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Mechanisms of conduit plug formation: Implications for vulcanian explosions
Author(s) -
Diller K.,
Clarke A. B.,
Voight B.,
Neri A.
Publication year - 2006
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 - 10.1029/2006gl027391
Subject(s) - electrical conduit , overpressure , geology , magma , petrology , volcano , spark plug , extrusive , magma chamber , seismology , mechanical engineering , physics , aerospace engineering , engineering , thermodynamics
We explore physical mechanisms controlling formation of a confining conduit plug using 1D, steady‐state numerical models of magma ascent. Model results for the well‐documented 1997 Vulcanian explosions at Soufrière Hills volcano were compared against subsurface conditions constrained by geophysical and petrologic analysis. We suggest that, if magma is permeable and overpressured and rock surrounding the conduit is permeable, degassing occurs both vertically and through conduit walls. This outgassing creates a region of low‐vesicularity, dense magma near the surface ( magma plug ) which eventually seals the conduit and promotes system overpressure. Driving pressure increases with increasing magma flow rate, hindering volatile exsolution and shifting open‐system degassing to shallower levels of the conduit. As a result, increasing magma flow rate for a fixed conduit width creates a vertically thinner plug and increases the magnitude and vertical extent of conduit overpressure. Plug thickness and density are also controlled by magma and edifice permeability.