A new view of the dynamics, stability and longevity of volcanic clouds

Carazzo, Guillaume; Jellinek, M.

doi:10.1016/j.epsl.2012.01.025

Cited by 68 publications

(165 citation statements)

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“…A different type of settling mechanism appears to control the sedimentation of fine ash, which reached the ground much closer to the vent than predicted by individual particle settling (Figure ), as has been documented in a number of other fallout deposits (e.g., Brazier et al, ; Engwell & Eychenne, ; Rose & Durant, ). As discussed above, numerous processes can explain the observed accelerated transfer of fine ash toward the ground, including aggregation (e.g., Brown et al, ; Rose & Durant, ; Taddeucci et al, ; van Eaton et al, ) and other collective sedimentation behaviors such as en masse settling in convective instabilities (Carazzo & Jellinek, ; Manzella et al, ), hydrometeor‐enhanced sedimentation (Durant & Rose, ; Durant et al, ), and entrainment of fine ash in the wake of settling coarser grains (Del Bello et al, ; Di Muro et al, ; Eychenne et al, ; Lovell & Rose, ). But does the accelerated sedimentation of fine ash cause the formation of the ASMMs in the Spurr fallout deposits?…”

Section: Discussionmentioning

confidence: 99%

“…New field and experimental evidence demonstrates that the sedimentation mechanisms controlling plume depletion can be complex. In particular, the fall of individual particles through the atmosphere at their terminal velocity only partially describes the settling behavior of tephra (e.g., Del Bello et al, ), while additional collective sedimentation processes such as aggregation (e.g., Bagheri et al, ; Taddeucci et al, ) and en masse collapse of gravitational instabilities (e.g., Carazzo & Jellinek, , ; Durant et al, ; Manzella et al, ) can be significant.…”

Section: Introductionmentioning

confidence: 99%

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Distal Enhanced Sedimentation From Volcanic Plumes: Insights From the Secondary Mass Maxima in the 1992 Mount Spurr Fallout Deposits

et al. 2017

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Some tephra fallout deposits show an increase of mass and thickness at distances from the source >100 km (areas of secondary mass maximum, ASMM) which demonstrates distal enhanced sedimentation from volcanic plumes. We explore development of the ASMMs during the 1992 August and September Mount Spurr eruptions, USA, by combining field data on the spatial distribution of mass and grain size with (1) simulations of individual particle settling through a homogeneous and horizontally stratified atmosphere and (2) mesoscale models of the three‐dimensional wind field that include the effect of the underlying topography. The crosswind and downwind variations of deposit characteristics indicate that the increase of sedimentation at the ASMMs is not formed solely because of preferential settling of small ash particles (<125 μm), as commonly assumed in aggregation models. Instead, ASMM grain sizes correspond to the fine modes of the bimodal total grain size distributions. There also appears to be a link between the ASMM and the topography: the mass local minima occur across the windward flank of 2 km high mountain ranges, while the ASMMs spread on the leeward flank. Mesoscale models of the three‐dimensional wind field show vertical oscillations in the wind over mountainous regions which may enhance mechanisms of en masse sedimentation (aggregation, hydrometeor formation, and particle boundary layers), as well as strong spatial variations of the horizontal wind field in the lower troposphere. Our study demonstrates the importance of using grain size, as well as mass, data to constrain the complex processes responsible for particle sedimentation from volcanic plumes.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Distal Enhanced Sedimentation From Volcanic Plumes: Insights From the Secondary Mass Maxima in the 1992 Mount Spurr Fallout Deposits

et al. 2017

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“…They include dust storms (e.g., Goudie & Middleton, 2001), powder snow avalanches (e.g., Carroll et al, 2013), and volcanic biphasic suspensions such as conduit flows, buoyant plumes, or pyroclastic density currents (e.g., Bonadonna et al, 2011;Carazzo & Jellinek, 2012;Dufek, 2016;Gonnermann & Manga, 2007). They include dust storms (e.g., Goudie & Middleton, 2001), powder snow avalanches (e.g., Carroll et al, 2013), and volcanic biphasic suspensions such as conduit flows, buoyant plumes, or pyroclastic density currents (e.g., Bonadonna et al, 2011;Carazzo & Jellinek, 2012;Dufek, 2016;Gonnermann & Manga, 2007).…”

Section: Introductionmentioning

confidence: 99%

Maximum Solid Phase Concentration in Geophysical Turbulent Gas‐Particle Flows: Insights From Laboratory Experiments

Weit

Roche

Dubois

et al. 2019

Geophysical Research Letters

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The maximum solid phase concentration in geophysical turbulent gas‐particle mixtures is essential for understanding the flow dynamics but is poorly known. We present laboratory experiments on turbulent mixtures of air and ceramic particles generated in a vertical pipe. The mixtures had maximum bulk concentrations Cmax = 0.7–2.4 vol. % set by the onset of clustering and that increased with the degree of turbulence. Comparison with results of similar experiments with less dense (glass) particles reveals that Cmax increases with the particle Reynolds number according to Cmax = 0.78 × Rep0.17. Published results of experiments at specific Rep in different configurations are consistent with our data, suggesting that the model for Cmax may be generally applicable to turbulent mixtures. From our empirical laws we infer that natural turbulent gas‐particle flows with Rep ~ 102–105 have maximum solid concentrations of ~2–5 vol. %.

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“…Within a few hundreds of kilometres from the vent, ϕ p in the plume can be as high as 10 −5 , and up to 10 −3 in more proximal regions293031. The observations and modelling of localized regions of instability, including particle-rich ‘fingers’ or ‘scalloped umbrella’3233, suggest that the dynamics of particle sedimentation is strongly governed by several factors mostly related to particle concentration34.…”

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confidence: 99%

Effect of particle volume fraction on the settling velocity of volcanic ash particles: insights from joint experimental and numerical simulations

Bello

Taddeucci

Vitturi

et al. 2017

Sci Rep

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Most of the current ash transport and dispersion models neglect particle-fluid (two-way) and particle-fluid plus particle-particle (four-way) reciprocal interactions during particle fallout from volcanic plumes. These interactions, a function of particle concentration in the plume, could play an important role, explaining, for example, discrepancies between observed and modelled ash deposits. Aiming at a more accurate prediction of volcanic ash dispersal and sedimentation, the settling of ash particles at particle volume fractions (ϕp) ranging 10−7-10−3 was performed in laboratory experiments and reproduced by numerical simulations that take into account first the two-way and then the four-way coupling. Results show that the velocity of particles settling together can exceed the velocity of particles settling individually by up to 4 times for ϕp ~ 10−3. Comparisons between experimental and simulation results reveal that, during the sedimentation process, the settling velocity is largely enhanced by particle-fluid interactions but partly hindered by particle-particle interactions with increasing ϕp. Combining the experimental and numerical results, we provide an empirical model allowing correction of the settling velocity of particles of any size, density, and shape, as a function of ϕp. These corrections will impact volcanic plume modelling results as well as remote sensing retrieval techniques for plume parameters.

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A new view of the dynamics, stability and longevity of volcanic clouds

Cited by 68 publications

References 65 publications

Distal Enhanced Sedimentation From Volcanic Plumes: Insights From the Secondary Mass Maxima in the 1992 Mount Spurr Fallout Deposits

Distal Enhanced Sedimentation From Volcanic Plumes: Insights From the Secondary Mass Maxima in the 1992 Mount Spurr Fallout Deposits

Maximum Solid Phase Concentration in Geophysical Turbulent Gas‐Particle Flows: Insights From Laboratory Experiments

Effect of particle volume fraction on the settling velocity of volcanic ash particles: insights from joint experimental and numerical simulations

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