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A review of volcanic ash aggregation.

Brown, R.J. and Bonadonna, C. and Durant, A.J. (2012) 'A review of volcanic ash aggregation.', Physics and chemistry of the earth, parts A/B/C., 45-46 . pp. 65-78.

Abstract

Most 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 10–100 s km from the volcano and a reduction in airborne fine ash mass concentrations 1000 s 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 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.

Item Type:Article
Keywords:Volcanic ash, Aggregation, Explosive eruption, Ash plume, Hydrometeors
Full text:(AM) Accepted Manuscript
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Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1016/j.pce.2011.11.001
Date accepted:No date available
Date deposited:11 February 2015
Date of first online publication:2012
Date first made open access:No date available

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