Violent Strombolian Eruptions Research Articles

The Explosive Activity of the 2021 Tajogaite Eruption (La Palma, Canary Islands, Spain)

AbstractThe explosive activity of the 2021 Tajogaite eruption eludes pigeonholing into well‐defined eruption styles, with a variety of pyroclast ejection modes occurring both alternately and simultaneously at multiple vents. Visually, we defined four endmembers of explosive activity, referred to as fountaining, spattering, ash‐poor jets and ash‐rich jets. To capture the physical parameters of these activities, we deployed a camera array including one high‐speed camera and three high‐definition cameras in two field campaigns. Transitions between and fluctuations within activity occurred at the time scale of minutes to hours, likely driven by the same shallow conduit and vent processes controlling Strombolian activity at other volcanoes, but at higher gas and magma fluxes. From a physical standpoint, mean pyroclast rise velocity ranged 5–50 m/s, maximum ejection velocity 10–220 m/s, and sub‐second mass flux of lapilli to bomb‐sized pyroclasts at the vent 0.2–200 × 103 kg/s. The largest mass flux occurred during fountaining, which contributed by far more than other activities to cone building. All explosive activity exhibited well‐defined pyroclast ejection pulses, and we found a positive correlation between the occurrence rate of ejection pulses and maximum pyroclast ejection velocity. Despite orders of magnitude variations, physical parameters shift gradually with no boundary from one activity endmember to another. As such, attributing this explosive activity specifically to any currently defined style variations is arbitrary and potentially misleading. The highly variable explosive activity of the Tajogaite eruption recalls previous definitions of violent Strombolian eruptions, an eruption style whose pyroclast ejection dynamics, however, were so far largely undefined.

Scenario-based probabilistic hazard assessment for explosive events at the San Salvador volcanic complex, El Salvador

We present a scenario-based, probabilistic hazard assessment for the San Salvador volcanic complex (SSVC), a volcanic field located in the vicinity of San Salvador that includes the El Boquerón stratovolcano and 25 monogenetic vents. We define a set of likely eruption scenarios for tephra fallout and pyroclastic density currents (PDCs). The eruption scenarios range from violent Strombolian eruptions with a significant uncertainty in source position to sub-Plinian and Plinian activity fed from the central cone. The adopted methodology is mainly based on numerical modeling using Tephra2 (adopting the software TephraProb) to study tephra fallout and the branching box model and the branching energy cone model (adopting the programs BoxMapProb 2.0 and ECMapProb 2.0) to describe inertial and frictional PDCs, respectively. Despite the dominant W-WSW-trending winds, numerical results show that Plinian eruptions at El Boquerón volcano are able to deposit thick tephra layers in the metropolitan area of San Salvador city, likely reaching mass loads of the order of 100 kg/m2 (conditional probability of 50%). The simulated sub-Plinian events highlight the seasonal influence of wind patterns. In fact, the conditional probability of significant tephra sedimentation in San Salvador city is strongly reduced when eruptions occur during the rainy season. Numerical modeling of violent Strombolian eruptions is performed considering uncertainty in vent position. Results show that the conditional probability of depositing tephra mass loads higher than 10 kg/m2 at a given point reaches a maximum value of ∼7% on the NW flank of the volcano, at about 8 km from the central crater. On the other hand, very low conditional probabilities (<1%) are obtained for San Salvador city for any relevant threshold (10 kg/m2 or more) of tephra mass load during violent Strombolian events. Regarding PDCs, results show that those produced during large-scale Plinian eruptions are able to invade significant areas of the volcano surroundings, including San Salvador city. PDCs generated from the partial collapse of a sub-Plinian eruption column exhibit maximum inundation probabilities on the N, W and S flanks of the volcano. Cerro El Picacho exerts a significant shield effect on the propagation of these PDCs, with low inundation probabilities for San Salvador city (<3%). Finally, coupling published vent opening probability maps and numerical modeling of small-scale PDCs yields maximum inundation probabilities on the NW flank of the volcano, reaching maximum conditional probabilities of the order of ∼10% and values of about 5% near the village of Nuevo Sitio del Niño.

Risk scenarios for a future eruption in the Chichinautzin monogenetic volcanic field, South México City

The Chichinautzin Monogenetic Volcanic Field creates volcanic risks for México City. To evaluate the possible effects and economic impacts of a future eruption, three scenarios based-on the spatial distribution of the most recent eruptions and the study of their characteristic are proposed. Scenario A, a Violent Strombolian eruption at the northwestern edge of the volcanic field, with eruptive columns 6–8 km high and emission of low-viscosity lava flows. Scenario B, Santiaguito-type eruption, a thick, high-viscosity lava flow that generates rock falls and short Merapi-type pyroclastic flows in the central northern area. Scenario C, a Hawaiian to Strombolian eruption with eruptive columns <6 km high and the emission of low viscosity lavas in the central part of the field. From these scenarios, numerical simulations of lava and tephra were carried out to obtain conditional hazard maps. The risk evaluation integrates the analysis of hazard, exposure, vulnerabilities, resilience, and the estimation of the costs of possible damages with physical and sociodemographic indicators available at the city block level, including rural areas. Two vulnerability curves were integrated for housing, the first for lava flows, which considers that a thickness ≥ 2 m of lava causes total loss (considering the loss of the function and accessibility); and a second curve for tephra that considers that an accumulated thickness in dry conditions of 20 cm of tephra produces generalized damage to all type of houses. By combining the vulnerability and hazard maps, two risk maps were constructed, one for lava flows and the other for tephra. The total direct cost of the expected damages was calculated for each scenario considering the cadastral value of the land and buildings for each property at risk. The costs for the most probable and the most catastrophic scenario amount to >14 billion US dollars, equivalent to 1.2% of the national GDP. Mitigation measures, mainly of the non-structural type are proposed.

The recent volcanism of Flores Island (Azores): Stratigraphy and eruptive history of Funda Volcanic System

Monogenetic volcanoes occur in many different geotectonic settings and are usually small and short-lived. They can experience a variety of eruptive styles, even during the same eruption. In monogenetic volcanic fields, volcanism usually migrates to different locations over time, making volcanic hazard assessment very challenging. The eruptive history of a volcanic region, including the size, style, and location of previous eruptions, provides valuable information to help predict the behaviour of future volcanic events and their associated hazards. Here, we reconstruct for the first time the eruptive history of the Funda Volcanic System (FVS), one of the most recent (∼3 ka) monogenetic eruptive centres of Flores Island (Azores), based on a detailed tephrostratigraphic work coupled with geochemical analysis of glass shards and radiocarbon dating. We identified at least three volcanic events at FVS spaced by time intervals of ∼100 yr. The first event (3430 cal yr BP) was a small Strombolian eruption, the second event (3330 cal yr BP) started as a violent Strombolian eruption and may have ended as phreatomagmatic, and the third event (3250 cal yr BP) was exclusively phreatomagmatic. Our results demonstrate that volcanism at the FVS was more prolonged and recurrent than previously reported. Moreover, we show that the FVS experienced different eruptive styles in a short timeframe, ranging from small basaltic eruptions to violent explosive phreatomagmatic events. Such diversity of eruptive styles results in different volcanic products, which have different hazard implications. Our new results contribute to the knowledge of the recent volcanic activity of Flores Island, and we anticipate them to be of paramount importance for future volcanic hazard assessment studies.

西之島の2020年6～8月のバイオレント・ストロンボリ式噴火

西之島の2020年6～8月のバイオレント・ストロンボリ式噴火

Hydrogeomorphic and sedimentary response to the Late Pleistocene violent Strombolian eruption of the Croscat volcano (Garrotxa Volcanic Field, Spain)

Explosive eruptions can severely alter the boundary conditions of fluvial systems around volcanoes by depositing large volumes of erodible fragmental material, increasing erosion rate and drainage mass flux (water and sediment) in the affected basin. In this paper, the environmental response to the 13 ka Croscat Violent Strombolian eruption in the Garrotxa Volcanic Field (NE Spain) has been investigated using a stratigraphic approach. Volcaniclastic material was mainly delivered at headwater tributaries (Les Tries plain in the Ser river basin) of the Fluvia River, one of the main drainage systems of NE Spain. Deposits in the Les Tries valley was initially reworked by hyperconcentrated-flows to braided stream-flows and by debris-flows involving mixed terrains (volcaniclastic materials and sands–gravels of the Eocene sedimentary basement) as registered in the stratigraphic record. The erosive pattern observed at the Les Tries valley reflects the erosion model of well-sorted and coarse-grained deposits (as the tephra deposited during the Violent Strombolian phase of the Croscat eruption), in which deep gullying and downstream aggradation are typically retarded where coarse tephra deposits remained highly permeable. Moreover, the Croscat eruption occurred soon after the Last Glacial Maximum, implying the shift from dry to wet conditions during the remobilization of the Croscat tephra. In this framework, the semiarid conditions retarded soil stabilization, driving the development of hyperconcentrated-flow-dominated alluvial fans, whereas the more humid environmental conditions favoured the partial stabilization of loose pyroclastic material, until it is periodically remobilization by mass-wasting processes as debris-flow-dominated lahars.

The forgotten eruption: The basaltic scoria cone of Montaña Grande, Tenerife

We report on the Strombolian to Violent Strombolian eruption of Montaña Grande which occurred between 789 and 725 BCE in the Güimar Valley on the NE flank of Tenerife island. The eruption produced a ca. 180 m-high scoria cone, a thick fallout deposit mostly dispersed southwest and a vast lava flow field that extends east of the cone, towards the coast, for 3.3 × 2.2 km. The eruption occurred in an unusual geodynamic context, outside the North West Rift and North East Rift zones and out of Las Cañadas caldera which are the main geological structures of Tenerife, where the volcanic activity concentrated during the Holocene. The tephra and lava have a trachybasalt composition similar to products of the recent activity of Tenerife but characterized by a distinct trace element pattern (Ta depletion relative to Nb), that points to a distinct source for the magma feeding the eruption and an ascent history along the whole crust which is independent and different from the central feeding system of the Teide-Pico Viejo volcanic complex. The study of this eruption, which until now had been completely neglected, adds new significant data for the correct definition of volcanic risk in Tenerife.

Characterizing magma fragmentation and its relationship with eruptive styles of Somma-Vesuvius volcano (Naples, Italy)

Among the active volcanoes worldwide, Somma-Vesuvius is one with the highest volcanic risk as the surrounding areas are highly populated. Somma-Vesuvius is quiescent since 1944, but geological and historical records reveal a frequent violent explosive activity in the last 4000 years, representing a severe risk for the ∼700,000 inhabitants currently living in the area having a high probability for being impacted by pyroclastic density currents (“red zone”) and more than one million people who can be potentially affected by tephra fallout. This study aims to analyze the distribution and grain-size of tephra fallout deposits from several Somma-Vesuvius eruptions of different styles, ranging from Violent Strombolian to sub-Plinian and Plinian, for characterizing the associated magmatic fragmentation through the assessment of their total grain-size distribution (TGSD). Chronologically, we focus on the Avellino (4365 BP) and Pompeii (A.D. 79) Plinian eruptions, the Pollena (A.D. 472) sub-Plinian eruption, and the 1906 and 1944 Violent Strombolian eruptions. The related TGSDs were estimated by means of the Voronoi tessellation method, which requires a suitable number of local grain-size distributions and estimation of the area of minimum tephra loading (zero-line contour). However, field-derived TGSDs can be biased towards the coarse and fine grain-size populations due to the typical paucity of available field outcrops of fallout deposits. To encompass this issue, we performed a sensitivity study on the assumption behind TGSD reconstructions and described TGSDs through analytical grain-size distributions that best fit the field TGSDs. Our main objective is a more robust estimation of the TGSDs associated with the different eruptive styles, which is crucial, together with the other eruption source parameters, for robustly predicting tephra loading and airborne ash dispersal of future eruptions at Somma-Vesuvius.

Examining the interior of Llaima Volcano with receiver functions

Llaima Volcano in Chile is one of the largest and most active volcanoes in the southern Andes, with over 50 eruptions since the 1600s. After years of persistent degassing, Llaima most recently erupted in a series of violent Strombolian eruptions in 2007–2009. This period had few precursory signals, which highlights the need to obtain accurate magma storage information. While petrologic advancements have been made in understanding magma degassing and crystallization trends, a comprehensive seismic study has yet to be completed. Here, we present results of a receiver function survey utilizing a dense seismic array surrounding Llaima volcano. Application of H-κ stacking and common conversion point stacking techniques reveals a new Moho estimate and two structural anomalies beneath Llaima Volcano. We interpret a low velocity zone between 8 and 13 km depth as a newly imaged magma body.

OUP accepted manuscript

On 1 January 2008 Llaima volcano, a basaltic andesite stratocone in southern Chile, entered a phase of violent Strombolian eruption. Llaima, like many passively degassing systems, has experienced prolonged (decades-long) periods of persistent summit degassing from its open vent. The rapid transition from long-lived passive degassing to violent explosive eruption occurred with limited precursory monitoring signals. This study is motivated by the desire to understand what occurs in these systems when that switch takes place. To this end, we study the products of the 2008 violent Strombolian eruption of Llaima volcano. We present new textural analyses of scoria and geochemical data for five whole-rock samples, troctolite glomerocrysts with and without Cr-spinel, and 182 olivine-hosted melt inclusions from tephra samples. Two populations of scoria (‘brown’ and ‘black’) are distinguished by their variable crystallinity and vesicularity, but are geochemically indistinguishable. Black scoria contains abundant microlites with tabular to acicular morphologies and convolute vesicles up to 1?75mm in effective diameter. The brown scoria tends to have fewer, acicular microlites, abundant matrix glass, and round vesicles with a narrower size distribution, constrained to 100MPa (4–14km depth), revealing that this eruption tapped a deep plumbing system. We propose here that passive degassing at Llaima is maintained by periodic, small-batch magma injections. Consequently, owing to extensive degassing the upper plumbing system magma crystallized and increased in viscosity. Before the 2008 eruption, some volatiles sourced from the repeatedly injected magmas exsolved from the inferred crystal mush and ascending from deeply sourced degassing magmas, and gradually accumulated within the crystal mush and beneath the stiffened conduit magma. Our results support a model in which eruption triggering occurred when magma injection remobilized the mush and, importantly, unlocked the accumulated gases, which ascended rapidly and generated the observed violent Strombolian explosive activity. Our proposed model contrasts with those models for explosive mafic volcanism that require rapid magma ascent under closed-system degassing conditions. Importantly, our proposed mechanism provides a means for systems with dominantly open-system degassing behavior to switch from passive degassing to explosive eruptions.

Formation of composite pyroclasts by welding inside a lithic-rich mafic eruption column (Los Marteles Caldera, Canary Islands)

The tuff ring of the Los Marteles phreatomagmatic maar (Gran Canaria, Canary Islands) includes a particular unit that comprises abundant composite spheroidal clasts. However, these clasts differ from cored clasts elsewhere that consist of erupted lithic pyroclasts with an adhering rim of coherent chilled magma. The composite clasts here studied range from lapilli to bombs, and are cored or concentrically banded. Among the welded components, several types of primary clasts are discerned that include: (i) juvenile clasts, resultant of the magma inertial fragmentation, and (ii) cognate or accessory lithic clasts. Juvenile clasts include glass spheres (nano- and microachneliths) and crystals. Lithic clasts include lava fragments, scoriae and olivine xenocrysts. Primary clasts are interpreted to have been produced by the explosion of a partially crystallized mafic (SiO2≈50–55%) magma that erupted into a maar, filled-up with scoriae plus lava fragments. The explosion would have originated as a dense and turbulent gas thrust into which the repeated collisions of melt droplets with solid clasts generated droplet-coated crystals, lithic clasts and single glass spheres. We interpret the cored and concentrically banded pyroclasts to be made of coalesced and/or agglutinated particles coated with a melt rim to the rest of the components. These composite clasts developed spheroidal shapes during transport within a violent Strombolian eruption column due to spin effect and, finally, landed in solid state.

Dynamics and tephra dispersal of Violent Strombolian eruptions at Vesuvius: insights from field data, wind reconstruction and numerical simulation of the 1906 event

Mt. Vesuvius is one of the most studied volcanoes in the world and its proximity to an extremely populated area makes it also one of the most threatening. Violent Strombolian (VS) events have occurred in the most recent history of the volcano, and they are the type most likely to occur in case of reactivation of the volcano in the near future. In order to investigate the dynamics and hazard of this type of eruption, we performed new field and laboratory work and numerical simulations of plume dynamics, fallout and tephra dispersal associated with such eruptions. Attention was specifically focused on the 1906 eruption, a recent and well-studied VS event. Based on new field analyses and historical observations, we reconstructed the temporal evolution of eruption source conditions during the event. The reconstructed explosive phase of the eruption is inferred to have been 8 days long and characterized by two distinct stages: a former short and intense period with sustained convective plume fed by powerful lava fountains (20 h) followed by a prolonged and less intense period of ash emission (172 h). The total grain-size distributions for both phases, used as inputs to the model, were obtained by field work and laboratory analyses. Based on these new volcanological data and reconstruction of wind field direction and intensity, partially derived from historical sources, the 1906 event was numerically simulated and results compared to deposit distributions. The modelling outcomes for the ash emission phase provide a better agreement with the measured tephra mass load for a simulation run in which ash aggregation (described by the models of Cornell et al. J Volcanol Geotherm Res 17:89–109, 1983, and Biass et al. Nat Hazard Earth Syst Sci 14:2265–2287, 2014) is specifically taken into account, confirming the importance of this process during tephra dispersal. The aggregation model that best fits the simulated results to the measured ground loadings has 80 % of particles Φ ≥ 4 that aggregate uniformly in the range Φ = −1 to 3. Two additional simulations of a VS event were carried out by using meteorological data of two specific periods to exemplify weather’s potential on impacts of such eruptions, particularly tephra loading, on the surrounding areas. The model outcomes clearly highlight the major effects of differences in local meteorology on plume dynamics and ash dispersal and the key role of wind shear in determining the cumulative thickness of ground deposits. Results also show that, due to the long duration of this kind of eruption and the large variability in zonal winds at this latitude, ash dispersal and fallout from VS events at Vesuvius represent a probable hazard for all of the territory near Vesuvius, including the city of Naples, where cumulative tephra loadings might reach critical thresholds for roof collapse and infrastructure damage.

A reappraisal of the eruptive history and recent (1991-2009) volcanic eruptions of the Barren Island, Andaman Sea

The Barren Island volcano in the Western Sunda Arc has displayed explosive Strombolian eruptions for more than two decades. This recent explosive event, together with the historic and prehistoric volcanic landforms, present reliable information about explosive Strombolian eruptions and the volcanological evolution of the Barren Island volcano. This study is a re-evaluation of existing knowledge and incorporates new information and interpretations of the recent and past volcanic activity on Barren Island. Direct observations of explosive eruptions since 1991 showed discrete events of bursting and ballistic transport of blocks and formation of sustained ash plumes, indicating Strombolian and violent Strombolian eruptions. Active lava flows were not seen during the observations which, instead, reveal intact preservation of the historic lava flows. A prehistoric mafic stratocone with a central depression (caldera), a central scoria cone with summit crater and abundant basaltic lava flows of historic eruptions and the scoria cones of the recent activity are the major volcanic landforms. They bear evidence of alternating effusive and explosive activity during prehistoric times accompanied by caldera forming activity; scoria cone Strombolian activity switches over to effusive events during the historic period and exclusively Strombolian activity during recent times. The results of this study differ from previous studies that interpreted several episodes of active lava flows and Hawaiian, Plinian and Vulcanian styles of the recent eruptions. It also provides new insights into the volcanological evolution of the Barren Island volcano which is crucial in understanding the future behaviour of the volcano and risk assessment.

Plate tephra: Preserved bubble walls from large slug bursts during violent Strombolian eruptions

Research Article| January 01, 2014 Plate tephra: Preserved bubble walls from large slug bursts during violent Strombolian eruptions Dawn C.S. Ruth; Dawn C.S. Ruth * 1Department of Geology, 411 Cooke Hall, State University of New York University at Buffalo, Buffalo, New York 14260, USA *E-mail: dcs34@buffalo.edu. Search for other works by this author on: GSW Google Scholar Eliza S. Calder Eliza S. Calder 1Department of Geology, 411 Cooke Hall, State University of New York University at Buffalo, Buffalo, New York 14260, USA2School of Geosciences, Grant Institute, University of Edinburgh, The King’s Buildings, West Mains Road, Edinburgh EH9 3JW, UK Search for other works by this author on: GSW Google Scholar Geology (2014) 42 (1): 11–14. https://doi.org/10.1130/G34859.1 Article history received: 20 Jun 2013 rev-recd: 09 Sep 2013 accepted: 10 Sep 2013 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Dawn C.S. Ruth, Eliza S. Calder; Plate tephra: Preserved bubble walls from large slug bursts during violent Strombolian eruptions. Geology 2014;; 42 (1): 11–14. doi: https://doi.org/10.1130/G34859.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract We describe unusual “plate tephra” particles that provide key information about rarely observed processes that occur during volcanic eruptions. The tephra formed during the 2008–2009 eruption of Llaima volcano, Chile, and dispersed as far as 9 km from the vent. The plates are angular clasts of vesicular basaltic andesite ranging in size from 1 to 14 cm and in thickness from 2 to 5 mm. External features such as ridges, varying degrees of curvature, and adhered material are present. Internal textures include strong crystal alignment and deformed enclaves. We propose that the plates are wall fragments formed during the rupture of large gas slugs associated with unsteady fire fountaining during the violent Strombolian phase of the eruption. The presence of plate tephra may be a diagnostic feature of highly unsteady activity where slug rupture is concurrent with the formation of a sustained eruption column. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Scoria cone formation through a violent Strombolian eruption: Irao Volcano, SW Japan

Scoria cones are common volcanic features and are thought to most commonly develop through the deposition of ballistics produced by gentle Strombolian eruptions and the outward sliding of talus. However, some historic scoria cones have been observed to form with phases of more energetic violent Strombolian eruptions (e.g., the 1943–1952 eruption of Paricutin, central Mexico; the 1975 eruption of Tolbachik, Kamchatka), maintaining volcanic plumes several kilometers in height, sometimes simultaneous with active effusive lava flows. Geologic evidence shows that violent Strombolian eruptions during cone formation may be more common than is generally perceived, and therefore it is important to obtain additional insights about such eruptions to better assess volcanic hazards. We studied Irao Volcano, the largest basaltic monogenetic volcano in the Abu Monogenetic Volcano Group, SW Japan. The geologic features of this volcano are consistent with a violent Strombolian eruption, including voluminous ash and fine lapilli beds (on order of 10−1 km3 DRE) with simultaneous scoria cone formation and lava effusion from the base of the cone. The characteristics of the volcanic products suggest that the rate of magma ascent decreased gradually throughout the eruption and that less explosive Strombolian eruptions increased in frequency during the later stages of activity. During the eruption sequence, the chemical composition of the magma became more differentiated. A new K–Ar age determination for phlogopite crystallized within basalt dates the formation of Irao Volcano at 0.4 ± 0.05 Ma.

Volcanic precursors in light of eruption mechanisms at Vesuvius

&lt;p&gt;Vesuvius entered a quiescent stage after the eruption of March-April 1944. The eruption was not much different or larger than other before, like for example the one of 1906, but it occurred at the end of a long period during which it was observed a decreasing trend of explosivity of eruptions [Scandone et al. 2008]. The parallel increase in the frequency of slow effusive eruptions, with respect to violent strombolian eruptions, point out to a process of average slower rate of magma ascent possibly due to a progressive sealing of the ascent path of magma to the surface. The small caldera collapse following the 1944 explosive phase effectively sealed the upper conduit, and since then the volcano entered a quiescence stage that was unusual with respect to the pattern of activity of the previous 300 years when the maximum repose time had been of 7 years (after the eruption of 1906). Most of the uncertainty on the duration of the present stage and character of a future renewal of activity derives by the basic questions regarding the nature of the current repose: due to a diminished supply of magma, related with structural condition or a sealing of the upper ascent path to the surface? Possibly the variation of structural conditions caused average slower ascent rates of magma favoring its cooling in the upper part of the crust, and effectively sealing the ascent path.&lt;/p&gt;

Hazard assessment of far-range volcanic ash dispersal from a violent Strombolian eruption at Somma-Vesuvius volcano, Naples, Italy: implications on civil aviation

Long-range dispersal of volcanic ash can disrupt civil aviation over large areas, as occurred during the 2010 eruption of Eyjafjallajokull volcano in Iceland. Here we assess the hazard for civil aviation posed by volcanic ash from a potential violent Strombolian eruption of Somma-Vesuvius, the most likely scenario if eruptive activity resumed at this volcano. A Somma-Vesuvius eruption is of concern for two main reasons: (1) there is a high probability (38 %) that the eruption will be violent Strombolian, as this activity has been common in the most recent period of activity (between AD 1631 and 1944); and (2) violent Strombolian eruptions typically last longer than higher-magnitude events (from 3 to 7 days for the climactic phases) and, consequently, are likely to cause prolonged air traffic disruption (even at large distances if a substantial amount of fine ash is produced such as is typical during Vesuvius eruptions). We compute probabilistic hazard maps for airborne ash concentration at relevant flight levels using the FALL3D ash dispersal model and a statistically representative set of meteorological conditions. Probabilistic hazard maps are computed for two different ash concentration thresholds, 2 and 0.2 mg/m3, which correspond, respectively, to the no-fly and enhanced procedure conditions defined in Europe during the Eyjafjallajokull eruption. The seasonal influence of ash dispersal is also analysed by computing seasonal maps. We define the persistence of ash in the atmosphere as the time that a concentration threshold is exceeded divided by the total duration of the eruption (here the eruption phase producing a sustained eruption column). The maps of averaged persistence give additional information on the expected duration of the conditions leading to flight disruption at a given location. We assess the impact that a violent Strombolian eruption would have on the main airports and aerial corridors of the Central Mediterranean area, and this assessment can help those who devise procedures to minimise the impact of these long-lasting low-intensity volcanic events on civil aviation.

Eruption chronology and petrologic reconstruction of the ca. 8500 yr B.P. eruption of Red Cones, southern Inyo chain, California

Research Article| September 01, 2010 Eruption chronology and petrologic reconstruction of the ca. 8500 yr B.P. eruption of Red Cones, southern Inyo chain, California Brandon Browne; Brandon Browne † 1Department of Geological Sciences, California State University, Fullerton, California 92834, USA †E-mail: bbrowne@fullerton.edu Search for other works by this author on: GSW Google Scholar Marcus Bursik; Marcus Bursik 2Department of Geology, State University of New York, Buffalo, New York 14260, USA Search for other works by this author on: GSW Google Scholar Justin Deming; Justin Deming 2Department of Geology, State University of New York, Buffalo, New York 14260, USA Search for other works by this author on: GSW Google Scholar Michael Louros; Michael Louros 1Department of Geological Sciences, California State University, Fullerton, California 92834, USA Search for other works by this author on: GSW Google Scholar Antonio Martos; Antonio Martos 1Department of Geological Sciences, California State University, Fullerton, California 92834, USA Search for other works by this author on: GSW Google Scholar Scott Stine Scott Stine 3Department of Geography and Environmental Studies, California State University, Hayward, California 94542, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Brandon Browne † 1Department of Geological Sciences, California State University, Fullerton, California 92834, USA Marcus Bursik 2Department of Geology, State University of New York, Buffalo, New York 14260, USA Justin Deming 2Department of Geology, State University of New York, Buffalo, New York 14260, USA Michael Louros 1Department of Geological Sciences, California State University, Fullerton, California 92834, USA Antonio Martos 1Department of Geological Sciences, California State University, Fullerton, California 92834, USA Scott Stine 3Department of Geography and Environmental Studies, California State University, Hayward, California 94542, USA †E-mail: bbrowne@fullerton.edu Publisher: Geological Society of America Received: 06 Apr 2009 Revision Received: 30 Oct 2009 Accepted: 01 Nov 2009 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2010 Geological Society of America GSA Bulletin (2010) 122 (9-10): 1401–1422. https://doi.org/10.1130/B30070.1 Article history Received: 06 Apr 2009 Revision Received: 30 Oct 2009 Accepted: 01 Nov 2009 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Brandon Browne, Marcus Bursik, Justin Deming, Michael Louros, Antonio Martos, Scott Stine; Eruption chronology and petrologic reconstruction of the ca. 8500 yr B.P. eruption of Red Cones, southern Inyo chain, California. GSA Bulletin 2010;; 122 (9-10): 1401–1422. doi: https://doi.org/10.1130/B30070.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Red Cones are a pair of basaltic cinder cones located 5 km SSW of Mammoth Mountain at the southern end of the Mono-Inyo volcanic chain, in eastern California. Charcoal recovered at two separate locations beneath the Red Cones scoria-fall deposits indicates that the eruption most likely occurred shortly after 8490 ± 90 14C yr B.P. and no later than 9325 ± 83 14C yr B.P., which implicates Red Cones as the most recent eruption of basalt in the Mono-Inyo volcanic chain. Results from geologic field mapping combined with geochemical and petrologic analysis suggest that the ca. 8500 yr B.P. eruption produced 10.1 × 106 m3 of magma, possibly beginning from south Red Cone and later from north Red Cone via Hawaiian, Strombolian, and violent Strombolian eruptions over a minimum of 28 days. All deposits contain plagioclase, olivine, clinopyroxene, chrome-spinel, and titanomagnetite. Material erupted from each cone can be classified as high-aluminum basalts that exhibit calc-alkaline differentiation trends and belong to the medium-K series. Red Cone basalt samples are generally similar in terms of many major and trace element concentrations, but south Red Cone samples typically contain more SiO2, Sr, Zr, Rb, and Ba, and less MgO, FeO, CaO, Ni, and Cr than north Red Cone samples. Clinopyroxene-liquid thermobarometry calculations indicate that the majority of Red Cones clinopyroxene crystal cores crystallized at temperatures of 1160–1210 °C and pressures equivalent to 10–25 km depth, which supports the possibility of a basaltic dike and sill plexus located 10–25 km beneath the west and southwest flanks of Mammoth Mountain. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Controls on the explosivity of scoria cone eruptions: Magma segregation at conduit junctions

Violent strombolian (transitional) eruptions are common in mafic arc settings and are characterized by simultaneous explosive activity from scoria cone vents and lava effusion from lateral vents. This dual activity requires magma from the feeder conduit to split into vertical and lateral branches somewhere near the base of the scoria cone. Additionally, if the flow is separated, gas and liquid (+ crystals) components of the magma may be partitioned unevenly between the two branches. Because flow separation requires bubbles to move independently of the liquid over time scales of magma ascent separation is promoted by low magma viscosities and by high magma H 2O content (i.e. sufficiently deep bubble nucleation to allow organization of the gas and liquid phases during magma ascent). Numerical modeling shows that magma and gas distribution between vertical and horizontal branches of a T-junction is controlled by the mass flow rate and the geometry of the system, as well as by magma viscosity. Specifically, we find that mass eruption rates (MERs) between 10 3 and 10 5 kg/s allow the gas phase to concentrate within the central conduit, significantly increasing explosivity of the eruption. Lower MERs produce either strombolian or effusive eruption styles, while MER > 10 5 kg/s prohibit both gas segregation and lateral magma transport, creating explosive eruptions that are not accompanied by effusive activity. These bracketing MER constraints on eruptive transitions are consistent with field observations from recent eruptions of hydrous mafic magmas.

Changing eruptive styles in basaltic explosive volcanism: Examples from Croscat complex scoria cone, Garrotxa Volcanic Field (NE Iberian Peninsula)

The Croscat pyroclastic succession has been analysed to investigate the transition between different eruptive styles in basaltic monogenetic volcanoes, with particular emphasis on the role of phreatomagmatism in triggering Violent Strombolian eruptions. Croscat volcano, an 11 ka basaltic complex scoria cone in the Quaternary Garrotxa Volcanic Field (GVF) shows pyroclastic deposits related both to magmatic and phreatomagmatic explosions. Lithofacies analysis, grain size distribution, chemical composition, glass shard morphologies, vesicularity, bubble-number density and crystallinity of the Croscat pyroclastic succession have been used to characterize the different eruptive styles. Eruptions at Croscat began with fissural Hawaiian-type fountaining that rapidly changed to eruption types transitional between Hawaiian and Strombolian from a central vent. A first phreatomagmatic phase occurred by the interaction between magma and water from a shallow aquifer system at the waning of the Hawaiian- and Strombolian-types stage. A Violent Strombolian explosion then occurred, producing a widespread (8 km 2), voluminous tephra blanket. The related deposits are characterized by the presence of wood-shaped, highly vesicular scoriae. Glass-bearing xenoliths (buchites) are also present within the deposit. At the waning of the Violent Strombolian phase a second phreatomagmatic phase occurred, producing a second voluminous deposit dispersed over 8.4 km 2. The eruption ended with a lava flow emission and consequent breaching of the western-side of the volcano. Our data suggest that the Croscat Violent Strombolian phase was related to the ascent of deeper, crystal-poor, highly vesicular magma under fast decompression rate. Particles and vesicles elongation and brittle failure observed in the wood-shaped clasts indicate that fragmentation during Violent Strombolian phase was enhanced by high strain-rate of the magma within the conduit.