glacial interglacial temperature change in the tropical west pacific a comparison of stalagmite based paleo thermometers in the tropics geochemical records from stalagmites have so far mainly been used to qualitatively reconstruct changes in precipitation but several new methods to reconstruct past temperatures from stalagmite material have emerged recently i liquid vapor homogenization of fluid inclusion water ii noble gas concentrations in fluid inclusion water iii the partitioning of oxygen isotopes between fluid inclusion water and calcite and iv the abundance of the 13 c 18 o 16 o clumped isotopologue in calcite we present for the first time a direct comparison of these four paleo thermometers by applying them to a fossil stalagmite covering nearly two glacial interglacial cycles marine isotope stages mis 12 9 and to two modern stalagmites all from northern borneo the temperature estimates from the different methods agree in most cases within errors for both the old and recent samples reconstructed formation temperatures of the recent samples match within 2 sigma errors with measured cave temperatures however slight but systematic deviations are observed between noble gas and liquid vapor homogenization temperatures whereas the temperature sensitivity of fluid inclusion 18 o and clumped isotopes is currently debated we find that the calibration of tremaine et al 2011 for fluid inclusion 18 o and a synthetic calcite based clumped isotope calibration ziegler et al in prep yield temperature estimates consistent with the other methods all methods with the potential exception of clumped isotopes show excellent agreement on the amplitude of glacial interglacial temperature change indicating temperature shifts of 4 5 c this amplitude is similar to the amplitude of mg ca based regional sea surface temperature records when correcting for sea level driven changes in cave elevation our reconstruction of tropical temperature evolution over the time period from 440 to 320 thousand years ago ka adds support to the view that climate sensitivity to varying greenhouse forcing is substantial also in the deep tropics

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

late holocene high resolution glacial chronologies and climate kenai mountains alaska recent retreat of outlet glaciers from the harding and grewingk yalik icefields has revealed a vast array of deposits on the eastern and western flanks of the kenai mountains that records multiple glacier advances into coastal forests during late holocene time treering dating together with radiocarbon and lichenometric analyses allows for the reconstruction of these glacial fluctuations to decadal precision over the past two thousand years the records of fluctuations are derived from 16 land terminating and seven tidewater glaciers in three fjord systems as well as two cirque glaciers three major intervals of holocene glacier expansions are evident they occurred about 3600 yr b p 600 a d and during the little ice age from 1300 to 1850 a d the earliest expansion beyond present ice margins is known only from the mccarty tidewater glacier the 600 a d event involved the simultaneous advance of land terminating and tidewater glaciers during the little ice age however tidewater glaciers were advancing several centuries prior to their land terminating neighbors those land terminating glaciers on the western mountain flank retreated from their little ice age maxima as much as two centuries before those on the eastern mountain flank land terminating tongues on the eastern more maritime mountain flank have shown more sensitivity to variations in winter precipitation during the little ice age and within recent decades than the more continental glaciers on the western flank that are affected more by summer temperatures the glacial and climatic records suggest that advances of the ice tongues from about 1420 to 1460 a d between 1640 and 1670 a d at about 1750 a d and from 1880 to 1910 a d reflected times of increased winter precipitation advances between 1440 to 1460 a d from 1650 to 1710 a d and from 1830 to 1860 a d followed intervals of lower summer temperatures

the relationship between current and paleo groundwater base levels abstract base levels are basically divided into two categories oceanic and marine base levels and continental terminal endorheic ones the marine domain serves as the ultimate base level for both surface and groundwater drainage systems continental inland depressions very often serve as terminal endorheic base levels to both surface drainage and groundwater systems many of the current both marine and inland base levels served also in the past as paleo base levels fluctuations of base level elevations affect the adjoined groundwater system in several ways such as changes in groundwater levels location of divides depths of fresh saline water interfaces and the amount of flow to the base levels this paper provides examples from many different parts of the world that describe the relationship between current and paleo base levels the examples include marine base levels as well as inland endorheic ones both currently above and below sea level close to and distant from the sea

hydromechanical triggering of landslides from progressive local failures to mass release 1 water infiltrating during intense rainfall on steep slopes gradually weakens the wet soil mass inducing localized failures that may initiate a cascade of load redistributions and successive failures propagating across a hillslope the challenge of linking the progressive nature of local events culminating in an abrupt landslide is addressed by a new hydromechanical triggering model that links key hydrologic processes with threshold based mechanical interactions a hillslope is represented as assembly of soil columns interconnected by frictional and tensile mechanical bonds represented as virtual bundles of fibers increasing water load exerted on mechanical bonds causes gradual failure of fibers until restraining forces are exceeded following failure at the soil bedrock interface the load on a column is redistributed to its neighbors via intact mechanical primarily tensile bonds which in turn may also fail and transmit the load downslope as compressive stresses when soil internal compressive strength is exceeded a load bearing column may liquefy and initiate a landslide release that could propagate downslope or retrogressively upslope the model reproduces observed power law frequency magnitude relationships of landslides with exponents ranging between 1 0 and 2 2 in agreement with landslide inventory data we applied a criticality measure defined by ramos 2011 to evaluate the specific influences of slope angle soil texture and root reinforcement on attainment of hillslope criticality in which a small local failure may trigger release of a large soil mass the model provides new insights on the conditions giving rise to an abrupt transition from a seemingly stable hillslope to a catastrophic landslide

the arid humid transition in the sahara and the sahel during the last deglaciation at the time of the last glacial maximum the sahara and sahel regions of north africa were extremely dry new records of rainfall show that during the subsequent deglaciation the transition from arid to humid conditions in these regions occurred synchronously in two main steps comparison with other records of palaeoclimate in europe and the north atlantic ocean shows that certain common factors controlled changes in ocean and atmosphere dynamics during the deglaciation

neural network modeling applications in active slope stability problems a back propagation artificial neural network approach is applied to three common challenges in engineering geology 1 characterization of subsurface geometry position of the slip or failure surface of active landslides 2 assessment of slope displacements based on ground water elevation and climate and 3 assessment of groundwater elevations based on climate data series of neural network models are trained validated and applied to a landslide study along lake michigan and cases from the literature the subsurface characterization results are also compared to a limit equilibrium circular failure surface search with specific adopted boundary conditions it is determined that the neural network models predict slip surfaces better than the limit equilibrium slip surface search using the most conservative criteria displacements and groundwater elevations are also predicted fairly well in real time the models ability to predict displacements and groundwater elevations provides a foundational framework for building future warning systems with additional inputs

optical dating of aeolian dynamism on the west african sahelian margin abstract the sahelian margin of west africa is widely recognised as an area of recent environmental catastrophe and human suffering arising from food shortage and land degradation associated with prolonged drought the propensity of this region to suffer drought has been related using environmental data collected during the period of instrumental records to a combination of low mean annual rainfall levels and a high degree of rainfall variability which relates to sea surface temperature anomalies in the adjacent tropical atlantic ocean despite the significant environmental and human consequences of such droughts there is a paucity of long term environmental data for the west african sahel aeolian dune reactivations in this area are a potentially highly useful environmental archive of past periods of extended drought conditions which may have resulted in localised or widespread dune reactivation here we describe the initial results from an ongoing programme of research which seeks to develop a detailed record of past dune reactivations in mali we find evidence for repeated holocene dune reactivation events and a significant number of reactivations which commenced at the time of onset of the last major drought cycle in the early 1970s we obtain ages as young as 20 30 years for some significant dune units thickness up to 1 m and describe the results of experiments which test the performance of our dating exercise we specifically test for the significance of preheat temperature on single aliquot regeneration sar equivalent dose determinations and recycling ratios neither are found vary significantly as a function of preheating optical dating of sand sized quartz could provide a useful tool for palaeogeographical mapping of ancient and historical dune reactivations in this region and elsewhere

snowline depression in the tropics during the last glaciation five primary methods have been used to reconstruct pleistocene snowlines or equilibrium line altitudes elas in the tropics 23 53n 23 53s during the last glaciation but each has inherent errors that limit the accuracy of the results additional potential errorsin determiningela depression involveestimates of modernsnowline altitude datingresolution topographicreconstructionof former glaciers orographic e ects the presence of rockfall debris on glaciers and calculation of regional ela gradients eustatic sea level lowering during the last glaciation is an additional factor in uencing estimates of ela depression ela in cases where modern snowline lies above a mountain summit only a minimum value for ela can be obtained at 12 tropical sites in africa the americas to 103s latitude and paci c islands estimates of average ela range from 440 to 1400m but most fall in the range of 800 1000m mean 1 900 135m in a regional study of ela depression in the southern tropical andes 8 223s an average ela of ca 920 250m has been reported based on the assumption that glacier mass balance was controlled solely by ablation season temperature and assuming a full glacial temperature lapse rate of 63c km depression of mean annual temperature in glaciated alpine areas was ca 5 4 0 83c if adjusted for a sea level fall of 120m at the glacial maximum this value is reduced to 4 7 0 83c the gure is based on the unlikely assumption that accumulation on alpine glaciers has been invariant nevertheless it is similar to values of temperaturedepresson 5 6 43c for the last glaciationobtainedfrom variousterrestrial sites but contrasts with tropical sea surface temperature estimates that are only 1 33c cooler than present 2001 elsevier science ltd all rights reserved

experimental investigation on progressive deformation of soil slope using acoustic emission monitoring abstract the deformation process of soil slopes observed during a landslide can have progressive characteristics which can be quantified through acoustic emission ae monitoring a model test is designed based on the geological model of a translational landslide and experiments are conducted to reproduce the three stage deformation process of a soil slope the deformation process of progressive landslides is described using equations and an entire loading process is realized using a programmable logic controller plc the maximum velocity of a sliding body is measured to be approximately 6 mm s with the final displacement exceeding 210 mm the ae deformation and mechanical measurements of the entire process are compared to comprehensively evaluate the evolution behavior of progressive soil landslides the experiments demonstrate that ae rates can linearly quantify slope velocity as well as help quantify slope acceleration a copper tube and an aluminum tube are compared as different waveguides and the quantitative relationship between the ae and deformation obtained by the active copper waveguide is found to be more distinct the experiments also show that the acceleration of a slope can be effectively used as a discriminant index of progressive landslides which has the potential to be applied in field monitoring

evidence for periods of wetter and cooler climate in the sahel between 6 and 40 kyr bp derived from groundwater 1 concentrations of noble gases stable isotopes and 14c in samples from the continental terminal groundwaters of niger provide evidence for more humid and cooler climate phases in west africa in the holocene and the late pleistocene during humid phases even within the holocene the soil temperature was up to 5 5 c cooler than today which is partly attributed to atmospheric cooling but also to a change in the relationship between air and soil temperature due to increased vegetation intense rainfall events and increased groundwater recharge are consistently indicated by stable isotope data and excess air concentrations i e the component of dissolved atmospheric gases in excess of solubility equilibrium this finding encourages the use of excess air as an additional humidity related climate indicator

controls on the size and geometry of landslides insights from discrete element numerical simulations abstract we use numerical two dimensional discrete element method dem to study the controls on the size and geometry of an individual landslide this method allows us to analyze the temporal and spatial evolution of slope failure and landsliding from the intact pre failure slope to the restabilized post failure slope the size of our simulated landslides reflects the amount of disintegrated material available for sliding which is controlled by the peak strength of the slope material and to a lesser degree by the pre failure slope angle the observed size of natural landslides therefore reflects mainly the local natural material strengths we hypothesize that the observed global characteristic landslide size is a result of the limited thickness generally up to a few meters of disintegrated and weathered material that exists on hillslopes poised and ready for sliding the primary controls on the landslide geometry quantified as the ratio of their thickness to length t l prove to be the residual friction angle of the slope material and the original slope angle the t l is observed to be unchanged for a given initial slope angle and independent of the slope material peak strength or the slope height we suggest that the narrow range of observed natural t l is a result of narrow ranges of mechanical properties and initial slope geometries involved in natural slope failure

properties and microstructure of a natural slip zone in loose deposits of red beds southwestern china abstract the loose deposits of red beds located in southwestern china are vulnerable to the occurrence of landslides in this paper a shallow progressive landslide developed in loose deposits of red beds was selected as a case study and the physical and mechanical properties of the main slip zone were analyzed in detail it was observed that the main slip zone of the progressive landslide is composed of fine grained soils with substantial amounts of expansive clay particles interlayered illite smectite and interlayered chlorite smectite the one dimensional consolidation test of the residual soils shows that the soils are overconsolidated the shear stress versus shear displacement curves reveal that the slip zone soil has exhibited a strain softening behavior the residual friction angle of the undisturbed slip zone soil determined by the ring shear tests is 7 2 indicating that the residual strength of the soil is very low when in a saturated state the microstructure of the slip zone was investigated using a combination of images captured by means of polarising microscopy pm and scanning electron microscope sem techniques it was found that the slip zone possessed generally softer structure with higher relative porosities than its confining materials the microstructure of the slip zone is generally characterized by its softer structure and higher degree of alignment of fine silts suggesting that the slip zone underwent two deformation processes i e dilatancy and particle rearrangement the global mechanical behavior of the investigated slip zone may be conceptualized as an overconsolidated clayey soil under drained conditions

forecasting the magnitude of potential landslides based on insar techniques abstract a new method combining empirical modeling with time series interferometric synthetic aperture radar insar data is proposed to provide an assessment of potential landslide volume and area the method was developed to evaluate potential landslides in the heitai river terrace of the yellow river in central gansu province china the elevated terrace has a substantial loess cover and along the terrace edges many landslides have been triggered by gradually rising groundwater levels following continuous irrigation since 1968 these landslides can have significant impact on communities affecting lives and livelihoods developing effective landslide risk management requires better understanding of potential landslide magnitude fifty mapped landslides were used to construct an empirical power law relationship linking landslide area al to volume vl vl 0 333 al1 399 insar derived ground displacement ranges from 64 mm y to 24 mm y along line of sight los further interpretation of patterns based on remote sensing insar optical image and field survey enabled the identification of an additional 54 potential landslides 1 9 102 m2 al 8 1 104 m2 in turn this enabled construction of a map that shows the magnitude of potential landslide activity this research provides significant further scientific insights to inform landslide hazard and risk management in a context of ongoing landscape evolution it also provides further evidence that this methodology can be used to quantify the magnitude of potential landslides and thus contribute essential information towards landslide risk management

drought and dust deposition in the west african sahel a 5500 year record from kajemarum oasis northeastern nigeria a high resolution multiproxy palaeolimnological record from the manga grasslands northeastern nigeria spanning the last 5500 calendar years reveals the episodic deterioration in sahelian climate as significant biogeophysical thresholds were crossed desert dust deposition began to increase 4700 cal bp rainfall during the summer monsoon season declined permanently after 4100 cal bp a further significant change in atmospheric circulation giving rise to multidecadal to centennial scale droughts and enhanced dust deposition occurred 1500 cal bp hence the post 1968 sahel drought is not unique the prolonged arid episode that occurred around 1200 1000 cal bp in ethiopia the sahel and tropical mexico may have been linked to an abrupt cooling event in the north atlantic and to a cluster of intense el nino southern oscillation events in the eastern equatorial pacific

dust clouds rain types and climatic variations in tropical north africa abstract dust and processes of raindrop formation in the clouds play a very important role in the climatic evolution of tropical north africa sedimentologic stratigraphic pedologic geomorphologic and palynologic data converge to show that a major environmental change occurred in tropical africa about 7000 yr b p in the sudanian and sudano guinean zones wet tropical zone from 15 000 to 7000 yr b p rivers deposited mostly clay while from 7000 to 4000 yr b p they deposited mostly sand during the first period pedogenesis was vertisolic montmorillonite dominant associated with pollen belonging mostly to vegetation typical of hydromorphic soils while during the second period pedogenesis was of ferruginous type kaolinite dominant with pollen belonging mostly to vegetation typical of well drained soils the great change near 7000 yr b p is linked chiefly to a major hydrological change that appears related to a change in the size of raindrops from fine rains associated with considerable atmospheric dust raindrop diameter essentially less than 2 mm to the second period associated with thunderstorm rains raindrop diameter mostly greater than 2 mm the size of raindrops is related particularly to cloud thickness and dust concentration in the troposphere thunderstorm activity is influenced also by fluctuations of the atmospheric electricity modulated by the sun

forecasting giant catastrophic slope collapse lessons from vajont northern italy rapid giant landslides or sturzstroms are among the most powerful natural hazards on earth they have minimum volumes of similar to10 6 10 7 m 3 and normally preceded by prolonged intervals of accelerating creep are produced by catastrophic and deep seated slope collapse loads similar to1 10 mpa conventional analyses attribute rapid collapse to unusual mechanisms such as the vaporization of ground water during sliding here catastrophic collapse is related to self accelerating rock fracture common in crustal rocks at loads similar to1 10 mpa and readily catalysed by circulating fluids fracturing produces an abrupt drop in resisting stress measured stress drops in crustal rock account for minimum sturzstrom volumes and rapid collapse accelerations fracturing also provides a physical basis for quantitatively forecasting catastrophic slope failure c 2003 elsevier science b v all rights reserved

correlation of alaskan varve thickness with climatic parameters and use in paleoclimatic reconstruction the thickness of varves in the sediments of skilak lake alaska are correlated with the mean annual temperature r 0 574 inversely correlated with the mean annual cumulative snowfall r 0 794 and not correlated with the mean annual precipitation r 0 202 of the southern alaska climatological division for the years 1907 1934 a d varve thickness in skilak lake is sensitive to annual temperature and snowfall because skilak glacier the dominant source of sediment for skilak lake is sensitive to these climatic parameters trends of varve thickness are well correlated with trends of mean annual cumulative snowfall r 0 902 of the southern alaska climatological division and with trends of mean annual temperature of the southern r 0 831 and northern r 0 786 alaska climatological divisions trends of varve thickness also correlate with trends of annual temperature in seattle and north head washington r 0 632 and 0 850 respectively comparisons of trends of varve thickness with trends of annual temperature in california oregon and washington suggest no widespread regional correlation trends of annual snowfall in the southern alaska climatological division and trends of annual temperature in the southern and northern alaska climatological divisions are reconstructed for the years 1700 1906 a d climatic reconstructions on the basis of varve thickness in skilak lake utilize equations derived from the regression of series of smoothed climatological data on series of smoothed varve thickness reconstruction of trends of mean annual cunulative snowfall in the southern alaska climatological division suggests that snowfall during the 1700s and 1800s was much greater than that during the early and mid 1900s the periods 1770 1790 and 1890 1906 show marked decreases in the mean annual snowfall reconstructed trends of the annual temperature of the northern and southern alaska climatological divisions suggest that annual temperatures during the 1700s and 1800s were lower than those of the early and mid 1900s two periods of relatively high annual temperatures coincide with the periods of low annual snowfall thus determined

characteristics and dynamic runout analyses of 1983 saleshan landslide abstract in 1983 a catastrophic landslide occurred in saleshan dongxiang gansu china which resulted in the death of 237 people and the destruction of 585 houses saleshan landslide was a rapid moving landslide in loess area china which moved with long run out distance on a gentle sliding surface this paper reviews the characteristics of the landslide and its consequence analyzes the possible triggers and the processes of development and back calculates the kinematic characteristics of the landslide the digital elevation models dems of the study area before and after the event were used to analyze the geomorphological characteristics before and after the event the authors inferred the possible deformation and failure processes of the landslide based on available observations direct shear tests were carried out to obtain the parameters of the soil involved in the failure and post failure process which was adopted in the following simulation using an energy based runout model the velocities of moving materials at a different time stage together with the variation of runout distance and maximum flow height are presented the authors also compared the calculated results with field observations and previous simulation results sensitivity analysis was conducted to understand the effect of internal and basal friction angles on the kinematic characteristics this study indicates that the saleshan landslide was a fast moving landslide with long traveling distance the landslide lasted more than one minute with a maximum velocity of approximately 25 m s according to the calculation using the energy based runout model which was consistent with the estimations based on the observation of eyewitness this study also gives an insight on the progressive failure mechanism and explains the high mobility of saleshan landslide in details which provides a reference for hazard zonation for areas along loess platforms

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

circulation changes and nutrient concentrations in the late quaternary aegean sea a nonsteady state concept for sapropel formation sapropel forming conditions we identify the start of seasonal stratification and highlight a lag in d 18 o response of the planktonic foraminifer n pachyderma to termination t1b as identified in the d 18 o record of g ruber by use of a simple model we determine that this offset cannot be a function of bioturbation effects the lag is of the order of 1 kyr and suggests that isolation of intermediate deep water preceded the start of sapropel formation by up to 1 5 kyr using this discovery we propose an explanation for the major unresolved problem in sapropel studies namely the source of nutrient supply required for export productivity to reach levels needed for sustained sapropel deposition we suggest that nutrients had been accumulating in astagnant basin for 1 1 5 kyr and that these accumulated resources wereutilized duringthe deposition of s1 in addition we provide a first quantitative estimate of the diffusive 1 e mixing timescale for the eastern mediterranean in its stratified sapropel mode which is of the order of 450 years index terms 1050 geochemistry marine geochemistry 4835 4850 3030 marine geology and geophysics micropaleontology 3339 meteorology and atmospheric dynamics ocean atmosphere interactions 0312 4504 4267 oceanography general paleoceanography 4870 oceanography biological and chemical stable isotopes keywords sapropel mediterranean holocene foraminifera climate variability

long term dynamics of rockslides and damage propagation inferred from mechanical modeling 1 long term observations of large active rockslides show accelerating deformation over many thousands of years since the last deglaciation the effect of deglaciation on slope stability is however poorly understood due to 1 limited long term observations and 2 a complex interaction between glacier retreat and hydrogeological mechanical and morphological processes to assess the sensitivity of rockslide dynamics to these different processes a model of progressive damage through intact rock mass is developed in this study based on the finite element method this model uses time to failure laws based on rock laboratory creep experiments it is able to reproduce progressive damage localization along shear bands associated with strain rate acceleration as observed during tertiary creep the model reproduces the different phases of deformation associated with morphologies typical of large rockslides this model is thus suitable for simulating the dynamics of large rockslides and the transition from initiation to rapid sliding the sensitivity of rockslide kinematics and morphology to different mechanical properties is analyzed this analysis shows that the time evolution of the rockslide can be inferred with the knowledge of only one time parameter independent of the knowledge of the mechanical properties of the rock mass this parameter is here chosen as the time when the summit slope displacement has reached 10 m a parameter that can be estimated with cosmogenic dating the model is then used to study the effects of deglaciation on the valley flank stability and the formation of large rockslides this study shows that the deglaciation velocity can affect the morphology of the rockslide with the shear band of the rockslide emerging at higher elevation as the velocity decreases we also show that the response to the deglaciation can last several thousands of years after the glacier retreat

morpho structural evolution of the valley slope systems and related implications on slope scale gravitational processes new results from the mt genzana case history central apennines italy abstract this work is aimed at constraining a slope scale deep seated gravitational slope deformation dsgsd and an associated rockslide avalanche in the frame of the quaternary morpho structural evolution of central apennines italy the study area is the western slope of the mt genzana calcareous ridge for which a conceptual slope evolutionary model had been already proposed the existing model has highlighted the role of inherited geological structural setting combined with quaternary morpho evolution in the onset of rock slope deformational processes until paroxysmal phases i e occurrence of massive rock slope failures in this work the previous conceptual evolutionary model was strengthened and detailed by means of a mid term landscape evolution model based on the study of geomorphic markers hanging at different elevations above the present valley floor the quaternary landscape evolution was also constrained by means of time dependent landscape metrics consequently it was possible to back analyse the observed dsgsd process from its onset up to the occurrence of localized massive rock slope failures through a time dependent stress strain numerical modeling the results of such a multi modeling approach i highlighted the importance of rock mass creep during some stages of the morpho evolution ii pointed out the relevant role of the inherited structural pattern in identifying the preferential strain concentration zones and failure surfaces and iii confirmed the hypothesis that the scanno rockslide avalanche scar is the result of two separate failure events as an initial landslide involving the lower part of the slope that favoured a subsequent failure in the upper part of the slope

patterns of movement in rotational and translational landslides the movement of rotational and translational landslides occurs as a result of either sliding on discrete shear surfaces or ductile deformation within a shear zone in this paper we examine the movement histories of a number of landslides that occurred in a variety of materials in a range of settings and demonstrate that one of two movement styles is evident during accelerating phases for all landslides observed the first style which has previously been noted has a linear form in a plot of 1 v against time v is velocity the second style has an asymptotic form in the same plot trending toward steady state movement rates we propose that the linear form occurs in landslides in which crack propagation i e shear surface generation is the dominant process whereas the second style occurs where movement is taking place across existing planes of weakness or as a result of ductile deformation processes this study demonstrates that the evaluation of plots of 1 v against time for landslides is a useful technique for forecasting movement styles and rates and for interpreting ongoing deformation processes in real time

estimating paleorecharge and paleoclimate from unsaturated zone profiles unsaturated zone solute and isotope profiles may be interpreted in terms of past changes in recharge rate in cases where water movement can be approximated by piston flow a model is presented which describes water movement in terms of piston flow below a surface mixing layer below the mixing layer diffusion and dispersion occur in the liquid phase in the case of solutes and in both the liquid and gas phases in the case of isotopically labeled water climatic events of 4 5 years duration may be preserved in the unsaturated zone for more than 50 years if the recharge rate is greater than approximately 20 mm yr 1 longer term fluctuations in climatic conditions century scale might be preserved for over 1000 years provided the recharge rate is greater than approximately 2 mm yr 1 and the unsaturated zone is sufficiently deep profiles from cyprus and northern senegal appear to record changes in recharge rate over periods up to 400 years the profiles are well correlated with known variations in rainfall and fluctuations in lake levels the model provides limiting conditions to be applied to the interpretation of profiles

applying terzaghi s method of slope characterization to the recognition of holocene land slippage abstract during site investigations engineering geologists are expected to recognize landslides both active and dormant those without substantial experience evaluating the evolution of geomorphic features associated with localized mass wasting often mischaracterize site conditions karl terzaghi suggested seven steps in characterizing natural hillslopes including 1 a literature review 2 site reconnaissance 3 a program of subsurface exploration 4 preparation of sketches and diagrams illustrating the essential features 5 preparation of a preliminary geology report 6 observation and mapping of geologic structures exposed during excavation for construction and 7 development of contingency plans for anticipated variations in old landslide features based on our interpretation of terzaghi s original principles we review some of the most common interpretive problems with nomenclature of landslide features describe common mistakes in characterizing old landslides and present technical approaches that often aid in the recognition of old landslide features a wide variance in geological terms exists for describing landslides and various terms have been applied to the same features by workers in different areas which often leads to confusion some of these terms include nomenclature such as slip surfaces alluvial fans colluvium and slope creep active surficial landslides are relatively easy to recognize when they are well exposed although these features tend to become obscured with time anomalous hummocky topography often provide key recognition features of a slope s geomorphic evolution deeper seated bedrock landslides can be more difficult to recognize because their features become increasingly mollified with time these features can often be identified by anomalous geomorphic features such as isolated saddles or anomalous discontinuous benches these features are some of the best locations to excavate borings or exploratory trenches well placed trenches across headscarp grabens can provide more detailed structure of old landslides and are usually a cost effective approach additional subsurface exploration can often be employed to characterize landslides small diameter borings are usually employed for geotechnical investigations but can easily be applied to landslides depending on the mean particle size diameter d50 downhole logging of large diameter holes is the best method to evaluate complex subsurface conditions such as dormant bedrock landslides

stability analysis of a human influenced landslide in eastern belgium article i nfo the area of the pays de herve in eastern belgium is strongly affected by recent landslide activity dormant landslides are widespread in the region and some of these dormant landslides have been reactivated by human activity such as highway construction suburban development or building of industrial sewage pipes the investigated landslide was reactivated by heavy rainfall events in the late 1990s during this reactivation an existing industrial sewage pipe was damaged and the chemically loaded waste water drained into the landslide mass the current landslide movement is assumed to be heavily influenced by the additional water supply as well as by the chemical activity of univalent ions in the clay fraction leading to a decreased shear resistance consequently the movement triggering rainfall thresholds are reduced and result in a decreased overall slope stability this study describes a general methodology of field investigation data collection and laboratory testing for an exploratory study influences of chemical properties of soil and soil water and their effects on landslide stability are analysed discussed and related to findings of other studies although no clear empirical evidence for a dependency between slope stability and ionic loaded soil water was found in this study we suggest the existence for such a relationship we conclude that this particular landslide would not have moved based on current environmental conditions the leaking waste water might favour current landslide movement

co evolution of riparian vegetation and channel dynamics in an aggrading braided river system mount pinatubo philippines increased bank stability by riparian vegetation can have profound impacts on channel morphology and dynamics in low energy systems but the effects are less clear in high energy environments here we investigate the role of vegetation in active aggrading braided systems at mount pinatubo philippines and compare results with numerical modeling results gradual reductions in post eruption sediment loads have reduced bed reworking rates allowing vegetation to finally persist year round on the pasig potrero and sacobia rivers from 2009 2011 we collected data detailing vegetation extent type density and root strength incorporating these data into the riproot model and bstem bank stability and toe erosion model shows cohesion due to roots increases from zero in unvegetated conditions to 10 2 kpa in densely growing grasses field based parameters were incorporated into a cellular model comparing vegetation strength and sediment mobility effects on braided channel dynamics the model shows both low sediment mobility and high vegetation strength lead to less active systems reflecting trends observed in the field the competing influence of vegetation strength versus channel dynamics is a concept encapsulated in a dimensionless ratio between timescales for vegetation growth and channel reworking known as t an estimated t between 1 5 and 2 3 for the pasig potrero river suggests channels are still very mobile and likely to remain braided until aggradation rates decline further vegetation does have an important effect on channel dynamics however by focusing flow and thus aggradation into the unvegetated fraction of braidplain leading to an aggradational imbalance and transition to a more avulsive state the future trajectory of channel vegetation interactions as sedimentation rates decline is complicated by strong seasonal variability in precipitation and sediment loads driving incision and armoring in the dry season by 2011 incision during the dry season was substantial enough to lower the water table weaken existing vegetation and allow for vegetation removal in future avulsions copyright 2015 john wiley sons ltd

hydrologic response of the crow wing watershed minnesota to mid holocene climate change in this study we have integrated a suite of holocene paleoclimatic proxies with mathematical modeling in an attempt to obtain a comprehensive picture of how watersheds respond to past climate change a three dimensional surface water groundwater model was developed to assess the effects of mid holocene climate change on water resources within the crow wing watershed upper mississippi basin in north central minnesota the model was first calibrated to a 50 yr historical record of average annual surface water discharge monthly ground water levels and lake level fluctuations the model was able to reproduce reasonably well long term historical records 1949 1999 of water table and lake level fluctuations across the watershed as well as stream discharge near the watershed outlet the calibrated model was then used to reproduce paleo groundwater and lake levels using climate reconstructions based on pollen transfer functions from williams lake just outside the watershed computed declines in mid holocene lake levels for two lakes at opposite ends of the watershed were between 6 and 18 m simulated streamflow near the outlet of the watershed decreased to 70 of modern average annual discharge after 200 yr the area covered by wetlands for the entire watershed was reduced by 16 the mid holocene hydrologic changes indicated by these model results and corroborated by several lake core records across the crow wing watershed may serve as a useful proxy of the hydrologic response to future warm dry climatic forecasts ca 2050 made by some atmospheric general circulation models for the glaciated midwestern united states

holocene landscape evolution of the manga grasslands ne nigeria evidence from palaeolimnology and dune chronology this paper presents a synthesis of results from investigations into palaeolimnology and dune chronology in the manga grasslands and adjacent areas of ne nigeria in order to reconstruct the evolution of this semi arid landscape since the late glacial a marked wet phase gave way to a fall in lake levels during the late glacial dune emplacement was active at this time to the south of the manga grasslands but seems to have been absent from the grasslands themselves wet conditions prevailed during much of the early to mid holocene accompanied by periods of significant barchanoid dune reactivation a marked deterioration in climate and vegetation commenced around 4 1 ka bp leading to the formation of the present day semi arid landscape the data suggest that there have been major changes in humidity in this part of subsaharan west africa during the late glacial to holocene and that the relationship between changes in precipitation and aeolian activity is complex

paleoclimatic investigations using isotopic signatures of the late pleistocene holocene groundwater of the stratified aquifers in kuwait abstract the study attempts to determine paleo recharge sources for two major aquifer units of kuwait namely kuwait group aquifer kga and dammam formation dfm were collected and analyzed for major ions and isotopes the obtained results of 14c ages indicated that the groundwater samples ranged from 31 9 ky to 3 9 ky in dfm and 23 3 ky to 0 8 ky in kga the variations in 18o signatures with respect to age reflected that there were two major sources of rainwater such as enriched southern indian ocean monsoon and the depleted northwesterly mediterranean vapor source the samples found to show variations during the three marine isotopic stages mis 1 3 heinrich events bolling allerod and dryas time periods in both aquifers a shift in the intertropical convergence zone itcz was witnessed in the groundwater of both aquifers from 7 8 ky to 4 9 ky the variation in the holocene climate is mainly due to the influence of tropospheric easterly jet governed by the swing in itcz as a result of holocene volcanism the mean 18o values of dfm samples 3 81 reflect depletion than kga samples 2 31 and the d excess values were 0 95 and 2 05 respectively thus it could be inferred that the dfm was predominantly recharged during late pleistocene period and it was in a relatively cooler climate than recharge environment of kga the study infers that kga was recharged between 26on and 26 8on latitudes and that of the dfm was noted to be recharged south west of kuwait in two different patches between 25 8on and 26 2on and 26 7on 27 4on latitudes during late pleistocene the kga was concluded to be recharged between 25 5on and 27 5on latitudes south of kuwait during holocene

flow pattern and residence time of groundwater within the south eastern taoudeni sedimentary basin burkina faso mali the knowledge about groundwater flow conditions within the southeastern taoudeni basin aquifer shared by burkina faso and mali is relatively limited with very little information on potentiometric heads recharge processes residence time and water quality a better evaluation of groundwater resources in this area is a strategic point for water resources management in the entire soudano sahelian region which endures since the beginning of the twentieth century a continuous decrease in precipitation amount this paper provides a transboundary synthesis using water 18o 2h and 3h and carbon isotopes 13c and 14c in conjunction with hydrogeological and hydrochemical data the objectives are to improve the conceptual model of groundwater recharge and flow within this sandstone reservoir and to assess the changes in the aquifer due to water abstraction and recent climate changes including an insight into sahelian aquifers palaeorecharge processes the local meteoric water line for the bobo dioulasso station is proposed 2h 8 0 0 5 18o 10 2 2 1 two main tendencies can be derived from groundwater chemistry first a slight evolution from the ca mg hco3 type towards a na k hco3 type that indicates developed interactions between groundwater and clay minerals related to the residence time of groundwater a second tendency towards cl no3 so4 hco3 water types indicates the anthropogenic influence on groundwater related to the poor sanitary conditions observed around wells the carbon 14 activity measured on the tdic varies between 0 3 and 122 pmc so our record contains samples covering a wide period from actual to pleistocene suggesting a continuous recharge of the system through time even if the sahel region has endured many different climate phases which have influenced the infiltration and recharge processes all groundwater samples have stable isotope compositions in the range of the present day regional and global meteoric water line which suggests that the sampled groundwater was not significantly affected by evaporation during recharge evolved waters are depleted relative to unevolved samples by 1 5 2 in 18o and 10 15 in 2h the whole dataset support the hypothesis of a largely unified homogeneous aquifer system with a multilayered structure but it also points out the very low renewability of the resource and a strong anthropogenic contamination of the shallowest horizons

methodological sensitivity of morphometric estimates of coarse fluvial sediment transport abstract the estimation of fluvial sediment transport rate from measurements of morphological change has received growing recent interest the revival of the morphological method reflects continuing concern over traditional methods of rate determination but also the availability of new survey methods capable of high precision high resolution topographic monitoring remote sensing of river channels through aerial digital photogrammetry is a potentially attractive alternative to labour intensive ground surveys however while photogrammetry presents the opportunity to acquire survey data over large areas data precision and accuracy particularly in the vertical dimension are lower than in traditional ground survey methods this paper presents results of recent research in which digital elevation models dems have been developed for a reach of a large braided gravel bed river in scotland using both digital photogrammetry and high resolution rtk gps ground surveys a statistical level of change detection is assessed by comparing surfaces with independent check points the methodological sensitivity of the annual channel sediment budget 1999 2000 to the threshold is presented results suggest that while the remote survey methods employed here can be used to develop qualitatively convincing moderate precision dems of channel topography rmse 0 21 m the remaining errors imply significant limits on reliable change detection which lead to important information losses tests at a 95 confidence interval for change detection show that over 60 of channel deposition and 40 of erosion may be obscured by the lower level of precision associated with photogrammetric monitoring when compared to ground survey measurements this bias reflects the difficulty of detecting the topographic signature of widespread but shallow deposition on bar tops

a spectral clustering search algorithm for predicting shallow landslide size and location the potential hazard and geomorphic significance of shallow landslides depend on their location and size commonly applied one dimensional stability models do not include lateral resistances and cannot predict landslide size multidimensional models must be applied to specific geometries which are not known a priori and testing all possible geometries is computationally prohibitive we present an efficient deterministic search algorithm based on spectral graph theory and couple it with a multidimensional stability model to predict discrete landslides in applications at scales broader than a single hillslope using gridded spatial data the algorithm is general assuming only that instability results when driving forces acting on a cluster of cells exceed the resisting forces on its margins and that clusters behave as rigid blocks with a failure plane at the soil bedrock interface this algorithm recovers predefined clusters of unstable cells of varying shape and size on a synthetic landscape predicts the size location and shape of an observed shallow landslide using field measured physical parameters and is robust to modest changes in input parameters the search algorithm identifies patches of potential instability within large areas of stable landscape within these patches will be many different combinations of cells with a factor of safety less than one suggesting that subtle variations in local conditions e g pore pressure and root strength may determine the ultimate form and exact location at a specific site nonetheless the tests presented here suggest that the search algorithm enables the prediction of shallow landslide size as well as location across landscapes

holocene glacier fluctuations in alaska abstract this review summarizes forefield and lacustrine records of glacier fluctuations in alaska during the holocene following retreat from latest pleistocene advances valley glaciers with land based termini were in retracted positions during the early to middle holocene neoglaciation began in some areas by 4 0 ka and major advances were underway by 3 0 ka with perhaps two distinct early neoglacial expansions centered respectively on 3 3 2 9 and 2 2 2 0 ka tree ring cross dates of glacially killed trees at two termini in southern alaska show a major advance in the ad 550s 720s the subsequent little ice age lia expansion was underway in the ad 1180s 1320s and culminated with two advance phases respectively in the 1540s 1710s and in the 1810s 1880s the lia advance was the largest holocene expansion in southern alaska although older late holocene moraines are preserved on many forefields in northern and interior alaska tidewater glaciers around the rim of the gulf of alaska have made major advances throughout the holocene expansions were often asynchronous with neighboring termini and spanned both warm and cool intervals suggesting that non climatic factors were important in forcing these advances however climatic warming appears to have initiated most rapid iceberg calving retreats large glaciers terminating on the forelands around the gulf of alaska may have had tidewater termini early in the holocene but have progressively become isolated from the adjacent ocean by the accumulation and subaerial exposure of their own sediments

the impact of persistent dynamics on suspended sediment load estimation abstract fluvial suspended sediment concentration and discharge is most commonly estimated by applying rating curves developed over a given base period of sediment monitoring to longer continuous records of water discharge this practice invokes the tacit assumption of stationary suspended sediment concentration water discharge relationships i e suspended sediment behavior here the ramifications of this assumption are explored through an investigation into the temporal dependence of suspended sediment concentration discharge relationships for all hydrologic stations on small rivers draining the west coast of the continental us that have been monitored for suspended sediment over a period of 10 years or more persistent suspended sediment behavior was found to be the norm with 19 of 24 stations expressing apparent monotonic trends over their base periods and 21 stations with finer scale subannual to interdecadal persistent patterns the identified persistent periods of suspended sediment behavior corresponded to distinct rating curves that differed significantly from other periods in terms of offset slope or both assuming stationary suspended sediment behavior resulted in 1 to 63 biasing of suspended sediment load applying rating curves developed for single persistent periods to broader discharge records resulted in up to 10 potential error in estimated sediment load the risk of falsely characterizing the long term interannual scale suspended sediment behavior of a river through a single persistent period of elevated or depressed behavior may be much higher than expected the average duration of identified persistent periods was 8 6 years which is longer than the base period of suspended sediment monitoring for most river stations in the us peak discharge high discharge events 20 to 1000 times mean discharge was usually followed by periods of increased sediment concentration across us pacific coast seven rivers in oregon and northern california displayed the same pattern of decadal to interdecadal scale elevated suspended sediment concentrations following the great christmas floods of 1964

diatom inferred salinity and carbonate oxygen isotopes in holocene waterbodies of the western sahara and sahel africa abstract thirteen holocene palaeolakes in the western sahara and sahel have provided diatom records with carbonate oxygen isotope profiles available from eight of them most of these palaeolakes were groundwater fed lake water chemistry is reconstructed using diatom transfer functions lake water salinity and 18 o records are assembled with some isotopic and chemical groundwater data to better understand the response of the hydrological systems to climate changes over the past 15 000 yr data are in general agreement with climate simulations using coupled atmosphere ocean vegetation models which show a mid holocene wetting over the whole of northwest africa and a rapid drying by 6 4 ka the lake record also shows that at many sites the major lake infilling lags the end of the younger dryas by 1 2 ka regional differences also appear in the timing of the lake hydrological optimum ca 10 5 8 5 and 7 5 4 5 ka in the northern sahara 10 8 5 ka in the air tenere 10 5 7 or 4 5 in the sahel and 7 5 ka in lake chad the whole of the holocene is punctuated by short term drying events changes in water isotopic composition through time are partly explained by changes in rainfall amount and air humidity during the wet holocene period however the very low values in the southern sahara also imply changes in the moisture transport pattern or rainfall mechanisms data suggest an apparent decrease in 18 o content of precipitation along the monsoon flow in contrast with modern patterns changes in water availability and quality have driven population migrations in and out of the sahara sahel but relationships between climate and cultures are complex short term dry events might have driven inventive adaptations in the sahara drying at 5 4 5 ka coincides with both the collapse of the classical neolithic civilization and the settlement of new cultures

glacial conditioning of stream position and flooding in the braid plain of the exit glacier foreland alaska abstract flow spilling out of an active braid plain often signals the onset of channel migration or avulsion to previously occupied areas in a recently deglaciated environment distinguishing between shifts in active braid plain location considered reversible by fluvial processes at short timescales and more permanent glacier conditioned changes in stream position can be critical to understanding flood hazards between 2009 and 2014 increased spilling from the exit creek braid plain in kenai fjords national park alaska repeatedly overtopped the only access road to the popular exit glacier visitor facilities and trails to understand the likely cause of road flooding we consider recent processes and the interplay between glacier and fluvial system dynamics since the maximum advance of the little ice age around 1815 patterns of temperature and precipitation the variables that drive high streamflow via snowmelt glacier meltwater runoff and rainfall could not fully explain the timing of road floods comparison of high resolution topographic data between 2008 and 2012 showed a strong pattern of braid plain aggradation along 3 km of glacier foreland not unexpected at the base of mountainous glaciers and likely an impetus for channel migration historically a dynamic zone follows the retreating glacier in which channel positions shift rapidly in response to changes in the glacier margin and fresh morainal deposits this period of paraglacial adjustment lasts one to several decades at exit glacier subsequently as moraine breaches consolidate and lock the channel into position and as the stream regains the lower elevation valley center upper elevation surfaces are abandoned as terraces inaccessible by fluvial processes for timescales of decades to centuries where not constrained by these terraces and moraines the channel is free to migrate which in this aggradational setting generates an alluvial fan at the breach of the final prominent moraine the position of this fan is glacially conditioned but the process of migration of the braided channels across it is not this broad perspective on channel controls identifies incipient avulsion into the roadside forest as part of a long term fan building process independent from changes in streamflow or sediment load

characterization of the groundwater response to rainfall on a hillslope with fractured bedrock by creep deformation and its implication for the generation of deep seated landslides on mt wanitsuka kyushu island abstract in this study the hydrogeological response of a hillslope affected by gravitational deformation was analyzed based on the data obtained for two observation boreholes a 10 m borehole representing a relatively superficial section of the hillslope dominated by soil and old landslide deposits and a 40 m borehole representing the bedrock aquifer for this analysis the precipitation events in the area groundwater levels of the two boreholes electrical conductivity and isotopic concentration oxygen and hydrogen of the groundwater in the boreholes and rainfall samples were measured derived from the rainfall data the antecedent precipitation index api with a 6 h half life offers a good correlation with the peaks in the groundwater levels in the bedrock aquifer the characteristics of the groundwater response suggest the existence of a single structure in the bedrock that controls the response of the hillslope the structure serves as a conduit which rapidly drives the rainfall water recharge into the bedrock evidently this process is unrelated to the superficial section represented by the observations in the 10 m borehole the structure is associated with an area of high hydraulic conductivity in the bedrock caused by the gravitational deformation in the hillslope the strong control of this structure in the hillslope s hydrogeological response makes it responsible for the hillslope s stability during high precipitation events this information is highly relevant to areas featuring the generation of several deep seated landslides under heavy rain conditions

are microseismic ground displacements a significant geomorphic agent this paper considers the role that microseismic ground displacements may play in fracturing rock via cyclic loading and subcritical crack growth using a coastal rock cliff as a case study we firstly undertake a literature review to define the spatial locations that may be prone to microseismic damage it is suggested that microseismic weakening of rock can only occur in damage accumulation zones of limited spatial extent stress concentrations resulting from cliff height slope angle and surface morphology may nucleate and propagate a sufficiently dense population of microcracks that can then be exploited by microseismic cyclic loading we subsequently examine a 32 day microseismic dataset obtained from a coastal cliff top location at staithes uk the dataset demonstrates that microseismic ground displacements display low peak amplitudes that are punctuated by periods of greater displacement during storm conditions microseismic displacements generally display limited preferential directivity though we observe rarely occurring sustained ground motions with a cliff normal component during storm events high magnitude displacements and infrequently experienced ground motion directions may be more damaging than the more frequently occurring reduced magnitude displacements characteristic of periods of relative quiescence as high magnitude low frequency events exceed and then increase the damage threshold these extremes may also render intervening reduced magnitude microseismic displacements ineffective in terms of damage accumulation as a result of crack tip blunting and the generation of residual compressive stresses that close microcracks we contend that damage resulting from microseismic ground motion may be episodic rather than being continuous and in quasi proportional and cumulative response to environmental forcing a conceptual model is proposed that describes when and where microseismic ground motions can operate effectively we hypothesise that there are significant spatial and temporal limitations on effective microseismic damage accumulation such that the net efficacy of microseismic ground motions in preparing rock for fracture and hence in enhancing erosion may be considerably lower than previously suggested in locations where high magnitude displacements punctuate standard displacement conditions determining and measuring the exact effects of microseismic ground displacement on damage accumulation and as a trigger to macro scale fracture in the field is not currently possible though our model remains consistent with field observations and conceptual models of controls on rockfall activity

varve studies at hector lake alberta canada and the relationship between glacial activity and sedimentation glacial lake sedimentary records from hector lake in banff national park alberta are examined with the aim of clarifying the relationship between glacial activity and outwash sedimentation rhythmic couplets in lake bottom sediments provide a method for accurate documentation and dating of recent sedimentation chronology as analysis of 137cs content indicates that the couplets are of annual periodicity i e varves a comparison of sedimentation rate records with recent regional glacial history indicates that high sedimentation rates of one to a few decades duration occur either during and immediately following periods of moraine deposition ie maximum ice stands or during periods of rapid ice recession comparison of sedimentary records with somewhat longer term glacial and vegetation records indicates that sedimentation rate variations of several centuries duration closely parallel changes in upvalley ice extent over this time scale high sedimentation rates occur during periods of relatively increased ice extent low rates during periods of reduced ice extent within this general pattern however sedimentation rates may remain very high for nearly a century following maximum ice stands due to the exposure of unstable glaciogenic deposits to fluvial reworking during ice recession

rainfall triggered shallow landslides at catchment scale threshold mechanics based modeling for abruptness and localization 1 rainfall induced shallow landslides may occur abruptly without distinct precursors and could span a wide range of soil mass released during a triggering event we present a rainfall induced landslide triggering model for steep catchments with surfaces represented as an assembly of hydrologically and mechanically interconnected soil columns the abruptness of failure was captured by defining local strength thresholds for mechanical bonds linking soil and bedrock and adjacent columns whereby a failure of a single bond may initiate a chain reaction of subsequent failures culminating in local mass release a landslide the catchment scale hydromechanical landslide triggering model chlt was applied to results from two event based landslide inventories triggered by two rainfall events in 2002 and 2005 in two nearby catchments located in the prealps in switzerland rainfall radar data surface elevation and vegetation maps and a soil production model for soil depth distribution were used for hydromechanical modeling of failure patterns for the two rainfall events at spatial and temporal resolutions of 2 5 m and 0 02 h respectively the chlt model enabled systematic evaluation of the effects of soil type mechanical reinforcement soil cohesion and lateral root strength and initial soil water content on landslide characteristics we compared various landslide metrics and spatial distribution of simulated landslides in subcatchments with observed inventory data model parameters were optimized for the short but intense rainfall event in 2002 and the calibrated model was then applied for the 2005 rainfall yielding reasonable predictions of landslide events and volumes and statistically reproducing localized landslide patterns similar to inventory data the model provides a means for identifying local hot spots and offers insights into the dynamics of locally resolved landslide hazards in mountainous regions

groundwater recharge estimation using chloride stable isotopes and tritium profiles in the sands of northwestern senegal a study of environmental chloride deuterium oxygen 18 and tritium in deep sand profiles 35 m has been carried out in order to estimate their relative value for measuring average groundwater recharge the investigation was located at a 0 1 km2 site in quaternary sands near the northwestern coast of senegal in a zone of rainfed agriculture by using a steady state model for duplicate unsaturated zone chloride profiles the long term average recharge at the site was estimated to be 30 mm yr 1 or around 10 of the average precipitation 290 mm the chloride concentration of adjacent shallow groundwater was relatively uniform and comparable to the unsaturated zone average while the spatial variability in the depth distribution of cl in the unsaturated zone was considerable stable isotope deuterium and oxygen 18 data show that there is some isotopic enrichment due to direct evaporation through the soil surface the degree of heavy isotope enrichment is proportional to the extent of evaporative loss and there is good correspondance with the chloride enrichment nevertheless stable isotopes cannot be used quantitatively to estimate the recharge the excellent preservation of the peak in thermonuclear tritium in precipitation in the unsaturated zone at depths between 12 and 20 m enables an estimated annual recharge of 24 mm yr 1 in this area to be calculated using the piston flow model agreement therefore between cl and3h as tools for recharge measurement is reasonable over the site

a change in seasonality in greenland during a dansgaard oeschger warming a new sub seasonal chemical record is presented from the north greenland icecore project northgrip ice core during the onset of one of the longest and strongest interstadials of the last glacial period dansgaard oeschger event 8 approximately 38 000 years ago this is the first time that a record of such resolution has been achieved over several metres of deep glacial ice and provides a unique opportunity for using additional parameters to carry out accurate dating using annual layer counting the very high resolution chemical data were used to assess the phasing of various ions and determine changes in the seasonal strength of chemical deposition and the shape of the seasonal cycle the study shows that a change in seasonality accompanied the dramatic warming transition from stadial to interstadial conditions in greenland thickness due to the exceptionally small sample size a new cutting method using a microtome device and a low volume ion chromatography method was developed the section of ice used in this study was from the outer most part of the ice core the outer surfaces were removed using a bandsaw to prevent contamination from drilling fluid and handling a sledge microtome was then used to cut 2 mm samples using several passes of the blade to cut a succession of 40 mm shavings with no ice loss that were placed in clean coulter accuvettes for melting and then transferred into clean ion chromatography auto sampler vials for analysis powder free gloves and protective clothing were worn throughout to minimize contamination ion chromatography ic was used to determine five anions chloride cl fluoride f methanesulphonate msa nitrate no3 and sulphate so4 2 the system used was a reagent free dionex ics 2500 with a 2 mm column and a 250 ml sample loop a potassium hydroxide eluent generator cartridge egc oh was used to reduce operational errors and contamination associated with eluent preparation the flow was set to 0 25 ml min 1 with an isocratic elution of 23 mm koh four cations calcium ca 2 potassium k sodium na and magnesium mg were analyzed using a reagent free dionex ic 2000 3 mm column and 250 ml sample loop the cation system is equipped with an msa eluent generator cartridge and the method followed set the flow to 0 5 ml min 1 with an isocratic elution of 20 mm msa a sequential flow method was used to analyze both anions and cations from the same sample vial using a dionex as50 auto sampler thus minimizing sample volume requirements the sample and the anion eluent are passed from the ics 2500 system into the ic 2000 system tests of this method were made using frozen ultra pure water to show that the blanks were negligible 5 of glacial concentration levels for all ions thomas 2006

forecasting landslide hazard by the 3d discrete element method a case study of the unstable slope in the lushan hot spring district central taiwan abstract catastrophic landslides and related phenomena are commonly facilitated by the subtropical climate with frequent typhoons and recurrent earthquakes in taiwan s mountainous areas one area susceptible to potentially catastrophic landslides is located at lushan in central taiwan which is famous for its hot springs and tourism the northern slope above the hot spring district slips gradually and frequently due to heavy rainfall for safety reasons the slip affected area has been under constant borehole monitoring by government agencies and a controversial public debate has arisen over permanent evacuation of the hot spring district in this study we attempt to simulate possible scenarios of catastrophic slope failure using slip geometries derived from the monitoring data and assess potential landslide impact areas by a discrete element method using the pfc3d code in the worst case scenario the lushan hot spring district is predicted to be destroyed by debris in 20 s besides the planned regional emergency refuge is rapidly jeopardized by flooding resulted from landslide dammed lakes this study addresses catastrophic slope failure under heavy rainfall conditions given a range of friction coefficients and varied continuity of the failure surfaces it is noted that the pfc3d code has limitations in modeling all complex mechanisms of landslide particularly in modeling loss of material shear strength due to increases in pore pressure nevertheless the numerical simulation results by the 3d discrete element method provide scenario based runout paths particle velocities and landslide affected areas which are useful information for decision support and future landslide hazard assessment

holocene palaeolimnology of kajemamm oasis northern nigeria an isotopic study of ostracodes bulk carbonate and organic carbon a high resolution 5500 year palaeolimnological record from kajemarum oasis a closed basin in the manga grasslands of northern nigeria provides evidence of environmental change in subsaharan africa during the holocene palaeohydrological variations mainly changes in the balance between precipitation and evaporation are recorded by stable oxygen isotope ratios in bulk carbonate and ostracod calcite and by the sr ca ratio in ostracode shells variations in the carbon isotope ratios in carbonates indicate changes in primary productivity in the lake whereas the carbon isotope composition of organic carbon reflects ecophysiological processes within the lake and its surrounding catchment results indicate that there have been marked environmental changes in the manga grasslands over the last 5500 years a more variable climate set in around 1500 cal a bp a prolonged drought between 1200 and 1000 cal a bp with reduced aquatic productivity was followed by a switch to a wetter but still unstable climate moist conditions prevailed during the little ice age the results indicate that drought has affected the sahel episodically over the last 1500 years and is not solely a twentieth century phenomenon

estimation of groundwater recharge in weathered basement aquifers southern zimbabwe a geochemical approach abstract geochemical techniques have been used to estimate groundwater recharge and its spatial variability in basement terrain in a semi arid area of southern zimbabwe recharge rates estimated by chloride mass balance have been determined in the romwe catchment a small 4 6 km2 headwater catchment underlain by banded gneisses with good hydrological and geological control the results support the findings from piezometric monitoring that there are significant differences in hydrogeological properties of weathered basement derived from different primary lithologies annual recharge estimates for shallow weathered aquifers derived from melanocratic bedrock dominated by pyroxene gneiss 22 mm and leucocratic felsic bedrock 6 7 mm are 3 7 and 1 1 respectively of the long term mean annual rainfall the significant uncertainties associated with the chloride mass balance recharge estimates are discussed groundwater derived from each lithology generally has a distinctive geochemistry na cl k na mg ca na cl b ba the information from the romwe catchment control area was then scaled up using information from remote sensing images which defined areas of dark and light soils above the banded gneiss to confirm the higher recharge rates in the melanocratic lithology in the unexplored greater romwe 225 km2 area it is concluded that properly calibrated remote sensing images could be further regionalized to site groundwater sources in basement terrain providing a relatively inexpensive development tool

quantifying 40 years of rockfall activity in yosemite valley with historical structure from motion photogrammetry and terrestrial laser scanning abstract rockfalls and rockslides are often dominant geomorphic processes in steep bedrock landscapes but documenting their occurrence can be challenging requiring frequent monitoring and well resolved spatial data repeat application of remote sensing methods such as terrestrial laser scanning tls and structure from motion sfm photogrammetry can detect even very small rockfalls but typically these acquisitions span only years and may not record rockfall activity representative of longer term rates of cliff erosion inventory databases can extend rockfall records but are commonly incomplete and prone to observation bias we employed tls and sfm on two adjacent cliffs el capitan and middle brother in yosemite valley integrating semi annual data collections from 2010 to 2017 with historical archival sfm models derived from oblique photographs taken in 1976 comparing the 1976 sfm models against more recent data allows for more accurate and precise rockfall detection and volume measurement over a 40 year period change detection indicates that 235 rockfalls occurred from the two cliffs more than twice as many events as are recorded in yosemite s inventory database although individual rockfall volumes reported in the inventory database vary from those measured by sfm tls reported cumulative volumes are similar to measured volumes likely because the large volume events that account for most of the cumulative volume tend to be widely observed and well documented volume frequency relationships indicate that the cliffs erode predominantly by less frequent larger volume rockfalls at rates of 0 9 to 1 7 mm yr our study demonstrates how integrated sfm and tls measurements especially utilizing sfm models derived from historical imagery allow detection and quantification of rockfalls spanning several decades complementing and improving inventory databases informing rockfall hazard assessment and providing longer term rates of cliff erosion

effects of hydromechanical loading history and antecedent soil mechanical damage on shallow landslide triggering evidence suggests that the sudden triggering of rainfall induced shallow landslides is preceded by accumulation of local internal failures in the soil mantle before their abrupt coalescence into a landslide failure plane the mechanical status of a hillslope at any given time reflects competition between local damage accumulated during antecedent rainfall events and rates of mechanical healing e g rebonding of microcracks and root regrowth this dynamic interplay between damage accumulation and healing rates determines the initial mechanical state for landslide modeling we evaluated the roles of these dynamic processes on landslide characteristics and patterns using a hydromechanical landslide triggering model for a sequence of rainfall scenarios the progressive nature of soil failure was represented by the fiber bundle model formalism that considers threshold strength of mechanical bonds linking adjacent soil columns and bedrock the antecedent damage induced by prior rainfall events was expressed by the fraction of broken fibers that gradually regain strength or mechanically heal at rates specific to soil and roots results indicate that antecedent damage accelerates landslide initiation relative to pristine undamaged hillslopes the volumes of first triggered landslides increase with increasing antecedent damage however for heavily damaged hillslopes landslide volumes tend to decrease elapsed time between rainfall events allows mechanical healing that reduces the effects of antecedent damage this study proposed a quantitative framework for systematically incorporating hydromechanical loading history and information on precursor events e g such as recorded by acoustic emissions into shallow landslide hazard assessment

organic geochemical evidence of late glacial holocene climate instability in the north aegean sea sedimentary molecular biomarker compositions organic carbon and caco3 concentrations and bulk organic 13c and total 15n values document a series of paleoclimatic changes that have affected organic matter production and sedimentation in the north aegean sea from the termination of the latest glacial maximum through the middle holocene continental environmental conditions have been inferred from land plant biomarkers paleoproductivity patterns of diatoms prymnesiophytes dinoflagellates and nannoplankton were discerned from marine derived biomarkers although organic matter is predominantly marine variations in the proportion of marine and land contributions and in its general preservation are evident rapid changes in the eastern mediterranean thermohaline circulation evidently occurred in parallel to sea surface temperature oscillations enhanced deep water ventilation accompanied cold intervals in the late last glacial the younger dryas and during an interruption of deposition of the s1 sapropel probably in response to strengthening of north winds over the region in contrast decreased thermohaline circulation occurred during the warm interval associated with the s1 sapropel during this period increased freshwater inputs diminished ventilation of deep water masses and enhanced organic matter production and preservation intriguing fluctuations in sea surface temperatures and the concentrations of marine and terrestrial biomarkers within the sapropelic layer most prominently in the interruption from 8 2 to 7 8 calibrated radiocarbon conventional kyr bp support the hypothesis that several distinct events of deep water reoxygenation occurred in the north aegean sea during deposition of the s1 sapropel these events reflect centennial excursions to the more common low productivity and well ventilated conditions of the mediterranean that may possibly be related to north atlantic oscillation cycles

the evolution of alkaline groundwaters in the continental intercalaire aquifer of the irhazer plain niger this paper discusses the hydrochemical evolution of groundwaters in the multilayer artesian aquifer of the continental intercalaire the mainly jurassic agadez dabla sandstones aquifer of northern niger isotopic and chemical changes in relation to the geological setting suggest that the increasing hco3 alkalinity of the groundwaters is caused by interaction of deep co2 with the aquifer matrix alteration of feldspars by co2 with a 13c value of 3 0 accounts for the observed alkalinity and isotopic and trends carbon 14 ages have been estimated for recent and holocene groundwaters which have a distinct stable isotopic 2h and 18o signature compared with 14c dead groundwaters from further west on the irhazer plain recharge temperatures estimated by analysis of noble gas contents show that the 14c dead waters were recharged under conditions cooler than present averages in the region possibly at the beginning of deglaciation 16 ka b p or during the period 23 30 ka b p trends in the hydrochemistry of u are related to the deep co2 alteration process radiogenic he contents increase along the flow direction and extremely high values occur in the proximity of u ores denitrification in the paleowaters of the irhazer was assessed by measurements of nitrogen argon ratios

controls on the geotechnical response of sedimentary rocks to weathering weathering reduces the strength of rocks and so is a key control on the stability of rock slopes recent research suggests that the geotechnical response of rocks to weathering varies with ambient stress conditions resulting from overburden loading and or stress concentrations driven by near surface topography in addition the stress history experienced by the rock can influence the degree to which current weathering processes cause rock breakdown to address the combined effect of these potential controls we conducted a set of weathering experiments on two sedimentary lithologies in laboratory and field conditions we firstly defined the baseline geotechnical behaviour of each lithology characterising surface hardness and stress strain behaviour in unconfined compression weathering significantly reduced intact rock strength but this was not evident in measurements of surface hardness the ambient compressive stress applied to samples throughout the experiments did not cause any observable differences in the geotechnical behaviour of the samples we created a stress history effect in sub sets of samples by generating a population of microcracks that could be exploited by weathering processes we also geometrically modified groups of samples to cause near surface stress concentrations that may allow greater weathering efficacy however even these pronounced sample modifications resulted in insignificant changes in geotechnical behaviour when compared to unmodified samples the observed reduction in rock strength changed the nature of failure of the samples which developed post peak strength and underwent multiple stages of brittle failure although weakened these samples could sustain greater stress and strain following exceedance of peak strength on this basis the multi stage failure style exhibited by weaker weathered rock may permit smaller magnitude higher frequency events to trigger fracture through intact rock bridges as well as influencing the characteristics of pre failure deformation these findings are consistent with patterns of behaviour observed in field monitoring results

oscillations of lake chad over the past 50 000 years new data and new hypothesis a recent sedimentological study of the chari deltas area allowed an evaluation of the oscillations of palaeolake chad over the past 50 000 years three maximum lake levels at circa 38 000 22 000 and between 12 000 and 8000 years b p have been described the levels reached by these large lakes were never very high and there has not been any major variation over the last 8000 years the hypothesis regarding a huge palaeolake chad of 320 000 km2 reaching the 320 m level at circa 6000 years b p instead of the present 279 5 282 m and approximatively 20 000 km2 is discussed and discarded on basis of stratigraphical sedimentological geomorphological hydrological and geophysical arguments taking into account geophysical data and the deep structures of the basin a new interpretation is proposed for the perilacustrine dune ridge which was considered to run along the shoreline of the 320 m level

progressive failure of sheeted rock slopes the 2009 2010 rhombus wall rock falls in yosemite valley california usa progressive rock fall failures in natural rock slopes are common in many environments but often elude detailed quantitative documentation and analysis here we present high resolution photography video and laser scanning data that document spatial and temporal patterns of a 15 month long sequence of at least 14 rock falls from the rhombus wall a sheeted granitic cliff in yosemite valley california the rock fall sequence began on 26 august 2009 with a small failure at the tip of an overhanging rock slab several hours later a series of five rock falls totaling 736 m3 progressed upward along a sheeting joint behind the overhanging slab over the next 3 weeks audible cracking occurred on the rhombus wall suggesting crack propagation while visual monitoring revealed opening of a sheeting joint adjacent to the previous failure surface on 14 september 2009 a 110 m3 slab detached along this sheeting joint additional rock falls between 30 august and 20 november 2010 totaling 187 m3 radiated outward from the initial failure area along cliff sub parallel sheeting joints we suggest that these progressive failures might have been related to stress redistributions accompanying propagation of sheeting joints behind the cliff face mechanical analyses indicate that tensile stresses should occur perpendicular to the cliff face and open sheeting joints and that sheeting joints should propagate parallel to a cliff face from areas of stress concentrations the analyses also account for how sheeting joints can propagate to lengths many times greater than their depths behind cliff faces we posit that as a region of failure spreads across a cliff face stress concentrations along its margin will spread with it promoting further crack propagation and rock falls published in 2012 this article is a us government work and is in the public domain in the usa

fiber bundle model for multiscale modeling of hydromechanical triggering of shallow landslides 1 sudden and rapid mass movements associated with landslides and snow avalanches present a hazard to life and infrastructure yet their predictions and triggering mechanisms remain poorly understood statistical methods and correlative studies have been used to produce landslide or avalanche susceptibility maps often with limited physical basis mechanistic approaches based on factor of safety computation seldom represent the progressive transition from local failure events to a landslide and in general do not include heterogeneities associated with land cover or with subsurface material properties and hydrologic pathways focusing on rainfall induced shallow landslides we propose the use of the fiber bundle model fbm a generic yet powerful and adaptable model used in modeling fatigue and fracture of complex and disordered materials the primary strength of the fbm is its ability to represent the progressive failure of cracks and shear zones and the ruptures of highly heterogeneous bonding elements that are present in soils at all scales the model also provides a natural framework for interpretation of acoustic emission signatures from failing slopes which may form the basis of a monitoring and warning system

climatic warming glacier recession and runoff from alpine basins after the little ice age maximum records of discharge of rivers draining alpine basins with between 0 and 70 ice cover in the upper aare and rhone catchments switzerland for the period 1894 2006 have been examined together with climatic data for 1866 2006 with a view to assessing the effects on runoff from glacierized basins of climatic warming coupled with glacier recession following the little ice age maximum annual runoff from ice free basins reflects precipitation variations rising from minima between 1880 and 1910 to maxima between the late 1960s and early 1980s the more highly glacierized the basin the more runoff mimicked mean may september air temperature during two periods of warming runoff increased gradually from the 1900s rapidly in the 1940s before decreasing to the late 1970s rising runoff levels during the second warming period failed to exceed those attained during the first despite higher summer temperatures although temperatures continued to rise discharge from glacierized basins declined after reaching maxima in the late 1980s to early 1990s in the first warming period rising specific melt rates augmented by increasing precipitation opposed the impact of declining glacier area on runoff although melt continued to increase in the second period enhanced melting even in the exceptionally warm summer of 2003 appears to have been insufficient to offset reducing glacier surface area exposed to melt low or reducing levels of precipitation and increasing evaporation thus runoff from glacierized basins peaked in the late 1940s to early 1950s

structural sedimentologic and sea level controls on sand distribution in a steep clinoform asymmetric wave influenced delta miocene billund sand eastern danish north sea and jylland abstract the lower miocene billund sand of jylland denmark provides an excellent opportunity to study the distribution of sands and the types of clinoform generated by a wave dominated delta prograding into a deep shelf environment in particular seismic sections the sand rich parts correlate with parallel clinoformal seismic facies in which the clinoforms dip 7 to 10 the stacking pattern of this seismic facies also indicates whether the progradation occurred during rising or falling sea level by displaying an ascending or descending shoreline trajectory respectively the billund delta was deposited in the eastern north sea basin during the early miocene and is on the available data recognized as a nw to se trending feature it forms a wave dominated delta with thick sand bodies deposited in relatively deep waters 100 m at the river mouth and in the up drift area of newly formed delta lobes sands and muds associated with a spit complex or a lagoonal complex dominated the down drift area in the distal delta front area alternating sands and muds were laid down the sands associated mainly with storm events progradation of the studied part of the delta occurred during high sea level and a subsequent fall in sea level that was caused by a eustatic fall during the mid aquitanian early miocene although sand intervals 10 to 20 m thick are common throughout the delta complex the thickest up to 100 m and cleanest sand is found in units deposited in narrow bands within structural lows and during periods of forced regression the billund delta may be an excellent analogue for hydrocarbon bearing wave dominated deltas and seems to exhibit similarities to jurassic deposits in the north sea area

toward a better understanding of palaeoclimatic regimes that recharged the fossil aquifers in north africa inferences from stable isotope and remote sensing data abstract the isotopic composition of modern precipitation collected monthly from the international atomic energy agency iaea stations over north africa is enriched average d morocco 25 8 algeria 21 3 tunisia 20 6 libya 17 7 egypt 11 7 compared to fossil groundwater across north africa which shows progressive west to east depletion this indicates that precipitation from paleowind regimes was different from those prevailing in the present day late holocene however a few monthly records march 1982 december 1987 december 1991 march 2002 and april 2002 collected from iaea stations sidi barrani cairo rafah and el arish showed isotopic depletions d 56 to 43 7 approaching those of the fossil groundwater in egypt for each of the five events we investigated the direction of cloud propagation in relation to the isotopic composition of precipitation as it travels over the african continent and surroundings cloud propagation directions and air parcel flow paths were extracted from temporal every 30 min meteosat image products 1 infra red eumetsat 2 cloud motion winds cmw and 3 back trajectory models btm the inferred wind regimes for each of these events were then compared to those for the remaining egyptian records 160 that produced precipitation with enriched to intermediate isotopic compositions d 39 7 to 34 6 the extracted cloud propagation directions and the observed spatial variation in the isotopic compositions of the precipitating rain support a model that attributes previous wet climatic periods over north africa to the intensification of palaeowesterlies during glacial periods

an accelerating precursor to predict time to failure in creep and volcanic eruptions real time prediction by monitoring of the evolution of response variables is a central goal in predicting rock failure a linear relation omega omega similar to 1 c t f t has been developed to describe the time to failure where li represents a response quantity c is a constant and tf represents the failure time observations from laboratory creep failure experiments and precursors to volcanic eruptions are used to test the validity of the approach both cumulative and simple moving window techniques are developed to perform predictions and to illustrate the effects of data selection on the results laboratory creep failure experiments on granites show that the linear relation works well during the final approach to failure for blind prediction the simple moving window technique is preferred because it always uses the most recent data and excludes effects of early data deviating significantly from the predicted trend when the predicted results show only small fluctuations failure is imminent c 2017 elsevier b v all rights reserved

the randolph glacier inventory a globally complete inventory of glaciers the randolph glacier inventory rgi is a globally complete collection of digital outlines of glaciers excluding the ice sheets developed to meet the needs of the fifth assessment of the intergovernmental panel on climate change for estimates of past and future mass balance the rgi was created with limited resources in a short period priority was given to completeness of coverage but a limited uniform set of attributes is attached to each of the 198 000 glaciers in its latest version 3 2 satellite imagery from 1999 2010 provided most of the outlines their total extent is estimated as 726 800 34 000 km 2 the uncertainty about 5 is derived from careful single glacier and basin scale uncertainty estimates and comparisons with inventories that were not sources for the rgi the main contributors to uncertainty are probably misinterpretation of seasonal snow cover and debris cover these errors appear not to be normally distributed and quantifying them reliably is an unsolved problem combined with digital elevation models the rgi glacier outlines yield hypsometries that can be com bined with atmospheric data or model outputs for analysis of the impacts of climatic change on glaciers the rgi has already proved its value in the generation of significantly improved aggregate estimates of glacier mass changes and total volume and thus actual and potential contributions to sea level rise

catastrophic landslide induced by typhoon morakot shiaolin taiwan abstract typhoon morakot induced the catastrophic and deadly shiaolin landslide in southern taiwan on 9 august 2009 resulting in more than 400 casualties we undertook a geological and geomorphological investigation with the aim of reconstructing the events leading up to this landslide and to clarify factors that contributed to its development cumulative rainfall reached up to 1676 5 mm in about three days under the influence of the typhoon and the shiaolin landslide with a volume of 25 106 m3 occurred one day after the peak in rainfall intensity the landslide occurred on a dip slope overlying late miocene to early pliocene sedimentary rocks consisting of silty shale massive mudstone and sandstone it started as a rockslide in the upper third of the landslide area and transformed into a rock avalanche that crossed a series of terraces and displaced or buried the village below it buried the riverbed of the chishan river and ran up the opposite slope creating a landslide dam 60 m high which was breached about 1 h and 24 min later flooding the village the velocity of the landslide is estimated to have been 20 4 to 33 7 m s 1 and its apparent friction angle was 14 which indicates its high mobility the detachments in the source area consist of combinations of bedding planes and joints or faults the landslide was preceded by gravitational deformation which appeared as hummocky landforms before the landslide and as buckle folds exposed after the event the landslide deposits consist of fragments of mudstone shale and sandstone as well as clayey material at its base this clayey material consisting of illite chlorite quartz feldspar and calcite is assumed to have strongly influenced the long rapid runout

cone penetration testing to assess slope stability in the 1979 nice landslide area ligurian margin se france abstract in the landslide prone area near the nice international airport southeastern france an interdisciplinary approach is applied to develop realistic lithological geometrical profiles and geotechnical strength sub seafloor models such models are indispensable for slope stability assessments using limit equilibrium or finite element methods regression analyses based on the undrained shear strength s u of intact gassy sediments are used to generate a sub seafloor strength model based on 37 short dynamic and eight long static piezocone penetration tests and laboratory experiments on one calypso piston and 10 gravity cores significant strength variations were detected when comparing measurements from the shelf and the shelf break with a significant drop in s u to 5 5 kpa being interpreted as a weak zone at a depth between 6 5 and 8 5 m below seafloor mbsf here a 10 reduction of the in situ total unit weight compared to the surrounding sediments is found to coincide with coarse grained layers that turn into a weak zone and detachment plane for former and present day gravitational retrogressive slide events as seen in 2d chirp profiles the combination of high resolution chirp profiles and comprehensive geotechnical information allows us to compute enhanced 2d finite element slope stability analysis with undrained sediment response compared to previous 2d numerical and 3d limit equilibrium assessments those models suggest that significant portions detachment planes at 20 m or even 55 mbsf of the quaternary delta and slope apron deposits may be mobilized given that factors of safety are equal or less than 1 when further considering the effect of free gas a high risk for a landslide event of considerable size off nice international airport is identified

a dynamic comprehensive method for landslide control a slope failure is developed due to progressive external loads and deteriorations of slope geomaterials thus forming a progressive and dynamic development and occurrence of landslides site geological properties and other active factors such as hydrodynamic load and human activities are complex and usually unknown thus this dynamic development and occurrence of landslides can only be understood through the progressive accumulation of knowledge on the landslides for such a progressive process this paper proposes a dynamic comprehensive control method for landslide control this control method takes full advantage of updated monitoring data and site investigations of landslides and emphasizes the implementation of possible measures for landslide control at reasonable stages and in different groups these measures are to prevent the occurrence of a landslide disaster as a case study a landslide project at the panluo open pit iron mine is analyzed to illustrate this dynamic comprehensive control method

creep behavior of slip zone soil of the majiagou landslide in the three gorges area the creep properties of slip zone soil are critical to deformation prediction and slope stability analysis a series of triaxial drained creep tests were conducted on the slip band soil from a creeping landslide the results indicate that soil creep occurs in two stages with confining and deviatoric stresses being critical factors the long term strength of the soil was estimated to be 60 75 of the conventional strength according to the isochronous curves the soil creep characteristics were used to predict the creep strain using both the burgers and the singh mitchell model and large discrepancies were found between the predicted strain and test results accordingly a new empirical model based on the morgan mercer flodin growth model has been developed to describe the creep behavior of gravely clay in the slip zone four parameters of this model are estimated by nonlinear regression the deformations predicted by this model are in reasonable agreement with experimental data

lakes groundwater and palaeohydrology in the sahel of ne nigeria evidence from hydrogeochemistry the geochemistry of natural waters from rain soil the unsaturated zone shallow aquifers lakes and the stratified aquifer system of the chad basin sediments has been investigated to interpret modern hydrological processes and to reconstruct the palaeohydrology of ne nigeria a type region of the southern sahel recharge to the confined middle and lower aquifers recorded in ne nigeria occurred between 24 and 18 6 ka bp prior to the last glacial maximum the mean annual temperature at this time derived from dissolved noble gas ratios was at least 6 c cooler than at the present day this groundwater is not coupled to the active modern recharge cycle and was not reactivated during the holocene wet phases as elsewhere in the saharan region a reflection of changing lake levels and or of changing climatic regimes the absence of groundwater recharge at the time of the last glacial maximum supports other evidence for aridity at this time present day direct recharge rates in the manga grasslands are high mean 44 mm a 1 however regional recharge in ne nigeria at the present day is even higher 60 mm a 1 emphasizing the importance of infiltration from surface runoff as input to groundwater the present study confirms that the shallow aquifer in the region contains significant renewable groundwater resources however the confined aquifer of the chad basin clearly contains palaeowater and this declining artesian basin will need careful conservation prior to a return to traditional water use methods via improved management of the renewable waters in the shallow phreatic aquifers

a model to describe precursory material failure phenomena applications to short term forecasting at colima volcano mexico some volcanoes exhibit at times accelerating strain and seismicity before eruptions different authors have used this behavior to predict eruptions and to develop materials science models here a linear kelvin voigt viscoelastic model is proposed to describe the observed behavior this model also has applications to other failure phenomena such as landslides the strain rate of a variety of materials under constant stress after an instantaneous elastic response is found to be well described by a general relaxation law dot varepsilon left t right b over 1 st where b and s are parameters depending on the material and its creep state whether the creep regime is primary or tertiary depends upon the sign of s s 0 corresponds to pseudoviscous flow the creep behavior of the viscoelastic body is analyzed for different load histories it is found that the body has an exponential distribution of retardation frequencies that may or may not converge depending on the sign of s according to the model tertiary creep implies material degradation and a critical weakening of the medium leading to a runaway growth of the strain and seismic energy release rates if tertiary creep is detected time of failure predictions may be done from field data through determination of two model parameters for varying loads the model response compare well with reported examples of pre eruptive volcano behavior and with reported results of landslide experiments the model is tested with the july 1994 in hindsight and november 1998 in foresight colima volcano eruptions although this method provides some guidance in estimating the time over which accelerating volcanic precursors may end in an eruption it is emphasized that eruptions may fail to occur at the estimated time or may not occur at all on the other hand eruptions may not be preceded by such a behavior

slope creep behavior observations and simulations rock slopes undergoing long term effects of weathering and gravity may gradually deform or creep downslope leading to geological structures such as bending bucking fracturing or even progressive failure this study uses geomechanics based numerical modeling to qualitatively explain the cause and evolution of slope creep behavior constitutive models used include the creep mohr coulomb and anisotropic models the last two models are used with the strength reduction in calculation first the results of field investigation around a landslide site occurring in slate are present the causes and modes of creep structures observed on slopes and underground are studied second the study investigates the influences of slope topography and anisotropy orientations on slope creep behavior finally progressive failure of slopes with different shapes is examined the simulated results show that the bending type of structures develops near slope surfaces and the buckling type of structures is associated with the deformation or slides of a slope the creep pattern varies with the orientation and position of an original planar structure the shear zone involves a joint or fracture along which displacement has taken place moreover creep behavior is more significant on slopes with greater height and inclination as well as on steeper portions whether on concave or convex slopes in addition with the same topographic conditions consequent slopes with coinciding cleavage and obsequent slopes with steep cleavage result in greater creep behavior without the effects of anisotropic cleavage concave and straight slopes develop failure surfaces from the crowns downwards whereas convex slopes develop failure surfaces from the toes upwards

paleorecharge by the niger river mali deduced from groundwater geochemistry stable isotopes major elements trace elements and noble gases in groundwater from northern mali permit a reconstruction of the paleohydrology of the sahelian and sub saharan regions of west africa major floods of the niger river during the more humid episodes of the holocene probably associated with northward migration of the interior river delta flood zone were responsible for groundwater recharge a marine aerosol input somewhat modified by rock water interaction dominates the groundwater chemistry stable isotope compositions distinguish the saharan zone groundwater from waters recharged in the sahelian zone south of the azaouad ridge carbon 14 dating shows that whereas the latter are modem the saharan zone was recharged in the early to middle holocene noble gas contents suggest that recharge north of azaouad occurred under cooler climatic conditions than presently prevail

spatial statistical modeling of shallow landslides validating predictions for different landslide inventories and rainfall events abstract statistical models that exploit the correlation between landslide occurrence and geomorphic properties are often used to map the spatial occurrence of shallow landslides triggered by heavy rainfalls in many landslide susceptibility studies the true predictive power of the statistical model remains unknown because the predictions are not validated with independent data from other events or areas this study validates statistical susceptibility predictions with independent test data the spatial incidence of landslides triggered by an extreme rainfall in a study area was modeled by logistic regression the fitted model was then used to generate susceptibility maps for another three study areas for which event based landslide inventories were also available all the study areas lie in the northern foothills of the swiss alps the landslides had been triggered by heavy rainfall either in 2002 or 2005 the validation was designed such that the first validation study area shared the geomorphology and the second the triggering rainfall event with the calibration study area for the third validation study area both geomorphology and rainfall were different all explanatory variables were extracted for the logistic regression analysis from high resolution digital elevation and surface models 2 5 m grid the model fitted to the calibration data comprised four explanatory variables i slope angle effect of gravitational driving forces ii vegetation type grassland and forest root reinforcement iii planform curvature convergent water flow paths and iv contributing area potential supply of water the area under the receiver operating characteristic roc curve auc was used to quantify the predictive performance of the logistic regression model the auc values were computed for the susceptibility maps of the three validation study areas validation auc the fitted susceptibility map of the calibration study area apparent auc 0 80 and another susceptibility map obtained for the calibration study area by 20 fold cross validation cross validation auc 0 74 the auc values of the first and second validation study areas 0 72 and 0 69 respectively and the cross validation auc matched fairly well and all auc values were distinctly smaller than the apparent auc based on the apparent auc one would have clearly overrated the predictive performance for the first two validation areas rather surprisingly the auc value of the third validation study area 0 82 was larger than the apparent auc a large part of the third validation study area consists of gentle slopes and the regression model correctly predicted that no landslides occur in the flat parts this increased the predictive performance of the model considerably the predicted susceptibility maps were further validated by summing the predicted susceptibilities for the entire validation areas and by comparing the sums with the observed number of landslides the sums exceeded the observed counts for all the validation areas hence the logistic regression model generally over estimated the risk of landslide occurrence obviously a predictive model that is based on static geomorphic properties alone cannot take a full account of the complex and time dependent processes in the subsurface however such a model is still capable of distinguishing zones highly or less prone to shallow landslides

the selborne cutting stability experiment the paper describes a field experiment in which a 9 m deep cut slope in gault clay was brought to failure by pore pressure recharge the geology of the site is described and the procedures used to

hydrogeology and its effect on slope stability along the coastal aquifer of nice france abstract along the ligurian continental margin off nice western mediterranean a considerable portion of the sediments is affected by pore pressure transients resulting from groundwater charging by the nearby river var and also from leaching clay mineral bearing deposits which results in sensitive weak clays in 1979 the area suffered a tsunamigenic landslide that generated several casualties and material damage to the coastal zone the seafloor presently shows evidence for soft sediment deformation and pore water freshening in this paper we present the first comprehensive in situ pore pressure data set collected over space and time between 2006 and 2009 in a landslide prone area using piezometers ifremer brest france and dynamic cone penetrometers ff cptu marum bremen germany as well as a simple modelling approach we illuminate what governing factors control strength and pore pressure in marine slope sediments affected by the var aquifer our results attest i a strong link between pore pressure transients and local precipitation over a period of 11 months ii overpressure at levels where groundwater flow occurs coarse intervals containing sand and gravel and iii fluidised fractures and channels that indicate high pore pressures at least temporarily in essence seepage and repeated pore pressure fluctuations weaken the sediment effectively so that it cannot be ruled out that the currently stable portion adjacent to nice airport may fail in the near future

detecting slope deformation using two pass differential interferometry implications for landslide studies on earth and other planetary bodies landslide features have been identified on earth and the moon mars venus as well on the jovian moons by focusing on a terrestrial landslide complex we test the operational parameters of radarsat 1 and the use of two pass differential interferometry to detect change to map its extent and to measure the amount of movement over a given time period radarsat 1 was chosen because of its variable imaging modes and geometry for investigations of landslide motions using remote sensing techniques repeat pass data are required synthetic aperture radar sar interferometry insar can ideally monitor movements across the whole surface of a landslide to a millimeteric precision yielding a coverage significantly better than that obtained by ground instrumentation obtaining optimal data for insar analysis requires controlled orbital characteristics and imaging geometries an understanding of the landslide characteristics and behavior a cooperative surface and mitigation of the factors that can affect phase using two pass differential interferometry a slope deformation map has been generated from radarsat 1 data for part of the black ven landslide 2 52 w 50 40 n on the south coast of england four months separate the insar pair during which time 0 03 m of subsidence was measured from this a movement rate of 0 09 m yr can be calculated this agrees well with ground observations and an in situ record of movement thus demonstrating that the technique can be used to investigate landslides with further refinement it can provide more direct measurements of landslide deformation on earth and other planetary bodies than are currently available

a conceptual model for alpine proglacial river channel evolution under changing climatic conditions this paper integrates concepts derived from the literature to focus upon interactions between riparian vegetation and river channel dynamics in alpine glacier basins discussion of the nature and variability of discharge and sediment regimes of alpine glacier fed rivers downstream variations in the physical character of the river channel and corridor consequent downstream variations in lateral processes and regional variations in alpine glacier dynamics lead to the proposal of a conceptual model of proglacial river channel riparian vegetation interactions under changing climatic conditions

progressive shear surface development in cohesive materials implications for landslide behaviour the aim of this study was to investigate mechanisms of progressive shear surface development using a series of specialised triaxial cell tests intact and remoulded samples of gault clay from the ventnor undercliff on the isle of wight in southern england were subjected to pore pressure reinflation ppr testing in a triaxial cell in which failure is generated by increasing pore pressure under a constant total stress state in addition a novel very long term 500 days creep test was undertaken in which the sample eventually failed at a constant stress state below the failure envelope the experiments showed that undisturbed samples of the gault clay failed in a brittle manner generating a linear trend when plotted using the saito technique on the other hand remoulded samples showed ductile behaviour as indicated by a non linear saito trend a number of otherwise identical ppr tests were conducted in which the rate of increase in pore water pressure was varied these tests showed that strain rate generated at any point in the ppr tests depended on both the effective stress and the rate of change of effective stress the latter is important because a change in stress generates a change in strain thus whilst tests at different rates of change of effective stress are similar when plotted in q p space and in strain p space they are markedly different in strain rate p space the long term creep test failed when the stress state had been constant for over 80 days this mechanism was reminiscent of creep rupture occurring below the failure envelope defined in the conventional experiments we conclude that first time failure in the gault clay is a progressive mechanism dominated by the development of micro cracking which leads to strain localisation and the development of one or more shear surfaces at failure whilst this mechanism may usually occur in response to a change in stress the study indicates that failure can develop progressively in the remoulded gault clay shear strains cannot localise along a singular shear surface the results provide new insight into the mechanisms of landslide movement operating within the ventnor landslide complex and indicate that present movements are likely to be occurring on a pre existing shear surface the lab tests suggest that this material is unlikely to undergo catastrophic failure