Characterization of shape and terminal velocity of tephra particles erupted during the 2002 eruption of Etna volcano, Italy

Coltelli, M.; Miraglia, L.; Scollo, Simona

doi:10.1007/s00445-007-0192-8

Cited by 36 publications

(43 citation statements)

References 29 publications

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“…By measuring V T for volcanic ash grains of varying shape and texture, Wilson and Huang [92] demonstrated a similar shape-dependency for ash particle settling, but suggested that the Shape Factor, F (F = b + c/2a), provided a more effective shape correction for irregular ash particles. These early shape parameters effectively quantify variation in particle form/elongation, but neglect the contribution of other morphological properties, such as surface roughness, to overall particle irregularity and the influence of this on particle aerodynamics [8,14,19]. Advances in particle imaging capabilities and computer processing during the 1990s revolutionised shape analysis.…”

Section: Area Of the Particle A Chmentioning

confidence: 98%

“…Roughness (textural) [65]; Malvern application note; [9,35,49] Roughness [69] Ap Ap+Ach [27] Convexity_feret CVX_f [19] 4π Ap…”

Section: Pch Ppmentioning

confidence: 99%

“…Particle diameter, for example, has been variably defined as the Feret diameter (D MaxFeret ; maximum distance between two parallel lines tangential to the particle outline), Form and roughness [2,19,20,28,32,44,48,49,65,73] Sphericity [1,7,56,69] Roundness [27,50,54] Circularity [9,18,35] Form and roughness [10,[21][22][23]25,39,47,[58][59][60] Shape factor [36]; Particle irregularity [57] Solidity SLD…”

Section: Area Of the Particle A Chmentioning

confidence: 99%

“…Aspect ratio AR [35,49] Aspect ratio [19,28,54,56,66,71,76] Ellipse aspect ratio [18] Ellipticity [54] Elongation El [47] Dmax f eret MIP [10,22,25,39,58,60] LG E [65] log 2 ( A B ) [44,54] Ap Dmax f eret [17] Roundness RD …”

Section: Pch Ppmentioning

confidence: 99%

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Optimising shape analysis to quantify volcanic ash morphology

Liu¹,

Cashman

Rust³

2015

GeoResJ

127

180

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a b s t r a c tAccurate measurements of volcanic ash morphology are critical to improving both our understanding of fragmentation processes and our ability to predict particle behaviour. In this study, we present new ways to choose and apply shape parameters relevant to volcanic ash characterisation. First, we compare shape measurements from different imaging techniques, including cross-sectional (2-D) and projected area images, and discuss their respective applications. We then focus on specific information that can be obtained from shape analysis of 2-D images. Using cluster analysis as an unbiased method to identify key controls on particle morphology, we find that four shape parameters -solidity, convexity, axial ratio, and form factor -can effectively account for the morphological variance within most ash samples. Importantly, these parameters are scaled to values between 0 and 1, and therefore contribute evenly to discrimination diagrams. In particular, co-variation in convexity and solidity can be used to distinguish different juvenile ash components based on characteristic bubble properties. By reducing observations of natural samples to simplified ash geometries, we quantify morphological changes associated with variations in the relative size and shape of bubbles and particles. Using this relationship, we assess the potential application of size-dependent shape analysis for inferring the underlying bubble size distribution, and thus the pre-fragmentation conditions. Finally, we show that particle shape analysis that includes the full range of available grain sizes can contribute not only measurements of particle size and shape, but also information on size-dependent densities.

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Section: Area Of the Particle A Chmentioning

confidence: 98%

“…Roughness (textural) [65]; Malvern application note; [9,35,49] Roughness [69] Ap Ap+Ach [27] Convexity_feret CVX_f [19] 4π Ap…”

Section: Pch Ppmentioning

confidence: 99%

Section: Area Of the Particle A Chmentioning

confidence: 99%

Section: Pch Ppmentioning

confidence: 99%

See 2 more Smart Citations

Optimising shape analysis to quantify volcanic ash morphology

Liu¹,

Cashman

Rust³

2015

GeoResJ

127

180

View full text Add to dashboard Cite

show abstract

“…In terms of aerodynamics, shape has a direct impact on the drag forces acting on rising and falling particles (Stringham et al, 1969;Bursik, 1989;Ganser, 1993;Mitchell, 1996;Chhabra et al, 1999;Mele et al, 2011;Dellino et al, 2012), which in turn influence the settling velocity (Wilson and Huang, 1979;Coltelli et al, 2008;Alfano et al, 2011), the atmospheric residence time (Riley et al, 2003), and the transport distance and dispersal of tephra (Sparks et al, 1997;Scollo et al, 2008). The aerial behavior of ash is also indirectly influenced by the surface-to-volume ratio, which affects the propensity of particles to form aggregates, both in dry and wet environments (e.g.…”

Section: Introduction and Previous Workmentioning

confidence: 99%

High-resolution 3D analyses of the shape and internal constituents of small volcanic ash particles: The contribution of SEM micro-computed tomography (SEM micro-CT)

Vonlanthen

Rausch

Ketcham

et al. 2015

Journal of Volcanology and Geothermal Research

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The morphology of small volcanic ash particles is fundamental to our understanding of magma fragmentation, and in transport modeling of volcanic plumes and clouds. Until recently, the analysis of 3D features in small objects (b250 μm) was either restricted to extrapolations from 2D approaches, partial stereo-imaging, or CT methods having limited spatial resolution and/or accessibility. In this study, an X-ray computed-tomography technique known as SEM micro-CT, also called 3D X-ray ultramicroscopy (3D XuM), was used to investigate the 3D morphology of small volcanic ash particles (125-250 μm sieve fraction), as well as their vesicle and microcrystal distribution. The samples were selected from four stratigraphically well-established tephra layers of the Meerfelder Maar (West Eifel Volcanic Field, Germany). Resolution tests performed on a Beametr v1 pattern sample along with Monte Carlo simulations of X-ray emission volumes indicated that a spatial resolution of 0.65 μm was obtained for X-ray shadow projections using a standard thermionic SEM and a bulk brass target as X-ray source. Analysis of a smaller volcanic ash particle (64-125 μm sieve fraction) showed that features with volumes N 20 μm 3 (~3.5 μm in diameter) can be successfully reconstructed and quantified. In addition, new functionalities of the Blob3D software were developed to allow the particle shape factors frequently used as input parameters in ash transport and dispersion models to be calculated. This study indicates that SEM micro-CT is very well suited to quantify the various aspects of shape in fine volcanic ash, and potentially also to investigate the 3D morphology and internal structure of any object b 0.1 mm 3 .

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Linking the IR transmittance to size and type of volcanic ash particles

et al. 2013

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[1] In this work, we applied infrared spectroscopy to investigate the spectral signature of the volcanic ash particles emitted during the 21-24 July 2001 eruption at Mount Etna, in Italy. We used a Bruker Equinox-55 Fourier transform infrared spectrometer in the range 7000-600 cm À1 (1.43-16.67 μm) and, for every collected spectrum, an image of the volcanic ash particles was recorded in the visible spectral range through the same microscope. These images were then analyzed by standard image analysis software in order to evaluate the main features of the particle: the length of the major and minor axes (Max and Min L), Feret diameter (FD), equivalent diameter (ED), and aspect ratio (AR). We measured transmission spectra in different conditions; spectra of one single particle (Single-Particle Measurement, SPM), spectra of a number of particles from two to ten (Multi-Particle Measurements type 1, MPM1) and of more than a hundred particles (Multi-Particle Measurements type 2, MPM2). For SPM, Max and Min L range between 5 and 24 μm and 3.5 and 15 μm, FD ranges between 5.5 and 25 μm, ED varies between 5 and 19 μm, and AR between 0.45 and 0.95. For MPM1 and MPM2, the mean values of Max and Min L are between 4-17 μm and 3-10 μm, FD and ED between 5 and 19 μm and 3.5 and 23 μm, and AR between 0.3 and 1. The optical depth spectra as a function of the wave number clearly show the presence of the Christiansen effect that produces high transmission at a given frequency in the infrared region (Christiansen frequency). We find that the effect depends on the particle size through a linear relation. Both the Christiansen effect and their relationship with the ash particle effective radius were compared with radiative transfer model simulations using different ash refractive indexes. The combined use of the linear relationship and the spectral position of the Christiansen frequency also indicated the possibility to characterize ash type. All these information can be used to improve the IR remote sensing volcanic ash quantitative estimations.Citation: Scollo, S., G. A. Baratta, M. E. Palumbo, S. Corradini, G. Leto, and G. Strazzulla (2013), Linking the IR transmittance to size and type of volcanic ash particles,

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Characterization of shape and terminal velocity of tephra particles erupted during the 2002 eruption of Etna volcano, Italy

Cited by 36 publications

References 29 publications

Optimising shape analysis to quantify volcanic ash morphology

Optimising shape analysis to quantify volcanic ash morphology

High-resolution 3D analyses of the shape and internal constituents of small volcanic ash particles: The contribution of SEM micro-computed tomography (SEM micro-CT)

Linking the IR transmittance to size and type of volcanic ash particles

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