Rheology of Bubbly Magmas and Lavas

University Of Oregon Eugene, Eugene OR

Investigators

Abstract

Manga EAR-0003303 Most erupting lavas have carried bubbles at some point during their ascent and emplacement. The effect of these bubbles on the rheological properties of magma will in turn affect the rate and style of eruption. The goal of the proposed work is thus to determine the effects of bubbles on the rheological properties of magmas and lavas for the ranges of physical parameters that are appropriate for magmatic systems. We will use three different research approaches, namely, numerical calculations, theoretical analysis, and experimental measurements. The numerical simulations will use the boundary integral technique to calculate the interaction and deformation of bubbles. The theoretical work will involve calculating bubble shapes and resulting flow in the limit that bubbles become highly deformed. In both the numerical and theoretical analyses, we will calculate all the components of the volume-averaged stress tensor. We can thus obtain quantities such as the effective shear viscosity and normal stress differences. We will make the experimental measurements in a large-volume, transparent viscometer that we have designed and built. The experimental measurements can be used to verify and extend results, and will allow us to study macroscopic features of the flows that might result from the non-Newtonian behaviour of the bulk suspension. We will also develop closed-form expressions for all our results that should be transferable to other problems and applications, such as models for eruption processes and lava flow models.