A review, consisting of 8 papers with 120 illustrations, this book aims to present an outline of the editors' current understanding of several aspects of the physics of volcanic eruptions. The aspects covered include the physical characterization of silicic magma relevant to explosive volcanism, vesiculation of silicic magmas, conduit flow and fragmentation, gas loss from magmas during eruption, observations and models of eruption columns, tephra dispersal, pyroclastic density currents, and future research directions. By no means a complete outline nor one that reflects all important issues regarding explosive volcanic eruption physics, the papers in this book reflect the research interests of the group of writers chosen for this review. As such there is a notable bias towards eruption of silicic magmas, which is fair considering that these magmas are perhaps the most common in explosive magmatic eruptions. Readers will find this book to be a useful guide to issues that have been recent topics of considerable attention in volcano physics. Because of the generous citation of background research, each paper in itself is an excellent starting point for students and professionals to rapidly grasp the salient topics, those that have experimental and theoretical as well as observational basis for discussion. Also available: Statistics in Volcanology - ISBN 1862392080 Pyroclastic Density Currents and the Sedimentation of Ignimbrites (Geological Society Memoirs M0027) - ISBN 978-1-86239-124-6 The Geological Society of LondonFounded in 1807, the Geological Society of London is the oldest geological society in the world, and one of the largest publishers in the Earth sciences.The Society publishes a wide range of high-quality peer-reviewed titles for academics and professionals working in the geosciences, and enjoys an enviable international reputation for the quality of its work.The many areas in which we publish in include:-Petroleum geology-Tectonics, structural geology and geodynamics-Stratigraphy, sedimentology and paleontology-Volcanology, magmatic studies and geochemistry-Remote sensing-History of geology-Regional geology guides
Author(s): J. S. Gilbert, R. S. J. Sparks
Year: 1998
Language: English
Pages: 186
Contents......Page 6
Future research directions on the physics of explosive volcanic eruptions......Page 8
Table 1. Porosity and permeability data for pumice and lava dome samples .........Page 10
Table 2. Topics for future research in explosive volcanism......Page 12
Recent experimental progress in the physical description of silicic magma relevant to explosive volcanism......Page 16
Fig. 1. The glass transition in temperature – time space for various geological .........Page 18
Fig. 2. The phenomenology of the glass transition expressed in scanning calorimetric .........Page 19
Fig. 4. The viscosities of hydrous calc-alkaline rhyolitic melts. This model for .........Page 20
Fig. 5. Peralkaline, peraluminous and metaluminous hydrous haplogranitic melt viscosities expressed as .........Page 21
Fig. 6. The onset of non-Newtonian flow in melts expressed as log .........Page 22
Fig. 8. The influence of suspended crystalline spheres and gas bubbles on .........Page 23
Fig. 9. Permeability of vesicular volcanic rocks at room temperature. Two sets .........Page 25
Fig. 10. Porosity and permeability in rhyolitic magma as a function of .........Page 26
Fig. 11. Determinations of the temperature-dependent thermal conductivities of (a) rhyolite and .........Page 27
Fig. 12. Estimates of the tensile strength of magma. The data labelled .........Page 28
Fig. 14. The compositional dependence of the solubility of water in haplogranitic .........Page 30
Fig. 15. The relative time scales associated with the relaxation of shear .........Page 31
Vesiculation processes in silicic magmas......Page 34
Fig. 1. The energy for formation of a nucleus as a function .........Page 36
Fig. 2. The effect of pressure, surface tension and the pre-exponential factor .........Page 37
Fig. 3. Comparison of the number of water molecules per unit volume .........Page 38
Fig. 5. The effect of wetting angle on nucleation measured as the .........Page 39
Fig. 6. Number density of bubbles as a function of decompression (ΔP) in .........Page 40
Fig. 7. Bubble size distribution in nucleation experiments of Lyakhovsky et al. (1996). .........Page 41
Fig. 8. Vesicle–melt–crystal relationship in JF1, a rhyolite from depth .........Page 42
Fig. 9. Schematic representation of bubbles and their melt shells. Each bubble .........Page 43
Fig. 10. Temporal evolution of internal pressure in a bubble growing in .........Page 45
Fig. 11. Bubble growth at constant final pressure. At the initial stages .........Page 46
Fig. 12. The time scale of transition from viscosity-controlled to diffusion-controlled growth .........Page 47
Fig. 14. Viscosities calculated by fitting the data of Bagdassarov et al. (1996) .........Page 48
Fig. 15. Bubble growth in a melt ascending from 4000 m to the .........Page 50
Fig. 16. Schematic illustration of foam with films separating pairs of bubbles .........Page 51
Fig. 17. Raptured melt film retracting (from the centre to the bottom .........Page 52
Fig. 18. Penetration of one bubble into its neighbour (sample LGB-58 of .........Page 53
Fig. 19. Final stages of film retraction. (Pumice from the island of .........Page 54
Conduit flow and fragmentation......Page 58
Fig. 1. Schematic diagram of steady-state flow conditions in Plinian eruptions.......Page 60
Fig. 2. (a) Idealized two-dimensional foams: spherical bubbles of constant size at maximum .........Page 61
Fig. 3. (a) Bubble size distribution of a pumice clast from 1980 deposit .........Page 62
Fig. 4. Model architecture of model of Dobran (1992) and Papale & .........Page 67
Fig. 5. Pressure and vesicularity as a function of depth in the .........Page 68
Fig. 6. Schematic diagram of model of Alidibirov (1994). Solid, vesicular magma .........Page 69
Fig. 8. Results of the Proussevitch et al. (1993b) model of foam stability .........Page 70
Table 3. Geometrical scaling for dynamical simulation experiments. After Anilkumar et al. (1993)......Page 73
Fig. 11. Flask arrangement: photographs. The timings of important events are as .........Page 74
Fig. 12. The graph shows the velocity at the neck entrance as .........Page 75
Table 1. Vesicularity data of silicic pumices. After Thomas et al. (1994)......Page 63
Table 2. Vesicularity data and inferred dynamical parameters for Mount St Helens .........Page 65
Gas loss from magmas through conduit walls during eruption......Page 80
Figures......Page 81
Fig. 3. (a) D : H versus H[Sub(2)]O for obsidian clasts in the AD .........Page 83
Fig. 4. CO[Sub(2)] versus H[Sub(2)]O for obsidian samples erupted during the AD .........Page 84
Fig. 5. The stability field of amphibole for Mount St Helens dacite for .........Page 85
Fig. 6. A summary of the main lithologies seen at the walls .........Page 87
Fig. 7. Void fraction as a function of depth in the Mule .........Page 88
Fig. 8. Diagram illustrating the mass balance of gas for an ascending .........Page 89
Fig. 9. Plot of gas volume fraction at the vent as a .........Page 90
Fig. 10. Dissolved water content of erupted samples as a function of .........Page 92
Observations and models of volcanic eruption columns......Page 98
Fig. 1. Photograph of the developing eruption column: (a) 13s and (b) 45 s after .........Page 99
Fig. 2. (a) Height as a function of time of: (i) the lateral .........Page 101
Fig. 3. Photograph of the thermal cloud which developed during the eruption .........Page 102
Fig. 4. NOAA thermal infra-red satellite image of the Mount Pinatubo ash .........Page 104
Fig. 5. Photograph of the 'basaltic Plinian' ash plume which developed during .........Page 105
Fig. 6. Variation of the eruption rate as a function of the .........Page 107
Fig. 7. Numerical model simulating the axisymmetric decompression of a high-pressure Volcanic .........Page 108
Fig. 8. A comparison of the velocity of a decompressed jet supplying .........Page 109
Fig. 9. (a) Eruption column height as a function of eruption rate (kgs[sup(-1)]) .........Page 111
Fig. 10. Variation of: (i) the velocity; and (ii) the density in .........Page 113
Fig. 11. Comparison of the height of the starting plumes which rose .........Page 115
Fig. 12. Photograph of laboratory experiments using jets of methanol and ethylene-glycol .........Page 117
Tephra disposal......Page 122
Fig. 1. Schematic diagram showing the dispersal of tephra both within plumes .........Page 124
Fig. 2. Results of numerical calculation of sea-level settling speed. The line .........Page 125
Fig. 3. Schematic illustration of eruption plumes generated from the volcanic vent .........Page 126
Fig. 5. Variation of umbrella cloud radius with time for a number .........Page 129
Fig. 6. Tracing of the Hekla 1947 plume redrawn from Thorarinsson (1950) .........Page 130
Fig. 7. The extreme spreading of the Rabaul plume of August 1992 .........Page 132
Fig. 11. The width of the Kliuchevskaya plume as a function of .........Page 133
Fig. 12. Schematic diagram showing the numerous trajectory that particles suspended within .........Page 134
Fig. 13. The grain size distributions in Φ units that are the .........Page 136
Fig. 16. Results of model of deposition from the umbrella cloud responsible .........Page 137
Fig. 17. The downwind plume deposition patterns from the Mount St Helens .........Page 138
Fig. 18. Initial shape typical for small to moderate-sized eruption plume in .........Page 139
Fig. 19. Initial shape typical for large eruption plume developed from an .........Page 140
Fig. 20. Atmospheric sounding for Buffalo, NY. USA. from 18 November 1993, .........Page 141
Fig. 21. TOMS SO[sub(2)] maps for the 4 April 1982 eruption plume .........Page 142
Fig. 22. Timed sequence of GOES imagery for Lascar eruption of 1986 .........Page 143
Fig. 23. Draughting and bending of the Spurr eruption cloud as imaged .........Page 144
Fig. 24. Draughting and bending of the Kliuchevskaya eruption plume, also imaged .........Page 145
Fig. 25. Results of (a) the ARAC code for 1903 Z, and .........Page 147
Pyroclastic density currents......Page 152
Fig. 1. (a) Vulcanian explosion and column collapse at the Soufriere Hills Volcano, .........Page 153
Fig. 2. Pyroclastic surge deposits of the 11 ka Upper Laacher See .........Page 155
Fig. 4. The 1800BP Taupo Ignimbrite, New Zealand, which extends up .........Page 157
Fig. 5. Plot of H/L for pyroclastic flow deposits plotted against volume. .........Page 158
Fig. 6. (a) Block-and-ash flow deposit formed by lava dome collapse at Soufrière .........Page 160
Fig. 8. Clast dispersal by various pyroclastic flows (dotted lines) and surges .........Page 161
Fig. 9. Ignimbrite from the 18 May 1980 eruption of Mount St Helens .........Page 162
Fig. 10. (a) Hypothetical section through a compound ignimbrite showing variation of grain .........Page 163
Fig. 11. Three types of grading observed in ignimbrite flow units. (a) Type 1. .........Page 164
Fig. 12. Model for the emplacement of the Acatlan Ignimbrite in Mexico. .........Page 165
Fig. 13. Distribution of four facies of the ignimbrite erupted at Mount .........Page 166
Fig. 14. Three facies of ignimbrite sheets. (a) Flat-topped valley facies from .........Page 167
Fig. 15. Relationship between the valley (VP) facis and veneer (IVD) facies .........Page 168
Fig. 16. Internal structure of the pyroclastic flow deposits at Mount Mazama .........Page 169
Fig. 17. Numerical simulations of a pyroelastic fountain for a 200 m .........Page 171
Fig. 19. Two flow regimes for a steady pyroelastic density current. See .........Page 173
Fig. 20. Particle Rouse numbers (Pn) for lithic clasts of three different .........Page 174
Fig. 22. Blocking of a density-stratified suspension current as it encounters a .........Page 175
Fig. 23. Model of the emplacement of the Mount St Helens lateral .........Page 177
Fig. 24. Model for the eruption and emplacement of a high-aspect ratio .........Page 179
Fig. 26. Velocity calculations for the 7 August 1980 pumice flow at .........Page 181
Fig. 27. Computer simulation of a granular avalanche in the rapid flow .........Page 183
E......Page 190
M......Page 191
S......Page 192
W......Page 193
