self sustained oscillations at volcan de colima mexico inferred by independent component analysis we have analyzed long period lp seismic events of volcan de colima mexico recorded by four three component broad band seismometers during january 2006 frequency domain analysis shows spectra mainly peaked in the range 0 3 2 hz and characterized by a monotonic decreasing envelope as those produced in a cylindrically symmetric self oscillating cavity interacting with a confined jet independent component analysis a time series decomposition method extracts two or three nonlinear oscillation modes depending on the station with the fundamental one peaked at 0 4 0 5 hz these decomposed waves have a well defined spectral content and are self sustained oscillations with low dimensionality as shown by dynamic system reconstruction methods moreover they show radial polarization in near field and transverse polarization in far field in north west south east direction finally we hypothesize a branched plumbing system with two principal conduits having alignments orthogonal to one another

lagoonal deposits in the upper cretaceous rock springs formation mesaverde group southwest wyoming abstract most paleogeographic reconstructions of the rock springs formation show shorelines having lobate to arcuate deltas these shorelines are oriented ne sw with the sea to the southeast brackish water bodies are usually shown in interdistributary areas or associated with abandoned delta lobes and are open to the sea in this study a sedimentary sequence 30 50 m thick is interpreted as interdeltaic deposits brackish water deposits within the sequence are interpreted as interdeltaic lagoons rather than interdistributary bays three facies associations units are recognized in nine measured sections of the study interval unit a consists of interbedded sandstone mudrock and coal which occur in both fining and coarsening upward sequences less than 10 m thick fining upward sequences decrease in thickness and frequency upwards in unit a and are interpreted as distributary channels coarsening upward sequences associated with the channels are interpreted as crevasse splays that filled lakes or interdistributary bays in the upper part of the unit where only minor channels are present the coarsening upward sequences are interpreted as bay deltas unit b consists of fossiliferous silty shale and bioturbated sandy siltstone a low diversity fauna of bivalves gastropods ostracods and foraminifers indicates that brackish water conditions existed unit b intertongues with unit a to the northwest and with unit c to the southeast and is interpreted as lagoonal deposits unit c consists of crossbedded and burrowed sandstone in beds 0 5 9 m thick sandstones are laterally continuous in the southeast but become tabular bodies enclosed within unit b to the northwest laterally continuous sandstones are interpreted as shoreface deposits on the basis of multidirectional crossbeds marine trace fossils and continuity tabular sandstones are interpreted as flood tidal deltas on the basis of nw oriented crossbeds pinchouts to the northwest and enclosure within unit b scoured surfaces and rip up clasts within unit c indicate the presence of tidal channels or inlets interpreting unit b as an interdeltaic lagoon rather than an interdistributary bay is dependent on understanding its enclosing strata the distributary channels of unit a supplied the majority of the sediment in the lower part of the sequence however after the lagoon formed tidal channels and inlets of unit c supplied more sediment to the area than channels of unit a the shift in sedimentation from a landward to a seaward source reflects the change from a delta plain to an interdeltaic lagoon following abandonment of distributary channels

modelling of the april 5 2003 stromboli italy paroxysmal eruption from the inversion of broadband seismic data abstract on april 5 2003 one of the largest eruptions in the last decades was observed at stromboli volcano italy the eruption occurred in a period of increased volcanic activity following a first explosion in december 2002 which interrupted the typical moderate strombolian behaviour we present an exhaustive analysis of the available broadband seismic data and relate them to the observed eruption phases prominent features of the seismic signals include an ultra long period signal starting a few tens of seconds prior to the explosive eruption as well as a strong energetic signal a few seconds after the onset of the eruption both signals are not exactly synchronized with the other geophysical observations we present a detailed study of those signals using spectral and particle motion techniques we estimate eruption parameters and seismic source characteristics by different inversion approaches results clearly indicate that the paroxysmal eruption was triggered by a shallow slow thrust faulting dislocation event with a moment magnitude of m w 3 0 and possibly associated with a crack that formed previously by dike extrusion at least one blow out phase during the paroxysmal explosion could be identified from seismic signals with an equivalent moment magnitude of m w 3 7 and is represented by a vertical linear vector dipole and two weaker horizontal linear dipoles in opposite direction plus a vertical force

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

magma dynamics during the 2007 stromboli eruption aeolian islands italy mineralogical geochemical and isotopic data abstract after the 6 month long effusive event of 2002 2003 a new lava effusion occurred at stromboli between 27 february and 2 april 2007 despite the different durations approximately the same volume of magma was emitted in both eruptions in the order of 107 m3 a paroxysmal eruption occurred at the summit craters in both the 2002 2003 and 2007 episodes during which a significant amount of low porphyritic lp volatile rich magma was erupted in both cases the paroxysm did not interrupt the lava emission here we present compositional data including texture mineralogy chemistry and sr and nd isotope ratios of bulk rock groundmass and separated minerals of lavas erupted in 2007 together with chemistry and sr and nd isotope composition of the pumices emitted during the 15 march paroxysm as a whole the lavas have the same texture and chemistry that characterize the highly porphyritic hp products usually erupted at stromboli during normal strombolian activity and effusive events compared to the previous hp products the 2007 lavas show minor but systematic mineralogical and isotopic variations which are consistent with a modest increase of the magma supply rate of the volcano compositional variations during the entire duration of the event are very modest glass chemistry changes in lavas erupted in the second half of march can be explained by the minor mixing between the volatile rich lp magma rising through the shallow magmatic system during the 15 march paroxysm and the degassed residing hp magma a first conclusion of this study is that there is no compositional evidence supporting major changes in the magma dynamics of the volcano accompanying the effusive activity as also suggested for the 2002 2003 event the activity of stromboli is controlled by a steady state feeding system in which refilling mixing degassing and crystallization at shallow level continuously operate with modest oscillations in the magma supply rate switching between normal strombolian and effusive activity is related to periods of relatively more vigorous refilling of the shallow system leading to progressive pressure increase in the upper conduits associated with only minor compositional variations in the erupted products

an inlet sequence produced by migration of a small microtidal inlet against longshore drift the keurbooms inlet south africa lateral migration of the keurbooms inlet along its barrier causes stratigraphic stacking of the different sedimentary units in the inlet area thus accumulating an inlet sequence under the newly formed barrier deposition in the inlet is controlled by wave and tidal action migration is caused by sediment accretion on the downdrift side of the inlet and erosion on its updrift side the migration direction is therefore in the opposite direction to the longshore current this is comparatively rare as most inlets with a tendency to migrate do so in the same direction as longshore drift tidal current directions in the inlet are highly variable and not bipolar the inlet associated environment is divided into a seaward wave dominated zone and a landward tide dominated zone these zones probably have laterally interfingering facies only the lower part of the sequence is likely to be preserved recognition of ancient analogues in the rock record may be obscured by the unidirectional palaeocurrent pattern of the lower part of the inlet sequence

correlation of gold in siliceous sinters with 3he4he in hot spring waters of yellowstone national park opaline sinter samples collected at yellowstone national park ynp were analyzed for gold by neutron activation and for other trace elements by the inductively coupled plasma optical emission spectroscopy icp oes method no correlation was found between au and as sb or total fe in the sinters although the sample containing the highest au also contains the highest sb there also was no correlation of au in the sinter with the h2s concentration in the discharged hot spring water or with the estimated temperature of last equilibration of the water with the surrounding rock the au in rhyolitic tuffs and lavas at ynp found within the yellowstone caldera show the same range in au as do those outside the caldera while thermal waters from within this caldera all have been found to contain relatively low dissolved au and to deposit sinters that contain relatively little au therefore it is not likely that variations in au concentrations among these sinters simply reflect differences in leachable au in the rocks through which the hydrothermal fluids have passed rather variations in h2s the concentration of total dissolved sulfide that result from different physical and chemical processes that occur in different parts of the hydrothermal system appear to exert the main control on the abundance of au in these sinters hydrothermal fluids at ynp convect upward through a series of successively shallower and cooler reservoirs where water rock chemical and isotopic reactions occur in response to changing temperature and pressure in some parts of the system the fluids undergo decompressional boiling and in other parts they cool conductively without boiling mixing of ascending water from deep in the system with shallow groundwaters is common all three processes generally result in a decrease in h2s and destabilize dissolved gold bisulfide complexes in reservoir waters in the ynp system thus different reservoirs in rocks of similar composition and at similar temperatures may contain waters with different h2s and au the h2s in a subsurface reservoir water is difficult to assess on the basis of analyses of hot spring waters because of uncertainties about steam loss during fluid ascent however the same processes that result in low h2s in reservoir waters also tend to result in decreases in the ratio of 3he4he r dissolved in that water values of r relative to this ratio in air ra attain values 15 in ynp thermal waters to date all of the thermal waters at ynp that have rra values 9 have been found to deposit sinters with relatively low gold concentrations these include all of the thermal waters that discharge from 180 215 c reservoirs at upper midway and lower geyser basins within the western part of the yellowstone caldera and thermal waters at norris geyser basin outside the yellowstone caldera where some of the waters flow directly to the surface from a reservoir where the temperature is about 300 c a high 3he4he ratio in thermal water discharged at the surface does not guarantee high gold concentrations in the sinter deposited by this water boiling with loss of steam the gas phase takes a separate route to the surface during rapid upflow from the shallowest reservoir to the surface decreases the h2s and total he dissolved in the residual liquid without appreciably changing the 3he4he ratio this is because the isotopic composition of the he of the initial bulk fluid is unchanged and there is too little time for much radiogenic 4he to build back into the liquid during this rapid ascent from the near surface reservoir however if boiling with phase separation and loss of steam occurs deep in the system the 3he4he ratio in the residual liquid now depleted in h2s and total he will be susceptible to dilution with radiogenic 4he that is acquired during the longer residence time underground some or all of the au that comes out of solution when an initial gold bisulfide complex breaks down as a result of loss of h2s may be swept up to the surface as solid probably colloidal particles depending on the rate of flow of the mixture of water and steam and the geometry of the channel where colloidal silica also forms as a result of this boiling free au apparently becomes attached to the colloidal silica and deposits where the silica deposits

time scale of hydrothermal water rock reactions in yellowstone national park based on radium isotopes and radon journal of volcanology and geothermal research 40 1990 169 180 elsevier science publishers b v amsterdam printed in the netherlands time scale of hydrothermal water rock reactions in yellowstone national park based on radium isotopes and radon jordan f clark and karl k turekian department of geology and geophysics yale university box 6666 new haven ct 06511 u s a received january 15 1989 revised and accepted august 8 1989 abstract clark j f and turekian k k 1990 time scale of hydrothermal water rock reactions in yellowstone national park based on radium isotopes and radon j volcanol geotherm res 40 169 180 we have measured 224ra 3 4 d 228ra 5 7 yr and 226ra 1620 yr and chloride in hot spring waters from the norris mammoth corridor yellowstone national park two characteristic cold water components mix with the primary hydrothermal water one for the travertine depositing waters related to the mammoth hot springs and the other for the sinter depositing norris geyser basin springs the mammoth hot springs water is a mixture of the primary hydrothermal fluid with meteoric waters flowing through the madison limestone as shown by the systematic decrease of the 228ra 22era activity ratio proceeding northward the norris geyser basin springs are mixtures of primary hydrothermal water with different amounts of cold meteoric water with no modification of the primary hydrothermal 228ra 226ra activity ratio using a solution and recoil model for radium isotope supply to the primary hydrothermal water a mean water rock reaction time prior to expansion at 350 c and supply to the surface is 540 years assuming that 250 g of water are involved in the release of the radium from one gram of rock the maximum reaction time allowed by our model is 1150 years introduction hydrothermal activity in the form of hot springs and geysers is the geologic feature which most vividly characterizes yellowstone na tional park the greatest diversity in dynamic and depositional features ascribable to this ac tivity is found in the norris geyser basin and the norris mammoth corridor see the recent summary by white et al 1988 the source of heat is clearly magmatic but the exact process by which the extensive heat loss is maintained is not well understood four nier and pitt 1985 and fournier 1989 sug gest that the hydrothermal system at yellow stone is driven by the crystallization of magma and the cooling of local hot rocks white et al 1988 suggest that the hot spot refluxing of basaltic magma beneath a cover of continental rocks and acidic volcanics is the source of the heat the scale of the reaction time between the percolating meteoric water and the rocks in the region of the magmatic activity is controlled by the flow rate the path length and the rate of heating to near the critical temperature at depth truesdell and fournier 1976 the high tem perature waters are subsequently cooled by steam separation conduction and mixing with a cold water reservoir during ascent the final temperature of the hot spring is generally well below the reaction temperature 1990 elsevier science publishers b v

the geothermal system of wairakei new zealand physical processes and age estimates inferred from noble gases abstract atmospheric and non atmospheric noble gases were identified by their isotopic composition in 31 samples from geothermal features from the wairakei tauhara and mokai geothermal fields north island new zealand in the fumaroles atmospheric noble gases ang were found in concentrations that exceed the values in air saturated recharge water asw by a factor of up to 14 significant concentrations of non atmospheric na 4 he he na and 40 ar ar na were observed up to 4 3 10 4 and up to2 9 10 4 cm 3 stp g fluid respectively in contrast the hot spring waters revealed significant depletions in ang as low as 0 02 of the asw concentrations and low but recognizable concentrations of he na and ar na in geothermal wells a wide spectrum of ang concentrations was observed from 0 02 to 30 times the concentrations in asw 4 he na and 40 ar na varied accordingly these observations lead to the simplified boiling model meteoric water penetrated into the geothermal compartment where it was heated and enriched by 4 he na and 40 ar na of mantle and crustal origins boiling of ascending fluid due to pressure decrease results in formation of a noble gas enriched steam phase issuing as fumaroles and drowned fumaroles and a noble gas depleted residual liquid the latter may cause secondary boiling of shallow groundwater emerging in hot springs geothermal wells tap fluids at various degrees of steam separation the depth of recharge of meteoric water into the geothermal system exceeds the depth of boiling which is 600 m at the studied area the ang patterns along with he na ang ratios are applied to identify the following physical processes a mixing of early separated steam with residual liquid b mixing of a few per cent groundwater with residual liquid c addition of air d addition of excess ne and e encroachment of recent groundwater due to pressure decrease retention enrichment values of the ang were applied to reconstruct non atmospheric initial nai concentrations of he nai ar nai and the initial co 2 in the geothermal water literature data on 3 he 4 he were used to separate the 4 he nai concentrations into crustal and mantle derived components the crustal radiogenic 4 he concentration calculated for the initial water was applied to derive an age estimate of the geothermal water assuming storage in rhyolitic rocks effective ages of 2 10 4 1 10 5 and2 10 5 a were obtained for the initial liquids feeding the wairakei wells fumaroles and mokai wells respectively crustal ar na concentrations were estimated from those of crustal he and from the rhyolitic 4 he 40 ar production ratio the calculated crustal 40 ar is 0 1 of 40 ar na and 4 he 40 ar contribution is found at wairakei to be 0 5 within the range of values measured by other workers in mantle derived rocks

holocene evolution of the canet st nazaire lagoon golfe du lion france as determined from a study of sediment properties the sedimentation in the lagoons of the golfe du lion coast mediterranean sea france records their post holocene evolution the canet st nazaire lagoon provides an example of such an evolution eight cores ranging from 13 5 to 19 7 m in length from a transect of the lagoon provide a cross section of the late quaternary stratigraphy the sedimentary sequence comprises mud and sand layers the two sand formations are identified as parts of two distinct shelf sedimentary prisms stratigraphic analysis defines three stages in the recent muddy infilling corresponding to the last divisions of the holocene sedimentation rates of the muds related to climatic and palaeogeomorphological events largely determine their geotechnical and geochemical properties it appears indeed to be the most important factor in determining the compressibility index the saturated bulk density and the organic and water contents of the deposits subboreal muds poorly consolidated and rich in organic matter correspond to a high rate of deposition in the subatlantic muds in contrast the sedimentation rate is lower whilst there is a decrease in the organic matter and an increase in the degree of cohesion

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

generation and evolution of hydrothermal fluids at yellowstone insights from the heart lake geyser basin 1 we sampled fumaroles and hot springs from the heart lake geyser basin hlgb measured water and gas discharge and estimated heat and mass flux from this geothermal area in 2009 the combined data set reveals that diverse fluids share an origin by mixing of deep solute rich parent water with dilute heated meteoric water accompanied by subsequent boiling a variety of chemical and isotopic geothermometers are consistent with a parent water that equilibrates with rocks at 205 c 10 c and then undergoes 21 2 adiabatic boiling measured diffuse co2 flux and fumarole compositions are consistent with an initial dissolved co2 concentration of 21 7 mmol upon arrival at the caldera boundary and prior to southeast flow boiling and discharge along the witch creek drainage the calculated advective flow from the basin is 78 16 l s 1of parent thermal water corresponding to 68 14 mw or 1 of the estimated thermal flux from yellowstone helium and carbon isotopes reveal minor addition of locally derived crustal biogenic and meteoric gases as this fluid boils and degasses reducing the he isotope ratio rc ra from 2 91 to 1 09 the hlgb is one of the few thermal areas at yellowstone that approaches a closed system where a series of progressively boiled waters can be sampled along with related steam and noncondensable gas at other yellowstone locations steam and gas are found without associated neutral cl waters e g hot spring basin or cl rich waters emerge without significant associated steam and gas upper geyser basin

evidence of vlp volcanic tremor in the band 0 2 0 5 hz at stromboli volcano italy 1 we analyze time series of strombolian volcanic tremor recorded with a network of broadband seismic stations we evidence the occurrence of a significant component of volcanic tremor in the range 0 2 0 5 hz by using linear and nonlinear methods the polarization and zlcc analysis show that the wave field is characterized by high apparent velocity 2 km s it comes mainly from the crater area with a clear amplitude decay towards the sea level the previous properties are loosed when the tremor level is higher suggesting that in this case the wave field is more affected by oceanic noise the waveform extracted by independent component analysis ica shows a behaviour like nonlinear beats as in the case of high frequency waveforms we conclude that this component displays a behaviour like the wave field at higher frequencies in spite of its low frequency and it is produced by the vibrations of the volcanic conduit

sulfur geochemistry of hydrothermal waters in yellowstone national park i the origin of thiosulfate in hot spring waters thiosulfate s sub 2 o sub 3 sup 2 minus polythionate s sub x o sub 6 sup 2 minus dissolved sulfide h sub 2 s and sulfate so sub 4 sup 2 minus concentrations in thirty nine alkaline and acidic springs in yellowstone national park ynp were determined the analyses were conducted on site using ion chromatography for thiosulfate polythionate and sulfate and using colorimetry for dissolved sulfide thiosulfate was detected at concentrations typically less than 2 micro mol l in neutral and alkaline chloride springs with low sulfate concentrations cl sup minus so sub 4 sup 2 minus 25 the thiosulfate concentration levels are about one to two orders of magnitude lower than the concentration of dissolved sulfide in these springs in most acid sulfate and acid sulfate chloride springs cl sup minus so sub 4 sup 2 minus 10 thiosulfate concentrations were also typically lower than 2 micro mol l however in some chloride springs enriched with sulfate cl sup minus so sub 4 sup 2 minus between 10 and 25 thiosulfate was found at concentrations ranging from 9 to 95 micro mol l higher than the concentrations of dissolved sulfide in these waters polythionate was detected only in cinder pool norris geyser basin at concentrations up to 8 micro mol l with an average s chain length from 4 1 to 4 9 sulfur atoms the results indicate that no thiosulfate occurs in the deeper parts of themore hydrothermal system thiosulfate may form however from 1 hydrolysis of native sulfur by hydrothermal solutions in the shallower parts 50 m of the system 2 oxidation of dissolved sulfide upon mixing of a deep hydrothermal water with aerated shallow groundwater and 3 the oxidation of dissolved sulfide by dissolved oxygen upon discharge of the hot spring upon discharge of a sulfide containing hydrothermal water oxidation proceeds rapidly as atmospheric oxygen enters the water the transfer of oxygen is particularly effective if the hydrothermal discharge is turbulent and has a large surface area less

evolution of geothermal fluids deduced from chemistry plots yellowstone national park u s a mazor e and thompson j m 1982 evolution of geothermal fluids deduced from chemistry plots yellowstone national park u s a j volcanol geotherm res 12 351 360 large amounts of chemical data obtained in geothermal fields may readily be sorted out by the aid of a simple set of graphs that provide a clear over all picture and facilitate the understanding of geochemical processes taking place as a case study data from several hundred samples of the thermal springs at the well known yellow stone national park are discussed the pattern obtained seems to indicate 1 geochemical similarity between the spring groups of heart lake shoshone upper midway lower and norris geyser basins i e a geochemical uniformity of major spring groups located over 40 km apart 2 these groups may be described as originating from a common fluid most resembling the composition of norris waters accompanied by co and other volatiles that react with igneous rocks forming local variations 3 the secondary reactions occur at medium depth before the ascent to the surface 4 extensive concentration dilution processes occur during the ascent to the surface the water of the mammoth group may be described as originating from the same norris like fluid that has been diluted low na and ci contents and intensively reacted with carbonaceous rocks thus gaining in ca mg so and hco

bedform and stratification characteristics of some modern small scale washover sand bodies washover sand bodies commonly develop along microtidal coastlines in beach barrier island or spit settings wave runup usually in conjunction with an abnormally high water level may overtop the most landward berm of the beach and the foredune crest if one exists to produce overwash and subsequent runoff across the more landward subaerial surface two main elements of the resulting deposit are the washover fan and runoff channel newly formed small scale washover deposits were examined along the outer banks north carolina near pt mugu california and at presque isle lake erie pennsylvania the fans were formed in response to unidirectional landward transport and the runoff channels in response to unidirectional flow usually in a landward direction but sometimes in shore parallel then seaward direction where overwash carried across the fan surface and entered a pond or lagoon a small scale delta microdelta developed in this case the washover fan consisted of two subfacies the wetted but subaerial part of the fan and the subaqueous washover delta flow associated with the development of the fan and runoff channel produced distinctive sets of bedforms and internal stratification high velocity discontinuous surges moving across the fan surface resulted in the development of a plane bed and subhorizontal to low angle landward dipping planar stratification which comprised the major part of the fan similarly rhomboid forms were produced by high velocity sheet flow across the fan surface where flow carried into a standing body of water delta type foreset strata developed for this case the lateral structural sequence was subhorizontal planar stratification merging landward into landward dipping delta tabular foreset strata in the runoff setting where flow became channelized and continuous both upper flow and lower flow regime currents were typical upper flow regime bedforms included antidunes standing waves and plane beds the most commonly observed lower flow regime bedforms included microdelta like bars low amplitude bars linguoid ripples and sinuous crested current ripple trains the sets of sedimentary structures comprising modern washover sand bodies provide criteria for the identification of similar deposits in ancient sediments and for more specific interpretation of the environment

a statistical study of the stromboli volcano explosion quakes before and during 2002 2003 eruptive crisis 1 we study the seismic wavefield and the statistical properties of the stromboli volcano explosions preceding and during the 2002 2003 crisis we analyze the recordings of a three component seismometer operating since 23 may 2002 to 30 january 2003 including the first 34 days of the crisis before the crisis we recognize three bell shaped classes of spectra with maxima falling in the range 1 5 hz spectral content has two main changes the most prominent one occurring at the crisis onset when the frequency peak at 0 3 hz increases in amplitude independent component analysis extracts three time stable independent oscillations that peaked at 1 1 1 8 and 2 5 hz with radial and shallow polarization indicating a stable source mechanism energy of the explosions is lognormally distributed except during a 2 month time interval before the crisis when it also shows a higher mean value the interoccurrence time distributions display an homogeneous poissonian behavior with a mean intertime of 250 s without changes at the crisis onset only swarms of explosions are not ruled by a poisson process and display higher occurrence rates and higher energies finally we depict a scheme of the crisis a modification of the equilibrium is induced by rising magma that produces a change in the boundary conditions of the plumbing system the escape from the equilibrium produces at first variations in the usual statistics of the explosions then it leads to the lava effusion and to a pressure drop in the plumbing system that induces a deep gas slug nucleation and the excitation of low frequencies

evolution of the barrier islands of southern long island new york three lines of evidence based on data from more than 400 boreholes and vibrocores have been used to reconstruct the evolution of the barrier islands during the holocene transgression in southern long island new york 1 the holocene transgressive stratigraphic sequence behind the present barriers 2 the stratigraphic patterns of the inner shelf and 3 the morphology of the now buried late pleistocene coastal features the extensive preservation of backbarrier sediments radiocarbon dated between 7000 and 8000 yr bp on the inner shelf of southern long island suggests that the barriers have not retreated by continuous shoreface erosion alone but have also undergone discontinuous retreat by in place drowning of barriers and stepwise retreat of the surf zone such stepwise retreat of the surf zone has prevented the backbarrier sediments from being reworked based on the presence of submerged barrier sand bodies in seismic records it is inferred that about 9000 years ago when the sea stood about 24 m below the present sea level a chain of barriers developed on the present shelf about 7 km offshore of the present barriers with continued sea level rise the 24 m barrier built upward until the sea reached about 15 m msl just prior to 7000 yr bp the barriers were then submerged by the rapidly rising sea and the surf zone shifted rapidly landward to a position about 2 km from the present shoreline the surf zone overstepped to the landward margin of the old lagoon which had become fixed at the steep seaward face of mid wisconsinan or sangamonian coastal barriers during the past 5000 or 6000 years the shoreface has retreated continuously by about 2 km evidence from southern long island and elsewhere in regions of coastal submergence indicates that rapid sea level rise and low sand supply seem to favour the stepwise retreat of barriers whereas slow rates of submergence and a greater supply of sand generally favour continuous shoreface retreat stationary upbuilding or seaward progradation of barriers may occur when supply of sand is great and or submergence is slowed or reversed morphologic highs on the pretransgression surface such as old barrier ridges tend to fix the migrating barrier shoreline during either continuous retreat or stepwise retreat of barriers

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

correlations between holocene flood tidal delta and barrier island inlet fill sequences back sound shackleford banks north carolina large well developed flood tidal deltas on a barrier island coastline generally indicate a wave dominated microtidal sedimentary regime vibracores in a lagoon behind the barrier island shackleford banks north carolina contain an upward fining sequence of coarse medium very shelly sand medium fine laminated sand fine very fine cross laminated sand and marsh mud this sequence is interpreted as being a flood tidal delta deposit based on analogy with modern flood tidal delta sediments and represents lagoonal deposition in response to a migrating or closing inlet the sand facies defined in lagoonal vibracores is found to be continuous beneath a lagoonal marsh and correlative with inlet sections identified in shackleford banks drill holes the correlation of flood tidal delta deposits with inlet sequences in this microtidal environment indicates a close relationship between barrier and backbarrier inlet controlled sedimentation

polarisation analysis of the independent components of low frequency events at stromboli volcano eolian islands italy abstract independent component analysis ica applied on low frequency lf events recorded at stromboli volcano reveals that these signals are composed of three independent components in three different frequency bands approximately 0 8 1 2 2 4 3 0 3 2 4 5 hz respectively the first two frequency ranges are mainly composed of body waves coming from a direction in a range of 30 30 around the crater area this result is a clear indication that the entire signal in these frequency bands comes from the source area in fact any scattered wave should have different back azimuth propagation due to the random distribution of scatterers location however the last independent component is dominated by other kinds of waves coming from many different directions

so2 flux from stromboli during the 2007 eruption results from the flame network and traverse measurements abstract so 2 fluxes emitted by stromboli during the 27th february 2nd april 2007 effusive eruption were regularly measured both by an automatic network of scanning ultraviolet spectrometers and by traverse measurements conducted by boat and helicopter the results from both methodologies agree reasonably well providing a validation for the automatic flux calculations produced by the network approximately 22 000 t of so 2 were degassed during the course of the 35 day eruption at an average rate of 620 t per day such a degassing rate is much higher than that normally observed 150 200 t d because the cross sectional area occupied by ascending degassed magma is much greater than normal during the effusion as descending degassed magma that would normally occupy a large volume of the conduit is absent we propose that the hydrostatically controlled magma level within stromboli s conduit is the main control on eruptive activity and that a high effusion rate led to the depressurisation of an intermediate magma reservoir creating a decrease in the magma level until it dropped beneath the eruptive fissure causing the rapid end of the eruption a significant decrease in so 2 flux was observed prior to a paroxysm on 15th march 2007 suggesting that choking of the gas flowing in the conduit may have induced a coalescence event and consequent rapid ascent of gas and magma that produced the explosion