three dimensional tomographic velocity structure of upper crust coaxial segment juan de fuca ridge implications for on axis evolution and hydrothermal circulation three dimensional models of compressional velocity and azimuthal anisotropy from tomographic inversions using 23 564 ocean bottom seismometer p wave arrivals define systematic lateral variations in seismic structure of the coaxial segment of the juan de fuca ridge jdfr over much of the segment the across axis structure is roughly axisymmetric characterized by a progressive increase in dike velocities moving away from the ridge axis this trend is most apparent in the basal dikes where on axis velocities are about 800 m s slower than those measured elsewhere within the rift valley the on axis sheeted dikes also exhibit ridge oriented azimuthal anisotropy with a peak to peak amplitude of about 600 m s outboard of the rift valley beneath ridge flanks with fault scarps velocities in the upper 1500 m of crust are reduced the maximum amplitude of this anomaly is about 700 m s located near the top of the sheeted dikes variations in the three dimensional velocity model are believed to reflect changes in crustal porosity from which we infer an axisymmetric porosity model for seismic layer 2 of the coaxial segment as the crust ages the evolution of layer 2 porosity could occur in the following way 1 the porosity of zero age on axis dikes is set at formation by the contraction of molten material 2 hydrothermal alteration fills pore spaces as the dikes move away from the center of the axial valley and 3 normal faulting on the ridge flank scarps opens fractures and increases porosity of the upper dikes as they move off axis at the north end of the segment dike velocities are several hundred meters per second slower on average and the across axis structure is lost the transition from a coherent aligned seismic structure to a less distinct pattern with reduced velocities may represent a shift from magmatic to amagmatic extension moving away from the cobb hotspot on the ridge axis the porosity structure we have derived for the coaxial segment suggests an alternative to the usual hydrothermal circulation model of cross axis convection cells a circulation model with along axis convection cells located entirely within the axial valley appears to be more compatible with our data

geometry and distribution of regional joint sets in a non homogeneous stress field case study in the ebro basin spain abstract three regional joint sets striking n s e w and wnw ese affect the tertiary rocks of the central ebro basin from analysis of their chronological relationships and spatial distribution it is concluded that they correspond to two different tectonic events the n s set oldest and the e w set younger are present in the southern and central sectors while the wnw ese joint set predominates in the northern one the n s joints propagated in response to joint normal and fluid loads under an intraplate stress field with shmax oriented near n s related to forces caused by the convergence of africa iberia and europe and rifting at the valencia trough during the sedimentary infilling of the basin these joints are only present in the southern part of the area the e w joint set in the southern central sector records the same fracturing event as the wnw ese set does in the northern one its orientation was modified by the presence of the older n s set in the south which perturbed the regional stress field the younger wnw ese and e w joint sets are interpreted as unloading joints these propagated as a consequence of flexural uplift and exhumation related to isostatic rebound at the pyrenees and the ebro foreland basin a numerical approach is used to explain the inhomogeneous distribution of the n s joint set in terms of their absence being controlled by the depth of the water table at the time of their formation

a sinkhole susceptibility zonation based on paleokarst analysis along a stretch of the madrid barcelona high speed railway built over gypsum and salt bearing evaporites ne spain abstract this paper presents a methodology for producing sinkhole susceptibility zonations along linear infrastructures based on the analysis of the subsidence and dissolution features exposed in the adjacent cuttings and the distribution of karstic depressions the proposed approach have been applied to a 24 km long stretch of the high speed madrid barcelona railway built on halite and glauberite bearing evaporites of the tertiary zaragoza gypsum formation more than 100 km of this railway line have been built over salt bearing tertiary evaporites and trains run at a cruising speed of 300 km h the susceptibility assessment has been restricted to the sections located in karstic depressions 2 98 km and trenches excavated in the ground 13 93 km a low susceptibility has been assigned to the sections built on thickened alluvium of the huerva fluvial system 0 5 km and those in which the evaporites exposed in the cuttings do not show evidence of dissolution or subsidence 3 52 km a total of 4 5 km have received an intermediate susceptibility the cuttings in these sections show sagging structures cavities above the railway roadbed irregular rockhead or shallow alluvium bedrock boundary a high susceptibility has been assigned to a total of 6 59 km these correspond to cavities and collapse structures that reach the railway roadbed 3 61 km and karstic depressions generated by interstratal karstification and subsidence 2 98 km the paleokarst and geomorphic evidence in these sections reveals that cavities either air or sediment filled do exist beneath the railway the distribution of the karst features and susceptibility zones seems to be controlled to a large extent by the lithostratigraphy of the bedrock wedging out of the evaporites to the se and increase in the proportion of halite and glauberite to the nw the proposed zonation could be used as the basis for the selection of the stretches where further investigations and the application of mitigation measures would have a better cost benefit ratio

geohazards monitoring in roma from insar and in situ data outcomes of the pangeo project within the pangeo project financed by the european commission under the 7th framework program the geological survey of italy ispra and the urban planning department of the city of roma developed a geodatabase and map of the geological hazards for the territory of roma integrating remotely sensed data psinsar permanent scatterer interferometry synthetic aperture radar and in situ geological information numerous thematic layers maps and inventories of hazards e g landslides sinkholes cavities geological and hydrogeological data added to historical and recent urbanization information were compared to the permanent scatterer ps data from the european remote sensing satellites ers 1 2 1992 2000 and envisat 2002 2005 descending scenes in order to produce a ground stability layer gsl based on the ps data most of the territory appears stable almost 70 of ps velocities are within 1 mm year about 14 of the pss show positive line of sight los velocities measured along the los of the satellite between 1 and 3 mm year and more than 2 exceed 3 mm year more than 11 of pss show negative los velocities between 1 and 3 mm year while about 3 exceed 3 mm year with tens of the pss showing velocities over 20 mm year the gsl is comprised of polygons or multi polygons multipart polygons grouping individual polygons under a single identifier geohazard enclosing areas where geohazards have been pointed out by ps data and or in situ surveys observed instabilities and by polygons enclosing areas potentially affected by geohazards based on the available knowledge of the territory potential instabilities in roma s gsl 18 multi polygons covering ca 600 km2 related to observed instabilities have been outlined where ground movements could be detected through insar data or where landslides and sinkholes are known to have occurred other 13 multi polygons covering nearly 900 km2 concern areas where the potential occurrence of geohazards was inferred by combining geological and or geothematic data potential instabilities the geohazards mapped in roma have been landslides collapsible grounds compressible grounds groundwater abstraction mining man made ground tectonic movements and volcanic inflation deflation the lattermost is the likely cause of the significant uplift observed in the alban hills area however this paper focuses on two more currently impending hazards subsidence and sinkholes in general sinkhole prone areas areas of dense underground cavities are hard to discern from satellite data but can be revealed by ruling out other potential causes of observed ground movement based on in situ data subsiding zones are effectively detected by the available psinsar dataset over a total extent of about 60 km2 mostly overlapping the recent alluvial areas of the tiber and its tributaries pss show a very different behaviour inside and outside the historical centre inside loading by anthropogenic construction and man made ground since ancient times has led to an almost complete consolidation of the recent river deposits marked by modest to absent subsidence in contrast outside subsidence clearly stands out with negative los velocities that although generally within several mm year can locally exceed 25 mm year ps data have provided motion information at both a regional and local scale up to the scale of a single building closer to the sea in the tiber delta area velocities increase especially above recently reclaimed marsh areas rich in peat and organic clays velocities can change significantly over short distances as in the international airport area reflecting the local stratigraphic setting the same occurs in the two subsiding areas located within the alban hills volcanic complex which is generally affected by ground uplift as a whole psinsar ground motion velocities offer a significant contribution to susceptibility and hazard recognition studies in particular such a method provides a fast and effective tool available to local authorities to monitor ground and building behaviour possibly allowing for timely prevention activities especially when coupled with appropriate in situ knowledge

discovery of a magma chamber and faults beneath a mid atlantic ridge hydrothermal field crust at slow spreading ridges is formed by a combination of magmatic and tectonic processes with magmatic accretion possibly involving short lived crustal magma chambers the reflections of seismic waves from crustal magma chambers have been observed beneath intermediate and fast spreading centres but it has been difficult to image such magma chambers beneath slow spreading centres owing to rough seafloor topography and associated seafloor scattering in the absence of any images of magma chambers or of subsurface near axis faults it has been difficult to characterize the interplay of magmatic and tectonic processes in crustal accretion and hydrothermal circulation at slow spreading ridges here we report the presence of a crustal magma chamber beneath the slow spreading lucky strike segment of the mid atlantic ridge the reflection from the top of the magma chamber centred beneath the lucky strike volcano and hydrothermal field is approximately 3 km beneath the sea floor 3 4 km wide and extends up to 7 km along axis we suggest that this magma chamber provides the heat for the active hydrothermal vent field above it we also observe axial valley bounding faults that seem to penetrate down to the magma chamber depth as well as a set of inward dipping faults cutting through the volcanic edifice suggesting continuous interactions between tectonic and magmatic processes

denitrification in the eastern arabian sea evaluation of the role of continental margins using ra isotopes abstract the 228 ra 226 ra activity ratios henceforth denoted as 228 226 have been measured both at the surface and at 300 m depth as a function of distance from the western continental margins of india to the open arabian sea between 15 n and 21 n a two dimensional eddy diffusion model is used to fit the measured 228 226 profiles to deduce horizontal eddy diffusivities in both zonal towards open ocean and meridional towards the equator directions these range between 1 3 106 and 3 1 106 cm2 s 1 assuming that the organic rich and deeply anoxic continental margin sediments at 300 m depth can be a source of organic c to the core of the denitrification layer and that the deficit flux in the carbon budget can be covered by this supply the required gradient dc dz in doc content of waters from coast to open arabian sea is computed using the kx value the required gradient is computed to be 4 mol dm 3 100 km 1 which is within the error associated with doc measurements

numerical modeling of phase separation at main endeavour field juan de fuca ridge 1 before being disrupted by a magmatic event in 1999 the vent temperatures and salinities along the axis of the main endeavour field on the juan de fuca ridge exhibited a quasi steady spatial gradient in which the southern vent fluids were hotter and less saline than the northern vent fluids we present 2 d numerical models of two phase flow in a nacl h2o system to understand these gradients we consider homogenous permeability models with a range of bottom boundary temperature distributions and heterogeneous permeability models by imposing layer 2a extrusives with a constant bottom boundary temperature distribution the aim is to understand the impact of both bottom boundary temperature and layer 2a permeability on hydrothermal fluids and to determine what combination of these controlling factors could cause the observed trend we find that variations in bottom boundary temperature alone cannot explain the span of surface temperatures and salinities measured at the main endeavour field heterogeneous permeability within layer 2a that has higher overall permeability in the northern part of the vent field than the southern part can reproduce the observed north to south temperature gradient but such a permeability distribution cannot reproduce the observed salinity gradient we conclude that both deep seated heterogeneous permeability perhaps localized by a fault zone and a heterogeneous layer 2a are required to produce the trend of temperatures and salinities in vent fluids at the main endeavour field prior to the 1999 event

recent volcanic events and the distribution of hydrothermal venting at the lucky strike hydrothermal field mid atlantic ridge 1 we present new high resolution bathymetry and backscatter data acquired in 2006 with the rov victor 6000 over the lucky strike hydrothermal field mid atlantic ridge as long term monitoring of the lucky strike area momar project is being implemented these new high resolution data offer an unprecedented view of the distribution of hydrothermal edifices eruptive facies and small scale tectonic features in the lucky strike vent field we show that vents located in the nw and ne correspond with wide expanses of lumpy seafloor which we interpret as primarily made of broken chimneys and sulfide edifices they are found above scarps with relief 50 m or on associated mass wasting deposits by contrast the se and sw vents correspond with small expanses of lumpy seafloor and are located near smaller scarps which we interpret as more recent faults hydrothermal edifices in the sw venting area appear very recent postdating the emplacement and faulting of the most recent lava we propose that this difference in the age of hydrothermal edifices does not mean that hydrothermal venting itself is more recent in the southern part of the lucky strike field because preexisting sulfide deposits there may have been buried by recent volcanic deposits instead the older edifices in the northern part of the hydrothermal field may have been allowed more time to grow because they are set above the level of recent lava flows the formation of a lava lake is the most recent eruptive event detected at lucky strike lava drainback is evidenced by benches and lava pillars suggesting a close connection with an underlying magma reservoir which probably corresponds to the melt body imaged by singh et al 2006 we have found no evidence that this lake was active for months to decades as lava lakes at terrestrial volcanoes it may instead have formed as a lava pond with successive lava flows covering the eruptive vents as proposed for similar features at the epr the horizontal surface of the lake is deformed only near its southwestern shore along a nne trending set of faults and fissures which appear to control the distribution of hydrothermal chimneys

the latest lgm culmination of the garda glacier italian alps and the onset of glacial termination age of glacial collapse and vegetation chronosequence abstract in the deglacial sequence of the largest end moraine system of the italian alps we focused on the latest culmination of the last glacial maximum before a sudden downwasting of the piedmontane lobe occupying the modern lake basin we obtained a robust chronology for this culmination and for the subsequent deglacial history by cross radiocarbon dating of a proximal fluvioglacial plain and of a deglacial continuous lake sedimentation we used reworked dinocysts to locate sources of glacial abrasion and to mark the input of glacial meltwater until depletion the palynological record from postglacial lake sediments provided the first vegetation chronosequence directly reacting to the early lateglacial withdrawal so far documented in the alps glacier collapse occurred soon after 17 46 0 2 ka cal bp which is the manerba advance culmination basin deglaciation of several overdeepened foreland piedmont lakes on southern and northern sides of the alps appears to be synchronous at millennial scale and near synchronous with large scale glacial retreat at global scale the pioneering succession shows a first afforestation step at a median modeled age of 64 years after deglaciation while rapid tree growth lagged 7 centuries between 16 4 0 16 and 15 5 0 16 ka cal bp a regressive phase interrupted forest growth marking a lateglacial phase of continental dry climate predating gi 1 this event spanning the most advanced phases of north atlantic h1 is consistently radiocarbon framed at three deglacial lake records so far investigated on the italian side of the alps relationships with the gschnitz stadial from the alpine record of lateglacial advances are discussed

geoscience of ancient mediterranean harbours abstract although much has been written on the subject of ancient mediterranean harbours the relatively new area of harbour geoarchaeology remains dispersed in the geoscience and archaeological literature over a decade of research has amassed rich and varied datasets of anthropogenically forced coastal evolution with a remarkable number of between site analogies this new research field also shows the rich potential of geoscience to reconcile important archaeological questions no single publication however has yet drawn on these geological patterns to yield a detailed overview suitable for geoscientists and environmental archaeologists the aim of this review article is to 1 discuss how ancient harbours have come to be preserved in the geological record 2 expound the basic principles and palaeoenvironmental tools underpinning ancient harbour geoarchaeology 3 outline some of the most significant research advances made and 4 discuss a new chrono stratigraphic model applicable to harbour sequences

crustal magnetization reveals subsurface structure of juan de fuca ridge hydrothermal vent fields a near bottom geophysical survey on the endeavour segment of the northern juan de fuca ridge shows that regions of well defined low crustal magnetization are strongly correlated with both active and extinct submarine hydrothermal vent sites in particular at the main endeavour field we find discrete magnetization lows associated with each cluster of vents magnetization lows are directly centered beneath the vent clusters and have diameters of 100 m which implies a near vertical narrow pipe like source region located directly beneath the surface expression of the vent edifices lows are also separated from each other by only 200 m which further implies highly focused zones magnetization lows are also associated with inactive and extinct vent areas which indicates that alteration of the magnetic minerals in the crust rather than necessarily temporary thermal demagnetization is the primary process responsible for the low magnetization these narrow pipe like bodies are highly characteristic of alteration pipes found in ophiolites and are indicative of hydrothermal fluid up flow zones thus each magnetization low may define an individual upwelling zone with distinct subsurface plumbing and thermal structure the crustal magnetization patterns provide important constraints on the geometry of the subsurface plumbing beneath these hydrothermal vent systems at the main endeavour field magnetization lows are distributed along the trend of the rift valley in a semiregular pattern with a spacing of 200 m arguing that upward flow may be partitioned into regularly spaced intervals along the axis of the rift valley

nutrient fluxes via radium isotopes from the coast to offshore and from the seafloor to upper waters after the 2009 spring bloom in the yellow sea abstract the horizontal and vertical transport of nutrient rich water both from the coast and from the seafloor to the overlying water column should play an important role in supplying nutrients required for the periods of vegetative or reproductive growth of phytoplankton in the present work radium isotopes 223ra 224ra and 226ra in the southern yellow sea were measured after a spring bloom in june 2009 the exponential like decrease of 223ra away from the coast to offshore waters yielded horizontal eddy diffusivities kh of 2 93 1 47 107 cm2 s 1 by neglecting the advection this estimate was smaller than that with advection indicator by as much as 21 when using an analytic model for 223ra and 226ra the corresponding horizontal nutrient fluxes were 1525 mol m 2 d 1 din 15 9 mol m 2 d 1 dip and 826 mol m 2 d 1 dsi which would supply around 16 of n and 3 of p requirements based on the primary productivity the decrease of 224ra and 223ra activities from sediments to the upper water column suggests the vertical eddy diffusion coefficient kz of 6 23 5 58 cm2 s 1 below the thermocline which was within the yellow sea cold water mass yscwm the calculated vertical fluxes of nutrient were 4945 mol m 2 d 1 din 236 mol m 2 d 1 dip and 5315 mol m 2 d 1 dsi accounting for up to 52 of n and 40 of p requirements for the phytoplankton growth these results demonstrate the role of yscwm as a relative nutrient rich pool for the supply of nutrient to the southern yellow sea via the vertical diffusion process relative to the horizontal process during the summer season such processes will be strengthened during the weak density stratification in spring when algal blooms occur

constraining crustal emplacement processes from the variation in seismic layer 2a thickness at the east pacific rise abstract a stochastic model for the emplacement of dikes and lava flows at a fast spreading ridge can generate an upper oceanic crustal structure similar to that observed in seismic data from the east pacific rise epr in ocean drill holes and in ophiolites in this model the location of successive dike intrusion events relative to the ridge axis is determined by a gaussian probability function and the cumulative flow lengths of the erupted lavas are chosen to build a gaussian shaped lava pile we interpret wide angle seismic reflections from the steep velocity gradient at the base of seismic layer 2a to be the extrusive sheeted dike contact seismic data from the northern and southern epr place constraints on the on axis extrusive layer thickness 230 50 m the distance over which the thickening of the extrusive layer occurs width of the accretion zone 1 3 km and its off axis thickness 300 800 m ophiolites and ocean drill holes dsdp hole 504b provide additional estimates of the thickness of the extrusive layer and constrain the thickness of the transition region from extrusives to sheeted dikes 100 200 m a simple stochastic emplacement model where the lavas are described by one mean flow length fits the thickening of the extrusive layer off axis inferred from the deepening of seismic layer 2a but the predicted transition from sheeted dikes to extrusives is too thick in order to match the dimensions and flat topped shape of the seismic layer 2a boundary as well as the thickness of the extrusive sheeted dike transition a bimodal distribution of lava flows is used short flows confined within the axial summit caldera asc build up approximately half the extrusive volume occasional voluminous flows spill out of the asc or erupt outside of the asc and pond at a considerable distance off axis to build up the remainder of the extrusive section the upper part of the final extrusive section will be dominated by the off axis flows while the lower portions will be primarily composed of short flows erupted within the asc magnetic transition widths predicted from the overlap of lavas 2 km in this model are similar to those measured in deep tow studies assuming a smoothing function which acts over one seismic wavelength the upper crustal velocity structure predicted by the bimodal lava emplacement model is consistent with the shallow seismic velocity structure measured on the epr the ages of seafloor lavas in this model are younger than the tectonic spreading model ages by 30 70 kyr in agreement with anomalously young lava ages obtained from radioisotope dating of seafloor basalts near the epr

holocene palaeohydrological changes in the northern mediterranean borderlands as reflected by the lake level record of lake ledro northeastern italy a lake level record of lake ledro northern italy spans the entire holocenewith a chronology derived from51 radiocarbon dates it is based on a specific sedimentological approach that combines data fromfive sediment profiles sampled in distinct locations in the littoral zone on a millennial scale the lake level record shows two successive periods from 11 700 to 4500 cal yr bp and from 4500 cal yr bp to the present characterized by lower and higher average lake levels respectively in addition to key seasonal and inter hemispherical changes in insolation the major hydrological change around 4500 cal yr bp may be related to a non linear response of the climate system to orbitally driven gradual decrease in insolation the ledro record questions the notion of an accentuated summer rain regime in the northern mediterranean borderlands during the boreal insolation maximum moreover the ledro record highlights that the holocenewas punctuated by successive centennial scale highstands correlations with the preboreal oscillation and the 8 2 ka event and comparisonwith the atmospheric 14c residual record suggest that short lived lake level fluctuations developed at ledro in response to 1 final steps of the deglaciation in the north atlantic area and 2 variations in solar activity

high resolution sequence stratigraphy from piezocone tests an example from the late quaternary deposits of the southeastern po plain abstract cone penetration tests are traditionally regarded as a major tool for geotechnical investigations this study based upon interpretation of 234 cone penetration tests with pore pressure measurements piezocone tests or cptu carried out in the late quaternary deposits of the southeastern po plain shows how cptu tests can also be used for sedimentological purposes including detailed facies characterization subsurface stratigraphic correlations and identification of the key surfaces for sequence stratigraphic interpretation the late quaternary depositional history of the southeastern po plain reconstructed on the basis of data from seventeen continuously cored boreholes includes 1 alluvial plain development during the late quaternary lowstand and the early stages of transgression 2 formation of a rapidly migrating barrier lagoon system during the late transgressive phases 8800 6000 y bp 3 construction and progradation of a wave dominated delta ancient po delta during the following sea level highstand 6000 800 y bp and 4 development of the present day alluvial plain following the delta lobe abandonment in the 13th century a d local execution of cptu tests in coincidence with drilling sites enables the calibration of borehole data with piezocone penetration profiles lithofacies characterization is based upon estimation of three major parameters corrected cone resistance q t sleeve friction f s and pore water pressure u plotting of q t versus the ratio of cone friction to cone bearing fr is adopted as the major tool for sediment texture classification eight major facies associations for the southeastern po plain are identified these are for decreasing q t values 1 fluvial channel sands 2 beach ridge sands 3 transgressive barrier sands 4 crevasse sands and silts 5 levee silts and sands 6 floodplain silts and clays 7 prodelta clays and 8 marsh clays and peats cptu profile interpretation also provides the basis for the identification of the three major key surfaces within the late quaternary 4th order depositional sequence 1 the transgressive surface ts marking the boundary between the locally pedogenized stiff pleistocene alluvial clays and the overlying holocene transgressive paralic deposits has a distinctive pore pressure response with very low u values and is characterized by a sharp downward increase in f s which is paralleled by a moderate increase in q t 2 the ravinement surface rs corresponding to the boundary between fine grained back barrier deposits and the overlying transgressive barrier sands is invariably marked by a sharp upward increase in q t and decrease in fr 3 the maximum flooding surface mfs which is not clearly recognizable on the sole basis of core data is identified within shallow marine prodelta clays in combination with minor peaks of q t which have been interpreted to reflect a laterally extensive fossil lag with transition in proximal areas to sand shell rich layers simplicity speed and comparatively low costs of cptu tests imply that an extensive use of this method when used in conjunction with core programs can be a very attractive alternative to economically less convenient methods for the geological mapping of alluvial coastal plain areas consisting of non gravel deposits

depletion of a brine layer at the base of ridge crest hydrothermal systems the variable salinity of fluid venting from mid ocean ridges is indicative of mixing between hydrothermal seawater and fluids that have undergone supercritical phase separation in order to study the stability of a brine saturated layer that may form in the lowermost part of the hydrothermal system we have performed numerical simulations of a system that has returned into the subcritical regime for typical geological parameters it is shown that the interface between the brine layer and the overlying fluids is not very stable but vanishes by one of two dynamical mechanisms convective breakdown or vertical migration this contradicts the conventional picture of a steady layered convective system in which the brine is depleted only by dispersion and diffusion across the interface the depletion mechanism depends on the fluid dynamical stability of the brine layer convection within the brine layer results either in the convective breakdown for low excess salinity of the brine as compared to seawater or the upward migration of the interface for higher excess salinities consequently the depletion times are much shorter than for models with pure dispersion diffusion across the interface if the brine layer is static high chlorinity liquid is entrained slowly by the convecting overlying fluids leading to downward migration of the interface this gradual depletion of the brine layer results in almost constant vent salinities in agreement with measured salinities of chronic high chlorinity vents fl 2000 elsevier science b v all rights reserved

first delimitation of areas affected by ground deformations in the guadalfeo river valley and granada metropolitan area spain using the dinsar technique abstract a differential interferometric sar dinsar analysis of terrain displacements in the province of granada southern spain is presented here for two different study zones the first zone concerns the guadalfeo river basin where abundant landslides and unstable slopes were previously identified and inventoried on a gis application however no instrumental quantification of landslide activity was available considering morphological criteria and field observations these deep seated landslides were considered to be dormant or moving extremely slowly the second study zone corresponds to the granada metropolitan area where no previous information was available on any vertical movement the analysis was based on ers1 and ers2 images covering the period from 1993 to 2000 by using dinsar we made an initial qualitative assessment of movements on landsliding slopes in the guadalfeo river basin and also vertical land movements in the alluvial quaternary sediments to the west and south of the granada metropolitan area the terrain instability assessment resulting from this research shows maximum annual velocities along the sar line of sight los of 6 mm yr for the tablones landslide and up to 13 mm yr for the albunuelas village where progressive differential settlement processes were established as the origin of the movement in the case of the granada metropolitan area two sites were detected with subsidence affecting two villages santa fe located in the western part of the area with an estimated average velocity of 8 mm yr and otura in the south of the area with maximum velocities of 12 mm yr a description of geological features of the different sites showing los ground displacement is presented with a discussion of the application of the rates to landslide activity assessment found local ground conditions or exploitation of subterranean water in urban areas

sinkhole swarms along the dead sea coast reflection of disturbance of lake and adjacent groundwater systems more than a thousand sinkholes have developed along the western coast of the dead sea since the early 1980s more than 75 of them since 1997 all occurring within a narrow strip 60 km long and 1 km wide this highly dynamic sinkhole development has accelerated in recent years to a rate of 150 200 sinkholes per year the sinkholes cluster mostly over specific sites up to 1000 m long and 200 m wide which spread parallel to the general direction of the fault system associated with the dead sea transform research employing borehole and geophysical tools reveals that the sinkhole formation results from the dissolution of an 10 000 yr old salt layer buried at a depth of 20 70 m below the surface the salt dissolution by groundwater is evidenced by direct observations in test boreholes these observations include large cavities within the salt layer and groundwater within the confined subaquifer beneath the salt layer that is undersaturated with respect to halite moreover the groundwater brine within the salt layer exhibits geochemical evidence for actual salt dissolution na cl 0 5 0 6 compared to na cl 0 25 in the dead sea brine the groundwater heads below the salt layer have the potential for upward cross layer flow and the water is actually invading the salt layer apparently along cracks and active faults the abrupt appearance of the sinkholes and their accelerated expansion thereafter reflects a change in the groundwater regime around the shrinking lake and the extreme solubility of halite in water the eastward retreat of the shoreline and the declining sea level cause an eastward migration of the fresh saline water interface as a result the salt layer which originally was saturated with dead sea water over its entire spread is gradually being invaded by fresh groundwater at its western boundary which mixes and displaces the original dead sea brine accordingly the location of the western boundary of the salt layer which dates back to the shrinkage of the former lake lisan and its transition to the current dead sea constrains the sinkhole distribution to a narrow strip along the dead sea coast the entire phenomenon can be described as a hydrological chain reaction it starts by intensive extraction of fresh water upstream of the dead sea continues with the eastward retreat of the lake shoreline which in turn modifies the groundwater regime finally triggering the formation of sinkholes

subsidence rates and urban damages in alluvial dolines of the central ebro basin ne spain in the central ebro basin alluvial dolines develop on quaternary materials overlying neogene evaporites this process is very active analysing aerial photographs of different years important differences can be observed since the 1970s when the urbanisation of the area took place karst processes have damaged many buildings and infrastructures from the dates of construction and the repair of a number of buildings and pavements we calculate subsidence rates 12 120 mm year moreover we decided to monitor for around 4 years three dolines developed on urban areas to determine their subsidence behaviour a water level device with an error of 2 3 mm was utilised for this purpose the subsidence rates so obtained are 64 5 39 and 21 mm year which fit with the previous data from repaired zones

sediment input and evolution of lacustrine deltas the breggia and greggio rivers case study lake como italy abstract a high resolution bathymetric survey is combined with erosion potential method to unravel the spatial and time evolution of the deltas formed by the breggia and greggio rivers in western branch of lake como southern alps italy this data set provides information on changes in the geometry and depositional centres of these deltas from holocene to present the morphology and structure of the lacustrine deltas was mapped using a 5 cm vertical resolution bathymetry acquired with multibeam system simrad em3000 the sediment input was calculated applying different magnitude equations suitable for the alpine watersheds and the erosion potential method in a geographic information systems gis environment two different sub lacustrine deltas were recognised in the south eastern corner of the breggia flood plain a simple cone shaped delta minimum volume 6 3 106 m3 develops in correspondence to the present breggia mouth about 600 m northward a complex delta develops in front of the greggio outlet this is a composite sub lacustrine body comprising a basal portion minimum volume 31 3 106 m3 interpreted as the breggia paleo delta and an overlapping smaller digitate sedimentary body minimum volume 0 7 106 m3 related to the present greggio river depositional centres of the breggia delta have changed through time indicating a sudden migration of the river input in historical times probably in the vi century ad

seismic evidence that black smoker heat flux is influenced by localized magma replenishment and associated increases in crustal permeability hydrothermal circulation at mid ocean ridges is responsible for 25 of earth s heat flux and controls the thermal and chemical evolution of young oceanic crust the heat flux of black smoker hydrothermal systems is thought to be primarily controlled by localized magma supply and crustal permeability nevertheless magma chamber characteristics and the nature of crustal permeability beneath such systems remains unclear here we apply three dimensional full waveform inversion to seismic data from the hydrothermally active endeavour segment of the juan de fuca ridge to image the upper crust in high resolution we resolve velocity variations directly above the axial magma chamber that correlate with variations in seismicity black smoker heat flux and the depth of the axial magmatic system we conclude that localized magma recharge to the axial magma lens along with induced seismogenic cracking and increased permeability influences black smoker heat flux

dike induced faulting in rift zones of iceland and afar geodetic data and field observations demonstrate that the emplacement of dikes in volcanic rift zones frequently generates normal faulting and graben subsidence at the earth9s surface elastic modeling of the vertical ground surface displacements above dikes and faults indicates that the extent of graben subsidence can be achieved only if fault slip extends virtually to or beyond the dike plane at depth a mechanical model that includes dikes and frictional faults shows that dike opening tends to compress and lock faults located to either side of the dike therefore slip extending into or beyond the dike cavity must occur either 1 on faults that intersect the dike near its top above the zone of dike induced compression or 2 on faults that slip ahead of the dike as it propagates laterally data from iceland indicate that slip occurred on deep faults that presumably slipped in advance of the laterally propagating dike

hydrothermal seismicity beneath the summit of lucky strike volcano mid atlantic ridge abstract we present two years july 2007 july 2009 of earthquake locations from a local seismological network on the lucky strike volcano mid atlantic ridge whose summit hosts one of the most active and largest deep sea hydrothermal fields known two clusters of small m l

space time distribution of ancient and active alluvial karst subsidence examples from the central ebro basin spain space and time variations of alluvial karst subsidence in the central ebro basin are analysed in trenches paleodolines aerial photographs historical dolines and field surveys present day active dolines the measured subsidence rates as well as a comparison between densities of paleodolines computed in randomly selected scan lines and density of active dolines computed in maps suggest that present day subsidence in favourable areas is more intense than that of pleistocene times according to diachronic maps drawn from a different aerial photographs taken after 1946 and b field surveys on deformations in urbanized areas subsidence behaved as a nearly steady process while the whole area was used for agriculture in contrast rapid changes through periods of several tens of years have occurred in urbanized areas in which dolines expand their boundaries through small marginal collapses shifting sharply their sinking centres to neighbouring sites these rapid changes do not have an equivalent in observed paleodolines

characteristics of magma driven hydrothermal systems at oceanic spreading centers 1 we use one and two limb single pass models to de termine vent field characteristics such as mass flow rate q bulk permeability in the discharge zone kd thickness of the conductive boundary layer at the base of the system magma replenishment rate and residence time in the discharge zone data on vent temperature vent field area heat output and the surface area and depth of the subaxial magma chamber amc constrain the models the results give q 100 kg s kd 10 13 m2 and 10 m essentially independent of spreading rate and detailed characteristics of the amc in addition we find no correlation between heat output at individual vent fields and spreading rate or depth to the amc we conclude that high temperature hydrothermal systems are driven by local magma supply rates in excess of that needed for steady state crustal production and that crustal permeability enables hydrothermal circulation to tap magmatic heat regardless of amc depth using data on partitioning of heat flow between focused and diffuse flow we find that 80 90 of the hydrothermal heat output is derived from high temperature fluid even though much of the heat output discharges as low temperature fluid in some cases diffuse flow fluids may exhibit considerable conductive cooling or heating by assuming conservative mixing of diffuse flow fluids at east pacific rise 9 50 n we find that most transport of metals such as fe and mn occurs in diffuse flow and that co2 h2 and ch4 are taken up by microbial activity

recent eruptions on the coaxial segment of the juan de fuca ridge implications for mid ocean ridge accretion processes the 1993 seismic swarm and volcanic eruption on the coaxial segment of the juan de fuca ridge was the first verified mid ocean ridge accretion event monitored by the national oceanic and atmospheric administration u s navy sound surveillance system sosus ambiguity in the location of the initial seismicity resulted in an uncertainty as to whether the dike intruded from the summit and north rift zone of the adjacent axial volcano or whether it arose locally within the coaxial segment however analyses of multibeam side scan sonar towed camera submersible and geochemical data show that the coaxial segment is morphologically structurally and geochemically distinct from the north rift zone of axial volcano there is no geologic or geochemical evidence that dike injections from axial volcano have extended north of 46 18 n in the past whereas the 1993 eruption site is at 46 31 n furthermore all seafloor manifestations of the 1993 dike injection lie along the central neovolcanic zone of the coaxial segment analyses of repeat seabeam surveys combined with seafloor observations show that two other eruptions of approximately the same volume as the 1993 eruption occurred along the coaxial segment in the 1981 1991 interval these three diking events may have relieved decades of accumulated stress over 35 km or more of this segment the spatial pattern and hydrothermal history of the 1993 event is consistent with a dike with a significant lateral component of injection

geological mapping of the menez gwen segment at 37 50 n on the mid atlantic ridge implications for accretion mechanisms and associated hydrothermal activity at slow spreading mid ocean ridges abstract slow spreading mid ocean ridges have the potential to form large seafloor massive sulphide sms deposits current exploration for sms deposits commonly targets associated active hydrothermal venting on the ridge axis which makes the discovery of inactive vent sites and sms deposits in the off axis regions unlikely geological maps of the seafloor which help understand the timing and location of sms formation usually focus on individual hydrothermal vent sites and their immediate surroundings and are often too small to aid in sms exploration this study uses ship based multibeam echosounder mbes data and a systematic classification scheme to produce a segment scale geological map when combined with spreading rate this allows us to not only reconstruct the segment s spreading history but also reveals important processes that localize hydrothermal venting geological mapping around two known hydrothermal vent sites on the menez gwen segment at 37 50 n on the slow spreading mid atlantic ridge showed that hydrothermal venting accompanies the tectonic break up of a large cooling magmatic body venting is focussed by faulting and resulting permeability changes the large magmatic body is associated with an axial volcano that formed as a last stage of a period with intense magmatic accretion such magmatic accretion periods occur every 300 to 500 ka at the menez gwen segment with increasing intensity over the past 3 5 ma years the most recent most intense magmatic period appears to be a regional phenomenon also affecting the neighbouring lucky strike and rifted hills segments understanding the accretional setting and the spatial and temporal constraints of hydrothermal venting enables us to develop criteria in mbes data to aid exploration for inactive sms deposits

lake sediments as natural seismographs a compiled record of late quaternary earthquakes in central switzerland and its implication for alpine deformation central switzerland lies tectonically in an intraplate area and recurrence rates of strong earthquakes exceed the time span covered by historic chronicles however many lakes are present in the area that act as natural seismographs their continuous datable and high resolution sediment succession allows extension of the earthquake catalogue to pre historic times this study reviews and compiles available data sets and results from more than 10 years of lacustrine palaeoseismological research in lakes of northern and central switzerland the concept of using lacustrine mass movement event stratigraphy to identify palaeo earthquakes is showcased by presenting new data and results from lake zurich the late glacial to holocene mass movement units in this lake document a complex history of varying tectonic and environmental impacts results include sedimentary evidence of three major and three minor simultaneously triggered basin wide lateral slope failure events interpreted as the fingerprints of palaeoseismic activity a refined earthquake catalogue which includes results from previous lake studies reveals a non uniform temporal distribution of earthquakes in northern and central switzerland a higher frequency of earthquakes in the late glacial and late holocene period documents two different phases of neotectonic activity they are interpreted to be related to isostatic post glacial rebound and relatively recent re activation of seismogenic zones respectively magnitudes and epicentre reconstructions for the largest identified earthquakes provide evidence for two possible earthquake sources i a source area in the region of the alpine or sub alpine front due to release of accumulated north west south east compressional stress related to an active basal thrust beneath the aar massif and ii a source area beneath the alpine foreland due to reactivation of deep seated strike slip faults such activity has been repeatedly observed instrumentally for example during the most recent magnitude 4 2 and 3 5 earthquakes of february 2012 near zug the combined lacustrine record from northern and central switzerland indicates that at least one of these potential sources has been capable of producing magnitude 6 2 to 6 7 events in the past

hydro geotechnical modelling of subsidence in the como urban area abstract the urban area of como italy is particularly susceptible to subsidence the reason is the particular structure of the subsoil combined with the anthropic modification of the lakeshore lands linked to the historical evolution of the area moreover this phenomenon exposes the lakefront areas to an increasing risk of flooding the primary purpose of this study was to develop an effective methodology for the assessment of subsidence in urban areas to be used as a support in groundwater management the development of a coupled hydrogeological geotechnical numerical model for the period 2004 2011 allowed recognizing the shoreline results as most susceptible areas to the phenomenon model results were critically evaluated through comparison with time series of psinsar and high precision levelling data available in the area the anthropic perturbations of groundwater flow linked to the construction of lake flooding defenses in 2008 2009 enhanced the subsidence phenomenon in a localized area pointing out the strong inter dependence of groundwater circulation lake level oscillations and geotechnical behavior of soils thus the model revealed the most critical zones and geotechnical units demonstrating to be a potential powerful tool to predict subsidence scenarios e g the future completion of the floods defense works in the shoreline area

gypsum karstification in the middle miocene fatha formation mosul area northern iraq abstract karstified middle miocene sediments are widely exposed in northern iraq particularly in the area surrounding the city of mosul the unit is dominated by gypsum and exposed in thirteen anticlinal structures within the investigated area of about 1600 square kilometers synclines though containing the same sequence are not karstified due to a quaternary cover karst features were located from air photos over 4000 were recorded the smallest detectable being two meters in diameter the majority are sinkholes dolines developed in gypsum and manifested in the overlying collapsing limestone they are singular in lines or clusters shafts and karren are fewer in number and are usually developed in uncovered gypsum sinkholes are visibly located along fractures and at fracture intersections over gently inclined limestone beds overlying the gypsum two karst systems were identified an active and recent system characteristic of all the anticlinal structures and an older pleistocene fossil karst system characteristic of alan ishkaft albu saif and hammam structures the fossil karst system is preserved on remnant elevated old land surfaces and produces characteristic tight undulations in the limestone due to collapse inwards in sinkholes and elongated tunnels formed along a series of sinkholes the fracture study of anticlinal structures reveals that the mean fracture density per area ranges between 4 and 8 km km 2 and shows a unimodal character for most of the structures however the distribution of karst in relation to fractures is bimodal for at least half of the structures with mean values ranging from 4 5 to 11 km km 2 the fractures in the anticlines are thought to have formed due to folding but some are associated with major lineaments cross cutting the structures which is reflected in the bimodality and the crude unimodal fracture karst distribution karst features are related to the general fracture pattern but are more localized in densely fractured areas karst areas were also found to correlate with lower slope gradient and lower drainage density

megaturbidite deposits in the holocene basin fill of lake como southern alps italy abstract for the first time limnogeological investigations have been carried out in lake como the deepest lake of the alps combining a bathymetric survey multibeam simrad 3000 with a high resolution seismic reflection study single channel 3 5 khz sub bottom profiler and a coring campaign gravity corer this data set enables detailed characterization of the sedimentary subsurface in the western branch of the lake the como branch which has a typical fjord morphology this paper focuses on the deepest part of the como branch argegno basin in which up to 3 5 m thick turbidite deposits are identified the basin fill of the como branch is characterized by well layered draping and onlapping pelagic sediments that are locally affected by creeping and that are intercalated with mass wasting deposits in particular with two large debris flow deposits evolving into megaturbidites in the deepest part of the basin the multibeam data together with the acoustic facies distributions and the volumes of these two major sedimentary deposits mt1 3 106 m3 and mt2 10 5 106 m3 indicate that they resulted from large slides at the northern tip of the como branch along the steep slopes of a sub lacustrine plateau the estimated ages of these events around the mid 12th mt1 and early 6th mt2 centuries are extrapolated from mean sedimentation rates based on radiocarbon 14c and radionuclide 137cs analyses from short cores in the argegno basin possible trigger mechanisms leading to these catastrophic events in the como branch include a combination of steep slope overloading with significant lake level fluctuations related to holocene climate change and or earthquake shaking the tentative age assignment places the age of both major mass movements near two other events mt1 near the occurrence of a major earthquake in the po plain in 1222 ad intensity ix mcs macroseismically derived magnitude 6 2 and mt2 near a megaturbidite triggered in 700 ad in a proglacial lake in southeastern switzerland blass a anselmetti f grosjean m sturm m 2005 the last 1300 years of environmental history in the sediments of lake sils engadine switzerland eclogae geologicae helvetiae 98 319 332 since dangerous tsunami like waves seiches can be generated by large sub aqueous landslides leading to such megaturbidites in this fjord like basin future studies are required 1 to constrain the age of these catastrophic events 2 to document the stabilities of the steep slopes in the como branch 3 to assess the expected frequency of such catastrophic events and 4 to model the propagation of large waves in the como branch and their potential damage along the highly populated lake shore

late quaternary environmental evolution of the como urban area northern italy a multidisciplinary tool for risk management and urban planning abstract the historical center of como northern italy is prone to lake flooding and subsidence due to the presence of unconsolidated silty sediments with poor mechanical properties the sedimentary basin beneath the town contains over 180 m thickness of late quaternary lacustrine palustrine and alluvial deposits the landscape evolution and the present day environmental setting of the como area have been reconstructed based on i more than 250 core logs and related geotechnical tests ii detailed stratigraphic sedimentological paleobotanical and geotechnical analysis of several key boreholes iii multi year hydrogeological monitoring iv estimation of subsidence rates and v integration of geomorphology archeological findings and historical documents based on our environmental analysis we derived an integrated geological and geomorphological model of the latest pleistocene to holocene local landscape evolution this model was used to help design an engineering facility to mitigate flood hazards in the como urban area in 2012 we carried out investigations during a re evaluation of the design parameters for the flood mitigation project at the como lake shore the new campaign included seven boreholes many in situ and laboratory tests and four 14c dates we found an organic silty unit historical in age with bad mechanical properties that was critical in the design of the flood mitigation project we also obtained index properties for static and dynamic conditions necessary for robust engineering planning the results were used to update the project and better define future executive phases although the importance of acquiring independent experimental data is often overlooked they can significantly improve the reliability of engineered systems as demonstrated by the como town case history

sensing the ups and downs of las vegas insar reveals structural control of land subsidence and aquifer system deformation land subsidence in las vegas nevada united states between april 1992 and december 1997 was measured using spaceborne interferometric synthetic aperture radar the detailed deformation maps clearly show that the spatial extent of subsidence is controlled by geologic structures faults and sediment composition clay thickness the maximum detected subsidence during the 5 75 yr period is 19 cm comparison with leveling data indicates that the subsidence rates declined during the past decade as a result of rising ground water levels brought about by a net reduction in ground water extraction temporal analysis also detects seasonal subsidence and uplift patterns which provide information about the elastic and inelastic properties of the aquifer system and their spatial variability

high resolution sedimentological and geotechnical characterization of the late quaternary deposits in the italian central adriatic coast tronto river mouth abstract in order to investigate the effective role of sedimentological analysis in the interpretation of geotechnical data with special reference to coastal transitional paleoenvironments a study on the quaternary alluvial and coastal plain successions forming the upper 30 m of the tronto river valley subsoil facing the italian central adriatic sea has been carried out according to the analysis of a continuously cored borehole and a few adjacent piezocone tests four depositional facies have been recognized from last deglaciation to present reflecting the changes in sedimentation due to sea level changes and local erosion subsidence phenomena furthermore three 14c dates have provided the basis to establish the chronological framework of the succession the interpretation of piezocone data has allowed an accurate geotechnical characterization of the different soil units also accounting for their sedimentological environment specific issues concerning the mechanical response and the determination of soil parameters of facies with special reference to the heterogeneous sedimentary formation known as flaser bedding have been discussed and appropriate piezocone based interpretation procedures have been identified the final aim of this combined geo sedimentological and geotechnical study is to propose a possible methodological approach in which both analyses can contribute to a better understanding of local subsoil for territorial planning and related engineering applications

controls of bathymetric relief on hydrothermal fluid flow at mid ocean ridges we present quantitative modeling results for the effects of surface relief on hydrothermal convection at ocean spreading centers investigating how vent site locations and subsurface flow patterns are affected by bathymetry induced sub seafloor pressure variations the model is based on a 2 d fem solver for fluid flow in porous media and is used to simulate hydrothermal convection systematically in 375 synthetic studies the results of these studies show that bathymetric relief has a profound effect on hydrothermal flow bathymetric highs induce subsurface pressure variations that can deviate upwelling zones and favor venting at structural highs the deviation angle from vertical upwelling can be expressed by a single linear dependence relating deviation angle to bathymetric slope and depth of the heat source these findings are confirmed in two case studies for the east pacific rise at 9 30 n and lucky strike hydrothermal fields in both cases it is possible to predict the observed vent field locations only if bathymetry is taken into account our results thereby show that bathymetric relief should be considered in simulations of submarine hydrothermal systems and plays a key role especially in focusing venting of across axis hydrothermal flow onto the ridge axis of fast spreading ridges

doline probability map using logistic regression and gis technology in the central ebro basin spain in the surroundings of zaragoza karstification processes are especially intense in covered karst areas where fluvial terraces lie directly on tertiary evaporites since the beginning of quaternary these processes have lead to the development of collapse and subsidence dolines with a wide range of sizes which have significant economic impacts to reduce economic impact and increase safety a regional analysis of this phenomenon is needed for spatial management therefore a probability map of dolines was developed using logistic regression and geographic information system gis techniques this paper covers the selection of input data manipulation of data using the gis technology and the use of logistic regression to generate a doline probability map the primary variable in the doline development in this area is geomorphology represented by the location of endorheic areas and different terrace levels secondary variables are the presence of irrigation and the water table gradient

along axis hydrothermal flow at the axis of slow spreading mid ocean ridges insights from numerical models of the lucky strike vent field mar the processes and efficiency of hydrothermal heat extraction along the axis of mid ocean ridges are controlled by lithospheric thermal and permeability structures hydrothermal circulation models based on the structure of fast and intermediate spreading ridges predict that hydrothermal cell organization and vent site distribution are primarily controlled by the thermodynamics of high temperature mid ocean ridge hydrothermal fluids using recent constraints on shallow structure at the slow spreading lucky strike segment along the mid atlantic ridge we present a physical model of hydrothermal cooling that incorporates the specificities of a magma rich slow spreading environment using three dimensional numerical models we show that in contrast to the aforementioned models the subsurface flow at lucky strike is primarily controlled by across axis permeability variations models with across axis permeability gradients produce along axis oriented hydrothermal cells and an alternating pattern of heat extraction highs and lows that match the distribution of microseismic clusters recorded at the lucky strike axial volcano the flow is also influenced by temperature gradients at the base of the permeable hydrothermal domain although our models are based on the structure and seismicity of the lucky strike segment across axis permeability gradients are also likely to occur at faster spreading ridges and these results may also have important implications for the cooling of young crust at fast and intermediate spreading centers

identification prediction and mitigation of sinkhole hazards in evaporite karst areas sinkholes usually have a higher probability of occurrence and a greater genetic diversity in evaporite terrains than in carbonate karst areas this is because evaporites have a higher solubility and commonly a lower mechanical strength subsidence damage resulting from evaporite dissolution generates substantial losses throughout the world but the causes are only well understood in a few areas to deal with these hazards a phased approach is needed for sinkhole identification investigation prediction and mitigation identification techniques include field surveys and geomorphological mapping combined with accounts from local people and historical sources detailed sinkhole maps can be constructed from sequential historical maps recent topographical maps and digital elevation models dems complemented with building damage surveying remote sensing and high resolution geodetic surveys on a more detailed level information from exposed paleosubsidence features paleokarst speleological explorations geophysical investigations trenching dating techniques and boreholes may help in investigating dissolution and subsidence features information on the hydrogeological pathways including caves springs and swallow holes are particularly important especially when corroborated by tracer tests these diverse data sources make a valuable database the karst inventory from this dataset sinkhole susceptibility zonations relative probability may be produced based on the spatial distribution of the features and good knowledge of the local geology sinkhole distribution can be investigated by spatial distribution analysis techniques including studies of preferential elongation alignment and nearest neighbor analysis more objective susceptibility models may be obtained by analyzing the statistical relationships between the known sinkholes and the conditioning factors chronological information on sinkhole formation is required to estimate the probability of occurrence of sinkholes number of sinkholes km2 year such spatial and temporal predictions frequently derived from limited records and based on the assumption that past sinkhole activity may be extrapolated to the future are non corroborated hypotheses validation methods allow us to assess the predictive capability of the susceptibility maps and to transform them into probability maps avoiding the most hazardous areas by preventive planning is the safest strategy for development in sinkhole prone areas corrective measures could be applied to reduce the dissolution activity and subsidence processes a more practical solution for safe development is to reduce the vulnerability of the structures by using subsidence proof designs

hydrothermal vents near a mantle hot spot the lucky strike vent field at 37 n on the mid atlantic ridge the lucky strike hydrothermal field occurs in the summit basin of a large seamount that forms the shallow center of a 65 km long ridge segment near 37 n on the mid atlantic ridge the depth and chemistry of the ridge segment are influenced by the azores hot spot and this hydrothermal field is the first atlantic site found on crust that is dominated by a hot spot signature multiple hydrothermal vents occur over an area of at least 300 m by 700 m vent morphologies range from flanges and chimneys with temperatures of 200 212 c to black smoker chimneys with temperatures up to 333 c cooler fluids from northern vents have higher chlorinities and lower gas volumes while hotter southern fluids have chlorinities 20 below seawater with higher gas volumes suggesting phase separation has influenced their compositions all gas volumes in fluids are higher than those at tag and snake pit hydrothermal fields black smokers exhibit their typical mineralogy except that barite is a major mineral particularly at lower temperature sites which contrasts with previously investigated atlantic sites the fluid chemistry distribution of the relict sulfide deposits on the seamount summit in the areas investigated using dsv alvin and contact relationships between active vent sites and surrounding basaltic and sulfide substrate suggest that the hydrothermal system has a long history and may have recently been rejuvenated fauna at the lucky strike vent sites are dominated by a new species of mussel and include the first reported sea urchins the lucky strike biological community differs considerably from other vent fauna at the species level and appears to be a new biogeographic province the lucky strike field helps to constrain how variations in the basaltic substrate influence the composition of hydrothermal fluids and solids because basalt compositions at lucky strike are 10 30 times enriched in incompatible elements compared to other atlantic hydrothermal sites such as tag snake pit and broken spur the incompatible element

geological and hydrogeological environment in shanghai with geohazards to construction and maintenance of infrastructures shanghai administrative region sar is located on the deltaic deposit of the yangtze river the bed rock under sar is generally buried in the depth of 200 m to 300 m except for several massifs where the bed rock is exposed to the ground surface the quaternary deposit in shanghai is soft sediment the variation of palaeoclimate influenced the sea level and resulted in a very complicated sedimentary environment the quaternary deposit in sar is composed of an alternated multi aquifer aquitard system maas the groundwater system is composed of one artesian aquifer and five confined aquifer layers with very high groundwater pressure head the maas was formed mainly within the warm geological era updated to 2 6 million years ago between two aquifers there is an aquitard which is composed of soft clayey soil formed mainly within the cold era the aquitards are composed of very soft clayey silt with very high compressibility and humus content the humus material was transformed into methane gas under a long term geological process with the development of economy the infrastructures were or are being constructed in the top shallow soft clayey deposit aquifer i and aquifer ii in sar the following geohazards occurred or possibly occur during the construction and maintenance of infrastructures i quicksand and piping hazards ii pumping induced hazards and recharge cutoff hazards iii long term settlement due to the seasonal fluctuation of groundwater level and iv geohazards of methane gas

subsurface conditions in hydrothermal vents inferred from diffuse flow composition and models of reaction and transport abstract chemical gradients in the subsurface of mid ocean ridge hydrothermal systems create an environment where minerals precipitate and dissolve and where chemosynthetic organisms thrive however owing to the lack of easy access to the subsurface robust knowledge of the nature and extent of chemical transformations remains elusive here we combine measurements of vent fluid chemistry with geochemical and transport modeling to give new insights into the under sampled subsurface temperature composition relationships from a geochemical mixing model are superimposed on the subsurface temperature distribution determined using a heat flow model to estimate the spatial distribution of fluid composition we then estimate the distribution of gibb s free energies of reaction beneath mid oceanic ridges and by combining flow simulations with speciation calculations estimate anhydrite deposition rates applied to vent endmembers observed at the fast spreading ridge at the east pacific rise our results suggest that sealing times due to anhydrite formation are longer than the typical time between tectonic and magmatic events the chemical composition of the neighboring low temperature flow indicates relatively uniform energetically favorable conditions for commonly inferred microbial processes such as methanogenesis sulfate reduction and numerous oxidation reactions suggesting that factors other than energy availability may control subsurface microbial biomass distribution thus these model simulations complement fluid sample datasets from surface venting and help infer the chemical distribution and transformations in subsurface flow

land subsidence and late glacial environmental evolution of the como urban area northern italy abstract the late glacial and holocene geological and environmental evolution of the como lacustrine palustrine basin has been broadly reconstructed based on a the collection and analysis of more than 100 borehole stratigraphies b the drilling of three new shallow boreholes and the analysis of a new geological section and c several in situ and laboratory analyses mineralogical organic and pollen content 14c dating the long term natural tendency of the ground surface to sink where the como urban area has developed has been verified and assessed this tendency has resulted clearly controlled by the compaction of young unconsolidated sediments accumulated at the hydrologically closed sw tip of lake como the definition of a minimum age for the deglaciation of the basin and for a correlated stratigraphic marker allowed broad quantification of the average velocity of land subsidence during the last ca 17 000 cal bp with a gradient of values close to 2 5 mm yr along the axial zone of the basin toward the present day lake burial depth of archaeological remains related to roman age and levelling monitoring since 1928 are in agreement with this estimate during 1950 1975 because of deep water withdrawal the como area was affected by a human induced accelerated subsidence with velocity 10 20 mm yr one order of magnitude higher than the natural one after a period of deceleration between the end of the 1970s and the end of the 1990s during which some benchmarks even reversed their trend persistent scatterer interferometry psi data provided by tele rilevamento europa tre for the period 1992 2003 and levelling data obtained by apat in 2004 show that during the last decade the subsidence rate has returned to its physiologic long term trend

biogeochemistry of iron in the arabian sea the arabian sea is a productive basin where seasonal upwelling and convective mixing result in high surface nutrient concentrations and widespread algal blooms the factors controlling primary productivity in the arabian sea are of interest because the region contains an intense oxygen minimum zone omz that is a major sink for nitrate in the ocean a survey of iron fe distribution and redox chemistry was carried out in 2007 to assess its role in arabian sea biogeochemistry including an investigation of the biological response to fe additions results show that fe is strongly enriched in the eastern arabian sea associated with the omz much of the fe within the omz is present as fe ii which enhances the residence time and accumulation of fe in contrast fe concentrations are lower in the western arabian sea separated from the fe rich omz by a water mass boundary consequently low surface values are associated with monsoon driven upwelling off the omani coast incubations revealed that primary production during the southwest monsoon was strongly limited by fe over much of the study area incubation of surface waters with fe resulted in rapid growth of phaeocystis and up to sixfold increase in chlorophyll this is the first demonstration of fe limitation in the arabian sea and the first high resolution zonal survey of dissolved fe and fe ii across the basin our findings suggest that models developed to predict the response of the arabian sea biogeochemistry to global warming need to consider effects on fe inputs

detection of underground cavities by combining gravity magnetic and ground penetrating radar surveys a case study from the zaragoza area ne spain a geophysical survey routine is proposed to detect underground cavities and dolines it is based on the sequential application of magnetic low frequency ground penetrating radar gpr and microgravity techniques a case study near zaragoza ebro valley spain demonstrates the applicability of these methods the strong contrast of magnetic and electromagnetic properties and to a lesser scale of density between the doline filling and the surrounding stratified tertiary and quaternary rocks allows the shape of filled cavities to be clearly outlined by these methods

subsidence induced by urbanisation in the city of rome detected by advanced insar technique and geotechnical investigations abstract we applied the interferometric point target analysis ipta technique to study the city of rome italy aiming to detect and measure the surface movements of buildings and urban structures the available sar dataset has been delivered by esa cat1 3258 and ranges the period 1992 2005 in particular ers1 ers2 data processed covers 1995 2000 while envisat asar 2002 2005 the point target velocity map shows a general stability except for some very local areas affected by subsidence rate larger than 10 mm year the analysis of the time series compared to a detailed geological and geotechnical investigation of the lithostratigraphy of the alluvial sediments of the tiber river and combined with a temporal reconstruction of the expansion of the city over the alluvial valleys allowed us to depict the main factors controlling the observed subsidence these are the in situ effective stress conditions the related compressibility and viscous characteristics of the loaded soils the thickness of the compressible stratum the time since loading instant and the entity of loading furthermore the observed subsidence is time dependent even at a long time scale with respect to the age of the buildings being most of the buildings constructed since the 50s still affected by slow subsidence we mainly focused on the grottaperfetta stream valley that is characterized by an anomalous high and time lasting subsidence original data on the lithostratigraphic setting of this alluvial valley indicate that the high subsidence rate measured up to 2005 is caused by a still active primary consolidation process

geotectonic setting of hydrothermal activity on the summit of lucky strike seamount 37 17 n mid atlantic ridge we have investigated the relations between volcanic tectonic and hydrothermal activity on lucky strike seamount 37 17 n mid atlantic ridge using a nested survey strategy involving collection of data from different deep sea mapping systems the highly tectonized seamount summit consists of three volcanic cones surrounding a relatively flat depression with a young lava lake in its center hydrothermal activity is focused mainly within the summit depression with most of the vents located proximal to the lava lake isolated active and inactive chimneys and mounds are widespread throughout the summit depression and occur on both volcanic pillow lava and hydrothermal sulfide rubble and hydrothermally cemented breccias substrates the large volume of sulfide rubble together with the nature of the sulfide structures indicates that hydrothermal activity has been episodic but ongoing for a long period of time hundreds to thousands of years on the basis of the distribution of hydrothermal deposits we propose a model of alternation between tectonic and volcanic control on hydrothermalism at lucky strike seamount midsegment melt focusing produces a spatially and temporally stable heat source that sustains focused high temperature hydrothermal activity over long time periods during periods of amagmatic extension active faulting within the summit depression provides multiple near surface fluid flow pathways for discharge of high temperature fluids and widespread deposition of massive sulfides during eruptive events rapid effusion of very hot lava creates a lava lake and hyaloclastite deposits the new sheet flows form a cap on the hydrothermal system and fluid upflow is reorganized discharge of high temperature fluids is restricted to isolated sites with relatively high permeability for example the edges of the lava lake much of the upwelling hydrothermal fluid pools in the subsurface conductively cools and mixes with entrained seawater before discharging as widespread low temperature diffuse flow hyaloclastites become cemented further augmenting the sealing of the system present day activity at lucky strike seamount represents this locally volcanically controlled phase of activity despite the segment as a whole being dominantly amagmatic

land subsidence in houston texas measured by radar interferometry and constrained by extensometers 1 we present results from a radar interferometry study over the houston galveston texas gulf coast region from the nearly 60 potential interferograms considered an atmospheric artifact assessment is performed and a tractable set of interferograms selected for detailed processing and error analysis the subsequent interferogram time series spanning 1996 1998 is constrained by coincident extensometer data with root mean square error less than 2 5 mm the interferogram time series confirms that historic subsidence in east houston has stopped consistent with current groundwater use patterns broad scale subsidence bowls are observed in west and northwest houston where maximum subsidence rates are in excess of 2 and 4 cm yr 1 respectively linear interferogram phase signatures associated with approximately 1 cm of differential subsidence across faults including the long point fault in northwest houston are observed near the seabrook extensometer a hereto unidentified subsidence bowl with a maximum subsidence rate in excess of 3 cm yr 1 is revealed this study demonstrates that when used in conjunction with a set of traditional geodetic measurements radar interferometry can measure the spatial and temporal evolution of urban land subsidence within even the most challenging of environments

a record of eruption and intrusion at a fast spreading ridge axis axial summit trough of the east pacific rise at 9 10 n 1 high resolution side scan sonar near bottom multibeam bathymetry and deep sea photo and bathymetry traverses are used to map the axial summit trough ast at the east pacific rise between 9 and 10 n we define three ridge axis morphologic types no ast narrow ast and wide ast which characterize distinct ridge crest domains spanning tens of kilometers along strike near bottom observations modeling of deformation above intruding dikes and comparisons to the geologic and geophysical structure of the ridge crest are used to develop a revised model of ast genesis and evolution this model helps constrain the record of intrusive and extrusive magmatism and styles of lava deposition along the ridge crest at time scales from hundreds to tens of thousands of years the grabens in the narrow ast domain 9 43 53 n are consistent with deformation above the most recent 10 diking events beneath the ridge crest frequent high effusion rate extrusive volcanism in this domain several eruptions every 100 years overprints near axis deformation and maintains a consistent ast width the most recent eruption at the ridge crest occurred in this area and did not significantly modify the physical characteristics of the ast the grabens in the wide ast domain 9 23 43 n originated with similar dimensions to the narrow ast spreading driven primarily by the intrusion of shallow dikes within a narrow axial zone causes the initial graben bounding faults to migrate away from the axis infrequent extrusive volcanism several eruptions every 1000 years fills a portion of the subsidence that accumulates over time but does not significantly modify the width of the ast outside of these domains lower effusion rate constructional volcanism without efficient drain back fills and erases the signature of the ast the relative frequency of intrusive versus extrusive magmatic events controls the morphology of the ridge crest and appears to remain constant over millennial time scales within the domains we have identified however over longer time scales 10 25 ka domain specific intrusive to extrusive ratios do not appear to be fixed in space resulting in a fairly consistent volcanic accretion over the length scale of the second order ridge segment between 9 n and 10 n

the timing of glacier advances in the northern european alps based on surface exposure dating with cosmogenic 10be 26al 36cl and 21ne

structure temporal evolution and heat flux estimates from the lucky strike deep sea hydrothermal field derived from seafloor image mosaics 1 here we demonstrate with a study of the lucky strike hydrothermal field that image mosaicing over large seafloor areas is feasible with new image processing techniques and that repeated surveys allow temporal studies of active processes lucky strike mosaics generated from 56 000 images acquired in 1996 2006 2008 and 2009 reveal the distribution and types of diffuse outflow throughout the field and their association with high temperature vents in detail the zones of outflow are largely controlled by faults and we suggest that the spatial clustering of active zones likely reflects the geometry of the underlying plumbing system imagery also provides constraints on temporal variability at two time scales first based upon changes in individual outflow features identified in mosaics acquired in different years we document a general decline of diffuse outflow throughout the vent field over time scales up to 13 years second the image mosaics reveal broad patches of seafloor that we interpret as fossil outflow zones owing to their association with extinct chimneys and hydrothermal deposits these areas encompass the entire region of present day hydrothermal activity suggesting that the plumbing system has persisted over long periods of time loosely constrained to hundreds to thousands of years the coupling of mosaic interpretation and available field measurements allow us to independently estimate the heat flux of the lucky strike system at 200 to 1000 mw with 75 to 90 of this flux taken up by diffuse hydrothermal outflow based on these heat flux estimates we propose that the temporal decline of the system at short and long time scales may be explained by the progressive cooling of the amc without replenishment the results at lucky strike demonstrate that repeated image surveys can be routinely performed to characterize and study the temporal variability of a broad range of vent sites hosting active processes e g cold seeps hydrothermal fields gas outflows etc allowing a better understanding of fluid flow dynamics from the sub seafloor and a quantification of fluxes

thermal infrared image analysis of a quiescent cone on piton de la fournaise volcano evidence of convective air flow within an unconsolidated soil abstract we report on the detection of air convection with infrared thermal images for two quasi circular craters 20 m and 40 m wide forming the volcanically inactive cone of formica leo reunion island the thermal images have been acquired from an infrared camera at regular time intervals during a complete diurnal cycle during the night and at dawn we observe that the rims are warmer than the centers of the craters the conductivity contrast of the highly porous soils filling the craters and their 30 slopes are unable to explain the systematic temperature drop from rim to centers we suggest that this signal could be attributed to air convection with gas entering the highly permeable soil at the center of each crater then flowing upslope along the bottom of the soil layer before exiting it along the crater rims to quantify this process we present a two dimensional numerical modelling of air convection in a sloped volcanic soil with a surface temperature evolving between day and night this convection depends on a unique dimensionless equivalent rayleigh number ra eq which is the product of the standard rayleigh number with the volumetric heat capacity ratio of the air and the soil the convective flow is unsteady during some periods the convective flow is entirely confined within the soil and at other times air enters the crater at its center and exits it at the rim crests when ra eq 6000 a value likely compatible with the soil permeability and the geothermal heat flux a very strong transient cold air plume occasionally develops along the center of the crater the interval of time between two plumes only depends on the thermal fluctuations within the top boundary layer of the convective cell and thus is not contrasted by the diurnal cycle the detachment of a cold plume can occur at any time after few days of quiescence and lasts several hours during the whole convective cycle the rim to center temperature drop persists and has an amplitude and a shape having an excellent agreement with that found in the ir images this work constitutes a preliminary step to explore the deep thermal structure of the active caldera of bory dolomieu and could help to improve the understanding of volcanic hazards of the reunion volcano

sinkholes in the salt bearing evaporite karst of the ebro river valley upstream of zaragoza city ne spain geomorphological mapping and analysis as a basis for risk management abstract a detailed sinkhole map has been produced in a stretch of the ebro valley 40 8 km2 including the western sector of zaragoza city ne spain during the last few decades around 70 of the original sinkhole area has been filled with anthropogenic sediments causing the disappearance of 137 ha of wetlands the interstratal karstification of salts halite and glauberite and a wnw ese trending joint set have played a major control in the development of sinkholes three morphometric types of sinkholes have been differentiated each attributed to a specific subsidence mechanism inferred from the paleosinkholes exposed in the surrounding of zaragoza city sagging of bedrock and cover collapse of bedrock and cover and collapse of cover material related to the downward migration of particles through dissolutional conduits each type of sinkhole is characterised by a distinctive behaviour in terms of controlling factors spatio temporal distribution and kinematics and consequently the proposed differentiation may have a practical utility the vast majority of the subsidence damage identified in the area occurs within the boundaries of pre existing sinkholes identifiable in old aerial photographs and topographical maps this fact demonstrates that the application of preventive planning strategies based on detailed geomorphological maps would have allowed avoidance of most of the large financial losses caused by subsidence in the area of the order of hundreds of thousands of euros per year

black smokers fuelled by freezing magma if ocean floor hot spring activity is to continue long enough to produce a large massive sulphide deposit heat must be stripped by the circulating water from a store within the ocean crust we argue here that this heat store can only be a magma chamber and that production of a large sulphide deposit requires very rapid crystallization of large volumes of magma 1 km3 per 100 yr for several hundred years the effects of such rapid solidification should be apparent in the gabbroic components of ophiolite complexes as well as in plutons in other environments where large high temperature massive sulphides are formed

hydrothermal activity along the slow spreading lucky strike ridge segment mid atlantic ridge distribution heatflux and geological controls we have reviewed available visual information from the seafloor and recently acquired microbathymetry for several traverses across the lucky strike segment to evaluate the distribution of hydrothermal activity we have identified a new on axis site with diffuse flow ewan and an active vent structure similar to 1 2 km from the axis capelinhos these sites are minor relative to the main field and our total heatflux estimate for all active sites 200 1200 mw is only slightly higher than previously published estimates we also identify fossil sites w of the main lucky strike field a circular feature similar to 200 m in diameter located on the flanks of a rifted off axis central volcano is likely a large and inactive hydrothermal edifice named grunnus we find no indicator of focused hydrothermal activity elsewhere along the segment suggesting that the enhanced melt supply and the associated melt lenses required to form central volcanoes also sustain hydrothermal circulation to form and maintain large and long lived hydrothermal fields hydrothermal discharge to the seafloor occurs along fault traces suggesting focusing of hydrothermal circulation in the shallow crust along permeable fault zones

228ra in the dead sea abstract the 228 ra concentrations of the dead sea waters range from 0 13 to 1 48 dpm kg 1 two to three orders of magnitude higher than those of ocean waters and lake waters however the 228 ra 226 ra activity ratios 0 12 1 29 10 2 are in the range reported for the hydrosphere the surface waters of the dead sea are enriched in 228 ra by a factor of about three over the near bottom waters there is a factor of about two spatial variability in the mid depth ra concentrations at the two profile stations the near bottom 228 ra gradients yield vertical eddy diffusivity coefficient k of 2 0 and 0 4 cm 2 s 1 at profile locations 1 and 2 respectively these values are comparable to those measured in oceans and lakes

submeter bathymetric mapping of volcanic and hydrothermal features on the east pacific rise crest at 9 50 n 1 recent advances in underwater vehicle navigation and sonar technology now permit detailed mapping of complex seafloor bathymetry found at mid ocean ridge crests imagenex 881 675 khz scanning sonar data collected during low altitude 5 m surveys conducted with dsv alvin were used to produce submeter resolution bathymetric maps of five hydrothermal vent areas at the east pacific rise epr ridge2000 integrated study site 9 50 n bull s eye data were collected during 29 dives in 2004 and 2005 and were merged through a grid rectification technique to create high resolution 0 5 m grid composite maps these are the first submeter bathymetric maps generated with a scanning sonar mounted on alvin the composite maps can be used to quantify the dimensions of meter scale volcanic and hydrothermal features within the epr axial summit trough ast including hydrothermal vent structures lava pillars collapse areas the trough walls and primary volcanic fissures existing autonomous benthic explorer abe bathymetry data 675 khz scanning sonar collected at this site provide the broader geologic context necessary to interpret the meter scale features resolved in the composite maps the grid rectification technique we employed can be used to optimize vehicle time by permitting the creation of high resolution bathymetry maps from data collected during multiple coordinated short duration surveys after primary dive objectives are met this method can also be used to colocate future near bottom sonar data sets within the high resolution composite maps enabling quantification of bathymetric changes associated with active volcanic hydrothermal and tectonic processes

surficial permeability of the axial valley seafloor endeavour segment juan de fuca ridge 1 hydrothermal systems at mid ocean spreading centers play a fundamental role in earth s geothermal budget one underexamined facet of marine hydrothermal systems is the role that permeability of the uppermost seafloor veneer plays in the distribution of hydrothermal fluid as both the initial and final vertical gateway for subsurface fluid circulation uppermost seafloor permeability may influence the local spatial distribution of hydrothermal flow a method of deriving a photomosaic from seafloor video was developed and utilized to estimate relative surface permeability in an active hydrothermal area on the endeavour segment of the juan de fuca ridge the mosaic resolves seafloor geology of the axial valley seafloor at submeter resolution over an area greater than 1 km2 results indicate that the valley walls and basal talus slope are topographically rugged and unsedimented providing minimal resistance to fluid transmission elsewhere the axial valley floor is capped by an unbroken blanket of low permeability sediment resisting fluid exchange with the subsurface reservoir active fluid emission sites were restricted to the high permeability zone at the base of the western wall a series of inactive fossil hydrothermal structures form a linear trend along the western bounding wall oriented orthogonal to the spreading axis high temperature vent locations appear to have migrated over 100 m along ridge strike over the decade between surveys while initially an expression of subsurface faulting this spatial pattern suggests that increases in seafloor permeability from sedimentation may be at least a secondary contributing factor in regulating fluid flow across the seafloor interface

mapping regional land displacements in the venice coastland by an integrated monitoring system abstract an original integrated monitoring method is designed to infer an accurate and reliable figure of regional land displacements in coastal areas where the presence of internal waters wetlands farmlands urban and industrial centers usually reduces the efficiency of single ground based and satellite based measuring techniques five different methods i e spirit leveling differential global positioning system dgps continuous gps cgps interferometric synthetic aperture radar insar and interferometric point target analysis ipta are integrated into a subsidence integrated monitoring system sims to overcome the limits characterizing each technique the sims has been used over the past decade to provide a new image of the land displacements in the venice region the result exhibits a resolution never obtained before the central lagoon including the city of venice shows a general stability while the northern and southern lagoon extremities and their related catchment sectors sink with serious rates averaging 3 to 5 mm year the sinking rates increase up to 10 15 mm year in the coastland south of the lagoon relatively small uplifts less than 1 mm year are observed at the alpine foothills and in a wide area comprised between the euganean hills and the lagoon the observed land displacements have been associated to the geological features of the study region i e tectonics seismicity differential consolidation of the middle upper pleistocene and holocene deposits and to anthropogenic activities such as land reclamation and groundwater withdrawal

subseafloor phase equilibria in high temperature hydrothermal fluids of the lucky strike seamount mid atlantic ridge 37 17 n abstract as part of an integrated study conducted at the lucky strike seamount mid atlantic ridge 37 17 n in 2008 gas tight sampling devices were used to collect high temperature 300 c hydrothermal fluids issuing from sulfide structures distributed throughout the vent field located in the summit depression compared with previous observations from 1993 to 1997 the most substantial changes in vent fluid compositions are dramatically increased co2 concentrations 5 up to 133 mmol l and the observation of vent fluids enriched in dissolved chloride relative to seawater combined with an increase in 13 c co 2 values by 4 in 2008 the elevated co2 indicates replenishment of the magmatic heat source and may be indicative of a recent magmatic event the additional supporting fluid chemistry is however similar to that of the previous sampling intervals necessitating a reassessment of the subseafloor controls on vent fluid chemistry at lucky strike in the context of recently obtained geophysical data that provides the depth extent of a steady state magma chamber two phase behavior is indicated by the chloride variability in the vent fluids and comparison with experimental data for the associated chloride dependent partitioning of minor trace elements suggests the possibility of a similar source fluid for all the vent structures while limiting the likelihood of shallow phase separation and subseafloor mixing for the hydrothermal end members a recently calibrated fe mn geothermometer indicates minimum subseafloor equilibration temperatures of 350 385 c however constraints imposed by dissolved si cl in conjunction with geophysical observations are consistent with peak reaction conditions at temperatures of 430 475 c and pressures near the top of the axial magma chamber 410 480 bars where magmatic co2 becomes entrained in the circulating fluids the distance between the magma chamber and the seafloor at lucky strike is substantially greater than at most faster spreading ridges and we propose the resulting increased residence time in the up flow zone leads to the re equilibration of temperature sensitive transition metals at conditions less extreme than those associated with peak reaction agreement between experimental data thermodynamic model calculations and dissolved concentrations of fe cu zn h2 and h2s in the lucky strike fluids reinforce the hypothesis of ph redox equilibria for transition metals at relatively oxidizing conditions and temperatures predicted by the empirical fe mn geothermometer in situ ph measurements of the high temperature fluids exiting the seafloor are also consistent with the model calculations

a critical evaluation of depositional parameters controlling the variability of organic carbon in arabian sea sediments abstract organic carbon distribution in the surficial sediments of the arabian sea to some extent mirrors the surface productivity being both high in the peripheral portions and low in the central region suggesting that the productivity is a primary source of organic matter however a critical examination reveals that the organic enrichment on the slope of the indian margin is two to four higher max 16 71 than on the slope of the arabian peninsula max 7 54 while the productivity in the former region is three to four times lower than the latter this observation suggests that the influence of productivity on organic enrichment is of secondary importance high concentrations 4 of organic carbon exactly coincide with the oxygen minimum zone 150 1500 m water depth evidently reflecting the crucial role played by the anoxic bottom waters in the preservation of organic carbon incidently the organic rich band along the western indian slope is wide long and highly concentrated as compared to that of the slope of the arabian peninsula and no organic enrichment is found on other continental slopes of the arabian sea although an equally intense oxygen minima impinge on the floor of the slope such a variability of organic carbon on the slopes is attributed to various geological parameters such as texture of sediments rates of fine terrigenous sediment deposition shelf width slope gradient bottom currents and adsorption capacity of individual clay minerals all these observations suggest that the productivity is not an ultimate control for the organic enrichment of bottom sediments but it is the bottom water anoxia in conjunction with various depositional parameters which determine the degree of preservation

microearthquake patterns following the 1998 eruption of axial volcano juan de fuca ridge mechanical relaxation and thermal strain 1 ocean bottom seismic networks deployed following the 1998 eruption of axial seamount reveal an evolving pattern of microearthquake activity associated with subsurface magmatism and thermal strain seismicity rates decay steadily over 15 months of observation february 8 1998 to april 30 1999 consistent with a trend toward thermal and mechanical equilibrium in the shallow crust after the magmatic event immediately after the eruption seismicity rates were high for about 60 days in the southeast corner of the caldera where lava flows from the 1998 eruption were mapped a small burst of seismic activity was observed on the southeast shoulder of the volcano from 100 to 150 days after the eruption these events which are characterized by slip on nearly vertical faults in the shallow crust extend about 6 km from the southeast corner of the caldera and overlie a mid crustal low velocity zone after this episode seismicity rates remain low until the end of the observation period 455 days after the eruption shallow 0 7 km depth events consistent with thermal contraction and volume changes of 2 10 3 m3 in 5 m3 sources are observed in individual clusters beneath hydrothermal vents within the 1998 lava flow at the southeast edge of the caldera microearthquakes observed during the last 70 days of observation are distributed around the central caldera most likely representing small amounts of subsidence on caldera faults during the final stages of equilibration following melt withdrawal associated with the 1998 eruption

compared geochemical signatures and the evolution of menez gwen 37 50 n and lucky strike 37 17 n hydrothermal fluids south of the azores triple junction on the mid atlantic ridge during the diva 1 cruise in may 1994 a series of 19 dives was conducted using the french submersible nautile at the topographic highs of three volcanic segments centered at 37 17 n 37 50 n and 38 20 n respectively south of the azores triple junction atj on the mid atlantic ridge mar hydrothermal fluids were collected at the lucky strike ls hydrothermal field discovered at 37 17 n in 1993 and at a new hydrothermal site called menez gwen mgw discovered at 37 50 n during this cruise both systems are relatively shallow compared to other mar systems with seafloor depths of 1700 and 850 m respectively characteristics which make them unique among the already known sites on the mar the characteristics of the ls fluids are the same as in 1993 and include temperatures ranging from 170 c to 324 c variable chlorinities lower than seawater low hydrogen sulfide 3 0 mmol kg high ba concentrations up to 80 mol kg low metal concentrations and high gas contents and distinct chemical end members indicative of significant geographic control of the venting system in contrast the very clear mgw fluids at 37 50 n show a rather uniform exit temperature 285 c and chemical compositions with chlorinities 360 380 mmol kg lower than at ls and corresponding lower concentrations of cations h2s 1 8 mmol kg metals and silica 8 11 5 mmol kg due to the lower temperature t and pressure p of the system in the two systems fluid chemistry is strongly affected by phase separation at the low pressure conditions of these sites phase relations in the nacl h2o system dictate production of an extremely low salinity the higher salinities observed in fluids thus indicate that mixing of extremely low salinity vapor with single phase hydrothermal seawater is the dominant process controlling cl concentrations depletions and enrichments of elements in solutions are also explained by the involvement of fluid rock reactions the enrichment of ba k cs and rb in the fluids is linked to the enriched character of these elements in basalts relatively high ph and ca low li sr and metals are related to the highly altered basaltic substrate in the reaction zone low sr ca and high ca na ratios are explained by albitization within the crust the increase of degassing when approaching the azores may be related to the carbon enriched basaltic crust near the azores hot spot isotopic ratios show that co2 ch4 and helium gases have a magmatic signature compared to other deeper sites on the mar all fluids collected at ls and mgw are gas enriched except for h2s and helium whose both concentration and isotopic ratio compare well with other hydrothermal fluids the high ch4 concentration associated with unsaturated hydrocarbons and the high ch4 3he ratios also suggest a contribution of ch4 generated by serpentinization of ultramafic rocks by fischer tropsch catalysis of co2 reduction

3d geological modelling at urban scale and mapping of ground movement susceptibility from gypsum dissolution the paris example france gypsum dissolution can be the cause of damage associated with subsidence and collapse in paris the authorities want to refine the current maps of the areas likely to be affected by ground movement due to gypsum dissolution in the bartonian saint ouen limestone and beauchamp sands and in the lutetian marl and limestone formation the proposed method involves assessing separately the probabilities relative to factors that control the ground subsidence i e thickness of gypsum strata sulphate unsaturated water flows groundwater level thickness and nature of the overburden the total susceptibility is represented in a map form by the product of these three values plotted on a grid map with a pixel size of 20 m for this we developed a multi layer 3d geological model using the same 20 m mesh grid integrating 21 lithostratigraphic units the hazard prone areas were calculated by geostatistical methods from the archived descriptions of more than 3900 boreholes and from existing geological maps at the same time the analysis of some 300 piezometers made it possible to construct the high water hw and low water lw levels of the groundwater likely to have an impact on the dissolution of the gypsum the obtained results correlate satisfactorily with the parisian authorities field knowledge and to the location of the known events the mapping also revealed some sensitive areas that had not been previously identified these will be checked by drilling the constructed geological model and the hydrogeological analysis have already been used for studying other phenomena e g sand flow and clay creep

a sedimentary record of holocene surface runoff events and earthquake activity from lake iseo southern alps italy this study presents a record of holocene surface runoff events and several large earthquakes preserved in the sediments of pre alpine lake iseo northern italy a combination of high resolution seismic surveying detailed sediment microfacies analysis non destructive core scanning techniques and ams 14c dating of terrestrial macrofossils was used to detect and date these events based on this approach our data shed light on past seismic activity in the vicinity of lake iseo and the influence of climate variability and human impact on allochthonous detrital matter flux into the lake the 19 m long investigated sediment sequence of faintly layered lake marl contains frequent centimetre to decimetre scale sandy silty detrital layers during the early to mid holocene these small scale detrital layers reflecting sediment supply by extreme surface runoff events reveal a distinct centennial scale recurrence pattern this is in accordance with regional lake level highstands and minima in solar activity and thus apparently mainly climate controlled after c 4200 cal yr bp intervals of high detrital flux occasionally also correlate with periods of enhanced human settlement activity in consequence deposition of small scale detrital layers during the late holocene apparently reflects a rather complex interplay between climatic and anthropogenic influences on catchment erosion processes besides the small scale detrital layers five up to 2 40 m thick large scale detrital event layers composed of basal mass wasting deposits overlain by large scale turbidites were identified which are supposed to be triggered by strong earthquakes the uppermost large scale event layer can be correlated to a documented mw 6 0 earthquake in ad 1222 in brescia the four other large scale event layers are supposed to correspond to previously undocumented local earthquakes these occurred around 350 bc 570 bc 2540 bc and 6210 bc and most probably also reached magnitudes in the order of mw 5 0 6 5