sector collapse sedimentation and clast population evolution at an active island arc volcano stromboli italy sciara del fuoco is the subaerial part of a partially filled sector collapse scar that extends to 700 m below sea level on stromboli volcano the collapse occurred 2200 m and 10 km from the shore to the nnw a fan shaped mounded feature comprises debris avalanche deposits 4 km3 from two or more sector collapses volcaniclastic density currents originating from sciara del fuoco follow the topographic margin of the debris avalanche deposits although overbank currents and other unconfined currents widely cover the mounded feature with turbidites historical recorded eruptive activity in sciara del fuoco is considerably less than that which occurred earlier and much of the partial fill may have formed from eruptions soon after the sector collapse it is possible that a mass of eruptive products similar to that in the collapse scar is dispersed as volcanogenic sediment in deep water of the tyrhennian basin evidence that the early post collapse eruptive discharge was greater than the apparent recent flux 2kg s counters suggestions that a substantial part of stromboli s growth has been endogenous the partial fill of sciaria del fuoco is dominated by lava and spatter layers rather than by the scoria and ash layers classically regarded as main constituents of strombolian cinder cones much of the volcanic slope beneath the vents is steeper than the angle of repose of loose tephra which is therefore rapidly transported to the sea delicate pyroclasts that record the magmatic explosivity are selectively destroyed and diluted during sedimentary transport mainly in avalanches and by shoreline wave reworking and thus the submarine deposits do not record well the extent and diversity of explosive activity and associated clast forming processes considerable amounts of dense non vesicular fine sand and silt grains are produced by breakage and rounding of fragments of lava and agglutinate the submarine extension of the collapse scar and the continuing topographic depression to 2200 m below sea level are zones of considerable by passing of fine sand and silt which are transported in turbidity currents evidently volcanogenic sediments dispersed around island volcanoes by density currents are unlikely to record well the true spectrum and relative importance of clast forming processes that occurred during an eruption marine sedimentary evidence of magmatic explosivity is particularly susceptible to partial or complete obliteration unless there is a high rate of discharge of pyroclastic material into the sea

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

the december 2002 july 2003 effusive event at stromboli volcano italy insights into the shallow plumbing system by petrochemical studies abstract on 28 december 2002 the persistent strombolian activity at stromboli was interrupted by the sudden onset of lava emission onto the sciara del fuoco slope a horseshoe shaped depression on the nw flank of the volcano the effusive episode went on until 22 july 2003 and produced a cumulative volume of lavas of 11 106 m3 ranking the event as the largest occurred in the past 30 years the eruptive vents were mainly located in the ne sector of the sciara del fuoco depression at an elevation of 550 600 m a s l on 30 december the eastern portion of the sciara del fuoco collapsed producing a tsunamigenic landslide on 5 april 2003 a paroxysmal eruption occurred at the summit craters during which crystal poor pumiceous products were emitted the paroxysm did not interrupt the lava emission the strombolian activity at the summit craters gradually resumed starting from march 2003 and fully recovered by the end of july periodic sampling of the lava at the active vents was carried out during the entire effusive event all the analysed samples are shoshonitic basalts sio2 48 5 50 4 wt k2o 2 1 2 4 wt in the range of composition observed in the products erupted during the past 20 years they bear about 50 vol zoned crystals of plagioclase an90 60 diopside augite and olivine fo70 73 in a compositionally homogeneous shoshonitic groundmass bulk rock major and trace element contents measured with different methodologies at different laboratories show only minor variations sr and nd isotope ratios are close to those of the crystal rich scoriae erupted in the previous years despite of small compositional variations related to the emptying of the zoned topmost portion of the conduit the data show that the switch from strombolian explosive to effusive activity is not associated with changes of the textures and composition of the erupted products slight but somehow systematic variation of trace elements and isotope ratios between products erupted before and after the 5 april eruption are likely accounted by limited mixing between the fresh volatile rich crystal poor magma erupted as pumice during the paroxysm and the volatile poor crystal rich magma feeding the lava flow the uniform composition of the erupted lava indicates the presence of a large volume of well mixed crystal rich homogeneous magma residing in the shallow plumbing system of the volcano two possible trigger mechanism of the effusive event are here proposed i a discrete input of fresh magma into the lower part of the shallow magmatic system occurred some months before the eruption and was followed by crystallisation degassing and mixing with the crystal rich shallow magma which re homogenised the system these processes eventually led to the rise of the magma at a higher level and failure of the conduit walls ii the onset of the effusion may represent the consequence of a gradual rise of the magma level in the conduits occurred in the past two decades the process of progressive refilling initiated after the 1985 effusive eruption ultimately culminated on 28 december 2002 with the failure of the conduit wall and the opening of vents 100 150 m below the summit craters

sulfur diffusion in basaltic melts abstract we measured the diffusion coefficients of sulfur in two different basaltic melts at reduced conditions i e in the sulfide stability field temperatures from 1225 c to 1450 c pressures of 0 5 and 1 gpa and water concentrations of 0 and 3 5 wt although each melt is characterized by slightly different sulfur diffusion coefficients the results can be combined to create a general equation for sulfur diffusion in anhydrous basalts d 2 19 10 4 exp 226 3 58 3 r t where d is the diffusion coefficient in m2s 1 the activation energy is in kj mol 1 r is the gas constant and t is the temperature in k sulfur diffusion in basalts with 3 5 wt water is a factor of three to seven higher than in anhydrous melts and can be described by d 5 91 10 7 exp 130 8 82 6 r t at the conditions of this study the pressure does not measurably affect sulfur diffusion sulfur diffusion in dry basaltic melts is one order of magnitude higher than sulfur diffusion in dry andesitic and dacitic melts whereas sulfur diffusion in hydrous basaltic and andesitic melts is within the same order of magnitude when compared to the diffusivity of other volatile species in nominally dry basaltic melts sulfur diffusion appears to be two times lower than co2 diffusion and two orders of magnitude lower than h2o diffusion

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

source mechanisms of explosions at stromboli volcano italy determined from moment tensor inversions of very long period data 1 seismic data recorded in the 2 30 s band at stromboli volcano italy are analyzed to quantify the source mechanisms of strombolian explosions during september 1997 to determine the source centroid location and source mechanism we minimize the residual error between data and synthetics calculated by the finite difference method for a point source embedded in a homogeneous elastic medium that takes topography into account two source centroids are identified each representative of the distinct event types associated with explosive eruptions from two different vents the observed waveforms are well reproduced by our inversion and the two source centroids that best fit the data are offset 220 and 260 m beneath and 160 m northwest of the active vents the source mechanisms include both moment tensor and single force components the principal axes of the moment tensor have amplitude ratios 1 1 2 which can be interpreted as representative of a crack if one assumes the rock matrix at the source to have a poisson ratio n 1 3 a value appropriate for hot rock both imaged cracks dip 60 to the northwest and strike northeast southwest along a direction parallel to the elongation of the volcanic edifice and a prominent zone of structural weakness as expressed by lineaments dikes and brittle structures for our data set the volume changes estimated from the moments are 200 m 3 for the largest explosion from each vent together with the volumetric source is a dominantly vertical force with a magnitude of 10 8 n consistent with the inferred movement of the magma column perched above the source centroid in response to the piston like rise of a slug of gas in the conduit index terms 7215 seismology earthquake parameters 7280 seismology volcano seismology 8419 8414 volcanology eruption mechanisms keywords very long period seismicity moment tensor inversions eruption mehanics

anomalous magmatic degassing prior to the 5th april 2003 paroxysm on stromboli 1 a major explosion occurred at stromboli on april 5 2003 being the most powerful event over a period of exceptional eruptive activity lasting from december to july here we describe results from a network of diffusive tubes set up on the stromboli s summit area aimed at a characterisation of plume composition so2 hcl hf prior to and after april 5 data analysis revealed anomalous sulphur degassing 2 3 days before the event when so2 hcl ratios 9 significantly higher than those typical of quiescent degassing 1 were recorded we interpret this exceptional plume signature as an evidence of s rich magmas ascending in the shallow plumbing system and propose high so2 hcl as a potential precursor of major explosions on the volcano the post april 5 phase was characterised by time decreasing so2 hcl and so2 hf plume ratios ascribed to declining magma feeding as a prelude to restoration of normal strombolian activity

modern pollen climate calibration for southern south america abstract using the response surface technique a modern pollen climate calibration is presented for the mid latitudes in southern south america between latitudes 39 s and 44 s extending from the west coast in chile across the andes into the patagonian steppe region the climate parameters identified that relate to the present day pollen distribution of the nine most important pollen types nothofagus dombeyi type nothofagus obliqua type podocarpus weinmannia caldcluvia eucryphia type cupressaceae myrtaceae misodendrum and steppe types are summer precipitation summer and winter temperatures using the modern pollen climate data set three fossil pollen records mallin aguado and lago moreno east of the andes and caunahue west of the andes are interpreted in terms of these three seasonal climate parameters despite intervals of no analog fossil pollen assemblages the reconstruction shows similar climate trends on both sides of the andes during the last 21 000 cal yr bp 17 000 yr bp with summer precipitation as low or markedly lower than today prior to 17 000 cal yr bp 14 500 yr bp as high or higher than today between 15 000 and 12 500 cal yr bp 12 500 and 10 500 yr bp and again lower than today between 12 500 and 8000 cal yr bp 10 500 and 7200 yr bp summer and winter temperatures were low or high when summer precipitation was high or low

olivine growth rates in a tholeiitic basalt an experimental study of melt inclusions in plagioclase abstract basaltic glass inclusions trapped in plagioclase phenocrysts an 84 are remnant of their parent magmatic liquid they can be used as natural reactors for the experimental investigation of olivine growth rate as a function of temperature the growth of one olivine nucleus can be observed at constant temperature supercooling from 15 to 150 c have been investigated growth habits vary from equant to feather in qualitative agreement with previous studies growth rates vary from 10 m s 1 to 6 10 7 m s 1 they vary with the direction the growth process planar or dendritic and the degree of supercooling chemical analysis of crystal overgrowth and the remaining liquid composition enables a mass balance calculation which confirms the rates determined optically the small number of results obtained so far does not permit to draw inferences on the growth mechanisms

highlights from a seismic broadband array on stromboli volcano an array of nine three component broadband seismometers was deployed in two different configurations on stromboli volcano the analysis of the seismic wavefield related to volcanic explosions revealed some observations which offer a completely new insight into the internal dynamics of a volcano these new observations are restricted to the low frequency range below 1 hz and underline therefore the superiority of broadband recordings over conventional short period observations surprisingly simple wavelets indicate an initially contracting source mechanism gas jets that could not be seen in a short period seismic record at all generate a clear dilatational wavelet in a broadband recording suggesting the same contracting source mechanism the analysis of particle motion and seismic array techniques permits a location of the seismic source we find low frequency signals of 3s and 6s period that are not related to eruptions and do not share a common source with the eruption related events a video recording of visible volcanic activity at the crater region allows one to correlate precisely eruptive features with seismic signals

dynamics of the december 2002 flank failure and tsunami at stromboli volcano inferred by volcanological and geophysical observations 1 the 2002 effusive flank eruption at stromboli volcano started on december 28 after several months of strong explosive activity at the summit craters on december 30 the seismic network recorded two large flank failures and associated tsunami waves this is the first time that a flank collapse and tsunami and their associated phenomena have been recorded by a multi disciplinary monitoring system volcanological and geophysical monitoring as well as thermal surveys performed immediately before and after the failure allowed us to define and interpret the sequence of events the still on going eruption has provided for the first time the opportunity to look into the dynamics of stromboli s effusive eruptions flank failure and landslide formation and their potential hazard

onset of the persistent activity at stromboli volcano italy stromboli known worldwide as the lighthouse of the mediterranean is commonly believed to have been in a state of persistent activity for the past 2000 2500 years however historical sources older than 1000 a d are not accurate enough to assess if the activity of the volcano was exactly the same as we see at present in order to attempt to identify the onset of the present eruptive regime and assess if it has been maintained with the same characteristics through time stratigraphic and radiometric studies of the recent tephra deposits were undertaken up to 4 m deep stratigraphic trenches dug at a height of approximately 500 m on the ne flank of the volcano exposed a conformable tephra pile containing charcoal fragments one of the most interesting finds was the discovery of a 7 cm thick weathered bed rich in organic matter thin palaeosol approximately 3 m below the surface the sequence underneath the palaeosol consists of decimetre thick lapilli fallout beds alternating with ash deposits bearing small charcoals with calibrated ages of between the fourth century b c and the first century a d the sequence above the palaeosol is charcoal free and consists of coarse ash deposits with discrete centimetre thick lapilli fallout beds composed of crystal poor golden pumice and subordinate crystal rich black scoriae similar to scoria pumice pairs emitted during the more energetic explosions of the present day activity the data collected indicate that between the third and seventh centuries a d after a period of quiescence the activity resumed with an eruptive style identical to the present one we conclude that the lighthouse of the mediterranean actually began its activity in a period much later than previously thought

magma budgets and steady state activity of vulcano and stromboli we present three models for magma budget during steady state volcanic activity by which non erupted magma is emplaced as dykes or cumulates or crystallises in place using gas and thermal data we apply our models at vulcano to calculate degassing cooling and crystallisation of magma at a rate of 40 375 kg s 1 within a magma body with an upper surface at a 2 km depth at stromboli we calculate a steady magma supply of 300 1300 kg s 1 to shallow 1 km depths

dynamics of magma mixing and degassing recorded in plagioclase at stromboli aeolian archipelago italy crystal rich materials scoriae and lava flows emitted during the 1985 2000 activity of stromboli were taken into consideration for systematic study of bulk rock matrix glass chemistry and in particular for the study of chemical and textural zoning of plagioclase the most abundant mineral phase over the considered time period bulk rock composition remained fairly constant in both major sio2 49 2 50 9 wt and k2o 1 96 2 18 wt and trace elements the quite constant chemistry of matrix glasses also indicates that the degree of crystallization of magma was maintained at around 50 vol plagioclase ranges in composition between an62 and an88 and is characterized by alternating 10 100 m thick bytownitic and labradoritic concentric layers although the dominant and representative plagioclase of scoriae is an68 the labradoritic layers an62 70 show small scale 1 5 m oscillatory zoning are free of inclusions and appear to record episodes of slow crystal growth in equilibrium with a degassed liquid having the composition of the matrix glass in contrast the bytownitic layers an70 an88 are patchy zoned show sieve structure with abundant micrometric glass inclusions and voids and are attributed to rapid crystal growth

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

volatile induced transport of hfse ree th and u in arc magmas evidence from zirconolite bearing vesicles in potassic lavas of lewotolo volcano indonesia potassium rich calc alkaline lavas of lewotolo volcano situated in the east sunda arc indonesia contain the rare mineral zirconolite cazrti2o7 samples in which tiny grains of this mineral 3 25 m in size were found span the entire range of lava compositions 47 62 wt sio2 to the best of our knowledge this is the first record of primary zirconolite in juvenile arc volcanics the mineral forms part of a vesicle filling assemblage consisting of a network of quenched feldspar crystals and an sio2 phase probably cristobalite high contents of th u and ree up to 9 3 4 3 and 15 6 wt oxide respectively and very high fe contents up to 13 5 wt fe2o3 distinguish these zirconolites from those of other rock types the extraction of volatile rich phases with changing compositions in successive stages is considered to be responsible for the zirconolite formation we hypothesise that a fluid capable of transporting hfse ree th and u was extracted from the magma and partly crystallised within voids which had formed earlier upon saturation of an aqueous fluid assuming that zirconolite compositions largely reflect trace metal contents of the coexisting fluid phase significant amounts of immobile elements must have been transported on a macroscopic scale our findings thus point to a late stage transfer of hfse ree th and u between different domains in a cooling magma body such a volatile induced redistribution of trace elements at shallow levels of high k volcanic systems may be significant for conventional geochemical modelling of magma evolution and for th u disequilibrium studies

volcanic craters pit craters and high level magma feeding systems of a mafic island arc volcano ambrym vanuatu south pacific

dynamics of the 5 april 2003 explosive paroxysm observed at stromboli by a near vent thermal seismic and infrasonic array 1 on 5 april 2003 an array of thermal infrasonic and seismic sensors tracked the dynamics of a major explosive paroxysmal event at stromboli the thermal signal recorded a decline 1 hour before the paroxysm which itself lasted 6 5 minutes and opened with a 14 s low thermal amplitude phase this was followed by three main explosive phases with gas and ejecta velocities of 324 and 185 m s being calculated for the first phase the delay time between thermal and infrasonic signals indicates a very shallow 150 m source for fragmentation a strong tilt component in the seismic signals shows that the conduit began to expand at least 90 s before the explosion large seismic amplitudes were recorded during the emission onset the seismic signal can thus be related to stress build up followed by release during the ejection of the gas particles mixture we calculate that the cloud of hot gas and ash emitted during the explosion had an overpressure of 3 8 mpa and involved 5 7 105 m3 2 9 106 kg of gas

a case history of paroxysmal explosion at stromboli timing and dynamics of the april 5 2003 event abstract on april 5 2003 stromboli volcano italy produced the most violent explosion of the past 50 years the event was exceptionally well documented thanks to the presence on the island of several scientists and a large number of instruments deployed over the preceding months to monitor the effusive eruption that began in december 2002 integration of visual documentation deposit features and geophysical data allowed an accurate reconstruction of the explosive event and its dynamics the eruption consisted of a 8 min long explosive event which evolved through four phases whose timing was precisely recorded by an infrared thermometer located about 450 m from the summit crater phases 2 and 3 lasted 39 and 42 s respectively both had an impulsive character were responsible for ejecting almost the entire mass of the pyroclastic products phases 1 and 4 represented respectively a short lived precursory event and a waning tale during phase 2 meter sized ballistic blocks were launched with velocities of 170 m s to altitudes of up to 1400 m above the craters these fell on the volcano flanks and on the village of ginostra about 2 km distant from the vent a vertical jet rose above the craters which developed to feed a convective plume that reached a height of up to 4 km the calculated mass of the phase 2 fallout deposit and mass discharge rate were 1 1 1 4 108 kg and 2 8 3 6 106 kg s respectively during phase 3 a scoria flow deposit with an estimated volume of 0 9 1 1 104 m3 was erupted from the same vent that fed the ongoing sustained lava flow the average mass discharge rate for this phase was 2 5 3 1 105 kg s products emitted during phases 2 and 3 consisted of lithic and fresh magmatic material in similar proportions the juvenile fraction consisted of a deep originated almost aphyric highly vesicular pumice mingled with a shallow derived crystal rich moderately vesicular scoria similarities with the eruption dynamics of other historical paroxysms at stromboli makes the april 5 2003 explosion representative of these highly energetic events that constitute the most hazardous volcanic phenomena at stromboli volcano

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

effects of magma storage and ascent on the kinetics of crystal growth the size distributions of crystals of olivine plagioclase and oxides of the 1991 93 eruption at mt etna italy are analyzed the simultaneous collection of this information for different minerals gives precious insight into the cooling history of lavas three distinct episodes are detectable a storage of the magma in a deep reservoir characterized by nearly constant and low nucleation and growth rates near to equilibrium an ascent phase with an ever increasing nucleation rate related to volatile exsolution and finally a quenching phase in addition to geochemical and geophysical evidence the similarity of the crystal size distributions of the present eruption with those of previous ones of this century makes it possible to exclude that crystal size distributions of etnean lavas are due to mixing of different populations this strongly suggests that the main features of the volcano feeding system have not changed despite observed variations in the magma output rates

rapid early middle miocene exhumation of the kazdag massif western anatolia apatite fission track analyses indicate that the kazdag massif in northwestern anatolia was exhumed above the apatite partial annealing zone between 20 and 10 ma i e early middle miocene with a cluster of ages at 17 14 ma the structural analysis of low angle shear zones high angle normal faults and strike slip faults as well as stratigraphic analysis of upper plate sedimentary successions and previous radiometric ages point to a two stage structural evolution of the massif the first stage encompassing much of the rapid thermal evolution of the massif comprised late oligocene early miocene low angle detachment faulting and the associated development of small supradetachment grabens filled with a mixture of epiclastic volcaniclastic and volcanic rocks kucukkuyu fm the second stage plio quaternary has been dominated by i strike slip faulting related to the westward propagation of the north anatolian fault system and ii normal faulting associated with present day extension this later stage affected the distribution of fission track ages but did not have a component of vertical normal movement large enough to exhume a new partial annealing zone the thermochronological data presented here support the notion that neogene extensional tectonism in the northern aegean region has been episodic with accelerated pulses in the early middle miocene and plio quaternary

the shallow plumbing system of stromboli island as imaged from 1 hz instantaneous gps positions 1 the stromboli volcano aeolian islands italy erupted suddenly on 28 december 2002 after a 17 year period of typically persistent but moderate eruptive activity followed two days later by a tsunamigenic landslide on its nw flank sciara del fuoco felt in the coastal areas of southern italy three continuous gps stations were quickly deployed near the volcano s rim sampling at 1 hz with instantaneous positions computed relative to a fourth station on its flank we report on two deformation episodes a vent migration on 16 17 february 2003 caused significant displacements at only one site and contributed to the decision not to issue a warning of an impending tsunamigenic landslide the second episode on 5 april 2003 a paroxystic explosion from the summit crater allowed us to model for the first time with geodetic data the shallow magma chambers that give rise to strombolian explosive activity

persistent polybaric rests of calc alkaline magmas at stromboli volcano italy pressure data from fluid inclusions in restitic quartzite nodules a fluid inclusion study has been performed on quartzite nodules of stromboli volcano hosted by calc alkaline lavas of both the strombolicchio 200 ka and paleostromboli ii 60 ka periods the nodules are mainly composed of quartz crystals with subordinate plagioclase and k feldspar small interstitial minerals such as plagioclase k feldspar clinopyroxene biotite and quartz are also found together with glass muscovite epidote and zircon occur as accessory minerals different quartzite nodules occur 1 equigranular polygonal granoblastic quartzite nodules forming a polygonal texture with clear triple points 2 inequigranular polygonal granoblastic quartzite nodules and 3 break up nodules with strongly resorbed quartz these quartzites are restites from partial melting involving felsic crustal rocks at the magma wall rock contact restitic quartz re crystallises at variable and generally high temperatures leading to the formation of quartzites with different textures quartz grains contain five types of fluid inclusions distinguished on the basis of both fluid type and textural phase relationships at room temperature type i are two phase liquid vapour co2 rich fluid inclusions they are primary and subordinately pseudosecondary in origin and have undergone re equilibration processes type ii mono phase two phase vapour liquid vapour co2 rich fluid inclusions are the most common and based on their spatial distribution and shape they can be divided into two subclasses type iia and type iib type ii inclusions are secondary or pseudosecondary and they are assumed to have formed after decrepitation of type i inclusions and cracking of the host quartz type iii inclusions are mono phase vapour they possibly contain co2 at very low density and surround the inner rims of quartz grains type iv two phase silicate melt inclusions contain glass co2 rich fluid some of them are cogenetic with type ii inclusions finally type v two phase liquid vapour aqueous inclusions are both vapour rich and liquid rich aqueous inclusions microthermometric experiments were performed on both type i and ii inclusions type i inclusions homogenise to liquid between 20 and 30 5 c type iia inclusions homogenise to vapour in the 24 to 30 c range with a maximum peak of frequency at 29 c type iib inclusions also homogenise to vapour between 14 and 25 c there appears to be no difference in homogenisation temperature distribution between the strombolicchio and paleostromboli ii samples the trapping pressures of the fluid inclusions have been obtained by combining the microthermometric data of the strombolicchio and paleostromboli ii samples with the pressure temperature volume i e density characteristics for a pure co2 system the data on the early inclusions type i suggest an important magma rest at a pressure of about 290 mpa i e about 11 km depth type iia co2 inclusions suggest that a second magma rest occurred at a pressure of about 100 mpa i e about 3 5 km depth whereas type iib inclusions were trapped later at a shallower depth during the final magma upwelling no pressure depth differences seem to occur between the strombolicchio and paleostromboli ii periods indicating the same polybaric rests for the calc alkaline magmas of stromboli despite their significantly different ages this persistence in magma stagnation conditions from 200 to 60 ka suggests a similar plumbing system for the present day strombolian activity

the stromboli volcano landslides of december 2002 a seismological description 1 we analyse seismograms of the slump episodes at stromboli on december 30 2002 using a simple single force model we estimate the volume involved in the individual subevents and attempt a chronological reconstruction of the whole process our results indicate the occurrence of two main events that could be interpreted as a submarine slump which caused the observed tsunami and a subaerial slump which did not produce destructive sea waves a total volume of about 20 106 m3 results for the submarine event which developed over about 2 minutes with several distinct detachments the first and largest displacing a volume of 10 8 106 m3 the second subaerial slump involved at least 2 5 106 m3 in about 90 s a large long period pulse is also recognizable in the seismograms of the stromboli station we tentatively interpret this feature as tilt caused by the water load associated with the inundation in the ficogrande area on the northeastern side of the island

crystal size distribution csd in rocks and the kinetics and dynamics of crystallization ii makaopuhi lava lake crystal size distribution csd theory has been applied to drill core samples from makaopuhi lava lake kilauea volcano hawaii plagioclase and fe ti oxide size distribution spectra were measured and population densities n were calculated and analyzed using a steady state crystal population balance equation n n0 exp l g slopes on ln n versus crystal size l plots determine the parameter g a product of average crystal growth rate g and average crystal growth time the intercept is j g where j is nucleation rate known temperature depth distributions for the lava lake provide an estimate of effective growth time allowing nucleation and growth rates to be determined that are independent of any kinetic model plagioclase growth rates decrease with increasing crystallinity 9 9 5 4 10 11 cm s as do plagioclase nucleation rates 33 9 1 6 10 3 cm3 s ilmenite growth and nucleation rates also decrease with increasing crystallinity 4 9 3 4 10 10 cm s and 15 2 2 10 3 cm3 s respectively magnetite growth and nucleation rates are also estimated from the one sample collected below the magnetite liquidus g 2 9 10 10 cm s j 7 6 10 2 cm3 s moments of the population density function were used to examine the change in crystallization rates with time preliminary results suggest that total crystal volume increases approximately linearly with time after 50 crystallization a more complete set of samples is needed for material with 50 crystals to define the entire crystallization history comparisons of calculated crystallization rates with experimental data suggests that crystallization in the lava lake occurred at very small values of undercooling this interpretation is consistent with proposed thermal models of magmatic cooling where heat loss is balanced by latent heat production to maintain equilibrium cooling

effusive to explosive transition during the 2003 eruption of stromboli volcano the persistent explosive activity of stromboli volcano italy ceased in december 2002 and correlated with the onset of a seven month long effusive eruption on the volcano flank from new vents that opened just below the summit craters we intensively monitored this effusive event collecting and interpreting in real time an extensive multiparametric geophysical data set the resulting data synergy allowed detailed insights into the conduit dynamics that drove the eruption and the transition back to the typical strombolian activity we present a direct link between gas flux magma volume flux and seismicity supporting a gas driven model whereby the balance between gas flux and gas overpressure determines whether the system will support effusive or explosive activity this insight enabled us to monitor the migration of the magma column up the conduit and to explain the onset of explosive activity

the 5 april 2003 vulcanian paroxysmal explosion at stromboli volcano italy from field observations and thermal data abstract the 5 april 2003 paroxysmal explosion at stromboli volcano was one of the strongest explosive events of the last century it occurred while the effusive eruption begun on 28 december 2002 and finished on 22 july 2003 was still on going and the summit craters of the volcano were obstructed in this paper we present a reconstruction of the sequence of events based on thermal and visual images collected from helicopter before during and immediately after the paroxysm one month before the blast ash emission and temperature increase at the bottom of the summit craters were observed an increasing amount of juvenile components in the emitted ash during march suggested that the magma level within the crater was rising accordingly hot degassing vents at the bottom of the summit craters were not persistent and the craters remained almost entirely obstructed by talus accumulation until the paroxysm occurred three minutes before the explosion we recorded a significant increase in temperature inside crater 1 accompanied by a thicker gas plume thirty two seconds before the blast reddish ash was emitted from crater 1 the paroxysm produced a vulcanian explosion that opened the feeder conduit obstructed for over three months the blast was accompanied by a shock wave recorded by the ingv seismic network at 07 13 37 gmt explosions with hot material started from crater 1 and after 15 s propagated to crater 3 about 100 m away the velocity of ejecta was 80 m s 1 and increased when the eruptive plumes from both craters merged together during the vulcanian phase an eruptive column rose 1 km above the top of the volcano and explosions continued mainly at crater 3 the paroxysm lasted about 9 min with bombs up to 4 m wide falling on the village of ginostra on the west flank of the island and destroying two houses this event signalled the start of the declining phase of the effusive eruption suggesting that the feeder conduit was returning to its former steady conditions with open vents and continuous mild strombolian activity

textural effects of steady state behaviour of the stromboli feeding system abstract the exceptionally persistent activity of stromboli volcano has lasted for at least 1400 years the normal strombolian activity is periodically interrupted by more energetic explosions 1 2 per year and by sporadic effusive episodes every 10 20 years normal activity and effusive episodes are characterized by crystal rich high k to shoshonitic basalts issuing from a volatile poor shallow system crystal poor pumice are emitted only during more violent explosions and are thought to derive from deep pulses of volatile rich magma shallow level degassing induces massive crystallization of deep pulses of feeding magma that continuously mixing with the resident one produces the crystal rich shoshonite of the persistent activity we examined the crystallization history of the crystal rich shallow reservoir using plagioclase crystal size distribution csd analysis of scoriae and lavas emitted in the past twenty years csds show a linear dependence from crystal size in the size interval 0 06 1 2 mm number density of larger crystals is biased by right hand truncation effects csds slopes and intercepts are quite constant during the whole considered time span revealing a system that is close to the equilibrium also from a kinetic point of view the linear crystal size distribution are reached by the system through episodes of growth and resorption respectively occurring in the degassed and undegassed magma during the continuous mixing in the feeding system plagioclase net growth rate 2 10 11 cm s results from a balance of growth 10 10 cm s and resorption episodes which induce spectacular zoning and resorption textures in crystals larger than 200 m csds of mafic phases cannot be accurately acquired on each single sample due to poor counting statistics the evaluation of pyroxene and olivine csd on the whole data set however confirms the conclusions acquired from plagioclase csds

cooling kinetics experiments on different stromboli lavas effects on crystal morphologies and phases composition abstract controlled cooling experiments at atmospheric pressure and fo2 of the nno buffer were performed on three stromboli lavas of calcalkaline ca high k calcalkaline hkca and shoshonitic sho affinities the experiments were conducted at cooling rates of 900 c h fast cooling rate fcr and 1 c h slow cooling rate scr respectively to investigate the kinetic factors governing textural and compositional features such as phase growth morphology phase relations and phase compositions the experiments produced different types of textures as both the cooling rate and the quenching temperatures were varied in general fcr experiments show a decrease of crystal size as well as a change in crystal shape from euhedral to granular to skeletal up to dendritic morphology with decreasing temperatures scr experiments produce less variable crystal size and crystal morphology measurements of plagioclases indicate that the crystal size and calculated crystal growth are functions of cooling rate crystal growth rates are about two orders of magnitude higher in fcr experiments than scr ones such textural responses are in agreement with the empirical calibration based on the plagioclase size dependence on cooling rate developed by cashman 1993 experimental phase relations display three main features of the crystallization process 1 the delay in the crystallization of the liquidus phase in the fcr experiments with respect to the scr ones 2 crystallization controlled by the multiphase cotectic relations plagioclase pyroxenes olivine is more enhanced for fcr experiments compared to that of scr ones at the lowest experimental temperature 1100 c 3 crystallization of augite and pigeonite is sensitive to cooling rate and system compositions pigeonite not found in the natural rocks crystallizes in the ca sample across scr and fcr runs and in the hkca sample just in the scr experiments fcr and scr experiments produce similar liquid lines of descent for both ca and hkca starting materials suggesting that the processes of nucleation and growth play reciprocal roles through mass balance as cooling rate varies this is not true for the sho composition where the trends of melt composition appear to be especially influenced by the different amounts of olivine crystallization at the different cooling rates data on mineral compositions show that plagioclase and clinopyroxene are the phases more strongly affected by the cooling gradients crystals from scr experiments and to a lesser extent from fcr experiments show zoning patterns mainly at the lowest experimental temperature

geochemical precursors of the activity of an open conduit volcano the stromboli 2002 2003 eruptive events 1 marked increases of co2 h2 and he dissolved in thermal waters and changes in the dissolved carbon isotopic composition were observed at stromboli before the 28 december 2002 eruption and before a violent explosive paroxysm occurred on 5 april 2003 high anomalous co2 flux values were recorded at the crater rim since a week before the eruption onset the first anomalies in the thermal waters dissolved co2 amount appeared some months before the eruption when magma column rose at a very high level in the conduit high peaks of dissolved h2 and he were recorded a few days before the paroxysm carbon isotopic composition indicates a magmatic origin of the dissolved co2 whose increase together with those of h2 and he is attributed to an increasing output of deep gases likely produced by depressurization of a rising batch of a deep gas rich magma whose fragments have been emitted during the explosion

stability of the seismic source during effusive and explosive activity at stromboli volcano 1 in december 2002 stromboli volcano erupted triggering a sector collapse and a tsunami during the 7 month long effusive eruption the typical persistent and moderate explosive activity of stromboli ceased however very long period vlp seismic events typically associated with the explosions at stromboli were recorded during the effusive eruption these were clustered mainly in two groups with stable waveforms this suggests that strombolian activity never ceased but was confined deep within the magma conduit a location method based on the seismic directivity recorded with an asynchronous seismic deployment positioned the two clusters 60 m apart from each other at 510 m a s l and 180 m nw from the summit craters however seismic polarization reveals a 50 m upward migration of the vlp source at the end of the eruption when volcanic activity moved from the effusive style to more typical strombolian activity

pressure changes associated with the ascent and bursting of gas slugs in liquid filled vertical and inclined conduits at basaltic volcanoes the sources of long period and very long period seismicity and acoustic signals are frequently described in terms of fluid dynamic processes in particular the formation and ascent of gas slugs within the magma column and their bursting at the surface to investigate pressure changes associated with these processes two phase flow experiments have been carried out in vertical and inclined pipes with both single gas slugs and a continuously supplied gas phase the ascent of individual gas slugs is accompanied by strong dynamic pressure variations resulting from the flow of liquid around the slug these dynamic transients generate sub static pressures below the ascending slug in viscosity controlled systems and produce super static pressures when the slug reaches the surface and motion ceases in inertia dominated systems conduit inclination promotes a change of regime from bubbly to slug flow and favours an increase in size and velocity of the slugs at the expense of their frequency of occurrence during continuously supplied two phase flow the experimental pressure data support previous theoretical analyses of oscillatory sources in ascending slugs as the slugs approach the surface and burst pressure oscillations are also observed during the release of gas slugs and in their wake region

seismological insight into the kinematics of the 5 april 2003 vulcanian explosion at stromboli volcano southern italy 1 on 5 april 2003 at 07 13 gmt 09 13 local time a violent vulcanian explosion occurred at stromboli volcano at the time of the event an eruptive crisis was ongoing at the volcano with a lava flow outpouring along the sciara del fuoco flank the seismic signals related to the event were recorded by 8 permanent broadband stations and gives information about the eruption kinematics an ultra long period signal period 20 s that we interpret as the effect of the ground tilt on the broadband sensors starts about 4 min before and terminates about 1 min after the explosion on the basis of the radial pattern of tilt directions we conclude that this signal is the effect of the deformation of the volcanic edifice due to the rapid rising of a batch of magma its ejection and the magma column readjustment about 1 min before the explosion we observe an high frequency signal period 0 1 s that we believe to be related to the vesiculation of the rising batch of gas rich magma at 07 13 35 gmt a powerful very long period signal period 2 20 s marking the onset of the explosive fragmentation is recorded this is confirmed by a blast wave following few seconds later the remaining seismic signal more than 3 min shows an higher frequency content being related only to the fall of ballistic ejecta and to landslides along sciara del fuoco we propose the implementation of an early warning system for the short term forecast of such explosions based on the real time automatic detection of the tilt signals preceding such events

tracking precursors and degassing by radon monitoring during major eruptions at stromboli volcano aeolian islands italy 1 we monitored radon anomalies before during and after the recent paroxysmal eruptions of stromboli major eruptive events are preceded by relative minima in radon emissions at stations located at the base of the cone whereas three of the summit stations reached peak values 20 000 bq m3 or higher 12 to 14 days before major eruptions and are nearly coeval with earth tides radon emissions at or above such high threshold values are proposed to result from the dynamic response of the fracture network due to degassing processes associated with magma ascent relative minima recorded at the base of the cone are related to fractures self sealing within the hydrothermal system eventually coupled with the atmospheric stack effect the coexistence of the above anomalies is interpreted as the first precursory signals to major eruptive events

triggering mechanism at the origin of paroxysms at stromboli aeolian archipelago italy the 5 april 2003 eruption 1 the 5 april 2003 paroxysm of stromboli occurred during an ongoing effusive episode that initiated on 28 december 2002 it mainly consisted in two a few seconds apart cannon like explosions followed by a vertical gas pyroclast jet the hk basaltic pumices that were generated mainly contain crystals that were drained back from the shallow parts of the plumbing system few euhedral to anhedral olivines and their melt inclusions testify to crystal fractionation and possible mixing between hk basaltic magmas variable in their volatile content extent of evolution and volume the most primitive volatile rich hk basalt term is sizable at micrometer scale only we propose that the triggering mechanism of the paroxysm was initiated at moderate pressures 240 mpa and was related to bubble driven ascent of magma blobs the latter rose through and interacted with overlying slightly more evolved melts and finally mingled with the shallow crystal rich magma just before the eruption