The influence of viscous and latent heating on crystal-rich magma flow in a conduit

Hale, Alina J., Wadge, Geoff and Muhlhaus, Hans B. (2007) The influence of viscous and latent heating on crystal-rich magma flow in a conduit. Geophysical Journal International, 171 3: 1406-1429. doi:10.1111/j.1365-246X.2007.03593.x

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Author Hale, Alina J.
Wadge, Geoff
Muhlhaus, Hans B.
Title The influence of viscous and latent heating on crystal-rich magma flow in a conduit
Journal name Geophysical Journal International   Check publisher's open access policy
ISSN 0956-540X
Publication date 2007-08-23
Sub-type Article (original research)
DOI 10.1111/j.1365-246X.2007.03593.x
Open Access Status File (Publisher version)
Volume 171
Issue 3
Start page 1406
End page 1429
Total pages 24
Place of publication Oxford, United Kingdom
Publisher Oxford University Press
Collection year 2008
Language eng
Abstract The flow dynamics of crystal-rich high-viscosity magma is likely to be strongly influenced by viscous and latent heat release. Viscous heating is observed to play an important role in the dynamics of fluids with temperature-dependent viscosities. The growth of microlite crystals and the accompanying release of latent heat should play a similar role in raising fluid temperatures. Earlier models of viscous heating in magmas have shown the potential for unstable (thermal run-away) flow as described by a Gruntfest number, using an Arrhenius temperature dependence for the viscosity, but have not considered crystal growth or latent heating. We present a theoretical model for magma flow in an axi-symmetric conduit and consider both heating effects using Finite Element Method techniques. We consider a constant mass flux in a 1D infinitesimal conduit segment with isothermal and adiabatic boundary conditions and Newtonian and non-Newtonian magma flow properties. We find that the growth of crystals acts to stabilize the flow field and make the magma less likely to experience a thermal run-away. The additional heating influences crystal growth and can counteract super-cooling from degassing-induced crystallization and drive the residual melt composition back towards the liquidus temperature. We illustrate the models with results generated using parameters appropriate for the andesite lava dome-forming eruption at Soufrière Hills Volcano, Montserrat. These results emphasize the radial variability of the magma. Both viscous and latent heating effects are shown to be capable of playing a significant role in the eruption dynamics of Soufrière Hills Volcano. Latent heating is a factor in the top two kilometres of the conduit and may be responsible for relatively short-term (days) transients. Viscous heating is less restricted spatially, but because thermal run-away requires periods of hundreds of days to be achieved, the process is likely to be interrupted. Our models show that thermal evolution of the conduit walls could lead to an increase in the effective diameter of flow and an increase in flux at constant magma pressure.
Keyword Fluid dynamics
Finite-element methods
Magma flow
Volcanic activity
Geochemistry & Geophysics
Soufriere Hills Volcano
Temperature-dependent Viscosity
Degassing-induced Crystallization
Lava Dome Extrusion
Experimental Constraints
Q-Index Code C1

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Created: Mon, 27 Aug 2007, 16:00:05 EST by Alina Jane Hale on behalf of Earth Systems Science Computational Centre