Flow localization in fissure eruptions |
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Authors: | Jonathan J Wylie Karl R Helfrich Brian Dade John R Lister John F Salzig |
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Institution: | (1) Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USSA,;(2) Department of Applied Mathematics and Theoretical Physics, Institute of Theoretical Geophysics, University of Cambridge, Silver Street, Cambridge CB3 9EW, UK, GB |
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Abstract: | During a basaltic fissure eruption heat transfer from the hot magma to the surrounding rock causes a dramatic increase in
the magmatic viscosity and solidification at the margins. Both viscosity contrast and solidification can amplify initial variations
in the flow rate and lead to localization of the flow along the strike of the fissure. However, for typical parameters, amplification
driven by solidification is slower and significantly weaker than amplification driven by viscosity variations. In fact, for
the parameters examined, the amplification due to solidification is so weak that its effect is almost insignificant, whereas
viscosity variation provides a strong active mechanism for flow localization. Laboratory experiments illustrate viscous localization
and suggest that this mechanism is robust. The dependence of viscosity on temperature can cause a small change in the pressure
of the magma chamber to lead to a large jump in the flow rate of magma through the fissure.
Received: 13 March 1998 / Accepted: 27 September 1998 |
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Keywords: | Fissure eruption Flow localization Temperature-dependent viscosity Solidification |
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