microstructures and c axis fabrics indicative of quartz dissolution in sheared quartzites and phyllonites abstract quartzites sheared in low metamorphic grade shear zones that extend along the contact with migmatitic gneissic complexes in the quadrilatere ferifero region southeastern brazil show quartz microstructures indicating deformation by dissolution dissolution occurred adjacent to the foliation planes preferentially in quartz porphyroclasts oriented with their 0001 planes parallel to the foliation dissolution worked as an efficient mechanism to remove porphyroclast edges smoothing foliations and enabling strain accommodation both dissolution and crystal plasticity were competitive crystallographically controlled processes operating in different domains of the evolving microstructure dissolution occurred along the foliation planes while isovolume crystal plasticity and accompanying recrystallization operated essentially in the quartzose domains between folia phyllonites formed in the most strained domains of the shear zones fine grained quartz grains in phyllonites show uncommon c axis fabrics c axis oriented at low angles to the stretching lineation which were interpreted to form either by direct reprecipitation or by residual concentration of grains unfavourably orientated to undergo dissolution domainal c axis fabrics reflect a deformation partitioning path with increasing participation of solution transfer strengthening c axis maxima at low angles with the stretching lineation at the expense of crystal plastic processes during progressive phyllonitization

dynamics of paleoenvironments in the cis ural steppes during the mid to late holocene the multi layered settlement of turganik in the tok river valley steppe region west of the urals has been studied using paleopedological and microbiomorphical methods early humans lived in the settlement during the eneolithic epoch the fifth millennium bc and in the early bronze age the fourth millennium bc the cultural layers attributable to the atlantic period of the holocene developed under conditions of a rather dry climate with the landscapes being dominated by the grass and herb steppe the settlement area was above the flood water level and was suitable for habitation the soils in its vicinity were kastanozems endosalic protosodic the final stages of the cultural layer formation bear traces of strong though short term floods with the deposits of the latter partly concealed traces of the preceding long term arid phase maximum aridity was during the final interval of the atlantic period the subboreal and subatlantic periods were noted for meadow chernozem soil formation luvic chernozems stagnic and an increasing proportion of arboreal species in the pollen assemblages some phytoliths of aquatic plants were found in the assemblages dominated by those of meadow grasses the climate was more humid and cool although short episodes of aridity were possible

ice moraine and landslide dams in mountainous terrain we review recent work on ice moraine and landslide dams in mountainous terrain thus complementing several comprehensive summaries on glacier dams in intracontinental and arctic areas of low relief we discuss the roles of tectonic and climatic forcing on ice moraine and landslide dam formation and sudden drainage and focus on similarities and differences between their geomorphic impacts on confined valleys drained by steep bedrock and gravel bed rivers despite numerous reported failures of natural dams in mountain belts throughout the world their relevance to long term dynamics of mountain rivers remains poorly quantified all types of dams exert local base level controls thus trapping incoming sediment and inhibiting fluvial bedrock incision pervasive geomorphic and sedimentary evidence of outburst events is preserved even in areas of high erosion rates suggesting that sudden dam failures are characterized by processes of catastrophic valley floor aggradation active channel widening and downstream dispersion of sediment during which little bedrock erosion seems to be achieved we find that in the absence of direct evidence of former dams a number of similarities among the geomorphic and sedimentologic characteristics of catastrophic outburst flows may give rise to ambiguous inferences on the dam forming process this is especially the case for tectonically active mountain belts where there is ample and comparable potential for the formation and failure of ice moraine landslide and polygenetic dams concomitant with climatic oscillations or earthquake disturbance hence the palaeoclimatic implications of erroneously inferring the cause of dam formation may be significant we recommend that future research on natural dams in mountainous terrain addresses a climate and earthquake controlled systematics in the pattern of formation and failure b quantification of response of mountain rivers to catastrophic outburst events and their concomitant process sequences c elaboration of a comprehensive classification of natural dams in mountainous terrain with special attention to polygenetic dams d physical based modelling of dam formation failure and routing of water and sediment outbursts and e quantitative controls on the contribution of natural dams to sediment budgets in mountainous terrain

river damming late quaternary rockslides in the otz valley region tyrol austria abstract the otz valley and adjacent regions in tyrol austria have been repeatedly affected by large rockslope failures following deglaciation six rockslides each over 107 m3 in volume were emplaced into the otz and inn valleys five of which formed persistent rockslide dams even though catastrophic rockslope failures are short lived events commonly minutes they can have long lasting impacts on the landscape for example large fans have built in the otz valley and knickpoints persist at the former dam sites even though the otz river has eroded through the deposits during the past thousands of years exact age constraints of rockslide dam failure however are still scarce empirical geomorphic stability indices from the literature successfully identified the least and the most stable dams of this group whereas the rest remain inconclusive with some indices variably placing the dams in the stable unstable and uncertain categories this shows a that further index calibrations and b better age constraints on dam formation and failure are needed and c that the exact processes of dam failure are not always trivial to pinpoint for ancient partially breached dams this study is a contribution towards better constraining the nature and landscape impact of dam formation following large rockslope failures

the internal structure of a rockslide dam induced by the 2008 wenchuan mw7 9 earthquake china abstract the internal structure of landslide dams plays a key role in their stability however it has not been much studied probably due to the difficulty in obtaining information on internal structure in most cases here we examined the shear wave velocity structure of a rockslide dam by a surface wave technique called multichannel analysis of surface waves masw during the 2008 wenchuan earthquake m w 7 9 more than 60 000 landslides were triggered and 800 landslide dams formed those dams with a high risk of collapse threatened rescue activities and almost all of the large landslide dams were treated by digging a sluiceway immediately after the earthquake although the risk of collapse of many landslide dams was removed or lowered not all of the countermeasures were based on well controlled methods to analyze the internal of landslide dams to assist in carrying out reliable countermeasures we made detailed investigations on some of the dams and here describe one landslide dam that occurred in the tianchi area grain size analysis revealed that the displaced landslide materials experienced fragmentation and segregation during the long movement the shear wave velocity profile of the dam revealed that the dam consisted of three facies carapace body and basal facies the boundary between facies is distinct the body facies had a greater shear wave velocity compared to those landside dams that had suffered collapse failure during the construction of a sluiceway showing that the dam consisted of more densely deposited materials this kind of dam body had a lower permeability capable of retarding seepage that triggers collapse failure of the dam body due to piping big blocks on the surface also enabled the dam body to have greater resistance to overflow and thus reducing possible collapse failure in the immediate aftermath of overtopping

on the structure of grain boundaries in tectonites abstract grain boundaries in several tectonites have been examined using high voltage and scanning transmission electron microscopy on a gross scale grain boundaries are observed to differ from the host crystal in exhibiting faster rates of preferential etching during ion beam thinning and faster rates of ionization damage during exposure to the electron beam grain boundary features can be grouped according to decreasing size as follows grain junction voids that can form linked networks of tubules arrays of isolated voids and inclusions along the grain boundary surface and a narrow grain boundary film of distorted crystal structure the presence of inclusions in voids and the propensity for electron damage along the boundary suggests that the former were initially fluid filled and that the latter may be hydrated initial microchemical analyses using stem indicate that no compositional difference exists between the grain boundaries and host crystals the overall complex grain boundary structure in tectonites suggests that the effective grain boundary width for intercrystalline diffusion is much greater than that proposed based on metals and that diffusion path lengths along grain boundaries are much less than the theoretical maximum the net effect is to greatly enhance deformation mechanisms dependent on intercrystalline mass transport

the slip fiber chrysotile asbestos deposit in the zidani area northern greece abstract the chrysotile asbestos deposit of zidani in northern greece is an example of a slip fiber deposit associated with alpine type peridotites the deposit occurs in the northern part of an antigorite serpentinite and peridotite body tectonically emplaced on the pelagonian basement of the area a continuous retrograde alteration event is recognizable along the thrust fault between a metaclastic and carbonate sequence and the serpentinite body a phase of ductile deformation that formed antigorite mylonites was followed by a brittle one which formed schistose serpentinite the sense of shear of the overthrusting metaclastic mylonite coincides with that of the immediate underlying schistose and mylonite serpentinites thus retrogression of both groups of rocks is assumed to be the result of the thrust event the numerous altered amphibolite dikes crosscutting the ore created planar anisotropies during the thrust related deformation these planar anisotropies localized the deformation and consequently the formation of the schistose serpentinite and the asbestos ore in the northern part of the serpentinite body slip fiber chrysotile asbestos was formed along anastomosing non penetrating shear surfaces in the schistose serpentinite the chrysotile fibers replaced antigorite in situ in shear planes most likely at a transitional stage of deformation exhibiting both ductile and brittle fabrics however syntectonic filling of shear veins at the brittle stage is the major cause of the origin of the asbestos deposit

the formation and failure of natural dams of the numerous kinds of dams that form by natural processes dams formed from landslides glacial ice and late neoglacial moraines present the greatest threat to people and property landslide dams form in a wide range of physiographic settings the most common types of mass movements that form landslide dams are rock and debris avalanches rock and soil slumps and slides and mud debris and earth flows the most common initiation mechanisms for dam forming landslides are excessive rainfall and snowmelt and earthquakes landslide dams can be classified into six categories based on their relation with the valley floor type i dams 11 of 184 landslide dams from around the world that we were able to classify do not reach from one valley side to the other type ii dams 44 span the entire valley floor in some cases depositing material high on opposite valley sides type iii dams 41 move considerable distances both upstream and downstream from the landslide failure type iv dams 1 are rare and involve the contemporaneous failure of material from both sides of a valley type v dams 1 also are rare and are created when a single landslide sends multiple tongues of debris into a valley and forms two or more landslide dams in the same reach of river type vi dams 3 involve one or more failure surfaces that extend under the stream or valley and emerge on the opposite valley side many landslide dams fail shortly after formation in our sample of 73 documented landslide dam failures 27 of the landslide dams failed less than 1 day after formation and about 50 failed within 10 days over topping is by far the most common cause of failure the timing of failure and the magnitude of the resulting floods are controlled by dam size and geometry material characteristics of the blockage rate of inflow to the impoundment size and depth of the impoundment bedrock control of flow and engineering controls such as artificial spill ways diversions tunnels and planned breaching by blasting or conventional excavation glacial ice dams can produce at least nine kinds of ice dammed lakes the most dangerous are lakes formed in main valleys dammed by tributary glaciers failure can occur by erosion of a drainage tunnel under or through the ice dam or by a channel over the ice dam cold polar ice dams generally drain supraglacially or marginally by downmelting of an outlet channel warmer temperate ice dams tend to fail by sudden englacial or subglacial breaching and drainage late neoglacial moraine dammed lakes are located in steep mountain areas affected by the advances and retreats of valley glaciers in the last several centuries these late neoglacial dams pose hazards because 1 they are sufficiently young that vegetation has not stabilized their slopes 2 many dam faces are steeper than the angle of repose 3 these dams and lakes are immediately downslope from steep crevassed glaciers and near vertical rock slopes and 4 downstream from these dams are steep canyons with easily erodible materials that can be incorporated in the flow and increase flood peaks the most common reported failure mechanism is overtopping and breaching by a wave or series of waves in the lake generated by icefalls rockfalls or snow or rock avalanches melting of ice cores or frozen ground and piping and seepage are other possible failure mechanisms natural dams may cause upstream flooding as the lake rises and downstream flooding as a result of failure of the dam although data are few for the same potential energy at the dam site ownstream flood peaks from the failure of glacier ice dams are smaller than those from landslide moraine and structed earth fill and rock fill dam failures moraine dam failures appear to produce some of the largest downstream flood peaks for potential energy at the dam site greater than 1011 1012 joules differences in flood peaks natural dam failures appear to be controlled by dam characteristics and failure mechanisms

experimental investigation on the longitudinal evolution of landslide dam breaching and outburst floods abstract accurate prediction of the evolution of a landslide dam that is breached due to overtopping failure is necessary to estimate the outflow hydrograph and the resulting inundation in this study physical flume tests on the breaching of landslide dams were conducted a wide grain size distribution with unconsolidated dam material was used dam breaching was initiated by cutting a notch across the crest of the dam adjacent to the side wall of the flume this allowed water to escape from the dam while a steady inflow of water was continuously supplied upstream the effects of upstream inflow on the timescales and magnitudes of the peak discharges and the time to inflection point were also investigated experimental results reveal that the whole hydrodynamic process of dam breaching can be divided into three stages defined by clear inflection points and peak discharge a new longitudinal evolution model is proposed this model captures the initial increase of the soil erosion rate of landslide dam and its subsequent decrease along the longitudinal direction in addition a linear relationship between the soil erosion rate and shear stress of water flow was observed and this is similar to that observed in large scale natural landslide dams furthermore soil erosion resistances of landslide dam against water flow above are observed to increase with the concentration of entrained sediments along the flow direction

analysis of landslide dams induced by the 2008 wenchuan earthquake abstract landslide dams caused by earthquakes are extremely hazardous disruptions of the flow of water and sediment in mountain rivers capable of delivering large outburst floods that may devastate downstream areas we analyzed a unique inventory of 828 landslide dams triggered by the m w 7 9 2008 wenchuan tectonic earthquake china constituting 1 4 of the 60 000 coseismic slope failures mapped and attributed to this event while 501 landslides blocked the rivers completely the remainder caused only partial damming or channel diversion the spatial distribution of landslide dams follows the same trend of that of the total landslide distribution with landslide dams being most abundant in the steep watersheds of the hanging wall of the yingxiu beichuan thrust fault and in the northeastern part of the strike slip fault near qingchuan besides the co seismic landslide density the river width also played a key role in determining the landslide dam formation narrow rivers are more prone to be dammed than the wide rivers the correlation between river width and landslide dam volume follows a linear relation which can be used to roughly estimate the dam formation possibility however the applicability of this correlation needs to be validated in other regions the decay failure rate of dams defined here as the percentage of the number and area of landslide dams that have failed over time shows that 25 of dams accounting for 30 of total landslide dam area failed one week after the earthquake these percentages increased to 60 within 1 month and to 90 within 1 year the geomorphometric parameters were analyzed revealing power law relations between landslide area and dam width landslide source area and dam area as well as lake area and lake volume the inventory presented in this study will enrich the worldwide earthquake induced landslide dam database and will also contribute to a better understanding of the post earthquake dam decay

discriminant analysis of the geomorphic characteristics and stability of landslide dams article i nfo landslides can cause the formation of dams but these dams often fail soon after lake formation thus rapidly evaluating the stability of a landslide dam is crucial for effective hazard mitigation this study utilizes discriminant analysis based on a japanese dataset consisting of 43 well documented landslide dams to determine the significant variables including log transformed peak flow or catchment area and log transformed dam height width and length in hierarchical order which affect the stability of a landslide dam the high overall prediction power 88 4 of the 43 training cases are correctly classified and the high cross validation accuracy 86 demonstrate the robustness of the proposed discriminant models phwl with variables including log transformed peak flow and log transformed dam height width and length and ahwl with variables including log transformed catchment area and log transformed dam height width and length compared to a previously proposed dbi index based graphic approach the discriminant model ahv which uses the log transformed catchment area dam height and dam volume as relevant variables shows better ability to evaluate the stability of landslide dams although these discriminant models are established using a japanese dataset only the present multivariate statistical approach can be applied for an expanded dataset without any difficulty when more completely documented worldwide landslide dam data are available

soils at archaeological monuments of the bronze age a key to the holocene landscape dynamics in the broadleaf forest area of the russian plain abstract during the second half of the holocene the russian plain experienced several climatic oscillations giving rise to changing vegetation patterns the spatial variability of vegetation changes and its effects on soils is still a matter of debate in the present study landscape response to holocene climatic cycles was analysed on the base of detailed morphological chemical and microbiomorphic analyses of a paleosol buried under the kurgan of the abashevo culture middle bronze age and a surface soil both soils located at the tokhmeyevo kurgan cemetery the middle volga region chuvash republic russia developed from the same parent material mantle loam at the same elevation and in close proximity to each other both soils classified as retisols show a similar morphology and key analytical features indicating similar environment the pollen and phytolith spectra confirm that both buried and surface soils formed under similar forest vegetation the buried and surface soils at the tokhmeyevo cemetery could be compared with the previously studied soils of the sareevo settlement of the early iron age and the taushkasy kurgan cemetery of the bronze age these studies confirm the stability of the forest environment at the southern boundary of the forest belt since the bronze age at the same time the buried soil at the tokhmeyevo cemetery has a thick mollic horizon and black organic coatings overlaying brown clay cutans in the argic horizons which sets it apart from the surface soil the radiocarbon dates for the humus in the mollic horizon and black coatings in the argic horizon are surprisingly close to each other about 5 5 cal ka bp and 5 2 cal ka bp respectively the data indicate that the black cutans are derived from degradation of the mollic horizon caused by a sudden increase in humidity during the episodes of extreme summer rainfall events our study also prove that the abashevo people had complicated burial funeral rites the earth mounds are made of the upper horizons of soils cut off from the surface in the vicinity the central part of the mound consists of soil bricks with albic material used for the interior while artificially rumpled material of the argic horizon was used for coverage the use of albic and artificially rumpled material of argic horizon for earth mound construction implies the similarity between the buried and surface soils since the bronze age until today thus the study of such construction techniques is important both for archaeology and paleogeography paleopedology

a new method in mineral magnetism for the separation of weak antiferromagnetic signal from a strong ferrimagnetic background 1 this paper describes a new magnetic method for determining the contribution of weakly magnetic hematite against a strongly magnetic e g magnetite background the method involves measurements of mfr a residual or final remanence after hysteretic demagnetization of saturated isothermal remanent magnetization in terms of sensitivity and precision our proposed method is superior to the currently popular approach known as the hirm method compared to the latter mfr has no error amplification caused by subtraction of terms the method utilizes the available software for hysteretic demagnetization function on an automated vibrating sample magnetometer vsm this in turn automatically decreases some of the disturbing effects of the strong magnetic background e g magnetic viscosity initially non zero offset of hirm for partially oxidized magnetite etc

the hattian bala rock avalanche and associated landslides triggered by the kashmir earthquake of 8 october 2005 the kashmir earthquake of the 8 october killed an estimated 87 350 people 25 500 through co seismic landslides the largest landslide associated with the earthquake was the 68 106 m3 hattian bala rock avalanche that destroyed a village and killed around 1000 people the deposit blocks the valley to a depth of 130 m impounding a lake that reached the dam crest in april 2007 an outburst flood now threatens a major settlement 3 km downstream a series of space images reveals landslide clusters in the rock avalanche source area prior to the earthquake the images also reveal a large slow moving landslide with its toe in the lake failure of this landslide may induce dam failure through overtopping and scour eighty five landslides in the hattian bala catchment predate the shaking of 8 october 2005 a further 73 are co seismic with the main shock and 21 postdate it in the period up to october 2006 landslide magnitude frequency distribution plots derived from satellite images allow an assessment of the contribution of seismically triggered events as compared to background rates of activity

near real time modelling of landslide impacts to inform rapid response an example from the 2016 kaikōura new zealand earthquake reliable methods for the near real time modeling of landslide hazard and associated impacts that follow an earthquake are required to provide crucial information to guide emergency responses after the 2016 kaikoura earthquake in new zealand we undertook such a near real time modeling campaign in an attempt to pinpoint the location of landslides and identify the locations where roads and rivers had been blocked the model combined an empirical analysis of landslide hazard based on previously published global relationships with a simple runout model based on landslide reach angles it was applied manually with a first iteration completed within 24 hrs of the earthquake and a second iteration based on updated shaking outputs within 72 hrs both models highlighted the expectation that landsliding would be widespread and that impacts to roads likely meant that the township of kaikoura was cut off from the surroundings these results were used by responders at the time to formulate aerial reconnaissance flight paths and to identify the risk that landslide dams could cause further damage subsequent model verification based on available landslide inventories shows that although these models were able to capture a large percentage of landslides and landslide impacts the outputs were overpredicted limiting their use for pinpointing the precise locations of triggered landslides to make future versions of the model more useful for informing emergency responses continued work must be done on modification and adaptation of the approach so that this overprediction is minimized nevertheless the results from this study show that the model is a promising initial attempt at near real time landslide modeling and that efforts to automate the approach would greatly increase the utility and speed of modeling in future earthquakes

deformation induced silica redistribution in banded iron formation hamersley province australia abstract the formation of banded iron formations bif remains controversial despite their potential to provide key information on precambrian atmospheres and hydrospheres it is widely agreed that bif are chemical sedimentary rocks comprising alternating layers of iron oxides and chert formed from poorly known precursor phases many models address the chemical transformation of such precursor iron oxide phases into bif during compaction and diagenesis however the formation of chert and the influence of physical forces in this process have received less attention microstructural analysis of bif from the hamersley province western australia reveals that significant amounts of silica were redistributed by dissolution precipitation creep during both diagenesis and regional scale deformation this physicochemical process led to silica remobilisation and volume loss by stress induced dissolution of microcrystalline quartz in an aqueous fluid the dissolved solid phase was transported by diffusion and fluid flow along grain boundaries or within available porosity and then reprecipitated in low pressure zones leading to local volume increase these processes were further enhanced by rheological contrasts between different minerals resulting in significant variations of chert band thickness microstructural observations combined with quantitative microfabric analysis reveal domains of crystallographic preferred orientations cpo in quartz grains within chert layers the cpo fabrics record strain regimes e g pure and simple shear extension and shortening that modified quartz aggregates by dissolution precipitation creep providing new insights into the metamorphic and deformation history of bif we document microstructures that indicate that non coaxial deformation was active during diagenesis and subsequent deformation of the hamersley province bif further relatively undeformed chert layers may have been similarly affected by significant amounts of dissolution precipitation creep providing a possible explanation for the destruction of primary features we show that different generations of chert alternate on a micro scale suggesting that the role of deformation has been underestimated in many aspects of bif research the discovery of dissolution precipitation creep in low grade metamorphic bif provides a potential link between the physical and chemical processes that occur within these rocks after deposition in the hamersley province dissolution precipitation creep was active from the compaction or diagenesis stage and probably operated during all major extensional and compressional deformation events we also suggest that chert layers without cpo record the least overprint by diagenesis and as the most pristine form of bif should be targeted for future paleo environmental research

the formation and breaching of a short lived landslide dam at hsiaolin village taiwan part ii simulation of debris flow with landslide dam breach abstract typhoon morakot 2009 caused serious damage in southern taiwan due to intensive rainfall with long duration the issue of greatest concern arising from the disasters brought about by this extreme event was the burying of the entire village of hsiaolin by a massive debris flow and landslide based on seismological and near surface magnetic data this tragic scenario arose due to a combination of events a massive landslide the formation of a landslide dam and the consequent debris flow when this dam was breached the objective of this part of the study is to investigate the spatial and temporal characteristics of the debris flow induced by the landslide breach the us national weather service breach model and the federal emergency management agency approved flo 2d model are integrated to facilitate the investigation of this catastrophe a series of simulations including a 2d rainfall runoff simulation over the cishan river basin landslide dam breach routing and 2d debris flow simulation around the hsiaolin village were conducted hydraulic calculations were performed to determine the equivalent top elevation of the landslide dam based on inflows computed from the 2d rainfall runoff simulation in association with the digital terrain model dtm and upstream constraint of the backwater inundation areas the hydrograph of the upstream inflow which induced overtopping failure was provided by a 2d rainfall runoff simulation using the flo 2d model calibrated by comparison with the downstream discharge record the longevity of the landslide dam was less than 1 h and it took only about 8 minutes to completely breach the peak discharge rate of this massive landslide dam breach was 70 649 m3 s the dam break hydrograph was then used for upstream inflow to drive the flo 2d debris flow simulation the average sediment concentration by volume was 0 362 the simulated deposited sediment depth showed a reasonable match to the differences of dtms before and after the disaster

effect of slope failures on river network pattern a river piracy case study from the flysch belt of the outer western carpathians abstract landslides are important geomorphic agents in various mountainous settings we document here a case of river piracy from the upper part of the mala brodska valley in the vsetinske mts czech republic raca unit of the flysch magura group of nappes flysch belt of the outer western carpathians controlled by mass movement processes based on the field geological geomorphological and geophysical data we found out that the landslide accumulations pushed the more active river of out of two subparallel river channels with different erosion activity westwards and forced intensive lateral erosion towards the recently abandoned valley apart from the landslide processes the presence of the n striking fault accentuated by higher flow rates of the eastern channel as a result of its larger catchment area were the most critical factors of the river piracy as a consequence of the river piracy intensive retrograde erosion in the elbow of capture and also within the upper portion of the western catchment occurred deposits of two landslide dams document recent minimum erosion rates to be 18 8 mm ky 1 in the western captured catchment and 3 6 mm ky 1 in the eastern catchment respectively the maximum age of the river piracy is estimated to be of the late glacial and or the early holocene

giant landslide triggerings and paleoprecipitations in the central western andes the aricota rockslide dam south peru abstract the central part of the western andes holds an exceptional concentration of giant paleolandslides involving very large volumes of rock material v km3 while those gravitational slope failures are interpreted consensually as an erosional response to the geodynamic activity of the andes relief formation and tectonic activity the question of their triggering mechanisms remains enigmatic to clarify the respective roles of climatic versus seismic forcing on the andean landslides new temporal constraints on paleo movements are essential here we focus on one of those giant slope failures the aricota giant rockslide that damned the locumba valley in southern peru we conducted fieldwork high resolution dem analysis and cosmogenic nuclide dating to decipher its development history and failure mechanisms our results point to the occurrence of two successive events a giant failure mobilizing a rock volume of ca 2 km3 first produced a dam at 17 9 0 7 ka considering its height of ca 600 m the aricota rockslide dam is one of the three largest landslide dams worldwide at 12 1 0 2 ka a second event produced ca 0 2 km3 of material and the rock avalanche debris spread out over the dam as the chronology of those two events is pointing to the two main paleoclimatic pluvial periods in this region heinrich stadial 1a and younger dryas we favor the interpretation of a climatic forcing at a regional scale the concomitant aggradation of alluvial terraces and fan systems along the nearby valleys highlights higher regional erosion sediments supply and mass wasting events during those paleoprecipitation events and strengthens this conclusion

earthquake induced chains of geologic hazards patterns mechanisms and impacts large earthquakes initiate chains of surface processes that last much longer than the brief moments of strong shaking most moderate and large magnitude earthquakes trigger landslides ranging from small failures in the soil cover to massive devastating rock avalanches some landslides dam rivers and impound lakes which can collapse days to centuries later and flood mountain valleys for hundreds of kilometers downstream landslide deposits on slopes can remobilize during heavy rainfall and evolve into debris flows cracks and fractures can form and widen on mountain crests and flanks promoting increased frequency of landslides that lasts for decades more gradual impacts involve the flushing of excess debris downstream by rivers which can generate bank erosion and floodplain accretion as well as channel avulsions that affect flooding frequency settlements ecosystems and infrastructure ultimately earthquake sequences and their geomorphic consequences alter mountain landscapes over both human and geologic time scales two recent events have attracted intense research into earthquake induced landslides and their consequences the magnitude m 7 6 chi chi taiwan earthquake of 1999 and the m 7 9 wenchuan china earthquake of 2008 using data and insights from these and several other earthquakes we analyze how such events initiate processes that change mountain landscapes highlight research gaps and suggest pathways toward a more complete understanding of the seismic effects on the earth s surface

transient water and sediment storage of the decaying landslide dams induced by the 2008 wenchuan earthquake china article earthquake triggered landslide dams are potentially dangerous disrupters of water and sediment flux in mountain rivers and capable of releasing catastrophic outburst flows to downstream areas we analyze an inventory of 828 landslide dams in the longmen shan mountains china triggered by the mw 7 9 2008 wenchuan earthquake this database is unique in that it is the largest of its kind attributable to a single regional scale triggering event 501 of the spatially clustered landslides fully blocked rivers while the remainder only partially obstructed or diverted channels in steep watersheds of the hanging wall of the yingxiu beichuan fault zone the size distributions of the earthquake triggered landslides landslide dams and associated lakes a can be modeled by an inverse gamma distribution b show that moderate size slope failures caused the majority of blockages and c allow a detailed assessment of seismically induced river blockage effects on regional water and sediment storage monte carlo simulations based on volumetric scaling relationships for soil and bedrock failures respectively indicate that 14 18 of the estimated total coseismic landslide volume of 6 4 14 6 10 9 m 3 was contained in landslide dams representing only 1 4 of the 60 000 slope failures attributed to the earthquake these dams have created storage capacity of 0 6 10 9 m 3 for incoming water and sediment about 25 of the dams containing 2 of the total river blocking debris volume failed one week after the earthquake these figures had risen to 60 20 and 90 90 within one month and one year respectively thus also emptying 92 of the total potential water and sediment storage behind these dams within one year following the earthquake currently only 0 08 10 9 m 3 remain available as natural reservoirs for storing water and sediment while 0 19 10 9 m 3 i e about a third of the total river blocking debris volume has been eroded by rivers dam volume and upstream catchment area control to first order the longevity of the barriers and bivariate domain plots are consistent with the observation that most earthquake triggered landslide dams were ephemeral we conclude that the river blocking portion of coseismic slope failures disproportionately modulates the post seismic sediment flux in the longmen shan on annual to decadal timescales

experimental study on the river blockage and landslide dam formation induced by rock slides abstract rock slides triggered by strong earthquake or heavy rainfall may cause different degrees of blockage in flow channels resulting in a significant impact on the continuity of mountainous rivers based on the extent of blocking the blockage type is divided into three categories in this paper no blockage submerged dam partial blockage and complete blockage the accumulation process of sliding materials in the course of rock slides is an important issue for understanding the formation of landslide dams in this study rock slide and river valley models are developed to investigate the typical kinematic process and emplacement of rock slides and the factors that dictate the formation of landslide dams are critically analyzed the experimental study suggests that there is a positive correlation between the deposit height and the rock slide volume despite differences of rock fragmentation and flow condition in addition the less fragmented rocks result in larger maximum deposit height maxi dh and smaller minimum deposit height mini dh while the better fragmented rocks result in smaller maxi dh and larger mini dh furthermore the water depth has a significant impact on the river blockage type a new blockage index bi that combines the landslide volume and the wet cross sectional area is proposed to assess the damming capacity of rock slides then a method for predicting the river blockage type of rock slides is developed based on the relationship between blockage index and the ratio of maxi dh or mini dh and water depth the model proposed in this work can be used to assist estimating the formation of landslide dam for similar rock slides in the future

new aspects of natural science studies of archaeological burial monuments kurgans in the southern russian steppes abstract soil archeological soil studies on the kurgan burial site peregruznoe located to the north of the yergeninskaya upland 80 km from the city of volgograd russia were performed for the first time data on the structure of soil cover in the dry steppe zone during sarmatian times ad 1 were obtained from paleosol data it was established that in the second half of the first century ad the prevailing humid climate progressively changed to more arid conditions similar to those of the modern time using the methodology and theoretical conceptions of archaeological soil science the age of the monuments investigated was detailed for one of the kurgans the original technology involved in erecting the monument was reconstructed and the time of year when construction had taken place was determined principally new information on the details of the funeral rites of the middle sarmatian tribes in the lower volga region was obtained

landslide amplified flash floods the june 2008 panay island flooding philippines abstract the role of landslides in generating or enhancing a flash flood event in aklan panay island philippines resulting from typhoon fengshen was investigated the flash flood occurred between 1100 h and 1400 h gmt 8 of 21 june 2008 and inundated sitios agbatan and abaya in the municipality of libacao peak discharges at kipot a channel constriction in aklan river about 10 km upstream were independently derived using a hydrologic model 302 6 m 3 s and manning s equation 7000 m 3 s the modeled flood peak reached kipot at 0300 h on 21 june 2008 and the communities between 0600 h and 1000 h on june 21 at the earliest the actual flood peak arrived at sitios agbatan and abaya between 1100 h and 1400 h on june 21 at least 1 h earlier than the modeled arrival while the flash flood may have been caused by the preceding rainfall alone 234 4 mm from 0600 h june 20 to 0600 h june 21 the discrepancies in peak discharges and the delayed arrival time suggest the possibility of damming and eventual breaching of the dam evidence of the damming was found at the channel constriction in kipot a landslide at this site was mapped characterized and inferred to have completely blocked the channel and caused the damming implications to flash flood risk assessment are discussed

dilatancy brittle strength and anisotropy of foliated rocks experimental deformation and micromechanical modeling 1 triaxial compression experiments were performed on the four mile gneiss the biotite foliation in the four mile gneiss results in dilatancy and strength anisotropies which become more pronounced with increasing confining pressure microstructural observations indicate that when there is high resolved shear stress on the macroscopic foliation dilatancy arises from extensile microcracks nucleated by frictional slip on biotite grains evolution of crack geometry and coalescence are also influenced by the biotite foliation motivated by these observations a damage mechanics model based on sliding wing cracks was adopted to analyze the anisotropic development of dilatancy and brittle fracture frictional coefficients for the sliding cracks are inferred to be comparable to those of cleavage surfaces of biotite the strength anisotropy data of the four mile gneiss can be explained by the variation of the initial damage with the foliation angle the damage derives from a set of preexisting microcracks with random orientation and a set of cleavage cracks in mica grains preferentially oriented along the foliation angle hence the initial damage is higher for the intermediate angles and consequently the strength is somewhat lower the observation that the mechanical strengths of a variety of foliated rocks decrease with increasing mica content can be explained by the same model with the implication that the initial damage and mica content are linearly related the mechanical and microstructural data show that dilatancy anisotropy may significantly influence the progressive development of borehole breakout and strain localization

analyzing successive landslide dam formation by different triggering mechanisms the case of the tangjiawan landslide sichuan china abstract the catastrophic tangjiawan landslide triggered by the 2008 wenchuan earthquake blocked the duba river impounding one of the most dangerous coseismic barrier lakes in beichuan china the lake was drained by an artificial spillway within one month after the earthquake to minimize the potential dam breach flooding risk however on september 5 2016 this landslide was reactivated and dammed the river again creating a 20 m high dam at the same location and resulting in the formation of a barrier lake with a volume of 0 6 million m3 the day after the event we carried out a field investigation of the landslide and obtained a high resolution image and dem using uav the satellite images from 2005 2008 2010 and 2015 were also collected to analyze the evolution of the landslide together with multi temporal dems the geometry and volumes of the displaced mass and the landslide dams and barrier lakes were calculated using image interpretation and 3d spatial analysis with gis this landslide is of great scientific interest as it presents a good example of multiple reactivation of a pre historical giant landslide under different triggering conditions a reactivation of an older landslide during the wenchuan earthquake and a second reactivation during a rainfall event several years later meanwhile from the hazard assessment and prevention perspective it is also representative as it dammed the river twice in 2008 and 2016 posing threats to both upstream and downstream areas we infer that the successive landslides in this region could be caused by the strong tectonic activities including earthquakes and high average uplifting rate the results of landslide volume analysis using multi temporal dems contribute to the landslide mechanism analysis and suggest that the landslide volume estimation is effected by the landslide type landslide rupture surface location and resolution of dem we also compare the performance of different empirical models of landslide stability and dam breach flood parameters and discuss their application during the quick assessment of the potential hazard of the landslide dams generally the successive landslide dams at the tangjiawan site are caused by the successive landslide reactivations on an anti dip slope controlled by strong tectonic activity and river erosion involve with a mass of loose materials of previous landslide deposition and possess high flood risk to the downstream area the experience gained in this work can be used to assist the hazard assessment and the planning of the emergency measures for similar landslide dams in the future

holocene development of soils in response to environmental changes the novosvobodnaya archaeological site north caucasus abstract soil archaeological studies in north caucasus indicate that the expansion of broad leaved deciduous forests from mountains to foothills and piedmont plain took place about 3000 years ago after the middle holocene steppe stage at this time steppe chernozems transformed into luvisols under forests often the luvisol profiles preserve the relict humus horizon and paleokrotovinas mole tunnels inherited from the chernozemic stage within the same period normally developed soils evolved on the surface of burial mounds luvisols on mounds composed of loess and chernozemic material and rendzinas and luvisols with a calcareous horizon on loamy mounds with a limestone paving stone armour used to strengthen the mounds the rates of profile differentiation and some pedogenic processes have been calculated in the eluvial horizons of luvisols developed on loess or charnozemic material the rate of clay loss was up to 7 8 g m 2 year

morpho sedimentary and stratigraphic characteristics of the 2000 yigong river landslide dam outburst flood deposits eastern tibetan plateau abstract sedimentary characteristics of landslide dam outburst flood deposits are distinct from those of rainfall flood deposits due to their very high hydraulic energy and sediment concentration while they have been studied well in the geological record investigations of modern outburst flood deposits are relatively rare well preserved flood deposits and landforms caused by the june 2000 landslide dam outburst flood in the yigong river eastern tibet provide an opportunity to evaluate such sedimentological response to a high energy modern event the sedimentary characteristics of boulder bars and channel evolution over c 17 km downstream of the breach were investigated by field survey and remote sensing interpretation the results show that the post flood channel migrated downstream and increased in curvature the bar shape is relatively stable downstream but the bar area shows a fluctuating decrease poorly sorted accumulations composed of massive granular gravels and boulders near the breach indicate sediment rich bedload depositing processes occurred during rapid rising stage flows in contrast there are eddy bars and deposition of fine gravel with horizontally bedded laminations 17 km downstream of the landslide suggesting suspended sediment dominated deposition with a rapid loss of transport capacity comparison with previous hydrodynamic simulations indicates that the rates of the rising stage and the falling stage strongly affect the sedimentary characteristics of boulder bars and slackwater deposits

analysis of past and future dam formation and failure in the santa cruz river san juan province argentina abstract around 11 5 106 m3 of rock detached from the eastern slope of the santa cruz valley san juan province argentina in the first fortnight of january 2005 the rockslide debris avalanche blocked the course resulting in the development of a lake with maximum length of around 3 5 km the increase in the inflow rate from 47 000 74 000 m3 d between april and october to 304 000 m3 d between late october and the first fortnight of november accelerated the growing rate of the lake on 12 november 2005 the dam failed releasing 24 6 106 m3 of water the resulting outburst flood caused damages mainly on infrastructure and affected the facilities of a hydropower dam which was under construction 250 km downstream from the source area in this work we describe causes and consequences of the natural dam formation and failure and we dynamically model the 2005 rockslide debris avalanche with dan3d additionally as a volume 24 106 m3of rocks still remain unstable in the slope we use the results of the back analysis to forecast the formation of a future natural dam we analyzed two potential scenarios a partial slope failure of 6 5 106 m3 and a worst case where all the unstable volume remaining in the slope fails the spreading of those potential events shows that a new blockage of the santa cruz river is likely to occur according to their modeled morphometry and the contributing watershed upstream the blockage area as the one of 2005 the dams would also be unstable this study shows the importance of back and forward analysis that can be carried out to obtain critical information for land use planning hazards mitigation and emergency management

layered internal structure and breaching risk assessment of the higashi takezawa landslide dam in niigata japan the internal structure and geotechnical properties of landslide dams have rarely been examined in detail although they largely control the longevity and potential failure mechanisms of the dams during the 2004 mid niigata prefecture earthquake thousands of landslides were triggered and many landslide dams were formed in the imo river basin among these landslides dams the biggest one that occurred in the higashi takezawa district threatened both the upstream and downstream areas emergency and eventual permanent countermeasures were successfully performed to mitigate the hazards presented by the dam the preserved landslide dam provides a good field study area for improving understanding of the formation and stability of similar features to characterize its internal structure and to provide more reliable information for stability analysis we used a multiple channel surface wave technique and microtremor array measurements to survey the dam s s wave velocity v s profile our results show that the integrated use of these methods is an effective approach for determining the s wave velocity structure of landslide dams irrespective of the mountainous environment in which they typically occur the v s profile suggests that the displaced landslide materials had been little disturbed during movement although movement was rapid and over a long distance we also discuss herein the landsliding mechanism and assess the breaching risk of the landslide dam due to overtopping c 2016 elsevier b v all rights reserved

logistic regression model for predicting the failure probability of a landslide dam landslides may obstruct river flow and result in landslide dams they occur in many regions of the world the formation and disappearance of natural lakes involve a complex earth surface process according to the lessons learned from many historical cases landslide dams usually break down rapidly soon after the formation of the lake regarding hazard mitigation prompt evaluation of the stability of the landslide dam is crucial based on a japanese dataset this study utilized the logistic regression method and the jack knife technique to identify the important geomorphic variables including peak flow or catchment area dam height width and length in sequence affecting the stability of landslide dams the resulting high overall prediction power demonstrates the robustness of the proposed logistic regression models accordingly the failure probability of a landslide dam can also be evaluated based on this approach ten landslide dams formed after the 1999 chi chi earthquake the 2008 wenchuan earthquake and 2009 typhoon morakot with complete dam geometry records were adopted as examples of evaluating the failure probability the stable tsao ling landslide dam which was induced by the chi chi earthquake has a failure probability of 27 68 using a model incorporating the catchment area and dam geometry on the contrary the tangjiashan landslide dam which was artificially breached soon after its formation during the wenchuan earthquake has a failure probability as high as 99 54 typhoon morakot induced the siaolin landslide dam which was breached within one hour after its formation and has a failure probability of 71 09 notably the failure probability of the earthquake induced cases is reduced if the catchment area in the prediction model is replaced by the peak flow of the dammed stream for these cases in contrast the predicted failure probability of the heavy rainfall induced case increases if the high flow rate of the dammed stream is incorporated into the prediction model consequently it is suggested that the prediction model using the peak flow as causative factor should be used to evaluate the stability of a landslide dam if the peak flow is available together with an estimation of the impact of an outburst flood from a landslide dammed lake the failure probability of the landslide dam predicted by the proposed logistic regression model could be useful for evaluating the related risk

the formation and breach of a short lived landslide dam at hsiaolin village taiwan part i post event reconstruction of dam geometry abstract in this paper technologies from multiple disciplines are used to reconstruct the shape of the hsiaolin landslide dam a short lived landslide dam sld that was triggered by typhoon morakot here the formation failure mode and breaching process of this sld are investigated the results indicate that the overtopping time and the debris budget constrained the dam geometry the inferred volume of the hsiaolin landslide dam 15 4 million m3 is much smaller than the actual landslide volume 25 2 million m3 even considering the rock mass dilation and debris entrainment meanwhile a 46 error could be induced if an over simplified equation a function of the dam height length and width is used to calculate the dam volume the saddle of the dam crest which is where overtopping occurred could be used as a reference to measure the dam height and length accordingly the determined dam dimensions of height 44 m length 370 m and width 1500 m are suggested to be the representative geometrical indices that influenced the stability of the hsiaolin landslide dam the flow rate of the dammed river another variable relevant to dam stability was determined from a run off simulation it is suggested that instead of the peak flow before the dam formation the flow rate during the blockage period 2974 m3 s should be used as the training data for building a statistical model for stability predictions finally the low hydraulic gradient at the toe of the dam s surface and the high safety factor of the dam slope indicate that the piping and slope instability were irrelevant to the failure of the hsiaolin short lived landslide dam it is postulated that overtopping about one hour after the blockage dominated the failure process of this heavy rainfall induced landslide dam

environmental trends during the bronze age recorded in paleosols buried under a big kurgan in the steppes of the ponto caspian area abstract the southern steppes of european russia are rich in archaeological monuments that were extensively studied for many decades nevertheless paleosols buried under the burial mounds and especially the big kurgans of the bronze age in the ponto caspian area did not receive proper attention the paper focuses on soil evolution and climate dynamics during the bronze age based on the study of soils buried during several stages of earthen mound construction within one big kurgan in the kuban azov plain russia the kurgan 1 in the beysuzhek 9 kurgan cemetery of the bronze age situated in the korenovsky district krasnodar region consists of three earthen mounds made at different times the soils buried under three mounds of the kurgan are located in close vicinity from each other and have similar lithology and geomorphic position they form a chronosequence representing three time slices moreover the chronosequence displays a certain chronological order of burial paleosols were first buried in the center of the kurgan and later closer to its periphery the height of the kurgan is about 4 m that ensures good preservation of the buried soils the research is based on the comparative analysis of morphology micromorphology and analytical properties of three paleosols buried under different constructions in the kurgan and surface soil also the palynological analysis was performed for the uppermost layers 0 5 cm of three paleosols during the first stage of the kurgan construction the novotitorovo archaeological culture of the early bronze age at the 27th 22nd centuries bc the climate of the region was sufficiently humid and provided a high bioproductivity for surrounding landscapes the interval between the second and third stages of kurgan construction was marked by the gradual increase in aridity during the third stage of the kurgan construction the catacomb archaeological culture the middle bronze age the 21st 16th centuries bc the climate was mostly arid the results of the palynological analysis are in agreement with the study of paleosols during the construction of the kurgan the vegetation pattern corresponded to a southern forest steppe the percentage of herbaceous plants increased markedly and steppe species appeared during the time of catacomb culture

plugs or flood makers the unstable landslide dams of eastern oregon abstract landslides into valley bottoms can affect longitudinal profiles of rivers thereby influencing landscape evolution through base level changes large landslides can hinder river incision by temporarily damming rivers but catastrophic failure of landslide dams may generate large floods that could promote incision dam stability therefore strongly modulates the effects of landslide dams and might be expected to vary among geologic settings here we investigate the morphometry stability and effects on adjacent channel profiles of 17 former and current landslide dams in eastern oregon data on landslide dam dimensions former impoundment size and longitudinal profile form were obtained from digital elevation data constrained by field observations and aerial imagery while evidence for catastrophic dam breaching was assessed in the field the dry primarily extensional terrain of low gradient volcanic tablelands and basins contrasts with the tectonically active mountainous landscapes more commonly associated with large landslides all but one of the eastern oregon landslide dams are ancient likely of order 10 3 to 10 4 years old and all but one has been breached the portions of the oregon landslide dams blocking channels are small relative to the area of their source landslide complexes 0 4 33 6 km 2 the multipronged landslides in eastern oregon produce marginally smaller volume dams but affect much larger channels and impound more water than do landslide dams in mountainous settings as a result at least 14 of the 17 82 large landslide dams in our study area appear to have failed cataclysmically producing large downstream floods now marked by boulder outwash compared to a 40 70 failure rate for landslide dams in steep mountain environments morphometric indices of landslide dam stability calibrated in other environments were applied to the oregon dams threshold values of the blockage and dimensionless blockage indices calibrated to worldwide data sets successfully separate dam sites in eastern oregon that failed catastrophically from those that did not accumulated sediments upstream of about 50 of the dam sites indicate at least short term persistence of landslide dams prior to eventual failure nevertheless only three landslide dam remnants and one extant dam significantly elevate the modern river profile we conclude that eastern oregon s landslide dams are indeed floodmakers but we lack clear evidence that they form lasting plugs

dissolution and precipitation processes in deformed amphibolites an example from the ductile shear zone of the ryoke metamorphic belt sw japan the granitic mylonite zone in the cretaceous ryoke metamorphic belt contains deformed amphibolites as thin layers the amphibolite layers do not exhibit pinch and swell or boudinage structures even when contained in a high strain granitic mylonite this mode of occurrence suggests that they were deformed as much as the surrounding granite mylonite in the highly deformed zone strongly foliated amphibolites contain ti rich brown amphibole porphyroclasts rimmed by ti poor green amphibole titanite and chlorite these porphyroclasts are elongated forming shear surfaces defined by preferential distribution of the chlorite and titanite porphyroclastic plagioclase in the strongly foliated amphibolites consists of two components an anorthite rich core and an anorthite poor rim based on these observations the mass balanced reaction occurring during deformation is defined as as the reaction products form a weak interconnected matrix the strain rate of the amphibolites may be controlled by the rate of dissolution precipitation through fluids weakly foliated amphibolites in the low strain zone exhibit cataclastic microstructures whereas the strongly foliated amphibolites do not exhibit such features these microstructural and chemical changes suggest that high strain amphibolites were initially deformed by cataclasis followed by deformation through metamorphic reactions during the metamorphism deformation old plagioclase grains with high xan were not stable and dissolved and new plagioclase grains with low xan crystallized at the old plagioclase rim dissolution of old plagioclase and precipitation of new plagioclase occurred normal to and parallel to the foliation respectively reflecting incongruent pressure solution due to differential stress and changes in p t h2o conditions the development of incongruent pressure solution is attributed to increased fluid flux in the strongly foliated amphibolites as evidenced by the greater abundance of hydration reaction products in the strongly foliated amphibolites than in the weakly foliated ones

sillimanite bearing shear zones in syntectonic leucogranite fluid assisted brittle ductile deformation under amphibolite facies conditions abstract in the imja kola valley eastern nepal miocene peraluminous leucogranite dykes were emplaced within transtensional shear zones synchronously with regional amphibolite facies metamorphism in the metamorphic host rocks within the dykes the magmatic foliations parallel to the metamorphic schistosity are cross cut by thin millimetre to centimetre size shear zones which are made up of prismatic and or fibrolitic sillimanite with a minor amount of white mica these structures have a heterogeneous distribution and form networks of strongly deformed and foliated layers wrapping around poorly deformed granitic pods the textural and strain features are consistent with development of sillimanite shear zones as a result of heterogeneous deformation and fluid action which allowed the replacement of strained magmatic minerals such as feldspar and biotite by means of incongruent pressure solution the described example illustrates that nucleation and development of heterogeneous shear zones under amphibolite facies conditions is also strongly favoured by brittle fracturing and fluid action at the grain scale along pre existing planes of weakness the growth of cracks and fractures can be regarded as a sequence of short lived brittle events due to work hardening which punctuate a history of plastic deformation

deformation and fluid rock interaction in metasomatic dilatant shear bands abstract the microstructure and microchemistry of shear bands from phyllonites along the merens fault in the axial zone of the pyrenees are described deformation was accompanied by the influx of a metasomatic fluid carrying fe and mg which altered muscovite to chlorite and precipitated chlorite and quartz in dilatant sites overall volume increases in shear bands were two to two and a half times if the mobility of al was low al was probably supplied to chlorites growing from solution by isovolumetric replacement of nearby muscovite by chlorite but fe and mg must have been transported on a larger scale chlorite platelets grew with a linear decussate fabric with 001 planes parallel to the local extension direction the most likely geometry for dilation was in pull apart sites on stepped micro faults or shear zones such sites acted as pumps drawing reactive fluid in from outside the rock along high permeability pathways parallel to the shearbands the larger scale pattern of circulation is unknown but field relations suggest fluid movement on a scale of hundreds of metres or more the relatively low concentration of fe and mg in natural hydrothermal brines implies that fluid rock ratios in the shear bands were high this requires a cyclical crack seal mode of infiltration reactions may have enhanced ductility by producing fine grained products and by allowing the opening of dilatant sites but deformation undoubtedly influenced the location of reactions and possibly their rates

laboratory experiments on the failure of coarse homogeneous sediment natural dams on a sloping bed we present the results of a systematic series of 168 laboratory experiments that examine the critical conditions for the failure of landslide dams which obstruct the course of mountain rivers the experiments were carried out by using three different sediment materials with a quasiuniform grain size distribution and with a flume bed slope angles that ranged between 0 and 5 71 0 10 three main typologies of dam failure were observed for increasing values of the dam s downstream face angle 1 overtopping 2 headcutting which led to the formation of an erosion channel on the dam s downstream face that progressively migrated up to the dam crest and 3 initial slide of large part of superficial layer of the dam s downstream face which was followed by headcutting the experiments focused on the second type of failure to provide a safety criterion based on the upstream reservoir level the quantities that govern this phenomenon have been identified and a functional relationship is proposed based on

stability of landslide dams and development of knickpoints the wenchuan earthquake triggered many landslides and numerous avalanches and created 100 odd quake lakes the quake lakes may be removed or preserved the removal strategy was applied to several large landslide dams which were dangerous because massive amounts of water pooled up in the quake lakes the dams could eventually fail under the action of dam outburst flooding potentially endangering the lives of people in the downstream reaches this paper studied the stability of landslide dams and the development of knickpoints by field investigations and experiments and analyzing satellite images the study concluded that if landslide dams were preserved they would develop into knickpoints and act as a primary control of riverbed incision and thus reduce the potential of new landslide the stability of landslide dams depends mainly on the development of the step pool system and stream power of the flood flow if a landslide dam consists of many boulders a step pool system may develop on the spillway channel of the dam which would maximize the resistance consume most of the flow energy and consequently protect the dam from incision the development degree of the step pool system is represented by a parameter s p which was measured with a specially designed instrument a preservation ratio of landslide dams is defined as the ratio of preserved height after flood scouring to the original height of the dam for streams with peak flood discharge lower than 30 m3 s the preservation ratio is linearly proportional to s p for rivers with a peak flood discharge higher than 30 m3 s 30 30 000 m3 s the minimum s p value for stable channel increases with log p in which p is the unit stream power for a landslide dam with a poorly developed step pool system s p is smaller than the minimum value and the outburst flood incises the spillway channel and causes failure of the dam for preserved landslide dams sediment deposits in the quake lakes a landslide dam may develop into a knickpoint if it is stabilized by long term action of the flow large knickpoints can totally change the fluvial processes and river morphology uplift of the qinghai tibetan plateau has caused extensive channel bed incision along almost all rivers for many rivers the incision has been partly controlled by knickpoints upstream reaches of a knickpoint have a new and unchanging base level this brings about a transition from degradation to aggradation and from vertical bed evolution to horizontal fluvial process multiple and unstable channels are prominent in the reaches upstream of the knickpoints if hundreds of landslide dams occurred simultaneously on a reach of a mountain river the potential energy of bank failure and the slope erosion would be greatly reduced and sediment yield from the watershed may be reduced to nearly zero the quake lakes may be preserved long term and become beautiful landscapes streams with long term unfilled quake lakes have good aquatic ecology

low stress deformation of garnet by incongruent dissolution precipitation creep abstract microstructures indicating incongruent dissolution precipitation creep of garnet in eclogite facies graphitic micaschist tauern window eastern alps are investigated garnet dissolution is observed where garnet poikiloblasts grown at eclogite facies metamorphism approached each other as a consequence of progressive deformation during exhumation with estimated p t conditions between 570 c 1 7 gpa and 470 c 0 9 gpa the poikiloblasts are separated by a dissolution seam and flanked by strain shadows filled with quartz white mica and chlorite there is no evidence for crystal plastic deformation of garnet two cases are investigated a stylolitic contact zone b smooth contact zone in both cases internal fabrics of the poikiloblasts and concentric chemical zoning are truncated material previously forming inclusions in the garnet poikiloblasts is now passively enriched in a dissolution seam the original microstructure of fine grained mica graphite aggregates remaining preserved though microstructures suggest that garnet dissolution was driven by local stress concentration the level of differential stress remained too low for plastic deformation of the fine grained white mica graphite aggregates set free from the stress supporting garnet incongruent dissolution precipitation creep appears to be a particularly effective deformation mechanism at low stress in a subduction channel

prediction of the overtopping induced breach process of the landslide dam abstract timely prediction of a landslide dam breach is particularly important for assessments of expected disaster consequences and to plan emergency responses however due to the complex composition and specific geotechnical properties of the landslide dam material such a prediction is challenging in this study geological survey results and landslide dam breach mechanisms were used to develop a numerical model for overtopping induced landslide dam breaches considering variation of soil erodibility with depth the model included a hydrodynamic process module a soil erosion module and a breach evolution module moreover a time step iteration algorithm was adopted to simulate the soil and water coupling process during dam breach a comparison of calculated and measured breach hydrographs variations of dammed lake water level breach sizes as well as two other typical models were used to validate the rationality of the numerical model by considering the baige landslide breach case of november 3 2018 with detailed measured data parameter sensitivity analysis showed that the soil erodibility coefficient exerted an important influence on the breach process while soil critical shear stress had a relatively small influence which remained within 15 for output parameters when it was multiplied by 0 5 1 0 and 2 0 furthermore spillway excavation was found to significantly reduce the peak breach flow if the dammed lake has a large storage capacity thus identifying it as an effective measure for disaster mitigation

fluid rock interaction in some shear zones from the pyrenees mylonites from shear zones cutting hercynian gneisses in the central pyrenees have been studied in thin section and using the electron microprobe the shear zones contain retrogressive greenschist facies assemblages implying introduction of an aqueous fluid during deformation in the zones textural evidence suggests that fluid rock interaction occurred throughout the active life of the shear zones whole rock chemical changes during deformation are documented in a variety of mylonitic lithologies and retrogressed country rocks the overall effect was to reduce chemical differences between lithologies activity diagrams show that this would be expected if a hydrous fluid was circulating between different lithologies during deformation in most cases fluid rock ratios were relatively small resulting in gradual chemical changes and repeated recrystallization open system behaviour with reduction in the number of phases is seen in some granite mylonites suggesting focusing of fluid movement in parts of the shear zones continual fluid rock interaction may have led to reaction enhanced ductility in the shear zones over a long period of time the source of fluid is uncertain but may be related to underthrusting of material beneath the area investigated

geomorphometric characteristics of new zealand landslide dams abstract this study presents results from a quantitative analysis of a new inventory of n 232 landslide dam occurrences in new zealand previously published data were expanded by documentation of recent events and evidence from a regional air photo reconnaissance focused on the upland regions of southwestern south island additional geomorphometric data on landslide dams associated lakes and contributing catchment characteristics were extracted from a 25 m digital elevation model dem augmented by limited ground truthing and compiled in a gis based inventory the new zealand case examples fall into the global trend although they contain both two extremely large features in terms of landslide dam volume vd and lake volume vl analysis suggests that landslide dam height hd landslide dam volume vd lake volume vl contributing catchment area ac and local relief hr are key variables for assessing landslide dam stability independently from other catchment parameters such as lithology climate or dam sedimentology they may be provisionally used as representative characteristics of landslide dams irrespective of environmental boundary conditions such as climate geology or site specific valley geomorphometry three newly proposed dimensionless indices i e the backstow index is basin index ia and relief index ir based on landslide dam height hd allow limited yet promising preliminary assessments of landslide dam stability compared with worldwide examples they also demonstrate a much narrower conditional range for the formation of stable landslide dams in new zealand catchment parameters such as maximum elevation emax upstream relief hr contributing catchment area ac and relief ratio rr are significantly different at sites of former and existing landslide dammed lakes and may be used as independent variables in future terrain based classification schemes generally data are incomplete with underreporting of small and ephemeral landslide dams and over representation of earthquake case studies nonparametric correlation highlights the statistical interdependence between geomorphometric variables as an artefact of initial data calculation while varying accuracy poses a significant drawback for complex multivariate statistical techniques such as principal component cluster or discriminant analyses

complex strain patterns developed at the frontal and lateral tips to shear zones and thrust zones abstract many of the complex strain patterns seen in shear zones and thrust zones such as variable fabric orientations refolded folds and fabrics together with folds with hinges almost parallel to the main transport direction can be explained in terms of differential movement within the shear zones these strains are developed at the frontal and lateral tips of the zones as they propagate examples are taken from the moine thrust zone of scotland which show variations in strains particularly at the lateral tips the form of differential movement described here may lead to complex strain paths and non plane strain ellipsoids and the spatial variations in finite strain may be used to delineate zones of extensional and compressional flow and differential movement in the shear zones or thrusts

3d dem investigation on the morphology and structure of landslide dams formed by dry granular flows abstract large scale landslide dams triggered by earthquakes or rainfall can cause disasters due to inundation upstream and outburst floods downstream after dam failure landslide dams formed by rock debris avalanches are loose in structure and have a lack of stability thus they are more susceptible to breaking the morphological and structural features of landslide dams directly depend on the formation process and greatly affect the dam stability as well as the dam failure modes this study presents the transportation and deposition characteristics of dry granular flows with grains of mixed sizes during the formation of landslide dams via 3d discrete element method dem simulations mainly taking into consideration of the influence of the sliding area length angle and roughness the results show reverse segregation during grain transportation and deposition processes the position of the particles forming the initial deposited layers was also reversed it was found that when the sliding area angle was larger the crest surface frontal angle and deposit width increased with the increment of the sliding area length for lower sliding area angles the deposit width and crest surface frontal angle showed little change the increase of sliding length and base friction coefficient as well as the decrease of the sliding area angle will enhance the size segregation as the slope angle increases the dominant direction of the force chains shifts significantly and the sliding length mainly influences the magnitude of the normal contact force in the other directions these considerations can contribute to a better understanding of the landslide dam morphology and structure after their formation

assessing the internal structure of landslide dams subject to possible piping erosion by means of microtremor chain array and self potential surveys abstract an integrated geophysical approach comprising microtremor chain array and self potential surveys was used to assess the internal structure of landslide dams subject to possible piping erosion in selected sites in japan and kyrgyzstan the non invasive geophysical approach is cost effective environmentally friendly and portable and hence it has proven to be valuable for the geotechnical assessment of landslide dams where piping can trigger failure of the dam while the microtremor chain array survey results revealed the internal structure of the landslide dam the self potential survey results indicated the path of anomalous seepage zones in the surveyed sites of long existing landslide dams the presence of a seepage path in the dam was confirmed by a good correlation between the areas of low phase velocity and large negative self potential anomalies in summary this integrated geophysical approach could be useful for the early risk assessment of landslide dams and prediction of landslide dam failure by piping

earthquake dammed lakes in new zealand eleven small lakes were formed by landslides caused by the 1929 buller earthquake four others were formed by other historic earthquakes in new zealand at least nine other new zealand lakes are also dammed by landslides and were probably formed by prehistoric earthquakes when recognized by morphology synchronous age and areal distribution earthquake dammed lakes could provide an estimate of paleoseismicity for the past few hundred or thousand years

the formation and impact of landslide dams state of the art abstract the blocking of river courses by mass movements is very common in mountainous areas with deep and narrow valleys landslide dams may pose serious threats to people and their livelihoods downstream in the case of abrupt dam failure since the publication of benchmark reviews of costa and schuster 1988 and korup 2002 there is a growing number of studies focusing on the formation stability and short term impacts of landslide dams this review combines the insights of all these studies builds on current concepts of landslide dams and suggests ways to unify terminologies and classifications we furthermore present a new worldwide database compiled from literature data it contains 410 landslide dams 1 million m3 in volume that were formed since 1900 since these have the most complete data entries these data show that dam longevity is among other factors correlated with the type of landslide forming the dam those formed by rock debris avalanches and rockslides have longest lifespans however the influence of landslide type or material on dam longevity decreases with time after dam formation to ensure consistency in the next database generation we suggest guidelines for data collection to provide a solid basis for evaluating dam stability and governing factors a preliminary classification matrix for landslide dam stability that combines topographic setting and the internal structure of the dam body is another outcome of our review furthermore an evaluation of the various geomorphic stability indices proposed in the literature regarding their suitability and limitations in assessing dam formation and stability shows that they predict the probability of dam formation reasonably well but that their application to longevity estimates requires further assessment the geomorphic impacts of landslide dams in the short medium and long term are summarized and illustrated with key examples finally for a better understanding of the factors controlling dam stability we recommend to 1 include dam composition and sedimentary structures in future case studies 2 maintain and update the worldwide database for sound statistical analyses 3 refine landslide dam stability indices and test them for different landslide types and 4 study hazard cascades related to multiple dams in one watershed for long term landscape evolution studies we suggest to 5 quantify terrestrial sediment flux related to landslide dams 6 detect ancient landslide dams in river profiles and 7 further exploit the sediment archives in former impoundment areas

crack reaction veins from the hodgkinson formation north queensland australia thin subplanar or parallel sided syntectonic quartz veins from the hodgkinson province north queensland australia contain mica inclusions that are identical to wallrock mica textures these ghost textures can only be produced by incomplete replacement of the wallrock by quartz the planar form of the veins indicates that there was a planar control on their formation we propose that the veins formed around syntectonic fractures that localized silica micrometasomatism of the fracture wall the formation of the veins can be explained by a model which involves fracture of the wallrock reaction between the fracture wall and the ambient metamorphic fluid and eventual sealing of the fracture by precipitation from the fluid the new vein is then a locus of further fracture replacement of wallrock micas occurs via a two stage process where biotite is replaced by muscovite which is in turn replaced by quartz we propose the term crack reaction to describe the resulting cyclic process because it can be compared with the crack seal model of vein formation crack seal and crack reaction are different only in the relative amounts of metasomatism and precipitation that occur subsequent to fracture and can be envisaged as end members of a more general vein forming process

grain boundary dissolution porosity in quartzofeldspathic ultramylonites implications for permeability enhancement and weakening of mid crustal shear zones abstract quartzofeldspathic ultramylonites from the alpine fault zone one of the world s major active plate boundary scale fault zones have quartz crystallographic preferred orientations cpo and abundant low angle 10 misorientation are decorated by faceted pores commonly with uniformly oriented pyramidal shapes only grain boundaries with 10 misorientation angles in polymineralic aggregates are decorated by pores mean grain boundary pore densities are 5 108 cm 2 grain boundary pores are dissolution pits generated during syn deformational transient grain boundary permeability nucleating on dislocation traces at dilatant grain boundary interfaces they have not been removed by subsequent grain boundary closure or annealing pore decoration could have led to grain boundary pinning triggering a switch in the dominant deformation mechanism to grain boundary sliding which is supported by evidence of cpo destruction in matrix quartz pore decorated grain boundaries have significantly reduced surface area available for adhesion and cohesion which would reduce the tensile and shear strength of grain boundaries and hence the bulk rock grain boundary decoration also significantly decreased the mean distance between pores potentially facilitating dynamic permeability consequently these microstructures provide a new explanation for strain weakening and evidence of fluid flow along grain boundaries in mylonites at mid crustal conditions

secondary cleavages in ductile shear zones abstract secondary cleavages developed at late stages in ductile shear zones show several features that are inconsistent with progressive simple shear in the zone these are the orientation of a single secondary cleavage oblique to the shear zone boundaries conjugate sets with opposite senses of shear and multiple sets with the same sense of shear these features can be explained if the bulk flow is partitioned into slip along discrete failure planes parallel to the primary foliation s coaxial stretching along the foliation and spin

an assessment of changes in properties of steppe kurgan paleosoils in relation to prevailing climates over recent millennia comparative analysis of morphological and chemical properties of the soil chronosequence on kastanozems soils in the steppe zone of the russian plain which included paleosoils buried beneath kurgans erected ca 2000 bc ad 50 ad 200 and ad 1250 was performed to reconstruct the paleoenvironmental conditions in this archeologically important region paleoenvironmental dynamics were traced using the state of microbial communities of paleo and modern soils including the dynamics of total and glucose reactive biomass and the abundance of microorganisms grown on selected media we demonstrate that the share of the glucose reactive microorganisms in the microbial community the ecological trophic structure and oligotrophicity index might serve as indicators of the state of microbial communities and be used for paleoenvironmental reconstructions the morphological chemical and microbial properties confirm an arid period ca 2000 bc slightly wetter conditions ca ad 50 and more humid conditions ca ad 1250

characteristics of the landslide dams induced by the 2008 wenchuan earthquake and dynamic behavior analysis using large scale shaking table tests abstract the ms 8 0 wenchuan earthquake triggered at least 257 landslide dams more than 300 aftershocks with the magnitudes higher than ms 4 0 occurred after the formation of these landslide dams which might largely influence the structure and soil properties of these dams this paper aims to comprehensively investigate the characteristics of the landslide dams induced by the 2008 wenchuan earthquake and study the dynamic behaviors of the landslide dams under aftershocks using large scale shake table tests first the characteristics of the landslide dams including the distribution geometric parameters stability and longevity mitigation measures and the influence of the aftershocks are proposed then two groups of shaking table tests to simulate the dynamic behaviors of two types of landslide dams under aftershocks are illustrated one with quartz sand contained 10 kaolin dam i and the other with quartz sands all dam ii finally the results of the tests including the acceleration distribution dam deformation and dam breaching process are discussed through this study it is found that the landslide dams caused by high magnitude earthquakes have distinctive characteristics which may largely influence the stability breach process and risks of these dams in the model tests the accelerations are generally higher on the surface of the dams either on the crest or on the both upstream and downstream slopes the dam i was prone to settlement and cracking the aftershocks may not directly trigger the failures of landslide dams but accelerate the overtopping failures by lowering the dam crest with settlement and cracking

assessment of a catastrophic rock avalanche in the west mongolian altai mountains abstract a giant rock avalanche that resulted in the formation of a dammed lake was discovered during geological mapping in the valley of the dund tsenkher gol river munhkhairkhan soum western mongolian altai field and satellite data worldview 2 and sentinel 1 were used to obtain a geomorphological description of the landslide and a 3d geometric reconstruction of the rock avalanche with deposits exceeding 14 million cubic meters in volume the rock avalanche is one of the largest catastrophic landslides in the world the rock avalanche was controlled by tectonic setting the slope instability was favored by the presence of nw se and ne sw trending fault systems steep foliation and morphology the rock avalanche was likely triggered by an earthquake related to the activity of the tolbonuur and hovd faults although the area is sparsely populated the settlement of munhkhairkhan soum is threatened by rockfalls or even by rock avalanches that could be triggered by future earthquakes along these faults

effects of tectonic deformation and landslides in the erosion of a mountain plateau in the transitional zone between the central and patagonian andes

dam break characteristics of landslide dams with different types of open channel discharge sections the excavation of artificial open channels in landslide dams is one efficient method for reducing the risks of landslide lake formation this method has often been used in emergencies to eliminate landslide lakes in earthquake prone areas of wenchuan china in this study the dam break characteristics of landslide dams with different open channel cross sections and longitudinal sections were evaluated the degree of headward erosion was extremely strong in the natural dam break experiment and moderately strong in the compound section dam break experiment the degree of headward erosion in the open channel with the trapezoidal section was comparatively mild furthermore the natural dam break resulted in large peak discharge and short dam break duration by contrast the artificially opened channel dam breaks resulted in peak discharges that were approximately 7 7 20 1 lower than those of natural dam breaks and the dam break duration i e the time until the dam broke was longer than that of the natural dam breaking the channels with gentle steep slopes or alternating gentle steep slopes resulted in greater discharge rates and a significant amount of erosion occurred due to these open channels the degree of headward erosion in the channel with alternating gentle steep slopes was greater than that in the other channels the peak discharges of the open channels with gentle steep slopes or alternating mild steep slopes were approximately 29 6 65 0 greater than those of the open channel with a linear section a channel with a triangular cross section and a linear longitudinal section should be used to dispose of small landslide lakes however channels with compound cross sections and longitudinal sections with alternating slopes should be used for large or medium landslide lakes

late holocene climate reconstructions for the russian steppe based on mineralogical and magnetic properties of buried palaeosols abstract insights into past climate changes and corresponding evolution of soils and the environment can be gained by multidisciplinary studies of palaeosols here we focus on palaeosols buried beneath archaeological monuments specifically funerary mounds kurgans in the russian steppe the kurgans were constructed and each of the palaeosols buried over a range of different timesteps from the mid holocene to 600 years before present yr bp integrated magnetic mineralogical and pedological data were used to obtain estimates of past climate especially precipitation changes through both time and space a soil magnetism based climofunction derived previously from modern steppe soils and modern climate was applied to each set of palaeosols to obtain quantitative reconstructions of annual precipitation for the time at which the soils were buried independent soil property data clay mineralogy salt content iron mineralogy from mossbauer analysis and optical and electron microscopy were also obtained in order to test and substantiate the magnetic inferences the data obtained indicate that the climate of the lower volga steppe area has varied from the mid holocene onwards precipitation minima occurred at 5000 3800 and 1600 yr bp with intervals of enhanced precipitation at 1900 yr bp and 600 yr bp these rainfall variations appear to occur synchronously with changes in middle eastern precipitation and lake levels suggesting they are controlled by index changes in the north atlantic oscillation

fluvial response to large rock slope failures examples from the himalayas the tien shan and the southern alps in new zealand we describe remnants of large 10 7 10 10 m 3 late pleistocene to holocene rockslides and rock avalanches that block ed rivers and are preserved in the himalayas the tien shan and the new zealand southern alps despite rates of uplift and erosion of up to 10 mm year 1 these natural dams control fluvial response on 10 1 10 4 year timescales by a storing and releasing sediment during forced alluviation and fluvial re incision b relocating river channels through diversion or seepage c inhibiting river erosion into bedrock d formingpersistentlong profileknickpointsandknickslopesassociatedwithsteephigh energy n10 3 wm 2 breachand epigenetic bypass gorges and fluvial hanging valleys and e shaping valley floor morphology sediments indicate that rockslidedammed lakes may persist up to 10 4 years before being drained or infilled several short lived 10 0 10 2 year historical rockslide dams in the indian and nepal himalayas and the southern alps have had marked volumetric impacts on catchment sediment budgets shortly following failure therefore we caution against the linear extrapolation of sediment delivery from prehistoric rockslide dams through time as a response variable we find reach scale changes to channel gradient to be prominent and persistent indicators of fluvial response to large rock slope failures 2006 elsevier b v all rights reserved

nucleation and growth of retrograde shear zones an example from the needle mountains colorado u s a abstract brittle and ductile deformation features are heterogeneously developed in late proterozoic retrograde normal slip shear zones that cross cut amphibolites and quartzo feldspathic gneisses in the needle mountains replacement of amphibolite grade minerals by greenschist facies assemblages is spatially related to transgranular fractures that cross cut the older gneissosity steeply dipping chlorite lined slip surfaces are associated with chlorite quartz muscovite filled dilational jogs and narrow breccia zones arrays of slip surfaces are transitional into similarly oriented phyllonite zones within which the foliation locally overprints early cataclastic zones the nucleation of these shear zones under greenschist facies conditions involved fluid infiltration along early transgranular fractures and hydration of fe mg bearing minerals initial displacement occurred by slip along these fractures and local cataclasite development fluids were episodically drawn into dilatant sites along these slip surfaces a transition to plastic deformation resulted directly from the metamorphic breakdown of feldspars and amphiboles to phyllosilicates which allowed strain localization into narrow phyllonite zones thus dilatancy produced by early brittle deformation appears to be the main process by which fluids infiltrate into developing greenschist grade retrograde shear zones reaction softening via hydration reactions causes a brittle to plastic transition and results in strain localization

large scale landslides in toyama prefecture central japan and their probable relationship with earthquakes large scale landslides along the kubusu and besso rivers in toyama prefecture are developed in the miocene iwaine formation which is composed of andesitic lava tuff and tuff breccia in the middle member of this formation the tuff is easily altered to montmorillonite bearing rock and subsequently plays an important role in the development of landslides events which tend to be large scale events as the massive lava of the upper member forms a cap rock over the tuff the kiritani and koinami basins which are flat intermontane basins located along the kubusu and besso rivers respectively are interpreted as landslide dammed lakes later filled with sediment accelerator mass spectrometry 14c ages show that the landslides forming each dam occurred simultaneously at approximately 2500 bp these ages were measured from wood fragments embedded in the landslide material of kiritani and from an in situ stump drowned during the impoundment of koinami if the trigger of these landslides was an earthquake it is most likely to have been the penultimate event along the atotsugawa fault zone

slope instability in relation to glacial debuttressing in alpine areas upper durance catchment southeastern france evidence from field data and 10be cosmic ray exposure ages the upper durance catchment is an area prone to rock slope failures such failures reflect the combination of high relief litho structural controls and paraglacial stress release the aim of this study is to determine the role of deglacial unloading and resulting paraglacial stress release in conditioning or triggering slope failure former dimensions of the durance glacier are reconstructed then combined with digital elevation model data in a raster geographic information system to quantify the spatial pattern of stresses associated with glacial loading at the last glacial maximum preliminary calculations suggest that major rock falls and rock avalanches are associated with areas subject to the highest decompression stresses focus on two case studies allows the consequences of paraglacial stress release on slope instability to be evaluated description of slope failure runout deposits allows reconstruction of the nature of slope failure surface exposure dates based on concentration of cosmogenic 10be allows the timing of both deglaciation and that of post glacial rock slope failures to be established it is shown that rock slope failures are concentrated on lower valley side slopes within the area occupied by ice at the last glacial maximum and that their locations coincide with zones of inferred high glacial loading stress consistent with interpretation of both bedrock disruption and large scale rock slope failures as paraglacial phenomena induced by stress release following deglaciation timing of initial rock avalanche runout deposition at one site is consistent with this conclusion though later instability episodes at the same site may have occurred independent of the influence of paraglacial stress release

strain localization and fluid pathways in mylonite inferences from in situ deformation of a water bearing quartz analogue norcamphor simple shearing of polycrystalline norcamphor containing 10 15 vol water at near atmospheric pore fluid pressure and a range of constant temperatures 3 35 c and shear strain rates 5 10 5 4 10 4 s 1 induces localization of both strain and fluid flow prior to deformation the water is located at grain triple junctions and pockets along grain boundaries it forms an average dihedral angle of 46 with the surrounding norcamphor grains during initial shearing c1 grain boundaries oriented subparallel to the principal shortening direction dilate and fill with water at 1 15 c the tips of the shear surfaces propagate alternately by intracrystalline plasticity and subcritical fracturing concomitant with dynamic recrystallization in the rest of the sample the episodic interconnection of dilatant shear surfaces is associated with short term increases in displacement rate parallel to the surfaces these surfaces coalesce to form a high strain fluid filled network subparallel to the experimental shear zone however this network never spans the entire length of the shear zone at any given time even after shearing to c 8 5 the deformation is more homogeneous and fewer dilatant shear surfaces develop at higher deformational temperatures and or lower strain rates due to the increased activity of dislocation creep prolonged stress annealing removes most microstructural evidence of the syntectonic fluid pathways dilatant shear surfaces in norcamphor resemble relics of mica filled synmylonitic fractures in dynamically recrystallized quartz from greenschist facies mylonite suggesting that fluid played a similar mechanical role in nature and experiment the coalescence of dilatant fluid filled shear surfaces represents a strain dependent increase in pore connectivity within mylonitic shear zones the experiments indicate that fluid flow along deep crustal mylonitic shear zones is probably limited by the rate at which the tips of the dilatant shear surfaces propagate subparallel to the shearing plane 2000 elsevier science b v all rights reserved

strain accumulation and fluid rock interaction in a naturally deformed diamictite willard thrust system utah usa implications for crustal rheology and strain softening abstract structural and geochemical patterns of heterogeneously deformed diamictite in northern utah usa record interrelations between strain accumulation fluid rock interaction and softening processes across a major fault willard thrust different clast types in the diamictite have varying shape fabrics related to competence contrasts with estimated effective viscosity ratios relative to micaceous matrix of 6 and 8 for large quartzite clasts respectively in the willard hanging wall and footwall 5 and 2 for less altered and more altered granitic clasts respectively in the hanging wall and footwall and 1 for micaceous clasts that approximate matrix strain within the footwall matrix x z strain ratios increase from 2 to 8 westward along a distinct deformation gradient microstructures record widespread mass transfer alteration of feldspar to mica and dislocation creep of quartz within matrix and clasts fluid influx along microcracks and mesoscopic vein networks increased westward and led to reaction softening and hydrolytic weakening in conjunction with textural softening from alignment of muscovite aggregates consistent si al and ti concentrations between matrix granitic clasts and protoliths indicate limited volume change mg gain and na loss reflect alteration of feldspar to phengitic muscovite within the hanging wall strain is overall lower with matrix x z strain ratios of 2 to 4 microstructures record mass transfer and dislocation creep concentrated in the matrix greater al and ti concentrations and lower si concentrations in matrix indicate volume loss by quartz dissolution na gain in granitic clasts reflects albitization large granitic clasts have less mica alteration and greater competence compared to smaller clasts differences in strain and alteration patterns across the willard thrust fault suggest overall downward up temperature fluid flow in the hanging wall and upward down temperature fluid flow in the footwall

complex pedological analysis of paleosols buried under kurgans as a basis for periodization of the timber grave archaeological culture in the southern cis ural russia abstract the problem of periodization of the timber grave culture of the late bronze age on the territory of the southern cis ural is far from being solved this situation exists because the funeral ceremony looks very similar throughout the history of the timber grave culture existence to assign stages of this culture s development a complex approach was used including archaeological observation radiocarbon dating technical and technological analysis of ceramics and study of paleosols buried under kurgans the paleopedological analysis was a key approach because the relative chronological order of the construction of kurgans was initially determined within one kurgan cemetery based on morphological observation and physical and chemical properties of the buried paleosols five kurgan cemeteries which included 19 kurgans overall of the timber grave culture were studied in the orenburg region the southern cis ural it was found that the paleosols buried under the earliest kurgans of the studied culture show the maximal values of soil bulk density in the humus and carbonate horizons the minimal content of humus in the uppermost 50 cm of the profile the highest content of carbonates and the closest to surface location of the bk horizon the highest content of gypsum and the highest portion of exchangeable sodium of the sum of exchangeable bases based on the set of mentioned properties of the buried paleosols the transitional and the latest groups of kurgans were also suggested in the latest group the paleosols show minimal values of bulk density maximal content of humus in the uppermost 50 cm minimal content of carbonates and total lack of gypsum and exchangeable sodium throughout profiles such differences in the paleosols properties buried under different groups of the timber grave kurgans were probably caused by climatic fluctuations during the period of the culture s functioning the reconstruction showed that in the most part this culture had been developed in favorable climatic conditions with a sufficient quantity of precipitation and comparatively soft climatic continentality whereas the previous period was characterized by an arid and continental climate based on archaeological observation radiocarbon dating technical and technological analysis of ceramics three chronological stages were allocated in the history of the functioning of the timber grave antiquities for the steppe cis ural according to calibrated radiocarbon dates the chronological limits are as follows the first stage xix century bc the second xviii xvii centuries bc and the third xvii xv centuries bc

40ar 39ar age of mylonites along the merens fault central pyrenees seven mylonitic samples and two coarse muscovites from the central pyrenees have been dated by the 40ar 39ar method whole rock specimens of mylonite were cut out of thin section chips allowing complete characterisation of mineralogy and texture several specimens showed rising staircase patterns in the range 50 90 ma with much higher ages in the highest temperature steps this is believed to reflect mixing of argon released from micas with excess argon contained in plagioclase and released mainly at high temperatures one biotite quartz mylonite gave a plateau age of 93 2 ma other inferred mica ages are about 60 73 ma for biotite and 50 60 ma for muscovite it is probable that biotite contains excess argon and that 50 ma approximates to the cooling age in the mylonites one coarse muscovite collected immediately below the major merens shear zone gave a hercynian plateau age while another collected within the merens zone gave a partially reset hercynian age taken together the data indicate that the shear zones were active in alpine times 100 ma and probably about 50 ma ago they are believed to have formed during the early stages of eocene compression in the pyrenees deformation and resultant uplift probably terminated an important thermal event in this part of the pyrenean basement which may have begun at the time of the mid cretaceous north pyrenean metamorphism 90 100 ma

the partitioning of deformation in flowing rock masses abstract most geological structures owe their development to heterogeneous and or non steady flow flow partitioning refers to the division of the instantaneous velocity field into components related to translation strain and rotation flow partitioning during the development of a geological structure usually changes with time and different histories of flow are involved at different points in the developing structure heterogeneity leads to the development of flow domains with different characteristics notably the degree of non coaxiality of deformation and different partitionings of the rotational component of flow into shear induced vorticity and spin during non steady flow there is often continual repartitioning of vorticity between the spin and shear induced components spin is an important aspect of flow leading to the development of structure this paper discusses the partitioning of deformation in a flowing rock mass coaxial flow tends to occur in isotropic materials in regions near weakly constrained boundaries non coaxial flow is favoured by suitably oriented material anisotropy and or the presence of well defined boundary constraints involving parallel relative displacements a developing anisotropy e g a crystallographic fabric in a shear zone can induce a change from coaxial to non coaxial flow other effects are related to the scale of approximation for example bulk shear induced vorticity can be locally converted to spin flow in the crust and mantle of the earth produces geological structures on all scales and involves many different types of rheological response the factors that affect flow partitioning e g spin versus non coaxial deformation are therefore of interest

a study of knickpoint surveys and their likely association with landslides along the hunza river longitudinal profile mass wasting and tectonic uplift are the major factors responsible for reshaping the northern pakistan that contains the world s most steeply inclined mountainous regions including karakoram himalayas and hindukush ranges the role of gis and remote sensing is inevitable to study the river geomorphology for the identification and evaluation of different mass wasting processes digital elevation models dems are frequently used to extract the longitudinal profile of the rivers to identify the knickpoints and their related geomorphic attributes for this study aster dem of 30 m spatial resolution satellite data was utilized to perform the geomorphological analysis of the longitudinal profile of the hunza river in arcgis and matlab environment the hunza river channel with having the watershed area of 13571 km2 has witnessed a number of historic landslide dams i e attabad ganesh and boultar glacier etc that blocked the main river channel at multiple sections in different episodes of time these past landslides presumably preserved in the river channel as knickpoints at their respective locations in this study a total of 77 knickpoints were identified along the main stem of the river channel the spatial locations of the extracted knickpoints and their normalized steepness index ks values were compared with the hunza river landslide inventory map lithologic contact tectonic faults and historic landslides data furthermore the likely role of these geomorphic factors was evaluated to ascertain their association with knickpoints formation the results of this gis based geomorphic analysis of the river profile and subsequent field visit of the area revealed that the formation of landslide dams and their subsequent breaching is one of the major trigger factor of knickpoints along the channel such studies highlight the benefits of inexpensive remote sensing data and gis tools to assess the likely role of various geomorphic features in the formation of significant knickpoints along the river profiles on a regional scale

how ductile are ductile shear zones three premises of ductile deformation in the middle and lower crust are widely accepted 1 rocks flow with power law viscous rheology 2 localization in ductile shear zones involves strain softening and 3 fluid flows into and is channelized within ductile shear zones ductile viscous shear zones should therefore initially develop along planes of maximum shear stress strain soften and rotate as material planes into the field of progressive extension however the mean stress or pressure within a weak elongate viscous band being stretched is higher than the surrounding matrix and this is difficult to reconcile with premise 3 in contrast mohr coulomb brittle faults always have lower pressure within the fault zone flow of fluid and melt into high temperature shear zones therefore implies that ductile shear zones are not perfectly viscous but have a pressure dependent viscoplastic rheology the continued pressure dependence may reflect significant microcracking on the grain scale even when localized deformation does not produce larger scale discrete fractures

influence of textural properties on the failure mode and process of landslide dams abstract the failure of a landslide dam is a sudden geo hazard which can significantly threatens the lives and property of local residents in this study 11 experiments were designed to reproduce the failure process of landslide dams with different grain size distributions and hydrodynamic conditions in order to fully consider the influence of seepage on the stability of landslide dams with different textural properties the inflow discharge was small in these tests by analyzing the experimental data we found that the textural properties plays a key role in the failure modes and process of landslide dams the eleven tests produced five different results the landslide dam in experiment 1 and 8 remained stable the landslide dam in experiment 2 partially failed in experiments 3 6 the dams failed due to overtopping and erosion while in experiment 7 the dam failed due to overtopping and soil collapse in experiment 9 11 the dams failed due to piping overtopping and erosion in addition the evolution of the outflow discharge and density also varied for the different textural properties of the dam materials based on the experimental results the landslide dam materials were classified as coarse matrix controlled medium particle controlled fine matrix controlled and balanced composition the failure modes and process as well as the evolution characteristics of the outflow discharge and flow density were all summarized providing a scientific reference for disaster prevention and mitigation research of landslide dams

deep fluid circulation in alpine shear zones pyrenees france field and oxygen isotope studies a combined field stable isotope and whole rock chemical study was made on late cretaceous to tertiary metasomatic shear zones cutting hercynian gneisses in the aston massif pyrenees france mylonitisation occurred during the early stages of alpine compression under retrograde conditions at 400 450 c and about 10 km depth whole rock 18o values of 11 to 12 in the gneisses was lowered to 5 to 9 in the shear zones with the quartz muscovite 18o 16o fractionations of about 2 to 4 essentially unchanged these 18o 16o systematics together with d muscovite 40 to 50 indicate that large volumes of formation waters or d rich meteoric waters passed through the shear zones during deformation the same fluids also redistributed major elements as shown by the correlation of 18o shift with muscovitisation and albitisation reactions in granitic wall rocks however even though 18o was universally lowered within the shear zones the 18o 16o ratios were not homogenised nor do they correlate in detail with the presence or absence of muscovitisation suggesting that fluid flow was probably fracture controlled and episodic field mapping shows that along the length of a particular shear zone muscovitisation of granite gneiss dies out 150m above the contact with underlying sillimanite gneiss thus muscovitisation and albitisation of granite gneiss in shear zones and their wall rocks probably occurred during re equilibration of acidic chloride rich aqueous fluids that had previously moved upward within the shear zones through underlying sillimanite gneiss extremely high material balance fluid rock ratios 103 are required to explain the extent of muscovitisation along this shear zone implying integrated fluid mass fluxes of about 108 kg m2 this is probably close to the maximum value for other shear zones in the network similar volumes of a more chemically evolved fluid must have passed through the unmuscovitised mylonites showing that the absence of alteration cannot necessarily be used to infer low values of fluid flux for reasonable pressure gradients and time scales of fluid movement effective permeabilities of 10 15 to 10 17 m2 are required such values can be accounted for by short lived widely spaced cracks produced during seismic activity a model is presented in which formation waters were seismically pumped down an underlying shallow southward dipping decollement and then upward through the steeply dipping shear zone network

a study of white mica microstructure and microchemistry in a low grade mylonite a suite of mylonites rich in white mica taken from the betic movement zone sierra alhamilla spain shows progressive grain refinement involving a two stage recrystallization history stage one is isochemical and possibly works by nucleation and growth of new crystals at sites of fracture and dilatancy stage two is nonisochemical and may be driven by differences in strain energy and chemical free energy between the two phases deformation is probably governed by brittle fracture and diffusional mass transfer along grain boundaries and cracks the two stages of recrystallization are thought to represent a single progressive episode of deformation under changing metamorphic conditions

controls on large landslide distribution and implications for the geomorphic evolution of the southern interior columbia river basin large landslides 0 1 km 2 are important agents of geomorphic change while most common in rugged mountain ranges large landslides can also be widespread in relatively low relief several 100 m terrain where their distribution has been relatively little studied a fuller understanding of the role of large landslides in landscape evolution requires addressing this gap since the distribution of large landslides may affect broad regions through interactions with channel processes and since the dominant controls on landslide distribution might be expected to vary with tectonic setting we documented 400 landslides between 0 1 and 40 km 2 across 140 000 km 2 of eastern oregon in the semiarid southern interior columbia river basin the mapped landslides cluster in a nw se trending band that is 50 100 km wide landslides predominantly occur where even modest local relief 100 m exists near key contacts between weak sedimentary or volcaniclastic rock and coherent cap rock fault density exerts no control on landslide distribution while 10 of mapped landslides cluster within 3 10 km of mapped fold axes landslide occurrence is curtailed to the ne by thick packages of coherent basalt and to the sw by limited local relief our results suggest that future mass movements will localize in areas stratigraphically preconditioned for landsliding by a geologic history of fluviolacustrine and volcaniclastic sedimentation and episodic capping by coherent lava flows in such areas episodic landsliding may persist for hundreds of thousands of years or more producing valley wall slopes of 7 13 and impacting local channels with an evolving array of mass movement styles

geomorphic indexing of landslide dams evolution abstract landslide dams are rather common events in hilly and mountainous areas and they occur when a landslide reaches a valley floor closing the riverbed if they form a lake basin unstable landslide dams can have catastrophic consequences when they occur in upstream of populated regions landslide dam behavior is not completely understood yet however several studies suggested implementing geomorphological index in order to assess their formation and evolution these indexes result from the composition of two or more morphological attributes that characterize the landslide e g landslide volume or length and the involved river valley e g valley width the objective of this work is the definition of a procedure based on the joint use of different indexes to assess landslide dams evolution over large areas e g entire river catchment or even a region or a nation and in short times in order to be used for emergency response or for planning activities about 300 landslide dam events collected in italy were analyzed and some state of the art geomorphological indexes were applied to characterize the damming phenomena at the national scale to overcome some limitations of the aforementioned indexes we introduce two new indexes the morphological obstruction index and the hydromorphological dam stability index the former combines the river width and the landslide volume and it can be used to identify the conditions associated to dam formation discriminating between circumstances where a landslide dam is formed and circumstances where it is not the latter uses a simplified stream power formulation combining the upstream catchment area and the local slope gradient to account for the river energy this index allows evaluating the stability of a dam in near real time as soon as it occurs and can be used to discriminate between stable and unstable dams if compared with the reviewed state of the art indexes the newly proposed ones show an improvement in the forecasting effectiveness and have the advantage of being based on morphometric input parameters that can be easily and quickly assessed on a distributed way even over large areas we propose a tool that is based on the joint use of the newly proposed indexes and that can be used to provide fast and effective assessment on landslide dam formation and stability during emergency or planning activities

crack seal fibre growth mechanisms and their significance in the development of oriented layer silicate microstructures abstract an analysis of crack seal fibre growth mechanisms has shown two important implications of the crack seal process for the interpretation of microstructures in low grade metamorphic rocks 1 1 the ability of fibre growth to track the incremental separation history of crack walls depends on details of the nucleation and growth mechanisms 2 2 fibrous crystals may develop cristallographic preferred orientations in certain crack seal situations the microstructures of layer silicates and associated phases developed in several examples of syntectonic intragranular microfracture sites and veins indicates that layer silicate 001 and grain shape preferred orientation can develop during crack seal deformation by oriented growth mechanisms during successive crack seal increments preferred orientation may develop in response to an interaction between anisotropic growth kinetics and the displacement history resulting in preferential rejoining by syntaxial overgrowth of pulled apart grains having fast growth directions parallel to the incremental displacement direction across a microcrack preferred orientation may also be developed and enhanced in crack seal growth sites by overgrowth of previously oriented layer silicates in the microcrack walls in this case the crystallographic preferred orientation need not be simply related to the displacement history during crack seal fibre growth since crack seal processes may operate on all scales down to the minimum size of a microfracture in a deforming rock such mechanisms of layer silicate preferred orientation development are expected to be very significant in developing and enhancing foliation during deformation involving microfracture and solution transfer processes

origin and incremental evolution of brittle ductile shear zones in granitic rocks natural examples from the southern abitibi belt canada abstract metre scale shear zones developed in the mooshla granitic pluton exhibit a plethora of internal mesoand microstructures revealing their mode of nucleation growth and termination the subvertical e w brittle ductile shear zones are developed in the most isotropic part of the intrusion and consist of phyllonites characterized by mylonitic fabrics and well developed down dip mineral lineations they are exposed on a single large and flat outcrop perpendicular to the mineral lineation these brittle ductile shear zones are in close spatial association with a fracture system along which they have nucleated and propagated joints fractures and brittle faults contain abundant evidence of ductilely deformed and recrystallized minerals suggesting that they underwent ductile shearing after their formation the deformation was accompanied by the influx of a metasomatic fluid which altered original fe mg bearing minerals and plagioclase into quartz epidote chlorite sericite and carbonate that precipitated in dilatant fractures and narrow breccia zones we recognize two different types of lateral terminations i shear zones that terminate into joints and fractures that are parallel or oblique to the shear direction and ii curved segments of shear zones that connected with neoformed splay fractures at high angle to the shear direction in the latter case sharp bending and severe perturbation of the shear zone orientation occur at the shear zone termination where ductile shearing is transfered into an adjacent shear zone via dilatational fractures this demonstrates that shear zones tended to grow towards each other and coalesce to form a well developed anastomosing network we propose that narrow dilatational fractures and joints acted as paleo weakness planes along which fluid rock interaction and resulting reaction softening occurred the deformation scenario involves episodic fluid drawn into dilatant sites responsible for cyclic fluid pressure fluctuation in the system dilatancy related fracturing and reaction softening lead to deformation under brittle to plastic conditions and to shear strain localization