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The fragmentation threshold of pyroclastic rocks
Language
English
Status
Published
Peer review journal
Yes
Title of the book
Issue/vol(year)
226 (2004)
Publisher
Elsevier
Pages (printed)
139-148
Issued date
September 30, 2004
Abstract
In response to rapid decompression, porous magma may fragment explosively. This occurs when the melt can no
longer withstand forces exerted upon it due to the overpressure in included bubbles. This occurs at a critical pressure
difference between the bubbles and the surrounding magma. In this study we have investigated this pressure threshold
necessary for the fragmentation of magma. Here we present the first comprehensive, high temperature experimental
quantification of the fragmentation threshold of volcanic rocks varying widely in porosity, permeability, crystallinity, and
chemical composition. We exposed samples to increasing pressure differentials in a high temperature shock tube apparatus
until fragmentation was initiated. Experimentally, we define the fragmentation threshold as the minimum pressure
differential that leads to complete fragmentation of the pressurized porous rock sample. Our results show that the
fragmentation threshold is strongly dependent on porosity; high porosity samples fragment at lower pressure differentials
than low porosity samples. The fragmentation threshold is inversely proportional to the porosity. Of the other factors,
permeability likely affects the fragmentation threshold at high porosity values, whereas chemical composition, crystallinity
and bubble size distribution appear to have minor effects. The relationship for fragmentation threshold presented here can
be used to predict the minimum pressure differential necessary for the initiation or cessation of the explosive fragmentation
of porous magma.
longer withstand forces exerted upon it due to the overpressure in included bubbles. This occurs at a critical pressure
difference between the bubbles and the surrounding magma. In this study we have investigated this pressure threshold
necessary for the fragmentation of magma. Here we present the first comprehensive, high temperature experimental
quantification of the fragmentation threshold of volcanic rocks varying widely in porosity, permeability, crystallinity, and
chemical composition. We exposed samples to increasing pressure differentials in a high temperature shock tube apparatus
until fragmentation was initiated. Experimentally, we define the fragmentation threshold as the minimum pressure
differential that leads to complete fragmentation of the pressurized porous rock sample. Our results show that the
fragmentation threshold is strongly dependent on porosity; high porosity samples fragment at lower pressure differentials
than low porosity samples. The fragmentation threshold is inversely proportional to the porosity. Of the other factors,
permeability likely affects the fragmentation threshold at high porosity values, whereas chemical composition, crystallinity
and bubble size distribution appear to have minor effects. The relationship for fragmentation threshold presented here can
be used to predict the minimum pressure differential necessary for the initiation or cessation of the explosive fragmentation
of porous magma.
References
[1] A.R. McBirney, T. Murase, Factors governing the formation of
pyroclastic rocks, Bull. Volcanol. 34 (1970) 372– 384.
[2] M. Alidibirov, A model for viscous magma fragmentation
during volcanic blasts, Bull. Volcanol. 56 (1994) 459– 465.
[3] Y. Zhang, A criterion for the fragmentation of bubbly magma
based on brittle failure theory, Nature 402 (1999) 648–650.
[4] B. Zimanowski, R. Bqttner, V. Lorenz, H.-G. H7fele,
Fragmentation of basaltic melt in the course of explosive
volcanism, J. Geophys. Res. 102 (1997) 803– 814.
[5] P. Papale, Strain-induced magma fragmentation in explosive
eruptions, Nature 397 (1999) 425– 428.
[6] D.B. Dingwell, S.L. Webb, Structural relaxation in silicate
melts and non-Newtonian melt rheology in igneous processes,
Phys. Chem. Miner. 16 (1989) 508–516.
[7] K.H. Wohletz, Mechanisms of hydrovolcanic pyroclast formation:
grain-size, scanning electron microscopy, and experimental
studies, J. Volcanol. Geotherm. Res. 17 (1983) 31– 63.
[8] B. Zimanowski, G. Frfhlich, V. Lorenz, Quantitative experiments
on phreatomagmatic explosions, J. Volcanol. Geotherm.
Res. 48 (1991) 341–358.
[9] B. Zimanowski, G. Frfhlich, V. Lorenz, Experiments on steam
explosions by interaction of water with silicate melts, Nucl.
Eng. Des. 155 (1995) 335–343.
[10] R.P. Hoblitt, D.C. Miller, J.W. Vallance, Origin and stratigraphy
of the deposits produced by the May 18 directed blast,
in: P.W. Lipman, D.R. Mullineaux (Eds.), The 1980 eruptions
of Mount St. Helens, Washington, 1981, pp. 401– 419.
[11] B. Voight, R.J. Janda, H. Glicken, P.M. Douglass, Nature and
mechanics of the Mount St. Helens rockslide-avalanche of 18
May 1980, Geotechnique 33 (1983) 243– 273.
[12] T.H. Druitt, S.R. Young, B. Baptie, C. Bonadonna, E.S.
Calder, A.B. Clarke, P.D. Cole, C.L. Harford, R.A. Herd, R.
Luckett, G. Ryan, B. Voight, Episodes of cyclic vulcanian
explosive activity with fountain collapse at Soufrie`re Hills
volcano, Montserrat, in: T.H. Druitt, B.P. Kokelaar (Eds.),
The Eruption of Soufrie`re Hills Volcano, Montserrat, from 1995 to 1999, Geological Society London Memoirs, vol. 21,
2002, pp. 281– 306.
[13] J.M. Bardintzeff, Merapi volcano (Java, Indonesia) and
Merapi-Type Nue´e Ardente, Bull. Volcanol. 47 (1984)
433–446.
[14] S. Tait, C. Jaupart, S. Vergniolle, Pressure, gas content and
eruption periodicity of a shallow, crystallising magma chamber
earth planet, Sci. Lett. 92 (1999) 107– 123.
[15] R.S.J. Sparks, S.R. Young, J. Barclay, E.S. Calder, P. Cole, B.
Darroux, M.A. Davies, T.H. Druitt, C. Harford, R. Herd, M.
James, A.-M. Lejeune, G. Norton, G. Skerrit, M.V. Stasiuk,
N.F. Stevens, J. Toothill, G. Wadge, Magma production and
growth of the lava dome of the Soufrie`re Hills volcano,
Montserrat, West Indies: November 1995 to December 1997,
Geophys. Res. Lett. 25 (1998) 3421– 3424.
[16] J. Stix, R.C. Torres, L.M. Narvaez, G.P.J. Corte´s, J.A. Raigosa,
D.M. Go´mez, R. Castonguay, A model of vulcanian eruptions
at Galeras volcano, Colombia, J. Volcanol. Geotherm. Res. 77
(1997) 285– 303.
[17] O. Navon, V. Lyankhovsky, Vesiculation processes in silicic
magmas, in: J.S. Gilbert, R.S.J. Sparks (Eds.), The Physics of
Explosive Volcanic Eruptions, Spec Pub-Geol Soc London,
vol. 145, 1998, pp. 27–50.
[18] H. Massol, C. Jaupart, The generation of gas overpressure in
volcanic eruptions, earth planet, Sci. Lett. 166 (1999) 57– 70.
[19] M. Alidibirov, D.B. Dingwell, Magma fragmentation by rapid
decompression, Nature 380 (1996) 146–148.
[20] M. Alidibirov, D.B. Dingwell, An experimental facility for
investigation of magma fragmentation by rapid decompression,
Bull. Volcanol. 58 (1996) 411– 416.
[21] M. Alidibirov, D.B. Dingwell, Three fragmentation mechanisms
for highly viscous magma under rapid decompression,
J. Volcanol. Geotherm. Res. 100 (2000) 413–421.
[22] O. Spieler, M. Alidibirov, D.B. Dingwell, Grain-size characteristics
of experimental pyroclasts of 1980 Mount St. Helens
cryptodome dacite: effects of pressure drop and temperature,
Bull. Volcanol. 65 (2003) 90– 104.
[23] C. Martel, D.B. Dingwell, O. Spieler, M. Pichavant, M. Wilke,
Experimental fragmentation of crystal- and vesicle-bearing
silicic melts, Bull. Volcanol. 63 (2001) 345– 359.
[24] D.B. Dingwell, Magma degassing and fragmentation: recent
experimental advances, in: A. Freundt, M. Rosi (Eds.), From
Magma to Tephra. Modelling Physical Processes of Explosive
Volcanic Eruptions, Elsevier, Amsterdam, 1998, pp. 1 – 23.
[25] O. Spieler, D.B. Dingwell, M. Alidibirov, Magma fragmentation
speed: an experimental determination, J. Volcanol. Geotherm.
Res. 129 (2004) 109–123.
[26] B. Scheu, O. Spieler, D.B. Dingwell, Dynamics of explosive
volcanism at Unzen: an experimental contribution. Bull.
Volcanol., submitted for publication.
[27] R.S.J. Sparks, The dynamics of bubble formation and growth
in magmas: a review and analysis, J. Volcanol. Geotherm. Res.
28 (1978) 257– 274.
[28] R.S.J. Sparks, J. Barclay, C. Jaupart, H.M. Mader, J.C.
Phillips, Physical aspects of magma degassing: I. Experimental
and theoretical constraints on vesiculation, Rev. Miner. 30
(1994) 414–445.
[29] N. Thomas, C. Jaupart, S. Vergniolle, On the vesicularity of
pumice, J. Volcanol. Geotherm. Res. 99 (1994) 15633– 15644.
[30] J. Barclay, M.R. Carroll, B.F. Houghton, C.J.N. Wilson, Preeruptive
volatile content and degassing history of an evolving
peralkaline volcano, J. Volcanol. Geotherm. Res. 74 (1996)
75– 87.
[31] J.E. Gardner, R.M.E. Thomas, C. Jaupart, S. Tait, Fragmentation
of magma during plinian volcanic eruptions, Bull.
Volcanol. 58 (1996) 144– 162.
[32] A.A. Griffith, The phenomena of rupture and flow in solids,
Trans. Phys. Soc. Lond., Ser. A 22 (1921) 163–198.
[33] J.K. MacKenzie, The elastic constants of a solid containing
spherical holes, Proc. Phys. Soc. Lond., B 63 (1950) 1– 11.
[34] C. Romano, J. Mungall, T. Sharp, D.B. Dingwell, Tensile
strengths of hydrous vesicular glasses: an experimental study,
Am. Mineral. 81 (1996) 1148–1154.
[35] H. Scholze, Glas—Natur, Struktur und Eigenschaften,
Springer-Verlag, 1988.
[36] S.L. Webb, D.B. Dingwell, Non-Newtonian rheology of
igneous melts at high stresses and strain rates: experimental
results for rhyolite, andesite, basalt and nephelinite, J. Geophys.
Res. 95 (1990) 15695– 15701.
[37] J.E. Mungall, N.S. Bagdassarov, C. Romano, D.B. Dingwell,
Numerical modelling of stress generation and microfracturing
of vesicle walls in glassy rocks, J. Volcanol. Geotherm. Res.
73 (1996) 33– 46.
[38] S. Mueller, O. Melnik, O. Spieler, B. Scheu, D.B. Dingwell,
Permeability and degassing of dome lavas undergoing rapid
decompression: an experimental determination. Bull. Volcanol.,
submitted for publication.
[39] C. Jaupart, Gas loss through conduit walls during eruption, in:
J.S. Gilbert, R.S.J. Sparks (Eds.), Physics of Explosive
Volcanic Eruptions, Geol. Soc. London Spec. Publ. 145
(1998) 73–90.
[40] J.C. Eichelberger, C.R. Carrigan, H.R. Westrich, R.H. Price,
Non-explosive silicic volcanism, Nature 323 (1986) 598–602.
[41] C. Klug, K.V. Cashman, Vesiculation of May 18, 1980, Mt. St.
Helens magma, Geology 22 (1994) 468–472.
[42] M. Ichihara, D. Rittel, B. Sturtevant, Fragmentation of a
porous viscoelastic material: implications to magma fragmentation,
J. Geophys. Res. 106 (2002) 2226– 2239.
[43] D.B. Dingwell, Volcanic dilemma: flow or blow? Science 273
(1996) 1054– 1055.
[44] J. Neuberg, C. O’Gorman, A model of the seismic wavefield in
gas-charged magma: application to the Soufrie`re Hills Volcano,
Montserrat, in: H. Druitt, P. Kolelaar (Eds.), The Eruption of
the Soufrie`re Hills Volcano, Montserrat, from 1995 to 1999,
Geol. Soc. London Memoirs, 2002, pp. 603– 609.
[45] S. Sturton, J. Neuberg, The effects of a decompression on
seismic parameter profiles in a gas-charged magma,
J. Volcanol. Geotherm. Res. 128 (2003) 187– 199.
[46] J. Taddeucci, O. Spieler, B. Kennedy, M. Pompilio, D.B.
Dingwell, P. Scarlato, Experimental and analytical modeling
of basaltic ash explosions at Mt. Etna, Italy, J. Geophys. Res.
(2004) (in press).
[47] U. Kueppers, B. Scheu, O. Spieler, D.B. Dingwell, Fieldbased
density measurements as tool to identify pre-eruption
dome structure: set-up and first results from Unzen volcano
Japan, J. Volcanol. Geotherm. Res. (submitted).
[48] S. Nakada, Y. Motomura, Petrology of 1990–1995 eruption,
J. Volcanol. Geotherm. Res. 89 (1999) 173– 196.
[49] J.E. Hammer, K.V. Cashman, B. Voight, Magmatic processes
revealed by textural and compositional trends of
Merapi dome lavas, J. Volcanol. Geotherm. Res. 100 (2000)
165– 192.
[50] J. Taddeucci, M. Pompilio, P. Scarlato, Monitoring the
explosive activity of the July–August 2001 eruption of Mt.
Etna (Italy) by ash characterization, Geophys. Res. Lett. 29
(2002) 71.
[51] M.A. Di Vito, R. Isaia, G. Orsi, J. Southon, S. de Vita, M.
D’Antonio, L. Pappalardo, M. Piochi, Volcanism and deformation
since 12,000 years at the Campi Flegrei caldera (Italy),
J. Volcanol. Geotherm. Res. 91 (1999) 221– 246.
[52] S. deVita, G. Orsi, L. Civetta, A. Carandente, M. D’Antonio,
A. Deino, T. di Cesare, M.A. Di Vito, R.V. Fisher, R. Isaia, E.
Marotta, A. Necco, M. Ort, L. Pappalardo, M. Piochi, J.
Southon, The Agnano–Monte Spina eruption (4100 years BP)
in the restless Campi Flegrei caldera (Italy), J. Volcanol.
Geotherm. Res. 91 (1999) 269– 301.
[53] T.H. Druit, R.A. Mellors, D.M. Pyle, et al., Explosive
volcanism on Santorini, Greece, Geol. Mag. 126 (1989)
95– 126.
[54] G.F. Zellmer, C.J. Hawkesworth, R.S.J. Sparks, L.E. Thomas,
C.L. Harford, T.S. Brewer, S.C. Loughlin, Geochemical
evolution of the Soufrie`re Hills volcano Montserrat, Lesser
Antilles volcanic arc, J. Petrol. 44 (2003) 1349–1374.
[55] M. Alidibirov, D.B. Dingwell, R.J. Stevenson, K.U. Hess,
S.L. Webb, J. Zinke, Physical properties of the 1980 Mount
St. Helens cryptodome magma, Bull. Volcanol. 59 (1997)
103– 111.
pyroclastic rocks, Bull. Volcanol. 34 (1970) 372– 384.
[2] M. Alidibirov, A model for viscous magma fragmentation
during volcanic blasts, Bull. Volcanol. 56 (1994) 459– 465.
[3] Y. Zhang, A criterion for the fragmentation of bubbly magma
based on brittle failure theory, Nature 402 (1999) 648–650.
[4] B. Zimanowski, R. Bqttner, V. Lorenz, H.-G. H7fele,
Fragmentation of basaltic melt in the course of explosive
volcanism, J. Geophys. Res. 102 (1997) 803– 814.
[5] P. Papale, Strain-induced magma fragmentation in explosive
eruptions, Nature 397 (1999) 425– 428.
[6] D.B. Dingwell, S.L. Webb, Structural relaxation in silicate
melts and non-Newtonian melt rheology in igneous processes,
Phys. Chem. Miner. 16 (1989) 508–516.
[7] K.H. Wohletz, Mechanisms of hydrovolcanic pyroclast formation:
grain-size, scanning electron microscopy, and experimental
studies, J. Volcanol. Geotherm. Res. 17 (1983) 31– 63.
[8] B. Zimanowski, G. Frfhlich, V. Lorenz, Quantitative experiments
on phreatomagmatic explosions, J. Volcanol. Geotherm.
Res. 48 (1991) 341–358.
[9] B. Zimanowski, G. Frfhlich, V. Lorenz, Experiments on steam
explosions by interaction of water with silicate melts, Nucl.
Eng. Des. 155 (1995) 335–343.
[10] R.P. Hoblitt, D.C. Miller, J.W. Vallance, Origin and stratigraphy
of the deposits produced by the May 18 directed blast,
in: P.W. Lipman, D.R. Mullineaux (Eds.), The 1980 eruptions
of Mount St. Helens, Washington, 1981, pp. 401– 419.
[11] B. Voight, R.J. Janda, H. Glicken, P.M. Douglass, Nature and
mechanics of the Mount St. Helens rockslide-avalanche of 18
May 1980, Geotechnique 33 (1983) 243– 273.
[12] T.H. Druitt, S.R. Young, B. Baptie, C. Bonadonna, E.S.
Calder, A.B. Clarke, P.D. Cole, C.L. Harford, R.A. Herd, R.
Luckett, G. Ryan, B. Voight, Episodes of cyclic vulcanian
explosive activity with fountain collapse at Soufrie`re Hills
volcano, Montserrat, in: T.H. Druitt, B.P. Kokelaar (Eds.),
The Eruption of Soufrie`re Hills Volcano, Montserrat, from 1995 to 1999, Geological Society London Memoirs, vol. 21,
2002, pp. 281– 306.
[13] J.M. Bardintzeff, Merapi volcano (Java, Indonesia) and
Merapi-Type Nue´e Ardente, Bull. Volcanol. 47 (1984)
433–446.
[14] S. Tait, C. Jaupart, S. Vergniolle, Pressure, gas content and
eruption periodicity of a shallow, crystallising magma chamber
earth planet, Sci. Lett. 92 (1999) 107– 123.
[15] R.S.J. Sparks, S.R. Young, J. Barclay, E.S. Calder, P. Cole, B.
Darroux, M.A. Davies, T.H. Druitt, C. Harford, R. Herd, M.
James, A.-M. Lejeune, G. Norton, G. Skerrit, M.V. Stasiuk,
N.F. Stevens, J. Toothill, G. Wadge, Magma production and
growth of the lava dome of the Soufrie`re Hills volcano,
Montserrat, West Indies: November 1995 to December 1997,
Geophys. Res. Lett. 25 (1998) 3421– 3424.
[16] J. Stix, R.C. Torres, L.M. Narvaez, G.P.J. Corte´s, J.A. Raigosa,
D.M. Go´mez, R. Castonguay, A model of vulcanian eruptions
at Galeras volcano, Colombia, J. Volcanol. Geotherm. Res. 77
(1997) 285– 303.
[17] O. Navon, V. Lyankhovsky, Vesiculation processes in silicic
magmas, in: J.S. Gilbert, R.S.J. Sparks (Eds.), The Physics of
Explosive Volcanic Eruptions, Spec Pub-Geol Soc London,
vol. 145, 1998, pp. 27–50.
[18] H. Massol, C. Jaupart, The generation of gas overpressure in
volcanic eruptions, earth planet, Sci. Lett. 166 (1999) 57– 70.
[19] M. Alidibirov, D.B. Dingwell, Magma fragmentation by rapid
decompression, Nature 380 (1996) 146–148.
[20] M. Alidibirov, D.B. Dingwell, An experimental facility for
investigation of magma fragmentation by rapid decompression,
Bull. Volcanol. 58 (1996) 411– 416.
[21] M. Alidibirov, D.B. Dingwell, Three fragmentation mechanisms
for highly viscous magma under rapid decompression,
J. Volcanol. Geotherm. Res. 100 (2000) 413–421.
[22] O. Spieler, M. Alidibirov, D.B. Dingwell, Grain-size characteristics
of experimental pyroclasts of 1980 Mount St. Helens
cryptodome dacite: effects of pressure drop and temperature,
Bull. Volcanol. 65 (2003) 90– 104.
[23] C. Martel, D.B. Dingwell, O. Spieler, M. Pichavant, M. Wilke,
Experimental fragmentation of crystal- and vesicle-bearing
silicic melts, Bull. Volcanol. 63 (2001) 345– 359.
[24] D.B. Dingwell, Magma degassing and fragmentation: recent
experimental advances, in: A. Freundt, M. Rosi (Eds.), From
Magma to Tephra. Modelling Physical Processes of Explosive
Volcanic Eruptions, Elsevier, Amsterdam, 1998, pp. 1 – 23.
[25] O. Spieler, D.B. Dingwell, M. Alidibirov, Magma fragmentation
speed: an experimental determination, J. Volcanol. Geotherm.
Res. 129 (2004) 109–123.
[26] B. Scheu, O. Spieler, D.B. Dingwell, Dynamics of explosive
volcanism at Unzen: an experimental contribution. Bull.
Volcanol., submitted for publication.
[27] R.S.J. Sparks, The dynamics of bubble formation and growth
in magmas: a review and analysis, J. Volcanol. Geotherm. Res.
28 (1978) 257– 274.
[28] R.S.J. Sparks, J. Barclay, C. Jaupart, H.M. Mader, J.C.
Phillips, Physical aspects of magma degassing: I. Experimental
and theoretical constraints on vesiculation, Rev. Miner. 30
(1994) 414–445.
[29] N. Thomas, C. Jaupart, S. Vergniolle, On the vesicularity of
pumice, J. Volcanol. Geotherm. Res. 99 (1994) 15633– 15644.
[30] J. Barclay, M.R. Carroll, B.F. Houghton, C.J.N. Wilson, Preeruptive
volatile content and degassing history of an evolving
peralkaline volcano, J. Volcanol. Geotherm. Res. 74 (1996)
75– 87.
[31] J.E. Gardner, R.M.E. Thomas, C. Jaupart, S. Tait, Fragmentation
of magma during plinian volcanic eruptions, Bull.
Volcanol. 58 (1996) 144– 162.
[32] A.A. Griffith, The phenomena of rupture and flow in solids,
Trans. Phys. Soc. Lond., Ser. A 22 (1921) 163–198.
[33] J.K. MacKenzie, The elastic constants of a solid containing
spherical holes, Proc. Phys. Soc. Lond., B 63 (1950) 1– 11.
[34] C. Romano, J. Mungall, T. Sharp, D.B. Dingwell, Tensile
strengths of hydrous vesicular glasses: an experimental study,
Am. Mineral. 81 (1996) 1148–1154.
[35] H. Scholze, Glas—Natur, Struktur und Eigenschaften,
Springer-Verlag, 1988.
[36] S.L. Webb, D.B. Dingwell, Non-Newtonian rheology of
igneous melts at high stresses and strain rates: experimental
results for rhyolite, andesite, basalt and nephelinite, J. Geophys.
Res. 95 (1990) 15695– 15701.
[37] J.E. Mungall, N.S. Bagdassarov, C. Romano, D.B. Dingwell,
Numerical modelling of stress generation and microfracturing
of vesicle walls in glassy rocks, J. Volcanol. Geotherm. Res.
73 (1996) 33– 46.
[38] S. Mueller, O. Melnik, O. Spieler, B. Scheu, D.B. Dingwell,
Permeability and degassing of dome lavas undergoing rapid
decompression: an experimental determination. Bull. Volcanol.,
submitted for publication.
[39] C. Jaupart, Gas loss through conduit walls during eruption, in:
J.S. Gilbert, R.S.J. Sparks (Eds.), Physics of Explosive
Volcanic Eruptions, Geol. Soc. London Spec. Publ. 145
(1998) 73–90.
[40] J.C. Eichelberger, C.R. Carrigan, H.R. Westrich, R.H. Price,
Non-explosive silicic volcanism, Nature 323 (1986) 598–602.
[41] C. Klug, K.V. Cashman, Vesiculation of May 18, 1980, Mt. St.
Helens magma, Geology 22 (1994) 468–472.
[42] M. Ichihara, D. Rittel, B. Sturtevant, Fragmentation of a
porous viscoelastic material: implications to magma fragmentation,
J. Geophys. Res. 106 (2002) 2226– 2239.
[43] D.B. Dingwell, Volcanic dilemma: flow or blow? Science 273
(1996) 1054– 1055.
[44] J. Neuberg, C. O’Gorman, A model of the seismic wavefield in
gas-charged magma: application to the Soufrie`re Hills Volcano,
Montserrat, in: H. Druitt, P. Kolelaar (Eds.), The Eruption of
the Soufrie`re Hills Volcano, Montserrat, from 1995 to 1999,
Geol. Soc. London Memoirs, 2002, pp. 603– 609.
[45] S. Sturton, J. Neuberg, The effects of a decompression on
seismic parameter profiles in a gas-charged magma,
J. Volcanol. Geotherm. Res. 128 (2003) 187– 199.
[46] J. Taddeucci, O. Spieler, B. Kennedy, M. Pompilio, D.B.
Dingwell, P. Scarlato, Experimental and analytical modeling
of basaltic ash explosions at Mt. Etna, Italy, J. Geophys. Res.
(2004) (in press).
[47] U. Kueppers, B. Scheu, O. Spieler, D.B. Dingwell, Fieldbased
density measurements as tool to identify pre-eruption
dome structure: set-up and first results from Unzen volcano
Japan, J. Volcanol. Geotherm. Res. (submitted).
[48] S. Nakada, Y. Motomura, Petrology of 1990–1995 eruption,
J. Volcanol. Geotherm. Res. 89 (1999) 173– 196.
[49] J.E. Hammer, K.V. Cashman, B. Voight, Magmatic processes
revealed by textural and compositional trends of
Merapi dome lavas, J. Volcanol. Geotherm. Res. 100 (2000)
165– 192.
[50] J. Taddeucci, M. Pompilio, P. Scarlato, Monitoring the
explosive activity of the July–August 2001 eruption of Mt.
Etna (Italy) by ash characterization, Geophys. Res. Lett. 29
(2002) 71.
[51] M.A. Di Vito, R. Isaia, G. Orsi, J. Southon, S. de Vita, M.
D’Antonio, L. Pappalardo, M. Piochi, Volcanism and deformation
since 12,000 years at the Campi Flegrei caldera (Italy),
J. Volcanol. Geotherm. Res. 91 (1999) 221– 246.
[52] S. deVita, G. Orsi, L. Civetta, A. Carandente, M. D’Antonio,
A. Deino, T. di Cesare, M.A. Di Vito, R.V. Fisher, R. Isaia, E.
Marotta, A. Necco, M. Ort, L. Pappalardo, M. Piochi, J.
Southon, The Agnano–Monte Spina eruption (4100 years BP)
in the restless Campi Flegrei caldera (Italy), J. Volcanol.
Geotherm. Res. 91 (1999) 269– 301.
[53] T.H. Druit, R.A. Mellors, D.M. Pyle, et al., Explosive
volcanism on Santorini, Greece, Geol. Mag. 126 (1989)
95– 126.
[54] G.F. Zellmer, C.J. Hawkesworth, R.S.J. Sparks, L.E. Thomas,
C.L. Harford, T.S. Brewer, S.C. Loughlin, Geochemical
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