scholarly journals Rheological control on the dynamics of explosive activity in the 2000 summit eruption of Mt. Etna

Solid Earth ◽  
2010 ◽  
Vol 1 (1) ◽  
pp. 61-69 ◽  
Author(s):  
D. Giordano ◽  
M. Polacci ◽  
P. Papale ◽  
L. Caricchi
Keyword(s):  
Solid Particles ◽  
Magma Ascent ◽  
Explosive Activity ◽  
Summit Eruption ◽  
Intermediate Phases ◽  
Strombolian Eruption ◽  
Mt Etna ◽  
Order Of Magnitude ◽  
Crystal Content ◽  
Fire Fountain

Abstract. In the period from January to June 2000 Mt. Etna exhibited an exceptional explosive activity characterized by a succession of 64 Strombolian and fire-fountaining episodes from the summit South-East Crater. Textural analysis of the eruptive products reveals that the magma associated with the Strombolian phases had a much larger crystal content (>55 vol%) with respect to the magma discharged during the fire-fountain phases (~35 vol%). Rheological modelling shows that the crystal-rich magma falls in a region beyond a critical crystal content where small addition of solid particles causes an exponential increase of the effective magma viscosity. When implemented into the modeling of steady magma ascent dynamics (as assumed for the fire-fountain activity), a large crystal content as the one found for products of Strombolian eruption phases results in a one order of magnitude decrease of mass flow-rate, and in the onset of conditions where small heterogeneities in the solid fraction carried by the magma translate into highly unsteady eruption dynamics. We argue that crystallization on top of the magmatic column during the intermediate phases when magma was not discharged favoured conditions corresponding to Strombolian activity, with fire-fountain activity resuming after removal of the highly crystalline top. The numerical simulations also provide a consistent interpretation of the association between fire-fountain activity and emergence of lava flows from the crater flanks.

scholarly journals Rheological control on the dynamics of explosive activity in the 2000 summit eruption of Mt. Etna

2010 ◽  
Vol 2 (1) ◽  
pp. 19-42 ◽  
Author(s):  
D. Giordano ◽  
M. Polacci ◽  
P. Papale ◽  
L. Caricchi
Keyword(s):  
Solid Particles ◽  
Magma Ascent ◽  
Explosive Activity ◽  
Summit Eruption ◽  
Intermediate Phases ◽  
Strombolian Eruption ◽  
Mt Etna ◽  
Order Of Magnitude ◽  
Crystal Content ◽  
Fire Fountain

Abstract. In the period from January to June 2000 Mt. Etna exhibited an exceptional explosive activity characterised by a succession of 64 Strombolian and fire-fountaining episodes from the summit South-East crater. Textural analysis of the eruptive products reveals that the magma associated with the Strombolian phases had a much larger crystal content >55 vol% with respect to the magma discharged during the fire-fountain phases (~35 vol%). Rheological modelling shows that the crystal-rich magma falls in a region beyond a critical crystal content where the small addition of solid particles causes an exponential increase of the effective magma viscosity. When implemented into the modelling of steady magma ascent dynamics, the large crystal content of the Strombolian eruption phases results in a one order of magnitude decrease of mass flow-rate, and in the onset of conditions where small heterogeneities in the solid fraction carried by the magma translate into highly unsteady eruption dynamics. Therefore, we argue that crystallization on top of the magmatic column during the intermediate phases when magma was not discharged caused the conditions to shift from fire-fountain to Strombolian activity. The numerical simulations also provide a consistent interpretation of the association between fire-fountain activity and emergence of lava flows from the crater flanks.

scholarly journals Effusive Monogenetic Volcanism

2020 ◽  
Author(s):  
Hugo Murcia ◽  
Károly Németh
Keyword(s):  
Classification Scheme ◽  
Wide Spectrum ◽  
Lava Flows ◽  
Magma Ascent ◽  
Explosive Activity ◽  
Monogenetic Volcanism ◽  
Future Studies ◽  
Lava Domes ◽  
Tectonic Settings ◽  
Monogenetic Volcanoes

The study of monogenetic volcanism around Earth is rapidly growing due to the increasing recognition of monogenetic volcanic edifices in different tectonic settings. Far from the idea that this type of volcanism is both typically mafic and characteristic from intraplate environments, it occurs in a wide spectrum of composition and geological settings. This volcanism is widely known by the distinctive pyroclastic cones that represent both magmatic and phreatomagmatic explosive activity; they are known as scoria or spatter cones, tuff cones, tuff rings, maars and maar-diatremes. These cones are commonly associated with lava domes and usually accompanied by lava flows as part of their effusive eruptive phases. In spite of this, isolated effusive monogenetic emissions also appear around Earth’s surface. However, these isolated emissions are not habitually considered within the classification scheme of monogenetic volcanoes. Along with this, many of these effusive volcanoes also contrast with the belief that this volcanism is indicative of rapidly magma ascent from the asthenosphere, as many of the products are strongly evolved reflecting differentiation linked to stagnation during ascent. This has led to the understanding that the asthenosphere is not always the place that directly gives rise to the magma batches and rather, they detach from a crustal melt storage. This chapter introduces four singular effusive monogenetic volcanoes as part of the volcanic geoforms, highlights the fact that monogenetic volcanic fields can also be associated with crustal reservoirs, and outlines the processes that should occur to differentiate the magma before it is released as intermediate and acidic in composition. This chapter also provides an overview of this particular volcanism worldwide and contributes to the monogenetic comprehension for future studies.

The Large Explosive Activity of Mt. Etna as Recorded in Distal Tephrostratigraphy

2014 ◽  
pp. 1281-1283
Author(s):  
Roberto Sulpizio ◽  
Gianluca Groppelli ◽  
Donatella Insinga ◽  
Stefano Branca ◽  
Paola Del Carlo ◽  
...  
Keyword(s):  
Explosive Activity ◽  
Mt Etna

Retrospection of Chernobyl Nuclear Accident for Decision Analysis Concerning Remedial Actions in Ukraine

2007 ◽  
Author(s):  
Vladimir Georgievskiy
Keyword(s):  
Radiation Exposure ◽  
Chernobyl Accident ◽  
Late Phase ◽  
Nuclear Accident ◽  
First Year ◽  
Radioactive Materials ◽  
Intermediate Phases ◽  
Radiological Data ◽  
Order Of Magnitude ◽  
Remedial Actions

It is considered the efficacy of decisions concerning remedial actions when of-site radiological monitoring in the early and (or) in the intermediate phases was absent or was not informative. There are examples of such situations in the former Soviet Union where many people have been exposed: releases of radioactive materials from “Krasnoyarsk-26” into Enisey River, releases of radioactive materials from “Chelabinsk-65” (the Kishtim accident), nuclear tests at the Semipalatinsk Test Site, the Chernobyl nuclear accident etc. If monitoring in the early and (or) in the intermediate phases is absent the decisions concerning remedial actions are usually developed on the base of permanent monitoring. However decisions of this kind may be essentially erroneous. For these cases it is proposed to make retrospection of radiological data of the early and intermediate phases of nuclear accident and to project decisions concerning remedial actions on the base of both retrospective data and permanent monitoring data. In this Report the indicated problem is considered by the example of the Chernobyl accident for Ukraine. Their of-site radiological monitoring in the early and intermediate phases was unsatisfactory. In particular, the pasture-cow-milk monitoring had not been made. All official decisions concerning dose estimations had been made on the base of measurements of 137Cs in body (40 measurements in 135 days and 55 measurements in 229 days after the Chernobyl accident). For the retrospection of radiological data of the Chernobyl accident dynamic model has been developed. This model has structure similar to the structure of Pathway model and Farmland model. Parameters of the developed model have been identified for agricultural conditions of Russia and Ukraine. By means of this model dynamics of 20 radionuclides in pathways and dynamics of doses have been estimated for the early, intermediate and late phases of the Chernobyl accident. The main results are following: • During the first year after the Chernobyl accident 75–93% of Commitment Effective Dose had been formed. • During the first year after the Chernobyl accident 85–90% of damage from radiation exposure had been formed. During the next 50 years (the late phase of accident) only 10–15% of damage from radiation exposure will have been formed. • Remedial actions (agricultural remedial actions as most effective) in Ukraine are intended for reduction of the damage from consumption of production which is contaminated in the late phase of accident. I.e. agricultural remedial actions have been intended for minimization only 10% of the total damage from radiation exposure. • Medical countermeasures can minimize radiation exposure damage by an order of magnitude greater than agricultural countermeasures. • Thus, retrospection of nuclear accident has essentially changed type of remedial actions and has given a chance to increase effectiveness of spending by an order of magnitude. This example illustrates that in order to optimize remedial actions it is required to use data of retrospection of nuclear accidents in all cases when monitoring in the early and (or) intermediate phases is unsatisfactory.

scholarly journals Magnetic signatures of subsurface faults on the northern upper flank of Mt Etna (Italy)

2021 ◽  
Vol 64 (1) ◽  
Author(s):  
Rosalba Napoli ◽  
Gilda Currenti ◽  
Antonino Sicali
Keyword(s):  
Source Parameters ◽  
Magma Ascent ◽  
Magnetic Survey ◽  
Tectonic Structures ◽  
Near Surface ◽  
North East ◽  
The North ◽  
3D Euler Deconvolution ◽  
Mt Etna ◽  
Structural Indices

A ground magnetic study was performed on the northern upper flank of Mt. Etna to provide new insights into subsurface volcano-tectonic structures. The high resolution magnetic survey was focused on the main structures of Piano delle Concazze, a large flat area dominated by the North- East crater and bounded by the rim of the Valle del Leone depression and the extremity of the North- East Rift. More than 2,500 measurements were gathered with a sampling step of about 3 m covering an area of about 0.2 km2. The total-intensity anomaly field shows the presence of intense South- North aligned maxima related to shallow geological structures affecting this area. Filtering techniques and 2.5D modeling have been applied for the determination of the magnetic source parameters. In order to distinguish the near surface structure, filters of the vertical derivatives, Butterworth high-pass and the tilt derivative were used. The 3D Euler deconvolution has been applied to estimate the depth and the structural indices of the causative sources. The calculated structural indices, that express the geometrical nature of the source, are in agreement with forward modeling. They show that the area is mainly affected by subvertical normal fault and the estimated depth of magnetic sources ranges between 10 m and 40 m. Our total field magnetic survey shows that characteristic magnetic anomalies are related to fault zones in the Piano delle Concazze that are well consistent with the local tectonics. The subsurface structures that have been detected allowed to delineate the general structural framework of the area. In particular, it was possible to clarify that these structures seem to be not deep rooted and consequently they can hardly act as preferential pathways for magma ascent.

Erosion Rate Testing at High Temperature of Alloys and Coatings for Use in Turbomachinery

1998 ◽  
Author(s):  
W. Tabakoff
Keyword(s):  
High Temperature ◽  
Solid Particles ◽  
Surface Erosion ◽  
Erosion Testing ◽  
Speed Flow ◽  
Order Of Magnitude ◽  
The University ◽  
Work Done ◽  
High Temperature Erosion ◽  
Reliable Methods

Because of the serious consequences of turbomachinery erosion on their performance and life, it is important to have reliable methods for predicting their erosion when solid particles are ingested with the incoming flow. This is a very challenging problem since turbomachinery erosion is affected by many factors such as blade passage geometry, blade row location, rotational speed flow conditions, blade material and particles’ characteristics. Several studies which are essential to predicting blade surface erosion intensity and pattern, have been conducted at the University of Cincinnati’s Propulsion Laboratory over the past twenty-five years. This paper describes only some of the work done on erosion testing at high temperatures and velocities for different materials and coatings. The testing has been performed with a special high temperature erosion wind tunnel which simulates the aerodynamic conditions on the blades. The coated substrates reveal one order of magnitude less wear compared to some commercial non-CVD coatings on the same alloys. This study demonstrates that some coatings provide an excellent erosion resistance to INCO 718, LNCO 738, MAR-246, X-40 and Tungsten Carbide.

A combined 2-D/1-D magma ascent model of explosive volcanic eruptions

2019 ◽  
Vol 219 (3) ◽  
pp. 1818-1835
Author(s):  
Hélène Massol
Keyword(s):  
Volume Fraction ◽  
Experimental Studies ◽  
Volcanic Eruptions ◽  
Gas Content ◽  
Magma Ascent ◽  
Explosive Eruptions ◽  
Shear Stresses ◽  
Order Of Magnitude ◽  
Gas Volume Fraction ◽  
Gas Volume

SUMMARY Explosive eruptions involve the fragmentation of magma that changes the flow regime from laminar to turbulent within the volcanic conduit during ascent. If the gas volume fraction is high, magma fragments and the eruption style is explosive, but if not, the magma flows effusively out of the vent. Gas escape processes depend on how the magma can rupture, and recent experimental studies measured rupture stress thresholds of the order of a few megapascals. It is thus critical to model the gas content and state of stress evolution in the flowing magma within the conduit. We present a new self-consistent model of an explosive eruption from the magma chamber to the surface, based on a critical gas volume fraction. Our model allows to explore irregular geometries below the fragmentation level (2-D). We first compare our model with classical 1-D models of explosive eruptions and find that in the case of straight conduits and fragmented flows, 1-D models are accurate enough to model the gas pressure and vertical velocity distribution in the conduit. However, in the case of an irregular conduit shape at depth, 2-D models are necessary. Despite a certain conduit radius visible at the surface, very different stress fields within the flow could be present depending upon the position and shape of any conduit irregularities. Stresses of the order of more than 1 MPa can be attained in some locations. High tensile stresses are located at the centre of the conduit, while high shear stresses are located at the conduit walls leading to several potential rupture locations. Due to the interplay between the velocity field and decompression rate, similar conduit radius visible at the surface might also lead to very different fragmentation depths with a difference of more than 1500 m between an enlarged conduit shape at some depth and a straight conduit. At depth, different conduit sizes might lead to the same order of magnitude for the mass flux, depending on the conduit geometry.

scholarly journals Rheological change and degassing during a trachytic Vulcanian eruption at Kilian Volcano, Chaîne des Puys, France

2020 ◽  
Vol 82 (12) ◽  
Author(s):  
Mathieu Colombier ◽  
Thomas Shea ◽  
Alain Burgisser ◽  
Timothy H. Druitt ◽  
Lucia Gurioli ◽  
...  
Keyword(s):  
Water Solubility ◽  
Pore Space ◽  
High Water ◽  
Magma Ascent ◽  
Explosive Activity ◽  
Pore Collapse ◽  
Melt Viscosity ◽  
Effusive Activity ◽  
Volatile Loss ◽  
Magma Viscosity

AbstractMagma ascent during silicic dome-forming eruptions is characterized by significant changes in magma viscosity, permeability, and gas overpressure in the conduit. These changes depend on a set of parameters such as ascent rate, outgassing and crystallization efficiency, and magma viscosity, which in turn may influence the prevailing conditions for effusive versus explosive activity. Here, we combine chemical and textural analyses of tephra with viscosity models to provide a better understanding of the effusive-explosive transitions during Vulcanian phases of the 9.4 ka eruption of Kilian Volcano, Chaîne des Puys, France. Our results suggest that effusive activity at the onset of Vulcanian episodes at Kilian Volcano was promoted by (i) rapid ascent of initially crystal-poor and volatile-rich trachytic magma, (ii) a substantial bulk and melt viscosity increase driven by extensive volatile loss and crystallization, and (iii) efficient degassing/outgassing in a crystal-rich magma at shallow depths. Trachytic magma repeatedly replenished the upper conduit, and variations in the amount of decompression and cooling caused vertical textural stratification, leading to variable degrees of crystallization and outgassing. Outgassing promoted effusive dome growth and occurred via gas percolation through large interconnected vesicles, fractures, and tuffisite veins, fostering the formation of cristobalite in the carapace and talus regions. Build-up of overpressure was likely caused by closing of pore space (bubbles and fractures) in the dome through a combination of pore collapse, cristobalite formation, sintering in tuffisite veins, and limited pre-fragmentation coalescence in the dome or underlying hot vesicular magma. Sealing of the carapace may have caused a transition from open- to closed- system degassing and to renewed explosive activity. We generalize our findings to propose that the broad spectrum of eruptive styles for trachytic magmas may be inherited from a combination of characteristics of trachytic melts that include high water solubility and diffusivity, rapid microlite growth, and low melt viscosity compared to their more evolved subalkaline dacitic and rhyolitic equivalents. We show that trachytes may erupt with a similar style (e.g., Vulcanian) but at significantly higher ascent rates than their andesitic, dacitic, and rhyolitic counterparts. This suggests that the periodicity of effusive-explosive transitions at trachytic volcanoes may differ from that observed at the well-monitored andesitic, dacitic, and rhyolitic volcanoes, which has implications for hazard assessment associated with trachytic eruptions.

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