Bulletin of Volcanology最新文献

{"title":"Airfall volume of the 15 January 2022 eruption of Hunga volcano estimated from ocean color changes","authors":"Liam J. Kelly, Kristen E. Fauria, Michael Manga, Shane J. Cronin, Folauhola Helina Latu’ila, Joali Paredes-Mariño, Tushar Mittal, Ralf Bennartz","doi":"10.1007/s00445-024-01744-6","DOIUrl":"https://doi.org/10.1007/s00445-024-01744-6","url":null,"abstract":"<p>On 15 January 2022, Hunga volcano erupted, creating an extensive and high-reaching umbrella cloud over the open ocean, hindering traditional isopach mapping and fallout volume estimation. In MODIS satellite imagery, ocean surface water was discolored around Hunga following the eruption, which we attribute to ash fallout from the umbrella cloud. By relating intensity of ocean discoloration to fall deposit thicknesses in the Kingdom of Tonga, we develop a methodology for estimating airfall volume over the open ocean. Ash thickness measurements from 41 locations are used to fit a linear relationship between ash thickness and ocean reflectance. This produces a minimum airfall volume estimate of <span>({1.8}_{-0.4}^{+0.3})</span> km³. The whole eruption produced &gt; 6.3 km³ of uncompacted pyroclastic material on the seafloor and a caldera volume change of 6 km³ DRE. Our fall estimates are consistent with the interpretation that most of the seafloor deposits were emplaced by gravity currents rather than fall deposits. Our proposed method does not account for the largest grain sizes, so is thus a minimum estimate. However, this new ocean-discoloration method provides an airfall volume estimate consistent with other independent measures of the plume and is thus effective for rapidly estimating fallout volumes in future volcanic eruptions over oceans.</p>","PeriodicalId":55297,"journal":{"name":"Bulletin of Volcanology","volume":"71 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141172910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"CO2 emissions during the 2023 Litli Hrútur eruption in Reykjanes, Iceland: ẟ13C tracks magma degassing","authors":"Tobias P. Fischer, Céline L. Mandon, Scott Nowicki, John Ericksen, Felipe Rojas Vilches, Melissa A. Pfeffer, Alessandro Aiuppa, Marcello Bitetto, Angelo Vitale, G. Matthew Fricke, Melanie E. Moses, Andri Stefánsson","doi":"10.1007/s00445-024-01751-7","DOIUrl":"https://doi.org/10.1007/s00445-024-01751-7","url":null,"abstract":"<p>We report CO₂ emission rates and plume δ¹³C during the July 2023 eruption at Litli Hrútur in the Fagradalsfjall region of the Reykjanes Peninsula. The CO₂ emission rates were measured by UAV utilizing a new method of data extrapolation that enables obtaining rapid flux results of dynamic eruption plumes. The δ¹³C values are consistent with degassing-induced isotopic fractionation of the magma during and after the eruption. Our results show that rapid, real-time CO₂ flux measurements coupled with isotopic values of samples collected at the same time provide key insights into the dynamics of volcanic eruptions and have the potential of forecasting the termination of activity.</p>","PeriodicalId":55297,"journal":{"name":"Bulletin of Volcanology","volume":"2012 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141198359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magma mingling during the 1959 eruption of Kīlauea Iki, Hawaiʻi","authors":"Jennifer Marsh, Marie Edmonds, Bruce Houghton, Iris Buisman, Richard Herd","doi":"10.1007/s00445-024-01748-2","DOIUrl":"https://doi.org/10.1007/s00445-024-01748-2","url":null,"abstract":"<p>Magma mingling and mixing are common processes at basaltic volcanoes and play a fundamental role in magma petrogenesis and eruption dynamics. Mingling occurs most commonly when hot primitive magma is introduced into cooler magma. Here, we investigate a scenario whereby cool, partially degassed lava is drained back into a conduit, where it mingles with hotter, less degassed magma. The 1959 eruption of Kīlauea Iki, Hawaiʻi involved 16 high fountaining episodes. During each episode, fountains fed a lava lake in a pit crater, which then partially drained back into the conduit during and after each episode. We infer highly crystalline tachylite inclusions and streaks in the erupted crystal-poor scoria to be the result of the recycling of this drain-back lava. The crystal phases present are dendrites of plagioclase, augite and magnetite/ilmenite, at sizes of up to 10 µm. Host sideromelane glass contains 7–8 wt% MgO and the tachylite glass (up to 0.5% by area) contains 2.5–6 wt% MgO. The vesicle population in the tachylite is depleted in the smallest size classes (&lt; 0.5 mm) and has overall lower vesicle number densities and a higher degree of vesicle coalescence than the sideromelane component. The tachylite exhibits increasingly complex ‘stretching and folding’ mingling textures through the episodes, with discrete blocky tachylite inclusions in episodes 1 and 3 giving way to complex, folded, thin filaments of tachylite in pyroclasts erupted in episodes 15 and 16. We calculate that a lava lake crust 8–35 cm thick may have formed in the repose times between episodes, and then foundered and been entrained into the conduit during drain-back. The recycled fragments of crust would have been reheated in the conduit, inducing glass devitrification and crystallisation of pyroxene, magnetite and plagioclase dendrites and eventually undergoing ductile flow as the temperature of the fragments approached the host magma temperature. We use simple models of magma mingling to establish that stretching and folding of recycled, ductile lava could involve thinning of the clasts by up to a factor of 10 during the timescale of the eruption, consistent with observations of streaks and filaments of tachylite erupted during episodes 15 and 16, which may have undergone multiple cycles of eruption, drain-back and reheating.</p>","PeriodicalId":55297,"journal":{"name":"Bulletin of Volcanology","volume":"125 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141172907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Release the crackin': The influence of brittle behavior on gas retention in crystal-rich magma","authors":"Thomas G. Herbst, Alan G. Whittington, Mattia Pistone, James D. Schiffbauer, Tara Selly","doi":"10.1007/s00445-024-01747-3","DOIUrl":"https://doi.org/10.1007/s00445-024-01747-3","url":null,"abstract":"<p>Crystal-rich silicic lavas commonly erupt from hazardous lava dome-forming volcanoes, characterized by both effusive and explosive eruptions. Magma explosivity is inherently dependent on its ability to store pressurized gas, which can be released through permeable pathways like fractures or connected bubbles, yet the role crystals play in regulating gas escape is poorly constrained in crystal-rich systems. We explored the gas storage capacity and outgassing efficiency of crystal-rich magmas through experimental vesiculation of hydrous dacite samples containing crystal volume fractions (<span>({phi }_{x})</span>) between 0.5 and 0.8. The maximum unconnected gas volume (isolated porosity) decreases exponentially with increasing crystallinity. We quantify the relative outgassing efficiency as a function of <span>({phi }_{x})</span> using changes in isolated melt porosity during open-system degassing (outgassing). Mean isolated porosity, for <span>({phi }_{x})</span> = 0.5, increases from ~ 0.33 at the start of outgassing to ~ 0.67 by the end, doubling its trapped bubbles. For <span>({phi }_{x})</span> = 0.7, isolated porosity increases from ~ 0.1 to ~ 0.2, implying gas retention and outgassing efficiency are strongly dependent on crystallinity. Outgassing occurs rapidly via fracturing at porosities &lt; 0.1 when <span>({phi }_{x})</span> ≥ 0.7. Fracturing and bubble coalescence are both inefficient outgassing mechanisms at <span>({phi }_{x})</span> = 0.5 due to viscoelastoplastic deformation, which leads to an increase of isolated porosity. Between <span>({phi }_{x})</span> of 0.5 and 0.7, samples sustained a three-fold difference in isolated porosity, implying that gas retention and eruptive behavior of crystal-rich magmas may be controlled by the onset and efficacy of crack-dominated outgassing and can be modulated by relatively small changes in crystallinity.</p>","PeriodicalId":55297,"journal":{"name":"Bulletin of Volcanology","volume":"26 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141165539","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Volcanic lightning reveals umbrella cloud dynamics of the 15 January 2022 Hunga volcano eruption, Tonga","authors":"P. A. Jarvis, T. G. Caldwell, C. Noble, Y. Ogawa, C. Vagasky","doi":"10.1007/s00445-024-01739-3","DOIUrl":"https://doi.org/10.1007/s00445-024-01739-3","url":null,"abstract":"<p>The 15 January 2022 eruption of Hunga volcano, Tonga, significantly impacted the Kingdom of Tonga as well as the wider Pacific region. The eruption column attained a maximum height of 58 km whilst the umbrella cloud reached a diameter approaching 600 km within about 3 h. The frequency of volcanic lightning generated during the eruption was also unprecedented, with the Vaisala Global Lightning Database (GLD360) recording over 3 × 10⁵ strikes over a 2-h period. We have combined Himawari-8 satellite imagery with the spatiotemporal distribution of lightning strikes to constrain the dynamics of umbrella spreading and infer a timeline of events for the climactic phase of the eruption. Lightning was initially concentrated directly above Hunga, with an areal extent that grew with the observed eruption cloud. However, about 20 min after the eruption onset, radial structure appeared in the lightning spatial distribution, with strikes clustered both directly above Hunga and in an annulus of radius ~ 50 km. Comparison with satellite imagery shows that this annulus coincided with the umbrella cloud front. The lightning annulus and umbrella front grew synchronously to a radius of ~ 150 km before the umbrella cloud growth rate decreased whilst the annulus itself contracted to a smaller radius of about 50 km again. We interpret that the lightning annulus resulted from an enhanced rate of particle collisions and subsequent triboelectrification due to enhanced vorticity in the umbrella cloud head. Our results demonstrate that volcanic lightning observations can provide insights into the internal dynamics of umbrella clouds and should motivate more quantitative models of umbrella spreading.</p>","PeriodicalId":55297,"journal":{"name":"Bulletin of Volcanology","volume":"44 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140939294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of crustal stress state on magmatic stalling and ascent: case study from Puyehue-Cordón Caulle, Chile","authors":"Katy J. Chamberlain, Daniel J. Morgan, Luis E. Lara, Richard Walshaw, Joe Gardner, Simon Chenery, Ian L. Millar, Doris Wagner","doi":"10.1007/s00445-024-01740-w","DOIUrl":"https://doi.org/10.1007/s00445-024-01740-w","url":null,"abstract":"<p>The Southern Volcanic Zone (SVZ) in Chile is an active continental arc with a complex history of volcanism, where a range of magmatic compositions have been erupted in a variety of styles. In the Central SVZ, both monogenetic and polygenetic volcanoes exist, in close proximity to the Liquiñe-Ofqui Fault System (LOFS), but with variable local stress states. Previous studies have inferred varying crustal storage timescales, controlled by the orientation of volcanic centres relative to the N-S striking LOFS and σ_HMax in this region. To assess the relationship between volcanism and crustal stress states affected by large-scale tectonic structures and edifice controls, we present whole rock geochemical data, to ensure consistency in source dynamics and crustal processing, mineral-specific compositional data, thermobarometry, and Fe–Mg diffusion modelling in olivine crystals from mafic lavas, to assess ascent timescales, from the stratovolcanic edifice of Puyehue-Cordón Caulle and proximal small eruptive centres. Textural observations highlight differences in crystal maturation timescales between centres in inferred compression, transpression, and extension, yet source melting dynamics remain constant. Only samples from the stratovolcanic edifice (in regional compression) preserve extensive zonation in olivine macrocrysts; these textures are generally absent from proximal small eruptive centres in transtension or extension. The zonation in olivines from stratovolcanic lavas yields timescales on the order of a few days to a few weeks, suggesting that even in environments which inhibit ascent, timescales between unrest and eruption of mafic magmas may be short. Significantly, high-resolution compositional profiles from olivine grains in the studied samples record evidence for post-eruptive growth and diffusion, highlighting the importance of careful interpretation of diffusion timescales from zoned minerals in more slowly cooled lavas when compared with tephra samples.</p>","PeriodicalId":55297,"journal":{"name":"Bulletin of Volcanology","volume":"2 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140884847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modeling dike trajectories in a biaxial stress field with coupled magma flow, fracture, and elasticity","authors":"Laura A. Blackstone, Benjamin E. Grossman-Ponemon, Elías R. Heimisson, Adrian J. Lew, Paul Segall","doi":"10.1007/s00445-024-01734-8","DOIUrl":"https://doi.org/10.1007/s00445-024-01734-8","url":null,"abstract":"<p>Because dike propagation depends on stress state, the geometry of dikes can be used to make inferences about crustal stress conditions during emplacement. Early work relied on analytical solutions for stress in a two-dimensional elastic medium with a pressurized circular magma chamber and biaxial far-field stress. The principal stress trajectories in this classical model depend on the ratio of deviatoric stress magnitude to chamber pressure. Assuming dikes follow principal stress trajectories and bounding plausible magma chamber excess pressures lead to estimates of deviatoric stress magnitudes from the map pattern of dikes. Mériaux and Lister (2002) pointed out that this approach ignored stresses due to the magma-filled dikes themselves, which significantly alter predicted dike trajectories. They estimated deviatoric stresses 2 to 5 times previous estimates. However, Mériaux and Lister (2002) assumed the pressure distribution within the dike rather than computing it from viscous magma flow. We revisit this simplification using a 2D model which fully couples a linear elastic host rock with a pressurized chamber and a fluid-filled dike, assuming the lubrication approximation for viscous flow. This model is solved using the finite element method (FEM). Ensuring that dike propagation is stable limits the dike-tip cavity pressure for realistic fracture toughness. We find that computed trajectories fall between the classical principal stress and Mériaux and Lister (2002) trajectories for given regional stress and chamber pressure conditions. This leads to deviatoric stress magnitude estimates that are 1 to 2 times the classical estimates, and 1/2 to 1/3 the Mériaux and Lister (2002) estimates. We also explore the consequences of chamber depressurization due to magma outflow during dike propagation. For a given melt compressibility, the resulting trajectories align more closely with those obtained from the classical model, compared to those obtained assuming a constant chamber pressure. At higher ratios of tectonic stress to chamber pressure, the trajectories are nearly identical. In both the constant pressure and depressurizing chamber cases, our results suggest that realistic magma pressure profiles within a dike lead to smaller estimated ratios of deviatoric stress to chamber pressure than found by Mériaux and Lister (2002). Future work should extend dike propagation models to three dimensions, and more thoroughly explore effects of magma compressibility.</p>","PeriodicalId":55297,"journal":{"name":"Bulletin of Volcanology","volume":"22 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140800413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The last 1100 years of activity of La Fossa caldera, Vulcano Island (Italy): new insights into stratigraphy, chronology, and landscape evolution","authors":"Federico Di Traglia, Marco Pistolesi, Costanza Bonadonna, Mauro Rosi","doi":"10.1007/s00445-024-01738-4","DOIUrl":"https://doi.org/10.1007/s00445-024-01738-4","url":null,"abstract":"<p>A detailed study of past eruptive activity is crucial to understanding volcanic systems and associated hazards. We present a meticulous stratigraphic analysis, a comprehensive chronological reconstruction, thorough tephra mapping, and a detailed analysis of the interplay between primary and secondary volcanic processes of the post-900 AD activity of La Fossa caldera, including the two main systems of La Fossa volcano and Vulcanello cones (Vulcano Island, Italy). Our analyses demonstrate how the recent volcanic activity of La Fossa caldera is primarily characterized by effusive and Strombolian activity and Vulcanian eruptions, combined with sporadic sub-Plinian events and both impulsive and long-lasting phreatic explosions, all of which have the capacity to severely impact the entire northern sector of Vulcano island. We document a total of 30 eruptions, 25 from the La Fossa volcano and 5 from Vulcanello cones, consisting of ash to lapilli deposits and fields of ballistic bombs and blocks. Volcanic activity alternated with significant erosional phases and volcaniclastic re-sedimentation. Large-scale secondary erosion processes occur in response to the widespread deposition of fine-grained ash blankets, both onto the active cone of La Fossa and the watersheds conveying their waters into the La Fossa caldera. The continuous increase in ground height above sea level, particularly in the western sector of the caldera depression where key infrastructure is situated, is primarily attributed to long-term alluvial processes. We demonstrate how a specific methodological approach is key to the characterization and hazard assessment of low-to-high intensity volcanic activity, where tephra is emitted over long time periods and is intercalated with phases of erosion and re-sedimentation.</p>","PeriodicalId":55297,"journal":{"name":"Bulletin of Volcanology","volume":"100 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140629983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tracking magma pathways and surface faulting in the Southwest Rift Zone and the Koaʻe fault system (Kīlauea volcano, Hawai ‘i) using photogrammetry and structural observations","authors":"Stefano Mannini, Joël Ruch, Richard W. Hazlett, Drew T. Downs, Carolyn E. Parcheta, Steven P. Lundblad, James L. Anderson, Ryan Perroy, Nicolas Oestreicher","doi":"10.1007/s00445-024-01735-7","DOIUrl":"https://doi.org/10.1007/s00445-024-01735-7","url":null,"abstract":"<p>Volcanic islands are often subject to flank instability, resulting from a combination of magmatic intrusions along rift zones and gravitational spreading causing extensional faulting at the surface. Here, we study the Koaʻe fault system (KFS), located south of the summit caldera of Kīlauea volcano in Hawaiʻi, one of the most active volcanoes on Earth, prone to active faulting, episodic dike intrusions, and flank instability. Two rift zones and the KFS are major structures controlling volcanic flank instability and magma propagation. Although several magmatic intrusions occurred over the KFS, the link between these faults, two nearby rift zones and the flank instability, is still poorly studied. To better characterize the KFS and its structural linkage with the surrounding fault and rift zones, we performed a detailed structural analysis of the extensional fault system, coupled with a helicopter photogrammetric survey, covering part of the south flank of Kīlauea. We generated a high-resolution DEM (~ 8 cm) and orthomosaic (~ 4 cm) to map the fracture field in detail. We also collected ~ 1000 ground structural measurements of extensional fractures during our three field missions (2019, 2022, and 2023). We observed many small, interconnected grabens, monoclines, rollover structures, and en-echelon fractures that were in part previously undocumented. We estimate the cumulative displacement rate across the KFS during the last 600 ~ 700 years and found a decrease toward the west of the horizontal component from 2 to 6 cm per year, consistent with GNSS data. Integrating morphology observations, fault mapping, and kinematic measurements, we propose a new kinematic model of the upper part of the Kīlauea’s south flank, suggesting a clockwise rotation and a translation of a triangular wedge. This wedge is bordered by the extensional structures (ERZ, SWRZ, and the KFS), largely influenced by gravitational spreading. These findings illustrate a structural linkage between the two rift zones and the KFS, the latter being episodically affected by dike intrusions.</p>","PeriodicalId":55297,"journal":{"name":"Bulletin of Volcanology","volume":"11 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140566181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unearthing concealed caldera complexes through geophysical methods: the Cretaceous Bumbeni Complex, South Africa","authors":"N. Hicks, E. Chirenje, M. Ncume, L. Hoyer, J. W. Bristow, C. Craill, J. Barkhuizen","doi":"10.1007/s00445-024-01733-9","DOIUrl":"https://doi.org/10.1007/s00445-024-01733-9","url":null,"abstract":"<p>Unveiling buried volcanic systems has been made easier through the application of high-resolution geophysical datasets in recent times. This improves the elucidation of systems related to caldera formation and collapse. An early Cretaceous bimodal volcanic suite, the Bumbeni Complex, crops out in a limited region of northern KwaZulu-Natal, South Africa and is dominated by felsic ignimbrites and rhyolitic lavas. However, the extent and evolution of the complex has remained ambiguous as much of the sequence is buried beneath recent sedimentary cover. This study has identified five nested caldera systems forming a caldera complex ~ 20 km in diameter through high-resolution aeromagnetic and radiometric surveys. Individual calderas are resolved by prominent positive and negative anomalies ranging from − 200 to + 300 nT based on International Geomagnetic Reference Field (IGRF) corrected Reduced to Pole (RTP) data. Field evidence and borehole core data indicate that caldera formation was accompanied by voluminous ignimbrite deposition with both intra- and extra-caldera volcaniclastic facies developed. Anomaly D, which represents the only exposed caldera structure within the complex, provides insights into the intrusive and extrusive rock types including syenite and granitic ring dykes, and ignimbrite units, resolved in radiometric data. Geophysical interpretations allow for the construction of an approximate relative-time-sequenced evolutionary model for the complex. Susceptibility modelling of the complex has identified circumferential dykes forming the margins of the calderas with a possible magma reservoir developed at ~ 4 km depth. The identification of silicic caldera systems in this region of southern Africa may have causal affiliations to the initiation and propagation of Gondwana rifting along the emergent northern KwaZulu-Natal margin.</p>","PeriodicalId":55297,"journal":{"name":"Bulletin of Volcanology","volume":"119 1","pages":""},"PeriodicalIF":3.5,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140566175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}