the role of calcining and basal fluidization in the long runout of carbonate slides an example from the heart mountain slide block wyoming and montana u s a abstract in order to understand the movement of large rock masses or allochthons on low angle surfaces we have studied the 3400 km2 heart mountain slide block of northwestern wyoming and southwestern montana the heart mountain slide block was initiated on a 2 gradient with its toe thrust a minimum of 45 km across an early eocene landscape the slide block moved on a basal layer that ranges in thickness from a few tens of centimeters to several meters this basal layer commonly has a concrete like appearance of rounded mixed lithology grains in a fine grained carbonate matrix and in some locations it has features similar to sedimentary deposits including both normal and inverse grading flow banding turbidite like structures and clastic dikes containing pieces of carbonized wood nowhere did we observe crosscutting relationships in the basal layer or overlying clastic dikes as would be expected from incremental or noncatastrophic emplacement results from cathodoluminescence and 18o 13c and 8

numerical modeling of the emplacement of socompa rock avalanche chile 1 the 7 5 ka socompa sector collapse emplaced 25 km3 of fragmented rock as a thin but widespread 500 km2 avalanche deposit followed by late stage sliding of 11 km3 as toreva blocks most of the avalanche mass was emplaced dry although saturation of a basal shear layer cannot be excluded modeling was carried out using the depth averaged granular flow equations in order to provide information on the flow behavior of this well preserved long run out avalanche results were constrained using structures preserved on the surface of the deposit as well as by deposit outline and run up a proxy for velocity models assuming constant dynamic friction fail to produce realistic results because the low basal friction angles 1 to 3 5 necessary to generate observed run out permit neither adequate deposition on slopes nor preservation of significant morphology on the deposit surface a reasonable fit is obtained however if the avalanche is assumed simply to experience a constant retarding stress of 50 100 kpa during flow this permits long run out as well as deposition on slopes and preservation of realistic depositional morphology in particular the model explains a prominent topographic escarpment on the deposit surface as the frozen front of a huge wave of debris reflected off surrounding hills the result that socompa avalanche experienced a small approximately constant retarding stress during emplacement is consistent with a previously published analysis of avalanche data

understanding how volume affects the mobility of dry debris flows 1 the prediction of the runout length l of large dry debris flows has long been the subject of a considerable research effort primarily due to the obvious concern caused by their destructive power one seemingly well established feature is the increase of the mobility of a rock avalanche defined as the ratio of the runout distance to the fall height with its volume v the physical nature of this lubrication mechanism remains however controversial in this paper we analyse field data and discrete numerical simulations of granular flows and demonstrate the geometrical origin of the apparent enhancement of the mobility with the volume we evidence the intertwined role of volume and topography and show the existence of two contributions in the runout defining two flow regimes one dominated by sliding in which the runout is independent of v and another dominated by spreading in which the runout is strongly dependent on v in the light of these results the search of a volume dependent lubrication mechanism appears to be an ill posed problem

critical slip surface and landslide volume of a soil slope under random earthquake ground motions finding the critical slip surface and estimating the landslide volume are of primary importance for slope seismic design however this may be difficult due to the uncertainty of ground motions to address this problem a new method for calculating uncertainties is recommended in this paper especially for the critical slip surface and landslide volume under random earthquake ground motions firstly a series of intensity frequency nonstationary random earthquake ground motions were generated based on an improved orthogonal expansion method a given number of potential slip surfaces were set in a soil slope subsequently the factor of safety fos of each slip surface for all ground motions was calculated and the minimum fos curves were obtained it was found that the critical slip surfaces and failure times are uncertain under different earthquakes the monte carlo method was used to verify the accuracy of probability density evolution method pdem and the results of the pdem and the monte carlo method are consistent meaning that the pedm has higher computational efficiency moreover the distributions of earthquake triggered landslide volume and landslide depth were analyzed by considering equivalent extreme events both landslide volume and depth exhibit a normal distribution for a homogeneous soil slope the framework of this study is meaningful for slope seismic design in engineering for example the location of critical slip surface can be used for slope reinforcement and the distribution of sliding volume can be used for disaster assessment

fragmentation and boosting of rock falls and rock avalanches fragmentation has been proposed as an important dynamical process in the propagation of rock avalanches the occurrence of an intense block fragmentation inside a rock avalanche traveling on smooth inclined terrain followed by a flat region a geometry common to many landslides is first studied numerically by means of a discrete element 2 d code in which blocks are subjected to mutual collisions and impact with the terrain this numerical model confirms that the locations where fragmentation is more likely to occur are those in correspondence of abrupt slope changes we thus analyze this geometry of impact in two cases low and high impact energy in the first case where recent experimental data are available a kinematic analysis shows that the energy released at impact causes high velocities of the smallest fragments a highly probable scenario in rock avalanche dynamics when the impact is so energetic to disintegrate the landslide we find that explosive fragmentation at the slope break provides an extra horizontal boost to a rock avalanche via a peculiar mechanism coupling the geometry of the slope path to the dynamics of the rock avalanche as a consequence a net momentum gain boost results along the horizontal direction due to the terrain asymmetry however under normal field conditions only when the slope angle is greater than 70 and fragmentation produces clasts of fairly uniform size the momentum and runout distance are significantly enhanced allowing for a spectrum of fragment sizes and velocities we find a relationship between the degree of fragmentation and the magnitude of the extra boost

numerical simulation of impact cratering on granular material a new numerical code based on the distinct element method dem is developed to study the impact cratering processes on granular material this code has a potential advantage to simulate the cratering process on granular material since the movement of discrete particles can be treated to show the physical plausibility of this code we conduct 3 d numerical simulations of vertical impact into granular material targets that consist of 384 000 particles and compare the results with those from experimental studies it is shown that the excavation stage of cratering derived from experimental studies is represented well by our simulation the size of the crater cavity and the ejecta velocity and angle distributions are consistent with those obtained in laboratory experiments the impact simulation code developed in this study is thus suggested to be useful for the analysis of the impact cratering process on granular material

initiation movement and run out of the giant tsaoling landslide what can we learn from a simple rigid block model and a velocity displacement dependent friction law abstract tsaoling landslide is the largest and best documented landslide among several large landslides induced by the 1999 taiwan chi chi earthquake pliocene sedimentary rocks of about 125 mm 3 in volume slid along very flat bedding planes dipping by 14 with an average speed of 35 40 m s for about 1650 m before hitting the bank of the chinshui river during the landslide detailed analysis of dtms before and after the earthquake using a gis software leads to an accurate determination of the locations of the centroids of landslide mass revealing the horizontal and vertical displacements of the 2524 m and 524 m respectively those displacements and landslide mass give an apparent friction coefficient of 0 21 and the release of the potential energy of 1 6 10 15 j we conducted rotary shear high velocity friction experiments on fault gouge from bedding parallel faults under semi wet conditions and at 3 mpa normal stress corresponding to the overburden pressure of the landslide mass we also compiled reported data on the frictional properties on shale powders and fault gouge from the landslide site under both dry and wet conditions and proposed a velocity displacement dependent friction law that can describe most experimental data newmark analysis of landslide motion with six scenarios for different landslide materials and conditions assuming a simple rigid block sliding and using measured frictional parameters revealed that the landslide did not occur with dry frictional properties and that the landslide occurred at 38 39 s with accumulated displacements of 0 62 m 1 09 m and reached at the river bank at 82 87 s after the generation of chi chi earthquake at its epicenter those timings are consistent with high frequency signals at 32 40 s and at 76 s recorded at a nearby seismic station and with a survivor s witness that the landslide initiated 10 s after he felt strong ground motion possible s wave arrival at 25 2 s slip weakening is essential in initiating the landslide and low friction coefficient 0 08 0 1 allowed high speed of the landslide possible the landslide was caused by a few peaks of northeast oriented strong accelerations of the ground motion frictional work during the sliding of the landslide mass was estimated to be of about 23 of potential energy and the rest of the released energy is likely to have been consumed during the stopping phase of the landslide after hitting the river bank in complex processes such as fragmentation heat dissipation and spreading of the landslide deposits

a conceptual model for block and ash flow basal avalanche transport and deposition based on deposit architecture of 1998 and 1994 merapi flows the 1998 block and ash flow baf deposits on the western flanks of merapi were described both immediately following emplacement and after one and two wet seasons of erosion this afforded a unique combination of data on deposit morphology and internal structure from proximal to distal reaches the deposits of the basal avalanches from individual baf events were classified into three major and two minor facies in channelised reaches primarily resulting from effects of channel confinement and slope termination reaches were classified into three facies related to preevent topography the deposit facies architecture was interpreted to understand particle transport and deposition within the framework of granular flow systematics the transport model we propose for these basal avalanches involves unsteady flow conditions generated by pulses of collapse as the source and or by development of kinetic waves during the granular flow the coarsest clasts along with low density material migrated to the wave pulse fronts within these flows whereas in bulk flow grain dispersive pressures and kinetic sieving result in coarsest clasts being buoyed to the flow top with this tendency being greatest on higher slopes greater kinetic energy and with greater flow confinement maximising particle collisions deposition begins as the flow reaches near its full extent an initial pulse or flow wave freezes rapidly from its base upward and its rear forward as it looses kinetic energy and dispersive pressure such that an upper higher energy part of the flow is still able to move downstream over the frozen base later waves or pulses then accrete progressively horizontally upslope banking up onto or overtopping earlier deposited sediment hence the overall flow freezes from its front to its tail at termination reaches in unconfined areas the overflowing upper part of flow gradually deposits from its base upward resulting in a slightly tapering sheet formed deposit marked by a front made up of wood fragments and large boulders on sudden slope breaks in termination areas piling up of sediment occurs in flat reaches producing whaleback type forms as the flows rapidly lost competence one implication of this model is that each kinetic wave or flow pulse crest developed within the basal avalanche represents a portion of greater flow depth or stage height hence development of these crests control the ability of parts of the basal avalanche to escape from confined channels and generate unexpected hazards

basaltic pyroclastic flows of fuji volcano japan characteristics of the deposits and their origin fuji volcano is the largest active volcano in japan and consists of ko fuji and shin fuji volcanoes although basaltic in composition small volume pyroclastic flows have been repeatedly generated during the younger stage of shin fuji volcano deposits of those pyroclastic flows have been identified along multiple drainage valleys on the western flanks between 1 300 and 2 000 m a s l and have been stratigraphically divided into the shin fuji younger pyroclastic flows syp 1 to 4 downstream debris flow deposits are found which contain abundant material derived from the pyroclastic flow deposits the new14c ages for syp1 to syp4 are 3 2 3 0 2 9 and 2 5 ka respectively and correspond to a period where explosive summit eruptions generated many scoria fall deposits mostly toward the east the syp1 to syp4 deposits consist of two facies the massive facies is about 2 m thick and contains basaltic bombs of less than 50 cm in size scoria lapilli and fresh lithic basalt fragments supported in an ash matrix the surge facies is represented by beds 1 to 15 cm thick consisting mainly of ash with minor amount of fine lapilli the bombs and scoria are 15 to 30 in volume within the massive facies the ashes within the syp deposits consist largely of comminuted basalt lithics and crystals that are derived from the middle stage lava flows exposed at the western flanks syp1 to syp4 were only dispersed down the western flanks the reason for this one sided distribution is the asymmetric topography of the edifice the western slopes of the volcano are the steepest over 34 degrees most pyroclastic materials cannot rest stably on the slopes steeper than 33 degrees therefore ejecta from the explosive summit eruptions that fell on the steep slopes tumbled down the slopes and were remobilized as high temperature granular flows these flows consisted of large pyroclastics and moved as granular avalanches along the valley bottom furthermore the avalanching flows increased in volume by abrasion from the edifice and generated abundant ashes by the collision of clasts the large amount of the fine material was presumably available within the transport system as the basal avalanches propagated below the angle of repose taking the typical kinetic friction coefficient of small pyroclastic flows such flows could descend the western flanks where scattered houses are below 1 000 m a s l a similar type of pyroclastic flow could result if explosive summit eruptions occur in the future

can dispersive pressure cause inverse grading in grain flows grain flows in the collisional regime are self regulated in such a way that dispersive pressure at every level tends to balance static pressure and so cannot promote the upward segregation of large particles in a steady flow le roux adds new insights to this analysis by pointing out that dispersive and static pressures would not balance in unsteady flows when shear strain rate increases in a grain flow dispersive pressure which is positively correlated to shear strain rate increases too and the gradient of dispersive pressure becomes higher than the gradient of static pressure as a consequence the grain flow expands thus lowering the dispersive pressure until the two gradients reequilibrate during the

global scale analysis of martian landslide mobility and paleoenvironmental clues the mobility of landslides on mars is studied based on a database of 3 118 events to establish the volume of the landslides for the whole dataset based on the deposit area a new volume area relationship based on a representative dataset of 222 landslides is used plotting the h l ratio between fall height h and runout l versus volume landslide mobility is analyzed and compared with existing empirical relationships for martian and terrestrial landslides analyzing the mobility in terms of normalized residuals i e the relative deviation of the h l ratio from the dataset best fit line mobility is found to depend on both the landslide location on mars and landslide typology this allows us to identify four different types of high mobility hypermobile landslides three classes of high mobility landslides are associated respectively to meteoroid impact the olympus mons aureoles and landslides with toreva block failure style and their mobility can be explained by the peculiar flow mechanics the fourth class includes landslides associated with isolated craters those in the regions wetted by the putative oceanus borealis and the ones at high latitudes we suggest that the common factor behind all the hypermobile landslides of this fourth kind is the presence of ice this is confirmed by our data showing that landslides increase in mobility with latitude the latitudinal trend mirrors the distribution of ice as detected by radar neutron probes and the presence of glacial and layered ejecta morphologies because the overall landslide distribution supports the presence of ice lubricated conditions two ice lubrication models are presented showing how ice melting within or underneath the landslides could enhance mobility by proper analysis in terms of apparent friction residuals we find that the mobility of landslides in valles marineris with the largest landslide concentration is lower than average we explain this circumstance partly from the smaller role of ice in equatorial valles marineris and partly because the collapses from high slope relief imply high speed impact with the floor valley confinement loss of momentum and decrease in mobility environmental consequences imply that the present subsurface ice distribution may have been persistent throughout the amazonian period

drop height and volume control the mobility of long runout landslides on the earth and mars long runout landslides are landslides with volumes of 105 m3 or more which move much farther from their source than expected the observation that martian landslides are generally less mobile than terrestrial landslides offers important evidence regarding the mechanism responsible for the high mobility of long runout landslides here we simulate landslides as granular flow using a soft particle discrete element model we show that while surface gravity plays a negligible role observed differences in fall height naturally reproduce the observed differences in mobility of martian and terrestrial landslides we also demonstrate that landslides on iapetus may fit this trend our simulations do not include any fluid and indicate that a mechanism similar to acoustic fluidization can explain the high mobility of long runout landslides this implies that long runout landslides on mars should not be considered as evidence for ice saturated clays or liquid water

the landslide stage of the hsiaolin catastrophe simulation and validation 1 typhoon morakot struck southern taiwan in the summer of 2009 causing the most severe flooding since the 1950s in the early morning of august 9 rainfall triggered the hsiaolin landslide and the resulting debris avalanche covered the township of hsiaolin village kaohsiung around five hundred people were buried alive reconstruction of the runout of the debris avalanche would increase understanding of the large scale avalanches for future hazard mitigation purposes simulation of the debris avalanche runout can provide valuable information for this purpose a new continuum shallow water model is applied to flow over general topography the coulomb friction law is adopted the friction coefficient is initially determined by high pressure rotary shearing tests and subsequently fine tuned by an iterative procedure to minimize the difference between the simulation and the measurement the friction coefficients measured by laboratory tests are found to be in reasonable agreement with the best fit result of the simulation in addition voellmy rheology is applied but it is found that the role of the fluid viscous drag is insignificant the simulation result in the village area is further corroborated by near surface magnetic surveys these indicate that the northern part of the village is dislocated while the artifact structures of the southern part are buried near their original locations by comparing the landslide front and the flow direction of the simulation we are able to confirm as also described by survivors that the landslide swept the northern part of the village into the cishan river while the southern part was flooded subsequently by the debris from a dam breach about 20 min after the landslide

comparing landslides to fluidized crater ejecta on mars 1 we use the mars global surveyor and viking data sets to compare and contrast the geomorphology of four large martian landslides located in valles marineris to fluidized ejecta of seven fresh martian craters located in lunae planum both mass movements have flowed over the martian surface and possess characteristics seen in terrestrial mass movements we combine these comparisons with simple flow models to determine how the planar geometry of landslides and the cylindrical geometry of ejecta can generate different topographic expressions for the same input constraints our purpose is to better understand the emplacement processes of both types of mass movements our geomorphic analyses are consistent with previous views that the large martian landslides resemble large terrestrial long run out flows the planar flow model supports this inference martian landslides probably flowed as a basal glide where motion is limited to a narrow interface at the base of the mass movement geomorphic investigations of fresh multilayered ejecta indicate that their inner portions with their subtle rampart probably flowed like their landslide counterparts as a basal glide distal pronounced contiguous ramparts however resemble features akin to terrestrial debris flows the cylindrical flow model shows that differences in geometry can mask the dynamics of flow emplacement this model suggests as expected a basal glide origin for the inner portions of the ejecta surprisingly basal glide also best explains the topography of the distal ejecta ramparts

effect of the mode of shear on static liquefaction analysis abstractthe current practices for determining the peak yield and postliquefaction critical undrained shear strength of liquefiable cohesionless soils for grounds subject to static shear stress e g sloping grounds or grounds beneath foundations require either a suite of costly laboratory shear tests on undisturbed field samples or empirical correlations with in situ penetration tests which do not account for the effect of the shearing mode on soil behavior improved correlations are developed in this study for estimating the undrained triggering and postliquefaction shear strengths of cohesionless soils which are based on the most reliable field liquefaction data from past cases of liquefaction flow failures and soil shearing behavior observed in a large database of 600 laboratory shear tests for different modes of shear the proposed method accounts for the variations in the mode of shear when providing estimates of the undrained triggering and postliquefaction strengths mobilized in static liqu

commentary on the reduction of friction in long runout landslides as an emergent phenomenon by brandon c johnson charles s campbell and h jay melosh

self lubrication for long runout landslides examination by computer simulation this paper describes the use of a discrete particle computer simulation to test whether the apparent low friction exhibited by long runout landslides could be explained in terms of simple granular mechanics the flow structure consists of an active basal shear zone supporting the majority of the landslide which travels as a relatively solid plug the observed runout appears to depend on the total energy dissipation which is a trade off between 1 the inelasticity of the particles which governs the energy dissipated in each event and 2 the size of the dissipating shear zone which governs the number of particles that are actively dissipating energy very inelastic particles quickly dissipate the work performed at boundaries and result in thin dissipative zones as a result these two factors balance and the runout is nearly independent of particle inelasticity along the same lines increasing the boundary roughness was found to increase the size of the dissipative shear zone and markedly decrease the runout also a distribution of particle sizes destroyed ordered structures within the body which once again increases the dissipation and decreases the runout unfortunately the simulations also indicate that the runout should be independent of the depth of the flow and thus cannot account for the observed volumetric effect on runout

rock and soil avalanches theory and simulation 1 we present a 2 d contact dynamics discrete element model for simulating initiation and motion of rock avalanches integrating hillslope geometry mohr coulomb rock behavior pore pressure before avalanche triggering and avalanche trigger avalanche motion is modeled as a dense granular flow of dry frictional and cohesive particles on the basis of granular physics and shear experiments we review some of the theories for the unexpectedly long runout of rock avalanches different causes are evoked according to the strength strong or weak of the slip surface relative to the bulk mechanical fluidization and acoustic fluidization theories state that agitation of rock particles reduces frictional strength increasing runout conversely granular mechanics suggests that as shear strain rate increases granular material becomes more agitated more dissipative and more resistant another theory states that dynamic fragmentation of clasts creates an isotropic pressure that drives longer runout in contrast granular mechanics suggests that fragmentation may induce fluidization and strengthening of the granular material while particle size reduction among others induces weakening of the granular flow and enhances long runout runout is also enhanced for column like rock masses collapsing from steep hillslopes long runout may also be linked to thermal weakening mechanisms at the slip surface e g thermal pressurization and shear melting which may lower drastically the shear strength the model is illustrated with a hypothetical example of a rain triggered avalanche mobilizing shallowly dipping layers several phases are identified including slope failure avalanche triggering resulting from slip weakening and avalanche motion in which rocks are folded and sheared

the rock avalanche of february 1995 at claix french alps abstract the sedimentology of a rock avalanche involving ca 7 10 3 m 3 that happened on february 1995 at claix the french alps is analysed here the talus shows a proximal depression due to the impact of the debris then a grooved area with few mainly sandy silt deposits and a downslope accumulation of coarse debris that reaches up to 3 m in thickness the material underwent mass movement as demonstrated by the steep distal front the strong fabric strength and the thrust planes the greatest part of the deposits consists of a clast supported to partially openwork debris with angular clasts over a sheared matrix supported basal layer the largest blocks often more than 1 m in length are concentrated at the surface and the front the overall sedimentological characteristics are similar to those of the small dry grain flows that occur usually on rockfall talus except for the abundance of fine grained particles that results from intense cataclasis during flow it is suggested that the deposits of such medium scale rock avalanches probably not uncommon in seismic regions may have been confused in previous studies with other slope mechanisms such as debris flow and rockfall

the mechanism of the 1941 tsaoling landslide taiwan insight from a 2d discrete element simulation tsaoling is located in southwestern taiwan 10 km east of the frontal thrusts of the mountain belt five large historical landslide events were recorded from 1862 to 1999 no details of the earliest landslide event 1862 are available thus this paper deals with the 1941 landslide event using the particle flow code in two dimensions pfc 2d to simulate the mechanism of the tsaoling landslide in 1941 this study shows that the landslide block developed cracks and slid down 0 2 1 8 m on the sliding plane the cracks concentrated in certain zones which corresponded to future landslide detachment planes during the vibration simulation the cracks spread from the shear plane to ground surface monitoring the variations of the displacements velocity and stress during vibration simulation showed that the peak velocity and stress in the transition zones occurred at 3 s the displacement of the left part of the block exceeded 1 3 m and the displacement of the right part was less than 1 3 m during vibration simulation these results suggest that the left part of the block was pushed down by the right part ultimately inducing a landslide during an earthquake

the pristine shape of olympus mons on mars and the subaqueous origin of its aureole deposits abstract the tallest volcano in the solar system olympus mons on mars is bordered by at least ten enormous sub circular hummocky deposits forming a welded halo termed the aureole the aureole units or simply aureoles which are the deposits of landslides from olympus mons have dramatically transformed the pristine size and shape of the volcanic edifice topographic data are used to determine the amount of collapsed material and so reconstruct the original outline of olympus mons before the landslides took place under the assumption that the edifice did not start failing until it had reached this maximum size due to post aureole deposition on the eastern and southern flanks and to the uncertainty of the slippage level on the northern side the reconstruction is sufficiently precise along the western and north western olympus mons flank it is more uncertain for the northern flank while it is not feasible around the rest of the volcano it appears that the radius along the western and north western olympus mons before the collapse of the aureole landslides was approximately 200 km longer or more the results show that the volume of the aureoles even if enormous is insufficient to fill the ideal conical edifice which would be obtained prolonging the olympus mons flanks with present slope angles thus an overhang remains in the pre aureole reconstructed olympus mons which would also explain the onset of instability that led to the aureole collapse further a drape deposit blanketing the southern acheron fossae ridge just at the front of the western w aureole landslide deposit and a fan channel system carved on the same w aureole are investigated and it is suggested that these morphologies have been emplaced in subaqueous setting while the drape may indicate a landslide thrust water splash akin to a tsunami deposit caused by the fast travelling w aureole landslide the fan channel system is similar to certain morphologies in the terrestrial oceans a numerical model of the collapse of the western aureole unit in water shows final runouts on both acheron ridge and amazonis planitia compatible with observations provided that the friction angle is extremely small of the order of a tenth of degree simulations indicate that the w aureole could have reached acheron fossae ridge with velocities in excess of 100 m s which would explain the several tens of km long distance reached by the landslide thrust tsunami deposit in short morphological and numerical lines of evidence would indicate a subaqueous origin for the largest w aureole landslide

short term beach dune sand budgets on the north sea coast of france sand supply from shoreface to dunes and the role of wind and fetch abstract three experimental plots covering the transition from the upper beach to the dune on the north sea coast of france were monitored at various intervals over a period of 18 24 months via high resolution terrain surveys in order to determine inter site sand budget variability as well as patterns and processes involved in sand exchanges between the upper beach and dune the wind regime consists of a fairly balanced mix of moderate 80 of winds are below 8 m s onshore offshore and shore parallel winds sustained dune accretion over several years depends on the periodic local onshore welding of shoreface tidal banks that have developed in the storm and tide dominated setting of the southern north sea the only site where this has occurred in the recent past is calais where bank welding has created a wide accreting upper beach sand flat at this site significant sand supply from the subtidal sand bank reservoir to the upper beach flat occurred only once over the 18 month survey following a major storm the bulk of the sand deposited over this large flat is not directly integrated into the adjacent embryo dunes by onshore winds but is progressively reworked in situ into developing dunes or transported alongshore by the balanced wind regime thus resulting in alongshore stretching of the embryo dune system the leffrinckoucke site near belgium shows moderate beach dune mobility and accretion while the wissant site exhibits significant upper beach bedform mobility controlled by strong longshore currents that result in large beach budget fluctuations with little net budget change to the detriment of the adjacent dunes accretion at these two sites which are representative of the rest of the north sea coast of france is presently constrained by the absence of a shore attached sand bank supply reservoir while upper beach dune sand exchanges are further limited by the narrow wave affected upper beach the intertidal morphology of bars and troughs which segments the aeolian fetch and the moderate wind energy conditions the balanced wind regime limits net sand mobilisation in favour of either the beach or the dune and may explain the relatively narrow longshore morphology of the dune ridges bounding this coast

mode i microfracturing and fluid flow in damage zones the key to distinguishing faults from slides abstract we have examined the distribution of microfractures in arenites and the evolution of vein forming fluids in the matrix of carbonate breccias within the damage zones of large detached blocks in order to characterize their modes of emplacement previous studies of microfractures in the damage zone associated with tectonic faulting have shown a clear pattern of increasing density as the fault is approached previous studies of carbonate breccia within damage zones of tectonic faults typically document evidence of multiple fluid events representing repeated rupture healing processes however in this study we find no change in the microfracture density with distance from the 45 km displaced gravity driven slide block at heart mountain wyoming in a previous study of the same massive slide block there was no evidence of multiple fluid infiltration events related to emplacement we interpret these observations as indicating the absence of rupture cycling that would be expected in the development of a process zone instead being consistent with catastrophic emplacement of gravity driven slide blocks we use this distinct pattern of microfracture density and fluid infiltration to demonstrate that several large 1 km2 detached blocks in the basin and range previously thought to be allochthons related to hyperextension detachment faults are actually slide blocks whose detachment surfaces represent no crustal extension

the beinn alligin rock avalanche nw scotland cosmogenic 10be dating interpretation and significance a tongue of very coarse rockslide debris that extends 1 25km downvalley below beinn alligin in nw scotland has been variously interpreted as a glacier cored rock glacier landslide debris redistributed by glacier ice or an excess runout landslide exposure dating with cosmogenic 10be demonstrates that the the debris mass was emplaced at 3950 320 yr bp and therefore was not associated with glacier ice calculations based on frictional considerations imply that the feature is an excess runout rock avalanche sturzstrom deposit the morphological characteristics of the deposit appear consistent with movement by grainflow or fragmental flow failure is inferred to reflect time dependent paraglacial stress release and consequent propagation of an internal joint network but may have been triggered by seismic activity the late holocene age of failure implies persistence of the e ects of paraglacial stress release over a time scale of several millennia

observations of grain scale interactions and simulation of dry granular flows in a large scale flume a series of 30 tests on dry granular flows were performed using a large scale flume under varying source volumes and basal friction conditions to capture grain scale interactions and their impact o

a kinematic model of the hsiaolin landslide calibrated to the morphology of the landslide deposit abstract this paper presents results of a case study on the hsiaolin catastrophic landslide including its kinematic process and the geometry of deposition based on geomorphologic analysis the landslide initiated in thick multi aged colluvium soils at the headwaters of a small stream upslope of hsiaolin village a 3d discrete element program pfc3d was used to model the kinematic process that led to the landslide and destruction of hsiaolin village the landslide advanced from debris slide to debris avalanche during the kinematic process assuming a friction coefficient of each particle of 0 1 the predicted maximum velocity was about 70 m s a velocity which permits the debris to cross qishanxi stream and deposit on the opposite bank based on simulation results hsiaolin village was inundated in 60 to 65 s after failure initiation and at 112 s after the event the debris avalanche came to rest forming a landslide dam

shear localisation strain partitioning and frictional melting in a debris avalanche generated by volcanic flank collapse abstract the arequipa volcanic landslide deposit to the east of arequipa peru originated from the pichu pichu volcanic complex covering an area 100 km2 the debris avalanche deposit exhibits internal flow structures and basal pseudotachylytes we present field microstructural and chemical observations from slip surfaces below and within the deposit which show varying degrees of strain localisation at one locality the basal shear zone is localised to a 1 2 cm thick extremely sheared layer of mixed ultracataclasite and pseudotachylyte containing fragments of earlier frictional melts rheological modelling indicates brittle fragmentation of the melt may have occurred due to high strain rates at velocities of 31 m s 1 and that frictional melting is unlikely to provide a mechanism for basal lubrication elsewhere we observe a

simulation of tsaoling landslide taiwan based on saint venant equations over general topography the 1999 chi chi earthquake triggered the catastrophic tsaoling landslide in taiwan the geomorphological change measured from the data of the 1989 and 2000 aerial photos reveals that the scar and deposit volumes are about 0 126 km3 and 0 15 km3 respectively the debris material ran over a distance of 1 6 km with 500 m descent in elevation in this paper we use the continuum model of hydraulic flow shaltop2d based on the equations of bouchut and westdickenberg to simulate numerically the landslide dynamics when the mass is moving the flow is assumed hydrostatic with a basal coulomb friction the best fit is obtained using the basal friction angle equal to 6 the only parameter of the simulation uniformly applied in the calculation domain the landslide front reaches the chinshui river valley the foothill of the slope within only about 25 s after initiation and the motion settles in about 113 s the maximum speed is estimated 75 m s the spreading of the deposit agrees well with the field measurement

development of characteristic volcanic debris avalanche deposit structures new insight from distinct element simulations large scale catastrophic collapse of volcanic edifices is a relatively common phenomenon in the geologic record however the processes that occur during debris avalanche emplacement remain poorly understood and must generally be inferred from analysis of avalanche deposits in the field which are recognized to contain a suite of recurrent features such as conical surface hummocks and toreva block ridges this study uses the distinct element numerical modelling method to investigate debris avalanche emplacement processes because it allows brittle deformation of the failure mass to be examined after describing the material calibration and model setup necessary for modelling the geomechanical behaviour of a failed edifice flank a sequence of emplacement snapshots is described the simulated debris avalanche is seen to evolve from initial block sliding through extension with horst and graben structures defined by propagation and offset of large scale discontinuities to a final stage in which the avalanche flows down valley the numerical model is consistent with emplacement theory in the literature and allows for a more precise view of the processes at work during failure and the deposits created thereby for example toreva blocks are formed in the medial and proximal sections of the failure through top down propagation of normally offset discontinuities developed from upper surface tension a mechanism for surface hummock formation is also recognized involving the retention of surface blocks as these and other characteristic deposit features are formed from a flank with homogeneous material properties brittle deformation of the initially listric shaped failure mass and associated macroscopic structural evolution are recognized as important factors in failure evolution and subsequent deposit morphology

large scale landslide simulations global deformation velocities and basal friction the cause of the apparent small friction exhibited by long runout landslides has long been speculated upon in an attempt to provide some insight into the matter this paper describes results obtained from a discrete particle computer simulation of landslides composed of up to 1 000 000 two dimensional discs while simplified the results show many of the characteristics of field data the volumetric effect on runout preserved strata etc and with allowances made for the two dimensional nature of the simulation the runouts compare well with those of actual landslides the results challenge the current view that landslides travel as a nearly solid block riding atop a low friction basal layer instead they show that the mass is completely shearing and indicate that the apparent friction coefficient is an increasing function of shear rate the volumetric effect can then be understood with all other conditions being equal different size slides appear to travel with nearly the same average velocity however as the larger landslides are thicker they experience smaller shear rates and correspondingly smaller fractional resistance

influence of particle shape on the frictional strength of sediments a numerical case study abstract numerous direct and ring shear tests supply that composition and texture of sediments are crucial for shear and frictional strength we simulate particle interactions on a micro scale level during shearing with a numerical shear box using the discrete element method dem based on the granular model approach detailed information about slip localisation and rates forces at particle contacts as well as particle rotation can be quantified as function of particle shape stress conditions and shear rate our numerical experiments show that the deformation behaviour of clay is largely controlled by their particle shape two key factors sphericity and roughness could be identified as relevant for frictional strength shear zone development and particle rotation with sphericity dominating over roughness decreasing sphericity leads to complex initial microfabrics whose breakdown with increasing strain is caused by particle rotation preferred particle orientation favours low friction decreasing volume strain and the evolution of particle domains of similar orientation decreasing roughness results in particle interlocking of different degrees which obstructs slip and rotation to preferred orientations so that friction is high and volume strain positive spatial and temporal shear zone development depends on the roughness of particles increasing roughness precludes shear zone development and particle domain evolution shear zone localisation depends on particle sphericity increasing sphericity leads to more localised but vertically dilated deformation

trouble with diffusion reassessing hillslope erosion laws with a particle based model 1 many geomorphic systems involve a broad distribution of grain motion length scales ranging from a few particle diameters to the length of an entire hillslope or stream studies of analogous physical systems have revealed that such broad motion distributions can have a significant impact on macroscale dynamics and can violate the assumptions behind standard local gradient flux laws here a simple particle based model of sediment transport on a hillslope is used to study the relationship between grain motion statistics and macroscopic landform evolution surface grains are dislodged by random disturbance events with probabilities and distances that depend on local microtopography despite its simplicity the particle model reproduces a surprisingly broad range of slope forms including asymmetric degrading scarps and cinder cone profiles at low slope angles the dynamics are diffusion like with a short range thin tailed hop length distribution a parabolic convex upward equilibrium slope form and a linear relationship between transport rate and gradient as slope angle steepens the characteristic grain motion length scale begins to approach the length of the slope leading to planar equilibrium forms that show a strongly nonlinear correlation between transport rate and gradient these high probability long distance motions violate the locality assumption embedded in many common gradient based geomorphic transport laws the example of a degrading scarp illustrates the potential for grain motion dynamics to vary in space and time as topography evolves this characteristic renders models based on independent stationary statistics inapplicable an accompanying analytical framework based on treating grain motion as a survival process is briefly outlined

precambrian basin margin fan deposits mesoproterozoic bagalkot group india abstract three dimensional facies variability in coarse clastic sedimentary rocks breccia conglomerates and coarse grained sandstones at the base of the ramdurg formation suggests terrestrial scree and fans giving way downslope to fluvial sediments along the margin of the mesoproterozoic bagalkot basin in india in consistency with the basic tenet of precambrian alluvial sedimentation fluvial architectural elements and field location specific consistency in channel flow direction support an invariably braided pattern for the rivers although the architectural element packaging pattern does show distinct changes downslope with channel belts thinning and becoming more regular in their geometry with possible persistence of a semi arid climate downslope change in flow durability in the channels was controlled primarily by water discharge depending on position of the channels with respect to the mean level of the water table basin margin slope intersection confined between an unconformity below and a granular lag succeeded by thoroughly wave featured sandstone and argillite carbonate above the coarse and poorly sorted clastic sedimentary rocks of the basal ramdurg are interpreted as a base level lowstand product for which the sedimentation rate exceeded the rate of space creation for sediment accumulation consequently the fan succession as a whole is coarsening upward fluvial sections nonetheless fine upward as the depositional slope gradient became progressively reduced with aggradation of channels tectonics related slope variation along and across the basin margin devoid of vegetation dictated the sediment distribution and sequence building pattern primarily eventual termination of this basin margin depositional system was caused by later enhancement in the rate of base profile rise

unraveling driving factors for large rock ice avalanche mobility large rock ice avalanches have attracted attention from scientists for decades and some of these events have caused high numbers of fatalities a relation between rock slope instabilities in cold high mountain areas and climate change is currently becoming more evident and questions about possible consequences and hazard scenarios in densely populated high mountain regions leading beyond historical precedence are rising to improve hazard assessment of potential rock ice avalanches their mobility is a critical factor this contribution is an attempt to unravel driving factors for the mobility of large rock ice avalanches by synthesizing results from physical laboratory experiments and empirical data from 64 rock ice avalanches with volumes 1x106 m3 from glacierized high mountain regions around the world the influence of avalanche volume water and ice content low friction surfaces and topography on the apparent coefficient of friction as a measure of mobility is assessed in laboratory experiments granular ice in the moving mass was found to reduce bulk friction up to 20 while water led to a reduction around 50 for completely saturated material compared with dry flows evidence for the effects of water as a key driving factor to enhance mobility was also found in the empirical data while the influence of the ice content could not be confirmed to be of much relevance in nature besides liquefaction it was confirmed that mobility increases with volumes and that frictional surface characteristics such as flow paths over glaciers are also dominant variables determining mass movement mobility effects of the topography along the flow path as well as channeling are assumed to be other critical factors the results provide an empirical basis to roughly account for different path and flow characteristics of large rock ice avalanches and to find appropriate ranges for friction parameters for scenario modeling and hazard assessments copyright 2011 john wiley sons ltd

comments on mount sedom salt diapir source for sulphate replenishment and gypsum supersaturation in the last glacial dead sea lake lisan by levy ej sivan o antler g lazar b stein m yechieli y gavrieli i abstract the paper under discussion ignores a published very large new data set charrach 2018a b which is multi disciplinary and integrates the most recent research the detailed study of the geology of mt sedom raises many questions regarding the interpretation and models presented in the paper the analysis of the new data set from mt sedom gathered from measured evidence with an analysis of the hydro geochemistry of the dead sea basin regarding the different sources of sulphate ions could considerably improve their paper

a model for frictional melt production beneath large rock avalanches 1 two puzzling traits of giant rock avalanches sturzstroms are the decrease of the effective friction coefficient as a function of the volume volume effect and the remarkable preservation of large geological structures during the flow demonstrating that the upper cap of a sturzstrom travels coherently on top of a basal shear layer hence frictional heat is rapidly produced along the shear layer which could explain the formation of sheets of molten rock inside certain landslide deposits it has been conjectured that a molten layer could potentially self lubricate the base of the sturzstrom to theoretically investigate this scenario we consider the model of a rock slab sliding on an inclined surface we present a set of coupled differential equations to calculate the frictional heat produced the properties of the molten layer thickness temperature and velocity distribution and the motion of the slab our simulations illustrate the onset of self lubrication and show the volume effect when the melt viscosity is low corresponding to a simulated mafic composition of the rock for a felsic composition and to some extent also for intermediate melts we find that the melting introduces more resistance at the beginning of the melting process in close similarity with frictional melting in tectonic faults however in contrast to faults the rock avalanche is capable of overcoming the initial resistance in at least two situations if the rock is rigid and the landslide is sufficiently thick or else if the material of the landslide is disintegrated the simulations also show that although self lubrication is a viable possibility to explain the runout of sturzstroms there are rather stringent conditions for the formation of a molten layer of good lubricating qualities more generally we suggest that the properties of the coulomb frictional law at the interfaces may change radically during sliding and that the assumption of constant friction does not represent a good model in landslide calculations

decoupling of small volume pyroclastic flows and related hazards at merapi volcano indonesia the november 1994 eruption at merapi volcano provided good evidence of decoupling of dome collapse pyroclastic flows and of large scale detachment of an ash cloud surge acs component from the basal block and ash flow baf timing and stratigraphic relationships of the largest 1994 acs indicate that this escaped from the valleys travelled well ahead of the baf arrived at the termination tens of seconds before it and deposited a discrete acs deposit beneath the baf unit this suggests that the acs detachment mostly occurred relatively high on the volcano slope likely at the foot of the proximal cone later pyroclastic flow eruptions in january 1997 and july 1998 also showed evidence of acs detachment although to a lesser extent suggesting that acss could be a frequent hazard at merapi volcano based on an extensive review of the available literature and on field investigations of historical deposits we show here that flow decoupling and acs detachment in the way inferred from the 1994 eruption is a common process at merapi the acs related destructions outside valleys were frequently reported in the recent past activity of the volcano i e in at least 16 pyroclastic flow eruptions since 1927 destruction occurred systematically in eruptions where maximum runout of the bafs was 6 5 km or more and occurred rarely for baf runouts of 4 5 km or less the acs deposits have been recognized beneath some valley filling baf units we attribute to some recent destructive eruptions i e the 1930 1954 1961 and 1969 eruptions topographic conditions at merapi volcano favouring acs detachment include a the high slope 30 of the proximal cone leading to high proximal velocities of the pyroclastic flows and thus to the transfer of large amounts of particles into the ash cloud b the strong break in slope at the foot of the proximal cone where the velocity of the basal baf is strongly reduced and a major acs component is thought to form and detach by shearing over the baf and c the small depth of most valleys in the first kilometres beyond the foot of the cone which allows minor acs components to escape from the valleys during travel of the baf however flow decoupling and acs detachment occur for only some of the numerous pyroclastic flows that follow the same path in a given eruption this indicates that topography alone cannot lead to flow decoupling we suggest two factors that control flow decoupling and its extent the main one is flow volume and thus flux as both are correlated in almost instantaneous dome collapse events as suggested by the observed relationship between flow decoupling and the travel distance of the pyroclastic flows the second factor is the amount of available ash in the flow at its early stage which influences the mass and thus momentum of the ash cloud the amount of ash in the pyroclastic flows of merapi may depend on several factors among which are a the physical and thermal state of the part of the active dome that collapses and b the proportion of older cold rocks incorporated in the flow either by undermining of surrounding summit rocks by the current pyroclastic flow activity or by erosion on the upper slopes

discrete element simulation of the jiufengershan rock and soil avalanche triggered by the 1999 chi chi earthquake taiwan we present contact dynamics discrete element simulations of the earthquake triggered jiufengershan avalanche which mobilized a 60 m thick 1 5 km long sedimentary layer dipping similar to 22 degrees se toward a valley the dynamic behavior of the avalanche is simulated under different assumptions about rock behavior water table height and boundary shear strength additionally seismic shaking is introduced using strong motion records from nearby stations we assume that seismic shaking generates shearing and frictional heating along the surface of rupture which in turn may induce dynamic weakening and avalanche triggering a simple slip weakening criterion was adopted to simulate shear strength drop along the rupture surface we investigate the mechanical processes occurring during triggering and propagation of an avalanche mobilizing shallowly dipping layers incipient deformation forms a pop up structure at the toe of the dip slope as the avalanche propagates the pop up deforms into an overturned fold which overrides the surface of separation along a decollement simultaneously uphill layers slide at high velocity 125 km h and are folded and disrupted as they reach the toe of the dip slope the avalanche foot forms a wedge that is pushed forward as deformed rocks accrete at its rear we simulated five cross sections across the jiufengershan avalanche which differ in the geometry of the surface of separation topographic and simulated surface profiles are similar the friction coefficient at the surface of separation determined from back analysis is abnormally low mu ss 0 2 possibly due to lubrication by liquefied soils the granular deposits of simulated earthquake and rain triggered avalanches are similar

a fragmentation spreading model for long runout rock avalanches based on the observation that deposits of large rock avalanches consist predominantly of intensely fragmented rock debris it is proposed that the processes of rock fragmentation are significant ca