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

volcano monitoring by microgravity and energy budget analysis microgravity monitoring of active volcanoes can provide evidence of sub surface mass and or density changes that precede eruptions if in addition precursory increases in thermal emissions are observed an integrated mechanistic model for volcanic activity may be developed with the potential for forecasting eruptions crater lake volcanoes provide an interesting target for such studies since thermal output can be monitored simply through lake water calotimetry here we summarize 10 years of gravity and thermal data from poas volcano costa rica mass energy balance calculations demonstrate that in the steady state the large thermal inertia of the crater lake acts as a buffer to short term changes in the energy input from the cooling magma feeder pipe since february 1986 it is postulated that there has been gradual emplacement of a shallow magma intrusion associated with vesiculation and gas loss to the surface this follows from unambiguous gravity increases constrained by elevation control that are coincident in time with a period of long term increased energy input to the crater lake progressive reduction of the lake volume by evaporation seepage culminated in an april 1989 ash eruption providing a good documented record of combined gravity and thermodynamic precursors to volcanic activity

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

the bimodal ph distribution of volcanic lake waters abstract volcanic lake waters have a bimodal ph distribution with an acidic mode at ph 0 5 1 5 and a near neutral mode at ph 6 6 5 with relatively few samples having ph 3 5 5 to investigate the reasons for this distribution the irreversible water rock mass exchanges during the neutralization of acid so4 cl waters with andesite under both low and high temperature conditions were simulated by means of the eq3 6 software package version 7 2 reaction path modeling under low temperature and atmospheric pco2 and fo2 suggests that several homogeneous and or heterogeneous ph buffers exist both in the acidic and neutral regions but no buffer is active in the intermediate central ph region again the same titration under high temperature hydrothermal magmatic conditions is expected to produce comparatively infrequent aqueous solutions with ph values in the 3 5 5 range upon their cooling below 100 c substantially different ph values are obtained depending on the cooling paths either through boiling or conductive heat losses these distinct ph values are governed by either hso4 and hcl aq in poorly neutralized aqueous solutions or the co2 aq hco3 couple and the pco2 value as well in neutralized aqueous solutions finally mixing of the acid lake water with the aqueous solutions produced through high temperature titration and cooled below 100 c is unlikely to generate mixtures with ph values higher than 3 unless the fraction of the acidic water originally present in the lake becomes very small which means its virtually complete substitution summing up the evidence gathered through reaction path modeling of the neutralization of acid lake waters with andesite both at low and high temperatures explains the scarcity of volcanic lake waters with measured ph values of 3 5 5

water chemistry of lake quilotoa ecuador and assessment of natural hazards a geochemical survey carried out in november 1993 revealed that lake quilotoa was composed by a thin 14 m oxic epilimnion overlying a 200 m thick anoxic hypolimnion dissolved co2 concentrations reached 1000 mg kg in the lower stratum loss of co2 from epilimnetic waters followed by calcite precipitation and a consequent lowering in density was the apparent cause of the stratification the cl so4 and hco3 contents of lake quilotoa are intermediate between those of acid so4 cl crater lakes and those of neutral hco3 crater lakes indicating that lake quilotoa has a memory of the inflow and absorption of hc1 and s bearing volcanic magmatic gases the mg ca ratios of the lake waters are governed by dissolution of local volcanic rocks or magmas but k na ratios were likely modified by precipitation of alunite a typical mineral in acid so 4 cl crater lakes the constant concentrations of several conservative chemical species from lake surface to lake bottom suggest that physical chemical and biological processes did not have enough time after the last overturn to cause significant changes in the contents of these chemical species this lapse of time might be relatively large but it cannot be established on the basis of available data besides the lake may not be close to steady state mixing of lake quilotoa waters could presently be triggered by either cooling epilimnetic waters by 48c or providing heat to hypolimnetic waters or by seismic activity although quilotoa lake contains a huge amount of dissolved co2o 3 10 11 gu at present the risk of a dangerous limnic eruption seems to be nil even though some gas exsolution might occur if deep lake waters were brought to the surface carbon dioxide could build up to higher levels in deep waters than at present without any volcanic re awakening due to either a large inflow of relatively cool co 2 rich gases or possibly a long interval between overturns periodical geochemical surveys of lake quilotoa are therefore recommended q 2000 elsevier science b v all rights reserved

energy partition in the 1982 eruption of el chichon volcano chiapas mexico abstract the 1982 eruption of el chichon volcano chiapas mexico has been extensively investigated from various standpoints including seismicity tephra geology atmospheric effects and tectonic structure in this paper the six largest of a series of explosions are isolated considering various sources of information then the seismic energy released by volcanic earthquakes and tremor is estimated using seismograms of low magnification in order to avoid saturation of seismic wave amplitudes the explosion kinetic energy is evaluated by two methods one by the initial velocity of the ejecta and the other by the air wave data recorded at a distance both the results are roughly coincident the thermal energy is classified into two components that transferred by volcanic ejecta and that consumed by convective clouds the thermal energy released by the explosions is very large compared with that of mechanical energy such as the seismic energy and explosion kinetic energy after the last major explosion of april 4 a type volcanic earthquakes swarmed till the end of april their occurrence rate decreased with time in an aftershock like sequence these earthquake swarms may have been due to post eruptive readjustment of the stress field within and near the volcano such seismic activity contrasts with other examples of similar major eruptions which were followed by growth of lava domes in the new craters after the paroxysmal eruptions the 1982 eruption of el chichon volcano has not been followed by the growth of a lava dome within the newly formed crater

sulphur eruptions at volcan poas costa rica since the recent desiccation of the crater lake at volcan poas costa rica vigorous fumarolic activity on the exposed lake bed has been associated with the manifestation of miniature sulphur volcanoes sulphur flows and sulphur pools in this paper observations of 2 3 m high active sulphur volcanoes are reported and mechanisms for their formation proposed and discussed their ejecta composed of milled particles crystals and accretionary lapilli of sulphur are unlike previously described pyroclastic sulphur deposits and probably form from a spray of crystallised sulphur forced to the surface by fumarolic gases passing upwards through shallow bodies of liquid sulphur while much of the erupted material is recycled the reservoir of molten sulphur can also be replenished by influxing magmatic hydrothermal fluids 34s isotope ratios of several samples of native sulphur collected at poas range between 9 4 and 12 3 cdt these are among the isotopically lightest volcanic deposits of elemental sulphur reported although this pronounced depletion is readily explained by the likely formation of the sulphur under the acidic conditions of the aqueous lake and hydrothermal system the total amount of native sulphur deposits contained within lake sediments at poas and perhaps at other active volcanoes with crater lakes is potentially substantial a large explosive eruption could by volatilisation and oxidation of this sulphur inject large volumes of sulphur dioxide into the atmosphere the greenish colouration of the sulphur reminiscent of other documented terrestrial sulphur eruptions is probably due to impurities this emphasises the point that interpretation of spectral reflectances of the jovian moon io regarding the possible contribution of sulphur cannot rely on extrapolation of laboratory data for pure materials

chemical characteristics of the crater lakes of popocatetetl el chichon and nevado de toluca volcanoes mexico abstract three crater lakes from mexican volcanoes were sampled and analyzed at various dates to determine their chemical characteristics strong differences were observed in the chemistry among the three lakes nevado de toluca considered as dormant el chichon at a post eruptive stage and popocatepetl at a pre eruptive stage not surprisingly no influence of volcanic activity was found at the nevado de toluca volcano while the other volcanoes showed a correlation between the changing level of activity and the evolution of chemical trends low phs so 4 2 and f decreased irregularly at el chichon from 1983 until 1997 major cations concentrations also diminished at el chichon a 100 increase in the so 4 2 content was measured at popocatepetl between 1985 and 1994 an increase in the mg cl ratio between 1992 mg cl 0 085 and 1994 mg cl 0 177 was observed at popocatepetl before the disappearance of the crater lake in 1994 it is concluded that chemical analysis of crater lakes may provide a useful additional tool for active volcano monitoring

modeling the formation of advanced argillic lithocaps volcanic vapor condensation above porphyry intrusions hypogene advanced argillic alteration typically quartz alunite with halos of kaolinite dickite and roots of pyrophyllite diaspore forms in the epithermal environment from condensates of magmatic vapor that contain so2 and hcl which exsolved from an underlying intrusive source the most aggressive nearly isochemical leaching of the host rock by the most acidic condensate commonly ph 1 leaves residual silica that recrystallizes to quartz within the flow channel at a high condensate rock ratio forming the core of alteration the alteration characteristically flares upward along feeder structures and if a permeable lithologic unit is intersected the alteration zones mushroom to form a subhorizontal blanket due to lateral flow where subsequently mineralized the residual quartz commonly with a vuggy texture that reflects the texture of the original lithology has higher au and cu grades than the quartz alunite halo tonnage in these high sulfidation systems may develop within the subhorizontal lithocap although the highest grades are typically confined to the structurally controlled feeders we modeled a typical volcanic vapor condensate starting with the measured composition of 877 c fumaroles from satsuma iwojima rhyolite dome japan as it cooled and reacted with a host rhyolite the predicted hydrothermal mineralogy reproduces the alteration pattern observed in lithocaps that host high sulfidation deposits the modeling confirms that aluminum rich minerals pyrophyllite diaspore locally andalusite are stable at higher temperature at depth whereas at lower temperature and shallower depth na and k alunite become stable at the lowest temperature 10 1 and where so2 h2s in the original volcanic vapor this so2 dominant composition is typical of andesitic to rhyolitic volcanoes the reason for this mineral transition and the upward flare widening of the alteration zone along structures is related to the dissociation and increased reactivity of h2so4 and hcl as the temperature decreases below 200 c only quartz pyrite native s and anhydrite are stable hence the formation of the dominant quartz from the silica residue a further check on our modeling is the observation that the calculated composition of the condensate after reaction with fresh satsuma iwojima rhyolite and alteration minerals and cooling to 100 c is similar within a factor of two to that of acidic springs with ph 1 that discharge around satsuma iwojima and other active volcanoes the most extensive lithocap alteration residual quartz and or quartz alunite is commonly offset from the surface projection of the causative intrusion this observation can be explained by a combination of two factors hydrology and temperature due to hydraulic gradients at shallow depths in a volcanic edifice the acidic condensate tends to flow along permeable lithologic units away from the locus of the high temperature vapor plume which rises directly over the intrusion where lateral flow occurs the most intense leaching and widespread advanced argillic alteration which develops largely at temperatures of 200 to 250 c based on our modeling will form away from the near surface projection of the intrusion which is the area of highest surface temperature due to ascent of the vapor plume this potential for lithocap alteration to form on the shoulder of the underlying causative intrusion must be assessed when exploring for high sulfidation ore the highest ore grades are commonly related to structures that are proximal to the parent intrusion but they are unlikely to lie directly over the intrusion in addition identifying the most likely location of the source intrusion will help the explorer to efficiently assess any potential for deeper porphyry style mineralization

estimates of the amount of sulphur dioxide injected into the stratosphere by the explosive volcanic eruptions el chichon mystery volcano mt st helens ground based remote sensing measurements of sulphur dioxide column amounts made with the brewer spectrophotometer have been used to estimate the total amount of sulphur dioxide injected into the stratosphere by the el chichon eruptions which occurred between march 28 and april 4 1982 measurements were made at the mauna loa observatory in hawaii at toronto and on nasa convair 990 flights between 20 n and 50 n the average amount of sulphur dioxide measured at mauna loa was about 4 7 matmcm during late april and early may 1982 the aircraft remote sensing measurements suggest that the cloud was distributed up to 35 n in early may assuming that it was dispersed in a uniform belt around the globe between the equator and 35 n we estimate that 13 4 megatons of sulphur dioxide were injected into the stratosphere by the el chichon eruptions the amount of sulphur dioxide from the january mystery volcano was estimated to be 5 6 megatons previously in 1980 an estimate of 0 6 megatons was made for the mt st helens eruption

d h and 18 o 16 o ratios of water in the crater lake at kusatsu shirane volcano japan abstract the d h and 18o 16o ratios of water in the active crater lake situated on the kusatsu shirane volcano japan are about 20 and 6 respectively higher than local meteoric water the ratios show seasonal variations superimposed on a gradual change over nine years the isotopic ratios started to increase in early 1990 and decrease in the spring of 1995 the seasonal variation which is high in winter and low in summer correlates with the temperature difference between lake water and ambient air the large temperature difference in winter enhances the evaporation of lake water and produces the enriched isotopic ratios relative to the ratios in summer the accumulation of snow and the decrease in the flux of meteoric water into the lake strengthens the winter time isotopic enrichment the enriched isotopic ratios of the lake water over a long time result from the addition of an end member with heavy isotopic ratios contained in a thermal fluid supplied to the lake considering the water balance in the lake the isotopic ratios of the thermal fluid were found to be close to the lake water itself suggesting the circulation of the lake water seeping through lake floor based on the correlation between cl concentration and the isotopic ratios the contribution by the heavy end member was estimated to be 25 36 relative to the enrichment by evaporation the heavy end member could be a liquid phase evolved from a parental fluid which is a mixture of local meteoric water and a magmatic fluid as found in high temperature volcanic gases

stratospheric sulfate from el chichon and the mystery volcano stratospheric sulfate was collected by high altitude aircraft and balloons to assess the impacts of el chichon and an unidentified volcano on the stratosphere the mystery volcano placed about 0 85 tg of sulfate in the northern hemisphere stratosphere el chichon injected about 7 6 tg sulfate into the global stratosphere

geochemistry of the magmatic hydrothermal system of kawah ijen volcano east java indonesia samples from kawah ijen crater lake spring and fumarole discharges were collected between 1990 and 1996 for chemical and isotopic analysis an extremely low ph 0 3 lake contains so 4 cl waters produced during absorption of magmatic volatiles into shallow ground water the acidic waters dissolve the rock isochemically to produce immature solutions the strong d and 18 o enrichment of the lake is mainly due to enhanced evaporation at elevated temperature but involvement of a magmatic component with heavy isotopic ratios also modifies the lake d and 18 o content the large so4 s d 23 8 26 4 measured in the lake suggest that dissolved so 4 forms during disproportionation of magmatic so 2 in the hydrothermal conduit at temperatures of 250 280 c the lake 18 o so4 and 18 o h2o values may reflect equilibration during subsurface circulation of the water at temperatures near 150 c significant variations in the lake s bulk composition from 1990 to 1996 were not detected however we interpret a change in the distribution and concentration of polythionate species in 1996 as a result of increased so 2 rich gas input to the lake system thermal springs at kawah ijen consist of acidic so 4 cl waters on the lakeshore and neutral ph hco 3 so 4 cl na waters in blawan village 17 km from the crater the cation contents of these discharges are diluted compared to the crater lake but still do not represent equilibrium with the rock the so 4 cl ratios and water and sulfur isotopic compositions support the idea that these springs are mixtures of summit acidic so 4 cl water and ground water the lakeshore fumarole discharges t 170 245 c have both a magmatic and a hydrothermal component and are supersaturated with respect to elemental sulfur the apparent equilibrium temperature of the gas is 260 c the proportions of the oxidized so 2 dominated magmatic vapor anti of the reduced h 2 s dominated hydrothermal vapor in the fumaroles varied between 1979 and 1996 this may be the result of interaction of so 2 bearing magmatic vapors with the summit acidic hydrothermal reservoir this idea is supported by the lower h 2 s so 2 ratio deduced for the gas producing the so 4 cl reservoir feeding the lake compared with that observed in the subaerial gas discharges the condensing gas may have equilibrated in a liquid vapor zone at about 350 c elemental sulfur occurs in the crater lake environment as banded sediments exposed on the lakeshore and as a subaqueous molten body on the crater floor the sediments were precipitated in the past during inorganic oxidation of h 2 s in the lake water this process was not continuous but was interrupted by periods of massive silica poorly crystallized precipitation similar to the present day lake conditions we suggest that the factor controlling the type of deposition is related to whether h 2 s or silica rich volcanic discharges enter the lake this could depend on the efficiency with which the lake water circulates in the hydrothermal cell beneath the crater quenched liquid sulfur products show 34 s values similar to those found in the banded deposits suggesting that the subaqueous molten body simply consists of melted sediments previously accumulated at the lake bottom

surveillance of ruapehu crater lake new zealand by aqueous polythionates abstract aqueous sulfur speciation of samples of crater lake water from crater lake collected at mt ruapehu new zealand since 1968 has been determined using high performance liquid chromatography polythionates s x o 6 2 are produced in the lake through reactions between sulfur dioxide and hydrogen sulfide gases from the subaqueous fumaroles their concentrations vary from 0 to a few hundred mg l corresponding to the activity of the volcano the concentration of the total polythionates s x o 6 2 s 4 o 6 2 s 5 o 6 2 s 6 o 6 2 is found to be a good indicator of changes in the subaqueous fumarolic activity at crater lake the molar s x o 6 2 cl ratios of the lake water can be used to divide the volcanic activity of crater lake into four stages 1 stage i period of weak volcanic activity with no hydrothermal explosions this stage is characterized by low total s x o 6 2 with a distribution order of s 5 o 6 2 s 4 o 6 2 s 6 o 6 2 h 2 s is predominant among dissolved gases in the lake water 2 stage iia quiescent period with minor hydrothermal explosions the lake water contains high s x o 6 2 with a distribution order of s 5 o 6 2 s 4 o 6 2 s 6 o 6 2 dissolved h 2 s and so 2 gases are very low 3 stage iib increased fumarolic activity with frequent hydrothermal explosions low s x o 6 2 with a distribution order of s 4 o 6 2 s 5 o 6 2 s 6 o 6 2 sulfur dioxide but no h 2 s is detected in the water 4 stage iii period of phreatomagmatic eruptions with lahars and intensive seismic activity no s x o 6 2 exists but dissolved so 2 is high in the lake water the moderate sized explosion of december 8 1988 which was not preceded by any changes in lake water polythionate chemistry or seismic activity is hypothesized to be a vent cleaning eruption caused by blockage of ascending magmatic gases that was caused by solidification of a molten sulfur pool at the bottom of crater lake

lateral and longitudinal successions in sedimentary structures in the middle mause esker scotland abstract facies changes and sedimentary structures in esker deposits as described in literature generally refer to mainly longitudinal transport directions i e a flow almost parallel to the esker axis however the middle mause esker scotland shows a mainly lateral transport direction normal to the axis of the ridge this lateral movement is tentatively explained by assuming a sediment supply along thrust planes present in the roof of a glacial tunnel the sediment is transported down the talus of an upbuilding ridge six facies have been recognized in the exposure of the esker ridge on the basis of the sedimentary characteristics the following succession in environmental conditions has been deduced 1 lateral sediment movement under subaerial fluvial conditions facies a 2 lateral sediment movement of the talus slope under submerged conditions facies b c and d and 3 longitudinal sediment movement under probably subaerial fluvial conditions facies e and f

monitoring of volcanic eruptions at yugama crater lake by aqueous sulfur oxyanions abstract variations of polythionates sulfane disulfonates and sulfate in the yugama crater lake japan have been monitored for more than 25 years just before the 1982 eruption at the crater lake polythionate ions decreased to zero from the normal level of about 2000 ppm and sulfate ions increased from 2500 to 5000 ppm during the 1982 eruption polythionate and sulfate ions varied inversely in concentration and the variations exactly coincided with the frequency of volcanic earthquakes and subsequent explosions these observations are interpreted in terms of aqueous reactions of fumarolic so2 h2s gases resulting in precipitation of alunite the behavior of polythionate and sulfate ions strongly suggests that they are useful indicator for prediction of impending volcanic hazards from active crater lakes

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

geochemistry of the acid kawah putih lake patuha volcano west java indonesia abstract kawah putih is a summit crater of patuha volcano west java indonesia which contains a shallow 300 m wide lake with strongly mineralized acid sulfate chloride water the lake water has a temperature of 26 34 c ph s tot 2500 4600 ppm and cl 5300 12 600 ppm and floating sulfur globules with sulfide inclusions are common sulfur oxyanion concentrations are unusually high with s 4 o 6 2 s 5 o 6 2 s 6 o 6 2 2400 4200 ppm subaerial fumaroles thermodynamic modeling of the lake fluids indicates that the lake water is saturated with silica phases barite pyrite and various pb sb cu as bi bearing sulfides when sulfur saturation is assumed precipitating phases predicted by the model calculations are consistent with the bulk chemistry of the sulfur rich bottom sediments and their identified mineral phases much of the lake water chemistry can be explained by congruent rock dissolution in combination with preferential enrichments from entering fumarolic gases or brines and element removal by precipitating mineral phases as indicated by a comparison of the fluids volcanic rocks and lake bed sediment flank springs on the mountain at different elevations vary in composition and are consistent with local rock dissolution as a dominant factor and ph dependent element mobility discharges of warm sulfate and chloride rich water at the highest elevation and a near neutral spring at lower level may contain a small contribution of crater lake water the acid fluid induced processes at patuha have led to the accumulation of elements that are commonly associated with volcano hosted epithermal ore deposits the dispersal of heavy metals and other potentially toxic elements from the volcano via the local drainage system is a matter of serious environmental concern

enormous increase of stratospheric aerosols over fukuoka due to volcanic eruption of el chichon in 1982 large increases of stratospheric aerosol particles caused by the eruption of mexican volcano el chichon in early april 1982 were observed by a yag lidar system at two wavelengths 1 06 m and 0 53 m over fukuoka for three months since april 18 most of the observations show high concentrations of aerosols in the altitude regions from 15 to 33 km with highest concentrations between 21 and 30 km the aerosol optical thickness at 0 55 m is about 0 1 0 3 this is about 10 to 30 times the maximum monthly mean values that were observed after the mt st helens event in 1980 the mean radius of aerosols in the densest part of the el chichon cloud is estimated to be approximately 0 1 m this estimate is based on the slow settling velocity of the peak of the cloud and from information obtained by comparison of the two wavelength lidar returns a significant impact of the presence of the cloud on the climate through variations of atmospheric circulation is suggested

genetic environments of the banded sulfur sediments at the tateyama volcano japan banded sulfur sediments characterized by alternate layers of yellowish fine grained sulfur and dark gray clays occur in a now extinct crater lake of the tateyama volcano central japan stratigraphic variations in the sulfur content sulfur isotopic ratio mineralogy and content of diatom fossils suggest that the lamination represents seasonal repetition of environmental conditions of the lake water colloidal sulfur formed by oxidation of volcanic h2s in the presence of dissolved oxygen and freshwater benthonic diatoms pinnularia braunii grun cl var amphicephala a mayer hust flourished during oxidative convective periods whereas detrital materials rich in clays were deposited onto the lake bottom during reducing stagnant periods a sedimentation period of 3000 to 4000 years is calculated from the total thickness of the banded sulfur sediments coupled with the sedimentation rates of 1 to 2 mm yr deduced from the above model the estimated period is in good agreement with the age of phreatic explosion 3000 to 6300 years ago based on tephra chronology which created the crater lake

crater lake and post eruption hydrothermal activity el chichon volcano mexico abstract explosive eruptions of volcan el chichon in chiapas mexico on march 28 and april 3 4 1982 removed 0 2 km3 of rock to form a 1 km wide 300 m deep summit crater by late april 1982 a lake had begun to form on the crater floor and by november 1982 it attained a maximum surface area of 1 4 105 m2 and a volume of 5 106 m3 accumulation of 4 5 m of rainfall between july and october 1982 largely formed the lake in january 1983 temperatures of fumaroles on the crater floor and lower crater walls ranged from 98 to 115 c by october 1983 the maximum temperature of fumarole emissions was 99 c in january 1983 fumarole gas emissions were greater than 99 vol h2o with traces of co2 so2 and h2s the water of the lake was a hot t 52 58 c acidic ph 0 5 dilute solution 34 046 mg l 1 dissolved solids cl s 20 5 sediment from the lake contains the same silicate minerals as the rocks of the 1982 pyroclastic deposits together with less than 1 of elemental sulfur the composition and temperature of the lake water is attributed to 1 solution of fumarole emissions 2 reaction of lake water with hot rocks beneath the lake level 3 sediments washed into the lake from the crater walls 4 hydrothermal fluids leaching sediments and formational waters in sedimentary rocks of the basement 5 evaporation and 6 precipitation

source strength assessment of volcanic trace elements emitted from the indonesian arc abstract we have for the first time estimated volcanic emission of volatile metals for a large regional volcanic source showing permanent activity namely the indonesian arc we have done this by normalizing concentrations of metals ratios in volcanic plumes to so 2 emission rates metal so 2 ratios measured in magmatic gases are used to estimate emissions from eruptive activity whereas those measured in fumarolic gases are used to estimate emissions from non eruptive activity the so 2 emission rate obtained is 3 5 10 6 tons per year which represents about 20 of the annual worldwide volcanic flux of so 2 the obtained trace metal 210 po pb bi cd zn and cu fluxes account for only about 5 to 30 of their global volcanic flux these relatively low values for trace metal emissions relative to the volcanic activity and the number of active volcanoes of the region appear to reflect the andesitic magma composition of the volcanoes of the arc

eruption of el chichon volcano chiapas mexico 28 march to 7 april 1982 el chichon volcano erupted at 2322 hours on 28 march 1982 after being dormant during historic times three major eruptions of tephra occurred between that date and 7 april discharging approximately 0 3 cubic kilometer of andesitic pyroclastic material the initial eruption produced crystal rich tephra of higher silica and alkali content than the lithic pyroclastic materials of the second and third eruptions the initial tephra consists of primarily juvenile materials whereas the later eruptions produced both lithic and juvenile fractions

using crater lake chemistry to predict volcanic activity at poas volcano costa rica monitoring of crater lake chemistry during the recent decline and disappearance of the crater lake of poas volcano revealed that large variations in so4 cl f cl and mg cl ratios were caused by the enhanced release of hcl vapor from the lake surface due to increasing lake temperature and solution acidity variation in the concentration of polythionic acids h2sxo6 x 4 6 was the most reliable predictor of renewed phreatic eruptive activity at the volcano exhibiting sharp decreases three months prior to the initiation of phreatic eruptions in june 1987 polythionic acids may offer a direct indicator of changing subsurface magmatic activity whereas chloride based element ratios may be influenced by surface volatilization of hcl and subsequent recycling of acidic fluids in crater lake volcanoes

petrogenesis of early cambrian granitoids in the western kunlun orogenic belt northwest tibet insight into early stage subduction of the proto tethys ocean

the crater lake and hydrothermal system of mount pinatubo philippines evolution in the decade after eruption the june 1991 eruption of mount pinatubo philippines breached a significant pre eruptive magmatic hydrothermal system consisting of a hot 300 c core at two phase conditions and surrounding cooler 260 c liquid outflows to the n and s the eruption created a large closed crater that accumulated hydrothermal upwellings near surface aquifer and meteoric inflows a shallow lake formed by early september 1991 and showed a long term increase in level of 1 m month until an artificial drainage was created in september 2001 comparison of the temporal trends in lake chemistry to pre and post eruptive springs distinguishes processes important in lake evolution the lake was initially near neutral ph and dominated by meteoric influx and cl so4 and cl hco3 hydrothermal waters with peaks in so4 and ca concentrations resulting from leaching of anhydrite and aerosol laden tephra magmatic discharge acidity ph 2 and rock dissolution peaked in late 1992 during and immediately after eruption of a lava dome on the crater floor since cessation of dome growth trends in lake ph increase from 3 to 5 5 temperature decline from 40 to 26 c and chemical and isotopic composition indicate that magmatic degassing and rock dissolution have declined significantly relative to the input of meteoric water and immature hydrothermal brine higher concentrations of cl na k li and b and lower concentrations of mg ca fe so4 and f up to 1999 highlight the importance of a dilute hydrothermal contribution as do stable isotope and tritium compositions of the various fluids however samples taken since that time indicate further dilution and steeper trends of increasing ph and declining temperature present gas and brine compositions from crater fumaroles and hot springs indicate boiling of an immature cl so4 geothermal fluid of near neutral ph at approximately 200 c rather than direct discharge from magma it appears that remnants of the pre eruptive hydrothermal system invaded the magma conduit shortly after the end of dome emplacement blocking the direct degassing path this along with the large catchment area 5 km2 and the high precipitation rate of the area led to a rapid transition from a small and hot acid lake to a large lake with near ambient temperature and ph this behavior contrasts with that of peak activity lakes that have more sustained volcanic gas influx e g kawah ijen indonesia poas and rincon de la vieja costa rica

chemical composition of fumarolic gases and spring discharges from el chichon volcano mexico causes and implications of the changes detected over the period 1998 2000 abstract since the march april 1982 eruption of el chichon volcano intense hydrothermal activity has characterised the 1 km wide summit crater this mainly consists of mud and boiling pools fumaroles which are mainly located in the northwestern bank of the crater lake during the period 1998 2000 hot springs and fumaroles discharging inside the crater and from the southeastern outer flank agua caliente were collected for chemical analyses the observed chemical fluctuations suggest that the physico chemical boundary conditions regulating the thermodynamic equilibria of the deep rock fluid interactions have changed with time the chemical composition of the lake water characterised in the period 1983 1997 by high na cl ca 2 and so 4 2 contents experienced a dramatic change in 1998 1999 turning from a na cl to a ca 2 so 4 2 rich composition in june 2000 a relatively sharp increase in na and cl contents was observed at the same time so 2 h 2 s ratios and h 2 and co contents in most gas discharges increased with respect to the previous two years of observations suggesting either a new input of deep seated fluids or local variations of the more surficial hydrothermal system migration of gas manifestations enhanced number of emission spots and variations in both gas discharge flux and outlet temperatures of the main fluid manifestations were also recorded the magmatic hydrothermal system of el chichon is probably related to interaction processes between a deep magmatic source and a surficial cold aquifer an important role may also be played by the interaction of the deep fluids with the volcanic rocks and the sedimentary limestone and evaporites basement the chemical and physical changes recorded in 1998 2000 were possibly due to variations in the permeability of the conduit system feeding the fluid discharges at surface as testified by the migration of gas and water emanations two different scenarios can be put forward for the volcanic evolution of el chichon 1 build up of an infra crater dome that may imply a future eruption in terms of tens to hundreds of years 2 minor phreatic phreatomagmatic events whose prediction and timing is more difficult to constrain this suggests that unlike the diminished volcanic activity at el chichon after the 1982 paroxistic event the volcano hydrothermal fluid discharges need to be more constantly monitored with regular and more frequent geochemical sampling and at the same time a permanent network of seismic stations should be installed

on some radiative features of the el chichon volcanic stratospheric dust cloud and a cloud of unknown origin observed at mauna loa we present some results of our initial optical observations of the el chichon volcanic cloud these observations were made at the geophysical monitoring for climatic change mauna loa observatory hawaii and consist of lidar profiles optical thickness spectral variation in optical thickness and changes in global and direct solar broadband fluxes particle size distribution and cloud mass information contained in the optical thickness observations are discussed it is clear that the atmospheric radiative effects of the el chichon cloud far exceed the effects of all other volcanic clouds observed at mauna loa since observations were begun in 1958

water chemistry of lakes related to active and inactive mexican volcanoes abstract water chemistry of crater lakes maars and water reservoirs linked to some mexican volcanoes within and outside the mexican volcanic belt has been determined for several years and examined regarding environmental and volcanic factors all the analyzed lakes are relatively small with a maximum depth of 65 m and are located in regions with different climates from semi arid to very humid with altitudes ranging from 100 to more than 4000 m a s l crater lakes in active volcanoes el chichon popocatepetl have very low ph moderate to high temperatures and major ion concentrations varying with the level of volcanic unrest lakes in sub arid and temperate arid regions like maars in puebla and guanajuato states show high alkalinity and ph with bicarbonate carbonate chloride sodium and magnesium as predominant ions lakes located in humid climates central michoacan and veracruz state have low mineralization and near neutral ph values in general conservative dissolved ions and conductivity appear to be mostly controlled by precipitation evaporation and by the ionic concentration of groundwater inputs calcium magnesium sulfate concentrations and ph are strongly influenced by volcanic rock or volcanic gas interactions with water the influence of low level volcanic activity on crater lakes may be obscured by water rock interactions and climatic factors one of the aims of this paper is to define the relative influence of these factors searching for a reference frame to recognize the early volcanic precursors in volcano related lakes