centennial to millennial scale hard rock erosion rates deduced from luminescence depth profiles abstract the measurement of erosion and weathering rates in different geomorphic settings and over diverse temporal and spatial scales is fundamental to the quantification of rates and patterns of earth surface processes a knowledge of the rates of these surface processes helps one to decipher their relative contribution to landscape evolution information that is crucial to understanding the interaction between climate tectonics and landscape consequently a wide range of techniques has been developed to determine short 10 2 a and long term 10 4 a erosion rates however no method is available to quantify hard rock erosion rates at centennial to millennial timescales here we propose a novel technique based on the solar bleaching of luminescence signals with depth into rock surfaces to bridge this analytical gap we apply our technique to glacial and landslide boulders in the eastern pamirs china the calculated erosion rates from the smooth varnished surfaces of 7 out of the 8 boulders sampled in this study vary between 0 038 0 002 and 1 72 0 04 mm ka 1 the eighth boulder gave an anomalously high erosion rate possibly due to a recent chipping cracking loss of surface given this preferential sampling of smooth surfaces assumed to arise from grain by grain surface loss we consider these rates as minimum estimates of rock surface denudation rates in the eastern pamirs china

nature and timing of large landslides in the himalaya and transhimalaya of northern india four large landslides each with a debris volume 10 6 m 3 in the himalaya and transhimalaya of northern india were examined mapped and dated using 10 be terrestrial cosmogenic radionuclide surface exposure dating the landslides date to 7 7 1 0 ka darcha 7 9 0 8 ka patseo 6 6 0 4 ka kelang serai and 8 5 0 5 ka chilam comparison of slip surface dips and physically reasonable angles of internal friction suggests that the landslides may have been triggered by increased pore water pressure seismic shaking or a combination of these two processes however the steepness of discontinuities in the darcha rock slope suggests that it was more likely to have started as a consequence of gravitationally induced buckling of planar slabs deglaciation of the region occurred more than 2000 years before the darcha patseo and kelang serai landslides it is unlikely that glacial debuttressing was responsible for triggering the landslides the four landslides their causes potential triggers and mechanisms and their ages are compared to 12 previously dated large landslides in the region fourteen of the 16 dated landslides occurred during periods of intensified monsoons seismic shaking however cannot be ruled out as a mechanism for landslide initiation because the himalaya has experienced great earthquakes on centennial to millennial timescales the average holocene landscape lowering due to large landslides for the lahul region which contains the darcha patseo and kelang serai landslides is w0 12 mm yr previously published large landslide landscape lowering rates for the himalaya differ significantly furthermore regional glacial and fluvial denudation rates for the himalaya are more than an order of magnitude greater this difference highlights the lack of large landslide data lack of chronology problems associated with single catchment large landslide based calculations and the need for regional landscape lowering determinations over a standardized time period

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

rock avalanches and the pace of late quaternary development of river valleys in the karakoram himalaya we discuss the implications of a set of terrestrial cosmogenic nuclide tcn ages on blocky cross valley deposits of large rock avalanches along upper indus streams the dated deposits are key to understanding late quaternary events that play a major role in landscape evolution in the karakoram himalaya the landslides occurred between 3 and 8 ka ago challenging existing chronologies of events along indus streams the tcn ages may support a mid holocene climatic role in preparing slopes for failure but the balance of evidence suggests that large earthquakes triggered the landslides each landslide dammed the indus or a major tributary and controlled base level and sedimentation for millennia they produced landforms long regarded as characteristic of the region including extensive lacustrine deposits flights of river terraces epigenetic gorges and sediment fans until the 1990s most of the landslides were interpreted as moraines related lacustrine and other sediments continue to be attributed to glacial damming and stream terraces to tectonic processes generally they were seen to originate tens of thousands to hundreds of thousands of years earlier than the new ages require instead we argue that they record interactions among different geomorphic processes in landslide fragmented valleys during the holocene rather than being geomorphic markers of tectonic and climatic events the landslides have buffered or redirected climatic and tectonic forcing in such an active orogen millennia long episodes of zero net bedrock incision at each site are surprising however rates of sedimentation above landslide barriers and erosion controlled by their breaching are close to today9s high measured rates for geomorphic activity we propose that landslide fragmented rivers may in fact characterize interglaciations and future patterns of upper indus landscape evolution at time scales of 10 3 to 10 4 years

influence of secular variation of the geomagnetic field on production rates of in situ produced cosmogenic nuclides abstract scaling factors are presented that allow a full description of the cosmic ray flux modulation during secular variation of the geomagnetic field these scaling factors are analogous to those determined in a similar work dunai t j earth planet sci lett 2000 176 157 169 that were accurate for field strengths equivalent to present day field strength but cannot accommodate field strength variations strategies to derive the relevant geomagnetic field parameters are discussed and are tested with existing production rate calibrations for 3 he a production rate of 103 4 2 atoms g olivine yr sea level and for zero cutoff rigidity was derived from calibration sites from hawaii western usa and canary islands covering the time range of 2 281 kyr

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

quaternary glaciation of the tashkurgan valley southeast pamir the quaternary glacial history of tashkurgan valley in the transition between the pamir and karakoram in xinjiang province china was examined using remote sensing field mapping geomorphic analysis of landforms and sediments and 10be terrestrial cosmogenic nuclide dating moraines were assigned to four glacial stages 1 the dabudaer glacial stage that dates to the penultimate glacial cycle and or earlier and may represent one or more glaciations 2 the tashkurgan glacial stage that dates to early last glacial most likely marine oxygen isotope stage mis 4 3 the hangdi glacial stage that dates to mis 2 possibly early mis 2 and 4 the kuzigun glacial stage that dates to the mis 2 possibly the global last glacial maximum and is younger than the hangdi glacial stage younger moraines and rock glaciers are present at the heads of tributary valleys but these were inaccessible because they are located close to politically sensitive borders with pakistan afghanistan and tajikistan glaciers during the dabudaer glacial stage advanced into the central part of the tashkurgan valley during the tashkurgan glacial stages glaciers advanced several kilometers beyond the mouths of the tributary valleys into the tashkurgan valley glaciers during the hangdi and kuzigun glacial stages advanced just beyond the mouths of the tributary valleys glaciation in this part of the himalayan tibetan orogen is likely strongly controlled by northern hemisphere climate oscillations although a monsoonal influence on glaciation cannot be ruled out entirely

cenozoic evolution of the eastern pamir implications for strain accommodation mechanisms at the western end of the himalayan tibetan orogen detailed field mapping geochronologic and thermochronologic analyses and petrologic investigations conducted along the southern segment of the late cenozoic kongur shan extensional system provide new information on the cenozoic tectonic evolution of the eastern pamir at the western end of the himalayan tibetan orogen field relations and cooling age patterns in the hanging wall and footwall of the active faults show a southward decrease in the magnitude of east west extension along the southern kongur shan extensional system from 20 km or less along the muztaghata massif in the north to l3 km along the tashkorgan fault in the south these results in conjunction with previously published work on the northern segment of the kongur shan extensional system show a general southward decrease in east west extension along the entire length of the extensional system consistent with models of extension primarily driven by oroclinal bending or radial thrusting of the pamir petrologic data 40 ar 39 ar cooling ages and monazite th pb ages from schists and gneisses in the footwall of the southern kongur shan normal fault along the muztaghata massif record two tectonic events that immediately preceded late miocene initiation of east west extension 1 high grade schists and gneisses experienced upper amphibolite facies metamorphic conditions 9 10 kbar 700 750 c dated as late oligocene to middle miocene by in situ ion microprobe analyses of monazite inclusions in garnet and 2 high grade schists and gneisses were subsequently rapidly exhumed to shallow crustal levels in the late miocene with 40 ar 39 ar biotite cooling ages of 7 5 9 ma rapid exhumation was accommodated in part by the east west striking south dipping shenti normal fault field relations and regional geologic correlations indicate that this exhumation event was related to the formation of the central pamir gneiss domes and the antiformal muztaghata massif is the eastward continuation of the sares dome of the central pamir these observations suggest that the antiformal gneiss domes of the central pamir have not been offset across the karakorum right slip fault from the qiangtang anticlinorium in tibet instead we propose that the development of the central pamir gneiss domes may have been related to oligocene miocene northward underthrusting and thickening of crust beneath the pamir

tectonic evolution of the northeastern pamir constraints from the northern portion of the cenozoic kongur shan extensional system western china the late cenozoic kongur shan extensional system lies along the northeastern margin of the pamir at the western end of the himalayan tibetan orogen accommodating east west extension in the pamir at the northern end of the extensional system the kongur shan normal fault juxtaposes medium to high grade metamorphic rocks in both its hanging wall and footwall which record several mesozoic to cenozoic tectonic events schists within the hanging wall preserve a buchan metamorphic sequence dated as late triassic to early jurassic 230 200 ma from monazite inclusions in garnet metamorphic ages overlap with u pb zircon ages from local granite bodies and are interpreted to be the result of regional arc magmatism created by subduction of the paleo tethys ocean the northern portion of the footwall of the extensional system exposes an upper amphibolite facies unit 650 c 8 kbar which structurally overlies a lowgrade metagraywacke unit the high grade unit records late early cretaceous crustal thickening at ca 125 110 ma followed by emplacement over the low grade metagraywacke along a north northeast directed thrust prior to ca 100 ma together these results indicate signifi cant middle cretaceous crustal thickening and shortening in the northern pamir prior to the indo asian collision a third late miocene ca 9 ma amphibolite facies metamorphic event 650 700 c 8 kbar is recorded in footwall gneisses of the kongur shan massif north of the kongur shan massif rapid cooling in the footwall beginning at 7 8 ma is interpreted to date the initiation of exhumation along the kongur shan normal fault a minimum of 34 km of east west extension is inferred along the kongur shan massif based on the magnitude of exhumation since the late miocene 29 km and the present dip of the kongur shan normal fault 40 field observations and interpretation of satellite images along the southernmost segment of the kongur shan extensional system indicate that the magnitude of late cenozoic east west extension decreases signifi cantly toward the south this observation is inconsistent with models in which east west extension in the pamir is driven by northward propagation of the right slip karakoram fault suggesting instead that extension is driven by vertical extrusion due to topographic collapse radial thrusting along the main pamir thrust or oroclinal bending of the entire pamir region

natural and human induced landsliding in the garhwal himalaya of northern india after the march 28 1999 garhwal earthquake 338 active landslides including 56 earthquake induced landslides were mapped in a 226 km 2 study area in the garhwal himalaya northern india these landslides mainly comprised shallow failures in regolith and highly weathered bedrock involving avalanches slides and flows the total volume of active 33 landslide debris in the region was estimated to be 1 3 million m including 0 02 million m 2 of the total volume moved during and within a few days of the earthquake the denudation produced by the active landsliding within the study area is equivalent to a maximum landscape lowering of 5 7 mm if active landsliding persists for a duration of between 1 and 10 years then denudation due to landsliding is in the order of 0 6 6 mm a y1 approximately two thirds of the landslides in this region were initiated or accelerated by human activity mostly by the removal of slope toes at road cuts suggesting that human activity is accelerating denudation in this region three ancient catastrophic landslides each involving 1 million m 3 of debris were identified and two were dated to the early middle holocene using cosmogenic radionuclide 10 be and 26 al cosmogenic radionuclide 10 be and 26 al were also used to date strath terraces along the alaknanda river in lower garhwal himalaya to provide an estimate of 4m m a y1 for the rate of regional denudation throughout the holocene natural landsliding therefore contributes 5 50 of the overall denudation in this region and is important as a formative process in shaping the landscape q 2001 elsevier science b v all rights reserved

holocene environmental changes in bangong co basin western tibet part 4 discussion and conclusions abstract a 12 4 m core taken in lake bangong provides a continuous holocene climatic record we summarize information on changes in stable isotope and radiocarbon balances in the lake hydrobiology and vegetal cover in the catchment deduced from detailed analytical results given in the three preceding papers the bangong record is then compared with the environmental history of the neighbouring lake sumxi also constructed from multidisciplinary analyses the two records show a major environmental change at 10 9 5 ka b p attributed to a rapid strengthening of the summer monsoonal circulation which led to wet warm conditions this event was followed by a long term trend toward aridity which culminated around 4 3 ka b p in western tibet maximum monsoon rainfall seems to have occurred from 9 5 to 8 7 ka b p and from 7 2 to 6 3 ka b p as two wet pulses separated by a reversal event centered on 8 0 7 7 ka b p our results broadly agree with the records from lake seling in central tibet and lake qinghai at the plateau s northeastern margin and with palaeoclimatic studies in western china which document conditions wetter and warmer than those of today during the early middle holocene the environmental fluctuations recorded in western tibet appear in phase with climatic changes recognized in tropical north africa suggesting that the 8 0 7 7 ka b p and the 4 0 3 0 ka b p dry events were caused by abrupt disequilibrium in the climatic system

landslides triggered by the 8 october 2005 kashmir earthquake abstract the 8 october 2005 kashmir earthquake triggered several thousand landslides these were mainly rock falls and debris falls although translational rock and debris slides also occurred in addition a sturzstrom debris avalanche comprising 80 million m3 buried four villages and blocked streams to create two lakes although landsliding occurred throughout the region covering an area of 7500 km2 the failures were highly concentrated associated with six geomorphic geologic anthropogenic settings including natural failures in 1 highly fractured carbonate rocks comprising the lowest beds in the hanging wall of the likely earthquake fault 2 tertiary siliciclastic rocks along antecedent drainages that traverse the hazara kashmir syntaxis 3 steep 50 slopes comprising precambrian and lower paleozoic rocks 4 very steep 50 lower slopes of fluvially undercut quaternary valley fills and 5 ridges and spur crests the sixth setting was associated with road construction extensive fissuring in many of the valley slopes together with the freshly mobilized landslide debris constitutes a potential hazard in the coming snowmelt and monsoon seasons this study supports the view that earthquake triggered landslides are highly concentrated in specific zones associated with the lithology structure geomorphology topography and human presence

quantification of both normal and right lateral late quaternary activity along the kongur shan extensional system chinese pamir the kongur shan extensional system kes is a 250 km long normal fault system that bounds the muji tashkorgan basin of the chinese pamir it accommodates e w extension due to the northward indentation of the pamir salient and its late miocene activity has been the focus of tectonic studies while the kes has a main normal component wnw ese striking segments have an additional right lateral strike slip component here we quantify late quaternary horizontal and vertical slip rates at three locations along the kes where active faults cut and offset abandoned geomorphic features we find rates of 3 4 mm a 1 horizontal along the western muji fault in the north and of 1 7 mm a 1 vertical and 1 mm a 1 horizontal along the kongur shan fault in the south during the late pleistocene these rates are consistent with gps and late miocene rates and imply that e w extension in the muji tashkorgan basin is faster in the north than in the south

catastrophic landslide deposits in the karakoram himalaya in july 1986 three catastrophic landslides deposited about 20 x 106 cubic meters of debris on bualtar glacier in the karakoram himalaya a sudden acceleration and superficial breakup of the glacier provided an opportunity to examine the fresh deposits in depth beneath a surface layer of large boulders finer materials mainly sand and silt made up half of the total volume the fine materials were formed during the rock avalanche from mostly intact massive rock of the source zone velocity estimates suggest that this disaggregation occurred in less than 2 minutes coarse materials remained in bands of uniform lithology but the fine materials had diffused throughout the landslides a small amount of carbonate appears to have been calcined by frictional heating presumably at the base of the initial sliding masses these observations are relevant to understanding the mechanisms of catastrophic landslides other nearby rock avalanche deposits indicate that landslides are an important geomorphic process in the area and that they pose a continuing risk to human activity

the role of footwall deformation and denudation in controlling cooling age patterns of detachment systems an application to the kongur shan extensional system in the eastern pamir china abstract determining the relationship between deformation and exhumation history in the footwall rocks of major low angle normal faults i e detachment faults provides a way to quantify different models of continental extension although pressure temperature time p t t datasets are commonly used to infer magnitude and rates of slip across detachment faults correct use of these datasets requires a sound understanding of coupling effects between footwall deformation and advection of isotherms on the distribution of cooling ages in this study we present thermo kinematic modeling results which examine the relationship between different footwall kinematic models erosion and the spatial distribution of muscovite and biotite 40 ar 39 ar cooling ages our results show that large magnitudes of footwall erosion during normal faulting significantly affect cooling age patterns as footwall rocks at different distances from the fault surface pass through different thermal gradients we apply our modeling results to simulating muscovite and biotite cooling age patterns from the footwall of the cenozoic kongur shan normal fault system in the pamir previous studies had interpreted a documented 5 fold increase in cooling rate at 2 ma to indicate an increase in exhumation rate during the quaternary however our results show that the observed cooling age patterns and increase in cooling rate can be produced by a constant exhumation rate over the last 7 ma due to the effect of changes in the rate of isotherm advection during exhumation

landforms and landscape evolution in the skardu shigar and braldu valleys central karakoram abstract the central karakoram which includes k2 in pakistan is one of the most rapidly rising areas on earth and exhibits complex topography and extreme relief impressive valley fills and glacial landforms are present throughout the valleys the dynamics of landscape evolution of the region are currently not well understood consequently the landforms were mapped and assessed in the skardu shigar and braldu valleys to elucidate the spatio temporal scale dependencies of surface processes active in the region these valleys were examined using geomorphic field methods remote sensing geomorphometry and terrestrial cosmogenic nuclides tcns surface exposure dating the glaciers in this region have oscillated considerably throughout the late quaternary and four glacial stages have been recognized including at least six glacial advances surface processes readjusted after glacier retreat and ubiquitous mass movements and catastrophic landsliding transported material from steep slopes to valley bottoms while glaciofluvial meltwater and glacier outburst floods redistributed sediment down valley glacier geochronology and late holocene ages of the outburst flood deposits indicate that landscape evolution has been dominated by glaciation and paraglaciation during the late quaternary

multiple origins of large hummock deposits in alai valley northern pamir implications for palaeoclimate reconstructions abstract this paper interprets the origin of several of the largest hummocky landform assemblages in the alai valley northern pamir a formerly glaciated intermontane depression the vast hummocky deposits in the koman suu and achik tash river catchments are found to be of two contrasting modes of formation glacial hummocks deposited during koman and lenin glaciers withdraw and avalanche hummocks produced during catastrophic koman and lenin rock avalanches the origins of the deposits we assessed through remote and field based geomorphological mapping as well as sedimentological investigations which included clast analysis and the identification of micro scale agglomerates indicative of rock avalanche emplacement both the koman and lenin rock avalanches were large catastrophic events with run outs of 34 and 24 km respectively and a volume over 1 109 m3 each that occurred subsequent to glacier withdrawal from the area the complex conditions on the moment of the rock avalanche emplacement promoted unusual deposits geomorphology and extensive run outs the landslide landforms formed over the pre existing glacial hummocks and fluvial deposits and are geomorphologically and sedimentologically distinct from the larger glacial hummocks the reconstruction of this sequence of events has implications for how hummock dating should be interpreted this research illustrates large scale catastrophic landsliding in the glacial environment and adds to the ongoing debate about the misidentification of rock avalanche deposits as of glacial origin and their relevance to palaeoclimatological and palaeoseismological reconstructions

timing and seismic origin of nixu rock avalanche in southern tibet and its implications on nimu active fault abstract in tectonically active mountain areas the identification dating and determination of origin of large landslides are of special importance in recognizing the seismicity and earthquake magnitude of regional faults reconstructing the prehistoric landscape evolution and estimating the seismic hazards based on field survey high resolution satellite image interpretation and 14c dating of substrate this paper studied the large long runout nixu rock avalanche the nxra in the angang graben of the southern tibetan plateau the study revealed that 1 the deep seated nixu rock avalanche straddles the nimu active normal fault and spreads onto the angang basin with a deposit volume of 47 mm3 and a travelling distance of 4960 m 2 humus samples immediately under the deposit of rock avalanche along the natural river erosion section suggest a 14c age of 820 30 bp 1220 30 calad for the nxra event the age well matches the 1264 ce chubushi earthquake recorded in tibetan documents 3 23 adjacent landslides have been recognized with co seismic distribution features such as clustering and distance effect ridge end amplification effect and slope aspect effect sand liquefaction and peat deformation were discovered in the substrate beneath and at a distance of 300 m away from the avalanche deposit 4 this information indicate that the nxra was triggered most likely by the 1264 chubushi earthquake with a magnitude of mw 7 0 7 2 estimated by empirical equations of keefer 1994 and wells coppersmith 1994 it is suggested that the nimu fault of the yadong gulu rift may be more hazardous than the northern and southern part due to its high susceptibility of large co seismic landslides

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

kongur shan normal fault type example of mountain building assisted by extension karakoram fault eastern pamir the northernmost segment of the karakoram fault is an active normal dextral wrench fault that bounds the muji tashgurgan pliocene quaternary basin eastern pamir the kongurshan 7719 m and mustaghata 7546 m mountains are interpreted as twin crustal ramp anticlines formed en echelon on the eastern side of the karakoram fault by subduction of the tarim lithosphere under the pamir west dipping s c mylonitic gneisses that have downdip stretching lineations form the western flank of kongur mountain kinematic criteria consistently indicate a top to the west sense of shear the mylonitic foliation is cut by a steeper active normal fault which is marked by prominent triangular facets on west facing spurs the ductile normal shearing deformation occurred during the interval 5 1 ma therefore like the himalayas the pamir mountain range shows the coeval development of frontal thrusting and rear normal faulting the kongur fault thus appears to be an excellent example of synorogenic extension where normal faulting contributes to relief

the role of mass movements on landscape evolution in the central karakoram discussion and speculation abstract mass movement constitutes an important process in the evolution of landscapes in mountain regions however the role of massive slope failures in denudational unloading and landscape evolution has not been extensively studied large scale mass movements in one of the greatest mountain ranges on earth the central karakoram in pakistan were therefore examined to help evaluate their role in landscape evolution in high mountains specifically four major mass movement complexes ghoro choh rock avalanche busper sackung and slope failure gomboro slope failure and urdokas rockslide each comprising 10 6 m 3 of debris were assessed and mapped in detail two of these mass movement complexes the ghoro choh rock avalanche and gomboro slope failure were dated using terrestrial cosmogenic nuclides the ages of occurrence of the mass movement complexes studied in the central karakoram date from the late pleistocene to the holocene the four major mass movement complexes all involved the removal of mass from the tops of mountain ridges and peaks that failed and were subsequently transported towards the bottom of their respective valleys such massive movement of mass is anomalous compared to other forms of mass movement and is generally spatially coincident with exposed deeply buried gneiss dome structures these large scale movements appear to be part of a coupled system involving river incision and glacial debuttrussing although earthquakes might have triggered these mass movements this study illustrates the role of climate forcing which is part of a coupled system of denudational unloading but it is unclear whether high magnitude low frequency events such as these initiate the isostatic and tectonic influx of mass or if sustained high magnitude denudation resulting from a coupled system is responsible for the exhumation of buried structures

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

a lateglacial rock avalanche event tianchi lake tien shan xinjiang abstract the genesis of a diamicton deposit that dams tianchi lake in the eastern tien shan xinjiang china has been debated for many years and it has generally been considered to have been either the result of landsliding or glacial deposition using geomorphic sedimentological and geochronological techniques we re examined this deposit to help elucidate its origin the outer margin of the deposit can be traced up the adjacent hillside where a series of steps within the bedrock are present and likely represent landslide scars within the lake the deposit has an undulating surface the deposit is unstratified comprising angular monomictic clasts that coarsen upward into boulders which armor the surface all these features suggest that the deposit was formed by landsliding furthermore 10be cosmogenic radionuclide surface exposure dating of boulders on the levee of the deposit show that the deposit probably formed during the lateglacial possibly at 12 ka and is likely coincident to the younger dryas stade the sedimentological and geomorphic evidence support our view that the diamicton deposit is not of glacial origin but was deposited by rock avalanching during the lateglacial

rates of fluvial bedrock incision within an actively uplifting orogen central karakoram mountains northern pakistan abstract terrestrial cosmogenic nuclide tcn 10 be surface exposure ages for strath terraces along the braldu river in the central karakoram mountains range from 0 8 to 11 ka this indicates that strath terrace formation began to occur rapidly upon deglaciation of the braldu valley at 11 ka fluvial incision rates for the braldu river based on the tcn ages for strath terraces range from 2 to 29 mm a the fluvial incision rates for the central gorged section of the braldu river are an order of magnitude greater than those for the upper and lower reaches this difference is reflected in the modern stream gradient and valley morphology the higher incision rates in the gorged central reach of the braldu river likely reflect differential uplift above the main karakoram thrust that has resulted in the presence of a knickpoint and more rapid fluvial incision the postglacial fluvial incision rate 2 3 mm a for the upper and lower reaches are of the same order of magnitude as the exhumation rates estimated from previously published thermochronological data for the baltoro granite in the upper catchment region and for the adjacent himalayan regions

high cooling and denudation rates at kongur shan eastern pamir xinjiang china revealed by 40ar 39ar alkali feldspar thermochronology orthogneiss samples taken from the kongur antiform show ages varying from 2 ma to 1 ma for 40ar 39ar ages of biotites and muscovites and fission tracks on apatites leading to cooling rates of 150 c m y modeling of k feldspars highlights the effect of a range of diffusion domains with contrasting diffusion characteristics yielding closure temperatures from 400 to 150 c the feldspar data document the cooling history since 5 ma and indicate a sudden change in cooling rates of the antiform at 2 ma at that time cooling increases by a factor of 5 from an average of 20 c m y to a minimum of 150 c m y consideration of the regional thermal history ongoing uplift and erosional history of the antiform during the quaternary suggests that denudation rates have been of the order of 5 7 km m y since 2 m y ago and could be associated with significant upward surface movement triggered by major normal faulting the antiform is interpreted to have formed during thrusting at the pamir front as a result of the development of thrust ramps and normal faulting at the crustal scale ramp stacking is an important process of mountain building and normal faulting in this context must be regarded as a very efficient way of building high relief

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

late quaternary holocene landscape evolution of a monsoon influenced high himalayan valley gori ganga nanda devi ne garhwal the garhwal himalaya provides an excellent natural laboratory in which to examine landscape evolution in a monsoon influenced high mountain environment geomorphic and sedimentological analysis and 10be cosmogenic radionuclide crn surface exposure dating of moraines fans and river and strath terraces in the gori ganga valley of nanda devi ne garhwal indicate that fans and river terraces developed rapidly by debris flow and flood processes during periods of deglaciation these phases of high sediment transfer occurred at 1 2 4 5 and 7 8 ka fan incision rates subsequent to major times of resedimentation after each glacial advance are between 19 and 57 mm year this contrasts with bedrock incision rates based on mid holocene strath terraces of 5 mm year these rates indicate that despite episodes of rapid denudation and resedimentation linked to glacial activity in this region the background rates of denudation are similar to those for other regions of the himalaya averaging several millimeters per year furthermore these data show the importance of climatic controls on landscape evolution and suggest a strong monsoonal control on the dynamics of earth surface processes in this region

cosmogenic age constraints on post lgm catastrophic rock slope failures in the tatra mountains western carpathians textcopyright 2015 elsevier b v although deglaciation is one of the crucial factors controlling the stability of slopes in high mountains the chronological response of rock slope failure rsf to glacier retreat still remains poorly known here we provide the first cosmogenic 10be age constraints on prominent rock avalanches and rockfalls collectively termed rock slope failures rsfs from the tatra mountains the highest mountain range with the most pronounced glacier morphology within the carpathians six representative rsfs were selected for surface exposure dating in the mountain range two sites are situated in the western part with less pronounced local relief and gentler slope gradient and four come from the highest eastern part with oversteepened rock slopes our dataset also contains the largest known rsf in the tatra mountains the koprova rock avalanche with a volume of 5 4 106m3 based on 26 10be dated boulders the weighted mean ages of individual rsf accumulations range between 20 2 1 2 and 10 1 0 3ka our results suggest that smaller structurally predisposed failures mainly rockfalls in the steepest parts of the mountains reacted immediately i e a few hundred years to deglaciation whereas more complex slope deformations in terrain with lower local relief involving the largest rock avalanche in the tatra mountains experienced a substantial time lag i e several millennia in respect to ice retreat in the case of delayed rsfs their origin can be well correlated with warmer and more humid periods in the lateglacial early holocene such as the bolling allerod chronozone and after the onset of the holocene

reconstruction of the 30 40 ka bp enhanced indian monsoon climate based on geological records from the tibetan plateau abstract multi proxy records from ice caps lakes and pollen records from the tibetan plateau are used to reconstruct the palaeoclimate during the period 30 40 ka bp lake geomorphological and lacustrine sedimentological studies show that numerous high lake level stands and or freshwater lakes occurred in large areas of western china at this time including over the tibetan plateau where the area contains mostly shallow water and saline hypersaline water lakes under extremely dry conditions of today pollen based reconstruction of tibetan vegetation shows systematic differences from the present alpine steppe forests were shifted ca 400 km further north and the alpine conifer forest extended ca 400 800 km beyond their present western limits variations in 18 o curves from ice cores from the plateau suggest that the temperature was 2 4 c higher and precipitation was 40 to over 100 higher than today all of the evidence consistently suggests the existence of an exceedingly strong summer monsoon climate over the plateau the vigorous evaporation of the tropical ocean surface would also play an important role in promoting the penetration of moisture rich southwest monsoon over the tibetan plateau these climate patterns with strong summer monsoon circulation during the period 30 40 ka bp reflect the 20 ka earth orbital precessional cycle when the tibetan plateau region received greater solar radiation which thus enlarged the thermodynamical contrast between the plateau and the mid south portion of the indian ocean

two shell ionospheric model for indian region a novel approach in the u s wide area augmentation system european geostationary navigation overlay service and indian global positioning system aided geo augmented navigation a near real time grid based single shell model is proposed to correct the ionospheric delay at the user aircrafts the single shell model is based on the assumption that the whole ionosphere is compressed at a fixed altitude at 350 km this assumption may not be appropriate for the indian region which falls in the equatorial ionospheric anomaly belt in this paper a two shell model which incorporates two different shells at 300 and 500 km altitudes having different weights at different time domains has been implemented a statistical comparison between single and two shell models has been done for all quiet days of year 2005 based on the results it is observed that there is at least 60 improvement in the performance of the two shell model in comparison to the single shell model for the indian region

landslides as a geomorphological proxy for climate change a record from the dolomites northern italy abstract this study investigates the relationships between climate changes and hillslope evolution in the dolomites eastern alps italy during the late quaternary with particular attention paid to landslide processes the basic premise is that modifications in landslide frequency may be interpreted as changes in the hydrological conditions of slopes which are in turn controlled by climate after the statistical analysis of a data set composed of 73 conventional radiocarbon ages obtained from 24 landslides four periods of enhanced landsliding have been identified i from 10 700 to 8400 cal bp between younger dryas and the preboreal ii from 8200 to 6900 cal bp during the older atlantic iii from 5800 to 4500 cal bp between atlantic and subboreal and iv from 4000 to 2100 cal bp between subboreal and subatlantic these periods have been compared with different lateglacial and holocene paleoclimatic records to check the correspondence between periods of enhanced landslide activity and cold and humid spells recognized at different spatial scales as the records show in the study areas slope instability processes can be considered geomorphological indicators of climatic changes and to a certain extent reliable proxies of environmental evolution

analysis of satellite derived landslide at central nepal from 2011 to 2016 practical landslide detection has been a challenging task for decades due to the limitations of algorithms and complicated landslide cases visual interpretation is still one of the most reliable methods for landslide detection owing to the development of machine learning google earth engine platform and free access to landsat series images this paper presents a pixel level landslide detection model based on change detection using the random forest method in nepal from the year 2012 2016 the annual landsat images are synthesized into one image based on a ranking sequence of ndvi normalized differential vegetation index six more indexes and texture information are calculated as features covering water snow and vegetation enhancement dem digital elevation model is used to provide landscape pattern the synthesized features and landsat images of every 2 nearby years and dem are used to detect landslides in the latter year our model achieves an average producer s accuracy of 68 20 and user s accuracy of 77 01 for landslide detection in terms of the 9278 7443 pixel study image through the 5 years moreover based on the landslide detection results we analyzed the landslide event pattern in central nepal from 2012 to 2016 which accords with the actual cases

green lake landslide and other giant and very large postglacial landslides in fiordland new zealand abstract green lake landslide is an ancient giant rock slide in gneiss and granodiorite located in the deeply glaciated fiordland region of new zealand the landslide covers an area of 45 km 2 and has a volume of about 27 km 3 it is believed to be new zealand s largest landslide and possibly the largest landslide of its type on earth it is one of 39 known very large 10 6 10 7 m 3 and giant 10 8 m 3 postglacial landslides in fiordland discussed in the paper green lake landslide resulted in the collapse of a 9 km segment of the southern hunter mountains slide debris moved up to 2 5 km laterally and 700 m vertically and formed a landslide dam about 800 m high impounding a lake about 11 km long that was eventually infilled with sediments geomorphic evidence supported by radiocarbon dating indicates that green lake landslide probably occurred 12 000 13 000 years ago near the end of the last otira glaciation the landslide is described and its geomorphic significance age failure mechanism cause and relevance in the region are discussed in relation to other large landslides and recent earthquake induced landslides in fiordland the slope failure occurred on a low angle fault zone undercut by glacial erosion and was probably triggered by strong shaking mm ix x associated with a large m 7 5 8 earthquake on the alpine fault c 80 km to the northwest geology was a major factor that controlled the style and size of green lake landslide and in that respect it is significantly different from most other gigantic landslides future large earthquakes on the alpine fault in fiordland are likely to trigger more very large and giant landslides across the region causing ground damage and devastation on a scale that has not occurred during the last 160 years with potentially disastrous effects on towns tourist centres roads and infrastructure the probability of such an event occurring within the next 50 years may be as high as 45

mass wasting triggered by the 2008 wenchuan earthquake is greater than orogenic growth shallow earthquakes lead to the uplift of mountain ranges but also trigger landslides that remove mass an analysis of the 2008 wenshuan earthquake suggests that more material was removed from the orogen by widespread landslides than was added by coseismic uplift

giant landslides topography and erosion abstract distributions of slope angles in tectonically active mountain belts point to the development of threshold conditions where hillslopes attain a critical inclination or height at which they fail readily because of limitations in material strength it has been proposed that hillslopes adjust to rapid uplift and bedrock incision through an increase in the rate of relief limiting landsliding rather than gradual slope steepening here we test this concept by investigating the relationship between mean local relief h which we take to be a proxy of long term erosion rates e and the occurrence of over 300 of the largest v 10 8 m 3 terrestrial landslides on earth we find that nearly two thirds of these giant landslides have occurred in the steepest 5 of the earth s land surface where relief is close to its proposed upper strength limit they are primarily located in deeply incised valleys along fault bounded fringes of active mountain belts and in volcanic arcs this distribution coincides with areas of high long term erosion rates 4 mm yr 1 confirming that giant landslides contribute to rapid denudation of mountains most of the eroded volume is concentrated in the smallest but steepest parts of mountain belts and volcanic arcs first order estimates of minimum erosion rates accomplished by the largest landslides are 0 01 mm yr 1 these rates are between 1 and 10 of the late pleistocene to holocene mean erosion rates in a given area importantly the landslide erosion rates show a nonlinear increase with mean local relief suggesting that the contribution of giant landslides in total and per event increases significantly with increasing overall erosion rates however giant landslides also occur in areas of lower than average relief h 300 700 m irrespective of whether threshold hillslopes have developed or not factors contributing to these failures include soft rocks extensive low angle discontinuities high rates of fluvial bedrock incision and tectonically driven deformation and slope loading

comment on the triple oxygen isotope composition of the earth mantle and understanding δ17o variations in terrestrial rocks and minerals by pack and herwartz earth planet sci lett 390 2014 138 145

catastrophic landslides glacier behaviour and moraine formation a view from an active plate margin the influence of large bedrock landslides rock avalanches on the behaviour of glaciers is incompletely recognised here we present an example from an active tectonic margin in south island new zealand where large earthquakes leave a significant imprint on glacial records we demonstrate that terminal moraines on the western side of the southern alps record both ordinary i e climate driven and landslide initiated glacial advances following consideration of the processes involved in rock avalanche initiated moraine construction we suggest ways of determining the nature of the advance that built the terminal moraine the implications of these observations are important in breaking the conventional linkage of individual terminal moraines with climate forcing

quaternary glaciation of muztag ata and kongur shan evidence for glacier response to rapid climate changes throughout the late glacial and holocene in westernmost tibet the glacial geology of two massifs muztag ata and kongur shan in western tibet was examined to help define the timing and style of glaciation in the semiarid regions of western tibet remote sensing geomorphic mapping and 10be terrestrial cosmogenic nuclide tcn surface exposure dating of boulders on the moraines and sediment in depth profiles show that glaciers advanced at least 12 times during at least the last two glacial cycles over this time the style of glaciation changed progressively from one that produced ice caps to one that produced less extensive and more deeply entrenched valley glaciers the timing of the two earliest glaciations is poorly defined but they likely occurred prior to the penultimate glacial cycle the karasu glacial stage and the early part of the last glacial cycle or during the penultimate glacial cycle the subaxh glacial stage in contrast the timing of later glacial advances the olimde glacial stage is relatively well defined showing quasiperiodical oscillations on millennial time scales 17 1 0 3 ka 13 7 0 5 ka 11 2 0 1 ka 10 2 0 3 ka 8 4 0 4 ka 6 7 0 2 ka 4 2 0 3 ka 3 3 0 6 ka 1 4 0 1 ka and a few hundred years before the present these data suggest that since the global last glacial maximum lgm the glaciers in western tibet likely responded to northern hemisphere climate oscillations rapid climate changes with minor influences from the south asian monsoon this study provides the first well defined glacial geologic evidence to suggest that glaciers in western tibet respond to rapid climate changes on millennial time scales throughout the late glacial and holocene

quaternary fans and terraces in the khumbu himal south of mount everest their characteristics age and formation large fans and terraces are frequent in the khumbu himal within the high himalayan valleys south of mt everest these features are composed of massive matrix and clast supported diamicts that were formed from both hyperconcentrated flows and coarse grained debris flows cosmogenic radionuclide crn exposure ages for boulders on fans and terraces indicate that periods of fan and terrace formation occurred at c 16 c 12 c 8 c 4 and c 1 5 ka and are broadly coincident with the timing of glaciation in the region the dating precision is insufficient to resolve whether the surfaces formed before during or after the correlated glacial advance however the sedimentology and morphostratigraphic and geomorphological relationships suggest that fan and terrace sedimentation in this part of the himalaya primarily occurs during glacier retreat and is thus paraglacial in origin furthermore modern glacial lake outburst floods and their associated deposits are common in the khumbu himal as the result of glacial retreat during historical times we therefore suggest that late quaternary and holocene fan and terrace formation and sediment transfer are probably linked to temporal changes in discharge and sediment load caused by glacier oscillations responding to climate change the timing of major sedimentation events in this region can be correlated with fans and terraces in other parts of the himalaya suggesting that major sedimentation throughout the himalaya is synchronous and tied to regional climatic oscillations bedrock incision rates calculated from strath terrace ages average c 3 9 mm a 1 suggesting that the overall rate of incision is set by regional uplift

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

mass movement in the himalaya new insights and research directions abstract ongoing studies that relate tectonics to the processes at the surface of earth show that many more sources of information about agents of shallow denudation such as mass movement are required to comprehend the long term erosion that leads to deep denudation over geologic time mass movement in the himalaya is scale dependent from the massive extension of whole mountain ranges gravity tectonics through the sackung failure of single peaks to the smallest slope failures generally denudation of the himalayan orogen begins with slope failure onto glaciers and into river valleys and continues by glacial and fluvial transport the maximum size of stable slopes and mean angles of slope that are produced by these failures are complex and controlled by a variety of factors including mass strength of the rocks stress fields angles of internal friction controlled by rock type cohesion that includes the control of rock temperature bulk unit weight of rock and discontinuities the processes of mass movement in the himalaya have been described many times for the past two centuries recently developments in a variety of fields have been introduced to assess the character of mass movement geomorphometry remote sensing digital elevation models and geographic information system technology are revolutionizing the study of mass movement in the himalaya

hillslope channel coupling in the nepal himalayas and threat to man made structures the middle kali gandaki valley abstract in mountain areas the confinement of valleys favours landslide interaction with rivers causing channel changes or short lived dams and lakes that may threaten trails roads and human settlements their impacts may occur successively in space and time and they affect randomly the functioning of the sediment fluxes the present study focuses on the interaction patterns between unstable mountain slopes and the kali gandaki river in the nepal himalayas in this valley the deepest on earth a road linking the myagdi and mustang districts has been under construction for the past 5 years either cutting into the bedrock or crossing areas affected episodically by debris slides earth flows debris flows and rock slides on the basis of the geomorphic evolution observed over the last three decades we assess the potential threats that now arise following completion of the road we mapped three areas of recurrent mass wasting features characteristic of the most frequent situations encountered in this valley we analyzed the combination of the hydro geomorphic processes involved with the use of a dem we assessed the volume and spatial impact of temporary river dams on infrastructure located along the valley floor we estimated hydraulic parameters to document the geomorphic efficiency of river flooding after dam breaching we reconstructed the spatial extent of 1 areas threatened by backwater flooding upstream of the dams and 2 areas threatened by the collapse of the dams we describe the current geomorphic and sedimentary adjustments still at work along the valley sides our findings confirm that in the high himalaya medium scale landslides 10 5 6 m 3 play a major role in the overall process of denudation and sediment transfer they highly influence the transient nature of bedload transport in the channel in reducing the residence time of sediments in temporary spatially limited traps of the valley bottom they enhance the vulnerability of land and people attracted by a roadside location

quaternary history and landscape evolution of a high altitude intermountain basin at the western end of the himalayan tibetan orogen waqia valley chinese pamir abstract quaternary valley fills and landforms in the waqia valley of the chinese pamir were examined using geomorphic mapping geomorphic and sedimentological analysis of landforms and sediments and cosmogenic 10be surface exposure dating six sets of moraines m 1 to m 6 are identified and date to the penultimate or an older glacial cycle m 1 penultimate glacial cycle m 2 early last glacial and probably marine oxygen isotope stage mis 4 m 3 mis 2 m 4 late glacial m 5 and early holocene m 6 younger moraines are also present but these were not examined in detail alluvial fans and outwash river terraces are present throughout the valley four surfaces on alluvial fans and river terraces were dated to 580 ka t 1 120 ka t 2 100 ka t 3 and 70 ka t 4 large landslide and lacustrine deposits are common within the valley fills and represent periods of major slope instability and possible damming of drainages glacial processes dominate the western side of the valley landsliding is the leading process on its eastern side defining the nature and timing of landform formation in this valley highlights the punctuated nature of landform evolution in the himalaya and tibet and provides a framework for considering the abundant valley fill successions elsewhere in the orogen

timing and features of a late mis 2 rock avalanche in the eastern himalayas constrained by 10be exposure dating abstract we investigate a previously unrecorded rock avalanche deposit yadong rock avalanche that resulted from a major mountain slope failure on the northwest slopes of mt chomo lhari in the eastern himalayas we provide detailed mapping of the yadong rock avalanche and date the rock avalanche using 10be surface exposure dating the 10be exposure ages of six samples suggest that the yadong rock avalanche occurred between 14 2 1 3 13 1 1 3 ka during the bolling allerod ba period the climate was semi arid during the ba period as it is today which suggests that precipitation was unlikely the trigger for this rock avalanche the relatively small paleo glaciers make glacial debuttressing trigger unlikely since the rock scar is situated above the lower permafrost limit degradation of permafrost associated with deglaciation was also unlikely to be the trigger given the rock avalanche is located near the yadong fault which is part of the active yadong gulu rift and the yadong gulu rift has experienced great earthquakes on centennial to millennial timescales we suggest that the most probable trigger for this rock avalanche was a seismic event associated with the yadong fault the result provides evidence for identifying a paleo seismic event occurred during 14 2 1 3 13 1 1 3 ka these findings have important implications for understanding the mechanisms for driving rock avalanches and associated landscape evolution across the himalayas as well as for extending the limited scientifically documented records of major mass movements in the eastern himalayan region

elevation dependence of cosmogenic 36cl production in hawaiian lava flows abstract we measured an elevation profile of cosmogenic 36cl in two well preserved lava flows on mauna kea hawaii 19 8 n 155 5 w in order to directly constrain the elevation dependence of cosmogenic nuclide production rates the flows are vertically extensive hawaiites erupted at 40 1 0 6 and 62 2 1 0 ka from point vents on the upper flanks of mauna kea the average paleo cutoff rigidity a measure of geomagnetic shielding of cosmic rays for these flows is 11 gv and their paleo elevation range is 2100 3700 m production of 36cl is dominated by neutron reactions with the high energy 39k n x and 40ca n x mechanisms accounting for nearly half of the 36cl production and the low energy reaction 35cl n responsible for the remaining half production by negative muons is small at the elevations of our samples accounting for less than 2 of the total production in the lowest elevation samples the elevation dependence of 36cl production measured in these lava flows is described by an effective attenuation length of 138 5 g cm 2 this result is close to the value of 140 g cm 2 determined from neutron monitor surveys of high energy nucleon fluxes but significantly below the value of 149 g cm 2 determined from measurements of low energy neutrons the predicted atmospheric attenuation length for these lava flows incorporating both high and low energy mechanisms is 144 g cm 2 the good agreement between the 36cl elevation profile and cosmic ray surveys validates the use of neutron flux measurements to scale 36cl production rates when production by muons is negligible

late quaternary intensified monsoon phases control landscape evolution in the northwest himalaya the intensity of the asian summer monsoon circulation varies over decadal to millennial time scales and is reflected in changes in surface processes terrestrial environments and marine sedi ment records however the mechanisms of long lived 2 5 k y intensified monsoon phases the related changes in precipitation distribution and their effect on landscape evolution and sedimen tation rates are not yet well understood the arid high elevation sectors of the orogen correspond to a climatically sensitive zone that currently receives rain only during abnormal i e strength ened monsoon seasons analogous to present day rainfall anom alies enhanced precipitation during an intensified monsoon phase is expected to have penetrated far into these geomorphic threshold regions where hillslopes are close to the angle of failure we as sociate landslide triggering during intensified monsoon phases with enhanced precipitation discharge and sediment flux leading to an increase in pore water pressure lateral scouring of rivers and ov ersteepening of hillslopes eventually resulting in failure of slopes and exceptionally large mass movements here we use lacustrine deposits related to spatially and temporally clustered large land slides 0 5 km 3 in the sutlej valley region of the northwest him alaya to calculate sedimentation rates and to infer rainfall patterns during late pleistocene 29 24 ka and holocene 10 4 ka inten sified monsoon phases compared to present day sediment flux measurements a fivefold increase in sediment transport rates re corded by sediments in landslide dammed lakes characterized these episodes of high climatic variability these changes thus em phasize the pronounced imprint of millennial scale climate change on surface processes and landscape evolution

nature and timing of large landslides within an active orogen eastern pamir china abstract large scale landsliding involving 106 m3 in volume is important in landscape development in high mountains to assess the importance of large landslides in high mountains four large landslides bulunkou muztagh taheman and yimake were mapped in the ne chinese pamir at the westernmost end of the himalayan tibetan orogen and dated using 10be terrestrial cosmogenic nuclides the bulunkou landslide at the southernmost end of muji valley is composed of 1 7 107 m3 of landslide debris and has an age of 2 0 0 1 ka the muztagh landslide located on the sw side of the massif muztagh ata is composed of 4 7 108 m3 of debris and has an age of 14 3 0 8 ka the taheman landslide located south of muztagh ata is composed of 2 6 108 m3 of landslide debris and has an age of 6 8 0 2 ka the yimake landslide on the northern frontal range of the pamir at the southwestern end of the tarim basin is composed of 1 4 109 m3 of landslide debris and has an age of 7 1 0 6 ka two other large landslides are present in the region the aerpa aigezi on a tributary of the gez river and the bile jiyi on the yarkand river landslides and are composed of 1 6 107 m3 and 5 2 106 m3 of landslide debris respectively however the aerpa aigezi and bile jiyi landslides were not studied in as much detail or dated because of their inaccessibility given the tectonically active nature of this region with numerous active faults and the morphology of the landslides these landslides were likely triggered by earthquakes however other causes including long term increased precipitation and geologic bedrock structure could be important contributing factors in their formation

geomorphology of anomalously high glaciated mountains at the northwestern end of tibet muztag ata and kongur shan article i nfo muztag ata and kongur shan massifs represent a significant area of anomalously high topography at the northwestern end of the tibetan plateau rising to n7500 m above sea level asl from the plateau that has an average elevation of 3500 m asl these massifs provide an excellent opportunity to test geomorphic concepts such as the glacial buzz saw model using remote sensing digital elevation modeling field mapping and terrestrial cosmogenic nuclide tcn methods the massifs were examined to determine the relative importance of tectonics and geomorphic processes in shaping the regional landscape and to provide a framework for testing geomorphic models the gneiss domes that underlie the peaks are the result of exhumation along the kongur detachment fault that has unroofed the massifs at a rate of between 4 6 km ma over the last few million years this has resulted in rapid uplift and active seismicity which is exemplified by the numerous fresh fault scarps throughout the region and large historic earthquakes the geomorphic system is dominated by glaciation and the region contains extensive successions of moraines and paraglacial landforms including fans terraces and landslides glaciers have oscillated considerably throughout the latter part of the quaternary and three major glacier stages are recognized karasu oldest olimde and subaxh youngest glacial stage that include at least 10 smaller glacial advance the style of glaciation has changed over time from expanded ice caps to piedmont glaciers to valley and cirque glaciers this possibly reflects a change in climate and or topographic constraints as the massifs grew and became incised the topography and glaciers in the region vary across the massifs divided by a broadly n s trending high ridge and watershed the western portion situated upwind the stoss slopes of the mid latitude westerlies that bring moisture to the region has gentle high topography and small valley glaciers in contrast on the eastern leeward slopes gradients are higher and long debris covered valley glaciers are present the hypsometry of the region indicate two peaks in the distribution frequency of elevation 3600 4100 m and 4400 4800 m asl these two elevation zones are consistent in space with the former equilibrium line altitudes during the olimde and subaxh glacial stages and suggest that glacial erosion most effective at the ela has helped control topography this observation supports the glacial buzz saw hypothesis which argues that glaciers determine hypsometry by means of rapid surface erosion based on tcn methods basin wide rates of erosion range from 0 1 to 1 4 km ma and are five to ten times lower than the unroofing rate of both massifs the discrepancy over different time scales suggests that initial unroofing was produced by abrupt tectonic uplift and that the unroofing of the massifs has continued at a slower pace during the late quaternary

coastal cliffs rock slope failures and late quaternary transgressions of the black sea along southern crimea abstract rock slope failures represent a significant hazard along global coastlines but their chronology remains poorly documented here we focus on the geomorphology and chronology of giant rockslides affecting the crimean mountains along the black sea coast geomorphic evidence suggests that high 100 m limestone cliffs flanking the southern slopes of the crimean mountains are scarps of rockslides nested within larger deep seated gravitational slope deformations dsgsds such pervasive slope failures originated due to lateral spreading of intensively faulted late jurassic carbonate blocks moving atop weak plastic late triassic flysch and tuff layers by introducing a dating strategy relying on the combination of the uranium thorium dating u th of exposed calcareous speleothems covering the landslide scarps with the 36cl exposure dating of rock walls we are able to approximate the time interval between the origin of incipient crevices and the final collapse of limestone blocks that exposed the cliff faces for the three representative large scale rockslides between the towns of foros and yalta the initiation of the dsgsds as evidenced by the widening of crevices and the onset of speleothem accumulation was 300 ka bp but the recent cliff morphology along the coast is the result of late pleistocene holocene failures spanning 20 0 5 ka bp the exposures of rockslide scarps occurred mostly at 20 15 8 5 4 and 2 0 5 ka which substantially coincide with the last major black sea transgressions and or more humid holocene intervals our study suggests that before ultimate fast and or catastrophic slope failures the relaxation of rock massifs correlative with karstification cracks opening and incipient sliding lasted on the order of 104 105 years rapid late glacial holocene transgressions of the black sea likely represented the last impulse for the collapse of limestone blocks and the origin of giant rockslides simultaneously affecting the majority of the sw coast of the crimean peninsula