microbially induced cementation to control sand response to undrained shear current methods to improve the engineering properties of sands are diverse with respect to methodology treatment uniformity cost environmental impact site accessibility requirements etc all of these methods have benefits and drawbacks and there continues to be a need to explore new possibilities of soil improvement particularly as suitable land for development becomes more scarce this paper presents the results of a study in which natural microbial biological processes were used to engineer a cemented soil matrix within initially loose collapsible sand microbially induced calcite precipitation micp was achieved using the microorganism bacillus pasteurii an aerobic bacterium pervasive in natural soil deposits the microbes were introduced to the sand specimens in a liquid growth medium amended with urea and a dissolved calcium source subsequent cementation treatments were passed through the specimen to increase the cementation level of the sand particle matrix the results of both micp and

paraglacial rock slope stability glaciation and deglaciation along with their associated climatic and non climatic processes modify slope stresses and influence slope stability paraglacial slope failures are those that are a part of or influenced by the transition from glacial conditions to non glacial conditions gravitational failure of rock slopes is a primary and dominant process of slope evolution in mountainous terrain and is the subject of this paper which 1 reviews the approaches taken for researching paraglacial rock slope failure patterns and processes 2 summarises the spatial and temporal patterns of post glacial failures 3 assesses the factors influencing slope stability during glaciation and deglaciation 4 explores some of the applications of paraglacial research and 5 highlights some of the outstanding issues to be resolved and provides recommendations for terminology relating to paraglacial slope processes

rock slope instabilities in sogn and fjordane county norway a detailed structural and geomorphological analysis rock slope failures form a frequent hazard to many populated mountain regions especially in western norway the topographical and meteorological characteristics increase the vulnerability for rock slope failures a major focus for studies in norway is to eciently nd and investigate possible future rock slope failures in order to prevent extensive humanitarian disasters the determination of the critical parameters involved in the development of rock slope failures is crucial in order to optimize hazard recognition in addition a better understanding of the spatial and temporal variability of prehistoric and historic rock slope failures as well as present day rock slope instabilities will optimize monitoring and further research on the susceptibility for future rock slope failures the primary aim of this study is to investigate the spatial and temporal distribution of rock slope instabilities within western norway it is further aimed to determine the controlling parameters on the development of rock slope instabilities within the study region the implemented approaches range from regional scale statistical analyses towards site specic numerical modelling while a focus is set on quantitative analyses within this thesis the main controlling parameters are dened for rockfalls and rock slope instabilities on a regional scale for the entire county of sogn fjordane western norway it is demonstrated that always a combination of several parameters is necessary to destabilize a mountain side rockfalls have the strongest spatial relation to the presence of bare rock as well as landslide deposits the degree of tectonic deformation and the geological lineament density large rock slope instabilities develop preferentially within relatively weak rock units such as phyllites or weathered mac gneisses and at convex slope breaks looking more into detail a strong structural control is conrmed by numerical modelling for the unstable rock slope at stampa susceptibility and hazard are assessed at dierent scales and with dierent measures quantitative rockfall susceptibility is mapped on a regional scale for the entire county of sogn fjordane based on the statistical analysis of a set of controlling factors in addition this statistical susceptibility model is combined with a physically based model restricting the susceptibility map to areas that are steep enough to represent a potential rockfall source this combination allows using road inventories with registered impact points instead of release areas for susceptibility modelling in contrast relative susceptibility and also hazard are assessed locally for single parts of the unstable rock slope at stampa based on morphology and past activity present day annual expectable frequencies for rock slope failures of certain volume classes are determined for the storfjord region in western norway based on magnitude frequency analyses furthermore a semi quantitative hazard estimation is obtained for each potential instability based on a qualitative susceptibility assessment of each instability in this region this phd thesis presents results of the rst attempts of quantitative statistical analyses of dierent inventories covering rock slope instabilities in norway it is shown that susceptibility and hazard can be assessed with dierent measures forming the basis for further decisions regarding risk assessment and mitigation

direct measurements of bed stress under swash in the field 1 utilizing flush mounted hot film anemometry the bed stress under swash was measured directly in a field experiment conducted on barret beach fire island new york the theory development and calibration of the instrument package are discussed and results from the field experiment are presented examples of bed stress time series throughout a swash cycle are presented and an ensemble averaged swash bed stress cycle is calculated strong asymmetry is observed between the uprush and backwash phases of the swash flow the maximum bed shear stress exerted by the uprush is approximately double that of the backwash while the duration of the backwash is 135 greater than that of the uprush friction coefficients in the swash zone are observed to be similar in magnitude to those from steady flow with the mean observed friction coefficient equal to 0 0037 swash friction coefficients derived from the current measurements exhibit a reynolds number dependence similar to that observed for other flows a systematic difference between coefficients for uprush and backwash is suggested

biogeochemical processes and geotechnical applications progress opportunities and challenges consideration of soil as a living ecosystem offers the potential for innovative and sustainable solutions to geotechnical problems this is a new paradigm for many in geotechnical engineering realising the potential of this paradigm requires a multidisciplinary approach that embraces biology and geochemistry to develop techniques for beneficial ground modification this paper assesses the progress opportunities and challenges in this emerging field biomediated geochemical processes which consist of a geochemical reaction regulated by subsurface microbiology currently being explored include mineral precipitation gas generation biofilm formation and biopolymer generation for each of these processes subsurface microbial processes are employed to create an environment conducive to the desired geochemical reactions among the minerals organic matter pore fluids and gases that constitute soil geotechnical applications currently being explored include cementation of sands to enhance bearing capacity and liquefaction resistance sequestration of carbon soil erosion control groundwater flow control and remediation of soil and groundwater impacted by metals and radionuclides challenges in biomediated ground modification include upscaling processes from the laboratory to the field in situ monitoring of reactions reaction products and properties developing integrated biogeochemical and geotechnical models management of treatment by products establishing the durability and longevity reversibility of the process and education of engineers and researchers

rift jump process in northern iceland since 10 ma from 40ar 39ar geochronology due to the westward american eurasian plate boundary migration the rift zone location in northern iceland imposed by the stable icelandic hotspot has jumped eastward the present day north volcanic zone of iceland is thus shifted about 100 km to the east with respect to the kolbeinsey ridge a miocene paleo rift location was proposed along the hunafloi skagi axis unconformities inside the lava pile on both sides of the present day rift as a result of the new rift formation have been used to date the rift jump but timing is still controversial whether extinction of the paleo rift was synchronous with initiation of the new rift or the two rifts were active during some time period is unknown using the 40ar 39ar radiochronology method 37 dykes were dated along a 350 km profile parallel to the divergent plate motion direction i e ese wnw crossing the present rift the unconformities and the inferred paleo rift our results reveal that the paleo rift axis was not located along the hunafloi skagi axis but 60 km to the east this previously unknown paleo rift is named the skagafjordur paleo rift it remained active until approximately 3 ma the activity of the present north volcanic zone started about 8 8 5 ma intruding 9 9 5 myr rocks located at least 10 km east of the skagafjordur paleo rift axis consequently the two rifts were simultaneously active for 5 5 5 myr during this time period their accretion rates were nearly equal but with asymmetrical opening the largest rates occurring on external flanks these results are coherent in the icelandic context and permit a first reconstruction of the evolution of northern iceland since 10 ma

three dimensional mathematical model of suspended sediment transport this paper presents the basic equations for a mathematical model of sediment laden flow in a nonorthogonal curvilinear coordinate system the equations were derived using a tensor analysis of two phase flow and incorporate a natural variable density turbulence model with nonequilibrium sediment transport correspondingly a free surface and the bottom sediment concentration are employed to provide the boundary conditions at the river surface and the riverbed the finite analytic method is used to solve the equations of mass and momentum conservation and also the transport equation for suspended sediment to demonstrate the method the sediment deposition for the three gorges project is considered the mathematical model specifies the boundary conditions for the inlet and outlet using data from physical model experiments the results for the mathematical model were tested against laboratory measurements from the physical model experiment good agreement and accuracy were obtained

hydrodynamics and sediment transport in the swash zone a review and perspectives the dominant hydrodynamic forcing and resulting sediment transport mechanisms in the swash zone are reviewed combined with a discussion of future measurement and modelling requirements the importance of swash zone processes in the overall behaviour of the nearshore littoral zone are identified with the paper subsequently focusing on aspects that directly relate to sediment transport on beaches the review considers analytical and numerical modelling work and both field and laboratory data the hydrodynamics of the swash zone are first discussed with reference to the surf zone boundary swash characteristics forcing mechanisms and shoreline oscillations subsequent sections consider more micro scale processes such as the internal flow kinematics turbulence the bed boundary layer and infiltration exfiltration through permeable beds the second part of the paper outlines the fundamental mechanics of sediment transport in the swash zone followed by a more detailed discussion of sediment transport modes induced by the dominant hydrodynamic conditions modelling concepts are reviewed and the strengths and weaknesses of different approaches identified a final summary and future modelling perspectives conclude the paper

uphill facing antislope scarps in the coast mountains southwest british columbia uphill facing scarps are examined at affliction creek a glacierized area within the meager creek volcanic complex of southwest british columbia scarps occur directly downslope of tension cracks and are considered to have developed from a combination of 1 antithetic movement between partly toppled slices of rock defined by a master joint set dipping into the slope and 2 erosion of the upslope face of each tension crack leaving the downslope face prominent as an antislope scarp a kinematic test for toppling failure is described glacial erosion and rapid glacial downwasting are probable causes of toppling lichenometric data indicate significant scarp development since affliction glacier attained its maximum neoglacial dimensions about 140 yr ago dilatancy is cited as a possible mechanism for scarp stabilization

rip current type spacing and persistence narrabeen beach australia abstract long term daily rip observations on narrabeen beach australia were made together with daily measurements of wave height period direction surf zone width and beach state a total of 3513 rips were observed on 270 days over a 19 month period results show that rips accompany moderate to high waves and are associated with intermediate beach types rip spacing follows wave conditions increasing in spacing size and intensity as waves rise and conversely as they fall rips are a function of both the prevailing and antecedent wave conditions and the rate and direction of change in wave conditions rips are classified into three types erosion mega and accretion erosion rips are initiated by rising seas in the transverse bar and rip and higher beach states they accompany general beach erosion they are widely spaced narrabeen ys 300 500 m 100 200 m increasing in size and intensity with the waves until the fully dissipative ripless state is reached they are both temporally and spatially highly variable persisting in one location for only hours to a day or so except where topographically controlled they are a major mechanism for the seaward transport of sediment and under extreme conditions may extend over a kilometer seaward of the breaker zone mega rips are large scale 1 km topographically controlled erosion rips that persist when nearshore and or embayment topography prevents the development of the fully dissipative state by inducing wave refraction and persist longshore gradients in surf zone dynamics that in turn drive the rip circulation accretion rips prevail during stable or falling wave conditions usually following erosion rip formation they are associated with general beach accretion are more closely spaced narrabeen ys 170 250 m 100 m less intense and become increasingly topographically arrested by crescentic bars and rhythmic bar beach morphology of the longshore bar trough rhythmic bar and beach and transverse bar and rip beach states they are relatively stable both spatially and temporally and may persist in one location for days to weeks if wave conditions remain favorable they are fair weather rips which may disappear by infilling in the low tide terrace beach state or be destroyed by rising seas rips generally are absent from the reflective low tide terrace and fully dissipative beach states

turbulence experiments in the swash zone abstract turbulence and water surface elevation measurements were carried out in the swash zone which was induced by plunging and collapsing breakers in a wave flume three different period regular waves were generated on a 1 10 smooth impermeable concrete beach and the water surface elevations were collected by a number of wave gauges and a run up meter lying on the bottom velocity measurements were carried out by a laser doppler velocimeter system at spatial steps of 1 mm from the bottom along three vertical sections in the swash zone the data have been used to describe the wave front dynamics to derive the length and velocity macro and micro scales and the eulerian frequency spectrum in some points it shows a double structure the results add to and expand on similar results obtained by other researchers in the surf zone

fast and partitioned postglacial rebound of southwestern iceland located both on the mid atlantic ridge and above a mantle plume iceland is subject to horizontal and vertical motions many studies described these deformations in terms of rifting episodes that have combined both extensional tectonics and magmatism however few studies have described the glacio isostatic response induced by the retreat of the weichselian ice cap the melting of this ice cap induced a postglacial rebound for the whole of iceland that may be controlled by the geodynamic setting and the rheological layering of the lithosphere this study is devoted to 1 understanding the holocene rebound on the southwestern coast and 2 estimating the asthenosphere viscosity and depth beneath iceland two stages of holocene evolution were determined by means of gps profiles morphological observations and data compilation the first stage corresponds to a vertical uplift of 67 5 to 157 5 m it started at 10 000 years bp and ended at 8500 years bp implying uplift rates between 4 5 and 10 5 cm a it was a quick isostatic response to the fast ice retreat the second stage had vertical motion of tens of meters with a probable tectonic origin and started at 8500 years bp the uplift rate is 1 to 2 orders of magnitude slower than the one during the first stage uplift partitioning during the first stage was controlled by the thermal state of the lithosphere the highest geothermal flux inducing the maximum uplift rates the relaxation time for uplift provides a viscosity estimate of 5 4 5 8 1019 pa s for the asthenosphere this value is similar to those determined for glacial areas in different continental contexts however the flexural wavelength indicates a shallower asthenosphere than that occurring in continental domains therefore this study highlights a coupling between the thermal structure of the icelandic asthenosphere and the glacial rebound

the hofðaholar rock avalanche sturzstrom chronological constraint of paraglacial landsliding on an icelandic hillslope the hof aholar rock avalanche in the skagafjor ur area of northern iceland was investigated on the basis of a geomorphological analysis of its landforms and close surrounding environment thanks

application of microbially induced calcite precipitation in erosion mitigation and stabilization of sandy soil foreshore slopes a preliminary investigation eroding foreshores endanger the floodplains of many estuaries as such effective and environmentally friendly interventions are sought to stabilise slopes and mitigate erosion as a step in forestalling these losses we developed laboratory microcosms to simulate tidal cycles and examined the mechanisms of erosion and failure on sandy foreshore slopes as an experimental aim we applied microbially induced calcite precipitation micp to selected slopes and compared the effectiveness of this microbial geo technological strategy to mitigate erosion and stabilise slopes to assess shoreline stability thirty cycles of slowly simulated tidal currents were applied to a sandy slope significant sediment detachment occurred as tides moved up the slope surface for steeper slopes one tidal event was sufficient to cause collapse of the slopes to the soil s angle of repose 35 subsequent tidal cycles gradually eroded surface sediments further reducing slope angle on an average 0 2 per tidal event these mechanisms were similar for all slopes irrespective of initial slope inclination micp was evaluated as a remedial measure by treating a steep slope of 53 and an erosion prone slope angle of 35 with sporosarcina pasteurii and cementation solution 0 7 m cacl2 and urea before tidal simulations micp produced 120 kg calcite per m3 of soil filling 9 9 of pore space cemented sand withstood up to 470 kpa unconfined compressive stress and showed significantly improved slope stability both slopes showed negligible sediment erosion with efforts towards optimisation for upscaling and further environmental considerations including effect of slope saturation on micp treatment saline water and estuarine coastal ecology amongst others the micp process demonstrates promise to protect foreshore slope sites

lateglacial rock slope failures in north west ireland age causes and implications nine postglacial quartzite rock slope failures rsfs in north west ireland were dated using cosmogenic 10be weighted mean rsf ages range from 17 7 0 9 to 12 5 0 7 ka or 16 6 0 7 to 11 7 0 5 ka depending on assumed 10be production rate all dated rsfs occurred within 5000 years following ice sheet deglaciation at 17 4ka 16 3 ka and all but two occurred within 2000 years after deglaciation the timing of rsfs rules out glacial debuttressing permafrost degradation and enhanced deglacial cleft water pressures as triggers of failure in most cases we infer that paraglacial stress release and associated fracture propagation were critical in reducing rock masses to critical stability although earthquakes caused by lateglacial glacio isostatic rebound and or release of stored tectonic stresses may have triggered failure in some or all cases in conjunction with data from related studies our results imply that most undated rsfs outside the limit of younger dryas glaciation in the british isles are of lateglacial age and that numerous lateglacial rsfs occurred inside these limits with subsequent removal of debris by glaciers they support the view that paraglacial rsf activity in tectonically stable intraplate terrains was concentrated within a few millennia following deglaciation

comparison of rates of ureolysis between sporosarcina pasteurii and an indigenous groundwater community under conditions required to precipitate large volumes of calcite ureolysis driven calcite precipitation has potential to seal porosity and fracture networks in rocks thus preventing groundwater flow and contaminant transport in this study urea hydrolysis and calcite precipitation rates for the model bacterium sporosarcina pasteurii were compared with those of indigenous groundwater communities under conditions required to precipitate large volumes of calcite up to 50 g l 1 we conducted microcosm experiments in oxic artificial and anoxic natural groundwaters collected from the permo triassic sandstone aquifer at birmingham uk that were inoculated with aerobically grown s pasteurii the rate constants for urea hydrolysis kurea ranged between 0 06 and 3 29 d 1 and were only affected by inoculum density higher ca2 concentration 50 500 mm ca2 as well as differences in fo2 did not inhibit the ureolytic activity of s pasteurii and did not significantly impact kurea these results demonstrate that s pasteurii has potential to improve calcite precipitation in both oxic and anoxic groundwaters especially if indigenous communities lack ureolytic activity urea hydrolysis by indigenous groundwater communities was investigated in anoxic natural groundwaters amended with urea and cacl2 a notable increase in ureolysis rates was measured only when these communities were stimulated with dilute nutrients with best results from blackstrap molasses furthermore there was a considerable lag time 12 20 days before ureolysis and calcite precipitation began calculated ureolysis rate constants kurea ranged between 0 03 and 0 05 d 1 and were similar to kurea values produced by s pasteurii at low inoculum densities overall this comparative study revealed that the growth of ureolytic microorganisms present within groundwaters can easily be stimulated to enhance rates of urea hydrolysis in the subsurface and thus can be used to induce calcite precipitation in these environments the time required for urea hydrolysis to begin is almost instantaneous if an inoculum of s pasteurii is included while it may take several weeks for ureolytic groundwater communities to grow and become ureolytically active

impacts of post glacial rebound on landslide spatial distribution at a regional scale in northern iceland skagafjorður in de glaciated areas para glaciation i e the conditioning of landscapes by prior glaciation has often been considered a major predisposing factor in landslide occurrence its consequences have been particularly well identified at a fine scale especially on bedrock jointing hitherto the relative impacts of para glaciation on hillslope dynamics at a regional scale had nevertheless not been quantified statistically we examine skagafjor ur area northern iceland where landslides are widespread at least 108 were mapped in an area of c 3000km2 we compare the role of para glaciation debuttressing influence of post glacial rebound with that of classic factors topography lithology etc in landslide occurrence and location using a spatial analysis based on a chi square test on the one hand the results highlight that landslides are over represented in areas where post glacial rebound was at its maximum with a stronger concentration of landslides in the northern part of the fjord on the other hand the distribution of landslides did not show any clear relationship with the pattern of glacial debuttressing tschuprow coefficient highlights that the influence of post glacial rebound on landslide location is higher than the combined influence of slope gradient curvature or geological structure this result is supported by our initial evidence for the timing of landslides in the area most landslides occurred during the first half of the holocene and a period of hillslope instability was initiated when the post glacial uplift was at its maximum finally the mechanisms that link post glacial rebound and landsliding as well as the geomorphic impacts of landslides are discussed

geotechnical properties of cemented sands in steep slopes an investigation into the geotechnical properties specific to assessing the stability of weakly and moderately cemented sand cliffs is presented a case study from eroding coastal cliffs located in central california provides both the data and impetus for this study herein weakly cemented sand is defined as having an unconfined compressive strength ucs of less than 100 kpa and moderately cemented sand is defined as having ucs between 100 and 400 kpa testing shows that both materials fail in a brittle fashion and can be modeled effectively using linear mohr coulomb strength parameters although for weakly cemented sands curvature of the failure envelope is more evident with decreasing friction and increasing cohesion at higher confinement triaxial tests performed to simulate the evolving stress state of an eroding cliff using a reduction in confinement type stress path result in an order of magnitude decrease in strain at failure and a more brittle response tests aimed at examining the influence of wetting on steep slopes show that a 60 decrease in ucs a 50 drop in cohesion and 80 decrease in the tensile strength occurs in moderately cemented sand upon introduction to water in weakly cemented sands all compressive cohesive and tensile strength is lost upon wetting and saturation the results indicate that particular attention must be given to the relative level of cementation the effects of groundwater or surficial seepage and the small scale strain response when performing geotechnical slope stability analyses on these materials

turbulence in the swash and surf zones a review this paper reviews mainly conceptual models and experimental work in the field and in the laboratory dedicated during the last decades to studying turbulence of breaking waves and bores moving in very shallow water and in the swash zone the phenomena associated with vorticity and turbulence structures measured are summarised including the measurement techniques and the laboratory generation of breaking waves or of flow fields sharing several characteristics with breaking waves the effect of air entrapment during breaking is discussed the limits of the present knowledge especially in modelling a two or three phase system with air and sediment entrapped at high turbulence level and perspectives of future research are discussed

3d characterization of microbially induced carbonate precipitation in rock fracture and the resulted permeability reduction abstract a new seepage control method for fractured rock is biogrouting through a microbially induced calcite precipitation micp process a study on the spatial distribution of biogrout in a rock fracture and its effect on permeability reduction is presented in this paper a series of experiments together with 3d scanning and 3d flow simulation were performed on rock fractures with various initial apertures treated by bio grouting a lognormal distribution of micp precipitates along the flow direction in a fracture was observed the 3d flow simulation of biogrouted fracture has revealed that the routinely adopted parallel plate model cubic law for estimating permeability of channel flow is no longer applicable when the fracture aperture is less than the critical value of 0 7 mm based on this study this is because partially clogging will occur when the fracture aperture is less than the critical value resulting in a transition of the flow type from surface flow to channel flow a semi empirical equation which can account for the effect of flow type has been proposed for estimating the permeability reduction due to bio grouting for rock fractures

deep seated gravitational slope deformations in the european alps abstract deep seated gravitational slope deformations dsgsd are widespread phenomena recognized in different mountain ranges worldwide the distribution of such phenomena at the scale of a mountain belt has rarely been systematically analysed in the past aim of the paper is to present and discuss an inventory map of dsgsd at the scale of the entire european alps in order to review existing knowledge and investigate general controls on these phenomena the criteria adopted for their classification and distinction are presented a total of 1033 dsgsds ranging in size between 0 03 and 108 km 2 have been mapped the inventory has been validated against available local or regional landslide inventories at different scales and prepared by different authors using different approaches the frequency area relationship for the mapped features is presented the spatial distribution of the mapped dsgsd has been quantified by discretizing the study area into regular square grids with different resolution and analysed with respect to a variety of geological geomorpohological and morphometric variables and of their clustering discriminant principal component and cluster analyses have been performed to define the most important controlling and predisposing factors results suggest that the occurrence of foliated metamorphic rocks lgm ice thickness local relief and related parameters slope size drainage density and river stream power are the local parameters most positively correlated to dsgsd occurrence the impact of these phenomena on slope morphology in terms of hypsometry and slope gradient adjustment is also discussed

suspended sediment transport in the swash zone of a dissipative beach abstract simultaneous high frequency field measurements of water depth flow velocity and suspended sediment concentration were made at three fixed locations across the high tide swash and inner surf zones of a dissipative beach the dominant period of the swash motion was 30 50 s and the results are representative of infragravity swash motion suspended sediment concentrations loads and transport rates in the swash zone were almost one order of magnitude greater than in the inner surf zone the vertical velocity gradient near the bed and the resulting bed shear stress at the start of the uprush was significantly larger than that at the end of the backwash despite similar flow velocities this suggests that the bed friction during the uprush was approximately twice that during the backwash the suspended sediment profile in the swash zone can be described reasonably well by an exponential shape with a mixing length scale of 0 02 0 03 m the suspended sediment transport flux measured in the swash zone was related to the bed shear stress through the shields parameter if the bed shear stress is derived from the vertical velocity gradient the proportionality coefficient between shear stress and sediment transport rate is similar for the uprush and the backwash if the bed shear stress is estimated using the free stream flow velocity and a constant friction factor the proportionality factor for the uprush is approximately twice that of the backwash it is suggested that the uprush is a more efficient transporter of sediment than the backwash because the larger friction factor during the uprush causes larger bed shear stresses for a given free stream velocity this increased transport competency of the uprush is necessary for maintaining the beach otherwise the comparable strength and greater duration of the backwash would progressively remove sediment from the beach

rip current review rip currents are shore normal narrow seaward flowing currents that originate within surf zone extend seaward of the breaking region rip head and can obtain relatively high velocities within the last decade there have been a significant number of laboratory and field observations within rip current systems an overview of rip current kinematics based on these observations and the scientific advances obtained from these efforts are synthesized rip current flows are partitioned into mean infragravity very low frequency vorticity and tidal contributions and it is found that each contributes significantly to the total data from the laboratory and the field suggest that the rip current strength increases with increasing wave energy and decreasing water depths the maximum mean current occurs inside the surf zone where the maximum forcing is present owing to the dissipation of waves

holocene and latest pleistocene climate and glacier fluctuations in iceland abstract multiproxy climate records from iceland document complex changes in terrestrial climate and glacier fluctuations through the holocene revealing some coherent patterns of change as well as significant spatial variability most studies on the last glacial maximum and subsequent deglaciation reveal a dynamic iceland ice sheet iis that responded abruptly to changes in ocean currents and sea level the iis broke up catastrophically around 15 ka as the polar front migrated northward and sea level rose indications of regional advance or halt of the glaciers are seen in late allerod early younger dryas time and again in preboreal time due to the apparent rise of relative sea level in iceland during this time most sites contain evidence for fluctuating tidewater glacier termini occupying paleo fjords and bays the time between the end of the younger dryas and the preboreal was characterized by repeated jokulhlaups that eroded glacial deposits by 10 3 ka the main ice sheet was in rapid retreat across the highlands of iceland the holocene thermal maximum htm was reached after 8 ka with land temperatures estimated to be 3 c higher than the 1961 1990 reference and net precipitation similar to modern such temperatures imply largely ice free conditions across iceland in the early to mid holocene several marine and lacustrine sediment climate proxies record substantial summer temperature depression between 8 5 and 8 ka but no moraines have been detected from that time termination of the htm and onset of neoglacial cooling took place sometime after 6 ka with increased glacier activity between 4 5 and 4 0 ka intensifying between 3 0 and 2 5 ka although a distinct warming during the medieval warm period is not dramatically apparent in icelandic records the interval from ca ad 0 to 1200 is commonly characterized by relative stability with slow rates of change the literature most commonly describes little ice age moraines ca ad 1250 1900 as representing the most extensive ice margins since early holocene deglaciation with temperature depressions of 1 2 c compared to the ad 1961 1990 average steep north south and west east temperature gradients are reconstructed in the holocene records of iceland suggesting a strong maritime influence on the terrestrial climate of iceland

large ice contact slope movements glacial buttressing deformation and erosion glaciers and slope movements may act simultaneously to erode and modify glaciated slopes undercutting by glaciers can destabilize slopes but the extent to which slope failure may progress prior to subsequent glacier withdrawal has not hitherto been considered the traditional view has been that the buttressing effect of ice prevents slope movement the problem with this view is that ice is one third the density of rock and flows under low applied stress consequently failed slopes may move into the glacier if they exert a stress in excess of the resistance provided by the glacier slope movement rate depends on ice rheology and other factors influencing driving and resisting stresses simple viscous equations are used to investigate these variables the equations predict that small 108 m3 rockslides to test these estimates field evidence is presented of slope movements in glaciated valleys of new zealand narrowing or squeezing of glaciers adjacent to unstable rock slopes is demonstrated and considered to be the result of slope movement for one site geomorphic mapping and slope movement monitoring data show that movement rates are of similar order of magnitude to those predicted by the viscous equations closer agreement could be achieved with the application of modelling techniques that can more realistically model the complex slope geometries and stability factors encountered or by obtaining additional empirical data to calibrate the models this research implies that while the concept of glacial debuttressing the reduction of slope support from withdrawal of glaciers is valid complete debuttressing is not a prerequisite for the movement of ice contact rock slopes these slope movements may contribute to the erosional processes of glaciers and the evolution of glaciated slopes in a previously unrecognized way copyright 2012 john wiley sons ltd

subglacial extensional fracture development and implications for alpine valley evolution 1 bedrock stresses induced through exhumation and tectonic processes play a key role in the topographic evolution of alpine valleys using a finite difference model combining the effects of tectonics erosion and long term bedrock strength we assess the development of near surface in situ stresses and predict bedrock behavior in response to glacial erosion in an alpine valley the matter valley southern switzerland initial stresses are derived from the regional tectonic history which is characterized by ongoing transtensional or extensional strain throughout exhumation of the brittle crust we find that bedrock stresses beneath glacial ice in an initial v shaped topography are sufficient to induce localized extensional fracturing in a zone extending laterally 600 m from the valley axis the limit of this zone is reflected in the landscape today by a valley shoulder separating linear upper mountain slopes from the deep u shaped inner valley we propose that this extensional fracture development enhanced glacial quarrying between the valley shoulder and axis and identify a positive feedback where enhanced quarrying promoted valley incision which in turn increased in situ stress concentrations near the valley floor assisting erosion and further driving rapid u shaped valley development during interglacial periods these stresses were relieved through brittle strain or topographic modification and without significant erosion to reach more highly stressed bedrock subsequent glaciation caused a reduction in differential stress and suppressed extensional fracturing a combination of stress relief during interglacial periods and increased ice accumulation rates in highly incised valleys will reduce the likelihood of repeat enhanced erosion events

influence of deep seated gravitational slope deformations on landslide distributions a statistical approach abstract the influence of deep seated gravitational slope deformations dsgsds on the distribution of translational landslides was analyzed in the milia basin tuscany italy detailed geomorphological mapping combined with the analysis of aerial photography enabled us to build two landslide inventories one inventory including landslides before 1975 was used to create statistical models whereas the other inventory including landslides after 1975 was used to validate the models geology slope angle slope aspect distance to hydrographic elements and distance to tectonic lineaments were considered as landslide predisposing factors to quantify the importance of dsgsds as another landslide predisposing factor the dsgsd presence absence map was introduced in the stepwise statistical analysis the landslide inventory maps and factor maps were processed using a conditional analysis on all possible factor combinations to produce landslide susceptibility maps with five susceptibility classes the results indicate that the dsgsds significantly affect landslide distribution

gravitational spreading of mountain ridges coeval with late weichselian deglaciation impact on glacial landscapes in trollaskagi northern iceland abstract during the late weichselian deglaciation the coastal mountains of northern central iceland have experienced significant paraglacial readjustment processes in the form of conspicuous rock slope failures and deep seated gravitational slope deformation dsgsd local topographic slopes and ridges were deeply reshaped by these large scale paraglacial processes located on the eastern side of skagafjor ur one of the largest fjords of northern iceland the oslandshli arfjoll and hnjukar ridges 65 49n 19 14w exhibit geomorphic evidence of spectacular dsgds several series of dsgsd induced landforms such as crestal graben and troughs initiated by ridge top splitting were investigated over a 30 km 2 area on the basis of geomorphological mapping we recognized i a ridge top splitting event mainly controlled by glacial debuttressing induced by a minimal 300 m lowering of the glacier surface in the deildardalur valley ii a rapid late weichselian deglaciation of the deildardalur valley spanning a few thousands of years ice free stage probably reached around 14 000 years cal bp iii ridge top splitting having an influence on large scale glacial patterns by guiding and facilitating glacial erosion along ridge top grabens resulting in accelerated trough widening based on these interpretations we propose an evolutionary sequence of both the kinematic stages of the dsgsd and the late weichselian deglaciation at the valley scale this work provides new insights into i the patterns of the late weichselian deglaciation in the skagafjor ur area especially in tributary valleys of the fjord ii the timing of large scale paraglacial ridge top deformations in relation to the post lgm deglaciation and iii the influence of paraglacial dsgsd features on large scale glacial erosional patterns

fluid inclusions in high pressure low temperature rocks from the calabrian arc southern italy the burial and exhumation history of the subduction related diamante terranova unit the diamante terranova unit diatu in the calabrian arc of southern italy is part of an ophiolitic sequence involved in a high pressure low temperature event p 8 kbar t 400 c followed by re equilibration at greenschist facies conditions p 3 kbar t 300 c the rocks contain two types of quartz calcite veins an earlier generation of deformed folded and faulted veins formed during or before subduction and a later set of planar undeformed veins formed during exhumation of the diatu the earlier folded quartz calcite veins contain regularly shaped aqueous inclusions as well as inclusions with a highly irregular dendritic texture the later planar veins contain only regularly shaped aqueous inclusions similar to those in the earlier veins in both vein types all inclusions are demonstrably secondary in origin regularly shaped inclusions from both vein types are low salinity 0 5 wt nacl most contain liquid and vapour and homogenize to the liquid th 135 180 c whereas others contain only liquid at room temperature both the two phase and monophase inclusions occur in the same fractures and are thought to record the same trapping event with the monophase inclusions remaining metastable liquid at room temperature no microthermometric data could be obtained from the dendritic inclusions in the earlier folded veins inclusions with the highly irregular dendritic texture found in the earlier veins are similar to those produced experimentally during laboratory induced deformation of synthetic inclusions in quartz under conditions of internal underpressure simulating either isobaric cooling or isothermal compression the occurrence of inclusions with the dendritic texture in the earlier folded veins and their absence from the later planar veins suggests that the earlier veins formed before or during subduction and were folded and faulted in a compressional environment and their contained fluid inclusions were modified to produce the dendritic texture during later uplift of the diatu planar veins containing regularly shaped aqueous inclusions formed and some of the fluids forming these veins were also trapped as secondary inclusions in the earlier folded veins the results of this study provide convincing evidence that inclusions with a highly irregular dendritic morphology represent early inclusions that have survived prograde conditions in a high pressure low temperature metamorphic environment but have been texturally modified the high pressure low temperature implosion texture is preserved over geological time even after being overprinted by internal overpressure conditions generated during retrograde decompression we suggest that inclusions that have survived prograde metamorphism are common in high pressure low temperature rocks but are often not identified as such due to their morphology which makes their recognition difficult

post glacial rebound of iceland during the holocene abstract the geodynamic context of iceland provides the rare opportunity to analyse the combined effects of a ridge and a hotspot on deformation processes from a digital elevation model field analysis and a compilation of previous work we propose a synthesis of vertical motions of iceland during the holocene with a focus on the post glacial rebound we determined two ancient marine limits one above and one below the present sea level estimated at 10 ka 300 years and 8150 350 years bp respectively we calculated an uplift phase of 40 170 m with a rate of 2 1 9 2 cm a 1 between 10 ka 300 years and 8150 350 years bp corresponding to the post glacial rebound of iceland following the weichselian glaciation spatial variations of the rebound are mainly related to the local glacial dynamics ice load and deglaciation history rather than the geodynamic context however the relaxation time deduced from uplift data is 4167 years in west iceland and 2000 years in ssw iceland we estimated viscosity from relaxation time ranging from 2 1 10 19 pa s to 3 2 10 19 pa s the significant difference in the relaxation time is due to local variation of the lithospheric thickness as a result of rifting rather than because of a variation of the viscosity

large rock slope failures in the highlands of scotland characterisation causes and spatial distribution abstract a comprehensive database of larger rock slope failures rsfs has been compiled and characterised for a whole mountain range possibly for the first time apart from iceland most rsfs in the scottish highlands occurred soon after deglaciation a threshold size of 0 25 km 2 focuses on rsfs which contribute significantly to gross erosion in the glacial paraglacial cycle and on the spatial concentration of this poorly recognised process database verification indicates that at least 90 of the total extant population in the highlands is covered standard mass movement typologies are broadly applicable but require some refinement to characterise rsfs in a passive margin glaciated mountain range comprised mainly of ancient metasediments most larger rsfs here are complex and difficult to categorise a continuum from cataclasmic failures including rock avalanches through arrested translational slides to almost in situ slope deformations is identified the prevailing modes of large rsf are arrested short travel translational sliding and gravitational sagging cataclasmic failure is rare and sub cataclasmic outcomes are more evident a significant class of deformations exhibits compressional rather than extensional features and may be responding to localised glacio isostatic rebound stresses the large rsf population is widely but very unevenly distributed across the main mountain areas 65 are in seven main clusters with the rest non randomly scattered previous glaciological lithological and seismotectonic explanations are insufficient to explain this spatial pattern and overlook the basic engineering geology prerequisites for failure massifs of similar relief and lithology can display intense or sparse rsf incidence geomorphological appraisal suggests an association with recently active glacial breaches of main and secondary watersheds with rsf being scarce or absent in valleys inherited from tertiary uplift and in mountain groups away from the main watersheds valleys which adapted early to ice discharge are seen as stress hardened with their slopes unlikely to reach critical thresholds for failure after subsequent reoccupations by ice concentrated erosion in the last glaciations is most likely to be found close to where breaches are actively forming or enlarging such erosion in the slope foot and valley floor may have daylighted failure planes or generated rebound stresses augmenting those from other endemic sources sufficiently to provoke widespread paraglacial rsf slope stress models for deglaciated valleys and comparative studies in other glaciated mountain ranges are required to test this concept and may assist in geohazard assessments