HR: 08:45h
AN: V11F-04    [Abstracts]
TI: A Numerical Model for the Development of Magma Permeability During Eruption
AU: * Llewellin, E W
EM: ed.llewellin@durham.ac.uk
AF: Department of Earth Sciences, University of Durham, Science Labs, Durham, DH1 3LE, United Kingdom
AB: Magma permeability and eruption rate are closely coupled. Permeable networks of bubbles may develop as magma rises and bubbles grow and impinge on one another. The rate of release of overpressure as gas escapes through these networks influences the rate of bubble growth, hence, the rate and style of eruption. Conversely, the eruption rate influences the changing pressure environment experienced by a rising packet of magma. This, in turn, controls the morphology and permeability of the bubble networks. I present a numerical model for the development of the permeability of a packet of magma as it rises in the volcanic conduit. An important result is that anisotropic expansion of the magma leads to anisotropic permeability: For magma expanding at low capillarity within a conduit, percolation occurs first across the conduit and permeability is enhanced across the conduit. This implies that lateral degassing predominates in such a system, facilitating rapid gas escape, reducing the likelihood of magma fragmentation and mitigating eruption explosivity.
DE: 0545 Modeling (4255)
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8430 Volcanic gases
DE: 8439 Physics and chemistry of magma bodies
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting