influence of temperature on the permeability of rocks changes in physical properties due to temperature increase have been investigated for three generically different types of rock marble sandstone and granite the hg porosity and permeability of the rocks were analysed the permeability of the specimens was determined during axial loading at a constant triaxial state of stress greater permeability changes were registered for rocks with compact structure and low porosity these types of rock are characterised by line contacts between the grains they are more sensitive to temperature increase pores with a radius greater than 500 nm increase due to the temperature influence with the permeability increasing considerably

influence of the interval length of hydraulic packer systems on thermally induced pore pressure measurements in rock abstract during the past several decades hydraulic packer systems have generally been used to measure the thermally induced pore pressures in many in situ experiments in nuclear waste management programs the measured value using hydraulic packer system is a combined value of the pore pressures in the rock along the packer interval and not the pore pressure at the middle point the suitability of using the packer system measured value to represent the thermally induced pore pressure at the middle point of the packer interval needs to be assessed the accuracy of using hydraulic packer systems is examined in this paper using a coupled thermal hydraulic mechanical thm model for fully saturated conditions developed using the finite element program comsol the results indicate that there could be large errors in the measured values with the size of the error dependent on the size of the packer interval the variation of pore pressure gradient along that interval and the orientation of the packer measurement borehole to improve the accuracy of the measurement using packer systems the variation in pore pressure gradient along the packer interval should be small or if a substantial gradient variation is expected the length of the packer interval should be made as small as possible a packer interval with a length less than 0 5 m is suggested if a packer system has been installed with a large interval length in a location where a large pore gradient variation may exist calibration of any associated numerical model using this measurement should incorporate the packer measurement system the numerical results of this coupled thm model are in good agreement with the integration of a point heat source theoretical solution throughout the heater line

analysis of thermally induced changes in fractured rock permeability during eight years of heating and cooling at the yucca mountain drift scale test analysis of thermally induced changes in fractured rock permeability during eight years of heating and cooling at the yucca mountain drift scale test j rutqvist 1 b freifeld 1 k b min 2 d elsworth 2 y tsang 1 earth sciences division lawrence berkeley national laboratory ms 90 1116 berkeley ca 947 20 usa department of energy and geo environmental engineering pennsylvania state university university park pa 16802 usa corresponding author tel 1 510 486 5432 fax 1 510 486 5432 e mail address jrutqvist lbl gov j rutqvist abstract we analyzed a data set of thermally induced changes in fractured rock permeability during a four year heating up to 200 c and subsequent four year cooling of a large volume partially saturated and highly fractured volcanic tuff at the yucca mountain drift scale test in nevada usa permeability estimates were derived from about 700 pneumatic air injection tests taken periodically at 44 packed off borehole intervals during the heating and cooling cycle from november 1997 through november 2005 we analyzed air permeability data by numerical modeling of thermally induced stress and moisture movements and their impact on air permeability within the highly fractured rock our analysis shows that changes in air permeability during the initial four year heating period which were limited to about one order of magnitude were caused by the combined effects of thermal mechanically induced stress on fracture aperture and thermal hydrologically induced changes in fracture moisture content at the end of the subsequent four year cooling period air permeability decreases to as low as 0 2 of initial and increases to as high as 1 8 of initial were observed by comparison to the calculated thermo hydro elastic model results we identified these remaining increases or decreases in air permeability as irreversible changes in intrinsic fracture permeability

effects of earthquake induced landslides on sediment budget and transport over a 50 yr period landsliding during a magnitude 7 7 earthquake in 1929 in northwestern south island new zealand delivered up to 400 000 m 3 km 2 of sediment to stream channels first to third order channels were buried to depths of as much as 10 m with sedimentary rock debris for distances ranging from 2 of the 92 km 2 study area because of the coarse grain size of the sedimentary rock debris and trapping of sediment in numerous landslide dammed lakes sand and pebble sized debris originating from landslides on a 6 6 km 2 area of granite has been transported downstream no more than 10 km at least 50 to 75 of this granitic debris is retained in the fourth order 92 km 2 catchment 50 yr after the earthquake the long retention times of sediment and the volume of debris supplied by landslides during a large earthquake suggest that earthquake induced landsliding is the principal sediment supply mechanism in the region

natural hazards extreme events and mountain topography the hazard of any natural process can be expressed as a function of its magnitude and the annual probability of its occurrence in a particular region here we expand on the hypothesis that natural hazards have size frequency relationships that in parts resemble inverse power laws we illustrate that these trends apply to extremely large events such as mega landslides huge volcanic debris avalanches and outburst flows from failures of natural dams we review quantitative evidence that supports the important contribution of extreme events to landscape development in mountains throughout the world and propose that their common underreporting in the quaternary record may lead to substantial underestimates of mean process rates we find that magnitude frequency relationships provide a link between quaternary science and natural hazard research with a degree of synergism and societal importance that neither discipline alone can deliver quaternary geomorphology stratigraphy and geochronology allow the reconstruction of times magnitudes and frequencies of extreme events whereas natural hazard research raises public awareness of the importance of reconstructing events that have not happened historically but have the potential to cause extreme destruction and loss of life in the future

effect of pore and confining pressures on vp in thermally pre cracked granites the acoustic p waves velocity vp is measured in a water saturated fine grained granite as a function of pore pressure for a series of confining pressures ranging from 10 to 75 mpa prior to vp measurements different crack contents were generated in the granite specimens by means of controlled thermal pre treatments at 450 510 and 555 c vp variations are interpreted as resulting from crack behaviour evolution in response to imposed pressures an effective pressure law with an effective pressure coefficient close to 0 9 is derived for vp from a delimited pressure domain this behaviour is interpreted in terms of crack deformation under pressure

on the connected porosity of mineral aggregates in crystalline rocks the 14 c pmma impregnation of rock samples and mineral staining methods provide the connected porosity map and the spatial distribution of mineral aggregates respectively combined image analysis of mineral and porosity maps allows quantification of the connected porosity distribution in rock forming mineral aggregates after the two maps have been superimposed numerically the 14 c pmma method provides an indication of the extent of pore connectivity for each pixel in the analyzed area which can be used to obtain the porosity distribution as a function of modal mineralogy when applied to undeformed and deformed kivetty granodiorite samples from finland the method allows for a detailed analysis of the rock porosity porosity distributions related to the undeformed rock are unimodal and approximately identical to each other on the other hand porosity distributions of the deformed granodiorite are multimodal and vary significantly constituent porosity sets of the deformed samples were albite crystals free of alkali feldspar patches and alkali feldspar phenocrysts average porosity 0 21 albite containing alkali feldspar patches 0 59 rapakivi albitic mantles 1 15 quartz 0 39 and mafic minerals 5 8 moreover the analysis indicates that the numerous micropores observed under sem within alkali feldspar phenocrysts and albite crystals free of alkali feldspar patches are unconnected in 3d

the formation and failure of natural dams of the numerous kinds of dams that form by natural processes dams formed from landslides glacial ice and late neoglacial moraines present the greatest threat to people and property landslide dams form in a wide range of physiographic settings the most common types of mass movements that form landslide dams are rock and debris avalanches rock and soil slumps and slides and mud debris and earth flows the most common initiation mechanisms for dam forming landslides are excessive rainfall and snowmelt and earthquakes landslide dams can be classified into six categories based on their relation with the valley floor type i dams 11 of 184 landslide dams from around the world that we were able to classify do not reach from one valley side to the other type ii dams 44 span the entire valley floor in some cases depositing material high on opposite valley sides type iii dams 41 move considerable distances both upstream and downstream from the landslide failure type iv dams 1 are rare and involve the contemporaneous failure of material from both sides of a valley type v dams 1 also are rare and are created when a single landslide sends multiple tongues of debris into a valley and forms two or more landslide dams in the same reach of river type vi dams 3 involve one or more failure surfaces that extend under the stream or valley and emerge on the opposite valley side many landslide dams fail shortly after formation in our sample of 73 documented landslide dam failures 27 of the landslide dams failed less than 1 day after formation and about 50 failed within 10 days over topping is by far the most common cause of failure the timing of failure and the magnitude of the resulting floods are controlled by dam size and geometry material characteristics of the blockage rate of inflow to the impoundment size and depth of the impoundment bedrock control of flow and engineering controls such as artificial spill ways diversions tunnels and planned breaching by blasting or conventional excavation glacial ice dams can produce at least nine kinds of ice dammed lakes the most dangerous are lakes formed in main valleys dammed by tributary glaciers failure can occur by erosion of a drainage tunnel under or through the ice dam or by a channel over the ice dam cold polar ice dams generally drain supraglacially or marginally by downmelting of an outlet channel warmer temperate ice dams tend to fail by sudden englacial or subglacial breaching and drainage late neoglacial moraine dammed lakes are located in steep mountain areas affected by the advances and retreats of valley glaciers in the last several centuries these late neoglacial dams pose hazards because 1 they are sufficiently young that vegetation has not stabilized their slopes 2 many dam faces are steeper than the angle of repose 3 these dams and lakes are immediately downslope from steep crevassed glaciers and near vertical rock slopes and 4 downstream from these dams are steep canyons with easily erodible materials that can be incorporated in the flow and increase flood peaks the most common reported failure mechanism is overtopping and breaching by a wave or series of waves in the lake generated by icefalls rockfalls or snow or rock avalanches melting of ice cores or frozen ground and piping and seepage are other possible failure mechanisms natural dams may cause upstream flooding as the lake rises and downstream flooding as a result of failure of the dam although data are few for the same potential energy at the dam site ownstream flood peaks from the failure of glacier ice dams are smaller than those from landslide moraine and structed earth fill and rock fill dam failures moraine dam failures appear to produce some of the largest downstream flood peaks for potential energy at the dam site greater than 1011 1012 joules differences in flood peaks natural dam failures appear to be controlled by dam characteristics and failure mechanisms

tectonic and lithologic controls on bedrock channel profiles and processes in coastal california 1 recent theoretical models suggest that topographic characteristics of bedrock channels are products of interactions among tectonics substrate resistance and the climatically modulated erosive ability of the river the degree to which these factors influence the form of channel profiles is poorly quantified at present here we investigate bedrock channels developed across the southern flank of the santa ynez mountains california uniform climate and systematic variations in lithology and rock uplift rate along the range allow comparison of channel morphology between 1 channels eroding rocks of uniform and nonuniform strength and 2 channels experiencing differences in tectonic forcing we combine field observations surveys and analysis of digital data to determine topographic and hydraulic characteristics of bedrock channels at a constant rock uplift rate streams flowing from resistant to less resistant bedrock exhibit highly concave profiles and increased gradients along lower reaches relative to channels developed in uniform bedrock these effects are interpreted as responses to 1 an increase in substrate resistance to channel incision in the upper reaches and 2 transport limited gradients along lower reaches comparisons of channels developed across uniform lithology but experiencing an approximately sevenfold difference in rock uplift rate reveal an approximately twofold increase in gradient and an approximately threefold decrease in width in this landscape the combined channel adjustments of gradient and width are consistent with a fluvial incision model in which channel incision rate is linearly proportional to mean bed shear stress

geomorphic imprint of landslides on alpine river systems southwest new zealand an inventory of 846 mass movements mainly landslides in two alpine regions of southwest new zealand was created to explore the geomorphic impacts of slope failure processes on river channels and valley floors in total 213 i e 27 per cent of the slope failures descended to valley floors affecting the geomorphology of trunk channels catchment area ac 10 km2 and valley floors in recurring patterns a nominal classification system is introduced for characterizing a the physical contact nature between landslides and river channels and b the resulting geomorphic consequences for drainage although landslide area a is useful for estimating the length of channel directly impacted by debris it does not necessarily predict the direction of fluvial response or type of impact dominant persistent geomorphic imprints of bedrock landslides include channel occlusions and landslide dams in south westland and fiordland respectively differences in size distribution and geomorphic effects on river systems between the two study regions are attributed to bedrock geology tectonics and sediment flux although south westland rivers are more frequently affected by landslides disrupting long term effects such as blockage are more persistent in fiordland copyright 2005 john wiley sons ltd

sediment generation and delivery from large historic landslides in the southern alps new zealand abstract there is much variability of sediment yield in mountain river systems because it is influenced by both periodic e g snowmelt monsoonal circulation and episodic high intensity rainstorms earthquakes controls in the southern alps of new zealand landslides are dominant mechanisms of conveying large amounts of debris to river channels this paper attempts to quantify catastrophic modes of sediment delivery by presenting three recent examples of large landslides on the western slopes of the southern alps a combination of ground surveys dem based volume calculations and air photo interpretation attributes immediate postfailure sediment yields in excess of 70 000 t km 2 a 1 in the short term such landslide derived sediment pulses pose significant hazards to downstream settlements and infrastructure on alluvial fans where they cause massive aggradation increased flooding frequency and large scale channel avulsion in addition to intramontane valley floor obliteration or channel metamorphosis these geomorphic impacts may thus occur far beyond the initial locations of slope failure these catastrophic off site effects involve apparent net sediment delivery rates in the order of 10 5 10 6 m 3 a 1 the accurate quantification of the relative contribution of debris from the disturbing landslide to overall sediment flux is extremely difficult nonetheless are quantitative estimates of landslide derived sediment production and delivery important data to develop a more comprehensive understanding of the variability in alpine sediment flux such data are essential not only for use in hydraulic engineering or catchment management but also in gauging potential future impacts from rainstorm and earthquake induced landsliding in the southern alps

persistent alluvial fanhead trenching resulting from large infrequent sediment inputs we present laboratory and field evidence that in mountainous catchment fan systems persistent alluvial fanhead aggradation and trenching may result from infrequent large sediment inputs we suggest that the river fan systems along the fault bounded range front of the western southern alps new zealand are likely to be in a dynamic equilibrium on 103 yr timescales superimposed on which their fanheads undergo long term cumulative episodic aggradation these fanheads are active only in rare events do not take part in the usual behaviour of the catchment fan system and require much longer to exhibit dynamic equilibrium than the rest of the fan these findings 1 increase our knowledge of the effects of extreme events on alluvial fan morphodynamics in humid climates 2 question the general applicability of inferring past climatic or tectonic regimes from alluvial fan morphology and stratigraphy and 3 provide a conceptual basis for hazard zonation on alluvial fans copyright 2006 john wiley sons ltd

evidence of thermally induced borehole elongation a case study at soultz france abstract when they occur borehole breakouts are considered strong markers of principal stress directions at depth an innovative processing method for automatically identifying breakouts from ultrasonic borehole wall images has been developed it has been applied to data sets from two deep sub vertical wells gpk1 and gpk2 at the soultz geothermal site in eastern france in well gpk1 below 3 km depth compression breakouts with a 95 7 azimuth increasingly occur with depth they result from time dependent compression failure at sub critical stress levels and are indicators of the minimum horizontal principal stress orientation however in the uppermost logged section of well gpk2 1 6 2 9 km depth continuous borehole elongations share roughly the same azimuth with so called drilling induced fractures 164 18 and 175 17 azimuth respectively both features concomitantly vanish with depth together with the amplitude of the thermal perturbation induced by drilling it is proposed that these latter borehole elongations result from a pervasive cooling induced tensile micro cracking process prior to macroscopic failure localization they are termed thermal elongations and are indicators of the maximum horizontal principal stress orientation had a simple logging caliper tool been used for this work these thermal elongations might have been confused with classical compression breakouts a simple criterion for differentiating compression breakouts from thermal elongation is proposed

reduction of long term bedrock incision efficiency by short term alluvial cover intermittency fluctuations of the sediment volume stored in mountain channels are driven by stochastic variations of discharge and sediment supply and can inhibit bedrock incision if sediment thickness is too large here i study how this short term stochasticity propagates into the long term reduction of bedrock incision efficiency the cover effect at geological time scales i introduce a new numerical model that resolves sediment transport and bedrock incision at daily time scales and is run for thousands of years it incorporates 1 a transport threshold and daily stochastic variations in water discharge and sediment supply 2 a freely evolving channel width and slope and 3 an explicit treatment of alluvial thickness variations and corresponding bed incision reduction for typical mountain river conditions the model predicts that alluvial cover oscillates between complete and negligible incision reduction in this intermittent regime the long term cover effect is mainly set by the fraction of time spent in full cover and the present day extent of alluvial cover is not representative of long term dynamics the long term integrated cover effect law differs strongly from proposed theoretical and experimental models and it is controlled by sediment supply stochasticity rather than the details of cover development at the hydraulic time scale model results also suggest that steady state channel configuration always depends on sediment supply rate while being never limited by transport capacity or strictly detachment limited these results point out that discharge and sediment supply stochasticity should not be considered less important than the intricate details of incision laws to model long term bedrock channel dynamics

comparison between connected and overall porosity of thermally stressed granites abstract the structural evolution of four granites heated from 20 to 700 c was examined after cooling the granites have four typical initial structures which can be sub divided into two groups rocks with high connected porosity comprising cracks with low aspect ratio and alteration pores type a pores and a few cracks type b or cracks type c and rocks with low connected porosity with cracks type d the connected porosity was measured by mercury injection and the total porosity by x ray computerized tomography at low temperature t the connected porosity decreases with increasing temperature particularly for the material with high crack density and connected porosity a and b the total porosity increases for b c and d and decreases for the material with low aspect ratio cracks a above 300 c both porosities increase the data show that the thermal history of a granite can be decomposed into two phases in the first stage the connected porosity decreases with increasing temperature cracks are initiated at low temperature and they form unconnected networks in the second stage the connected and total porosities increase the previously initiated cracks form a connected network by opening and they interact with newly created cracks

micro crack enhanced permeability in tight rocks an experimental and microstructural study abstract the elastic and hydraulic response of a rock and its stress sensitivity are strongly affected by the presence of micro cracks therefore a full characterization and quantification of cracks at the micro scale is essential for understanding the physical and transport properties of rocks under stress as yet there is no uniquely accepted method to precisely quantify the density and geometrical characteristics of such microstructural features in this contribution we present results of quantitative analyses of 2d scanning electron microscopy sem images and 3d x ray microtomograms acquired on three samples of carrara marble artificially cracked by thermal shock new semi automatic workflows have been developed to perform these 2d and 3d analyses the main outcome is the quantification of average length aspect ratio and density per unit surface 2d or volume 3d of micro cracks observed the thermal treatment only opens grain boundaries and does not result in the creation of new intragranular cracks the results are consistent with the degree of thermal cracking artificially induced on the rock sample prior to the imaging analysis procedure i e more and wider micro cracks are measured on samples heated to higher temperatures the results of these quantitative microstructural analyses are also consistent with nuclear magnetic resonance nmr data independently acquired on the same samples saturated with water

slope distributions threshold hillslopes and steady state topography digital elevation models of two steady state mountain ranges the olympic mountains om and oregon coast range ocr are used to examine relationships between slope distributions the development of threshold hillslopes and steady state topography plots of drainage area versus slope for these mountain ranges exhibit substantial scatter that complicates comparison of range form to analytical theories and landscape evolution models contour plots of the density of such data reveal an attractor at the scale of the transition from hillslope processes to channel processes and log bin averaging reveals trends that parallel predictions of steady state erosion laws but with different rate laws for five distinct process domains hillslopes valley heads and colluvial bedrock and alluvial valley segments slope histograms computed for 100 km2 areas defined by a 10 10 km grid throughout the om exhibit approximately normal or exponential distributions in areas of active rock uplift and depositional topography respectively local slope distributions in the ocr also tend to be normally distributed but some are left skewed in areas with gentler slopes mean slopes determined both over the above referenced grid and a 10 km diam moving window are relatively invariant in the core of the om in spite of strong contrasts in bedrock erodibility and gradients in long term rock uplift rates in contrast the mean slopes in the ocr parallel latitudinal gradients in rock uplift rates and bedrock erodibility hence the slope distributions in the om and ocr reflect distinct relationships between development of threshold bedrock and soil mantled hillslopes and steady state topography

thermal strain in a water saturated limestone under hydrostatic and deviatoric stress states abstract the present study is aimed at investigating the evolution of thermally induced bulk strain in a water saturated limestone blaubeuren at three different stress states three cylindrical rock samples are respectively loaded to a constant stress state 1 3 15 mpa 1 45 mpa 3 15 mpa 1 75 mpa 3 15 mpa at drained conditions in a conventional triaxial rock deformation apparatus before the sample temperature is cycled between 30 c and defined levels up to 120 c strain measurements are performed by one circumferential and two axial extensometers irreversible strain in both the lateral and axial sample directions are measured after each temperature cycle indicating permanent increases in diameter and in length the measured bulk strain is separated into different strain components related to 1 initial stress loading 2 reversible thermal expansion and contraction of rock matrix and 3 some residual strain the magnitudes of the residual strain increase with increasing deviatoric stress 1 3 in the lateral direction but decrease with increasing deviatoric stress in the axial direction the derived matrix thermal expansion coefficients range from 6 10 6 c 1 to 1 8 10 5 c 1 and from 9 10 6 c 1 to 1 5 10 5 c 1 respectively in the axial and lateral directions and present lower values at higher deviatoric stresses microstructural analyses evidence tensile cracks which are interpreted to have been induced during the temperature cycles these cracks have the potential to offset matrix thermal expansion yielding lower matrix thermal expansion coefficients at higher deviatoric stresses

behaviour of granites and limestones subjected to slow and homogeneous temperature changes abstract we have studied the evolution of the texture in two granites and two limestones subjected to slow and uniform temperature change each granite has a different grain size and each limestone a different texture carrare crystalline limestone and crepey oolitic limestone temperature was varied from 200 c to 700 c scanning electron microscope observations of different rock samples show that during thermal cycling intercrystalline boundaries in granites widen out progressively and porosity increases new microcracks appear in crystals between 500 c and 600 c in carrare crystalline limestone intercrystalline cracks appear at temperatures as low as 200 c due to its heterogeneous cracks appear at temperatures as low as 200 c due to its heterogeneous increasing temperature longitudinal wave velocity and intrinsic permeability show good correlation with the scanning electron microscope observations

modelling the compliance of crustal rock ii response to temporal changes before earthquakes summary there have been several claims that seismic shear waves respond to changes in stress before earthquakes the companion paper develops a stress sensitive model ape for the behaviour of low porosity low permeability crystalline rocks containing pervasive distributions of fluid filled intergranular microcracks and this paper uses ape to model the behaviour before earthquakes modelling with ape shows that the microgeometry and statistics of distributions of such fluid filled microcracks respond almost immediately to changes in stress and that the behaviour can be monitored by analysing seismic shear wave splitting the physical reasons for the coupling between shear wave splitting and differential stress are discussed in this paper we extend the model by using percolation theory to show that large crack densities are limited at the grain scale level by the percolation threshold at which interacting crack clusters lead to pronounced increases in rock matrix permeability in the simplest formulation the modelling is dimensionless and almost entirely constrained without free parameters nevertheless ape modelling of the evolution of fluid saturated rocks under stress reproduces the observed fracture criticality and the narrow range of shear wave azimuthal anisotropy in crustal rocks it also reproduces the behaviour of temporal variations in shear wave splitting observed before and after the 1986 m 6 north palm springs earthquake southern california and several other smaller earthquakes the agreement of ape modelling with a wide range of observations confirms that fluid saturated crystalline rocks are stress sensitive and respond to changes in stress by critical fluid rock interactions at the microscale level this means that the effects of changes in stress and other parameters can be numerically modelled and monitored by appropriate observations of seismic shear waves

thermal stress cracking in granite we have developed a comprehensive experimental capability to study thermally induced microfractures in rock we count acoustic emissions and measure compressional wave velocities while a sample is heated to a maximum temperature of 300 c under confining pressures up to 55 mpa after a heating cycle we measure crack porosity and crack compressibility we count the cracks under an sem sorting them by grain boundary and intragranular types and by mineral pair occurrence our observations reveal that 1 significant thermal cracking occurs in granites heated above 200 or 250 c under 28 and 55 mpa and above 100 c in granites heated under 7 mpa 2 most newly created thermal cracks close at pressures below 40 mpa 1 5 km depth 3 grain boundaries between quartz grains or between quartz and another mineral are preferentially cracked 4 the threshold temperature for acoustic emissions is a positive linear function of pressure 5 total acoustic emission counts in westerly granite heated to 300 c are slightly lower under 55 than 28 mpa confining pressure and are substantially lower under 28 than 7 mpa 6 the compressional velocity decreases 22 as westerly granite is heated to 300 c at 7 mpa 15 at 28 mpa and 10 at 55 mpa and 7 greater hysteresis in compressional velocities occurs in samples heated at lower pressures the acoustic emission counts in westerly granite during heating show one or more peaks of activity as a function of temperature with more peaks at lower pressures we interpret this result to mean that additional crack populations are able to open at lower confining pressures the curves of acoustic emission count rates can be fit by summing one to three gaussian density functions

landscape response to tectonic forcing digital elevation model analysis of stream profiles in the mendocino triple junction region northern california the topographic evolution of orogens is fundamentally dictated by rates and patterns of bedrock channel incision quantitative field assessments of process based laws are needed to accurately describe landscape uplift and denudation in response to tectonics and climate we evaluate and calibrate the shear stress or similar unit stream power bedrock incision model by studying stream profiles in a tectonically active mountain range previous work on emergent marine terraces in the mendocino triple junction region of northern california provides spatial and temporal control on rock uplift rates digital elevation models and field data are used to quantify differences in landscape morphology associated with along strike northwest to southeast changes in tectonic and climatic conditions analysis of longitudinal profiles supports the hypothesis that the study area channels are in equilibrium with current uplift and climatic conditions consistent with theoretical calculations of system response time based on the shear stress model within uncertainty the profile concavity of the trunk streams is constant throughout the study area 0 43 as predicted by the model channel steepness correlates with uplift rate these data help constrain the two key unknown model parameters the coefficient of erosion k and the exponent associated with channel gradient n this analysis shows that k cannot be treated as a constant throughout the study area despite generally homogeneous substrate properties for a reasonable range of slope exponent values n best fit values of k are positively correlated with uplift rate this correlation has important implications for landscape evolution models and likely reflects dynamic adjustment of k to tectonic changes due to variations in orographic precipitation and perhaps channel width sediment load and frequency of debris flows the apparent variation in k makes a unique value of n impossible to constrain with present data

variations of connected porosity and inferred permeability in a thermally cracked granite connected porosity volume and throat diameter were measured in granitic samples with different porosity structures heated from 20 to 700 c three types of microstructures are recognized from scanning electron microscopy sem analysis 1 a crack network of transgranular cracks with few intersections 2 a pipe network of intragranular and intergranular tubes with high connectivity 3 a mixed structure of transgranular cracks connected by intragranular tube structures calculations predict a decrease of permeability through crack and mixed networks between 50 and 400 c followed by a sharp increase at higher temperatures the decrease in permeability is associated predominantly with the decrease in throat diameter whereas the increase in both throat diameter and the porosity volume account for the temperature rise only small variations of the permeability are predicted for the pipe network

catastrophic rock slope failures and late quaternary developments in the nanga parbat haramosh massif upper indus basin northern pakistan abstract the nanga parbat haramosh massif has some of the greatest relief on earth and highest measured rates of uplift denudation and river incision in bedrock many studies have sought to understand how its morphology relates to geotectonic evolution and glaciations however few catastrophic rock slope failures had been recognised and many of their impacts had been attributed to other processes recently more than 150 of these landslides have been found within a 100 km radius of nanga parbat 8125 m new discoveries are reported east north and west of nanga parbat along the indus streams most generated long run out rock avalanches that dammed the indus or its tributaries some impounding large lakes they initiated episodes of intermontane sedimentation followed by trenching and removal of sediment valley floor features record a complex interplay of impoundment and sedimentation episodes superimposition of streams in pre landslide valley floors and exhumation of buried features these findings depart from existing reconstructions of quaternary events a number of the rock avalanche deposits were previously misinterpreted as tills or moraine and their associated lacustrine deposits attributed to glacial lakes features up to 1000 m above the indus formerly seen as tectonically raised terraces are depositional features emplaced by landslides or erosion terraces recording the trenching of valley fill in landslide interrupted river reaches unquestionably tectonics and glaciation have been important but decisive and misread formative events of the holocene involve a post glacial landslide fragmented fluvial system the latter has kept valley developments in a chronic state of disequilibrium with respect to climatic and geotectonic controls accepted glacial chronologies are put in doubt particularly the extent and timing of the last major glaciation the pace and role processes in the holocene have been seriously underestimated

bedrock incision rock uplift and threshold hillslopes in the northwestern himalayas the topography of tectonically active mountain ranges reflects a poorly understood competition between bedrock uplift and erosion dating of abandoned river cut surfaces in the northwestern himalayas reveals that the indus river incises through the bedrock at extremely high rates 2 12 mm yr 1 in the surrounding mountains the average angles of hillslopes are steep and essentially independent of erosion rate suggesting control by a common threshold process in this rapidly deforming region an equilibrium is maintained between bedrock uplift and river incision with landsliding allowing hillslopes to adjust efficiently to rapid river down cutting

earthquake dammed lakes in new zealand eleven small lakes were formed by landslides caused by the 1929 buller earthquake four others were formed by other historic earthquakes in new zealand at least nine other new zealand lakes are also dammed by landslides and were probably formed by prehistoric earthquakes when recognized by morphology synchronous age and areal distribution earthquake dammed lakes could provide an estimate of paleoseismicity for the past few hundred or thousand years

an automated method for producing synoptic regional maps of river gradient variation procedure accuracy tests and comparison with other knickpoint mapping methods abstract the study of abrupt changes in longitudinal river profiles or knickpoints is currently approached through an empirical power law the slope area relationship results based on digital elevation model dem analyses and stream extractions are generally intended to determine crustal uplift rates and identify transient landscape conditions in this article we present an alternative geomorphometric method for locating knickpoints and knickzones based on local slope gradient and curvature attributes intended as a rapid regional scale automated knickpoint detection technique the accuracy of this slope curvature method is tested on two digital elevation grids nasa s srtm ground resolution of 90 m resampled here to 75 m and the aster dem 15 m in the sierra nacimiento new mexico usa a basement cored mountain range recently exhumed by waves of headward drainage integration in response to remote tectonic deformation in the adjacent rio grande rift out of every 10 gradient anomalies detected by the srtm derived numeric routine up to 8 are certifiable knickpoints recognized among a population of georeferenced occurrences surveyed in the field an independent comparison with the slope area method provided a further accuracy test which was particularly useful at sites that could not be validated in the field for practical reasons given the low tectonic activity of the study area the majority of knickpoints was also found to coincide with lithologic boundaries making it difficult without further geomorphological data to single out dynamic knickpoints directly caused by the upstream propagation of channel instabilities relating to base level change

rock slope failure and the river long profile this study examines the geomorphic effects of large 10 6 m 3 rock slope failures on long profiles of rivers in the swiss alps and the new zealand southern alps regression of channel slope versus drainage basin area objectively highlights knickpoints separating incised from aggraded reaches that often correspond to locations of large rock slope failures for a fixed concavity index the highest values of the steepness index and erosion index along a given profile spatially coincide with breach channels cut into formerly river damming rockslide debris as old as 10 k y assuming that the knickpoints do not predate slope failure data show that high profile steepness and inferred specific stream power are not always the cause but often a result of large river blocking rock slope failure in mountain basins omission of rockslide data from slope area plots lowers the steepness index and increases the concavity index on average yet only in few cases more than one standard deviation

glacier and landslide feedbacks to topographic relief in the himalayan syntaxes despite longstanding research on the age and formation of the tibetan plateau the controls on the erosional decay of its margins remain controversial pronounced aridity and highly localized rock uplift have traditionally been viewed as limits to the dissection of the plateau by bedrock rivers recently however glacier dynamics and landsliding have been argued to retard headward fluvial erosion into the plateau interior by forming dams and protective alluvial fill here we report a conspicuous clustering of hundreds of natural dams along the indus and the tsangpo rivers where these cross the himalayan syntaxes the indus is riddled by hundreds of dams composed of debris from catastrophic rock avalanches forming the largest concentration of giant landslide dams known worldwide whereas the tsangpo seems devoid of comparable landslide dams in contrast glacial dams such as river blocking moraines in the headwaters of both rivers are limited to where isolated mountain ranges intersect the regional snowline we find that to first order high local topographic relief along both rivers corresponds to conspicuously different knickzones and differences in the type and potential longevity of these dams in both syntaxes glacier and landslide dams act as a negative feedback in response to fluvial dissection of the plateau margins natural damming protects bedrock from river incision and delays headward knickpoint migration thereby helping stabilize the southwestern and southeastern margins of the tibetan plateau in concert with the effects of upstream aridity and localized rock uplift

the formation and impact of landslide dams state of the art abstract the blocking of river courses by mass movements is very common in mountainous areas with deep and narrow valleys landslide dams may pose serious threats to people and their livelihoods downstream in the case of abrupt dam failure since the publication of benchmark reviews of costa and schuster 1988 and korup 2002 there is a growing number of studies focusing on the formation stability and short term impacts of landslide dams this review combines the insights of all these studies builds on current concepts of landslide dams and suggests ways to unify terminologies and classifications we furthermore present a new worldwide database compiled from literature data it contains 410 landslide dams 1 million m3 in volume that were formed since 1900 since these have the most complete data entries these data show that dam longevity is among other factors correlated with the type of landslide forming the dam those formed by rock debris avalanches and rockslides have longest lifespans however the influence of landslide type or material on dam longevity decreases with time after dam formation to ensure consistency in the next database generation we suggest guidelines for data collection to provide a solid basis for evaluating dam stability and governing factors a preliminary classification matrix for landslide dam stability that combines topographic setting and the internal structure of the dam body is another outcome of our review furthermore an evaluation of the various geomorphic stability indices proposed in the literature regarding their suitability and limitations in assessing dam formation and stability shows that they predict the probability of dam formation reasonably well but that their application to longevity estimates requires further assessment the geomorphic impacts of landslide dams in the short medium and long term are summarized and illustrated with key examples finally for a better understanding of the factors controlling dam stability we recommend to 1 include dam composition and sedimentary structures in future case studies 2 maintain and update the worldwide database for sound statistical analyses 3 refine landslide dam stability indices and test them for different landslide types and 4 study hazard cascades related to multiple dams in one watershed for long term landscape evolution studies we suggest to 5 quantify terrestrial sediment flux related to landslide dams 6 detect ancient landslide dams in river profiles and 7 further exploit the sediment archives in former impoundment areas

quaternary moraines vs catastrophic rock avalanches in the karakoram himalaya northern pakistan a history and conception of glacial events for the central karakoram himalaya proposed some 80 years ago by giotto dainelli are largely accepted today however certain deposits identified as terminal moraine complexes marking glacial episodes were actually emplaced by rock avalanches in the skardu and shigar intermontane basins of baltistan at least 15 rock avalanche events were previously mapped as moraine or till criteria used for distinguishing these catastrophic landslide deposits emphasize homogeneous lithology of rubble and matrix clast shape facies characteristics the large scale unity of emplacement and morphological relations to valley topography the deposits of three events at katzarah satpura and the north end of shigar valley have been reconstructed in detail thick supraglacial debris does not result in similar deposits extensive valley fills river terraces large sediment fans and lacustrine sediments formerly attributed to late glacial conditions are reinterpreted as postglacial events involving rock avalanches that interrupted fluvial development existing reconstructions of glaciations are left in doubt especially late glacial events in the central karakoram as are the roles assigned to karakoram main indus valley and western himalayan ice

modeling the thermal hydrologic processes in a large scale underground heater test in partially saturated fractured tuff the drift scale test dst is being conducted in an underground facility at yucca mountain nevada to probe the coupled thermal hydrological mechanical and chemical processes likely to occur in the fractured rock mass around a potential high level nuclear waste repository thermal hydrological processes in the dst have been simulated using a three dimensional numerical model the model incorporates the realistic test configuration and all available site specific measurements pertaining to the thermal and hydrological properties of the unsaturated fractured tuff of the test block the modeled predictions were compared to the extensive set of measured data collected in the first year of this 8 year long test the mean error between the predictions and measurement at 12 months of heating for over 1600 temperature sensors is about 2 degrees c heat pipe signature in the temperature data indicating two phase regions of liquid vapor counterflow is seen in both the measurements and simulated results the redistribution of moisture content in the rock mass resulting from vaporization and condensation was probed by periodic air injection testing and geophysical measurements good agreement also occurred between the model predictions and these measurements the general agreement between predictions from the numerical simulations and the measurements of the thermal test indicates that ourmore fundamental understanding of the coupled thermal hydrologic processes at yucca mountain is sound however effects of spatial heterogeneity from discrete fractures that are observed in the temperature data are not matched by simulations from the numerical model which treat the densely spaced fractures as a continuum less

the effect of heating on the microstructural evolution of la peyratte granite deduced from acoustic velocity measurements the acoustic p waves velocity vp was measured in a water saturated fine grained granite as a function of pore pressure for a series of confining pressures ranging from 10 to 75 mpa different crack contents were generated in the granite specimens by means of controlled thermal pre treatment at 450 510 555 and 600 c vp variations are interpreted as resulting from crack behaviour evolution in response to imposed pressures data analysis is proposed by using an effective medium approach the elastic behaviour of the cracked rock is controlled by the crack density parameter which varies with applied pressures due to crack closure two crack families corresponding to intragranular cracks and cracked grain boundaries and a decreasing exponential distribution of crack aspect ratios are introduced to take into account the heterogeneity of the rock samples and allows us to calculate the acoustic velocity vp for various effective pressures comparison between theoretical and experimental values shows that the model leads to consistent velocity variations moreover when applied to the four pre treatment temperatures the model gives informations on the effect of heating on the microstructural parameters of the samples in particular the behaviour of both crack families when the quartz transition is passed

sediment flux from a mountain belt derived by landslide mapping in humid uplands landsliding is the dominant mass wasting process in the western southern alps of new zealand landslides are scale invariant and have a power law magnitude frequency distribution independent studies from other regions suggest that this is a general property of landsliding this observation is of critical importance to the evaluation of the impact of events of different length scales over different time intervals on landscape evolution it is particularly useful when estimating regional geomorphic rates because it constrains the frequency and overall significance of extreme events which cannot otherwise be evaluated by integrating the complete response of the system we estimate the regional denudation rate due to landsliding to be 9 4 mm yr 1 sediment discharge from the western southern alps is dominated by landslide derived material

quantitative relationships between uplift and relief parameters for the southern alps new zealand as determined by fission track analysis the southern alps mountain chain new zealand has formed as a consequence of late cenozoic collision of the continental parts of the pacific and australia plates fission track analysis has yielded estimates of the amount age of initiation and rate of late cenozoic rock uplift for 82 surface samples taken from transects across the southern alps the mean surface summit and valley elevations in the vicinity of each of the rock sample sites have also been measured regression of the geomorphic variables on the uplift variables has been used to establish quantitative relationships between uplift and geomorphology there are strong and consistent linear associations between uplift and the elevations of the mean surface summits and valleys the preferred regression models have uniform slope but varying elevation response between transects substitution of space for time has allowed the evolution of landforms to be studied to the east of the main divide elevation and relief are proportional to and closely related to the age of initiation of rock uplift uplift age and the amount of rock uplift r2 0 8 mean surface uplift was delayed for 2 ma after the start of rock uplift a result of the stripping of a soft cover rock succession that prior to rock uplift overlaid the harder greywacke basement inter transect variations in regression response and x intercept are inferred therefore to reflect the variable preuplift thickness of cover rocks however the regular regression slope for the transects reflects the consistent nature of the interaction between uplift and the erodibility of greywacke basement uplift of the mean surface proceeded at 0 4 km km and 0 4 km ma of rock uplift while the rock uplift rate was 0 8 km ma summit elevations have increased at a rate of 0 6 km ma and valley elevations have increased at 0 2 km ma regression lines relating mean surface summit and valley elevations to rock uplift and uplift age diverge from common intercepts it is concluded therefore that the mountains east of the main divide have continued to increase in elevation and relief and change in form over time since the start of mean surface uplift mountain elevation has little relationship with late cenozoic mean rock uplift rates of 0 8 1 0 km ma or inferred contemporary rock uplift rates r2 0 3 in contrast to the west of the main divide elevation is shown to be closely related to rock uplift rate r2 0 3 in contrast to the west of the main divide elevation is shown to be closely related to rock uplift rate r2 0 8 transects with higher rock uplift rates support higher topography landforms are therefore in a stable equilibrium with rock uplift rate and the landscape contains no residual evidence of the total amount of rock uplift or the age of uplift lithological variation appears to have no relationship with elevation

elastic anisotropy and pore space geometry of schlieren granite direct 3 d measurements at high confining pressure combined with microfabric analysis pore space geometry of granitic rocks and its evolution with depth are key factors in large scale seismics or in projects of enhanced geothermal systems or of deep hazardous waste repositories in this study we studied macroscopically anisotropic schlieren bearing granite by experimental p wave velocity v p measurements on spherical sample in 132 directions at seven different confining pressures in the range 0 1 400 mpa in order to discriminate the phenomena affecting the rock elastic properties we analysed the orientation of microcracks and of grain boundaries and we measured the anisotropy of magnetic susceptibility of the rock three sets of microcracks were defined with two of them linked to the massif exfoliation process and one to cooling contraction of the massif during pressurization the measured mean v p and v p anisotropy degree at ambient pressure and at highest confinement 400 mpa yielded 3 3 km s 1 and 24 per cent and 6 2 km s 1 and 3 per cent respectively the associated v p anisotropy pattern was transversely isotropic and governed by the schlieren with a minimum v p direction perpendicular to them and a girdle of high v p directions parallel to them the highest change in v p was observed between 0 1 and 10 mpa suggesting a significant closure of porosity below depths of 500 m change of the v p anisotropy pattern to orthorhombic together with increase of mean v p and v p anisotropy degree during depressurization was attributed to inelastic response of one of the sets of microcracks to the loading unloading cycle

coupled thermal hydrological mechanical analyses of the yucca mountain drift scale test comparison of field measurements to predictions of four different numerical models abstract the yucca mountain drift scale test dst is a multiyear large scale underground heating test designed to study coupled thermal hydrological mechanical chemical behavior in unsaturated fractured and welded tuff as part of the international cooperative code comparison project development of coupled models and their validation against experiments four research teams used four different numerical models to simulate and predict coupled thermal hydrological mechanical thm processes at the dst the simulated processes included heat transfer liquid and vapor water movements rock mass stress and displacement and stress induced changes in fracture permeability model predictions were evaluated by comparison to measurements of temperature water saturation displacement and air permeability the generally good agreement between simulated and measured thm data shows that adopted continuum model approaches are adequate for simulating relevant coupled thm processes at the dst moreover thermal mechanically induced rock mass deformations were reasonably well predicted using elastic models although some individual displacements appeared to be better captured using an elasto plastic model it is concluded that fracture closure opening caused by change in normal stress across fractures is the dominant mechanism for thermal stress induced changes in intrinsic fracture permeability at the dst whereas fracture shear dilation appears to be less significant this indicates that such changes in intrinsic permeability at the dst which are within one order of magnitude are likely to be mostly reversible

triassic high strain shear zones in hainan island south china and their implications on the amalgamation of the indochina and south china blocks kinematic and 40ar 39ar geochronological constraints abstract a kinematic and geochronological study has been carried out on the triassic high strain shear zones in hainan island the southern south china block there are wnw and ne trending high strain shear zones with greenschist to amphibolite facies metamorphism in this island kinematic indicators suggest a dextral top to the nne thrust shearing for the wnw trending high strain shear zones and a sinistral top to the se thrust shearing for the ne trending shear zones the quartz c axis orientations of mylonitic rocks exhibit the domination of basal slip and some activation of a rhombohedra gliding system the timing of shearing for these shear zones has been constrained by the 40ar 39ar dating analyses of synkinematic minerals middle triassic 242 250 ma and late triassic early jurassic 190 230 ma have been identified for the wnw and ne trending shear zones respectively a synthesis of these kinematic and thermogeochronological data points to a two stage tectonic model for hainan island that is top to the nne oblique thrusting at 240 250 ma followed by top to the se oblique thrusting at 190 230 ma in combination with the available data from the southern south china and indochina blocks it is inferred that south hainan and north hainan have affinity to the indochina and south china blocks respectively the tectonic boundary between south hainan and north hainan lies roughly along the wnw trending changjiang qionghai tectonic zone probably linking to the song ma and ailaoshan zones the middle triassic structural pattern of hainan island is spatially and temporally compatible with those of the south china and indochina blocks and thus might be a derivation from the amalgamation of the indochina with south china blocks in response to the closure of the paleotethys ocean and subsequent subduction collision

comment on discovery of the fossiliferous cu brei formation lower devonian in the kon tum block south viet nam tong dzuy thanh than duc duyen nguyen huu hung bui phu my abstract the publication of tong dzuy thanh et al calls for two remarks the metamorphism in the kon tum block cannot be younger than permian because the outcrop they describe is not metamorphic their very interesting discovery is a new piece of evidence for the exotic origin of the dien binh series

the influence of large landslides on river incision in a transient landscape eastern margin of the tibetan plateau sichuan china deep landscape dissection by the dadu and yalong rivers on the eastern margin of the tibetan plateau has produced high relief narrow river gorges and threshold hillslopes that frequently experience large landslides large landslides inundate river valleys and overwhelm channels with large volumes 10 5 m 3 of coarse material commonly forming stable landslide dams that trigger extensive and prolonged aggradation upstream these observations suggest that strong feedbacks among hillslope processes channel morphology and incision rate are prevalent throughout this landscape and are likely characteristic of transient landscapes experiencing large increases in local relief in general landslide effects are a by product of rapid incision initiated by regional uplift however over timescales relevant to landscape evolution 10 4 yr large landslides can also act as a primary control on channel morphology and longitudinal river profiles inhibiting incision and further preventing the complete adjustment of rivers to regional tectonic climatic and lithologic forcing we explore a probabilistic numerical model to provide a quantitative framework for evaluating how landslides influence bedrock river incision and landscape evolution the time average number of landslide dams along a river course and thus the magnitude of the landslide influence is set by two fundamental timescales the time it takes to erode landslide deposits and erase individual dams and the recurrence interval of large landslides that lead to stable dams stable gradually eroding landslide dams create mixed bedrock alluvial channels with spatial and temporal variations in incision ultimately slowing long term rates of river incision thereby reducing the total amount of incision occurring over a given length of river a stronger landslide effect implies that a higher percentage of channel length is buried by landslide related sediment leading to reduced river incision efficiency the longer it takes a river channel to incise into a landslide dam and remove all landslide related sediment the more control these events have on the evolution of the river profile and landscape evolution this can be the result of slow erosion of stable dams or a higher frequency of large events

discovery of the fossiliferous cu brei formation lower devonian in the kon tum block south viet nam abstract lower devonian corals and stromatoporoids have recently been discovered in limestones among low grade metamorphic rocks on the western margin of the kon tum block south viet nam this unit has been identified as the cu brei formation coral and stromatoporoid species have been described including squameofavosites aff spongiosus parallelostroma cf multicolumnum amphipora cf rasilis a cf raritalis simplexodictyon cf artyschtense stromatopora cf boriarchinovi and stromatopora sp indet the cu brei formation is exposed in a small area 6 km in length and 3 km wide at the foot of cu brei mountain sa thay district kon tum province as this formation is in marine shelf facies it is probable that further exposures of lower devonian sediments may be discovered in the kon tum block this discovery raises the question of the tectonic history of the metamorphic kon tum block it is possible that the block was not an area of positive uplift from the beginning of paleozoic as has been supposed but was submerged in a marine environment at least on its outer margins in the devonian and possibly even earlier in early paleozoic

effects of rock avalanches on glacier behaviour and moraine formation although large rock avalanches are infrequent sediment production in active orogens is dominated by such events which may strongly influence geomorphic processes where rock avalanches fall onto glaciers they may affect glacier behaviour and moraine formation we outline the processes of rock avalanche initiation and motion and show that supraglacial deposits of rock avalanche debris have distinct sedimentological and thermal properties laboratory experiments on the effects of such debris on ice ablation are supplemented by field data from two rock avalanches in the southern alps new zealand their effects are compared with those of the thinner supraglacial debris that results from small rockfalls and melt out of englacial debris implications of rock avalanche debris cover for glacier behaviour are explored using a mass balance model of the franz josef glacier in new zealand demonstrating a likely supraglacial rock avalanche origin for the waiho loop moraine and considering the potential hazard of a large rock avalanche onto the present day glacier

catastrophic landslides and their effects on the upper indus streams karakoram himalaya northern pakistan abstract the paper examines the nature and geomorphic influences of deposits from rock avalanches that obstruct rivers most of the 115 rockslide rock avalanche events identified in the karakoram himalaya straddled one or more stream valleys at least 73 of these landslides formerly dammed the indus or its tributaries upstream of the barriers remnants exist of once very extensive lacustrine deposits the stability and long term survival of dams from large rock avalanches is addressed and the reasons for the gradual or phased rather than catastrophic and sudden breaching case histories emphasise the erosional and depositional forms associated with the barriers they are reconstructed in terms of the emplacement and properties of the deposits from rock avalanches and the response of the river to interruption by them these barriers have exerted a substantial control over stream response and development for most of the holocene at least today they are associated with distinctive features of channel form and thalweg river terrace systems intermontane sediment sinks and sources and local erosional forms in bedrock more broadly the landslide barriers have created a naturally fragmented river system deposition and erosion in the lower few tens or hundreds of meters of the upper indus stream valleys have been dominated by epicycles of aggradation trenching and downcutting that mainly reflect the scale timing and history of each barrier the landforms involved are only indirectly related to the late glacial and paraglacial conditions that have hitherto been regarded as the main explanation

reconstructing the transport history of glacigenic sediments a new approach based on the co variance of clast form indices abstract two indices are used to describe the aggregate shape and roundness characteristics of glacially transported clasts the c40 index the percentage of clasts with c a ratios 0 4 and the ra index the percentage of very angular and angular clasts in a sample analysis of the between and within sample co variance of these indices provides a powerful tool for discriminating actively and passively transported clasts in glacigenic deposits use of these indices is illustrated in an analysis of the form characteristics of clasts from lateral and frontal moraines at storbreen jotunheimen these fall between those of actively transported clasts in basal till low c40 and ra values and those of unmodified frost weathered clasts high c40 and ra values both indices decline down moraine within sample analyses of clast shape demonstrates that these aggregate clast form gradients reflect changes in the relative proportions of actively and passively transported debris on the moraines rather than progressive modification of actively transported clasts these analyses also indicate that actively transported clasts form the dominant component of the moraines particularly near the former glacier terminus further applications of the approach developed here are suggested

the role of landslides in mountain range evolution abstract we review the role of landslides in current concepts of the topographic development of mountain ranges we find that many studies in this field address basin or orogen scale competition between rock uplift and fluvial bedrock erosion hillslopes in general and bedrock landslides in particular are often assumed to respond rapidly to incision and development of the fluvial drainage network this leads to a one sided view of the geomorphic coupling between hillslopes and rivers that emphasizes the fluvial control of hillslopes but ignores the alternative view that landslides can affect the fluvial network there is growing evidence that landslides are a dominant source of sediment in mountain belts and that they exert a direct geomorphic control on fluvial processes landslides can influence the river network in a variety of ways from determining basin area and drainage divide positions to setting streamwise variations in sediment load and calibre the geomorphic legacy of large landslides on hillslope and channel morphologies may persist for up to 104 yr adding considerable variability to fluvial erosion and sedimentation patterns over these timescales we identify a number of questions for future research and conclude that a better understanding and quantification of the geomorphic feedbacks between landslides and river channels builds an important link between short term 105 yr landscape evolution models

a comparative simulation study of coupled thm processes and their effect on fractured rock permeability around nuclear waste repositories this paper presents an international multiple code simulation study of coupled thermal hydrological and mechanical thm processes and their effect on permeability and fluid flow in fractured rock around heated underground nuclear waste emplacement drifts simulations were conducted considering two types of repository settings 1 open emplacement drifts in relatively shallow unsaturated volcanic rock and 2 backfilled emplacement drifts in deeper saturated crystalline rock the results showed that for the two assumed repository settings the dominant mechanism of changes in rock permeability was thermal mechanically induced closure reduced aperture of vertical fractures caused by thermal stress resulting from repository wide heating of the rock mass the magnitude of thermal mechanically induced changes in permeability was more substantial in the case of an emplacement drift located in a relatively shallow low stress environment where the rock is more compliant allowing more substantial fracture closure during thermal stressing however in both of the assumed repository settings in this study the thermal mechanically induced changes in permeability caused relatively small changes in the flow field with most changes occurring in the vicinity of the emplacement drifts

post rock avalanche dam outburst flood sedimentation in ram creek southern alps new zealand rock avalanches are common in mountainous regions that are tectonically active they are capable of forming natural dams of uncertain persistence that have significant impacts on the river system over wide spatial scales and possibly over geological time scales here we combine field data and digital elevation model dem analysis to show the response of ram creek new zealand to 28 years of sediment dispersion following the 1968 emplacement of a co seismic rock avalanche dam that breached catastrophically in 1981 the results show a system that has not attained equilibrium being unable to move the quantity of dam derived sediments and will likely not attain equilibrium before the next major sediment input it is in a state of persistent disturbance where localised reworking dominates erosion in ram creek is focussed on lateral bevelling and bedrock gorge widening rather than vertical incision to keep pace with tectonic uplift importantly for studies of tectonic geomorphology this widening which if sustained will form a strath terrace does not represent a period of reduced uplift stream metrics concavity and steepness are unable to differentiate the identified rock avalanche induced knickpoint from tectonic and lithological knickpoints

saturated heating and quenching of three crustal rocks and implications for thermal stimulation of permeability in geothermal reservoirs abstract thermal stimulation is a reservoir enhancement technique that relies on the generation of permeable fractures by thermal gradients replication of thermal stimulation in a controlled laboratory environment provides insight to the physical changes that may be expected at the field scale and assist in stimulation optimization we present a new methodology designed to replicate thermal stimulation in such an environment we developed an apparatus to allow rocks to be heated to 375 c at up to 35 mpa confining pressure and rapidly quenched with cold water to ambient temperature while maintaining system pressure to test our methodology we characterized three rocks that represent a range of geothermal developments and laboratory based investigations lanhelin granodiorite granite from brittany france allandale rhyolite from the lyttelton volcano new zealand and halswell basalt also from the lyttelton volcano our characterization consists of profiling microstructure porosity density dynamic elastic moduli and permeability prior to thermal stressing results indicate that we have increased porosity decreased density attenuated elastic moduli and significantly enhanced the permeability of the rocks rapidly cooled and slowly cooled samples are presented with the rapidly cooled samples showing an increase in permeability the results are compared to similar studies previously carried out under dry conditions and implications discussed for geothermal operations

a fragmentation spreading model for long runout rock avalanches based on the observation that deposits of large rock avalanches consist predominantly of intensely fragmented rock debris it is proposed that the processes of rock fragmentation are significant ca