VOLCANIC ROCKS
GEOLOGICAL HAZARDS AT THE AZORES REGION CHARACTERIZATION OF VOLCANIC FORMATIONS GEOMECHANICAL CHARACTERIZATION OF VOLCANIC MATERIALS IN TENERIFE GEOTECHNICAL FEATURES OF THE WELDED IGNIMBRITES OF THE CANARY ISLANDS STRENGTH AND DEFORMABILITY OF LOW DENSITY PYROCLASTS THE JAMEOS DEL AGUA CAVE (LANZAROTE, CANARY ISLANDS): SOME MORPHOLOGICAL AND GEOLOGICAL FEATURES OF A SPECTACULAR LAVA TUBE ADAPTED TO AUDITORIUM THE VOLCANIC ROCKS OF THE CANARY ISLANDS GEOTECHNICAL PROPERTIES VOLCANOSTRATIGRAPHIC PROFILES FOR THE AZORES REGION: A CONTRIBUTION FOR THE EC8 REGULATIONS AND THE CHARACTERIZATION OF VOLCANIC ROCKS GEOMECHANICAL BEHAVIOUR CASE STUDIES EFFECTS OF FLOW STRUCTURE IN LAVAS FROM SIERRA DE GUADALUPE, NORTHERN MEXICO CITY, ON POINT LOAD INDEX AND ROCK MASS QUALITY EVALUATION PART PART THE STABILITY STATE OF THE JAMEOS DEL AGUA LAVA TUBE CAVE OVER THE AUDITORIUM BY ACCURATE GEOMECHANICAL SITE INVESTIGATIONS CONSTRUCTION MATERIALS GEOAVALIA PROJECT: A CONTRIBUTION TO THE AZOREAN MINERAL RESOURCES PROSPECTING AND EVALUATION EARTHQUAKE ENGINEERING AND ROCK DYNAMICS EFFECTS OF VOLCANIC SEISMIC EVENTS ON THE STROMBOLI STABILITY BY FINITE DIFFERENCE NUMERICAL MODELING FOUNDATIONS FOUNDATION OF THE “LOS TILOS” ARCH BRIDGE IN LA PALMA ISLAND FOUNDATIONS ON GROUNDS WITH CAVERNS SHALLOW FOUNDATIONS ON COLLAPSIBLE ROCKS SLOPE STABILITY COLLAPSE OF WELDED TUFF CAUSED BY GROUNDWATER FLOW DEBRIS SLOPE STABILITY ANALYSIS IN AN ACTIVE VOLCANO AREA PRELIMINARY ANALYSIS OF INSTABILITY PHENOMENA AT VULCANO ISLAND, ITALY ROCK FAILURES IN VOLCANIC ROCK AREA IN HOKKAIDO SLOPE STABILITY ON VOLCANIC ROCKS – THE CASE STUDY OF THE CUT SLOPES OF THE FUNCHAL AIRPORT STABILIZATION OF LANDSLIDES IN THE LISBON VOLCANIC COMPLEX STRENGTH OF VOLCANIC ROCK MASSES IN EDIFICE INSTABILITY: INSIGHTS FROM TEIDE, TENERIFE PART PART PART PART CONTEMPORARY VIEWS OF SLOPE INSTABILITY ON ACTIVE VOLCANOES ABSTRACT: EXCESS FLUID PRESSURES EXERT IMPORTANT CONTROLS ON THE STABILITY OF LAVA DOMES AND THE FLANKS OF VOLCANOES MIGRATING OVERPRESSURES REDUCE THE SHEAR STRENGTH OF THE EDIFICE AND MAY CONTROL THE TIMING, MORPHOLOGY, AND ENERGETICS OF FAILURE EXCESS PRESSURES MAY BE DEVELOPED BOTH DIRECTLY FROM MAGMA DEGASSING, AND INDIRECTLY FROM THE INTERACTION OF MAGMA WITH INFILTRATING RAINWATER OR GROUNDWATER INTERIOR GASES INFLUENCE THE STRENGTH OF THE VOLCANIC PILE, AND HENCE ITS STABILITY, IN AT LEAST TWO WAYS: (1) IN THE FRACTURED AND SOLIDIFIED OUTER CARAPACE, HIGH GAS CONTENTS REDUCE EFFECTIVE STRESSES AND CONCOMITANTLY LOWER SHEAR STRENGTH, AND (2) IN THE DOME INTERIOR, MAGMAS THAT AVOID OFF-GASSING OF VOLATILES EXHIBIT A LOW STRENGTH, DOMINATED BY COHESION SIGNATURES OF THESE VARIOUS PROCESSES ARE EVIDENT IN THE EXTENSIVE RECORD OF COLLAPSES THAT CHART EPISODIC GROWTH AND DESTRUCTION OF THE LAVA DOME AT SOUFRIÈRE HILLS VOLCANO, MONTSERRAT MECHANISMS INCLUDE INTERIOR PRESSURIZATION BY MAGMA DEGASSING, AND THE INTERACTION OF RAINWATER WITH THE HOT DOME RIND THE INFLUENCE OF GAS OVERPRESSURES APPLIED INTERIOR TO A BRITTLE CARAPACE IS TYPIFIED BY THE RESPONSE TO EPISODES OF CYCLIC INFLATION, WHERE, IN ADDITION TO DELAYS IN THE EXPECTED TIMING OF FAILURE, COLLAPSE MAY BE TRIGGERED AT INFERRED PRESSURES BELOW THE PEAK OBTAINED IN THE PRIOR CYCLE SIMILAR INFLUENCES ON TIMING AND COLLAPSE STYLE ARE PRESENT FOR RAINFALL-TRIGGERED EVENTS WHERE DELUGES BEYOND A GIVEN INTENSITY AND DURATION ARE REQUIRED TO PROMOTE FAILURE, AND THE STYLE OF COLLAPSE IS INFLUENCED BY ANTECEDENT CONDITIONS OF GAS PRESSURIZATION WITHIN THE LAVA DOME IN ALL INSTANCES, INTERIOR GAS OVERPRESSURES OR THE PRESENCE OF A SEGREGATED PLASTIC CORE ARE BOTH VIABLE MECHANISMS TO PROMOTE A SWITCH BETWEEN SHALLOW INSTABILITY OF THE DOME CARAPACE TO DEEP TRANSACTION OF THE DOME CORE SUCH SWITCHING TO A MORE HAZARDOUS AND MOBILE FAILURE MODE MAY OCCUR ABSENT THE USUAL SEISMIC, GEODETIC, OR CHEMICAL SIGNATURES THAT HERALD A COLLAPSE EVENT, AND PRESENTS SPECIAL CHALLENGES IN MONITORING FOR HAZARD ASSESSMENT JULY 2001 (CARN ET AL 2004), CANNOT BE EXPLAINED BY SLOPE OVERSTEEPENING OR TRADITIONAL MECHANISMS OF GAS OVERPRESSURIZATION WHILE LARGELY CHARACTERIZED BY A DEFICIENCY IN TRADITIONAL PRE-COLLAPSE INDICATORS, THESE EVENTS HAVE DIRECTLY COINCIDED WITH PERIODS OF INTENSE PRECIPITATION (MATTHEWS ET AL 2002; NORTON ET AL 2002; HERD ET AL 2003; MATTHEWS & BARCLAY, 2004; ELSWORTH ET AL 2004; CARN ET AL 2004) IN THE FOLLOWING WE EXAMINE THE ROLE OF (1) INTE- RIOR PRESSURIZATION BY MAGMA DEGASSING, AND (2) THE INTERACTION OF RAINWATER WITH THE HOT DOME RIND IN CONTRIBUTING TO STYLES AND THE TIMING OF DOME COLLAPSE SUPPORT FOR RAINFALL MECHANISMS: SHV FIGURE 1 SCHEMATIC VIEWS OF DOME COLLAPSE (A) SECTION THROUGH A DOME OF EXTERNAL RADIUS, B, SUBJECT TO GAS PRESSURE, PI, IN A CAVITY OF RADIUS, A THE DIFFUSIVE GAS PRESSURE ACTS ON THE BOUNDARIES OF A FAILING BLOCK OF WEIGHT, W THIS BLOCK RESTS ON A PLANE, INCLINED AT ANGLE, ?, AND IS ACTED UPON BY UPLIFT FORCE, P, AND DOWNSLOPE FORCES (F?IN TEXT) REPRESENTING GAS PRESSURES (FG M) OR MAGMASTATIC PRESSURES (FM M) ACTING ON THE BLOCK REAR (B) THE THREE-DIMENSIONAL GEOMETRY IS DEFINED BY THE SECTOR ANGLE , ? (C) FAILURE INITIATES WITH RELEASE OF A TOE-BLOCK, WITH FAILURE RETROGRESSING TO UNLOAD THE PRESSURIZED CORE, RESULTING IN THE POTENTIAL FOR SPONTANEOUS DISINTEGRATION OR A DIRECTED EXPLOSION RAINFALL (MATTHEWS ET AL 2002; MATTHEWS & BARCLAY, 2004; ELSWORTH ET AL 2004) TO EXAMINE RAINFALL DRIVEN COLLAPSE MODES, THIS STUDY FOCUSES ON THE 20 MARCH 2000 AND 29–30 JULY 2001 EVENTS, EACH OF WHICH INTER- RUPTED A PERIOD OF ACTIVE DOME GROWTH, EXHIBITED AN ABSENCE OF ELEVATED PRECURSORY SEISMIC ACTIVITY, AND PROCEEDED CONCURRENTLY WITH AN INTENSE RAINFALL EVENT, WITHRETROGRESSIVECOLLAPSESINITIATEDINTHELATTERSTAGES OF HEAVY RAINFALL, LIKELY CONTRIBUTING TO A DEEPENING FAILURE SURFACE CYCLIC EVOLUTION OF THE DOME, SEGRE- GATED BY THESE RAINFALL TRIGGERED COLLAPSE EVENTS, HAS BEEN EXTENSIVELY CHARTED BY THE MONTSERRAT VOLCANO OBSERVATORY (MVO) BY MID MARCH 2000, ANDESITIC GROWTH WITHIN THE JULY 1998 COLLAPSE SCAR HAD REACHED ?29 × 106 M3, OF WHICH ?28 × 106 M3 (?95%) WAS REMOVED THROUGH NUMEROUS PYROCLASTIC FLOWS OVER A PERIOD OF ?5 H ON 20 MARCH 2000 (CARN ET AL 2004) THE JULY 2001 COL- LAPSE WAS SIMILAR IN FORM, BUT ACCUMULATED A TOTAL COLLAPSEVOLUMEOF?45 × 106 M3 (CARNETAL 2004),OR APPROXIMATELY 50% OF ACTIVE DOME VOLUME (UTILIZING UNPUBLISHED DATA FROM MVO TO INTERPOLATE EXTRU- SION RATES FROM MEASURED ACTIVE DOME VOLUMES ON DECEMBER 2000 AND 23 SEPTEMBER 2001) REAL-TIME RAINFALL AND SEISMIC DATA FOR THE JULY COLLAPSE INDICATE A CORRESPONDING AND DRASTIC INCREASE IN ROCKFALL-TYPE SEISMIC ACTIVITY (USED AS A PROXY FOR THE EVOLVING INSTA FAILURE GEOMETRY THE POTENTIAL FAILURE GEOMETRY IS SHOWN IN FIGURE (VOIGHT & ELSWORTH, 2000), AND IS DESCRIBED BY A VOLCANIC ROCKS FIGURE 2 VARIATION IN FACTOR OF SAFETY, FS, WITH INCLINA- TION OF THE FAILURE PLANE, ? RESULTS FOR A DOME OF EXTERNAL RADIUS B = 200 M AND CAVITY RADIUS A = 15 M WITHIN MATE- RIAL OF C = 0 5 MPA AND ? = 25?, UNLESS OTHERWISE NOTED ALL RESULTS ARE FOR GAS PRESSURE LOADING OF THE BLOCK REAR, EXCEPT MAGMASTATIC (SHOWN DASHED) IDEALIZED FAILURE PLANE PIVOTS UPWARDS FROM DOME BASE SEISMIC ACCELERATIONS ARE ? = 0 1 G AND ? = 0 2 G FACTOR OF SAFETY (FS) AS A FUNCTION OF BASAL FAILURE PLANE INCLINATION IS NOTED ON FIGURE 2 FOR A VARIETY OF CONDITIONS, FOR MATERIAL OF COHESION C = 0 5 MPA AND FRICTION ANGLE ? = 25?, UNLESS OTHERWISE NOTED, AND HOLDING FLUID DIFFUSIVITY (?) CONSTANT AT 103 M2/DAY IF THE EXTERNAL CARAPACE OF THE DOME IS A PURELY FRIC- TIONAL, INTERLOCKED, FRACTURED CRYSTALLINE SOLID (C = 0, ? = 60?), EXFOLIATION OF BLOCKS CAN OCCUR ON A STEEPLY INCLINED SURFACE THAT DOES NOT TRANSECT THE DOME CORE (FIG 2) INTHEABSENCEOFINTERNALPRESSUREANDFORINTE- RIOR STRENGTH PARAMETERS OF C = 0 1 MPA AND ? = 45?, FAILURE ON A LESS-STEEPLY-INCLINED BASAL SURFACE IS POS- SIBLE, BUT THE FAILURE SURFACE STILL DOES NOT PENETRATE DEEPLY INTO THE DOME INTERIOR HOWEVER, ALTHOUGH THE ACTUAL STRENGTH PROPERTIES OF HOT DOME LAVA (?800?C) WITH SOME RESIDUAL MELT HAVE NOT YET BEEN FULLY MEA- SURED, ITS FRICTIONAL PROPERTY MAY BE MUCH REDUCED FROM THESE SUPPOSED VALUES ASSUMING, THEN, A MORE COHESIVE AND LESS FRICTIONAL CORE, SAY C = 0 5 MPA AND ? = 25?, AN UNPRESSURIZED DOME IS MORE STABLE THAN FOR THE PREVIOUS CASE HOWEVER, AS INTERNAL GAS PRES- SURE BUILDS, STABILITY IS REDUCED ON A CRITICAL FAILURE PLANE INCLINED AT ABOUT 35?TO THE HORIZONTAL (FIG 2) SPALLING AT THE BLOCK TOE HAS A MINOR INFLUENCE ON THIS RESULT, BUT STRONG SHAKING BY VOLCANIC EARTHQUAKES OR TREMOR (VOIGHT ET AL 1998A; NEWHALL & VOIGHT, 1997), BACK-SCARP “MAGMASTATIC” PRESSURIZATION BY VISCOUS EXTRUSION FROM THE DOME CORE (ELSWORTH & VOIGHT, 1995), OR RAISING THE CAVITY GAS PRESSURE (PI > 5 MPA), REDUCED (I E THE CURVE OF FS VERSUS PLANE INCLINATION FLATTENS IN FIG 2), SO THAT MINOR AMOUNTS OF STRENGTH HETEROGENEITY COULD RESULT IN CRITICAL (FS ?1) FAILURE SURFACE INCLINATIONS NEARING 10?–20? THUS, THE COM- BINATION OF GAS PRESSURIZATION AND AUGMENTATION BY SEISMIC LOADS CAN RESULT IN DEEP-SEATED FAILURE SURFACES THAT CAN APPROACH THE HIGHLY PRESSURIZED CORE THE MAGMASTATIC CASE VALUES IN FIGURE 2 (COMBINED WITH A GAS-PRESSURIZED BASAL SURFACE) IMPLY FAILURE AT ALL GEOMETRIES THESE CASES ARE EXTREME EXAMPLES IN THATFULLDEVELOPMENTOFMAGMATICPRESSURESALONGSEC- TOR FRACTURES MAY BE UNLIKELY IN GENERAL HOWEVER THE EXAMPLE ILLUSTRATES THAT LOCALIZED INJECTIONS OF MAGMA CAN PLAY AN IMPORTANT ROLE ON STABILITY OBSERVED FAILURE MODES TWO FAILURE STYLES ARE TYPIFIED BY THE MONTSERRAT COL- LAPSES OF 3 JULY 1998 AND 20 MARCH 2000 THE EARLIER EVENT REMOVED A LARGE VOLUME, BUT LIMITED FRACTION (?20%), OF AN IMMENSE METASTABLE DOME ERUPTED 4 MONTHS PREVIOUSLY IN CONTRAST, THE LATTER EVENT REMOVED ?90% OF A MUCH SMALLER BUT NEWLY GROWN DOME THE 29 JULY 2001 COLLAPSE WAS SIMILAR TO MARCH 2000, BUT DOUBLE ITS SIZE (MATTHEWS ET AL 2002), AND THE 13 JULY 2003 EVENT WAS MORE THAN DOUBLE THAT OF 29 JULY 2001 (HERD ET AL 2003) THE 3 JULY EVENT OCCURRED DURING THE PERIOD OF NO DOME GROWTH BETWEEN MARCH 1998 AND NOVEMBER 1999 (NORTON ET AL 2002) AND REMOVED ?20% OF AN OVERSIZED LAVA DOME (?110 × 106 M3) THAT HAD BEEN ERUPTED (AND PARTLY ERODED) FROM NOVEMBER 1995 TO FEBRUARY 1998 THE COLLAPSE LEFT A CANYON-LIKE SLOT SCAR OF THIS PREVI- OUS FAILURE, COLLAPSED ON 20 MARCH 2000; ?90% OF THE DOME WAS REMOVED IN EACH CASE, RETROGRESSIVE COLLAPSES WERE INITIATED IN THE LATTER OPEN TO THE EAST (FIG 1A) IN CONTRAST, A SMALLER DOME (?27 × 106 M3), WHICH HAD GROWN AT ?2 5 M3/S SINCE NOVEMBER WITHIN THE ENLARGED SLOPING STAGES OF HEAVY RAINFALL, GENERATING A SHARP INCREASE IN ROCKFALL-TYPE SEISMICITY (FIG 3), AND IN SOME CASES WERE FOLLOWED BY ELE- VATED GAS FLUX MEASUREMENTS IMMEDIATELY AFTER THE COLLAPSE (NORTON ET AL 2002) THE COLLAPSES OCCURRED VOLCANIC ROCKS RAINFALL-INDUCED FAILURE MECHANISMS WE CONSIDER MULTIPLE POTENTIAL MECHANISMS THAT MAY HAVE CONTRIBUTED TO COLLAPSE (ELSWORTH ET AL 2004; TARON ET AL 2007) CONVENTIONAL MECHANISMS NOT INVOLVING RAIN INCLUDE SLOPE OVERSTEEPENING (SPARKS ET AL 2000), GAS OVERPRESSURIZATION OF THE DOME INTE- RIOR (VOIGHT & ELSWORTH, 2000; ELSWORTH & VOIGHT, 2001), AND HYDROTHERMAL WEAKENING OF THE DOME OR ITS SUBSTRATE STORM-TRIGGERED DESTABILIZATION OF THE STEEP APRON OF DOME TALUS HAS BEEN OBSERVED ON MONTSER- RAT ON A NUMBER OF OCCASIONS, E G , 14 OCTOBER RAINFALL INFILTRATION FOR 75 MM OF RAINFALL OVER 3 H, THE RESULTING HYDRAULIC PENETRATION IS SMALLEST FOR THE VERY NARROW SPACING OF FRACTURES (S < 0 2 M) OR EQUIVALENT POROUS MEDIUM, WHERE THE DOME CARAPACE IS QUENCHED TO A MAXIMUM DEPTH OF ABOUT ONE-THIRD THE STORM TOTAL RAINFALL ABOVE THIS SPACING (S < 0 2 M), HYDRAULIC PENETRATION DEPTH (D) GROWS LINEARLY WITH SPACING TO REACH 8 M FOR FRAC- TURES SPACED 80 M APART IN ROCKS OF 800?C AND 20 M PENETRATION FOR ROCKS AT 400?C FOR FRACTURES SPACED VOLCANIC ROCKS CORRELATIONS WITH OBSERVED COLLAPSE THESE PROPOSED MECHANISTIC MODELS BROADLY REPRO- VOLCANIC ROCKS FIGURE 5 VARIATION IN FACTOR OF SAFETY FOR SMALL AND LARGE DOMES, SUBJECT TO APPLIED RADIALLY DIMINISHING CORE PRESSURES (MAXIMUM CORE VALUES OF 0, 5, AND 10 MPA) AND SUPPLE- MENTED BY UNIFORM GAS PRESSURES (0, 10, AND 20 M OF WATER HEAD) (JULY 1998) – DURING A PERIOD OF VOLCANIC REPOSE AND ABSENT OBVIOUS PRECURSORS OTHER THAN A RAINSTORM – IS CONSISTENT WITH TRIGGERING BY HIGH-LEVEL GAS PRESSURIZA- TION WITHIN THE DOME ELEVATED GAS FLUX MEASUREMENTS IMMEDIATELY AFTER THE COLLAPSE (NORTON ET AL 2002) SUGGEST THAT PRESSURIZED GAS EXISTED WITHIN THE DOME PRIOR TO THE COLLAPSE, CAPPED BY RAINFALL PERCOLATING INTO THE CARAPACE THE NEAR-COMPLETE REMOVALS OF LAVA DOMES IN MARCH 2000 AND JULY 2001, BOTH IN A PERIOD OF REINITIATED EFFUSIVE ACTIVITY AND ABSENT OTHER PRE- CURSORS, ARE CONSISTENT WITH GAS PRESSURIZATION OF THE DOME CORE, CRITICALLY AUGMENTED BY THE PARTIAL SEALING OF THE DOME CARAPACE IN EACH CASE, COLLAPSE GEOME- TRY AND TIMING ARE REASONABLY CONSISTENT WITH AVAILABLE GEOMETRIC, TRANSPORT, AND STRENGTH PARAMETERS USED IN MODELING, ALTHOUGH IT SHOULD BE APPRECIATED THAT THE COLLAPSES ARE ALSO INFLUENCED STRONGLY BY RETROGRESSIVE FAILURE PROCESSES THAT ENSUE ONCE THE KEY BLOCKS HAVE FAILED UNDERSTANDINGTHECOMPLEXMECHANISMSOFRAINFALL- TRIGGERED INSTABILITY IS IMPORTANT BECAUSE SUCH FAIL- URES CAN OCCUR WITHOUT WARNING FROM STANDARD SOLID- EARTH PRECURSORY SIGNATURES AND YET MAY GENER- ATE EXTREMELY HAZARDOUS, LARGE-VOLUME, GAS-CHARGED DOME-COLLAPSE PYROCLASTIC FLOWS AND SURGES SUCH COR- RELATIONS EMPHASIZE THE NEED TO INCLUDE RAINFALL MONI- TORING WITH TRADITIONAL VOLCANO MONITORING METHODS IN ORDER TO AID THE ANTICIPATION OF HAZARDOUS COLLAPSES CONCLUSIONS TILT HAVE NOTED THAT COLLAPSE EVENTS DO NOT OCCUR SYN- CHRONOUSLY WITH PEAK DOME TILT – RATHER COLLAPSES ARE OBSERVED ON THE DOWN-SWING FROM PEAK PRESSURIZATION, AND PROCESSES OF TRANSIENT INFLATION ARE IMPLICATED THE PENETRATION OF THE INTERIOR PRESSURE PULSE INTO THE OUTER CARAPACE OF THE DOME IS ONE MECHANISM WHEREBY THIS ASYNCHRONOUS FAILURE MAY OCCUR, AND IS CONSISTENT WITH PREDICTIONS THE ROLE OF RAINFALL IN TRIGGERING SLOPE INSTABILITY ALSO DEVIATES FROM EXPECTED NORMS IN THESE UNUSUAL ENVIRONMENTS THE HOT SURFACE OF THE DOME CANNOT BE INFILTRATED UNDER NORMAL CIRCUMSTANCES – THE HIGH TEM- PERATURE REPELS THE INFLUENT PULSE WHERE THE DELUGE IS SUFFICIENTLY INTENSE, QUENCHING BY CONDUCTION AND BY LATENT HEAT IS CAPABLE OF TEMPORARILY COOLING THE SUR- FACE, AND OF ALLOWING INFILTRATION TO SUFFICIENT DEPTHS TO GENERATE EXCESS PRESSURES IN THE DOME INTERIOR, AND TO PUSH THE DOME TOWARDS FAILURE ACKNOWLEDGEMENTS THIS WORK IS A RESULT OF PARTIAL SUPPORT FROM NATIONAL SCIENCE FOUNDATION GRANTS CMS-9908590, EAR- 9909673, AND EAR-0116826 THE GENEROUS SUPPORT OF COLLEAGUES AT THE MONTSERRAT VOLCANO OBSERVATORY (MVO) IS ACKNOWLEDGED, AND WE THANK A MATTHEWS AND J BARCLAY, UNIVERSITY OF EAST ANGLIA, FOR PERMIS- SION TO USE RAIN-GAUGE DATA REFERENCES ABDURACHMAN, E K , BOURDIER, J L & VOIGHT, B , 2000 NUEES ARDENTES OF 22 NOVERMBER 1994 AT MERAPIVOLCANO, JAVA, INDONESIA JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH 100(1–4): 345–361 CALDER, E S , LUCKETT, R , SPARKS, R S J & VOIGHT, B , 2002 MECHANISMS OF LAVA DOME INSTABILITY AND GENERATION OF ROCKFALLS AND PYROCLASTIC FLOWS AT SOUFRIÈRE HILLS VOLCANO, MONTSERRAT IN: DRUITT, T H , KOKELAAR, B P (EDS ), THE ERUPTION OF SOUFRIÈRE HILLS VOLCANO, MONTSERRAT, FROM 1995 TO 1999 GEOLOGICAL SOCIETY, LONDON, MEMOIRS V 21: 173–190 CARN S A , WATTS, R B , THOMPSON, G & NORTON, G E , 2004 ANATOMY OF A LAVA DOME COLLAPSE: THE 20 MARCH EVENT AT SOUFRIÈRE HILLS VOLCANO MONTSERRAT JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH 31: 241–264 COLE, P ET AL 1998 PYROCLASTIC FLOWS GENERATED BY GRAVITA- TIONAL INSTABILITY OF THE 1996–1997 LAVA DOME OF SOUFRIÈRE HILLS VOLCANO, MONTSERRAT GEOPHYSICAL RESEARCH LETTERS 25: 3425–3428 EDMONDS, M , PYLE, D M , OPPENHEIMER, C M & HERD, R A , 2003 SO2 EMISSIONS 1995–2001 FROM SOUFRIÈRE HILLS VOLCANO, MONTSERRAT WI AND THEIR RELATIONSHIP TO CON- DUIT PERMEABILITY, HYDROTHERMAL INTERACTION AND DEGASSING REGIME JOURNAL OFVOLCANOLOGY AND GEOTHERMAL RESEARCH VOLCANIC ROCKS ELSWORTH, D & VOIGHT, B , 2001 THE MECHANICS OF HARMONIC GAS-PRESSURIZATION AND FAILURE OF LAVA DOMES GEOPHYSICAL JOURNAL INTERNATIONAL 145: 187–198 ELSWORTH, D , VOIGHT, B , THOMPSON, G &YOUNG, S R , 2004 A THERMAL-HYDROLOGIC MECHANISM FOR RAINFALL-TRIGGERED COLLAPSE OF LAVA DOMES GEOLOGY 32(11): 969–972 DOI:10 1130/G20730 1 FINK, J H & GRIFFITHS, R W , 1998 MORPHOLOGY, ERUPTION RATES, AND RHEOLOGY OF LAVA DOMES: INSIGHTS FROM LABORA- TORY MODELS JOURNAL OF GEOPHYSICAL RESEARCH 103(B1): 527–545 HERD, R , EDMONDS, M , STRUTT, M & OTTERMEILER, L , 2003 THE COLLAPSE OF THE LAVA DOME AT SOUFRIÈRE HILLS VOL- CANO, 12–15 JULY 2003: EOS (TRANSACTIONS, AMERICAN GEOPHYSICAL UNION) 84(46): F1596 MASTIN, L , 1994 EXPLOSIVE TEPHRA EMISSIONS AT MOUNT ST HELENS, 1989–1991 THE VIOLENT ESCAPE OF MAGMATIC GAS FOLLOWING STORMS GEOLOGICAL SOCIETY OFAMERICA BULLETIN 106: 175–185 MATTHEWS, A , BARCLAY, J , CARN, S , THOMPSON, G , ALEXAN- DER, J , HERD, R , AND WILLIAMS, C , 2002 RAINFALL-INDUCED VOLCANIC ACTIVITY ON MONTSERRAT: GEOPHYSICAL RESEARCH LETTERS, 29(13): 1644 DOI: 10 1029/2002GL014863 MATTHEWS, A J & BARCLAY, J , 2004 A THERMODYNAMI- CAL MODEL FOR RAINFALL-TRIGGERED VOLCANIC DOME COL- LAPSE GEOPHYSICAL RESEARCH LETTERS 31(5), L05614 DOI:10 1029/2003GL019310 MELNIK, O & SPARKS, R S J , 2002 DYNAMICS OF MAGMA ASCENT AND LAVA EXTRUSION AT SOUFRIÈRE HILLS VOLCANO, MONTSERRAT, IN: DRUITT, T H , AND KOKELAAR, B P (EDS ), THE ERUPTION OF SOUFRIÈRE HILLS VOLCANO, MONTSERRAT, FROM 1995 TO 1999: GEOLOGICAL SOCIETY [LONDON] MEMOIR, V 32: 153–172 MILLER, T , 1994 DOME GROWTH AND DESTRUCTION DURING THE 1989–1990 ERUPTION OF REDOUBT VOLCANO JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH 62: 197–212 MILLER, A D ET AL 1998 SEISMICITY ASSOCIATED WITH DOME GROWTH AND COLLAPSE AT THE SOUFRIÈRE HILLS VOL- CANO, MONTSERRAT GEOPHYSICAL RESEARCH LETTERS 25(18): 3401–3404 NAKADA, S & FUJII, T , 1993 PRELIMINARY REPORT ON THE ACTIV- ITY AT UNZEN VOLCANO (JAPAN) NOVEMBER 1990-NOVEMBER 1991: DACITE LAVA DOMES AND PYROCLASTIC FLOWS JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH 54: 319–333 NEWHALL, C G & MELSON, W G , 1987 EXPLOSIVE ACTIVITY ASSOCIATED WITH GROWTH OF VOLCANIC DOMES JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH 17: 111–131 NEWHALL, C G & VOIGHT, B , 1997 A SURVEY OF PRECURSORS TO DOME COLLAPSE, MERAPI DECADE INT WORKSHOP II: 48–49 NORTON, G E , ET AL , 2002 PYROCLASTIC FLOW AND EXPLOSIVE ACTIVITY OF THE LAVA DOME OF SOUFRIÈRE HILLS VOLCANO, MONTSERRAT, DURING A PERIOD OF VIRTUALLY NO MAGMA EXTRU- SION, IN DRUITT,T H , AND KOKELAAR, B P , EDS ,THE ERUPTION OFSOUFRIÈREHILLSVOLCANO,MONTSERRAT,FROM1995TO1999: GEOLOGICAL SOCIETY [LONDON] MEMOIR, V 21: 467–482 ROBERTSON, R ET AL 1998 THE EXPLOSIVE ERUPTION OF SOUFRIÈRE HILLS VOLCANO, MONTSERRAT, WEST INDIES, SEPTEMBER 17, 1996, GEOPHYSICAL RESEARCH LETTERS 25: 3429–3433 SATO, H , FUJII, T & NAKADA, S , 1992 CRUMBLING OF DACITE DOME LAVA AND GENERATION OF PYROCLASTIC FLOWS AT UNZEN VOLCANO NATURE 360: 664–666 SPARKS, R S J , ET AL 1998 MAGMA PRODUCTION AND GROWTH OF THE LAVA DOME OF THE SOUFRIÈRE HILLS VOLCANO, MONTSER- RAT, WEST INDIES: NOVEMBER 1995 TO DECEMBER 1997 GEOPHYSICAL RESEARCH LETTERS 25(18): 3421–3424 SPARKS, R S J , MURPHY, M D , LEJEUNE, A M , WATTS, R B , BARCLAY, J & YOUNG, S R , 2000 CONTROL ON THE EMPLACE- MENT OF THE ANDESITE LAVA DOME OF THE SOUFRIÈRE HILLS VOLCANO, MONTSERRAT BY DEGASSING-INDUCED CRYSTALLIZATION TERRA NOVA 12: 14–20 TARON, J ELSWORTH, D , THOMPSON, G & VOIGHT, B , 2007 MECHANISMS FOR RAINFALL-CONCURRENT LAVA DOME COLLAPSE AT SOUFRIÈRE HILLS VOLCANO, 2000–2002 JOURNAL OF VOLCANOL- OGY AND GEOTHERMAL RESEARCH 160: 195–209 VOIGHT, B & ELSWORTH, D , 1997 FAILURE OF VOLCANO SLOPES, GEOTECHNIQUE 47(1): 1–31 VOIGHT, B ET AL 1998A REMARKABLE CYCLIC GROUND DEFORMA- TION MONITORED IN REAL TIME ON MONTSERRAT AND ITS USE IN ERUPTION FORECASTING GEOPHYSICAL RESEARCH LETTERS 25: 3405–3408 VOIGHT, B ET AL 1998B DEFORMATION AND SEISMIC PRECURSORS TO DOME-COLLAPSE PYROCLASTIC FLOWS AT MERAPI VOLCANO, JAVA, 1994–1998, EOS (TRANSACTIONS, AMERICAN GEOPHYS- ICAL UNION) 79(45): F1001 VOIGHT, B & ELSWORTH, D , 2000 INSTABILITY AND COLLAPSE OF LAVA DOMES: GEOPHYSICAL RESEARCH LETTERS 27: 1–4 VOIGHT, B , CONSTANTINE, E , SISWOWIDJOYO, S & TORLEY, R , 2000 HISTORICAL ERUPTIONS OF MERAPI VOLCANO, CENTRAL JAVA, INDONESIA, 1768–1998: JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH 100: 69–138 WATSON, I M ET AL 2000 THE RELATIONSHIP BETWEEN DEGASSING AND GROUND DEFORMATION AT SOUFRIÈRE HILLS VOLCANO, MONTSERRAT JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH 98(1–4): 117–126 WATTS, R B , HERD, R A , SPARKS, R S J &YOUNG, S R , 2002 GROWTH PATTERNS AND EMPLACEMENT OF THE ANDESITE DOME AT SOUFRIÈRE HILLS VOLCANO, MONTSERRAT IN: DRUITT, T H , KOKELAAR, B P (EDS ),THE ERUPTION OF SOUFRIÈRE HILLSVOL- CANO, MONTSERRAT, FROM 1995 TO 1999 GEOLOGICAL SOCIETY, LONDON, MEMOIRS, V 21: 115–152 WIDIWIJAYANTI, C , CLARKE, A , ELSWORTH, D & VOIGHT, B , 2005 GEODETIC CONSTRAINTS ON THE SHALLOW MAGMA SYSTEM AT SOUFRIÈRE HILLS VOLCANO, MONTSERRAT GEO- PHYSICAL RESEARCH LETTERS 32, L11309 DOI:10 1029/ 2005GL022846 YAMASATO, H , KITAGAWA, S & KOMIYA, M , 1998 EFFECT OF RAINFALL ON DACITIC LAVA DOME COLLAPSE AT UNZEN VOLCANO, JAPAN: PAPERS IN METEOROLOGY AND GEOPHYSICS 48 (3): 73–78 YOUNG, S R ET AL 1998 OVERVIEW OF THE ERUPTION OF SOUFRIÈRE HILLS VOLCANO, MONTSERRAT, JULY 18, 1995, TO DECEMBER 1997, GEOPHYSICAL RESEARCH LETTERS 25: 3389–3393 VOLCANIC ROCKS