slope instability from ground water seepage previous researchers have treated the magnitude and direction of the seepage vector as independent variables and found that seepage parallel to the surface does not result in the minimum stable seepage slope in the present paper the magnitude and direction of the seepage vector is shown to be uniquely related at the seepage face and seepage parallel to the slope results is the minimum stable seepage slope slope failures under seepage are found to be progressive and the stable slope angle depends on the direction of the seepage vector the effect of seepage direction on static liquefaction is investigated and the seepage directions that initiate static liquefaction depend on the slope angle and soil unit weight analytical predictions of the minimum stable seepage slope compare favorably with experimental results

slope failures in the ochil hills scotland november 1984 intense rainfall in november 1984 caused several slope failures on the steep slopes of the ochil hills each failure was of soil and till no more than 2 m thick over bedrock in a steep bowl from 30 350 m3 of sediment was removed failure seems to have been by shallow sliding triggered by saturation but each slide became a debris flow the largest one menstrie filling a house with mud which was at twice the liquid limit two days after the event the storm which caused the failures had an estimated recurrence interval of 50 years but the frequency of heavy rain is increasing and similar failures occurred nearby the following year

reversing bottom circulation in the somali basin two sets of direct velocity measurements were taken concurrent with hydrographic data in the bottom waters of the northern somali basin in june and september 1995 the velocities indicate a temporal flow reversal in the bottom circulation which is consistent with the changing density structure between the sections in june there is evidence of a southward deep western boundary current with a transport of 5 sv by september flow close to the boundary is northward with a transport of 2 6 sv furthermore the deep density gradient across the interior of the somali basin also changes between occupations implying a cyclonic circulation in june and anticyclonic flow in september rossby wave activity is high in this region during the southwest monsoon yet there is also evidence of a strong barotropic component to the great whirl in september which may cause the reversal in the abyssal circulation

the 2010 yushu earthquake triggered landslide hazard mapping using gis and weight of evidence modeling the yushu county qinghai province china april 14 2010 earthquake triggered thousands of landslides in a zone between 96 20 32 9 e and 97 10 8 9 e and 32 52 6 7 n and 33 19 47 9 n this study examines the use of geographic information system gis technology and bayesian statistics in creating a suitable landslide hazard zone map of good predictive power a total of 2 036 landslides were interpreted from high resolution aerial photographs and multi source satellite images pre and post earthquake and verified by selected field checking before a final landslide inventory map of the study area could be established using gis software the 2 036 landslides were randomly partitioned into two subsets a training dataset which contains 80 1 628 landslides for training the model and a testing dataset 20 408 landslides twelve earthquake triggered landslide associated controlling parameters such as elevation slope gradient slope aspect slope curvature topographic position distance from main surface ruptures peak ground acceleration distance from roads normalized difference vegetation index distance from drainages lithology and distance from all faults were obtained from variety of data sources landslide hazard indices were calculated using the weight of evidence model the landslide hazard map was compared with training data and testing data to obtain the success rate and predictive rate of the model respectively the validation results showed satisfactory agreement between the hazard map and the existing landslide distribution data the success rate is 80 607 and the predictive rate is 78 855 the resulting landslide hazard map showed five classes of landslide hazard i e very high high moderate low and very low the landslide hazard evaluation map should be useful for environmental recovery planning and reconstruction work

petrogenesis of the late cretaceous northern alberta kimberlite province abstract at present 48 late cretaceous ca 70 88 ma kimberlitic pipes have been discovered in three separate areas of the northern alberta the mountain lake cluster the buffalo head hills field and the birch mountains field the regions can be distinguished from one another by their non archetypal kimberlite signature mountain lake or in the case of kimberlite fields primitive buffalo head hills to evolved birch mountains magmatic signatures the dominant process of magmatic differentiation is crystal fractionation and accumulation of olivine which acts as the main criteria to distinguish between primitive and evolved group i type kimberlite fields in the northern alberta this is important from the viewpoint of diamond exploration because the majority about 80 of the more primitive buffalo head hills kimberlites are diamondiferous whereas the more evolved birch mountains pipes are barren of diamonds for the most part petrographically the buffalo head hills samples are distinct from the birch mountains samples in that they contain less carbonate have a smaller modal abundance of late stage minerals such as phlogopite and ilmenite and have a higher amount of fresh coarse macrocrystal 0 5 mm olivine consequently samples from the buffalo head hills have the highest values of mgo cr and ni and have chemistries similar to those of primitive hypabyssal kimberlite in the northwest territories based on whole rock isotopic data the buffalo head hills k6 kimberlite has 87sr 86sr and end values similar to those of south african group i kimberlites whereas the birch mountains legend and phoenix kimberlites have similar end values between 0 and 1 9 but distinctly higher 87sr 86sr values 0 7051 0 7063 the lack of whole rock geochemical overlap between kimberlite and the freshest least contaminated mountain lake south pipe rocks reflects significant mineralogical differences and mountain lake is similar geochemically to olivine alkali basalt and or basanite intra field geochemical variations are also evident the k4 pipe buffalo head hills and xena and kendu pipes birch mountains are characterized by anomalous concentrations of incompatible elements relative to other northern alberta kimberlite pipes including chondrite normalized rare earth element distribution patterns that are less fractionated than the other kimberlite samples from the buffalo head hills and birch mountains the xena pipe has similar major element chemical signatures and high al clinopyroxene similar to or trending towards the mountain lake pipes in addition k4 and kendu have higher 87sr 86sr and lower end than bulk earth and plot in the bottom right quadrant of the nd sr diagram we suggest therefore that the k4 and kendu pipes contain a contribution from old lree enriched low sm nd lithosphere that is absent from the other kimberlites are affected by crustal contamination or both based on xenocryst populations the northern alberta kimberlite province mantle is dominated by carbonate saturated lherzolitic mantle higher levels of melt depletion characterize the buffalo head hills mantle sample despite high diamondiferous to barren pipe ratios in the buffalo head hills pipes mineral indicators of high diamond potential such as g10 garnet diamond inclusion composition chrome spinels and high sodium eclogitic garnet are rare

experiments on piping in sandy gravels tests on internally unstable sandy gravels show that a significant proportion of the sand content is washed out by piping at hydraulic gradients far lower than the critical gradient given by a classical theory the probable explanation is that a major part of the overburden load is carried on a framework of gravel particles leaving the sand under relatively small pressures by contrast piping of the sand from stable sandy gravels occurs at approximately the full theoretical gradient the tests broadly confirm kenney s criterion for the internal stability of granular materials des essais realises sur des graves sableuses a instabilite interne importante montrent qu une proportion non negligeable du sable est lessivee pour des gradients hydrauliques bien inferieurs au gradient critique donne par les theories classiques l explication la plus probable est que la majeure partie de la surcharge des couches subjacentes est transmise au reseau des particules graveleuses le sable n etant alors plus soumis qu

effect of seepage on shallow landslides in consideration of changes in topography case study including an experimental sandy slope with artificial rainfall abstract many studies on shallow landslides have focused on seepage mechanisms however most of these studies assumed that the hillslope was parallel to the seepage direction and force they did not consider how the seepage was changed by the topography during failure to investigate the seepage mechanism particularly the influence of the topographic change during failure flume experiments using a 30 sandy slope were performed with artificial rainfall the factor of safety fs equation which considers the seepage direction and force and the numerical simulation were also applied to analyze the effect of topographic change on the seepage mechanism the experiments were divided into two stages rainfall induced experiment rie and seepage induced experiment sie with rainfall in the rie with a rainfall intensity of 80 mm h seepage erosion occurred followed by undercutting which resulted from seepage erosion to upward direction of sandy slope the analysis of fs in rie are showing an instability when seepage direction is be a slope parallel with theoretical value i hydraulic gradient in the numerical model when topographic changes of the surface of the sandy flume were applied seepage flow concentrated from failure surface of the toe of flume to middle part of flume which is affected by saturation in sie multiple failures caused by the seepage in the vertically upward direction occurred with a high seepage force and the failure mass then moved in the downward direction with the seepage flow fs for sie showed a high instability than those of rie when seepage direction with high force already changed from vertically downward seepage flow to increasing slope parallel seepage flow applying changed topography more deep from sandy flume surface in numerical model is showing concentrated seepage flow at the bottom of failures this is one of mechanism developing failure mass to downward direction to the toe of flume because soil moisture sensors installed near failures 25 cm depth show high value than porosity value indicating soil mobilization therefore the seepage direction and force play important roles in landslide mechanism and these factors should be considered in landslide studies

ferric iron in catio3 perovskite as an oxygen barometer for kimberlitic magmas i experimental calibration a method to estimate the oxygen fugacity fo2 during the crystallization of kimberlites is developed using the fe content of catio3 perovskite pv a common groundmass phase in these rocks with increasing fo2 more fe exists in the kimberlitic liquid as fe3 and thus partitions into pv experiments to study the partitioning of fe between pv and kimberlite liquid were conducted at 100 kpa on simple and complex anhydrous kimberlite bulk compositions from 1130 to 13008c over a range of fo2 from nno 5 to nno 4 where nno is the nickel nickel oxide buffer and atnb and rare earth element ree contents in the starting materials of 0 5 wt and 1500 ppm respectively the partitioning of fe between pv and kimberlite liquid is influenced mostly by fo2 although the presence of nb increases the partition of fe3 into perovskite at a given t and fo2 multiple linear regression mlr of all the experimental data produces a relationship that describes the variation of fe andnbinpvwith fo2relative to thennobuffer

rb sr and u pb geochronology and setting of the buffalo head hills kimberlite field northern albertathis 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 new rb sr phlogopite and u pb perovskite age determinations for 12 of 38 known ultramafic bodies in the buffalo head hills area of north central alberta show that kimberlitic magmatism occurred in at least two separate episodes during late cretaceous and paleocene time nine kimberlites yield coniacian to campanian ages of between 88 5 ma u pb perovskite k5a and 81 2 2 3 ma rb sr phlogopite k252 a danian u pb perovskite isochron age of 63 5 0 7 ma was obtained for the bm2 kimberlite and selandian rb sr ages of 59 6 2 8 and 60 3 0 8 ma were determined for the k1a and k19 bodies respectively these specific periods of magmatism correspond to characteristic intra field features such as kimberlite spatial distribution diamond content rock classification and mechanisms of emplacement the 88 81 ma group generally occurs in the northwestern part of the field and defines the diamond window for the buffalo head hills kimberlite field this volcanism is contemporaneous with sedimentary host

influence of subsurface flow by lidar dems and physical soil strength considering a simple hydrologic concept for shallow landslide instability mapping abstract high resolution dems and physical soil strength among other factors have significant effects on the shallow landslide instability mapping subsurface flow in soil mantle normally is assumed by slope parallel flow based on resolution of dems and measuring soil strength which is affected by subsurface flow within the soil mantle is difficult in both the field and the laboratory thus the aims of this study are to investigate the effect of subsurface flow by high resolution lidar dems and the effect of physical soil strength attributes on shallow landslide instability mapping respectively in this study two dems with 1 m and 5 m resolutions were used and physical soil strength was calibrated using a simple subsurface hydrological concept with lidar and field survey data in order to quantify the influence of soil strength on shallow landslide instability mapping to this end various field surveys were performed at woomyeon mountain seoul republic of korea where shallow landslides occurred in 2012 the physical shallow landslide stability shalstab model were applied the modified success rate msr method were applied to assess the predicted results in the first series of simulations using the two dems and experimentally derived soil strength values relatively low msr values of 0 42 0 468 for the 1 m dem and 0 42 0 47 for the 5 m dem were recorded in the second series of simulations using soil strength calibrated using a simple theoretical approach the msr for the 1 m dem was 0 78 0 823 and the msr for the 5 m dem was 0 723 0 80 these results indicated that soil strength had a more important role in shallow landslide instability mapping than assuming subsurface flow by topographic resolution therefore it may be useful to apply field collected soil strength data using hydrological concepts to improve the accuracy of predictive models based on high resolution surface data

flow of variably fluidized granular masses across three dimensional terrain 2 numerical predictions and experimental tests numerical solutions of the equations describing flow of variably fluidized coulomb mixtures predict key features of dry granular avalanches and water saturated debris flows measured in physical experiments these features include time dependent speeds depths and widths of flows as well as the geometry of resulting deposits three dimensional 3 d boundary surfaces strongly influence flow dynamics because transverse shearing and cross stream momentum transport occur where topography obstructs or redirects motion consequent energy dissipation can cause local deceleration and deposition even on steep slopes velocities of surge fronts and other discontinuities that develop as flows cross 3 d terrain are predicted accurately by using a riemann solution algorithm the algorithm employs a gravity wave speed that accounts for different intensities of lateral stress transfer in regions of extending and compressing flow and in regions with different degrees of fluidization field observations and experiments indicate that flows in which fluid plays a significant role typically have high friction margins with weaker interiors partly fluidized by pore pressure interaction of the strong perimeter and weak interior produces relatively steep sided flat topped deposits to simulate these effects we compute pore pressure distributions using an advection diffusion model with enhanced diffusivity near flow margins although challenges remain in evaluating pore pressure distributions in diverse geophysical flows riemann solutions of the depth averaged 3 d coulomb mixture equations provide a powerful tool for interpreting and predicting flow behavior they provide a means of modeling debris flows rock avalanches pyroclastic flows and related phenomena without invoking and calibrating rheological parameters that have questionable physical significance

global ocean meridional overturning abstract a decade mean global ocean circulation is estimated using inverse techniques incorporating air sea fluxes of heat and freshwater recent hydrographic sections and direct current measurements this information is used to determine mass heat freshwater and other chemical transports and to constrain boundary currents and dense overflows the 18 boxes defined by these sections are divided into 45 isopycnal neutral density layers diapycnal transfers within the boxes are allowed representing advective fluxes and mixing processes air sea fluxes at the surface produce transfers between outcropping layers the model obtains a global overturning circulation consistent with the various observations revealing two global scale meridional circulation cells an upper cell with sinking in the arctic and subarctic regions and upwelling in the southern ocean and a lower cell with sinking around the antarctic continent and abyssal upwelling mainly below the crests of the major bathymetric ridges

geochemical and nd pb isotopic systematics of late archean granitoids southwestern slave province canada constraints for granitoid origin and crustal isotopic structure new geochemical and nd pb isotopic data for 2 62 2 59 ga granitoids from the southwest slave province are used to determine the source s of granitoid magmas to evaluate the role of pre 2 8 ga basement during this magmatism and to refine the existing nd pb isotopic structure of the western slave province the pb isotopic data require crust older than 3 2 ga as a granitoid protolith whereas the nd isotopic data require input from juvenile crustal material this discrepancy is explained if the granitoid protoliths are mixtures of ancient basement and 2 7 ga juvenile crust in varying proportions specifically granitoids from the southwestern slave province require 10 30 basement whereas granitoids from other parts of the western slave province require 50 incorporation of basement as a protolith may be achieved indirectly by assimilation of basement during juvenile 2 7 ga magmatism or directly during 2 62 2 59 ga magmatism the granitoid isotopic data suggest that indirect basement input was

deep electrical structure of northern alberta canada implications for diamond exploration geophysical studies of upper mantle structure can provide constraints on diamond formation teleseismic and magnetotelluric data can be used in diamond exploration by mapping the depth of the lithosphere asthenosphere boundary studies in the central slave craton and at fort a la corne have detected conductors in the lithospheric mantle close to or beneath diamondiferous kimberlites graphite can potentially explain the enhanced conductivity and may imply the presence of diamonds at greater depth petrologic arguments suggest that the shallow lithospheric mantle may be too oxidized to contain graphite other diamond bearing regions show no upper mantle conductor suggesting that the correlation with diamondiferous kimberlites is not universal the buffalo head hills in alberta host diamondiferous kimberlites in a proterozoic terrane and may have formed in a subduction zone setting long period magnetotelluric data were used to investigate the upper mantle resistivity structure of this region magnetotell

north american margin origin of quesnel terrane strata in the southern canadian cordillera inferences from geochemical and nd isotopic characteristics of triassic metasedimentary rocks new geochemical and nd isotopic data from triassic ca 220 ma clastic metasedimentary rocks assigned to the quesnel terrane quesnellia in southeastern british columbia show that detritus was derived from both primitive and evolved sources twenty four samples yield end 2 2 0 values between 9 1 and 5 6 independent of sample location these samples have eu anomalies between 0 6 and 1 0 la n yb n ratios between 3 8 and 11 4 la sc ratios ranging from 0 38 to 4 76 and th sc ratios between 0 09 and 1 62 this range of isotopic and geochemical values overlaps that of samples from upper paleozoic to mesozoic rocks of the north american miogeocline and upper triassic nicola group volcanic rocks of the quesnel terrane the range in nd isotopic and geochemical values supports the interpretation that detritus was derived from both continental north america evolved cratonic source and a volcanic arc primitive source developing on the continental margin these data do not support previous interpretations of the quesnel terrane as an intraoceanic arc the inferred depositional link between north america and the quesnel arc in triassic time is ca 40 ma older than the hypothesized obduction of the quesnel terrane onto the north american continental margin and when combined with existing geological information strongly supports a pericratonic nonexotic origin for the quesnel terrane in southeastern british columbia

late wisconsin ice flow history in the buffalo head hills kimberlite field north central alberta ice flow of the last glaciation in the buffalo head hills kimberlite field of northern alberta is reconstructed from landform interpretations and clast orientations for the purpose of aiding kimberlite exploration in the region the paucity of bedrock outcrop and the absence of preserved striae and other erosional ice flow indicators on the soft cretaceous marine sediments inhibit detailed interpretations on glacial flow chronology poorly developed bedrock drumlins on the buffalo head hills and erosional ice flow indicators preserved on the kimberlite outcrops indicate southwestward ice flow during the maximum extent of ice during the last glaciation during the deglaciation of northern alberta later phases of ice flow were controlled by lobes of surging ice which surged into proglacial lakes west of the buffalo head hills the maximum phase of southwest flow was followed by southeastward ice movement of the peace river ice lobe similarly east of the buffalo head hills the maximum phase of ice flow was superceded by a south southwest ice advance of the wasbasca ice lobe

diamonds through time diamonds form in the upper mantle during episodic events and have been transported to the earth s surface from at least the archean to the phanerozoic small diamonds occur as inclusions in robust minerals in tectonically activated ultrahigh pressure metamorphosed crustal rock establishing an association with subduction processes and recycled carbon but providing no economic deposits diamonds in economic deposits are estimated to be mainly 99 derived from subcontinental lithospheric mantle and rarely approx 1 from the asthenosphere harzburgite and eclogite are of roughly equal importance as source rocks followed by lherzolite and websterite diamonds which provide evidence of extensive residence time in the mantle are with minimal exceptions smooth surfaced crystalline diamonds scd with potential commercial value the oldest prolific scd formation event documented on the world s major diamond producing cratons occurs in archean lithospheric mantle harzburgite metasomatized by likely subduction related potassic carbonatitic fluids disaggregation of the diamondiferous carbonated peridotite on decompression during volcanic transit gives rise to the association between diamonds g10 garnets and diamond inclusion type chromites well used in diamond exploration within the mantle domains of diamond stability there have been repeated episodes of further diamond crystallization and or growth these are associated with old often proterozoic subduction related melt generation metasomatic fluid migration and reaction with preexisting mantle eclogite websterite and peridotite using improved methods of isotope analysis diamond formation ages can be correlated with specific major processes such as craton accretion craton edge subduction and magmatic mantle refertilization fibrous cuboid diamond and fibrous coats on scd are rough surfaced diamonds with abundant fluid inclusions they have low mantle residence time forming rapidly from late stage metasomatic fluids in diamond stable domains that may already contain scd the symbiotic relationship between formation of fibrous diamond and magmatic sampling and transport of diamonds into the crust suggest that the associated fluids contribute diamond friendly volatile loading of the deep lithospheric mantle shortly before the triggering of a volcanic eruption continuing a process of volatile enrichment in the lithospheric mantle already identified in the archean harzburgite diamond event mantle derived scd commonly shows evidence of resorption illustrating that diamond unfriendly processes including lamproite and kimberlite generation are also active and may have a substantial negative effect in extreme cases on scd crystal size exposure of scd to a long period of changing conditions during mantle residence contributes to the difficulty of assigning specific parageneses and ages to individual inclusion free diamonds with our current state of knowledge

hillslope runoff processes and models abstract hillslope hydrology is concerned with the partition of precipitation as it passes through the vegetation and soil between overland flow and subsurface flow flow follows routes which attenuate and delay the flow to different extents so that a knowledge of the relevant mechanisms is important in the 1960s and 1970s hillslope hydrology developed as a distinct topic through the application of new field observations to develop a generation of physically based forecasting models in its short history theory has continually been overturned by field observation thus the current tendency particularly among temperate zone hydrologists to dismiss all hortonian overland flow as a myth is now being corrected by a number of significant field studies which reveal the great range in both climatic and hillslope conditions some recent models have generally attempted to simplify the processes acting for example including only vertical unsaturated flow and lateral saturated flows others explicitly forecast partial or contributing areas with hindsight the most complete and distributed models have generally shown little forecasting advantage over simpler approaches perhaps trending towards reliable models which can run on desk top microcomputers the variety now being recognised in hillslope hydrological responses should also lead to models which take account of more complex interactions even if initially with a less secure physical and mathematical basis than the richards equation in particular there is a need to respond to the variety of climatic responses and to spatial variability on and beneath the surface including the role of seepage macropores and pipes which call into question whether the hillside can be treated as a darcian flow system

internal soil moisture and piezometric responses to rainfall induced shallow slope failures summary better knowledge regarding internal soil moisture and piezometric responses in the process of rainfall induced shallow slope failures is the key to an effective prediction of the landslide and or debris flow initiation to this end internal soil moisture and piezometric response of 0 7 m deep 1 5 m wide 1 7 m high and 3 94 m long semi infinite sandy slopes rested on a bi linear impermeable bedrock were explored using a chute test facility with artificial rainfall applications the internal response time defined by the inflection point of the soil moisture and piezometric response curves obtained along the soil bedrock interface were closely related to some critical failure states such as the slope toe failure and extensive slope failures it was also found that the response times obtained at the point of abrupt bedrock slope decrease can be used as indicators for the initiation of rainfall induced shallow slope failures an investigation of spatial distributions of soil water content or degrees of saturation s r in the slope at critical failure states shows that the 0 2 m below surface zone remains unsaturated with s r 40 60 regardless of their distances from the toe and the rainfall intensity non uniform distributions of or s r along the soil bedrock interface at critical failure states were always associated with near saturation states s r 80 100 around the point of bedrock slope change or around the transient toe upstream of the slumped mass induced by the retrogressive failure of the slope these observations suggest the important role of the interflow along the soil bedrock interface and the high soil water content or high porewater pressure around the point of bedrock slope deflection in the rainfall induced failure of sandy slopes consisting of shallow impermeable bedrocks the present study proposes an internal response time criterion to substantiate the prediction of rainfall induced shallow slope failures it is believed that the internal response time reflects the overall characteristics of a slope under rainfall infiltration and can be as useful as the conventional meteorology based threshold times the internal response time theory can be generalized via numerical modeling of slope hydrology slope geology and slope stability in the future

deep water exchange through the owen fracture zone in the arabian sea from geostrophic calculations the exchange of deep water from the somali into the arabian basin through the owen fracture zone has been estimated to be about 2 sv with a seasonal modulation of the same magnitude after leaving the fracture zone the flow bifurcates into a northern and a southern branch each closely following the slope of the carlsberg ridge the weaker vertical gradients of the hydrographic properties in the deep arabian basin are consistent with enhanced vertical mixing at the rugged topography over the carlsberg ridge

rainfall triggered mass movements on steep loess slopes and their entrainment and distribution abstract mass movements are predominant geomorphic processes on steep hillslopes however the mechanisms governing the erosion and entrainment of mass movements remain poorly understood in this study experiments on natural loess slopes were conducted to induce a series of mass movements under simulated rainfalls in the liudaogou catchment on the loess plateau of china a novel topography meter was used to observe random mass movements a total of 499 mass movements in 42 rainfall events and an average of 11 mass movements for each rainfall event were observed three mass movement types were detected landslides 67 mudflows 21 avalanches 12 the volume of landslides dramatically increased through the entrainment of a wet gully bed material and the volume of landslide mass was magnified by 29 on average through material entrainment based on the observed data the probability of mass movement occurrences decreased with the increasing mass movement volume in a power law relationship the critical rainfall amount for mass movement failure was approximately 25 6 mm at a rainfall intensity of 50 mm h 1 these results can serve as guides to mitigate geological hazards and assess erosion processes on steep loess slopes of the loess plateau

subsurface flow velocities through selected forest soils south island new zealand subsurface flow through soils in tawhai big bush and craigieburn state forests has been studied by applying water at a line source 1 m upslope from a pit in the base of which an intercepting trough is located by measuring lag times between the centres of mass of input and outflow and between the start of input and start of outflow minimum estimates of mean and maximum flow velocity v and vmax at 51 locations were obtained mean values for the tawhai sites were for v 0 3 cm s and for vmax 0 42 cm s but a considerable degree of variability was present with coefficients of variation up to 90 a number of different pathways through the soil are followed by flowing water macropore networks root channels etc are effective transmitters of water and at some sites conveyed up to 40 of the input rapidly to the interception trough variability in flow velocity and the proportion of the input appearing as rapid outflow is a function of antecedent moisture conditions and of the relative importance of the various pathways at a given site which is in turn a function of the characteristics of the soil the macropore network and the parent material at the base of the soil at sites where the soil had an open structure and the parent material was shattered or permeable the macropore network was a less important control upon soil hydrological behavior than where the subsoil had a less open structure and was underlain by impermeable bedrock measurements of flow velocities on undisturbed logged and logged burned planted sites were made at tawhai sf but the spatial and temporal variability was such that no statistically significant differences could be discerned the time lapse since logging may be insufficient for changes in the root systems to be having a hydrological impact but the high variability would require a sample size of over 1000 to show a significant difference in velocity of even 10 for rapid flow through macropores to have a significant influence on streamflow saturation of the soil is necessary before water can enter the macropores soil topographic geologic and climatic conditions in tawhai sf are such that saturation of the lower layers of the soil regularly occurs so that rapid flow through macropores can contribute to storm period streamflow water may reach the channel system from a proportion of the catchment which varies with antecedent moisture conditions and storm duration and intensity but which may attain 100 in moderate to large rain events because of the drier climate and deeper soils subsurface flow contributions to stormperiod streamflow should be less important in the big bush area and particularly in the craigieburn area where the parent materials shattered sandstone or ancient scree deposits do not provide an impermeable layer which diverts flow laterally

a physically based model for the topographic control on shallow landsliding a model for the topographic influence on shallow landslide initiation is developed by coupling digital terrain data with near surface through flow and slope stability models the hydrologic model topog o loughlin 1986 predicts the degree of soil saturation in response to a steady state rainfall for topographic elements defined by the intersection of contours and flow tube boundaries the slope stability component uses this relative soil saturation to analyze the stability of each topographic element for the case of cohesionless soils of spatially constant thickness and saturated conductivity the steady state rainfall predicted to cause instability in each topographic element provides a measure of the relative potential for shallow landsliding the spatial distribution of critical rainfall values is compared with landslide locations mapped from aerial photographs and in the field for three study basins where high resolution digital elevation data are available tennessee valley in marin county california mettman ridge in the oregon coast range and split creek on the olympic peninsula washington model predictions in each of these areas are consistent with spatial patterns of observed landslide scars although hydrologic complexities not accounted for in the model e g spatial variability of soil properties and bedrock flow control specific sites and timing of debris flow initiation within areas of similar topographic control

flow of variably fluidized granular masses across three dimensional terrain 1 coulomb mixture theory rock avalanches debris flows and related phenomena consist of grain fluid mixtures that move across three dimensional terrain in all these phenomena the same basic forces govern motion but differing mixture compositions initial conditions and boundary conditions yield varied dynamics and deposits to predict motion of diverse grain fluid masses from initiation to deposition we develop a depth averaged three dimensional mathematical model that accounts explicitly for solid and fluid phase forces and interactions model input consists of initial conditions path topography basal and internal friction angles of solid grains viscosity of pore fluid mixture density and a mixture diffusivity that controls pore pressure dissipation because these properties are constrained by independent measurements the model requires little or no calibration and yields readily testable predictions in the limit of vanishing coulomb friction due to persistent high fluid pressure the model equations describe motion of viscous floods and in the limit of vanishing fluid stress they describe one phase granular avalanches analysis of intermediate phenomena such as debris flows and pyroclastic flows requires use of the full mixture equations which can simulate interaction of high friction surge fronts with more fluid debris that follows special numerical methods described in the companion paper are necessary to solve the full equations but exact analytical solutions of simplified equations provide critical insight an analytical solution for translational motion of a coulomb mixture accelerating from rest and descending a uniform slope demonstrates that steady flow can occur only asymptotically a solution for the asymptotic limit of steady flow in a rectangular channel explains why shear may be concentrated in narrow marginal bands that border a plug of translating debris solutions for static equilibrium of source areas describe conditions of incipient slope instability and other static solutions show that nonuniform distributions of pore fluid pressure produce bluntly tapered vertical profiles at the margins of deposits simplified equations and solutions may apply in additional situations identified by a scaling analysis assessment of dimensionless scaling parameters also reveals that miniature laboratory experiments poorly simulate the dynamics of full scale flows in which fluid effects are significant therefore large geophysical flows can exhibit dynamics not evident at laboratory scales

assessment of rainfall induced shallow landslide susceptibility using a gis based probabilistic approach abstract this study proposes a probabilistic analysis method to assess shallow landslide susceptibility over an extensive area by integrating an infinite slope model with gis geographic information system and monte carlo simulation taking into consideration the inherent uncertainty and variability in input parameters the mechanical parameters of soil materials such as cohesion and friction angle used in the infinite slope analysis have been identified as the major source of uncertainty because of their spatial variability therefore these parameters were considered as random variables in this probabilistic landslide analysis to properly account for the uncertainty in input parameters the probabilistic analysis method used was monte carlo simulation the process was carried out in a gis based environment because gis has effective spatial data processing capacity over broad areas in addition the hydrogeological model was coupled with the infinite slope model to evaluate increases in pore water pressure caused by rainfall the proposed approach was applied to a practical example to evaluate its feasibility the landslide inventory map and the spatial database for input parameters were constructed in a grid based gis environment and a probabilistic analysis was implemented using monte carlo simulation to evaluate the performance of the model the results of the probabilistic landslide susceptibility analysis were compared with the landslide inventory the probabilistic approach demonstrated good predictive performance when compared with the landslide occurrence location in addition deterministic analysis was carried out using fixed single input data for comparison with the results from the proposed approach in this comparison the probabilistic analysis showed better performance than the deterministic analysis in addition the results showed that proper consideration and understanding of uncertainties play an important role in accurately predicting shallow landslide susceptibility

spatially heterogeneous diapycnal mixing in the abyssal ocean a comparison of two parameterizations to observations 1 the spatial distributions of the diapycnal diffusivity predicted by two abyssal mixing schemes are compared to each other and to observational estimates based on microstructure surveys and large scale hydrographic inversions the parameterizations considered are the tidal mixing scheme by jayne st laurent and co authors jsl01 and the roughness diffusivity model rdm by decloedt and luther comparison to microstructure surveys shows that both parameterizations are conservative in estimating the vertical extent to which bottom intensified mixing penetrates into the stratified water column in particular the jsl01 exponential vertical structure function with fixed scale height decays to background values much nearer topography than observed jsl01 and rdm yield dramatically different horizontal spatial distributions of diapycnal diffusivity which would lead to quite different circulations in ogcms yet they produce similar basin averaged diffusivity profiles both parameterizations are shown to yield smaller basin mean diffusivity profiles than hydrographic inverse estimates for the major ocean basins by factors ranging from 3 up to over an order of magnitude the canonical 10 4 m2 s 1abyssal diffusivity is reached by the parameterizations only at depths below 3 km power consumption by diapycnal mixing below 1 km of depth between roughly 32 s and 48 n for the rdm and jsl01 parameterizations is 0 40 tw 0 28 tw respectively the results presented here suggest that present day mixing parameterizations significantly underestimate abyssal mixing in conjunction with other recently published studies a plausible interpretation is that parameterizing the dissipation of bottom generated internal waves is not sufficient to approximate the global spatial distribution of diapycnal mixing in the abyssal ocean

alteration styles in the orion central volcanic complex fort a la corne kimberlite field saskatchewan and their effects on primary volcaniclastic textures implications for facies mapping and diamond exploration diamond grade distributions within individual kimberlite bodies are controlled by physical emplacement processes which are generally determined from volcaniclastic facies characteristics however the effects and distribution of secondary alteration styles which usually mask primary kimberlite facies have been given little attention at the fort a la corne kimberlite field saskatchewan complex overprinting alteration textures and mineral phases are recognized this study documents the characteristics overprinting relationships and spatial distribution of alteration styles within a crater filling volcaniclastic deposit body 219 of the orion central volcanic complex data were acquired from macroscopic drill core observations microscopic petrography sem imaging eds element mapping and xrd analyses olivine crystals display a mesh fracture pattern and have been replaced by multiple generations of serpentine and magnetite late stage serpentine has migrated into the interstitial medium bulk rock alteration textures include 1 fine grained crystal rich domains which are alteration pseudoclasts and or relict juvenile pyroclasts 2 a heterogeneous interstitial medium varying from early stage disseminated calcite rich serpentine to amorphous serpentine and crystalline calcite and 3 overprinting serpentine carbonate and magnetite veins and serpentine nodules alteration styles defined by unique alteration characteristics are spatially zoned through the body 219 volcaniclastic deposit and this is a result of multiple reaction fronts associated with the influx of fluids of varying composition over time and permeating different parts of the deposit recognition of alteration processes their paragenesis and spatial controls can assist in defining and constraining the distribution of primary kimberlite facies and by consequence the distribution of diamond grades

canadian kimberlites geological characteristics relevant to emplacement in canada more than 770 kimberlites have erupted in diverse tectonic settings over a period of 1000 ma and over an area at least 5000 km across the kimberlites represent at least 30 comagmatic fields one pipe type dominates each of the different kimberlite fields even with the discovery of a significant number of new kimberlite fields this review of recent data substantiates the previous proposal that there are at least three distinct classes of kimberlite pipes which show a correlation with the nature of the country rocks into which they were emplaced new data show that a variation on the prairies pipe type occurs when kimberlites were emplaced into competent paleozoic sediments resulting in steeper sided pipes infilled with similar pyroclastic kimberlite new data for each pipe type are summarised and the contrasting characteristics of the three pipe types are considered to reflect fundamentally different styles of eruption and deposition apparently uniform near surface olivine and volatile rich kimberlite magmas were modified differently during the contrasting emplacement processes resulting in distinct textural rock types pyroclastic kimberlite pk tuffisitic kimberlite tk and associated hypabyssal kimberlite hk or resedimented kimberlite rvk dominating each type of pipe the substantiated correlation of pipe type with country rock geology could indicate variable constraints on volatile exsolution which affected the nature of the magmatic eruptions in different settings

experimental study of shallow mass movements on gully slopes and associated sediment under rainfall on the chinese loess plateau abstract mass movements on gully slopes are the main contributors to gully bank expansion and are the major source of sediment delivered to rivers however they are often overlooked because they are either too small or too time consuming to measure in the field to resolve this challenge a novel topography meter was used to observe shallow mass movements on the gully slopes of the loess plateau under simulated rainfall the experiment showed that the cumulative shallow mass movement volume logarithmically increased with the rainfall amount the critical rainfall for shallow mass movement occurrence was about 28 mm at a rainfall intensity of 50 mm h 1 the results also show that soil water content was a key element controlling the occurrence of the shallow mass movements and the minimal soil water content for permitting shallow mass movements was about 23 1 25 6 for 10 20 cm deep soil shallow mass movement on gully slopes has a significant influence on sediment yield the sediment concentration and sediment transport rate during mass movement failure were on average 3 6 times and 4 0 times higher than that during pre failure events respectively our results have important implications for understanding the connectivity of sediment discharge and mass movements on gully slopes in hilly and gully watersheds

how hydrological factors initiate instability in a model sandy slope knowledge of the mechanisms of rain induced shallow landslides can improve the prediction of their occurrence and mitigate subsequent sediment disasters here we examine an artificial slope s subsurface hydrology and propose a new slope stability analysis that includes seepage force and the down slope transfer of excess shear forces we measured pore water pressure and volumetric water content immediately prior to a shallow landslide on an artificial sandy slope of 32 the direction of the subsurface flow shifted from downward to parallel to the slope in the deepest part of the landslide mass and this shift coincided with the start of soil displacement a slope stability analysis that was restricted to individual segments of the landslide mass could not explain the initiation of the landslide however inclusion of the transfer of excess shear forces from up slope to down slope segments improved drastically the predictability the improved stability analysis revealed that an unstable zone expanded down slope with an increase in soil water content showing that the down slope soil initially supported the unstable up slope soil destabilization of this down slope soil was the eventual trigger of total slope collapse initially the effect of apparent soil cohesion was the most important factor promoting slope stability but seepage force became the most important factor promoting slope instability closer to the landslide occurrence these findings indicate that seepage forces controlled by changes in direction and magnitude of saturated and unsaturated subsurface flows may be the main cause of shallow landslides in sandy slopes copyright 2013 john wiley sons ltd

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

implications of the deep circulation and ventilation of the indian ocean on the renewal mechanism of north atlantic deep water in the indian ocean sector of the great ocean conveyor scheme the north atlantic deep water nadw replacement is realized by the transformation of the sinking circumpolar deep water cdw from the southern ocean to a prevailingly upward flow in the northern indian ocean this water mass transformation scenario has been studied by using hydrographie data including potential temperature salinity dissolved oxygen and nutrients in a water mass mixing model and by calculation of dianeutral velocity the model comprises a mixing system of three major deep water masses nadw cdw and north indian deep water this third water mass is introduced as a virtual water mass to represent the aged cdw the assumption is feasible as the artificial water mass can be eliminated on the deepest n 28 12 neutral surface characterized by isopycnal mixing the experiment is fulfilled when a conservative variable initial phosphate po40 is introduced and all conservative parameters are used in the mixing scheme the n 28 12 surface provides a major isopycnal transition path of cdw to the northern indian ocean and thus cdw is transformed to an upward flow dominant dianeutral up welling is detected on all four neutral surfaces north of 30 s showing increasingly strong dianeutral velocity toward shallower surfaces with the water mass mixing pattern and spreading path dianeutral circulation and dynamical information of the acceleration potential 10 m2 s 2 mapped on neutral surfaces a schematic of deep water circulation and ventilation of the indian ocean emerges from this study the contribution of nadw is largely limited to the southwest indian ocean the northward cdw is found mainly in two paths one in the western indian ocean apparent between 2000 and 3000 m through the western crozet and madagascar basins and farther north into the somali basin and arabian basin and another in the central indian basin apparent below 3000 m where ridge blocking becomes effective in the west and nadw salinity reaches a maximum while the major path switches from west to the central basin in the deeper layer 3000 3500 m the flow in the western indian ocean reverses southward north of the southeast indian ridge the deep path bifurcates from which point the eastern branch feeds the deep western boundary flow in the west australian basin except for part of the transformed cdw which is contributed to the upward flow in the north the return flow of cdw is found on the eastern side of these basins

abyssal circulation in the somali basin the bottom and deep circulation in the somali basin are investigated on the basis of hydrographic and direct velocity profiles from three shipboard surveys carried out during the southwest monsoon in 1995 and of velocity time series from the woce mooring array icm7 the inflow of bottom water into the somali basin through the amirante passage drives a thermohaline circulation which may be modulated by the monsoon wind forcing details of the abyssal circulation have been discussed controversially deep velocity records from the mooring array in the northern somali basin are dominated by fluctuations with periods of 30 50 days and amplitudes above full size image 1 k despite this strong variability annual record averages indicate the existence of a deep western boundary current dwbc below full size image 1 k at the base of the continental slope south of socotra island as part of a cyclonic bottom circulation the southwestward dwbc transport off socotra island is estimated to full size image 1 k the bottom and deep water exchange between the somali and arabian basin north of 7 n is estimated from two cross basin geostrophic velocity sections referenced by vertically averaged ladcp currents for the bottom water an eastward transport into the arabian basin of full size image 1 k and full size image 1 k was determined in june and august respectively while for the deep water layer above full size image 1 k eastward transports of full size image 1 k in june and full size image 1 k in august were obtained

landslides on coastal sage scrub and grassland hillslopes in a severe el nino winter the effects of vegetation conversion on sediment delivery during the 1997 1998 el nino record rainfall triggered 150 shallow landslides within a 9 5 km2 area near santa barbara cal ifornia they were studied to analyze the sediment delivery to val ley floors from landslides in coastal sage scrub and converted grasslands the conversion of coastal sage to grasslands primarily to provide pasturage for cattle is common in the region and the landscape s response may affect water quality reservoir infilling and debris flow hazards we explore the relationship between lateral root reinforcement and landslide volume by developing a slope stability analysis that incorporates root cohesion along the sides of the failure the stability analysis correctly predicts an inverse re lationship between landslide volume and hillslope angle in the sage the volumes of failures in the grasslands do not vary systemati cally with slope and are generally smaller than those in the sage from aerial photograph analysis and field mapping we find that there are 22 9 failures per square kilometer in the grasslands com pared to 13 2 failures per square kilometer in the sage despite the lower failure density in the coastal sage greater failure volumes and longer transport distances delivered more sediment to valley floors with a specific volumetric flux of 2 8 3 10 2 m 3 m 1 for this el nino compared to 1 73 10 2 m 3 m 1 in the grasslands we con clude that the conversion from vegetation with stronger and deeper roots coastal sage to vegetation with weaker and shallower roots grass has caused a pulse of increased landsliding in the grasslands because the soils are currently too thick for the prevailing root reinforcement we suggest that over time soils in the grassland hollows will become thinner as the evacuation by landslides is re peated until the landsliding rate declines to balance the soil sup plied from local colluvium production and diffusive processes upslope

rainfall induced debris flows in pyroclastic deposits campania southern italy abstract a combination of empirical and physically based hydrological models has been used to analyze historical data on rainfall and debris flow occurrence in western campania to examine the correlation between rainfall and debris flow events rainfall data from major storms recorded in recent decades in western campania were compiled including daily series from several rain gauges located inside landslide areas supplemented by hourly rainfall data from some of the principal storms a two phase approach is proposed during phase 1 soil moisture levels have been modelled as the hydrological balance between precipitation and evapotranspiration on a daily scale using the method of thornthwaite geograph rev 38 1948 55 phase 2 is related to the accumulation of surplus moisture from intense rainfall leading to the development of positive pore pressures these interactions take place on an hourly time scale by the leaky barrel lb model described by wilson and wiezoreck env eng geoscience 1 1995 11 in combination with hourly rainfall records the lb model has been used to compare hydrological effects of different storms the critical level of retained rain water has been fixed by the timing of debris flow activity related to recorded storm events new rainfall intensity duration thresholds for debris flow initiation in western campania are proposed these thresholds are related to individual rain gauge and assume a previously satisfied field capacity condition the new thresholds are somewhat higher than those plotted by previous authors but are thought to be more accurate and thus need less conservatism

bank undercutting and tension failure by groundwater seepage predicting failure mechanisms groundwater seepage can lead to the erosion and failure of streambanks and hillslopes two groundwater instability mechanisms include i tension failure due to the seepage force exceeding the soil shear strength or ii undercutting by seepage erosion and eventual mass failure previous research on these mechanisms has been limited to non cohesive and low cohesion soils this study utilized a constant head seepage soil box packed with more cohesive 6 and 15 clay sandy loam soils at prescribed bulk densities 1 30 to 1 70 mg m 3 and with a bank angle of 90 to investigate the controls on failure mechanisms due to seepage forces a dimensionless seepage mechanism sm number was derived and evaluated based on the ratio of resistive cohesion forces to the driving forces leading to instability including seepage gradients with an assumed steady state seepage angle tension failures and undercutting were both observed dependent primarily on the saturated hydraulic conductivity effective cohesion and seepage gradient also shapes of seepage undercuts for these more cohesive soils were wider and less deep compared to undercuts in sand and loamy sand soils direct shear tests were used to quantify the geotechnical properties of the soils packed at the various bulk densities the sm number reasonably predicted the seepage failure mechanism tension failure versus undercutting based on the geotechnical properties and assumed steady state seepage gradients of the physical scale laboratory experiments with some uncertainty due to measurement of geotechnical parameters assumed seepage gradient direction and the expected width of the failure block it is hypothesized that the sm number can be used to evaluate seepage failure mechanisms when a streambank or hillslope experiences steady state seepage forces when prevalent seepage gradient forces should be considered when analyzing bank stability and therefore should be incorporated into commonly used stability models copyright 2013 john wiley sons ltd

are diamond bearing cretaceous kimberlites related to low angle subduction beneath western north america abstract diamond bearing cretaceous kimberlites of western north america were emplaced 1000 1500 km inboard of the farallon plate subduction margin and overlap with the development of the western interior seaway shut down of the sierra nevada arc and the laramide orogeny these events are consistent with a decrease in subduction angle along much of the margin which placed the subducted farallon plate in close proximity to the continental interior at the time of kimberlite magmatism our numerical models demonstrate that low angle subduction can result from high plate convergence velocities and enhanced westward motion of north america further rapid subduction allows hydrous minerals to remain stable within the cool interior of the subducting plate to more than 1200 km from the trench destabilization of these minerals provides a fluid source that can infiltrate the overlying material potentially triggering partial melting and kimberlite lamproite magmatism

systematic variations in xenocryst mineral composition at the province scale buffalo hills kimberlites alberta canada abstract the buffalo hills kimberlites define a province of kimberlite magmatism occurring within and adjacent to proterozoic crystalline basement termed the buffalo head terrane in north central alberta canada the kimberlites are distinguished by a diverse xenocryst suite and most contain some quantity of diamond the xenocryst assemblage in the province is atypical for diamondiferous kimberlite including an overall paucity of mantle indicator minerals and the near absence of compositionally subcalcic peridotitic garnet g10 the most diamond rich bodies are distinguished by the presence of slightly subcalcic chromium rich garnet and the general absence of picroilmenite with the majority forming a small cluster in the northwestern part of the province barren and near barren pipes tend to occur to the south with increasing proximity to the basement structure known as the peace river arch niobian picroilmenite compositionally restricted low to moderate cr peridotitic garnet and megacrystal titanian pyrope occur in kimberlites closest to the arch major element data for clinopyroxene and trace element data for garnet from diamond rich and diamond poor kimberlites suggests that metasomatism of lithospheric peridotite within the diamond stability field may have caused destruction of diamond and diamond source rocks proximal to the arch were the most affected

seepage caused tension failures and erosion undercutting of hillslopes summary seepage has been suggested as an important factor in gully and river bank erosion this study investigated the underlying mechanisms of instability by seepage in laboratory studies a 25 cm tall 50 cm wide and 20 cm long soil block with a focused inflow reservoir was constructed to investigate seepage gradient forces and the three dimensional nature of seepage particle mobilization i e seepage erosion and undercutting experiments included sand and loamy sand soil blocks packed at prescribed bulk densities 1 30 1 70 mg m 3 and with an outflow face at various angles 90 75 and 60 constant heads of 15 25 and 35 cm were imposed on the soil to induce flow a laser scanner was utilized to obtain the three dimensional coordinates of the bank and undercut surfaces at approximately 15 30 s intervals the bulk density of the two different soil types controlled which seepage failure mechanism occurred 1 tension or pop out failures due to the seepage force exceeding the soil shear strength which was being concurrently reduced by increased soil pore water pressure or 2 particle entrainment in the seepage flow particle mobilization bank undercutting and bank collapse when the initial seepage force gradient was less than the resistance of the soil block for cases experiencing particle mobilization and undercutting seepage erosion initiated as unimodal i e concentrated at one point or as multimodal i e initiating at several locations across the bank face and this result was largely controlled by the bank angle a five parameter gaussian function was fitted to the measured three dimensional undercut shapes to derive parameters for the maximum depth of undercutting position of the center of the peak and the vertical and lateral spreads of the undercut the parameters of this distribution can be useful in the development of improved sediment transport functions and the incorporation of this failure mechanism into hillslope stability models

kimberlite sourced bentonite its paleoenvironment and implications for the late cretaceous k14 kimberlite cluster northern albertathis 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 kimberlite sourced bentonite layers have been discovered in late cretaceous sedimentary drill cores located within the buffalo head hills kimberlite field north central alberta two bentonites are unambiguously differentiated from common intermediate to felsic volcanic derived alberta bentonite by having similar whole rock geochemical composition to ultramafic rocks from the buffalo head hills kimberlite field and worldwide crater facies kimberlite the results demonstrate that the geochemical analysis of bentonite can provide a quick cost effective means of testing for low volume kimberlite volcanism the kimberlite sourced bentonite is associated with a cluster of buffalo head hills kimberlites known as the k14 complex the k14a kimberlite occurrence has a previously reported 206pb 238u perovskite emplacement age of 86 8 2 1 ma this age is compatible with early or mid cenomanian 99 96 ma and mid coniacian to santonian 88 84 ma palynological results for mudstone underlying and bracketing the

large scale mass transports water mass formation and diffusivities estimated from world ocean circulation experiment woce hydrographic data 1 a global inversion is used to estimate the oceanic mass transports and vertical diffusivities based on a subset of hydrographic data from the world ocean circulation experiment woce and java australia dynamic experiment the analysis is based on the linear inverse box model of ganachaud and wunsch 2000 that consistently combines the transoceanic sections a globally consistent solution is obtained for a depth independent adjustment to the thermal wind field the freshwater flux divergences the ekman transport and the advective and diffusive dianeutral fluxes between layers a detailed error budget permits calculation of statistical uncertainties taking into account both the nonresolved part of the solution and the systematic errors due to the temporal oceanic variability the horizontal structure of the transports for different density classes is analyzed regionally during the woce period 1985 1996 net meridional transports are estimated with 16 2 sv 106 m3 s of north atlantic deep water nadw being produced in the northern north atlantic moving southward entraining antarctic bottom water aabw and antarctic intermediate water increasing in volume transport to 23 3 sv at 30 s in the southern ocean 21 6 sv of bottom water was formed from lower circumpolar deep water which corresponds approximately to the lower nadw density range bottom water inflows nadw aabw mixture to the atlantic indian and pacific oceans are estimated at 6 1 3 11 4 and 7 2 sv respectively in the indian and pacific oceans this water returns southward at deep and intermediate levels property anomaly conservation constraints permit estimation of dianeutral diffusivities in deep layers with a global average of 3 7 0 7 cm2s 1 north of 30 s

the climatological distribution of potential vorticity over the abyssal ocean climatological maps of the large scale potential vorticity field q along isopycnals are diagnosed for the abyssal waters over the global ocean the inferred patterns of q vary with density the basin and hemisphere at middepths the distribution of q is controlled by the background planetary vorticity gradient on deeper isopycnals there are regions where q contours deviate from latitude circles and even regions of nearly uniform q these different regimes appear to be robust features over the interior of ocean basins as the standard error is found to be relatively small there the nearly uniform q occurs in the deep waters of the north pacific and possibly in the bottom waters of the western north atlantic and north pacific the nearly uniform q has a low magnitude in each case as well as a relatively low variability for the deep waters of the north pacific this nearly uniform q signal appears to be formed when a single water mass enters the basin from a low latitude source

the mechanism of high speed motion and damming of the tangjiashan landslide abstract understanding the mechanisms of landslide failure and resulting damming processes is crucial for constraining the hazard chain associated with landslide damming events on may 12 2008 the wenchuan earthquake caused a large number of secondary hazardous events such as landslides and collapses most of which occurred in high mountain gorges in these areas the sliding distance of landsides is often very short and the landslides are often characterized by high speed short distance and damming using the tangjiashan landslide damming events induced by the wenchuan earthquake as a model this paper reconstructs the three dimensional failure and associated damming caused by the landslide based on a detailed geological investigation of the landslide area and using the dynamic finite element technique the study proposes a four stage model for the failure and damming process of the tangjiashan landslide earthquake induction and progressive destruction of the slide body destruction and high speed sliding of the slide body slide body impact disintegration and river blockage for the formation of a damming body and vibration compression the average speed of the tangjiashan landslide reached a maximum value of 22 m s about 30 s after the earthquake and the landslide reached stability about 60 s later

northward abyssal transport through the samoan passage and adjacent regions a conductivity temperature depth hydrographic survey in january february 1994 and a 17 month deployment of current meter moorings from september 1992 to march 1994 were carried out to determine the volume transport water mass characteristics and diathermal fluxes of northward flowing abyssal waters in the samoan passage and adjacent regions of the south pacific ocean geostrophic calculations relative to 1 2 c potential temperature indicated northward transport of 7 8 sv in the samoan passage 1 1 sv through a gap in robbie ridge and 2 8 sv along the eastern flank of the manihiki plateau all of the total of 11 7 sv of northward geostrophic transport was in waters colder than 1 1 c the northward transport distribution was bimodal in temperature with a cold mode of 3 6 sv in the range 0 65 0 70 c occurring entirely in the samoan passage and a warm mode of 3 0 sv in the range of 0 80 0 85 c occurring mainly along the manihiki plateau within the samoan passage 7 1 sv of the northward transport was below 4000 m where the geostrophic calculation was confirmed by an equal estimate of transport from current meters during the simultaneous 3 day period the 17 month mean transport from the moored array was 6 0 sv 0 5 by using the observed temporally varying flow within the samoan passage together with the hydrographic snapshot across the region an estimate of the total mean northward transport of 10 6 sv 1 7 was obtained estimates of the flow across near bottom potential temperature surfaces indicate extraordinarily high rates of mixing with heating of the abyssal layer up to 20 w m 2 corresponding to diffusivities up to 10 1 m2 s 1

a boundary exchange influence on deglacial neodymium isotope records from the deep western indian ocean the use of neodymium nd isotopes to reconstruct past water mass mixing relies upon the quasi conservative behaviour of this tracer whereas recent studies in the modern oceans have suggested that boundary exchange involving the addition of nd from ocean margin sediments may be an important process in the nd cycle here we suggest that the relative importance of water mass advection versus boundary exchange can be assessed where the deep western boundary current in the indian ocean flows past the madagascan continental margin a potential source of highly unradiogenic nd foraminiferal coatings and bulk sediment reductive leachates are used to reconstruct bottom water nd isotopic composition end in 8 holocene age coretops with excellent agreement between the two methods these data record spatial variability of 4 end units along the flow path of circumpolar deep water end 8 8 in the deep southern inflow upstream of madagascar which evolves towards end 11 5 offshore northern madagascar whereas end 7 3 where deep water re circulates in the eastern mascarene basin this variability is attributed to boundary exchange and together with measurements of detrital sediment end an isotope mass balance suggests a deep water residence time for nd of 400 yr along the madagascan margin considering deglacial changes a core in the deep inflow upstream of madagascar records end changes that agree with previous reconstructions of the circumpolar deep water composition in the southern ocean consistent with a control by water mass advection and perhaps indicating a longer residence time for nd in the open ocean away from local sediment inputs in contrast sites along the madagascan margin record offset end values and reduced glacial interglacial variability underlining the importance of detecting boundary exchange before inferring water mass source changes from nd isotope records the extent of madagascan boundary exchange appears to be unchanged between the holocene and late glacial periods while a consistent shift towards more radiogenic end values at all sites in the late glacial compared to the holocene may represent a muted signal of a change in water mass source or composition

a method for producing digital probabilistic seismic landslide hazard maps abstract the 1994 northridge california earthquake is the first earthquake for which we have all of the data sets needed to conduct a rigorous regional analysis of seismic slope instability these data sets include 1 a comprehensive inventory of triggered landslides 2 about 200 strong motion records of the mainshock 3 1 24 000 scale geologic mapping of the region 4 extensive data on engineering properties of geologic units and 5 high resolution digital elevation models of the topography all of these data sets have been digitized and rasterized at 10 m grid spacing using arc info gis software on a unix computer combining these data sets in a dynamic model based on newmark s permanent deformation sliding block analysis yields estimates of coseismic landslide displacement in each grid cell from the northridge earthquake the modeled displacements are then compared with the digital inventory of landslides triggered by the northridge earthquake to construct a probability curve relating predicted displacement to probability of failure this probability function can be applied to predict and map the spatial variability in failure probability in any ground shaking conditions of interest we anticipate that this mapping procedure will be used to construct seismic landslide hazard maps that will assist in emergency preparedness planning and in making rational decisions regarding development and construction in areas susceptible to seismic slope failure

moisture content pore water pressure and wetting front in granite residual soil during collapsing erosion with varying slope angle abstract collapsing erosion is very severe in subtropical regions that are covered extensively by granite residual soil however detailed information about hydraulic responses during collapsing erosion especially for different slope angles remains unclear therefore to control collapsing erosion it is important to attain a more comprehensive understanding of the complex hydraulic responses due to rainfall in this study an artificial rainfall simulator and an experimental device were used to evaluate the collapsing erosion process with particular consideration of the influence of slope angle flume experiments using three slope angles 0 10 and 20 were performed under artificial rainfall this study explored the evolutions and hydraulic responses of collapsing erosion of granite residual soil by simultaneously monitoring moisture content pore water pressure and wetting front during heavy rainfall the results showed that collapsing erosion occurred faster with steeper slope angle collapse occurred in an upslope direction when the corresponding moisture content of the soil was between 30 and 40 pore water pressure increased until the development of collapsing erosion but was released when the soil mass collapsed the descending process of the wetting front on a gentle slope and a steep slope can be divided into two stages and three stages respectively this study presents an improved characterization of collapsing erosion and provides valuable evidence for slope angle impacts on infiltration events during collapsing erosion under heavy rainfall

paleomagnetic dating of the northern alberta kimberlites due to the vast amount of economic interest diamonds have created in northern alberta there is a need to pro duce an accurate geological model for the northern alberta kimberlite province to aid in the development of such a model the emplacement ages of two kimberlite occurrences k5 and k6 from the buffalo head hills region of north central alberta and the ultramafic mountain lake body from northwestern alberta were estimated using paleomagnetic methods paleomagnetic poles obtained in our study do not differ statistically from the reference poles for late mesozoic cenozoic for north america besse and courtillot 2002 with the aid of polarity determinations palynology and radio genic dating the paleomagnetic results allow for new constraints on the emplacement age of the selected ultramafic occurrences the paleomagnetic emplacement ages established for the k5 k6 and mountain lake bodies are 90 83 ma 83 0 79 1 ma and not older than 79 1 ma respectively resume en raison du grand intereteconomique que les diamants ont creedans le nord de l alberta il est necessaire de developper un modele geologique precis de la province kimberlitique du nord de l alberta afin d aider au developpement d un tel modele les ages de la mise en place de deux occurrences de kimberlite k5 et k6 de la region des collines buffalo head du centre nord de l alberta et de l amas ultrabasique mountain head du nord ouest de l alberta ont eteestimes par une methode paleomagnetique les poles paleomagnetiques obtenus dans notre etude ne different statistiquement pas des poles de reference pour l amerique du nord au mesozoo que tardif cenozoo que besse and courtillot 2002 grace aux determinations de polarite ala palynologie et ala datation radiogenique les resultats paleomagnetiques limitent l age de la mise en place des occurrences ultramafiques selectionnees les ages paleomagnetiques de la mise en place etablis pour les amas k5 k6 et mountain lake sont respectivement de 90 83 ma 83 0 79 1 ma et pas plus vieux que 79 1 ma traduit par la redaction

flow of bottom and deep water in the amirante passage and mascarene basin in the indian ocean the amirante passage is the sill through which rel atively cold fresh oxygen rich and nutrient poor bottom water spreads northward into the somali basin from the mascarene basin the passage is also a conduit through which relatively warm salty oxygen poor and nutrient rich deep water spreads south previous estimates for northward transport of bottom water in the passage have been made from station pairs and sections without benefit of tracer measurements previous estimates of southward transport of deep water are scarce three hydrographic sections were made across the passage in 1995 and 1996 as part of the world ocean circulation experiment woce two woce sections were also made perpendicular to the western boundary in the mascarene basin just south of the passage the geostrophic shear field is used with the salinity dissolved oxygen and silica distributions to select a range of zero velocity surfaces zvss on potential isotherms from 1 0 o to 1 1oc hence a range of geostrophic transports for which the flow direction is consistent with the tracer distributions objective mapping is used to obtain flux estimates below the deepest common level of station pairs estimates in the mascarene basin result in a bottom water volume transport from 2 5 to 3 8 x 10 m 3 s 1 northward toward the passage below the zvss and a deep water transport between the zvss and 2 5oc from 11 6 to 6 4 x 10 m a s southward estimates within the passage result in transports from 1 0 to 1 7 x 10 m a s northward for the bottom water and from 8 6 to 3 8 x 10 m 3 s southward for the deep water

scaling and design of landslide and debris flow experiments abstract scaling plays a crucial role in designing experiments aimed at understanding the behavior of landslides debris flows and other geomorphic phenomena involving grain fluid mixtures scaling can be addressed by using dimensional analysis or more rigorously by normalizing differential equations that describe the evolving dynamics of the system both of these approaches show that relative to full scale natural events miniaturized landslides and debris flows exhibit disproportionately large effects of viscous shear resistance and cohesion as well as disproportionately small effects of excess pore fluid pressure that is generated by debris dilation or contraction this behavioral divergence grows in proportion to h3 where h is the thickness of a moving mass therefore to maximize geomorphological relevance experiments with wet landslides and debris flows must be conducted at the largest feasible scales another important consideration is that unlike stream flows landslides and debris flows accelerate from statically balanced initial states thus no characteristic macroscopic velocity exists to guide experiment scaling and design on the other hand macroscopic gravity driven motion of landslides and debris flows evolves over a characteristic time scale l g 1 2 where g is the magnitude of gravitational acceleration and l is the characteristic length of the moving mass grain scale stress generation within the mass occurs on a shorter time scale h gl 1 2 which is inversely proportional to the depth averaged material shear rate a separation of these two time scales exists if the criterion h l

optimal estimation of hydrographic station data and derived fields abstract optimal estimation is applied to contouring and analysis of hydrographic sections measured fields such as temperature and salinity and derived fields such as geostrophic velocity are decomposed into large scale and small scale components first a heavily sampled basin scale field is estimated and subtracted from the data a small scale field barely resolved by the hydrography is then found from the residuals the power and utility of the technique are illustrated by means of examples using a short section from the straits of florida and a transatlantic section along 24 n

an effective antecedent precipitation model derived from the power law relationship between landslide occurrence and rainfall level abstract antecedent rainfall is an important predisposing factor in triggering landslides because it reduces soil suction and increases the pore water pressure in soils the existing approaches to quantify the antecedent rainfall were derived from empirical methods used to develop rainfall runoff models in which the daily decays of rainfall within a given period preceding a given day are considered as independent processes in this study a methodology accounting for the effective antecedent rainfall that influences landslide occurrence is developed from a power law relationship between the frequency of landslide occurrence and the landslide triggering rainfall level in this model the decay rate of the daily rainfall is related to a scaling exponent defined by the power law relationship the decay process of daily rainfall within a given period preceding a given day is not independent but is interrelated and the impact of rainfall in the preceding k days on soil moisture is associated with the precipitation from the preceding k 1 days

deep flow in the madagascar mascarene basin over the last 150 000 years the sw indian ocean contains at least four layers of water masses with different sources deep antarctic lower circumpolar deep water flow to the north midwater north indian deep water flow to the south and upper circumpolar deep water to the north meridional convergence of intermediate waters at 500 1500 m and the shallow south equatorial current flowing west sedimentation rates in the area are rather low being less than 1 cm ka 1 on madagascar ridge but up to 4 cm ka 1 at amirante passage bottom flow through the madagascar mascarene basin into amirante passage varies slightly on glacial interglacial time scales with faster flow in the warm periods of the last interglacial and minima in cold periods far more important are the particularly high flow rates inferred from silt grain size which occur at warm to cold transitions rather than extrema this suggests the cause is changing density gradient driving a transiently fast flow corroboration is found in the glacial interglacial range of benthic d18o which is ca 2 suggesting water close to freezing and at least 1 2 more saline and thus more dense glacial bottom waters than present significant density steps are inferred in isotope stage 6 the 5e 5d and 5a 4 transitions oxygen isotope data suggest little change by mixing in glacial bottom water on their northward path benthic carbon isotope ratios at amirante passage differ from glacial southern ocean values due possibly to absence of a local productivity effect present in the southern ocean

the influence of diapycnal mixing on quasi steady overturning states in the indian ocean abstract a regional general circulation model gcm of the indian ocean is used to investigate the influence of prescribed diapycnal diffusivity kd on quasi steady states of the meridional overturning circulation moc the model has open boundaries at 35 s and 123 e where velocity temperature and salinity are prescribed at each time step the results suggest that quasi steady overturning states in the indian ocean are reached on centennial time scales the size and structure of the moc are controlled by the distribution of kd and the southern boundary conditions the distribution of kd required to support an overturning circulation in the model interior of a magnitude equal to that prescribed at the southern boundary is estimated using a 1d advection diffusion balance in isopycnal layers implementing this approach 70 90 of the prescribed deep inflow can be supported in quasi steady state thus one is able to address the systematic discrepancy between past estimates of the deep moc based on hydrog

ferric iron in catio3 perovskite as an oxygen barometer for kimberlite magmas ii applications we apply an oxygen barometer based on the fe content of catio3 perovskite to estimate the oxygen fugacity fo2 during the crystallization and emplacement of kimberlites in different eruptive phases of a single pipe or between different pipes clusters or provinces mineral chemical data for perovskite were compiled from the literature and obtained in our detailed study of perovskites from 11 kimberlites at somerset island and lac de gras canada perovskite compositions in kimberlites record a range in fo2 of many orders of magnitude from nno 5 to nno 6 where log fo2 is given relative to the nickel nickel oxide nno buffer the range of fo2 recorded by different parageneses of perovskite within a single pipe can vary up to three orders of magnitude with trends toward both oxidation and reduction during crystallization kimberlites record some of the greatest ranges and the highest known fo2 conditions for any terrestrial magma this is attributed to the presence of deep and oxidized source regions and the variable interplay of ferric ferrous vs carbon fluid equilibria during ascent of kimberlite magmas three kimberlite pipes from the lac de gras field show that higher fo2 values correlate with higher proportions of more resorbed diamonds suggesting that this variable has a measurable effect on the physical properties of diamonds in a pipe

dynamic earth system and ecological controls of rainfall initiated landslides abstract rainfall initiated landslides continue to inflict damages and loss of life throughout the world processes and mechanisms revealed from hydrological geomorphic geotechnical pedological geological hydrochemical and biological investigations have advanced our understanding of these effects on slope stability however the interactions amongst these processes and attributes as they affect the initiation and propagation of landslides are not as well understood too often landslide studies are conducted from only one or at most two of these perspectives moreover while precipitation and hydrology are recognized as dynamic influences the earth system and ecological effects are often assumed to be static we assess the interplay of these processes related to landslides triggered by positive pore water accretion and loss of soil suction each of these conditions arguably requires a different view on the processes that cause slope failure and predictive approaches this review starts from the perspective of dynamic adapting earth and ecological systems and discusses how these attributes relate to landslide initiation mode location and timing specifically the role that large and small scale preferential flow plays in both contributing to and mitigating instability is elucidated including effects of bedrock exfiltration we also examine how and under what conditions these pathways manifest in different soils lithology and landforms the multiple effects of rhizosphere processes on slope stability are discussed including root reinforcement evaporation from canopies and litter layers transpiration and the role of root structure affecting preferential flow paths rainfall initiated landslides involve highly dynamic hydrologic earth surface and ecological processes that persist over a range of spatial and temporal scales however guidance for overcoming these challenges has been elusive a conceptual framework is presented to shed light on these dynamic and interactive processes that should lend insights into why and when certain slopes fail during storms while other seemingly similar slopes do not fail such advances will benefit landslide hazard assessments and disaster responsiveness protocols

the development of multiple seepage faces on layered slopes this study provides an analysis of the water table configuration and hydraulic head distribution in layered hillsides a finite element model was used to simulate two dimensional saturated unsaturated steady state flow through layered slopes a laboratory sand tank experiment was used to verify the physical foundation of the mathematical model it is shown that layered slopes feature multiple seepage faces perched water tables and wedge shaped unsaturated zones the hydraulic head distribution and water table configuration are strongly dependent on the position of the impending layers and the ratio of the hydraulic conductivity between adjacent layers this work has geotechnical implications with regard to slope stability and the control of groundwater inflows into excavations it has hydrogeological implications with regard to flow path analysis in contamination studies it has geomorphological implications with respect to landform development by mass movements and surface water erosions and to drainage network development through piping

investigating landslides with space borne synthetic aperture radar sar interferometry abstract this paper is addressed to readers without advanced knowledge of remote sensing it illustrates some current and potential uses of satellite synthetic aperture radar interferometry insar for landslide assessment data acquired by sar systems can provide 3d terrain models and be used to assist in regional scale investigations e g aimed at evaluation of susceptibility of slopes to failure under favourable environmental conditions the innovative permanent scatterers ps technique which overcomes several limitations of conventional sar differential interferometry dinsar applications in landslide studies is suitable for monitoring slope deformations with millimetric precision the ps technique combines the wide area coverage typical of satellite imagery with the capability of providing displacement data relative to individual image pixels with the currently available radar satellites however only very slow ground surface displacements can be reliably detected and measured the presented case study of a landslide from the liechtenstein alps indicates that the most attractive and reliable contribution provided by this remote sensing technique lies in the possibility of i wide area qualitative distinction between stable and unstable areas and ii qualitative relative hazard zonation of large slow landslides based on the identification of segments characterised by different movement rates since only the radar line of sight projection of the displacements can be detected a quantitative exploitation of the ps data is possible only where sufficient ground truth is available in site specific or single landslide investigations the ps data can represent a very useful complementary data source with respect to the information acquired through ground based observations and in situ surveying however the difficulties associated with the feasibility assessments of the applicability of sar data to local scale problems as well as with the interpretation of ps results require a close collaboration between landslide experts and specialists in advanced processing of radar satellite data the interpretation of the exact geotechnical significance of small radar sensed ground surface deformations is challenging especially where ground truth is lacking although any ground deformation is potentially of interest to an engineering geologist detection of movements in both vertical and horizontal directions is needed in the case of landslides to evaluate slope failure mechanisms with their high radar viewing angles however the current space borne systems can detect only a fraction of the horizontal component of movement it is expected that the upcoming sar dedicated missions with new sensors and different acquisition geometries combined with the rapid developments in the field of advanced radar data processing will allow a full 3d reconstruction of deformation data and help to further reduce the current limitations of the ps and similar dinsar approaches

runoff process on a steep forested slope abstract three slope units are defined by combining nine basic slope types a convergent slope unit is called a zero order basin because it combines a slope and a stream field measurements of the runoff process of stormflow on pliocene slopes are presented pipe flow and saturated overland flow play an important part on convergent colluvial slope units surface soils significantly influence saturated throughflow on creeping middle slopes the depth of weathering has a major effect on initial moisture storage for residual and creeping slopes a subsurface storm flow pattern on a typical pliocene slope is reconstructed based on the field measurements

deep currents in the arabian sea in 1987 abstract new features of the deep circulation in the arabian sea were revealed by four sections of deep ctd o 2 stations occupied by the r r s charles darwin late in 1986 and early in 1987 during the northeast monsoon and repeated during the succeeding southwest monsoon the most prominent elements in the bottom water layer were 1 a northward flowing western boundary current of volume transport of about 4 10 6 m 3 s 1 in the southern somali basin which appeared to turn eastward at the equator and supply water to the northern somali basin from along the equator and 2 a southeastward flowing boundary current along the northeastern flank of the carlsberg ridge in the arabian basin which demonstrated that the bottom water of the arabian basin enters mainly from the somali basin through the owen fracture zone rather than from the central indian basin the strength of the boundary current in the somali basin implies an unusually large upward velocity at the top of the bottom water about 12 10 5 cm s 1 mapping of water properties in the deep water layer above the bottom water during successive monsoons was undertaken because three earlier surveys had shown differing horizontal distributions there and had thus raised the possibility of a monsoonal reversal of the circulation paralleling that in the near surface water however the patterns of variation in the salinity and oxygen fields were essentially the same on the two darwin cruises suggesting a broad southwestward flow in the deep water layer of the somali basin during both monsoons we propose that this pattern was not forced by the monsoons but reflected mainly the mean circulation of the deep water as driven by the upwelling of the bottom water from below that that pattern might be enhanced during the northeast monsoon if the wind forcing penetrates into the deep water and that a moderately strong southwest monsoon in contrast to the extraordinarily weak monsoon of 1987 would be required to disrupt this distribution of water properties

the zonal dimension of the indian ocean meridional overturning circulation abstract the three dimensional structure of the meridional overturning circulation moc in the deep indian ocean is investigated with an eddy permitting ocean model the amplitude of the modeled deep indian ocean moc is 5 6 sv 1 sv 106 m3 s 1 a broadly realistic but somewhat weak overturning although the model parameterization of diapycnal mixing is inaccurate the model s short spinup allows the effective diapycnal velocity the sum of model drift and the explicitly modeled diapycnal velocity to resemble the true real ocean diapycnal velocity for this reason the model is able to recover the broad zonal asymmetry in the turbulent buoyancy flux that is suggested by observations the model features a substantial deep depth reversing zonal circulation of nearly 50 of the moc the existence of this circulation brought about by the zonally asymmetric distribution of diapycnal mixing implies a much slower ventilation of the deep indian ocean by a factor of 5 6 than would be in place without zon

pore pressure response during failure in soils three experiments were performed on natural slopes to investigate variations of soil pore water pressure during induced slope failure two sites in the wasatch range utah and one site in the san dimas experimental forest of southern california were forced to fail by artificial subsurface irrigation the sites were instrumented with electronic piezometers and displacement meters to record induced pore pressures and movements of the slopes during failure piezometer records show a consistent trend of increasing pressure during the early stages of infiltration and abrupt decreases in pressure from 5 to 50 minutes before failure displacement meters failed to register the amount of movement due to location and ineffectual coupling of meter pins to soil observations during the experiments indicate that fractures and macropores controlled the flow of water through the slope and that both water flow paths and permeability within the slopes were not constant in space or time but changed continually during the course of the experiments

suspended sediment discharge in subsurface flow from the head hollow of a small forested watershed northern japan surface flow and suspended sediment discharge from the head hollow of the jozankei experimental watershed in hokkaido northern japan were measured to clarify the implications of subsurface hydrology for soil movement subsurface discharges during the extremely large storms of 1993 to 1994 were measured in a v notch weir installed at a natural spring near the bottom of the head hollow and shallow groundwater levels were observed in the wells excavated in the hollow sediment samples whose particle size range from 0 001 to 0 1 mm were manually and automatically collected at 15 to 60 min intervals by use of 1 or 21 polyethylene bottles maximum concentration and flux of suspended sediment during the storms preceded the peak discharge of subsurface flow by several hours neither the changes in concentration mg l 1 nor flux mg s 1 of suspended sediment coincided with those in subsurface discharge l s 1 furthermore sediment concentration was poorly correlated with the rate of change in subsurface discharge l s 2 during the rising limb of the hydrograph suspended sediment flux during the acceleratory limb however was closely correlated with the rate of change in subsurface discharge the relationship between suspended sediment flux and rate of change in subsurface discharge were in inverse proportion to initial subsurface discharge before the storm runoff and they represented rare seasonal variation subsurface hydraulic erosion and transport of suspended sediment resulting from changes in rate of change in subsurface discharge actively occur during the acceleratory rising limb of the hydrograph accordingly subsurface hydraulic erosion during the acceleratory rising limb of the hydrograph can be physically understood by analysing suspended sediment flux associated with rate of change in subsurface discharge and initial subsurface discharge 1997 john wiley sons ltd

landslide fluidization process by flume experiments abstract an almost real size slope model was used to study the generation process of landslide fluidization during torrential rain experiments were conducted by filling an inclined flume with loose sand and spraying water over the flume with a rainfall simulator to induce the sand to collapse both the movement volumetric strain and the pore water pressure of the sand were monitored throughout the experiments from the start of spraying to the cessation of the landslide our experiments showed the following 1 landslide fluidization caused by undrained sudden loading undergoes three stages compaction of the sand layer by the sliding mass from upper slope generation of excess pore water pressure in saturated zone and induction of fast shearing 2 fluidization at the collapse source area also undergoes three stages destruction and compaction of sand layer skeleton by outbreak of shearing increase of pore water pressure in saturated zone and shift to fast shearing but these three stages take place almost simultaneously

on the origins of deep and bottom waters of the indian ocean the characteristics of the deep and bottom waters of the indian ocean when illustrated on potential density anomaly surfaces indicate that the waters enter from both the atlantic and pacific oceans the paths of spreading are constrained by the complex topography and characteristics are seen to be altered by exchange with the overlying and underlying water and with the sediments especially in the northern indian ocean the weddell sea contributes to the densest waters found in the western basins and the ross sea and adelie coast to the densest waters found in the eastern basins both dense water varieties are altered by and incorporated in the less dense water above initially water carried by the circumpolar current then water from the north atlantic and finally by deep water whose characteristics are derived in the northern indian ocean contact with the sediments increases the silica content of the bottom water in the southern ocean in the northern indian ocean the sediments alter the silica of the water at the bottom and together with enhanced salinity from diffusion of saline overflows from the marginal seas above imprint unique markers to the deep water that flows back to the south at middepths the series of ridges between madagascar and australia confine the flow to a series of gyres that carry characteristics from the circumpolar current equatorward and the northern indian ocean characteristics southward within the circumpolar current low oxygen deep water from the pacific is carried across the atlantic and into the indian ocean south of africa part flows around the cyclonic weddell sea gyre and part extends across the southern ocean water from another pacific source can be seen near 2000 m extending westward from the tasman sea south of aus tralia and across the indian ocean and perhaps to the aghulas current region southeast of africa in this study we show some maps of deep and bottom water characteristics of the indian ocean which may be used in a qualitative sense to infer pathways of spreading of water below a depth of about 2000 m the indian ocean has numerous ridges and basins figure 1 that severely restrict possible pathways of deep and bottom wa ter flow in the following we will begin by looking at char acteristics at the bottom of the ocean to reveal the path ways of spreading of the densest bottom waters from basin to basin then a series of six potential density anomaly surfaces at progressively shallower depths from about 4000 m up to about 2000 m will be shown to see what character istics influence the deep waters and how pathways of flow are constrained by the bathymetry of the indian ocean the choice of the specific density levels table 1 was based primarily on various property extrema shown by the 18os atlantis ii cruise 93 colored sections that accompany warren s 1981 detailed discussion of the major features of the central indian ocean between madagascar and aus tralia the sections approximately midway between antarctica and the northern indian ocean boundaries are well positioned to show features originating from both the north and the south as well as some brought into the indi an ocean by the antarctic circumpolar current the full ocean area isopycnal maps provide essential evidence on the origins and fates of features seen in the sections and

petrology of the hypabyssal kimberlite of the kroonstad group ii kimberlite orangeite cluster south africa evolution of the magma within the cluster abstract we report here a detailed petrographic study accompanied by the first whole rock major and trace element geochemical analyses as well as the first sr and nd isotope data for the kroonstad group ii kimberlite cluster hypabyssal kimberlite is described from the lace voorspoed and besterskraal north kimberlite pipes the lace kimberlite is a monticellite phlogopite kimberlite with mineralogy and geochemistry more similar to typical group i kimberlites the voorspoed kimberlite is an aegirine and sanidine bearing kimberlite and along with the geochemistry shows a more evolved composition relative to the lace kimberlite the besterskraal north kimberlite is a highly evolved type group ii kimberlite containing abundant k richterite sanidine aegirine and leucite the magma evolutionary trend is linked to a variation in olivine macrocryst abundance the lace unevolved magma contains abundant olivine macrocrysts and has not been affected by significant fractionation whereas the voorspoed and besterskraal north kimberlite contain far fewer olivine macrocrysts which indicates that significant fractionation has affected these magmas en route to the surface we evaluate the potential for fractionation to result in differentiation of a common parent magma or magma generated from a common source en route to the surface this process is complicated by the fact that olivine macrocrysts are essentially xenocrysts within the magma and the loss of these xenocrysts will not affect the primary magma composition furthermore we present two alternate hypotheses for the evolution of the magmas a contamination en route to the surface and b varying degrees of partial melting at the source the evolutionary trend is also linked with diamond characteristics in particular diamond parcels at the voorspoed pipe between 1906 and 1911 were deficient in large stones which indicate that fractionation has likely also removed the large stones from the voorspoed magma along with the olivine macrocrysts

on slope instability induced by seepage erosion this paper is focused on seepage erosion causing liquefaction processes and rapid slope failures one case history which occurred along an old fluvial terrace in the po plain northern italy is