the 25 september 2007 eruption of mount ruapehu new zealand directed ballistics surtseyan jets and ice slurry lahars abstract at 20 26 nzdt on 25 september 2007 a moderate gas driven eruption beneath the summit crater lake of mt ruapehu new zealand generated a directed ballistic fallout apron and surtseyan jet that impacted an area of c 2 5 km2 to the north of the vent two climbers were caught in the blast at a hut 600 m from the vent primary ice slurry lahars were generated in two catchments draining the summit region including a flow that entered a commercial ski field the ejecta consists of blocks of andesitic lava and scoria erupted during previous volcanic episodes a variety of mineral cemented lake floor sediments vent fill debris and rare glassy material interpreted to be derived from a fresh batch of magma a minority of clasts contain formerly molten elemental sulphur indicating that vent temperatures at the base of the lake were in excess of 119 c the ballistic deposit is confined to a c 40 wide swath directed northwards that extends up to 2 km from the inferred vent location beneath crater lake the strong directionality of the jetted deposits and ballistic free shadow zones sheltered by intervening topography all point to a relatively low angle directed blast previous similar eruptions at ruapehu also show preferred deposit orientations that are here correlated with an inclined and off centre vent beneath crater lake the 25 september 2007 eruption appears to have resulted from failure of a relatively shallow hydrothermal seal composed of elemental sulphur and other mineral precipitates developed in the vent breccia which breached following overpressurization by a pulse of magmatic gases released from deeper in the conduit this event highlights the potential hazard from relatively minor gas driven eruptions at ruapehu that can occur with little or no warning improved understanding of the eruption mechanism for this style of eruption will inform future risk assessments for ruapehu and other similar volcanoes worldwide

automatic approach for increasing the location accuracy of slow moving landslide endogenous seismicity the apoloc method seismological observations offer valuable insights on the stress strain states the physical mechanisms and the possible precursory signs of activation of various earth surface processes i e volcanoes glaciers and landslides comprehensive catalogues of the endogenous landslide seismicity that is corresponding to seismic sources generated by the unstable slope from either mechanical or hydrological origins should include the typology and an estimate of the source parameters location magnitude of the event these advanced catalogues constitute a strong basis to better describe the slope deformation and its time evolution and better understand the controlling factors because the number of seismic events in landslide catalogues is generally large automatic approaches must be considered for defining both the typology and the location of the sources we propose here a new location approach called automatic picking optimization and location method apoloc for locating landslide endogenous seismic sources from seismological arrays located at close distance the approach is based on the automatic picking of the p waves arrivals by optimizing the intertrace correlations the method is tested on calibration shots realized at the super sauze landslide southeast french alps and compared to other location approaches by using a realistic velocity model obtained from a seismic tomography campaign apoloc reduces the epicentre errors to 23 m on average compared to ca 40 m for the other approaches apoloc is then applied for documenting the endogenous seismicity i e slopequakes and rockfalls at the landslide

laurentide cordilleran and montane glaciation in the western peace river grande prairie region alberta and british columbia canada abstract geological investigations over the last decade in the western peace river grande prairie district of northwestern alberta and northeastern british columbia have provided important chronostratigraphic information regarding laurentide cordilleran and montane quaternary glacial events numerous 14 c age determinations as well as stratigraphic and sedimentological analyses of numerous exposures indicate that this area was first glaciated by cordilleran ice sometime before the late wisconsinan during the late wisconsinan ca 22 000 14 000 bp laurentide glacier ice covered much of the area between approximately 15 000 and 10 000 bp montane ice affected only the western part of the peace region there is no evidence for synchroneity of the ice advances and therefore no evidence for ice coalescence in this region the resultant ice free corridor was most likely a laterally fluctuating zone which existed during a several thousand year period in the late pleistocene climatic conditions along the corridor during this period were probably unfavorable for human migration but adequate for some plants and small animals numerous isolated areas along the western foothills of the northern rocky mountains west of the laurentide glaciation limit were never glaciated during the late wisconsinan

microseismic emissions from flowslide type movements in south wales abstract many of the unstable hillslopes of south wales have landslides that turn into flowslides over part of their tract the valley slopes at pant teg and glynrhigos are unstable as they possess the optimum requirements for slope failure they have probably been affected by repeated movements during the last 10 000 years significant acoustic emissions ae have been recorded from two landslide sites both subsequent to a major failure pant teg and during continuous movement glynrhigos four distinct types of ae have been recognised so far with frequencies in the 1 7 khz bandwidth with particular peaks at 1 2 2 0 4 2 4 9 5 5 and 6 5 khz the results indicate that there is a potential in developing a warning system for identifying increasing instability

a facies model for a quaternary andesitic composite volcano ruapehu new zealand ruapehu composite volcano is a dynamic volcanic sedimentary system characterised by high accumulation rates and by rapid lateral and vertical change in facies four major cone building episodes have occurred over 250 ka from a variety of summit flank and satellite vents eruptive styles include subplinian strombolian phreatomagmatic vulcanian and dome related explosive eruptions and extrusion of lava flows and domes the volcano can be divided into two parts a composite cone of volume 110 km3 surrounded by an equally voluminous ring plain complementary portions of ruapehu s history are preserved in cone forming and ring plain environments cone forming sequences are dominated by sheet and autobrecciated lava flows which seldom reach the ring plain the ring plain is built predominantly from the products of explosive volcanism both the distal primary pyroclastic deposits and the reworked material eroded from the cone much of the material entering the ring plain is transported by lahars either generated directly by eruptions or triggered by the high intensity rain storms which characterise the region ring plain detritus is reworked rapidly by concentrated and hyperconcentrated streams in pulses of rapid aggradation immediately following eruptions and more gradually in the longer intervals between eruptions

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

velocity of debris flow determined by grain composition abstractvelocity is one of the most important parameters of debris flows and it is usually calculated using manning formula in hydraulics mostly ignoring the granular effects due to flow material

estimation of lahar flow velocity on popocatepetl volcano mexico during 1997 and 2001 two lahars took place in the tenenepanco and huiloac gorges on the northeastern sector of the popocatepetl volcano in mexico these lahars were the result of volcanic activity characterized by a pyroclastic fall and flow the lahars were triggered by the mass failures produced hours after the eruption the well known superelevation technique commonly used in this kind of study was applied to infer the lahar s mean velocity estimations show a broad flow velocity range of 1 3 13 8 m s depending on the following geomorphological parameters channel depth and slope peak discharge and distance from the initial source these results were compared with lahar velocities from mount st helens 1980 and nevado del ruiz 1985 which were obtained by the same superelevation technique according to the data the lahars from nevado del ruiz and popocatepetl were triggered by similar conditions while at mount st helens they were the result of the conversion of a pyroclastic surge cloud actually the mount st helens lahars were almost twice as fast as the ones at nevado del ruiz and popocatepetl this observation shows the importance of the lahars genesis in that the pyroclastic surge clouds produce faster lahars than do pyroclastic falls such results should be taken into account in lahar risk assessment studies for communities located near active volcanoes 2007 elsevier b v all rights reserved

determining rheological parameters of debris flow material abstract a 2 0 m diameter steel 30 inverted cone and plate viscometer rheometer was designed constructed and used to test the behaviour of coarse grained debris flow materials a 1 5 scale model machine was also constructed and used to test the internal flow dynamics of the viscometer rheometer and to obtain results for fluids grain fluid mixtures and debris flow fines for fluids and grain fluid mixes our results were similar to those obtained earlier using standard viscometric systems derived rheological parameters for debris flow materials and clay slurries agreed well with those determined from calculation direct measurement and field observation apparent viscosities were shear rate dependent extremely sensitive to water content and as high as 6000 pa s instantaneous stresses within shearing debris flow material varied over a wide range debris flow materials with bimodal grain size distributions had a dilatant plastic rheology those with a low content of coarse material and unimodal grain size distribution or exceptionally high fines content had a plastic or viscoplastic rheology

seismic monitoring of rockfalls slide quakes and fissure development at the super sauze mudslide french alps applying the method nanoseismic monitoring to the fast moving mudslide in super sauze french alps we observed different types of seismic events caused by varying slope dynamics we identified signals caused by rockfalls in the source area of the slope and different types of signals which had obviously been generated by material failure within the unstable part of the mudslide signal analysis and further investigations e g the analysis of magnitude frequency distribution and simultaneous measurements by nanoseismic monitoring and extensometer devices revealed the generation of the observed seismic signals fracture processes i e slide quakes within the unstable sediments and the development of fissures at the slope s surface the spatial distribution of the epicenters slide quakes respectively the estimated source area fissure development correlates well with parts of the slope moving with higher velocities at the surface most of these signals were generated close to the in situ crests which are mostly covered by the mudslide material today indicating specific dynamics in these particular slope areas

ground based multi view photogrammetry for the monitoring of landslide deformation and erosion recent advances in multi view photogrammetry have resulted in a new class of algorithms and software tools for more automated surface reconstruction these new techniques have a great potential to provide topographic information for geoscience applications at significantly lower costs than classical topographic and laser scanning surveys based on open source libraries for multi view stereo photogrammetry and structure from motion this study investigates the accuracy that can be obtained from several processing pipelines for the 3d surface reconstruction of landslides and the detection of changes over time two different algorithms for point cloud comparison are tested and the accuracy of the resulting models is assessed against terrestrial and airborne lidar point clouds change detection over a period of more than two years allows a detailed assessment of the seasonal dynamics of the landslide the possibility to estimate sediment volumes and 3d displacement are illustrated for the most active parts of the landslide algorithm parameters and the image acquisition protocols are found to have important impacts on the quality of the results and are discussed in detail

image based mapping of surface fissures for the investigation of landslide dynamics abstract the development of surface fissures is an important indicator for understanding and forecasting slope movements landslide investigations therefore frequently include the elaboration and interpretation of maps representing their spatial distribution typically comprising intensive field work and instrumentation it is only recently that aerial photography with sub decimetre spatial resolution is becoming more commonly available and opens a window to analyse such features from a remote sensing perspective while these data are in principle helpful to elaborate maps from image interpretation techniques there is still no image processing technique available to extract efficiently these geomorphological features this work proposes a largely automated technique for the mapping of landslide surface fissures from very high resolution aerial images the processing chain includes the use of filtering algorithms and post processing of the filtered images using object oriented analysis the accuracy of the resulting maps is assessed by comparisons with several expert maps in terms of affected area fissure density and fissure orientation under homogenous illumination conditions true positive rates up to 65 and false positive rates generally below 10 are achieved the resulting fissure maps provide sufficient detail to infer mechanical processes at the slope scale and to prioritize areas for more detailed ground investigations or monitoring

rheological properties of mudflows associated with the spring 1980 eruptions of mount st helens volcano washington rheological properties of three recent mudflows at mount st helens were estimated using techniques developed for determining the properties of debris flows based on the geometry of their deposits calculated yield strengths of 1100 1000 and 400 pa maximum flow velocities of 10 to 31 m s volumetric flow rates of 300 to 3400 m s and plastic viscosities of 20 to 320 pa s all compare favorably with measured and estimated values cited in the literature a method for determining likely sites of future mudflow initiation based on these data is outlined

seismic precursory patterns before a cliff collapse and critical point phenomena 1 we analyse the statistical pattern of seismicity before a 1 2 103 m3 chalk cliff collapse on the normandie ocean shore western france we show that a power law acceleration of seismicity rate and energy in both 40 hz 1 5 khz and 2 hz 10khz frequency range is defined on 3 orders of magnitude within 2 hours from the collapse time simultaneously the average size of the seismic events increases toward the time to failure these in situ results are derived from the only station located within one rupture length distance from the rock fall rupture plane they mimic the critical point like behavior recovered from physical and numerical experiments before brittle failures and tertiary creep failures our analysis of this first seismic monitoring data of a cliff collapse suggests that the thermodynamic phase transition models for failure may apply for cliff collapse

the thickness of neogene and quaternary cover across the central interior plateau british columbia analysis of water well drill records and implications for mineral exploration potential abstract analysis of over 10 000 water well records has been used to produce new depth to bedrock maps for areas around five cities on the central interior plateau of central british columbia 100 mile house prince george quesnel vanderhoof and williams lake hitherto exploration for mineral and hydrocarbon resources has been hampered by a lack of basic knowledge of the thickness of neogene and quaternary lithologies interpretation of these new maps provides first order constraints on the localization of thick drift in pre late wisconsinan bedrock paleovalleys some of which are now buried basalt lavas of the chilcotin group are restricted to erosional remnants of previously extensive sheets emplaced onto an older peneplain our results confirm that the neogene and quaternary cover is primarily controlled by paleotopography and is generally thin and patchy across much of the region increased understanding of the three dimensional distribution of cover produces a corresponding increase in the utility of geological geochemical and geophysical exploration techniques and a reduction in the risk for future mineral exploration activities especially when combined with more sophisticated data sets

field observations rheological testing and numerical modelling of a debris flow event debris flows generated from landslides are common processes and represent a severe hazard in mountain regions due to their high mobility and impact energy we investigate the dynamics and the rheological properties of a 90 000 m3 debris flow event triggered by a rapid regressive landslide with high water content field evidence revealed a maximum flow depth of 7 8 m with an estimated peak discharge of 350 400 m3 s 1 depositional evidence and grain size distribution of the debris pose the debris flow in an intermediate condition between the fluid mud and grain flow behaviour the debris flow material has silt clay content up to 15 per cent the rheological behaviour of the finer matrix was directly assessed with the ball measuring system the measurements performed on two samples at 45 63 per cent in sediment concentration by volume gave values of 3 5 577 pa for the yield strength and 0 6 27 9 pa s for the viscosity based on field evidence we have empirically estimated the yield strength and viscosity ranging between 4000 200 pa and 108 134 pa s respectively we used the flo 2d code to replicate the debris flow event we applied the model with rheological properties estimated by means of direct measurements and back analyses the results of these models show that the rheological behaviour of a debris flow mass containing coarse clasts can not be assessed solely on the contribution of the finer matrix and thus neglecting the effects of direct grain contacts for debris flows composed by a significant number of coarse clasts a back analysis estimation of the rheological parameters is necessary to replicate satisfactorily the depositional extent of debris flows in these cases the back estimated coefficients do not adequately describe the rheological properties of the debris flow copyright 2006 john wiley sons ltd

kinematic properties of mudflows on mt st helens summarized are findings of a computer based study of the mud flows on mt st helens following its eruption on may 18 1980 analyses were made of the start up dynamics and flow of mud down various drainages of the mountain and of the surge wave generation in swift reservoir when the mudflow down east pine creek entered the reservoir viscosities of mudflows in the muddy creek and pine creek drainages were evaluated in order to establish a basis for general analysis of mudflow phenomena starting with estimates of snow deposition on the mountain and incorporating the characteristics of the pyroclastic blast of the eruption initiation of flow was approximated subsequent flow down different drainages was modeled and time sequencing of the flows into swift reservoir was compared with measured reservoir elevations recorded on the morning following the eruption additional kinematics of the flows were compared with corresponding field measured data where possible

factors influencing the morphology of volcanic landforms an earth moon comparison abstract the products of volcanism on the earth and moon differ widely in terms of morphology distribution composition and age these differences result partly from the different thermal histories of the two bodies and partly through the different controls on volcanic eruption conditions the controls of volcanism are here separated into three groups 1 controls which remain constant on any one body but which differ from planet to planet 2 parameters that are controlled by the rheology of the magma and 3 controls which are intrinsic properties of individual eruptions and are themselves dependent upon the planetary and rheological variables in terms of planetary variables it can be predicted that lunar volcanic morphologies are influenced by greater tephra range hemispherical eruption clouds lesser lithostatic pressures at corresponding depths slower cooling slower erosion lesser horizontal stress differences and no features typical of hydrosphere magma interaction in terms of rheology the lunar eruptions had different rock and gas compositions low yield strengths and viscosities and high densities many lunar basalts appear to have been produced at high eruption rates to have been derived from monogenetic volcanoes and to have flowed in a turbulent manner the weight of available data points to the vast majority of lunar craters being of impact origin though some dark halo craters sinuous rille source craters rimless pits and craters atop domes and cones are undoubtedly of volcanic origin other impact craters appear to have been modified by volcanic events included within this latter group are the floor fractured craters and the mare basins studies of volcanic morphologies on bodies other than the earth may help isolate the effectiveness of those controls of volcanism which remain constant on any one body although volcanology has advanced substantially within the last few decades much more detailed integrated scientific research is required before we are able to predict confidently the environmental hazards that result from volcanism and to understand the role of volcanism in planetary evolution

friction weakening in granular flows deduced from seismic records at the soufriere hills volcano montserrat accurate modeling of rockfalls and pyroclastic flows is still an open issue partly due to a lack of measurements related to their dynamics using seismic data from the soufriere hills volcano montserrat and granular flow modeling we show that the power laws relating the seismic energy e s to the seismic duration t s and relating the loss of potential energy e p to the flow duration t f are very similar like the power laws observed at piton de la fournaise reunion island observations showing that t f t s suggest a constant ratio e s e p 10 5 this similarity in these two power laws can be obtained only when the granular flow model uses a friction coefficient that decreases with the volume transported furthermore with this volume dependent friction coefficient the simulated force applied by the flow to the ground correlates well with the seismic energy highlighting the signature of this friction weakening effect in seismic data

automated identification location and volume estimation of rockfalls at piton de la fournaise volcano since the collapse of the dolomieu crater floor at piton de la fournaise volcano la reunion in 2007 hundreds of seismic signals generated by rockfalls have been recorded daily at the observatoire volcanologique du piton de la fournaise ovpf to study rockfall activity over a long period of time automated methods are required to process the available continuous seismic records we present a set of automated methods designed to identify locate and estimate the volume of rockfalls from their seismic signals the method used to automatically discriminate seismic signals generated by rockfalls from other common events recorded at ovpf is based on fuzzy sets and has a success rate of 92 a kurtosis based automated picking method makes it possible to precisely pick the onset time and the final time of the rockfall generated seismic signals we present methods to determine rockfall locations based on these accurate pickings and a surface wave propagation model computed for each station using a fast marching method these methods have successfully located directly observed rockfalls with an accuracy of about 100 m they also make it possible to compute the seismic energy generated by rockfalls which is then used to retrieve their volume the methods developed were applied to a data set of 12 422 rockfalls that occurred over a period extending from the collapse of the dolomieu crater floor in april 2007 to the end of the undervolc project in may 2011 to identify the most hazardous areas of the piton de la fournaise volcano summit

location of long period events below kilauea volcano using seismic amplitudes and accurate relative relocation 1 we present methods for improving the location of long period lp events deep and shallow recorded below kilauea volcano by the permanent seismic network lp events might be of particular interest to understanding eruptive processes as their source mechanism is assumed to directly involve fluid transport however it is usually difficult or impossible to locate their source using traditional arrival time methods because of emergent wave arrivals at kilauea similar lp waveform signatures suggest the existence of lp multiplets the waveform similarity suggests spatially close sources while catalog solutions using arrival time estimates are widely scattered beneath kilauea s summit caldera in order to improve estimates of absolute lp location we use the distribution of seismic amplitudes corrected for station site effects the decay of the amplitude as a function of hypocentral distance is used for inferring lp location in a second stage we use the similarity of the events to calculate their relative positions the analysis of the entire lp seismicity recorded between january 1997 and december 1999 suggests that a very large part of the lp event population both deep and shallow is generated by a small number of compact sources deep events are systematically composed of a weak high frequency onset followed by a low frequency wave train aligning the low frequency wave trains does not lead to aligning the onsets indicating the two parts of the signal are dissociated this observation favors an interpretation in terms of triggering and resonance of a magmatic conduit instead of defining fault planes the precise relocation of similar lp events based on the alignment of the high energy low frequency wave trains defines limited size volumes

laurentide and montane glaciation along the rocky mountain foothills of northeastern british columbia mapping the surficial geology of the trutch map area nts 94g provides new data on the timing of continental and montane glaciations along the foothills of northeastern british columbia striated surfaces on mountain crests were dated to the late wisconsinan substage by cosmogenic dating the striations were produced by eastward flowing ice emanating from the region of the continental divide this ice was thick enough to cross the main ranges and overtop the rocky mountain foothill summits at 2000 m above sea level asl it is argued here that such a flow unhindered by topography could only have been produced by the cordilleran ice sheet and not by local cirque glaciation during this time the cordilleran ice sheet dispersed limestone and schist erratics of western provenance onto the plains beyond the mountain front conversely the laurentide ice sheet did not reach its western limit in the foothills until after cordilleran ice retreated from the area during its maximum the laurentide ice penetra

a discriminatory diagram of massive versus stratified deposits based on the sedimentation and bedload transportation rates experimental investigation and application to pyroclastic density currents

dynamics of a confined lava flow on kilauea volcano hawaii this paper presents a new method of analysing lava flow deposits which allows the velocity discharge rate and rheological properties of channelled moving lavas to be calculated the theory is applied to a lava flow which was erupted on kilauea in july 1974 this flow came from a line of fissures on the edge of the caldera and was confined to a pre existing gully within 50 m of leaving the vent the lava drained onto the floor of the caldera when the activity stopped but left wall and floor deposits which showed that the lava banked up as it flowed around each of the bends field surveys established the radius of curvature of each bend and the associated lava levels and these data together with related field and laboratory measurements are used to study the rheology of the lava the results show the flow to have been fast moving but still laminar with a mean velocity of just over 8 m s 1 the lava had a low or negligible yield strength and viscosities in the range 85 140 pa s an extension of the basic method is considered and the possibility of supercritical flow discussed

fluid outflows from venus impact craters analysis from magellan data many impact craters on venus have unusual outflow features originating in or under the continuous ejecta blankets and continuing downhill into the surrounding terrain these features clearly resulted from flow of low viscosity fluids but the identity of those fluids is not clear in particular it should not be assumed a priori that the fluid is an impact melt a number of candidate processes by which impact events might generate the observed features are considered and predictions are made concerning the rheological character of flows produced by each mechanism a sample of outflows was analyzed using magellan images and a model of unconstrained bingham plastic flow on inclined planes leading to estimates of viscosity and yield strength for the flow materials it is argued that at least two different mechanisms have produced outflows on venus an erosive channel forming process and a depositional process the erosive fluid is probably an impact melt but the depositional fluid may consist of fluidized solid debris vaporized material and or melt

a scaling distribution for grain composition of debris flow debris flow is composed of a wide range of grains this study proposes a general form of grain size distribution p d cd mu exp d d c which is satisfied well by various debris flows and by soils and sediments related to debris flows the parameters mu and d c are found to be related to debris flow density in power laws in particular represents some characteristic porosity of soil in a natural condition and controls the variation of soils in developing debris flows and d c defines a characteristic size governing the sediment concentration field observations indicate that debris flows fall into a certain range of parameters mu d c almost all debris flows have mu 0 10 and most debris flows of high density have mu 0 05 moreover experiments show that the exponent p increases during soil failures under rainfall providing an index varying in the course of debris flow initiation finally grain size distribution is used to evaluate the properties of debris flows in different regions the distribution provides a simple but quantitative method of predicting a potential flow through the source soils c 2013 elsevier b v all rights reserved

microseismic investigation of an unstable mountain slope in the swiss alps 1 risks associated with unstable rocky slopes are growing as a result of climate change and rapid expansions of human habitats and critical infrastructure in mountainous regions to improve our understanding of mountain slope instability we developed a microseismic monitoring system that operates autonomously in remote areas afflicted by harsh weather our microseismic system comprising 12 three component geophones was deployed across 60 000 m 2 of rugged crystalline terrain above a huge 30 million m 3 recent rockfall in the swiss alps during its 31 month lifetime signals from 223 microearthquakes with approximate moment magnitudes ranging from 2 to 0 were recorded determining the hypocenters was challenging for several reasons 1 p wave velocities were highly heterogeneous varying abruptly from 3 8 km s 2 first break picks were either inaccurate or lacking for some microearthquakes 3 there were no reliable s wave picks 4 numerous microearthquakes occurred just outside the network boundaries these issues were addressed by using a three dimensional 3 d p wave velocity model of the mountain slope determined from refraction tomography in a nonlinear inversion for hypocenter parameters and their probability density functions recordings from geophones at different altitudes and in boreholes constrained microearthquake depth estimates most microearthquakes were concentrated within 50 100 m of the surface in two zones one that followed the recent rockslide scarp and one that spanned the volume of highest fracture zone fault density these two active zones delineated a mass of rock that according to geodetic measurements has moved toward the scarp at 1 2 cm yr

development of progressive landslide failure in cohesive materials the development of progressive failure in slopes is a poorly understood process and relatively few advances in terms of the mechanics of the development of failure have been made since 1967 however advances in the understanding of the development of fractures in brittle materials provide new insights into landslide mechanics in addition the link between the deformation mechanism and movement type allows interpretation of displacement records to determine the mechanisms acting within a slope this paper utilizes these insights into deformation processes combined with reinflation stress path triaxial experiments to propose a new model for the development of a progressive first time failure within a slope this model is able to explain the development of failure when the factor of safety is greater than unity the existence of saito linearity a linear trend when the reciprocal of velocity prior to failure is plotted against time during tertiary creep and the development of failures during periods of apparently increasing normal effective stress

mapping quaternary paleovalleys and drift thickness using petrophysical logs northeast british columbia fontas map sheet nts 94ithis article is one of a selection of papers published in this special issue on the theme geology of northeastern british columbia and northwestern alberta diamonds shallow gas gravel and glaciers the relatively subdued topography of british columbia s northern interior plains does not reflect the irregular buried bedrock surface many areas have been deeply incised by preglacial rivers tha

lidar derived surface roughness texture mapping application to mount st helens pumice plain deposit analysis statistical measures of patterns textures in surface roughness are used to quantitatively differentiate volcanic deposit facies on the pumice plain on the northern flank of mount st helens msh surface roughness values are derived from a light detection and ranging lidar point cloud collected in 2004 from a fixed wing airborne platform patterns in surface roughness are characterized using co occurrence texture statistics pristine pyroclastic reworked pyroclastic mudflow boulder beds eroded lava flows braided streams and other units within the pumice plain are all found to have significantly distinct roughness textures the msh deposits are reasonably accessible and the textural variations have been verified in the field results of this work indicate that by affecting the distribution of large clasts and tens of meter scale landforms modification of pyroclastic deposits by lahars alters the morphology of the surface in detectable quantifiable ways when a lahar erodes a pyroclastic deposit surface roughness increases as does the randomness in the deposit surface conversely when a lahar deposits material the resulting landforms are less rough but more random than pristine pumice rich pyroclastic deposits by mapping these relationships and others volcanic deposit facies can be differentiated this new method of mapping based on roughness texture has the potential to aid mapping efforts in more remote regions both on this planet and elsewhere in the solar system

seismic monitoring of sechilienne rockslide french alps analysis of seismic signals and their correlation with rainfalls 1 in the french alps sechilienne rockslide is one of the natural phenomena that presents one of the highest levels of risk in terms of socioeconomical outcomes this rockslide has been active for a few decades and has been instrumented since 1985 the current very active volume of this rockslide is estimated to be up to 5 million m3 located on the border of a slowly moving mass reaching 50 100 million m3 the velocity of the most active zone reached 1 4 m yr in 2008 about twice the value of 2000 a seismic network was installed on this rockslide in may 2007 to supplement the monitoring system it has now recorded several thousand events mostly rockfalls but also hundreds of local and regional earthquakes which can be distinguished and classified from their signal characteristics rockfalls and microseismicity which occur in bursts of activity are found to be weakly but significantly correlated with rainfall rockfall occurrence increases linearly with precipitation with however strong fluctuations of the numbers of rockfalls per day for the same rainfall intensity no threshold was found for rainfall triggering with even 1 mm of rain being enough to trigger rockfalls rockfall activity starts almost immediately during a rainfall episode and lasts for several days after the rainfall rain also induces strong accelerations of the rockslide movement which also start quasi instantaneously and last for about a month

landslide faults and tectonic faults analogs the slumgullion earthflow colorado recent geophysical observations of landslide movement support the hypothesis that processes involved in landslide faulting are analogous to those that operate in crustal scale faulting relative to crustal faulting studies quantitative seismic geodetic and creep measurements of landslide deformation may be made in a very short time with readily available instrumentation and at relatively minimal expense our results indicate that the displacement of landslide material occurs along discrete faults exhibiting a combination of brittle failure indicated by slide quakes and creep events and as stable sliding observed as steady state creep although slide quakes were observed a more steady state failure process of relieving accumulating strain is indicated

landform assemblages produced by the laurentide ice sheet in northeastern british columbia and adjacent northwest territories constraints on glacial lakes and patterns of ice retreatthis article is one of a selection of papers published in this special issue on the theme geology of northeastern british columbia and northwestern alberta diamonds shallow gas gravel and glaciers the laurentide ice sheet reached the canadian cordillera during the last glacial maximum in northeastern british columbia and adjacent northwest territories and all regional drainage to unglaciated areas in the north was dammed by the ice converging ice flow patterns near the mountain front suggest that the laurentide ice sheet likely coalesced with the cordilleran ice sheet during the last glaciation with deglaciation the ice masses separated but earlier ice retreat in the south meant that meltwater pooled between the mountain front and the laurentide margin the level of the flooding was controlled by persistent ice cover on the southern franklin mountains glacial lake liard formed when the laurentide ice sheet retreated east of the southern liard range and at its maximum extent may have impounded water at least as far south as the fort nelson river deglaciation of the plains was marked by local variations in ice flow caused by a thin ice sheet becoming more affected by the topography and formin

small mammal taphonomy and the middle pleistocene environments of dolina northern spain abstract the study of past ecosystems can be complex due to taphonomic processes these processes may alter the spatial and temporal location of fossils during site formation the dolina site burgos spain provides an example of the contribution of taphonomy to the interpretation of the past environments this site belongs to the atapuerca ibeas cave complex with extensive evidence of human activity throughout the pleistocene the small mammal assemblages from dolina show evidence that predation has biased species composition to some degree especially in two levels td4 and td11 predator activity appears to have interfered with palaeoecological interpretations and exaggerated inferred climatic changes during the middle pleistocene once possible bias due to taphonomic agents is recognized a more realistic and precise interpretation of the palaeoecology of this area is possible as well as a history of the cave infilling as a background to human use of the cave

quaternary stratigraphy of the prophet river northeastern british columbiathis article is one of a selection of papers published in this special issue on the theme geology of northeastern british columbia and northwestern alberta diamonds shallow gas gravel and glaciers exposures in the prophet river valley in northeast british columbia provide a unique glimpse into the quaternary history of the northwest canadian boreal plains the region shows evidence of late wisconsinan laurentide glaciation in the form of widespread till containing abundant erratic clasts derived from the canadian shield vertical sections along the prophet river expose non glacial and advance glacial sediments below this till pre late wisconsinan non glacial or interglacial floodplain sediments are interbedded with fluvial gravels at many sites macrofossils within horizontally laminated organic rich black clay and silt indicate deposition on the floodplain of the paleo prophet river within an oxbow lake the climate during deposition is interpreted to be similar to present supporting a dominantly spruce forest wood obtained from eight sites provided non finite radiocarbon ages and one sample provided an age of 49 300 2000 bp which is also considered non finite glaciolacustrine clays and s

cosmogenic 36cl dating of the foothills erratics train alberta canada the foothills erratics train of alberta was carried into place during coalescence between montane glaciers and the laurentide ice sheet its age has been controversial late wisconsinan and pre wisconsinan ages have been assigned to it cosmogenic 36 cl exposure dating was carried out on erratics over a 130 km segment of the erratics train seven of eight age determinations support emplacement during the late wisconsinan glaciation these ages eliminate the possibility of an ice free corridor during the last glacial maximum they are also consistent with the hypothesis that the laurentide ice sheet was the most extensive of all pleistocene continental ice sheets in western canada

shear wave velocity as an indicator for rheological changes in clay materials lessons from laboratory experiments 1 clay rich geological formations are responsible for many landslides the dynamics of which are still poorly understood and intensely debated analysis of landslide motion shows that slow clayey slope movements can suddenly accelerate and fluidize as a result of sudden loading or heavy rainfall this solid fluid transition which involves disorganization of the particle network is accompanied by a loss in rigidity that could potentially be monitored by s wave velocity vs variations to investigate this hypothesis two types of laboratory experiments were performed on clay samples originating from an area affected by numerous landslides trieves french alps first creep and oscillatory rheometric tests revealed the thixotropic behavior of the clay with a highly pronounced viscosity bifurcation at a critical stress c in relation with this reduction in apparent viscosity a significant drop in vs is also observed over c second at zero stress acoustic surface wave propagation experiments showed a rapid linear vs decrease with the gravimetric water content w in the plastic domain and a much lower decay in the liquid domain the geotechnically defined liquid limit then appears as a break in thevs wcurve for water contents in the liquid domain in particular both experiments gave consistent results these laboratory results demonstrate that rheological changes in clay can be revealed through vs variations offering the possibility of monitoring solid to fluid transitions in the field

influence of landslide geometry and kinematic deformation to describe the liquefaction of landslides some theoretical considerations abstract the generation of excess pore pressure and possible liquefaction can be explained by different mechanisms in literature less attention is given to the effects of landslide geometry and kinematic deformation on the generation of excess pore pressure and possible liquefaction of sliding blocks the objective of this paper is to discuss these factors by proposing a simple analytical model of landslide liquefaction using classic soil mechanics theory the model describes the initial state of failure and solves forces for each slice with the bishop s limit equilibrium method immediately after failure the difference in movement for each slice is calculated assuming a viscous shear band and using the coulomb viscous model the differential movements conduct to differential strains which are transferred to excess pore pressures in slides characterized by curved slip surfaces the lower parts showed compaction and increase in pore pressures during displacement while the upper parts showed dilatation and a decrease in pore pressures the potential liquefaction is then evaluated for each slice in relation to the displacement the model is applied to a slump type failure that occurred on the super sauze mudslide southeast france in compact clay rich material it was observed that the slump completely liquefied into a flow however the model simulations were not able to completely liquefy all the slices of the slump in case a decrease in pore pressures through dilatation was assumed in the upper part of the slump the decrease in pore pressures caused a rapid stabilisation of the remaining sliding body in case a neutral pore pressure was assumed in the upper part with dilatation movement and deformation of the remaining slices could continue leading to a nearly complete liquefaction of the slump model simulations for many geometries of curved slip surfaces reveal that the liquefied volume increases with steeper slopes and more curved slip surfaces it is discussed also how planar slides which in theory show small differential movement of the individual slices and hence no large compaction can completely liquefy through deformation at the toe

imaging the dynamics of magma propagation using radiated seismic intensity 1 at shallow depth beneath the earth s surface magma propagates through strongly heterogeneous volcanic material inversion of buoyancy and or solidification have strong impacts on the dynamics of propagation without any change of magma supply in this paper we study the spatial and time evolution of magma intrusions using induced seismicity we propose a new method based on ratio analysis of estimates of radiated seismic intensities recorded at different stations during seismic swarms by applying this method to the january 2010 piton de la fournaise volcano eruption we image complex dike propagation dynamics which strongly differ from a model of constant velocity dike propagation we provide a new method to image in real time the dynamics of dike propagation and to infer the position of eruptive fissures

recognition classification and mechanical description of debris flows abstract various types of flow or mass movement involving water and sediments occur on steep slopes in mountainous areas among them debris flows are peculiar events during which a large volume of a highly concentrated viscous water debris mixture flows through a stream channel throughout the world these phenomena cause considerable damage but remain poorly understood although a basic knowledge is already available concerning their recognition and propagation firstly a synthesis of the useful practical criteria of recognition is proposed debris flows must be seen as intermediate phenomena between hyperconcentrated flows intense bed load transport and landslides separated from them by sharp transitions of some characteristics celerity deposit nature and flow type two parameters solid fraction and material type thought to be appropriate for a sound and practical classification are brought out and the corresponding complete classification of flow and mass movements in mountain areas is presented two extreme debris flow types are thus distinguished muddy debris flows and granular debris flows a critical review of recent advances in debris flow dynamic is then proposed it is pointed out that adequate work must be carried out in the field of non newtonian fluid mechanics in particular one fundamental rheological property of debris flow materials is the yield stress which explains thick deposits on steep slopes and can be inferred from field measurements furthermore it can be used to estimate viscous dissipation within the bulk during flow relevant models predicting muddy debris flow dynamics are already available whereas further progress is needed concerning granular flows

slow unconfined spreading of a mudflow mudflows are natural highly concentrated water clay grain mixtures that flow in mountain streams after long or intense rainy periods and may cause considerable damage if they overflow on the alluvial fan the possibility of predicting the extent of these flows on the basis of material and flow parameters is examined the simplest realistic case of a yield stress mudflow moving through a narrow open channel followed by a wide long plane is considered it is demonstrated that the unconfined flow of a yield stress fluid over an inclined plane cannot be uniform even in steady state the flow width should increase continuously from the channel exit a complete treatment of the flow equation on the basis of the long wave approximation including an appropriate three dimensional expression for the constitutive equation makes it possible to establish a system of equations from which flow characteristics at any point longitudinal and lateral mean velocities and fluid depth can be deduced in particular for a herschel bulkley fluid with a flow index of 1 3 it is found that the lateral extent will increase proportionally to the distance from the channel exit to the power 9 20 and that in the sheared part the fluid depth in a cross section will have a parabolic distribution experiments have been carried out with fine mud suspensions at different solid fractions whose rheological behavior is similar to that of natural mudflows the theory is in fair agreement with experimental data concerning fluid depth distribution but systematically overestimates lateral extent by 30 this is certainly due to the fact that the assumption of lateral extent much smaller than flow length is not respected in our tests

precursory swarms of long period events at redoubt volcano 1989 1990 alaska their origin and use as a forecasting tool abstract during the eruption of redoubt volcano from december 1989 through april 1990 the alaska volcano observatory issued advance warnings of several tephra eruptions based on changes in seismic activity related to the occurrence of precursory swarms of long period lp seismic events dominant period of about 0 5 s the initial eruption on december 14 occurred after 23 years of quiescence and was heralded by a 23 hour swarm of lp events that ended abruptly with the eruption after a series of vent clearing explosions over the next few days dome growth began on december 21 another swarm with lp events similar to those of the first began on the 26th and ended in a major tephra eruption on january 2 eruptions continued over the next two weeks and then ceased until february 15 when a large eruption initiated a long phase of repetitive dome building and dome destroying episodes that continued into april warnings were issued before the major events on december 14 and january 2 but as the eruptive sequence continued after january 2 the energy of the swarms decreased and forecasting became more difficult a significant but less intense swarm preceded the february 15 eruption which was not forecast this eruption destroyed the only seismograph on the volcanic edifice and stymied forecasting until march 4 when the first of three new stations was installed within 3 km of the active vent from march 4 to the end of the sequence on april 21 there were eight eruptions six of which were preceded by detectable swarms of lp events although weak these swarms provided the basis for warnings issued before the eruptions on march 23 and april 6 the initial swarm on december 13 had the following features 1 short duration 23 hours 2 a rapidly accelerating rate of seismic energy release over the first 18 hours of the swarm followed by a decline of activity during the 5 hours preceding the eruption 3 a magnitude range from 0 4 to 1 6 4 nearly identical lp signatures with a dominant period near 0 5 s 5 dilatational first motions everywhere and 6 a stationary source location at a depth of 1 4 km beneath the crater this occurrence of long period events suggests a model involving the interaction of magma with groundwater in which magmatic gases steam and water drive a fixed conduit at a stationary point throughout the swarm the initiation of that sequence of events is analogous to the failure of a pressure relief valve connecting a lower supercharged magma dominated reservoir to a shallow hydrothermal system a three dimensional model of a vibrating fluid filled crack recently developed by chouet is found to be compatible with the seismic data and yields the following parameters for the lp source crack length 280 380 m crack width 140 190 m crack thickness 0 05 0 20 m crack stiffness 100 200 sound speed of fluid 0 8 1 3 km s compressional wave speed of rock 5 1 km s density ratio of fluid to rock 0 4 and ratio of bulk modulus of fluid to rigidity of rock 0 03 0 07 the fluid filled crack is excited intermittently by an impulsive pressure drop that varies in magnitude within the range of 0 4 to 40 bar such disturbance appears to be consistent with a triggering mechanism associated with choked flow conditions in the crack

location of seismic signals associated with microearthquakes and rockfalls on the sechilienne landslide french alps the sechilienne rockslide in the french alps has recently been instrumented with three seismic arrays this network has recorded numerous rockfalls and local microearthquakes because the media is highly fractured it is difficult to identify and pick first arrivals beam forming methods were therefore used to locate these events the method has been adapted to take into account the heterogeneity of seismic wave velocities the location accuracy has been estimated to be about 50 m for epicenters by applying the method to calibration shots depth is less constrained due to uncertainties on the velocity model and due to the seismic network geometry this method of location has then been applied to rockfalls and microearthquakes most rockfalls initiate in the most active part of the rockslide called les ruines the others are located on a recent eroded area aside from les ruines the network also allows the estimation of the rockfall trajectory and propagation speed finally 55 microearthquakes have been located within two zones microearthquakes are located within the first 250 m below the surface most microearthquakes are located in les ruines the most active part of the rockslide where the velocity has increased from 0 5 m yr in 1996 to 1 4 m yr in 2008 these events are located close to three faults that delimit a mass of about 3 6 million m3 other events are located close to the summital scarp in a zone moving at a few centimeters per year the western part of the rockslide which moves more slowly did not produce any event large enough to be detected simultaneously by all stations this seismic monitoring suggests that only a very small fraction of the deformation is released through seismic events

triggering conditions and mobility of debris flows associated to complex earthflows landslides on black marl slopes of the french alps are in most cases complex catastrophic failures in which the initial structural slides transform into slow moving earthflows under specific hydrological conditions these earthflows can transform into debris flows due to their sediment volume and their high mobility debris flow induced by landslides are far much dangerous than these resulting from continuous erosive processes a fundamental point to correctly delineate the area exposed to debris flows on the alluvial fans is therefore to understand why and how some earthflows transform into debris flow while most of them stabilize in this paper a case of transformation from earthflow to debris flow is presented and analysed an approach combining geomorphology hydrology geotechnics and rheology is adopted to model the debris flow initiation failure stage and its runout postfailure stage using the super sauze earthflow alpes de haute provence france as a case study the objective is to characterize the hydrological and mechanical conditions leading to debris flow initiation in such cohesive material results show a very good agreement between the observed runout distances and these calculated using the debris flow modeling code cemagref 1 d the deposit thickness in the depositional area and the velocities of the debris flows are also well reproduced furthermore a dynamic slope stability analysis shows that conditions in the debris source area under average pore water pressures and moisture contents are close to failure a small excess of water can therefore initiate failure seepage analysis is used to estimate the volume of debris that can be released for several hydroclimatic conditions the failed volumes are then introduced in the cemagref 1 d runout code to propose debris flow hazard scenarios results show that clayey earthflow can transform under 5 year return period rainfall conditions into 1 km runout debris flow of volumes ranging between 2000 to 5000 m 3 slope failures induced by 25 year return period rainfall can trigger large debris flow events 30 000 to 50 000 m 3 that can reach the alluvial fan and cause damage

shear wave velocity drop prior to clayey mass movement in laboratory flume experiments abstract clay slopes are susceptible to suddenly liquefy into rapidly accelerating landslides thereby threatening people and facilities in mountainous areas because the shear wave velocity v s characterizes the medium stiffness this parameter can potentially be used to investigate the rheological behavior of clay materials before and during the solid to fluid transition associated to such landslide failures previous rheometrical studies performed on clay samples coming from trieves landslides french alps have established that this material behaves as a yield stress fluid with a marked viscosity bifurcation when the applied stress reaches a critical level the viscosity decreases abruptly along with v s which tends to zero in the fully fluidized material here we monitor the rayleigh wave velocity v r variations in a saturated clay layer placed in a flume and progressively brought to failure by tilting the device experiments performed on clay samples with different water contents show a significant relative drop in v r values and hence in v s before the onset of the mass movement additional rheometrical analyses point out that this precursory drop in v s is presumably due to a complex transient rheological response of the clay these new results confirm that v s variations constitute a good indicator for monitoring clay slope stability

coarse grained debris flow deposits in the miocene fan deltas se korea a scaling analysis abstract the viscoplastic and inertial grain flow models have been widely used as tools for description and interpretation of ancient debris flow deposits providing a basis to estimate yield strength viscosity cohesion and internal friction angle recent studies suggest however that a debris flow is an intimate mixture of solid and fluid in which a number of momentum transfer mechanisms operate it is therefore necessary to evaluate the relative importance of different momentum transport processes to properly describe a debris flow scaling analysis may be useful to this end using the bagnold number the ratio of inertial grain stress to viscous shear stress savage number the ratio of inertial grain stress to shear stress borne by sustained grain contacts friction number the ratio of frictional shear stress to viscous shear stress and darcy number the ratio of grain fluid interaction stress to inertial grain stress scaling analyses of miocene gravelly debris flow deposits in korea suggest that different types of debris flows can be better distinguished by the analyses providing some implications for debris flow processes

geology of northeast british columbia and northwest alberta diamonds shallow gas gravel and glaciersthis article introduces a selection of papers published in this special issue on the theme geology of northeastern british columbia and northwestern alberta diamonds shallow gas gravel and glaciers this special issue reports on some of the results of a multi disciplinary research program conducted in the boreal plains of northwest alberta and northeast british columbia several innovative approaches to conducting geoscientific research in this remote drift covered region are presented including geochemical analysis of bentonites for evaluating kimberlite potential the use of electromagnetic surveys for mapping buried aggregate deposits and paleo topographic mapping techniques to define buried channels results of the program include the discovery of several large aggregate deposits the first kimberlite indicator minerals in northeast british columbia a significant sphalerite dispersal train in northwest alberta the first documented report of kimberlite sourced bentonites and numerous previously unknown interglacial sites together these papers provide a greatly enhanced understanding of the glacial history quaternary stratigraphy and kimberlite geology of northwest alberta and northeast bri

peak flow responses to landscape disturbances caused by the cataclysmic 1980 eruption of mount st helens washington years of discharge measurements that precede and follow the cataclysmic 1980 eruption of mount st helens washington provide an exceptional opportunity to examine the responses of peak fl ows to abrupt widespread devastating landscape disturbance multiple basins surrounding mount st helens 300 1300 km 2 drainage areas were variously disturbed by 1 a debris avalanche that buried 60 km 2 of valley 2 a lateral volcanic blast and associated pyroclastic fl ow that destroyed 550 km 2 of mature forest and blanketed the landscape with silt capped lithic tephra 3 debris fl ows that reamed riparian corridors and deposited tens to hundreds of centimeters of gravelly sand on valley fl oors and 4 a plinian tephra fall that blanketed areas proximal to the volcano with up to tens of centimeters of pumiceous silt sand and gravel the spatially complex disturbances produced a variety of potentially compensating effects that interacted with and infl uenced hydrological responses changes to water transfer on hillslopes and to fl storage and routing along channels both enhanced and retarded runoff rapid posteruption modifi cations of hillslope surface textures adjustments of channel networks and vegetation recovery in conjunction with the complex nature of the eruptive impacts and strong seasonal variability in regional climate hindered a consistent or persistent shift in peak discharges overall we detected a short lived 5 10 yr increase in the magnitudes of autumn and winter peak fl ows in general peak fl ows were larger and moderate to large fl ows q 2 yr were more substantively affected than predicted by early modeling efforts proportional increases in the magnitudes of both small and large fl ows in basins subject to severe channel disturbances but not in basins subject solely to hillslope disturbances suggest that eruptioninduced modifi cations to fleffi ciency along alluvial channels that have very mobile beds differentially affected fl ows of various magnitudes and likely played a prominent and additional role affecting the nature of the hydrological response

the pattern and style of deglaciation at the late wisconsinan laurentide and cordilleran ice sheet limits in northeastern british columbia this paper reports on the landform assemblages at the northern confluence of the late wisconsinan laurentide and cordilleran ice sheets with montane and piedmont glaciers in the northern rockies and southern mackenzie mountains recent observations in northeastern british columbia refine our knowledge of the pattern and style of ice sheet retreat glacial lake formation and meltwater drainage at the onset of deglaciation confluent laurentide and cordilleran terminal ice margins lay between 59 n 124 30 w and 60 n 125 15 w from this terminal limit ice sheets retreated into north central british columbia and yukon territory with remnant cordilleran ice and montane glaciers confined to mountain valleys and the liard plateau distinctive end moraines are not associated with the retreat of cordilleran ice in these areas laurentide ice retreated northeastward from uplands and the plateaus then separated into lobes occupying the fort nelson and petitot river valleys ice retreat landforms include recessional end moraines sometimes overridden and drumlinized hill hole pairs crevasse fill deposits de geer like ribbed till ridges hummocky moraines kames meltwater features and glacial lake deposits that fall within the elevation range of glacial lake liard and glacial lake fort nelson ca 840 380 m meltwater and sediment transport into glacial lakes fort nelson liard nahanni and mackenzie was sustained by remnant ice in the liard river and fort nelson river drainage basins until the end of glaciation optical dating of sand from stabilized parabolic dunes on the liard plateau indicates that proglacial conditions lake formation and drainage began before 13 0 0 5 ka calendar years the petitot fort nelson and liard rivers all occupy spillways incised into glacial deposits and bedrock by meltwater overflow from glacial lakes peace and hay

particle interaction inside debris flows evidence through experimental data and quantitative clast shape analysis abstract results of analytical experiments related to the dynamic behavior of debris flows are presented particle interaction and the amount and type of fines content present in the matrix aspects that govern debris flow behavior are studied via the morphological evolution of constituent particles four different mixtures of water and sediment with compositions resembling debris flows were prepared and put into a rotating drum known as a los angeles standard abrasion machine and studied at different time intervals for each sampling time quantitative shape analysis was performed using three morphological coefficients mc 2 mc 3 8 and mc 30 34 coefficient mc 2 gives information about particle ellipticity mc 3 8 is related to basic irregularities at a macro scale such as roundness mc 30 34 is related to microscale irregularities like surface texture coefficient mc 3 8 was shown to be very sensitive to silt content in the matrix and coefficient mc 30 34 to the presence of clay all three coefficients point to the fact that changes in shape between granulometric classes are gradual and follow a power law coarse granulometric classes acquire more circular and smooth profiles while small particles maintain their irregular profiles this phenomenon is the result of clast interaction processes within mixtures clast collisions between particles produce comminution of the coarsest fractions while finer particles fracture along their entire surface the rate at which these changes occur is related to the type of fine sediment present in the matrix changes in particle shape are an important tool for revealing internal dynamics because they are related to clast interaction and affect sedimentation processes inside these flows this type of experiment although not on a real scale provides important physical information for understanding the phenomena that occur inside debris flows enabling the study of a variety of textural parameters and their changes at regular time intervals the experimental patterns observed offer new insights into clast clast interaction rounding and comminuting theory with important implications for understanding rheological behavior and kinematics of flows and related hazards