HR: 0800h
AN: V31D-0650    [Abstracts]
TI: Macroscopic Bubble Network Formation in the Presence of Crystals
AU: * Saar, M O
EM: saar@umn.edu
AF: Department of Geology and Geophysics, University of Minnesota, 310 Pillsbury Hall, Minneapolis, MN 55455 United States
AU: Manga, M
EM: manga@seismo.berkeley.edu
AF: Department of Earth and Planetary Science, University of California - Berkeley, 307 McCone Hall, Berkeley, CA 94720 United States
AB: Large-scale magma permeabilities for volatile gases and associated degassing rates are poorly understood even though the flow of gases through bubble networks is central to understanding a wide range of magmatic properties and processes. These include bubble and crystal content and related magma rheology, emissions of volcanic gases, pressurization and destruction of conduit plugs, magma fragmentation and subsequent expansion, and transitions in eruption dynamics as well as lava flow emplacement characteristics. Here, we present a numerical, percolation-theory-based approach to investigate bubble and fracture connectivity over larger spatial scales (e.g., volcanic conduit cross section size) that may be important for degassing processes (e.g., conduit magma degassing). We show how the critical volume fraction, φ_c, for macroscopic object connectivity decreases as a function of object deformation (elongation or flattening), how results of φ_c are related between prisms (crystals) and ellipsoids (bubbles), and how the simultaneous presence of crystals and bubbles may influence their respective φ_c values. The latter condition is often given in a multiphase magmatic system where both crystal- and bubble connectivity can initiate important threshold material properties such as the onset of yield strength and permeability, respectively, with implications for magma rheology and degassing rates. Eventually, in order to test simulations, the microstructure of small-scale samples from eruption products will be compared with numerical microstructures produced by larger-scale simulations by employing spatial correlation functions. Later, the overall synthetic bubble network will be used in gas flow simulations to estimate syneruptive macroscopic magma permeabilities and degassing rates in volcanic conduits. These results may then serve as input parameters for studies and simulations of eruption dynamics (e.g., effusive versus explosive) and other volcanological processes.
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8428 Explosive volcanism
DE: 8429 Lava rheology and morphology
DE: 8430 Volcanic gases
DE: 8434 Magma migration and fragmentation
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005