sub volcanic crystallization at stromboli aeolian islands southern italy preceding the sciara del fuoco sector collapse evidence from monzonite lithic suite we describe texture mineralogy and whole rock composition of cognate monzonite sub volcanic clasts within debris flow deposits related to the 5000 years catastrophic phreatomagmatic eruption probably linked to the sciara del fuoco sector collapse the debris flows are at the top of accretionary lapilli rich ash deposits overlying potassic ks shoshonites lavas of the neostromboli period the monzonites are inferred to be crystallized in situ at low p at the side walls and or roof margins of a shallow magma chamber and to be cogenetic with the ks neostromboli extrusives they can be considered ideal orthocumulates since they approximately retain a bulk liquid composition and possibly represent slowly cooled equivalents of their ks shoshonite host rock the closure temperature of final solidification of the monzonite lithic suite was estimated through ternary feldspar geothermobarometry plagioclase k feldspar and k feldspar biotite equilibria and is in the range of 750 790 c with a maximum logfo2 around 15 1 15 3 the estimated pressure of crystallization is 0 5 kbar potassic lavas and dikes previously emplaced during the neostromboli period also resemble the monzonites in both major trace elements and mineral chemistry the cogenetic relationship between ks neostromboli extrusives and the monzonite host rock magma from which the sub volcanic clasts were derived is clear evidence that a shallow magma chamber existed between the caldera collapse of the vancori period and the sciara del fuoco sector collapse i e between 13 000 and 5000 years the monzonite clasts were derived from crystallization at very shallow depth ca 1 km and strongly support the hypothesis of violent decompression of the shallow magmatic plumbing system during the sciara del fuoco sector collapse climax of the regressive landslide event with maximum disruption of the chamber walls took place during emplacement of the debris flows i e during the late stage of the neostromboli phreatomagmatic eruption

volcaniclastic dykes tell on fracturing explosive eruption and lateral collapse at stromboli volcano italy abstract in the upper part of the stromboli volcano in the le croci and bastimento areas two dyke like bodies of volcanic breccia up to two metre thick crosscut and intrude the products of vancori and neostromboli volcanoes we describe the lithofacies association of these unusual volcaniclastic dykes interpret the setting of dyke forming fractures and the emplacement mechanism of internal deposits and discuss their probable relationships with the explosive eruption and major lateral collapse events that occurred at the end of the neostromboli period the dyke volcaniclastic deposits contain juvenile magmatic fragments pyroclasts suggesting a primary volcanic origin their petrographic characteristics are coincident with the neostromboli products the architecture of the infilling deposits comprises symmetrically nested volcaniclastic units separated by sub vertical boundaries which are parallel to the dyke margins the volcanic units are composed of distinctive lithofacies the more external facies is composed of fine and coarse ash showing sub vertical laminations parallel to the contact wall the central facies comprises stratified lithic rich breccia and lapilli tuff whose stratification is sub horizontal and convolute discordant to the dyke margins only at le croci dyke the final unit shows a massive tuff breccia facies the volcaniclastic dykes experienced a polyphasic geological evolution comprising three stages the first phase consisted in fracturing explosive intrusion related to magma rising and upward injection of magmatic fluids and pyroclasts the second phase recorded the dilation of fractures and their role as pyroclastic conduits in an explosive eruption possibly coeval with the lateral collapse of the neostromboli lava cone finally in the third phase the immediately post eruption mass flow remobilization of pyroclastic deposits took place on the volcano slopes

what controls sheet intrusion in volcanoes structure and petrology of the stromboli sheet complex italy abstract a multidisciplinary study has been conducted on 109 intrusive sheets of stromboli the relation between sheet injection conditions with the magmatic and structural variations of the volcano and the parameters governing the preferential intrusion geometry inside the volcano in a time perspective have been determined during its subaerial activity the last 100 ka stromboli experienced periods of extrusive growth and sheet intrusions alternated to caldera and lateral collapses of the nw sciara del fuoco flank the sheet intrusions similar to the extrusive rocks span a large compositional range from calc alkaline to potassic through high k calc alkaline and shoshonitic series the most evolved compositions of the effusive rocks however have not been found as intrusions whereas some mafic and basic magmas of sheets were never erupted the repeated time change of location of the intrusions from strombolicchio to the ne sw trend passing trough the inferred paleostromboli summit cone and the southern flank could represent the expression of the shift of the magma chamber towards the southeast and the subsequent onset of a clear ne sw elongated magma chamber located along the main stromboli weakness zone the stromboli evolution in the last 100 ka has been characterized by the persistent n 10 55 e intrusion direction which reflects the influence of the edifice s state of stress on the magma feeding paths after 13 ka ago sheets mainly intruded along to the sector collapse scarps in a circum amphitheatre geometry which has been demonstrated to be influenced by the new cone morphostructure and not by different magma rheological characters

the holocene secche di lazzaro phreatomagmatic succession stromboli italy evidence of pyroclastic density current origin deduced by facies analysis and ams flow directions the edifice of stromboli volcano gravitationally collapsed several times during its volcanic history 100 ka present the largest holocene event occurred during the final stage of the neostromboli activity 13 5 ka and was accompanied by the emplacement of phreatomagmatic and lahar deposits known as the secche di lazzaro succession a stratigraphic and paleomagnetic study of the secche di lazzaro deposits allows the interpretation of the emplacement and the eruptive processes we identify three main units within the succession that correspond to changing eruption conditions the lower unit ua consists of accretionary lapilli rich thinly bedded parallel to cross stratified ash deposits interpreted to indicate the early stages of the eruption and emplacement of dilute pyroclastic density currents upward the second unit ub of the deposit is more massive and the beds thicker indicating an increase in the sedimentation rate from pyroclastic density currents the upper unit uc caps the succession with thick immediately post eruptive lahars which reworked ash deposited on the volcano s slope flow directions obtained by anisotropy of magnetic susceptibility ams analysis of the basal bed of ua at the type locality suggest a provenance of pyroclastic currents from the sea this is interpreted to be related to the initial base surges associated with water magma interaction that occurred immediately after the lateral collapse which wrapped around the shoulder of the sector collapse scar upward in the stratigraphy upper beds of ua and ub paleoflow directions change and show a provenance from the summit vent probably related to the multiple collapses of a vertical pulsatory eruptive column

importance of structural history in the summit area of stromboli during the 2002 2003 eruptive crisis inferred from temperature soil co2 self potential and electrical resistivity tomography the 2002 2003 eruptive crisis of stromboli volcano in the aeolian islands raised the question of how to assess the stability of the flanks of this volcanic edifice during such a crisis to provide a response to this question we analyzed a detailed fluid flow mapping plus the reiteration of a profile located in the vicinity of the active vents using the self potential method temperature data soil gas co2 measurements and electric resistivity tomography coupling the interpretation of these methods that are sensitive to the flow of gas and water in the ground indicates the position of areas of mechanical weakness in addition they can be used to monitor the change in the discharge of fluids associated with these features before and during the 2002 2003 eruptive crisis our results emphasize the importance of old structural boundaries such as the large fossa crater in the development of the new set of fractures observed during the 2002 2003 eruptive crisis between october 2002 and january 2003 the use of co2 soil gas technique evidenced an increase in the discharge of co2 outside the large fossa crater boundaries along the failure boundary of the southern sciara del fuoco area self potential and temperature measurements made before the 2002 2003 eruptive crisis reveal significant changes along the main structural boundaries of the fossa area the development of these anomalies is interpreted as an increase of the permeability of the structure from may 2000 to may 2002 between january 2003 and march 2003 the reiteration of self potential temperature and co2 measurements shows an increase of fluid discharge along weakness planes located inside the large fossa crater boundary they evidence no change outside this structural boundary the importance of the large fossa crater boundary in controlling the deformation and fluid flow from january to march 2003 has been attested by the development of the fractures inside the large fossa crater boundary and also with a network of electrooptical distance measurement stations located inside and outside this ancient crater this multidisciplinary approach to fluid flow assessment before and during an eruptive crisis is complementary to geodetic measurements of the deformation of the edifice it demonstrates for the first time the powerful potential of combining electrical resistivity tomography self potential temperature and soil co2 measurements in assessing the position of the planes of mechanical weakness in a volcanic edifice

flank instability of stromboli volcano aeolian islands southern italy integration of gb insar and geomorphological observations abstract stromboli is characterized by frequent explosions of variable energy and periodically interrupted by more energetic blasts emitting large volumes of material the pressurization of a volatile poor high porphyritic magma column that is gas recharged by the deep seated volatile rich low porphyritic magma precedes such events and produces deformations on the nw flank of the volcano sciara del fuoco by integrating geomorphological observations with long term displacements from ground based interferometric radar since december 2007 we identified two landslides whose movements are strongly related with volcanic activity movement patterns obtained through a novel long term analysis of gb insar data permitted us to hypothesize the type of movement and depth for both landslides furthermore their position allowed us to affirm that the effusive vent formed in 2007 at 400 m a s l was the result of the deflection of a feeder dike caused by landslide fractures thus showing the important role of geomorphological discontinuities in volcanic environments

paroxysmal activity at stromboli lessons from the past the persistent normal activity of stromboli is occasionally interrupted by sudden and highly energetic explosive events called strombolian paroxysms these phenomena together with landslide generated tsunamis represent the most hazardous manifestations of present day volcanic activity at stromboli the most recent paroxysms on 5 april 2003 and 15 march 2007 have drawn attention to these energetic events because they significantly threatened inhabitants and tourists historical accounts and field evidence indicate however that even larger paroxysms in terms of volume dispersal of products and intensity of explosive phenomena occurred in the recent past during these paroxysms incipiently welded spatter deposits mantled the north and south rims of the sciara del fuoco down to low elevations extending much farther than the similar deposits from recent observed events 5 april 2003 and 15 march 2007 in order to identify characterize and discriminate among products of these outstanding spatter forming eruptions more than 50 stratigraphic sections were measured and sampled stratigraphic sedimentological and radiometric 14c data indicate that only two paroxysms produced spatter that reached very low elevations and inhabited areas the first occurred in the 16th century and the last in ad 1930 analysis of texture and deposit components reveals that the early phases of the two eruptions were driven by distinctly different eruptive dynamics both identified paroxysms are at least one order of magnitude greater than any similar event observed by monitoring systems at stromboli these two large paroxysms were the most powerful volcanic events at stromboli in the last eighteen centuries

geological evidence for recurrent collapse driven phreatomagmatic pyroclastic density currents in the holocene activity of stromboli volcano italy abstract we present a multidisciplinary geological study of lithified to unconsolidated ash rich lapilli tuff deposits bearing accretionary lapilli that crop out in scattered sites along the lower slopes of the stromboli volcano southern italy these deposits are related to three pyroclastic successions called semaforo nuovo secche di lazzaro and semaforo labronzo with distinctive lithologic and volcanologic features and different stratigraphic position within the neostromboli volcano stratigraphy holocene their juvenile clasts have slightly different major and trace element compositions whole rock and glass isotopic ratios and mineralogical characteristics although they are all within the most evolved high k shoshonites typical of neostromboli the three successions are independently recognized in distinct sectors of the volcano displaying an asymmetric areal distribution that is interpreted as the result of directed pyroclastic density currents and minor fallout generated from summit eruptive vents lithological characteristics and morphoscopic features of ash particles indicate phreatomagmatic fragmentation combined with mechanisms of volatile exsolution or decompression which is atypical with respect to the dominant strombolian effusive eruptive behaviour of stromboli during the holocene we suggest that the three phreatomagmatic eruptions are linked to different major lateral collapses associated to flank fissure eruptions that occurred along the nw dipping sciara del fuoco collapsed flank it is argued that the collapses have unloaded the magmatic and hydrothermal system enabling magma water interaction and explosive decompression of a shallow magma reservoir the recurrent collapse eruption link with generation of directed pdcs able to reach the lower slopes of the volcano highlights a previously underestimated source of volcanic hazard at stromboli

growth after collapse the volcanic and magmatic history of the neostromboli lava cone island of stromboli italy this study focuses on the holocene neostromboli lava cone which is part of the stromboli volcano aeolian islands italy it represents an important example of the structure and behaviour of lava cone re growth shortly after a large scale volcano sector collapse neostromboli s eruptive style is dominated by extrusion of sheet like a a lava flows and associated autoclastic breccias the lava cone developed during five phases of activity phases a to e representing discrete episodes of lava effusion characterised by rapid changes in magma composition spatial development of the feeder system and physical properties of erupted lavas through time although they all belong to the potassic series ks with sio2 49 55 wt and mgo 2 50 6 25 wt the neostromboli lavas have distinct petrogenetic characteristics ranging from leucite free and low sr shoshonitic basalts phases a and b to leucite bearing shoshonitic basalts with high phase c and intermediate phase d sr contents and to leucite free biotite bearing shoshonites phase e three different batches of mantle derived relatively primitive basic magmas fed the activity of phases a c and d the evolution phases a to b is inferred to have occurred in a continuously replenished tapped and crystallizing rtf magma chamber whereas phase e products were dominantly generated by fractional crystallization from phase d magmas the neostromboli cone shows summit flank and satellite vents and sheet intrusions with different geometry and location through time reflecting the interplay of regional tectonics precursory instability processes and volcano load

the evolution of volcanic systems following sector collapse abstract sector collapses affect volcanic edifices across all tectonic settings and involve a rapid redistribution of mass comparable in scale to the largest magmatic eruptions the eruptive behaviour of a volcano following sector collapse provides a test of theoretical relationships between surface loading and magma storage which imply that collapse driven unloading may lead to changes in eruption rate and erupted magma compositions large sector collapses are infrequent events globally with all historical examples being relatively small in comparison to many of the events documented in the geological record as a result exploration of the impacts of sector collapse on eruptive behaviour requires detailed investigation of prehistoric collapses but this is often hindered by poorly resolved stratigraphic relationships and dating uncertainties nevertheless observations from a number of volcanoes indicate sharp changes in activity following sector collapse here a global synthesis of studies from individual volcanoes in both arc and intraplate settings is used to demonstrate a number of common processes in post collapse volcanism multiple examples from large 5 km3 sector collapses in arc settings show that collapse may be followed by compositionally anomalous large volume and often effusive eruptions interpreted to originate via disruption of a previously stable upper crustal reservoir these anomalous eruptions highlight that magma compositions erupted during periods of typical i e unperturbed by sector collapse volcanism may not be representative of the range of compositions stored within a vertically extensive crustal reservoir if eruptible magma is not present upper crustal reservoirs may rapidly solidify following collapse without further eruption allowing more mafic compositions to ascend to the surface with only limited upper crustal modification resulting in edifice regrowth at temporarily elevated eruption rates subsequent re establishment of an upper crustal reservoir further supports a relationship between surface loading and crustal storage but long term chemical and mineralogical differences between pre and post collapse evolved magmas imply that a newly developed reservoir can overprint the influence of a preceding reservoir forming a spatially and compositionally distinct plumbing system these broad patterns are replicated in intraplate settings despite differences in scale and melting processes current evidence suggests that post collapse evolution of intraplate volcanoes can be explained by unloading induced destabilisation of the magma plumbing system rather than increased melt production what emerges from an apparently diverse set of observations is a systematic behaviour that strongly supports a coupling between edifice growth and magma ascent storage and pressurisation eruption rates erupted compositions and the style of volcanism at any particular system may thus be modulated from the surface and long term shifts in surface behaviour may occur without any changes in the deep parts of magmatic systems observations of sharp post collapse changes in erupted compositions including the ascent of primitive mafic magmas also require a crystal dominated mid to upper crustal reservoir consistent with recent models of crustal magmatic systems

deformation at stromboli volcano italy revealed by rock mechanics and structural geology abstract we approach the reconstruction of the recent structural evolution of stromboli volcano italy and the analysis of the interplay between tectonics gravity and volcanic deformation by tying together structural lithostratigraphic and rock mechanics data we establish that since 100 ka bp the edifice has faulted and jointed mainly along ne striking planes faults mostly dip to the nw with normal displacement taking also into account the presence of a nw trending regional least principal stress and of tectonic earthquake hypocenters inside the cone we suggest that this fracturing can be related to the transmission of tectonic forces from the basement to the cone dyking concentrated along a main ne trending weakness zone nez across the volcano summit resembling a volcanic rift whose geometry is governed by the tectonic field in the past 13 ka stromboli experienced a reorganisation of the strain field which was linked with the development of four sector collapses affecting the nw flank alternating with growth phases the tectonic strain field interplayed with dyking and fracturing related to unbuttressing along the collapse shoulders we propose that tectonics control the geometry of dykes inside the cone and that these in turn contribute to destabilise the cone flanks

transient processes in stromboli s shallow basaltic system inferred from dolerite and magmatic breccia blocks erupted during the 5 april 2003 paroxysm we describe the mineralogy geochemistry and mesomicrostructure of fresh subvolcanic blocks erupted during the 5 april 2003 paroxysm of stromboli aeolian islands italy these blocks represent 50 vol of the total erupted ejecta and consist of fine to medium grained basaltic lithotypes ranging from relatively homogeneous dolerites to strongly or poorly welded magmatic breccias the breccia components are represented by angular fragments of dolerites entrapped in a matrix of vesiculated lava like to scoriae crystal rich cr basalt all of the studied blocks are cognates with the cr basalt of the normal strombolian activity or lavas and they are often coated by a few centimeter thick layer of crystal poor cp basaltic pumice erupted during the paroxysm we suggest that they result from the rapid increase of pressure and related subvolcanic rock failure that occurred shortly before the 5 april 2003 explosion when the uppermost portion of the edifice inflated and suffered brecciation as the result of the sudden rise of the gas rich cp basalt that triggered the eruption dolerites and magmatic matrix of the breccias show major and trace element compositions that match those of the cr basalts erupted during normal strombolian activity and effusive events at stromboli volcano dolerites consist of a phenocrysts normally found in the cr basalts and b late stage magmatic minerals such as sanidine an60 28 plagioclase fe mn rich olivines fo68 48 phlogopite apatite and opaque mineral pairs magnetite and ilmenite most of which are never found both in lava flows and scoriae erupted during the persistent explosive activity that characterizes typical strombolian behavior subvolcanic crystallization of the stromboli cr magma leading to slowly cooled equivalents of basalts could result from transient drainage of the magma from the summit craters to lower levels fingering and engulfing of the material that collapsed from the summit crater floor into the shallow basaltic system during the late evening of 28 december 2002 coupled with the short break in the summit persistent explosions between december 2002 and march 2003 permitted the cr magma pockets to solidify as dolerites which were confined to the uppermost portion of the system and thus not involved in the ongoing flank effusive activity crystal size distribution of the basaltic blocks and crystallization of the finer grained 0 1 mm mafic minerals of the dolerites over a time interval of 100 days closely agrees with the above interpretation vesicle filling miarolitic cavities locally found in some dolerites with minerals deposited as vapor phase crystallization is a result of continuous gas percolation through the rocks of the uppermost portion of the volcanic system poorly welded magmatic breccias formed during syn eruptive processes of 5 april 2003 when the paroxysm strongly shattered the shallow subvolcanic system and many dolerite fragments were entrapped in the cr magma in contrast the high degree of welding between the dolerite clasts and the cr basaltic matrix in the strongly welded magmatic breccias provides a snapshot of subvolcanic intrusions of the cr basalt into the dolerite when after a 2 month break in activity cr magmas started to rise again to the summit craters blocks similar to these subvolcanic ejecta of 5 april 2003 were also erupted during previous paroxysms e g 1930 suggesting that changes in the usual strombolian activity e g short breaks in the persistent mild explosions and or flank effusive activity lead to transient crystallization of dolerites in the shallow plumbing system

the secche di lazzaro pyroclastics of stromboli volcano a phreatomagmatic eruption related to the sciara del fuoco sector collapse widespread phreatomagmatic ash deposits secche di lazzaro pyroclastics overlying the lavas of the neostromboli period 13000 to ca 5000 years b p have been identified at stromboli volcano the deposits consist of accretionary lapilli rich ash fall layers and debris flows ash fall layers originated by phreatomagmatic explosive activity from a vent probably located in the uppermost part of the sector collapse scarp sciara del fuoco which formed at the end of neostromboli period stratigraphic position composition of fresh lapilli identical to the neostromboli lavas and an unusually large scale of explosions suggest that the secche di lazzaro pyroclastics were erupted in connection with the sciara del fuoco slope failure characteristics of the deposits are consistent with phreatomagmatic hydrothermal explosivity related to catastrophic decompression of the plumbing hydrothermal system occurrence of multiple ash fall episodes coupled with variation of nature of lithics lithology is suggestive of repeated explosions eventually triggered by multiple backward migrating block detachments

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

understanding the collapse eruption link at stromboli italy a microanalytical study on the products of the recent secche di lazzaro phreatomagmatic activity abstract the secche di lazzaro sdl phreatomagmatic activity with the associated neostromboli sector collapse represents the most powerful activity of the last 6 ky at stromboli as revealed by its present day activity stromboli is one of the most eruptive volcanoes in italy and flank instability along its nw flank is a common process volcano instability is often dramatised by explosive eruptions thus it is of crucial importance to understand the linking between volcano collapse and the plumbing system itself the possible role of pre eruptive magmatic processes as triggers of explosive eruptions can be mainly preserved by minerals and revealed by petrochemical studies we studied the juvenile components scoria and pumice of the pyroclastic deposits from the sdl phreatomagmatic activity with the aim to understand the eruption collapse link the sdl pyroclastic sequence has been investigated in three different outcrops at secche di lazzaro sdl sw sequence at vallone del monaco sdl s and along the old path from stromboli village to the active craters sdl n juvenile components are ks shoshonites similar to the most evolved lavas erupted at the end of the neostromboli potassic period our study indicates that the sdl system is strongly heterogeneous and made up by at least two different sequences sdl n and sdl sw sdl s with different textural characteristics of the deposits and composition of the juvenile components mineral chemistry data show a variable presence of recycled crystals antecrysts possibly deriving from the previous neostromboli activity up to 13 ky ago whole rocks are characterised by small but significant differences between the sdl n and the southern samples pointing out the presence of compositionally different potassic magmas and the crystallization and recycling of slightly different mineral assemblages a clear isotope heterogeneity has been also found and explained by the presence of 10 minimum of less radiogenic antecrysts whereas crustal contamination would have only affected the higher sr radiogenic residual melt these data suggest that the sdl phreatomagmatic eruptions were fed by compositionally distinct potassic magmas which rested and evolved in two shallow magma conduits when the magma supply ceased in the waning phase of the neostromboli activity our results also rule out the occurrence of new arrivals of refreshing magmas in the sdl feeding system as well as other internal magma related causes as triggers for the sdl explosive eruptions accordingly external collapse related causes seem effectively more suitable for triggering the sdl phreatomagmatic eruptions by decompression of the magmatic systems we also suggest the sdl n and sdl sw sdl s sequences are generated by two respective explosive events separated in time and or space they can be respectively related to multiple failures of sciara del fuoco which successively depressurised the sdl n and the sdl sw sdl s magma conduits

late orogenic basins in the archaean superior province canada characteristics and inferences abstract the late orogenic archaean duparquet kirkland and stormy basins of the canadian superior province are characterized by bounding crustal scale faults and abundant porphyry stock emplacement lava flows and pyroclastic deposits are restricted to the kirkland and stormy basins and coarse clastic detritus characterizes the duparquet basin seven distinct lithofacies are identified 1 mafic volcanic 2 felsic volcanic 3 pyroclastic 4 volcaniclastic 5 conglomerate sandstone 6 sandstone argillite conglomerate and 7 argillite sandstone tuffaceous sandstone the mafic and felsic volcanic lithofacies represent effusive lava flows the pyroclastic lithofacies is formed of subaerial surge and airfall deposits and the volcaniclastic lithofacies is composed of reworked volcanic debris the conglomerate sandstone lithofacies is interpreted as alluvial fan fan delta or proximal braided stream deposits whereas the sandstone argillite lithofacies is consistent with sandy dominated flood or braidplain deposits a dominantly shallow water lacustrine setting is inferred for the argillite sandstone lithofacies these different lithofacies record the basin history and can be used to identify basin forming processes lithofacies stacking and rapid lateral changes of lithological units in conjunction with interformational unconformities and basin margin faults suggest tectonically induced sedimentation volcanism can also influence basin evolution and the delicate balance between erosion sedimentation and prevalent transport processes is affected by volcanic input catastrophic influx of pyroclastic material facilitated mass wasting processes and formation of non confined hyperconcentrated flood flow deposits account for local congestion of alluvial or fluvial dispersal patterns confined stream flow processes govern sedimentation during intravolcanic phases or prominent tectonic uplift in addition climate which controls the weathering processes and vegetation which stabilizes unconsolidated material affects the transport and depositional process a co 2 rich aggressive weathering humid archaean atmosphere favours traction current deposits and an absence of vegetation promotes rapid denudation although tectonism is the prevalent long term controlling factor in restricted basins the effects of volcanism climate and lack of vegetation can also be detected

the solubility of fish produced high magnesium calcite in seawater 1 fish have been shown to produce high 10 to 48 mol magnesium calcite as part of the physiological mechanisms responsible for maintaining salt and water balance the importance of this source to the marine carbon cycle is only now being considered in this paper we report the first measurements of the solubility of this caco3 in seawater the resulting solubility pk sp 5 89 0 09 is approximately two times higher than aragonite and similar to the high magnesium calcite generated on the bahamas banks pk sp 5 90 this high solubility of fish produced caco3 is a result of the high magnesium content and not a product of micro environments created by microbial activity this material is soluble in near surface waters contributing to the input of carbonate to surface ocean waters and may at least partially explain the observed increase in total alkalinity above the aragonite saturation horizon

stability of a collapsing volcano stromboli italy limit equilibrium analysis and numerical modelling abstract stromboli is an active island volcano belonging to the aeolian archipelago italy in the last 13 ka it experienced four lateral collapses affecting its northwestern flank with its most recent volcanic crisis december 2002 associated with landslides and related tsunami events this paper presents the first stability analysis of the stromboli volcanic edifice the main input is the geotechnical model of the volcano defined on the basis of stratigraphical lithological material properties and structural data collected from in situ surveys and laboratory tests two dimensional stability analysis was performed by limit equilibrium methods lem and finite difference modelling flac 4 0 code mainly focusing on the subaerial part of stromboli s nw flank sciara del fuoco the variability of the safety factor was studied by deterministic sensitivity and probabilistic analysis focusing on the effect of external forces such as magma pressure and seismicity as potential triggering mechanisms of lateral collapse the lem analyses were developed considering a maximum depth of 150 350 m for the sliding surface to which correspond collapse volumes of 95 000 185 000 m 3 m respectively the study shows that without external forces the investigated rock mass is stable and that the tectonic seismicity of the area alone does not destabilize the studied slope on the contrary magma pressure in dykes can represent a destabilizing factor numerical modelling results are concordant with those from lem in addition the simulation reveals that deformations and superficial landslides preannounce and contribute to retrogressive plasticization and maybe to failure surface deepening shallow submarine landslides represent a possible triggering mechanism and the landslide events of 30 december 2002 consistently fit the simulated evolution flac has revealed to be a useful tool for modelling such a complex system it allowed to calibrate the response of the geotechnical model test the validity of the assumptions simulate the stress strain evolution and prepare a possible model for future scenarios

reconstruction of the eruptive activity on the ne sector of stromboli volcano timing of flank eruptions since 15 ka a multidisciplinary geological and compositional investigation allowed us to reconstruct the occurrence of flank eruptions on the lower ne flank of stromboli volcano since 15 ka the oldest flank eruption recognised is roisa which occurred at 15 ka during the vancori period and has transitional compositional characteristics between the vancori and neostromboli phases roisa was followed by the san vincenzo eruption that took place at 12 ka during the early stage of neostromboli period the eruptive fissure of san vincenzo gave rise to a large scoria cone located below the village of stromboli and generated a lava flow most of which lies below sea level most of the flank eruptions outside the barren sciara del fuoco occurred in a short time between 9 and 7 ka during the neostromboli period when six eruptive events produced scoria cones spatter ramparts and lava flows the neostromboli products belong to a potassic series ks and cluster in two differently evolved groups after an eruptive pause of 5 000 years the most recent flank eruption involving the ne sector of the island occurred during the recent stromboli period with the formation of the large highly k calc alkaline lava flow field named san bartolo the trend of eruptive fissures since 15 ka ranges from n30 e to n55 e and corresponds to the magma intrusions radiating from the main feeding system of the volcano

civil protection preparedness and response to the 2007 eruptive crisis of stromboli volcano italy abstract stromboli one of the very few tourist volcanic islands in the world in permanent state of activity has been the site of two important volcanic crises coupled with slope failure episodes in 2002 2003 and 2007 due to the lucky circumstance that both crises have occurred in winter the actual consequences on people were moderate nevertheless the first crisis caused a few injuries threatened the local population and caused relevant economic losses the emotional impact on public opinion of the 30th december 2002 tsunami acted in particular as a trigger for civil protection initiatives aimed at structurally improving the standard volcano safety and preparedness measures to effectively deal with future crises the main initiatives carried out during the 2003 crisis consisted in the setting up of 1 new geophysical and geochemical volcano surveillance networks and 2 a local permanent scientific civil protection structure coa centro operativo avanzato where signals from volcano monitoring are visualized in real time and eventually used by the personnel of the department of civil protection dpc for immediate activation of response procedures this was followed by the setting up in 2005 at the dpc in rome of a centre named centro funzionale centrale rischio vulcanico cfcrv where the most relevant monitoring signals of italian active volcanoes are visualized in real time and where activities of simple elaboration for hazard assessment purpose are daily carried out and data sharing within the scientific community is coordinated by civil protection personnel with training in volcanic problems the response effectiveness of the new system was tested on february march 2007 when a new volcanic crisis occurred an internal dpc state of attention was declared by the cf 15 days before the eruption onset when seismic and deformation parameters showed an abrupt increase up to values much higher than background on february 27th the sudden onset of explosive activity outside the main craters and the occurrence of a small landslide down slope of the active craters were detected in real time on the screens of the cfcrv and by monitoring centres of the national institute of geophysics and volcanology ingv and university of florence unifi this enabled the dpc to immediately activate emergency crisis procedures and start a coordinated management of the crisis between civil protection personnel in rome and coa as accelerating slope movements were detected by ground deformation monitoring of unifi a tsunami warning was launched shortly afterward warnings were also declared on 8th march and 15th march when slope movements resumed and a large explosion at the central craters occurred respectively from the end of february to may 2007 a scientific committee named scientific synthesis group ssg appointed by the dpc made daily evaluations of impending hazards in cooperation with cfcrv during the crisis the dpc coordinated information activities with the media and island residents the successful managing of the crisis consisted in minimizing risk for people and meanwhile facilitating normal activities and regular access to island

the uluru ayers rock australia earthquake of 28 may 1989 abstract at 02 hr 55 min 21 sec utc on 28 may 1989 a richter m l 5 6 earthquake occurred in central australia in crystalline basement beneath the southern margin of the amadeus basin near mt olga and uluru ayers rock in the northern territory it had a well constrained focal depth of 31 km which explains why no surface faulting was discovered it is the deepest earthquake known to have occurred in australia prior to 1992 the largest to have been recorded in the region and had no observed foreshocks or aftershocks the earthquake was felt over a radius of 220 km and caused minor damage at yulara the fault plane solution indicates almost pure thrust faulting with a pressure axis striking n 64 e

review of ten years of volcano deformations recorded by the ground based insar monitoring system at stromboli volcano a tool to mitigate volcano flank dynamics and intense volcanic activity abstract stromboli volcano southern italy is one of the most monitored volcano in the world with a surveillance network that includes a permanently sited ground based sar interferometer gbinsar this work is the review of the gbinsar data gained from the last decade of monitoring activity the analysis of the entire dataset of gbinsar measurements allowed the assessment of the deformation field of the northern part of the summit crater area and the sciara del fuoco depression in detail the main displacements recognized can be related to different factors 1 the inflation deflation respectively immediately before and after each new effusive event 2 the bulging of localized sectors of the volcano involved in the vent opening 3 the gravitational sliding of the sciara del fuoco infill 4 the movement of lava flows accelerations in this sector are related to sheet intrusions while the possibility of vent opening associated with small sliding or catastrophic flank failure are related to highly overpressurized sheets able to produce high displacement rate in the sciara del fuoco in the summit crater area the increases in the displacement rate are related to the pressurization of the shallow conduit system as the consequence of the variation in the magma level magmastatic pressure or to the lateral magma migration lateral conduit expansion or dike intrusion in response to the increase of the overpressure component fluctuations in the displacement rate in the summit crater area can be related to the magma overturning within the conduit with the increases in displacement rate during the upwelling of less dense magma while displacement rate decreases as the degassed magma column is pushed out from the conduit lava flows or overflows instead the decrease in the displacement rate without coeval lava outpouring could be related to the sink of the degassed magma due to density contrast between the gas poor and the gas charged magmas using the displacement rate in the summit crater area as a proxy for the variation in the pressure condition in conduit both magmastatic and overpressure components thresholds for the crises characterized by the occurrence of overflows eventually associated with major explosions and flank effusions eventually associated with paroxysmal explosions are identified small conduit overpressure will produce overflows sometimes associated with crater rim collapses while large magma overpressure will laterally expand the conduit forming ne sw striking sheets feeding eruptive vents at the base of the summit crater area and within the sciara del fuoco generating conditions of instability that can evolve into catastrophic collapse of the instable flank

evidence of two holocene phreatomagmatic eruptions at stromboli volcano aeolian islands from paleomagnetic data 1 we present detailed stratigraphic sedimentological and paleomagnetic analyses of holocene phreatomagmatic deposits at stromboli volcano aeolian islands italy the investigated deposits belong to the secche di lazzaro succession sdl and to the advanced operations center of the department of civil defense coa succession both lying on the neostromboli lavas ca 13 5 ka the two stratigraphic successions have similar stratigraphic position and show a phreatomagmatic origin likely related to catastrophic magma water interaction processes during sector collapse events however the thermal remanent magnetization data of the lava lithics indicate that deposits of the sdl succession were emplaced at very low temperatures less than 140 c whereas the basal part of the coa deposit was emplaced at temperatures between 300 340 c paleomagnetic results indicate that the two investigated deposits may be related to two distinct eruptive events occurred during the holocene recent phreatomagmatic activity at stromboli apparently has occurred more frequently than previously believed consequently we must reconsider the recurrence interval of this dangerous eruptive scenario for stromboli

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

glass geochemistry of pyroclastic deposits from the aeolian islands in the last 50 ka a proximal database for tephrochronology abstract volcanic ash 1000 analyses provides a basis for proximal distal and distal distal tephra correlations tephra deposits from the different aeolian islands are geochemically diverse with some individual eruptions showing diagnostic geochemical heterogeneity recognised both stratigraphically and or spatially major element glass analyses reveal that vulcano 0 21 ka and stromboli 4 13 ka have erupted potassic shoshonitic and k series tephra with broadly overlapping compositions but data presented here demonstrates that their eruptive products can be distinguished using either tio2 contents or their hfse th ratios whilst individual volcanic sources often produce successive tephra deposits with near identical major and minor element compositions through time i e lipari vulcano trace element glass data can help to decipher successive eruptions changes in lree and th concentrations of volcanic glasses erupted spanning approximately the last 50 ka greatly enhance the potential to discriminate successive eruptive units on lipari the new proximal glass database has been used to verify new ionian sea core m25 4 12 and existing distal occurrences of aeolian island derived tephra enabling the reassessments of past ash dispersals finally proximal and distal data have been used to establish an integrated proximal distal eruptive event stratigraphy for the aeolian islands