the use of multivariate statistics to elucidate patterns of floodplain sedimentation at different spatial scales floodplains are depositional features of riverine landscapes that display complex sedimentation patterns that are amenable to multi scale approaches we examined sedimentation in the lower balonne floodplain queensland australia at three different spatial scales the channel 103 km floodplain process zone 10 km and geomorphic unit 102 m scales and compared scale related patterns evident from stratigraphy with those evident from quantitative multivariate analysis three stratigraphic sequences were found in the lower balonne floodplain generally fining upward episodic fining upward and mud dominated stratigraphical analysis revealed the detailed character of sedimentary sequences embedded within the scale patterns derived from multivariate analysis multivariate statistical analyses of a range of textural and geochemical data revealed different patterns of floodplain sedimentation at each scale at the channel scale sediment texture and geochemistry were more heterogeneous in the culgoa river than in briarie creek at the floodplain process zone scale clear patterns of sediment texture and geochemistry were observed along the upper mid and lower floodplain process zones of briarie creek but not along the culgoa river at the geomorphic unit scale clear patterns of sediment texture and geochemistry were observed among the bank buried channel and flat floodplain units of the culgoa river but were not as clear in briarie creek recognition of rivers as hierarchically organized systems is an emerging paradigm in river science our study supports this paradigm by demonstrating that different sedimentation patterns occur at different scales to reveal a hierarchically organized floodplain environment copyright 2006 john wiley sons ltd

paleolatitudes determined from paleomagnetic data from vertical cores most of the paleomagnetic data available from oceanic plates consist of measurements of inclination but not declination from azimuthally unoriented vertical cores similarly the basic paleomagnetic data to be analyzed from crustal blocks that have rotated by varying amounts about vertical axes are a set of paleoinclinations a new method is proposed for determining the paleocolatitude of a sampling site and the associated confidence limits paleomagnetic inclinations are first converted to paleocolatitudes and averaged to produce a mean colatitude after showing that this mean is biased we derive a paleocolatitude correction to remove the bias using a model for geomagnetic secular variation based on the latitude dependence of secular variation during the past 5 million years after testing the validity of the model by applying it to paleomagnetic data from quaternary lavas for which both inclination and declination are known we apply the method to inclination only paleomagnetic data from suiko seamount the most complete data set from a drilling site the method is then applied to paleomagnetic data from all deep sea drilling project sites for the pacific plate to obtain for each site an unbiased mean paleocolatitude and its confidence limits these paleocolatitudes and confidence limits are then used as input for a least squares analysis to obtain early and late cretaceous poles for the pacific plate and 95 confidence limits for these poles it is shown that the scatter of individual site paleocolatitudes about the best fit pole is consistent with the confidence limits at each site as determined by the new method of analysis

tracking the late jurassic apparent or true polar shift in u pb dated kimberlites from cratonic north america superior province of canada different versions of a composite apparent polar wander apw path of variably selected global poles assembled and averaged in north american coordinates using plate reconstructions show either a smooth progression or a large 30 gap in mean paleopoles in the late jurassic between about 160 and 145 ma in an effort to further examine this issue we sampled accessible outcrops subcrops of kimberlites associated with high precision u pb perovskite ages in the timiskaming area of ontario canada the 154 9 1 1 ma peddie kimberlite yields a stable normal polarity magnetization that is coaxial within less than 5 of the reverse polarity magnetization of the 157 5 1 2 ma triple b kimberlite the combined 156 ma triple b and peddie pole 75 5 n 189 5 e a95 2 8 lies about midway between igneous poles from north america nearest in age 169 ma moat volcanics and the 146 ma ithaca kimberlites showing that the polar motion was at a relatively steady yet rapid 1 5 myr pace a similar large rapid polar swing has been recognized in the middle to late jurassic apw path for adria africa and iran eurasia suggesting a major mass redistribution one possibility is that slab breakoff and subduction reversal along the western margin of the americas triggered an episode of true polar wander

spectrally based remote sensing of river bathymetry this paper evaluates the potential for remote mapping of river bathymetry by 1 examining the theoretical basis of a simple ratio based technique for retrieving depth information from passive optical image data 2 performing radiative transfer simulations to quantify the effects of suspended sediment concentration bottom reflectance and water surface state 3 assessing the accuracy of spectrally based depth retrieval under field conditions via ground based reflectance measurements and 4 producing bathymetric maps for a pair of gravel bed rivers from hyperspectral image data consideration of the relative magnitudes of various radiance components allowed us to define the range of conditions under which spectrally based depth retrieval is appropriate the remotely sensed signal must be dominated by bottom reflected radiance we developed a simple algorithm called optimal band ratio analysis obra for identifying pairs of wavelengths for which this critical assumption is valid and which yield strong linear relationships between an image derived quantity x and flow depth d obra of simulated spectra indicated that water column optical properties were accounted for by a shorter wavelength numerator band sensitive to scattering by suspended sediment while depth information was provided by a longer wavelength denominator band subject to strong absorption by pure water field spectra suggested that bottom reflectance was fairly homogeneous isolating the effect of depth and that radiance measured above the water surface was primarily reflected from the bottom not the water column obra of these data 28 of which were collected during a period of high turbidity yielded strong x versus d relations r2 from 0 792 to 0 976 demonstrating that accurate depth retrieval is feasible under field conditions moreover application of obra to hyperspectral image data resulted in spatially coherent hydraulically reasonable bathymetric maps though negative depth estimates occurred along channel margins where pixels were mixed this study indicates that passive optical remote sensing could become a viable tool for measuring river bathymetry copyright 2009 john wiley sons ltd

riverscape mapping and hyperscale analysis of the sediment links concept abstract longitudinal patterns in channel complexity play an important role in our understanding of fluvial systems the spatial scales over which external controls such as tributaries landslides and debris flows alter channel form and influence the broader basin wide trends in channel form channel complexity across a basin has important implications for how we conceptualize basin wide trends in channel form such as downstream hydraulic geometry and the sediment links concept this study takes a hyperscale approach to mapping channel morphology across 200 km of the rogue river in southwest oregon that is high resolution data over large spatial extents allowing analysis to be conducted simultaneously at and across multiple spatial scales using a suas and digital photosieving we measured gravels on exposed gravel bars for the study area we also measured thalweg depth in the field using a singlebeam echo sounder slope and channel width were derived using existing gis datasets we used these data to create a hyperscale view of the rogue river examining the impact of tributary and non tributary sediment links we used a statistical approach to determine if changes in channel form were truly unique in the context of larger scale channel variability our findings show inconsistent statistical significance of the identified lateral sediment sources lss between variables e g a statistically significant change in slope would not necessarily correlate with an increase in unit stream power there were many lss which triggered statistically significant changes to channel form we used hyperscale graphs to reveal the complexity and spatial trends associated with the relationships between a given sediment link and channel form the results of this study illustrate the complexity with which sediment links impact channel form and the distances below a given sediment link that a detectable signal exists if a detectable signal exists

spatial variation in the power of mountain streams in the sangre de cristo mountains new mexico the principle indicator of river energy expenditure stream power has a significant influence on many forms and process attributes of the fluvial system yet few basin wide analyses of stream power variations have ever been conducted recent studies hypothesize a peak in the mean stream power distribution in small 10 km2 to intermediate 100 km2 sized basins to test hypothetical stream power profiles in a high mountain setting 129 cross sections of stream networks within the costilla basin of northern new mexico and southern colorado were measured for channel form local sediment conditions and basin characteristics geomorphic and hydrologic analysis of these river sites throughout the costilla basin yielded evidence of abundant local control over fluvial processes and forms within the basin the spatial deviations of stream power from the hypothetical patterns derived from hydraulic geometry in some cases 200 deviation match areas of specific geologic and hydrogeologic control as an alternative to traditional hydraulic descriptions of downstream channel form a probabilistic process response model can incorporate local and basin scale variables and allow more realistic feedback mechanisms than in traditional regime theory the probabilistic nature of this type of model also allows prediction of multiple modes of channel adjustment an ever present challenge to extremal and physically based simulations

tributary connectivity confluence aggradation and network biodiversity in fluvial networks some confluences are associated with tributary driven aggradation where coarse sediment is stored downstream sediment connectivity is interrupted and substantial hydraulic and morphological heterogeneity is generated to the extent that biological diversity is supported by physical diversity it has been proposed that the distribution and frequency of tributary driven aggradation is important for the magnitude and spatial structure of river biodiversity relevant ideas are formulated within the link discontinuity concept and the network dynamics hypothesis but many of the issues raised by these conceptual models have not been systematically evaluated this paper first tests an automated method for predicting the likelihood of tributary driven aggradation in three large drainage networks in the rocky mountain foothills canada the method correctly identified approximately 75 of significant tributary confluences and 97 of insignificant confluences the method is then used to evaluate two hypotheses of the network dynamics hypothesis that linear shaped basins are more likely to show a longitudinal downstream decline in tributary driven aggradation and that larger and more compact basins contain more confluences with a high probability of impact the use of a predictive model that included a measure of tributary basin sediment delivery rather than symmetry ratio alone mediated the outcomes somewhat but as anticipated the number of significant confluences increased with basin size and basin shape was a strong control of the number and distribution of significant confluences doubling basin area led to a 1 9 fold increase in the number of significant confluences and compact basins contained approximately twice as many significant confluences per unit channel length as linear basins in compact basins significant confluences were more widely distributed whereas in linear basins they were concentrated in proximal reaches interesting outstanding issues include the possibility of using spatially distributed sediment routing models to predict tributary driven confluence aggradation and the need to gather ecological data sufficient to properly test for increases in local and network scale biodiversity associated with significant confluences and their network scale controls

anomalous late jurassic motion of the pacific plate with implications for true polar wander abstract true polar wander or tpw is the rotation of the entire mantle crust system about an equatorial axis that results in a coherent velocity contribution for all lithospheric plates one of the most recent candidate tpw events consists of a 30 rotation during late jurassic time 160 145 ma however existing paleomagnetic documentation of this event derives exclusively from continents which compose less than 50 of the earth s surface area and may not reflect motion of the entire mantle crust system additional paleopositional information from the pacific basin would significantly enhance coverage of the earth s surface and allow more rigorous testing for the occurrence of tpw we perform paleomagnetic analyses on core samples from ocean drilling program odp site 801b which were taken from the oldest available pacific crust to determine its paleolatitude during the late jurassic and early cretaceous 167 133 ma we find that the pacific plate underwent a steady southward drift of 0 49 0 74 my 1 except for an interval between kimmeridgian and tithonian time 157 147 ma during which it underwent northward motion at 1 45 0 76 my 1 1 this trajectory indicates that the plates of the pacific basin participated in the same large amplitude 30 rotation as continental lithosphere in the 160 145 ma interval such coherent motion of a large majority of the earth s surface strongly supports the occurrence of tpw suggesting that a combination of subducting slabs and rising mantle plumes was sufficient to significantly perturb the earth s inertia tensor in the late jurassic

machine detection of martian impact craters from digital topography data research on automatic identification of impact craters on mars and other planetary bodies has concentrated on detecting them from imagery data we present a novel approach to crater detection that utilizes digital topography data instead of images craters are delineated by topographic curvature thresholding maps of curvature transforms topographic data into a binary image from which craters are identified using a combination of segmentation and detection algorithms we apply our method to a large and technically demanding test site and compare the results to the existing catalog of manually identified craters our algorithm finds many small craters not listed in the manual catalog but it fails to detect heavily degraded craters a detailed quality assessment of the algorithm is presented the topography based crater detection algorithm offers a relatively simple and ready to use tool for identification and characterization of fresh impact craters with an adequate performance for the immediate application to martian geomorphology

high resolution 40ar 39ar dating of the oldest oceanic basement basalts in the western pacific basin 1 we report new 40ar 39ar ages for the oldest pacific oceanic floor at ocean drilling program site 801c in the pigafetta basin and site 1149d close to the izu bonin subduction zone in the nadezhda basin these ages were determined by applying high resolution incremental heating experiments including 15 30 heating steps to better resolve the primary argon signal from interfering alteration signatures in these low potassium ocean crust basalts combined with previous results from pringle 1992 for site 801b and 801c we arrive at a multistage history for the formation of the pigafetta ocean crust the oldest part of the pacific plate was formed at the spreading ridges at 167 4 1 4 3 4 ma n 2 2 internal absolute error offering an important calibration point on the geological reversal timescale grts since it represents the old end of the mesozoic magnetic anomalies this mid ocean ridge basalt sequence however is overlain by more tholeiites and alkali basalts that were formed 7 3 1 5 myr later around 160 1 0 6 ma n 7 2 internal error the older age group is confirmed independently by radiolarian ages ranging from late bajocian to middle bathonian 167 173 ma bartolini and larson 2001 and by profound differences in the structural characteristics of this basement section pockalny and larson 2003 thin layers comprising hydrothermal deposits separate these sequences which in addition to the difference in isotopic age show distinct major and trace element compositions this indicates that key volcanic and hydrothermal activity took place 400 600 km away from the spreading ridges on the basis of a jurassic 66 km myr half spreading rate in the pacific it remains unclear if these processes were active continuously after the initial formation of the pacific oceanic crust but all our observations seem to point to an episodic history site 1149d gives another important calibration point on the grts of 127 0 1 5 3 6 ma n 1 2 internal absolute error for anomaly m12 that is slightly younger when compared to current timescale compilations 134 2 2 1 ma gradstein et al 1995 this might suggest that the dated basalt from site 1149d does not represent the age of the ocean crust formed at its ridge axis it may also be part of the early cretaceous intraplate events that have produced dolerite sills in the pacific crust at sites 800 and 802 around 114 126 ma

the drift history of adria and africa from 280 ma to present jurassic true polar wander and zonal climate control on tethyan sedimentary facies article i nfo the orogenic belts surrounding the undeformed adriatic sea represent the margins of an area known as adria the african promontory we have undertaken a critical appraisal of paleomagnetic data from regions of adria considered parautochthonous relative to africa obtained either from biostratigraphically dated sed imentary rocks corrected for inclination shallowing or from igneous rocks that are regarded as free from any inclination shallowing bias paleomagnetic directions were used to calculate paleomagnetic poles for compar ison with coeval and inclination flattening free paleomagnetic poles from stable africa visual coherence of paleopoles for several time slices from the early permian to the eocene supports the construction of a com posite apparent polar wander path apwp valid for parautochthonous adria and stable africa this compos ite apwp is compared to previous apwps finding good agreement with the global apwp of kent and irving 2010 both apwps show a remarkable and rapid polar shift of 40 in the jurassic that other apwps tend to underestimate we interpret this shift to represent a major episode of true polar wander tpw from 183 ma in the early jurassic to 151 ma in the late jurassic using a simple zonal climate model the drift motion of adria attached to africa appears to be consistent with the distribution of permian cretaceous sed imentary facies on adria

late cretaceous polar wander of the pacific plate evidence of a rapid true polar wander event we reexamined the late cretaceous early tertiary apparent polar wander path for the pacific plate using 27 paleomagnetic poles from seamounts dated by 40ar 39ar geochronology the path shows little motion from 120 to 90 million years ago ma northward motion from 79 to 39 ma and two groups of poles separated by 16 to 21 degrees with indistinguishable mean ages of 84 2 ma the latter phenomenon may represent a rapid polar wander episode 3 to 10 degrees per million years whose timing is not adequately resolved with existing data similar features in other polar wander paths imply that the event was a rapid shift of the spin axis relative to the mantle true polar wander which may have been related to global changes in plate motion large igneous province eruptions and a shift in magnetic field polarity state

towards absolute plate motions constrained by lower mantle slab remnants the movement of tectonic plates before the cretaceous period is poorly understood a global mantle tomography model suggests that the longitude of oceanic subduction zones up to 300 million years ago was offset by up to 18 compared with tectonic reconstructions for the same period

mapping gravel bed river bathymetry from space 1 understanding river form and behavior requires an efficient means of measuring channel morphology this study evaluated the potential to map the bathymetry of two clear flowing shallow 3 m deep gravel bed rivers 60 m wide from 2 m pixel worldview2 satellite images direct measurements of water column optical properties were used to quantify constraints on depth retrieval the smallest detectable change in depth was 0 01 0 04 m and the maximum detectable depth was 5 m in green bands but 2 m in the near infrared lower sensor radiometric resolution yields less precise estimates over a smaller range an algorithm for calibrating a band ratiox to field measurements of depth d proved effective when applied to spectra extracted from images r2 0 822 and 0 594 for the larger and smaller stream respectively or measured in the field r2 0 769 and 0 452 this procedure also identified optimal wavelength combinations but different bands were selected for each site accuracy assessment of bathymetric maps produced using various calibration approaches and image types indicated that 1 a linear d vs xrelation provided depth estimates nearly as accurate as a quadratic formulation 2 panchromatic and pan sharpened multispectral images with smaller 0 5 m pixels did not yield more reliable depth estimates than the original images and 3 depth retrieval was less reliable in pools due to saturation of the radiance signal this investigation thus demonstrated the feasibility as well as the limitations of measuring the bathymetry of clear shallow gravel bed rivers from space

depth probability distributions in stream reaches modeling spatial probability distributions of depth in natural stream reaches is of major interest to ecologists analyses of data from a wide range of streams at various stages show that depth probability distributions in reaches tend from exponential to normal with increasing stage this trend is modeled using a simple one parameter density function the model is robust and is a simple tool no topographic sampling nor expensive numerical calculation for predicting the evolution of depth probability distributions as a function of stage

mapping spatial patterns of stream power and channel change along a gravel bed river in northern yellowstone abstract stream power represents the rate of energy expenditure along a river and can be calculated using topographic data acquired via remote sensing or field surveys this study sought to quantitatively relate temporal changes in the form of soda butte creek a gravel bed river in northeastern yellowstone national park to stream power gradients along an 8 km reach aerial photographs from 1994 to 2012 and ground based surveys were used to develop a locational probability map and morphologic sediment budget to assess lateral channel mobility and changes in net sediment flux a drainage area to discharge relationship and dem developed from lidar data were used to obtain the discharge and slope values needed to calculate stream power local and lagged relationships between mean stream power gradient at median peak discharge and volumes of erosion deposition and net sediment flux were quantified via spatial cross correlation analyses similarly autocorrelations of locational probabilities and sediment fluxes were used to examine spatial patterns of sediment sources and sinks energy expended above critical stream power was calculated for each time period to relate the magnitude and duration of peak flows to the total volumetric change in each time increment collectively we refer to these methods as the stream power gradient spg framework the results of this study were compromised by methodological limitations of the spg framework and revealed some complications likely to arise when applying this framework to small wandering gravel bed rivers correlations between stream power gradients and sediment flux were generally weak highlighting the inability of relatively simple statistical approaches to link sub budget cell scale sediment dynamics to larger scale driving forces such as stream power gradients improving the moderate spatial resolution techniques used in this study and acquiring very high resolution data from recently developed methods in fluvial remote sensing could help improve understanding of the spatial organization of stream power sediment transport and channel change in dynamic natural rivers

quantifying fluvial non linearity and finding self organized criticality insights from simulations of river basin evolution abstract a numerical study was undertaken to investigate non linearity and the potential for self organized criticality soc in the evolution of river basins twenty three simulations were carried out using the authors caesar landscape evolution model in which the magnitude of storm events variability of storm events sediment heterogeneity sources of sediment supply and catchment morphology are systematically varied to evaluate their importance as possible drivers for non linear behavior and soc temporal fluctuations in simulated sediment yield show notable non linear behavior storm magnitude and occurrence of landslides appear to have little impact on variability of the sediment yield when compared to the impacts of sediment heterogeneity rainfall variability and catchment morphology particularly it appears that the non linearity of sediment yields results from the manner in which the catchment processes the variable rainfall rather than just the rainfall variability itself the variations in sediment yield show a power law magnitude frequency distribution which is a possible but inconclusive indicator of soc however several other more qualitative arguments can be made to support the case for soc in these simulations specifically we identify the nature of the critical state and suggest two cascade mechanisms by which the system can organize itself around this critical state combined these arguments indicate that simulated evolution of river basins indeed exhibits soc at least with respect to sediment yield the critical state appears to be an indicator of the connectivity of the drainage network thus the simulations indicate that unlike traditional soc systems the critical state of the system can vary in time as sudden changes in drainage network connectivity may result in sudden changes in the soc behavior of the system

streambank erosion rates and loads within a single watershed bridging the gap between temporal and spatial scales abstract the importance of streambank erosion to watershed scale sediment export is being increasingly recognized however few studies have quantified bank erosion and watershed sediment flux at the basin scale across temporal and spatial scales in this study we evaluated the spatial distribution extent and temporal frequency of bank erosion in the 5218 ha walnut creek watershed in iowa across a seven year period we inventoried severely eroding streambanks along over 10 km of stream and monitored erosion pins at 20 sites within the watershed annual streambank recession rates ranged from 0 6 cm yr during years of hydrological inactivity to 28 2 cm yr during seasons with high discharge rates with an overall average of 18 8 cm yr the percentage of total basin export attributed to streambank erosion along the main stem of walnut creek ranged from 23 to 53 large variations in individual site annual rates and percentage of annual load suggested that developing direct relationships between streambank erosion rates and total sediment discharge may be confounded by the timing and magnitude of discharge events storage of sediments within channel system and the remobilization of eroded material

hyperscale terrain modelling of braided rivers fusing mobile terrestrial laser scanning and optical bathymetric mapping quantifying the morphology of braided rivers is a key task for understanding braided river behaviour in the last decade developments in geomatics technologies and associated data processing methods have transformed the production of precise reach scale topographic datasets nevertheless generating accurate digital elevation models dems remains a demanding task particularly in fluvial systems this paper identifies a threefold set of challenges associated with surveying these dynamic landforms complex relief inundated shallow channels and high rates of sediment transport and terms these challenges the morphological wetted channel and mobility problems respectively in an attempt to confront these issues directly this paper presents a novel survey methodology that combines mobile terrestrial laser scanning and non metric aerial photography with data reduction and surface modelling techniques to render dems from the resulting very high resolution datasets the approach is used to generate and model a precise dense topographic dataset for a 2 5 km reach of the braided rees river new zealand data were acquired rapidly between high flow events and incorporate over 5 x 109 raw survey observations with point densities of 1600 pts m 2 on exposed bar and channel surfaces a detailed error analysis of the resulting sub metre resolution is described to quantify dem quality across the entire surface model this reveals unparalleled low vertical errors for such a large and complex surface model between 0 03 and 0 12 m in exposed and inundated areas of the model respectively copyright 2013 john wiley sons ltd

morphology and flow fields of three dimensional dunes rio parana argentina results from simultaneous multibeam echo sounding and acoustic doppler current profiling 1 most past studies of river dune dynamics have concentrated on two dimensional 2 d bed forms with constant heights and straight crest lines transverse to the flow and their associated turbulent flow structure this morphological simplification imposes inherent limitations on the interpretation and understanding of dune form and flow dynamics in natural channels where dune form is predominantly three dimensional for example studies over 2 d forms neglect the significant influence that lateral flows and secondary circulation may have on the flow structure and thus dune morphology this paper details a field study of a swath of 3 d dunes in the rio parana argentina a large 0 35 km wide 1 2 km long area of dunes was surveyed using a multibeam echo sounder mbes that provided high resolution 3 d detail of the river bed simultaneous with the mbes survey 3 d flow information was obtained with an acoustic doppler current profiler adcp revealing a complicated pattern of dune morphology and associated flow structure within the swath dune three dimensionality appears intimately connected to the morphology of the upstream dune with changes in crest line curvature and crest line bifurcations junctions significantly influencing the downstream dune form dunes with lobe or saddle shaped crest lines were found to have larger more structured regions of vertical velocity with smaller separation zones than more 2 d straight crested dunes these results represent the first integrated study of 3 d dune form and mean flow structure from the field and show several similarities to recent laboratory models of flow over 3 d dunes

uas based remote sensing of fluvial change following an extreme flood event the effects of large floods on river morphology are variable and poorly understood in this study we apply multi temporal datasets collected with small unmanned aircraft systems uass to analyze three dimensional morphodynamic changes associated with an extreme flood event that occurred from 19 to 23 june 2013 on the elbow river alberta we documented reach scale spatial patterns of erosion and deposition using high resolution 4 5 cm pixel orthoimagery and digital elevation models dems produced from photogrammetry significant bank erosion and channel widening occurred with an average elevation change of 0 24 m the channel pattern was reorganized and overall elevation variation increased as the channel adjusted to full mobilization of most of the bed surface sediments to test the extent to which geomorphic changes can be predicted from initial conditions we compared shear stresses from a two dimensional hydrodynamic model of peak discharge to critical shear stresses for bed surface sediment sizes we found no relation between modeled normalized shear stresses and patterns of scour and fill confirming the complex nature of sediment mobilization and flux in high magnitude events however comparing modeled peak flows through the pre and post flood topography showed that the flood resulted in an adjustment that contributes to overall stability with lower percentages of bed area below thresholds for full mobility in the post flood geomorphic configuration overall this work highlights the potential of uas based remote sensing for measuring three dimensional changes in fluvial settings and provides a detailed analysis of potential relationships between flood forces and geomorphic change copyright 2015 john wiley sons ltd

high resolution basin extent observations and implications for understanding river form and process fifty years of fluvial studies have posited a variety of conceptual frameworks for characterizing river forms and processes throughout entire basins including hydraulic geometry the river continuum concept self organized criticality and sediment links this article uses basin extent high resolution observations of fluvial forms in the nueces river basin texas and yellowstone national park to evaluate the ability of these frameworks to characterize system behavior across a multitude of scales the nueces data were collected with remote sensing methods and the yellowstone data were collected through extensive field surveys the data resolution spatial extent and quality of these data sets allow direct comparison between the two areas the hyperscale comparison supports using of each these frameworks at specific scales but also indicates an irreducible amount of variation in both datasets across many different scales that is not captured by the conceptual frameworks moreover the scales and locations where one framework such as hydraulic geometry works well are often not the same scales and locations where another framework such as the river continuum concept works well because the conceptual frameworks appear to operate at scales and locations distinct from one another the measurement approaches necessary to observe them must also be at different scales and locations for example seeing self organized criticality in a river system is difficult without an extensive survey through space whereas the recognition of sediment links requires quite intense sampling in specific river regions we suggest that these separations between measurement scales represent an incommensurability issue in river studies making it very difficult to both communicate among and test between two or more competing theories making simultaneous hyperscale observations of the river is one approach to minimizing the theory ladeness of observation as deviations from different predictions can be plotted at every scale copyright 2010 john wiley sons ltd

catchment scale mapping of surface grain size in gravel bed rivers using airborne digital imagery 1 this study develops and assesses two methods for estimating median surface grain sizes using digital image processing from centimeter resolution airborne imagery digital images with ground resolutions of 3 cm and 10 cm were combined with field calibration measurements to establish predictive relationships for grain size as a function of both local image texture and local image semivariance independently acquired grain size data were then used to assess the algorithm performance results showed that for the 3 cm imagery both local image semivariance and texture are highly sensitive to median grain size with semivariance being a better predictor than image texture however in the case of 10 cm imagery sensitivity of image semivariance and texture to grain size was poor and this scale of imagery was found to be unsuitable for grain size estimation this study therefore demonstrates that local image properties in very high resolution digital imagery allow for automated grain size measurement using image processing and remote sensing methods

the emergence of topographic steady state in a perpetually dynamic self organized critical landscape we conducted a series of four physical modeling experiments of mountain growth at differing rates of uplift and three distinct climates ranging from relatively wet to relatively dry the spatial and temporal pattern of landscape behavior is characterized by f 1 scaling in sediment discharge and power law scaling in the magnitude and frequency of ridge movement in all four experiments we find that internally generated self organized critical soc processes generate dynamically stable catchment geometries after 1 relief depths of erosion these regularly spaced catchments have an average outlet spacing ratio of 2 16 well within the range of values reported in field studies once formed large catchment bounding ridges oscillate about a critically balanced mean location with occasional large scale changes in catchment size ridge movement appears to be driven by the competition for discharge as landslides push ridges back and forth these dynamics lead to the emergence of a complex twofold scaling in catchment dynamics that is fully established by 1 8 relief depths of erosion at this stage a clear threshold has emerged separating two distinct scaling regimes where large ridge mobility is insensitive to relief and small ridge mobility is relief dependent overall we demonstrate that the development of dynamically stable large scale landforms is related to the emergence of a complex system hierarchy in topographic dynamics once formed these landscapes do not evolve statistical properties such as average topography and discharge become stationary while topography remains highly dynamic at smaller length scales

characterizing fluvial systems at basin scale by fuzzy signatures of hydromorphological drivers in data scarce environments despite the relevance of river hydromorphology hymo for integrated water resource management consistent geomorphic information at the scale of whole river basin is still scarce especially in emerging economies in this paper we propose a new scalable and globally applicable framework to analyze and classify fluvial systems in data scarce environments the framework is based on a data driven analysis of a multivariate data set of 6 key hydro morphologic drivers derived using freely available remote sensing information and several in situ hydrological time series core of the framework is a fuzzy classifier that assigns a characteristic signature of hymo drivers to individual river reaches we demonstrate the framework on the red river basin a large trans boundary river basin in vietnam and china where human induced morphological change concretely endangering local livelihoods is contrasted by very limited hymo information the derived hymo information covers spatial scales from the entire basin to individual reaches it conveys relevant information on subbasin hydro morphologic characteristic as well as on local geomorphologic forms and processes the fuzzy classifier successfully distinguishes abrupt from continuous downstream change and spatially dissects the river system in segments with homogeneous hydro morphologic forcings successful numerical modelling of morphologic forms and process rates based on the hymo signatures indicates that the multivariate basin scale classification captures relevant morphological drivers outperforms an analysis based on local drivers only and can support river management from diverse morphology related perspectives over a wide range of scales

a geostatistical framework for quantifying the reach scale spatial structure of river morphology 1 variogram models related metrics and relation to channel form abstract fluvial geomorphology is fundamentally concerned with the association between form and process in rivers examining these interactions in complex natural channels requires a means of quantifying the variability and organization of bed topography this paper introduces a geostatistical framework for characterizing reach scale spatial structure transformation to a channel centered coordinate system allows topographic variations to be resolved into along and across stream components dimensionless variables obtained by scaling distances by the mean channel width and de trended elevations by the mean bankfull depth account for channel size and allow spatial patterns to be compared over time or among sites these patterns are effectively described by the variogram a spatial statistic that expresses dissimilarity as a function of distance fitting a parametric model to the sample variogram provides a rich description of channel form for example multiple nested structures can be combined to account for anisotropy with varying degrees of spatial variability observed over different length scales along and across the channel integral metrics derived from the variogram model yield a more compact summary and variogram maps a useful visualization to guide interpretation of these metrics i used a simple channel builder to isolate the effects of specific aspects of river morphology on the variogram this analysis indicated that geostatistical models were sensitive to changes in the size shape and orientation of channel features but not to a pure translation of the morphology the results also highlighted the importance of considering streamwise and transverse components jointly rather than in isolation

channel reach morphology in mountain drainage basins a classification of channel reach morphology in mountain drainage basins synthesizes stream morphologies into seven distinct reach types colluvial bedrock and five alluvial channel types cascade step pool plane bed pool rime and dune ripple coupling reach level channel processes with the spatial arrangement of reach morphologies their links to hillslope processes and external forcing by confinement ripar ian vegetation and woody debris defines a process based framework within which to assess channel condition and response potential in mountain drainage basins field investigations demonstrate character istic slope grain size shear stress and roughness ranges for different reach types observations consistent with our hypothesis that alluvial channel morphologies reflect specific roughness configurations ad justed to the relative magnitudes of sediment supply and transport ca pacity steep alluvial channels cascade and step pool have high ratios of transport capacity to sediment supply and are resilient to changes in discharge and sediment supply whereas low gradient alluvial channels pool rime and dune ripple have lower transport capacity to supply ra tios and thus exhibit significant and prolonged response to changes in sediment supply and discharge general differences in the ratio of transport capacity to supply between channel types allow aggregation of reaches into source transport and response segments the spatial distribution of which provides a watershed level conceptual model linking reach morphology and channel processes these two scales of channel network classification define a framework within which to in vestigate spatial and temporal patterns of channel response in moun tain drainage basins

theoretical constraints on true polar wander 1 for the present geologic epoch true polar wander tpw is relatively small but simple theoretical considerations suggest that it could have been larger in other epochs in this work we use scaling arguments to assess the qualitative behavior of tpw and a simple maxwell model to analytically describe how changes in mass anomalies translate into tpw unlike previous work we derive simple analytical estimates of tpw based on the characteristic amplitudes and timescales for changes in the moment of inertia we find estimates for both the amplitude and speed of tpw as a function of earth properties the following four main factors influence how large the maximum tpw can be the geological timescale over which the desired tpw occurs tpw the viscosity structure of the mantle which yields a weighted average viscosity the characteristic amplitude of the nonhydrostatic changes in the moment of inertia c and the added moment of inertia due to the equatorial bulge c a for the nominal values 3 1022 pa s and c c a 0 003 the maximum tpw is 61 over 100 myr and 8 over 10 myr the maximum tpw speed is only sensitive to c and c a and is 2 4 myr 1 for the nominal values tpw is shown to act as a low pass filter rapid changes in moment of inertia produce smaller and delayed tpw a consequence of this is that inertial interchange tpw does not have a different character than tpw tpw can have an important contribution to plate motions over relatively long timescales but not over shorter timescales our simple approach allows us to assess whether multiple tpw events are possible but the major uncertainty continues to be the mantle viscosity structure

late cretaceous apparent polar wander of the pacific plate evidence for a rapid shift of the pacific hotspots with respect to the spin axis paleomagnetic data from the pacific plate show that the average azimuth of the pacific plate decreased by 12 between 90 ma and 81 ma whereas trends of late cretaceous seamount chains suggest that the pacific plate moved northwestward relative to the hotspots with little change in azimuth during the same time interval this difference is used to infer a 13 4 shift of the spin axis relative to the hotspots in the pacific ocean basin this shift occurred within 5 m y of the occurrence of anomalous behavior of the paleomagnetic field recorded in anomalies 33 and 34 this coincidence in timing suggests there may be a causal link between these three phenomena

downscaling of coarse grained geomorphological data one of the basic limitations to the use of geomorphological maps is their coarse resolution relative to the needs of pure and applied geomorphological research in response to this attempts have been made to downscale geomorphological information to finer spatial resolutions however the potential of statistical downscaling in geomorphology has been insufficiently examined we downscaled four different periglacial features wind deflation palsa mire earth hummock and sorted solifluction sheet from a 100 ha grid to a 1 ha grid resolution utilizing two different techniques point sampling psa and direct da approaches we assessed the predictive accuracy of the models with the area under the curve auc of a receiver operating characteristic plot using independent evaluation data the psa technique yielded encouraging results with a mean accuracy of 0 81 whereas the performance of da was poorer the predictive performance of the palsa mire and solifluction sheet models was excellent auc values from 0 89 to 0 96 whereas the auc values of deflation and earth hummock models were lower auc 0 57 0 81 the application of a point sampling approach as used here provides an efficient method to translate geomorphological information to finer resolution however further testing of the downscaling approaches is required before they can be applied to real world situations copyright 2007 john wiley sons ltd

recent large magnitude floods and their impact on valley floor environments of northeastern yellowstone abstract the lamar river watershed of northeastern yellowstone contains some of the most diverse and important habitat in the national park broad glacial valley floors feature grassland winter range for ungulates riparian vegetation that provides food and cover for a variety of species and alluvial channels that are requisite habitat for native fish rapid neogene uplift and quaternary climatic change have created a dynamic modern environment in which catastrophic processes exert a major influence on riverine riparian ecosystems uplift and glacial erosion have generated high local relief and extensive cliffs of friable volcaniclastic bedrock as a result steep tributary basins produce voluminous runoff and sediment during intense precipitation and rapid snowmelt recent major floods on trunk streams deposited extensive overbank gravels that replaced loamy soils on flood plains and allowed conifers to colonize valley floor meadows tree ring dating identifies major floods in 1918 ca 1873 and possibly ca 1790 in 1996 and 1997 discharge during snowmelt runoff on soda butte creek approached the 100 year flood estimated by regional techniques with substantial local bank erosion and channel widening indirect estimates show that peak discharges in 1918 were approximately three times greater than in 1996 with similar duration and much greater flood plain impact nonetheless 1918 peak discharge reconstructions fall well within the range of maximum recorded discharges in relation to basin area in the upper yellowstone region the 1873 and 1918 floods produced lasting impacts on the channel form and flood plain of soda butte creek channels may still be locally enlarged from flood erosion and net downcutting has occurred in some reaches leaving the pre 1790 flood plain abandoned as a terrace gravelly overbank deposits raise flood plain surfaces above levels of frequent inundation and are well drained therefore flood plain soils are drier noncohesive gravels also reduce bank stability and may have persistent effects on channel form overall floods are part of a suite of catastrophic geomorphic processes that exert a very strong influence on landscape patterns and valley floor ecosystems in northeastern yellowstone

application of wavelet analysis to the study of spatial pattern of morphotectonic lineaments in digital terrain models a case study tectonic faults are often associated with characteristic geomorphological features such as linear valleys ridgelines and slope breaks that can be identified as lineaments in remotely sensed images or digital terrain models lineaments of tectonic origin are often characterised by periodicity and characteristic spatial pattern unlike traditional methods of autocorrelation variogram lineament density and fourier analysis wavelet analysis is capable of capturing and describing both periodicity and spatial pattern of lineaments in this paper a case study is shown for the application of wavelet analysis to morphotectonic lineament investigation results of wavelet analysis are compared to traditional methods although this study involves dem derived morphological lineaments the presented wavelet analysis can be also used for lineaments derived from remotely sensed images these results hold for this case study and provide a good assessment of the relative abilities of wavelet analysis but it remains to be seen how effective it is for other data sources areas and geological terrain

m sequence geomagnetic polarity time scale mhtc12 that steadies global spreading rates and incorporates astrochronology constraints 1 geomagnetic polarity time scales gptss have been constructed by interpolating between dated marine magnetic anomalies assuming uniformly varying spreading rates a strategy to obtain an optimal gpts is to minimize spreading rate fluctuations in many ridge systems however this has been possible only for a few spreading centers we describe here a monte carlo sampling method that overcomes this limitation and improves gpts accuracy by incorporating information on polarity chron durations estimated from astrochronology the sampling generates a large ensemble of gptss that simultaneously agree with radiometric age constraints minimize the global variation in spreading rates and fit polarity chron durations estimated by astrochronology a key feature is the inclusion and propagation of data uncertainties which weigh how each piece of information affects the resulting time scale the average of the sampled ensemble gives a reference gpts and the variance of the ensemble measures the time scale uncertainty we apply the method to construct mhtc12 an improved version of the m sequence gpts late jurassic early cretaceous 160 120 ma this gpts minimizes the variation in spreading rates in a global data set of magnetic lineations from the western pacific north atlantic and indian ocean nw of australia and it also accounts for the duration of five polarity chrons established from astrochronology cm0r through cm3r this gpts can be updated by repeating the monte carlo sampling with additional data that may become available in the future

limits of downstream hydraulic geometry adjustments to flow width depth and velocity in response to changes in discharge are commonly characterized by using downstream hydraulic geometry relationships the spatial limits of these relationships within a drainage basin have not been systematically quantified where the erosional resistance of the channel substrate is sufficiently large hydraulic driving forces presumably will be unable to adjust channel form data sets from 10 mountain rivers in the united states panama nepal and new zealand are used in this study to explore the limits of downstream hydraulic geometry relationships where the ratio of stream power to sediment size d 84 exceeds 10 000 kg s3 downstream hydraulic geometry is well developed where the ratio falls below 10 000 kg s3 downstream hydraulic geometry relationships are poorly developed these limitations on downstream hydraulic geometry have important implications for channel engineering and simulations of landscape change

upwelling plumes superswells and true polar wander summary the geological evolution of the rotational axis of the earth is most likely controlled by internal mass redistribution within the mantle palaeomagnetic observations suggest that it is episodic in nature with periods of quasi standstill alternating with periods of faster wander here we investigate two models for the influence of mantle plumes that vary at different spatial wavelengths on the time variations of the rotational axis true polar wander tpw in the first model we represent an upwelling plume as a sphere whose radius varies as a function of the flux of material in the conduit and that traverses the mantle at the stokes velocity such a plume produces very little wander of the rotational axis we then study the effects of two superswells that mimic the ones observed with seismic tomography and conclude that a doming regime within the mantle involves significant polar wander some of the features of this tpw that are directly linked to the periodicity of doming are reminiscent of observed phases of slow and fast tpw with similar peak velocities

intra oceanic subduction shaped the assembly of cordilleran north america the western quarter of north america consists of accreted terranes crustal blocks added over the past 200 million years but the reason for this is unclear the widely accepted explanation posits that the oceanic farallon plate acted as a conveyor belt sweeping terranes into the continental margin while subducting under it here we show that this hypothesis which fails to explain many terrane complexities is also inconsistent with new tomographic images of lower mantle slabs and with their locations relative to plate reconstructions we offer a reinterpretation of north american palaeogeography and test it quantitatively collision events are clearly recorded by slab geometry and can be time calibrated and reconciled with plate reconstructions and surface geology the seas west of cretaceous north america must have resembled today s western pacific strung with island arcs all proto pacific plates initially subducted into almost stationary intra oceanic trenches and accumulated below as massive vertical slab walls above the slabs long lived volcanic archipelagos and subduction complexes grew crustal accretion occurred when north america overrode the archipelagos causing major episodes of cordilleran mountain building a new explanation for the origin of the accreted terranes that form the mountainous cordillera of western north america is proposed and tested stationary intra oceanic subduction deposited massive slab walls in the mantle and grew volcanic archipelagos at the surface which were overridden by and accreted to north america during cretaceous times the generally accepted account of how the geology of western north america developed involves the oceanic farallon plate acting as a conveyor belt sweeping crustal terranes onto the continental margin as it moves beneath the north american plate this model fails to explain many aspects of this accreted terrane and here karin sigloch and mitchell mihalynuk present an alternative model based on new tomographic images of lower mantle slabs and modelling of deep mantle structure in the region they propose that during the cretaceous period there were a series of island arcs west of north america beneath which proto pacific plates subducted into almost stationary trenches long lived volcanic archipelagos and subduction complexes grew above the slabs and then accreted onto north america as it overrode the archipelagos causing episodes of cordilleran mountain building

remote sensing of stream depths with hydraulically assisted bathymetry hab models this article introduces a technique for using a combination of remote sensing imagery and open channel flow principles to estimate depths for each pixel in an imaged river this technique which we term hydraulically assisted bathymetry hab uses a combination of local stream gage information on discharge image brightness data and manning based estimates of stream resistance to calculate water depth the hab technique does not require ground truth depth information at the time of flight hab can be accomplished with multispectral or hyperspectral data and therefore can be applied over entire watersheds using standard high spatial resolution satellite or aerial images hab also has the potential to be applied retroactively to historic imagery allowing researchers to map temporal changes in depth we present two versions of the technique hab 1 and hab 2 hab 1 is based primarily on the geometry discharge and velocity relationships of river channels manning s equation assuming average depth approximates the hydraulic radius the discharge equation and the assumption that the frequency distribution of depths within a cross section approximates that of a triangle are combined with discharge data from a local station width measurements from imagery and slope measurements from maps to estimate minimum average and maximum depths at a multiple cross sections these depths are assigned to pixels of maximum average and minimum brightness within the cross sections to develop a brightness depth relation to estimate depths throughout the remainder of the river hab 2 is similar to hab 1 in operation but the assumption that the distribution of depths approximates that of a triangle is replaced by an optical beer lambert law of light absorbance in this case the flow equations and the optical equations are used to iteratively scale the river pixel values until their depths produce a discharge that matches that of a nearby gage r 2 values for measured depths versus depths estimated by hab 1 and hab 2 are 0 51 and 0 77 respectively in the relatively simple brazos river texas r 2 values for hab 1 and hab 2 are 0 46 and 0 26 respectively in the lamar river a complex mountain river system in yellowstone national park although the r 2 values are moderate depth maps and crosssections derived from the hab techniques are consistent with typical stream geomorphology patterns and provide far greater

grain size along two gravel bed rivers statistical variation spatial pattern and sedimentary links a new set of field data facilitates a detailed analysis of variations in bed material grain size within two confluent gravel bed rivers in northeastern british columbia canada a preliminary assessment of grain size variability establishes a basis for examination of the spatial pattern of grain size change standard anova techniques are inappropriate because individual samples have unequal variances and are not normally distributed alternative tests for homoscedasticity and comparison of means are therefore utilized within site between sample variability is not significant the grain size distributions that were obtained at individual sites are therefore representative of the depositional environments that were sampled in both rivers mean grain size does vary significantly between sites and there is therefore a basis for examining the data for spatial patterns such as downstream fining textural variations along the two rivers studied here are complex and show negligible overall fining in over 100 km this is the consequence of a large number of tributary inputs and non alluvial sediment sources which are the legacy of late pleistocene glaciation the identification of lateral sources like these is fundamental for understanding textural changes within rivers the sedimentary link a channel reach between significant lateral sediment inputs provides a means of isolating fluvial maturation processes abrasion and sorting from contingent lateral inputs strong fining trends are apparent in most links and classification of grain size measurements according to their location within particular links greatly improves the statistical explanation of textural variation identification of sedimentary links provides a means of applying models of fluvial fining processes so isolation of link networks will aid the development of basin scale models of textural variation 1998 john wiley sons ltd

making riverscapes real abstract the structure and function of rivers have long been characterized either by 1 qualitative models such as the river continuum concept or serial discontinuity concept which paint broad descriptive portraits of how river habitats and communities vary or 2 quantitative models such as downstream hydraulic geometry which rely on a limited number of measurements spread widely throughout a river basin in contrast authors such as fausch et al 2002 and wiens 2002 proposed applying existing quantitative spatially comprehensive ecology and landscape ecology methods to rivers this new framework for river sciences which preserves variability and spatial relationships is called a riverine landscape or a riverscape application of this riverscape concept requires information on the spatial distribution of organism scale habitats throughout entire river systems this article examines the ways in which recent technical and methodological developments can allow us to quantitatively implement and realize the riverscape concept using 3 cm true color aerial photos and 5 m resolution elevation data from the river tromie scotland we apply the newly developed fluvial information system which integrates a suite of cutting edge high resolution remote sensing methods in a spatially explicit framework this new integrated approach allows for the extraction of primary fluvial variables such as width depth particle size and elevation from these first order variables we derive second order geomorphic and hydraulic variables including velocity stream power froude number and shear stress channel slope can be approximated from available topographic data based on these first and second order variables we produce riverscape metrics that begin to explore how geomorphic structures may influence river habitats including connectivity patchiness of habitat and habitat distributions the results show a complex interplay of geomorphic variable and habitat patchiness that is not predicted by existing fluvial theory riverscapes thus challenge the existing understanding of how rivers structure themselves and will force development of new paradigms

fluvial response a decade after wildfire in the northern yellowstone ecosystem a spatially explicit analysis forest fire is a vital ecological process capable of inducing complex fluvial response but the integration of these effects across entire watersheds remains poorly understood we collected downstream cross sectional and geomorphic data acquired geographic information on land cover and forest fire and performed spatially explicit statistical analyses to examine fire related impacts in catchments burned to varying degrees generalized least squares gls regression models suggested that channels with a greater percentage of burned drainage area were associated with markedly higher cross sectional stream power relatively smaller width depth ratios and lower bank failure rates 12 to 13 years after the fires these results implied that streams became more powerful in the aftermath of forest fire and that net incision had been the primary response in second to fourth order channels since the 1988 yellowstone fires the extensive geographic coverage of our data spanning multiple basins with measurements spaced every 100 m allowed us to hypothesize a process response model based on these results we suggest that a wave of fire related sediment propagates through burned catchments high runoff events or even moderate flows provide sufficient energy to evacuate the finer grained material delivered from burned hillslopes to the channel network over a period of 5 10 years the combination of elevated post fire discharges and decreased sediment supply then induces an episode of incision site specific channel changes are highly variable because streams can accommodate post fire increases in energy and sediment supply through multiple modes of adjustment characterizing the spatial distribution of stream power would provide a valuable management tool because this variable is strongly associated with percent burned drainage area and integrates several elements of complex fluvial response future research focused on the channel substrate and its evolution through time is needed but our results indicate a fundamental linkage between fire and fluvial processes d 2002 elsevier science b v all rights reserved

role of ocean continent contrast and continental keels on plate motion net rotation of lithosphere and the geoid three dimensional spherical shell models of mantle convection have been formulated to investigate the effects of ocean continent contrast i e different viscosity for continental and oceanic lithospheres and continental keels on plate motion net rotation of lithosphere i e degree 1 toroidal plate motion and the geoid the models include relatively realistic plate rheology i e strong plate interiors and weak plate margins and continental keel structure based on seismic models the mantle flow in the models is driven by slab buoyancy the models demonstrate that the ocean continent contrast and continental keels have minor effects on the long wavelength geoid for degrees 2 5 however continental keels overriding subducted slabs for example in north america can produce large negative gravity anomalies at a regional scale this may have important implications to interpreting the gravity anomalies in north america our models show that when plates bounded by weak plate margins have the same thickness neither weak plate margins nor the ocean continent contrast efficiently excite net rotation of lithosphere although they excite toroidal motion at higher harmonic degrees however plate thickness variations like continental keels excite the net rotation in spite of their ability to excite the net rotation continental keels as thick as 300 km cannot provide the necessary coupling to the deep mantle to produce the observed net rotation of lithosphere and slow continental motion if there is a weak asthenosphere underlying them if the thermomechanic structure of north american continental upper mantle derived from seismic and heat flow studies is representative our models suggest that the temperature and pressure dependent mantle rheology may not produce sufficiently high viscosity below continental keels that is needed to explain the observed plate motion our study hints the necessity to include more realistic treatment of plate boundaries in future studies to assess possible effects of plate plate coupling on plate motion

incorporating ecogeomorphic feedbacks to better understand resiliency in streams a review and directions forward decades of interdisciplinary research show river form and function depends on interactions between the living and nonliving world but a dominant paradigm underlying ecogeomorphic work consists of a top down unidirectional approach with abiotic forces driving biotic systems stream form and location within the stream network does dictate the habitat and resources available for organisms and overall community structure yet this traditional hierarchal framework on its own is inadequate in communicating information regarding the influence of biological systems on fluvial geomorphology that lead to changes in channel morphology sediment cycling and system scale functions e g sediment yield biogeochemical nutrient cycling substantial evidence that organisms influence fluvial geomorphology exists specifically the ability of aquatic vegetation and lotic animals to modify flow velocities and sediment deposition and transport thus challenging the traditional hierarchal framework researchers recognize the need for ecogeomorphic frameworks that conceptualize feedbacks between organisms sediment transport and geomorphic structure furthermore vital ecosystem processes such as biogeochemical nutrient cycling represent the conversations that are occurring between geomorphological and biological systems here we review and synthesize selected case studies highlighting the role organisms play in moderating geomorphic processes and likely interact with these processes to have an impact on an essential ecosystem process biogeochemical nutrient recycling we explore whether biophysical interactions can provide information essential to improving predictions of system scale river functions specifically sediment transport and biogeochemical cycling and discuss tools used to study these interactions we suggest that current conceptual frameworks should acknowledge that hydrologic geomorphologic and ecologic processes operate on different temporal scales generating bidirectional feedback loops over space and time hydro and geomorphologic processes operating episodically during bankfull conditions influence ecological processes e g biogeochemical cycling occurring over longer time periods during base flow conditions this ecological activity generates the antecedent conditions that influence the hydro and geomorphologic processes occurring during the next high flow event creating a bidirectional feedback this feedback should enhance the resiliency of fluvial landforms and ecosystem processes allowing physical and biological processes to pull and push against each other over time

tectonic evolution of the northern pacific plate and pacific farallon izanagi triple junction in the late jurassic and early cretaceous m21 m10 abstract magnetic lineations in the northwestern pacific near the shatsky plateau were interpreted to trace the tectonic history of the northern pacific plate from the time of anomalies m21 to m10 at m22 time the pacific farallon izanagi p f i triple junction was located southwest of the plateau and migrating north northwest with respect to the pacific plate shortly thereafter the stress field acting on the three plates changed significantly and the pacific lzanagi ridge reacted by pivoting 24 clockwise from m21 to m19 time several ridge propagation events occurred while the ridge adjusted to the new spreading regime to the east of the m22 location of the junction it appears that this reorganization triggered a series of at least three ridge jumps along the pacific farallon ridge the geometry of magnetic isochron m21 suggests that several triple junctions existed simultaneously during the reorganization bordering one or more microplates differences in the spreading rate of the japanese magnetic lineations north of the plateau imply that one microplate which we call the shatsky microplate existed until about m15 m13 time it was probably captured by either the farallon or the izanagi plate and subsequently destroyed by subduction after m15 the p f i triple junction was reformed on seafloor that is now beneath the shatsky plateau the junction drifted generally northeast either in a ridge ridge ridge or in a ridge fault fault configuration perhaps alternating between the two from m11 m10 time the stress field on the three plates changed again and the pacific farallon ridge southeast of the plateau reoriented 15 clockwise at this time the p f i junction assumed a ridge ridge ridge geometry at the northeast end of the plateau

late jurassic early cretaceous closure of the mongol okhotsk ocean demonstrated by new mesozoic palaeomagnetic results from the trans baikal area se siberia summary we present new palaeomagnetic results from the transba ikal area se siberia from the mongol okhotsk suture zone the boundary between the amuria and siberia blocks in order to better constrain the time of closure of the mongol okhotsk ocean in the mesozoic we col lected 532 rock samples at 68 sites in six localities of basalts trachy basalts and andesites from both sides of the mongol okhotsk suture at unda river j 3 51 7 n 117 4 e kremljevka peak k1 51 8 n 117 5 e and torey lakes k 1 50 1 n 115 9 e on the southern side of the suture and at monostoy river j 1 51 1 n 106 8 e ingoda river k 1 51 2 n 112 2 e and bichura town k 1 50 6 n 107 6 e on the northern side progressive thermal demagnetization enabled us to resolve low ltc and high htc temperature components of magnetization at most sites jurassic palaeopoles computed from the htcs show a large discrepancy with respect to the apparent polar wander path of eurasia which we interpret in terms of 1700 2700 km of post late jurassic northward movement of amuria with respect to siberia although ge ological data suggest a middle jurassic closure of the mongol okhotsk ocean in the west trans baikal region our data give evidence of a large remaining palaeolatitude difference between the amuria and siberia blocks in contrast early cretaceous sites cluster remarkably well along a small circle which is centred on the average site location this implies the absence of post early cretaceous northward motion of amuria relative to siberia and demonstrates the pre early cretaceous closure of the mongol okhotsk ocean finally we interpret the very large tectonic rotations about local vertical axes evidenced by the small circle distribution of poles as arising both from collision processes and from left lateral shear movement along the suture zone due to the eastward extrusion of amuria under the effect of the collision of india into asia

time dependent subduction dynamics driven by the instability of stagnant slabs in the transition zone abstract seismic tomographic images indicate that subducted slabs are commonly deflected within the transition zone and that accumulated slab material may be subject to localized flux into the lower mantle these observations are consistent with numerical models of mantle flow in which slab flux through phase transition at 660 km depth is impeded by the combination of rheological contrast and thermodynamic effects we use a suite of 2d numerical experiments to explore the impact of slab avalanches on plate boundary dynamics the experiments are initiated at the onset of the avalanche and two distinct classes of model geometry are considered in the first the stagnant deflected slab within the transition zone is connected to subduction at the surface of the model domain in this case we find that the location of the avalanche relative to the trench governs whether the slab dip steepens or shallows in response to the instability at 660 km depth these experiments show a relatively modest impact on plate dynamics at the surface in the second class of models the stagnant slab material is not connected to the shallow subduction and the former is interpreted as a remnant of either a relic subduction event or an accumulation of material from a distant zone of convergence in this case the impact on plate boundary dynamics is more profound for example when the avalanche is positioned under or forward of the island arc it drives a significant retreat of the trench in contrast an avalanche that initiates under the back arc leads to a thrusting of the island arc over the retro plate and a reversal in the polarity of subduction we test the influence of various boundary conditions on the evolution of these models and consider several different rheological parameterizations for the lithosphere and mantle the models are intended as general templates for the impact of slab avalanches however we discuss the potential connection of these results to various zones of convergence along the western pacific margin

estimation of river discharge propagation speed and hydraulic geometry from space lena river siberia 1 moderate resolution imaging spectroradiometer modis derived measurements of lena river effective width we display a high predictive capacity r2 0 81 mean absolute error 60 90 km 2 3 time valley width satellite derived we q rating curves and hydraulic geometry b exponents converge upon stable values b 0 48 indicating transferability of the discharge retrieval method between different locations put another way at length scales exceeding 60 90 km all subreaches display similar behavior everywhere at finer reach length scales e g 0 25 1 km longitudinal extraction of b exponents represents the first continuous mapping of a classical hydraulic geometry parameter from space while at least one gauging station is required for calibration results suggest that multitemporal satellite data can powerfully enhance our understanding of water discharge and flow conveyance in remote river systems

true polar wander as a mechanism for second order sea level variations long term wander of the rotation pole can be a significant contributor to second order time scales of 100 million years sea level variations numerical predictions based on realistic viscoelastic earth models and paleomagnetically constrained polar motion yield global scale differential sea level trends that can be as large as 200 meters from the results presented here it is argued that the well documented second order cretaceous tertiary sea level cycle should be reinterpreted as some combination of a eustatic and a regionally varying rotational signal

high resolution grain size characterisation of gravel bars using imagery analysis and geo statistics abstract the scarcity of grain size data from gravel bed rivers has traditionally hindered hydraulic sediment transport and river habitat studies a new remote sensing methodology to estimate grain size distribution is presented it combines textural digital images of the riverbed at 1 1000 and 1 40 scales with grain size sampling it was applied to a 12 km reach of the isabena river central pyrenees ne spain first textural patterns for each grain size range were obtained selecting the most closely related texture variables including the use of semivariograms second multiple linear regression equations were derived from the textural variables to estimate each value of the grain size distribution the highest correlation values r 2 were obtained from the central part of the distribution d 50 with a rms error of 12 7 finally new multiple linear regression equations to estimate the d 50 and d 84 were obtained from 1 1000 images and four textural variables these were used to derive d 50 and d 84 maps of the riverbed re sampled at a resolution of 1 5 m pixels with rms estimation errors of 26 and 32 respectively downstream change in grain size is also well reproduced by the method the mean d 50 of 72 and 32 mm were estimated in the upper and the lower reaches of the river respectively the methodology shows great potential for application the relation between the spatial resolution of the images and the mean grain size of the riverbed sediment being the main issue for future development

cenozoic global plate motions cenozoic global plate motions relative to the hot spots are investigated and compared to plate motions in a mean lithosphere reference frame plate motions were analyzed over six time intervals divided by ages 10 25 43 48 and 56 ma chosen as much as possible to coincide with key plate reorganizations alternative motion circuits and rotational parameters were considered and evaluated with paleomagnetic data from the pacific and north american plates the circuit found to be in best agreement with the paleomagnetic data is one in which the hot spots in the atlantic region are assumed to be fixed relative to the hot spots in the pacific region throughout the cenozoic the hot spot and mean lithosphere reference frames have been in continual slow relative motion the rate of motion is nonuniform however most of the motion having occurred during the middle cenozoic the net cenozoic rotation of the lithosphere relative to the hot spots is described by a right handed rotation of 7 about a euler pole at 46 s 87 e which yields a 5 displacement of the north poles of the two reference frames this motion is small enough that inferences drawn about plate speeds in one reference frame should be valid in the other analysis of the global motions resulting from our preferred model showed that many characteristics of current plate motions have persisted throughout the cenozoic plate speeds correlate with latitude plates moving faster near the equator than near the poles throughout the cenozoic as at present continental plates except for the indian plate moved slower than oceanic plates throughout the cenozoic even the structure of the velocity fields as revealed in a contour of root mean square velocities in equatorial bands persists throughout the cenozoic the migration of the paleomagnetic axis over time is also compared to the hot spot and mean lithosphere reference frames the paleomagnetic axis has shifted 5 10 relative to the hot spot frame and a lesser amount relative to the mean lithosphere frame

the nature and controls on downstream fining within sedimentary links abstract at scales of 100 to 102 km grain size change in gravelly alluvial systems is characterized by punctuated downstream fining significant lateral sediment inputs define a sequence of sedimentary links within which fluvial processes produce fining trends using a new set of surface grain size data eighteen such links along two canadian gravel bed rivers are examined negative exponential functions are found to be most appropriate for describing within link grain size changes development of a pragmatic means of predicting grain size is then pursued by searching for a means to relate model diminution coefficients to link attributes consideration of lithologically differentiated fining trends indicates that lithology plays an insignificant role in controlling fining rate examination of within link longitudinal profiles indicates a reasonable relation between fining rate and the rate of change of channel slope the predictive value of this relation is limited by the regional nature of the data upon which it is based and the relative difficulty of obtaining accurate gradient information however as previously noted for alluvial fans although for different reasons channel gradient is correlated with link length and a reasonable predictive tool is apparent in a relation between link length and diminution rate the validity of the derived relation cannot be tested for want of a suitable data set several lines of evidence indicate that abrasion is unimportant as a fining mechanism on these rivers and it is argued that this may be typical of sedimentary links fining rate must then be a function of the efficiency with which sorting processes operate and it is suggested that this efficiency is dependent on aggradation rates associated with the lateral sediment influxes at the head and terminus of individual links

statistical models of fluvial systems abstract statistical methods have dominated quantitative analyses of fluvial systems over the last 40 years this paper assesses the utility of statistical models by examining methodological issues associated with empirical analysis of hydraulic and channel geometry relationships it also describes and presents examples of advanced statistical models that promise to enhance our understanding of the structure and dynamics of fluvial systems bivariate and multivariate power function models of fluvial systems provide objective numerical descriptions of the relationship between channel geometry and hydrologic hydraulic sedimentologic and biotic controls traditional regression models are limited in that they only describe simple input output relations between the states of dependent and independent variables advanced statistical models transcend these limitations simultaneous equation models continuously varying parameter models and distributed lag models are statistical tools for explicitly analyzing 1 mutual adjustments among fluvial variables 2 the factors controlling the spatial structure of channel geometry flow relations and 3 the equilibrium or disequilibrium dynamics of fluvial systems respectively these advanced statistical techniques can be used to empirically test conceptual models of fluvial systems at a variety of spatial and temporal scales

pleistocene deglaciation and the earth s rotation a new analysis summary this paper is concerned with an analysis of the effect of the pleistocene glacial cycle upon the earth s rotation we demonstrate that two important geophysical observables may be explained as aspects of the rotational response to surface mass loading by ice sheets these are the astronomically observed non tidal component of the acceleration of planetary rotation and the secular drift of the rotation pole relative to the surface geography which is evident in the ils pole path the former observation is shown to provide an unambiguous constraint upon the viscosity of the planetary mantle and requires a depth dependence of this parameter which is the same as that which has previously been inferred in studies of the relative sea level variations and free air gravity anomalies associated with post glacial rebound the observed secular drift of the pole cannot provide an independent estimate of the viscosity of the mantle because it depends jointly upon mantle viscosity and lithospheric thickness with the viscosity profile fixed by the rebound data the observed speed of polar wander suggests a continental lithospheric thickness which is in excess of that appropriate for old ocean basins but nevertheless in accord with independent constraints

which tributaries disrupt downstream fining along gravel bed rivers tributaries and other lateral sediment sources can have a significant impact on river bed sediment texture and in turn on channel form sufficiently voluminous or distinct sediment inputs redefine the mainstem grain size distribution punctuating downstream maturation and isolating a sequence of discrete sedimentary links within these links fining processes usually dominate such that models of sorting and abrasion when applied to individual links provide reasonable predictions of grain size change links represent the fundamental natural unit within which fining models can be tested developed and applied identification of significant lateral sources is therefore important yet beyond vague references to relative tributary size sediment load and sediment calibre no criteria exist for the a priori discrimination of such sources in this paper a procedure for identifying significant lateral tributary sources without the benefit of grain size information is outlined a high resolution characterisation of bed material texture along two canadian gravel bed rivers facilitated classification of all their perennial tributaries as either significant or insignificant three absolute tributary basin parameters and their relative counterparts chosen to reflect the likely controls on tributary significance are then used to develop a discriminant function which isolates a large proportion of significant tributaries while minimising incorrect classifications examination of consistently misclassified anomalous tributaries reveals the importance of lateral source spacing and of inconsistencies in the geomorphic history of the contributing basins in turn a general tributary categorisation procedure is suggested which includes a logistic regression model for attaching probability statements to individual classifications the generality of the discriminant and logistic functions cannot be assessed because of the lack of other suitable data sets

revised pacific m anomaly geomagnetic polarity timescale summary the current m anomaly geomagnetic polarity timescale gpts is mainly based on the hawaiian magnetic lineations in the pacific ocean m anomaly gpts studies to date have relied on a small number of magnetic profiles a situation that is not ideal because any one profile contains an uncertain amount of geologic noise that perturbs the magnetic field signal compiling a polarity sequence from a larger array of magnetic profiles is desirable to provide greater consistency and repeatability we present a new compilation of the m anomaly gpts constructed from polarity models derived from magnetic profiles crossing the three lineation sets hawaiian japanese and phoenix in the western pacific polarity reversal boundary locations were estimated with a combination of inverse and forward modelling of the magnetic profiles separate gpts were established for each of the three pacific lineation sets to allow examination of variability among the different lineation sets and these were also combined to give a composite timescale owing to a paucity of reliable direct dates of the m anomalies on ocean crust the composite model was time calibrated with only two ages one at each end of the sequence these two dates are 125 0 ma for the base of m0r and 155 7 ma for the base of m26r relative polarity block widths from the three lineation sets are similar indicating a consistent pacific wide spreading regime the new gpts model shows slightly different spacings of polarity blocks as compared with previous gpts with less variation in block width it appears that the greater polarity chron irregularity in older models is mostly an artifact of modelling a small number of magnetic profiles the greater averaging of polarity chron boundaries in our model gives a gpts that is statistically more robust than prior gpts models and a superior foundation for late jurassic early cretaceous geomagnetic and chronologic studies

the use of multi temporal lidar to assess basin scale erosion and deposition following the catastrophic january 2011 lockyer flood se queensland australia advances in remote sensing and digital terrain processing now allow for a sophisticated analysis of spatial and temporal changes in erosion and deposition digital elevation models dems can now be constructed and differenced to produce dems of difference dod which are used to assess net landscape change for morphological budgeting to date this has been most effectively achieved in gravel bed rivers over relatively small spatial scales if the full potential of the technology is to be realised additional studies are required at larger scales and across a wider range of geomorphic features this study presents an assessment of the basin scale spatial patterns of erosion deposition and net morphological change that resulted from a catastrophic flood event in the lockyer creek catchment of se queensland seq in january 2011 multitemporal light detection and ranging lidar dems were used to construct a dod that was then combined with a one dimensional flow hydraulic model hec ras to delineate five major geomorphic landforms including inner channel area within channel benches macrochannel banks and floodplain the lidar uncertainties were quantified and applied together with a probabilistic representation of uncertainty thresholded at a conservative 95 confidence interval the elevation change distribution ecd for the 100 km2 study area indicates a magnitude of elevation change spanning almost 10 m but the mean elevation change of 0 04 m confirms that a large part of the landscape was characterised by relatively low magnitude changes over a large spatial area mean elevation changes varied by geomorphic feature and only two the within channel benches and macrochannel banks were net erosional with an estimated combined loss of 1 815 149 m3 of sediment the floodplain was the zone of major net deposition but mean elevation changes approached the defined critical limit of uncertainty areal and volumetric ecds for this extreme event provide a representative expression of the balance between erosion and deposition and importantly sediment redistribution which is extremely difficult to quantify using more traditional channel planform or cross sectional surveys the ability of lidar to make a rapid and accurate assessment of key geomorphic processes over large spatial scales contributes to our understanding of key processes and as demonstrated here to the assessment of major geomorphological hazards such as extreme flood events

global plate motion frames toward a unified model 1 plate tectonics constitutes our primary framework for understanding how the earth works over geological timescales high resolution mapping of relative plate motions based on marine geophysical data has followed the discovery of geomagnetic reversals mid ocean ridges transform faults and seafloor spreading cementing the plate tectonic paradigm however so called absolute plate motions describing how the fragments of the outer shell of the earth have moved relative to a reference system such as the earth s mantle are still poorly understood accurate absolute plate motion models are essential surface boundary conditions for mantle convection models as well as for understanding past ocean circulation and climate as continent ocean distributions change with time a fundamental problem with deciphering absolute plate motions is that the earth s rotation axis and the averaged magnetic dipole axis are not necessarily fixed to the mantle reference system absolute plate motion models based on volcanic hot spot tracks are largely confined to the last 130 ma and ideally would require knowledge about the motions within the convecting mantle in contrast models based on paleomagnetic data reflect plate motion relative to the magnetic dipole axis for most of earth s history but cannot provide paleolongitudes because of the axial symmetry of the earth s magnetic dipole field we analyze four different reference frames paleomagnetic african fixed hot spot african moving hot spot and global moving hot spot discuss their uncertainties and develop a unifying approach for connecting a hot spot track system and a paleomagnetic absolute plate reference system into a hybrid model for the time period from the assembly of pangea 320 ma to the present for the last 100 ma we use a moving hot spot reference frame that takes mantle convection into account and we connect this to a pre 100 ma global paleomagnetic frame adjusted 5 in longitude to smooth the reference frame transition using plate driving force arguments and the mapping of reconstructed large igneous provinces to core mantle boundary topography we argue that continental paleolongitudes can be constrained with reasonable confidence

plate motions crustal and lithospheric mobility and paleomagnetism prospective viewpoint the shift in viewpoint from a static to a mobilistic solid earth as brought about by paleomagnetism opened many new directions of research that continue to be exciting today and hold prospects for an exciting future here five topics of current research on earth s mobilistic surface are reviewed and their future directions discussed first dividing earth s solid surface into two domains 1 nearly rigid plate interiors and 2 plate boundaries some of them very wide leads to a review and discussion of the kinematics of wide plate boundaries many more adjustable parameters will be needed to describe the complex kinematics of plate boundaries which cover 15 of earth surface than the few dozen parameters needed to describe the kinematics of plate interiors which cover 85 of earth s surface second the question of the degree of rigidity of plate interiors is discussed the integral of the velocity gradient across plates interiors is at least a few hundredths or tenths of millimeters per year and in several well determined cases less than 2 or 3 mm yr future investigations will no doubt be aimed at narrowing these limits and to expanding the area of earth s surface over which limits are known third space geodetic data mainly from very long baseline inter ferometry satellite laser ranging and the global positioning system have demonstrated a remarkable similarity of velocities of stable plate interiors averaged over a few to a dozen years with plate velocities averaged over a few million years already however significant differences of a few millimeters per year are emerging and the tectonic and dynamic significance of these differences need to be evaluated fourth despite more than two decades of investigation the question of how fast hotspots move relative to one another is still a contentious issue one group of researchers maintains that maximum speeds are 3 mm yr whereas another maintains that speeds are 10 20 mm yr or more the differences cannot be reconciled until the uncertainties in plate reconstructions relative to hotspots are systematically and properly incorporated into analyses of hotspot motion fifth paleomagnetists have estimated true polar wander over the past 200 myr by equating it with the apparent polar wander of hotspots however the possible motion among hotspots and the neglect of the uncertainties in reconstructions relative to the hotspots have left these analyses unconvincing further progress requires the incorporation of these uncertainties a possible exception is the apparent polar wander of the hotspots over the past 10 20 myr or less which requires only small adjustments for plate motion and has presumably smaller uncertainties due to plate reconstructions the cause of this apparently significant geologically recent shift of the pole is poorly understood compared with the rate and direction of the secular shift of the pole observed this century from the international latitude service and for 1976 to 1994 from space geodetic data the paleomagnetically observed shift is unlikely to be due to the removal of northern hemisphere midlatitude ice sheets which is the commonly accepted explanation for the shift observed over the past century i speculate instead that the apparently rapid uplift of the tibetan plateau sometime during the past 10 20 myr is at least partly responsible for the geologically recent shift of the pole finally i conclude that the theory of plate tectonics has provided a framework that leads naturally to further quantification of the kinematics and deformation of earth s solid surface chiefly because of the key assumption of the rigidity of plate interiors which permits specific predictions to be made this revolution in quantification still has far to go and holds exciting prospects for future tectonic studies

pacific microplate and the pangea supercontinent in the early to middle jurassic new biostratigraphic data based on radiolarians recovered from deep within the oceanic crustal section of ocean drilling program hole 801c in the western pacific along with existing radiometric information date this oceanic crust as late bajocian early bathonian 170 165 ma the overlying basal sediments at hole 801c are essentially identical in age middle bathonian 164 162 ma to the basal sediments at deep sea drilling program hole 534a in the central atlantic we estimate the time of formation of the pacific plate as 175 170 ma and the time of initial separation of the pangea supercontinent in the central atlantic as 190 180 ma we also identify a time of extensive subduction zone magmatism 175 159 ma at the eastern and western edges of pangea we suggest that the initial plate separation of pangea increased subduction rates at its outer margins and altered the plate boundaries in the pacific superocean leading to formation of the pacific plate

riverscape mapping with helicopter based structure from motion photogrammetry abstract recent developments in the remote sensing of fluvial systems have provided researchers with unprecedented views on the complexity of rivers an aerial perspective is key to mapping and understanding the river at a variety of spatial scales i employed a helicopter mounted digital slr camera and structure from motion sfm photogrammetry to bridge the gap between smaller scale aerial surveys from platforms like small unmanned aerial systems and larger scale commercial aerial photography or airborne lidar collections this low cost solution produced high spatial resolution aerial photography and digital elevation models for a 32 km segment of the middle fork john day river in east central oregon using these data i extracted channel morphology data at 3 m intervals downstream and took an inductive approach to evaluating the controls on channel morphology and the human influences on the river using a combination of segment scale and hyperscale analyses the sfm process produced 10 cm pixel orthophotographs and dems with submeter horizontal accuracy but the dems suffered from a systematic distortion that resulted from the parallel camera geometry of the flight plan the riverscape has been affected by human actions such as mining cattle grazing and restoration however differentiating a human signal from the natural patterns of channel morphology was difficult the hyperscale analysis provided insight into several interesting downstream patterns in channel morphology that with further analysis could provide explanations on the physical controls of channel morphology overall sfm has the potential to be a powerful low cost addition to the fluvial remote sensing toolkit

hydrologic and topographic variability modulate channel change in mountain rivers summary the relationships between flow hydrology topography and channel change in mountain rivers is important to understanding landscape evolution the structure and persistence of aquatic habitat and also the physiochemical cycling of upstream derived organic and inorganic materials there is a paucity of detailed studies that analyze the joint roles of hydrology and topography in controlling multiple mechanisms of channel change in mountain rivers in this study gravel and cobble channel change in a bedrock river canyon were analyzed in light of a controlled yet natural experiment where 4491 metric tonnes of rounded gravel and cobble was augmented below a sediment barrier dam in a 1200 m long mountain river reach that had no prior sources of rounded gravel or cobble and still experiences floods above the bankfull discharge the overall study goal was to investigate how flow hydrology can modulate multiple channel change processes depending on the topographic features engaged by the flow channel change was assessed via differencing of high resolution repeat topographic and bathymetric surveys along with cm scale aerial photography post injection statistical tests used to implicate topographic feature specific mechanisms of channel change that vary with discharge included analyzing geomorphic covariance structures of flow dependent width bed elevation and channel change as well as autocorrelation of flow width spatial series stage dependent topographic steering was inferred from associations of erosion and deposition with changes in 2d model derived flow directions at multiple discharges a variety of mechanisms of channel change were qualitatively and quantitatively confirmed including particle hiding topographic steering eddying and flow convergence no single mechanism explained the observed patterns of channel change but rather it is thought that process blending occurs as modulated by the interactions of flow hydrology with complex topography results from this study suggest that both existing channel boundary variability and input hydrologic variability work together to create hydrodynamic spatial patterns that control the fate and transport of sediments in mountain rivers and ultimately their spatial structure

late cretaceous true polar wander not so fast using recalculated paleopoles from seamount anomaly modeling sam sager and koppers 1 1 proposed an episode of rapid late cretaceous true polar wander tpw a critical review of the data used however suggests that sager and koppers have underestimated the effects that errors and data