Deep-sea fragmentation style of Havre revealed by dendrogrammatic analyses of particle morphometry

Abstract

In 2012, the eruption of deep-sea volcano Havre produced an abundance of fine ash at a depth of ~1000 m below sea level. In this study the 2D shapes of Havre ash grains retrieved from the seafloor were compared quantitatively with those of particles generated in a suite of different fragmentation experiments, which used remelted rhyolitic rock and pumice from the eruption site. A new statistical data analysis technique, denoted Dendrogrammatic Analysis of Particle Morphology (DAPM) is introduced. It is designed to compare large numbers of morphometric data sets containing shape information for a set of ash particles, to group them by morphological similarities and to visualize these clusters in a dendrogram. Further steps involve t-tests and equivalence tests and reveal morphometric differences as well as matching features. The DAPM suggests that the majority of Havre ash was thermohydraulically produced by induced fuel coolant-interaction. A subset of ash particles feature an elongate tube morphology. Their morphometry matches that of particles that were experimentally produced by a combination of shearing and quenching, and we infer that the natural particles were formed by synextrusive ash-venting.

External surface water influence on explosive eruption dynamics, with implications for stratospheric sulfur delivery and volcano-climate feedback

“…How to capture thoroughly these particle-scale effects and their consequences for the mean particle size distribution in an evolving volcanic jet mixture is unclear and remains a subject of vigorous research (e.g. Wohletz, 1983;Büttner et al, 2002Büttner et al, , 2006Mastin, 2007a;Woodcock et al, 2012;Patel et al, 2013;Liu et al, 2015;van Otterloo et al, 2015;Fitch and Fagents, 2020;Dürig et al, 2020b;Moitra et al, 2020). However, with a specified magmatic heat flow at the vent, considerations of the surface energy consumed to generate fine ash fragments (Sonder et al, 2011), guided by published experiments along with observational constraints on the hydromagmatic evolution of particle sizes (Costa et al, 2016), provide a way forward that is appropriate for a 1D integral model.…”

Assessing Volcanic Hazard and Exposure at Obscure Volcanic Fields: A Case Study from the Bolaven Volcanic Field, Laos

“…Explosive interaction between magma and water (here broadly referred to as phreatomagmatic activity), is a potentially hazardous volcanic phenomenon known to occur in a wide range of environmental settings (e.g. Thorarinsson, 1964;Fagents and Thordarson, 2007;Wohletz et al, 2013;Verolino et al, 2018Verolino et al, , 2019Dürig et al, 2020aDürig et al, , 2020b, including areas dominated by lava flow effusions (e.g. Lorenz and Haneke, 2004;Hamilton et al, 2010;Fitch and Fagents, 2020).…”

Standardized analysis of juvenile pyroclasts in comparative studies of primary magma fragmentation; 1. Overview and workflow

“…Fine to extremely fine ash allows particle surface features and particle morphologies to be determined on the same carbon tape grain mount. Grains with certain surface features are inferred to have been formed by contact with external water during explosive magma-water interaction, and are called "interactive" particles, based on a comparison between magma fragmentation experiments and nature (Dellino et al 2001Austin-Erickson et al 2008;Zimanowski et al 2015;Valentine and White 2017;Dürig et al , 2020c.…”

“…The ash fraction (≤2 mm; see and Table 1 for definition of grain size terms) has often been preferred, since ash particles are rapidly quenched in air or water. Such characteristics have been studied for several decades (e.g., Heiken 1972Cioni et al, , 2008bBüttner et al 1999;Dellino et al 2001Dürig et al, , 2020cRoss and White 2012;Lautze et al 2012Lautze et al , 2013Bagheri et al 2015;Liu et al 2015aLiu et al , 2015bDioguardi et al 2017).…”