the neapolitan yellow tuff caldera offshore the campi flegrei stratal architecture and kinematic reconstruction during the last 15ky abstract in this study we integrate high resolution swath bathymetry single channel reflection seismic data and gravity core data to provide new insights into the shallow structure and latest quaternary to holocene evolution of the submerged sector of the neapolitan yellow tuff nyt caldera campi flegrei in the pozzuoli bay the new data allow for a reconstruction of the offshore geometry of the nyt caldera collapse ring fault system along with the style and timing of deformation of the inner caldera resurgence our interpretation shows that the nyt eruption 15 ka bp was associated with a caldera collapse bounded by an inward dipping ring fault system the ring fault system consists in a 1 2 km wide fault zone that encircles an inner caldera region 5 km in diameter and is often marked by the occurrence of pore fluids ascending through the fault zone up to the seafloor particularly in the western sector of the bay a shallow magmatic intrusion along the ring fault zone was also detected offshore bagnoli in the eastern part of the pozzuoli bay following the nyt eruption the inner caldera region underwent significant deformation and resurgence with a maximum cumulative uplift of the offshore structure in the order of 180 m the net uplift rate of the caldera resurgent dome was 9 12 mm year during the period 15 0 6 6 ka bp the style of deformation of the resurgent structure can be described in terms of a broad doming accompanied by subordinate brittle deformation mostly concentrated in a small apical graben at the summit of the resurgent dome chronostratigraphic calibration of seismic profiles obtained by three tephra layers cored in the pozzuoli bay indicates 5 to 25 m of post roman differential subsidence and tilting towards ese of the inner caldera resurgence as recorded by the drowning of the infralittoral prograding wedge below the present day storm wave base

the mechanics of the campi flegrei resurgent caldera a model abstract a model of caldera resurgence has been applied to the campi flegrei southern italy to interpret a the processes observed during the recent bradyseismic crises of 1970 1972 and 1982 1984 b ground movements recorded for the past 2000 years and c the volcanic history of the area the two dimensional mechanical model involves an area larger than the caldera itself the crust is considered as a viscous plate overlying a viscous half space geometric dimensions and mechanical parameters are the assumed variables and have been assigned a range of values of 50 100 km for length 5 15 km for thickness and 10 21 to 10 22 pa s for viscosity the process controlling volcanic activity in the neapolitan area is attributed to a tensile stress field causing the opening of the tyrrhenian basin and the rising of the mantle to depths of about 15 25 km beneath campi flegrei while regional tumescence can be related to magmatic upwelling detumescence can be linked to the major eruptions in the area the green tuff of epomeo ischia 55 000 yr b p the campanian ignimbrite 30 35 000 yr b p and the neapolitan yellow tuff 12 000 yr b p together involving more than 100 km 3 dre we propose that regional detumescence is likely to have triggered caldera resurgence indeed the model suggests that detumescence may have generated an axial tectonic stress of about 1000 bar 100 mpa a value which is of the correct order of magnitude for initiating caldera resurgence in the campi flegrei furthermore we show that such a stress decreases the vertical pressure needed for uplift to occur

deformation and stress in hydrothermal regions the case of a disk shaped inclusion in a half space abstract hydrothermal regions are affected by a wide variety of phenomena including ground inflation and deflation episodes among them calderas offer the opportunity to study the complex interactions between magmatic processes at depth and permeable rocks saturated with fluids in the upper sedimentary layers one of such regions is the campi flegrei caldera in southern italy where several source models have been applied over the years to reproduce the ground displacement and seismicity observed during the most recent phase of major unrest 1982 1984 the present work aims at introducing a new source model consisting of a thermo poro elastic inclusion embedded in a homogeneous poroelastic half space the inclusion is meant to represent a permeable rock layer stressed and strained by hot and pressurized volatiles released upward by an underlying magmatic reservoir and is modeled as a thin horizontal disk inside which a sudden change of temperature and pore pressure occurs we provide semi analytical solutions for the displacement and stress fields both within and outside the source and check them by comparison with those obtained through a fully numerical approach results provided by our model are compared with two other deformation source models often used to describe volcanic environments in terms of pressurized cavities describing a spherical magma chamber mogi source or a sill like magma intrusion fialko source for the campi flegrei 1982 84 unrest our model provides a better reproduction of ground deformation data and manages to explain the widespread presence of compressive focal mechanisms since the stress field promoted both inside and outside the thermo poro elastic inclusion is very different from pressurized cavities

statistical analysis and clustering features of the phlegraean fields earthquake sequence may 1983 may 1984 abstract the seismic activity at the phlegraean fields volcanic area southern italy during the period may 1983 may 1984 5 301 selected events has been analyzed from a statistical point of view the analysis of the time series associated to the microearthquakes shows a high degree of interdependence among the events the main feature being the occurrence of dense swarms the generalized poisson process provides a good fit for the sequence the clustering of the events has not substantially changed during the analyzed period while the mean rate of occurrence of the swarms has generally increased the distribution of the magnitudes within the swarms shows pronounced maxima of energy around the center of the subsequences in agreement with theoretical models of fractures in highly heterogeneous media

coupled caldera subsidence and stirring inferred from analogue models analogue modelling of caldera forming eruptions suggests that sinking of the magma chamber roof is variable in space and time leading to substantial stirring and mixing of magma this can explain the common occurrence of geochemical zonation and magma mingling in deposits erupted from calderas

distortions rotations and crustal thinning at ridge transform intersections when an oceanic ridge intersects a transform fault the newly formed oceanic crust may be severely distorted frequently exhibiting major rotations of fault blocks1 4 such effects typically extend over a 10 km wide strip parallel to the transform by contrast studies of contemporary oceanic transforms suggest that deformation is restricted to a single fault trace within the transform domain5 9 this apparent inconsistency can be reconciled if the rotations occurred at the ridge transform intersection during accretion of the crust here i develop a kinematic model that considers the effect of an ephemeral period of stretching on a region that broadens as the transform is approached along the ridge the strains calculated from this model indicate extension at the ridge simple shear at the transform and composite strains in the region of distributed deformation the model predicts very rapid rotation rates 100 in 104 105 yr the implications for the topography and structure of ridge transform intersections are considered and the alternating periods of extension by stretching and by intrusion are illustrated by reference to contemporary transforms on the mid atlantic ridge the model may also explain the common occurrence of cross cutting dykes near transform faults in ophiolites

a geochemical and geophysical reappraisal to the significance of the recent unrest at campi flegrei caldera southern italy volcanic unrest at calderas involve complex interaction between magma hydrothermal fluids and crustal stress and strain campi flegrei caldera cfc located in the naples italy area and characterised by the highest volcanic risk on earth for the extreme urbanisation undergoes unrest phenomena involving several meters of uplift and intense shallow micro seismicity since several decades despite unrest episodes display in the last decade only moderate ground deformation and seismicity current interpretations of geochemical data point to a highly pressurized hydrothermal system we show that at cfc the usual assumption of vapour liquid coexistence in the fumarole plumes leads to largely overestimated hydrothermal pressures and accordingly interpretations of elevated unrest by relaxing unconstrained geochemical assumptions we infer an alternative model yielding better agreement between geophysical and geochemical observations the model reconciles discrepancies between what observed 1 for two decades since the 1982 84 large unrest when shallow magma was supplying heat and fluids to the hydrothermal system and 2 in the last decade compared to the 1980 s unrest the post 2005 phenomena are characterized by much lower aquifers overpressure and magmatic involvement as indicated by geophysical data and despite large changes in geochemical indicators our interpretation points out a model in which shallow sills intruded during 1969 1984 have completely cooled so that fumarole emissions are affected now by deeper co2 richer magmatic gases producing the modest heating and overpressure of the hydrothermal system our results have important implications on the short term eruption hazard assessment and on the best strategies for monitoring and interpreting geochemical data this article is protected by copyright all rights reserved

spreading structure of the troodos ophiolite cyprus orientations of dikes within the sheeted dike complex of the troodos ophiolite reveal primary spreading structure produced at a complex ridge transform intersection three structural grabens are defined by listric and planar normal faults and rotated dikes that dip symmetrically toward graben axes faults flatten at depth into a detachment within the upper parts of the plutonic complex large exhalative massive sulfide deposits occur within the pillow sections of two of the grabens and appear to be associated with underlying altered and mineralized normal fault zones that channeled hydrothermal fluids we suggest that the grabens are fossil axial valleys produced by successive eastward jumps of an approximately north trending present coordinates slow spreading ridge crest a simple model for ridge migration indicates eastward jumps of 8 13 km changes in ridge orientation are suggested by changes in trends of dikes and graben axes comparison of the pattern of dikes near the arakapas fault zone with the structure of active ridge transform intersections suggests that the fault is a right offset sinistral transform in contrast to earlier models in which a ridge to the west of the exposed troodos complex was proposed

the volcanic and geothermally active campi flegrei caldera an integrated multidisciplinary image of its buried structure the campi flegrei caldera in southern italy is one of the greatest geohazard areas on earth evidence of an active magmatic and geothermal system is provided by ongoing ground uplift with volcano tectonic and long period lp seismicity the persistent degassing of 1500 tonnes of co2 per day the presence of hot fumaroles at temperatures of 90 150 c brine rich aquifers with total dissolved solids up to 33 g l 1 and high thermal gradients in the crust with temperatures reaching 420 c at 3 050 m b s l since the 1940s more than 100 exploratory boreholes have been drilled in the area to depths of 80 3 100 m by the azienda geologica italiana petroli agip and the societa anonima forze endogene napoletane safen to date however no systematic reanalysis of the drilling data has been carried out and the buried volcanic structure has not been updated using the most recent scientific results and previous findings by integrating unpublished data from the agip and safen reports with published information from geological volcanological petrological petrophysical and geophysical studies this paper presents an improved picture of the campi flegrei caldera that will be useful for volcanic hazard assessment and mitigation in the naples area and for future research planning the results suggest that intra caldera activity has been influenced by how the magmatic system at depths greater than about 4 km has determined the transfer of magma volatiles and heat to the overlying geothermal system and ultimately to the surface in particular intriguing is that the most volcanically active central eastern sector of the caldera which is subject to intense bradyseismic ground movement and gas emission coincides with a structurally delimited subsurface rock volume characterized by an uprising of the 100 c isotherm a deep water supply to the shallower aquifer the early disappearance of secondary calcite lp seismicity and high seismic s wave attenuation in this area we also document evidence of repeated injection at depths of c 1 5 3 0 km of isolated and small volume batches of magma where occurred their crystallization and degassing shallow intrusions and degassing of magma are thus identified as two of the key processes that drive unrest in campi flegrei

understanding caldera structure and development an overview of analogue models compared to natural calderas abstract understanding the structure and development of calderas is crucial for predicting their behaviour during periods of unrest and to plan geothermal and ore exploitation geological data including that from analysis of deeply eroded examples allow the overall surface setting of calderas to be defined whereas deep drillings and geophysical investigations provide insights on their subsurface structure collation of this information from calderas worldwide has resulted in the recent literature in five main caldera types downsag piston funnel piecemeal trapdoor being viewed as end members despite its importance such a classification does not adequately examine a the structure of calderas particularly the nature of the caldera s bounding faults and b how this is achieved including the genetic relationships among the five caldera types various sets of analogue models specifically devoted to study caldera architecture and development have been recently performed under different conditions apparatus materials scaling parameters stress conditions the first part of this study reviews these experiments which induce collapse as a result of underpressure or overpressure within the chamber analogue the experiments simulating overpressure display consistent results but the experimental depressions require an exceptional amount of doming seldom observed in nature to form therefore these experiments are not appropriate to understand the structure and formation of most natural calderas the experiments simulating underpressure reveal a consistent scenario for caldera structure and development regardless of their different boundary conditions these show that complete collapse proceeds through four main stages proportional to the amount of subsidence progressively characterized by 1 downsag 2 reverse ring fault 3 peripheral downsag 4 peripheral normal ring fault the second part of this study verifies the possibility that these latter calderas constitute a suitable analogue to nature and consists of a comprehensive comparison of the underpressure experiments to natural calderas this shows that all the experimental structures as well as their progressive development are commonly observed at natural calderas highlighting a consistency between models and nature as the shallow structure of experimental calderas corresponds to a precise architecture at depth it provides a unique key to infer the deeper structure of natural calderas recognizing diagnostic surface features within a caldera will thus allow it to be categorized within a precise structural and evolutionary context the general relationship between the evolutionary stage of a caldera and its d s diameter subsidence ratio allows such a quantification with stage 1 calderas characterized by d s 40 stage 2 by 18 the four stages adequately explain the architecture and development of the established caldera end members along a continuum where one or more end members downsag piston funnel piecemeal trapdoor may correspond to a specific stage while such a continuum is controlled by progressive subsidence specific collapse geometries will result from secondary contributory factors roof aspect ratio collapse symmetry pre existing faults these considerations allow proposing an original classification of calderas incorporating their structural and genetic features

oceanic inside corner detachments of the limassol forest area troodos ophiolite cyprus abstract flat lying extensional detachment faults have been imaged in the inside corner regions of ridge transform intersections on the mid atlantic ridge exposed detachment surfaces are 10 km or more across and are corrugated in the direction of spreading as are continental detachments beneath the detachments lie core complexes of peridotite and gabbro these are overlain by blocks of crustal material we argue here that similar detachments are an essential component of the limassol forest area of the troodos ophiolite in cyprus which lies south of the arakapas fault zone previously recognized as a palaeo transform fault and here interpreted as a transform fault that evolved into a fracture zone in the limassol forest core complexes of mantle peridotite can be shown to have been exposed at the sea floor or to have been covered by overlapping crustal blocks separated from the peridotite core and from each other by low angle extensional faults the extension can be shown to have occurred shortly after crustal construction and the already extended terrain was then intruded by swarms of dykes and plutons we interpret these relations as arising when crust is constructed in an inside corner area extended by detachment faulting deformed further during slip along the transform and then intruded by new magma as it passes the second spreading centre the structurally deeper parts of the crustal blocks that overlie the detachment lie broadly towards the west indicating that the spreading axis lay in that direction the ophiolite north of the transform is much less extended and we interpret this as a section of outside corner crust in this interpretation the troodos ophiolite formed to the east in its current orientation of a ridge transform ridge intersection in which the transform had a dextral offset and sinistral slip the part of the ophiolite that forms the limassol forest was produced at the western inside corner and spread eastwards until it passed the second spreading axis at which point the ophiolite north of the arakapas fault was created and welded to the limassol forest when the transform became a fracture zone

the age of the neapolitan yellow tuff caldera forming eruption campi flegrei caldera italy assessed by 40ar 39ar dating method abstract the neapolitan yellow tuff nyt is the product of the largest known trachytic phreatoplinian eruption it covered an area larger than 1000 km2 with an estimated volume of about 40 km3 of erupted magma during the course of the eruption a caldera collapsed within the previously formed campanian ignimbrite caldera the resulting nested structure strongly influenced the following volcanic activity in the campi flegrei caldera as previous dating of the nyt does not converge toward a unique result a new set of 40ar 39ar age determinations has been carried out to better constrain the age of the eruption two variants of the 40ar 39ar dating method were applied to determine the age of the nyt eruption 1 single crystal total fusion sctf on an individual phenocryst of feldspar and 2 laser incremental heating lih on bulk aliquots of feldspar phenocrysts the results of the sctf analyses show that the overall sample weighted mean age derived from the conventional age calculation is 15 6 0 8 ka a weighted mean of the isochron age is 15 3 1 2 ka 2 and has been assumed as the best indicator of age to be derived from the sctf analyses the lih analyses results show that plateau ages vary from 15 4 0 5 to 14 5 0 5 ka the overall weighted mean age of the isochron results is 14 9 0 4 ka 2 this result has been assumed as the reference age for the nyt eruption and agrees with the sctf age the new age obtained for the nyt deposits is of great relevance for the understanding of the evolution and the present state of the campi flegrei caldera and collocates the nyt in a crucial stratigraphical position to date the climatic oscillations that occurred between the late glacial and the holocene

formation and development of normal fault calderas and the initiation of large explosive eruptions the ring fractures that form most collapse calderas are steeply inward dipping shear fractures i e normal faults at the surface of the volcano within which the caldera fault forms the tensile and shear stresses that generate the normal fault caldera must peak at a certain radial distance from the surface point above the center of the source magma chamber of the volcano numerical results indicate that normal fault calderas may initiate as a result of doming of an area containing a shallow sill like magma chamber provided that the area of doming is much larger than the cross sectional area of the chamber and that the internal excess pressure in the chamber is smaller than that responsible for doming this model is supported by the observation that many caldera collapses are preceded by a long period of doming over an area much larger than that of the subsequently formed caldera when the caldera fault does not slip eruptions from calderas are normally small nearly all large explosive eruptions however are associated with slip on caldera faults during dip slip on and doming of a normal fault caldera the vertical stress on part of the underlying chamber suddenly decreases this may lead to explosive bubble growth in this part of the magma chamber provided its magma is gas rich this bubble growth can generate an excess fluid pressure that is sufficiently high to drive a large fraction of the magma out of the chamber during an explosive eruption

paleomagnetic arguments for block rotations along the arakapas fault cyprus paleomagnetic data from the sheeted dike complex north of the arakapas fault reveal significant internal rotations the north south trending dikes have remanent magnetization directions close to the well known westerly paleomagnetic direction of the troodos massif whereas the east west trending dikes near the arakapas fault have northerly remanent magnetization directions the paleomagnetic data are in agreement with the apparent clockwise rotation of the dikes contrary to recent geological analyses which postulate that the pattern of dike trends is due to dike injection into a sigmoidal stress field along a sinistral transform fault the paleomagnetic results indicate clockwise rotations about vertical axes in response to a dextral shear in addition to the rotations around vertical axes small rotations around subhorizontal axes are inferred from the paleomagnetic data for tilted dikes thus these data reinforce the vertical intrusion hypothesis

eruptive versus non eruptive behaviour of large calderas the example of campi flegrei caldera southern italy caldera eruptions are among the most hazardous of natural phenomena many calderas around the world are active and are characterised by recurrent uplift and subsidence periods due to the dynamics of their magma reservoirs these periods of unrest are in some cases accompanied by eruptions at campi flegrei caldera cfc which is an area characterised by very high volcanic risk the recurrence of this behaviour has stimulated the study of the rock rheology around the magma chamber in order to estimate the likelihood of an eruption this study considers different scenarios of shallow crustal behaviour taking into account the earlier models of cfc ground deformation and caldera eruptions and including recent geophysical investigations of the area a semi quantitative evaluation of the different factors that lead to magma storage or to its eruption such as magma chamber size wall rock viscosity temperature and regional tectonic strain rate is reported here for elastic and viscoelastic conditions considering the large magmatic sources of the cfc ignimbrite eruptions 400 2 000 km3 and a wall rock viscosity between 1018 and 1020 pa s the conditions for eruptive failure are difficult to attain smaller source dimensions a few cubic kilometres promote the condition for fracture eruption rather than for the flow of wall rock we also analyse the influence of the regional extensional stress regime on magma storage and eruptions and the thermal stress as a possible source of caldera uplift the present study also emphasises the difficulty of distinguishing eruption and non eruption scenarios at cfc since an unambiguous model that accounts for the rock rheology magma source dimensions and locations and regional stress field influences is still lacking

calderas and caldera structures a review abstract calderas are important features in all volcanic environments and are commonly the sites of geothermal activity and mineralisation yet it is only in the last 25 years that a thorough three dimensional study of calderas has been carried out utilising studies of eroded calderas geophysical analysis of their structures and analogue modelling of caldera formation as more data has become available on calderas their individuality has become apparent a distinction between caldera caldera complex cauldron and ring structure is necessary and new definitions are given in this paper descriptions of calderas based on dominant composition of eruptives basaltic peralkaline andesitic dacitic rhyolitic can be used and characteristics of each broad group are given styles of eruption may be effusive or explosive with the former dominant in basaltic calderas and the latter dominant in andesitic dacitic rhyolitic and peralkaline calderas four end member collapse styles occur plate or piston piecemeal trapdoor and downsag but many calderas have multiple styles features of so called funnel and chaotic calderas proposed in the literature can be explained by other collapse styles and the terms are considered unnecessary ground deformation comprises subsidence or collapse essential characteristics of a caldera and uplifting doming and fracturing due to tumescence and or resurgence frequent but not essential collapse may occur on pre existing structures such as regional faults or on faults created during the caldera formation and the shape of the collapse area will be influenced by depth size and shape of the magma chamber the final morphology of a caldera will depend on how the caldera floor breaks up whether collapse takes place in one event or multiple events whether vertical movement is spasmodic or continuous throughout the eruptive sequence and whether blocks subside uniformly or chaotically at one or more collapse centres a meaningful description of any caldera should therefore include number of collapse events presence or absence of resurgence caldera floor coherency caldera floor collapse geometry and dominant composition of eruptives

40ar 39ar dating of hydrothermal activity biota and gold mineralization in the rhynie hot spring system aberdeenshire scotland this study presents a new high precision 40ar 39ar age for the devonian hot spring system at rhynie hydrothermal k feldspar sampled from two veins that represent feeder conduits and a hydrothermally altered andesite wall rock date the hydrothermal activity the fossilised biota and syn k feldspar gold mineralization at 403 9 2 1 ma 2 oxygen isotope data for the parent fluid 4 to 2 show that the k feldspar was precipitated from a dominantly meteoric fluid which mixed with magmatic fluids from a degassing magma chamber the 40ar 39ar age 403 9 2 1 ma 2 when recalculated 407 1 2 2 ma 2 with respect to the astronomically tuned age for fish canyon sanidine 28 201 0 023 ma 1 also provides a robust marker for the polygonalis emsiensis spore assemblage biozone within the pragian earliest emsian furthermore the age identifies the devonian pull apart volcano sedimentary basins of the british and irish caledonides and their root zones as specific targets for future gold exploration

the campi flegrei deep drilling project cfddp new insight on caldera structure evolution and hazard implications for the naples area southern italy the 501 m deep hole of the campi flegrei deep drilling project located west of the naples metropolitan area and inside the campi flegrei caldera gives new insight to reconstruct the volcano tectonic evolution of this highly populated volcano it is one of the highest risk volcanic areas in the world but its tectonic structure eruptive history and size of the largest eruptions are intensely debated in the literature new stratigraphic and 40ar 39ar geochronological dating allow us to determine for the first time the age of intracaldera deposits belonging to the two highest magnitude caldera forming eruptions i e campanian ignimbrite ci 39 ka and neapolitan yellow tuff nyt 14 9 ka and to estimate the amount of collapse tuffs from 439 m of depth yield the first 40ar 39ar age of ca 39 ka within the caldera consistent with the ci volcanic rocks from the nyt were moreover detected between 250 and 160 m our findings highlight i a reduction of the area affected by caldera collapse which appears to not include the city of naples ii a small volume of the infilling caldera deposits particularly for the ci and iii the need for reassessment of the collapse amounts and mechanisms related to larger eruptions our results also imply a revaluation of volcanic risk for the eastern caldera area including the city of naples the results of this study point out that large calderas are characterized by complex collapse mechanisms and dynamics whose understanding needs more robust constraints which can be obtained from scientific drilling

understanding the seismic velocity structure of campi flegrei caldera italy from the laboratory to the field scale we report laboratory measurements of p and s wave velocities on samples of tuff from campi flegrei italy and a new tomographic velocity map of the campi flegrei caldera laboratory measurements were made in a hydrostatic pressure vessel during both increasing and decreasing effective pressure cycles selected samples were also thermally stressed at temperatures up to 600 c to induce thermal crack damage acoustic emission output was recorded throughout each thermal stressing experiment and velocities were measured after thermal stressing laboratory p and s wave velocities are initially low for the tuff which has an initial porosity of 45 but both increase by between 25 and 50 over the effective pressure range of 5 to 80 mpa corresponding to a decrease of porosity of 70 marked velocity hysteresis due to inelastic damage processes is also observed in samples subjected to a pressurization depressurization cycle tomographic seismic velocity distributions obtained from field recordings are in general agreement with the laboratory measurements integration of the laboratory ultrasonic and seismic tomography data indicates that the tuffs of the campi flegrei caldera can be water or gas saturated and shows that inelastic pore collapse and cracking produced by mechanical and thermal stress can significantly change the velocity properties of campi flegrei tuffs at depth these changes need to be taken into account in accurately interpreting the crustal structure from tomographic data

v s of the uppermost crust structure of the campi flegrei caldera southern italy from ambient noise rayleigh wave analysis abstract shear wave velocities v s are defined in the uppermost 1 2 km of the campi flegrei caldera through the non linear inversion of the group velocity dispersion curves of fundamental mode rayleigh waves extracted from ambient noise cross correlations between two receivers noise recordings three months long at 12 seismic stations are cross correlated between all couples of stations the experiment provided successful results along 54 paths inter stations distance of which 27 sampled a depth 1 km v s contour lines are drawn from 0 06 km b s l to 1 km depth b s l and show difference between the offshore gulf of pozzuoli and coastline and the onshore areas at 0 06 km b s l the gulf of pozzuoli and the coastline are characterized by v s of 0 3 0 5 km s and of 0 5 0 7 km s respectively such velocities are typical of neapolitan pyroclastic soils and fractured or altered tuffs the inland shows v s in the range 0 7 0 9 km s typical of neapolitan compact tuffs velocities increase with depth and at 1 km depth b s l velocities lower than 1 5 km s are still present in the gulf and along the coastline while velocities higher than 1 9 km s characterize the eastern sector grossly coincident with the neapolitan yellow tuff caldera rim the s vito plain and the area between solfatara and sw of astroni such features are much more evident along two cross sections drawn in the offshore and onshore sectors by integrating our v s models with literature data our models join previous noise cross correlation studies at greater scale at depths of 0 7 0 8 km hence the picture of the campi flegrei caldera is shown up to a depth of 15 km v s of about 1 7 km s corresponding to compression velocities v p of about 3 km s computed by using the v p v s ratio resulted in the inversion are found at depths of 1 1 km in the centre of the gulf of pozzuoli and at a depth of about 0 7 km b s l onshore an increment of v s velocity 1 9 2 0 km s is locally observed onshore which might be attributed to a layer of tuffs and tuffites interbedded with thin lava beds according to the correlation of v s with stratigraphies in the deep drillings of s vito

comment on the campi flegrei deep drilling project cfddp new insight on caldera structure evolution and hazard implications for the naples area southern italy by g de natale et al

structure of a fossil ridge transform intersection in the troodos ophiolite recent palaeomagnetic studies of sheeted dykes adjacent to the east west trending southern troodos transform fault of cyprus have demonstrated significant clockwise block rotations which are most easily interpreted as being due to drag induced by dextral strike slip faulting along the transform1 6 we show here that such rotations have not occurred along the entire length of the transform instead to the west of the areas previously studied the sheeted dykes have been subjected to simple tilting only indicating normal faulting but no strike slip the changeover between these two domains of differing structural styles near the village of mandria is approximately in line with the centre of the solea graben a north south trending structure within the troodos massif which has previously been interpreted as a fossil ridge axis7 we suggest that the mandria area represents a fossilized ridge transform intersection and present the results of a detailed field investigation of the area together with preliminary palaeomagnetic data to determine the relationship between tectonism and magmatism at such plate boundary zones we use our findings to test a recent theoretical model8 of deformation processes at ridge transform intersections and show that distributed deformation due to block rotation is largely confined to the ridge transform corner itself

a mechanism for decoupling within the oceanic lithosphere revealed in the troodos ophiolite contrasting kinematic histories recorded in the sheeted dykes and underlying plutonic rocks of the troodos ophiolite provide a new perspective on the mechanical evolution of oceanic spreading centres the kinematic framework of the decoupling zone that partitions deformation between the sheeted dykes and plutonics contrasts with low angle detachment models for slow spreading ridges based on continental rift analogues a model for the generation of multiple horizontal decoupling horizons linked by planar normal faults demonstrates new possibilities for the kinematic and rheological significance of seismic reflectors in oceanic lithosphere

understanding volcanic hazard at the most populated caldera in the world campi flegrei southern italy naples and its hinterland in southern italy are one of the most urbanized areas in the world under threat from volcanic activity the region lies within range of three active volcanic centers vesuvius campi flegrei and ischia the campi flegrei caldera in particular has been in unrest for six decades the unrest followed four centuries of quiescence and has heightened concern about an increased potential for eruption innovative modeling and scientific drilling are being used to investigate campi flegrei and the results highlight key directions for better understanding the mechanisms of caldera formation and the roles of magma intrusion and geothermal activity in determining the volcano s behavior they also provide a framework for evaluating and mitigating the risk from this caldera and other large ones worldwide

monitoring super volcanoes geophysical and geochemical signals at yellowstone and other large caldera systems earth s largest calderas form as the ground collapses during immense volcanic eruptions when hundreds to thousands of cubic kilometres of magma are explosively withdrawn from the earth s crust over a period of days to weeks continuing long after such great eruptions the resulting calderas often exhibit pronounced unrest with frequent earthquakes alternating uplift and subsidence of the ground and considerable heat and mass flux because many active and extinct calderas show evidence for repetition of large eruptions such systems demand detailed scientific study and monitoring two calderas in north america yellowstone wyoming and long valley california are in areas of youthful tectonic complexity scientists strive to understand the signals generated when tectonic volcanic and hydrothermal hot ground water processes intersect one obstacle to accurate forecasting of large volcanic events is humanity s lack of familiarity with the signals leading up to the largest class of volcanic eruptions accordingly it may be difficult to recognize the difference between smaller and larger eruptions to prepare ourselves and society scientists must scrutinize a spectrum of volcanic signals and assess the many factors contributing to unrest and toward diverse modes of eruption

quantifying volcanic ash dispersal and impact of the campanian ignimbrite super eruption 1 we apply a novel computational approach to assess for the first time volcanic ash dispersal during the campanian ignimbrite italy super eruption providing insights into eruption dynamics and the impact of this gigantic event the method uses a 3d time dependent computational ash dispersion model a set of wind fields and more than 100 thickness measurements of the ci tephra deposit results reveal that the ci eruption dispersed 250 300 km 3 of ash over 3 7 million km 2 the injection of such a large quantity of ash and volatiles into the atmosphere would have caused a volcanic winter during the heinrich event 4 the coldest and driest climatic episode of the last glacial period fluorine bearing leachate from the volcanic ash and acid rain would have further affected food sources and severely impacted late middle early upper paleolithic groups in southern and eastern europe citation costa a a folch g macedonio b giaccio r isaia and v c smith 2012 quantifying volcanic ash dispersal and impact of the campanian ignimbrite super eruption geophys res lett 39 l10310 doi 10 1029 2012gl051605

the bay of naples southern italy constraints on the volcanic structures inferred from a dense seismic survey 1 the bays of naples and pozzuoli host volcanic areas that have been active within recent history in addition the vicinities areas around the vesuvius volcano and the campi flegrei caldera are extremely densely inhabited over the past decade this situation has prompted several active seismic experiments focused on the vesuvius volcano more recently the serapis active seismic survey covered the entire bay of naples with particular attention to pozzuoli bay the processed serapis p wave travel time collection extended with a previously acquired data set has allowed the computation of the most comprehensive three dimensional p wave velocity distribution for the bay of naples which includes a small scale high resolution model of the campi flegrei caldera the joint interpretation of the velocity distribution together with both the available gravity measurements and models and the geothermal drilling information has allowed us to locate and map lithological units at depths we propose a model of the campi flegrei caldera in relation to the underlying mesozoic limestone unit in this model no magma chamber exists in the upper 6 km beneath the bay of naples the feeding system of the campi flegrei caldera is directly controlled by the tectonic structures affecting the limestone unit beneath the bay of naples two ne sw normal faults run beneath the vesuvius volcano and campi flegrei which are related to the pre pleistocene apenninic tectonics

the restless resurgent campi flegrei nested caldera italy constraints on its evolution and configuration abstract we have collected new stratigraphic data in the campi flegrei caldera through surface geological mapping and study of cores drilled to various depths we integrate these data with geological geochronological and geophysical constraints available in the literature to reconstruct the volcanic and deformational history of the caldera the caldera is a resurgent nested structure resulting from two main collapses related to the campanian ignimbrite 37 ka and the neapolitan yellow tuff 12 ka eruptions while the structure is affected by a broad subsidence ongoing local resurgence and unrest occur inside the younger nested caldera structure although most of the caldera floor consists of multiple structural blocks due to long term deformations magmas were able to erupt only in one sector of the resurgent part the caldera has shown signs of unrest during the past 25 years with short term deformations that have generated a net uplift of 3 5 m the short term deformations are related to the neapolitan yellow tuff caldera resurgence and interpreted as the net result of brittle and ductile components the long term deformations likely represent the sum of the permanent brittle component of each short term deformational event

structure and evolution of the bay of pozzuoli italy using marine seismic reflection data implications for collapse of the campi flegrei caldera digital marine seismic reflection data acquired in 1973 in the bay of pozzuoli and recently reprocessed were used to study the volcanological evolution of the marine sector of campi flegrei caldera during the last 37 ka in order to gain more information interpretation also involved estimation of the pseudo velocity and the pseudo density from the resistivity logs of two onshore deep exploration wells the main results are 1 discovery of ancient pre 18 ka and post 37 ka submarine and mainly effusive volcanic activity along coeval emission centers located at the edges of campi flegrei caldera 2 confirmation that the caldera collapse in the marine sector of campi flegrei seems strongly controlled by regional ne sw and nw se structural discontinuities 3 the finding of at least two episodes of collapse in the bay and 4 identification of a post 18 ka volcanic deflation phase that has caused about 150 200 m of subsidence in the central sector of the bay of pozzuoli in the last 18 ka

western limassol forest complex cyprus part of an upper cretaceous leaky transform fault field petrographic and geochemical studies suggest that the limassol forest complex formed in a leaky left lateral oceanic transform fault multiple mafic and ultramafic intrusions into tectonized harzburgite were synchronous with ductile and later brittle tectonism a history of increasingly chilled intrusive contacts a transition from ductile to brittle deformation and a decrease in metamorphic grade all indicate continuous cooling and uplift of the harzburgite mantle host while it was part of an active transform domain the occurrence of multiple 040 n trending mafic and picrite dikes with extremely depleted high field strength element abundance suggests that strike slip movement along the transform fault was accompanied by extension that led to magma emplacement and eruption

morphotectonic fabric of the orozco transform fault results from a sea beam investigation we have used data collected with the sea beam system to produce a detailed regional bathymetric map of the medium to fast slipping 90 mm yr orozco transform fault the morphotectonic fabric of the 90 50 km transform domain is spatially heterogeneous and is composed of relatively shallow areas 3200 m the plate boundary geometry is clearly identified morphologically and is characterized by a series of linked basins and troughs that approximate a zed pattern in plan view east west trending basins define the northern and southern boundaries of the transform domain and these troughs are thought to mark the location of strike slip tectonism a central north south trending ridge with an axial valley called here the mid orozco spreading center is thought to represent a short 30 km ridge segment that links two transform faults morphotectonic relationships developed along the southeastern flank of the survey area suggest that this plate boundary geometry has recently become unstable and is presently undergoing a transformation as the tip of the east pacific rise axis propagates northward across the transform domain bypassing the mid orozco spreading center if the southern ridge axis continues to propagate northward it will link with the aseismic extension of the northern strike slip strand and the present day plate boundary will evolve into a simple ridge transform ridge r t r geometry with an offset of approximately 70 km

tephra in caves distal deposits of the minoan santorini eruption and the campanian super eruption abstract tephra deposits in caves are not only significant as stratigraphic markers the comparatively sheltered position of cave environments protected from rainfall may preserve original distal tephra deposition features unlikely to have survived in the open landscape most reported findings of tephra in caves are from the campanian super eruption which originated in the area of naples italy these findings facilitate evaluation in different caves of facies variability and modes of tephra deposition derived from the same eruption the campanian volcanic event about 40 000 years ago was the largest eruption in europe and the mediterranean region during the late pleistocene another major volcanic event during the quaternary was the more recent santorini eruption in the eastern mediterranean aegean sea during the late minoan cultural period approximately 3600 years ago this was the largest holocene eruption in the region but tephra deposits in caves from this event appear to be very rare we present here the first ever finding of a visible tephra layer from the minoan santorini eruption in a cave the pure tephra situated in the pelekita cave in eastern crete near kato zakros has a thickness of up to 9 cm geochemistry analyses of major elements by electron probe micro analysis epma and trace elements by laser ablation inductively coupled plasma mass spectrometry la icp ms prove the tephra to be derived from the minoan santorini eruption radiocarbon dating also fits the time frame of this eruption our findings indicate that the tephra layer in the pelekita cave is an air fall deposit the lower boundary of the tephra layer is sharp and wavy draping over the underlying irregular cave surface particle size distribution of the tephra is bimodal and typical for suspended aeolian transport the consistently smaller size of heavier feldspar particles adjacent to larger but lighter volcanic glass particles in thin sections of undisturbed samples corroborate emplacement of the tephra inside the pelekita cave from high altitude fallout

emplacement of deep crustal and mantle rocks on the west median valley wall of the mark area mar 23 n abstract exposures of deep crustal and mantle rocks within the axial rift valley characterize accretion processes in the slow spreading mid atlantic ridge nine dives of the submersible nautile explored the western axial valley wall in the northern cell of the mark area mid atlantic ridge kane fracture zone where peridotite and gabbro outcrops had been previously reported in order to constrain the structure and determine emplacement mechanisms the ridge transform intersection massif on the western wall shows a section of gabbros from 6000 to 2500 mbsl locally overlain by metabasalts and metadolerites capped by slightly weathered basalts the morphology is controlled by ridge parallel faults dipping moderately 40 65 to the east transform parallel scarps present in the northernmost dives become rare toward the south brittle deformation along moderately dipping fault scarps produced a dense microcrack network filled with greenschist facies minerals chlorite actinolite epidote quartz locally overprinting high temperature ductile deformation fabrics the small hill located at 23 20 in the western wall shows good exposures of serpentinized peridotite between 3700 and 3100 mbsl above 3100 mbsl the summit of the hill is composed of pillow basalts and sediments the peridotite outerops display a strong schistosity dipping 20 40 to the east parallel to striated normal fault planes some steeper east facing fault scarps truncate the lower dipping fault surfaces the serpentinites deriving from a harzburgitic protolith are cut by rare dikelets of highly differentiated gabbro these new data combined with previous results of alvin dives are used to draw a generalized geological map of the western axial valley wall this map suggests a variation in the thickness of crustal units and composition along strike in the northern cell of the mark area the gabbro body disappears toward the south where basalts appear to directly overlie the mantle peridotites which are cut by isolated gabbroic dikelets low angle stretching affecting this heterogeneous lithosphere is probably responsible for the exposure of gabbros in the intersection massif and of peridotites further south

multiple closely spaced transform faults in fast slipping fracture zones the 400 km long offset of the east pacific rise spreading axis between the quebrada fracture zone lat 3 5 s and the gofar fracture zone lat 4 6 s has been surveyed using the long range sidescan sonar gloria the offset is accomplished in three distinct fracture zones each of which contains up to four actively slipping transform faults separated by short spreading centers transform spacings range from 5 to 16 km each transform is associated with its own transverse valley but at quebrada fracture zone and to some extent at the other two these valleys merge into one large slightly oblique fracture zone valley the morphological trends of fracture zone valleys are therefore not necessarily reliable for estimating directions of relative plate movement multitransform fracture zones appear to be much commoner on the fast spreading east pacific rise than on slower spreading ridges the tectonic spreading fabric which comprises closely spaced normal faults formed near the spreading axes and striking subparallel to them is modified to a sigmoidal pattern between the closely spaced transforms even midway between transforms these faults remain oblique to the spreading direction the degree of obliquity increases as the transform separation decreases showing progressive rotation of the stress ellipse as transforms are approached

fault strain and seismic coupling on mid ocean ridges the contribution of extensional faulting to seafloor spreading along the east pacific rise epr axis near 3 s and between 13 n and 15 n is calculated using data on the displacement and length distributions of faults obtained from side scan sonar and bathymetric data it is found that faulting may account for of the order of 5 10 of the total spreading rate which is comparable to a previous estimate from the epr near 19 s given the paucity of normal faulting earthquakes on the epr axis a maximum estimate of the seismic moment release shows that seismicity can account for only 1 of the strain due to faulting this result leads us to conclude that most of the slip on active faults must be occurring by stable sliding laboratory observations of the stability of frictional sliding show that increasing normal stress promotes unstable sliding while increasing temperature promotes stable sliding by applying a simple frictional model to mid ocean ridge faults it is shown that at fast spreading ridges 90 mm yr the seismic portion of a fault ws is a small proportion of the total downdip width of the fault w the ratio ws w interpreted as the seismic coupling coefficient x and in this case x 0 in contrast at slow spreading rates 40 mm yr ws w and therefore x 1 which is consistent with the occurrence of large magnitude earthquakes mb 5 0 to 6 0 occurring for example along the mid atlantic ridge axis

response to the comment by w h schwarz et al on joint determination of 40k decay constants and 40ar 40k for the fish canyon sanidine standard and improved accuracy for 40ar 39ar geochronology by p r renne et al 2010

relationship between caldera collapse and magma chamber withdrawal an experimental approach collapse calderas have received considerable attention due to their link to earth s ore deposits and geothermal energy resources but also because of their tremendous destructive potential although calderas have been investigated through fieldwork numerical models and experimental studies some important aspects on their formation still remain poorly understood one key issue concerns the volume of magmas involved in caldera forming eruptions we perform analogue experiments to correlate the structural evolution of a collapse with the erupted magma chamber volume fraction the experimental device consists of a transparent box 60 60 40 cm filled with dry quartz sand and a water filled latex balloon as a magma chamber analogue evacuation of water through a pipe causes a progressive deflation of the balloon that leads to a collapse of the overlying structure the experimental design allows to record the temporal evolution of the collapse and to track the evolution of fractures and faults we study the appearance and development of specific brittle structures such as surface fractures or internal reverse faults and correlate each different structure with the corresponding removed magma chamber volume fraction we also determine the critical conditions for caldera onset experimental results show that at any stage of caldera developments the experimental relationship between volume fraction and chamber roof aspect ratio fits a logarithmic curve it implies that volume fractions required to trigger caldera collapse are lower for chambers with low aspect ratios shallow and wide than for chambers with high aspect ratios deep and small these results are in agreement with natural examples and previous theoretical studies

mineralogical geochemical and isotopic features of tuffs from the cfddp drill hole hydrothermal activity in the eastern side of the campi flegrei volcano southern italy abstract a 506 m drill hole has been recently drilled in the framework of the campi flegrei deep drilling project cfddp and the international continental scientific drilling program icdp with the intention of coring the subsurface in the eastern sector of the campi flegrei caldera the borehole located in the western district of the neapolitan city bagnoli plain 3 km to the east of the most active volcanic area and about 5 m above sea level is now targeted for monitoring purposes this paper reports the results obtained from the analysis of two short cores collected at depths of 443 and 506 m below the ground level the cores sampled two pre caldera tuffs observations performed by optical and scanning electron microscopy energy dispersive spectroscopy and powder x ray diffraction were used to achieve data on the primary lithology both primary and secondary mineralogical assemblages and the relationship between texture and secondary mineralization sr isotope ratios were determined on selected primary feldspars whereas 13c and 18o analyses were performed on carbonates from veins and filled voids in tuffs our results provide information on the hydrothermal system in the eastern sector of the caldera that was not among the goals in the previous drilling programs secondary mineralization suggests a saline hydrothermal environment characterized by fluids that progressively evolved from boiling toward more alkaline and cooler conditions a paleo temperature of ca 160 c has been inferred from authigenic mineral occurrences and calculated on the basis of equilibria between cored calcites and fluids presently emitted at the surface by using carbon and oxygen isotope data the temperature measured at the bottom of the drilling is about 80 c

toward establishing precise 40ar 39ar chronologies for late pleistocene palaeoclimate archives an example from the lake suigetsu japan sedimentary record the varved suigetsu sg06 sediment core is potentially one of the most important and well constrained mid latitude palaeoclimate archives recording continuous deposition during the last 150 kyrs numerous visible and non visible volcanic ash layers form unique age markers within sg06 these ash layers are too fine and crystal poor to be directly dated using the 40ar 39ar technique so the tephra were correlated to proximal volcanic deposits using their glass shard compositions a high precision 40ar 39ar sanidine age of 10 0 0 3 ka 1 n 34 mswd 0 71 p 0 89 was obtained for the sg06 1288 u oki proximal tephra ulleungdo u4 40ar 39ar yields a precision of 3 near the younger limit of the method with improved precision possible for older sg06 samples such 40ar 39ar ages for tephra layers can provide invaluable tie points within the lake suigetsu sg06 sequence giving independent verification of the core s varve chronology allowing for the calibration of cosmogenic nuclide production and providing a precise chronology beyond the varve limit

little ice age fluctuations of small glaciers in the monte fitz roy and lago del desierto areas south patagonian andes argentina abstract current knowledge about late holocene glacier fluctuations in the south patagonian andes is mainly based on evidence from large outlet glaciers of the north and south patagonian icefields and few data exist for the smaller glaciers elsewhere in the region here we provide dendrogeomorphological evidence for little ice age lia and post lia activity for five small glaciers near the northeast margin of the south patagonian icefield the study sites include glaciar torre and piedras blancas in the monte fitz roy area and three adjacent glaciers near lago del desierto at these sites the lia maximum position was identified by massive moraines with mature trees dating to the late 1500s early 1600s several older moraines were observed beyond these limits but could not be precisely dated relatively synchronous advances occurred at most glaciers in the early 1700s and were dated using living trees and in situ subfossil material all glaciers show three to five subsequent advances mostly concentrated between the mid 19th and early 20th centuries estimates based on landsat tm imagery indicate these glaciers lost between 15 and 46 of their lia areas by 1984 and a further 5 18 by 2005 with the smallest glaciers showing the greatest proportional loss paired comparisons of contemporary and the earliest known photography for the glaciers in the fitz roy area confirm this mass loss these results provide important new information on the glacier history of this area but additional more precisely dated records are needed from many more sites before we can fully elucidate the complex late holocene glacial history of this region

analogue models of collapse calderas and resurgent domes collapse calderas and resurgent domes are a common association related to inflation deflation processes in volcanic systems the structure of calderas and domes depends upon the permitted relative movements of crustal volumes at depth the so called space problem in order to study the structures of collapse calderas and resurgent domes and to take the space problem into account several analogue models were made dry quartz sand was used to simulate the rheology of the brittle crust while newtonian silicone putty located at the base of the sand pack simulated the ductile behaviour of the magma a piston moved the silicone putty downward or upward inducing collapse and doming within the sand three separate sets of experiments simulated 1 caldera collapse 2 resurgence and 3 superimposition of resurgence on collapse and vice versa collapse experiments are characterized by the development of two concentric depressions the first formed depression is bordered by outward dipping reverse ring faults the subsequent outer concentric depression is bordered by inward dipping normal ring faults the deformation pattern during resurgence is a function of the overburden thickness t and the dome diameter d for higher t d ratios a dome forms bordered by inward dipping high angle reverse ring faults outward dipping normal ring faults develop at late stages for lower t d ratios the dome shows at late stages a crestal depression accompanied by radial fractures subsequently an apical extrusion of silicone occurs the superimposition of resurgence over collapse and vice versa is characterized by the complete reactivation with opposite kinematics of all the pre existing ring faults during inversion both in caldera and resurgence reverse ring faults form in the early stages due to differential uplift extensional structures subsequently form to accommodate gravitational collapse during the activity of the reverse faults the experiments and the overall similarities with nature suggest that the activity of both reverse and normal faults constitutes a possible solution to the space problem during major collapses or resurgences

the breccia museo formation campi flegrei southern italy geochronology chemostratigraphy and relationship with the campanian ignimbrite eruption the breccia museo is one of the most debated volcanic formations of the campi flegrei volcanic district the deposit made up of six distinctive stratigraphic units has been interpreted by some as the proximal facies of the major caldera forming campanian ignimbrite eruption and by others as the product of several more recent independent and localized events new geochemical and chemostratigraphical data and ar ar age determinations for several units of the breccia museo deposits 39 ka correlate well with the campanian ignimbrite forming eruption the chemical zoning of the breccia museo deposits is interpreted here to be a consequence of a three stage event that tapped a vertically zoned trachytic magma chamber

constructing the upper crust of the mid atlantic ridge a reinterpretation based on the puna ridge kilauea volcano the volcanic morphology of a number of segments of the slow spreading mid atlantic ridge mar have been reinterpreted based on our understanding of dike emplacement dike propagation and eruption at the east rift zone of kilauea volcano hawaii and its submarine extension the puna ridge the styles of volcanic eruption at the submarine puna ridge are remarkably similar to those of the axial volcanic ridges avrs constructed on the median valley floor of the mar we use this observation to relate volcanic processes occurring at kilauea volcano to the mar we now consider that volcanic features e g seamounts and lava terraces built on the flanks of the avrs are secondary features that are fed from lava tubes or channels not primary features fed directly from an underlying dike we examine simple models of pipe flow and conclude that lava tubes can transport lava down the flanks of submarine rifts to build all of the volcanic features observed there in addition deep water lava tubes are strong enough to withstand the pressures of a few megapascals that the building of a volcanic structure 150 m high at the end of the tube would generate the volumes of individual volcanic terraces and seamounts on the puna ridge and at the mar are large 0 1 1 km3 and similar to the volumes of lava flows that are broadly distributed at the subaerial east rift zone of kilauea this striking difference in the volcanic morphology on a scale of 1 2 km producing terraces and seamounts underwater and low relief flows on land must be related to the enhanced cooling and to the greater mechanical stability of tubes in the submarine environment we suggest that at the mar a crustal magma reservoir most likely located beneath shallow flat sections of the segment provides magma to the rift axis through dikes that propagate laterally tens of kilometers the zone of dike intrusion at least in the neighborhood of the magma body is likely narrower than the width resurfaced by flows yielding a crustal structure that has a rapid vertical transition from lavas to sheeted dikes at segment ends the zone of dike intrusion is likely to be wider giving a resulting structure with a more gradual transition from lavas to dikes

tectonic stress and renewed uplift at campi flegrei caldera southern italy new insights from caldera drilling deep drilling is a key tool for the investigation of active volcanoes in the modern earth sciences as this provides the only means to obtain direct information on processes that occur at depth data acquired from drilling projects are fundamental to our understanding of volcano dynamics and for mitigation of the hazards they pose for millions of people who live close to active volcanoes we present here the first borehole measurement of the stress field in the crust of campi flegrei southern italy a large active caldera and one of the highest risk volcanoes worldwide measurements were performed to depths of 500 m during a pilot study for the campi flegrei deep drilling project these data indicate an extensional stress field with a minimum horizontal stress of ca 75 to 80 of the maximum horizontal stress which is approximately equal to the vertical stress the deviation from lithostatic conditions is consistent with a progressive increase in applied horizontal stress during episodes of unrest since at least 1969 as the stress field is evolving with time the outcome of renewed unrest cannot be assessed by analogy with previous episodes interpretations of future unrest must therefore accommodate the possibility that campi flegrei is approaching conditions that are more favourable to a volcanic eruption than has previously been the case such long term accumulation of stress is not expected to be unique to campi flegrei and so might provide a basis for improved forecasts of eruptions at large calderas elsewhere