climatology and dynamics of the link between dry intrusions and cold fronts during winter part i global climatology cold fronts are a primary feature of the day to day variability of weather in the midlatitudes and feature in conceptual extratropical cyclone models alongside the dry intrusion airstream here the climatological frequency and spatial distribution of the co occurrence of these two features are quantified and the differences in cold front characteristics intensity size and precipitation when a dry intrusion is present or not are calculated fronts are objectively identified in the ecmwf era interim dataset for the winter seasons in each hemisphere and split into three sub types central fronts within a cyclone area trailing fronts outwith the cyclone area but connected to a central front and isolated fronts not connected to a cyclone these are then associated with dry intrusions identified using lagrangian trajectory analysis trailing fronts are most likely to be associated with a di in both hemispheres and this occurs more frequently in the western parts of the major storm track regions isolated fronts are linked to dis more frequently on the eastern ends of the storm tracks and in the subtropics all front types when co occurring with a di are stronger in terms of their temperature gradient are much larger in area and typically have higher average precipitation therefore climatologically the link with dis increases the impact of cold fronts there are some differences in the statistics of the precipitation for trailing and isolated fronts that are further investigated in part ii of this study from the front centred perspective

climatological characteristics of fronts in the western north pacific based on surface weather charts composite front climatology in the western north pacific is determined using a newly developed 1 0 gridded data set here we propose a research strategy for determining the spatiotemporal distribution of fronts using weather chart images published by the japan meteorological agency one of the major data providers in the region a preliminarily investigation of the internal data characteristics for the period of 2000 2010 is undertaken and the final 4 years of data are used for an analysis of front climatology to avoid the effect of any spurious trends this enables in depth analyses to be conducted which have not previously been possible in the region including the composites of cross sectional patterns for the thermal fields and precipitation near fronts front length seasonality and the significance of the thermal gradient near the fronts in addition to determining the frontal frequency and spatial distribution of frontal precipitation pixel wise analysis reveals that 56 of the local precipitation maximum is located on the warm side of a cold front caused by less tilted upward motion on the warm side with the intrusion of the upper level cold dry air into the warm side this new data set also enables a further analysis of the occluded fronts which are not correctly distinguished in the existing objective detection method

the dead sea transform fault system abstract a new map showing the major features of the dead sea transform fault system based on seismicity satellite imagery geological maps and bathymetric charts is presented special attention is given to the possible northward continuation of the transform system beneath the mediterranean sea near ed damur south of beirut the map shows the dead sea transform system to be a series of offset overlapping left lateral transform faults with a rhombochasm between each pair the system has similarities with the equatorial fracture zones in the atlantic ocean throughout the dead sea transform system is considered in its regional setting i e as extending from the red sea spreading centre in the south to the eurasian collision zone in the north it is suggested that it may intersect the latter somewhere east of cyprus making that area the northernmost termination of the dead sea transform system

dike deflection modelling for inferring magma pressure and withdrawal with application to etna 2001 case abstract we studied the stress effects of the topography load on dike propagation by considering the results from analogue experiments in addition we refined the results by applying numerical simulations using the finite element method fem in order to also consider the medium rheology and real topography we investigated the dike deflection observed during the final dike emplacement accompanying etna s 2001 eruption we cross related the information on the position of the dike from ground deformation modelling with the numerical simulation results with the aim of estimating the final excess pressure of the dike when it started to deflect which proved to be about 4 8 mpa assuming that the pressure decreases linearly with the volume of magma moving from the chamber into the dike we estimated 7 15 mpa as the initial overpressure accumulated at the intermediate magma chamber before its breakout although the previous modelling overestimated the stress the approach presented here leads to infer a compatible stress with the strength of the rocks

beyond cold and warm an objective classification for maritime midlatitude fronts this study introduces a detailed and objective classification for mid latitude maritime fronts the classification is based on a principal component analysis pca to determine the dominant patterns of variability between fronts here fronts are defined as three dimensional frontal volumes which are detected in the era interim data set for a large number of locations in the atlantic pacific and indian oceans during both winter and summer in addition to the well established distinction between warm and cold fronts the pca exposes several new dimensions of variability a front intensity b surface fluxes and c along front transports linked to the intensity of the associated conveyor belts these new dimensions of variability are regionally and seasonally robust and a lagged composite analysis demonstrates that each of the new front types evolves in a dynamically characteristic way further the new front types can be related to established ones like katafronts and anafronts the new front types are finally redefined based on simple parameter thresholds to simplify their application in future studies

a global climatology of atmospheric fronts 1 atmospheric fronts in the lower troposphere often mark regions of significant weather and serve as an important conceptual tool that is frequently used and well understood by the public this study uses an objective method to identify fronts in the era 40 reanalysis and to compile a quantitative global climatology of their occurrence the climatology confirms the mid latitude storm tracks as the regions of highest front frequency and identifies slow moving frontal boundaries in the subtropics corresponding to major climate features such as the mei yu front the climatology also shows fronts to be common features of the south pacific convergence zone in the northern hemisphere fronts shift poleward in summer in the southern hemisphere this and other aspects of seasonal behavior are rather different

late cenozoic tectonics and volcanism in the northwestern corner of the arabian plate a consequence of the strike slip dead sea fault zone and the lateral escape of anatolia abstract the study area is the northwestern corner of the arabian plate near the triple junction of anatolian arabia and africa late cenozoic tectonics and volcanism have developed essentially east of the dead sea fault zone dsfz the strike slip boundary of the arabian and african plates including vents situated in front of the bitlis collisional belt isotopic and rare elements data indicate deep mantle sources for volcanism our mapping based on radar imagery and digital elevation models suggests that elongate volcanoes volcanic ridges and linear clusters of adjacent volcanic vents are rooted on tension fractures which are a kilometer or several kilometers in length and infers similar development in depth we have also observed non volcanic tension fractures we have been able to map the northern segment of the dsfz as a continuous but broken fault line the ghab pull apart basin connects with appended faults including the choukhour fault that ends northward in a tail crack feature and the aafrine fault that ends in a tail thrust the amik pull apart basin is bounded in the west by a small but distinct scarp shown by radar imagery our image analysis and field data suggest that the left lateral amanos fault has a reverse throw component in consequence the amanos range has to be regarded as an anticline and the karasu valley as a syncline in the southern part of the study area the regional stress field is mainly strike slip with n020 striking tension fractures east of the amanos fault it becomes transpressive with n120 to n140 striking tension fractures in the north near the triple junction albeit compressional faults and belt environment predominate it is influenced by e w lowering horizontal stress component triggered by the lateral escape of anatolia and remains of the strike slip type associated with n020 striking tension fractures more east of the dsfz in front of the bitlis belt isolated volcanoes e g karacadag elongated n160 show in the rigid arabian crust local weak lines that can be influenced at a distance by the lowering horizontal stress component

the geochemical evolution of clinopyroxene in the roman province a window on decarbonation from wall rocks to magma abstract we present results from magma carbonate interaction experiments designed to shed light on the geochemical evolution of clinopyroxene in the roman province central italy atmospheric pressure experiments were performed at 1140 1160 and 1180 c under nno mh and air oxygen buffering conditions the starting materials were a shoshonite and a phonotephrite doped with different amounts of cao and cao mgo whose stoichiometric proportions reproduced the assimilation by magmas of calcite and dolomite respectively the results show that clinopyroxenes spinels and residual glasses are ubiquitous phases in all run products calcite doped runs crystallize more clinopyroxene than dolomite doped runs at the same conditions this leads to the formation of strong desilicated cao rich melts showing compositions comparable to those of magmatic skarns during magma carbonate interaction the content of fe3 in clinopyroxene increases with increasing fo2 promoting the substitution of al for si in tetrahedral site local charge imbalances are also compensated by the incorporation of highly charged cations such as ti into the crystal lattice according to this cation substitution al ca fe3 ti rich clinopyroxenes of the skarn environment testify to continuous co2 fluxes produced by the thermal decomposition of carbonate wall rocks nevertheless the oxidative capacity of co2 progressively decreases from the skarn shells towards the interior of the magma chamber driving the crystallization of si fe2 mg rich clinopyroxenes

influence of calcite decarbonation on the frictional behavior of carbonate bearing gouge implications for the instability of volcanic flanks and fault slip abstract the impact of heat readily provided by magma circulating hot fluids or rapid fault slip on carbonate substrata is an important factor in determining the flank stability of volcanoes and the mechanical behavior of faults in areas where carbonate lithologies are prevalent the mineralogy and mechanical properties of carbonate rocks are demonstrably altered by thermally induced decarbonation while previous studies have considered the role of decarbonation in bulk strength loss at subvolcanic conditions and dynamic weakening during coseismic fault slip little is known about the effects of decarbonation on the frictional properties of carbonate rocks during both the nucleation and inter seismic phases here we present results from experiments performed on a portlandite rich material a typical hydrous product of the decarbonation reaction to evaluate frictional strength stability and healing at shallow crustal conditions we sheared gouge layers of this material under saturated conditions at room temperature and at velocities comparable to those involved in earthquake nucleation our data indicate that the reaction of calcite to portlandite results in a distinct change in the mechanical behavior of the gouge decarbonated shear zones are 1 frictionally weaker at higher normal stresses 2 more frictionally unstable and 3 likely to regain their frictional strength more quickly than unaltered calcite rich zones the occurrence of portlandite could be key for interpreting the stability of volcanic flanks that root into carbonate substrata and for seismogenic normal faults located within thick sedimentary sequences and thus provide a better understanding of the hazards they pose

volcanic edifice weakening via decarbonation a self limiting process 1 the inherent instability of volcanic edifices and their resultant propensity for catastrophic collapse is a constant source of volcanic risk structural instability of volcanic edifices may be amplified by the presence of carbonate rocks in the sub volcanic strata due to the debilitating response of carbonates to thermally induced alteration nonetheless decarbonation reactions the primary weakening mechanism may stall when the system becomes buffered by rising levels of a reaction product carbon dioxide such thermodynamic stalling might be inferred to serve to circumvent the weakness of volcanic structures however the present study shows that even when decarbonation is halted rock physical properties continue to degrade due to thermal microcracking furthermore as a result the pathways for the escape of carbon dioxide are numerous within a volcanic edifice therefore in the case of an edifice with a sub volcanic sedimentary basement the generation of carbon dioxide via decarbonation is unlikely to hinder its impact on instability and thus potentially devastating flank collapse

catastrophic collapse at stratovolcanoes induced by gradual volcano spreading unlike ordinary mountains which are formed by slow uplift and erosion volcanoes are constructed rapidly as a consequence many are liable to massive flank failures leading to debris avalanches for example at mount st helens in 1980 such failures occur worldwide about once every 25 years ref 1 and even small ones can present a major hazard in particular if far reaching tsunamis are generated as at mayu yama in 1792 ref 2 previous work has tended to emphasize differences in eruption style associated with flank failure2 but here we focus on the fundamental structural causes of failure most volcanic failures are generated by magmatic intrusion and flank spreading3 we present evidence however that mombacho volcano in nicaragua experienced a previously unrecognized type of failure triggered by sub volcanic basement spreading notably collapses related to basement spreading do not require that the volcano be magma tically active and thus flank failure may pose a significant risk even at inactive volcanoes which are rarely monitored

coherent synoptic disturbances in the australian monsoon abstractcoherent synoptic scale weather systems within the australian monsoon are identified and tracked in the isentropic potential vorticity pv field from the ecmwf interim reanalysis era interim dataset during the southern hemisphere summer the resulting dataset is then used to compile statistics and synoptic composites of australian monsoon disturbances on average a synoptic system is found in the region every 2 5 days however the time interval between consecutive events is highly variable meaning that the synoptic activity in the australian monsoon is not well represented by commonly employed spectral techniques the analysis reveals that most synoptic systems originate within the australian monsoon but at the 315 k level approximately 700 hpa a significant proportion of systems are first detected near the east coast of the continent where extratropical rossby waves are observed to frequently break the average australian monsoon weather system propagates from east to west at approximatel

carbonate assimilation at merapi volcano java indonesia insights from crystal isotope stratigraphy recent basaltic andesite lavas from merapi volcano contain abundant complexly zoned plagioclase phenocrysts analysed here for their petrographic textures major element composition and sr isotope composition anorthite an content in individual crystals can vary by as much as 55 mol an

3 d modeling of geologic maps from surface data recent discoveries in earth sciences are mostly related to technologies allowing graphical representations of volumes we present a way to produce mathematically and geometrically correct three dimensional 3 d geologic maps consisting of the volume and shape of all geologic features of a given area the method is innovative in that it only uses surface information based on the combination of a standard geologic map a satellite image and a digital elevation model it is based on a modeling algorithm that only uses surfaces calculated from scattered data points and that intersects them following a series of geologically sound rules the major advantage of using such technology is that it provides the user with a way to quantify geology to illustrate how a 3 d geologic map can be computed we explain the steps taken to build a dummy model with simple faulting and depositional sequencing the case study chosen to illustrate the method is the beirut watershed lebanon an area with relatively simple geology the 3 d visualization and cross sections help in the understanding of the geometrical relationship between the different geologic features allowing a reexamination of the tectonic history of the area during the late mesozoic

passive infrared remote sensing evidence for large intermittent co2 emissions at popocatepetl volcano mexico abstract passive infrared ftir and correlation spectrometer cospec measurements were conducted at popocatepetl volcano during february 10 to 26 1998 from sites 4 to 17 km distant from the summit volcano behavior was relatively quiet and so 2 flux averaged 1670 1420 t day 51 measurements relatively small for popocatepetl concurrent hcl so 2 and hf so 2 ratios were 0 17 0 01 and 0 031 0 003 respectively about the same as ratios measured from 1994 to 1997 the amount of co 2 in the volcanic plume was quantified using fascode in which atmospheric co 2 is numerically subtracted from the total infrared spectrum to obtain the residual magmatic co 2 surprisingly co 2 so 2 mass ratios rose dramatically to values as high as 140 about 30 times higher than typical values of 2 to 8 measured from 1994 to 1996 these excursions in high co 2 so 2 ratios were short lived lasting no longer than about 0 5 to 3 0 h but co 2 flux occasionally exceeded 100 000 t day we estimate that the average co 2 so 2 ratio for the period was about 23 yielding an average co 2 flux of roughly 38 000 t day chemical and petrographic analyses of lava and pumice erupted during explosions on june 30 1997 and january 1 1998 show conclusively that popocatepetl produces mixed products formed by injection of mafic magma into a more silicic chamber at temperatures and pressures of roughly 1040 c and 5 kbar in addition popocatepetl eruptive products include xenoliths of metamorphosed carbonate rocks containing wollastonite and other calc silicate minerals indicating reaction of magma with cretaceous limestone underlying the volcano using a normal co 2 so 2 ratio of 4 for reference we calculate an average excess co 2 production of 32 000 t day for 17 days this would require assimilation of only 5 10 4 km 3 of limestone an amount easily accessible in the 3 km thick cretaceous section beneath the volcano we also examine two scenarios in which excess co 2 is produced by degassing of subjacent basalt magma but these explanations seem less plausible to us because many other volcanoes are underlain by carbonate sequences short duration bursts of co 2 flux and increased co 2 so 2 ratio might be observed at other sites if simultaneous real time measurements of major gas species are made

low pressure experiments in piston cylinder apparatus calibration of newly designed 25mm furnace assemblies to p 150mpa abstract we present new pressure calibration experiments demonstrating that the piston cylinder apparatus is suitable for experiments at pressure as low as 150 mpa two newly designed 25 mm furnace assembly have been developed and calibrated using two different calibration methods the nacl melting curve and the solubility of h2o in albitic and rhyolitic melts the nacl calibration experiments performed in the pressure range 150 500 mpa yield the pressure correction that has to be applied to the nominal pressure in order to have the equivalent real pressure on the sample this correction varies as a function of the experimental pressure as follows p correction mpa 0 115 xp nominal mpa 78 23 the h2o solubility experiments in albitic and rhyolitic melts confirm the corrections determined using the nacl calibration method moreover because these experiments are performed at temperatures higher than those used for nacl calibration they demonstrate that the pressure correction is not affected by temperature in the range 800 1000 c the accuracy of the pressure estimate associated with the calibration methods is 25 mpa the major advantage of using the new assemblies is that low pressure experiments which require rapid heating and quenching rates e g volcanic and hydrothermal systems can be performed with the same ease and precision as standard high pressure experiments for which piston cylinder is routinely used

behaviour of granites and limestones subjected to slow and homogeneous temperature changes abstract we have studied the evolution of the texture in two granites and two limestones subjected to slow and uniform temperature change each granite has a different grain size and each limestone a different texture carrare crystalline limestone and crepey oolitic limestone temperature was varied from 200 c to 700 c scanning electron microscope observations of different rock samples show that during thermal cycling intercrystalline boundaries in granites widen out progressively and porosity increases new microcracks appear in crystals between 500 c and 600 c in carrare crystalline limestone intercrystalline cracks appear at temperatures as low as 200 c due to its heterogeneous cracks appear at temperatures as low as 200 c due to its heterogeneous increasing temperature longitudinal wave velocity and intrinsic permeability show good correlation with the scanning electron microscope observations

transcurrent fault activity on the dead sea transform in lebanon and its implications for plate tectonics and seismic hazard fault activity within the lebanese transpression zone one of the classic examples of restraining bend development on a continental transform is here investigated using dated geomorphological features the northern part of the yammouneh fault commonly considered to be the principal active strand on this part of the dead sea transform has been inactive for the past 5 ma field observations show that basalts dated as late pliocene hi age apparently offset by the yammouneh fault unconformably overlie it the active transcurrent structure is principally perhaps exclusively the roum fault the lebanese transpressive zone has evolved through tune with migration of fault activity these results confirm the overlapping transform hypothesis for the dead sea system require the active triple junction between the transform and the tethyan collision belt to lie offshore se cyprus and have profound implications for assessing seismic hazard hi the levant

structural architecture of the colima volcanic complex 1 the colima volcanic complex cvc is currently the most active mexican volcano and is located in the western sector of the trans mexican volcanic belt inside the active colima rift a regional n s striking extensional structure the colima rift is filled by a 1 km thick sequence of quaternary lacustrine sediments alluvium and colluvium mostly underling the about 3000 m thick volcanic pile of the cvc in this work we present the results of a detailed morphostructural and field study of quaternary faults and fractures in the cvc and the surrounding area including the regional structures of the colima rift we also present a geometrical modeling of the faults inside the volcano and a numerical model of the gravity induced stress and strain fields of the cvc the study attempts to characterize the geometry kinematics and dynamics of the deformation features of the cvc and relate it with the volcano structure the geology of the substratum and the geodynamic setting of the region our model considers that the observed deformation of the cvc and the surroundings results from the interplay between the active n s trending regional extensional tectonics and the southward spreading of the volcano over its basement forming an e w oriented volcanotectonic graben the interaction between regional tectonics and previously unrecognized volcanic spreading can control magma migration and flank instability in an area where eruptions and sector failures represent a potential high risk for more than 500 000 people

detecting major terrain parameters relating to mass movements occurrence using gis remote sensing and statistical correlations case study lebanon abstract among the various natural hazards mass movements mm are probably the most damaging to the natural and human environment in mediterranean countries including lebanon which represents a good case study this research deals with how to use geographic information systems gis for establishing the relationships between mm occurrence and different factor terrain parameters over a representative region of lebanon parameters expressed by 1 ancillary data like lithology proximity to fault zone soil type land cover use distance to drainage line and rainfall quantity and 2 derived data like slope gradient and slope aspect were correlated with mm using gis approaches the mm were first detected through visual interpretation of two stereo pairs of spot 4 images anaglyph at 10 m resolution this study indicates depending on bivariate remote sensing and gis statistical correlations kendall tau b correlation that the lithology is the most influencing factor on mm occurrence it also shows that statistical correlations to mass movements exist best between factors at the following decreasing order of importance lithology proximity to fault line lithology soil type and lithology distance to drainage line at 1 level of significance and soil land cover use slope aspect land cover use and soil slope gradient at 5 level of significance these correlations were verified and checked through field observations and explained using univariate statistical correlations therefore they could be extrapolated to other mediterranean countries having similar geoenvironmental conditions

damage and recovery of calcite rocks deformed in the cataclastic regime compressional and shear wave velocities have been measured during the experimental deformation of carrara marble and solnhofen limestone in the cataclastic regime both in dry and wet conditions at room temperature measurements were performed under hydrostatic conditions up to 260 mpa confining pressure and 10 mpa pore pressure during triaxial loading at the constant strain rate of 10 s as well as during differential stress relaxation during a full cycle our results show that the seismic velocities first increase as effective mean stress increases however when the stress onset of cataclastic deformation was reached elastic velocities showed rapid decrease due to stress induced damage in the rock during stress relaxation tests we observed an increase of elastic velocities with time which suggested a fast recovery of the microstructure a substantial and rapid drop in the velocities occurred when reloading suggesting that the previous recovery was only transient subsequent relaxation tests showed other marked increases in velocities these experimental results suggest that during the deformation of low porosity calcite rich rocks dilatant crack opening and frictional sliding and compaction micromechanism pore closure compete evolutions of elastic properties mainly sensitive to crack density and macroscopic volumetric strain more sensitive to porosity are therefore not systematically correlated and depend on the strain rate the solid stress conditions and the

ductile flow in sub volcanic carbonate basement as the main control for edifice stability new experimental insights abstract limestone in volcanic basements has been identified as a hazard in terms of edifice stability due to the propensity of calcite to decompose into lime and co2 at high temperatures 600 c causing a decrease in mechanical strength to date such hypotheses have been tested by experiments performed at ambient pressure the present work determines the mechanical strength of limestone under sub volcanic conditions of pressure and temperature and evaluates the effect of calcite decomposition to this end we use mt etna as a case study deforming sub etnean carbonate samples under triaxial compression using a paterson deformation apparatus we evaluate the effect of thermal decomposition of calcite on sample strength by comparing closed and open systems and measuring the permeability evolution under static conditions mechanical and micro structural observations at a constant strain rate of 10 5 s 1 and at a confining pressure of 50 mpa indicate that the rocks are brittle up to and including 300 c at higher temperatures the deformation becomes macroscopically ductile i e deformation is distributed throughout the sample the brittle to ductile transition is accompanied by an irreversible permeability decrease from 10 17 to 10 19 m 2 between 200 and 600 c we present new evidence that permanent change in permeability is due to ductile processes closing the initial pore space samples deformed at temperatures up to 900 c do not contain any decarbonation products at these temperatures permeability is sufficiently low to permit co2 pore pressures to increase thereby increasing local co2 fugacity which in turn strongly limits the decarbonation reaction we note that for non pure calcite rocks permeability might be sufficient to allow decarbonation reactions to occur as such variability in lithologies may slightly influence the efficiency of decarbonation reactions we conclude that in a closed system the instability of mt etna is related to high temperature induced ductile flow of basement limestone rather than chemical mineralogical changes this may have important implication for the stability of volcanoes within carbonate rich basement as carbonates become significantly weak at high temperatures which may increase the risk of sector collapse

an approach using sar ers images to relate extension fractures to volcanic vents examples from iceland and madagascar abstract a new approach to the study of geometric relationships between tectonic structures and volcanic vents is presented it is based on the mapping of tectonic and volcanic features using high resolution imagery including synthetic aperture radar sar images of the european remote sensing satellite number one ers 1 we have evidenced new faults 1 n striking normal faults in the husavik fault zone of the north atlantic ridge and 2 nw striking faults belonging to the husavik transform fault zone associated to drag folds which testify to a dextral strike slip movement component we show that most of the volcanic edifices are located on extension fractures responsible for fissure eruptions volcanic linear clusters and elongated volcanoes this relationship is studied first in iceland where the geodynamics is well known using sar ers 1 imagery applied to the montagne d ambre in northern madagascar using aerial photographs this approach makes it possible to identify faults and the regional plio quaternary direction of extension i e n65 e to n85 e volcanoes forming linear clusters together with elongated volcanoes are interpreted to be located on extension fractures s or z shape of the linear clusters allowed us to determine the tips of extension fractures and consequently the orientation of the regional tension alignments of extension fractures depending on their s or z shape permitted us to infer conjugated faults

present day kinematics of the middle east and eastern mediterranean the middle east and eastern mediterranean regions contain three major strike slip fault zones the dead sea fault zone dsfz and the north and east anatolian fault zones nafz and eafz these accommodate northward motion of the african and arabian plates relative to eurasia and westward motion of the small turkish plate this study deduces an internally consistent solution for the present day kinematics of these plates which is accurate to better than 20 and applicable throughout time since 5 ma by constraining the slip senses and rates on these strike slip fault zones the 7 0 5 mm yr 1 left lateral slip rate on the dsfz is associated with counterclockwise rotation of arabia relative to africa at 0 33 m y 1 around an eulcr pole near 33 n 23 e the nafz takes up counterclockwise rotation of the turkish plate relative to eurasia at 0 83 m y 1 13 around a pole at 31 n 35 5 e with right lateral slip rate 15 mm yr 1 the resulting prediction for the eafz involves 14 mm yr 1 left lateral motion and 2 mm yr 1 of shortening between arabia and turkey the triple junction of africa arabia and turkey is near the city of kahramanmaras this locality contains a narrow promontory bounded by ssw trending left lateral faults at the edges of the arabian and turkish plates which is loosely attached to the african plate moving westward relative to its interior at 4 mm yr 1

a simple model for the synoptic analysis of cold fronts a split cold front model with an over running upper front or humidity front ahead of a surface front or humidity front is shown to provide a useful representation of the principal characteristics of many katafronts the use of such a model leads to more consistent analyses especially of cloud and rain than are achieved using unmodified classical concepts

tectonics of the pliocene homs basalts syria and implications for the dead sea fault zone activity timing of activity along the yammuneh segment lebanon syria of the dead sea fault zone and its northward continuation is still a subject of controversy our field structural analysis and observations on radar landsat and digital elevation model imagery of the homs region syria are of concern for plio quaternary tectonics of the whole northern part of the dead sea fault zone we show in this paper that the northern dead sea fault zone has remained active since the onset of the homs basalts at c 6 ma continuing movement in recent times is indicated by the occurrence of quaternary pull apart structures and offset of active ravines along the fault the homs basalts are related to the distinct oval shaped shin volcanic edifice of which the long axis trends nw the volcano was fed through nw striking tension fractures which now form dykes and volcanic ridges these patterns are consistent with a ne sw extension that occurred c 6 ma ago the northwestern end of the shin volcano is left laterally displaced c 20 km yielding a c 3 3 mm a 1 mean rate of relative movement between the arabian and african plates in the northern part of the dead sea fault zone the overall trace of the main active dead sea fault zone is not a single transform but forms an irregular plate boundary composed of transform fault and collision belt segments fine grained mylonite developed in the fault corridor may have favoured aseismic deformation in the shin volcano area

magma chambers emplaced in carbonate substrate petrogenesis of skarn and cumulate rocks and implications for co2 degassing in volcanic areas crystal rich lithic clasts occurring in volcanic deposits are key tools to understand processes of storage cooling and fractionation of magmas in pre eruptive volcanic systems these clasts represent snapshots of the magma chamber host rock interface before eruption and provide information on crystallization differentiation and degrees of interaction between magma and wall rock in this study we have focused on the petrology of clasts of cumulate and skarn rocks from the colli albani volcanic district with the aim of shedding light on magma carbonate interaction and co2 emission in volcanic areas by means of phase relations bulk rock chemistry mineral compositions and isotope data we have identified different types of cumulates and skarns cumulates containing either clinopyrox

strain accommodation at the lateral margin of an active transpressive zone geological and seismological evidence from the lebanese restraining bend geological geomorphological and seismological data are used to postulate the existence of a lateral domain bounding fault the roum fault zone in sw lebanon the fault zone accommodates transpression at the margins of the lebanese restraining bend abruptly dividing the transpressional mount lebanon jebel barouk uplift from the extension of the tyre nabatiye plateau transpressional deformation at the sw margin of the restraining bend is mainly seen through large scale folding trending parallel to the restraining bend such folding is thought to be accommodated laterally along a 100 km length of fault zone in sw lebanon the roum fault zone mapped lineaments and topographic expression show the fault zone to die out to the south of beirut offsets of incised river valleys decrease northwards from 7 2 km to 0 2 km along the length of the fault zone over a distance of 80 km also inferring a postulated fault tip to the south of beirut strain gradients along both sides of the fault zone wall rocks shows several deformation mechanisms to be involved pressure solution folding distributed shear and normal faulting the postulated fault tip coincides with the extent of transpression of the mount lebanon block a new seismicity catalogue 2100 bc ad 1995 32 35 n 34 37 e 1725 events all magnitudes converted to isn reported m l was compiled from published sources seismicity is apparently sparse around the northern yammouneh fault but concentrates in sw lebanon especially in a diffuse 50 100 km wide zone around the southern roum fault zone epicentral uncertainties are typically 10 25 km for modern reporting although depths are poorly known the seismic b value is 0 75 0 07 for the beirut area compared to 0 88 0 09 for the dead sea transform to the south mapping of b values for the sw lebanon area suggests a gradual reduction northward along the roum fault zone these observations are interpreted as the signature of a fault zone whose tip lies to the south of beirut the transition from transpression to extended crust at the western edge of the lebanese restraining bend is accommodated along a 100 km length of fault zone decreasing seismic activity over the time of the catalogue and seismic b values imply a differing style or mechanism of faulting in the short term along the roum fault zone toward beirut

climatological lower tropospheric frontogenesis in the midlatitudes due to horizontal deformation and divergence abstract the frontogenetic function given by petterssen is calculated for the four months january april july and october and the year as a whole using the climatological wind and temperature data for 85 and 70 kpa levels over the global band between 45 n and 45 s the well known frontogenetic regions of the northern hemisphere nh off the rockies and japan sea are reproduced satisfactorily four nw se inclined bands of frontogenesis are observed in the southern hemisphere sh the mid south pacific and the western south atlantic bands correspond respectively to the south pacific convergence zone spcz and the south atlantic convergence zone sacz which are observed in the outgoing longwave radiation olr charts the other two are located in the western indian ocean and west australia the frontogenetic function in the sacz region is strongest in southern summer in contrast to the nh case which is dominant in winter

limestone assimilation and the origin of co2 emissions at the alban hills central italy constraints from experimental petrology abstract the alban hills volcanic region 20 km south of rome in the roman province emitted a large volume of potassic magmas 280 km 3 during the quaternary chemical interactions between ascending magmas and the 7000 8000 m thick sedimentary carbonate basement are documented by abundant high temperature skarn xenoliths in the eruptive products and have been frequently corroborated by geochemical surveys in this paper we characterize the effect of carbonate assimilation on phase relationships at 200 mpa and 1150 1050 c by experimental petrology calcite and dolomite addition promotes the crystallization of ca rich pyroxene and mg rich olivine respectively and addition of both carbonates results in the desilication of the melt furthermore carbonate assimilation liberates a large quantity of co 2 rich fluid a comparison of experimental versus natural mineral glass and bulk rock compositions suggests large variations in the degree of carbonate assimilation for the different alban hills eruptions a maximum of 15 wt assimilation is suggested by some melt inclusion and clinopyroxene compositions however most of the natural data indicate assimilation of between 3 and 12 wt carbonate current high co 2 emissions in this area most likely indicate that such an assimilation process still occurs at depth we calculate that a magma intruding into the carbonate basement with a rate of 1 2 10 6 m 3 year estimated by geophysical studies and assimilating 3 12 wt of host rocks would release an amount of co 2 matching the current yearly emissions at the alban hills our results strongly suggest that current co 2 emissions in this region are the shallow manifestation of hot mafic magma intrusion in the carbonate hosted reservoir at 5 6 km depth with important consequences for the present day volcanic hazard evaluation in this densely populated and historical area

cooling dominated cracking in thermally stressed volcanic rocks most studies of thermally induced cracking in rocks have focused on the generation of cracks formed during heating and thermal expansion both the nature and the mechanism of crack formation during cooling are hypothesized to be different from those formed during heating we present in situ acoustic emission data recorded as a proxy for crack damage evolution in a series of heating and cooling experiments on samples of basalt and dacite results show that both the rate and the energy of acoustic emission are consistently much higher during cooling than during heating seismic velocity comparisons and crack morphology analysis of our heated and cooled samples support the contemporaneous acoustic emission data and also indicate that thermal cracking is largely isotropic these new data are important for assessing the contribution of cooling induced damage within volcanic structures and layers such as dikes sills and lava flows

scaled experiments of volcanic spreading experiments were conducted to study the spreading of volcanic constructs volcanoes are simulated by a sand cone and the volcanic substratum is simulated by a sand layer brittle substratum overlying a silicone layer ductile substratum similarity conditions between natural volcanoes and experimental prototypes led to the definition of dimensionless numbers experiments determine values which predict whether or not spreading takes place of particular importance are the ratio between the thickness of the brittle substratum and the height of the volcano 2 and the brittle ductile ratio of the substratum 3 2 indicates that the volcano must be large enough to break the substratum before spreading occurs whereas 3 controls the style of deformation during spreading these dimensionless numbers change with time reaching values that tend toward those observed for stable configurations experimental values are compared with those from well constrained natural examples it is found that an essential requirement for volcanic spreading is the presence of a low viscosity layer within the substratum flow of the weak layer away from the excess load is responsible for the spreading the overlying edifice displays radial intersecting grabens due to concentric stretching dissected summit areas concentric zones of thrusts and folds form in the substratum around the edifice and diapirs of the ductile substratum rise within the fault zones

an objective study of 500 hpa moving troughs in the southern hemisphere abstract the location and movement of 500 hpa troughs using an automated method are studied with data from a 24 yr period with the objective of determining the trough formation and dissipation regions in the southern hemisphere to identify the 500 hpa mobile troughs an objective method that uses the eulerian centripetal acceleration eca is developed on average 868 troughs per year were identified by the method with an increase in trend during the period studied the troughs have an average lifetime of 4 3 days being longer shorter in subtropical high latitudes the average calculated phase velocity was 13 6 m s 1 being higher lower in middle high latitudes the troughs are normally found in the 60 40 s latitudinal band with maximum occurrence at 50 s the longitudinal distribution of trough genesis has three maximum regions over the drake strait and the south atlantic ocean over the indian ocean around 50 s and over the southwestern pacific ocean between 150 e and 150 w the trough d

the three dimensional distribution of clouds around southern hemisphere extratropical cyclones 1 the organization and for the first time the three dimensional structure of clouds associated with the southern hemisphere cyclones are studied using active observations from the cloudsat and calipso satellites first a composite cyclone is constructed from more than 800 individual cases in the years 2007 and 2008 using the cyclone centre as the composite reference point it is shown that the three dimensional cloud distribution around the composite cyclone agrees well with conceptual models of extratropical cyclones composite mean fields of sea level pressure vertical motion potential temperature and relative humidity are superposed on the three dimensional cloud structure to better define the relationship between the clouds and dynamical properties of extratropical cyclones the methodology used here reveals the relationship between dynamical and cloud processes in three dimensions around cyclones and provides the foundation for in depth evaluations of the ability of climate models to simulate the cloud and dynamical structures of southern hemisphere extratropical cyclones

active faulting in the dead sea rift abstract manifestations of late quaternary and holocene faulting were studied in a 500 km long segment of the dead sea transform rift most prominent are left slip faults whose characteristic physiographic features are recognizable along most of the studied segment where these faults bend or are stepped to the left rhomb shaped grabens or pull aparts are produced forming depressions in the reverse situation compressional features such as pressure ridges domes and folds form positive topographic features such structures are combined on a variety of scales ranging from a few hundred meters long to tens of kilometers normal faults sub parallel to the left slip faults produce a trough like valley along much of the dead sea transform but are most prominent along the margins of the large rhomb grabens e g the dead sea trough they apparently record a small component of transverse extension generally their motion is slow young slip did not occur along some segments during the last few 10 4 y elsewhere throws of 10 20 m at least occurred in this period the dead sea transform is seismically active the instrumental and historic records indicate a seismic slip rate of 0 15 0 35 cm y during the last 1000 1500 y while estimates of the average pliocene pleistocene rate are 0 7 1 0 cm y either much creep takes place or the slip rate varies over periods of a few 10 3 y

insights into fluid circulation across the pernicana fault mt etna italy and implications for flank instability article i nfo we conducted geophysical geochemical measurements on a 2k m n s profile cutting across the pernicana fault one of the most active tectonic features on the ne flank of mt etna the profile passes from the unstable e flank of the volcano to the south to the stable n flank and significant fluctuations in electrical resistivity self potential and soil gas emissions co2 rn and th are found the detailed multidisciplinary analysis reveals a complex interplay between the structural setting uprising hydrothermal fluids meteoric fluids percolating downwards ground permeability and surface topography in particular the recovered fluid circulation model highlights that the southern sector is heavily fractured and faulted allowing the formation of convective hydrothermal cells although the existence of a hydrothermal system in a volcanic area does not surprise these results have great implications in terms of flank dynamics at mt etna indeed the hydrothermal activity interacting with the pernicana fault activity could enhance the flank instability our approach should be further extended along the full extent of the boundary between the stable and unstable sectors of etna for a better evaluation of the geohazard in this active tectonic area

some outstanding issues in the geology of lebanon and their importance in the tectonic evolution of the levantine region abstract the concept of pervasive and disruptive late neogene quaternary strike slip tectonics in lebanon has made establishing a satisfactory pre neogene palaeogeographic and palaeotectonic history for the area difficult research has allowed clarification of three fundamental issues that permit the setting of lebanon against its adjacent regions to be more firmly assigned the first issue is the identification of the significance of the 100 km long nne ssw trending monocline of the western lebanon flexure this feature is interpreted as a modified and rejuvenated early mesozoic hinge line that is presumed to be the northern continuation of the carmel sinai hinge line to the south the second issue is the correlation of the mount lebanon bekaa and anti lebanon complex with the adjacent intracontinental palmyride fold belt of syria through recognition in each of common divisions in structural style between a higher northern zone dominated by broadly spaced box folds and a lower southern zone with more numerous closely spaced and more internally complex folds the third issue involves the identification of major two stage late cretaceous to palaeogene syrian arc tectonism within lebanon resolution of these issues suggests a tectonic model for the region whereby the levantine region formed in two main phases the first of these was the multiphase late palaeozoic early mesozoic rifting of the area which imposed a fundamental extensional fabric over much of the region the second tectonic phase was the subsequent inversion of these extensional structures in the two stage syrian arc deformation of senonian and late palaeogene age which gave rise to the main lebanon structures it is this syrian arc tectonism rather than the late cenozoic strike slip that was probably the main structuring agent which affected the lebanon area the transpression from the braided dead sea fault motion although locally complex is an essentially neotectonic overprint on an already existing fabric offset of syrian arc structures in lebanon suggests that the total sinistral motion of the yammouneh fault segment of the dead sea fault is around 47 km

extratropical fronts in the lower troposphere global perspectives obtained from two automated methods in this study two commonly used automated methods to detect atmospheric fronts in the lower troposphere are compared in various synoptic situations the first method is a thermal approach relying on the gradient of equivalent potential temperature th while the second method is based on temporal changes in the 10 m wind wnd for a comprehensive objective comparison of the outputs of these methods of frontal identification both schemes are firstly applied to an idealised strong baroclinic wave simulation in the absence of topography then two case studies one in the northern hemisphere nh and one in the southern hemisphere sh were conducted to contrast fronts detected by the methods finally we obtain global winter and summer frontal occurrence climatologies derived from era interim for 1979 2012 and compare the structure of these th is able to identify cold and warm fronts in strong baroclinic cases that are in good agreement with manual analyses wnd is particularly suited for the detection of strongly elongated meridionally oriented moving fronts but has very limited ability to identify zonally oriented warm fronts we note that the areas of the main th frontal activity are shifted equatorwards compared to the wnd patterns and are located upstream of regions of main wnd front activity the number of wnd fronts in the nh shows more interseasonal variations than th fronts decreasing by more than 50 from winter to summer in the sh there is a weaker seasonal variation of the number of observed wnd fronts however th front activity reduces from summer djf to winter jja the main motivation is to give an overview of the performance of these methods such that researchers can choose the appropriate one for their particular interest

a new method to objectively classify extratropical cyclones for climate studies testing in the southwest pacific region abstract extratropical cyclones can vary widely in their configuration during cyclogenesis development mechanisms spatial and temporal characteristics and impacts an automated method to classify extratropical cyclones identified in era interim data from 1979 to 2010 in the australia and new zealand region has been developed the technique uses k means clustering on two upper tropospheric flow fields at the time of cyclogenesis and identifies four distinct clusters composites of these clusters are investigated along with their life cycles and their spatial and temporal variability the four clusters are similar to a previous manual classification cluster 1 develops in the equatorward entrance region of the subtropical jet clusters 2 and 4 develop in the poleward exit region of the subtropical jet but with different relative positions of the upper level trough and jet streak and cluster 3 resembles secondary cyclogenesis on a preexisting front far poleward of the subtropical jet the clusters have

identification and climatology of southern hemisphere mobile fronts in a modern reanalysis abstractpresented here is an objective approach to identify characterize and track southern hemisphere mobile fronts in hemispheric analyses of relatively modest resolution such as reanalyses among the principles in its design were that it should be based on broadscale synoptic considerations and be as simple and easily understood as possible the resulting eulerian scheme has been applied to the european centre for medium range weather forecasts ecmwf re analysis era interim and a climatology of frontal characteristics at both the 10 m and 850 hpa levels derived for the period 1 january 1989 28 february 2009 the knowledge of the character of these features is central to understanding weather and climate over the hemisphere in both summer and winter the latitude belt 40 60 s hosts the highest frequency of frontal points but there are significant zonal asymmetries within this band the climatology reveals that the longest fronts are in the indian ocean where mean lengths exceed 2000 km the me

lithology of the basement underlying the campi flegrei caldera volcanological and petrological constraints abstract a geologically reasonable working hypothesis is proposed for the lithology of the basement underlying the campi flegrei caldera in the ca 4 8 km depth range in most current geophysical modeling this portion of crust is interpreted as composed of meso cenozoic carbonate rocks underlain by a ca 1 km thick sill of partially molten rock thought to be a main magma reservoir shallower magma reservoirs likely occur in the 3 4 km depth range however the lack of carbonate lithics in any campi flegrei caldera volcanic rocks does not support the hypothesis of a limestone basement considering the major caldera forming eruptions which generated widespread and voluminous ignimbrites during late quaternary times including the campanian ignimbrite and neapolitan yellow tuff eruptions the total volume of trachytic to phonolitic ejected magma is conservatively estimated at not less than 350 km 3 results of least squared mass balance calculations suggest that this evolved magma formed through fractional crystallization from at least 2500 km 3 of parent shoshonitic magma in turn derived from even more voluminous more mafic k basaltic magma calculations suggest that shoshonitic magma likely emplaced at ca 8 km depth must have crystallized about 2100 km 3 of solid material dominated by alkali feldspar and plagioclase with a slightly lower amount of mafic minerals during its route toward shallower magma reservoirs before feeding the campi flegrei large volume eruptions the calculated volume of cumulate material likely syenitic in composition at least in its upper portions is more than enough to completely fill the basement volume in the 4 8 km depth range beneath the campi flegrei caldera estimated at ca 1250 km 3 thus it is proposed that the basement underlying the campi flegrei caldera below 4 km is composed mostly of crystalline igneous rocks as for many large calderas worldwide syenite sensu lato would meet physical properties requirements for geophysical data interpretations explain some geochemical and isotopic features of the past 15 ka volcanics and justify the carbon isotopic composition of fumaroles at the campi flegrei caldera this implies that meso cenozoic limestones if still present today beneath the campi flegrei caldera no longer constitute significant portions of its basement

eruptive history and petrologic evolution of the albano multiple maar alban hills central italy a comprehensive volcanological study of the albano multiple maar alban hills italy using i 40ar 39ar geochronology of the most complete stratigraphic section and other proximal and distal outcrops and ii petrographic observations phase analyses of major and trace elements and sr and o isotopic analyses of the pyroclastic deposits shows that volcanic activity at albano was strongly discontinuous with a first eruptive cycle at 69 1 ka producing at least two eruptions and a second cycle with two peaks at 39 1 and 36 1 ka producing at least four eruptions contrary to previous studies we did not find evidence of magmatic or hydromagmatic eruptions younger than 36 1 ka the activity of albano was fed by a new batch of primary magma compositionally different from that of the older activity of the alban hills moreover the ree and 87sr 86sr data indicate that the albano magma originated from an enriched metasomatized mantle according to the modeled liquid line of descent this magma differentiated under the influence of magma limestone wall rock interaction our detailed eruptive and petrologic reconstruction of the albano maar evolution substantiates the dormant state of the alban hills volcanic district

meteorological tower measurements of a surface cold front abstract measurements from the boulder atmospheric observatory meteorological research tower are used to describe the structure and physical processes of a strong surface cold front analysis reveals that the horizontal gradients in temperature and wind velocity at the front are concentrated within a 200 m distance and measured vertical velocities exceed 5 m s 1 at the leading edge of the front calculations with the miller frontogenesis equation show the magnitude and relative importance of cross frontal confluence versus differential vertical motion tilting in forcing frontogenesis

precipitation associated with convergence lines precipitation is often organized along coherent lines of low level convergence which at longer time and space scales form well known convergence zones over the world s oceans here an automated objective method is used to identify instantaneous low level convergence lines in reanalysis data and calculate their frequency for the period 1979 2013 identified convergence lines are combined with precipitation observations to assess the extent to which precipitation around the globe is associated with convergence lines in the lower troposphere it is shown that a large percentage of precipitation between 65 and 90 over the tropical oceans is associated with such convergence lines with large regional variations of up to 30 throughout the year especially in the eastern pacific and atlantic oceans over land the annual mean proportion of precipitation associated with convergence lines ranges between 30 and 60 and the lowest proportions less than 15 associated with convergence lines occur on the eastern flank of the subtropical highs overall much greater precipitation is associated with long coherent lines greater than 300 km in length than with shorter fragmented lines less than 300 km and the majority of precipitation associated with shorter lines occurs over land the proportion of precipitation not associated with any convergence line primarily occurs where both precipitation and frequency of convergence lines are low the high temporal and spatial resolution of the climatology constructed also enables an examination of the diurnal cycle in the relationship between convergence lines and precipitation here an example is provided over the tropical maritime continent region

global climatologies of fronts airmass boundaries and airstream boundaries why the definition of front matters abstractclimatologies of fronts airmass boundaries and airstream boundaries can be calculated using automated approaches on gridded data such approaches may require choices to define a front in

time dependent geochemistry of clinopyroxene from the alban hills central italy clues to the source and evolution of ultrapotassic magmas abstract we investigated chemical and isotopic compositions of clinopyroxene crystals from well age constrained juvenile scoria clasts lava flows and hypoabyssal magmatic ejecta representative of the whole eruptive history of the alban hills volcanic district the alban hills is a quaternary ultra potassic district that was emplaced into thick limestone units along the tyrrhenian margin of italy alban hills volcanic products even the most differentiated are characterised by low sio2 content we suggest that the low silica activity in evolving magmas can be ultimately due to a decarbonation process occurring at the magma limestone interface according to the liquid line of descent we propose the differentiation process is driven by crystallisation of clinopyroxene leucite apatite magnetite coupled with assimilation of a small amount of calcite and or with interaction with crustal co2 by combining age chemical data strontium and oxygen isotopic compositions and ree content of clinopyroxene we give insights into the evolution of primitive ultrapotassic magmas of the alban hills volcanic district over an elapsed period of about 600 kyr geochemical features of clinopyroxene crystals consistent with data coming from other italian ultrapotassic magmas indicate that alban hills primary magmas were generated from a metasomatized lithospheric mantle source in addition our study shows that the 87sr 86sr and lree hree of alban hills magmas continuously diminished during the 600 35 ka time interval of the alban hills eruptive history possibly reflecting the progressive depletion of the metasomatized mantle source of magmas

pervasive assimilation of carbonate and silicate rocks in the hortavaer igneous complex north central norway the intrusive complex at hortav r represents a magma transfer zone in which multiple pulses of gabbroic and dioritic magmas evolved along fe and alkali enrichment trends extreme alkali enrichment resulted in nepheline normative and sparse nepheline bearing monzodioritic and monzonitic rocks more evolved monzonitic and syenitic rocks are silica saturated and in some cases quartz bearing previous and current research recognized an abundance of clinopyroxene and other ca rich phases such as scapolite grossular rich garnet and igneous textured calcite among the mafic and intermediate rocks even the most pyroxene rich samples contain low sc concentrations which suggests early intense fractionation of clinopyroxene these features and the alkali enrichment are consistent with assimilation of carbonate rich host rocks carbon isotope ratios of the igneous textured calcite indicate an origin of the carbon from host rocks rich in calcite consistent with assimilation however low end values 3 4 to 10 2 and moderate initial 87 sr 86 sr values 0 7052 to 0 7099 indicate the need for assimilation of quartzofeldspathic rocks as well models of combined assimilation and fractional crystallization indicate that assimilation of simple end members either carbonate or silicate cannot explain the entire data set instead variable proportions of carbonate and silicate materials were assimilated with the most pronounced assimilation effects in the mafic rocks the reasons for variable degrees of assimilation are as yet uncertain it is possible that assimilation of calc silicate rocks with variable carbonate silicate proportions resulted in the range of observed compositions however the importance of carbonate assimilation in mafic rocks compared to felsic ones suggests that assimilation of carbonates was predominant at high temperature and or mafic magma compositions and assimilation of silicates was predominant at lower temperature and or felsic magma compositions we suggest that the ability of the mafic magma to dissolve higher proportions of carbonate contaminants is the result of the magma s ability to form clinopyroxene as a product of assimilation in any case extensive carbonate assimilation was possible because co2 escaped from the system d 2004 elsevier b v all rights reserved

volcanic edifice weakening via devolatilization reactions summary edifice instability that can result in catastrophic flank collapse is a fundamental volcanic hazard the subvolcanic basement can encourage such instability especially if it is susceptible to mechanical weakening by devolatilization reactions near magmatic temperatures for this reason understanding how the physical and chemical properties of representative lithologies deteriorate at high temperatures is potentially highly relevant for volcanic hazard mitigation this is particularly true for sedimentary rock commonly found underlying volcanic edifices worldwide that undergo rapid deterioration even under modest temperatures therefore here we present the first experimental study of devolatilization reactions induced by magmatic temperatures on sedimentary rock comprising a subvolcanic basement our results show that for a marly limestone representative of the basement at mt etna devolatilization reactions namely the dehydroxylation of clay minerals and the decarbonation of calcium carbonate result in a dramatic reduction of mechanical strength and seismic velocities these temperature driven reactions can promote volcanic instability at stresses much lower than previously estimated

the arctic frontal zone as seen in the ncep ncar reanalysis abstract calculations of a thermal front parameter using ncep ncar reanalysis data over the period 1979 98 reveal a relative maximum in frontal frequencies during summer along northern eurasia from about 60 to 70 n best expressed over the eastern half of the continent a similar relative maximum is found over alaska which is present year round although best expressed in summer these high latitude features can be clearly distinguished from the polar frontal zone in the midlatitudes of the pacific basin and collectively resemble the summertime arctic frontal zone discussed in several early studies while some separation between high and midlatitude frontal activity is observed in all seasons the summer season is distinguished by the development of an attendant mean baroclinic zone aligned roughly along the arctic ocean coastline and associated wind maxima in the upper troposphere the regions of maximum summer frontal frequency correspond to preferred areas of cyclogenesis and to where the summertime

characteristics of the marine atmospheric boundary layer over the southern ocean in response to the synoptic forcing the characteristics of the marine atmospheric boundary layer mabl in relation to synoptic meteorology over the southern ocean are examined using upper air soundings and surface precipitation at macquarie island 54 62 s 158 85 e with a primary focus on the post cold frontal environment where large cloud and radiative biases are presented in a multitude of climate models thermodynamic profiles from the european centre for medium range weather forecasts era interim reanalyses are compared with the observations to evaluate their representation of the mabl characteristics observations confirm that boundary layer clouds over the southern ocean commonly reside within a shallow mabl under the influence of frequent midlatitude cyclones and fronts the evaluation of mabl height shows that for both observations and reanalysis the inversion is higher northward of the low center and under postcold front conditions under cold frontal passages however the main inversions are not well represented by era interim which is featured by an underestimate of the mabl height by 22 significant differences are found in the moisture profiles within the mabl between the observations and era interim soundings within the context of cold frontal passages the moisture in the era interim is found to be too confined to the surface layer which is consistent with the shallower mabl represented by the era interim analysis of the surface precipitation shows that era interim overestimates the amount of precipitation over macquarie island in the vicinity of cyclone cores but underestimates the precipitation not immediately associated with cold fronts leading to an overall underestimate of the annual precipitation by 11

magmatic stoping during the caldera forming pomici di base eruption somma vesuvius italy as a fuel of eruption explosivity abstract magma carbonate interactions and the subsequent co2 release can occur before and during an eruption critically affecting magma storage and ascent processes however the mechanisms and timescales of those interactions are unclear particularly during the fast magma withdrawal that feeds high intensity eruptions in order to better understand magma carbonate interactions we selected the caldera forming pomici di base plinian eruption the oldest 22 ka and largest 4 4 km3 explosive event in the history of the somma vesuvius volcanic system as case study during this event the emission of trachytic and latitic shoshonitic 25 and 75 of the erupted magma volume respectively magmas generated a long lasting plinian column hypothetically driven by co2 liberation during magma carbonate interaction in this study we reconstruct in detail the evolution of the plumbing system during the pomici di base eruption combining geochemical major minor elements and radiogenic stable isotopes analyses of juvenile products with thermodynamic and kinetic calculations our results demonstrate that magmatic stoping i e the formation and transport of host rock pieces into a magma body during caldera collapse evolution can promote rapid magma assimilation of carbonate blocks and co2 rich fluids resulting from destabilization of the carbonate bedrock thus triggering co2 release and acting as a fuel for the eruption explosivity especially when residual hot mafic magmas are involved our findings suggest that the accurate knowledge of these processes and their influence on eruptive dynamics are critical for improving the hazard assessments of volcanoes with plumbing systems located in carbonate bedrocks

the south pacific convergence zone spcz a review abstract the circulation features associated with the south pacific convergence zone spcz and its accompanying cloud band are reviewed and discussed the paper focuses on the following topics location structure and characteristics of the spcz theories and observations concerning its existence the significance and scope of the spcz in global scale circulation patterns quasi periodic changes in its location and strength and synoptic scale features within its regional influence e g cyclones subtropical jets it concludes with some challenging problems for the future

the effect of cao on the partitioning behavior of ree y and sc between olivine and melt implications for basalt carbonate interaction processes abstract the partitioning of ree y and sc r3 between olivine and melt has been investigated experimentally during basalt carbonate interaction three synthetic basalts meltmg 72 meltmg 75 and meltmg 78 were doped with 0 10 and 20 wt caco3 and then equilibrated for 72 h at 1 atm 1 150 1 200 and 1 250 c and the qfm oxygen buffer the thermal decomposition of caco3 produced cao contents in the melt up to 22 wt regular relationships are found between the ionic radius and the partition coefficient dr3 showing typical near parabolic patterns dr3 is weakly dependent on temperature but decreases with increasing caco3 in the starting material e g dsc decreases from 0 20 to 0 13 from the point of view of the lattice strain theory dr3 is described in terms of the radius of the crystal site r0 the young modulus e due to the elastic response of that site to lattice strain caused by cation insertion and the strain free partition coefficient d 0 3 the value of r0 decreases as ca cations are accommodated into the more distorted m2 site of olivine via progressive ca fe substitutions this mechanism is accompanied by a higher proportion of mg cations entering into the smaller m1 site making the optimum ionic radius smaller and favoring the crystallization of more forsteritic olivines from decarbonated melts the enrichment of ca in the crystal lattice is also proportional to the number of si and ca cations available in the melt this causes e to be anticorrelated either with ca in olivine or the activity of cao in the melt r3 cations behave as network modifiers and during basalt carbonate interaction the increasing abundance of non bridging oxygens enhances the solubility of ree y and sc in the melt as a consequence d 0 3 is negatively correlated with the degree of melt depolymerization additionally the strain of the crystal lattice dominates the dr3 parabolic patterns and d 0 3 is strongly controlled by forsterite and aluminium concentrations in olivine the accommodation of ree y and sc in the crystal lattice requires maintenance of local charge balance by the generation of vacancies in accord with a paired substitution of r3 and a vacancy for mg in octahedral sites

thermal weakening of the carbonate basement under mt etna volcano italy implications for volcano instability abstract the physical integrity of a sub volcanic basement is crucial in controlling the stability of a volcanic edifice for many volcanoes this basement can comprise thick sequences of carbonates that are prone to significant thermally induced alteration these debilitating thermal reactions facilitated by heat from proximal magma storage volumes promote the weakening of the rock mass and likely therefore encourage edifice instability such instability can result in slow gravitational spreading and episodic to continuous slippage of unstable flanks and may also facilitate catastrophic flank collapse understanding the propensity of a particular sub volcanic basement to such instability requires a detailed understanding of the influence of high temperatures on the chemical physical and mechanical properties of the rocks involved the juxtaposition of a thick carbonate substratum and magmatic heat sources makes mt etna volcano an ideal candidate for our study we investigated experimentally the effect of temperature on two carbonate rocks that have been chosen to represent the deep heterogeneous sedimentary substratum under mt etna volcano this study has demonstrated that thermal stressing resulted in a progressive and significant change in the physical properties of the two rocks porosity wet i e water saturated dynamic poisson s ratio and wet vp vs ratio all increased whilst p and s wave velocities bulk sample density dynamic and static young s modulus dry vp vs ratio and dry dynamic poisson s ratio all decreased at temperatures of 800 c the carbonate in these rocks completely dissociated resulting in a total mass loss of about 45 and the release of about 44 wt of co 2 uniaxial deformation experiments showed that high in situ temperatures 500 c significantly reduced the strength of the carbonates and altered their deformation behaviour above 500 c the rocks deformed in a ductile manner and the output of acoustic emissions was greatly reduced we speculate that thermally induced weakening and the ductile behaviour of the carbonate substratum could be a key factor in explaining the large scale deformation observed at mt etna volcano our findings are consistent with several field observations at mt etna volcano and can quantitatively support the interpretation of 1 the irregularly low seismic velocity zones present within the sub volcanic sedimentary basement 2 the anomalously high co 2 degassing observed 3 the anomalously high vp vs ratios and the rapid migration of fluids and 4 the increasing instability of volcanic edifices in the lifespan of a magmatic system we speculate that carbonate sub volcanic basement may emerge as one of the decisive fundamentals in controlling volcanic stability