quantifying periglacial erosion in the nepal high himalaya abstract quantifying erosion rates in high mountain environments is challenging because the erosional processes are often stochastic and catastrophic distinguishing between periglacial and glacial rates is especially challenging in this study we focus on determining erosion rates from a glaciated alpine landscape where the bedrock sidewalls are eroding predominantly by blockfall we utilize a topographically well constrained debris covered glacier on the north slope of the annapurna range central nepal himalaya to quantify an average headwall retreat rate by measuring supraglacial debris depths from 0 1 to 2 4 m and average short term down valley transport rates of 17 m yr we calculate a yearly sediment flux of 5820 1990 m3 yr the supraglacial debris originates from the steep rocky headwall of the valley and we use the calculated flux with an estimated headwall contributing area to determine a slope perpendicular headwall retreat rate of 1 3 0 5 mm yr which corresponds to a vertical lowering rate of 0 42 0 16 mm yr and a horizontal retreat rate of 1 2 0 5 mm yr this rate is significantly greater than the steady state erosion rates that we determine for the valley ridge crests and sidewalls 0 08 0 03 mm yr and 0 20 0 05 mm yr respectively using concentrations of the in situ produced cosmogenic radionuclide 10be additionally 10be exposure ages of the lateral moraine crests and supraglacial debris suggest a glacial advance about 470 yr ago and a long term supraglacial transport rate of about 10 m yr using this long term transport rate reduces our inferred headwall retreat and suggests that the up glacial bedrock slopes are eroding at roughly the same rate while our results do not quantify the rate of glacial erosion the absence of a glacial gorge suggests that there may be a rough balance between glacial downcutting and the erosion of the valley sidewalls rates quantified here are almost an order of magnitude lower than fluvial incision rates of the upper marsyandi river that drains the study area suggesting that even glaciated catchments are not keeping pace with the rapidly down cutting rivers of the himalaya

topography relief and trmm derived rainfall variations along the himalaya 1 along the southern himalayan topographic front the indian summer monsoon modulates erosive processes and rates to investigate the influence of topography and relief on rainfall generation and resultant erosion we processed satellite rainfall amounts for the last 8 years 1998 2005 from the tropical rainfall measurement mission trmm based upon a spatial resolution of 5 5 km for the himalaya we identify 1 the spatial distribution of rainfall and 2 the large scale relationships between topography relief and rainfall locations our results show two distinct rainfall maxima along strike in the himalaya the first outer rainfall peak occurs along the southern margin of the lesser himalaya within a narrow band of mean elevation 0 9 0 4 km and mean relief 1 2 0 2 km the second discontinuous inner band typically occurs along the southern flank of the greater himalaya elevation and relief both 2 1 0 3 km

the tectonostratigraphy and structure of the eastern nepal himalaya six years of geological research in eastern nepal has resulted in a new geological map of the eastern nepal himalaya which includes the region stretching from the sikkhim border in the east to the kathmandu valley in the west and from the summits of the higher himalaya in the north to the ganges plain in the south this research has permitted the determination of the tectonostratigraphy and structure of one section of the central himalayan arc south of the tibetan plateau the eastern nepal himalaya can be divided into three distinct thrust bound tectonic packages 1 the higher himalayan thrust sheet composed of the higher himalayan crystallines 2 the lesser himalayan thrust sheet composed of the lesser himalayan series and 3 the sub himalayan imbricate zone composed of sedimentary rocks belonging to the siwalik group the higher himalayan thrust sheet of eastern nepal has been thrust over the lesser himalayan metasediments a minimum of 140 km and possibly as much as 175 210 km along the main central thrust mct the lesser himalayan thrust sheet is overlain by the mct and is underlain by the main detachment fault mdf and the main boundary thrust mbt out of sequence thrust faults in the hanging wall of the mbt have breached and offset the presently inactive mct the sub himalayan imbricate zone is an emergent imbricate fan bounded by the mbt to the north and the main frontal thrust mft to the south and is underlain by the mdf which lies at a depth of between 5 km and 7 km a balanced cross section constructed across the higher lesser and sub himalaya of eastern nepal shows that the eastern nepal himalayan orogenic wedge has undergone a minimum of between 210 and 280 km of horizontal north south tectonic shortening since the initiation of the mct the lesser and sub himalaya have absorbed 70 km of north south shortening by thrusting along the basal mdf of which the sub himalayan imbricate zone has accommodated 25 km the sun kosi thrust has accommodated about 10 km and the mbt has accommodated the remaining 35 km of shortening since the initiation of the mct between 15 ma and 25 ma shortening across the eastern nepal himalaya has occurred at an average rate of 8 4 18 6 mm per year the structural geometry of the eastern nepal himalaya suggests an overall piggyback sequence of thrusting with motion transferred from the mct to the underlying mdf and its emergent splay thrust the mbt and with the mbt rotated to its present steep orientation by imbricate thrusting within the sub himalaya

climatic controls on hillslope angle and relief in the himalayas comparison of rainfall data and mean hillslope angles in the himalayas of central nepal shows that mean hillslope angles decrease with increasing mean annual rainfall higher pore pressures and higher rates of chemical weathering in the wetter regions may decrease the threshold angle of hillslopes prone to landsliding when valley spacing is held constant the sensitivity of mean hillslope angle to climate implies that relief in the absence of limits due to rock strength is also dependent on climate these results suggest that wet to dry climatic changes increase relief in regions with incising bedrock channels and that dry to wet climatic changes reduce relief

beyond threshold hillslopes channel adjustment to base level fall in tectonically active mountain ranges numerous empirical and model based studies argue that in general hillslopes and river channels increase their gradients to accommodate high rates of base level fall to date however few data sets show the dynamic range of both these relationships needed to test theoretical models of hillslope evolution and river incision here we utilize concentrations of 10 be in quartz extracted from river sand on the eastern margin of the tibetan plateau to explore relationships among short term 10 2 10 5 a erosion rate hillslope gradient and channel steepness our data illustrate nonlinear behavior and a threshold in the relationship between erosion rate and mean hillslope gradient confi rming the generalization that hillslopes around the world are limited by slope stability and cease to provide a metric for erosion at high rates 0 2 mm a the relationship between channel steepness index and erosion rate is also nonlinear but channels continue to steepen beyond the point where threshold hillslopes emerge up to at least 0 6 mm a demonstrating that channel steepness is a more reliable topographic metric than mean hillslope gradient for erosion rate and that channels ultimately drive landscape adjustment to increasing rates of base level fall in tectonically active settings

neotectonics of the central nepalese himalaya constraints from geomorphology detrital 40ar 39ar thermochronology and thermal modeling 1 the southern flanks of the central nepalese himalaya correspond to a sharp transition in landscape morphology and bedrock mineral cooling ages that suggests a change in rock uplift rate this transition can be explained by either 1 accretion of footwall material to the hanging wall across a ramp in the decollement separating india from eurasia thereby enhancing rock uplift rates above the zone of accretion or 2 out of sequence surface thrust faulting at the physiographic transition here we use geomorphic data 649 new detrital 40ar 39ar cooling ages and a simple thermokinematic model to evaluate which of these tectonic configurations is most appropriate for the central nepalese himalaya we first define and delineate the physiographic transition in central nepal using maps of knickpoints river steepness indices local relief and the distribution of thick alluvial fill deposits we then report new detrital 40ar 39ar data from two trans himalayan transects each of which suggests a rapid northward increase in the total amount of exhumation across the physiographic transition thermokinematic modeling suggests that either of the two developmental scenarios for the transition is plausible but that an accretion model is viable only under an extremely narrow range of conditions we contend that the physiographic and thermochronologic data in our study area are most simply explained by recent out of sequence surface thrusting within the lesser himalayan metasedimentary sequence approximately 15 30 km south of the mapped surface trace of the main central thrust system an important finding of this work is that there are substantial along strike variations in physiography and thermal history that reflect along strike changes in the degree and location of out of sequence surface thrusting

frictionite as evidence for a large late quaternary rockslide near kanchenjunga sikkim himalayas india implications for extreme events in mountain relief destruction abstract we present sedimentologic and petrographic field evidence of an extremely large 2 5 109 m3 late quaternary rockslide around dzongri 24 km s of kanchenjunga 8585 m a s l widespread occurrence of shattered leucogranites and migmatites deposited discordantly on top of undisturbed augen gneisses and separated by micro brecciated sliding surfaces indicate rapid movement during a large rockslide event occurrence of frictionite hyalomylonite in mineral samples indicates short term temperatures of 600 c in the moving rockslide mass along a 12 sliding plane from a sw direction of movement we infer a source 8 km ne of the deposit 5 km s of pandim 6691 m a s l where today a thick leucogranite intrusion marks a zone of weakness and failure of a postulated former mountain crest the mechanism of movement the dip of the sliding surface and the deposit preservation along ridge tops require that the dzongri rockslide ran out over an ice filled prek chu valley hence we prefer earthquake shaking over undercutting and glacial debuttressing as a possible trigger mechanism a regional review of other similarly large and catastrophic himalayan rockslides indicates that leucogranite intrusions are highly conducive to large scale failure in the higher himalayan crystalline hhc importantly high erosion rates have rendered this large rockslide deposit undetectable by remote sensing or digital elevation data which are commonly used for identifying evidence of such extreme events quantifying the contribution of such giant landslides in destroying some of the highest relief on earth will thus need further research attention

predesign failure and displacement mechanisms of large rockslides in the annapurna himalayas nepal abstract the paper analyses and compares four major mass movements rockslides and rock avalanches with volumes of 1 to 5 km3 around the annapurna himalayan region from engineering geological quaternary geological and geomorphological viewpoints it shows how paleotectonic and neotectonic predesign as well as morphological overprint caused by glacial activities are the main preparatory causal factors for the sliding events that is why giant failures of mountain crests have mainly occurred in areas of tectonic activity the mechanism of failure and displacement of the resulting large mass movements also strongly depends on this litho tectonic predesign and continues in giant translational rockslides in which the primary rock structure or fabric is preserved but shattered by mechanical stress during the sliding event

comparison of new and existing global digital elevation models aster g dem and srtm 3 1 a new global elevation dataset known as g dem based on the aster satellite imagery will be released in late 2008 g dem will be the best freely available global digital elevation model dem at a horizontal resolution of 1 arc second we assess the quality of g dem in comparison with 3 arc second srtm dem the best current global elevation dataset basic geomorphometric parameters elevation slope and curvature were examined for a pre release version of g dem and srtm dem for western japan g dem has fewer missing cells than srtm dem particularly in steep terrain also g dem gives smoother and more realistic representations of lowlands valleys steep slopes and mountain ridges whereas srtm dem includes many local spikes and holes and tends to overestimate valley floor elevation and underestimate ridge elevation g dem will be commonly used in geoscientific studies because of its higher resolution fewer missing data and better topographic representation than srtm dem

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

climatic limits to headwall retreat in the khumbu himalaya eastern nepal ice free bedrock headwalls are widespread landforms of many glacial landscapes but their formation and evolution are not well understood here i present observations from the khumbu himalaya eastern nepal of a distinct elevation zone that aligns the base of many steep headwalls with the highest predicted frost cracking intensity fci below this zone median ice free hillslope angles are 40 and similar to those of other areas in the himalaya where threshold hillslopes that are close to the critical angle of stability have been inferred at higher elevations ice free hillslopes of different rock types have median slope angles of 50 55 suggesting threshold hillslopes with higher rock mass strength possibly related to the presence of deep reaching permafrost high altitude meteorological data combined with fci models support frost cracking as a mechanism for headwall retreat by undercutting of threshold headwalls while glacial transport inhibits the accumulation of scree deposits at their base this mechanism could account for continued headwall retreat as long as climatic conditions enable frost cracking near the base of headwalls that are high enough to sustain glaciers at their base even if subglacial erosion is minor

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

tectonic and lithological controls on denudation rates in the central bolivian andes abstract the topographic signature of a mountain belt depends on the interplay of tectonic climatic and erosional processes whose relative importance changes over times while quantifying these processes and their rates at specific times remains a challenge the eastern andes of central bolivia offer a natural laboratory in which such interplay has been debated here we investigate the rio grande catchment which crosses orthogonally the eastern andes orogen from the eastern cordillera into the subandean zone exhibiting a catchment relief of up to 5000 m despite an enhanced tectonic activity in the subandes local relief mean and modal slopes and channel steepness indices are largely similar compared to the eastern cordillera and the intervening interandean zone nevertheless a dataset of 57 new cosmogenic 10 be and 26 al catchment wide denudation rates from the rio grande catchment reveals up to one order of magnitude higher denudation rates in the subandean zone mean 0 8 mm yr compared to the upstream physiographic regions we infer that tectonic activity in the thrusting dominated subandean belt causes higher denudation rates based on cumulative rock uplift investigations and due to the absence of a pronounced climate gradient furthermore the lower rock strength of the subandean sedimentary units correlates with mean slopes similar to the ones of the eastern cordillera and interandean zone highlighting the fact that lithology and rock strength can control high denudation rates at low slopes low denudation rates measured at the outlet of the rio grande catchment abapo are interpreted to be a result of a biased cosmogenic nuclide mixing that is dominated by headwater signals from the eastern cordillera and the interandean zone and limited catchment sediment connectivity in the lower river reaches therefore comparisons of short i e sediment yield and millennial denudation rates require caution when postulating tectonic and or climatic forcing without detailed studies

erosion history of the tibetan plateau since the last interglacial constraints from the first studies of cosmogenic 10be from tibetan bedrock abstract the cosmogenic 10be exposure histories of in situ bedrock surfaces from the tibetan plateau indicate low erosion rates of

brahmaputra sediment flux dominated by highly localized rapid erosion from the easternmost himalaya the brahmaputra river slices an exceptionally deep canyon through the eastern himalaya fission track and laser ablation u pb ages of detrital zircon grains from the river document very rapid erosion from this region and its impact on sediment fluxes downstream in the brahmaputra downstream from the canyon 47 of the detrital zircons in the river s modern sediment load comprise a fission track age population averaging only 0 6 ma equally young cooling ages are reported from bedrock in the canyon through the namche barwa gyala peri massif but are absent from riverbank sands of major tributaries upstream simple mixing models of u pb ages on detrital zircons from samples taken above and below this massif independently suggest that 45 of the downstream detrital zircons are derived from the basement gneisses extensively exposed in the massif constraints on the extent of the source area provided by bedrock cooling ages together with sediment flux estimates at pasighat india suggest exhumation rates averaging 7 21 mm yr 1 in an area of 3300 km 2 centered on the massif this rapid exhumation which is consistent with the very young cooling ages of the detrital zircons from this area produces so much sediment that 50 of the vast accumulation in the brahmaputra system at the front of the himalaya comes from only 2 of its drainage this extreme localization of rapid erosion sediment evacuation and bedrock cooling bear on 1 common assumptions in geodynamic and geochemical studies of the himalaya about sources of sediment and 2 plans for hydroelectric development and flood management in southeastern tibet and the heavily populated areas of eastern india

sand petrology and focused erosion in collision orogens the brahmaputra case abstract the high relief and tectonically active himalayan range characterized by markedly varying climate but relatively homogeneous geology along strike is a unique natural laboratory in which to investigate several of the factors controlling the composition of orogenic sediments coupling of surface and tectonic processes is most evident in the eastern namche barwa syntaxis where the tsangpo siang brahmaputra river draining a large elevated area in south tibet plunges down the deepest gorge on earth here composition of river sands changes drastically from lithic to quartzofeldspathic after confluence with the lohit river draining the transhimalayan equivalent mishmi arc batholiths sediment composition remains remarkably constant across assam indicating subordinate contributions from himalayan tributaries independent calculations based on petrographical mineralogical and geochemical data indicate that the syntaxis representing only 4 of total basin area contributes 35 6 to the total brahmaputra sediment flux and 20 of total detritus reaching the bay of bengal such huge anomalies in erosion patterns have major effects on composition of orogenic sediments which are recorded as far as the bengal fan in the brahmaputra basin in spite of very fast erosion and detrital evacuation chemical weathering is not negligible sand sized carbonate grains are dissolved partially in mountain reaches and completely in monsoon drenched assam plains where clinopyroxenes are selectively altered plagioclase instead is preferentially weathered only in detritus from the shillong plateau which is markedly enriched in microcline most difficult to assess is the effect of hydraulic sorting in bangladesh where quartz garnet and epidote tend to be sequestered in the bedload and trapped on the coastal plain whereas cleavable feldspars and amphiboles are concentrated in the suspended load and eventually deposited in the deep sea high resolution petrographic and dense mineral studies of fluvial sands provide a basis for calculating sediment budgets for tracing patterns of erosion in mountain belts and for better understanding the complex dynamic feedback between surface processes and crustal scale tectonics

geomorphic limits to climate induced increases in topographic relief recognition of the potential for strong dynamic coupling between atmospheric and tectonic processes has sparked intense cross disciplinary investigation and debate on the question of whether tectonics have driven long term climate change or vice versa it has been proposed that climate change might have driven the uplift of mountain summits through an isostatic response to valley incision because isostasy acts to compensate mean elevations the debate hinges on the question of whether climate change can significantly increase topographic relief or more precisely increase the volume of missing mass between summits and ridges here we show that in tectonically active mountain ranges geomorphic constraints allow only a relatively small increase in topographic relief in response to climate change thus although climate change may cause significant increases in denudation rates potentially establishing an important feedback between surficial and crustal processes neither fluvial nor glacial erosion is likely to induce significant isostatic peak uplift

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

erosion and exhumation in the himalaya from cosmogenic isotope inventories of river sediments the outward erosional flux is a key factor in the tectonic evolution of mountain belts and there is much debate about the feedbacks between tectonics erosion and climate here we use cosmogenic nuclides 10be and 26al analysed in quartz from river sediments from the upper ganges catchment to make the first direct measurements of large scale erosion rates in a rapidly uplifting mountain belt the erosion rates are highest in the high himalaya at 2 7 0 3 mm yr 1 errors fall to 1 2 0 1 mm yr on the southern edge of the tibetan plateau and are 0 8 0 3 to 0 6 mm yr in the foothills to the south of the high mountains these relative estimates are corroborated by the nd isotopic mass balance of the river sediment analysis of sediment from an abandoned terrace suggests that similar erosion rates have been maintained for at least the last few thousand years the data presented here along with data recently published for european river catchments demonstrate that a log linear relationship between relief and erosion rate holds over three orders of magnitude variation in erosion rate and between very different climatic and tectonic regimes the erosion rate estimates from cosmogenic nuclides correlate well with exhumation rates calculated from previously published apatite fission track ages in the indian himalaya this confirms that much of the exhumation in the himalayan mountain chain is now balanced by erosion however exhumation rates calculated from high blocking temperature systems such as 40ar 39ar in muscovite imply lower exhumation rates rocks presently at the surface must have undergone a three to six fold increase in exhumation rate within the last few million years we show how this could be explained either by climatic forcing of erosion rate changes or by tectonics published evidence for equally rapid changes of exhumation rate in the past and the probable diachroneity in the time at which the present exhumation rates accelerated imply that tectonics has moderated at least some of the change in exhumation rates

spatial distribution of denudation in eastern tibet and regressive erosion of plateau margins article i nfo the longmen shan range is one of the major topographic and structural features of the eastern margin of the tibetan plateau with an impressive topographic gradient and low convergence rates across the range this region has raised important questions concerning the dynamics of plateau margin settings such as the long term mechanisms of topographic evolution the investigation of the distribution in space and time of denudation can provide critical insight into such dynamics and shed light on still unresolved controversies for that purpose we present a new dataset that documents the intensity and distribution of denudation processes across this plateau margin through field survey of fluvial incision markers quantitative geomorphology and cosmogenic nuclide derived basin wide erosion rates erosion is b0 5 mm year in the frontal region of the longmen shan and between 0 5 and 1 mm year further west with a gradual decrease when reaching the northern headwaters of the min jiang watershed adjacent to the beginning of the tibetan plateau the spatial distribution of denudation inferred from the various methods we use suggests that most of the differential uplift in the central longmen shan is accommodated by the beichuan fault and frontal structures located in the foothills the denudation pattern seems also to reflect the large scale propagation of erosion from the sichuan basin toward the plateau this suggests that the longmen shan range is submitted to the combined influences of slow thrusting activity on the frontal structures and progressive westward regressive erosion as a probable response to a pulse of uplift of the tibetan plateau eastern margin that

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

petrologic and structural controls on geomorphology of prehistoric tsergo ri slope failure langtang himal nepal high relief h up to 2600 m and spatial orientation of discontinuities such as leucogranitic intrusions mylonitic and pseudotachylitic horizons and related ore structures were the preparatory causal factors for the giant prehistoric tsergo ri landslide high himalayan crystalline langtang himal nepal other controlling factors include overthrusting detachment faulting and paleoseismics related to the main central thrust mct and southern tibet detachment system stds neotectonically generated structures and predesigned form of the scarp broken crest and the direction of movement towards the wsw coherently displacement of several 109 m3 materials caused frictional fusion landslide dynamics and specific morphologic conditions created four different types of sliding surfaces in chronological sequence i primary at the basement ii secondary parallel or subparallel to i iii tertiary vertical to i and ii and iv quarternary sliding surfaces local variety of iii note ordinal numeric terms are not in time stratigraphic sense these planes represented the main discontinuities conducting different syn event stresses in the sliding mass and for further landslide dynamics spatial difference and widespread distribution of sliding planes and sets of discontinuities all over the landslide area caused different classes of rock quality which subsequently determined specific erosional processes within the landslide accumulation area the subsequent glacial and fluvial erosional processes were controlled by the correlating preexisting lithotectonic patterns the hyalomylonitic and or breccious sliding planes and the recent morphologic features or shapes of tsergo ri i the se part is gradationally brecciated to the top and includes tsergo ri itself the residual mass of the bulk has been eroded almost isometrically as far as the primary sliding plane crops out along the intact gneissic basement differences in rock quality along a horizon of secondary sliding planes indicate a steplike break in the relief after the last main glaciation ii the earlier halted nw part still preserved micromountainous shape of compact sliding blocks phushung i and ii kyimoshung separated by landslide dynamic triggered faults tertiary and quarternary sliding planes primary and secondary sliding planes almost covered by holocene sediments produced an insignificant morphology iii the highest brecciated strike slip fault generated during collision with the obstacle of pangshungtramo peak in the southwest is the deeply eroded dranglung chu valley which has been kept morphologically active in a major way until recent times iv except for the collision obstacle of pangshungtramo peak with recent semi active erosion and a small secondary rockslide block of tsangbu north of it all surrounding parts show typical features of high altitude erosion

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

oblique stepwise rise and growth of the tibet plateau two end member models of how the high elevations in tibet formed are i continuous thickening and widespread viscous flow of the crust and mantle of the entire plateau and ii time dependent localized shear between coherent lithospheric blocks recent studies of cenozoic deformation magmatism and seismic structure lend support to the latter since india collided with asia 55 million years ago the rise of the high tibetan plateau likely occurred in three main steps by successive growth and uplift of 300 to 500 kilometer wide crustal thrust wedges the crust thickened while the mantle decoupled beneath gently dipping shear zones did not sediment infilling bathtub like of dammed intermontane basins formed flat high plains at each step the existence of magmatic belts younging northward implies that slabs of asian mantle subducted one after another under ranges north of the himalayas subduction was oblique and accompanied by extrusion along the left lateral strike slip faults that slice tibet s east side these mechanisms akin to plate tectonics hidden by thickening crust with slip partitioning account for the dominant growth of the tibet plateau toward the east and northeast

rock type leaves topographic signature in landslide dominated mountain ranges 1 the idea that hillslopes in active mountain belts are limited to a threshold inclination by the rate of landsliding has guided landscape evolution models for over a decade however widely applied topographic diagnostics of threshold hillslopes remain debated and unverified this study relates landslide occurrence to hillslope metrics of several active mountain ranges throughout new zealand which are formed in uniform greywacke and its schist derivative all these ranges share a distinctive peak in hillslope inclination despite order of magnitude variations in rates of rock uplift and precipitation landslide density and extent of quaternary glaciation comparison with landslide dominated terrain in different lithologies highlights this peak as diagnostic of rock type reflecting a conspicuous tendency in hillslope evolution to adjust to rock mass strength irrespective of the intensity of tectonic and climatic forcing this finding expands the model perspective that only undisturbed strength equilibrium slopes may adjust to their rock mass strength

nukundamite cu3 38fe0 62s4 bearing copper ore in the bingham porphyry deposit utah result of upflow through quartzite nukundamite is an important ore mineral in a geologic resource of approximately 90 million metric tons mt of 0 8 wt percent cu in quartzite on the northeast contact of the bingham stock in contrast with other deposits where nukundamite occurs as a minor phase in relatively low temperature sericitic assemblages nukundamite at bingham is widespread in higher temperature potassic assemblages the coexistence of this high sulfidation sulfide with potassic assemblages suggests an unusual evolutionary path for magmatic hydrothermal fluids in quartzite wall rocks nukundamite bearing copper ore restricted to a 240 m thick quartzite unit of the pennsylvanian bingham mine formation extends 170 m from the northeast margin of the mineralized stock along the strike of beds and plunges 1 km down the dip of beds 30 nnw the quartzite unit is cut off at depth by a thrust fault below which beds of the bingham mine formation are vertical and cut by abundant northeast striking steeply dipping faults dikes and isoclinal folds the fortuna zone ore forming hydrothermal assemblages in quartzite can be classified as main and late stage main stage minerals are predominantly disseminated quartz phlogopite k feldspar with nukundamite replaced by chalcopyrite and bornite and no pyrite replacement of nukundamite by chalcopyrite and bornite reduced its abundance from possibly as high as 90 to 10 vol percent of total sulfides at the end of the main stage late stage assemblages consist of quartz sericite kaolinite with abundant pyrite lesser amounts of bornite digenite enargite and traces of nukundamite based on experimental data and retrieved thermodynamic properties nukundamite is stable within a highly limited range of a fe 2 a h 2 f s2 and f o2 at temperatures between 501 and 223 c at very high sulfidation states values of a fe 2 a h 2 in the nukundamite field are also appropriate for the stable assemblages chalcopyrite bornite and chalcopyrite pyrite but nukundamite requires higher values of f s2 and f o2 than the latter more common assemblages phase equilibria indicate that nukundamite bearing sulfide assemblages of the main stage are metastable supersaturated with respect to pyrite we hypothesize that early brine and vapor known to be of magmatic origin on the basis of isotopic and fluid inclusion evidence traveled upward through several kilometers of quartzite along the stock contact and the fortuna zone and then up to the south southeast along bedding at its source region the brine had so2 g h2s g 1 typical of degassing magmas of intermediate composition on cooling and due to lack of redox buffers in quartzite the brine became increasingly oxidized and evolved to so2 g h2s g 0 1 at 450 c at constant f s2 precipitation of nukundamite with k feldspar phlogopite at temperatures below 400 c so2 g h2s g 0 01 was possible due to relatively high concentrations of s and k in the brine s aq 0 2 m k 0 5 m also resulting from lack of exchange reactions with quartzite subsequent replacement of nukundamite by bornite chalcopyrite during the late main stage required a different fluid at lower sulfidation and oxidation states and slightly higher a fe 2 a h 2 we suggest that this late main stage fluid rising within the faulted northeast margin of the stock had been enriched in iron and depleted in sulfur during main stage potassic alteration and ore deposition in the stock

effects of large deep seated landslides on hillslope morphology western southern alps new zealand 1 morphometric analysis and air photo interpretation highlight geomorphic imprints of large landslides i e affecting 1 km2 on hillslopes in the western southern alps wsa new zealand large landslides attain kilometer scale runout affect 50 of total basin relief and in 70 are slope clearing and thus relief limiting landslide terrain shows lower mean local relief relief variability slope angles steepness and concavity than surrounding terrain measuring mean slope angle smoothes out local landslide morphology masking any relationship between large landslides and possible threshold hillslopes large failures also occurred on low gradient slopes indicating persistent low frequency high magnitude hillslope adjustment independent of fluvial bedrock incision at the basin and hillslope scale slope area plots partly constrain the effects of landslides on geomorphic process regimes landslide imprints gradually blend with relief characteristics at orogen scale 102 km while being sensitive to length scales of slope failure topography sampling and digital elevation model resolution this limits means of automated detection and underlines the importance of local morphologic contrasts for detecting large landslides in the wsa landslide controls on low order drainage include divide lowering and shifting formation of headwater basins and hanging valleys and stream piracy volumes typically mobilized yet still stored in numerous deposits despite high denudation rates are 107 m3 and theoretically equal to 102 years of basin wide debris production from historic shallow landslides lack of absolute ages precludes further estimates deposit size and mature forest cover indicate residence times of 101 104 years on these timescales large landslides require further attention in landscape evolution models of tectonically active orogens

coupling of rock uplift and river incision in the namche barwa gyala peri massif tibet geodynamic modeling demonstrates the strong potential for erosion to influence the pattern and style of deformation in active mountain belts but field studies yield conflicting views on the importance of erosion in influencing orogenesis here we compare patterns in river power inferred excess fluvial transport capacity topographic relief precipitation and mineral cooling ages to assess the coupling between surface erosion and rock uplift within the vicinity of the namche barwa gyala peri massif an active antiformal structure within the eastern himalayan syntaxis our rich and dense data set reveals a tight spatial correspondence of fluvial incision potential high relief and young cooling ages the spatial coincidence is most easily explained by a sustained balance between rock uplift and denudation driven by river incision over at least the last 1 m y the yarlung tsangpo brahmaputra river is the largest and most powerful river in the himalaya and two lines of evidence point to its active role in the dynamic interaction of local erosion rock uplift thermal weakening of the lithosphere and deformation 1 whereas along the rest of the himalayan front high relief and high rock uplift rates are essentially continuous the high relief and rapid exhumation in the syntaxis is restricted to a bull s eye pattern exactly where the largest river in the himalaya the yarlung tsangpo brahmaputra has the most energy per unit area available to erode its channel and transport sediment 2 the location of rapid incision on the yarlung tsangpo brahmaputra has been pinned for at least 1 m y and without compensatory uplift of the namche barwa gyala peri massif during this time the river would have eroded headward rapidly incising deeply into tibet

mass transport by active rockglaciers in the khumbu himalaya abstract this paper investigates the talus transport and geomorphic work accomplished by active rockglaciers in the khumbu himalaya nepal active rockglaciers are responsible for a considerable amount of horizontal and vertical sediment movement in this area rates of sediment displacement are in the order of 7 1 106 m t yr 1 km 2 the most effective mechanism of sediment transport however is a debris covered glacier with rates of 1 2 107 m t yr 1 km 2 a comparison with geomorphic work accomplished by active rockglaciers in the swiss alps shows that geomorphic effectiveness exceeds the one determined in the khumbu himalaya rockglaciers debris covered glaciers and rockfall amount to a total of geomorphic work two orders of magnitude higher than similar phenomena in the rocky mountains of colorado active tectonics recent glacier activity and climatic conditions specific to this region are possible explanations for this difference

fluvial incision and tectonic uplift across the himalayas of central nepal the pattern of fluvial incision across the himalayas of central nepal is estimated from the distribution of holocene and pleistocene terraces and from the geometry of modern channels along major rivers draining across the range the terraces provide good constraints on incision rates across the himalayan frontal folds sub himalaya or siwaliks hills where rivers are forced to cut down into rising anticlines and have abandoned numerous strath terraces farther north and upstream in the lesser himalaya prominent fill terraces were deposited probably during the late pleistocene and were subsequently incised the amount of bedrock incision beneath the fill deposits is generally small suggesting a slow rate of fluvial incision in the lesser himalaya the terrace record is lost in the high range where the rivers are cutting steep gorges to complement the terrace study fluvial incision was also estimated from the modern channel geometries using an estimate of the shear stress exerted by the flowing water at the bottom of the channel as a proxy for river incision rate this approach allows quantification of the effect of variations in channel slope width and discharge on the incision rate of a river the determination of incision rates requires an additional lithological calibration the two approaches are shown to yield consistent results when applied to the same reach or if incision profiles along nearby parallel reaches are compared in the sub himalaya river incision is rapid with values up to 10 15 mm yr it does not exceed a few millimeters per year in the lesser himalaya and rises abruptly at the front of the high range to reach values of 4 8 mm yr within a 50 km wide zone that coincides with the position of the highest himalayan peaks sediment yield derived from the measurement of suspended load in himalayan rivers suggests that fluvial incision drives hillslope denudation of the landscape at the scale of the whole range the observed pattern of erosion is found to closely mimic uplift as predicted by a mechanical model taking into account erosion and slip along the flat ramp flat geometry of the main himalayan thrust fault the morphology of the range reflects a dynamic equilibrium between present day tectonics and surface processes the sharp relief together with the high uplift rates in the higher himalaya reflects thrusting over the midcrustal ramp rather than the isostatic response to reincision of the tibetan plateau driven by late cenozoic climate change or late miocene reactivation of the main central thrust

giant rockslides from the inside the growing body of research on large scale mass wasting events so far has only scarcely investigated the sedimentology of chaotic deposits from non volcanic terrestrial landslides such that any overarching and systematic terminological framework remains elusive yet recent work has emphasized the need for better understanding the internal structure and composition of rockslide deposits as a means to characterise the mechanics during the final stages of runout and emplacement we offer a comprehensive overview on the occurrence of rock fragmentation and frictional melt both at different geographic locations and different sections within large 10 6 m 3 rockslide masses we argue that exposures of pervasively fragmented and interlocked jigsaw cracked rock masses basal melange containing rip up clasts and phantom blocks micro breccia and thin bands of basal frictionite are indispensable clues for identifying deposits from giant rockslides that may remain morphologically inconspicuous otherwise these sedimentary assemblages are diagnostic tools for distinguishing large rockslide debris from macro and microscopically similar glacial deposits tectonic fault zone breccias and impact breccias and thus help avoid palaeoclimatic and tectonic misinterpretations let alone misestimates of the hazard from giant rockslides moreover experimental results from mossbauer spectroscopy of frictionite samples support visual interpretations of thin sections and demonstrate that short lived 1500 degrees c in the absence of water occurred at the base of several giant moving rockslides this finding supports previous theories of dry excess runout accompanied by comminution of rock masses down to gm scale and indicates that catastrophic motion of large fragmenting rock masses does not require water as a potential lubricant

geoecology and mass movement in the manaslu ganesh and langtang jugal himals nepal this study describes and explains the spatial distribution of mass movement in the central nepal himalaya judgments were formulated on the origin and rates of mass movement using field evidence topographic maps geologic maps and spot imagery mass movement scars were mapped in the field during a 240 km traverse of the langtang jugal himal and a 300 km traverse of the manaslu ganesh himal chi square analyses revealed that the frequency of slope failures varies with slope aspect and position above below the main central thrust mct human disturbance did not account for a statistically significant increase in mass movement except in sites occupied by mid slope roads and where excessively steep slopes marginal for agriculture or grazing have been deforested

complex rupture mechanism and topography control symmetry of mass wasting pattern 2010 haiti earthquake the 12 january 2010 mw 7 0 haiti earthquake occurred in a complex deformation zone at the boundary between the north american and caribbean plates combined geodetic geological and seismological data posited that surface deformation was driven by rupture on the leog ne blind thrust fault while part of the rupture occurred as deep lateral slip on the enriquillo plantain garden fault epgf the earthquake triggered 4490 landslides mainly shallow disrupted rock falls debris soil falls and slides and a few lateral spreads over an area of 2150 km2 the regional distribution of these slope failures defies those of most similar earthquake triggered landslide episodes reported previously most of the coseismic landslides did not proliferate in the hanging wall of the main rupture but clustered instead at the junction of the blind leog ne and epgf ruptures where topographic relief and hillslope steepness are above average also low relief areas subjected to high coseismic uplift were prone to lesser hanging wall slope instability than previous studies would suggest we argue that a combined effect of complex rupture dynamics and topography primarily control this previously rarely documented landslide pattern compared to recent thrust fault earthquakes of similar magnitudes elsewhere we conclude that lower static stress drop mean fault displacement and blind ruptures of the 2010 haiti earthquake resulted in fewer smaller and more symmetrically distributed landslides than previous studies would suggest our findings caution against overly relying on across the board models of slope stability response to seismic ground shaking

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

geologic constraints on bedrock river incision using the stream power law denudation rate in unextended terranes is limited by the rate of bedrock channel incision often modeled as work rate on the channel bed by water and sediment or stream power the latter can be generalized as ka m s n where k represents the channel bed s resistance to lowenng whose variation with lithology is unknown a is drainage area a surrogate for discharge s is local slope and m and n are exponents whose values are debated we address these uncertainties by simulating the lowering of ancient river profiles using the finite difference method we vary m n and k to match the evolved profile as closely as possible to the corresponding modern river profile over a time period constrained by the age of the mapped paleoprofiles we find at least two end member incision laws ka 0 3 0 5 s for australian rivers with stable base levels and k f a 0 1 0 2 s n for rivers in kauai subject to abrupt base level change the long term lowering rate on the latter expression is a function of the frequency and magnitude of knickpoint erosion characterized by k f incision patterns from japan and california could follow either expression if they follow the first expression with m 0 4 k varies from 10 7 10 6 m 0 2 yr for granite and metamorphic rocks to 10 5 10 4 m 0 2 yr for volcaniclastic rocks and 10 4 10 2 m 0 2 yr for mudstones this potentially large variation in k with lithology could drive strong variability in the rate of long term landscape change including denudation rate and sediment yield

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

quantifying landscape differences across the tibetan plateau implications for topographic relief evolution 1 we quantify the bulk topographic characteristics of the tibet qinghai plateau with specific focus on three representative regions northern central and southeastern tibet quantitative landscape information is extracted from shuttle radar topography mission digital elevation models we find that the morphology of the tibetan plateau is nonuniform with systematic regional differences the northern and central parts of the plateau are characterized by what we suggest to call positive topography i e a topography in which elevation is positively correlated with relief and mean slope a major change from the internally drained central part of tibet to the externally drained part of eastern tibet is accompanied by a transition from low to high relief and from positive to negative topography i e a topography where there is an inverse or negative correlation between elevation and relief and between elevation and mean slope relief in eastern tibet is largest along rivers as they cross an ancient eroded plateau margin at high angle to the major strike slip faults the yalong yulong thrust belt implying strong structural control of regional topography we propose that the evolution of river systems and drainage efficiency the ability of rivers to transport sediments out of the orogen coupled with tectonic uplift is the simplest mechanism to explain systematic regional differences in tibetan landscapes basin filling due to inefficient drainage played a major role in smoothing out the tectonically generated structural relief this mode of smoothing started concurrently with tectonic construction of the relief as most clearly illustrated today in the qilian shan qaidam region of the northeastern plateau in the interior of tibet further passive filling due to internal drainage only continued to smooth the local relief millions of years after the cessation of major phases of surface uplift due to crustal shortening thus diachronous beveling at high elevation produced the low relief surface of the high plateau in southeast tibet headward retreat of external drainages brought back in the global ocean base level first disrupting then interrupting the relief reduction process it produced a transitional topography by dissecting the old remnant plateau surface which introduced younger and steeper incision of this hitherto preserved high base level this provides a unifying mechanism for the formation of the low relief plateau interior and for the origin of the high elevation low relief relict surface in southeastern tibet our analysis brings forth the importance of surface processes in particular drainage efficiency in shaping plateau morphology and landscape relief such key processes appear to have been mostly ignored in numerical models of plateau deformation our results also cast doubt on and provide a more realistic alternative to the fashionable contention that a continuous preuplift low relief surface first formed at low elevation extending all the way to the south china sea shore before being warped upward in the late miocene pliocene by lower crustal channel flow