profiles of steady state suction stress in unsaturated soils application of the effective stress principle in unsaturated geotechnical engineering problems often requires explicit knowledge of the stress acting on the soil skeleton due to suction pore water pressure this stress is defined herein as the suction stress a theoretical formulation of suction stress profiles based on the soil water characteristics curve the soil permeability characteristic curve and previous shear strength experimental verification is developed the theory provides a general quantitative way to calculate vertical suction stress profiles in various unsaturated soils under steady flow rate in the form of infiltration or evaporation

monitoring soil water and displacement conditions leading to landslide occurrence in partially saturated clays abstract shallow landslides frequently occur during transient rainfall infiltration and under partially saturated conditions however a detailed analysis of what triggers them particularly in clayey soils is often hindered by the lack of field measurements it is uncommon in fact to capture their occurrence in an instrumented natural slope this paper presents results from an integrated field experiment monitoring the soil water and displacement conditions that lead to the occurrence of a shallow landslide in partially saturated clays the integration of a variety of experimental techniques allowed for the examination of interplay between soil hydrological and mechanical properties this research also evaluates a slope stability model based on the suction stress concept since the model was applied after the occurrence of the landslide the results are interpreted as a hind casting technique for model evaluation nevertheless the detailed field measurements acquired during the monitoring activity and the occurrence of a landslide during the experiment provided significant information on model parameters and data interpretation the station provides remote satellite monitoring of data on weather variables soil water content and soil suction a time domain reflectometry cable was installed vertically to detect potential soil failure the experimental area had a high probability of landslide occurrence indeed slope failure occurred during the observation period showing the effectiveness of the station in detecting the occurrence time and depth of landslides the landslide was triggered in consequence of changes in suction stress the failure plane occurred at a depth of 1 4 m corresponding to the interface between a superficial layer of higher permeability of 1 to 1 45 m thickness slipping over a compacted substrate having lower permeability the analysis allowed for testing of the validity of the model and the description of the triggering mechanisms of the observed shallow landslide in unsaturated conditions indicating that oscillations in soil matric suction were the dominant variables determining soil failure

drained shear strength parameters for analysis of landslides this paper presents recommendations for selecting the type and magnitude of drained shear strength parameters for analysis of landslides in particular the importance existence and use of the cohesion shear strength parameter is reviewed for slope stability analyses it is recommended that the shear strength be modeled using a stress dependent failure envelope or a friction angle that corresponds to the average effective normal stress acting on the slip surface passing through that particular material instead of using a combination of cohesion and friction angle to represent soil shear strength other recommendations for stability analyses include using an effective stress cohesion of zero for residual and fully softened strength situations to facilitate selection of shear strength parameters for landslide analyses empirical relationships for the drained residual and fully softened strengths are updated from the previous empirical relationships presented by stark and eid finally the paper presents torsional ring shear test results that indicate that pre existing shear surfaces exhibit self healing that results in increased shear resistance the magnitude of healing appears to increase with increasing soil plasticity and this increase could have implications for the size timing and cost of landslide remediation

in situ x ray observations of phase assemblages in peridotite and basalt compositions at lower mantle conditions implications for density of subducted oceanic plate 1 phase relationships in klb 1 peridotite normal type mid oceanic ridge basalt nmorb and k rich basalt compositions were investigated experimentally from 28 to 143 gpa and 2050 to 3000 k a laser heated diamond anvil cell with the synchrotron x ray diffraction was developed to perform in situ observations of samples at simultaneous high pressures and temperatures we confirmed that the peridotite composition crystallized into an assemblage of mg perovskite ca perovskite magnesiowustite at pressures below 97 gpa and that nmorb and k rich basalt compositions both crystallized as mg perovskite ca perovskite stishovite an aluminous phase with a cafe2o4 type structure at pressures below 68 gpa the orthorhombic mg perovskite is stable in natural rock compositions at pressures less than 97 gpa corresponding to about 2200 km depth phase transition of silica phase from stishovite to cacl2 type phase was observed at 78 gpa in nmorb composition moreover we observed that nmorb crystallized in to an assemblage of cairo3 type mg fe sio3 ca perovskite pbo2 type silica an aluminous phase with a calcium cati2o4 type structure at 143 gpa corresponding to the core mantle boundary depth we measured the unit cell volumes of minerals in the nmorb composition at high p t and thereby estimated the density of subducted morb to a depth of 1800 km in the lower mantle in this depth regime morb is denser than model mantle densities e g prem and ak135 the estimated density of morb may contribute to an understanding of dynamics of the subducted slab in the deep lower mantle

laboratory measurements of electrical conductivity of hydrous and dry silicic melts under pressure an interpretation of the electrical signature of molten rocks within the earth s interior in terms of nature and temperature conditions of magma requires additional laboratory data on the electrical conductivity of silicate melts this paper describes an experimental setup and presents measurements of the electrical impedance of dry and hydrous 1 3 wt h2o metaluminous obsidians determined in an internally heated pressure vessel in the range of 50 400 mpa and 350 1325 c it is shown that the temperature and pressure dependences of electrical conductivity of both hydrous and dry obsidian can be fitted by an arrhenius law applying in the melt and the glass regions this suggests that a similar transport mechanism operates in both melt and glass the determined activation energies are 70 kj mol for the dry obsidian and 65 and 61 kj mol for the 1 and 3 wt h2o melts respectively the activation volume is 20 cm3 mol combination of tracer diffusion and electrical conductivity reveals that sodium is the dominant charge carrier in the hydrous and dry obsidians the temperature and pressure effects on conductivity are therefore interpreted in terms of activation energy and activation volume for na mobility in dry and hydrous rhyolites an increase in conductivity associated with addition of water was observed and is shown to reflect the effect of water incorporation in melts on the mobility of sodium as a prospective it is anticipated that both the mobility and content of sodium could control the electrical conductivity of most terrestrial silicate melts magma under differentiation becomes more conductive due to sodium and water enrichment associated with fractional crystallization therefore its electrical signature must reveal its nature and maturity

spatial interaction between collapsed pipes and landslides in hilly regions with loess derived soils while most studies focus on the effect of soil pipes on hillslope stability this present study investigates the impact of landsliding on pipe development it is hypothesized that poorly drained active and dormant landslides change the hillslope hydrology through i surface flow obstruction by changing topography as well as ii subsurface flow obstruction by tilting less permeable clay rich substrates hence new preferential flow paths are created at reverse slopes within the landslide zone and at the boundary of the landslide enhancing pipe formation this study aims at a better understanding of the interaction between collapsed pipe cp occurrence and landslide ls occurrence in the flemish ardennes belgium by comparing their respective spatial patterns at least 24 5 of the 139 sites with cp were related to the occurrence of an observed ls poorly drained ls may create favourable conditions for pipe development outside ls natural and anthropogenic e g broken field drains road drainage causes may result in concentrated subsurface flow resulting in pipe development no evidence was found that pipe development enhanced ls probably because the subsurface drainage discharge generated upslope of the ls is too low even when pipes become blocked it is more likely that new pipes develop and new collapses occur than they trigger or reactivate ls a conceptual model is presented summarizing all elements that influence piping erosion in the flemish ardennes including the role of ls copyright 2012 john wiley sons ltd

radiolarian flux at an images site at the western margin of the subarctic pacific and its seasonal relationship to the oyashio cold and tsugaru warm currents seasonal changes of radiolarian flux in the far western area of the western subarctic gyre in the pacific ocean were examined based on samples from a sediment trap experiment deployed at a site off the northern honshu island of japan from june 2002 to may 2003 warm and neritic water species associated with the tsugaru warm current tgc originating from the japan sea were dominant while the cold water species associated with the oyashio cold current were relatively few in spite of the location of the site in the subarctic province r mode cluster analysis was used to divide species specific flux patterns into 5 groups of fauna associated with 1 the tgc forerunner in june 2002 2 the tgc main flow from september to november 2002 3 the neritic water in december 2002 4 the oyashio cold current in may 2003 and 5 surface productivity in the spring of 2002 2003 together with the tgc in summer 2002

properties of magmatic liquids by molecular dynamics simulation the example of a morb melt abstract a new atom atom interaction potential is introduced for describing by classical molecular dynamics md simulation the physical properties of natural silicate melts the equation of state the microscopic structure the viscosity the electrical conductivity and the self diffusion coefficients of ions in a mid oceanic ridge basalt morb melt are evaluated by md over a large range of temperature and pressure 1673 3273 k and 0 60 gpa a detailed comparison with experimental data shows that the model reproduces the thermodynamic structural and transport properties of a morb with an unprecedented accuracy in particular it is shown that the morb melt crystallizes at lower mantle conditions into a perovskite phase whose the equation of state eos is compatible with those proposed in the experimental literature moreover in accordance with experimental findings the simulation predicts not only that the morb viscosity exhibits a slight minimum with the pressure but also that the viscosity at high temperature remains very low 2273 k even at high pressure up to 40 gpa however the evolution of the electrical conductivity with temperature and pressure is not always the symmetrical of that of the viscosity in fact the relationship between viscosity and electrical conductivity shows a crossover at around 2073 k

mechanisms of shallow landslides on soil mantled hillslopes with permeable and impermeable bedrocks in the boso peninsula japan abstract rainfall induced shallow landslides play a vital role in hillslope denudation processes in humid temperate regions this study demonstrates the contrasting mechanisms of landslides in adjoining hills with permeable sandstone and impermeable mudstone bedrock in the boso peninsula japan the characteristics of slope hydrology were inferred from pressure head monitoring and rainfall runoff observations an analysis of slope stability provided critical conditions for several previously occurring landslides the results are as follows 1 in slopes with the permeable sandstone infiltrated rainwater percolates through the bedrock as an unsaturated gravitational flow the wetting front migration results in a decrease of soil cohesion and causes landsliding at the steep lower part of the hillslopes 2 in contrast the impermeable mudstone beneath a thin soil layer causes a transient positive pressure head that generates a saturated subsurface storm flow the reduction in effective normal stress triggers shallow soil slipping at the uppermost part of a hollow

physical state of an early magma ocean constrained by the thermodynamics and viscosity of iron silicate liquid abstract the initial cooling stage and crystallization of a magma ocean were significantly affected by the thermodynamics and viscosity of iron silicate liquid here we use first principles molecular dynamics based on density functional theory plus the hubbard u method to study the structures thermodynamics and viscosities of fe2sio4 liquid at 3000 6000 k under pressure conditions spanning the entire mantle our calculations show that the compressibility of fe2sio4 liquid is weakened at pressures above 50 gpa the densification of fe2sio4 liquid under compression is mainly manifested by a decrease in the distance among si o polyhedra and an increase in the cation anion coordination number we find that the viscosity of the fe2sio4 liquid has a positive pressure dependence and the effect of pressure on viscosity decreases with increasing temperature the predicted behaviour of viscosity coefficients of the fe2sio4 liquid at different p t conditions can be described well as p t exp 7 89 0 0042 p 0 0000632 p 2 3800 61 6 p 0 18 p 2 t 1000 compared to mg2sio4 liquid the viscosity of fe2sio4 liquid is lower under the pressure of the lower mantle along isotherms we calculate the adiabat of the fe2sio4 liquid in a magma ocean and the results show that the iron content has little effect on the adiabats of mg fe 2sio4 liquid in the magma ocean combining our calculated thermodynamic properties and viscosities with those of previous studies the physical properties of an early magma ocean were constrained the upper bound of the potential temperature for magma ocean crystallization is 3250 k we constructed the range of the viscosity profile of a magma ocean and found that the lower viscosity of iron rich silicate liquid would maintain the viscosity of an early magma ocean in the range of several mpa s as the magma ocean starts to crystallize the lower bound of the viscosity at the surface and the core mantle boundary are 0 0020 pa s and 0 0068 pa s respectively the weakening of the viscosity of the iron silicate liquids would have a significant impact on the evolution of the magma ocean

stability of infinite slopes under transient partially saturated seepage conditions 1 prediction of the location and timing of rainfall induced shallow landslides is desired by organizations responsible for hazard management and warnings however hydrologic and mechanical processes in the vadose zone complicate such predictions infiltrating rainfall must typically pass through an unsaturated layer before reaching the irregular and usually discontinuous shallow water table this process is dynamic and a function of precipitation intensity and duration the initial moisture conditions and hydrologic properties of the hillside materials and the geometry stratigraphy and vegetation of the hillslope as a result pore water pressures volumetric water content effective stress and thus the propensity for landsliding vary over seasonal and shorter time scales we apply a general framework for assessing the stability of infinite slopes under transient variably saturated conditions the framework includes profiles of pressure head and volumetric water content combined with a general effective stress for slope stability analysis the general effective stress or suction stress provides a means for rigorous quantification of stress changes due to rainfall and infiltration and thus the analysis of slope stability over the range of volumetric water contents and pressure heads relevant to shallow landslide initiation we present results using an analytical solution for transient infiltration for a range of soil texture and hydrological properties typical of landslide prone hillslopes and show the effect of these properties on the timing and depth of slope failure we follow by analyzing field monitoring data acquired prior to shallow landslide failure of a hillside near seattle washington and show that the timing of the slide was predictable using measured pressure head and volumetric water content and show how the approach can be used in a forward manner using a numerical model for transient infiltration

hydrate dissolution as a potential mechanism for pockmark formation in the niger delta received 17 february 2010 accepted 9 march 2010 published 11 august 2010 1 based on acquired geophysical geological and geotechnical data and modeling we suggest hydrate dissolution to cause sediment collapse and pockmark formation in the niger delta very high resolution bathymetry data acquired from the niger delta reveal the morphology of pockmarks with different shapes and sizes going from a small ring depression surrounding an irregular floor to more typical pockmarks with uniform depression geophysical data in situ piezocone measurements piezometer measurements and sediment cores demonstrate the presence of a common internal architecture of the studied pockmarks inner sediments rich in gas hydrates surrounded by overpressured sediments the temperature pressure and salinity conditions of the studied area have allowed us to exclude the process of gas hydrate dissociation gas hydrate turns into free gas water mixture as a trigger of the observed pockmarks based on numerical modeling we demonstrate that gas hydrate dissolution gas hydrate becomes mixture of water and dissolved gas under a local decrease of the gas concentration at the base of the gas hydrate occurrence zone ghoz can explain the excess pore pressure and fluid flow surrounding the central hydrated area and the sediment collapse at the border of the ghoz the different deformation or development stages of the detected pockmarks confirm that a local process such as the amount of gas flow through faults rather than a regional one is at the origin of those depressions

electrical conductivity of magma in the course of crystallization controlled by their residual liquid composition 1 the electrical conductivity of a magma in the course of crystallization was experimentally investigated in the temperature range of 1350 1018 c large samples of basaltic composition with a homogeneous crystal content were synthesized in a gas mixing furnace at 1 atm pressure the samples were analyzed by electron microprobe the relative proportions of the phases as a function of temperature were determined depending on temperature the phase assemblies included quenched silicate liquid plagioclase pyroxene fe ti oxides the crystal content varied from 0 to 80 wt in response to partial crystallization the residual liquid changed composition from basalt to andesite to dacite liquid the electrical conductivity of the partially crystallized basaltic samples was measured in addition above liquidus conductivity measurements were conducted on compositions matching the residual liquid at different temperature these supplemental electrical measurements allowed us to discriminate the effect of crystal content from the effect of changing liquid composition associated with partial crystallization combining with the modified archie s law a set of constraints describing the conductivity of the residual liquid versus chemical composition and temperature we propose an equation to calculate changes in conductivity associated with partial magma crystallization we showed how the composition of the residual liquid is critical on the electrical behavior of crystal liquid system the model overcomes the previous difficulties in finding a robust model for describing the electrical behavior of crystal liquid systems the effect of liquid composition on the electrical conductivity is related to diffusion mechanisms and transport properties in molten silicate combining known constraints on na tracer diffusion and our conductivity results confirms the statements that sodium is the dominant charge carrier silicate liquids from basalt to rhyolite these findings revealed that we need a comprehensive model that can predict the conductivity of molten silicate as a function of chemical composition

electrical conductivity of molten basalt and andesite to 25 kilobars pressure geophysical significance and implications for charge transport and melt structure electrical conductivities of molten hawaiian tholeiite and crater lake andesite were measured between 1200 c and 1400 c at atmospheric pressure and at pressures up to 17and 25 kbar respectively isobaric plots of log versus 1 t is electrical conductivity are linear with the exception of the zero pressure tholeiite melt data conductivities decrease with increasing pressure in both melts with the andesitic melt exhibiting a greater pressure dependence between 5 and 10 kbar abrupt decreases in the slopes of isothermal log versus p plots i e decreases in activation volume are observed for both rock melts this discontinuity probably reflects changes in melt structure as opposed to changes in conduction mechanism in each pressure range the data for each rock melt can be described reasonably well by an equation of the form 0 exp ea p v kt where 0 is a preexponential constant ea is the activation energy and v is the activation volume a qualitative model involving depolymerization of the melt with increased pressure leading to increased efficiency of packing can explain the observed discontinuity in activation volume as well as the observed pressure dependences of other melt physical properties such as viscosity and density conductivity versus melt fraction curves for partially molten peridotite are reevaluated using high pressure tholeiitic melt conductivities and crystalline conductivity values recently determined by other workers minimum melt fraction estimates of 5 10 are required to explain upper mantle regions of anomalously high electrical conductivity in terms of a partial melting hypothesis

the effect of na si on the structure of sodium silicate and aluminosilicate glasses quenched from melts at high pressure a multi nuclear al 27 na 23 o 17 1d and 2d solid state nmr study abstract we report multi nuclear na 23 and o 17 solid state nmr mas and triple quantum 3q mas spectra for sodium tetrasilicate glasses ns4 quenched from melts at high pressure up to 8 gpa the results show clear evidence for the pressure induced structural changes in the glasses forming oxygen linking 4 si and 5 6 si 4 si o 5 6 si with increasing pressure whereas the general trend in the effect of pressure is consistent with that of sodium trisilicate glasses ns3 detailed pressure induced structural changes for ns4 are largely different from ns3 these differences include the larger fraction of 4 si o 5 6 si and smaller fraction of na o 5 6 si for ns4 than ns3 at isobaric conditions topological disorder due to si o bond length distribution in 4 si o 4 si is also larger for more polymerized ns4 than that for ns3 demonstrating the complexity in structural rearrangement with pressure in silicate glasses and melts with composition at elevated pressure na 23 mas nmr spectra at 14 1 t for the ns4 and aluminosilicate glasses albite composition reveal distinct differences in na environments within sodium silicate and aluminosilicate glasses at high pressure variation of isotropic chemical shift with pressure for ns4 though minor may suggest increasing na o distance with pressure possibly due to a slight increase in na coordination at high pressure on the other hand na 23 isotropic chemical shift for albite composition glass increases with increasing pressure implying the decrease in average na o distance and thus free volume for non framework cations with pressure higher magnetic field coupled with 2d al 27 3qmas nmr improves the resolution of al sites for aluminosilicate glasses at high pressure and may suggest two 5 al sites in partially polymerized aluminosilicate glasses na 2 o al 2 o 3 sio 2 15 5 60 quenched from melts at 8 gpa the current results together with our previous results imply that the pressure induced structural changes and the corresponding changes in properties in silicate melts and glasses are complex function of composition

radiolaria and pollen records from 0 to 50 ka at odp site 1233 continental and marine climate records from the southeast pacific abstract site 1233 drilled during leg 202 of the ocean drilling program provides a detailed record of marine and continental climate change in the southeast pacific and south american continent splits from over 500 samples taken at 20 cm intervals for quantitative analysis of radiolarian and pollen populations yield a temporal resolution of 200 400 years in each sample 39 pollen taxa and 40 radiolarian species and genera were evaluated age control is provided by 25 ams 14c dates lamy f kaiser j ninnemann u hebbeln d arz h w stoner j 2004 science 304 1959 1962 multivariate statistical analyses of these data allow us to conclude the following 1 during the past 50 ka the region of the central chile coast is not directly influenced by polar water from the antarctic region 2 changes in ocean conditions off central chile during this time interval primarily reflect north south shifts in the position of the south pacific transition zone 3 changes in chilean vegetation reflect comparable latitudinal shifts in precipitation and the position of the southern westerlies 4 the first canonical variate of radiolarian and pollen records extracted from site 1233 are remarkably similar to each other as well as to temperature records from the antarctic which suggests that marine and continental climate variability in the region is tightly coupled at periods longer than 3000 years 5 the phase coupling of these climate records which lead variations of continental erosion based on iron abundance at the same site are consistent with a hypothesis that erosion is linked to relatively long i e few thousand years response times of the patagonian ice sheet and thus is not a direct indicator of regional climate

diffusivity and thermodynamic properties of diopside and jadeite melts by computer simulation studies abstract we report the results of ion dynamics computer experiments on two liquid silicates of geochemical interest in which the charge characteristics of the cations other than si cause differences in the extent to which the integrity of the open network structure of liquid sio 2 is maintained the two cases are jadeite the transport behavior of which was described in an earlier paper and diopside the focus of the study is on the pressure density relations in diopside mg is found to exist in four fold coordination up to pressures above 50 kbar at 4000 k while ca like na in jadeite has a large and poorly defined coordination likewise ca in diopside is the most mobile element at low pressures but becomes jammed at high pressures the activation volume corresponds to the ion volume both melts show highly similar pressure density relations the compressibility of jadeite becoming larger than that of diopside only below 30 kbar the calculated values fall between the measured value for diopside and the estimated value of jadeite but show the same form of pressure dependence by taking advantage of the low probability of cavitation in simulated systems we carry the simulations into the expanded negative pressure region to show how the increasing compressibility at low pressures is a reflection of the impending mechanical stability limit which is found at weakly negative pressures at the temperatures of these simulations

how do radiolarian sediment assemblages represent surface ocean ecology in the central equatorial pacific ever since q mode factor analysis has been applied to microfossil data investigators have attempted to determine whether statistical groupings of species in deep sea sediments are ecologically meaningful we address this question for radiolaria using living death and sediment assemblages from the equatorial pacific of the seven sediment assemblages identified from a basin wide analysis four are important in the tropics eastern boundary and transitional sediment assemblages identify ecological environments similar to living assemblages the western pacific sediment assemblage does not appear to represent a natural grouping of species the dominant tropical sediment end member represents a combination of warm water species from subtropical and western pacific environments of the two the predominant signal in tropical sediments is that of the western pacific the implication of a sediment bias toward warm water species may be due to the lack of an important cold water indicator species lophophaena hispida in the sediment analysis

electrical conductivity and partial melting of mafic rocks under pressure we demonstrate the importance of electric conductivity measurements of partially molten mafic rocks by examining of oman gabbro karelia olivinite ronda and spitzbergen peridotites the electrical conductivities of these rocks were estimated using the impedance spectroscopy at temperatures between 800 c and 1450 c and at pressures between 0 3 and 2 gpa in experiments performed in a piston cylinder apparatus at temperatures below and above melting samples were equilibrated during durations on the order of 200 h our results show that a jump in electrical conductivity can be correlated with the temperature range slightly above the solidus due to the delayed formation of an interconnected melt phase thin sections of quenched samples were used to estimate volume fractions and chemical compositions of the partial melts the increase of the electrical conductivity compares well with the connectivity of melt in partially molten samples above the solidus the electrical conductivity increases by 1 to 2 orders of magnitude in comparison with the conductivity of non melted rock below solidus when a complete melt connectivity is established the charge transport follows the network of the formed melt films at grain boundaries durations of up to 200 h are required in order to reach a steady state electrical resistance in a partially molten rock sample the experimental results were compared with the conductivity data obtained from magnetotelluric mt and electromagnetic em measurements in the northern part of the mid atlantic ridge where a series of axial magma chambers amc are presumably located there is good agreement between the measured electric conductivity of gabbroic samples with a melt fraction of 10 to 13 vol and the conductivity estimated at amc beneath the central part of reykjanes ridge as well as between the conductivity of partially molten peridotites and the source zone beneath the mid atlantic ridge at 60 km

spatial distribution pattern of living polycystine radiolarian taxa baseline study for paleoenvironmental reconstructions in the southern ocean atlantic sector the horizontal and vertical distribution of living polycystine radiolarian taxa was investigated at seven locations on a n s transect between the antarctic zone 54 s in the southern ocean and the subtropical zone 30 s in the southeastern south atlantic during austral autumn four to five depth intervals from 0 to 1000 m depth were sampled with 55 m mesh opening closing nets in combination with a hydrographic ctd survey a factor analysis for the delineation of specific assemblages and the relation between different taxa and taxa groups resulted in eight factors of which five represent surface and subsurface factors and three deep water factors the spatial distribution pattern of the factors shows that distinct radiolarian assemblages are closely related to water depth distribution of water masses hydrographic boundaries such as frontal systems and nutrients this documents that the distribution of individual radiolarian assemblages is controlled by specific hydrographic conditions and water depth and allows the definition and consolidation of the autecological demands these data are crucial for the paleoenvironmental interpretation of fossil polycystine radiolarian assemblages the comparison of living polycystine radiolarian taxa with those preserved in surface sediments shows general similarities this study includes the first documentation on the distribution of living cycladophora davisiana in circumpolar deep water and supports previous studies stating that c davisiana also lives in deep water masses

melting of morb at core mantle boundary abstract we investigated the melting properties of natural mid ocean ridge basalt morb up to core mantle boundary cmb pressures using laser heated diamond anvil cell textural and chemical characterizations of quenched samples were performed by analytical transmission electron microscopy we used in situ x ray diffraction primarily for phase identification whereas our melting criterion based on laser power versus temperature plateau combined with textural analysis of recovered solidus and subsolidus samples is accurate and unambiguous at cmb pressure 135 gpa the morb solidus temperature is 3970 150 k quenched melt textures observed in recovered samples indicate that casio3 perovskite capv is the liquidus phase in the entire pressure range up to cmb the partial melt composition derived from the central melt pool is enriched in feo which suggests that such melt pockets may be gravitationally stable at the core mantle boundary

a numerical framework for infinite slope stability analysis under transient unsaturated seepage conditions abstract this paper presents a simple numerical framework for infinite slope stability analysis under transient unsaturated seepage conditions the advantage of the proposed framework from the practical point of view is to predict the variability in stability of partially saturated slope along with rainfall data moreover the presented framework is adaptable to different types of soil water characteristic curve swcc models hydraulic boundary conditions and heterogeneity in soil properties a series of stability analyses for hypothetical hillslopes under various conditions was performed to scrutinize the potential failure mechanisms induced by rainfall the examined factors include the soil texture rainfall intensity heterogeneity in soil properties and hydraulic boundary conditions also four widely used swcc models were applied to assess the influence of this component the swcc model was demonstrated to strongly dominate the results of the infinite slope stability analysis under transient unsaturated seepage conditions for homogeneous hillslopes with a fixed water table when the rainfall intensity q equals the saturated hydraulic conductivity ks slope failure was expected to occur after a short time of rainfall with a relatively shallow slip depth in contrast for heterogeneous hillslopes or hillslopes with impermeable bedrock the failure could take place when q is less than ks and the potential failure surface was close to the discontinuity interface or at the bottom of the hillslope finally three case studies of landslides documented in literature were utilized to demonstrate the predictability of the proposed framework in practical applications

snowball earth a thin ice solution with flowing sea glaciers 1 the late neoproterozoic era 600 800 myr ago was marked by at least two intervals of widespread cold that left glacial deposits at low paleolatitudes both snowball solutions with global ice cover and slushball solutions with ice free tropical oceans have been proposed to explain the paleomagnetic data the snowball model is best able to explain the auxiliary geological evidence particularly the existence of cap carbonates but it implies drastic survival pressure on the photosynthetic biota if the ice cover was everywhere thick enough to prevent sunlight from reaching the underlying ocean a thin ice solution that avoids this problem has been proposed but is thought to be inconsistent with realistic optical properties of sea ice and with the equatorward flow of sea glaciers here we use a coupled energy balance climate sea glacier model to argue that these apparent difficulties can be overcome and that thin tropical ice may have prevailed during these remarkable glacial episodes we also suggest that 1 some processes beyond the scope of zonal mean energy balance models may significantly affect the solutions and 2 thin ice could have prevailed on low latitude seas or large lakes protected from large scale sea glacier flow by surrounding land even if most of the earth was in a hard snowball state

magma crystallization and viscosity a study of molten basalts from the piton de la fournaise volcano la reunion island abstract the viscosity of three molten basalts produced by fusion of lavas issued from different eruptions of the piton de la fournaise la reunion island has been investigated above the liquidus and at high degrees of supercooling for all basalts crystallization took place rapidly above the glass transition range which made static measurements problematic because of time dependent non newtonian rheology by contrast reproducible results were obtained in dynamic measurements made at a constant heating rate of 5 k mn partial crystallization resulted in strong viscosity increases which were primarily due to the presence of solid inclusions comparisons with phase equilibria experiments performed for the same samples at higher temperatures show that crystallization takes place differently below the liquidus and at strong degrees of supercooling as recently described for simpler systems these differences in nucleation and growth are controlled by the relative mobilities of the cations diffusing within the melt to attach themselves to crystal melt interfaces a consequence is that the composition evolution of the residual melt differs in equilibrium and irreversible crystallization in turn this contrast induces opposite viscosity variations for the residual melt

phase transition and density of subducted morb crust in the lower mantle abstract phase relations mineral chemistry and density of a natural mid oceanic ridge basalt morb composition were investigated up to 134 gpa and 2300 k by a combination of in situ x ray diffraction measurements and chemical analyses using transmission electron microscope tem results demonstrate that the morb composition consists of mgsio 3 rich perovskite stishovite casio 3 perovskite and cafe 2 o 4 type al phase in the upper part of the lower mantle the most abundant mineral of mgsio 3 rich perovskite undergoes phase transition to a cairo 3 type post perovskite phase above 110 gpa and 2500 k post perovskite phase is similar in composition to perovskite except considerably high na 2 o content stishovite transforms to cacl 2 type sio 2 phase above 62 gpa and 2000 k and further to pbo 2 type phase above 110 gpa pbo 2 type sio 2 phase includes large amount of al 2 o 3 which significantly expands its stability relative to cacl 2 type phase phase transition of casio 3 perovskite from tetragonal to cubic was also observed with increasing temperature cafe 2 o 4 type al phase is stable to the bottom of the mantle the density of morb crust was calculated using volume data combining with measured chemical compositions and calculated mineral proportions the former morb crust is denser than the average lower mantle at all depths greater than 720 km contrary to earlier predictions the subducted basaltic crust may have accumulated at the base of the mantle

a radiolarian based modern analogue dataset for palaeoenvironmental reconstructions in the southwest pacific abstract radiolarian species relative abundances have been estimated for a suite of 88 surface sediment samples obtained from a broad area of the southwest pacific southern ocean bounded by 10 s to 65 s in latitude and 145 e to 170 w in longitude this allowed the documentation of a long environmental gradient 28 8 to 1 4 c for mean annual sea surface temperature sst and covered the most important surface oceanographic features in the area including the subtropical stf subantarctic saf and antarctic polar apf fronts the most abundant species in the dataset show strong relationships to surface hydrography examples are antarctissa spp 5 abundance isoline is a good indicator for the average position of the saf colonials 5 isoline approximates the average location of the tasman front between new zealand and australia dictyocoryne profunda and tetrapyle octacantha essentially absent in subantarctic antarctic waters and documenting warm water connections to higher latitudes being present in the tasmanian retroflection region and or on the campbell plateau the factor analysis model with a calibration error of 1 3 c was based on 93 taxa of the 243 taxa recognised in this study and 7 factors assemblages which explained 87 4 of the total information contained in the dataset the first five assemblages are readily interpreted in terms of water masses oceanographic fronts and regions subtropical water tasman front factor 1 circumpolar surface water factor 2 equatorial pacific factor 3 subantarctic water campbell plateau factor 4 and as a subfactor for subtropical water factor 5 a canonical correspondence analysis identified sea surface temperature as the main environmental explanatory variable for samples with sst 7 c 28 c due to the elevated nitrate concentrations in high southern latitude surface waters nitrate concentration is the main explanatory variable when all samples are considered in a companion paper this modern analogue dataset has been applied to relative abundance data from sediment core y9 in order to reconstruct the sst changes over the last 160 ka at the easternmost boundary of the campbell plateau east of new zealand

infinite slope stability under steady unsaturated seepage conditions 1 we present a generalized framework for the stability of infinite slopes under steady unsaturated seepage conditions the analytical framework allows the water table to be located at any depth below the ground surface and variation of soil suction and moisture content above the water table under steady infiltration conditions the framework also explicitly considers the effect of weathering and porosity increase near the ground surface on changes in the friction angle of the soil the factor of safety is conceptualized as a function of the depth within the vadose zone and can be reduced to the classical analytical solution for subaerial infinite slopes in the saturated zone slope stability analyses with hypothetical sandy and silty soils are conducted to illustrate the effectiveness of the framework these analyses indicate that for hillslopes of both sandy and silty soils failure can occur above the water table under steady infiltration conditions which is consistent with some field observations that cannot be predicted by the classical infinite slope theory a case study of shallow slope failures of sandy colluvium on steep coastal hillslopes near seattle washington is presented to examine the predictive utility of the proposed framework

root tensile strength relationships and their slope stability implications of three shrub species in the northern apennines italy abstract the role of root strength is important in stabilising steep hillslopes which are seasonally affected by storm induced shallow landslides in the italian apennines steep 25 40 slopes underlain by mudstone are generally stable if they are covered by shrubs whose roots anchor into the soil mantle to quantify the mechanical reinforcement of roots to soil the root tensile breaking force and the root tensile strength of three autochthonous shrub species commonly growing on stiff clay soils of the northern italian apennines rosa canina l inula viscosa l and spartium junceum l were measured by means of field and laboratory tests for each test approximately 150 root specimens were used the tensile force increases with increasing root diameter following a second order polynomial regression curve the tensile strength decreases with increasing root diameter following a power law curve the field in situ tensile force required to break a root is always smaller than that obtained from laboratory tests for the same root diameter although their difference becomes negligible if the root diameter is smaller than 5 mm the influence of root tensile strength on soil shear strength was verified based on the infinite slope stability model the root reinforcement was calculated using the number and mean diameter of roots the factor of safety was calculated for three different soil thickness values 0 1 0 3 and 0 6 m and topographic slopes between 10 and 45 the factor of safety for the combination of 0 6 m soil thickness slopes smaller than 30 and vegetation of i viscosa l or s junceum l is always larger than 1 if a slope is steeper the factor of safety may be smaller than 1 for i viscosa l although it is still larger than 1 for s junceum l in the stiff clayey areas of the northern italian apennines i viscosa l mainly colonizes fan cone taluses and stabilises these zones up to a topographic gradient

distribution of polycystine radiolarians in the northern south china sea in september 2005 we studied the distribution of polycystine radiolarians in the northern south china sea scs in september 2005 in order to document the relation between radiolarian assemblages and environmental parameters vertical plankton tows were collected at depth intervals from 0 to 250 m at thirteen stations using a closing net 62 pm mesh the highest abundance of polycystine radiolarians generally occurred at depths of 0 75 m i e above the chlorophyll a maximum and thermocline in contrast the maximum polycystine abundance occurred below the chlorophyll a maximum at station e105 75 150 m possibly as a result of down welling of warm waters and the maximum fell within the chlorophyll a maximum at station e702 as a result of upwelling of intermediate cold waters during our sampling period the southwestern monsoon caused upwelling in the northern scs the taiwan bank region as shown by the high abundance of tetrapyle octacantha acanthodesimia vinculata cladococcus cervicoris octopyle octospinosa spongaster tetras streblacantha circumtexta and spongotrochus glacialis the patterns of distribution and the abundances of the species botryocyrtis scutum pterocorys hertwigii collosphaera tuberosa and didymocyrtis tetrathalamus tetrathalamus suggested that western equatorial pacific waters did not yet influence the region at the time of sampling the first two species were dominant in the northern scs during our sampling the species cornutella profunda and cyrtopera laguncula were rare at depths of 150 250 m in the tropical region of the scs and assemblages in northern and southern scs were very similar the relative abundance of b scutum and p hertwigii is an indicator for seasonal changes in monsoonal circulation c 2008 elsevier b v all rights reserved

sea surface temperature changes in the northeastern pacific ocean during the past 20 000 years and their relationship to climate change in northwestern north america abstract modern ocean atmosphere interactions in the northeastern pacific ocean have a significant effect on the climate of the west coast of north america we present radiolarian microfossil based temperature reconstructions for the eastern north pacific spanning the past 20 000 yr to examine possible correlations and linkages between continental climate change and changes in sea surface temperature sst in the northeastern pacific ocean on millennial time scales the reconstructions indicate that the regional pattern of ocean circulation off the west coast of north america was further south 15 000 cal yr b p than it is today and reached its present location 13 000 cal yr b p the north pacific drift and transition zone were further south as a result of a more southerly north pacific high pressure cell prior to 13 000 cal yr b p while two continental paleoclimate records from northwestern north america show regional differences they also can be correlated to the sst changes a coastal site at 48 n shows similar patterns in summer temperatures as observed in offshore marine records of ssts however an inland continental record seems to reflect more regional scale changes in sea surface conditions showing a thermal maximum centered at 10 000 cal yr b p which is observed in the marine transect south of 42 n we conclude based on the pattern of oceanographic change as reflected in radiolarian assemblages that changes in the past latitudinal position of the north pacific drift played a significant role in controlling continental climate immediately to its east as it does in the present environment we also conclude that during the past 20 000 yr much of the evolution of oceanographic change is related to the migration of the atmospheric pressure cells the north pacific high and aleutian low of the northeastern pacific

radiolarian based transfer functions for estimating mean surface ocean temperatures and seasonal range new radiolarian based transfer functions to estimate sea surface temperature sst and seasonal range are presented the transfer fonctions are based on the approach originated by imbrie and kipp 1971 the transfer functions differ from previous studies in the following three important ways 1 extensions to q mode factor analysis provide an objective method to cull species in the very diverse radiolarian population 2 a log transform of the relative abundance data is used to normalize the species percent data and 3 rather than writing equations for specific seasons which are not independent data sets statistically independent equations are developed to predict mean annual sea surface temperatures as well as seasonal temperature range one hundred and seventy surface sediment samples from the pacific ocean are used to generate the sst and season temperature range transfer functions all samples were counted using a standardized radiolarian taxonomy forty one radiolarian species were used in the final regression equation q mode factor analysis of this data set identified seven assemblages these assemblages the tropical transitional antarctic bering sea western pacific central gyre and eastern boundary current are named for the oceanographic regions where these assemblages are important the seven assemblages are used in a regression analysis to predict sst and seasonal temperature range the standard error of estimates for both mean sst and seasonal temperature range is 1 6 c comparison between radiolarian based ssts and sst estimates from alkenone uk37 in a 20 000 year long record from the northeast pacific shows excellent agreement comparison of mean sst estimates for the last glacial maximum lgm based on radiolarian and foraminifera in 10 eastern equatorial pacific also show excellent concordance these new lgm estimates suggest that the original climate long range investigation mapping and prediction climap reconstruction for this region underestimated surface ocean cooling

landslide displacement prediction based on multi source data fusion and sensitivity states abstract owing to the complexity of the coupling relationship between multiple external triggering factors and the internal sensitivity state of landslides it is difficult to accurately predict the displacement response of landslides to triggering factors using existing methods to overcome this setback two new concepts namely the trend sequence and sensitivity states were introduced to quantificationally characterize landslide displacement caused by external factors and the landslide internal states respectively the support vector regression method was used to predict the trend sequence while the long short term memory neural network was employed to predict the sensitivity state thereafter by fusing the predicted trend sequence and the sensitivity state a non linear model for landslide displacement prediction was proposed moreover with the baishuihe landslide located in the three gorges reservoir area as a case study the proposed model was evaluated and validated using a large quantity of rainfall reservoir water level and displacement monitoring data spanning a period of over 11 years based on the results obtained the performance of the proposed model with respect to landslide displacement prediction was satisfactory furthermore compared with three existing traditional prediction models of landslide displacement the proposed model achieved a higher accuracy therefore this study is helpful because it provides new insights that can be used to develop deep data mining approaches for landslide displacement prediction

holocene variability of the kuroshio current in the okinawa trough northwestern pacific ocean abstract cores 255 and b 3gc from the southern and northern okinawa trough respectively were studied for determining the variability of the kuroshio current on centennial scales during the holocene based on detailed ams 14 c dates stable isotope and planktonic foraminiferal distribution the main flow of the kuroshio current was inferred to re enter the okinawa trough at 7 3 calendar cal kyr bp leading to abrupt changes in sedimentation rate remarkably increased abundance of the kuroshio current indicator pulleniatina obliquiloculata increased sea surface temperature sst and depth of thermocline dot during 4 6 2 7 cal kyr bp the abundance of p obliquiloculata sharply decreased corresponding to a decreases in sst and dot implying that the influence of the kuroshio current weakened at that time possibly as a result of the intensified winter monsoon significantly the kuroshio current proxies e g the difference in sst between the southern and northern okinawa trough display periodicities of 1500 yr and 700 800 yr ascribed to the second harmonic of the 1500 yr cycle in oceanic thermohaline circulation during the holocene the holocene events at 0 6 1 7 3 3 4 6 5 9 8 1 9 4 cal kyr bp in the okinawa trough appear to be the most recent manifestation of the millennial scale climate cycle recorded in the north atlantic arabian sea marine sediment cores and greenland ice cores suggesting global climatic tele connections

melting relations and the equation of state of magmas at high pressure application to geodynamics abstract the melting relations of mantle minerals together with the physical properties of silicate melts at high pressure have been extensively studied during the previous decade the melting relation of minerals and the equation of state of magmas are important properties for deducing the formation and differentiation of the earth and especially for elucidating the nature of the terrestrial magma ocean and the subsequent formation of the core mantle and crust of the earth because these magmas are compressible we expect that the olivine magma density crossover played an important role in controlling the geochemical characteristics of the primitive mantle after the magma ocean stage of the primordial earth the crystal magma density crossover is also expected to occur at the base of the upper mantle in the presence of volatiles and at the base of the lower mantle in the earth today the existence of dense magmas is consistent with seismological observations of low velocity regions existing at the base of the upper mantle beneath japan europe and the usa and the ultralow velocity zone ulvz at the core mantle boundary of the present earth

ponded melt at the boundary between the lithosphere and asthenosphere the boundary between earth s rigid lithosphere and ductile asthenosphere is marked by a seismic discontinuity laboratory experiments on basaltic magmas show that melts should pond at pressures that correspond to the lithosphere asthenosphere boundary thus magma ponding could explain the observed seismic discontinuity

depth related radiolarian assemblage in the water column and surface sediments of the japan sea plankton tows and surface sediments from the japan sea a marginal sea of the northwestern pacific were examined to study the depth distribution of modern radiolarians the depth distribution patterns between the living assemblage in the water column and the thanatocoenose in surface sediments are similar to each other indicating that the depth related assemblage in sediments is closely related to the living depths of major species four clear restrictions of many species to discrete depth zones are recognized in the water column from the surface down to 2000 m 1 upper subsurface water species which are abundant from 40 to 120 m larcopyle butschlii juvenile form spirocyrtis subscalaris spongodiscus resurgens and lipmanella virchowii 2 lower subsurface water species which are abundant from 40 to 300 m larcopyle butschlii adult form ceratocyrtis histricosa and spongotrochus glacialis 3 intermediate water species which have population maxima from 160 to 300 m ceratospyris borealis and 4 deep water species which have maxima between 1000 and 2000 m cycladophora davisiana and actinomma boreale only a few specimens of a boreale were found in the water column ranging from 1000 to 2000 m depth although this is a dominant species in surface sediments from depths below 2000 m of which the dominance increases with water depth a boreale may live mainly in the bottom water cycladophora davisiana and a boreale which characterize the japan sea deep assemblage are naturally shallow or intermediate dwellers in other oceans on the other hand the typical deep dwellers e g cornutella profunda cyrtopera languncula and peripyramis circumtexta of other oceans have not been found in the japan sea such a peculiar deep assemblage is a result of the deep circulation system in the japan sea and the shallow depths of the sills around it

first principles computation of mantle materials in crystalline and amorphous phases abstract first principles methods based on density functional theory are used extensively in the investigation of the behavior and properties of mantle materials over broad ranges of pressure temperature and composition that are relevant a review of computational results reported during the last couple of decades shows that essentially all properties including structure phase transition equation of state thermodynamics elasticity alloying conductivity defects interfaces diffusivity viscosity and melting have been calculated from first principles using mgo the second most abundant oxide of earth s mantle as a primary example and considering many other mantle materials in their crystalline and amorphous phases we have found that most properties are strongly pressure dependent sometimes varying non monotonically and anomalously with the effects of temperature being systematically suppressed with compression the overall agreement with the available experimental data is excellent it is remarkable that the early calculated results such as shear wave velocities of two key phases mgo and mgsio 3 perovskite were subsequently reproduced by experimentation covering almost the entire mantle pressure regime as covered in some detail the defect formation and migration enthalpies of key mantle materials increase with pressure the predicted trend is that partial mgo schottky defects are energetically most favorable in mg silicates but their formation enthalpies are high so the diffusion in the mantle is likely to be in the extrinsic regime preliminary results on mgo and forsterite hint that the grain boundaries can accommodate point defects including impurities and enhance diffusion rates at all pressures the structures are highly distorted in the close vicinity of the defects and at the interface with excess space recent simulations of mgo sio 2 binary and other silicate melts have found that the melt self diffusion and viscosity vary by several orders of magnitudes with pressure temperature and composition the predicted high compressibility and complex dynamical behavior can be associated with structural changes involving non bridging oxygen oxygen tri clusters si o pentahedra etc occurring on compression we envision future prospect for massively parallel distributed computing of unprecedented magnitude and scope in the study of relevant materials for earth super earth and other planets a renewed computational theme perhaps should be the first principles simulations of large systems with long runs that are necessary to explore realistic natural compositions polycrystalline phases multi component melts crystal melt interfaces trace element partitioning etc

slope stability analysis under unsaturated conditions case studies of rainfall induced failure of cut slopes abstract we present two case studies of rainfall induced failure of engineered slopes the traditional limit equilibrium and finite element methods are expanded to unsaturated conditions using a generalized effective stress framework because effective stress is represented by the suction stress characteristic curve sscc and the sscc and the soil water retention curve swrc have been unified with the same set of hydromechanical parameters the expanded framework requires only three hydromechanical parameters in addition to those used for saturated slope stability analysis using recorded rainfall measured shear strength parameters and the swrc and site geology transient slope stability analyses are conducted to reconstruct the failure events we find that despite differences in slope geometry hydromechanical properties shear strength and rainfall history the actual failure occurred when the simulated factor of safety approaches its minimum below 1 0 it is shown that the hydromechanical framework under the suction stress based effective stress can reconcile the observed timing of failure

earth pressure profiles in unsaturated soils under transient flow abstract assessing the effect of heavy precipitations on earthen structures warrants studying earth pressure profiles in unsaturated soils under transient flow this paper presents an analytical framework to determine the changes in at rest active and passive earth pressures of unsaturated soils due to transient infiltration a closed from solution for one dimensional transient unsaturated flow is incorporated into a suction stress based representation of effective stress to obtain the tempo spatial changes in matric suction suction stress and effective stress the profiles are used to extend hooke s law and rankine s earth pressure theory leading to the determination of unsaturated at rest active and passive earth pressures at different depths and times the analytical framework is used in a set of parametric study for three hypothetical soils of clay silt and fine sand the results reveal the nonlinear characteristics of earth pressure profiles during transient infiltration for all three soils whereas a linear trend is generally seen under steady state flow conditions further the depth of tension crack under transient flow is different than the one resulted from steady state analysis a transition from tension to compression stress is seen near the soil surface this observation can be particularly important for fine grained soils implying that the depth of tension zone is affected by suction stress changes findings of this study can contribute toward a better understanding of service state behavior and forensic studies of earthen structures under heavy precipitations

molecular dynamics simulation of structures bulk moduli and volume thermal expansivities of silicate liquids in the system cao mgo al2o3 sio2 materials in the system cao mgo al2o3 sio2 are important constituents of the earth s lower crust and mantle silicate liquids in this geophysically important system have been studied using molecular dynamics md simulation with an empirical interatomic potential cmas94 md simulations are quite satisfactory in reproducing well the observed structure and pressure volume temperature equation of state parameters of molten enstatite mgsio3 wollastonite casio3 diopside camgsi2o6 and anorthite caal2si2o8 at 1900 k and 0 gpa however the md simulated bulk modulus of molten forsterite mg2sio4 at 2300 k and 0 gpa k0 18 0 6 gpa is found to be much smaller than the value k0 60 gpa at similar temperature and pressure conditions estimated previously based on melting curve analyses of forsterite in an attempt to investigate the possible occurrence of the density inversion between magmatic liquids and residual crystals in the upper mantle conditions as proposed by stolper et al 1981 we have further applied the md technique with the cmas94 potential to the diopside system at 1900 k as an example and have found that the density inversion between crystal and liquid in this system actually occurs at approximately 11 gpa

paleoenvironmental changes in the northern area of the east china sea during the past 42 000 years a 33 65 m long images md982195 core with very high sedimentation rate ca 80 cm kyr retrieved from the northern part of the east china sea was analyzed at 10 cm intervals about 125 years for oxygen carbon isotope of globigerinoides ruber sensu stricto sea surface temperature sst from alkenones u37 k and principal component analysis of planktonic foraminiferal assemblage the general pattern of the 18o curve resembling the alkenone sst curve is similar to the standard open ocean oxygen isotope curve it reveals many light 18o peaks apparently corresponding to dansgaard oeschger d o cycles as observed in greenland ice cores for the last 42 ka the alkenone sst at the core top is 24 c which is close to the modern annual mean sst around the core site on the other hand sst during the last glacial maximum lgm was about 5 c lower than that in the present day alkenone derived sst does not correlate with the light negative 18o peaks corresponding to the d o cycles the oxygen isotope ratios for the surface waters based on oxygen isotopes of g ruber and alkenone ssts indicate approximately 1 0 increase on average during the lgm and many light peaks at the warm d o events this suggests that fresh water was supplied to the core site during these events the meandering of the westerlies during the cold and warm d o cycles would have caused an atmospheric tele connection between east asia and greenland the core was divided into four periods based on q mode factor analysis of the planktonic foraminiferal assemblage i e 1 a strong upwelling period from 42 to 24 ka indicated by abundant occurrence of globigerina bulloides 2 a cold and low salinity water mass period from 24 to 14 ka suggested by increase of neogloboquadrina pachyderma neogloboquadrina incompta and globigerina quinqueloba 3 a transitional period from cold to warm water masses from 14 to 8 ka as indicated by the increase of warm water species such as pulleniatina obliquiloculata and globigerinoides ruber and 4 the present day warm kuroshio current condition after 8 ka the kuroshio current flowed into the ecs since the last 42 ka and weakened during the last glacial maximum lgm due to the expansion of the coastal water in the northern part of the ecs

foraminiferal faunal estimates of paleotemperature circumventing the no analog problem yields cool ice age tropics the sensitivity of the tropics to climate change particularly the amplitude of glacial to interglacial changes in sea surface temperature sst is one of the great controversies in paleoclimatology here we reassess faunal estimates of ice age ssts focusing on the problem of no analog planktonic foraminiferal assemblages in the equatorial oceans that confounds both classical transfer function and modern analog methods a new calibration strategy developed here which uses past variability of species to define robust faunal assemblages solves the no analog problem and reveals ice age cooling of 5 o to 6oc in the equatorial current systems of the atlantic and eastern pacific oceans classical transfer functions underestimated temperature changes in some areas of the tropical oceans because core top assemblages misrepresented the ice age faunal assemblages our finding is consistent with some geochemical estimates and model predictions of greater ice age cooling in the tropics than was inferred by climate long range investigation mapping and prediction climap 1981 and thus may help to resolve a long standing controversy our new foraminiferal transfer function suggests that such cooling was limited to the equatorial current systems however and supports climap s inference of stability of the subtropical gyre centers

density of basaltic melt at high pressure and stability of the melt at the base of the lower mantle abstract we made density measurements of model morb and picritic melts up to about 15 gpa using the floating diamond method the compression behavior of the melts is fitted by the vinet equation of state and extrapolated to higher pressure a density crossover between the morb melt and the mantle peridotite is suggested at the base of the lower mantle thus the ultra low velocity zone in the d layer may be explained by the existence of gravitationally stabilized basaltic melt formed by melting of the accumulated slab materials this region might become unstable due to progressive melting of slab materials and or supply of volatiles

melting of subducted basalt at the core mantle boundary the geological materials in earth9s lowermost mantle control the characteristics and interpretation of seismic ultra low velocity zones at the base of the core mantle boundary partial melting of the bulk lower mantle is often advocated as the cause but this does not explain the nonubiquitous character of these regional seismic features we explored the melting properties of mid oceanic ridge basalt morb which can reach the lowermost mantle after subduction of oceanic crust at a pressure representative of the core mantle boundary 135 gigapascals the onset of melting occurs at 3800 kelvin which is 350 kelvin below the mantle solidus the sio2 rich liquid generated either remains trapped in the morb material or solidifies after reacting with the surrounding mgo rich mantle remixing subducted morb with the lowermost mantle

prediction of silicate melt viscosity from electrical conductivity a model and its geophysical implications 1 our knowledge of magma dynamics would be improved if geophysical data could be used to infer rheological constraints in melt bearing zones geophysical images of the earth s interior provide frozen snapshots of a dynamical system however knowledge of a rheological parameter such as viscosity would constrain the time dependent dynamics of melt bearing zones we propose a model that relates melt viscosity to electrical conductivity for naturally occurring melt compositions including h2o and temperature based on laboratory measurements of melt conductivity and viscosity our model provides a rheological dimension to the interpretation of electromagnetic anomalies caused by melt and partially molten rocks melt fraction 0 7