Gravity flows sourced from volcanoes: a review on their flow and emplacement mechanisms

Transcript

1 /* (,**/) S,/- S,1, Gravity flows sourced from volcanoes: a review on their flow and emplacement mechanisms Kazuhiko KANO This paper gives a brief review on the gravity flows sourced from volcanoes on land and under water. Pyroclastic flows are supported by internal gas and the air incorporated during flowage and run out a long distance as density currents. Ash-cloud umbrella is a special case of density current and the particle fallout from the umbrella is a transition to a dilute, pyroclastic density current. Subaqueous equivalents of pyroclastic flows are supported by internal gas and/or the water incorporated during flowage and are thus interpreted as either subaqueous pyroclastic flows in the strict sense or eruption-fed density currents. Debris avalanches and lahars are also important elements of volcaniclastic gravity flows both on land and under water. These pyroclastic and volcaniclastic gravity flows are thought to transform into traction-dominated flow, particle dispersion-dominated flow (grain or granular flow), fluid escape-dominated flow, or debris flows during flowage in response to the changes mainly of flow velocity, particle concentration, and shear stress. The details of these processes still remain in debate. The role of the heat in pyroclastic density current and subaqueous eruption-fed density current is a future subject to be solved. Key words : gravity flow, pyroclastic density current, eruption-fed density current, flow dynamics, emplacement mechanism + (pyroclastic flow) ash-cloud surge ground -*/ 2/ Institute of Geology and Geoinformation, Geological surge +33+ gravity flow gravity current (pyroclastic density current : Druitt, +332) (Branney and Kokelaar,,**,), density flow density current Survey of Japan, AIST, Tsukuba Central 1, + +, Higashi +-chome, Tsukuba, Ibaraki -*/ 2/01, Japan kazu.kano@aist.go.jp

2 S254 (sediment) sediment gravity flow sediment mass flow, + (turbidity current) (underflow) (overflow) (Fig. +) (interflow) (Fig. +) Rayleigh-Taylor (Fig. +) (vertical flow) W i W s W i W s + (Marsh, +322) W i W s (Marsh, +322 ; Fiske et al., +332) W i W s C h a, r i r f r s r f (+) C h a Fig. +. Principal types of eruption-fed density current. r density of the flowing fluid. r a density of the air. r b density of water. g r s r i r f (+) (Carey, +331 ; Fiske et al., +332) (Manville and Wilson,,**.) (Fig.,) (Fig.,) (cleft) (lobe) (Fig.,) (Fig.,) (Fig. -)

3 S255 Fig. -. Structure of a turbulent density current. Head velocity U head is smaller than body velocity U body, so the main body feeds the flow head. Fig.,. Structure of the head of a density current with streamlines and current directions relative to the ground. Modified from Allen (+32.). U body U body 2 + r f r c ghsinq f D* f D+ +, (,) g q r c r f h f D* f D+ Darcy-Weisbach (,) +, -. (Allen, +32.),, q t c r c, r f ( r c) y (Fig..) t t r c r f gysinq (-) t c (plug) (plug flow) Fig... Structure and velocity profile of a plug flow by basal shear (laminar) flow. (Bingham body) t c t (debris avalanche), m (Ui et al.,,***) plug U y m t t c mdu dy (.) (-) du dy r c r f gysinq t c m (/) du dy

4 S256 du dy r.c r f gysinq t c m (0) du dy du dy * t c t (r c-r f) gysinq h du dy * y c U c y h U * U U c y c y * (1) U r c r f g h, y, sinq, t c h y m h y y c (2) (2), - (grain flow) P T a T P T P tan a (3) Bagnold (+3/.) : T K +l -, mdu dy (+*) : Fig. /. Two-dimensional model of a grain flow. U y m r s D K + K, l (linear grain concentration) l + C m C (+,) C C m C (Bagnold number) Ba Ba D r st +, l +, m Dr s T lr s +, m (+-) Ba +* /* q U (Fig. /) y h, C, r s, r f T C r s r f g h y cosq (+.) T (+*) (++) T y * U * : U C r s r f gcosq h, h y, K +l -, m (+/) : T K,r sl, D, du dy, (++)

5 S257 U, - C r s r f gcosq K,r s +, h -, h y -, ld (+0) (upward coarsening) inverse grading reverse grading (kinematic sieve),. (liquefaction) (fluidization) (fluid-escape structure) Fig. 0. Five types of fluidization. Modified from Allen (+32.) and Branney and Kokelaar (,**,). U flow velocity, V fluidization velocity. (Fig. 0) +) Fig. 0a: stationary fluidization,) Fig. 0b: flow-fluidization -) Fig. 0c: bulk self-fluidization.) Fig. 0d: grain self-fluidization /) Fig. 0e: sedimentation fluidization (Allen, +32.) Sparks (+313)

6 S258 Fig. 2. Mechanism of particle support in sediment gravity flows. Modified from Middleton and Hampton (+31-). Fig. 1. Fluidization and transport velocities for particles withdensity + g/cm - and porosity./ in CO, gas at /** and +***. Modified from Sparks (+310). Particles can be entrained where gas flow velocity exceeds their settling velocities. Branney and Kokelaar (,**,) (particulate fluidization) (aggregative fluidization) (plug) (settling velocity) (Fig. 1) CO, + g cm -./ (Fig. 1) + g cm - (, 0. mm) + +* m s, (, mm) + m s +* /* m s, +* m s +* m s (Sparks, +310) (particle-support mechanism) (Fig. 2) (turbidity current) (liquefied or fluidized sediment flow) (grain flow) (debris flow)

7 S259 -, (flow transformation) +) (body transformation),) (gravity transformation) -) + supercritical flow : subcritical flow : (hydraulic jump) (surface transformation) (Fisher, +32.) (Frude number) Fr U, L Fr U, gl +, U gl +, (+1) (gl) +, (+1) + (Fr +) (Fr +) F g F i F g r c r f gahcosq (+2) Fi r f AU,, (+3) r c r f A h q F i F g r f U,, r c r f ghcosq (,*) F i F g afr, a : (,+) (,*) (,,) (densiometric Frude number) Fr d Fr d r f r c r f Fr (,,) (Richardson number) Ri Ri r c r f ghcosq r cu, (,-) (Bursik and Woods, +330) (Ri +) (Ri +) (Woods and Bursik, +33.)

8 S260 Fig. 3. Transition between laminar and turbulent flows in terms of Bingham number B and Rheynolds number Re. Based on Hampton (+31,) and Hiscott and Middleton (+313). (Bingham number) B t cl mu (,.) Re ULr c m (,/) Re +*. B + Re B : Hampton number Re B r cu, t c +*** (,0) (Fig. 3) L r c m t c U B + B Re (Fig. 3) (Hampton, +31,) *.. Fig. +*. Features of sediment gravity flow deposits. Modified from Middleton and Hampton (+31-). (Mohrig et al., +332) (,**/) (*.2 +) Kelvin-Helmholtz - - (Fig. +*) (Fig. +*a) Middleton and Hampton (+31-)

9 S261 Sohn (+331) (Fig +*a) (imbrication) (Fig. +* b) (Fig. +*c) (Allen, +32.) du dt (,1) U t x U U x du dt U t U U x (,1) U t (steadiness) U U x (uniformity) U t Fig. ++. Domains of erosion by and deposition from a density current, classified in terms of its steadiness and uniformity. Modified from Knellar and Branney (+33/). * U U x * (Fig. ++) du dt U t (waxing) (waning) U U x (accumulative) (depletive) (Fig. +,a)

10 S262 Fig. +,. Four modes of particles emplacement from a density current under steady conditions, with their profiles of particle concentration and current velocity. Modified from Branney and Kokelaar (,**,). (Fig. +, b) (Fig. +,c) (Fig. +,d) (Fig. +*d).. + (Ui et al.,,***) +33. (Melosh, +321),**, (Voight et al., +32-) +),)

11 S263 m, U, x, g, W d d mu,, gmdx dw (,2) H, L U * * gmh W (,3) m F mmg (-*) W FL mmgl (-+) (-*) (-+) (,3) m H L (-,) Dade and Huppert (+332) t A, L W tal (--),l A ll, (-.) (-*) A l + - gmh t, - l +, t, - gmh, - (-/) Fig. +-. (a) Plots of total spreading area A vs. potential energy for debris avalanche deposits. The curve is given by A (l +/, t),/- (gmh),/- with t/l +/,./ 0 kpa. The correlation coe$cient is R *.3- (n 0/). (b) Plots of area A vs. volume V for debris avalanche deposits. Modified from Dade and Huppert (+332). gmh A (Fig. +-a) (--) gmh t A - l +, (-0) V N f N f rgh t A -, l +, V (-1) r N f gh U, (Re/B r cu, /t c) +,***

12 S264 Fig. +- N f +,/** 0** A l +, N f V -, (-2) (Fig. +-b) l +, N f +* + +*.., (Takahashi,,**+) (stony debris flow) (hyper concentrated flow) (mud flow) Pinatubo (Pierson et al., +330) +32. (+322). - (Carey and Sparks, +320) (Carey and Sigurdsson, +32,).. Pyroclastic flow Gilbert, +3-2 (+3/1) (+3/1) +320 ; / ; Wright et al., +32* (block and ash flow) ( 0. mm) (, mm)

13 S265 (ash flow) (pumice flow) (scoria flow) (blast surge) (base surge) (ash cloud surge) (Fisher et al., +321) +32* / +2 (Heiken and Wohletz, +32/) -* /* Fig. +..Standard ignimbrite flow unit, proposed by Sparks et al. (+31-) and modified by Fisher (+313).The depositional system (flow boundary zone) of each layer can be interpreted according to the concept of flow boundary approach of Branney and Kokelaar (,**,). (Layers +,, and - : Sparks et al., +31-) (Layers a, b, c and d: Fisher, +313) (Fig. +.) Layer a Layer b (Layer b,) (Layer b +) (Layer b -) Layer c Layer d Sparks et al. (+31-)

14 S266 (standard ignimbrite flow unit) (lag breccia) Layer a Layer b+ Fisher et al. (+32*) (Layers A, B and C) Layer A Layer B Layer C layer Layer b, c, d (Fisher and Heiken, +32,) Layer a : ground surge Lag breccia (Druitt and Sparks, +32+) (Sparks and Walker, +31-) Wilson and Walker (+32,) Layer a (ground layer) Layer a (jetted deposit) Layer b Sparks (+310) Layer b (Hildreth, +32+) Layer b (Freundt and Schmincke, +32/, +320 ; Cole et al., +33-) Oregon Bend (Kamata and Mimura, +32- ; Mimura, +32.) (Hiscott and Middleton, +313, +32*) Campanian Ignimbrite (AMS) (Suzuki and Ui, +32, ; Fisher et

15 S267 Fig. +/. Succession ofthe Kurofuji pyroclastic flow deposits (a), (b), (c) and (d) and a wood log fallen down to the flow direction and burnt in the deposit (b). CA and FA are ash layers, and CA is altered to clay. PF denotes pyroclastic flow deposit. After Mimura and Kobayashi (+31/). al., +33-) (Fig. +/) (b) Layer b (Fisher, +300 ; Branney and Kokelaar,,**,) Layer b + Layer b, Layer b, Layer b - (Fisher, +313) Layer c Layer d (co-ignimbrite ash) Layer d (Fisher, +300) Sparks (+310) Fisher (Fisher, +313) Cole et al. (+33-)

16 S268 Fisher (+300) Branney and Kokelaar (,**,) Grunewald et al. (,***) Soufriere +33/ +333 / +* mm, *./ +* cm, + m cataclasite pseudotachylite Branney and Kokelaar (,**,) (flow boundary approach). / (Fisher, +32.) (Kano, +33* ;Cole and DeCeles, +33+) (Kokelaar and Köninger,,***) (Head and Wilson,,**-) (Wright et al.,,**-) (Head and Wilson,,**- ;Allen and McPhie,,**,) (Kano, +330) (Kano et al., +330 ;Fiske et al.,,**+ ;Yuasa and Kano,,**- ; Wright et al.,,**-) (Head and Wilson,,**- ; Kano,,**-) (Kano et al., +330) (Kokelaar and Busby, +33,) (Cas and Wright, +33+) (Kano et al., +33.) (subaqueous eruption-fed density current : White,,***)

17 S269,**-) Fig. +0. Idealized flowunits presumably fed by subaqueous pumice eruption and subaqueous explosive collapse of pumiceous dome, respectively. Modified from Kano et al. (+330) and Kano (+330). (Yamada, +32.) (Kano, +330) +33* (Kano et al., +33.) (Fig. +0) (White,,*** ; Kano,,**-) (Kokelaar and Köninger,,***) (Kano, +33*) (Kano et al., +33.) (Cole and DeCeles, +33+) +31. ; +320 (Kano et al., +330 ; Allen and McPhie,,***) (Kurokawa and Watanabe, +33+) Fiske and Matsuda (+30.) (Cas and Wright, +33+ ; Müeller and White, +33, ; Kano, +33*, +330,,**- ; Kano et al., +33., +330 ; Fiske et al., +332,,**+ ; White et al., / (nue e ardente : Lacroix, +3*.) (Yamamoto et al.,,**/) / (Fujii and Nakada, +333) +320 (Brusik and Woods, +330 ; Takahashi,,**+),** +*** 3* -** * (Kiefer and Sturtevant, +322) +33, +* -** m s +33* +33/

18 S270 Sato et al., +33, ; +33- ; Uhira and Yamasato, +33. ; +330 ;Ui et al., +333 ; Miyabuchi et al., +333 Allen, J. R. L. (+32.) Sedimentary Structure: Their Character and Physical Basis. Development in Sedimentology -*, Elsevier Sci. Publ., Amsterdom, /3-p. (Volume I) 00- p. (Volume II). Allen, S. R. and McPhie, J. (,***) Water settling and sedimentation of submarine rhyolitic pumice at Yali, eastern Aegean, Greece. J. Volcanol. Geotherm. Res., 3/,,2/ -*1. (+3/1) Pyroclastic flow +.1 /1. (+320) 3/.23.3/. Bagnold, R. A. (+3/.) Experiments on a gravity-free dispersion of large soild spheres in Newtonian fluid under shear. Proceed. Roy. Soc. London, A,,/, Branney, M. J. and Kokelaar, P. (,**,) Pyroclastic Density Currents and the Sedimentation. Geol. Soc. Memoir, no.,1, +.-p. Brusik, M. I. and Woods, A. W. (+330) The dynamics and thermodynamics of large ash flows. Bull. Volcanol., /2, +1/ +3-. Carey, S. N. (+331) Influence of convective sedimentation on the formation of widespread tephra layers in the deep sea. Geology,,/, ,. Carey, S. N. and Sigurdsson, H. (+32,) Influence of particle aggregatin on deposition of distal tephra from the May +2, +32* eruption of Mount St. Helens volcano. J. Geophys. Res., 21, 1*0+ 1*1,. Carey, S. N. and Sparks, R. S. J. (+320) Quantitative models of the fallout and dispersal of tephra from volcanic eruption column. Bull. Volcanol.,.2, +*3 +,/. Cas, R. A. F. and Wright, J. V. (+33+) Subaqueous pyroclastic flows and ignimbrites, an assessment. Bull. Volcanol., /-, -/1-2*. Cole, R. B. and DeCelles, P. G. (+33+) Subaerial to submarine transitions in early Miocene pyroclastic flow deposits, southern San Joaquin basin, California. Geol. Soc. Am. Bull., +*-,,,+,-/. Cole, P. D., Guest, J. E. and Duncan, A. M. (+33-) The emplacement of intermediate volume ignimbrites: A case study from Roccamonfina Volcano, southern Italy. Bull. Volcanol., //,.01.2*. Dade, W. D. and Huppert, H. E. (+332) Long-runout rock falls. Geology,,0, 2*- 2*0. Druitt, T. H. (+332) Pyroclastic density currents. In: Gilbert, J. and Sparks, R. S. J. (eds.), The Physics of Explosive Volcanic Eruptions. Geol. Soc. London Spec. Publ., +./, +./ +2,. Druitt, T. H. and Sparks, R. S. J. (+32+) A proximal ignimbrite breccia facies on Santorini, Greece. J. Volcanol. Geotherm. Res., +-, Fisher, R. (+300) Mechanism of deposition from pyroclastic flows. Am. J. Sci.,,0., -/* -0-. Fisher, R. (+313) Models for pyroclastic surges and pyroclastic flows. J. Volcanol. Geotherm. Res., 0, -*/ -+2. Fisher, R. (+32.) Submarine volcanic rocks. In: Kokelaar, B. P. and Howells, M. F. (eds.), Marginal Basin Geology : Volcanic and Associated Processes in Modern and Ancient Basins. Geol. Soc. London Spec. Publ., no. +0, p./,1. Fisher, R. V. and Heiken, G. (+32,) Mt. Pelee, Martinique May 2 and,*, +3*,, pyroclastic flows and surges. J. Volcanol.Geotherm. Res., +-, Fisher, R. V., Smith, A. L. and Roobol, M. J. (+32*) Destruction of St. Pierre, Martinique by ash cloud surges, May 2 and,*, +3*,. Geology, 2,.1,.10. Fisher, R. V., Glicken, H. X. and Hoblit, R. P. (+321) May +2, +32*, Mount St. Helens deposits in South Coldwater Creek, Washington. J. Geophys. Res., 3,, +*,01 +*,2-. Fisher, R. V., Orsi, G., Ort, M. and Heiken, G. (+33-) Mobility of large-volume pyroclastic flow emplacement of the Campanian ignimbrite, Italy. J. Volcanol. Geotherm. Res., /0,,*/,,*. Fiske, R. S. and Matsuda, T. (+30.) Submarine equivalents of ash flows in the Tokiwa Formation, Japan. Am. J. Sci.,,0,, 10 +*0. Fiske, R. S., Cashman, K. V., Shibata, A., and Watanabe, K. (+332) Tephra dispersal from Myojinsho, Japan, during its shallow submarine eruption of +3/, +3/-. Bull. Volcanol., /3,,0,,1/. Fiske, R. S., Naka, J., Iizasa, K., Yuasa, M. and Klaus, A. (,**+) Submarine silicic caldera at the front of the Izu-Bonin arc, Japan : Voluminous seafloor eruptions of rhyolite pumice. Geol. Soc. Am. Bull., ++-, 2+- 2,.. Freundt, A. and Schmincke, H.-U. (+32/) Lithic-enriched segregation bodies in pyroclastic flow deposits of Lacher See Volcano (East Eifel, Germany). J. Volcanol. Geotherm. Res.,,/, +3-,,.. Freundt, A. and Schmincke, H.-U. (+320) Emplacement of small volume pyroclastic flows of Lacher See Volcano (East Eifel, Germany). Bull. Volcanol.,.2, -3 /3. Fujii, T. and Nakada, S. (+333) The +/ September +33+ pyroclastic flows at Unzen Volcano (Japan) : a flow model for associated ash-cloud surges. J. Volcanol. Geotherm. Res., 23, +/3 +1,.

19 S271 Gilbert, C. M. (+3-2) Welded tu# in Eastern California. Bull. Geol. Soc. Am.,.3, +2,3 +20,. Grunewald, U., Sparks, R. S. J., Kearns, S. and Komorowski, J. C. (,***) Friction marks on blocks from pyroclastic flows at the Soufriere Hills volcano, Montserrat : Implication for flow mechanism. Geology,,2, 2,1 2-*. (+33+) -0 -/1-1*. Hampton, M. A. (+31,) The role of subaqueous debris flow in generating turbidity currents. J. Sediment. Petrol.,.,, 11/ 13-. Head, J. W. and Wilson, L. (,**-) Deep submarine pyroclastic eruptions: theory and predicted landforms and deposits. J. Volcanol. Geotherm. Res., +,+, +// +3-. Heiken, G. and Wohletz, K. H. (+32/) Volcanic Ash. Univ. California Press, Berkley,,.0 p. Hildreth, W. (+32+) Gradients in silicic magma chambers : implication for lithospheric magmatism. J. Geophys. Res., 20, +*+/- +*+3,. Hiscott, R. N. and Middleton, G. V. (+313) Depositional mechanics of thick-bedded sandstone at the base of a submarine slope, Tourelle Formation (Lower Ordovician), Quebec, Canada. In: Doyle, L. J. and Pilkey, O. H. (eds.), Geology of Continental Slope. Soc. Econ. Paleont. Mineral., Spec. Publ., no.,1, p.-*1 -,0. Hiscott, R. N. and Middleton, G. V. (+32*) Fabric of coarse deepwater sandstones, Tourelle Formation, Quebec, Canada. J. Sediment. Petrol., /*, 1*- 1,,. Kamata, H. and Mimura, K. (+32-) Flow directions inferred from imbrication in the Handa pyroclastic flow deposit in Japan. Bull. Volcanol.,.0,,11,2,. Kano, K. (+33*) An ash-flow tu# emplaced in shallow water, Early Miocene Koura Formation, Southwest Japan. J. Volcanol. Geotherm. Res.,.*, + 3. Kano, K (+330) A Miocene coarse volcaniclastic mass-flow deposit in the Shimane Peninsula, SW Japan : product of a deep submarine eruption? Bull. Volcanol., /2, Kano, K. (,**-) Subaqueous pumice eruptions and their deposits: A review. In White, J. D. L., Smellie, J. L. and Clague, D. (eds.), Subaqueous Explosive Volcanism, AGU Geophys. Monogr., +.*,,+-,,3. (+32,) / + -* p. - pls. Kano, K, Orton, G. J. and Kano, T. (+33.) A hot Miocene subaqueous scoria-flow deposit in the Shimane Peninsula, SW Japan. J. Volcanol. Geotherm. Res., 0*, Kano, K., Yamamoto, T. and Ono, K. (+330) Subaqueous eruption and emplacement of the Shinjima Pumice, Shinjima (Moeshima) Island, Kagoshima Bay, SW Japan. J. Volcanol. Geotherm. Res., 1+, +21,*0 Kiefer, S. W. and Sturtevant, B. (+322) Erosional furrows formed during the lateral blast at Mount St. Helens, May +2, +32*. J. Geophys. Res., 3-, Knellar, B. C. and Branney, M. J. (+33/) Sustained highdensity turbidity currents and the deposition of thick massive sands. Sedimentology,.,, 0* Kokelaar, B. P. and Busby, C. (+33,) Subaqueous explosive eruption and welding of pyroclastic deposits. Science,,/1, +30,*+. Kokelaar, B. P. and Köninger, S. (,***) Marine emplacement of welded ignimbrite: the Ordovician Pitt Head Tu#, North Wales. J. Geol. Soc. London, +/1, /+1 /-0. (+33*) Kurokawa, K. and Watanabe, T. (+33+) The SK*,* (Uonuma Pink) Ash and its grain-size characteristics : the early Pleistocene subaqueous ash containing accretionary lapilli in the Niigata region, central Japan. Mem. Fac. Educ., Niigata Univ., -,, 1/ +,+. Lacroix, A. (+3*.) La Montagne Pelée et ses éruption. Masson et Cie, Paris, 00, p. Manville, V. and Wilson C. J. N. (,**.) Vertical density currents : a review of their potential role in the deposition and interpretation of deep-sea ash layers. J. Geol. Soc., London, +0+, 3.1 3/2. Marsh, B. D. (+322) Crystal capture, sorting, and retention in convecting magmas. Geol. Soc. Am. Bull., +**, +1,* Melosh, H. J. (+321) The mechanic of large rock avalanchee. In: Costa, J.E. and Wieczorek, G.F. (eds.), Debris flows/ Avalanches: Process, Recognition and Mitigation. Reviews in Engineering Geology, vol. IV, Geol. Soc. Am., p Middleton G. V. and Hampton, M. A. (+31-) Sediment gravity flows: Mechanics of flow and deposition. In: G. V. Middleton and A.H. Bouma (eds.), Turbidites and Deep-water Sedimentation, Short Course, Soc. Econ. Paleont.Mineral., Pacific Section, p Mimura, K. (+32.) Imbrication, flow direction and possible source areas of the pumice flow tu#s near Bend, Oregon, U.S.A. J. Volcanol. Geotherm. Res.,,+,./.0. (+31/),* (+322) / /,-. Miyabuchi, Y. (+333) Deposits associated with the +33* +33/ eruption of Unzen Volcano, Japan. J. Volcanol. Geotherm. Res., 23, +-3 +/2. Mohrig, D., Whipple, K. X., Gondzo, M., Ellis, C. and Parker, G. (+332) Hydroplaning of subaqueous debris flowa. Geol. Soc. Am. Bull., ++*, Müeller, W. M. and White, J. D. L. (+33,) Felsic firefountaining beneath Archean sea : pyroclastic deposits of the,1-* Ma Hunter Mine Group, Quebec, Canada. J. Volcanol. Geotherm. Res., /., (,**/) :,**/ p. +/ +0. Pierson, T. C., Daag, A. S., Reyes, P. J. D., Regalado, M. T.

20 S272 M., Solidum, R. U. and Tubianosa, B. S. (+330) Flow and deposition of posteruption hot lahars on the east side of Mount Pinatubo, July-October In: Newhall, C. G. and Punongbayan, R. S. (eds.), Fire and Mud: Eruption and Lahars of Mount Pinatubo, Philippines. Philippine Inst. Volcanol. Seismol. and Univ. Washington Press, p. 3,+ 3/*. Sato, H., Fujii, T. and Nakada, S. (+33,) Crumbling of dacite dome lava and generation of pyroclastic flows at Unzen volcano. Nature, -0*, Sohn, Y. K. (+331) On traction-carpet sedimentation. J. Sediment. Res., 01, /*, /*3. Sparks, R. S. J. (+310) Grain size variations in ignimbrite and implications for the transport of pyroclastic flows. Sedimentology,,-, Sparks, R. S. J. (+313) Gas release rates from pyroclastic flow: An assessment of the role of fluidization in their emplacement. Bull. Volcanol.,.+, + 3. Sparks, R. S. J. and Walker, G. P. L. (+31-) The ground surge deposits: a third type of pyroclastic rock. Nature,,.+, 0, 0.. Sparks, R. S. J., Self, S. and Walker, G. P. L. (+31-) Products of ignimbrite eruptions. Geology, +, ++/ ++2. (,**,) +32* Suzuki, K. and Ui, T. (+32,) Grain orientation and depositional ramps as flow direction indicators of largescale pyroclastic flow deposits, Japan. Geology, +*,.,3.-,. Takahashi, T. (,**+) Mechanics and simulatin of snow avalansches, pyroclasic flows and debris flows. In: McCa#rey, W.D., Knellar, B. C. and Peakall, J. (eds.), Particle Gravity Currents, Int. Assoc. Sedimentol. Spec. Publ., no. -+, p (+33-) , ,.. (+330) -/ (+-3) ++,*. Uhira, K. and Yamasato, H. (+33.) Source mechanism of seismic waves excited by pyroclastic flows observed at Unzen volcano, Japan. J. Geophys Res., 33, +11/ Ui, T., Takarada, S. and Yoshimoto, M. (,***) Debris Avalanche. In: Sigurdsson, H., Houghton, B., McNutt, S. R., Rymer, H. and Stix, J. (eds), Encyclopedia of Volcanoes. Academic Press, San Diego, p ,0. Ui, T., Matsuo, N., Sumita, M., Fujinawa, A. (+333) Generation of block and ash flows during the +33* +33/ eruption of Unzen Volcano, Japan. J. Volcanol. Geotherm. Res., 23, +, Voight, B., Janda, R. J., Glicken, H. and Douglas, P. M. (+32-) Nature and mechanics of the Mount St. Helens rock-slide avalanche of +2 May +32*. Geotechnique, --,,.-,1-. White, J. D. L. (,***) Subaqueous eruption-fed density currents and their deposits. Precamb. Res. +*+, 21 +*3. White, J. D. L., Smellie, J. L. and Clague, D. (eds.) (,**-) Subaqueous Explosive Volcanism, AGU Geophys. Monogr., +.*, -13p. Wilson, C. J. N. and Walker, G. P. L. (+32,) Ignimbrite depositional facies : the anatomy of pyroclastic flow. J. Geol. Soc. London, +-3, /2+ /3,. Woods, A. W. and Bursik, M. I. (+33.) A laboratory study of ash flows. J. Geophys. Res., 33,.-1/.-3.. Wright, I. C., Gamble, J. A. and Shane P. A. R. (,**-) Submarine silicic volcanism of the Healy caldera, southern Kermadec arc (SW Pacific) : I volcanology and eruption mechanisms. Bull. Volcanol., 0/, +/,3. Wright, J. V., Smith, A. L. and Self, S. (+32*) A woking terminology of pyroclastic deposits. J. Volcanol. Geotherm. Res., 2, -+/ --0. Yamada, E. (+32.) Subaqueous pyroclasic flows: their development and their deposits. In: Kokelaar, B. P. and Howells, M. F. (eds.), Marginal Basin Geology : Volcanic and Associated processes in Modern and Ancient Basins. Geol. Soc. London Spec. Publ., no. +0, p.,3 -/. (+31.) no..0, p (+33.)./ +-/ +//. Yamamoto, T., Takada, A., Ishizuka, Y., Miyaji, N. and Tajima, Y., (,**/) Basaltic pyroclastic flows of Fuji volcano, Japan : characteristics of the deposits and their origin. Bull. Vocanol., 01, 0,, 0--. Yuasa, M. and Kano, K. (,**-) Submarine silicic calderas on the northern Schichito-Iwojima Ridge, Izu-Ogasawara (Bonin) Arc, western Pacific. In White, J. D. L., Smellie, J. L. and Clague, D. (eds.), Subaqueous Explosive Volcanism, AGU Geophys. Monogr., +.*,,-+,.-.