yardang geometries in the qaidam basin and their controlling factors abstract the hyperarid qaidam basin features extensive fields of yardangs covering an area of 40 000km2 sculpted in tectonically folded sedimentary rocks we extracted the geometries of 16 749 yardangs such as length to width ratio l w spatial density and spacing from multi source remote sensing data provided by google earth we classified the yardangs into four types based on their l w short axis 1 2 whale back 2 6 hogsback 6 10 and long ridge 10 210 we interpreted the yardang geometries in the context of their geologic setting bedding orientation location along anticline crests or syncline troughs and lithologic heterogeneity our results show that the yardang geometries in the qaidam basin are mainly controlled by the structural geology and rheology of the sedimentary rocks e g strike and dip of bedding the presence or absence of interbedded soft and hard beds and structural position with folds the angle between geomorphically effective wind directions and the strike of bedding and the relative cumulative wind shear force where two geomorphically effective wind directions are present our analysis revealed the following 1 nearly 69 of the yardangs with long ridge and hogsback geometries are distributed in syncline areas whereas 73 of the yardangs with short axis geometries are distributed in anticline areas 2 the l w ratio of yardangs exposed along the windward limbs of anticlines is lower than that of yardangs exposed along the leeward limbs and 3 in the westernmost parts of the basin yardangs are locally sculpted into mounds by two geomorphically effective wind directions

mountains and arid climates of middle latitudes simulations from a global climate model with and without orography have been used to investigate the role of mountains in maintaining extensive arid climates in middle latitudes of the northern hemisphere dry climates similar to those observed were simulated over central asia and western interior north america in the experiment with mountains whereas relatively moist climates were simulated in these areas in the absence of orography the experiments suggest that these interior regions are dry because general subsidence and relatively infrequent storm development occur upstream of orographically induced stationary wave troughs downstream of these troughs precipitation bearing storms develop frequently in association with strong jet streams in contrast both atmospheric circulation and precipitation were more zonally symmetric in the experiment without mountains in addition orography reduces the moisture transport into the continental interiors from nearby oceanic sources the relative soil wetness of these regions in the experiment without mountains is consistent with paleoclimatic evidence of less aridity during the late tertiary before substantial uplift of the rocky mountains and tibetan plateau is believed to have occurred

wind as the primary driver of erosion in the qaidam basin china deserts are a major source of loess and may undergo substantial wind erosion as evidenced by yardang fields deflation pans and wind scoured bedrock landscapes however there are few quantitative estimates of bedrock removal by wind abrasion and deflation here we report wind erosion rates in the western qaidam basin in central china based on measurements of cosmogenic 10 be in exhumed miocene sedimentary bedrock sedimentary bedrock erosion rates range from 0 05 to 0 4 mm yr although the majority of measurements cluster at 0 12570 05 mm yr these results combined with previous work indicate that strong winds hyper aridity exposure of friable neogene strata and ongoing rock deformation and uplift in the western qaidam basin have created an environment where wind instead of water is the dominant agent of erosion and sediment transport its geographic location upwind combined with volumetric estimates suggest that the qaidam basin is a major source up to 50 of dust to the chinese loess plateau to the east the cosmogenically derived wind erosion rates are within the range of erosion rates determined from glacial and fluvial dominated landscapes worldwide exemplifying the effectiveness of wind to erode and transport significant quantities of bedrock

cenozoic environmental evolution of the qaidam basin and its implications for the uplift of the tibetan plateau and the drying of central asia abstract a complete cenozoic pollen sequence of the qaidam basin has been constructed with absolute age control the cenozoic environmental evolution of the qaidam basin and its implications for the uplift of the tibetan plateau and the drying of central asia during the cenozoic era is discussed based on the interpretation of the pollen sequence the commencement of eolian deposition in central china and the change of climatic distribution pattern of china the results suggest that in the qaidam basin relatively dry climates prevailed in the eocene oligocene and pliocene pleistocene these dry periods resulted from the effects of a subtropical high pressure zone and the uplift of the surrounding mountains and the tibetan plateau respectively about a 600 km northward drift of western china has probably occurred during the late cenozoic resulting in the eocene oligocene arid climate belt twisting about six degrees of latitude the tibetan plateau reached probably 1500 m elevation by the latest miocene 8 5 ma not as high as it was thought previously the cenozoic environmental evolution of northwest china does not support the idea that the retreat of the paratethys sea played an important role in the late cenozoic drying of central asia at least not in northwest china

application of self organizing map and srtm data to characterize yardangs in the lut desert iran abstract yardangs an exclusive landform due to intensive wind erosion cover a large area in the hyper arid lut desert of iran this paper presents a new approach using self organizing map som as unsupervised algorithm of artificial neural networks for analysis and characterization of yardangs nowadays the shuttle radar topography mission srtm with 3 arc sec data approximately 90 m resolution and nearly world wide coverage provides uniform good quality data the srtm 3 arc sec data were re projected to a 90 m utm grid bivariate quadratic surfaces with moving window size of 5 5 were fitted to this dem the first derivative slope steepness and the second derivatives minimum maximum curvature and cross sectional curvatures were calculated as geomorphometric parameters used as input to the soms 42 soms with different learning parameter settings e g initial and final radius number of iterations and the effect of random initial weights on average quantization error were investigated a som with a low average quantization error 0 1040 was used for further analysis feature space analysis morphometric signatures three dimensional inspection auxiliary data like landsat etm and high resolution satellite imagery from quickbird facilitated the assignment of semantic meaning to the output classes in terms of geomorphometric features results are provided in a geographic information system as thematic maps of landform entities based on form and slope e g yardangs ridge corridors valley or planar areas the results showed that all yardangs and corridors were clearly recognized and classified by this method when their width was larger than the dem resolution but became unrecognizable if their width is much smaller than the grid resolution the identified yardangs and corridors are aligned nnw sse parallel to the prevailing direction of the strong local 120 days wind and cover about 31 and 42 of the study area respectively the results demonstrate that som is a very efficient tool for analyzing aeolian landforms in hyper arid environments that provides very useful information for terrain feature analysis in remote regions

north atlantic deepwater temperature change during late pliocene and late quaternary climatic cycles variations in the ratio of magnesium to calcium mg ca in fossil ostracodes from deep sea drilling project site 607 in the deep north atlantic show that the change in bottom water temperature during late pliocene 41 000 year obliquity cycles averaged 1 5 c between 3 2 and 2 8 million years ago ma and increased to 2 3 c between 2 8 and 2 3 ma coincidentally with the intensification of northern hemisphere glaciation during the last two 100 000 year glacial to interglacial climatic cycles of the quaternary bottom water temperatures changed by 4 5 c these results show that glacial deepwater cooling has intensified since 3 2 ma most likely as the result of progressively diminished deepwater production in the north atlantic and of the greater influence of antarctic bottom water in the north atlantic during glacial periods the ostracode mg ca data also allow the direct determination of the temperature component of the benthic foraminiferal oxygen isotope record from site 607 as well as derivation of a hypothetical sea level curve for the late pliocene and late quaternary the effects of dissolution on the mg ca ratios of ostracode shells appear to have been minimal

holocene yardangs in volcanic terrains in the southern andes argentina yardangs of different sizes were developed in the payun matru volcanic field a semiarid area east of the southern andes mountains yardangs from volcanic terrains have not been described previously from earth although studies from mars interpreted linear ridges found by mariner and viking images as yardangs the payun matru volcanic field is an extensive plateau at 2000 m a s l covered by basaltic lava and ignimbrite flows strong westerly winds affect the extensive plateau micro and mesoyardangs are formed on the ignimbrite rock blanket and macroforms or megayardangs several kilometres in length are developed in the basaltic lava flows as long parallel troughs they all have a distinctive 320 azimuth which is the prevailing wind direction no yardang features are noted in the more recent lava flows younger than 1000 years indicating that their formation needed a longer time or they developed in earlier periods with stronger winds the yardang development is explained by the strong unidirectional winds the poor vegetational cover due to the aridity of the region the available quartz sand and volcanic ash particles as abrasive agents and the volcanic lithology texture and flow structure copyright 2001 john wiley sons ltd

foehn jets over the larsen c ice shelf antarctica previously unknown foehn jets have been identified to the east of the antarctic peninsula ap above the larsen c ice shelf these jets have major implications for the east coast of the ap a region of rapid climatic warming and where two large sections of ice shelf have collapsed in recent years during three foehn events across the ap leeside warming and drying is seen in new aircraft observations and simulated well by the met office unified model metum at 1 5 km grid spacing in case a weak southwesterly flow and an elevated upwind inversion characterise a highly nonlinear flow regime with upwind flow blocking in case c strong northwesterly winds characterise a relatively linear case with little upwind flow blocking case b resides somewhere between the two in flow regime linearity the foehn jets apparent in aircraft observations where available and metum simulations of all three cases are mesoscale features up to 60 km in width originating from the mouths of leeside inlets through back trajectory analysis they are identified as a type of gap flow in cases a and b the jets are distinct being strongly accelerated relative to the background flow and confined to low levels above the larsen c ice shelf they resemble the shallow foehn of the alps case c resembles a case of deep foehn with the jets less distinct the foehn jets are considerably cooler and moister relative to adjacent regions of calmer foehn air this is due to a dampened foehn effect in the jet regions in case a the jets have lower upwind source regions and in the more linear case c there is less diabatic warming and precipitation along jet trajectories due to the reduced orographic uplift across the mountain passes

aeolian bedforms yardangs and indurated surfaces in the tharsis montes as seen by the hirise camera evidence for dust aggregates abstract hirise images of mars with ground sampling down to 25 cm pixel show that the dust rich mantle covering the surfaces of the tharsis montes is organized into ridges whose form and distribution are consistent with formation by aeolian saltation other dusty areas near the volcanoes and elsewhere on the planet exhibit a similar morphology the material composing these reticulate bedforms is constrained by their remote sensing properties and the threshold curve combined with the saltation suspension boundary both of which vary as a function of elevation atmospheric pressure particle size and particle composition considering all of these factors dust aggregates are the most likely material composing these bedforms we propose that airfall dust on and near the volcanoes aggregates in situ over time maybe due to electrostatic charging followed by cementation by salts the aggregates eventually reach a particle size at which saltation is possible aggregates on the flanks are transported downslope by katabatic winds and form linear and accordion morphologies materials within the calderas and other depressions remain trapped and are subjected to multidirectional winds forming an interlinked honeycomb texture in many places on and near the volcanoes light toned low thermal inertia yardangs and indurated surfaces are present these may represent duststone formed when aggregates reach a particle size below the threshold curve such that they become stabilized and subsequently undergo cementation

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

discrimination of fluvial and eolian features on large ignimbrite sheets around la pacana caldera chile using landsat and srtm derived dem abstract satellite images and ground based observations were used to investigate the morphology and origin of valleys and ridges across large ignimbrite provinces around la pacana caldera n chile we studied 12 separate sites that included five different ignimbrite units that range in age from 5 6 0 5 ma to 1 35 0 15 ma over 400 features from within these study sites were quantified study sites typically have dimensions of 25 35 km measurements were made using landsat tm etm and srtm derived dem and shaded relief images morphological measurements were made of the ridges and channels including the direction of regional slope length orientation and gradient of each feature a classification of the different ignimbrite erosion influences resulting in varying landscape morphologies identified 4 landscape types fluvial eolian modified and complex we conclude that the most prevalent features are fluvial derived channels but the most distinctive are linear wind derived ridges the orientation of these ridges suggests that strong uni directional winds from the northwest have been constant over a long period of time 1 my

eastward migration of the qaidam basin and its implications for cenozoic evolution of the altyn tagh fault and associated river systems the qaidam basin is the largest cenozoic intermontane basin within the tibetan plateau bounded by the qilian shan range to the north the east kunlun range to the south the altyn tagh range to the west and the ela shan range to the east its deposits consist of nonmarine sedimentary rocks with a maximum thickness exceeding 13 400 m modern sedimentation mainly takes place along the marginal areas of the basin where alluvial fans are formed along a series of rivers that originate from the surrounding mountains nevertheless drilling sedimentary and seismic data reveal that the depocenter of the basin during much of cenozoic time was not developed as foreland basins of the qilian shan belt to the north and the east kunlun belt to the south but instead the depocenter was in the center of the western part of the basin and had a northwest southeast trend that shifted eastward 380 km during oligocene to quaternary time this indicates that most of the basin sediments were not derived from the surrounding mountain ranges the results of the fi ssion track age dating reveal that the rapid uplift of the yousha shan anticline bounding the depocenter to the southwest initiated at ca 31 ma indicating that the southeastward shift of the depocenter began at that time yielding a migration rate for the depocenter of 10 2 mm yr the northwestern margin of the depocenter of the qaidam basin lies to the east of the westward prolongation of the qaidam basin the tula trough a 300 km long narrow trough fl anked by the altyn tagh range along the altyn tagh strikeslip fault on the north and the east kunlun thrust belt on the south the sedimentary and deformational evidence from this region indicates that the tula trough was formed as a syncline along which a paleoriver fl owed to the east into the qaidam basin to the southwest this river valley merges with the trace of the altyn tagh fault the latter and its westward continuation are interpreted to have extended to the northern margin of the pamir folded belt north of the western syntaxis of the himalaya we propose that most of the sediments within the depocenter of the qaidam basin were transported from the northern margin of the pamir folded belt along a progressively lengthening 2000 kmlong longitudinal river that developed along the left lateral altyn tagh fault and its western continuation as the eastward extrusion of the tibetan plateau took place in oligocene time both the crustal uplift and continuous southeastward aggradations of the sediments carried by the paleo kunlun river are interpreted to be the cause for southeastward migration of the depocenter of the qaidam basin the longitudinal river disappeared in late cenozoic time 2 4 ma due to stream capture and climate change

impact of wind erosion on detecting active tectonics from geomorphic indexes in extremely arid areas a case study from the hero range qaidam basin nw china abstract geomorphologic analysis has been used widely to detect active tectonics in regions where fluvial incision is the major erosional process in this paper however we assess the feasibility of utilizing these frequently used geomorphic indexes e g hypsometric curves longitudinal channel profiles normalized stream length gradient slk index to determine active tectonics in extremely arid areas where wind erosion also plays an important role the case study is developed on the hero range in the western qaidam basin one of the driest regions on earth with severe wind erosion since late pliocene the result shows that in the west and south sectors as well as the western part of the east sector of the hero range where fluvial incision prevails these geomorphic indexes are good indicators of active faulting and consistent with the geological result based on study of fault traces scarps faulted holocene fans and historical seismicity within the past four decades in contrast along the northeastern margin the ne and the se parts of the east sector of the range where wind erosion is also important the results from the geomorphic indexes show quite active tectonics contrary with the geological evidence favoring weakly active tectonics moreover the positive slk anomaly lies oblique to the fault trace and the anticline axis but parallel to the wind direction to reconcile the contradiction we propose that wind erosion caused by northwestern winds has a tendency to make geomorphic indexes exhibit anomalous values that indicate higher activities by way of 1 lowering the base level to generate knickpoints on the longitudinal channel profiles and therefore positive slk anomalies and 2 lateral erosion of the mountain front making the hypsometric curves and even the longitudinal channel profiles more convex and producing obvious slope breaks

aeolian scours as putative signatures of wind erosion and sediment transport direction on mars abstract obstacle marks specifically current crescents scours formed by aeolian erosion have not been previously identified on mars from orbit however recent mars reconnaissance orbiter images of an unnamed intracrater dune field within the hellespontus region have shown innumerable meter scale scours around fine and medium grade blocks the types relative numbers and distributions of scour features served to determine by proxy the modes of surface wind direction and pathways of sediment transport across the crater floor the orientations of scours of u type morphology as well as the facing directions of leeward slopes for crescentic dunes barchans and barchanoids and megaripples were examined by statistical methods to determine their reference directions and dispersion of modal classes we showed that although the dune field has evolved primarily under the influence of winds from the southwest u type scours have developed predominantly from a significant northwesterly wind direction these data suggest that the dune field has evolved under the influence of a bimodal wind regime furthermore such an aeolian system may help to explain the intermediary morphology between crescentic and linear for the central part of the dune field in which the dunes appear to have undergone longitudinal as well as lateral sediment transport in the absence of direct measurements of wind directions and strengths current crescents offer detailed data from which planetary air flow at the surface air interface can be better interpreted for the many intracrater settings across mars

deflation in the dustiest place on earth the bodele depression chad the bodele depression in chad is the largest single source of dust on earth because of a combination of strong near surface winds and a large reservoir of readily eroded and easily entrained low density sediment during the holocene and late pleistocene the bodele depression was host to a great lake palaeolake megachad that is now completely desiccated leaving the lake bed sediments exposed to deflation deflation in the bodele depression is revealed in erosional remnants of lake bed deposits exposed as yardangs on the lake floor erosional remnants indicate that locally up to 4 m of sediment has been removed by deflation optically stimulated luminescence dating shows that this occurred in less than 2400 years giving a rate of deflation of at least 1 6 mm yr 1 a range of other geomorphological features indicate that in some areas rates of deflation may be greater than or equal to 10 mm yr 1 deflation appears to be greatest in an arc around the northeastern margins of the lake basin where the diatomite deposits have been removed and revealed an underlying network of distributary channels preserved as gravel capped ridges the ridges which are part of an inverted topography are interpreted as deltaic distributary channels from an inland delta similar to the okavango delta examples of barchan dunes exist that were flooded by the palaeolake and which have now been exhumed from beneath layers of diatomite the distribution of extensive deflation around the northeasterly upwind end of the bodele depression probably results from a combination of large wind velocities an upwind source of abrasive sand and thinner diatomite deposits around the lake margin satellite image analysis shows that outcropping diatomite covers 24 049 km2 of the bodele depression furthermore the area from which diatomite has been removed by deflation is around 14 000 km2 combining this information with the ages and rates of deflation mentioned above indicates that some 61 000 km3 of diatomite has been eroded from the bodele depression during the past 1000 years

wind erosion on the north eastern tibetan plateau constraints from osl and u th dating of playa salt crust in the qaidam basin the arid qaidam basin is the largest 3 88 x 10 4 km 2 basin on the north eastern tibetan plateau wind erosion in the area has been regarded as an important trigger for intra basin tectonic balance upheaval geomorphologic development and as a major supplier of dust to the chinese loess plateau downwind an initial estimate of the rate of wind erosion kapp et al 2011 based on geological cross sections has suggested up to 3 2 x 10 4 km 3 of sediments has been deflated over the past 2 8 ma lowering the landscape by an average of 0 29 mm yr in this paper we re evaluate this estimate by dating surface crusts present on three playas within the basin understanding the development of these playas is crucial to assessing the overall role of the wind in shaping the regional landscape because they are typically capped with a thick salt crust which effectively protects them from wind erosion optically stimulated luminescence osl and u series dating from a pit section and from the top of a deep drill core together with results from magnetostratigraphy and a climate proxy record correlated to the marine oxygen isotope record are used here to determine the age of the playa plains and suggest that the salt crusts have an age of c 0 1 ma this young age and the wide distribution of resistant thick salt crusts of the playa plains indicate a much lower degree of wind erosion than previously suggested the crusts protect the surface from significant surface erosion including sediment exhumation and unloading and whilst some wind erosion does occur it is unlikely to be sufficient to trigger tectonic uplift of the basin or to be a major dust source for the loess plateau as previously suggested copyright c 2013 john wiley sons ltd

evolution of the yardangs at rogers lake california yardangs are streamlined wind eroded hills common to most deserts yardangs at rogers lake mojave desert california have streamlined forms characteristic of objects eroded by moving fluids a teardrop shape that approaches an ideal 1 4 width to length ratio in wind tunnel simulations miniature forms of various shapes changed sequentially by 1 erosion of the windward corners 2 erosion of the windward slope 3 erosion of the leeward corners and flanks and 4 erosion of the leeward slope prominent mechanisms in yardang evolution apparently are abrasion at the windward end and deflation and reverse air flow near the middle and at the downstream end width to length ratios of yardangs are grossly similar to those of some fluvial and glacial streamlined landforms the low kinetic energy of wind relative to ice and water the erosional resistance to wind of most rocks the rarity of long term unidirectional winds and the presence of running water topographic roughness and vegetation all limit the abundance of yardangs

origin and characteristics of yardangs in the um al rimam depressions n kuwait article i nfo although arabia hosts one of the largest deserts in the world studies regarding aeolian erosional features in general and yardangs in particular are rare the principal aim of this study is to delineate and investigate the various forms of yardangs in the um al rimam depressions in the northern part of kuwait the study area consists of two main depressions connected by neck area made up of continental sediments both depressions are surrounded by a dissected escarpment and their floors host muddy playas on lithological bases three main types of yardang have been identified 7 yardangs are sculptured in sandstones of lower fars formation lower to middle miocene 23 are carved in calcretic rocks of ghar formation oligocene to lower miocene and 11 yardangs are developed in quaternary sediments their mean orientation nw 297 coincides with the prevailing direction of the strong local northwesterly wind called the shamal the average length width ratio is 1 5 1 the wide geographic distribution of yardangs around the margins of the northern depression is due to sand blasting this is explained by the annual sand accumulation measured in the study area where the northern depression shows 143 times higher accumulation than the southern depression the neck area and the platform above the depressions also the field measurements for annual erosional rates show that the sides of the yardangs are more affected by erosion compared to their middle parts remarkably slight mineralogical variations were detected within the surface sediments of um al rimam depressions and the quaternary muddy yardangs which indicate a common origin the age of yardangs is unknown but annual erosional rates on a small quaternary muddy yardang suggest that they range in age between 44 and 1500 years depending on yardang size it is believed as indicated from field observation and interpretation of aerial photos that the majority of yardangs are pre existing bedrock forms these forms were developed by paleo surface hydrological processes which were modified by wind action in latter phase

on origin of near axis volcanism and faulting at fast spreading mid ocean ridges at fast and superfast spreading mid ocean ridges such as the east pacific rise a plate boundary is defined by a narrow tens to hundreds of meters wide neovolcanic zone within which the bulk of the upper oceanic crust is created however detailed near bottom observations indicate that the volcanic construction may occasionally persist several kilometers off of the ridge axis it has been proposed that off axis volcanism manifests tapping of a wide melting region that supplies magma to the ridge axis or spatial migration of magmatic sources in the crust and upper mantle we demonstrate that off axis eruptions may be a natural consequence of variations in magma supply rate even if the ridge axis is stationary in space and the magma delivery is perfectly focussed at the ridge axis theoretical modeling and field observations indicate that off axis volcanism may result from magma emplacement in sills that propagate toward the surface after their characteristic horizontal size exceeds their emplacement depth volcanic construction and faulting due to sill intrusions may contribute to the formation of abyssal hills arguably the most abundant relief form on earth fl 2001 elsevier science b v all rights reserved

holocene late pleistocene climatic ice core records from qinghai tibetan plateau three ice cores to bedrock from the dunde ice cap on the north central qinghai tibetan plateau of china provide a detailed record of holocene and wisconsin wurm late glacial stage lgs climate changes in the subtropics the records reveal that lgs conditions were apparently colder wetter and dustier than holocene conditions the lgs part of the cores is characterized by more negative 18 o ratios increased dust content decreased soluble aerosol concentrations and reduced ice crystal sizes than the holocene part these changes occurred rapidly 10 000 years ago in addition the last 60 years were apparently one of the warmest periods in the entire record equalling levels of the holocene maximum between 6000 and 8000 years ago

yardang evolution from maturity to demise yardangs are enigmatic wind parallel ridges sculpted by aeolian processes that are found extensively in arid environments on earth and mars no general theory exists to explain the long term evolution of yardangs curtailing modeling of landscape evolution and dynamics of suspended sediment release we present a hypothesis of yardang evolution using relative rates of sediment flux interyardang corridor downcutting yardang denudation substrate erodibility and substrate clast content to develop and sustain yardangs corridor downcutting must exceed yardang vertical denudation and deflation however erosion of substrate yields considerable quantities of sediment that shelters corridors slowing downcutting we model the evolution of yardangs through various combinations of rates and substrate compositions demonstrating the life span suspended sediment release and resulting landscape evolution we find that yardangs have a distinct and predictable evolution with inevitable demise and unexpectedly dynamic and autogenic erosion rates driven by subtle differences in substrate clast composition

quantifying dust emissions from desert landforms eastern mojave desert usa abstract the measurement of natural dust emissions from desert landforms is crucial in environmental hazard assessment and field checking the accuracy of global dust models more than 500 individual dust measurements from eight common desert landforms in southern california were collected using the pi swerl portable in situ wind erosion lab the largest emitters of dust are dry washes 13 787 to 0 007 mg m 2 s 1 dunes playa margins distal alluvial fans and lacustrine beaches low emitters include salt crusted playas 0 692 to 0 002 mg m 2 s 1 silt clay crusted playas and desert pavements high emissions are a function of saltating sand that bombards the surface liberating dust sized particles for entrainment low dust emissions are primarily a function of surface crusting gravel armoring and vegetation density pi swerl measurements reveal that emission rates can vary by at least three orders of magnitude reflecting local variability in soil texture and continuity of surface crusts shear stress partitioning models can be applied to dust data measured by the pi swerl to account for large surface roughness features such as vegetation the results presented here give an approximation of the contributions to atmospheric dust loading by landforms in the mojave desert and can potentially be used to improve atmospheric dust models

role of river incision in enhancing deformation many active compressional belts contain examples of transverse rivers intersecting anticlines at their highest structural and topographic position this unusual association between rivers and doubly plunging anticlines at relatively small scales is usually explained by some form of antecedence or superposition in this article i suggest an alternative explanation i e that river erosion unloads the crust and that this process causes local deformation to be enhanced in the vicinity of rivers i show the plausibility of this hypothesis with the aid of a coupled three dimensional mechanical surface process mathematical model the conclusion is that river incision can have a major influence on deformation of the surrounding crust if incision occurs at the same time that the crust is deforming plastically in response to regional compression in this case incision amplifies background deformation at a relatively small scale leading to the formation of noncylindrical folds with culminations coinciding with river incision in the absence of regional deformation the response of the crust to river incision is small and of long wavelength because it is governed by flexural isostasy of relatively rigid elastic crust thus whether rivers exert an influence on local deformation depends critically on the timing between river incision and regional deformation this point may explain why in some cases rivers appear to have had no significant influence on local deformation whereas in other cases they have