changes in coral reef structure through the miocene in the mediterranean province adaptive versus environmental influence well documented mediterranean examples of miocene carbonate platforms with complete exposures from shallow water to basinal facies provide evidence for temporal changes in reef building capacity of zooxanthellate corals in pre late tortonian platforms small coralgal patches and mounds occur from platform top to the toe of slope but they did not build to sea level in contrast barrier reefs with unequivocal reef crest structures that reached sea level are documented in late tortonian early messinian platforms we suggest that a change in both calcification rates and bathymetric zonation was the result of coevolution of corals and symbiodinium zooxanthellae coeval to global cooling and at least at a regional scale a geochemical change that supported widespread aragonite precipitation through the late miocene

fluid infiltration and transport of major minor and trace elements during regional metamorphism of carbonate rocks wepawaug schist connecticut usa geochemical alteration of metacarbonate layers due to fluid infiltration during greenschist and amphibolite facies metamorphism was investigated based on 149 whole rock analyses of the wepawaug schist usa ankerite albite ank ab rare ankerite oligoclase ank ol biotite bt amphibole amp and diopside di index mineral zones developed during progressive metamorphism acadian orogeny and devolatilization co2 h2o s loss ank ab ank ol and bt zone rocks were altered along some lithologic contacts and in reaction selvages around veins mass changes included gains of na y and in many cases p and fe k rb and ba were typically lost and sr was lost except where calcite precipitated in and around calcite bearing veins na gain and k loss reflect muscovite destruction and albite growth in response to infiltration of fluids from surrounding metapelitic and metapsammitic metaclastic rocks at higher metamorphic grades k rb and ba were lost when biotite broke down to form amphibole or diopside these elements were transported out of metacarbonate layers down chemical potential gradients at lithologic contacts and in selvages na was lost as plagioclase reacted to form clinozoisite zoisite czo zo calc silicates cm to dm scale thickness rich in amphibole and czo zo amp zones or diopside and zo di zones formed at layer margins and in selvages via extreme metasomatism including major 1 addition of al si and in many rocks fe 2 destruction of calcite and 3 loss of ca and volatiles volatile losses near 90 percent relative to low grade precursors demonstrate that calc silicate formation resulting from al si metasomatism is an important source of co2 to be considered when assessing regional devolatilization al mass gains for calc silicates indicate that large quartz veins and some lithologic contacts were loci for massive time integrated fluid fluxes of 105 m3 m 2 heavy rare earth elements hree were gained in the ank ab through the amp zones and a di zone example gained light and mid ree including sm and nd the ree gains coincide with gains of y and in most cases p suggesting that p and y complexes transport ree volume was lost progressively from the unveined interiors of metacarbonate beds attaining 20 to 30 percent loss in the di ii zone mass addition due to veining reduced volume losses and in some cases produced volume gains reaction transport modeling indicates that fluid flow was mostly layer parallel was focused along lithologic contacts fractures and permeable horizons and was accompanied by diffusion and or mechanical dispersion at high angles to the flow directions the metasomatic fluids infiltrated from surrounding metaclastic and or syn metamorphic igneous rocks thus interaction of fluids derived from different rock types must be considered when assessing mass transfer in lithologically diverse mountain belts

natural hazards in central java province indonesia an overview central java province indonesia suffers from natural hazard processes such as land subsidence coastal inundation flood volcanic eruption earthquake tsunami and landslide the occurrence of each kind of natural hazard is varied according to the intensity of geo processes it is necessary to learn from the historical record of coastal inundation flood volcanic eruption earthquake tsunami and landslide hazards in central java province to address issues of comprehensive hazard mitigation and management action through the understanding about the nature and spatial distribution of natural hazards treatments can be done to reduce the risks this paper presents the natural hazard phenomena in central java province and provides critical information for hazard mitigation and reduction

rainfall runoff properties of tephra simulated effects of grain size and antecedent rainfall abstract rain triggered lahars rtls are a significant and often persistent secondary volcanic hazard at many volcanoes around the world rainfall on unconsolidated volcaniclastic material is the primary initiation mechanism of rtls the resultant flows have the potential for large runout distances 100 km and present a substantial hazard to downstream infrastructure and communities rtls are frequently anticipated in the aftermath of eruptions but the pattern timing and scale of lahars varies on an eruption by eruption and even catchment by catchment basis this variability is driven by a set of local factors including the grain size distribution thickness stratigraphy and spatial distribution of source material in addition to topography vegetation coverage and rainfall conditions these factors are often qualitatively discussed in rtl studies based on post eruption lahar observations or instrumental detections conversely this study aims to move towards a quantitative assessment of rtl hazard in order to facilitate rtl predictions and forecasts based on constrained rainfall grain size distribution and isopach data calibrated simulated rainfall and laboratory constructed tephra beds are used within a repeatable experimental set up to isolate the effects of individual parameters and to examine runoff and infiltration processes from analogous rtl source conditions laboratory experiments show that increased antecedent rainfall and finer grained surface tephra individually increase runoff rates and decrease runoff lag times while a combination of these factors produces a compound effect these impacts are driven by increased residual moisture content and decreased permeability due to surface sealing and have previously been inferred from downstream observations of lahars but not identified at source water and sediment transport mechanisms differ based on surface grain size distribution a fine grained surface layer displayed airborne remobilisation accretionary pellet formation rapid surface sealing and infiltration excess overland flow generation whilst a coarse surface layer demonstrated exclusively rainsplash driven particle detachment throughout the rainfall simulations this experimental protocol has the potential to quantitatively examine the effects of a variety of individual parameters in rtl initiation under controlled conditions

instability of exogenous lava lobes during intense rainfall on many volcanoes there is evidence of a relationship between dome collapse and periods of high precipitation we propose a mechanism for this relationship and investigate the conditions that optimize failure by this process observations of elongate lobes that evolve through exogenous growth of lava domes reveal that they commonly develop tensile fractures perpendicular to the direction of motion these cracks can increase in depth by localized cooling and volumetric contraction during periods of high rainfall water can fill these cracks and the increase in fluid pressure on the base of the lobes and within the crack can trigger the collapse of the hot exogenous lava domes using limit equilibrium analysis it is possible to calculate the water and vapor forces acting on the rear and base of the potentially unstable part of the lobe the model presented is rectangular in cross section with material properties representative of andesitic dome rocks vapor pressures at the base of cracks are sealed by the penetrating rainfall which forms a saturated cap within the lobe this leads to an increase in fluid pressurization both through the underlying gas pressure and the downslope component of the liquid water cap fluid pressurization increases as the penetration depth increases this rainfall penetration depth is dependent on the thermal properties of the rocks antecedent temperature lobe geometry and the intensity and duration of precipitation dominant parameters influencing the stability of the lobe are principally lobe thickness duration and intensity of rainfall and antecedent lobe temperature our modeling reveals that thicker lobes are intrinsically more unstable due to the amplification of downslope forces in comparison to cohesive strength the increase in the duration and intensity of rainfall events also increases the potential for collapse as it leads to deeper liquid penetration deeper penetration depths are also achieved through lower antecedent temperatures since less fluid is lost through vaporization thus the potential for rain triggered collapse increases with time from emplacement

slab derived fluids and quartz vein formation in an accretionary prism otago schist new zealand regional quartz vein formation and the fluxes flow paths and sources of metamorphic fluids were investigated in the mesozoic accretionary prism of new zealand by using a new chemical mass balance analysis of outcrops samples were collected at meter or submeter intervals along outcrop length traverses and combined to obtain average chemical compositions of whole outcrops mass balance analysis used zr as an immobile reference frame and as a monitor of sedimentary sorting processes sio2 zr systematics produced by sedimentary processes differ greatly from those caused by metasomatic mass transfer of silica allowing evaluation of vein formation mechanisms relatively undeformed metasedimentary outcrops of low metamorphic grade mostly prehnite pumpellyite facies are nearly unveined and characterized by sedimentary compositional trends more deformed outcrops of higher metamorphic grade mostly greenschist facies contain 10 30 vol quartz veins these outcrops underwent mass addition of externally derived silica into quartz veins accompanied by addition of na and removal of k and w average silica additions suggest a time integrated fluid flux of 104 105 batchmode documentclass fleqn 10pt legalpaper article usepackage amssymb usepackage amsfonts usepackage amsmath pagestyle empty begin document m 3 fluid end document batchmode documentclass fleqn 10pt legalpaper article usepackage amssymb usepackage amsfonts usepackage amsmath pagestyle empty begin document m 2 rock end document for fluids ascending through the prism dehydration of spilitized oceanic crust subducting beneath the prism is the most probable source for this large fluid flux and could also have caused the na k metasomatism the w removed from deep levels of the prism may have been deposited in focused retrograde au w quartz veins at shallow levels by ascending fluids transfer of sio2 from subducting slabs into accretionary prisms is a plausible mechanism for long term bulk silica enrichment of the continents beyond that possible by magmatic differentiation

geochronology and geochemistry of multiple generations of monazite from the wepawaug schist connecticut usa implications for monazite stability in metamorphic rocks u pb isotope analyses rare earth and trace element analyses and petrographic observations are presented for monazites from the wepawaug schist in southern connecticut usa two samples of kyanite zone schist were collected less than a meter apart each sample contains a different variety of monazite with distinct morphology chemistry and pb isotopic composition one sample preserves a largely amphibolite facies mineralogy including kyanite staurolite garnet biotite and chlorite with little textural evidence of later shearing monazites from this sample are xenoblastic with about 1 wt tho2 0 3 wt cao and a more lree enriched pattern than monazites from the second sample these xenoblastic monazites preserve textural evidence of a retrograde reaction to apatite which involves chlorite indicating that these monazites became unstable during retrograde chloritization of biotite these monazites give strongly discordant u pb ages which fit a chord with an upper intercept age of 411 18 ma interpreted as the minimum growth age of these xenoblastic monazites perhaps during amphibolite facies metamorphism the second sample contains s c banding evidence of dynamic recrystallization and abundant retrograde chlorite this sample contains idioblastic monazites with about 3 wt tho2 0 8 wt cao and with less fractionated ree patterns these monazites give close to concordant u pb ages with a mean 207pb 206pb age of 388 2 ma this age is interpreted as probably representing the time of monazite growth during retrogression of the sample from an amphibolite to greenschist facies mineralogy

facies analysis and palaeoenvironmental interpretation of the late oligocene attard member lower coralline limestone formation malta the oligocene represents a key interval during which coralline algae became dominant on carbonate ramps and luxuriant coral reefs emerged on a global scale so far few studies have considered the impact that these early reefs had on ramp development consequently this study aimed at presenting a high resolution analysis of the attard member of the lower coralline limestone formation late oligocene malta in order to decipher the internal and external factors controlling the architecture of a typical late oligocene platform excellent exposures of the lower coralline limestone formation occurring along continuous outcrops adjacent to the victoria lines fault reveal in detail the three dimensional distribution of the reef associated facies a total of four sedimentary facies have been recognized and are grouped into two depositional environments that correspond to the inner and middle carbonate ramp the inner ramp was characterized by a very high energy shallow water setting influenced by tide and wave processes this setting passed downslope into an inner ramp depositional environment which was colonized by seagrass and interfingered with adjacent areas containing scattered corals the middle ramp lithofacies were deposited in the oligophotic zone the sediments being generated from combined in situ production and sediments swept from the shallower inner ramp by currents compositional characteristics and facies distributions of the attard ramp are more similar to the miocene ramps than to those of the eocene an important factor controlling this similarity may be the expansion of the seagrass colonization within the euphotic zone this expansion may have commenced in the late oligocene and was associated with a concomitant reduction in the aerial extent of the larger benthonic foraminifera facies stacking pattern analysis shows that the depositional units parasequences at the study section are arranged into transgressive regressive facies cycles this cyclicity is superimposed on the overall regressive phase recorded by the attard succession furthermore a minor highstand correlated with the ru4 ch1 sequence and subsequent minor lowstand ch2 sequence have been recognized the biota assemblages of the attard member suggest that carbonate sedimentation took place in subtropical waters and oligotrophic to slightly mesotrophic conditions the apparent low capacity of corals to form wave resistant reef structures is considered to have been a significant factor affecting substrate stability at this time the resulting lack of resistant mid ramp reef frameworks left this zone exposed to wave and storm activity thereby encouraging the widespread development of coralline algal associations dominated by rhodoliths

toward a revised hazard assessment at merapi volcano central java abstract of 1 1 million people living on the flanks of the active merapi volcano 440 000 are at relatively high risk in areas prone to pyroclastic flows surges and lahars for the last two centuries the activity of merapi has alternated regularly between long periods of viscous lava dome extrusion and brief explosive episodes at 8 15 year intervals which generated dome collapse pyroclastic flows and destroyed part of the pre existing domes violent explosive episodes on an average recurrence of 26 54 years have generated pyroclastic flows surges tephra falls and subsequent lahars the 61 reported eruptions since the mid 1500s killed about 7000 people the current hazard zone map of merapi pardyanto et al 1978 portrays three areas termed forbidden zone first danger zone and second danger zone based on successively declining hazards revision of the hazard map is desirable because it lacks details necessary to outline hazard zones with accuracy in particular the valleys likely to be swept by lahars and excludes some areas likely to be devastated by pyroclastic gravity currents such as the 22 november 1994 surge in addition risk maps should be developed to incorporate social technical and economic factors of vulnerability eruptive hazard assessment at merapi is based on reconstructed eruptive history on eruptive behavior and scenarios and on existing models and preliminary numerical modeling firstly the reconstructed eruptive activity in particular for the past 7000 years and from historical accounts of eruptions helps to define the extent and recurrence frequency of the most hazardous phenomena newhall et al 2000 camus et al 2000 pyroclastic flows traveled as far as 9 15 km from the source pyroclastic surges swept the flanks as far as 9 20 km away from the vent thick tephra fall buried temples in the vicinity of yogyakarta 25 km to the south and subsequent lahars spilled down the radial valleys as far as 30 km to the west and south at least one large edifice collapse has occurred in the past 7000 years newhall et al 2000 camus et al 2000 secondly four eruption scenarios are portrayed as hazardous zones on two maps and derived from the past eruptive behavior of merapi and from the most affected areas in the past thirdly simple numerical simulation based on a digital elevation model a stereo pair of spot satellite images and one 2d orthoimage helps to simulate pyroclastic and lahar flowage on the flanks and in radial valley channels and to outline areas likely to be devastated three major threats are identified 1 a collapse of the summit dome in the short to mid term that can release large volume pyroclastic flows and high energy surges towards the south southwest sector of the volcano 2 an explosive eruption much larger than any since 1930 may sweep all the flanks of merapi at least once every century 3 a potential collapse of the summit area involving the fumarolic field of gendol and part of the southern flank which can contribute to moderate scale debris avalanches and debris flows

fluid flow mineral reactions and metasomatism a general model that relates fluid flow along a temperature gradient to chemical reaction in rocks can be used to quantitatively interpret petrologic and geochemical data on metasomatism from ancient flow systems in terms of flow direction and time integrated fluid flux the model is applied to regional metamorphism quartz veins and a metasomatized ductile fault zone

dependence of reaction kinetics on h2o activity as inferred from rates of intergranular diffusion of aluminium quantitative constraints on the accelerative effects of h2o on the kinetics of metamorphic reactions arise from a comparison of rates of intergranular diffusion of al in natural systems that are fluid saturated hydrous but fluid undersaturated and nearly anhydrous widths of symplectitic reaction coronas around partially resorbed garnet crystals in the contact aureole of the makhavinekh lake pluton northern labrador combined with time temperature histories from conductive thermal models yield intergranular diffusivities for al from 700 900 c under nearly anhydrous conditions those rates when extrapolated down temperature are approximately three orders of magnitude slower than rates derived from re analysis of garnet resorption coronas formed under hydrous but fluid undersaturated conditions near 575 c in rocks of the llano uplift of central texas which are in turn approximately four orders of magnitude slower than rates at comparable temperatures derived from numerical simulations of prograde garnet growth in fluid saturated conditions in rocks from the picuris range of north central new mexico thus even at constant temperature rates of intergranular diffusion of al and corresponding length scales and timescales of metamorphic reaction and equilibration may vary by as much as seven orders of magnitude across the range of h2o activities found in nature

monitoring active volcanoes and mitigating volcanic hazards the case for including simple approaches abstract simple approaches to problems brought about eruptions and their ensuing hazardous effects should be advocated and used by volcanologists while awaiting more sophisticated remedies the expedients we advocate have all or many of the following attributes only locally available materials are required no extensive training of operators or installation is necessary they are affordable and do not require foreign aid or exports they are often labor intensive and are sustainable without outside assistance where appropriate the involvement of local residents is advocated examples of simple expedients which can be used in forecasting or mitigating the effects of crises emphasize the relative ease and the less elaborate requirements with which simple approaches can be activated emphasis is on visual observations often by untrained observers simple meteorogical measurements observations of water level in lakes temperature and chemistry of springs and fumaroles new springs and collapse areas and observations of volcanic plumes simple methods are suggested which can be applied to mitigating damage from mudflows nuees ardentes tephra falls and gas discharge a review in hindsight at ruiz includes the use of both chemical indicators and simple mudflow alarms simple expedients are sufficiently effective that any expert volcanologist called to aid in a crisis must include them in the package of advice offered simple approaches are a critical and logical complement to highly technical solutions to hazardous situations

sediment transportation and deposition by rain triggered lahars at merapi volcano central java indonesia abstract a lahar is a general term for a rapidly flowing mixture of rock debris and water other than normal streamflow from a volcano and refers to the moving flow located in the populated area of central java the stratovolcano merapi 2965 m is prone to lahar generation due to three main factors 1 millions of cubic meters of pyroclastic deposits are the product of frequent pyroclastic flows which have occurred on 2 to 4 year intervals 2 rainfall intensity is high often 40 mm in 2 h on average during the rainy season from november to april and 3 drainage pattern is very dense following the 22 november 1994 eruption of merapi 31 rain triggered lahar events were recorded in the boyong river between december 1994 and may 1996 on merapi s slopes instantaneous sediment concentration at any given time of the lahars varies widely over time and space lahars are transient sediment water flows whose properties are unsteady so that the sediment load fluctuates during the flow the boundary between the flow types debris flow with sediment concentration 60 volume or hyperconcentrated flow with sediment concentration ranges from 20 to 60 volume may fluctuate within the flow itself grain size distribution physical composition of sediments shear stress yield stress and water temperature play each a role on this boundary natural self damming and rapid breakout are partly responsible for the sediment variations of the flows debris flow phases at merapi typically last a few minutes to 10 min and are often restricted to the lahar front debris flow surges are sometimes preceded and always followed by longer hyperconcentrated flow phases as a result mean sediment concentration of the lahars is low commonly from 20 to 50 volume besides transient normal streamflow phases sediment concentration low sediment load and frequent transient flows in the merapi channels may result from at least three factors 1 several breaks in slope along the channel increase the deposition rate of sediment and hinder the bulking capacity of the lahars 2 source material is mainly coarse debris of merapi type block and ash flows consequently the remobilization of coarse debris is more difficult and the clast deposition is accelerated 3 variations of rainfall intensity over time and space common in tropical monsoon rainfall also influence the sediment load variations of the lahars sedimentologic analyses of the lahar deposits in the boyong river at merapi encompass clast supported and matrix supported debris flow deposits hyperconcentrated flow deposits and streamflow deposits the stratigraphic succession of massive and stratified beds observed immediately after any given lahar event in the boyong river indicates that the sediment concentration varies widely over time and space during a single lahar event sedimentation rate varies from 3 to 4 5 cm min during relatively long lived surges to as much as 20 cm min during short lived surges these results indicate that the sediment load fluctuates during lahar flow further demonstrating that lahars are transient sediment water flows with unsteady flow properties

field measurement of high temperature bulk reaction rates i theory and technique knowledge of metamorphic reaction rates is crucial to accurately interpret rock and mineral chemistry the local equilibrium assumption used in geochronology geothermobarometry and material flux estimates requires that local reaction rates among system phases are fast relative to local rates of p t x change natural metamorphic reaction rates are essentially unknown and difficulties and disagreements exist regarding extrapolations of existing laboratory data to natural conditions growing recognition of natural effects that could be attributed to slower reaction rates justifies the need for a field based quantification of reaction rates to assess the accuracy of lab based predictions we describe in detail the theory and methodology of a technique for extracting bulk reaction rates directly from isotopic data derived from natural samples baxter and depaolo 2000 reaction rates measured using this technique may be judiciously applied to isotopic exchange or net reaction kinetics in other natural systems the technique requires collection of whole rock and garnet 87sr 86sr data along a sampling traverse normal to a lithologic contact where there was prior to metamorphism a sharp isotopic discontinuity garnet data provide information on syn metamorphic conditions and the time interval for the exchange process forward modeling of the reactive transport process using numerical methods and the equations for diffusive reactive transport allow determination of the reaction rate and bulk sr diffusivity that provides the best fit to the data measurement of reaction rates is best constrained if an isotopic step is preserved at the contact the size of which is directly proportional to the bulk reaction rate this contribution is intended to serve as a template for future use and development of this technique to acquire natural reaction rate data from metamorphic systems

instrumental lahar monitoring at merapi volcano central java indonesia abstract more than 50 volcanic debris flows or lahars were generated around mt merapi during the first rainy season following the nuees ardentes of 22 november 1994 the rainfalls that triggered the lahars were analyzed using such instruments as weather radar and telemetered rain gauges lahar dynamics were also monitored using new non contact detection instrumentation installed on the slopes of the volcano these devices include real time seismic amplitude measurement rsam seismic spectral amplitude measurement ssam and acoustic flow monitoring afm systems calibration of the various systems was accomplished by field measurements of flow velocities and discharge contemporaneously with instrumental monitoring the 1994 1995 lahars were relatively short events their duration in the boyong river commonly ranging between 30 min and 1 h 30 min the great majority 90 of the lahars was recognized at kaliurang village between 13 00 and 17 30 h due to the predominance of afternoon rainfalls the observed mean velocity of lahar fronts ranged between 1 1 and 3 4 m s whereas the peak velocity of the flows varied from 11 to 15 m s under the gardu pandang viewpoint location at kaliurang to 8 10 m s at a section 500 m downstream from this site river slopes vary from 28 to 22 m km at the two sites peak discharges recorded in various events ranged from 33 to 360 m3 s with the maximum value of peak discharge 360 m3 s on 20 may 1995 to improve the lahar warning system along boyong river some instrumental thresholds were proposed large and potentially hazardous lahars may be detected by rsam units exceeding 400 ssam units exceeding 80 on the highest frequency band or afm values greater than 1500 mv on the low gain broad band setting

nuees ardentes of 22 november 1994 at merapi volcano java indonesia nuees ardentes associated with dome collapse on 22 november 1994 at merapi volcano traveled to the south southwest as far as 6 5 km and collectively accumulated roughly 2 5 3 million cubic meters of deposits the damaged area comprises 9 5 km2 and is covered by two nuee ardente facies a conventional merapi type valley fill block and ash flow facies and a pyroclastic surge facies the proximal deposits reflect the accumulation of dozens of nuees ardentes with many subsidiary flow units the distal deposits are more simply organized as only a few individual events reached to distances 3 5 km the stratigraphic relationships north of turgo hill indicate that the surge deposits are a facies of particularly mobile nuees ardentes that also deposited channeled block and ash flow facies they further suggest that the surge facies beyond the channel margins correlate laterally with a finer grained sublayer locally developed at the base of the block and ash flow facies eyewitness reports suggest that the emplacement of the block and ash flow facies in the distal part of the boyong river may have followed by a short time interval the destruction and deposition of the surge facies at turgo village the stratigraphy is in accord with the eyewitness reports the surge facies was emplaced by a dilute surge current detached from the same dome collapse nuee ardente that as a separate flow unit subsequently emplaced the distal block and ash deposit in the boyong valley the detachment occurred at higher elevations likely at or above the slope break at about 2000 m elevation this flow separation enabled the surge current to shortcut over the landscape and to emplace its deposit even as the block and ash flow continued its tortuous southward movement in the boyong channel dome collapse nuee ardente activity formed the bulk of the eruption which was accompanied by virtually no significant vertical summit explosive activity

gradients in fluid composition across metacarbonate layers of the wepawaug schist connecticut usa metamorphic index mineral zones pressure temperature p t conditions and co2 h2o fluid compositions were determined for metacarbonate layers within the wepawaug schist connecticut usa peak metamorphic conditions were attained in the acadian orogeny and increase from 420 c and 6 5 kb in the low grade greenschist facies to 610 c and 9 5 kb in the amphibolite facies the index minerals oligoclase biotite calcic amphibole and diopside formed with progressive increases in metamorphic intensity in the upper greenschist facies and in the amphibolite facies prograde reaction progress is greatest along the margins of metacarbonate layers in contact with surrounding schists or in reaction selvages bordering syn metamorphic quartz veins new index minerals typically appear first in these more highly reacted contact and selvage zones it has been postulated that this spatial zonation of mineral assemblages resulted from infiltration largely by diffusion of water rich fluids across lithologic contacts or away from fluid conduits like fractures in this model the infiltrating fluids drove prograde co2 loss and were derived from surrounding dehydrating schists or sources external to the metasedimentary sequence the model predicts that significant gradients in the mole fraction of co2 x co 2 should have been present during metamorphism but new estimates of fluid composition indicate that differences in x co 2 preserved across layers or vein selvages were very small 0 02 or less however analytical solutions to the two dimensional advection dispersion reaction equation show that only small fluid composition gradients across layers or selvages are needed to drive prograde co2 loss by diffusion and mechanical dispersion these gradients although typically too small to be measured by field based techniques would still be large enough to dominate the effects of fluid flow and reaction along regional t and p gradients larger gradients in fluid composition may have existed across some layers during metamorphism but large gradients favor rapid reaction and would therefore seldom be preserved in the rock record most of the h2o needed to drive prograde co2 loss probably came from regional dehydration of surrounding metapelitic schists although h2o rich diopside zone conditions may have also required an external fluid component derived from syn metamorphic intrusions or the metavolcanic rocks that structurally underlie the wepawaug schist

extraordinary sediment delivery and rapid geomorphic response following the 2008 2009 eruption of chaiten volcano chile u s geological survey volcano science center sernageomin s programa de riesgos volcanicos conicyt fondecyt grants 1110609 1141064 11130671 conicyt fondap 15090013 vamos research centre

volcano topography structure and intrinsic attenuation their relative influences on a simulated 3d visco elastic wavefield the seismic wavefield recorded on volcanoes can be significantly influenced by path effects scattering from the topography and internal volcanic structure can play a dominant role in the recorded seismograms intrinsic attenuation is also thought to play an important role in the characteristics of volcano seismic signals we use 3d numerical modelling of wave propagation in elastic and visco elastic media including complex velocity models and topography to investigate the scattering and attenuation characteristics of synthetic seismograms we generate 5 distinct volcano models and simulate wave propagation through these models using shallow and deep double couple broadband sources we then analyse 129 synthetic seismograms calculated on the free surface the synthetic seismograms resemble vt a and vt b events the scattering effect of the topography alone is capable of producing complex seismograms the introduction of an internal velocity structure increases the duration of these seismograms while the introduction of intrinsic attenuation decreases the duration but not the complexity we fitted our synthetic seismograms to the diffusion in a half space model to quantify the scattering and attenuation coefficients the scattering quality factor measured on all 129 stations for all 5 volcano models was similar therefore we deduce that the topography appears to be the dominant scatterer the intrinsic attenuation quality factor for each of the specific models cannot be accurately recovered using the diffusion in a half space model the measured quality factor is not only sensitive to the attenuation properties but also to the structural properties in all cases the scattering is more dominant than the intrinsic attenuation

matrix rheology effects on reaction rim growth i evidence from orthopyroxene rim growth experiments the rim forming reaction quartz olivine orthopyroxene is used to investigate the effect of matrix rheology on rim growth rates orthopyroxene rim growth around olivine grains in quartz matrix is compared to rim growth around quartz grains in an olivine matrix at constant p t within one single capsule orthopyroxene rims grow faster around quartz clasts in olivine matrix than around olivine clasts in quartz matrix fourier transform infra red spectra indicate that the entire samples are water saturated because of water adsorption on the reactant grain surfaces the increased orthopyroxene growth rates in olivine matrix as opposed to quartz matrix are interpreted in terms of matrix rheology where in the two different matrix inclusion arrangements the olivine matrix behaves softer and the quartz matrix more rigid the strain energy associated with accommodation of the negative reaction volume is higher for the quartz than the olivine matrix and reduces the free energy that drives orthopyroxene rim growth growth textures in both kinds of orthopyroxene rims indicate that the diffusivity of mgo slightly exceeds the diffusivity of sio2 the relative mobility of mgo and sio2 at given p t fh2o seems to be controlled by energy minimization during orthopyroxene growth at the compressive ol opx interface our experiments provide evidence for two previously overlooked effects relevant to rim growth reactions in metamorphic rocks i diffusivity along chemical potential gradients to reaction sites is a function of rheology and ii the relative diffusivity of components during reaction rim or corona growth is a function of local volume changes at the rim s interfaces

deformation mass transfer and mineral reactions in an eclogite facies shear zone in a polymetamorphic metapelite monte rosa nappe western alps this study analyses the mineralogical and chemical transformations associated with an alpine shear zone in polymetamorphic metapelites from the monte rosa nappe in the upper val loranco n italy in the shear zone the pre alpine assemblage plagioclase biotite kyanite is replaced by the assemblage garnet phengite paragonite at eclogite facies conditions of about 650 c at 12 5 kbar outside the shear zone only minute progress of the same metamorphic reaction was attained during the alpine metamorphic overprint and the pre alpine mineral assemblage is largely preserved textures of incomplete reaction such as garnet rims at former grain contacts between pre existing plagioclase and biotite are preserved in the country rocks of the shear zone reaction textures and phase relations indicate that the alpine metamorphic overprint occurred under largely anhydrous conditions in low strain domains in contrast the mineralogical changes and phase equilibrium diagrams indicate water saturation within the alpine shear zones shear zone formation occurred at approximately constant volume but was associated with substantial gains in silica and losses in aluminium and potassium changes in mineral modes associated with chemical alteration and progressive deformation indicate that plagioclase biotite and kyanite were not only consumed in the course of the garnet and phengite producing reactions but were also dissolved congruently during shear zone formation a large fraction of the silica liberated by plagioclase biotite and kyanite dissolution was immediately re precipitated to form quartz but the dissolved aluminium and potassium bearing species appear to have been stable in solution and were removed via the pore fluid the reaction causes the localization of deformation by producing fine grained white mica which forms a mechanically weak aggregate

sedimentary signatures of cyclic growth and destruction of stratovolcanoes a case study from mt taranaki new zealand abstract the long term behaviour of andesite stratovolcanoes is characterised by a repetition of edifice growth phases followed by collapse this cyclic pattern represents a natural frequency at varying timescales in the growth dynamics of stratovolcanoes worldwide around the 130 ka mt taranaki egmont volcano new zealand coastal cliff successions at 20 40 km distance comprise repeating packages of lithologically and sedimentologically distinctive mass flow deposits varying depositional mechanisms and source properties of these units record growth and collapse cycles of the central edifice these are used to construct a model for cyclic volcaniclastic sedimentation in the surrounds of stratovolcanoes during edifice construction phases thick packages of tabular predominantly monolithologic hyperconcentrated flow and debris flow deposits accumulate with intercalated tephra beds the mass flow units commonly contain large proportions of fresh pumice or juvenile lithic andesite intervals of quiescence separating eruptive periods are characterised by landscape re adjustment accompanied by deposition of fluvial and aeolian sediments along with steady accretion of medial ash in contrast brief episodes of destruction are marked by wide spread distinctively clay rich polylithologic debris avalanche deposits and related marginal debris flow units the growth stages can be terminated by an eruption triggered sector collapse or by external forces once the edifice exceeds a critical stable height or profile dependent on eruptive style and local geo tectonic conditions once the edifice becomes metastable regional tectonic earthquakes or shallow level intrusion events are likely triggers for collapse although the resulting debris avalanches represent the greatest individual hazard from such andesite stratovolcanoes their frequency is relatively low compared with other types of mass flows generated during edifice growth phases accurate forecasts of future hazard from mass flow events are therefore dependent on recognition of both the frequency of a stratovolcano s growth cycle and its current position in that cycle

the 26 may 2006 magnitude 6 4 yogyakarta earthquake south of mt merapi volcano did lahar deposits amplify ground shaking and thus lead to the disaster 1 indonesia is repeatedly unsettled by severe volcano and earthquake related disasters which are geologically coupled to the 5 7 cm a tectonic convergence of the australian plate beneath the sunda plate on saturday 26 may 2006 the southern coast of central java was struck by an earthquake at 2254 utc in the sultanate yogyakarta although the magnitude reached only mw 6 4 it left more than 6 000 fatalities and up to 1 000 000 homeless the main disaster area was south of mt merapi volcano located within a narrow topographic and structural depression along the opak river the earthquake disaster area within the depression is underlain by thick volcaniclastic deposits commonly derived in the form of lahars from mt merapi volcano which had a major influence leading to the disaster in order to more precisely understand this earthquake and its consequences a 3 month aftershock measurement campaign was performed from may to august 2006 we here present the first location results which suggest that the yogyakarta earthquake occurred at 10 20 km distance east of the disaster area outside of the topographic depression using simple model calculations taking material heterogeneity into account we illustrate how soft volcaniclastic deposits may locally amplify ground shaking at distance as the high degree of observed damage may have been augmented by the seismic response of the volcaniclastic mt merapi deposits this work implies that the volcano had an indirect effect on the level of earthquake destruction

u pb isotopic behaviour of zircon during upper amphibolite facies fluid infiltration in the napier complex east antarctica understanding the factors that contribute to u pb discordance in zircon is essential for interpreting isotopic data and for assessing the validity of concordia intercept ages modification caused by interaction with metamorphic fluids is often cited as a primary means by which significant or even complete isotopic resetting of u pb systematics in zircon might be achieved under subsolidus conditions we present a field example from the napier complex east antarctica in which a palaeoproterozoic 2450 70 ma zircon population interacted locally with an early palaeozoic 498 1 7 ma aqueous fluid at upper amphibolite facies conditions conventional ion microprobe analysis of sectioned and polished grain surfaces indicates that fluid interaction resulted in minor disturbance of u and pb in zircons both normal and reverse discordance with limited displacement along a chord with a lower intercept that coincides with the timing of fluid infiltration in contrast ion probe drilling or depth profiling into unpolished natural zircon crystal surfaces revealed extensive disturbance of u pb systematics to depths of 0 2 m with near surface ages consistent with the timing of fluid influx at 498 ma although zircon underwent some radiogenic pb redistribution during fluid interaction infiltrating fluids resulted in minimal grain scale isotopic modification of zircon based on ion probe depth profiling results we propose that limited normal discordance observed in the conventional ion microprobe zircon analyses in this case is controlled by an analytical mixture of reset and or recrystallised zircon along penetrative micro fracture networks with that of adjacent unaffected zircon we also suggest that the observed reverse discordance is genuine resulting from localised intra grain net accumulations of radiogenic pb we conclude that the isotopic response of zircon in this case is controlled by the interaction of an aqueous metamorphic fluid of low to moderate salinity resulting in sub micrometre depth scale isotopic modification at natural crystal faces and along penetrative micro fracture networks and that grain scale isotopic modification was negligible therefore we urge caution when considering regional chronological interpretations that appeal to significant zircon isotopic resetting caused exclusively by metamorphic fluid interaction at upper amphibolite facies conditions

using tree ring analysis to evaluate intra eruptive lahar activity in the nexpayantla gorge popocatepetl volcano central mexico abstract lahar activity is one of the most important processes capable of mobilizing large volumes of sediment and producing devastating effects on human populations and infrastructure estimating the frequency distribution and climatic controls on lahar activity is necessary for understanding how sediment is mobilized from hillslopes to channels and how the landscape is modified by this type of process in this study we evaluate the intra eruptive lahar activity in the nexpayantla gorge nw of popocatepetl volcano central mexico by using a dendrogeomorphological analysis of growth ring records of abies religiosa trees n 100 based on the identification of 322 growth disturbances gd and field evidences we identify 23 intra eruptive lahars that occurred from 1959 to 2013 by analyzing the lahar chronology and climatic data we observed that 83 of lahar activity coincides with moderate to strong cold and dry phases of el nino southern oscillation based on the seasonal timing of gd we explored the intra annual lahar activity we found that 43 of the lahars occurred in the latewood season from july to october when the mean summer monthly rainfall is 120 mm approximately 37 of lahars occurred during the first heavy rainfalls from march to june which corresponds to the earlywood season the remaining 20 of the lahar activity corresponds to the dormancy period winter season when snowmelt and or occasional strong rainfalls 100 mm day 1 occur the gd indicate that in nexpayantla gorge intra eruptive lahar activity takes place around every two years we also found that the effects of lahars are concentrated around the transitional and depositional zone of nexpayantla gorge

seismic tracking of lahars using tremor signals debris flows or lahars frequently occur in volcanic regions and cause serious disasters to nearby communities lahars are commonly observed as long lasting high frequency tremor in seismic records we propose a seismic technique to locate the source of tremor originating from lahars by using waveform data from a seismic network in this method we fit the surface wave amplitudes from point sources positioned over the surface of a volcano to the observed tremor amplitudes and estimate the spatial distributions of the normalized residuals in successive time windows the observed tremor amplitudes at individual stations are corrected by site amplification factors independently estimated from coda waves of tectonic earthquakes the positions of time windows applied to the observed tremor signals are corrected for the travel times of individual source and receiver pairs we track the source of tremor or lahars as temporal changes of the best fit locations in the residual distributions this method is an extension of the existing methods used to locate seismic events and tremor associated with volcanic eruptions we applied this technique to tremor signals of lahars observed by a seismic network at cotopaxi volcano ecuador our analysis showed regions with small residuals on the ne flank of the volcano this suggests that lahars descended on this flank which is consistent with the result of a field survey that found fresh lahar deposits on the ne flank our method which can be easily automated may be useful for the rapid detection and monitoring of lahars

acute sedimentation response to rainfall following the explosive phase of the 2008 2009 eruption of chaiten volcano chile the 10 day explosive phase at the start of the 2008 2009 eruption of chaiten volcano in southern chile 42 83 s 72 65 w blanketed the steep rain forest cloaked 77 km2 chaiten river drainage basin with 3 to 100 cm of tephra predominantly fine to extremely fine rhyolitic ash fell during the latter half of the explosive phase rain falling on this ash blanket within days of cessation of major explosive activity generated a hyperconcentrated flow lahar followed closely by a complex multi day muddy flood streamflow bordering on dilute hyperconcentrated flow sediment mobilized in this lahar flood event filled the chaiten river channel with up to 7 m of sediment buried the town of chaiten 10 km downstream of the volcano in up to 3 m of sediment and caused the lower 3 km of the channel to avulse through the town although neither the nature nor rate of the sedimentation response is unprecedented they are unusual in several ways 1 nearly 70 percent of the aggradation almost 5 m in the 50 70 m wide chaiten river channel was caused by a lahar triggered by an estimated 20 mm of rainfall over a span of about 24 h an additional 2 m of aggradation occurred in the next 24 36 h 2 direct damage to the town was accomplished by the sediment laden water flood phase of the lahar flood event not the lahar phase 3 the volume of sediment eroded from hillslopes and delivered to the chaiten river channel was at least 3 8 106 m3 roughly 15 40 of the minimum tephra volume that mantled the chaiten river drainage basin 4 the acute sedimentation response to rainfall appears to have been due to the thickness and fineness of the ash blanket inhibiting infiltration of rain and the steepness of the basin s hillslopes other possible factors such as the prior formation of an ash crust development of a hydrophobic surface layer or large scale destruction of rain intercepting vegetation did not play a role

seismic analysis of the 13 october 2012 te maari new zealand lake breakout lahar insights into flow dynamics and the implications on mass flow monitoring abstract on 6 august 2012 an eruption of the upper te maari vent tongariro volcano and subsequent debris flow in the mangatetipua channel created a debris dam and ephemeral lake the lake reached its maximum volume of 50 000 m3 by 13 october initiating dam breaching at 22 30 nzdt 11 30 utc after a period of intense rainfall the breach eventually grew to 29 12 m causing eroded debris flow sediment and water to remobilize as a lahar the event comprising multiple surges lasted 30 min and displaced 57 000 m3 of remobilized sediment up to 4 5 km downstream to determine the dynamics of the event the seismic signals generated by the lahar were compared with active seismic source data collected in february 2013 the comparison used a common frequency band range of 3 10 hz to compute amplitude for four near field seismic stations for periods with signal to noise ratios above 2 0 we obtained lahar amplitude distributions that match best the equivalent active source amplitudes within 0 5 km of the dam breakout the accumulated seismic energy of the lahar was estimated at 1 93 109 nm whereas the peak energy was 6 88 107 nm results of this work may improve the characterization of future mass flow events in the te maari mangatetipua area through the calibration of seismic stations used in this study

the characteristics of seismic signals produced by lahars and pyroclastic flows volcan de colima mexico abstract the general characteristics of seismic signals produced by pyroclastic flows generated by either the collapse of a lava dome or an eruptive column and lahars at volcan de colima mexico are discussed the paper concentrates on the 2004 2006 activity associated with and following the extrusion of andesitic block lava in october november 2004 it is shown that the duration of the broad band seismic records of pyroclastic flows lasts a few minutes while the duration of seismic records of lahars continues for tens of minutes or hours the spectra of seismic records produced by pyroclastic flows are characterized by lower peak frequencies around 3 4 hz than for lahars around 6 8 hz this difference in the frequency content together with the difference in the duration of seismic signals allows early diagnostic of the events in real time

syndepositional tectonics affecting cenozoic and mesozoic deposition in the malta and se sicily areas central mediterranean and their bearing on mesozoic reservoir development in the n malta offshore region abstract tertiary sedimentation patterns within the maltese islands and se sicily pelagian block of the central mediterranean reflect subtle depositional control by the concurrent evolution of the malta graben lying to the south west and reactivation of regionally important mesozoic fault systems the visible structural style of the maltese islands is the product of malta graben development and commenced some 24 million years ago however north south oriented structures identified from maltese tertiary facies strike patterns can be closely related to reactivated mesozoic faults in se sicily here synsedimentary tectonogenesis is recognized in both mesozoic and cenozoic strata mesozoic synsedimentary faulting was initiated during a former tectonic regime when the pelagian block african plate lay at the southern side of a wide tethys ocean reactivation of these fractures during the tertiary is believed to be related to subsequent african european plate collision the unsuccessful oil search in maltese territorial waters results from the mistaken significance attached to the young malta graben related tectonic pattern of the maltese islands potential traps are more likely to be associated with a cryptic though formerly dominant mesozoic tectonic pattern the hypothesis presented predicts hydrocarbon prospects in horst traps immediately to the north of the malta shelf these can be expected to show many of the characteristics of the gela and ragusa fields

rainfall triggered lahars at volcan de colima mexico surface hydro repellency as initiation process article volcan de colima is currently the most active volcano in mexico since 1998 intermittent activity has been observed with vulcanian eruptions lava flows and growing domes that have collapsed producing several block and ash flow deposits during the period of heightened activity since 1998 at volcan de colima pyroclastic flows from dome or column collapse have not reached long distances most of the time less than 6k m from the crater in contrast rain induced laharswere more frequent and have reached relatively long distances upto 15 km causing damage to infrastructureand affecting small villages in 2007 tworain gauge stationswereinstalledonthesouthern flankofthevolcanoregisteringeventsfromjunethroughtooctober the period when rains are intense and lahars frequent by comparing lahar frequency with rainfall intensity and the rainfall accumulated during the previous 3 days lahars more frequently occur at the beginning of the rainfall season with low rain accumulation 10 mm and triggered by low rain intensities 20 mm h during the months with more rainfall july and august lahars are less frequent and higher peak intensities up to 70 mm h are needed to trigger an event in both cases lahars were initiated as dilute sediment laden streamflows which transformed with entrainment of additional sediment into hypercon centratedanddebris flows withalternationsbetweenthesetwo flowtypes ahydro repellencymechanism in highly vegetated areas i e evergreen tree types with considerable amount of resins and waxes such as pines with sandy soils can probably explain the high frequency of lahars at the beginning of the rain season during low rainfall events under hydrophobic conditions infiltration is inhibited and runoff is facilitated at more highly peaked discharges that are more likely to initiate lahars

ree bearing minerals in a ti rich vein from the adamello contact aureole italy zirconolite aeschynite ce titanite and apatite have been found as minor or accessory minerals in a ti rich tio2 2 1 4 5 wt hydrothermal vein occurring in dolomite marbles at the contact with a tonalite intrusion of the tertiary adamello batholith northern italy the vein consists of four distinct mineral zones comprising from margin to center 1 forsterite calcite 2 pargasite calcite titanite sulfides 3 phlogopite calcite titanite sulfides and 4 titanian clinohumite spinel calcite sulfides zirconolite occurs in two vein zones only in the phlogopite zone it is invariably anhedral often corroded and exhibits complex chemical zonation patterns in the titanian clinohumite zone zirconolite is idiomorphic and characterized by a pronounced discontinous chemical zoning but shows no evidence of corrosion the considerable compositional variation observed for zirconolite in wt ree2o3 0 74 16 8 uo2 0 59 24 0 tho2 0 67 17 1 is due to the zoning and may be attributed to four major substitutions described by the exchange vectors 1 th u mg fe2 ca 1 ti 1 2 ree al ca 1 ti 1 3 ree fe2 nb ta ca 1 ti 1 4 hf zr 1

geomorphological evolution of a fluvial channel after primary lahar deposition huiloac gorge popocatepetl volcano mexico abstract popocatepetl volcano 19 02 n 98 62 w 5424 m began its most recent period of volcanic activity in december 1994 the interaction of volcanic and glacier activity triggered the formation of lahars through the huiloac gorge located on the northern flank of the volcano causing significant morphological changes in the channel the most powerful lahars occurred in april 1995 july 1997 and january 2001 and were followed by secondary lahars that formed during the post eruptive period this study interprets the geomorphological evolution of the huiloac gorge after the january 2001 lahar variations in channel morphology at a 520 m long research site located mid way down the gorge were recorded over a 4 year period from february 2002 to march 2005 and depicted in five geomorphological maps scale 1 200 for 14 february and 15 october 2002 27 september 2003 9 february 2004 and 16 march 2006 a gis was used to calculate the surface area for the landforms identified for each map and detected changes and erosion deposition processes of the landforms using the overlay function for different dates findings reveal that secondary lahars and others types of flows like sediment laden or muddy streamflows caused by precipitation rapidly modified the gorge channel following the january 2001 non eruptive lahar a period associated with volcanic inactivity and the disappearance of the glacier once located at the headwall of the gorge field observations also confirmed that secondary flows altered the dynamics and geomorphological development of the channel these flows incised and destroyed the formations generated by the primary lahars 1997 and 2001 causing a widening of the channel that continues today after february 2004 a rain triggered lahar and other flows infilled the channel with materials transported by these flows the deposits on the lateral edges of the channel form terraces a recent lull in lahar activity contrasts with the increasing instability of the edges of the channel and the continuous edification and destruction of recent lahar terraces

fluid production and isograd reactions at contacts of carbonate rich and carbonate poor layers during progressive metamorphism with increasing temperature during prograde metamorphism reactions will occur first at the lithological contacts of mixed pelite and calcsilicate terranes at these interfaces a fluid of lower chemical potential of h2o and co2 than that required to produce a fluid in either layer can be produced whether reaction is caused by fluid infiltration or is initially fluid absent if the interface region does not allow fluid transport then as temperature increases a fluid pressure greater than lithostatic can develop at some degree of over pressure relative to rock pressure the fluid hydraulically fractures the rock and a gradient in fluid composition away from the contact can be produced these phenomena occur at the compositional interfaces whenever univariant reactions in the differing layers cross on a temperature vs mole fraction of co2 diagram with slopes of opposite sign the first occurrence of these reaction products at lithological contacts delineates an isograd that defines temperature as well as the mole fraction of co2 at constant pressure in systems open to fluid transport these isograds can be contrasted with fluid producing isograds in closed systems as an illustration of possible effects the reactions quartz clinozoisite muscovite anorthite k feldspar h2o and phlogopite quartz calcite tremolite k feldspar h2o co2 at 4 kbar are analysed and equations for fluid production and transport are developed

historical eruptions of merapi volcano central java indonesia 1768 1998 abstract information on merapi eruptive activity is scattered and much is remotely located a concise and well documented summary of this activity has been long needed to assist researchers and hazard mitigation efforts and the aim of this paper is to synthesize information from the mid 1700s to the present a descriptive chronology is given with an abbreviated chronology in a table that summarizes events by year assigns preliminary volcanic explosivity index vei ratings and hartmann classifications and provides key references the history of volcano monitoring is also outlined the study reveals that a major difference in eruption style exists between the twentieth and nineteenth centuries although the periodicity between larger events seems about the same during the twentieth century activity has comprised mainly the effusive growth of viscous lava domes and lava tongues with occasional gravitational collapses of parts of oversteepened domes to produce the nuees ardentes commonly defined as merapi type in the 1800s however explosive eruptions of relatively large size occurred to vei 4 and some associated fountain collapse nuees ardentes were larger and farther reaching than any produced in the twentieth century these events may also be regarded as typical eruptions for merapi the nineteenth century activity is consistent with the long term pattern of one relatively large event every one or two centuries based on the long term eruptive record deduced by others from volcanic stratigraphy it is uncertain whether or not a recurrence time model continues to apply to merapi but if so merapi could soon be due for another large event and its occurrence with only modest or inadequately appreciated precursors could lead to a disaster unprecedented in merapi s history because the area around the volcano is now much more densely populated

landscape development preceding homo erectus immigration into central java indonesia the sangiran formation lower lahar abstract the sangiran dome is the primary stratigraphic window for the solo basin a coastal feature on the pliocene pleistocene sunda subcontinent south margin in the dome the lower lahar unit llu is a lahar type debris flow overlying near shore marine sediments the event that emplaced the llu likely originated from sector collapse on a neighboring volcanic edifice freshwater mollusc fossils in the llu indicate that swamps or shallow lakes lay between the edifice and the current dome area 40ar 39ar analyses on hornblende separates from six pumice lenses suggest that the llu was deposited as early as 1 90 0 02 ma the event resulting in deposition of the llu transformed late pliocene near shore marine environments into estuarine and marsh settings shortly thereafter glacioeustatic sea level falls completed the local transition to fully terrestrial environments that attracted homo erectus to southernmost sunda in the early pleistocene

characterization of debris flows by rainstorm condition at a torrent on the mount yakedake volcano japan abstract we analyzed rainstorm control on debris flow magnitude and flow characteristics using the 14 sets of rainstorm and debris flow data obtained from 1980 to 2005 at the kamikamihorizawa creek of mount yakedake with the principal component analysis on five parameters of debris flows frontal velocity peak velocity peak flow depth peak discharge and total discharge and with video record of boulder dams in motion and the preceding rainfall intensities we conclude that the 14 debris flows could be categorized into three groups the flows in the first group have large hydraulic magnitude and massive and turbulent boulder dams filled with slurry matrix the flows in the second group have small hydraulic magnitude and boulder dams scarcely filled with slurry matrix and the dam is observed to alternate between stopping and starting the flows in the third group have small hydraulic magnitude and boulder dams filled with slurry matrix analysis of hillslope hydrology and debris flow data asserted that the antecedent rainfall conditions control not only the hydraulic magnitude of debris flows but also the boulder dam features large rainstorms of high intensity and durations as short as 10 minutes induces fast and large storm runoff to the headwaters and the source reaches of debris flow while rainstorms with durations as long as 24 h raises water content in the bottom deposits along the debris flow growth reaches and generates substantial runoff from the tributaries classification of the three groups is done based on water availability to debris flows on the source and growth reaches at the occurrence of debris flow

rain triggered lahars following the 2010 eruption of merapi volcano indonesia a major risk abstract the 2010 vei 4 eruption of merapi volcano deposited roughly ten times the volume of pyroclastic materials of the 1994 and 2006 eruptions and is recognized as one of the most intense eruption since 1872 however as the eruptive phase is now over another threat endangers local communities rain triggered lahars previous papers on lahars at merapi presented lahar related risk following small scale dome collapse pdcs thus the aim of this study is to provide new insights on lahar related risk following a large scale vei 4 eruption the paper highlights the high number of events 240 during the 2010 2011 rainy season october 2010 may 2011 the frequency of the 2010 2011 lahars is also the most important ever recorded at merapi lahars occurred in almost all drainages located under the active cone with runout distances exceeding 15 km the geomorphic impacts of lahars on the distal slope of the volcano are then explained as they directly threaten houses and infrastructures creation of large corridors avulsions riverbank erosion and riverbed downcutting are detailed through local scale examples related damage is also studied 860 houses damaged 14 sabo dams and 21 bridges destroyed sedimentological characteristics of volcaniclastic sediments in lahar corridors are presented with emphasis on the resource in building material that they represent for local communities risk studies should not forget that thousands of people are exposing themselves to lahar hazard when they quarry volcaniclastic sediment on lahar corridors finally the efficient community based crisis management is explained and shows how local people organize themselves to manage the risk 3 fatalities were reported although lahars reached densely populated areas to summarize this study provides an update of lahar risk issues at merapi with emphasis on the distal slope of the volcano where lahars had not occurred for 40 years and where lahar corridors were rapidly formed

10 000 years of explosive eruptions of merapi volcano central java archaeological and modern implications abstract stratigraphy and radiocarbon dating of pyroclastic deposits at merapi volcano central java reveals 10 000 years of explosive eruptions highlights include 1 construction of an old merapi stratovolcano to the height of the present cone or slightly higher our oldest age for an explosive eruption is 9630 60 14 c y b p construction of old merapi certainly began earlier 2 collapse s of old merapi that left a somma rim high on its eastern slope and sent one or more debris avalanche s down its southern and western flanks impoundment of kali progo to form an early lake borobudur at 3400 14 c y b p hints at a possible early collapse of merapi the latest somma forming collapse occurred 1900 14 c y b p the current cone new merapi began to grow soon thereafter 3 several large and many small buddhist and hindu temples were constructed in central java between 732 and 900 a d roughly 1400 1000 14 c y b p explosive merapi eruptions occurred before during and after temple construction some temples were destroyed and or buried soon after their construction and we suspect that this destruction contributed to an abrupt shift of power and organized society to east java in 928 a d other temples sites though were occupied by caretakers for several centuries longer 4 a partial collapse of new merapi occurred 14 c y b p eruptions 700 800 14 c y b p 12 14th century a d deposited ash on the floors of still occupied candi sambisari and candi kedulan we speculate but cannot prove that these eruptions were triggered by the same partial collapse of new merapi and that the eruptions in turn ended caretaker occupation at candi sambisari and candi kedulan a new or raised lake borobudur also existed during part or all of the 12 14th centuries probably impounded by deposits from merapi 5 relatively benign lava dome extrusion and dome collapse pyroclastic flows have dominated activity of the 20th century but explosive eruptions much larger than any of this century have occurred many times during merapi s history most recently during the 19th century are the relatively small eruptions of the 20th century a new style of open vent less hazardous activity that will persist for the foreseeable future or alternatively are they merely low level background activity that could be interrupted upon relatively short notice by much larger explosive eruptions the geologic record suggests the latter which would place several hundred thousand people at risk we know of no reliable method to forecast when an explosive eruption will interrupt the present interval of low level activity this conclusion has important implications for hazard evaluation

metasomatic coronas around hornblendite xenoliths in granulitefacies marble ivrea zone n italy i constraints on componentmobility centimeter to decimeter thick reaction bands occur at hornblendite marble interfaces in val fiorina in the granulite facies metamorphic ivrea zone from hornblendite to marble the reaction bands show a consistent succession of sharply bounded mineral layers comprising a monomineralic clinopyroxene layer a garnet clinopyroxene layer and a scapolite clinopyroxene layer reaction band formation occurred as a response to gradients in the chemical potentials of calcium and magnesium as defined by the hornblendite assemblage and the marble matrix the metasomatic corona primarily replaced the hornblendite and only minor amounts of marble were consumed the reaction band behaved as an open system with net transfer of calcium from the marble into the reaction band and a net transfer of iron and magnesium in the opposite direction mass balance considerations allow us to constrain a range of feasible mass balance scenarios for which major element fluxes across the boundaries of the reaction band may be quantified modeling of layer growth as a steady diffusion process yields ratios of the phenomenological diffusion coefficients for si al mg and ca of l sisi over l caca 2 5 kern 1pt rm l alal over l caca 1 the relative diffusivities are primarily constrained by the sequence of mineral layers of the reaction band and by the relative thickness of the layers the results of steady state diffusion modeling are relatively insensitive with respect to variations in the major element boundary fluxes

morphological and structural changes at the merapi lava dome monitored in 2012 15 using unmanned aerial vehicles uavs abstract dome building volcanoes undergo rapid and profound topographic changes that are important to quantify for the purposes of hazard assessment however as hazardous lava domes often develop on high altitude volcanoes that exhibit steep sided topography it is challenging to obtain direct field access and thus to analyze these morphological and structural changes merapi volcano in indonesia is a type example of such a volcano as soon after its 2010 eruption a new lava dome developed this dome was partially destroyed during six distinct steam driven explosions that occurred between 2012 and 2014 here we investigate the topographic and structural changes associated with these six steam driven explosions by comparing close range photogrammetric data obtained before and after these explosions to accomplish this we performed two uav campaigns in 2012 and 2015 by applying the structure from motion sfm technique we are able to construct three dimensional point clouds assess their quality by comparing them to a terrestrial laser scanning tls dataset and generate high resolution digital elevation models dems and photomosaics the comparison of these two dems and photomosaics reveals changes in topography and the appearance of fractures in the 2012 dataset we find a dense fracture network striking to the nnw sse in the post eruptive 2015 dataset we see that this nnw sse fracture trend is much more strongly expressed we also detect the formation of aligned and elongated explosion craters which are associated with the removal of over 200 000 m3 of dome material most of which 70 was deposited outside the crater region therefore this study suggests that the locations of the steam driven explosions at merapi volcano were controlled by the reactivation of preexisting structures moreover some of the newly developed and reactivated fractures delineate a block on the southern slope of the dome which could become structurally unstable and potentially lead to rock avalanche hazards this study therefore demonstrates the significance of characterizing structural fingerprints during the development of lava domes and exemplifies the value of topographic and fracture mapping which is becoming increasingly feasible when using uavs even on high and steep stratovolcanoes

installation of a doppler radar monitoring system at merapi volcano indonesia merapi volcano indonesia is one of the most active dome building volcanoes worldwide instabilities at the growing dome cause rockfalls and hot block and ash flows which can reach run out distances of several kilometers therefore merapi has been monitored extensively for many years however direct visual observation of the dome is often impossible due to cloud coverage of the summit in october 2001 a first prototype doppler radar system was installed to overcome this shortcoming the system is able to penetrate clouds and observe material movements at the dome giving valuable information about dynamic processes in the dome area the system also allows detection of rainfall in several distance intervals for precise positioning of the beam the system was equipped with an electromechanical mounting in 2003 a charge coupled device ccd camera attached to the radar mirror documents the radar beam position and provides visual observation of the dome recorded data camera images and status information are telemetered to the merapi volcano observatory where they can be processed and interpreted status information is also sent via short message service via a global system for mobile communications gsm modem by processing the doppler radar data we are able to discriminate between three different types of instability events sliding dome material dome material gravitationally breaking off the dome and explosive outbursts of dome material due to expansion of volcanic gas in order to independently verify our observations we compared rockfall events detected by the radar system to seismic recordings and found a good correlation

lahars at merapi volcano central java an overview abstract merapi volcano in central java is one of the most active volcanoes in the world at least 23 of the 61 reported eruptions since the mid 1500s have produced source deposits for lahars the combined lahar deposits cover about 286 km 2 on the flanks and the surrounding piedmonts of the volcano at merapi lahars are commonly rain triggered by rainfalls having an average intensity of about 40 mm in 2 h most occur during the rainy season from november to april and have average velocities of 5 7 m s at 1000 m in elevation a wide range of facies may be generated from a single flow which may transform downvalley from debris flow to hyperconcentrated streamflow because of the high frequency and magnitude of the lahar events lahar related hazards are high below about 450 600 m elevation in each of the 13 rivers which drain the volcano hazard zone maps for lahar were produced by pardyanto et al volcanic hazard map merapi volcano central java 1 100 000 geol surv of indonesia bandung ii 4 1978 and the japanese indonesian cooperation agency master plan for land conservation and volcanic debris control in the area of mt merapi jakarta 1980 but these maps are of a very small scale to meet modern zoning requirements more recently a few large scale maps 1 10 000 and 1 2000 scale and risk assessments have been completed for a few critical river systems

volcanic hazards at mount semeru east java indonesia with emphasis on lahars mt semeru the highest mountain in java 3 676 m is one of the few persistently active composite volcanoes on earth with a plain supporting about 1 million people we present the geology of the edifice review its historical eruptive activity and assess hazards posed by the current activity highlighting the lahar threat the composite andesite cone of semeru results from the growth of two edifices the mahameru old semeru and the seloko young semeru on the se flank of the summit cone a n130 trending scar branched on the active jonggring seloko vent is the current pathway for rockslides and pyroclastic flows produced by dome growth the eruptive activity recorded since 1818 shows three styles 1 the persistent vulcanian and phreatomagmatic regime consists of short lived eruption columns several times a day 2 increase in activity every 5 to 7 years produces several kilometer high eruption columns ballistic bombs and thick tephra fall around the vent and ash fall 40 km downwind dome extrusion in the vent and subsequent collapses produce block and ash flows that travel toward the se as far as 11 km from the summit and 3 flank lava flows erupted on the lower se and e flanks in 1895 and in 1941 1942 pyroclastic flows recur every 5 years on average while large scale lahars exceeding 5 million m3 each have occurred at least five times since 1884 lumajang a city home to 85 000 people located 35 km e of the summit was devastated by lahars in 1909 in 2000 the catchment of the curah lengkong river on the ese flank shows an annual sediment yield of 2 7 105 m3 km 2 and a denudation rate of 4 105 t km 2 yr 1 comparable with values reported at other active composite cones in wet environment unlike catchments affected by high magnitude eruptions sediment yield at mt semeru however does not decline drastically within the first post eruption years this is due to the daily supply of pyroclastic debris shed over the summit cone which is remobilised by runoff during the rainy season three hazard prone areas are delineated at mt semeru 1 a triangle shaped area open toward the se has been frequently swept by dome collapse avalanches and pyroclastic flows 2 the s and se valleys convey tens of rain triggered lahars each year within a distance of 20 km toward the ring plain 3 valleys 25 km s se and the ring plain 35 km e toward lumajang can be affected by debris avalanches and debris flows if the steep sided summit cone fails

simple models of co2 release from metacarbonates with implications for interpretation of directions and magnitudes of fluid flow in the deep crust simple one dimensional models of coupled advection hydrodynamic surroundings can account for basic t fluid composition reaction dispersion reaction are used to investigate processes of co2 release progress relationships observed in much of the acadian orogen of from metacarbonate beds during deep crustal 8 kbar acadian new england the results provide an alternative to up t flow prograde metamorphism in new england usa two broad models scenarios that account for these relationships by large pervasive in which reaction progress is controlled by gradients in h2o co2 horizontal fluid fluxes up regional t gradients fluid composition between diverent rock types are presented in the first divusional exchange of volatiles across lithologic contacts is significant co2 generated during prograde temperature t rise is transported away from metacarbonate layers to surrounding 1 metapelitic layers which generate h2o by dehydration and or 2 key words metamorphism fluid flow flow direction carbon dioxide

automated block detection in lahars through 3 bands spectral analysis of video images abstract lahars present a particular problem for automated block detection using machine vision because their patterns and apparent sizes and shapes vary with the flow to address this difficulty we developed a simple algorithm to detect blocks in lahars at semeru volcano based on traditional rgb red green blue 25 frame per second videos the detection algorithm is based on the combination of two methods 1 a determination of blocks by color segregation and 2 objects movements detection after image processing we converted the data into a signal that emphasizes the presence of large blocks results compare very well with video images since 100 of peaks of amplitude 300 corresponded to large blocks traveling down the channel this method ultimately aims at contributing to lahars automatic detection systems where little funding is available since it only requires a traditional camera and a computer

a method for assessing regional debris flow risk an application in zhaotong of yunnan province sw china based on the definitions of the united nations the assessment of risk involves the evaluation of both hazard and vulnerability this forms the basis of a generalized assessment model of debris flow risk hazard is a measure of the threatening degree of an extreme event and is expressed theoretically as a function of event magnitude and frequency of occurrence mathematically it is the definite integral area under the magnitude frequency curve based on the need for a model applicable in regions that lack data a new method that incorporates theoretical concepts with empirical analysis is presented to calculate the regional hazardousness of debris flows debris flow hazard can be estimated from gully density mean annual rainfall and percentage of cultivated land on steep slope vulnerability is defined as the potential total maximum losses due to a potential damaging phenomenon for a specified area and during a reference period on a regional scale it is dependent on the fixed assets gross domestic product land resources and population density as well as age education and wealth of the inhabitants a nonlinear power function model to compute the vulnerability degree is presented an application of the proposed method to zhaotong prefecture of yunnan province sw china provides high accuracy and reasonable risk estimates the highest risk of debris flow is in zhaotong county with a value of 0 48 the lowest risk of debris flow is in yanjin county with a value of 0 16 the other counties have debris flow risks ranging from 0 22 to 0 46 this provides an approach for assessing the regional debris flow risk and a basis for the formulation of a regional risk management policy in zhaotong prefecture

high spatial resolution imagery helps map deposits of the large vei 4 2010 merapi volcano eruption and their impact the 26 october 23 november 2010 eruption is merapi s largest event vei 4 over the past 140 years we used high spatial resolution hsr imagery from geoeye pleiades ikonos and spot5 satellites to assess the extent and effects of the pyroclastic density currents pdcs and subsequent lahars we have tracked the geomorphic and structural fracturing changes of merapi s summit crater and dome between 2008 and 2012 the 4 september 2011 geoeye image shows that due to the explosive eruption the summit area lost about 10 106 m3 the eruption enlarged the sse trending gendol breach to be 1 3 0 3 0 2 km the 2010 tephra and pdc deposits covered about 26 km2 in the two catchments of gendol and opak rivers on merapi s south flank i e 60 75 of the total pdc deposit area with a total bulk volume of 45 106 m3 the tephra fall deposit covered an area of about 1300 km2 with a range in volume of 18 21 106 m3 supervised and object oriented classification on hsr imagery enables us to map in detail the pdc deposits across the gendol opak catchment we delineated 16 spectrally and or texturally distinct units of pdc deposits and compared them with previously published results they encompass high energy surge deposits within ca 8 km of the summit valley confined pdc deposits channeled as far as 16 5 km in the gendol river and widespread overbank pdc with ash cloud surge deposits on valley margins

slope stability models for rainfall induced lahars during long lasting eruptions abstract in this study we analyse the spatial distribution of potential lahar sources during long lasting eruptions using two slope stability models shalstab and trigrs the analysis is based on observed deposit grain size and thickness rainfall data and slope angle of the lahar events in the area surrounding the cordon caulle volcano chile that occurred during the 2011 eruption the main phase of the eruption 4 7 june was characterized by eruptive plumes from 7 to 11 km high which dispersed most of the tephra eastward toward argentina with a total estimated volume of about 1 km3 tephra fallout blanketed the region from ese to ene of the volcano with the thickness of the tephra fallout layers between approximately 1 m 15 km from vent and 0 06 m 240 km from the vent on 10 june 2011 a major lahar occurred close to the argentina chile border that reached the national road 231 28 km from the vent three field campaigns were undertaken to collect samples and data from tephra fallout deposits and triggering mechanisms in the lahar source area model input parameters were obtained from geotechnical tests and field measurements several metrics were used for model evaluation and best fit to the data were obtained for simulations considering non cohesive ash layers for shalstab and a cohesion of 0 5 kpa for trigrs both models are sensitive to the physical properties of the tephra fallout deposit and the hydraulic and materiel strength properties of the study area they both also show good agreement with field data but provide different information trigrs provides an estimate of the timing based on a storm event and location of a potentially unstable area while shalstab simulations result in landslide susceptibility classes based on critical rainfall value these outcomes provide fundamental insights into lahar triggering during long lasting volcanic eruptions and are crucial to the compilation of lahar hazard maps and emergency management plans in the south andes volcanic region

slope instability induced by volcano tectonics as an additional source of hazard in active volcanic areas the case of ischia island italy ischia is an active volcanic island in the gulf of naples whose history has been dominated by a caldera forming eruption ca 55 ka and resurgence phenomena that have affected the caldera floor and generated a net uplift of about 900 m since 33 ka the results of new geomorphological stratigraphical and textural investigations of the products of gravitational movements triggered by volcano tectonic events have been combined with the information arising from a reinterpretation of historical chronicles on natural phenomena such as earthquakes ground deformation gravitational movements and volcanic eruptions the combined interpretation of all these data shows that gravitational movements coeval to volcanic activity and uplift events related to the long lasting resurgence have affected the highly fractured marginal portions of the most uplifted mt epomeo blocks such movements mostly occurring since 3 ka include debris avalanches large debris flows lahars smaller mass movements rock falls slumps debris and rock slides and small debris flows and deep seated gravitational slope deformation the occurrence of submarine deposits linked with subaerial deposits of the most voluminous mass movements clearly shows that the debris avalanches impacted on the sea the obtained results corroborate the hypothesis that the behaviour of the ischia volcano is based on an intimate interplay among magmatism resurgence dynamics fault generation seismicity slope oversteepening and instability and eruptions they also highlight that volcano tectonically triggered mass movements are a potentially hazardous phenomena that have to be taken into account in any attempt to assess volcanic and related hazards at ischia furthermore the largest mass movements could also flow into the sea generating tsunami waves that could impact on the island s coast as well as on the neighbouring and densely inhabited coast of the neapolitan area

geomorphological effects of the 1840 ahora gorge catastrophe on mount ararat eastern turkey abstract ahora gorge is a 400 m deep canyon located along the north eastern flank of mt ararat turkey a compound volcanic complex covered by an ice cap in the past several diarists and scientific authors reported a calamitous event on july 2 1840 when a landslide triggered by a volcanic eruption and or an earthquake obliterated several villages located at the foot of the volcano the reasons and effects of this ahora gorge catastrophe agc event have been obscure and ambiguous to reappraise the 1840 catastrophe and the geomorphic evolution of the ahora gorge we used high resolution satellite images remote sensing thermal data supplemented by observations collected during two field surveys according to our interpretation an earthquake in 1840 triggered an abrupt volcanic eruption which caused the consequent rapid melting of glacial ice and mountain snow this event produced significant mud and ice flow along the ahora gorge that inundated the villages downslope the flooding which we interpret as a lahar deposited a wide alluvial fan at the foot of the volcano today an elongated landform present within the ahora gorge has alternately been interpreted as a landslide deposit our multi data integrated analysis and ground based observations demonstrate that this feature is an unmapped glacier the shape of the landform coupled with aster thermal satellite data and ground based observations reveal that a debris covered glacier dcg formed soon after the catastrophic lahar our discovery of the ahora gorge glacier in context of a reappraisal of the ahora gorge catastrophe demonstrates the contribution of glaciers in shaping the landscape near ice capped volcanoes moreover our data underscore the importance of being more aware of the potential future geo hazards posed by mount ararat particularly where glaciers are still present along several valleys and seismically induced lahar events might occur

a comparative geochemical study of pelitic schists and metamorphosed carbonate rocks from south central maine usa whole rock major element chemical analyses of progressively metamorphosed impure carbonate rocks and pelitic schists collected from the same metamorphic terrain reveal similarities and differences in the chemical response of these rock types to the metamorphic event relative to a constant aluminum reference frame both schist and carbonate exhibit no detectable change in their contents of fe mg ti si and ca with change in metamorphic grade carbonate rocks become progressively depleted in k and na with increasing grade of metamorphism while schists exhibit no statistically significant change in their contents of k and na both rock types become depleted in volatiles principally co2 and h2o with increasing grade

the anatomy of a pyroclastic density current the 10 july 2015 event at volcan de colima mexico pyroclastic density currents pdcs represent one of the most dangerous phenomena occurring in explosive volcanic eruptions and any advance in the physical understanding of their transport and sedimentation processes can contribute to improving their hazard assessment the 10 11 july 2015 eruption at volcan de colima provided a unique opportunity to better understand the internal behaviour of pdcs based on seismic monitoring data on 10 july 2015 the summit dome collapsed producing concentrated pdcs that filled the main channel of the montegrande ravine a lahar monitoring station installed 6 km from the volcano summit recorded a pdc before being completely destroyed real time data acquisition from a camcorder and a geophone that were part of the station along with field observations and grain size data of the pyroclastic deposits are used here to interpret the internal flow structure and time variant transport dynamics of low volume valley confined concentrated pdcs the pdc that reached the monitoring station moved at a velocity of 7 m s and filled a 12 m deep channel the outcrops show massive block and ash flow deposits with trains of coarse clasts in the middle and towards the top of the depositional units the seismic record gathered with the geophone was analysed for the time window when the flow travelled past the sensor the geophone record was also compared with the recordings of a broadband seismic station located nearby two main frequency ranges were recognised which could be correlated with the basal frictional forces exerted by the flow on the channel bed 10 20 hz and a collisional regime 20 40 hz interpreted to be associated with a clast segregation process i e kinematic squeezing this latter regime promoted the upward migration of large blocks which subsequently deviated towards the margin of the flow where they interacted with the sidewall of the main channel the energy calculated for both seismic components shows that the collisional regime represents 30 of the total energy including an important sidewall stress component these results gathered directly from a moving flow contribute to unravelling the internal behaviour of concentrated pdcs providing information on energy partitioning and particle particle interactions this confirms previous assumptions inferred from field observations and tested by analogue or numerical modelling the nature of the contact between grains is still poorly documented in natural pdcs and there is still much uncertainty and discussion about dominant forces in such currents data reported here may thus be useful to better constrain the physics of low volume valley confined concentrated pdcs and our findings need to be considered in theoretical models in parallel this study shows how geophones can provide a cheap alternative for pdc detection

the geological evolution of merapi volcano central java indonesia merapi is an almost persistently active basalt to basaltic andesite volcanic complex in central java indonesia and often referred to as the type volcano for small volume pyroclastic flows generated by gravitational lava dome failures merapi type nuees ardentes stratigraphic field data published and new radiocarbon ages in conjunction with a new set of 40k 40ar and 40ar 39ar ages and whole rock geochemical data allow a reassessment of the geological and geochemical evolution of the volcanic complex an adapted version of the published geological map of merapi wirakusumah et al 1989 peta geologi gunungapi merapi jawa tengah geologic map of merapi volcano central java 1 50 000 is presented in which eight main volcano stratigraphic units are distinguished linked to three main evolutionary stages of the volcanic complex proto merapi old merapi and new merapi construction of the merapi volcanic complex began after 170 ka the two earliest proto merapi volcanic edifices gunung bibi 109 60 ka a small basaltic andesite volcanic structure on merapi s north east flank and gunung turgo and gunung plawangan 138 3 ka 135 3 ka two basaltic hills in the southern sector of the volcano predate the merapi cone sensu stricto old merapi started to grow at 30 ka building a stratovolcano of basaltic andesite lavas and intercalated pyroclastic rocks this older merapi edifice was destroyed by one or possibly several flank failures the latest of which occurred after 4 8 1 5 ka and marks the end of the old merapi stage the construction of the recent merapi cone new merapi began afterwards mostly basaltic andesite pyroclastic and epiclastic deposits of both old and new merapi 11 792 90 14c years bp cover the lower flanks of the edifice a shift from medium k to high k character of the eruptive products occurred at 1 900 14c years bp with all younger products having high k affinity the radiocarbon record points towards an almost continuous activity of merapi since this time with periods of high eruption frequency interrupted by shorter intervals of apparently lower eruption rates which is reflected in the geochemical composition of the eruptive products the holocene stratigraphic record reveals that fountain collapse pyroclastic flows are a common phenomenon at merapi the distribution and run out distances of these flows have frequently exceeded those of the classic merapi type nuees ardentes of the recent activity widespread pumiceous fallout deposits testify the occurrence of moderate to large subplinian eruptions vei 3 4 during the mid to late holocene vei 4 eruptions as identified in the stratigraphic record are an order of magnitude larger than any recorded historical eruption of merapi except for the 1872 ad and possibly the october november 2010 events both types of eruptive and volcanic phenomena require careful consideration in long term hazard assessment at merapi

cumulate hornblendite enclaves in diorite porphyrite intrusions from the shuangyashan northeast china and implications for the transition from lower crust to upper mantle in subduction setting a suite of hornblendite amphibole proportion 90 enclaves were found in late cretaceous diorite porphyrite stocks intruding the lower cretaceous coal strata around the shuangyashan city eastern heilongjiang province northeast china the enclaves have similar mineralogy and may be divided into clinopyroxene bearing and clinopyroxene free hornblendites and both of them show cumulate textures pargasitic amphibole and clinopyroxene are cumulus and anorthitic plagioclase is intercumulus the accumulation might have occurred in the magma chamber minor clinopyroxene enclosed in amphibole was earlier crystallized followed by a large amount of amphibole and the residual melt trapped between cumulate crystals finally formed the intercumulus plagioclase probably such a crystallization process could produce layered cumulates lower part is dominated by clinopyroxene bearing hornblendite and upper part is composed of clinopyroxene free one the enclaves have similar geochemistry and imply a hydrous basaltic parental magma enriched rb ba th and other large ion lithophile elements the generation of the parental magma might be related to the subduction of paleo pacific plate beneath eastern eurasian continent at that time estimated crystallization pressure p wave velocity and density for the cumulate hornblendite enclaves are generally in agreement with the values of the local crust mantle transition zone suggesting that these cumulates may have the origin in the transition from the lower crust to upper mantle in arc and back arc settings

fluid flow and chemical reaction kinetics in metamorphic systems the treatment and effects of chemical reaction kinetics during metamorphism are developed along with the incorporation of fluid flow diffusion and thermal evolution the interplay of fluid flow and surface reaction rates the distinction between steady state and equilibrium and the possible overstepping of metamorphic reactions are discussed using a simple analytic model this model serves as an introduction to the second part of the paper which develops a reaction model that solves the coupled temperature fluid flow chemical composition differential equations relevant to metamorphic processes consideration of stable isotopic evidence requires that such a kinetic model be considered for the chemical evolution of a metamorphic aureole a general numerical scheme is discussed to handle the solution of the model the results of this kinetic model allow us to reach several important conclusions regarding the factors controlling the chemical evolution of mineral assemblages during a metamorphic event 41 refs 19 figs 5 tabs

short paper a standardized model for tethyan tertiary carbonate ramps low latitude carbonates in massive and clinoform bedded sheets termed ramps occur throughout the tertiary tethyan realm and are characterized by recurring biofacies usually including large foraminifera rhodolithic algae coralgal patch reef and gastropod dominated sequences all can be interpreted broadly within a standardized tertiary carbonate ramp model biota can be used to define precise palaeobathymetric zones which have a predictive utility in palaeoenvironmental modelling especially where data are limited the carbonate ramp model of earlier authors has been elaborated by read 1982 and ramp formation occurs mostly in passive margin and extensional tectonic settings ramps are characterized by slope gradients of less than 1 degree and once established are conservative to change much use has been made of the ramp model for palaeozoic and mesozoic lithofacies modelling in contrast published work on cenozoic ramps is limited however tethyan ramps are particularly widespread and extend tens to hundreds of kilometres along strike and occupy tens of kilometres of slope many studies have dealt with cenozoic ramp associations and sequences e g pedley 1983 reiss hottinger 1984 purser 1973 and have demonstrated the diversity of biotal and sediment detail but without ascribing them to a ramp model biota were quick to adapt to the tertiary environments left vacant after the k t boundary extinction events new genera of foraminifera mollusca bryozoa and echinoder mata rapidly replaced the extinct forms in bursts of innovative opportunism codiacean algae rhodophyta and marine angiosperms were equally adaptive colonizers of the carbonate platforms novel biofacies associations were derived from

insights into lahar deposition processes in the curah lengkong semeru volcano indonesia using photogrammetry based geospatial analysis near surface geophysics and cfd modelling abstract semeru volcano is an active stratovolcano located in east java indonesia where historic lava flows occasional pyroclastic flows and vulcanian explosions on average every 5 min to 15 min generate a stock of material that is remobilized by lahars mostly occurring during the rainy season between october and march every year several lahars flow down the curah lengkong valley on the south east flank of the volcano where numerous lahar studies have been conducted in the present contribution the objective was to study the spatial distribution of boulder size clasts and try to understand how this distribution relates to the valley morphology and to the dynamic and deposition dynamic of lahars to achieve this objective the method relies on a combination of 1 aerial photogrammetry derived geospatial data on boulders distribution 2 ground penetrating radar data collected along a 2 km series of transects and 3 a cfd model of flow to analyse the results from the deposits results show that

mid crustal metasomatic reaction veins ina spinel peridotite in central dronning maud land east antarctica rare metresized lenses of spinel peridotite are enclosed in high grade metamorphic rocks the rocks experienced a medium p granulite facies metamorphism at 575ma and a low p amphibolite facies overprint at 530ma the latter is probably related to extensive granitoid magmatism between 530 and 500ma which produced large volumes about half of the outcrops today of granitic to syenitic rocks as well as abundant k feldspar quartz pegmatites one of the spinel peridotite lenses in the schirmacher oasis of central dronning maud land is crosscut by several small up to 10 cm wide veins with a characteristic zoned sequence of mineral assemblages which was formed by reaction of a hydrous sio2 saturated fluid or pegmatitic melt with the peridotite the zoned sequence consists of the following mineral assemblages from the centre of the vein towards the outer margin zone 0 plagioclase quartz zone 1 green biotite intergrown with zircon clinoamphibole zone 2 cummingtonite dark brown biotite intergrown with rutile clinoamphibole zone 3 cummingtonite light brown biotite spinel zone 4 olivine orthopyroxene spinel clinopyroxene unaltered peridotite this sequence was investigated with respect to its conditions of formation modal mineralogy mineral chemistry fluid inclusions and oxygen and hydrogen isotope compositions of selected minerals based on the stability of cummingtonite and on equilibrium calculations in the mgo sio2 h2o system and on quartz biotite oxygen isotope thermometry the reaction vein formed at 650 c which is in accord with typical pegmatite crystallization temperatures the pegmatite of zone 0 is interpreted to have formed in an open fissure whereas on textural grounds zone 3 replaces former peridotite on the basis of mass balance constraints the boundary between zones 1 and 2 is interpreted to approximately represent the former boundary between peridotite and the open fissure before reaction oxygen isotope systematics show that the infiltrating fluid had an isotopic composition of 9 101 2 smow all minerals of the reaction vein with the exception of the inherited spinel and olivine in the adjacent peridotite are in equilibrium with such a fluid spinel in the peridotite is depleted in o compared with coexisting olivine which suggests isotopic disequilibrium spinel in zone 3 has a distinctly different isotopic composition compared with that in the peridotite apparently approaching but not reaching equilibrium the combination of mineral chemistry and mass balance constraints of the modal mineralogy constrains the volume change during metasomatism and the direction of elemental diffusion it is indicated that mg cr and ni always diffused towards the vein whereas si al k na h2o and possibly fe diffused into the peridotite

modeling the october 2005 lahars at panabaj guatemala an extreme rainfall event in october of 2005 triggered two deadly lahars on the flanks of toliman volcano guatemala that caused many fatalities in the village of panabaj we mapped the deposits of these lahars then developed computer simulations of the lahars using the geologic data and compared simulated area inundated by the flows to mapped area inundated computer simulation of the two lahars was dramatically improved after calibration with geological data specifically detailed field measurements of flow inundation area flow thickness flow direction and velocity estimates collected after lahar emplacement were used to calibrate the rheological input parameters for the models including deposit volume yield strength sediment and water concentrations and manning roughness coefficients simulations of the two lahars with volumes of 240 200 55 400 and 126 000 29 000 m3 using the flo 2d computer program produced models of lahar runout within 3 of measured runouts and produced reasonable estimates of flow thickness and velocity along the lengths of the simulated flows we compare areas inundated using the jaccard fit model sensitivity and model precision metrics all related to bayes theorem these metrics show that false negatives areas inundated by the observed lahar where not simulated and false positives areas not inundated by the observed lahar where inundation was simulated are reduced using a model calibrated by rheology the metrics offer a procedure for tuning model performance that will enhance model accuracy and make numerical models a more robust tool for natural hazard reduction

automatic classification of dome instabilities based on doppler radar measurements at merapi volcano indonesia part i summary in this paper we analyse a 3 yr long time series of activity at merapi volcano indonesia which was recorded using a doppler radar system between november 2001 and july 2004 about 57 000 events associated with dome instabilities have been recorded by the radar system because of the huge amount of data an automatic classification system has been developed which identifies different types of instabilities at the lava dome i e sliding material gravitational break offs and explosive outbursts as well as rainfall comparing the record of detected instabilities to rockfall measurements deduced from the seismic network of the volcanological technology research center vtrc we are able to demonstrate the high potential of doppler radar measurements for monitoring of dome activity when aligned to the most active area at the dome the radar detects significantly more events than the seismic system in combination with seismic measurements the doppler radar allows for identifying changes in the location of the most active area at the dome this is particularly helpful since the dome of merapi is covered by clouds about 50 per cent of the time additionally the radar data can help to distinguish between rockfalls and multiphase events in the seismic measurements the different types of instabilities have been analysed for their occurrence frequency in terms of size volume and mean velocity significant temporal changes in the relative occurrence frequencies or the characteristic properties of the different types of instabilities have not been observed however during the period of fastest activity decrease explosive instability events with a gravitational precursor decreased faster than events starting explosively because the radar system is able to observe rainfall the data has been analysed for a link between rain and dome activity throughout the observation period no such link could be found however this might be due to the fact that the activity has been almost continuously decreasing

posteruption suspended sediment transport at mount st helens decadal scale relationships with landscape adjustments and river discharges received 11 december 2002 revised 30 september 2003 accepted 18 november 2003 published 17 january 2004 1 widespread landscape disturbance by the cataclysmic 1980 eruption of mount st helens abruptly increased sediment supply in surrounding watersheds the magnitude and duration of the redistribution of sediment deposited by the eruption as well as decades to centuries old sediment remobilized from storage have varied chiefly with the style of disturbance posteruption suspended sediment transport has been greater and more persistent from zones of channel disturbance than from zones of hillslope disturbance despite the severe landscape disturbances caused by the eruption relationships between discharge magnitudes and frequencies and suspended sediment transport have been remarkably consistent discharges smaller than mean annual flows generally have transported 5 but locally 15 of the annual suspended sediment loads and infrequent p 0 01 large floods have transported as much as 50 of the annual suspended sediment loads in a single day however moderate magnitude discharges those greater than mean annual flows but less than 2 year floods have transported the greatest amounts of sediment from all disturbance zones such discharges have transported on average 60 to 95 of the annual suspended sediment loads usually within cumulative periods of 1 3 weeks each year although small magnitude and largemagnitude discharges have locally and episodically transported considerable amounts of suspended sediment there has not been any notable change in the overall nature of the effective discharges moderate magnitude flows have been the predominant discharges responsible for transporting the majority of suspended sediment during 20 years of posteruption landscape adjustment index terms 1824 hydrology geomorphology 1625 1815 hydrology erosion and sedimentation 1860 hydrology runoff and streamflow keywords sediment yield suspended sediment transport mount st helens erosion volcano geomorphology

reply to the discussion by peter a gatt on facies analysis and palaeoenvironmental interpretation of the late oligocene attard member lower coralline limestone formation malta by brandano et al 2009 sedimentology 56 1138 1158

multi scale topographic analysis of merbabu and merapi volcanoes using wavelet decomposition with the increasing availability of data geo sciences have experienced deep changes in handling and processing it one of the presently explored research directions concerns the systematic decomposition and understanding of topographical features without the subjective interactions of humans this can eventually lead to fully automated algorithms for topographic analysis and understanding this paper aims at being a contribution to this broad research area for the specific cases of stratovolcanoes whose general geometry are very similar to a perfect cone more specifically this paper addresses two issues 1 is it possible to separate erosion features local variations from structural features large variations on stratovolcanoes through mathematical expression 2 can information on volcanic activity intensity age etc be retrieved from a topographic analysis the study has been conducted from two volcanoes in central java indonesia the merapi and the merbabu the dem of these volcanoes has been sampled using concentric circles with a radius ranging from 500 to 5 000 m horizontal distance to the summit the data conversion and sampling was performed in arcmap while the data analysis was carried out with matlab using discrete meyer wavelet decomposition results provide an insight on large scale topographic variations long wave wavelet that have been separated from rapidly varying topographic features such as lahar channels short wave wavelets observations proved that flanks where the most recent volcanic activity occur like at merapi volcano on the s se flank present a very low variability of long wave variations whereas short wave variations are important the author argues that this feature is due to highly erosive lahars that dig the valleys combined with a recent production of material and volcanic growth keeping the overall structure regular flanks with lesser activity are characterized at the two volcanoes by important long wave variations most certainly due to long term differential erosion and different level of short waves variations comparing the two volcanoes results show that the valleys of merapi and merbabu volcanoes are deeply incised indicating recent periods of high activity with reworkable material eroded by lahars and other channels deepening processes the topography of the summit area of merapi volcano is smoother than at merbabu volcano where deep erosion features extend up to the summit area this difference is most certainly due by the material production at the summit of merapi volcano developing such classification is important for automated mapping and computer recognition of volcanic past activities and their impacts on landscapes it is the based for the development of decision trees that assist computer assisted and automated computer vision

reductive deposition of graphite at lithological margins in east central vermont a sr c and o isotope study o sr and c isotopes from east central vermont are used to provide information on the timing and volume of metamorphic fluid flow the results are then used to assess the evidence for redox transformations between c species oxygen profiles are homogenised on a metre scale comparison with sr isotopes suggest that o alteration may have occurred over a significantly larger timescale than that of sr possibly because o was modified during dewatering and diagenesis in addition to the high temperature alteration recorded by strontium sr isotope distributions are consistent with cross layer fluid fluxes of 104 106 moles m 2 absolute values depend on the sr fluid rock distribution coefficient which is poorly known however reaction progress constraints suggest that fluxes were towards the lower end of this range high 13c values observed at lithological boundaries cannot be explained by volume loss or closed system processes and are taken to indicate reductive precipitation of graphite as a result of mixing between co2 and ch4 bearing fluids mass balance calculations indicate that redox reactions occurring under metamorphic conditions convert a minimum of 10 of the co2 released from limestones into graphite thus providing a potentially important control on the average residence time of c within the crust with implications for c cycling models

assessing metasomatic mass and volume changes using the bootstrap with application to deep crustal hydrothermal alteration of marble a statistically rigorous approach for determining likely errors on estimates of mass and volume change in metasomatic systems is presented and then used to assess mass transfer resulting from hydrothermal alteration of marble during regional metamorphism analysis of metasomatic effects using standard statistical methods designed for unconstrained univariant data often fails to provide useful results for several important reasons 1 the concentration of any constituent in a composition is constrained to be between 0 and 100 wt percent 2 the sum of the concentrations of all constituents must be 100 wt percent the closure constraint compositions are multivariate and provide information only about the relative proportions of constituents 3 the maximum possible mass or volume loss is 100 percent 100 corresponds to complete mass or volume loss 4 rock bulk density must be greater than 0 g cm super 3 5 the underlying probability distributions for mass and volume changes are commonly non normal to address these issues we use statistical procedures recently developed to treat the special properties of compositional data including closure and the bootstrap method to compute accurate confidence intervals for assessing how far in error best estimates of mass and volume change are likely to be the bootstrap deals effectively with non normality and constraints 1 3 and 4 we apply our approach to gain a better understanding of synmetamorphic acadian orogeny hydrothermal alteration of upper greenschist facies and amphibolite facies marble beds of the wepawaug schist connecticut the marbles lost significant amounts of volatiles dominantly co 2 and h 2 o si ti k rb sr and ba best estimates of total mass and volume change are 27 and 32 percent respectively the bulk of the lost mass was volatiles approximately 140 g kg super 1 sio 2 approximately 60 g kg super 1 and k 2 o approximately 15 g kg super 1 numbers are g lost per kg of parent rock volatile loss was probably regional in scope loss of si ti k rb sr and ba occurred over minimum length scales on the order of typical hand sample dimensions maximum length scales remain to be determined the fortran 77 computer code that performs the calculations described herein is available from the senior author

self potential and ground temperature at merapi volcano prior to its crisis in the rainy season of 2000 2001 abstract rainwater infiltration into the active lava dome of merapi volcano central java has often been suggested as a triggering mechanism for partial dome collapse and subsequent eruptive behavior however the phenomenon has not been systematically investigated we use a multi parametric approach to study the interaction of the hydrologic and magmatic system near the lava dome prior to its crisis in early 2001 we describe the hardware concept for a continuous monitoring system for self potentials u sp and ground temperature t installed in august 2000 at the solfatara woro only 150 m from the active lava dome relating the data from this station to measurements of rainfall air pressure solfatara temperature and seismicity several effects can be distinguished a a long term correlation is observed between electrode temperature difference and sp with estimated coupling coefficients of 2 1 0 5 mv c b after individual rainfall events u t signatures show a typical pattern of positive charge accumulation at the hot electrodes near the fumarolic vents c an exceptional anti correlation between u and t is observed in january 2001 during a period of rapid dome growth prior to the collapse and eruptive crisis d wavelet analysis of sp reveals the sporadic occurrence of periodic fluctuations with a clear 12 h s2 component because of their amplitude of up to 100 mv km and their periodicity s2 but not 24 h or lunar 12 h 25 min these fluctuations are unlikely to be caused by natural magnetic field variation or by earth tides instead they do seem correlated but not in phase with atmospheric pressure changes we discuss effects a d in the framework of source mechanisms related to water lava interactions

local origin of high pressure vein material in eclogite facies rocks of the zermatt saas zone switzerland prograde dehydration reactions within metabasalts at the blueschist eclogite facies transition produce kyanite veins usually with quartz sometimes with omphacite or chloritoid of up to several meters length and 20 cm width bulk rock analyses show clear depletion haloes for al2o3 and sio2 near the veins mass balance calculations support the suggestion that the vein material must have been derived from the immediate surroundings these veins are interpreted as local segregation phenom ena and not as fluid dehydration channels of the eo alpine subduction zone calcula tions have been performed for a stagnant vein formation model that considers the rate of the dehydration reactions k responsible for providing the h2o for al and si transport and the rate of diffusion d of these from wall rock to growing vein the model is satisfied for quite a wide range of values for k d and upper limits on the duration of diffusional vein formation of about 1 ma are indicated

scales of disequilibrium and rates of equilibration during metamorphism mounting evidence suggests that partial disequilibrium meaning disequilibrium for some elements but not for others may be a common but rarely detected phenomenon during metamorphic mineral growth even in ordinary prograde reactions that progress to completion detailed examination of compositional variations in garnet crystals over a range of metamorphic grade suggests distinctly different scales of equilibration for common elements with strong temperature dependence under lower greenschist facies conditions fe and mg may equilibrate at hand sample scale whereas mn and ca may not equilibrate even at millimeter scale although mn may achieve hand sample scale equilibration under upper greenschist facies conditions ca and many trivalent cations e g rees may not do so until temperatures exceed those of the middle amphibolite facies even in the lower granulite facies some elements e g y yb show indications of disequilibrium at sub centimeter scales during garnet growth analysis and numerical modeling of undisputed disequilibrium textures demonstrate that the most common impediment to equilibration during metamorphism is the sluggishness of intergranular diffusion the same mechanism known to govern porphyroblast crystallization in many metamorphic environments despite this importance to petrology few quantitative determinations exist of inter granular diffusion rates under metamorphic conditions using numerical simulations of coupled intergranular and intracrystalline diffusion processes in coronal textures around partially resorbed garnet crystals from the llano uplift u s a a very precise and relatively accurate estimate is obtained for the rate of intergranular diffusion of al in fluid undersaturated systems this result and an earlier estimate for fluid saturated systems provide bracketing values for al diffusivity during metamorphism

build up and depositional dynamics of an arc front volcaniclastic complex the miocene tepoztlan formation transmexican volcanic belt central mexico volcanic terrains such as magmatic arcs are thought to display the most complex surface environments on earth ancient volcaniclastics are notoriously difficult to interpret as they describe the interplay between a single or several volcanoes and the environment the early miocene tepoztlan formation at the southern edge of the transmexican volcanic belt belongs to the few remnants of this ancestral magmatic arc and therefore is thought to represent an example of the initial phase of evolution of the transmexican volcanic belt based on geological mapping detailed logging of lithostratigraphic sections palaeocurrent data of sedimentary features and anisotropy of magnetic susceptibility mapping of two dimensional panels from outcrop to field scale and geochronological data in an area of ca 1000 km 2 three periods in the evolution of the tepoztlan formation were distinguished which lasted around 4 myr and are representative of a volcanic cycle edifice growth phases followed by collapse in a magmatic arc setting the volcaniclastic sediments accumulated in proximal to medial distances on partly coalescing aprons similar to volcanic ring plains around at least three different stratovolcanoes these volcanoes resulted from various eruptions separated by repose periods during the first phase of the evolution of the tepoztlan formation 22ae 8t o 22 ae2 ma deposition was dominated by fluvial sediments in a braided river setting pyroclastic material from small andesitic dacitic composite volcanoes in the near vicinity was mostly eroded and reworked by fluvial processes resulting in sediments ranging from cross bedded sand to an aggradational series of river gravels the second phase 22ae 2t o 21 ae3 ma was characterized by periods of strong volcanic activity resulting in voluminous accumulations of lava and tuff which temporarily overloaded and buried the original fluvial system with its detritus continuous build up of at least three major volcanic centres further accentuated the topography and in the third phase 21ae 3t o 18 ae8 ma mass flow processes represented by an increase of debris flow deposits became dominant marking a period of edifice destruction and flank failures

developing building damage scales for lahars application to merapi volcano indonesia lahar damage to buildings can include burial by sediment and or failure of walls infiltration into the building and subsequent damage to contents the extent to which a building is damaged will be dictated by the dynamic characteristics of the lahar i e the velocity depth sediment concentration and grain size as well as the structural characteristics and setting of the building in question the focus of this paper is on quantifying how buildings may respond to impact by lahar we consider the potential for lahar damage to buildings on merapi volcano indonesia as a result of the voluminous deposits produced during the large vei 4 eruption in 2010 a building damage scale has been developed that categorises likely lahar damage levels and through theoretical calculations of expected building resistance to impact approximate ranges of impact pressures we found that most weak masonry buildings on merapi would be destroyed by dilute lahars with relatively low velocities ca 3 m s and pressures ca 5 kpa however the majority of stronger rubble stone buildings may be expected to withstand higher velocities to 6 m s and pressures to 20 kpa we applied this preliminary damage scale to a large lahar in the putih river on 9 january 2011 which inundated and caused extensive building damage in the village of gempol 16 km southwest of merapi the scale was applied remotely through the use of public satellite images and through field studies to categorise damage and estimate impact pressures and velocities within the village results were compared with those calculated independently from manning s calculations for flow velocity and depth within gempol village using an estimate of flow velocity at one upstream site as input the results of this calculation showed reasonable agreement with an average channel velocity derived from travel time observations the calculated distribution of flow velocities across the area of damaged buildings was consistent with building damage as classified by the new damage scale the complementary results even given the basic nature of the tools and data suggest that the damage scale provides a valid representation of the failure mode that is consistent with estimates of the flow conditions the use of open source simplified tools and data in producing these consistent findings is very promising

probabilistic analysis of rain triggered lahar initiation at tungurahua volcano semi continuous production of pyroclastic material by intermittent strombolian vulcanian and sub plinian eruptions at volcan tungurahua ecuador has created a persistent rain triggered lahar hazard during the 1999 present eruptive episode lahars threaten the city of banos which lies approximately 8 km from the crater as well as other villages and vital infrastructure situated in close proximity to the dense radial drainage network of the volcano this study analyses the initiation of rain triggered lahars and the influence of antecedent rainfall on this process in two northern instrumented drainages la pampa and the vazcun analysis of lahar triggering rainfall intensity and duration between march 2012 and june 2013 yields a power law relationship whilst receiver operating characteristic roc analysis indicates that peak rainfall intensity 10 30 and 60 min is the most effective single predictor of lahar occurrence the probability of a lahar exceeding a pre defined magnitude increases with peak rainfall intensity incorporation of antecedent rainfall 24 h and 3 5 and 7 days as a secondary variable significantly impacts lahar probabilities particularly during moderate high intensity rainfall events the resultant two and three dimensional lahar probability matrices are applied to rainfall data between 1st july and 31st december 2013 with the aim of predicting lahar occurrence composite lahar indicators comprised from the mean lahar probability estimates of individual matrices are shown to perform this task most effectively roc analysis indicates a probability 80 that these composite indicators will generate a higher estimated lahar probability for a randomly selected lahar event than a randomly selected non lahar event this method provides an average of 24 min of additional warning time compared with the current acoustic flow monitors afms used for lahar detection effectively doubling warning times for key downstream infrastructure in the two drainages ultimately this method of lahar analysis could be used to construct real time probabilistic rain triggered lahar forecasts as an aid to current lahar hazard mitigation techniques at any location with a significant rain triggered lahar hazard and a basic instrumental setup

landscape and sedimentary response to catastrophic debris avalanches western taranaki new zealand abstract catastrophic volcanic debris avalanches reshape volcanic edifices with up to half of pre collapse cone volumes being removed deposition from this debris avalanche deposit often fills and inundates the surrounding landscape and may permanently change the distribution of drainage networks on the weakly incised mt taranaki ring plain volcanic debris avalanche deposits typically form a large wedge shape in plan view over all flat lying fans following volcanic debris avalanches a period of intense re sedimentation commonly begins on ring plain areas particularly in wet or temperate climates this is exacerbated by large areas of denuded landscape ongoing instability in the scarp source region damming of river stream systems and in some cases inherent instability of the volcanic debris avalanche deposits in addition on mt taranaki the collapse of a segment of the cone by volcanic debris avalanche often generates long periods of renewed volcanism generating large volumes of juvenile tephra onto unstable and unvegetated slopes or construction of new domes with associated rock falls and block and ash flows the distal ring plain impact from these post debris avalanche conditions and processes is primarily accumulation of long run out debris flow and hyperconcentrated flow deposits with a variety of lithologies and sedimentary character common to these post debris avalanche units is evidence for high water content flows that are typically non cohesive hence sedimentary variations in these units are high in lateral and longitudinal exposure in relation to local topography the post collapse deposits flank large scale fans and hence similar lithological and chronological sequences can form on widely disparate sectors of the ring plain these deposits on mt taranaki provide a record of landscape response and ring plain evolution in three stages that divide the currently identified warea formation 1 the deposition of broad fans of material adjacent to the debris avalanche unit 2 channel formation and erosion of stage 1 deposits primarily at the contact between debris avalanche deposits and the stage 1 deposits and the refilling of these channels and 3 the development of broad tabular sheet flows on top of the debris avalanche leaving sediments between debris avalanche mounds after a volcanic debris avalanche these processes represent an ever changing and evolving hazard scape with hazard maps needing to be regularly updated to take account of which stage the sedimentary system is in