core mantle boundary shape constraints inferred from the pressure torque acting between the core and the mantle summary in the last few years models of the flow at the top of the earth s core and of the related pressure field have been calculated from the secular variation of the geomagnetic field and core mantle topographies have been computed by seismologists a pressure torque results from the action of the pressure field on the core topography which can theoretically be computed from models of both the pressure field and the core mantle interface small scale features of the flow and of the topography are shown to be capable of contributing strongly to the pressure torque it is thus impossible to calculate the exact value of the torque from the knowledge of only the long wavelength components of the models but the interaction between the large scale components generates by itself torques two orders of magnitude larger than the torques inferred from the irregularities of the length of the day it is nevertheless possible to reconcile the topographic coupling mechanism with the length of the day observations keeping the amplitude of the core topography proposed by seismologists if an orthogonality relation between the geometry of the fluid upwellings and downwellings at the top of the core and the topography is satisfied it is shown how to compute such a topography for a given flow and close to an original topography provided by seismic tomography some consequences of the so inferred link between the fluid flow at the top of the core and the core mantle boundary topography are discussed

intermediate wavelength magnetic anomalies over ocean basins we have examined three very long magnetic field profiles taken over ocean basins for the presence of intermediate wavelength magnetic anomalies one profile was from the atlantic ocean in the transatlantic geotraverse area one ran along latitude 35 sup 0 s in the se pacific and one ran along 150 sup 0 w in the pacific all three profiles show the presence of intermediate wavelength 65 1500 km magnetic anomalies generated in the crust or upper mantle the analysis of magnetic field power spectra shows that the core field becomes unimportant at about a wavelength of 1500 km sea floor spreading anomalies should produce a maximum in power at about a wavelength of 65 km between these two wavelengths there should be a minimum in power which is not seen on observed records inverting the anomalous field to obtain some idea of the magnetization necessary to explain these intermediate wavelength magnetic anomalies shows that values of magnetization in excess of 1 a m sup 1 are needed if the magnetized layer is as thick as the ocean crust alternatively rather large thicknesses of upper mantle material with lower intensities of magnetization need to be used the reason why such magnetization variations exist is not known itmore can be shown that upward continuation of the magnetic anomaly signature to an altitude of 350 km about the perihelion altitude of magsat will produce anomalies up to 10 nt in amplitude these should be capable of being seen by magsat and thus allow us to determine the spatial arrangement of the intermediate wavelength anomalies and hence hopefully a clue as to their origin less

azimuthal flows in the earth s core and changes in length of day at millennial timescales summary variations in the length of day lod reconstructed from ancient records of eclipses contain an oscillating component with a periodicity of roughly 1500 yr a part of the time dependent variations observed in archaeomagnetic field models consist of episodic eastward and westward motions with a similar periodicity using standard inversion techniques we obtain time dependent azimuthal flows at the surface of the core that can explain parts of the archaeomagnetic secular variation and with amplitude and characteristic timescale of variation consistent to explain the lod signal on this basis we argue that exchanges of angular momentum between core flows and the mantle are responsible for the observed millennial oscillations in the earth s rotation rate however we do not obtain a detailed match between the observed changes in lod and the prediction based on simple flow profiles inside the core we argue that this is due to the presence of time dependent azimuthal flows that have an important shear in the direction of the rotation axis such flows are interpreted as oscillations in thermal and magnetic winds

steady surficial core motions an alternate method a new method for deriving steady surficial core motions from geomagnetic field models is presented and applied the original method determines the steady velocity field at the top of a frozen flux core which best fits in both the spatial and temporal linear least squares sense a model of the large scale geomagnetic secular variation sv at the base of a source free mantle voorhies 1986 the new method is based upon the same physical assumptions but fits sv at earth s surface instead of the core mantle boundary cmb the newly derived flow differs somewhat from prior solutions and shows but slight westward drift however other key global properties are virtually unchanged over a 15 year interval the new method provides a better fit to the time varying geomagnetic field at earth s surface than does the old

diffuse emission of carbon dioxide methane and helium 3 from teide volcano tenerife canary islands diffuse emission of co2 ch4 and he was investigated in the summit crater of teide volcano tenerife canary islands the results indicate that teide volcano releases abundant co2 not only from its active crater but also from its flanks as diffuse soil emanations the spatial distribution of these emanations correlates quite closely with that of geothermal anomalies and manifestations our flux measurements indicate a total output of 380 ton day 1 of co2 and 1 6 on day 1 of ch4 by diffuse degassing from the he co2 ratios and the co2 flux we estimate a diffuse he flux of 0 052 mol year 1 isotopic analysis of carbon in soil gas samples from sites of high soil co2 flux indicates a magmatic origin for the co2 also reported by high he 4he ratios of 5 50 and 5 87 ra the origin of methane is more uncertain with low 13c values suggesting a biogenic contribution

comparative soil co2 flux measurements and geostatistical estimation methods on masaya volcano nicaragua we present a comparative study of soil co2 flux f rm co 2 measured by five groups groups 1 5 at the iavcei ccvg eighth workshop on volcanic gases on masaya volcano nicaragua groups 1 5 measured f rm co 2 using the accumulation chamber method at 5 m spacing within a 900 m2 grid during a morning am period these measurements were repeated by groups 1 3 during an afternoon pm period measured f rm co 2 ranged from 218 to 14 719 g m 2 day 1 the variability of the five measurements made at each grid point ranged from 5 to 167 however the arithmetic means of fluxes measured over the entire grid and associated total co2 emission rate estimates varied between groups by only 22 all three groups that made pm measurements reported an 8 19 increase in total emissions over the am results based on a comparison of measurements made during am and pm times we argue that this change is due in large part to natural temporal variability of gas flow rather than to measurement error in order to estimate the mean and associated co2 emission rate of one data set and to map the spatial f rm co 2 distribution we compared six geostatistical methods arithmetic and minimum variance unbiased estimator means of uninterpolated data and arithmetic means of data interpolated by the multiquadric radial basis function ordinary kriging multi gaussian kriging and sequential gaussian simulation methods while the total co2 emission rates estimated using the different techniques only varied by 4 4 the f rm co 2 maps showed important differences we suggest that the sequential gaussian simulation method yields the most realistic representation of the spatial distribution of f rm co 2 but a variety of geostatistical methods are appropriate to estimate the total co2 emission rate from a study area which is a primary goal in volcano monitoring research

gas emission from diffuse degassing structures dds of the cameroon volcanic line cvl implications for the prevention of co2 related hazards abstract in the mid 1980s lakes nyos and monoun violently released massive gas mainly magmatic co 2 killing about 1800 people subsequent geochemical surveys and social studies indicate that lakes nyos and monoun event is cyclic in nature and may occur anywhere in the about 37 other volcanic lakes located in the corridor of the cameroon volcanic line cvl this potential threat motivated us to check if alike nyos and monoun the internal dynamic of the other lakes is also controlled by inputs of deep seated derived co 2 and attempt to measure and provide comprehensive insights on the passive gas emission along the cvl this knowledge shall contribute to the prevention of volcanic lake related hazards in cameroon and the refinement of the global carbon cycle we used in situ fixation and dry gas phase sampling methods to determine co 2 origin and the concentration and the accumulation chamber technique to measure diffuse co 2 emission from nine lakes and on soil at nyos valley and mount manenguba caldera the results suggest that although in minor concentrations compared to nyos and monoun ranging from 0 56 mmol kg 1 to 8 75 mmol kg 1 the bottom waters of some lakes also contain measurable magmatic co 2 with 13 c varies from 4 42 to 9 16 vs pdb that finding implies that under certain circumstances e g increase to volcanic and or tectonic activities along the cvl the concerned lakes could develop a nyos type behavioural scheme the diffuse gas emission results indicate that the nine surveyed lakes release approximately 3 69 0 37 kt km 2 yr 1 of co 2 to the atmosphere extrapolation to the approximately 39 volcanic lakes located on the cvl yields an approximate co 2 output of 27 37 0 5 kt km 2 yr 1 representing 0 023 of the global co 2 output from volcanic lakes in addition to the precedent value the gas removal operation in lakes nyos and monoun released approximately 2 52 0 46 10 8 mol km 2 yr 1 co 2 to the atmosphere from january 2001 to march 2013 more than double the per area co 2 released by the yellowstone volcanic system the co 2 emission from soil was estimated to be 4 57 1 30 kt km 2 yr 1 the soil gas geochemistry of the mount manenguba caldera also indicates a dominant magma derived co 2 mean 13 c 8 6 vs vpdb

carbon dioxide emissions from soils at hakkoda north japan 1 a soil gas and co2 efflux survey was carried out at hakkoda north japan to investigate the spatial distribution and origin of the gas which caused the accidental death of three japanese soldiers on 12 july 1997 in the study area no fumarolic and or thermal activity is observed chemical composition of the gas from areas with high co2 effluxes 5 000 g m 2 d 1 and high co2 contents 15 vol indicate a strong deep sourced contribution for co2 whereas air and or air saturated water is suggested for the rest of the discharged gases which are mainly released from a shallow aquifer isotopic analysis of soil gas and hot spring discharges suggests a combination of magmatic degassing and thermal decarbonation with magmatic degassing being the main contributior to the high co2 emission approximately 74 t d 1 of deep seated magmatic plus thermal decarbonation origin co2 were estimated to contribute to the total output of co2 from this area

on the use of horizontal components of magnetic field in determining core motions summary geomagnetic secular variation is caused by flow of fluid in the earth s core if electrical diffusion can be ignored field lines are frozen to the core fluid and can be used as tracers for the flow at the top of the free stream which lies beneath the diffusive boundary layer in this paper we assume the flux is frozen in and investigate the jump in the horizontal field across the boundary layer theoretical studies indicate that such a jump will be small about 1000 nt we test the hypothesis that the jump is zero within the errors of measurement of the magnetic field integral constraints which are conserved if the horizontal components of field at the base of the mantle can be equated to the components at the top of the free stream are derived and computed using seven main field models from epochs 1935 5 to 1980 0 these main field models have been forced to satisfy all the conditions of frozen flux theory the integral constraints are found to be constant within their expected errors and we conclude that the observations are consistent with zero jump in horizontal field across the boundary layer this result implies that use can be made of the horizontal components of field in determining core flow we attempt to compute the flow along null flux curves which is not determined at all by the radial component of the field for epoch 1970 the result is very noisy because of its reliance on gradients of the secular variation at the core mantle boundary which are poorly determined we do not attempt to compute reasonable core flows consistent with these observations although presumably many such flows exist because they would be so poorly constrained by observation

toroidal flow in the outer core and the thermal regime below the core mantle boundary numerical calculations of fluid dynamos are used to constrain the probable origin of toroidal flows in the outer core azimuthal drift of the core fluid relative to the mantle is the sum of three components 1 uniform differential rotation of the core relative to the mantle produced by electromagnetic torques on the mantle 2 cylindrical flow driven by electromagnetic torques in the core and 3 buoyantly driven thermal wind flow produced by lateral variations of temperature and composition dynamo calculations indicate that electromagnetic torques on the mantle contribute to long term drift but are not likely to be its primary cause zonal flow driven by electromagnetic torques in the core and thermal wind flows driven by zonal temperature gradients are both sufficiently energetic to account for azimuthal flows with angular velocities of 0 1 0 5 yr 1 as inferred from frozen flux analyses of secular variation

historic and paleomagnetic secular variation and the earth s core dynamo process this paper attempts to summarize briefly the recent and ongoing efforts of the geomagnetism and paleomagnetism community to understand both the earth s magnetic field secular variation and its implications for the core dynamo process secular variation is defined in this paper as the general spatio temporal variation of the field secular change will refer to the first time derivative of the spatial field strict geomagnetic definition of secular variation we will emphasize here the long term 10 year or longer behavior of the historic secular variation hsv for this is the variation that is comparable with the paleomagnetic secular variation psv two important related topics the 1969 1970 geomagnetic jerk in secular acceleration and the spatial geomagnetic field components due to crustal or mantle sources are treated more fully in other reviews

precursory diffuse co2 and h2s emission signatures of the 2011 2012 el hierro submarine eruption canary islands 1 on october 12 2011 a submarine eruption began 2 km off the coast of la restinga south of el hierro island co2 and h2s soil efflux were continuously measured during the period of volcanic unrest by using the accumulation chamber method at two different geochemical stations hie01 and hie07 recorded co2 and h2s effluxes showed precursory signals that preceded the submarine eruption beginning in late august the co2 efflux time series started increasing at a relatively constant rate over one month reaching a maximum of 19 gm 2d 1 one week before the onset of the submarine volcanic eruption the h2s efflux time series at hie07 showed a pulse in h2s emission just one day before the initiation of the submarine eruption reaching peak values of 42 mg m 2 d 1 10 times the average h2s efflux recorded during the observation period since co2 and h2s effluxes are strongly influenced by external factors we applied a multiple regression analysis to remove their contribution a statistical analysis showed that the long term trend of the filtered data is well correlated with the seismic energy we find that these geochemical stations are important monitoring sites for evaluating the volcanic activity of el hierro and that they demonstrate the potential of applying continuous monitoring of soil co2 and h2s efflux to improve and optimize the detection of early warning signals of future volcanic unrest episodes at el hierro continuous diffuse degassing studies would likely prove useful for monitoring other volcanoes during unrest episodes

diffuse emission of carbon dioxide from cerro negro volcano nicaragua central america we report the first detailed soil co2 efflux survey carried out at cerro negro volcano nicaragua central america soil co2 efflux values ranged from 0 5 to 35 000 g m 2 d 1 spatial distribution of co2 efflux shows that volcanic gas is mainly released from the summit crater and the fissures opened during the august 1999 eruption the total co2 output of cerro negro is conservatively estimated to be 2 800 t d 1 based on a study area of 0 58 km contour maps of soil co2 efflux ground temperature and 13c co2 distributions support an important magmatic contribution for the total output of co2 at cerro negro volcano

secular variation crustal contributions and tectonic activity in california 1976 1984 five to ten years of data from an array of 34 total field magnetometers are used to define the temporal and spatial characteristics of secular variation throughout central and southern california for this period well determined rates of secular variation are obtained at each site these rates are temporally linear but spatially variable ranging from 45 nt a near san francisco to 54 nt a near the mexican border least squares analysis of all data indicates secular variation decreases in a general southeasterly direction according to f k1 k2 k where f is in nanoteslas per year and are the geographic latitude and longitude and k1 k2 and k are 1 66 0 13 nt a deg 0 13 0 10 nt a deg and 123 2 0 2 nt a respectively deviations of as much as 1 nt a occur on scales of a few tens of kilometers these apparent small scale secular variation anomalies result in part from differences in local induction and remanent magnetization and may be reduced by determination of a site transfer function a planar surface fit to the corrected data has the form f k1 k2 k where k1 k2 and k are now 1 50 0 08 nt a deg 0 23 0 06 nt a deg and 129 2 0 1 nt a respectively residual field variations obtained after correction of all data for secular variation are most apparent on the san andreas fault in southern california between palm springs and the salton sea and marginally so along the recent coyote ml 5 9 of august 6 1979 and morgan hill ml 5 8 of april 24 1984 aftershock zones these residuals could be explained by stress localization in these regions and particularly in the case of the southern san andreas anomaly may indicate the location of a future damaging earthquake incomplete correction for complex site effects may be an alternative explanation in the first large scale test of global secular variation models we find that the models for this region do not predict either the amplitudes or the mean isogram directions of these data to better than several tens of nanoteslas per year and several tens of degrees respectively this may result from a failure to correct for site response effects at some observatories before using the data in global spherical harmonic expansions local magnetization response can therefore bias estimates of secular variation and yield apparent impulsive behavior when external fields are perturbed

time average and time dependent parts of core flow abstract we infer fluid motions below the core mantle boundary by inverting geomagnetic secular variation data over a 150 years assuming helical geostrophic flow we obtain snapshot images of core flow at 5 year intervals which we combine to give time average and time dependent parts of the motion over this time interval the most prominent time average flow structure is a large anti cyclonic vortex in the southern hemisphere beneath the atlantic and indian oceans the time average zonal core flow outside the inner core tangent cylinder is significantly westward in the southern hemisphere but nearly zero in the northern hemisphere westward polar vortices occur inside the tangent cylinder in both hemispheres particularly in the north in terms of mantle versus core origins mantle driving appears to be responsible for the mid latitude asymmetry in the zonal core flow whereas core driving appears to be responsible for the flow at high latitudes we also compare changes in the core s angular momentum calculated from our time dependent core flow with changes in the mantle s angular momentum derived from decade scale length of day variations and find adequate agreement a fit of our time dependent core flow to a torsional oscillations model yields dominant periods of 110 and 53 years

limits on lateral pressure gradients in the outer core from geodetic observations abstract lateral variations in pressure associated with flow at the core mantle boundary will produce deformations of the mantle it is shown here that geostrophically plausible pressure gradients are sufficient to produce measurable changes in the length of day polar motion j2 sea level tilt gravity and strain of these polar motion is the most discriminating and limits intra annual variations in the lateral pressure field at planetary wavelength to less than 104 pa satellite observations of changes in j2 are potentially even more useful however at present the time span of observations is short and the separation of a residual which might be due to a change in the distribution of pressure at the core mantle boundary from other causes such as post glacial rebound is ambiguous it is suggested that not more than 10 of the decade variations in the length of day may be caused by pressure fluctuations at the core mantle boundary

tangentially geostrophic flow at the core mantle boundary compatible with the observed geomagnetic secular variation the large scale component of the flow abstract we present a method for determining the large scale component of a tangentially geostrophic flow beneath the core mantle boundary compatible with magnetic secular variation observations we use a tangentially geostrophic basis to ensure the geostrophy of the motion the fit of the secular variation sv generated by the motion to the observed sv in fact sv models is adequate taking into account the existing error level as in any horizontal geostrophic motion the flow is expressed as a sum of two independent tangentially geostrophic flows a zonal component which is toroidal and a non zonal component which is directly linked with the motions deeper in core the flow derived for the recent epoch 1970 1985 presents interesting symmetry properties the non zonal velocities are the same at two antipodal points while the zonal velocities are the same at two points symmetrical about the equator the non zonal component of the flow is more vigorous than the zonal one the consoidal ingredient though weaker than the toroidal ingredient is essential and indicates strong vertical motion at depth in low latitude areas the sv is actually compatible with a geostrophic motion at the core mantle boundary and appears to be mainly due to the action of the non zonal component of the flow

three year decline of magmatic co2 emissions from soils of a mammoth mountain tree kill horseshoe lake ca 1995 1997 we used the closed chamber method to measure soil co2 efflux over a three year period at the horseshoe lake tree kill hltk the largest tree kill on mammoth mountain in central eastern california efflux contour maps show a significant decline in the areas and rates of co2 emission from 1995 to 1997 the emission rate fell from 350 t d 1 metric tons per day in 1995 to 130 t d 1 in 1997 the trend suggests a return to background soil co2 efflux levels by early to mid 1999 and may reflect exhaustion of co2 in a deep reservoir of accumulated gas and or mechanical closure or sealing of fault conduits transmitting gas to the surface however emissions rose to 220 t d 1 on 23 september 1997 at the onset of a degassing event that lasted until 5 december 1997 recent reservoir recharge and or extension enhanced gas flow may have caused the degassing event

a model of diffuse degassing at three subduction related volcanoes and 13c in soil gas were measured at three active subduction related stratovolcanoes arenal and poas costa rica galeras colombia in general rn co2 and 13c values are higher on the lower flanks of the volcanoes except near fumaroles in the active craters the upper flanks of these volcanoes have low rn concentrations and light 13c values these observations suggest that diffuse degassing of magmatic gas on the upper flanks of these volcanoes is negligible and that more magmatic degassing occurs on the lower flanks where major faults and greater fracturing in the older lavas can channel magmatic gases to the surface these results are in contrast to findings for mount etna where a broad halo of magmatic co2 has been postulated to exist over much of the edifice differences in radon levels among the three volcanoes studied here may result from differences in age the degree of fracturing and faulting regional structures or the level of hydrothermal activity volcanoes such as those studied here act as plugs in the continental crust focusing magmatic degassing towards crater fumaroles faults and the fractured lower flanks

geomagnetic evidence for fluid upwelling at the core mantle boundary summary previous studies both geomagnetic and seismic have been unable to show conclusively whether or not there is fluid upwelling at the core mantle boundary here a new method is developed in which an attempt is made to invert geomagnetic secular variation data measured at the earth s surface for a frozen flux purely toroidal core mantle boundary cmb velocity field under the assumption that the mantle is electrically insulating and flux is frozen in at the cmb these data have previously been inverted for the core mantle boundary radial secular variation from which the appropriate fit between model and data is known two different main field models were used to assess the effect of uncertainty in its radial component at the cmb the conclusions were the same in both cases frozen flux purely toroidal motions provide a poor fit a statistical test allows very firm rejection of the hypothesis that the residuals are not significantly larger whereas there is no statistical difference between the residuals of inversions for radial secular variation and frozen flux velocity fields at the cmb if upwelling and down welling is included the inherent non uniqueness in the velocity field obtained is not of concern since only their statistical properties are utilized and no physical significance is attached to the flows obtained

the structure of the core mantle boundary from diffracted waves diffracted p and s waves pd sd traveling around the core mantle boundary cmb of the earth give us information about the velocity structure and therefore the thermochemistry of d the base of the earth s mantle by examining pd and sdarrivals we determined the apparent ray parameter for different regions at the base of the mantle by comparing the data slownesses to those found from reflectivity synthetic seismograms we were able to quantify d average velocities using these averaged velocities with a thermochemical modeling of lower mantle minerals using a birch mumaghan equation of state we have been able to make chemical and physical inferences as to the causes of lateral variations at the cmb examinations found significant lateral heterogeneity at the base of the mantle amounting to 4 for both p and s velocities these velocities did not always vary in parallel and the poisson ratio varied regionally by almost 6 the most unusual region of the cmb found was under indonesia where velocities 3 slower than the preliminary reference earth models were found adjacent to a region of faster than average velocities these regions currently correspond to areas of core up welling and down welling respectively found by voorhies 1986 which if mostly held in place by core mantle coupling might cause a flux of heat and iron into the mantle making the anomaly both thermally and chemically derived at the cmb under the northern pacific rim the fastest shear velocities were found but the same region yielded slower than average p velocities while the presence of fast shear velocities here would support the idea that we are seeing the cold dregs of mantle convection perhaps continuing down from the north pacific subduction zones the presence of slow p velocities suggests additional complications our thermochemical modeling suggests that the d poisson ratio is very sensitive to variations in the silicate oxide ratio and that a decrease in the amount of perovskite relative to magnesiowustite may play an important role in this region

testing recent geomagnetic field models via magnetic flux conservation at the core mantle boundary abstract the 28 candidate main field models submitted for the international geomagnetic reference field model revision 1985 reveal that a dramatic increase in the rate of decline of the earth s total pole strength began around 1960 nevertheless all but one field model conserves the absolute magnetic flux linking the core mantle boundary cmb fairly well during the 40 year time span 1945 1985 this supports the frozen flux approximation on global length and decade time scales geostrophic fluid motion at the top of a frozen flux core conserves the total magnetic flux linking either geographic hemisphere of the cmb this constraint is poorly satisfied by the candidate secular variation sv models yet other sv models truncated at higher degree and models based upon temporal interpolation rather than extrapolation satisfy this constraint very well these results lead us to make several recommendations for the 1985 and future igrf revisions

constraints on magnetic energy and mantle conductivity from the forced nutations of the earth observations of the earth s nutations are used to explore the possible presence of a conducting layer at the base of the mantle the existence of such a layer is suggested by recent experiments on iron and silicate mixtures at high pressures and temperatures knittle and jeanloz 1986 1989 which indicate that iron may react with silicate minerals to produce metallic compounds nutations provide an ideal tool for investigating the existence of such a layer because they are sensitive to the electrical properties within a thin magnetic boundary layer along the core mantle boundary cmb evidence in favor of a conducting layer is found in the effects of ohmic dissipation which cause the amplitude of the earth s nutation to be out of phase with tidal forcings although out of phase components in the earth s nutations are conventionally attributed to the dissipative influences of ocean tides and mantle anelasticity these effects appear incapable of explaining nutation amplitudes determined from very long baseline interferometry vlbi observations the additional effects of ohmic dissipation enhanced by the presence of a thin conducting layer at the cmb are sufficient to reconcile theory and observation the largest mismatch between observations and theory taking account of ocean tides and mantle anelasticity is a discrepancy of 0 39 0 04 milliarcseconds in the out of phase component of the retrograde annual nutation this discrepancy can be eliminated if the lowermost 200 m of the mantle has a conductivity of 5 105s m 1 and the magnetic energy in the spherical harmonic components of the field at the cmb in degrees l 12 is approximately 4 times greater than the energy inferred in degrees l 12 from surface observations unfortunately the vlbi observations do not uniquely resolve the mantle conductivity and magnetic energy so that trade offs exist between these two parameters nevertheless a high mantle conductivity is favored on the grounds that the alternative involving high levels of magnetic energy yields an excessive amount of ohmic heating other interpretations of the vlbi discrepancy are also discussed one such alternative involves viscous dissipation at the cmb requiring a kinematic viscosity of 0 1m2s 1

the steady part of the secular variation of the earth s magnetic field the secular variation of the earth s magnetic field results from the effects of magnetic induction in the fluid outer core and from the effects of magnetic diffusion in the core and the mantle adequate observations to map the magnetic field at the core mantle boundary extend back over three centuries providing a model of the secular variation at the core mantle boundary here we consider how best to analyze this time dependent part of the field we propose that the first step should be to seek the steady core flow that best fits the field maps isolating what we call the steady secular variation the part of the secular variation explained by steady core flow to calculate steady core flow over long time periods we introduce an adaptation of our earlier method of calculating the flow in order to achieve greater numerical stability we perform this procedure for the periods 1840 1990 and 1690 1840 and find that well over 90 of the variance of the time depedent field can be explained by simple steady core flow the core flows obtained for the two intervals are broadly similar to each other and to flows determined over much shorter recent intervals although we can explain a large part of the signal with these flows none of them provides an adequate explanation of the secular variation in particular the fit to the original observations from which the field models were derived is inadequate we examine the residual secular variation the part of the signal that remains we argue that it is dominated by the effects of nonsteady flow and magnetic diffusion we do not find any compelling evidence for torsional oscillations as the dominant ingredient of this nonsteady part of the secular variation

fluid flow near the surface of earth s outer core maps of the fluid flow at the core surface are important for a number of reasons foremost they may provide some insight into the workings of the geodynamo and may place useful constraints on geodynamo models from the flow the force balance at the top of the core can at least in part be deduced the flow can provide short term predictions of the secular variation the flow is important in understanding changes in the length of day and constraints on lateral temperature variations and topography at the core mantle boundary may be derived unlike the case of mantle convection only very small lateral variations in core density are required to drive the flow these density variations are too small by several orders of magnitude to be imaged seismically so instead we use the geomagnetic secular variation to infer the flow despite considerable recent progress in mapping the core flow substantial differences exist between maps produced by different researchers here we examine the possible underlying reasons for these differences paying particular attention to the inherent problems of nonuniqueness we focus on the aspects of the flow which do seem to be well determined and discuss their geophysical implications

anomalous diffuse co2 emissions at the masaya volcano nicaragua related to seismic volcanic unrest anomalous changes in the diffuse emission of carbon dioxide within the masaya caldera have been observed before two seismic events that occurred at 10 and 30 km from the observation site their epicenters are located respectively south of managua in las colinas 4 3 magnitude and the xiloa caldera 3 6 magnitude in 2002 and 2003 recorded by the geochemical station located at el comalito masaya volcano nicaragua anomalous increases were observed which occurred around 50 and 8 days before the main seismic event that took place in las colinas and 4 days before the seismic swarm at the xiloa caldera with a maximum co2 efflux of 9 3 and 10 7 kg m 2 day 1 respectively the anomalous co2 efflux increases remained after filtering with multiple regression analysis was applied to the co2 efflux time series which indicated that atmospheric variables during the first 4 months explained 23 co2 variability whereas during the rest of the time series co2 efflux values are poorly controlled with only 6 the observed anomalies of the diffuse co2 emission rate might be related to pressure changes within the volcanic hydrothermal system and or to geostructural changes in the crust due to stress strain changes caused before and during the earthquakes formation and seem not to be related to the activity of the main crater of masaya volcano

carbon dioxide degassing by advective flow from usu volcano japan magmatic carbon dioxide co2 degassing has been documented before the 31 march 2000 eruption of usu volcano hokkaido japan six months before the eruption an increase in co2 flux was detected on the summit caldera from 120 september 1998 to 340 metric tons per day september 1999 followed by a sudden decrease to 39 metric tons per day in june 2000 3 months after the eruption the change in co2 flux and seismic observations suggests that before the eruption advective processes controlled gas migration toward the surface the decrease in flux after the eruption at the summit caldera could be due to a rapid release of co2 during the eruption from ascending dacitic dikes spreading away from the magma chamber beneath the caldera

diffuse co2 efflux from iwojima volcano izu ogasawara arc japan abstract iwojima volcano located on the southernmost part of the izu ogasawara arc is characterized by the extrusion of trachyte or trachy andesite lavas and pyroclastic rocks of holocene and surface thermal manifestations small phreatic explosions have been recorded frequently during the last 100 years with the most recent in 1999 and 2001 in order to elucidate the behavior of volcanic volatiles and to assess the potential activity of this volcano diffuse co 2 efflux co 2 content and 13 c co 2 in soil gas and soil temperature at 30 cm depth were measured at 272 sites in march 2000 112 sites in december 2000 and 40 sites in december 2001 we found that high co 2 efflux values of more than 100 g m 2 day 1 occurred at several locations on motoyama volcano corresponding with high soil temperatures more than 60 c at 30 cm depth region and with areas where co 2 with magmatic 13 c was observed here the magmatic 13 c determined for fumarolic co 2 data ranged from 2 to 3 which is clearly higher than magmatic gas values 8 to 2 typically found in island arc settings around the world however this can be explained in terms of carbon isotope fractionation between calcite and co 2 under subsurface temperature and pressure conditions at iwojima a total efflux of co 2 for iwojima volcano is estimated to be 760 t day 1 with a magmatic contribution of about 450 t day 1 this value is rather high compared with other volcanoes in island arc settings since iwojima has no visible plume almost all volcanic co 2 is released as diffuse efflux through the volcanic edifice

atmospheric dispersion of natural carbon dioxide emissions on vulcano island italy la fossa quiescent volcano and its surrounding area on the island of vulcano italy are characterized by intensive persistent degassing through both fumaroles and diffuse soil emissions periodic degassing crises occur with marked increase in temperature and steam and gas output mostly co2 from crater fumaroles and in co2 soil diffuse emission from the crater area as well as from the volcano flanks and base the gas hazard of the most inhabited part of the island vulcano porto was investigated by simulating the co2 dispersion in the atmosphere under different wind conditions the disgas dispersion of gas code an eulerian model based on advection diffusion equations was used together with the mass consistent diagnostic wind model numerical simulations were validated by measurements of air co2 concentration inside the village and along the crater s rim by means of a soil co2 automatic station and a tunable diode laser device the results show that in the village of vulcano porto the co2 air concentration is mostly due to local soil degassing while the contribution from the crater gas emission is negligible at the breathing height for humans and always remains well below the lowest indoor co2 concentration threshold recommended by the health authorities 1000 ppm outdoor excess co2 maxima up to 200 ppm above local background co2 air concentration are estimated in the center of the village and up to 100 ppm in other zones however in some ground excavations or in basements the health code threshold can be exceeded in the crater area because of the combined effect of fumaroles and diffuse soil emissions co2 air concentrations can reach 5000 7000 ppm in low wind conditions and pose a health hazard for visitors

self potential soil co2 flux and temperature on masaya volcano nicaragua we investigate the spatial relationship between self potential sp soil co sub 2 flux and temperature and the mechanisms that produce sp anomalies on the flanks of masaya volcano nicaragua we measured sp soil co sub 2 fluxes 1 to 5 0 x 10 sup 4 g m sup 2 d sup 1 and temperatures 26 to 80 c within an area surrounding a normal fault adjacent to comalito cinder cone 2002 2003 these variables are well spatially correlated wavelengths of sp anomalies are le 100 m and high horizontal sp gradients flank the region of elevated flux and temperature carbon isotopic compositions of soil co sub 2 delta sup 13 c 3 3 to 1 1 per thousand indicate a deep gas origin given the presence of a deep water table 100 to 150 m high gas flow rates and subsurface temperatures above liquid boiling points we suggest that rapid fluid disruption is primarily responsible for positive sp anomalies here concurrent measurement of sp soil co sub 2 flux and temperature may be a useful tool to monitor intrusive activity

an alternative explanation for intermediate wavelength magnetic anomalies harrison and carle this issue and others have examined very long profiles of the magnetic field and have calculated one dimensional power spectra in these they expect to see but do not find a minimum in power at intermediate wavelengths between 65 and 150 km conventional one dimensional models of the field predict very little power in this band which lies between the spectral peaks arising from sources in the crust and the core mantle sources or high intensity long wavelength magnetizations have been proposed to account for the observations an alternative more plausible explanation is that one dimensional spectra of two dimensional fields contain contributions from wavenumbers in the perpendicular i e nonsampled direction unless the seafloor spreading anomalies are perfectly lineated at right angles to the profile some low wavenumber energy must be attributed to this effect we propose that such directional aliasing is a major factor in the power spectra to support this idea we discuss theoretical models and analyze a large scale marine survey

the near earth magnetic field at 1980 determined from magsat data data from the magsat spacecraft for november 1979 through april 1980 and from 91 magnetic observatories for 1978 through 1982 are used to derive a spherical harmonic model of the earth s main magnetic field and its secular variation at epoch 1980 0 the model is called gsfc 12 83 constant coefficients are determined through degree and order 13 and secular variation coefficients through degree and order 10 the first degree external terms and corresponding induced internal terms are given as a function of dst preliminary modeling using separate data sets at dawn and dusk local time showed that the dusk data contain a substantial field contribution from the equatorial electrojet current the final data set was therefore selected first from dawn data and then augmented by dusk data to achieve a good geographic data distribution for each of three time periods 1 november december 1979 2 january february 1980 and 3 march april 1980 a correction for the effects of the equatorial electrojet was applied to the dusk data utilized the solution included calculation of fixed biases or anomalies for the observatory data although similar in many respects gsfc 12 83 differs from international geomagnetic reference field 1980 by 3 6 nt in the g10 term and shows a slightly negative b in the northern polar region as well as other differences in secular variation pattern

geomagnetic field analysis v determining steady core surface flows directly from geomagnetic observations summary geomagnetic secular variation is a result of inductive effects of fluid motion at the top of the earth s liquid core which can be mapped using the frozen flux approximation and inverting mathematical models of the secular variation nonuniqueness may be removed by assuming the flow to be stationary the use of an intermediate mathematical model of secular variation makes comparison of the derived models with observation unsatisfactory and here we devise a new method inverting the geomagnetic measurements directly to obtain steady core motion the method is applied to observatory annual mean data for the 30yr period 1960 1990 to produce six separate models of steady flow three that are stationary over 10yr intervals 1960 1970 1970 1980 and 1980 1990 two 20 yr models 1960 1980 and 1970 1990 and one 30yr model 1960 1990 the method is not restricted to continuous time series or linear x y z data the 10 yr models fit the weighted data with misfits of 1 0 1 3 the 20 yr models fit less well and the 30yr model has a misfit of 1 7 when constrained to have the same norm as the 10yr models all models appear to fit the central decade with a gross misfit close to unity suggesting that changes in core motion may be associated with the two geomagnetic jerks that occurred around 1969 and 1978 furthermore close inspection of the fits at individual observatories shows that steady core motions with this norm cannot produce the secular accelerations required at a large number of high quality observatories steady flows can predict magnetic fields that follow the trend at most observatories but cannot follow the detailed time variations of the past three

simple models of fluid flow at the core surface derived from geomagnetic field models summary we examine the problem of determining the fluid flow at the core surface given a model of the temporal variation of the magnetic field seeking to fit the field over a finite time interval the flow is assumed steady over the time interval and we adopt the frozen flux approximation we produce a range of solutions of varying complexity and subject to different constraints estimate the errors on the solutions and assess their consistency with the underlying assumptions we find both direct evidence for ageostrophic flow in the form of flow across the geographical equator and indirect evidence in the form of poorer fits to the field when the flow is contained to be geostrophic on account of this evidence we do not adopt the geostrophic approximation however we find that unconstrained flows are poorly determined and consider the various alternatives for producing better determined solutions we choose to restrict our attention to determining the large scale toroidal part of the flow and find a simple pattern of flow which is nearly symmetric about the equator from a sequence of maps of the flow over 5 year time intervals back to 1915 we are still able to identify many of the basic aspects of this simple pattern but changes in the flow pattern are discernible although our models of the flow explain a large proportion of the signal typically 95 per cent of the variance the fits which we obtain are not as good as might be expected failure of the underlying assumptions together with our decision to map only the large scale toroidal part of the flow explains the poorer than expected fit

diffuse emission of co2 from the fossa crater vulcano island italy numerous measurements of co2 degassing from the soil carried out with the accumulation chamber method indicate that in the period april july 1995 the upper part of the fossa cone released a total output of 200 t d 1 of co2 which corresponds to approximately 1000 t d 1 of steam these large amounts of fluids are of the same order of magnitude as those released by the high temperature fumarolic field located inside the crater the spatial distribution of soil gas fluxes shows that the main structures releasing co2 are the inner slopes of the crater and a nw se line located ne of the crater rim which correspond to the main direction of vulcano island active faults the comparison of the co2 maps with the soil temperature distribution derived from both direct measurements and airborne infrared images indicates the occurrence of extensive condensation of fumarolic steam within the upper part of the fossa cone whose total amount is comparable to the rainfall budget part of the condensate which originates from this process contributes to the recharge of the phreatic aquifer of porto plain modifying the chemical and isotopic composition of the groundwater

steady flows at the top of earth s core derived from geomagnetic field models select models of the main geomagnetic field and its secular variation are extrapolated to the base of an insulating mantle and used to estimate the adjacent fluid motion of a perfectly conducting outer core the assumption of steady motion provides formally unique solutions and is tested along with that of no upwelling the hypothesis of no upwelling is found to be substantially worse than that of steady motion although the actual motion is not thought to be steady the large scale secular variation at the top of the core can be adequately described by a large scale combined toroidal poloidal circulation which is steady for intervals of at least a decade or two the derived flows include a bulk westward drift but are complicated by superimposed jets gyres and surface divergence indicative of vigorous vertical motion at depth the circulation pattern and key global properties including rms speed upwelling and westward drift are found to be fairly insensitive to variations in modeling parameters

mean electromotive force generated by asymmetric fluid flow near the surface of earth s outer core the phi component of the mean electromotive force etf generated by asymmetric flow of fluid just beneath the core mantle boundary cmb is obtained using a geomagnetic field model this analysis is based on the supposition that the axisymmetric part of fluid flow beneath the cmb is tangentially geostrophic and toroidal for all the epochs studied the computed phi component is stronger in the southern hemisphere than that in the northern hemisphere assuming a linear relationship between etf and the azimuthally averaged magnetic field aamf the only nonzero off diagonal components of the pseudotensor relating etf to aamf are estimated as functions of colatitude and the physical implications of the results are discussed 14 refs

the secular variation of earth s magnetic field models of the magnetic field at the core mantle boundary at selected epochs from 1715 0 to 1980 0 reveal novel features in the field at the core these suggest that the flow of core fluid is coupled to the mantle and that magnetic diffusion is significant

geomagnetism earth rotation and the electrical conductivity of the lower mantle abstract a new approximation is derived for the electromagnetic torque acting on an electrically conducting mantle as a result of fluid flow in the core the torque considered is that associated with the toroidal field induced in the mantle by advection of poloidal field which is assumed to be frozen into an infinitely conducting liquid core by the flow of liquid at the top of the core the expression relies on the assumption that the mantle is an insulator apart from a thin with respect to the core radius layer of finite conductance adjacent to the core mantle boundary this allows the toroidal field scalar in the mantle to be expressed as a first order taylor approximation the time dependent torque calculated at a sequence of epochs this century is compared with the torque which has previously been inferred from astronomical observations of the length of day although the initial results appear unpromising a significant correlation exists when poorly determined components of the velocity field which contribute substantially to variations in the calculated torque are ignored by regression analysis the conductance of the assumed thin layer is determined as 6 7 108 s and the lag of the electromagnetic torque behind the astronomical torque as 6 years which is interpreted as the delay time for electromagnetic signals through the mantle finally the implications of these results for the conductivity of the lower mantle are discussed they imply that the bottom few hundred kilometres of the mantle probably have a conductivity of a few hundred to a few thousand siemens per metre previously published lower mantle conductivity models are examined in light of this conclusion the close correlation of the variations in the calculated electromagnetic torque which depend primarily on fluctuations in the core velocity field with the length of day torque provides independent evidence that core flow is not steady on the decade time scale

core mantle interactions abstract recent studies of the magnetic field at the core mantle boundary have revealed fixed sites of either static magnetic features or persistent secular variation this suggests part of the magnetic field behaviour is controlled by the mantle the most plausible mechanism for core mantle interaction is thermal coupling although topography may also be significant the magnetic sites coincide with anomalies in lower mantle seismic velocity as determined from tomography and density as determined by flow models of mantle convection constrained by tomography and the geoid some magnetic features coincide with subduction zones particularly those near indonesia they may be caused by bumps on the core mantle boundary beneath trenches paleomagnetic pole positions suggest the magnetic behaviour has persisted for at least 5 myr as would be expected if it were controlled from the mantle

does secular variation involve motions in the deep core abstract the time evolution or secular variation of different components of the geomagnetic field at many observatories presents a broken line pattern along time invervals whose length is typically a few tens of years the secular variation is linear or the field is parabolic with a high accuracy sudden changes of slope take place at the ends of these intervals identified as magnetic jerks we show that it is difficult to make these characteristics compatible with the hypothesis that the secular variation is generated by a flow involving only a thin say of the order of 10 km layer at the top of the core indeed diffusion would then prohibit the observed broken line pattern and its linear parts unless rather unlikely assumptions are made about the time behaviour of the flow

mapping the fluid flow and shear near the core surface using the radial and horizontal components of the magnetic field summary we examine the problem of determining the fluid flow and the shear the radial derivative of the flow at the core surface given a model of the temporal variation of the magnetic field whereas most previous work has focused on determining only the flow which requires only the use of the radial component of the magnetic field here in addition we determine the shear for which we must use the horizontal component of the magnetic field estimates of the jump in the value of the horizontal magnetic field bh across the boundary layer between the top of the free stream and the base of the mantle are small and suggest that to a high level of accuracy the mantle valuks of bh can be used at the top of the core except in the special case of an insulating mantle only the horizontal poloidal field is known at the core mantle boundary and supplies one extra equation for the determination of velocity and shear we show how the matrix elements relating the coefficients of the spectral expansion of the flow and shear are related to the geomagnetic secular variation coefficients in closed form we examine the uniqueness of the resulting inverse problem and show that one part of the non uniqueness from which the shear suffers is particularly easy to describe it takes the same form as that which affects the flow namely a toroidal ambiguity in the field u b however certain uniqueness theorems can be derived we extend the steady motions theorem of voorhies backus 1985 and the geostrophic motions theorem of hills 1979 and backus lemouel 1986 to the determination of the flow and shear and derive closely analogous results uniqueness in the steady case depends on the value of the same discriminant as the velocity and in the geostrophic case the shear can be determined uniquely in the same areas as can the velocity i e outside certain ambiguous patches for the geostrophic regime the lateral density or temperature variations at the top of the core can be found in a self consistent manner we apply our method to the temporal evolution of the field over the period 1960 1980 and produce solutions for each of the assumptions of unconstrained steady motions geostrophic motions and purely toroidal motions we find that the form of the flow changes very little from solutions based only on the radial induction equation and that the shear is weak and aligned with the flow with a sense such that the strength of the flow decreases with depth with a length scale for linear decay of half the core radius this suggests that the flow near the core surface is indicative of whole core flow rather than a flow confined to a layer near the core surface

geomagnetism the next millenium abstract the earth has possessed a magnetic field for most of its history it is therefore strange that the present day field is changing so rapidly at the recent rate of decay the magnetic field will be removed altogether in the next 1500 years if this fall persists as seems likely our future magnetic environment would be quite different from that of today a long term program of observation and development of theory for the origin of the magnetic field are needed in order to understand the processes influencing the magnetic field

time varying fluid flow at the top of earth s core derived from definitive geomagnetic reference field models the effects of a time varying fluid velocity have been included in the estimation of frozen flux core surface flow this has been done to improve the quality performance and accuracy of kinematic analyses of the geomagnetic secular variation the derived flows consist of a reference velocity plus a steady acceleration and thus evolve linearly with time the method features simultaneous solution for the initial radial geomagnetic field component at the core mantle boundary and the subadjacent time varying fluid motion the trade off between time averaged spatial complexity of the derived flows and misfit to the weighted definitive geomagnetic reference field models for 1945 1980 is explored at fixed flow complexity simultaneous solution for both initial geomagnetic field and steadily accelerating flow gives substantial reductions in the square weighted residuals per degree of freedom when compared with previous solutions for either initial field and steady flow or steady flow alone the apparent timescale for flow change varies nonmonotonically with flow complexity between about 23 and 41 years the single maximum value is associated with unit negative slope of the log log trade off curve and is used to help identify a preferred solution this solution has an rms speed of but 7 50 km yr l and an rms acceleration of 0 183 km yr 2 or 1 84x10 13 m s 2 the latter indicates extremely weak net forces upon the liquid outer core

hydrological behaviour of sub mediterranean alpine headwater streams in a badlands environment summary investigations of flash floods generation processes are very few compared with studies in humid areas the rapidity and intensity of these processes make difficult any data acquisition on the field the present study aims to improve our knowledge on these environments by using the facilities of the draix erbs southern french alps where well documented black marls show a typical badlands morphology with v shaped gullies time varying components of total flow and flow sources have been investigated from a long term isotopic and hydrochemical survey of rainwaters overland waters soil waters and streamwaters we present in greater detail two flood events which occurred in three adjacent basins and had contrasting antecedent soil moisture conditions isotopic data were used to apply time based hydrograph separations due to the very short transfer time of waters convolution of the rainfall isotopic signal with a two parameter transfer function dispersive transfer function proved the best way to assess the event isotopic concentration end members mixing analysis emma has been carried out using non reactive chemical species to get source areas of runoff new water participation by direct surface transfer was the main mechanism at the peak discharge this contribution was found to dominate irrespective of whether the antecedent soil moisture was dry or wet nevertheless up to 20 of subsurface water has been observed at peak discharge for dry pre event conditions during the flow recession phases this subsurface water contribution was greater for wet antecedent conditions in dry initial conditions subsurface water was mostly new water whereas in wet conditions pre event water could contribute to the flow a deep groundwater reservoir may take part in the pre event component in the larger basin but in the smaller basins pre event water was mostly made of short residence time water from previous rainfall events originating from sporadic highly transmissive shallow hillslope reservoirs loose detrital cover and upper regolith differences regarding the hierarchy of the processes were not found to be simply proportional to the basins area nor were they clearly related to the mean slope gradients or to the percentage of vegetal cover it is suggested that controls on streamflow generation occur at local scale and consist in the spatial organisation and the gradual accumulation downwards of first order basins with their respective physical specificities mostly orientation and slope gradient

the time varying geomagnetic field the scope of this review is limited to papers on the large scale geomagnetic field of deep internal origin and its secular variation published by u s authors and their colleagues during the 1983 1986 quadrennial the many fine papers on this broad topic by authors outside the u s are regretfully excluded fortunately most of them are cited by the u s authors listed in the reference section of this review labreque and mayhew this issue review papers treating the smaller scale fields usually attributed to visco inductively and remanently magnetized crustal geologic structures review articles dealing with external fields are surveyed by m schulz in the magnetosphere section of this u s national report booker and chave this issue review papers concerning the use of more rapidly fluctuating externally induced internal fields to probe the electrical properties of the crust and upper mantle lund and olson this issue review papers concerning paleo secular variation and core geodynamo theory

the effects of environmental parameters on diffuse degassing at stromboli volcano insights from joint monitoring of soil co2 flux and radon activity abstract soil co 2 flux and 222 rn activity measurements may positively contribute to the geochemical monitoring of active volcanoes the influence of several environmental parameters on the gas signals has been substantially demonstrated therefore the implementation of tools capable of removing or minimising the contribution of the atmospheric effects from the acquired time series is a challenge in volcano surveillance here we present 4 years long continuous monitoring from april 2007 to september 2011 of radon activity and soil co 2 flux collected on the ne flank of stromboli volcano both gases record higher emissions during fall winter up to 2700 bq m 3 for radon and 750 g m 2 day 1 for co 2 than during spring summer seasons short time variations on 222 rn activity are modulated by changes in soil humidity rainfall and changes in soil co 2 flux that may be ascribed to variations in wind speed and direction the spectral analyses reveal diurnal and semi diurnal cycles on both gases outlining that atmospheric variations are capable to modify the gas release rate from the soil the long term soil co 2 flux shows a slow decreasing trend not visible in 222 rn activity suggesting a possible difference in the source depth of the of the gases co 2 being deeper and likely related to degassing at depth of the magma batch involved in the february april 2007 effusive eruption to minimise the effect of the environmental parameters on the 222 rn concentrations and soil co 2 fluxes two different statistical treatments were applied the multiple linear regression mlr and the principal component regression pcr these approaches allow to quantify the weight of each environmental factor on the two gas species and show a strong influence of some parameters on the gas transfer processes through soils the residual values of radon and co 2 flux i e the values obtained after correction for the environmental influence were then compared with the eruptive episodes that occurred at stromboli during the analysed time span 2007 2011 but no clear correlations emerge between soil gas release and volcanic activity this is probably due to i the distal location of the monitoring stations with respect to the active craters and to ii the fact that during the investigated period no major eruptive phenomena paroxysmal explosion flank eruption occurred comparison of mlr and pcr methods in time series analysis indicates that mlr can be more easily applied to real time data processing in monitoring of open conduit active volcanoes like stromboli where the transition to an eruptive phase may occur in relatively short times

diffuse emission of co2 from miyakejima volcano japan abstract two soil gas surveys were carried out in may and september 1998 at miyakejima volcano in the izu mariana arc japan co 2 flux values for may and september surveys ranged from 0 1 to 18 150 g m 2 day 1 and from 0 1 to 9685 g m 2 day 1 respectively statistical graphical analysis showed three overlapping populations the spatial distribution of these emissions correlated quite closely with the geothermal and geological characteristics of the studied area the structure releasing higher co 2 is the summit cone oyama and surrounding areas where the most obvious geothermal features occur a total output about 100 150 t day 1 is estimated from this area a good correlation was observed between soil co 2 flux and soil temperature at the summit caldera indicating extensive condensation of fumarolic steam within the upper part of miyakejima carbon isotopic analysis of selected samples inside the summit caldera 13 c co 2 0 90 to 5 70 suggests a mixing of carbon derived from marine limestone and magmatic co 2 while a clear biogenic origin 13 c co 2 14 76 to 25 52 is observed for the diffuse degassing of co 2 outside summit caldera