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Silicic lava effusion controlled by the transition from viscous magma flow to friction controlled flow
Author(s) -
Okumura S.,
Kozono T.
Publication year - 2017
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2017gl072875
Subject(s) - geology , silicic , magma , petrology , viscosity , lava , flow (mathematics) , lava dome , brittleness , mechanics , geophysics , materials science , volcano , geochemistry , composite material , physics
Abstract Silicic magma forms a vertical fault in volcanic conduits via the brittle‐ductile transition. The formation of the fault changes flow type from viscous flow to friction controlled flow. Here we investigate flow dynamics of magma by coupling a one‐dimensional conduit flow model with an experimentally calibrated brittle‐ductile transition. The numerical simulation demonstrates that the length of magma plug at which friction controlled flow becomes the main flow type depends on magma flux, because of crystallization kinetics and the ductile‐brittle transition. At high flux, a short plug forms, because nonequilibrium crystallization inhibits an increase of magma viscosity. This results in the effusion of less viscous lava and large shear stress at the shallow part of the conduit. In contrast, the long plug that forms under low flux cannot maintain large shear stress due to weakness of the magmatic fault, which causes the extrusion of a solidified lava spine.