Volcanic activity typically switches between high-activity states with many eruptions and low-act... more Volcanic activity typically switches between high-activity states with many eruptions and low-activity states with few or no eruptions. We present a simple two-regime physics-informed statistical model that allows interpreting temporal modulations in eruptive activity. The model enhances comprehension and comparison of different volcanic systems and enables homogeneous integration into multivolcano hazard assessments that account for potential changes in volcanic regimes. The model satisfactorily fits the eruptive history of the three active volcanoes in the Neapolitan area, Italy (Mt. Vesuvius, Campi Flegrei, and Ischia) which encompass a wide range of volcanic behaviors. We find that these volcanoes have appreciably different processes for triggering and ending high-activity periods connected to different dominant volcanic processes controlling their eruptive activity, with different characteristic times and activity rates (expressed as number of eruptions per time interval). Pres...
We have carried out a complete study of the Upper-Triassic alkaline magmatism on the northwestern... more We have carried out a complete study of the Upper-Triassic alkaline magmatism on the northwestern margin of the Iberian Chain. This magmatism is composed of mafic sills, which intrude the Keuper facies in two geographic sectors: the Cameros Massif (NW) and the Moncayo Massif (SE). In both of these sectors, the rocks are characterised by an intense alteration (spilitisation). The field relationships point to an Upper Triassic age for the studied sills, given that: 1) interactions are recognised between the magma and wet, unconsolidated host sediments, suggesting that the magma was emplaced during or shortly after the deposition of the Keuper facies; 2) in the Moncayo sector a conglomerate bed that includes igneous clasts overlaies the sills and passes upwards to the Norian-Rhaetian Imón Fm. According to the petrological and geochemical features of the sills, an internal differentiation can be recognised inwards, with the developments of three zones: chilled margins, central facies and pegmatoid facies. The rocks are porphyritic and are mainly composed of phenocrysts of pseudomorphed olivine and microcrysts of plagioclase, opaque minerals and minor clinopyroxene. Vesicles and xenoliths of the host sedimentary rocks are also recognised, especially at the chilled margins. The mineral assemblage is constant across the sills but the mineral proportions vary among the different zones. The sills are basic to intermediate rocks. They are classified as basalts to dacites with an alkaline geochemical affinity. According to the trace element contents, this magmatism is related to an enriched sub-lithospheric mantle source affected by crustal contamination. Considering the Upper Triassic magmatisms from southwestern Europe, two types can be distinguished. On the one hand, the magmatisms in the Catalonian Coastal Ranges and SE France are paleogeographically located in the inner platform and are related to deep, astenospheric mantle sources with no evidence of crustal contamination. On the other hand, the magmatisms in the NW Iberian Chain -this study-, the External Betics and the Brescian Prealps are situated in a more litoral position and are related to a shallower, lithospheric mantle with evidence of crustal contamination. These differences could be related to the thickness of the continental crust, which might be thinner in the inner areas of the platform
ABSTRACT Small igneous intrusions can be regarded as scale models of the behaviour of large magma... more ABSTRACT Small igneous intrusions can be regarded as scale models of the behaviour of large magma chambers. We have carried out a detailed petrological and geochemical study across a thin (< 0.5 m) mafic sill located in the Catalonian Coastal Ranges, in the vicinity of Calella de Palafrugell (NE Spain). It is a late-Cretaceous sub-horizontal alkaline lamprophyre, classified as a camptonite. The sill is visibly zoned, showing well developed chilled margins, several levels of vesicles and accumulation of large mafic crystals towards the bottom. According to their composition, these crystals are inherited antecrysts. The whole-rock composition varies across the sill, indicating that the sill is compositionally zoned. However, the mineral compositions are constant, suggesting that the magma emplaced in a single pulse. The whole-rock compositional variations reveal that the chilled margins are more evolved than the centre of the sill; this is especially clear for the lower chilled margin, which defines a marginal reversal. Therefore, the compositional zoning of the sill does not correlate with a normal fractionation trend inwards. Instead, it agrees with the variable proportions of antecrysts across the sill: the higher the proportion of antecrysts, the more primitive the whole-rock composition. In order to verify that the presence of antecrysts controls the whole-rock variations, a trace element model has been developed. Given that the sill displays a porphyritic texture defined by large antecrysts set in a fine-grained groundmass, the geochemical model quantifies the relative contributions of the antecrysts and the groundmass to the whole-rock compositions. Because the antecryst and whole-rock compositions were analysed for the different samples collected across the sill, the groundmass composition could be calculated for each sample. The obtained groundmass compositions are constant and more evolved than whole-rock compositions, supporting that the whole-rock variations are solely produced by the different proportions of antecrysts across the sill. The mean groundmass composition can be therefore considered representative of the homogeneous groundmass of the sill. It represents the host magma which carried the antecrysts up to the emplacement level. The results of the model have been statistically tested by means of a principal component analysis (PCA). The distribution of the antecryst, whole-rock and groundmass compositions in a PC2 vs. PC1 plot shows that the whole-rock compositions define a linear trend between the groundmass and the antecryst compositions, where whole-rocks plot closer to the antecrysts as the proportion of antecrysts in the rock increases. The obtained results prove that antecrysts affect whole-rock compositions. The accumulation of the antecrysts towards the bottom of the sill, together with the calculation of settling velocities for the antecrysts and cooling velocities for the magma, indicate that the gravitational settling of antecrysts during cooling is responsible for the varying proportions of antecrysts and therefore for the whole rock compositional zoning. This study reveals that crystal settling is a significant process in triggering compositional zoning of igneous intrusions even at the cm-scale, provided that the magma carries large crystals upon emplacement.
Electronic Supplementary Material: "Event trees and epistemic uncertainty in long-term volca... more Electronic Supplementary Material: "Event trees and epistemic uncertainty in long-term volcanic hazard assessment of rift volcanoes: the example of Aluto (Central Ethiopia)", by Tierz, P., Clarke, B., Calder, E. S., Dessalegn, F., Lewi, E., Yirgu, G., Fontijn, K., Crummy, J. M., and Loughlin, S. C., submitted to Geochemistry, Geophysics, Geosystems. The datasets contain volcanological data on analogue (i.e. similar) volcanoes of Aluto volcano (Ethiopia), including conditional probabilities of eruption size, number of eruptions with specific volcanic phenomena reported and values of volcano analogy calculated using the VOLCano ANalogues Search tool (VOLCANS, Tierz et al., 2019, https://doi.org/10.1007/s00445-019-1336-3). These type of data can be used to parameterise event tree models (e.g. Newhall and Hoblitt, 2002, https://doi.org/10.1007/s004450100173; Marzocchi et al., 2010, https://doi.org/10.1007/s00445-010-0357-8) and, thus, quantify volcanic hazard at a particular v...
The manuscript presents a collection of 'thematic' maps for the probability of vent opening, give... more The manuscript presents a collection of 'thematic' maps for the probability of vent opening, given eruption, at San Salvador (El Salvador) and Nejapa-Chiltepe (Nicaragua) volcanic complexes. By 'thematic', the authors interpret that vent-opening-probability Interactive comment on Nat.
The manuscript presents a collection of 'thematic' maps for the probability of vent opening, give... more The manuscript presents a collection of 'thematic' maps for the probability of vent opening, given eruption, at San Salvador (El Salvador) and Nejapa-Chiltepe (Nicaragua) volcanic complexes. By 'thematic', the authors interpret that vent-opening-probability maps are built using data points (or areas, including epistemic uncertainty) of past C1 Printer-friendly version Discussion paper pyroclastic density current generation at Soufrière Hills volcano.
The Panticosa pluton is one of multiple granitic plutons cropping out in the Pyrenean Axial Zone,... more The Panticosa pluton is one of multiple granitic plutons cropping out in the Pyrenean Axial Zone, which corresponds to the Palaeozoic core of the Pyrenees. Mafic dikes cut both the Panticosa pluton and its Devonian metasedimentary country rocks. According to their mineralogy and mineral composition, these dikes can be classified into two different groups, with little textural variations: a calc-alkaline group and an alkaline group. The calcalkaline rocks (spessartites and calc-alkaline diabases) include calcic to sodic Pl, slightly Ti-rich Amp and substantial Qz. In contrast, the alkaline rocks (camptonites and alkaline diabases) are composed of calcic Pl, Ti-rich Cpx, Ol pseudomorphs and inherited constituents (megacrysts and enclaves). The composition of Pl and the main ferromagnesian phase (Amp in calc-alkaline group and Cpx in alkaline group) is coherent with the geochemical affinity assigned to both groups. The megacrysts in the alkaline group are predominantly Krs and Ts, with a deep-origin according to thermobarometric calculations. A detailed mineral chemistry study of the phases observed inside the enclaves is necessary to better comprehend the petrogenesis of the magmas which generated these alkaline rocks.
Dynamically scaled brittle/ductile analogue models have been performed. Experiments consisted of ... more Dynamically scaled brittle/ductile analogue models have been performed. Experiments consisted of the compression of a sand-pack with a basal ductile layer of silicone putty acting as a decollement level. The boundary conditions were chosen to analyze the influence of the lateral migration of the ductile level and the strain rate on the deformational pattern. Results show that when the ductile level migrates laterally, the higher thickening is obtained far from the back-stop creating a high relief in the pro-wedge region.
Hazard assessments of PDCs and lahars represent the foundation for estimating the substantial ris... more Hazard assessments of PDCs and lahars represent the foundation for estimating the substantial risk that these volcanic mass flows pose to the human environment. Unfortunately, these hazard assessments are complicated by the spatio-temporal complexity associated with the processes of triggering, propagation (including flow transitions) and emplacement of PDCs and lahars (e.g.
Penelitian ini bertujuan untuk mengetahui kemampuan pemahaman konsep matematika melalui model pem... more Penelitian ini bertujuan untuk mengetahui kemampuan pemahaman konsep matematika melalui model pembelajaran auditory intellectually repetition pada siswa kelas VIII MTs Negeri 1 Makassar. Jenis penelitian ini adalah quasi eksperiment, dengan teknik pengumpulan data menggunakan tes, dokumentasi, dan wawancara. Populasi dalam penelitian ini adalah seluruh siswa kelas VIII MTs Negeri 1 Makassar sebanyak 40 orang yang terdiri dari 10 kelas. Teknik pengambilan sampel yang digunakan adalah simple random sampling. Sampel yang terpilih kelas VIII.4 sebagai kelas kontrol dan kelas VIII.5 sebagai kelas eksperimen. Teknik analisis data yang digunakan adalah analisis deskriptif dan inferensial. Hasil penelitian diperoleh bahwa:(1) kemampuan pemahaman konsep matematika melalui model pemberlajaran auditory intellectually repetition pada siswa kelas VIII MTs Negeri 1 Makassar sebesar 27,50% berada pada kategori sedang, sedangkan tanpa menggunakan model pembelajaran auditory intellectually repetition sebesar 27,50% pada kategori rendah, (2) terdapat perbedaan kemampuan pemahaman konsep matematika yang menggunakan model pembelajaran auditory intellectually repetition dan tanpa menggunakan model auditory intellectually repetition pada siswa kelas VIII MTs Negeri 1 Makassar.
The definition of a suite of analogue volcanoes, or volcanoes that are considered to share enough... more The definition of a suite of analogue volcanoes, or volcanoes that are considered to share enough characteristics as to be considered exchangeable to a certain extent, is becoming a key component of volcanic hazard assessment. This is particularly the case for volcanoes where data are lacking or scarce. Moreover, volcano comparisons have often been based on similarities and differences inferred through expert judgement and not necessarily informed by volcano characteristics from global datasets. These similarities can be based on a range of features, from very simplified (e.g. statrovolcanoes) to very specific (e.g. detailed eruption chronologies), and may be strongly influenced by the personal experience of individuals or teams conducting the analogue analysis. In this work, we present VOLCANS (VOLCano ANalogues Search)—an objective, structured and reproducible method to identify sets of analogue volcanoes from global volcanological databases. Five overarching criteria (tectonic se...
Two important reverse dipolar magnetic anomalies in the Iberian Chain (Spain) are located over Pe... more Two important reverse dipolar magnetic anomalies in the Iberian Chain (Spain) are located over Permian igneous rocks. A detailed study of one of them, the Loscos magnetic anomaly, where the geological structure is well constrained, reveals that the source of the anomaly must be a reverse remanent magnetisation carried by igneous rocks, acquired during the period of the Kiaman reverse magnetic superchron. Magnetic and gravimetric detailed survey (with 50 new gravimetric measurements and 8 main magnetic profiles-six of them N-S and the rest E-Wwith a total length of 40km), together with a study of the petrophysical characteristics of igneous materials, data processing and interpretation (upward continuation, 2.5D modelling, etc.) allowed to characterize qualitatively the anomaly and its source. Two overlapping anomalies with different wavelength were identified, indicating the presence of a shallower strongly altered igneous body with heterogeneous magnetic properties, and a deeper, large igneous body, responsible for the main, long-wavelength anomaly.
Journal of Geophysical Research: Solid Earth, 2018
The metropolitan area of Napoli (∼3 M inhabitants) in southern Italy is located in between two ex... more The metropolitan area of Napoli (∼3 M inhabitants) in southern Italy is located in between two explosive active volcanoes: Somma-Vesuvius and Campi Flegrei. Pyroclastic density currents (PDCs) from these volcanoes may reach the city center, as witnessed by the Late Quaternary stratigraphic record. Here we compute a novel multivolcano Probabilistic Volcanic Hazard Assessment of PDCs, in the next 50 years, by combining the probability of PDC invasion from each volcano (assuming that they erupt independently) over the city of Napoli and its surroundings. We model PDC invasion with the energy cone model accounting for flows of very different (but realistic) mobility and use the Bayesian Event Tree for Volcanic Hazard to incorporate other volcano-specific information such as the probability of eruption or the spatial variability in vent opening probability. Worthy of note, the method provides a complete description of Probabilistic Volcanic Hazard Assessment, that is, it yields percentile maps displaying the epistemic uncertainty associated with our best (aleatory) hazard estimation. Since the probability density functions of the model parameters of the energy cone are unknown, we propose an ensemble of different hazard assessments based on different assumptions on such probability density functions. The ensemble merges two plausible distributions for the collapse height, reflecting a source of epistemic (specifically, parametric) uncertainty. We also apply a novel quantification for a spatially varying epistemic uncertainty associated to PDC simulations.
for data/knowledge sharing as well as fruitful discussions. We are very grateful to Raffaello Cio... more for data/knowledge sharing as well as fruitful discussions. We are very grateful to Raffaello Cioni and Eisuke Fujita for their thorough revision and to Roberto Sulpizio and Valerio Acocella for their careful editorial handling and their comments on our research work. All the received feedback helped us improve our manuscript.
Pyroclastic density currents (PDCs) are gravity-driven hot mixtures of gas and volcanic particles... more Pyroclastic density currents (PDCs) are gravity-driven hot mixtures of gas and volcanic particles which can propagate at high speed and cover distances up to several tens of kilometers around a given volcano. Therefore, they pose a severe hazard to the surroundings of explosive volcanoes able to produce such phenomena. Despite this threat, probabilistic volcanic hazard assessment (PVHA) of PDCs is still in an early stage of development. PVHA is rooted in the quantification of the large uncertainties (aleatory and epistemic) which characterize volcanic hazard analyses. This quantification typically requires a big dataset of hazard footprints obtained from numerical simulations of the physical process. For PDCs, numerical models range from very sophisticated (not useful for PVHA because of their very long runtimes) to very simple models (criticized because of their highly simplified physics). We present here a systematic and robust validation testing of a simple PDC model, the energy cone (EC), to unravel whether it can be applied to PVHA of PDCs. Using past PDC deposits at Somma-Vesuvius and Campi Flegrei (Italy), we assess the ability of EC to capture the values and variability in some relevant variables for hazard assessment, i.e., area of PDC invasion and maximum runout. In terms of area of invasion, the highest Jaccard coefficients range from 0.33 to 0.86 which indicates an equal or better performance compared to other volcanic mass-flow models. The p values for the observed maximum runouts vary from 0.003 to 0.44. Finally, the frequencies of PDC arrival computed from the EC are similar to those determined from the spatial distribution of past PDC deposits, with high PDC-arrival frequencies over an ∼8-km radius from the crater area at Somma-Vesuvius and around the Astroni crater at Campi Flegrei. The insights derived from our validation tests seem to indicate that the EC is a suitable candidate to compute PVHA of PDCs.
Volcanic activity typically switches between high-activity states with many eruptions and low-act... more Volcanic activity typically switches between high-activity states with many eruptions and low-activity states with few or no eruptions. We present a simple two-regime physics-informed statistical model that allows interpreting temporal modulations in eruptive activity. The model enhances comprehension and comparison of different volcanic systems and enables homogeneous integration into multivolcano hazard assessments that account for potential changes in volcanic regimes. The model satisfactorily fits the eruptive history of the three active volcanoes in the Neapolitan area, Italy (Mt. Vesuvius, Campi Flegrei, and Ischia) which encompass a wide range of volcanic behaviors. We find that these volcanoes have appreciably different processes for triggering and ending high-activity periods connected to different dominant volcanic processes controlling their eruptive activity, with different characteristic times and activity rates (expressed as number of eruptions per time interval). Pres...
We have carried out a complete study of the Upper-Triassic alkaline magmatism on the northwestern... more We have carried out a complete study of the Upper-Triassic alkaline magmatism on the northwestern margin of the Iberian Chain. This magmatism is composed of mafic sills, which intrude the Keuper facies in two geographic sectors: the Cameros Massif (NW) and the Moncayo Massif (SE). In both of these sectors, the rocks are characterised by an intense alteration (spilitisation). The field relationships point to an Upper Triassic age for the studied sills, given that: 1) interactions are recognised between the magma and wet, unconsolidated host sediments, suggesting that the magma was emplaced during or shortly after the deposition of the Keuper facies; 2) in the Moncayo sector a conglomerate bed that includes igneous clasts overlaies the sills and passes upwards to the Norian-Rhaetian Imón Fm. According to the petrological and geochemical features of the sills, an internal differentiation can be recognised inwards, with the developments of three zones: chilled margins, central facies and pegmatoid facies. The rocks are porphyritic and are mainly composed of phenocrysts of pseudomorphed olivine and microcrysts of plagioclase, opaque minerals and minor clinopyroxene. Vesicles and xenoliths of the host sedimentary rocks are also recognised, especially at the chilled margins. The mineral assemblage is constant across the sills but the mineral proportions vary among the different zones. The sills are basic to intermediate rocks. They are classified as basalts to dacites with an alkaline geochemical affinity. According to the trace element contents, this magmatism is related to an enriched sub-lithospheric mantle source affected by crustal contamination. Considering the Upper Triassic magmatisms from southwestern Europe, two types can be distinguished. On the one hand, the magmatisms in the Catalonian Coastal Ranges and SE France are paleogeographically located in the inner platform and are related to deep, astenospheric mantle sources with no evidence of crustal contamination. On the other hand, the magmatisms in the NW Iberian Chain -this study-, the External Betics and the Brescian Prealps are situated in a more litoral position and are related to a shallower, lithospheric mantle with evidence of crustal contamination. These differences could be related to the thickness of the continental crust, which might be thinner in the inner areas of the platform
ABSTRACT Small igneous intrusions can be regarded as scale models of the behaviour of large magma... more ABSTRACT Small igneous intrusions can be regarded as scale models of the behaviour of large magma chambers. We have carried out a detailed petrological and geochemical study across a thin (< 0.5 m) mafic sill located in the Catalonian Coastal Ranges, in the vicinity of Calella de Palafrugell (NE Spain). It is a late-Cretaceous sub-horizontal alkaline lamprophyre, classified as a camptonite. The sill is visibly zoned, showing well developed chilled margins, several levels of vesicles and accumulation of large mafic crystals towards the bottom. According to their composition, these crystals are inherited antecrysts. The whole-rock composition varies across the sill, indicating that the sill is compositionally zoned. However, the mineral compositions are constant, suggesting that the magma emplaced in a single pulse. The whole-rock compositional variations reveal that the chilled margins are more evolved than the centre of the sill; this is especially clear for the lower chilled margin, which defines a marginal reversal. Therefore, the compositional zoning of the sill does not correlate with a normal fractionation trend inwards. Instead, it agrees with the variable proportions of antecrysts across the sill: the higher the proportion of antecrysts, the more primitive the whole-rock composition. In order to verify that the presence of antecrysts controls the whole-rock variations, a trace element model has been developed. Given that the sill displays a porphyritic texture defined by large antecrysts set in a fine-grained groundmass, the geochemical model quantifies the relative contributions of the antecrysts and the groundmass to the whole-rock compositions. Because the antecryst and whole-rock compositions were analysed for the different samples collected across the sill, the groundmass composition could be calculated for each sample. The obtained groundmass compositions are constant and more evolved than whole-rock compositions, supporting that the whole-rock variations are solely produced by the different proportions of antecrysts across the sill. The mean groundmass composition can be therefore considered representative of the homogeneous groundmass of the sill. It represents the host magma which carried the antecrysts up to the emplacement level. The results of the model have been statistically tested by means of a principal component analysis (PCA). The distribution of the antecryst, whole-rock and groundmass compositions in a PC2 vs. PC1 plot shows that the whole-rock compositions define a linear trend between the groundmass and the antecryst compositions, where whole-rocks plot closer to the antecrysts as the proportion of antecrysts in the rock increases. The obtained results prove that antecrysts affect whole-rock compositions. The accumulation of the antecrysts towards the bottom of the sill, together with the calculation of settling velocities for the antecrysts and cooling velocities for the magma, indicate that the gravitational settling of antecrysts during cooling is responsible for the varying proportions of antecrysts and therefore for the whole rock compositional zoning. This study reveals that crystal settling is a significant process in triggering compositional zoning of igneous intrusions even at the cm-scale, provided that the magma carries large crystals upon emplacement.
Electronic Supplementary Material: "Event trees and epistemic uncertainty in long-term volca... more Electronic Supplementary Material: "Event trees and epistemic uncertainty in long-term volcanic hazard assessment of rift volcanoes: the example of Aluto (Central Ethiopia)", by Tierz, P., Clarke, B., Calder, E. S., Dessalegn, F., Lewi, E., Yirgu, G., Fontijn, K., Crummy, J. M., and Loughlin, S. C., submitted to Geochemistry, Geophysics, Geosystems. The datasets contain volcanological data on analogue (i.e. similar) volcanoes of Aluto volcano (Ethiopia), including conditional probabilities of eruption size, number of eruptions with specific volcanic phenomena reported and values of volcano analogy calculated using the VOLCano ANalogues Search tool (VOLCANS, Tierz et al., 2019, https://doi.org/10.1007/s00445-019-1336-3). These type of data can be used to parameterise event tree models (e.g. Newhall and Hoblitt, 2002, https://doi.org/10.1007/s004450100173; Marzocchi et al., 2010, https://doi.org/10.1007/s00445-010-0357-8) and, thus, quantify volcanic hazard at a particular v...
The manuscript presents a collection of 'thematic' maps for the probability of vent opening, give... more The manuscript presents a collection of 'thematic' maps for the probability of vent opening, given eruption, at San Salvador (El Salvador) and Nejapa-Chiltepe (Nicaragua) volcanic complexes. By 'thematic', the authors interpret that vent-opening-probability Interactive comment on Nat.
The manuscript presents a collection of 'thematic' maps for the probability of vent opening, give... more The manuscript presents a collection of 'thematic' maps for the probability of vent opening, given eruption, at San Salvador (El Salvador) and Nejapa-Chiltepe (Nicaragua) volcanic complexes. By 'thematic', the authors interpret that vent-opening-probability maps are built using data points (or areas, including epistemic uncertainty) of past C1 Printer-friendly version Discussion paper pyroclastic density current generation at Soufrière Hills volcano.
The Panticosa pluton is one of multiple granitic plutons cropping out in the Pyrenean Axial Zone,... more The Panticosa pluton is one of multiple granitic plutons cropping out in the Pyrenean Axial Zone, which corresponds to the Palaeozoic core of the Pyrenees. Mafic dikes cut both the Panticosa pluton and its Devonian metasedimentary country rocks. According to their mineralogy and mineral composition, these dikes can be classified into two different groups, with little textural variations: a calc-alkaline group and an alkaline group. The calcalkaline rocks (spessartites and calc-alkaline diabases) include calcic to sodic Pl, slightly Ti-rich Amp and substantial Qz. In contrast, the alkaline rocks (camptonites and alkaline diabases) are composed of calcic Pl, Ti-rich Cpx, Ol pseudomorphs and inherited constituents (megacrysts and enclaves). The composition of Pl and the main ferromagnesian phase (Amp in calc-alkaline group and Cpx in alkaline group) is coherent with the geochemical affinity assigned to both groups. The megacrysts in the alkaline group are predominantly Krs and Ts, with a deep-origin according to thermobarometric calculations. A detailed mineral chemistry study of the phases observed inside the enclaves is necessary to better comprehend the petrogenesis of the magmas which generated these alkaline rocks.
Dynamically scaled brittle/ductile analogue models have been performed. Experiments consisted of ... more Dynamically scaled brittle/ductile analogue models have been performed. Experiments consisted of the compression of a sand-pack with a basal ductile layer of silicone putty acting as a decollement level. The boundary conditions were chosen to analyze the influence of the lateral migration of the ductile level and the strain rate on the deformational pattern. Results show that when the ductile level migrates laterally, the higher thickening is obtained far from the back-stop creating a high relief in the pro-wedge region.
Hazard assessments of PDCs and lahars represent the foundation for estimating the substantial ris... more Hazard assessments of PDCs and lahars represent the foundation for estimating the substantial risk that these volcanic mass flows pose to the human environment. Unfortunately, these hazard assessments are complicated by the spatio-temporal complexity associated with the processes of triggering, propagation (including flow transitions) and emplacement of PDCs and lahars (e.g.
Penelitian ini bertujuan untuk mengetahui kemampuan pemahaman konsep matematika melalui model pem... more Penelitian ini bertujuan untuk mengetahui kemampuan pemahaman konsep matematika melalui model pembelajaran auditory intellectually repetition pada siswa kelas VIII MTs Negeri 1 Makassar. Jenis penelitian ini adalah quasi eksperiment, dengan teknik pengumpulan data menggunakan tes, dokumentasi, dan wawancara. Populasi dalam penelitian ini adalah seluruh siswa kelas VIII MTs Negeri 1 Makassar sebanyak 40 orang yang terdiri dari 10 kelas. Teknik pengambilan sampel yang digunakan adalah simple random sampling. Sampel yang terpilih kelas VIII.4 sebagai kelas kontrol dan kelas VIII.5 sebagai kelas eksperimen. Teknik analisis data yang digunakan adalah analisis deskriptif dan inferensial. Hasil penelitian diperoleh bahwa:(1) kemampuan pemahaman konsep matematika melalui model pemberlajaran auditory intellectually repetition pada siswa kelas VIII MTs Negeri 1 Makassar sebesar 27,50% berada pada kategori sedang, sedangkan tanpa menggunakan model pembelajaran auditory intellectually repetition sebesar 27,50% pada kategori rendah, (2) terdapat perbedaan kemampuan pemahaman konsep matematika yang menggunakan model pembelajaran auditory intellectually repetition dan tanpa menggunakan model auditory intellectually repetition pada siswa kelas VIII MTs Negeri 1 Makassar.
The definition of a suite of analogue volcanoes, or volcanoes that are considered to share enough... more The definition of a suite of analogue volcanoes, or volcanoes that are considered to share enough characteristics as to be considered exchangeable to a certain extent, is becoming a key component of volcanic hazard assessment. This is particularly the case for volcanoes where data are lacking or scarce. Moreover, volcano comparisons have often been based on similarities and differences inferred through expert judgement and not necessarily informed by volcano characteristics from global datasets. These similarities can be based on a range of features, from very simplified (e.g. statrovolcanoes) to very specific (e.g. detailed eruption chronologies), and may be strongly influenced by the personal experience of individuals or teams conducting the analogue analysis. In this work, we present VOLCANS (VOLCano ANalogues Search)—an objective, structured and reproducible method to identify sets of analogue volcanoes from global volcanological databases. Five overarching criteria (tectonic se...
Two important reverse dipolar magnetic anomalies in the Iberian Chain (Spain) are located over Pe... more Two important reverse dipolar magnetic anomalies in the Iberian Chain (Spain) are located over Permian igneous rocks. A detailed study of one of them, the Loscos magnetic anomaly, where the geological structure is well constrained, reveals that the source of the anomaly must be a reverse remanent magnetisation carried by igneous rocks, acquired during the period of the Kiaman reverse magnetic superchron. Magnetic and gravimetric detailed survey (with 50 new gravimetric measurements and 8 main magnetic profiles-six of them N-S and the rest E-Wwith a total length of 40km), together with a study of the petrophysical characteristics of igneous materials, data processing and interpretation (upward continuation, 2.5D modelling, etc.) allowed to characterize qualitatively the anomaly and its source. Two overlapping anomalies with different wavelength were identified, indicating the presence of a shallower strongly altered igneous body with heterogeneous magnetic properties, and a deeper, large igneous body, responsible for the main, long-wavelength anomaly.
Journal of Geophysical Research: Solid Earth, 2018
The metropolitan area of Napoli (∼3 M inhabitants) in southern Italy is located in between two ex... more The metropolitan area of Napoli (∼3 M inhabitants) in southern Italy is located in between two explosive active volcanoes: Somma-Vesuvius and Campi Flegrei. Pyroclastic density currents (PDCs) from these volcanoes may reach the city center, as witnessed by the Late Quaternary stratigraphic record. Here we compute a novel multivolcano Probabilistic Volcanic Hazard Assessment of PDCs, in the next 50 years, by combining the probability of PDC invasion from each volcano (assuming that they erupt independently) over the city of Napoli and its surroundings. We model PDC invasion with the energy cone model accounting for flows of very different (but realistic) mobility and use the Bayesian Event Tree for Volcanic Hazard to incorporate other volcano-specific information such as the probability of eruption or the spatial variability in vent opening probability. Worthy of note, the method provides a complete description of Probabilistic Volcanic Hazard Assessment, that is, it yields percentile maps displaying the epistemic uncertainty associated with our best (aleatory) hazard estimation. Since the probability density functions of the model parameters of the energy cone are unknown, we propose an ensemble of different hazard assessments based on different assumptions on such probability density functions. The ensemble merges two plausible distributions for the collapse height, reflecting a source of epistemic (specifically, parametric) uncertainty. We also apply a novel quantification for a spatially varying epistemic uncertainty associated to PDC simulations.
for data/knowledge sharing as well as fruitful discussions. We are very grateful to Raffaello Cio... more for data/knowledge sharing as well as fruitful discussions. We are very grateful to Raffaello Cioni and Eisuke Fujita for their thorough revision and to Roberto Sulpizio and Valerio Acocella for their careful editorial handling and their comments on our research work. All the received feedback helped us improve our manuscript.
Pyroclastic density currents (PDCs) are gravity-driven hot mixtures of gas and volcanic particles... more Pyroclastic density currents (PDCs) are gravity-driven hot mixtures of gas and volcanic particles which can propagate at high speed and cover distances up to several tens of kilometers around a given volcano. Therefore, they pose a severe hazard to the surroundings of explosive volcanoes able to produce such phenomena. Despite this threat, probabilistic volcanic hazard assessment (PVHA) of PDCs is still in an early stage of development. PVHA is rooted in the quantification of the large uncertainties (aleatory and epistemic) which characterize volcanic hazard analyses. This quantification typically requires a big dataset of hazard footprints obtained from numerical simulations of the physical process. For PDCs, numerical models range from very sophisticated (not useful for PVHA because of their very long runtimes) to very simple models (criticized because of their highly simplified physics). We present here a systematic and robust validation testing of a simple PDC model, the energy cone (EC), to unravel whether it can be applied to PVHA of PDCs. Using past PDC deposits at Somma-Vesuvius and Campi Flegrei (Italy), we assess the ability of EC to capture the values and variability in some relevant variables for hazard assessment, i.e., area of PDC invasion and maximum runout. In terms of area of invasion, the highest Jaccard coefficients range from 0.33 to 0.86 which indicates an equal or better performance compared to other volcanic mass-flow models. The p values for the observed maximum runouts vary from 0.003 to 0.44. Finally, the frequencies of PDC arrival computed from the EC are similar to those determined from the spatial distribution of past PDC deposits, with high PDC-arrival frequencies over an ∼8-km radius from the crater area at Somma-Vesuvius and around the Astroni crater at Campi Flegrei. The insights derived from our validation tests seem to indicate that the EC is a suitable candidate to compute PVHA of PDCs.
Uploads
Papers by Pablo Tierz