eu/EuN = 0,69 a 0,77). As razões 143Nd/144Nd estão entre 0.512106 e 0.512148, valores que geram εNd(0) entre - 9.56 a -10.37, e as razões 87Sr/86Sr estão entre 0.71016 a 0.71036, indicando fonte mantélica enriquecida com processo de contaminação crustal. Os valores de TDM (Ga) variam de 1.09 a 1.29. Com base nos dados geoquímicos e petrológicos sugere-se que os magmas derivam de fusões de uma fonte metassomatizada relacionada à subducção e que a evolução deste magmatismo foi dominada por processos de fracionamento mineral, envolvendo principalmente clinopiroxênio, feldspato e leucita. This work reports the study of depositional sequences of the Onano Superior Formation, referring to the final phases of the Onano eruption, in Latera Caldera, Roman Province, Vulsini Volcanic District (0,6-0,13 Ma), Italy. The volcanic activity is characterized by the alternation between the eruptive strombolian and phreatomagmatic styles, diagnosed by pyroclastic deposits of scoriae, pumice, lithic, spatter and surge deposits. The juvenile fragments are characterized by clinopyroxene (Mg# = 40.99 to 89.66), sanidine (Or = 60.74 to 81.29 mol%), plagioclase (An = 85.00 to 94.20 mol%), phlogopite and leucite phenocrysts. The accessory phases include magnetite and apatite microcrystals. Total rock geochemical data classify the volcanic components as alkaline potassic and ultrapotassic unsaturated in silica, indicating a bimodal magmatism of traquibasaltic and thephritic to phonolitics compositions. Values include SiO2 = 46.18 to 55.99 wt%, (Na2O + K2O) = 7.21 to 13.21 wt%, Al2O3 = 14.8 to 19.27 wt%, CaO = 4 to 11.87 wt%, Fe2O3 = 4.37 to 8.77 wt% and MgO = 0.89 to 6.66 wt%. The geochemistry of the trace and rare earths elements indicate compositions similar to the compositions of volcanic arc magmatism with enrichment in LILEs and LREEs, and depletion in HFSEs and HREEs. The multielement pattern shows positive anomalies in Th, U, K, Pb, Nd and Dy and negative anomalies in Ba, Nb, Ta, P and Ti. They exhibit strong fractionation in the LREEs in relation to the HREEs ([La/Yb]N = 21.96 to 31.94) and discrete negative anomaly in Eu (Eu/EuN = 0.69 to 0.77). The 143Nd/ 144Nd ratios are between 0.512106 and 0.512148, values that generate εNd(0) are between -9.56 and -10.37, and the 87Sr/86Sr ratios are between 0.71016 and 0.71036, indicating mantle source enriched with crustal contamination process. TDM values (Ga) range from 1.09 to 1.29. Based on the geochemical and petrological data it is suggested that the magmas derive from melts of a subduction-related metassomatized source, and that the evolution of this magmatism was dominated by mineral fractionation processes, mainly involving clinopyroxene, feldspar and leucite.