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Mechanisms of conduit plug formation: implications for Vulcanian explosions.
Language
English
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
/33 (2006)
Publisher
Agu
Pages (printed)
L20302
Issued date
2006
Keywords
Abstract
We explore physical mechanisms controlling formation
of a confining conduit plug using 1D, steady-state numerical
models of magma ascent. Model results for the welldocumented
1997 Vulcanian explosions at Soufrie`re 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
of a confining conduit plug using 1D, steady-state numerical
models of magma ascent. Model results for the welldocumented
1997 Vulcanian explosions at Soufrie`re 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
References
Alidibirov, M., and D. Dingwell (1996), Magma fragmentation by rapid
decompression, Nature, 380, 146– 148.
Barclay, J., M. R. Carroll, M. J. Rutherford, M. D. Murphy, J. D.
Devine, J. Gardner, and R. S. J. Sparks (1998), Experimental phase
equilibria constraints on pre-eruptive storage conditions of the
Soufrie`re Hills magma, Geophys. Res. Lett., 25, 3437– 3440.
Belousov, A., B. Voight, M. Belousova, and A. Petukhin (2002), Pyroclastic
surges and flows from the 8 – 10 May 1997 explosive eruption of
Bezymianny volcano, Kamchatka, Russia, Bull. Volcanol., 64, 455– 471.
Bluth, G. J. S., and W. I. Rose (2004), Observations of eruptive activity at
Santiaguito volcano, Guatemala, J. Volcanol. Geotherm. Res., 136, 297–
302.
Cashman, K. V., and S. M. McConnell (2005), Multiple levels of magma
storage during the 1980 summer eruptions of Mount St. Helens, WA,
Bull. Volcanol., 68, 57– 75.
D’Oriano, C., E. Poggianti, A. Bertagnini, R. Cioni, P. Landi, M. Polacci,
and M. Rosi (2005), Changes in eruptive style during the A.D. 1538
Monte Nuovo eruption (Phlegrean Fields, Italy): The role of syn-eruptive
crystallization, Bull. Volcanol., 67, 601– 621.
Druitt, T. H., et al. (2002), Episodes of cyclic vulcanian explosive activity
with fountain collapse at Soufrie`re Hills volcano, Montserrat, Geol. Soc.
London Mem., 21, 281– 306.
Eichelberger, J. C., C. R. Carrigan, H. R. Westrich, and R. H. Price (1986),
Non-explosive silicic volcanism, Nature, 323, 598– 602.
Gonnermann, H. M., and M. Manga (2003), Explosive volcanism may not
be an inevitable consequence of magma fragmentation, Nature, 426,
432– 435.
Hammer, J. E., K. V. Cashman, R. P. Hoblitt, and S. Newman (1999),
Degassing and microlite crystallization during pre-climactic events of
the 1991 eruption of Mt. Pinatubo, Philippines, Bull. Volcanol., 60,
355– 380.
Heiken, G., K. Wohletz, and J. Eichelberger (1988), Fracture fillings and
intrusive pyroclasts, Inyo Domes, California, J. Geophys. Res., 93,
4335– 4350.
Hess, K. U., and D. B. Dingwell (1996), Viscosities of hydrous
leucogranitic melts: A non-Arrhenian model, Am. Mineral., 81, 1297–
1300.
Jaupart, C., and C. J. Alle`gre (1991), Gas content, eruption rate and
instabilities of eruption regime in silicic volcanoes, Earth Planet. Sci.
Lett., 102, 413–429.
Klug, C., and K. V. Cashman (1996), Permeability development in vesiculating
magmas: Implication for fragmentation, Bull. Volcanol., 58, 87–
100.
Lejeune, A. M., Y. Bottinga, T. W. Trull, and P. Richet (1999), Rheology of
bubble-bearing magmas, Earth Planet. Sci. Lett., 166, 71– 84.
Lensky, N. G., O. Navon, and V. Lyakhovsky (2004), Bubble growth during
decompression of magma: Experimentally and theoretical investigation,
J. Volcanol. Geotherm. Res., 129, 7 – 22.
Llewellin, E. W., and M. Manga (2005), Bubble suspension rheology and
implications for conduit flow, J. Volcanol. Geotherm. Res., 143, 205– 217.
Melnik, O., and R. S. J. Sparks (1999), Nonlinear dynamics of lava dome
extrusion, Nature, 402, 37– 41.
Melnik, O., and R. S. J. Sparks (2002a), Dynamics of magma ascent and
lava extrusion at Soufrie`re Hills Volcano, Montserrat, Geol. Soc. London
Mem., 21, 153– 171.
Melnik, O., and R. S. J. Sparks (2002b), Modelling of conduit flow
dynamics during explosive activity at Soufrie` re Hills Volcano,
Montserrat, Geol. Soc. London Mem., 21, 307– 317.
Melnik, O., A. A. Barmin, and R. S. J. Sparks (2005), Dynamics of magma
flow inside volcanic conduits with bubble overpressure buildup and gas
loss through permeable magma, J. Volcanol. Geotherm. Res., 143, 53– 68.
Morrissey, M. M., and L. G. Mastin (2000), Vulcanian eruptions, in
Encyclopedia of Volcanoes, edited by H. Sigurdson et al., pp. 463 –
476, Elsevier, New York.
Murphy, M. D., R. S. J. Sparks, J. Barclay, M. R. Carroll, A. M. Lejeune,
T. S. Brewer, R. Macdonald, S. Black, and S. Young (1998), The role of
magma mixing in triggering the current eruption at the Soufrie`re Hills
volcano, Montserrat, West Indies, Geophys. Res. Lett., 25, 3433–3436.
Saar, M. O., and M. Manga (1999), Permeability-porosity relationship in
vesicular basalts, Geophys. Res. Lett., 26, 111 – 114.
Sparks, R. S. J. (1997), Causes and consequences of pressurisation in lava
dome eruptions, Earth Planet. Sci. Lett., 150, 177– 189.
Spieler, O., B. Kennedy, U. Kueppers, D. B. Dingwell, B. Scheu, and
J. Taddeucci (2004), The fragmentation threshold of pyroclastic rocks,
Earth Planet. Sci. Lett., 226, 139–148.
Stix, J., C. R. Torres, M. L. Narva´ez, J. G. P. Corte´s, A. J. Raigosa, M. D.
Go´mez, and R. Castonguay (1997), A model of Vulcanian eruptions at
Galeras volcano, Colombia, J. Volcanol. Geotherm. Res., 77, 285– 303.
Taddeucci, J., M. Pompilio, and P. Scarlato (2004), Conduit processes during
the July– August 2001 explosive activity of Mt. Etna (Italy): Inferences
from glass chemistry crystal size distribution of ash particles,
J. Volcanol. Geotherm. Res., 137, 33–54.
Takeuchi, S., S. Nakashima, A. Tomiya, and H. Shinohara (2005), Experimental
constraints on the low gas permeability of vesicular magma during
decompression, Geophys. Res. Lett., 32, L10312, doi:10.1029/
2005GL022491.
Tuffen, H., and D. Dingwell (2005), Fault textures in volcanic conduits:
Evidence for seismic trigger mechanisms during silicic eruptions, Bull.
Volcanol., 67, 370– 387.
Voight, B., R. P. Hoblitt, A. B. Clarke, A. B. Lockhart, A. D. Miller,
L. Lynch, and J. MacMahon (1998), Remarkable cyclic ground deformation
monitored in real time on Montserrat and its use in eruption forecasting,
Geophys. Res. Lett., 25, 3405–3408.
Voight, B., et al. (1999), Magma flow instability and cyclic activity at
Soufrie`re Hills Volcano, Montserrat, Science, 283, 1138–1142.
Watson, I. M., et al. (2000), The relationship between degassing and ground
deformation at Soufrie`re Hills Volcano, Montserrat, J. Volcanol.
Geotherm. Res., 98, 117– 126.
Widiwijayanti, C., A. B. Clarke, D. Elsworth, and B. Voight (2005), Geodetic
Constraints on the Shallow Magma System at Soufrie`re Hills Volcano,
Montserrat, Geophys. Res. Lett., 32, L11309, doi:10.1029/
2005GL022846.
Wilson, L., R. S. J. Sparks, and G. P. L. Walker (1980), Explosive volcanic
eruptions: IV. The control of magma properties and conduit geometry on
eruption column behavior, Geophys. J. R. Astron. Soc., 63, 117– 148.
decompression, Nature, 380, 146– 148.
Barclay, J., M. R. Carroll, M. J. Rutherford, M. D. Murphy, J. D.
Devine, J. Gardner, and R. S. J. Sparks (1998), Experimental phase
equilibria constraints on pre-eruptive storage conditions of the
Soufrie`re Hills magma, Geophys. Res. Lett., 25, 3437– 3440.
Belousov, A., B. Voight, M. Belousova, and A. Petukhin (2002), Pyroclastic
surges and flows from the 8 – 10 May 1997 explosive eruption of
Bezymianny volcano, Kamchatka, Russia, Bull. Volcanol., 64, 455– 471.
Bluth, G. J. S., and W. I. Rose (2004), Observations of eruptive activity at
Santiaguito volcano, Guatemala, J. Volcanol. Geotherm. Res., 136, 297–
302.
Cashman, K. V., and S. M. McConnell (2005), Multiple levels of magma
storage during the 1980 summer eruptions of Mount St. Helens, WA,
Bull. Volcanol., 68, 57– 75.
D’Oriano, C., E. Poggianti, A. Bertagnini, R. Cioni, P. Landi, M. Polacci,
and M. Rosi (2005), Changes in eruptive style during the A.D. 1538
Monte Nuovo eruption (Phlegrean Fields, Italy): The role of syn-eruptive
crystallization, Bull. Volcanol., 67, 601– 621.
Druitt, T. H., et al. (2002), Episodes of cyclic vulcanian explosive activity
with fountain collapse at Soufrie`re Hills volcano, Montserrat, Geol. Soc.
London Mem., 21, 281– 306.
Eichelberger, J. C., C. R. Carrigan, H. R. Westrich, and R. H. Price (1986),
Non-explosive silicic volcanism, Nature, 323, 598– 602.
Gonnermann, H. M., and M. Manga (2003), Explosive volcanism may not
be an inevitable consequence of magma fragmentation, Nature, 426,
432– 435.
Hammer, J. E., K. V. Cashman, R. P. Hoblitt, and S. Newman (1999),
Degassing and microlite crystallization during pre-climactic events of
the 1991 eruption of Mt. Pinatubo, Philippines, Bull. Volcanol., 60,
355– 380.
Heiken, G., K. Wohletz, and J. Eichelberger (1988), Fracture fillings and
intrusive pyroclasts, Inyo Domes, California, J. Geophys. Res., 93,
4335– 4350.
Hess, K. U., and D. B. Dingwell (1996), Viscosities of hydrous
leucogranitic melts: A non-Arrhenian model, Am. Mineral., 81, 1297–
1300.
Jaupart, C., and C. J. Alle`gre (1991), Gas content, eruption rate and
instabilities of eruption regime in silicic volcanoes, Earth Planet. Sci.
Lett., 102, 413–429.
Klug, C., and K. V. Cashman (1996), Permeability development in vesiculating
magmas: Implication for fragmentation, Bull. Volcanol., 58, 87–
100.
Lejeune, A. M., Y. Bottinga, T. W. Trull, and P. Richet (1999), Rheology of
bubble-bearing magmas, Earth Planet. Sci. Lett., 166, 71– 84.
Lensky, N. G., O. Navon, and V. Lyakhovsky (2004), Bubble growth during
decompression of magma: Experimentally and theoretical investigation,
J. Volcanol. Geotherm. Res., 129, 7 – 22.
Llewellin, E. W., and M. Manga (2005), Bubble suspension rheology and
implications for conduit flow, J. Volcanol. Geotherm. Res., 143, 205– 217.
Melnik, O., and R. S. J. Sparks (1999), Nonlinear dynamics of lava dome
extrusion, Nature, 402, 37– 41.
Melnik, O., and R. S. J. Sparks (2002a), Dynamics of magma ascent and
lava extrusion at Soufrie`re Hills Volcano, Montserrat, Geol. Soc. London
Mem., 21, 153– 171.
Melnik, O., and R. S. J. Sparks (2002b), Modelling of conduit flow
dynamics during explosive activity at Soufrie` re Hills Volcano,
Montserrat, Geol. Soc. London Mem., 21, 307– 317.
Melnik, O., A. A. Barmin, and R. S. J. Sparks (2005), Dynamics of magma
flow inside volcanic conduits with bubble overpressure buildup and gas
loss through permeable magma, J. Volcanol. Geotherm. Res., 143, 53– 68.
Morrissey, M. M., and L. G. Mastin (2000), Vulcanian eruptions, in
Encyclopedia of Volcanoes, edited by H. Sigurdson et al., pp. 463 –
476, Elsevier, New York.
Murphy, M. D., R. S. J. Sparks, J. Barclay, M. R. Carroll, A. M. Lejeune,
T. S. Brewer, R. Macdonald, S. Black, and S. Young (1998), The role of
magma mixing in triggering the current eruption at the Soufrie`re Hills
volcano, Montserrat, West Indies, Geophys. Res. Lett., 25, 3433–3436.
Saar, M. O., and M. Manga (1999), Permeability-porosity relationship in
vesicular basalts, Geophys. Res. Lett., 26, 111 – 114.
Sparks, R. S. J. (1997), Causes and consequences of pressurisation in lava
dome eruptions, Earth Planet. Sci. Lett., 150, 177– 189.
Spieler, O., B. Kennedy, U. Kueppers, D. B. Dingwell, B. Scheu, and
J. Taddeucci (2004), The fragmentation threshold of pyroclastic rocks,
Earth Planet. Sci. Lett., 226, 139–148.
Stix, J., C. R. Torres, M. L. Narva´ez, J. G. P. Corte´s, A. J. Raigosa, M. D.
Go´mez, and R. Castonguay (1997), A model of Vulcanian eruptions at
Galeras volcano, Colombia, J. Volcanol. Geotherm. Res., 77, 285– 303.
Taddeucci, J., M. Pompilio, and P. Scarlato (2004), Conduit processes during
the July– August 2001 explosive activity of Mt. Etna (Italy): Inferences
from glass chemistry crystal size distribution of ash particles,
J. Volcanol. Geotherm. Res., 137, 33–54.
Takeuchi, S., S. Nakashima, A. Tomiya, and H. Shinohara (2005), Experimental
constraints on the low gas permeability of vesicular magma during
decompression, Geophys. Res. Lett., 32, L10312, doi:10.1029/
2005GL022491.
Tuffen, H., and D. Dingwell (2005), Fault textures in volcanic conduits:
Evidence for seismic trigger mechanisms during silicic eruptions, Bull.
Volcanol., 67, 370– 387.
Voight, B., R. P. Hoblitt, A. B. Clarke, A. B. Lockhart, A. D. Miller,
L. Lynch, and J. MacMahon (1998), Remarkable cyclic ground deformation
monitored in real time on Montserrat and its use in eruption forecasting,
Geophys. Res. Lett., 25, 3405–3408.
Voight, B., et al. (1999), Magma flow instability and cyclic activity at
Soufrie`re Hills Volcano, Montserrat, Science, 283, 1138–1142.
Watson, I. M., et al. (2000), The relationship between degassing and ground
deformation at Soufrie`re Hills Volcano, Montserrat, J. Volcanol.
Geotherm. Res., 98, 117– 126.
Widiwijayanti, C., A. B. Clarke, D. Elsworth, and B. Voight (2005), Geodetic
Constraints on the Shallow Magma System at Soufrie`re Hills Volcano,
Montserrat, Geophys. Res. Lett., 32, L11309, doi:10.1029/
2005GL022846.
Wilson, L., R. S. J. Sparks, and G. P. L. Walker (1980), Explosive volcanic
eruptions: IV. The control of magma properties and conduit geometry on
eruption column behavior, Geophys. J. R. Astron. Soc., 63, 117– 148.
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