sector collapse sedimentation and clast population evolution at an active island arc volcano stromboli italy sciara del fuoco is the subaerial part of a partially filled sector collapse scar that extends to 700 m below sea level on stromboli volcano the collapse occurred 2200 m and 10 km from the shore to the nnw a fan shaped mounded feature comprises debris avalanche deposits 4 km3 from two or more sector collapses volcaniclastic density currents originating from sciara del fuoco follow the topographic margin of the debris avalanche deposits although overbank currents and other unconfined currents widely cover the mounded feature with turbidites historical recorded eruptive activity in sciara del fuoco is considerably less than that which occurred earlier and much of the partial fill may have formed from eruptions soon after the sector collapse it is possible that a mass of eruptive products similar to that in the collapse scar is dispersed as volcanogenic sediment in deep water of the tyrhennian basin evidence that the early post collapse eruptive discharge was greater than the apparent recent flux 2kg s counters suggestions that a substantial part of stromboli s growth has been endogenous the partial fill of sciaria del fuoco is dominated by lava and spatter layers rather than by the scoria and ash layers classically regarded as main constituents of strombolian cinder cones much of the volcanic slope beneath the vents is steeper than the angle of repose of loose tephra which is therefore rapidly transported to the sea delicate pyroclasts that record the magmatic explosivity are selectively destroyed and diluted during sedimentary transport mainly in avalanches and by shoreline wave reworking and thus the submarine deposits do not record well the extent and diversity of explosive activity and associated clast forming processes considerable amounts of dense non vesicular fine sand and silt grains are produced by breakage and rounding of fragments of lava and agglutinate the submarine extension of the collapse scar and the continuing topographic depression to 2200 m below sea level are zones of considerable by passing of fine sand and silt which are transported in turbidity currents evidently volcanogenic sediments dispersed around island volcanoes by density currents are unlikely to record well the true spectrum and relative importance of clast forming processes that occurred during an eruption marine sedimentary evidence of magmatic explosivity is particularly susceptible to partial or complete obliteration unless there is a high rate of discharge of pyroclastic material into the sea

the neapolitan yellow tuff caldera offshore the campi flegrei stratal architecture and kinematic reconstruction during the last 15ky abstract in this study we integrate high resolution swath bathymetry single channel reflection seismic data and gravity core data to provide new insights into the shallow structure and latest quaternary to holocene evolution of the submerged sector of the neapolitan yellow tuff nyt caldera campi flegrei in the pozzuoli bay the new data allow for a reconstruction of the offshore geometry of the nyt caldera collapse ring fault system along with the style and timing of deformation of the inner caldera resurgence our interpretation shows that the nyt eruption 15 ka bp was associated with a caldera collapse bounded by an inward dipping ring fault system the ring fault system consists in a 1 2 km wide fault zone that encircles an inner caldera region 5 km in diameter and is often marked by the occurrence of pore fluids ascending through the fault zone up to the seafloor particularly in the western sector of the bay a shallow magmatic intrusion along the ring fault zone was also detected offshore bagnoli in the eastern part of the pozzuoli bay following the nyt eruption the inner caldera region underwent significant deformation and resurgence with a maximum cumulative uplift of the offshore structure in the order of 180 m the net uplift rate of the caldera resurgent dome was 9 12 mm year during the period 15 0 6 6 ka bp the style of deformation of the resurgent structure can be described in terms of a broad doming accompanied by subordinate brittle deformation mostly concentrated in a small apical graben at the summit of the resurgent dome chronostratigraphic calibration of seismic profiles obtained by three tephra layers cored in the pozzuoli bay indicates 5 to 25 m of post roman differential subsidence and tilting towards ese of the inner caldera resurgence as recorded by the drowning of the infralittoral prograding wedge below the present day storm wave base

mechanical interactions between rigid particles in a deforming ductile matrix analogue experiments in simple shear flow abstract the mechanical interaction between two or more particles is investigated in newtonian simple shear flow the experimental models allow observation of both the particle rotation and the deformation pattern around the particles the finite and instantaneous strain patterns around rigid particles are strongly heterogeneous and asymmetric with high finite strain zones aligned to the direction of maximum finite stretch these correspond to local flow with low vorticity number heterogeneous strain patterns around rigid particles spread over a distance of 1 2 times the particle length and this distance increases with increasing bulk strain where rigid particles are more concentrated these patterns coalesce and the overall pattern is then strongly controlled by the particles and cannot be simply related to the external boundary conditions in rocks the characteristic asymmetric strain pattern around rigid isolated particles is a reliable shear criterion which becomes unreliable with high concentrations of rigid particles particle rotation is significantly disturbed when the distance between adjacent particles of equal size is shorter than their length that is only in very concentrated suspensions of rigid particles in a composite shape fabric the development of the sub fabric corresponding to the smaller minerals will be more disturbed

evolution of mica fish in mylonitic rocks abstract mineral fish are lozenge shaped porphyroclasts single crystals in a finer grained matrix which occur in ductile shear zones and which are commonly used as shear sense indicators mineral fish of biotite tourmaline k feldspar garnet hypersthene and quartz occur in mylonites but most common are white mica fish these mica fish can be subdivided into six morphological groups that develop by different mechanisms determined by different initial shapes and orientations the principal mechanisms of formation are intracrystalline deformation combined with rigid body rotation concomitant selective grain size reduction occurs by recrystallisation cataclastic separation pressure solution and diffusional mass transfer microboudinage has been proposed for the breakdown of large mica fish into smaller ones but many mica fish undergo shortening rather than extension along their long axes evidence is presented for an alternative process in which the tips of mica fish are isoclinally folded and then break off along the hinge of these microfolds all the presented fish shaped porphyroclasts or mineral fish have a specific shape preferred orientation with their long axis at a small antithetic angle with respect to the foliation they represent a special group of objects with a stable orientation due to flow partitioning into narrow shear bands

dynamics of avalanches along general mountain slopes a continuum dynamical hydraulic model for the flow of a finite mass of cohesionless shallow granular material down an inclined plane was proposed by savage and hutter sh in 1989 this model consists of depth averaged equations for the time and space evolution of the velocity profile and the avalanche depth their model was generalised to incorporate more complicated topography in which the coordinate lines in the downhill direction are curved but not twisted we present recently developed model equations by pudasaini and hutter for free surface geophysical gravity driven flows such as avalanches debris and pyroclastic flows down complicated realistic mountain terrain generated by arbitrary space curves with slowly varying curvature and torsion these are very important extensions to the successful sh theory which incorporate curvature and torsion effects of the sliding surface shock capturing numerical schemes are used to integrate the hyperbolic conservation system of equations the physical significance of the numerical solutions is discussed

the effect of microstructural and rheological heterogeneity on porphyroblast kinematics and bulk strength in porphyroblastic schists abstract the kinematic record and bulk viscous strength of polyphase rocks depend in part upon the relative strengths and distributions of rheologically distinct fabric elements here we explore the effects of microstructural and rheological heterogeneity in porphyroblastic schists electron backscatter diffraction and petrographic analyses reveal asymmetric microboudinage of staurolite indicating relative rotation of staurolite porphyroblasts synchronous with bulk non coaxial strain boudinage and relative rotation both require porphyroblast matrix shear coupling based on 2d optical observations the extent of the coupling appears related to the initial and boudinaged staurolite grain shape and orientation as well as the geometry of heterogeneities such as mica domains or shear bands we designed 2d finite element numerical models to assess the role of microstructural variation and rheological heterogeneity on the degree of porphyroblast matrix shear coupling and bulk viscous strength model results indicate that the bulk strength of a three phase system comprising inclusion weak domain and matrix is sensitive to the relative proximity of weak and strong domains particularly at high viscosity contrasts i e matrix weak 10 the threshold for bulk weakening below the matrix strength occurs over a narrow range of weak domain viscosities matrix weak 2 6 5 5 regardless of the relative abundance and spatial distribution of weak domains kinematic decoupling of porphyroblasts occurs at low viscosity contrasts when weak domains are proximal matrix weak 2 5 but for all other spatial distributions and modal abundances investigated kinematic decoupling occurs at viscosity contrasts of matrix weak 15 20 these data indicate that bulk weakening due to rheological heterogeneity is not necessarily coincident with kinematic decoupling

an evaluation of criteria to deduce the sense of movement in sheared rocks some of the most useful criteria for the deduction of the sense of shear are summarized for use in areas where unequivocal field evidence is lacking apparently conflicting evidence from rotated pressure shadow regions around porphyroclasts and porphyroblasts is clarified the use of quartz crystallographic fabric asymmetry to deduce the shear sense in the bulk rock should be treated with caution and used only together with detailed microstructural observations

flow of variably fluidized granular masses across three dimensional terrain 2 numerical predictions and experimental tests numerical solutions of the equations describing flow of variably fluidized coulomb mixtures predict key features of dry granular avalanches and water saturated debris flows measured in physical experiments these features include time dependent speeds depths and widths of flows as well as the geometry of resulting deposits three dimensional 3 d boundary surfaces strongly influence flow dynamics because transverse shearing and cross stream momentum transport occur where topography obstructs or redirects motion consequent energy dissipation can cause local deceleration and deposition even on steep slopes velocities of surge fronts and other discontinuities that develop as flows cross 3 d terrain are predicted accurately by using a riemann solution algorithm the algorithm employs a gravity wave speed that accounts for different intensities of lateral stress transfer in regions of extending and compressing flow and in regions with different degrees of fluidization field observations and experiments indicate that flows in which fluid plays a significant role typically have high friction margins with weaker interiors partly fluidized by pore pressure interaction of the strong perimeter and weak interior produces relatively steep sided flat topped deposits to simulate these effects we compute pore pressure distributions using an advection diffusion model with enhanced diffusivity near flow margins although challenges remain in evaluating pore pressure distributions in diverse geophysical flows riemann solutions of the depth averaged 3 d coulomb mixture equations provide a powerful tool for interpreting and predicting flow behavior they provide a means of modeling debris flows rock avalanches pyroclastic flows and related phenomena without invoking and calibrating rheological parameters that have questionable physical significance

mylonites from the towaliga fault zone central georgia products of heterogeneous non coaxial deformation abstract retrograde mylonitic rocks occur in the segment of the towaliga fault southeast of jackson georgia mylonite protoliths are heterogeneous quartz feldspathic gneisses upper amphibolite facies sillimanite zone from the pine mountain and piedmont terranes protoliths contain no distinctive lithological markers that can be used to determine fault displacement shear sense can only be determined using microstructural criteria and type porphyroclast systems shear bands asymmetric microfolded quartz ribbons subgrain fabrics in quartz ribbons the most common porphyroclast system developed in mylonites and ultramylonites is type type systems do not have readily identifiable tails but do produce distinctive asymmetrical pile ups in the matrix such that the angle of intersection between the perturbed zone and the mylonitic foliation points in the shear direction differences in morphology between and type systems can be related to differences in the recrystallization rate deformation rate ratio r reflecting changes in ductility contrast between matrix and porphyroclast that controls the amount of recrystallized material in a porphyroclast mantle that is potentially available to form tails in early stages of mylonitization with low ductility contrasts and large r ratios large mantles occur around porphyroclasts and tailed systems develop in advanced stages of mylonitization with large ductility contrasts and small r ratios either very small or partially or totally missing mantles occur and type systems develop microstructural criteria ubiquitously record a right lateral strike slip motion component to the deformation textural evidence e g unidirectional shear bands consistent vorticity recorded by porphyroclasts and asymmetrical microfolds suggest that the mylonites are the products of non coaxial deformation the local presence of fabrics with coaxial symmetry result from heterogeneity in the deformation the right lateral offset on the towaliga fault most likely occurred during the late paleozoic alleghanian orogeny

high velocity ring shear tests on sand ring shear tests on sand materials have been carried out to show whether there is a change in the behaviour of these materials at high shearing rates and normal stresses this question is relevant to the problem of the mobility of large rock avalanches sturzstroms but is also of more general academic interest a ring shear apparatus of unusual although simple design has been constructed capable of achieving circumferential velocities of 2 m s at normal stresses of up to 200 kpa tests were carried out on two types of coarse sand wet or dry sand rock flour mixtures and polystyrene beads perfect frictional behaviour was observed in all the tests uninfluenced by either velocity or normal stress over the entire range of these variables change in frictional behaviour due to high rate of shearing therefore cannot be used to explain the high observed mobility of sturzstroms des essais de cisaillement circulaire par torsion ont ete effectes afin de decouvrir si un changement ait lieu dans le comportem

a model for the analysis of rapid landslide motion across three dimensional terrain a new numerical model for the dynamic analysis of rapid flow slides debris flows and avalanches has been developed the model is an extension of an earlier algorithm and is implemented using a nu

strain and fabric analyses based on porphyroclast interaction abstract two dimensional computer models of the interaction of elliptical clasts in a variety of kinematic conditions are used to study how clast imbrication and shape fabric development relate to strain and strain history the models provide templates for a known clast density and clast ellipticity that correlate clast imbrication angle of collision and clast shape fabric to strain and kinematics of deformed rocks modeling also shows that the mode of clast interaction plays a significant role in the accumulation of imbricated clasts and the development of shape fabric upon collision between clasts the trains formed can remain fixed or rotate if they rotate imbricated clasts can become independent when they are no longer forced together by the flow based upon the mode of clast and train rotation using the march rotation of passive lines and the jeffery rotation of rigid particles as end members three models are defined in an attempt to simulate the conditions of clast interaction under varying conditions the march fixed train march rotating train and jeffery rotating train models simulate solid state intermediate and magmatic conditions respectively modeling shows that the two march models produce similar results but the jeffery model of train rotation always produces a lower proportion of imbricated clasts and a much weaker shape fabric application of the modeling to the study of a syntectonic granite in the sierra nevada suggests that deformation was dominated by simple shear some k feldspar imbrication and fabric development took place initially in the magmatic stage and culminated in the solid state to produce a large proportion of imbricated k feldspar porphyroclasts which define a strong shape fabric this type of analysis provides a rationale to determine syn vs post emplacement deformation in the granite

ordovician marine volcanic and sedimentary record of rifting and volcanotectonism snowdon wales united kingdom wales was part of a continental convergent plate margin for 50 m y during ordovician time the crustal stress regime was one of sinistral transtension due largely to oblique subduction early uplift and subsequent growth of subaerial arc volcanoes were followed by development of a broad fault bound marine basin 150 km wide in an infra arc or back arc setting within the basin relatively narrow grabens became sites of pronounced subsidence and bimodal basalt rhyolite volcanism the grabens developed in fault splays above steep crust penetrating discontinuities that focused extension and plumbing of magmas at these sites at snowdon the bedded pyroclastic formation records submarine and island basaltic volcanism with associated sedimentation at the site of an active rhyolitic caldera volcano the volcanoes formed on the axis of the snowdon graben and the basaltic succession which contains several unconformities due to marine abrasion at sea level shows a complex history of alternate uplift and subsidence the uplift is attributable to resurgence of rhyolitic magma and was 336 m in total subsidence due mainly to crustal extension was 500 m at a rate of 500 m m y the bedded pyroclastic formation shows clear evidence of tectonic influence in the timing location and style of basaltic magmatism repeated reactivation of magmatic plumbing systems demonstrates fault or fault intersection controlled channeling of magmas in the upper crust episodes of relatively vigorous subsidence preceded copious magmatism and both intrusive and extrusive basalt magmas exploited contemporaneously active normal faults pronounced topographic ponding of extrusive products and highly variable trends of fault block subsidence and rotation evident from the volcanogenic sedimentary deposits testify to chaotic piecemeal displacements on faults spaced commonly at

a rigid circular inclusion in an anisotropic host subject to simple shear abstract the solution for velocity and rate of deformation in an incompressible homogeneously anisotropic viscous host embedding a cylindrical rigid inclusion subjected to a far field shearing parallel to the anisotropy direction is presented the rotation rate of the inclusion is equal to half the ambient shear rate independently of the anisotropy factor the flow in the matrix localizes into conjugate shear bands sub parallel to the anisotropy directions as the anisotropy factor increases the presented anisotropic analytical solution which neglects the bending stiffness approximates the flow in a layered medium in the limit of infinitely thin layers an initially planar layering is deflected adjacent to the inclusion and fold trains propagate into the host with progressing deformation numerical simulations show that the structural development leads to a decrease in the inclusion rotation rate and eventually to inclusion stagnation at high strains the fold shapes become more angular and the fold trains reach further out into the host as the anisotropy factor is increased increasing the layering thickness up to only 9 layers intercepting the inclusion has no significant effect on how the layer inclusion rotation rate evolves with strain a coarse layering in the host leads to a strongly reduced outreach of the fold trains and the absence of tight folds the analytical solution which is derived for a planar anisotropy in the host can be employed to approximate the structural development for a weakly anisotropic host or small deformation structural development of an anisotropic medium plays a major role in determining the system behavior for large deformation

the dilemma of asymmetric porphyroclast systems and sense of shear abstract asymmetric porphyroclast systems have long been used as independent shear sense indicators based on their clast tail asymmetry and or stair stepping tail geometry over the last two decades advances in exploring the mechanical behavior of rigid clasts in a viscous flow has shed new light on understanding the formation of porphyroclast systems embedded in noncoaxial viscous flow and subsequently quantifying many aspects of flow kinematics using examples from naturally deformed rocks combined with results from recent advances our study indicates that 1 in general only porphyroclast systems composed of equant shaped clasts can be treated as independent shear sense indicators 2 special attention should be given to type porphyroclast systems composed of high angle intermediate aspect ratio clasts which may contain meaningful information on bulk flow kinematics 3 bookshelf structures cannot serve as independent shear sense indicators multi criteria and thorough three dimensional shape analyses are suggested for a proper interpretation of flow kinematics in ductile shear zones

the landslide stage of the hsiaolin catastrophe simulation and validation 1 typhoon morakot struck southern taiwan in the summer of 2009 causing the most severe flooding since the 1950s in the early morning of august 9 rainfall triggered the hsiaolin landslide and the resulting debris avalanche covered the township of hsiaolin village kaohsiung around five hundred people were buried alive reconstruction of the runout of the debris avalanche would increase understanding of the large scale avalanches for future hazard mitigation purposes simulation of the debris avalanche runout can provide valuable information for this purpose a new continuum shallow water model is applied to flow over general topography the coulomb friction law is adopted the friction coefficient is initially determined by high pressure rotary shearing tests and subsequently fine tuned by an iterative procedure to minimize the difference between the simulation and the measurement the friction coefficients measured by laboratory tests are found to be in reasonable agreement with the best fit result of the simulation in addition voellmy rheology is applied but it is found that the role of the fluid viscous drag is insignificant the simulation result in the village area is further corroborated by near surface magnetic surveys these indicate that the northern part of the village is dislocated while the artifact structures of the southern part are buried near their original locations by comparing the landslide front and the flow direction of the simulation we are able to confirm as also described by survivors that the landslide swept the northern part of the village into the cishan river while the southern part was flooded subsequently by the debris from a dam breach about 20 min after the landslide

internal flow variations and diachronous sedimentation within extensive sustained density stratified pyroclastic density currents flowing down gentle slopes as revealed by the internal architectures of ignimbrites on tenerife during a protracted explosive eruption at least four laterally extensive and sustained pyroclastic density currents radiated across the flanks of las canadas volcano tenerife each pyroclastic current developed marked local and regional spatial variations in response to the incised gently concave substrate topography the locations of these variations shifted in space as rapid sedimentation from the current progressively buried and modified the topography this complex shifting response of the density currents to minor topographic variations has been reconstructed in high resolution over a wide area 500 km2 using the internal architecture of cryptic time surfaces entrachrons marked by compositional zoning in the deposit including variations in clast types valley side field relations reveal that the currents were density stratified yet at a single instant in time the lower levels of each current comprised a granular fluid at some locations but were fully dilute and turbulent at others moreover the locations of these variations shifted geographically as the topography changed during the eruption the variations within the current are recorded by numerous superbly exposed gradational transitions from various stratified to massive lithofacies both laterally and in the downcurrent direction individual currents were regionally widespread and travelled 15 km but deposited only in longitudinally restricted localised zones that spanned several small valleys and interfluves the currents bypassed slopes up and downcurrent of the restricted depositional zones without depositing the locations of deposition then gradually shifted with time such that the extensive deposit sheet was gradually assembled beneath the sustained current in a diachronous fashion onlap relationships of internal entrachrons reveal that the base of the ignimbrite sheet and even the bases of individual flow units are markedly diachronous deposition of a flow unit commenced and ceased at different times in different places this study suggests that in hazard assessments a models of density currents that incorporate only pre existing topography e g from dems may give misleading results in the case of sustained currents because sedimentation from these significantly modifies the topography during emplacement altering flow paths b frequencies and scales of previous pyroclastic currents determined from pyroclastic successions are likely to be significantly under estimated because currents commonly bypass without leaving a deposit record and c even where preservation appears to be complete an ignimbrite at a single exposure commonly will not record the current s entire flow history at that site

the savage hutter avalanche model how far can it be pushed the savage hutter sh avalanche model is a depth averaged dynamical model of a fluid like continuum implementing the following simplifying assumptions i density preserving ii shallowness of the avalanche piles and small topographic curvatures iii coulomb type sliding with bed friction angle delta and iv mohr coulomb behaviour in the interior with internal angle of friction phi or delta and an ad hoc assumption reducing the number of mohr s circles in three dimensional stress states to one we scrutinize the available literature on information regarding these assumptions and thus delineate the ranges of validity of the proposed model equations the discussion is limited to relatively large snow avalanches with negligible powder snow component and laboratory sand avalanches starting on steep slopes the conclusion of the analysis is that the sh model is a valid model for sand avalanches but its mohr coulomb sliding law may have to be complemented for snow avalanches by a second velocity dependent contribution for very small snow avalanches and for laboratory avalanches starting on moderately steep and bumpy slopes it may not be adequate

dynamic modelling of entrainment in rapid landslides entrainment of path material is an important feature of many rapid landslides the associated increases in volume and changes in flow character can significantly influence mobility a simple material entrainment algorithm based on the assumption of natural exponential growth with displacement has been incorporated into a new computer model designed to simulate rapid landslide motion across 3d terrain the user controls the growth rate and can also implement a change in rheology at the onset of entrainment a hypothetical example is used to demonstrate the influence of the mass and momentum transfer assumptions a back analysis of the 1999 nomash river landslide is included to show that the simple model is capable of simulating the bulk characteristics of a complex event involving substantial entrainment key words landslides debris flows rock avalanches entrainment erosion dynamic modelling

instability and surge development in debris flows 1 debris flows are often described as a succession of surges which are characterized by enhanced peak depth and velocity and therefore by a tremendous increase of their destructive power for given characteristics of the base flow if the channel is sufficiently long to allow an appreciable wave development the linear stability analysis in shallow streams is shown to provide a reasonable prediction of the critical flow condition and of the instability growth rate the one dimensional 1 d theory however does not allow the determination of the wave period of the fastest growing perturbations debris waves most frequently develop following a mechanism similar to water roll waves instabilities grow up becoming clearly distinguishable waves and then waves overtake one another with increasing wave period and amplitude the typical hydrograph of a multiple peak event is shown to be composed of a first surge which is usually characterized by the highest depth the longest duration the greatest erosive power and the most symmetrical shape and of secondary waves that burst on the flow tail in the recession phase the characteristics of the first surge can be explained by two different mechanisms all waves that rise up near the flood crest run faster than this first surge and coalesce into it causing its high depth and great volume moreover segregation during the flow induces the concentration of boulders at the fronts contributing to its depth enhancement erosive power and symmetrical shape when a debris surge impacts a structure the force pattern can be interpreted as the superposition of the reflection of the bouldery front and the formation of a vertical muddy jet due to the impact of the front wedge wave reflection can be described by a 1 d mass and momentum balance across the front whereas the pressure impulse due to the incompressibility of the interstitial fluid can be analyzed through inviscid formulations validated for the representation of tsunami forces

influence of a permanent low friction boundary on rotation and flow in rigid inclusion viscous matrix systems from an analogue perspective abstract natural occurrences and recent experimental work show that a low friction inclusion matrix boundary can be responsible for antithetical rotation and development of stable shape preferred orientations in simple shear the flow of a viscous matrix around a rigid inclusion to which it may or may not be adherent is still not well studied but it is relevant to the understanding of the behaviour of structural elements in mylonite zones we used two dimensional 2 d analogue experiments to address these issues the experimental results with a permanent low friction inclusion matrix boundary nonadherent mode show the following 1 the rotation behaviour of inclusions in this mode is markedly different from the theoretical predictions and experimental results for the adherent mode 2 inclusions with aspect ratio equal to 1 rotate synthetically at a rate that depends upon inclusion shape and orientation 3 ellipse rectangle and lozenge shaped inclusions rotate antithetically when starting with their greatest axis parallel to the shear direction 4 back rotation is limited in all cases studied and the angle between the inclusion greatest axis and the shear direction represents a stable orientation which depends on inclusion aspect ratio and shape 5 a metastable orientation exists which is strongly dependent upon inclusion shape and aspect ratio and separates fields of antithetic and synthetic rotation our experimental results show that the overall flow pattern is bow tie shaped in adherent and nonadherent modes however there are major differences in the way the matrix flows near the inclusion i in the nonadherent mode the nearby matrix flows past the inclusion whereas in the adherent mode the nearby matrix flows with and follows the inclusion therefore in the adherent mode passive marker lines parallel to the shear direction and streamlines show considerable deflections at the inclusion crests in marked contrast with their straight character in the nonadherent mode ii stagnation points or closed flow lines near the inclusion were not observed in the nonadherent mode which means that there is no closed separatrix around the inclusion in this mode despite the fact that the overall flow shape is bow tie iii in the adherent mode the line of flow reversal is stable throughout deformation but in the nonadherent mode it changes position and orientation with progressive shearing this shifting of the line of flow reversal can be an important factor controlling rotation behaviour in the nonadherent mode iv in the nonadherent mode the inclusion behaviour is similar to that observed in confined flow v the flow pattern in the nonadherent mode provides an explanation for the observed lack of drag folds associated with small scale rigid inclusions in mylonites

a laboratory study of the retarding effects of braking mounds on snow avalanches a series of laboratory experiments in a 6 m long chute using glass particles of mean diameter 100 m were performed to investigate the interaction of a supercritical granular flow with obstacles it was found that the collision of the flow with a row of mounds led to the formation of a jet whereby a large fraction of the flow was launched from the top of the mounds and subsequently landed back on the chute the retarding effect of the mounds was investigated quantitatively by direct measurements of the velocity of the flow its runout length and the geometry of the jet the effects of several aspects of the layout of the mounds on their retarding effects were examined it was observed that a row of steep mounds with an elongated shape in the transverse direction to the flow and with a height several times the flow depth led to dissipation of a large proportion of the kinetic energy of the flow

shape fabrics of particles in low concentration suspensions 2d analogue experiments and application to tiling in magma abstract jeffery s equations ascribe a theoretical cyclic nature to the shape fabric of non interacting rigid particles immersed in a viscous fluid undergoing simple shear flow this theoretical behaviour is confirmed at low shear strains 5 first experiment 134 identical particles or 1 second experiment 178 particles with two size classes then become stable at 17 first experiment and at more than 50 second experiment of the population of particles due to the contribution of the tiled particles the shape fabric becomes asymmetrical in its orientation distribution with a maximum lying above the shear plane the latter result provides a new shear sense indicator in addition to the statistical determination of the tiled features the study also suggests that crystalline fabrics in magmas could be acquired at high melt fractions i e early in the crystallization history of the magma

tracing tectonic deformation using the sedimentary record an overview tectonic activity on a range of scales is a fundamental control on sedimentary activity the range of structural deformation within a region extends from the plate tectonic scale governing for example rift initiation to the basin scale with the formation of basin bounding faults internal basin configuration is also strongly influenced by tectonic activity however the relationship between tectonic activity and sedimentation is a complex one given the many additional factors which can also influence sedimentary activity including erosion sediment transport source area lithology groundwater chemistry range of depositional environments climate eustasy and the relative location of an area and its distality to marine influences in this paper we provide a selective overview of the issues associated with the interlinked themes of tectonics and sedimentation examining the main basin types forming in both extensional and compressional plate settings we then review the various models of sedimentation in the selected basins both on a local and a basinal scale finally we look to the future providing a series of possible research areas almost exclusively multidisciplinary which would help to improve existing models of interlinked sediment tectonics systems

a model for geotechnical analysis of flow slides and debris flows flow slides and debris flows incorporate a broad range of sediment fluid mixtures that are intermediate between dry rock avalanches and hyperconcentrated flows following a comprehensive review of some existing analytical approaches to debris flow runout analysis a new analytical model based on energy conservation has been formulated the new analytical model was developed to deepen the understanding of fundamental aspects in modeling of granular flows and to improve the geotechnical mobility analysis of flow slides and debris flows the lagrangian finite difference method was used to solve the governing equations the model and numerical scheme have been tested against analytical solutions and experiments of granular flows with simplified geometries for sliding mass and basal topography results of granular flow simulations indicate that the model based on energy conservation performs well and is robust the model can be used for geotechnical analysis of a wide range of dense granular flows such as flo

applications of inclusion behaviour models to a major shear zone system the nordfjord sogn detachment zone in western norway rigid inclusion models have reached a stage where one should be able to use them to obtain quantitative values from ductile shear zones we used natural data collected in three sites and combined analogue and theoretical modelling to assess vorticity strain nature of rigid inclusion matrix interface and confinement in the large scale ductile nordfjord sogn detachment zone nsdz of the caledonides of western norway our study shows that 1 the observed shape preferred orientation spo at higher structural levels of the nsdz at site 1 gjervika can be explained by simple shear pure shear simple shear ratio sr 0 associated with a slipping inclusion matrix interface 2 the observed spo at deeper structural levels of the nsdz at site 2 near sandane can be produced by simple shear associated with a significant amount of shortening across the shear zone sr z 1 acting upon rigid inclusions in slipping contact with the enclosing matrix 3 observed back rotated boudins deeper in the nsdz at site 3 biskjelneset can form in confined flow associated with a considerable amount of shortening across the shear zone sr 0 4 4 the observed tails of porphyroclasts indicate a minimum at least local strain of ca g z 20 5 the clasts in the studied shear zones strongly depart from jeffery s model jeffery g b 1922 the motion of ellipsoidal particles immersed in a viscous fluid proceedings of the royal society of london a102 161e179 the large scale extensional nsdz under investigation shows evidence of strain partitioning rocks vary from protomylonites to ultramylonites and the simple shear and pure shear components are heterogeneously distributed therefore we conclude that flow in the nsdz was very heterogeneous both at the kilometre and the metre scale however the present study suggests that the amount of shortening across the shear plane throughout the nsdz increases with depth and the flattening component contributes to exhumation of the eclogite facies rocks in its footwall 2007 elsevier ltd all rights reserved

numerical modelling of magma transport in dykes the rheology and dynamics of an ascending pure melt in a dyke have been extensively studied in the past from field observations it is apparent that most dykes actually contain a crystalline load the presence of a crystalline load modifies the effective rheology of such a system and thus the flow behaviour indeed the higher density and viscosity of each crystal compared to the melt cause a decrease of the ascent velocity and modify the shape of the velocity profile from a typical poiseuille flow to a bingham type flow a common feature observed in the field is the arrangement of crystals parallel or at a very low angle to the edge of the dyke such a structural arrangement is often interpreted as the result of magma flow which caused the crystals to rotate and align within the flow direction but this process remains unclear another issue related to the introduction of a crystalline load concerns the possibility for crystals to be segregated from a viscous granitic melt phase during magma ascent the implications of such a process on magmatic differentiation have not previously been considered nor has such a process been previously investigated via numerical models in this study we examine the flow dynamics of a crystal bearing granitic melt ascending in a dyke via numerical models in our models both the crystal and melt phases are represented as highly viscous fluids in a stokes regime our results reveal that the presence of crystals in the melt modifies the magma velocity profile across the dyke furthermore we observe that whilst crystals continually rotate in the shear flow over one period of revolution their major axis has a high probability to be aligned parallel to the flow direction moreover some experiments showed that the melt phase can effectively be squeezed out from a crystal rich magma when subjected to a given pressure gradient range this demonstrates that crystal melt segregation in dykes during granitic magma ascent constitutes a viable mechanism for magmatic differentiation

numerical modelling of porphyroclast and porphyroblast rotation in anisotropic rocks abstract the rotational behaviour of rigid objects in a weaker rock matrix during deformation has been the subject of many field experimental and numerical modelling studies often centred on the question whether objects rotate or not in non coaxial deformation with numerical studies gaining increasing popularity and importance we here provide an overview of the results published so far and provide new simulations originally shape and orientation were investigated while the emphasis shifted to rheology and slip between object and matrix in the nineties of the last century due to improved numerical techniques anisotropic rheology has become the focus of most recent studies indicating that it is a primary factor in the rotation behaviour of objects we present new simulations investigating the role of anisotropy on different scales relative to the object and show how this influences the rotation rate as well as the inclusion patterns in case of syntectonically growing porphyroblasts these simulations show that a variety of factors play a role to determine the rate and sense of rotation of objects the variability of the inclusion patterns that can develop necessitates extreme caution in the kinematic interpretation of these structures when observed in the field

gravity driven granular free surface flow around a circular cylinder snow avalanches and other hazardous geophysical granular flows such as debris flows lahars and pyroclastic flows often impact on obstacles as they flow down a slope generating rapid changes in the flow height and velocity in their vicinity it is important to understand how a granular material flows around such obstacles to improve the design of deflecting and catching dams and to correctly interpret field observations in this paper small scale experiments and numerical simulations are used to investigate the supercritical gravity driven free surface flow of a granular avalanche around a circular cylinder our experiments show that a very sharp bow shock wave and a stagnation point are generated in front of the cylinder the shock standoff distance is accurately reproduced by shock capturing numerical simulations and is approximately equal to the reciprocal of the froude number consistent with previous approximate results for shallow water flows as the grains move around the cylinder the flow expands and the pressure gradients rapidly accelerate the particles up to supercritical speeds again the internal pressure is not strong enough to immediately push the grains into the space behind the cylinder and instead a grain free region or granular vacuum forms on the lee side for moderate upstream froude numbers and slope inclinations the granular vacuum closes up rapidly to form a triangular region but on steeper slopes both experiments and numerical simulations show that the pinch off distance moves far downstream

rotation of rigid elliptical cylinders in viscous simple shear flow analogue experiments we used experiments to investigate the behaviour of rigid elliptical cylinders embedded in a viscous fluid of finite thickness and for very small ratios s between shear zone width z and the shortest principal axis e2 of the ellipse that constitutes the base of the elliptical cylinder 3 5 s z e2 1 2 former theoretical and experimental work on the rotation of rigid inclusions immersed in a viscous matrix considered infinite shear zone thickness and or a very large ratio between shear zone thickness and inclusion size s 1 and concluded that inclusions rotate continuously and synthetically with the applied bulk simple shear flow except for inclusions with infinite axial ratio our results depart greatly from the analytical predictions experiments were carried out at constant shear zone thickness but variable s and degree of coupling at the inclusion matrix interface the results show that 1 confined inclusion rotation always deviates from theoretical predictions for infinite shear zone thickness even for synthetic rotation 2 the deviation in the angular velocity and or in the sense of rotation increases as s approaches 1 and antithetic rotation is possible from a position with ellipse longest axis parallel to the shear plane and 3 a slipping inclusion matrix interface greatly enhances deviation from theoretical predictions with antithetic rotations to as much as 20

an outline of shear sense analysis in high grade rocks ductile shear zones are important in tectonic reconstructions as a source of information on the relative motion of large crustal blocks or plates in the geological past methods to interpret fabric in ductile shear zones were mostly developed for low grade rocks where overprinting relations are usually well preserved however high grade shear zones are common and dominate in many precambrian terrains high grade shear zones should be analysed in a different way from low grade zones the plane on which shear sense markers should be observed the vorticity profile plane is more difficult to find than in low grade shear zones the most reliable shear sense markers in high grade shear zones are shear bands mineral fish mantled porphyroclasts sigmoids and asymmetric boudins 2006 published by elsevier b v on behalf of international association for gondwana research

deflecting dams and the formation of oblique shocks in snow avalanches at flateyri iceland snow avalanches are a threat in many populated mountainous regions and deflecting dams are often built to divert them away from people and infrastructure into less harmful areas when an avalanche is deflected by a dam or wedge it often generates rapid changes in the flow thickness and velocity which can be modeled as an oblique shock wave this paper reviews classical oblique shock theory which was originally developed for shallow water flows and uses it to make predictions of the maximum runup height on a deflecting dam the downstream flow velocity and the width of the channelized stream the theory is used to investigate field observations of snow avalanches at flateyri in iceland where a dam has deflected two avalanches away from the town and produced a channelized stream that flowed parallel to the dam the results indicate that there is no one single set of upstream flow conditions that parameterizes the flow behavior but the solution evolves as the avalanche propagates along the dam in response to the deceleration imposed by the slope fully time dependent shock capturing numerical simulations of the skollahvilft avalanche which hit the dam on 21 february 1999 are used to show how the channelized stream widens as the avalanche slows down and thickens toward the end of the runout zone the oblique shock relations nevertheless provide useful local order of magnitude estimates for the flow conditions immediately upstream of the shock

reference frame angular momentum and porphyroblast rotation abstract rotation of small rigid objects in a deforming ductile matrix can produce two different types of microstructure a shape fabric due to alignment of the principal axes of a population of elongate objects and the inclusion trail microstructure preserved in syntectonic porphyroblasts we use numerical modeling to show that inclusion trails of elongate porphyroblasts are expected to be extremely complex in contrast snowball garnets are readily interpretable but misuse of reference frame and kinematic misconceptions have obfuscated the discussion on the formation of porphyroblast inclusion trails in general and snowball garnet inclusion trails in particular we clarify this point models for snowball garnet formation that are based on the notion of garnets being irrotational with respect to the earth can be rejected on a geometrical and kinematic basis further the notion that rigid objects embedded in a deforming ductile matrix generally do not rotate is unsound it violates the fundamental physical law of balance of angular momentum

geochemistry and origin of a black mudstone in a volcaniclastic environment ordovician lower rhyolitic tuff formation north wales uk black mudstones in marine volcaniclastic environments have been interpreted both as non volcanic background sedimentation and as fine grained vitric dust from the waning stages of primary volcanism although difficult to distinguish by standard petrographic techniques differentiation between the two is crucial when attempting to determine sedimentation rates or to infer periods of volcanic quiescence in the ordovician lower rhyolitic tuff formation of north wales such a fine grained black unit at cwm idwal is geochemically similar to an underlying rhyolite ash flow tuff its chemical index of alteration cia is identical to that of the tuff these data suggest that the black mudstone unit is a vitric tuff related to the underlying ash flow tuff use of a cia in addition to trace element geochemistry should in most cases serve to distinguish tuffs from silicified mudstones

shock waves dead zones and particle free regions in rapid granular free surface flows shock waves dead zones and particle free regions form when a thin surface avalanche of granular material flows around an obstacle or over a change in the bed topography understanding and modelling these flows is of considerable practical interest for industrial processes as well as for the design of defences to protect buildings structures and people from snow avalanches debris flows and rockfalls these flow phenomena also yield useful constitutive information that can be used to improve existing avalanche models in this paper a simple hydraulic theory first suggested in the russian literature is generalized to model quasi two dimensional flows around obstacles exact and numerical solutions are then compared with laboratory experiments these indicate that the theory is adequate to quantitatively describe the formation of normal shocks oblique shocks dead zones and granular vacua such features are generated by the flow around a pyramidal obstacle which is typical of some of the defensive structures in use today

deformation around rigid particles the influence of slip at the particle matrix interface abstract theoretical and previous experimental studies of rigid particle structures have only considered the behaviour of rigid particles for which the interface between particle and matrix is coherent in natural rocks the boundary behaviour may cover the whole range from free slip to complete coherence examples where slip may be promoted include crack seal deformation during the development of pressure shadows core mantle structures where the mantle is composed of much weaker fine recrystallized material and crystallizing magmas or partially molten rocks where grain boundaries are lubricated by the melt phase analogue scale model experiments have been performed under pure shear and simple shear conditions to compare the particle rotation and the flow in the matrix for both slipping and non slipping particle matrix interfaces when slip does occur particles rotate faster in pure shear and slower in simple shear than for non slip leading to the more rapid development of a shape preferred orientation the preferred orientation tends to be bimodal in simple shear flow the flow and finite strain patterns in the matrix are also strongly influenced by slip at the interface and porphyroclast systems can develop geometries with ambiguous or contradictory shear senses dependent on the original particle orientation in multi particle experiments slip on the interfaces enhances strong strain localization in non linear viscous material to produce patterns very similar to natural s c fabrics

stable positions of rigid objects in non coaxial flow a study in vorticity analysis abstract distortions of a homogeneous fabric which occur around rigid objects in rocks deformed by non coaxial ductile flow are useful to determine the sense of shear but also contain information on other aspects of the flow rigid objects in a non coaxial flow fall into two categories those which are permanently rotating and those which can reach stable positions at high finite strain the orientation of such immobilized objects with respect to eigenvectors of instantaneous flow is a function of the vorticity number of the flow the ratio of instantaneous stretches and the axial ratio of the object in naturally deformed rocks immobilized rigid objects may be recognized from the geometry of the surrounding fabric tails of recrystallized material around porphyroclasts in a mylonite rotate towards parallellism with the extensional eigenvector of the flow and the shape of tails reflects the rotational behaviour of the porphyroclast the axial ratio of immobilized porphyroclasts and their orientation with respect to the tails can theoretically be used to determine the vorticity number of the flow and deviations from isochoric plane strain in practice such an analysis is as yet difficult but a tentative example is given of the way in which the vorticity number can be calculated from a population of feldspar porphyroclasts in a quartzite mylonite from the french pyrenees

analogue modelling of the influence of shape and particle matrix interface lubrication on the rotational behaviour of rigid particles in simple shear abstract the rotational behaviour of a rigid particle embedded in a linear viscous matrix undergoing cylindrical simple shear couette flow was studied in 2d rock analogue experiments the influence of particle shape elliptical vs monoclinic aspect ratio and the nature of the matrix particle interface lubricated vs unlubricated was investigated both matrix pdms and lubricant liquid soap were linear viscous with a viscosity ratio of ca 10 4 without lubricant the rotational behaviour of all particles closely approximates the jeffery theory lubricated monoclinic particles with the long diagonal initially parallel to the shear direction show back rotation and approach a stable position lubricated elliptical particles initially parallel to the shear direction also show back rotation but only transiently stabilize weak planar zones in the matrix adjacent to unlubricated elliptical particles do not induce backward rotation in general for elliptical particles rotation rate as a function of orientation depends on axial ratio and thickness of the lubricant mantle for thick mantles initially 10 of the volume of the particle rotation rates are faster than jeffery theory for very thin mantles they are markedly slower compared with thick mantles particularly when the long axis is nearly parallel to the shear direction rotation rates are never strictly zero so true stabilization does not occur however for more elongate particles axial ratio 6 rotation rates are so slow that a very strong shape preferred orientation would develop in a lubricated elliptical particle population in experiments the volume of lubricant is constant and the thickness adjacent to the long side of the particle progressively decreases with increasing strain in natural examples of porphyroclast systems the weak mantle continually develops by recrystallization and or cataclasis of the rigid clast core and a steady state between production and thinning could be attained potentially leading to true stabilization for particles with a high axial ratio

rotation behaviour of rigid inclusions in multiple association insights from experimental and theoretical models many rocks are representative of inclusion matrix systems where rigid inclusions float on a ductile matrix the geological analogues of such inclusion matrix systems are theoretically modelled with the help of jeffery s 1922 theory in recent years there have been a number of reinvestigations on the rotational motion of rigid inclusions to account for some geological observations that are not yet predicted in models based on jeffery s theory adding to this effort this paper investigates the effects of 1 inclusion concentration and 2 the degree of coherence at the inclusion matrix interface on the rotation behaviour of rigid inclusions in a multiple inclusion system during simple shear deformation shear box experiments were run on models containing multiple identical elliptic cylinders of wax mimicking rigid inclusion embedded within putty representing ductile matrix two sets of experiments were performed with and without lubrication at the inclusion matrix interfaces each model had an isolated inclusion to reveal the variation of rotations of single and multiple inclusions increase in inclusion concentration results in contrasting rotation behaviour of isolated and multiple inclusions initially oriented parallel to the shear direction when the interfaces were not lubricated inclusions in multiple association rotated antithetically whereas the isolated one almost remained stationary in models wherein the inclusion matrix interfaces were lubricated with liquid soap both isolated and multiple inclusions rotated antithetically but the isolated inclusion rotated at a lower rate with increasing inclusion concentration the difference in the rates of antithetic rotation between isolated and multiple inclusions tended to be larger in both lubricated and non lubricated conditions the sense of rotation of isolated as well as multiple inclusions initially oriented perpendicular to the shear direction was always synthetic irrespective of the nature of the interface lubricated or non lubricated however the instantaneous rotation rates of inclusions in multiple association were higher than that of the isolated inclusions disposed in the same orientation rotation of inclusion in an inclusion matrix system is basically induced by the traction exerted by the flowing matrix on the surface of the inclusion during deformation employing a hydrodynamic model it is shown that mutual mechanical interaction among inclusions which is a function of inclusion concentration modifies the stresses at the inclusion matrix interface to a large extent moment calculations reveal that inclusions oriented parallel to the shear direction experience an antithetic moment in response to the normal stress components the magnitude of which increases with increasing inclusion concentration this implies that rotation of shear parallel inclusions in antithetic sense is favoured by higher inclusion concentration on the other hand inclusions oriented perpendicular to shear direction experience a moment that induces synthetic rotation the magnitude of the synthetic moment is larger for larger inclusion concentration leading to increase in the rate of synthetic rotation using the theoretical model the moments are calculated as a function of the aspect ratio of inclusions and the inferences based on this moment calculation are complemented with experimental findings

insights into caldera and regional structures and magma body distribution from lava domes at rotorua caldera new zealand abstract lava domes emplaced after caldera forming eruptions are often the only clue to the structure of the caldera and to the regional structure at the time of caldera formation this is because the deposits from the subsequent eruptions commonly bury subsidence controlling caldera faults and regional cross faults within calderas other calderas and lava domes in the taupo volcanic zone tvz new zealand have been previously reported to show strong regional control at rotorua caldera there is a general lack of surface expression of faults but rhyolite lava domes are well exposed and aligned with regional structures that have been mapped outside of the caldera our summary of published data and new observations allows these lava domes to be subdivided into three groups based upon their petrology geochemistry relative age and spatial distribution 1 the kaikait huna group of pre collapse 451 ka crystal rich domes at the caldera boundary 2 the utuhina group of crystal poor high alkali post collapse domes c 200 ka surrounding the locus of collapse and directly related to the earlier 240 ka mamaku ignimbrite eruption and 3 the ruamata group of crystal rich more calcic less devitrified post collapse 60 36 ka domes further out from the collapse locus mapping of the morphology and internal structures of the utuhina group domes shows an ene wsw elongation direction and vent alignment which is parallel to and down strike of a the extensional rift orientation independently mapped either side of the caldera b the local caldera morphology and c structures mapped at nearby okataina caldera complex a second nw se trending orientation in the caldera morphology is parallel to a pre collapse basement fabric and has partially controlled the locations of the domes a third orientation is hinted at through consistent n s striking flow bands within ngongotaha dome which are parallel with a gravity anomaly we suggest that this orientation is a n s section of a caldera ring fault that links regional structures and was utilised during caldera collapse a subsequent dike intrusion also used this structure erupting a fissure style dome that contains radiating flow bands which mimic the orientation of the feeder dike however the structure morphology and location of post collapse lava domes generally echo the unburied regional structures outside the caldera indicating that dike intrusion also occurred along regional structures we suggest that the regional structures at rotorua caldera which are similar to those at okataina caldera complex show that the kink in the orientation of the rift across the tvz to the se of rotorua was active to at least 240 ka and possibly earlier this kink is significant due to its proximity and influence on both rotorua and okataina caldera systems and their associated geothermal fields we conclude that internal structures such as flow bands and morphology of lava domes are direct consequences of the shape and location of the feeder dike which in turn is controlled by the structure of the caldera and region we also suggest that lava dome eruptions at rotorua were from a series of small related nestled magma bodies a key outcome of this study is the reconstruction of the wider structure of the caldera and surrounding structure based upon the localised internal features distribution and morphology of related lava domes

nonhydrostatic granular flow over 3 d terrain new boussinesq type gravity waves understanding granular mass flow is a basic step in the prediction and control of natural or man made disasters related to avalanches on the earth savage and hutter 1989 pioneered the mathematical modeling of these geophysical flows introducing saint venant type mass and momentum depth averaged hydrostatic equations using the continuum mechanics approach however denlinger and iverson 2004 found that vertical accelerations in granular mass flows are of the same order as the gravity acceleration requiring the consideration of nonhydrostatic modeling of granular mass flows although free surface water flow simulations based on nonhydrostatic depth averaged models are commonly used since the works of boussinesq 1872 1877 they have not yet been applied to the modeling of debris flow can granular mass flow be described by boussinesq type gravity waves this is a fundamental question to which an answer is required given the potential to expand the successful boussinesq type water theory to granular flow over 3 d terrain this issue is explored in this work by generalizing the basic boussinesq type theory used in civil and coastal engineering for more than a century to an arbitrary granular mass flow using the continuum mechanics approach using simple test cases it is demonstrated that the above question can be answered in the affirmative way thereby opening a new framework for the physical and mathematical modeling of granular mass flow in geophysics whereby the effect of vertical motion is mathematically included without the need of ad hoc assumptions

the influence of matrix rheology and vorticity on fabric development of populations of rigid objects during plane strain deformation abstract the influence of vorticity and rheology of matrix material on the development of shape preferred orientation spo of populations of rigid objects was experimentally studied experiments in plane strain monoclinic flow were performed to model the fabric development of two populations of rectangular rigid objects with object aspect ratios rob 2 and 3 the density of the rigid object populations was 14 of the total area objects were dispersed in a newtonian and a non newtonian power law matrix material with a power law exponent n of 1 2 the kinematic vorticity number wn of the plane strain monoclinic flow was 1 0 8 and 0 6 with finite simple shear strain of 4 6 3 0 and 0 9 respectively in experiments with rob 3 the spo is strongly influenced by wn and the material properties of the matrix deformation of a power law matrix material and low wn resulted in a stronger spo than deformation of a linear viscous matrix and high wn strain localization coupled with particle interaction plays a significant role in the development of a shape preferred orientation high strain simple shear zones separate trains of rigid objects that are surrounded by low strain zones with wn lower than the bulk wn in fabrics involving populations of objects with rob 2 rheology of the matrix materials does not systematically influence the intensity of the spo

experiments on the flow behaviour of granular materials at high velocity in an open channel a series of laboratory flume experiments has been conducted to investigate the flow behaviour of dry sand at high velocities the first incentive for this experimental programme was an attempt to explain the high mobility of apparently dry masses of rapidly moving broken rock during rock avalanches sturzstroms test velocities of over 5 m s and most other parameters of the tests were found to be dimensionally similar to those for a typical rock avalanche yet the conclusion was negative even the most rapid of the experiments indicated flow behaviour which is in conformity with the constant volume uniform coulomb friction relationship as applicable to slow shearing this conclusion was confirmed independently both by direct measurements of base friction and mean density of the flows and by detailed observations of flow uniformity acceleration and velocity profiles the surprising mobility of st umlrzstroms therefore requires a different explanation une serie de tests a canaux a ete entreprise dans le

simulation of tsaoling landslide taiwan based on saint venant equations over general topography the 1999 chi chi earthquake triggered the catastrophic tsaoling landslide in taiwan the geomorphological change measured from the data of the 1989 and 2000 aerial photos reveals that the scar and deposit volumes are about 0 126 km3 and 0 15 km3 respectively the debris material ran over a distance of 1 6 km with 500 m descent in elevation in this paper we use the continuum model of hydraulic flow shaltop2d based on the equations of bouchut and westdickenberg to simulate numerically the landslide dynamics when the mass is moving the flow is assumed hydrostatic with a basal coulomb friction the best fit is obtained using the basal friction angle equal to 6 the only parameter of the simulation uniformly applied in the calculation domain the landslide front reaches the chinshui river valley the foothill of the slope within only about 25 s after initiation and the motion settles in about 113 s the maximum speed is estimated 75 m s the spreading of the deposit agrees well with the field measurement

the development of δ clasts in non linear viscous materials a numerical approach abstract winged porphyroclasts are often used as kinematic or strain indicators in shear zones in particular it has been suggested that the geometry of clasts in mylonites can give information about the rheological behaviour of the matrix around the clast passchier et al 1993 we tested this hypothesis with a numerical finite element simulation of the flow field of a viscous matrix around a relatively rigid clast power law viscous flow properties of the matrix with stress exponents of 1 linear viscous 3 and 5 were tested as well as three different sets of approximately simple shear boundary conditions which are relevant to experimental and or natural situations the simulations show that the flow field is primarily determined by the boundary conditions the stress exponent is of secondary importance in general the different boundary conditions produce two types of flow fields about the rigid clast an eye shaped flow field and a bow tie shaped flow field the former is produced by boundary conditions that approximate simple shear applied at an infinite distance from the rigid clast and the latter is produced by boundary conditions which are equivalent to a shear box or ring shear apparatus although both the shear box and ring shear boundary conditions produce bow tie flow patterns the wing geometries which result from the flow patterns for these two cases can be significantly different the geometry of the wings that develop on a clast is a direct function of the flow field around the clast for linear and non linear rheologies only the ring shear boundary conditions produce wings that show stair stepping i e wings that are parallel but not in the same plane in natural shear zones clasts both with and without stair stepping are observed in comparing geologic observations with experimental or numerical modelling it is essential to understand which boundary conditions are appropriate

interplay of structural climatic and volcanic controls on late quaternary lacustrine deltaic sedimentation patterns in the western branch of the east african rift system rukwa rift basin tanzania abstract this paper presents the first detailed outcrop based sedimentologic investigation of the pleistocene holocene upper lake beds succession in the rukwa rift basin located in the western branch of the east african rift system southwestern tanzania the goal of this investigation is to examine the sedimentary facies and reconstruct the depositional environments of this important archive of quaternary climate and environmental change eleven diagnostic facies associations comprising 24 facies were identified and provide the basis for recognition of three key deposystems 1 alluvial to fluvial channel system 2 lake delta system and 3 profundal lacustrine system analysis of paleocurrent indicators and sandstone provenance indicate widely dispersed source regions and drainage patterns that were strongly influenced by major border fault systems and episodic volcanism six stratigraphic sequences a f ranging from 2 to 17 m thick were identified based on stratal stacking patterns and the development of sequence bounding unconformities and lacustrine flooding surfaces sedimentation processes facies architecture and stratigraphic packaging record a complex interplay between quaternary climate fluctuations and intense episodic volcanism in the nearby rungwe volcanic province set against large scale tectonic controls associated with synchronous development of the east african rift system sequence stratigraphic analysis reveals that the rukwa rift basin episodically shifted between a balanced fill lake basin and an overfilled lake basin deep water basin wide lake expansion occurred at different times during the late quaternary the final depositional sequence preserved in the basin a fluvial underfilled lake basin initiated 7 9 ka and has persisted to the present day high frequency climate change played the key role in sequence development in the upper lake beds however voluminous rift related volcanism and erosion of abundant labile volcanic materials from the rungwe volcanic province as well as syntectonic evolution of the rift led to high sedimentation rates and transformation of flash floods and debris flows in the hinterlands rift margin to hyperpycnal flows towards the basin depocenter

deformation of granitic rocks experimental studies and natural examples crustal deformation is inherently complex because the crust is inhomogeneous and anisotropic on a wide variety of scales advances in our understanding have come from a combination of field observations laboratory experiments and theoretical models what necessarily links all these investigations is a focus on process crystal plasticity dislocation creep is one of several grain scale deformation processes or mechanisms each process is dominant over a certain range of conditions in the crust has a particular form of the flow law and produces a characteristic set of microstructures characterizing the deformation mechanisms for different minerals over a range of conditions allows one to link the mechanical behavior or flow law associated with that process to the microstructures it produces the information on microstructures can be used to help interpret the thermomechanical history of naturally deformed rocks and flow laws can be used to create more realistic models predicting crustal behavior in different tectonic settings iterations among field theoretical and experimental approaches are critical for making progress in our understanding the deformation process of crystal plasticity is the main focus of this volume crystal plastic deformation of the crust is in many ways more complex than that of the mantle because most crustal rocks are polyphase aggregates and the strengths of common crustal silicates such as quartz feldspar and mica are very different at a given set of conditions yield strength envelopes for the crust as shown schematically in figure 1 are commonly plotted using the dislocation creep flow law for quartz which inherently assumes that quartz is the controlling phase and undergoes steady state flow but is the flow law for dislocation creep of quartz a good approximation for the deformation of a granite let alone a crustal plum pudding of regions and layers of different lithologies the crust

sheath folds formed by drag induced by rotation of rigid inclusions in viscous simple shear flow nature and experiment abstract natural examples of fold patterns associated with rotated boudins occur in the ossa morena zone s portugal and triggered the present study in ductile marbles with embedded competent mafic boudins the folds seem to have originated by rotation of these bodies and show differential development from gentle deflections to sheath folds this suggests a dependence of the structure type on the distance of the metamorphic layering to the rigid body the experimental work presented here was performed with rotating inclusions in bulk simple shear and introduces a new variable the distance of the marker layer from the rigid inclusion d expressed in terms of e the ratio between the spacing between marker layers d and the greater principal dimension of the inclusion a contrary to previous experimental work in the literature we used planar marker layers without concomitant boudinage our results show new processes of development of sheath folds from planar layers and also that some non cylindrical layer deflections are transient and thus that sheath folds do not originate from them when d is small and the inclusion starts with its longest axis normal to the shear plane sheath folds develop by drag pull processes on originally planar marker layers transient non cylindrical deflections develop on originally planar marker layers when the distance between the marker layers is smaller than the longest principal dimension of the rigid particle the monoclinic symmetry of the drag sheath fold patterns associated with rotating rigid inclusions indicate non coaxial flow and can be used as a shear sense criterion quarter structure

shape fabric development in rigid clast populations under pure shear the influence of no slip versus slip boundary conditions abstract shape fabrics of elliptical objects in rocks are usually assumed to develop by passive behavior of inclusions with respect to the surrounding material leading to shape based strain analysis methods belonging to the rf family a probability density function is derived for the orientational characteristics of populations of rigid ellipses deforming in a pure shear 2d deformation with both no slip and slip boundary conditions using maximum likelihood a numerical method is developed for estimating finite strain in natural populations deforming for both mechanisms application to a natural example indicates the importance of the slip mechanism in explaining clast shape fabrics in deformed sediments

experimental observations on the effect of interface slip on rotation and stabilisation of rigid particles in simple shear and a comparison with natural mylonites for axial ratios r not vert similar3 porphyroclasts from three mylonites all show a very strong spo with the long axis of the best fit ellipse at an antithetic angle of 5 10 to the shear direction this is more consistent with a stable end orientation than with the transient fabrics predicted by theory for elliptical rigid particles in simple shear the cause of this divergence is investigated in a series of high simple shear strain 15 analogue experiments performed in a ring shear machine couette flow using a linear viscous matrix pdms the rotational behaviour of elongate r not vert similar5 rigid particles with elliptical and rhomboidal shapes comparable with the natural examples is modelled for both coherent and slipping particle matrix interfaces interface slip causes a dramatic reduction in the rotation rate of the elliptical particle compared with theory when the long axis is close to the shear direction but not stabilisation interface slip does result in stabilisation of the rhomboidal particle with the long diagonal oriented at a small antithetic angle to the shear direction for monoclinic particles mirror image shapes referred to here as types 1 and 2 show different rotational behaviour for the type 1 particle with a shape comparable to porphyroclast systems and mica fish the long side rotates asymptotically into parallelism with the shear direction natural examples of type 1 particles such as hornblende and olivine porphyroclasts measured from the finero mylonites southern alps show a very strong preferred orientation for r not vert similar3 with the long side parallel or at a small 5 antithetic angle to the mylonitic foliation for type 2 particles the short side stabilises close to the shear direction or at a small synthetic angle as also observed for sillimanite porphyroclasts from the mont mary mylonites western alps in this natural case stabilisation of the short sides is against an extensional crenulation cleavage rather than the mylonitic foliation the analogue experiments establish that interface slip is one mechanism for stabilisation of elongate rhomboidal particles in natural examples decoupling from the matrix may be affected by extensional crenulation cleavage or c planes in s c fabrics

marine emplacement of welded ignimbrite the ordovician pitts head tuff north wales the pitts head welded ignimbrite records a subaerial large volume eruption and associated pyroclastic current that flowed into the sea the current 15 km from source was steadily sustained with high mass flux and high particle concentration towards its base and it entered the sea without substantial mixing with water and thus without large scale hydroexplosivity and without general cooling it continued to aggrade ignimbrite at 580 c for at least 3 4 km from the original shoreline in water initially 50 m deep entirely subaqueous hot state progressive aggradation and welding of the ignimbrite occurred where the water could not be wholly displaced by the current although eventually the deposit displaced the shore 4 km seawards wet sea floor sediments buried by the ignimbrite were heated and locally fluidized by steam and several square kilometres of hot ignimbrite with variable thicknesses of sedimentary substrate detached and slid downslope directions of sliding and the order of piling up of slide sheets are shown by hot state rheomorphic deformation fabrics and the geometric relations of detachment surfaces extensional disruption of the ignimbrite is marked by breaks in the sheet via which fluidized sediments were mobilized locally to form rootless vents both the initial incursion of the pyroclastic current into the sea and the subsequent submarine sliding of the ignimbrite are likely to have caused tsunamis similar occurrences at modern coastlines presently susceptible to incursion of high mass flux pyroclastic currents e g taupo volcanic zone new zealand neapolitan region italy vicinity of manila taal philippines would according to tsunami propagation behaviour cause significant near and far field coastal hazard

llanvirnian ord iron ooids in baltoscandia element mobility ree distribution patterns and origin of the ree abstract the chemical and mineralogical compositions of llanvimian ordovician iron and associated phosphate ooids from sweden estonia and russia have been examined the oolites are generally thin and lean mud supported and dominated by fe oxyhydroxide goethite limonite ooids one swedish oolite contains a mixture of chamosite goethite and hematite ooids and it is suggested that the two latter types were derived from chamosite ooids by early diagenetic alteration the ree distribution patterns were unaffected by these reactions all ooids in the area show a typical negative eu anomaly inherited from the source material major and minor element contents in limonite and chamosite ooids are similar whereas their ree patterns are different limonite ooids have a lree hree ratio from 1 to 2 4 and chamosite ooids from 3 to 5 the amounts of ree in the ooids are strongly dependent on the amount of phosphate

an analytical solution in 2d for the motion of rigid elliptical particles with a slipping interface under a general deformation a mathematical model for rigid inclusions with a slipping interface immersed in a general 2d homogeneous deformation is developed under bulk pure shear inclusions are expected to rapidly approach the stretching axis when compared to the behaviour of inclusions with no slip at the interface the derived model predicts synthetic and antithetic motion into a stable orientation under simple shear and thereafter the inclusion makes an antithetic angle with the shear direction under simple shear rotation rates can be higher or lower than those of no slip inclusions depending on orientation a direct relationship between object inclination to the shear direction and the vorticity of the bulk flow is predicted the model compares well with published analogue and numerical experiments

strain and kinematic analysis in general shear zones we present a unifying theory for the development and distribution of strain markers and kinematic indicators in zones of general shear and thus provide a framework in which data previously considered contradictory may be understood rigid and deformable porphyroclast systems including and complex grains are potential indicators of both strain and flow the shapes and distribution of such porphyroclast systems may be used to distinguish among different tectonic regimes general shear is divided into two fields sub simple shear in which the rotational component of the strain is less than that for simple shear and super simple shear in which the rotational component is greater than for simple shear sub simple shear may involve narrowing or broadening of shear zones super simple shear regimes are possible in local regions such as the vicinities of deformable porphyroclasts but must be enclosed by regimes of sub simple shear the polar mohr constructions for finite deformation and flow are useful to analyze general shear in theory the hyperbolic net is employed for practical plotting of real data and derivation of the kinematic vorticity number wn this number represents the relative contributions of pure and simple shear in steady flow in nature deformation is thought to build up and decay by processes that may invalidate the assumption of constant flow regime we therefore introduce the concept of accelerating deformation and analyze the implications of non steady flow for the shearing histories of deformed objects

strain localization and porphyroclast rotation it has been debated for decades whether rigid inclusions such as porphyroclasts and porphyroblasts do or do not rotate in a softer matrix during deformation experiments and numerical simulations with viscous matrix rheologies show ongoing rotation of circular inclusions whereas using mohr coulomb plasticity results in nonrotation because the rocks in which inclusions are found normally undergo deformation by dislocation creep we applied a full field crystal plasticity approach to investigate the rotation behavior of rigid circular inclusions we show that the inclusion9s rotation strongly depends on the anisotropy of the matrix minerals strongly anisotropic minerals will develop shear bands that reduce the rotation of inclusions inhibition of rotation can only occur after a significant amount of strain our results may help to explain why geologic rigid objects often show evidence for rotation but not necessarily in accordance with the viscous theory that is usually applied to these systems

channelized free surface flow of cohesionless granular avalanches in a chute with shallow lateral curvature received 29 november 1997 and in revised form 15 february 1999 a series of laboratory experiments and numerical simulations have been performed to investigate the rapid fluid like flow of a nite mass of granular material down a chute with partial lateral connement the chute consists of a section inclined at 40 to the horizontal which is connected to a plane run out zone by a smooth transition the flow is conned on the inclined section by a shallow parabolic cross slope prole photogrammetric techniques have been used to determine the position of the evolving boundary during the flow and the free surface height of the stationary granular deposit in the run out zone the results of three experiments with dierent granular materials are presented and shown to be in very good agreement with numerical simulations based on the savage hutter theory for granular avalanches the basal topography over which the avalanche flows has a strong channelizing eect on the inclined section of the chute as the avalanche reaches the run out zone where the lateral connement ceases the head spreads out to give the avalanche a characteristic tadpole shape sharp gradients in the avalanche thickness and velocity began to develop at the interface between the nose and tail of the avalanche as it came to rest indicating that a shock wave develops close to the end of the experiments

porphyroblast rotation eppur si muove in a number of recent papers the theory has been postulated that porphyroblasts as a rule do not rotate with respect to geographical coordinates and can be used to determine the original orientation of older foliations complex inclusion patterns in spiral garnets have even been used to advocate a new model of orogenesis involving several alternating phases of horizontal shortening and extension critical assessment of the assumptions and data used to support the theory of irrotational porphyroblasts reveals numerous flaws millipede structures used as proof for flow partitioning can also form by other flow geometries evidence quoted to support irrotational behaviour of porphyroblasts is unsound porphyrobl asts do occur in sets with a preferred orientation of the internal foliation trace but these cannot be shown to represent original orientations microstructures which resemble truncation planes in spiral garnets are used as evidence that these structures developed by several phases of deformation and as proof for periodic extension and horizontal shortening in orogenesis they can however also be explained by intermittent growth of a rotating porphyroblast during a single phase of deformation finally porphyroblast sets in which orientation is a function of aspect ratio indicate that porphyroblast rotation with respect to kinematic axes does occur in at least some situations

controls on the geometry of tails around rigid circular inclusions insights from analogue modelling in simple shear abstract we used analogue modelling to investigate the factors controlling tail geometry in porphyroclast systems results show that 1 inclusions can develop in both slipping and non slipping modes but inclusions only form in the latter 2 inclusions develop when the mantle production rate is constant and the mantle is transected by the separatrix inclusions form when the mantle is initially outside the separatrix and later comes inside this line 3 in the slipping mode the wedge shaped tail of inclusions always has a straight external surface parallel to the shear plane whereas in the non slipping mode the external surface is curved inwards external embayments 4 together with earlier theoretical results and inclusions always show stair stepping of tails when embedded in a viscous matrix under homogeneous simple shear deformation 5 maximum stair stepping occurs in the slipping mode and is at least equal to the inclusion diameter if our models bear significant similarity to nature then i the straight or curved character of inclusions could mean that they had respectively a slipping or non slipping interface with the surrounding recrystallized matrix and ii inclusions may result from shear deformation under retrogressive metamorphic conditions in thrust systems

experimental modelling of mantled porphyroclasts abstract mantled porphyroclasts are commonly used as sense of shear indicators in mylonites analogue experiments have been carried out to model the development of such objects rigid spheres mantled by a viscous plasticene putty mixture with power law behaviour were suspended in an optically transparent newtonian polymer matrix the samples were deformed between two cylinders one placed within the other and with coinciding axes this induces a non coaxial flow between the cylinders and allows the achievement of high finite strain the viscous mantle around the rigid sphere remained undeformed deformed into an ellipsoid or developed wings the final geometry depends mainly on the induced viscosity contrast between the mantle and the matrix which is a function of the flow induced stress on the surface of the mantle winged mantles only develop if the induced viscosity contrast between the mantle and the matrix polymer is sufficiently small if this critical induced viscosity contrast is exceeded the mantled sphere remains undeformed or obtains a stable ellipsoidal shape even at high finite strain shaped winged mantles only develop in simple shear flow if the mantle around a rigid sphere is thin

microstructural and mechanical effects of strong fine grained muscovite in soft halite matrix shear strain localization in torsion 1 torsion experiments were performed on polymer jacketed samples of 80 halite 20 fine mica at 373 473 and 573 k a confining pressure of 250 mpa and a shear strain rate of 3 10 4 s 1 the strength of the aggregate depended on temperature strain rate mica distribution produced by cold pressing and mica orientation emerging during experiments comparison with synthetic aggregates of pure halite shows that halite mica mixtures were stronger in all cases from strain rate stepping tests we deduced stress exponents of 12 and 10 at 373 and 473 k respectively in contrast to values of approximately 4 and 3 for halite at the same temperatures strain localized only at 573 k except for one run at 373 k and high strain shear bands formed parallel to the applied shear plane at 573 k we infer that the strength contrast between halite and mica increased with temperature and promoted strain localization which occurred where the local mica content was low while unstrained domains persisted where the locally high mica content formed a strong framework mica reorientation and strain softening at 573 k increased with strain from which we deduce that mica alignment promoted softening we conclude that small amounts of a strong mineral phase can significantly increase the strength and stress dependence of a rock and that the heterogeneous connectivity between strong grains can trigger shear strain localization

initiation of turbidity currents outcrop evidence for eocene hyperpycnal flow turbidites abstract the most widely used although not as widely documented explanation for initiation of turbidites is the conversion of catastrophic sediment failures into turbidites such instantaneous sediment failures generate short lived surge type flows that deposit turbidite beds described as bouma sequences in this communication we present data from the eocene central basin of spitsbergen that shows turbidite systems that are volumetrically dominated by thick ungraded and laminated sandy turbidite beds deposited by gradual aggradation from sustained flows sustained flows are long lived and more or less continuous they can be generated by a variety of mechanisms e g 1 instability during volcanic eruptions and the consequent remobilisation of unconsolidated material 2 seismically triggered subaerial sliding within the drainage 3 storm surges 4 retrogressive slope failure 5 breaching and 6 hyperpycnal flows our database shows that in the eocene central basin the sustained flows were generated by hyperpycnal flows i e by direct river effluent the hyperpycnal flow turbidites have been recognized on the basis of 1 physical connection between fluvial and turbidite channels at the shelf edge 2 abundance of thick turbidite sandstone beds 3 sand prone nature of the turbidite systems 4 downslope changes of individual thick sandy turbidite beds and their collapsed pinch out segments 5 great abundance of continental material leaves coal fragments in turbidite beds 6 low abundance of associated slumped or debris flow beds and 7 the occurrence of turbidites in systematically accreted shelf margins these features strongly suggest that hyperpycnal flow generated by direct river effluent deposited significant number of turbidite beds in the documented slope and basin floor turbidite successions we also argue that the hyperpycnal flows are preferentially fed into the deepwater slopes beyond the shelf edge during the falling stage and lowstand of relative sea level the turbidite beds were studied in the context of seismic scale 1 15 km dip oriented outcrops by measuring detailed vertical sections following individual beds and packages of beds downslope for distances over 5 km lateral mapping and helicopter taken photomosaics

tectonic influences in piecemeal caldera collapse at glencoe volcano scotland glencoe volcano is renowned as the archetype for caldera collapse that results from piston like subsidence of a coherent crustal block on a ring fault however the caldera floor rocks and the geometry of seven intracaldera units that record large volume explosive eruptions show that the collapse involved incremental and haphazard subsidence of numerous crustal blocks before development of the ring fault some subsidence involved flexure downsag with associated development of extensional crevasses hundreds of metres deep a system of orthogonal faults and related grabens records the influence of two intersecting basement discontinuities one of which is inferred to have linked with the active great glen fault substantial extensional and or transtensional faulting with distinct related sedimentary responses occurred without eruptions the tectonic framework substantially controlled the magmatic plumbing and the locations of vents caldera depocentres and through going rivers the related sediments influenced contrasting eruption styles e g transitions between phreatomagmatic and magmatic and the shallow level emplacement of sills

flow of dense avalanches past obstructions one means of preventing areas from being hit by avalanches is to divert the flow by straight or curved walls or tetrahedral or cylindrical type structures thus there arises the question how a given avalanche flow is changed regarding the diverted flow depth and flow direction in this paper a report is given on laboratory experiments performed for gravity driven dense granular flows down an inclined plane obstructed by plane wall and tetrahedral wedge it was observed that these flows are accompanied by shocks induced by the presence of the obstacles these give rise to a transition from super to subcritical flow of the granular avalanche associated with depth and velocity changes it is demonstrated that with an appropriate shock capturing integration technique for the savage hutter theory the shock formation for a finite mass granular flow sliding from an inclined plane into a horizontal run out zone is well described as is the shock formation of the granular flow on either side of a tetrahedral protection structure

relation between dry granular flow regimes and morphology of deposits formation of levees in pyroclastic deposits experiments on dry granular matter flowing down an inclined plane are performed in order to study the dynamics of dense pyroclastic flows the plane is rough and always wider than the flow focusing this study on the case of laterally unconfined free boundary flows we found that several flow regimes exist depending on the input flux and on the inclination of the plane each flow regime corresponds to a particular morphology of the associated deposit in one of these regimes the flow reaches a steady state and the deposit exhibits a levee channel morphology similar to those observed on small pyroclastic flow deposits the levees result from the combination between lateral static zones on each border of the flow and the drainage of the central part of the flow after the supply stops particle segregation features are created during the flow corresponding to those observed on the deposits of pyroclastic flows moreover the measurements of the deposit morphology thickness of the channel height of the levees width of the deposit are quantitatively related to parameters of the dynamics of the flow flux velocity height of the flow leading to a way of studying the flow dynamics from only measurements of the deposit some attempts to make extensions to natural cases are discussed through experiments introducing the polydispersity of the particle sizes and the particle segregation process