global and local influences on the chemical composition of snowfall at dye 3 greenland the record between 10 ka b p and 40 ka b p abstract wisconsin age ice from dye 3 greenland shows a number of 18o level changes which indicate the occurrence of rapid climate transitions in order to study the effect of climate change on geochemical fluxes we have selected several of these transitions for chemical analysis at each transition we have measured chloride nitrate and sulfate concentrations with 5 cm depth resolution all three anionic species show significant variations which correlate with the measured 18o shifts in general periods of high 18o warm periods have lower anion concentrations than adjacent periods of low 18o cold periods however the relative concentration shifts are not the same for all species indicating that the concentration variations cannot be caused only by changes in snow accumulation rate acting on a constant anion flux in addition to these rapid concentration changes over the last 40 ka slower secular variations in baseline concentrations also occurred baseline chloride and sulfate concentrations reached maxima near time of maximum ice volume baseline nitrate on the other hand remained relatively constant until near the end of the glaciation when its concentration rose if a constant sulfate flux is assumed the measured sulfate concentrations imply a dependence of snow accumulation rate on 18o for the wisconsin which is similar to that presently observed in greenland the sulfate concentrations would then suggest that wisconsin snowfall rates were at times as much as eight times lower than today

anisotropy of compressional wave velocities complex electrical resistivity and magnetic susceptibility of mylonites from the deeper crust and their relation to the rock fabric abstract laboratory measurements of compressional wave velocities v p complex electrical resistivity and magnetic susceptibility have been carried out on a mylonitic clinopyroxene amphibolite mca and an epidote muscovite quartz ultramylonite mqu from the ivrea zone both mylonites exhibit significant anisotropies that are related to the rock fabric at low pressure of about 50 mpa the anisotropy of v p for the mca and mqu is 17 and 34 respectively it is due to oriented microcracks intragranular transgranular grain boundary cracks and cleavage cracks in addition to preferred orientation of anisotropic rock forming minerals at high pressure 600 mpa where most of the cracks are closed a residual anisotropy of about 10 and 12 respectively is observed that is mainly controlled by preferred orientations of mineral constituents the anisotropies of the complex electrical resistivity measured with an electrolyte tap water at 0 1 mpa are 40 and 36 for the mca and mqu whereas at 80 mpa these values increase to 44 for both samples in contrast measured with an electrolyte of 0 1 m nacl solution the resistivity is lower and gives anisotropies of 71 mca and 63 mqu at 0 1 mpa the anisotropies of the magnetic susceptibility ams are about 27 mca and 14 mqu for both mylonites the axes of the ams ellipsoid coincide with the macroscopic fabric elements where the main axis of magnetic susceptibility k max lies approximately parallel to the lineation an intercorrelation of the different physical properties in terms of rock composition and anisotropic rock fabric is difficult nevertheless the laboratory determination of anisotropic in situ physical properties provide more objective data for the modelling of in situ crustal conditions

neogene evaporites in desert volcanic environments atacama desert northern chile the upper miocene and pliocene evaporite deposits of the atacama desert of northern chile hilaricos and soledad formations are among the few nonmarine evaporites in which aridity not only formed the deposits but has also preserved them almost unaltered under near surface conditions these deposits are largely composed of displacive ca sulphate and halite together with minor amounts of glauberite thenardite and polyhalite however at the base and top of these deposits there are also beds of gypsum crystal pseudomorphs that originally formed as free growth forms within shallow brine bodies rather than as displacive sediments the halite is present as interstitial cement displacive cubes and shallow water bottom growth chevron crusts most of the calcium sulphate is presently anhydrite pseudomorphous after gypsum that was the primary depositional sulphate mineral the secondary anhydrite formed under early diagenetic conditions after slight burial some metres resulting from the effect of strongly evolved pore brines the anhydrite has been preserved without rehydration during late diagenetic and exhumation stages on account of the arid environment of the atacama desert both the hilaricos and the soledad formations contain geochemical markers indicating that these neogene evaporites had a largely non marine origin bromine content in the halite is very low few p p m indicating neither a sedimentological relation with sea water nor the likelihood of direct recycling of prior marine halites moreover the d 34 s of sulphates 4ae5 to 9 also reflects a non marine origin with a strong volcanic influence although some recycling of mesozoic marine sulphates cannot be ruled out d 34 s of dissolved sulphate from hot springs and streams in the area commonly displays positive values 2 to 10 leaching of oxidized sulphur and chlorine compounds from volcanoes and epithermal ore bodies very common in the associated drainage areas have been the main contribution to the accumulation of evaporites the sedimentary and diagenetic evolution of the hilaricos and soledad evaporites based on lithofacies analysis provides information about the palaeohydrological conditions in the central depression of northern chile during the neogene in addition the diagenesis and exhumation history of these evaporites confirms the persistence of strongly arid conditions from late miocene until the present a final phase of tectonism took place permitting the internal drainage to change and open to the sea resulting in dissolution and removal of a significant portion of these deposits despite the extensive dissolution the remaining evaporites have undergone little late exhumational hydration

crustal and upper mantle electrical conductivity structure in southern scotland summary magnetotelluric measurements were made during 1978 79 at nine sites on a linear traverse across south scotland extending from kinloch rannoch in the highlands to borthwickbrae in the southern uplands both one and two dimensional modelling of the apparent resistivities and phases indicate the existence of a low resisitivity 75 am zone at 20 90 km depth beneath the southern uplands rising closer to the surface beneath the midland valley to the north a zone of slightly higher resistivity 500s2m but still relatively conducting compared to the surrounding structure is shown to exist beneath the highlands the real part of the ratio of vertical to horizontal magnetic fields is shown to be suitably modelled by a combination of induction and conduction

structure of the crust in the vicinity of the banggong nujiang suture in central tibet from indepth magnetotelluric data 1 magnetotelluric data from a 150 km long profile crossing the banggong nujiang suture bns central tibet acquired as part of the international deep profiling of tibet and the himalaya indepth project have been examined for crustal and upper mantle structure strike and dimensionality analyses demonstrate that regional scale electrical structures are two dimensional and oriented approximately parallel to surface geological strike as seen elsewhere in tibet the double thickness crust is generally characterized by resistive upper crust hundreds to thousands of ohm meters overlying conductive middle and lower crust tens to hundreds of ohm meters but in detail there are lateral variations at all levels regionally a northward transition from thick 45 km to thin 15 km resistive upper crust coincides with 1 the surface trace of the bns 2 a prominent strand of the karakorum jiali fault system 3 northward decrease in upper mantle seismic velocities and increase in attenuation and 4 pronounced northward onset of seismic polarization anisotropy the latter two seismological features have been taken to mark the northern limit of indian mantle lithosphere thrust beneath southern tibet on the basis of our electrical model we speculate that 1 the resistive upper crustal root beneath the neogene lunpola and duba basins was produced by crustal shortening localized along the northern edge of the lhasa terrane 2 the low midcrustal resistivity beneath the bns reflects enhanced neogene melting and or metamorphic dewatering of relatively fertile subduction zone complex rocks 3 observed steep upper crustal low resistivity anomalies are produced by hydrothermal fluids within active faults localized within and adjacent to the bns and 4 these strike slip and extensional fault arrays are surface manifestations of lithosphere penetrating shear localized along the northern edge of the underthrust indian plate

crust and upper mantle velocity structure in the appalachian orogenic belt implications for tectonic evolution the crust and upper mantle structure of the northeastern united states neus was studied by combining teleseismic and regional body wave observations with surface wave dispersion measurements the velocity models suggest that structures as much as 200 km deep and even deeper can be correlated with surficial geologic and tectonic features and that the grenville and appalachian orogenic belts show marked differences in crustal structure this has the important implication that major orogenic belts have effects that reach well into the lithosphere and are stable for extended periods of time perhaps as long as 1 b y regional travel times recorded across the neus seismic network indicate that the northern appalachians are characterized by a well defined two layer crust with a relatively high velocity lower layer the crust of the grenville province in new york state is slightly thinner than that of the new england appalachians and it is vertically homogeneous with nearly constant p and s velocities lateral variations in structure were studied using time term analysis and teleseismic p wave residuals the suture between the grenville and appalachian provinces in the northeastern united states probably occurs along a north northeast trending belt extending from northwestern vermont to southwestern connecticut high crustal velocities and or crustal thinning a linear gravity high a serpentinite belt precambrian uplifts and the taconic thrusts are found along much of this belt comparison of seismic velocities with resistivity measurements suggests that the lower crust of the grenville province may be composed of rocks with hydrous mineral phases resulting in lowered velocities and a higher poisson s ratio alternatively the rocks of the lower crust beneath the grenville province may be similar to those found on the surface while higher velocity mafic mineralogies are prevalent in the lower crust of the appalachians this is consistent with the hypothesis that the grenville crust underwent substantial reactivation thickened and became vertically uniform during the grenville orogeny in contrast the rocks of the appalachian belt probably were associated with a cycle of oceanic opening and closure which suggests an ensimatic origin of the lower crust in this region recent cocorp results indicate that the orogenic belt of the southern appalachians is allochthonous and is underlain by a basal decollement that extends eastward to the coastal plain however contrasts in structural style and tectonic evolution between the northern and southern appalachians suggest that it may not be possible to extrapolate the cocorp results to the northern appalachians north of about 41 latitude and that the suture between the grenville province and the appalachian orogenic belt in new england is located in the vicinity of or just east of the serpentinite belt

ocean chemistry during glacial time abstract measurements of co2 to air ratios in the gas trapped in bubbles in ice of glacial age suggest that the co2 content of the atmosphere was considerably lower during peak glacial time than during holocene time the purpose of this paper is to show that such a change must in all likelihood be the result of alterations in the nutrient element chemistry of sea water two possible scenarios are presented one involves alternate storage and erosion of phosphorous leaving residues from shelf sediments the other involves changes in the c p ratio in the organic debris falling to the deep sea means of verifying the nutrient cycle hypothesis are also given it is shown that the 13c record as we know it in planktonic and benthic foraminifera the oxygen record as inferred from benthic foraminifera species distributions and the early post glacial caco3 preservation event as recorded by aragonitic pteropods are consistent with both of the hypotheses presented only if an early post glacial spike in the 13c record for planktonic shells could be found would it be possible to eliminate one of these hypotheses i e that involving shelf storage the implications of these nutrient hypotheses to climate theory are as follows if shelf storage is responsible for the glacial to interglacial co2 increase then the co2 change must be considered an amplifier of some primary cause the reason is that sea level changes are needed to drive deposition on and erosion from the shelves on the other hand if changes in the c p ratio for falling debris are responsible then the co2 change could either be an amplifier or a primary cause for the major glacial to interglacial climatic cycle the latter is possible as self sustained oscillations in ocean chemistry might be driven by interactions between ocean ecology and ocean nutrient chemistry

long term climatic changes indicated by crystal growth in polar ice the reconstruction of palaeotemperatures from polar ice samples is essentially based on the isotopic composition of the ice in this paper we propose a new and independent way to obtain such data by using crystal size change profiles from central antarctica dome c and vostok ice cores data we suggest that crystal growth rate is mainly driven by a built in memory9 of the surface temperature conditions at the time of deposition a semi empirical model of crystal grain growth is proposed leading to last glacial maximum holocene temperature change estimates in good agreement with isotope interpretations however the possible palaeocli matic application of this model suffers some limitations connected in particular with in situ strain conditions

impurity sources of f cl no3 and so4 2 in greenland and antarctic precipitation five polar impurity sources are proposed anthropogenic no3 and so42 in recent greenland but not antarctic snow marine aerosols the dominant cl source volcanic eruptions which produce detectable but variable peaks in so42 f and or cl concentrations biogenic sulfurous gases from soil and coastal waters the dominant source for so42 in nonvolcanic strata an unidentified source of background nitrate which is more active in the northern hemisphere and which displays a summer concentration maximum solar activity and supernova events do not modulate no3 concentrations in greenland snow

crustal structure of the adirondacks determined from broadband teleseismic waveform modeling broadband receiver functions developed from teleseismic p waveforms recorded on the midperiod passband of the department of energy s regional seismic test network station rsny are analyzed to examine the crustal structure beneath the adirondack highlands of upstate new york radial receiver functions are inverted in the time domain to determine the vertical shear velocity structure at four distinct back azimuths lateral changes in structure are identified by examining azimuthal variations in the vertical structure southeast of rsny our model consists of a thick crust including a broad crust mantle transition the most prominent structure is a high velocity zone shear velocity 4 0 km s between 18 and 26 km depth which overlies a lower crust of low average shear velocity 3 7 km s the extent of the high velocity zone correlates in depth with a highly reflective zone in consortium for continental reflection profiling profiles se of rsny while the deep low velocity zone may be correlated with a broad electrical conductivity anomaly in the adirondacks this general structure is also seen sw of rsny but is more difficult to document at nw and ne azimuths

individual orientation measurements in quartz polycrystals advantages and limitations for texture and petrophysical property determinations individual orientation determination of quartz grains by electron channelling in principle gives the complete orientation however in routine analysis the noise level in electron channelling patterns ecps does not permit the determination of handedness of a quartz grain in a polycrystal in practice all quartz grains are arbitrarily indexed as right handed hence dauphine twins can be identified but not brazil twins this practice also means that only the centrosymmetric petrophysical properties can be determined from texture measurements these include most geologically relevant properties e g thermal conductivity thermal expansion and elasticity however other properties e g piezoelectricity which are not centrosymmetric cannot be calculated from such texture measurements some texture forming processes e g dislocation glide can also be considered to be centrosymmetric in quartz whereas others e g grain boundary migration may not be the method of quantitative texture analysis from individual measurements is briefly recalled as an example 382 grains from tongue quartzite are used to illustrate the advantages of texture analysis from ecps the orientation distribution function odf is calculated from ecps and x ray pole figures of the same sample the agreement is found to be good between the two methods proving that ecps can be used for quantitative analysis the methods used in local texture analysis and the definitions of the various misorientation distribution functions modfs are given data collected from a traverse of a quartzo feldspathic shear zone in lewisian gneiss torridon quartzite are used to illustrate local texture analysis examples from a region of shear strain of about one are given of core and mantle subgrains and dauphine twins dispersion trails of the crystallographic axes within a single grain show an apparent rotation about the intermediate structural axis y detailed analysis of the subgrain misorientation axes in specimen and crystallographic co ordinates show an important scatter implying that the subgrains resulted from local incompatibility strains rather than specimen scale kinematics the method of calculation of physical properties from individual orientation measurements is given for second and fourth order tensors using the texture data from tongue quartzite we have calculated thermal conductivity thermal expansion and seismic velocities all these properties are extremely anisotropic in quartz however it is emphasized that the presence of a second phase on grain boundaries e g water graphite may completely alter a physical property e g electric and render the values calculated from texture measurements inappropriate

a new greenland deep ice core the polar ice sheets are rich sources of information on past atmospheric conditions including paleoclimates a new deep ice core has been drilled in south greenland comparison of the oxygen isotopic profile with that from camp century and with a deep sea foraminifera record indicates that the new core reaches back to about 90 000 years before present in a continuous sequence the details in the wisconsin part of the ice core records seem to be climatically significant and the general trends reveal all of the relevant emiliani stages recorded in deep sea cores the redated camp century record suggests a dramatic termination of the eem sangamon interglacial

first observations of turbulence parameters in the troposphere over the bay of bengal and the arabian sea using radiosonde 1 this paper discusses the turbulence characteristics of the free atmosphere over the bay of bengal and the arabian sea during the premonsoon season of 2006 the turbulence scaling concepts developed over the past decades for application to oceanic mixing are used for retrieving turbulence properties in the free atmosphere from high resolution soundings as described by clayson and kantha 2008 the variability in the vertical turbulence structure over a large spatial region is studied using this novel method for the first time investigations revealed the presence of a highly turbulent band at upper troposphere below the cold point tropopause cpt with significant enhancements in thorpe length and eddy diffusion coefficient this increased turbulence is studied in conjunction with the observations of the tropical tropopause layer ttl it is seen that the lower and upper boundaries of this turbulence band nearly coincide with the height where the potential temperature lapse rate begins to show a decrease lrhmin and cold point tropopause respectively the ttl is the transition regime from convectively dominated troposphere to radiatively dominated stratosphere and is characterized by a decrease in the static stability the enhanced zonal and meridional wind shear observed in this region shows that the stability in this region is further weakened because of the breaking of kelvin helmholtz waves which results in the enhancement of turbulence the study reveals the potential of high resolution soundings to be used in the investigations of turbulence in the free atmosphere

airborne observations of turbulence mixing and gravity waves in the tropopause region 1 in situ observations of small scale dynamics and compositional structure in the tropopause region are presented the measurements were made aboard the grob egrett high altitude research aircraft above aberystwyth wales in the summer of 2000 the observations presented here show evidence of mixing of ozone and water vapor in a patch of intense turbulence just above the tropopause this turbulence is shown to be the result of wind shear above a tropospheric jet stream the value of the vertical eddy diffusion coefficient in this turbulence is estimated to be 0 9 m2 s 1 it is also shown that wavelike perturbations superimposed on the overall tracer structure can be accounted for by a gravity wave

small scale motions observed by aircraft in the tropical lower stratosphere evidence for mixing and its relationship to large scale flows abstract measurments of temperature and ozone from instrumental aircraft in the tropical lower stratosphere show the presence of small scale disturbances generated by 1 underlying cumulus convection and 2 kelvin helmholtz instability the disturbances associated with underlying convection have peak to peak vertical parcel excursions of 300 m flying conditions were smooth suggesting an ensemble of gravity waves and little or no turbulent mixing it is nevertheless possible that these waves break at other altitudes leading to turbulent mixing and net fluxes of vertically stratified tracers disturbances attributed to kh instability implied vertical parcel excursions of 300 400 m the disturbances coincided with rough flying conditions suggesting turbulent mixing a linear stability analysis of the atmospheric basic state defined by high resolution radiosondes shows fastest growing waves with horizontal wavelengths of 1 4 1 8 km consistent with the aircraft observations the strong shears responsible

lithospheric structure of the yukon northern canadian cordillera obtained from magnetotelluric data 1 two goals of lithoprobe s geoscientific studies in the phanerozoic accretionary cordillera of western north america were to define the subsurface geometries of the terranes and to infer the physical conditions of the crust these questions were addressed in canada s southern cordillera a decade ago and have more recently been addressed in the northern cordillera of which one component of the new studies is magnetotelluric mt profiling from ancestral north american rocks to the coast we present a resistivity cross section and its interpretation of the northern cordillera derived from modeling data from 42 mt sites along a 470 km long ne sw profile beneath the coast belt southwestern end of the profile a deep crustal low resistivity layer dips inland we interpret the crustal part of this conductor as being due to metasedimentary rocks emplaced and metamorphosed during paleocene kula plate subduction a strong lateral transition in lithospheric mantle resistivity exists below the intermontane belt that is spatially coincident with changes in chemical and isotopic characteristics of tertiary to recent alkaline lavas suggesting that isotopically enriched lithosphere related to the coast belt basalts extends partly beneath the intermontane belt the unusually high lower crustal resistivity in the intermontane and omineca belts similar in value to the resistivity found in the unextended part of central british columbia excludes the presence of fluids or conducting metasediments finally our resistivity model displays strong lateral variation of the middle and lower crust between different terranes within the same belt as a result of the complex structural evolution of the lithosphere index terms 0925 exploration geophysics magnetic and electrical methods 1515 geomagnetism and paleomagnetism geomagnetic induction 8110 tectonophysics continental tectonics general 0905 8120 tectonophysics dynamics of lithosphere and mantle general keywords magnetotelluric accreted terranes northern canadian cordillera

metamorphic fluids and anomalous porosities in the lower crust abstract because of the plastic behavior of rocks at high temperature and confining pressure the porosity of lower crustal rocks is a variable dependent on the amount of free fluid present on the basis of hydrologic theory it is predicted that the permeability k of such rocks can be expressed by a relationship of the form k n where and n are material specific constants the exponent n is likely to vary between 3 and 6 whereas which is ultimately related to grain size and shape probably varies over several orders of magnitude consequently substantial contrasts between the k relationships of lower crustal rocks are to be expected the case in which thin crustal layers aquitards are characterized by relatively low values of or n with respect to the crust in general is of particular interest such layers would acquire high porosities in the presence of miniscule steady state crustal fluid fluxes and are a possible explanation for anomalous seismic brightspots and high electrical conductivities in the lower crust modelling of collision belt metamorphism suggests that even long after the cessation of active metamorphism and isostatic reequilibration relict metamorphic fluid fluxes could generate aquitard porosities between 0 1 and 0 4 adequate to explain such geophysical anomalies

electrical properties of granite with implications for the lower crust the electrical properties of granite appear to be dominantly controlled by the amount of free water in the granite and by temperature minor contributions to the electrical properties are provided by hydrostatic and lithostatic pressure structurally bound water oxygen fugacity and other parameters the effect of sulfur fugacity may be important but is experimentally unconfirmed in addition to changing the magnitude of electrical properties the amount and chemistry of water in granite significantly changes the temperature dependence of the electrical properties with increasing temperature changes in water content retain large but lessened effects on electrical properties near room temperature a monolayer of water will decrease the electrical resistivity by an order of magnitude several weight percent water may decrease the electrical resistivity by as much as 9 orders of magnitude and decrease the thermal activation energy by a factor of 5 at elevated temperatures just below granitic melting a few weight percent water may still decrease the resistivity by as much as 3 orders of magnitude and the activation energy by a factor of 2 above the melting temperature 650 to 1100 c depending upon water pressure a few weight percent water will decrease the resistivity by less than an order of magnitude and will barely change the activation energy remarkably the few weight percent water must be present as free water experiments with hydrated hornblende schist with structural water indicate an electrical resistivity very similar to that for dry granite the implications of these results together with the findings of deep magnetic sounding and magnetotelluric surveys suggest much more free water than is commonly associated with the lower crust and possibly into the upper mantle

velocity and temperature structure functions in the upper troposphere and lower stratosphere from high resolution aircraft measurements abstract high resolution measurements obtained from noaa best atmospheric turbulence bat probes mounted on an egrett high altitude research aircraft were used to characterize turbulence in the upper troposphere and lower stratosphere at scales from 2 m to 20 km focusing on three dimensional behavior in the sub kilometer scale range data were analyzed for 129 separate level flight segments representing 41 h of flight time and 12 600 km of wind relative flight distances the majority of flights occurred near the tropopause layer of the winter subtropical jet stream in the southern hemisphere second order structure functions for velocity and temperature were analyzed for the separate level flight segments individually and in various ensembles a 3d scaling range was observed at scales less than about 100 m with power law exponents for the structure functions of the velocity component in the flight direction varying mostly between 0 4 and 0 75 for the separate flight segments but close to for the

an integrated magnetotelluric and aeromagnetic investigation of the serra da cangalha impact crater brazil abstract the research is aimed at delineating the post impact structural characteristics across the serra da cangalha impact crater in brazil using a combination of magnetotelluric mt and aeromagnetic data the mt survey was carried out along three radial mt profiles trending nw se ene wsw and nne ssw across the crater for mt sites located further away from the centre of the crater isotropic mt responses were observed suggesting a 1d conductivity distribution in the subsurface in the frequency range of 100 10 hz for sites located in the vicinity of the inner ring of the crater anisotropic responses were observed for the same frequency range we believe that this zone probably represents the areas of structural disturbance a 2d resistivity inversion of these data reveals a four layer model representing a thin resistive layer underlain by a conductive layer a weathered basement and a resistive crystalline basement the depth to the top of the basement is estimated to be about 1 2 km this is in good agreement with the estimation of depth to the basement of about 1 1 km calculated using the aeromagnetic data however in view of the circular geometry of the crater we have carried out a 3d forward modeling computation to supplement the derived 2d model the 3d resistivity forward model fitting the mt responses by trial by error revealed a five layer model showing a significant reduction in the basement resistivity this perhaps could be due to the structural disturbances that have been caused by the impact on the crater resulting in brecciation fracturing alteration and shocked zone filled with weak magnetic materials and fluids we have calculated the effect of the impact on the overall structural deformation beneath the serra da cangalha crater following the classical crater scaling relation of holsapple and schmidt holsapple k a schmidt r m 1982 on the scaling of crater dimensions ii impact processes j geophys res 87 1849 1870 and found to be about 2 km

a salt oscillator in the glacial atlantic 1 the concept as shown by the work of dansgaard and his colleagues climate oscillations of one or so millennia duration punctuate much of glacial section of the greenland ice cores these oscillations are characterized by 5 c air temperature changes severalfold dust content changes and 50 ppm co2 changes both the temperature and co2 change are best explained by changes in the mode of operation of the ocean in this paper we provide evidence which suggests that oscillations in surface water conditions of similar duration are present in the record from a deep sea core at 50 n based on this finding we suggest that the greenland climate changes are driven by oscillations in the salinity of the atlantic ocean which modulate the strength of the atlantic s conveyor circulation

physical changes in the lithosphere associated with thermal relaxation after rifting we define the terms modem rift and paleorift with respect to the thermal state of the lithosphere the former being rifted lithosphere not in thermal equilibrium and the latter being thermally stabilized rifted lithosphere a comparison of the physical characteristics of modern rifts with paleorifts shows that they share many of the same geomorphic structural and magmatic features but have important differences in their geophysical signatures using a simple model for the thermal relaxation of the lithosphere in the transition from modern rift to paleorift we show that differences in upper mantle seismic velocities and density surface heat flow thermal structure and curie point depth and magnetotelluric properties of the lithosphere between modern and paleorifts can be explained by lithospheric cooling cooling alone cannot explain the complex subsidence histories associated with and following rifting however nor the presence of high velocity crustal layers and sometimes thickened crust in paleorifts these features can be explained by consideration of lithospheric flexural strength and magmatic thickening of the crust associated with rifting we speculate that the anomalous upper mantle beneath many modern rifts may be associated with the process of magmatic thickening of the rifted crust

electrical resistivities of crustal fluids results of calculations on the electrical resistivities of crustal fluids as a function of temperature pressure and fluid composition indicate that crustal fluids can range in resistivity from approximately 1 m the dominant contribution to decreasing the resistivities of crustal fluids comes from increased concentrations of chloride and bicarbonate salts and increased temperature and density of the fluids calculations indicate that the sharpest decrease in fluid resistivity occurs at shallow depths 10 km and temperatures 300 c can not be readily explained as a product of variations in resistivities of crustal fluids these results indicate that a transition in mineralogy or pore shape geometry is more likely responsible for the observed decrease in electrical resistivity of the middle crust than a major change in fluid resistivity

magnetotelluric results opposing magma origin of crustal conductors in the rio grande rift although conductive intracrustal layers appear to be characteristic of continental rift zones they also have been detected in stable crustal environments the low resistivity layers are often explained by free water or crustal magma however alternative explanations are possible purely geometrical effects can be mistaken as conductive layers at depth in the interpretation of magnetotelluric or geomagnetic depth soundings certain minerals such as graphite and hydrated minerals e g serpentine may be important thermally activated processes associated with ductile flow mechanisms may also enhance conductivity two dimensional analysis of a portion of 25 new magnetotelluric stations in the central rio grande rift supports the presence of a conductive zone at 10 km depth or less however very significant differences are apparent in the crustal sections at two close localities mid crustal magma lenses well defined by seismic data cannot explain these differences in fact the crust is modeled to be more conductive by at least an order of magnitude where magma is not detected compared to where it occurs at shallow and intermediate levels only the possible effects of regional three dimensional current channeling could conceivably alter this conclusion to explain the unexpected result it is suggested that a conductive horizon occurs where an impermeable ductile cap traps pore fluids beneath the cap may be nearly an order of magnitude more conductive 100 s m than the dry brittle crust above the zone of trapped pore fluids much more conductive by more than an order of magnitude 10 m where active magma injection destroys the integrity of the ductile cap trapped fluids may escape and produce an overall decrease in conductivity the final electrical signature with this dynamic concept depends on the thermal gradient the relative impermeability of the cap the extent of pore fluids beneath and the amount and frequency of magma intrusion the temporal and spatial distribution of earthquake foci in our study area supports the existence of a ductile layer at about 10 km depth and the hypothesis of magma injection

the electrical conductivity distribution beneath vancouver island a region of active plate subduction magnetotelluric mt and geomagnetic depth sounding gds data were recorded at 25 locations across vancouver island canada over the subducting juan de fuca plate the gds data respond to a number of local conductive features at frequencies above 10 hz while at longer periods the in phase and quadrature induction arrows are colinear and are aligned approximately normal to the continental shelf with a maximum amplitude response near the southwest coast interpretation of the mt data show the presence of a conducting zone at depths greater than 20 km beneath vancouver island and correlating with a strong seismic reflector extensive testing with two dimensional models shows the mt and gds data are consistent with a proposed geoelectrical structure containing a conducting layer extending from the pacific ocean dipping beneath vancouver island and in electrical contact with the mainland conductive region the layer has a horizontal conductance of 200 s that may decrease to 100 s beneath the northeast side of vancouver island related geophysical studies suggest the conductive zone is above the actual thrust surface of the juan de fuca plate the conducting layer is most likely the result of cracks and pores filled with saline fluids which are supplied bymore water subducted with the oceanic crust and by dehydration reactions the presence of fluids has significant implications for thrust earthquakes and for metamorphic reactions that occur in subduction zones the conductance of the upper mantle between 90 and 390 km is best modeled at approximately 1 500 s less

global change over the last climatic cycle from the vostok ice core record antarctica abstract the study of ice cores provides the opportunity of access to numerous parameters which are related to climate or environmental changes many of these variables are of regional or even global geographical significance there are now several ice cores which penetrate into ice which has formed at the surface of polar ice sheets during the last ice age and the recently obtained vostok antarctica record provides detailed information over the last climatic cycle 160 ka in comparison with current holocene conditions the last glacial maximum 20 ka bp is characterized by much colder conditions up to 10 c and reduced precipitation 1 2 a large increase of continental and marine aerosols is explained by a more vigorous large scale atmospheric circulation associated with changing continental deserts and shelves as well as changes in sea ice extent the drastic climatic change occurring at the last glacial termination is correlated with a large increase of atmospheric co 2 from about 200 to 270 ppmv the isotopic temperature record from the vostok ice core depicts two drastic glacial interglacial terminations around 15 and 140 ka bp and a long glacial period 110 15 ka bp which includes two interstadials full glacial stages are characterized by larger aerosol loadings the co 2 record of global significance is well correlated with the isotope temperature profile with high 270 ppmv during interglacials and low 200 ppmv during full glacial conditions spectral analysis of the yostok temperature record supports the existence of a relationship between the pleistocene climate and orbital forcing on the other hand the existence of a co 2 climate correlation suggests that co 2 changes have had an important climatic role in amplifying the relatively weak orbital forcing

magnetotelluric image of the crust and upper mantle in the backarc of the northwestern argentinean andes magnetotelluric data from the backarc of the central andes in nw argentinawere re examined by employing impedance tensor decomposition and 2 d inversion and modelling techniques the data in the period range of 50 15 000 s were collected on a profile of 220 km length reaching from the eastern cordillera across the santa barbara system to the andean foreland of the argentinean chaco after a dimensionality analysis data from most sites were treated as regional 2 d the exception was the eastern section of the profile where the magnetotelluric transfer functions for periods 1000 s reflect a 3 d earth application of two tensor decomposition schemes yielded a regional strike direction of n s which is the azimuth of the central andean mountain chains several 2 d models were obtained by pseudo and full 2 d occam inversion schemes special emphasis was placed on the inversion of phase data to reduce the influence of static shifts in the apparent resistivity data the smooth inversion models all show a good conductor at depth a final model was then calculated using a finite element forward algorithm the most prominent feature of the resulting model is a conductor which rises from depths of 180 km below the chaco region to 80 km beneath the santa barbara system and the eastern cordillera its interpretation as a rise of the electrical asthenosphere is supported by seismic attenuation studies magnetotelluric results surface heat flow distribution in the area and the electrical properties of crustal and mantle rocks suggest that the upper mantle is predominantly ductile beneath the eastern cordillera and the western santa barbara system this generally agrees with anelastic seismic attenuation models of the area and is useful in discriminating between models of q quality factor distribution

modeling the three dimensional structure of macroscopic magma transport systems application to kilauea volcano hawaii we report the results of modeling the three dimensional internal structure of kilauea s magmatic passageways the approach uses a clear plexiglass model containing equally spaced levels upon which well located seismic hypocenters are plotted application of constraining geologic and geophysical criteria to this distributed volume of earthquakes permits the interpretation of seismic structures produced by fracturing in response to locally high fluid pressures four magma transport and storage structures have been identified within and beneath kilauea 1 primary conduit the conduit transporting magma into kilauea s summit storage reservoir rises from the model base 14 6 km to the 6 5 km depth level it is a zone of intense fracturing and inferred intrusion whose horizontal sections are elliptical in planform over its height the average major axis of the component horizontal sections is 3 3 km with an average minor axis of 1 7 km this yields an aspect ratio of 0 52 at the 14 6 km level the strike of the major axis is n67 e during passage from the upper mantle through the oceanic crust this axis rotates in a right handed sense until the strike is n41 w at the 6 5 km level 2 magma chamber complex floor the interval from 6 5 to 5 7 km immediately over the primary conduit is aseismic this suggests differentially high fluid to rock ratios and relatively weak pathways for further vertical transport into higher levels of the storage complex as well as lateral leakage eastward into the mauna ulu staging area for later vertical ascent beneath the upper east rift zone seismicity within the immediately subjacent rocks that form the top of the primary conduit at 6 5 km suggests that this inferred magma rich horizon forms the effective floor of the summit storage complex 3 magma chamber crown intense seismicity over the 1 1 1 9 km depth interval defines an elliptical region in plan view the top of this region has a broad apex with an average major axis of 1 5 km and an average minor axis of 1 1 km producing an aspect ratio of 0 73 this region coincides with the epicentral position of summit vertical displacement maxima during inflationary deformation and is interpreted as a region of intense diking crowning the summit storage complex 4 upper east rift zone pipe from a depth of 5 7 km a cylindrical region of seismicity rises beneath the upper east rift zone to the 1 9 km level where it merges with the subhorizontal upper east rift zone duct this pipe like zone has a mean diameter of 1 4 km and a vertical axis that pierces the surface of the volcano at the intersection of the koae fracture system and the upper east rift zone we suggest this pipe forms a principal connection between the base of the summit storage reservoir and near surface storage compartments and ducts in the upper east rift zone in this role the pipe is suggested to have contributed heavily to mauna ulu s magma supply during 1969 1974 the model of magma transport and storage thus constructed provides a context in which other types of data e g ground deformation and electrical conductivity may be interpreted as well as a means of refining petrological inferences based on lava chemistry

adirondack appalachian crustal structure the cocorp northeast traverse reflection surveys from northeastern new york and central vermont the first elements of a cocorp seismic traverse of grenville and appalachian terranes in the northeastern united states indicate that an unusual zone of layered reflections characterizes the lower crust beneath the eastern adirondacks and that grenville age basement of the green mountains may actually be allochthonous perhaps thrust over paleozoic shelf rocks the top of the adirondack deep layered sequence is found at about 20 km beneath the marcy meta anorthosite massif it appears to dip about 10 northwestward and wedge out against more horizontal reflections at about 28 km this intracrustal sequence may correspond with a previously inferred increase in electrical conductivity possible interpretations range from its being a layered igneous complex to its representing a tectonically buried metasedimentary assemblage although graphitic schists and iron or sulfide segregations in such an assemblage might contribute to its electrical characteristics the problematical issue of water in the lower crust if and how it got there and remained is again raised if not resolved other intrabasement features include major east and west dipping reflections possibly corresponding to faults arched reflections that may represent folds a well defined lens shaped zone virtually devoid of reflections and possible moho reflections unequivocal sub moho reflections are absent superimposed at shallower levels on the eastern part of the traverse are appalachian structures reflections down to about 4 5 km beneath the taconic mountains are interpreted to represent paleozoic shelf sediments of the middlebury synclinorium underlying the taconic allochthons possibly correlative although less well defined reflections appear to extend in disrupted fashion beneath the precambrian rocks of the green mountains suggesting a major basement overthrust the inferred decollement for this overthrust steepens rapidly beneath the east flank of the green mountains east dipping reflections at the east side of the green mountains may represent another major thrust zone involving basement and overlying metasedimentary slices the basement overthrusting suggested by this study is similar in certain respects to the style if not the extent of that demonstrated by previous cocorp surveys in the southern appalachians

observations of the electrical asthenosphere beneath scandinavia the recent recognition that long period i e of the order of hours electromagnetic induction studies could play a major role in the detection of the asthenosphere has led to much interest amongst the geophysical and geological communities of the geomagnetic response functions derived for differing tectonic environments experiments carried out on the ocean bottom have met with considerable success in delineating the electrical asthenosphere i e a local maximum in electrical conductivity minimum in electrical resistivity in the upper mantle in this paper observations of the time varying magnetic field recorded in three regions of scandinavia northern sweden kiruna kir northern finland northeastern norway kevo kev and southern finland sauvamaki sau are analysed in order to obtain estimates of the inductive response function c for each region the estimated response functions are compared with one from the centre of the east european platform eep and it is shown that the induced eddy currents at periods of the order of 103 104 s in the three regions flow much closer to the surface than under the platform centre specifically at a period of 3000 s these currents are flowing at depths of the order of kev 120 km kir 180 km sau 210 km eep 280 km implying that the transition to a conducting zone of 0 2 s m occurs at around these depths one dimensional inversion of ckev and ckir shows that there must exist a good conducting zone of 0 1 1 0 s m under each of the two regions of 40 km minimum thickness at depths of kev 105 115 km kir 160 185 km this is to be contrasted with eep where the d profile displays a monotonically decreasing resistivity with depth reaching 0 1 s m at 300 km finally a possible temperature range for the asthenosphere consistent with the deduced conducvitity is discussed it is shown that at present there is insufficient knowledge of the conditions water content melt fraction etc likely to prevail in the asthenosphere to narrow down the probable range of 900 1500 c

deep electrical structure of the colorado plateau as determined from magnetotelluric measurements magnetotelluric measurements made on the colorado plateau near farmington new mexico characterize the province as consisting of conductive surficial sediments underlain by a more resistive crystalline crust down to about 28 km beneath this zone the average resistivity is anomalously low 13 ohm m down to at least 130 km on the other hand seismic evidence indicates a crustal thickness of approximately 40 km for the interior of the plateau with lower than normal velocities in the upper mantle the two sets of measurements are compatible providing an electrical transition zone is present in the lower crust separating a highly resistive upper crust from more conductive mantle material below 40 km depth constraints on the allowable upper mantle resistivity values when combined with the theoretical analysis of shankland and waff on the effects of partial melt concentrations suggest that the bulk resistivity of the mantle is being influenced by the presence of a small degree of partial melt a few percent by volume temperature estimates associated with the allowable resistivity variations lie within the range 1100 1200 c at 50 km depth and yield a geothermal gradient over the same depth interval of 3 4 c km or less a comparison with electrical data that are available in the surrounding tectonic provinces indicates that the upper mantle beneath the colorado plateau has resistivities at least as low as those for the basin and range rio grande rift and great plains and may in fact be substantially more conducting than any of these surrounding tectonic provinces

deep crustal geoelectric structure beneath the northumberland basin in terms of lateral variations in conductivity structure the southern southern uplands and northumberland basin are characterized by a region of attenuated vertical magnetic fields with small spatial gradients reflecting the presence of a substantial conducting zone five magnetotelluric data sets from the region have been analysed to provide accurate and unbiased estimates of the impedance tensor the response data are used to investigate the deep geoelectric crustal structure of the region three appropriate sets of response data have been subjected to two construction algorithms for 1 d inversion the geoelectric profiles recovered identify a deep crustal conducting zone underlying the northumberland basin the zone modelled as a layered structure dips steeply from mid crustal depths underneath the northumberland basin to lower crustal depths to the nw the structure thus correlates in location and geometry with a deep crustal reflecting wedge detected offshore by a deep seismic reflection profile

resistivity structure to a depth of 5 km beneath kilauea volcano hawaii from large loop source electromagnetic measurements 0 04 8 hz a deep resistivity study of kilauea volcano using the controlled source electromagnetic csem technique has revealed that the summit region i e the area bounded by the east rift zone the southwest rift zone and the koa e fault zone consists of subhorizontal layers having resistivities ranging from 2 ohm m to greater than several hundred ohm meters the vertical sequence of resistivities is consistent with an increase in temperature from 20 c at the surface to over 1000 c at a depth of about 5 km temperatures beneath the adjacent but inactive area of mauna loa probably do not exceed 300 c at a comparable depth a deep conductor which is indicated by data at five observation locations on kilauea may be magma the source for the csem study is a horizontal wire square approximately 2 km on a side through which a sinusoidal current of about 80 a peak to peak is driven at frequencies between 0 04 and 8 hz

balloon borne observations of short vertical wavelength gravity waves and interaction with qbo winds the quasi biennial oscillation qbo a ubiquitous feature of the zonal mean zonal winds in the equatorial lower stratosphere is forced by selective dissipation of atmospheric waves that range in

deep structures along the boundary of a collisional belt attenuation tomography of p and s waves in the greater caucasus summary seismic attenuation q 1 o fp and s waves shows a major discontinuity from the russian platform to the tectonically active greater caucasus broadband records show this boundary over paths 4 long as revealed by the decay of amplitude spectra from a digital seismic network flanking the greater caucasus we measure attenuation from individual spectra using a non linear least squares procedure to determine an attenuation parameter t simultaneously with source parameters at frequencies between 1 and 15 hz the t measurements are then inverted for spatial variations of q 1 with parametrizations of varying complexity model variance for heterogeneous structures improves by more than 30 per cent compared with homogeneous parametrizations site corrections also significantly improve the fit in these inversion results mountainous regions exhibit q values 2 3 times lower q s 775 75 than do the adjacent shields q s 2060 315 showing that the discontinuity is large for both regions q p is roughly equal to q s comparison of body wave to coda spectra indicates that intrinsic absorption rather than scattering dominates the q 1 measurements at least beneath the mountains hence q 1 variations may give a reasonable proxy for temperature if so then temperature beneath the mountains exceeds that beneath the shield by 70 400 c these temperature increases may not be high enough to generate widespread partial melting beneath the mountains but could produce regional metamorphism and could contribute substantially to isostatic compensation of the mountains whatever their origin the boundary in seismic attenuation is abrupt and large between stable craton and an adjacent mountain belt demonstrating that q 1 is a sensitive indicator of tectonic process

crustal structure of mauna loa volcano hawaii from seismic refraction and gravity data abstract in october 1978 the u s geological survey established a 100 km long seismic refraction profile normal to the kona coast of hawaii island analysis of these data along with available gravity data suggest that the oceanic crust dips about 3 landward under the submerged flank of the island increasing to 8 5 under the kona coast maximum vertical deflection of the base of crust from beneath the deep ocean to a point beneath the summit of mauna loa is about 9 km high velocity high density rocks vp about 7 1 km sec density about 2 9 gm cm 3 comprise the bulk of the volcanic edifice and reach to within a few kilometers of the surface beneath the north flank of mauna loa the data also suggest that an elongate high velocity high density body lies parallel to the kona coast just below the surface this body probably represents an extinct buried rift zone

recent studies of time variations of natural electromagnetic fields in scotland abstract a series of geomagnetic induction studies has been undertaken in scotland since 1973 it includes the operation of two geomagnetic arrays one over northern scotland and the other over southern scotland subsequent individual station and small scale geomagnetic array studies and three sets of magnetotelluric soundings which traverse scotland from the lewisian foreland to the english border the problems associated with the interpretation of induction data from an island located in the subauroral region are discussed qualitatively and the manner in which both coast and source field effects can be accounted for is described the geomagnetic deep sounding data gds from all the observation sites have been collated and examples of hypothetical event contour maps and traverses across the great glen and of individual events from the northern array are presented they indicate that significant lateral variations in electrical conductivity structure within the crust and upper mantle are associated with the major geological faults in the region examples of the results of the magnetotelluric soundings are also presented together with an outline of the procedure used for one and two dimensional modelling models of the geo electric structure in both northern and southern scotland have been obtained these show distinctive features which are compatible with the qualitative interpretation of the magnetovariational data for example the major granitic blocks are highly resistive while regions of relatively low resistivity exist at upper crustal depths near the great glen highland boundary and southern uplands faults a zone of low resistivity exists at lower crust uppermost mantle depths throughout much of the region the lowest value occurring under the southern uplands

the effects of saturant salinity and pressure on the electrical resistivity of hawaiian basalts summary ac electrical resistivity of several hawaiian basalts saturated with four solutions of varying salinity is investigated in the hydrostatic pressure range of 0 1 mpa to 0 5 gpa 5 kbar with pore pressure of nearly 0 1 mpa at 0 1 mpa the archie s empirical relationship holds well for basalts ranging in porosity from 1 to 30 per cent and saturated with high salinity solution resistivity of saturated basalts increases with pressure as compared to the data for the low porosity crystalline rocks reports by brace orange the resistivity of porous basalts 2 13 per cent porosity increases less rapidly the empirical relationship d log p dp 1 o gpa found for the crystalline rocks also holds for basalts

electrical conductivity temperatures and fluids in the lower crust we have compiled both laboratory and worldwide field data on electrical conductivity to help understand the physical implications of deep crustal electrical profiles regional heat flow was used to assign temperatures to each layer in regional electrical conductivity models we avoided those data where purely conductive heat flow suggested temperatures more than about 1000 sup 0 c substantially higher than solidus temperatures and outside the range of validity of heat flow models the resulting plots of log conductivity sigma versus 1 t demonstrate that even low conductivity layers lcl have conductivities several orders of magnitude higher than dry laboratory samples and that the data can be represented by straight line fits in addition tectonically active regions show systematically higher conductivities than do shield areas because volatiles are usually lost in laboratory measurements and their absence is a principal difference between laboratory and field conditions these materials probably account for the relatively higher conductivities of rocks in situ in the crust free water in amounts of 0 01 0 1 in fracture porosity could explain crustal conductivities other possibilities are graphite hydrated minerals in rare instances and sulfur in combination with other volatiles as most of the temperatures are less than 700 sup 0 c partial melting seems likely onlymore in regions of highest heat flow where the conductive temperature profiles are inappropriate another result is that at a given temperature crustal high conductivity layes hcl are more conductive by another order of magnitude and show more scatter than do lcl s less

an investigation of terrain effects on the mesoscale spectrum of atmospheric motions abstract wind and temperature data collected on commercial aircraft during the global atmospheric sampling program gasp are used to investigate the effects of underlying terrain on mesoscale variability and the observational results are interpreted within the theories of gravity wave motions and quasi two dimensional turbulence the data show the variances are up to six times larger over mountainous terrain than over oceans or plains with the most striking differences at horizontal scales from 4 to 80 km results were subdivided between the stratosphere and troposphere and between high and low background wind speed cases and show basically the same response to topography in all cases the linear theory of gravity waves is found to predict correctly the scaling of wave amplitude with background stability in the case of low background wind speeds while the two dimensional turbulence theory correctly predicts the shape of the variance spectrum and the observed amplitude scales with as required by t

electrical conductivity of dry lower crustal rocks this study provides values of electrical conductivity of possible lower crustal materials to assist interpretation of lower crustal magnetotelluric soundings we present mean values of conductivity measurements collected from the literature for dry mafic and silicic rocks in the temperature range of 500 c to 1000 c we observe statistically significant differences between rock types mafic rocks are better conductors than granites by about half an order of magnitude and within the mafic group aphanitic fine grained rocks have higher conductivity than phaneritic coarse grained ones best fitting curves of log conductivity versus temperature are presented for each rock type to show mean log conductivity values together with standard deviations so that most probable temperature ranges can be inferred from conductivity because the laboratory rocks are dry their conductivities are lower at a given temperature than they would be if fluids or volatiles were present hence any temperatures inferred from

gravity waves over antarctica and the southern ocean consistent momentum fluxes in mesoscale simulations and stratospheric balloon observations stratospheric balloons from the vorcore campaign have provided a unique description of the gravity wave field in the lower stratosphere above antarctica and the southern ocean during the austral spring of 2005 mesoscale simulations are carried out to analyze further the gravity wave field first the realism of the simulated waves is assessed by comparison to the observations a satisfactory overall agreement is found but different behaviour is noted for orographic waves overestimation in the simulations relative to the observations and non orographic waves underestimation second the gravity wave field is analyzed in more detail than was possible from observations alone it is necessary to distinguish and quantify orographic and non orographic waves separately orographic waves are larger and more intermittent yet affect only a limited geographical region hence although orographic sources stand out as hot spots for gravity waves their contribution to momentum fluxes entering the stratosphere is comparable to or smaller than the contribution of non orographic sources a diagnostic for intermittency the gini coefficient is proposed it clearly marks the distinction between orographic and non orographic sources intermittencies of 0 8 and 0 5 respectively sensitivity to resolution is quite small regarding the spatial structure of the gravity wave field but is significant for the amplitudes the momentum flux values increase by 2 when the horizontal resolution is doubled and possible biases of both simulations and observations are discussed nonetheless the good agreement between observations and simulations and the complementary information on the biases of each dataset promises that in the future these different estimates of gravity wave momentum fluxes may converge copyright 2012 royal meteorological society

the significance of terrestrial electrical conductivity variations the degree to which different materials of the earth can conduct electricity varies enormously from the insulating qualities of cold quartz rich crys talline rock to the metallic behavior of the liquid core a well recognized physical property the specific resistance or resistivity expresses quanti tatively the resistance to current flow and the fact that it can be sensed through measurements on the earth s surface makes it an important geophysical parameter the history of the investigation of resistivity is similar to that of other geophysical quantities such as seismic velocity when it was recognized that the earth as a whole was in some degree a conductor the initial aim was to determine a global average value of resistivity this was followed by the search for a function describing the radial variation while the latter effort is by no means completed a great deal of recent work has been concerned with departures from the average behavior and that aspect forms the basis of this paper lateral variations in electrical resistivity may provide information on the composition and water content of the crust and on the temperature and degree of partial melting in zones of the mantle the success of any investigation depends on the adequacy of electromagnetic measurements at the earth s surface the ability to mathematically infer a distribution of resistivities on the basis of induction theory and by no means least the knowledge through laboratory mea surements of electrical properties of earth materials under different phys ical conditions recent progress in each of these aspects is considered first a word as to units resistivity is conveniently expressed in ohm meters qm the resistance of a meter cube of the material as an indication

nitrate in the greenland ice sheet in the years following the 1908 tunguska event abstract the tunguska event on 30 june 1908 has been subjected to much speculation within different fields of research publication of the results of the 1961 expedition to the tunguska area florensky 1963 supports that a cometary impact caused the event based on this interpretation calculations of the impactor energy release and explosion height have been reported by ben menahem 1975 and velocity mass and density of the impactor by petrov and stulov 1975 park 1978 and turco et al 1981 turco et al 1982 used these numbers to calculate a production of ca 30 106 tons of no during atmospheric transit this paper presents a high resolution study of nitrate concentration in the greenland ice sheet in ca 10 years covering the tunguska event no signs of excess nitrate are found in three ice cores from two different sites in greenland in the years following the tunguska event by comparing these results with results for other aerosols generally found in the ice the lack of excess no3 following the tunguska event can be interpreted as indicating that the impactor nitrate production calculated by park 1978 and turco et al 1981 turco et al 1982 are 1 2 orders of magnitude too high to explain this it is suggested from other lines of reasoning that the impactor density determined by petrov and stulov 1975 probably is too low

small scale wind fluctuations in the tropical tropopause layer from aircraft measurements occurrence nature and impact on vertical mixing abstractthe contribution of turbulent mixing to heat and tracer transport in the tropical tropopause layer ttl is poorly constrained partly due to a lack of direct observations here the authors use high resolution 20 hz airborne measurements to study the occurrence and properties of small scale 100 m wind fluctuations in the ttl 14 19 km over the tropical pacific the fluctuations are highly intermittent and appear localized within shallow 100 m patches furthermore active turbulent events are more frequent at low altitude near deep convection and within layers of low gradient richardson number a case study emphasizes the link between the turbulent events and the occurrence of inertio gravity waves having small horizontal or vertical scale in order to evaluate the impact of the observed fluctuations on tracer mixing their characteristics are examined during active events they are in broad agreement with inertial range turbulence theory the motions are close to 3d isotropic and the sp

internal structure of mount merapi indonesia derived from long offset transient electromagnetic data 1 a long offset transient electromagnetic lotem survey was carried out on merapi volcano indonesia in 1998 lotem data have been recorded at 41 receiver locations which cover a 10 km w e and a 15 km s n profile the signals were transmitted at four locations on the south west and north sides of merapi the data were interpreted with one dimensional 1 d inversions in addition two particular features were investigated with 3 d modeling on the south flank the magnetic field data show strong 3 d distortions consistently over the profile which can only be explained by a conductive near surface structure like a fracture filled with conductive fluids the simulation of topographic effects shows that the interpretation is not significantly affected on both profiles the most striking feature is a conductive layer of 20 m at depths of 500 1000 m below the surface and a thickness of 1 2 km the cause of the increased conductivity may be different for the summit area the intermediate zone and at the flanks below the summit in vicinity of the conduit the decrease in resistivity is produced either by hydrothermal fluids by partial melts or rocks altered by the hydrothermal system or by a combination in the intermediate zone between the conduit and the flanks either alteration or hydrothermal fluids may be the source of the conductivity increase fluids seem to be the most likely cause for the conductive layer at the flanks and the west east striking anomaly from the resistivity of the conductive layer and the typical porosity of volcanic rock we estimate fluid resistivities of 0 2 1 m

lithospheric dismemberment and magmatic processes of the great basin colorado plateau transition utah implied from magnetotellurics 1 to illuminate rifting processes across the transition zone between the extensional great basin and stable colorado plateau interior we collected an east west profile of 117 wideband and 30 long period magnetotelluric mt soundings along latitude 38 5 n from southeastern nevada across utah to the colorado border regularized two dimensional inversion shows a strong lower crustal conductor below the great basin and its transition zone in the 15 35 km depth range interpreted as reflecting modern basaltic underplating hybridization and hydrothermal fluid release this structure explains most of the geomagnetic variation anomaly in the region first measured in the late 1960s hence the transition zone while historically included with the colorado plateau physiographically possesses a deep thermal regime and tectonic activity like that of the great basin the deep crustal conductor is consistent with a rheological profile of a brittle upper crust over a weak lower crust in turn on a stronger upper mantle jelly sandwich model under the incipiently faulted transition zone the conductor implies a vertically nonuniform mode of extension resembling early stages of continental margin formation colorado plateau lithosphere begins sharply below the western boundary of capitol reef national park as a resistive keel in the deep crust and upper mantle with only a thin and weak moho level crustal conductor near 45 km depth several narrow steep conductors connect conductive lower crust with major surface faulting some including modern geothermal systems and in the context of other great basin mt surveying suggest connections between deep magma sourced fluids and the upper crustal meteoric regime the mt data also suggest anisotropically interconnected melt over a broad zone in the upper mantle of the eastern great basin which has supplied magma to the lower crust consistent with extensional mantle melting models and local shear wave splitting observations we support a hypothesis that the transition zone location and geometry ultimately reflect the middle proterozoic suturing between the stronger yavapai lithosphere to the east and the somewhat weaker mojave terrane to the west we conclude that strength heterogeneity is the primary control on locus of deformation across the transition zone with modulating force components

assessment of the accuracy of re analyses in the equatorial lower stratosphere the accuracy of horizontal winds and temperature in the equatorial lower stratosphere is evaluated in different re analyses european centre for medium range weather forecasts ecmwf operational analysis era interim and modern era retrospective analysis for research and applications using an independent data set collected at low latitudes during long duration balloon flights in early 2010 the three analyzed wind products are found significantly less accurate than in the extratropics with periods of 10m sdisagreement with the observations lasting several days to highlight the dynamical context in which the major disagreement events occur case studies are carried out the events are shown to be related to an improper representation of large scale equatorial kelvin and yanai wave packets with vertical wavelengths smaller than 5 km such events can induce large errors on trajectories computed with analyzed winds relatively to the actual balloon trajectory 4000 km separation after 5 days of calculation reasons for analyses inaccuracy are discussed the vertical resolution of the underlying model likely plays a role but the main factor responsible for deficiencies appears to be the lack of wind observations indeed errors in analyzed winds during the campaign have a strong longitudinal structure with root mean square errors twice as large over the indian ocean and western pacific poorly covered by radiosounding stations as over the maritime continent or south america for the ecmwf analysis this structure mirrors that of the analysis increments which have largest amplitudes over observed regions we argue that the reported events are more likely to happen during maximum shear phases of the quasi biennial oscillation

heat production in the continental lithosphere part ii variational approach abstract a variational approach to identify the depth distribution of radiogenic heat generation in the crust is utilized it is inferred that in the crust in which at least the upper section represents a porous medium where fluid circulation may exist the exponential distribution including an additional term corresponding to the removed part of radioelements is optimal

deep crustal extensional faulting in the ivrea zone of northern italy abstract the ivrea zone in northern italy consists of amphibolite and granulite facies metasedimentary metabasic and ultrabasic rocks and is thought to represent a section through the deep continental crust detailed mapping of the high grade part of this zone has revealed a series of high temperature shear zones which after the effects of later low temperature faulting and folding have been removed appears to accommodate extension of the sequence the shear zones formed at temperatures similar to those at which thermal equilibration occurred in the host rocks and locally show evidence for development under prograde conditions these observations fit well with thermal effects calculated from a simple heat flow model for extensional faulting in this model the effects of shear heating and displacement of cool hanging wall rocks against hotter footwall rocks are calculated these observations indicate that faulting as a mode of failure may be important during extension of the lower continental crust especially when basic rocks are the dominant components of the rock pile a restored section through the extended lower crust as observed in the ivrea zone is presented and the extent to which the features observed are able to explain seismic reflectivity of the lower crust is discussed

the 1919 1920 eruption of mauna iki kilauea chronology geologic mapping and magma transport mechanisms utilizing historical accounts field mapping and photogeology this paper presents a chronology of and an analysis of magma transport during the december 1919 to august 1920 satellitic shield eruption of mauna iki on the sw rift zone of kilauea volcano hawaii the eruption can be divided into four stages based on the nature of the eruptive activity stage 1 consisted of the shallow injection of a dike from the summit region to the eventual eruption site 10 km downrift during stage 2 a low ridge of pahoehoe formed in the vent area later a large a a flow broke out of this ridge and flowed 8 5 km sw at an average flow front velocity of 0 5 km day the eruption continued until mid august producing almost exclusively pahoehoe first as gas rich overflows from a lava pond stage 3 and later as denser tube fed lava stage 4 that reached almost 8 km from the vent at an average flow front velocity of 0 1 km day magma transport during the mauna iki eruption is examined using three criteria 1 eruption characteristics and volumetric flow rates 2 changes in the surface height of the halemaumau lava lake and 3 tilt measurements made at the summit of kilauea we find good correlation between halemaumau lake activity and the eruptive stages additionally the e w component of summit tilt tended to mimic the lake activity the n s component however did not multiple storage zones in the shallow summit region probably accounted for the decoupling of e w and n s tilt components analysis of these criteria shows that at different times during the eruption magma was either emplaced into the volcano without eruption hydraulically drained from halemaumau to mauna iki or fed at steady state conditions from summit storage to mauna iki volume calculations indicate that the supply rate to kilauea during the eruption was around 3 m3 s similar to that calculated during the mauna ulu and kupaianaha shield building eruptions and consistent with previously determined values of long term supply to kilauea

electrical resistivity structure of the eastern moroccan atlas system and its tectonic implications the electrical resistivity structure of the crust and upper mantle of the atlas mountain system was studied using magnetotelluric and geomagnetic deep soundings field experiments were done in eastern morocco along a traverse from the anti atlas to the rides rifaines in two campaigns in 1983 and 1988

a magnetotelluric sounding across vancouver island detects the subducting juan de fuca plate magnetotelluric1 mt and geomagnetic2 depth sounding measurements have been made at 18 sites 7 with remote reference3 across vancouver island fig 1 beneath which the juan de fuca plate is underthrusting4 5 vancouver island is part of the old accretionary wrangellia terrane6 and is located in the central portion of a 350 km forearc region that extends from the sediment filled trench7 to the garibaldi volcanic belt8 gravity9 and seismic refraction studies10 suggest that the descending plate has a shallow northeasterly dip of 8 16 with perhaps higher dips beneath northeastern vancouver island a high resolution seismic reflection survey11 along lines 1 and 3 fig 1 located a zone of strong acoustic reflections the e horizon11 near the top of the subducting juan de fuca plate at depths of 23 34 km our model of the broad band mt data defines a sloping highly conducting zone also near the top of the subducting plate at the same depths as the seismic e horizon the high electrical conductivity in this zone the e conductor is the result of saline fluid within the pore spaces of sedimentary and mafic materials of the upper oceanic crust that have been subducted to those depths beneath vancouver island these are the first data which clearly define a dipping conductive layer associated with the boundary region between converging plates they have significant implications for thrust earthquakes and metamorphic reactions that occur in subduction zones

geophysical images of the deep crust the iapetus suture the iapetus suture arguably the most fundamental lineament of british and irish structure has been previously identified on the birps winch deep seismic reflection profiles offshore as a nw dipping feature new depth migrated interpretations of these and other reflection data show good correlation of structure for 100 km along strike in the northern irish sea towards magnetotelluric stations onshore in the north of england and southern uplands of scotland three different methods of inverting data from these sites all reveal a thin nw dipping slab of high conductivity a contour map of the suture trace dipping at 15 25 nw can be constructed down to and through the moho at 28 km depth this map suggests crustal stretching below the solway basin the mylonitic suture zone is characterized by good seismic reflection layering high conductivity presumably fluid produced and a steep increase of p wave velocity over the few kilometres of its width crustal refraction experiments lispb and cssp provide useful velocities but locally misleading structure so that the combination of the seismic reflection and geoelectric methods may be the most powerful means of determining deep crustal structure with a good degree of both vertical and lateral resolution

imaging of deep fluids in archaean crust despite the importance of aqueous fluids in tectonic metamorphic and magmatic activity in the earth s crust few techniques are available for directly observing their distribution at depth even in stable continental crust such observations as have been made electromagnetic deep sounding which by inference1 2 images saline fluids and super deep drilling3 suggest that fluids are present in varying amounts throughout the crust in direct conflict4 with the normal petrological inference of a very dry deep crust here we report the results of an unusually high resolution electromagnetic sounding method to image the deep electrical conductivity structure below a 30 km profile in ontario which crosses archaean lower crustal material of high metamorphic grade exposed by a proterozoic thrust fault the ivanhoe lake cataclastic zone the electrical resistivity image obtained shows embedded in very resistive crystalline crust two nearly continuous sub horizontal zones of enhanced electrical conductivity at depths of 2 3 and 5 6 km below this the commonly observed2 5 7 mid crustal rise in conductivity is seen at depths of 15 20 km the image does not correlate well with the structure inferred from surface geology suggesting that the transport and distribution of fluids was not strongly controlled by lithological boundaries or the thrust fault itself

seasonal variability of vertical eddy diffusivity in the middle atmosphere 1 three year observations by the middle and upper atmosphere radar the vertical eddy diffusivity k due to atmospheric turbulence with spatial scales of 100 102 m has been computed from the echo power spectral width observed by the middle and upper atmosphere radar for almost every month from january 1986 to december 1988 the method of analysis follows lilly et al 1974 sato and woodman 1982 and hocking 1983a 1985 1988 and the contamination due to beam broadening vertical shear and transience has been removed although observations for horizontal wind speeds larger than approximately 40 m s such as occur near the tropopause jet stream in winter have been omitted because of excessive beam broadening sufficient numbers of observations have been accumulated to produce a reasonable climatology for the upper troposphere and lower stratosphere 6 20 km altitude and for the mesosphere 60 82 km altitude the monthly median of k shows a local maximum near the tropopause jet stream altitude it becomes larger in the mesosphere increasing gradually with height maxima of k are observed in winter near the tropopause and in summer in the mesosphere and the seasonal variability of k reaches approximately an order of magnitude a semiannual variability is apparent in the mesosphere with minima in the equinoctial seasons

magma reservoir subsidence mechanics theoretical summary and application to kilauea volcano hawaii an analytic model has been developed for the prediction of the three dimensional deformation field generated by the withdrawal of magma from a sill like storage compartment during an intrusion or eruption cycle the model is based on the work of berry and sales 1961 1962 and predicts the vertical displacement components over the areal plane model parameters are the depth of burial h the intrusion half width a the intrusion half length b the thickness of the magmatic interior at the moment of melt withdrawal tm and the planform aspect ratio a b the products of the model include areal deformation maps systematic variation in model parameters within the context of kilauea volcano hawaii have revealed that circular and elliptical deformation patterns result from the collapse of draining rectilinear intrusions at depth moreover the geometric parameters of a storage compartment may interact in complex ways to produce similar deformation patterns the model has been applied to kilauea volcano for three periods of pronounced summit subsidence 1 1921 1927 bracketing the steamblast eruptive phases of 1924 2 june 1972 to december 1972 and 3 december 1972 to may 1973 application of the model requires the simultaneous optimization of five predicted deformation features with respect to field measurements and the derivative deformation maps 1 the vertical displacement maxima 2 the vertical displacement gradients over the areal plane 3 the lateral extent of the deformation field 4 the aspect ratio of the subsidence pattern and 5 the strike of the major axis of the deformation field the constrained geometries and volumes of the inferred collapsed storage cavities for each period are 1 1921 1927 depth 3 km a 1500 m b 4500 m tm 20 m v 540 106 m3 2 june 1972 to december 1972 depth 3 3 km a 600 m b 2000 m tm 1 m v 4 8 106 m3 and 3 december 1972 to may 1973 depth 2 2 km a 500 m b 1612 m tm 1 m v 3 2 106 m3 for 2 and 3 calculated magmatic thicknesses tm happen to be in the range 3 48 0 15 m of measurements for sill like bodies in deeply dissected hawaiian shield volcanoes the fits obtained between calculated and observed deformation patterns allow quantification of the location overall dimensions orientation and volume of the discrete still molten interior of sill like compartments from which magma is tapped during eruption or intrusion

dynamical structure and turbulence in cirrus clouds aircraft observations during fire abstract aircraft data collected during the first international satellite cloud climatology project regional experiment fire i are used to examine dynamical processes operating in cirrus cloud systems observed on 19 and 28 october 1986 measurements from lagrangian spiral soundings and constant altitude flight legs are analyzed comparisons are made with observations in clear air each cirrus case contained a statically stable layer a conditionally unstable or neutrally stratified layer ice pseudoadiabatic in which convection was prevalent and a neutral layer in which convection was intermittent the analysis indicates that a mixture of phenomena occurred including small scale convective cells gravity waves 2 9 km quasi two dimensional waves 10 20 km and larger two dimensional mesoscale waves 100 km the intermediate scale waves observed both in clear air and in the cloud systems likely played an important role in the development of the cloud systems given the magnitude of the associ

interpretation of long period magnetotelluric soundings in friuli north east italy and the electrical characteristic of the lithosphere summary one year long records of two magnetotelluric mt stations located in the seismic friuli region north east italy were analysed in the 60 28 800s period range the aim was the investigation of the deep lithospheric electric structure the computation of the impedances was made by an iterative signal to noise enhancing method impedances were analysed with complex singular value decomposition svd some tests were made trying to consider the distortion due to the shallow in homogeneities 1 d inversion of the apparent resistivity curves was carried out the models obtained indicate that the lithosphere thickens from 90 to 120 km westward in agreement with surface wave inversion the westernmost sounding located in an area of thickened crust indicates the presence of a 10 km thick intracrustal conductor which may be associated with incipient melting of lower crustal rocks

geothermal evolution of an intruded dike in the rift zone of kilauea volcano hawaii from vlf and self potential measurements abstract self potential sp and vlf measurements were made in 1973 1975 1995 1997 and 2012 across a basaltic dike that intruded into the koae fault zone of kilauea volcano hawaii in may 1973 the sp anomaly remained strong throughout in 2012 it was at about 60 of the strength it had in 1973 in contrast the vlf anomaly though diminished was still observable in 1995 1997 but by 2012 it had disappeared a hydrothermal dike model with parameters calibrated by modeling the solidification of kilauea iki lava lake is used to calculate temperatures and conductivity variation following jaeger s 1957 method we find that the time in years for a dike of width w m to solidify is 0 0075w2 thus a 1 m dike solidifies within the first few days and after 39 years is only tens of degrees above ambient given the orders of magnitude difference between the conductivities of wet and dry basalt we infer that after solidification the vlf anomalies were caused by induction in a localized veil of wet hot basalt enveloping the dike that was generated initially by condensation of steam and subsequently by condensation of evaporated water as temperatures reduced the conductivity anomaly persisted until the mid nineties by 2012 temperatures and condensation were too small for a vlf signal the persistent sp anomaly is attributed to localized fluid disruption with evaporation mainly at the water table and in the vadose zone streaming potentials are associated with evaporative circulation in the vadose zone next to the dike a positive potential is generated by upward flow of moisture laden air with a smaller negative potential on its flanks from downward infiltrating rainwater the analysis indicates that the combination of sp and vlf measurements can characterize the evolving geothermal regime of intrusions above the water table

on the electrical crust mantle structure in fennoscandia no moho and the asthenosphere revealed summary an interpretation of the geomagnetic inductive response function c 0 observed at kiruna in northern sweden is herein undertaken the bounds of acceptable solutions are initially discovered by a monte carlo random search procedure and the best fitting solutions are examined by the application of linear theory to the problem the data are shown to have a higher degree of internal consistency than that described by the estimated variances of each datum a further monte carlo inversion of the variance reduced data set gives solutions with well defined model parameters the two major features of the models are 1 a small or non existent electrical conductivity variation across the seismic moho boundary and 2 the unequivocal existence of an electrical asthenosphere under the fenno scandian shield beginning at a depth of between 155 185 km and of 60km minimum thickness both of these observations have seismic counterparts finally possible mantle temperature profiles are deduced which depend on the assumptions and laboratory data employed

seismic tomography of compressional wave attenuation structure for kilauea volcano hawai i we present a frequency independent three dimensional 3 d compressional wave attenuation model indicated by the reciprocal of quality factor qp for kilauea volcano in hawai i we apply the simul2000 tomographic algorithm to the attenuation operator t values for the inversion of qp perturbations through a recent 3 d seismic velocity model and earthquake location catalog the t values are measured from amplitude spectra of 26708 p wave arrivals of 1036 events recorded by 61 seismic stations at the hawaiian volcanology observatory the 3 d qp model has a uniform horizontal grid spacing of 3 km and the vertical node intervals range between 2 and 10 km down to 35 km depth in general the resolved qp values increase with depth and there is a correlation between seismic activity and low qp values the area beneath the summit caldera is dominated by low qp anomalies throughout the entire resolved depth range the southwest rift zone and the east rift zone exhibit very high qp values at about 9 km depth whereas the shallow depths are characterized with low qp anomalies comparable with those in the summit area the seismic zones and fault systems generally display relatively high qp values relative to the summit the newly developed qp model provides an important complement to the existing velocity models for exploring the magmatic system and evaluating and interpreting intrinsic physical properties of the rocks in the study area

ice core sample measurements give atmospheric co 2 content during the past 40 000 yr recent measurements1 2 on ice samples from camp century greenland 77 10 n 61 08 w byrd station antarctica 80 01 s 110 31 w and dome c 74 40 s 125 10 e suggest that during the late part of the last glaciation the atmospheric co2 concentration was significantly lower than during the holocene further investigation of this natural increase of the atmospheric co2 concentration in the past should aid our understanding of the climatic implications of the man made co2 increase since the beginning of industrialization3 here we report new and precise measurements of the co2 concentration of the air occluded in bubbles of ice samples from camp century and byrd station using a new dry extraction technique the extracted gases were analysed with an ir laser spectrometer irls samples from 22 different depths were analysed from each core the samples are distributed over a depth interval corresponding approximately to the past 40 000 yr in addition results for ice samples from selected depth horizons from a colder region north central greenland 74 37 n 39 36 w and from a warmer region dye 3 greenland 65 11 n 43 50 w are given based on these results we estimate the trend of the atmospheric co2 concentration during the past 40 000 yr

lower crustal petrology from wide angle p and s wave measurements in the black forest abstract the lower crust of the black forest in southwest germany is strongly reflective for compressional waves but almost non reflective for shear waves if the reflectivity for p waves is caused by alternating high and low velocity rocks the s wave observations require that the low velocity rocks have a low poisson s ratio and vice versa a purely compositional petrological model for lower crustal rocks can fit the observed p and s wave velocity data provided a rather high quartz content 50 is acceptable for the lower crust

magnetotelluric evidence for a deep crustal mineralizing system beneath the olympic dam iron oxide copper gold deposit southern australia the iron oxide copper gold olympic dam deposit situated along the margin of the proterozoic gawler craton south australia is the world s largest uranium deposit and sixth largest copper deposit it also contains significant reserves of gold silver and rare earth elements gaining a better understanding of the mechanisms for genesis of the economic liberalization is fundamental for defining exploration models in similar crustal settings to delineate crustal structures that may constrain mineral system fluid pathways coincident deep crustal seismic and magnetotelluric mt transects were obtained along a 220 km section that crosses olympic dam and the major crustal boundaries in this paper we present results from 58 long period 10 104 s mt sites with site spacing of 5 10 km a two dimensional inversion of mt data from 33 sites to a depth of 100 km shows four notable features 1 sedimentary cover sequences with low resistivity 1000 m archean crustal core from a more conductive crust and mantle to the north typically 500 m 3 to the north of olympic dam the upper middle crust to 20 km is quite resistive 1000 m but the lower crust is much more conductive 100 m and 4 beneath olympic dam we image a low resistivity region 100 m throughout the crust coincident with a seismically transparent region we argue that the cause of the low resistivity and low reflectivity region beneath olympic dam may be due to the upward movement of co2 bearing volatiles near the time of deposit formation that precipitated conductive graphite liberalization along grain boundaries simultaneously annihilating acoustic impedance boundaries the source of the volatiles may be from the mantle degassing or retrograde metamorphism of the lower crust associated with proterozoic crustal deformation

vertical diffusivity in the lower stratosphere from lagrangian back trajectory reconstructions of ozone profiles 1 we present a simple stochastic dynamical approach to estimate the turbulent vertical diffusivity d in the lower stratosphere from routinely observed ozone profiles first an observed ozone profile is reconstructed using three dimensional back trajectories obtained from analyzed winds and initializing the trajectories with ozone values from the output of a chemistry transport model assuming that diffusion in the vertical follows a simple random walk leading to a gaussian probability distribution for the particle displacements we perform monte carlo simulations with ensembles of particles originating along each point in the vertical profile by choosing different values of d as input in the calculations we generate different profiles that are smoothed through diffusion comparing with the observed profile we can identify that value of d which is in best agreement at an intermediate range of vertical length scales as an upper bound of the actual d for northern midlatitude lower stratospheric conditions during winter over a period of 12 days the best estimate is d 0 1 m2 s 1 or slightly larger the present results are discussed in the context of comparable estimations of vertical diffusivity in the literature