the taupo eruption new zealand i general aspects the ca a d 186 taupo eruption was the latest eruption at the taupo volcanic centre occurring from a vent at horomatangi reefs now submerged beneath lake taupo in the central north island of new zealand minor initial phreatomagmatic activity was followed by the dry vent 6 km 3 hatepe plinian outburst large amounts of water then entered the vent during the 2 5 km 3 hatepe phreatoplinian ash phase eventually stopping the eruption though large amounts of water continued to be ejected from the vent area causing gullying of the ash deposits after a break of several hours to weeks phreatoplinian activity resumed generating the 1 3 km 3 rotongaio ash notable for its fine grainsize and for containing significant quantities of non or poorly vesicular juvenile material the vent area then became dry again and eruption rates and power markedly increased into the 23 km 3 taupo ultraplinian phase which is the most powerful plinian outburst yet documented synchronous with this ultraplinian activity lesser volumes of non to partially welded ignimbrite were generated by diversion of ejecta from or partial collapse of the eruption column the rapid rate of magma withdraw al during this phase removed support from the vent area to trigger local vent collapse and initiate the catastrophic eruption of the ca 30 km 3 taupo ignimbrite finally after some years lava was extruded on to the floor of the reformed lake taupo and floating fragments derived from the lava carapace were driven ashore the known eruption volume is more than 65 km 3 while additional volumes are represented by primary material now beneath lake taupo and layer 3 to the ignim brite phases a total volume of more than 105 km 3 is likely equivalent to more than 35 km 3 of magma plus more than 3 km 3 of lithic debris airfall deposits more than 10 cm thick blanketed 30000 km 2 of land east of the vent while ignimbrite covers a near circular area of 20000 km 2 widespread and locally severe ground shaking occurred during but mostly after the eruption associated with subsidence in the lake taupo basin secondary deposits are abundant above and extending beyond the taupo ignimbrite consisting of the products of surface water interacting with the still hot ignimbrite and subsequent water reworking of the light pumiceous materials the complexity and size of this eruption preclude accurate forecasting of the size nature and return period of the inevitable next eruption from the taupo volcanic centre

the pre quaternary history of fire abstract although evidence for land vegetation comes from the silurian and maybe even earlier the first record of fossil charcoal fusain is from the late devonian for this period there are only one or two isolated records not until the early carboniferous is there a record of extensive charcoal deposits mainly preserved in near shore clastic sediments which provide evidence of significant and widespread wildfires by the late carboniferous charcoal was common or abundant in a wide range of facies including tropical wetland peats wildfire played an important role in shaping the environment at this time the latest palaeozoic and early mesozoic records of charcoal are fewer whereas important deposits of late mesozoic age are found worldwide the occurrence of charcoal at the cretaceous tertiary boundary has been highlighted as evidence for a global fire following a meteorite impact but this interpretation is questionable charcoal has been widely reported from tertiary sediments and its appearance in the quaternary and recent is not solely as a result of human impact through the past 400 million years there have been major changes in atmospheric oxygen levels that affected fire intensity and frequency fire systems thus have a long history and their impact on shaping the environment is assessed

effects of soil heterogeneity on martian ground ice stability and orbital estimates of ice table depth abstract data from the mars odyssey gamma ray spectrometer grs instrument suite and results from numerical simulations of subsurface ground ice stability have been used to estimate the depth of martian ground ice geographic correlation between these estimates is remarkable the relative ice table depth distributions also agree well however grs based estimates of ice table depth are generally deeper than predictions based on ground ice stability simulations this discrepancy may be related to heterogeneities in the martian surface such as rocks dust and albedo variations we develop a multi dimensional numerical model of ground ice stability in a heterogeneous martian subsurface and use it to place the first quantitative constraints on the response of the ice table to meter scale heterogeneities we find that heterogeneities produce significant undulations topography in the ice table at horizontal length scales of a few meters decimeter scale rocks create localized areas of deep ice producing a vertical depression of 10 60 cm in the ice table over a horizontal range of 1 2 rock radii decimeter scale dust lenses produce locally shallow ice however the magnitude of the vertical deflection of the ice table is small 1 4 cm the effects of decimeter scale albedo variations on the ice table are nearly negligible although albedo very weakly enhances the effects of dark rocks and bright dust on the ice table additionally we investigate the role played by rocks in estimates of ice table depth based on orbital data surface rocks can account for more than half of the discrepancy between ice table depths inferred from grs data and those predicted by theoretical ice stability simulations that utilize thermophysical observations our results have considerable relevance to the up coming mars scout mission phoenix because they indicate that the uncertainty in the ice table depth of a given region is greater than differences between current depth estimates likewise small scale depth variability due to heterogeneities at the eventual landing site is potentially greater than differences between current depth estimates

continuous h2o co2 222rn and temperature measurements on merapi volcano indonesia abstract a set of analytical instruments consisting of a gas chromatograph for water and carbon dioxide an alpha scintillation counter to measure radon and a temperature sensor was especially designed and constructed to monitor volcanic gases and was successfully operated over weeks in the high temperature fumaroles at the summit of merapi volcano indonesia the analytical unit runs automatically and is remote controlled through a radio link over a period of several weeks concentrations of h 2 o and co 2 were measured every 35 min and rn activity was monitored at about 90 min intervals the fumarole temperatures were continuously recorded every minute from july 2000 to the end of january 2001 the composition and temperature of the gas emitted at merapi volcano show significant variations due to a regular stronger degassing of the magma concentrations of co 2 increase periodically while h 2 o concentrations decrease on the other hand rn activity rises with increasing atmospheric pressure and higher water concentrations after intensive rainfall infiltration of cold meteoric water into the volcanic edifice possibly causes an increase in the concentration of water vapour and a decrease in the temperature of the gases in the fumarole several seismic events recorded at merapi correlate with gas temperature

valley pond and ignimbrite veneer deposits in the small volume phreatomagmatic peperino albano basic ignimbrite lago albano maar colli albani volcano italy influence of topography abstract the ca 23 ka small volume basic phreatomagmatic peperino albano ignimbrite from the polygenetic albano maar colli albani volcano central italy shows valley pond facies as well as veneer deposits along the maar rim and along topographic ridges valley pond facies is characterised mainly by massive structure and chaotic texture and can be up to 30 m thick veneer deposit facies is characterised by parallel to low angle cross stratified bedforms alternating fines depleted lapilli sized layers and massive matrix supported beds occurrence of uncharred wood remains and accretionary lapilli suggests temperature of emplacement comprised between 246 and 100 c we have interpreted the lateral facies variations in terms of temporal and spatial variations of the sediment supply from the transport system to the depositional system of the pyroclastic flow ignimbrite veneer facies at the maar rim may reflect pulsatory eruption dynamics whereas valley pond facies may reflect the bulking of the pyroclastic flow inside the valleys and consequent high sedimentation rates ignimbrite veneer facies at topographic ridges has been interpreted to reflect detachment processes of more concentrated undercurrents draining within valleys from the more dilute upper part of the pyroclastic flow that climbs the ridges the present interpretation suggests that processes of pyroclastic flow transformation downcurrent and induced by topography are not necessarily peculiar of hot high mobility pyroclastic density currents the more likely source of water interacting with magma is interpreted to be groundwater contained within the karstic aquifer located at approximately 1 km below the ground level this is inferred by both the large amount of limestone xenoliths present in the peperino albano and the absence of vesicular juvenile clasts the latter implying that magma water interaction occurred before gas exolution processes were significant

magmatic processes revealed by textural and compositional trends in merapi dome lavas syn eruptive degassing of volcanoes may lead to syn eruptive crystallization of groundmass phases we have investigated this process using textural and compositional analysis of dome material from merapi volcano central java indonesia samples included dome lavas from the 1986 88 1992 93 1994 and 1995 effusive periods as well as pyroclastic material deposited by the november 1994 dome collapse with total crystallinities commonly in excess of 70 phenocrysts 1 microlites the liquids present in merapi andesites are highly evolved rhyolitic at the time of eruption feldspar microlites in dome rocks consist of plagioclase cores ab63an29or8 surrounded by alkali feldspar rims ab53an5or42 compositional pairs which are not in equilibrium a change in the phase relations of the ternary feldspar system caused by degassing best explains the observed transition in feldspar composition a small proportion of highly vesicular airfall tephra grains from the 1994 collapse have less evolved glass compositions than typical dome material and contain rimless plagioclase microlites suggesting that the 1994 collapse event incorporated less degassed partially liquid magma in addition to fully solidified dome rock as decompression drives volatile exsolution rates of degassing and resultant microlite crystallization may be governed by magma ascent rate microlite crystallinity is nearly identical among the 1995 dome samples an indication that similar microlite growth conditions ph2 o and temperature were achieved throughout this extrusive period however microlite number density varied by more than a factor of four in these samples and generally increased with distance from the vent low vent ward microlite number densities and greater microlite concentrations down flow probably reflect progressively decreasing rates of undercooling at the time of crystal nucleation during extrusion of the 1995 dome comparison between dome extrusion episodes indicates a correlation between lava effusion rate and microlite number density suggesting that extrusion slowed during 1995 crystal textures and compositions in the 1992 93 and 1994 domes share the range exhibited by the 1995 dome suggesting that transitions in crystallization conditions i e rates of undercooling determined by effusion rate are cyclic q 2000 elsevier science b v all rights reserved

a new method for sampling and analyzing volcanic sublimates application to merapi volcano java abstract a new method for the sampling of sublimates from high temperature volcanic gases has been used at merapi volcano java in 1978 the sublimates were collected on the inner walls of silica tubes introduced into fumarolic vents volcanic gases were allowed to move freely through the tubes and as they cooled a fraction of the volatile components condensed on the inner walls of the tubes along the temperature gradient the sublimates were then analyzed by a combination of light microscopy scanning electron microscopy electron microprobe and x ray diffraction six successive zones of different compositions and mineralogical associations have been identified along the covered range of temperatures 900 to around 400 c from the high to the low temperatures these zones are composed of 1 cristobalite magnetite hercynite 2 molybdenite 3 acmite 4 halite sylvite 5 sphalerite pyrite and 6 galena equilibrium calculations show that these crystalline phases are stable for ps 2 pc 1 and po 2 values typical of magma buffered gases that have not been contaminated by atmospheric oxygen the deposits observed in the tubes may be useful in aiding the understanding of the mechanisms acting during the cooling of the gaseous phase on its way to the surface and before its emission into the atmosphere

observations and experiments on the origin and formation of inertinite group macerals the inertinite group macerals include fusinite semifusinite inertodetrinite macrinite micrinite and funginite and secretinite which together replace sclerotinite the macrolithotype fusain comprises fusinite and semifusinite and is now widely accepted as charcoal formed by wildfire activity however alternative origins for fusinite and semifusinite are still claimed this paper considers the use of the terms pyrofusinite degradofusinite rank fusinite and primary fusinite misleading while the definitions of the terms funginite and secretinite are also considered problematic observations made on modern wildfire derived and volcanogenic charcoal assemblages using reflectance and scanning electron microscopy together with experimental charcoalification studies demonstrate that most if not all inertinite macerals have acquired their optical and physical characteristics through the action of elevated temperatures the criteria for the identification of charcoals produced by wildfire and volcanic activity are outlined and the role of the petrographic nomenclature system is discussed

field gas chromatograph analyses of gases from a glowing dome at merapi volcano java indonesia 1977 1978 1979 abstract a new field gas chromatograph fgc and conventional evacuated bottle eb techniques have been used to study high temperature 600 c volcanic gases from merapi volcano indonesia during 1977 1978 and 1979 the fgc design allows analysis of h2o co2 so2 h2s h2 cos ch4 co n2 ar and o2 in a manner that prevents loss of sulfur and water by condensation inhibits corrosion from reactions of gases with lead in tubes and minimizes atmospheric contamination the fgc analyses are highly superior to the eb data especially with respect to prevention of sulfur loss from reaction of so2 and h2s in addition to providing much improved h2s data the fgc system minimizes oxidation of h2 and co from contaminating atmospheric o2 because of the elimination of a lengthy time interval between collection and analysis thermodynamic calculations indicated small errors for h2 and ch4 in the 1978 analyses provided by the proto type fgc device a later model fgc provided excellent analyses that were shown by thermodynamic calculations to be nearly equilibrium mixtures requiring only minor corrections the merapi gases are h2o rich 88 95 containing small amounts of co2 3 5 to 7 5 so2 0 3 to 1 2 and h2s 0 3 to 1 2 they resemble excess volatiles rubey 1955 except for too high a sulfur content thermodynamic calculations based on the analyses indicate that the gases were once at temperatures of at least 915 c with o2 fugacities near quartz magnetite fayalite and that they have not been significantly diluted by disequilibrium admixture of meteoric water below these temperatures this conclusion takes on special importance because stable isotope studies allard 1980 1982 of merapi gases have shown that the water is meteoric and that much of the carbon and sulfur could be from sedimentary sources the merapi gases therefore may be magmatic even though they are not juvenile but recycled crustal volatiles

volcanic lightning as a source of reactive radical species in eruption plumes volcanic lightning has accompanied most recent major explosive eruptions and provides a source of intense thermal energy to drive the formation of reactive radical species these radicals may have an impact upon the chemical evolution of the eruption plume and its interaction with the atmosphere equilibrium modeling shows that within each lightning channel 1 of total n o and f and 100 of h cl br and i may remain as radicals after quenching the production of radicals generally increases with the quenching temperature of the gas mixture and the dilution of the eruption plume and decreases with increasing atmospheric pressure despite the small volume fraction of the plume directly exposed to volcanic lightning i e 10 4 the production of o h f and no is predicted to be quantitatively significant over the entire plume furthermore these radicals may indirectly lead to the production of br cl ho2 and o3 through reactions occurring at low temperature we suggest that volcanic lightning may promote the oxidation of magmatic gases e g hbr and so2 and result in a wide range of atmospheric impacts including tropospheric ozone depletion the production of fixed nitrogen species and the formation of cloud condensation nuclei

observations on the nature and origin of fusain abstract evidence for a wildfire origin of fusain is examined charcoal produced by natural fires and artificial charring resembles fossil fusain both in physical size and shape and in optical reflectance artificially charred leaves and naturally burnt wood are illustrated using the sem reflectance studies on modern charcoals suggest that much semifusinite may be produced by pyrolysis the ecological implications of a wildfire origin of fusain are discussed and it is concluded that fires have been a feature of terrestrial ecosystems from at least the late devonian

mechanism of energy transfer in the lava lake of niragongo zaire 1959 1977 abstract heat and mass transfer rates were studied at the niragongo lava lake during two expeditions directed by h tazieff in 1959 and 1972 the results of this study are as follows heat is transferred to the surface of the lake by the movement of lava gas discharge is a result and not the cause of convection the chemical composition of the gases and magma has changed very little between 1959 and 1972 whereas the mass and energy outputs differ by an order of magnitude in 1977 a catastrophic explosion seems to have been caused by tectonic factors stopping the slow convection of magma under the volcano and hence reducing surface manifestations in the form of the lava lake and escaping fumarolic and magmatic gases the gas discharge was in tons day 1 5000 for h2o 11 000 for co2 1000 for so2 in 1959 and in 1972 7700 for h2o 180 000 for co2 and 23 000 for so2 these values correspond to an energy transfer of 0 9 109 w in 1959 and 16 109 w in 1972

the chicxulub asteroid impact and mass extinction at the cretaceous paleogene boundary the cretaceous paleogene boundary similar to 65 5 million years ago marks one of the three largest mass extinctions in the past 500 million years the extinction event coincided with a large asteroid impact at chicxulub mexico and occurred within the time of deccan flood basalt volcanism in india here we synthesize records of the global stratigraphy across this boundary to assess the proposed causes of the mass extinction notably a single ejecta rich deposit compositionally linked to the chicxulub impact is globally distributed at the cretaceous paleogene boundary the temporal match between the ejecta layer and the onset of the extinctions and the agreement of ecological patterns in the fossil record with modeled environmental perturbations for example darkness and cooling lead us to conclude that the chicxulub impact triggered the mass extinction

the evolution of exposed ice in a fresh mid latitude crater on mars abstract recent observations of the surface of mars have shown several fresh mid latitude craters some of these craters show exposed ice byrne s et al 2009 science 325 1674 1676 in some craters albedo of ice slowly decreases while in others it remains nearly constant we attempt to determine influence of the regolith structure on the rate of sublimation of ice for this purpose we performed numerical simulations describing evolution of the exposed ice in model craters located at middle latitudes we consider a new model for the structure and evolution of the material at and beneath the crater floors in contrast to the previous study by dundas and byrne dundas c m byrne s 2010 icarus 206 716 728 we do not investigate sublimation of dirty ice and the related formation of a sublimation lag instead we consider sublimation of a pure ice layer on top of layered regolith in our model the observed reflectivity decreases due to the sublimation driven changes of the optical properties of thinning clean ice this offers an alternative to the deposition of the dust embedded in ice sublimation lag we have shown that in our model among many parameters affecting ice sublimation rate volumetric fraction of water ice in the subsurface beneath the crater has the strongest influence hence observed darkening of the ice patch on the crater floor might be sufficient to determine the content of water ice in the subsurface our calculations show that an albedo decrease of fresh ice patches in mid latitude craters can be explained by either strong dust sedimentation or if this is excluded by sublimation of a thin layer of water ice from the regolith with large thermal inertia this is consistent with a large volumetric fraction of water ice beneath the crater floor and contributes to evidence for an extended subsurface water reservoir on mars the overall conclusion of our work is that a thin post impact surface ice coating over ice rich ground beneath the crater floors is consistent with the observations

in situ10be 26al exposure ages at meteor crater arizona a new method of dating the surface exposure of rocks from in situ production of 10be and 26al has been applied to determine the age of meteor crater arizona a lower bound on the crater age of 49 200 1 700 years has been obtained by this method

high resolution thermal inertia derived from the thermal emission imaging system themis thermal model and applications 1 thermal inertia values at 100 m per pixel are determined using nighttime temperature data from the thermal emission imaging system themis on the mars odyssey spacecraft producing the highest resolution thermal inertia data set to date themis thermal inertia values have an overall accuracy of 20 a precision of 10 15 and are consistent with both thermal emission spectrometer orbital and miniature thermal emission spectrometer surface thermal inertia values this data set enables the improved quantification of fine scale surface details observed in high resolution visible images in the tharsis region surface textures and crater rims observed in visible images have no corresponding variation in the themis thermal inertia images indicating that the dust mantle is pervasive at themis scales and is a minimum of a few centimeters and up to 1 2 m thick the thermal inertia of bed form material indicates particle diameters expected for aeolian sediments and these materials are likely currently saltating variations in the thermal inertia within interior layered deposits in hebes chasma can be distinguished and the thermal inertia is too low to be consistent with bedrock or a lava flow thus a secondary emplacement of volcanic material or a volcanic ash deposit is a more likely method of formation higher resolution themis thermal inertia enables the identification of exposed bedrock on the martian surface in nili patera and ares vallis bedrock material corresponds to distinct compositional and morphologic surfaces indicating that a specific unit is exposed and is likely currently being kept free of unconsolidated material by aeolian processes

gas and aerosol emissions from villarrica volcano chile here we report results from a multidisciplinary field campaign at villarrica volcano chile in march 2009 a range of direct sampling and remote sensing techniques was employed to assess gas and aerosol emissions from the volcano and extend the time series of measurements that have been made during recent years airborne traverses beneath the plume with an ultraviolet spectrometer yielded an average so2 flux of 3 7 kg s 1 this value is similar to previous measurements made at villarrica during periods of quiescent activity the composition of the plume was measured at the crater rim using electrochemical sensors and for the first time open path fourier transform infrared spectroscopy yielding a composition of 90 5 mol h2o 5 7 co2 2 6 so2 0 9 hcl 0 3 hf and 0 01 h2s comparison with previous gas measurements made between 2000 and 2004 shows a correlation between increased so2 hcl ratios and periods of increased activity base treated filter packs were also employed during our campaign yielding molar ratios of hbr so2 1 1 10 4 hi so2 1 4 10 5 and hno3 so2 1 1 10 3 in the gas phase our data represent the most comprehensive gas inventory at villarrica to date and the first evaluation of hbr and hi emissions from a south american volcano sun photometry of the plume showed the near source aerosol size distributions were bimodal with maxima at 0 1 and 1 m these findings are consistent with results from analyses in 2003 electron microscope analysis of particulate matter collected on filters showed an abundance of spherical micron sized particles that are rich in si mg and al non spherical s rich particles were also observed

review of the evolution of geochemical monitoring networks and methodologies applied to the volcanoes of the aeolian arc italy abstract fluids discharged from volcanic systems are the direct surface manifestation of magma degassing at depth and provide primary insights for evaluating the state of volcanic activity we review the geochemical best practice in volcanic surveillance based to a huge amount of monitoring data collected at different active volcanoes using both continuous and discontinuous approaches the targeted volcanoes belong to the aeolian arc located in the tyrrhenian sea italy and they have exhibited different activity states during the monitoring activities reported here la fossa cone on vulcano island has been in an uninterrupted quiescent stage characterized by variable solfataric activity in contrast stromboli island has shown a persistent mild explosive activity episodically interrupted by effusive eruptions in 1985 2002 2007 and 2014 panarea island which is the summit of a seamount rising from the seafloor of the southern tyrrhenian sea showed only undersea fluid release the only observable clues of active volcanism at panarea island have been impulsive changes in the undersea fluid release with the last submarine gas burst event being observed in november 2002 the geochemical monitoring and observations at each of these volcanoes has directly involved the volcanic plume and or the fumarole vents thermal waters and diffuse soil degassing depending on the type of manifestations and the level of activity encountered through direct access to the magmatic samples when possible and the collection of as much observable data related to the fluid release as possible the aim has been i to verify the thermodynamic equilibrium condition ii to discern among the possible hydrothermal magmatic marine and meteoric sources in the fluid mixtures iii to develop models of the fluid circulation supported by data iv to follow the evolution of these natural systems by long term monitoring and v to support surveillance actions related to defining the volcanic risk and the evaluation and possible mitigation of related hazards the examples provided in this review article show the close relationships among data analysis interpretation and modeling we particularly focus on describing the fieldwork procedures since any theoretical approach must always be verified and supported by field data rather than just by experiments controlled in laboratory indeed the natural systems involve many variables producing effects that cannot be neglected the monitored volcanic systems have been regarded as natural laboratories and all of the activities have focused on both volcanological research and surveillance purposes in order to ensure that these two goals have overlapped an appendix is also included that explains the scientific approach to the systematic activities regarding geochemical monitoring of volcanic activity

the role of sublimation for the formation of the northern ice cap results from the mars orbiter laser altimeter abstract the evolutionary history of the martian ice caps is practically unknown and the caps are key to understanding the climatic history of mars sublimation and ice flow are two hypotheses that have recently been suggested to explain the observed form of the northern ice cap here we present a sublimation model and compare the shape of the cap obtained from this model with mars orbiter laser altimeter mola observations of the north polar region this model can reproduce the shape of the cap and individual troughs sublimation is an important process as are flow and wind erosion we were able to constrain the time scales of sublimation only to about two orders of magnitude 1 100 million years this estimate depends on many unknown parameters such as friction velocity and wind speed over the ice caps these can be determined only by direct measurement over the surface

temperature proxy data and their significance for the understanding of pyroclastic density currents a major dome collapse of the soufriere hills volcano montserrat on 26 december 1997 generated a devastating pyroclastic density current that destroyed vegetation and left a distinc tive tar like deposit on the surface the deposit included a range of charred mainly herbaceous angiosperm axes and roots studies of refl ectance of these charcoalifi ed plants indicated mean refl ectances of 0 72 1 16 for the three samples with a maximum refl ectance of 1 77 recorded for all readings these data provide minimum temperatures of the fl ow of 300 425 c con sistent with organic geochemical data obtained by 13 c solid state nuclear magnetic resonance and gas chromatography mass spectrometry these temperatures have been used to calculate characteristics of the pyroclastic density current we estimate fl ow front current densities near the ground of 1 8 3 kg m 3 using constraints from a mean fl ow speed of 90 m s estimated from seismic data the mean temperature of the ash component is estimated as 400 610 c

orientation of logs in the taupo ignimbrite as an indicator of flow direction and vent position the taupo ignimbrite is an unwelded rhyolitic ignimbrite that originated about 1 820 yr ago from an eruptive vent within lake taupo in the taupo volcanic zone new zealand this ignimbrite is rich in carbonized plant matter including many logs the logs lie subhorizontally throughout all levels of the ignimbrite but are especially common in the lower half regionally the logs show a strong radial orientation indicating flow directions and position of the source vent log orientation is thus a reliable indicator of vent position

high resolution subsurface water ice distributions on mars theoretical models predict that the depth at which water ice is stable in the subsurface of mars will vary due to local surface features such as rocks and slopes and the thermal inertia of the ground above the water so far measurements have been limited to overviews of the several hundred kilometre footprint covered by the ray spectrometer on board the mars odyssey spacecraft but joshua bandfield has now used the seasonal temperature response of the martian surface from odyssey s themis package to map water ice distribution at the sub kilometre scale the observations reveal significant regional and local water ice depth variability at potential landing sites for the mars phoenix mission due for launch later this year the phoenix lander s robotic arm will be able to dig up to half a metre or so into the soil to search for water ice and these results suggest that it may encounter considerable variation in the depth to the ice layer the seasonal temperature response of the martian surface is used to map local surface heterogeneities such as rocks slopes and thermal inertia of ground cover at subkilometre scale these observations show significant regional and local water ice depth variability and indicate that the depth to the water ice table is highly variable in the potential phoenix spacecraft landing ellipses theoretical models indicate that water ice is stable in the shallow subsurface depths of 1 2 m of mars at high latitudes1 2 3 4 5 6 7 these models have been mainly supported by the observed presence of large concentrations of hydrogen detected by the gamma ray spectrometer suite of instruments on the mars odyssey spacecraft8 9 10 the models and measurements are consistent with a water ice table that steadily increases in depth with decreasing latitude more detailed modelling has predicted that the depth at which water ice is stable can be highly variable owing to local surface heterogeneities such as rocks and slopes and the thermal inertia of the ground cover11 12 13 measurements have however been limited to the footprint several hundred kilometres of the gamma ray spectrometer suite preventing the observations from documenting more detailed water ice distributions here i show that by observing the seasonal temperature response of the martian surface with the thermal emission imaging system on the mars odyssey spacecraft14 it is possible to observe such heterogeneities at subkilometre scale these observations show significant regional and local water ice depth variability and in some cases support distributions in the subsurface predicted by atmospheric exchange and vapour diffusion models the presence of water ice where it follows the depth of stability under current climatic conditions implies an active martian water cycle that responds to orbit driven climate cycles15 16 17 several regions also have apparent deviations from the theoretical stability level indicating that additional factors influence the ice table depth the high resolution measurements show that the depth to the water ice table is highly variable within the potential phoenix spacecraft landing ellipses and is likely to be variable at scales that may be sampled by the spacecraft

reconstruction of the morasko meteoroid impact insight from numerical modeling the morasko strewn field located near poznan poland comprises seven impact craters with diameters ranging from 20 to 90 m all of which were formed in glacial sediments around 5000 yr ago numerous iron meteorites have been recovered in the area and their distribution suggests a projectile with the trajectory from ne to sw similar impact events producing crater strewn fields on average happen every 500 yr and pose a serious risk for modern civilization which is why it is of utmost importance to study terrestrial strewn fields in detail in this work we investigate the morasko meteoroid passage through the atmosphere the distribution of its fragments on the ground and the process of forming individual craters by means of numerical modeling by combining atmospheric entry modeling pi group scaling of transient crater size and hydrocode simulations of impact processes we constructed a comprehensive model of the morasko strewn field formation we determined the preatmospheric parameters of the morasko meteoroid the entry mass is between 600 and 1100 tons the velocity range is between 16 and 18 km s 1 and the trajectory angle is 30 40 such entry velocities and trajectory angles do not deviate from typical values for near earth asteroids although the initial mass we determined can be considered as small our studies on velocities and masses of crater forming fragments showed that the biggest morasko crater was formed by a projectile about 1 5 m in diameter with the impact velocity 10 km s 1 environmental consequences of the morasko impact event are very localized

improved general circulation models of the martian atmosphere from the surface to above 80 km we describe a set of two new generation general circulation models of the martian atmosphere derived from the models we originally developed in the early 1990s the two new models share the same physical parameterizations but use two complementary numerical methods to solve the atmospheric dynamic equations the vertical resolution near the surface has been refined and the vertical domain has been extended to above 80 km these changes are accompanied by the inclusion of state of the art parameterizations to better simulate the dynamical and physical processes near the surface boundary layer scheme subgrid scale topography parameterization etc and at high altitude gravity wave drag in addition radiative transfer calculations and the representation of polar processes have been significantly improved we present some examples of zonal mean fields from simulations using the model at several seasons one relatively novel aspect previously introduced by wilson 1997 is that around northern winter solstice the strong pole to pole diabatic forcing creates a quasi global angular momentum conserving hadley cell which has no terrestrial equivalent within such a cell the coriolis forces accelerate the winter meridional flow toward the pole and induce a strong warming of the middle polar atmosphere down to 25 km this winter polar warming had been observed but not properly modeled until recently in fact thermal inversions are generally predicted above one and often both poles around 60 70 km however the mars middle atmosphere above 40 km is found to be very model sensitive and thus difficult to simulate accurately in the absence of observations

mt pelee martinique may 8 and 20 1902 pyroclastic flows and surges abstract the distribution stratigraphic relationships and fragmental components of the may 8 and 20 1902 pyroclastic flows from mt pelee martinique together with eyewitness accounts suggest the following explanation for those eruptions the eruptions were vertically directed magmatic perhaps initiated phreatically and contained abundant juvenile lithics from congealed magma of the dome and neck this resulted in a two part eruption column having 1 a dense lithic charged part which collapsed into the crater and flowed out of a pre existing notch in its side giving rise to pyrochlastic flows and 2 a magmatically derived column containing gases juvenile vitric material and crystals which largely by passed the neck and dome and escaped into the atmosphere all of the energy of the flows was apparently focused through the notch they emerged fully turbulent and flowed down riviere blanche gravity segregation of large and abundant fragments soon resulted in a dense high concentration poorly fluidized block and ash flow confined to the valley leaving above a fully turbulent high energy ash cloud surge as the ash cloud surge moved down the mountain it continued to expand outward the process of gravity segregation continued as the ash cloud surge expanded resulting in secondary block and ash underflows toward st pierre the secondary block and ash flows developed on a gently sloping upland surface 100 m or more above the valley of riviere blanche the turbulent fragment depleted surges above the secondary block and ash flows maintained sufficient energy to devastate the landscape outward to about 3000 m including st pierre the surges refracted around obstacles and in one place moved up a small valley in a direction opposite to the main flows

geochemical monitoring of the thermal waters of the phlegraean fields abstract thermal waters from the phlegraean fields pf caldera area have been periodically sampled and analysed during the period 1990 1999 for major chemical constituents and chemico physical parameters to define the most useful variables for geochemical surveillance the variations observed in waters from different locations were compared with ground movements and microseismic events recorded at the time of observation the discontinuous monitoring of the hydrothermal system of the pf has given indications about the geochemical variations brought about by changes in the chemical and physical characteristics of the deep aquifers because of the complexity of the pf geothermal system in each sampling location different variations have been observed and then evaluated on the basis of the different kinds and degrees of deep fluid supply characterising waters sampled in the different zones in some cases a good correspondence between vertical soil movements and chemical changes in the waters has been observed in particular in pools and wells located around the solfatara crater interesting variations in some chemical parameters ph ammonia and or so 4 2 cl ratios have been recorded variations can be observed in all of the sampling locations but pools and wells located near the solfatara crater are the best sites for detecting changes occurring in the deep hydrothermal system and possibly in the activity of the underlying magma chamber

volatilization transport and sublimation of metallic and non metallic elements in high temperature gases at merapi volcano indonesia abstract condensates silica tube sublimates and incrustations were sampled from 500 800 c fumaroles and lava samples were collected at merapi volcano indonesia in jan feb 1984 with respect to the magma merapi gases are enriched by factors greater than 105 in se re bi and cd 104 105 in au br in pb and w 103 104 in mo cl cs s sn and ag 102 103 in as zn f and rb and 1 102 in cu k na sb ni ga v fe mn and li the fumaroles are transporting more than 106 grams day g d of s cl and f 104 106 g d of al br zn fe k and mg 103 104 g d of pb as mo mn v w and sr and less than 103 g d of ni cu cr ga sb bi cd li co and u with decreasing temperature 800 500 c there were five sublimate zones found in silica tubes 1 cristobalite and magnetite first deposition of si fe and al 2 k ca sulfate acmite halite sylvite and pyrite maximum deposition of cl na k si s fe mo br al rb cs mn w p ca re ag au and co 3 aphthitalite k na sulfate sphalerite galena and cs k sulfate maximum deposition of zn bi cd se and in higher deposition of pb and sn 4 pb k chloride and na k fe sulfate maximum deposition of pb sn and cu and 5 zn cu and k pb sulfates maximum deposition of pb sn ti as and sb the incrustations surrounding the fumaroles are also chemically zoned bi cd pb w mo zn cu k na v fe and mn are concentrated most in or very close to the vent as expected with cooling atmospheric contamination and dispersion the highly volatile elements br cl as and sb are transported primarily away from high temperature vents ba si p al ca and cr are derived from wall rock reactions incomplete degassing of shallow magma at 915 c is the origin of most of the elements in the merapi volcanic gas although it is partly contaminated by particles or wall rock reactions the metals are transported predominantly as chloride species as the gas cools in the fumarolic environment it becomes saturated with sublimate phases that fractionate from the gas in the order of their equilibrium saturation temperatures devolatilization of a cooling batholith could transport enough acids and metals to a hydrothermal system to play a significant role in forming an ore deposit however sublimation from a high temperature high velocity carrier gas is not efficient enough to form a large ore deposit re se cd and bi could be used as supporting evidence for magmatic fluid transport in an ore deposit

possible remnants of a frozen mud lake in southern elysium mars in this work we estimate the minimum persistence time of subsurface ice in water rich sediment layers remaining after sublimation of a martian lake we simulate sublimation of ice from layers of different granulations and thicknesses presented results assume insolation and atmospheric conditions characteristic for the present day southern elysium where data from mars express have identified surface features possibly indicating the very recent presence of a frozen body of water murray et al 2005 nature 434 352 356 the age of these features is estimated to be several million years on this time scale we find that most of the water ice must have sublimated away however remnant ice at a few percent level cannot be excluded this amount of water ice is sufficient for chemical cementation of the observed features and explains their relatively pristine appearance without significant signs of erosion

small scale polygonal features on mars seasonal thermal contraction cracks in permafrost a time dependent viscoelastic model of thermal stress in martian ice rich permafrost is developed to test the hypothesis that small scale polygonal features observed from orbit and by the viking lander 2 are the result of thermal contraction cracking as commonly occurs in terrestrial permafrost results indicate that significant tensile stress occurs in martian ice rich permafrost as a result of seasonal cycles in the ground temperature using conservative rheological parameters appropriate for ice at low temperatures tensile stresses poleward of about 20 to 30 latitude easily exceed the tensile strength assumed to be 2 to 3 mpa and fractures should readily form in the equatorial regions special conditions may allow tensile stresses to approach the tensile strength these results support a thermal contraction origin of observed small scale polygonal features and emphasize the utility of these features as valuable morphological indicators of ground ice

ecological catastrophe in connection with the impact of the kaali meteorite about 800 400 b c on the island of saaremaa estonia ecological catastrophe in connection with the impact of the kaali meteorite about 800 400 b c on the island of saaremaa estonia

high latitude patterned grounds on mars classification distribution and climatic control patterned grounds such as polygonal features and slope stripes are the signature of the presence of ground ice and of temperature variations in cold regions on earth identifying similar features on mars is important to understand its past climate as well as the ground ice distribution in this study young patterned grounds are classed and mapped from the systematical analysis of mars observer camera high resolution images these features are located poleward of 55 latitude which fits the distribution of ground ice found by the neutron spectrometer onboard mars odyssey thermal contraction due to seasonal temperature variations is the predominant process of formation of polygons formed by cracks which sizes vary from 15 to 300 m the small 40 m widespread polygons are very recent and degraded by the desiccation of ground ice from the cracks which enhances the effect of ice sublimation the large polygons 50 to 300 m located only around the south co2 polar cap indicate the presence of ground ice and thus outline the limit of the co2 ice cap they could be due to the blanketing of water ice deposits by the advances and retreats of the residual co2 ice cap during the last thousand years large 50 250 m and homogeneous polygons similar to ice wedge polygons hillslope stripes and solifluction lobes may indicate that specific environments such as crater floors and hillslopes could have been submitted to freeze thaw cycles possibly related to higher summer temperatures in periods of obliquity higher than 35 these interpretations must be strengthened by higher resolution images such as those of the hirise mission of the mars reconnaissance orbiter because locations with past seasonal thaw could be of major interest as potential landing sites for the phoenix mission

merapi volcano central java indonesia a case study of radionuclide behavior in volcanic gases and its implications for magma dynamics at andesitic volcanoes for more than 20 years volcanic gases have been regularly collected at merapi volcano indonesia and have been subsequently analyzed for their 210pb 210bi and 210po activities and so2 contents these new results show the high volatility of the three radionuclides in andesitic gases although their emanation coefficients 0 94 3 5 and 53 for 210pb 210bi and 210po respectively are significantly lower than those observed at basaltic volcanoes this emphasizes the major role of magma temperature on the degassing of these metals which are mainly transported in volcanic gases as pb chloride compounds and as bi and po metallic species radioactive disequilibria between 210pb 210bi and 210po in the gas phase are characteristic of degassing processes and gas paths within the edifice gases released at both gendol and woro fumarolic fields are of magmatic origin but their radionuclide content is strongly altered by secondary processes chemical reactions with surrounding brines and deposition of sublimates in the ground high temperature gases collected in the summit gas plume are of pure primary magmatic origin and are likely directly tapped in the degassing reservoir gases arising from the growing domes are strongly depleted in the most volatile isotopes and gas species this suggests that magma mostly degasses at depth in open system explaining why the volcano usually undergoes no explosive eruptions the gas flux at merapi is sustained by a deep magma supply which is twice the extrusion rate of lava unerupted degassed magma thus progressively accumulates beneath the summit yielding an overpressure which can trigger dome collapse without precursor

condensation of volatile elements in high temperature gases of mount st helens abstract the cooling of high temperature 675 650 c volcanic gases in silica tubes produces successive condensation of volatile elements as solids on the inner walls of the tubes the chemistry of the solid phases obtained by these reactions varies along the temperature gradient 675 400 c fe3o4 and sio2 occur above 570 c mos2 and fewo4 are mainly enriched between 570 and 480 c nacl and kcl occur in the range 550 450 c and cds occurs at 520 450 c pb and bi sulfides are typical of the low temperature zone 480 400 c thermodynamic calculations performed to define the nature of the stable solid phases in equilibrium with the oxygen sulfur and chlorine fugacities of the gas phase show that the observed solid phases reflect a formation in a low o2 fugacity environment the chemistry of fumarolic incrustations collected around high temperature vents 300 c 5 15 cm below the surface reveals that condensation processes similar to those observed in the tubes occur naturally in the ground these incrustations show marked differences with those generally collected at the outlet of fumarolic vents where reactions with atmospheric gases and wall rocks are the major processes leading to the formation of these incrustations

geochemical and isotopic evidence for seawater contamination of the hydrothermal system of taal volcano luzon the philippines the hydrologic structure of taal volcano has favored development of an extensive hydrothermal system whose prominent feature is the acidic main crater lake ph 3500 mg kg and low so4 cl ratios 0 3 the br cl ratio of most samples suggests incorporation of seawater into the hydrothermal system water and dissolved sulfate isotopic compositions reveal that the main crater lake and spring discharges are derived from a deep parent fluid t approximate to 300 degrees c which is a mixture of seawater volcanic water and lake taal water the volcanic end member is probably produced in the magmatic hydrothermal environment during absorption of high temperature gases into groundwater boiling and mixing of the parent water give rise to the range of chemical and isotopic characteristics observed in the thermal discharges incursion of seawater from the coastal region to the central part of the volcano is supported by the low water levels of the lakes and by the fact that lake taal was directly connected to the china sea until the sixteenth century the depth to the seawater meteoric water interface is calculated to be 80 and 160 m for the main crater lake and lake taal respectively additional data are required to infer the hydrologic structure of taal geochemical surveillance of the main crater lake using the so4 cl na k or mg cl ratio cannot be applied straightforwardly due to the presence of seawater in the hydrothermal system

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

volatiles of mount st helens and their origins abstract analyses have been made of gases in clouds apparently emanating from mount st helens despite appearances most of the water in these clouds does not issue from the volcano even directly above a large fumarole d and 18o data indicate that only half the water can come from the volcano isotopic and chemical evidence also shows the steam in the volcano 33 0 per mol d from which a condensate of 0 2 n hci was obtained is not a major cause of the explosions the steam in the volcano is derived from a metamorphic brine in the underlying tertiary meta andesite the gas that caused the explosive eruptions is carbon dioxide

ignimbrite depositional facies the anatomy of a pyroclastic flow a model is presented for the depositional regimes in a pyroclastic flow to explain the origin of facies in the taupo ignimbrite and to compare these with other published examples in this model a pyroclastic flow consists of a head a body and a tail the head which is where fluidization caused by air ingestion occurs generates layer 1 deposits on lithological grounds these are divided into layers 1 p which is fines depleted and rich in pumice and 1 h which is fines depleted and rich in lithics and crystals layer 1 p represents material thrown forwards from the flow head and is termed the jetted deposits layer 1 h represents material sedimented from within the flow head and is termed the ground layer the body represents the bulk of the flow and the tail is its trailing part which is slowed by ground friction these parts generate the layer 2 deposits which include the valley pond ignimbrite and its associated ignimbrite veneer deposit localized depositional modes within the body and tail generate distinctive coarse pumice concentration zones and pumiceous lee side lenses behind obstacles at its outer limits all of the flow on interfluves is affected by air ingestion fluidization producing the distant facies which combines features of both layer 1 and 2 deposits one important conclusion of this work is that the thicknesses and compositions of the various facies are not related in any simple way to the thickness and composition of the parent flow

small scale trench in the north polar region of mars evolution of surface frost and ground ice concentration in this paper we attempt to answer the question how formation of a small scale trench in the martian regolith affects local distribution of the subsurface ice we are especially interested in the consequences of digging a trench to search for buried ice as has been done during the phoenix mars lander mission however the results may be also applicable for natural troughs or cracks we present results of simulations of diurnal exchange of water between the regolith and the atmosphere our model includes the heat and vapor migration in the regolith surrounding the trench as well as formation of diurnal frost we take into account scattering of light in the atmosphere and on the trench facets as well as changes of atmospheric humidity on diurnal and seasonal time scales our calculations show that the measurements of ice content in a sample obtained within one or two days from the beginning of digging should not be affected however on somewhat longer time scale at the south facing site of the trench the regolith can be significantly depleted from ice this effect should be taken into account if the excavation and taking samples from different depths will be performed in stages separated in time by a month or more

global distribution and migration of subsurface ice on mars a thermal diffusive model of h2o kinetics and equilibrium was developed to investigate the long term evolution and depth distribution of subsurface ice on mars the model quantitatively takes into account 1 obliquity variations 2 eccentricity variations 3 long term changes in the solar luminosity 4 variations in the argument of subsolar meridian in planetocentric equatorial coordinates 5 albedo changes at higher latitudes due to seasonal phase changes of co2 and the varying extent of co2 ice cover 6 planetary internal heat flow 7 temperature variations in the regolith as a function of depth time and latitude due to the above factors 8 atmospheric pressure variations over a 104 year time scale 9 the effects of factors 1 through 5 on seasonal polar cap temperatures and 10 knudsen and molecular diffusion of h2o through the regolith the migration of h2o into or out of the regolith is determined by two boundary conditions the h2o vapor pressure at the subsurface ice boundary and the annual average h2o concentration at the base of the atmosphere these are controlled respectively by the annual average regolith temperature at the given depth and seasonal temperatures at the polar cap starting from an arbitrary initial uniform depth distribution of subsurface ice h2o fluxes into or out of the regolith are calculated for 100 selected obliquity cycles each representing a different epoch in mars history the h2o fluxes are translated into ice thicknesses and extrapolated over time to give the subsurface ice depth as a function of latitude and time the results show that obliquity variations influence annual average regolith temperatures in varying degrees depending on latitude with the greatest effect at the poles and almost no effect at 40 lat insolation changes at the pole due to obliquity argument of subsolar meridian and eccentricity variations can produce enormous atmospheric h2o concentration variations of 6 orders of magnitude over an obliquity cycle superimposed on these cyclic variations is a slow monotonic change due to the increasing solar luminosity albedo changes at the polar cap due to seasonal phase changes of co2 and the varying thickness of the co2 ice cover are critically important in determining annual average atmospheric h2o concentrations despite the strongly oscillating character of the boundary conditions only small amounts of h2o are exchanged between the regolith and the atmosphere per obliquity cycle 10 g cm2 the net result of h2o migration is that the regolith below 30 40 lat is depleted of subsurface ice while the regolith above 30 40 lat contains permanent ice due to the depth of penetration of the annual thermal wave this result is supported by recent morphological studies the rate of migration of h2o is strongly dependent on average pore capillary radius for which we have assumed values of 1 and 10 m we estimate that the h2o ice removed from the regolith would produce a permanent ice cap with a volume between 2 106 and 6 106 km3 this generally agrees with estimates deduced from deflationary features at lower latitudes depositional features at higher latitudes and the mass of the polar caps

thermal behavior of horizontally mixed surfaces on mars abstract current methods for deriving thermal inertia from spacecraft observations of planetary brightness temperature generally assume that surface properties are uniform for any given observation or co located set of observations as a result of this assumption and the nonlinear relationship between temperature and thermal inertia sub pixel horizontal heterogeneity may yield different apparent thermal inertia at different times of day or seasons we examine the effects of horizontal heterogeneity on mars by modeling the thermal behavior of various idealized mixed surfaces containing differing proportions of either dust sand duricrust and rock or slope facets at different angles and azimuths latitudinal effects on mixed surface thermal behavior are also investigated we find large several 100 j m 2 k 1 s 1 2 diurnal and seasonal variations in apparent thermal inertia even for small 10 admixtures of materials with moderately contrasting thermal properties or slope angles together with similar results for layered surfaces mellon m t putzig n e 2007 lunar planet sci xxxviii abstract 2184 this work shows that the effects of heterogeneity on the thermal behavior of the martian surface are substantial and may be expected to result in large variations in apparent thermal inertia as derived from spacecraft instruments while our results caution against the over interpretation of thermal inertia taken from median or average maps or derived from single temperature measurements they also suggest the possibility of using a suite of apparent thermal inertia values derived from single observations over a range of times of day and seasons to constrain the heterogeneity of the martian surface

dating a small impact crater an age of kaali crater estonia based on charcoal emplaced within proximal ejecta the estimates of the age of the kaali impact structure saaremaa island estonia provided by different authors vary by as much as 6000years ranging from similar to 6400 to similar to 400 before current era bce in this study a new age is obtained based on c 14 dating charred plant material within the proximal ejecta blanket which makes it directly related to the impact structure and not susceptible to potential reservoir effects our results show that the kaali crater was most probably formed shortly after 1530 1450 bce 3237 10 c 14 yr bp saaremaa was already inhabited when the bolide hit the earth thus the crater forming event was probably witnessed by humans there is however no evidence that this event caused significant change in the material culture e g known archeological artifacts or patterns of human habitation on saaremaa

apparent thermal inertia and the surface heterogeneity of mars abstract thermal inertia derivation techniques generally assume that surface properties are uniform at horizontal scales below the footprint of the observing instrument and to depths of several decimeters consequently surfaces with horizontal or vertical heterogeneity may yield apparent thermal inertia which varies with time of day and season to investigate these temporal variations we processed three mars years of mars global surveyor thermal emission spectrometer observations and produced global nightside and dayside seasonal maps of apparent thermal inertia these maps show broad regions with diurnal and seasonal differences up to 200 j m 2 k 1 s 1 2 at mid latitudes 60 s to 60 n and 600 j m 2 k 1 s 1 2 or greater in the polar regions we compared the seasonal mapping results with modeled apparent thermal inertia and created new maps of surface heterogeneity at 5 resolution delineating regions that have thermal characteristics consistent with horizontal mixtures or layers of two materials the thermal behavior of most regions on mars appears to be dominated by layering with upper layers of higher thermal inertia e g duricrusts or desert pavements over fines prevailing in mid latitudes and upper layers of lower thermal inertia e g dust covered rock soils with an ice table at shallow depths prevailing in polar regions less common are regions dominated by horizontal mixtures such as those containing differing proportions of rocks sand dust and duricrust or surfaces with divergent local slopes other regions show thermal behavior that is more complex and not well represented by two component surface models these results have important implications for mars surface geology climate modeling landing site selection and other endeavors that employ thermal inertia as a tool for characterizing surface properties

exposed water ice discovered near the south pole of mars the mars odyssey thermal emission imaging system themis has discovered water ice exposed near the edge of mars southern perennial polar cap the surface h2o ice was first observed by themis as a region that was cooler than expected for dry soil at that latitude during the summer season diurnal and seasonal temperature trends derived from mars global surveyor thermal emission spectrometer observations indicate that there is h2o ice at the surface viking observations and the few other relevant themis observations indicate that surface h2o ice may be widespread around and under the perennial co2 cap

organic block coatings in block and ash flow deposits at merapi volcano central java the 1954 1994 1998 and 2006 block and ash flow deposits from merapi volcano indonesia contain andesite blocks that display localized dark surface coatings these coated blocks are typically found in clusters but may also occur isolated within the block and ash flow deposits the coatings form irregular patches tens of centimetres across on block surfaces and are characterized by a silver metallic appearance the origin and composition of the coatings have not previously been determined and no comparable deposits have been described in detail from any other volcanically active region of the world carbon isotope analyses of coated and uncoated bulk rock material and of a range of charred and uncharred wood samples suggest that the dark block coatings at merapi volcano are organic in origin scanning electron microscopy and reflected light microscopy indicate that such coatings may form due to the migration and subsequent deposition of organic carbon in cavities within the andesite blocks the most recent field evidence from the 2006 block and ash flow deposits at merapi indicates that in situ charcoalification of plant material after block deposition and or during the final stages of flow is the major mechanism that forms localized concentrations of block coatings isolated coated blocks may result either from recycling of older deposits or more likely from charcoalification and redistribution of plant material caught between colliding lava blocks during flow

anatomy of a young impact event in central alberta canada prospects for the missing holocene impact record small impact events recorded on the surface of earth are signifi cantly underrepresented based on expected magnitude frequency relations we report the discovery of a 36 m diameter late holocene impact crater located in a forested area near the town of whitecourt alberta canada although undetectable using visible imagery the presence of the crater is revealed using a bare earth digital elevation model obtained through airborne light detection and ranging lidar the target material comprises deglacial quaternary sediments with impact ejecta burying a late holocene soil dated to ca 1100 14 c yr b p most of the 74 iron meteorites 0 1 1196 g recovered have an angular exterior morphology these meteorites were buried at depths 25 cm and are interpreted to result from fragmentation of the original projectile mass either at low altitude or during the impact event impact of the main mass formed the simple bowl shaped impact structure associated with an ejecta blanket and crater fi ll the increasing availability of lidar data for many terrestrial surfaces will serve as a useful tool in the discovery of additional small impact features

episodic fire runoff and deposition at the palaeocene eocene boundary qualitative and quantitative coal petrological analyses have been undertaken on the laminated lignite at the base of the cobham lignite bed from scalers hill kent england the maximum negative carbon isotope excursion which marks the beginning of the palaeocene eocene thermal maximum petm occurs near the top of the laminated lignite the lignite contains inertinite a petrographic term used to describe charcoal the laminated lignite has inertinite rich and inertinite poor layers indicative of episodic fires and post fire erosion charcoal clasts are derived from living or recently senesced plants and are dominated by the leaf stalks of herbaceous ferns and wood fragments from flowering plants the charcoal assemblage reflects a low diversity flora possibly adapted to disturbance by fire derived from a source vegetation subjected to seasonal surface wildfires the environmental conditions leading up to and across the onset of the petm are therefore interpreted as incorporating a persistent fire regime with episodic wildfires followed by rainfall and runoff events abundant charcoal indicates near modern oxygen levels whereas the absence of charred peat in this area calls into question previous suggestions that burning of palaeocene peats might have contributed to the short lived negative carbon isotope excursion at the palaeocene eocene boundary

rapid oxidation of mercury hg at volcanic vents insights from high temperature thermodynamic models of mt etna s emissions a major uncertainty regarding the environmental impacts of volcanic hg is the extent to which hg is deposited locally or transported globally an important control on dispersion and deposition is the oxidation state of hg compounds hg 0 is an inert insoluble gas while hg ii occurs as reactive gases or in particles which deposit rapidly and proximally near the volcanic vent using a new high temperature thermodynamic model we show that although hg in etna s magmatic gases is almost entirely hg 0 i e gaseous elemental mercury significant quantities of hg ii are likely formed at etna s vents as gaseous hgcl2 when magmatic gases are cooled and oxidised by atmospheric gases these results contrast with an earlier model study and allow us to explain recent measurements of hg speciation at the crater rim of etna without invoking rapid 1 min low temperature oxidation processes we further model hg speciation for a series of additional magmatic gas compositions compared to etna hg ii production i e hg ii hgtot is enhanced in more hcl rich magmatic gases but is independent of the hg hbr and hi content of the magmatic gases hg ii production is not strongly influenced by the initial oxidation state of magmatic gases above nno although production is hindered in more reduced magmatic gases the model and results are widely applicable to other open vent volcanoes and may be used to improve the accuracy of chemical kinetic models for low temperature hg speciation in volcanic plumes

subsurface ice on mars with rough topography high latitude ground ice on mars discovered by the gamma ray spectrometer suite is thought to be thermally stable owing to the presence of vapor in the martian atmosphere however local slopes can alter surface and subsurface temperatures substantially and hence allow ground ice to persist at locations where it would otherwise be unstable global statistics of the topography of mars are computed processed and extrapolated to derive a description of surface roughness on spatial scales to which ground ice should be sensitive this slope distribution is convolved with a new thermal model for the dependence of subsurface ice on slope to produce a prediction of the global ice distribution that includes the effect of topographic roughness in the highest latitudes slopes reduce the amount of buried ice while in lower latitudes the ice fraction increases widening the geographic boundary of the ice table at the high latitudes where ice is stable beneath horizontal ground the estimated reduction of ice is small compared to the existing ice volume areas in the midlatitudes with high surface roughness that have previously been predicted to be ice free are predicted to contain quantities of ice that may be detectable at present and accessible in the future slopes cause ground ice to be stable to latitudes of about 25 degrees in both hemispheres including for example areas within the northern olympus mons aureole deposits hecates tholus and hellas basin ice is unstable at equatorial latitudes even when accounting for surface slopes

evaluation of gas data from high temperature fumaroles at mount st helens 1980 1982 abstract the mount st helens fumarole gases show linear composition trends during periods of noneruptive degassing between september 1980 and october 1981 the trends are characterized by increasing h2o and decreasing co2 and sulfur maximum fumarole temperatures also show a linear decrease during this period high temperature fumarole gases collected from the crater and dome between september 1980 and july 1982 are all h2o rich 90 with 1 10 co2 and small amounts of h2s so2 h2 co hc and hf trace amounts of cos and s2 are present and occasional observations of minor ch4 appear to result from contamination or low temperature reactions in sample vessels the o2 fugacities of the gases remain near ni nio during cooling the low sulfur content of the gases obviates the need for extensive gas rock oxygen exchange to maintain fo2 s near ni nio a detailed thermodynamic analysis of 50 gas samples collected between september 1980 and december 1981 led to improved compositions for 22 samples the gases were initially in a state of equilibrium but disequilibrium modifications from atmospheric oxidation of h2 and to a lesser extent co occurred within the upper portions of the fumarole vents the last temperatures of equilibrium for the fumarole gases range from 800 c to 650 c and are nearly always higher than the collection temperatures no evidence was found of disequilibrium admixture of surface waters if such modifications of the fumarole gases occurred the water must have been added at depth and have reequilibrated with the other gas species at magmatic or near magmatic temperatures the highest quality analytical data are obtained by field gas chromatograph measurements and from caustic soda bottle samples samples collected in evacuated bottles or by pumping through double stopcock tubes tend to be severely deficient in sulfur due to post collection reactions between h2s and so2 it is also necessary to infer the water content of the latter samples

charcoal reflectance as a proxy for the emplacement temperature of pyroclastic flow deposits hot pyroclastic flow deposits often entomb and preserve vegetation as charcoal when studied in polished section this charcoal is highly reflective novel data from experimentally charred woods demonstrate that reflectance increases with both temperature and time at temperatures above 250 c reflectance rises rapidly for the first hour effectively stabilizing after 4 h for temperatures below 400 c however for higher temperatures reflectance only stabilizes after 24 h charcoalified woods from block and ash flow deposits generated by the soufriere hills volcano in montserrat have yielded interpreted deposit temperatures based on reflectance data of 325 525 c these temperatures compare favorably with directly measured data 365 640 c from the same deposits indicating that charcoal reflectance is useful as a temperature proxy for ancient pyroclastic flow deposits particularly where magnetic or mineral data are absent for this purpose however caution should be exercised as only a minimum temperature can be inferred where the heating duration of the deposit is unknown unlike magnetic or mineral data temperature data from charcoalified woods can be obtained from reworked deposits providing a valuable means of validating observations made about the style of eruption of volcanoes in ancient settings

an ignimbrite veneer deposit the trail marker of a pyroclastic flow abstract the term ignimbrite veneer deposit ivd is proposed for a new kind of pyroclastic deposit which is found associated with and passes laterally into taupo ignimbrite of valley pond type in new zealand it forms a thin layer mantling the landscape over 15 000 km 2 and is regarded as the deposit from the trailing tail of a pyroclastic flow where a relaxation of shear stress favoured the deposition of the basal part of the flow the ivd differs little in grain size from the associated ignimbrite but it shows a crude internal stratification attributed to the deposition of a succession of layers one after the passage of each pulse of the pyroclastic flow it locally contains laterally discontinuous lenses of coarse pumice lee side lenses on the far vent side of topographic obstacles in nearvent exposures the taupo ivd shows lensoid and cross stratified bed forms even where it stands on a planar surface attributed to deposition from a flow travelling at an exceedingly high velocity an ivd can be distinguished from a poorly sorted pyroclastic fall deposit because the beds in it show more rapid lateral variations in thickness it may show a low angle cross stratification and it contains carbonised wood from trees not in the position of growth from the deposit of a wet base surge because it lacks vesicles and strong antidune like structures and contains carbonised vegetation and from a hot and dry pyroclastic surge deposit because it possesses a high content of pumice and fines the significance of an ivd is that it records the passage of a pyroclastic flow where the flow itself has moved farther on

thermal analysis of fractures at cerberus fossae mars detection of air convection in the porous debris apron abstract this study investigates the cause of high nighttime temperatures within cerberus fossae a system of fractures affecting the central elysium planitia the inner parts walls and floor of the fractures are up to 40 k warmer than the surrounding plains however several temperature profiles exhibit a local temperature minima occurring in the central part of the fractures we examined first the influence of cooling efficiency at night in the case of a strong reduction of the sky proportion induced by the fracture s geometry however the lack of correlation between temperature and sky proportion calculated from extracted mars orbiter laser altimeter mola profiles argues against this hypothesis albedo variations were considered but appear to be limited within the fractures and are generally not correlated with the temperatures variations of the thermal properties of bedrocks exposures debris aprons and sand dunes inferred from high resolution images do not either correlate with temperature variations within the fractures as none of these factors taken alone or combined can satisfactorily explain the temperature variations within and near the fracture we suggest that geothermal heat transported by air convection within the porous debris aprons may contribute to explain high temperatures at night and the local minima on the fracture floor the conditions for the occurrence of the suggested phenomenon and the consequences on the surface temperature are numerically explored a conservative geothermal gradient of 20 mw m2 was used in the simulations this value being consistent with either inferred lithosphere elastic thicknesses below the shield volcanoes of the tharsis dome or values predicted from numerical simulations of the thermal evolution of mars the model results indicate that temperature differences of 10 20 k between the central and upper parts of the fracture are explained in the case of high darcy velocities which require high permeability values 5 10 6 m2 the presence of coarse material composing the debris aprons may explain why this key criteria was met in the context of cerberus fossae

motion of a fragmented meteoroid through the planetary atmosphere meteor observations and crater field investigations support the view that some meteoroids undergo fragmentation into a finite number of splinters which move a long distance without further disruption the motion of these fragments cannot be described in the frame of liquid like models the primary purpose of this study is to achieve some success in improving the alternative model of separate fragments which is based on studying the motion of a finite number of fragments interacting with each other through the air pressure the three dimensional 3 d numerical technique is elaborated for the direct modeling of the flow around several arbitrarily arranged fragments the model allows us to calculate the ablation mass rate and aerodynamic loading for each fragment the new approach hybrid model based on the simultaneous solution of the 3 d hydrodynamic equations for the airflow and the differential equations for the motion of discrete particles is proposed to study the debris cloud evolution taking into account successive fragmentation the simplified version of this model was applied to the sikhote alin meteorite shower benesov bolide and small meteoroids impacts against the martian surface

the role of discontinuous magma inputs in felsic magma and ore generation for a long time granites have been considered as passive bodies ascending under intrinsic negative density and viscosity contrasts with their host rocks chemical variations within a granitic body resulted from in situ differentiation and crystal fractionation since the mid 1980s this global view has been significantly modified by i shifting melting from water saturated conditions to fluid absent reactions ii increasing the role played by the mantle during granite generation iii reassessing the rheology of partially molten rocks iv demonstrating stepwise segregation and ascent of magmas by analogue and numerical models v combining structural geophysical and geochemical studies to reveal the internal structures in granitic plutons it results that a granitic body is built up by a discontinuous accumulation of successive magma intrusions the discontinuous nature of magma emplacement has also significant consequences for its ability to generate ore the processes that lead to ore deposits are examined with a brief review of the magmatic and fluid phases that concentrate ore forming elements examples are taken from crustal derived granites and porphyry type deposits those are considered as the two end members of magmatic and hydrothermal ore deposits the source characteristics of the magma the emplacement mechanisms and magma mixing processes are the frame that controls the potential to carry base metals with the magma the distribution of elements is controlled by diffusion partition between minerals and melt solubility and redox conditions variations of those parameters are examined by considering their activation energy which controls the exponential dependence with temperature a characteristic length depending on the activation energy temperature variation and time is estimated for a characteristic time lag of 30 ka the intrusion of a magma into a magma chamber of similar composition hence temperature has few effects on diffusion partition coefficient and redox conditions because of a too low temperature contrast the intrusion of a mafic magma into a felsic one induces a variation of 300 c in both magmas the characteristic length of diffusion may vary by up to two orders of magnitude whereas the variation of partition coefficients is only one order of magnitude the redox conditions are about 2 5 log unit in the mafic magma but they can vary by 7 log units in the felsic magma hence a strong decrease in d values is observed in porphyry type deposits the effect is a removal of the elements with higher activation energy w sn zr from the mafic to the felsic magma deformation during the late stages of emplacement also controls ore formation

merapi volcano java indonesia and merapi type nuee ardente a particular nuee ardente type merapi type avalanche nuee has been defined at the merapi volcano because of its prominent role in the recent activity of the volcano gravity plays a significant role during the eruption

the distribution and behavior of martian ground ice during past and present epochs mars undergoes significant oscillations in its orbit which will have a pronounced effect on its climate and in particular on the behavior of subsurface water ice we explore and map the behavior of ice in the martian near surface regolith over the past 1 m y using a diffusion and condensation model presented in an earlier paper with two primary modifications to include orbitally induced variations in insolation and atmospheric water abundance we find that the past behavior of ground ice differs significantly from that at the present epoch primarily the result of high amplitude oscillations in obliquity presently 25 in midlatitude and equatorial regions ground ice will condense from atmospheric water during times of higher obliquity filling the top few meters of the regolith with significant amounts of ice at an obliquity of 32 ground ice becomes stable globally during times of lower obliquity ground ice will sublime and diffuse back into the atmosphere dessicating the regolith to a depth of about 1 to 2 m equatorward of 60 to 70 latitude in the high latitude regions these oscillations are considerably subdued below this depth of cyclic saturation and dessication a long term stability of ice exists in some geographic regions we present a map of the distribution of ice expected at the present epoch cyclic exchange of water between the global regolith and polar regions will have significant implications for surface geology and the polar layered deposits

long term geochemical surveillance of fumaroles at showa shinzan dome usu volcano japan this study investigates 31 years of fumarole gas and condensate trace elements data from showa shinzan a dacitic dome cryptodome complex that formed during the 1943 1945 eruption of usu volcano forty two gas samples were collected from the highest temperature fumarole named a 1 from 1954 800 c to 1985 336 c and from lower temperature vents condensates were collected contemporaneously with the gas samples and we reanalyzed ten of these samples mostly from the a 1 vent for 32 cations and three anions modeling using the thermochemical equilibrium program solvgas shows that the gas samples are mild disequilibrium mixtures because they a contain unequilibrated sedimentary ch4 and nh3 b have unequilibrated meteoric water or c lost co either by air oxidation or by absorption by the sodium hydroxide sampling solution solvgas also enabled us to restore the samples by removing these disequilibrium effects and to estimate their equilibrium oxygen fugacities and amounts of s2 and ch4 the restored compositions contain 98 h2o with minor to trace amounts of co2 h2 hcl so2 hf h2s co s2 and ch4 we used the restored gas and condensate data to test the hypotheses that these time series compositional data from the dome s fumaroles provide 1 sufficient major gas data to analyze long term degassing trends of the dome s magma hydrothermal system without the influence of sampling or contamination effects 2 independent oxygen fugacity versus temperature estimates of the showa shinzan dacite 3 the order of release of trace elements especially metals from magma and 4 useful information for assessing volcanic hazards the 1954 1985 restored a 1 gas compositions confirm the first hypothesis because they are sufficient to reveal three long term degassing trends 1 they became increasingly h2o rich with time due to the progressive influx of meteoric water into the dome 2 their csandscl ratios decreased dramatically while their clf ratios stayed roughly constant indicating the progressive outgassing of less soluble components f cl s c from the magma reservoir and 3 their h2oh2 co2coandh2sso2 ratios increased significantly in concert with equilibrium changes expected for the 500 c temperature drop when plotted against reciprocal temperature the restored gas log oxygen fugacities follow a tight linear trend from 800 c to nno 2 5 at 400 c this trend largely disproves the second hypothesis because the oxygen fugacities for the 800 c restored gases can only be explained by mixing of hot magmatic gases with 350 c steam from superheated meteoric water but above 800 c this trend intersects the opposing linear trend for other usu eruptive products implying a log oxygen fugacity of 11 45 at 902 c for the showa shinzan magma the time series trace element data also disprove the third hypothesis because rock and incrustation particle contaminants in the condensates account for most of the trace element variation nonetheless highly volatile elements like b and as are relatively unaffected by this particle contamination and they show similar time series trends as cl and f finally except for infrequent sampling around the 1977 usu eruption the results generally confirm the fourth hypothesis since the time series trends for the major gases and selected trace elements indicate that with time the system cooled degassed and was infiltrated by meteoric water all of which are positive signs that volcanic activity declined over the 31 year history this study also suggests that second boiling of shallow magma within and possibly beneath the cryptodome sustained magmatic degassing for at least 20 years after emplacement

interfacial liquid water on mars and its potential role in formation of hill and dune gullies abstract gullies are among the most intriguing structures identified on the surface of mars most common are gullies located on the slopes of craters which are probably formed by liquid water transported by shallow aquifers heldmann j l carlsson e johansson h mellon m t toon o b 2007 icarus 188 324 344 two particular types of gullies are found on slopes of isolated hills and dunes the hill slope gullies are located mostly at 50 s which is at the high end of latitudes of bulk of the gullies found so far the dune gullies are found in several locations up to 65 s reiss d jaumann r kereszturi a sik a neukum g 2007 lunar planet sci xxxviii abstract 1993 but the best known are those in russel crater at 54 s the hill and dune gullies are longer than others making the aquifers explanation for their formation unlikely balme m mangold n baratoux d costard f gosselin m masson p pnet p neukum g 2006 j geophys res 111 doi 10 1029 2005je002607 recently it has been noted that thin liquid films of interfacial water can play a role in rheological processes on the surface of mars moehlmann d 2008 icarus 195 131 139 kereszturi a moehlmann d berczi sz ganti t kuti a sik a horvath a 2009 icarus 201 492 503 here we try to answer the question whether interfacial liquid water may occur on mars in quantities large enough to play a role in formation of gullies to verify this hypothesis we have calculated thermal models for hills and dunes of various steepness orientation and physical properties we find that within a range of average expected values of parameters it is not possible to have more than a few monolayers of liquid water at depths greater than a centimeter to create subsurface interfacial water film significantly thicker and hence to produce conditions for the slope instability parameters have to be chosen to have their extreme realistic values or an additional source of surface heating is needed one possibility for additional heating is a change of atmospheric conditions due to a local dust storm we conclude that if interfacial water is responsible for the formation of the hill slope gullies our results may explain why the hill gullies are rare

the age of the kaalijarv meteorite craters abstract precise radiometric age determination of the kaalijarv meteorite craters on the island of saaremaa in estonia have so far proved inconclusive here we present trace element analyses of peat cores taken several kilometers away from the kaalijarv craters that reveal a distinct ir enriched layer produced by the meteorite impact by radiocarbon dating the peat cores we have determined for the first time the precise age of the impact that generated the kaalijarv craters the calibrated date of the impact is 400 370 b c at 1

degassing of halogens from basaltic volcanism insights from volcanic gas observations abstract the currently available data set of s cl f abundances in volcanic gas plumes and high temperature fumarolic gas samples from basaltic volcanism is reviewed here in the attempt to derive constraints on the modes of halogen degassing from mafic silicate melts apart from large volcano to volcano variations reflecting remarkable differences in volatile abundances in the source magmas each of the explored volcanoes displays large changes of so2 hcl and so2 hf ratios with the style of volcanic activity with hcl hf staying fairly constant halogen abundances are low and so2 hcl and so2 hf are high when fresh volatile rich magmas sustain degassing as during explosive eruptions at the onset of eruptive cycles or shortly before paroxysmal events low so2 hcl and so2 hf ratios are instead characteristic of late stages of volcanic degassing typically being observed in the concluding stages of basaltic eruptions or during periods of reduced magma supply at persistently degassing volcanoes these observations are taken as evidence of halogens being less keen to enter the gas phase relative to s during degassing of basaltic magmas and quantitatively interpreted in light of a rayleigh type open system degassing model the model though simple quantitatively reproduces the range of volcanic gas compositions observed at basaltic volcanoes worldwide and allows prediction of vapour melt partitioning contrasts of factors 9 and 36 for the volatile couples s cl and s f respectively these predictions require validation from appropriately designed experiments of halogen partitioning between magmatic vapours and silicate melts over a range of p t x conditions

interpretation of volcanic gas data from tholeiitic and alkaline mafic lavas the analyses of approximately 100 high temperature gas samples from erupting lavas of surtsey erta ale ardoukoba kilauea mount etna and nyiragongo exhibit erratic compositions resulting from analytical errors condensation effects reactions with sampling devices and contamination by atmospheric gases meteoric water and organic material computational techniques have been devised to restore reported analyses to compositions representative of the erupted gases the restored analyses show little evidence of short term variations the principal species are h2o co2 so2 h2 co h2s s2 and hcl the o2 fugacities range from nickel nickel oxide to a half order of magnitude below quartz magnetite fayalite there is no evidence for a unique magmatic gas composition instead the erupted gases show regular compositional trends characterized by decreasing co2 with progressive outgassing the gases from more alkaline lavas etna nyiragongo are distinctly richer in co2 while those from less alkaline surtsey or tholeiitic lavas erta ale ardoukoba tend to be richer in h2o kilauean gases range from co2 rich to h2o rich the total sulfur contents of the erupted gases show an excellent positive correlation with lava o2 fugacity all restored analyses are significantly lower in h2o and enriched in sulfur and co2 compared to the excess volatiles

fluid immiscibility in volcanic environments volatile components enter the atmosphere oceans and other surface waters through pre syn and post eruptive volcanic processes that involve a variety of fluids aluminosilicate poor fluids include aqueous or carbonic to sulfide sulfate chloride fluoride carbonate and phosphate rich compositions in volcanic environments but other more complex combinations of these constituents may be involved giggenbach 1977 roedder 1984 1992 lowenstern 1995 other rare gases and dissolved constituents e g h2 n2 he ar h3bo3 hg ch4 and other hydrocarbon compounds metals and metalloids are also present but in general they are not sufficiently concentrated to form their own phases or control bulk fluid composition and volcanic processes as a result of their diverse compositions volcanic fluids ranging from vapor to liquid exhibit widely different densities and show strong distinctions in heat capacity dielectric behavior viscosity and other chemical and physical characteristics geiger et al 2006a the density of a saline liquid in the system nacl h2o at 50 mpa and 800 c for example is more than 7 times that of the coexisting aqueous vapor e g 0 2 gm cm3 henley and mcnabb 1978 multiple fluids move mix and or unmix in magma chambers and volcanic conduits in the root zone of fumaroles and in the convective hydrothermal systems that are ubiquitous to volcanic environments hydrothermal systems are typically centered on magmatic intrusions and may include crater lakes at the top of eruptive conduits hydrothermal processes involving two or more fluid phases operate through a variety of geologically relevant shallow crustal pressure temperature composition conditions volcanic fluids occur at supersolidus to subsolidus conditions meaning that the dense aluminosilicate melt that is common to volcanism may or may not be present this chapter addresses the evidence for and occurrence of two or more low density aluminosilicate poor fluids

numerical ages for plio pleistocene glacial sediment sequences by 26al 10be dating of quartz in buried paleosols abstract we describe a method for dating plio pleistocene sediments by analysing 26 al and 10 be in quartz from buried paleosols the method amounts to a generalization of the technique of burial dating which has previously been used to date river sands deposited in caves as well as fluvial terraces we a measure nuclide concentrations at multiple depths in the paleosol b use the geologic context of the sample to construct an exposure burial history an exposure model that can be used to predict the nuclide concentrations in the samples as a function of whatever unknown parameters are of geological interest e g the ages of geologic units and then c find the parameters in the exposure model that result in the best fit between predicted and observed nuclide concentrations we apply the method to a paleosol developed on the uppermost till in eastern nebraska which is buried by several middle to late pleistocene loess units the ages of some of which are known independently the lowest loess unit whose age was not previously known was deposited 0 58 0 12 ma and the till was emplaced 0 65 0 14 ma which agrees with existing age constraints from paleomagnetic measurements and the position of the lava creek ash in the regional stratigraphy the most important source of uncertainty in these age determinations is the analytical uncertainty in 26 al and 10 be measurements uncertainties in either the nuclide production rates or the geologic model are comparatively unimportant

charring of woods by volcanic processes an example from the taupo ignimbrite new zealand abstract one of the most violent and explosive eruptions in historic times was that of the taupo volcano in new zealand 1800 years ago this culminated in emplacement of the taupo ignimbrite laid down by a single vent generated pyroclastic density current that entombed and preserved abundant plant material the ignimbrite consists of two layers generated by processes within the concentrated part of the density current flow sensu stricto and where the current interacted with the atmosphere and the pre eruptive vegetative cover eighty four wood samples were collected from eight localities representing both layers at varying distances from the vent including the previously described pureora fossil forest samples were studied by light scanning electron and reflectance microscopy in order to determine their systematic affinity angiosperm or conifer degree of charring and reflectance values most samples 59 were conifer probably derived from podocarps that are known to have been common in the pre eruptive vegetation samples ranged from uncharred through incompletely charred to fully charred woods the variation in degrees of charring and reflectance values implies that the entrained charcoal did not equilibrate with the flow temperature minimum charring temperatures interpreted from the mean of the three highest maximum reflectance values showed no major differences between ignimbrite layers and were generally low ranging from 269 to 398 c both ignimbrite layers also show a trend of increasing deposit temperature away from the vent consistent with estimates from palaeomagnetic techniques

the presence and stability of ground ice in the southern hemisphere of mars abstract we calculate new estimates of ground ice stability and the depth distribution of the ice table the depth boundary between ice free soil above and ice cemented soil below and compare these theoretical estimates of the distribution of ground ice with the observed distribution of leakage neutrons measured by the neutron spectrometer instrument of the mars odyssey spacecraft s gamma ray spectrometer instrument suite our calculated ground ice distribution contains improvements over previous work in that we include the effects of the high thermal conductivity of ice cemented soil at and below the ice table we include the surface elevation dependence of the near surface atmospheric humidity and we utilize new high resolution maps of thermal inertia albedo and elevation from mars global surveyor observations results indicate that ground ice should be about 5 times shallower than in previous predictions while results are dependent on the atmospheric humidity depths are generally between a few millimeters and a few meters with typical values of a few centimeters results are also geographically similar to previous predictions with differences due to the higher resolution of thermal inertia and the inclusion of elevation effects on humidity comparison with the measured epithermal neutron count rates in the southern hemisphere indicate that the geographic distribution of the count rate is best correlated with ground ice in equilibrium with 10 to 20 pr m precipitable micrometers column abundance of atmospheric water assuming a uniform distribution with co2 however given the uncertainties 5 to 30 pr m also may be viable this water abundance represents a longer term average over 100 to 1000 yr there is a high degree of correlation between the depth of the ice table and the epithermal count rate that agrees remarkably well with predicted count rates as a function of ice table depth these results indicate that ground ice in the upper meter of the martian soil is in diffusive equilibrium with the atmosphere since ground ice in this depth zone is expected to undergo saturation desiccation cycles with orbital variations this ice should be younger than about 500 kyr and was emplaced under similar cold and dry climate conditions of today remaining differences between the predicted depths of the ice table and those inferred from the neutron data are likely to be due to subpixel heterogeneity in the martian surface including the presence of rocks slopes and patches of soil with varying thermophysical properties

evaluation of gases condensates and so2 emissions from augustine volcano alaska the degassing of a cl rich volcanic system after the march april 1986 explosive eruption a comprehensive gas study at augustine was undertaken in the summers of 1986 and 1987 airborne cospec measurements indicate that passive so2 emission rates declined exponentially during this period from 380 45 metric tons day t d on 7 24 86 to 27 6 t d on 8 24 87 these data are consistent with the hypothesis that the augustine magma reservoir has become more degassed as volcanic activity decreased after the spring 1986 eruption gas samples collected in 1987 from an 870 c fumarole on the andesitic lava dome show various degrees of disequilibrium due to oxidation of reduced gas species and condensation and loss of h2o in the intake tube of the sampling apparatus thermochemical restoration of the data permits removal of these effects to infer an equilibrium composition of the gases although not conclusive this restoration is consistent with the idea that the gases were in equilibrium at 870 c with an oxygen fugacity near the ni nio buffer these restored gas compositions show that relative to other convergent plate volcanoes the augustine gases are very hcl rich 5 3 6 0 mol hcl s rich 7 1 mol total s and h2o poor 83 9 84 8 mol h2o values of d and 18o suggest that the h2o in the dome gases is a mixture of primary magmatic water pmw and local seawater part of the cl in the augustine volcanic gases probably comes from this shallow seawater source additional cl may come from subducted oceanic crust because data by johnston 1978 show that cl rich glass inclusions in olivine crystals contain hornblende which is evidence for a deep source 25km for part of the cl gas samples collected in 1986 from 390 642 c fumaroles on a ramp surrounding the inner summit crater have been oxidized so severely that restoration to an equilibrium composition is not possible h and o isotope data suggest that these gases are variable mixtures of seawater fmw and meteoric steam these samples are much more h2o rich 92 97 h2o than the dome gases possibly due to a larger meteoric steam component the 1986 samples also have higher cl s s c and f cl ratios which imply that the magmatic component in these gases is from the more degassed 1976 magma thus the 1987 samples from the lava dome are better indicators than the 1986 samples of degassing within the augustine magma reservoir even though they were collected a year later and contain a significant seawater component future gas studies at augustine should emphasize fumaroles on active lava domes condensates collected from the same lava dome fumarole have enrichments ot 107 102 in cl br f b cd as s bi pb sb mo zn cu k li na si and ni lower temperature 200 650 c fumaroles around the volcano are generally less enriched in highly volatile elements however these lower termperature fumaroles have higher concentration of rock forming elements probably derived from the wall rock

restoration of new volcanic gas analyses from basalts of the afar region further evidence of co2 degassing trends abstract the restored compositions for approximately 70 new analyses reported recently for erta alelava lake leguern et al 1979 are in good agreement with restored compositions gerlach 1980a based on previously published data the results confirm earlier indications that gas collections taken at different times from the lava lake are related principally by variations in co 2 content restored compositions for gas samples collected in the final stages of a november 1978 ardoukoba eruption along the asal rift spreading axis resemble the erta ale gases except for a much lower co 2 content the ardoukoba gases fall close to a co 2 decreasing control line for gases with initial compositions similar to the 1971 1973 erta ale gases these results suggest that gases released from basaltic lava along zones of crustal spreading follow compositional trends dominated by changes in co 2 content