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arXiv · 1107.2555

Influence of Non-Newtonian rheology on magma degassing

Thibaut Divoux·Valérie Vidal·Maurizio Ripepe·Jean-Christophe Géminard
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Abstract

Many volcanoes exhibit temporal changes in their degassing process, from rapid gas puffing to lava fountaining and long-lasting quiescent passive degassing periods. This range of behaviors has been explained in terms of changes in gas flux and/or magma input rate. We report here a simple laboratory experiment which shows that the non- Newtonian rheology of magma can be responsible, alone, for such intriguing behavior, even in a stationary gas flux regime. We inject a constant gas flow-rate Q at the bottom of a non-Newtonian fluid column, and demonstrate the existence of a critical flow rate Q* above which the system spontaneously alternates between a bubbling and a channeling regime, where a gas channel crosses the entire fluid column. The threshold Q* depends on the fluid rheological properties which are controlled, in particular, by the gas volume fraction (or void fraction) ϕ. When ϕ increases, Q* decreases and the degassing regime changes. Non-Newtonian properties of magma might therefore play a crucial role in volcanic eruption dynamics.

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Thibaut Divoux, Valérie Vidal, Maurizio Ripepe, Jean-Christophe Géminard. 2011-07-13. Influence of Non-Newtonian rheology on magma degassing. https://doi.org/10.1029/2011gl047789

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