a multi method monitoring of timing magnitude and origin of rockfall activity in the japanese alps abstract a multi method monitoring was conducted to detect the timing and trigger of rockfall activity on an alpine rockslide cliff composed of cretaceous sandstone and shale in the southern japanese alps aresawa rockslide 2900 m above sea level the monitoring programme includes manual measurements of flaking from painted rock surface and collection of fallen debris daily time lapse imaging of the rockwall automated recordings of rock temperature rock moisture and influencing meteorological factors air temperature and precipitation a stereographic pair of sequential photographs is used to visually identify the location of new erosion and semi quantitative evaluation of detached materials at daily resolution six years 2010 2016 of debris trapping show major rockfall activity in winter between november and may and occasional activity associated with heavy rains in summer and yield an average rate of rockwall retreat on the order of 1 mm a 1 the rockwall shows heterogeneous debris production mainly reflecting joint spacing time lapse imaging displays at least 10 15 rockfall events per year within the shot area 500 m2 the integration of multiple data suggests at least five types of triggering processes towards rockfalls which recur annually 1 in summer and early autumn heavy rainfalls raise the moisture content of the shallow bedrock often triggering significant rockfalls probably due to raised water pressure in rock joints or lubrication of joints 2 in late autumn and late spring light or intermediate rainfalls are sometimes followed by high moisture shallow freezing rapid thawing and eventually by different scales of rockfalls 3 in winter and early spring the same process as in the second case but rainfall is replaced by snowfall triggers submeter scale rockfalls 4 deep seasonal freezing to about 5 m enables release of meter scale rockfalls during seasonal thawing periods from late spring to early summer 5 short term large thermal fluctuations that produce cyclic thermal stress may also contribute to submeter scale rockfalls mainly in winter locally enhanced by freeze thaw action

the timing of martian valley network activity constraints from buffered crater counting abstract valley networks concentrations of dendritic channels that often suggest widespread pluvial and fluvial activity have been cited as indicators that the climate of mars differed significantly in the past from the present hyperarid cold desert conditions some researchers suggest that the change in climate was abrupt while others favor a much more gradual transition thus the precise timing of valley network formation is critical to understanding the climate history on mars we examine thirty valley network incised regions on mars including both cratered upland valley networks and those outside the uplands and apply a buffered crater counting technique to directly constrain when valley network formation occurred the crater populations that we derive using this approach allow assessment of the timing of the last activity in a valley network independent of the mapping of specific geological units from these measurements we find that valley networks cluster into two subdivisions in terms characteristics and age 1 valley network activity in the cratered highlands has an average cessation age at the noachian hesperian boundary and all valleys that we crater counted are early hesperian or older no evidence is found for valley networks in the cratered uplands of late hesperian or amazonian age the timing of the cessation of cratered upland valley network activity at the noachian hesperian boundary also corresponds to a decline in the intensity of large crater formation and degradation and to the apparent end of phyllosilicate type weathering 2 a few valley network incised regions formed outside of the cratered uplands on volcanic edifices in association with younger impact craters and on the rim of valles marineris we applied our buffered crater counting technique to four such valleys on the volcanoes ceraunius tholus hecates tholus and alba patera and on the rim of echus chasma and find that each has distinctive and different late hesperian or early amazonian ages indicating that valley networks formed from time to time in the post noachian period unlike the cratered upland valley networks these isolated occurrences are very local and have been interpreted to represent local conditions e g snowpack melted during periods of intrusive volcanic activity in contrast to a gradual cessation in the formation of valley networks proposed by some workers our new buffered crater counting results indicate a relatively abrupt cessation in the formation of the widespread cratered upland valley networks at approximately the end of the noachian followed only by episodic and very localized valley network formation in later mars history very likely due to specific conditions e g local magmatic heating these valley network ages and correlations are thus consistent with a major change in the near surface aqueous environment on mars at approximately the noachian hesperian boundary the noachian environment supported surface running water and fluvial erosion across mars in the cratered uplands enhanced crater degradation and a weathering environment favoring the formation of phyllosilicates the hesperian amazonian environment was more similar to the hyperarid cold desert of today with valley networks forming only extremely rarely and confined to localized special conditions sources of water for these latter occurrences are likely to be related to periodic mobilization and equatorward migration of polar volatiles due to variations in spin axis orbital parameters and to periodic catastrophic emergence of groundwater

long term gravitational deformation of rocks by mass rock creep abstract subsurface rocks beneath slopes are deformed to various degrees in various ways by mass rock creep mrc when they are subjected to a gravitationally unstable state for a long period mrc forms folds faults and numerous kinds of fractures such deformation is one of the main factors for deteriorating rock masses on slopes and also precursors of many landslides mrc deformations which have often been ascribed to tectonic origins can be distinguished from tectonic ones by their deformational features landforms and relationships between slope morphology and subsurface structures mrc folds are flexural slip folds that have the following mesoscopic to microscopic characteristics their axial surfaces are not smooth but are jagged and many visible openings or open fractures develop in association with the folds the jagged axial surfaces become smoother at depth and openings decrease in width with increasing overburden at the deformation site macroscopic types of mrc folds change according to the relationship between foliations and slopes buckling folds form in consequent slopes drag folds form in a deeper part of obsequent slopes and bending folds form in slopes with steep dipping foliations consequent or obsequent by downslope bowing of foliations shear fractures and tension fractures are the main deformational structures formed by mrc in massive rocks among shear fractures those of listric origin are remarkable tension fractures in general occur either in networks dividing rocks into fragments that slip and rotate irregularly in relation to each other or in parallel arrays of steeply dipping fractures an mrc fault has a shear zone consisting of a pulverized zone with gouge and a phyllitic or brecciated zone in a densely foliated rock the phyllitic zone is formed by microscopic slip along foliations in a sparsely foliated rock the brecciated zone is formed by random crushing except for the faults made through the shear fractures in massive rocks landforms due to mrc are gentle slopes bounded by horseshoe knicklines upslope convex slopes ridge top depressions multiple ridges uphill facing scarps and ridge crossing depressions

rock slope instability and erosion toward improved process understanding rock slopes in a range of environments are among the landscape elements most sensitive to climate change the latter affecting rock mass properties altering slope boundary conditions and changing geosystem configurations major climate dependent influences promoting destabilization include stress redistribution with changing glacial ice extents degradation of mountain permafrost altered slope hydrology and weathering environments loading and unloading due to deposition and erosion and changes in the spectrum of magnitude and frequency of driving forces in steep bedrock terrain erosional processes control slope morphology by modulating rates of i weathering in response to climate and pre disposition ii rock slope retreat in response to magnitude and frequency of detachment and iii channel incision or valley infilling in response to variable sediment supply modelling landscape evolution and anticipating natural hazards in these environments thus requires deeper insights into the processes driving rock slope instability and erosion this special issue emphasizes new understanding of rock slope processes through a collection of manuscripts at the forefront of research in the field copyright 2014 john wiley sons ltd

discrete element modeling of the mass movement and loose material supplying the gully process of a debris avalanche in the bayi gully southwest china abstract the dynamic process of a debris avalanche in mountainous areas is influenced by the landslide volume topographical conditions mass material composition mechanical properties and other factors a good understanding of the mass movement and loose material supplying the gully process is very important for understanding the dynamic properties of debris avalanches three dimensional particle flow code pfc3d was used to simulate a debris avalanche in quaternary deposits at the bayi gully southwest china fortran and autocad were used for the secondary development to display the mass movement process and to quantitatively describe the mass movement and loose material supplying the gully process the simulated results show that after the landslide is initiated the gravitational potential energy is converted into kinetic energy with a variation velocity for the sliding masses two stages exist for the average movement velocity the acceleration stage and the slowdown stage which are influenced by the topographical conditions for the loose materials supplying the gully process the cumulative volume of the sliding masses into the gully gradually increases over the time when the landslide volume is not large enough the increasing landslide volume does not obviously influence the movement process of the sliding masses the travel distance and movement velocity increase with the decreasing numerical parameters and the mass movement process is finished more quickly using low value parameters the deposition area of the sliding masses decreases with the increasing numerical parameters and the corresponding deposition thickness increases the mass movement of the debris avalanche is not only influenced by the mechanical parameters but is also controlled by the topographical conditions

topographic influences on development of martian valley networks 1 some morphometric differences between terrestrial and martian valley networks may reflect the precursor topography on mars particularly impact basins or tectonic slopes to evaluate these possible influences we mapped highland watersheds in nine study areas that sample a range of geographic and topographic settings we collected data including latitude longitude watershed length divide and terminal elevations watershed relief and slope slope orientation and qualitative descriptors including whether a drainage basin was open or closed the longest valley networks and most overflowed basins occur on preexisting intercrater slopes of 0 1 1 particularly on north facing slopes associated with the crustal dichotomy the control of watershed length by earlier noachian topographic features which the relict networks did not significantly modify suggests that the early to middle noachian geomorphic environment was nominally much drier than the later noachian to hesperian transition the distribution of fluvial valleys and likely orographic effects created by the crustal dichotomy suggest that evaporation from the northern lowlands was an important source of atmospheric humidity over short time scales much of the highland plateau consists of smaller enclosed watersheds which along with cooler temperatures detained surface water at high elevations lengthening or impeding the global water cycle ponding and evaporation may have partly offset a continentality effect of the highland landmass prolonged modification of the intercrater geomorphic surface prior to incision of valley networks included substantial weathering reduction of relief and gravity driven sediment transport indicating a long term role for surface water in a transport limited arid to hyperarid noachian paleoclimate

formation timescales of large martian valley networks abstract assessing timescales for formation of the ancient martian valley networks is key to interpreting the early climate on mars we determined the likely formation times for seven of the largest ancient valley networks on mars using the darcy weisbach equation for average flow velocity three different sediment transport models and a range of input parameters to encompass possible formation conditions with runoff rates similar to intense storms in arid regions on earth the minimum formation timescales of these martian valley networks range from 10 5 to 10 7 yr depending on the specific valley network shorter formation timescales require hurricane scale flows that if minimized with assumptions of continuous formation unlike even terrestrial rates could complete large valley network formation in as little as 200 to 5000 yr though this is not the preferred interpretation while these results do not support impact induced climate change as the sole mechanism for creating precipitation sufficient to incise the large valley networks neither do they extend the amount of time required to form the networks beyond their range in age consistent with hypotheses that valley incision was constrained to a relatively short period of martian history near the noachian hesperian boundary approximately 3 6 to 3 8 ga

examples of multiple rock slope collapses from kofels otz valley austria and western norway abstract this paper describes the effects of large massive rock slope failures on subsequent slope stability three examples of large rock slope failures from the austrian alps and norway demonstrate that failure increases the probability of further collapses at kofels austria a holocene rock slope failure several km3 in size filled the otz valley the morphology of the deposits indicates that at least one subsequent failure occurred along the head scarp of the first failure most likely a slide of similar size debris of the second landslide slid over the older deposits forming the famous kofels frictionite at least three rock slope failures all of them in excess of 106 m3 occurred from the same mountainside within the last 6000 8000 years at tafjord in western norway the most recent of these failures in 1934 triggered a destructive tsunami five large failures with volumes 50 000m3 occurred at ramnefjell norway within 50 years two of them caused considerable damage and a large number of death due to the formation of destructive tsunamis two dimensional finite element models of rock slope stability before and after the kofels and tafjord landslides show that massive rock slope failures produce a irregular slopes parts of which are as steep or steeper than the slope before failure and which represent new zones of instability and b zones of weakness related to slow slope deformation and related cracking

structural constraints on deep seated slope deformation kinematics abstract a significant sackung type deep seated slope gravitational deformation dsgsd was recognised for the first time by the authors in the middle part of valfurva east of bormio rhaetian alps italy the reconstruction of its kinematics age and state of activity is presented through a detailed description of its morphological geomechanical and structural features an integrated multi disciplinary approach was performed to achieve a clear comprehension of the phenomenon field surveys and aero photo interpretation were carried out in order to clarify the structural geological and geomorphological setting in which the dsgsd developed a kinematic conceptual model of the slope deformation was developed through the analysis of morpho structures of their significance and relationships with lithological markers and quaternary deposits after a geomechanical characterisation of the rock mass involved in the slope deformation numerical modelling was performed to verify the hypotheses made on kinematics and driving factors of the phenomenon the sackung affects pre permian metapelites metabasites and marbles belonging to the upper austroalpine basement of the campo nappe as well as late pleistocene and holocene glacial and rock glacier deposits the deformation started after the late wurmian age 15 000 11 000 years b p and continued until few centuries ago not excluding a present day low rate activity deformation consists in a large oblique sagging along a deep confined sliding surface associated with gravitational reactivation of pre existing late alpine and recent tectonic brittle structures leading to the formation of n s and wnw ese trending gravitational morpho structures the evolution of the wnw ese trending system resulting in asymmetric trenches led to progressive failure of the lower part of the slope during the last 10 000 years as testified by large paleo landslide accumulations and it is still in progress numerical modelling indicates post glacial unloading as the main triggering factor of the slope deformation the importance of this deep seated slope deformation is enhanced by the occurrence of the 30 mm 3 active ruinon landslide in the lower part of the slope such landslide is subjected to rapid evolution and threatens the valley floor establishing an important risk factor connected to human lives and socio economic activities

holocene rockwall retreat in svalbard a triple rate evolution volumetric calculations of slope deposits direct measurements of rockwall retreat and chronological control based on lichenometry provide a wide range of rockwall retreat rates in svalbard 0 1580 mm ka 1 that appears consistent with previous evaluations from other arctic areas in northwest and central spitsbergen 79 n a triple rate rockwall retreat is suggested for the last two millennia very slow biogenic flaking 2 mm ka 1 moderate retreat due to frost shattering 100 ka 1 and rapid retreat associated with post glacial stress relaxation c 1000 mm ka 1 examination of the distribution of various processes indicates that the holocene retreat of most rockwalls has not exceeded one or two metres bedrock conditions appear to be the main control on retreat rates the massiveness of igneous and metamorphic outcrops widespread in arctic shield areas largely accounts for the slowness of rockwall retreat which on these lithologies is primarily due to chemical and biological processes more rapid rates are usually associated with stress relaxation following glacial surges or with local frost susceptibility of bedrock often where faulting has induced high joint density at such sites rockwall retreat rates are of the same order of magnitude as those reported from alpine areas 1000 3000 mm ka 1 where both bedrock weakening due to tectonic stresses and the greater height of steep rockwalls account for the more rapid rockwall retreat rate 1997 by john wiley sons ltd

seismic signatures of landslides the 1990 brenda mine collapse and the 1965 hope rockslides abstract we present the well documented case of a 2 10 6 m 3 rockslide that was recorded by seismographs to distances of several hundred kilometers and might have entered the canadian catalog as a bona fide earthquake except for independent knowledge to the contrary motivated by the observation of this event we reexamined the seismograms associated with the 1965 hope slide in british columbia the largest known historical landslide in the canadian cordillera and conclude that these seismograms were the signatures of two rockslides and not of hypothetical tectonic earthquake triggers as previously suggested mathews and mctaggart 1969 wetmiller and evans 1989 these events raise the general question of differentiation between seismic signals from landslides and true earthquakes we suggest an lp sp discriminant as the most obvious although a resolvable mechanism solution may be even more convincing efficiency of energy conversion from potential to seismic is also a diagnostic aid and correlates well with the slope of the slide detachment surface

regional dust deposits on mars physical properties age and history major dust storms on mars play an important role in the deposition and removal of fine dust material thermal radar and visual remote sensing observations provide important constraints on the martian regolith which have been used to determine the location and physical properties of regional dust deposits these deposits are located in three northern equatorial regions tharsis 20 s to 50 n 60 to 190 w arabia 5 s to 30 n 300 to 360 w and elysium 10 to 30 n 210 to 225 w they are covered by fine 2 40 m bright albedo 0 27 particles with fewer exposed rocks and coarse deposits than found elsewhere dust is currently deposited uniformly throughout the equatorial region at a rate of 40 m global storm over geologic time the rate of accumulation may vary from 0 to 250 m yr due to changes in atmospheric conditions produced by orbital variations dust deposited during global storms is subsequently removed only from dark regions resulting in a net accumulation in the low inertia bright regions the thickness of these current dust deposits is 0 1 2 m the thermal inertia places a lower limit of 0 1 m on the thickness of these deposits while the sparse but ubiquitous presence of exposed rocks and the degree of visible mantling indicate that the thickness is less than 5 m dual polarization radar observations of a very rough texture in tharsis are consistent with this model with a 2 m thick dust layer burying most of the surface rocks but permitting radar sampling of the rough subsurface based on their thickness and rate of accumulation the age of these deposits is 105 106 years suggesting a cyclic process of deposition and removal one possible cause may be cyclic variations in the magnitude and location of maximum wind velocities related to variations in mars orbit at present perihelion and maximum wind velocities occur in the south whereas regional dust deposits occur in the north suggesting net transport from south to north orbital parameters oscillate with periods ranging from 5 104 to 106 years the agreement between these periods and the dust deposit age suggests a possible link at different stages in orbit evolution maximum wind velocities will occur in the north with subsequent erosion and redistribution of the accumulated fines based on this model much of the uppermost martian surface is very young and is being continually reworked

evidence for extensive denudation of the martian highlands high resolution topographic data from the mars orbiter laser altimeter reveal evidence for widespread denudation from margaritifer sinus to northern arabia terra an area of 1 107 km2 a major resurfacing event is indicated by 1 a heavily degraded landscape hosting numerous inliers 2 truncation or absence of valley networks and 3 a break in slope at the edge of early to middle noachian plateau materials geomorphic mapping was completed on the type locale of denudation 0 30 s 0 30 w superposition relations and crater counts for geomorphic units indicate that large scale resurfacing took place in the late noachian eroding the martian highlands and resulting in transportation and deposition of 4 5 106 km3 of sediment in the northern plains this is equivalent to a 120 m thick uniform layer of sediment on the surface of mars north of 30 n geomorphic mapping and crater counts limit the timing of denudation to the late noachian an interval of 350 500 m y using this limit we estimate a minimum rate of denudation of 2 0 m yr comparable to denudation of typical slopes in a temperate maritime climate on earth the morphology rate of denudation and extensive nature of upland degradation suggest that precipitation fed surface runoff is the most likely geomorphic agent capable of such a process indicative of a warm wet mars during the late noachian epoch

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

significance of rockfall magnitude and carbonate dissolution for rock slope erosion and geomorphic work on alpine limestone cliffs reintal german alps abstract the proportional contribution of low mid and high magnitude rock slope failure orchestrates rock slope erosion and rockfall hazard in alpine and arctic environments in this study we compare sediment yield geomorphic work and rock wall retreat of carbonate dissolution and five different magnitudes of rock slope failure in the steep alpine reintal trough valley we combine a four year rockfall collector measurement of 140 mg of fragmental rockfall a 20th century scientific record of mid magnitude rockfall as well as carbon dating and a historical record of 15th to 19th century rock avalanche activity the total rockfall sediment yield of 8 6 3 4 10 3 m 3 year 1 is dominated by high magnitude rock avalanches 10 6 m 3 62 and low magnitude debris falls 3 18 while mid magnitude boulder block and cliff falls are less important the magnitude signal contradicts studies on siliceous rocks where mid magnitude rockfall dominates rock slope erosion the geomorphic work released in the 17 3 km 2 large catchment by rockfalls 123 47 w km 2 i e 0 38 0 15 mm year 1 and solute transport 34 18 w km 2 i e 0 05 0 03 mm year 1 exceeds previously published alpine values by one to multiple orders of magnitude we hypothesise that the magnitude signal of enhanced small and high magnitude rockfall is characteristic for carbonate cliffs the elevated porosity related susceptibility to fragmentation and persistent carbonate dissolution along potential sliding planes are likely to favour both low and high magnitude rock slope failures here we show how the magnitude signal of rock slope failure influences rock wall retreat geomorphic work rockfall deposition and sediment connectivity

kinematics of an alpine retrogressive rockslide in the japanese alps the aresawa rockslide in the japanese alps experienced a partial collapse 5 10 105 m3 in 2004 followed by an accelerated downward movement of the head area rather than stabilization this paper discusses the kinematics of a retrogressive rockslide area and factors promoting slope instability subsequent to the 2004 collapse on the basis of geodetic surveys and meteorological observations from 2006 to 2010 the unstable area covers at least 2 3 104 m2 and consists of five active blocks the main blocks are separated from the stable rock slope by pre existing sackung features that follow the strike of the bedding plane shear zones below these sackung features have developed into slip planes potentially causing the next collapse in particular the propagation of a slip plane causing movement at 70 cm yr 1 in the head area is promoted by bidirectional movement it consists of slow dip slip movement in snow accumulating periods and rapid side slip movement in snow melting and snow free periods both of which occur on the same slip plane this bidirectional movement appears to result from the combination of a loss of lateral support by the 2004 event and the immature state of the slip plane the primary trigger of the acceleration in the unstable area is the stress release by the 2004 collapse in addition the presence of a potential slip plane below the sackung features also promotes slope instability suggesting that sackung features behind a rockslide area may predefine the new head scarp of a forthcoming collapse copyright 2012 john wiley sons ltd

updated global map of martian valley networks and implications for climate and hydrologic processes 1 martian valley networks have long been viewed as some of the best evidence of prolonged surface water on mars analysis from viking data showed that valleys were primarily contained on the ancient crust drainage networks were immature and large undissected regions occurred in between individual systems these observations led many to propose that they formed primarily by groundwater processes and limited or no climate change from the present state was required using more recent and higher resolution data sets including visible infrared and topographic data we have manually remapped valleys on a global scale more than eight times as many valleys have been identified on the surface and calculated drainage densities are on average higher by a factor of 2 further regions previously thought to be undissected have significant incision by fluvial processes most of these systems seem to have formed around the noachian hesperian boundary 3 8 3 6 ga minor valley formation continued through the hesperian and into the early amazonian epoch approximately 2 8 ga ago the new data reveal characteristics of sustained precipitation and surface runoff including inner braided channels terraces multiple periods of formation complex network morphology and correlation with other fluviosedimentary features and chloride salts on mars groundwater processes or a transient steam atmosphere generated by impacts played at most a minor role these new results imply that mars had a long lived period or periods of clement conditions toward the end of the noachian epoch that supported a hydrologic cycle and potentially a biosphere

apparent thermal inertia and the surface heterogeneity of mars abstract thermal inertia derivation techniques generally assume that surface properties are uniform at horizontal scales below the footprint of the observing instrument and to depths of several decimeters consequently surfaces with horizontal or vertical heterogeneity may yield apparent thermal inertia which varies with time of day and season to investigate these temporal variations we processed three mars years of mars global surveyor thermal emission spectrometer observations and produced global nightside and dayside seasonal maps of apparent thermal inertia these maps show broad regions with diurnal and seasonal differences up to 200 j m 2 k 1 s 1 2 at mid latitudes 60 s to 60 n and 600 j m 2 k 1 s 1 2 or greater in the polar regions we compared the seasonal mapping results with modeled apparent thermal inertia and created new maps of surface heterogeneity at 5 resolution delineating regions that have thermal characteristics consistent with horizontal mixtures or layers of two materials the thermal behavior of most regions on mars appears to be dominated by layering with upper layers of higher thermal inertia e g duricrusts or desert pavements over fines prevailing in mid latitudes and upper layers of lower thermal inertia e g dust covered rock soils with an ice table at shallow depths prevailing in polar regions less common are regions dominated by horizontal mixtures such as those containing differing proportions of rocks sand dust and duricrust or surfaces with divergent local slopes other regions show thermal behavior that is more complex and not well represented by two component surface models these results have important implications for mars surface geology climate modeling landing site selection and other endeavors that employ thermal inertia as a tool for characterizing surface properties

ancient ocean on mars supported by global distribution of deltas and valleys the climate of early mars could have supported a complex hydrological system analysis of ancient deltaic deposits and valley networks reveals the presence of a planet wide equipotential surface in the northern lowlands indicative of the existence of a vast ocean on mars 3 5 billion years ago

deep seated rockslide avalanches preceded by mass rock creep of sedimentary rocks in the akaishi mountains central japan abstract seven large rockslide avalanches of sedimentary rocks are known in japan almost all of these major landslides were preceded by gravitational deformation of rocks mass rock creep mrc as inferred from geologic and geomorphic investigations of five rockslide avalanches in the akaishi mountains the mrc that preceded the rockslide avalanches in the akaishi mountains was characterized by a slow but steady downslope bowing of steeply dipping foliations which accompanied intensive deformation and fragmentation of the rock mass by shearing along foliations this deformation and fragmentation of the rock mass provides a basic cause for the occurrence of rockslide avalanches which occur when a creeping rock mass has lost its support from the lower part of a slope by stream erosion this type of mrc continues for a long time after a part of the creeping area has slid and results in longterm generation of debris by the landslide sear of the rockslide avalanche

are sackungen diagnostic features of de glaciated mountains abstract deep seated gravitational slope deformations dsgsds with characteristic sackung landforms e g double crests trenches uphill facing scarps and toe bulging are considered by some researchers to be diagnostic features indicating past mountain glaciations however an extensive literature review on sackung features throughout the world reveals that in some regions paraglacial processes are not the causes of such phenomena sackungen occur across a diverse spectrum of mountain types with different morphoclimatic histories including regions that have never experienced glaciation to reinforce that sackungen may originate independently of glaciation we also include two case studies from the western carpathians czech republic and slovakia which are supported by detailed geomorphic mapping trenching and absolute dating 10 be 14 c and osl on the ond ejnik ridge outer western carpathians czech republic sackungen occur in the mid holocene in the medium high mountains which are beyond the pleistocene glacial limits on the salatin mt tatra mts slovakia the sackungen which occur in formerly glaciated terrain date between 7 5 and 4 2 ka bp representing a 4 ka time lag after the disappearance of glaciers this suggests that the direct link between the ice retreat and the onset of sackung formation is not obvious even in the case of the once glaciated mountain range although paraglacial stress release is undoubtedly one of the crucial causes of sackung genesis in many mountain regions it is not the only important mechanism therefore despite occurring in numerous de glaciated mountains sackung features cannot be considered as proof of past mountain glaciations e g during analysis of extra terrestrial settings

contribution of deep seated bedrock landslides to erosion of a glaciated basin in southern alaska landslides represent a key component of catchment scale denudation though their relative contribution to the erosion of glaciated basins is not well known bedrock landslide contribution was investigated on the surface of one of eleven glaciers on a glaciated ridge in the chugach st elias range of southern alaska where the debris from four major landslides is easily distinguished from moraines and other supraglacial material a series of aerial and satellite photos from 1972 to 2000 and field observations in 2001 and 2002 indicate that three of four landslides have fallen onto the surface of the glacier since about 1978 the landslides which originated from the steeply dipping 60 70 bedrock walls were deposited onto the glacier in the ablation zone and are currently being transported downstream supraglacially individual glacial valleys with topographic relief of 400 m are cut into highgrade metamorphic rock characterized by a steep north dipping foliation and fractured by numerous large joints measurements of landslide area and average thickness obtained from high resolution survey data indicate a total landslide volume of 2 3 10 5 m 3 this volume suggests a basin averaged erosion rate from landslides of 0 48 mm a 1 an overall basin scale erosion rate of 0 7 to 1 7 mm a 1 can be inferred but depends on the percentage of the totalbasin sediment yield contributed by supraglacial sources a mean rockwall retreat rate of 6 7 mm a 1 is calculated and is considerably higher than published rates which range from 0 04 to 4 0 mm a 1 controls on landslide generation include seismicity freeze thaw processes topography rock strength and debuttressing it is likely all of these factors contribute to failure although the primary controls for the landslides in this study are thought to be rock strength and topography the absence of landslides on ten of the eleven glaciers on this ridge is attributed to landslide magnitude frequency relationships and short temporal scale of this study large volume bedrock landslides 100 000 m 3 may have low frequency occurring less than once in a 55 year time frame copyright 2005 john wiley sons ltd

large sackung along major tectonic features in the central italian alps deep seated gravitational slope deformation sackung is common in alpine mountain belts it is controlled by lithological geomorphological and structural features we describe and discuss five examples of dsgsd along the insubric line periadriatic fault in the central italian alps the five examples are different in morphology size state of activity and distribution and are located along both primary and secondary valleys we demonstrate relations between structural and gravitational features and discuss the possibility that structural has both passive and active roles in sackung development analysis of ps sar data shows that the studied examples are not active today numerical modelling demonstrates the importance of lithological and structural constraints postglacial debuttressing groundwater fluctuations and weathering on sackung triggering and development

sediment transport part i bed load transport a method is presented which enables the computation of the bed load transport as the product of the saltation height the particle velocity and the bed load concentration the equations of motions for a solitary particle are solved numerically to determine the saltation height and particle velocity experiments with gravel particles transported as bed load are selected to calibrate the mathematical model using the lift coefficient as a free parameter the model is used to compute the saltation heights and lengths for a range of flow conditions the computational results are used to determine simple relationships for the saltation characteristics measured transport rates of the bed load are used to compute the sediment concentration in the bed load layer a simple expression specifying the bed load concentration as a function of the flow and sediment conditions is proposed a verification analysis using about 600 alternative data shows that about 77 of the predicted bed load transport rates are within 0 5 and 2 times the observed values

the massabesic gneiss complex new hampshire a study of a portion of the avalon terrane geochemical data from the 625 ma massabesic gneiss complex of southern new hampshire show strong affinities for other avalonian rocks of southern new england and suggest continental rifting in the late proterozoic migmatized paragneiss the dominant rock type in the complex has major and trace element compositions that are compatible with graywackes from continental arcs the para gneiss also has strong lithologic metamorphic and isotopic similarities to the rocks of the hope valley zone of connecticut avalon suggesting a possible hope valley massabesic correlation at 625 ma the paragneiss end values are similar to avalonian crust in other locations of the orogen two types of amphibolite are present in minor amounts in the paragneiss of the massabesic gneiss complex the first type is a paramphibolite and consists of calc silicate layers in the massabesic paragneiss the second type is metaigneous major and trace element abundances reveal that the protoliths of the orthoamphibolites range from continental rift alkaline basalts and tholeiites to n type morbs orthoam phibolite end 625 ma values range from 2 4 to 4 as expected of rift related magmas derived from partial melting of a depleted mantle source and have the same values as iapetus ocean floor rocks of similar age orthoamphibolite major and trace element geochemical characteristics overlap those of the middlesex fells amphibolites of the esmond dedham zone of eastern massachusetts avalon which range from alkaline to transitional basalts erupted in a continental rift setting the compositions of orthoam phibolites define a potential magmatic continuum produced by batch partial melting of the mantle initiated during continental rifting and proceeded to ocean basin forma tion the inferred continuity of mafic magmatism from the esmond dedham mid dlesex fells formation to the massabesic gneiss complex and hope valley zone suggests that these zones are not distinct lithotectonic zones but are parts of a single landmass massachusetts avalon esmond dedham represents the continental section of avalon where the alkaline to transitional magmas of the early rifting stages are preserved according to our tectonic reconstruction the massabesic gneiss complex is the oceanward continental margin represented by volcanoclastic sediments with the morbs representing the initiation of ocean basin development the leading edge of this landmass of which the massabesic gneiss complex is the only observable remnant collided with laurentia during the acadian orogeny the inboard thicker more continental trailing edge that is platform avalon esmond dedham collided later during the alleghanian orogeny

monitoring rapid head scarp movement in an alpine rockslide abstract the aresawa rockslide in the japanese alps which partially collapsed in may 2004 produced a number of new tension cracks in the head area this paper discusses the dynamics of the rock slope and controls on the surface velocity based on the results of on site monitoring of the surface movement and meteorological parameters air and ground surface temperatures precipitation and snow depth the rock mass deformation progressed at ca 60 cm yr 1 mainly along a slip plane dipping downslope at ca 50 the surface velocity of the slipping rock mass showed a significant seasonal variation in response to the water infiltration the velocity was small 1 mm day 1 in winter subzero air temperatures and a heat insulating snow cover and resulting growth of seasonal frost prevent water infiltration into the bedrock and contribute to the rock slope stability most of the movement in this period is attributed to gravitational deformation originating from the overburden pressure in contrast the surface velocity increased up to 10 mm day 1 during snow melting and snow free periods snowmelt and rainfalls promote water infiltration into the bedrock destabilizing the rock slope and accelerating the rock slip such a rapid movement is attributed to water induced sliding superimposed on gravitational deformation

headwater channel dynamics in semiarid rangelands colorado high plains usa incised ephemeral channels provide a window into the fluvial processes that help sculpt rangeland landscapes this paper presents observations of ephemeral channels and valley networks in the high plains of colorado usa with an eye toward painting a picture of the ingredients that must be included in mathematical models of landscape evolution in such environments channel incision in the study area is driven by summer thunderstorms which can with reasonable frequency 3 5 yr generate boundary shear stresses high enough to penetrate the highly resistant vegetation armor but only within erosional hot spots where hydraulic forces are amplified by channel constriction and locally steep gradients focusing of erosion at these hot spots which correspond to knickpoints and channel heads is amplified by the small areal footprint and short erosional reach of most convective storms upstream migration of knickpoints creates a pattern of short active channel reaches separated by unchanneled or weakly channeled fully vegetated stable reaches based on our observations we interpret the necessary and sufficient conditions leading to the observed channel forms and dynamics as 1 a resistant vegetation layer overlying an erodible substrate which sets up a conditional instability through which erosional perturbations can grow by positive feedback 2 high flow variability 3 moderate to high substrate cohesion and 4 a high volume fraction of fine grained erodible material concave upward valley long profiles are interpreted as a trade off between downstream increasing flood frequency and downstream decreasing flood effectiveness the observed process dynamics imply that long term rates of valley incision should be especially sensitive to climatic oscillations between episodes of drought and warm season convective rainfall

aeolian processes in proctor crater on mars sedimentary history as analyzed from multiple data sets 1 proctor crater is a 150 km diameter crater in noachis terra within the southern highlands of mars the analysis leading to the sedimentary history incorporates several data sets including imagery elevation composition and thermal inertia mostly from the mars global surveyor mission the resulting stratigraphy reveals that the sedimentary history of proctor crater has involved a complex interaction of accumulating and eroding sedimentation aeolian features spanning much of the history of the crater interior dominate its surface including large erosional pits stratified beds of aeolian sediment sand dunes erosional and depositional streaks dust devil tracks and small bright bed forms that are probably granule ripples long ago up to 450 m of layered sediment filled the crater basin now exposed in eroded pits on the crater floor these sediments are probably part of an ancient deposit of aeolian volcaniclastic material since then some quantity of this material has been eroded from the top layers of the strata small bright dune forms lie stratigraphically beneath the large dark dune field relative to the large dark dunes the bright bed forms are immobile although in places their orientations are clearly influenced by the presence of the larger dunes their prevalence in the crater and their lack of compositional and thermal distinctiveness relative to the crater floor suggests that these features were produced locally from the eroding basin fill dust devil tracks form during the spring and summer following a west southwesterly wind early in the spring the dust devils are largely restricted to dark patches of sand as the summer approaches dust devil tracks become more plentiful and spread to the rest of the crater floor indicating that the entire region acquires an annual deposit of dust that is revealed by seasonal dust devils the dark dunes contain few dust devil tracks suggesting that accumulated dust is swept away directly by saltation rather than by the passage of dust devils spectral deconvolution indicates that the dark dunes have infrared spectra consistent with basalt like materials the average thermal inertia calculated from thermal emission spectrometer bolometric temperatures is 277 17 j m 2 s 0 5 k 1 leading to an effective grain size of 740 170 mm which is consistent with coarse sand and within the range expected for martian sand the coarse sand that composes the large dune field may have originated from outside the crater saltating in from the southwest most of the transport pathway that delivered this sand to the dune field has since been eroded away or buried the sand was transported to the east center of the crater floor where beneath the present day dunes a 50 m high mound of sand has accumulated dune slip faces indicate a wind regime consisting of three opposing winds some of these wind directions are correlated with the orientations of dust devil tracks and bright bed forms the combination of a tall mound of sand and three opposing winds is consistent with a convergent wind regime which produces the large reversing transverse and star dunes that dominate the dune field the dark dunes have both active slip faces and seemingly inactive slip faces suggesting that the dunes vary spatially in their relative activity nevertheless the aeolian activity that has dominated the history of proctor crater still continues today index terms 5415 planetology solid surface planets erosion and weathering 5470 planetology solid surface planets surface materials and properties 5410 planetology solid surface planets

martian stepped delta formation by rapid water release deltas and alluvial fans preserved on the surface of mars provide an important record of surface water flow understanding how surface water flow could have produced the observed morphology is fundamental to understanding the history of water on mars to date morphological studies have provided only minimum time estimates for the longevity of martian hydrologic events which range from decades to millions of years here we use sand flume studies to show that the distinct morphology of martian stepped terraced deltas could only have originated from a single basin filling event on a timescale of tens of years stepped deltas therefore provide a minimum and maximum constraint on the duration and magnitude of some surface flows on mars we estimate that the amount of water required to fill the basin and deposit the delta is comparable to the amount of water discharged by large terrestrial rivers such as the mississippi the massive discharge short timescale and the associated short canyon lengths favour the hypothesis that stepped fans are terraced delta deposits draped over an alluvial fan and formed by water released suddenly from subsurface storage

internal structure and deformation of an unstable crystalline rock mass above randa switzerland part ii three dimensional deformation patterns the monitoring of slope displacements over time provides the basis for most rockslide early warning systems yet the prediction of catastrophic failure from these records is highly problematic and tenuous especially if the underlying kinematics and instability mechanism are poorly understood an example is the moving slope above the town of randa in the swiss alps this slope is considered typical of those in crystalline rock that lacks a natural highly persistent weakness plane dipping towards the valley that can serve as a through going detachment surface for kinematic release in part i the companion paper to this the findings from a comprehensive geological and geophysical investigation to image the internal structures of the unstable rock mass were presented in this paper we develop a kinematic model that describes the pattern of displacement vectors for the rock mass along these structures both on surface and at depth the displacements were estimated from 5 years of data from an extensive monitoring system which included surface geodetic and crackmeter measurements borehole inclinometer and extensometer measurements up to 120 m depth and microseismicity the results showed that the displacement field is highly heterogeneous internal deformation is accommodated by both shear and opening mode dislocation of faults and fracture zones which dip moderately to steeply into the slope microseismicity is most intense near the front of the scarp where surface translation in large part reflects the toppling of blocks accommodated by slip along the steeper dipping fractures the small displacement rates at the study site of up to 2 cm year coupled with a modest deviation of up to 15 from vertical of the boreholes posed severe problems for the estimation of horizontal displacements from the inclinometer data we describe the error analysis of these data in some detail since it is relevant for similar installations elsewhere conclusions drawn from this work highlight the importance of integrating various types of data in order to better understand the complex block kinematic processes whose evolution governs the long term progressive failure of unstable rock slopes