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Zouzias, D., et K. St. Seymour. « MAGMA INTRUSION IN 'PROTO-CALDERA CALDERA' SYSTEMS : EXAMPLE FROM THE NISYROS VOLCANO ». Bulletin of the Geological Society of Greece 40, no 1 (8 juin 2018) : 512. http://dx.doi.org/10.12681/bgsg.16660.
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The interdependence of volcanism and tectonism has been focused upon in the last decade as a result of previously accumulated evidence, as well as, due to the application of remote sensing techniques in both these fields. Volcanoes depend on tectonic features such as faults for their positioning and operation and on petrotectonic environment for the chemistry of their magmas. Faults provide the plumbing system for magma ascent and therefore volcano localisation and distribution in space greatly depends on the tectonic pattern of an area. On the other hand, volcanoes locally imprint their volcanotectonic features such as radial and ring faults which result from cycles of magma replenishment (inflation) and evacuation (deflation) of magmatic reservoirs (magma chambers). Under this light, the area in the easternmost extremity of the Aegean Arc is being reconsidered. Our main preliminary findings of ongoing research in the area, using field and remote sensing methods indicate localization of volcanic activity on Kos and on the Datca Peninsula of Asian Minor since Miocene due to the northbounding faults of the Datca Graben. Localisation of volcanic vents and calderas in the Kos-Nisyros area follows intersection of a major tectonic line of northnorthwesterly trending faults the 'Kos-Nisyros-Tilos Line' with N50°E, N30°E and N20°W trending faults. On the well-preserved volcano ofNisyros the architecture of the volcanic edifice has significantly been affected by 'trap-door' volcanotectonics of a major volcanic infrastructure in the area namely the Kos-Caldera
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Ko, Kyoungtae, Sungwon Kim et Yongsik Gihm. « U-Pb Age Dating and Geochemistry of Soft-Sediment Deformation Structure-Bearing Late Cretaceous Volcano-Sedimentary Basins in the SW Korean Peninsula and Their Tectonic Implications ». Minerals 11, no 5 (14 mai 2021) : 520. http://dx.doi.org/10.3390/min11050520.
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Cretaceous volcano-sedimentary basins and successions in the Korean Peninsula are located along NE-SW- and NNE-SSW-trending sinistral strike–slip fault systems. Soft-sediment deformation structures (SSDS) of lacustrine sedimentary strata occur in the Wido, Buan, and Haenam areas of the southwestern Korean Peninsula. In this study, systematic geological, geochronological, and geochemical investigations of the volcanic-sedimentary successions were conducted to constrain the origin and timing of SSDS-bearing lacustrine strata. The SSDS-bearing strata is conformably underlain and overlain by volcanic rocks, and it contains much volcaniclastic sediment and is interbedded with tuffs. The studied SSDSs were interpreted to have formed by ground shaking during syndepositional earthquakes. U-Pb zircon ages of volcanic and volcaniclastic rocks within the studied volcano-sedimentary successions were ca. 87–84 Ma, indicating that active volcanism was concurrent with lacustrine sedimentation. Geochemical characteristics indicate that these mostly rhyolitic rocks are similar to subduction-related calc-alkaline volcanic rocks from an active continental margin. This suggests that the SSDSs in the study area were formed by earthquakes related to proximal volcanic activity due to the oblique subduction of the Paleo-Pacific Plate during the Late Cretaceous.
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McGUIRE, W. J. « Volcanic plumbing systems ». Journal of the Geological Society 150, no 2 (mars 1993) : 411–12. http://dx.doi.org/10.1144/gsjgs.150.2.0411.
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Tilling, R. I. « Volcanism and associated hazards : the Andean perspective ». Advances in Geosciences 22 (14 décembre 2009) : 125–37. http://dx.doi.org/10.5194/adgeo-22-125-2009.
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Abstract. Andean volcanism occurs within the Andean Volcanic Arc (AVA), which is the product of subduction of the Nazca Plate and Antarctica Plates beneath the South America Plate. The AVA is Earth's longest but discontinuous continental-margin volcanic arc, which consists of four distinct segments: Northern Volcanic Zone, Central Volcanic Zone, Southern Volcanic Zone, and Austral Volcanic Zone. These segments are separated by volcanically inactive gaps that are inferred to indicate regions where the dips of the subducting plates are too shallow to favor the magma generation needed to sustain volcanism. The Andes host more volcanoes that have been active during the Holocene (past 10 000 years) than any other volcanic region in the world, as well as giant caldera systems that have produced 6 of the 47 largest explosive eruptions (so-called "super eruptions") recognized worldwide that have occurred from the Ordovician to the Pleistocene. The Andean region's most powerful historical explosive eruption occurred in 1600 at Huaynaputina Volcano (Peru). The impacts of this event, whose eruptive volume exceeded 11 km3, were widespread, with distal ashfall reported at distances >1000 km away. Despite the huge size of the Huaynaputina eruption, human fatalities from hazardous processes (pyroclastic flows, ashfalls, volcanogenic earthquakes, and lahars) were comparatively small owing to the low population density at the time. In contrast, lahars generated by a much smaller eruption (<0.05 km3) in 1985 of Nevado del Ruiz (Colombia) killed about 25 000 people – the worst volcanic disaster in the Andean region as well as the second worst in the world in the 20th century. The Ruiz tragedy has been attributed largely to ineffective communications of hazards information and indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent hazardous eruptions in Chile, Colombia, Ecuador, and Peru has spurred significant improvements in reducing volcano risk in the Andean region. But much remains to be done.
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Bischoff, Alan, Andrew Nicol, Jim Cole et Darren Gravley. « Stratigraphy of Architectural Elements of a Buried Monogenetic Volcanic System ». Open Geosciences 11, no 1 (25 octobre 2019) : 581–616. http://dx.doi.org/10.1515/geo-2019-0048.
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Abstract Large volumes of magma emplaced and deposited within sedimentary basins can have an impact on the architecture and geological evolution of these basins. Over the last decade, continuous improvement in techniques such as seismic volcano-stratigraphy and 3D visualisation of igneous bodies has helped increase knowledge about the architecture of volcanic systems buried in sedimentary basins. Here, we present the complete architecture of the Maahunui Volcanic System (MVS), a middle Miocene monogenetic volcanic field now buried in the offshore Canterbury Basin, South Island of New Zealand. We show the location, geometry, size, and stratigraphic relationships between 25 main intrusive, extrusive and sedimentary architectural elements, in a comprehensive volcano-stratigraphic framework that explains the evolution of the MVS from emplacement to complete burial in the host sedimentary basin. Understanding the relationships between these diverse architectural elements allows us to reconstruct the complete architecture of the MVS, including its shallow (<3 km) plumbing system, the morphology of the volcanoes, and their impact in the host sedimentary basin during their burial. The plumbing system of the MVS comprises saucer-shaped sills, dikes and sill swarms, minor stocks and laccoliths, and pre-eruptive strata deformed by intrusions. The eruptive and associated sedimentary architectural elements define the morphology of volcanoes in the MVS, which comprise deep-water equivalents of crater and cone-type volcanoes. After volcanism ceased, the process of degradation and burial of volcanic edifices formed sedimentary architectural elements such as inter-cone plains, epiclastic plumes, and canyons. Insights from the architecture of the MVS can be used to explore for natural resources such as hydrocarbons, geothermal energy and minerals in buried and active volcanic systems elsewhere.
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Nakamura, Yoichi, Kazuyoshi Fukushima, Xinghai Jin, Motoo Ukawa Teruko Sato et Yayoi Hotta. « Mitigation Systems by Hazard Maps, Mitigation Plans, and Risk Analyses Regarding Volcanic Disasters in Japan ». Journal of Disaster Research 3, no 4 (1 août 2008) : 297–304. http://dx.doi.org/10.20965/jdr.2008.p0297.
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More than 60 volcanic hazard maps have been published on 38 of Japan’s 108 active volcanoes. Two maps were published before 1990, 17 after the 1991 eruptions of Unzen, and 19 after the 2000 eruptions of Usuzan and Miyakejima. Large eruptions greatly increase concern over volcanic hazards. The earlier academic maps themselves have changed from being specialist-oriented to being designed to be more easily understood with volcanic terms clearly explained. This is especially true of revised maps. The 1961 Disaster Countermeasures Basic Act directs that local disaster management plans be promoted by local governments, but only 5 of the local governments in the 25 prefectures neighboring on active volcanoes have set up established specific volcano-oriented antidisaster programs. Others mention volcanic disaster measures in the context of general or storm and flood disaster measures, and another six make no mention of particular measures for volcanic disasters. This lack of concern is somewhat understandably related to budget policies, but real-time hazard maps with probability tree algorithms for forecasting volcanic events are needed to manage potential volcanic disasters effectively. For this purpose, volcanic disaster measures with volcanic risk, or threat analyses assessments must be completed, but no local governments have yet conducted assessments of volcanic risk analyses. Whatever and however complex the reasons, local governments should, cooperating with volcanologists and supported by local residents, take action before an eruption next occurs.
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Uchôa, Jéssica, Fátima Viveiros, Rafaela Tiengo et Artur Gil. « Detection of Geothermal Anomalies in Hydrothermal Systems Using ASTER Data : The Caldeiras da Ribeira Grande Case Study (Azores, Portugal) ». Sensors 23, no 4 (17 février 2023) : 2258. http://dx.doi.org/10.3390/s23042258.
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Current-day volcanic activity in the Azores archipelago is characterized by seismic events and secondary manifestations of volcanism. Remote sensing techniques have been widely employed to monitor deformation in volcanic systems, map lava flows, or detect high-temperature gas emissions. However, using satellite imagery, it is still challenging to identify low-magnitude thermal changes in a volcanic system. In 2010, after drilling a well for geothermal exploration on the northern flank of Fogo Volcano on São Miguel Island, a new degassing and thermal area emerged with maximum temperatures of 100 °C. In the present paper, using the ASTER sensor, we observed changes in the near-infrared signals (15 m spatial resolution) six months after the anomaly emerged. In contrast, the thermal signal (90 m spatial resolution) only changed its threshold value one and a half years after the anomaly was recognized. The results show that wavelength and spatial resolution can influence the response time in detecting changes in a system. This paper reiterates the importance of using thermal imaging and high spatial resolution images to monitor and map thermal anomalies in hydrothermal systems such as those found in the Azores.
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Cas, Ray, et Wilson Wildner. « Volcanism and associated regimes - the complexity of volcanic systems ». Journal of Volcanology and Geothermal Research 118, no 1-2 (novembre 2002) : vii. http://dx.doi.org/10.1016/s0377-0273(02)00246-9.
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Sahagian, D. L., et A. A. Proussevitch. « Bubbles in volcanic systems ». Nature 359, no 6395 (octobre 1992) : 485. http://dx.doi.org/10.1038/359485a0.
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Aiuppa, A., D. R. Baker et J. D. Webster. « Halogens in volcanic systems ». Chemical Geology 263, no 1-4 (juin 2009) : 1–18. http://dx.doi.org/10.1016/j.chemgeo.2008.10.005.
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Ziska, Heri, Uni Árting et Morten S. Riishuus. « Interaction between volcanic and non-volcanic systems and its implication for prospectivity in the Faroe–Shetland Basin, NE Atlantic continental margin ». Petroleum Geoscience 28, no 2 (17 février 2022) : petgeo2021–058. http://dx.doi.org/10.1144/petgeo2021-058.
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Exploration in the Faroe–Shetland Basin on the Faroese Continental Shelf has revealed thick and complex volcanic successions and discovery of inter-volcanic oil-bearing siliciclastic sandstone fan deposits in the central parts of the basin. The possibility for such play types at the fringe of the North Atlantic Igneous Province requires a better understanding of the interaction between competing sedimentary and volcanic depositional transport systems. We have re-examined volcanic units in cuttings from exploration wells in the greater Judd Sub-basin area for evaluation of facies and geochemical affinity. This allows for chemostratigraphical correlation of wells to the absolute radiometrically age-constrained Faroe Islands Basalt Group. The collective well data were subsequently tied to a regional interpretation of 2D seismic data which facilitated a detailed interpretation of temporal development of the volcanic successions in the Judd Sub-basin area in terms of geometry, volcanic facies, depositional environment, and interdigitation with non-volcanic sedimentary units.The Judd Sub-basin was influenced by major volcanic phases during pre-breakup and syn-breakup. The influence was both direct, in the form of volcanic deposits, and indirect, in the form of obstructing established sedimentary transport systems and creating new provenance areas. The volcanic transport systems reached different areas of the Judd Sub-basin at different times during pre-breakup volcanism. The earliest incursion in the west was during late Mid Paleocene (T-sequence T31/T32). With at least three stratigraphically discrete incursions of volcanic material into the Judd Sub-basin, possibilities arise for sub- and inter-volcanic stratigraphic and structural traps for each incursion.
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Phillips, Thomas B., et Craig Magee. « Structural controls on the location, geometry and longevity of an intraplate volcanic system : the Tuatara Volcanic Field, Great South Basin, New Zealand ». Journal of the Geological Society 177, no 5 (5 juin 2020) : 1039–56. http://dx.doi.org/10.1144/jgs2020-050.
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Intraplate volcanism is widely distributed across the continents, but the controls on the 3D geometry and longevity of individual volcanic systems remain poorly understood. Geophysical data provide insights into magma plumbing systems, but, as a result of the relatively low resolution of these techniques, it is difficult to evaluate how magma transits highly heterogeneous continental interiors. We use borehole-constrained 2D seismic reflection data to characterize the 3D geometry of the Tuatara Volcanic Field located offshore New Zealand's South Island and investigate its relationship with the pre-existing structure. This c. 270 km2 field is dominated by a dome-shaped lava edifice, surrounded and overlain by c. 69 volcanoes and >70 sills emplaced over 40 myr from the Late Cretaceous to Early Eocene (c. 85–45 Ma). The Tuatara Volcanic Field is located above a basement terrane boundary represented by the Livingstone Fault; the recently active Auckland Volcanic Field is similarly located along-strike on North Island. We suggest that the Livingstone Fault controlled the location of the Tuatara Volcanic Field by producing relief at the base of the lithosphere, thereby focussing lithospheric detachment over c. 40 myr, and provided a pathway that facilitated the ascent of magma. We highlight how observations from ancient intraplate volcanic systems may inform our understanding of active intraplate volcanic systems, including the Auckland Volcanic Field.Supplementary material: Interpreted seismic section showing well control on stratigraphic interpretation is available at https://doi.org/10.6084/m9.figshare.c.5004464
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Sigmarsson, Olgeir, et Sæmundur Ari Halldórsson. « Delimiting Bárðarbunga and Askja volcanic systems with Sr- and Nd-isotope ratios ». Jökull 65, no 1 (15 décembre 2015) : 17–27. http://dx.doi.org/10.33799/jokull2015.65.017.
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Volcanic systems represent a fundamental component of the neovolcanic zones in Iceland. They are composed of a central volcano and a fissure swarm, or a combination of the two. The 2014–2015 rifting event at the Bárðarbunga volcanic system produced basaltic lava approximately 40 km to the north of the central volcano, within a fissure swarm commonly attributed to the Askja volcanic system, highlighting the complex tectonic structure of a region, directly above the Iceland mantle plume. New analyses of Sr- and Nd-isotope ratios from the new lava (Holuhraun), and the underlying older Holuhraun lava, show that they have identical values to those of the Bárðarbunga-Veiðivötn lavas and tephra erupted during the Holocene. Moreover, comparison with published high-precision radiogenic isotope data, reveals that Holocene lavas and tephra from the Bárðarbunga and Askja systems are characterized by contrasting Sr- and Nd-isotope ratios, with the notable exception of the Þjórsárhraun lava and two early Holocene lavas from the extreme west and east of the Veiðivötn fissure swarm. The $^{87}$Sr/$^{86}$Sr and $^{143}$Nd/$^{144}$Nd isotope ratios can thus be utilized to define the provenance of lava flows north of the Vatnajökull ice cap, ascertaining that the large lava fields of Krepputunguhraun and Fjallsendahraun (Frambruni) must also have originated within the Bárðarbunga volcanic system.
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Flower, Verity J. B., Thomas Oommen et Simon A. Carn. « Improving global detection of volcanic eruptions using the Ozone Monitoring Instrument (OMI) ». Atmospheric Measurement Techniques 9, no 11 (16 novembre 2016) : 5487–98. http://dx.doi.org/10.5194/amt-9-5487-2016.
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Abstract. Volcanic eruptions pose an ever-present threat to human populations around the globe, but many active volcanoes remain poorly monitored. In regions where ground-based monitoring is present the effects of volcanic eruptions can be moderated through observational alerts to both local populations and service providers, such as air traffic control. However, in regions where volcano monitoring is limited satellite-based remote sensing provides a global data source that can be utilised to provide near-real-time identification of volcanic activity. This paper details a volcanic plume detection method capable of identifying smaller eruptions than is currently feasible, which could potentially be incorporated into automated volcanic alert systems. This method utilises daily, global observations of sulfur dioxide (SO2) by the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite. Following identification and classification of known volcanic eruptions in 2005–2009, the OMI SO2 data, analysed using a logistic regression analysis, permitted the correct classification of volcanic events with an overall accuracy of over 80 %. Accurate volcanic plume identification was possible when lower-tropospheric SO2 loading exceeded ∼ 400 t. The accuracy and minimal user input requirements of the developed procedure provide a basis for incorporation into automated SO2 alert systems.
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Susetyono, Mardhiawan Tri, et Lucas Donny Setijadji. « Study of Active and Fossil Hydrothermal Systems in Ijen Caldera Complex and Merubetiri Mountains, East Java ». Indonesian Journal of Economic Geology 1, no 1 (30 décembre 2021) : 23–38. http://dx.doi.org/10.51835/ijeg.2021.1.1.340.
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Ore deposits formed at subduction zone are associated with magmatism activities that are represented by volcanic activities at the surface. In the Eastern Sunda Arc, one of active volcanic activity can be found in Ijen Caldera Complex. The complex has hydrothermal volcanic manifestations with a very acidic pH. Meanwhile in the south of Ijen Complex, there is ancient volcanic complex called Merubetiri Mountains that is proven to be well-mineralized at Tumpangpitu as high sulfidation and porphyry-style mineralizations. An understanding of hydrothermal activity and volcanic landforms in active volcanic systems can be used as a powerful tool to understanding hydrothermal systems. This paper presents the distinction between active hydrothermal systems and fossil hydrothermal systems as an exploration’s tool in ancient volcanic systems. The method used in this study is remote sensing with focus on volcanic landforms, geological structures, and distribution of alteration minerals. ASTER satellite imagery, Landsat 8 satellite imagery, and DEMNAS are used in this study. ASTER and Landsat 8 images are processed with Principle Component Analysis (PCA) and Direct Principle Component (DPC) methods to determine the distribution of alteration minerals that are associated with propylithic, argillic, advanced argillic, and silisic alterations. Semi-quantitative method is used to identify geological structures by automatic lineament detection. Meanwhile, qualitative method is used by manual lineaments delineation on the DEM imagery. Delineations of volcanic landforms in active and ancient volcanic complex use semi-quantitative methods include ridge lineaments and flow pattern. Then, volcanic landform is manually delineated by determining the distribution pattern of ridges, flow pattern, morphological texture, and cross-cutting relationship of volcanic products as a key in determine the eruption centers. The results show a relationship between volcanic distribution and the main stresses in the Ijen Caldera Complex with NE-SW direction, which is represented by the elliptic and elongation of volcanic depression zone, monogenetic volcano, and intrusion distribution. Geological structures that are found in the Ijen Caldera Complex show E-W and NE-SW directions. Meanwhile, Merubetiri complex shows E-W, NW-SE, and N-S structural direction patterns. The distribution of alteration minerals associated with silisic, argillic, and advance argillic in the Ijen Caldera Complex are found in the central zone of stratovolcano, intra-caldera zone, and structural zone that intersects the caldera. This shows that active hydrothermal system is related to volcanic activity and geological structures. Meanwhile, in the Merubetiri complex, alteration minerals are associated with the eruption centers, diorite/granodiorite intrusions, and NW-SE strike slip fault. The understandings of volcanic setting and volcanic landforms are very important in the early stages of exploration to determine the prospect of mineral deposits related to hydrothermal system.
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Sahagian, D. L. « More bubbles in volcanic systems ». Nature 361, no 6410 (janvier 1993) : 308. http://dx.doi.org/10.1038/361308b0.
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De Vivo, B., A. Lima et J. D. Webster. « Volatiles in Magmatic-Volcanic Systems ». Elements 1, no 1 (1 janvier 2005) : 19–24. http://dx.doi.org/10.2113/gselements.1.1.19.
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Di Capua, Andrea, Federica Barilaro et Gianluca Groppelli. « Deep-Water Accumulation of Volcaniclastic Detritus from a Petrographic Point of View : Beginning a Discussion from the Alpine Peripheral Basins ». Geosciences 11, no 11 (27 octobre 2021) : 441. http://dx.doi.org/10.3390/geosciences11110441.
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The interpretation of eruptive mechanisms accumulating ancient submarine volcaniclastic sequences is still extremely challenging, particularly when no spatial nor temporal constraints are identifiable. The present work reviews petrographic results gained during the last few decades on three different Paleogene Formations accumulated around the Alpine and Apennine Mountain belts, discussing how their detritus could have been formed and moved from the volcanic centers to the depo-centers, taking into account the volcanic mechanisms which are at the base of the production, transportation and accumulation of volcaniclastic detritus. In doing this, we reconsider the classical diagrams of Folk and Gazzi–Dickinson, rediscussing their significance on the basis of how orogenic volcanism delivers detritus to the environment. In addition, this work highlights the need of the scientific community for gaining new petrographic data on modern sedimentary systems to better constrain interpretative criteria for the petrographic study of ancient volcano–sedimentary sequences.
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L'Heureux, I. « The effect of volatile bubble growth rate on the periodic dynamics of shallow volcanic systems ». Nonlinear Processes in Geophysics 17, no 2 (20 avril 2010) : 221–35. http://dx.doi.org/10.5194/npg-17-221-2010.
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Abstract. Many volcanic eruptions exhibit periodic behavior. For instance, periodic ground inflations and deflations in proximity to a volcano are the consequences of periodic overpressure variations in the magma conduit and periodic magma flow rate. The period varies from a few hours to many years, depending on the volcano parameters. On the other hand, volatile components exsolve from an ascending magma by forming bubbles. The strong dependence of the melt viscosity with the volatile concentration generates a positive feedback on the magma flow. We consider here the effect of the growth of volatile bubbles on the dynamics of a magmatic flow in a shallow volcanic system. Various expressions for the bubble growth rate are treated, thus generalizing previous work. In particular, a growth rate law derived from a recent many-bubble theory is considered. It is seen that, for a range of flow rate values at the base of the magma conduit, the system undergoes a Hopf bifurcation. Periodic solutions compatible with the observations are generated. This work shows that measurements of volcanic activity have the potential to test various bubble growth models in magmatic systems.
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Geyer, A. « Chapter 1.4 Antarctic volcanism : active volcanism overview ». Geological Society, London, Memoirs 55, no 1 (2021) : 55–72. http://dx.doi.org/10.1144/m55-2020-12.
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AbstractIn the last two centuries, demographic expansion and extensive urbanization of volcanic areas have increased the exposure of our society to volcanic hazards. Antarctica is no exception. During the last decades, the permanent settlement and seasonal presence of scientists, technicians, tourists and logistical personnel close to active volcanoes in the south polar region have increased notably. This has led to an escalation in the number of people and the amount of infrastructure exposed to potential eruptions. This requires advancement of our knowledge of the volcanic and magmatic history of Antarctic active volcanoes, significant improvement of the monitoring networks, and development of long-term hazard assessments and vulnerability analyses to carry out the required mitigation actions, and to elaborate on the most appropriate response plans to reduce loss of life and infrastructure during a future volcanic crisis. This chapter provides a brief summary of the active volcanic systems in Antarctica, highlighting their main volcanological features, which monitoring systems are deployed (if any), and recent (i.e. Holocene and/or historical) eruptive activity or unrest episodes. To conclude, some notes about the volcanic hazard assessments carried out so far on south polar volcanoes are also included, along with recommendations for specific actions and ongoing research on active Antarctic volcanism.
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Blake, Stephanie A. P., Sophie C. Lewis, Allegra N. LeGrande et Ron L. Miller. « Assessing the impact of large volcanic eruptions of the last millennium (850–1850 CE) on Australian rainfall regimes ». Climate of the Past 14, no 6 (18 juin 2018) : 811–24. http://dx.doi.org/10.5194/cp-14-811-2018.
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Abstract. Explosive volcanism is an important natural climate forcing, impacting global surface temperatures and regional precipitation. Although previous studies have investigated aspects of the impact of tropical volcanism on various ocean–atmosphere systems and regional climate regimes, volcanic eruptions remain a poorly understood climate forcing and climatic responses are not well constrained. In this study, volcanic eruptions are explored in particular reference to Australian precipitation, and both the Indian Ocean Dipole (IOD) and El Niño–Southern Oscillation (ENSO). Using nine realisations of the last millennium (LM) (850–1850 CE) with different time-evolving forcing combinations, from the NASA GISS ModelE2-R, the impact of the six largest tropical volcanic eruptions of this period are investigated. Overall, we find that volcanic aerosol forcing increased the likelihood of El Niño and positive IOD conditions for up to four years following an eruption, and resulted in positive precipitation anomalies over north-west (NW) and south-east (SE) Australia. Larger atmospheric sulfate loading during larger volcanic eruptions coincided with more persistent positive IOD and El Niño conditions, enhanced positive precipitation anomalies over NW Australia, and dampened precipitation anomalies over SE Australia.
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Infante-Paez, Lennon, et Kurt J. Marfurt. « Seismic expression and geomorphology of igneous bodies : A Taranaki Basin, New Zealand, case study ». Interpretation 5, no 3 (31 août 2017) : SK121—SK140. http://dx.doi.org/10.1190/int-2016-0244.1.
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Very little research has been done on volcanic rocks by the oil industry due to the misconception that these rocks cannot be “good reservoirs.” However, in the past two decades, significant quantities of hydrocarbons have been produced from volcanic rocks in China, New Zealand, and Argentina. In frontier basins, volcanic piles are sometimes misinterpreted to be hydrocarbon anomalies and/or carbonate buildups. Unlike clastic and carbonate systems, the 3D seismic geomorphology of igneous systems is only partially documented. We have integrated 3D seismic data, well logs, well reports, core data, and clustering techniques such as self-organizing maps to map two distinct facies (pyroclastic and lava flows), within a Miocene submarine volcano in the Taranaki Basin, New Zealand. Three wells; Kora-1–3 drilled the pyroclastic facies within the volcano encountering evidence of a petroleum system, whereas the Kora-4 well drilled the lava-flow facies, which was barren of hydrocarbons. By integrating results from geochemistry and basin modeling reports prepared for Crown Mineral, New Zealand, we concluded that the reason that Kora-4 was dry was due to a lack of source charge — not to the absence of reservoir quality. Moreover, the Kora-1 well drilled a thick sequence (>[Formula: see text]) of pyroclastic flows in this submarine volcano by chance and found high peaks of gas in the mudlogs near the top 25 m of this sequence. A long-term test in this upper volcanic section resulted in 32 API oil flow of 668 barrels of oil per day for 254 h — a result that challenges the misconception that volcanic rocks cannot be good reservoirs.
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Metcalf, Rodney V. « Volcanic–plutonic links, plutons as magma chambers and crust–mantle interaction : a lithospheric scale view of magma systems ». Earth and Environmental Science Transactions of the Royal Society of Edinburgh 95, no 1-2 (mars 2004) : 357–74. http://dx.doi.org/10.1017/s0263593300001127.
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ABSTRACTThe northern Colorado River extensional corridor (NCREC, USA) provides an excellent record of coeval volcanic and mid- to upper-crustal (<13 km) plutonic suites. The NCREC is a 50–100-km-wide zone that records late Tertiary lithospheric extension, volcanism, continental sedimentation and plutonism. Compilation of published studies of NCREC magmatic rocks permits an assessment of volcanic–plutonic links, magma sources and magmatic processes. The volcanic sections provide an excellent record of magma compositions (basalt, trachyandesite, trachyte and rhyolite) which span a 9-million-year period in the Miocene age (20–11 Ma).Contemporaneous Miocene plutons span a similar compositional range (gabbro, diorite, quartz monzonite and granite) and were emplaced during a 4·5-million-year interval from 17 to 12·5 Ma. Geochemical and isotopic compositions and compositional trends allow direct correlation between plutonic and volcanic suites across the entire compositional range. Petrogenetic models demonstrate that intermediate magmas formed by a combination of magma mixing and fractional crystallisation involving mantle-derived mafic with crustal-derived felsic end-member magmas. Plutons exhibit a variety of features which suggest magma chamber processes, including (1) mafic cumulate sequences, (2) felsic cumulate sequences, and (3) magma mingling and advanced stages of magma mixing. Thus, the NCREC plutonic-volcanic record provides a link between magmatic processes recorded in pluton magma chambers and magmatic products in the form of extrusive igneous rocks. The NCREC plutons represent upper crustal magma chambers which connected volcanic eruptive centres to deeper-level magma chambers, and ultimately, to zones of mantle and crustal mel
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Tuffen, Hugh. « How will melting of ice affect volcanic hazards in the twenty-first century ? » Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 368, no 1919 (28 mai 2010) : 2535–58. http://dx.doi.org/10.1098/rsta.2010.0063.
Texte intégralRésumé :
Glaciers and ice sheets on many active volcanoes are rapidly receding. There is compelling evidence that melting of ice during the last deglaciation triggered a dramatic acceleration in volcanic activity. Will melting of ice this century, which is associated with climate change, similarly affect volcanic activity and associated hazards? This paper provides a critical overview of the evidence that current melting of ice will increase the frequency or size of hazardous volcanic eruptions. Many aspects of the link between ice recession and accelerated volcanic activity remain poorly understood. Key questions include how rapidly volcanic systems react to melting of ice, whether volcanoes are sensitive to small changes in ice thickness and how recession of ice affects the generation, storage and eruption of magma at stratovolcanoes. A greater frequency of collapse events at glaciated stratovolcanoes can be expected in the near future, and there is strong potential for positive feedbacks between melting of ice and enhanced volcanism. Nonetheless, much further research is required to remove current uncertainties about the implications of climate change for volcanic hazards in the twenty-first century.
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Strehlow, K., J. Gottsmann, A. Rust, S. Hautmann et B. Hemmings. « The influence of long- and short-term volcanic strain on aquifer pressure : a case study from Soufrière Hills Volcano, Montserrat (W.I.) ». Geophysical Journal International 223, no 2 (25 juillet 2020) : 1288–303. http://dx.doi.org/10.1093/gji/ggaa354.
Texte intégralRésumé :
Summary Aquifers are poroelastic bodies that respond to strain by changes in pore pressure. Crustal deformation due to volcanic processes induces pore pressure variations that are mirrored in well water levels. Here, we investigate water level changes in the Belham valley on Montserrat over the course of 2 yr (2004–2006). Using finite element analysis, we simulate crustal deformation due to different volcanic strain sources and the dynamic poroelastic aquifer response. While some additional hydrological drivers cannot be excluded, we suggest that a poroelastic strain response of the aquifer system in the Belham valley is a possible explanation for the observed water level changes. According to our simulations, the shallow Belham aquifer responds to a steadily increasing sediment load due to repeated lahar sedimentation in the valley with rising aquifer pressures. A wholesale dome collapse in May 2006 on the other hand induced dilatational strain and thereby a short-term water level drop in a deeper-seated aquifer, which caused groundwater leakage from the Belham aquifer and thereby induced a delayed water level fall in the wells. The system thus responded to both gradual and rapid transient strain associated with the eruption of Soufrière Hills Volcano (Montserrat). This case study gives field evidence for theoretical predictions on volcanic drivers behind hydrological transients, demonstrating the potential of hydrological data for volcano monitoring. Interrogation of such data can provide valuable constraints on stress evolution in volcanic systems and therefore complement other monitoring systems. The presented models and inferred results are conceptually applicable to volcanic areas worldwide.
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Bischoff, Alan Patrick, Andrew Nicol et Mac Beggs. « Stratigraphy of architectural elements in a buried volcanic system and implications for hydrocarbon exploration ». Interpretation 5, no 3 (31 août 2017) : SK141—SK159. http://dx.doi.org/10.1190/int-2016-0201.1.
Texte intégralRésumé :
The interaction between magmatism and sedimentation creates a range of petroleum plays at different stratigraphic levels due to the emplacement and burial of volcanoes. This study characterizes the spatio-temporal distribution of the fundamental building blocks (i.e., architectural elements) of a buried volcano and enclosing sedimentary strata to provide insights for hydrocarbon exploration in volcanic systems. We use a large data set of wells and seismic reflection surveys from the offshore Taranaki Basin, New Zealand, compared with outcropping volcanic systems worldwide to demonstrate the local impacts of magmatism on the evolution of the host sedimentary basin and petroleum system. We discover the architecture of Kora volcano, a Miocene andesitic polygenetic stratovolcano that is currently buried by more than 1000 m of sedimentary strata and hosts a subcommercial discovery within volcanogenic deposits. The 22 individual architectural elements have been characterized within three main stratigraphic sequences of the Kora volcanic system. These sequences are referred to as premagmatic (predate magmatism), synmagmatic (defined by the occurrence of intrusive, eruptive, and sedimentary architectural elements), and postmagmatic (degradation and burial of the volcanic structures after magmatism ceased). Potential petroleum plays were identified based on the distribution of the architectural elements and on the geologic circumstances resulting from the interaction between magmatism and sedimentation. At the endogenous level, emplacement of magma forms structural traps, such as drag folds and strata jacked up above intrusions. At the exogenous level, syneruptive, intereruptive, and postmagmatic processes mainly form stratigraphic and paleogeomorphic traps, such as interbedded volcano-sedimentary deposits, and upturned pinchout of volcanogenic and nonvolcanogenic coarse-grained deposits onto the volcanic edifice. Potential reservoirs are located at systematic vertical and lateral distances from eruptive centers. We have determined that identifying the architectural elements of buried volcanoes is necessary for building predictive models and for derisking hydrocarbon exploration in sedimentary basins affected by magmatism.
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Kavanagh, Janine L., Samantha L. Engwell et Simon A. Martin. « A review of laboratory and numerical modelling in volcanology ». Solid Earth 9, no 2 (27 avril 2018) : 531–71. http://dx.doi.org/10.5194/se-9-531-2018.
Texte intégralRésumé :
Abstract. Modelling has been used in the study of volcanic systems for more than 100 years, building upon the approach first applied by Sir James Hall in 1815. Informed by observations of volcanological phenomena in nature, including eye-witness accounts of eruptions, geophysical or geodetic monitoring of active volcanoes, and geological analysis of ancient deposits, laboratory and numerical models have been used to describe and quantify volcanic and magmatic processes that span orders of magnitudes of time and space. We review the use of laboratory and numerical modelling in volcanological research, focussing on sub-surface and eruptive processes including the accretion and evolution of magma chambers, the propagation of sheet intrusions, the development of volcanic flows (lava flows, pyroclastic density currents, and lahars), volcanic plume formation, and ash dispersal. When first introduced into volcanology, laboratory experiments and numerical simulations marked a transition in approach from broadly qualitative to increasingly quantitative research. These methods are now widely used in volcanology to describe the physical and chemical behaviours that govern volcanic and magmatic systems. Creating simplified models of highly dynamical systems enables volcanologists to simulate and potentially predict the nature and impact of future eruptions. These tools have provided significant insights into many aspects of the volcanic plumbing system and eruptive processes. The largest scientific advances in volcanology have come from a multidisciplinary approach, applying developments in diverse fields such as engineering and computer science to study magmatic and volcanic phenomena. A global effort in the integration of laboratory and numerical volcano modelling is now required to tackle key problems in volcanology and points towards the importance of benchmarking exercises and the need for protocols to be developed so that models are routinely tested against real world data.
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Putirka, K. D. « Thermometers and Barometers for Volcanic Systems ». Reviews in Mineralogy and Geochemistry 69, no 1 (1 janvier 2008) : 61–120. http://dx.doi.org/10.2138/rmg.2008.69.3.
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Farquharson, Jamie I., et Fabian B. Wadsworth. « Upscaling permeability in anisotropic volcanic systems ». Journal of Volcanology and Geothermal Research 364 (septembre 2018) : 35–47. http://dx.doi.org/10.1016/j.jvolgeores.2018.09.002.
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Corradino, Claudia, Gaetana Ganci, Giuseppe Bilotta, Annalisa Cappello, Ciro Negro et Luigi Fortuna. « Smart Decision Support Systems for Volcanic Applications ». Energies 12, no 7 (28 mars 2019) : 1216. http://dx.doi.org/10.3390/en12071216.
Texte intégralRésumé :
The huge amount of information coming from remote sensors on satellites has allowed monitoring changes in the planetary environment from about 50 years. These instruments are widely adopted to observe extreme thermal events such as eruptive phenomena in volcanic areas. Although the availability of so many different infrared sensors makes these instruments suitable to observe different kind of thermal phenomena, choosing the right infrared sensor to monitor each thermal event is not straightforward. In fact, the decision should take into account both the main features of the phenomena under investigation, e.g., its size and temperatures, that are often not known a priori, and the instruments specifications, e.g., spatial resolution. Here, a smart decision support system (SDSS) is proposed to address this task. In particular, we used a SDSS to simulate remote sensors responses, collect data coming from three different classes of remote sensors, retrieve information about the main features of the observed thermal event and, consequently, select the most suitable infrared remote sensor for the specific observed phenomena. Results obtained for a real case of study at Etna volcano is shown.
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Vogel, L., B. Galle, C. Kern, H. Delgado Granados, V. Conde, P. Norman, S. Arellano et al. « Early in-flight detection of SO<sub>2</sub> ; via Differential Optical Absorption Spectroscopy : a feasible aviation safety measure to prevent potential encounters with volcanic plumes ». Atmospheric Measurement Techniques Discussions 4, no 3 (16 mai 2011) : 2827–81. http://dx.doi.org/10.5194/amtd-4-2827-2011.
Texte intégralRésumé :
Abstract. Volcanic ash constitutes a risk to aviation, mainly due to its ability to cause jet engines to fail. Other risks include the possibility of abrasion of windshields and potentially serious damage to avionic systems. These hazards have been widely recognized since the early 1980s, when volcanic ash provoked several incidents of engine failure in commercial aircraft. In addition to volcanic ash, volcanic gases also pose a threat. Prolonged and/or cumulative exposure to sulphur dioxide (SO2) or sulphuric acid (H2SO4) aerosols potentially affects e.g. windows, air frame and may cause permanent damage to engines. SO2 receives most attention among the gas species commonly found in volcanic plumes because its presence above the lower troposphere is a clear proxy for a volcanic cloud and indicates that fine ash could also be present. Up to now, remote sensing of SO2 via Differential Optical Absorption Spectroscopy (DOAS) in the ultraviolet spectral region has been used to measure volcanic clouds from ground based, airborne and satellite platforms. Attention has been given to volcanic emission strength, chemistry inside volcanic clouds and measurement procedures were adapted accordingly. Here we present a set of experimental and model results, highlighting the feasibility of DOAS to be used as an airborne early detection system of SO2 in two spatial dimensions. In order to prove our new concept, simultaneous airborne and ground-based measurements of the plume of Popocatépetl volcano, Mexico, were conducted in April 2010. The plume extended at an altitude around 5250 m above sea level and was approached and traversed at the same altitude with several forward looking DOAS systems aboard an airplane. These DOAS systems measured SO2 in the flight direction and at ± 40 mrad (2.3°) angles relative to it in both, horizontal and vertical directions. The approaches started at up to 25 km distance to the plume and SO2 was measured at all times well above the detection limit. In combination with radiative transfer studies, this study indicates that an extended volcanic cloud with a concentration of 1012 molecules cm−3 at typical flight levels of 10 km can be detected unambiguously at distances of up to 80 km away. This range provides enough time (approx. 5 min) for pilots to take action to avoid entering a volcanic cloud in the flight path, suggesting that this technique can be used as an effective aid to prevent dangerous aircraft encounters with potentially ash rich volcanic clouds.
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Vogel, L., B. Galle, C. Kern, H. Delgado Granados, V. Conde, P. Norman, S. Arellano et al. « Early in-flight detection of SO<sub>2</sub> ; via Differential Optical Absorption Spectroscopy : a feasible aviation safety measure to prevent potential encounters with volcanic plumes ». Atmospheric Measurement Techniques 4, no 9 (8 septembre 2011) : 1785–804. http://dx.doi.org/10.5194/amt-4-1785-2011.
Texte intégralRésumé :
Abstract. Volcanic ash constitutes a risk to aviation, mainly due to its ability to cause jet engines to fail. Other risks include the possibility of abrasion of windshields and potentially serious damage to avionic systems. These hazards have been widely recognized since the early 1980s, when volcanic ash provoked several incidents of engine failure in commercial aircraft. In addition to volcanic ash, volcanic gases also pose a threat. Prolonged and/or cumulative exposure to sulphur dioxide (SO2) or sulphuric acid (H2SO4) aerosols potentially affects e.g. windows, air frame and may cause permanent damage to engines. SO2 receives most attention among the gas species commonly found in volcanic plumes because its presence above the lower troposphere is a clear proxy for a volcanic cloud and indicates that fine ash could also be present. Up to now, remote sensing of SO2 via Differential Optical Absorption Spectroscopy (DOAS) in the ultraviolet spectral region has been used to measure volcanic clouds from ground based, airborne and satellite platforms. Attention has been given to volcanic emission strength, chemistry inside volcanic clouds and measurement procedures were adapted accordingly. Here we present a set of experimental and model results, highlighting the feasibility of DOAS to be used as an airborne early detection system of SO2 in two spatial dimensions. In order to prove our new concept, simultaneous airborne and ground-based measurements of the plume of Popocatépetl volcano, Mexico, were conducted in April 2010. The plume extended at an altitude around 5250 m above sea level and was approached and traversed at the same altitude with several forward looking DOAS systems aboard an airplane. These DOAS systems measured SO2 in the flight direction and at &pm;40 mrad (2.3°) angles relative to it in both, horizontal and vertical directions. The approaches started at up to 25 km distance to the plume and SO2 was measured at all times well above the detection limit. In combination with radiative transfer studies, this study indicates that an extended volcanic cloud with a concentration of 1012 molecules cm−3 at typical flight levels of 10 km can be detected unambiguously at distances of up to 80 km away. This range provides enough time (approx. 5 min) for pilots to take action to avoid entering a volcanic cloud in the flight path, suggesting that this technique can be used as an effective aid to prevent dangerous aircraft encounters with potentially ash rich volcanic clouds.
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Johnston, David, Brad Scott, Bruce Houghton, Douglas Paton, David Dowrick, Pilar Villamor et John Savage. « Social and economic consequences of historic caldera unrest at the Taupo volcano, New Zealand and the management of future episodes of unrest ». Bulletin of the New Zealand Society for Earthquake Engineering 35, no 4 (31 décembre 2002) : 215–30. http://dx.doi.org/10.5459/bnzsee.35.4.215-230.
Texte intégralRésumé :
In 1998, changes in a number of indicators (earthquakes and uplift) at two of New Zealand's active volcanic caldera systems (Okataina and Taupo) resulted in increased public, local and central government awareness and some concern about the potential significance of volcanic unrest at a caldera volcano. This paper summarises the episodes of unrest recorded at Taupo caldera since 1895. There have been four significant events (1895, 1922, 1963-64 and 1983) that have included earthquake activity and ground deformation. Caldera unrest is one of the most difficult situations the volcanological and emergency management communities will have to deal with. There is potential for adverse social and economic impacts to escalate unnecessarily, unless the event is managed appropriately. Adverse response to caldera unrest may take the form of the release of inappropriate advice, media speculation, unwarranted emergency declarations and premature cessation of economic activity and community services. A non-volcanic-crisis time provides the best opportunity to develop an understanding of the caldera unrest phenomena, and the best time to establish educational programmes, funding systems for enhanced emergency response and volcano surveillance and to develop co-ordinated contingency plans.
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Faria, B., et J. F. B. D. Fonseca. « Investigating volcanic hazard in Cape Verde Islands through geophysical monitoring : network description and first results ». Natural Hazards and Earth System Sciences 14, no 2 (28 février 2014) : 485–99. http://dx.doi.org/10.5194/nhess-14-485-2014.
Texte intégralRésumé :
Abstract. We describe a new geophysical network deployed in the Cape Verde Archipelago for the assessment and monitoring of volcanic hazards as well as the first results from the network. Across the archipelago, the ages of volcanic activity range from ca. 20 Ma to present. In general, older islands are in the east and younger ones are in the west, but there is no clear age progression of eruptive activity as widely separated islands have erupted contemporaneously on geological timescales. The overall magmatic rate is low, and there are indications that eruptive activity is episodic, with intervals between episodes of intense activity ranging from 1 to 4 Ma. Although only Fogo Island has experienced eruptions (mainly effusive) in the historic period (last 550 yr), Brava and Santo Antão have experienced numerous geologically recent eruptions, including violent explosive eruptions, and show felt seismic activity and geothermal activity. Evidence for recent volcanism in the other islands is more limited and the emphasis has therefore been on monitoring of the three critical islands of Fogo, Brava and Santo Antão, where volcanic hazard levels are highest. Geophysical monitoring of all three islands is now in operation. The first results show that on Fogo, the seismic activity is dominated by hydrothermal events and volcano-tectonic events that may be related to settling of the edifice after the 1995 eruption; in Brava by volcano-tectonic events (mostly offshore), and in Santo Antão by volcano-tectonic events, medium-frequency events and harmonic tremor. Both in Brava and in Santo Antão, the recorded seismicity indicates that relatively shallow magmatic systems are present and causing deformation of the edifices that may include episodes of dike intrusion.
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Faria, B., et J. F. B. D. Fonseca. « Investigating volcanic hazard in Cape Verde Islands through geophysical monitoring : network description and first results ». Natural Hazards and Earth System Sciences Discussions 1, no 5 (25 septembre 2013) : 4997–5032. http://dx.doi.org/10.5194/nhessd-1-4997-2013.
Texte intégralRésumé :
Abstract. We describe a new geophysical network deployed in the Cape Verde archipelago for the assessment and monitoring of volcanic hazards, and the first results from the network. Across the archipelago, the ages of volcanic activity range from ca. 20 Ma to present. In general, older islands are in the east and younger ones are in the west, but there is no clear age progression and widely-separated islands have erupted contemporaneously on geological time scales. The overall magmatic rate is low, and there are indications that eruptive activity is episodic, with intervals between episodes of intense activity ranging from 1 to 4 Ma. Although only Fogo island has experienced eruptions (mainly effusive) in the historic period (last 550 yr), Brava and Santo Antão have experienced numerous geologically recent eruptions including violent explosive eruptions, and show felt seismic activity and geothermal activity. Evidence for recent volcanism in the other islands is more limited and the emphasis has therefore been on monitoring of the three critical islands of Fogo, Brava and Santo Antão, where volcanic hazard levels are highest. Geophysical monitoring of all three islands is now in operation. The first results show that in Fogo the seismic activity is dominated by hydrothermal events and volcano-tectonic events that may be related to settling of the edifice after the 1995 eruption; in Brava by volcano-tectonic events (mostly offshore), and in Santo Antão by volcano-tectonic events, medium frequency events and harmonic tremor. Both in Brava and in Santo Antão, the recorded seismicity indicates that relatively shallow magmatic systems are present and causing deformation of the edifices that may include episodes of dike intrusion.
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Verkhoturov, Alexey A. « ANALYSIS OF CHANGES IN THE STATE OF ECOSYSTEMS ON ATLASOVA ISLAND (KURIL ISLANDS) ». Vestnik SSUGT (Siberian State University of Geosystems and Technologies) 25, no 3 (2020) : 139–50. http://dx.doi.org/10.33764/2411-1759-2020-25-3-139-150.
Texte intégralRésumé :
The territory of the Kuril Islands is a chain of volcanic structures and is subject, to certain extent, to volcanic hazards. Atlasova Island is composed of products of the Alaid volcano, which is characterized by effusive and explosive activity. The article analyzes the changes in ecosystems on Atlasov island, which are periodically caused by the Alaid volcano eruption. Large amount of pyroclastic material are brought to the surface during explosive eruptions: blocks, bombs, tephra, lapilli and volcanic ash, which is transported in the atmosphere over very long distances. Ecosystems are affected by pyroclastic deposition over a large area of island land. The purpose of this study was to identify the nature and extent of changes in the state of ecosystems affected by volcanic eruptions from multi-zone satellite images of medium resolution. Analysis of data obtained from space systems Landsat and Sentinel for the period 1972 to 2020, in GIS environment allowed us to trace the dynamics and character of the successions to the affected areas on the calculated values of the vegetation index NDVI. Techniques developed in the process of studying this issue can further facili-tate rapid assessment of impacts on ecosystems at the effusive-explosive eruptions and forecast volcanic hazard for surrounding areas.
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Fujii, Toshitsutgu, et Kazuhiro Ishihara. « Special Issue on Volcanic Disasters ». Journal of Disaster Research 3, no 4 (1 août 2008) : 251. http://dx.doi.org/10.20965/jdr.2008.p0251.
Texte intégralRésumé :
The volcanic disasters are quite variable depending on the nature of the volcanic eruptions, the degrees of land-use surrounding the volcanic areas and preparedness against the eruptions. In order to mitigate the volcanic disasters, therefore, multidisciplinary approach is required. The International Volcanic Conference, ``Cities on Volcanoes 5," held in Shimabara Japan on the November 19-23, 2007 encouraged a wide range of people who are engaged in the volcanic disaster mitigation to gather to discuss topics related to volcanic eruptions and their hazards. The aim of this conference was to evaluate and improve mitigation measures, emergency management, and all required to successfully confront volcanic crises in densely populated area and to recover from any devastation. As the main topics discussed during the conference is quite adequate for the aim of this journal, this special issue tried to include papers read at the conference as many as possible. For the mitigation of the volcanic disasters, several different approaches should be included. Volcano monitoring through observation is the basis for most eruption forecasts and other measures for volcanic disaster mitigation. Impacts on human health and sustainability in volcanic areas in the fields of air and water pollution are also important issues to be included in the management of volcanic hazards. The practical lessons learned through the case histories of actual events should be shared to prepare for and respond to volcano crises that may affect communities. Hiroaki Takahashi proposes a method to estimate the real-time eruption magnitude that might be utilized to judge the duration of eruption in the early stage of eruption. Yoshikazu Kikawada et al. summarize arsenic pollution of rivers originated from the Kusatsu volcanic region. Tsuneomi Kagiyama and Yuichi Morita discuss the strategy to understand the preparing process of caldera forming eruption as a first step to assess the risk of gigantic eruption. Hiroshi Ikeya describes the prevention works executed by the central and local governments during and after the Mt. Unzen 1990-1995 eruption. Harry J. R. Keys summarizes the aspects of risk assessment and mitigation for a dome-break lahar that was predicted in 1995 and actually occurred on 18 March 2007 at Ruapehu volcano. Yoichi Nakamura et al. describe the mitigation systems on volcanic disasters in Japan emphasizing the importance of preparing hazard maps. We know the topics covered by this special issue do not represent the wide-ranging aspect of the conference, but include some significant portion. We hope that this special issue will be utilized to share the lessons learned through the practical trial to mitigate the actual disasters during the volcanic crisis.
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Tárraga, Marta, Joan Martí, Rafael Abella, Roberto Carniel et Carmen López. « Volcanic tremors : Good indicators of change in plumbing systems during volcanic eruptions ». Journal of Volcanology and Geothermal Research 273 (mars 2014) : 33–40. http://dx.doi.org/10.1016/j.jvolgeores.2014.01.003.
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Cañón-Tapia, Edgardo, et George P. L. Walker. « Global aspects of volcanism : the perspectives of “plate tectonics” and “volcanic systems” ». Earth-Science Reviews 66, no 1-2 (juin 2004) : 163–82. http://dx.doi.org/10.1016/j.earscirev.2003.11.001.
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Le Cozannet, G., M. Bagni, P. Thierry, C. Aragno et E. Kouokam. « WebGIS as boundary tools between scientific geoinformation and disaster risk reduction action in volcanic areas ». Natural Hazards and Earth System Sciences 14, no 6 (25 juin 2014) : 1591–98. http://dx.doi.org/10.5194/nhess-14-1591-2014.
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Abstract. As the amount of spatial data is growing, there is increased interest in developing tools to explore, visualize and interpret them, with the final aim of informing decision making efficiently. Within the European MIAVITA project, we examined this issue in the case of volcanic areas, where existing geospatial databases are particularly complex due to the number of threats to be considered, including volcanic (e.g. lava flows, ash fall) and non-volcanic hazards, such as landslides or tsunamis. We involved a group of hazard and risk analysts and managers, civil security officers, GIS analysts and system developers to design a Web-based geographical information system (WebGIS). We tested the system at the Mount Cameroon volcano, taking advantage of a complex hazard and risk geographical database. This study enabled identifying key requirements for such tools in volcanic areas, such as the need to manage user privileges differently according to their profile and the status of the volcano. This work also highlights that, in addition to the development of large geoinformation clearinghouses, there is a need for site-specific information systems focused on working procedures of users, in order to fill the last gap between data producers and users.
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Li, Yu-Juan, Lü-Yun Zhu, Wen Xu, Wei Meng, Min Lin, Zhong Yang et Run-Sheng Chen. « Stratigraphic Section and Geochronological Studies of the Shoushan Basin, Fujian Province, South China, and Its Implications for the Mineralization of Shoushan Stone ». Minerals 12, no 12 (30 novembre 2022) : 1542. http://dx.doi.org/10.3390/min12121542.
Texte intégralRésumé :
As one of the most famous craft-carving stones in China, Shoushan stone commonly consists of clay minerals, including the kaolinite, pyrophyllite, or illite group, which is the product of hydrothermal alteration. In Fujian Province, the Xiaoxi Formation of the Early Cretaceous is a critical formation containing pyrophyllite deposits (including Shoushan stone). Here, we carry out a geological field investigation of a typical section in the Shoushan basin of southeastern China to identify lithology and volcanic sequences of the Xiaoxi Formation. The section included four lithofacies: eruption facies, flood lava facies, sedimentary facies, and volcanic channel facies. The petrogenesis of these lithofacies demonstrates the evolution of volcanism, which is critical for understanding the formation of the Shoushan-stone-associated hydrothermal system. For the geochronological study, the samples of unaltered rhyolitic tuff are collected from the layers topping and bottoming a pyrophyllite orebody. The zircon U-Pb dating results constrain the age of pyrophyllite alteration during the episodic eruption. Shoushan stone is formed in an epithermal hydrothermal environment, so we suggest that high-quality Shoushan stone is formed by the hydrothermal alterations in the interval time of the volcanic episode (135–131 Ma) and after volcanic activity (<131 Ma). Furthermore, the Shoushan basin’s stratigraphic section suggests that there have been large-scale hydrothermal systems in the volcanic basin during the Early Cretaceous volcanism. The stratigraphic correlation and geochemical results indicate that the Mesozoic basins in the Fu’an-Yongtai volcanic eruption belt have the potential for pyrophyllite deposit exploration.
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Pappalardo, G., L. Mona, G. D'Amico, U. Wandinger, M. Adam, A. Amodeo, A. Ansmann et al. « Four-dimensional distribution of the 2010 Eyjafjallajökull volcanic cloud over Europe observed by EARLINET ». Atmospheric Chemistry and Physics Discussions 12, no 11 (22 novembre 2012) : 30203–57. http://dx.doi.org/10.5194/acpd-12-30203-2012.
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Abstract. The eruption of the Icelandic volcano Eyjafjallajökull in April/May 2010 represents a "natural experiment" to study the impact of volcanic emissions on a continental scale. For the first time, quantitative data about the presence, altitude, and layering of the volcanic cloud, in conjunction with optical information, are available for most parts of Europe derived from the observations by the European Aerosol Research Lidar NETwork (EARLINET). Based on multi-wavelength Raman lidar systems EARLINET is the only instrument worldwide that is able to provide dense time series of high-quality optical data to be used for aerosol typing and for the retrieval of particle microphysical properties as a function of altitude. In this work we show the four-dimensional (4-D) distribution of the Eyjafjallajökull volcanic cloud over Europe as observed by EARLINET during the entire volcanic event (15 April–26 May 2010). All optical properties directly measured (backscatter, extinction, and particle linear depolarization ratio) are stored in the EARLINET database available at http://www.earlinet.org. A specific relational database providing the volcanic mask over Europe, realized ad hoc for this specific event, has been developed and is available on request at http://www.earlinet.org. During the first days after the eruption, volcanic particles were detected over Central Europe within a wide range of altitudes, from the lower stratosphere down to the local Planetary Boundary Layer (PBL). After 19 April 2010, volcanic particles were detected over South and South Eastern Europe. During the first half of May (5–15 May), material emitted by the Eyjafjallajökull volcano was detected over Spain and Portugal and then over the Mediterranean and the Balkans. Last observations of the event were recorded until 25 May in Central Europe and in the Eastern Mediterranean area. For the first time, volcanic aerosol layering and optical properties are presented and discussed for the entire volcanic event on a continental scale providing an unprecedented data set for evaluating satellite data and aerosol dispersion models for these kind of volcanic events.
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King, E. M., J. W. Valley et D. W. Davis. « Oxygen isotope evolution of volcanic rocks at the Sturgeon Lake volcanic complex, Ontario ». Canadian Journal of Earth Sciences 37, no 1 (1 avril 2000) : 39–50. http://dx.doi.org/10.1139/e99-106.
Texte intégralRésumé :
Igneous zircons from the Sturgeon Lake volcanic complex, host to several massive sulphide deposits in the Superior Province, Canada, have an average δ18O(zircon) of 5.4 ± 0.3 VSMOW (n = 9 rocks). These zircons are from units differing in age by 18 million years in the 2.7 Ga complex. There is no detectable interaction of high δ18O, supracrustal lithologies in the magma. Quartz from volcanic units beneath the largest ore body, the Mattabi deposit, has an average δ18O of 9.3 ± 0.6. Quartz phenocrysts from the Mattabi unit and overlying volcanics have elevated and heterogeneous δ18O values averaging 13.8 ± 0.9 and are not in magmatic equilibrium with zircons. The δ18O values of whole-rock powders range from 5.6 to 14.3 and follow the trend observed in the δ18O values of quartz. Healed microcracks are visible in cathodoluminescence images (but are not obvious optically) of quartz phenocrysts from units with high δ18O values and disequilibrium Δ(quartz-zircon) suggesting that recrystallization facilitates the elevation of δ18O. Quartz phenocrysts from volcanic units with Δ(quartz-zircon) values near equilibrium at magmatic temperatures do not display healed microcracks in cathodoluminescence. The elevated δ18O(quartz) values are not restricted to units hosting orebodies, but are seen in all rocks in the volcanic stratigraphy that postdate eruption of the Mattabi unit. Oxygen isotope ratios combined with physical volcanology studies suggest that impermeable volcanic layers control the size and location of the many hydrothermal systems that may have occurred in the Sturgeon Lake complex.
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Reysenbach, Anna-Louise, Emily St. John, Jennifer Meneghin, Gilberto E. Flores, Mircea Podar, Nina Dombrowski, Anja Spang et al. « Complex subsurface hydrothermal fluid mixing at a submarine arc volcano supports distinct and highly diverse microbial communities ». Proceedings of the National Academy of Sciences 117, no 51 (4 décembre 2020) : 32627–38. http://dx.doi.org/10.1073/pnas.2019021117.
Texte intégralRésumé :
Hydrothermally active submarine volcanoes are mineral-rich biological oases contributing significantly to chemical fluxes in the deep sea, yet little is known about the microbial communities inhabiting these systems. Here we investigate the diversity of microbial life in hydrothermal deposits and their metagenomics-inferred physiology in light of the geological history and resulting hydrothermal fluid paths in the subsurface of Brothers submarine volcano north of New Zealand on the southern Kermadec arc. From metagenome-assembled genomes we identified over 90 putative bacterial and archaeal genomic families and nearly 300 previously unknown genera, many potentially endemic to this submarine volcanic environment. While magmatically influenced hydrothermal systems on the volcanic resurgent cones of Brothers volcano harbor communities of thermoacidophiles and diverse members of the superphylum “DPANN,” two distinct communities are associated with the caldera wall, likely shaped by two different types of hydrothermal circulation. The communities whose phylogenetic diversity primarily aligns with that of the cone sites and magmatically influenced hydrothermal systems elsewhere are characterized predominately by anaerobic metabolisms. These populations are probably maintained by fluids with greater magmatic inputs that have interacted with different (deeper) previously altered mineral assemblages. However, proximal (a few meters distant) communities with gene-inferred aerobic, microaerophilic, and anaerobic metabolisms are likely supported by shallower seawater-dominated circulation. Furthermore, mixing of fluids from these two distinct hydrothermal circulation systems may have an underlying imprint on the high microbial phylogenomic diversity. Collectively our results highlight the importance of considering geologic evolution and history of subsurface processes in studying microbial colonization and community dynamics in volcanic environments.
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Rüdiger, Julian, Jan-Lukas Tirpitz, J. Maarten de Moor, Nicole Bobrowski, Alexandra Gutmann, Marco Liuzzo, Martha Ibarra et Thorsten Hoffmann. « Implementation of electrochemical, optical and denuder-based sensors and sampling techniques on UAV for volcanic gas measurements : examples from Masaya, Turrialba and Stromboli volcanoes ». Atmospheric Measurement Techniques 11, no 4 (26 avril 2018) : 2441–57. http://dx.doi.org/10.5194/amt-11-2441-2018.
Texte intégralRésumé :
Abstract. Volcanoes are a natural source of several reactive gases (e.g., sulfur and halogen containing species) and nonreactive gases (e.g., carbon dioxide) to the atmosphere. The relative abundance of carbon and sulfur in volcanic gas as well as the total sulfur dioxide emission rate from a volcanic vent are established parameters in current volcano-monitoring strategies, and they oftentimes allow insights into subsurface processes. However, chemical reactions involving halogens are thought to have local to regional impact on the atmospheric chemistry around passively degassing volcanoes. In this study we demonstrate the successful deployment of a multirotor UAV (quadcopter) system with custom-made lightweight payloads for the compositional analysis and gas flux estimation of volcanic plumes. The various applications and their potential are presented and discussed in example studies at three volcanoes encompassing flight heights of 450 to 3300 m and various states of volcanic activity. Field applications were performed at Stromboli volcano (Italy), Turrialba volcano (Costa Rica) and Masaya volcano (Nicaragua). Two in situ gas-measuring systems adapted for autonomous airborne measurements, based on electrochemical and optical detection principles, as well as an airborne sampling unit, are introduced. We show volcanic gas composition results including abundances of CO2, SO2 and halogen species. The new instrumental setups were compared with established instruments during ground-based measurements at Masaya volcano, which resulted in CO2 ∕ SO2 ratios of 3.6 ± 0.4. For total SO2 flux estimations a small differential optical absorption spectroscopy (DOAS) system measured SO2 column amounts on transversal flights below the plume at Turrialba volcano, giving 1776 ± 1108 T d−1 and 1616 ± 1007 T d−1 of SO2 during two traverses. At Stromboli volcano, elevated CO2 ∕ SO2 ratios were observed at spatial and temporal proximity to explosions by airborne in situ measurements. Reactive bromine to sulfur ratios of 0.19 × 10−4 to 9.8 × 10−4 were measured in situ in the plume of Stromboli volcano, downwind of the vent.
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Sigvaldadóttir, Sigríður Inga, Sæmundur Ari Halldórsson et Guðmundur Heiðar Guðfinnsson. « Geochemistry and petrology of Holocene lavas in the Bárðardalur region, N-Iceland. Part I : Geochemical constraints on source provenance ». Jökull 67, no 1 (15 décembre 2017) : 17–42. http://dx.doi.org/10.33799/jokull2017.67.017.
Texte intégralRésumé :
Because of extensive volcanic production in Iceland during the Holocene, many of the early postglacial large-volume fissure lavas cannot be unambiguously traced to their eruptive craters solely by observations in the field. For example, the Bárðarbunga volcanic system has been suggested as a likely source of the large Holocene lava flows found in Bárðardalur valley, but this idea mainly relies on petrographic observations. We conducted a chemical and isotopic study of the lavas in Bárðardalur. For comparative purposes, we also targeted basement rocks of the Bárðarbunga central volcano, as well as several eruptive units in the region north of Vatnajökull. Based on a comparison of chemical and radiogenic isotope data of lavas from the Bárðardalur region and the eruptive units north of Vatnajökull and the Bárðarbunga central volcano, it appears most likely that the lavas of Bárðardalur valley belong to the Bárðarbunga volcanic system. These new data, and a compiled dataset for other selected volcanic systems of the NRZ, shed light on possible limitations when assigning erupted material to its source volcano by means of chemical composition. Furthermore, this study demonstrates that our understanding of the relative importance of the different processes at play during the petrogenesis of Icelandic basalts is likely to be greatly improved by multi-parameter datasets for geologically well-characterized eruptive units.
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Maddila, Vijay Souri, Katady Sai Shirish et M. V. S. Ramprasad. « A machine learning based sensing and measurement framework for timing of volcanic eruption and categorization of seismic data ». ACTA IMEKO 11, no 1 (31 mars 2022) : 5. http://dx.doi.org/10.21014/acta_imeko.v11i1.1209.
Texte intégralRésumé :
The circumstances and factors which determine the volcanic explosive ejection are unknown, and currently, there is no effective way to determine the end of a volcanic explosive ejection. At present, the end of an eruption is determined by either generalized standards or the measurement which is unique to the volcano. We investigate the use of controlled machine learning techniques such as Support Vector Machine (SVM), Random Forest (RF), Logistic Regression (LR), and Gaussian Process Classifiers (GPC), and create a decisiveness index D to assess the uniformity of the groups provided by these machine learning models. We analyzed the measured end-date obtained by seismic information categorization is two to four months later than the end-dates determined by the earliest instance of visible eruption for both volcanic systems. Likewise, the measurement systems, measurement technology becomes key elements in the seismic data analysis. The findings are consistent across models and correspond to previous, broad definitions of ejection. Obtained classifications demonstrate a more significant relationship between eruptive movement and visual activity than information base records of ejection start and completion timings. Our research has presented a new measurement-based categorization technique for studying volcanic eruptions, which provides a reliable tool for determining whether or not an emission has stopped without the need for visual confirmation.
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Bredemeyer, Stefan, Franz-Georg Ulmer, Thor Hansteen et Thomas Walter. « Radar Path Delay Effects in Volcanic Gas Plumes : The Case of Láscar Volcano, Northern Chile ». Remote Sensing 10, no 10 (21 septembre 2018) : 1514. http://dx.doi.org/10.3390/rs10101514.
Texte intégralRésumé :
Modern volcano monitoring commonly involves Interferometric Synthetic Aperture Radar (InSAR) measurements to identify ground motions caused by volcanic activity. However, InSAR is largely affected by changes in atmospheric refractivity, in particular by changes which can be attributed to the distribution of water (H2O) vapor in the atmospheric column. Gas emissions from continuously degassing volcanoes contain abundant water vapor and thus produce variations in the atmospheric water vapor content above and downwind of the volcano, which are notably well captured by short-wavelength X-band SAR systems. These variations may in turn cause differential phase errors in volcano deformation estimates due to excess radar path delay effects within the volcanic gas plume. Inversely, if these radar path delay effects are better understood, they may be even used for monitoring degassing activity, by means of the precipitable water vapor (PWV) content in the plume at the time of SAR acquisitions, which may provide essential information on gas plume dispersion and the state of volcanic and hydrothermal activity. In this work we investigate the radar path delays that were generated by water vapor contained in the volcanic gas plume of the persistently degassing Láscar volcano, which is located in the dry Atacama Desert of Northern Chile. We estimate water vapor contents based on sulfur dioxide (SO2) emission measurements from a scanning UV spectrometer (Mini-DOAS) station installed at Láscar volcano, which were scaled by H2O/SO2 molar mixing ratios obtained during a multi-component Gas Analyzer System (Multi-GAS) survey on the crater rim of the volcano. To calculate the water vapor content in the downwind portion of the plume, where an increase of water vapor is expected, we further applied a correction involving estimation of potential evaporation rates of water droplets governed by turbulent mixing of the condensed volcanic plume with the dry atmosphere. Based on these estimates we obtain daily average PWV contents inside the volcanic gas plume of 0.2–2.5 mm equivalent water column, which translates to a slant wet delay (SWD) in DInSAR data of 1.6–20 mm. We used these estimates in combination with our high resolution TerraSAR-X DInSAR observations at Láscar volcano, in order to demonstrate the occurrence of repeated atmospheric delay patterns that were generated by volcanic gas emissions. We show that gas plume related refractivity changes are significant and detectable in DInSAR measurements. Implications are two-fold: X-band satellite radar observations also contain information on the degassing state of a volcano, while deformation signals need to be interpreted with care, which has relevance for volcano observations at Láscar and for other sites worldwide.
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Pappalardo, G., L. Mona, G. D'Amico, U. Wandinger, M. Adam, A. Amodeo, A. Ansmann et al. « Four-dimensional distribution of the 2010 Eyjafjallajökull volcanic cloud over Europe observed by EARLINET ». Atmospheric Chemistry and Physics 13, no 8 (29 avril 2013) : 4429–50. http://dx.doi.org/10.5194/acp-13-4429-2013.
Texte intégralRésumé :
Abstract. The eruption of the Icelandic volcano Eyjafjallajökull in April–May 2010 represents a "natural experiment" to study the impact of volcanic emissions on a continental scale. For the first time, quantitative data about the presence, altitude, and layering of the volcanic cloud, in conjunction with optical information, are available for most parts of Europe derived from the observations by the European Aerosol Research Lidar NETwork (EARLINET). Based on multi-wavelength Raman lidar systems, EARLINET is the only instrument worldwide that is able to provide dense time series of high-quality optical data to be used for aerosol typing and for the retrieval of particle microphysical properties as a function of altitude. In this work we show the four-dimensional (4-D) distribution of the Eyjafjallajökull volcanic cloud in the troposphere over Europe as observed by EARLINET during the entire volcanic event (15 April–26 May 2010). All optical properties directly measured (backscatter, extinction, and particle linear depolarization ratio) are stored in the EARLINET database available at http://www.earlinet.org. A specific relational database providing the volcanic mask over Europe, realized ad hoc for this specific event, has been developed and is available on request at http://www.earlinet.org. During the first days after the eruption, volcanic particles were detected over Central Europe within a wide range of altitudes, from the upper troposphere down to the local planetary boundary layer (PBL). After 19 April 2010, volcanic particles were detected over southern and south-eastern Europe. During the first half of May (5–15 May), material emitted by the Eyjafjallajökull volcano was detected over Spain and Portugal and then over the Mediterranean and the Balkans. The last observations of the event were recorded until 25 May in Central Europe and in the Eastern Mediterranean area. The 4-D distribution of volcanic aerosol layering and optical properties on European scale reported here provides an unprecedented data set for evaluating satellite data and aerosol dispersion models for this kind of volcanic events.
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Manville, V., D. Johnston, S. Stammers et B. Scott. « Comparative preparedness in New Zealand and the Philippines for response to, and recovery from, volcanic eruptions ». Bulletin of the New Zealand Society for Earthquake Engineering 33, no 4 (31 décembre 2000) : 445–76. http://dx.doi.org/10.5459/bnzsee.33.4.445-476.
Texte intégralRésumé :
New Zealand and the Philippines are two of the most tectonically and volcanically active regions in the world, due to their setting as large island chains on the convergent margin of the Pacific Plate. The Philippines has experienced numerous volcanic disasters over the past 400 years with the loss of over 7000 lives and considerable damage to infrastructure. The 1991 eruption of Mount Pinatubo, after 500 years of dormancy, was the largest volcanic eruption globally in the last 50 years, with serious socio-economic consequences for the Philippines. The 1995-6 eruptions of New Zealand's Mount Ruapehu, were the most serious volcanic activity experienced in the country over the last 50 years, but occurred at a frequently active volcano for which monitoring, hazard assessment, and response systems were already in place. Although the eruptions differ in size by two orders of magnitude, they illustrate how volcanic activity impacts infrastructure and society at different levels of economic development and vulnerability. Two of New Zealand's volcanic centres, Taupo and Okataina, have the potential to generate eruptions of a similar, or even greater, scale than Pinatubo. Therefore, lessons learnt from the Philippine experience will be of vital importance in planning for the mitigation of future volcanic disasters in New Zealand.