effects of winter convection on the deep layer of the southern adriatic sea in 2012 1 we analyze aspects concerning the thermohaline changes observed in the near bottom layer of the southern adriatic pit sap in the eastern mediterranean after the arrival of abundant and exceptionally dense water 30 kg m 3 produced in the shallow northern adriatic sea during winter 2012 for this purpose we use temperature t salinity s and current time series collected at the e2m3a deep ocean observatory of the southern adriatic and conductivity temperature depth data obtained both in the southern and middle adriatic from freely drifting profiling floats the dense water produced in the northern adriatic arrived in the central and deepest part of the sap as a series of individual pulses starting on 10 march 2012 while a stronger and prolonged signal that significantly modified the local deep water stratification arrived after 10 april 2012 as a consequence t and s suddenly decreased 0 15 c and 0 015 thus interrupting positive t and s bottom trends observed during the previous 5 years and producing a density increase of 0 02 kg m 3 such variability has been rarely observed in the area we ascribe its occurrence to the concomitance of exceptionally harsh and long lasting bora wind scarce precipitation and low river discharge over the northern adriatic during winter 2011 2012 eventually this newly formed addw reached the strait of otranto during july 2012 its characteristics profoundly differed from those observed in the previous decade hence a noticeable variability in structure and circulation of the abyssal layers of the ionian basin is likely to occur in the near future

particle transport in the bari canyon southern adriatic sea to define the sediment transport pathways along the southern adriatic shelf and slope two oceanographic cruises were carried out in the southern adriatic in july 2004 and in march april 2005 to study the role of the bari canyon system on sediment dispersal three moorings including sediment traps and current meters have been deployed near the bottom at depths of 600 m for one year march 2004 march 2005 two moorings were deployed within the canyon station b in the northern branch and station c in the southern branch and one on the adjacent open slope north of the canyon system station a total mass fluxes tmfs measured by sediment traps were always higher in the canyon than on the adjacent slope the highest values were measured at station c average 8 07 g m 2 d 1 roughly double those of station b 3 07 g m 2 d 1 and the lowest outside the canyon at station a 1 69 g m 2 d 1 the highest tmf were recorded in spring 2004 a period characterized by the lowest water temperatures and the highest current speeds up to 72 cm 1 which were associated with the highest across slope current component along the canyon axes the simultaneous variations of fluxes occurring at the three stations imply that similar processes are active along the entire southern adriatic margin and that they are amplified inside the canyon in spring a vein of southward flowing north adriatic dense water naddw was observed along the adriatic shelf this was related to an enhanced across slope current component which was responsible for the higher particle fluxes both on the open slope and at the canyon stations these data suggest that the bari canyon is an efficient conduit for sediment from the adriatic continental shelf to the deep basin downcore profiles of 210 pb in sediments collected below the traps have been used to estimate sediment mass accumulation rates mars on a century scale on the open slope the annual trap flux recorded in 2004 2005 was lower than mar on the contrary in the bari canyon the annual trap flux was higher than mar indicating that the lateral advection of particles becomes predominant and that a fraction of the particles intercepted by sediment traps was only in transit through the canyon 2007 elsevier b v all rights reserved

simulating the formation and fate of dense water in a midlatitude marginal sea during normal and warm winter conditions 1 dense shelf water production and the deep convection process in the adriatic sea are investigated considering two case studies the first is representative of the present climatic situation whereas the second may be expected in a scenario characterized by mild winter conditions over the basin dense water production and spreading are studied using a high resolution implementation of the massachusetts institute of technology general circulation model that is initialized and forced with realistic conditions this paper provides qualitative and quantitative information on mass transport dense water pathways thermohaline structures and the mixing properties of the basin in the northern adriatic shelf seawater temperature is the key element for winter dense water production because it contributes more relevantly than salinity in determining density in the southern adriatic sea a small amount of dense water that cascades directly into the pit can be formed on the narrow western shelf only during cold winter conditions moreover open ocean deepwater formation occurs in the middle of the southern basin in late winter and spring although only when winter conditions have been sufficiently cold northern adriatic dense shelf water forms a subsurface stream of which the densest part rapidly sinks in the southern pit along the shelf break whereas its lighter part flows southward and reaches the otranto strait the frequent occurrence of mild winter conditions could lead to lower dense water production with a reduced dense water flow from the adriatic sea to the ionian sea and a potential great impact on the eastern mediterranean thermohaline circulation

broken hill pb zn ag deposit a product of mantle metasomatism broken hill ore deposition occurred during the highest geothermal gradient coeval with an event of bimodal basic rhydacitic volcanism the depositional environment is interpreted as an ensialic rift on the basis of the sedimentary facies ferro and low k tholeiitic basalts and bimodal basic calc alkaline rhyolite rhyodacite volcanism the orebody is of unusual composition characterised by abundant carbonate fluorite and fluorapatite abundant lil k and rb rich premetamorphic alteration assemblages primordial s and pb isotopic values sr isotopes possibly indicating a heterogeneous source s se in the magmatic range and zoning suggestive of cooling of the ore fluid

a volcano bursting at the seams inflation faulting and eruption at sierra negra volcano galapagos the results of geodetic monitoring since 2002 at sierra negra volcano in the galapagos islands show that the filling and pressurization of an 2 km deep sill eventually led to an eruption that began on 22 october 2005 continuous global positioning system cgps monitoring measured 2 m of accelerating inflation leading up to the eruption and contributed to nearly 5 m of total uplift since 1992 the largest precursory inflation ever recorded at a basaltic caldera this extraordinary uplift was accommodated in part by repeated trapdoor faulting and coseismic cgps data provide strong constraints for improved deformation models these results highlight the feedbacks between inflation faulting and eruption at a basaltic volcano and demonstrate that faulting above an intruding magma body can relieve accumulated strain and effectively postpone eruption

subsidence in the paricutin lava field causes and implications for interpretation of deformation fields at volcanoes abstract assessment of volcanic hazards includes interpretation of ground deformation signal which at polygenetic volcanoes often results from the superposition of deformation due to pressure changes in the magmatic system and due to surficial processes such as cooling of emplaced lava the deformation signal associated with emplaced lava is sometimes considered negligible if fields are decades old but if the lava thickness is great deformation may still be occurring possibly leading to misinterpretation of the observed deformation here i evaluate the 2007 2011 ground motion of the 1943 1952 lava field of the paricutin monogenetic cinder cone mexico interferometric synthetic aperture radar insar time series reveal patchy subsidence restricted to the lava field and following linear rates up to 5 5 cm year there is a clear correlation between subsidence rates and topography suggesting a causal relationship with deposits or lava thickness i estimate these thicknesses in the subsiding areas using pre and post eruption topographic maps and show that they reach up to 200 m a numerical model for lava flow cooling was developed considering radiation and convection from the surface conductive transfer inside the flow and to the ground and vesiculation and latent heat generation at the top and bottom of the flow the model shows that compaction induced by cooling of the thick deposits emplaced 60 years ago explains the observed subsidence when conductive transfer to the ground is considered these results demonstrate that thick deposits can keep deforming significantly even decades after their emplacement emphasizing the importance of considering cooling processes when interpreting deformation fields at polygenetic volcanoes producing massive lava fields

reconciling seismic and geodetic models of the 1989 kilauea south flank earthquake 1 the inconsistency in depth between geodetic and seismic models of the 1989 kilauea earthquake has long been puzzling previous attempts to incorporate elastic heterogeneity have deepened geodetic models substantially bringing them closer to the seismic depth however recent studies that have included heterogeneity for other faults indicate that the effect is not so great we show here that elastic heterogeneity has a relatively minor effect on the geodetic model depth for this earthquake also however by combining three different sets of geodetic data we are able to get a more accurate estimate of the depth which does in fact coincide with the hypocentral depth at the 95 confidence level when we consider that static elastic parameter values are commonly less than dynamic values the agreement is even better furthermore the depth is consistent with the earthquake having occurred at the interface between the volcanic pile and the pre volcanic seafloor

post eruptive deformation associated with the 1986 87 and 1989 lava flows of etna detected by radar interferometry we analysed 92 interferograms produced using ers1 sar images taken on etna between may 1992 and october 1993 nineteen show a local subsidence in the eastern flank of the volcano correlated with the location of the 30 october 1986 1 march 1987 and 27 september 9 october 1989 lava flows using fringe unwrapping and data gridding techniques and assuming that over the sampled time window deformation was a linear function of time we derive a map of along range rate of motion the correlation between the deformation field and the area covered by recent lavas suggests that compaction of the lava flows continues several years after the eruptions the area of maximum subsidence 47 mm yr is localised at the narrowing of the 1989 flow between 1500 and 1700 m a s l we observe that subsidence extends outside the lava flows accounting for at least 12 mm yr assuming a relaxation process of the substrate in response to loading produced by recent lavas a simple 1d maxwell visco elastic model predicts a maximum subsidence rate of 25 mm yr and a relaxation time of about 3 5 years the relaxation time agrees with those derived from post eruptive displacements observed by levelling on etna and piton de la fournaise after several eruptions we conclude that at the time of our measurements 25 to 50 of the deformation was related to relaxation of the substrate and the other part due to compaction of the lava flows

submarine gold mineralization near lihir island new ireland fore arc papua new guinea gold rich siliceous veins with disseminated polymetallic sulfides and pyritic stockwork mineralization have been recovered from the top of conical seamount a shallow 1 050 m water depth submarine volcano located about 10 km south of lihir island papua new guinea grab samples from the summit of conical seamount contain the highest concentration of gold yet reported from the modern sea floor max 230 ppm au avg 26 ppm n 40 the gold occurs in sulfide rich veins of black amorphous silica hosted by intensely altered high k calc alkaline basalts sulfides in the veins consist of sphalerite galena pyrite chalcopyrite marcasite and a variety of cu pb as sb sulfosalts the gold occurs as native gold and electrum in the amorphous silica and as inclusions in the sulfides the highest gold concentrations are associated with high ag as sb and hg zoned alteration adjacent to the veins consists of illite smectite amorphous silica k feldspar secondary plagioclase minor chlorite and trace carbonate the association of gold with illite smectite amorphous silica and k feldspar indicates deposition from near neutral ph hydrothermal fluids however the auriferous polymetallic sulfide veins and the associated alteration are overprinted on stockwork pyrite mineralization that is associated with earlier acid alteration containing alunite aluminum phosphate sulfates kaolinite and other clay minerals the platy habit of the alunite in this assemblage the presence of alumium posphate sulfate minerals and the sulfur isotope ratios of the crystalline pyrite 8 6 to 0 2 34 s n 28 and alunite 7 5 and 6 4 34 s are consistent with a contribution of magmatic volatiles in the earliest stages of the hydrothermal system framboidal pyrite within and at the margins of the mineralized zone has 34 s values suggesting involvement of biogenic activity 11 6 to 13 9 34 s the gold rich veins at conical seamount are distinct from sea floor massive sulfide deposits and represent a new style of mineralization on the modern sea floor the mineralogy alteration geochemistry and texture of the veins resemble those of some subaerial epithermal gold deposits and indicate that features long considered to define a subaerial setting can also form in a submarine environment the proximity of conical seamount to the giant ladolam epithermal gold deposit on nearby lihir island also raises the possibility that both subaerial and submarine gold mineralization in the region may be related to the same district scale magmatic events

inversion of surface deformation data for rapid estimates of source parameters and uncertainties a bayesian approach new satellite missions e g the european space agency s sentinel 1 constellation advances in data downlinking and rapid product generation now provide us with the ability to access space geodetic data within hours of their acquisition to truly take advantage of this opportunity we need to be able to interpret geodetic data in a prompt and robust manner here we present a bayesian approach for the inversion of multiple geodetic data sets that allows a rapid characterization of posterior probability density functions pdfs of source model parameters the inversion algorithm efficiently samples posterior pdfs through a markov chain monte carlo method incorporating the metropolis hastings algorithm with automatic step size selection we apply our approach to synthetic geodetic data simulating deformation of magmatic origin and demonstrate its ability to retrieve known source parameters we also apply the inversion algorithm to interferometric synthetic aperture radar data measuring co seismic displacements for a thrust faulting earthquake 2015 mw 6 4 pishan earthquake china and retrieve optimal source parameters and associated uncertainties given its robustness and rapidity in estimating deformation source parameters and uncertainties our bayesian framework is capable of taking advantage of real time geodetic measurements thus our approach can be applied to geodetic data to study magmatic tectonic and other geophysical processes especially in rapid response operational settings e g volcano observatories our algorithm is fully implemented in a matlab based software package geodetic bayesian inversion software that we make freely available to the scientific community

the displacement field of the landers earthquake mapped by radar interferometry geodetic data obtained by ground or space based techniques can be used to infer the distribution of slip on a fault that has ruptured in an earthquake although most geodetic techniques require a surveyed network to be in place before the earthquake1 3 satellite images when collected at regular intervals can capture co seismic displacements without advance knowledge of the earthquake s location synthetic aperture radar sar interferometry first introduced4 in 1974 for topographic mapping5 8 can also be used to detect changes in the ground surface by removing the signal from the topography9 10 here we use sar interferometry to capture the movements produced by the 1992 earthquake in landers california11 we construct an interferogram by combining topographic information with sar images obtained by the ers 1 satellite before and after the earthquake the observed changes in range from the ground surface to the satellite agree well with the slip measured in the field with the displacements measured by surveying and with the results of an elastic dislocation model as a geodetic tool the sar interferogram provides a denser spatial sampling 100 m per pixel than surveying methods1 3 and a better precision 3 cm than previous space imaging techniques12 13

estimating source parameters from deformation data with an application to the march 1997 earthquake swarm off the izu peninsula japan we have applied two monte carlo optimization techniques simulated annealing and random cost to the inversion of deformation data for fault and magma chamber geometry these techniques involve an element of randomness that permits them to escape local minima and ultimately converge to the global minimum of misfit space we have tested the monte carlo algorithms on two synthetic data sets we have also compared them to one another in terms of their efficiency and reliability we have applied the bootstrap method to estimate confidence intervals for the source parameters including the correlations inherent in the data additionally we present methods that use the information from the bootstrapping procedure to visualize the correlations between the different model parameters we have applied these techniques to gps tilt and leveling data from the march 1997 earthquake swarm off of the izu peninsula japan using the two monte carlo algorithms we have inferred two sources a dike and a fault that fit the deformation data and the patterns of seismicity and that are consistent with the regional stress field

an analysis of dense water production on the north adriatic shelf abstract the aim of this paper is to investigate the mechanism of dense water formation in the northern shelf region of the adriatic sea and its spreading towards the middle and south adriatic the analyses encompass temperature salinity sigma t and dissolved oxygen data collected during 1951 1989 interval in the deep trench located in the middle of the adriatic hydrographic sections as well as current and temperature time series collected in the north and middle adriatic were analysed too the data outline linear trends of salinity by 0 0036 0 0017 year 1 and of dissolved oxygen content by 0 022 0 008 ml l 1 year 1 whereas temperature data reveal three periods having different attributes strong fluctuations 1951 1962 higher 1966 1980 and lower 1981 1989 temperature values two types of north adriatic dense water naddw formation result from the analysis the first with rather low temperatures high rates of surface buoyancy losses e g 1956 1981 1984 and the second with high salinity large inflow of levantine intermediate water liw e g 1955 1968 after formation on the shelf naddw can bifurcate and goes close to the western main branch and or eastern secondary branch flanks by correlating hydrological data collected at the bottom of the trench with the north adriatic surface buoyancy fluxes and the po river discharges main naddw current velocity is calculated to be higher than 8 cm s 1 therefore reaching the jabuka pit about 1 month after generation whereas the secondary branch arrives there about 1 month later naddw current lasted for about 2 months spring 1984 preconditionings favourable for the naddw formation are achieved too by correlating both surface buoyancy fluxes and the po river discharges with temperature data measured at the bottom of the jabuka pit

the influence of loading by lavas on the siting of volcanic eruption vents on mt etna abstract until now it has been considered that the positioning of magma conduits dykes and eruption sites on mt etna is controlled by stresses set up by regional tectonism it is also likely that gravitational stresses have some influence on the subsurface path taken by etnean magmas prior to eruption an additional effect discussed here is based mainly on convincing field evidence gathered over a number of years it is proposed that fracturing of the surface and changes in the stress pattern due to loading by recent lava flows may strongly influence the siting of eruptions detailed field observations are presented showing that cracks and fumaroles have consistently appeared round the edges of recent lava flows and that these cracks are sometimes later used by erupting lavas eruption statistics indicate that since 1970 50 of new eruptive vents have appeared within 80 m of a recent flow edge and field measurements show that downward flexure is still occurring at the edges of lava flows more than sixteen years old simple theoretical modelling indicates that this effect is strongest at the surface with gravitational and regional tectonic control of eruption sites dominating at progressively deeper levels

petrology of lavas from sierra negra volcano isabela island galapagos archipelago sierra negra volcano is a voluminous active basaltic shield situated in the western galapagos archipelago a hotspot related chain adjacent to the galapagos spreading center the volcano has erupted fe rich tholeiitic basalts of very limited compositional range comparison of lavas from each of five stratigraphic units covering the entire volcano indicates that the lavas are mineralogically similar and compositionally restricted 4 4 to 6 9 wt mgo the lavas are fe rich and hypersthene normative and plot in both the alkaline and tholeiite fields of the alkali silica diagram rare earth element ree patterns are steep and parallel the major and trace element data indicate a comagmatic relationship by fractional crystallization of the observed phenocryst phases projections into pseudoternary phase diagrams suggest that the magmas cooled and crystallized at pressures between 1 and 3 kbar calculated melt densities range from 2 73 to 2 77 g cm3 which are higher than those of typical mid ocean ridge basalt morb hawaiian tholeiite and other galapagos lavas the high calculated melt densities may be caused by fractionation at greater depths than is ordinary for the other basaltic magmas suppression of plagioclase and olivine crystallization in favor of augite may eliminate the minimum density window that has been proposed for morb fractionation sierra negra lavas have the most radiogenic lead and strontium isotopic ratios in the western galapagos indicating that the magmas have a relatively large contribution of plume material and have been minimally contaminated by entrainment of morb producing mantle magmatic 3he 4he isotopic ratios from sierra negra are approximately 15 times the atmospheric ratio although these ratios clearly indicate plume helium they are not the highest 3he 4he in the archipelago suggesting that helium is decoupled from the heavier isotopes high sm yb ratios light rare earth element lree enrichment and a steep ree slope are consistent with an origin by moderate extents 5 15 of partial melting of a garnet lherzolite source with ree characteristics that are between chondrite and depleted earth mantle sources sierra negra lavas are compositionally monotonous because homogeneous plume rich material has experienced long term exposure to a well regulated sublithospheric thermal environment with additional compositional restrictions imposed in the lithosphere by high magma flux

unexpected covariant behavior of the aegean and ionian seas in the period 1987 2008 by means of a nondimensional sea surface height index

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

the 2008 eruptive unrest at cerro azul volcano galapagos revealed by insar data and a novel method for geodetic modelling

evolution of galapagos magmas mantle and crustal fractionation without assimilation summary of helium isotopic data from the gala pagos islands and dredged samples from the gala pagos platform data from graham et al 1993 and kurz et al 1993 data are normalized to the atmospheric value r ra most gala pagos samples are intermediate betweenmorb value of 8 1 and the fernandina value 22 material in those magmas the exception is floreana structure first the depth to the magma chambers mayisland which ranges from 14 5 to 7 7 ra it is possible be due to the rate at which magma is supplied from thethat the low value at floreana re ects assimilation of mantle as the volcano is carried away from the focus ofmaterial with excess radiogenic 4 he by a magma with the hotspot the volcanoes in a juvenile growing stage 3 he 4 he ra 14 most floreana lavas contain abundant of evolution those that have had numerous historicdisaggregated debris from ultrama c xenoliths bow eruptions are dominated by lavas with mgo con geist 1992 a potential source of helium contamination centrations between 5 and 6 e g reynolds geist 1995 a narrow deep caldera characterizes the juvenilestage e g cerro azul wolf and fernandina and iteventually broadens and shallows because of lling with

slopes of western galapagos volcanoes from airborne interferometric radar the distribution of slopes on the six basaltic shield volcanoes in the western galapagos islands is investigated using a digital elevation model derived from airborne interferometric radar topsar data these measurements have a spatial sampling of 10 m pixel a vertical accuracy of 3 to 5 m and constitute the highest resolution most complete topographic data set available for the islands volcano heights are determined to range from 1 124 m sierra negra to 1 710 m wolf over extensive areas of each volcano slopes exceed 25 with the highest slopes being 37 on wolf and 36 on fernandina we confirm that two morphologic subgroups exist cerro azul fernandina and wolf with deep calderas depth between 40 60 of the subaerial height of the volcano and steep 20 maximum slopes at elevations between 60 and 80 of the volcano height and alcedo darwin and sierra negra with shallow calderas depth 25 of subaerial height and slopes that remain 15 until 90 of the total height is reached our data show that steep slopes are not uniquely correlated with the occurrence of arcuate fissures at the summit leaving the origin of the steep slopes unresolved

goes satellite and field observations of the 1998 eruption of volcan cerro azul galapagos islands the 1998 eruption of volcan cerro azul isla isabela galapagos islands was observed in near real time by the geostationary operational environmental satellite 8 goes 8 weather satellite due to the remote location of the eruption site 3 9 m radiance values derived from goes band 2 provide the best timing of the start and termination of the eruption which occurred on 15 sept and 21 oct respectively throughout the 36 day long eruption a total of 1335 thermal infrared images were collected of which 851 were cloud free and permitted the thermal anomaly to be detected a detailed chronology including 77 separate events was assembled from the goes data and field observations numerous attributes of the eruption were observed from the goes data including the sizes and dispersal of seven eruption plumes and the occurrence and timing of intra caldera effusive activity the growth of a lava flow on the se flank the formation of smoke and volcanic haze from the flank vent and burning of vegetation caused by lava flows entering vegetated areas were monitored both on the ground and with the satellite data in most cases goes images were processed as they were received every 30 min and were then distributed over the internet within minutes of reception these data provided timely high temporal information to field parties as well as enabled the documentation of the eruption the goes observations of cerro azul serve as a further example of the way in which the remote sensing community and field volcanologists can collaborate during future eruptions and permit the temporal and spatial resolution requirements for future satellites systems to be better defined

deflation of the askja volcanic system constraints on the deformation source from combined inversion of satellite radar interferograms and gps measurements the askja central volcano in northern iceland has been continuously subsiding at least since 1983 gps and optical leveling tilt measurements show subsidence of at least 75 cm from 1983 to 1998 in the center of the askja caldera without any eruptive activity we have performed an interferometric analysis of synthetic aperture radar images insar of the area utilizing data from the ers satellites we observe subsidence of the askja caldera and its fissure swarm up to a distance of 25 km from the volcano we evaluate the geometry of the magma chamber at askja from a combined inversion of satellite radar interferograms and gps measurements several models were tested including a mogi point source as well as an ellipsoidal source the use of an ellipsoidal source instead of a mogi source gives an estimate of the dimensions of the magma chamber and its deflating pressure whereas these parameters are not independently resolved if a mogi source is used two source models were also considered in order to explain the additional subsidence observed along the askja fissure swarm we tested a model using two mogi sources at different depths a shallow ellipsoidal cavity with a deeper mogi source and then a shallow mogi source with a deeper elongated ellipsoid oriented along the fissure swarm results indicate that an ellipsoidal source at about 3 km depth can accommodate most of the deflation occurring in the caldera residual subsidence occurs along the askja fissure swarm suggesting the existence of a deeper source of contraction we interpret this signal in terms of subsidence of the plate boundary

physical volcanology and structural development of cerro azul volcano isabela island galapagos implications for the development of galapagos type shield volcanoes erupted from circumferential vents near the summit these flows are nearly an order of magnitude smaller in volume than the predominantly aa flows erupted from radial eruptive fissures near the break in slope 0 06 0 1 km3 the differences in volume and flow morphology with altitude are due to slower eruption rates from summit vents than from flank vents which in turn are attributable to the different heights the magmas must ascend from shallow reservoirs these observations support the contention that the steep upper flanks were constructed by the buildup of short lava flows rather than by the structural deformation of originally gently dipping flanks in addition to the higher eruption rates a subdued lower flank geometry is promoted by the deposition of lava deltas onto the shallow galapagos platform on the western northern and eastern flanks of the volcano 40ar 39ar geochronology and volume estimates show that despite their morphologic differences the growth of the western galapagos shields has been nearly synchronous precluding an evolutionary model for their development the wide variations in elevation volume area and the distribution of slope angles among the western volcanoes can be linked instead to different long term eruption rates and to a lesser degree the position of each volcano relative to the edge of the galapagos platform

water mass characteristics in the deep layers of the western ionian basin observed during may 2003 1 ctd measurements carried out in the southern adriatic sea and in the western ionian basin eurafrican mediterranean sea during may 2003 by the german research vessel poseidon poseidon cruise 298 and numerical simulations are used to elucidate aspects of the abyssal circulation of this oceanic region the observations reveal that dense waters of adriatic origin were strongly diluted along their way on the italian continental slope whilst their characteristics remained better preserved in a region located further east numerical simulations carried out by means of a nonlinear reduced gravity plume model confirm the observations and contribute to explain their cause the very steep topographic slope along the italian shelf in the region of the gulf of taranto induces strong entrainment of intermediate waters in the bottom layers instead the bottom waters of adriatic origin which along their path further east encounter gentler topographic variations are weakly diluted by turbulent mixing and therefore better preserve their original characteristics the remarkable differences in the simulated turbulent mixing along these two different paths are accentuated by the presence of a noticeable zonal gradient of potential density existing in the near bottom layers of the northern ionian basin

physical volcanology and structural development of sierra negra volcano isabela island galapagos archipelago sierra negra is the most voluminous of the western galapagos shields and exhibits many unusual morphologic features extensive lower flank apron steep upper flanks a broad summit plateau a large complex caldera ubiquitous occurrence of aa and radial and circumferential fissures a field based investigation of the volcano was conducted in order to establish the distribution and characteristics of eruptive zones and associated flow fields and to construct a volcano wide surface flow stratigraphy geochronologic data were used to determine the age of the units and combined with flow volume calculations to estimate both the historic and total volcano eruption rates ninety one kilometers of radial and circumferential fissures were mapped and grouped into four eruptive zones which form a volcano wide east northeast trending rift system that deflects around the caldera the eruptive zones are restricted spatially and temporally and document long term changes in the volcano s development long fluid lava flows are broadly distributed among five ages resulting in a subdued flank profile by the development of an extensive lower flank apron around the volcano ten historical eruptions have occurred with eruption rates of 44 to 248 m3 s and an average growth rate of 12 106 m3 yr age determinations of lava flows by 14c and cosmogenic 3he range from 400 to 6900 yr the total volcano growth rate is estimated to be 1 106 m3 yr these results confirm the young age of sierra negra lavas and the validity of the relative ages determined from stratigraphic study in total the volcano has undergone over 90 resurfacing in the past 4500 yr the summit of sierra negra is entirely occupied by a shallow elliptical 7 10 km caldera near vertical ring faults circumscribe the summit and expose 100 to 140 m of lava flows subparallel sets of caldera growth faults cut the western and southern caldera walls and are not associated with eruptive activity the inclination of remnant magnetism and the attitudes of the flows exposed in the caldera walls indicate that the lavas have not been appreciably deformed nor have they been intruded by dikes or sills the caldera interior is structurally complex and contains a 14 km long c shaped sinuous ridge composed of a complex set of normally faulted blocks with inward dipping 20 60 flow tops the sinuous ridge is interpreted to have formed gradually as the caldera floor pivoted in a trap door fashion jammed its western edge and then fractured in several places concomitant with the long term vertical and lateral growth of the volcano a regional tectonic stress field superimposed upon the galapagos platform appears to have exerted primary control on the location of sierra negra including the early development of the east northeast rift system intervolcano stresses have controlled the distribution of eruptive zones only where significant subaerial overlap of adjacent volcanoes occurs large volume high discharge rate eruptions from fissures along the east northeast rift system are responsible for the development of an extensive coastal apron flow stacking at mid flank elevations and generally subdued slopes in comparison to other western galapagos volcanoes the summit caldera and underlying magma chamber are subordinate in influencing the distribution of lower flank stress but dominate the development of the summit stress field and orientation of eruptive fissures the absence of summit deformation together with the ubiquitous occurrence of short stubby summit flows indicates that the steep upper flanks are constructional in origin

saw tooth modulation of the deep water thermohaline properties in the southern adriatic sea in this study we investigate the dynamics of the bottom layer of the southern adriatic sea eastern mediterranean basin by merging experimental measurements and numerical simulations we hypothesize that the recently observed continuous density decrease over time which was basically related to a temperature increase and the following sudden density rise which was caused by the intrusion of very dense water masses cold but relatively fresh constitute one cycle of a general saw tooth pattern the alternation of long lasting and almost linear density decreases mixing phases and sudden density increases dense water intrusion phases the model results which provide a basin scale view of the process corroborate this theory because they satisfactorily reproduced the observed oceanographic features we describe the almost linear density decrease in terms of local mixing fostered by the advection of flow instabilities that originate from the large scale quasi permanent cyclonic circulation conversely diffusive processes play a minor role in determining the bottom layer thermohaline variability the interpretation of the experimental findings supported by the numerical simulations suggests that similar dynamics might be observed in other basins characterized by similar bathymetric and hydrodynamic features

off shelf fluxes across the southern adriatic margin factors controlling dense water driven transport phenomena abstract the northern adriatic sea is a basin where dense shelf waters form during winters if the following favorable conditions are attained high salinities mainly related to low river water discharge po river in primis during fall season and strong heat fluxes induced by cold and dry bora wind events blowing from north east extremely favorable conditions to northern adriatic dense waters naddw formation characterized winter 2012 when following several months of low po river runoff a strong event of cold air outbreak cao occurred from the end of january until mid february consequently the mean temperature of northern adriatic waters dropped to about 6 c and exceptional densities potential density anomaly locally exceeding 30 0 kg m 3 were reached the production and spreading mechanisms of dense water in the adriatic sea have been modeled by means of the coawst coupled ocean atmosphere wave sediment transport modeling system the model builds upon a high resolution 1 km spaced horizontal grid fully 3 d primitive equations hydrodynamic model coupled with a phase averaged wave model and sediment routines and is driven by simulated atmospheric forcings the dataset used to assess model outputs relies on the measurements acquired during the dedicated field campaigns operation dense water a set of two rapid response cruises carried out in southern adriatic during winter 2012 and by five mooring arrays deployed in the southern adriatic margin sam that allowed the continuous acquisition of temperature salinity currents and suspended matter samples results from the integrated data model approach suggest that the naddw propagates along the shelf to the southern basin following both a shallower vein and a deeper stream with a process characterized by a strong variability mean value of 0 31 sv with peaks rapidly growing in the first weeks after the cao up to 2 19 sv additionally coawst capability to couple different numerical models allowed to disentangle the relative importance of aspects on dense water generation mixing and spreading demonstrating how coupled runs can lead to volumes up to 50 larger with respect to uncoupled simulations additional light is shed on the transport pathways off the shelf and on possible sediment transport phenomena in the area in this benefiting from an unprecedented spatial resolution and a new bathymetry reflecting very high resolution data acquired via multi beam techniques although dense water propagation appears as a relatively large scale process involving the whole western side of the sam topographic local discontinuities and seabed slopes appear crucial in triggering descent and governing flow patterns the presence of suspended sediment along the water column despite not significantly influencing the overall fluxes across sections is responsible of pulling part of the veins towards deeper zones

multiple inflation and deflation events at kenyan volcanoes east african rift the presence or absence of magma exerts a fundamental control on the distribution of strain in continental rift zones yet the time scales of magma intrusion remain unconstrained using more than a decade of measurements from interferometric synthetic aperture radar insar we detected geodetic activity at four of the eleven central rift volcanoes in the kenyan sector of the east african rift subsidence of 2 5 cm occurred at suswa and menengai over the period 1997 2000 9 cm of uplift was recorded at longonot in 2004 2006 and 21 cm of uplift occurred at paka during 2006 2007 the deformation is episodic and no deformation was observed at these volcanoes during other time periods preceding the infl ation at paka we observed transient uplift and subsidence of a second nearby source likely associated with fl ow through a complex plumbing system the best fi tting source models for each episode include infl ation or defl ation of a horizontal penny shaped crack at a depth of 2 5 km the episodic nature of the activity its lack of correlation with seasons and the preferred source geometry are all consistent with activity in the volatile rich cap to a crystal rich magma chamber beneath each of the four volcanoes the presence of active magmatic systems beneath more than 40 of the volcanoes and the 2007 2008 explosive eruptions at nearby oldoinyo lengai volcano have implications for models of continental rifting caldera volcanoes geothermal resources and volcanic and seismic hazard in rift zones

boundary currents and watermass transformation in marginal seas the properties of watermass transformation and the thermohaline circulation in marginal seas with topography and subject to a spatially uniform net surface cooling are discussed the net heat loss within the marginal sea is ultimately balanced by lateral advection from the open ocean in a narrow boundary current that flows cyclonically around the basin heat loss in the interior is offset by lateral eddy fluxes originating in the boundary current the objectives of this study are to understand better what controls the density of waters formed within the marginal sea the temperature of the outflowing waters the amount of downwelling and the mechanisms of heat transport within the marginal sea the approach combines heat budgets with linear stability theory for a baroclinic flow over a sloping bottom to provide simple theoretical estimates of each of these quantities in terms of the basic parameters of the system the theory compares well to a series of eddy resolving primitive equation model calculations the downwelling is concentrated within the boundary current in both a diffusive boundary layer near topography and an eddy driven region on the offshore edge of the boundary current for most high latitude regions the horizontal gyre is expected to transport more heat than does the overturning gyre

a shallow dipping dike fed the 1995 flank eruption at fernandina volcano galapagos observed by satellite radar interferometry satellite radar interferometry data reveal strong localized uplift in a semi circular pattern on the southwest flank of fernandina volcano galapagos where an eruption took place in january to april 1995 the observations show a maximum decrease in radar range of 0 75 m and they are consistent with a model of a shallow dipping dike intrusion feeding this fissure eruption we solve for the best fit single rectangular dislocation dike source using non linear inver sion techniques where simulated annealing searching algo rithm is used to avoid local minima the best fit dike is 3 8 km long 2 3 km high 0 86 m thick and with a 34 dip the total dike volume 7 5 x 10 3 km 3 is 40 of the vol ume of extrusive materials estimated to have been produced during the eruption the data do not permit a sub vertical dike implying that the least principal stress direction is not horizontal as is usually assumed

extreme cooling and dense water formation estimates in open and coastal regions of the adriatic sea during the winter of 2012 generation of dense waters in the adriatic sea during an extreme cooling event in the winter of 2012 including its preconditioning and spreading phases have been investigated using the one way coupled roms and the aladin hr modeling system both climatological and real river fluxes are used in the simulations aside from the convenient dense water formation areas located at the northernmost adriatic shelf we found that a similar amount of dense water with slightly lower density was formed in the eastern and deeper adriatic coastal area which was subjected to extreme heat losses up to 2000 w m2 during peak cooling periods this part of the adriatic has been known for extreme cooling during wintertime bora outbreaks nevertheless no ocean model study has previously reproduced dense water formation in this area the most likely reason for that was an overestimate of river discharges introduced to ocean models from newly available data we estimated that the contribution of eastern adriatic rivers between the neretva river and rijeka bay is more than six times lower than what has been previously documented transport of dense water toward the middle adriatic had a peak value of about 0 6 sv while the speed of initial bottom density current surpassed 40 50 cm s which is several times faster than past events different pathways of the dense water toward the middle and south adriatic depressions have also been documented the contribution of the eastern coastal adriatic area to the overall north adriatic dense water formation has been quantified and discussed for average and low freshwater load conditions indicating that this part of the adriatic is a common place for dense water generation

imaging rapidly deforming ocean island volcanoes in the western galapagos archipelago ecuador using local body wave arrival time tomography methods to determine 3 d seismic velocity structure we imaged the plumbing system of sierra negra volcano galapagos this hot spot volcanic chain includes some of the fastest deforming volcanoes in the world making this an ideal location to study shield volcano plumbing systems we inverted p and s wave arrivals recorded on a 15 station temporary array between july 2009 and june 2011 using an a priori 1 d velocity model constrained by offshore refraction studies with local seismicity from nearby volcanoes as well as the ring fault system the model resolution is good between depths of 3 and 15 5 km the propagation of s waves throughout this volume argues against any large high melt accumulations although a shallow melt sill may exist above 5 km we image a broad low velocity region 25 km laterally below sierra negra at depths 8 15 km no large regional velocity increase is found within the limits of good resolution suggesting that crust is thicker than 15 km beneath the western galapagos archipelago our results are consistent with crustal accretion of mafic cumulates from a large volume magma chamber that may span the boundary between preplume and accreted crust the similarity between our results and those of hawaii leave open the possibility that the crust has also been thickened by under plating

deep water dynamics and boundary mixing in a nontidal stratified basin a modeling study of the baltic sea recent results from a tracer release experiment have shown that similar to many lakes and ocean basins deep water mixing in the baltic sea is largely determined by mixing processes occurring in the energetic near bottom region due to the complexity and small vertical extent of this region however previous modeling studies of the baltic sea have so far not been able to provide a numerically and physically sound representation of boundary mixing here we discuss first results from a nested high resolution simulation of the central baltic sea that aims at a realistic description of the turbulent bottom boundary layer with the help of new numerical techniques adaptive coordinates and state of the art turbulence modeling using a comprehensive data set from the baltic sea tracer release experiment we show that the model is able to reproduce the key dynamical processes near inertial waves topographic waves and a rim current with excellent accuracy boundary mixing triggered by these processes was found to result in simulated basin scale mixing rates in close agreement with observations including a seasonal variability that has been emphasized in previous studies these results may be relevant also for the description of mixing in large lakes and other stratified basins

on the derivation of coseismic displacement fields using differential radar interferometry the landers earthquake we present a map of the coseismic displacement field resulting from the landers california june 28 1992 earthquake derived using data acquired from an orbiting high resolution radar system we achieve results more accurate than previous space studies and similar in accuracy to those obtained by conventional field survey techniques data from the ers 1 synthetic aperture radar instrument acquired in april july and august 1992 are used to generate a high resolution wide area map of the displacements the data represent the motion in the direction of the radar line of sight to centimeter level precision of each 30 m resolution element in a 113 km by 90 km image our coseismic displacement contour map gives a lobed pattern consistent with theoretical models of the displacement field from the earthquake fine structure observed as displacement tiling in regions several kilometers from the fault appears to be the result of local surface fracturing comparison of these data with global positioning system and electronic distance measurement survey data yield a correlation of 0 96 thus the radar measurements are a means to extend the point measurements acquired by traditional techniques to an area map format the technique we use is 1 more automatic 2 more precise and 3 better validated than previous similar applications of differential radar interferometry since we require only remotely sensed satellite data with no additional requirements for ancillary information the technique is well suited for global seismic monitoring and analysis

space geodetic evidence for multiple magma reservoirs and subvolcanic lateral intrusions at fernandina volcano galapagos islands 1 using interferometric synthetic aperture radar insar measurements of the surface deformation at fernandina volcano galapagos ecuador acquired between january 2003 and september 2010 we study the structure and the dynamics of the shallow magmatic system of the volcano through the analysis of spatial and temporal variations of the measured line of sight displacement we identify multiple sources of deformation beneath the summit and the southern flank at least two sources are considered to represent permanent zones of magma storage given their persistent or recurrent activity elastic deformation models indicate the presence of a flat topped magma reservoir at 1 1 km below sea level and an oblate spheroid cavity at 4 9 km b s l the two reservoirs are hydraulically connected this inferred structure of the shallow storage system is in agreement with previous geodetic studies and previous petrological analysis of both subaerial and submarine lavas the almost eight year long observation interval provides for the first time geodetic evidence for two subvolcanic lateral intrusions from the central storage system in december 2006 and august 2007 subvolcanic lateral intrusions could provide the explanation for enigmatic volcanic events at fernandina such as the rapid uplift at punta espinoza in 1927 and the 1968 caldera collapse without significant eruption

can internal processes sustain reversals of the ocean upper circulation the ionian sea example 1 in 1997 an inversion in the ionian upper layer circulation was documented and ascribed to a massive inflow of aegean dense waters associated with the eastern mediterranean transient emt and not to the wind stress borzelli et al 2009 here we generalize the concept hypothesizing that such inversions are possible even in the absence of the aegean influence indeed salinity and density data collected in the southern adriatic the main source of the eastern mediterranean deep water show decadal variations coherent with changes in the sea level height in the northern ionian scaling considerations suggest that the redistribution of ionian water masses resulting from changes in the thermohaline properties of waters entering the basin can sustain inversions of the upper layer circulation therefore we propose a feedback mechanism named the adriatic ionian bimodal oscillating system bios between variations in the thermohaline properties of waters formed in the southern adriatic and the ionian circulation

the role of magma chamber fault interaction in caldera forming eruptions this paper examines the role of the position and orientation of a regional fault in the roof of a magma chamber on stress distribution mechanical failure and dyking using 2d finite element numerical simulations the study pertains to the magma chamber behavior in the relatively short time intervals of several hundreds to thousand of years the magma chamber is represented as an elliptical inclusion eccentricity a b 0 12 at a relative depth h a of 0 9 the fault has a 45 dip and is represented by a frictionless fracture the temperature field in the host rock is calculated assuming a quasisteady state thermal regime that develops through periodic episodes of magma supply the rheology of the surrounding rocks is treated using viscoelasticity with temperature activated strain rate dependent viscosity strain weakening of the rocks in the ductile zone is described within the frame of the dynamic power law model the magma pressure is coupled with the deformation of the rock mass hosting the chamber including the fault the variation of magma pressure in response to magma supply and chamber deformation is calculated in the elastic and viscoelastic regimes the latter corresponds to slow filling while the former represents a filling time much less than the viscous relaxation time scale the resulting equation of state for the magma chamber couples the magma pressure with the chamber volume in the elastic regime and with the filling rate for the viscoelastic regime analysis of stresses is used to predict dyke propagation conditions and the mechanical failure of the chamber roof for different fault positions and magma overpressures results show that an outward dipping fault located on the periphery of the chamber roof hinders the propagation of dykes to the surface causing magma to accumulate under the footwall of the fault at high to moderate overpressures 30 40 mpa the fault causes localized shear failure and chamber roof collapse that might lead to the first stage of a caldera forming eruption

carbonate recrystallisation and organic matter maturation in heat affected sediments from the shaban deep red sea parasound profiles across the shaban deep in the red sea indicate turbiditic transport of surface sediments from the topographic hight basalt ridge into the interior of the deep this is supported by petrographical and isotope geochemical evidence in the east basin of the shaban deep where the presence of variable mixtures of authochtonous and allochthonous sediment compounds had been found the uppermost 170 cm of both sediment cores 17008 1 and 17009 3 reveal normal stable oxygen isotope values for the planktonic foraminifera g ruber near 1 which is indicative for carbonate formation in red sea surface water around 27 c however below 182 cm in core 17008 1 highly variable 18o values for g ruber between 0 26 and 10 68 occur which are not the result of temperature controlled oxygen isotope fractionation between foraminiferal carbonate and red sea surface water the lowest 18o values of 10 68 measured for highly altered foraminifera shells suggests carbonate precipitation higher than 90 c organic petrographical observations show a great diversity of marine derived macerals and terrigenous organic particles based on petrographical investigations sediment core 17008 1 can be subdivided in intervals predominantly of authochtonous character i e 1 3 5 corresponding to core depths 0 170 cm 370 415 cm 69 136 cm and allochthonous thermally altered character e g 2 4 corresponding to core depths 189 353 cm 515 671 cm allochthonous thermally altered material displays a wide to an extremely wide range of maturities 0 38 1 42 rr and also natural coke particles were found similarily the organic geochemical and pyrolysis data indicate the predominance of well preserved immature algal and bacterial remains with a minor contribution of land plant material sediments below 170 cm core 17008 1 contain contributions of re sedimented pre heated material most likely from the area of the basaltic ridge this is documented by individual coke particles reduced hydrogen indices and elevated tmax values up to 440 c an oil type contribution evidenced by mature biomarkers hopene hopane ratios elevated background fluorescence n alkane distribution is also present in the sediments which most likely originated at greater depth and impregnated the surface sediments the heat source responsible for recrystallisation of foraminiferal carbonate and maturation of organic particles in shaban deep sediments most likely is attributed to modern basalt extrusions which now separate the shaban deep subbasins

volcan ecuador galapagos islands erosion as a possible mechanism for the generation of steep sided basaltic volcanoes volcan ecuador 0 02 s 91 35 w consists of two strongly contrasting components the eroded and vegetated remnant of a once circular main volcano with a probable caldera and a prominent rift zone extending to the northeast that is neither strongly eroded nor weathered there are about 20 young looking flows and vents on this caldera floor but only one on the higher remnant of the main volcano the southwest half of the main volcano is faulted into the ocean the main part of volcan ecuador possesses steep erosional slopes average 30 40 that cut into a sequence of flows that dip radially outward at 10 in contrast the northeast rift zone consists entirely of young flows and vents the upper 10 km of the rift zone forms a peninsula about 7 5 km wide that connects volcan ecuador to volcan wolf the rift zone bends to the southeast and the lower 8 km is tangential to the coast of volcan wolf the rift zone axis dips away from the northeast edge of the main volcano and its flanks slope roughly northwest and southeast at 4 the rift zone is the galapagos structure that most closely resembles a hawaiian rift zone because it is constructed of lavas from subparallel linear vents shows evidence of a deep feeder conduit and has changed its direction to avoid a direct intersection with neighboring volcan wolf the steep erosional slopes extending around the perimeter of the main volcano except to the southwest where slumping occurred were probably generated by marine erosion during a prolonged period of eruptive inactivity perhaps 20 000 30 000 years only a few post erosional eruptions have taken place at the main volcano in and near what was once the caldera the entire rift zone postdates the period of prolonged erosion using the evidence for prolonged inactivity at volcan ecuador we propose that erosion may have helped to produce steep slopes on the other western galapagos volcanoes on these more active volcanoes however numerous subsequent eruptions have completely mantled the erosional slopes with lava the mechanism by which the volcanoes may shut off for long periods of time is unknown but the fact that the galapagos hotspot is presently supplying nine active volcanoes suggests that the magma supply at an individual volcano could vary greatly over periods of tens of thousands of years

widespread uplift and trapdoor faulting on galapagos volcanoes observed with radar interferometry volcanic uplift caused by the accumulation of magma in subsurface reservoirs is a common precursor to eruptions1 2 but for some volcanoes uplift of metres or more has not yet led to an eruption3 here we present displacement maps of volcanoes in the galapagos islands constructed using satellite radar interferometry that might help explain this dichotomy we show that all but one of the seven volcanoes on the islands of isabela and fernandina deformed during 1992 99 cerro azul and fernandina erupted4 5 6 during the observation period and show evidence of inflation co eruptive deflation and shallow dyke intrusion in contrast the largest volcano sierra negra has not erupted yet exhibits spatially and temporally variable deformation with a maximum uplift of 2 7 m between 1992 and 1999 which can be modelled by a shallow inflating sill inflation during 1997 98 however was accompanied by trapdoor faulting on a steeply dipping fracture system within the caldera repeated trapdoor faulting over geological time has formed an arcuate intra caldera ridge within sierra negra and may have acted to relax stresses above the magma chamber inhibiting summit eruptions similar processes may help explain large uplift unaccompanied by eruptive activity at other volcanoes

increased capture of magma in the crust promoted by ice cap retreat in iceland retreating ice caps overlying volcanoes are thought to relieve surface pressure causing enhanced magma generation and volcanic activity analysis of crustal stress during a dyke intrusion event associated with retreat of iceland s largest ice cap indicates that ice retreat could instead promote storage of magma in the crust rather than eruption at the surface

modelling gravity variations consistent with ground deformation in the campi flegrei caldera italy abstract in recent years 1970 72 and 1982 84 two inflation episodes took place in the campi flegrei caldera italy characterized by significant ground uplift and gravity variations an elastic half space model with vertical density stratification is employed to compute the displacement field and the gravity variations produced by the deformation of buried layers following the inflation of a spherically symmetric deformation source contributions to gravity variations are produced by dilation contraction of the medium by the displacements of density interfaces the free surface and subsurface layers and of source boundaries and possibly by new mass input from remote distances into the source volume three cases were examined in detail in case i the magma chamber is identified as the deformation source and volume and pressure increase in the magma chamber is due to input of new magma from remote distances in case ii deformation is due to magma differentiation within the magma chamber deformation source with constant mass in case iii the geothermal system is identified as the deformation source and a pressure increase possibly driven by the exsolution of high temperature and high pressure volatiles in the magma chamber is assumed to play a dominant role from the comparison between measured and computed gravity residuals free air corrected gravity variations we can assess that in case i an inflation source with constant density would predict gravity residuals compatible with observations whereas an expansion at constant mass case ii would predict gravity residuals much lower than observed the resolving power of gravity data however prevents accurate assessment of the density of the emplaced material in case iii the pervasive density increase of the geothermal fluids induced by pressure increase is assumed to be the main source of gravity variations the average porosity value required for this model to match both the ground deformation and the gravity residuals is found to be 10 a value which is compatible with measured porosity values at campi flegrei in deep wells the subsidence phases following both inflation episodes and the gravity residuals during subsidence lead us to consider case iii as more plausible even if a suitable combination of cases i and iii cannot be discarded

constraints on magma chamber geometry at sierra negra volcano galapagos islands based on insar observations abstract we investigate the problem of estimating magma chamber geometry using insar observations of sierra negra volcano galapagos ascending and descending interferograms are combined to determine vertical and one horizontal component of displacement the ratio of maximum horizontal to vertical displacement suggests a sill like source spherical or stock like bodies are inconsistent with the data we estimate the geometry of the sill assuming a horizontal uniformly pressurized crack with unknown periphery and depth the sill is discretized into small elements that are either open and are subjected to the pressure boundary condition or remain closed we find the best fitting sill to be located beneath sierra negra s inner caldera at a depth of about 2 km using boundary element calculations we show that any magma chamber with a flat top coincident with the sill model fits the data equally well the data are insensitive to the sides and bottom of the magma chamber

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

application of independent component analysis to multi temporal insar data with volcanic case studies a challenge in the analysis of multi temporal interferometric synthetic aperture radar insar data is distinguishing and separating volcanic tectonic and anthropogenic displacements from each other and from atmospheric or orbital noise independent component analysis ica is a method for decomposing a mixed signal based on the assumption that the component sources are non gaussian and statistically independent ica has potential as a tool for exploratory analysis of insar data and in particular for testing whether geophysical signals are related or independent this article presents tests of the applicability of ica to insar using synthetic data and application to sentinel 1a archive images from two contrasting examples of volcano deformation co eruptive subsidence associated with the april 2015 eruption of calbuco chile was identified in spatial patterns found by maximising both spatial and temporal independence spatial patterns and rates of lava subsidence were retrieved using ica analysis of interferograms from paricutin lava fields mexico and found to be consistent with previous observations i demonstrate that ica is an appropriate method for the analysis of volcanic signals in the presence of atmospheric noise and propose a strategy for the automatic identification of geophysical displacements using cluster analysis of the spatial patterns of independent components this approach allows the detection of geophysical processes on a range of scales and provides a test of signal independence where multiple displacement sources are active

organic rich sediments in brine filled shaban and kebrit deeps northern red sea the element compositions si ca and al of up to 2 1 1 ka old sediments in about 10 in long cores from the southern basin of the shaban and kebrit deeps in the northern red sea allowed a classification of major sediment types in carbonate sands and muds and siliceous oozes a feooh enriched sediment horizon and a few samples with high zn values in the kebrit core indicate a hydrothermal origin probably near the brine sea water interface with subsequent transport of hydrothermal compounds into the deep sediments high organic carbon contents up to 8 4 are positively correlated with the ba concentrations which suggests that high bioproductivity and rapid deposition c 14 dating suggests a sedimentation rate near 70 cm ka led to the formation of sapropelic sediments between 11 8 and 13 6 ka younger dryas organic petrological observations showed that the sediment organic material largely consists of 20 gm sized roundish fecal pellets intimate mixtures of organic matter and inorganic constituents and bituminite terrestrial organic matter pollens of land plants fusinite etc is very rare in the sediment cores from both deeps organic geochemical investigations of kerogens and organic extracts show that a significant hydrothermal hydrocarbon production did not occur in near surface sediments of the shaban and kebrit deeps rock eval pyrolysis of kerogens characterised the organic matter to be of type ii quality the delta c 13 values of the kerogens from the most prominent sapropel in the shaban deep indicate an enrichment of c 12 rich nutrients in the water column during postglacial sapropel formation in the younger dryas the n alkane spectra are dominated by short chain lengths between n c 15 and n c 25 prevailing n c 15 to n c 25 alkanes in low mature sediments are indicative of algal and microbial source pristane phytane ratios are generally low i to similar to 1 which suggests that anoxic conditions prevailed within the anaerobic brine filled deeps for the whole time covered by the sediments this again indicates that sapropel formation was caused by high bioproductivity in the northern red sea rather than episodic stagnation with better preservation of the organic matter long chain alkenones and sterols are the dominating compounds of the lipid fraction cholesterol contents in the sediment cores reflect phases of eukaryotes production in the water column whereas the positive correlations of dinosterol with toc and the amounts of total extract suggests that the major organic carbon source in the northern red sea during postglacial high productivity stages were dinoflagellates another important carbon source however is indicated by the occurrence of 22 29 30 trisnorhopan 21 one tnh although the formation of tnh from its precursors is not fully understood this compound probably results from microbial degradation of intact bacteriohopanepolyols bhp which can be used as indicators for bacterial abundances and phyla tnh is most likely produced at the brine sea water interface where sedimenting organic matter accumulates and if the redoxcline corresponds to the density gradient the organic matter is subjected to efficient aerobic bacterial degradation processes however during high bioproductivity stage younger dryas the redoxcline was probably higher in the water column and thus a significant tnh production at the brine sea water interface did not occur at times of sapropel formation in the northern red sea deeps c 2007 elsevier b v all rights reserved

on trapdoor faulting at sierra negra volcano galapagos abstract rapid uplift observed during 1992 1997 at sierra negra volcano western galapagos was followed by deformation that we have previously interpreted as trapdoor faulting on an intra caldera fracture system at that time no direct evidence for the trapdoor faulting was available to support this interpretation here we report field evidence of recent faulting at sierra negra and provide direct measurements of the faulting using pixel offsets between satellite radar amplitude backscatter images our field observations carried out in 2001 indicate that recent faulting occurred along the southern part of the intra caldera fault system with maximum offset of at least 0 5 1 m differences between two satellite radar amplitude images show 1 4 0 2 m range change across this fault system this suggests that 1 5 0 2 m of faulting occurred assuming vertical ground displacements consistent with our previous modeling results results of numerical modeling indicate that growing sills can cause faulting of the intrusion roof on outward dipping or nearly vertical faults this occurs at high excess magma pressure when the lateral extent half length of the sill becomes greater than its depth the derived 2 km deep sierra negra sill exhibits trapdoor faulting 3 km south of the center of the sill therefore these modeling results provide a plausible mechanical explanation for the trapdoor fault at sierra negra

fernandina volcano s evolved well mixed basalts mineralogical and petrological constraints on the nature of the galapagos plume fernandina volcano the most active of galapagos volcanoes and the one most directly overlying the galapagos hotspot is one of a small number of active plume related oceanic island volcanoes with a well documented recent eruptive record whole rock and glass analyses of lava and tephra from all 12 known eruptions from 1958 to the present show them to be evolved mg mg mg fe2 of 0 47 0 56 plagioclase phyric clinopyroxene and olivine bearing tholeiites thermodynamic modeling indicates that this phase assemblage erupted at 1100 1130 c and is stable only at low pressures 0 1 0 2 gpa thereby representing crystallization within a shallow magma chamber underlying the well defined 850 m deep 5 by 6 5 km caldera these tholeiites are remarkably homogenous as is shown by narrow ranges in zr y 5 7 6 3 la sm n 1 4 1 7 and la yb n 3 8 4 3 prehistoric fernandina lavas selected for petrographic and geographic variation over the entire subaerial volcano are of remarkably similar composition e g zr y is 5 2 6 1 la sm n is 1 5 1 6 and la yb n is 3 4 4 1 with a single example of a more primitive lava having an mg of 0 63 with 8 5 feo at 8 mgo cr spinel and glass melt inclusions in plagioclase together with zoned olivine give evidence for a range of parental melts in the recent shallow magmatic system with mg as high as 0 62 extensive shallow magma mixing is required to explain these variations in mineral and inclusion chemistry indicating more thermal variation within the shallow magmatic system than is implied by the relatively monotonous whole rock compositions apparently fernandina s shallow magma chamber has physically blocked passage of more primitive magmas to the surface and homogenized the erupted lavas by extensive mixing small variations in lava isotopic and compatible element composition combined with the need to resupply melt to maintain thermal balance indicate that replenishment of the magma chamber is semicontinuous with resupply occurring of the order of a decade or less plagioclase dominated evolved fernandina lavas are in sharp contrast to more primitive olivine dominated hawaiian lavas the total lack of primitive melts in the shallow fernandina magmatic system implies that substantial fractionation and heat loss occurred during melt transportation from the mantle source to the edifice magma chamber despite the fact that these melts were transported through relatively warm young and thin lithosphere adjacent to the cocos nazca ridge the diffuse nature of galapagos volcanism with 20th century eruptions from eight distinct volcanoes over a 20 000 km2 area further supports this interpretation and suggests that the galapagos plume is relatively diffuse weak and significantly less thermally intense than the vigorous hawaiian plume it may in fact be waning

stress interaction between magma accumulation and trapdoor faulting on sierra negra volcano galapagos abstract understanding the state of stress within volcanoes and how it changes with active geophysical processes is important to assess when and where magma may propagate to the surface and initiate an eruption observations of volcanic deformation help to constrain parameters of models that can be used to describe these processes and to calculate the resulting stress changes within volcanoes here i use geodetic observations to constrain elastic dislocation models of magma accumulation and faulting at sierra negra volcano galapagos in the years before the october 2005 eruption which was the first eruption at sierra negra since 1979 both insar and gps data document a remarkable story of 5 m pre eruption uplift during 1992 2005 which was accompanied by at least three trapdoor faulting events on an intra caldera fault system in january 1998 april 2005 and just before the eruption in october 2005 the pattern of uplift observed in the insar data from different time periods during 1992 2005 is consistent with filling and pressurization of a 2 2 km deep sill under the caldera modeling results for the trapdoor faulting in april 2005 on the other hand indicate that slip occurred on a thrust fault that dips steeply 71 in towards the center of the caldera and extends from the surface down to the sill at 2 2 km depth independently the calculated stress changes caused by the inflating sill show that the coulomb failure stress change cfs at the fault s location is maximized on a 72 dipping thrust fault agreeing almost exactly with the deformation modeling result and implying that the inflation triggered the faulting the calculations also show that the cfs for optimally oriented faults any strike and dip is significantly larger in the southern part of the caldera where the faulting took place than at any other location the trapdoor faulting in turn relieved the pressure within the sill but caused compression to the south of the faults this suggests that while the faulting provides a mechanism for the sill to thicken and postpone eruptions it also prevents the sill from growing to the south

the volcanic history of volcan alcedo galapagos archipelago a case study of rhyolitic oceanic volcanism volcan alcedo is one of the seven western galapagos shields and is the only active galapagos volcano known to have erupted rhyolite as well as basalt the volcano stands 4 km above the sea floor and has a subaerial volume of 200 km3 nearly all of which is basalt as volcan alcedo grew it built an elongate domal shield which was partly truncated during repeated caldera collapse and partial filling episodes an outward dipping sequence of basalt flows at least 250 m thick forms the steepest to 33 flanks of the volcano and is not tilted thus a constructional origin for the steep upper flanks is favored about 1 km3 of rhyolite erupted late in the volcano s history from at least three vents and in 2 5 episodes the most explosive of these produced a tephra blanket that covers the eastern half of the volcano homogeneous rhyolitic pumice is overlain by dacite rhyolite commingled pumice with no stratigraphic break the tephra is notable for its low density and coarse grain size the calculated height of the eruption plume is 23 30 km and the intensity is estimated to have been 1 2x108 kg s rhyolitic lavas vented from the floor of the caldera and from fissures along the rim overlie the tephra of the plinian phase the age of the rhyolitic eruptions is 120 ka on the basis of k ar ages between ten and 20 basaltic lava flows are younger than the rhyolites recent faulting resulted in a moat around part of the caldera floor alcedo most resently erupted sometime between 1946 and 1960 from its southern flank alcedo maintains an active transient hydrothermal system acoustic and seismic activity in 1991 is attributed to the disruption of the hydrothermal system by a regional scale earthquake