Ascent and decompression of viscous vesicular magma in a volcanic conduit

Massol, Hélène; Jaupart, Claude; Pepper, Darrell W.

doi:10.1029/2001jb000385

Cited by 35 publications

(14 citation statements)

References 30 publications

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“…It thus involves complex physical processes. Since 1980, 1‐D and 2‐D models have been developed to determine which parameters govern eruptive dynamics (Wilson 1980; Wilson et al 1980; Slezin 1983; Woods 1995; Sparks 1997; Melnik & Sparks 1999; Melnik 2000; Massol et al 2001; Melnik & Sparks 2002; Collier 2005). In particular, the amount of gas plays an important role in the flow style since it influences both magma viscosity and velocity (Melnik & Sparks 1999; Melnik 2000; Llewellin & Manga 2005).…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional gas loss for silicic magma flows: toward more realistic numerical models

Collombet¹

2009

Geophysical Journal International

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SUMMARY Among the physical parameters that govern magma flows, gas content plays a major role. In particular, the presence of gas controls the magma viscosity and velocity gradients, which characterize the eruptive style. Depending on whether gas can escape the volcanic conduit or not, the magma pressure will increase (or not), leading to an effusive or an explosive regime. Gas loss is thus a key point for understanding the physics of magma flows. Its role during the magma ascent is studied numerically. In this paper, I introduce, for the first time, both horizontal and vertical magma permeabilities into a 2‐D magma flow model. The magma permeability is defined specifically for every point of the conduit as a function of the gas content and the bubble shape. Starting from an (unrealistic) closed system, I calculate iteratively the evolution of a degassing dyke to reach the stationary state for an open system. Gas loss does not occur homogeneously within the conduit, which leads to degassed magma sections presenting both vertical and lateral discrepancies. Its major influence lies within 500 m below the surface, where it leads to the formation of a 30–100 m thick degassed cover at the top of the conduit and the presence of 1–2 m thick degassed material near the conduit walls. Globally, the range of gas content decreases from 60–90 vol. % for a closed system down to 10–60 vol. % for an open system. This distribution in gas content and the associated flow are in good agreement with several field observations.

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Section: Introductionmentioning

confidence: 99%

Two-dimensional gas loss for silicic magma flows: toward more realistic numerical models

Collombet¹

2009

Geophysical Journal International

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“…In simple form, these models consist of the laminar 1D steady state ascent of magma through a rigid cylinder [e.g., Jaupart, 1996;Sparks, 1999, 2002;Mastin and Ghiorso, 2000]. Even these simple models may display strongly nonlinear behavior and have multiple steady state solutions due to nonlinearity in constitutive laws and dependencies between different parameters, and additional complexity is introduced by consideration of lateral variation of magma properties in the conduit [Massol et al, 2001;Collier and Neuberg, 2006;Mastin, 2005], non-Newtonian rheologies [Melnik and Sparks, 2005], noncylindrical or depth-varying conduit geometries [Costa et al, 2007a[Costa et al, , 2007bde' Michieli Vitturia et al, 2008], and elastic or viscoelastic behavior of the conduit walls and/or inclusion of the magma chamber feeding the eruption [Maeda, 2000;Barmin et al, 2002;Costa et al, 2007a].…”

Section: Previous Studiesmentioning

confidence: 99%

Physics-based models of ground deformation and extrusion rate at effusively erupting volcanoes

Anderson¹,

Segall²

2011

J. Geophys. Res.

115

154

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[1] We present a model of effusive silicic volcanic eruptions which relates magma chamber and conduit physics to time-dependent data sets, including ground deformation and extrusion rate. The model involves a deflating chamber which supplies Newtonian magma through a cylindrical conduit. Solidification is approximated as occurring at fixed depth, producing a solid plug that slips along its margins with rate-dependent friction. Changes in tractions acting on the chamber and conduit walls are used to compute surface deformations. Given appropriate material properties and initial conditions, the model predicts the full evolution of an eruption, allowing us to examine the dependence of observables on initial chamber volume, overpressure, and volatile content. Employing multiple data sets in combination with a physics-based model allows for better constraints on these parameters than is possible using kinematic idealizations. Modeling posteruptive deformation provides an improved constraint on the rate of influx into the magma chamber from deeper sources. We compare numerical results to analytical approximations and to data from the 2004-2008 eruption of Mount St. Helens. For nominal parameters the balance between magma chamber pressure and frictional resistance of the solid plug controls the evolution of the eruption, with little contribution from the fluid magma below the idealized crystallization depth. While rate-dependent plug friction influences the timedependent evolution of the eruption, it has no control on the final chamber pressure or extruded volume.Citation: Anderson, K., and P. Segall (2011), Physics-based models of ground deformation and extrusion rate at effusively erupting volcanoes,

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“…[4] Models of volcanic eruptions that include the physics governing magmatic processes [e.g., Jaupart, 1996;Melnik and Sparks, 1999;Mastin and Ghiorso, 2000;Massol et al, 2001;Barmin et al, 2002;Costa et al, 2007] provide valuable insight into various types of eruptive behavior, including cyclic activity. In order to use these models in an inversion, they must relate changes in pressures and tractions in magma to stresses and strains in the host rock in order to predict observations such as ground deformation.…”

Section: Introductionmentioning

confidence: 99%

Bayesian inversion of data from effusive volcanic eruptions using physics‐based models: Application to Mount St. Helens 2004–2008

2013

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[1] Physics-based models of volcanic eruptions can directly link magmatic processes with diverse, time-varying geophysical observations, and when used in an inverse procedure make it possible to bring all available information to bear on estimating properties of the volcanic system. We develop a technique for inverting geodetic, extrusive flux, and other types of data using a physics-based model of an effusive silicic volcanic eruption to estimate the geometry, pressure, depth, and volatile content of a magma chamber, and properties of the conduit linking the chamber to the surface. A Bayesian inverse formulation makes it possible to easily incorporate independent information into the inversion, such as petrologic estimates of melt water content, and yields probabilistic estimates for model parameters and other properties of the volcano. Probability distributions are sampled using a Markov-Chain Monte Carlo algorithm. We apply the technique using GPS and extrusion data from the 2004-2008 eruption of Mount St. Helens. In contrast to more traditional inversions such as those involving geodetic data alone in combination with kinematic forward models, this technique is able to provide constraint on properties of the magma, including its volatile content, and on the absolute volume and pressure of the magma chamber. Results suggest a large chamber of >40 km 3 with a centroid depth of 11-18 km and a dissolved water content at the top of the chamber of 2.6-4.9 wt%.

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Ascent and decompression of viscous vesicular magma in a volcanic conduit

Cited by 35 publications

References 30 publications

Two-dimensional gas loss for silicic magma flows: toward more realistic numerical models

Two-dimensional gas loss for silicic magma flows: toward more realistic numerical models

Physics-based models of ground deformation and extrusion rate at effusively erupting volcanoes

Bayesian inversion of data from effusive volcanic eruptions using physics‐based models: Application to Mount St. Helens 2004–2008

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