calcareous duricrust al qasim province saudi arabia occurrence and origin in al qasim province saudi arabia calcareous pedogenic duricrust overlies the upper permian carbonates and clays of the khuff formation and ranges in thickness from 60 cm to 2 m it consists of white sandy duricrust capped by brown nodular porous duricrust petrographic investigation led to recognition of three lithofacies that show spatial distribution 1 structureless sandy calcareous mudstone 2 brecciated nodular calcareous mudstone and 3 pisolitic calcareous mudstone the diagenetic changes in duricrust are aggrading neomorphism and formation of calcite rims around quartz grains microprobe chemical analysis was performed on the diagenetically altered material the development of the duricrust is controlled by four factors the climate changes the type of underlying rocks source of carbonate and biological effects the repeated changes from semi arid climate with alternating wet and dry seasons are the main controlling factor in generation of duricrust development during humid periods descending water carries the dissolved carbonates downward as bicarbonates whereas dry and interpluvial period the carbonate rich solutions are carried upwards by capillary or evaporation the claystone and sandstone interbeds possibly affect the development of calcareous duricrust more than the sandstones and dolostones because the former have the ability to attach calcium carbonate to form the duricrust the development of calcareous duricrust is mainly attributed to the pleistocene and early holocene alternating humid and arid periods that prevailed over the arabian peninsula during this time

prediction of the behaviour of landslide dams using a geomorphological dimensionless index landslide dams are a common phenomenon they form when a landslide reaches the bottom of a river valley causing a blockage the first effect of such a dam is the infilling of a lake that inundates the areas upstream while the possibility of a sudden dam collapse with a rapid release of the impounded waters poses a higher flood risk to the downstream areas the results of the main inventories carried out to date on landslide dams have been examined to determine criteria for forecasting landslide dam evolution with particular emphasis on the assessment of dam stability not all landslides result in the blockage of a river channel this only occurs with ones that can move a large amount of material with moderate or high velocities in most cases these landslides are triggered by rainfall events or high magnitude earthquakes a relationship also exists between the volume of the displaced material and the landslide dam stability several authors have proposed that landslide dam behaviour can be forecast by defining various geomorphological indexes that result from the combination of variables identifying both the dam and the dammed river channel further developments of this geomorphological approach are presented in this paper by the definition of a dimensionless blockage index starting with an analysis of 84 episodes selected worldwide it proved to be a useful tool for making accurate predictions concerning the fate of a landslide dam copyright 2002 john wiley sons ltd

dynamical link between the barents kara sea ice and the arctic oscillation abstractthe recent accelerated arctic sea ice decline has been proposed as a possible forcing factor for midlatitude circulation changes which can be projected onto the arctic oscillation ao and or north atlantic oscillation nao mode however the timing and physical mechanisms linking ao responses to the arctic sea ice forcing are not entirely understood in this study the authors suggest a connection between november sea ice extent in the barents and kara seas and the following winter s atmospheric circulation in terms of the fast sea ice retreat and the subsequent modification of local air sea heat fluxes in particular the dynamical processes that link november sea ice in the barents and kara seas with the development of ao anomalies in february is explored in response to the lower tropospheric warming associated with the initial thermal effect of the sea ice loss the large scale atmospheric circulation goes through a series of dynamical adjustment processes the decelerated zonal mean zonal

using fractal analysis to quantitatively characterize the shapes of volcanic particles 1 the shapes of volcanic particles reflect numerous eruptive parameters e g magma viscosity volatile content and degree of interaction with water and are useful for understanding fragmentation and transport processes associated with volcanic eruptions however quantitative analysis of volcanic particle shapes has proven difficult because of their morphological complexity and variability here a newly developed procedure for shape analysis based on fractal geometry is described and tested although volcanic particle shapes are not truly fractal their complexity can be effectively characterized in terms of fractal values pseudofractal dimensions reflecting morphological invariance over discrete ranges of scale using fractal data produced by dilation of a particle s two dimensional boundary a spectrum of fractal dimensions is calculated for each particle by taking the first derivative of the dilation data compared with fractal methods that express shape in terms of only one or two fractal dimensions typically derived from the slope of data on a richardson plot this technique results in better discrimination between samples in addition use of multiple fractal values allows incorporation of multivariate statistical analysis further strengthening the differentiating power of the technique this fractal spectrum technique yields promising results for samples of sideromelane shards from iceland and is likely to be effective at characterizing other kinds of volcanic particle shapes

deep sea fragmentation style of havre revealed by dendrogrammatic analyses of particle morphometry in 2012 the eruption of deep sea volcano havre produced an abundance of fine ash at a depth of 1000 m below sea level in this study the 2d shapes of havre ash grains retrieved from the seafloor were compared quantitatively with those of particles generated in a suite of different fragmentation experiments which used remelted rhyolitic rock and pumice from the eruption site a new statistical data analysis technique denoted as dendrogrammatic analysis of particle morphology dapm is introduced it is designed to compare large numbers of morphometric data sets containing shape information for a set of ash particles to group them by morphological similarities and to visualize these clusters in a dendrogram further steps involve t tests and equivalence tests and reveal morphometric differences as well as matching features the dapm suggests that the majority of havre ash was thermohydraulically produced by induced fuel coolant interaction a subset of ash particles features an elongated tube morphology their morphometry matches that of particles that were experimentally produced by a combination of shearing and quenching and we infer that the natural particles were formed by synextrusive ash venting

high resolution 3d analyses of the shape and internal constituents of small volcanic ash particles the contribution of sem micro computed tomography sem micro ct abstract the morphology of small volcanic ash particles is fundamental to our understanding of magma fragmentation and in transport modeling of volcanic plumes and clouds until recently the analysis of 3d features in small objects 20 m3 3 5 m in diameter can be successfully reconstructed and quantified in addition new functionalities of the blob3d software were developed to allow the particle shape factors frequently used as input parameters in ash transport and dispersion models to be calculated this study indicates that sem micro ct is very well suited to quantify the various aspects of shape in fine volcanic ash and potentially also to investigate the 3d morphology and internal structure of any object

first evidence of a distal early holocene ash layer in eastern mediterranean deep sea sediments derived from the anatolian volcanic province article i nfo a hitherto unknown distal volcanic ash layer has been detected in a sediment core recovered from the southeastern levantine sea eastern mediterranean sea radiometric stratigraphic and sedimentological data show that the tephra here termed as s1 tephra was deposited between 8970 and 8690 cal yr bp the high silica rhyolitic composition excludes an origin from any known eruptions of the italian aegean or arabian volcanic provinces but suggests a prevailing central anatolian provenance we compare the s1 tephra with proximal to medial distal tephra deposits from well known mediterranean ash layers and ash fall deposits from the central anatolian volcanic field using electron probe microanalyses on volcanic glass shards and morphological analyses on ash particles we postulate a correlation with the early holocene dikkartin dome eruption of erciyes dag volcano cappadocia turkey so far no tephra of the central anatolian volcanic province has been detected in marine sediment archives in the eastern mediterranean region the occurrence of the s1 tephra in the south eastern part of the levantine sea indicates a wide dispersal of pyroclastic material from erciyes dag more than 600 km to the south and is therefore an important tephrostratigraphical marker in sediments of the easternmost mediterranean sea and the adjacent hinterland

fractal analysis of fracture patterns using the standard box counting technique valid and invalid methodologies abstract on the basis of results of simple box counting analysis it has been suggested in several recent publications that natural fracture patterns are fractal fractal patterns are characterized by self similarity of structure on a range of scales and provide straight line distributions on box counting plots new analysis of a fracture pattern that provided the most convincing straight line box counting curve previously published shows that the curve is non linear and therefore that the fracture pattern is not fractal non linear box counting curves are also characteristic of other natural fracture patterns analysed but spurious linear curves can be obtained if the area analysed extends beyond the mapped area

mechanisms of hydrovolcanic pyroclast formation grain size scanning electron microscopy and experimental studies pyroclasts produced by explosive magma water interactions are of various sizes and shapes data from analysis of over 200 samples of hydrovolcanic ash are interpreted by comparison with experimentally produced ash grain size and scanning electron microscopy sem reveal information on the formation of hydrovolcanic pyroclasts strombolian explosions result from limited water interaction with magma and the pyroclasts produced are dominantly centimeter sized with increasing water interaction hydrovolcanism increases in explosivity to surtseyan and vulcanian activity these eruptions produce millimeter to micron sized pyroclasts the abundance of fine ash 63 m diameter increases from 5 to over 30 percent as water interaction reaches an explosive maximum this maximum occurs with interactions of virtually equal volumes of melt and water five dominant pyroclast shape types determined by sem result from hydrovolcanic fragmentation 1 blocky and equant 2 vesicular and irregular with smooth surfaces 3 moss like and convoluted 4 spherical or drop like and 5 plate like types 1 and 2 dominate pyroclasts greater than 100 m in diameter types 3 and 4 are typical of fine ash type 5 pyroclasts characterize ash less than 100 m in diameter resulting from hydrovolcanic fragmentation after strong vesiculation fragmentation mechanisms observed in experimental melt water interactions result from vapor film generation expansion and collapse fragments of congealed melt are products of several alternative mechanisms including stress wave cavitation detonation waves and fluid instability mixing all result in rapid heat transfer these mechanisms can explain the five observed pyroclast shapes stress wave fracturing cavitation of the melt results from high pressure and temperature gradients at the melt water interface simultaneous brittle fracture and quenching produces type 1 pyroclasts type 2 develops smooth fused surfaces due to turbulent mixing with water after fracture and before quenching fluid instabilities promote turbulent mixing of melt and water and produce fine ash this kind of fragmentation occurs during high energy explosions the increased melt surface area due to fine fragmentation promotes high efficiency heat exchange between the melt and water shapes of resulting pyroclasts are determined by maximum surface area type 3 and surface tension effects type 4 type 5 pyroclasts result from nearly simultaneous vesicle burst and melt water fragmentation

towards fast and routine analyses of volcanic ash morphometry for eruption surveillance applications the morphometry of volcanic ash produced by explosive eruptions yields ample information on fragmentation processes e g magmatic vs magma water interactions and on transport and sedimentation mechanisms most previous works on volcanic clast morphometry focused on the apparent 2d projected shape of ash grains here termed apash to infer processes and eruptive styles however textural analyses of ash grains has remained a long and tedious task that made such approaches inappropriate for eruption surveillance duties in this work we show that new technological advances on automated dispersion of granular materials imaged with a camera coupled microscope and enhanced computer capabilities enable fast and high resolution image acquisition of thousands of ash grains that resolve this limitation with a morpho grainsizer designed for such fast and routine measurements we perform a series of apash analyses on selected ash fractions of tephra deposits from known eruptive styles we record the size aspect ratio circularity and convexity of apash images and assess resolution reproducibility minimum population size and total analytical duration and offer recommendations for the reporting of apash data for inter laboratory comparisons to avoid fractal geometry concerns our analyses are carried out at constant size range 250 300 m and optical magnification 5 on 3000 grains per samples collected from homogenized samples results from the andesitic 1999 ongoing eruption of tungurahua volcano ecuador show that ash particles from the moderate 2001 phase are relatively equant and convex in shape while the stronger 2006 subplinian phase produced ash grains with more elongated less circular and less convex apash signatures ash grains from a basaltic scoria cone forming eruption show even more ragged apash characteristics overall our protocol allows obtaining accurate and reproducible morphometric measurements that reveal subtle variations of the morphological signature and the short duration 1 8 hours of the whole analytical process renders high resolution analyses of ash shape achievable for volcano surveillance applications this research ultimately aims to set up a morphometric database of apash results for well defined eruptive styles in order to interpret on a short term basis any apash data from active volcanoes for monitoring purposes

estimates of sea ice mechanical properties in the kara sea on the basis of available public data an approximate theoretical approach for characterizing the arctic sea ice engineering properties is explored and discussed in the kara sea the corrected era interim sea ice thickness and orap5 sea ice temperature database are selected as the basic ice physical parameters the formulas recommended by iso 19906 are chosen as the estimation criteria for the ice mechanical properties the generalized extreme value theory is used to analyze the ice extreme statistics specifically the typical mechanical properties including compressive strength flexural strength shear strength and elastic modulus are comprehensively studied the results reveal that all the mechanical properties show higher levels in the northeastern zone than in the southwestern zone with the heaviest ice regime around the southwestern severnaya zemlya in addition an uncertainty analysis is provided compared to the published measurements the snowless flexural strength values obtained are relatively conservative additionally the shear equation in iso 19906 should be pre corrected before practical application

characteristics of stratospheric polar vortex fluctuations associated with sea ice variability in the arctic winter the leading two modes of winter november february arctic sea ice cover variability and their linkage to stratospheric polar vortex variations are analyzed based on the cyclostationary eof techniques the first mode represents an accelerating trend of arctic sea ice decline associated with arctic amplification particularly in the barents and kara seas the second mode is associated with decadal scale phase shifts of dipole sea ice anomalies in the north atlantic caused by nao circulation the first two modes of sea ice variability represent respectively a forced climate change and internal variability and result in temporally and spatially distinct stratospheric polar vortex weakening sea ice reduction in the barents and kara seas for the first mode is linked to a stratospheric vortex weakening during mid january late february the second mode with the dipole structure of positive sea ice anomalies in the barents and greenland seas and negative anomalies in the hudson bay and labrador sea is related to a stratospheric vortex weakening during december early february the spatial evolutionary structure of anomalous polar vortex also exhibits differences between the two modes when stratospheric anomalies are fully developed stratospheric vortex is shifted to eurasia in the first mode and to europe in the second mode

a link between reduced barents kara sea ice and cold winter extremes over northern continents the recent overall northern hemisphere warming was accompanied by several severe northern continental winters as for example extremely cold winter 2005 2006 in europe and northern asia here we show that anomalous decrease of wintertime sea ice concentration in the barents kara b k seas could bring about extreme cold events like winter 2005 2006 our simulations with the echam5 general circulation model demonstrate that lower troposphere heating over the b k seas in the eastern arctic caused by the sea ice reduction may result in strong anti cyclonic anomaly over the polar ocean and anomalous easterly advection over northern continents this causes a continental scale winter cooling reaching 1 5 c with more than three times increased probability of cold winter extremes over large areas including europe our results imply that several recent severe winters do not conflict the global warming picture but rather supplement it being in qualitative agreement with the simulated large scale atmospheric circulation realignment furthermore our results suggest that high latitude atmospheric circulation response to the b k sea ice decrease is highly nonlinear and characterized by transition from anomalous cyclonic circulation to anticyclonic one and then again back to cyclonic type of circulation as the b k sea ice concentration gradually reduces from 100 to ice free conditions we present a conceptual model which may explain the nonlinear local atmospheric response in the b k seas region by counter play between convection over the surface heat source and baroclinic effect due to modified temperature gradients in the vicinity of the heating area

optical modeling of volcanic ash particles using ellipsoids the single scattering properties of volcanic ash particles are modeled here by using ellipsoidal shapes ellipsoids are expected to improve the accuracy of the retrieval of aerosol properties using remote sensing techniques which are currently often based on oversimplified assumptions of spherical ash particles measurements of the single scattering optical properties of ash particles from several volcanoes across the globe including previously unpublished measurements from the eyjafjallajokull and puyehue volcanoes are used to assess the performance of the ellipsoidal particle models these comparisons between the measurements and the ellipsoidal particle model include consideration of the whole scattering matrix as well as sensitivity studies on the point of view of the advanced along track scanning radiometer aatsr instrument aatsr which flew on the envisat satellite offers two viewing directions but no information on polarization so usually only the phase function is relevant for interpreting its measurements as expected ensembles of ellipsoids are able to reproduce the observed scattering matrix more faithfully than spheres performance of ellipsoid ensembles depends on the distribution of particle shapes which we tried to optimize no single specific shape distribution could be found that would perform superiorly in all situations but all of the best fit ellipsoidal distributions as well as the additionally tested equiprobable distribution improved greatly over the performance of spheres we conclude that an equiprobable shape distribution of ellipsoidal model particles is a relatively good yet enticingly simple approach for modeling volcanic ash single scattering optical properties

furthering the investigation of eruption styles through quantitative shape analyses of volcanic ash particles abstract volcanic ash morphology has been quantitatively investigated for various aims such as studying the settling velocity of ash for modelling purposes and understanding the fragmentation processes at the origin of explosive eruptions in an attempt to investigate the usefulness of ash morphometry for monitoring purposes we analyzed the shape of volcanic ash particles through a combination of 1 traditional shape descriptors such as solidity convexity axial ratio and form factor and 2 fractal analysis using the euclidean distance transform edt method we compare ash samples from the hydrothermal eruptions of iwodake japan in 2013 tangkuban perahu indonesia in 2013 and marapi sumatra indonesia in 2015 the dome explosions of merapi java indonesia in 2013 the vulcanian eruptions of merapi in 2010 and tavurvur rabaul papaua new guinea in 2014 and the plinian eruption of kelud indonesia in 2014 particle size and shape measurements were acquired from a particle size analyzer with a microscope camera attached to the instrument clear differences between dense blocky particles from hydrothermal or dome explosions and vesicular particles produced by the fragmentation of gas bearing molten magma are well highlighted by conventional shape descriptors and the fractal method in addition subtle differences between dense blocky particles produced by hydrothermal explosions dome explosions or quench granulation during phreatomagmatic eruptions can be evidenced with the fractal method the combination of shape descriptors and fractal analysis is therefore potentially able to distinguish between juvenile and non juvenile magma which is of importance for eruption monitoring

tropospheric precursors of anomalous northern hemisphere stratospheric polar vortices regional extratropical tropospheric variability in the north pacific and eastern europe is well correlated with variability in the northern hemisphere wintertime stratospheric polar vortex in both the ecmwf reanalysis record and in the whole atmosphere community climate model to explain this correlation the link between stratospheric vertical eliassen palm flux variability and tropospheric variability is analyzed simple reasoning shows that variability in the north pacific and eastern europe can deepen or flatten the wintertime tropospheric stationary waves and in particular its wavenumber 1 and 2 components thus providing a physical explanation for the correlation between these regions and vortex weakening these two pathways begin to weaken the upper stratospheric vortex nearly immediately with a peak influence apparent after a lag of some 20 days the influence then appears to propagate downward in time as expected from wave mean flow interaction theory these patterns are influenced by enso and october eurasian snow cover perturbations in the vortex induced by the two regions add linearly these two patterns and the quasi biennial oscillation qbo are linearly related to 40 of polar vortex variability during winter in the reanalysis record

identifying magma water interaction from the surface features of ash particles the deposits from explosive volcanic eruptions those eruptions that release mechanical energy over a short time span1 are characterized by an abundance of volcanic ash2 3 this ash is produced by fragmentation of the magma driving the eruption and by fragmenting and ejecting parts of the pre existing crust host rocks interactions between rising magma and the hydrosphere oceans lakes and ground water play an important role in explosive volcanism4 5 because of the unique thermodynamic properties of water that allow it to very effectively convert thermal into mechanical energy although the relative proportion of magma to host rock fragments is well preserved in the pyroclastic rocks deposited by such eruptions it has remained difficult to quantitatively assess the interaction of magma with liquid water from the analysis of pyroclastic deposits2 3 4 5 here we report the results of a study of natural pyroclastic sequences combined with scaled laboratory experiments we find that surface features of ash grains can be used to identify the dynamic contact of magma with liquid water the abundance of such ash grains can then be related to the water magma mass ratios during their interaction

quantitative discrimination of magma fragmentation and pyroclastic transport processes using the fractal spectrum technique abstract the morphology of volcanic particles can yield insight into magma fragmentation transport processes and style of eruption however the complexity and variability of volcanic particle shapes make quantitative characterization difficult the technique applied in this study is based on fractal geometry which has been successfully used to characterize a wide variety of particles and shapes here fractal data is produced by dilation of the 2 d particle boundary to produce a full spectrum of fractal dimensions over a range of scales for each particle multiple fractal dimensions which can be described as a fractal spectrum curve are calculated by taking the first derivative of data points on a standard richardson plot use of multiple fractal dimensions results in more effective discrimination than expressions of shape based on one or two fractal dimensions quantitative comparisons are carried out using multivariate statistical techniques such as cluster and principal components analysis applications to samples from well documented eruptions e g mt st helens 1980 tambora 1815 surtsey 1963 64 indicate that the fractal spectrum technique provides a useful means of characterizing volcanic particles and can be helpful for identifying the products of specific fragmentation processes volatile exsolution phreatomagmatic quench granulation and modes of volcanic transport deposition tephra fall pyroclastic flow blast surge

the effects of north atlantic sst and sea ice anomalies on the winter circulation in ccm3 part ii direct and indirect components of the response the wintertime atmospheric circulation responses to observed patterns of north atlantic sea surface temperature and sea ice cover trends in recent decades are studied by means of experiments with an atmospheric general circulation model here the relationship between the forced responses and the dominant pattern of internally generated atmospheric variability is focused on the total response is partioned into a portion that projects onto the leading mode of internal variability the indirect response and a portion that is the residual from that projection the direct response this empirical decomposition yields physically meaningful patterns whose distinctive horizontal and vertical structures imply different governing mechanisms the indirect response which dominates the total geopotential height response is hemispheric in scale with resemblance to the north atlantic oscillation or northern hemisphere annular mode and equivalent barotropic in the vertical from the surface to the tropopause in contrast the direct response is localized to the vicinity of the surface thermal anomaly sst or sea ice and exhibits a baroclinic structure in the vertical with a surface trough and upper level ridge in the case of a positive heating anomaly consistent with theoretical models of the linear baroclinic response to extratropical thermal forcing both components of the response scale linearly with respect to the amplitude of the forcing but nonlinearly with respect to the polarity of the forcing the deeper vertical penetration of anomalous heating compared to cooling is suggested to play a role in the nonlinearity of the response to sst forcing

fragmentation versus transportation mechanisms in the pyroclastic sequence of monte pilato rocche rosse lipari italy abstract monte pilato is a rhyolitic pumice cone formed about 1400 years ago during the last volcanic activity which occurred at lipari its activity consisted of numerous explosive episodes ending with the extrusion of the rocche rosse obsidian lava flow we have identified nine different pyroclastic lithofacies of which four main lithofacies represent 90 of the erupted products they include 1 deposits consisting of decimeters to meters thick well sorted graded beds of pumice lapilli which are of fall origin 2 massive deposits consisting of decimeters thick beds of pumice lapilli in an ash matrix interpreted as being of pyroclastic flow origin 3 deposits of centimeters thick ash beds of surge origin 4 decimeter thick fine ash layers with scattered subcentimetric accretionary lapilli of turbulent flow origin the complex grain size distributions of the main lithofacies were distinguished using a multivariate statistic analysis r mode factor analysis variations of the grain size characteristics in relation to the distance from the vent area have been investigated in order to discriminate the roles played by fragmentation and transportation processes in the lithofacies 1 fall deposits the grain size distribution is always unimodal and varies from a rosin type distribution near the vent to a gaussian one in the distal outcrops this is caused by the transport process and the different particle trajectories in lithofacies 2 3 and 4 the grain size distributions are always polymodal the polymodality is not caused by preferential processes occurring during transportation but seems rather to be connected with the original fragmentation of the pyroclastic material the pumice lapilli present both in lithofacies 1 and 2 have mean vesicularity index values always in excess of 65 and the value is homogeneous throughout the sample these data suggest that for these two lithofacies the pumice lapilli originated from exsolution of magmatic gases in contrast the fine ash particles in lithofacies 2 and also the main mode of lithofacies 3 and 4 deposits show typical features of hydromagmatic fragmentation processes the grain size population is always centered at 4 5 0 032 0 064 mm and interestingly the same grain size has been obtained recently zimanowski et al 1991 for fragments produced by experimental magma water interaction field and laboratory data suggest that during monte pilato rocche rosse eruptions magmatic and hydromagmatic mechanisms were frequently operative at the same time

influence of low arctic sea ice minima on anomalously cold eurasian winters 1 influence of low arctic sea ice minima in early autumn on the wintertime climate over eurasia is investigated observational evidence shows that significant cold anomalies over the far east in early winter and zonally elongated cold anomalies from europe to far east in late winter are associated with the decrease of the arctic sea ice cover in the preceding summer to autumn seasons results from numerical experiments using an atmospheric general circulation model support these notions the remote response in early winter is regarded as a stationary rossby wave generated thermally through an anomalous turbulent heat fluxes as a result of anomalous ice cover over the barents kara seas in late autumn which tends to induce an amplification of the siberian high causing colder conditions over the far east the late winter cold anomalies over eurasia are also reproduced in our experiment which is associated with the negative phase of the north atlantic oscillation

use of fractal analysis for discrimination of particles from primary and reworked jokulhlaup deposits in se iceland abstract the morphology of sideromelane particles from jokulhlaup deposits in southeastern iceland has been studied by fractal analysis to assess post depositional changes associated with reworking fractal dimensions of particle boundaries were calculated from data obtained by the caliper and dilation methods most particles exhibit multifractal relationships with a textural d1 and structural d2 fractal dimension particles from primary jokulhlaup deposits have significantly greater textural and structural fractal dimensions compared to reworked deposits differences in the fractal dimensions indicate that reworking in the littoral zone has reduced both the amount of fine scale features on particle surfaces and the complexity of the overall particle shapes the caliper and dilation methods yield similar values of textural fractal dimension for each particle for the same particles the dilation method yields higher values of structural fractal dimension reworked particles used in this study can be effectively discriminated from primary particles using a combination of d1 and d2 fractal dimensions the results indicate that fractal analysis provides a useful quantitative characterization of complex volcanic particles and can be utilized to examine aspects of particle origin transport and deposition

compounding effects of warm sea surface temperature and reduced sea ice on the extreme circulation over the extratropical north pacific and north america during the 2013 2014 boreal winter unprecedented atmospheric circulations with extreme weather were observed in the extratropical northern hemisphere during the winter of 2013 2014 the anomalous circulations were the manifestation of the pacific pattern or the north pacific oscillation western pacific pattern but with extremely large amplitude simulation results suggest that the anomalous atmospheric circulations were constructively induced by anomalous sea surface temperature in the tropical pacific and extratropical north pacific as well as the low sea ice concentration in the arctic natural variability played a major role in inducing the anomaly pattern whereas the anomalously warm sea surface temperature and low arctic sea ice concentration in the bering sea contributed to the intensity if the anthropogenic warming has a significant impact on causing the synchronization of the aforementioned anomalies in sea surface temperature and sea ice concentration and this trend continues severe winters similar to that in 2013 2014 may occur more frequently in the future

grain shape of basaltic ash populations implications for fragmentation here we introduce a new quantitative method to produce grain shape data of bulk samples of volcanic ash and we correlate the bulk average grain shape with magma fragmentation mechanisms the method is based on automatic shape analysis of 2d projection ash grains in the size range 125 63 m loose bulk samples from the deposits of six different basaltic eruptions were analyzed and 20 000 shape measurements for each were obtained within 45 min using the particle insight dynamic shape analyzer pidsa we used principal component analysis on a reference grain dataset to show that circularity rectangularity form factor and elongation best discriminate between the grain shapes when combined the grain population data show that the studied eruptive environments produce nearly the same range of grain shapes although to different extents our new shape index the regularity index ri places an eruption on a spectrum between phreatomagmatic and dry magmatic fragmentation almost vesicle free surtseyan ash has an ri of 0 207 0 002 2 whereas vesiculated hawaiian ash has an ri of 0 134 0 001 2 these two samples define the end member ri while two subglacial one lacustrine and another submarine ash sample show intermediate ris of 0 168 0 002 2 0 175 0 002 2 0 187 0 002 2 and 0 191 0 002 2 respectively the systematic change in ri between wet and dry eruptions suggests that the ri can be used to assess the relative roles of magmatic vs phreatomagmatic fragmentation we infer that both magmatic and phreatomagmatic fragmentation processes played a role in the subglacial eruptions

prolonged effect of the stratospheric pathway in linking barents kara sea sea ice variability to the midlatitude circulation in a simplified model to better understand the dynamical mechanism that accounts for the observed lead lag correlation between the early winter barents kara sea bks sea ice variability and the later winter midlatitude circulation response a series of experiments are conducted using a simplified atmospheric general circulation model with a prescribed idealized near surface heating over the bks a prolonged effect is found in the idealized experiments following the near surface heating and can be explicitly attributed to the stratospheric pathway and the long time scale in the stratosphere the analysis of the eliassen palm flux shows that as a result of the imposed heating and linear constructive interference anomalous upward propagating planetary scale waves are excited and weaken the stratospheric polar vortex this stratospheric response persists for approximately 1 2 months accompanied by downward migration to the troposphere and the surface this downward migration largely amplifies and extends the low level jet deceleration in the midlatitudes and cold air advection over central asia the idealized model experiments also suggest that the bks region is the most effective in affecting the midlatitude circulation than other regions over the arctic

the melting arctic and midlatitude weather patterns are they connected abstractthe potential of recent arctic changes to influence hemispheric weather is a complex and controversial topic with considerable uncertainty as time series of potential linkages are short 10 yr and understanding involves the relative contribution of direct forcing by arctic changes on a chaotic climatic system a way forward is through further investigation of atmospheric dynamic mechanisms during several exceptionally warm arctic winters since 2007 sea ice loss in the barents and kara seas initiated eastward propagating wave trains of high and low pressure anomalous high pressure east of the ural mountains advected arctic air over central and eastern asia resulting in persistent cold spells blocking near greenland related to low level temperature anomalies led to northerly flow into eastern north america inducing persistent cold periods potential arctic connections in europe are less clear variability in the north pacific can reinforce downstream arctic changes and arctic amplification

source and dispersal of jokulhlaup sediments discharged to the sea following the 1996 vatnajokull eruption the october 1996 gjalp eruption beneath vatnajokull glacier led to one of the largest jokulhlaups glacial floods in iceland in the twentieth century a catastrophic discharge of meltwater and sediment swept across the skeidararsandur flood plain to the sea tephra from the eruption consists of vesicular sideromelane shards with a basaltic andesite composition 53 sio 2 3 mgo 0 8 k 2 o after the flood sediment samples were collected from the flood plain and off the southeast coast of iceland where a major sediment plume had been created by the discharge compositions of glass shards from flood plain and seafloor deposits do not match those of the gjalp magma flood plain samples consist primarily of blocky to poorly vesicular sideromelane clasts with compositions that are characteristic of grimsvotn volcanic products 50 sio 2 5 5 mgo 0 4 k 2 o marine samples collected near the jokulhlaup outflow into the sea also consist primarily of blocky to poorly vesicular sideromelane clasts with compositions that are for the most part similar to products of the grimsvotn volcanic center distal marine samples have more vesicular sideromelane clasts with compositions that are similar to products of the katla volcanic center e g 48 sio 2 4 5 mgo 0 8 k 2 o significant deposition to the seafloor was apparently limited to an area just offshore of the skeidararsandur there is no indication that juvenile volcanic material from the gjalp eruption was carried by the 1996 jokulhlaup onto the flood plain or into the ocean instead the jokulhlaup carried primarily older volcaniclastic material eroded by the flood

explosive energy during volcanic eruptions from fractal analysis of pyroclasts abstract despite recent advances by means of experiments and high resolution surveys and the growing understanding of the physical processes before and during volcanic eruptions duration and type of eruptive activity still remain highly unpredictable this uncertainty hinders appropriate hazard and associated risk assessment tremendously in an effort to counter this problem experimentally generated pyroclasts have been studied by fractal statistics with the aim of evaluating possible relationships between eruption energy and fragmentation efficiency rapid decompression experiments have been performed on three differently porous sample sets of the 1990 1995 eruption of unzen volcano japan at 850 c and at initial pressure values above the respective fragmentation threshold u kueppers b scheu o spieler d b dingwell fragmentation efficiency of explosive volcanic eruptions a study of experimentally generated pyroclasts j volcanol geotherm res 153 2006 125 135 o spieler b kennedy u kueppers d b dingwell b scheu j taddeucci the fragmentation threshold of pyroclastic rocks epsl 226 2004 139 148 the size distribution of generated pyroclasts has been studied by fractal fragmentation theory and the fractal dimension of fragmentation df a value quantifying the intensity of fragmentation has been measured for each sample results show that size distribution of pyroclastic fragments follows a fractal law i e power law in the investigated range of fragment sizes indicating that fragmentation of experimental samples reflects a scale invariant mechanism in addition df is correlated positively with the potential energy for fragmentation pef while showing a strong influence of the open porosity of the samples results obtained in this work indicate that fractal fragmentation theory may allow for quantifying fragmentation processes during explosive volcanic eruptions by calculating the fractal dimension of the size distribution of pyroclasts it emerges from this study that fractal dimension may be utilised as a proxy for estimating the explosivity of volcanic eruptions by analysing their natural pyroclastic deposits

observational evidence of a stratospheric influence on the troposphere by planetary wave reflection abstract recent studies have pointed out the impact of the stratosphere on the troposphere by dynamic coupling in the present paper observational evidence for an effect of downward planetary wave reflection in the stratosphere on northern hemisphere tropospheric waves is given by combining statistical and dynamical diagnostics a time lagged singular value decomposition analysis is applied to daily tropospheric and stratospheric height fields recomposed for a single zonal wavenumber a wave geometry diagnostic for wave propagation characteristics that separates the index of refraction into vertical and meridional components is used to diagnose the occurrence of reflecting surfaces for zonal wavenumber 1 this study suggests that there is one characteristic configuration of the stratospheric jet that reflects waves back into the troposphere when the polar night jet peaks in the high latitude midstratosphere this configuration is related to the formation of a reflecting surface for vertical propagation

the 17 july 1999 block and ash flow baf at colima volcano new insights on volcanic granular flows from textural analysis abstract on july 17 1999 a strong explosion occurred at colima volcano mexico that produced a 10 km high eruptive column the partial column collapse originated a block and ash flow baf that flowed to the south along the san antonio and montegrande ravines travelling 3 3 km from the volcano summit the flow filled the ravines with a volume estimated at 7 9 105 m3 the erosion of these deposits occurred between 1999 and 2002 time of sampling providing excellent longitudinal outcrops that allowed their detailed textural study the study was carried out by means of quantitative textural analysis 1 rosiwal intersections for carrying out vertical granulometric profiles 2 total grain size analysis from 11 to 9 and 3 fourier and fractal analysis of the particle morphology grain size and morphometric parameters obtained with these methods were used to identify vertical and longitudinal variation patterns in the baf deposit the grain size variations allowed to infer the main particle segregation mechanisms that acted during transport and deposition of the studied bafs the two methods used for studying the particle shape morphologies yielded results with different accuracy and reliability in particular fractal analyses have been found to be the most effective in describing the particle support mechanisms that acted during transport and deposition of the studied bafs the results highlight the importance of the information obtained by means of these techniques and provide new insights in transportation and deposition mechanisms of bafs

eifel maars quantitative shape characterization of juvenile ash particles eifel volcanic field germany abstract the eifel region in western central germany is the type locality for maar volcanism which is classically interpreted to be the result of explosive eruptions due to shallow interaction between magma and external water i e phreatomagmatic eruptions sedimentary structures deposit features and particle morphology found in many maar deposits of the west eifel volcanic field wevf in contrast to deposits in the east eifel volcanic field eevf lack the diagnostic criteria of typical phreatomagmatic deposits the aim of this study was to determine quantitatively the shape of wevf and eevf maar ash particles in order to infer the governing eruption style in eifel maar volcanoes the quantitative shape characterization was done by analyzing fractal dimensions of particle contours 125 250 m sieve fraction obtained from scanning electron microscopy sem and sem micro computed tomography sem micro ct images the fractal analysis dilation method and the fractal spectrum technique confirmed that the wevf and eevf maar particles have contrasting multifractal shapes whereas the low small scale dimensions of eevf particles eppelsberg green unit coincide with previously published values for phreatomagmatic particles the wevf particles meerfelder maar pulvermaar and ulmener maar have larger values indicating more complex small scale features which are characteristic for magmatic particles these quantitative results are strengthening the qualitative microscopic observations that the studied wevf maar eruptions are rather dominated by magmatic processes the different eruption styles in the two volcanic fields can be explained by the different geological and hydrological settings found in both regions and the different chemical compositions of the magmas

magma water interactions in subaqueous and emergent basaltic in the subaqueous growth and emergence of a basaltic volcano clasts are formed by one or a combination of 1 explosive release of magmatic volatiles 2 explosive expansion and collapse of steam formed at magma water contact surfaces 3 explosive expansion of steam following enclosure of water in magma or entrapment of water close to magma and 4 cooling contraction these processes named respectivelymagmatic explosivity contact surface steam explosivity bulk interaction steam explosivity andcooling contraction granulation can be enhanced by mutual interaction and feedback the first three explosive processes are limited at certain water depths hydrostatic pressures and become increasingly vigorous at shallower levels the depth of onset of magmatic explosivity depends largely on juvenile volatile content it is up to 200 m for tholeiitic magmas and up to 1 km for alkalic magmas at the depth where formation of clastic deposits becomes predominant over effusion of lavas magmatic explosivity is subordinate to steam explosivity as a clast forming process the upward transition to accumulation of dominantly clastic deposits is not simply related to the onset of substantial exsolution of magmatic volatiles and can occur without it contact surface explosivity commonly requires initiation by a vigorous impact between magma and water and although no certain depth limit is known likelihood of such explosivity decreases rapidly with depth clast generation by bulk interaction explosivity appears to be restricted to depths much shallower than that of the critical pressure of water which in sea water is at about 3 km cooling contraction granulation can occur in any depth of water but at shallow levels may be replaced by contact surface explosivity during continuous eruption under water tephra can be ejected and deposited within a cupola of steam such that rapid quenching does not occur emergent volcanoes are characterized by distinctive steam explosive activity that results primarily from a bulk interaction between rapidly ascending magma and a highly mobile slurry of clastic material water and steam the water gets into the vent by flooding across or through the top of the tephra pile and violent explosions cease when this access is sealed the eruptions during emergence of surtsey and capelinhos typify the distinctive explosive activity the style and controls of which are different from those of maar volcanoes

textural variation in juvenile pyroclasts from an emergent surtseyan type volcanic eruption the capelas tuff cone sao miguel azores abstract here i present textural data i e vesicularity vesicle size distributions vsd plagioclase crystallinity crystal size distributions csd combined with fractal analyses of particle outlines from a natural succession of alternating fall and surge deposits in the emergent capelas tuff cone azores the textural variation in the capelas succession is surprisingly small considering the wide variety of fragmentation processes vent activity and emplacement mechanisms that are characteristic of emergent eruptions the plagioclase crystal content varies between 24 and 33 vol csd analyses of plagioclase show near linear trends with a slight increase in time for the smallest crystal sizes with surge deposits having more groundmass plagioclase when compared with fall deposits this is consistent with crystallization induced by degassing and decompression at lower eruption rates the vesicularities of the capelas pyroclasts are more variable 18 to 59 vol with vsds displaying kinked trends characteristic of coalescence this is especially evident in the fall deposits and consistent with being formed in continuous uprush jetting with an overall shallow fragmentation level within the conduit bubble coalescence can also be identified in the surge deposits although to a much lesser extent the amount of bubble coalescence is negatively correlated with the amount of groundmass crystallization i e plagioclase in the capelas deposits a relatively broad range of fractal dimensions with average dbox 1 744 and 0 032 for the outlines of pyroclastic fragments emplaced by fall or as surges indicate that there is little difference in the fragmentation process itself at capelas in addition to this the fact that the fractal dimensions for both the fall and surge end members completely overlap suggests that shape modification due to abrasion and chipping of grain edges was minor during emplacement of base surges these results are consistent with emergent eruptions building tuff cones to be a relatively low energy phreatomagmatic landform e g at least when compared with more energetic phreatomagmatic eruptions producing tuff rings and maar volcanoes

a comparison of fourier and fractal techniques in the analysis of closed forms abstract forty one samples of quartz sand grains derived from four different sources are analyzed using fourier grain shape and multi component fractal techniques the results from the two techniques are sufficiently similar to demonstrate clearly the potential usefulness of the fractal based technique in the analysis of sedimentary particles additionally the fact that the fractal technique is shown to extract information from shapes suitable for analysis via a radius expansion method lends credence to the expectation that it will yield comparable information when applied to more complex shapes not amenable to the radius expansion fourier technique

the evolution of the samaoding paleolandslide river blocking event at the upstream reaches of the jinsha river tibetan plateau abstract a large number of landslides have occurred in the upstream reaches of the jinsha river tibetan plateau due to the intensity of tectonic movement in the area remote sensing and field investigation indicate that one of them the samaoding paleolandslide previously blocked the river various river blocking phenomena are well preserved including the old landslide dam and deposits fluvial sediments and hydrostatic sandy sediment to better understand the evolution of the samaoding landslide the authors carried out thermoluminescence tl dating and numerical simulations the tl analysis shows that the landslide occurred at 10 6 0 5 ka bp discrete element method dem simulation of the landslide based on landform restoration provided results that are consistent with field observations the simulation indicates that the entire landslide process lasted for 80 s and the sliding mass reached a maximum velocity of 64 m s the landslide formed a landslide dam with a length of 1900 m a width of 600 m and a depth of 200 m the simulation results show that the level of the riverbed at that the time of the landslide was at least 25 m higher than it is today on the combined basis of the simulation results and field observations the authors propose explanation that the following valley evolution sequence occurred after river blocking the landslide dam experienced flood overtopping and then was eroded until it had mostly had been transported away by river flow and the river then rapidly incised the bedrock to form the present day landform based on the field investigations the authors summarize the failure mechanism of steep inclined antidip rockslides and found that tectonics play an important role in the formation of landslide dams or trigger of landslides and the failure of landslide dams in an active tectonic environment of tibetan plateau

volcanic ash generation effects of componentry particle size and conduit geometry on size reduction processes abstract grain size distributions gsd of pyroclastic materials are the product of processes ranging from primary fragmentation efficiency to tephra transport as such a detailed description of their physical and chemical state can provide pivotal information regarding such processes by constraining the gsd of volcanic deposits one can thereby deliver powerful constraints on the energetics and dynamics of eruptions in order to do so we must distinguish between two primary controls 1 fragmentation of magma to tephra and 2 secondary transport related processes such as abrasion and comminution within the conduit and until deposition of the particles variations in particle interactions in the conduit together with conduit geometry may be major factors in modifying the gsd as in all physicochemical processes for eruptive dynamics an experimental basis is an essential element of calibration and quantification here we have conducted the first experimental investigation linking fragmentation and ash production via the influence of 1 particle componentry and particle size and 2 the conduit geometry constricted versus unconstricted on the gsd rapid decompression experiments with loose tephra material from the fall deposit of pomici principali eruption 10 3 ka campi flegrei have been conducted in an optically transparent setup that enables the optical monitoring of particle dynamics with a high speed camera the samples employed can be classified into two main groups 1 pumices and 2 dense clasts including crystals lava clasts and wall rock fragments our results indicate that 1 a conduit diameter constriction simulating obstacles in the conduit walls is likely to reduce the average diameter of individual clasts and increase the generation of ash

quantifying the effect of rheology on lava flow margins using fractal geometry this study aims at quantifying the effect of rheology on plan view shapes of lava flows using fractal geometry plan view shapes of lava flows are important because they reflect the processes governing flow emplacement and may provide insight into lava flow rheology and dynamics in our earlier investigation bruno et al 1992 we reported that flow margins of basalts are fractal having a characteristic shape regardless of scale we also found we could use fractal dimension d a parameter which quantifies flow margin convolution to distinguish between the two endmember types of basalts a a d 1 05 1 09 and pahoehoe d 1 13 1 23 in this work we confirm those earlier results for basalts based on a larger database and over a wider range of scale 0 125 m 2 4 km additionally we analyze ten silicic flows sio2 52 74 over a similar scale range 10 m 4 5 km we note that silicic flows tend to exhibit scale dependent or non fractal behavior we attribute this breakdown of fractal behavior at increased silica contents to the suppression of small scale features in the flow margin due to the higher viscosities and yield strengths of silicic flows these results suggest we can use the fractal properties of flow margins as a remote sensing tool to distinguish flow types our evaluation of the nonlinear aspects of flow dynamics indicates a tendency toward fractal behavior for basaltic lavas whose flow is controlled by internal fluid dynamic processes for silicic flows or basaltic flows whose flow is controlled by steep slopes our evaluation indicates non fractal behavior consistent with our observations

the 2000 yigong landslide tibetan plateau rockslide dammed lake and outburst flood review remote sensing analysis and process modelling abstract in april 2000 a large scale rock avalanche dammed the yigong zangpo river forming an extensive rockslide dammed lake the impoundment lasted for 62 days before a catastrophic breaching caused a massive outburst flood in the yarlung zangpo tibet and the dihang rivers india that travelled downstream to the main floodplain of the brahmaputra in northeastern india in response to discrepancies in the published literature on the event we present a review and re evaluation of the characteristics of the rock avalanche and associated landslide dammed lake we use digital topographical data srtm 3 and dynamic landslide modelling dan w and dan3d to determine the salient characteristics of the damming landslide and to characterise its behaviour our analysis indicates that the volume of the damming rockslide was ca 115 mm3 including 91 mm3 from the initial rockslope failure bulked during disaggregation to 109 mm3 and 6 mm3 from entrainment during its 10 1 km travel down zhamulong gully the debris travelled with an average velocity of 15 18 m s and resulted in a landslide dam on the yigong river with a minimum height of about 55 m using landsat 7 imagery obtained before during and after impoundment in conjunction with an srtm 3 dem we reproduced the filling of the lake we determine that the landslide dam formed an extensive reservoir with an impounded volume of 2 015 gm3 and a maximum possible lake level of 2264 m asl rounded to 2265 m asl our figures differ from those previously published but are believed to be well constrained verifiable estimates of the volumes of the 2000 yigong events the outburst occurred after an attempt by army personnel to manually dig a spillway over the landslide debris and resulted in the entire volume of the lake draining in about 12 h the outburst flood travelled over 500 km south into india with a recorded rise in river level of 5 5 m at the pasighat gauging station 462 km downstream in terms of historical outburst volumes from rockslide dammed lakes the volume of the 2000 yigong event is only exceeded by that of the 1841 outburst flood from the indus river rockslide dammed lake northern pakistan

age and extent of a giant glacial dammed lake at yarlung tsangpo gorge in the tibetan plateau many glacier dams on major rivers at the southeastern edge of the tibetan plateau had been previously determined through remote sensing and glacier terminal position calculation it was hypothesized that such damming substantially impeded river incision into the plateau interior investigation on the large glacial dammed lake at the entrance of tsangpo gorge is critical for understanding this hypothesis so far the issues such as age lake surface elevation and stages of this dammed lake are still in debate our field survey of lacustrine deposits and loess distribution along the middle yarlung tsangpo river and its tributary nyang river suggested that the lake surface elevation was at about 3180 m asl the 23 quartz optically stimulated luminescence osl and 4 organic ams 14 c ages all fall into the last glacial period 41 13 ka the osl and 14 c ages are in general agreement with each other where applicable there might be only one long damming event because the ages of lacustrine deposits from 2970 to 3100 m asl are similar and every lacustrine section is sustained for a long time the estimated lake surface area was 1089 km 2 and the volume was 170 km 3 which differ from previous estimations which suggested two stage about early holocene and 1 5 ka lakes and the largest lake surface elevation reached 3500 m

application of fractal fragmentation theory to natural pyroclastic deposits insights into volcanic explosivity of the valentano scoria cone italy abstract the extent of fragmentation triggered by basaltic volcanic eruptions has been studied by analyzing the grain size distribution of natural pyroclastic deposits and applying the fractal fragmentation theory for this purpose 75 samples have been collected from individual layers along horizontal section of the well exposed valentano scoria cone italy the cone is constituted by well defined layers of fall deposits of up to 180 cm in thickness an important feature of the stratigraphic sequence is the occurrence of several intercalated layers called breccias with clasts of different characteristics angular shape low porosity and high crystallinity in respect to the normal layers results indicate that all achieved grain size distributions show fractal behavior and can be clearly correlated with a single fragmentation event namely the magmatic fragmentation during the eruption the fractal dimension of fragmentation d increases as fragmentation efficiency increases values of d are found to vary significantly along the pyroclastic sequence defining two major trends 1 a general long range increase of d during the course of the eruption and 2 a superimposed high frequency oscillating variation of fragmentation efficiency noteworthy is the fact that the highest values of d are measured for pyroclastic deposits following breccia deposits application of a conceptual model of fractal fragmentation as claimed by natural data indicates that larger values of d have to be associated with a higher probability of fragmentation thus suggesting that the d value can be used as a proxy for the fragility i e ability to fragment of samples fractal dimension of fragmentation of single layers is positively correlated with the vesicularity of clasts this indicates that the bubble content in the ascending magma prior to and at fragmentation likely was the key factor modulating the variable fragmentation efficiency observed in the studied pyroclastic sequence we hypothesize that the long range variation of d may be associated with magma fragmentation triggered by expansion of gas bubbles progressively coalescing below solid plugs during later stages of eruptive activity whereas high frequency variations of d are interpreted as due to magma fragmentation during the slug flow regime characterizing the strombolian activity of the scoria cone

fractal analysis applied to characteristic segments of the san andreas fault fractal theory is applied in a quantitative analysis of the san andreas fault saf geometry the method which directly measures the increase in total fault length with a decrease in ruler size gives the fractal dimension d and scaling properties for the chosen length band 0 5 1000 km a physical interpretation of d is that it measures the irregularity of the fault trace in the selected band the fault is subdivided into six segments of distinctive seismic behavior a main fault trace which shows either maximum coseismic slip or creeping was selected for analysis with three alternative branches examined for the saf system south of san bernardino branches of the fault trace are not considered in this work fractal dimensions calculated for the different segments range from 1 0008 to 1 0191 and are different from 1 0 to the 95 confidence interval these small changes reflect the overall smoothness of the main fault trace significant variations in d among segments indicate heterogeneities in the fault smoothness along strike d also changes significantly from the short length band to the long length band where the demarcation point ranges from 1 to 2 km the short length band has larger d values a slight correlation is obtained between the fractal dimension of the main trace and the extent of subparallel faulting this indicates some correspondence between the main fault trace irregularity and the complexity of subsidiary fault traces in plan view

optical dating of landslide dammed lake deposits in the upper yellow river qinghai tibetan plateau china abstract two large landslides dehenglong and suozi blocked the upper yellow river from longyang gorge to liujia gorge on the qinghai tibetan plateau this research is significant because no relevant chronologies for this landslide dammed lake had been reported twelve osl samples were collected from the lacustrine sediments of the landslide dammed lake deposited on both banks of the upper yellow river samples yielded similar ages of ca 80 ka the dehenglong landslide and suozi landslide are thus inferred to be triggered by ca 80 ka tectonic movements

the role of linear interference in the annular mode response to extratropical surface forcing abstract the classical problem of predicting the atmospheric circulation response to extratropical surface forcing is revisited in the context of the observed connection between autumnal snow cover anomalies over siberia and wintertime anomalies of the northern annular mode nam previous work has shown that in general circulation model gcm simulations in which autumnal siberian snow forcing is prescribed a vertically propagating rossby wave train is generated that propagates into the stratosphere drives dynamical stratospheric warming and induces a negative nam response that couples to the troposphere important questions remain regarding the dynamics of the response to this surface cooling it is shown that previously unexplained aspects of the evolution of the response in a comprehensive gcm can be explained by examining the time evolution of the phasing and hence the linear interference between the rossby wave response and the background climatological stationary wave when the wave response a

image processing analysis in reconstructing fragmentation and transportation mechanisms of pyroclastic deposits the case of monte pilato rocche rosse eruptions lipari aeolian islands italy abstract a quantitative study of particle morphology of samples from monte pilato rocche rosse deposits lipari aeolian islands italy shows a significant variability in particle structure and texture the study consisted of image processing techniques and multivariate statistical methods in analysis of the quantitative particle morphology data with the goal of identifying the genetic processes responsible for the formation of the deposits from these investigations we numerically define the form of the clasts thus avoiding subjectivity in the classification of clast morphology starting from this clast definition we then construct diagrams in which clasts due to different genetic processes i e magmatic vs hydromagmatic fragmentation are discriminated based on simple nondimensional parameters the application of the methods used seems to be of general interest in discriminating the fragmentation and transportation dynamics responsible for the formation of pyroclastic deposits