analysis of massif fracturing during deep seated gravitational slope deformation by physical and numerical modeling abstract both 3 d physical modeling and 2 d numerical modeling were used to analyze the development of deep seated gravitational slope deformations we focused especially on the link between fracturing and morphological features such as sagging sackung physical modeling was performed by using properly scaled analogue materials as well as an original vertical accelerator device this device enables cyclic loading of the model and to advance step by step in the deformation process this technique is thus particularly well suited to analyze rupture initiation and evolution surface deformation is registered with a high resolution digital camera internal model deformation was studied by making cross sections at different experiment stages the failure of one or both mountain sides was observed with a deep seated failure zone that follows an almost circular trajectory it intersects the surface perpendicularly in the upper part other fractures are generated in the moving mass in response to its motion fracture network becomes wider and morphological features such as counterscarps are generated numerical models were performed with a 2 d finite element code named adeli we tried to reproduce physical modeling results by using the same mechanical behaviour and parameters of the analogue material the results reproduced failure initiation well but poorly described moving mass deformation furthermore rupture initiation in the 2 d numerical models occurs more easily e g for a lower acceleration value than in the 3 d physical models confirming the importance of the three dimensional analysis

the acheron dorsum on mars a novel interpretation of its linear depressions and a model for its evolution abstract the acheron dorsum north of olympus mons on mars is a unique 800 km long arcuate ridge apparently unrelated to other adjacent morphologies acheron dorsum is crossed by deep and wide fractures fossae here referred to also as linear depressions or lds commonly interpreted as grabens formed by local lithosphere stress in response to endogenous mantle upwelling we suggest an alternate view that the linear depressions may result from gravitational self adjustment of a loose deposit similar to the deep seated gravitational slope deformations dsgsd or sackung a kind of slow mass movement well documented on earth numerical simulations based on a finite difference numerical model devised for terrestrial dsgsds reproduce the timing and position of lds reasonably well provided that the viscosity of the viscoplastic layer is between 7 10 15 and 10 17 pa s while rock masses typically exhibit much higher values based on comparison with glacial examples we find that these viscosities could be compatible to a rock ice mixture this leads to the hypothesis that the rock underneath acheron dorsum may be highly fragmented and that ice might have been involved in its deformation our hypothesis could shed light on the puzzling stress pattern on acheron dorsum which follows approximately the ridge without requiring the presence of hypothetical small scale endogenous currents

evolution of uphill facing scarps by flexural toppling of slate with high angle faults abstract uphill facing scarps are typical surface expressions of deep seated gravitational slope deformations and are commonly created by flexural toppling however their evolution mechanisms are not well understood partly because of the difficult in observing their internal structures this study therefore performed high resolution geomorphic analyses and thorough geological mapping in a slate rich area where flexural toppling has occurred and uphill facing scarps have developed following slope failures was crucial in exposing the inside of the toppled slate amid the toppled area uphill facing scarps developed when slate contained a crush zone of a high angle fault as a weak layer uphill facing scarps developed with the rotation of a wedge which was defined by the high angle fault and cleavage that passed through the intersection of the fault and basal hinge surface of the toppling the wedge developed up or downslope of the fault depending on whether the fault dipped into the slope or valleyward during wedge rotation displacement occurred along the fault and an uphill facing scarp developed along the fault the uphill facing scarp became higher when the cleavage dipped into the slope and the fault dipped valleyward when the fault dipped into the slope the uphill facing scarp did not grow significantly when a high angle fault was not involved flexural toppling of slate continuously deformed the slope and was unlikely to form an uphill facing scarp when flexural toppling extended to the ridge top it generally formed a ridge top depression regardless of whether a fault was involved flexural toppling of rock mass created many openings making the rock highly permeable however when a high angle fault with a thick crush zone was involved groundwater was stored between the fault crush zone and flexural toppling hinge surface which could predispose the flexural toppling to catastrophic failure during a rainstorm and or earthquake

quantitative assessment of weathering degree of the touzhai rock avalanche deposit in southwest china abstract weathering is one of the main preparatory causal factors for rock avalanche events and weathering assessment of involved materials can refine understanding of geomorphic processes of this class the weathering degree of the deposit of the touzhai basalt rock avalanche in china is quantitatively evaluated herein through an integrated geochemical analysis coupled with meso and micro scopic examination of fragments which can help to understand the inhomogeneity of weathering in rock slopes the clasts of 12 size classes of the debris making up the deposit ranging from meter sized boulder to fines of

long term gravitational deformation of rocks by mass rock creep abstract subsurface rocks beneath slopes are deformed to various degrees in various ways by mass rock creep mrc when they are subjected to a gravitationally unstable state for a long period mrc forms folds faults and numerous kinds of fractures such deformation is one of the main factors for deteriorating rock masses on slopes and also precursors of many landslides mrc deformations which have often been ascribed to tectonic origins can be distinguished from tectonic ones by their deformational features landforms and relationships between slope morphology and subsurface structures mrc folds are flexural slip folds that have the following mesoscopic to microscopic characteristics their axial surfaces are not smooth but are jagged and many visible openings or open fractures develop in association with the folds the jagged axial surfaces become smoother at depth and openings decrease in width with increasing overburden at the deformation site macroscopic types of mrc folds change according to the relationship between foliations and slopes buckling folds form in consequent slopes drag folds form in a deeper part of obsequent slopes and bending folds form in slopes with steep dipping foliations consequent or obsequent by downslope bowing of foliations shear fractures and tension fractures are the main deformational structures formed by mrc in massive rocks among shear fractures those of listric origin are remarkable tension fractures in general occur either in networks dividing rocks into fragments that slip and rotate irregularly in relation to each other or in parallel arrays of steeply dipping fractures an mrc fault has a shear zone consisting of a pulverized zone with gouge and a phyllitic or brecciated zone in a densely foliated rock the phyllitic zone is formed by microscopic slip along foliations in a sparsely foliated rock the brecciated zone is formed by random crushing except for the faults made through the shear fractures in massive rocks landforms due to mrc are gentle slopes bounded by horseshoe knicklines upslope convex slopes ridge top depressions multiple ridges uphill facing scarps and ridge crossing depressions

a deep seated compound rotational rock slide and rock spread in se spain structural control and dinsar monitoring abstract the northern slope of the sierra de aitana eastern betic cordillera is characterized by a long mountain front with a prominent eocene limestone scarp overlying ductile eocene marlstones this stratigraphic feature and the highly stepped topography produced by several normal faults favor gravitational processes such as rock avalanches rock slides and rock falls this paper reports a compound landslide comprising a rotational rock slide and slab type lateral spreading affecting these materials with blocks of volumes up to 106 m3 this lateral spread process produced singular and spectacular morphological features the simas de partagat which are trenches 20 m wide and up to 40 m deep formed by the widening of discontinuities the use of a differential sar interferometry technique for monitoring this landslide over a time span of 11 yr has revealed that velocity of movement is insignificant with rates comprised between 0 and 2 mm yr 1 and cumulative negligible displacements individual rock blocks initially located at the free face of the scarp were affected by slides at the base of the scarp descending from a few to several dozen meters along the slope blocks broke up as displacement progresses with several in different stages of evolution being recognizable along the slope differential sar interferometry shows a greater activity in the area north of compound landslide although velocity is extremely low below 16 mm yr 1 this extremely slow movement revealed by interferometry is in agreement with other geological and geomorphological evidence such as the existence of speleothems and cemented breccias against the head walls of the trenches both deposits are indicative of a long period of discontinuity widening also undisturbed debris deposits covering ancient rock slides are indicative of very slow gravitational processes characterized by long dormant periods in addition a historical picture from 1898 shows nearly negligible change in the simas de partagat over this 112 yr period

fluvial incision history that controlled the distribution of landslides in the central range of taiwan abstract hillslope processes which are affected by long term river incision give rise to the risk of landsliding in active orogens we studied the river incision history and the subsequent response of rock slopes in the upstream dahan river catchment north taiwan by analyzing river long profiles hillslopes and landslide scars the results were combined with chronological data from several landform surfaces to reconstruct the history of landscape evolution at the study area the landscape comprises three levels of knickpoints and corresponding slope breaks these knickpoints propagated upstream along trunk and tributary rivers undercutting and destabilizing nearby slopes of which the oldest is a paleosurface dated to ca 150 kyr by cosmogenic nuclide dating consequently three levels of v shaped inner gorges up to 600 m deep are incised into the paleosurface the inner slopes of the three levels of gorges have mean inclinations of 35 6 37 7 and 39 8 and steepen from the higher to the lower inner gorges these three series of knickpoints and corresponding slope breaks suggest the occurrence of three phases of river incision based on analyses of the steepness indices of the river long profiles cosmogenic nuclide dating and the regional tectonic and climatic history the two earlier phases of incision are inferred to have been caused by prevailing tectonic uplifts during the middle to late pleistocene and the most recent phase by climate change in addition to uplift the long term history of river incision has controlled the distribution of deep seated gravitational slope deformation and landslides many areas of deep seated gravitational slope deformation and deep seated rockslide avalanches are aligned along the higher and middle slope breaks and debris slide avalanches are concentrated along the middle and lower slope breaks

exhaustion and steady state models for predicting landslide hazards in the canadian rocky mountains abstract the temporal distribution of landslides can be evaluated by steady state and exhaustion models the probability of landsliding remains constant through time in the steady state model but the probability decreases in the exhaustion model as more slopes fail rock sliding down bedding surfaces on overdip slopes exhausts hazardous sites to leave stable dipslope landforms in kananaskis country in the canadian rocky mountains the distribution of rock slides in this area can be better explained by the exhaustion model than by the steady state model

effects of tectonic structures and long term seismicity on paraglacial giant slope deformations piz dora switzerland abstract the interplay of tectonic and climatic forcing in the development of alpine deep seated gravitational slope deformations dsgsd is still poorly understood we investigate a giant dsgsd affecting the piz dora slope val mustair switzerland by geological structural and geomorphological analyses spaceborne sar interferometry and numerical modelling the dsgsd affects permian terrigenous and volcanoclastic successions folded into a kilometre scale asymmetric anticline during the alpine orogenesis the area is characterized by active tectonic uplift and widespread shallow seismicity with dominant dip slip fault mechanisms experienced fast deglaciation after the last glacial maximum and periglacial conditions between the lateglacial and holocene the slope is affected by morpho structural features testifying to the deep seated gravitational sliding of 1 85 km3 of rock along a basal shear zone over 400 m deep analysis of rock glaciers and dinsar data show that the dsgsd was active in lateglacial times and is presently deforming at rates o 15 mm yr integrated kinematic analysis of field and radar data outlines a key control of the inherited fold structure on the dsgsd with a transition from deep compound sliding to the west controlled by massive conglomerates chazfora formation to shallower roto translational sliding to the east controlled by volcanoclastic foliated rocks ruina formation 2dfem stress strain numerical models simulating the post lgm slope evolution in static pseudo static and dynamic conditions allowed evaluating the contribution of long term seismicity to dsgsd in a paraglacial setting dynamic modelling was performed starting from the characterization of a real earthquake representative of the recent local seismotectonic activity and scaled to obtain dynamic scenarios with different return periods results suggest that deglaciation related perturbations promoted the inception of the dsgsd but not its complete development that was likely stimulated by the long term contribution of recurrent small earthquakes our results suggest that inherited structures active seismicity and deglaciation cooperate to promote paraglacial rock slope deformation in tectonically active alpine settings

paraglacial history and structure of the moosfluh landslide 1850 2016 switzerland abstract rock slopes next to the tongue of the great aletsch glacier switzerland are characterized by rapid environmental adjustment to non glacial conditions this study investigates and describes in detail the historic development of the largest rock slope instability in this area called moosfluh landslide we study in detail the structure evolution and stability since the end of the little ice age lia until september 2016 and discuss their relationships with the evolution of the great aletsch glacier since the lateglacial period in 2016 around 50 m of glacial ice thickness were left at the moosfluh landslide toe where in 1850 glacial ice was 400 m thick the changing stability conditions at the interface with the melting valley glacier are studied based on novel balanced cross sections and kinematic model of the moosfluh landslide dominated by toppling phenomena in metamorphic rock the morphology and evolution of this landslide since the lia are investigated with multi temporal landslide maps based on aerial digital photogrammetry adp applied to historic images since 1961 internal deformation at moosfluh is accommodated by shear slip along uphill facing foliation and fault planes and by extensional faulting forming tension cracks and graben structures at the landslide head together with digital image correlation dic and total station monitoring tps the moosfluh landslide displacement history was reconstructed evidencing post egesen landslide displacements and an acceleration of movements since the lia and especially since 2007 the displacement rates increase from few mm per year until the nineties to several meter per day in september 2016 different kinematic models have been tested and changes in the moosfluh rock slope stability in response to retreating glacial ice and changing groundwater conditions was explored with limit equilibrium analysis of the stepped planar block toppling model of goodman and bray 1976 for the observed conditions and a toppling joint friction angle of 19 the simulated factor of safety drops non linearly from the lia maximum 1 12 to the year 2007 1 02 when the height of ice above the valley bottom melted down to 100 m this study illustrates with unprecedented detail the time scales displacement magnitudes and structural evolutions of a large toppling mode slope instability in a paraglacial setting the long term cumulative slope displacements between the egesen stadial and the lia are of the same magnitude as the cumulative displacements between the lia and the year 2016 as large portions of the studied slope underwent multiple retreats and advances of the great aletsch glacier during the lateglacial and postglacial period the observed onset of large slope displacements should be related to incremental damage slip weakening and weathering occurring along steeply dipping toppling fractures during the lia

uphill facing antislope scarps in the coast mountains southwest british columbia uphill facing scarps are examined at affliction creek a glacierized area within the meager creek volcanic complex of southwest british columbia scarps occur directly downslope of tension cracks and are considered to have developed from a combination of 1 antithetic movement between partly toppled slices of rock defined by a master joint set dipping into the slope and 2 erosion of the upslope face of each tension crack leaving the downslope face prominent as an antislope scarp a kinematic test for toppling failure is described glacial erosion and rapid glacial downwasting are probable causes of toppling lichenometric data indicate significant scarp development since affliction glacier attained its maximum neoglacial dimensions about 140 yr ago dilatancy is cited as a possible mechanism for scarp stabilization

laser scanning based recognition of rotational movements on a deep seated gravitational instability the cinque torri case north eastern italian alps abstract the cinque torri group cortina d ampezzo italy is an articulated system of unstable carbonatic rock monoliths located in a very important tourism area and therefore characterized by a significant risk the instability phenomena involved represent an example of lateral spreading developed over a larger deep seated gravitational slope deformation dsgsd area after the recent fall of a monolith of more than 10 000 m 3 a scientific study was initiated to monitor the more unstable sectors and to characterize the past movements as a fundamental tool for predicting future movements and hazard assessment to achieve greater insight on the ongoing lateral spreading process a method for a quantitative analysis of rotational movements associated with the lateral spreading has been developed applied and validated the method is based on i detailed geometrical characterization of the area by means of laser scanner techniques ii recognition of the discontinuity sets and definition of a reference frame for each set iii correlation between the obtained reference frames related to a specific sector and a stable external reference frame and iv determination of the 3d rotations in terms of euler angles to describe the present settlement of the cinque torri system with respect to the surrounding stable areas in this way significant information on the processes involved in the fragmentation and spreading of a former dolomitic plateau into different rock cliffs has been gained the method is suitable to be applied to similar case studies

structural constraints on deep seated slope deformation kinematics abstract a significant sackung type deep seated slope gravitational deformation dsgsd was recognised for the first time by the authors in the middle part of valfurva east of bormio rhaetian alps italy the reconstruction of its kinematics age and state of activity is presented through a detailed description of its morphological geomechanical and structural features an integrated multi disciplinary approach was performed to achieve a clear comprehension of the phenomenon field surveys and aero photo interpretation were carried out in order to clarify the structural geological and geomorphological setting in which the dsgsd developed a kinematic conceptual model of the slope deformation was developed through the analysis of morpho structures of their significance and relationships with lithological markers and quaternary deposits after a geomechanical characterisation of the rock mass involved in the slope deformation numerical modelling was performed to verify the hypotheses made on kinematics and driving factors of the phenomenon the sackung affects pre permian metapelites metabasites and marbles belonging to the upper austroalpine basement of the campo nappe as well as late pleistocene and holocene glacial and rock glacier deposits the deformation started after the late wurmian age 15 000 11 000 years b p and continued until few centuries ago not excluding a present day low rate activity deformation consists in a large oblique sagging along a deep confined sliding surface associated with gravitational reactivation of pre existing late alpine and recent tectonic brittle structures leading to the formation of n s and wnw ese trending gravitational morpho structures the evolution of the wnw ese trending system resulting in asymmetric trenches led to progressive failure of the lower part of the slope during the last 10 000 years as testified by large paleo landslide accumulations and it is still in progress numerical modelling indicates post glacial unloading as the main triggering factor of the slope deformation the importance of this deep seated slope deformation is enhanced by the occurrence of the 30 mm 3 active ruinon landslide in the lower part of the slope such landslide is subjected to rapid evolution and threatens the valley floor establishing an important risk factor connected to human lives and socio economic activities

deep seated gravitational deformation of mountain slopes caused by river incision in the central range taiwan spatial distribution and geological characteristics abstract fluvial undercutting can cause the large scale destabilization of mountain slopes and induce deep seated gravitational slope deformation dgsd that eventually leads to catastrophic failures this study analyses these processes in the catchment of the dahan river northern taiwan the area has experienced phases of river incision of up to 600 m since the middle to late pleistocene and middle pleistocene paleosurfaces at higher elevations were incised to form v shaped valleys a dgsd inventory was compiled by visual interpretation of high resolution images and field surveys were conducted to clarify the geological structures associated with dgsds and major rockslide avalanches the observed relationships between dgsds and the topography modified by long term river incision show that about 53 of all dgsds occurred on slopes along the rims of paleosurfaces which is approximately 2 and 2 5 times as many as in the incised valleys and on the paleosurfaces respectively a comparison of the power law scaling exponents of cumulative frequency area distributions shows that the frequency of dgsds along the rims of the paleosurfaces decreases less rapidly with dgsd area than for dgsds on other slopes geological investigations suggest that there are two dominant types of dgsd one is flexural toppling of slate and argillite with high angle cleavage and the other is buckling of alternating beds of sandstone and mudstone on parallel or underdip cataclinal slopes catastrophic landslides observed along or below the rims of paleosurfaces were preceded by buckling of alternating beds of sandstone and shale these beds dipped at 50 to 58 and each bed was 10 1 10 0 m thick this study suggests that the peripheral zones of the paleosurfaces may be most susceptible to future catastrophic landslides particularly on parallel or underdip cataclinal slopes comprising alternating beds of sandstone and mudstone dipping at 50 to 60 thus an understanding of the geological characteristics spatial distribution of dgsd occurrence and landscape evolution within a particular area can provide important information for landslide hazard level zoning

late quaternary sackungen in the highest mountains of the carpathians sackungen represents a common mode of deep seated rock slope failures in alpine landscapes but proof of their temporal and causal relationship to extrinsic factors such as climatic changes glacier retreat or seismic activity remains elusive based on the terrestrial cosmogenic nuclide tcn dating of 18 sackung scarps supported by one radiocarbon dated scarp we reconstructed the post glacial chronology of sackungen in the tatra mts central europe slovakia and poland the highest part of the carpathians the obtained ages 15 7 4 3 ka indicate that sackungen post date the regional lgm and some of them originated soon after the glacier withdrawal from adjacent valleys furthermore systematic decrease of scarp ages with their increasing altitude suggests a direct link between sackung origin and post lgm glacier thinning however substantial lag 5 ka of some sackungen in respect to glacier retreat implies complex relationships between sackung onset and deglaciation where retreat of glaciers acted predominantly as a preparatory not a triggering factor during the genesis of these slope deformations they originated either as a consequence of stress relaxation within the rock mass lasting several ka or alternatively could be triggered by climatic processes or seismicity indeed a significant part of sackung activity took place during predominantly warmer and more humid periods with some dates coinciding with the belling allerod chronozone but especially with the onset of the holocene and the holocene climatic optimum earthquake triggering is less probable as the tatra mts lack significant modern and historic seismic activity and there is no geomorphic evidence of fault offsets on the late quaternary landforms in concert with other recent studies we propose that large rock slope failures in high mountains seldom react immediately to glacier withdrawal but could display temporal delay lasting up to several millennia c 2017 elsevier ltd all rights reserved

the role of tectonic deformation on rock avalanche occurrence in the pampeanas ranges argentina abstract both tectonic and long term gravitational slope deformation in several mountain settings have been shown to be key drivers of large scale slope instability the roles of both mechanisms are investigated in this study of the potrero de leyes rock avalanche one of the largest and better preserved slope failures in the pampeanas ranges in argentina this rock avalanche involved 0 25 km3 of highly fractured granitic rocks cropping out on an uplifted planation surface the rock avalanche left a lobate deposit up to 4 km run out into the piedmont a field survey 3d terrestrial lidar photogrammetry and gigapixel panoramic photos allowed us to map the structures on the headscarp and on the planation surface we observed a dense network of fractures with joints sets striking nne ssw ene wsw and nw se respectively representing foliation riedel and anti riedel structures that developed during the paleozoic as suggested by previous studies the decrease of rock mass strength caused by tectonic fracturing the exposure of those highly fractured rocks along a tectonically active mountain front and potential deep seated gravitational deformation occurring along nne ssw foliation planes along the mountain front suggest that tectonic and gravitational processes were key causal factors leading to the occurrence of the potrero de leyes rock avalanche

nonlinear subsidence rate estimation using permanent scatterers in differential sar interferometry discrete and temporarily stable natural reflectors or permanent scatterers ps can be identified from long temporal series of interferometric sar images even with baselines larger than the so called critical baseline this subset of image pixels can be exploited successfully for high accuracy differential measurements the authors discuss the use of ps in urban areas like pomona ca showing subsidence and absidence effects a new approach to the estimation of the atmospheric phase contributions and the local displacement field is proposed based on simple statistical assumptions new solutions are presented in order to cope with nonlinear motion of the targets

development of deep seated gravitational slope deformation on a shale dip slope observations from high quality drill cores abstract we analyzed high quality drill cores with 100 recovery drilled into a gravitationally deformed dip slope of a shale dominated sequence of sediments in japan the slope had undulating surfaces but no well defined landslide scarps suggesting that parts of the slope had undergone gravitational deformation but had not completely separated from the surrounding bedrock the gravitational deformation of shale and sandstone is characterized by disintegration and brecciation of sediments and the formation of pulverized zones with poorly developed planar structures jigsaw like structures and fracture openings shear zones are distributed intermittently within the slope but have not merged discernably into a through going master sliding surface incipient landslide shear zones form openings within coherent rock by shearing along bedding with these shear zones potentially developing downward in a stepwise manner which may be related to stress redistribution induced by river incision

glacial rebound and sea level change in the british isles observations of sea levels around the coastline of the british isles for the past 10 000 15 000 years exhibit a major regional variation and provide an important data base for testing models of glacial rebound as well as models of the late devensian ice sheet a high resolution rebound model has been developed which is consistent with both the spatial and temporal patterns of sea level change and which demonstrates that the observations are the result of i the glacio isostatic crustal rebound in response to the unloading of the ice sheet over britain and to a lesser degree of the ice sheet over fennoscandia and ii the rise in sea level from the melting late pleistocene ice sheets including the response of the crust to the water loading the hydro isostatic effect the agreement between model and observations is such that there is no need to invoke vertical crustal movements for great britain and ireland of other than glacio hydro isostatic origin the rebound contributions are important throughout the region and nowhere is it sufficiently small for the sea level change to approximate the eustatic sea level rise the observational data distribution around the periphery as well as from sites near the centre of the former ice sheet is sufficient to permit constraints to be established on both earth model parameters specifying the mantle viscosity and lithospheric thickness and the extent and volume of the ice sheet at the time of the last glaciation preliminary solutions are presented which indicate an upper mantle viscosity of 3 5 1020 pas a lithospheric thickness of about 100 km or less and an ice model that was not confluent with the scandinavian ice sheet during the last glaciation and whose maximum thickness over scotland is unlikely to have exceeded about 1500 m

rock slope deformation at affliction creek southern coast mountains british columbia a 7 year record of rock slope deformation is reported from affliction creek in the southern coast mountains of british columbia an estimated 3 107 m3 of monzonite basement and overlying garibaldi aged volcanic material is involved in a slow gravitational movement ground motion vectors suggest that movement has occurred along a deep seated shear zone and was accompanied by a downslope extension of the moving mass near surface flexural toppling producing antislope scarps has taken place where tension cracks crop out on steep slopes or wherever rock faces with strong planar jointing are glacially undercut structural data indicate the feasibility of both sliding and toppling at this site the stratigraphic evidence indicates that most of the tension cracks grabens and antislope scarps constituting the slope movement complex are less than 4300 years old and that many of these landforms may have developed quite recently as a result of rock slope debuttressing during the retreat of affliction glacier

kinematics of an alpine retrogressive rockslide in the japanese alps the aresawa rockslide in the japanese alps experienced a partial collapse 5 10 105 m3 in 2004 followed by an accelerated downward movement of the head area rather than stabilization this paper discusses the kinematics of a retrogressive rockslide area and factors promoting slope instability subsequent to the 2004 collapse on the basis of geodetic surveys and meteorological observations from 2006 to 2010 the unstable area covers at least 2 3 104 m2 and consists of five active blocks the main blocks are separated from the stable rock slope by pre existing sackung features that follow the strike of the bedding plane shear zones below these sackung features have developed into slip planes potentially causing the next collapse in particular the propagation of a slip plane causing movement at 70 cm yr 1 in the head area is promoted by bidirectional movement it consists of slow dip slip movement in snow accumulating periods and rapid side slip movement in snow melting and snow free periods both of which occur on the same slip plane this bidirectional movement appears to result from the combination of a loss of lateral support by the 2004 event and the immature state of the slip plane the primary trigger of the acceleration in the unstable area is the stress release by the 2004 collapse in addition the presence of a potential slip plane below the sackung features also promotes slope instability suggesting that sackung features behind a rockslide area may predefine the new head scarp of a forthcoming collapse copyright 2012 john wiley sons ltd

the role of the spatial scale and data accuracy on deep seated gravitational slope deformation modeling the ronco landslide italy abstract in recent decades numerical models have been developed and extensively used for landslide hazard and risk assessment the reliability of the outcomes of these numerical simulations must be evaluated carefully as it mainly depends on the soundness of the physical model of the landslide that in turn often requires the integration of several surface and subsurface surveys in order to achieve a satisfactory spatial resolution merging diverse sources of data may be particularly complex for large landslides because of intrinsic heterogeneity and possible great data uncertainty in this paper we assess the spatial scale and data accuracy required for effective numerical landslide modeling we focus on two particular aspects the model extent and the accuracy of input datasets the ronco landslide a deep seated gravitational slope deformation dsgsd located in the north of italy was used as a test bed geological geomorphological and geophysical data were combined and as a result eight models with different spatial scales and data accuracies were obtained the models were used to run a back analysis of an event in 2002 during which part of the slope moved after intense rainfalls the results point to the key role of a proper geomorphological zonation to properly set the model extent the accuracy level of the input datasets should also be tuned we suggest applying the approach presented here to other dsgsds with different geological and geomorphological settings to test the reliability of our findings

are icelandic rock slope failures paraglacial age evaluation of seventeen rock slope failures in the skagafjorður area based on geomorphological stacking radiocarbon dating and tephrochronology in iceland there are numerous rock slope failures especially in the tertiary basaltic formations of the northern eastern and northwestern regions the temporal pattern of rock slope failures is fundamental for understanding post glacial events in the skagafjor ur district central northern iceland 17 rock slope failures were investigated to determine the age of their occurrence a geomorphic survey was carried out to identify and characterize landform units both on the rock slope failures and in their immediate vicinity in this coastal area we used geomorphological stacking which included the relationship between rock slope failures and raised beaches caused by glacial isostatic rebounds the chronology of which was established in previous studies we searched for depressions on the rock slope failures to then excavate a series of pits and map the stratigraphy the resulting stratigraphic framework was then validated using i radiocarbon dating of wood remains and ii tephrochronology both of which were complemented by age depth model calibration the results confirm that all the rock slope failures potentially occurred before the boreal 8 ka while 94 occurred before the preboreal 10 ka they all potentially occurred after the glacial retreat following the maximal ice extent and the preboreal more precisely 11 of them potentially occurred between the preboreal and the first half of the holocene this study demonstrates the relationship between the deglaciation and destabilization of slopes during the paraglacial phase debuttressing decompression glacial isostatic rebound seismic activity etc which are also controlling factors favouring landsliding but are difficult to identify for each individual rock slope failure

giant non catastrophic landslides and the long term exhumation of the european alps landslides influence local slope morphology affect sediment flux from hillslopes to rivers and mass wasting in response to tectonics and climate forcing however the links between giant non catastrophic landslides known as deep seated gravitational slope deformations dsgsds and the long term evolution of orogenic landscapes are almost unknown we explore these links in the european alps using the first orogen scale inventory of dsgsds 900 over an area 105 km2 and a dataset of published apatite fission track ages 1000 that provides an estimate of the long term exhumation patterns of the orogen we show that dsgsds are more widespread than previously considered and exhibit an orogen scale distribution not explained by well known local lithological and structural controls we test the hypothesis that this orogen scale distribution correlates to the long term evolution of the alps by subdividing the study area into 37 square sub areas 50 50 km classified according to combinations of long term exhumation and mean annual rainfall on each sub area we perform a morphometric analysis of topography hypsometry relief slope excluding local and regional controls due to rock type and structure dsgsds tend to cluster in areas with intermediate exhumation rates fission track age between 10 and 40 ma where large scale topography is less dissected and incision is localised along major valleys here dsgsd abundance correlates positively with the degree of valley incision and related relief instead dsgsds lack in areas which underwent either low exhumation rates resulting in insufficient relief production or high exhumation rates associated to rapid uplift or higher erosional dissection of topography negative correlation between dsgsd abundance and mean annual rainfall suggests that effective hydrological surface processes contribute on the long term timescale to the development of large scale topography unfavourable to dsgsds especially in areas of high exhumation rates where dsgsds are abundant long lasting slope deformations effectively adjust post glacial relief by reducing slope inclination values and are thus expected to significantly contribute to the long term denudation of active orogens

tectonic control on the development and distribution of large landslides in the northern apennines italy abstract the causes of landslides generally invoked in the northern apennines of italy do not fully explain some observed oriented distributions of large landslides along regional scale tectonic structures late orogenic antiforms the aim of the work is to deeply explore the role of tectonics in controlling the development and arrangement of large landslides we employed a multidisciplinary approach which took into account geomorphological and geological field data topographic analysis and deep seismic reflection profiles integrated with previously published apatite fission track cooling ages shallow geophysical and gps data in order to explore these relationships the valmozzola area was selected as suitable case study owing to the presence of clearly expressed relationships between recent extensional faults and related fractures and elements of active landslides moreover in the valmozzola area contractional tectonics acted to produce rock uplift and thus topographic growth these processes caused hillslopes to approach their threshold angle and promoted landslides triggered mainly by climate factors the geological and geomorphological features characterizing the valmozzola case study affect the entire study area as they evolved during the same tectonic and climatic phases that characterized this part of the northern apennines therefore the results from the valmozzola area act as a proxy to constrain the control exerted by tectonics on large landslides across a wider area the distribution of the large landslides has been controlled by tectonics which determined lines of weakness and failure surfaces passive role affecting the slopes on the other hand tectonics also caused the topographic growth and over steepening of the slopes active role that promoted the occurrence of large landslides the distribution of large landslides may therefore highlight the existence of tectonic processes and it may be used as an indicator of regional scale tectonic activity once the geological and geomorphological framework is well constrained

deep seated gravitational slope deformations along the active bocono fault in the central portion of the merida andes western venezuela abstract two very large deep seated gravitational slope deformations in the highlands of the merida andes venezuela are herein described the mucubaji pass and cerro la camacha these slope movements have slid in post last glacial maximum times in addition both landslides are in very close association with the active bocono fault trace the cerro la camacha camacha range landslide is fault bounded along its northwest flank whereas the mucubaji pass mass movement is even cut by the active fault trace the almost 10 km long mucubaji slide mobilizes lgm moraine deposits along the unconformable basement contact la camacha slope movement is a sackung type landslide involving two huge masses that affect the entire northwestern slope of the la camacha range this sackung is at least 20 km long paralleling the active bocono fault trace combination of high relief energy gravitational forces and seismic shaking related to an on site active fault could be responsible for the destabilization of the slopes or massif in both cases although the seismically induced re activation of the la camacha landslide is very likely there is no proof for that yet conversely the mucubaji slide shows geomorphic geodetic and sedimentary evidence of episodic activity in recent times which could be ascribed to seismic triggering in the particular case of the la camacha sackung the combination of dextral slip along the bocono fault and a se dipping fault plane could additionally favor the destabilization of the nw slope of the la camacha range

temporal behavior of deep seated gravitational slope deformations a review abstract deep seated gravitational slope deformations dsgsds are slow moving hillslope scale mass movements featuring characteristic landforms such as double crested ridges and upslope facing scarps that occur in diverse landscapes throughout the world although these deformations have been studied since the 1960s significant insights to the rates of dsgsds have only been gained within the last two decades owing to progress in geochronology remote sensing and instrumental monitoring absolute age and monitoring data indicate that dsgsd movements are observable over long term 102 years and short term future research directions include constraining the lifespan of dsgsds with absolute age dating and precise high resolution monitoring of spatio temporal displacement across dsgsd bodies it is of great importance to include absolute time scales in the numerical models of dsgsds furthermore combining remote sensing techniques such as synthetic aperture radar interferometry with high resolution lidar scanning and near surface geophysics offers a promising toolkit for collecting very detailed and accurate data on the short term deformation rates of dsgsds

active normal fault control on landscape and rock slope failure in northern norway structural geomorphic and interferometric synthetic aperture radar insar surface displacement data show that uplift of the northernmost onshore scandinavian passive margin is associated with active normal faulting and anomalous clusters of landslides regional scale normal faults separate alpine footwall ranges with impressive range front scarps from more gentle hanging wall topography in the lyngen region rockslides sackung features i e deep seated slope gravitational deformation and active faults cluster inside an 1000 km 2 area of hanging wall subsidence parallel to an 30 km long faceted range front scarp from postglacial to recent time rockslides have been released along the main range front and other propagating scarps both in the footwall range and in structurally controlled glacially oversteepened valleys of the hanging wall the active rockslides moving at rates of 10 mm yr show a variety of relationships to the controlling structures reflecting tectonic as well as gravitational faulting recent and present day landscape evolution and large volume rockslide distribution in scandinavia should be viewed from the perspective of tectonic processes involving active normal faults

large sackung along major tectonic features in the central italian alps deep seated gravitational slope deformation sackung is common in alpine mountain belts it is controlled by lithological geomorphological and structural features we describe and discuss five examples of dsgsd along the insubric line periadriatic fault in the central italian alps the five examples are different in morphology size state of activity and distribution and are located along both primary and secondary valleys we demonstrate relations between structural and gravitational features and discuss the possibility that structural has both passive and active roles in sackung development analysis of ps sar data shows that the studied examples are not active today numerical modelling demonstrates the importance of lithological and structural constraints postglacial debuttressing groundwater fluctuations and weathering on sackung triggering and development

formation of paleoproterozoic eclogitic mantle slave province canada insights from in situ hf and u pb isotopic analyses of mantle zircons abstract in situ hf isotope analyses and u pb dates were obtained by laser ablation mc icp ms for a zircon bearing mantle eclogite xenolith from the diamondiferous jericho kimberlite located within the archean slave province nunavut canada the u pb zircon results yield a wide range of ages 2 0 to 0 8 ga indicating a complex geological history of importance one zircon yields a u pb upper intercept date of 1989 67 ma providing a new minimum age constraint for zircon crystallization and eclogite formation in contrast hf isotope systematics for the same zircons display an intriguing uniformity and corresponding hf depleted mantle model ages range between 2 1 0 1 and 2 3 0 1 ga the youngest hf model age is within error to the oldest u pb date the jericho eclogites have previously been interpreted as representing remnants of metamorphosed oceanic crust and their formation related to paleoproterozoic subduction regimes along the western margin of the archean slave craton during the wopmay orogeny hf isotope compositions and u pb results for the jericho zircons reported here are in good agreement with a paleoproterozoic subduction model suggesting that generation of oceanic crust and eclogite formation occurred between 2 0 and 2 1 ga the slightly older hf depleted mantle model ages 2 1 to 2 3 ga may be reconciled with this model by invoking mixing between crustal derived hf from sediments and more radiogenic hf associated with the oceanic crust during the 2 ga subduction event this results in intermediate hf isotope compositions for the jericho zircons that yield fictitiously older hf model ages

distribution of gravitational slope deformation and deep seated landslides controlled by thrust faults in the shimanto accretionary complex abstract the cretaceous shimanto accretionary complex is a typical accretionary complex uplifted without significant deformation after accretion and in which many rain induced deep seated landslides dls have occurred we undertook a thorough geological and geomorphological investigation of the middle kii peninsula where many rain induced dls occurred in 1889 and 2011 during intense and prolonged rainfall associated with typhoons geomorphological investigations using 1 m digital terrain models dtms obtained from airborne light detection and ranging lidar before and after the 2011 typhoon allowed us to examine the microtopography e g small scarps and linear depressions and to locate deep seated gravitational slope deformations dgsds and dls low angle thrust faults with 1 m thick incohesive fault rocks were found to be aligned subparallel to each other with spacings of a few kilometers and control the distribution of dls and dgsds when a thrust fault forms a cataclinal slope river incision removes the overburden and undercuts and destabilizes the slope this process causes gravitational deformation which forms downhill facing scarps and linear depressions at higher elevations on the slope tephrochronology applied to the deposits in the dgsd induced depressions revealed that such deformation began at least 30 000 50 000 years ago and is ongoing when a high angle fault strikes along the line of maximum slope it separates a volume of the rock mass from the juxtaposing slope and facilitates gravitational slope deformation and ultimately catastrophic failure a rock mass on a thrust fault that forms a downslope plunging syncline can also be gravitationally deformed and fail a crush zone of a large scale thrust fault is a continuous weak layer that also forms a barrier to groundwater flow thus leading to a rapid increase in pore pressure during rainstorms potentially triggering catastrophic slope failure accretionary complexes which typically contain thrust faults with incohesive fault rocks thus provide a location for dgsds and dls

influence of large scale topography on gravitational rock mass movements new insights from physical modeling 1 gravitational slope failures and associated rock mass movements can be observed at various scales in the same area it seems obvious that the different movement scales should be interrelated but their relationships are poorly understood we address this problem using 3 d physical modeling experiments were conducted with mechanically homogeneous models with two scale topographic features a large scale corresponds to the whole mountain several kilometers and a smaller one to a part of a mountain slope one kilometer results show that large scale relief induces large scale large volume gravitational movements introduction of small scale topographic features results not only in the generation of smaller scale landslides but also in considerable changes in the deformation pattern the various scale processes occur simultaneously and affect each other to predict the evolution of a landslide it is therefore necessary to take into account the topography and deformation pattern at various scales

anatomy of the kitimat fiord system british columbia abstract the geomorphic complexity of the kitimat fiord system on the active margin of british columbia canada is analysed from several perspectives sub glacial landforms and sediments show that grounded ice exiting the fiord system at the last glacial maximum streamed down moresby trough towards the queen charlotte trough mouth fan after brief halts on the inner shelf grounded ice margins cleared the fiord threshold perhaps by c 15 5 ka cal yrs bp and certainly before 13 ka cal yrs bp just outside the fiords meltwater plumes deposited stratified glaciomarine sediments interbedded with submarine slides inside the fiords thick glaciomarine sediments were deposited and large transverse moraines formed during temporary halts in retreat several glacial outburst floods eroded the kitkiata moraine and deposited distinctive mud deposits postglacial sedimentation on fiord floors has been spatially variable drifts of mud 90 m thick corresponding with areas of low current velocity alternate with areas of non deposition and erosion corresponding with areas of high velocity the fiord system hosts more than a hundred morphologically diverse fan deltas that can be classified in the prior and bornhold 1989 1990 system submarine mass transport was most frequent immediately following ice retreat 15 5 11 5 ka cal yrs bp the largest event 1 2 km 3 involved failure of glaciomarine sediment on a submarine moraine at squally channel and consequent movement of material into the adjacent deep basin this event occurred post 13 ka cal yrs bp in the postglacial phase mass transport continued on a lesser scale up to the present day most intensively in kitimat arm from the perspective of glacial landforms postglacial sedimentation and mass transport this pacific active margin fiord system has some parallels with fiord systems on canada s east coast passive margin and with norwegian fiords but the intensive development of holocene fan deltas is strongly distinctive

paraglacial slope failures in the aran valley central pyrenees abstract slope failures are widespread phenomena in mid latitude mountain environments that were glaciated during the last glacial cycle this is the case of the aran valley in the upper garonne catchment central pyrenees that included glaciers several hundred meters thick following postglacial warming and ice thinning the recently deglaciated slopes were subject to intense stress readjustments the so called paraglacial dynamics we have identified up to 135 major slope failures in the aran valley with only 10 units occurring outside the glaciated domain of the maximum ice extent of the last glacial the presence of polished bedrock surfaces till and moraine ridges next to some of these features evidence a close connection between glacial and slope processes we have detected different types of slope failures affecting both bedrock 12 large catastrophic rock slope failures 16 rock slope deformation 34 rockfalls and 49 rockslides and unconsolidated glacial sediments 14 slope readjustments on drift mantled slopes the average altitude of rock slope failures oscillates between 1551 and 1991 m with a mean length ranging from 147 to 905 m and a width between 247 and 513 m the affected surface is also highly variable oscillating between 0 02 and 126 2 ha slope failures occur in different lithological settings but they are most frequent in slate lutite and limestone bedrocks we conclude that most of the failures show a paraglacial origin though other factors i e lithology and topography promoted slope instability

large scale thin skinned thrusting in the southern alps kinematic models the tectonics of the southern alps are dominated by thrusting on extensive ramp flat systems and by folding some of which is ramp folding basement slivers are involved that frontally are not thicker than 5 km the most unequivocal section is that of the grigna mountains east of lake como for which kinematic modeling based on material balance considerations results in a shortening of 40 km it is separated from the grona section in the west and the valtorta section in the east by probably pre existing transverse zones that cut through the important decollement horizons and define blocks of different depths to basement local tectonics across these transverse zones change abruptly while over all shortening remains constant in particular both east and west of the grigna section basement ramp folds were wedged into the very incompetent raibl beds provoking back thrusting of the thick hauptdolomit and higher sediments with the substitution of the original cover of the frontal limb of the basement fold this new kinematic interpretation is compatible with the information facilitates the construction of balanced sections and is required for lateral constancy of shortening

10be dating reveals pronounced mid to late holocene activity of deep seated landslides in the highest part of the czech flysch carpathians abstract although the highest part of the czech outer western carpathians lacks significant recent landslide activity the vast area 20 of their territory is occupied by relict deep seated landslides and deep seated gravitational slope deformations dating these deformations might help to determine degrees of present day landslide hazard in that area based on the 10be exposure dating of eight rocky scarps and walls of ridge top trenches we estimated the minimal ages of the deep seated landslides dsls and one deep seated gravitational slope deformation dsgsd in the satina river basin in the moravskoslezske beskydy mts the obtained ages 9 7 2 9 ka suggest holocene slope instability in the area with a pronounced cluster of ages spanning from 6 0 to 2 9 ka except for one dsl the ages reveal rather episodic activity of gravitational movements mid to early late holocene activity of large landslides in the study area corresponds to the ages of several previously dated landslides both in an adjacent region as well as within the central european context with respect to the historical quiescence of the dsls and dsgsds in the area and because the slopes have not been destabilized even during the most extreme hydrometeorological events within the last few decades we infer that the hydrometeorological thresholds necessary for their activation are seldom exceeded in this area therefore the highest parts of the carpathians built by rigid thick bedded lithology reveal a rather lower frequency of events in comparison with adjacent parts formed by claystone dominated flysch where several large dsls originated in the last few decades as a consequence of heavy rainfalls

mid holocene cluster of large scale landslides revealed in the southwestern alps by 36cl dating insight on an alpine scale landslide activity abstract although it is generally assumed that the internal structure of a slope e g lithology and rock mass properties inherited faults and heterogeneities etc is preponderant for the progressive development of large scale landslides the ability to identify triggering factors responsible for final slope failures such as glacial debuttressing seismic activities or climatic changes especially when considering landslide cluster at an orogen scale is still debated highlighting in this study the spatial and temporal concordant clustering of deep seated slope failures in the external southwestern alps we discuss and review the possible causes for such wide spread slope instabilities at both local and larger alpine scale high resolution field mapping coupled with electrical resistivity tomography first allows establishing an inventory of large landslides in the southwestern alps determining their structural model precising their depth limit 100 200 m as well as the involved rock volumes 10 7 m 3 we show that they developed in the same geostructural context of thick mudstone layers overlain by faulted limestone and followed a block spread model of deformation that could evolve in rock collapse events cosmic ray exposure dating cre using both 36 cl and 10 be in coexisting limestone and chert respectively has been carried out from the main scarps of six deep seated landslides dsl and leads to landslide failure cre ages ranging from 3 7 to 4 7 ka they highlighted i mainly single and fast ruptures and ii a possible concomitant initiation with a main peak of activity between 3 3 and 5 1 ka centered at ca 4 2 ka because this region was not affected by historical glaciations events landslide triggering by glacial unloading can be excluded the presented data combined with field observations preferentially suggest that these failures were climatically driven and were most likely controlled by high pressure changes in the karstic medium in effect the chronicle of failure ages is concomitant to a well known climatic pulse the 4 2 ka climate event characterized by intense hydrological perturbations associated to the heaviest rainfall period of the entire holocene despite requiring further investigations and discussions the dating of numerous events across the entire alps during the middle holocene period suggests a potential synchronous triggering of several large scale gravitational failures induced by the mid holocene climatic transition

september 2005 rain induced catastrophic rockslides on slopes affected by deep seated gravitational deformations kyushu southern japan river rejuvenation forms convex slope breaks that can destabilize nearby slopes leading to gravitational deformation and in some cases catastrophic sliding of the slopes during heavy rainstorms such landslides were induced by typhoon 0514 which passed to the west of kyushu island japan on 6 september 2005 five large catastrophic rockslides occurred aligning along convex slope breaks 150 to 300 m above the present river bed of the mimi river the slope breaks are inferred to have been formed by rejuvenation of the river geological and geomorphological investigation revealed that these slides occurred in sandstone and mudstone of the cretaceous shimanto group and were preceded by slope deformation which generated gravitational folds and faults that appeared as scarplets at the tops of the deformed areas the slopes seem to have been in critical condition just before catastrophic failure which was triggered by the rainstorm

lgm and late glacial fluctuations in the eastern alps abstract studies of glacier development in the eastern alps around the last glacial maximum lgm for more than a hundred years have created a reasonably well based knowledge of glacier extent sedimentation and palaeoclimate as well as chronology this was obtained from broad and detailed mapping palynological investigations and radiocarbon dating despite a very cold climate between 31 and 21 ka bp topographical constraints meant that glacier extent was limited to tributary valleys of the main trenches until about 24 ka bp then rapid ice build up in the main longitudinal valleys led to extended ice streams and to piedmont glaciers in the foreland this build up virtually ended at ca 21 ka bp according to radiocarbon dates obtained from organic matter embedded in the outwash and periglacial gravels niederterrasse the lgm possibly lasted 3000 4000 years and shows a short maximalstand and a more prolonged hochstand both connected with outwash deposits the ice decay was apparently very fast and the glaciers vanished from the longitudinal valleys probably within some hundreds of years this retreat was interrupted by two short oscillations of active glaciers in contact with huge masses of inactive ice occupying the main valley floors before these became totally ice free these events at the beginning of the oldest dryas ca 16 ka bp were followed by a distinct glacier readvance gschnitz marked by end moraines and outwash fans according to some radiocarbon dates this occurred around 14 ka bp during the bolling interstade the valleys became almost ice free the next two glacier readvances daun and egesen were limited to cirques and the higher parts of the valleys and are dated to the older and younger dryas stades respectively

gravitational spreading of mountain ridges coeval with late weichselian deglaciation impact on glacial landscapes in trollaskagi northern iceland abstract during the late weichselian deglaciation the coastal mountains of northern central iceland have experienced significant paraglacial readjustment processes in the form of conspicuous rock slope failures and deep seated gravitational slope deformation dsgsd local topographic slopes and ridges were deeply reshaped by these large scale paraglacial processes located on the eastern side of skagafjor ur one of the largest fjords of northern iceland the oslandshli arfjoll and hnjukar ridges 65 49n 19 14w exhibit geomorphic evidence of spectacular dsgds several series of dsgsd induced landforms such as crestal graben and troughs initiated by ridge top splitting were investigated over a 30 km 2 area on the basis of geomorphological mapping we recognized i a ridge top splitting event mainly controlled by glacial debuttressing induced by a minimal 300 m lowering of the glacier surface in the deildardalur valley ii a rapid late weichselian deglaciation of the deildardalur valley spanning a few thousands of years ice free stage probably reached around 14 000 years cal bp iii ridge top splitting having an influence on large scale glacial patterns by guiding and facilitating glacial erosion along ridge top grabens resulting in accelerated trough widening based on these interpretations we propose an evolutionary sequence of both the kinematic stages of the dsgsd and the late weichselian deglaciation at the valley scale this work provides new insights into i the patterns of the late weichselian deglaciation in the skagafjor ur area especially in tributary valleys of the fjord ii the timing of large scale paraglacial ridge top deformations in relation to the post lgm deglaciation and iii the influence of paraglacial dsgsd features on large scale glacial erosional patterns

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

mechanical conditions and modes of paraglacial deep seated gravitational spreading in valles marineris mars deep seated gravitational spreading dsgs affects the slopes of formerly glaciated mountain ridges on mars dsgs has played a key role in shaping the landforms of the giant valles marineris troughs though less spectacular dsgs is common in terrestrial orogens where understanding its mechanics is critical in the light of the ongoing climate change because it is a potential source of catastrophic landslides in deglaciated valleys we conducted parametric numerical studies in order to identify important factors responsible for dsgs initiation dsgs models are computed using an elastoviscoplastic finite element code using adeli s software we reproduce topographic ridge spreading under the effect of valley unloading two types of spreading topographic ridges are investigated homogeneous or with horizontal rheological layering we find that gravitational instabilities are enhanced by high slopes which increase gravitational stress and low friction and cohesion which decrease yield stress in the unlayered ridge instability is triggered by glacial unloading with plastic strain concentration inside the ridge and at the base of the high slopes vertical fractures develop in the upper part of the slope potentially leading to fault scarps ridge homogeneity promotes a deformation mode controlled by uphill facing normal faulting and basal bulging in the second case the ridge encompasses horizontal geological discontinuities that induce rock mass anisotropy discontinuity located at the base of the slope accumulates plastic strain leading to the formation of a sliding plane evolving into a landslide the presence of a weak layer at ridge base therefore promotes another slope deformation mode ending up with catastrophic failure mechanical conditions and slope height being equal these conclusions can probably be extrapolated to earth compared with mars dsgs on earth is inhibited because terrestrial topographic gradients are lower than in valles marineris an effect counterbalanced by increased gravitational stress where the intensity of deformation is enhanced because of the earth gravity potential

slope tectonics a short introduction geomorphology structuralgeologyandengineeringgeology allow description of the main character istics of a slope in distinct ways that can be com bined to provide a complementary view of theoperative slope processes the subjects presentedin this special publication include slope mor phology and evolution mechanical behaviour ofthe material modes of failure and collapse in u ence of lithology and structural features and therole played by controlling factors this slope tec tonics volume comprises a series of very differentcontributions that attempt to underline a multidisci plinary approach thatshould form the framework ofslope instability studies slope tectonics is adopted in this volume tomeandeformationthatisinducedorfullycontrolledbytheslopemorphologyandthatgeneratesfeaturesthatcanbecomparedtotectonicfeatures thestress eld in a slope is the result of gravity topographyand the geological setting created by an ensembleof geodynamic processes active tectonics alsocalled neotectonics generates a stress eld thatcancontrolslopeprocesses astrongfeedbackexist ingbetween geological history tectonics lithology geomorphological evolution and topography as a consequence a list of factors and theirrela tive in uence can be presented 1 fabric induced by a local stress eld within aslope discontinuities and local faults with cata clastic bands of variable thickness folds fig 1 associated predominantlywith brittle structures complex failure paths stepped or multi surface localfailures rockbridgefailuresorexten sional failures graben like or pseudo graben like subsidence due to weak or soluble mate rials causing complex sliding topplingphenomena 2 reactivation of pre existing faults disconti nuities joints foliations or rock anisotropies surfaces characterized by residual or lowerthan peak strength formation of composite failure surfaces 3 regional tectonic movements inducing newslope morphologies uplift major fault movement pull apart zones folding the boundary between classical tectonics andslope deformations especially at a large scale hasalways been indistinct as emphasized by antoine 1988 schultz ela 2001 in his paper antoinediscussed mechanisms like diverticulation def ined by lugeon 1943 and badoux 1963 wherepart of pre alpine nappes were reversed in geo metry by huge landslides inverting the stratigraphy antoine 1988 a remarkable geometrical analogyexists between basin extensional tectonics wer nicke 1981 and certain landslide spreading inclays voight 1973 varnes 1978 hutchinson1988 this is despite the fact that wernicke shypothesis demonstrated that basin and rangeregions were not produced by huge landslides butby low angle faulting induced by geodynamic pro cesses regional extension has produced changesin topography and as a consequence signi cantgravity induced deformations therefore we suggest that the term slope tec tonics is justi ed and must be recognized as animportant component in slope deformation slopeinstability implies movements driven by gravitythat can produce irreversible deformations in thepast slopes were viewed as privileged erosionzones de la noe de margerie 1888 strahler1950 whereas few erosion processes were attribu ted to landslides young 1972 since the work ofsimonett 1967 and hovius et al 1997 the link