Dynamics of magma flow inside volcanic conduits with bubble overpressure buildup and gas loss through permeable magma

Melnik, Oleg; Бармин, А. А.; Sparks, R. S. J.

doi:10.1016/j.jvolgeores.2004.09.010

Cited by 120 publications

(68 citation statements)

References 27 publications

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“…Transitions in eruptive style can occur in either direction, and be quite sudden, making volcanic risk very difficult to evaluate (Melnik 2000). Gas loss from a permeable magmatic foam is increasingly considered in eruption models (Papale 2001;Slezin 2003;Melnik et al 2005), as it affects viscosity of the magma, density variation and pressure distribution in the magma column, and ultimately the location and style of magma fragmentation. Quantification of permeability development during magma ascent in conduits is therefore critical to the implementation of accurate eruption models, which are highly sensitive to the sharp decreases in bulk viscosity and density that accompany vesiculation.…”

Section: Introductionmentioning

confidence: 99%

Characterization of juvenile pyroclasts from the Kos Plateau Tuff (Aegean Arc): insights into the eruptive dynamics of a large rhyolitic eruption

Maisonneuve

Burgisser

2008

Bull Volcanol

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International audienceSilicic pumices formed during explosive volcanic eruptions are faithful recorders of the state of the magma in the conduit, close to or at the fragmentation level. We have characterized four types of pumices from the non-welded rhyolitic Kos Plateau Tuff, which erupted 161,000 years ago in the East Aegean Arc, Greece. The dominant type of pumice (>90 vol.%) shows highly elongated tubular vesicles. These tube pumices occur throughout the eruption. Less common pumice types include: (1) “frothy” pumice (highly porous with large, sub-rounded vesicles), which form 5–10 vol.% of the coarsest pyroclastic flow deposits, (2) dominantly “microvesicular” and systematically crystal-poor pumices, which are found in early erupted, fine-grained pyroclastic flow units, and are characterized by many small (<50 μm in diameter) vesicles and few mm-sized, irregular voids, (3) grey or banded pumices, indicating the interaction between the rhyolite and a more mafic magma, which are found throughout the eruption sequence and display highly irregular bubble shapes. Except for the grey-banded pumices, all three other types are compositionally identical and were generated synchronously as they are found in the same pyroclastic units. They, therefore, record different conditions in the volcanic conduit leading to variable bubble nucleation, growth and coalescence. A total of 74 pumice samples have been characterized using thin section observation, SEM imagery, porosimetry, and permeametry. We show that the four pumice types have distinct total and connected porosity, tortuosity and permeability. Grey-banded pumices show large variations in petrophysical characteristics as a response to mingling of two different magmas. The microvesicular, crystal-poor, pumices have a bimodal bubble size distribution, interpreted as reflecting an early heterogeneous bubble nucleation event followed by homogeneous bubble nucleation close to fragmentation. Finally, the significant differences in porosity, tortuosity and permeability in compositionally identical tube and frothy pumices are the result of variable shear rates in different parts of the conduit. Differential shear rates may be the result of either: (1) pure shear, inducing a vertical progression from frothy to tube and implying a relatively thick fragmentation zone to produce both types of pumices at the same time or (2) localized simple shear, inducing strongly tubular vesicles along the wall and near-spherical bubbles in the centre of the conduit and not necessarily requiring a thick fragmentation zone

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Section: Introductionmentioning

confidence: 99%

Characterization of juvenile pyroclasts from the Kos Plateau Tuff (Aegean Arc): insights into the eruptive dynamics of a large rhyolitic eruption

Maisonneuve

Burgisser

2008

Bull Volcanol

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“…Brittle (dilatant) deformation triggers permeability increases for volcanic rock (Nara et al 2011;Heap et al 2015a;Heap and Kennedy 2016;Farquharson et al 2016b) that can enhance the outgassing of the nearby magma-filled conduit therefore promoting effusive, rather than explosive, behavior (as discussed by many authors, e.g., Eichelberger et al 1986;Sparks 1997;Melnik et al 2005). KeJ is known for producing both effusive and explosive eruptions and these contrasting styles are thought to be related to the rate and extent of eruptive outgassing (≤5 wt% juvenile H 2 O) and potential magma interaction with external water (Devine and Sigurdsson 1995).…”

Section: Discussionmentioning

confidence: 99%

Flank instability assessment at Kick-’em-Jenny submarine volcano (Grenada, Lesser Antilles): a multidisciplinary approach using experiments and modeling

et al. 2016

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Kick-'em-Jenny (KeJ)-located ca. 8 km north of the island of Grenada-is the only active submarine volcano of the Lesser Antilles Volcanic Arc. Previous investigations of KeJ revealed that it lies within a collapse scar inherited from a past flank instability episode. To assess the likelihood of future collapse, we employ here a combined laboratory and modeling approach. Lavas collected using a remotely operated vehicle (ROV) provided samples to perform the first rock physical property measurements for the materials comprising the KeJ edifice. Uniaxial and triaxial deformation experiments showed that the dominant failure mode within the edifice host rock is brittle. Edifice fractures (such as those at Champagne Vent) will therefore assist the outgassing of the nearby magma-filled conduit, favoring effusive behavior. These laboratory data were then used as input parameters in models of slope stability. First, relative slope stability analysis revealed that the SW to N sector of the volcano displays a deficit of mass/volume with respect to a volcanoid (ideal 3D surface). Slope stability analysis using a limit equilibrium method (LEM) showed that KeJ is currently stable, since all values of stability factor or factor of safety (Fs) are greater than unity.The lowest values of Fs were found for the SW-NW sector of the volcano (the sector displaying a mass/volume deficit). Although currently stable, KeJ may become unstable in the future. Instability (severe reductions in Fs) could result, for example, from overpressurization due to the growth of a cryptodome. Our modeling has shown that instabilityinduced flank collapse will most likely initiate from the SW-NW sector of KeJ, therefore mobilizing a volume of at least ca. 0.7 km 3 . The mobilization of ca. 0.7 km 3 of material is certainly capable of generating a tsunami that poses a significant hazard to the southern islands of the West Indies.

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“…Jaupart and Allègre 1991;Melnik et al 2005;Castro and Gardner 2008). The seismicity recorded during transitional periods offers useful clues to the underlying processes.…”

Section: Transition and Evolution Of Activitymentioning

confidence: 99%

Long-period seismicity during magma movement at Volcán de Colima

et al. 2010

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During the period from February to September 2005, Volcán de Colima produced 30 Vulcanian explosions of sufficient magnitude to produce pyroclastic flows of variable size, with a total volume of at least 2.5×10 6 m 3 . Swarms of long-period events were associated with each event, their duration ranging from about 6 h to 3 days and each swarm containing up to 886 events. The characteristics of the swarms have been studied to understand the source mechanism and their relationship with the Vulcanian explosions. In total, 12,548 long-period events were analysed using various comparative and statistical methods. Patterns were not apparent in the data with no correlation between different properties of the swarms (duration, magnitude or frequency of occurrence of LP events) and the magnitude of the associated Vulcanian explosion, whether recorded by seismicity, volume of pyroclastics or altitude of the eruption column. This, along with other characteristics of the swarms, such as the continuation of the swarm after the explosion, with an increase in longperiod event amplitude in some cases, suggests that the mechanism is not merely associated with the pressurization under an impermeable cap and resulting pressure differentials between adjacent volumes within the system. It is more likely that the production of long-period events is dominated by brittle fracturing on the margins of an ascending magma body. A model is proposed whereby the unloading above the ascending magma column produced by a Vulcanian explosion resulted in an increase in ascent rate, reflected in the increasing amplitude of long-period events. The results reflect the complexity of non-linear processes involved during magma ascent, degassing, crystallization and rupture of the impermeable plug during the Vulcanian process. At Volcán de Colima, as at many volcanoes, long-period events represent a useful precursor for eruptive activity. For monitoring, this paper highlights some useful analyses that can be carried out, which could illustrate certain characteristics of an eruptive episode. A preliminary model is presented of the conduit processes at work during the cyclic extrusive and explosive activity during 2005.

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Dynamics of magma flow inside volcanic conduits with bubble overpressure buildup and gas loss through permeable magma

Cited by 120 publications

References 27 publications

Characterization of juvenile pyroclasts from the Kos Plateau Tuff (Aegean Arc): insights into the eruptive dynamics of a large rhyolitic eruption

Characterization of juvenile pyroclasts from the Kos Plateau Tuff (Aegean Arc): insights into the eruptive dynamics of a large rhyolitic eruption

Flank instability assessment at Kick-’em-Jenny submarine volcano (Grenada, Lesser Antilles): a multidisciplinary approach using experiments and modeling

Long-period seismicity during magma movement at Volcán de Colima

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