investigation of the relationships between basin morphology tectonic uplift and denudation from the study of an active fold belt in the siwalik hills central nepal the present study investigates correlations between an extensive range of geomorphic properties that can be estimated from a digital elevation model and the uplift rate on geological timescales the analysis focuses on an area in the siwalik hills central nepal where lithology and climate can be considered as uniform this area undergoes rapid tectonic uplift at rates of up to 15 mm yr 1 which are derived from the geometric pattern of a fault bend model of fold growth the selected geomorphic properties can be divided in two categories depending on whether or not the vertical dimension is taken into account none of the planar properties are significantly correlated to uplift rate unlike those that include the vertical dimension such as the mean elevation of basins hypsometric curve and hypsometric integral and relief defined by the amplitude factor of length scaling analysis correlation between relief and uplift rate is observed for all length scales of topography shorter than 600 m which suggests that all orders of the streams are able to adjust to the tectonic signal simple mass balance considerations imply that the average elevation is only 10 of surface uplift suggesting that a dynamic equilibrium has been reached quite rapidly using a simple two process model for erosion we find that fairly high diffusion coefficients order of 10 m 2 yr 1 and efficient transport of the material by rivers are required this unusually high value for mass diffusivity at small length scales may be obtained by either a very efficient linear diffusion or by landsliding actually both processes may be active which appears likely given the nature of the unconsolidated substratum and the favorable climatic conditions local relief in the study area may therefore be used to predict either uplift or denudation but the prediction is calibrated only for that specific climatic and lithologic conditions and cannot be systematically applied to other contexts

landsliding and the evolution of normal fault bounded mountains much of the tectonic and climatic history in high relief regions such as the mountains of the western u s basin and range province is contained in the morphology of hillslopes drainage networks and other landforms that range in scale from 10 1 to 101km to understand how these landforms evolve we have developed a numerical landscape evolution model that combines a detailed tectonic displacement field with a set of physically based geomorphic rules bedrock landsliding long recognized as a significant geomorphic process in mountainous topography is for the first time explicitly included in the rule set in a series of numerical experiments we generate synthetic landscapes that closely resemble mountainous topography observed in the basin and range the production of realistic landscapes depends critically on the presence of bedrock landslides and landsliding yields rates of long term erosion that are comparable in magnitude to those of fluvial erosion the erosive efficiency of bedrock landsliding implies that hillslopes may respond very quickly to changes in local base level and that fluvial erosion is the rate limiting process in steady state experimental landscapes our experiments generate power law distributions of landslide sizes somewhat similar to both field and laboratory observations thus even a simple model of bedrock landsliding is capable of quantitatively reproducing mountainous topography and landslide distributions and represents a significant step forward in our understanding of the evolution of normal fault bounded ranges

deepening of inner gorges through subglacial meltwater an example from the unesco entlebuch area switzerland this paper explores the mechanisms by which inner gorges in the alps were formed it focuses on the ca 1 5 km long 80 m deep and a few hundred meter wide lammschlucht located in the northern foothills of the central alps we reconstructed the glacial cover using lateral moraines and hanging talus cones that record the elevation of the ice surface at the deglaciation stage of the lgm last glacial maximum we used the reconstructed ice thickness patterns to calculate the erosional potential of the subglacial meltwater the applied model is based on the principle of energy conservation and yields the pattern of downstream changes of the dynamic pressure which is considered a measure for erosion potential the model results suggest a maximum of the dynamic pressure at the end of the inner gorge we interpret therefore that the subglacial meltwater scoured the reach toward the end of the lammschlucht because of the enhanced dynamic pressure which was ultimately controlled by the ice overburden post glacial fluvial erosion then resulted in a readjustment through a regressive shift of the erosional front along the inner gorge farther upstream the current location of this front lies almost in the middle of the lammschlucht inner gorge where a step pool channel changes into a straight plane bed channel flowing on a deeply scoured bedrock

quasi 3d modeling of water flow in vadose zone and groundwater summary the complexity of subsurface flow systems calls for a variety of concepts leading to the multiplicity of simplified flow models one habitual simplification is based on the assumption that lateral flow and transport in unsaturated zone are not significant unless the capillary fringe is involved in such cases the flow and transport in the unsaturated zone above groundwater level can be simulated as a 1d phenomenon whereas the flow and transport through groundwater are viewed as 2d or 3d phenomena a new approach for a numerical scheme for 3d variably saturated flow using quasi 3d richards equation and finite difference scheme is presented the corresponding numerical algorithm and the quasi 3d computer code were developed results of the groundwater level simulations were compared with transient laboratory experimental data for 2d data constant flux infiltration quasi 3d hydrus modflow numerical model and a full 3d numerical model using richards equation hypothetical 3d examples of infiltration pumping and groundwater mound dissipation for different spatial time scales are presented water flow simulation for the alto piura aquifer peru demonstrates the quasi 3d model application at the regional scale computationally the quasi 3d code was found to be more efficient by an order of 10 300 while being accurate with respect to the benchmark fully 3d variable saturation code when the capillary fringe was considered

preservation of inner gorges through repeated alpine glaciations the origins of alpine valleys are controversial topographic data from the swiss alps suggest that the valleys have been incised progressively during consecutive glacial interglacial cycles

on the seasonal variability of the canary current and the atlantic meridional overturning circulation the atlantic meridional overturning circulation amoc is continually monitored along 26 n by the rapid mocha array measurements from this array show a 6 7 sv seasonal cycle for the amoc with a 5 9 sv contribution from the upper mid ocean recent studies argue that the dynamics of the eastern atlantic is the main driver for this seasonal cycle specifically rossby waves excited south of the canary islands using inverse modelling hydrographic mooring and altimetry data we describe the seasonal cycle of the ocean mass transport around the canary islands and at the eastern boundary under the influence of the african slope where eastern component of the rapid mocha array is situated we find a seasonal cycle of 4 1 0 5 sv for the oceanic region of the canary current and 3 7 0 4 sv at the eastern boundary this seasonal cycle along the eastern boundary is in agreement with the seasonal cycle of the amoc that requires the lowest contribution to the transport in the upper mid ocean to occur in fall however we demonstrate that the linear rossby wave model used previously to explain the seasonal cycle of the amoc is not robust since it is extremely sensitive to the choice of the zonal range of the wind stress curl and produces the same results with a rossby wave speed of zero we demonstrate that the seasonal cycle of the eastern boundary is due to the recirculation of the canary current and to the seasonal cycle of the poleward flow that characterizes the eastern boundaries of the oceans

on the vorticity balance over steep slopes kuroshio intrusions northeast of taiwan abstractthe circulation of the kuroshio northeast of taiwan is characterized by a large anticyclonic loop of surface intrusion and strong upwelling at the shelfbreak to study the mechanisms of kur

characterizing structural and lithologic controls on deep seated landsliding implications for topographic relief and landscape evolution in the oregon coast range usa in mountainous areas landslides regulate temporal variations in sediment production and may suppress simple linkages between topographic development and tectonic forcing rates and mechanisms of mass wasting depend on lithology bedrock structure and climatic and tectonic setting these factors tend to vary signifi cantly in active tectonic regions thus clouding our ability to predict how landsliding modulates topographic development over human and geological time scales here we use a novel dem based technique to document the distribution of large landslides in the oregon coast range ocr and quantify how they affect topographic relief we developed an automated algorithm that exploits the distinctive topographic signature specifi cally the relationship between curvature and gradient of large landslides to map their distribution within the gently folded tyee formation eocene deltaicsubmarine ramp sediments in contrast to steep and highly dissected terrain frequently identifi ed as characteristic of the ocr which exhibits steep planar sideslopes and highly curved low gradient ridgetops and valleys terrain prone to large landslides tends to have low values of both drainage density and curvature and gradient values that cluster between 0 16 and 0 44 the distribution of failure dominated terrain in our 10 000 km2 study area is infl uenced by systematic variations in sedimentary facies and bedrock structure the fraction of terrain altered by large landslides 0 1 km2 varies from 5 in the sand rich delta slope and proximal ramp facies southern section of our study area to 25 in the north distal ramp facies coincident with an increase in the thickness of siltstone beds and a decrease in the sandstone siltstone ratio local relief declines progressively northward suggesting that deep seated landsliding is sensitive to the thickness and frequency of low shearstrength siltstone beds and may serve to limit topographic development in the ocr structural controls are superimposed on facies related variations as deep seated landslides are frequently found on slopes whose downslope aspect corresponds to the bedrock dip direction for 1516 strike and dip measurements in our study area we calculated the fraction of proximal terrain 2 5 km altered by deep seated landsliding in the sand rich southern region the proportion of proximal slide dominated terrain increases modestly with bedrock dip in the silt rich northern region terrain altered by deep seated landsliding is pervasive and an increase in dip from 0 to 16 corresponds to a change in the fraction of slide prone terrain from 10 to 28 our technique for mapping large landslides has utility for hazard analysis and land management over million year time scales the progradational character of the tyee formation suggests that continued uplift and exhumation of the ocr should result in a southward propagation of slide prone silt rich distal facies as a result deep seated landsliding will become increasingly prominent and topographic relief in the central and southern ocr will progressively decline whereas spatial variability in climatic or tectonic forcing is often invoked to explain systematic variations in topographic development our results emphasize the importance of structural and intraformation lithologic controls on landsliding as such analyses linking surface processes climate tectonics and landscapes should be couched in the context of diverse geologic and topographic data

distribution and inferred age of exfoliation joints in the aar granite of the central swiss alps and relationship to quaternary landscape evolution abstract exfoliation joints are well known natural fractures limited to near the ground surface relatively few details however are known about their distribution and age in the swiss alps exfoliation joints follow the landscape surface at the time of their formation the age of the associated landscape feature then provides a maximum age of exfoliation joints while landscape forms can change through time exfoliation joints preserve elements of former landscape morphologies by their undisturbed orientations the grimsel region of the central alps is well suited for analyzing the impact of erosional episodes and accompanying stress changes on exfoliation joint formation in granitic rocks mapping above and below ground revealed that exfoliation joints are widespread and occur between valley bottoms and mountain crests within glacial inner and hanging u shaped trough valleys glacial cirques and steep mountain crests and predominantly fluvial landforms gently inclined linear slopes above the inner trough valleys narrow inner valley gorges and steep v shaped side gullies based primarily on their geometric properties at the ground surface three exfoliation joint types were distinguished in our study area 1 closely spaced

formation of inner gorges abstract under certain conditions a distinctive type of landform the inner gorge evolves in drainage basins undergoing persistent base level lowering inner gorges are typical of basins in north coastal california u s a and one such basin was selected for detailed study based on analysis of along channel distribution of rock types streamside land sliding and stored sediment as well as computation of stream power the following set of conditions appears to accompany the formation of an inner gorge 1 inner gorge parent materials are relatively competent homogenous rock types 2 in inner gorge reaches there is an absence of any base level control that would prevent downcutting 3 continued downcutting occurs due to continued base level fall and this fall is most likely induced by tectonic uplift 4 mass slope failures that form steep straight slopes debris slides are the main denudational hillslope process in the inner gorge 5 sufficient stream power is available to transport landslide derived material out of the inner gorge reach such that alluvial sediment does accumulate in the reach over time and 6 the initial condition of the landscape is a low relief erosionally mature land surface into which the inner gorge is cut this initial condition implies that inner gorges develop in tectonically rejuvenated landscapes the processes of denudation on inner gorge slopes acting over a time scale of 105 years result in a style of landform evolution that approximates parallel slope retreat this type of slope retreat maintains the distinct inner gorge morphology during sustained downcutting though the analysis is confined to one basin in northern california so as to provide a detailed framework to understand inner gorge landform inner gorges appear to be commonplace in areas of moderate to high uplift where lithologic and tectonic conditions are appropriate for their formation a global search for this landform yet to be undertaken is needed to confirm whether it indeed occurs where the above conditions are met

fluvial incision history that controlled the distribution of landslides in the central range of taiwan abstract hillslope processes which are affected by long term river incision give rise to the risk of landsliding in active orogens we studied the river incision history and the subsequent response of rock slopes in the upstream dahan river catchment north taiwan by analyzing river long profiles hillslopes and landslide scars the results were combined with chronological data from several landform surfaces to reconstruct the history of landscape evolution at the study area the landscape comprises three levels of knickpoints and corresponding slope breaks these knickpoints propagated upstream along trunk and tributary rivers undercutting and destabilizing nearby slopes of which the oldest is a paleosurface dated to ca 150 kyr by cosmogenic nuclide dating consequently three levels of v shaped inner gorges up to 600 m deep are incised into the paleosurface the inner slopes of the three levels of gorges have mean inclinations of 35 6 37 7 and 39 8 and steepen from the higher to the lower inner gorges these three series of knickpoints and corresponding slope breaks suggest the occurrence of three phases of river incision based on analyses of the steepness indices of the river long profiles cosmogenic nuclide dating and the regional tectonic and climatic history the two earlier phases of incision are inferred to have been caused by prevailing tectonic uplifts during the middle to late pleistocene and the most recent phase by climate change in addition to uplift the long term history of river incision has controlled the distribution of deep seated gravitational slope deformation and landslides many areas of deep seated gravitational slope deformation and deep seated rockslide avalanches are aligned along the higher and middle slope breaks and debris slide avalanches are concentrated along the middle and lower slope breaks

wrench faulting in northern california and its tectonic implications the plio pleistocene prairie creek group of sediments lies unconformably on mesozoic franciscan assemblage rocks in north coastal california 120 km north of the mendocino triple junction the sediments are pervasively fractured and cut by three nnw trending faults collectively called the grogan lost man fault zone these sediments contain a record of quaternary deformation in an area of the california coast otherwise devoid of young sedimentary cover rocks detailed field mapping and structural analysis reveal a pattern of conjugate fracturing folding and outcrop scale faulting that strongly suggests the sediments have been deformed by wrench faulting the spatial relationship of structures is typical both of other known regions with well documented wrench faulting and of structural patterns produced by simple shear modeling of wrench faults the three major faults diverge slightly from expected fault trends based on the wrench fault model because the faults follow the structural grain of underlying franciscan basement rocks because of the orientation of these inherited faults with respect to the quarternary strain field wrench faulting is accompanied by convergence field exposures which show that two of the faults have high angle reverse separation confirm that offset includes vertical as well as horizontal components net quaternary right lateral displacement cannot be determined because of poor exposure and erosional stripping of the cover sediments but it is probably less than 5 km the grogan lost man wrench faults are interpreted as the northernmost part of the san andreas transform system we propose that northward movement of the san andreas transform boundary will entail a shift of major san andreas type fault activity to this northernmost right lateral fault system this shift will coincide with the northward migration of the mendocino triple junction to a position close to where the grogan lost man wrench faults intersect the continental margin

gigantic rockslides induced by fluvial incision in the diexi area along the eastern margin of the tibetan plateau abstract a number of large landslides which have strongly affected fluvial processes in the upstream catchment of the minjiang river along the eastern margin of the tibetan plateau sichuan were investigated with regard to both geological structure and topographic development topographic analysis suggested that there is a major knickpoint that formed not as a result of landslides but via tectonic activity and that the knickpoint propagated upstream forming an inner gorge and undercutting and destabilizing nearby slopes the effects of the knickpoint propagation and inner gorge formation on slope stability are dependent on the geometrical relationships between the river and geological structures when the geological trend is normal or highly oblique to the river axis landslides generally do not occur but gigantic rockslides have occurred on one side of the minjiang valley which can be attributed to a wedge structure consisting of bedding planes and joints with intersections dipping valleyward and tight folds with hinges plunging valleyward when the beds are planar moderately dipping and strike nearly parallel to the river buckling deformation commonly occurs on cataclinal slopes often transforming into catastrophic failure landslide dams form another type of knickpoint on the river channel that gradually disappear from the downstream to upstream as a result of river erosion our findings strongly suggest that the study of slope development by river incision must consider geological structures and that an understanding of geological structures and river incision history can provide a conceptual model for the prediction and mitigation of geohazards in tectonically active drainage basins

eddy kuroshio interactions local and remote effects quasi geostrophic mesoscale eddies regularly impinge on the kuroshio in the western north pacific but the processes underlying the evolution of these eddy kuroshio interactions have not yet been thoroughly investigated in the literature here this interaction is examined with results from a semi idealized three dimensional numerical model and observations from four pressure sensor equipped inverted echo sounders piess in a zonal section east of taiwan and satellite altimeters both the observations and numerical simulations suggest that during the interaction of a cyclonic eddy with the kuroshio the circular eddy is deformed into an elliptic shape with the major axis in the northwest southeast direction before being dissipated the poleward velocity and associated kuroshio transport decrease and the sea level and pycnocline slopes across the kuroshio weaken in contrast for an anticyclonic eddy during the eddy kuroshio interaction variations in the velocity sea level and isopycnal depth are reversed the circular eddy is also deformed to an ellipse but with the major axis parallel to the kuroshio the model results also demonstrate that the velocity field is modified first and consequently the ssh and isopycnal depth evolve during the interaction furthermore due to the combined effect of impingement latitude and realistic topography some eddy kuroshio interactions east of taiwan are found to have remote effects both in the luzon strait and on the east china sea shelf northeast of taiwan

flexure of the north american lithosphere above the subducted mendocino fracture zone and the formation of east west faults in the transverse ranges during the middle and late tertiary several prominent topographic scarps the farallon plate equivalents of present day fracture zones in the pacific plate were subducted under the western margin of north america if subduction occurred at a shallow angle so that the underthrust farallon plate was in isostatic balance with the overlying north american plate then differential uplift of the north american plate would have occurred the mendocino fracture zone was the tallest of the subducted scarps and isostasy calculations indicate that the surface of the north american plate south of the trace of the subducted fracture zone should have been 500 to 1000 m higher than the surface north of the trace flexure calculations in which the north american plate is treated as a thin slab predict that this uplift should have been spread over a north south distance of 70 to 120 km yielding an average slope of around 0 5 a regional slope of this magnitude would have been great enough to account for observed late oligocene and miocene disruptions of drainage and sedimentation in southern california calculated stresses in the upper part of the flexed plate are 50 to 80 mpa these stresses exceed the tensile failure strength of crustal rocks and suggest that the plate should have failed by tensile cracking tensile fracture would decrease the elastic thickness of the plate enhance bending and perhaps lead to failure by normal faulting this mechanism may explain the formation of east west faults in southern california

deep seated gravitational deformation of mountain slopes caused by river incision in the central range taiwan spatial distribution and geological characteristics abstract fluvial undercutting can cause the large scale destabilization of mountain slopes and induce deep seated gravitational slope deformation dgsd that eventually leads to catastrophic failures this study analyses these processes in the catchment of the dahan river northern taiwan the area has experienced phases of river incision of up to 600 m since the middle to late pleistocene and middle pleistocene paleosurfaces at higher elevations were incised to form v shaped valleys a dgsd inventory was compiled by visual interpretation of high resolution images and field surveys were conducted to clarify the geological structures associated with dgsds and major rockslide avalanches the observed relationships between dgsds and the topography modified by long term river incision show that about 53 of all dgsds occurred on slopes along the rims of paleosurfaces which is approximately 2 and 2 5 times as many as in the incised valleys and on the paleosurfaces respectively a comparison of the power law scaling exponents of cumulative frequency area distributions shows that the frequency of dgsds along the rims of the paleosurfaces decreases less rapidly with dgsd area than for dgsds on other slopes geological investigations suggest that there are two dominant types of dgsd one is flexural toppling of slate and argillite with high angle cleavage and the other is buckling of alternating beds of sandstone and mudstone on parallel or underdip cataclinal slopes catastrophic landslides observed along or below the rims of paleosurfaces were preceded by buckling of alternating beds of sandstone and shale these beds dipped at 50 to 58 and each bed was 10 1 10 0 m thick this study suggests that the peripheral zones of the paleosurfaces may be most susceptible to future catastrophic landslides particularly on parallel or underdip cataclinal slopes comprising alternating beds of sandstone and mudstone dipping at 50 to 60 thus an understanding of the geological characteristics spatial distribution of dgsd occurrence and landscape evolution within a particular area can provide important information for landslide hazard level zoning

terrain attributes of earthquake and rainstorm induced landslides in orogenic mountain belt taiwan landsliding induced by earthquakes and rainstorms in montane regions is not only a sculptor for shaping the landscape but also a driver for delivering sediments and above ground biomass downstream however the terrain attributes of earthquake and rainstorm induced landslides are less discussed comprehensively in taiwan as part of an island wide inventory we here compare and contrast the landslide terrain attributes resulting from two catastrophic events the chi chi earthquake mw 7 6 september 1999 and typhoon morakot rainfall 2500 mm august 2009 results show that the earthquake induced landslides are relatively small round shaped and prone to occur primarily in middle and toe of slopes in contrast the rainstorm induced landslides are larger horseshoe shaped and preferentially occurring in slope toes also earthquake induced landslides particularly large landslides are usually found at steeper gradients whereas rainstorm induced landslides aggregate at gradients between 25 and 40 lithologic control plays a secondary role in landsliding from an island wide perspective high landslide density locates in the region of earthquake intensity vi or one day rainfall 600 mm day 1 through the landslide patterns and their terrain attributes our retrospective approach shed lights on accessing the historical and remote events for close geophysical investigations finally we should bear in mind that the landslide location size and terrain attributes varying with triggers may affect the landscape evaluation or biogeochemical processes in landslide dominated regions this article is protected by copyright all rights reserved

development of deep seated gravitational slope deformation on a shale dip slope observations from high quality drill cores abstract we analyzed high quality drill cores with 100 recovery drilled into a gravitationally deformed dip slope of a shale dominated sequence of sediments in japan the slope had undulating surfaces but no well defined landslide scarps suggesting that parts of the slope had undergone gravitational deformation but had not completely separated from the surrounding bedrock the gravitational deformation of shale and sandstone is characterized by disintegration and brecciation of sediments and the formation of pulverized zones with poorly developed planar structures jigsaw like structures and fracture openings shear zones are distributed intermittently within the slope but have not merged discernably into a through going master sliding surface incipient landslide shear zones form openings within coherent rock by shearing along bedding with these shear zones potentially developing downward in a stepwise manner which may be related to stress redistribution induced by river incision

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

long river profiles tectonism and eustasy a guide to interpreting fluvial terraces along three rivers at the mendocino triple junction northern california strath cut and fill terraces have formed in response to tectonic and eustatic processes detailed surveying and radiometric dating at multiple sites indicate that lower reaches of the rivers are dominated by the effects of oscillating sea level primarily aggradation and formation of fill terraces during sea level high stands alternating with deep incision during low stands a eustasy driven deposi tional wedge extends tens of kilometers upstream on all rivers tapering to zero thickness this distance is greater than expected from studies of the effects of check dams on much smaller streams elsewhere due in part to the large size of these rivers however the change in gradient is nearly identical to other base level rise studies the depositional gradient is about half that of the original channel middle to upper reaches of each fiver are dominated by the effects of long term uplift primarily lateral and vertical erosion and formation of steep unpaired strath terraces exposed only upstream of the depositional wedge vertical incision at a rate similar to that of uplift has occurred even during the present sea level high stand along rivers with highest uplift rates strath terraces have steeper gradients than the modem channel bed and do not merge with marine terraces at the river mouth consequently they cannot be used to determine altitudes of sea level high stands strath formation is a continuous process of response to long term uplift and its occurrence varies spatially along a river depending on stream power and hence position upstream strath terraces are found only along certain parts of a coastal stream upstream of the aggradational effects of oscillating sea level and far enough downstream that stream power is in excess of that needed to transport the prevailing sediment load for a given size fiver the greater the uplift rate the greater the rate of vertical incision and consequently the less the like lihood of strath terrace formation and preservation

seasonal circulation patterns of the yellow and east china seas derived from satellite tracked drifter trajectories and hydrographic observations abstract we investigated seasonal circulation patterns of the yellow and east china seas yecs by reviewing previous works on the circulation and its dominant currents and taking into account newly compiled trajectories of satellite tracked drifters collected between the 1980s and 2000s the circulation patterns suggested before the 1990s can be categorized into two groups depending on the identified origin of the tsushima warm current in the korea tsushima straits i branching from the kuroshio southwest of kyushu or ii northeastward continuation of the taiwan strait throughflow the branching of the kuroshio southwest of kyushu and northeast of taiwan was clearly evidenced by current measurements and concurrent hydrographic surveys however there is still no clear evidence for the northeastward pathway of taiwan strait throughflow across the mid shelf area of the east china sea target oriented surveys in the 1990s and 2000s employing advanced instruments such as drifter tracking and acoustic doppler current profiler measurements now provide decisive proof of the clockwise rounding of the cheju warm current around jeju do throughout the year of the northeastward extension of changjiang discharge in summer and of the presence of the yellow sea warm current only in winter thus both coastal currents in shallow water and secondary branch currents of the kuroshio such as the yellow sea warm current are found to significantly change from winter to summer to better present the basic pattern of yecs circulation and its seasonality we have constructed seasonal circulations patterns based on review results on the newly compiled drifter trajectories and on hydrographic observations further investigations should be carried out in future with support of comprehensive current measurements on shelf areas and through elaborate numerical modeling

three dimensional geometry of the gorda plate beneath northern california the isostatic residual gravity field over northern california displays a gravity gradient interpreted to reflect the south edge of the gorda plate where it is subducted eastward beneath the north american plate the locus of points of maximum slope defines a line trending s60 e from a coastal point approximately 20 km south of cape mendocino a point where the buried plate boundary is inferred from magnetic and seismicity data southeast from the coast for a distance of 120 km the gravity anomaly parallels the strike of the blanco fracture zone and the present direction of relative motion between the pacific and northern gorda plates calculations from the form of the anomaly yield depth estimates that fit an east southeast plunge of approximately 9 for the top of the gorda south edge the sense of the anomaly higher gravity to the south supports the hypothesis that a window developed in the subducted slab east of the san andreas fault and south of the gorda plate south of the gorda boundary the base of the north american plate is thus in contact with hot material from the asthenosphere that invaded the window because the overlying north american plate has been moving relatively south across the gorda boundary the north american plate beneath the coast ranges east of the san andreas fault in central california may be decoupled from the underlying material at a depth slightly deeper than the depth to the top of the boundary at the time the north american plate passed over it

influence of late holocene hillslope processes and landforms on modern channel dynamics in upland watersheds of central nevada stratigraphic geomorphic and paleoecological data were collected from upland watersheds in the great basin of central nevada to assess the relationships between late holocene climate change hillslope processes and landforms and modern channel dynamics these data indicate that a shift to drier warmer climatic conditions from approximately 2500 to 1300 ypb led to a complex set of geomorphic responses the initial response was massive hillslope erosion and the simultaneous aggradation of both side valley alluvial fans and the axial valley system the final response was fan stabilization and axial channel incision as fine grained sediments were winnowed from the hillslope sediment reservoirs and sediment yield and runoff processes were altered the primary geomorphic response to disturbance for approximately the past 1900 years has been channel entrenchment suggesting that the evolutionary history of hillslopes has produced watersheds that are prone to incision the magnitude of the most recent phase of channel entrenchment varies along the valley floor as a function of geomorphic position relative to side valley alluvial fans radial fan profiles suggest that during fan building fan deposits temporarily blocked the flow of sediment down the main stem of the valley commonly creating a stepped longitudinal valley profile stream reaches located immediately upvalley of these fans are characterized by low gradients and alternating episodes of erosion and deposition in contrast reaches coincident with or immediately downstream of the fans exhibit higher gradients and limited valley floor deposition thus modern channel dynamics and associated riparian ecosystems are strongly influenced by landforms created by depositional events that occurred approximately 2000 years ago

erosional response to northward propagating crustal thickening in the coastal ranges of the u s pacific northwest we measured basin scale erosion rates using cosmogenic 10 be concen trations in quartz from fluvial sediment in rivers draining the coastal mountain ranges of the u s pacific northwest between 40 and 47 n apparent erosion rates are 0 1 to 0 2 mm yr 1 throughout the oregon coast ranges north of 43 n and increase to the south to 0 6 to 1 1 mm yr 1 in the northern california coast ranges near 40 n we propose that these observations display the erosional response to northward migrating crustal thickening associated with subduction of the mendocino triple junction north south variations in erosion rate range elevation and metrics of landscape relief and steepness are consistent with the hypotheses that i their primary cause is northward migrating crustal thickening ii erosion rates are strongly controlled by topographic relief and weakly if at all controlled by climate and iii the dependence of erosion on relief is nonlinear and obeys a threshold relief relationship

buried preglacial fluvial gorges and valleys preserved through quaternary glaciations beneath the eastern laurentide ice sheet the geomorphology geometry and sedimentary infill of buried gorges and v shaped valleys observed at the base of major river valleys in the formerly glaciated southeastern canadian shield region have been revealed from excavation and drilling data acquired during the construction of hydro electric dams and seismic data collected on lakes and offshore compilation of these previously published and unpublished data provided an exceptional opportunity to examine the morphology and spatial distribution of buried bedrock gorges and the mechanical processes responsible for their erosion in some valleys detailed observations of deep gorges have been allowed by their exhumation over large areas archive photographs show deep and large potholes natural pillars furrows flutes and scallops on the well polished bedrock walls of the gorges they also reveal that gorges and valleys have a sharp ending v shape and very narrow base and are superimposed by a u shaped valley forming a buried valley within valley topography the narrow and deep cross profile of these gorges their well polished slopes and the type of bedforms observed within them are typical features of fluvial bedrock channels drilling operations at many sites have also provided data on bedrock topography of these gorges within valleys and on the nature of their sedimentary infill the different lines of evidence presented in this paper indicate that gorges and v shaped valleys of the region were not eroded by the laurentide ice sheet during quaternary glaciations but are relics of a preserved preglacial fluvial system eroded during a lower base level this paleofluvial system is interpreted to be linked to fluvially cut channels observed on the seafloor of the estuary and gulf of st lawrence

the sinuous bedrock channel of the tapi river central india its form and processes abstract the tapi gorge lies in the monsoon dominated region of the indian subcontinent because of the seasonality of rainfall and flows all the fluvial activity in the bedrock gorge is confined to the monsoon season in general and during a few high magnitude monsoon floods in particular field investigations along a 30 km reach of the sinuous bedrock gorge indicate that the river displays all the morphologic properties of a meandering alluvial channel albeit with a much higher level of energy expenditure considering the perimeter lithology and channel morphology two types of reaches are evident in the field a predominantly rocky and relatively straight reach close to the gorge head and a longer sinuous reach of gravel deposition downstream hydraulic modeling of a rainfall induced dam failure flood indicates that large magnitude events that exceed the threshold of bedrock resistance for a sustained length of time are capable of erosion it appears that the overall channel and gorge morphology is adjusted to two types of thresholds a threshold of boulder transport which is associated with large floods that are competent to entrain boulders but are incapable of bedrock erosion and another higher threshold that is exceeded by truly high energy processes that generate large total energy and exceed the threshold of bedrock resistance the later threshold is exceeded only episodically with fairly long periods of little or no bedrock erosion in between interestingly meso scale erosional features such as inner channels and well developed potholes are nearly absent or inconspicuous within the gorge section whilst this could be partly attributed to the bedrock resistance it appears that under the present hydro geomorphic conditions the dominant fluvial activity is not directed towards the channel bed but towards the banks this is evident from the concentration of erosion on the outer banks and deposition of coarse gravel on the inner banks and armoring of the channel bed the main conclusion of the study is that the bedrock channel is increasing the flow resistance and energy losses by developing and enhancing the meandering pattern

topography representation methods for improving evaporation simulation in groundwater modeling summary in a groundwater model surface elevations which are used in simulating the phreatic evaporation process are usually incorporated as spatially constant over discretized cells traditionally a modeler obtains the data for surface elevations from point data or a digital elevation model dem by means of extrapolation or interpolation in this way a smoothing error of surface elevations is introduced which via the depth to groundwater propagates into evaporation simulation as a consequence the evaporation simulation results can be biased in order to explore the influence of surface elevations on evaporation simulation three alternative methods of representation of topography in calculating evaporation were studied the first one is a traditional method which uses cell wise constant elevations obtained by averaging surface elevations from the dem with higher resolution for the corresponding model cells the second one retains some information on the sub pixel statistics of surface elevations from the dem by a perturbation approach calculating the second order first moment of evaporation with a taylor expansion in the third method a finer discretization is used to represent the topography in calculating evaporation than is used to compute global groundwater flow this allows to take into account the smaller scale variations of the surface elevation as given in the high resolution dem data for all the three methods two different evaporation functions a linear segment function and an exponential function have been used individually in this paper a groundwater model with a discretization of 500 500 m has been established while dem data with a resolution of 90 90 m are available and resampled to 100 100 m cells for convenience of model input the evaporation rates from a groundwater model with a discretization of 100 100 m which has the same spatial distribution pattern of hydraulic parameters as the 500 500 m model is taken as validation data the comparisons of evaporation rates were carried out on different averaging scales ranging from 500 m to 2 km the compared evaporation rates for each scale are obtained by summing up the corresponding evaporation rates from the 500 500 m model and the 100 100 m model it is shown that the third method which uses a finer resolution of topography in the evaporation calculation yields the best results no matter which evaporation function is used it is also seen that the correlation between the evaporation rates from the 500 500 m model and the 100 100 m model increases and values converge when comparing the evaporation results on an increasingly coarser scale independently of the selected method and evaporation function

inner gorges incision history a proxy for deglaciation insights from cosmic ray exposure dating 10be and 36cl of river polished surfaces tinee river sw alps france editor a yin keywords river gorges incision cre 10 be and 36 cl dating river polished surfaces 10 be and 36 cl cosmic ray exposure cre dating performed on river polished surfaces of river gorges in a mountain to sea river system in the french sw alps highlights transient erosional events involving incision rates 10 mm a 1 these events took place during the last two major deglaciation phases following 1 the last glacial maximum lgm at 16 14 ka 2 the younger dryas at 8 11 ka and during the warm and humid holocene climatic optimum at 4 5 ka these periods of high incision rates 3 30 mm a 1 alternated with periods of low incision rates 1 mm a 1 which probably correspond to a long term equilibrium between incision and relative uplift the alpine river staircase shape profiles evidence local and transient responses that are ascribed to cumulate disequilibrium after the long time spanned glaciations after each glaciation rivers rush down to get closer to their equilibrium profile incision is amplified both by the sediment discharge due to the erosion of moraines and by landslides triggered by the glacier retreat

landscape analysis and the search for geomorphic unity geomorphology has been an integral part of geological science since the inception of the geological society of america even though different investigative goals have existed continuously in the discipline the dichotomy of purpose began with the vastly different perception of landscape analysis embraced by william morris davis and g k gilbert historical and physical geomorphic studies have always been conducted simultaneously but one of these research activities has dominated the field at any given time during the first half of this century most geomorphic work was devoted to the interpretation of long term evolutionary history of regional landscapes in the past four decades however research has concentrated on the study of geomorphic processes this revised direction placed greater emphasis on the physical component of geomorphology and provided a more complete understanding of the time factor in landscape analysis historical geomorphology is now less concerned with theories of cyclic time landscape development and more involved in determining the time and sequence of shorter episodes of geomorphic disequilibrium caused by tectonism and or climate change the tenor of future research in surficial geology will require input from both physical and historical geomorphology and therefore a greater unity of purpose among geomorphologists can be expected geomorphologists will have the opportunity to provide geologists and engineers with useful data about major scientific and technical problems related to plate tectonic theory interpretation of the stratigraphic record and prediction of landform stability for environmental planning

integration of swap and modflow 2000 for modeling groundwater dynamics in shallow water table areas summary reasonable estimates of groundwater recharge and discharge through evapotranspiration is critical for sustainable water resources management in shallow water table areas the hydrologic processes are highly interactive between the vadose zone and groundwater under shallow water table conditions in traditional groundwater flow models the recharge and evapotranspiration fluxes are often oversimplified as a simple sink source term however the recharge and evapotranspiration are observed to vary with topography soil type land use and water management practices additionally they are known to vary temporally and spatially and are difficult to estimate especially in arid and semi arid regions thus it is important to devise an appropriate method to estimate the recharge and evapotranspiration fluxes in groundwater modeling in this study a soil water atmosphere plant swap package was integrated into a groundwater flow model modflow in such a way that the swap package calculates vertical flux for modflow while modflow provides averaged water table depth to determine the bottom boundary condition for swap zones the swap zones in modflow are derived from a combination of topology soil type land use water management practices using geographic information systems gis then the modflow with swap package was tested using a two dimensional saturated unsaturated water table recharge experiment results showed that the simulated water table elevations matched well with the observed ones except at the early period during which they were slightly higher than the observed ones probably due to neglecting lateral diffusion in the unsaturated zone finally we applied modflow with swap package to simulate a regional groundwater flow problem in hetao irrigation district upper yellow river basin of north china the simulation results validated the applicability of the developed modflow with swap package for practical regional groundwater modeling

stochastic model for the long term transport of stored sediment in a river channel we develop a stochastic model for the transport of stored sediment down a river channel the model is based on probabilities of transition of particles among four different sediment storage reservoirs called active often mobilized semiactive inactive and stable hardly ever mobilized the probabilities are derived from computed sediment residence times two aspects of sediment storage are investigated flushing times of sediment out of a storage reservoir and changes in the quantity of sediment stored in different reservoirs due to seasonal sediment transport into and out of a reach we apply the model to redwood creek a gravel bed river in northern california although the redwood creek data set is incomplete the application serves as an example of the sorts of analyses that can be done with the method the application also provides insights into the sediment storage process sediment flushing times are highly dependent on the degree of interaction of the stable reservoir with the more mobile sediment reservoirs the most infrequent and highest intensity storm events which mobilize the stable reservoir are responsible for the long term shifts in sediment storage turnover times of channel sediment in all but the stable reservoir are on the order of 750 years suggesting this is all the time needed for thorough interchange between these sediment compartments and cycling of most sediment particles from the initial reservoir to the ocean finally the markov model has adequately characterized sediment storage changes in redwood creek for 1947 1982 especially for the active reservoir the model replicates field observation of the passage of a slug of sediment through the active reservoir of the middle reach of redwood creek in the 18 years following a major storm in 1964 that introduced large quantities of landslide debris to the channel

geomorphic and paleoclimatic implications of latest pleistocene radiocarbon dates from colluvium mantled hollows california radiocarbon analyses of charcoal from basal colluvium in 11 california hollows show a clustering of dates between 9000 and 15 000 b p an indication that changes in the storage and discharge of colluvium from hillslopes accompanied the pleistocene holocene transition hollows are sites of topographically induced convergence and deposition of colluvial debris and evacuation of this debris was apparently more thorough and possibly more frequent in the latest pleistocene perhaps due to a combination of changes in vegetation and rainfall characteristics one hypothesis is that greater storm intensities occurred in the latest pleistocene and induced a higher frequency of landslides in hollows and a regional extension of channel heads upslope relative to the holocene during the last pleistocene california hollows apparently contained smaller volumes of colluvium in storage the increased storage of debris during the holocene may have resulted in a diminished supply of sediment to stream channels

landslides induced by the 2008 wenchuan earthquake sichuan china the 2008 wenchuan earthquake with a magnitude of mw 7 9 induced numerous slope movements on the hanging walls of fault surface ruptures and on steep inner valleys along the minjiang river landslide moving directions showed preferred orientations normal to the fault ruptures indicating the effect of the directivity of the seismic wave the most common landslides were of carbonate rocks which are easily dissolved and decrease the contact surfaces the largest non volcanic landslide in history was induced in bedded dolomite by the earthquake and was preceded by gravitational deformation with ridge top depressions valley fill materials were mobilized at 36 locations probably by pore water pressure build up

topographic fingerprints of bedrock landslides bedrock landslides in mountainous regions may be triggered by either storms or earthquakes the dominant mechanism in a region affects both landscape evolution and landslide hazard we describe a simple observational test to distinguish between storm and earthquake triggers based on a probabilistic measure of hillslope morphology in areas that are dominated by storm triggered landslides steep topographic slopes are concentrated on the lowermost parts of the hillslopes storm triggers act primarily on the hillslope toes and landslides preferentially remove material from those locations giving rise to inner gorges areas where most landslides are earthquake triggered have more uniform spatial distributions of steep topographic slopes because coseismic shaking causes failures at both ridge crests and hillslope toes earthquake triggered landslides lead to planar hillslopes and rare or absent inner gorges

multi channel patterns of bedrock rivers an example from the central narmada basin india abstract an anomalous multiple channel pattern in bedrock is observed on a predominantly downcutting reach of the narmada river the multi channel reach 800 2750 m in width and 8500 m in length is bounded by major faults and is underlain by granite and gneiss bedrock geomorphological investigations reveal differences among the upstream middle and downstream sub reaches of the multi channel study area whereas the upstream sub reach is dominated by deep flows and fine sediments the lower sub reach is characterized by a steep gradient and rapids the middle sub reach is the widest and is marked by thickly forested islands and boulder berms the characteristics of the three different sub reaches suggest control by the interactions of lithology flood processes and tectonics estimations of hack s 1973 stream gradient index values indicate considerable variations for the sl values along the length of narmada river the highest value of gradient index sl 797 is associated with the multi channel reach implying lithologic or tectonic control given the dimensions of the reach and its channels it appears that the present hydrological regime is inadequate to produce the feature we hypothesize that the multi channel pattern development in bedrock was initiated by block or domal uplift enhanced gradients and extreme floods permitted the system to exploit linear weaknesses in the bedrock leading to the development of anabranches and establishment of multiple channels in bedrock abrupt changes in the channel planform and morphology at the study site indicate that the river is adjusting its channel geometry width depth gradient and plan configuration to a new equilibrium channel morphology through the action of the extreme floods characteristic of this fluvial environment

bedrock landsliding river incision and transience of geomorphic hillslope channel coupling evidence from inner gorges in the swiss alps 1 the formation of inner gorges cut into bedrock has been explained as relief rejuvenation by fluvial incision in response to rapid base level drop repeated glaciations frequent pore pressure driven landsliding focused at hillslope toes or catastrophic outburst flows from natural dam failures prominent inner gorges occur in soft mesozoic bundner schist and lower tertiary flysch units of the formerly glaciated alpenrhein catchment eastern swiss alps their channel and hillslope morphologies differ from basins characterized by strong glacial or landslide imprints while formally resembling the theoretically predicted transient response of detachment limited bedrock rivers to rapid base level fall by headward knickpoint migration assuming a postglacial onset of fluvial bedrock incision into a last glacial maximum surface in response to base level drop induced by downwasting of trunk valley glaciers requires downcutting rates e 20 mm yr 1 and requires hillslopes to adjust by frequent landsliding toward development of a threshold state we test this scenario using data on surface uplift geomorphometry geomorphic hillslope coupling and probabilistic slope stability models we find that adjustment of inner gorge walls through landsliding is mainly strength limited and structurally controlled and threshold conditions are restricted to the lower 25 of local hillslope relief mass movement processes on upper hillslopes remain largely decoupled from channel incision despite inferred postglacial specific sediment yields of 104 m3 km 2 yr 1 from the studied basins conversely several constraints imposed by fluvial bedrock detachment postglacial sediment yields and bedrock landsliding argue for a pre holocene origin for at least some of the inner gorges in the area this implies partial protection of fluvial gorge topography by subglacial sediment fill during the last wurm extensive glaciation and implies that glaciers were insufficient to fully eradicate fluvially sculpted bedrock topography this leads us to conclude that lithology and major climate oscillations should be considered as further alternative controls on inner gorge formation

a neogene structural dome in the klamath mountains california and oregon regional structural doming of neogene age has affected rocks of the klamath and cascade mountains near the california oregon border evidence for this is seen in 1 subannular outcrop patterns of pre cretaceous lithotectonic units 2 a crude pattern of radially oriented high angle faults 3 tilted jurassic plutons 4 tilted cretaceous to miocene strata and 5 various geomorphological features the age of doming is constrained by a major middle miocene to earliest pliocene angular unconformity within the cascade mountains and uplifted upper miocene marine beds on the western edge of the klamath mountains uplift and doming may be the result of shortening in the cascade fore arc region or more speculatively the recent accretion of subducted material to the north american plate beneath the klamath mountains

topographic precursors and geological structures of deep seated catastrophic landslides caused by typhoon talas abstract typhoon talas crossed the japanese islands between 2 and 5 september 2011 causing more than 70 deep seated catastrophic landslides in a jurassic to paleogene lower miocene accretion complex detailed examination of the topographic features of 10 large landslides before the event recorded on 1 m dems based on airborne laser scanner surveys showed that all landslides had small scarps near their future crowns prior to the slide and one landslide had linear depressions along its future crown as precursor topographic features these scarps and linear depressions were caused by gravitational slope deformation that preceded the catastrophic failure although the scarps may have been enlarged by degradation their sizes relative to the whole slopes suggest that minimal slope deformation had occurred in the period immediately before the catastrophic failure the scarp ratio defined as the ratio of length of a scarp to that of the whole slope both measured along the slope line ranged from 5 to 21 careful examination of aerial photographs from another four large landslides for which no high resolution dems were available suggested that they also developed scarps at their heads beforehand twelve of the 14 landslides we surveyed in the field had sliding surfaces with wedge shaped discontinuities that consisted of faults and bedding suggesting that the buildup of pore pressure occurs readily on wedge shaped discontinuities in a gravitationally deformed rock body most of the faults were undulatory and were probably thrust faults that formed during accretion other types of gravitational deformation were also active e g flexural toppling and buckling were observed to have preceded one landslide

distribution of gravitational slope deformation and deep seated landslides controlled by thrust faults in the shimanto accretionary complex abstract the cretaceous shimanto accretionary complex is a typical accretionary complex uplifted without significant deformation after accretion and in which many rain induced deep seated landslides dls have occurred we undertook a thorough geological and geomorphological investigation of the middle kii peninsula where many rain induced dls occurred in 1889 and 2011 during intense and prolonged rainfall associated with typhoons geomorphological investigations using 1 m digital terrain models dtms obtained from airborne light detection and ranging lidar before and after the 2011 typhoon allowed us to examine the microtopography e g small scarps and linear depressions and to locate deep seated gravitational slope deformations dgsds and dls low angle thrust faults with 1 m thick incohesive fault rocks were found to be aligned subparallel to each other with spacings of a few kilometers and control the distribution of dls and dgsds when a thrust fault forms a cataclinal slope river incision removes the overburden and undercuts and destabilizes the slope this process causes gravitational deformation which forms downhill facing scarps and linear depressions at higher elevations on the slope tephrochronology applied to the deposits in the dgsd induced depressions revealed that such deformation began at least 30 000 50 000 years ago and is ongoing when a high angle fault strikes along the line of maximum slope it separates a volume of the rock mass from the juxtaposing slope and facilitates gravitational slope deformation and ultimately catastrophic failure a rock mass on a thrust fault that forms a downslope plunging syncline can also be gravitationally deformed and fail a crush zone of a large scale thrust fault is a continuous weak layer that also forms a barrier to groundwater flow thus leading to a rapid increase in pore pressure during rainstorms potentially triggering catastrophic slope failure accretionary complexes which typically contain thrust faults with incohesive fault rocks thus provide a location for dgsds and dls

new insight into the factors leading to the 1998 flank collapse and lahar disaster at casita volcano nicaragua during unusually high rainfall associated with hurricane mitch in 1998 a flank collapse leading to a disastrous lahar occurred at casita volcano nicaragua the lack of a similar failure during a rainfall event of comparable magnitude in 1982 tropical storm alleta suggests that additional factors influenced the 1998 collapse we have investigated the potential contribution of erosional flank undercutting seismic activity and anthropogenic land cover change at the collapse site except for seismic events prior to mitch which may have increased flank instability none of these factors appears significant instead for failure to occur the following conditions were required 1 highly fractured slope material allowing deep and rapid infiltration of meteoric water 2 a less permeable underlying layer to obstruct drainage 3 strong continuous antecedent rainfall to build up high pore water pressure and 4 episodic high intensity precipitation during mitch to generate recurrent pressure waves prerequisite 1 was provided by edifice wide deformation towards the south east seismic activity and proximity to a prominent fault and local subsidence condition 2 was met by clay rich layers resulting from hydrothermal alteration more than 1 900 mm of rain fell in the 6 months prior to mitch without significant interruption while intense episodic precipitation occurred during the hurricane satisfying conditions 3 and 4 respectively the main difference with alleta was that it occurred at the beginning of the rainy season and therefore without sufficient antecedent rainfall anthropogenic activity including land cover change did not affect slope stability i e the hazard however vulnerability was generated when two towns were established in the lowlands south of casita on top of previous lahar deposits it was greatly increased when approximately 4 km of forest between the collapse site and the towns were cleared paving the way for a largely unobstructed debris flow deforestation also facilitated erosion along the flanks to provide about 78 of the material contained in the lahar when it destroyed the towns killing more than 2 500 people

modulation of kuroshio transport by mesoscale eddies at the luzon strait entrance measurements of kuroshio current velocity at the entrance to luzon strait along 18 75 n were made with an array of six moorings during june 2012 to june 2013 strong positive relative vorticity of the order of the planetary vorticity f was observed on the western flank of the kuroshio in the upper 150 m on the eastern flank the negative vorticity observed was about an order of magnitude smaller than f kuroshio transport near its origin is computed from direct measurements for the first time kuroshio transport has an annual mean of 15 sv with a standard deviation of 3 sv it is modulated strongly by impinging westward propagating eddies which are identified by an improved eddy detection method and tracked back to the interior ocean eight kuroshio transport anomalies 5 sv are identified seven are explained by the westward propagating eddies cyclonic anticyclonic eddies decrease increase the zonal sea level anomaly sla slope and reduce enhance kuroshio transport large transport anomalies of 10 sv within o 10 days are associated with the pairs of cyclonic and anticyclonic eddies the observed kuroshio transport was strongly correlated with the sla slope correlation 0 9 analysis of sla slope data at the entrance to luzon strait over the period 1992 2013 reveals a seasonal cycle with a positive anomaly i e an enhanced kuroshio transport in winter and spring and a negative anomaly in summer and fall eddy induced vorticity near the kuroshio has a similar seasonal cycle suggesting that seasonal variation of the kuroshio transport near its origin is modulated by the seasonal variation of the impinging mesoscale eddies

impact of mesoscale eddies on kuroshio intrusion variability northeast of taiwan abundant mesoscale eddies propagate to the east of taiwan and affect the kuroshio current and its onshore intrusion northeast of taiwan but the dynamical process of how eddy activities modulate the kuroshio intrusion is still unclear in this study in situ ocean velocity observations drifter trajectories tide gauge measurements satellite sea surface height data and assimilative hybrid coordinate ocean model hycom reanalysis outputs were used to analyze a cyclonic eddy induced large kuroshio onshore intrusion during late autumn 2008 along with nine anticyclonic eddy events and seven cyclonic eddy events extracted from long term hycom reanalysis outputs the variability of the eddy induced intrusion were quantified the impacts of the cyclonic eddy and the anticyclonic eddy were opposite under the impact of cyclonic anticyclonic eddy the total onshore intrusion between 122 e and 124 e across the 200 m isobaths was decreased increased by 15 7 7 3 while the onshore intrusion west of 122 6 e and the northeastward current on the outer shelf was increased decreased by 30 6 4 7 and 31 10 1 respectively the arrival of cyclonic anticyclonic eddy brought positive negative potential vorticity pv flux and modulated the local ocean vertical stratification which weakened enhanced the cross slope pv gradient and the shelf slope constraint on the upper layer current therefore favored inhibited the kuroshio onshore intrusion this article is protected by copyright all rights reserved

tectonic uplift of a middle wisconsin marine platform near the mendocino triple junction california an uplifted wave cut marine platform eroded across bedrock of the franciscan complex at point delgada northern california is overlain by 0 5 to 5 m of wave worked pea gravel which is in turn directly overlain by fluvial gravel and silt deposited as alluvial fans woody plant debris at the base of the fluvial deposits includes cones of brewer spruce picea breweriana which today are found only at higher elevations and latitudes fossil wood debris from this horizon yields a 14c date of 44 800 1 300 yr the 44 800 yr radiocarbon age for the base of the fluvial deposits establishes an approximate age for the immediately underlying marine gravels and wave cut platform we tentatively correlate this terrace with the middle wisconsin high sea level stand at 37 m dated at about 45 000 yr b p if this age is correct the tectonic uplift since middle wisconsin time has been 44 m and the average rate of uplift has been at least 1 0 m 1 000 yr this relatively high rate is probably related to interaction among the pacific gorda and north american plates at the mendocino triple junction

the tug of war between the west philippine sea and south china sea tropical waters and intermediate waters in the okinawa trough kuroshio subsurface waters are the major source of nutrients to the east china sea continental shelf a major fishing ground these subsurface waters are heavily affected by the south china sea scs tropical and intermediate waters which contain more nutrients than the tropical smax and intermediate smin waters from the west philippine sea wps a front was found to separate these waters from the scs and wps the reported front in the okinawa trough however was identified based only on one time data from a single cross section here historical hydrographic data between march 1950 and december 2011 are analyzed a vertical front tilted toward the west is found in all seasons in all years in the okinawa trough in winter the presence of the scs tropical water is the most prominent it is the weakest in autumn as for intermediate waters smin the wps and scs intermediate waters show much weaker seasonality compared with tropical waters although in summer the wps intermediate water contribution is slightly larger than during other times

effects of kuroshio intrusions on the atmosphere northeast of taiwan island the kuroshio loses bathymetric support off northeast taiwan island causing large variability in its path the resultant covariability of sea surface temperature sst and the lower atmosphere is investigated using satellite observations in winter and spring off northeast taiwan island the intrusions of warm kuroshio water onto the continental shelf cause a large increase in local sst intensify the northeasterly monsoonal winds and lead to the increases in water vapor and rainfall key to this air sea interaction is the existence of anomalous heat advection by the kuroshio intrusions the kuroshio intrusions are partly due to westward propagating ocean eddies east of taiwan island with a lead time of 3 weeks hinting at the possibility of improved weather prediction near northeast taiwan island by considering ocean variability east of taiwan island

effects of mesoscale eddies on the volume transport and branch pattern of the kuroshio east of taiwan using satellite altimeter data and a long term altimetric transport index for the kuroshio inflow northeast of taiwan the effects of mesoscale eddies on the kuroshio volume transport kvt at the east taiwan channel and the branching pattern of the kuroshio east of taiwan are investigated at scales from those of individual events to interannual timescales both anticyclonic and cyclonic eddies are found to be able either to strengthen or weaken the kvt depending on the relative strength of mass convergence and divergence produced upstream and downstream of the eddies the major factor influencing the intensity of the kuroshio inflow is the meridional location of the eddies for single eddy events the kvt is significantly correlated with the latitude of the eddy s center the correlations being 0 44 and 0 48 for anticyclonic and cyclonic eddies respectively for dipole eddy events when the direction angle falls in the interval 40 150 240 300 the kvt anomaly tends to be positive negative furthermore low kvt events generally correspond to the formation of the ryukyu current branch which is also generated from strong mass divergence produced by the eddies in addition on interannual time scales the variation of kvt is closely related to the relative number of anticyclonic to cyclonic eddies west of 125 e with a correlation of 0 5 this article is protected by copyright all rights reserved

large landslides lie low excess topography in the himalaya karakoram ranges mass wasting is an important process for denuding hillslopes and lowering ridge crests in active mountain belts such as the himalaya karakoram ranges hkr such a high relief landscape is likely to be at its mechanical threshold maintained by competing rapid rock uplift river incision and pervasive slope failure we introduce excess topography z e for quantifying potentially unstable rock mass volumes inclined at angles greater than a specified threshold angle we find that z e peaks along major fluvial and glacial inner gorges which is also where the majority of 492 large 0 1 km 2 rock slope failures occur in the himalaya9s largest cluster of documented pleistocene to holocene bedrock landslides our data reveal that bedrock landslides in the hkr chiefly detached from near or below the median elevation whereas glaciers and rock glaciers occupy higher elevation bands almost exclusively less than 10 of the area of the hkr is upslope of glaciers such that possible censoring of evidence of large bedrock landslides above the permanent snow line barely affects this finding bedrock landslides appear to preferentially undermine topographic relief in response to fluvial and glacial incision along inner gorges unless more frequent and smaller undetected failures or rigorous peri glacial erosion compensate for this role at higher elevation either way the distinct patterns of excess topography and large bedrock landsliding in the hkr juxtapose two stacked domains of landslide and peri glacial erosion that may respond to different time scales of perturbation our findings call for more detailed analysis of vertical erosional domains and their geomorphic coupling in active mountain belts