bristlecone pine tree rings and volcanic eruptions over the last 5000 yr many years of low growth identified in a western usa regional chronology of upper forest border bristlecone pine pinus longaeva and pinus aristata over the last 5000 yr coincide with known large explosive volcanic eruptions and or ice core signals of past eruptions over the last millennium the agreement between the tree ring data and volcano ice core data is high years of ring width minima can be matched with known volcanic eruptions or ice core volcanic signals in 86 of cases in previous millennia while there is substantial concurrence the agreement decreases with increasing antiquity many of the bristlecone pine ring width minima occurred at the same time as ring width minima in high latitude trees from northwestern siberia and or northern finland over the past 4000 5000 yr suggesting climatically effective events of at least hemispheric scale in contrast with the ice core records the agreement between widely separated tree ring records does not decrease with increasing antiquity these data suggest specific intervals when the climate system was or was not particularly sensitive enough to volcanic forcing to affect the trees and they augment the ice core record in a number of ways by providing confirmation from an alternative proxy record for volcanic signals by suggesting alternative dates for eruptions and by adding to the list of years when volcanic events of global significance were likely including the mid 2nd millennium bc eruption of thera

the 25 september 2007 eruption of mount ruapehu new zealand directed ballistics surtseyan jets and ice slurry lahars abstract at 20 26 nzdt on 25 september 2007 a moderate gas driven eruption beneath the summit crater lake of mt ruapehu new zealand generated a directed ballistic fallout apron and surtseyan jet that impacted an area of c 2 5 km2 to the north of the vent two climbers were caught in the blast at a hut 600 m from the vent primary ice slurry lahars were generated in two catchments draining the summit region including a flow that entered a commercial ski field the ejecta consists of blocks of andesitic lava and scoria erupted during previous volcanic episodes a variety of mineral cemented lake floor sediments vent fill debris and rare glassy material interpreted to be derived from a fresh batch of magma a minority of clasts contain formerly molten elemental sulphur indicating that vent temperatures at the base of the lake were in excess of 119 c the ballistic deposit is confined to a c 40 wide swath directed northwards that extends up to 2 km from the inferred vent location beneath crater lake the strong directionality of the jetted deposits and ballistic free shadow zones sheltered by intervening topography all point to a relatively low angle directed blast previous similar eruptions at ruapehu also show preferred deposit orientations that are here correlated with an inclined and off centre vent beneath crater lake the 25 september 2007 eruption appears to have resulted from failure of a relatively shallow hydrothermal seal composed of elemental sulphur and other mineral precipitates developed in the vent breccia which breached following overpressurization by a pulse of magmatic gases released from deeper in the conduit this event highlights the potential hazard from relatively minor gas driven eruptions at ruapehu that can occur with little or no warning improved understanding of the eruption mechanism for this style of eruption will inform future risk assessments for ruapehu and other similar volcanoes worldwide

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

south american cold surges types composites and case studies abstract this paper examines the climatological large scale and synoptic scale aspects of south american cold surges using ncep ncar gridded reanalyses for the 1992 96 period three common cold surge types are identified on the basis of a thickness 1000 850 hpa criteria type 1 a transient surge associated with weak anticyclone development east of the andes in the absence of ridging aloft type 2 a strong and persistent surge associated with dynamic anticyclogenesis aloft and strong surface anticyclone development east of the andes and type 3 a surge east of the brazilian coastal mountains cold surges are most common during the winter and spring jun nov accounting for 189 of the 256 events 74 case studies of two events 19 22 jul 1992 and 12 14 apr 1993 are conducted from both a conventional isobaric and a potential vorticity pv perspective the upper air flow pattern in the july 1992 type 2 case is characterized by the presence of a strong ridge trough couplet which amplifies and becomes

frost rings in trees as records of major volcanic eruptions new data about climatically effective volcanic eruptions during the past several thousand years may be contained in frost damage zones in the annual rings of trees there is good agreement in the timing of frost events and recent eruptions and the damage can be plausibly linked to climatic effects of stratospheric aerosol veils on hemispheric and global scales the cataclysmic proto historic eruption of santorini thera in the aegean is tentatively dated to 1628 26 bc from frost ring evidence

extreme temperature events in summer in northwest siberia since ad 742 inferred from tree rings abstract frost and light rings of living and dead individuals of siberian juniper juniperus sibirica burgsd and siberian larch larix sibirica ledeb growing at the upper polar ural mountains and polar yamal peninsula tree lines in northwest siberia have been studied to reconstruct summer frosts and abrupt temperature declines during the second half of the growing season over the past 1250 years the most severe temperature events in both regions were in ad 801 1109 1259 1278 1466 1601 and 1783 comparison of our data with data from other regions of the world shows that there is agreement in the timing of extreme temperature events in ad 800 801 1109 1258 1259 1453 1466 1585 1601 1783 1884 1912 and 1992 between several regions most probably these extremes have been caused by climatically effective explosive volcanic eruptions

temperature changes at depths to 150 metres near the active crater of aso volcano preliminary analysis of seasonal and volcanic effects abstract two holes were drilled to depths of 150 m and 70 m from the surface about 200 m from the active crater of aso volcano and quartz thermometers were installed in the holes at depth intervals of 30 m and 35 m respectively this series of observations is one of the first measurements of temperature at depth so close to an active crater the ground temperature at a depth of 2 m had an annual variation with a range of about 10 c as expected clearly corresponding to the atmospheric temperature variation but delayed by about 1 month temperatures measured at depths from 30 m to 70 m had very small annual temperature variations the range of temperature at 30 m depth was about 0 04 c the temperature at a depth of 60 m however was particularly stable probably because at this depth the hole is in the middle of a massive lava flow at depths of 70 m or more small less than 0 2 c annual temperature variations were again observed these variations are probably due to the effects of surface water descending to these levels through cracks and fissures at 120 m depth the average temperature is about 17 5 c over 5 c above the surface average temperature and the annual temperature variation has a range of about 2 c out of phase with the atmospheric changes this is probably due to the interaction of rainfall descending from the surface with convecting hotter fluids from below the temperature gradient below 100 m depth is very high with the average temperature at a depth of 150 m being about 31 c the temperature variations at this depth are dominated by long period variations with a steady decline after a peak in november december 1989 overlain by a rather irregular seasonal variation with a range of about 0 5 c october 1989 was the time of most active volcanic activity with strombolian eruptions depositing ash to a distance of 50 km from the crater accompanied by very high amplitude volcanic tremor so the temperature changes at 150 m seem to be mainly the result of volcanic activity the maximum temperature at this depth occurred 1 or 2 months after the peak of observed volcanic activity so it is likely that the temperature variations show a delayed influence of the level of volcanic activity these results show that in the unconsolidated materials often found by active volcanic craters the effects of seasonal atmospheric variations are carried to substantial depths by groundwater flows so that at aso volcano only at the maximum depth of 150 m are the temperature variations clearly dominated by the level of volcanic activity

eddy covariance measurements of hydrothermal heat flux at solfatara volcano italy abstract the first measurements of volcanic hydrothermal water vapor and heat flux using eddy covariance ec were made at solfatara crater italy june 8 25 2001 deployment at six different locations within the crater allowed areas of focused gas venting to be variably included in the measured flux turbulent ec fluxes of water vapor varied between 680 and 11 200 g h2o m 2 d 1 heat fluxes varied diurnally with the solar input and the volcanic component of sensible heat ranged from 25 to 238 w m 2 the highest measurements of both sensible and latent heat flux were made downwind of hot soil regions and degassing pools and during mid day the ratio of average volcanic heat both latent and sensible to co2 flux resulted in an equivalent h2o co2 flux ratio of 2 2 by weight which reflects the deep source h2o co2 gas ratio the amount latent heat flux evaporation was determined to be consistent both with what would be expected from the magnitude of co2 fluxes and the fumarolic h2o co2 ratio as well as with observed surface temperatures and wind speeds given a moist soil this suggests that the water vapor that condenses in the shallow subsurface is remobilized at the soil atmosphere interface through variable evaporation dependent on the deep heat flux and surface temperature the results suggest that ec provides a quick and easy method to monitor average h2o co2 ratios continuously in volcanic regions providing another important tool for volcanic hazards monitoring

a facies model for a quaternary andesitic composite volcano ruapehu new zealand ruapehu composite volcano is a dynamic volcanic sedimentary system characterised by high accumulation rates and by rapid lateral and vertical change in facies four major cone building episodes have occurred over 250 ka from a variety of summit flank and satellite vents eruptive styles include subplinian strombolian phreatomagmatic vulcanian and dome related explosive eruptions and extrusion of lava flows and domes the volcano can be divided into two parts a composite cone of volume 110 km3 surrounded by an equally voluminous ring plain complementary portions of ruapehu s history are preserved in cone forming and ring plain environments cone forming sequences are dominated by sheet and autobrecciated lava flows which seldom reach the ring plain the ring plain is built predominantly from the products of explosive volcanism both the distal primary pyroclastic deposits and the reworked material eroded from the cone much of the material entering the ring plain is transported by lahars either generated directly by eruptions or triggered by the high intensity rain storms which characterise the region ring plain detritus is reworked rapidly by concentrated and hyperconcentrated streams in pulses of rapid aggradation immediately following eruptions and more gradually in the longer intervals between eruptions

sulphur flows at lastarria volcano in the north chilean andes although several authors have suggested that sulphur plays an important role in the volcanism on the jovian moon io1 8 some deny the participation of elemental sulphur there at least in the form of cooled flows9 studies of volcanism on io have focused attention on the role of sulphur in terrestrial volcanism on earth fumarolic sulphur is very common in almost all active volcanoes but sulphur flows are rare having been reported only on siretoko iosan volcano in japan10 on sierra negra and azufre volcanoes in the galapagos islands11 12 and on mauna loa in hawaii13 14 of these the siretoko iosan example is the only natural molten sulphur flow to have been observed in the process of formation the others being rather poorly exposed i describe here a singularly well exposed example of sulphur lava flows on lastarria volcano in chile where the liquid sulphur appears to have been formed by melting of fumarolic sulphur deposits caused by a rise in the thermal gradient owing to the renewed activity of the magmatic source

saturated and subcooled hydrothermal boiling in groundwater flow channels as a source of harmonic tremor the potential of hydrothermal boiling in groundwater flow channels for generating harmonic tremor a relatively monochromatic ground vibration associated with volcanic activity is examined we use simple organ pipe theory of normal mode fluid vibration and fundamental energy considerations to develop a first order analytical model of a hydrothermal boiling source of harmonic tremor we use this model to estimate order of magnitude groundwater flow channel lengths and boiling heat transfer rates required to produce harmonic tremor with dominant frequencies in the range 0 5 5 hz and surface wave reduced displacements of up to 100 cm2 depending on groundwater sound speed flow channel lengths of the order of 1 1000 m are required to produce fluid vibration eigenfrequencies in the range 0 5 5 hz the boiling heat transfer rate required to produce tremor with a given surface wave reduced displacement depends on the tremor frequency and on whether saturated boiling or subcooled boiling is the cause of the tremor saturated boiling produces groundwater vibration via steam bubble growth whereas subcooled boiling produces groundwater vibration via steam bubble collapse we find that subcooled hydrothermal boiling is from 102 to 104 times more efficient than saturated boiling in converting boiling thermal power to seismic power for example the boiling heat transfer rates required to produce 1 hz tremor with reduced displacements of up to 100 cm2 via subcooled boiling are generally less than a few thousand megawatts for saturated boiling the required boiling heat transfer rates are several orders of magnitude larger than this the highest values of heat flow reported in the literature for volcanic crater lakes and terrestrial and ocean floor geothermal areas are of the order of 1000 mw taking this value as a first order estimate of an upper limit on possible boiling heat transfer rates in volcanic hydrothermal systems our results suggest that saturated hydrothermal boiling is capable of generating only low amplitude harmonic tremor with surface wave reduced displacements no higher than a few square centimeters however subcooled hydrothermal boiling could potentially generate high amplitude harmonic tremor with reduced displacements as large as several hundred square centimeters as a specific application of our model we evaluate the potential of hydrothermal boiling for generating harmonic tremor at recently active mount st helens and nevado del ruiz volcanoes we conclude that subcooled boiling likely could have produced the tremor episodes considered at both volcanoes saturated boiling also could explain the nevado del ruiz tremor but probably not the more powerful mount st helens tremor

on the terrestrial heat flow and physical limnology of crater lake oregon the heat flow into 7000 year old crater lake caldera is dominated by hydrothermal processes the average of the conducted heat flow value is 138 121 mw m sup 2 3 3 2 9 hfu the total heat flow is estimated to be between 669 and 1381 mw m sup 2 16 and 33 hfu hydrothermal fluids penetrate into the lake floor to a depth of at least 1 5 to 2 0 km and possibly much deeper two thermal spring areas were discovered on the deep lake floor these springs and probably other as yet undiscovered ones have a dramatic effect on the water temperature circulation and stratification of the lake dense thermal waters pond in the southwest basin the deep waters of the east and northwest basin are warmed to the point that they convect causing the lake to be vertically mixed a hyperadiabatic temperature gradient results from this convection and possibly the stagnating effects of small quantities of suspended solids thermal fluids carrying dissolved solids cause anomalously high concentrations of chloride and sulfate in the relatively pure lake water

variability of volcanic gas emissions during a crater lake heating cycle at ruapehu volcano new zealand abstract we present the first routine measurements of emissions co 2 so 2 and h 2 s from ruapehu volcano new zealand during a crater lake heating cycle emissions were generally at a low level consistent with quiescent degassing of the volcano and the presence of a crater lake maximum concentrations 3 4 km downwind during the highest measurement in may 2004 were 14 ppm 0 37 ppm and 7 ppb for co 2 so 2 and h 2 s respectively co 2 emissions varied between not detectable to 900 t d 1 over periods of months so 2 was not detectable until february but gradually increased to 35 t d 1 emissions of h 2 s were detected in april and may although were 1 the co 2 so 2 ratio in the plume was 37 by weight for each measurement during the peak of the cycle suggesting that significant scrubbing of so 2 occurs through the crater lake and that a common source exists for both gases magma volumes estimated from co 2 emissions 0 001 0 004 km 3 are consistent with eruptive volumes given repose periods of 20 30 years delays between peaks in crater lake heating and degassing suggests that volcanic emissions do not primarily reside in the shallow hydrothermal system directly beneath the crater further data is needed to adequately model the system but first indications of the travel time associated with the degassing cycle suggests that the gas resides at minimally 300 m depth beneath the crater lake depths greater than 300 m are consistent with the top of the single phase steam zone in heat pipe models 200 700 m depth or perhaps even below the plastic brittle transition zone above the cooling magmas 1 km deep

direct video and hydrophone observations of submarine explosive eruptions at nw rota 1 volcano mariana arc 1 extraordinary video and hydrophone observations of a submarine explosive eruption were made with a remotely operated vehicle in april 2006 at a depth of 550 560 m on nw rota 1 volcano in the mariana arc the observed eruption evolved from effusive to explosive while the eruption rate increased from near zero to 10 100 m3 h during the peak in activity cyclic explosive bursts 2 6 min long were separated by shorter non eruptive pauses lasting 10 100 s the size of the ejecta increased with the vigor of the explosions a portable hydrophone deployed near the vent recorded sounds correlated with the explosive bursts the highest amplitudes were 50 db higher than ambient noise at frequencies between 10 and 50 hz the acoustic data allow us to quantify the durations amplitudes and evolution of the eruptive events over time the low eruption rate high gas lava ratio and rhythmic eruptive behavior at nw rota 1 are most consistent with a strombolian eruptive style we interpret that the eruption was primarily driven by the venting of magmatic gases which was also the primary source of the sound recorded during the explosive bursts the rhythmic nature of the bursts can be explained by partial gas segregation in the conduit and upward migration in a transitional regime between bubbly flow and fully developed slug flow the strongest explosive bursts were accompanied by flashes of red glow and oscillating eruption plumes in the vent apparently caused by magma seawater interaction and rapid steam formation and condensation this is the first time submarine explosive eruptions have been witnessed with simultaneous near field acoustic recordings

one and two dimensional inversion of magnetotelluric data in continental regions abstract for a preliminary inversion of magnetotelluric mt data obtained in continental regions it is common practice to assume initially that the underlying structure is one dimensional id so that one of the readily available routines for simple id inversion may be applied if the continental structure is actually 2d as is often the case such approximate inversions may lead to different conclusions depending on whether transverse electric te or transverse magnetic tm data are used and for this reason rotationally invariant impedances the berdichevsky average or the effective impedance are sometimes preferred in practice when the composite 2d model obtained by applying these inversions at different sites in an array is used as a starting model for optimizing the fit between model and observed responses it is desirable that all significant structural features are included in it with this is mind the effectiveness of the te tm and rotationally invariant impedances in yielding meaningful 1d inversions in a 2d environment is tested by studying various basic models horst resistive and conductive blocks alone and together surface conducting edge and conducting sill with the aid of a new 2d finite difference program and a recently developed automatic scheme for 1d inversion the paper concludes with the construction of a 2d structure from the real coprod2r data using as a starting model the layered models obtained from separate 1d inversions at various mt sites in the array and then optimizing the least squares fit of both the te and tm model responses to the observed responses by adjusting the parameters of the initial model the north american central plains anomaly beneath a shallow sedimentary cover is identified by this procedure in the form of two upright and adjacent conductive blocks this differs somewhat from some previously proposed models but yields a good fit to the apparent resistivity and phase responses at 20 sites

variations in the thermal output of the subglacial grimsvotn caldera iceland a 69 year record 1922 1991 of heat release has been obtained from the subglacial geothermal system of the grimsvotn caldera within the vatnajokull ice cap the data were derived from in situ measurements of the volume of meltwater accumulated in the caldera lake subtracting climatically induced melting the overall fluctuations in the heat flux are closely related to volcanic activity and are dominated by a main pulse of 11 600 mw caused by a major eruption in 1938 gradually declining to 1600 mw in 1976 1982 heat extracted from the roof of a magma chamber with the aid of hydrothermal convection may have given a basic contribution to the heat flux of 1500 to 2000 mw an upper bound the variable part of the heat flux from 0 to 10 000 mw was released from magma erupted at the base of the glacier and from shallow intrusions the total heat released over the period 1922 to 1991 was 8 1 1 6 1018j equivalent to the energy released by the solidification and cooling of 2 1 0 4 km of basaltic magma the contribution to the total heat flux was 45 max from a magma chamber 35 min from shallow intrusions and 20 from eruptions this implies that magma at the roof of a chamber solidified and cooled at the rate of 1 2 1 6 107 m a 1 or about 1 km over the last 69 years heat release at grimsvotn was probably more intense in the 19th century when volcanic eruptions were more frequent

volcanic hazard assessment for ruapehu composite volcano taupo volcanic zone new zealand ruapehu is a very active andesitic composite volcano which has erupted five times in the past 10 years historical events have included phreatomagmatic eruptions through a hot crater lake and two dome building episodes ski field facilities road and rail bridges alpine huts and portions of a major hydroelectrical power scheme have been damaged or destroyed by these eruptions destruction of a rail bridge by a lahar in 1953 caused the loss of 151 lives other potential hazards with holocene analogues include strombolian and sub plinian explosive eruptions lava extrusion from summit or flank vents and collapse of portions of the volcano the greatest hazards would result from renewed phreatomagmatic activity in crater lake or collapse of its weak southeastern wall three types of hazard zones can be defined for the phreatomagmatic events inner zones of extreme risk from ballistic blocks and surges outer zones of disruption to services from fall deposits and zones of risk from lahars which consist of tongues down major river valleys ruapehu is prone to destructive lahars because of the presence of 107 m3 of hot acid water in crater lake and because of the surrounding summit glaciers and ice fields the greatest risks at ruapehu are to thousands of skiers on the ski field which crosses a northern lahar path three early warning schemes have been established to deal with the lahar problems collapse of the southeastern confining wall would release much of the lake into an eastern lahar path causing widespread damage this is a long term risk which could only be mitigated by drainage of the lake

frost record in tree rings linked to atmospheric circulation in northern patagonia abstract cold air incursions over subtropical south america are the precursor conditions for frost a recognized extreme thermal weather event affecting plant growth damaging agricultural production over the whole argentinian territory given that sub freezing temperatures occurring during the active growing season may harm the cambium tissues and their daughter cells frost injury can be recorded in annual tree rings in the form of anatomical anomalies for this study six forest sites of araucaria araucana a multi centennial tree species from nw patagonia were considered from 321 trees 1374 frost injuries in the growth rings named frost rings were identified and their calendar dating allowed the development of a regional chronology of frost rings covering the period ad 1256 to ad 1993 738 yrs this represents the longest record at present of extreme low thermal events for patagonia frost injuries were mostly restricted to the middle section of the growth rings suggesting the incidence of late spring frosts moreover frost rings were observed mainly in the juvenile portions

ramifications of the skin effect for crater lake heat budget analysis abstract mass energy and chemical balance analysis for volcanic crater lakes offers a means to interpret magmatic hydrothermal processes in addition to water temperature several meteorological parameters including windspeed rainfall solar irradiation air temperature and humidity need to be evaluated in order to balance heat fluxes conventional contact thermometry yields bulk water temperatures however these are typically a few degrees or tenths of a degree higher than the water surface temperatures which should be used in several bulk aerodynamic and other formulae for heat flux calculations the magnitude of overestimation of derived evaporative flux that can arise from ignoring this skin effect is shown here to depend on bulk water temperature air temperature and other meteorological factors field observations obtained at kawah ijen indonesia with a lake bulk temperature of 43 1 c suggest a bulk skin temperature difference of around 1 5 c leading to an overestimation of evaporative and sensible heat fluxes of 10 if the skin effect is overlooked this error can be minimised by assuming a value for the bulk skin temperature difference or eliminated by ensuring that evaporation formulae are parameterised with the temperatures skin or bulk for which they were originally defined

earthquake swarms to the west of mt ruapehu preceding its 1995 eruption abstract some months prior to the 1995 eruption of mt ruapehu new zealand a series of shallow earthquake swarms occurred about 15 20 km west of the summit of ruapehu several earthquakes in these swarms were felt and the largest event was m l 4 8 crustal earthquakes of m l 3 0 within 20 km of the summit of ruapehu have been rather uncommon in recent years furthermore the two periods of strongest activity were both just before times when the temperature of crater lake showed rapid increases the second of these rapid heating phases was immediately followed by increases in the mg 2 ion concentration in crater lake indicating that chemical interactions were occurring between fresh magmatic material and the lake water the coincidence between seismicity and lake changes suggested a link with the following eruption a 1 d simultaneous inversion to locate the earthquakes more accurately showed that most of the earthquakes fell into three spatial clusters each cluster having a small horizontal cross section the predominant depth was about 10 16 km the b value of this swarm was 0 74 quite compatible with ordinary tectonic earthquakes each cluster of earthquakes lies close to the normal raurimu fault which runs predominantly north south to the west of ruapehu with an east trending branch splaying off near its northern end see fig 1 b composite focal mechanisms of events in the two more southern clusters are oblique normal while the other cluster to the north has an oblique reverse mechanism the two oblique normal mechanisms suggest that extension has occurred on part of the fault this stress pattern was also observed in the focal mechanism solutions of events that occurred after the eruption when a denser network of portable seismographs covered the region although we cannot definitely connect the occurrence of these swarms to the eruptions later in 1995 there is a strong suggestion that the seismicity was connected to the process of magma movement which temperature and chemical changes in crater lake suggest was occurring during the first half of 1995

formation structure and climatic significance of blue rings and frost rings in high elevation bristlecone pine pinus longaeva d k bailey abstract the study of anatomical irregularities in tree rings has recently gained momentum as a complement to traditional tree ring measurements as they may provide information on extreme climatic events two anomalies blue rings br and frost rings fr were analyzed in bristlecone pine pinus longaeva d k bailey trees located along an elevation gradient in northeastern nevada these two subannual ring anomalies were systematically compiled for two periods one centered on 536 ce well known for a volcanically induced period of climatic cooling and the other on 1965 ce useful due to the availability of instrumental climate data during the period 523 545 ce n 10 trees both br and latewood fr lwfr were recorded abundantly in 532 and 536 as well as a br cluster from 539 to 542 ce years when trees solely recorded a br without an accompanying lwfr were more frequent in the earlier period than in the modern period 1954 2006 ce n 10 trees when both anomalies tended to co occur these results suggest a shorter growing season in the 536 period than in the 20th century modern br lwfr were most abundant in 1965 and 1978 ce both anomalies were mainly observed in the highest elevation trees and both were produced in years characterized by cooler than average temperatures throughout the growing season anatomically br and lwfr did not differ significantly in tracheid dimensions except that lwfr clearly showed damages associated with sub freezing temperatures the main feature distinguishing br and lwfr from normal tree rings was a significant reduction in latewood secondary wall thickness in p longaeva br like pale latewood light rings result from short and cool growing seasons which leads to reduced or interrupted lignification of tracheids in species producing extremely narrow latewood like p longaeva it may be difficult to macroscopically identify pale latewood years thus rendering microscopic investigation of br as a climate proxy useful in paleoclimatic research

cold air incursions over subtropical south america mean structure and dynamics abstract synoptic scale incursions of midlatitude air moving into subtropical south america to the east of the andes cordillera are observed to occur year round with a periodicity of about 1 2 weeks during wintertime they have a profound impact upon the low level temperature field and extreme episodes produce freezing conditions from central argentina to southern brazil and bolivia warm season episodes produce less dramatic variations of temperature but they organize deep convection in the form of synoptic scale bands of convective cloudiness along the leading edge of the cool air on the basis of 17 yr of ncep ncar reanalysis and outgoing longwave radiation fields the mean synoptic scale structure and evolution of these incursions is documented using a simple compositing technique the underlying physical mechanisms responsible for the occurrence of these incursions are also investigated by diagnosing the leading dynamic and thermodynamic forcing of their development

acoustic noise and temperature monitoring of the crater lake of mount ruapehu volcano abstract acoustic signals in ruapehu crater lake which are now being telemetered via a satellite transmission system show promise as a possible precursor of increased volcanic activity from ruapehu the start of a recent period of rapid heating of crater lake was preceded by low frequency 2 hz acoustic signals these accompanied similar frequency seismic signals but seemed to be produced independently audio frequency 350 3000 hz acoustic noise also showed a very clear peak shortly before the lake temperature started to rise

atmospheric circulation associated with persistent generalized frosts in central southern south america abstract this paper describes the large scale atmospheric circulation associated with persistent generalized frosts gfs at least 75 of the stations report frosts in the east central region of argentina known as the wet pampa the gf events are grouped according to their persistence and ncep ncar reanalysis data are used to create daily composites of mass and wind field anomalies during the 1961 90 winters the gfs are caused by an anticyclonic anomaly that enters south america generating southerly wind anomalies and cold air advection that are strengthened by the meridional layout of a cyclonic anomaly over the south atlantic ocean in the case of the more persistent events the wind anomaly grows during the previous days and becomes quasi stationary also the study identifies at 250 hpa a double train of eastward moving rossby waves along the subtropical and subpolar latitudes respectively of the southern hemisphere the layout of both wave trains favors the development of an intense southerly wi

analogue modeling of instabilities in crater lake hydrothermal systems 1 we carried out analogue experiments on two phase boiling systems using a porous vertical cylinder saturated with water the base of the cylinder was heated and the top was cooled as in a natural hydrothermal system previous work had shown that once the two phase zone reached a certain level thermal instabilities would develop we made measurements of the acoustic energy related to boiling and we found that high levels of acoustic noise were associated with the part of the cycle in which there was upward water movement we repeated our experiments with a cooling water tank at the top of the system representing a crater lake this showed that periodic thermal instabilities still developed in this situation we then compared our analogue measurements to two natural systems known to exhibit periodic behavior there is good agreement between the thermal and acoustic cycling seen in our model and the observations made at inferno crater lake in the waimangu geothermal area new zealand whose level cycles by nearly 10 m with a typical period of 38 days particularly notable is how in both systems high levels of acoustic noise are associated with rising water level the much larger ruapehu crater lake also in new zealand cycled with a period of several months to a year for over a decade prior to the 1995 eruption strong acoustic and seismic energy usually occurred just before the lake temperature started to rise this suggests a slightly different model in which the increasing two phase flow zone triggers more general convection once it reaches the base of the lake

rates of sulfur dioxide and particle emissions from white island volcano new zealand and an estimate of the total flux of major gaseous species airborne correlation spectrometry cospec was used to measure the rate of so2 emission at white island on three dates i e november 1983 1230 300 t d november 1984 320 120 t d and january 1985 350 150 t d t metric tons the lower emission rates are likely to reflect the long term emission rates whereas the november 1983 rate probably reflects conditions prior to the eruption of december 1983 the particle flux in the white island plume as determined with a quartz crystal microbalance cascade in november 1983 was 1 3 t d unusually low for volcanic plumes the observed plume particles as shown from scanning electron microscopy include halite native sulfur and silicates and are broadly similar to other volcanic plumes

electrical conductivity and paleo proterozoic foredeeps sedimentary facies associated with paleo proterozoic foredeeps are apparently highly conductive the conductive lithology appears to be a euxinic carbonaceous shale deposited on preforedeep continental margin facies the shale is overlaid by axial turbidites and often incorporated into the succeeding fold and thrust belt carbonaceous shales can be made highly conducting if graphitized by exposure to temperatures exceeding 400 c although foredeep facies develop diachronously the most conductive unit is usually found in the core of the fold and thrust belt suggesting that deformation may be essential for the complete graphitization of the carbon the foredeep hypothesis offers an attractive explanation for several highly conductive features detected in the upper and middle crust in laurentia and possibly throughout the world the euxinic facies represent highly specific tectonic marker horizons that are readily delineated by using electromagnetic methods

plumbing the depths of ligeia considerations for depth sounding in titan s hydrocarbon seas saturn s moon titan is the only satellite in this solar system with a dense atmosphere and hydrocarbon seas the titan mare explorer time mission would splashdown a capsule to float for 3 months on ligeia mare a several hundred kilometer wide sea near titan s north pole among time s scientific goals is the determination of the depth of ligeia to be achieved with an acoustic depth sounder since titan s surface temperature is known to vary around 92 k all instruments must be ruggedized to operate at cryogenic temperatures this paper s contributions include an approach to infer key acoustic properties of this remote environment and the extraterrestrial environment s influence on the development of a cryogenic depth sounder additionally an approach is formulated to infer the transducer s response sensitivity and performance when in situ calibration is impossible or when replicating key environmental conditions is too costly

evolution of a vent hosted hydrothermal system beneath ruapehu crater lake new zealand a two year chemical monitoring program of ruapehu crater lake shows that it has evolved considerably since the volcano s more active eruptive periods in the early 1970s the present ph 20 c of 0 6 is about one half unit more acid than the baseline values in the 1970s whereas s cl ratios have increased markedly owing in part to declining hcl inputs into the lake but also to absolute increases in so4 levels which now stand at the highest values ever recorded increases in k mg and na mg ratios over the 20 year period are attributed to hydrothermal reaction processes in the vent which are presently causing dissolution of previously formed alteration phases such as natroalunite these observations combined with results of a recent heat budget analysis of the lake have led to the development of hydrothermal convection model for the upper portion of the vent possible vent lake chemical reaction processes between end member reactants have been modelled with the computer code chiller the results are consistent with the view that variations in lake chemistry which are initiated by the introduction of fresh magmatic material into the vent reflect the extent of dissolution reaction progress on the magmatic material and or its alteration products the results also provide insights into the role of such vent processes in the formation of high sulfidation type ore deposits

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

a general model for mt ruapehu lahars a mathematical model of the motion of lahars is presented lahar flows and travel speeds are calculated using a kinematic wave model which equates gravitational accelerations to frictional losses a chezyor manning type law of friction is assumed in which lahar flow rate is a simple power function of lahar depth multiplied by another simple power of the chanel slope use of the model requires knowledge of essentially only one parameter which appears to be relatively insensitive for flows down a given channel variable channel slope effects are removed by a longitudinal scaling which applies to all flows down a given channel for lahars generated by a single explosive event it is unnecessary to perform numerical calculations to predict lahar flow and travel time but for lahnars produced by multiple sources in which different lahar flows are interacting numerical calculations appear necessary the model is applied to all recorded lahar flows from mt ruapehu and satisfactorily described all lahar flows generated by a single explosive mechanism such flows depend essentially only on total lahar volume the 1968 mt ruapehu lahar generated by a series of smaller eruptive mechanisms was modelled as the interaction of seven point sources of fluid originating from positions mathematically extrapolated up the mountain good agreement was obtained between the predicted times of formation of these 1968 lahars and the times of greatest seismic amplitude

the north american central plains conductivity anomaly and its correlation with gravity magnetic seismic and heat flow data in saskatchewan canada abstract the north american central plains conductivity anomaly nacp lies virtually in its entirety within the trans hudson orogen accordingly should these two features prove to be contemporaneous then the geometrical relationship between these two is of foremost importance to any evolutionary tectonic model proposed to explain the collision of the superior and churchill provinces in the hudsonian and a model that does not include a mechanism for the generation of this anomaly is obviously untenable in order to map better the trend of the nacp in the province of saskatchewan canada two magnetotelluric mt profiles were conducted over the nacp previously defined by magnetometer arrays and profiles data from these two profiles along with an earlier mt profile just north of the u s canadian border suggest that the nacp is not a continuous feature but rather that it exhibits a definite break at latitude 51 n other geophysical evidence examined herein is concordant with this characteristic if a second mt anomaly mapped to the northwest of this break is in fact a manifestation of the same geological structure then one possible interpretation is of a major nw se trending sinistral fault in the deep crust previously undetected with a movement of some 100 150 km along strike the mt data from the southernmost profile after correction for static shift are modelled in a 2d manner and it is shown that the nacp is consistent with an arcuate structure in vertical section of high conductivity 2 s m 1 beginning at a depth of 10 km centred on 103 w dipping down to the west reaching possibly the base of the crust it is also shown that such an arcuate shape in section can explain an observed gravity high of 40 mgal such high conductivities cannot be explained in terms of connected fluids as it would require implausibly high porosities 12 20 a comprehensive interpretation of all the geophysical data would have to account for the observed characteristics of the anomalous region which are high electrical conductivity positive density contrast no magnetization and high heat flow in the basement in terms of a single causative body one possible explanation is presented in terms of a zone of lithospheric weakness along which was emplaced low density differentia from a mantle derived body an alternative explanation could be the phase transformation of obducted material into eclogite or serpentinite however difficulties exist with both of these explanations and further data are required

investigating crater lake warming using aster thermal imagery case studies at ruapehu poas kawah ijen and copahue volcanoes abstract a two channel or split window algorithm designed to correct for atmospheric conditions was applied to thermal images taken by the advanced spaceborne thermal emission and reflection radiometer aster of lake yugama on kusatsu shirane volcano in japan in order to measure the temperature of its crater lake these temperature calculations were validated using lake water temperatures that were collected on the ground overall the agreement between the temperatures calculated using the split window method and ground truth is quite good typically 1 5 c for cloud free images data from fieldwork undertaken in the summer of 2004 at kusatsu shirane allow a comparison of ground truth data with the radiant temperatures measured using aster imagery further images were analyzed of ruapehu poas kawah ijen and copahue volcanoes to acquire time series of lake temperatures a total of 64 images of these 4 volcanoes covering a wide range of geographical locations and climates were analyzed results of the split window algorithm applied to aster images are reliable for monitoring thermal changes in active volcanic lakes these temperature data when considered in conjunction with traditional volcano monitoring techniques lead to a better understanding of whether and how thermal changes in crater lakes aid in eruption forecasting

the sound field near hydrothermal vents on axial seamount juan de fuca ridge high quality acoustic noise measurements were obtained by two hydrophones located 3 m and 40 m from an active hydrothermal vent on axial seamount juan de fuca ridge in an effort to determine the feasibility of monitoring hydrothermal vent activity through flow noise generation most of the measured noise field could be attributed to ambient ocean noise sources of microseisms distant shipping and weather punctuated by local ships and biological sources long period low velocity water rock interface waves were detected with high amplitudes which rapidly decayed with distance from the seafloor detection of vent signals was hampered by unexpected spatial nonstationarity due to the shadowing effects of the caldera wall no continuous vent signals were deemed significant based on a criterion of 90 probability of detection and 5 probability of false alarm however a small signal near 40 hz with a power level of 10 4pa2 hz was noticed on two records taken within 3 m of the inferno black smoker hie frequency of this signal is consistent with predictions and the power level suggests the occurrence of jet noise amplification due to convected density inhomogeneities

numerical simulation of the steam water flow instability as a mechanism of long period ground vibrations at geothermal areas summary we present a model for the excitation of continuous ground vibration at geothermal areas and active volcanoes which is based on the instability of water steam two phase flow through a series of numerical experiments we evaluate the amplitude and period of ground vibrations excited by density wave oscillation called dwo one of the flow instability phenomena which is known in the nuclear reactor engineering to occur under a wide variety of boundary conditions we consider a vertical cylindrical pipe buried underground and 1 d flows through it driven by the lithostatic pressure gradient water flows into the pipe from below and is evaporated by the heat supplied from outside when the heating rate is low after a perturbation such as a change in heating rate is given to the flow system a decaying oscillation of pressure flow velocity and void fraction occurs being followed by a stationary flow on the other hand when the heating rate exceeds a threshold the perturbation grows to a continuous oscillation with a fixed amplitude forming a limit cycle dwo we investigate how various parameters such as pipe length pressure and heating rate affect the stability of the two phase flow we then estimate the amplitudes of seismic waves excited by dwo assuming that the pipe is embedded in a elastic half space we find that a longer pipe can excite a dwo of longer period and of larger maximum amplitude for a pipe of length of 100 m with its bottom at the depth of 150 m the dwo period is nearly 10 s in this case the maximum pipe diameter for the excitation of limit cycle dwo for reasonable rates of stationary conductive heat supply from country rocks to the two phase mixture inside the pipe less than about 35 mw m 3 is 0 02 m the maximum amplitudes of ground displacement due to dwo are of the order of 7 10 8 m and 4 10 9 m at epicentral distances of 200 and 1000 m respectively typical geothermal areas and active volcanoes can supply heat and discharged water mass which are required to excite dwo larger than typical background noises therefore dwo due to a shallow water steam flow could excite ground motions with periods longer than 10 s which is large enough to be observed with suitably designed broadband seismic experiments at geothermal fields

the electrical resistivity of canada s lithosphere and correlation with other parameters contributions from lithoprobe and other programmes over the last 30 years through lithoprobe and other programmes modern high quality magnetotelluric mt measurements probing deep into the lithosphere and underlying asthenosphere have been made at over 6000 sites across canada in all provinces and territories except nova scotia some regions are well covered particularly alberta southern british columbia and western ontario whereas others remain poorly covered such as quebec and large swaths of nunavut prior publications from individual studies have added significantly to the wealth of canada s geoscience knowledge and have demonstrated that mt can contribute significantly to understanding of the tectonic processes that have shaped canada however to date no continent scale maps of lithospheric electrical parameters have been constructed from the extensive mt database herein we review the contributions made by the mt components of lithoprobe and present new continental scale maps of various electrical parameters at crustal and upper mantle

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

strombolian explosions 2 eruption dynamics determined from acoustic measurements strombolian activity consists of a series of explosions due to the breaking of a large overpressurized bubble at the surface of the magma column acoustic pressure due to sound waves has been measured and analyzed at stromboli for more than 50 explosions three parts can be distinguished in the acoustic pressure waveform which are related to the behavior of the bubble before during and after its bursting before the sharp rise in acoustic pressure the signal is dominated by waves with a frequency of 2 hz which develop on the nose of the bubble they produce sound in air by imposing a rapid motion to the interface and one could detect a bubble travelling in the uppermost 30 m of the magma column when the bubble reaches the air magma interface its strong vibration driven by a large overpressure inside the gas generates the main event with a frequency around 9 hz after the bubble has burst kinematic waves of frequency around 4 5 hz are the main source of sound they develop at the surface of the magma left on the conduit side the three types of motion although determined independently give consistent results furthermore combining the results obtained for the two types of kinematic waves the magma viscosity is estimated to be of 300 65 pa s which is in good agreement with petrological constraints and corroborates the validity of our analysis this suggests that acoustic measurements constitute a powerful tool in the understanding of eruption dynamics

volcanic earthquakes and their relationship to eruptions at ruapehu and ngauruhoe volcanoes abstract crustal earthquakes near ruapehu and ngauruhoe fall into two classes each of which can be subdivided on the one hand there are high frequency events 3 hz with sharp well defined phases mainly concentrated beneath ruapehu crater lake low frequency events the low frequency events resemble minakami s b type and explosion earthquakes but sometimes occur where no vent exists and rather deeper than his formal definition difficulty in applying minakami s classification rigorously and the fact that low frequencies may be due to abnormal attenuation of higher frequencies along the path rather than to their suppression or absence at the source has led to reclassification of earthquakes near the volcanoes into two broad groups tectonic and volcanic the former includes all high frequency earthquakes and those discrete events in which dominant low frequencies are due to path effects the latter includes multiple and emergent events which show evidence of prolonged or repetitive source mechanism dominant low frequencies are ascribed to occurrence in heat weakened material and high frequencies to instantaneous source mechanisms operating in competent rock the term volcano tectonic describes tectonic earthquakes within some arbitrary distance of a volcano at ngauruhoe and ruapehu volcanic earthquakes accompany explosive vent clearing eruptions subsequent open vent degassing and ash emission however although often powerful and prolonged usually occurs without earthquakes such activity is however frequently accompanied by volcanic tremor at ruapehu under closed vent conditions when lake temperature is low low frequency earthquakes up to magnitude ml 3 4 have occurred without any eruption five types of phreatic eruptions are identified at ruapehu each having a distinctive seismic pattern the three most explosive types appear to be generated by a chain reaction process and all involve flashing of water to steam the first by failure of the roof with little precursory seismicity after a closed vent period during which lake temperature decreases the second after prolonged heating of the lake and much preliminary volcanic tremor interpreted as due to rising magma and the third under open vent conditions in the wake of one of the two preceding types a fourth probably occurs in wet sediments near the base of the lake as a result of upward migration of hot gas and a fifth aseismic or accompanied by very weak volcanic tremor is associated with convective overturn within crater lake

bathymetry heat output and convection in ruapehu crater lake new zealand abstract bathymetric observations of ruapehu crater lake show that it became shallower and its volume decreased by 3 10 6 m 3 between 1965 and 1970 it is likely that this was due to lava moving upwards in the region under the lake from the regular measurements of crater lake temperature outflow and chloride and magnesium ion concentrations the inflows of steam cold water and chloride and magnesium ions were calculated using the 1970 volume only about half the precipitation falling on and around the lake mixes with the lake water since the cold fresh water floats on top of the denser lake water and travels to the outlet without mixing with the main body of water in the lake the chloride content of the input steam appears to vary with time in a similar fashion to that of white island fumaroles temperature and density profiles of the lake in 1965 and 1966 indicated that convection was occurring the temperature profile of the top 175 m of the lake agreed with a model of turbulent convection in small cells giving a temperature gradient at any level in the lake proportional to the heat flux at that level the convection model predicted that the temperature at depth would exceed the local boiling point if the thermal power input reached a value which would sustain a surface temperature approaching 60 c this prediction of instability was not inconsistent with observations convection in the present crater lake probably occurs in the form of thermal plumes from small sources

underestimation of volcanic cooling in tree ring based reconstructions of hemispheric temperatures a large volcanic eruption in ad 1258 1259 is expected to have caused substantial climate cooling but evidence for this effect is absent from tree ring based temperature reconstructions numerical modelling of tree growth shows that the lack of cooling is probably an artefact caused by low sensitivity to cooling in trees growing near the treeline

engineering geology model of the crater lake outlet mt ruapehu new zealand to inform rim breakout hazard abstract mt ruapehu in the central north island of new zealand hosts a hot acidic crater lake over the active volcanic vent with a surface elevation of c 2530 m a s l volcanic activity and other montane processes have previously resulted in catastrophic releases of some or all of the c 10 mm3 of water retained in the lake creating serious hazards downstream a major lahar in march 2007 exposed a 10 m high face representative of the rock units impounding the lake providing an opportunity to conduct both field and laboratory analysis to characterise the rock mass conditions at the outlet to assess the stability of the outlet area this paper presents an engineering geology model of crater lake outlet our model shows three andesitic geological units at the outlet each with different geological histories and physical and mechanical properties which impact its stability geotechnical methods used to characterise the outlet include laboratory testing of the strength stiffness porosity and unit weight and field based rock mass characterisation using the geological strength index gsi and rock mass rating rmr field observations geomorphology mapping historic and contemporary photographs and laboratory results are combined to create cross sections that provide key information for establishing the engineering geology model the units are recognised in what is informally termed the crater lake formation i the upper surface layer is a c 2 m thick sub horizontal dark grey lava unit armoured lava ledge with sub horizontal cooling joints spaced at 0 2 m to 2 0 m intervals the intact rock has a porosity range of 15 27 density range of 1723 2101 kg m3 gsi range of 45 75 and unconfined compressive strength ucs range of 19 48 mpa ii below this and outcropping down the majority of the outlet waterfall is a poorly sorted breccia unit composed of block and matrix material lava breccia the blocks range from 0 1 m to 0 8 m in diameter with an average porosity of 21 a density of 1956 kg m3 and strength of 85 mpa the matrix has soil like properties with an estimated ucs of 1 5 mpa iii at the base of the waterfall the material sharply transitions into a light grey slightly weathered unit lower grey member this lower unit has an irregular surface expression with sub vertical discontinuities porosity is 6 density is 2569 kg m3 the gsi range is 65 75 and the ucs is 98 mpa the engineering geology model portrays the relationships between the units in three dimensions highlights key structures and takes into consideration the material source transportation and depositional processes historical outlet photographs suggest past eruptive and glacial activities are both significant factors controlling the deposition and erosion of material at the outlet the lower grey member appears to be a sound material for the outlet and water fall to be founded on the upper aa armoured lava ledge currently has moderate strength and gsi and is resistive providing protection for the underlying weaker block and matrix unit however continued incision by the outlet stream will eventually expose the weaker block and matrix material of the lava breccia once exposed the lava breccia could rapidly erode or fail down to the lower grey member and could potentially release 1 mm3 of hot acidic crater lake water we recommend that erosion rates for the upper armoured lava ledge be established to aid in preparation for eventual rim breakout

infrared surveillance of crater lakes using satellite data abstract under optimum circumstances thermal infrared data recorded from satellites can measure water surface temperatures to accuracies of a few tenths of a degree celsius such techniques are applied here to evaluate volcanic crater lake temperatures at present band 6 of the landsat thematic mapper tm is the most pertinent sensor in this respect although its nominal 120 120 m footprint only permits useful measurements of circular lakes exceeding 340 m in diameter in addition the radiative properties of the atmosphere between sensor and target at the instant of observation should be well characterised in order to make confident measurements of surface temperatures with single band infrared data an analysis is presented of three tm band 6 images of the crater lake at poas volcano costa rica recorded on february 6 1986 march 13 1987 and may 10 1988 in the february 1986 scene the band 6 derived water surface temperature is 36 c which is 3 c less than a field measurement made in the same month since the satellite measurement was integrated over some 14 400 m 2 of the lake surface while the field measurement was obtained at a single point below the surface the former may be more representative of surface heat losses subsequent tm data reveal an increasing discrepancy between contemporaneous field and satellite observations probably because the lake diameter had decreased to 250 m by march 1987 and to less than 200 m by mid 1988 greatly reducing the likelihood of obtaining a pure lake pixel the advanced spaceborne thermal emission and reflection radiometer aster which is earmarked for orbit on the first of nasa s earth observing system satellite platforms later this decade has five discrete spectral bands in the thermal infrared region and will produce data composed of 90 90 m pixels these specifications could enable the determination of water surface temperatures of 250 m diameter crater lakes by algorithms that implicitly account for atmospheric effects

carbon dioxide dynamics in kelud volcanic lake 1 in november 2007 the extrusion of a new lava dome evaporated kelud volcanic lake in java indonesia four months before a detailed echo sounding survey of the volcanic lake coupled to floating accumulation chamber measurements detected abnormally high carbon dioxide emissions it constituted the earliest sign of the volcanic unrest well before any other monitored parameter co2 flux is quantified using an empirical equation based on the volume of bubbles backscattered in the water column its comparison with the fluxes retrieved from the floating chamber method better constrain carbon dioxide dynamics in the volcanic lake it reveals that 70 of the carbon dioxide enters the lake in a dissolved form while the remaining 30 is supplied to the lake on a gaseous state almost three quarter of the ascending bubbles dissolve in the water column leaving the majority of the 330 tons day 1 of carbon dioxide diffusing at the air water interface

instabilities during liquid migration into superheated geothermal reservoirs we examine the stability of a vaporizing liquid front migrating through a permeable rock we show that such liquid vapor fronts may become unstable if a sufficient fraction of the liquid vaporizes this instability is a result of the different speed of the fluid on each side of the front we also identify that short wavelength perturbations are stabilized by thermal conduction while long wavelength perturbations are stabilized as a result of the compressibility of the vapor furthermore under conditions typical of geothermal reservoirs where the pressure is 10 atm and the temperature is 200 300 c we find that if the permeability of the system is smaller than 10 15 m 2 then these two stabilizing mechanisms overlap and the system becomes stable to perturbations of any wavelength we also examine the role of gravity in suppressing the instability of an ascending front and promoting the instability of a descending front we apply our results to the vapor dominated geothermal reservoirs at larderello italy and the geysers california to predict conditions under which liquid fronts advancing into superheated vapor are stable

stress and mass changes at a wet volcano example during the 2011 2012 volcanic unrest at kawah ijen volcano indonesia since 2010 kawah ijen volcano has been equipped with seismometers and its extremely acid volcanic lake has been monitored using temperature and leveling sensors providing unprecedented time resolution of multiparametric data for an acidic volcanic lake the nature of stress and mass changes of the volcano is studied by combining seismic analyses and volcanic lake measurements that were made during the strongest unrest ever recorded by the seismic network at kawah ijen the distal vt earthquake swarm that occurred in may 2011 was the precursor of volcanic unrest in october 2011 that caused an increase in shallow earthquakes the proximal vt earthquakes opened pathways for fluids to ascend by increasing the permeability of the rock matrix the following months were characterized by two periods of strong heat and mass discharge into the lake and by the initiation of monochromatic tremor mt activity when steam gases interacted with shallow portions of the aquifer significant seismic velocity variations concurrent with water level rises in which water contained a large amount of steam gas were associated with the crises that caused an although the unrest did not affect the shallow hydrothermal system at a large scale whereas shallow vt earthquakes likely reflect a magmatic intrusion mt and relative seismic velocity changes are clearly associated with shallow hydrothermal processes these results will facilitate the forecast of future crises

a magnetotelluric investigation under the williston basin of southeastern saskatchewan discussion the recent publication by maidens and paulson consists of two distinct parts the first part is a comparison of two processing schemes for magnetotelluric mt data and as such i applaud the efforts of the authors for their very worthwhile addition to our knowledge the second part is an interpretation of the responses derived from their five mt sites located within the williston basin close to the canada united states border with conclusions regarding the enigmatic north american central plains conductivity anomaly known by the acronym nacp it is about the latter that i have four comments to make to refute the statement made by maidens and paulson p 66 italics added although there is no question about the existence of the major anomaly reported by jones and savage there is a question about the name assigned to it since its discovery in the mid central united states during the late 1960 s the nacp has been studied in canada by a geomagnetic depth sounding gds array and two profiles alabi et al 1975 handa and camfield 1984 gupta et al 1985 and more recently by mt surveys jones and savage 1986 jones and craven in preparation rankin and pascal in preparation this feature concluded to be linear and continuous over 2000 km from these gds studies has been interpreted variously as i associated with conductive minerals such as graphite in schistose rocks in a belt mapped by lidiak 1971 in the basement beneath the great plains camfield et al 1970 gough and camfield 1972 ii due to the presence of saline water in fractured rocks handa and camfield 1984 and iii due to partial serpentinization of oceanic mafic and ultramafic rocks at the ridge crest of an ancient former oceanic crust gupta et al 1985 certainly interpretations of the tectonic history of the region e g green et al 1985 in particular of the transhudson orogen would be remiss if they did not include a mechanism for the generation of this continental scale feature accordingly it is of the greatest import that the true location of the anomaly be known as precisely and as unequivocally as possible in order to aid paleotectonic reconstructions in their paper jones and savage 1986 stated that at the latitude of the canada united states border the location of the nacp anomaly fig l as mapped from the gds work

use of a weather buoy to derive improved heat and mass balance parameters for ruapehu crater lake abstract heat and mass balance calculations are important for monitoring volcanoes with heated crater lakes but for these lakes the critical process of evaporation can be substantially affected by the lake s influence on the air mass above it measurements in 2010 using a weather station on a buoy floating in ruapehu crater lake enabled us to derive a relation between wind velocity above the lake and that measured at nearby weather stations as well as providing direct evidence of the effect of the warm lake on the air above it this supported the use of evaporation equations that allowed for the changing air conditions as incoming air became warmer and wetter from interaction with the lake so decreasing the overall evaporation rate heat and mass balance calculations using these parameters and equations during the period 2003 to early 2007 as crater lake filled before it overflowed confirm the previously observed high ratio of total heat flow to steam volume

fluid volcano interaction in an active stratovolcano the crater lake system of poas volcano costa rica rowe g l jr brantley s l fernandez m fernandez j f borgia a and barquero j 1992 fluid volcano interaction in an active stratovolcano the crater lake system of po is volcano costa rica j volcanol geotherm res 49 2351 seismic and geochemical data collected at po is volcano costa rica since 1978 suggest that temperature and chemical variations recorded in subaerial fumaroles and the crater lake are related to episodic release of heat and volatiles associated with hydrofracturing of the upper margin of the shallow magma body power outputs associated with these events approach 600 mw and are superimposed on a baseline energy flux of approximately 200 mw the baseline heat flux suggests a magma solidification rate of 0 012 km3 yr and background volatile release rates of 1000 t d h20 66 t d s 13 t d ci and 0 5 t d f these fluxes are comparable to fluxes of f c1 and s exiting the magmatic hydrothermal system through acidic flank springs and are about a factor of five less than estimated volatile fluxes through summit fumaroles during the high temperature event of 1981 1983 mass balance considerations suggest that heat released at the lake surface is primarily supplied by the ascent of heated brines supplemented by condensation of fumarolic steam calculated average seepage rates out of the lake 450 kg s indicate rapid convection of acidic lake brine through underlying lake sediments and pyroclastic deposits circulation of the extremely corrosive lake brine through the volcanoclastic material beneath the lake may enhance subsurface permeabilities fluxes of rock forming elements observed in the rio agrio basin on the northwest flank of po is suggest that dissolution and removal of volcano elastic material occurs at a rate of approximately 1650 m3 yr however estimated sulfur fluxes from the cooling magma body suggest that porosity created by this dissolution could quickly be filled by the deposition of native sulfur finally analysis of heat and water budgets for the crater lake over the period 1978 1989 indicates that the recent decline and disappearance of the lake was caused by variations in summit rainfall combined with an increase in subsurface heat flow to the lake in 1987 1988 the increase in heat flow is related to continued degassing of high temperature volatiles following a hydrofracturing magma ascent episode that occurred in 1986

cyclic processes and factors leading to phreatic eruption events insights from the 25 september 2007 eruption through ruapehu crater lake new zealand abstract a dangerous block ash eruption occurred without warning from ruapehu crater lake on 25 september 2007 ending a 6 month period of temperature decline in the lake the northerly directed blast sent ballistics of up to 2 m diameter more than 2 km from the source the ejecta comprised a variety of volcano lacustrine lithologies many showing evidence of intense hydrothermal alteration petrographic studies of the ballistics reveal numerous examples of pores vesicles being filled with assemblages of elemental sulphur anhydrite pyrite and natroalunite and many ballistics exuded liquid sulphur from their pores during cooling at atmospheric pressure up to 5 of the ash was comprised of fine grained juvenile glass material confirming the presence of magma in the shallow vent environment a long recognised characteristic of this volcano is the thermal cycling behaviour of the crater lake behaviour which has remained effectively unchanged through two magmatic eruption events in 1945 and in 1995 96 airborne measurements of co2 and so2 flux from the volcano since 2003 show a strong positive correspondence with temperature cycling in the lake pointing to a definitive link between heat and mass discharge through the system low so2 emission rates and c s mole ratios 30 were typical of the period 2003 to early 2007 and appear to reflect vigorous scrubbing of s gases in the hydrothermal system during this time to better understand the chemical and physical processes operating in this very dynamic volcanic hydrothermal system and its propensity to develop potentially dangerous hydrothermal seals we have developed an integrated finite difference tough2 heat mass transport simulation of the hydrothermal environment the model which is constrained by observed heat and mass flux characteristics of the volcano demonstrates the transient nature of the heating cycles on the vent lake system of particular interest is the role of co2 as a relatively inert pressure transmitting medium in the hydrothermal environment seal formation was simulated using the reactive transport code x1t which showed that condensation of magmatic vapour into a highly porous medium of andesitic composition leads to rapid formation of an elemental sulphur anhydrite natroalunite mineral assemblage and a drastic reduction in permeability we suggest that since the 1995 96 vent clearing eruptions a shroud of elemental sulphur and other alteration phases formed along the margins of the 2 phase liquid vapour region enclosing the conduit this effectively seals the upper portion of the vent from the adjacent hydrostatically controlled environment and allows for development of pressurised vapour static gas columns beneath the northern and central vents

hydroacoustic noise precursors of the 1990 eruption of kelut volcano indonesia abstract the results of a hydroacoustic monitoring experiment in the kelut crater lake indonesia prior to its 1990 eruption are presented with the benefit of hindsight indeed the underwater noise levels in three widely separated frequency bands together with the lake water temperature was radio transmitted and almost continuously recorded from a period of quiescence of the volcano till the onset of its 10 february 1990 eruption which destroyed the monitoring buoy the comparative analysis of the noise variations in the three bands together with seismic and temperature data have shed light on the mechanisms underlying the pre eruptive activity the three acoustic levels had shown conspicuous yet distinctive changes prior to the eruption acoustic level in the low frequency 1 50 hz band which increased one year before the resumption of seismic activity and the lake warming up is interpreted as the result of boiling at depth the source of high acoustic level in the audiometric 500 5000 hz range is clearly the bubbling of volcanic gases occurring as a strong convective column in the middle of the lake from the variations of this audiometric level we have estimated that the degassing rate in the lake increased by a hundred fold during the pre eruptive period variations of ultrasonic 20 100 khz frequency acoustic level seem to be related with pressure and thermal changes within the hydrothermal system and its rock matrix beneath the lake in conclusion this experiment demonstrates the potential of hydroacoustic monitoring as an early warning system at crater lake volcanoes

the heat source of ruapehu crater lake deductions from the energy and mass balances abstract regular observations of temperature outflow rates and water chemistry of crater lake mt ruapehu new zealand have been made for the last 25 years these data have been used to derive a model of the dynamics of the lake and determine the input of energy mass and chloride from the volcano to the crater lake the recent relatively quiescent state of the volcano when virtually no heat has been input to the lake has also enabled an assessment to be made of the surface heat loss characteristics which play an important role in the model of the lake the modelling suggests that since about 1982 the ratio of the volcanic heat to mass added to the base of the lake is about 6 mj kg which is not compatible with heating of the lake by magmatic steam alone thus only about 50 of the heating has been by magmatic steam it is suggested that heat could be transferred from a magmatic source to the region below the lake by a heat pipe mechanism commonly associated with geothermal systems the simultaneous upward movement of vapour phase and downward movement of liquid phase from condensed vapour allows efficient heat transfer without overall mass transfer the permeability necessary to supply the required heat is of the order of 10 darcy and is consistent with a rubble filled vent for at least the last five years there has been a characteristic pattern in the crater lake temperature record with alternate heating and cooling phases the heating phase generally lasts for one or two months while the cooling phase lasts for six months to a year a possible explanation for this cyclic behaviour is the presence of a layer of liquid sulphur under crater lake acting as a partial barrier between the heat pipe and the lake the unusual variations of the viscosity of liquid sulphur with temperature will mean that at temperatures greater than 160 c the layer of sulphur becomes highly viscous and would block any upwards steam flow and hence stop the heat input to crater lake so producing a cooling phase this blockage would last until the heating from below raised the temperature of the sulphur beyond the high viscosity region so gases could again pass through the sulphur

indices of el nino evolution abstract to characterize the nature of el nino southern oscillation enso sea surface temperature sst anomalies in different regions of the pacific have been used an optimal characterization of both the distinct character and the evolution of each el nino or la nina event is suggested that requires at least two indices i sst anomalies in the nino 3 4 region referred to as n3 4 and ii a new index termed here the trans nino index tni which is given by the difference in normalized anomalies of sst between nino 1 2 and nino 4 regions the first index can be thought of as the mean sst throughout the equatorial pacific east of the date line and the second index is the gradient in sst across the same region consequently they are approximately orthogonal tni leads n3 4 by 3 to 12 months prior to the climate shift in 1976 77 and also follows n3 4 but with opposite sign 3 to 12 months later however after 1976 77 the sign of the tni leads and lags are reversed

a telemetering system for monitoring aqueous polythionates in an active crater lake abstract we have developed an in situ monitoring system for aqueous polythionates in the yugama crater lake at kusatsu shirane volcano a commercially available nitrate selective electrode has a nernstian response to the concentration of polythionates in solution in the range of ph 2 5 11 however many active crater lakes contain highly acidic water ph ranges from 0 2 to 2 the monitoring system reduces the acidity of the lake water to ph 4 without changing the concentration of polythionates using a high efficiency cation exchange membrane technique the monitoring system was placed in a submersed station because the yugama surface lake water freezes in mid winter the system is described and preliminary data are reported

implications for the thermal regime of acoustic noise measurements in crater lake mount ruapehu new zealand hydrophone measurements of acoustic noise levels in the crater lake of mount ruapehu new zealand were made on 18 january 1991 from an inflatable rubber boat on the lake the greatest sound pressures were recorded in the 1 10 hz band with sound levels generally decreasing about 20 db per decade from 10 hz to 80 khz the low frequency noise did not have an obvious relationship to the tremor observed at a seismic station within 1 km of the lake the comparatively low levels of middle and high frequency sound meant that at the time of measurement direct steam input did not make a significant contribution to the heating of crater lake this is consistent with the earlier conclusion that during the last decade a major part of the heat input of crater lake has come from lake water that was heated below the lake and recycled back into the lake

new insights into the kawah ijen hydrothermal system from geophysical data corentin caudron 1 2 3 guillaume mauri 4 glyn williams jones 5 thomas lecocq2 devy kamil syahbana 6 raphael de plaen 7 loic peiffer 8 alain bernard 3 ginette saracco 9 1 earth observatory of singapore nanyang technological university 50 nanyang av block n2 01a 15 singapore 639798 2 royal observatory of belgium seismology section 3 avenue circulaire 1180 uccle belgium 3 department of earth environmental sciences universite libre de bruxelles 50 ave roosevelt 1050 brussels belgium 4 center for hydrogeology and geothermics university of neuchtel neuchtel switzerland 5 department of earth sciences simon fraser university 8888 university drive burnaby british columbia v5a 1s6 canada 6 centre for volcanology and geological hazard mitigation geological agency ministry of energy and mineral resources jalan diponegoro 57 bandung 40122 indonesia 7 university of luxembourg faculte des sciences de la technologie et de la communication 6 rue richard coudenhove kalergi l 1359 luxembourg 8 instituto de energi as renovables universidad nacional auto noma de me xico privadaxochicalco s n centro 62580 temixco morelos mexico 9 cnrs umr7330 centre europeen de recherche et d enseignement en geosciences de l environnement cerege equipe modelisation aix marseille universite amu europole de l arbois bp 80 13545 aix en provence cedex 4 france ginet cerege fr corresponding author e mail corentin caudron gmail com abstract the magmatic hydrothermal system of kawah ijen volcano is one of the most exotic on earth featuring the largest acidic lake on the planet a hyper acidic river and a passively degassing silicic dome while previous studies have mostly described this unique system from a geochemical perspective to date there has been no comprehensive geophysical investigation of the system in our study we surveyed the lake using a thermocouple a thermal camera an echo sounderand co2 sensors furthermore we gained insights into the hydrogeological structures by combining self potential surveys with ground and water temperatures our results show that the hydrothermal system is self sealed within the upper edifice and releases pressurized gas only through the active crater we also show that the extensive hydrological system is formed by not one but three aquifers a south aquifer that seems to be completely isolated a west aquifer that sustains the acidic upper springs and an east aquifer that is the main source of fresh water for the lake in contrast with previous research we emphasize the heterogeneity of the acidic lake illustrated by intense subaqueous degassing these findings provide new insights into this unique hazardous hydrothermal system which may eventually improve the existing monitoring system

laboratory and theoretical models of fluid recharge in superheated geothermal systems the phase changes that occur as water invades a superheated geothermal reservoir were studied experimentally cold liquid ether was injected into a hot isothermal bed of sand and the rate of vaporization and thermal evolution of the sand bed were measured when the ether was injected from below the ascending vaporization front remained nearly planar in accord with theoretical models an isothermal layer of saturated liquid developed behind the front and the mass fraction vaporizing was proportional to the reservoir superheat in a second experiment liquid was injected from below into a thermally stratified reservoir in which an initially superheated layer was overlain by a supercooled layer as vapor produced at the ascending front rose into the supercooled region it condensed and produced a two phase saturated layer above the superheated zone even though injection was from below in a third experiment liquid was injected from above into an isothermal superheated bed of sand as the vaporizing liquid front migrated downward hot vapor rose through the descending liquid this vapor maintained the upper part of the reservoir close to the saturation temperature even though cold liquid was continuously supplied from above in addition fingers of liquid descended ahead of the main front into the superheated zone liquid transported in these fingers accumulated at the base of the reservoir in a layer of saturated liquid much of the subsequent vaporization occurred at the ascending front as the thickness of this liquid layer increased only the intermediate part of the reservoir remained superheated our experiments demonstrate that the geometry of recharge and the initial thermal structure of the reservoir have an important control on the phase changes in active geothermal systems in many cases recharge of liquid in a superheated region of a reservoir can lead to vapor production and transport and this may cause initially supercooled regions to become saturated also if the liquid front becomes unstable a two phase zone may develop from an initially superheated region

geochemistry mineralogy and chemical modeling of the acid crater lake of kawah ijen volcano indonesia the kawah ijen volcano with a record of phreatic eruptions has its 1000 m wide crater filled with a lake that has existed for at least one century at present the lake waters are hot t 37 c strongly mineralized tds 105 g l and extremely acidic ph 0 4 by its volume the javanese lake is probably the largest accumulation in the world of such acidic waters mineralogy of the suspended solids within the lake waters suggests that concentrations of si ca ti and ba are controlled by precipitation of silica gypsum anatase and barite lake sediment is composed of chemical precipitates with composition similar to the suspended solids thermodynamic calculations predict that the lake waters have reached equilibrium with respect to cristobalite barite gypsum anglesite celestite and amorphous silica in agreement with the analytical observations significant concentrations of ferric iron suggest that the current lake waters are fairly oxidized sulfides are absent in the water column but are always present in the native s spherules that form porous aggregates which float on the lake the presence of native s provides direct evidence of more reduced conditions at the lake floor where h 2 s is probably being injected into the lake with progressive addition of h 2 s to the acid waters native s pyrite and enargite are theoretically predicted to be saturated reactions between upward streaming h 2 s bearing gases discharged by subaqueous fumaroles and metals dissolved in the acidic waters could initiate precipitation of these sulfides a model of direct absorption of hot magmatic gases into cool water accounts for the extreme acidity of the crater lake results show that strongly acidic sulfate rich solutions are formed under oxidizing conditions at high gas water ratios reactions between the acidic fluids and the ijen andesite were modeled to account for elevated cation concentrations in lake water current concentrations of conservative rockforming elements are produced by dissolution of approximately 60 g of andesite per kg of acid solution complete neutralization of the acid lake waters by reaction with the wallrock produces a theoretical alteration assemblage equivalent to that observed in volcano hosted acid sulfate epithermal ore deposits

electromagnetic images of the trans hudson orogen the north american central plains anomaly revealed magnetotelluric studies of the trans hudson orogen over the last two decades prompted by the discovery of a significant conductivity anomaly beneath the north american central plains nacp from over 300 sites yield an extensive database for interrogation and enable three dimensional information to be obtained about the geometry of the orogen from southern north dakota to northern saskatchewan the nacp anomaly is remarkable in its continuity along strike testimony to along strike similarity of orogenic processes where bedrock is exposed the anomaly can be associated with sulphides that were metamorphosed during subduction and compression and penetratively emplaced deep within the crust of the internides of the orogen to the boundary of the hearne margin a new result from this compilation is the discovery of an anomaly within the upper mantle beginning at depths of 80 100 km this lithospheric mantle conductor has electrical properties similar to those for the central slave craton mantle conductor

warm and cold events in argentina and their relationship with south atlantic and south pacific sea surface temperatures 1 a singular value decomposition svd analysis was performed jointly on extreme temperature events in argentina and sea surface temperature sst in the south atlantic and south pacific sea level pressure slp patterns associated with the first svd coupled mode were also analyzed winter is the season of the year that is best represented by the first mode accounting for up to 70 of the winter covariance between temperature events and sst the warm and cold events in argentina are essentially a consequence of the creation of meridional atmospheric circulations over the continent such atmospheric patterns result from displacements and intensity changes of the subtropical anticyclones over the oceans and of the continental low pressure center in northwestern argentina the temperature events in southern argentina are also closely related to the warming and cooling of the coastal waters in the south atlantic and south pacific the analysis suggests that in summer and winter high low occurrence of warm events and low high occurrence of cold events are related to similar oceanic and atmospheric circulation situations the temperature events in argentina show higher correlation with the atlantic than with the pacific which reflects the importance of the orographic barrier of the andes mountains in driving the atmospheric circulation the only exception to this rule concerns the warm events in spring for which the warming of the equatorial pacific the enso pattern appears as the dominant mode the temporal patterns of the temperature events in argentina exhibit significant interannual variability in fall winter and spring with periods of 3 to 5 years the summer patterns suggest a very low frequency variation with a period longer than 20 years

effect of sonic and ultrasonic frequencies on the crystallization of basalt experiments were conducted to determine whether vibrations with frequencies in the sonic to ultrasonic range have any effect on the crystallization of basalt one atmosphere melting experiments were done at the qfm buffer on a sample of alkali basalt a piezoelectric quartz crystal and a function generator were used to generate waves of 1 5 mhz and 150 khz and waves were propagated along the platinum quench wire to which the experimental charge was attached experiments were conducted at 1182 c at this temperature the sample was about 25 crystalline and contained olivine and plagioclase compared to the static control experiments vibrated experiments produced plagioclase crystals that were less euhedral and had lower aspect ratios crystal size distributions for plagioclase were steeper for the vibrated experiments with a higher population density of smaller crystals the effect on olivine crystal size distributions was less if the effect on plagioclase extends to lower vibrational frequencies it is possible that this phenomenon may occur in magmas prior to eruption the experimental technique developed to produce vibrations is potentially useful for improving homogeneity of melt and increasing likelihood of achieving mineral melt equilibrium in partitioning experiments

lahars of ruapehu volcano new zealand risk mitigation a dam break lahar resulting from the last eruption of ruapehu is expected when crater lake reaches a critical high level probably within the next 1 5 summers a high level of public consultation political decision making and ongoing scientific input has occurred to address the risks decisions about managing lahar risk have taken into account the fact that lahars are common on the active ruapehu volcano 2797 m and in valleys draining the mountain and that most lahars are generated by eruptions about half of which have no useful precursors lahars threaten new zealand s largest ski area and nationally important infrastructure public safety has been the main consideration but the need for long term risk mitigation and reducing impacts on tongariro national park world heritage area have also been important lahar mitigation on ruapehu now includes six lahar warning systems each with active response plans and some infrastructure isolated from or hardened against lahars

active mud volcanism observed with landsat 7 etm abstract mud volcanoes are relatively small spatter cones that erupt water laden mud and gases and occur throughout the world for many mud volcanoes the eruption of warm mud 10 40 c can be detected with high resolution thermal satellite imagery we demonstrate the utility of landsat 7 enhanced thematic mapper plus etm imagery for thermal monitoring of active mud volcanism we constrain the temperature and area of active mud discharge and estimate surface heat flux for two isolated mud volcanoes in the copper river basin alaska using band 6 10 4 12 5 m the heat flux results span a wide range due to uncertainties in the environmental conditions at the time of image acquisition but can be constrained to be less than 0 24 mw for each of the two mud volcanoes considering previously published field measurements with this higher resolution band 6 on the etm sensor as well as the high resolution thermal bands on the aster sensor reliable monitoring of mud volcanism on this scale is possible for the first time

volatile fluxes integrated over four decades at grimsvotn volcano iceland samples of the subglacial lake in the crater of the tholeiitic basaltic caldera grimsvotn in iceland were obtained by using a hot water drill to sink two boreholes through the 250 m thick ice shelf covering the lake the lake generally shows an increase in solutes with increased depth as solutes are added from the lake s bottom and dilute glacial meltwater is added continuously from above the crater lake temperature ranges from 0 c in the upper part to temperatures of 1 c to 4 c near the bottom of the lake the lake water ph ranges between 7 0 and 5 7 the crater lake is assumed to be closed with respect to volatile components released from subsurface magma except for periodic draining by jokulhlaups from the periodicity and water chemistry of the jokulhlaups we have estimated the volcano s average release rates of carbon sulfur chlorine and fluorine between 1954 and 1991 and corrected these rates for dissolution of bedrock into the lake water and seepage of solutes to groundwater the corrected mean release rates are 5 3 107 kg c yr 1 5 3 106 kg s yr 1 6 6 105 kg cl yr 1 and 1 5 105 kg f yr 1 the emission rate estimates for grimsvotn one of the most active volcanoes in iceland are the longest integrated estimates obtained for an active volcano and are equal to or lower than those of other major active volcanoes worldwide this difference may imply that published release rates for other volcanoes are overestimated because they are usually not integrated over time the values of the s cl and f cl ratios for noneruptive periods are 0 53 0 20 and 0 013 0 003 and for the two eruptive events are 0 69 and 2 14 and 0 034 and 0 041 respectively the response of the elemental ratios to eruptive events followed by the return to lower ratios supports the assumption of steady state because no long term accumulation of volatiles occurs the energy output from the volcano estimated from the amount of ice melted by hydrothermal heat is 4250 mw over the last four decades using the energy output to calculate magma solidification rates and maximum possible volatile release rates we observe that emissions of f and s are strongly suppressed at grimsvotn while a significant portion of available cl and c are released these calculations also reveal that coverage of a volcano by a glacier and subsequent raising of the water table may cause significant scrubbing of magmatic gases so that these gases do not reach the atmosphere

large scale control on the patagonian climate abstractpatagonia located in southern south america is a vast and remote region holding a rich variety of past environmental records but a small number of meteorological stations precipitation over this region is mostly produced by disturbances embedded in the westerly flow and is strongly modified by the austral andes uplift on the windward side leads to hyperhumid conditions along the pacific coast and the western slope of the andes in contrast downslope subsidence dries the eastern plains leading to arid highly evaporative conditions the authors investigate the dependence of patagonia s local climate precipitation and near surface air temperature year to year variability on large scale circulation anomalies using results from a 30 yr long high resolution numerical simulation variations of the low level zonal wind account for a large fraction of the rainfall variability at synoptic and interannual time scales zonal wind also controls the amplitude of the air temperature annual cycle by changi