Pulsed Vulcanian explosions: A characterization of eruption dynamics using Doppler radar

Scharff, L.; Hort, Matthias; Varley, Nick

doi:10.1130/g36705.1

Cited by 17 publications

(20 citation statements)

References 29 publications

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“…A short acceleration exists but is not observed here due to geometrical constrains. Second and most relevant, almost all our explosions featured not one but multiple ejection pulses, also from more than one vent (Capponi et al, ; Gaudin et al, ; Scharff et al, ; Taddeucci et al, ). Our observations focus on the initial development of plumes in a region, which is relatively close to the vent area, and it remains open to discussion how much of the complexity we observe is preserved in the morphology of plumes at later moments and higher elevations above the vent.…”

Section: Discussionmentioning

confidence: 87%

The Initial Development of Transient Volcanic Plumes as a Function of Source Conditions

et al. 2017

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Transient volcanic plumes, having similar eruption duration and rise timescales, characterize many unsteady Strombolian to Vulcanian eruptions. Despite being more common, such plumes are less studied than their steady state counterpart from stronger eruptions. Here we investigate the initial dynamics of transient volcanic plumes using high‐speed (visible light and thermal) and high‐resolution (visible light) videos from Strombolian to Vulcanian eruptions of Stromboli (Italy), Fuego (Guatemala), and Sakurajima (Japan) volcanoes. Physical parameterization of the plumes has been performed by defining their front velocity, velocity field, volume, and apparent surface temperature. We also characterized the ejection of the gas‐pyroclast mixture at the vent, in terms of number, location, duration, and frequency of individual ejection pulses and of time‐resolved mass eruption rate of the ejecta's ash fraction. Front velocity evolves along two distinct trends related to the initial gas‐thrust phase and later buoyant phase. Plumes' velocity field, obtained via optical flow analysis, highlights different features, including initial jets and the formation and/or merging of ring vortexes at different scales. Plume volume increases over time following a power law trend common to all volcanoes and affected by discharge history at the vent. Time‐resolved ash eruption rates range between 102 and 107 kg/s and may vary up to 2 orders of magnitude within the first seconds of eruption. Our results help detailing how the number, location, angle, duration, velocity, and time interval between ejection pulses at the vents crucially control the initial (first tens of second), and possibly later, evolution of transient volcanic plumes.

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Section: Discussionmentioning

confidence: 87%

The Initial Development of Transient Volcanic Plumes as a Function of Source Conditions

et al. 2017

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“…Once the gas has decompressed, particles will overtake the gas because of their inertia, as observed during Strombolian eruptions [ Taddeucci et al ., ]. Similar velocity decay trends have also been reported for pyroclast ejections on different volcanoes [ Dubosclard et al ., ; Gouhier and Donnadieu , ; Taddeucci et al ., ; Scharff et al ., ].…”

Section: Discussionmentioning

confidence: 99%

“…This study focuses on the near-vent region, where, independently of fragmentation mechanism, impulsively released gas-pyroclast mixtures are ejected into the atmosphere following rapid decompression and gas expansion [Kieffer, 1984;Woods and Bower, 1995;Carcano et al, 2013]. This takes place over a wide range of eruption styles as, e.g., Strombolian or Vulcanian eruptions, parts of Plinian eruptions, or phreatomagmatic explosions [Koyaguchi and Woods, 1996;Gouhier and Donnadieu, 2011;Taddeucci et al, 2012;Scharff et al, 2015]. Moreover, if sonic conditions are reached at vent exit a gas-particle jet with supersonic characteristics can form [Kieffer, 1984;Kieffer and Sturtevant, 1984;Woods and Bower, 1995;Ogden, 2011;Carcano et al, 2014].…”

Section: Introductionmentioning

confidence: 99%

“…We aim at a better determination of the relative control of these parameters on mixture ejection as well as a better determination of the relation between observable eruption dynamics and the underlying conditions during an explosive eruption. Particle exit velocity, opening angle, and their dynamic evolution with time have been measured successfully [Dubosclard et al, 2004;Gouhier and Donnadieu, 2011;Taddeucci et al, 2012Taddeucci et al, , 2015Scharff et al, 2015], but the knowledge of source conditions stays uncertain. For this reason, we are investigating tube length (=conduit length or depth of magma surface), particle load (=erupted mass) [Gaudin et al, 2014], and vent geometry [Turner et al, 2017].…”

Section: Introductionmentioning

confidence: 99%

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The dynamics of volcanic jets: Temporal evolution of particles exit velocity from shock‐tube experiments

et al. 2017

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Pyroclast ejection during explosive volcanic eruptions occurs under highly dynamic conditions involving great variations in flux, particle sizes, and velocities. This variability must be a direct consequence of complex interactions between physical and chemical parameters inside the volcanic plumbing system. The boundary conditions of such phenomena cannot be fully characterized via field observation and indirect measurements alone. In order to understand better eruptive processes, we conducted scaled and controlled laboratory experiments. By performing shock‐tube experiments at known conditions, we defined the influence of physical boundary conditions on the dynamics of pyroclast ejection. If applied to nature, we are focusing in the near‐vent processes where, independently of fragmentation mechanism, impulsively released gas‐pyroclast mixtures can be observed. These conditions can be met during, e.g., Strombolian or Vulcanian eruptions, parts of Plinian eruptions, or phreatomagmatic explosions. The following parameters were varied: (1) tube length, (2) vent geometry, (3) particle load, (4) temperature, and (5) particle size distribution. Gas and particles in the experiments are not coupled (St >> 1). The initial overpressure, with respect to atmosphere, was always at 15 MPa. We found a positive correlation of pyroclast ejection velocity with (1) particle load, (2) diverging vent walls, and (3) temperature as well as a negative correlation with (1) tube length and (2) particle size. Additionally, we found that particle load strongly affects the temporal evolution of particle ejection velocity. These findings stress the importance of scaled and repeatable laboratory experiments for a better understanding of volcanic phenomena and therefore volcanic hazard assessment.

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“…), enabling variation with time to be observed in detail (e.g. [9][10][11][12]). Due to the non-steady nature of the process, monitoring dynamic source conditions (e.g.…”

Section: Introductionmentioning

confidence: 99%

Investigating Source Conditions and Controlling Parameters of Explosive Eruptions: Some Experimental-Observational- Modelling Case Studies

Dioguardi¹,

Dürig²,

Engwell³

et al. 2016

Updates in Volcanology - From Volcano Modelling to Volcano Geology

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Explosive volcanic eruptions are complex systems that can generate a variety of hazardous phenomena, for example, the injection of volcanic ash into the atmosphere or the generation of pyroclastic density currents. Explosive eruptions occur when a turbulent multiphase mixture, initially predominantly composedf of fragmented magma and gases, is injected from the volcanic vent into the atmosphere. For plume modelling purposes, a specific volcanic eruption scenario based on eruption type, style or magnitude is strictly linked to magmatic and vent conditions, despite the subsequent evolution of the plume being influenced by the interaction of the erupted material with the atmosphere. In this chapter, different methodologies for investigating eruptive source conditions and the subsequent evolution of the eruptive plumes are presented. The methodologies range from observational techniques to large-scale experiments and numerical models. Results confirm the relevance of measuring and observing source conditions, as such studies can improve predictions of the hazards of eruptive columns. The results also demonstrate the need for fundamental future research specifically tailored to answer some of the still open questions: the effect of unsteady flow conditions at the source on the eruptive column dynamics and the interaction between a convective plume and wind.

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Pulsed Vulcanian explosions: A characterization of eruption dynamics using Doppler radar

Cited by 17 publications

References 29 publications

The Initial Development of Transient Volcanic Plumes as a Function of Source Conditions

The Initial Development of Transient Volcanic Plumes as a Function of Source Conditions

The dynamics of volcanic jets: Temporal evolution of particles exit velocity from shock‐tube experiments

Investigating Source Conditions and Controlling Parameters of Explosive Eruptions: Some Experimental-Observational- Modelling Case Studies

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