landslide generated tsunamis at reunion island 1 landslides that occur on oceanic volcanoes can reach the sea and trigger catastrophic tsunamis reunion island has been the location of numerous huge landslides involving tens to hundreds of cubic kilometers of material we use a new two fluid seawater and landslide numerical model to estimate the wave amplitudes and the propagation of tsunamis associated with landslide events on reunion island a 10 km3 landslide from the eastern flank of piton de la fournaise volcano would lift the water surface by about 150 m where it entered the sea the wave thus generated would reach saint denis the capital of reunion island population of about 150 000 people in only 12 min with an amplitude of more than 10 m and would reach mauritius island in 18 min although mauritius is located about 175 km from the impact waves reaching its coast would be greater than those for reunion island this is due to the initial shape of the wave and its propagation normal to the coast at mauritius but generally coast parallel at reunion island a submarine landslide of the coastal shelf of 2 km3 would trigger a 40 m high wave that would severely affect the proximal coast in the western part of reunion island for a landslide of the shelf of only 0 5 km3 waves of about 2 m in amplitude would affect the proximal coast

late pleistocene and holocene activity of the atacazo ninahuilca volcanic complex ecuador abstract the atacazo ninahuilca volcanic complex anvc is located in the western cordillera of ecuador 10 km southwest of quito at least six periods of pleistocene to holocene activity n1 to n6 have been preserved in the geologic record as tephra fallouts and pyroclastic flow deposits new field data including petrographic and whole rock geochemical analyses of over forty soil and tephra sections 100 pumice and lithic samples and 10 new 14 c ages allow us to constrain 1 the tephra fall isopachs and detailed characteristics of the last two events n5 n6 including volume estimates of the tephra and pyroclastic flow deposits and the corresponding volcanic explosivity index vei 2 the petrographical and geochemical correlations between domes tephras and pyroclastic flow deposits and 3 the timing of the last 4 eruptive events and a period of quiescence that endured a few thousand years 1000 4000 the last two eruptive events n5 and n6 took place at around 4400 35 yr bp and 2270 15 yr bp producing huge plinian and pyroclastic flow deposits taking into account the widely spread deposits of these vei 5 eruptions the present population of about 70 000 people and the current infrastructure the development of mitigation plans and deployment of monitoring systems at anvc is highly recommended

phosphate retention relative dating of holocene soil development abstract measurements of percentage phosphate retention are presented for two soil chronosequences on till deposits in the mount cook region new zealand changes in the capacity of phosphate retention as a function of time and depth in the soil profile is a useful relative dating tool for examining post depositional surface modifications as an index of soil development it has the advantage that it is applicable to all stages of holocene soil development unlike other more temporally restricted techniques estimates of surface age are taken from earlier work using rock weathering rind thickness analysis the corresponding pattern of soil development for corresponding members of both sequences demonstrates the consistency between different relative age dating techniques

numerical modeling of tsunami waves generated by the flank collapse of the cumbre vieja volcano la palma canary islands tsunami source and near field effects 1 in this work we study waves generated by the potential collapse of the west flank of the cumbre vieja volcano cvv la palma canary island spain through numerical simulations performed in two stages i the initial slide motion and resulting free surface elevation are first calculated using a 3d navier stokes model ii generated waves are then input into a 2d horizontal boussinesq model to further simulate propagation to the nearby islands unlike in earlier work on cvv besides a similar extreme slide volume scenario of 450 km3 in our simulations i we consider several slide scenarios featuring different volumes i e 20 40 80 km3 which partly result from a geotechnical slope stability analysis ii we use a more accurate bathymetry and iii an incompressible version of a multiple fluid material navier stokes model we find wave trains for each scenario share common features in terms of wave directivity frequency and time evolution but maximum elevations near cvv significantly differ ranging from 600 to 1200 m for increasing slide volume additionally our computations show that significant energy transfer from slide to waves only lasts for a short duration order 200 s which justifies concentrating our best modeling efforts on the early slide motion phase the anticipated consequences of such wave trains on la palma and other canary islands are assessed in detail in the paper

onset of neoglaciation in the southern hemisphere a review of evidence documenting an early neoglacial mid holocene advance of mountain glaciers in south america and new zealand reveals that of 16 glaciers for which radiocarbon age control exists only two have associated dates that may approximate the culmination of an advance advances of the remaining glaciers are controlled only by minimum or maximum limiting ages additional dates for several new zealand glaciers are based on weathering rind measurements having large potential errors twelve of the glaciers now terminate or have terminated in lakes or in tidewater and are subject to instabilities associated with calving termini an extensive debris cover in the ablation zone of nearly half of the glaciers makes their moraine succession potentially suspect as a record of detailed climatic variation the two glaciers with seemingly reliable age control are located in valleys where large rock avalanches could affect glacier mass balance and lead to random advances or where rock avalanche deposits might easily be mistaken for moraines and tills the early neoglacial interval has been defined primarily based on this set of data the ages taken at face value suggest that the early neoglacial advance culminated between ca 5400 and 4900 cal yr ago ca 4600 4400 14c yr bp this chronology however should remain provisional until improved age control is obtained for a large population of glaciers based on closely bracketing radiocarbon dates and or an adequate number of cosmogenic isotope ages data from calving glaciers and those subject to rock avalanche activity should be avoided or assessed critically copyright 2000 john wiley sons ltd

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

the role of rock fragmentation in the motion of large landslides abstract by considering the implications of the comminution generally associated with very large landslides we arrive at a simple explanation for the remarkably low frictional resistance to motion demonstrated by large intact blockslides e g waikaremoana new zealand volcanic debris avalanches e g socompa chile and large rock avalanches e g falling mountain n z which allows such mass movements to achieve unexpectedly high velocities and long runout distances during rapid grain flow under high direct stress the overall grain motion generates stresses in many force chains that strain individual grains to failure most of the elastic strain energy accumulated in these force chains before failure is returned at failure to the resulting grain fragments resulting in apparent instantaneous pressures of 3q on the surroundings where q is the ambient strength of the previously intact grains gpa these intense pressures support some of the direct force on the shear layer so that the effective intergranular stress in the shear layer is reduced because frictional resistance is proportional to effective stress this reduces the overall frictional resistance to shear the steady state effective stress is that which just allows fragmentation to continue the resistance to motion estimated from this relationship explains to much better than order of magnitude accuracy the reported motions of the large rapid mass movements we also deduce that grain fragmentation can be sustained for sufficiently long to explain the phenomena without reducing the mean grain size by volume in the granular layer to unrealistically small values the presence of pore fluid does not appear to influence the effect of fragmentation dynamics in a major way the proposed mechanism requires further laboratory and simulation studies to reduce its current dependence on limited field data but its success suggests that it is worthwhile investigating further as an explanation for large mass movements in the types of brittle rock in which fragmentation occurs

numerical modeling of self channeling granular flows and of their levee channel deposits when not laterally confined in valleys pyroclastic flows create their own channel along the slope by selecting a given flowing width furthermore the lobe shaped deposits display a very specific morphology with high parallel lateral levees a numerical model based on saint venant equations and the empirical variable friction coefficient proposed by pouliquen and forterre 2002 is used to simulate unconfined granular flow over an inclined plane with a constant supply numerical simulations successfully reproduce the self channeling of the granular lobe and the levee channel morphology in the deposits without having to take into account mixture concepts or polydispersity numerical simulations suggest that the quasi static shoulders bordering the flow are created behind the front of the granular material by the rotation of the velocity field due to the balance between gravity the two dimensional pressure gradient and friction for a simplified hydrostatic model competition between the decreasing friction coefficient and increasing surface gradient as the thickness decreases seems to play a key role in the dynamics of unconfined flows the description of the other disregarded components of the stress tensor would be expected to change the balance of forces the front s shape appears to be constant during propagation the width of the flowing channel and the velocity of the material within it are almost steady and uniform numerical results suggest that measurement of the width and thickness of the central channel morphology in deposits in the field provides an estimate of the velocity and thickness during emplacement citation mangeney a f bouchut n thomas j p vilotte and m o bristeau 2007 numerical modeling of self channeling granular flows and of their levee channel deposits

inactive and relict rock glaciers of the deboullie lakes ecological reserve northern maine usa lobate talus slopes in the deboullie lakes ecological reserve dler of northern maine exhibit parabolic profiles characteristic of inactive and relict talus derived rock glaciers vegetated rock glacier surfaces suggest that the landforms are no longer active and lobes comprising two dler rock glaciers document periods of past growth observations of perennial subsurface ice are supported by datalogger temperature measurements indicating that sporadic permafrost exists throughout the dler we compare the dler rock glaciers along with similar features elsewhere in new england and adjacent quebec to the modern alpine permafrost distribution results indicate that a mean annual temperature cooling of 68c is required to promote active rock glacier growth ages of plant remains recovered from the basal sediments of a local pond constrain deglaciation to before 11 320 14 c a bp and core stratigraphy and organic content reveal that a periglacial environment persisted during the early postglacial era thus we hypothesise that the dler rock glaciers were active during lateglacial time despite the lack of glacier activity in the region we take this to suggest that north eastern us rock glaciers formed in response to mean annual temperatures skewed towards the frigid winters of the younger dryas chronozone copyright 2009 john wiley sons ltd

pedogenic gradients for iron and aluminum accumulation and phosphorus depletion in arctic and alpine soils as a function of time and climate pedogenically significant chemical extracts of iron aluminum and phosphorus are related mainly to time in chronosequences from baffin island canadian arctic the alpine sierra nevada and wind river range western united states the alpine khumbu glacier area himalaya nepal and the alpine southern alps new zealand based on the accumulation index for fe and al and the depletion index for p in each region the following ranking of chemical pedogenic development is obtained southern alps khumbu glacier area wind river range sierra nevada coastal baffin island inland baffin island the ranking mainly follows regional climate with the greatest accumulation and depletion to the warmest and wettest environment and the least accumulation and depletion in the coldest and driest environment

spatial distribution of trends and seasonally in the hemispheric sea ice covers 1978 1996 we extend earlier analyses of a 8 8 year sea ice data set that described the local seasonal variations and trends in each of the hemispheric sea ice covers to the recently merged 18 2 year sea ice record from four satellite instruments the seasonal cycle characteristics remain essentially the same as for the shorter time series but the local trends are markedly different in some cases reversing sign the sign reversal reflects the lack of a consistent long term trend and could be the result of localized long term oscillations in the hemispheric sea ice covers by combining the separate hemispheric sea ice records into a global one we have shown that there are statistically significant net decreases in the sea ice coverage on a global scale the change in the global sea ice extent is 0 01 0 003 106 km2 per decade the decrease in the areal coverage of the sea ice is only slightly smaller so that the difference in the two the ice free areas within the packs has no statistically significant change

soil stratigraphic techniques in the study of soil and landform evolution across the southern alps new zealand the southern alps lie along the convergent pacific indian plate boundary geomorphically distinct eastern axial and western regions reflect the east west gradient in tectonic uplift 1 to 10 mm a 1 and precipitation 600 to 10 000 mm a 1 the eastern region is divided into front ange and basin and range subregions soil sequence studies on terraces established temporal contrasts in pedogenesis within and between eastern and western regions encompassing entisols inceptisols and spodosols on late pleistocene and early holocene terraces dystrochrepts are persistent soils in the eastern region and aquods in the western region these soil sequences are used in the interpretation of relative soil age stratigraphy and erosion history in hill and mountain drainage basins of the eastern and western regions in the subhumid to humid eastern front range subregion simple soil forms occur as catenary sequences and there is little evidence of erosion following the destruction of forests in the last millenium mollisols are dominant in the subhumid and dystrochrepts in humid areas respectively soil debris mantle regoliths date from the early holocene and are still developing on slopes the soil pattern on mountain slopes in the humid eastern basin and range subregion is a complex array of simple eroded composite and compound soils this pattern has resulted from erosion following forest destruction within the last millenium the oldest surface or buried forest soils are dystrochrepts dating from the late pleistocene to early holocene wind erosion of these low fertility soils contributes to the loessial sediments in which younger soils have formed in the western region soil patterns and soil stratigraphy indicate continous instability with a complex pattern of highly leached shallow orthents and bedrock outcrops on slopes the soils are eroded from slopes within 2 ka these contrasts in soil development and erosion periodicity in the eastern and western regions of the southern alps parallel the east west contrasts in erosion rates of ca 1 10 mm a 1

holocene soil chronofunctions southern alps new zealand abstract field and laboratory data for two soil chronosequences from the high country of the south island of new zealand suggest rapid soil formation rates the areas studied are the ben ohau range and the mt cook area where mean annual precipitation is about 1 and 4 m respectively most soil ages are estimated from the thicknesses of rock weathering rinds soil chronofunctions are derived for indices that depict field profile and color development and a modified index of profile anisotropy for laboratory data out of a possible 21 chronofunctions 16 are statistically significant at the 0 05 level and 8 are from each area most 13 of the chronofunctions best fit a power model and the remaining ones are split between linear 2 and exponential 1 models although problems exist in the purity of the chronosequences because other soil forming factors are not constant duration of pedogenesis seems to be the most significant factor in explaining the trends despite the large differences in mean annual precipitation between the two areas many of the derived curves for property vs time are quite similar

influence of the scar geometry on landslide dynamics and deposits application to martian landslides received 24 january 2011 revised 23 june 2011 accepted 30 june 2011 published 4 october 2011 1 landslides dynamics prediction remains difficult in spite of a considerable number of studies the runout distance is widely used in analysis of landslide dynamics and in the calibration of the rheological parameters involved in numerical modeling however the unknown impact of the significant uncertainty in the shape of the initial released mass on the runoutdistanceandontheoverallshapeofthedepositraisesquestionsabouttherelevanceof these approaches the impact of the initial scar geometry on flow and distribution of the deposits is studied here using satellite data and numerical modeling of theoretical landslides and martian landslides informed by geomorphological analysis by varying the initial scar geometry from spoon shaped to steep wall geometry our results show that the runout distance is a very robust parameter that is only slightly affected by the change in the geometry of the initial scar on the contrary the lateral extent of the deposit is shown to be controlled by the scar geometry providing unique insights into the initial landsliding conditionsonmarsandmakesitpossibletoaccuratelyrecoverthevolumeinitiallyinvolved an essential ingredient for volume balance calculation a feedback analysis of valles marineris landslides can be drawn showing good agreement between numerical results and geomorphological analysis the geometry of the initial scar inferred from numerical modeling is strongly correlated with the regional tectonic history in valles marineris area

climatic significance of glacier retreat and rockglaciers re assessed in the light of cosmogenic dating and weathering rind thickness in claree valley brianconnais french alps recent advances in geochronology provide opportunities to identify the glacial and periglacial sequences in mountain area in this paper we focus on the upper durance catchment southern french alps in the claree valley where no absolute chronological benchmark was defined glacial remnants and periglacial features were investigated integrated within a chronological scenario thanks to relative weathering rind thickness and absolute cre technique dates we find evidence of the existence of a late glacial valley glacier that has never been reported before then the upper valleys became ice free during a period corresponding to the early holocene climate optimum whereas two sequences of cirque glaciation are identified during the second half of the holocene we also show evidence of three main generations of rockglaciers which also mainly developed during the second half of the holocene probably at the end of the subboreal period the location and the altitudes of rockglaciers are strongly dependent on the geomorphic setting especially the location of the sediment sources hence complicating their palaeo climatic interpretations

geochemical insights into the internal dynamics of debris avalanches a case study the socompa avalanche chile one way to infer the internal dynamics of debris avalanches is to characterize the heterogeneity of their deposits here we present high precision sr nd isotope compositions plus major and trace element concentrations of matrix samples and rock fragments from the socompa debris avalanche deposit chile the socompa blocks are easily identifiable in the field but distinguishing substrate debris from disaggregated material formed at the volcano is difficult to do with only field criteria combining isotope data with field observations can help with this measured sr and nd isotope ratios show significant variations defining a binary mixing array where matrix and rock deposits overlap this testifies to the mixing of crushed rocks during collapse and or movement assimilation of socompa basement appears to be variable overall it is far lower than was previously proposed comparison between matrix and block samples in contact over the whole surface area of the deposit shows that the isotopic heterogeneity increases from source to front close to the socompa matrices are resulting from simple crushing of adjacent rocks at the front rock samples with distinct compositions are found in a close relationship with matrices that result either from mixing of these or some of these rocks or from crushing of basement material between the source and the front the efficient mixing of socompa rocks and basement rocks generates matrices with isotopic compositions distinct from those of the blocks they are in contact with we interpret these results as being due to more efficient vertical mixing during the avalanche emplacement

climate change a glacial test of timing meticulous reconstruction of the former extent of a glacier high in the mountains of new zealand will help in interpreting global scale climatic adjustments that occurred at the end of the last glaciation

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

insights into rock ice avalanche dynamics by combined analysis of seismic recordings and a numerical avalanche model 1 rock ice avalanches larger than 1 106 m3 are high magnitude low frequency events that may occur in all ice covered high mountain areas around the world and can cause extensive damage if they reach populated regions the temporal and spatial evolution of the seismic signature from two events was analyzed and recordings at selected stations were compared to numerical model results of avalanche propagation the first event is a rock ice avalanche from iliamna volcano in alaska which serves as a natural laboratory with simple geometric conditions the second one originated on aoraki mt cook new zealand southern alps and is characterized by a much more complex topography a dynamic numerical model was used to calculate total avalanche momentum total kinetic energy and total frictional work rate among other parameters these three parameters correlate with characteristics of the seismic signature such as duration and signal envelopes while other parameters such as flow depths flow path and deposition geometry are well in agreement with observations the total frictional work rate shows the best correlation with the absolute seismic amplitude suggesting that it may be used as an independent model evaluation criterion and in certain cases as model calibration parameter the good fit is likely because the total frictional work rate represents the avalanche s energy loss rate part of which is captured by the seismometer deviations between corresponding calculated and measured parameters result from site and path effects which affect the recorded seismic signal or indicate deficiencies of the numerical model the seismic recordings contain additional information about when an avalanche reaches changes in topography along the runout path and enable more accurate velocity calculations the new concept of direct comparison of seismic and avalanche modeling data helps to constrain the numerical model input parameters and to improve the understanding of rock ice avalanche dynamics

subdivision of holocene glacial deposits ben ohau range new zealand using relative dating methods relative dating methods measure post depositional alteration of surficial deposits measured in this study are the size of the yellow green rhizocarpon lichen percent lichen cover weathering rind thickness quartz vein height surface oxidation and pitting of clasts the data are used to subdivide holocene deposits in the ben ohau range and to suggest correlation with moraines in other parts of the southern alps glacial and or rock glacier deposits of five different ages are identified in the ben ohau range ages can be approximated mainly from the rind development curve of chinn 1981 from youngest to oldest the deposits are dun fiunary 100 yr whale stream 250 yr jacks stream 3 000 yr ferintosh 4 000 yr and birch hill 9 000 yr all but the whale stream have been previously named but data presented here result in improved definitions of mapping units and more accurate age assignment the present climate of the ben ohau range is increasingly continental to the south a similar climatic gradient existed for much of the post birch hill holocene as shown by the glacial depositional facies moraines are common to the north whereas rock glaciers especially of jacks stream and ferintosh ages are common to the south in some areas rock glaciers that have long been inactive have recently been reactivated data from moraines in the waimakariri drainage and the mount cook cameron valley and rakaia river areas improve previous correlations as relative dating methods provide age information where 14c ages are either lacking or limiting or when a single relative dating method is subject to erroneous interpretation

model space exploration for determining landslide source history from long period seismic data the seismic signals generated by two large volcanic debris avalanches montserrat lesser antilles 1997 and mount st helens usa 1980 and a large rock ice avalanche mount steller usa 2005 have been analyzed for the two debris avalanches given the times and locations of such landslides their signals were recorded by only a few seismic stations moreover these signals cover only a very narrow frequency band and include considerable noise the mount steller on the contrary was precisely recorded for each event the source mechanism i e point force has been determined by waveform inversion using at most two broadband seismic stations the resulting force is very difficult to interpret in terms of landslide characteristics a monte carlo inversion was therefore performed by imposing a simple force model associated with the landslide based on the schematic view of an accelerating decelerating mass traveling down the slope the best parameter set of the force model was then found by minimizing misfits and maximizing correlations between data and synthetic signals this model appears to contain the minimum degree of complexity required to well reproduce the seismic data we detail here the method for the montserrat debris avalanche and then present it s validation on the well studied mount st helens debris avalanche and the well recorded mount steller rock ice avalanche the horizontal and vertical components of the resulting force have different source time functions the best force model compares well with the force obtained by waveform inversion finally this simple force model was interpreted using analytical and empirical relations derived from the sliding block model granular flow model and landslide studies this made it possible to estimate the order of magnitude of the mass flow duration and direction initial topography slope mean velocity and travel distance of the avalanches for these three avalanches the calculated characteristics are consistent with former studies

the hypermobility of huge landslides and avalanches abstract catastrophic failure of large land masses which generate landslides rockfalls and debris avalanches can have hazardous consequences extending far beyond the source observations show that the mobility of such events depends strongly on the volume for volumes larger than 10 6 m 3 with many different processes invoked to explain higher mobilities hypermobility for both terrestrial and extraterrestrial events although the mobility of large events has been extensively studied there is no generally accepted mechanism for predicting extreme travel distances because the underlying physical processes are poorly understood here we show using physical and rheological arguments that the wide scatter observed for very large mass wasting events in all environments collapses to a single relationship between event volume or inundation area and mobility hypermobility is defined to be the reciprocal of the effective friction coefficient e where the scale dependent e is derived analytically as a function of the mechanical volumetric and topographical parameters of the flow the dominant term in the coefficient is the degree of fluidization involved in the flow our results show that fluidization is limited in extraterrestrial events that significant fluidization occurs in non volcanic and volcanic events and fluidization dominates submarine events this analysis demonstrates that fluidization is associated with long run out distances and that the degree of fluidization can be predicted by the volume and physical and topographic parameters the methodology is simple physically based and validated with datasets of very large terrestrial and extraterrestrial avalanche events we demonstrate that the effective coulomb friction rheology and the hypermobility function are applicable to avalanche events of any size providing an opportunity to simulate past and or potential huge landslide and debris avalanche events run out distances destructive impact and assessment of risk the model can be used to estimate the overrun area and volume in terms of known mobility data