reynolds stress and sand transport over a foredune reynolds shear stress rs u w and sand transport patterns over a vegetated foredune are explored using three dimensional velocity data from ultrasonic anemometers at 0 2 and 1 2 m and sand transport intensity from laser particle counters at 0 014 m a mid latitude cyclone on 3 4 may 2010 generated storm force winds exceeding 20 m s 1 that shifted from offshore to obliquely alongshore quadrant analysis was used to characterize the spatial variation of rs quadrant components q1 through q4 and their relative contributions were parameterized using the flow exuberance relation exfl q1 q3 q2 q4 the magnitudes of rs and sand transport varied somewhat independently over the dune as controlled by topographic forcing effects on flow dynamics a flow exuberance effect was evident such that q2 ejection like and q4 sweep like quadrants that contribute positively to rs dominated on the beach dune toe and lower stoss whereas q1 and q3 that contribute negatively to rs dominated near the crest this exuberance effect was not expressed however in sand transport patterns instead q1 and q4 with above average streamwise velocity fluctuations u were most frequently associated with sand transport q4 activity corresponded with most sand transport at the beach toe and stoss locations 52 60 100 at the crest 25 to 86 of transport was associated with q1 while q4 corresponded with most of the remaining transport 13 to 59 thus the relationship between sand transport and rs is not as straightforward as in traditional equations that relate flux to stress in increasing fashion generally rs was poorly associated with sand transport partly because q1 and q4 contributions offset each other in rs calculations thus large amounts of transport can occur with small rs turbulent kinetic energy or reynolds normal stresses u 2 w 2 may provide stronger associations with sand transport over dunes although challenges exist on how to normalize and compare these quantities copyright 2013 john wiley sons ltd

role of sedimentation during basin inversion in analogue modelling sand box experiments were designed to reproduce the effect of sedimentation during extensional basin development and tectonic inversion these experiments were motivated by growing evidence for tectonic inversion in early miocene times of an extensional basin abanico basin in the central chilean andes with contemporaneous intense volcanic activity the experiments perform an extension followed by compression the first series of experiments were performed without sedimentation in the developing basin the second series were performed with partial filling of the basin and the third series with total filling of the extensional basin the effect of sedimentation on the sides of the basin was also controlled compression experiments reproducing tectonic inversion of the previously developed extensional basin were also performed with and without coeval sedimentation series with null partial or total fill and also external sedimentation the analogue experiments show that high amounts of sediments accumulated during the evolution of an extensional basin enhance subsidence and lead to the development of shortcuts in the footwall of the basin bounding faults during tectonic inversion during extension the earliest appearance of normal faults occurs in the compartment with the greater sedimentary fill and this causes asymmetric basin development the post extension compressional models show that the greater burden caused by a thicker accumulation of sediments within the basin inhibits tectonic inversion causing the development of thrust structures rooted in the basin bounding faults the accumulated sedimentary load affects both the extension and compression phases of the experiments but has greater influence in the case of sedimentation during extension a higher burden on the outer edges of the basin compared to the interior enhances the reactivation of normal faults and hampers the development of new thrust structures the thrust fault s originating from the most loaded basin compartment develops as a footwall shortcut from the reactivated fault with increasing sedimentation the shortcut is developed more superficially the shortcut absorbs less deformation than the associated main fault

modeling of surface deformation in volcanic areas the 1970 1972 and 1982 1984 crises of campi flegrei italy campi flegrei is a densely inhabited volcanic area within a caldera 12 14 km in diameter immediately west of naples italy in 1970 1972 and in 1982 1984 campi flegrei experienced considerable ground surface deformation producing a bulge about 3 5 m high at its peak in the two inflation episodes the point of maximum uplift did not change coinciding with the caldera center about which the displacements exhibited radial symmetry the 1982 1984 uplift was accompanied by considerable seismic activity gravity changes have been interpreted as reflecting the occurrence of a subvertical magmatic intrusion volcanological petrological and geophysical data point to the existence of a shallow magma chamber just beneath the center of the caldera we assume that the observed surface displacements are the response of an essentially elastic medium to a pressure increase in the magma chamber static deformation is calculated by using a finite element method assuming axial symmetry around a vertical axis through the caldera center the role played by various components of the model geometry boundary conditions elastic properties is analyzed it is shown that models assuming uniform elasticity are inadequate therefore the major volcanotectonic features as well as the influence of temperature and pressure on the elastic properties are taken into account the results of various more complex models are presented it is suggested that a progressively fractured zone whose size and shape depend also on the possible occurrence of magmatic intrusions may explain the observed surface displacements and the other data collected at campi flegrei it is suggested that the 1970 1972 uplift was possibly accompanied by larger scale changes in the stress field

problems of scale in the modeling and interpretation of coastal dunes abstract coastal dune systems are studied at time scales from seconds to millennia and space scales from millimeters to kilometers present approaches to the study of coastal dunes make it difficult to integrate models and interpretations of these systems over these scale ranges and arrive at reasonable conclusions it is argued that identification of key controls on dune development measurement of those controls and synthesis of data describing past and present conditions and used as calibration points will improve the viability of coastal dune models theoretical and empirical advances are necessary to improve the reliability of predictions across a range of geomorphological scales attempts at linking theoretical systematic models process synoptic measurement and historical or paleoenvironmental synthetic approaches make explicit the recognition that at time scales of more than a few hours and space scales greater than a few hundred meters deterministic models become unstable vis a vis prototype environments process climatologies provide one means to link process based work with broader scaled analysis as scales increase such climatologies will become less appropriate as the data become less reliable or as the systems change or as the scales become too large relative to the process record lengths in these conditions specific data i e samples representing points in time and space become check points for calibrating models it should be possible ideally to integrate both up and down time and space scales this is not yet possible

submarine landslides at subduction margins insights from physical models abstract submarine landslides which commonly develop along subduction margins at the front of accretionary prisms have recently been recognized as one of the most serious geohazards to investigate the mechanical processes involved in the development of these landslides a series of sandbox experiments were performed and the results were analyzed using the digital image correlation dic technique numerous slope failures which may be analogous to natural submarine landslides were produced on the model surface the slope failures can be classified as follows type i failures which are relatively small but are frequently developed on the lower parts of the slope and type ii failures which are relatively large and cover the entire slope but occur less frequently detailed observations reveal that the failure process can be divided into four stages 1 pre failure 2 steepening of the lower slope 3 type i failure and 4 type ii failure the minor type i slides act as precursors of major type ii failures each slope failure produces a topographic undulation triggering events in adjacent areas and a lateral migration of discrete slope failures although such experiments provide useful insight into slope failure processes a detailed 3d analysis of the failed sediment is vital if we are to understand the precise history of thrust activity at subduction margins recent and miocene accretionary prisms along the nankai trough japan display the geometric and lithologic characteristics of type i and type ii failures in their slide deposits

influence of topography on wind speed over a coastal dune and blowout system at jockey s ridge nc usa this study examines the spatial distribution of wind speed across a coastal dune system located at jockey s ridge state park north carolina the study area consists of a trough blowout through a foredune ridge and the landforms that have developed behind the foredune wind speed and direction were measured simultaneously with single sensors placed at a fixed height in 13 locations across the blowout dune complex fractional wind speed up is computed for sampling stations using data from a mast located on the beach as the reference results show that wind speeds were generally accelerated across the study site the highest speeds were recorded on the foredune ridges adjacent to the blowout wind was accelerated through the center of the blowout throat and along the downwind lateral wall further into the blowout at the base of the ramp to the depositional lobe higher wind speeds shifted to the upwind lateral wall and continued to accelerate up the ramp as air exited to the rear significant variations in the wind speed up pattern were associated with different wind approach angles with greater speed up occurring when the winds were aligned normal to the dune system the speed up decreased as the angle of approach became increasingly oblique to the ridge the patterns of wind speed up across the site point to the influence of topography on airflow to quantify the relationship measures of several topographic variables were obtained along sample transects running upwind from each sample station along flow lines representing different wind approach angles examination of correlation coefficients between wind speed up and topographic variables suggests that for groups of stations with similar topographic characteristics 30 50 of the variations in speed up may be explained by the upwind topographic variability copyright 2014 john wiley sons ltd

role of basin width variation in tectonic inversion insight from analogue modelling and implications for the tectonic inversion of the abanico basin 32 34 s central andes

restoration of the cretaceous uplift of the harz mountains north germany evidence for the geometry of a thick skinned thrust reverse movement on the harz northern boundary fault was responsible for the late cretaceous uplift of the harz mountains in northern germany using the known geometry of the surface position and dip of the fault and a published cross section of the base permian horizon we show that it is possible to predict the probable shape of the fault at depth down to a detachment level we use the inclined shear method with constant heave and argue that a shear angle of 30 was most likely in this case the detachment level is at a depth of ca 25 km kinematic restoration of the harz mountains using this fault geometry does not produce a flat horizon rather it results in a ca 4 km depression airy heiskanen isostatic equilibrium adjustment of the harz mountains restores the base permian horizon to the horizontal as well as raising the moho to a depth of 32 km a typical value for northern germany restoration also causes a rotation of tectonic fabrics within the harz mountains of about 11 clockwise we show that this model geometry is very good fit to the interpreted dekorp basin 9601 deep seismic profile

evaluation of approximations in modeling the thermal history of a volcanic area the thermal history of a relatively young volcanic area characterized by a shallow magmatic reservoir and the occurrence of a major eruption accompanied by caldera collapse is simulated numerically geometry geology and volcanic history of the system are chosen having in mind the campi flegrei volcanic area southern italy the 3d axially symmetric model adopted is nonhomogeneous with variable geometry and thermal properties depending on temperature heat transfer is treated using the conduction equations convection in the magma undoubtedly vigorous in the early stages of the cooling process is taken into account by a temperature averaging procedure moderate convection in the permeable rocks overlying the reservoir is simulated by using effective thermal parameters the mathematical problem is solved by a finite difference method this model is then adopted as reality and its results are compared with those obtained with other models referred to as approximations in which some features of the conventional reality have been neglected it is found that the temperature field of a static model in which the eruption of about 110 km3 of magma caldera collapse and the related physical changes are neglected is in good agreement with reality 30 000 years after the eruption the assumption of magma and surrounding rocks having the same constant thermal properties yields poor results errors of 100 150 k at shallow depth on the axis of symmetry if homogeneity is assumed only for the host rocks while the magma is assigned real properties the temperature field above the reservoir is affected by quite similar errors the temperature field is quite well approximated by solving the reality in a vertical plane through the axis of symmetry errors 20 k and 40 k in the central part of the caldera for t 120 000 years and t 250 000 years respectively after the emplacement of the magmatic body the solution of reality in just one dimension yields slightly poorer results

meso scale aeolian sediment input to coastal dunes the nature of aeolian transport events abstract observations of aeolian transport in coastal areas have focused on short term experiments because of limitations imposed by instrumentation this paper uses a case study at greenwich dunes prince edward island national park canada to analyze how sediment transport takes place at the beach over periods of weeks to months a monitoring station provided hourly time series of vegetation cover shoreline position fetch distances surficial moisture content presence of ice and snow wind speed and direction and transport processes over nine months analysis shows that high wind speeds may not generate any net transport into the dunes because of the limitations imposed by snow ice cover moisture and short fetch distances despite extreme winds during intense storms such events often lead to wave scarping rather than aeolian sediment input to the foredunes when sediment was transported on the beach the magnitude was regulated by a combination of factors including angle of wind approach fetch distance moisture content and duration of the wind event in particular angle of wind approach and therefore fetch distance may demote a high magnitude wind event with strong transport potential to one with no transport at all which poses challenges for predicting the effects of individual storms over the course of several months a significant proportion of sediment delivery to the foredunes was associated with wind events of low to medium magnitude it is suggested here that large magnitude wind events have low probabilities of resulting in transport towards the foredune because factors such as wave inundation play an increasing role in preventing sediment movement across the beach this has implications for modelling and management and highlights differences between the magnitude and frequency of aeolian transport events in the coastal environment compared to those in deserts and to fluvial sediment transport

meso scale modelling of aeolian sediment input to coastal dunes the collection of a time series coupling hourly wind data speed and direction with sand transport over months has provided new insights into the dynamics of transport events that input sediment to the foredune at greenwich dunes prince edward island national park canada this paper summarises the key aspects of aeolian sedimentmovement for a period of 9 months and presents amodelling approach for resolving aeolian transport to coastal dunes at the meso scale the main hypothesis of the modelling approach is that a small number of key factors control both the occurrence and the magnitude of transport events thresholds associated with these factors may be used to filter the time series and isolate potential transport periods over the year the impacts of nearshore processes are included in the approach as part of the dynamics of coastal dunes as are supply limiting factors and trade offs between fetch distances angle of wind approach and beach dimensions a simple analytical procedure based on previously published equations is carried out to assess the general viability of the conceptual approach results show that the incorporation of moisture and fetch effects in the calculation of transport for isolated potential transport periods result in improved predictions of sediment input to the dune net changes measured with three different techniques suggest that survey data with coarse temporal resolution underestimates the amount of sand input to the dune because sediment is often removed from the embryo dune and foredune by other processes such as wave scarping predictions obtained by the proposed modelling approach are of the same order of magnitude as measured deposition andmuch less than predicted bymodels based solely onwind speed and direction areas for improvement and alternative modelling approaches such as probabilistic approaches similar to weather forecasting are covered in the discussion

seismological evidence of an active footwall shortcut thrust in the northern itoigawa shizuoka tectonic line derived by the aftershock sequence of the 2014 m 6 7 northern nagano earthquake abstract a destructive m 6 7 earthquake struck northern nagano prefecture on november 22 2014 the main shock occurred on the kamishiro fault segment of the northern itoigawa shizuoka tectonic line istl we used data recorded at 41 stations of the local seismographic network in order to locate 2118 earthquakes that occurred between november 18 and november 30 2014 to estimate hypocenters we assigned low vp models to stations within the northern fossa magna nfm basin thus accounting for large lateral crustal heterogeneities across the kamishiro fault in order to further improve accuracy the final hypocenter locations were recalculated inside a 3d velocity model using the double difference method we used the aftershock activity distribution and focal mechanism solutions of major events in order to estimate the source fault area of the main shock our analysis suggests that the shallow part of the source fault corresponds to the surface trace of the kamishiro fault and dips 30 45 se while the deeper part of the source fault corresponds to the downdip portion of the otari nakayama fault a high angle fault dipping 50 65 se that formed during the opening of the nfm basin in the miocene along its surface trace the otari nakayama fault has been inactive during the late quaternary we verified the validity of our model by calculating surface deformation using a simple homogeneous elastic half space model and comparing it to observed surface deformation from satellite interferometry assuming large coseismic slip in the areas of low seismicity and small coseismic slip in the areas of high seismicity shallowing of the source fault from 50 65 to 30 45 in the upper 4 km in the areas where both surface fault traces are visible is a result of footwall shortcut thrusting by the kamishiro fault off the otari nakayama fault

the influence of topography and approach angles on local deflections of airflow within a coastal blowout the spatial variability of air flow through complex topography is an important but not fully understood component of dune development and dynamics this study examines the spatial variability of the wind field in a linear blowout in coastal dunes at jockey s ridge state park on the outer banks of north carolina a spatial array of single height anemometers and wind vanes were placed within the blowout topography exerted a significant steering effect when onshore winds approached from directions within 50 of the blowout axis under those conditions wind flow in the blowout aligned to the axis regardless of approach angle maximizing the potential for erosion and transport in the trough in other locations aspect variations caused deflection both proportional and disproportional to changes in the approaching wind when prevailing winds approached from directions more oblique than 50 to the blowout axis topographic steering through the blowout trough was reduced and secondary flow generated by flow separation over the trough became more prominent during those approach angles wind directions and speeds within the upper blowout trough became erratic as vortices and turbulence dominated the flow minimizing transport potential the changing characteristics of airflow in the blowout relative to differing approach angles has implications on dune development and variations in transport potential under changing conditions copyright 2013 john wiley sons ltd

holocene aeolian sand mobilization vegetation history and human impact on the stabilized sand dune area of the southern nyirseg hungary abstract almost 20 of the territory of hungary is covered by stabilized dunes formed during the pleistocene with the climate amelioration during the early holocene the aeolian activity ceased however various environmental and anthropogenic factors could have reactivated the aeolian processes today there is an increasing climatic stress on the dune fields of the carpathian basin which is coupled with inadequate land use it is therefore necessary to determine the timing and circumstances of sand mobilization during the holocene the site of the present study is located in a dune interdune system on the southern part of the nyirseg alluvial fan where periods of holocene aeolian activity and environmental change were investigated using palynological and sedimentological methods optically stimulated luminescence and radiocarbon dating the data achieved show climate driven boreal aeolian activity at approximately 8 2 ka and also demonstrate for the first time that during the atlantic phase 6 4 and 5 3 ka in spite of the relatively humid climate and dense vegetation aeolian activity has taken place induced probably by agricultural practices following subboreal morphological stability aeolian activity occurred several times in the subatlantic phase 2 4 2 2 1 2 0 8 and 0 4 0 1 ka as a result of vegetation changes and human activity

foredunes and blowouts initiation geomorphology and dynamics this paper reviews the initiation dynamics geomorphology and evolution of incipient foredunes established foredunes and blowouts incipient foredunes may be initiated in a variety of ways leading to the formation of ramps terraces or ridges depending on progradation rates vegetation type and cover sediment transport rates and scale of erosional processes vegetation cover morphology growth rates and types combine with aerodynamic processes to determine dune and swale morphology established foredunes are classified into five morpho ecological types and the flow behaviour over two types is detailed a new model of foredune evolutionary paths at various possible time scales is presented blowout initiation dynamics and sediment transport and evolution is examined throughout the review the gaps in present understanding of dune processes and a range of ideas for new research possibilities are provided

three years of morphologic changes at a bowl blowout cape cod usa this study presents measurements of blowout topography obtained with annual terrestrial laser surveys carried out over a three year period at a single large bowl blowout located in the provincelands dunes section of cape cod national seashore in massachusetts the study blowout was selected because its axis is aligned with northwest winds that dominate the region and because it was seemingly interacting with a smaller saucer blowout that had recently formed on the southern rim of the primary feature assuming that blowouts enlarge both horizontally and vertically in response to the wind regime the objectives of the study were to determine both the amount of horizontal growth that the blowout experiences annually and the spatial patterns of vertical change that occur within the blowout changes to the blowout lobe surrounding the feature were also determined for areas with sparse enough vegetation cover to allow laser returns from the sand surface the results show that the blowout consistently expanded outward during the three years with the greatest expansion occurring at its southeast corner opposite the prevailing winds the most significant occurrence was the removal in the first year of the ridge that separated the two blowouts resulting in a major horizontal shift of the southern rim of the new combined blowout this displacement then continued at a lesser rate in subsequent years the rim also shifted horizontally along the northwest to northeast sections of the blowout significant vertical loss occurred along the main axis of the blowout with the greatest loss concentrated along the southeast rim on the lobe there were large areas of deposition immediately downwind of the high erosion zones inside the blowout however there were also small erosion areas on the lobe extending downwind from eroding sections of the rim this study shows that 1 blowouts can experience significant areal and volumetric changes in short periods of time 2 significant changes may occur relatively suddenly when adjacent blowouts combine into a single feature and 3 the sediment transport paths are highly controlled by the topography the joining of two blowouts not only creates a new larger feature but it also releases large amounts of sediment that are then distributed across the landscape downwind creating a potential for major changes to a landscape over the longer term

a new instantaneous aeolian sand trap design for field use a new aeolian sediment trap is described which can give up to 1 hz measurement frequency in held conditions the trap adopts a circular horizontal trap design with a load cell connection to give continuous unobtrusive trap measurement of sediment flux simultaneous velocity recording is carried out using an anemometer trap construction costs are approximately pound 200 initial results in held conditions using a direct comparison of wind velocity data sampled at an equivalent frequency have given a first order relationship between sediment flux and velocity the trap enables simultaneous sampling of wind velocity and sediment flux at a sufficiently short interval to enable investigation of sediment transport dynamics under a variety of field conditions

geometry and kinematics of glaciotectonic deformation superimposed on the cenozoic fault tectonic framework in the central polish lowlands abstract the distribution of glaciotectonic structures can be controlled by the occurrence of tectonic or neotectonic faulting of the pre quaternary basement the faulted and thus undulated pre quaternary basement influenced the thinning or pinching out of weak deformable surficial sediments and could play a role of buried obstacles to forcing by ice sheets in both cases such faulting could result in a predisposition to the development of glaciotectonic deformations the present study has demonstrated how the geometry and kinematics of the glaciotectonic structures was controlled by the pre quaternary framework related to the kleczew graben tectonics the central polish lowlands the assumption has been made in this study that the tectonic fractures and faults could influence the reduction of strength and mechanical anisotropy within the pre quaternary sediments which were also remobilised by glaciotectonic forces the renewed stress build up by the glaciotectonic forces assumed herein could reactivate the pre existing fractures and faults at a lower stress level rather than produce new structures that require a higher stress level the results presented in this study are focused on detailed structural and kinematic analysis of the glaciotectonic faults and fractures for each glaciotectonic fault studied the slip vector was directly calculated based on the orientation of the fault striations and indirectly calculated from analysis of the small fractures that developed along the fault additionally the data from this analysis were integrated with the surface based 3d structural model obtained from the borehole data this approach revealed the relationships between the geometry orientation and kinematics of the glaciotectonic structures and the tectonic framework of the pre quaternary basement the different modes of glaciotectonic faulting were determined depending on the geometry and orientation of the pre existing reactivated faults and fractures with respect to the direction of the glaciotectonic contraction in addition to reverse dip slip displacements the strike slip and oblique slip displacements were recognised this study was performed in the kleczew graben the middle part of the polish lowlands in which the quaternary and the miocene sediments are affected by glaciotectonic deformations moreover the miocene sediments were also tectonically deformed in response to the development of the graben

turbulent reynolds stress and quadrant event activity in wind flow over a coastal foredune recent research on quasi instantaneous turbulent kinematic reynolds stresses rs u w and decomposed quadrant event activity e g ejections and sweeps over dunes in fluvial settings and in wind tunnels has shown that turbulent stresses at the toe of a dune often exceed time averaged streamwise shear stress u 2 estimates it is believed that semi coherent turbulent structures are conveyed toward the bed along concave streamlines in this region and that impact of these structures cause fluctuations in local surface stresses that assist in grain entrainment this has been hypothesized to explain how sand is supplied to the windward slope through a region of flow stagnation toward the crest surface stress increases and becomes dominated by streamwise accelerations resulting from streamline compression and convexity that suppress vertical motions high frequency 32 hz measurements of turbulent wind flow from 3 d ultrasonic anemometers are analyzed for oblique onshore flow over a vegetated coastal foredune in prince edward island canada reynolds stress and quadrant activity distributions varied with height 0 60 m and 1 66 m and location over the dune in general quadrant 2 ejection u 0 and quadrant 4 sweep activity u 0 w 0 w 0 and quadrant 3 inward interaction u 0 w 0 activity on the lower stoss slope significant ejection and sweep event activity was most frequent 85 to 92 ejections plus sweeps whereas at the upper crest significant ejection and sweep activity became less frequent while significant outward and inward interactions increased in frequency 25 to 36 an exuberance effect i e changing shape of quadrant frequency distribution skewed toward ejection and sweep activity is observed whereby streamline compression and convexity effects inhibit vertical fluctuations in flow and thus reduce the frequency of ejections and sweep activity toward the crest in separated flow in the lee of the crest quadrant distributions were more symmetrical as a result of more mixed multi directional flow these trends in turbulent event distributions and reynolds stress have implications for sediment transport dynamics across the dune and may help to explain sand transport potential and dune maintenance for example areas with a high frequency of ejection and sweep activity may have higher rates of sediment entrainment and transport whereas areas with lower ejection and sweep activity and an increase in outward and inward interactions which contribute negatively to reynolds stress generation may experience a greater potential for deposition further research on associations between quadrant event activity and coincident sand transport is required to confirm this hypothesis and the resultant significance of the flow exuberance effect in aeolian dune morphodynamics

flow dynamics and geomorphology of a trough blowout the dynamics and geomorphological development of a trough blowout located at fiona beach in the myall lakes national park in nsw australia are examined wind speeds velocities and flow structure were measured utilizing an array of miniature rimco cup anemometers gill bivane and uvw instruments and wind vanes flow measurements indicate that when the wind approaches the trough blowout parallel to the throat orientation jets occur both in the deflation basin and along the erosional walls relative flow deceleration and expansion occurs up the depositional lobe jets are formed over the depositional lobe crest accompanied by downwind flow separation on the leeward side of the lobe and flow separation and the formation of corkscrew vortices occur over the crests of the erosional walls maximum erosion and transport occurs up the deflation basin and onto the depositional lobe trough blowout morphologies are explained as a function of these flow patterns when the wind approaches the blowout obliquely the flow is steered considerably within the blowout and the degree and complexity of topographic steering is dependent on the blowout topography the flow is usually extremely turbulent and large corkscrew vortices are common the local topography of a blowout can be very important in determining overall sand transport and blowout evolutionary conditions and paths estimates of potential sand transport within the blowout may be up to two orders of magnitude lower than actual rates if remotely sensed wind data are used

ecogeomorphic state variables and phase space construction for quantifying the evolution of vegetated aeolian landscapes cellular automaton modelling for the simulation of dune field formation and evolution has developed progressively in aeolian geomorphology in the last decade or so a model that incorporates the effects of vegetation and its interactions with geomorphic landscape development the discrete ecogeomorphic aeolian landscapes decal model can replicate a number of important visual and qualitative aspects of the complex evolution of aeolian dune landscapes under the influence of vegetation dynamics in coastal environments a key challenge in this research area is the analysis and comparison of both simulated and real world vegetated dune landscapes using objective and quantifiable principles this study presents a methodological framework or protocol for numerically quantifying various ecogeomorphic attributes using a suite of mathematically defined landscape metrics to provide a rigorous and statistical evaluation of vegetated dune field evolution within this framework the model parameter space can be systematically explored and simulation outcomes can be methodically compared against real world landscapes based on a simplified scenario of parabolic dunes developing out of blow outs the resulting dune field realizations are investigated as a function of variable growth vigour of two simulated vegetation types pioneer grass and successional woody shrub by establishing a typological phase diagram of different landscape classes the set of simulation outcomes furthermore defines a higher dimensional phase space whose axes or dimensions can be interpreted by analysing how individual ecogeomorphic landscape metrics or state variables contribute to the data distribution principal component analysis can reduce this to a visual three dimensional 3d phase space where landscape evolution can be plotted as time trajectories and where we can investigate the effects of changing environmental conditions partway through a simulation scenario the use of landscape state variables and the construction of a 3d phase space presented here may provide a general template for quantifying many other eco geomorphic systems on the earth s surface

investigation of three dimensional wind flow behaviour over coastal dune morphology under offshore winds using computational fluid dynamics cfd and ultrasonic anemometry the behaviour of offshore directed winds over coastal dune and beach morphology was examined using a combination of modelling 3 d computational fluid dynamics cfd and field measurement both model simulations and field measurements showed reversal of offshore flows at the back beach and creation of an onshore sediment transport potential the influence of flow reversals on the beach dune transport system and foredune growth patterns has previously received little attention detailed wind flow measurements were made using an extensive array of mast mounted 3 d ultrasonic anemometers 50 hz arranged parallel to the dominant incident wind direction large eddy simulation les of the offshore wind flow over the dune was conducted using the open source cfd tool openfoam the computational domain included a terrain model obtained by airborne lidar and detailed ground dgps measurements the computational grid 22 million cells included localized mesh refinement near the complex foredune terrain to capture finer details of the dune morphology that might affect wind flows on the adjacent beach measured and simulated wind flow are presented and discussed the cfd simulations offer new insights into the flow mechanics associated with offshore winds and how the terrain steering of wind flow impacts on the geomorphological behaviour of the dune system simulation of 3 d wind flows over complex terrain such as dune systems presents a valuable new tool for geomorphological research as it enables new insights into the relationship between the wind field and the underlying topography the results show that offshore and obliquely offshore winds result in flow reversal and onshore directed winds at distances of up to 20m from the embryo dune toe the potential geomorphological significance of the findings are discussed and simple calculations show that incoming offshore and obliquely offshore winds with mean velocities over 13m s 1 and 7m s 1 respectively have the potential to create onshore directed winds at the back beach with mean velocities above 3 3m s 1 these are above the threshold of movement for dry sand and support previous conclusions about the significance of offshore winds in dune and beach budget calculations

evaluation of approximations in modelling the cooling of magmatic bodies abstract the cooling of a magmatic intrusion is simulated by a simple model of a non homogeneous earth with thermal properties depending on temperature in which heat transfer is assumed to take place by conduction only the mathematical problem consists in solving a non linear partial differential equation with continuity conditions on temperature and heat flux imposed at the contacts between different rocks this has been done numerically by a finite difference method the model is then adopted as reality against which a number of commonly used approximations are tested it is found that the effect of latent heat liberation can be reasonably taken into account by attributing an effective initial temperature to the magma errors within 20 c for t 10 5 years when the temperature of the magma is still as high as 600 c the effective specific heat approximation does not work as well the dependence of thermal conductivity and specific heat on temperature may be eliminated by maintaining the errors within 30 c for t 5 years the assumption that magma and country rocks have the same thermal properties allows an estimate of the temperature field in the host rocks with errors of 50 c at most the assumption that all rocks have the same constant conductivity yields results that are far from reality errors of 100 200 c even at shallow depth

influence of fault geometries and mechanical anisotropies on the growth and inversion of hanging wall synclinal basins insights from sandbox models and natural examples

mobility of a remobilised parabolic dune in kennemerland the netherlands abstract a parabolic dune in the netherlands was remobilised in december 1998 by removing vegetation and soil the main aim of the experiment was ecological to investigate whether permanent rejuvenation at the landscape scale is possible by restoration of natural processes if processes can be reactivated at coarse scale periodic rejuvenation of the landscape over the long term is possible without the need for managers to interfere further the experiment provides the opportunity to address another important question can large parabolic dunes in the netherlands be mobile in the present climate mobility of the dune is investigated by means of erosion pins aerial photography and measurement of cross sections activity indices are derived from erosion pin recordings and correlated to weather conditions from 1999 to 2001 displacement of the dune ranged from 0 to 12 m in east northeasterly direction activity of the dune is related to wind conditions but the relationship is strongly influenced by precipitation and therefore differs for wet and dry periods periods with extreme wind speeds resulted in much less geomorphic change than expected

application of geometric models to inverted listric fault systems in sandbox experiments paper 2 insights for possible along strike migration of material during 3d hanging wall deformation abstract fault geometry is a primary control on hanging wall deformation in this study a series of positive inversion analogue experiments was conducted using rigid fault surfaces of true 3d geometry with consistent listric geometry along the transport direction the deformed geometry of the top horizon of the syn extension sequence on vertical serial sections was examined with a conventional 2d geometric restoration technique to calculate the inclined antithetic shear angle that best approximates the actual fault shape and to estimate the amount of apparent horizontal shortening during contraction the apparent shear inclination and the estimated apparent shortening show a systematic change along strike corresponding to the plan geometry of the master detachment surface at the hanging wall above embayments in the fault geometry the uplift is highest the apparent shear inclination is gentlest and the apparent horizontal shortening is greatest in contrast the apparent shear inclination is steepest and the estimated shortening is smallest above salients in the master detachment geometry where the uplift is lowest these changes suggest that the hanging wall displacement had an along strike component during deformation the hanging wall material moves from the regions above salients to those above embayments in the detachment surface during contraction average of the estimated apparent shortening was smaller than the actual amount of the experiments probably due to tectonic compaction this study shows that the geometry of the master detachment in plan view has the primary control on the lateral variation of the hanging wall deformation the data presented in this paper help understand 3d geometric relations between the hanging wall deformation and the underlying detachment surfaces

human impact on fixed sand dunes revealed by morphometric analysis the nyirseg is the second largest alluvial fan in hungary covered by fixed sand dunes the primary aim of the paper is to describe the morphology of dunes in the region and classify them based on their morphometric characteristics the other major aim is to select those dunes which were exposed to significant anthropogenic impact and to determine the spatial and temporal differences in the intensity of human activity the following dune types were separated valley marginal transitional valley marginal transitional parabolic filled partially and unfilled parabolic dunes after defining different dune types and their parameters certain dunes were selected based on exposure to significant anthropogenic impact definite connection was demonstrated between the intensity of human environmental impact and the rate of erosion on fixed sand dunes the erosion of sand dunes was most intensive in medieval times most likely due to concentration of agricultural land use copyright 2009 john wiley sons ltd

streamline correction for the analysis of boundary layer turbulence abstract improvements in the design and affordability of ultrasonic anemometers have provided significant contributions to aeolian research by facilitating high frequency monitoring of three dimensional wind velocities from these data it is possible to calculate quasi instantaneous reynolds stresses to evaluate boundary layer turbulence moving beyond time averaged measures such as shear velocity u as ultrasonic anemometry is used more frequently in aeolian geomorphology it is important to question accepted conventions concerning data processing and analysis this paper examines data processing questions associated with the application of ultrasonic anemometry to field studies in aeolian geomorphology through an investigation of three streamline correction routines the two step three step and planar fit methods on data recorded on a gently sloping beach at magilligan strand northern ireland in may 2010 the planar fit technique has not previously been used in aeolian geomorphology results are compared with data that have been corrected only for wind direction yaw the effects that these different methods have on quadrant analysis and reynolds stress calculation are discussed streamline correction is applied as a time variable procedure using a characteristic timescale of 8 s following analysis of the resultant wind speed energy spectrum it is found that reynolds shear stress is dependent on streamline correction method with run mean estimates of resultant horizontal shear stress ranging from 0 05 to 0 11 n m 2 depending on the technique the two step method consistently maximises the shear stress and when the resultant horizontal shear is calculated it produces the most robust estimate for application to aeolian research in contrast the different methods have little effect on the identification or sequencing of turbulent structures using quadrant analysis streamline correction is an essential processing step when using reynolds decomposition however the method used has an effect on data quality as each correction re distributes stress across the whole tensor altering both normal and shear stresses the total stress tensor magnitude itself is a conserved value and may provide a suitable parameter to quantify boundary layer turbulence

airflow and aeolian sediment transport patterns within a coastal trough blowout during lateral wind conditions blowouts are depressions that occur on coastal dunes deserts and grasslands the absence of vegetation in blowouts permits high speed winds to entrain and remove sediment whereas much research has examined patterns of wind flow and sediment transport on the stoss slopes and lee of sand dunes no study has yet investigated the connections between secondary air flow structures and sediment transport in a blowout where zones of streamline compression expansion and steering are less clearly delineated in this study we investigated the variability of sediment flux and its relation to near surface wind speed and turbulence within a trough blowout during wind flow that was oblique to the axis of the blowout wind flow was measured using six three dimensional 3d ultrasonic anemometers while sediment flux by eight sand traps all operating at 25 hz results demonstrated that sediment flux rates were highly variable throughout the blowout deflation basin even over short distances 0 5 m where flow was steadiest flux was greatest consequently the highest rates of sediment transport were recorded on the erosional wall crest where flow was compressed and accelerated the strength of correlation between sediment flux and wind parameter improved with an increase in averaging interval from 10 seconds to 1 minute at an interval of 10 seconds however wind speed correlated best with flux at seven of eight traps whereas at an interval of one minute turbulent kinetic energy tke provided the best correlation with flux at six of the eight traps correlation between sediment flux and wind parameters was best in the centre of the blowout and poorest on the erosional wall crest the evidence from this paper suggests for the first time that tke may be a better predictor of sediment transport at minute scale averaging intervals particularly over landforms where wind flow is highly turbulent

investigating parabolic and nebkha dune formation using a cellular automaton modelling approach vegetation plays an important role in shaping the morphology of aeolian dune landscapes in coastal and semi arid environments where ecogeomorphic interactions are complex and not well quantified we present a discrete ecogeomorphic aeolian landscape model decal capable of simulating realistic looking vegetated dune forms permitting exploration of relationships between ecological and morphological processes at different temporal and spatial scales the cellular automaton algorithm applies three simple rules that lead to self organization of complex dune environments including nebkhas with distinctive deposition tails that form in association with mesquite type shrubs and hairpin long walled parabolic dunes with trailing ridges that evolve from blowouts in association with vegetation succession changing the conditions of simulations produces differing landscapes that conform qualitatively to observations of real world dunes the model mimics the response of the morphology to changes in sediment supply vegetation distribution density and growth characteristics as well as initial disturbances the introduction of vegetation into the model links spatial and temporal scales previously dimensionless in bare sand cellular automata grid resolutions coarser than the representative size of the modelled vegetation elements yield similar morphologies but when cell size is reduced to much smaller dimensions the resultant landscape evolution is dramatically different the model furthermore demonstrates that the relative response characteristics of the multiple vegetation types and their mutual feedback with geomorphological processes impart a significant influence on landscape equilibria suggesting that vegetation induces a characteristic length scale in aeolian environments this simple vegetated dune model illustrates the power and versatility of a cellular automaton approach for exploring the effects of interactions between ecology and geomorphology in complex earth surface systems

structural geological interpretations from unrolled images of drill cores abstract structures hidden at depth can be assessed through drill cores recovered from them a crucial part of petroleum geology study is to interpret structures from these cores collected from vertical and inclined drilling operations reaching different depths we deduce analytically ideal structures in unrolled unwrapped images of cylindrical drill cores these structures are i orthogonal and conjugate fractures ii single generation periodic folds and type 1 and type 2 superposed folds iii listric faults and iv different types of angular unconformities the sinuous curves as found in unrolled images are not always characteristic of the structures therefore accurate identification of structures would require additional information such as the drill core itself

high frequency sediment transport responses on a vegetated foredune wind flow and sand transport intensity were measured on the seaward slope of a vegetated foredune during a 16 h storm using an array of sonic anemometers and wenglor laser particle counters the foredune had a compound seaward slope with a wave cut scarp about 0 5 m high separating the upper vegetated portion from the lower dune ramp which was bare of vegetation wind direction veered from obliquely offshore at the start of the event to obliquely onshore during the storm peak and finally to directly onshore during the final 2 h as wind speed dropped to below threshold sand transport was initially inhibited by a brief period of rain at the start of the event but as the surface dried and wind speed increased sand transport was initiated over the entire seaward slope transport intensity was quite variable both temporally and spatially on the upper slope as a result of fluctuating wind speed and direction but overall magnitudes were similar over the whole length ten minute average transport intensity correlates strongly with mean wind speed measured at the dune crest and there is also strong correlation between instantaneous wind speed and transport intensity measured at the same locations when the data are smoothed with a 10 s running mean transport on the beach for onshore winds is decoupled from that on the seaward slope above the small scarp when the wind angle is highly oblique but for wind angles 45 from shore perpendicular some sand is transported onto the lower slope copyright 2012 john wiley sons ltd

high resolution measured and modelled three dimensional airflow over a coastal bowl blowout abstract blowouts are common landforms found within coastal dunes their dynamics are primarily driven by aeolian transport caused by surface wind stress though patterns of deflation and deposition within blowouts are poorly understood as near surface wind flow is complex three dimensional wind flows around blowouts have yet to be properly quantified especially within zones of separation re attachment and acceleration this has been largely due to inadequate measurement of airflow and a lack of suitable airflow models with this in mind we present results from a study that has quantified alongshore and oblique onshore wind flow dynamics over a bowl blowout on the belmullet peninsula ireland using ultrasonic three dimensional anemometry measuring at 50 hz and three dimensional computational fluid dynamic cfd modelling we measure and model for the first time in 3d a detailed picture of the heterogeneity of wind flow over this type of terrain during alongshore wind conditions wind speeds within the deflation basin were retarded by 50 compared to the foredune zone and flow separation restricted to a small zone in lee of the windward rim wind was directed into the deflation basin through a gap in a western erosional wall termed the blowout throat in oblique onshore wind airflow orientated with the blowout throat remained unchanged in direction and slowed by only 30 compared to wind speed on the foredune in lee of the erosional wall adjacent to the blowout throat small zones of flow separation occurred close to the erosional wall in both cases the highest variation in wind speed and direction occurred in zones of separation and attachment whilst flow increased in steadiness with height over the erosional walls the results illustrate that wind is manipulated according to localised topography within the bowl blowout itself resulting zones of potential sediment transport erosion and deposition are spatially complex and alter with wind direction the presence of a blowout throat has a significant influence on airflow patterns within a deflation basin modelled cfd and measured anemometer data demonstrated excellent comparisons for wind direction and speed allowing much greater spatial measurement resolution than physical instrumentation simulated turbulence did not correlate well with measured data highlighting the requirement for high frequency three dimensional anemometry in areas of complex flow

the phlegraean fields structural evolution volcanic history and eruptive mechanisms abstract the main event within the volcanic history of the phlegraean fields was the eruption about 35 000 years ago of a huge alkali trachytic ignimbrite 80 km 3 dre followed by caldera collapse the pre caldera activity evidence from geothermal wells and surface outcrops changed from submarine to subaerial shortly before the ignimbrite eruption the caldera was subsequently invaded by the sea and became progressively filled with tuffites and subordinate submarine flows in its northern half the last submarine explosive activity dates back to 12000 10500 yr with the eruption of mostly hydroplinian yellow tuffs recent mostly subaerial activity consists of a series of explosive eruptions whose volume decreases with time until the last eruption of mt nuovo in 1538 a d two peaks in recent activity occur at 10000 8000 and 4700 3000 years ago during post caldera activity eruptive vents migrated from the caldera rim toward the center where there are two distinct zones of recent vents minor collapses occurred within the caldera after the main eruptions often they are eccentric to the vent and displaced toward the caldera center phlegraean explosive activity is characterized by water magma interaction eruptive events without a hydromagmatic component are extremely rare in most cases the evolved trachytic magmas interacted with surface water either the sea or intracaldera lakes however there is evidence of interaction of magma with deep seated aquifers for some plinian events explosivity i e the efficiency of the transformation of thermal into kinetic energy during magma water interaction is largely controlled by the primary fragmentation of the magmatic melt

basin inversion and contractional reactivation of inherited normal faults a review based on previous and new experimental models abstract compressional inversion of former extensional sedimentary basins is a particularly common phenomenon given that passive margins share the same destiny of being subsequently incorporated into fold and thrust belts during basin inversion pre existing faults may concentrate stress and localise future thrust ramps or may be reactivated recording reversal of movement from extension to reverse this process has attracted attention largely because of its economic implications related to petroleum and ore deposit prospects and seismic hazard assessment since more than two decades analogue modelling has been used to indentify and or test a number of parameters relevant for the inversion process this paper aims therefore to offer a reasoned review of the analogue modelling work done on the subject coupling such previous results with those of a new experimental series inspired to the northern apennines stratigraphy and evolution past models have explored the role of main factors governing fault reactivation susceptibility such as fluid pressure fault weakness fault steepness angle of shortening and sediment loading the new models have addressed the role played by geometry and strength of a basal ductile layer during inversion two sets of sand silicone models were first extended orthogonally at different velocities to produce dissimilar pre inversion internal geometries and then shortened coaxially at different velocities to vary the brittle ductile coupling the experimental results confirm the selectiveness of fault inversion and reveal strong similarities with structural styles of tectonic inversion reported from the northern apennines and various areas worldwide the preferred geological model inferred from this modelling involves contribution of 1 syn inversion rotation of pre existing faults to shallower dip and 2 rotation of principal stress axes which could explain the invariable reactivation of only one of the two oppositely dipping graben bounding faults these factors would thus interact with the other well established parameters controlling the fault reactivation process

parabolic dune reactivation and migration at napeague ny usa insights from aerial and gpr imagery abstract observations from mapping since the 19th century and aerial imagery since 1930 have been used to study changes in the aeolian geomorphology of coastal parabolic dunes over the last 170 years in the walking dune field napeague ny the five large parabolic dunes of the walking dune field have all migrated across or are presently interacting with a variably forested area that has affected their migration stabilization and morphology this study has concentrated on a dune with a particularly complex history of stabilization reactivation and migration we have correlated that dune s surface evolution as revealed by aerial imagery with its internal structures imaged using 200 mhz and 500 mhz ground penetrating radar gpr surveys both 2d transect and high resolution 3d gpr imagery image downwind dipping bedding planes which can be grouped by apparent dip angle into several discrete packages of beds that reflect distinct decadal scale episodes of dune reactivation and growth from aerial and high resolution gpr imagery we document a unique mode of reactivation and migration linked to upwind dune formation and parabolic dune interactions with forest trees this study documents how dune dune and dune vegetation interactions have influenced a unique mode of blowout deposition that has alternated on a decadal scale between opposite sides of a parabolic dune during reactivation and migration the pattern of recent parabolic dune reactivation and migration in the walking dune field appears to be somewhat more complex and perhaps more sensitive to subtle environmental pressures than an idealized growth model with uniform deposition and purely on axis migration this pattern believed to be prevalent among other parabolic dunes in the walking dune field may occur also in many other places where similar observational constraints are unavailable

airflow and sand transport variations within a backshore parabolic dune plain complex ne graham island british columbia canada onshore aeolian sand transport beyond the beach and foredune is often overlooked in the morphodynamics and sediment budgets of sandy coastal systems this study provides detailed measurements of airflow sand transport via saltation and modified suspension vegetation density and surface elevation changes over an extensive 325 30 m swath of a backshore foredune parabolic dune plain complex near surface 30 cm wind speeds on the backshore ranged from 4 3 to 7 3 m s 1 gusting to 14 0 m s 1 oblique onshore flow is steered alongshore near the incipient foredune then landward into a trough blowout where streamline compression flow acceleration to 1 8 times the incident speed and increasing steadiness occur highest saltation rates occur in steady topographically accelerated flow within the blowout as such the blowout acts as a conduit to channel flow and sand through the foredune into the foredune plain beyond the blowout flow expands vegetation roughness increases and flow decelerates over the foredune plain localized flow steering and acceleration to 1 6 times the incident speed occurs followed by a drop to 40 of incident flow speed in a densely vegetated zone upwind of an active parabolic dune at 250 m from the foredune sediment properties reflect variations in near surface flow and transport processes well sorted fine skewed backshore sands become more poorly sorted and coarse skewed in the blowout due to winnowing of fines sorting improves and sands become fine skewed over the foredune plain toward the parabolic dune due to grainfall of finer sands winnowed from the beach and foredune during the fall winter season significant amounts of sand up to 110 kg m 2 are transported via modified suspension and deposited as grainfall up to 300 m landward of the foredune no distinct trend in grainfall was found although most fell on the depositional lobe of the blowout and at 200 m near an isolated active parabolic dune grainfall amounts may reflect several transporting events over the measurement period and the transport process is likely via localized modified suspension from the crest of the foredune and other compound dune features in the foredune plain this evidence suggests that the process of grainfall delivery though often overlooked in coastal research may be a key process in maintaining active dunes hundreds of metres from the shoreline in a densely vegetated foredune plain the effectiveness of this process is controlled by seasonal changes in vegetation cover and wind strength as well as shorter term e g tidally controlled variations in sand availability from the beach

patterns of wind flow and aeolian deposition on a parabolic dune on the southeastern shore of lake michigan abstract sand deposition and patterns of wind flow were studied on green mountain beach gmb dune a large lake michigan coastal dune that is transitional between a trough blowout and a fully developed parabolic dune deposition pins were used to study the amount and pattern of aeolian sand deposition on the lee slopes of gmb dune over 20 months in the late fall and winter sand supported by ice between the grains accumulated on the upper to mid slopes and became over steepened 38 during measurement periods containing two major storms with wind gusts up to 25 m s a total of 44 of the deposition on the lee slope occurred compared to an average of 9 for comparable time periods between storms sand was delivered by mass movement to the lower slopes during the spring thaw very little sand was deposited on lee slopes during the summer maximum sand deposition occurred near the dune axis oriented southwest northeast and then decreased rapidly along the limbs maximum sand transport and dune migration were oriented towards the northeast despite the dominant regional winds during the fall and winter being from the west and northwest arrays of anemometers and wind vanes were used to study airflow patterns within gmb dune on five different days these studies indicate that steering of winds in the deflation area of the dune may be responsible for the northeasterly sediment transport they also suggest however that the ability of the dune to steer winds and thus control the direction of sand transport and deposition decreases when the angle between the oncoming winds and the dune axis is too great

application of geometric models to inverted listric fault systems in sandbox experiments paper 1 2d hanging wall deformation and section restoration abstract fault geometry is a primary control on hanging wall deformation in order to examine their geometrical relationships a positive inversion analogue experiment was conducted using a rigid fault surface of listric geometry the hanging wall deformation observed on a representative vertical section was examined with conventional 2d geometric models and was restored to its pre inversion phase with two techniques these results suggest that the deformation can be best approximated by inclined simple shearing iss the iss model can determine the inclination of the apparent shear plane and the amount of apparent horizontal shortening which is equivalent to that calculated with the conventional depth to detachment method this estimated apparent shortening was generally smaller than the actual amount of the experiments probably due to tectonic compaction

airflow reversal and alternating corkscrew vortices in foredune wake zones during perpendicular and oblique offshore winds on all sandy coastlines fringed by dunes understanding localised air flow allows us to examine the potential sand transfer between the beach and dunes by wind blown aeolian action traditional thinking into this phenomenon had previously included only onshore winds as effective drivers of this transfer recent research by the authors however has shown that offshore air flow too can contribute significantly through lee side back eddies to the overall windblown sediment budget to coastal dunes under rising sea levels and increased erosion scenarios this is an important process in any post storm recovery of sandy beaches until now though full visualisation in 3d of this newly recognised mechanism in offshore flows has not been achieved here we show for the first time this return flow eddy system using 3d computational fluid dynamics modelling and reveal the presence of complex corkscrew vortices and other phenomena the work highlights the importance of relatively small surface undulations in the dune crest which act to induce the spatial patterns of airflow and transport found on the adjacent beach

geophysical characterization of the ota vila franca de xira lisbon sesimbra fault zone portugal summary this paper focuses on the reprocessing of seismic reflection profiles aeromagnetic and seismicity data to locate and characterize the ota vila franca de xira lisbon sesimbra fault zone the studied structure is sited in the lower tagus valley an area with over 2 million inhabitants that has experienced historical earthquakes causing many casualties serious damage and economical losses e g 1531 january 26 and 1909 april 23 earthquakes whose tectonic sources are mostly unknown the fault zone trends nne ssw to n s is located near the eastern border of the mesozoic lusitanian basin and partially delimits the lower tagus cenozoic basin at the west mostly hidden under the cenozoic sedimentary fill according to the data presented here the normal structures that compose the fault zone were reactivated in cenozoic times with positive inversion and the development of splays towards the east the fault zone shows three distinct segments with different behaviour in conformity with their various orientations relative to the nw se maximum compressive stress the northern segment splays into a series of nne ssw oriented east verging imbricate thrusts which merge to the west into a major reverse fault that resulted from the tectonic inversion of the former normal fault bordering the

thermal history of phlegraean fields italy in the last 50 000 years a schematic numerical model an attempt is made to reproduce by numerical simulation the last 50 000 years of the phlegraean fields volcanic history in terms of a magma chamber with volume progressively reduced by magma extraction to the surface and without refillings from depth since the aim is just to verify the plausibility of such an assumption attention is focused on the major volcanic events and a rather crude model is adopted it turns out that the main features of the phlegraean fields thermal history namely the campanian ignimbrite the yellow tuffs emission and the high temperatures measured in the geothermal wells drilled inside the caldera can reasonably be reproduced under the not refilled system assumption the magmatic body is predicted to have an average temperature of 1000 c at present

a note on fault reactivation reactivation of existing faults whose normal lies in the 1 3 plane of a stress field with effective principal compressive stresses 1 2 3 is considered for the simplest frictional failure criterion n n p where and n are respectively the shear and normal stresses to the existing fault p is the fluid pressure and is the static friction for a plane oriented at to 1 the stress ratio for reactivation is 1 3 1 cot 1 tan this ratio has a minimum positive value at the optimum angle for reactivation given by 12tan 1 1 but reaches infinity when 2 beyond which 3 0 is a necessary condition for reactivation an important consequence is that for typical rock friction coefficients it is unlikely that normal faults will be reactivated as high angle reverse faults or thrusts as low angle normal faults unless the effective least principal stress is tensile

seasonal sand transport through a trough blowout at pinery provincial park ontario trough blowouts represent transport pathways for sediment through coastal dune systems this paper documents seasonal differences in sand transport through a trough blowout measurements were made by trapping sand in rosen style traps installed at the mouth and crest of the parabolic dune and with erosion pins in the throat erosion pin data indicated that the surface of the dune was generally accreting in late summer and eroding in winter suggesting that the major loss of sediment from the dune was occurring in winter the traps were emptied every 2 4 weeks and showed that in general more sand left the dune system than entered it the amount of sand transported past the traps at the mouth of the dune varied seasonally with smaller amounts during the summer months than in winter the upper traps showed greater variability but had more sediment transported in all months when compared with the lower traps amounts of sand transported during winter were greater than in summer

the crustal scale architecture of the eastern succession mount isa the influence of inversion the three dimensional crustal architecture of the eastern part of the mount isa inlier is investigated from serial cross sections constructed using geological map data revised chronostratigraphy gravity magnetics worms multiscale wavelet edges of potential field data and seismic data the top part of the crust consists of rift and platform type metasediments that were deposited in three cover sequences from 1850 to 1610 ma these rocks constitute the mount isa eastern succession and they were intruded by mafic felsic plutons dykes and sills of various ages before and during the isan orogeny ca 1 6 1 5 ga the eastern succession overlies a felsic metamorphic basement which in turn sits on a tonalitic gabbroic lower crust the depositional basin architecture for the eastern succession was controlled by major n s trending structures that penetrated the lower crust and accommodated e w extension these structures also underlie major upper crustal structures such as the mitakoodi culmination and snake creek anticline that were formed by contraction in the isan orogeny positive inversion may therefore have been a key process in the evolution of the eastern part of the inlier and governs its architecture at the crustal scale inversion involved reactivation of basement penetrating structures which localised contractional structures in the cover sequences above as well as influencing pluton emplacement the felsic metamorphic basement may have been penetratively deformed during inversion the spatial association between the basin controlling and contractional structures suggests that either early extensional displacements were completely reversed by later contraction or that much of the eastern succession has remained essentially parauthochthonous relative to the basement

event scale dynamics of a parabolic dune and its relevance for mesoscale evolution parabolic dunes are widespread aeolian landforms found in a variety of environments despite modeling advances and good understanding of how they evolve there is limited empirical data on their dynamics at short time scales of hours and on how these dynamics relate to their medium term evolution this study presents the most comprehensive data set to date on aeolian processes airflow and sediment transport inside a parabolic dune at an event scale this is coupled with information on elevation changes inside the landform to understand its morphological response to a single wind event results are contextualized against the medium term years allowing us to investigate one of the most persistent conundrums in geomorphology that of the significance of short term findings for landform evolution our field data suggested three key findings 1 sediment transport rates inside parabolic dunes correlate well with wind speeds rather than turbulence 2 up to several tonnes of sand can move through these landforms in a few hours and 3 short term elevation changes inside parabolic dunes can be complex and different from long term net spatial patterns including simultaneous erosion and accumulation along the same wall modeled airflow patterns along the basin were similar to those measured in situ for a range of common wind directions demonstrating the potential for strong transport during multiple events mesoscale analyses suggested that the measured event was representative of the type of events potentially driving significant geomorphic changes over years with supply limiting conditions playing an important role in resultant flux amounts

prediction of erosion intermittency using large eddy simulation abstract the present cfd computational fluid dynamics study investigates the triggering of aeolian erosion which takes place on two transverse sand piles placed in tandem the urans unsteady reynolds averaged navier stokes des detached eddy simulation and les large eddy simulation approaches are evaluated on their prediction capability of the friction velocity each predicted friction velocity is evaluated against a proposed threshold condition which considers the surface slope along with the near surface flow direction to be compliant with established recirculation regions the des and les approaches are found to be capable of predicting aeolian erosion intermittency a phenomenon characterized by burst activity the urans approach by yielding a nearly steady state solution predicts erosion only on a time averaged basis des and les approaches corroborate the reshaping observed in the wind tunnel tests where the erosion is substantial on the leeward pile and insignificant on the windward one

measurements and numerical simulations of the degree of activity and vegetation cover on parabolic dunes in north eastern brazil in this work we present measurements of vegetation cover over parabolic dunes with different degrees of activation along the north eastern brazilian coast we extend the local values of the vegetation cover density to the whole dune by correlating measurements with the relative brightness index c of high resolution quickbird panchromatic satellite images of the dune field we then introduce the vegetation data into a continuous model for vegetated dunes coupling sand erosion and vegetation growth and perform simulations of the evolution of the morphology and vegetation cover of parabolic dunes finally from the comparison of both the measurements and the simulation results we show that the model is able to predict the dune shape and the vegetation distribution of real parabolic dunes as result of the evolution of a blow out