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Bulletin of Volcanology

, Volume 74, Issue 8, pp 1807–1820 | Cite as

Depositional processes and gas pore pressure in pyroclastic flows: an experimental perspective

  • Olivier RocheEmail author
Research Article

Abstract

The depositional processes and gas pore pressure in pyroclastic flows are investigated through scaled experiments on transient, initially fluidized granular flows. The flow structure consists of a sliding head whose basal velocity decreases backwards from the front velocity (U f) until onset of deposition occurs, which marks transition to the flow body where the basal deposit grows continuously. The flows propagate in a fluid-inertial regime despite formation of the deposit. Their head generates underpressure proportional to U f 2 whereas their body generates overpressure whose values suggest that pore pressure diffuses during emplacement. Complementary experiments on defluidizing static columns prove that the concept of pore pressure diffusion is relevant for gas-particle mixtures and allow characterization of the diffusion timescale (t d) as a function of the material properties. Initial material expansion increases the diffusion time compared with the nonexpanded state, suggesting that pore pressure is self-generated during compaction. Application to pyroclastic flows gives minimum diffusion timescales of seconds to tens of minutes, depending principally on the flow height and permeability. This study also helps to reconcile the concepts of en masse and progressive deposition of pyroclastic flow units or discrete pulses. Onset of deposition, whose causes deserve further investigation, is the most critical parameter for determining the structure of the deposits. Even if sedimentation is fundamentally continuous, it is proposed that late onset of deposition and rapid aggradation in relatively thin flows can generate deposits that are almost snapshots of the flow structure. In this context, deposition can be considered as occurring en masse, though not strictly instantaneously.

Keywords

Pyroclastic flow Density current Pore pressure Deposition Experiments Dam-break 

Notes

Acknowledgments

This work was supported by the Institut de Recherche pour le Développement (IRD, France), and the ANR Volbiflo (France) and ECOS-Conicyt C06U01 and C11U01 (France-Chile) projects. This is Laboratory of Excellence ClerVolc contribution n° 25. The paper benefited from useful reviews of Editor J. White, AE M. Manga, D. Doronzo, and an anonymous reviewer.

Supplementary material

ESM 1

Proximal detail view of a flow generated from the release of a fluidized column of fine (d = 80 μm) glass beads and containing black markers (colored beads, d = 700 μm). The movie is ten times slower than actual and shows the sliding flow head and the aggrading basal deposit in the flow body. The basal horizontal plate is 1-cm thick. (AVI 18,906 kb)

445_2012_639_MOESM2_ESM.avi (8.2 mb)
ESM 2 Distal detail view of a flow generated from the release of a fluidized column of fine (d = 80 μm) glass beads and containing black markers (colored beads, d = 700 μm). The movie is ten times slower than actual, and shows the sliding flow head and the aggrading basal deposit in the flow body. The basal horizontal plate is 1-cm thick. (AVI 8,355 kb)
445_2012_639_MOESM3_ESM.avi (28.3 mb)
ESM 3 Flow generated from the release of a fluidized column (20 × 20 cm) of fine (d = 80 μm) glass beads and containing black PVC markers (d = 1–2 mm). The movie is ten times slower than actual. (AVI 29,010 kb)
445_2012_639_MOESM4_ESM.avi (31.7 mb)
ESM 4 Flow generated from the release of a dry column (20 × 20 cm) of fine (d = 80 μm) glass beads and containing black PVC markers (d = 1–2 mm). The movie is ten times slower than actual. (AVI 32,477 kb)
445_2012_639_MOESM5_ESM.avi (12.7 mb)
ESM 5 Detail view of a flow generated from the release of a fluidized column of fine (d = 80 μm) glass beads and containing black markers (colored beads, d = 700 μm), showing a subtle caterpillar-type motion at the flow front. The movie is fifty times slower than actual. (AVI 12,992 kb)

References

  1. Andrews B, Manga M (2012) Experimental study of turbulence, sedimentation, and coignimbrite mass partitioning in dilute pyroclastic density currents. J Volcanol Geotherm Res 225–226:30–44. doi: 10.1016/j.jvolgeores.2012.02.011 CrossRefGoogle Scholar
  2. Branney MJ, Kokelaar P (1992) A reappraisal of ignimbrite emplacement: progressive aggradation and changes from particulate to non-particulate flow during emplacement of high-grade ignimbrite. Bull Volcanol 54:504–520CrossRefGoogle Scholar
  3. Carslaw HS, Jaeger JC (1959) Conduction of heat in solids, 2nd edn. Oxford University Press, New YorkGoogle Scholar
  4. Cas RAF, Wright HMN, Folkes CB, Lesti C, Porreca M, Giordano G, Viramonte JG (2011) The flow dynamics of an extremely large volume pyroclastic flow, the 2.08-Ma Cerro Galán Ignimbrite, NW Argentina, and comparison with other flow types. Bull Volcanol 73:1583–1609. doi: 10.1007/s00445-011-0564-y CrossRefGoogle Scholar
  5. Charbonnier SJ, Gertisser R (2009) Numerical simulations of block-and-ash flows using the Titan2D flow model: examples from the 2006 eruption of Merapi volcano, Java, Indonesia. Bull Volcanol 71:953–959. doi: 10.1007/s00445-009-0299-1 CrossRefGoogle Scholar
  6. Denlinger RP, Iverson RM (2001) Flow of variably fluidized granular masses across three-dimensional terrain 2. Numerical predictions and experimental tests. J Geophys Res 106:553–566Google Scholar
  7. Doyle EE, Hogg AJ, Mader HM, Sparks RSJ (2010) A two-layer model for the evolution and propagation of dense and dilute regions of pyroclastic currents. J Volcanol Geotherm Res 190:365–378. doi: 10.1016/j.jvolgeores.2009.12.004 CrossRefGoogle Scholar
  8. Druitt TH (1998) Pyroclastic density currents. In: Gilbert JS, Sparks RSJ (eds) The physics of explosive volcanic eruptions. Geol Soc London Spec Pub 145: 145–182.Google Scholar
  9. Druitt TH, Sparks RSJ (1982) A proximal ignimbrite breccias facies on Santorini, Greece. J Volcanol Geotherm Res 13:147–171CrossRefGoogle Scholar
  10. Druitt TH, Avard G, Bruni G, Lettieri P, Maez F (2007) Gas retention in fine-grained pyroclastic flow materials at high temperatures. Bull Volcanol 69:881–901CrossRefGoogle Scholar
  11. Dufek J, Manga M (2008) In situ production of ash in pyroclastic flows. J Geophys Res 113:B09207. doi: 10.1029/2007JB005555 CrossRefGoogle Scholar
  12. Fisher RV (1966) Mechanism of deposition from pyroclastic flows. Am J Sci 264:350–363CrossRefGoogle Scholar
  13. Freundt A, Carey S, Wilson CJN (2000) Ignimbrites and block-and-ash flow deposits. In: Sigurdsson H et al (eds) Encyclopedia of volcanoes. Academic Press, NY-London, pp 581–600Google Scholar
  14. Geldart D (1986) Gas fluidization technology. Wiley, New YorkGoogle Scholar
  15. Girolami L, Druitt TH, Roche O, Khrabrykh Z (2008) Propagation and hindered settling of laboratory ash flows. J Geophys Res 113:B02202. doi: 10.1029/2007JB005074 CrossRefGoogle Scholar
  16. Girolami L, Roche O, Druitt TH, Corpetti T (2010) Velocity fields and depositional processes in laboratory ash flows. Bull Volcanol 72:747–759. doi: 10.1007/s00445-010-0356-9 CrossRefGoogle Scholar
  17. Goren L, Aharonov E, Sparks D, Toussaint R (2010) Pore pressure evolution in deforming granular material: a general formulation and the infinitely stiff approximation. J Geophys Res 115:B09216. doi: 10.1029/2009JB007191 CrossRefGoogle Scholar
  18. Gröbelbauer HP, Fannelop TK, Britter RE (1993) The propagation of intrusion fronts of high density ratios. J Fluid Mech 250:669–687CrossRefGoogle Scholar
  19. Hoblitt RP (1986) Observations of the eruptions of July 22 and August 7, 1980, at Mount St. Helens, Washington. US Geol Surv Prof Pap 1334:44Google Scholar
  20. Iverson RM (1997) The physics of debris flows. Rev Geophys 35:245–296CrossRefGoogle Scholar
  21. Iverson RM, Denlinger RP (2001) Flow of variably fluidized granular masses across three-dimensional terrain 1. Coulomb mixture theory. J Geophys Res 106:537–552CrossRefGoogle Scholar
  22. Kelfoun K, Samaniego P, Palacios P, Barba D (2009) Testing the suitability of frictional behaviour for pyroclastic flow simulation by comparison with a well-constrained eruption at Tungurahua volcano (Ecuador). Bull Volcanol 71:1057–1075. doi: 10.1007/s00445-009-0286-6 CrossRefGoogle Scholar
  23. Levine AH, Kieffer SW (1991) Hydraulics of the August 7, 1980, pyroclastic flow at Mount St. Helens, Washington. Geology 19:1121–1124CrossRefGoogle Scholar
  24. Lube G, Cronin SJ, Platz T, Freundt A, Procter JN, Henderson C, Sheridan MF (2007a) Flow and deposition of pyroclastic granular flows: a type example from the 1975 Ngauruhoe eruption, New Zealand. J Volcanol Geotherm Res 161:165–186CrossRefGoogle Scholar
  25. Lube G, Huppert HE, Sparks RSJ, Freundt A (2007b) Static and flowing regions in granular collapses down channels. Phys Fluids 19:043301. doi: 10.1063/1.2712431 CrossRefGoogle Scholar
  26. Lube G, Huppert HE, Sparks RSJ, Freundt A (2011) Granular column collapses down rough, inclined channels. J Fluid Mech 675:347–368. doi: 10.1017/jfm.2011.21 CrossRefGoogle Scholar
  27. Major JJ, Iverson RM (1999) Debris-flow deposition: effects of pore-fluid pressure and friction concentrated at flow margins. Geol Soc Am Bull 111:1424–1434CrossRefGoogle Scholar
  28. Manga M, Patel A, Dufek J (2011) Rounding of pumice clasts during transport: field measurements and laboratory studies. Bull Volcanol 73:321–333. doi: 10.1007/s00445-010-0411-6 CrossRefGoogle Scholar
  29. McElwaine J, Nishimura K (2001) Ping-pong ball avalanche experiments. Special Publications of the International Association of Sedimentology 31:135–148Google Scholar
  30. McElwaine JN (2005) Rotational flow in gravity current heads. Philosophical Transactions of the Royal Society (A) 363:1603-1623. doi: 1610.1098/rsta.2005.1597 Google Scholar
  31. McElwaine JN, Turnbull B (2005) Air pressure data from the Vallée de la Sionne avalanches of 2004. J Geophys Res 110:F03010. doi: 03010.01029/02004JF000237
  32. Montserrat S, Tamburrino A, Roche O, Niño Y (2012). Pore fluid pressure diffusion in defluidizing granular columns. J Geophys Res 117:F02034. doi: 10.1029/2011JF002164
  33. Roche O, Gilbertson MA, Phillips JC, Sparks RSJ (2004) Experimental study of gas-fluidized granular flows with implications for pyroclastic flow emplacement. J Geophys Res 109:B10201CrossRefGoogle Scholar
  34. Roche O, Gilbertson MA, Phillips JC, Sparks RSJ (2005) Inviscid behaviour of fines-rich pyroclastic flows inferred from experiments on gas-particle mixtures. Earth Planet Sci Lett 240:401–414. doi: 10.1016/j.epsl.2005.09.053 CrossRefGoogle Scholar
  35. Roche O, Montserrat S, Niño Y, Tamburrino A (2008) Experimental observations of water-like behavior of initially fluidized, dam break granular flows and their relevance for the propagation of ash-rich pyroclastic flows. J Geophys Res 113:B12203. doi: 10.1029/2008JB005664 CrossRefGoogle Scholar
  36. Roche O, Montserrat S, Niño Y, Tamburrino A (2010) Pore fluid pressure and internal kinematics of gravitational laboratory air-particle flows: insights into the emplacement dynamics of pyroclastic flows. J Geophys Res 115:B09206. doi: 10.1029/2009JB007133 CrossRefGoogle Scholar
  37. Savage SB, Hutter K (1991) The dynamics of avalanches of granular materials from initiation to runout. Part I: Analysis Acta Mech 86:201–223Google Scholar
  38. Simpson JE (1997) Gravity currents in the environment and the laboratory. Cambridge University Press, CambridgeGoogle Scholar
  39. Sparks RSJ (1976) Grain size variations in ignimbrites and implications for the transport of pyroclastic flows. Sedimentology 23:147–188CrossRefGoogle Scholar
  40. Sparks RSJ, Self S, Walker GPL (1973) Products of ignimbrites eruptions. Geology 1:115–118CrossRefGoogle Scholar
  41. Sulpizio R, Dellino P (2008) Sedimentology, depositional mechanisms and pulsating behaviour of pyroclastic density currents. In: Gottsmann J, Martí J. (eds) Caldera volcanism. Analysis, modelling, and response. Development in volcanology 10. Elsevier, Amsterdam, pp 57–96.Google Scholar
  42. Turnbull B, McElwaine J (2008) Experiments on the non-Boussinesq flow of self-igniting suspension currents on a steep open slope. J Geophys Res 113:F01003. doi: 01010.01029/02007JF000753
  43. Wilson CJN (1980) The role of fluidization in the emplacement of pyroclastic flows: an experimental approach. J Volcanol Geotherm Res 8:231–249CrossRefGoogle Scholar
  44. Wilson L, Head JW (1981) Morphology and rheology of pyroclastic flows and their deposits, and guidelines for future observations. In: Lipman PW, Mullineaux DR (eds) The 1980 eruptions of Mount St Helens, Washington. US Geol Surv Prof Paper 1250: 513–524.Google Scholar
  45. Wilson CJN, Hildreth W (2003) Assembling an ignimbrite: mechanical and thermal building blocks in the Bishop tuff, California. J Geol 111:653–670CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  1. 1.Laboratoire Magmas et VolcansClermont Université, Université Blaise PascalClermont-FerrandFrance
  2. 2.CNRS, UMR 6524, LMVClermont-FerrandFrance
  3. 3.IRD, R 163, LMVClermont-FerrandFrance

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