carbon dioxide and carbon monoxide emission rates from an alkaline intra plate volcano mt erebus antarctica abstract this is the first report of co and co 2 flux from mt erebus antarctica an alkaline intra plate volcano with a convecting lava lake the co 2 flux from the mt erebus plume was measured by in plume infrared analysis during december 1997 december 1999 and january 2001 the co 2 emission rates were consistently close to the average of 22 3 kg s 1930 mg day for the three measurements conducted over a 4 year period even though the third measurement january 2001 was conducted at a time of elevated activity as co 2 is considered a good indicator of eruptive activity a more frequent type of monitoring system may be necessary to detect changes related to activity at mt erebus increased co 2 emissions lost via strombolian eruptions in the lava lake were not accounted for in our airborne measurements carbon monoxide flux determined by fourier transform infrared spectroscopy in december 1995 yielded a rate of 1 74 kg s 150 mg day and a high co co 2 ratio of 0 12

application of stochastic simulation to co2 flux from soil mapping and quantification of gas release 1 conditional sequential gaussian simulations sgs have been applied for the first time to the study of soil diffuse degassing from different volcanic and nonvolcanic systems the application regards five data sets of soil co2 fluxes measured with the accumulation chamber methodology at the volcanic areas of solfatara of pozzuoli italy vesuvio cone italy nisyros greece and horseshoe lake california and at the nonvolcanic degassing area of poggio dell olivo italy the sgs algorithm was used to generate 100 realizations of co2 flux for each area probabilistic summaries of these simulations together with the information given by probability plots were used 1 to draw maps of the probability that co2 fluxes exceed thresholds specific for a background flux i e to define the probable extension of the degassing structures 2 to calculate the total co2 output and 3 to quantify the uncertainty of the estimation the results show that the sgs is a suitable tool to model soil diffuse degassing producing realistic images of the distribution of the co2 fluxes that honor the histogram and variogram of the original data moreover the relation between the sample design and the uncertainty of estimation was investigated leading to an empirical relation between uncertainty and the sampling density that can be useful for the planning of future co2 flux surveys

determination of the direction of magnetization and orientation of a tilted sheet from downhole magnetic gradient tensor data a tilted sheet model can usefully represent a dipping vein dyke sedimentary layer or metasedimentary unit downhole magnetometer measurements provide proximal remote sensing of magnetic properties of magnetized sheets from a different perspective than ground or aeromagnetic surveys however a priori geometric information about a sheet is still required to constrain its magnetization unless the measurements include data acquired in a borehole that penetrates the sheet in particular if only external measurements are available knowledge of the dip of the sheet is required to constrain the direction of magnetization and an estimate of the thickness of the sheet is required to constrain the intensity of magnetization this article describes a program for determination of both the direction of magnetization and geometry of a sheet from downhole magnetic gradient tensor data we give expressions for the magnetic gradient tensor on the axis of a vertical borehole within a tilted sheet we use an invariant of the tensor to determine the location and thickness of the sheet and tensor components to obtain the direction of magnetization and orientation of the sheet an iterative procedure can improve the accuracy of the estimated parameters we also discuss the robustness of the proposed program in the presence of variations in the diameter of the borehole measurement offset from the center of the borehole and nonuniform dip of the sheet experiments verify the proposed program and demonstrate the advantages of downhole magnetic gradient tensor measurements the method can be extended to inclined boreholes by a straightforward rotation of coordinate axes

carbon isotopic changes in benthic foraminifera from the western south atlantic reconstruction of glacial abyssal circulation patterns oxygen and carbon isotopic analyses have been performed on the benthic foraminifer planulina wuellerstorfi in seven late quaternary cores from the vema channel rio grande rise region the cores are distributed over the water depth interval of 2340 to 3939 m which includes the present transition from north atlantic deep water nadw to antarctic bottom water aabw the carbon isotopic records in the cores vary as a function of water depth the shallowest and deepest cores show no significant glacial interglacial difference in 13c four of the five cores presently located in the nadw have benthic foraminiferal 13c that is lower during glacial isotopic stages based on bathymetric gradients in 13c we conclude that like today there were two water masses present in the vema channel during glacial intervals a water mass enriched in 13c overlying another water mass depleted in 13c the largest gradient of change of 13c with depth however occurred at 2 7 km 1 km shallower than the present position of this gradient on the basis of paleontologic and sedimentologic evidence we consider it unlikely that the nadw aabw transition shallowed to this level reduced carbon isotopic gradients between the deep basins of the north atlantic and pacific oceans during the last glaciation suggest that production of nadw was reduced lower production of nadw may have modified the local abyssal circulation pattern in the vema channel region

diffuse carbon dioxide emissions from hidden subsurface structures at asama volcano japan we measured diffuse carbon dioxide co2 flux and soil temperature around the summit of asama volcano japan to assess the diffuse degassing structure around the summit area soil co2 flux was measured using an accumulation chamber method and the spatial distributions of co2 flux and soil temperature were derived from the mean of 100 sequential gaussian simulations results show that soil co2 flux was high on the eastern flank of kamayama cone and the eastern rim of maekake crater the outer cone these areas mostly correspond to high temperature anomalies the average emission rate of diffuse co2 was calculated to be 12 6 t day 1 12 2 14 6 t day 1 such diffuse emissions account for 12 of the total diffuse and plume co2 emissions from the summit area the diffuse co2 anomalies probably reflect permeable zones controlled by local topography and hidden fractures bordering maekake crater the permeable zones are connected to the low electrical resistivity zone inferred to indicate both a hydrothermal fluid layer and an upper sealed layer made of clay minerals magmatic gas from the main conduit ascends to the volcano surface through this fluid layer and the permeable zones these insights emphasize that the pathways and the connection between the pathways and the source of diffuse co2 combine to create the pattern of heterogeneous diffuse co2 emission seen at the surface only by using a combination of gas measurements and geophysical tools can we begin to understand the dynamics of this system as a whole

paleomagnetic inclination and declination from three component borehole magnetometer data new insights from logging in the louisville seamounts we carried out measurements of the magnetic field vector at two sites during integrated ocean drilling program iodp expedition 330 to the louisville seamount chain the aim was to impose constraints on the magnetization direction and to contribute to the reconstruction of possible hot spot motion the measurements were conducted using the gottingen borehole magnetometer gbm it comprises three fiber optic gyros fog that can be used to reorient the magnetic field data to improve accuracy we are using a new algorithm that combines fog data and data of two inclinometers as can be evaluated by comparing downlog and uplog of the measurements the three dimensional magnetic field data obtained is of good quality an interpretation of the magnetic field data using a state of the art method based on horizontal layers yields results inconsistent with measurements of the natural remanent magnetization nrm of drill core samples in the following we define the magnetization from the horizontal layer as apparent magnetization and develop a new interpretation method based on dipping layers our method includes a new approximate forward modeling algorithm and considerably improves the consistency of the borehole measurements and the nrm data we show that a priori information about the geometry of a layer is required to constrain the inclination and declination of magnetization especially the azimuth of a layer and the declination of magnetization cannot be determined separately using azimuth and layer dip information from borehole images we obtain constraints on inclination and declination for one particular layer

total co2 output from vulcano island aeolian islands italy 1 total co2 output from fumaroles soil gas bubbling gas discharges and water dissolved gases discharged from the island was estimated for vulcano island italy the co2 emission from fumaroles from the la fossa summit crater was estimated from the so2 crater output while co2 discharged through diffuse soil emission was quantified on the basis of 730 measurements of co2 fluxes from the soil of the island performed by using the accumulation chamber method the results indicate an overall output of 500 t day 1 of co2 from the island the main contribution to the total co2 output comes from the summit area of the la fossa cone 453 t day 1 with 362 t day 1 from crater fumaroles and 91 t day 1 from crater soil degassing the release of co2 from peripheral areas is 20 t day 1 by soil degassing palizzi and istmo areas mainly an amount comparable to both the contribution of water dissolved co2 6 t day 1 as well as to seawater bubbling co2 4 t day 1 measured in the istmo area presented data september 2007 refer to a period of moderate solphataric activity when the fumaroles temperature were 450 c and gas water molar ratio of fumaroles was up to 0 16 the calculated total co2emission allows the estimation of the mass release and related thermal energy from the volcanic hydrothermal system

co2 output and δ13c co2 from mount etna as indicators of degassing of shallow asthenosphere an estimated average co2 output from etna s summit craters in the range of 13 3 mt a has recently been determined from the measured so2 output and measured co2 so2 molar ratios to this amount the co2 output emitted diffusely from the soil 1 mt a and the amount of co2 dissolved in etna s aquifers 0 25 mt a must be added data on the solubility of co2 in etnean magmas at high temperature and pressure allow the volume of magma involved in the release of such an amount of this gas to be estimated this volume of magma 0 7 km3 a is approximately 20 times greater than the volume of magma erupted annually during the period 1971 1995 on the basis of c isotopic data of co2 collected in the etna area and of new hypotheses on the source of mediterranean magmas significant contributions of co2 from non magmatic sources to the total output from etna are unlikely such large outputs of co2 and also of so2 from etna could be due to an anomalously shallow asthenosphere beneath the volcano that allows a continuous escape of gases toward the surface even without migration of magma

the vema channel physiography structure and sediment current interactions abstract the east flank of the vema channel in the southwestern atlantic is an opportune location for interpreting the pleistocene holocene record of deep thermohaline circulation the channel and the adjacent sediment covered rio grande rise intersect each of the principal sub thermocline water masses of the western atlantic we analyzed a suite of 25 giant gravity cores in transects extending between 1400 and 4150 m depth this interval includes the upper and lower branches of circumpolar water north atlantic deep water and antarctic bottom water the late pleistocene holocene sediments along these transects are pelagic carbonates with excellent stratigraphic continuity shallower and deeper regions are relatively unsuitable due to poor core recovery or widespread erosional unconformities extensive hydrographic and direct current observations near the location of our prime coring transect at 30 s indicate a notable cross channel asymmetry in the abyssal hydrography and velocity structure which is reflected in the underlying lithofacies distribution the near bottom flow field shows marked temporal and spatial variability on a local scale even in the channel axis where one would anticipate relatively steady uniform flow much of this variability appears to reflect the effects of transient mesoscale eddies rather than regional variations in the integrated north ward transport of aabw in spite of temporal variations in the flow field the nadw aabw transition zone appears to have remained remarkably stable over time scales of 10 5 10 6 yrs on geological evidence discussed elsewhere in this volume jones 1984 jones and johnson 1984 this observation is somewhat surprising because in the modern oceans the density contrast between nadw and aabw is relatively small if the transition zone between the two water masses has indeed remained relatively stationary then the density determining water properties t and s may also have remained relatively constant with only the rates of production changing if this interpretation proves correct upon further studies it implies that pale oceanographic interpretations of deep thermohaline flow should in some instances utilize geological indices of non conservative water properties e g co 2 13 c for monitoring paleocirculation changes

mechanism of energy transfer in the lava lake of niragongo zaire 1959 1977 abstract heat and mass transfer rates were studied at the niragongo lava lake during two expeditions directed by h tazieff in 1959 and 1972 the results of this study are as follows heat is transferred to the surface of the lake by the movement of lava gas discharge is a result and not the cause of convection the chemical composition of the gases and magma has changed very little between 1959 and 1972 whereas the mass and energy outputs differ by an order of magnitude in 1977 a catastrophic explosion seems to have been caused by tectonic factors stopping the slow convection of magma under the volcano and hence reducing surface manifestations in the form of the lava lake and escaping fumarolic and magmatic gases the gas discharge was in tons day 1 5000 for h2o 11 000 for co2 1000 for so2 in 1959 and in 1972 7700 for h2o 180 000 for co2 and 23 000 for so2 these values correspond to an energy transfer of 0 9 109 w in 1959 and 16 109 w in 1972

rare earth elements in manganese nodules from the south atlantic ocean as indicators of oceanic bottom water flow abstract the mineralogy and geochemistry of a suite of nine manganese nodules from the south atlantic have been determined the ce la ratios of the nodules were investigated to see if they could be used as redox indicators to trace the oxygen content of the ambient water mass and the flow path of the antarctic bottom water as has previously been successfully carried out in the pacific ocean the ce la ratios of the nodules decrease in the sequence lazarev sea weddell sea 10 4 and 9 7 east georgia basin 6 5 and 7 1 argentine basin 5 0 but then increase in the brazil basin 6 2 and angola basin 9 8 and 15 1 a further decrease was observed in the cape basin 7 6 an extremely high ce la ratio of 24 4 had already been determined for nodules sampled north of the nares abyssal plain in the western north atlantic these data reflect the more complicated pattern of bottom water flow in the south atlantic than in the south pacific the penetration of more oxygenated north atlantic deep water into the south atlantic accounts for the higher ce la ratios in the nodules from the angola and brazil basins based on this study the flow path of the antarctic bottom water could only be traced as far north as the argentine basin the unique geochemistry of nodules from the central angola basin high mn fe and ce la ratios high contents of ni cu zn and mo appears to be a function of the nature of the overlying water mass and of the multiple diagenetic sources of metals to the nodules

modeling magnetostratigraphy in a borehole the magnetic field along a hole bored through a sequence of dipping layers with varying magnetization and planar interfaces is calculated the emphasis is on recovering remanent magnetization polarity transitions for magnetostratigraphic applications dating correlations although intensity of remanent magnetization can in itself be a useful rock property results are presented for various cases of geologic interest in the form of axial vertical profiles and section maps of the holes at varying distances from polarity reversal interfaces the vertical profiles demonstrate a resolving power of about six times the hole radius meaningful magnetostratigraphies can be expected for rocks with a magnetization larger than 10 3am 1 for instruments with a sensitivity of 0 1 nt in a number of natural occurrences it may not be necessary to resort to progressive demagnetization to recover the polarity sequence depending on which magnetic field and magnetization component one looks at the section maps display c

volatiles and energy released by purace volcano total co2 output of purace volcano colombia was estimated on the basis of fluids discharged by fumaroles soil gases and dissolved carbon species in the aquifer the soil co2 emission was computed from a field survey of 512 points of co2 soil flux measurements at the main degassing areas of purace volcano the co2 flux from purace s plume was estimated using an indirect method that used the so2 plume flux and co2 so2 ratio of the main high temperature fumarole the total output of co2 was estimated at 1500 t day the main contribution of co2 comes from the plume summit degassing and from soil degassing that emit 673 and 812 t day respectively the contributions of summit and soil degassing areas are comparable indicating an intermediate degassing style partitioned between closed and open conduit systems the estimated water vapor discharge as derived from the chemical composition of the fumaroles the h2o co2 ratio and the so2 plume flux allowed calculation of the total thermal energy fumarolic soil degassing and aquifer released from the purace volcanic system this was 360 mw

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

deep water circulation in the northeast atlantic and climatic changes during the late neogene dsdp site 141 abstract oxygen and carbon stable isotope data of pyrgo murrhina and flux rates of calcium carbonate in the bio and magnetostratigraphically dated sediment sequence at dsdp site 141 were used for a reconstruction of the deep water circulation in the northeast atlantic during late miocene and pliocene times a distinct change towards reduced advection of deep water recorded near 5 4 ma is contemporaneous with the cessation of the outflow of the saline mediterranean water into the atlantic during the pliocene between 4 5 and 2 75 ma and between 2 1 and 1 8 ma north atlantic deep water nadw circulation was sluggish and site 141 possibly influenced by antarctic bottom water aabw near 2 75 ma the advection of well oxidized nadw was strongly intensified this change is related to an onset of major arctic ice growth and or a major cooling of nadw

recent benthic foraminifera from the continental margin of northwest africa community structure and distribution abstract sediment grab samples were collected at 107 locations along the continental margin of northwest africa these samples form a series of depth transects between the straits of gibraltar and dakar senegal the greater than 250 m size fraction was retained for a census of both the live and dead foraminifera after deleting trace occurrences jaccard and correlation coefficient based cluster analyses were performed to decipher the community structure for this margin the geographic distribution of the four major faunal provinces recognized is conventional in that for both the live and dead assemblages three are related to depth upper slope and shelf middle slope and lower slope and continental rise the biotopes and thanatotopes within these provinces are strongly restricted along vertical or latitudinal boundaries when the data are analysed using jaccard coefficients dendrograms constructed from correlation coefficients emphasize depth related faunal communities dominant species such as cibicides lobatulus trifarina fornasinii planulina ariminensis uvigerina finisterrensis and c wuellerstorfi are generally distributed within a definite depth range along this margin and strongly influence the correlation coefficient based dendrograms other distributions are clearly not depth related but correspond to various environmental variables for example cancris auriculus coarse substrate bolivina subaenariensis oxygen minimum cibicidoides kullenbergi and hoeglundina elegans low organic carbon uvigerina peregrina is also a notable exception to depth dependence in that this dominant species and the province it represents are generally confined to the continental slope south of cape blanc its preference for that region may arise from the high organic carbon and fine grain size of the sediment there from low salinity of the bottom water or from other unknown variables the most important vertical faunal boundary occurs between cape barbas and cape blanc between 22 and 21 n latitude in contrast the canary island ridge intersects the continental margin at a saddle depth of about 1500 m but that physiographic barrier has little effect on provincialism of the deep water benthic foraminifera

volcanism and vertical tectonics in the pacific basin related to global cretaceous transgressions abstract the dominance of volcanic processes and the importance of vertical tectonics in the geological evolution of the pacific basin has been recognised since the time of charles darwin data gathered on several legs of the deep sea drilling project dsdp and numerous marine expeditions in the past decade have confirmed menard s postulate that the pacific basin was the scene of volcanism on an enormous scale in mesozoic time widespread mid plate volcanism between 110 and 70 m y b p characterised the area bounded by the line islands the mid pacific mountains and the nauru basin marshall islands heating of the pacific lithospheric plate during this period of volcanism resulted in regional uplift and the bathymetric evolution of the area diverged significantly from a normal parsons sclater subsidence curve the farallon plate now almost entirely subducted was also the scene of mid plate volcanism that produced such features as the nicoya plateau now found as an allochthonous ophiolitic terrain landward of the middle america trench large benthonic reef associated foraminifera comprising a pseudorbitoid fauna hitherto considered to be largely restricted to central america have now been additionally recorded from dsdp sites 165 315 and 316 in the line islands site 462 in the nauru basin and in new guinea the distribution of this fauna of campanian maastrichtian age is interpreted as indicating stepping stone connections aseismic ridges plateaus and seamounts between the caribbean farallon and pacific plates 70 80 m y b p similarities between the geology of the nauru basin and the caribbean ocean crust reinforce the interpretation of the latter as a former part of the farallon plate estimates of the sea level and continental freeboard change caused by the thermally induced uplift of the pacific and farallon plates as well as substantial areas in the atlantic and indian ocean basins indicate that such shallowing of the sea floor could have been the major factor in causing global cretaceous transgressions

geochemical evidence of the renewal of volcanic activity inferred from co2 soil and so2 plume fluxes the 2007 stromboli eruption italy on 27 february 2007 a new eruption occurred on stromboli which lasted until 2 april it was characterized by effusive activity on the sciara del fuoco and by a paroxysmal event 15 march this crisis represented an opportunity for us to refine the model that had been developed previously 2002 2003 eruption and to improve our understanding of the relationship between the magmatic dynamics of the volcano and the geochemical variations in the fluids in particular the evaluation of the dynamic equilibrium between the volatiles co2 and so2 released from the magma and the corresponding fluids discharged from the summit area allowed us to evaluate the level of criticality of the volcanic activity one of the major accomplishments of this study is a 4 year database of summit soil co2 flux on the basis of which we define the thresholds low medium high for this parameter that are empirically based on the natural volcanological evolution of stromboli the so2 fluxes of the degassing plume and the co2 fluxes emitted from the soil at pizzo sopra la fossa are also presented it is noteworthy that geochemical signals of volcanic unrest have been clearly identified before during and after the effusive activity these signals were found almost simultaneously in the degassing plume so2 flux and in soil degassing co2 flux at the summit although the two degassing processes are shown to be clearly different the interpretation of the results will be useful for future volcanic surveillance at stromboli

abyssal teleconnections interactive dynamics of the deep ocean circulation abstract a teleconnective linkage between two abyssal water masses consists of one or more zones of interaction arranged sequentially in space and time the properties spatial extent and advective nature of one of these water masses are directly influenced by the presence of the other via the zones of interaction the sequence of components in the linkage may in some instances be configured linearly and respond in an irreversible fashion in other instances the linkage is not unidirectional but may include one or more feedback loops representing the dependence of each water mass upon the properties and extent of the other three types of water mass interaction are represented in the modern oceans these are designated as 1 re inforcing 2 lateral blocking re direction and 3 wedging the criteria for discriminating between these types are geometrical yet the physical processes and rates of interaction may be distinguishable between and perhaps characteristics of these different configurations regions of water mass interaction are marked by sharp gradients of water column properties each of which is spatially restricted to a narrow interval of the overall mixing zone sediment characteristics exhibit a similar pattern there is a broad transition zone within which each geological gradient is restricted to a relatively narrow interval one must distinguish between sediment indicators which reflect water properties and those which reflect water column advection and avoid inferring one type of waters characteristic from geological indices which are inappropriate for identifying such characteristics it is not possible to specify a priori all of the components of a teleconnection linkage we can identify critical zones of interaction and search for evidence of threshold events which contributed to the initiation or the breaking of a particular linkage in order to establish the spatial and temporal sequence of components in a complex linkage we must identify the frequency response and phase response spectra in high resolution time series of appropriate paleocenographic indices at key locations

review of the evolution of geochemical monitoring networks and methodologies applied to the volcanoes of the aeolian arc italy abstract fluids discharged from volcanic systems are the direct surface manifestation of magma degassing at depth and provide primary insights for evaluating the state of volcanic activity we review the geochemical best practice in volcanic surveillance based to a huge amount of monitoring data collected at different active volcanoes using both continuous and discontinuous approaches the targeted volcanoes belong to the aeolian arc located in the tyrrhenian sea italy and they have exhibited different activity states during the monitoring activities reported here la fossa cone on vulcano island has been in an uninterrupted quiescent stage characterized by variable solfataric activity in contrast stromboli island has shown a persistent mild explosive activity episodically interrupted by effusive eruptions in 1985 2002 2007 and 2014 panarea island which is the summit of a seamount rising from the seafloor of the southern tyrrhenian sea showed only undersea fluid release the only observable clues of active volcanism at panarea island have been impulsive changes in the undersea fluid release with the last submarine gas burst event being observed in november 2002 the geochemical monitoring and observations at each of these volcanoes has directly involved the volcanic plume and or the fumarole vents thermal waters and diffuse soil degassing depending on the type of manifestations and the level of activity encountered through direct access to the magmatic samples when possible and the collection of as much observable data related to the fluid release as possible the aim has been i to verify the thermodynamic equilibrium condition ii to discern among the possible hydrothermal magmatic marine and meteoric sources in the fluid mixtures iii to develop models of the fluid circulation supported by data iv to follow the evolution of these natural systems by long term monitoring and v to support surveillance actions related to defining the volcanic risk and the evaluation and possible mitigation of related hazards the examples provided in this review article show the close relationships among data analysis interpretation and modeling we particularly focus on describing the fieldwork procedures since any theoretical approach must always be verified and supported by field data rather than just by experiments controlled in laboratory indeed the natural systems involve many variables producing effects that cannot be neglected the monitored volcanic systems have been regarded as natural laboratories and all of the activities have focused on both volcanological research and surveillance purposes in order to ensure that these two goals have overlapped an appendix is also included that explains the scientific approach to the systematic activities regarding geochemical monitoring of volcanic activity

onset of the persistent activity at stromboli volcano italy stromboli known worldwide as the lighthouse of the mediterranean is commonly believed to have been in a state of persistent activity for the past 2000 2500 years however historical sources older than 1000 a d are not accurate enough to assess if the activity of the volcano was exactly the same as we see at present in order to attempt to identify the onset of the present eruptive regime and assess if it has been maintained with the same characteristics through time stratigraphic and radiometric studies of the recent tephra deposits were undertaken up to 4 m deep stratigraphic trenches dug at a height of approximately 500 m on the ne flank of the volcano exposed a conformable tephra pile containing charcoal fragments one of the most interesting finds was the discovery of a 7 cm thick weathered bed rich in organic matter thin palaeosol approximately 3 m below the surface the sequence underneath the palaeosol consists of decimetre thick lapilli fallout beds alternating with ash deposits bearing small charcoals with calibrated ages of between the fourth century b c and the first century a d the sequence above the palaeosol is charcoal free and consists of coarse ash deposits with discrete centimetre thick lapilli fallout beds composed of crystal poor golden pumice and subordinate crystal rich black scoriae similar to scoria pumice pairs emitted during the more energetic explosions of the present day activity the data collected indicate that between the third and seventh centuries a d after a period of quiescence the activity resumed with an eruptive style identical to the present one we conclude that the lighthouse of the mediterranean actually began its activity in a period much later than previously thought

preliminary estimate of co 2 output from pantelleria island volcano sicily italy evidence of active mantle degassing abstract total co2 output from fumaroles bubbling and water dissolved gases and soil gases was investigated at pantelleria island volcano italy the preliminary results indicate an overall output of 0 39 mt a 1 of co2 from the island the main contribution to the total output was from diffuse soil degassing about 0 32 mt a 1 followed by dissolved co2 0 034 mt a 1 focussed soil degassing 0 028 mt a 1 and bubbling co2 0 013 mt a 1 the contribution of co2 from fumarole gases was found to be negligible 1 4 10 6 mt a 1 carbon 13 values for co2 coupled with those for associated he in gases from fumaroles and sites of focussed soil degassing clearly rule out any significant organic co2 component and suggest a common mantle origin for these gas species the inferred mantle source beneath pantelleria would seem to have peculiar geochemical characteristics quite distinct from those of mantle producing morb but compatible with those of magmatic sources of central mediterranean and central european volcanoes these findings indicate that the pantelleria volcanic complex is a site of active mantle degassing that is worthy of attention for future geochemical surveillance of the island

soil co2 flux baseline in an urban monogenetic volcanic field the auckland volcanic field new zealand the auckland volcanic field avf is a dormant monogenetic basaltic field located in auckland new zealand though soil gas co2 fluxes are routinely used to monitor volcanic regions there have been no published studies of soil co2 flux or soil gas co2 concentrations in the avf to date or many other monogenetic fields worldwide we measured soil gas co2 fluxes and soil gas co2 concentrations in 2010 and 2012 in varying settings seasons and times of day to establish a baseline soil co2 flux and to determine the major sources of and controlling influences on auckland s soil co2 flux soil co2 flux measurements varied from 0 to 203 g m 2 day 1 with an average of 27 1 g m 2 day 1 higher fluxes were attributed to varying land use properties e g landfill using a graphical statistical approach two populations of co2 fluxes were identified isotope analyses of 13co2 confirmed that the source of co2 in the avf is biogenic with no volcanic component these data may be used to assist with eruption forecasting in the event of precursory activity in the avf and highlight the importance of knowing land use history when assessing soil gas co2 fluxes in urban environments

co2 output discharged from stromboli island italy abstract total co 2 output from soil gas and plume discharged from the stromboli island was estimated the co 2 emission of the plume emitted from the active crater was estimated on the basis of the so 2 crater output and c s ratio while co 2 discharged through diffuse soil emission was quantified on the basis of 419 measurements of co 2 fluxes from the soil of the whole island performed by using the accumulation chamber method the results indicate an overall output of 416 t day 1 of co 2 from the island the main contribution to the total co 2 output comes from the summit area 396 t day 1 with 370 t day from the active crater and 26 t day 1 from the pizzo sopra la fossa soil degassing area the release of co 2 from peripheral areas is 20 t day 1 by soil degassing scari area mainly the result of the soil degassing survey confirms the persistence of the highest co 2 degassing areas located on the north east crater side and scari area

displaced antarctic diatoms in the amirante passage abstract displaced antarctic source diatoms are found in surface sediments below 4100 in the amirante passage area but not above this depth their distribution tends to support the conclusion that a sharp velocity gradient exists within the antarctic bottom water aabw in this region below about 4100 m flow velocities are sufficient to resuspend and transport sediment while above this level the aabw is incapable of transporting sediment in suspension

a gyro oriented 3 component borehole magnetometer for mineral prospecting with examples of its application1 a triple axis borehole magnetometer is described that consists of a foerster probe fluxgate triplet sensitivity 1 nt a foerster probe gradiometer sensitivity 2 nt 40 cm a gyro unit mean angular drift approx 0 5 sup 0 h which is equipped with accelerometers sensitivity 1 100 sup 0 and a data transmission unit with multiplexer and 16 bit ad converter the sensitive fluxgate magnetometer can detect weakly magnetic or small source bodies data from the gyro and the accelerometers allow the 3 component magnetic field values to be transformed to north east and vertical components since they do not rely on magnetically determined directional data the results are not disturbed by local anomalies of the magnetic declination furthermore the magnetometer can also be used in vertical boreholes 3 component measurements are carried out at discrete points in the neighbourhood of a source body to locate its position and within the source body to determine the direction of magnetization the strength of magnetization and information on magnetic classification are obtained by continuous measurement of one or more components within the source body calculation algorithms and computer programs are available to simplify data processing and interpretation survey examples are discussed

zirconium hafnium and rare earth element signatures discriminating the effect of atmospheric fallout from hydrothermal input in volcanic lake water geochemical behaviour of rare earth elements ree zr and hf was investigated in co2 rich waters circulating in pantelleria island also including specchio di venere lake within a calderic depression a wide range of total dissolved ree concentrations was found 2 77 12 07 nmol l 1 with the highest contents in the lake the main ree complexes in the co2 rich waters are ree co3 2 and reeco3 showing changeable proportions as a function of ph the ree normalized to post archean australian shale paas showed similar features with heavy ree hree enrichments in co2 rich waters collected from springs and wells whereas a different ree pattern was found in the specchio di venere lake water with middle ree mree enrichments the paas normalized concentration ratios lree hree n and mree hree n in waters are 1 positive eu anomalies were found in the investigated waters owing to water rock interactions with less evolved host rocks ce anomalies as a function of eh values were recognized with the highest ce anomaly occurring in the lake water with respect to the co2 rich waters the y ho and zr hf molar ratios are higher in the investigated waters except for lake water than that in the local rocks with values ranging from 35 4 to 77 9 and from 76 3 to 299 respectively the precipitation of authigenic phases was considered to be responsible for the increase in the y ho and zr hf ratios owing to enhanced hf and ho removal with respect to zr and y

multivariate analysis of co2 h2s and ch4 diffuse degassing and correlation with fault systems in agua caliente tzitzio michoacan mexico abstract the quantitative relationships between soil gas flux anomalies and faults systems in agua caliente tzitzio geothermal system were analyzed statistically the main degassing features are related with thermal springs the data used in the multivariate analysis are geothermal gas fluxes and spatial structural data i e local fault strike exploratory data analysis eda and multivariate analysis of variance manova were implemented for the first time to statistically describe the relation between the location of degassing features and the presence of some local fault systems discriminating the direction of the main discharge channels and pointing to higher permeability faults the results show that there is a statistically significant correlation between diffuse degassing of co2 and ch4 and the n s and e w fault systems conversely h2s degassing does not show any correlation with the fault systems which may be related with the higher h2s reactivity compared with that of co2 and ch4 it is highly recommended to use eda and manova techniques in order to establish the main degassing directions in geothermal and volcanic areas

carbon dioxide emissions from specchio di venere pantelleria italy we have mapped the diffuse co2 efflux from the specchio di venere lake area using the accumulation chamber method we calculated a co2 emission of 43 5 t day 1 for the area studied accounting for both diffuse degassing from soil and bubbling through the lake we also present data on the water composition of specchio di venere lake the polla 3 spring and liuzza well on the basis of water chemistry two physical chemical processes evaporation and mineral precipitation of carbonate species are invoked to explain the co2 degassing for the lake area

late tertiary quaternary magnetostratigraphy and biostratigraphy of vema channel sediments abstract twenty one piston cores in a transect of the vema channel near 31 s were analyzed magnetostratigraphically and biostratigraphically in order to ascertain the depositional continuity in the late tertiary and quaternary the cores span a depth interval of 2941 4235 m and represent three distinct physiographic provinces each of which shows a relatively consistent accumulation pattern the deepest cores are from the broad terraces which flank the vema channel axis on both the west 3650 mm and east 4150 4250 m these cores show the highest accumulation rates in the region 20 m m y 2 and no evidence of unconformities twelve cores from the flanks of the rio grande rise 2941 3950 m show depositional continuity in the late quaternary and normal pelagic accumulation rates 5 10 m m y 2 with evidence in two of the cores for minor erosional hiatuses on a local scale perhaps due to slumping a relatively narrow transition zone between the rio grande rise flanks and the eastern terrace 3950 4150 m shows buried manganese pavements and near outcrops of miocene pliocene strata indicating intermittent erosion during the late tertiary and quaternary perhaps due to episodes of intensified aabw flow modern flow within this transition zone and over the eastern terrace is relatively weak gu 2 cm s 2 and southward the presence of well developed sediment waves on the terrace and buried erosional unconformities upslope to the east suggests substantially higher current velocities during the late tertiary than those present today

cretaceous ocean floor in the amirante passage tectonic and oceanographic implications abstract core v34 76 obtained near the summit of a basement ridge in the axis of the amirante passage recovered in situ pelagic chalk of latest cretaceous age abathomphalus mayaroensis zone ca 66 ma this minimal age for the nne trending basement ridges places important constraints on the crustal age of the amirante passage region in the western indian ocean and indicates that the passage has provided a deep water connection between the mascarene and somali basins throughout the entire cenozoic

geochemical characterisation of gases along the dead sea rift evidences of mantle co2 degassing abstract the dead sea transform dst fault system where a lateral displacement between the african and arabian plates occurs is characterised by anomalous heat flux in the israeli area close to the border with syria and jordan the concentration of he and co2 and isotopic composition of he and total dissolved inorganic carbon were studied in cold and thermal waters collected along the dst in order to investigate the source of volatiles and their relationship with the tectonic framework of the dst the waters with higher temperature up to 57 2 c are characterised by higher amounts of co2 and helium up to 55 72 and 1 91 10 2 cc l 1 respectively helium isotopic data r ra from 0 11 to 2 14 and 4he 20ne ratios 0 41 106 86 show the presence of deep deriving fluids consisting of a variable mixture of mantle and crust end members with the former reaching up to 35 carbon isotope signature of total dissolved carbon from hot waters falls within the range of magmatic values suggesting the delivery of deep seated co2 the geographical distribution of helium isotopic data and isotopic carbon co2 values coupled with co2 3he ratios indicate a larger contribution of mantle derived fluids affecting the northern part of the investigated area where the waters reach the highest temperature these evidences suggest the occurrence of a favourable tectonic framework including a moho discontinuity up rise and or the presence of a deep fault system coupled with the recent magmatic activity recognised in the northern part of israel

oceanic mechanisms for amplification of the 23 000 year ice volume cycle situated adjacent to the largest northern hemispher ice sheets of the ice ages the mid latitude north atlantic ocean has an important role in the earth s climate history it provides a significant local source of moisture for the atmosphere and adjacent continents forms a corridor that guides moisture bearing storms northward from low latitudes and at times makes direct contact along its shorelines with continental ice masses evidence of major ice ocean air interactions involving the north atlantic during the last 250 000 years is summarized outflow of icebergs and meltwater initially driven by summer insolation over the ice sheets affects midlatitude ocean temperatures summer heat storage winter sea ice extent and global sea level these oceanic responses in turn influence the winter moisture flux back to the ice sheets as well as ablation of land ice by calving spectral data indicate that the oceanic moisture and sea level feedbacks in part controlled by glacial melt products amplify milankovitch insolation forcing of the volumetrically dominant mid latitude ice sheets at the 23 000 year precessional cycle

comparison of cretaceous and present earth albedos implications for the causes of paleoclimates a planetary albedo model is developed to examine the influence of geologic variables specifically land sea distribution temperature sea ice vegetation and cloud cover on the solar radiation absorbed by the earth by specifying conditions 100 million years ago based on a paleo continental reconstruction which includes paleogeography and on interpretation of the paleoclimatic record we compare the planetary albedo and absorbed solar radiation of the mid cretaceous and present day the warm equable mid cretaceous characterized by extensive inland seas provides the greatest known geologic and climatic contrast from the present day for which boundary conditions can be specified we compute an increase of 2 3 in global mean absorbed solar radiation for 100 million years ago using present day cloud cover paleogeography and land surface albedo are important components of the change although the planetary albedo is only one component of the climate system the results have considerable significance

the 2002 2003 eruption of stromboli italy evaluation of the volcanic activity by means of continuous monitoring of soil temperature co2 flux and meteorological parameters 1 from december 2002 to july 2003 stromboli volcano was characterized by a new effusive stage of eruption after a period of extraordinary strombolian activity signals recorded in two continuous monitoring stations during the eruption which have already been presented in very recent papers evidenced anomalies in the co2 flux just before the onset of the eruption a more detailed analysis carried out on the data subset acquired during the eruption integrated by daily field observations of the scientific personnel working at the volcanological observatory in stromboli showed that co2 flux and soil temperature are strictly related to volcanic events furthermore the relative minima and maxima of the two parameters showed a strong correlation with wind speed and direction this fact was especially true at the summit station whereas at the coastal sites seasonal and meteorological effects masked the volcanic signal the analysis of the wind data particularly the relationships between wind speed and direction air and soil temperature and local circulation of atmospheric air masses revealed that during the eruption in the summit area of stromboli air movements were not only related to atmospheric circulation but were also significantly affected and in certain cases caused by volcanic activity this conclusion was reached by observing several anomalies such as the discrepancies in the wind direction between the two stations higher air temperatures at the summit site and inversion of direction for wind before and after the reopening of the conduit in a major explosion on 5 april 2003 the relationships found between volcanic activity soil temperatures co2 fluxes and wind speed and direction indicate that soil temperature measurements in an open conduit volcano such as in this case could be used to monitor the level of volcanic activity along with co2 flux furthermore the possible volcanic origin of a peculiar type of air circulation identified in the summit area of stromboli suggests that the separation between volcanic and atmospheric signals might not be obvious requiring monitoring over a wide area rather than a single location

unusually large magmatic co2 gas emissions prior to a basaltic paroxysm 1 the low intensity activity of basaltic volcanoes is occasionally interrupted by short lived but energetic explosions which whilst frequently observed are amongst the most enigmatic volcanic events in nature the combination of poorly understood and deep challenging to measure source processes make such events currently impossible to forecast here we report increases in quiescent degassing co2 emissions 10 000 t day prior to a powerful explosive event on stromboli volcano on 15 march 2007 we interpret such large co2 flux as being sourced by passive gas leakage from a deeply 4 km stored magma whose depressurization possibly caused by the onset of an effusive eruption on 28 february 2007 was the explosion trigger our observations suggest that continuous co2 flux monitoring may allow anomalously large explosions to be accurately forecast at basaltic volcanoes

late miocene early pliocene planktonic foraminiferal biostratigraphy and paleoceanography of low latitude marine sequences abstract plate reorganization and development of polar glaciation are closely associated with the changing climatic conditions of the cenozoic the planktonic foraminiferal fauna in three low latitude dsdp sites 224 ninety east ridge 317b manihiki plateau 366a sierra leone rise has been examined to determine how these regions responded to the late miocene climatic cooling that has been previously observed in high latitude regions it has been proposed that an expansion of antarctic glaciation and a resultant eustatic regression are associated with this cooling with the latter being at least partially responsible for the messinian salinity crisis in the mediterranean only one of the sites 366a shows any significant faunal change during the late miocene and early pliocene approximately 8 3 ma during the late miocene there is a decrease in the abundance of species considered to be tropical subtropical suggesting the incursion of a cool water mass into the sierra leone rise region during this time the lack of any major faunal changes at sites 214 and 317b indicates that the water masses of the low latitude regions of the indo pacific were relatively unaffected by this cooling in the late miocene the three sites also show no evidence for a change in the level of the ccd between the late miocene and early pliocene however this is most likely due to their equatorial position and shallow water depth higher latitude sites from both the atlantic and the pacific reveal a definite shoaling of the ccd during the late miocene

geochemical monitoring of the 2002 2003 eruption at stromboli volcano italy precursory changes in the carbon and helium isotopic composition of fumarole gases and thermal waters significant changes in the helium and carbon isotopic composition of shallow thermal waters vs gas and a crater fumarolic gas have been recorded at stromboli prior and during the 2002 2003 eruption the3he 4he ratios corrected for air contamination rc ra and 13c of fumarolic gases gradually increased from may to november 2002 before the eruption onset these variations imply early degassing of a gas rich magma at depth that likely fed both the intense strombolian activity and small lava overflows recorded during that period the lava effusion of late december 2002 was shortly preceded by a marked rc ra decrease both in water and fumarolic gases comparison of he co2 and ch4 co2 ratios in dissolved gas and with rm delta 13 rm c rm co 2 values rules out the rc ra decrease due to an increasing input of radiogenic4he the rc ra decrease is attributed to the he isotope fractionation during rapid magma ascent and degassing a new uprising of 3he rich magma probably occurred in january to february 2003 when rc ra ratios displayed the highest values in dissolved gases ever measured before 4 56 rc ra the increase in he co2 and ch4 co2 ratios and decrease in 13c of dissolved co2 was recorded after the 5 april 2003 explosive paroxysm likely caused by enhanced gas water interaction inducing co2 dissolution no anomalous rc ra values were recorded in the same period when usual strombolian activity gradually resumed

a late pleistocene time series of bottom current speed in the vema channel abstract a coarsening of the mean particle size of the carbonate free silt fraction from sea floor samples below 4000 m in the vema channel has been used to separate high velocity antarctic bottom water aabw from the overlying slower north atlantic deep water nadw a time series of fluctuations in bottom current speed within the modern aabw nadw transition zone was examined by determining the particle size distribution of sediments from eight gravity cores with a high resolution stratigraphy for the past 250 kyrs the bottom current paleospeed was inferred from a correlation of particle size in seafloor samples with mean current speed from nearby current meters the mean bottom current speed at depths comparable to modern aabw was highest 7 10 cm s during interglacial to glacial transitions corresponding to the oxygen isotopic stage 6 7 and 4 5 boundaries and at present the mean bottom current speed at depths comparable to modern nadw was nearly uniform for most of the past 250 kyrs except during glacial oxygen isotopic stage 2 when the speed dropped to 2 cm s or one half of the present speed the application of the calibrated particle size method to examine bottom current paleospeed allows testing of paleoceanographic models which rely on assumptions or inferences of changes in bottom water production rate during the late pleistocene paleoclimatic fluctuations

bottom current speed in the vema channel recorded by particle size of sediment fine fraction abstract the particle size distribution of the carbonate free silt fraction was determined in forty two core top samples from the east flank of the vema channel in order to allow comparison of the mean particle size with near bottom current speed based on nearby ctd and current meter observations the silt mean particle size fluctuates insignificantly between 1450 3950 m but coarsens markedly below 4000 m under antarctic source bottom currents the top of the zone of coarse sizes approximates the top of lower circumpolar water lcpw at 4000 m the steep gradient to coarsest sizes in the axis of the channel marks the transition to antarctic bottom water aabw the vertical profile of mean particle size on the east flank correlates in general respects with the vertical velocity gradient in the channel axis although the core sites on the east flank are as far as 200 miles from the current meter arrays nevertheless this relationship is used to infer that the non carbonate particle sizes deposited on the east flank of the channel may be an indication of bottom current speed and therefore the mean size is used to reconstruct profiles of mean current speed for three time slices 18 120 and 140 ka b p during glacial isotopic stages 2 and 6 the particle sizes deposited on the east flank of the channel are characterized by finer sizes at nearly all depths and the zone of coarse sizes corresponding to lcpw and aabw deepens during interglacial isotopic stage 5e the particlesize profile is very similar to the modern profile however lcpw and aabw appear to be deeper than at present the finer particle sizes deposited at nearly all depths during glacial periods indicates that the velocity of deep circulation in the atlantic was reduced in response to the ice ages deep circulation during isotopic stage 5e closely resembled modern circulation however aabw production rates may have been less that at present

do layer 3 rocks make a significant contribution to marine magnetic anomalies in situ magnetization of gabbros at ocean drilling program hole 735b we estimate the average magnetization of a vertical section of oceanic gabbros using paleomagnetic and downhole magnetic logging techniques and evaluate the ability of these crustal rocks to contribute to marine magnetic anomalies results from ocean drilling program hole 735b show that the drilled crustal section has a mean effective remanent magnetization of 2 5 a m olivine gabbros which make up 60 of the section have an average effective magnetization between 1 and 2 a m we used two dimensional forward modeling and the average effective magnetization of olivine gabbros to predict the magnitude of a typical layer 3 anomaly observable at sea surface these results indicate that if polarity boundaries within oceanic layer 3 are near vertical crustal sections similar to 735b would contribute from 25 to 75 of the overlying marine magnetic anomalies at the sea surface the shape of the polarity boundaries in lower crust will be controlled by its thermal evolution and potentially could be constrained by systematic analyses of the amplitude and skewness of marine magnetic anomalies at individual spreading centers

deep circulation changes in the south atlantic ocean response to initiation of northern hemisphere glaciation particle size statistics coarsest 1 percentile and mean of the nonbiogenic silt fraction of samples from deep sea drilling project sites 514 516a 517 518 and 548 were used to infer relative changes in paleospeed of deep water masses in the atlantic ocean during the late pliocene initiation of northern hemisphere glaciation grain size statistics were integrated with previous studies of geochemical and faunal assemblages to examine how climatic forcing regulates deepwater mass paleospeed and stratification on the basis of between site comparison of particle size the late pliocene was divided into four intervals of deepwater activity 3 2 to 2 9 ma 2 9 to 2 6 ma 2 6 to 2 5 ma and 2 5 to 2 3 ma with pulses of increased paleospeed occurring at 3 15 3 10 2 85 2 7 2 6 and 2 4 ma except for a brief increase in paleospeeds at 3 1 ma the first time interval is characterized by low inferred antarctic bottom water aabw paleospeed corresponding to depleted 13c and enriched 18o values in all but the shallowest core enriched 13c and depleted 18o values in the shallowest core correspond to coarse grain sizes and are inferred to represent a deep and intense antarctic intermediate water aaiw the expansion of aabw and aaiw precludes a significant north atlantic deep water nadw incursion to 30 s at this time the interval from 2 9 to 2 6 ma is dominated by climatic cooling and an influx of deep waters originating in the north atlantic the introduction of significant volumes of mediterranean outflow water mow as demonstrated by increased inferred paleospeed at site 548 and an expanding glaciation beginning at 2 9 ma resulted in increased paleospeed and an expansion of nadw in the south atlantic a pulse of increased inferred paleospeed at 2 7 ma resulted in the temporary deepening of nadw to the depth of site 518 presently 3944 m from 2 9 to 2 6 ma aabw velocity remained low but aaiw deepened and intensified the 2 6 to 2 5 ma interval represents the retreat of deep water originating in the north atlantic from the depth of site 518 to the depth of site 517 presently 2963 m increased inferred paleospeed at site 518 corresponds with depleted 13c values and a northward shift in the polar front thus suggesting the reintroduction of circumpolar water to the depth of site 518 and the establishment of a deepwater stratification similar to today s a continuing trend toward a modern stratification continued into the latest time interval 2 5 2 3 ma as inferred deepwater paleospeed at all depths increased in response to the formation of extensive northern hemisphere ice sheets

co2 and he degassing at el chichon volcano chiapas mexico gas flux origin and relationship with local and regional tectonics during 2007 2008 three co2 flux surveys were performed on el chichon volcanic lake chiapas mexico with an additional survey in april 2008 covering the entire crater floor including the lake the mean co2 flux calculated by sequential gaussian simulation from the lake was 1 190 march 2007 730 december 2007 and 1 134 g m 2 day 1 april 2008 with total emission rates of 164 9 5 march 2007 59 2 5 december 2007 and 109 6 6 t day 1 april 2008 the mean co2 flux estimated from the entire crater floor area was 1 102 g m 2 day 1 for april 2008 with a total emission rate of 144 5 9 t day 1 significant change in co2 flux was not detected during the period of survey and the mapping of the co2 flux highlighted lineaments reflecting the main local and regional tectonic patterns the 3he 4he ratio as high as 8 1 ra for gases in the el chichon crater is generally higher than those observed at the neighbouring transmexican volcanic belt and the central american volcanic arc the co2 3he ratios for the high 3he 4he gases tend to have the morb like values 1 41 109 and the co2 3he ratios for the lower 3he 4he gases fall within the range for the arc type gases the high 3he 4he ratios the morb like co2 3he ratios for the high 3he 4he gases and high proportion of morb co2 m 25 15 at el chichon indicate a greater depth for the generation of magma when compared to typical arc volcanoes

the hawaii to tahiti shuttle experiment the shuttle experiment conducted between hawaii and tahiti from january 1979 to june 1980 was designed to observe the changing equatorial ocean structure and circulation to study the variations and interactions of the four major equatorial ocean currents and to develop a scientific basis for their monitoring by simple observations of thermal structure and sea level preliminary analyses of the results show that the equatorial thermal structure remains intact during a normal year and that only the positions and intensities of the currents are subject to change the water transport of the equatorial undercurrent varied from 25 x 106 cubic meters per second in january to 51 x 106 cubic meters per second in july but also exhibited strong short term pulsations the equatorial surface flow responded strongly to the winds at periods of 1 month and longer an array of drifter buoys in the equatoral countercurrent was subject to very little dispersion while traveling over 4500 kilometers in 4 months low frequency fluctuations in the north equatorial countercurrent can be monitored by means of the difference in sea level between fanning and majuro

heat flux based strategies for the thermal monitoring of sub fumarolic areas examples from vulcano and la soufriere de guadeloupe although it is relatively easy to set up the monitoring of soil temperature in sub fumarolic areas is quite rarely used to monitor the evolution of hydrothermal systems indeed measurements are highly sensitive to environmental conditions in particular daily and seasonal variations of atmospheric temperatures and rainfalls which can be only partially filtered by the established statistical analysis in this paper we develop two innovative processing methods both based on the computation of the heat flux in the soil the upward heat flux method uhf designed for dry environments consists in computing both the conductive and convective components of the heat flux between two thermocouples placed vertically in the cases of wet environments the excess of total heat method eth allows the integration of rain gauges data in order to correct the heat balance from the superficial cooling effect of the precipitations the performances of both processing techniques are faced to established methods temperature gradient and coefficient of determination on soil temperature time series from two test volcanoes at la fossa di vulcano italy the uhf method undoubtedly detects three thermal crises between 2009 and 2012 enabling to quantify not only the intensity but also the precise timing of the heat flux increase with respect to corresponding geochemical and seismic crises at la soufriere de guadeloupe french lesser antilles despite large rainfalls dramatically influencing the thermal behavior of the soil a constant geothermal heat flux is retrieved by the eth method confirming the absence of fumarolic crisis during the observation period february august 2010 being quantitative robust and usable in almost any context of sub fumarolic zones our two heat flux based methods increase the potential of soil temperature for the monitoring but also the general interpretation of fumarolic crises together with geochemical and seismological observations a spreadsheet allowing direct computation of uhf and eth is provided as supplemental material

borehole magnetic surveys in weakly magnetic sediments chicxulub impact crater versus strongly magnetic volcanics bathurst mining camp borehole navigation surveys performed using a triaxial fluxgate magnetometer record the change in orientation of the magnetic vector versus depth variations in the orientation of the magnetic vect

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

isotopic chemical and dissolved gas constraints on spring water from popocatepetl volcano mexico evidence of gas water interaction between magmatic component and shallow fluids abstract geochemical research was carried out on cold and hot springs at popocatepetl popo volcano mexico in 1999 to identify a possible relationship with magmatic activity the chemical and isotopic composition of the fluids is compatible with strong gas water interaction between deep and shallow fluids in fact the isotopic composition of he and dissolved carbon species is consistent with a magmatic origin the presence of a geothermal system having a temperature of 80 100 c was estimated on the basis of liquid geothermometers a large amount of dissolved co 2 in the springs was also detected and associated with high co 2 degassing

deep sea drilling project leg 72 southwest atlantic paleocirculation and rio grande rise tectonics in order to investigate south atlantic paleocirculation and the tectonic and sedimentary history of the rio grande rise d v glomar challenger occupied four sites during deep sea drilling project dsdp leg 72 site 515 in the brazil basin site 516 near the crest of the rio grande rise and sites 517 and 518 on the lower western flank of the rise site 515 recovered sediments deposited by antarctic bottom water aabw entering the brazil basin through the vema channel we penetrated 617 m of rapidly accumulated terrigenous and siliceous muds and mudstones before encountering an unconformity spanning 20 to 25 m y between the late oligocene and early eocene the hiatus brackets the time of the proposed onset of aabw flow in the southwestern pacific at 37 m y however evidence in the sediments at site 515 suggests the presence of bottom water circulation in the brazil basin by early eocene time sites 517 and 518 recovered calcareous sediments deposited under the influence of aabw and north atlantic deep water nadw within the vema channel at both sites an increase in the abundance of the aabw indicator species n umbonifera during the late pliocene implies that aabw extended to significantly shallower depths at that time than it does today detailed carbonate analyses at site 518 may extend the late pleistocene climatic signal through the entire pleistocene and perhaps into the miocene at site 516 near the crest of the rio grande rise we penetrated 1 250 m of dominantly calcareous sediments and 21 m of basaltic basement rocks of santonian coniacian age with the exception of some minor hiatuses in the middle and late miocene sedimentation at this site was continuous for the past 80 m y magneto stratigraphic and biostratigraphic control is excellent and the section may therefore be useful as a stratigraphic reference the cretaceous tertiary boundary was recovered intact and is directly comparable with the italian gubbio section this interval may also provide some new evidence pertaining to the proposed association between mass extinctions and geochemical anomalies at the boundary the igneous basement rocks recovered at site 516 are t type mid ocean ridge basalts morb similar to those found on iceland and are unlike the alkalic basalts exposed on tristan da cunha their chemistry together with the occurrence of shallow water fossils in vein fillings suggests that these basalts were erupted on an anomalously shallow part of the mid atlantic ridge a santonian coniacian age for basement is inferred from the age of the overlying sediments and is consistent with the identification of magnetic anomalies 33 and 34 on the rise to the east of the site the basal sediments and underlying volcanic basement recovered at site 516 may provide constraints on the subsidence history of the rio grande rise however this history may have been complicated by a middle eocene episode of tectonic and volcanic activity as suggested by ash layers volcaniclastic sediments and slump blocks in the mid eocene sediment section the occurrence of reef debris in this interval implies that the uppermost part of the rise was very shallow and perhaps subaerial during this time

geochemical precursors of the activity of an open conduit volcano the stromboli 2002 2003 eruptive events 1 marked increases of co2 h2 and he dissolved in thermal waters and changes in the dissolved carbon isotopic composition were observed at stromboli before the 28 december 2002 eruption and before a violent explosive paroxysm occurred on 5 april 2003 high anomalous co2 flux values were recorded at the crater rim since a week before the eruption onset the first anomalies in the thermal waters dissolved co2 amount appeared some months before the eruption when magma column rose at a very high level in the conduit high peaks of dissolved h2 and he were recorded a few days before the paroxysm carbon isotopic composition indicates a magmatic origin of the dissolved co2 whose increase together with those of h2 and he is attributed to an increasing output of deep gases likely produced by depressurization of a rising batch of a deep gas rich magma whose fragments have been emitted during the explosion

the contribution of fluid geochemistry to the volcano monitoring of stromboli abstract the persistent open vent mild explosive activity of stromboli volcano is episodically interrupted by more violent and dangerous explosive events major explosions and paroxysms according to the nature of erupted products paroxysms can be related either to the explosion of overpressured gas pockets located in the proximity of the magma column or to the sudden uprise of hot gas rich magma from a deep part of the plumbing system in both cases these more energetic explosive events should be preceded by an escape or a preferential uprise of the highly mobile volatiles which in turn should produce gas leakage anomalies at the surface in sites of high vertical permeability such as deep reaching faults in order to identify such gas leaking sites a systematic co2 soil flux survey has been carried out on the island using an accumulation chamber four hundred sixty one points have been measured with a high density in the summit crater area where high flux values have been found 10 3 10 2 cm s anomalous points are concentrated along the main ne sw axial feeding system of the volcano co2 soil flux decreases from the crater zone to the base of the volcanic cone where however an interesting gas leakage anomaly occurs pizzillo mofette in the pizzillo area thermal water wells also occur whose chemistry indicates an origin by sea water heated by hot gas soil gases have been sampled in the sites with the highest co2 flux in the crater area and at the base of the cone chemical and isotopic analyses indicate the presence of a deep gas component especially in the crater zone samples high co2 appreciable contents of he and h2 3he 4he values up to 3 55 13c of co2 2 the sc5 low flux fumarole on the crater rim has shown during six years a remarkable persistence of temperature 93 95 c with only minor fluctuations of chemistry appearance of anomalous peaks of h2 in correspondence with strombolian explosions was observed during a 2 h 30 min experiment of continuous recording of hydrogen content of the fumarole together with previous data on h2o co2 and he this experiment confirms that strombolian blasts produce rapid fluctuations in the fumarolic gas composition in the light of this study sc5 fumarole and pizzillo mofette look promising sites for the testing of a continuous geochemical monitoring system of stromboli volcano

the escarot gas seep french massif central co 2 discharge from a quiescent volcanic system characterization and quantification of gas emissions abstract natural co2 emissions from the volcanic rocks of the french massif central are poorly constrained it is of interest better to assess the emission of such non anthropogenic gases that may significantly contribute to the global carbon budget we quantified the co2 emissions to the atmosphere in a small area 0 052 km2 located in the massif central close to lake pavin the most recent volcanic edifice in metropolitan france the specific character of this area known as the escarot mofette was earlier studied for soil gas concentrations only in june 2017 we used the accumulation chamber method for measuring co2 flux and related o2 depletion in the gases emitted at the soil atmosphere interface resulting in 176 data acquisitions over four days in addition 44 soil gas concentration measurements were made at selected locations co2 emission rates are estimated at 8100 1800 tons year of deep seated co2 and at 660 440 tons year of biologically produced co2 the uncertainty on these evaluations comes from the high frequency variability of co2 efflux in the more emissive areas and from the occurrence of heavy precipitation events though unexpected these events were used for quantifying the decreases in co2 efflux which were as high as 500 over a few hours or even days in some locations however repeat acquisitions performed under more favourable weather conditions showed errors of commonly accepted amplitude 15 the area showed several degassing centres aligned along a nnw sse direction that correlates well with known geological structures proving the ability of soil gas methods to map hidden faults the whole area is characterized by strong co2 enrichment and related o2 depletion but it is nonetheless possible to detect areas influenced by the rise of deep seated gases and a few peripheral areas where biological processes dominate co2 up to 10 vol this study of gas emissions in a non urban area also provides complementary information that is of use when extrapolated to similar structures in urban areas where the occurrence of such gas releases and its potential hazard may be more difficult to assess

paleo oceanography global ocean evolution paleoceanography one of the youngest branches of earth sciences is concerned with the development of oceanic circulation through geologic time this is a multifaceted and integrated endeavor since none of the subdisciplines is easily separated from the others the field is holistic in character and includes the history and effects of bottom intermediate and surface circulation patterns planktonic and benthonic biogeographic development and rates of organic evolution the history of biogenic productivity and dissolution and their effect on sediment distribution and the consequences of sea level change paleoceanography was largely born of the deep sea drilling project dsdp and continues to be nourished by it because problems are of global scope the appetite for new sediment core material is large and is being supplied by numerous expeditions of dsdp this article is a brief overview of a number of advances that have occurred in paleoceanography and related fields during the period from 1979 to 1982 because of page limitations all publications cannot be cited which is not meant to indicate any lack of importance

paleoflow history determined from mudwave migration argentine basin abstract a mudwave site in the central argentine basin was investigated to determine its present and past mudwave activity site 7 on the south flank of the ewing drift in the northern argentine basin has mudwaves that have migrated primarily throurgh preferential deposition resulting in a relatively complete sediment on both wave flanks thus a history of mudwave migration can be determined for this site the mudwave studied shows migration from before 420 ka until 32 ka with paleocurrent speeds near 15 cm s 1 and with minor changes in current speeds around 110 120 ka the wave migration rate became less from 32 ka to 26 ka with paleospeeds of 9 cm s 1 wave migration ceased about 26 ka suggesting a cessation in flow this study indicates that bottom water velocities at this site were high during the last glacial period but dropped abruptly near the end of the last glacial period however bottom current velocities appear to have been moderately high during the previous interglacial period 120 ka suggesting that there is no simple relationship between flow speed and paleoclimate at this site

geochemical evaluation of observed changes in volcanic activity during the 2007 eruption at stromboli italy abstract on february 27 2007 a new eruption started at stromboli that lasted until april 2 and included a paroxysmal explosion on march 15 geochemical monitoring carried out over several years revealed some appreciable variations that preceded both the eruption onset and the explosion the carbon dioxide co 2 flux from the soil at pizzo sopra la fossa markedly increased a few days before the eruption onset and continued during lava effusion to reach its maximum value at 90 000 g m 2 d 1 a few days before the paroxysm almost contemporarily the 13 c co 2 of the sc5 fumarole located in the summit area increased markedly peaking just before the explosion 13 c co 2 1 8 following the paroxysm helium he isotopes measured in the gases dissolved in the basal thermal aquifer sharply increased almost contemporarily the automatic station of co 2 flux recorded an anomalous degassing rate also temperatures and the vertical thermal gradient which had been measured since november 2006 in the soil at pizzo sopra la fossa showed appreciable variabilities that lasted until the end of the eruption the geochemical variations indicated the degassing of a new batch of volatile rich magma that preceded and probably fed the paroxysm the anomalous 3 he 4 he ratio suggested that the ascent of a second batch of volatile rich magma toward the surface was probably responsible of the resumption of the ordinary activity a comparison with the geochemical variations observed during the 2002 2003 eruption indicated that the 2007 eruption was less energetic

the role of the aquifer in soil co 2 degassing in volcanic peripheral areas a case study of stromboli island italy abstract the peripheral area of stromboli island italy named scari was continuously studied between january 2009 and december 2010 data on soil co 2 flux and the partial pressure of co 2 pco 2 in equilibrium with the thermal aquifer linked to the magmatic system are presented soil co 2 fluxes range from 20 to 370 g m 2 d 1 and have been strongly affected by soil temperature variations soil co 2 flux data were filtered with respect to the soil temperature and the calculated values called residuals were considered to detect changes induced by the magmatic system the pco 2 values change in a wide range from 0 03 to 0 6 atm showing rapid variations the results of this study show that in the volcanic peripheral area the degassing process of soil co 2 is determined not only by the co 2 released directly from the magma but also by gas water interactions in the aquifer the aquifer is able to dissolve the high amount of co 2 discharged by the magmatic system moreover the residuals of co 2 flux diffused from the soil show a delay on the order of 1 month with respect to the pco 2 in equilibrium with the aquifer the soil co 2 flux is therefore not directly linked to the uprising of magmatic co 2 but instead depends on the co 2 discharged from the aquifer which buffers and modulates the volatile changes released by the magmatic system

how much did glacial north atlantic water shoal observations of 13c and cd ca from benthic foraminifera have been interpreted to reflect a shoaling of northern source waters by about 1000 m during the last glacial maximum with the degree of shoaling being significant enough for the water mass to be renamed glacial north atlantic intermediate water these nutrient tracers however may not solely reflect changes in water mass distributions to quantify the distribution of glacial north atlantic water we perform a glacial water mass decomposition where the sparsity of data geometrical constraints and nonconservative tracer effects are taken into account and the extrapolation for the unknown water mass end members is guided by the modern day circulation under the assumption that the glacial sources of remineralized material are similar to that of the modern day we find a steady solution consistent with 241 13c 87 cd ca and 174 18o observations and their respective uncertainties the water mass decomposition indicates that the core of glacial north atlantic water shoals and southern source water extends in greater quantities into the abyssal north atlantic as previously inferred the depth of the deep northern southern water mass interface and the volume of north atlantic water however are not grossly different from that of the modern day under this scenario the vertical structure of glacial 13c and cd ca is primarily due to the greater accumulation of nutrients in lower north atlantic water which may be a signal of the hoarding of excess carbon from the atmosphere by the glacial atlantic

relationships between diffuse co2 emissions and volcanic activity on the island of vulcano aeolian islands italy during the period 1984 1994 measurements of co2 flux from the ground were periodically carried out on the island of vulcano aeolian islands italy between 1984 and 1994 three high flux areas were identified at the foot of the volcanic cone la fossa either inside or very close to the main village effect of the choice of the sampling grid was evaluated a different sampling grid resulted in similar distribution patterns but with different co2 fluxes therefore the absolute estimate of the total flux from the investigated area includes a large degree of uncertainty but repeated measurements with permanent sampling sites are accurate and can detect small changes no correlation of the flux with atmospheric parameters was found at sites with high fluxes some periods characterized by high co2 fluxes were observed and a close correlation was found between the gas emissions from the ground and other geochemical and geophysical parameters such as temperature chemical composition steam and so2 flux from fumaroles seismic energy release and ground deformations the results show that major temporal variations of diffuse co2 flux are related to variations in volcanic activity

introduction to the special issue on frontiers in gas geochemistry abstract the study of the geochemistry of gases pervades the earth and environmental sciences this is due in no small measure to the well established thermodynamic properties of gases which allow their application to a variety of processes occurring over a wide spectrum of natural conditions in this respect both major and associated minor gases have been proven useful indeed the trace gases have been particularly important given their role as sensitive geochemical tracers examples where gas geochemistry places key constraints on geochemical processes include the degassing history of the solid earth to form the atmosphere and oceans the origin and migration characteristics of hydrocarbon deposits the scale of climate variability the p t characteristics of geothermal reservoirs and the dynamics of the earthquake cycle and volcanic activity to name but a few this volume continues this rich tradition with an eclectic selection of papers aimed at exploring and exploiting gas geochemistry over a myriad set of research themes

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

the gradient tensor of potential field anomalies some implications on data collection and data processing of maps the full gradient tensor is presently not measured routinely onboard airplanes or on land this paper describes some improvements that can be made in strategies of data collection and in processing of potential field maps if such tensor measurements were available we suggest that in addition to producing for example standard total field anomaly maps the invariants of the tensor be mapped strikes of magnetic or gravimetric structures may be determined from minimizing the power in the first row and column of the tensor invariants can be looked upon as nonlinear filters enhancing sources with big volumes their lateral resolution is superior to that of the field proper and for a given resolution the flight altitude and separation between flight lines can be increased compared with the standard mode of operation in airborne surveys the distance between flight lines is normally much larger than the height above the ground this may introduce severe aliasing effects in the direction perpendicular to the

deep co2 release revealed by stable isotope and diffuse degassing surveys at vulcano aeolian islands in 2015 2018 abstract the partitioning of carbon dioxide co2 released by soils at vulcano island aeolian islands italy was performed by combining the co2 flux and the carbon isotope measurements based on this method the amount of co2 of volcanic origin was quantified six times during the period 2015 2018 the data analysis allowed us to establish the correlation between co2 soil degassing and changes in the contribution of volcanic fluids carbon isotope determinations were performed in situ to enhance the coverage of data collection in space and time these data were combined with both the co2 contents in the ground gases and the soil co2 flux the amount of volcanic co2 was distinguished from that of biogenic origin by implementing a three component mixing model the results of this study indicate that the increase in co2 output in september 2018 reflects the increase in volcanic gas emissions the measurement method and analysis presented in this work are sufficiently general to be applicable to the monitoring programs of active volcanoes

unmanned aerial vehicle measurements of volcanic carbon dioxide fluxes i we report the first measurements of volcanic gases with an unmanned aerial vehicle uav the data were collected at la fossa crater vulcano italy during april 2007 with a helicopter uav of 3 kg payload carrying an ultraviolet spectrometer for remotely sensing the so 2 flux 8 5 mg d 1 and an infrared spectrometer and electrochemical sensor assembly for measuring the plume co 2 so 2 ratio by multiplying these data we compute a co 2 flux of 170 mg d 1 given the deeper exsolution of carbon dioxide from magma and its lower solubility in hydro thermal systems relative to so 2 the ability to remotely measure co 2 fluxes is significant with promise to provide more profound geochemical insights and earlier eruption forecasts than possible with so 2 fluxes alone the most ubiquitous current source of remotely sensed volcanic gas data

three dimensional interpretation of the ktb gravity and magnetic anomalies a combination of a closely spaced surface gravity survey with a high resolution helicopter aeromagnetic survey as well as borehole gravity and magnetometer measurements allowed a detailed three dimensional 3 d modeling of the anomalies at the ktb drill site the models could be constrained by new evidence from a 3 d seismic survey and by structural geology and petrophysical data from drill cores and cuttings the source body for the positive gravity anomaly consist of high density metabasite the vertical derivative of the bouguer anomaly does not resemble the aeromagnetic anomaly in all areas indicating that parts of the metabasites are more or less nonmagnetic surprisingly and confirming the observation in other deep drill holes into continental crystalline basement rocks pyrrhotite is the dominant magnetic mineral below a depth of about 300 m magnetite mainly occurs in the depth intervals 360 520 m and 7300 7900 m the lower interval causes the anomalous vertical gradient of 60 nt km for the geomagnetic field the occurrence of strongly magnetic minerals in the borehole down to about 3000 m correlates with the lithology while in the deeper parts it is more related to fissures and fault zones where chemical processes reduction oxidation are active

dissolved helium isotope ratios in ground waters a new technique based on gas water re equilibration and its application to stromboli volcanic system here a new technique for the determination of dissolved he isotope ratios in ground waters is presented this method is based on the extraction and subsequent equilibrium of dissolved gases in an added host gas phase ultra pure n2 is placed in glass flasks 250 cc containing water samples that were hermetically sealed after their collection after shaking in an ultrasonic bath for 10 min an aliquot of the separated gas phase was removed from the flask for ms analysis 3he 4he ratios are measured by using a modified double collector mass spectrometer vg 5400 tft helium and ne concentrations are calculated by comparing the partial pressures of masses 4 and 20 of the samples with those of the air standard measured by a quadrupole mass spectrometer qms vg quartz using he and ne equilibrium partitioning coefficients it is possible to calculate the amount of gas originally dissolved in the water the technique was tested on both air saturated waters asw and thermal waters from stromboli aeolian islands south italy the results of which confirmed good reproducibility 5 and accuracy 3 of the data the method was then applied to three thermal water samples collected from the same volcanic area and the results compared with those of a fumarolic and a soil gas the isotope ratios for dissolved he gave values of 4 06 4 23 ra which are significantly higher than those previously reported in the literature 3 0 3 5 and 2 9 ra and that measured at the fumarole 3 09 ra suggesting a newer and higher isotopic signature for the volcanic system the proposed method appears to be a useful tool in the determination of 3he 4he ratios in ground water systems especially when free gases are not available or are dangerous to collect

post miocene disconformities and paleoceanography in the atlantic sector of the southern ocean abstract the magnetostratigraphy and biostratigraphy of 166 islas orcadas piston cores in the atlantic sector of the southern ocean reveal disconformities in the sedimentary record which are attributed to bottom current erosion the hiatus frequency as a function of water depth reveals both shallow erosion by circumpolar deep water cdw and deep erosion by antarctic bottom water aabw the post miocene history of erosion by both bottom currents is delineated by analysis of areal and temporal fluctuations of hiatus frequency erosion by cdw caused disconformities on the maud rise astrid ridge indian antarctic ridge scotia sea and islas orcadas rise the shallow disconformities increased in frequency and size from 4 0 to 1 0 ma with two periods of distinctly widespread disconformities from 5 5 to 4 5 ma and 2 5 to 1 5 ma after 1 0 ma the frequency and extent of the hiatuses decreased erosion by aabw caused disconformities in the weddell abyssal plain argentine basin and through a narrow conduit in the south sandwich basin downstream from the bullard fracture zone the deep disconformities increased in frequency and size from 4 5 to 5 0 ma 3 5 to 4 0 ma and from 1 0 to 2 5 ma after 1 5 ma the frequency and extent of hiatuses decreased fluctuations in hiatus frequency are consistent with results of a similar study in the southeast indian ocean and may be correlated with paleoceanographic events southern ocean cooling and possible re establishment of the west antarctic ice sheet and fringing ice shelves at 4 3 3 5 ma was accompanied by increased aabw and cdw activity the formation expansion of the northern hemisphere ice sheets at 2 5 3 0 ma resulted in a decrease in aabw velocity and was accompanied by increased cdw activity both deep and shallow bottom currents increased in velocity during the late matuyama chron 2 0 1 5 ma as a result of antarctic cooling after 1 0 ma however the frequency and extent of shallow and deep hiatuses was reduced and the modern extent of hiatuses is the lowest within the post miocene