Particle aggregation in volcanic eruption columns

Veitch, Graham; Woods, Andrew W.

doi:10.1029/2000jb900343

Cited by 45 publications

(90 citation statements)

References 44 publications

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“…Particle aggregation is a complex time-dependent process and is better described by a numerical solution. However, numerical models only exist for wet aggregation (Veitch and Woods, 2001;Textor et al, 2006a,b: Costa et al, 2010Folch et al, 2010) and wet sedimentation (i.e., removal of ash due to rain; Stohl et al, 2005;Draxler and Hess, 1998;D'Amours et al, 2010;Jones et al, 2007;. Here we will only describe details of wet-aggregation modelling.…”

Section: Empirical and Numerical Studies On Aggregationmentioning

confidence: 99%

“…The availability and abundance of water in the eruption cloud exerts a dominant control on aggregation (Gilbert and Lane, 1994;Veitch and Woods, 2001;Costa et al, 2010;Folch et al, 2010;Textor et al, 2006a and b). Initial fragmentation, particle collisions, mixed phase clouds and particle separation all lead to particle charging (Mather and Harrison, 2006) which influences particle collisions and may provide binding forces in the absence of water (more relevant for clouds 1000s km from source or >24 hours in age).…”

Section: Aggregation Within Ash Plumes: Conditions and Downwind Changesmentioning

confidence: 99%

“…As collision and sticking efficiency is decoupled and the relative speed of particles is enhanced by turbulence, the collision rate is high in the eruption column. Veitch and Woods (2001) According to Textor and Ernst (2004) the plume model considered by Veitch and Woods (2001) provides an overly-simplistic description of the aggregation process as it does not consider microphysical processes crucial for the aggregation of ash in the presence of water. Textor et al (2006a, b) presented a more sophisticated model of wet aggregation using ATHAM (Active Tracer High-resolution Atmospheric Model, Graf et al 1999;Herzog et al 2003;Oberhuber et al 1998) which accounts for the formation of liquid and solid hydrometeors and the effect on the plume dynamics from the latent heat generated by water phases changes.…”

Section: Empirical and Numerical Studies On Aggregationmentioning

confidence: 99%

“…Here we will only describe details of wet-aggregation modelling. Veitch and Woods (2001) focused on the process of wet aggregation which may arise when cloud water vapor cools and condenses during rise, thereby providing a binding agent for ash particles within the eruption column. It is assumed that particle aggregation only occurs in presence of liquid water and therefore they focus on wet aggregation in the eruption column (and assume the downwind plume of large Plinian eruptions is always below freezing temperature).…”

Section: Empirical and Numerical Studies On Aggregationmentioning

confidence: 99%

“…While aggregation exerts a first order control on the dispersal of fine ash within eruption clouds, the physical and chemical processes involved are not completely understood despite significant progress over the past twenty years (Schumacher and Schmincke, 1995;Gilbert and Lane, 1994;James et al, 2002James et al, , 2003Textor et al, 2006a and b;Costa et al, 2010). Fine airborne particles adhere to each other as a result of electrostatic attraction, moist adhesion between particles (e.g., Sorem, 1982;Gilbert and Lane, 1994;Schumacher andSchmincke, 1991, 1995;James et al, 2002) and hydrometeor formation (e.g., Veitch and Woods, 2001;Textor et al, 2006a;. The atmospheric residence time of fine ash determines the hazard to aviation (Casadevall, 1994), and ash fallout impacts local environments and infrastructure (Stewart et al, 2006;Spence et al, 2005;Wardman et al, 2011) and may present a health hazard over an extended period of exposure (Horwell and Baxter, 2006).…”

Section: Introductionmentioning

confidence: 99%

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A review of volcanic ash aggregation

Brown

Bonadonna

Durant

2012

Physics and Chemistry of the Earth, Parts A/B/C

227

298

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. (2012) 'A review of volcanic ash aggregation.', Physics and chemistry of the earth, parts A/B/C., 45-46 . pp. 65-78. Further information on publisher's website:http://dx.doi.org/10.1016/j.pce. 2011.11.001 Publisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractMost volcanic ash particles with diameters < 63 µm settle from eruption clouds as particle aggregates that cumulatively have larger sizes, lower densities, and higher terminal fall velocities than individual constituent particles. Particle aggregation reduces the atmospheric residence time of fine ash, which results in a proportional increase in fine ash fallout within 10s km to 100s km from the volcano and a reduction in airborne fine ash mass concentrations 1000s km from the volcano. Aggregate characteristics vary with distance from the volcano: proximal aggregates are typically larger (up to cm size) with concentric structures, while distal aggregates are typically smaller (sub-millimetre size). Particles comprising ash aggregates are bound through hydro-bonds (liquid and ice water) and electrostatic forces, and the rate of particle aggregation correlates with cloud liquid water availability. Eruption source parameters (including initial particle size distribution, erupted mass, eruption column height, cloud water content and temperature) and the eruption plume temperature lapse rate, coupled with the environmental parameters, determines the type and spatiotemporal distribution of aggregates. Field studies, lab experiments and modelling investigations have already provided important insights on the process of particle aggregation. However, new integrated observations that combine remote sensing studies of 2 ash clouds with field measurement and sampling, and lab experiments are required to fill current gaps in knowledge surrounding the theory of ash aggregate formation. Abstract word count: 222

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Section: Empirical and Numerical Studies On Aggregationmentioning

confidence: 99%

Section: Aggregation Within Ash Plumes: Conditions and Downwind Changesmentioning

confidence: 99%

Section: Empirical and Numerical Studies On Aggregationmentioning

confidence: 99%

Section: Empirical and Numerical Studies On Aggregationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A review of volcanic ash aggregation

Brown

Bonadonna

Durant

2012

Physics and Chemistry of the Earth, Parts A/B/C

227

298

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Ash aggregation in explosive volcanic eruptions

Telling

Dufek

Shaikh

2013

Geophysical Research Letters

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[1] Eruption dynamics are sensitive to ash aggregation, and aggregates are commonly found in eruptive deposits. While ash dispersal and associated hazards are sensitive to aggregation, few experiments have been conducted on this phenomena using natural materials across the diverse range of conditions expected in volcanic flows. We have isolated two regimes, wet and dry, in which aggregation occurs due to two different forces, electrostatic and hydrodynamic. Using a closed chamber to create a controlled atmosphere, we found that relative humidity, residence time, and kinetic energy are the three variables necessary to define wet and dry flow regimes. A series of processbased equations defining the behavior of ash particles have been developed. We propose an aggregation model that can be used for ash dispersal forecasts across a range of conditions in an eruptive plume.

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