geophysical and geochemical methods applied to investigate fissure related hydrothermal systems on the summit area of mt etna volcano italy abstract a multidisciplinary approach integrating self potential soil temperature heat flux co 2 efflux and gravity gradiometry signals was used to investigate a relatively small fissure related hydrothermal system near the summit of mt etna volcano italy measurements were performed through two different surveys carried out at the beginning and at the end of july 2009 right after the end of the long lived 2008 2009 flank eruption and in coincidence with an increase in diffuse flank degassing related to a reactivation of the volcano leading to the opening of a new summit vent nsec the main goal was to use a multidisciplinary approach to the detection of hidden fractures in an area of evident near surface hydrothermal activity despite the different methodologies used and the different geometry of the sampling grid between the surveys all parameters concurred in confirming that the study area is crossed by faults related with the main fracture systems of the south flank of the volcano where a continuous hydrothermal circulation is established results also highlighted that hydrothermal activity in this area changed both in space and in time these changes were a clear response to variations in the magmatic system notably to migration of magma at various depth within the main feeder system of the volcano the results suggest that this specific area initially chosen as the optimal test site for the proposed approach can be useful in order to get information on the potential reactivation of the summit craters of mt etna

a contribution of co2 released from mineral springs into overall volume of annual co2 emissions in the slovak republic complex geological and tectonic structure of the western carpathians within the slovak territory has conditioned generation of abundant mineral springs 1782 with various levels of mineralization and chemical types many of them possess a high content of co2 and therefore they may be considered as permanent point sources of co2 they are a part of natural analogues due to this fact an approximate estimation of overall annual volume of co2 has been carried out however such seemingly simple calculation requests an introduction of necessary corrections professional estimates and some limitations based on knowledge and practical experience from a long term monitoring the final result of this process of all considered sources provided volume of around 4 mt of co2 year 1 this amount represents annual co2 emission of standard thermal power plant ca 500 mw and creates practically 10 of the annual slovak co2 production it means that the volume of co2 produced from mineral springs is not a negligible item and may create remarkable share of aggregated emissions in countries of similar geological and hydrogeological structure that is why it should be included in the emission evaluation of the countries concerned

volcanic tremor at mount etna january 1984 march 1985 its relationship to the eruptive activity and modelling of the summit feeding system spectral analyses of volcanic tremor at etna during january 1984 march 1985 have been performed and the relationship between tremor energy and observed volcanic phenomena have been examined the highest energy levels have been observed during the paroxysmal phases of eruptions whereas a gradual decrease was linked to the lowering of eruptive activity amplitude variations with time of some spectral frequency peaks 0 95 1 20 1 45 1 65 1 80 and 2 40 hz have been compared with volcanic activity at the summit craters and on the basis of these results a new schematic diagram for the feeding system of the summit vents is proposed

broad synchrony of a late glacial glacier advance and the highstand of palaeolake tauca in the bolivian altiplano the morphology and sedimentology of glacially influenced fan deltas on massifs at the margin of the southern altiplano bolivia suggest a broadly synchronous expansion of glaciers and palaeolake tauca during the late glacial interval this is shown by sedimentary successions of glacigenic glacifluvial and glacideltaic facies linking palaeoglaciers with palaeolake tauca on the flanks of cerro azanaques and cerro tunupa at altitudes of 3770 3720 m radiocarbon dates from peat overlain by glacial diamict and glacifluvial outwash indicate that glaciers in this area reached their last glacial maximum extent after ca 13 300 14 c yr bp glacifluvial fan deltas contiguous with the moraines confirm that the advance coincided with a highstand of palaeolake tauca radiocarbon dated to the interval ca 13 500 11 500 yr bp modeling of climatic controls on this glacier advance suggests the primary forcing was increased summer wet season moisture possibly amounting to 600 mm above the modern values of 200 400 mm greater cloud cover probably depressed local temperatures and reduced the evaporation rate the consequent rise in effective annual moisture p e comfortably accommodates a palaeolake 48 50 10 3 km 2 in area and up to 100 m deep in the southern altiplano because the palaeoglacier equilibrium line altitudes rose toward the south and west like the gradient of modern precipitation totals we conclude that the increased late glacial moisture was brought by weather systems similar to those of the present but that atmospheric conditions were cloudier and cooler 1997 john wiley sons ltd

observations and analysis of b type earthquakes explosions and volcanic tremor at pavlof volcano alaska an eight station network of short period seismometers has been operated near pavlof volcano 55 25 n 161 54 w alaska peninsula since 1976 high quality analog to digital and direct digital data were recorded during eruptions in 1980 through 1983 data are analyzed from explosions with distinct air phases b type volcanic earthquakes shallow low frequency events lacking clear s phases and volcanic tremor to determine source and propagation effects between zero and several hundred b type events and explosions per day are recorded with higher numbers during eruptions magnitudes range between 0 5 and 1 3 and b values range between 1 9 0 1 and 2 6 0 1 with no systematic relation to eruptive activity six results are most important 1 data from a recently installed three component station reveal that the highest amplitude waves of the b type events show retrograde elliptical particle motion and normal dispersion and are hence probably rayleigh waves 2 stacking of the events enhances the p wave which has a velocity of 3 1 0 1 km sec 1 3 the explosions and b type events have similar hypocenters as evidenced by signal characteristics and wave arrival times 4 the b type events contain virtually no high frequency energy even when allowing for attenuation effects in particular we estimate the anelastic attenuation coefficient q to have a value of 45 20 for rayleigh waves in the shallow part of the volcano 5 volcanic tremor spectra exhibit evenly spaced narrow peaks which we model as eigenvalues of organ pipe resonance in the magma conduit we estimate the length of the conduit to be a maximum of 1 6 km 6 the volcano shows evidence of extreme lateral variation of velocity and attenuation in its shallow structure

climatic controls on holocene lake level changes in europe sensitivity experiments with a simple water balance model were used to constrain the possible climatic causes of distinct holocene patterns of lake level variation in different regions of europe lakes in s sweden were low at 9 ka high around 6 5 ka low again around 4 ka and are high now lakes in estonia show similar but weaker trends lakes in s france were highest around 9 ka lowest around 4 ka intermediate now lakes in greece were also high around 9 ka but continued rising until 7 5 ka then fell gradually from 5 ka with a brief high phase around 3 ka and are low now the model was forced with insolation anomalies deduced from orbital variations temperature anomalies inferred from the pollen record and cloudiness anomalies derived from changes in the position of the subtropical anticyclone inferred from reconstructed changes in the equator to pole temperature gradient in order to evaluate the effects of resultant evaporation changes on catchment water balance the resulting simulated changes in runoff precipitation minus actual evapotranspiration were slight and frequently opposite to the observed trends larger changes in precipitation are plausible and are required to explain the data the required precipitation increase in n europe from 9 ka low to 6 ka high is suggested by gcm experiments to have been a consequence of interacting insolation and residual ice sheet effects on the atmospheric circulation over the north atlantic the explanation of other observed changes including the drying trend during the holocene in s europe has not been provided by gcm experiments to date explanations may lie in changes in mesoscale circulation sea surface temperature patterns and the coupling between these phenomena that may not follow orbital changes in any simple way

paroxysmal summit activity at mt etna italy monitored through continuous soil radon measurements 1 soil radon emissions have been proved as a useful tool for predicting earthquakes and volcanic eruptions and furthermore aided in determining the location of active faults continuous radon monitoring was carried out near southeast crater of mt etna in september november 1998 during a period of frequent eruptive episodes at that crater radon anomalies were detected when eruptive episodes and the accompanying volcanic tremor became increasingly intense no anomalies in radon activity were observed during the first five and weaker eruptive episodes whereas significant spikes in radon activity preceded the latter five episodes by 46 hours this probably reflects increased gas leakage through fractures intersecting the shallow plumbing system as gas pressure in the southeast crater conduit became higher with time radon monitoring thus might serve to better understand eruptive mechanisms and possible precursors making further studies in this field a promising perspective

relationship between soil co2 flux and volcanic tremor at mt etna implications for magma dynamics large variations of the co2 flux through the soil were observed between november 2002 and january 2006 at mt etna volcano in many cases the co2 flux was strongly influenced by changes in air temperature and atmospheric pressure a new filtering method was then developed to remove the atmospheric influences on soil co2 flux and at the same time to highlight the variations strictly related to volcanic activity successively the co2 corrected data were quantitatively compared with the spectral amplitude of the volcanic tremor by cross correlation function cross wavelet spectrum and wavelet coherence these analyses suggested that the soil co2 flux variations preceded those of volcanic tremor by about 50 days given that volcanic tremor is linked to the shallow a few kilometer magma dynamics and soil co2 flux related to the deeper 12 km b s l magma dynamics the delayed similarity between the co2 flux and the volcanic tremor amplitude was used to assess the average speed in the magma uprising into the crust as about 170 260 m per day finally the large amount of co2 released before the onset of the 2004 2005 eruption indicated a deep ingression of new magma which might have triggered such an eruption

statistical analysis reveals spatial and temporal anomalies of soil co2 efflux on mount etna volcano italy abstract extensive geochemical surveys were carried out on the western flank of mt etna volcano for the determination of soil co 2 effluxes in order to study the relationship between soil gas anomalies faults and volcanic activity the areas of santa maria di licodia sml and w rift wr were selected because of their importance within the volcano tectonic framework of etna two gas surveys were performed in each area in different periods november 2005 and may 2006 in sml september 2007 and june 2008 in wr with 2140 measurements in total in each survey data were log normally distributed and were statistically different from the other surveys therefore their standard normal form was used to compare them log probability plots revealed five populations of data in each survey due to varying degrees of mixing between biogenic and magmatic co 2 and indicated anomalous co 2 effluxes for values 36 g m 2 d 1 magmatic output was 39 2 t d 1 in november 2005 15 8 t d 1 in may 2006 98 4 t d 1 in september 2007 and 234 1 t d 1 in june 2008 natural neighbor interpolation of standardized data produced distribution maps that showed some clustering of anomalous values along directions possibly related to hidden faults compatible with volcanic or regional structural trends analysis of magmatic co 2 emissions in time suggested a possible influence from seasonal variations but comparison with volcanic activity of etna also indicated a volcanic influence accompanying the 2008 2009 flank eruption

new insights into banded tremor from the 2008 2009 mount etna eruption 1 we investigated the banded tremor activity occurring at mt etna volcano between august october 2008 during the 2008 2009 eruption the banded tremor occurred in episodes lasting 25 30 min with intervals in between the episodes of about 25 min seismic signal analyses showed that the banded tremor was characterized by spectral contents wavefields and source locations that differed from the ordinary volcanic tremor the infrasound recordings exhibited an intermittent infrasonic tremor alternating with the banded tremor episodes finally nonlinear analyses suggested that a banded tremor system can be considered chaotic implying 1 sensitive dependence on initial conditions suggesting not only that a banded tremor system requires particular conditions to generate but also that slight variations of these conditions are able to greatly change the features of the banded tremor or even to stop it and 2 long term unpredictability that is the impossibility to forecast the long term evolution of the banded tremor on the basis of all these results and analogies with geyser models we suggest a model of banded tremor that invokes alternating recharge discharge phases banded tremor is due to perturbations in shallow aquifers such as fluid movement and bubble growth or collapse due to hydrothermal boiling triggered by the heat and hot fluid transfer from the underlying magma bodies this heat fluid transfer also causes an increasing pressure in the aquifer leading to fluid discharge during this process the seismic radiation decreases and if the fluid discharge is well coupled with the atmosphere acoustic signals are generated

pollen derived rainfall and temperature estimates from lake tanganyika and their implication for late pleistocene water levels abstract palaeoclimatic estimates of mean annual temperature and rainfall in the southern tanganyika basin between 25 000 and 9000 yr b p have been established from two pollen sequences based on the best analogue method the results give evidence of a mean temperature decrease of about 4 2 c during the last glaciation a value consistent with that previously obtained in the catchment area on the burundi highlands this cooling was synchronous with a decrease of mean annual precipitation of about 180 mm yr postglacial climatic conditions were established by 12 700 yr b p with warming and wetness continuing to increase from this date onward these new palaeoclimatic data will be useful for hydrological reconstructions of lake tanganyika particularly during the last glacial age for which the magnitude of water level fall has been a controversial issue our rainfall estimates are more consistent with low values 250 to 300 m fall than with high ones 600 m previously proposed

megalakes in the sahara a review the sahara was wetter and greener during multiple interglacial periods of the quaternary when some have suggested it featured very large mega lakes ranging in surface area from 30 000 to 350 000 km2 in this paper we review the physical and biological evidence for these large lakes especially during the african humid period ahp 11 5 ka megalake systems from around the world provide a checklist of diagnostic features such as multiple well defined shoreline benches wave rounded beach gravels where coarse material is present landscape smoothing by lacustrine sediment large scale deltaic deposits and in places tufas encrusting shorelines our survey reveals no clear evidence of these features in the sahara except in the chad basin hydrologic modeling of the proposed megalakes requires mean annual rainfall 1 2 m yr and a northward displacement of tropical rainfall belts by 1000 km such a profound displacement is not supported by other paleo climate proxies and comprehensive climate models challenging the existence of megalakes in the sahara rather than megalakes isolated wetlands and small lakes are more consistent with the sahelo sudanian paleoenvironment that prevailed in the sahara during the ahp a pale green and discontinuously wet sahara is the likelier context for human migrations out of africa during the late quaternary

estimates of holocene precipitation for rajasthan india based on pollen and lake level data abstract a pollen profile obtained from lake sediments at lunkaransar rajasthan in northwest india was used along with a pollen climate calibration function to estimate past precipitation between 10 500 and 3500 yr b p the estimated precipitation was about 500 mm yr or about 200 mm yr above the modern value a model was used for the energy and hydrologic budget of a lake basin and lake at sambhar located 240 km se of lunkaransar to calculate that a 200 mm yr increase in rainfall above the modern amount would have raised the lake level about 20 m above the modern level topographic charts and satellite imagery provided some evidence in support of an enlarged paleolake of that elevation but field exploration would be required to confirm the size and date of a former lake after about 3500 yr b p the lunkaransar profile indicated a desiccated lake bed because no pollen was preserved the pollen climate calibration function was of no use for estimating the amount of the precipitation decline a reduction of precipitation of about 200 mm yr below the modern amount was estimated from the energy and hydrologic budget for paleolake sambhar by assuming that the lake was one tenth of its present size during the dry interval

etna 2004 2005 an archetype for geodynamically controlled effusive eruptions 1 the 2004 05 eruption of etna was characterised by outpouring of degassed lava from two vents within valle del bove after three months of eruption lava volumes were estimated to be between 18 5 and 32 106 m3 with eruption rate between 2 3 and 4 1 m3 s petrological analyses show that magma is resident in the shallow plumbing system emplaced during the last south east crater activity so2 flux data show no increase at the onset of the eruption and so2 hcl ratios in gas emitted from the eruptive fissure are consistent with a degassed magma no seismic activity was recorded prior to eruption unlike eruptions observed since the 1980 s the purely effusive nature of this eruption fed by a degassed resident magma and the fracture dynamics suggest that magmatic overpressure played a limited role in this eruption rather lateral spreading of etna s eastern flank combined with general inflation of the edifice triggered a geodynamically controlled eruption

reconciliation of conflicting tectonic models for proterozoic rocks of northern new mexico two major proterozoic tectonic events are documented in the taos range of northern new mexico regional structures involving the tectonic interleaving of c 1 65 ga granitoids with supracrustal rocks are interpreted to have formed before 1 42 ga and probably during collisional assembly of island arc crust into new 1 7 1 6 ga continental lithosphere supracrustal rocks record 650 750 c 6 8 kbar metamorphism m2 these high temperatures may have been reached during sandwiching between c 1 65 ga granitoids however the early history has been obscured by renewed tectonism at c 1 4 ga that resulted in partial melting fabric reactivation and new mineral growth at 4 kbar m3 metamorphic temperature variations from uppermost amphibolite to amphibolite facies rocks may be associated with c 1 65 and or 1 4 ga plutonism but not to a 1 4 ga extensional shear zone as previously proposed syn and post 1 4 ga contraction is suggested by high and low temperature microstructures showing top to the south east thrusting this work reconciles conflicting models by suggesting that the geometry of the structures was mainly established by c 1 65 ga but that the present fabric also records 1 4 ga tectonism involving high t metamorphism and fabric reactivation

motif discovery on seismic amplitude time series the case study of mt etna 2011 eruptive activity algorithms searching for similar patterns are widely used in seismology both when the waveforms of the events of interest are known and when there is no a priori knowledge such methods usually make use of the cross correlation coefficient as a measure of similarity if there is no a priori knowledge they behave as brute force searching algorithms the disadvantage of these methods preventing or limiting their application to very large datasets is computational complexity the mueen keogh mk algorithm overcomes this limitation by means of two optimization techniques the early abandoning concept and space indexing here we apply the mk algorithm to amplitude time series retrieved from seismic signals recorded during episodic eruptive activity of mt etna in 2011 by adequately tuning the input to the mk algorithm we found eight motif groups characterized by distinct seismic amplitude trends each related to a different phenomenon in particular we observed that earthquakes are accompanied by sharp increases and decreases in seismic amplitude whereas lava fountains are accompanied by slower changes these results demonstrate that the mk algorithm because of its particular features may have wide applicability in seismology

in situ permeability measurements based on a radial gas advection model relationships between soil permeability and diffuse co2 degassing in volcanic areas in this paper we have developed a new method for measuring in situ soil permeability which is based on the theory of radial gas advection through an isotropic porous medium the method was tested in the laboratory and at several locations on the island of vulcano aeolian islands italy it consists of a special device which generates a gas source at a depth of 50 cm and it permits measurement of the relative induced pressure in nearby soil at different depths the characteristic error of the method was less than 10 furthermore soil permeability measurements were carried out in the island of vulcano during different periods of the year between may 2000 and june 2001 a strong decrease in permeability in the upper layers of the soil during and after rainfall was noted with very poor correlations between the spatial distributions of soil co2 flux and shallow soil permeability

influence of the arctic oscillation and el nino southern oscillation enso on ice conditions in the baltic sea the wavelet approach 1 variability in time series of ice conditions in the baltic sea is examined within the context of atmospheric circulation represented by the north atlantic oscillation nao and arctic oscillation ao winter indices using the wavelet approach we develop methods of assessing statistical significance and confidence intervals of cross wavelet phase and wavelet coherence cross wavelet power for the time series indicates that the times of largest variance in ice conditions are in excellent agreement with significant power in the ao at 2 2 3 5 5 7 7 8 and 12 20 year periods similar patterns are also seen with the southern oscillation index soi and nino3 sea surface temperature nino3 series wavelet coherence shows in phase linkages between the 2 2 7 8 and 12 20 year period signals in both tropical and arctic atmospheric circulation and also with ice conditions in the baltic sea these results are consistent with gcm simulations showing dynamical connections between high latitude surface conditions tropical sea surface temperatures mediated by tropical wave propagation the wintertime polar vortex and the ao and with models of sea ice and oceanic feedbacks at decadal periods

the effects of solar irradiation changes on the migration of the congo air boundary and water levels of paleo lake suguta northern kenya rift during the african humid period 15 5 ka bp abstract the water level record from the 300 m deep paleo lake suguta northern kenya rift during the african humid period ahp 15 5 ka bp helps to explain decadal to centennial intensity variations in the west african monsoon wam and the indian summer monsoon ism this water level record was derived from three different sources 1 grain size variations in radiocarbon dated and reservoir corrected lacustrine sediments 2 the altitudes and ages of paleo shorelines within the basin and 3 the results of hydro balance modeling providing important insights into the character of water level variations abrupt or gradual in the amplifier paleo lake suguta the results of these comprehensive analyses suggest that the ahp highstand in the suguta valley was the direct consequence of a northeastwards shift in the congo air boundary cab which was in turn caused by an enhanced atmospheric pressure gradient between east africa and india during a northern hemisphere insolation maximum rapidly decreasing water levels of up to 90 m over less than a hundred years are best explained by changes in solar irradiation either reducing the east african indian atmospheric pressure gradient and preventing the cab from reaching the study area or reducing the overall humidity in the atmosphere or a combination of both these effects in contrast although not well documented in our record we hypothesize a gradual end of the ahp despite an abrupt change in the source of precipitation when a decreasing pressure gradient between asia and africa prevented the cab from reaching the suguta valley the abruptness was probably buffered by a contemporaneous change in precession producing an insolation maximum at the equator during october whether or not this is the case the water level record from the suguta valley demonstrates the importance of both orbitally controlled insolation variations and short term changes in solar irradiation as factors affecting the significant water level variations in east african rift lakes

the late pleistocene and holocene stratigraphy and paleolimnology of lakes kivu and tanganyika abstract evidence from diatoms chemistry and sedimentology shows that lakes kivu and tanganyika experienced late pleistocene low stands 86 to 300 m for kivu and 250 to 350 m for tanganyika both lakes had higher 2 10 fold sedimentation rates prior to 11 500 yr b p about 9900 yr b p upwelling became important in southern lake tanganyika which had been deepening for at least several millenia by 9400 yr b p kivu had become deep and dilute with overflow via the ruzizi river to lake tanganyika southern lake tanganyika became more stably stratified about 5200 yr b p volcanism and hydrothermal activity in kivu began about 5000 yr b p and the salinity reached 3 ppt and the lake became strongly stratified the ruzizi river outflow was interrupted from 3500 yr b p until recently the sedimentary record implies that sudden hydrothermal activity and sublacustrine volcanism in kivu has probably been the cause of its impoverished fauna these results show that high lake levels in the eastern rift of africa from 10 000 to 7000 yr b p were paralleled in the western rift given the great volumes of these lakes climate has not caused great variations in salinity the diatom floras however have been remarkably sensitive to changes in stratification and nutrient supply volcanism has been a major force in the limnological and biological evolution of lake kivu while both kivu and tanganyika have responded to changes in precipitation and wind stress

degassing of so2 and co2 at mount etna sicily as an indicator of pre eruptive ascent and shallow emplacement of magma abstract we studied soil co 2 emissions together with crater so 2 fluxes from mt etna during the period july 1997 to march 1999 this period was characterized by high levels of volcanic activity and ended with the onset of a 10 month long sub terminal eruption on february 4 1999 soil co 2 degassing was measured at two sites p39 on the lower sw flank of etna and p78 on the e flank known for being connected to deep faults that allow the escape of magmatic gas site p39 is inferred to drain gas from a deep 15 km magma reservoir whereas site p78 is connected to a shallower 5 10 km reservoir based on the temporal variations of measured soil co 2 and crater so 2 data five intervals of anomalous degassing were recognized each of them is interpreted as due to massive gas release from a magma batch that is moving toward the surface the time lag between the occurrence of degassing anomalies of co 2 and those of so 2 agrees well with the different depth of exsolution of the two gases our data also indicate a step like migration of magma to the surface which bears on the existence of at least three different temporary storage levels within etna s feeder system lastly the observed anomalies preceded by months to weeks increases in the summit activity of mt etna including the february 4 1999 eruption comparison between the amounts of degassing magma during each interval of anomalous degassing based on so 2 fluxes and erupted volumes of lava during the same periods seems to indicate that the 1999 eruption was largely fed by magma that started entering the upper feeder system of etna about 1 year earlier

trends in long period seismicity related to magmatic fluid compositions abstract sound speeds and densities are calculated for three different types of fluids gas gas mixture ash gas mixture and bubbly liquid these fluid properties are used to calculate the impedance contrast z and crack stiffness c in the fluid driven crack model chouet j geophys res 91 1986 13 967 101 1988 4375 a seismic model for the source of long period events and harmonic tremor in gasparini p scarpa r aki k eds volcanic seismology iavcei proceedings in volcanology springer berlin 3133 the fluid driven crack model describes the far field spectra of long period lp events as modes of resonance of the crack results from our calculations demonstrate that ash laden gas mixtures have fluid to solid density ratios comparable to and fluid to solid velocity ratios lower than bubbly liquids gas volume fractions spectral characteristics are described in terms of the quality factor q 1 q 1 is measured by the ratio of the frequency of the dominant spectral peak to the bandwidth of the peak measured at one half of its amplitude this factor expresses the losses of energy due to elastic radiation q r 1 and other dissipative mechanisms q i 1 at the source q 1 q r 1 q i 1 spectra for lp events recorded at active volcanoes such as galeras in colombia and kilauea in hawaii have q 1 factors in the range of 0 1 0 002 the q r 1 factors due to radiation loss calculated for a sphere filled with a h 2 o co 2 or h 2 o so 2 gas mixture vary between 0 0015 and 0 0040 with a change in wt h 2 o at 800 1600 k and 10 50 mpa for gas rich mixtures q r 1 has a strong dependence on resonator geometry spherical versus rectangular the spectra from a resonating sphere filled with gas rich mixture yields values of q r 1 an order of magnitude smaller than those from a rectangular crack for a resonating crack filled with an ash gas mixture or pseudogas q r 1 varies parabolically from 0 006 for an ash rich mixture to 0 0015 or 0 0023 for a h 2 o rich or co 2 rich mixture at 800 k and 25 mpa for low q r 1 are independent of crack geometry spectra associated with a foam gas volume fractions 10 90 or bubbly basalt gas volume fractions q r 1 on the order of 0 01 and 0 1 respectively the spectra from a resonating sphere filled with a foam containing 20 gas volume fraction yields values of q r 1 similar to those for a rectangular crack as with gas gas and ash gas mixtures an increase in mass fraction narrows the bandwidth of the dominant mode and shifts the spectra to lower frequencies including energy losses due to dissipative processes in a bubbly liquid increases attenuation attenuation may also be higher in ash gas mixtures and foams if the effects of momentum and mass transfer between the phases were considered in the calculations

investigating the deepest part of a volcano plumbing system evidence for an active magma path below the western flank of piton de la fournaise la reunion island abstract peripheral diffuse degassing of co 2 from the soil occurs across the western flank of piton de la fournaise volcano la reunion island indian ocean along a narrow zone in this area carbon isotopic analysis on soil gas samples highlights significant mixing between magmatic and organic end members the zones with the strongest magmatic signature highest 13 c overlap spatial distribution of hypocenters recorded shortly before and during volcano reactivation and allow discriminating a n135 degassing lineament with a minimum length of 11 km and 140 20 m width such orientation is in accordance with that of an old dyke network along the rift zone and with n120 130 and n140 155 lineaments related to the inheritance of oceanic lithosphere structures our findings show that this n135 lineament represents a preferential magmatic pathway for deep magma transfer below the volcano flank moreover spatial distributions of recent eccentric cones indicate a well founded possibility that future eruptions may by pass the shallow plumbing system of the central area of the volcano taking a lateral pathway along this structure our results also confirm that piton de la fournaise activity is linked to a laterally shifted plumbing system and represent a major improvement in identifying the main high risk area on the densely populated western flank of the volcano

soil co2 degassing on mt etna sicily during the period 1989 1993 discrimination between climatic and volcanic influences wide variations were measured in the diffuse co2 flux through the soils in three selected areas of mt etna between august 1989 and march 1993 degassing of co2 from the area of zafferana etnea s venerina on the eastern slope of the volcano has been determined to be more strongly influenced by meteorological parameters than the other areas the seasonal component found in the data from this area has been excluded using a filtering algorithm based on the best fitting equation calculated from the correlation between co2 flux values and those of air temperature the filtered data appear to have variations temporally coincident with those from the other areas thus suggesting a common and probably deep source of gas the highest fluxes measured in the two most peripheral areas may correlate well with other geophysical and volcanological anomalous signals that preceded the strong eruption of 1991 1993 and that were interpreted as deep pressure increases anomalous decreases in co2 fluxes accompanied the onset and the evolution of that eruption and have been interpreted as a sign of upward migration of the gas source the variations of co2 flux at the 1989 se fracture have also given interesting information on the timing of the magmatic intrusion that has then fed the 1991 1993 eruption

paleoclimatic significance of lake level fluctuations in the lahontan basin abstract an energy flux balance model has been developed which treats evaporation as a function of air temperature surface water temperature precipitable water aloft the amount height and type of sky cover and the optical air mass the model has been used to estimate the mean historical evaporation rate for pyramid lake nevada using as input climatic data from the reno area averaged over the period 1950 1975 estimated and measured values of the mean annual evaporation rate were found to be in good agreement the model was used to simulate changes in the level the surface area and the volume of paleo lake lahontan in particular possible climatic states responsible for past high stands 1270 and 1330 m were investigated a conservative range of discharge values was used in the calculations results of the simulations indicate the fundamental importance of sky cover in the creation and destruction of large lake systems

monsoon climate of the early holocene climate experiment with the earth s orbital parameters for 9000 years ago values for the precession and obliquity of the earth 9000 years ago indicate that the global average solar radiation for july 9000 years ago was 7 percent greater than at present when the estimated solar radiation values are used in a low resulation climate model the model simulates an intensified continent scale monsoon circulation this result agrees with paleoclimatic evidence from africa arabia and india that monsoon rains were stronger between 10 000 and 5000 years ago than they are today

lake evolution during the past 30 000 years in china and its implications for environmental change abstract taking china as a whole lake expansion occurred 500 b c 0 a d 650 950 a d and 1250 1650 a d over the past 3000 yr the expansions were mainly due to climatic fluctuations and correspond to frequent flood reports three regional characteristics of lake development have been recognized 1 fluctuations of near coastal lakes and those in other regions as well were out of phase during 500 b c 500 a d which possibly resulted from out of phase fluctuations of climate and sea level on 10 to 100 yr time scale 2 as the lower yellow river channel migrated southward the lakes in the south of the north china plain formed and reached their largest sizes much later than those in the north 3 for the lakes in the middle and lower yangtze river valley the higher a lake basin lies above a neighboring river and the further the lake is from the river s mouth in general the younger the lake is through land reclamation the ancient chinese have changed most of the lakes greatly however human activities were also constrained in certain ways by the natural changes of the lakes reclamation usually was banned and farmland was abandoned to repair reservoirs while lakes were expanding

volcanic tremor location during the 2004 mount etna lava effusion 1 a lava emission started at mt etna italy on 7 september 2004 neither earthquake seismicity heralded or accompanied the opening of the fracture field from which the lava poured out nor volcanic tremor changed in amplitude and frequency content at the onset of the effusive activity to highlight long term changes we propose a method for the location of the tremor source based on a 3d grid search using the amplitude decay of the seismic signal from january to november 2004 we find the centroid of the tremor source within a zone close to and partially overlapped with the summit craters pre effusive phase which extended up to 2 km south of them effusive phase the depths are of between 1698 and 2387 m a s l we hypothesize the lava effusion stemmed from a degassed magma body although we find evidence of temporary magma overpressure conditions such as those documented on 25 september

time variation of spectral and wavefield features of volcanic tremor at mt etna january june 1999 abstract we have studied the volcanic tremor recorded at mt etna during january june 1999 by using three component seismic stations this time period was characterised by both explosive and effusive eruptions occurring at the summit craters we found significant time variations in the trend of the overall spectral amplitude of tremor as well as in the dominant spectral peaks moreover the tremor wavefield features polarization particle motion and ratios between the amplitude of the three components of the ground velocity have been studied too confirming significant time variations this leads us to suggest the existence of at least two tremor sources a shallow one mainly characterised by relatively high frequencies 3 5 7 hz is linked to the upper portions of the active conduits and directly related to the observed eruptive activity the latter deeper source was active for only a few weeks and characterised by frequencies lower than about 2 5 hz it had no relationship with the observed eruptive activity and was speculatively related to the gas exsolution from fresh magma refilling a small batch

ten years of soil co2 continuous monitoring on mt etna exploring the relationship between processes of soil degassing and volcanic activity 1 the measurement of soil co2 flux variations is a well established practice in many volcanic areas around the world until recently however most of these were made using direct sampling methods these days a variety of automatic devices providing real time data now make the continuous monitoring of volcanic areas possible a network of automatic geochemical monitoring stations etnagas network was developed by ingv palermo and installed at various sites on the flanks of mt etna here we present a large set of soil co2 flux data recorded by the network dating back 10 years a period in which several noteworthy eruptive phenomena occurred our statistical analysis strongly suggests that anomalous measurements of soil co2 flux are attributable to volcanic origin and in almost all cases precede volcanic activity here we present the actual data series recorded by etnagas and an interpretative model of the expected behavior of soil co2 flux in terms of increase decrease cycles which corresponded well with the volcanic activity during this period through the use of a comparative approach incorporating both volcanological and geochemical data the global soil co2 flux trends are put into a coherent framework highlighting close links between the time flux variations and volcanic activities these insights made possible from 10 years of uninterrupted data confirm the importance of continuous monitoring of volcanic soil degassing and may contribute in the forecasting of imminent eruptive activity or the temporal evolution of an in progress eruption therefore facilitating civil defense planning in volcanic areas under high hazard conditions

evidence of deep magma degassing and ascent by geochemistry of peripheral gas emissions at mount etna italy assessment of the magmatic reservoir pressure 1 five gas discharges in the area of mount etna volcano italy and in the near hyblean plateau have been monitored since 1996 all the emissions displayed low contributions from crustal fluids whereas magmatic gases were the main component selective dissolution of these gases into hydrothermal aquifers has been recognized and modeled allowing us to calculate the original composition of the magma released gases the inferred composition of the magmatic gases exhibits synchronous variations of he ne and he co2 ratios which are coherent with the magma degassing process on the basis of numerical simulations of volatile degassing from etnean basalts we have computed the initial and final pressures of the magma batches feeding the emissions we thus can define the levels of the etna plumbing system where magmas are stored pressure values were around 360 and 160 mpa for initial and final stages respectively meaning related depths of about 10 and 3 km below sea level matching those obtained by geophysical investigations for the deep and shallow magma reservoirs in addition we have been able to recognize episodes of magma migration from the deeper reservoir toward the shallow one an important magma injection into the shallow storage volume was detected during the onset of the 2001 eruption 17 july no further injection had taken place during this period until september 2001 providing a possible reason for the quick exhaustion of the eruption in view of this we suggest that the sampled emissions are a powerful geochemical tool to investigate the etna s plumbing system and its magma dynamics as well as the development of eruptive events

late quaternary lake level record from northern eurasia lake records from northern eurasia show regionally coherent patterns of changes during the late quaternary lakes peripheral to the scandinavian ice sheet were lower than those today but lakes in the mediterranean zone were high at the glacial maximum reflecting the dominance of glacial anticyclonic conditions in northern europe and a southward shift of the westerlies the influence of the glacial anticyclonic circulation attenuated through the late glacial period and the westerlies gradually shifted northward such that drier conditions south of the ice sheet were confined to a progressively narrower zone and the mediterranean became drier the early holocene shows a gradual shift to conditions wetter than present in central asia associated with the expanded asian monsoon and in the mediterranean in response to local monsoon type circulation there is no evidence of mid continental aridity in northern eurasia during the mid holocene in contrast the circum baltic region was drier reflecting the increased incidence of blocking anticyclones centered on scandinavia in summer there is a gradual transition to modern conditions after ca 5000 yr b p although these broad scale patterns are interrupted by shorter term fluctuations the long term trends in lake behavior show a clear response to changes in insolation and glaciation

east african climate change and orbital forcing during the last 175 kyr bp abstract variations in the temporal and spatial distribution of solar radiation caused by orbital changes provide a partial explanation for the observed long term fluctuations in african lake levels the understanding of such relationships is essential for designing climate prediction models for the tropics our assessment of the nature and timing of east african climate change is based on lake level fluctuations of lake naivasha in the central kenya rift 0 55 s 36 20 e inferred from sediment characteristics diatoms authigenic mineral assemblages and 17 single crystal 40ar 39ar age determinations assuming that these fluctuations reflect climate changes the lake naivasha record demonstrates that periods of increased humidity in east africa mainly followed maximum equatorial solar radiation in march or september interestingly the most dramatic change in the naivasha basin occurred as early as 146 kyr bp and the highest lake level was recorded at about 139 133 kyr bp this is consistent with other well dated low latitude climate records but does not correspond to peaks in northern hemisphere summer insolation as the trigger for the ice age cycles the naivasha record therefore provides evidence for low latitude forcing of the ice age climate cycles

shallow magma pathway geometry at mt etna volcano 1 a fundamental goal of volcano seismology is to understand the dynamics of active magmatic systems in order to assess eruptive behavior and the associated hazard imaging of magma conduits quantification of magma transport and investigation of long period seismic sources together with their temporal variations are crucial for the comprehension of eruption triggering mechanisms at mt etna volcano several intense episodes of tremor activity were recorded during 2007 in association with strombolian activity and or intense fire fountaining episodes occurring from the south east crater sec the locations of the tremor sources and of the long period seismic events are used here to constrain both the area and the depth range of magma degassing highlighting the geometry of the shallow conduits feeding sec the imaged conduits consist of two connected resonating dike like bodies nnw sse and nw se oriented extending from sea level to the surface in addition we show how tremor long period lp and very long period vlp event locations and signatures reflect pressure fluctuations in the plumbing system associated with the ascent discharge of gas rich magma linked to the lava fountains the evidence here reported also corroborated by ground deformation variations can help develop a better prediction and early warning system for those eruptions effusive or explosive that apparently manifest no clear precursors

volcanic tremor at mt etna state of the art and perspectives volcanic tremor on etna seems to have its origin within the main magma feeding system on the basis of both spectral analyses at two permanent seismic stations and periodical measurements along the slopes of the volcano two distinct sources are proposed the former characterized by low frequency contents f 1 5 hz is located in a 2 km deep flat magma chamber whereas the latter source seems to be linked to the upper part of the active vents

remotely sensed evapotranspiration estimates for an improved hydrological modeling of the early holocene mega lake suguta northern kenya rift abstract the actual evapotranspiration is an important but difficult to determine element in the water balance of lakes and their catchment areas reliable data on evapotranspiration are not available for most lake basins for which paleoclimate reconstructions and modeling have been performed particularly those in remote parts of africa we have used thermal infrared multispectral data for 14 aster scenes from the terra satellite to estimate the actual evapotranspiration in the 12 800 km2 catchment of the suguta valley northern kenya rift evidence from sediments and paleo shorelines indicates that during the african humid period ahp 14 8 to 5 5 kyrs bp this valley contained a large lake 280 m deep and covering 2200 km2 which has now virtually disappeared evapotranspiration estimates for the suguta basin were generated using the surface energy balance algorithm for land sebal climate data required for the model were extracted from a high resolution gridded dataset obtained from the climatic research unit east anglia uk results suggest significant spatial variations in evapotranspiration within the catchment area ranging from 450 mm yr in the basin to the north to 2000 mm yr in more elevated areas and precipitation that was 20 higher during the ahp than in recent times these results are in agreement with other estimates of paleo precipitation in east africa the extreme response of the lake system 280 m greater water depth than today and a lake surface area of 2200 km2 to only moderately higher precipitation illustrates the possible sensitivity of this area to future climate change

paleoclimatic estimates from water and energy budgets of east african lakes abstract the turkana nakuru elmenteita and naivasha basins in the rift valley of east africa experienced high water levels during the period of 10 000 7000 yr b p analyses of the modern hydrologic and energy budgets for these basins along with that of lake victoria were used to infer the amount of precipitation that would have been required to maintain the enlarged paleolakes of the early holocene precipitation must have been at least 150 300 mm yr 15 to 35 above the modern average the precipitation estimates were fairly consistent among the various basins but no quantitative estimate was made for the additional precipitation required to account for overflow from the rift valley lake basins discharge from the lake victoria basin around 1880 a d was considerably above the more recent average and the increased discharge into the white nile for that period might have been similar to that of the early holocene a sensitivity analysis showed that temperature changes were probably not too important for changing the hydrologic energy budget changes of albedo bowen ratio and cloudiness were likely to have been of greater importance

quaternary glaciations in africa abstract glaciers were active on the african mountains during several periods of the quaternary evidence exists of three old glaciations before 100 ka bp on kilimanjaro and two on mount kenya and ruwenzori the last glaciation which was synchronous with the last major glacial phase in temperate latitudes affected kilimanjaro mount kenya ruwenzori nyandarua range mount elgon the ethiopian highlands and several of the high mountains within and around the sahara desert the ice disappeared from most of these areas during the early holocene except from kilimanjaro mount kenya and ruwenzori where glaciers exist at the present day

oxygen isotope records of holocene climate variability in the pacific northwest abstract oxygen isotope 18o measurements of authigenic carbonate from cleland lake southeastern british columbia paradise lake central british columbia and lime lake eastern washington provide a 9000 year holocene record of precipitation evaporation balance variations in the pacific northwest both cleland lake and paradise lake are small surficially closed basin systems with no active inflows or outflows lime lake is surficially open with a seasonally active overflow water isotope values from cleland and paradise plot along the local evaporation line indicating that precipitation evaporation balance is a strong influence on lake hydrology in contrast lime lake water isotope values plot on the local meteoric water line signifying minimal influence by evaporation to infer past hydrologic balance variations at a high temporal resolution we sampled the cleland paradise and lime lake sediment cores at 1 60 mm intervals 3 33 years per sample on average and measured the isotopic composition of fine grained

searching for a significant correlation between volcanic tremor amplitude and so2 emissions at mount etna volcano sicily summary a strong correlation between the amplitude of volcanic tremor and the flux of so2 has been found at mount etna volcano sicily corresponding to enhanced volcanic activity in the period 1987 1995 we therefore suggest that tremors and so2 emissions have a common physical origin linked to the magma dynamics of the volcano

insights into magma and fluid transfer at mount etna by a multiparametric approach a model of the events leading to the 2011 eruptive cycle 1 since the second half of the 1990s the eruptive activity of mount etna has provided evidence that both explosive and effusive eruptions display periodic variations in discharge and eruption style in this work a multiparametric approach consisting of comparing volcanological geophysical and geochemical data was applied to explore the volcano s dynamics during 2009 2011 in particular temporal and or spatial variations of seismicity volcano tectonic earthquakes volcanic tremor and long period and very long period events ground deformation gps and tiltmeter data and geochemistry so2 flux co2 flux co2 so2 ratio were studied to understand the volcanic activity as well as to investigate magma movement in both deep and shallow portions of the plumbing system feeding the 2011 eruptive period after the volcano deflation accompanying the onset of the 2008 2009 eruption a new recharging phase began in august 2008 this new volcanic cycle evolved from an initial recharge phase of the intermediate shallower plumbing system and inflation followed by i accelerated displacement in the volcano s eastern flank since april 2009 and ii renewal of summit volcanic activity during the second half of 2010 culminating in 2011 in a cyclic eruptive behavior with 18 lava fountains from new southeast crater nsec furthermore supported by the geochemical data the inversion of ground deformation gps data and the locations of the tremor sources are used here to constrain both the area and the depth range of magma degassing allowing reconstructing the intermediate and shallow storage zones feeding the 2011 cyclic fountaining nsec activity

the zambezi river tectonism climatic change and drainage evolution abstract the longitudinal profile of the zambezi river forms two concave upwards sections with their boundary at the victoria falls this form has been ascribed to the process of pediplantation and the victoria falls identified as one of several knick points that have traversed the river since the breakup of gondwanaland an alternative model explains the river s long profile by suggesting that the upper and middle zambezi evolved as entirely separate river systems which only joined together in comparatively recent times the alluvial sequence of the middle zambezi is described and interpreted in terms of the latter hypothesis the river capture event caused a change in grade and is marked by a deposit believed to record a cataclysmic flood capture is inferred to have resulted from overtopping of the lake that formed the end sink of the proto upper zambezi rather than from headward erosion of the proto middle zambezi this event is dated from archaeological evidence to the peak of the last interglacial at the end of the middle pleistocene subsequent drainage diversions between the middle zambezi and the kalahari are interpreted as the product of rifting of the chobe graben and aggradation of the chobe swamps river capture by overtopping implies high rainfall over central southern africa at the peak of the last interglacial which is contrary to predictions that africa s rain belts then lay north of their modern mean positions this anomaly is resolved by postulating a southern polar warming episode at that time and agrees with suggestions that the last interglacial was marked by large scale ablation of the west antarctic ice sheet

volcanic tremor at mt etna inferences on magma dynamics during effusive and explosive activity abstract during 1999 the volcanic activity at mt etna was both explosive and effusive at the summit craters strombolian activity lava fountains and lava flows affected different areas of the volcano involving three of the four summit craters results from analysis of the 1999 volcanic tremor features are shown at two different time scales first the long term time variation of the features of the volcanic tremor including spectral and polarization parameters during the entire year was compared with the evolution of the eruptive activity this approach demonstrated the good agreement between tremor data and observed eruptive activity the activation of different tremor sources was suggested then a more refined analysis of the volcanic tremor recorded during 14 lava fountain eruptions was performed in particular a shift of the dominant frequencies towards lower values was noted which corresponds with increasing explosive activity similar behaviour in the frequency content has already been observed in other explosive eruptions at mt etna as well as on other volcanoes this behaviour has been explained in terms of either an increase in the tremor source dimension or a decrease in the sound speed in the magma within the conduit these results confirm that the volcanic tremor is a powerful tool for better understanding the physical processes controlling explosive eruptions at mt etna volcano

monitoring crustal changes at volcanoes by seismic noise interferometry mt etna case of study abstract in this work we analysed the seismic noise recorded at mt etna by 18 stations during the interval 2007 2015 in the frequency band 0 1 0 3 hz chosen to avoid contamination from volcanic tremor variations in time of medium seismic velocity in the range 0 8 to 0 8 were found mostly affecting the stations located on the volcano summit and flanks based on the investigated frequency content the v v changes took place from the surface to a depth of 4 5 6 5 km to identify the source mechanism of the observed medium changes the variations were quantitatively compared by wavelet transform coherence with volcano tectonic and meteorological parameters a significant relationship with meteorological parameters with seasonal periodicity especially air temperature and snow loading was found probably caused by thermo elastic strain and increasing decreasing surface loading cycles moreover a sharp medium velocity decrease taking place in mid december 2009 and clearly time related to the largest volcano tectonic strain release phenomenon of the investigated period was also found such a velocity decrease was interpreted as resulting from ascent of fluids and gas exsolution taking place at the same time as the volcano tectonic swarm