162,248 research outputs found
Corrigendum. Maars to calderas: end-members on a spectrum of explosive volcanic depressions
No full textA corrigendum on
Maars to calderas: end-members on a spectrum of explosive volcanic depressions
by Palladino, D. M., Valentine, G. A., Sottili, G., and Taddeucci, J. (2015). Front. Earth Sci. 3:36.
doi: 10.3389/feart.2015.00036
Reason for Corrigendum:
In the original article (Palladino et al., 2015), there was an error in Figure 1. The vertical axis
of the qualitative plot reported erroneously “ratio of juvenile to lithic materials in deposits outside
of depression”. The correct wording is as follows: “ratio of juvenile to total (i.e., juvenile+lithic)
materials in deposits outside of depression”. In fact, as it was reported correctly in the text, the
amount of juvenilematerial (i.e., scoria or pumice) deposited ouside the different types of explosive
volcanic depressions increases from zero (i.e., no juvenile, all lithic products), as is the case of
hydrothermal (phreatic) explosion craters, to become largely dominant over the lithic component
in the case of ash flow deposits associated with large overpressure collapse calderas. The corrected Figure 1 appears below. The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way
Volcanologic and Geo-petrographic map of the South-western sector of the Vulsini Volcanic District, central Italy
No full textextended abstract FIST-Geoitalia 1999, Bellaria (RN
High-speed imaging of Strombolian explosions: The ejection velocity of pyroclasts
No full textExplosive volcanic eruptions are defined as the violent ejection of gas and hot fragments from a vent in the Earth's crust. Knowledge of ejection velocity is crucial for understanding and modeling relevant physical processes of an eruption, and yet direct measurements are still a difficult task with largely variable results. Here we apply pioneering high-speed imaging to measure the ejection velocity of pyroclasts from Strombolian explosive eruptions with an unparalleled temporal resolution. Measured supersonic velocities, up to 405 m/s, are twice higher than previously reported for such eruptions. Individual Strombolian explosions include multiple, sub-second-lasting ejection pulses characterized by an exponential decay of velocity. When fitted with an empirical model from shock-tube experiments literature, this decay allows constraining the length of the pressurized gas pockets responsible for the ejection pulses. These results directly impact eruption modeling and related hazard assessment, as well as the interpretation of geophysical signals from monitoring networks. Citation: Taddeucci, J., P. Scarlato, A. Capponi, E. Del Bello, C. Cimarelli, D. M. Palladino, and U. Kueppers (2012), High-speed imaging of Strombolian explosions: The ejection velocity of pyroclasts, Geophys. Res. Lett., 39, L02301, doi:10.1029/2011GL050404
The basal ash deposit of the Sovana Eruption (Vulsini Volcanoes, central Italy): the product of a dilute pyroclastic density current
No full textA low aspect ratio, decimeter-thick ash deposit, axisymmetrically distributed around the Latera Caldera (Western Vulsini Volcanoes, central Italy) has been studied by means of field and laboratory investigations. Field studies comprise facies analysis at centimeter scale and maximum clast size and deposit thickness measurements. Grain size and component distribution, chemical composition and particle morphoscopic features have been determined on selected samples. We discuss the co-ignimbrite ash fall vs, pyroclastic surge origin of the deposit and the hydrovolcanic vs. magmatic eruption nature. Complex facies association, textural features and grain size data rule out an ash fall origin for the whole deposit. The hydrovolcanic nature of the eruption has been discarded on the grounds of componentry and morphoscopic features of vitric fragments. We propose that the main body of the ash deposit formed from a radially expanding, dilute, turbulent pyroclastic density current, originated by a continuous collapse of a low-altitude (a few kilometers) eruptive column with a possible radial jet component. (C) 1998 Elsevier Science B.V. All rights reserved
Scanning Electron Microscope micrographs of broken crystals and related textures in support of: Fracturing and healing of basaltic magmas during explosive volcanic eruptions
No full textA single PDF file includes 317 microphotographs detailing pyroclast textures related to the fracturing and healing of basaltic magmas in explosive volcanic eruptions and in fragmentation experiments
Fracturing and healing of basaltic magmas during explosive volcanic eruptions
No full textRaw measurements of fracture parameters in volcanic and experimental products.
Point count measurements of intact crystals, crystal fragments, and vesicle-free area for all the 30 images of the mosaic in Extended Data Figure 1.
Point count and image segmentation crystallinity for all measured images of natural and experimental products
Constraints on magma-wall rock thermal interaction during explosive eruptions from textural analysis of cored bombs
No full textCored bombs, a kind of pyroclast consisting of a lithic core surrounded by a chilled shell of juvenile material, record the thermal interaction of magma with wall rocks. We performed textural analysis of cored bombs, solid-melt heat-transfer theoretical modelling, and high-temperature coating experiments to put temporal and intensity constraints on the thermal interaction of potassic magma feeder systems with carbonate wall rocks during explosive eruptions in the Quaternary, Colli Albani Volcanic District (Roman Province). It appears that the degree of thermal alteration of lithic cores records the duration of magma-core heat transfer, whereas the core/shell size ratio records the initial entrainment temperature of the lithic fragment. Both parameters appear to vary significantly with the eruptive style, magnitude and vent location. Specifically, small-scale (similar to 0.1-1 km(3) DRE) hydromagmatic eruptions show magma-core heat-transfer durations of 0.1-10 s and entrainment temperatures in the range of 100-300 degrees C in the case of a monogenetic maar located in the Colli Albani peripheral area, while entrainment temperature is as high as to 800 degrees C for a polygenetic maar in a high-enthalpy geothermal system at the margins of the main Colli Albani magma chamber. A large-scale (similar to 30 km(3) DRE) caldera-forming explosive event shows magma-core heat-transfer duration in the order of 10(2)-10(3)s and temperature of 100-500 degrees C at the initial magma-wall rock contact. On these grounds, we derived the cooling rate of magmas as a function of the initial temperature, mass and size distribution of lithic clasts entrained. Magma cooling by lithic entrainment may have occurred on the same time-scale as that of eruptive pulses (seconds to hours), implying that lithic entrainment may effect changes in magma physico-chemical properties on a short time-scale and, consequently, affect eruptive conduit dynamics. (C) 2010 Elsevier B.V. All rights reserved
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
Strombolian explosions: relationships between the conduit system and the resulting explosive activity at the vents
No full textI vulcani in stato di attività persistente a condotto aperto spesso ospitano un’attività definita stromboliana. Questo stile di attività è caratterizzato da rilasci frequenti (intervalli da secondi a minuti) e impulsivi (della durata di alcuni secondi) di piroclasti e gas, dovuti alla risalita e allo scoppio di grosse bolle di gas (dette slug) vicino alla superficie della colonna di magma. Nel tempo, tali vulcani possono mostrare continui cambiamenti nell’evoluzione e nella migrazione delle proprie bocche attive, dalle quali si può osservare anche un comportamento altamente variabile dell’attività. Le origini di tale variabilità devono essere studiate a scale spaziali e temporali variabili. In una scala di anni/centinaia di metri, l’osservazione diretta della migrazione delle bocche nello spazio e nel tempo nei vulcani contraddistinti da più bocche è ancora limitata, e resta da capire la relazione tra questa attività variabile e il sistema di condotti superficiale. Su una scala di secondi/metri, molti autori si sono focalizzati sulla dinamica del rilascio di gas e sulle modalità di formazione dei piroclasti, finora trascurando ampiamente la dinamica di risalita dei piroclasti dalla profondità di rilascio, dove gli slug scoppiano, sino alla loro espulsione dalla bocca. Lo scopo del mio studio è la definizione delle relazioni tra i parametri fisici all’interno del condotto vulcanico e la loro influenza sulla modalità di espulsione dei piroclasti nelle eruzioni stromboliane, tenendo conto delle due scale sopramenzionate. Per raggiungere tale scopo ho adottato due metodologie separate ma complementari.
La prima richiede la caratterizzazione delle eruzioni stromboliane in natura, indagando i cambiamenti temporali nella posizione delle bocche sulla terrazza craterica di Stromboli e i parametri di esplosione (durata e geometria del getto) usando i video delle telecamere di sorveglianza a infrarossi raccolti tra il 2005 e il 2009. I risultati di questa prima metodologia forniscono un database dettagliato dell’attività stromboliana normale a diverse scale temporali, oltre a consentire di delineare una gerarchia di profondità a cui il sistema di condotti superficiale controlla l’attività esplosiva entro le tre principali aree (cioè la nord-est, la centrale e la sud-ovest) che raggruppano più bocche vicine a Stromboli. Alla profondità più bassa, dove gli slug scoppiano, la forma della bocca e le dimensioni degli slug controllano i parametri di esplosione locali, mentre la ramificazione più in superficie dei condotti determina l’evoluzione delle bocche che esplodono simultaneamente o alternativamente. Al di sotto della profondità di scoppio degli slug, il sistema di condotti che alimenta ciascuna area di bocche controlla quale specifica bocca ospiterà le esplosioni e anche alcune caratteristiche generali di esplosione all’interno di queste aree. A questa profondità si suppone ci sia un collegamento tra l’area centrale e quella sudovest, come supportato da diverse osservazioni. Al livello più profondo, il sistema di condotti è comune a tutte le aree e imposta il tasso eruttivo globale del vulcano, bilanciandolo tra l’area nord-est e quella congiunta sud-ovest e centrale. Questo tipo di analisi può essere eseguito anche in altri sistemi persistenti contraddistinti da più bocche in tutto il mondo, fornendo deduzioni di base sulla geometria e la dinamica del loro sistema di condotti e sulla valutazione della pericolosità connessa.
La seconda metodologia è dedicata alle simulazioni di getti gas-particelle per mezzo di esperimenti analogici in scala utilizzando uno shock-tube trasparente. Questo approccio è incentrato sull’effetto delle condizioni iniziali (cioè, pressione e volume del gas, posizione del campione, dimensione e quantità di particelle, geometria della bocca) sia sull’accelerazione delle particelle all’interno del condotto che sull’espulsione risultante dalla bocca. I risultati mostrano che la velocità massima delle particelle ha una correlazione positiva con l’energia iniziale e una correlazione negativa sia con la profondità del campione rispetto alla bocca che con la dimensione delle particelle. Inoltre, gli esperimenti mostrano tendenze di accelerazione e decelerazione delle particelle all’interno dello shock-tube che dipendono in modo variabile da alcune condizioni iniziali (cioè energia iniziale, profondità del campione e dimensione delle particelle) e influiscono sulla velocità massima delle particelle registrata all’uscita. Rispetto ai processi che si verificano durante le eruzioni esplosive a piccola scala, questi risultati aprono la strada a nuove potenziali deduzioni riguanti i processi che controllano la dinamica dei piroclasti. Le tendenze di accelerazione e decelerazione all’interno dei condotti influenzano i modelli correnti che correlano la velocità di espulsione dei piroclasti con la loro profondità di origine nel condotto vulcanico. Dimostro che le assunzioni del modello non sono più valide nei casi di bassa energia iniziale e un campione più profondo. Pertanto, è necessaria una revisione del modello che tenga conto anche di queste tendenze prima di applicarlo alle eruzioni reali. Questi risultati aprono la strada a numerosi scenari futuri. Ad esempio, ulteriori esperimenti possono chiarire meglio gli effetti dell’accoppiamento gas- particella, analizzare il ruolo di altri parametri sull’espulsione dei piroclasti (ad esempio il diametro del condotto) o studiare altri aspetti (ad esempio, i pennacchi vulcanici utilizzando particelle molto fini, o collisioni particella-particella e particelle-parete nel condotto).Persistent, open-vent volcanoes frequently host Strombolian explosions. This style of activity is characterized by frequent (intervals of seconds to minutes) and impulsive (seconds- long) releases of pyroclasts and gases, due to the rise and burst of large gas bubbles (i.e., slugs) near the surface of the magma column. Over time, such volcanoes can show continuous changes in the evolution and migration of their active vents, from which also a highly variable behavior of the activity can be observed. The sources of such variability need being investigated at variable spatial and temporal scales. On a scale of years/hundred of meters, direct observation of space-time vent migration at multi-vent volcanoes is still limited, and the relationship between this variable activity and the shallow conduit system remains to be understood. On a scale of seconds/meters, many authors are focused on the dynamics of gas release and modes of pyroclasts formation, so far largely neglecting the ascent dynamics of pyroclasts from their release depth, where slugs burst, to their ejection from the vent. The aim of my study is the definition of the relationships between the physical parameters inside the volcanic conduit and their influence on the modes of pyroclast ejection in Strombolian explosions, accounting for the two scales abovementioned. To achieve this aim, I considered two separate yet complementary methodologies.
The first one requires the characterization of Strombolian eruptions in nature investigating temporal changes in vent position at the crater terrace of Stromboli and explosion parameters (jet duration and geometry) using infrared surveillance camera videos collected between 2005 and 2009. Results by this first methodology provide a detailed database of normal Strombolian activity at different time-scales, as well as allowing one to outline a hierarchy of depths at which the shallow conduit system controls the explosive activity within the three main vent areas (i.e., south-west, central, and north-east) at Stromboli. At the shallowest depth, where slugs burst, vent shape and slug size control local explosion parameters, while shallower conduit branching determines the evolution of simultaneous or alternating twin vents. Below the depth of the slug burst, the conduit system feeding each vent area controls which specific vent will host the explosions and also some more general explosion features within a vent area. A link between the central and south-west vent areas is supposed at this depth, as supported by several observations. At the deepest level, the conduit system is common to all vent areas and sets the overall explosion rate of the volcano, balancing it between the north-east and the joint south-west and central vent areas. This kind of analysis may be performed also in other persistent multi-vent systems worldwide, providing basic inferences on geometry and dynamics of their conduit systems and on the hazard assessment.
The second methodology is addressed on gas-particle jet simulations by means of scaled analogue experiments using a transparent shock-tube. This approach focuses on the effect of the initial source conditions (i.e., gas pressure and volume, sample position, size and amount of particles, vent geometry) both on the acceleration of the particles within the conduit and on the resulting ejection from the vent. Results show that maximum particle velocity has a strong positive correlation with initial energy and a weaker, negative correlation with both sample depth from the vent and particle size. Moreover, the experiments show trends of particle acceleration-deceleration in the shock-tube that variably depend on some initial conditions (i.e., initial energy, sample depth, and particle size) and influence particle maximum velocity recorded at the exit. When compared to processes occurring during low-scale explosive eruptions, these results open the way for potential, new inferences on the processes controlling the dynamics of pyroclasts. The acceleration-deceleration trends inside the conduits impact current models relating pyroclast ejection velocity with their source depth in the volcanic conduit. I show that, for a lower initial energy and a deeper sample, the model assumptions do not hold true anymore. Therefore, a model revision taking into account these trends is necessary before applying it to real eruptions. These results open the way to numerous future scenarios. Further experiments may, for instance, clarify, the effects of particle-gas coupling, analyze the role of other source parameters on pyroclast ejection (e.g., conduit diameter) and study other aspects (e.g., the volcanic plumes using very fine particles, or particle-particle and particle-wall collisions in the conduit)
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