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

superheated steam hot co2 and dynamic recrystallization from frictional heat jointly lubricated a giant landslide field and experimental evidence abstract we used thermogravimetry to determine that the frictionally heated sliding surface reached 850 c at the base of the 1 16 10 9 m 3 daguangbao landslide triggered during the 2008 ms8 2 wenchuan earthquake optical and electron microscope images reveal evidence of dolomite thermal decomposition hot fluid penetrating fine cracks and dynamic recrystallization of minerals a high speed rotary shear apparatus simulated the rapid sliding and provided data on very low frictional resistance friction coefficient 0 05 during shearing above 1 m s electron probe analysis of samples from the experiments showed lime and magnesia from thermal decomposition of dolomite some of the sheared minerals formed a dynamically recrystallized layer 0 1 mm thick and its viscous resistance would have contributed to the low apparent friction during high speed sliding a further explanation however was very high pore fluid pressure from hot supercritical co2 and superheated steam at a partial pressure of 10 mpa in the field situation with groundwater these friction reducing mechanisms are not mutually exclusive and both were present simultaneously at the landslide base

the formation of peak ring basins working hypotheses and path forward in using observations to constrain models of impact basin formation abstract impact basins provide windows into the crustal structure and stratigraphy of planetary bodies however interpreting the stratigraphic origin of basin materials requires an understanding of the processes controlling basin formation and morphology peak ring basins exhibiting a rim crest and single interior ring of peaks provide important insight into the basin formation process as they are transitional between complex craters with central peaks and larger multi ring basins new image and altimetry data from the lunar reconnaissance orbiter as well as a suite of remote sensing datasets have permitted a reassessment of the origin of lunar peak ring basins we synthesize morphometric spectroscopic and gravity observations of lunar peak ring basins and describe two working hypotheses for the formation of peak rings that involve interactions between inward collapsing walls of the transient cavity and large central uplifts of the crust and mantle major facets of our observations are then compared and discussed in the context of numerical simulations of peak ring basin formation in order to plot a course for future model refinement and development

topographic reflection of the socompa debris avalanche chile one of the most remarkable features of the exceptionally well preserved 26 km3 socompa debris avalanche deposit is the evidence for topographically driven secondary flow the avalanche formed by sector collapse of socompa stratovolcano and spread 40 km across a pre existing basin forming a sheet of 50 m average thickness as the avalanche impinged on the western and northern margins of the basin it was reflected back forming a secondary flow that continued to travel 15 km down a gentle slope at an oblique angle to the primary flow the front of the return wave being preserved frozen on the surface of the deposit as a prominent escarpment satellite images aerial photos digital elevation models and field observations were used to reconstruct the sequence of events during avalanche emplacement and in particular during secondary flow the avalanche sheet was divided into distinct terrane groups each believed to have experienced a particular strain history during emplacement evidence for avalanche reflection includes clearly recognizable secondary slide masses sub parallel sets of curvilinear shear zones headwall scarps separating the primary levee from the secondary terranes extensional jigsaw breakup of surface lithologies during return flow and cross cutting or deflection of primary flow fabrics by secondary terranes reflection off the basin margin took place in an essentially continuous manner most major return motions being simultaneous with or shortly following primary flow the secondary flow occurred as a wave that swept obliquely across the primary avalanche direction remobilizing the primary material which was first compressed then stretched as it passed over and rearward of the wave front as return flow occurred surface lithologies were rifted in a brittle manner and the slabs were sheared pervasively as they glided and rotated back into the basin some sank into the more fluidal interior of the avalanche which drained out into a prominent distal lobe extension by factors of up to 1 8 took place during return flow secondary flow took place on slopes of only a few degrees and the distal lobe flowed 8 km on a slope of 1 overall the avalanche is inferred to have slid into place as a fast moving sheet of fragmental rock debris with a leading edge and crust with near normal friction and an almost frictionless fluidal interior and base the avalanche emplacement history deduced from field evidence is consistent with the results of a previously published numerical model of the socompa avalanche

acoustic fluidization and the extraordinary mobility of sturzstroms 1 sturzstroms are a rare category of rock avalanche that travel vast horizontal distances with only a comparatively small vertical drop in height their extraordinary mobility appears to be a consequence of sustained fluid like behavior during motion which persists even for driving stresses well below those normally associated with granular flows one mechanism that may explain this temporary increase in the mobility of rock debris is acoustic fluidization where transient high frequency pressure fluctuations generated during the initial collapse and subsequent flow of a mass of rock debris may locally relieve overburden stresses in the rock mass and thus reduce the frictional resistance to slip between fragments in this paper we develop the acoustic fluidization model for the mechanics of sturzstroms and discuss the conditions under which this process may sustain fluid like flow of large rock avalanches at low driving stresses

massive ice avalanches on iapetus mobilized by friction reduction during flash heating the great distance travelled by long runout landslides observed previously on the earth and mars requires a mechanism of friction reduction identification and analysis of long runout landslides on saturn s moon iapetus suggests that the iapetian landslides are enabled by flash heating of the icy sliding surface

increased ice loading in the antarctic peninsula since the 1850s and its effect on glacial isostatic adjustment antarctic peninsula ap ice core records indicate significant accumulation increase since 1855 and any resultant ice mass increase has the potential to contribute substantially to present day glacial isostatic adjustment gia we derive empirical orthogonal functions from climate model output to infer typical spatial patterns of accumulation over the ap and by combining with ice core records estimate annual accumulation for the period 1855 2010 in response to this accumulation history high resolution ice sheet modeling predicts ice thickness increases of up to 45 m with the greatest thickening in the northern and western ap whilst this thickening is predicted to affect grace estimates by no more than 6 2 gt yr it may contribute up to 7 mm yr to the present day gia uplift rate depending on the chosen earth model with a strong east west gradient across the ap its consideration is therefore critical to the interpretation of observed gps velocities in the ap

noise and target strength degradation accompanying shallow buried explosions ground shock from shallow buried explosions is commonly accompanied by acoustic noise analysis of records from a series of 10 ton chemical detonations in gulf coast sediments provides a basis for the first quantitative description of such noise during a cratering event the test series included shots at depths of 3 12 m leading to craters about 20 m in radius most of the records studied were taken within the eventual crater they include stress velocity and acceleration oscillations arising from reflections off the free surface or subsurface layers are evident in stress records high frequency oscillations attributed to reflections or scattering from smaller scale inhomogeneities are particularly striking in the acceleration records where peak accelerations were 10 100 km s2 oscillations with frequencies of 5 25 khz are obvious they exhibit exponential decay with the dominant frequency decreasing with time approximate values of q estimated from these accelerograms are 30 20 agreeing with q for similar materials derived from seismic techniques since seismic q s include both internal dissipation and scattering losses whereas explosive q s include internal dissipation and radiative losses the magnitude of scattering and radiative losses must be comparable the latter alone correspond to an effective q of about 300 so that internal dissipation dominates q in these poorly consolidated sediments acoustic fluidization may have occurred for a couple of milliseconds in the top 1 or 2 m of soil within the eventual crater by this we mean that the material was liable to flow if the threshold shear stress were exceeded this result is inferred from ground shock stress duration acoustic amplitude decay and initial overburden stress fluidization of such limited duration and extent would have no effect on crater growth just as would be expected for such a low yield event

discrete element simulation of the jiufengershan rock and soil avalanche triggered by the 1999 chi chi earthquake taiwan we present contact dynamics discrete element simulations of the earthquake triggered jiufengershan avalanche which mobilized a 60 m thick 1 5 km long sedimentary layer dipping similar to 22 degrees se toward a valley the dynamic behavior of the avalanche is simulated under different assumptions about rock behavior water table height and boundary shear strength additionally seismic shaking is introduced using strong motion records from nearby stations we assume that seismic shaking generates shearing and frictional heating along the surface of rupture which in turn may induce dynamic weakening and avalanche triggering a simple slip weakening criterion was adopted to simulate shear strength drop along the rupture surface we investigate the mechanical processes occurring during triggering and propagation of an avalanche mobilizing shallowly dipping layers incipient deformation forms a pop up structure at the toe of the dip slope as the avalanche propagates the pop up deforms into an overturned fold which overrides the surface of separation along a decollement simultaneously uphill layers slide at high velocity 125 km h and are folded and disrupted as they reach the toe of the dip slope the avalanche foot forms a wedge that is pushed forward as deformed rocks accrete at its rear we simulated five cross sections across the jiufengershan avalanche which differ in the geometry of the surface of separation topographic and simulated surface profiles are similar the friction coefficient at the surface of separation determined from back analysis is abnormally low mu ss 0 2 possibly due to lubrication by liquefied soils the granular deposits of simulated earthquake and rain triggered avalanches are similar

landslides on charon abstract we investigated five large landslides identified in the serenity chasma region of charon the identification of these landslides involved a search for these features in images taken by cameras onboard the new horizons spacecraft various landslide properties were analyzed based on their morphologies using a digital terrain model of the region we found that landslides are confined to the walls of the large normal fault scarps that make up serenity chasma based on extensive landslide runout lengths l relative to their drop heights h we classified these features as long runout landslides by analyzing their geometries we estimated the friction coefficients of the landslide material h l to be between 0 15 to 0 31 and the runout efficiencies l h to be between 3 2 and 6 8 we also estimated that the specific energy released during landslide motion ranged from 0 8 to 1 3 kj kg 1 these amounts of energy were too low to have generated significant melt around landslide particles

volcanic avalanche fault zone with pseudotachylite and gouge in french massif central abstract structures and textures with sedimentological variations at different scales of the lithofacies assemblage help us to constrain the basal kinematic transition from non depositional to depositional conditions during volcanic avalanche emplacement in the well exposed impact sheared contact along volcanic avalanche fault zone in the french massif central we observe how the granular textures of the pseudotachylite and fault gouge have recorded the propagation of shock wave with granular oscillatory stress sequential events of basal aggradation along avalanche fault zone have been established related to fractal d values temperature pressure regime and oscillatory stress during slow wave velocity a typical lithofacies assemblage with a reverse grading shows the pseudotachylite and fault gouge a cataclastic gradient is characterised by the fractal d values from 2 7 in jigsaw breccias with pseudotachylite partial melt to 2 6 in the polymodal gouge shock brecciation and comminution produce cataclastic shear bands in the pseudotachylite and quartz microstructures along the basal contact of the volcanic debris avalanche deposit gouge microstructures show granular segregation cataclasis with antithetic rotational riedel shear and an arching effect between the riedel shear bands x ray microtomography provided 3d microfabrics along the clastic vein in the sandy gouge from the available statistical dataset a few equations have been developed implicating the same cataclastic origin with a co genetic evolution of lithofacies an impact wave during primary shear propagation may contribute to produce hydroclastic matrix pseudotachylite partial melt and proximal gouge thixotropy with v 50m s and a t

global scale analysis of martian landslide mobility and paleoenvironmental clues the mobility of landslides on mars is studied based on a database of 3 118 events to establish the volume of the landslides for the whole dataset based on the deposit area a new volume area relationship based on a representative dataset of 222 landslides is used plotting the h l ratio between fall height h and runout l versus volume landslide mobility is analyzed and compared with existing empirical relationships for martian and terrestrial landslides analyzing the mobility in terms of normalized residuals i e the relative deviation of the h l ratio from the dataset best fit line mobility is found to depend on both the landslide location on mars and landslide typology this allows us to identify four different types of high mobility hypermobile landslides three classes of high mobility landslides are associated respectively to meteoroid impact the olympus mons aureoles and landslides with toreva block failure style and their mobility can be explained by the peculiar flow mechanics the fourth class includes landslides associated with isolated craters those in the regions wetted by the putative oceanus borealis and the ones at high latitudes we suggest that the common factor behind all the hypermobile landslides of this fourth kind is the presence of ice this is confirmed by our data showing that landslides increase in mobility with latitude the latitudinal trend mirrors the distribution of ice as detected by radar neutron probes and the presence of glacial and layered ejecta morphologies because the overall landslide distribution supports the presence of ice lubricated conditions two ice lubrication models are presented showing how ice melting within or underneath the landslides could enhance mobility by proper analysis in terms of apparent friction residuals we find that the mobility of landslides in valles marineris with the largest landslide concentration is lower than average we explain this circumstance partly from the smaller role of ice in equatorial valles marineris and partly because the collapses from high slope relief imply high speed impact with the floor valley confinement loss of momentum and decrease in mobility environmental consequences imply that the present subsurface ice distribution may have been persistent throughout the amazonian period

drop height and volume control the mobility of long runout landslides on the earth and mars long runout landslides are landslides with volumes of 105 m3 or more which move much farther from their source than expected the observation that martian landslides are generally less mobile than terrestrial landslides offers important evidence regarding the mechanism responsible for the high mobility of long runout landslides here we simulate landslides as granular flow using a soft particle discrete element model we show that while surface gravity plays a negligible role observed differences in fall height naturally reproduce the observed differences in mobility of martian and terrestrial landslides we also demonstrate that landslides on iapetus may fit this trend our simulations do not include any fluid and indicate that a mechanism similar to acoustic fluidization can explain the high mobility of long runout landslides this implies that long runout landslides on mars should not be considered as evidence for ice saturated clays or liquid water

the reduction of friction in long runout landslides as an emergent phenomenon campbell et al 1995 modeled long runout landslides as granular flow using a soft particle code their model essentially simulates landslides from first principles and although no fluid or obvious mechanism for reduction of friction is included the model successfully reproduced many field observations of landslides e g the preservation of source stratigraphy in the final slide mass and a decreasing effective friction with increasing slide volume we extend the work of campbell et al 1995 with a focus on the mechanism that reduces friction in these slides we find sliding preferentially occurs when the overburden is relieved by pressure variations in the slide further analysis shows that our results are very similar to the predictions of the acoustic fluidization hypothesis moreover we determine that for long runout landslides the wavelength of vibrations associated with acoustic fluidization is determined by the size of the rock fragments in the slide

comparing landslides to fluidized crater ejecta on mars 1 we use the mars global surveyor and viking data sets to compare and contrast the geomorphology of four large martian landslides located in valles marineris to fluidized ejecta of seven fresh martian craters located in lunae planum both mass movements have flowed over the martian surface and possess characteristics seen in terrestrial mass movements we combine these comparisons with simple flow models to determine how the planar geometry of landslides and the cylindrical geometry of ejecta can generate different topographic expressions for the same input constraints our purpose is to better understand the emplacement processes of both types of mass movements our geomorphic analyses are consistent with previous views that the large martian landslides resemble large terrestrial long run out flows the planar flow model supports this inference martian landslides probably flowed as a basal glide where motion is limited to a narrow interface at the base of the mass movement geomorphic investigations of fresh multilayered ejecta indicate that their inner portions with their subtle rampart probably flowed like their landslide counterparts as a basal glide distal pronounced contiguous ramparts however resemble features akin to terrestrial debris flows the cylindrical flow model shows that differences in geometry can mask the dynamics of flow emplacement this model suggests as expected a basal glide origin for the inner portions of the ejecta surprisingly basal glide also best explains the topography of the distal ejecta ramparts

commentary on the reduction of friction in long runout landslides as an emergent phenomenon by brandon c johnson charles s campbell and h jay melosh

crustal evolution of the north qinling terrain of the qinling orogen china evidence from detrital zircon u pb ages and hf isotopic composition abstract the north qinling terrain reveals a different geological history from the north china block to the north and the south qinling micro continental block to the south the timing of events and geochemical features of the north qinling terrain are essential for understanding the evolution of the qinling orogenic belt that joins the north and south china blocks this study presents detrital zircon ages and hf isotopic compositions from the guandaokou group a cover sequence of the north china block and from the kuanping group an upper basement sequence of the north qinling terrain the youngest detrital zircon u pb ages constrain the initiation of sedimentation in the guandaokou group to 1 85 ga and the maximum depositional age of the kuanping group to 640 ma zircon u pb ages and hf data testify to a major phase of magmatism in the north qinling terrain at 1000 900 ma the magmatic rocks were largely produced from reworking of early paleoproterozoic 2 5 2 0 ga crust with minor contribution of late paleoproterozoic 1 7 ga juvenile material this age record differs in time from the two important thermal events of 1 85 ga and 2 5 ga widely manifested in the north china block the north qinling terrain can thus be regarded as a separate micro continent with a pre neoproterozoic evolution different from that of the north china block the final assembly of the north qinling terrain to the north china block took place after about 640 ma

rock and soil avalanches theory and simulation 1 we present a 2 d contact dynamics discrete element model for simulating initiation and motion of rock avalanches integrating hillslope geometry mohr coulomb rock behavior pore pressure before avalanche triggering and avalanche trigger avalanche motion is modeled as a dense granular flow of dry frictional and cohesive particles on the basis of granular physics and shear experiments we review some of the theories for the unexpectedly long runout of rock avalanches different causes are evoked according to the strength strong or weak of the slip surface relative to the bulk mechanical fluidization and acoustic fluidization theories state that agitation of rock particles reduces frictional strength increasing runout conversely granular mechanics suggests that as shear strain rate increases granular material becomes more agitated more dissipative and more resistant another theory states that dynamic fragmentation of clasts creates an isotropic pressure that drives longer runout in contrast granular mechanics suggests that fragmentation may induce fluidization and strengthening of the granular material while particle size reduction among others induces weakening of the granular flow and enhances long runout runout is also enhanced for column like rock masses collapsing from steep hillslopes long runout may also be linked to thermal weakening mechanisms at the slip surface e g thermal pressurization and shear melting which may lower drastically the shear strength the model is illustrated with a hypothetical example of a rain triggered avalanche mobilizing shallowly dipping layers several phases are identified including slope failure avalanche triggering resulting from slip weakening and avalanche motion in which rocks are folded and sheared

grain size distribution and sedimentology in volcanic mass wasting flows implications for propagation and mobility the sedimentological characteristics of mass wasting flow deposits are important for assessing the differences between phenomena and their propagation and emplacement mechanisms in the present study nine volcanic debris avalanche deposits and eight lahar deposits are considered from the literature their sedimentology is expressed in the descriptive statistics median grain size sand gravel and finer particle fractions skewness and sorting analysis of the data confirms that lahars and debris avalanches diverge in their grain size distribution and in their evolution during propagation water saturation in lahars is the main factor enabling debulking a mechanism that is not recorded in the data derived from debris avalanches deposits on the contrary evidence of comminution of particles due to particle particle interactions is observed in debris avalanches and not in lahars these findings support previous studies suggesting that although water content in debris avalanches plays a role in propagation the effects of inertial collision of solid fragments are more important than fluid effects confirming that particle particle interactions are the main factor influencing the mobility of non saturated mass wasting flows

dynamical weakening of faults by acoustic fluidization when a fault slips seismically some of the energy released may excite strong short wavelength vibrations near the fault core such vibrations can temporarily reduce the normal stress on the fault allowing it to slip at lower shear stresses than predicted by laboratory coefficients of friction this phenomenon of acoustic fluidization provides an alternative to theories that invoke pressurized fluids as an explanation for why some faults appear to be so weak

transport and emplacement mechanisms of channelised long runout debris avalanches ruapehu volcano new zealand the steep flanks of composite volcanoes are prone to collapse producing debris avalanches that completely reshape the landscape this study describes new insights into the runout of large debris avalanches enhanced by topography using the example of six debris avalanche deposits from mount ruapehu new zealand individual large flank collapses 1 km3 produced all of these units with four not previously recognised five major valleys within the highly dissected landscape surrounding mount ruapehu channelled the debris avalanches into deep gorges 15 m and resulted in extremely long debris avalanche runouts of up to 80 km from source classical sedimentary features of debris avalanche deposits preserved in these units include the following very poor sorting with a clay sand matrix hosting large subrounded boulders up to 5 m in diameter jigsaw fractured clasts deformed clasts and numerous rip up clasts of late pliocene marine sediments the unusually long runouts led to unique features in distal deposits including a pervasive and consolidated interclast matrix and common rip up clasts of tertiary mudstone as well as fluvial gravels and boulders the great travel distances can be explained by the debris avalanches entering deep confined channels 15 m where friction was minimised by a reduced basal contact area along with loading of water saturated substrates which formed a basal lubrication zone for the overlying flowing mass extremely long runout debris avalanches are most likely to occur in settings where initially partly saturated collapsing masses move down deep valleys and become thoroughly liquified at their base this happens when pore water is available within the base of the flowing mass or in the sediments immediately below it based on their h l ratio confined volcanic debris avalanches are two to three times longer than unconfined spreading flows of similar volume the hybrid qualities of the deposits which have some similarities to those of debris flows are important to recognise when evaluating mass flow hazards at stratovolcanoes

from cinderella s dilemma to rock slides a mixture of two different types of grain can undergo spontaneous stratification simply by being poured this surprising behaviour may be significant in fields from pharmaceuticals to geology

revisiting the field geology of taurus littrow abstract integration of apollo 17 field observations and photographs sample investigations lunar reconnaissance orbiter camera images chandrayaan 1 moon mineralogy mapper m3 spectra and miniature radio frequency mini rf s band radar images provides new insights into the geology of the valley of taurus littrow on the moon connecting the various remote observations to sample data enables a set of new conclusions to be drawn regarding the geological evolution of the valley structural considerations and published and recalculated 40ar 39ar analyses of samples from the north massif and the sculptured hills indicate that the crisium basin formed about 3 93 ga the serenitatis basin about 3 82 ga and the imbrium basin no earlier than 3 82 ga and no later than the average of 3 72 ga for 33 age dates from samples of the valley s mare basalts strong evidence continues to support the conclusion of others lucchitta 1972 spudis et al 2011 fassett et al 2012 that the sculptured hills physiographic unit consists of imbrium ejecta interpretation of m3 spectral data and apollo 17 samples indicate that rock units of the sculptured hills consist of a largely coherent mg suite pluton lroc nac stereo images and mini rf data indicate the presence of several exposed pyroclastic fissures across the sculptured hills rim boulders at camelot crater constitute nearly in situ wall rocks of that crater rather than ejecta and provide an opportunity for investigations of remanent magnetic field orientation at the time of the eruption of late mare basalt lavas in the valley paleomagnetic field orientation information also may be obtained relative to melt breccia contacts in north massif boulders that suggest original horizontal orientations lroc images indicate the existence of two temporally separate light mantle avalanche deposits the origin potential flow mechanisms and geology of the youngest avalanche from the south massif have been clarified the existence of two distinct light mantle avalanches raises doubt about the association of either light mantle avalanche with secondary impacts related to the tycho impact event alternatively the lee lincoln thrust fault appears to have triggered the second light mantle avalanche between 70 and 110 ma a simple structural analysis shows that this thrust fault dips 20 25 to the southwest where it crosses the north massif and to the west where it crosses the valley floor mini rf data reveal a line of reduced reflections roughly perpendicular to contours on the north massif about 3 km to the east of the lee lincoln fault although this line is possibly an older ancillary fault lroc nac stereo images indicate that it may be best explained as a pyroclastic fissure a debris flow of dark apparent pyroclastic ash lies below the southeast end of the potential fissure finally young lunar impact glass sample 70019 has been precisely located within lroc nac images and oriented for the first time using 60 mm f l sample documentation photographs sample 70019 can now be employed in lunar paleomagnetic field orientation studies

cassini observations of flow like features in western tui regio titan 1 a large 3 104 km2 lobate 5 m bright region seen by cassini on titan s leading equatorial region is best explained as a flow field we discuss observations from the visual and infrared mapping spectrometer and imaging science subsystem of the feature and present a map of the field we establish relative ages of flow features and discuss possible formation mechanisms and the implications of this finding for the evolution of titan s surface

collapse of a two dimensional brittle granular column implications for understanding dynamic rock fragmentation in a landslide we investigate numerically the failure collapse and flow of a two dimensional brittle granular column over a horizontal surface in our discrete element simulations we consider a vertical monolayer of spherical particles that are initially held together by tensile bonds which can be irreversibly broken during the collapse this leads to dynamic fragmentation within the material during the flow compared to what happens in the case of a non cohesive granular column the deposit is much rougher and the internal stratigraphic structure of the column is not preserved during the collapse as has been observed in natural rockslides we find that the deposit consists of large blocks laying on a lower layer of fine fragments the influence of the aspect ratio of the column on the run out distance is the same as in the non cohesive case finally we show that for a given aspect ratio of the column the run out distance is higher when the deposit is highly fragmented which confirms previous hypotheses proposed by davies et al 1999

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

surface refreshing of martian moon phobos by orbital eccentricity driven grain motion the surface of the martian moon phobos exhibits two distinct geologic units red and blue characterized by their spectral slopes the provenance of these units is uncertain yet crucial to understanding the origin of the martian moon and its interaction with the space environment here we present a combination of dynamical analyses and numerical simulations of particle dynamics to show that periodic variations in dynamic slopes driven by orbital eccentricity can cause surface grain motion for regions with steep slopes that vary substantially over one phobos orbit the surface is excavated at a faster rate than the space weathering timescale our model predicts that this new mechanism is most effective in regions that coincide with blue units therefore space weathering is the likely driver of the dichotomy on the moon s surface reddening blue units that represent pristine endogenic material the distribution of two distinct geologic units on mars s moon phobos red and blue units can be explained by surface grain motion triggered by orbital variations in slope steepness according to dynamical analyses and numerical simulations

investigation of rock fragmentation during rockfalls and rock avalanches via 3 d discrete element analyses this paper investigates the characteristics of dynamic rock fragmentation and its influence on the postfailure fragment trajectory a series of numerical simulations by discrete element method dem were performed for a simple rock block and slope geometry where a particle agglomerate of prismatic shape is released along a sliding plane and subsequently collides onto a flat horizontal plane at a sharp kink point the rock block is modeled as an assembly of bonded spherical particles with fragmentation arising from bond breakages bond strength and stiffness were calibrated against available experimental data we analyzed how dynamic fragmentation occurs at impact together with the generated fragment size distributions and consequently their runout for different slope topographies it emerges that after impact the vertical momentum of the granular system decreases sharply to nil while the horizontal momentum increases suddenly and then decreases the sudden boost of horizontal momentum can effectively facilitate the transport of fragments along the bottom floor the rock fragmentation intensity is associated with the input energy and increases quickly with the slope angle gentle slopes normally lead to long spreading distance and large fragments while steep slopes lead to high momentum boosts and impact forces with efficient rock fragmentation and fine deposits the fragment size decreases while the fracture stress and fragment number both increase with the impact loading strain rate supporting the experimental observations the fragment size distributions can be well fitted by the weibull s distribution function

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

dynamic disintegration processes accompanying transport of the holocene flims sturzstrom swiss alps abstract a sturzstrom is a large scale landslide that evolves during transport into a rapid granular flow rock avalanche by a dynamic disintegration process numerous theoretical hypotheses have been proposed to explain the excessive mobility of these catastrophic mass movements but the role of disintegration processes remains poorly understood exceptional outcrop conditions at the giant 12 km3 flims sturzstrom swiss alps permit the analysis of disintegration processes that result from shearing during transport in confined zones of the rock mass shearing is concentrated along preferred surfaces originating as bedding planes which evolve into shear band layers differential velocities of slabs separated by these shear layers induce oblique fractures in the slabs by accommodation contacts between grains are maintained in the shear layers in unconfined zones near the top and the lateral margins shearing generates dilatancy the rock mass is affected by anisotropic dispersion without mixing and disintegrated material is preferentially produced to the top due to inflation the rock slide then evolves to a granular flow the consequence of these processes is the formation of two distinct depositional facies in the sturzstrom the structured facies exhibits a stratified aspect close to the base reflecting confined slab on slab shearing motion towards the top and distally it evolves into a chaotic facies with some isolated pockets of the structured facies reduction of confining forces on the moving sturzstrom allows transformation of the structured facies into the chaotic facies this characteristic transition observable in many sturzstrom deposits seems to be necessary for the rock avalanche process to occur and offers insights into the long runout characteristics of these catastrophic mass movements

the extreme mobility of debris avalanches a new model of transport mechanism large rockslide debris avalanches resulting from flank collapses that shape volcanoes and mountains on earth and other object of the solar system are rapid and dangerous gravity driven granular flows that travel abnormal distances during the last 50 years numerous physical models have been put forward to explain their extreme mobility the principal models are based on fluidization lubrication or dynamic disintegration however these processes remain poorly constrained to identify precisely the transport mechanisms during debris avalanches we examined morphometric fractal dimension and circularity grain size and exoscopic characteristics of the various types of particles clasts and matrix from volcanic debris avalanche deposits of la reunion island indian ocean from these data we demonstrate for the first time that syn transport dynamic disintegration continuously operates with the increasing runout distance from the source down to a grinding limit of 500 m below this limit the particle size reduction exclusively results from their attrition by frictional interactions consequently the exceptional mobility of debris avalanches may be explained by the combined effect of elastic energy release during the dynamic disintegration of the larger clasts and frictional reduction within the matrix due to interactions between the finer particles

a depth averaged two phase model for debris flows over erodible beds mass exchange between debris flow and the bed plays a vital role in debris flow dynamics here a depth averaged two phase model is proposed for debris flows over erodible beds compared to previous depth averaged two phase models the present model features a physical step forward by explicitly incorporating the mass exchange between the flow and the bed a widely used closure model in fluvial hydraulics is employed to estimate the mass exchange between the debris flow and the bed and an existing relationship for bed entrainment rate is introduced for comparison also two distinct closure models for the bed shear stresses are evaluated one uses the coulomb friction law and manning s equation to determine the solid and fluid resistances respectively while the other employs an analytically derived formula for the solid phase and the mixing length approach for the fluid phase a well balanced numerical algorithm is applied to solve the governing equations of the model the present model is first shown to reproduce average sediment concentrations in steady and uniform debris flows over saturated bed as compared to an existing formula underpinned by experimental datasets then it is demonstrated to perform rather well as compared to the full set of usgs large scale experimental debris flows over erodible beds in producing debris flow depth front location and bed deformation the effects of initial conditions on debris flow mass and momentum gain are resolved by the present model which explicitly demonstrates the roles of the wetness porosity and volume of bed sediments in affecting the flow by virtue of extended modeling cases the present model produces debris flow efficiency that as revealed by existing observations and empirical relations increases with initial volume which is enhanced by mass gain from the bed copyright 2017 john wiley sons ltd

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

origin of mountains on io by thrust faulting and large scale mass movements voyager stereoimages of euboea montes io indicate that this mountain formed when a large crustal block was uplifted 10 5 kilometers and tilted by approximately 6 degrees uplift triggered a massive slope failure on the northwest flank forming one of the largest debris aprons in the solar system this slope failure probably involved relatively unconsolidated layers totaling approximately 2 kilometers in thickness overlying a rigid crust or lithosphere at least 11 kilometers thick mountain formation on io may involve localized deep rooted thrust faulting and block rotation due to compression at depth induced during vertical recycling of io s crust

large mass movements on callisto galileo images reveal the presence of mass movement deposits within impact craters on callisto eleven such deposits were found in 830 candidate craters imaged at sufficient resolutions 86 280 m pixel for their identification all of the deposits are located within impact craters and their sources appear to be crater wall material the morphologies of the callistan deposits are similar to terrestrial mass movements and rock glaciers rock glaciers involve ductile flow of ice and rock but in the callistan environment water ice is likely to undergo brittle deformation consequently rock glaciers are unlikely analogs for the features on callisto three morphologies are observed one blocky one slump like and nine lobate deposits blocky deposits are characterized by massive blocks on the crater floor while slump like deposits appear as debris piles along the base of the crater wall lobate deposits are 1 7 9 9 km long average 90 m in thickness and have tapered or semicircular terminations callistan lobate deposits are morphologically similar to rapidly emplaced dry rock avalanches on earth their significant thickness and steep frontal margins suggest that they may have behaved similarly to bingham plastic material with a critical yield strength the callistan deposits have yield strengths similar to those estimated for terrestrial dry rock avalanches the blocky deposit appears similar to terrestrial block glide deposits in which large blocks detach and slide downslope individual blocks within the blocky deposits may be up to 1 km across and stand 30 60 m high callistan slump like deposits are similar to terrestrial slumps which fail along rotational planes mass movements on callisto are not confined to craters they have also been observed along the base of scarps knobs and ridges three of the callistan deposits may have been impact triggered because of the proximity of an impact crater near the source first order analyses of the ground force generated by impacts show that two of the candidate deposits are capable of being impact triggered the callistan mass movements are probably set into motion by a combination of sublimation of ice which undermines a near surface layer of lag material and seismic triggering associated with nearby impact events

large scale landslide simulations global deformation velocities and basal friction the cause of the apparent small friction exhibited by long runout landslides has long been speculated upon in an attempt to provide some insight into the matter this paper describes results obtained from a discrete particle computer simulation of landslides composed of up to 1 000 000 two dimensional discs while simplified the results show many of the characteristics of field data the volumetric effect on runout preserved strata etc and with allowances made for the two dimensional nature of the simulation the runouts compare well with those of actual landslides the results challenge the current view that landslides travel as a nearly solid block riding atop a low friction basal layer instead they show that the mass is completely shearing and indicate that the apparent friction coefficient is an increasing function of shear rate the volumetric effect can then be understood with all other conditions being equal different size slides appear to travel with nearly the same average velocity however as the larger landslides are thicker they experience smaller shear rates and correspondingly smaller fractional resistance

rupture mechanism and interface separation in foam rubber models of earthquakes a possible solution to the heat flow paradox and the paradox of large overthrusts abstract spontaneous stick slip along the interface between stressed foam rubber blocks is a simple analog of earthquake rupture and stick slip results from this model are used to elucidate the role of normal stress variations along the interface in the stick slip process observations indicate significant normal interface vibrations and separation during slip suggesting that dynamic changes in normal stress rather than a drop in the coefficient of friction may control stick slip as suggested for example by tolstoi oden and martins and brune and co workers observations of particle trajectories indicate that stick slip shear motion is associated with various degrees of fault separation for an asymmetric model the motion is consistent with slipping motion of the type suggested by schallamach and price for a symmetric model the motion is similar to that suggested by comninou and dundurs if interface waves of this type involving separation during slip occur in earthquakes they may be a solution to the heat flow paradox since a major part of the slip occurs during separation and during low normal stress thus frictional heat generation is reduced normal interface vibrations during stick slip may explain the high corner frequency of p wave spectra and the generally high levels of p wave spectra beyond the corner frequency schallamach comninou type waves are consistent with the partial stress drop abrupt locking self healing models of brune and heaton

energy flux model of seismic coda separation of scattering and intrinsic attenuation a new model of seismic coda is presented based on the balance between the energy scattered from the direct wave and the energy in the seismic coda this energy flux model results in a simple formula for the amplitude and time decay of the seismic coda that explicitly differentiates between the scattering and intrinsic anelastic attenuation of the medium this formula is valid for both weak and strong scattering and implicitly includes multiple scattering the model is tested using synthetic seismograms produced in finite difference simulations of wave propagation through media with random spatial variations in seismic velocity some of the simulations also included intrinsic dissipation the energy flux model explains the coda decay and amplitude observed in the synthetics for random media with a wide range of scattering q in contrast the single scattering model commonly used in the analysis of microearthquake coda does not account for the gradual coda decay observed in the simulations for media with moderate or strong scattering attenuation scattering q less than or equal to 150 the simulations demonstrate that large differences in scattering attenuation cause only small changes in the coda decay rate as predicted by the energy flux model the coda decay rate is sensitive however more to the intrinsic q of the medium the ratio of the coda amplitude to the energy in the direct arrival is a measure of the scattering attenuation thus analysis of the decay rate and amplitude of the coda can in principle produce separate estimates for the scattering and intrinsic q values of the crust we analyze the coda from two earthquakes near anza california intrinsic q values determined from these seismograms using the energy flux model are comparable to coda q values found from the single scattering theory the results demonstrate that coda q values are at best measures of the intrinsic attenuation of the lithosphere and are unrelated to the scatteing q less

spatiotemporal evolution mineralogical composition and transport mechanisms of long runout landslides in valles marineris mars abstract long runout landslides with transport distances of 50 km are ubiquitous in valles marineris vm yet the transport mechanisms remain poorly understood four decades of studies reveal significant variation in landslide morphology and emplacement age but how these variations are related to landslide transport mechanisms is not clear in this study we address this question by conducting systematic geological mapping and compositional analysis of vm long runout landslides using high resolution mars reconnaissance orbiter imagery and spectral data our work shows that 1 a two zone morphological division i e an inner zone characterized by rotated blocks and an outer zone expressed by a thin sheet with a nearly flat surface characterizes all major vm landslides 2 landslide mobility is broadly dependent on landslide mass and 3 the maximum width of the outer zone and its transport distance are inversely related to the basal friction that was estimated from the surface slope angle of the outer zone our comprehensive compact reconnaissance imaging spectrometer for mars crism compositional analysis indicates that hydrated silicates are common in landslide outer zones and nearby trough floor deposits furthermore outer zones containing hydrated minerals are sometimes associated with longer runout and increased lateral spreading compared to those without detectable hydrated minerals finally with one exception we find that hydrated minerals are absent in the inner zones of the investigated vm landslides these results as whole suggest that hydrated minerals may have contributed to the magnitude of lateral spreading and long distance forward transport of major vm landslides

early holocene 8 6 ka rock avalanche deposits obernberg valley eastern alps landform interpretation and kinematics of rapid mass movement in the obernberg valley the eastern alps landforms recently interpreted as moraines are re interpreted as rock avalanche deposits the catastrophic slope failure involved an initial rock volume of about 45 million m with a runout of 7 2 km over a total vertical distance of 1330 m fahrboschung 10 36cl surface exposure dating of boulders of the avalanche mass indicates an event age of 8 6 0 6 ka a 14c age of 7785 190 cal yr bp of a palaeosoil within an alluvial fan downlapping the rock avalanche is consistent with the event age the distal 2 km of the rock avalanche deposit is characterized by a highly regular array of transverse ridges that were previously interpreted as terminal moraines of late glacial jigsaw puzzle structure of gravel to boulder size clasts in the ridges and a matrix of cataclastic gouge indicate a rock avalanche origin for a wide altitude range the avalanche deposit is preserved and the event age of mass wasting precludes both runout over glacial ice and subsequent glacial overprint the regularly arrayed transverse ridges thus were formed during freezing of the rock avalanche deposits

the lawn hill annulus an ordovician meteorite impact into water saturated dolomite the lawn hill impact structure lhis is located 250 km n of mt isa in nw queensland australia and is marked by a highly deformed dolomite annulus with an outer diameter of similar to 18 km overlying low metamorphic grade siltstone sandstone and shale along the ne margin of the georgina basin this study provides detailed field observations from sections of the lawn hill annulus and adjacent areas that demonstrate a clear link between the deformation of the dolomite and the lawn hill impact ar 40 ar 39 dating of impact related melt particles provides a time of impact in the ordovician 472 8 ma when the georgina basin was an active depocenter the timing and stratigraphic thickness of the dolomite sequence in the annulus suggest that there was possibly up to 300 m of additional sedimentary rocks on top of the currently exposed thorntonia limestone at the time of impact the exposed annulus is remarkably well preserved with preservation attributed to postimpact sedimentation the lhis has an atypical crater morphology with no central uplift the heterogeneous target materials at lawn hill were probably low strength porous and water saturated with all three properties affecting the crater morphology the water saturated nature of the carbonate unit at the time of impact is thought to have influenced the highly brecciated nature of the annulus and restricted melt production the impact timing raises the possibility that the lawn hill structure may be a member of a group of impacts resulting from an asteroid breakup that occurred in the mid ordovician 470 6 ma

the coriolis effect on mass wasting during the rheasilvia impact on asteroid vesta we investigate the influence of the coriolis force on mass motion related to the rheasilvia impact on asteroid vesta observations by the nasa dawn mission revealed a pattern of curved radial ridges which are related to coriolis deflected mass wasting during the initial modification stage of the crater utilizing the projected curvature of the mass wasting trajectories we developed a method that enabled investigation of the initial mass wasting of the rheasilvia impact by observational means we demonstrate that the coriolis force can strongly affect the crater formation processes on rapidly rotating objects and we derive the material s velocities 28 9 22 5 m s viscosities 1 5 9 0 106 pa s and coefficients of friction 0 02 0 81 during the impact modification stage the duration of the impact modification stage could be estimated to 1 1 0 5 h by analyzing the velocity distribution with respect to the topography we deduce that the rheasilvia impactor hit a heterogeneous target and that the initial crater walls were significantly steeper during the modification stage

mobility of large rock avalanches evidence from valles marineris mars measurements of h l height of drop length of runout vs volume for landslides in valles marineris on mars show a trend of decreasing h l with increasing volume this trend which is linear on a log log plot is parallel to but lies above the trend for terrestrial dry rock avalanches this result and estimates of 10 4 to 10 5 pa yield strength suggest that the landslides were not water saturated as suggested by previous workers the offset between the h l vs volume trends shows that a typical martian avalanche must be nearly two orders of magnitude more voluminous than a typical terrestrial avalanche in order to achieve the same mobility this offset might be explained by the effects of gravity on flows with high yield strengths these results should prove useful to future efforts to resolve the controversy over the mechan ics of long runout avalanches

on the dynamic fragmentation and lubrication of coseismic landslides national natural science foundation of china fundamental research funds for the central universities and rockhorizon advanced tools for rockfall hazard and risk zonation at the regional scale

dynamics and physical parameters of the lastarria debris avalanche central andes abstract volcanic debris avalanches are extremely destructive phenomena with the potential to travel many kilometers from their source region either as rockslides or as mass flows given that they may even be triggered at inactive volcanoes their hazard is often underestimated understanding the dynamics of such mass movements is essential for evaluating and mitigating hazards a number of case studies have been carried out around the world but there is still a need for further studies of flow dominated avalanches which remain poorly constrained these studies would have high educational value providing striking examples to teach decision makers and at risk populations about the hazard in this study we investigate the 7500 cal year b p lastarria debris avalanche it is a 7 km long deposit with exceptional preservation of both the flow structures and the collapse scar detailed fieldwork morphometric mapping of over 600 surface features and numerical modelling was carried out to constrain the avalanche s trigger and flow parameters numerical models and field scaling relationships are in good agreement suggesting maximum velocities of 210 to 270 km h 1 negligible basal friction low cohesion 50 kpa and an intermediate friction coefficient structures are dominantly oriented parallel to transport direction suggesting minimal influence from a smooth paleotopography lastarria provides an example of a shallow flank failure initiated along stratigraphic planes that allowed low strength pyroclastic strata to disaggregate rapidly and then quickly accelerate to flow as a granular material at high velocity beyond the base of the volcano overall lastarria provides excellent constraints on granular avalanche initiation and flow which are valuable for hazard assessments and for the study of less well preserved flow deposits elsewhere the question of which precursory signs may warn of such a flank failure remains open and is important to address in future studies

laboratory observation of acoustic fluidization in granular fault gouge and implications for dynamic weakening of earthquake faults 1 several lines of evidence including remote triggering of earthquakes and modulation of seismic tremor by earth tides suggest that faults weaken when subject to shaking and dynamic stresses associated with the passage of seismic waves however the origin of such dynamic weakening is poorly understood here we explore the role of acoustic resonance for dynamic fault weakening using laboratory measurements experiments were conducted using a split hopkinson pressure bar assembly with dynamic stressing via impact loading samples were composed of crushed rock particles from mine tailings with a particle size distribution similar to that found in a natural fault gouge we used pulse shaper techniques and carefully evaluated dynamic stresses recorded at the front and rear of the sample to ensure that dynamic force balance was satisfied our experiments document acoustic induced fluidization and dramatic dynamic weakening frictional strength and elastic modulus of a simulated fault gouge are reduced by a factor of 5 10 via acoustic fluidization we find a threshold acoustic pressure for fluidization that varies systematically with gouge zone properties our observations could help explain dynamic fault weakening and triggering of earthquake fault slip by dynamic stressing

unraveling driving factors for large rock ice avalanche mobility large rock ice avalanches have attracted attention from scientists for decades and some of these events have caused high numbers of fatalities a relation between rock slope instabilities in cold high mountain areas and climate change is currently becoming more evident and questions about possible consequences and hazard scenarios in densely populated high mountain regions leading beyond historical precedence are rising to improve hazard assessment of potential rock ice avalanches their mobility is a critical factor this contribution is an attempt to unravel driving factors for the mobility of large rock ice avalanches by synthesizing results from physical laboratory experiments and empirical data from 64 rock ice avalanches with volumes 1x106 m3 from glacierized high mountain regions around the world the influence of avalanche volume water and ice content low friction surfaces and topography on the apparent coefficient of friction as a measure of mobility is assessed in laboratory experiments granular ice in the moving mass was found to reduce bulk friction up to 20 while water led to a reduction around 50 for completely saturated material compared with dry flows evidence for the effects of water as a key driving factor to enhance mobility was also found in the empirical data while the influence of the ice content could not be confirmed to be of much relevance in nature besides liquefaction it was confirmed that mobility increases with volumes and that frictional surface characteristics such as flow paths over glaciers are also dominant variables determining mass movement mobility effects of the topography along the flow path as well as channeling are assumed to be other critical factors the results provide an empirical basis to roughly account for different path and flow characteristics of large rock ice avalanches and to find appropriate ranges for friction parameters for scenario modeling and hazard assessments copyright 2011 john wiley sons ltd

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

mass movements on venus preliminary results from magellan cycle 1 observations mass movements on venus seen in radar images acquired by the magellan spacecraft during its first mapping cycle are easily interpreted within the scheme commonly used to classify terrestrial landslides rock slumps rock and or block slides rock avalanches debris avalanches and possibly debris flows are seen in areas of high relief and steep slope gradients and are most abundant in the tectonic troughs that crisscross much of the equatorial region of venus many classes of regolith and sediment movements are not seen such features might be too small to resolve in the 75 meter per picture element radar images or their absence may reflect the relatively thin cover of fine sediments inferred from emissivity measurements and other observations venusian landslides like those found within the valles marineris on mars tend to come from escarpments typically higher than those on earth they appear to fall between the terrestrial and martian height to length trends they are also somewhat larger using length as a surrogate for volume than terrestrial subaerial landslides but smaller than their martian counterparts good morphologic analogs can be found in terrestrial volcanic slides both subaerial and submarine oversteepening of volcanic edifices by intrusion and subsequent lateral collapse appears responsible for shaping a number of large isolated volcanos on venus faulting and seismically induced accelerations are probably responsible for the majority of non volcanic mass movements the atmosphere may participate in promoting the movement of some of the landslide debris but environmental factors e g rainfall temperature cycling do not appear to play as dominant a role as they do on earth based on the types and locations of landslides seen in the magellan data it is possible to scale the terrestrial occurrence rate to venus if venus is as seismically and volcanically active as the earth than of order one major landslide i e discernable in magellan images or 5 10 km in runout distance should occur per year which careful re examination of magellan images acquired during later mapping cycles may be able to detect