complete dynamic modeling calibration for the thurwieser rock avalanche italian central alps abstract few rock avalanches have been witnessed and no exact real time description is available the 2 5 m m 3 punta thurwieser rock avalanche september 2004 italian central alps is a unique event for which many quantitative observations have been gathered this is the first case ever of a natural rock avalanche being recorded on video and for which an almost exact value of the total time duration from initial detachment to final deposition is available the landslide travelled over 2 9 km from its source partially in a glacial environment the initial failure and the time for the complete evacuation of the source area were studied and assessed by a series of photos the mean front velocities along the path have been estimated from the video the final geometry and the characteristics of the deposit have been obtained by gps measurements aerial photos field surveys and laboratory tests a quasi 3d continuum dynamic analysis of the landslide motion has been performed assuming both a voellmy and a frictional rheology in the model dan 3d for the first time the landslide front velocities have been used for back analyses and calibration of the rheological parameters together with the final shape and thickness of the deposit and its developing extension the dynamic flow resistance parameters initially calibrated with dan were adopted and validated in dan 3d showing good consistency they are consistent with the existing database for calibrated landslides of similar type and scale flow velocities on the path segment underlain by glacial deposits up to 55 65 m s 1 are more accurately predicted by adopting a frictional rheology up to 50 55 m s 1 with zero pore pressure and a 26 friction angle than by a voellmy rheology up to 40 45 m s 1 both observations and modelling show that glacial ice plays a substantial role in increasing the rock avalanche mobility

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

dynamic analysis and field investigation of a fluidized landslide in guanling guizhou china abstract on june 28 2010 a large catastrophic landslide was triggered by a heavy rainfall in guanling guizhou china this catastrophic event destroyed two villages and caused 99 casualties the landslide involved the failure of about 985 000 m 3 of sandstone from the source area the displaced materials traveled about 1300 m with a descent of about 400 m covering an area of 129 000 m 2 with the final volume being accumulated to be 1 840 000 m 3 approximately to provide information for hazard zonation of similar type of landslides in the same area we used a dynamic model dan3d to simulate the runout behavior of the displaced landslide materials and found that a combined frictional vollemy model could provide the best performance in simulating this landslide and the runout is precisely duplicated with a dynamic friction angle of 30 and a pore pressure ratio r u of 0 55 for the materials at the source area and with vollemy parameters of friction coefficient f 0 1 dimensionless and turbulent coefficient 400 m s 2 the simulated results indicated that the duration of the movement is estimated at about 60 s for a mean velocity 23 m s to examine the effectiveness of simulation by means of dan3d and also to evaluate the reactivation potential of these displaced landslide materials depositing on the valley we used electrical resistivity tomography ert method to survey the depth and internal structure of landslide deposits the ert results showed that dan3d gave a good prediction on the shape and runout distance of the landslide deposits although the predicted maximum depths of landslide deposit on some areas were differing from those obtained by ert method

dynamics of the 1984 rock avalanche and associated distal debris flow on mount cayley british columbia canada implications for landslide hazard assessment on dissected volcanoes abstract in 1984 a mass of quaternary pyroclastic rock est vol 0 74 106m3 slid from the western flank of mount cayley volcano in southwest british columbia the disintegrating rock mass entrained a further 0 20 106 m3 and formed a rock avalanche that travelled a horizontal distance of 3 46 km from its source over a vertical elevation difference of 1 18 km equivalent to a fahrboschung of 19 from the superelevation of the debris trimline in the mid path it is estimated that velocities reached at least 42 m s in the upper part of its path velocities may have approached 70 m s the rock avalanche was partially transformed into a distal debris flow that travelled a further 2 6 km down turbid creek in a narrow channelised path to the squamish river temporarily blocking it the motion of the rock avalanche including the production of a distal debris flow was successfully simulated using a dynamic analytical model both the results of this analysis and field evidence indicate that the rock avalanche did not come to a halt in the upper part of its path as suggested by cruden and lu 1992 but travelled to its distal limit in one uninterrupted movement this finding has important implications for landslide hazard assessment at mount cayley and similar sites the landslide is typical of those which occur on the steep slopes of dissected volcanoes and is one of seven high velocity rock avalanches that have occurred in the garibaldi volcanic belt of southwest british columbia since 1855

dynamics and emplacement mechanisms of the successive baige landslides on the upper reaches of the jinsha river china abstract two successive baige landslides are presented in this study to investigate the dynamics and emplacement mechanisms field survey shows that the deposit characteristics of the first landslide are affected by the extremely fractured rock masses and the complex spatial distribution of lithologies in the source area this deposit consists of abundant angular megablocks on the surface supported by clasts with a relatively abundant content of rubble ranging from micrometre to decimetre sizes and rarely well preserved original stratigraphic sequence diapiric structure and convoluted structure these sedimentological characteristics imply that a simple differential shear process induced by compression is distributed through the entire avalanche masses with low internal disturbance during the emplacement of the first landslide the three dimensional discrete element simulations show that i the first landslide reaches its maximum average velocity of 41 m s in 28 s and eventually is bulldozed to a halt in the river within 80 s ii the second landslide is controlled by entrainment which impedes the avalanche from further accelerating and simultaneously imparts kinematic energy to the substrate eventually becoming entirely mobilized and reaching a maximum average velocity of 35 m s in 36 s in the dynamic process of the second landslide the significant entrainment induced enlarged volume its entrainment ratio reaches 3 3 is associated with the steep concave terrain water bearing substrate and lower roughness substrate basal boundary and overloading impact induced erosion is proposed to be the most significant contribution to this entrainment

simulation of a long runout rock avalanche triggered by the lushan earthquake in the tangjia valley tianquan sichuan china abstract only one long runout rock avalanche was triggered by the 2013 lushan earthquake in the tangjia valley tianquan sichuan china the rock avalanche involved the failure of 530 000 m3 of sandstone from the source area the displaced material travelled a horizontal distance of 1600 m with an elevation descent of 480 m equivalent to a fahrboschung of 16 7 based on a detailed field investigation we introduce basic characteristics of the rock avalanche and find that the rock avalanche resulted in one run up in the chunwojian valley a superelevation in the gangoutou valley and increase in volume due to the entrainment of path materials a numerical model dan3d was used to simulate the post failure behavior of the rock avalanche by means of trial and error a combination of the frictional model and voellmy model is found to provide the best performance in simulating this rock avalanche the simulation results reveal that of the rock avalanche lasted approximately 160 s and an average velocity of 10 m s

lessons from ontake san a comparative analysis of debris avalanche dynamics abstract dynamic aspects of the long runout ontake san debris avalanche are evaluated by a comparison of several models an unsteady numerical model assumes two dimensional flow of an incompressible biviscous or newtonian fluid represented as a continuum with a free surface internal deformation of the flowing mass is considered as well as boundary resistances thus flow thinning and deposit shape as well as flow kinematics may be modeled parameters are adjusted to match observed runout with additional constraints on velocity and emplacement time with abundant constraints for ontake san from careful field investigations by japanese research teams our analysis indicates that a substantial decrease in flow resistance occurred as a function of displacement constant property models that match runout tend to overestimate the peak velocities and to underestimate the emplacement times a staged increase in mobility in both constant volume and variable volume models leads to results consistent with field data runout in a channel overflow area was also modeled qualitatively similar results have been obtained by other researchers using simple sliding block models with empirical parameters a slide block model with rational parameter selection a modified flood simulation and a multi element frictional slide model the relative merits of these models are compared the field mechanisms associated with this mobility increase with displacement are poorly understood but the question is now identified as a target for future research at debris avalanche sites and some plausible mechanisms are considered the main reason probably involves the entrainment of river water and saturated sediment leading to enhanced efficiency of fluid pressure mechanisms with undrained shear in addition progressive shearing reduced the mean particle size and angularity and the cohesion and friction and apparent viscosity of avalanche debris near the wetted perimeter hydroplaning the shearing of water films and slurries may have occurred locally

dynamic analysis of the multi staged ice rock debris avalanche in the langtang valley triggered by the 2015 gorkha earthquake nepal abstract on april 25 2015 a disastrous rock avalanche was triggered by the gorkha earthquake in the langtang valley of central nepal that buried a touristic village and killed 350 people this was a dual phase avalanche comprising of glacier snow ice and rock debris mixture which interacted in multiple paths from different source areas in this study the runout and deposition process of the langtang avalanche were analyzed using a two phase mass flow model pudasaini 2012 with the r avaflow software to recreate the flow heights velocity and deposition structure and sequence the simulation results indicated that the duration of the total failure process was 140 s and the avalanche flowed with an average velocity of 36 m s the interaction of the avalanche material from two different stages deflected its path directing it toward the downstream end of the valley and generating a splashing air blast which caused significant damage in that direction parameter calibration model performance and verification were performed numerically and based on field observations this study gave insight into the failure mechanisms of the dual phase and multi staged avalanche occurring in the snowline regions and explained the path deflections due to the stage interactions the results provide a reference for hazard zonation in such mountainous regions

the time scale of the silicate weathering negative feedback on atmospheric co2 the ultimate fate of co2 added to the ocean atmosphere system is chemical reaction with silicate minerals and burial as marine carbonates the time scale of this silicate weathering negative feedback on atmospheric pco2 will determine the duration of perturbations to the carbon cycle be they geological release events or the current anthropogenic perturbation however there has been little previous work on quantifying the time scale of the silicate weathering feedback with the primary estimate of 300 400 kyr being traceable to an early box model study by sundquist 1991 here we employ a representation of terrestrial rock weathering in conjunction with the genie grid enabled integrated earth system model to elucidate the different time scales of atmospheric co2 regulation while including the main climate feedbacks on co2 uptake by the ocean in this coupled model the main dependencies of weathering runoff temperature and biological productivity were driven from an energy moisture balance atmosphere model and parameterized plant productivity long term projections 1 myr were conducted for idealized scenarios of 1000 and 5000 pgc fossil fuel emissions and their sensitivity to different model parameters was tested by fitting model output to a series of exponentials we determined the e folding time scale for atmospheric co2 drawdown by silicate weathering to be 240 kyr range 170 380 kyr significantly less than existing quantifications although the time scales for reequilibration of global surface temperature and surface ocean ph are similar to that for co2 a much greater proportion of the peak temperature anomaly persists on this longest time scale 21 compared to 10 for co2

sea level variations induced by heating and cooling an evaluation of the boussinesq approximation in ocean models in this paper a sigma coordinate ocean model is modified to remove the commonly used boussinesq approximation so that the effect of thermal expansion is exactly included in the basic equations in order to cope with the seasonal heating cycle and the detection of climate change through variation in sea level height tests are performed to evaluate the differences between boussinesq and non boussinesq calculations under different heating and cooling conditions and different model domains for an idealized case of a flat bottom shallow ocean basin without wind forcing simulations of a warm eddy show that the non boussinesq dynamics have only a minor effect on the baroclinic current field however vertically averaged velocities though small compared with the baroclinic velocities are cyclonic for the boussinesq calculation and anticyclonic for the non boussinesq calculation the results indicate that global or closed basin boussinesq models should be able to simulate most of the observed steric sea level changes on seasonal or climate timescales when corrected by a spatially uniform time dependent factor calculated from the volume averaged density change the seasonal variation of the globally averaged sea level calculated from climatological data is small about 1 cm variations in steric sea level in regional models both boussinesq and non boussinesq may differ from those of global models owing to the unknown transport across their boundaries associated with the local heating and cooling a spatially uniform time dependent correction similar to that associated with thermal expansion is proposed to account for transport across open boundaries of regional models variations of sea level obtained from a boussinesq model of the atlantic ocean approximate the seasonal signal due to the heating cooling cycle of each hemisphere as observed by satellite altimeter data

an analysis of the supply process of loose materials to mountainous rivers and gullies as a result of dry debris avalanches a dry debris avalanche will produce different volumes of colluviums or depositions loose materials which can have a significant impact on mountainous rivers or gullies the loose material supply process caused by a debris avalanche is an important issue for understanding secondary disasters that form via the coupling of water flow and loose materials two flumes were designed for laboratory tests of the loose materials supply process to rivers gullies and the related impact factors were analyzed experimental results show that the supply of loose materials is a continuous process that directly relates to the avalanche s mass movement processes the sliding masses with smaller particle sizes are more sensitive to the flume slope and exhibited a longer supply time the time consuming for the debris avalanche travel in the flume decreased with the increasing particle size such as flume b time consuming is decreased 0 2 s when the particle size increased from 1 0 to 20 60 mm landslide volume and flume slope flume a consuming 1 6 2 1 s when flume slope is 29 decreased to consuming 1 3 1 5 s when flume slope is 41 which means the increasing mobility of loose materials the total supply time increased with the increasing landslide volume or decreasing particle size and flume slope an empirical model for the process is presented based on numerous laboratory tests and numerical simulations which can successfully describe the supply process for loose materials to a river gully the supply process of loose materials to mountainous gully from a dry debris avalanche is controlled by the material compositions of sliding masses topographical conditions landslide volume and bed friction where large volume debris avalanches that occur in mountainous river regions are more likely to obstruct the river flow and form a landslide dammed lake

influence of runout path material on emplacement of the round top rock avalanche new zealand factors influencing the distance a disintegrating rock mass travels as it spreads across the landscape after detaching from a slope include the volume and mechanical properties of the material local topography and the materials encountered in the runout path here we investigate the influence of runout path material on the mobility and final morphology of the round top rock avalanche deposit new zealand this rock avalanche of mylonitic schist ran out over a planar surface of saturated fluvial gravel longitudinal ridges aligned radial to source grade into smaller aligned hummocks and digitate lobes in the distal reach soils and river gravels in the runout path are found bulldozed at elongate ridge termini where they formed local obstacles halting avalanche motion at these locations thus aiding development of prominent elongate ridges on the deposit further travel over the disrupted substrate led to avalanche substrate mixing at the base of the debris mass field observations combined with subsurface geophysical investigations and laboratory analogue models illustrate the processes of substrate deformation features at the round top rock avalanche copyright 2009 john wiley sons ltd

forensic investigations of the cima salti landslide northern italy using runout simulations abstract over the last decades a movement has begun to reclassify deposits previously misidentified as having origins other than landsliding the reverse problem of incorrectly assigning deposits a mass movement origin however has been addressed less in the landslide community the cima salti landslide in the lake garda region of northern italy is a cautionary tale of assuming source areas and volumes it was traditionally thought to have dammed tenno lake in the middle ages and to have a volume of 20 30 mm3 we show through geological field data and simple runout simulations with the codes dan3d and shaltop which produced comparable results that the volume of the landslide was likely significantly overestimated in the past and that it most likely did not dam tenno lake as has been assumed we propose that a smaller volume landslide 2 5 mm3 was deposited on stagnant ice melting in situ in the lateglacial period a relatively minor event in the complex history of the magnone valley this interpretation emphasizes the importance of careful field investigations and assumption validation at cima salti and in a broader context it also shows the unique capacity of landslide simulation to guide field observation and discriminate mass emplacement processes

the rockslide and debris flow from mount cayley b c in june 1984 a major rockslide and debris flow occurred on mount cayley british columbia in june 1984 approximately 3 2 million cubic metres of volcanics travelled 2 0 km down avalanche creek at velocities up to 35 m s to dam the confluence of avalanche and turbid creeks the breaking of the landslide dam caused an extremely fast debris flow the velocity of the debris flow and associated wind gusts up to 34 m s caused superelevations hurled rocks and wood through the air uprooted trees and spattered mud 16 m up trees the debris flow removed the logging road bridge and road approaches at the mouth of turbid creek blocked the squamish river during surges and introduced huge quantities of sediment to the squamish river the uniaxial compressive strength of wet tuff collected from the head scarp of the rock slide is 1 0 1 5 mpa about two thirds of the strength of dry specimens the friction angle on wet tuff bedding surfaces is 30 and the slake durability index is 26 weak tuffs form the rupture surface of

nitrogen in rock occurrences and biogeochemical implications 1 there is a growing interest in the role of bedrock in global nitrogen cycling and potential for increased ecosystem sensitivity to human impacts in terrains with elevated background nitrogen concentrations nitrogen bearing rocks are globally distributed and comprise a potentially large pool of nitrogen in nutrient cycling that is frequently neglected because of a lack of routine analytical methods for quantification nitrogen in rock originates as organically bound nitrogen associated with sediment or in thermal waters representing a mixture of sedimentary mantle and meteoric sources of nitrogen rock nitrogen concentrations range from trace levels 200 mg n kg 1 in granites to ecologically significant concentrations exceeding 1000 mg n kg 1 in some sedimentary and metasedimentary rocks nitrate deposits accumulated in arid and semi arid regions are also a large potential pool nitrogen in rock has a potentially significant impact on localized nitrogen cycles elevated nitrogen concentrations in water and soil have been attributed to weathering of bedrock nitrogen in some environments nitrogen released from bedrock may contribute to nitrogen saturation of terrestrial ecosystems more nitrogen available than required by biota nitrogen saturation results in leaching of nitrate to surface and groundwaters and where soils are formed from ammonium rich bedrock the oxidation of ammonium to nitrate may result in soil acidification inhibiting revegetation in certain ecosystems collectively studies presented in this article reveal that geologic nitrogen may be a large and reactive pool with potential for amplification of human impacts on nitrogen cycling in terrestrial and aquatic ecosystems

testing the suitability of frictional behaviour for pyroclastic flow simulation by comparison with a well constrained eruption at tungurahua volcano ecuador we use a well monitored eruption of tungurahua volcano to test the validity of the frictional behaviour also called mohr coulomb which is generally used in geophysical flow modelling we show that the frictional law is not appropriate for the simulation of pyroclastic flows at tungurahua with this law the longitudinal shape of the simulated flows is a thin wedge of material progressively passing over several hundreds of metres from an unrealistic thickness at the front 1 mm to some tens of centimetres simulated deposits form piles which accumulate at the foot of the volcano and are more similar to sand piles than natural pyroclastic deposits finally flows simulated with a frictional rheology are not channelised by the drainage system but affect all the flanks of the volcano in addition their velocity can exceed 150 m s 1 allowing pyroclastic flows to cross interfluves at bends in the valley affecting areas that would not have been affected in reality and leaving clear downstream areas that would be covered in reality instead a simple empirical law a constant retarding stress i e a yield strength involving only one free parameter appears to be much better adapted for modelling pyroclastic flows a similar conclusion was drawn for the socompa debris avalanche simulation kelfoun and druitt j geophys res 110 b12202 2005

prehistoric debris avalanches from mount cayley volcano british columbia reply an investigation of diamicton units exposed in an extensive accumulation of volcanic debris in the squamish valley west of mount cayley volcano has yielded evidence for at least three major debris avalanches initiated by the collapse of the western flank of mount cayley in the mid holocene radiocarbon ages obtained from tree fragments contained in the deposits indicate that the events took place at 4800 1100 and 500 bp all three debris avalanches dammed the squamish river and formed temporary lakes upstream of the debris failure of the cone took place after considerable dissection of the original edifice had exposed weak pyroclastic materials at the base of the steep upper slope of the volcano no evidence of older debris avalanches from mount cayley has been discovered smaller scale debris avalanches probably have been common and at least two have occurred in historic time 1963 and 1984 debris avalanches from mount cayley and the effects of a possible damming of the squamish river are major

an empirical method for estimating travel times for wet volcanic mass flows travel times for wet volcanic mass flows debris avalanches and lahars can be forecast as a function of distance from source when the approximate flow rate peak discharge near the source can be estimated beforehand the near source flow rate is primarily a function of initial flow volume which should be possible to estimate to an order of magnitude on the basis of geologic geomorphic and hydrologic factors at a particular volcano least squares best fits to plots of flow front travel time as a function of distance from source provide predictive second degree polynomial equations with high coefficients of determination for four broad size classes of flow based on near source flow rate extremely large flows 1 000 000 m3 s very large flows 10 000 1 000 000 m3 s large flows 1000 10 000 m3 s and moderate flows 100 1000 m3 s a strong nonlinear correlation that exists between initial total flow volume and flow rate for instantaneously generated debris flows can be used to estimate near source flow rates in advance differences in geomorphic controlling factors among different flows in the data sets have relatively little effect on the strong nonlinear correlations between travel time and distance from source differences in flow type may be important especially for extremely large flows but this could not be evaluated here at a given distance away from a volcano travel times can vary by approximately an order of magnitude depending on flow rate the method can provide emergency management officials a means for estimating time windows for evacuation of communities located in hazard zones downstream from potentially hazardous volcanoes

a re examination of the mechanism and human impact of catastrophic mass flows originating on nevado huascaran cordillera blanca peru in 1962 and 1970 abstract the 1962 and 1970 huascaran mass movements originated as rock ice falls from the mountain s north peak transformed into higher volume high velocity mud rich debris flows by incorporation of snow from the surface of a glacier below huascaran and the substantial entrainment of morainic and colluvial material from slopes below the glacier terminus water for fluidization of the entrained material originated in the melting of incorporated snow and the liberation of soil moisture contained within the entrained materials eyewitness reports indicate very high mean velocities for the events 17 35 m s 1962 and 50 85 m s 1970 the runout distances and velocity profiles of both events were simulated using dan w both mass movements continued downstream in the rio santa as debris floods aluviones that in 1970 reached the pacific at a distance of 180 km in strong contrast to publications in the geosciences literature 1961 peru census data indicates that the death toll of the 1970 event is ca 6000 and that total life loss in the two events did not exceed 7000 people

interaction between landsliding materials and the underlying erodible bed in a loess flowslide abstract loess landslides exhibit strong interactions with the terrace sediments of the jing river on the south jingyang platform jingyang xi an china analysis of past landslide events revealed that the sand layer of this terrace was thrust up to the surface accompanied by other terrace sediments of carrying this led to the formation of a thrust nappe structure over a long distance we performed ring shear tests to examine the shear behavior of this sand layer with the finding that saturated sand was highly susceptible to liquefaction induced failure the groundwater level of the study area is high resulting in near saturation of the sand layer therefore topographic interferences contributed additional variables and increased interaction complexities simulations indicated that the liquefied sand layer was compressed and forced due to the absence of constraints the sand layer near the bottom of the slope was sheared out over a relatively short distance on the other hand particle interia and constraints of the stable layer resulted in the sand layer near the distal part of the deposits being sheared upward to the ground finally an initiation movement model of loess flowslides is proposed it describes static liquefaction of the loess layer of the slope resulted in occurrence of flowslides collisions between the deposits from the platform edge slope and terrace sediments resulted in the shear liquefaction of sands the landslide experienced four stages as they moved scraping collisions floating scrapes folded thrusts and nappe accumulation

two early holocene rock avalanches in the bernese alps rinderhorn switzerland abstract large rock avalanches constitute a critical process modulating the evolution of alpine landscapes however the relatively infrequent occurrence of these high magnitude events makes identifying underlying process controls challenging here we describe two rock avalanches in the rinderhorn area of the bernese alps switzerland providing new mapping of rock avalanche source areas and deposits refined volume estimates for each event runout modeling back analyses and absolute age constraint from cosmogenic 36 cl surface exposure dating results reveal that the daubensee rock avalanche released 4 million m 3 of limestone sliding from the western crest of the rinderhorn debris ran out across a lateglacial moraine before reaching the valley bottom and spreading leaving thin on average 7 m deposits across a broad area the runout resulted in a fahrboschung angle of 21 part of the deposit now lies beneath lake daubensee the klein rinderhorn rock avalanche released 37 million m 3 of limestone along a dip slope sliding plane with a maximum runout distance of 4 3 km and estimated fahrboschung angle of 14 deposits bulked to 47 million m 3 running up the opposing slope with distinct hummocky morphology in the proximal area and a distal longitudinal flow ridge these deposits were later modified and partly obscured by ice avalanches from the nearby altels peak cosmogenic 36 cl surface exposure dating revealed nearly coincident ages for both rock avalanches of 9 8 0 5 ka the large lag time between local deglaciation and failure suggests that the events were not directly triggered by deglaciation rather the concurrent exposure ages also coinciding with the nearby kander valley rock avalanche as well as paleoseismic records from nearby lakes strongly suggest seismic triggering

lidar derived morphology of the 1993 lascar pyroclastic flow deposits and implication for flow dynamics and rheology abstract pumice flows are potentially destructive volcanic events that derive from eruption column collapse and whose dynamics are poorly understood the challenges in studying these flows include the lack of constraints on the dynamics kinematics and initial conditions that control their emplacement we present a morphological study of the distal deposits lobes of the pumice flows resulting from the 1993 eruption at lascar chile the surface geometry of the lobes was measured in detail using a lidar device which allowed for detailed characterisation of their morphology consisting of central channel and lateral levees and terminal frontal snout in particular we find that the ratio of channel levee height as a function of the ratio of the distance between levees total width of the lobe has a characteristic curve for these pumice flow lobes our analysis of several of the lascar pumice lobe deposits south east sector identified several dimensionless groups of the available parameters which when compared against published results from both experimental and numerical investigations allowed us to constrain crucial kinematic and dynamic information on the terminal phase of the pumice flows notably we estimate the velocity of the terminal phase of pumice flows to be 5 10 m s froude numbers of 1 5 2 are comparable with values found for experimental granular flows height width aspect ratios for the levee channel section of the pumice lobes are similar to those for experimental flows although these same aspect ratios for the snout are much larger for the natural deposits than their small scale analogues finally we discuss the possible emplacement dynamics of the terminal lascar 1993 pumice flows a pseudo reynolds number based on the velocity estimation is found to be up to 100 times larger for the pumice flows than experimental scale flows this suggests that the flow retarding frictional forces for large scale flows are relatively unimportant compared to flows at smaller scales mechanical effects such as fluidisation mobilisation of material lying on the slopes over which they propagate and lubrication due to polydispersivity could provide an explanation for their ability to propagate on shallow slopes 6 11

the pandemonium creek rock avalanche british columbia in 1959 a rock spur became detached from the headwall of a cirque near pandemonium creek in the southern coast mountains of british columbia approximately 5 000 000 cu m of blocky gneissic quartz diorite debris travelled 9 0 km along a highly irregular path descending a vertical distance of 2 km to the valley of south atnarko river the high mobility of the rock avalanche is manifested by superelevation in valley bends two run ups and two right angle changes in flow direction this mobility is due in part to 1 peculiarities in the path of the landslide lateral moraines for example funnelled and accelerated the debris and 2 travel over a glacier below the detachment zone although most of the debris came to rest on the upper part of a fan at the mouth of pandemonium creek one lobe traversed the fan and entered knot lakes where it generated displacement waves that destroyed trees along the shore run up and superelevation data indicate that the debris was moving between 81 and 100 m s as it entered the run up zone at pandemonium creek and 21 38 m s in pandemonium valley to the east these velocities were analysed by applying the dynamic model of h j korner rock mechanics 1976 8 225 256 to the path of the landslide the analysis suggests that the rock avalanche had two phases a very rapid initial phase from detachment to the beginning of the run up and following sudden energy losses at the run up a second phase involving much lower velocities the pandemonium creek landslide is similar in many respects to much larger highly mobile rock avalanches in other parts of the world for example huascaran peru and little tahoma peak washington u s a although much less common than rockfalls and debris flows rock avalanches are capable of far greater damage this is a consequence of their size and the fact that they travel great distances at high velocities the potential exists for other highly mobile landslides of the pandeminium creek type in the mountains of western canada highlighting the need for caution in the future development of this region

environmental signal propagation in sedimentary systems across timescales abstract earth surface processes operate across erosionally dominated landscapes and deliver sediment to depositional systems that can be preserved over a range of timescales the geomorphic and stratigraphic products of this source to sink sediment transfer record signals of external environmental forcings as well as internal or autogenic dynamics of the sedimentary system here we evaluate environmental signal propagation across sediment routing systems with emphasis on sediment supply qs as the carrier of up system forcings we review experimental numerical and natural examples of source to sink sediment routing and signal propagation during three timescales 1 historic which includes measurement and monitoring of events and processes of landscape change and deposition during decades to centuries 2 centuries to several millions of years referred to as intermediate timescale and 3 deep time we discuss issues related to autogenic dynamics of sediment transport transient storage and release that can introduce noise lags and or completely mask signals of external environmental forcings we provide a set of conceptual and practical tools for evaluating sediment supply within a source to sink context which can inform interpretations of signals from the sedimentary record these tools include stratigraphic and sediment routing system characterization sediment budgets geochronology detrital mineral analysis e g thermochronology comparative analog approaches and modeling techniques to measure calculate or estimate the magnitude and frequency of external forcings compared to the characteristic response time of the sediment routing systems

granular flow experiments on the interaction with stationary runout path materials and comparison to rock avalanche events the central focus of this work is to study the processes acting well below the surface of a moving rock or debris avalanche during travel over stationary substrate material small scale physical models at a linear scale of 1 104 used coal as avalanche analogue material and different granular material simulating sedimentary substrates varying in frictional resistance thickness and relative basal boundary roughness as well as inerodible non deformable runout path conditions substrate materials with the least frictional resistance showed the greatest response to granular flow overriding becoming entirely mobilized beneath and ahead of the moving mass and producing the longest runout observed with a unique deposit profile shape with a smooth substrate basal contact failure occurred along this plane and avalanche and substrate became coupled during runout with a rough base however temporary force chains of grain contacts in the substrate prevailed longer imparted their resistance to motion shear into the granular flow and the flow rear section consequently halted earlier than when moving over substrates with a weak base reducing substrate thickness diminished the effect of basal contact roughness on granular flow runout and deposit length inerodible non deformable substrate conditions caused changes in granular flow behaviour from essentially en masse sliding on low friction surfaces to increasing granular agitation over rougher paths copyright 2012 john wiley sons ltd

river discharge influences on particulate organic carbon age structure in the mississippi atchafalaya river system 1 applying ramped pyrolysis radiocarbon analysis to suspended river sediments we generate radiocarbon 14c age spectra for particulate organic carbon poc from the lower mississippi atchafalaya river system mars to better understand a major river system s role in carbon transport ramped pyrolysis 14c analysis generates age distributions of bulk carbon based on thermochemical stability of different organic components our results indicate higher proportions of older material in the poc during higher discharge ages increase throughout the high discharge age spectra indicating that no single component of the poc is responsible for the overall age increases observed instead older material is contributed across the poc age spectrum and unrelated to increased bedload suspension in this comparison of 2 spring discharges less than half of the poc transported during higher discharge is less than 1000 14c years in age constraining of the role of the mars as a flux of atmospheric co2 toward longer term sedimentary sinks in the mississippi delta and the gulf of mexico the results suggest that delta building processes benefit disproportionately from high discharge events carrying larger amounts of sediment because these events involve both a higher proportion of millennially aged carbon from floodplain exchange of poc and a potentially higher proportion of petrogenic carbon 30 530 increase overall an internally consistent picture of po14c age distributions from a major river system emerges as differences in space and time are small compared to the range of ages of poc sources in such a large basin

observations from the large rapid yigong rock slide debris avalanche southeast tibet the yigong rock slide debris avalanche yra which occurred on 9 april 2000 received worldwide attention as one of the largest nonseismic landslides in recent years with a volume of 0 3 109

a note on the representation of steric sea level in models that conserve volume rather than mass this note discusses the representation of steric sea level in ocean circulation models changes in steric sea level are caused when changes in the density of the water column imply an expansion or contraction of the column models usually make the boussinesq approximation and conserve volume rather than mass and so do not properly represent expansion or contraction this means that although expansion contraction is included in the equation of state it is not accounted for by the model dynamics in this note we examine the equation governing the time evolution of the sea level displacement it is shown that requiring conservation of mass rather than volume introduces a new term to this equation a simple example is used to show the relationship of the new term to the surface buoyancy flux the equilibrium response to the new term has two parts one part consists of the goldsbrough and stommel gyres for which in the ocean interior vortex stretching due to the local expansion contraction of the water column is balanced by changes in planetary vorticity the other part corresponds to the inverse barometer the effect is to adjust sea level by a globally uniform but timevarying factor determined by the net expansion contraction of the global ocean since this correction is globally uniform it has no dynamical significance both the goldsbrough stommel gyres and the inverse barometer solution are missing from models as currently formulated this does not represent a serious error however if comparison is made with observations of sea level model calculated sea level should be adjusted by a globally uniform time varying factor determined by the net expansion contraction of the global ocean this would be important for assessing the likely rise in sea level in response to global warming

the geomorphic impact of the catastrophic october 1984 flood on the planform of the squamish river southwestern british columbia discussion depending on the type of river planform the degree of channel change during the 1984 flood varied from a relatively minor response to a major reorganization of the channel despite its large size the 1984 flood accomplished little more floodplain modification in the meandering and transitional semibraided reaches than had previous smaller floods of similar duration in contrast in the braided reach the 1984 flood caused floodplain erosion and major reorganization of the channel to an extent previously unrecorded apparently here exceeding a threshold for channel stability

including non boussinesq effects in boussinesq ocean circulation models abstract a set of equations is derived to modify z level boussinesq ocean circulation models to account for non boussinesq effects these equations take the same form as those of the boussinesq models except for the addition of a few correction terms that require the calculation of integral density sources these corrections are estimated to be significant based on a scale analysis

production storage and output of particulate organic carbon waipaoa river basin new zealand 1 we compute the particulate organic carbon poc yield of the waipaoa river new zealand using sediment rating curves in conjunction with measurements of the carbon content of the suspended sediment to ascertain the source of the carbon and the extent to which the poc flux is tied to different erosion processes we determined the stable isotopic carbon composition 13c and carbon to nitrogen c n ratio of weathered bedrock soil and regolith most poc is derived from suspended sediment generated by gully erosion incision into weathered bedrock supplemented by landsliding during extreme events the specific yield of poc from the headwaters drainage area 1580 km2 is 55 g m 2 yr 1 which is very high by global standards and by comparison with other turbid steep land rivers the annual loss to floodplain storage is 4 3 6 kt of the mean annual poc yield 86 7 kt thus the waipaoa river is a very effective conduit for transporting poc to the ocean

dda validation of the mobility of earthquake induced landslides abstract this paper studies the run out of earthquake induced landslides there are more than 20 mechanical models to explain long run out of rapid landslides including some earthquake induced landslides however notably few of them considered the effect of seismic loading on the run out of landslides in a previous study we have proposed a model which is called the multiplex acceleration model mam to interpret the long run out mechanism and a shaking table test has been performed to verify the mam because the previous mam is a conceptual model and only a single stone has been examined under sine waves by the shaking table test the mam needs to be extended and further verified in this paper the mam was extended by introducing the movement change that was induced by the so called trampoline effect of earthquake loading and the latest practical numerical simulation program discontinuous deformation analysis dda was used to verify the mobility of earthquake induced landslides after a conceptual landslide model was used to verify the effect of seismic loading on the mobility the donghekou landslide which was a typical long run out landslide that was induced by the 2008 wenchuan earthquake was analyzed the results show that the seismic loading could be one of the factors that could eventually help increase the run out of landslides

geohazard cascade and mechanism of large debris flows in tianmo gully se tibetan plateau and implications to hazard monitoring abstract alpine glaciers and permafrost are sensitive to climate change and their degradation due to annual temperature increasing has already induced many mass movements such as debris flows on september 4 of 2007 july 25 31 and september 5 8 of 2010 three large debris flows took place in tianmo gully a left bank tributary of parlung river southeast tibetan plateau the debris flows blocked the river and a section of highway 450 m long including a bridge 76 m long were destroyed by the subsequent outburst flood this paper based on post event investigations witness accounts news reports and satellite image interpretation systematically analyses the geo environments climate conditions and sources of these debris flow events their differences in flow process surge numbers and velocity suggest that they resulted from different geohazard processes cascades and initiation mechanisms the 2007 debris flow originated from a bare rock moraine collapse next to the cirque due to strong alternation of wet and dry conditions the mass moved down the gully with velocity of 30 40 m s estimated by back calculation using superelevation and run up it entrained moraine avalanched snow ice and water from the channel and transformed into high speed debris flow crossing the parlung river and finally depositing onto the highway the other two events in july and september of 2010 initiated from two channel bank landslides triggered by melt water and concentrated rainfall which dammed the channel the subsequent landslide dam failure generated debris flows over several days with velocities of 12 14 m s that temporally blocked parlung river the initiation mechanisms of most large debris flows recorded in parlung region are similar to the events in tianmo gully originating either from rock moraine avalanches or from the collapse of a landslide dam this implies that the periglacial degradation of bedrock and moraine is the key process to be monitored and assessed under climate warming the paper applies the geohazard mechanisms and cascade to hazard monitoring in order to protect the existing sichuan tibet highway and the forthcoming railway

source to sink sedimentary systems and global carbon burial a river runs through it abstract source to sink sedimentary systems are important settings of carbon cycling serving as sites of carbon transfer between terrestrial and marine reservoirs and as the primary locations for organic carbon burial on earth the age and character of the carbon that is buried at the terminal ends of these systems reflects the sources and transformations of the organic carbon oc throughout their linked terrestrial and marine segments profound differences are observed between large passive and small active margin systems large passive margin systems are characterized by large floodplains and relatively broad shelves where oc has protracted exposure to oxidants rapid burial in prograding subaqueous deltaic clinoforms or bypass to submarine fans however leads to high burial efficiency of terrestrial biospheric oc in some passive margin settings the oc in small active margin systems in contrast follows relatively short pathways from headwaters to seabed this rapid transit facilitated by the important role of storm driven transport in such settings can lead to high oc burial efficiencies the study of oc sources and transformations in contemporaneous source to sink sedimentary systems informs interpretations about the systems in which oc was buried in the geologic past their stratigraphic records of environmental change and their potential to produce petroleum resources

evolution of cheekye fan squamish british columbia holocene sedimentation and implications for hazard assessment cheekye fan a large 25 km 2 fan located at the head of howe sound southwestern british columbia has its origins in the collapse of the western flank of mount garibaldi onto a waning late pleistocene glacier followed by post glacial redistribution of colluvial glacial sediments reconstruction of internal fan architecture allowed characterization of the rapid decline in sediment delivery to the lower fan through the paraglacial period a result holding important implications for hazard assessment a ground penetrating radar profile on lower cheekye fan has reflectors with a steep 25 westerly dip lying between 48 and 26 m above sea level which are interpreted as foreset beds radiocarbon ages from marine deltaic deposits at the head of howe sound indicate that the sea stood at about 45 m above sea level at 10 200 bp together the data indicate that the head of howe sound was deglaciated by 10 200 bp that the fan had prograded 2 5 km into the fjord by this time and continued to prograde as relative sea level fell reflectors at 10 m above sea level with a steep southerly dip along the southern edge of the lower fan and radiocarbon ages in this vicinity indicate it had reached close to its modern extent by 8000 9000 bp calculation of the volume of sediment stored in the lower fan indicates that at least 90 of the material was deposited before 6000 bp this indicates that the cheekye fan is largely a relict feature putting its large size into context for future hazard assessments

large holocene landslides from pylon peak southwestern british columbia mount meager massif the northernmost volcano of the cascade volcanic belt has been the site of very large 10 7 m 3 landslides in the holocene epoch we document two complex landslides at pylon peak one of the peaks of the mount meager massif about 7900 14 c and 3900 14 c years ago about 8700 and 4400 calendar years ago together the two landslides displaced 6 1 0 8 m 3 of volcanic rock from the south flank of pylon peak into nearby meager creek valley each landslide consisted of at least two phases an early debris flow resulting from failure of hydrothermally altered pyroclastic rock at mid levels on the mountain and a later rock avalanche from a higher source both debris flows likely traveled down meager creek and preliminary evidence from drilling indicates the 4400 year old event traveled down lillooet river into areas that are now settled and where population density is increasing rapidly the mobility of the debris flows was due to the high content of fine weathered volcanic sediment and the availability of sufficient water the causes of the landslides are a wet climate and the presence of weak hydrothermally altered volcanic rock containing abundant phreatic water on glacially oversteepened slopes the landslides may have been triggered by earthquakes or by upwelling of magma to shallow depths within the volcano however they may also have occurred without specific triggers following extended periods of progressive weakening of the volcanic rocks

continuum simulation of flow failures dynamic aspects of several catastrophic slope failures have been evaluated by unsteady flow modelling assuming two dimensional or quasi three dimensional transient flow of an incompressible bivi

climatic and geomorphic controls on the erosion of terrestrial biomass from subtropical mountain forest 1 erosion of particulate organic carbon poc occurs at very high rates in mountain river catchments yet the proportion derived recently from atmospheric co2 in the terrestrial biosphere pocnon fossil remains poorly constrained here we examine the transport of pocnon fossil in mountain rivers of taiwan and its climatic and geomorphic controls in 11 catchments we have combined previous geochemical quantification of poc source accounting for fossil poc from bedrock with measurements of water discharge qw and suspended sediment concentration over 2 years in these catchments pocnon fossil concentration mg l 1 was positively correlated with qw with enhanced loads at high flow attributed to rainfall driven supply of pocnon fossil from forested hillslopes this climatic control on pocnon fossil transport was moderated by catchment geomorphology the gradient of a linear relation of pocnon fossil concentration and qw increased as the proportion of steep hillslopes 35 in the catchment increased the data suggest enhanced supply of pocnon fossil by erosion processes which act most efficiently on the steepest sections of forest across taiwan pocnon fossil yield was correlated with suspended sediment yield with a mean of 21 10 tc km 2 yr 1 at this rate export of pocnon fossil imparts an upper bound on the time available for biospheric growth of 800 yr over longer time periods pocnon fossil transferred with large amounts of clastic sediment can contribute to sequestration of atmospheric co2 if buried in marine sediments our results show that this carbon transfer should be enhanced in a wetter and stormier climate and the rates moderated on geological timescales by the regional tectonic setting

olokele rock avalanche island of kauai hawaii in october 1981 a mass of rock and soil having an estimated volume of 500 000 m 3 fell as a rock fall avalanche from a steep slope 800 m high near the head of olokele canyon on the island of kauai hawaii boulders were launched into the air from a bench on the slope for a downstream distance of about 850 m the velocity of the avalanche was rapidly diminished by impact against the valley sides and it became a muddy debris flow that traveled 4 6 km downstream severely eroding the valley sides the volume of debris deposited on the canyon bottom is estimated to be 2 500 000 m 3 or about four times the volume derived from the slope slope failure is attributed to gradual undercutting and loss of shear strength in beds of weathered ash and to joints in a thick basaltic cap rock

characteristics and runout behaviour of the disastrous 28 august 2017 rock avalanche in nayong guizhou china abstract on 28th august 2017 a disastrous rock avalanche occurred in nayong guizhou china this catastrophic event killed 35 people and destroyed 23 houses in this study the failure process of the avalanche was analyzed using uav video footage and seismic signal recordings obtained for the pre and post failure stages of the landslide to better understand the possible mechanism of the avalanche and its dynamic characteristics a numerical simulation was conducted using a dynamic model dan3d to simulate the runout behaviour of the displaced materials simulated results indicate that the failure process of the nayong rock avalanche lasted approximately 30 s the duration of the failure process is close to that from the uav video footage and seismic signal recordings 35 s the duration of movement during the landslide process is estimated to be approximately 90 s with a maximum velocity of 40 m s the combined frictional voellmy model delivered the most accurate results when simulating this event the selected models and parameters are expected to aid in clarifying the propagation processes of similar rock avalanches and thus improve the accuracy of hazard prediction in mountainous karst areas

catastrophic debris flows on 13 august 2010 in the qingping area southwestern china the combined effects of a strong earthquake and subsequent rainstorms in the wenchuan area in sw china an abundance of loose co seismic landslide debris was present on the slopes after the wenchuan earthquake which in later years served as source material for rainfall induced debris flows or shallow landslides slopes composed of cambrian sandstones and siltstones intercalated with slates appeared to be most susceptible to co seismic landsliding a total of 20 debris flows are described in this paper all were triggered by heavy rainfall on 13th of august 2010 field reconnaissance and measurements supported by aerial photo interpretation were conducted to identify the locations and morphological characteristics of the debris flow gullies in order to obtain information about surface area and volume of landslides and the debris flows the debris flows in the study area were initiated by two processes a run off erosion on co seismic landslide material and concentrated erosion of landslide debris in steep channels b new landslides that transform into debris flows the volume of debris flow deposits on individual fans varies by many orders of magnitude the smallest deposit has a volume of from 5760 to 3 1 million m3 a comparison of the measured volumes deposited on the fan with the volumes of debris stored in the catchment shows the huge potential for future debris flow activity whilst there is a weakly significant positive correlation between these two volumes no significant statistical correlation could be established between volumes of debris flow deposits and other morphometric parameters of the catchment a catastrophic debris flow catchment the wenjia catchment was selected as an extreme case to show in detail the mechanism of debris flow formation as a result of intensive erosion in loose material which was deposited by a rock avalanche during the 2008 earthquake event analyses of the meteorological conditions that triggered these debris flows show one day antecedent precipitation varying between 67 7 and 137 6 mm with a mean rainfall intensity of about 7 3 to 22 5 mm h a rainfall event with peak intensity of 38 7 mm h triggered the largest debris flow event rainfall data related to five debris flow events in the wenjia torrent was used to establish a primary rainfall intensity duration relationship for the triggering of debris flows which was compared to other rainfall duration thresholds from other parts of the world in the discussion emphasis is laid on the need to unravel the process mechanisms which initiated the debris flows for a better understanding and assessment of meteorological thresholds

a model for the runout analysis of rapid flow slides debris flows and avalanches runout analyses are used for risk assessment and design of remedial measures against rapid landslides such as debris flows debris avalanches rockslide avalanches large scale liquefaction failure

source and behavior of pyroclastic density currents generated by vulcanian style explosions of popocatepetl volcano mexico on 22 january 2001 abstract since 1994 popocatepetl volcano has extruded 85 lava domes each of which has been destroyed by vulcanian style explosions the paroxysmal vulcanian explosion of 22 january 2001 has been unique by generating multiple pyroclastic density currents pdcs scientists and civil protection authorities have used those pdcs to remap the high risk hazard zone of the volcano although little study has been carried out to understand the generation and evolution of those pdcs here we examine 38 stratigraphic sections and analyze the granulometry componentry vesicularity and petrology glass melt inclusions in plagioclase of collected samples to interpret the origins of the vulcanian explosions and the pdc behavior the 22 january event generated two series of dense pdcs that detached from the base of the eruption column the first set of pdcs traveled northwest across a glacier on the volcano partially scouring and melting the ice that hours later generated a lahar two pulses of these pdcs were confined within a large ravine surpassed the slope break and traveled up to 3 km away from the vent the deposits are matrix supported throughout their extent the second set of pdcs traveled to the northeast mainly as unconfined currents that split into two lobes prior to the slope break the farthest traveled current followed a western ravine and reached the forest 3 5 km from the summit the eastern lobe buried a local hiking hut and reached 2 1 km the deposits from these northeastern currents are massive and block supported all deposits volume of 5 71 105 m3 have finger like morphology with levees and frontal snouts all pdcs flowed as a dense basal granular current with turbulent upper clouds at minimum speeds of 7 10 m s in terms of hazards pdcs that interact with glaciers on the volcano are expected to travel farther and potentially generate extensive lahars at present small intermittent patches of glacier occur on the northern upper slopes of the volcano the components of the deposits are in order of abundance black scoria 53 62 wt sio2 banded scoria pumice 63 wt sio2 dome lithics 60 61 wt sio2 accidental lithics and free crystals juvenile pumice and scoria contain phenocrysts of plagioclase an47 10 clinopyroxene en48 3 orthopyroxene en64 1 ilmenite and titanomagnetite set in a rhyolitic glass pumice clast 74 39 wt sio2 or microlite rich matrix scoria clast the dome lithics also contain these phenocrysts as well as rare olivine phenocrysts fe2 fe2 mg 0 1 dissolved h2o co2 contents in melt inclusions hosted by pumice plagioclase phenocrysts suggest the felsic magma was stored at depths of 2 4 km thus the 2001 event was triggered by the injection of mafic magmas into a small volume of felsic magma probably forming dikes left from the previous eruptive episode we propose that the vulcanian explosions tap a column of magma 2 km depth equivalent to the volume that contained the felsic dikes this mechanism has been acting during the destruction of all summit domes of the ongoing eruption of the volcano

riverine particulate organic carbon from an active mountain belt importance of landslides 1 we investigate the routing and transfer of particulate organic carbon poc from the western southern alps new zealand using organic carbon corg and nitrogen norg concentrations and stable carbon isotopes 13corg in this active mountain belt sediment discharge is dominated by landslide derived material landsliding acts to homogenize the geochemically diverse hillslope poc mixing poc from the standing biomass and soil with the fossil poc from bedrock as a result the poc in river sediment at the mountain front is a binary mixture of fossil and nonfossil carbon sourced from many landslide deposits we calculate that nonfossil biogenic poc makes up 63 7 of the total poc in the suspended load of rivers draining the western southern alps the erosional flux of biogenic poc from these catchments represents a transfer of 39 tc km 2 a 1 of atmospheric co2 averaged over the west flank of the mountain belt if more than 10 of this poc is preserved in sediments on geological timescales then this process is the most significant way in which the southern alps and similar tectonically active mountain belts with restricted alluvial aprons consume atmospheric co2

evaluation of approaches to calculate debris flow parameters for hazard assessment abstract many different runout prediction methods can be applied to estimate the mobility of future debris flows during hazard assessment the present article reviews the empirical analytical simple flow routing and numerical techniques all these techniques were applied to back calculate a debris flow which occurred in 1982 at la guingueta catchment in the eastern pyrenees a sensitivity analysis of input parameters was carried out while special attention was paid to the influence of rheological parameters we used the voellmy fluid rheology for our analytical and numerical modelling since this flow resistance law coincided best with field observations the simulation results indicated that the basal friction coefficients rather affect the runout distance while the turbulence terms mainly influence flow velocity a comparison of the velocity computed on the fan showed that the analytical model calculated values similar to the numerical ones the values of our rheological parameters calibrated at la guingueta agree with data back calculated for other debris flows empirical relationships represent another method to estimate total runout distance the results confirmed that they contain an important uncertainty and they are strictly valid only for the conditions which were the basis for their development with regards to the simple flow routing algorithm this methods could satisfactorily simulate the total area affected by the 1982 debris flow but it was not able to directly calculate total runout distance and velocity finally a suggestion on how different runout prediction methods can be applied to generate debris flow hazard maps is presented taking into account the definition of hazard and intensity the best choice would be to divide the resulting hazard maps into two types final hazard maps and preliminary hazard maps only the use of numerical models provided final hazard maps because they could incorporate different event magnitudes and they supplied output values for intensity calculation in contrast empirical relationships and flow routing algorithms or a combination of both could be applied to create preliminary hazard maps the present study only focussed on runout prediction methods other necessary tasks to complete the hazard assessment can be looked up in the guidelines for landslide susceptibility hazard and risk zoning included in this special issue

suitability of simple rheological laws for the numerical simulation of dense pyroclastic flows and long runout volcanic avalanches 1 the rheology of volcanic rock avalanches and dense pyroclastic flows is complex and it is difficult at present to constrain the physics of their processes the problem lies in defining the most suitable parameters for simulating the behavior of these natural flows existing models are often based on the coulomb rheology sometimes with a velocity dependent stress e g voellmy but other laws have also been used here i explore the characteristics of flows and their deposits obtained on simplified topographies by varying source conditions and rheology the coulomb rheology irrespective of whether there is a velocity dependent stress forms cone shaped deposits that do not resemble those of natural long runout events a purely viscous or a purely turbulent flow can achieve realistic velocities and thicknesses but cannot form a deposit on slopes the plastic rheology with e g bingham or without a velocity dependent stress is more suitable for the simulation of dense pyroclastic flows and long runout volcanic avalanches with this rheology numerical flows form by pulses which are often observed during natural flow emplacement the flows exhibit realistic velocities and deposits of realistic thicknesses the plastic rheology is also able to generate the frontal lobes and lateral levees which are commonly observed in the field with the plastic rheology levee formation occurs at the flow front due to a divergence of the driving stresses at the edges once formed the levees then channel the remaining flow mass the results should help future modelers of volcanic flows with their choice of which mechanical law corresponds best to the event they are studying

on characteristics and dynamic analysis of the niumian valley rock avalanche triggered by the 2008 wenchuan earthquake sichuan china on may 12 2008 a large catastrophic rock avalanche was triggered by the wenchuan earthquake on niumian valley in yingxiu town wenchuan county china the displaced landslide materials traveled about 2 640 m with a descent of about 850 m and buried several houses and caused nearly 20 casualties based on detailed field investigation some basic characteristics of this landslide are introduced field investigation showed that the displaced landslide materials experienced three times of run up and twice of superelevation along the run out path and downslope enlargement due to the entrainment of run out path materials a numerical model dan3d is used to simulate the landsliding process by means of trial and error it can be seen that the voellmy model and values of friction coefficient f 0 19 dimensionless and turbulent coefficient xi 2 000 m s2 can provide the best performance in the prediction of sliding and depositing areas the simulated results show that the duration of the rock avalanche is about 120 s with an average velocity of 22 m s

landslides triggered by the 1949 khait earthquake tajikistan and associated loss of life abstract earthquake triggered landslides are a major geological hazard in central asia in july 1949 the m7 4 khait earthquake triggered many hundreds of landslides in a mountainous region near the southern limit of the tien shan mountains central tajikistan these landslides involved widespread rock slope failure as well as large numbers of flowslides in loess that mantles the steep slopes of the region in the yasman valley hundreds of loess landslides coalesced to form a massive loess flow est vol 245 mm 3 that travelled up to 20 km on a slope of only 2 in an adjacent valley the khait landslide involved transformation of an earthquake triggered rockslide into a very rapid flow by the entrainment of saturated loess into its movement it travelled 7 41 km over a vertical distance of 1421 m with an estimated average velocity of 30 m s we estimate its volume as 75 mm 3 an order of magnitude less that previously published estimates the khait landslide was simulated using dan the number of casualties due to earthquake triggered landslides in the epicentral region was considerable approximately 4000 people were killed in the yasman valley loess flow as 20 villages kishlaks were overwhelmed in the khait landslide alone we estimate ca 800 people lost their lives when the villages of khait and khisorak were overrun by rapidly moving debris our data indicates that a total of approximately 7200 people were killed by earthquake triggered landslides in the epicentral region of the khait earthquake and that in terms of loss of life the 1949 yasman valley loess flow was one of the most destructive landslides in recent history

morphology and substrate control on the dynamics of flowlike landslides a numerical model set up to simulate rapid flowlike landslide motion across three dimensional terrain has been used to investigate the capability of various constitutive relationships to model the dynamics of complex events characterized by a changing type of substrate and morphology e g glacier bends the numerical procedure is based on a continuum mechanics approach and on depth averaged st venant equations for shallow flows the developed rash3d code includes the possibility of using several rheological laws whose parameter values can vary along the runout path two rock avalanche cases with some morphological peculiarities along the propagation path have been numerically back analyzed with both a frictional and a voellmy rheology of the two considered rheologies the voellmy model produces the most consistent results in terms of runout area as well as velocity values the main drawbacks of the frictional model are the tendency to predict excessive spreading of the mass and to overestimate the velocities the results show that when a complex problem of runout of rapid flowlike landslides has to be analyzed it is necessary to have detailed knowledge of the geological and morphological features and to resort to increasingly complex rheologies

surface microscopic examination of quartz grains from rock avalanche basal facies the wenchuan earthquake which occurred on 12 may 2008 triggered many rock avalanches that presented abundant fractured surface textures the surface textures of the rock avalanche clasts bear abundant characteristic signatures that are significant for understanding the mechanical behavior of rock avalanche dynamic fragmentation to study this mechanism of rock avalanche basal facies further two large rock avalanches were investigated using microscopic surface texture examination of quartz grains sampled from their basal facies with a scanning electron microscope after the morphological and statistical analyses of the surface textures on the quartz grains the following features are noted i surface textures on the quartz grains are all fresh with obvious irregular shapes and very sharp edges ii the display of brittle fractures including conchoidal fractures step fractures concavities and v depressions or marks is very common iii cracks or fissures are also visible on the quartz grains t

climate regulates the erosional carbon export from the terrestrial biosphere erosion drives the export of particulate organic carbon from the terrestrial biosphere pocbiosphere and its delivery to rivers the carbon transfer is globally significant and can result in drawdown of atmospheric carbon dioxide co2 if the eroded pocbiosphere escapes degradation during river transfer and sedimentary deposition despite this recognition we lack a global perspective on how the tectonic and climatic factors which govern physical erosion regulate pocbiosphere discharge obscuring linkages between mountain building climate and co2 drawdown to fill this deficit geochemical 13c 14c and c n hydrometric water discharge suspended sediment concentration and geomorphic slope measurements are combined from 33 globally distributed forested mountain catchments radiocarbon activity is used to account for rock derived organic carbon and reveals that pocbiosphere eroded from mountain forests is mostly 1300 14c years old annual pocbiosphere yields are positively correlated with suspended sediment yields confirming results from taiwan and a recent global analysis and are high in catchments with the steepest slopes based on these relationships and the global distribution of slope angles 3 arc second it is suggested that topography steeper than 10 16 of the continental area may contribute 40 of global pocbiosphere erosional flux climate is shown to regulate pocbiosphere discharge by mountain rivers by controlling hydrologically driven erosion processes in catchments where discharge measurements are available 8 of the 33 a significant relationship exists between daily runoff mm day 1 and pocbiosphere concentration mg l 1 r 0 53 p 0 0001 the relationship can be described by a single power law and suggests a high connectivity between forested hillslopes and mountain river channels as a result annual pocbiosphere yields are significantly correlated with mean annual runoff r 0 64 p 0 0001 a shear stress pocbiosphere erosion model is proposed which can explain the patterns in the data the model allows the climate sensitivity of this carbon flux to be assessed for the first time for a 1 increase in annual runoff pocbiosphere discharge is predicted to increase by 4 in steeper catchments pocbiosphere discharge increases more rapidly with an increase in annual runoff for comparison a 1 increase in annual runoff is predicted to increase carbon transfers by silicate weathering solute fluxes in mountains by 0 4 0 7 depending on the fate of the eroded pocbiosphere river export of pocbiosphere from mountains may act as an important negative feedback on rising atmospheric co2 and increased global temperature erosion of carbon from the terrestrial biosphere links mountain building and climate to the geological evolution of atmospheric co2 while the carbon fluxes are sensitive to predicted changes in runoff over the coming century

initiation and flow behavior of the 1980 pine creek and muddy river lahars mount st helens washington two large high velocity lahars volcanic debris flows were triggered by a pyroclastic surge during the first few minutes of the may 18 1980 eruption of mount st helens the initial surge cloud evolved progressively by gravity segregation from a gas mobilized highly inflated density flow to a dense water mobilized basal debris flow lahar and accompanying ash cloud as it flowed down the east flank of the volcano the main source of the water for the lahars was probably from eroded snow and ice incorporated into the flow by turbulent mixing but ground water expelled together with the rock debris by the initiating volcanic explosions also may have contributed peak lahar discharge from the pine muddy fan upper smith creek and ape canyon probably exceeded 250 000 m 3 s initially but decreased exponentially in the downstream direction total volume of the lahars was in excess of 1 4 10 7 m 3 initial peak flow velocities in excess of 30 m s also decreased markedly downstream where flow was not impeded velocity was strongly related to the depth slope term r 2 3 s 1 2 from the manning uniform flow equation as a power law function during much of the route traveled lahar flow appears to have been supercritical deposits left in channels were generally thin relative to flow depth 0 to 2 5 m particles up to small boulder size were randomly distributed in the poorly sorted nonstratified matrix indicating complete suspension in a fully developed debris flow slurry however much larger clasts were transported as bed load computed sediment concentrations of matrix slurry samples ranged from 84 to 91 solids by weight and were similar for the two lahars two indirect methods for computing peak flow velocity previously only tentatively applied to debris flows were tested for accuracy by comparing computed lahar arrival times with recorded arrival times at swift reservoir the computed velocities appear to be 15 slower than the recorded velocities which is consistent with the restriction that the velocity formulas produce only minimum values

field observations and surface characteristics of pristine block and ash flow deposits from the 2006 eruption of merapi volcano java indonesia abstract a series of pristine block and ash flow deposits from the may june 2006 eruption of merapi represent an exceptional record of small volume pyroclastic flows generated by gravitational lava dome collapses over a period of about two months the deposits form nine overlapping lobes reaching 7 km from the summit in the gendol river valley on the volcano s southern flank which were produced by successive flows generated during and after the major dome collapse event on june 14 both single pulse post june 14 events and multiple pulse pyroclastic flows generated by sustained dome collapses on june 14 are recognised and three types of deposits spread over an area of 4 7 km are distinguished totalling 13 3 10 6 m 3 1 valley confined basal avalanche deposits 11 7 10 6 m 3 in the gendol river valley 2 overbank pyroclastic flow and associated surge deposits 1 4 10 6 m 3 where parts of the basal avalanche spread laterally onto interfluves and were subsequently channeled into the surrounding river valleys and 3 dilute ash cloud surge deposits 0 2 10 6 m 3 along valley margins variations in the distribution surface morphology and lithology of the deposits are related to the source materials involved in individual pyroclastic flow forming events and varying modes of transport and deposition of the different flows inferred flow velocities of the largest block and ash flows generated on june 14 vary from 43 8 13 5 m s for the basal avalanche and from 62 6 24 2 m s for the ash cloud surge the minimum temperatures range from 400 c for the basal avalanche to 165 c for the overlying ash cloud due to the potential of being re channeled into adjacent river valleys and flowing laterally away from the main river channel the overbank pyroclastic flows are considered the most hazardous part of the block and ash flow system the conditions that lead to their development during flow transport and deposition must be taken into account when assessing future pyroclastic flow hazards at merapi and similar volcanoes elsewhere

the sedimentology and geomorphology of rock avalanche deposits on glaciers this article describes and compares the deposits of four large landslides on two glaciers in alaska using field mapping and remote sensing digital image analysis is used to compare the sedimentological characteristics of nearly 200 000 individual surface blocks deposited by three landslides at black rapids glacier in 2002 the debris sheets of one of the three landslides on black rapids glacier and a landslide emplaced on sherman glacier in 1964 are also investigated the three landslides on black rapids glacier have undergone little post depositional modification by glacier flow whereas the sherman glacier landslide has been transported supraglacially up to ca 1k m over the past 46 years the three debris sheets on black rapids glacier have coarse blocky rims at their distal edges and all four debris sheets have longitudinal flowbands characterized by differences in texture and produced by shearing within the moving debris elongated blocks are parallel to flow except at the perimeter of the debris sheets where they are aligned more perpendicular to flow blocks on the sherman glacier debris sheet have been reoriented by glacier flow the matrix shows no systematic differences with depth or distance from the source however it appears to become coarser over a time scale of decades due to weathering

the kolka karmadon rock ice slide of 20 september 2002 an extraordinary event of historical dimensions in north ossetia russian caucasus on 20 september 2002 an enormous rock ice slide and subsequent mud flow occurred on the northern slope of the kazbek massif northern ossetia russian caucasus it started on the north northeast wall of dzhimarai khokh 4780 ma s l and seriously affected the valley of genaldon karmadon immediate governmental actions available scientific information first reconstructions hazard assessments and monitoring activities as well as initial expert judgments recommendations are documented in order to enable more detailed analyses and modelling of the event by the wider scientific community among the most remarkable aspects related to this event are 1 the relation between the recent event and somewhat smaller but quite similar events that occurred earlier in historical times 1835 1902 2 the interactions between unstable local geological structures and complex geothermal and hydraulic conditions in the starting zone with permafrost cold to polythermal hanging glaciers and volcanic effects hot springs in close contact with each other 3 the erosion and incorporation of a debris covered valley glacier largely enhancing the sliding volume of rocks ice firn snow water and probably air to a total of about 100 106m3 and 4 the astonishingly high flow velocities up to 300 km h 1 and enormous length of travel path 18 km plus 15 km of debris mud flow this extraordinary case illustrates that large catastrophic events in high mountain regions typically involve a multitude of factors and require integrated consideration of complex chains of processes a task which must be undertaken by qualified groups of experts

the giant paleolandslide deposits of tafi del valle tucuman province argentina abstract in the present study seven landslide deposits that took place during the pleistocene in the northern part of tafi del valle tucuman province argentina are described the recognition and mapping of them were carried out using satellite images aerial photograph interpretation and field survey the analysis of the area covered by the deposits and their runout distances were undertaken using aerial photographs at a scale of 1 50 000 and the software image tool all the deposits overcome the 106 m3 of volume with smaller coefficients of friction at 0 22 that gives an idea of the great mobility that they had reaching average speeds 100 km h these deposits could have originated as a consequence of a combination of internal slow deformation and fragmentation under periglacial conditions followed by a sudden collapse of the rock mass generated by strong earthquakes of magnitudes 6 at the base of the cumbres calchaquies ranges

the 2000 yigong landslide tibetan plateau rockslide dammed lake and outburst flood review remote sensing analysis and process modelling abstract in april 2000 a large scale rock avalanche dammed the yigong zangpo river forming an extensive rockslide dammed lake the impoundment lasted for 62 days before a catastrophic breaching caused a massive outburst flood in the yarlung zangpo tibet and the dihang rivers india that travelled downstream to the main floodplain of the brahmaputra in northeastern india in response to discrepancies in the published literature on the event we present a review and re evaluation of the characteristics of the rock avalanche and associated landslide dammed lake we use digital topographical data srtm 3 and dynamic landslide modelling dan w and dan3d to determine the salient characteristics of the damming landslide and to characterise its behaviour our analysis indicates that the volume of the damming rockslide was ca 115 mm3 including 91 mm3 from the initial rockslope failure bulked during disaggregation to 109 mm3 and 6 mm3 from entrainment during its 10 1 km travel down zhamulong gully the debris travelled with an average velocity of 15 18 m s and resulted in a landslide dam on the yigong river with a minimum height of about 55 m using landsat 7 imagery obtained before during and after impoundment in conjunction with an srtm 3 dem we reproduced the filling of the lake we determine that the landslide dam formed an extensive reservoir with an impounded volume of 2 015 gm3 and a maximum possible lake level of 2264 m asl rounded to 2265 m asl our figures differ from those previously published but are believed to be well constrained verifiable estimates of the volumes of the 2000 yigong events the outburst occurred after an attempt by army personnel to manually dig a spillway over the landslide debris and resulted in the entire volume of the lake draining in about 12 h the outburst flood travelled over 500 km south into india with a recorded rise in river level of 5 5 m at the pasighat gauging station 462 km downstream in terms of historical outburst volumes from rockslide dammed lakes the volume of the 2000 yigong event is only exceeded by that of the 1841 outburst flood from the indus river rockslide dammed lake northern pakistan

large rock avalanches triggered by the m 7 9 denali fault alaska earthquake of 3 november 2002 the moment magnitude m 7 9 denali fault alaska earthquake of 3 november 2002 triggered thousands of landslides primarily rock falls and rock slides that ranged in volume from rock falls of a few cubic meters to rock avalanches having volumes as great as 20 10 6 m 3 the pattern of landsliding was unusual the number and concentration of triggered slides was much less than expected for an earthquake of this magnitude and the landslides were concentrated in a narrow zone about 30 km wide that straddled the fault rupture zone over its entire 300 km length despite the overall sparse landslide concentration the earthquake triggered several large rock avalanches that clustered along the western third of the rupture zone where acceleration levels and ground shaking frequencies are thought to have been the highest inferences about near field strong shaking characteristics drawn from interpretation of the landslide distribution are strikingly consistent with results of recent inversion modeling that indicate that high frequency energy generation was greatest in the western part of the fault rupture zone and decreased markedly to the east d 2005 elsevier b v all rights reserved

flow and deposition of pyroclastic granular flows a type example from the 1975 ngauruhoe eruption new zealand small volume pyroclastic density currents pdcs are generated frequently during explosive eruptions with little warning assessing their hazard requires a physical understanding of their transport and sedimentation processes which is best achieved by the testing of experimental and numerical models of geophysical mass flows against natural flows and or deposits to this end we report on one of the most detailed sedimentological studies ever carried out on a series of pristine small volume pdc deposits from the 1975 eruption of ngauruhoe volcano whose emplacement were also witnessed during eruption using high resolution gps surveys a series of lateral excavations across the deposits and bulk sedimentological analysis we constrained the geomorphology internal structure and texture of the deposits with respect to laterally varying modes of deposition deposition from these pdcs began only on slopes at or around the material s angle of repose c 30 in unconfined settings the granular pdcs are interpreted to have been quasi steady forming sheets and lobes around the angle of repose where flows were confined sheet like proximal facies made up around 10 of the deposit volume at the angle of repose but 90 of the material was deposited from apparently unsteady inertial granular pdcs as a distal levee and channel facies on slopes well below the repose angle hence confined pdcs were able to travel up to 50 farther than unconfined flows in the distal facies the deposit width is inversely correlated to the local slope and the height of the levees above the deposit centreline is positively correlated with slope internally the deposits comprise three parts a coarse grained fines free sole layer that laterally connects to levees zone i an ashy matrix supported central body zone ii and an overlying coarse plaster of clasts zone ii trends in grain size data suggests these zones derive from a continuous un mixing of coarse particles from the initial bulk material by granular segregation that preferentially drives large particles to the upper free surface of the flow where they are concentrated at the front of flow before being deposited and overrun by comparison to analogue experiments we suggest a model of flow and deposition where the temporally and spatially varying mode of deposition is determined by the flow velocity the local slope the vertical velocity gradient the velocity gradient at the free surface and the vertical deposition rate using this model estimated vertical deposition rates of c 5 cm s 1 from the ngauruhoe pdcs agree with those determined in laboratory experiments on inertial granular flows

innovative consideration of a directional appraisal parameter as destabilized criterion of the colluvial landslide as the instability criteria of the singular dimension displacement of a landslide are limited and insufficient a new appraisal parameter the vertical displacement direction rate is considered in landslide stability model in this paper then the displacement directional rate variation at different evolutional stages of landslide stability and its significance in landslide forecasting are systematic analyzed on the basis of the different evolutional rules of the vertical displacement directional rate in the different deformation stages the destabilized criterion of this kind of parameter is established in terms of the principle of statistics furthermore according to the destabilized criterion a calculation and evaluation of the stability of xintan landslide is carried out by means of the appraisal parameter of the vertical displacement direction rate the result of analysis is basically consistent with the practical deforming law of the landslide the result above indicates that the vertical displacement direction rate is an effective appraisal parameter serving as an essential and stable criterion for the stability evaluation of a slope therefore this directional appraisal parameter is of very special significance and also suitable and effective in the prediction of landslides

the dusty creek landslide on mount cayley british columbia a large ca 5 106 m3 landslide occurred on the west flank of mount cayley in the southern coast mountains of british columbia in 1963 failure commenced when a large block of poorly consolidated tuff breccia and columnar jointed dacite was detached from the subvolcanic basement and slid into the valley of dusty creek a small tributary of turbid creek as the detached block accelerated it quickly fragmented into an aggregate consisting of angular clasts up to several metres across partially supported by a matrix of fine comminuted rock material the landslide debris moved about 1 km down dusty creek as a wedge shaped mass up to 70 m thick banking up on turns and attaining a maximum velocity of 15 20 m s the debris mass thinned as it spread across the broader flatter valley of turbid creek and was deposited as an irregular blanket with a maximum thickness of 65 m along a 1 km length of this valley as a result of the landslide turbid and dusty creeks were blocked and lakes formed behind the deb

fragmentation in the val pola rock avalanche italian alps 1 grain size data from the deposit of the 1987 val pola rock avalanche central italian alps are compared with data concerning rock avalanching rock fragmentation and comminution the weibull distribution fits a small part of the entire particle size distribution of debris samples with a mean value of the curve shape factor of 0 54 0 28 this is typical of multiple comminution or fragmentation with much shearing a fractal distribution fits over a greater size range computed fractal dimensions range between 1 3 and 3 2 within the deposit with average values of about 2 6 2 7 these values cover the range between the theoretical values of the plane of weakness model 1 97 and the pillar of strength model 2 84 and are close to the theoretical value for the constrained comminution model 2 58 these suggest that both texturally mature and immature deposits are present and that more than a single comminution process acted during the rock avalanche motion variation of the grain size distribution within the deposit and grain size segregation show as trends in the fractal dimension and arise from variation in the fragmentation process a variety of different physical and empirical laws suggest that 1 30 of the energy expended in the rock avalanche was consumed in fragmentation

eruptive history and k ar geochronology of the late cenozoic garibaldi volcanic belt southwestern british columbia the cenozoic garibaldi belt comprises 6 volcanic fields spaced at irregular intervals along an axis extending 240 km north northwest from the head of howe sound to the bridge river area 2 additional fields the franklin glacier and silvert lie 140 and 190 km west of the north end of the main volcanic belt the volcanoes erupted lavas ranging in composition from augite olivine basalt through hypersthene andesite hornblende andesite and hornblende biotite andesite to biotite rhyodacite many of the volcanic complexes are characterized by geomorphic features which indicate complex interactions between volcanism and the pleistocene ice sheets but preglacial and postglacial phases are also present whole rock samples from 18 volcanic complexes have been dated by the k ar method most of the results are internally consistent with stratigraphic relationships and with limited 14 c and paleomaguetic data they suggest that volcanic activity was episodic most of the analyzed andesitic and dacitic lavas were erupted in the intervals 2 3 to 1 7 ma and 1 1 ma to present in the northern part and in the intervals 1 4 to 1 0 ma and 0 7 ma to present in the southern part of the belt basaltic volcanism occurred only during the past 0 15 m y except in the salal glacier area where hawaiite and alkali olivine basalt which are perhaps an edge effect related to subduction of the juan de fuca plate were erupted as early as 0 97 ma the timing of garibaldi belt volcanism provides information bearing on the distribution of pre wisconsin glaciers in southwestern british columbia and constrains interpretations of late cenozoic changes in explorer juan de fuca north american plate configuration along the continental margin

dynamics of the 2008 earthquake triggered wenjiagou creek rock avalanche qingping sichuan china abstract the wenjiagou creek rock avalanche was triggered by the 2008 wenchuan earthquake it traveled 4 6 km and left a granular deposit of 1 5 108 m3 in wenjiagou creek valley the dynamics of the rock avalanche were studied through field and laboratory investigations and remote sensing the dynamic course was divided into three segments 1 failing the original slope failed due to the huge earthquake ground accelerations acting on a rock mass weakened by severe karstification 2 falling the rock mass experienced several drops due to abrupt changes in slope and broke into granular debris during collisions with the ground and mountain flanks and 3 flow the broken granular mass flowed approximately 3 km down the valley of wenjiagou creek the transport mechanism of the granular mass of debris was studied by analyzing the structure of the deposit and through ring shear tests a gully incised into the deposit by rainfall runoff and debris flows enabled the internal structure of the deposit to be examined and sampled in cross section the exposed deposit was finest near the base and gradually became coarser towards the surface inverse grading in longitudinal section deposits near the base and on the surface both became finer with increasing travel distance near the base the granular debris experienced the maximum normal and shear stresses and fragmented into the finest grains both normal and shear stresses between the grains gradually decreased from near the base to the surface samples were sheared in a ring shear apparatus to simulate the shearing within the granular debris shear resistance between grains was found to decrease as grains became finer due to pervasive fragmentation which is one of the possible mechanisms by which the granular debris was able to travel a long distance at a high speed

evaluating titan2d mass flow model using the 1963 little tahoma peak avalanches mount rainier washington the titan2d geophysical mass flow model is evaluated by comparing its simulation results and those obtained from another flow model flow3d with published data on the 1963 little tahoma peak avalanches on mount rainier washington the avalanches totaling approximately 10 10 6 m 3 of broken lava blocks and other debris traveled 6 8 km horizontally and fell 1 8 km vertically h l 0 246 velocities calculated from runup range from 24 to 42 m s and may have been as high as 130 m s while the avalanches passed over emmons glacier titan2d is a code for an incompressible coulomb continuum it is a depth averaged dshallow watert granular flow model the conservation equations for mass and momentum are solved with a coulomb type friction term at the basal interface the governing equations are solved on multiple processors using a parallel adaptive mesh godunov scheme adaptive gridding dynamically concentrates computing power in regions of special interest mesh refinement and coarsening key on the perimeter of the moving avalanche the model flow initiates as a pile defined as an ellipsoid by a height z and an elliptical base defined by radii in the x and y planes flow parameters are the internal friction angle and bed friction angle results from the model are similar in terms of velocity history lateral spreading location of runup areas and final distribution of the little tahoma peak deposit the avalanches passed over the emmons glacier along their upper flow paths but lower in the valley they traversed stream gravels and glacial outwash deposits this presents difficulty in assigning an appropriate bed friction angle for the entire deposit incorporation of variable bed friction angles into the model using gis will help to resolve this issue d 2004 elsevier b v all rights reserved

new views on old carbon in the amazon river insight from the source of organic carbon eroded from the peruvian andes 1 mountain rivers play a key role in the delivery of particulate organic carbon poc to large river systems and the ocean due to the extent of its drainage area and runoff the amazon river is one of earth s most important biogeochemical systems however the source of poc eroded from the humid region of the eastern andes and the input of fossil poc from sedimentary rocks pocfossil remains poorly constrained here we collected suspended sediments from the kosnipata river during flood events to better characterize andean poc measuring the nitrogen to organic carbon ratio n c stable carbon isotopes 13corg and radiocarbon 14corg 14corg values ranged from 711 to 15 and significant linear trends between 14corg n c and 13corg suggested that this reflects the mixing of pocfossil with very young organic matter 14corg 50 from the terrestrial biosphere pocnon fossil using n c and 14corg in an end member mixing analysis we quantify the fraction of pocfossil to within 0 1 and find that it contributes a constant proportion of the suspended sediment mass 0 37 0 03 and up to 80 of total poc in contrast the relative contribution of pocnon fossil was variable being most important during the rising limb and peak discharges of flood events the new data shed light on published measurements of old poc low 14corg in andean fed tributaries of the amazon river with their 14corg and 13corg values consistent with variable addition of pocfossil the findings suggest a greater persistence of andean poc in the lowland amazon than previously recognized

transferability of a calibrated numerical model of rock avalanche run out application to 20 rock avalanches on the nuussuaq peninsula west greenland long run out rock avalanches are one of the most hazardous geomorphic processes and risk assessments of the potential threat they pose are often reliant on numerical modelling of their potential run out distance the development of such models requires a thorough understanding of past flow behaviour inferred from deposits emplaced by previous events despite this few records exist of multiple rock avalanches that occurred in conditions sufficiently consistent to develop a set of more generalised and hence transferrable rules we conduct field and imagery based mapping and use numerical modelling to investigate the emplacement of 20 adjacent rock avalanches on the southern flanks of the nuussuaq peninsula west greenland the rock avalanches run out towards the vaigat strait and are sourced from a range of coastal mountains of relatively uniform geology we calibrate a three dimensional continuum dynamic flow code volcflow with data from a modern well constrained event that occurred at paatuut ad 2000 the best fit model assumes a constant retarding stress with a collisional stress coefficient simulating run out to within 0 3 of that observed this calibration was then used to model the emplacement of deposits from five other neighbouring rock avalanches before simulating the general characteristics of a further 14 rock avalanche deposits on simplified topography our findings illustrate that a single calibration of volcflow can account for the observed deposit morphology of a uniquely large collection of rock avalanche deposits emplaced by a series of events spanning a large volume range although the prevailing approach of tuning models to a specific case may be useful for detailed back analysis of that event we show that more generally applied models even using a single pair of rheological parameters can be used to model potential rock avalanches of varied volumes in a region and therefore to assess the risks that they pose

rock avalanches triggered by oblique thrusting during the 12 may 2008 ms 8 0 wenchuan earthquake china the 12 may 2008 wenchuan earthquake ms 8 0 triggered over 56 000 landslides over a broad area including shallow disrupted landslides rock falls deep seated landslides and rock avalanches among these landslides rock avalanches are of great concern because of the large volume of displaced material the long runout distance and the resulting fatalities in this paper some rock avalanches including the woqian the tangjiawan the hongyancun the xiejiadianzi and the shuimogou rock avalanches were selected for detailed study mapping of coseismic surface rupture has been carried out at regional and site scales the minor scarps or stepped topographic features observed at the source areas of the rock avalanches correspond spatially to the surface rupture indicating that they should be created by thrusting of a fault that ruptured during the 2008 wenchuan earthquake avalanche deposits of some rock avalanches are shifted northeastward the same direction with the strike slip of the fault rupture compared with the sources of the rock avalanches indicating that the component of strike slip of the fault rupture exerted a horizontal initial velocity on the failed mass for the woqian rock avalanche the source rock on the hanging wall was pushed northeastward creating a hummocky topographic feature because of the right lateral slip of the fault rupture these rock avalanches are therefore triggered by oblique thrust faulting in addition the source rock mass was of poor quality resulting from the shearing and brecciation associated with fault movement in history rendering the rock slopes prone to failure and contributing to the high degree of disintegration of the failed rock mass

the origin of a tephra like bed near mount cayley volcano southwestern british columbia canada a distinct white bed 1 2 cm thick is present within backwater deposits at the upstream end of the turbid creek debris fan southwestern british columbia canada this white bed and the enclosing backwater deposits accumulated within an impoundment of squamish river caused by a large ca 4800 bp debris avalanche originating from mount cayley a pliocene pleistocene volcano the white bed is composed of silt and clay detritus and resembles tephra about 5 of the grains exhibit optical characteristics consistent with volcanic glass the remainder however are mineral and lithic particles mainly cristobalite and na feldspar with minor quartz and trace amphibolite mica group and chlorite the white bed is interpreted to be dust derived from the debris avalanche and washed into the impoundment based upon i the high proportion of mineral and lithic grains within the bed ii the contemporaneity of the bed and the debris avalanche iii the lack of holocene volcanic activity at mount cayley and iv

dynamics mobility controlling factors and transport mechanisms of rapid long runout rock avalanches in china abstract the dynamics and occurrence conditions of 43 rapid and long run out rock avalanches in china were summarized their dynamics were classified into 5 types the standard dynamic type was designated to be fail squirt and flow where part of the landslide path always has a parabolic airborne course because the slide body has an initial speed and the toe of the surface of rupture projects the landslide into the air the occurrence conditions of rock avalanches of the standard dynamic type are huge kinetic energy elevated toe to the surface of rupture and enough transport space to run out into the occurrence conditions of the other four types were then compared with the standard dynamic type statistical analysis showed that volume topography huge kinetic energy and an elevated toe to the surface of rupture were the principal factors controlling mobility in the rock avalanches four of the rapid long run out rock avalanches each in a different geological setting were then examined in more detail to reveal the transport mechanisms leading to their high speed and long runout the results suggested that besides their huge kinetic energy high pore water pressure produced by undrained shear and elastic energy released by grain fragmentation were the main transport mechanisms contributing to the long travel distances and high speeds of rock avalanches field investigation indicated that air was involved during the transport but whether it influenced the transport or how much the influence was is still much disputed

the failure mechanism of a late glacial sturzstrom in the subalpine molasse leckner valley vorarlberg austria a number of prehistoric landslides and rock avalanches occurred in the folded and faulted section of the molasse zone in vorarlberg austria some developed into a sturzstrom defined as a rapidly moving fluidised mass movement of large volumes of rock derived from the disintegration of a falling rock mass that spread under the influence of gravity their impact on the landscape usually is related to obstruction of rivers and valleys in this paper we analyse the geomorphology and the failure mechanism of a relative small sturzstrom the failure mechanism can be described as a buckling failure the morphological situation indicates that failure took place after local deglaciation by the end of the upper wurm the period of failure coincides with glacial and ice marginal remnants which developed between 15 000 and 14 600 bp the lithological sequence and rock structure as well as the impact of the processes related to the former glacial environment were major causal conditions the rock sequence consists of conglomerates sandstone layers and marls next to glacial scouring which increased the inclination of the valley slopes the effect of late glacial unloading and postglacial processes such as weathering and fluvial erosion subsequently weakened the mass rock fabric until failure occurred discontinuity orientation measurements geostructural and geomechanical conditions and the former hydrological and geomorphological conditions support bucklings failure in fact three hinge buckling may have occurred the frontal section of the sturzstrom consists mainly of large conglomerate blocks averaging 1 5 m3 in volume although megablocks reaching of up to 4000 m3 are present as well the volume of the entire sturzstrom equals approximately 10 107 m3 present activity is only restricted to minor rock falls derived from the conglomerates and mudflows originating from the marl layers

long runout mechanism and landsliding behaviour of large catastrophic landslide triggered by heavy rainfall in guanling guizhou china a large catastrophic landslide was triggered by a heavy rainfall on 28 june 2010 in guanling guizhou china the landslide buried two villages and killed 99 people along the runout path the lands

organic carbon export in the form of wood during an extreme tropical storm upper rio chagres panama widespread intense rainfall over the upper rio chagres watershed 414 km2 in central panama during december 2010 triggered numerous landslides that introduced large numbers of trees to the river network we flew by helicopter along the mainstem upper chagres and the adjacent margins of lake alhajuela into which the upper chagres flows in february and june 2011 we used low elevation video photography from these flights to tally the number of wood pieces stored along the lake margin and within the channel and the number of landslides reaching the mainstem we used these tallies with ground verified estimates of average wood piece size and landslide surface area and assumptions about wood density carbon content and aboveground biomass to develop a first order estimate of carbon export in the form of wood from the upper chagres following the 2010 storms based on the wood tally we estimate 9 6 to 16 mg c km2 export and from the landslide tally we estimate 24 mg c km2 we believe the landslide tally provides a more accurate minimum estimate of carbon export from the upper chagres during the december 2010 storms these values are an order of magnitude higher than limited data for average or background rates of wood based carbon export from other catchments but two orders of magnitude lower than wood based carbon export during extreme storms in taiwan the findings suggest that duration of flood flow above a threshold for mobilizing wood within the channel network exerts a more important control on wood export from the upper chagres than magnitude of flood peak copyright 2013 john wiley sons ltd

landslide and tsunami hazard at yate volcano chile as an example of edifice destruction on strike slip fault zones the edifice of yate volcano a dissected stratocone in the andean southern volcanic zone has experienced multiple summit collapses throughout postglacial time restricted to sectors ne and sw of the summit the largest such historic event occurred on 19th february 1965 when 6 1 10 106 m3 of rock and ice detached from 2 000 m elevation to the sw of the summit and transformed into a debris flow in the upper part of the flow path velocities are estimated to have reached 40 m s 1 after travelling 7 500 m and descending 1 490 m the flow entered an intermontane lake lago cabrera a wavemaker of estimated volume 9 3 106 m3 generated a tsunami with an estimated amplitude of 25 m and a run up of 60 m at the west end of the lake where a settlement disappeared with the loss of 27 lives the landslide followed 15 days of unusually heavy summer rain which may have caused failure by increasing pore water pressure in rock mechanically weathered through glacial action the preferential collapse directions at yate result from the volcano s construction on the dextral strike slip liquine ofqui fault zone movement on the fault during the lifetime of the volcano is thought to have generated internal instabilities in the observed failure orientations at 10 to the fault zone in the riedel shear direction this mechanically weakened rock may have led to preferentially orientated glacial valleys generating a feedback mechanism with collapse followed by rapid glacial erosion accelerating the rate of incision into the edifice through repeated landslides debris flows with magnitudes similar to the 1965 event are likely to recur at yate with repeat times of the order of 102 years with a warming climate increased glacial meltwater due to snowline retreat and increasing rain at the expense of snow may accelerate rates of edifice collapse with implications for landslide hazard and risk at glaciated volcanoes in particular those in strike slip tectonic settings where orientated structural instabilities may exist

a super large landslide in tibet in 2000 background occurrence disaster and origin on april 9 2000 a super large landslide 3 x 10 8 m 3 occurred along zhamu creek southeast tibet as a result a landslide dam formed and the yigong river was blocked a channelized diversion was constructed for prevention of overtopping two months later on june 10 a catastrophic flood resulting from the failure of the landslide dam caused a serious loss of property this is the second of landslide occasion dam formation and flooding occurrence at the same site since 1900

late holocene catastrophic slope collapse affected by deep seated gravitational deformation in flysch ropice mountain czech republic the region of the flysch western carpathians is characterized by abundant deep seated gravitational slope deformations dsgsds this study deals with a detailed analysis of late holocene catastrophic collapse of a fault created slope of mountain ropice in the moravskoslezske beskydy mountains eastern czech republic the catastrophic collapse was initialized by huge compound rotational slide toppling deformation which occurs on the upper part of the studied slope and affects tectonically weakened subhorizontally inclined sandstone beds detailed geomorphological mapping accompanied by morphotectonic analysis and geophysical sounding revealed at least two historic flowslides the older event f1 affected 0 5 0 8 mm3 of bedrock and created a 1000 m long and up to 150 m wide accumulation with abundant transverse steps and a carapace like surface the landslide toe blocked an adjacent valley which led to the development of a small impoundment with 4 m thick deposits containing lacustrine peat bog floodplain and alluvial fan facies radiocarbon dating and pollen analysis indicate the valley blockage at 1 5 ka bp the other flowslide f2 of much smaller dimensions 10 000 12 000 m3 overlaid the main landslide body and according to the dating of minerogenic horizon in the impoundment may have taken place 0 3 ka bp the organisation of landforms character of slope failures and dynamic back modelling point to a likely rock avalanche or combined rock slide debris avalanche mechanism of movement this case study shows that rapid rock avalanches can operate also in mountainous terrain with moderate relief if toppling together with deep seated gravitational deformation of slopes modifies the original stable position of bedding planes