A review of statistical tools for morphometric analysis of juvenile pyroclasts

Abstract

Morphometric analyses are based on multiparametric datasets that describe quantitatively the shapes of objects. The stochastic nature of fracture-formation processes that break up magma during explosive eruptions yields mixtures of particles that have highly varied shapes. In volcanology morphometric analysis is applied to these mixtures of particles with diverse shapes for two purposes: (1) to fingerprint tephra from individual eruptions and use the fingerprints to distinguish among tephra layers and determine their extents, and (2) to reconstruct eruption processes, by linking particles formed by known fragmentation processes in experiments with particles from natural pyroclastic deposits. Here we review the most commonly adopted statistical techniques for morphometric analysis of pyroclasts. We provide sets of objects with different shapes, along with their morphometric data, in order to demonstrate and illustrate the methods. They can be used not only for addressing the processes of fragmentation during explosive eruptions, but also for the characterization of other types of solid particles with complex morphologies.

Experimental Multiblast Craters and Ejecta—Seismo‐Acoustics, Jet Characteristics, Craters, and Ejecta Deposits and Implications for Volcanic Explosions

“…Attenuation and site-specific response (Equation 17) depend on the host's strength and density, both of which also depend on the moisture content of the ground (e.g., Lamb et al, 1991;Rickman et al, 2011). Part of the energy which does not cause seismic or airborne waves is likely used to fragment the host rock (Dürig et al, 2021;Ouchterlony & Sanchidrián, 2019). Even though fragmentation is an important part of explosive volcanic processes (Zimanowski et al, 2003), the size of the presented experiments did not allow one to measure changes in collected representative samples of the ejected material.…”

Physical properties of pyroclastic density currents: relevance, challenges and future directions

“…This range makes cross-comparison between different studies and deposits challenging and the frequent use of alternative nomenclature (e.g., roundness vs. circularity vs. form factor) further hinders useful comparisons. The use of shape parameters for juvenile volcanic pyroclasts, associated statistical tests and classifications, and the protocols for data collection have been extensively reviewed and this will not be repeated here (Leibrandt and Le Pennec, 2015;Liu et al, 2015;Dürig et al, 2021;Comida et al, 2022;Ross et al, 2022;Benet et al, 2023). The detailed work of Liu et al (2015) leads to the recommendation of the following bounded (i.e., scaled from 0 to 1) shape descriptors: solidity, convexity, and axial ratio.…”

Characteristics of ash particles from the maar complex of Lamongan Volcanic Field (LVF), East Java, Indonesia: How textural features and magma composition control ash morphology

“…The clustering referred to the degree of similarity using the Euclidean distance scale (height) [e.g. Maria and Carey 2002;Jordan et al 2014;Liu et al 2015;Dürig et al 2021]. Three clusters of particles are distinguished using this procedure: [1] blocky and equant shapes Figure 10: Summary of textural features and morphology of ash particles from the LVF maar complex with their corresponding rheological variations.…”