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Research Abstracts Online
January 2010 - March 2011

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University of Minnesota Twin Cities
College of Science and Engineering
Department of Geology and Geophysics

PI: Martin O. Saar

Numerically Identifying Missing Films Between Pumice Bubbles in Three Dimensions Using Microtomography

Eruption dynamics (effusive vs. explosive) are largely determined by magma permeability. If magma permeability in the volcano conduit is low, gas bubbles are disconnected and unable to depressurize into the surrounding rock. This results in a large pressure build-up, leading to an explosive eruption. Conversely, if magma permeability is high, bubble connectivity is also high. In this case, gas is able to escape from the magma, reducing the overall system’s pressure, resulting in an effusive eruption. To measure and visualize bubble connectivity, these researchers use x-ray microtomography to obtain a three-dimensional image of pumice microstructure. They can scan pumice samples up to a resolution of 4.6 microns. However, some of the thin films separating two bubbles are thinner than the given resolution, resulting in inaccurate calculations of permeability, tortuosity, and total bubble connectivity. This leads to a misinterpretation of how permeability and bubble connectivity relate to volcanic eruption dynamics. In collaboration with colleagues, the researchers have developed a code to find locations in the three-dimensional images where (due to the tomography resolution) the wall connecting two bubbles is missing, and then replace that wall. The code is written in IDL, and is used on very large datasets. The SDVL is an ideal location to run these simulations.

Group Members

Maria Davis, Graduate Student
Stuart D.C. Walsh, Research Associate