mechanical properties of shale gas reservoir rocks part 2 ductile creep brittle strength and their relation to the elastic modulus we studied the elastic moduli ductile creep behavior and brittle strength of shale gas reservoir rocks from barnett haynesville eagle ford and fortst john shale in a series of triaxial laboratory experiments we found a strong correlation between the shale compositions in particular the volume of clay plus kerogen and intact rock strength frictional strength and viscoplastic creep viscoplastic creep strain was approximately linear with the applied differential stress the reduction in sample volume during creep suggested that the creep was accommodated by slight pore compaction in a manner similar to instantaneous strain there was more viscoplastic creep in samples deformed perpendicular to the bedding than parallel to the bedding the tendency to creep also correlated well with the static young s modulus we explained this apparent correlation between creep behavior and elastic modulus by appealing to the stress partitioning that occurs between the soft components of the shales clay and kerogen and the stiff components quartz feldspar pyrite and carbonates through a simple 1d analysis we found that a unique relation between the creep compliance and elastic modulus independent of composition and orientation can be established by considering the individual creep behavior of the soft and stiff components that arises from the stress partitioning within the rock this appears to provide a mechanical explanation for why long term ductile deformational properties can appear to correlate with short term elastic properties in shale gas reservoir rocks

mechanical properties of shale gas reservoir rocks part 1 static and dynamic elastic properties and anisotropy abstractunderstanding the controls on the elastic properties of reservoir rocks is crucial for exploration and successful production from hydrocarbon reservoirs we studied the static and dynamic elastic properties of shale gas reservoir rocks from barnett haynesville eagle ford and fort st john shales through laboratory experiments the elastic properties of these rocks vary significantly between reservoirs and within a reservoir due to the wide variety of material composition and microstructures exhibited by these organic rich shales the static young s modulus and dynamic p and s wave moduli elastic parameters generally decrease monotonically with the clay plus kerogen content the variation of the elastic moduli can be explained in terms of the voigt and reuss limits predicted by end member components however the elastic properties of the shales are strongly anisotropic and the degree of anisotropy was found to correlate with the amount of clay and organic content as well as the shale fab

spectral mixture modeling a new analysis of rock and soil types at the viking lander 1 site a viking lander 1 image was modeled as mixtures of reflectance spectra of palagonite dust gray andesitelike rock and a coarse rocklike soil the rocks are covered to varying degrees by dust but otherwise appear unweathered rocklike soil occurs as lag deposits in deflation zones around stones and on top of a drift and as a layer in a trench dug by the lander this soil probably is derived from the rocks by wind abrasion and or spallation dust is the major component of the soil and covers most of the surface the dust is unrelated spectrally to the rock but is equivalent to the global scale dust observed telescopically a new method was developed to model a multispectral image as mixtures of end member spectra and to compare image spectra directly with laboratory reference spectra the method for the first time uses shade and secondary illumination effects as spectral end members thus the effects of topography and illumination on all scales can be isolated or removed the image was calibrated absolutely from the laboratory spectra in close agreement with direct calibrations the method has broad applications to interpreting multispectral images including satellite images

an assessment procedure for glacial hazards in the swiss alps glacial hazards such as ice avalanches glacial lake outburst floods and debris flows have caused severe damage in populated mountain regions such as the swiss alps assessment of such hazards mus

accumulation characteristics on a cold high alpine firn saddle from a snow pit study on colle gnifetti monte rosa swiss alps diverses caracteristiques de la neige isotopes 18 o 3 h conductivite electrique poussieres trace d elements et pollen ont ete etudies dans une tranchee englobant environ deux ans et demi d accumulation neigeuse afin de determiner une clef pour l interpretation stratigraphique des carottages dans les regions de neves froids en haute montagne sur le colle gnifetti 4 450 m s m mont rose on observe que la forte influence du vent mene a des phenomenes de melange et de resedimentation des couches superficielles toutefois sur la base de l information tiree de la combinaison des differents parametres observes il est possible de dater une grande part des couches de neige et parfois d en determiner l origine en plus des horizons de glace qui n apparaissent que dans les couches estivales des indices marquants sont les poussieres sahariennes caracterisees par la pointe de teneur en poussiere et de conductivite

dehydration induced damage and deformation in gypsum and implications for subduction zone processes 1 experimental heating tests were performed on volterra gypsum to study the micromechanical consequences of the dehydration reaction the experimental conditions were drained at 5 mpa fluid pressure and confining pressures ranging from 15 to 55 mpa one test was performed with a constantly applied differential stress of 30 mpa the reaction is marked by 1 a porosity increase and homogeneous compaction 2 a swarm of acoustic emissions 3 a large decrease in p and s wave velocities and 4 a decrease in vp vs ratio wave velocity data are interpreted in terms of crack density and pore aspect ratio which modeling pores as spheroids is estimated at around 0 05 crack like spheroid complementary tests performed in an environmental scanning electron microscope indicate that cracks first form inside the gypsum grains and are oriented preferentially along the crystal structure of gypsum most of the visible porosity appears at later stages when grains shrink and grain boundaries open extrapolation of our data to serpentinites in subduction zones suggest that the signature of dehydrating rocks in seismic tomography could be a low apparent poisson s ratio although this interpretation may be masked by anisotropy development due to preexisting crystal preferred orientation and or deformation induced cracking the large compaction and the absence of strain localization in the deformation test suggests that dehydrating rocks maybe seen as soft inclusions and could thus induce ruptures in the surrounding nonreacting rocks

exploration of crustal mantle material for the earth and moon using reflectance spectroscopy abstract near infrared reflectance spectra have been acquired a for moses rock diatreme in se utah using an airborne imaging spectrometer ais and b for small areas in and around the large lunar impact crater copernicus using a spectrometer on earth based telescopes the high spectral resolution and precision of these data allow several mineral components of surface material to be identified and analyzed in a spatial context the derived mineralogical information is used to address specific geological problems for the terrestrial study the distribution of the measured abundance of mantle derived ultramafic microbreccia across moses rock dike indicates that flow stabilized into a few channels during the violent eruption for the lunar study the variety of rock types identified in crustal material of deep seated origin is distinct from the dominant rock types sampled from the upper lunar crust and suggests a complex crustal evolution

effect of undrained creep on instability behaviour of loose sand prefailure instability in the form of a runway deformation can occur for loose sand under undrained conditions the effect of creep on the instability behaviour of loose sand is studied experimentally in this note previous studies have established that instability can only occur when the stress state is above the instability line however if creep is allowed to develop under undrained conditions instability can still possibly occur even when the stress state at which creep develops is below the instability line a boundary that specifies the condition in which instability may be induced by undrained creep is determined based on the experimental data key words laboratory test liquefaction sands shear strength

time dependent deformation of shale gas reservoir rocks and its long term effect on the in situ state of stress abstract laboratory testing of shale gas reservoir rocks reveal varying amounts of time dependent viscous deformation in response to applied differential stress the time dependent deformation is an inherent property of the dry rock as it occurs in the absence of pore fluid the contribution of the time dependent deformation is generally larger for rocks with more clay and organic content the time dependent behavior can be modeled as a power law function of time its magnitude is approximately linear with the magnitude of the applied differential stress and nearly insensitive to the confining pressure by applying linear viscoelastic theory and using laboratory constrained constitutive parameters we evaluated the effect of the time dependent deformation in modifying the in situ differential stress over time modeling suggests that a significant proportion of a differential stress change would be relaxed over time scales on the order of days because of this short time scale the composition of the rock as it influences the time dependent behavior may influence the in situ differential stress magnitudes stronger than the formation s geological loading history for these reservoirs

snow accumulation and ice flow at dome du gouter 4300 m mont blanc french alps glaciological experiments have been carried out at dome du gouter 4300 m a s l mont blanc in order to understand the flow of firn ice in this high altitude alpine glacierized area accumulation measurements from stakes show a very strong spatial variability and an unusual feature of mass balance fluctuations for the alps i e the snow accumulation does not show any seasonal patterns measured vertical velocities which should match with long term mean mass balance are consistent with observed accumulations therefore the measurement of vertical velocities seems a good way of quickly obtaining reliable mean accumulation values for several decades in such a region a simple flow model can be used to determine the main flowlines of the glacier and to propose snow ice age of core samples from the two boreholes drilled down t the bedrock in june 1994 these results coincide with radioactivity measurements made to identify the well known radioactive snow layers of 1963 and 1986 we can hope to obtain ice samples 55 60 years old about 20 or 30 m above the bedrock 110 m deep below the deformation of the ice layers is loo great to be dated accurately

origin of coexisting minette and ultramafic breccia navajo volcanic field trace element evidence indicates that at the buell park diatreme navajo volcanic field the felsic minette can be best explained by crystal fractionation from a potassic magma similar in composition to the mafic minettes compatible trace element cr ni sc abundances decrease while concentrations of most incompatible elements ce yb rb ba sr remain constant or increase from mafic to felsic minette in particular the nearly constant ce yb ratio of the minettes combined with the decrease in cr ni and sc abundances from mafic to felsic minette is inconsistent with a model of varying amounts of partial melting as the process to explain minette compositions the uniformity of rare earth element ree abundances in all the minettes requires that an accessory mineral apatite dominated the geochemistry of the ree during fractionation a decrease in p2o5 from mafic to felsic minette and the presence of apatite in cognate inclusions are also consistent with apatite fractionation higher initial87sr 86sr ratios in the felsic minettes relative to the proposed parental mafic minettes however is inconsistent with a simple fractionation model also a separated phlogopite has a higher initial87sr 86sr ratio than host minette these anomalous isotopic features probably reflect interaction of minette magma with crust the associated ultramafic breccia at buell park is one of the navajo kimberlites but ree concentrations of the matrix do not support the kimberlite classification although the matrix of the breccia is enriched in the light ree relative to chondrites and has high la rb ba and sr concentrations relative to peridotites the concentrations of these elements are significantly lower than in south african kimberlites a high initial87sr 86sr ratio combined with petrographic evidence of ubiquitous crustal xenoliths in the navajo kimberlites suggests that the relatively high incompatible element concentrations are due to a crustal component apparently navajo kimberlites are most likely a mixture of comminuted mantle wall rock and crustal material there is no evidence for an incompatible element rich magma which is characteristic of south african kimberlites if the mafic minettes are primary magmas derived from a garnet peridotite source with chondritic ree abundances then ree geochemistry requires very small less than 1 degrees of melting to explain the minettes alternatively the minettes could have formed by a larger degree of melting of a metasomatized relatively light ree enriched garnet peridotite the important role of phlogopite and apatite in the differentiation of the minettes supports this latter hypothesis

210pb dating of cold alpine firn ice cores from colle gnifetti switzerland datation 210 pb 210 po d une carotte de glacier froid le taux d accumulation corrige est de 39 cm an pour une carotte de 1977 65 m

brittle creep in basalt and its application to time dependent volcano deformation time dependent brittle deformation is a fundamental and pervasive process operating in the earth s upper crust its characterization is a pre requisite to understanding and unraveling the complexities of crustal evolution and dynamics the preferential chemical interaction between pore fluids and strained atomic bonds at crack tips a mechanism known as stress corrosion allows rock to fail under a constant stress that is well below its short term strength over an extended period of time a process known as brittle creep here we present the first experimental measurements of brittle creep in a basic igneous rock a basalt from mt etna volcano under triaxial stress conditions results from conventional creep experiments show that creep strain rates are highly dependent on the level of applied stress and can be equally well fit by a power law or an exponential law with a 20 increase in stress producing close to three orders of magnitude increase in creep strain rate results from stress stepping creep experiments show that creep strain rates are also influenced by the imposed effective confining pressure we show that only part of this change can be attributed to the purely mechanical influence of an increase in effective pressure with the remainder interpreted as due to a reduction in stress corrosion reactions the result of a reduction in crack aperture that restricts the rate of transport of reactive species to crack tips overall our results also suggest that a critical level of crack damage is required before the deformation starts to accelerate to failure regardless of the level of applied stress and the time taken to reach this point the experimental results are discussed in terms of microstructural observations and fits to a macroscopic creep law and compared with the observed deformation history at mt etna volcano c 2011 elsevier b v all rights reserved

glaciochemical dating of an ice core from upper grenzgletscher 4200 m a s l one crucial condition for the interpretation of ice core records is the establishment of an accurate time scale this task is especially difficult for glacier sites in a complex topography such as the alps due to the often irregular deposition of fresh precipitation in this work dating techniques were applied to an alpine ice core from upper grenzgletscher monte rosa massif 4200 m a s l representing about two thirds of the total glacier thickness they are based on i the radioactive decay of the isotope 210 pb ii seasonally varying signals such as the concentrations of nh 4 and the isotopic ratio 18 o and iii stratigraphic markers from saharan dust falls atmospheric nuclear weapon tests and the reactor accident in chernobyl from the combined application of these dating methods a time period of 1937 94 covered by the ice core was derived dating uncertainty is 1 year for the period 1970 94 and 2 years for the period 1937 69 the observed thinning of the annual layers as a function of depth could be well described by a simple kinematic glacier flow model

subdivision of the mg suite noritic rocks into mg gabbronorites and mg norites mg suite noritic rocks can be divided into two groups the mg gabbronorites and the mg norites the rocks of these groups differ in ratios of high ca pyroxene to total pyroxene compositions of pyroxene and plagioclase assemblages of ti nb and zr bearing minerals compositions of chrome spinel bulk rock ti sm and sc sm and measured ages the two groups probably crystallized from different types of parent magmas two hypotheses are offered for the differences in composition of the parent magmas one hypothesis ascribes the differences to compositional heterogeneity of the mantle source areas the other hypothesis ascribes the differences to variations in extent of partial melting of the mantle source regions and variations in extent of assimilation of the anorthosite and the highly differentiated residual liquid that were produced during the primordial lunar differentiation

coupled reservoir geomechanical analysis of the potential for tensile and shear failure associated with co2 injection in multilayered reservoir caprock systems coupled reservoir geomechanical simulations were conductedto study the potential for tensile and shear failure e g tensilefracturing and shear slip along pre existing fractures associated withunderground co2 injection in a multilayered geological system thisfailure analysis aimed to study factors affecting the potential forbreaching a geological co2 storage system and to study methods forestimating the maximum co2 injection pressure that could be sustainedwithout causing such a breach we pay special attention to geomechanicalstress changes resulting from upward migration of the co2 and how theinitial stress regime affects the potential for inducing failure weconclude that it is essential to have an accurate estimate of thethree dimensional in situ stress field to support the design andperformance assessment of a geological co2 injection operation moreover we also conclude that it is important to consider mechanical stresschanges that might occur outside the region of increased reservoir fluidpressure e g in the overburden rock between the co2 injectionreservoir and the ground surface

abundance and distribution of ultramafic microbreccia in moses rock dike quantitative application of mapping spectroscopy moses rock dike is a tertiary diatreme containing serpentinized ultramafic microbreccia sum located on the colorado plateau in utah field evidence indicates that sum was emplaced first followed by breccias derived from the permian strata exposed in the walls of the diatreme and finally by complex breccias containing basement and mantle derived rocks sum is primarily found dispersed throughout the matrix of the diatreme we examined the nature of sum abundance and spatial distribution using data collected remotely by the airborne imaging spectometer ais the minerals serpentine gypsum and illite as well as desert varnish and the lithologies sum and various sandstones were identified from the ais data six end members sum two types of sandstone gypsiferous soil clay rich soil desert varnish were chosen to represent the dominant lithologies of the surface in moses rock dike region spectra of these end members were used in an intimate mixing model to deconvolve the ais spectral data into surface abundance coefficients for each component using a nonnegative least squares inverse algorithm the results of this calculation of surface composition are consistent with field observations and investigations sum distribution and abundance in the matrix of the diatreme were examined in detail and two distinct styles of sum dispersion were observed one style is characterized by high to moderate sum abundance surrounded by halos of lesser sum abundance the dispersion halos grade steeply into regions of the matrix with little to no sum the second style is characterized by moderate sum abundances and broad dispersion halos with sum distributed across the entire width of the diatreme these dispersion styles are consistent with emplacement of the dike as a fluidized solid volatile system where sum which is emplaced early becomes reincorporated into the turbulent flow of the diatreme by abrasion and comminution by paniculate matter carried along in the eruption this eroded material is then dispersed throughout the matrix by eddy diffusion the first style represents an early arrested phase of the eruption sequence while the second style represents a more mature phase distributions of the second style probably indicate the location of channels where flow was concentrated during later stages of eruption since both styles are observed at the same level of erosion this indicates that the duration of eruption varied along strike at moses rock dike

elastic anisotropy reversal during brittle creep in shale we conducted two brittle creep experiments on shale samples under upper crustal conditions confining pressure of 80 mpa at 26 c and 75 c we deformed the samples to failure with bedding oriented perpendicular to the maximum compressive stress direction using the stress stepping methodology in both experiments the failure stress was 64 higher than the short term peak strength throughout each differential stress step ultrasonic wave velocities initially decreased and then gradually increased with deformation time the magnitude of these variations depends both on the direction of measurement with respect to the bedding and the temperature and it is largest for velocities measured parallel to the bedding and at high temperature elastic wave anisotropy was completely reversed at 75 c following a limited amount of axial strain 0 6 sem investigation confirmed evidence of a time dependent pressure solution localized compaction crack sealing healing and mineral rotation our observations reveal that elastic anisotropy can evolve rapidly in both time and space which has implications on the stress state and its rotation near fault zones

quantitative analysis of planetary reflectance spectra with principal components analysis a technique is presented for quantitative analysis of planetary reflectance spectra as mixtures of particles on microscopic and macroscopic scales using principal components analysis this technique allows for determination of the endmembers being mixed their abundance and the scale of mixing as well as other physical parameters eighteen lunar telescopic reflectance spectra of the copernicus crater region from 600 nm to 1800 nm in wavelength are modeled in terms of five likely endmembers mare basalt mature mare soil anorthosite mature highland soil and clinopyroxene these endmembers were chosen from a similar analysis of 92 lunar soil and rock samples the models fit the data to within 2 rms it is found that the goodness of fit is marginally better for intimate mixing over macroscopic mixing

coupled multiphase flow and poromechanics a computational model of pore pressure effects on fault slip and earthquake triggering the coupling between subsurface flow and geomechanical deformation is critical in the assessment of the environmental impacts of groundwater use underground liquid waste disposal geologic storage of carbon dioxide and exploitation of shale gas reserves in particular seismicity induced by fluid injection and withdrawal has emerged as a central element of the scientific discussion around subsurface technologies that tap into water and energy resources here we present a new computational approach to model coupled multiphase flow and geomechanics of faulted reservoirs we represent faults as surfaces embedded in a three dimensional medium by using zero thickness interface elements to accurately model fault slip under dynamically evolving fluid pressure and fault strength we incorporate the effect of fluid pressures from multiphase flow in the mechanical stability of faults and employ a rigorous formulation of nonlinear multiphase geomechanics that is capable of handling strong capillary effects we develop a numerical simulation tool by coupling a multiphase flow simulator with a mechanics simulator using the unconditionally stable fixed stress scheme for the sequential solution of two way coupling between flow and geomechanics we validate our modeling approach using several synthetic but realistic test cases that illustrate the onset and evolution of earthquakes from fluid injection and withdrawal

investigating the dynamics of an alpine glacier using probabilistic icequake locations triftgletscher switzerland 1 in order to improve our understanding of the dynamics of potentially unstable steep glacier tongues we monitored during summer 2010 the micro seismicity of triftgletscher switzerland our system comprising 8 three component seismometers coupled with the ice surface was installed upstream of the glacier s tongue which is likely to evolve toward an unstable regime complementary surface motion and proglacial runoff measurements allowed the icequake activity to be interpreted in terms of glacier dynamics and hydraulics the strong contrast in seismic wave velocities due to the underlying bedrock was taken into account using a three dimensional 3 d velocity model implemented in a nonlinear probabilistic location procedure allowing to accurately define the hypocenter uncertainty we located 120 icequakes with a focal depth accuracy that allowed distinguishing between shallow events 87 events and near bedrock icequakes 33 events the first motions of most of the deep events argue against pure shear sources expected in case of stick slip motion and our suggested source mechanism is a superimposed tensile crack and shear dislocation the analysis of surface strain showed that near surface events represent the opening and transverse extension of surface crevasses in a confluent flow regime

origin of olivine at copernicus the central peaks of copernicus are among the few lunar areas where near infrared telescopic reflectance spectra indicate extensive exposures of olivine other parts of copernicus crater and ejecta which were derived from highland units in the upper parts of the target site contain only low ca pyroxene as a mafic mineral the exposure of compositionally distinct layers including the presence of extensive olivine may result from penetration to an anomalously deep layer of the crust or to the lunar mantle we suggest that the procellarum basin and the younger superposed insularum basin have provided access to these normally deep seated crustal or mantle materials by thinning the upper crustal material early in lunar history the occurrences of olivine in portions of the compositionally heterogeneous aristarchus region in a related geologic setting may be due to the same sequence of early events

nonlinear viscoelastic behavior of sedimentary rocks part ii hysteresis effects and influence of type of fluid on elastic moduli uniaxial stress cycling experiments were conducted on dry brine saturated and hexadecane saturated berea sandstone samples to observe in detail the hysteresis in stress strain diagrams and to understand the influence of different fluids on the strain amplitude dependence of elastic moduli and attenuation cycling experiments were also conducted with sandstone samples saturated with ctab a cationic surfactant that renders the mineral surfaces hydrophobic hexadecane and ctab were selected so as to investigate the relative contributions of adhesion hysteresis and stick slip sliding on attenuation in sedimentary granular rocks young s moduli and poisson s ratios obtained from the cycling tests show a significant dependence on strain amplitude on dry as well as water and hexadecane saturated samples bow tie shaped diagrams are obtained when loading and unloading tangent moduli are plotted against strain the type of fluid in the pore space and at the grain contacts has a large influence on the hysteresis observed in the stress strain diagrams

cold firn and ice of high altitude glaciers in the alps measurements and distribution modelling the thermal regime of high altitude accumulation areas in the swiss alps was systematically investigated on the jungfraufirn bernese alps on the breithornplateau valais alps and on grenzgletscher valais alps in 1991 1992 and 1994 temperatures were measured in a deep hole 120 m deep and in several shallow holes 14 30 m deep whereas the wide neve of the jungfraufirn at 3400 3600 m a s l and the 3800 m high breithorn plateau seems to be predominantly temperate cold firn and ice temperatures were measured throughout on grenzgletscher 3900 4450 m a s l mean firn temperatures on grenzgletscher vary strongly and range between 3 and 14 c a comparison between the measured temperature profiles and a one dimensional heat conduction calculation shows that the release of latent heat by penetrating and refreezing meltwater decisively influences the thermal pattern of the firn pack a multiple linear regression model based on measured firn temperatures from the european alps and the parameters altitude and aspect yields aspect dependent lower boundaries for the occurrence of cold firn ranging between 3400 northerly aspects and 4150 m a s l southerly aspects a total of 120 glaciers with cold firn areas are found when applying the model to glacier inventory data from the european alps

is climate change responsible for changing landslide activity in high mountains climate change manifested by an increase in mean minimum and maximum temperatures and by more intense rainstorms is becoming more evident in many regions an important consequence of these changes may be an increase in landslides in high mountains more research however is necessary to detect changes in landslide magnitude and frequency related to contemporary climate particularly in alpine regions hosting glaciers permafrost and snow these regions not only are sensitive to changes in both temperature and precipitation but are also areas in which landslides are ubiquitous even under a stable climate we analyze a series of catastrophic slope failures that occurred in the mountains of europe the americas and the caucasus since the end of the 1990s we distinguish between rock and ice avalanches debris flows from de glaciated areas and landslides that involve dynamic interactions with glacial and river processes analysis of these events indicates several important controls on slope stability in high mountains including the non linear response of firn and ice to warming three dimensional warming of subsurface bedrock and its relation to site geology de glaciation accompanied by exposure of new sediment and combined short term effects of precipitation and temperature based on several case studies we propose that the following mechanisms can significantly alter landslide magnitude and frequency and thus hazard under warming conditions 1 positive feedbacks acting on mass movement processes that after an initial climatic stimulus may evolve independently of climate change 2 threshold behavior and tipping points in geomorphic systems 3 storage of sediment and ice involving important lag time effects

temperature and accumulation of high altitude firn in the alps data on temperature and accumulation of high altitude firn in the alps are compiled and discussed firn temperature varies with incoming radiation slope aspect at a given altitude the altitudinal gradient of temperature in highly permeable firn bodies appears to be about twice as high as the mean lapse rate of air temperature cold infiltration takes place above about 3500 m a s firn temperatures on the highest peaks are around 15 c accumulation net balance also decreases with increasing altitude from about 3m h20 at 3500 m a s to around 0 5 m h20 at wind exposed sites between 4300 and 4800 m a s l probably this is strongly due to wind erosion and topographical effects however temperature and accumulation not only appear to be interrelated but also seem to be positively correlated to the heat applied to the surface assuming the observed altitudinal gradients have remained constant in time it can be estimated that high altitude firn bodies have become considerably warmer since the last century co2 induced atmospheric warming could lead to a drastic change in the mass turnover and flow activity of high glaciers in wind exposed places where wind erosion of the snowpack becomes a controlling factor of accumulation introduction studies on mass and heat exchange at the surface of alpine firn have usually been carried out at altitudes below about 3500 m a s where firn is temperate and accumulation is high eg lang and others 1977 muller 1977 access to firn regions of higher altitudes is difficult however rather unusual construction work eg refuge lenkins on mont blanc and a number of tunnels dug into the firn of the monte rosa region by j e fisher in the 1950s furnished some information which indicated that at high altitudes firn is cold and accumulation does not further increase with altitude interest in temperature and accumulation of high altitude firn has grown recently in connection with i englacial temperatures 2 ice avalanches and 3 alpine core drilling temperature distribution in the tongue of grenzgletscher one of the largest ice bodies in the alps must be caused by advection of cold ice from high altitudes blatter and haeberli 1984 the frequency of ice avalanches ultimately depends on the accumulation of firn alean 1985 and the stability of steep mountain glaciers seems to depend on firn and ice temperatures rothlisberger 198 1 alean 1984 finally core drilling projects in cold high alpine firn and ice provide important information about the evolution of the composition of the atmosphere in heavily industrialized regions over past decades and centuries eg wagenbach and others in press but require knowledge about the distribution of accumulation in space and time the aims of the present study are to compile information available and point to possible effects of recent atmospheric warming firn temperature temperature measurements from deep pits tunnels and shallow bore holes in high altitude firn of the alps have been compiled by haeberli 1976 cf also hooke and others 1983 new information is available from chli titlis jungfraujoch sphinxgrat and monte rosa colle gnifetti all swiss alps at chli titlis 3070 m a s i 15 m temperature in the summit s 22 m thick firn and ice was 0 7 c 1979 80 cf haeberli and others 1979 temperatures in the sphinxgrat crest were measured in a 70 m borehole through firn ice and perennially frozen rocks in connection with recent construction work at the jungfraujoch the ice rock interface 10 m below the surface at 3525 m a s had a temperature close to 6 c 198 1 temperatures around 14 c at 15 m depth were registered in all core drilling boreholes made so far on colle gnifetti 4450 m a s the fim ice transition in this cold firn saddle occurs about 40 m below the surface schotterer and others 1981 when presently known firn temperatures are compiled figure i two groups seem to exist group i incorporates summits crests and probably also very steep slopes 45 which mainly consist of impermeable ice or high density firn with high concentrations of ice layers temperatures in such ice bodies decrease with increasing altitude at a rate about i c ioo m which is slightly higher than the assumed lapse rate of mean annual air temperature 0 65 c ioo m no temperate firn bodies are known in such situations in contrast more gentle slopes and basins group 2 where highly permeable firn accumulates are temperate up to about 3600 m a s above this upper boundary of the warm infiltration zone of the alps percolating meltwater cannot

cold ice in the ablation zone its relation to glacier hydrology and ice water content 1 cold ice within a polythermal ice body controls its flow dynamics through the temperature dependence of viscosity and affects glacier hydrology by blocking water flow paths lakes on the surface linked by persistent deeply incised meltwater streams are hallmark features of cold ice in the ablation zone of a glacier or ice sheet ice radar is a convenient method to map scattering from internal water bodies present in ice at the pressure melting temperature pmt consequently lack of internal scatters is indicative of cold ice we use a helicopter borne 30 mhz ice radar to delineate the extent of cold ice within grenzgletscher zermatt swiss alps the inferred thermal structure is validated with temperature measurements in 15 deep boreholes showing excellent agreement the cold ice occupies 80 90 of the total ice thickness in a 400 m wide flow band along the central flow line quantitative interpretation of ice radar scattering power indicates a decrease of ice water content between pmt and 0 5 k below pmt as predicted by theory and observed in the laboratory the cold ice which emerges at the surface in the lower ablation zone is impermeable to water and is thus devoid of moulins if not crevassed the surface water from melt and rain is routed through deeply incised persistent streams and lakes and cryoconite holes are frequent in stark contrast to the adjacent temperate ice from other tributaries the cold ice thus has a strong control on glacier hydrology but is likely to change due to continued warming

improved discrimination of subglacial and periglacial erosion using 10be concentration measurements in subglacial and supraglacial sediment load of the bossons glacier mont blanc massif france deciphering the complex interplays between climate uplift and erosion is not straightforward and estimating present day erosion rates can provide useful insights glaciers are thought to be powerful erosional agents but most published glacial erosion rates combine periglacial subglacial and proglacial erosion processes within a glaciated catchment sediments found in subglacial streams originate either from glacial erosion of substratum or from the rock walls above the glacier that contribute to the supraglacial load terrestrial cosmogenic nuclides tcn are produced by interactions between cosmic ray particles and element targets at the surface of the earth but their concentration becomes negligible under 15 m of ice measuring tcn concentrations in quartz sand sampled in subglacial streams and in supraglacial channels is statistically compliant with stochastic processes e g rockfalls and may be used to discriminate subglacial and periglacial erosion results for two subglacial streams of the bossons glacier mont blanc massif france show that the proportion of sediments originating from glacially eroded bedrock is not constant it varies from 50 to 90 n 6 the difference between the two streams is probably linked to the presence or absence of supraglacial channels and sinkholes which are common features of alpine glaciers therefore most of the published mean catchment glacial erosion rates should not be directly interpreted as subglacial erosion rates in the case of catchments with efficient periglacial erosion and particularly rockfalls the proportion of sediments in the subglacial stream originating from the supraglacial load could be considerable and the subglacial erosion rate overestimated here we estimate warm based subglacial and periglacial erosion rates to be of the same order of magnitude 0 39 0 33 and 0 29 0 17 mm a 1 respectively

lunar and terrestrial crust formation planetary crusts may be accreted produced in primordial differentiation or built up piecemeal by serial magmatism the existence of old polygenetic laterally heterogeneous partial melt rocks in the lunar highlands suggests that the moon produced its early crust by serial magmatism this view can be reconciled with lunar eu anomalies previously thought to support the magma ocean model of crust formation if complications in the fractionation of mare basalts are recognized phase equilibrium and magmatic density information for mare basalts suggest a model in which plagioclase fractionation can occur even though plagioclase is not a near liquidus phase the cryptic fractionation of clinopyroxene in morb provides a precedent for this model the necessity for a lunar magma ocean is questioned but a role for a terrestrial magma ocean of sorts at depth is suggested

copernicus crater central peak lunar mountain of unique composition olivine is identified as the major mafic mineral in a central peak of copernicus crater information on the mineral assemblages of such unsampled lunar surface material is provided by near infrared reflectance spectra 0 7 to 2 5 micrometers obtained with earth based telescopes the composition of the deep seated material comprising the copernicus central peak is unique among measured areas other lunar terra areas and the wall of copernicus exhibit spectral characteristics of mineral assemblages comparable to the feldspathic breccias returned by the apollo missions with low calcium orthopyroxene being the major mafic mineral