major pathways of atlantic water in the northern north atlantic and nordic seas toward arctic 1 the major pathways of near surface atlantic water in the northern north atlantic and nordic seas are identified as current speeds above 30 cm s using 1014 lagrangian drifters combined with previously published hydrography the inflow over the scotland greenland ridge and establishment of the two branch norwegian atlantic current nwac are described in light of the circulation in the northern north atlantic the western branch of the nwac appears as a jet in the polar front topographically guided from the iceland faroe front through the nordic seas toward fram strait the eastern branch starts as a shelf edge current above the irish scottish continental shelf and after passing through the faroe shetland channel it continues northward along the norwegian shelf edge toward the arctic with a branch bifurcating into the barents sea the nwac appears to maintain its two branch structure throughout the nordic seas with the atlantic water confined to a 200 600 km wide wedge

paraglacial rock slope stability glaciation and deglaciation along with their associated climatic and non climatic processes modify slope stresses and influence slope stability paraglacial slope failures are those that are a part of or influenced by the transition from glacial conditions to non glacial conditions gravitational failure of rock slopes is a primary and dominant process of slope evolution in mountainous terrain and is the subject of this paper which 1 reviews the approaches taken for researching paraglacial rock slope failure patterns and processes 2 summarises the spatial and temporal patterns of post glacial failures 3 assesses the factors influencing slope stability during glaciation and deglaciation 4 explores some of the applications of paraglacial research and 5 highlights some of the outstanding issues to be resolved and provides recommendations for terminology relating to paraglacial slope processes

eddy formation near the west coast of greenland abstract this paper extends a bracco and j pedlosky s investigation of the eddy formation mechanism in the eastern labrador sea by including a more realistic depiction of the boundary current the quasigeostrophic model consists of a meridional coastally trapped current with three vertical layers the current configuration and topographic domain are chosen to match as closely as possible the observations of the boundary current and the varying topographic slope along the west greenland coast the role played by the bottom intensified component of the boundary current on the formation of the labrador sea irminger rings is explored consistent with the earlier study a short localized bottom trapped wave is responsible for most of the perturbation energy growth however for the instability to occur in the three layer model the deepest component of the boundary current must be sufficiently strong highlighting the importance of the near bottom flow the model is able to reproduce important features o

gravitational slope deformation of a resurgent caldera new insights from the mechanical behaviour of mt nuovo tuffs ischia island italy abstract ischia island italy is an impressive example of the rare phenomenon of caldera resurgence the emplacement and replenishment of magmas at shallow depth resulted in a vertical uplift of about 900 m concentrated in the western portion of mt epomeo 789 m a s l as a consequence of this uplift the island has experienced several slope instabilities at different scales since the holocene from shallow mass movements to large rock and debris avalanches these mass wasting events which mobilised large volumes of greenish alkali trachytic tuff the mt epomeo green tuff megt were strictly related to volcano tectonic activity and the interaction between the volcanic slopes and the hydrothermal system beneath the island deep seated gravitational slope deformation dsgsd at mt nuovo located adjacent to densely populated coastal villages is an ongoing process that covers an area of 1 6 km 2 the mt nuovo dsgsd involves a rock mass volume of 190 mm 3 and is accommodated by a main shear zone and a series of sub vertical fault zones associated with high angle joint sets to improve our understanding of this gravity induced process we performed a physical porosity and permeability and mechanical uniaxial and triaxial deformation experiments characterisation of two ignimbrite deposits both from the megt that form a significant component of the nw sector of mt epomeo the main conclusions drawn from our experiments are twofold first the presence of water dramatically reduces the strength of the tuffs suggesting that the movement of fluids within the hydrothermal system could greatly impact slope stability second the transition from brittle dilatant to ductile compactant behaviour in the tuffs of the megt occurs at a very low effective pressure analogous to a depth of a couple of hundred metres and that this transition is likely moved closer to the surface in the presence of water we hypothesise that compactant porosity decreasing behaviour at the base of the layer could therefore facilitate slope instability although our results show that transient exposure to 300 c does not influence the short term strength of the tuff we speculate that the high in situ temperature could increase the efficiency of brittle and compactant creep and therefore increase the rate of slope deformation taken together our experimental data highlight a potentially important role for the hydrothermal system that reaches a minimum depth of 1 km in dictating the dsgsd at mt nuovo an understanding of this deformation process is not only important for the proximal coastal villages at risk of engulfment by a large debris avalanche but also for the towns and cities along the coast of the gulf of naples that are at risk to a secondary consequence of such an avalanche a tsunami wave

numerical analysis of initiation and progressive failure in natural rock slopes the 1991 randa rockslide the 1991 randa rockslide in the swiss alps involved several complex mechanisms relating to geological mechanical and hydrological processes for which no clear trigger can be asserted this paper investigates the concept of progressive failure and the numerical modelling of rock mass strength degradation in natural rock slopes using the randa rockslide as a working example results from continuum i e finite element modelling are presented to illustrate a hypothesis suggesting that initiation of a progressive rock mass degradation process ultimately leading to failure began following deglaciation of the valley below discontinuum distinct element modelling is then applied to investigate the underlying mechanisms contributing to the episodic nature of the rockslide finally the use of a hybrid method that combines both continuum and discontinuum techniques to model fracture propagation are discussed in the context of modelling progressive slide surface development linking initiation and degradation to eventual catastrophic failure

boundary current eddies and their role in the restratification of the labrador sea an idealized model is used to study the restratification of the labrador sea after deep convection with emphasis on the role of boundary current eddies shed near the west coast of greenland the boundary current eddies carry warm buoyant irminger current water into the labrador sea interior for a realistic end of winter state it is shown that these irminger current eddies are efficient in restratifying the convected water mass in the interior of the labrador sea in addition it is demonstrated that irminger current eddies can balance a significant portion of the atmospheric heat loss and thus play an important role for the watermass transformation in the labrador sea

composite rock slope kinematics at the current randa instability switzerland based on remote sensing and numerical modeling abstract kinematic analysis of slope instabilities in brittle rock is crucial for understanding the reaction of the rock mass to external forcing factors in steep terrain inaccessibility often limits collection of relevant data and remote sensing techniques must be applied this is the case at the current randa rock slope instability in southern switzerland where a total volume of about 5 6 million m3 moves at a rate of up to 30 mm yr a large portion of the unstable rock mass is exposed in an 800 m high inaccessible cliff the main scarp of the may 1991 rock slope failure between 2005 and 2007 a comprehensive suite of remote sensing techniques including photogrammetry lidar and gb dinsar was combined with 3d geodetic measurements to characterize the rock mass structure and displacement patterns photogrammetry and lidar data were measured simultaneously from a helicopter using a system allowing for oblique view angles which provided optimal observations of the steep rock cliff we used these datasets to map large scale structures and extract their orientation and minimum persistence as well as to characterize the 1991 failure scarp the northern part of the may 1991 failure surface shows a transition from stepped planar sliding at the base to failed rock bridges in the center to tensile failure close to the vertical head scarp kinematic analysis of the discontinuity sets in the currently moving rock mass shows that both toppling and translational sliding are feasible failure mechanisms toppling is more likely for steep faces above 2200 m whereas translational failure is more likely in the lower portion of the instability interpretation of gb dinsar displacement maps revealed similar kinematic behavior and also allowed identification of a basal rupture zone and lateral release plane bounding the instability displacement vectors derived from geodetic surveying provided new insights into the 3d kinematic behavior of the instability all information extracted from different data sets were integrated in a conceptual model which was then investigated with 2d numerical simulation using the discontinuum code udec the numerical models were able to reproduce the hypothesized kinematic behavior well

observed sources and variability of nordic seas overflow the overflows from the nordic seas maintain the deep branch of the north atlantic circulation that is an important part of the global climate system an analysis of observed ocean temperatures and salinities between 1950 and 2005 shows that the atlantic water circulating in the nordic seas is the main source for change in the overflow waters

near surface circulation in the northern north atlantic as inferred from lagrangian drifters variability from the mesoscale to interannual 1 the near surface circulation of the nordic seas is basically cyclonic and consists of jets and recirculation cells which are tightly linked to the bottom topography variable forcing by the large scale rotation of the wind leads to a modulation in the strength of the gyres and their interconnecting jets this is seen in drifter and altimeter data currents are stronger during winter and during phases of high north atlantic oscillation index the exchanges between the north atlantic and the nordic seas do not seem to be directly affected by this variable forcing the narrow boundary currents and the intergyre jets are subject to instability causing mesoscale current fluctuations which contribute to the stirring and mixing of polar and atlantic water masses

parent material controlled subsoil weathering in a chronosequence the allier terraces limagne rift valley france abstract the chronosequence in the allier terraces is subject to erratic changes in parent material composition with time approximately 65 of the total variance in the basaltic elements content in the allier terrace sands can be explained by the combined effect of parent material and time related neoformation of clay in the subsoil it is shown that parent material composition as a function of transport distance strongly influences weathering rate in the allier terrace chronosequence in order to evaluate parent material controlled weathering effects a process model simulation was made based on an exponential decrease of mgo and neoformation of clay long term simulations with this model suggest that parent material controlled subsoil weathering is significant for sediments with easy weatherable fragments after prolonged weathering the role of parent material decreases and becomes untraceable in strongly weathered materials

thermally vs seismically induced block displacements in masada rock slopes we compare thermally and seismically induced sliding mechanisms of blocks that are separated from the rock mass by a tension crack and slide along a frictional interface the rock slopes of masada mountain israel are used to demonstrate our approach crack displacement coupled with thermal fluctuations is measured in the west slope of the mountain during two years 2009 11 physical and mechanical lab tests provide the assumed depth of penetration of the heating front during seasonal cycles of exposure as well as the thermal expansion coefficient of the rock mass these along with the shear stiffness of the sliding interface allow us to quantify the expected thermally induced displacement rate of blocks in masada through a proposed wedging ratcheting failure mechanism a distinct block in the east slope of the mountain exhibiting a tension crack opening of 200 mm was monitored for displacement and temperature during a single seasonal cycle in 1998 based on the assumed seismicity of the region and the known topographic site effect along with the laboratory measured frictional resistance and shear stiffness of the sliding interface we subject the mapped geometry of the block in the east face to simulated cycles of earthquake vibrations utilizing the numerical discrete element discontinuous deformation analysis dda method we find that for a time window of 5000 years the observed 200 mm displacement of the east slope block is more likely to have been thermally rather than seismically controlled this result implies that in climatic regions where the temperature amplitude over a seasonal cycle is sufficiently high thermally induced displacements play an important role in rock slope erosion

thermomechanical forcing of deep rock slope deformation 1 conceptual study of a simplified slope 1 thermo elastic rock slope deformation is often considered to be of relatively minor importance and limited to shallow depths subject to seasonal warming and cooling in this study we demonstrate how thermomechanical tm effects can drive rock slope deformation at greater depths below the annual thermal active layer here in part 1 of two companion papers we present 2d numerical models of a simplified slope subject to annual surface temperature cycles the slope geometry and discontinuity sets are loosely based on the randa instability considered in detail in part 2 results show that near surface thermo elastic stresses can propagate to depths of 100 m and more as a result of topography and elasticity of the rock mass shear dislocation along discontinuities can have both a reversible component controlled by discontinuity compliance and provided that the stress state is sufficiently close to the strength limit an irreversible component i e slip induced slip increments are followed by stress redistribution resulting in the propagation of slip fronts thus deformation and progressive rock slope failure can be driven solely by thermomechanical forcing the influence of tm induced stress changes becomes stronger for increasing numbers of critically stressed discontinuities and is enhanced if failure of discontinuities involves slip weakening the net tm effect acts as a meso scale fatigue process involving incremental discontinuity slip and hysteresis driven by periodic loading

dynamics of downwelling in an eddy resolving convective basin the mean downwelling in an eddy resolving model of a convective basin is concentrated near the boundary where eddies are shed from the cyclonic boundary current into the interior it is suggested that the buoyancyforced downwelling in the labrador sea and the lofoten basin is similarly concentrated in analogous eddy formation regions along their eastern boundaries use of a transformed eulerian mean depiction of the density transport reveals the central role eddy fluxes play in maintaining the adiabatic nature of the flow in a nonperiodic region where heat is lost from the boundary current the vorticity balance in the downwelling region is primarily between stretching of planetary vorticity and eddy flux divergence of relative vorticity althougha narrowviscous boundarylayeris ultimately importantin closingtheregionalvorticitybudget this overall balance is similar in some ways to the diffusive viscous balance represented in previous boundary layer theories and suggests that the downwelling in convective basins may be properly represented in lowresolution climate models if eddy flux parameterizations are adiabatic identify localized regions of eddy formations and allow density to be transported far from the region of eddy formations

kinematics of steep bedrock permafrost 1 the mechanisms that control climate dependent rockfall from permafrost mountain slopes are currently poorly understood in this study we present the results of an extensive rock slope monitoring campaign at the matterhorn switzerland with a wireless sensor network a negative dependency of cleft expansion relative to temperature was observed at all clefts for the dominant part of the year at many clefts this process is interrupted by a period with increased opening and shearing activity in the summer months more specific this period lasts from sustained melting within the cleft to the first freezing in autumn based on these empirical findings we identify two distinct process regimes governing the cleft motion observed combining current theories with laboratory evidence on rock slope movement and stability we postulate that 1 the negative temperature dependency is caused by thermomechanical forcing and is reinforced by cryogenic processes during the freezing period and 2 the enhanced movement in summer originates from a hydro thermally induced strength reduction in clefts containing perennial ice it can be assumed that the irreversible part of the process described in 1 slowly modifies the geometric settings and cleft characteristics of permafrost rock slopes in the long term the thawing related processes 2 can affect stability within hours or weeks such short term stability minima may activate rock masses subject to the slow changes and lead to acceleration and failure

variability of the norwegian atlantic current and associated eddy field from surface drifters the norwegian atlantic current nwac and its eddy field are examined using data from surface drifters the data set used spans nearly 20 years from june 1991 to december 2009 the results are largely consistent with previous estimates which were based on data from the first decade only with our new data set statistical analysis of the mean fields can be calculated with larger confidence the two branches of the nwac one over the continental slope and a second further offshore are clearly captured the norwegian coastal current is also resolved in addition we observe a semipermanent anticylonic eddy in the lofoten basin a feature seen previously in hydrography and in models the eddy kinetic energy eke is intensified along the path of the nwac with the largest values occurring in the lofoten basin the strongest currents exceeding 100 cm s 1 occur west of lofoten lateral diffusivities were computed in five domains and ranged from 1 5 107 cm2 s 1 the lagrangian integral time and space scales are 1 2 days and 7 23 km respectively the data set allows studies of seasonal and interannual variations as well the strongest seasonal signal is in the nwac itself as the mean flow strengthens by approximately 20 in winter the eke and diffusivities on the other hand do not exhibit consistent seasonality in the sampled regions there are no consistent indications of changes in either the mean or fluctuating surface velocities between the 1990s and 2000s

beyond debuttressing mechanics of paraglacial rock slope damage during repeat glacial cycles cycles of glaciation impose mechanical stresses on underlying bedrock as glaciers advance erode and retreat fracture initiation and propagation constitute rock mass damage and act as preparatory factors for slope failures however the mechanics of paraglacial rock slope damage remain poorly characterized using conceptual numerical models closely based on the aletsch glacier region of switzerland we explore how in situ stress changes associated with fluctuating ice thickness can drive progressive rock mass failure preparing future slope instabilities our simulations reveal that glacial cycles as purely mechanical loading and unloading phenomena produce relatively limited new damage however ice fluctuations can increase the criticality of fractures in adjacent slopes which may in turn increase the efficacy of fatigue processes bedrock erosion during glaciation promotes significant new damage during first deglaciation an already weakened rock slope is more susceptible to damage from glacier loading and unloading and may fail completely we find that damage kinematics are controlled by discontinuity geometry and the relative position of the glacier ice advance and retreat both generate damage we correlate model results with mapped landslides around the great aletsch glacier our result that most damage occurs during first deglaciation agrees with the relative age of the majority of identified landslides the kinematics and dimensions of a slope failure produced in our models are also in good agreement with characteristics of instabilities observed in the field our results extend simplified assumptions of glacial debuttressing demonstrating in detail how cycles of ice loading erosion and unloading drive paraglacial rock slope damage

direct observation of frost wedging in alpine bedrock width and temperature of rock joints were automatically monitored in the japanese alps three years of monitoring on a sandstone rock face shows two seasonal peaks of joint widening in autumn and spring the autumn events are associated with short term freeze thaw cycles and the magnitude of widening reflects the freezing intensity and water availability the short term freezing can produce wedging to a depth of at least 20 cm the spring events follow a rise in the rock surface temperature to 0 c beneath the seasonal snowcover and likely originate from refreezing of meltwater entering the joint some of these events contribute to permanent enlargement of the joint two other joints on nearby rock faces experience only sporadic widening accompanying freeze thaw cycles and insignificant permanent enlargement observations indicate that no single thermal criterion can explain frost weathering the temperature range at which wedging occurs varies with the bedrock conditions water availability and duration of freezing copyright 2001 john wiley sons ltd

a 2400 yr record of natural events and anthropogenic impacts in intercorrelated terrestrial and marine sediment cores waipaoa sedimentary system new zealand the waipaoa sedimentary system spans 100 km from terrestrial upland to continental rise alluvial buffering has little effect on sediment flux at the outlet of this mesoscale dispersal system and hinterland to margin transport is accomplished rapidly because of this synergy the floodplain and shelf depocenters are sensitive to changes in sediment production in the hinterland and natural and anthropogenically forced changes in sediment source dynamics that occur at several temporal and spatial scales leave distinctive signals in the stratigraphic record manifested as variations in sediment properties these signals appear in intercorrelated sediment cores from a headwater riparian storage area and the major terrestrial and marine repositories for sediment discharged during the past 2 4 k y the signals represent the landscape response to vegetation and land use change short term fluctuations in climate that affect surface properties and processes and extreme storms and subduction thrust earthquakes extreme storms are the minimum geomorphologically effective event preserved in the sediment records lower magnitude storms that are integral components of the prevailing hydrometeorological regime create high frequency fluctuations in sediment properties and collectively contribute to event sequences of 100 yr duration events and event sequences comprise a hierarchy of temporally sensitive phenomena the impacts of which are conditioned by frequency and magnitude by contrast vegetation disturbance is a spatially sensitive phenomenon that directly impacts sediment source areas and lowers the threshold of landscape sensitivity to erosion for this reason the taupo eruption of 1 718 ka and the piecemeal vegetation changes that occurred after the arrival of polynesian settlers also generated strong depositional signals after european colonization deforestation of the hinterland altered landscape sensitivity and precipitated the transition to an erosional regime that impacted sediment production and dispersal across the entire magnitude frequency spectrum of events regulating sediment delivery to and transport in stream channels no other perturbation had such a profound impact on the late holocene depositional record

air circulation in deep fractures and the temperature field of an alpine rock slope the subsurface temperature field of a rock slope is a key variable influencing both bedrock fracturing and slope stability however significant unknowns remain relating to the effect of air and water fracture flow which can rapidly transmit temperature changes to appreciable depths in this work we analyze a unique set of temperature measurements from an alpine rock slope at 2400 m a s l in southern switzerland the monitored area encompasses part of an active slope instability above the village of randa vs and is traversed by a network of open cracks some of which have been traced to 80 m depth we first describe distributed temperature measurements and borehole profiles highlighting deep steady temperatures and different transient effects and then use these data to approximate the conductive temperature field at the site in a second step we analyze the impact of air and water circulation in deep open fractures on the subsurface thermal field on multiple visits to the study site in winter we consistently noted the presence of warm air vents in the snowpack following the trace of deep tension cracks measurements showed that venting air changed temperature gradually from 3 to 2 c between december and may which is similar to the rock temperature at around 50 m depth comparison with ambient air temperature suggests that winter conditions favor buoyancy driven convective air flow in these fractures which acts to cool the deep subsurface as the rock gives up heat to incoming air the potential impact of this process on the local thermal field is revealed by a disturbed temperature profile in one borehole and transient signals observed at depths well below the thermal active layer seasonal water infiltration during snowmelt appears to have little impact on the temperature field in the monitored area copyright 2011 john wiley sons ltd

in pursuit of anomalies analyzing the poleward transport of atlantic water with surface drifters we examine the trajectories of 168 drifters as a proxy for atlantic water flowing through the nordic seas the drifters were released at or passed through the svinoy section off the west coast of norway for comparison we generate a set of synthetic trajectories using a stochastic model with a range of diffusivities with the both sets we determine the transit times of both drifters and particles from svinoy to arctic gateways the barents sea and spitsbergen the mean arrival times to these locations are roughly 200 and 500 days respectively this implies ample time for cooling of the surface waters which increases densities and permits subduction before reaching the arctic however a range of transit times is seen some parcels reach fram strait in only 4 months while others are still in the southern nordic seas after 2 years the results do not support the idea that temperature or salinity anomalies can exist as coherent packets the drifters passing svinoy when treated as a group quickly spread over large distances mixing with water in the norwegian and lofoten basins thus an anomaly entering the nordic seas would quickly be obliterated however the velocity of the clusters center of mass is consistent with anomaly propagation speeds inferred previously from hydrographic measurements suggesting the observed variability is advective in nature

observed and modeled surface eddy heat fluxes in the eastern nordic seas large scale budget calculations and numerical model process studies suggest that lateral eddy heat fluxes have an important cooling effect on the norwegian atlantic current nwac as it flows through the nordic seas but observational estimates of such fluxes have been lacking here wintertime surface eddy heat fluxes in the eastern nordic seas are estimated from surface drifter data satellite data and an eddy permitting numerical model maps of the eddy heat flux divergence suggest advective cooling along the path of the nwac integrating the flux divergence over temperature classes yields consistent estimates for the three data sets the waters warmer than about 6 c are cooled while the cooler waters are warmed similar integrations over bottom depth classes show that regions shallower than about 2000 m are cooled while deeper regions are warmed finally integrating the flux divergence along the core of the nwac suggests that the highest eddy induced heat loss at the surface is along the steepest part of the continental slope east of the lofoten basin the model fields indicate that cooling of the current by lateral eddy fluxes is comparable to or larger than the local heat loss to the atmosphere

on the shear failure of incipient rock discontinuities under cnl and cns boundary conditions insights from dem modelling abstract this paper presents a numerical investigation of the effects of boundary conditions i e constant normal load cnl and constant normal stiffness cns on the failure mechanism of incipient rock discontinuities in direct shear a series of numerical simulations were performed using the particle based discrete element method dem in which rock matrix and rock bridges on incipient joint planes were modeled as an assembly of rigid particles that were bonded together at their contacts smooth joint model was assigned to particles of the persistent portions of incipient rock joints input micro parameters of particles bonds and smooth joint were calibrated against a series of laboratory experiments the study reveals that cnl and cns boundary conditions significantly affect shear characteristics of incipient rock discontinuities peak shear stress increased significantly up to three times in the cns direct shear in comparison with that measured in the cnl direct shear under the same initially applied normal stresses the significant increase of shear stress in the cns direct shear tests conducted in this study was related to the opening of newly created micro cracks and creation of the rupture zones within the rock bridges leading to a dramatic increase in the normal stresses in the meanwhile yield behavior was observed in the cns direct shear while brittle failure was noticed in the cnl direct shear it is also found that micro cracks initiated at the vicinity of rock bridges in both cnl and cns shear tests while they propagated differently due to the gradual increase of normal stress under cns boundary conditions

application of bulk sand geochemistry in mineral exploration and quaternary research a methodological study of the allier and dore terrace sands limagne rift valley france abstract the bulk geochemistry of unconsolidated sands from river terraces in two drainage basins of contrasting geology in the limagne rift valley france was studied data processing and interpretation was done with multivariate statistics notably factor analysis in the allier drainage basin underlain by volcanic rocks and crystalline basement the abundance of basaltic rock fragments causes significantly higher bulk concentrations of tio 2 al 2 o 3 fe 2 o 3 mgo cao p 2 o 5 v cr ni zn sr zr and nb in the dore basin underlain only by crystalline basement sands have a significantly higher sio 2 k 2 o rb and pb content originating from quartz k feldspars and micas comparison between different terrace levels shows the impact of weathering and changes in supplied sediment composition over time approximately 65 of the total variance in the basaltic element content in the allier terrace sands can be explained by the combined effect of parent material and weathering the effect of grain size on sediment composition is only significant for al 2 o 3 na 2 o and rb content in the allier sands and for tio 2 fe 2 o 3 and nb content in the dore sands approximately 60 of the total variability in these elements is grain size related these results show that the technique of studying the bulk geochemical composition of stream sediments has direct applications for mineral exploration and quaternary research

are microseismic ground displacements a significant geomorphic agent this paper considers the role that microseismic ground displacements may play in fracturing rock via cyclic loading and subcritical crack growth using a coastal rock cliff as a case study we firstly undertake a literature review to define the spatial locations that may be prone to microseismic damage it is suggested that microseismic weakening of rock can only occur in damage accumulation zones of limited spatial extent stress concentrations resulting from cliff height slope angle and surface morphology may nucleate and propagate a sufficiently dense population of microcracks that can then be exploited by microseismic cyclic loading we subsequently examine a 32 day microseismic dataset obtained from a coastal cliff top location at staithes uk the dataset demonstrates that microseismic ground displacements display low peak amplitudes that are punctuated by periods of greater displacement during storm conditions microseismic displacements generally display limited preferential directivity though we observe rarely occurring sustained ground motions with a cliff normal component during storm events high magnitude displacements and infrequently experienced ground motion directions may be more damaging than the more frequently occurring reduced magnitude displacements characteristic of periods of relative quiescence as high magnitude low frequency events exceed and then increase the damage threshold these extremes may also render intervening reduced magnitude microseismic displacements ineffective in terms of damage accumulation as a result of crack tip blunting and the generation of residual compressive stresses that close microcracks we contend that damage resulting from microseismic ground motion may be episodic rather than being continuous and in quasi proportional and cumulative response to environmental forcing a conceptual model is proposed that describes when and where microseismic ground motions can operate effectively we hypothesise that there are significant spatial and temporal limitations on effective microseismic damage accumulation such that the net efficacy of microseismic ground motions in preparing rock for fracture and hence in enhancing erosion may be considerably lower than previously suggested in locations where high magnitude displacements punctuate standard displacement conditions determining and measuring the exact effects of microseismic ground displacement on damage accumulation and as a trigger to macro scale fracture in the field is not currently possible though our model remains consistent with field observations and conceptual models of controls on rockfall activity

ambient resonance of mesa arch canyonlands national park utah we analyzed the resonance characteristics of a prominent natural arch in canyonlands national park mesa arch as measured from ambient seismic data evaluating spectral and polarization attributes we distinguished the first four resonant frequencies of the arch 2 9 6 0 6 9 and 8 5 hz as well as basic properties of the associated mode shapes we then affirmed experimental data using 3 d numerical modal analysis providing estimates of material properties and clarifying vibrational mode shapes monitoring resonant frequencies over time we searched for shifts associated with changing environmental conditions and long term progressive damage we measured 3 direct daily variation in resonant frequency associated with changing rock temperature thermal stress and stiffening of the rock matrix independent tilt data showed similar diurnal cycles associated with thermoelastic stresses and deformation of the arch we observed no permanent resonant frequency shifts related to irreversible damage of mesa arch during our study period

rockfall triggering by cyclic thermal stressing of exfoliation fractures exfoliation of rock deteriorates cliffs through the formation and subsequent opening of fractures which in turn can lead to potentially hazardous rockfalls although a number of mechanisms are known to trigger rockfalls many rockfalls occur during periods when likely triggers such as precipitation seismic activity and freezing conditions are absent it has been suggested that these enigmatic rockfalls may occur due to solar heating of rock surfaces which can cause outward expansion here we use data from 3 5 years of field monitoring of an exfoliating granite cliff in yosemite national park in california usa to assess the magnitude and temporal pattern of thermally induced rock deformation from a thermodynamic analysis we find that daily seasonal and annual temperature variations are sufficient to drive cyclic and cumulative opening of fractures application of fracture theory suggests that these changes can lead to further fracture propagation and the consequent detachment of rock our data indicate that the warmest times of the day and year are particularly conducive to triggering rockfalls and that cyclic thermal forcing may enhance the efficacy of other more typical rockfall triggers some rockfalls occur without obvious triggers such as seismicity or freeze thaw conditions temperature and deformation patterns on a granite cliff suggest that cyclical thermal forcing can progressively open fractures and trigger rockfalls

thermo cryogenic controls of fracture kinematics in permafrost rockwalls thermo cryogenic processes prepare and trigger rockfalls and rockslides in alpine environments temporal occurrence controls and applied stresses of thermo cryogenic processes on rock masses are poorly understood this paper reports annual crackmeter measurements with 3 h resolution across perennially ice filled fractures in an unstable rock permafrost crestline thermo cryogenic processes are controlled by snow cover onset and duration thermal changes in snow free periods control expansion and contraction coincident temperature gradients on a daily to seasonal scale we can show how snow cover promotes sustained temperatures from 9 to 1 c and boosts ice segregation related fracture opening up to 1 cm in 8 months during snowmelt meltwater induces ice erosion and ice relaxation which occur in the freeze thaw window close to the thawing point we hypothesize that thermo cryogenic processes and their cyclic repetition can lead to thermo cryogenic fatigue preparing rock slope failure and can control type and location of rockfalls in a changing climate

near surface circulation of the nordic seas as measured by lagrangian drifters in the period june 1991 to august 1993 107 argos tracked drifters drogued to 15 m depth were released in the nordic seas or greenland iceland and norwegian seas the drifter movements revealed the strong and spatially confined current systems along the surface salinity fronts of the iceland faroe frontal zone and of the norwegian coast and along the continental margins and their extensions to the barents sea and spitsbergen the norwegian atlantic current is composed of three distinct streams two continental margin and one coastal branches which join into one single swift mean current west of the lofoten and vesteralen islands where the strongest measured currents are in excess of 110 cm s 1 in addition to the general cyclonic gyre circulation in the nordic seas the drifters indicate smaller cyclonic circulation patterns in all the major subbasins i e the iceland plateau the norwegian the lofoten and the greenland basins no surface signature of the east icelandic current is disclosed by the drifters interpolated and low pass filtered position data were used to construct maps of 15 m depth ensemble mean velocity velocity variability and residence time vigorous eddy fields are dominant in the strong currents and in the lofoten basin eulerian correlations indicate that they tend to propagate to the west in contrast the iceland plateau appears quiescent both in the mean and eddy velocities single particle diffusivities are computed and are found to be in the range 1 7 107 cm2 s 1 the corresponding lagrangian timescale and space scale are 1 3 days and 10 40 km respectively these lagrangian drifter measurements compose the first basin scale accurate near surface velocity data set of the nordic seas

boundary currents and watermass transformation in marginal seas the properties of watermass transformation and the thermohaline circulation in marginal seas with topography and subject to a spatially uniform net surface cooling are discussed the net heat loss within the marginal sea is ultimately balanced by lateral advection from the open ocean in a narrow boundary current that flows cyclonically around the basin heat loss in the interior is offset by lateral eddy fluxes originating in the boundary current the objectives of this study are to understand better what controls the density of waters formed within the marginal sea the temperature of the outflowing waters the amount of downwelling and the mechanisms of heat transport within the marginal sea the approach combines heat budgets with linear stability theory for a baroclinic flow over a sloping bottom to provide simple theoretical estimates of each of these quantities in terms of the basic parameters of the system the theory compares well to a series of eddy resolving primitive equation model calculations the downwelling is concentrated within the boundary current in both a diffusive boundary layer near topography and an eddy driven region on the offshore edge of the boundary current for most high latitude regions the horizontal gyre is expected to transport more heat than does the overturning gyre

direct observations of a three million cubic meter rock slope collapse with almost immediate initiation of ensuing debris flows abstract catastrophic collapse of large rock slopes ranks as one of the most hazardous natural phenomena in mountain landscapes the cascade of events from rock slope failure to rock avalanche and the near immediate release of debris flows has not previously been described from direct observations we report on the 2017 3 0 106 m3 failure on pizzo cengalo in switzerland which led to human casualties and significant damage to infrastructure based on remote sensing and field investigations we find a change in critical slope stability prior to failure for which permafrost may have played a destabilizing role the resulting rock avalanche traveled for 3 2 km and removed over one million m3 of glacier ice and debris deposits from a previous rock avalanche in 2011 whereas this entrainment did not lead to an unusually large runout distance it favored debris flow activity from the 2017 rock avalanche deposits the first debris flow occurred with a delay of 30 s followed by ten debris flows within 9 5 h and two additional events two days later notably in the absence of rainfall we hypothesize that entrainment and impact loading of saturated sediments explain the initial mobility of the 2017 rock avalanche deposits leading to a near immediate initiation of debris flows this explains why an earlier rock avalanche at the same site in 2011 was not directly followed by debris flows and underlines the importance of considering sediment saturation in a rock avalanche s runout path for alpine hazard assessments

modelling of thermo mechanical effects in a rock quarry wall induced by near surface temperature fluctuations abstract mechanical response of rock masses to the periodical fluctuation of surface temperatures is a relevant topic to be focused on for the comprehension of short to long term stability of rock slopes continuously stressed by slight yet periodical actions to better understand how preparatory factors can lead rock masses toward failure thermal and strain monitoring activities are ongoing in a selected quarry wall where an experimental test site was implemented on a jointed rock block the role of pervasive joints in perturbing the heating cooling process of the rock mass and their related effects was already output by direct and remote monitoring for these purposes fdm numerical modelling was focused on the comprehension and simulation of induced mechanical effects due to cyclical thermal forcings over a simplified 2d half space therefore the role of rock mass joints on both heat propagation and resulting thermo mechanical effects was analysed basing on monitoring data field experiments and numerical modelling numerical results output the role of periodic daily annual and compound thermal input in inducing irreversible deformation along joints under different rock mass jointing configuration as a function of the intrinsic period of thermal input and joint attitude temperature distribution across joints was also analysed as a possible constraining effect for time and space distribution of yielding a sensitivity analysis of heat propagation conditions was performed in order to infer the role of joint sets on induced thermo mechanical strains at the rock block scale a non negligible influence on surficial as well as deeper portions of the rock mass was observed highlighting how near surface temperature fluctuations can drive the long term evolution of rock block conditions towards failure

element partitioning in sediment soil and vegetation in an alluvial terrace chronosequence limagne rift valley france a landscape geochemical study abstract the geochemical behaviour of specific elements in fluvial sediments topsoils soil profiles and plant material on a sequence of quaternary alluvial terraces was reconstructed semi quantitatively using indices of accumulation or depletion with respect to abundance in the lithosphere local soils and sediments topsoils of different ages and soil profiles are most clearly differentiated by the degree of leaching of ca mg and some minor elements with respect to less mobile si and ti clay translocation within soil profiles of older terraces leads to accumulation of al and associated elements in deeper horizons and accumulation of fe and mn in pseudogley horizons in the upper part of the clay accumulation layers p k ca mn and zn are strongly concentrated in plant materials relative to the topsoils ca is accumulated more strongly in oak bark than in grasses and the relative accumulation is greater on the older terraces due to the low ca content in their topsoils mn contents of both grasses and oak bark are greater on the older terraces than the younger for most elements topsoil and plant material contents show little correlation probably because plant requirements exert a greater control on element uptake than does availability the results illustrate that landscape geochemical analysis is useful for rapid appraisal of long term landscape processes such as erosion sedimentation weathering and preferential plant uptake

observations of the labrador sea eddy field this paper is an observational study of small scale coherent eddies in the labrador sea a region of dense water formation thought to be of considerable importance to the north atlantic overturning circulation numerical studies of deep convection emphasize coherent eddies as a mechanism for the lateral transport of heat yet their small size has hindered observational progress a large part of this paper is therefore devoted to developing new methods for identifying and describing coherent eddies in two observational platforms current meter moorings and satellite altimetry details of the current and water mass structure of individual eddy events as they are swept past by an advecting flow can then be extracted from the mooring data a transition is seen during mid 1997 with long lived boundary current eddies dominating the central labrador sea year round after this time and convectively formed eddies similar to those seen in deep convection modeling studies apparent prior to this time the topex poseidon altimeter covers the labrador sea with a loose net of observations through which coherent eddies can seem to appear and disappear by concentrating on locating and describing anomalous events in individual altimeter tracks a portrait of the spatial and temporal variability of the underlying eddy field can be constructed the altimeter results reveal an annual pulsation of energy and of coherent eddies originating during the late fall at a particular location in the boundary current pinpointing the time and place of the boundary current type eddy formation the interannual variability seen at the mooring is reproduced but the mooring site is found to be within a localized region of greatly enhanced eddy activity notably lacking in both the annual cycle and interannual variability is a clear relationship between the eddies or eddy energy and the intensity of wintertime cooling these eddy observations as well as hydrographic evidence suggest an active role for boundary current dynamics in shaping the energetics and water mass properties of the interior region

internal structure and deformation of an unstable crystalline rock mass above randa switzerland part i internal structure from integrated geological and geophysical investigations 6m 3 of material occurred in fractured gneissic rock whose principal foliation faults and fracture zones dip into the slope above the scarp of the second rockslide the mountain continues to move at rates of up to 2 cm year in an attempt to understand failure mechanisms in fractured crystalline rock masses we have carried out a comprehensive multidisciplinary study that included detailed geological mapping borehole logging and imaging and surface and borehole geophysical surveys an integrated interpretation of the resultant data has revealed the presence of three prominent fault and fracture zone sets that define the internal structure of the rock mass some faults and fracture zones could be traced up to 85 m into the subsurface using borehole radar reflection methods the dips of the faults and fracture zones estimated from surface mapping matched those from radar reflection and borehole televiewer surveys no evidence was found for significant faults or persistent weakness planes that paralleled the 1991 rockslide failure surfaces instead the new observations were consistent with dominant failure mechanisms that involve the progressive development of major shear and brittle fracturezones and the eventual destruction of intact rock bridges immediately prior to catastrophic collapse this integrated study provides the first reliable model of the 3 d fault structure associated with and contributing to a large rock slope instability in a brittle crystalline rock mass

influence of daily surface temperature fluctuations on rock slope stability case study of the rochers de valabres slope france the present paper describes a rockfall that has affected the rochers de valabres slope france s southern alps region and discusses one possible mechanism for the occurrence of this rockfall along with the potential for future ones in the absence of an obvious explanatory trigger factor we set out to examine whether natural daily surface temperature changes could have played a role in this event in particular it is suspected that these slight yet repeated perturbations may be a preparatory factor for rockfalls with a day to day cumulative effect a numerical model strengthens this hypothesis by showing that thermally induced deformations can be sufficient to cause the gradual downward creep of a rock block located in an awkward position to investigate this notion more thoroughly a currently vulnerable part of the rochers de valabres slope has been instrumented with a high precision geodetic monitoring system total station it is believed that this device is able to capture thermally induced movements if specific precautions are taken the instrumented rock volume is used as a test site in the aim of better understanding the consequences of surface temperature changes on slope stability measured data with a precision level never before achieved on rock slopes are compared herein with numerical modelling results the initial conclusions of the long term study we are conducting indicate that surface temperature changes play an important while not easily quantifiable role in preparing rockfalls

thermomechanical forcing of deep rock slope deformation 2 the randa rock slope instability 1 deformation monitoring between 2004 and 2011 at the rock slope instability above randa switzerland has revealed an intriguing seasonal trend relative dislocation rates across active fractures increase when near surface rock temperatures drop in the fall and decrease after snowmelt as temperatures rise this temporal pattern was observed with different monitoring systems at the ground surface and at depths up to 68 m and represents the behavior of the entire instability in this paper the second of two companion pieces we interpret this seasonal deformation trend as being controlled by thermomechanical tm effects driven by near surface temperature cycles while part 1 of this work demonstrated in a conceptual manner how tm effects can drive deep rock slope deformation and progressive failure we present here in part 2 a case study where temperature controlled deformation trends were observed in a natural setting a 2d discrete element numerical model is employed which allows failure along discontinuities and successfully reproduces the observed kinematics of the randa instability by implementing simplified ground surface temperature forcing model results were able to reproduce the observed deformation pattern and tm induced displacement rates and seasonal amplitudes in the model are of the same order of magnitude as measured values model results however exhibit spatial variation in displacement onset times while field measurements show more synchronous change additional heat transfer mechanisms such as fracture ventilation likely create deviations from the purely transient conductive temperature field modeled we suggest that tm effects are especially important at randa due to the absence of significant groundwater within the unstable rock mass

integrated multi temporal analysis of the displacement behaviour and morphology of a deep seated compound landslide cerentino switzerland abstract deep seated gravitational slope deformations dsgsds are complex slope instabilities commonly involving long term evolution with significant spatial and temporal variations in slope kinematics the cerentino compound landslide in southern switzerland exemplifies the long term evolution of dsgsds as well as short term movements causing substantial damage to infrastructure using an integrated analysis of surface geomorphology displacement monitoring data borehole core and cosmogenic nuclide dating we discuss the preconditioning and driving factors kinematic behaviour and long term evolution of the instability we demonstrate that foliation orientation and lithological boundaries together with slope geometry and alpine faults likely played significant roles in preconditioning the slope for failure based on morphology mapping and hierarchical clustering analysis of 2007 2018 detrended surface displacement data we show that the landslide is separated into up to eight compartments at surface revealing differences in kinematic behaviour from very active at the toe to insignificant movements in the upper region of the landslide above the village of cerentino these surficial compartments likely correspond to secondary sliding zones within the landslide mass the analysis of data from inclinometer and fibre optic strain sensors installed in a new deep borehole 230 m provided insight into movement within the landslide mass results show vertical heterogeneity in total displacement which appears to be controlled by an active discrete shear zone located at 107 m by shallower secondary sliding surfaces and by distributed movement particularly in the upper 20 m of the instability extrapolation of cosmogenic nuclide dating results from five samples taken on the exposed upper sliding scar reveals a possible age of failure initiation of 5 6 ka with long term decelerating movement trends these generally slow averaged movements show multi annual responses to long term changes in precipitation and locally rapid responses to strong recharge events the rare combination of dating and detailed analysis of displacement allows us to demonstrate the behaviour of dsgsds at long and short timescales with implications for hazard assessment and mitigation of these complex failures

classification of slope processes based on multitemporal dinsar analyses in the himalaya of nw bhutan abstract slope deformation in mountainous terrain can be driven by different processes the nature of which is either gravitational and irreversible or seasonal and reversible the latter induced by permafrost variations or by hydromechanical or thermomechanical effects the importance of identifying such deformations is not only related to the hazard they can pose but also to the understanding of changes that permafrost or local hydrological conditions undergo here we carry out a multi temporal insar analysis over a mountainous area 8000 km2 large straddling north western bhutan and southern tibet we propose a methodology to separate locally deforming areas from the effects of long wavelength signals through the analysis of the spatio temporal behaviour of 4 years long time series of surface displacements we present the mapping of hundreds of small scale features that appear to be actively deforming as well as several examples of reversible deformation rarely detected at this scale in such a challenging and vast region the analysis of the multi annual trend of ground deformation shows a relatively small number of irreversible gravitational movements clearly related to rock slides which attests a low level of recent activity of large rock slope instabilities in the region in the southernmost lower elevation parts of the study area we quantify reversible surface displacements with amplitudes ranging between 5 and 17 mm and showing maximum displacements towards the satellite in summer months thus compatible with hydro mechanical effects related to groundwater table variations in addition the ground movement induced by the active layer s response to thawing and freezing over the gentler slopes and high elevation permafrost regions of bhutan and southern tibet is on average around 10 mm with maxima up to 28 mm the localised displacements appear to be largely associated to braided stream plains glacier outwash plains or low angle fine sediment covered slopes

isotopic and geochemical identification of main groundwater supply sources to an alluvial aquifer the allier river valley france summary hydrodynamic hydrochemical and isotopic investigations were carried out on 18 points including boreholes piezometers and surface waters from february 2011 to august 2012 to assess groundwater quality in the unconfined shallow alluvial aquifer of the allier river one of the main tributary of the loire river the study area located near the city of clermont ferrand france plays an important socio economic role as the alluvial aquifer is the major source of drinking water for about 100 000 inhabitants the objective of the project aims at understanding the functioning of alluvial aquifers that occupy a pre eminent position in the hydrogeologic landscape both for their economic role production of drinking water and agricultural development and for their ecological role moreover this study also targets at determining the factors and processes controlling shallow groundwater quality and origin the water circulates from the south with a natural alimentation from the hills in the non pumped part of the alluvial aquifer in the pumping zone this general behaviour is altered by the pumping that makes the water from the allier river enter the system in a large proportion four end members have been identified for the recharge of the alluvial groundwater rainfall allier river surrounding hills aquifer and the southern non pumped part of the alluvial system results indicate that despite the global ca hco 3 water type of the groundwater spatial variations of physico chemical parameters do exist in the study area ionic concentrations increase from the allier river towards east due either to the increase in the residence time or a mixing with groundwater coming from the aquifer s borders stable isotopes of the water molecule show the same results boreholes close to the river bank are recharged by the allier river depleted values while boreholes far from the river exhibit isotopic contents close to the values of hills spring or to the southern part of the alluvial aquifer both recharged by local precipitation one borehole b65 does not follow this scheme of functioning and presents values attesting of a probable sealing of the allier river banks based on these results the contribution of each end member has been calculated and the functioning of the alluvial system determined

large scale brittle and ductile toppling of rock slopes slow ductile toppling of rock masses commonly creates large scale mountain slope deformations in some cases rock toppling can initiate an extremely rapid catastrophic landslide this theoretical and field based study was aimed at distinguishing the two alternative modes of toppling the idea that certain key parameters of the undeformed rock mass may influence failure behaviour in a quantifiable way was examined through a parametric study of a large rock slope using the universal distinct element code udec the slope was modelled using variations of rock mass strength discontinuity orientation and persistence and toe over steepening the results indicated two distinct types of failure behaviour i ductile self stabilizing flexural toppling in weak rock with a single dominant joint set and ii brittle catastrophic block toppling in strong rock containing persistent down slope oriented or horizontal cross joints which act as surfaces of separation at the base of the toppling blocks the two m

growth of exfoliation joints and near surface stress orientations inferred from fractographic markings observed in the upper aar valley swiss alps abstract granitic rock mass of the upper aar valley grimsel area switzerland contains distinct generations of exfoliation joints which formed during different stages of the pleistocene subparallel to distinct glacial valley palaeotopography the bulk of exfoliation joints shows prominent common fractographic features 1 radial plumose structures with distinct plume axes 2 arrest marks superimposed by plumose striations and 3 gradually developing en echelon fringe cracks multiple arrest marks reveal that exfoliation joints formed incrementally and together with the absence of hackle fringes suggest stable i e subcritical fracturing conditions smooth transitions from plumose structures on the parent plane to en echelon fringe cracks combined with non systematic stepping senses of fringe cracks suggest local vs temporal stress field variations assuming that plume axes formed parallel to the maximum principal compressive stress 1 enables us to infer near surface palaeostress orientations and compare them with classical borehole based in situ stress data the majority of plume axes suggest 1 persistently subhorizontal to slightly inclined 1 orientations at trough valley slopes and 2 near surface variability of 1 orientations originating from topographic perturbation caused by glacial valley erosion superimposed on the regional stress field our investigations of fracture surface morphologies yield unique insights into exfoliation fracture formation such as directional trends of fracture propagation and associated palaeostress orientations within alpine valley slopes

environmental controls of frost cracking revealed through in situ acoustic emission measurements in steep bedrock 1 frost cracking the breakdown of rock by freezing is one of the most important mechanical weathering processes acting on earth s surface insights on the mechanisms driving frost cracking stem mainly from laboratory and theoretical studies transferring insights from such studies to natural conditions involving jointed bedrock and heterogeneous thermal and hydrological properties is a major challenge we address this problem with simultaneous in situ measurements of acoustic emissions used as proxy of rock damage and rock temperature moisture content the 1 year data set acquired in an alpine rock wall shows that 1 liquid water content has an important impact on freezing induced rock damage 2 sustained freezing can yield much stronger damage than repeated freeze thaw cycling and 3 that frost cracking occurs over the full range of temperatures measured extending from 0 down to 15 c these new measurements yield a slightly different picture than previous field studies where ice segregation appears to play an important role

generation and stability of a quasi permanent vortex in the lofoten basin abstract in the nordic seas the lofoten basin is a region of high mesoscale activity the generation mechanism and the conditions for the stability of a quasi permanent vortex in the center of the lofoten basin are studied with a high resolution ocean circulation model and altimeter data the vortex and its generation mechanism manifest themselves by a pronounced sea surface height ssh signature and variability which are found to be in agreement with altimeter data the vortex results primarily from anticyclonic eddies shed from the eastern branch of the norwegian atlantic current which propagate southwestward the large scale bottom depression of the lofoten basin plays a crucial role for attracting anticyclones into the trough and for enabling the dynamical stability of the vortex the water mass characteristics of the anticyclone lead to enhanced atmospheric interaction heat loss during wintertime the cold water trapped in the upper part of the vortex preconditions convection in the following wi

thermomechanical stress strain numerical modelling of deglaciation since the last glacial maximum in the adamello group rhaetian alps italy abstract deglaciated areas in the valleys of the italian alps have recently exhibited a high potential for geomorphologic hazards from diffuse deep seated gravitational deformations dsgsds caused by rock mass creep processes that can evolve into rock falls and rock avalanches a multidisciplinary approach that integrated geomorphologic surveys and stress strain numerical simulations was used to investigate the effects of the stress release that was induced by the last glacial maximum lgm in the adame valley italian alps no evidence of dsgsds has been found in this area however data are available to develop a well constrained evolutionary model of the valley deglaciation the extent and thickness of the southern extension of the adamello glacier the widest glacier in italy during its primary growth phases including those of the lgm three late glacial stages and the little ice age lia were reconstructed using glacial geological surveys and were reproduced using a finite difference stress strain sequential model spanning from the lgm to the present a thermomechanical numerical configuration was developed based on geomechanical field measurements that were collected from rock outcrops and data from laboratory tests specifically performed on intact rock samples the numerical simulations demonstrate that thermomechanical viscous behaviour cannot be neglected because the resulting strains on the slopes are significantly higher than those resulting from conventional elastoplastic behaviour the last major thermal effect in the rock masses reproduced using the model occurred from 11 5 ka until the lia the resulting displacement rates are as much as several tens of mm ka which are consistent with the absence of dsgsds in the adame valley as these rates are significantly lower than those previously obtained from dsgsds and other large landslides in the alps based on thermomechanical numerical solutions these rates should persist for the next 1000 years assuming that no variations in current climatic conditions occur

post glacial rock avalanches in the obersee valley glarner alps switzerland abstract the geological record of prehistoric rock avalanches provides invaluable data for assessing the hazard posed by these rare but destructive mass movements here we investigate two large rock avalanches in the obersee valley of the glarner alps switzerland providing detailed mapping of landslide and related quaternary phenomena revised volume estimates for each event and surface exposure dating of rock avalanche deposits the rautispitz rock avalanche originated from the southern flank of the obersee valley releasing approximately 91 million m 3 of limestone on steeply dipping bedding planes debris had maximum horizontal travel distance of 5000 m a fahrboeschung angle relating fall height to length of 18 and was responsible for the creation of lake obersee deposits are more than 130 m thick in places the platten rock avalanche encompassed a source volume of 11 million m 3 sliding from the northern flank of the obersee valley on similar steeply dipping limestone beds bedrock forms a syncline under the valley debris had a maximum horizontal travel distance of 1600 m with a fahrboeschung angle of 21 and is more than 80 m thick in places deposits of the platten rock avalanche are superposed atop those from the rautispitz event at the end of the obersee valley where they dam lake haslensee runout for both events was simulated using the dynamic analysis code dan3d results showed excellent match to mapped deposit extents and thickness and helped confirm the hypothesized single event failure scenarios 36 cl cosmogenic nuclide surface exposure dating of 13 deposited boulders revealed a younger dryas age of 12 6 1 0 ka for the rautispitz rock avalanche and a mid holocene age of 6 1 0 8 ka for the platten rock avalanche a seismological trigger is proposed for the former event due to potentially correlated turbidite deposits in nearby lake zurich

monitoring rapid head scarp movement in an alpine rockslide abstract the aresawa rockslide in the japanese alps which partially collapsed in may 2004 produced a number of new tension cracks in the head area this paper discusses the dynamics of the rock slope and controls on the surface velocity based on the results of on site monitoring of the surface movement and meteorological parameters air and ground surface temperatures precipitation and snow depth the rock mass deformation progressed at ca 60 cm yr 1 mainly along a slip plane dipping downslope at ca 50 the surface velocity of the slipping rock mass showed a significant seasonal variation in response to the water infiltration the velocity was small 1 mm day 1 in winter subzero air temperatures and a heat insulating snow cover and resulting growth of seasonal frost prevent water infiltration into the bedrock and contribute to the rock slope stability most of the movement in this period is attributed to gravitational deformation originating from the overburden pressure in contrast the surface velocity increased up to 10 mm day 1 during snow melting and snow free periods snowmelt and rainfalls promote water infiltration into the bedrock destabilizing the rock slope and accelerating the rock slip such a rapid movement is attributed to water induced sliding superimposed on gravitational deformation

forensic analysis of rockfall scars abstract we characterise and analyse the detachment scar surfaces of rockfalls to understand the mechanisms that underpin their failure rockfall scars are variously weathered and comprised of both discontinuity release surfaces and surfaces indicative of fracturing through zones of previously intact rock known as rock bridges the presence of rock bridges and pre existing discontinuities is challenging to quantify due to the difficulty in determining discontinuity persistence below the surface of a rock slope rock bridges form an important control in holding blocks onto rockslopes with their frequency extent and location commonly modelled from the surface exposure of daylighting discontinuities we explore an alternative approach to assessing their role by characterising failure scars we analyse a database of multiple rockfall scar surfaces detailing the areal extent shape and location of broken rock bridges and weathered surfaces terrestrial laser scanning and gigapixel imagery were combined to record the detailed texture and surface morphology from this scar surfaces were mapped via automated classification based on rgb pixel values our analysis of the resulting data from scars on the north yorkshire coast uk indicates a wide variation in both weathering and rock bridge properties controlled by lithology and associated rock mass structure importantly the proportion of rock bridges in a rockfall failure surface does not increase with failure size rather larger failures display fracturing through multiple rock bridges and in contrast smaller failures fracture occurs only through a single critical rock bridge this holds implications for how failure mechanisms change with rockfall size and shape additionally the location of rock bridges with respect to the geometry of an incipient rockfall is shown to determine failure mode weathering can occur both along discontinuity surfaces and previously broken rock bridges indicating the sequential stages of progressively detaching rockfall our findings have wider implications for hazard assessment where rock slope stability is dependent on the nature of rock bridges how this is accounted for in slope stability modelling and the implications of rock bridges on long term rock slope evolution

distributed acquisition characterization and process analysis of multi field information in slopes the slope is a multiphase composite system including solid liquid and gas phases slope stability changes under the actions of stress temperature and seepage slopes will be very prone to landslide if in an unstable state in this paper considering the contributions of different fields to the landslide the distributed acquisition characterization and stability analysis of multi field information from slopes was studied systematically using distributed fiber optic sensing dfos technology a sensing system based on dfos was designed and developed for multi field information monitoring including stress temperature seepage and deformation the corresponding methods for data processing identification and methods for characterization description are also proposed on this basis the evolution of the slope is analyzed finally monitoring results of the dfos system from the majiagou landslide are shown as a case study for verification

new cnes cls09 global mean dynamic topography computed from the combination of grace data altimetry and in situ measurements 1 an accurate knowledge of the ocean mean dynamic topography mdt is mandatory for the optimal use of altimetric data including their assimilation into operational ocean forecasting systems a new global 1 4 resolution mdt was computed for the 1993 1999 time period with improved data and methodology compared to the previous rio05 mdt field first a large scale mdt is obtained from the cls01 altimetric mean sea surface and a recent geoid model computed from 4 5 years of grace gravity recovery and climate experiment data altimetric sea level anomalies and in situ measurements are then combined to compute synthetic estimates of the mdt and the corresponding mean currents while the rio05 mdt was based on 10 years of in situ dynamic heights and drifting buoy velocities the new field benefits from an enlarged data set of in situ measurements ranging from 1993 to 2008 and includes all hydrological profiles from the argo array moreover the processing of the in situ data has been updated a new ekman model was developed to extract the geostrophic velocity component from the drifting buoy measurements the handling of hydrologic measurements has also been revisited compared to the previous rio05 solution the new global mdt resolves much stronger gradients in western boundary currents with mean velocities being doubled in some places moreover in comparison to several other recent mdt estimates we find that the new cnes cls09 mdt is in better agreement with independent in situ observations

soil formation in a quaternary terrace sequence of the allier limagne france macro and micromorphology particle size distribution chemistry abstract soil formation in a terrace chronosequence of nine gravelly quaternary terraces was studied based on macro and micromorphological mineralogical chemical and physical characteristics based on textural characteristics the c horizon of the youngest soil appears to be representative for the parent material of lower b and c horizons in the youngest soils and of all horizons in older soils the parent materials contain a volcanic and a granitic component with increasing age of soils the following stages of soil formation were observed holocene soils on lowest terraces show evidence for mixing of sedimentary layers by biological activity resulting in texturally homogeneous a and b horizons in the absence of periglacial processes soil formation in holocene and in late pleistocene terraces took place under continuously well drained conditions late pleistocene soils on higher terraces show effects of clay illuviation with prominent weathering features in a horizons middle and early pleistocene soils on the highest terraces were influenced by periglacial conditions and display effects of various cycles of soil forming processes alternated with periglacial processes increasing in complexity with age weathering of all minerals except quartz neoformation of clay and clay illuviation has resulted in distinct differentiation between sandy a and e horizons and a clayey b horizon periglacial processes during the quaternary weathering clay formation and clay illuviation have caused a considerable compaction and decreased water permeability this has resulted in imperfect drainage now reflected by abundant locally cemented iron and manganese oxide segregations in the surface horizon typical for surface water gley with evidence of ferrolysis ferrolysis the increased weathering of clay under influence of alternating oxidation reduction in the seasonally waterlogged surface soil may have further contributed to the marked textural change between a and e versus b horizons easily weatherable minerals observed in strongly leached surface layers of older end members of the terrace sequence might be attributed to aeolian volcanic inputs the holocene and late pleistocene soils are intensively used as arable land as a result of the continuously well drained conditions on account of the poor drainage the middle and early pleistocene soils are used mainly for grassland and forest

wind driven variability of the large scale recirculating flow in the nordic seas and arctic ocean the varying depth integrated currents in the nordic seas and arctic ocean are modeled using an integral equation derived from the shallow water equations this equation assumes that mass divergence in the surface ekman layer is balanced by convergence in the bottom ekman layer the primary flow component follows contours of f h the model employs observed winds and realistic bottom topography and has one free parameter the coefficient of the linear bottom drag the data used for comparison are derived from in situ current meters satellite altimetry and a primitive equation model the current meter data come from a 4 yr record at 75 8 ni n the greenland sea the currents here are primarily barotropic and the model does well at simulating the variability the best bottom friction parameter corresponds to a spindown time of 30 60 days a further comparison with bottom currents from a mooring on the norwegian continental slope deployed over one winter period also shows reasonable correspondence the principal empirical orthogonal function obtained from satellite altimetry data in the nordic seas has a spatial structure that closely resembles f h a direct comparison of this mode s fluctuations with those predicted by the theoretical model yields linear correlation coefficients in the range 0 75 0 85 the primitive equation model is a coupled ocean ice version of the princeton ocean model for the north atlantic and arctic monthly mean depth averaged velocities are calculated from a 42 yr integration and then compared with velocities predicted from an idealized model driven by the same reanalyzed atmospheric winds in the largely ice free norwegian sea the coherences between the primitive equation and idealized model velocities are as high as 0 9 on timescales of a few months to a few years they are lower in the remaining partially or fully ice covered basins of the greenland sea and the arctic ocean presumably because ice alters the momentum transferred to the ocean by the wind the coherence in the canadian basin of the arctic can be increased substantially by forcing the idealized model with ice velocities rather than the wind estimates of the depth integrated vorticity budget in the primitive equation model suggest that bottom friction is important but that lateral diffusion is of equal or greater importance in compensating surface ekman pumping

internal structure and deformation of an unstable crystalline rock mass above randa switzerland part ii three dimensional deformation patterns the monitoring of slope displacements over time provides the basis for most rockslide early warning systems yet the prediction of catastrophic failure from these records is highly problematic and tenuous especially if the underlying kinematics and instability mechanism are poorly understood an example is the moving slope above the town of randa in the swiss alps this slope is considered typical of those in crystalline rock that lacks a natural highly persistent weakness plane dipping towards the valley that can serve as a through going detachment surface for kinematic release in part i the companion paper to this the findings from a comprehensive geological and geophysical investigation to image the internal structures of the unstable rock mass were presented in this paper we develop a kinematic model that describes the pattern of displacement vectors for the rock mass along these structures both on surface and at depth the displacements were estimated from 5 years of data from an extensive monitoring system which included surface geodetic and crackmeter measurements borehole inclinometer and extensometer measurements up to 120 m depth and microseismicity the results showed that the displacement field is highly heterogeneous internal deformation is accommodated by both shear and opening mode dislocation of faults and fracture zones which dip moderately to steeply into the slope microseismicity is most intense near the front of the scarp where surface translation in large part reflects the toppling of blocks accommodated by slip along the steeper dipping fractures the small displacement rates at the study site of up to 2 cm year coupled with a modest deviation of up to 15 from vertical of the boreholes posed severe problems for the estimation of horizontal displacements from the inclinometer data we describe the error analysis of these data in some detail since it is relevant for similar installations elsewhere conclusions drawn from this work highlight the importance of integrating various types of data in order to better understand the complex block kinematic processes whose evolution governs the long term progressive failure of unstable rock slopes

genesis of two planosols in the massif central france abstract two planosols developed on gravelly quaternary sediments of the river allier in the limagne rift valley massif central france were studied parent material contained in addition to a granitic component large amounts of volcanic particles morphological chemical mineralogical and physical properties of both profiles were investigated to indicate some of the changes which have taken place during pedogenesis both profiles were characterized by pronounced textural contrasts between sandy a and e horizons and clayey b horizons soil formation rather than a transient depositional environment is thought to be responsible for this marked textural change clear dissolution features of all mineral grains except quartz and increasing amounts of volcanic fragments with depth suggested weathering increasing ratios of mobile basic cations to tio 2 with increasing depth corroborated this observation the presence of non laminated isotropic and anisotropic limpid clay coatings were also evidence of in situ mineral weathering in both profiles kaolinite predominated as clay mineral and increased towards the surface micromorphological observations of microlaminated dusty and impure clay coatings in b horizons of both profiles were clear signs of clay illuviation bulk densities were high in lower e horizons and upper b horizons field observations and micromorphological data showed clear signs of periglacial features the combination of pedogenic and periglacial processes has apparently lead to a considerable compaction abundant cemented iron and manganese features predominantly occurring in e horizons suggested surface water gleying micromorphological observations of illuviation coatings in b horizons and of fine material in a and e horizons demonstrated grainy aspects suggesting ferrolysis