uranium series isotopes in river materials insights into the timescales of erosion and sediment transport abstract the uranium series isotope signatures of the suspended and dissolved load of rivers have emerged as an important tool for understanding the processes of erosion and chemical weathering at the scale of a watershed these signatures are a function of both time and weathering induced fractionation between the different nuclides provided appropriate models can be developed they can be used to constrain the residence time of river sediment this chronometer is triggered as the bedrock starts weathering and the inferred timescale encompasses the residence time in the weathering profile storage in temporary sediment deposits e g floodplain and transport in the river this approach has been applied to various catchments over the past five years showing that river sediments can reside in a watershed for timescales ranging from a few hundreds of years iceland to several hundreds of thousands of years lowlands of the amazon various factors control how long sediment resides in the watershed the longest residence times are observed on stable cratons unaffected by glacial cycles or more generally climate variability and human disturbance shorter residence times are observed in active orogens andes or fast eroding recently glaciated catchments iceland in several cases the residence time of suspended sediments also corresponds to the time since the last major climate change the u series isotope composition of rivers can also be used to predict the river sediment yield assuming steady state erosion is reached by comparing this estimate with the modern sediment yield obtained by multi year sediment gauging it is clear that steady state is seldom reached this can be explained by climate variability and or human disturbance steady state is reached in those catchments where sediment transport is rapid iceland or where the region has been unaffected by climate change and or human disturbance u series are thus becoming an important tool to study the dynamics of erosion

control on the emplacement of the andesite lava dome of the soufriere hills volcano montserrat by degassing induced crystallization lava solidification is controlled by two mechanisms external cooling and gas exsolution the latter inducing crystallization due to increasing liquidus temperature the andesite lava dome of the soufriere hills volcano montserrat is an extrusion dominated by crystallization caused by gas exsolution where cooling is unimportant in controlling emplacement in the magma chamber the magma has an estimated viscosity of 7 106 pa s during ascent gas exsolution caused the magma to extrude in a highly crystalline state with only 5 15 residual melt viscosities in the range 1013 1014 pa s and mechanical strength 1 mpa deformation can be heterogeneous with extrusion along shear zones rheological stiffening in the upper conduit also causes large overpressures shallow seismicity and cyclic patterns of dome extrusion gas rich porphyritic andesites tend to be the least mobile kind of lava because transition from magma into hot crystalline material was reached during ascent

contents of natural radioactive nuclides in soil in relation to their surface area concentrations of uranium series nuclides 238u 226ra 210pb thorium series nuclides 228ra 212bi and potassium in soil of a granitic belt were examined in relation to their surface area of soil clay mineral composition and the sio2 and fe contents in soil which is less weathered and has a surface area of around 10 m2 g the 238u 226ra 210pb 228ra and 40k contents increase with an increase the sio2 content related to the elemental compositions of their parents rocks in homologous soils resulting from progressive weathering the 238u 226ra 210pb and 228ra contents are found to increase with increasing surface area for an homologous soil which is free from the clay consisting of three layer units the 40k content decrease with increasing surface area however in an homologous soil which contains a clay consisting of three layer units the 40k content is not surface area dependent

petrology and geochemistry of lava and ash erupted from volcan colima mexico during 1998 2005 abstract lava n 8 and bulk ash samples n 6 erupted between july 1999 and june 2005 were investigated to extend time series compositional and textural studies of the products erupted from volcan colima since 1869 in particular we seek to evaluate the possibility that the current activity will culminate in major explosive plinian style event similar to that in 1913 lava samples continue to show relatively heterogeneous whole rock compositions with some significant mafic spikes 1999 2001 as have prevailed since 1976 groundmass sio2 contents continue trends to lower levels that have prevailed since 1961 in the direction of the still lower groundmass sio2 contents found in 1913 scoriae importantly ash samples from investigated vulcanian style explosive eruptions in 2005 are devoid of particles with micro vesiculated groundmass textures such textures characterized the 1913 scoriae signifying expansion of in situ magmatic gas as the propellant of the 1913 eruption all magmas erupted since 1913 appear to have arrived in the upper volcanic conduit system in a degassed state the small to moderate vulcanian style explosive eruptions which have been common since 1999 16 000 events have blasted ash clouds as high as 11 km a s l and sent pyroclastic flows out to distances of 5 km these eruptions do not appear to be powered by expansion of in situ magmatic gas new small lava domes have been observed in the crater prior to many explosive eruptions these plugs of degassed lava may temporarily seal the conduit and allow the build up of magmatic gases streaming upward from below ahead of rising and degassing magma in this interpretation when gas pressure exceeds the strength of the plug seal in the upper conduit an explosive vulcanian style eruption occurs alternatively these explosive eruptions may represent interactions of hot rock and groundwater phreato magmatic

endogenous growth of dacite dome at unzen volcano japan 1993 1994 a dacite dome at unzen volcano grew mainly exogenously when it was small and the effusion rate was high but endogenously when the dome became large and the effusion rate declined the endogenous dome that has grown since late 1993 shows a shape classified as pelean whereas the earlier stage had a low lava dome shape the carapace of the endogenous dome moved like the crust of a basaltic lava pillow although the dome is several hundred times larger than such pillows the surface carapace was carried from the inside of the dome where it had been produced and it thickened as it cooled the crater floor was strongly deformed by the advancing endogenous dome the movement and crater floor deformation can be compared to that of a tractor tread moving on unconsolidated ground

modelling the lava dome extruded at soufriere hills volcano montserrat august 2005 may 2006 part i dome shape and internal structure lava domes comprise core carapace and clastic talus components they can grow endogenously by inflation of a core and or exogenously with the extrusion of shear bounded lobes and whaleback lobes at the surface internal structure is paramount in determining the extent to which lava dome growth evolves stably or conversely the propensity for collapse the more core lava that exists within a dome in both relative and absolute terms the more explosive energy is available both for large pyroclastic flows following collapse and in particular for lateral blast events following very rapid removal of lateral support to the dome knowledge of the location of the core lava within the dome is also relevant for hazard assessment purposes a spreading toe or lobe of core lava over a talus substrate may be both relatively unstable and likely to accelerate to more violent activity during the early phases of a retrogressive collapse soufriere hills volcano montserrat has been erupting since 1995 and has produced numerous lava domes that have undergone repeated collapse events we consider one continuous dome growth period from august 2005 to may 2006 that resulted in a dome collapse event on 20th may 2006 the collapse event lasted 3 h removing the whole dome plus dome remnants from a previous growth period in an unusually violent and rapid collapse event we use an axisymmetrical computational finite element method model for the growth and evolution of a lava dome our model comprises evolving core carapace and talus components based on axisymmetrical endogenous dome growth which permits us to model the interface between talus and core despite explicitly only modelling axisymmetrical endogenous dome growth our core talus model simulates many of the observed growth characteristics of the 2005 2006 shv lava dome well further it is possible for our simulations to replicate large scale exogenous characteristics when a considerable volume of talus has accumulated around the lower flanks of the dome model results suggest that dome core can override talus within a growing dome potentially generating a region of significant weakness and a potential locus for collapse initiation

identification of structural controls in an active lava dome with high resolution dems volcan de colima mexico monitoring the topography of active lava domes is critical for detecting changes that may trigger or influence collapse or explosive activity internal dome structure and conditions are more difficult to elucidate but also play vital roles here we describe the exposure following an explosion of significant scarps in the active dome at volcan de colima mexico that are interpreted as evidence of brittle failure planes and a complex internal dome morphology in the first use of automated 3d computer vision reconstruction techniques structure from motion and multi view stereo sfm mvs on an active volcanic dome we derive high resolution surface models from oblique and archive photographs taken with a consumer camera the resulting 3d models were geo referenced using features identified in a web sourced orthoimage no ground based measurements were required in december 2010 the dome 2 14 106 m3 had a flat upper surface reflecting an overall ductile emplacement regime between then and may 2011 a period of low explosivity was accompanied by a small volume loss 0 4 105 m3 and arcuate steps appeared in the dome surface suggesting the presence of localized planes of weakness the complex array of summit scarps was exposed following a significant explosion in june 2011 and is interpreted to be the surface expression of fault planes in the dome the 1 m resolution dems indicated that the region of greatest volume loss was not coincident with the assumed location of the conduit and that heterogeneity within the dome may have been important during the june explosion

magmatic architecture of dome building eruptions at volcan de colima mexico changes in the physical chemical and rheological properties of ascending magma regulate the style of volcanic eruptions volcan de colima s eruptive cycles of lava dome growth and explosions have been thoroughly monitored during the period 1998 2010 and provide a remarkable opportunity for deepening our understanding of the underlying processes responsible for the evolution of magma properties here we integrate direct observation with analytical and experimental data to 1 constrain the configuration of the shallow plumbing system and its influence on eruptive activity 2 describe the rheological behaviour of the magma and 3 assess the conditions that lead to fragmentation and ultimately to explosive eruptions the configuration of the shallow plumbing system was inferred from direct observation of extrusion sites and porosity of the erupted products during the ongoing eruptive phase magma was never extruded from a central vent both explosive and effusive activities were restricted to discrete vents inside the crater extensive field based density measurements on 500 blocks in pyroclastic flow deposits reveal a bimodality of porosity at values of 12 and 26 vol the least porous rocks tend to be altered whereas the more porous rocks are pristine this bimodal distribution combined with the lack of a central vent suggests the presence of a central dense altered plug the fragments of which are entrained during explosive eruptions during effusive periods the plug appears to deflect the ascent of magma at a shallow depth and consequently the site of lava extrusion the rheological properties and deformation induced seismogenic behaviour of the magmas were investigated using a uniaxial deformation apparatus instrumented with acoustic sensors the homogeneity in the physicochemical properties of the erupted magma permits the description of a flow law at eruptive temperature and strain rate conditions the crystal rich magma of volcan de colima exhibits a shear thinning rheology and becomes increasingly brittle at higher strain rates complete failure of magma can be predicted using the material failure forecast method which integrates the acceleration of released acoustic energy throughout the deformation rapid decompression experiments of samples pressurised with argon were performed to assess the fragmentation conditions under which explosive eruptions progress in the absence of gas loss due to permeable flow the pore pressure required to fragment volcanic products is inversely proportional to the porosity at volcan de colima a rapid decompression of 6 mpa is required to fragment magma averaging 26 vol pores and to thereby instigate an explosive eruption analysis of ballistic impacts 4 6 km away from the vent from recent explosive eruptions further requires decompression as great as 20 mpa which is sufficient to disrupt the more porous material as well as a fraction of the denser plug the continuing growth of a lava dome and of a larger more impermeable plug could have consequences for the stability of the edifice and development of stronger and more erratic explosive activity at volcan de colima

using a discrete element approach to model lava dome emplacement and collapse abstract lava dome collapses can lead to explosive activity and pyroclastic flow generation which makes them one of the most deadly consequences of volcanic activity the mechanisms linked to a collapse are however still poorly understood and very few numerical models exist that investigate the actual collapse of a lava dome after emplacement we use a discrete element method implemented in the modelling software particle flow code to investigate lava dome growth but also go further to test the stability of the dome under the following conditions increased internal pressure switch in extrusion direction caused by partial cooling of the dome and extrusion of lava onto variable underlying topography we initially show the morphology development of a growing lava dome and how the rheological boundary between core and talus evolves throughout the lifetime of a dome and with varied solidus pressures through visualisation of strain accumulation within the lava dome we show superficial rockfall development due to interaction with topography whereas large deep seated failures occur when the dome is exposed to internal overpressures we find that a switch in extrusion direction promotes a transition from endogenous to exogenous dome growth and leads to lava lobe formation we demonstrate that lava dome collapse exhibits many features similar to common landslides and by investigating strain patterns within the dome we can use numerical modelling to understand features that elude field observations

magma production and growth of the lava dome of the soufriere hills volcano montserrat west indies november 1995 to december 1997 from november 1995 to december 1997 a total volume of 246 106 dre m of andesite magma erupted partitioned into 93 106 m of the dome 125 106 m of pyroclastic flow deposits and 28 106 m of explosive ejecta in the first 11 weeks magma discharge rate was low 0 5 m s from february 1996 to may 1997 discharge rates have averaged 2 1 m s but have fluctuated significantly and have increased with time three pulses lasting a few months can be recognised with discharge rates reaching 3 to 8 m s short term pulsations in growth lasting a few days reach discharge rates of over 10 m s and there are periods of days to a few weeks when dome growth is 0 5 m s discharge rate increased from may 1997 with an average rate of 7 5 m s to december 1997 the observations indicate an open magmatic system

anatomy of a lava dome collapse the 20 march 2000 event at soufriere hills volcano montserrat abstract a second extrusive phase of the currently ongoing 1995 2003 eruption of soufriere hills volcano shv montserrat commenced in mid november 1999 following 19 months during which no fresh lava had reached the surface by mid march 2000 a new andesite lava dome constructed within a collapse scar girdled by remnants of the 1995 1998 dome complex had attained an estimated volume of 29 3 million m3 mm3 on 20 march 2000 during a period of heavy rainfall on the island a significant collapse event ensued that removed 95 of the new lava dome 28 3 mm3 during 5 hours of activity that generated 40 pyroclastic flows and at least one magmatic explosion the associated ash cloud reached an altitude of 9 km and deposited ash on the island of guadeloupe to the southeast and a number of lahars and debris flows occurred in valleys on the flanks of shv a large quantity of observational data including contemporaneous field observations and continuous data from the broadband seismic network on montserrat allow a detailed reconstruction of this dome collapse event in contrast to most of the large dome collapses at shv the 20 march 2000 event is distinguished by a lack of short term precursory elevated seismicity at shallow depths beneath the lava dome broadband seismic amplitude data recorded during the event are used to infer the cumulative volume of collapsed dome as the collapse progressed these data indicate that the high velocity pyroclastic flows observed at the climax of the event removed by far the largest portion 68 of the lava dome at peak discharge rates estimated from the seismic record of 2 104 m3 s 1 following the 20 march 2000 collapse lava dome growth recommenced immediately and continued without significant interruption until another larger dome collapse occurred on 29 july 2001 the 29 july 2001 event also coincided with heavy rainfall on montserrat matthews et al 2002 geophys res lett 29 doi 10 1029 2002gl014863 and lacked precursory elevated seismic activity we attribute the initiation of the 20 march 2000 collapse to a prolonged spell of heavy rainfall on the lava dome prior to and during the event the precise causal mechanism remains controversial though some combination of mechanical erosion and or destabilization of a critically poised face of the lava dome the action of pressurized steam or water on potential failure surfaces within the dome rapid cooling of hot lava and small phreatic explosions seems likely anecdotal evidence exists for other rainfall induced activity on montserrat and the triggering of explosive or pyroclastic flow activity by rainfall has been noted at dome forming volcanoes elsewhere including merapi indonesia voight et al 2000 j volcanol geotherm res 100 69 138 unzen japan yamasato et al 1997 papers meteorol geophys 48 santiaguito guatemala smithsonian institution global volcanism network bull 15 1990 and mount st helens usa mastin 1994 geol soc am bull 106 175 185 hazard mitigation plans at dome forming volcanoes would therefore benefit from the inclusion of meteorological forecasting and rain monitoring equipment particularly in the tropics

thermal resilience of microcracked andesitic dome rocks abstract the strength of the rocks forming a lava dome informs on its structural stability important for volcanic hazard assessments dome forming rocks are persistently challenged by thermal stresses from recurring eruptive events that may reduce their strength and jeopardise the structural stability of the dome here we present a series of experiments to better understand the impact of thermal stresses on the strength of an andesitic dome rock from volcan de colima mexico a volcano that has witnessed some substantial dome collapses in recent years uniaxial compressive strength ucs was first tested at room temperature on as collected samples and samples that had undergone either slow heated and cooled at 1 c min or shock heated at 1 c min and shock cooled in cold water thermal stressing to target temperatures of 400 700 c slow and shock cooling thermal stressing did not measurably alter sample strength connected porosity or permeability ucs tests performed at high in situ temperatures 400 700 c however showed an increase in sample strength and stiffness we interpret that the resistance of this rock to thermal stresses results from both the presence of abundant pre existing microcracks and the thermal stability of its mineral assemblage unchanged physical properties for the thermally stressed samples deformed at room temperature suggests that the pre existing microcracks close and reopen respectively as the rock expands and contracts during heating and cooling to accommodate the volumetric changes without further microcracking the increase in strength and stiffness at high in situ temperatures can be explained by the closure of microcracks due to thermal expansion these observations suggest that the strength of microcracked dome rocks 1 may be slightly higher when hot below the glass transition of the groundmass glass although upscaled strength estimates highlight that dome strength will be largely unchanged by an increase in temperature 2 may only be reduced following the first thermal stressing event and 3 may not be further reduced by repeated thermal stressing events therefore thermal perturbations often observed at active domes may not as perhaps expected repeatedly degrade the strength of individual blocks forming the lava dome and therefore may not jeopardise dome stability

measuring large topographic change with insar lava thicknesses extrusion rate and subsidence rate at santiaguito volcano guatemala lava flows can produce changes in topography of the order of 10s 100s of metres a knowledge of the resulting volume change provides evidence about the dynamics of an eruption using differential insar phase delays it is possible to estimate height differences between the current topography and a digital elevation model dem this does not require a pre event sar image so it does not rely on interferometric phase remaining coherent during eruption and emplacement synthetic tests predict that we can estimate lava thicknesses of as little as 9 m given a minimum of five interferograms with suitably large orbital baseline separations in the case of continuous motion such as lava flow subsidence we invert interferometric phase simultaneously for topographic change and displacement we apply this to santiaguito volcano guatemala and measure increases in lava thickness of up to 140 m between 2000 and 2009 largely associated with activity between 2000 and 2005 we find a mean extrusion rate of 0 437 0 06 m

insights into lava dome and spine extrusion using analogue sandbox experiments abstract lava dome formation is a common process at stratovolcanoes involving the shallow intrusion or extrusion of viscous lava and may lead to the rise of spines spines are protrusions observed to extrude episodically during lava dome growth yet the structural and mechanical factors controlling their formation are only partially understood here we provide new detailed insight into lava dome growth and the production of spines using a novel set of analogue experiments extruding sand plaster mixtures from a fixed diameter conduit under isothermal conditions we trace displacement and strain with photogrammetric methods for precise and detailed monitoring of the extrusion process results show initial dome growth forming a steep sided and flat topped shape through extrusion of new material leading to slumping of oversteepening slopes forming a talus spines are found to protrude at a later stage through the dome surface along discrete circular faults that originate from the conduit walls starting a cycle of spine growth and collapse as our spines only appear after prolonged extrusion we relate their appearance to the compaction and strengthening of material within the conduit we find that spine diameter height and volume are positively correlated with increasing cohesion and therefore material strength the spine diameter was also observed to be smaller or equal to the diameter of the underlying conduit as shear extrusion occurs along vertical to outward dipping fault planes for natural domes our findings imply that spine growth may be the consequence of compaction and densification via porosity loss shearing and or outgassing of conduit magma during ascent more efficient compaction will yield wider and taller spines as a result of increasing rock strength our study further highlights the relevance of analogue experiments in the study of lava domes and spines which remain one of the most hazardous and unpredictable features at dome forming volcanoes worldwide

the evolution of weathering profiles through time new insights from uranium series isotopes the sustainability of soil is a major issue for society in principle the evolution of soil resources can be constrained by comparing the rates of soil erosion and production cosmogenic isotopes provide one measurement of soil erosion rates they can also be used to estimate soil production rates but only if erosion is assumed to be balanced by production this implies that the evolution of soil resources thinning thickening or constant since soil thickness is assumed to be constant with time here we utilise an independent method to estimate soil production rates using uranium series u series isotopes the study of a site in temperate australia undisturbed by human activity shows that soil production rates inferred from u series isotopes are similar to erosion rates derived from beryllium 10 10be measurements implying that at this site there is no net accumulation or loss of soil saprolite production rates the migration rate of the weathering front into the bedrock are also similar to erosion rates so the thickness of the entire weathering profile is effectively in steady state this study demonstrates that the combination of u series and cosmogenic isotopes can be used to quantitatively assess soil evolution and the development of weathering profiles preliminary observations suggest that the rate of bedrock weathering i e saprolite production in temperate australia is of the same order of magnitude as that inferred for laterites in tropical climates this may suggest that for thick weathering profiles although the extent of weathering strongly differs between temperate and tropical climates the migration of the weathering front into the bedrock occurs at a relatively uniform rate regardless of present day climatic conditions

hillslope runoff processes and models abstract hillslope hydrology is concerned with the partition of precipitation as it passes through the vegetation and soil between overland flow and subsurface flow flow follows routes which attenuate and delay the flow to different extents so that a knowledge of the relevant mechanisms is important in the 1960s and 1970s hillslope hydrology developed as a distinct topic through the application of new field observations to develop a generation of physically based forecasting models in its short history theory has continually been overturned by field observation thus the current tendency particularly among temperate zone hydrologists to dismiss all hortonian overland flow as a myth is now being corrected by a number of significant field studies which reveal the great range in both climatic and hillslope conditions some recent models have generally attempted to simplify the processes acting for example including only vertical unsaturated flow and lateral saturated flows others explicitly forecast partial or contributing areas with hindsight the most complete and distributed models have generally shown little forecasting advantage over simpler approaches perhaps trending towards reliable models which can run on desk top microcomputers the variety now being recognised in hillslope hydrological responses should also lead to models which take account of more complex interactions even if initially with a less secure physical and mathematical basis than the richards equation in particular there is a need to respond to the variety of climatic responses and to spatial variability on and beneath the surface including the role of seepage macropores and pipes which call into question whether the hillside can be treated as a darcian flow system

the thermal stealth flows of santiaguito dome guatemala implications for the cooling and emplacement of dacitic block lava flows thick slow moving block lava flows are associated with extrusive activity in dacitic systems where lava core depressurization during flow front collapse generates devas tating block and ash flows dimensional and rare thermal data collected during jan uary 2000 for an active dacitic block flow at santiaguito guatemala provide insight into cooling and emplacement mechanisms flow velocity was low 12 5 m d 21 in spite ginal shear zones the axial part of the flow front was thicker than the marginal zones and was oversteepened this geometry can be explained by a higher vertical velocity gradient in the axial zone causing more frequent and larger volume flow front col lapses axial zone collapses also penetrate farther up flow but not sufficiently to de pressurize the flow core and generate a block and ash flow for such a block and ash flow to occur we calculate that an in crease in velocity and or thickness due to increased slope or topographic confine ment must occur whereas low surface temperatures make block flows invisible to short wave infrared sensors the low veloc ity also contributes to the stealthy behavior of these flows their stealthy nature how ever masks the fact that they can extend many kilometers moving block and ash flow sources closer to vulnerable communities

unusual microseisms seen in the reelfoot fault zone northern tennessee from a reflection experiment abstract a swarm of microseisms with ground motions equivalent to earthquakes of m l 1 and smaller was fortuitously detected in 100 of 162 14 sec duration long offset vibroseis shot gathers collected for a seismic reflection experiment near mooring tennessee directly over the reelfoot fault zone on the afternoon of 16 november 2006 these natural events show up in the shot gathers as near vertically incident p waves with a dominant frequency of 8 10 hz and probably occurred at depths of greater than 10 km the inferred seismicity rate of 250 1000 events per hour is 2 3 orders of magnitude higher than the background seismicity rate for the new madrid seismic zone this detection of microseismic swarms in the reelfoot fault zone indicates active physical processes that may be similar to nonvolcanic tremor seen in the cascadia and san andreas fault zones and merits long term monitoring to understand its source

localized and distributed erosion triggered by the 2015 hurricane patricia investigated by repeated drone surveys and time lapse cameras at volcan de colima mexico abstract in october 2015 patricia a major category 5 hurricane made landfall in western mexico resulting in 500 mm cumulated rainfall and lahar generation along the southerly directed montegrande valley of volcan de colima we monitored lahar deposition and erosion using time lapse trail cameras and conducted repeated camera drone overflights two days before and after the hurricane using photogrammetric processing we derive a unique dataset of high resolution digital terrain models and study the geomorphologic impacts of a single lahar event results reveal different types of erosion at 8 km distance from the volcano with overland flow and rill networks developing into major erosion gullies exceeding a depth of 4 m as well as bank collapse oversteepening and marginal erosion we find alternating deposition and erosion zones that depend on general slope and valley width and find that the overland flow related erosion is an important contributor to the bulking process of lahars moreover this study shows that camera monitoring is very useful for studying the relationship between volcano landscape evolution and hydrometeorological extremes and for rapid assessment associated with single lahar events

evidences of volcanic unrest on high temperature fumaroles by satellite thermal monitoring the case of santa ana volcano el salvador on october 1st 2005 santa ana volcano el salvador underwent a vei 3 phreatomagmatic eruption after approximately one century of rest casualties and damages to some of the local infrastructures and surrounding plantations were followed by the evacuation of the nearby communities the analysis of modis moderate resolution imaging spectroradiometer infrared data reveals that the main explosion was preceded by a one year long thermal unrest associated to the development of a fumaroles field located at the western rim of the summit crater lake by combining space based thermal flux and ground based measurements seismicity sulfur emissions and lake temperatures we suggest that the activity observed at santa ana between 2004 and 2005 was driven by the gradual intrusion of an undegassed magma body at a very shallow depth magma injection induced thermal anomalies associated with sustained degassing from the fumaroles field and promoted the interaction between the magmatic hydrothermal system and the overlying water table this process culminated into the vei 3 phreatomagmatic eruption of october 2005 that strongly modified the shallow structure of the crater area the subsequent three years long activity resulted from self sealing of the fracture system and by the opening of a new fracture network directly connecting the deeper hydrothermal system with the crater lake our results show that satellite based thermal data allow us to detect the expansion of the high temperature fumarolic field this may precede an explosive eruption and or a lava dome extrusion in particular we show that thermal records can be analyzed with other geochemical i e so2 emissions and geophysical seismicity data to track a shallow magmatic intrusion interacting with the surrounding hydrothermal system this provides a remarkable support for volcano monitoring and eruption forecasting particularly in remote areas where permanent ground data acquisition is hazardous expensive and difficult

modvolc near real time thermal monitoring of global volcanism modvolc is a non interactive algorithm developed at the hawaii institute of geophysics and planetology higp that uses low spatial resolution 1 km pixel size infrared satellite data acquired by the moderate resolution imaging spectroradiometer modis to map the global distribution of volcanic thermal anomalies in near real time modvolc scans the level 1b modis data stream on a pixel by pixel basis for evidence of pixel and sub pixel sized high temperature radiators once a hot spot has been identified its details location emitted spectral radiance time satellite observation geometry are written to ascii text files and transferred via ftp to higp from where the results are disseminated via the internet http modis higp hawaii edu in this paper we review the underlying principles upon which the algorithm is based before presenting some of the results and data that have been obtained since its inception we show how modvolc reliably detects thermal anomalies at a large number of persistently and sporadically active volcanoes that encompass the full range of common eruptive styles including erebus antarctica colima mexico karymsky kamchatka popocatepetl mexico etna italy and nyiragongo democratic republic of congo amongst others we also present a few cautionary notes regarding the limitations of the algorithm and interpretation of the data it provides

evaluating links between deformation topography and surface temperature at volcanic domes results from a multi sensor study at volcan de colima mexico abstract dome building activity is common at many volcanoes and due to the gravitational instability a dome represents one of the most hazardous volcanic phenomena shallow volcanic processes as well as rheological and structural changes of the dome affecting the fluid transport have been linked to transitions in eruptive activity also hydrothermal alteration may affect the structural integrity of the dome increasing the potential for collapse however mapping the deformation and details of fluid escape at the summit of steep sloped volcanoes and integrating these with other types of data is challenging due to difficult access and poor coverage here we present for the first time the near vertical and near horizontal surface deformation field of a quiescent summit dome and the relationships with degassing and topographic patterns our results are derived from high resolution satellite radar interferometry insar time series based on a year of terrasar x spotlight acquisitions and structure from motion sfm processing of overflight infrared data at volcan de colima mexico the identified deformation is dominated by localized heterogeneous subsidence of the summit dome exceeding rates of 15 cm yr and strongly decreasing over the year 2012 up to the renewal of explosive and extrusive activity in early 2013 we tentatively attribute the deformation to the degassing cooling and contraction of the dome and shallow conduit material we also find that the results strongly differ depending on the chosen insar time series method which potentially overprints the true physical complexities of small scale shallow deformation processes the combined interpretation of the deformation and infrared data reveals a complex spatial relationship between the degassing pathways and the deformation while we observe no deformation across the crater rim fumaroles discontinuities in the deformation field are more commonly observed around the dome rim fumaroles and occasionally on the dome upper surface we propose that the deformation pattern is also linked to processes controlling the fumarole formation and distribution topography permeability and volcanic activity and the lack of direct relationships may be explained by how the influence of these processes varies across the volcanic summit the presented work provides a new approach for safely monitoring the activity and stability of internal dome structures as well as for constraining and validating models of dome degassing pathways and densification processes

fracture and compaction of andesite in a volcanic edifice the failure mode of lava dilatant or compactant depends on the physical attributes of the lava primarily the porosity and pore size and the conditions under which it deforms the failure mode for edifice host rock has attendant implications for the structural stability of the edifice and the efficiency of the sidewall outgassing of the volcanic conduit in this contribution we present a systematic experimental study on the failure mode of edifice forming andesitic rocks porosity from 7 to 25 from volcan de colima mexico the experiments show that at shallow depths 1 km while low porosity 10 lava remains dilatant the failure of high porosity lava is compactant and driven by cataclastic pore collapse although inelastic compaction is typically characterised by the absence of strain localisation we observe compactive localisation features in our porous andesite lavas manifest as subplanar surfaces of collapsed pores in terms of volcano stability faulting in the upper edifice could destabilise the volcano leading to an increased risk of flank or large scale dome collapse while compactant deformation deeper in the edifice may emerge as a viable mechanism driving volcano subsidence spreading and destabilisation the failure mode influences the evolution of rock physical properties permeability measurements demonstrate that a throughgoing tensile fracture increases sample permeability i e equivalent permeability by about a factor of two and that inelastic compaction to an axial strain of 4 5 reduces sample permeability by an order of magnitude the implication of these data is that sidewall outgassing may therefore be efficient in the shallow edifice where rock can fracture but may be impeded deeper in the edifice due to compaction the explosive potential of a volcano may therefore be subject to increase over time if the progressive compaction and permeability reduction in the lower edifice cannot be offset by the formation of permeable fracture pathways in the upper edifice the mode of failure of the edifice host rock is therefore likely to be an important factor controlling lateral outgassing and thus eruption style effusive versus explosive at stratovolcanoes

pulsed vulcanian explosions a characterization of eruption dynamics using doppler radar understanding the dynamics of ongoing volcanic eruptions is essential for predicting the input and transport of volcanic ash in the atmosphere to constrain near vent dynamic processes of explosive vulcanian events we used doppler radar measurements providing tephra velocities and a proxy of the mass flux in two field experiments at volcan de colima mexico and santiaguito guatemala we find that explosive eruptions at both volcanoes consist of individual degassing pulses the analysis of the timing of such pulses shows that both volcanoes have preferred interpulse times of 3 s santiaguito and 2 5 s volcan de colima the interpulse time during one event may change but it often returns to the preferred interpulse time this behavior is similar at both volcanoes and the interpulse time roughly follows a log logistic distribution indicating the interplay of two competing processes these could be short duration degassing of the uppermost conduit versus decreasing permeability due to progressive gas loss and compaction during an eruption

uranium isotopes and dissolved organic carbon in loess permafrost modeling the age of ancient ice abstract the residence time of ice in permafrost is an indicator of past climate history and of the resilience and vulnerability of high latitude ecosystems to global change development of geochemical indicators of ground ice residence times in permafrost will advance understanding of the circumstances and evidence of permafrost formation preservation and thaw in response to climate warming and other disturbance we used uranium isotopes to evaluate the residence time of segregated ground ice from ice rich loess permafrost cores in central alaska activity ratios of 234 u vs 238 u 234 u 238 u in water from thawed core sections ranged between 1 163 and 1 904 due to contact of ice and associated liquid water with mineral surfaces over time measured 234 u 238 u values in ground ice showed an overall increase with depth in a series of five neighboring cores up to 21 m deep this is consistent with increasing residence time of ice with depth as a result of accumulation of loess over time as well as characteristic ice morphologies high segregated ice content and wedge ice all of which support an interpretation of syngenetic permafrost formation associated with loess deposition at the same time stratigraphic evidence indicates some past sediment redistribution and possibly shallow thaw among cores with local mixing of aged thaw waters using measures of surface area and a leaching experiment to determine u distribution a geometric model of 234 u 238 u evolution suggests mean ages of up to 200 ky bp in the deepest core with estimated uncertainties of up to an order of magnitude evidence of secondary coatings on loess grains with elevated 234 u 238 u values and u concentrations suggests that refinement of the geometric model to account for weathering processes is needed to reduce uncertainty we suggest that in this area of deep ice rich loess permafrost ice bodies have been preserved from the last glacial period 10 100 ky bp despite subsequent fluctuations in climate fire disturbance and vegetation radiocarbon 14 c analysis of dissolved organic carbon doc in thaw waters supports ages greater than 40 ky bp below 10 m doc concentrations in thaw waters increased with depth to maxima of 1000 ppm despite little change in ice content or cryostructures these relations suggest time dependent production of old doc that will be released upon permafrost thaw at a rate that is mediated by sediment transport among other factors

clastic and core lava components of a silicic lava dome the formation of a lava dome involves fractionation of the lava into core and clastic components we show that for three separate successive andesitic lava domes that grew at soufriere hills volcano montserrat between 1999 and 2007 the volumetric proportion of the lava converted to talus or pyroclastic flow deposits was 50 90 of the lava extruded currently only 8 of the total magma extruded during the 1995 2007 eruption remains as core lava the equivalent representation in the geological record will probably be even lower most of the lava extruded at the surface flowed no further than 150 300 m from the vent before disaggregation resulting in a lava core whose shape tends to a cylinder moderate to high extrusion rates at the soufriere hills domes may have contributed to the large clastic fraction observed creating talus dissipates much of the energy that would otherwise be stored in the core lava of domes the extreme hazards from large pyroclastic flows and blasts posed by wholesale collapse of a lava dome depend largely on the size of the lava core and hence on the aggregate history of the partitioning process not on the size of the dome

the relationship between riverine u series disequilibria and erosion rates in a basaltic terrain u series isotopes have been measured in the dissolved phase suspended load and bedload of the main rivers draining basaltic catchments in iceland for the dissolved phase 234u 238u and 238u 230th range between 1 08 and 2 2 and 7 4 and 516 respectively for the suspended load and bedload 234u 238u and 238u 230th range from 0 97 to 1 09 and from 0 93 to 1 05 respectively chemical erosion rates calculated from dissolved major elements range between 13 and 333 t km 2 yr 1 physical erosion rates have also been estimated from existing data and range between 21 and 4864 t km2 yr with an average of 519 t km 2 yr 1 u series disequilibria indicate that weathering in iceland operates at close to steady state conditions a model of continuous weathering indicates a maximum weathering timescale of 10 kyr with an average rate of uranium release into water of 1 6 10 4 yr 1 which is significant when compared to granitic terrains located at similar latitudes and to tropical basaltic terrains all river waters display 234u 238u greater than secular equilibrium consistent with the effects of alpha recoil the same dissolved phase 234u 238u exhibit a negative trend with physical erosion rates explained by the dominant effect of close to congruent chemical weathering of hyaloclastites in the younger basaltic terrains therefore chemical erosion rate and mineral weathering susceptibility play a major role in determining 234u 238u disequilibria in basaltic river waters comparison of global data for river basins in which weathering was recently strongly limited indicates a negative correlation between silicate weathering rates estimated with major elements and the age of weathering estimated with u series disequilibria this strongly suggests a key role of time and soil thickness on the chemical erosion of silicates

coupling meteoric 10be with pedogenic losses of 9be to improve soil residence time estimates on an ancient north american interfluve we couple meteoric 10 be measurements with mass balance analysis of 9 be to estimate the soil residence time srt of a biogeomorphically stable ultisol in the southern piedmont physiographic region of the southeastern united states we estimate srt after correcting the meteoric 10 be inventory to account for observed 9 be losses which indicate that more than half of the 9 be weathered from primary minerals has been leached from the upper 18 3 m of the ultisol our estimates of minimum srt range between 1 3 1 4 ma and between 2 6 3 1 ma under high and low 2 0 and 1 3 10 6 atoms cm 2 yr 1 respectively estimates of 10 be delivery denudation rates of the physiographic region corroborate our estimates we redefine pedogenic time constraints in the southern piedmont and demonstrate that the assumption of complete meteoric 10 be retention in acidic soil systems cannot always be made the latter has far reaching consequences for soil sediment river and ocean research using meteoric 10 be

long period seismicity during magma movement at volcan de colima during the period from february to september 2005 volcan de colima produced 30 vulcanian explosions of sufficient magnitude to produce pyroclastic flows of variable size with a total volume of at least 2 5 106 m3 swarms of long period events were associated with each event their duration ranging from about 6 h to 3 days and each swarm containing up to 886 events the characteristics of the swarms have been studied to understand the source mechanism and their relationship with the vulcanian explosions in total 12 548 long period events were analysed using various comparative and statistical methods patterns were not apparent in the data with no correlation between different properties of the swarms duration magnitude or frequency of occurrence of lp events and the magnitude of the associated vulcanian explosion whether recorded by seismicity volume of pyroclastics or altitude of the eruption column this along with other characteristics of the swarms such as the continuation of the swarm after the explosion with an increase in long period event amplitude in some cases suggests that the mechanism is not merely associated with the pressurization under an impermeable cap and resulting pressure differentials between adjacent volumes within the system it is more likely that the production of long period events is dominated by brittle fracturing on the margins of an ascending magma body a model is proposed whereby the unloading above the ascending magma column produced by a vulcanian explosion resulted in an increase in ascent rate reflected in the increasing amplitude of long period events the results reflect the complexity of non linear processes involved during magma ascent degassing crystallization and rupture of the impermeable plug during the vulcanian process at volcan de colima as at many volcanoes long period events represent a useful precursor for eruptive activity for monitoring this paper highlights some useful analyses that can be carried out which could illustrate certain characteristics of an eruptive episode a preliminary model is presented of the conduit processes at work during the cyclic extrusive and explosive activity during 2005

fumarole monitoring with a handheld infrared camera volcan de colima mexico 2006 2007 abstract this paper describes a methodology for the monitoring of fumarole temperatures at medium ranges 6 km using a handheld infrared camera wavelength range 8 13 5 m as a relationship between fumarole temperatures gas flux and volcanic activity has been demonstrated by a number of studies fumarole temperature data has a potential use as a monitoring tool volcan de colima is an andesitic stratovolcano with a 300 m diameter summit crater formed by the destruction of the 2004 lava dome by a series of explosions in 2005 between january 2006 and august 2007 sequences of thermal images were recorded from a viewpoint 6 km to the north during regular 24 48 hour monitoring excursions the temperatures of fumaroles on the crater rim and the ground surface on the volcano s flanks were measured a methodology was developed to remove data affected by clouds or volcanic water vapour based on rates of temperature change and scatter within the data for the remaining data it is demonstrated mathematically that at this range typical variations in atmospheric transmissivity will affect the apparent temperatures by 2 c while a 25 change in fumarole heat flux would change it by 5 10 c the mean night time apparent temperature of the fumaroles was calculated for each excursion and showed an irregular decline over the 19 month period subtracting the radiant heat flux of flank rocks from those of the fumaroles removes seasonal variations and gives the clearest view of trends in the fumarole heat flux a sharp drop in fumarole temperature during february 2007 coincided with the emergence of a lava dome in the crater the declining fumarole temperature is interpreted to reflect decreasing gas flux from the crater in line with a change in eruptive regime from frequent small ash rich explosions to slow effusion of lava

emplacement of pyroclastic flows during the 1998 1999 eruption of volcan de colima mexico after three years of quiescence volcan de colima reawakened with increasing seismic and rock fall activity that reached its peak on november 20 1998 when a new lava dome forced its way to the volcano s summit the new lava rapidly reached the s sw edge of the summit area beginning the generation of merapi type pyroclastic flows that traveled down la lumbre and the el cordoban western and eastern ravines reaching distances of 3 4 5 and 3 km respectively on december 1 1998 the lava flow split into three fronts that in early 1999 had reached 2 8 3 1 and 2 5 km in length advancing down the el cordoban ravines the lava flow fronts disaggregated into blocks forming pyroclastic flows one of the best examples occurred on december 10 1998 as the lava flow ceased moving in early 1999 activity became more explosive strong blasts were recorded on february 10 may 10 and july 17 1999 the last event developed a 10 km high eruptive column from which a pyroclastic flow developed from the base traveling 3 3 km sw from the summit into the san antonio montegrande ravines regardless of the mechanism of pyroclastic flow generation each flow immediately segregated into a basal avalanche that moved as a granular flow and an upper ash cloud in which particles were sustained in turbulent suspension when the basal avalanche lost velocity and eventually stopped the upper ash cloud continued to move independently as a dilute pyroclastic flow that produced a massive pyroclastic flow deposit and an upper dune bedded surge deposit the dilute pyroclastic flow scorched and toppled maguey plants and trees and sandblasted vegetation in the direction of the flow at the end of the dilute pyroclastic flow path the suspended particles lifted off in a cloud from which a terminal ash fall was deposited the basal avalanche emplaced block and ash flow deposits up to 8 m thick that filled the main ravines and consisted of several flow units each flow unit was massive monolithologic matrix supported and had a clast supported steep front ca 1 5 to 2 m thick composed of boulders up to 1 7 m in diameter the juvenile lithic clasts had an average density of 1800 kg m3 the dilute pyroclastic flow emplaced overbank deposits found on valley margins or beyond the tip of block and ash flow deposits they consist from bottom to top of a massive medium to coarse sand size flow layer 2 4 cm thick a dune bedded surge layer 2 10 cm thick and a massive silt size layer 0 5 cm thick the total estimated volume of the pyroclastic flow deposits produced during the 1998 1999 eruption is 24 105 m3

a holocene pollen record from lowland tropical australia a pollen record from a dunefield lake on groote eylandt northern australia is presented this is the first substantially complete holocene terrestrial record from the seasonally humid lowland tropics of northern australia the lake originated as a seasonal swamp prior to 10 000 bp a progressive rise in water tables occurred until a permanent lake was established at about 9000 bp from 9000 to 7500 bp the lake shows evidence of disruption in the surrounding dunefield prior to 7500 bp an open grassland covered the dunefield after 7500 bp the area was rapidly colonized by eucalyptus open forest and acacias these types remain dominant to the present the data suggest that conditions continuously ameliorated from the base of the record to the mid holocene and there is evidence of an effective precipitation maximum at about 4000 bp effective precipitation declined after 3800 bp but a recovery took place about 1000 bp

mobility of u series nuclides during basalt weathering an example from the deccan traps india abstract u series disequilibria have been measured by tims and mc icp ms in dissolved phases and suspended sediments of the main basaltic rivers from the deccan trap region india for dissolved phases 234u 238u 230th 238u and 226ra 238u range between 1 11 and 1 28 between 0 03 10 2 and 1 35 10 2 and between 0 02 and 0 16 respectively for suspended particles 234u 238u 230th 238u and 226ra 238u range from 0 95 to 1 1 from 1 23 to 1 59 and from 0 1 to 0 47 respectively 230th 238u and 234u 238u systems show direct links with indices of weathering the data also indicate possible redistributions between the solid and aqueous phases and indicate that erosion processes do not presently operate at steady state because present day physical erosion rates are higher than expected 100 400 mm ka versus 40 mm ka for a steady state process for the narmada and the tapti basins models assuming either discrete or continuous particle leaching yield timescales for chemical erosion of 40 90 ka in contrast with basins located in northern latitudes erosion in the deccan basins does not appear to have been significantly disturbed during the last glaciation 234u 238u disequilibria in the dissolved phase of large rivers world wide are also explored and two key factors are highlighted in this study the dissolution of carbonates releasing dissolved u at secular equilibrium and the silicate weathering rate estimated at the scale of the watershed in particular a positive correlation is found between dissolved 234u 238u and basaltic weathering rates for the deccan that could reflect a key role of physical erosion since for silicate monolithological basins chemical erosion rates are primarily controlled by physical erosion rates for basins with mixed lithology dissolved organic matter also plays a key role in the preferential release of 234u from silicate minerals 234u 238u ratios in rivers therefore reflect a mixture between u released by carbonate dissolution and 234u preferentially released from silicate minerals located in high physical erosion and peat areas

effects of a volcanic plume on thermal imaging data ground based thermal imaging is becoming an increasingly important tool for volcano surveillance however the impact of volcanic plumes on quantitative measurements of surface temperature has not been previously evaluated here we use a radiative transfer model to simulate gas primarily h2o and so2 and aerosol absorptions over the path between a thermal camera and a heat source on stromboli volcano italy a ftir spectrometer was used to quantify path amounts of gases likely to be encountered when making thermal measurements of the active craters we find that when using a camera sensitive from 7 5 to 13 mu m underestimates of similar to 400 k may be produced when viewing a source with an actual temperature of 1200 k cameras that operate between 3 and 5 mu m are somewhat less susceptible to these errors

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

temporal trends in lava dome extrusion at santiaguito 1922 2000 we present a means of extracting lava dome extrusion rates from data provided by the thematic mapper and enhanced thematic mapper plus instruments flown on the landsat satellites extrusion rates derived from the landsat data for santiaguito dome complex guatemala during november 1987 and january 2000 of 0 72 0 08 and 0 48 0 09 m3 s 1 compare favorably with ground based estimates of 0 63 0 28 and 0 48 0 17 m3 s 1 a satellite data derived set of 18 extrusion rate estimates between 1987 and 2000 along with ground based volume estimates prior to 1987 allow us to infer volumes of magma erupted since 1922 these data reveal cyclic extrusion at santiaguito each cycle begins with a 3 6 year long phase of high extrusion rate 0 5 2 1 m3 s 1 followed by a longer 3 11 years phase of low extrusion rate 0 2 m3 s 1 the 8th cycle began in 1996 and was still in its high extrusion rate phase during january 2000 with time however the durations of the low extrusion rate phases have increased peak extrusion and time averaged extrusion rates for each cycle have decreased and the difference between extrusion rates during the high and low extrusion rate phases of each cycle has decreased these trends may be the result of depressurization and exhaustion of the source in this case the current eruption may be expected to end around 2020 alternatively santiaguito may be entering a period of persistent activity maintained by a stable magma supply in this case we may expect extrusion to become less cyclic and to stabilize at 0 2 0 4 m3 s 1 however a 2 wt decrease in sio2 content of erupted products since 1970 appears to be consistent with chamber exhaustion as well as an increase in block lava flow lengths during 1970 2000

multiple timescales of cyclical behaviour observed at two dome forming eruptions article i nfo cyclic behaviour over a range of timescales is a well documented feature of many dome forming volcanoes but has not previously been identified in high resolution seismic data from volcan de colima mexico using daily seismic count datasets from volcan de colima and soufriere hills volcano montserrat this study explores par allels in the long term behaviour of seismicity at two long lived systems datasets are examined using multiple techniques including fast fourier transform detrended fluctuation analysis and probabilistic distribution analysis and the comparison of results from two systems reveals interesting parallels in sub surface processes operating at both systems patterns of seismicity at both systems reveal complex but broadly similar long term temporal patterns with cycles on the order of 50 to 200 days these patterns are consistent with previously published spectral analyses of so2 flux time series at soufriere hills volcano and are attributed to variations in the movement of magma in each system detrended fluctuation analysis determined that both volcanic systems showeda systematic relationship betweenthe numberofseismic eventsand the relative roughness ofthetime series and explosionsatvolcande colimashoweda1 5 2 yearcycle neither observation hasaclear explanatory mechanism atvolcandecolima analysisofreposeintervalsbetweenseismiceventsshowslong termbehaviour that responds to changes in activity at the system similar patterns for both volcanic systems suggest a common process or processes driving the observed signal but it is not clear from these results alone what those processes may be furtherattempts to modelconduitprocessesateach volcanomustaccountfor thesimilarities anddiffer ences in activity within each system the identification of some commonalities in the patterns of behaviour dur ing long lived dome forming eruptions atandesiticvolcanoes provides a motivation for investigating further use of time series analysis as a monitoring tool

silicate weathering in the ganges alluvial plain the ganges is one of the world s largest rivers and lies at the heart of a body of literature that investigates the interaction between mountain orogeny weathering and global climate change three regions can be recognised in the ganges basin with the himalayan orogeny to the north and the plateaus of peninsular india to the south together delimiting the ganges alluvial plain despite constituting approximately 80 of the basin weathering processes in the peninsula and alluvial plain have received little attention here we present an analysis of 51 water samples along a transect of the alluvial plain including all major tributaries we focus on the geochemistry of silicon and its isotopes area normalised dissolved si yields are approximately twice as high in rivers of himalaya origin than the plain and peninsular tributaries 82 51 and 32 kmol sio2 km 2 yr 1 respectively such dissolved si fluxes are not widely used as weathering rate indicators because a large but variable fraction of the dsi mobilised during the initial weathering process is retained in secondary clay minerals however the silicon isotopic composition of dissolved si expressed as delta si 30 varies from 0 8 parts per thousand in the ganges mainstem at the himalaya front to 3 0 parts per thousand in alluvial plain streams and appears to be controlled by weathering congruency i e by the degree of incorporation of si into secondary phases the higher delta si 30 values therefore reflect decreasing weathering congruency in the lowland river catchments this is exploited to quantify the degree of removal using a rayleigh isotope mass balance model and consequently derive initial silica mobilisation rates of 200 150 and 107 kmol sio2 km 2 yr 1 for the himalaya peninsular india and the alluvial plain respectively because the non himalayan regions dominate the catchment area the majority of initial silica mobilisation from primary minerals occurs in the alluvial plain and peninsular catchment 41 and 34 respectively c 2015 the authors published by elsevier b v less

estimate of pyroclastic flow velocities resulting from explosive decompression of lava domes apparently benign silicic domes or lava flows can travel for several kilometres and then suddenly collapse to generate pyroclastic phenomena capable of causing widespread destruction as happened recently at mount unzen in japan1 two sources have been proposed for the energy that propels such pelean or merapi type2 pyroclastic flows gravitational col lapse supplemented by heating and expansion of air and sudden expansion of pressurized gases from inside the lava flow if gravity controls the energy transfer then areas likely to be affected can be predicted on the basis of topography3 and the resulting deposits will bear a simple relationship to the part of the lava flow from which they issued but if gas pressure adds a significant contribution hazard assessment becomes more difficult because gas decompression adds velocities beyond those acquired by gravitational forces putting much larger areas at risk and forming pyroclastic deposits that are much more difficult to relate to their source here we estimate the initial velocities of pyroclastic flows generated by dome disintegration for a range of lava compositions and volatile contents and offer a conceptual framework for correlating the dynamics of dome front collapse with the resulting sediment record our results indicate that explosive decompression at distal portions of domes can cause velocities comparable to gravitational collapse especially in cases where volatiles become locally concentrated above equilibrium values

presentation and analysis of a worldwide database for lava dome collapse events the global archive of dome instabilities gladis lava dome collapses generate hazardous pyroclastic flows rockfalls and debris avalanches despite advances in understanding lava dome collapses and their resultant products the conditions that occur prior to collapse are still poorly understood here we introduce the global archive of dome instabilities gladis a database that compiles worldwide historical dome collapses and their reported properties including original dome volume at the time of collapse dome morphology emplacement conditions precursory activity dome geometry and deposit characteristics we determine the collapse magnitude for events where possible using both absolute deposit volumes and relative collapse volume ratios this being deposit volume as a proportion of original dome volume we use statistical analysis to explore whether relationships exist between collapse magnitude and extrusion rate dome growth style original dome volume and causal mechanism of collapse we find that relative collapse magnitude is independent of both the extrusion rate and the original dome volume relative collapse volume ratio is dependent on dome growth style where endogenous growth is found to precede the largest collapses 75 original volume collapses that comprise a higher proportion 50 of original dome volume are particularly attributed to both gravitational loading and the development of gas overpressure whilst collapses comprising a small proportion 10 of original dome volume are associated with the topography surrounding the dome and variations in extrusion direction by providing validation and or source data we intend these data on various dome growth and collapse events and their associated mechanisms to be the focus of future numerical modelling efforts whilst the identified relationships with relative collapse volume ratios can inform collapse hazard assessment based on observations of a growing dome

regional cooling in a warming world recent temperature trends in the southeast pacific and along the west coast of subtropical south america 1979 2006 1 while it is widely accepted that the global mean atmospheric temperature has increased in recent decades the spatial distribution of global warming has been complex in this study we comprehensively characterize the spatial pattern including vertical structure of temperature trends along the subtropical west coast of south america continental chile for the period 1979 2006 and examine their consistency with expectations based on the cmip 3 ensemble of coupled ocean atmosphere simulations for the late 20th century in central and northern chile 17 37 s the most notable feature is a strong contrast between surface cooling at coastal stations 0 2 c decade and warming in the andes 0 25 c decade only 100 200 km further inland coastal radiosonde data imply that the coast andes variation is largely due to strong vertical stratification of temperature trends in the atmosphere west of the andes the coastal cooling appears to form part of a larger scale la nina like pattern and may extend below the ocean mixed layer to depths of at least 500 m over continental chile the cmip 3 gcm ensemble predicts temperature trends similar to those observed in the andes the cooling along the chilean coast is not reproduced by the models but the mean sst warming is weaker there than any other part of the world except the southern ocean it is proposed that the intensification of the south pacific anticyclone during recent decades which is also a simulated consequence of global warming is likely to play a major role in maintaining cooler temperatures off the coast of chile

volcano surveillance using infrared cameras abstract volcanic eruptions are commonly preceded accompanied and followed by variations of a number of detectable geophysical and geochemical manifestations many remote sensing techniques have been applied to tracking anomalies and eruptive precursors and monitoring ongoing volcanic eruptions offering obvious advantages over in situ techniques especially during hazardous activity whilst spaceborne instruments provide a distinct advantage for collecting data remotely in this regard they still cannot match the spatial detail or time resolution achievable using portable imagers on the ground or aircraft hand held infrared camera technology has advanced significantly over the last decade resulting in a proliferation of commercially available instruments such that volcano observatories are increasingly implementing them in monitoring efforts improved thermal surveillance of active volcanoes has not only enhanced hazard assessment but it has contributed substantially to understanding a variety of volcanic processes drawing on over a decade of operational volcano surveillance in italy we provide here a critical review of the application of infrared thermal cameras to volcano monitoring following a summary of key physical principles instrument capabilities and the practicalities and methods of data collection we discuss the types of information that can be retrieved from thermal imagery and what they have contributed to hazard assessment and risk management and to physical volcanology with continued developments in thermal imager technology and lower instrument costs there will be increasing opportunity to gather valuable observations of volcanoes it is thus timely to review the state of the art and we hope thereby to stimulate further research and innovation in this area

thermal photogrammetric imaging a new technique for monitoring dome eruptions abstract structure from motion sfm algorithms greatly facilitate the generation of 3 d topographic models from photographs and can form a valuable component of hazard monitoring at active volcanic domes however model generation from visible imagery can be prevented due to poor lighting conditions or surface obscuration by degassing here we show that thermal images can be used in a sfm workflow to mitigate these issues and provide more continuous time series data than visible light equivalents we demonstrate our methodology by producing georeferenced photogrammetric models from 30 near monthly overflights of the lava dome that formed at volcan de colima mexico between 2013 and 2015 comparison of thermal models with equivalents generated from visible light photographs from a consumer digital single lens reflex dslr camera suggests that despite being less detailed than their dslr counterparts the thermal models are more than adequate reconstructions of dome geometry giving volume estimates within 10 of those derived using the dslr significantly we were able to construct thermal models in situations where degassing and poor lighting prevented the construction of models from dslr imagery providing substantially better data continuity than would have otherwise been possible we conclude that thermal photogrammetry provides a useful new tool for monitoring effusive volcanic activity and assessing associated volcanic risks

volcano monitoring applications of the ozone monitoring instrument the ozone monitoring instrument omi is a satellite based ultraviolet uv spectrometer with unprecedented sensitivity to atmospheric sulphur dioxide so2 concentrations since late 2004 omi has provided a high quality so2 dataset with near continuous daily global coverage in this review we discuss the principal applications of this dataset to volcano monitoring 1 the detection and tracking of large eruption clouds primarily for aviation hazard mitigation and 2 the use of omi data for long term monitoring of volcanic degassing this latter application is relatively novel and despite showing some promise requires further study into a number of key uncertainties we discuss these uncertainties and illustrate their potential impact on volcano monitoring with omi through four new case studies we also discuss potential future avenues of research using omi data with a particular emphasis on the need for greater integration between various monitoring strategies instruments and datasets

monitoring eruptive activity at mount st helens with tir image data 1 thermal infrared tir data from the master airborne imaging spectrometer were acquired over mount st helens in sept and oct 2004 before and after the onset of recent eruptive activity pre eruption data showed no measurable increase in surface temperatures before the first phreatic eruption on oct 1 master data acquired during the initial eruptive episode on oct 14 showed maximum temperatures of 330 c and tir data acquired concurrently from a forward looking infrared flir camera showed maximum temperatures 675 c in narrow 1 m fractures of molten rock on a new resurgent dome master and flir thermal flux calculations indicated a radiative cooling rate of 714 j m2 s over the new dome corresponding to a radiant power of 24 mw master data indicated the new dome was dacitic in composition and digital elevation data derived from lidar acquired concurrently with master showed that the dome growth correlated with the areas of elevated temperatures low so2 concentrations in the plume combined with sub optimal viewing conditions prohibited quantitative measurement of plume so2 the results demonstrate that airborne tir data can provide information on the temperature of both the surface and plume and the composition of new lava during eruptive episodes given sufficient resources the airborne instrumentation could be deployed rapidly to a newly awakening volcano and provide a means for remote volcano monitoring

overview of the eruption of soufriere hills volcano montserrat 18 july 1995 to december 1997 the onset of phreatic volcanic activity at the soufriere hills volcano montserrat on 18 july 1995 followed a three year period of heightened volcano seismic activity beneath the island phreatic explosions gave way to continuous eruption of juvenile andesitic magma in the form of a lava dome on or around 15 november 1995 magma production rate has varied leading to changes in eruptive style an explosive eruption on 17 september 1996 followed a period of enhanced dome growth and large scale gravitational collapses from its eastern flank increasing dome volume led to stressing and overtopping of the confining crater walls to the southwest north and west during early 1997 sustained high magma production rate since june 1997 has led to three periods of major gravitational dome collapses followed by vulcanian explosive eruptions dome growth re started immediately after the cessation of the latest of these explosive phases in october 1997 and continues as of december 1997

thermal imaging and analysis of short lived vulcanian explosions at volcan de colima mexico abstract vulcanian explosions present a major hazard at many active volcanoes but they also provide useful insights into the underlying behaviour of the volcanic system and therefore require close monitoring thermal infrared cameras are an effective tool for imaging vulcanian explosion plumes since they capture detailed temperature information and can reveal the internal dynamics of the plume forming explosions high spatial resolution thermal images of 200 small to moderate sized vulcanian explosions from the summit crater of volcan de colima mexico recorded between 2006 and 2011 were analysed to distinguish different event types and develop an explosion classification scheme explosions display a broad spectrum of sizes and characteristics ranging between two typical end members large impulsive events producing rapidly ascending explosion plumes up to heights of 600 1600 m above the crater rim and small diffusive events with plumes restricted to heights 1 to 29 m s 1 a time series of thermal imagery throughout the period 2006 2011 reveals a weak relationship between apparent plume temperatures and lava dome extrusion with the highest explosion temperatures coinciding with the onset of dome growth in early 2007 temporal variations in the source locations of explosions across the summit crater are also identified and appear to show a close relationship to the patterns of lava dome growth and thermal evolution with explosion source locations associated with the highest temperature thermal features

monitoring volcanic thermal anomalies from space size matters measuring temperatures on volcanoes from space provides important constraints on the transfer of mass and heat to the earth s surface time series of multispectral infrared images acquired by the advanced spaceborne thermal emission and reflection radiometer aster between 2000 and 2009 were inspected to investigate fluctuations in thermal anomalies at both mount erebus antarctica and lascar volcano chile several thermal metrics were explored i maximum pixel temperatures above background ii the spatial extent of low moderate and high temperature anomalies and iii the spatial extent of short wave infrared anomalies the maximum pixel temperature metric correlated to eruptive events at lascar volcano yet displayed significant scatter at erebus the spatial extent of both temperature and short wave infrared anomalies correlates well with eruptive activity at both volcanoes limited variation in the size of thermal anomalies was observed at erebus throughout the time series due to the stability of a long lived lava lake with the exception of a seasonal expansion in low temperature anomalies associated with localized snow melt at the peak this finding has implications for the interpretation of low temperature anomalies at other volcanoes at least two different types of precursory signals are identified at lascar i a gradual increase and ii a dip in the size and intensity of thermal anomalies these thermal precursors appear to be associated with different eruptive styles the former precedes a relatively shallow short lived eruption the later a prolonged eruptive period such thermal precursors could therefore help to constrain not only the timing but also the style and duration of an imminent eruptive episode

lava effusion rate definition and measurement a review measurement of effusion rate is a primary objective for studies that model lava flow and magma system dynamics as well as for monitoring efforts during on going eruptions however its exact definition remains a source of confusion and problems occur when comparing volume flux values that are averaged over different time periods or spatial scales or measured using different approaches thus our aims are to 1 define effusion rate terminology and 2 assess the various measurement methods and their results we first distinguish between instantaneous effusion rate and time averaged discharge rate eruption rate is next defined as the total volume of lava emplaced since the beginning of the eruption divided by the time since the eruption began the ultimate extension of this is mean output rate this being the final volume of erupted lava divided by total eruption duration whether these values are total values i e the flux feeding all flow units across the entire flow field or local i e the flux feeding a single active unit within a flow field across which many units are active also needs to be specified no approach is without its problems and all can have large error up to 50 however good agreement between diverse approaches shows that reliable estimates can be made if each approach is applied carefully and takes into account the caveats we detail here there are three important factors to consider and state when measuring giving or using an effusion rate first the time period over which the value was averaged second whether the measurement applies to the entire active flow field or a single lava flow within that field and third the measurement technique and its accompanying assumptions

the transition from endogenous to exogenous growth of lava domes with the development of shear bands the transition from an endogenous to an exogenous regime of lava dome growth must be achieved by the formation of discontinuities within the dome such transitions and vice versa are an important characteristic of most long lived lava domes and often coincide with significant changes in the dynamics of magma supply and lava dome collapse events for the purpose of this paper following recent experimental and observational evidence we assume that such a transition occurs when shear bands are generated a model for the formation of shear bands and therefore the growth transition within a dome and coupled conduit domain is presented shear bands are most likely to initiate at the junction of the conduit and base of the dome where the shear stress experienced between new lava entering the dome and existing lava is greatest stress accumulation within the shear bands is likely to lead to brittle shear resulting in the formation of fractures finite element modelling of lava flow shows that such shear bands only develop for certain extrusion rates and lava viscosities similarly the growth regime of the lava dome will depend upon the extrusion rate and viscosity within the conduit which is largely controlled by volatile loss and the growth of crystals in the upper part of the conduit we consider a simplified rheology during lava dome growth considering isothermal conditions with crystal growth the development of shear bands in the conduit is explored with a numerical model parameterized with values appropriate for soufriere hills volcano montserrat during october to december 1996 this lava dome forming eruption experienced a transition from endogenous to exogenous growth as it grew in height by about 90 m modelling indicates that the observed fall in magma extrusion rate from about 2 0 m3s 1 to 0 5 m3s 1 as a result of the increased pressure head from the dome and the evolution in viscosity could have subsequently changed the dome growth regime due to the development of shear bands our models provide insight into the shear stress fields possible within the conduit and the shear stresses required for shear band development

stable runoff and weathering fluxes into the oceans over quaternary climate cycles the effect of glacial interglacial cycles on surface weathering rates has been unclear a beryllium based proxy for weathering shows minimal variations in the input of silicate weathering products to the oceans for the past two million years

chemical mobilizations in laterites evidence from trace elements and 238u 234u 230th disequilibria geochemical and mineralogical investigations including measurements of major and trace elements sr isotope ratios and 238u 234u 230th activity ratios were made on an old african laterite to reconstruct its formation steps and assess recent chemical mobilization the present data support a scenario of discontinuous formation for the laterite with different bedrock weathering conditions during the formation of each unit rather than a scenario of continuous formation absolute accumulation of fe u and lanthanides in the uppermost ferruginous unit suggests an autochthonous origin of this iron cap by leaching of an older overlying profile present chemical distributions of lanthanides as well as of rb k ba and sr within the profile cannot be linked to the mineralogical distribution of both relictual primary and authigenic secondary phases complementary lanthanide patterns indicate that these elements were primarily accumulated in the uppermost ferruginous unit before further remobilization and accumulation in the underlying horizons these redistribution processes may be related to the chemical instability of the ferruginous cap the 238u 234u 230th disequilibria indicate that recent u mobilization occurs in the whole profile and that as for lanthanides there is a vertical redistribution of u from the uppermost ferruginous unit to the underlying horizons moreover these data show that both u losses and gains exist at each level of the profile a simple modeling of this double u mobilization process is proposed to interpret the 238u 234u 230th data differences in the mobilization and fractionation intensities of the u input and removal processes can account for the two evolution trends which distinguish the ferruginous unit from the underlying ones furthermore on the basis of this modeling the profile appears to be in a transient state because of recent changes in the u mobilization conditions which could correspond to major pleistocene climatic variations

physical models of fumarolic flow abstract transport of gas from subsurface magma to the atmosphere is modelled as flow through a narrow rough pipe and through a wider conduit filled with spheres representing flow in a porous pipe macroscopic mass momentum and energy balances are written for a control volume representing a short vertical section of the pipe the balances are solved for a perfect gas with the approximate thermodynamic properties of steam losing heat by steady state radial conduction through the pipe walls with boundary conditions of magmatic temperature at the base of the pipe atmospheric pressure at the surface and an ambient geotherm at a specified distance from the conduit results yield the variation of exit temperature with magmatic source depth conduit radius mass flow rate per unit area distance to ambient temperatures vent porosity and porous particle size two ambient geotherms are used 1 a linear gradient from atmospheric to magmatic temperatures and 2 a hydrothermal geotherm based on water saturation temperatures assuming a hydrostatic pressure gradient because individual vents commonly cluster the porous pipe model is considered to be more realistic than the rough pipe model mainly because the conductive cooling approximation is more likely to remain valid exit temperatures fall as conductive losses increase i e as the source depth increases the conduit narrows the mass flow decreases the distance to ambient temperatures reduces or the ambient geotherm cools the porous pipe model is applied to data from two fumarole fields and indicates magmatic source depths of

sediment transport time measured with u series isotopes results from odp north atlantic drift site 984 abstract high precision uranium isotope measurements of marine clastic sediments are used to measure the transport and storage time of sediment from source to site of deposition the approach is demonstrated on fine grained late pleistocene deep sea sediments from ocean drilling program site 984a on the bjorn drift in the north atlantic the sediments are siliciclastic with up to 30 carbonate and dated by 18o of benthic foraminifera nd and sr isotopes indicate that provenance has oscillated between a proximal source during the last three interglacial periods volcanic rocks from iceland and a distal continental source during glacial periods an unexpected finding is that the 234u 238u ratios of the silicate portion of the sediment isolated by leaching with hydrochloric acid are significantly less than the secular equilibrium value and show large and systematic variations that are correlated with glacial cycles and sediment provenance the 234u depletions are inferred to be due to recoil loss of 234th and are used to calculate comminution ages of the sediment the time elapsed between the generation of the small 50 m sediment grains in the source areas by comminution of bedrock and the time of deposition on the seafloor transport times the difference between comminution ages and depositional ages vary from less than 10 ky to about 300 to 400 ky for the site 984a sediments long transport times may reflect prior storage in soils on continental shelves or elsewhere on the seafloor transport time may also be a measure of bottom current strength during the most recent interglacial periods the detritus from distal continental sources is diluted with sediment from iceland that is rapidly transported to the site of deposition the comminution age approach could be used to date quaternary non marine sediments soils and atmospheric dust and may be enhanced by concomitant measurement of 226ra 230th 230th 234u and cosmogenic nuclides

the magmatic plumbing system beneath santiaguito volcano guatemala abstract the silicic dome complex of santiaguito guatemala has exhibited continuous extrusive activity for 90 years despite its longevity remarkably little is known about the magmatic plumbing system beneath santiaguito here we use petrological analyses of lava samples to define this plumbing system from storage in the lower to mid crust through to extrusion onto the surface magmatic storage conditions are constrained using amphibole and plagioclase phenocrysts ascent processes are examined using the breakdown rims of amphibole phenocrysts and the texture and composition of groundmass while shallow processes are revealed by the alteration of titanomagnetites and matrix glass santiaguito magmas contain amphiboles that formed from 24 km to 12 km beneath the surface with temperatures of 940 to 980 c and f o2 of nno 0 4 to nno 1 2 amphibole breakdown rims suggest that during the final phases of ascent magma may rise from 12 km the limit of amphibole stability relatively rapidly 27 to 84 m h 1 we infer from the texture of the groundmass that melt rigidifies prior to extrusion a finding that may have important consequences for conduit dynamics

remote sensing of volcanoes and volcanic processes integrating observation and modelling introduction volcanoes are often remote and have footprints that may extend across many hundreds or thousands of square kilometres they are generally inaccessible during eruption and may continue to be inaccessible for extended periods of time after eruption while their products can be scattered or dispersed over regional or global scales consequently since direct measurement can only provide us with part of the picture of many volcanic processes remote sensing is now playing an increasingly important role in advancing understanding of the science underlying volcanic behaviour on this planet and beyond e g mouginis mark et al 2000 sparks et al 2012 satellite airborne and ground based remote sensing are increasingly vital tools for monitoring active or potentially active volcanoes and assessing their likely real time or time averaged impact fig 1 at the same time the synoptic scale surveys that are often well suited to remote sensing techniques allow us to address questions about the fundamental processes that control volcano behaviour in a way that is not necessarily possible from individual case studies new research is often driven by technological advancements in the development of novel sensors or launching of new platforms meaning that the space agencies are increasingly involved in identifying scientific questions and priorities e g ferruci et al 2012 multiple and complementary data streams are increasingly being used both to monitor active volcanoes and advance volcanological science the key geophysical parameters that comprise monitoring data streams typically include the categories of i seismicity ii surface deformation iii thermal measurements and iv gas flux and composition data as major components while measurements of seismicity remain the domain of ground based seismometers remote sensing techniques have made major contributions in each of the others this special publication volume is concerned with the use of remote sensing at volcanoes it is split into three parts roughly arranged from the subsurface to the surface and then further afield as volcanic products are injected and dispersed into the atmosphere the papers span a range of applications of remote sensing techniques to monitor and understand a surface deformation b surface thermal anomalies and c gas fluxes as well as tracking ash and gas plumes from eruptions to gain insights into the extent of a volcano s impacts volcanology is driven in part by the operational concerns surrounding volcano monitoring and hazard and crisis management but the goal of volcanological science is at its heart to understand the processes that underlie volcanic activity this special publication is also concerned with how we go from observations to this deeper understanding including the progress that can be made by integrating observations and modelling while this volume focuses mainly on satellite based remote sensing integrating datasets from different platforms is also of vital importance and so papers on airborne remote sensing and measurement from both manned and unmanned aircraft are also included

lava dome growth and evolution with an independently deformable talus subduction zone volcanism occurs due to partial melting from subducting slabs which generally results in high viscosity magma containing a large amount of volatiles such volcanic eruptions can form a lava dome from which collapse events are a common and important part of their evolution collapse events can have devastating consequences in the form of block and ash avalanche deposits pyroclastic ows surges and the generation of tsunamis if they enter the sea in addition to this once a mass of lava dome has been removed during a collapse event this results in a drop in pressure in the remaining volatile rich magma which may then erupt explosively the internal structure of a lava dome and the extent of the surrounding carapace talus is unknown but likely to be critical for hazard assessment and is the motivation for this research presented is a computational model for the growth and evolution of an endogenous lava dome including an independently deformable talus using the finite element method dome growth is modelled to occur under two time scales continuous dome expansion via the addition of new magma into the molten core interior and relatively instantaneous talus readjustments due to rockfalls and the disintegration of the solid surface the continuous deformation of the dome is modelled as a uid with a yield strength in the talus region while talus deformation is modelled as a granular material that rests at angles below its angle of repose both surfaces dome and core talus interface are displaced using the level set method the model is axi symmetric and assumes that solidi cation and therefore talus growth occurs due to gas exsolution which promotes crystallisation rather than from surface cooling appropriate for intermediate composition lava ows for the purpose of this paper we consider and apply the model to the soufriere hills volcano montserrat but the techniques used are generic allowing the model to be applied to other dome forming eruptions the model provides information on the shape of the dome with the growth and extent of the talus and core found to be predominantly governed by the lava extrusion rate degree of solidi cation i e a solidus pressure the friction angle associated with the talus and lava dome viscosity

causes and consequences of pressurisation in lava dome eruptions abstract high total and fluid pressures develop in the interior of high viscosity lava domes and in the uppermost parts of the feeding conduit system as a consequence of degassing two effects are recognised and are modelled quantitatively first large increases in magma viscosity result from degassing during magma ascent strong vertical gradients in viscosity result and large excess pressures and pressure gradients develop at the top of the conduit and in the dome calculations of conduit flow show that almost all the excess pressure drop from the chamber in an andesitic dome eruption occurs during the last several hundred metres of ascent second microlites grow in the melt phase as a consequence of undercooling caused by gas loss rapid microlite growth can cause large excess fluid pressures to develop at shallow levels theoretically closed system microlite crystallization can increase local pressure by a few tens of mpa although build up of pressure will be countered by gas loss through permeable flow and expansion by viscous flow microlite crystallization is most effective in causing excess gas pressures at depths of a few hundred metres in the uppermost parts of the conduit and dome interior some of the major phenomena of lava dome eruptions can be attributed to these pressurisation effects including spurts of growth cycles of dome growth and subsidence sudden onset of violent explosive activity and disintegration of lava during formation of pyroclastic flows the characteristic shallow level long period and hybrid seismicity characteristic of dome eruptions is attributed to the excess fluid pressures which are maintained close to the fracture strength of the dome and wallrock resulting in fluid movement during formation of tensile and shear fractures within the dome and upper conduit

on lava dome growth with application to the 1979 lava extrusion of the soufriere of st vincent abstract a theoretical analysis is presented for the spread of a viscous liquid flowing under its own hydrostatic pressure on a horizontal surface in order to model lava dome formation two situations are considered in detail the spreading of a constant volume of liquid and the case where the amount of liquid is continually increased experiments with silicone liquids show close agreement with theory the formation of a basaltic andesite lava extrusion in 1979 on the crater floor of the soufriere of st vincent west indies provided the motivation for and an application of the model the extrusion reached a diameter of 868 m and a height of 133 m over a period of 150 days over the first 90 days the growth relationships were consistent with those predicted by theory application of the theory to the soufriere dome suggests an effective viscosity of 2 x 10 12 poise for the basaltic andesite lava the large effective viscosity calculated for the lava may be attributed to the dominant influence of a high viscosity skin which forms at the margins of the flow as it cools after 70 days the rate of growth of the extrusion markedly decreased because a substantial collar of rubble accumulated at the flow front due to this collar the growth of the extrusion ceased after 150 days from approximately two weeks after the initiation of the extrusion the discharge rate of lava decreased approximately linearly with increasing dome height this observation suggests that the lava ascended under a decreasing hydrostatic driving pressure and that extrusion ceased when the lava column reached hydrostatic equilibrium

continuous monitoring of high temperature fumaroles on an active lava dome volcan colima mexico evidence of mass flow variation in response to atmospheric forcing rapid multichannel monitoring of fumaroles on volcan colima mexico provides new insight into the time scales and magnitudes of fumarole temperature variation temperatures in five fumaroles all located along a single fracture cutting the summit lava dome of the volcano were monitored at 20 min intervals between may 1991 and may 1992 measurements were made using a programmable data logger deployed near the fumarole field and data were radiotelemetered to a nearby volcano observatory at regular intervals mean fumarole temperatures varied between 350 c and 550 c statistical analysis of these time series shows that significant diurnal variation occurs in each fumarole magnitudes of these daily fluctuations are generally between 25 c and 50 c although larger amplitude variations occur especially in cooler fumaroles simultaneous monitoring of atmospheric pressure at the fumaroles indicates that these variations in temperature are inversely correlated with barometric pressure these observations indicate that fumarole temperatures respond to atmospheric forcing a numerical model developed to explore the dependence of fumarole temperature on mass flow demonstrates that many aspects of observed temperature variation are accounted for by mass flow variation resulting from small changes in barometric pressure the relationship between mass flow and fumarole temperature is nonlinear the response of fumarole temperatures to a given change in mass flow is greatest in fumaroles with low mass flow and cool temperatures the nature of this dependence is little affected by fumarole geometry for the cases considered continuous measurement of fumarole temperatures may be an effective means of monitoring local mass flow on volcanoes at volcan colima average temperatures changed by less than 100 c during the 1 year sampling period during and immediately following effusive activity changes in degassing were abrupt and inconsistent along the length of the fracture following this period temperatures decreased gradually and there was a higher degree of correlation between fumaroles the method described here represents a substantial improvement over traditional fumarole monitoring techniques because subtle variation can be quickly identified using standard statistical techniques and the method provides regular information about thermal activity on a volcano minimizing the hazards normally associated with the collection of these data on a regular basis

predicting the block and ash flow inundation areas at volcan de colima colima mexico based on the present day february 2010 status abstract maps of areas potentially affected by block and ash flows and associated ash clouds are here presented for the volcan de colima titan2d 2 0 1 code has been used to simulate block and ash flows using as an input volume that of the actual summit dome assessed at 2 10 6 m 3 while the energy cone model has been used to delimit the possible inundated area from associated ash clouds both merapi and soufriere type block and ash flows were generated using different basal friction angles and maintaining fixed the volume and the internal friction angle the setting of the input parameters takes into account some flow characteristics such as the stepwise aggradation of different pulses that piled up to form the total thickness of the block and ash flow deposits the outputs of the computational routines are reported as two maps describing the total thickness of the final deposits they predict that thick deposits will engulf the ravines descending from the main cone to the west south and southeast with expected maximum runouts between 4 5 and 7 km the associated ash clouds have slightly longer runouts and the model predicts they will inundate some higher grounds that are not affected by the concentrate underflows the presented maps represent useful tools for managing the current block and ash flow hazard at volcan de colima

predicting the thickness and aeolian fraction of soils in upland watersheds of the mojave desert abstract soil thickness and soil texture and their spatial variability at hillslope scales are important inputs for hydrologic models recent studies have demonstrated that mechanistic models can accurately predict the spatial distribution of soil thickness in areas where soil thickness varies gradually along hillslope profiles to date however these models have not been tested in arid regions where soils are often thin and highly variable at small scales i e 1 10 m and where the influence of aeolian accretion on soil thickness and soil texture may be significant in addition most of the data available for the fraction of the soil derived from aeolian deposition which can serve as a proxy for soil texture originate from soils developed on stable depositional landforms data for aeolian fractions from upland soils are scarce in this study we developed and tested a numerical model for the prediction of thickness and aeolian fraction of soils in arid upland areas the model assumes a long term balance between the rates of soil production from bedrock aeolian accretion and soil erosion rates of soil production are quantified in the model using the exponential and humped soil production functions and soil erosion rates are quantified using the nonlinear depth and slope dependent transport functions assuming that only the upper soil horizons a b are capable of transport the rate of aeolian deposition is assumed to be spatially uniform we calibrated the three free parameters of the model at a site in the mojave desert with a granite lithology using a combination of 1 field measured data for soil thickness and 2 estimation of the aeolian fraction in the soil using laboratory analysis of immobile element concentrations we validated the model results in three nearby sites using a combination of measured soil thickness in soil pits and the presence absence of soil and laboratory analysis of the aeolian fraction of soil the study area is characterized by generally thin soils

susceptibility of lava domes to erosion and collapse by toppling on cooling joints the shape of lava domes typically leads to the formation of radial patterns of cooling joints these cooling joints define the orientation of the columnar blocks which plunge toward the center of the dome in the lower parts of the dome the columns plunge into the dome at low angles and are relatively stable higher in the dome the columns plunge into the dome at steep angles these steeply plunging columns are susceptible to toppling and if the lower part of a dome is partially removed by erosion or collapse the unstable part of the dome becomes exposed leading to toppling failure examples of this process are provided from coastal erosion of lava domes at katsura island shimane peninsula western japan an analogue model is presented to demonstrate the mechanism it is proposed that the mechanism can contribute to collapse of lava domes during or after emplacement

seismic signals of rockfalls as indicators of the origin of lava fragments emplaced during the 2010 endogenous and exogenous growth in the crater of volcan de colima mexico the 2010 2011 exogenous emplacement of a lava lobe during the 2007 2011 lava dome growth at andesitic volcan de colima mexico interrupted the previous endogenous regime and allowed us to obtain seismic signals associated with rockfalls triggered by both exogenous and endogenous growth we analyzed a total of 410 seismic signals of rockfalls with durations from 50 to 150 s recorded during january april 2010 two characteristic populations of seismic signal peak frequencies were identified a low frequency lf group mean 1 76 0 44 hz and a high frequency hf group mean 3 13 0 63 hz associated respectively with rockfalls caused by endogenous and exogenous growth in the crater application of the kolmogorov smirnov test showed at the 0 01 significance level that the databases of lf and hf seismic signals of rockfalls belong to different groups of signals and may be considered as having different origins the results show that the spectral properties of the seismic signals produced by rockfalls may serve as indicators of the origin of falling lava fragments and thus can be used to monitor effusive volcanic activity

sediment residence times in catchments draining to the gulf of carpentaria northern australia inferred by uranium comminution dating abstract uranium u isotopes are useful for constraining the timescales of weathering and erosion processes the 234u 238u activity ratio parentheses denote activity ratio of fine grained detrital minerals is proposed to record the time elapsed since mineral grains were reduced to

movement and emplacement of lava flows at volcan de colima mexico november 1998 february 1999 abstract the first lava eruption of volcan de colima since 1991 was anticipated beginning in mid 1997 when seismic activity began to exceed background levels on 20 november 1998 growth of a new andesitic lava dome began inside a crater produced by an explosion through the summit dome in july 1994 the 1998 block lava dome grew rapidly at a rate of 4 4 m 3 s attaining a volume of 3 8 10 5 m 3 in 24 h about mid day on 21 november the lava dome began to collapse generating a series of block and ash flows that descended the ssw flank at speeds of 80 90 km h at intervals of 3 5 min these pyroclastic flows were mostly deposited in the three branches of barranca el cordoban reaching a maximum distance of 4 8 km from the summit at an altitude of 2040 m the largest pyroclastic flows were emplaced on 25 26 november and their deposits had an estimated volume of 7 3 10 5 m 3 an andesitic block lava flow 59 wt sio 2 then followed down the three branches of barranca el cordoban reaching a maximum distance of 3 8 km in the central branch the lava fronts of the western and central branches almost touched at 2300 m elevation the eastern lava flow reached 2 8 km at 2560 m elevation the total volume of the three lava flows is estimated as 39 10 6 m 3 assuming an average thickness of 20 m the advance rate of the lava fronts in the early hours reached 36 m h on steep slopes up to 40 these diminished to 0 2 1 0 m h on flatter slopes 14 in early february as the activity waned the viscosity of the block lava flows estimated from field observations was extremely high 10 9 10 10 pa s 6 orders of magnitude greater than viscosities estimated for fluid basaltic magmas the lava flows ceased movement in early february 1999 and the style of eruptive activity entered a more explosive phase with a series of dome explosions that have continued into february 2001