estimating thermal inflow to el chichon crater lake using the energy budget chemical and isotope balance approaches abstract el chichon crater lake appeared immediately after the 1982 catastrophic eruption in a newly formed 1 km wide explosive crater during the first 2 years after the eruption the lake transformed from hot and ultra acidic caused by dissolution of magmatic gases to a warm and less acidic lake due to a rapid magmatic to hydrothermal transition input of hydrothermal fluids and oxidation of h 2 s to sulfate chemical composition of the lake water and other thermal fluids discharging in the crater stable isotope composition d and 18 o of lake water gas condensates and thermal waters collected in 1995 2006 were used for the mass balance calculations cl so 4 and isotopic composition of the thermal flux from the crater floor the calculated fluxes of thermal fluid by different mass balance approaches become of the same order of magnitude as those derived from the energy budget model if values of 1 9 and 2 mmol mol are taken for the catchment coefficient and the average h 2 s concentration in the hydrothermal vapors respectively the total heat power from the crater is estimated to be between 35 and 60 mw and the co 2 flux is not higher than 150 t day or 200 gm 2 day 1

the 1982 el chichon volcano eruptions a satellite perspective abstract the march 28 april 3 and april 4 1982 eruptions of el chichon volcano were detected and monitored using the goes and noaa 6 environmental satellites the satellite data provided information about the height and dispersal of the eruption plume and subsequent ash cloud on each of these dates based on the satellite data it was concluded that the march 28 eruption the second of two eruptions on april 3 and the april 4 eruption injected material into the stratosphere at heights between 17 and 31 km

a compositional tipping point governing the mobilization and eruption style of rhyolitic magma measurements of the composition dependent viscosity of rhyolitic magma reveal a tipping point that changes the physical properties of the melt and controls the transition between effusive and explosive eruptions calcalkaline rhyolites produce the largest explosive volcanic eruptions but these eruptions can switch repeatedly between being effusive and explosive this is difficult to attribute to the rheological effects of magma water content or crystallinity danilo di genova and co authors report the viscosity of a series of melts spanning the compositional range of the yellowstone rhyolitic volcanic system they find that within a narrow compositional zone melt viscosity increases by up to two orders of magnitude which they propose to be the consequence of melt structure reorganization the authors confirm that such a compositional tipping point exists in the global geochemical record of rhyolites which separates effusive from explosive deposits they conclude that the anhydrous water free composition of calcalkaline rhyolites is decisive in determining mobilization and eruption dynamics of the earth s largest volcanic systems the most viscous volcanic melts and the largest explosive eruptions1 on our planet consist of calcalkaline rhyolites2 3 these eruptions have the potential to influence global climate4 the eruptive products are commonly very crystal poor and highly degassed yet the magma is mostly stored as crystal mushes containing small amounts of interstitial melt with elevated water content5 it is unclear how magma mushes are mobilized to create large batches of eruptible crystal free magma further rhyolitic eruptions6 7 8 can switch repeatedly between effusive and explosive eruption styles and this transition is difficult to attribute to the rheological effects of water content or crystallinity9 10 here we measure the viscosity of a series of melts spanning the compositional range of the yellowstone volcanic system and find that in a narrow compositional zone melt viscosity increases by up to two orders of magnitude these viscosity variations are not predicted by current viscosity models11 12 and result from melt structure reorganization as confirmed by raman spectroscopy we identify a critical compositional tipping point independently documented in the global geochemical record of rhyolites at which rhyolitic melts fluidize or stiffen and that clearly separates effusive from explosive deposits worldwide this correlation between melt structure viscosity and eruptive behaviour holds despite the variable water content and other parameters such as temperature that are inherent in natural eruptions thermodynamic modelling demonstrates how the observed subtle compositional changes that result in fluidization or stiffening of the melt can be induced by crystal growth from the melt or variation in oxygen fugacity however the rheological effects of water and crystal content alone cannot explain the correlation between composition and eruptive style we conclude that the composition of calcalkaline rhyolites is decisive in determining the mobilization and eruption dynamics of earth s largest volcanic systems resulting in a better understanding of how the melt structure controls volcanic processes

lithologic controls on morphology of pressure dissolution surfaces stylolites and dissolution seams in paleozoic carbonate rocks from the mideastern united states abstract examination of pressure dissolution surfaces stylolites and dissolution seams in carbonate rocks from the mideastern u s demonstrates that the morphology of these surfaces varies with rock fabric one can quantify the morphology of these pressure dissolution surfaces using four parameters thickness t of the insoluble residue defining the surface amplitude of irregularity i of the surface between vertical offsets amplitude of vertical offsets o of the surface and frequency f of vertical offsets along the surface i and o increase with t reflecting progressive development of stylolites whereas f is proportional to 1 t apparently because the physical strength of a stylolite inhibits the formation of offsets mean values of f o and t are greater in grainstones and packstones than in mudstones and wackestones and the abundance of dissolution seams relative to that of stylolites decreases through the lithologic spectrum from mudstones to grainstones these relationships suggest that development of pressure dissolution surfaces to form large stylolites depends on the heterogeneity of the limestone fabric maximum values of t and o in grainstones correlate with cement abundance t and o are low in grain rich cement poor grainstones even though grains are favored as leading or penetrating elements of stylolite columns dissolution seams surfaces with o and f near zero are found only in rocks containing fine grained dolomite t and i of those seams decrease with increasing dolomite abundance in dolomitic limestones and t and o are lower in dolostones than in limestones taken together these relationships suggest that extreme abundance of pressure resistant components such as carbonate grains and dolomite inhibit development of pressure dissolution surfaces in contrast stylolites are most extensively developed i e i t o and f are greatest in carbonate rocks in which these pressure resistant elements are mixed with less resistant components such as cement and carbonate mud the latter rocks which include packstones well cemented grainstones and slightly dolomitic limestones may undergo preferential removal from the stratigraphic record by pressure dissolution

textural and compositional evidence for magma mixing and its mechanism abu volcano group southwestern japan quaternary basalts andesites and dacites from the abu monogenetic volcano group sw japan composed of more than 40 monogenetic volcanoes show two distinct chemical trends especially on the feo mgo vs sio2 diagram one trend is characterized by feo mgo enrichment with a slight increase in sio2 content fe type trend whereas the other shows a marked sio2 enrichment with relatively constant feo mgo ratios si type trend the fe type trend is explained by fractional crystallization with subtraction of olivine and augite from a primitive alkali basalt magma rocks of the si type trend are characterized by partially melted or resorbed quartz and sodic plagioclase phenocrysts and or fine grained basaltic inclusions they are most likely products of mixing of a primitive alkali basalt magma containing olivine phenocrysts with a dacite magma containing quartz sodic plagioclase and hornblende phenocrysts petrographic variation as well as chemical variation from basalt to dacite of the si type trend is accounted for by various mixing ratios of basalt and dacite magmas pargasitic hornblende and clinopyroxene phenocrysts in andesite and dacite may have crystallized from basaltic magma during magma mixing olivine and spinel and quartz sodic plagioclase and common hornblende had crystallized in basaltic and dacitic magmas respectively before the mixing within a lava flow the abundance of basaltic inclusions decreases from the area near the eruptive vent towards the perimeter of the flow and the number of resorbed phenocrysts varies inversely suggesting zonation in the magma chamber

hydrogeochemical surveillance at el chichon volcano crater lake chiapas mexico abstract el chichon volcano has an eruptive record of at least 12 major eruptions in the holocene the latest one in march april 1982 causing the worst volcanic disaster in the history of mexico after about 6 centuries of quiescence this eruption destroyed a large dome and opened a 1 km wide crater a lake formed within the crater shortly after the eruption has been an important source of information about the evolution of the post eruptive processes the fluctuations of the crater lake water physicochemical parameters observed since 1983 have allowed in identifying hydrothermal waters and h 2 s rich gases influenced by tectonic and meteorological effects as the main contributors to its composition here we propose some methods to help in assessing the state of the volcano derived from the relative contribution of these factors as an easy to implement volcanic surveillance method in potentially active volcanoes with crater lakes or other volcano influenced water sources

major and trace element geochemistry of neutral and acidic thermal springs at el chichon volcano mexico implications for monitoring of the volcanic activity abstract four groups of thermal springs with temperatures from 50 to 80 c are located on the s sw w slopes of el chichon volcano a composite dome tephra edifice which exploded in 1982 with a 1 km wide 160 m deep crater left very dynamic thermal activity inside the crater variations in chemistry and migration of pools and fumaroles drastic changes in the crater lake volume and chemistry contrasts with the stable behavior of the flank hot springs during the time of observations 1974 2005 all known groups of hot springs are located on the contact of the basement and volcanic edifice and only on the w sw s slopes of the volcano at almost same elevations 600 650 m asl and less than 3 km of direct distance from the crater three groups of near neutral ph 6 springs at sw s slopes have the total thermal water outflow rate higher than 300 l s and are similar in composition the fourth and farthest group on the western slope discharges acidic ph 2 saline 10 g kg of cl water with a much lower outflow rate water rock interaction modeling of main types of the el chichon thermal waters using regular log q k graphs saturation indices vs temperature showed maximum equilibrium temperature slightly higher than 200 c acidic waters are equilibrated with some clay minerals at about 120 c three main sources of the salinity of thermal water are suggested on the basis of mixing plots and isotopic data a magmatic source for co2 boron sulfur and a limited part of cl volcanic rock source for the major cations and trace elements the oil bearing evaporitic basement source oil field brine for nacl br a part of ca and some trace elements all flank thermal springs end up in the river rio magdalena that has a variable seasonal flow rates from 4 to 20 m3 s any changes in the chemistry of springs must notably change the composition of the streams draining hot springs and eventually rio magdalena a monthly geochemical monitoring of rio magdalena and streams draining main hot springs would be a useful tool for surveying the activity of the volcano

explosive eruption of el chichon volcano mexico disrupted 6th century maya civilization and contributed to global cooling a remarkably long period of northern hemispheric cooling in the 6th century ce which disrupted human societies across large parts of the globe has been attributed to volcanic forcing of climate a major tropical eruption in 540 ce is thought to have played a key role but there is no consensus about the source volcano to date here we present evidence for el chichon in southern mexico as the most likely candidate based on a refined reconstruction of the volcano s eruption history a new chronological framework derived from distal tephra deposits and the world s largest holocene beach ridge plain along the gulf of mexico enabled us to positively link a major explosive event to a prominent volcanic sulfur spike in bipolar ice core records dated at 540 ce we speculate that voluminous tephra fall from the eruption had a severe environmental impact on maya societies leading to temporary cultural decline site abandonment and migration within the core area of maya civilization

intrusive reawakening of el chichon volcano prior to its holocene eruptive hyperactivity abstract el chichon volcano in southeastern mexico chiapas has produced compositionally homogeneous trachyandesite throughout its ca 372 kyr eruptive history but crystal scale heterogeneity reveals a complex interplay between magmas generated and stored at different crustal levels high sensitivity ion microprobe 238u 230th zircon dating from the last two eruptions of el chichon 1982 and 550 bp demonstrates that most zircon crystallized between 0 and ca 40 ka few zircon crystals date back to ca 130 kyr and none to the middle pleistocene phase of eruptions trace elements and oxygen isotope variations in zircon indicate fairly stable conditions in the magma chamber between ca 20 and 130 ka with average ti in zircon temperatures estimated at 712 c and 18o values of 6 6 however excursions to high ti in zircon temperatures and high 18o values in zircon occurred at ca 24 ka these excursions also mark the onset of subsequent progressive changes to occasionally higher ti in zircon temperatures lower 18o values and more primitive magma compositions e g high eu eu zr hf and th u systematic rim ward decrease in 18o is recorded by juvenile zircon domains which quasi continuously crystallized for up to 30 kyr prior to eruption textural relationships and o isotopic variations within single zircon crystals are thus evidence for magma recharge causing initial resorption of xenocrystic zircon rapid zircon re saturation driven by local supersaturation and effective magma mixing with sediment contaminated high 18o melts from a boundary layer at the contact of the magma reservoir to country rock initial thermal and compositional defrosting of an intermediate boundary layer and its crystal cargo may have been rapid due to the brief duration of high temperature recharge events as evidenced by the preservation of zircon xenocrysts the delay of at least 12 kyr between major recharge episodes recorded by zircon and the onset of holocene eruptions at brief recurrence intervals suggests that frequent eruptions only started when trachybasaltic magma recharge continued or intensified during the holocene

the 23 500 y 14 c bp white pumice plinian eruption and associated debris avalanche and tochimilco lava flow of popocatepetl volcano mexico abstract the white pumice wp is one of the thickest and most voluminous plinian fallouts produced by popocatepetl volcano in central mexico during the late pleistocene holocene its eruption 23 500 14 c y bp 27 800 cal bp was triggered by the catastrophic failure of the sw flank of the volcano the resulting debris avalanche was highly mobile reaching 72 km from the cone with an apparent coefficient of friction l h of 0 06 the deposit covers an area of 1200 km 2 and has a volume of 10 4 km 3 this gigantic landslide characterized by exceptionally large proximal hummocks 400 m provoked the sudden decompression of the hydrothermal and magmatic systems which produced an initial blast followed by the rise of a plinian column that reached an altitude of 33 km the isopach map allows the recognition of a dispersal axis pointing toward the south where an area of 2490 km 2 was covered by 10 cm of pumice and ash the total volume of the pumice fallout was estimated at 1 9 km 3 dre dense rock equivalent pumice clasts are dacitic 62 66 wt sio 2 anhydrous basis highly vesicular 55 88 vol and display a seriate texture with phenocrysts of plagioclase hornblende augite hypersthene oxides ti magnetite and ilmenite apatite as the eruption advanced discharge rates became more intermittent and the height of the column fluctuated and finally collapsed generating pumice and ash flows that were emplaced around the volcano this short but intense activity was followed during subsequent years by rain induced lahars that reached great distances from the volcano at the same time more degassed andesitic dacitic 61 65 wt sio 2 magma was erupted effusively 4 4 km 3 dre in the new horseshoe shaped 5 km wide crater from which the tochimilco lava flow descended toward the sse where it inundated an area of 68 km 2 and reached as far as 22 km from its source since then multiple eruptions have reconstructed the summit cone almost completely obliterating the horseshoe shaped crater during the course of this catastrophic eruption vei 5 a total volume of 6 3 km 3 dre of juvenile magma pumice and lava were emitted and at least an additional 10 km 3 of pre existing rocks debris avalanche mobilized it surpasses in magnitude most other known plinian eruptions from popocatepetl and can be envisaged as an example of a worst case scenario for hazard evaluation purposes it dramatically changed the morphology of the volcano and had profound and far reaching effects beyond its immediate vicinity along rivers draining surrounding plains as well as on the lacustrine basins e g chalco to the ne a repeat of such an eruption in this densely populated area would certainly cause a major calamity of unprecedented dimensions

using the spatial distribution and lithology of ballistic blocks to interpret eruption sequence and dynamics august 6 2012 upper te maari eruption new zealand the ballistic ejection of blocks during explosive eruptions constitutes a major hazard near active volcanoes fields of ballistic clasts can provide important clues towards quantifying the energy dynamics and directionality of explosive events but detailed datasets are rare during the 6 august 2012 hydrothermal eruption of upper te maari tongariro new zealand three explosions occurred in rapid succession within less than 20 s the first two produced laterally directed pyroclastic density currents pdc and the final vertical explosion generated an ash plume each of these explosions was associated with the ejection of ballistic blocks we present detailed maps of the resulting 5 1 km2 block impact field and the distribution of the 2200 impact craters with diameters 2 5 m there are two distinct regions of high crater concentration where crater densities reach more than six times the average background density these occur at distances of 500 700 m east and 1000 1350 west of a 430 m long fissure that was created during the eruption the high density fields are characterized by a narrow radial spread of 45 and are located along the proximal transport direction of the pyroclastic density currents a provenance analysis of ballistic blocks allowed us to reconstruct two different eruptive vents for the explosions the first two laterally directed explosions were sourced from the fissure while the third explosion occurred through the pre existing upper te maari crater generating a roughly axisymmetric shower of ballistics stratigraphic relationships between impact craters pdc and fall deposits suggest that the ballistic blocks were initially coupled with the rapidly expanding gas particle mixtures that produced the pdcs ballistic trajectory modeling reproducing the lateral extent and main impact density pattern of the western impact field allows estimation of the vertical expansion angle of the second and largest explosion the calculations show that the largest proportion of the explosion energy was strongly focused as a narrow and extremely shallow from 3 to 15 from the horizontal laterally expanding hydrothermal blast the results presented here constitute an important data set for ballistic hazard assessment at tongariro volcano and they can provide further clues towards better understanding highly energetic laterally directed volcanic explosions at similar hydrothermal fields

hydrochemical dynamics of the lake spring system in the crater of el chichon volcano chiapas mexico abstract el chichon volcano chiapas mexico erupted violently in march april 1982 breaching through the former volcano hydrothermal system since then the 1982 crater has hosted a shallow 1 3 3 m acidic ph 2 2 and warm 30 c crater lake with a strongly varying chemistry cl so 4 0 79 molar ratio the changes in crater lake chemistry and volume are not systematically related to the seasonal variation of rainfall but rather to the activity of near neutral geyser like springs in the crater soap pool these soap pool springs are the only sources of cl for the lake their geyser like behaviour with a long term months to years periodicity is due to a specific geometry of the shallow boiling aquifer beneath the lake which is the remnant of the 1983 cl rich 24 000 mg l crater lake water the soap pool springs decreased in cl content over time the zero time extrapolation 1982 year of the eruption approaches the cl content in the initial crater lake meanwhile the extrapolation towards the future indicates a zero cl content by 2009 1 this particular situation offers the opportunity to calculate mass balance and cl budget to quantify the lake spring system in the el chichon crater these calculations show that the water balance without the input of sp springs is negative implying that the lake should disappear during the dry season the isotopic composition of lake waters d and 18 o coincide with this crater lake sp dynamics reflecting evaporation processes and mixing with sp geyser and meteoric water future dome growth not observed yet in the post 1982 el chichon crater may be anticipated by changes in lake chemistry and dynamics

reconciling li and o diffusion in zircon with protracted magmatic crystal residence lithium and o in zircon have strong potential as diffusion chronometers for assessing thermal histories of magmatic and metamorphic systems but their diffusion mechanisms remain controversial zircon populations erupted from el chichon volcano chiapas mexico often contain xenocrysts of detrital origin with juvenile overgrowth forming a natural diffusion boundary within individual crystals high spatial resolution o and li isotope analyses u pb and u th geochronology and li along with al and y scanning ion imaging were acquired to compare diffusion model timescales with those derived from radiometric dating oxygen isotopes in el chichon zircon xenocrysts preserve source heterogeneities with xenocrystic and juvenile domains of zircon being in o isotopic disequilibrium with the melt at the time of eruption preservation of these heterogeneities is consistent with recently determined o isotope diffusion parameters when crystal residence at magmatic temperatures is assumed over the 103 104 year timescales indicated by u th geochronology lithium concentration gradients across the same boundaries are sharp within the 2 5 m lateral resolution of the ion beam whereas li isotopic compositions for xenocrystic cores are homogeneous at 7li 7 8 2 3 1 standard error and different from their putative source diffusive equilibration of li isotopes in zircon is consistent with protracted magmatic crystal residence but preservation of li abundance heterogeneities is difficult to reconcile with evidence for recurrent high temperature exposure of zircon in a highly active magmatic system we speculate that li partitioning in zircon is in part coupled to slow diffusing trivalent cations which can cause severe underestimation of diffusion timescales extracted from li diffusion modeling

a 550 year old plinian eruption at el chichon volcano chiapas mexico explosive volcanism linked to reheating of the magma reservoir 1 some 550 years ago 1320 1433 a d a powerful plinian eruption at el chichon volcano in southern mexico produced a widespread pumice fall deposit we subdivided the deposit into three parts on the basis of structural and textural characteristics pumice lithology and density granulometry and petrologic geochemical attributes the deposit covers an area of 1500 km2 within the 1 cm isopach and has a minimum estimated bulk volume of 2 8 km3 1 1 km3 dense rock equivalent dre its eruptive column reached an altitude of 31 km consideration of field evidence the presence and nature of mafic enclaves and chemical data strongly suggest that the 550 year b p eruption is linked with the intrusion of a high temperature basaltic magma into preexisting but stagnated trachyandesitic magma beneath el chichon thorough mixing of the two magmas produced a compositionally uniform hybrid trachyandesite magma average sio2 55 3 wt which subsequently underwent crystal growth and gas exsolution ultimately overpressurizing the zoned magmatic system to erupt explosively on the basis of el chichon s known eruptive history the intrusion mixing event occurred sometime after the 900 year b p eruption the hybrid magma had a preeruption temperature of 820 830 c and was water undersaturated 5 6 wt h2o at pressures of 2 2 5 kbar

strike slip faults and k alkaline volcanism at el chichon volcano southeastern mexico abstract el chichon volcano is located in the northern part of the state of chiapas in southeastern mexico the volcano is situated within the transcurrent fault province characterized by a series of rising and sinking blocks bounded by sinistral strike slip faults the basement around el chichon is a sequence of jurassic evaporates cretaceous limestones and tertiary terrigenous rocks folded into open and an echelon structures the main structures in the area are the la union and caimba anticlines and the buena vista syncline the region is cross cut by two conjugate fault systems a dextral strike slip n s trending set and a sinistral strike slip e w set the most significant fault of the latter system is the san juan fault which controlled the emplacement of a basaltic dike near the village of chapultenango some 1 1 ma ago and the activity of el chichon during the last 0 2 ma additionally a series of n45 e trending faults chapultengo fault system have produced a half graben geometry of blocks on top of which el chichon has been emplaced microstructures such as slickensides tension fractures layer parallel slip stylolites and macro and meso folds of the sedimentary rocks indicate that during the late miocene the el chichon area was affected by a maximum principal stress 1 oriented n70 e a minimum principal stress 3 oriented n20 w and a vertical intermediate principal stress this stress pattern indicates that the area underwent a strike slip motion that produced widespread deformation the occurrence of crustal earthquakes

risk assessment of residential buildings for an eruption of furnas volcano sao miguel the azores this paper presents the results of a study of the risks to human settlements of a future eruption of the furnas volcano in the azores it makes use of previous geological studies to estimate the likely impact of the volcanic hazards on the surrounding settlements given an eruption comparable with the last major eruption in the island in 1630 it presents the results of a comprehensive building by building survey of the settlements at risk to determine the exposure of the residential building stock to these hazards and it uses data from recent experience of volcanic eruptions elsewhere to estimate the vulnerability of the buildings to each hazard and the likely scale of human casualties and building damage the paper concludes with some recommendations for preparedness and protective measures which could be taken before an eruption to reduce the risk of human casualties from roof and building collapses principal among these are recommendations for strengthening the lateral load resistance of buildings built with the traditional vernacular techniques to better resist groundshaking during eruptions and earthquakes upgrading local building code requirements with view to increasing the live load resistance of roofs to levels similar to those applied in areas of heavy snowfalls to prevent roof collapse from tephra loading other preparedness measures are also discussed with respect to volcanic earthquakes volcanic bomb impact pyroclastic flows and tephra falls many aspects of this paper are relevant to other volcanic areas around the world

deposition temperature of some pdc deposits from the 1982 eruption of el chichon volcano chiapas mexico inferred from rock magnetic data abstract thermal remanent magnetization trm analyses were carried out on lithic fragments from two different typologies of pyroclastic density current pdc deposits of the 1982 eruption of el chichon volcano in order to estimate their equilibrium temperature tdep after deposition the estimated tdep range is 360 400 c which overlaps the direct measurements of temperature carried out four days after the eruption on the pdc deposits this overlap demonstrates the reliability of the trm method to estimate the tdep of pyroclastic deposits and to approximate their depositional temperature these results also constraint the time needed for reaching thermal equilibrium within four days for the studied pdc deposits in agreement with predictions of theoretical models sedimentological analysis demonstrates that different thickness of aggrading granular dominated pulses does not affect significantly the estimated tdep for the two studied pdcs the component analysis highlights how the entrapment of a significant amount of pre heated lithic fragments from the dome and the conduit walls reduced the cooling of the pyroclastic mixture

repeated recharge assimilation and hybridization in magmas erupted from el chichon as recorded by plagioclase and amphibole phenocrysts abstract compositional and isotopic zoning patterns in plagioclase and amphibole phenocrysts from el chichon record multiple cycles of country rock assimilation magma injection hybridization and mixing laser ablation icp ms and electron microprobe analyses of plagioclase crystals from 7 eruptions spanning 3100 years reveal four types of zoning these compositional and isotopic zones are often associated with textural changes observed in the crystals in thin section e g sieved or patchy regions amphiboles are frequently zoned in al and si and in two magmas may have clinopyroxene rims interestingly most plagioclase show multiple and repeated zoning patterns moreover all magmas contain all zoning patterns and textures and crystals with substantially different sequences of zones occur within mm of one another the most reasonable explanation for the origin of these textures is a frequently recharged chamber plagioclase zones with increasing anorthite contents an and decreasing 87sr 86sr ratios record injection by a hotter possibly wetter and more primitive magma lower 87sr 86sr ratio zones with decreasing an and increasing 87sr 86sr ratios record assimilation of country rock and or hybridization of the host and injected magmas injection of hot magma may provide the heat for country rock assimilation changes in an without corresponding changes in 87sr 86sr ratio likely record slight variations in pressure or temperature during crystallization or the far field thermal effects of magma injection variations in 87sr 86sr ratio unaccompanied by anzoning record assimilation of country rock amphibole zoning patterns also record periodic heating events amphibole with clinopyroxene rims record episodes where the magma was heated beyond the amphibole stability field bulk compositional homogeneity and the juxtaposition of many crystals with disparate zoning patterns in single pumice require the magmatic system to be well mixed strontium diffusion rates indicate that the plagioclase zoning patterns cannot have persisted at magmatic pressures and temperatures for more than 500 years thus cycles of injection and assimilation occur on timescales equal to or shorter than the eruption recurrence interval long term compositional and isotopic homogeneity indicate that there is a balance between recharge assimilation and crystallization

pedosediments of karstic sinkholes in the eolianites of ne yucatan a record of late quaternary soil development geomorphic processes and landscape stability abstract the pedogenetic and geomorphic processes controlling soil development in tropical karstic landscapes are still poorly understood we have discovered and studied thick pedosediments in karst pockets developed in late pleistocene lithified calcareous dunes eolianites in the ne coast of the yucatan peninsula the morphological geochemical and mineralogical characteristics of the pocket fills were interpreted as a record of pedogenesis and geomorphic dynamics that shaped the soil mantle during the holocene sand fraction mineralogy and the zr ti ratio indicated a mixed origin of the soil parent material volcanic and granitic metamorphic components redeposited in the lithoral and coastal environments were identified within the soil matrix primary minerals were transformed by weathering and caused desilicification accumulation of clay hydroxy interlayered vermiculite and kaolinite and dithionite citrate bicarbonate extractable iron oxides fed reworked pedofeatures indicative of clay illuviation and redoximorphic processes were observed this set of processes points to a continuous phase of humid pedogenesis several thousand years long in the early middle holocene however the development of thick recalcified pedosediments in the pockets contrasting with the thin background rendzinas requires active soil redeposition during a late phase of geomorphic activity the available accelerator mass spectrometry ams radiocarbon date indicates that the switch of the erosion sedimentation processes could be related to ancient maya land use impact

assessment of the record of the 1982 el chichon eruption as preserved in greenland snow variability in the so42 and cl time series for the 1980s from 12 shallow snow pits across the greenland ice sheet is used to evaluate the record of the 1982 el chichon eruption and the potential for recording a moderate northern equatorial eruption in a single greenland ice core composition of volcanic glass found in spring 1983 snow in one of the pits in the summit region matches that from el chichon glass thereby verifying the deposition of material from the eruption high na and cl concentrations in this same layer probably represent deposition of the reaction products of halite and h2so4 as observed in the stratosphere following the eruption these findings and the presence of a cl signal in five of the other pits indicate that the cl aerosol component of some eruptions has the potential to remain aloft for at least 1 year after the eruption some of these aerosols may be adsorbed onto tephra particles distinct so42 peaks that can be confidently linked to el chichon were found in only 50 of the records developed through subseasonal sampling however in several other pits an elevated baseline thought to represent more lengthy periods of el chichon aerosol deposition as opposed to deposition from a single snowfall event were observed smoothing of the original data by the calculation of annual so42 flux resulted in the presence of high flux values between 1982 and 1984 years thought to be affected by el chichon aerosol deposition in 9 of the 12 pits these results suggest that a single ice core from anywhere in greenland may record a signal from a northern equatorial eruption of magnitude similar to that of el chichon about 75 of the time this is despite the overall high levels of so2 4 deposition from anthropogenic sources that now make identification and quantification of the volcanic so2 portion of the record more difficult than obtaining the same data for preindustrial volcanism nevertheless composite records from all the pits sampled yielded stratospheric loading 20 mt and optical depth 0 13 estimates similar to stratospheric and satellite based measurements following the eruption equally high so42 concentration and flux values in snow from 1980 to 1982 reflect deposition from the series of middle to high northern latitude volcanic eruptions 1979 1981

evolution of the seismic activity from the 1982 eruption of el chichon volcano chiapas mexico we analyzed more than 1700 earthquakes related to the 1982 eruption of el chichon volcano in southern mexico the data were recorded at specific periods throughout the whole eruptive interval of march to april 1982 by three different networks the seismic activity began several months before the first eruption on 28 march during this period the seismicity consisted of hybrid and long period shallow earthquakes most likely related to processes of faulting fracturing and fluid movement underneath the volcano the foci of events occurring before the eruption circumscribe an aseismic zone from approximately 7 to 13 km below the volcano after the eruption the seismic activity consisted of tectonic type earthquakes that peaked at 1200 events h this later activity occurred over a wide range of depths mostly between 5 and 20 km that includes the former aseismic zone and is roughly limited by the major tectonic faults in the area

constraints on cooling rates and permeabilities of pumice in an explosive eruption jet from colour and magnetic mineralogy abstract in explosive volcanic eruptions vesicular magma droplets produced by fragmentation are propelled into the atmosphere where they are chilled to form pumices the thermal history of droplets and the permeability of their internal bubble networks determine how much they are deformed in the eruption jet and hence what information pumices record about the state of the magma at fragmentation we study these aspects of the minoan plinian eruption of santorini volcano by quantifying the rate of oxidation reactions that took place when air entered the hot magma fragments in our experiments white minoan pumices were heated for minutes to hours between 600 and 850 c either in air or in an atmosphere with an oxygen fugacity at the ni nio buffer pumices were unchanged by heating at ni nio those heated in air often became pink to dark pink depending on heating time and their curie temperatures as determined by magnetic susceptibility measurements increased we use oxidation rates deduced from these experiments in conjunction with calculations of the rate of conductive cooling and of the rate at which air can enter a pumice to constrain the conditions experienced by pumices during the eruption natural minoan pumices less than about 5 cm in radius are white whereas larger ones often have white rims and pink interiors with curie temperatures higher than those of white material we infer that small pumices were cooled before being oxidized and that oxidation of the interiors of large clasts mostly took place during flight at temperatures within a few tens of degrees of magmatic values white rims of large pumices despite being permeable were cooled before oxidation could occur permeability developed in the liquid state but did not develop early enough with respect to cooling or was not large enough to allow extreme oxidation we give measurements of pumice permeabilities that should be close to magmatic values

fragmentation of magma during plinian volcanic eruptions the ratio of the volume of vesicles gas to that of glass liquid in pumice clasts v g v l reflects the degassing and dynamic history experienced by a magma during an explosive eruption v g v l in pumices from a large number of plinian eruption deposits is shown here to vary by two orders of magnitude even between pumices at a given level in a deposit these variations in v g v l do not correlate with crystallinity or initial water content of the magmas or their eruptive intensities despite large ranges in these variables gas volume ratios of pumices do however vary systematically with magma viscosity estimated at the point of fragmentation and we infer that pumices do not quench at the level of fragmentation but undergo some post fragmentary evolution on the timescale of plinian eruptions pumices with viscosities 109 pa s can expand after fragmentation as long as their bubbles retain gas at a rate inversely proportional to their viscosity once the bubbles connect to form a permeable network and lose their gas expansion halts and pumices with viscosities 105 pa s can collapse under the action of surface tension textural evidence from bubble sizes and shapes in pumices indicates that both expansion and collapse have taken place the magnitudes of expansion and collapse therefore depend critically on the timing of bubble connectivity relative to the final moment of quenching we propose that bubbles in different pumices become connected at different times throughout the time span between fragmentation and quenching after accounting for these effects we derive new information on the fragmentation process from two characteristics of pumices the most important is a relatively constant minimum value of v g v l of 1 78 64 vol vesicularity in all samples with viscosities 105 pa s this value is independent of magma composition and thus reflects a property of the eruptive mechanism the other characteristic is that highly expanded pumices 85 vol vesicularities are common which argues against overpressure in bubbles as a mechanism for fragmenting magma we suggest that magma fragments when it reaches a vesicularity of 64 vol but only if sheared sufficiently strongly the intensity of shear varies as a function of velocity in the conduit which is related to overpressure in the chamber so that changes in overpressure with time are important in controlling the common progression from explosive to effusive activity at volcanoes

dynamics of the ca 4965 yr 14c bp ochre pumice plinian eruption of popocatepetl volcano mexico abstract the ochre pumice op plinian fallout was produced by popocatepetl volcano in central mexico during a major plinian eruption that occurred 4965 65 14 c yr bp 3700 bc the op is part of the ochre pumice sequence ops that consists of surge fall and pyroclastic flow deposits the op plinian fallout shows a bimodal grain size distribution with poor to moderate sorting that improves progressively towards the upper beds the juvenile component is mainly pumice 83 wt whereas the accidental components consist of igneous sedimentary and metamorphic clasts from the walls of the magma chamber and or conduit the vesicularity of the pumice decreases from bottom to top of the stratigraphic sequence while the crystal and glass contents increase this suggests increasing magma degassing prior and during the eruption the chemical composition of the pumice varies insignificantly at the base it is less evolved sio 2 61 wt and it becomes slightly more silicic towards the top sio 2 63 wt pumice clasts have a crystallinity index that ranges between 10 and 25 vol and display a seriate texture with phenocrysts of euhedral plagioclase pl clinopyroxene cpx orthopyroxene opx olivine ol oxide ox apatite ap the size of the maximum lithic 2 5 cm at a horizontal distance of 19 km indicates an eruption column height of 37 41 km the isopach map allows the recognition of a dispersal axis that points towards the nne where an area of 300 km 2 was covered by 6 cm of pumice and ash a minimum volume for the op plinian fallout deposit was calculated using a minimum thickness of 6 cm found at distal outcrops and was estimated at 4 9 km 3 which corresponds to 2 km 3 of dense rock equivalent dre stratigraphic relations indicate that the entire ops was emplaced during a short time interval of a few days to weeks and consisted of three main different phases phreato magmatic plinian and vulcanian it started violently with the emplacement of surges and then culminated with the eruption of the op fallout deposit as the eruption advanced discharge rates became more intermittent and the height of the column fluctuated and finally collapsed generating pumice and ash flows that were emplaced around the volcano this short but intense activity was followed during subsequent years by the growth of domes in the crater and the emplacement of block and ash flows generated by vulcanian explosions

volcanic ash in ancient maya ceramics of the limestone lowlands implications for prehistoric volcanic activity in the guatemala highlands abstract in the spirit of collaborative research glicken and ford embarked on the problem of identifying the source of volcanic ash used as temper in prehistoric maya ceramics verification of the presence of glass shards and associated volcanic mineralogy in thin sections of maya ceramics was straightforward and pointed to the guatemala highland volcanic chain considering seasonal wind rose patterns target volcanoes include those from the area west of and including guatemala city joint field research conducted in 1983 by glicken and ford in the limestone lowlands of belize and neighboring guatemala 300 km north of the volcanic zone and 150 km from the nearest identified ash deposits was unsuccessful in discovering local volcanic ash deposits the abundance of the ash in common maya ceramic vessels coupled with the difficulties of long distance procurement without draft animals lead glicken to suggest that ashfall into the lowlands would most parsimoniously explain prehistoric procurement it literally dropped into their hands a major archaeological problem with this explanation is that the use of volcanic ash occurring over several centuries of the late classic period ca 600 900 ad to accept the ashfall hypothesis for ancient maya volcanic ash procurement one would have to demonstrate a long span of consistent volcanic activity in the guatemala highlands for the last half of the first millennium ad should this be documented through careful petrographic microprobe and tephrachronological studies a number of related archaeological phenomena would be explained in addition the proposed model of volcanic activity has implications for understanding volcanism and potential volcanic hazards in central america over a significantly longer time span than the historic period these avenues are explored and a call for further collaborative research of this interdisciplinary problem is extended in this paper

the 1982 eruptions of el chichon volcano mexico stratigraphy of pyroclastic deposits abstract following a repose period of 500 to 600 years el chichon volcano in se mexico erupted explosively during the months of march and april 1982 three major eruptions involving trachyandesite magma injected ash into the stratosphere on 29 march at 0515 gmt and on 4 april at 0139 and 1110 gmt the first major eruption generated only tephra fall which was dispersed ene in the troposphere over the yucatan peninsula and wsw in the stratosphere towards the pacific ocean the second eruption produced tephra fall and pyroelastic surges and pyroclastic flows by repeated collapse of a lithicrich eruption column the surge and flow activity devastated a roughly circular area 153 km 2 around el chichon to a distance of about 6 km from the vent nine villages within the zone were either partially or completely destroyed and loss of human life was perhaps as high as 2000 pyroclastic flows and surges were also generated during the third eruption although ash fall was the primary activity as a result of both the second and third eruptions tephra was transported ene in the troposphere and wsw in the stratosphere the total volume of material ejected during the three major eruptions 0 50 km 3 d r e is represented by tephra fall 0 37 km 3 pyroclastic surges 0 09 km 3 and pyroclastic flows and debris flows 0 04 km 3 as a result of the eruptions a new 1 km wide and 300 m deep crater was formed by the disruption and excavation of a pre existing summit dome

reconstruction of the sibinal pumice an andesitic plinian eruption at tacana volcanic complex mexico guatemala abstract the tacana volcanic complex located on the mexico guatemala border has had numerous small historical explosions the latest being a phreatic explosion in 1986 the stratigraphic record however suggests that much more voluminous eruptions have occurred in the past here we document one such eruption the sibinal pumice deposit which occurred ca 23 540 years b p the deposit consists of two pumice rich units 1 a lower stratified member sm that consists of at least seven normally graded fall layers interbedded with pyroclastic wet surge layers and 2 an upper massive member mm made up of a single fall deposit both members can reach up to 2 5 m in thickness and are separated by a single massive indurated yellowish pumice rich reworked layer sm was dispersed to the northeast n70 e with its 6 cm isopach covering an area of 275 km2 whereas mm was dispersed to the north n22 e with its 70 cm isopach covering an area of ca 330 km2 yellow vesicular pumice fragments light gray lithics and hydrothermally altered red and black dense lithics are abundant in both members although altered lithics are more abundant at the base of each reaching 15 vol pumice compositions range from basaltic to andesitic 48 61 wt sio2 anhydrous basis but are highly altered they contain plagioclase andesine labradorite augite hypersthene fe ti oxides and rare amphibole no compositional or mineralogical differences occur between the units indicating a common magma source during the same eruption the sibinal pumice eruption started with a weak pulsating column that reached at most 19 km in height ejecting 2 9 km3 of tephra 1 1 km3 dre at an average mass discharge rate of 4 7 107 kg s with repeated hydromagmatic explosions that generated wet surges down the slopes of the volcano the eruption ceased for a while during which rainfall generated a widespread lahar that eroded the top of sm the eruption began anew with a sustained and stable plinian column that ejected 4 6 km3 1 9 km3 dre of tephra at a mass discharge rate of 8 1 107 kg s the lack of any compositional differences in the magma suggests that the change in eruptive style was driven by influxes of external water provoking hydromagmatic explosions that cleared the conduit then the system changed to dry system and the eruption style changed from pulsating to stable plinian as the conduit became wider the mass discharge rate also increased

late holocene paleopedological records contained in tephra from el chichon volcano chiapas mexico abstract high rates of pedogenesis on unconsolidated volcanic materials imply the accelerated generation of the soil memory the purpose of this research was to extract the high resolution centennial scale paleopedological records from the late holocene paleosols of the el chichon volcano formed during the last 2000 years we studied buried monogenetic andosols on the dated tephras and a pedocomplex formed from a set of thin ash layers deposited on older acrisol derived from shales particle size distribution dcb extractable fe oxalate extractable fe al and si sand and clay mineralogy organic carbon content and stable c isotope composition in humus were evaluated and interpreted as the elements of the soil memory however some differences were found in properties of two buried soils especially in the kind of a horizons we attribute such differences of individual andosols to be caused by ancient human impact because it has been demonstrated that humid conditions persisted during the last 1300 years thus the drought that was supposed to provoke the collapse of the maya civilization at the end of i millennium a d should have been a short term event below the resolution of this paleopedological record the andic acrisol pedocomplex demonstrated the domination of the humid tropical climate over longer time intervals probably major part of the holocene with possible minor dry episodes

a process based model of pre eruption seismicity patterns and its use for eruption forecasting at dormant stratovolcanoes abstract using long term data sets the eruptive size timing and style can typically be successfully forecast for dormant volcanoes using current monitoring data and knowledge of precursory eruptive patterns the usaid usgs volcano disaster assistance program vdap utilizes seismic data over multiple eruption cycles and across volcano types to successfully forecast eruption size style and onset times as well as changes within ongoing eruptions from millions of seismic event observations we show that seismic data a proxy for rate dependent strain changes in the magmatic system combined with a process based conceptual geologic model enables eruption forecasting especially for stratovolcanoes dormant 20 years we show that this model often works for some open systems ones that sufficiently reseal to plug the conduit and also where a deep intrusion occurs after phreatic or phreatomagmatic explosions have begun this model is divided into four seismicity and geologic stages we describe each of the four stages of seismicity in detail and how they relate to the ongoing geologic process of that stage stage 1 deep intrusion and seismicity occurring at 10 to 40 km depth below the volcanic edifice stage 2 distal vt seismicity induced at distances from 2 to 30 km laterally from the summit by magma intruding into and inflating the upper crustal magma storage region stage 3 vent clearing seismicity associated with the initial vent creation and clearing phase of eruptive activity stage 4 repetitive event seismicity associated with the final ascent of magma from 2 km to the surface we present 36 examples of this seismic progression from 26 volcanoes we believe that this progression generally correlates with the magma flux and the eventual explosivity and is invaluable for forecasting eruptions

use of soils and palaeosols on volcanic materials to establish the duration of soil formation at different chronological scales abstract in this paper we present an overview of the mexican volcanic palaeosol sequences as a valuable tool to establish the duration of soil formation at different chronological scales we have selected four study cases which cover time intervals from decennial centennial to millennial pedogenesis the first case corresponds to the soils in el chichon volcano where the short interval between the eruptions gives the opportunity to study the soil formation in periods less than 500 years in this interval the transformation from regosol to andosol is observable in el nevado de toluca pedogenesis of longer duration 4000 to 6000 y characterizes a vitric andosol stage in this area the transformation of andosol to luvisol is also shown in periods longer than 10 000 years the third study case corresponds to the tlaxcala palaeosol sequence where pedogenesis in intervals from 10 000 to 100 000 years is observable in this case no andosols are present and a complete set of luvisols showing different properties is found this differentiation is not only related to the duration of the pedogenesis but also to the climatic conditions which lead to changes in specific properties clay content weathering of the primary minerals fed content in this way these soils are valuable for palaeoenvironmental reconstruction the fourth case is related to faster pedogenesis in the volcanic regions of mexico where highly developed luvisols are found formed in intervals less than 15 000 y in this case the influence of a pre weathered volcanic material as a source of clay allows the rapid transformation

tsunami fragility functions for road and utility pole assets using field survey and remotely sensed data from the 2018 sulawesi tsunami palu indonesia the 2018 sulawesi tsunami caused widespread impacts in palu city indonesia including to components of infrastructure lifeline networks lifeline networks are key to the operation of society and are particularly crucial during post disaster relief and recovery efforts understanding their vulnerability to tsunami hazards is important for disaster risk reduction but is an understudied topic this study uses field survey and remotely sensed data to develop a single dataset used to create tsunami fragility functions for road and utility pole assets in palu tsunami inundation depths were estimated at component locations from a spatial interpolation of field measured flow depths and wave run up component attributes and geometries exposed to tsunami inundation were compiled from both field surveys and remote sensing on satellite imagery and street view imagery which included component construction material capacity roads and height poles roads demonstrate a 0 16 probability of exceeding complete damage at 2 m inundation depth while utility poles see a 0 47 probability the probability of exceeding complete damage at 2 m inundation depth for concrete asphalt collector and local roads is 0 34 0 17 0 19 and 0 13 respectively and for concrete steel steel 5 m height utility poles is 0 42 0 48 0 49 and 0 47 respectively when comparing the synthesised tsunami fragility functions to those from other global events palu roads were more vulnerable at 2 m inundation depth 0 16 compared to roads exposed to the 2011 tohoku tsunami in japan 0 06 and 2015 illapel tsunami in chile 0 05

tephra cushioning of ballistic impacts quantifying building vulnerability through pneumatic cannon experiments and multiple fragility curve fitting approaches abstract ballistic projectiles are the most frequently lethal volcanic hazard close to the vent recent eruptions of ontake in 2014 and kusatsu shirane in 2018 showed that un reinforced timber framed buildings those typically considered highly vulnerable to the dangerous penetration of ballistics provided life saving shelter from ballistic impact modelled kinetic energies of some non penetrating impacts were an order of magnitude above expected penetration thresholds it has been hypothesised that a pre existing layer of tephra on the roofs cushioned impacts to quantitatively test this and improve our understanding of how buildings respond to projectile impacts we used a pneumatic cannon to simulate block impacts to clay tiles and reinforced concrete roof slabs covered with tephra layers 0 20 cm thick substantially higher impact energies were resisted when tephra was present with 5 cm of tephra approximately tripling the penetration threshold of both building materials fragility curves which relate ballistic hazard intensity with the probability of building damage were developed from our experimental data following three curve fitting approaches generalised link models cumulative link models and data binning a key benefit of these approaches is that confidence in these curves can be robustly quantified from the data the first time that this has been attempted for volcanic fragility curves this study shows how the extent of building damage can be strongly influenced by the sequence of volcanic hazards and provides an example of proactive risk management through testing of physical mitigation strategies in a laboratory environment

the 31 ka rhyolitic plinian to sub plinian eruption of tlaloc volcano sierra nevada central mexico abstract tlaloc is a late pleistocene stratovolcano located ne of mexico city it is the northernmost volcano of the n s sierra nevada volcanic range which consists from north to south of tlaloc telapon iztaccihuatl and popocatepetl volcanoes tlaloc has always been considered the oldest and extinct volcano of the sierra nevada volcanic range recent field data revealed that tlaloc was very active during late pleistocene through a series of explosive eruptions one of these eruptions produced the multilayered white pumice mwp a rhyolitic pyroclastic sequence the eruption began with a 24 km high plinian column mwp f1 that was dispersed to the ne by prevailing winds it was interrupted by fountaining of the column with the generation of a pyroclastic density current that emplaced mwp s1 layer then followed five unstable sub plinian columns mwp f2 to f6 that reached altitudes between 16 and 19 km fall deposits as a whole are 1 m thick at 12 km from the vent cover a minimum area of 577 km2 for a total volume of 4 68 km3 dre 1 58 km3 the eruption ejected a total mass of 3 45 1012 kg at different mass discharges the last sub plinian column mwp f6 collapsed and produced dense pyroclastic density currents that deposited pumiceous pyroclastic flows mwp pf following main ravines to the north and east of the vent these density currents filled gullies with 23 m thick deposits at a distance of 12 km from the vent totaling a minimum dre volume of 0 2 km3 pyroclastic flow deposits charred tree trunks that yielded an age of 31 490 1995 1595 yr b p that closely date the age of the eruption rain during this phase of the eruption generated syn eruptive lahars mwp df post eruptive lahars mwp ed finally swept the volcano flanks the mwp deposits consist of abundant white pumice up to 96 vol rare gray pumice cognate lithics accidental altered lithics xenocrysts white and gray pumice clasts contain phenocrysts of quartz plagioclase sanidine biotite rare fe ti oxides monazite zircon and apatite xenocrysts are represented by plagioclase microcline orthoclase and quartz likely coming from a deeper plutonic body both pumices have a rhyolitic composition 74 98 1 wt sio2 in water free basis representing one of the most acidic products of tlaloc and the entire sierra nevada volcanic range the rhyolitic liquid was likely extracted from a mush like plutonic body reaching the minimum predicted vesicularity values for plinian fragmentation for which the triggering mechanism of the mwp eruption is attributed to the high viscosity of the magma that provoked overpressure of the magmatic system the parameters studied suggest that eruption behavior evolved from plinian to sub plinian eruptive columns over time due to conduit dynamics rather than variations in magma properties of the mwp products

volcanz a volcanic loss model for auckland new zealand abstract volcanz is a probabilistic volcanic loss model developed for the auckland region in new zealand that currently considers tephra fall hazards from the auckland volcanic field avf tuhua volcano okataina volcanic centre taupo volcano tongariro volcanic centre and egmont volcano in this first version of the model structural and non structural damage to residential building envelopes and associated cleanup costs are calculated using monte carlo simulation volcanz assigns a minimum and maximum damage value to groups of buildings for every simulation dependent on tephra thickness a central damage value representing loss as a percentage of total replacement cost is then randomly selected between these limits even with small thickness falls non structural damage is expected to roof and wall coatings air conditioning units aerials and satellite dishes due to the corrosive and abrasive properties of tephra an average loss of 583 attributed to non structural damage was assigned to all residential buildings impacted by any thickness of tephra greater than 0 1 mm the costs of tephra removal from buildings cleaning of building exteriors and tephra transport and disposal are also calculated within the model assuming much of the cleanup process will be carried out by homeowners losses from all simulations are plotted against calculated average recurrence intervals aris to produce loss curves structural damage does not become apparent until aris of approximately 8000 years 1 billion losses due to structural damage occur at about 35 000 years and this increases to about 26 billion at 1 million years loss due to non structural damage is constant at approximately 160 million for aris above about 600 years between 600 and 3000 years cleanup loss is approximately 50 million increasing to over 450 million at a return period of 1 million years at aris between 600 and 3000 years total loss is approximately 210 million increasing to 10 billion at 100 000 years and over 26 billion at 1 million years because we only consider residential building damage and associated cleanup these values greatly underestimate total loss from the next volcanic event to impact auckland loss calculations will be improved by adding additional hazard and loss modules to volcanz resulting in a complete catastrophe loss model

buildings vs ballistics quantifying the vulnerability of buildings to volcanic ballistic impacts using field studies and pneumatic cannon experiments abstract recent casualties in volcanic eruptions due to trauma from blocks and bombs necessitate more rigorous ballistic specific risk assessment quantitative assessments are limited by a lack of experimental and field data on the vulnerability of buildings to ballistic hazards an improved quantitative understanding of building vulnerability to ballistic impacts is required for informing appropriate life safety actions and other risk reduction strategies we assessed ballistic impacts to buildings from eruptions at usu volcano and mt ontake in japan and compiled available impact data from eruptions elsewhere to identify common damage patterns from ballistic impacts to buildings we additionally completed a series of cannon experiments which simulate ballistic block impacts to building claddings to investigate their performance over a range of ballistic projectile velocities masses and energies our experiments provide new insights by quantifying 1 the hazard associated with post impact shrapnel from building and rock fragments 2 the effect of impact obliquity on damage and 3 the additional impact resistance buildings possess when claddings are struck in areas directly supported by framing components this was not well identified in previous work which may have underestimated building vulnerability to ballistic hazards to improve assessment of building vulnerability to ballistics we use our experimental and field data to develop quantitative vulnerability models known as fragility functions our fragility functions and field studies show that although unreinforced buildings are highly vulnerable to large ballistics 20 cm diameter they can still provide shelter preventing death during eruptions

magma mixing recharge and eruption histories recorded in plagioclase phenocrysts from el chichon volcano mexico operative throughout the 200 ky history of the el chichon magma consistent core to rim decreases of sr sr ratios and coincident system increases in sr concentrations in plagioclase phenocrysts of varying size 1 cm to 2 mm are reported from samples of the 1982 and pre 1982 200 ka eruptions of el chichon volcano maximum sr sr ratios of 0 7054 significantly higher than the wholerock isotopic ratios 0 7040 0 7045 are found in the cores

andesitic plinian eruptions at mt ruapehu quantifying the uppermost limits of eruptive parameters new tephro stratigraphic studies of the tongariro volcanic centre tgvc on the north island new zealand allowed reconstruction of some of the largest andesitic explosive eruptions of mt ruapehu large eruptions were common in the late pleistocene before a transition to strombolian vulcanian and phreatomagmatic eruptive styles that have predominated over the past 10 000 years considering this is the most active volcano in north island of new zealand and the uppermost hazard limits are unknown we identified and mapped the pyroclastic deposits corresponding to the five largest eruptions since 27 ka the selected eruptive units are also characterised by distinctive lithofacies associations correlated to different behaviours of the eruptive column in addition we clarify the source of the 10 9 7 ka pahoka tephra identified by previous authors as the product of one of the largest eruptions of the tgvc the most common explosive eruptions taking place between 13 6 and 10 ka cal years bp involved strongly oscillating partially collapsing eruptive columns up to 37 km high at mass discharge rates up to 6 108 kg s and magnitudes of 4 9 ejecting minimum estimated volumes of 0 6 km3 our results indicate that this volcano as well as the neighbouring andesitic mt tongariro can generate plinian eruptions similar in magnitude to the chaiten 2008 and askja 1875 events such eruptions would mainly produce pyroclastic fallout covering a minimum area of 1 700 km2 ese of the volcano where important touristic agricultural and military activities are based as for the 1995 1996 eruption our field data indicate that complex wind patterns were critical in controlling the dispersion of the eruptive clouds developing sheared commonly bilobate plumes

volcanic ashfall accumulation and loading on gutters and pitched roofs from laboratory empirical experiments implications for risk assessment abstract volcanic ash load is dependent on the migration and accumulation of ash on roofing surfaces and guttering of which limited research has been conducted this study investigates this knowledge gap through the empirical experimental testing of volcanic ash on variably pitched metal sheet roofs with modern pvc gutter systems highlighting the relative importance of accumulation migration remobilization saturation and subsequent load a testing rig delivered ash onto variably pitched roofs pitches 15 25 30 35 and 45 with two 45 tests involving a wet surface with subsequent ashfall and the second of ashfall with periods of wetting followed by wetting until failure in testing dry ash on a dry roof accumulates at pitches up to 35 above this pitch the percentage of ash accumulating reduces with greater percentages infilling guttering and or lost to the ground with the introduction of a wet roof surface at 45 pitch adherence of dry ash greatly increases increasing accumulated ash thickness as compared to dry tests from 8 to 38 for testing involving periods of wetting at 45 roof pitch accumulation percentages further increased to 50 ash migrating from the roof surface filled guttering more rapidly at greater pitches which once full resulted in further migrating ash to spill over the front or back gutter lips collapse of guttering did not occur during testing but deformation and bracket detachment did occur at loads 1 kpa this study provides data on load calculations on roofing and pvc guttering through the quantification and utilization of relationships between ash fate pitch and the influence of water in the development of two scenarios for both roof and gutter these two scenarios then enable the estimation of ash accumulation and thus the load and collapse thresholds for roof and gutter at different roof pitch which could be adopted for volcanic risk modeling or risk management

the 1982 eruptions of el chichon volcano mexico 2 observations and numerical modelling of tephra fall distribution tephra fallout from the a 1 march 29 0532 ut b april 4 0135 ut and c april 4 1122 ut 1982 explosive eruptions of el chichon produced three tephra fall deposits over southeastern mexico bidirectional spreading of eruption plumes as documented by satellite images was due to a combination of tropospheric and stratospheric transport with heaviest deposition of tephra from the ene tropospheric lobes maximum column heights for the eruptions of 27 32 and 29 km respectively have been determined by comparing maximum lithic clast dispersal in the deposits with predicted lithic isopleths based on a theoretical model of pyroclast fallout from eruption columns these column heights suggest peak mass eruption rates of 1 1 108 1 9 108 and 1 3 108 kg s maximum column heights and mass eruption rates occured early in each event based on the normal size grading of the fall deposits sequential satellite images of plume transport and the production of a large stratospheric aerosol plume indicate that the eruption columns were sustained at stratospheric altitudes for a significant portion of their duration new estimates of tephra fall volume based on integration of isopach area and thickness yield a total volume of 2 19 km3 1 09 km3 dre dense rock equivalent or roughly twice the amount of the deposit mapped on the ground up to one half of the erupted mass was therefore deposited elsewhere as highly dispersed tephra

eyewitness stratigraphy chemistry and eruptive dynamics of the 1913 plinian eruption of volcan de colima mexico abstract based on the stratigraphic record of the deposits analysis of previous works historic archives and eyewitness accounts the 1913 eruption of volcan de colima was reconstructed the eruption started in 17 january and peaked in 20 january 1913 it occurred in three main phases 1 an opening phase with the generation of merapi type pyroclastic flows units f1 f2 f3 and a pyroclastic surge s1 2 a vent clearing phase with strong explosions that produced vulcanian soufriere type pyroclastic flows f4 and a pyroclastic surge s2 which destroyed the summit dome decompressing the magma system and 3 a plinian phase with the establishment of a 23 km high column dispersing a fallout c1 to the ne followed by the collapse of the column that generated a pyroclastic surge s3 and 15 km long pumice rich pyroclastic flows f5 after the eruption remobilization of the pyroclastic material generated lahars in main gullies around the crater fallout c1 blanketed an area of 191 318 km2 covering the cities of guzman guadalajara and saltillo coahuila located at 725 km from the source it had a volume of 1 4 km3 0 57 km3 dre dense rock equivalent the total volume of pyroclastic flow and surge deposits was 0 26 km3 0 07 km3 dre giving a total volume of the eruption of 1 66 km3 0 64 km3 dre the plinian column lasted 4 6 h with a total mass of 1 5 1012 kg and a mass eruption rate of 9 02 107 kg s the column height and the ejected magma volume indicate that the 1913 eruption had a vei 5 being the largest event in the historical record of colima volcano juvenile scoria and pumice consisted of pl opx cpx hbl accessory titanomagnetite ap and ol with reaction rims chemistry of juvenile scoria and pumice samples is andesitic very homogeneous 58 3 0 5 wt sio2 and similar to the 1818 juvenile products 58 9 0 2 wt sio2 the presence of banded scoria olivine phenocrysts with reaction rims and trace element variations strongly suggest that the 1913 eruption was caused by a magma mixing event

volcan el chichon mexico pre 1982 s rich eruptive activity abstract mapping and sampling of the interior of el chichon volcano was made possible by the exposures of the 1982 explosion crater the 1 km diameter 200 m deep crater exposes rocks produced during several eruptive episodes volcanic domes talus breccias plinian airfall deposits and pyroclastic flow deposits of compositionally similar alkalic hornblende trachyandesites with phenocrysts of anhydrite all of the rocks except those leached of anhydrite have extremely high s contents el chichon consists of a volcanic dome complex airfall debris and pyroclastic outflow sheets prior to 1982 its last major activity was about 650 100 yr b p

deposit temperature of pyroclastic density currents emplaced during the el chichon 1982 and colima 1913 eruptions new data on the pyroclastic density current pdc deposit temperature t dep are provided for two prominent eruptions of mexican volcanoes of the twentieth century the 1982 eruption of el chichon and the 1913 eruption of colima in spite of similar lithofacies magma composition and pre eruptive conditions the t dep of the pdcs from the 1982 el chichon and 1913 colima eruptions differ significantly with intervals of t dep of 360 420 c and 250 330 c respectively these new data emphasize that a full understanding of the physical mechanisms responsible for equilibrium temperature attainment within a pyroclastic deposit has not yet been realized the t dep measured for el chichon pdc deposits confirm the preliminary data published elsewhere while colima magnetic temperatures provide different values to those published previously

impact resistance to ballistic ejecta of wooden buildings and a simple reinforcement method using aramid fabric abstract many of the casualties in the phreatic eruption of mt ontake which is located in central japan on september 27 2014 were climbers near the summit the main cause of death was injury by lapilli and block ejecta ballistic ejecta the absence of shelters at the summit and along the climbing trails may be a major factor in the large number of casualties attributable to ballistic ejecta and establishing and improving shelters on active volcanoes is an urgent need the climbers who evacuated to wooden mountain huts survived the 2014 mt ontake eruption this research focuses on the impact characteristics of wooden materials we therefore performed an experimental investigation into the safety of wooden materials under impact by simulated ballistic ejecta with a mass of 2 66 kg equivalent to a diameter of 128 mm as by assembling cylindrical abrasive travelling at up to 300 km h approximately 83 m s with abrasives acting as ballistic ejecta the simulated shelter facility components serving as targets were wooden structures composed of japanese cedar which found on volcanoes at high elevations in japan the components of the fabricated roof were japanese cedar with a thickness of 15 mm as roofboard installed on the surface waterproof sheet and 0 4 mm thick galvalume steel sheet with an additional rafter installed the impact absorption energy of the fabricated roof increased with simulated ballistic ejecta impact velocity because the localization of bending deformation progressed at the impact part and the frequency of splitting failure increased with increasing impact velocity this is attributable to variation in the mode of splitting failure of cedar boards and the dependence of the material strength on projectile velocity we also experimentally investigated simple reinforcement methods in order to obtain basic data on conversion of mountain huts to shelters the reinforced wooden structure could withstand simulated ballistic ejecta impacts of up to approximately 13 kj by incorporating two layers of aramid fabric between a waterproof sheet and a cedar board review of the roof structures of existing wooden buildings based on these results promises further advances in safe impact resistant design

holocene eruptive activity of el chichon volcano chiapas mexico geologic and radiometric age data indicate that el chichon was frequently and violently active during the holocene including eruptive episodes about 600 1250 and 1700 years ago and several undated older eruptions these episodes involving explosive eruptions of sulfur rich magma and associated dome growth processes were apparently separated by intervals of approximately 350 to 650 years some of el chichon s eruptions may correlate with unusual atmospheric phenomena around a d 1300 and possibly a d 623

the intensity and magnitude of holocene plinian eruptions from mount st helens volcano dispersal characteristics of the t we wn pu ps ye yn and yb plinian fall deposits of mount st helens have been measured at 80 sites downwind of the volcano in order to model eruption dynamics and atmospheric transport isopleth contours for the sizes of maximum pumice and lithic clasts are used to calculate peak eruption column heights and intensities magma discharge based on a theoretical model of tephra dispersal new proximal thickness measurements are combined with an empirical distal extrapolation based on studies of 53 plinian deposits to calculate the magnitude erupted mass of each eruption layer yn 3510 y r b p represents the highest intensity and largest magnitude eruption at mount st helens in post glacial times modeling suggests column height grew to about 31 km before gradually declining at the end of the plinian phase 26 hours several intraplinian surge deposits are present in the upper part of the fall layer close to the volcano and up to 15 km to the northeast of mount st helens peak intensity of the plinian phase was 108 kg s and the total erupted volume was 4 km3 dre of magma small plinian style eruptions are represented by layers such as ps and pu of the pine creek eruptive period 3000 2500 yr b p and have intensities of only 106 kg s when compared with plinian eruptions from other volcanoes the holocene eruptions of mount st helens span from the lower to the middle part of the known range in intensity and magnitude and are typical of events derived from intermediate sized stratovolcanoes there is also a general correlation between the intensity of plinian eruptions within eruptive cycles and the repose period prior to each cycle this relationship may be related to a time dependent process for the accumulation of differentiated and volatile rich magma within the chamber beneath mount st helens

the application of a calibrated 3d ballistic trajectory model to ballistic hazard assessments at upper te maari tongariro abstract on 6 august 2012 upper te maari crater tongariro volcano new zealand erupted for the first time in over one hundred years multiple vents were activated during the hydrothermal eruption ejecting blocks up to 2 3 km and impacting 2 6 km of the tongariro alpine crossing tac hiking track ballistic impact craters were mapped to calibrate a 3d ballistic trajectory model for the eruption this was further used to inform future ballistic hazard orthophoto mapping revealed 3587 impact craters with a mean diameter of 2 4 m however field mapping of accessible regions indicated an average of at least four times more observable impact craters and a smaller mean crater diameter of 1 2 m by combining the orthophoto and ground truthed impact frequency and size distribution data we estimate that approximately 13 200 ballistic projectiles were generated during the eruption the 3d ballistic trajectory model and a series of inverse models were used to constrain the eruption directions angles and velocities when combined with eruption observations and geophysical observations the model indicates that the blocks were ejected in five variously directed eruption pulses in total lasting 19 s the model successfully reproduced the mapped impact distribution using a mean initial particle velocity of 200 m s with an accompanying average gas flow velocity over a 400 m radius of 150 m s we apply the calibrated model to assess ballistic hazard from the august eruption along the tac by taking the field mapped spatial density of impacts and an assumption that an average ballistic impact will cause serious injury or death casualty over an 8 m 2 area we estimate that the probability of casualty ranges from 1 to 16 along the affected track assuming an eruption during the time of exposure future ballistic hazard and probabilities of casualty along the tac are also assessed through application of the calibrated model we model a magnitude larger eruption and illustrate that the probability of casualty could reach 100 in localised areas of the track in contrast ballistics ejected from a smaller eruption did not reach the track as was the case with the 21 november 2012 eruption the calibrated ballistic model can therefore be used to improve management of ballistic hazards both at tongariro and also once recalibrated to other volcanoes worldwide

hazard map of el chichon volcano chiapas mexico constraints posed by eruptive history and computer simulations abstract el chichon volcano consists of a 2 km wide somma crater compound cone 0 2 ma old with peripheral domes with a central crater reactivated several times during the holocene the most recent eruption at el chichon occurred from march 28 to april 4 1982 resulting in the worst volcanic disaster during historical times in mexico killing more than 2000 people and destroying nine towns and small communities the volcanic hazard map of el chichon is based on detailed field work that documented twelve eruptions during the last 8000 years and computer simulations to validate the results computer simulations were first performed over pre 1982 topography mimicking the extent of the actual deposits produced and afterwards run over post 1982 topography these eruptions have produced pyroclastic fall surge flow and lahar deposits pyroclastic flows have different volumes and heim coefficients varying from 0 2 pumice flows to 0 15 block and ash flows and 0 10 ash flows simulations using flow3d and titan2d indicate that pumice flows and block and ash flows can fill the moat area and follow main ravines up to distances of ca 3 km from the crater with no effect on populations around the volcano on the other hand more mobile ash flows related to column collapse events can reach up to 4 km from the vent but will always follow the same paths and still not affect surrounding populations the energy cone model was used to simulate the outflow of pyroclastic surges based on the 1982 event h l 0 1 and 0 2 and shows that surges may reach some towns around the volcano explosive activity also produced plinian columns higher than 27 km that were dispersed towards the ne by prevailing winds future fallout will seriously disturb the lives of more than 70 000 inhabitants of cities and towns located in a radius of 35 km from the volcano lahar events in the past originated from unconsolidated pyroclastic deposits with volumes varying from 1 to 4 10 6 m 3 for single pulses to a large one from dam breakout with a volume of 40 10 6 m 3 we used the laharz code to model future events with volumes of 1 2 and 3 10 6 m 3 that will reach as far as 10 14 and 16 km from the crater posing some danger to the communities of nicapa volcan and ostuacan even some time after the climax of the eruption

miocene to holocene marine tephrostratigraphy offshore northern central america and southern mexico pulsed activity of known volcanic complexes we studied the tephra inventory of fourteen deep sea drill sites of three dsdp and odp legs drilled offshore guatemala and el salvador legs 67 84 138 and one leg offshore mexico leg 66 marine tephra layers reach back from the miocene to the holocene we identified 223 primary ash beds and correlated these between the drill sites with regions along the volcanic arcs and to specific eruptions known from land in total 24 correlations were established between marine tephra layers and to well known quaternary eruptions from el salvador and guatemala additional 25 tephra layers were correlated between marine sites another 108 single ash layers have been assigned to source areas on land resulting in a total of 157 single eruptive events tephra layer correlations to independently dated terrestrial deposits provide new time markers and help to improve or confirm age models of the respective drill sites applying the respective sedimentation rates derived from the age models we calculated ages for all marine ash beds hence we also obtained new age estimates for eight known but so far undated large terrestrial eruptions furthermore this enables us to study the temporal evolution of explosive eruptions along the arc and we discovered five pulses of increased activity 1 a pulse during the quaternary 2 a pliocene pulse between 6 and 3 ma 3 a late miocene pulse between 10 and 7 ma 4 a middle miocene pulse between 17 11 ma and 5 an early miocene pulse 21 ma

sulfur as a binding agent of aggregates in explosive eruptions understanding the mechanisms that govern ash aggregation is of critical importance in volcanology aggregation reduces the residence time of ash 2 mm in the atmosphere strongly by enhancing the sedimentation of finer grained material generated during explosive eruptions to date experimental studies have focused on the expectation that water provides the strongest bonds between particles to form spherical to oblate aggregates typically less than or equal to a few mm occasionally up to several cm preserved in pyroclastic deposits under water rich conditions individual accreted particles rarely exceed 1 mm in pyroclastic density current deposits produced during the 1982 eruption of el chichon mexico which emitted 7 5 tg of so2 in the atmosphere aggregate particles one to several millimeters strongly cemented by a s rich film are common they exhibit similarities with aggregates found in sulfur cones at poas volcano costa rica we propose that sulfur is the binder between the silicate grains such a binding capacity implies a relatively fluid behavior of sulfur such as might be expected in the low viscosity temperature regime just above its melting point if so then the explosive ejection of sulfur during eruptions combined with its ability to act as a cement for particles 2 mm would imply that size fractions of lapilli can be efficiently removed from eruptive clouds a few kilometers from the vent such an aggregation mechanism would have important implications for pyroclast dispersal models and hazard assessment

a 3100 year history of argon isotopic and compositional variation at el chichon volcano abstract el chichon volcano has produced at least 11 eruptive events in the past 8000 years all of which display a relatively constant trachyandesitic composition the constancy of the eruptive products attests to the tapping of a long lived magma chamber and suggests a system held in steady state between the influx of basaltic magma and differentiation of resident magma we have sampled eruptive products from eight of these events subjecting their dominant phenocryst phases plagioclase and hornblende to argon isotopic analysis in order to investigate the dynamics of a steady state magmatic system plagioclase from the older eruptions 1500 yr bp 1600 yr bp 2000 yr bp and 3100 yr bp display variable enrichment of 40 ar excess argon whereas hornblende from the same eruptions shows little or no enrichment in contrast both plagioclase and hornblende phenocrysts from the younger eruptions in 1982 550 yr bp 900 yr bp and 1250 yr bp have argon isotopic ratios near atmospheric values isochron analysis of these mineral phases rules out xenocrystic contamination as the source of excess argon while mafic enclaves and isotopic and compositional zoning evidence frequent recharge events suggesting the source of this argon is most likely the same as the source of this basaltic magma correlation with cl points to melt vapor inclusions as the primary host for ar within the phenocrysts argon isotopic variations point to a disturbance of the system between 1500 yr bp and 1250 yr bp while compositional evidence for a major mafic input is present in the 900 yr bp eruption indicating a complex relationship between recharge and isotopic signature of eruptive products the amount of excess argon within a plagioclase phenocryst are a function of variations in melt and vapor inclusion abundance time elapsed between melt vapor inclusion entrapment and eruption variations in ar abundance in melt itself a function of vapor exsolution timing and time variations in ar isotopic composition of the melt subdued behavior of hornblende is due to slower diffusion and minimal inclusions

experimental constraints on degassing of magma isothermal bubble growth during continuous decompression from high pressure numerical models predict that rapid ascent of hydrous magma can lead to supersaturation of dissolved volatile constituents possibly leading to explosive eruption we have performed controlled decompression experiments to investigate the ascent rates required to maintain bubble melt equilibrium high silica rhyolitic melts were saturated with water at 200 mpa and 825 c decompressed to lower pressures at constant rates of 0 025 0 25 0 5 and 1 0 mpa s 1 and then rapidly quenched isobarically other samples were saturated with water over the pressure range investigated to determine equilibrium water solubility in order to quantify degassing efficiency during decompression at a decompression rate of 0 025 mpa s 1 melt vapor equilibrium was maintained over the entire pressure range examined 200 to 17 5 mpa a single bubble nucleation event occurred in response to decompression and quenched bubble sizes can be modeled by a equilibrium bubble growth model that takes into account the number density of bubbles at decompression rates of 0 25 0 5 and 1 0 mpa s 1 rhyolitic melts could not degas in equilibrium when pressure decreased from 200 mpa to 140 mpa and water supersaturation p in the melt reached up to 60 mpa with higher values at faster decompression rates further pressure release resulted in near equilibrium degassing and p dropped significantly in each case p decreased when bubbles exceeded 10 vol a single heterogeneous bubble nucleation event occurred in each experiment when p 20 mpa no other bubbles nucleated despite p reaching 60 mpa which is probably too low to trigger homogeneous nucleation compared to estimates for magma decompression rates during lava dome eruptions our results indicate that magmas can degas efficiently throughout their ascent to the surface in explosive eruptions decompression rates may exceed those of this study and hence melts may become supersaturated with water such fast decompressions are expected however only when magma is highly vesicular which would aid approach to equilibrium degassing

timber framed building damage from tephra fall and lahar 2015 calbuco eruption chile abstract assessing the damage to buildings from volcanic eruptions is an important aspect of volcanic risk assessment and management however there is a limited empirical evidence base to draw upon when describing the relation between volcanic hazard intensity and resulting physical damage the 2015 subplinian eruption of calbuco volcano chile caused damage to buildings near the volcano because of tephra fall and lahars chilean authorities conducted a damage assessment of 961 properties 990 buildings to inform an assistance programme for property owners affected by the eruption property assessments typically contained observations and classification of damage to a house and in some instances accessory buildings such as sheds garages and exterior storage rooms in this study we used this unique damage data set to adapt damage state frameworks for tephra fall and lahar for classifying and analysing damage observations we developed data quality indicators to provide transparency for how we accounted for data quality issues we assigned a tephra and or lahar damage state to 571 buildings 530 houses and 41 accessory buildings the 419 buildings for which we did not assign a damage state either had too little information or fell outside of tephra and or lahar hazard zones the minimum tephra thickness isopach band that caused complete collapse was 10 to 15 cm dry deposit loading 1 to 1 6 kn m 2 saturated deposit loading 1 6 to 2 4 kn m 2 but most commonly 55 of tephra exposed ds5 houses n 11 this occurred at 15 to 30 cm dry deposit loading 1 5 to 3 3 kn m 2 saturated deposit loading 2 4 to 4 8 kn m 2 lahar damage was typically described as complete ds5 with 26 houses being swept away or destroyed around the blanco south river our results add to the limited evidence base of post eruption tephra and lahar impacts to buildings and contribute to volcanic risk and impact assessment

magma recharge contamination and residence times revealed by in situ laser ablation isotopic analysis of feldspar in volcanic rocks we illustrate a rapid and effective method for determining variations in 87sr 86sr across single plagioclase feldspar crystals using laser ablation interfaced to a multicollector inductively coupled plasma source mass spectrometer the speed of analysis proves to be a particular advantage permitting representative populations of crystals to be characterized or enabling reconnaissance analysis of rocks to test for mineral scale isotopic heterogeneity our results from magmatic crystals in lavas from el chichon volcano confirm trends previously obtained by the more time consuming microdrilling method for the first time with confidence the laser data allow us to associate abrupt changes in 87sr 86sr with distinct petrographic discontinuities such as dissolution surfaces in the crystal because the isotopic variations within crystals would be expected to equilibrate diffusively with time the width over which abrupt changes in 87sr 86sr occur can also be used to constrain timescales at which the crystal has been held at magmatic temperatures

volcanic risk assessment quantifying physical vulnerability in the built environment abstract this paper presents structured and cost effective methods for assessing the physical vulnerability of at risk communities to the range of volcanic hazards developed as part of the mia vita project 2009 2012 an initial assessment of building and infrastructure vulnerability has been carried out for a set of broadly defined building types and infrastructure categories with the likelihood of damage considered separately for projectile impact ash fall loading pyroclastic density current dynamic pressure and earthquake ground shaking intensities in refining these estimates for two case study areas kanlaon volcano in the philippines and fogo volcano in cape verde we have developed guidelines and methodologies for carrying out physical vulnerability assessments in the field these include identifying primary building characteristics such as construction material and method as well as subsidiary characteristics for example the size and prevalence of openings that may be important in assessing eruption impacts at risk buildings around kanlaon were found to be dominated by timber frame buildings that exhibit a high vulnerability to pyroclastic density currents but a low vulnerability to failure from seismic shaking around fogo the predominance of unreinforced masonry buildings with reinforced concrete slab roofs suggests a high vulnerability to volcanic earthquake but a low vulnerability to ash fall loading given the importance of agriculture for local livelihoods around kanlaon and fogo we discuss the potential impact of infrastructure vulnerability for local agricultural economies with implications for volcanic areas worldwide these methodologies and tools go some way towards offering a standardised approach to carrying out future vulnerability assessments for populated volcanic areas

thermal and rheological controls on the formation of mafic enclaves or banded pumice magma mixing can occur in a fluid manner to produce banded pumice or in a brittle manner to form enclaves we propose that the critical control on mixing style is a competition between developing networks of crystals in the intruding magma that impart a strength to the magma and melting and disrupting those networks in the host x ray computed tomography analysis demonstrates that banded pumice from the 1915 mt lassen eruption lacks crystal networks in contrast rhyodacite hosts with mafic enclaves from chaos crags contain well developed networks of large crystals we present a one dimensional conductive cooling model that predicts mixing style either ductile or brittle as a function of magma compositions temperatures and the size of the intruding dike our model relies on three assumptions 1 mixing is initiated by the injection of a hot dike into a cooler magma body with a yield strength 2 when magma crystallinity exceeds a critical value 13 vol plagioclase the magma develops a yield strength and 3 when total crystallinity exceeds 40 vol the magma has a penetrative crystal network and is effectively solid importantly because the two magmas are of different compositions their crystallinities and viscosities do not have the same variations with temperature as the intruding magma cools it crystallizes from the outside in while simultaneously host magma temperature near the intruder rises mixing of the two magmas begins when the host magma is heated sufficiently to 1 disrupt the crystal network and 2 initiate convection if the shear stress exerted by the convecting host magma on the dike is greater than the yield strength of the dike margin and dike crystallinity does not exceed 40 then fluid mixing occurs otherwise enclaves form by brittle deformation of the dike application of the model to magma compositions representative of lassen and chaos crags shows that emplacement of dikes 1 m thick should produce enclaves whereas thicker dikes should generate fluid mixing and form banded pumice within days to weeks of emplacement similar relationships apply to other modeled magmatic systems including pinatubo unzen and ksudach shtuybel volcanoes for all studied systems the absolute size of the intruding dike not just its proportion relative to the host influences mixing style

a model for mixing basaltic and dacitic magmas as deduced from experimental data it has been demonstrated experimentally that basaltic and dacitic magmas can be easily mixed to form both banded dacite and homogeneous andesite in less than a few hours the presence of phenocrysts larger than 0 5 mm increased considerably the efficiency of mixing flow patterns in the experimental system were visualized using pt spheres which indicated that convection occurs in basalt melt but not in dacite melt the reynolds numbers of the basaltic and dacitic melts in the experimental system were calculated to be about 10 3 and 10 6 respectively mixing proceeds initially by mechanical mixing of the two magmas in a large scale but later by coupling interfacial convection and mutual diffusion thus depending on the depth where vesiculation and following disruption of the magma occurs banded pumice homogeneous pumice and homogeneous andesite lava are erupted the observed textures of mixed rocks of plinian type eruption and the limiting occurrence of banded pumice are satisfactorily accounted for on this model

zircon xenocryst resorption and magmatic regrowth at el chichon volcano chiapas mexico abstract el chichon volcano is the only active volcano located within the chiapanecan volcanic arc in southern mexico which lies between the trans mexican volcanic belt and the central american volcanic arc previous studies have shown that 12 eruptions have occurred at el chichon within the last 8000 years forming a complex of lava domes with a central crater and surrounding pyroclastic deposits here we report the discovery of zircon in holocene el chichon rocks which were analyzed by high spatial resolution imaging color cathodoluminescence ccl and isotopic secondary ionization mass spectrometry sims methods to resolve core and rim crystallization ages pumice samples from five proximal pyroclastic flow and fall out deposits were collected based on published stratigraphy two of the samples were further re classified by new 14c dates in addition we sampled two lavas from the 1982 eruption and from remnants of the older somma lava complex zircon crystals were dated using 230th 238u disequilibrium u th and u pb geochronology u th zircon ages fall between near eruption ages and ca 84 ka with overlapping ages in all samples by contrast zircon core u pb ages range between ca 290 ma and 1 9 ga these ages are consistent with xenocrystic origins and their heterogeneity indicates derivation from clastic country rocks strong age contrasts between inherited xenocrystic and young magmatic domains in individual zircon crystals are evidence for arrested assimilation of crustal rocks where initially zircon undersaturated magmas cooled rapidly to form a crystal mush or subsolidus amalgamate as a crustally contaminated boundary layer this layer contributed zircon crystals to eruptible magma during episodic recharge events followed by partial melt extraction mixing and homogenization zircon overgrowths are significantly older than major minerals whose u series ages and sharp zonation boundaries suggest crystallization only within a few ka before eruption this implies that zircon can detect magmatic longevity which is obscured in the major mineral record

the october 1902 plinian eruption of santa maria volcano guatemala abstract the october 1902 eruption of santa maria volcano guatemala was one of the largest this century it was preceded by a great earthquake on april 19 centered at the volcano as well as numerous other major earthquakes the 18 20 hour long plinian eruption on october 25 produced a column at least 28 km high reaching well into the stratosphere the airfall pumice deposit covered more than 1 2 million km2 with a trace of ash and was only two meters thick at the vent white dacitic pumice dark gray scoriaceous basalt with physically and chemically mixed intermediate pumice and loose crystals of plagioclase hornblende hypersthene biotite and magnetite make up the juvenile components of the deposit lithic fragments are of volcanic plutonic and metamorphic origin the plinian deposit is a fine grained crystal rich single pumice fall unit and shows inverse grading mapping of the deposit gives a volume of 8 3 km3 within the one mm isopach crystal concentration studies show that the true volume erupted was at least 20 km3 equivalent to 8 5 km3 of dense dacite and that 90 of the ejecta was less than 2 mm in diameter the plinian volume eruption rate averaged 1 2 105 m3s 1 and the average gas muzzle velocity of the column exceeded 270 ms 1 a total of 8 3 1018 j of energy were released by the eruption a knowledge of both theoretically derived eruption parameters and contemporary information allows a detailed analysis of eruption mechanisms this eruption was the major stratospheric aerosol injection in the 1902 1903 period however mid to low latitude northern hemisphere temperature deviation data for the years following the eruption show no significant temperature decrease this may be explained by the sulfur poor nature of dacite magmas suggesting that volatile composition rather than mass of volatiles is the controlling parameter in climatic response to explosive eruptions