Effects of thermal quenching on mechanical properties of pyroclasts

Patel, Amish J.; Manga, Michael; Carey, Rebecca J.; Degruyter, Wim

doi:10.1016/j.jvolgeores.2013.04.001

Cited by 14 publications

(7 citation statements)

References 37 publications

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“…Depending on the magnitude of thermal stress (a function of cooling rate and particle size, as well as material properties such as glass composition or bulk porosity), brittle failure can occur either during or after solidification (e.g. Chandrasekar and Chaudhri 1994;Patel et al 2013). In this way, thermal stresses may trigger synchronous, or secondary, brittle fragmentation of pyroclasts formed hydrodynamically during volatile-driven acceleration (Schmid et al, 2010;Schipper et al 2011;Liu et al 2015b;Jutzeler et al 2016).…”

Section: The Influence Of Cooling Rate On Hydromagmatic Fragmentationmentioning

confidence: 99%

Contrasting mechanisms of magma fragmentation during coeval magmatic and hydromagmatic activity: the Hverfjall Fires fissure eruption, Iceland

et al. 2017

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Growing evidence for significant magmatic vesiculation prior to magma-water interaction (MWI) has brought into question the use of 'diagnostic' features, such as low vesicularities and blocky morphologies, to identify hydromagmatic pyroclasts. We address this question by quantifying co-variations in particle size, shape and texture in both magmatic and hydromagmatic deposits from the Hverfjall Fires fissure eruption, Iceland. Overlapping vesicularity and bubble number density distributions measured in rapidly quenched magmatic and hydromagmatic pyroclasts indicate a shared initial history of bubble nucleation and growth, with substantial vesiculation prior to MWI. Hydromagmatic fragmentation occurred principally by brittle mechanisms, where the length scale and geometry of fracturing was controlled by the bubble population. This suggests that the elevated fragmentation efficiency of hydromagmatic deposits is driven, at least in part, by brittle disintegration of vesicular pyroclasts due to high thermal stress generated during rapid cooling. In this way, the shape and size distributions of hydromagmatic pyroclasts, both critical input parameters for ash dispersion models, are strongly influenced by the dynamics of vesiculation prior to MWI. This result underlines the need to analyse multiple grain-size fractions to characterise the balance between magmatic and hydromagmatic processes. During the Hverfjall Fires eruption, the external water supply was sufficient to maintain MWI throughout the eruption, with no evidence for progressive exhaustion of a water reservoir. We suggest that both the longevity and the spatial distribution of MWI were determined by the pre-existing regional hydrology and represent continuous interaction between a propagating dike and a strong groundwater flow system hosted within permeable basalt lavas.

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Section: The Influence Of Cooling Rate On Hydromagmatic Fragmentationmentioning

confidence: 99%

Contrasting mechanisms of magma fragmentation during coeval magmatic and hydromagmatic activity: the Hverfjall Fires fissure eruption, Iceland

et al. 2017

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“…Turbulent velocity fluctuations are then expected to cause tensile stresses capable of fragmenting these glassy rinds, perhaps accounting for a significant portion of the fine ash produced during phreatomagmatic eruptions (Mastin 2007, Mastin et al 2009, Wohletz et al 1989). However, highly vesicular magma may be less susceptible to such secondary fragmentation (Patel et al 2013).…”

Section: Hydromagmatic Fragmentationmentioning

confidence: 99%

Magma Fragmentation

Gonnermann

2015

Annu. Rev. Earth Planet. Sci.

144

109

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Magma fragmentation is the breakup of a continuous volume of molten rock into discrete pieces, called pyroclasts. Because magma contains bubbles of compressible magmatic volatiles, decompression of low-viscosity magma leads to rapid expansion. The magma is torn into fragments, as it is stretched into hydrodynamically unstable sheets and filaments. If the magma is highly viscous, resistance to bubble growth will instead lead to excess gas pressure and the magma will deform viscoelastically by fracturing like a glassy solid, resulting in the formation of a violently expanding gas-pyroclast mixture. In either case, fragmentation represents the conversion of potential energy into the surface energy of the newly created fragments and the kinetic energy of the expanding gas-pyroclast mixture. If magma comes into contact with external water, the conversion of thermal energy will vaporize water and quench magma at the melt-water interface, thus creating dynamic stresses that cause fragmentation and the release of kinetic energy. Lastly, shear deformation of highly viscous magma may cause brittle fractures and release seismic energy.14.1

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“…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.…”

Section: Quench Fragmentation Modelmentioning

confidence: 99%

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

Rowell¹,

Jellinek²,

Hajimirza³

et al. 2022

Preprint

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Explosive volcanic eruptions can inject sulfur dioxide (SO2) into the stratosphere to form aerosol particles that modify Earth’s radiation balance and drive surface cooling. Eruptions involving interactions with shallow layers (< 500 m) of surface water and ice modify the eruption dynamics that govern the delivery of SO2 to the stratosphere. External surface water potentially controls the evolution of explosive eruptions in two ways that are poorly understood: (1) by modulating the hydrostatic pressure within the conduit and at the vent, and (2) through the ingestion and mixing of external water, which governs fine ash production as well as eruption column buoyancy flux. To make progress, we couple one-dimensional models of magma flow in the conduit and atmospheric column rise through a novel ”magma-water interaction” model that simulates the occurrence, extent and consequences of water entrainment depending on the depth of a surface water layer. We explore the effects of hydrostatic pressure on magma ascent in the conduit and gas decompression at the vent, and the conditions for which water entrainment drives fine ash production by quench fragmentation, eruption column collapse, or outright failure of the jet to breach the water surface. We show that the efficiency of water entrainment into the jet is the predominant control on jet behavior. For an increase in water depth of 50 to 100 m, the critical magma mass eruption rate required for eruption columns to reach the tropopause increases by an order of magnitude. Finally, we estimate that enhanced emission of fine ash leads to up to a 2-fold increase in the mass flux of particles < 125 microns to spreading umbrella clouds, together with up to a 10-fold increase in water mass flux, conditions that can enhance the removal of SO2 via chemical scavenging and ash sedimentation. Overall, compared to purely magmatic eruptions, we suggest that hydrovolcanic eruptions will be characterized by a reduced delivery of SO2 to the stratosphere. Our results thus suggest the possibility of an unrecognized volcano-climate feedback mechanism arising from modification of volcanic climate forcing by direct interaction of erupting magma with varying distributions of water and ice at the Earth’s surface.

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Effects of thermal quenching on mechanical properties of pyroclasts

Cited by 14 publications

References 37 publications

Contrasting mechanisms of magma fragmentation during coeval magmatic and hydromagmatic activity: the Hverfjall Fires fissure eruption, Iceland

Contrasting mechanisms of magma fragmentation during coeval magmatic and hydromagmatic activity: the Hverfjall Fires fissure eruption, Iceland

Magma Fragmentation

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

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