dependence of volcanic systems on tectonic stress conditions as revealed by features of volcanoes near izu peninsula japan abstract five volcanoes asama fuji izu tobu izu oshima and miyakejima which are aligned along the same volcanic chain in central japan are subjected to different degrees to the stress conditions associated with the continental collision and subduction along wedge shaped trenches near izu peninsula at a great distance from the collision boundary asama is characterized by an axially symmetric edifice with a unique summit crater for magma effusion and miyakejima has a similar symmetric structure accompanied by radial eruptive fissures at the opposite extreme izu tobu which is the closest to the collision boundary consists of many small monogenetic volcanoes that lack a central vent in intermediate locations fuji and izu oshima exhibit elongated volcanic edifices with both summit vents and parallel fissures on their flanks for magma effusion to understand this systematic trend of volcanic features growth of volcanic systems is analyzed based on magma transport in cylindrical conduits and planar fissures available in individual stress conditions it is assumed in this analysis that fissures are produced with extensional stresses or high magma pressures enough to overcome compressive stresses and that cylindrical conduits that have arisen from localization of fissures can be persistently used for repeated magma supply the analysis predicts that volcanoes are classified into the following three types that represent their growth processes in different stress conditions 1 a polygenetic volcano having an axially symmetric edifice grows with unique magma supply through the central conduit under compressive or neutral stresses 2 a polygenetic volcano having an elongated edifice grows with a summit crater and eruptive fissures parallel to the elongation under weak extensions and 3 a group of small monogenetic volcanoes is constructed along many parallel fissures under strong extensions this classification is examined for the five volcanoes and some other volcanoes in the world the alternate occurrences of summit and flank eruptions observed at some polygenetic volcanoes are interpreted to be controlled by the summit height magma densities and stress conditions that influence the pressure of a common magma source

geochemistry of metalliferous hydrothermal deposits in the aeolian arc tyrrhenian sea abstract in shallow water areas of the submerged volcanic complex around the island of panarea aeolian archipelago hydrothermal precipitation of both low temperature fe oxyhydroxide rich red muds and crusts and high temperature sediment hosted massive sulfides was discovered during an integrated high resolution survey iron rich crusts were also found on the bathymetric high of secca del capo north of salina island the exhalative iron rich sediments occur in small closed depressions or in proximity to faults and scarps at water depths ranging from 55 to 285 m the principal chemical characteristics of these deposits are high but variable fe content ranging from 12 2 to 45 and low contents of the transition elements mn cu zn ni and co the low contents of cu ni and co suggest a hydrothermal origin the fe oxyhydroxide deposits are enriched in light rare earth element ree 35 110 chondrite compared to heavy ree 10 25 chondrite their ree patterns are similar to those of associated calc alkaline volcanics negative slope of light ree and a horizontal distribution of the heavy ones this contrasts with the pattern for iron and manganese oxides of hydrogenous origin which have tilted trends of heavy ree paralleling that of seawater the mineralogy of the polymetallic sulfide deposits consists of galena sphalerite pyrite and barite in the form of silt sand grains and decimeter sized fragments disseminated in clay 30 cm below the seabed at a waterdepth of 80 m the chemistry of the aeolian iron rich low temperature deposits and of the high temperature ba rich pb and zn sulfides suggests that they are genetically analogous to respectively the kuroko type iron formation tetsusekiei and the black ore exposed in the miocene hokuroku district of japan

tectonic seismicity at stromboli volcano italy from historical data and seismic records abstract we describe the main features of crustal tectonic seismicity in the area of stromboli aeolian islands a volcano known worldwide for its typical strombolian activity we consider data from the italian catalogues of earthquakes along with records of the local seismic network covering the time span from 1885 to 1998 in the historical catalogues we find a low occurrence rate of earthquakes with a small number of seismic events having intensity viii in the mercalli cancani sieberg scale recent instrumental data confirm this finding achieving a maximum magnitude m d 3 7 we explain this low tectonic seismicity as the effect of conditions which allow only a limited storage of stress from a seismic viewpoint the aeolian archipelago shows two different seismogenic domains spatially separated by the aeolian tindari giardini fault system one domain which includes the western and southern parts of the aeolian islands is characterized by crustal seismic activity the second domain which includes the eastern part of the archipelago where stromboli lies has a large number of intermediate and deep earthquakes but little crustal seismicity we surmise that each domain has vertical heterogeneity separating ductile deformation from brittle failure of rock induced by temperature conditions and or hydration dehydration reactions which affect the mechanical strength of the medium

la fossa caldera breaching and submarine erosion vulcano island italy abstract la fossa caldera lfc on vulcano island in the aeolian archipelago italy is a multi collapse caldera whose north eastern part lies underwater through the integration of marine geophysical surveys and sampling carried out in the last decade its submarine extension and offshore areas have been reconstructed in unprecedented detail strong erosive processes breached the submarine portion of lfc and gradually dismantled the caldera rims and infill leading to the emplacement of a wide volcaniclastic fan from the base of lfc down to over 1000 m the bathy morphologic setting seismoacoustic facies and analyses of sediment samples from the fan together with volumetric considerations suggest that this feature is the pathway deposit of submarine unconfined gravity flows and turbidity currents deriving from the gradual dismantling of lfc submarine erosive processes are still active and the progressive erosion of the northern caldera sector threatens the stability of the active la fossa cone and the nearby coastal settlements

tectonics structural evolution and caldera formation on vulcano island aeolian archipelago southern tyrrhenian sea abstract a detailed structural study and a review of the eruptive history of the island of vulcano aeolian arc southern tyrrhenian sea have been carried out with the purpose of understanding the evolution of both volcanic and tectonic structures the island is composed of four main volcanoes which date from about 120 ka to historical times two calderas occur in the central sector of the island the time space evolution of the volcanism indicates a shifting of the activity from the southeastern sectors towards the northwest two main systems of nw se trending right lateral strike slip faults affect the island ne sw and n s trending normal faults are also present geophysical investigation indicate the nw se trending strike slip faults are likely to be the surface expression of a main regional crustal structure this system of discontinuity is related with the stress field acting in the southern sector of the aeolian archipelago normal n s and ne sw oriented faults represent extensional fractures the ne sw trending structures are related to a local stress field the results of the kinematic analysis as well as the geometric relationships between the faults and the constant subsidence velocities are consistent with the opening of a pull apart basin volcanological and geochronological data are also consistent with the proposed model in the general deformative style affecting the island the calderas can be explained as the consequence of different opening phases of a pull apart basin

vertical and lateral collapses on tenerife canary islands and other volcanic ocean islands recent studies demonstrate that tenerife has undergone large lateral collapses this has led to the suggestion that the las canadas caldera one of the best exposed calderas in the world is the result of lateral collapse we have tested this idea using the available structural stratigraphic volcanological and geochronological data we conclude that the las canadas caldera is the result of a complex sequence of vertical collapse events associated with a long history of phonolitic explosive activity in the central part of tenerife our results indicate however that vertical collapses may have played a major role in triggering lateral collapses we propose that the association of vertical and lateral collapse events such as inferred for tenerife can also explain similar sequences of events interpreted to have affected other large volcanic ocean islands

the ionian and alfeo etna fault zones new segments of an evolving plate boundary in the central mediterranean sea highlights plate boundary re organization in the central mediterranean sea segmentation of the subduction complex along lithospheric transverse faults step faults in the ionian sea pleistocene active faulting and mt etna formation abstract the calabrian arc is a narrow subduction rollback system resulting from africa eurasia plate convergence while crustal shortening is taken up in the accretionary wedge transtensive deformation accounts for margin segmentation along transverse lithospheric faults one of these structures is the nnw sse transtensive fault system connecting the alfeo seamount and the etna volcano alfeo etna fault aef a second nw se crustal discontinuity the ionian fault if separates two lobes of the ca subduction complex western and eastern lobes and impinges on the sicilian coasts south of the messina straits analysis of multichannel seismic reflection profiles shows that 1 the if and the aef are transfer crustal tectonic features bounding a complex deformation zone which produces the downthrown of the western lobe along a set of transtensive fault strands 2 during pleistocene times transtensive faulting reactivated structural boundaries inherited from the mesozoic tethyan domain which acted as thrust faults during the messinian and pliocene 3 the if and the aef and locally the malta escarpment accommodate a recent tectonic event coeval and possibly linked to the mt etna formation regional geodynamic models show that whereas aef and if are neighboring fault systems their individual roles are different faulting primarily resulting from the ese retreat of the ionian slab is expressed in the northwestern part of the if the aef on the other hand is part of the overall dextral shear deformation resulting from differences in africa eurasia motion between the western and eastern sectors of the tyrrhenian margin of northern sicily and accommodating diverging motions in the adjacent compartments which results in rifting processes within the western lobe of the calabrian arc accretionary wedge as such it is primarily associated with africa eurasia relative motion

volcanic geomorphology and tectonics of the aeolian archipelago southern italy based on integrated dem data the geomorphological and morphometric analysis of the sea floor topography surrounding the aeolian islands south tyrrhenian sea italy provides insights into the relationships between the volcanological evolution of the islands and their tectonic features we constructed geomorphological maps of the submarine portions of the seven large edifices constituting the islands on the basis of a dem with a 5 m resolution step these maps include constructional and destructional landforms such as submarine volcanic vents located west of lipari and north of alicudi and hummocky surfaces recognised north of lipari and salina the latter landforms together with the occurrence of large scars affecting the main edifices on land suggest that sector collapses affected some islands geomorphological data indicate that the location of subaerial and submarine vents is strongly controlled by local tectonic structures striking wnw ese alicudi filicudi sector nnw sse salina lipari vulcano sector and ne sw panarea stromboli sector the islands can be divided into two groups on the basis of some morphometric parameters a first group with a pancake like shape dp d abrasion platform diameter basal diameter higher than 0 40 and h d total height basal diameter lower than 0 13 and a second group with a conical shape characterised by dp d lower than 0 34 and h d higher than 0 14 these ratios and other morphometric parameters reflect the different volcanological and structural evolution of the aeolian islands the pancake like shaped complexes have been created in addition to their submarine stage by extrusive and highly explosive activity whereas the cone shaped edifices have been characterised by effusive or moderate explosive activity

continental collision and basin opening in southern italy a new plate subduction in the tyrrhenian sea an analysis of the spatial distribution of the seismicity of the southern tyrrhenian sea is presented with the aim of putting constraints on the geometry of the complex benioff zone of this area by relocating the earthquakes that occurred in the period 1985 1990 the data set used in this analysis is based on information from ing isc and neis databases in order to ensure the quality of epi hypocentral locations we based our selection of earthquakes on both the available number of p and s readings at least eight p and two s pickings and the epicentral distances of the stations reporting the event 5 such a selection enabled us to obtain a catalogue of 450 well located events with focal depths of up to 500 km the seismogenetic volumes estimated from the distribution of hypocentres of the whole seismicity analysed were interpreted according to a recent geodynamic model proposed for this area this has led us to the hypothesis of an active nw se oriented subduction of the lithosphere generated and stressed by the opening of the tyrrhenian basin

relationships among crustal structure volcanism and strike slip tectonics in the lipari vulcano volcanic complex aeolian islands southern tyrrhenian sea italy abstract the lipari vulcano volcanic complex lvvc aeolian arc southern tyrrhenian sea italy develops along a strike slip fault system that bisects the aeolian arc the lvvc crustal structure is investigated by applying seismic methods to two data sets p wavefronts generated by local and distant events constrain the shallow velocity structure dss data provide shape and depth of the main crustal discontinuities the obtained velocity model shows that the lvvc shallow structure is characterized by the presence of two sharp lateral discontinuities the northern discontinuity bounds a low velocity basin like structure including the la fossa caldera and mt guardia caldera depressions the southern discontinuity coincides with the southern boundary of a high velocity diffractor located beneath the la fossa cone direct modeling of dss data define three crustal discontinuities showing a complex geometry the intra crustal interfaces and the moho discontinuity show an upheaval beneath the lvvc central sector the estimated crustal velocities are lower than those generally reported for the continental crust this feature is due to the high heat flux and fluid circulation affecting the lvvc area the ratio between the thickness of the upper and lower crust and the presence of the moho upheaval are consistent with that reported for continental areas affected by extensional strain the collected geophysical data combined with volcanological and structural information indicate that a the mt guardia and la fossa caldera depressions represent the surface expression of a single structure whose formation is mainly due to tectonic processes b the lvvc crustal structure and the evolution of the volcanism are consistent with those recognized in zones of transition from arc related to rift volcanism in addition results of a preliminary mechanical analysis based on the available structural data indicate low values of the ratio between magmatic overpressure and tectonic stress this suggests a passive mechanism of mantle upwelling the mantle upwelling is due the post collisional normal strike slip tectonics affecting the aeolian arc

the role of the crust in the magmatic evolution of the island of lipari aeolian islands italy volcanic rocks on the island of lipari show the entire range of sr nd pb isotopic compositions displayed by other islands in the aeolian archipelago the rapid isotopic evolution of subaerial volcanic rocks on lipari towards crustal values together with the appropriate isotopic composition of the neighbouring calabrian crust serre indicate that many geochemical characteristics observed in the lavas can be attributed to contamination and mixing with crustal materials and melts interpretation of the data is complicated by the fact that underplating onto the crust mantle boundary and the specific lithologies present in the crustal section differ underneath each individual sector of the island in the central and northern parts of the island metapelitic rocks were incorporated to provide the more radiogenic sr isotopic compositions of some lavas the products from m guardia in the southern part of lipari where activity is restricted to the last 30 40 ka bear geochemical similarities to the island of vulcano where it is proposed that considerable remobilization of the crust took place in the presence of mafic mantle derived melts on lipari the petrogenetic processes of magma mixing and assimilation dominate over fractional crystallization and the observed increase of k2o over na2o can be correlated with contributions from metapelitic crustal lithologies it is suggested that the variability in isotopic composition and the budget of alkalis na2o versus k2o in the lavas can be explained by invoking a heat source from an intruding asthenospheric morb type mantle into a cooler lithospheric crust mantle during the opening of the tyrrhenian basin

rock magnetism and compositional investigation of brown tuffs deposits at lipari and vulcano aeolian islands italy abstract a rock magnetic investigation was carried out on the nonwelded ash deposits of the brown tuffs aeolian islands southern tyrrhenian sea to improve the stratigraphic correlation between the deposits cropping out on lipari and vulcano islands and locate their source area the study was supplemented by petrographical and geochemical analyses on selected strata with the intent to compare the brown tuffs to other rocks emplaced at vulcano in the same time span more than 30 levels were sampled in the intermediate 56 4 ka ibt 21 22 ka and upper 21 22 ka ubt parts of the brown tuffs sequences on the two islands their characteristic remanent magnetization chrm directions were derived from stepwise thermal demagnetization and the magnetic fabric from measurements of the anisotropy of magnetic susceptibility the levels with indistinguishable chrm directions were regarded as coeval and to form an individual stratigraphic unit the units were referred to the brown tuffs sequence of lucchi et al 2008 on the grounds of their emplacement age provided by comparison of their mean paleomagnetic direction with the paleosecular variation curves of the southern tyrrhenian region as well as the field constraints the closer correlation between the sequences of lipari and vulcano contributes to a better understanding of the volcanic activity that produced the brown tuffs and shows that most of the ibt and the oldest ubt levels were emplaced in a short time span between 24 and 20 17 ka the magnetic fabric is typically well developed but at most sites the magnetic foliation is very close to horizontal and no imbrication is defined the source area of the brown tuffs parent pyroclastic flows as constrained from the intersection of the magnetic lineations falls in the northeastern part of la fossa caldera structure although limited to major elements compositional data provide further indication about the parent plumbing system and its behaviour magma batch es involved in the ibt eruptions have homogeneous features and underwent frequent refilling and tapping processes conversely those involved in the early ubt eruptions are compositionally more variable this suggests more complex evolution and plumbing system activity the ubt eruptions represent either residual mafic magmas from the previous eruptions or the arrival of new fresh shoshonitic magma in the system

petrology and geochemistry of volcanic rocks from the island of panarea implications for mantle evolution beneath the aeolian island arc southern tyrrhenian sea abstract major trace element and radiogenic isotope sr nd pb data are reported for a suite of rocks from the panarea volcano a large structure that is largely hidden below sea level and outcrops only as a group of small islands between lipari vulcano and stromboli in the eastern aeolian arc the exposed rocks mostly consist of high potassium calc alkaline hkca andesites dacites and some rhyolites shoshonitic basalts have been collected from submarine centres mafic calc alkaline ca rocks occur as thin layers of late erupted strombolian scoriae major and trace element data are scattered but define generally linear trends on inter element diagrams sr isotope ratios do not display significant increase with evolution although rough positive trends of 87sr 86sr versus sio2 and rb sr can be recognised within some units the mafic rocks display varying enrichment in potassium from ca to shoshonitic compositions and are characterised by variable abundances of incompatible trace elements which increase with potassium there is an increase of 87sr 86sr ratios and a decrease of 143nd 144nd and 206pb 204pb ratios from ca to hkca and shoshonitic mafic rocks the scattered and incomplete nature of the outcrops make it difficult to constrain magmatic evolution at panarea geochemical and isotopic data suggest that afc and mixing were important evolutionary processes however geochemical modelling does not support the possibility that the first order compositional variations observed in the mafic rocks are the result of these processes and suggests a genesis in a heterogeneous mantle source recent studies have highlighted strong differences in terms of incompatible trace element ratios and isotopic signatures between the western central and the eastern aeolian arc rocks from the western islands alicudi filicudi salina vulcano have typical magmatic arc geochemical signatures and relatively unradiogenic sr isotope compositions by contrast the eastern island of stromboli has a more radiogenic sr isotope signature and shows trace element abundances and ratios that are intermediate between arc and intraplate compositions panarea mafic rocks have geochemical and isotopic signatures that are intermediate between those observed in the two sectors of the arc the late erupted ca scoriae of panarea have trace element and isotopic compositions similar to those of the mafic rocks from the western islands of filicudi and alicudi whereas the hkca and shoshonitic mafic rocks have isotopic and trace element signatures that are closer to those of stromboli this reflects the particular position of panarea which is sited midway between the western central arc and stromboli according to some recent views subduction of the ionian sea plate is actively occurring beneath the eastern aeolian arc with rollback of the subduction zone toward the southeast the tindari letoianni malta escarpment fault zone is considered to be the boundary between the active subducting plate in the east and the african plate and western aeolian arc in the west it is suggested that the rollback of the ionian plate generated inflow of mantle material from below the western arc into the mantle wedge above the subducting ionian slab this situation generated a hybrid mantle beneath panarea which resulted in a mixture of western type and resident eastern arc mantle materials the latter had a composition akin to the source of stromboli magmas early hkca and shoshonitic magmatism tapped such a hybrid source whereas the younger ca activity has been derived from melting of unmodified western type mantle material the late eruption of ca rocks with a composition similar to western arc can be explained by assuming that a continuing inflow process had increased the amount of western type mantle with time thus favouring the late appearance of ca magmas this hypothesis accounts for the overall decrease of potassium with time which is the opposite of the trend observed in other aeolian islands

a global database of composite volcano morphometry we present a global database on the subaerial morphometry of composite volcanoes data was extracted from the 90 m resolution shuttle radar topography mission srtm digital elevation model dem the 759 volcanoes included in the database are the composite i e polygenetic volcanoes listed in the smithsonian institution global volcanism program gvp database that are covered by the srtm dem have a constructional topography and a basal width larger than 2 km the extent of each volcano edifice was defined using the netvolc algorithm which computes outlines by minimizing a cost function based on breaks in slope around the edifices morphometric parameters were then calculated using the morvolc algorithm the parameters characterize and quantify volcano size basal width summit width height and volume profile shape height basal width and summit width basal width ratios plan shape ellipticity and irregularity indexes and slopes in addition 104 well defined and relatively large summit craters calderas were manually delineated and specific parameters were computed most parameters show large variation without clear separations indicating a continuum of volcano morphologies large overlap between the main gvp morphologic types highlights the need for a more rigorous quantitative classification of volcano morphology the database will be maintained and updated through a website under construction

aeromagnetic anomalies reveal hidden tectonic and volcanic structures in the central sector of the aeolian islands southern tyrrhenian sea italy 1 salina island italy in the central aeolian chain is the northernmost volcanic structure of an elongated ridge on a regional shear zone with nnw sse strike slip faults and second order n s and ne sw faults modeling of high resolution low altitude aeromagnetic data collected in 2003 and 2005 using volcanological data constraints reveals the inner structure of the salina volcanoes and surrounding marine regions regional negative anomalies overlie e w elongated sedimentary basins related to the early pliocene pleistocene opening of the southern tyrrhenian sea these negative anomalies flank positively magnetized crust of salina and seamounts off its eastern coast where the shorter wavelength anomalies map late pleistocene holocene volcanic conduits dikes and faults the magnetic and volcanological data indicate that the early circa 168 100 ka basaltic to andesitic salina volcanism developed along n s and ne sw tectonic faults whereas the more recent andesitic lavas and rhyolitic pyroclastics circa 100 13 ka were emitted by vents related to the main nw se faults the tectonic structures also controlled the location of the seamounts around the island and the geometry of the volcano tectonic collapses salina volcanism was emplaced on a nnw sse tear fault of the presently developing roll back slab in the southern tyrrhenian sea

the role of slab detachment processes in the opening of the western central mediterranean basins some geological and geophysical evidence abstract a review of the geological and geophysical data from the central and western mediterranean region and the present day upper mantle structure derived from tomographic studies are utilized in order to define the oligocene recent geodynamic evolution for the area in line with previous work we suggest that the miocene quaternary opening of the western and central mediterranean basins is the result of back arc extension due to the roll back toward the southeast of a northwestward subducting african slab in a geodynamic setting pinned between the alpine and betic collisional zones we find however that this general pattern is complicated by four different detachment events which occurred beneath the alps early oligocene the betic chain aquitanian northern africa langhian and the apennines late miocene pliocene we show that each of these events determines a major tectonic reorganization within the european plate

compositional spatial zonation and 2005 2013 temporal evolution of the hydrothermal magmatic fluids from the submarine fumarolic field at panarea island aeolian archipelago southern italy abstract the november 2002 submarine gas blast at panarea island sicily southern italy was an unexpected reactivation event able to locally affect this hydrothermal magmatic system whose the youngest eruptive products were dated at 20 000 2000 years bp the presence of magmatic gases so 2 and hf in the fumarolic gas discharges after the violent exhalative event was indicative of a magmatic input that temporary displaced the hydrothermal system a few months later these acidic gases were indeed not detected in any of the studied fumaroles nevertheless new geochemical data obtained by periodical sampling up to june 2013 suggest that the chemical physical conditions of the hydrothermal magmatic system at panarea were not completely restored with respect to the geochemical data obtained in the early nineties thus the 2002 gas burst has unequivocally caused a permanent modification to the fluid circulation system feeding the submarine fumaroles in addition strong compositional differences were observed by the 46 gases collected in 2012 2013 from submarine fumaroles located in different sites of the studied area allowing to distinguish three different groups of fumaroles a h 2 and co rich gases which also show relatively low ar concentrations b h 2 s rich gases having variable co ch 4 ratios and c ar rich gases having relatively low h 2 concentrations gases from group a are distributed along nw and ne trending fault systems whereas those of groups b and c discharge at increasing distance from the intersection of the two fault systems indicating a spatial and compositional control by the local tectonic setting the h 2 co ratios of groups a and b gases are significantly lower than those measured prior to 2012 this would imply an increase of gas pressure at depth possibly caused by continuous addition of gas and energy from the magmatic source to the hydrothermal reservoir continuation of this process may lead to the occurrence of gas burst events in the next future a hypothesis that is supported by the strong ongoing degassing activity at the surface notwithstanding a decrease of temperatures at depth a geochemical seismological and ground deformation monitoring of the panarea submarine fumarolic field is highly recommended to obtain precursory signals of new strong degassing phenomena

mechanical relationship between catastrophic volcanic landslides and caldera collapses large scale sector collapses of volcanic edifices and collapse calderas represent some of the most catastrophic geological events taking place at the earth s surface examples of these two processes occurring simultaneously suggest that a mechanical relationship between landslides and collapse calderas may exist we demonstrate that a caldera collapse can trigger large scale landslides in volcanic terrains moderate seismic shocks caused by seismogenic slip on the ring fault on which the caldera subsidence takes place act as the driving force necessary to destabilize the volcano flank this process is favored on steep volcanoes and where flank strength is reduced by agents such as hydrothermal alteration pore fluid pressure increase or the presence of weak soils

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

shallow water polymetallic sulfide deposits in the aeolian island arc back arc basins represent the best known present day sites of ongoing massive sulfide deposition in subduction related tectonic settings here we present results obtained from shallow water sea floor sampling of barium rich zinc and lead sulfides genetically analogous to kuroko type black ore on an active island arc the samples come from a newly discovered hydrothermally active depression on the submerged volcanic edifice of panarea in the aeolian island arc tyrrhenian sea hydrothermal activity in the area is represented by extensive gas venting associated with white sea floor aprons of sulfate and iron oxide precipitates a series of barite rich sediment samples containing galena sphalerite and pyrite was recovered 40 cm below the sea bed at a water depth of 80 m the deposits represent a unique example of massive sulfide deposition in an active island arc not yet affected by strong extensional tectonics and reveal that in this environment the formation of kuroko type black ore sulfides can take place at shallow water depths

the monte guardia eruption lipari aeolian islands an example of a reversely zoned magma mixing sequence the monte guardia rhyolitic eruption 22 ka lipari aeolian islands italy produced a sequence of pyroclastic deposits followed by the emplacement of lava domes the total volume of dense magma erupted was nearly 0 5 km3 the juvenile clasts in the pyroclastic deposits display a variety of magma mixing evidence mafic magmatic enclaves streaky pumices mineral disequilibria and heterogeneous glass composition petrographic mineralogical and geochemical investigations and melt inclusion studies were carried out on the juvenile clasts in order to reconstruct the mixing process and to assess the pre eruptive chemico physical magmatic conditions the results suggest that the different mingling and mixing textures were generated during a single mixing event between a latitic and a rhyolitic end member a denser mixed magma was first erupted followed by a larger volume of an unmixed lighter rhyolitic one this compositional sequence is the reverse of what would be expected from the tapping of a zoned magma chamber the monte guardia rhyolitic magma stored below 200 mpa was volatile rich and fluid saturated or very close to this despite its relatively low explosivity in contrast to previous interpretations there exists the possibility that the rhyolite could rise and erupt without the trigger of a mafic input the entire data collected are compatible with two possible mechanisms that would generate a reversely zoned sequence 1 the occurrence of thermal instabilities in a density stratified salic to mafic magma chamber and 2 the intrusion of rising rhyolite into a shallower mafic sill dike

growth and mass wasting of volcanic centers in the northern south sandwich arc south atlantic revealed by new multibeam mapping new multibeam swath bathymetric sonar data acquired using an em120 system on the rrs james clark ross supplemented by sub bottom profiling reveals the underwater morphology of a not vert similar 12 000 km2 area in the northern part of the mainly submarine south sandwich volcanic arc the new data extend between 55 45 s and 57 20 s and include protector shoal and the areas around zavodovski visokoi and the candlemas islands groups each of these areas is a discrete volcanic center the entirely submarine protector shoal area close to the northern limit of the arc forms a 55 km long east west trending seamount chain that is at least partly of silicic composition the seamounts are comparable to small subaerial stratovolcanoes in size with volumes up to 83 km3 indicating that they are the product of multiple eruptions over extended periods zavodovski visokoi and the candlemas island group are the summits of three 3 3 5 km high volcanic edifices the bathymetric data show evidence for relationships between constructional volcanic features including migrating volcanic centers structurally controlled constructional ridges satellite lava flows and domes and mass wasting of the edifices mass wasting takes place mainly by strong erosion at sea level and dispersal of this material along chutes probably as turbidity currents and other mass flows that deposit in extensive sediment wave fields large scale mass wasting structures include movement of unconsolidated debris in slides slumps and debris avalanches volcanism is migrating westward relative to the underlying plate and major volcanoes are asymmetrical being steep with abundant recent volcanism on their western flanks and gently sloping with extinct eroded volcanic sequences to their east this is consistent with the calculated rate of subduction erosion of the fore arc

the calabrian arc and the ionian sea in the dynamic evolution of the central mediterranean in the central mediterranean area it is possible to recognize three main realms the tyrrhenian sea the pelagian block and the ionian block these domains are limited by important fracture zones that are easily recognizable on land and offshore these fracture zones can be grouped into four main trends 1 the nw se trend which is characterized by dextral horizontal movements 2 the ne sw trend which is generally characterized by sinistral lateral horizontal movements 3 the e w trend which also shows dextral shear movements and 4 the n s trend which is characterized by normal faults only the tyrrhenian sea realm is characterized by a thinned crust of oceanic type and is connected to the apenninic chain by means of listric faults from a geophysical point of view the area shows a high heat flow which follows the main structural trends and positive gravimetric anomalies which are compatible with seismic refraction data and can be explained by the proposed model the pelagian block shows a continental crust about 20 km thick which progressively increases beneath the sicilian chain here an abrupt interruption with the tyrrhenian block takes place in the pelagian realm rifting processes developed according to the nw se and n s trend the n s trend characterizes the westernmost zone of the realm where volcanic processes and a relatively high heat flow can also be observed the ionian block is characterized by the following a thinned crust 17 20 km which increases 40 km towards the southern calabrian chain a thick sedimentary sequence high positive bouguer anomalies 300 mgal and very low heat flow 50 mw m 2 geophysical and structural analyses allowed us to evaluate the post tortonian evolution of the whole area under consideration this evolution resulted in continental crust formation according to a rigid plastic deformation model according to our model the ionian block can be considered as a domain characterized by a thinned continental crust and affected by intrusive material derived from the upper mantle furthermore this domain of probably jurassic age can be considered as a pelagic basin bordered by the pelagian block to the west and by the apulian block to the east northeast this basin according to its position with respect to the apenninic and sicilian chains has not been affected by tectogenesis and still represents a site of continuous sedimentation from a kinematic point of view the ionian realm can be linked with the pelagian block shifting towards the east northeast whereas it is limited towards the north by an e w fracture zone which regulates the opening of the tyrrhenian sea and the counterclockwise rotation of the apenninic chain according to the proposed model the opening of the tyrrhenian sea can be considered as a megaextension fracture which developed parallel to the maximum principal stress direction and evolved as a triangular shaped structural feature in preparing the model the authors have taken into account a large set of data collected both on land and offshore

interactions between volcanism and tectonics in the western aeolian sector southern tyrrhenian sea summary new high resolution bathymetric and magnetic data from the western aeolian sector southern tyrrhenian sea provide insights into structural and volcanic development of the area suggesting a strong interaction between volcanism and tectonics the analysis of these data combined with relocated earthquake distribution focal plane solutions and strain rate evaluation indicates that the dextral strike slip sisifo alicudi shear zone is a complex and wide area of active deformation representing the superficial expression of the deep seated lithospheric tear fault separating the subduction slab below sicily and calabria most of the observed volcanic features are aligned along a nw se trend such as the filicudi island alicudi north seamount and eolo enarete alignments and are dissected by hundred metre high scarps along conjugate nne ssw trending fault systems the magnetic field pattern matches the main trends of volcanic features spectral analysis and euler deconvolution of magnetic anomalies show the existence of both deep and shallow sources high amplitude high frequency anomalies due to shallow sources are dominant close to the volcanic edifices of alicudi and filicudi while the main contribution on the surrounding eolo enarete alicudi north and filicudi north seamounts is given by low amplitude anomalies and or deeper magnetic sources this is probably related to different ages of the volcanic rocks although hydrothermal processes may have played an important role in blanketing magnetic anomalies in particular at enarete and eolo seamounts relative chronology of the eruptive centres and the inferred deformation pattern outline the quaternary evolution of the western aeolian arc sisifo alicudi north and filicudi north seamounts might have developed in an early stage following the late pliocene early pleistocene se ward migration of arc related volcanism due to the ionian subduction hinge retreat eolo enarete and filicudi represent later manifestations that led volcanoes to develop during mid late pleistocene when the stress regime in the area changed due to the sse ward propagation of the subduction slab tear fault and the consequent reorientation and decrease of trench migration velocity finally volcanic activity occurred in a very short time span at alicudi where an almost conical volcanic edifice emerged suggesting negligible interactions with regional fault systems

a giant landslide on the north flank of tenerife canary islands the extent of mass wasting along the north flank of tenerife has been mapped using swath bathymetry gloria side scan sonar and 3 5 khz echo sounder data the marine surveys show that north of tenerife a giant landslide is exposed over an area of 5500 km2 of the seafloor more than twice the surface area of the island the landslide truncates an older ridge and valley topography that is associated with the shield building basalts on tenerife we interpret the ridge and valley topography as the result of subaerial erosion the landslide is estimated to have a length of 100 km a width of up to 80 km and a volume of about 1000 km3 it extends onshore into the orotava and icod valleys which have been interpreted as of landslide origin k ar dating of basaltic flows in the steep headwall of orotava suggests an age of formation for the valley is younger than 0 78 ma and may even be younger than 0 27 ma the icod valley is located immediately to the north of the most recent volcano on tenerife las canadas and has been associated with the collapse of its caldera between 1 2 and 0 2 ma a young age for the landslide is supported by the 3 5 khz echo sounder data which show that the landslide is draped by a thin 10 m layer of younger sediment the landslide did not form however during a single catastrophic event but represents the amalgamation of a number of separate landslides the occurrence of the ridge and valley topography in water depths of up to 2 5 km suggests that the shield building basalts have subsided by at least this amount since they formed 3 3 8 0 ma we speculate that this subsidence is caused by some form of stress relaxation that occurs in the underlying lithosphere the giant landslide imaged in our sonar data is associated with the late stages in the development of the most recent volcano on tenerife las canadas which only began at about 1 8 ma thus landsliding may be a particular feature of the time soon after emplacement when because of incomplete isostatic adjustment oceanic volcanoes have their greatest elevations above sea level and therefore are most susceptible to slope failure

systematic morphometric characterization of volcanic edifices using digital elevation models abstract quantitative characterization of the size and shape of volcanic edifices is an essential step towards the understanding of factors controlling volcano growth and morphology the recent advent of digital elevation models dems with worldwide coverage offers the opportunity to systematically document the morphometry of all types of volcanoes using quantitative well formalized methodologies we present a methodology for the morphometric characterization of volcanic edifices after reviewing previous studies on volcano morphometry and the various existing dem sources we describe an integrated procedure that uses a dem and its derived products slope curvature to extract a coherent set of morphometric parameters for a given volcanic edifice edifice boundaries are manually defined by searching for breaks in slope around the base the parameters describe the overall size basal and summit region area and widths height volume planar shape ellipticity and irregularity index of elevation contours profile shape height width ratios and slope of the edifice similar parameters for relatively large depending on dem spatial resolution summit craters calderas are also computed slope values and ellipticity and irregularity indexes are extracted for successive height intervals providing detailed information of volcano shape as a function of height the number of secondary peaks is also estimated the method is tested on thirteen composite volcanoes in nicaragua using three dem datasets 90 m srtm 30 m aster g dem and an 80 m topographic map derived dem and the resulting parameters are evaluated in terms of boundary delineation and dem source finally the parameters obtained for the nicaraguan volcanoes are discussed as an illustrative example of the type of data and information that can be extracted systematically for volcanoes worldwide

multiple sector collapses at stromboli volcano italy how they work this paper demonstrates that four large sector collapses have affected the nw flank of the stromboli volcano in the past 13 ka alternating with growth phases in order to contribute to the evaluation of the critical conditions which trigger lateral collapses a reconstruction of the geometry of each collapse of the volcano edifice in the four stages that preceded the relative collapse events is also presented and a computation of the landslide volume this reconstruction is based on new field data plotted in three dimensions prior to the initial 13 ka collapse the volcano was 1125 100 m high above sea level the collapse had a volume of 2 23 0 87 km3 whereas the pre collapse volcano volume was 218 8 7 7 km3 the next edifice that failed was 900 70 m high a s l the collapse volume was 1 0 54 km3 with a precollapse volcano volume of 201 4 5 4 km3 the edifice then grew to 1000 60 m a s l the third collapse had a volume of 1 08 0 39 km3 and occurred within a volcano with a volume of 209 1 4 6 km3 this was followed by a new growth phase followed by the last collapse with a volume of 0 73 0 22 km3 the volcano volume was about the same as the present one the present active crater zone is at 780 m a s l in the first three collapses sliding surfaces cut the main magma conduit in the last collapse the upper scarp coincided with the conduit location dyking along a main ne trending weakness zone across the volcano summit exerted a lateral force for collapse inception the decrease of the landslide volumes with the age and the concentric scarps of the four collapses suggest that the younger sliding planes tended to become more superficial and to decrease the areal extent this is interpreted as due to a successively weaker eruptive products from dominantly lavas to dominantly pyroclastics and b the feedback effects between collapses and dykes that injected along the lateral segments of the first collapse slide plane

marine continental tephra correlations volcanic glass geochemistry from the marsili basin and the aeolian islands southern tyrrhenian sea italy abstract major minor and trace element analysis of volcanic glass in proximal and distal it is evident that correlation of proximal continental and distal marine tephras at a high level of confidence requires a full complement of major minor and trace element data in conjunction with considerations of the mineralogy and morphology of juvenile deposits these data help define petrological lineages such that precise provenance can be established whilst a precise proximal distal match must be based on identical major minor and trace element concentrations it is clear that resurgent activity from a single volcano can produce magmas with identical compositions in such cases stratigraphic relationships must complement any geochemical study occasionally proximal stratigraphies may be unrepresentative of the complete eruptive history because of a lack of exposure due to burial by more recent effusive and explosive activity or sector collapse which can remove vital stratigraphy particularly on volcanic islands

recurrent large scale landsliding on the west flank of la palma canary islands a large area of debris avalanche deposits has been discovered on the western submarine flanks of the island of la palma multibeam bathymetry and its derivative backscatter data towed ocean bottom instrument tobi sidescan sonar images and 3 5 khz and airgun seismic reflection data have been used to identify at least two and possibly as many as four major landslide events the youngest of the events the cumbre nueva debris avalanche extends onshore into the valleys bounded by the caldera de taburiente and cumbre nueva ridge which mark the degraded collapse scars radiometric dating of the volcanic flows in the headwall indicate an age of between 536 and 125 ka for this landslide the debris avalanche covers an area of 780 km2 has a maximum thickness of 500 m and has an estimated volume of 95 km3 older deposits collectively referred to as the playa de la veta debris avalanche complex are probably as the name indicates an amalgamation of at least two or three events rather than the result of a single catastrophic failure the playa de la veta debris avalanche complex is associated onshore with an unconformity dated as late matuyama 1 ma to 800 ka it covers an area of 1200 km2 has a maximum thickness of 1300 m and may represent a total volume of up to 650 km3 the greater thicknesses and limited areas occupied by debris avalanches on the western flank of la palma compared to other landslides in the canary archipelago suggest that the la palma landslide masses have relatively low mobility the different debris avalanche lobes formed by each landslide event are separated by channels 2 2 5 km wide the clear relationship between channel position and the boundaries of each debris avalanche lobe indicates that debris avalanches control later channel formation and pathways the relief of the submarine flanks of the la palma volcanoes in the areas of island slope unaffected by landslides is mainly the result of constructional volcanic processes however the older submarine slopes such as in the northern taburiente volcano may also have been modified by smaller scale submarine mass wasting and sediment flows

tectonic and volcanic evolution of panarea aeolian islands italy abstract based on new geophysical volcanological structural and radiometric data a morphological structural reconstruction of the submarine part of the panarea volcanic edifice is provided and a model for the evolution of the entire complex is proposed panarea is a small part of a much larger submarine edifice whose overall shape is one of a truncated cone with an eastern protrusion the base of the cone is about 1500 m below sea level it has a diameter of about 23 km and an area of 460 km2 several lobes are present on the steep eastern slopes of the cone and the wide submarine top is of a morphology which is more complex than previously thought the evolution of the panarea volcanic complex occurred in three stages 1 1 development of a central volcano in the western sector of the complex the island of panarea represents the top of this volcano 2 2 eastward shifting of volcanic activity producing development of the lobed eastern sector of the complex 3 3 extensive caldera collapse of the central part of the complex and emplacement within the collapsed area of domes and lava bodies of various affinities some of which are basaltic ne sw oriented structures seem to have had a fundamental role during the development of the panarea volcanic complex these structures have been active until recent times and are of regional significance indeed the evolution of nearby stromboli has been controlled by the ne sw trending structures panarea and stromboli also display similar magnetic anomaly trends geochemical affinities and temporal relationships in volcanism

volcanological and magmatological evolution of stromboli volcano aeolian islands the roles of fractional crystallization magma mixing crustal contamination and source heterogeneity the present paper reports the results of a detailed stratigraphical petrological and geochemical investigation on the island of stromboli aeolian arc southern tyrrhenian sea major and trace element data determined on a large quantity of samples from well established stratigraphic positions indicate that the magmatological evolution of the island through time was more complex than previously known the activity of the exposed part of stromboli which occurred over a time span of about 100 000 years started with the emission of high k calc alkaline hkca volcanics which were covered by calc alkaline ca shoshonitic sho high k calc alkaline hkca and potassic ks products the most recent activity consists of hkca lavas and the present day sho basaltic volcanics emitted by mildly explosive strombolian activity most of the products are lavas with minor amounts of pyroclastic rocks emplaced mainly during the early stages of activity the transition from the sho to the ks cycle was associated with the collapse of the upper part of the volcanic apparatus the transition from ks to the present day sho activity has been found to have occurred at the time of the sliding of the western portion of the volcano that generated the sciara del fuoco depression the rock series cropping out at stromboli show variable enrichment in potassium incompatible trace elements and radiogenic sr which increase from ca through hkca and sho up to ks rocks major trace element and sr isotopic data agree in indicating that the hkca and sho series evolved by crystal liquid fractionation starting from different parental liquids whereas crustal assimilation appears to have been the leading process during the evolution of ks volcanics mixing processes also played a role although they can be well documented only when they occurred between magmas with different isotopic and geochemical characteristics geochemical modelling based on trace element and isotopic data indicates that the mafic magmas of the different volcanic series may be generated by melting of an upper mantle heterogeneously enriched in incompatible elements and radiogenic sr by addition via subduction of different amounts of crustal material geochemical data however are also in agreement with the alternative hypothesis that the most mafic magmas of the different series have been generated by combined processes of fractional crystallization assimilation and mixing of a ca magma in a deep sited magma chamber the mafic magmas formed by these complex processes were successively emplaced in a shallow reservoir where they evolved by simple fractional crystallization hkca and sho series and by assimilation of crustal material ks the occurrence of changes in the geochemical signatures of the magmas at the time of the structural modification of the volcano is believed to favour the hypothesis that the variable composition observed in the volcanic rocks of stromboli is the result of processes occurring within the volcanic system

reply to comments to volcanic geomorphology and tectonics of the aeolian archipelago southern italy based on integrated dem data by favalli et al bull volcanol 68 157 170 2005 doi 10 1007 s00445 005 0429 3 by calanchi et al 2007 bull volcanol doi 10 1007 s00445 007 0134 5

provenance of volcaniclastic beach sand in a magmatic arc setting an example from lipari island aeolian archipelago tyrrhenian sea lipari an active volcanic island in the aeolian magmatic arc is an excellent area to determine the effects of multiple source lithology climate weathering transport and depositional environment on epiclastic sand composition volcaniclastic sand samples from 12 modern beaches were petrographically characterized using the gazzi dickinson method and the proportions of source rocks in combination with topography in associated coastal drainage basins were quantified using gis several types of bedrock in the 12 drainage basins that are the likely prominent sources for sand at each sampled beach were recognized and divided into two categories of provenance lithotypes lavas and pyroclastic rocks ranging in composition from basaltic andesitic to andesitic to rhyolitic volcanic lithic fragments from lipari beach sand consist of colourless and black glassy volcanic fragments with lathwork felsitic vitric and microlitic textures moreover high amounts of detrital less durable minerals such as pyroxene olivine and fe oxides illustrate how the analysed sands preserve the source rock s provenance signals applying the concept of sand generation index we see that these lithotypes have different propensities to create detritus in terms of both grain size and composition clastic contribution from pyroclastic rock outcrops such as pumice is not found in the size ranges studied suggesting that these pumiceous source rocks probably only produce gravel or very fine sand and silt this finding has implications for the stratigraphic record because pumice clasts ranging from medium to fine grain size could be underrepresented in older volcaniclastic deposits and overrepresented in other size fractions

morphology of the faial island shelf azores the interplay between volcanic erosional depositional tectonic and mass wasting processes 1 the extents of volcanic island shelves result from surf erosion which enlarges them and volcanic progradation which reduces them however mass wasting tectonics and sediment deposition also contribute to their morphology in order to assess the relative significance of these various processes we have mapped in detail faial island s shelf in the azores archipelago based on interpretation of geophysical and geological data the nearshore substrates of the island down to 30 50 m depth are rocky and covered by volcaniclastic boulder deposits formed by surf action on now submerged lava flows below those depths sandy and gravel volcaniclastic beds dominate building clinoforms up to the shelf edge in some sectors of the coast prograding lava has narrowed the shelf but in contrast to nearby pico island we find fewer submarine emplaced lavas on the shelf in this island we interpret the distance between the coastline and the shelf edge as almost entirely a result of a straightforward competition between surf erosion and lava progradation in which erosion dominates therefore shelf width can be used as a proxy for coastline age as well as for wave energy exposure the stratigraphy of shelf deposits in boomer seismic data is examined in detail to assess the roles of different sediment sources accommodation space and wave exposure in creating these deposits we also show evidence of mass wasting at the shelf edge and discuss the possible origins of slope instability finally we discuss the contributing role of tectonics for the development of the shelf

multiple hazards and paths to eruptions a review of the volcanic system of vulcano aeolian islands italy abstract vulcano is one of the 7 volcanic islands and 6 seamounts forming the aeolian volcanic district italy vulcano has a long eruptive record and its last eruption 1888 90 originated the definition of the vulcanian eruptive style like most volcanic islands vulcano generates many potentially interconnected hazards determining a potentially high risk here we review the state of knowledge on its geology eruptive activity historical accounts structural setting geophysical and geochemical surveillance and available hazard quantifications in order to have an updated picture of the state knowledge on volcanic hazard we follow a prototypal reviewing scheme based on three standardized steps i review of the volcanic system ii review of available eruptive and non eruptive hazard quantifications iii development of a conceptual interpretative model we find that while a rather vast literature is dedicated to the volcanic system of vulcano and the reconstruction of past events few quantitative hazard assessments exist in addition the range of natural variability considered for each hazard is potentially underestimated e g limited range of considered eruption magnitude and style and of vent position as it is the potential effect of multi hazard impact the developed conceptual model for the feeding system provides a synthetic picture of the present knowledge about the system as emerged from the review in addition it allows for the identification of potential paths to eruption and provides a first order link among the main hazards this review provides an up to date snapshot of existing knowledge on volcanic hazard at vulcano on which to build future hazard quantifications as well as to support present and future decision making

explosion craters associated with shallow submarine gas venting off panarea island italy explosions of hot water steam and gas are common periodic events of subaerial geothermal systems these highly destructive events may cause loss of life and substantial damage to infrastructure especially in densely populated areas and where geothermal systems are actively exploited for energy we report on the occurrence of a large number of explosion craters associated with the offshore venting of gas and thermal waters at the volcanic island of panarea italy demonstrating that violent explosions similar to those observed on land also are common in the shallow submarine environment with diameters ranging from 5 to over 100 m the observed circular seafloor depressions record a history of major gas explosions caused by frequent perturbation of the submarine geothermal system over the past 10 000 years estimates of the total gas flux indicate that the panarea geothermal system released over 70 mt of co2 over this period of time suggesting that co2 venting at submerged arc volcanoes contributes significantly to the global atmospheric budget of this greenhouse gas the findings at panarea highlight that shallow submarine gas explosions represent a previously unrecognized volcanic hazard around populated volcanic islands that needs to be taken into account in the development of risk management strategies

reconstructing the vulcano island evolution from 3d modeling of magnetic signatures abstract high resolution ground and marine magnetic data are exploited for a detailed definition of a 3d model of the vulcano island volcanic complex the resulting 3d magnetic imaging obtained by 3 d inverse modeling technique has delivered useful constraints both to reconstruct the vulcano island evolution and to be used as input data for volcanic hazard assessment models our results constrained the depth and geometry of the main geo structural features revealing more subsurface volcanic structures than exposed ones and allowing to elucidate the relationships between them the recognition of two different magnetization sectors approximatively coincident with the structural depressions of piano caldera in the southern half of the island and la fossa caldera at the north suggests a complex structural and volcanic evolution magnetic highs identified across the southern half of the island reflect the main crystallized feeding systems intrusions and buried vents whose nnw sse preferential alignment highlights the role of the nnw sse tindari letojanni regional system from the initial activity of the submarine edifice to the more recent activity of the vulcano complex the low magnetization area in the middle part of the island may result from hydrothermally altered rocks their presence not only in the central part of the volcano edifice but also in other peripheral areas is a sign of a more diffuse historical hydrothermal activity than in present days moreover the high magnetization heterogeneity within the upper flanks of la fossa cone edifice is an imprint of a composite distribution of unaltered and altered rocks with different mechanical properties which poses in this area a high risk level for failure processes especially during volcanic or hydrothermal crisis

landslides and the evolution of el hierro in the canary islands seismic and sonar data have been used to evaluate the extent and characteristics of giant landslides on the flanks of el hierro in the canary islands as the youngest and most southwesterly of the canary islands el hierro has experienced rapid growth and destructive events in its 1 12 million year history at least four giant landslides el golfo el julan san andres and las playas have modified 450 km3 of el hierro during the last 200 300 thousand years with each landslide event removing around 3 of the total edifice volume the extent of landsliding indicates that it is the main process of decay we characterise flank morphology around el hierro and distinguish between rugged unfailed flank failed flank and steep gullied ridge flanks affected by landsliding have downslope long profiles with distinctive b coefficients and exponential forms the el golfo landslide is the most recent 15 ka best described and clearly defined landslide in the canary islands the el julan landslide sw flank has an estimated volume of 130 km3 an age of 200 ka and is characterised by gravitational slumping on the se flank two new landslide events are reported the younger landslide las playas occurred 145 176 ka has a narrow steep sided embayment and a corresponding blocky debris avalanche deposit the older landslide san andres is recognised on the basis of a highly chaotic seismic facies offshore and reduced upper flank gradients its lack of an upper flank embayment and offshore blocky debris avalanche lead us to interpret that the landslide involved gravitational slumping possibly a series of events which reduced upper flank gradients but did not catastrophically collapse to produce a debris avalanche

volcanic history of lipari aeolian islands italy during the last 10 000 years abstract examination of the volcanic stratigraphy of deposits younger than 10 000 years on lipari indicates four principal periods of volcanic activity related to specific centers the products from each different volcanic center are defined as volcano stratigraphic unit vsu from the oldest these are the canneto dentro gabellotto fiume bianco forgia vecchia and monte pilato rocche rosse vsus the study of textures and dispersal of the deposits permitted the vents to be localized and the recent volcanic history of lipari to be reconstructed the oldest event formed a small explosion breccia cone with a final obsidian lava in the canneto dentro area immediately afterward a complex series of explosions produced the widespread dry surge deposits of the gabellotto fiume bianco sequence this activity ended with the extrusion of a domical lava flow the renewal of activity occurred in the pirrera area with an explosive eruption that produced explosion breccia deposits the last eruptions from this vent were coeval with the first eruption of m pilato the rim of the explosion breccia cone was partially destroyed by the forgia vecchia lava flow m pilato cone grew in a very short period of time due to a continuous swarm of explosive events after a short repose time a series of more energetic and superficial explosions occurred through a vent slightly to the south the extrusion of the rocche rosse lava flow about 729 a d ended this cycle of activity all the volcanic centers follow a quite similar stochastic pattern starting with a fall or surge eruption and ending with effusion of viscous rhyolitic lavas the four centers are aligned along either nw se or ne sw fault systems according to the structural pattern of the island they can be placed into two groups the canneto dentro gabellotto centers and the forgia vecchia m pilato centers a long quiescence 3 500 years separates the activity of these two groups while inside of each the activities were nearly contemporaneous or in rapid succession

volcanological evolution of the rivi capo volcanic complex at salina aeolian islands magma storage processes and ascent dynamics lava flows and pyroclastic deposits from strombolian fallout related to the activity of the rivi and capo volcanoes which are representative of early subaerial volcanoes on salina aeolian islands have been investigated through a geological petrological approach our geological field survey shows that rivi and capo volcanoes are part of a single n50 e aligned volcanic complex here named rivi capo volcanic complex rcvc stratigraphically specific rock sampling has allowed reconstruction of the magma feeding processes through time whole rock major element compositions together with core to rim profiles of plagioclase and clinopyroxene crystals show a general evolution toward more basic compositions through the three formations constituting the capo volcano and within the rivi center melts simulations and mass balance modeling suggest that the rcvc rocks are the result of fractional crystallization of plagioclase clinopyroxene and olivine ca 45 of solid removed from a primary magma in addition to fractional crystallization continuous recharge and mixing with more basic magma coming from deeper parts of the magmatic plumbing system contributed to the final volcanic rock compositions our textural and microanalytical data on plagioclase and clinopyroxene crystals allow the definition of a multilevel magmatic storage system with reservoirs at 20 and 3 km below sea level when processes of magma differentiation ascent and storage are considered together with the stratigraphic position of each sample a history of continuous modification of the rcvc plumbing system can be constructed volcanism may have been characterized by fissure type eruptions during the early stages lower capo lower rivi and middle capo formations gradually changing later to central type volcanism upper capo and upper rivi formations

imaging and modelling the subsurface structure of volcanic calderas with high resolution aeromagnetic data at vulcano aeolian islands italy in this paper we present a magnetic model of the subsurface structure of vulcano island based on high resolution aeromagnetic data three profiles across the most intense magnetic anomalies over the piano and fossa calderas were selected for the magnetic modelling which was constrained by structural and volcanological data previous geophysical models paleomagnetic data and borehole stratigraphy obtained from two deep wells the interpretation of the magnetic sources represents a significant contribution to the understanding of the piano and fossa calderas underlying structure providing us with evidence of the lateral discontinuity between them at depth we propose that the positive magnetic anomalies in the piano caldera area are caused by a the remnants of an early submarine volcano b an outcropping dyke swarm related to the feeding system of the primordial vulcano phase beneath mt saraceno and c the presence of a non outcropping dyke system intruded along a ne sw oriented intra caldera fault beneath the eastern part of the piano caldera offshore to the west the magnetic anomaly map suggests the presence of a submarine volcanic structure not revealed by bathymetric data which could represent the eruptive centre the presence of which has been indirectly deduced from the outcrop of eastern dipping lavas on the western seashore magnetic modelling of the fossa caldera points to the presence of a highly magnetized cone like body inside the fossa cone centred beneath the oldest crater rims we interpret this body as a pile of tephritic lavas emplaced in an early phase of activity of the fossa cone suggesting that the volume of mafic lavas that erupted at the beginning of the construction of the fossa edifice was more significant than has previously been deduced furthermore the presence of a magnetized body inside the fossa cone implies that high temperatures are contained in very limited spaces do not affect its bulk inner structure and are restricted to fumarolic conduits and vents in addition structures beneath the western and northern part of the fossa caldera are revealed to have null or low magnetization which can be ascribed to the presence of pyroclasts and hyaloclastites in this area as well as to a large volume of hydrothermally altered materials this suggests that the hydrothermal system with a very limited extension at present affected a larger area in the past especially beneath the western part of the caldera

temporal evolution of a three component system the island of lipari aeolian arc southern italy the volcanic products from lipari define an evolutionary trend with a high gradient of k enrichment similar to the calc alkaline to potassic volcanism of other islands in the aeolian arc stratigraphic reconstruction of the island based on field and geochronological data indicate that the volcanic activity can be subdivided in two stages the first stage from 223 to 42 ka consists of six eruptive cycles and is characterized by basalts and basalt andesites showing progressive increase in both sio2 and k2o contents with time the second stage consists of four cycles erupted since 42 ka and is marked by an apparent rejuvenation of the geochemical system with the appearance of the first rhyolitic products fractional crystallization assimilation and mixing models suggest that the geochemistry of lipari volcanism evolved with time by a complex interplay between two mantle derived components one sub alkaline and the other alkaline in addition to crustal melts and or crustally derived materials a petrogenetic model in which fractional crystallization was subordinate to mixing best fits the geochemical data and petrographic observations of macro and microscopic features melts from the crustal and mantle end members are almost always present in the system but the relative proportions appear to vary with time the sub alkaline mantle component source of tyrrhenian tholeiites is an important contributor to the early evolution of the volcanism in lipari input from the alkaline mantle component source of the roman comagmatic province increases with time and the crustal component becomes dominant in the later activity the preferred petrogenetic model for the temporal evolution of the volcanic system in lipari involves melting initially caused by an increase in the thermal input related to the opening of the tyrrhenian sea and or to subduction processes the quick rise of the isotherms and almost contemporaneous melting of source materials with different compositions favored complex mixing during ascent of the melts

mitigation of atmospheric phase delays in insar data with application to the eastern california shear zone we present a method for estimating radar phase delays due to propagation through the troposphere and the ionosphere based on the averaging of redundant interferograms that share a common scene estimated atmospheric contributions can then be subtracted from the radar interferograms to improve measurements of surface deformation inversions using synthetic data demonstrate that this procedure can considerably reduce scatter in the time series of the line of sight displacements we demonstrate the feasibility of this method by comparing the interferometric synthetic aperture radar insar time series derived from ers 1 2 and envisat data to continuous global positioning system data from eastern california we also present results from several sites in the eastern california shear zone where anomalous deformation has been reported by previous studies including the blackwater fault the hunter mountain fault and the coso geothermal plant

scale dependent location of hydrothermal vents stress field models and infrared field observations on the fossa cone vulcano island italy article i nfo hydrothermal venting occurs on numerous volcanoes of various age setting topographic and structural expression vent locations are commonly found not within volcanic craters only but predominantly at the crater margins and topographic highs a case example is vulcano island italy where the control on such vent locations along crater margins remained poorly understood however this paper describes numerical models combined with field observations and infrared imaging to explore the mechanisms that control the ascent paths of fluids in the fossa cone on vulcano using finite element modelling we calculate the gravitational stress in the volcanic edifice imposed by the topography results predict hydrofractures to be arranged in radial patterns at depth and in concentric patterns close to the surface furthermore low compressive stress values are found at the rims of the nested craters we compare the stress models to fumarole field data using a forward looking infrared camera we recorded images of the entire cone images were assembled to a mosaic and geocoded providing the first map of a remotely sensed temperature field in high resolution at la fossa the degassing and high temperature anomalies are found to be located mainly at the crests of the craters predominately in the northern and southern sector of the main crater therefore the stress distribution favours and indeed corresponds to the occurrence of fumaroles at la fossa the stress models also yield compression at the bottom of the crater where temperatures are cool thus we consider that the overall distribution of the fumaroles at the fossa cone is controlled by topography additional mechanisms contribute to the exact position of the degassing sites the influence of the lithological control seems to be strong in the southwestern part of the crater where the fumaroles are located 10 20 m below the inner crater rim in bedded strata in the northern part of the crater the exhalation sites can mainly be found at surface fractures and cracks emphasizing the structural control on the location of the fumaroles at this sector of the fossa cone using combined theoretical modelling and field observations this study helps to shed light into the processes directing fluids in volcanic edifices elsewhere and might contribute to the evaluation of upcoming hazard scenarios

magmatic feeding system and crustal magma accumulation beneath vulcano island italy evidence from co2 fluid inclusions in quartz xenoliths 1 pure co2 fluid inclusions are observed in quartz xenoliths from four lava flows in the island of vulcano corresponding to distinct activity stages during the last 120 kyr xenoliths which consist of aggregates of quartz grains are present in lavas of contrasting composition ranging from basaltic andesites to rhyolites two main generations of co2 inclusions are observed early type i inclusions were trapped prior to the ascent of the host xenoliths while type ii inclusions were trapped during the ascent into the host magma fluid inclusions show a bimodal distribution of homogenisation temperatures corresponding to two distinct density intervals 0 89 0 52 g cm 3 type i and 0 42 0 13 g cm 3 type ii type i inclusions indicate pressures of 0 56 0 33 gpa 21 13 km relating to the levels of xenolith entrapment in the host lavas type ii fluid inclusions show considerably lower pressures ranging from 0 14 to 0 03 gpa 5 5 3 km present data suggest ponding of mantle derived magmas in at least two distinct reservoirs located at lower crustal depths and at shallow levels respectively combined fluid inclusion and petrological data suggest that the deep reservoirs were the sites of extensive fractional crystallization mixing with source derived magmas and various degrees of crustal assimilation evolutionary processes also occurred inside shallow magma chambers in which deep magma mixed with residing melts and rested for short periods of time before being erupted to the surface index terms 5480 planetology solid surface planets volcanism 8450 8414 volcanology eruption mechanisms 8434 volcanology magma migration

pattern of deformation around the central aeolian islands evidence from multichannel seismics and gps data the tectonics of the central aeolian islands which are located within the tyrrhenian backarc basin has been investigated through a marine seismic reflection survey we find that compressional structures dominate around the islands whereas extensional faults occur only to the north of salina and filicudi towards the marsili basin this pattern of deformation although different from previously reported is in agreement with the strain field and stress regime obtained from gps measurements and seismological data age constraints suggest that contractional deformation was active since middle pleistocene being coeval with the building of the volcanic edifices of the aeolian islands and is superimposed on pre existing extensional deformation compressional and extensional regimes therefore can coexist within a backarc setting seismic profiles show that the tindari letojanni fault considered as a major tectonic element does not extend to the north towards the island of vulcano as a throughgoing fault rather deformation is accommodated in a broader belt displaying greater structural complexity

tectonic volcanic and hydrothermal features of a submarine portion of the aeolian arc tyrrhenian sea abstract multibeam side scan sonar remotely operated vehicle and bottom sampling data have been acquired over a sector of the aeolian arc to assess its volcano tectonic characteristics and hydrothermal mineralization potential in this paper we report a description of the areas where major tectonic volcanic and hydrothermal activity has been observed there areas are the basiluzzo area the secca dei pesci area the southwestern panarea platform the secca del capo highs the offshore area between salina and lipari and the eastern slope of vulcano the study region lies at the junction of two major e w and ne sw trending tectonic lineaments through which the extensional faulting of the calabrian and sicilian margins leading to the formation of the tyrrhenian back arc sea took place the recent tectonics of the study area dominated by ne sw and e w trending extensional structures appears to be still controlled by the processes which have originated the tyrrhenian back arc opening many newly discovered recent volcanic features have been observed e g 1 three pairs of volcanic cones aligned along ne sw tectonic lineaments in the offshore between salina and lipari 2 a field of fresh tube and pillow lavas in the eastern offshore of vulcano 3 outcrops of fresh volcanic rocks in the panarea platform in particular around basiluzzo islet suggesting recent volcanic activity two types of hydrothermal mineralization were sampled i e sediment hosted sulphide deposits and fe rich crusts and sediments the polymetallic sulphide deposits were sampled in a depression south of basiluzzo islet for which area a kuroko type hydrothermal system reaching high temperature black ore deposition is suggested in the other sectors of the study area however a lower temperature hydrothermal circulation is thought to have originated the fe rich tetsusekiei type samples

aeromagnetic data provide new insights on the volcanism and tectonics of vulcano island and offshore areas southern tyrrhenian sea italy 1 the active vulcano island southern tyrrhenian sea represents the southernmost portion of a nw se elongated volcanic ridge that includes also lipari and salina islands the ridge is affected by a regional nw se to n s striking fault system the elaboration and analysis of data from three high resolution aeromagnetic surveys carried out between 1999 and 2004 on vulcano and offshore allow us to recognize high intensity magnetic anomalies related to volcanic centers conduits or shallow intrusions previously unreported offshore submarine vents have been also recognized some of them may correspond with source areas of outcropping exotic pyroclastics on vulcano the spatial analysis of the recognized magnetic anomalies and volcanic structures shows that they are preferably aligned along the strikes of the main regional faults that affect the volcanic ridge submarine volcanic conduits revealed by the aeromagnetic survey might represent potential sources for future submarine effusive or explosive activity

a modeling study on the development of a bowing structure and associated rear inflow within a squall line over south china abstractthrough convection permitting simulations this study examines a large bowing structure within a squall line that occurred during the rainy season in south china the bowing structure is closely associated with a local enhancement of and balance between the cold pool and the line normal environmental low level vertical shear rear inflow plays an essential role in the formation and evolution of this large bowing structure it is found that the low level rear inflow is largely a natural consequence of the baroclinically generated horizontal vorticity near the surface while the midtropospheric rear inflow is forced by several pairs of bookend vortices vorticity budget and vortex line analyses show that the bookend vortices form mainly through the tilting of horizontal vorticity consolidation of these pairs of bookend vortices forms a broad zone of contiguous rear inflow the environmental flow and horizontal pressure gradient force associated with the midlevel pressure deficit induced by the re

prodigious submarine landslides on the hawaiian ridge the extensive area covered by major submarine mass wasting deposits on or near the hawaiian ridge has been delimited by systematic mapping of the hawaiian exclusive economic zone using the side looking sonar system gloria these surveys show that slumps and debris avalanche deposits are exposed over about 100 000 km2 of the ridge and adjacent seafloor from kauai to hawaii covering an area more than 5 times the land area of the islands some of the individual debris avalanches are more than 200 km long and about 5000 km3 in volume ranking them among the largest on earth the slope failures that produce these deposits begin early in the history of individual volcanoes when they are small submarine seamounts culminate near the end of subaerial shield building and apparently continue long after dormancy consequently landslide debris is an important element in the internal structure of the volcanoes the dynamic behavior of the volcanoes can be modulated by slope failure and the structural features of the landslides are related to elements of the volcanoes including rift zones and fault systems the landslides are of two general types slumps and debris avalanches the slumps are slow moving wide up to 110 km and thick about 10 km with transverse blocky ridges and steep toes the debris avalanches are fast moving long up to 230 km compared to width and thinner 0 05 2 km they commonly have a well defined amphitheater at their head and hummocky terrain in the lower part oceanic disturbance caused by rapid emplacement of debris avalanches may have produced high level wave deposits such as the 365 m elevation hulopoe gravel on lanai that are found on several islands most present day submarine canyons were originally carved subaerially in the upper parts of debris avalanches subaerial canyon cutting was apparently promoted by the recently steepened and stripped slopes of the landslide amphitheaters

what drives centuries long polygenetic scoria cone activity at barren island volcano abstract barren island in the andaman sea is an active mafic stratovolcano which had explosive and effusive eruptions followed by caldera formation in prehistoric time poorly dated a scoria cone within the caldera marking volcanic resurgence was active periodically from 1787 to 1832 the historic eruptions since 1991 the same scoria cone has produced six eruptions commonly including lava flows links between barren island s eruptions and giant earthquakes such as the 26 december 2004 great sumatra megathrust earthquake have been suggested though there is no general correlation between them the 227 year long activity of the scoria cone named here shanku cone is normally driven by purely magmatic processes i present a source to surface model for barren island and shanku including the source region deeper and shallow magma chambers volcanotectonics dyking from magma chambers and eruptions and eruptive style as controlled by crustal stresses composition and volatile content calculations show that dykes 0 5 m thick and a few hundred meters long originating from shallow level magma chambers 5 km deep are suitable feeders of the shanku eruptions shanku a polygenetic scoria cone at least 13 eruptions since 1787 has three excellent analogues namely anak krakatau 40 eruptions since 1927 cerro negro 23 eruptions since 1850 and yasur persistent activity for the past hundreds of years this is an important category of volcanoes gradational between small monogenetic scoria cones and larger polygenetic volcanoes

composition and temporal variability of particle fluxes in an insular canyon of the northwestern mediterranean sea abstract particle fluxes have been widely studied in canyons located in continental margins conversely particle fluxes in canyons in sediment starved margins incising small island margins have received very little attention and remain poorly understood the menorca canyon is the largest canyon system in the balearic archipelago despite the high oligotrophic conditions of the balearic archipelago the canyon and surrounding areas host diverse communities dominated by benthic suspension feeders understanding the magnitude and variability of environmental factors influencing these communities thus remain crucial in order to characterize the temporal variability of particle fluxes analyze its geochemical and macroscopic composition and identify the main processes that modulate particle fluxes in the menorca canyon one instrumented line with a sediment trap and a current meter was deployed at 430 m water depth from september 2010 to october 2012 particle fluxes ranged between 190 and 2300 mg m2 d 1 being one of the lowest ever registered in a mediterranean submarine canyon s head the caco3 fraction was the major constituent contrasting with the general trend observed in other mediterranean canyons macroscopic constituents fecal pellets posidonia oceanica detritus and pelagic and benthic foraminifera presented a wide variability throughout the sampling period and were not significantly correlated with the total mass flux the low magnitude of the registered fluxes and the lack of correlation with the observed environmental variables e g currents winds wave height chlorophyll a biomass suggest that there is no evident controlling mechanism however we could infer that resuspension processes and the presence of different hydrodynamic features e g eddies interchange of water masses condition the magnitude and composition of particle fluxes

comment on reconstructing the architectural evolution of volcanic islands from combined k ar morphologic tectonic and magnetic data the faial island example azores by hildenbrand et al 2012 j volcanol geotherm res 241 242 2012 39 48 abstract hildenbrand et al 2012 have presented a model for the geological evolution of faial island in their interpretation the oldest volcanic system extended much further than the present day eastern part of the subaerial island with a ridge like morphology into the faial s jorge channel furthermore the western side of the system was suggested to have been later destroyed by mass wasting based on now extensive multibeam bathymetry collected surrounding faial island we find no evidence supporting such interpretations the geometry of the shelf edge suggests that a near circular edifice occupied the eastern part of the present day subaerial island in addition the submarine morphology does not show massive mass wasting deposits around the base of the edifice rather bathymetric gradients and morphology suggest that the submarine slopes were formed from volcanic emplacements or from material displaced in only small scale mass movements or sedimentary flows and have not failed catastrophically evidence that a ridge like feature extended into the faial s jorge channel is also lacking these observations highlight the potentially valuable information that sonar data can provide to evaluating ocean island evolution from the more limited extend of outcrops on land

deep water gravity core from the marsili basin tyrrhenian sea records pleistocenic holocenic explosive events and instability of the aeolian archipelago italy abstract a 4 8 m long gravity core was recovered on a relative topographic high in the northern part of the marsili basin southern tyrrhenian sea at a water depth of 3200 m the core was taken in order to decipher the sedimentary record of the past volcanic events of the nearby aeolian arc a succession of thin 2 cm to 5 cm thick fine grained turbidites mainly of volcaniclastic origin topped by hemipelagic mud layers and a number of primary tephra layers were recovered by the core the most prominent turbidite occurs in the lower part of the core at 385 cm it consists of a 20 cm thick thinning upward pebble to sand sized bed grain size analysis and component compositions in the 0 063 0 250 mm size fractions were determined on thirty samples taken from primary tephra beds and the silty sandy basal part of the volcaniclastic turbidite units sem scans and glass fraction chemical analyses were successively carried out on a selection of 17 samples to aid source correlation and comparison sub aerial tephras of the lower pollara salina 24 3 6 ka gabellotto fiumebianco lipari 8 5 or 11 5 ka monte pilato lipari 749 or 580 ad and secche di lazzaro stromboli 5 ka eruptions were also analyzed with the same procedure primary tephra respectively belonging to the eruptions of lower pollara gabellotto fiumebianco and vesuvius ap eruptions 3 5 ka 79 ad were identified in the core at the expected relative stratigraphic depths two turbidite beds composed of monogenic glass shards were also identified and interpreted as the remobilisation of primary tephras of secche di lazzaro stromboli 5 ka and pilato lipari 580 or 749 ad tephrochronology results indicate that the cored sequence formed in the last 30 ka suggesting an average sedimentation rate of 0 15 0 17 mm y the thick pebbly sandy turbidite unit in the lower part of the core has component and glass composition compatible with the lower pollara volcanic sequence of salina island in view of the grain size and thickness of the turbidite unit we suggest that it represents the deposit of a large failure event the tephra corresponding to the lower pollara event lies below the turbidite unit separated by 16 cm of hemipelagic mud indicating that the collapse took place sometime after the eruption

oblique rifting in salina lipari and vulcano islands aeolian islands southern italy a structural analysis carried out on the volcanic products of the islands of salina lipari and vulcano aeolian archipelago points out that the large scale tectonic setting is dominated by nw se trending right lateral extensional strike slip faults and by n s to ne sw trending normal faults and fractures this fault pattern generates pull apart type structures developing between different right hand overlapping fault segments and a characteristic extensional imbricate fan geometry at the tip of the major strike slip faults all the structures representing the surface expression of an active crustal discontinuity which controls the evolutionary history of the magmatism of the three islands are kinematically compatible with a n100 e extension related to a rifting process affecting southern italy

active upper crust deformation pattern along the southern edge of the tyrrhenian subduction zone ne sicily insights from a multidisciplinary approach abstract using a multidisciplinary dataset based on gravimetric seismic geodetic and geological observations we provide an improved picture of the shallow structure and dynamics of the southern edge of the tyrrhenian subduction zone with a local earthquake tomography we clearly identify two main crustal domains in the upper 15 km characterized by different p wave velocity values a high velocity domain comprising southeasternmost tyrrhenian sea ne sicily and messina straits and a low velocity domain comprising mt etna and eastern sicily the transition between the two domains shows a good spatial correspondence with a wider set of faults including the taormina fault system tfs and the aeolian tindari letojanni fault system atlfs two nearly se striking fault systems crossing northeastern sicily and ending on the ionian shoreline of sicily according to many investigators within this set of faults most of the deformation seismicity occurs along the northern and central segments of atlfs compared to low activity along tfs a lack of seismicity both recent and historical is observed in the southern sector of atlfs where however geodetic data reveal significant deformation our multidisciplinary dataset including offshore observations suggests the southeastward continuation of the atlfs into the ionian sea until joining with the faults cutting the ionian accretionary wedge described in the recent literature our findings imply the existence of a highly segmented crustal shear zone extending from the aeolian islands to the ionian abyssal plain that we believe plays the role of accommodating differential motion between the southern tyrrhenian unit and the western compressional domain of sicily the atlfs which is a main part of the inferred shear zone behaves similarly to what often observed at the edges of retreating subduction slabs where the overriding plate drifts with a highly non uniform transform motion along the lateral borders