Type Of Eruption Research Articles

The quaternary eruptive sequence of the Tengchong volcanic group, southwestern China

The Tengchong volcanic group in SW China is situated along the NS-oriented tectonic belt in the southeastern margin of the Tibetan plateau. The volcanic field has experienced intense tectonic stress due to the continuous subduction of the Indian plate under the Eurasian plate, and throughout Quaternary has experienced pervasive volcanism. The present volcanic rocks cover the successive domains of basic, intermediate (Group II) and acid (Group I) rocks, belonging to the high-K calc-alkaline series. Correspondingly, the eruption types of the Tengchong volcanoes roughly fall into two categories: explosive eruptions with large amounts of volcaniclastics and lava; and moderately quiet central eruptions with small amounts of scoria and lava overflow.According to systematic geochronological dating methods such as K-Ar, Ar-Ar, 14C AMS, and OSL dating, as well as field work, we separate the eruptive sequence of the Tengchong volcanic group during the Quaternary into four subsequences: the early Pleistocene, middle Pleistocene, late Pleistocene and the Holocene epoch. The early to middle Quaternary eruption sequence consists of a series of explosive eruptions, with almost all the eruptive dacitic volcaniclasts and lava constituting the bottom layer of the Tengchong basin. The Tengchong volcanism reached its climax in the late Pleistocene when it formed numerous cinder cones. A series of moderately quiet central eruptions occurred in the late Quaternary, and basic and intermediate-acid volcanic rocks formed the upper layer of the basin. From this study, three volcanoes are determined to be of Holocene age, and we conclude that the volcanic activity moved from the south and periphery to the north and center, and ended in the Heikongshan eruption ∼ 3600 years ago.

Stable hydrogen and oxygen isotopic compositions of water vapor in volcanic plumes sampled in glass bottles using cavity ring-down spectroscopy

The isotopic compositions (δ2H and δ18O) of fumarolic H2O emitted during volcanic eruptions can distinguish the type of eruption (magmatic or phreatic), but direct sampling of fumarolic H2O in eruptive volcanoes is often neither practical nor safe. In this study, we developed a new analytical system to safely determine the isotopic compositions of fumarolic H2O from the volcanic plume samples taken in glass bottles. The system consisted of stainless steel gas introduction line and a cavity ring-down spectroscopic unit. In the 1 L glass sample bottles, analytical precision (1σ) was estimated to be better than 2‰ and 0.3‰, respectively, when >3400 ppmv of H2O was introduced, and better than 3‰ (δ2H) and 0.4‰ (δ18O) when >1800 ppmv of H2O was introduced. The H2O concentration accuracy was better than 5%. Using this in-situ collection method and the analytical system, we determined the isotopic compositions of H2O in volcanic plume samples taken at Iwo-yama in the Kirishima volcano group (Japan), and deduced the isotopic composition of fumarolic H2O from the volcanic plume. The reciprocal of the H2O concentration in the plume samples showed a good linear relationship with the isotopic composition. The isotopic composition of fumarolic H2O from Iwo-yama estimated from the plume samples directly corresponded to the determined fumarolic H2O. This method improves upon previous analyses to obtain the isotopic compositions of fumarolic H2O, particularly by reducing tedious, time consuming, and dangerous sampling of water vapor at volcanic fumaroles.

Cutaneous manifestations of adult T-cell leukemia/lymphoma.

Adult T-cell leukemia/lymphoma (ATLL) is an aggressive peripheral T-cell lymphoma caused by the human T-lymphotropic virus type-1 (HTLV-1). The skin is affected in approximately half of ATLL patients, and it may be the first manifestation of the disease. The skin lesions of ATLL are polymorphous, and depending on the type of skin eruption, it is possible to predict the prognosis of the disease. Besides specific skin lesions, other non-specific lesions and increased risk of cutaneous and systemic infections are observed. In this article, we describe the different skin lesions of ATLL patients (specific, non-specific, and infectious lesions), the different histopathological patterns, and the association of clinicopathological characteristics with prognosis. Recognition of ATLL skin lesions is essential for the correct management and the search for the virus, even in non-endemic regions, where global migration may bring HTLV-1 infected individuals.

The color of skin: purple diseases of the skin, nails, and mucosa

The color purple can be seen in several types of eruptions including inflammatory dermatoses like lichen planus, infectious dermatoses like ecthyma gangrenosum, neoplasms like Kaposi sarcoma, and vasculitis and vasculopathy. The current review focuses on the clinical appearance, pathophysiology, and treatment of several vasculitides and vasculopathies including capillaritis, cutaneous small-vessel vasculitis, immunoglobulin A (IgA) vasculitis, cryoglobulinemia, granulomatosis with polyangiitis, eosinophilic granulomatosis with polyangiitis, microscopic polyangiitis, polyarteritis nodosum, warfarin-induced skin necrosis, heparin-induced thrombocytopenia, purpura fulminans, antiphospholipid antibody syndrome, calciphylaxis, levamisole-induced vasculopathy, and thrombotic thrombocytopenic purpura. Dermatologists play a central role in treating patients with cutaneous vasculitis and vasculopathy and may have the opportunity to facilitate identification of systemic disease by diagnosing cutaneous vasculitis and vasculopathy.

Impact of incorporation of volcanic ash on geopolymerization of eco-friendly geopolymer composites: A review

Volcanic ash is a product from an explosive type of volcanic eruptions. Fresh particles of volcanic ash are gritty, abrasive, vexatious and corrosive with huge scale dispersion. Consequently, it is the need of the hour to dispose this waste systematically to have relief from dilemmas like land fillings; climatic changes, pollution of the environment, water, and health hazards although the soil is a mineral intake. This crucially reviewed manuscript includes not merely the comprehension of the incorporation of volcanic ash to develop novel green Geopolymer composites but also to study its impact on the geopolymerization reaction kinetics and reactivity at dissimilar temperatures along with a precise account of its chemistry, mineralogy and the morphology.

COVER (PMS 180&K) (p/u from previous issue w/updates)

Adult T-cell leukemia/lymphoma (ATLL) is an aggressive peripheral T-cell lymphoma caused by the human T-lymphotropic virus type-1 (HTLV-1). The skin is affected in approximately half of ATLL patients, and it may be the first manifestation of the disease. The skin lesions of ATLL are polymorphous, and depending on the type of skin eruption, it is possible to predict the prognosis of the disease. Besides specific skin lesions, other non-specific lesions and increased risk of cutaneous and systemic infections are observed. In this article, we describe the different skin lesions of ATLL patients (specific, non-specific, and infectious lesions), the different histopathological patterns, and the association of clinicopathological characteristics with prognosis. Recognition of ATLL skin lesions is essential for the correct management and the search for the virus, even in non-endemic regions, where global migration may bring HTLV-1 infected individuals.

Diversity of soluble salt concentrations on volcanic ash aggregates from a variety of eruption types and deposits

Ash aggregation is a common phenomenon in particle-laden environments of volcanic eruption plumes and pyroclastic density currents. Many of these initially fragile aggregates gain sufficient mechanical strength to remain intact after atmospheric transport and deposition. Several processes contribute to ash aggregate stability, including electrostatic and hydrostatic bonding, ice formation, and cementation by salt precipitates. Here, we compare leachate chemistry from aggregates from a variety of eruption and sedimentation conditions, ranging from dry magmatic eruptions with immediate deposition, to eruptions through seawater. The leachate data shows that the broad window of opportunity for aggregation and aggregate break-up may be used to qualitatively constrain suspended ash concentration and its temporal evolution. We show that aggregation rate and aggregate stability largely depend on the availability of external water and salt source. In particular, high humidity and extensive salt precipitation in seawater environments, such as during the Surtseyan eruptions, promote high aggregation rates and aggregate stability, with accordingly accentuated proximal deposition and aggregate concentration in the deposits. On the other hand, low humidity and salt concentrations during dry magmatic eruptions promote less aggregation and more efficient aggregate break-up, explaining the rarity of aggregates in the deposits. These results have strong implications for the ash budget in volcanic plumes and associated models of plume dispersal and related hazards.

Three-dimensional imaging of Miocene volcanic effusive and conduit facies: Implications for the magmatism and seafloor spreading of the South China Sea

Abstract An integrated and practical seismic-based three-dimensional (3D) visualization technique of volcanic effusive and conduit facies is proposed in the Miocene Lower Zhujiang Formation of the Baiyun Sag, Pearl River Mouth Basin (PRMB), South China Sea (SCS). The technique is based mainly on the 3D visualization to separately described the strong amplitude reflection volcanic effusive facies and the weak amplitude chaotic reflection volcanic conduit facies with different seismic-cube attributes (instantaneous amplitude attribute and variance cube attribute). The detail work-flow of the method has been proposed with eight steps, including the original data type, seismic attributes selection, the visualizing skills and the final validation with borehole and thin sections. It is convenient to operate and describe the spatial distribution and interrelation of various volcanic facies effectively and intuitively. The 3D imaging result of different volcanic facies described in the Baiyun Sag can be viewed from any perspectives and better understand the related genesis mechanism which associated with the NW–SE trend normal fault system during the breakup stage. The two volcanic facies indicate that the spatial distribution of the volcanic rocks is parallel to the normal faults strike and the magma probably flows along the normal fault plane and then feds into the volcanic mounds with eruption. The volcanic mounds are mostly belonged to the central-fissure eruption types, and mainly correspond to the second magmatic episode (∼23.8 Ma) of Early Miocene in the PRMB and were induced associated with the seafloor spreading of the northern SCS. We may easier to find effective volcanic reservoirs or other volcano-related metallic minerals based on the proposed new method. This significant work can also serve as a useful reference for other continental margins or sedimentary basins with typical volcanic influence.

Rate of Melt Ascent Beneath Iceland From the Magmatic Response to Deglaciation

AbstractObservations of the time lag between the last deglaciation and a surge in volcanic activity in Iceland constrain the average melt ascent velocity to be ≥50 m/year. Although existing theoretical work has explained why the surge in eruption rates increased 5–30‐fold from the steady‐state rates during the last deglaciation, they cannot account for large variations of Rare Earth Element (REE) concentrations in the Icelandic lavas. Lavas erupted during the last deglaciation are depleted in REEs by up to 70%; whereas existing models, which assume instantaneous melt transport, can only produce at most 20% depletion. Here we develop a numerical model with finite melt ascent velocity and show that the variations of REEs are strongly dependent on the melt ascent velocity. When the average melt ascent velocity is 100 m/year, the variation of La calculated by our model is comparable to that of the observations. In contrast, when the melt ascent velocity is 1,000 m/year or above, the model variation of La becomes significantly lower than observed, which explains why previous models with instantaneous melt transport did not reproduce the large variations. We provide the first model that takes account of the diachronous response of volcanism to deglaciation. We show by comparing our model calculations of the relative volumes of different eruption types (subglacial, finiglacial, and postglacial) and the timing of the bursts in volcanic eruptions with the observations across different volcanic zones that the Icelandic average melt ascent velocity during the last deglaciation is likely to be ∼100 m/year.

Origin of Shallow Volcanic Tremor: The Dynamics of Gas Pockets Trapped Beneath Thin Permeable Media

AbstractLinking volcano‐seismic signals with subsurface processes is crucial to improve the forecasting of volcanic eruptions. One of the most enigmatic signals is shallow volcanic tremor, a highly periodic ground vibration that is typically sourced beneath the crater of active volcanoes, is long lasting (from minutes to years), appears during unrest periods, and frequently precedes eruptions. In this paper, we demonstrate that shallow tremor can be produced by periodic pressure oscillations emerging spontaneously beneath permeable media (e.g., fractured magma caps). These pressure oscillations are the result of three concurrent processes: (a) the transient porous flow of gases through the permeable cap; (b) the temporary accumulation of these gases beneath the cap, forming a gas pocket; and (c) the random supply of volatiles from deeper levels. For highly permeable media (≥10−12 m2; realistic for shallow volcanic edifices), the pressure in subsurface gas pockets is governed by the equation of a linear oscillator; hence, under proper conditions, periodic pressure oscillations emerge during the transfer of gases from the Earth's interior to the surface. Our model is consistent with geophysical data showing that the tremor source is localized at a fixed region and can explain the main characteristics of ground vibrations, including frequency gliding, variations of seismic amplitude prior to eruptions, and the different types of tremor observed. For thin permeable caps (<100 m), we find that different eruption mechanisms (e.g., magma ascent vs. cap sealing) leave distinct footprints in the tremor properties, thus opening new perspectives to forecast the type and style of impending eruptions.

Cutaneous leishmaniasis: an evolving disease with ancient roots.

Cutaneous leishmaniasis (CL) remains a prioritized neglected tropical disease. CL novel presentations call for updating its features. A multiregional cohort of 396 patients with confirmed CL was reviewed. Lesion's clinical stage and eruption type were assigned. Disease was considered as extensive if numerous (≥5), large (>3 cm), disfiguring, threatening vital sensory organs, and/or older than 12 months. Microscopically, Ackerman's inflammatory pattern, Ridley's pattern (RP), and parasitic index (PI) were recorded. Microscopic variables pertaining to the organisms, epidermis, and host's inflammatory response were also assessed. All cases were confirmed and speciated molecularly. In our region, 71.8% of cases showed extensive disease with 15.7% exceeding 12 months duration. Leishmania tropica accounted for 91.3% of cases while Leishmania major constituted 8.7% and presented solely as dry lesions. The dominant inflammatory composite consisted of plasma cells, lymphocytes, and histiocytes. Granulomatous inflammation was present in 55.5%. Most cases showed interface changes (72.7%), spongiosis (75.3%), and marked epidermal hyperplasia (63.9%). Transepidermal elimination of organisms was present in 29.2% of cases. None of traditional classification patterns (clinical stage, microscopic pattern, and RP) showed the predicted linear correlation with lesion age. High and low PI levels correlated with early and healing microscopic patterns, respectively, but did not correlate with the corresponding RPs. PI was bimodal with peaks at 3-6 and 9-12 months. Cutaneous leishmaniasis is an evolving disease defying the traditional prediction classifications. Our study sets the ground for adopting updated clinical courses, microscopic presentation, and species mapping.

Distribution and gas-bearing properties of Permian igneous rocks in Sichuan Basin, SW China

Abstract Based on the analysis of outcrop, seismic, logging and drilling data, combined with exploration practice, the characteristics, distribution, reservoir performance and gas-bearing properties of Permian igneous rocks in Sichuan Basin are studied. The study shows that central volcanic eruptive facies are developed in Sichuan Basin, and their lithological assemblages and distribution characteristics show obvious differences. The igneous rocks are mainly distributed in three regions: the southwestern part of the basin has dominantly large- scale overflow facies basalts; the central and western part of the basin, Jianyang-Santai area, develop intrusive rocks, volcanic lavas (basalts) and pyroclastic rocks; and the eastern part of Sichuan, Dazhou-Liangping area, only develop diabase and basalts. Five aspects of understandings are achieved: (1) The Upper Permian igneous rocks can be divided into intrusive rocks and extrusive rocks, with the extrusive rocks as the main body. The chemical compositions of the extrusive rocks are characterized by both alkaline basalt and tholeiitic basalt, and belong to the subalkaline type of transitional basalt magma eruption. (2) There are obvious rhythmic structures vertically among overflow facies basalt, and the single rhythmic layer consists of, from bottom up, pyroclastic rocks (undeveloped), gray and dark gray porphyritic basalts (unstable), dark gray and purple microcrystalline-cryptocrystalline basalts, dark greyish green porous and amygdaloid basalts; the central volcanic eruption shows the rhythm and the vertical sequence of volcanic clastic rocks (agglomerates and breccias), volcanic lava, tuffaceous lava from bottom to top. (3) The pore types of basalt and pyroclastic rocks are diverse, mainly dissolution pore and de-vitrification micropore, but their physical properties are different. Basalt is characterized by ultra-low pore permeability, small reservoir thickness, and reservoirs are distributed in the upper and middle parts of the cycle, with poor lateral comparability. Volcanic clastic rocks are medium to high porous reservoirs (Well YT1: porosity: 8.66%−16.48%, average 13.76%) with large thickness and good reservoir quality. (4) Natural gas in basalts in southwestern basin mainly comes from Middle Permian, and natural gas in volcanic clastic rocks in central and western basin comes from Cambrian Qiongzhusi Formation. (5) Analysis of igneous reservoir-forming conditions in different areas shows that there are relatively insufficient gas sources and great differences in preservation conditions in southwestern basin. Reservoirs are poorly developed and gas-bearing is complex. The Jianyang-Santai area in the central and western part of Sichuan Basin has abundant hydrocarbon sources, developed reservoir, favorable preservation conditions and favorable gas geological conditions, and it is a favorable area for gas exploration.

Mangement of Yuvana Pidaka using Mukha Lepa

Yuvana Pidaka (acne vulgaris) is one of the most common, troublesome and frustrating skin care problem for people around the world. It is caused by to Kapha, Vata and Rakta Dhatu involving Rasavaha and Raktavaha Srotas. Apart from others unhealthy life style is identified as the major reason behind the eruption of such lesions. It has adverse effect on self esteem of the subjects and decreases one’s self confidence. Present study tries to understand the therapeutic effect of Mukha Lepa - an external application of Manjishta, Chandana, Yastimadhu and Kushta over the face mixed with milk once every morning for fifteen days after Sadhyovirechana with Avipathi Churna. Study was conducted on ten subjects and assessed with the parameters like Ruja, Kandu, Daha, number and type of eruptions before and after the procedure. The response to the treatment was recorded and the therapeutic effect was evaluated by statistical tests. A considerable change in the complexion over the face of subjects was also noted. It is observed that this particular Lepa is beneficial in the treatment of Yuvana Pidaka apart from improving the complexion of the skin.

COVER (PMS 180&K) (p/u from previous issue w/updates)

Adult T-cell leukemia/lymphoma (ATLL) is an aggressive peripheral T-cell lymphoma caused by the human T-lymphotropic virus type-1 (HTLV-1). The skin is affected in approximately half of ATLL patients, and it may be the first manifestation of the disease. The skin lesions of ATLL are polymorphous, and depending on the type of skin eruption, it is possible to predict the prognosis of the disease. Besides specific skin lesions, other non-specific lesions and increased risk of cutaneous and systemic infections are observed. In this article, we describe the different skin lesions of ATLL patients (specific, non-specific, and infectious lesions), the different histopathological patterns, and the association of clinicopathological characteristics with prognosis. Recognition of ATLL skin lesions is essential for the correct management and the search for the virus, even in non-endemic regions, where global migration may bring HTLV-1 infected individuals.

The Geomorphology, Structure, and Lava Flow Dynamics of Peralkaline Rift Volcanoes From High‐Resolution Digital Elevation Models

AbstractDetailed topographic data from volcanoes can yield key insights into the controls on volcanic activity as well as hazards. High‐resolution digital elevation models generated from remote sensing data enable comparison of the geomorphology and structure of large and inaccessible volcanoes. We present new topographic data for three peralkaline volcanoes in the Main Ethiopian Rift (Fentale, Corbetti, and Gedemsa) and one volcano in the Afar Rift (Dabbahu), combined with field observations, reveal previously unidentified post‐caldera deposits and craters. Vent and crater locations are aligned with rift‐parallel faults and also with rift‐cutting structures in a variety of orientations. Caldera shape is controlled by interaction with these structures. The relative frequency and type of eruption varies greatly between these volcanoes over the past 150 kyr. Gedemsa is now largely inactive; Fentale hosts deposits from many small volume eruptions (<0.1 km3); while Corbetti has produced several large eruptions (~0.4–0.5 km3). Morphometry of peralkaline rhyolite deposits at Corbetti and Fentale, including ogives and levees, provides constraints on rheology. Emplacement viscosities of ~108–1011 Pa s at Fentale are similar to or lower than calc‐alkaline rhyolites and consistent with experimental and theoretical studies. The observations presented here have significant implications for hazard assessment in the Ethiopian rift and highlight the importance of structural features in controlling the location, magnitude, and style of volcanic activity in the Main Ethiopian Rift.

Special Issue on Integrated Study on Mitigation of Multimodal Disasters Caused by Ejection of Volcanic Products: Part 2

Our research project titled “Integrated study on mitigation of multimodal disasters caused by ejection of volcanic products” began in 2014 under SATREPS (Science and Technology Research Partnership for Sustainable Development) and is now coming to an end in 2019. Indonesia has 127 active volcanoes distributed along its archipelago making it a high risk location for volcano-related disasters. The target volcanoes in our study are Guntur, Galunggung, Merapi, Kelud, and Semeru in Java, and Sinabung in North Sumatra. Guntur and Galunggung are currently dormant and are potentially high-risk volcanoes. Merapi generated pyroclastic flows along the Gendol River in 2010, which resulted in over 300 casualties and induced frequent lahars. New eruptive activity of Merapi began in 2018. The 2014 eruption of Kelud formed a gigantic ash plume over 17 km high, dispersing ash widely over the island of Java. Semeru continued minor eruptive activity, accompanying a risk of a dome collapse. The aim of our research includes disaster mitigation of the Sinabung volcano, whose eruption began to form a lava dome at its summit at the end of 2013, followed by frequent pyroclastic flows for approximately 4 years, and the deposits became the source of rain-triggered lahars. Our goal is to implement SSDM (Support System for Decision-Making), which would allow us to forecast volcano-related hazards based on scales and types of eruptions inferred from monitoring data. This special issue collects fundamental scientific knowledge and technology for the SSDM as output from our project. The SSDM is an integrated system of monitoring, constructed scenarios, forecasting scale of eruption, simulation of sediment movement and volcanic ash dispersion in the atmosphere. X-band radars newly installed by our project in Indonesia were well utilized for estimation of spatial distribution not only of rain fall in catchments but also of volcanic ash clouds. Finally, we hope the SSDM will continue to be utilized under a consortium in Merapi, which was newly established in collaboration with our projects, and extended to other volcanoes.

Varicella (chickenpox) morbidity and mortality in hospital: about 19 cases collected at the Yalgado Ouedraogo University Hospital, Burkina Faso

La varicelle est une virose dont l'épidémiologie est mal connue au Burkina Faso. Cette étude s'est donnée pour objectif de décrire le profil hospitalier de la pathologie dans le service des maladies infectieuses du Centre Hospitalier Universitaire Yalgado Ouedraogo (CHU-YO). Il s'est agi d'une série de 19 patients hospitalisés entre le 1er janvier 2005 et le 31 décembre 2014. Ont été inclus, tous les patients avec un dossier complet et exploitable, dont le diagnostic positif de varicelle a été fait. La proportion périodique de varicelle était de 6,2% et a représenté 14,6% des éruptions fébriles. Elle était plus fréquente en 2011, de janvier à mars. L'âge médian était de 19 ans, et la moitié des patients avaient entre 6 et 30 ans. Les comorbidités étaient dominées par l'infection à VIH et l'herpès. Sur le plan clinique, la fièvre et le prurit étaient les symptômes communs et la vésicule la principale éruption. A l'admission, les principales complications étaient pulmonaires, hématologiques et cutanées. La durée médiane d'hospitalisation était de 5 jours, avec des extrêmes de 0 et 13 jours. Les principaux traitements étaient antiviral dans 9 cas, antipyrétique dans 19 cas, local dans 17 cas et antihistaminique dans 11 cas. Sur 19 cas de varicelle, 14 ont guéri et deux sont décédés, dont un adulte sur 10 et 1 enfant sur 9. Si la varicelle est une affection habituellement bénigne, elle peut être fatale chez l'adulte et l'enfant en cas de complications graves.

How Do Tropical, Northern Hemispheric, and Southern Hemispheric Volcanic Eruptions Affect ENSO Under Different Initial Ocean Conditions?

AbstractCurrent understanding of volcanic effects on El Niño–Southern Oscillation in terms of eruption type and initial ocean condition (IOC) remains elusive. We use last‐millennium proxy reconstructions to show how volcanic impacts depend on eruption type and IOC. When the IOC is not a strong El Niño, it is likely that an El Niño will mature in the second winter following 79% (p < 0.01) of Northern Hemispheric eruptions and in the first winter following 81% (p < 0.01) of tropical and 69% of Southern Hemispheric eruptions. For a strong El Niño‐IOC, no significant El Niño will occur in the first winter after any type of eruption. The eruptions need to be large enough to cause these diverse effects. Our last‐millennium simulation confirms the IOC effect, except that a La Niña occurs in the first winter following most tropical eruptions due to overestimated volcanic cooling in the model.

Geological mapping of volcanic terrains: Discussion on concepts, facies models, scales, and resolutions from New Zealand perspective

Geological mapping in volcanic terrains is a challenging task as there needs to be input from various geologists' groups and only limited, often ambiguous guidelines exist. Volcanoes and volcanic successions are in many ways viewed and treated differently than normal sedimentary successions. Volcanic systems are very much a part of the normal sedimentary environment and as such need to integrated into the stratigraphic framework of the enclosing deposits. Most volcanoes supply large volumes of material (pyroclasts) into the sedimentary system. The type and style of eruption determines the time frame of the process, while the type of volcano defines the interaction between volcano and background sedimentation (e.g. monogenetic versus polygenetic volcanic systems). A sound lithostratigraphic framework for mapping geological units in volcanic terrains should also adopt the latest developments in volcanology and understanding of volcanic systems. The lithostratigraphic classification needs to define the mapping unit and apply it to the 1) proximal to distal volcanic facies, 2) eruption styles and their temporal changes, and 3) mode of pyroclast transportation (i.e. fallout versus pyroclastic density current). Differentiation of syn- and post-eruption re-sedimentation, during either within- or between eruptive phases, will determine the most useful stratigraphic nomenclature system to apply to the volcanic units. The approach to geological mapping in ancient and modern volcanic terrains can be different but the same basic stratigraphic principles and classification apply. The purpose of the geological mapping project, whether it be in ancient or modern volcanic systems, will define the style and scale of mapping. The type of output depends upon the objectives and available resources, including the volcanological experience of the mapping team. Here we provide some insight from a New Zealand perspective to geological mapping on active volcanic terrains in a convergent plate margin.

Bayesian Network Modeling and Expert Elicitation for Probabilistic Eruption Forecasting: Pilot Study for Whakaari/White Island, New Zealand

Bayesian Networks (BNs) are probabilistic graphical models that provide a robust and flexible framework for understanding complex systems. Limited case studies have demonstrated the potential of BNs in modeling multiple data streams for eruption forecasting and volcanic hazard assessment. Nevertheless, BNs are not widely employed in volcano observatories. Motivated by the need to assess the probability of fatality when conducting field work, we have worked closely with the New Zealand volcano monitoring team to explore the potential utility of BNs. We adapted a previously published BN for a pilot study to forecast volcanic eruption on Whakaari/White Island. Developing the model structure provided a useful framework for the members of the volcano monitoring team to share their knowledge and interpretation of the volcanic system. We aimed to capture the conceptual understanding of the volcanic processes and represent all observables that are regularly monitored. The pilot model has a total of 30 variables, four of them describing the volcanic processes that can lead to three different types of eruptions: phreatic, magmatic explosive and magmatic effusive. The remaining 23 variables are grouped into observations related to seismicity, fluid geochemistry and surface manifestations. To estimate the model parameters, we held a workshop with eleven experts, including two from outside the monitoring team. To reduce the number of conditional probabilities that the experts needed to estimate, each variable is described by only two states. However, experts were concerned about this limitation, in particular for continuous data. Therefore, they were reluctant to define thresholds to distinguish between states. We conclude that volcano monitoring requires BN modeling techniques that can accommodate continuous variables. More work is required to link unobservable (latent) processes with observables and with eruptive patterns, and to model dynamic processes. A provisional application of the pilot model revealed several key insights. Refining the BN modeling techniques will help advance understanding of volcanoes and improve capabilities for forecasting volcanic eruptions. We consider that BNs will become essential for handling ever-burgeoning observations, and for assessing data’s evidential meaning for operational eruption forecasting.