volcanic conduit controls on effusive explosive transitions and the 2010 eruption of merapi volcano indonesia abstract individual volcanoes can produce both effusive and explosive eruptions a transition between these two eruption styles dramatically changes the hazards and can occur either between distinct eruption events or within one eruption episode the causes of these transitions are difficult to determine due to the number of system parameters that can influence whether or not magma fragments in a runaway process we apply a numerical model of magma ascent in a volcanic conduit to isolate and test the effects of key parameters related to magma rheology and system geometry we find that for a given volcanic system parameters that control magma viscosity such as initial water mass fraction initial crystal volume fraction and temperature have the greatest influence on whether or not magma fragments during ascent and erupts explosively we also define a critical condition for the full set of initial parameters under which a transition in eruption style from effusive to explosive or the reverse is more likely to occur under these conditions small heterogeneities in the water or crystal content of the magma or small perturbations to the conduit pressure gradient due to magma chamber overpressure or dome growth or collapse can disrupt the magmatic conditions and cause a transition in eruption style the 2010 vei 4 eruption of merapi volcano included both effusive and explosive phases and was larger by an order of magnitude than its eruptions during the previous century we constrain our model for the merapi system using published literature values and show that between the previous eruption in 2006 and the 2010 eruption the shallow magmatic system at merapi reached critical conditions due to the ascent from depth of a large hotter more volatile rich magma under these critical conditions and according to our model results small changes in the volatile content of the magma small dome collapses subtle changes in degassing rate or the addition of co2 to the magma through decarbonation of the bedrock are all feasible mechanisms for triggering rapid transitions between effusive and explosive activity during the 2010 eruption period

lessons learned from the 2010 evacuations at merapi volcano abstract the rapid onset and large magnitude of the 2010 eruption of merapi posed significant challenges for evacuations and resulted in a peak number of almost 400 000 internally displaced persons idps a pre existing hazard map and an evacuation plan based on the relatively small magnitude of previous eruptions of the 20th century were utilized by emergency officials during the initial phase of the eruption 25 october 3 november 2010 however when the magnitude of the eruption increased greatly on 3 5 november 2010 the initial evacuation plan had to be abandoned as danger zones were expanded rapidly and the scale and pace of the evacuation increased dramatically fortunately orders to evacuate were communicated quickly through a variety of communication methods and as a result many thousands of lives were saved however there were also problems that resulted from this rapid and larger than expected evacuation and there were lessons learned that can improve future mass evacuations at merapi and other volcanoes we analyzed the results of 1969 questionnaires and conducted a series of interviews with community leaders and emergency officials results were compiled for periods both during and after the 2010 eruption our results show that 1 trust in the indonesian government and volcanologists was very high after the eruption 2 multiple modes of communication were used to relay warnings and evacuation orders 3 50 to 70 of idps returned to the danger zone during the crisis despite evacuation orders 4 preparation before the eruption was critical to the successes and included improvements to roads and education programs 5 public education about hazards and evacuation protocols before the eruption was focused in the perceived highest danger zone where it was effective yet confusion and loss of life in other areas demonstrated that education programs in all hazard zones are needed to prepare for larger than normal eruptions and 6 improvements in registration of evacuees in providing for livestock and in activities and work programs in evacuation camps as well as government restrictions and policy changes are also needed to prevent evacuees from returning to their homes during the crisis period

volcaniclastic sediments process interaction and depositional setting of the mio pliocene miura group se japan abstract the mid miocene to early pliocene 14 3 ma miura group exposed on the miura and boso peninsulas around tokyo bay in southern honshu comprises at least a 2 km thick succession of volcaniclastic sediments these accumulated in a forearc basin or basins on the eastern side of a proto izu bonin arc prior to and during accretion of the miura block onto the honshu arc and its subsequent dextral transcurrent eduction the basin fill shows a complex admixture of facies that result from multiple processes which operated on a relatively shallow slope basin the main facies groups include dark coloured mostly coarse grained scoriaceous beds pale coloured muddy silty pumiceous bioturbated sediment yellowish and whitish coloured tuffaceous horizons and chaotic slump debris flow and injection units many of the facies and beds in the older misaki formation can be readily interpreted as the result of a direct pyroclastic fall through the air and water b downslope resedimentation via turbidity currents and related processes in some cases derived from subaqueous base surge pyroclastic flow or vertical density currents c hemipelagic settling commonly under the influence of thermohaline bottom currents in other cases composite beds are believed to result from the interaction of these processes in more complex events the younger hasse formation is dominated by more shallow water marine currents and storm events and in parts by fluvial or proximal fan delta processes the distribution of these different facies illustrates the evolution and shallowing of the miura boso forearc basins during accretion and emplacement

absolute calibration of the greenland time scale implications for antarctic time scales and for δ14c abstract we propose a new age scale for the two ice cores grip and gisp2 that were drilled at greenland summit based on accelerator mass spectrometry 14c dating of foraminifera in core md95 2042 paleoceanography 15 2000 565 calibrated by means of recently obtained paired 14c and 230th measurements on pristine corals marine radiocarbon calibration curve spanning 10 500 to 50 000 years bp thousand years before present based on paired 230th 234u 238u and 14c dates on pristine corals geological society of america bulletin 2003 submitted for publication the record of core md95 2042 can be correlated very precisely to the greenland ice cores between 30 and 40 ka bp our scale is 1 4 ka older than the grip ss09sea time scale journal of quaternary science 16 2001 299 at the older end of marine isotope stage 3 we use published 230th dates from speleothems to calibrate the record using this scale we show a 14c record that is broadly consistent with the modelled record earth planet sci lett 200 2002 177 and with the data of hughen et al science 303 2004 202 but not consistent with the high values obtained by beck et al science 292 2001 2453 or by voelker et al radiocarbon 40 1998 517 we show how a set of age scales for the antarctic ice cores can be derived that are both fully consistent with the greenland scale and glaciologically reasonable

new late permian paleomagnetic data from argentina refinement of the apparent polar wander path of gondwana the late paleozoic early mesozoic apparent polar wander path of gondwana is largely constructed from relatively old paleomagnetic results many of which are considered unreliable by modern standards paleomagnetic results derived from sedimentary sequences which are generally poorly dated and prone to inclination shallowing are especially common here we report the results of a joint paleomagnetic geochronologic study of a volcanic complex in central argentina u pb dating of zircons has yielded a robust age estimate of 263 0 1 6 2 0 ma for the complex paleomagnetic analysis has revealed a pretilting primary permian magnetization with dual polarities rock magnetic experiments have identified pseudo single domain titano magnetite and hematite as the mineralogic carriers of the magnetization lightning induced isothermal remagnetizations are widespread in the low coercivity magnetic carriers the resulting paleomagnetic pole is 80 1 s 349 0 e a95 3 3 n 35 and it improves a late permian mean pole calculated from a filtered south american paleomagnetic data set more broadly this new high quality igneous based paleomagnetic pole falls between the previously distinct late permian segments of the laurussian and gondwanan apparent polar wander paths suggesting that the long recognized disparity between these large paleomagnetic data sets may be primarily due to the inclusion of low quality or systemically biased data

rapid topographic change measured by high resolution satellite radar at soufriere hills volcano montserrat 2008 2010 high resolution satellite radar observations of erupting volcanoes can yield valuable information on rapidly changing deposits and geomorphology using the terrasar x tsx radar with a spatial resolution of about 2 m and a repeat interval of 11 days we show how a variety of techniques were used to record some of the eruptive history of the soufriere hills volcano montserrat between july 2008 and february 2010 after a 15 month pause in lava dome growth a vulcanian explosion occurred on 28 july 2008 from a vent that was hidden by dense cloud we were able to show the civil authorities using tsx difference images of surface roughness change that this explosion had not disrupted the dome sufficiently to warrant continuation of a previous precautionary evacuation change difference images also proved to be valuable in mapping new pyroclastic flow deposits the valley occupying block and ash component tended to increase backscatter and the marginal surge deposits to reduce it with the pattern reversing after the event due to erosion and deposition by comparing east and west looking images acquired 12 h apart the deposition of some individual pyroclastic flows can be inferred from change differences some of the narrow upper sections of valleys draining the volcano received many tens of metres of rockfall and pyroclastic flow deposits over periods of a few weeks by measuring the changing radar shadows cast by these valleys in tsx images the changing depth of infill by deposits could be estimated in addition to using the amplitude data from the radar images we also used their phase information within the insar technique to calculate the topography during a period of no surface activity this enabled areas of transient topography crucial for directing future flows to be captured

large time step numerical modelling of the flow of maxwell materials summary maxwell viscoelastic materials are commonly simulated numerically in order to model the stresses and deformations associated with large scale earth processes such as mantle convection or crustal deformation both implicit and explicit time marching methods require that the time steps used be small compared with the maxwell relaxation time if accurate solutions are to be obtained for crustal tectonic modelling where maxwell times in a ductile lower crust may be of order of a decade or less the large number of time steps required to model processes lasting many millions of years imposes a huge computational burden this burden is avoidable in this paper i show that with the appropriate formulation of the problem time steps may be taken which are much larger than the maxwell time without loss of accuracy as long as they are not large compared with the times over which strain rates vary significantly tectonic timescales in the model the method relies on explicit analytic integration of the maxwell constitutive relation for the stress over time intervals which may be longer than the relaxation time as long as they are short compared with the timescale over which crustal stresses and geometries change the validity of the formulation is also demonstrated numerically by comparison with the analytic solutions for three simple plane strain models extension of a uniform block shear of a composite layer and development of a rayleigh taylor instability

no evidence of a new magmatic gas contribution to the solfatara volcanic gases during the bradyseismic crisis at campi flegrei italy a volcano tectonic crisis with strong seismic activity and rapid uplift started in 1982 and continued until its abrupt disappearance at the beginning of 1985 at campi flegrei caldera southern italy the chemical composition of the fumarolic fluids has been recorded during the last five years and from geochemical and thermodynamical considerations it has been deduced that the shallow reservoir feeding the fumaroles remained chemically isolated at least with respect to major magmatic components from the magma chamber inferred to be located at depth

a better radiocarbon clock reliable radiocarbon dating is essential in many fields from geology and archaeology to geochemistry and paleoclimatology but because the atmosphericc c ratio has changed over time obtaining accurate dating is difficult in their perspective bard et al discuss efforts to improve the accuracy of radiocarbon dating presented at a recent conference in new zealand stratigraphic results from ocean sediments off the coast of venezuela reported by hughen et al were presented at this meeting and are put into context by bard et al taken together these and other findings give hope that reliable radiocarbon calibration curves will be ready for the next such meeting in 2006

early landslide detection based on d insar technique at the wudongde hydropower reservoir differential interferometric synthetic aperture radar d insar is an effective technique for geological disaster prevention in this study an early landslide detection method based on the d insar technique is proposed first sar data are used to monitor landslide deformation in the wudongde hydropower reservoir then the ground surface deformation is derived by using the d insar technique which includes both soil and non soil deformations to remove the non soil deformation the vertical deformation filter method and slope deformation filter method for extracting soil deformations are established and the error of d insar results is analyzed by using two methods permanent scatterers insar and corner reflectors insar the errors caused by the atmospheric delay are estimated quantitatively additionally the relationship between the landslide deformation and the temporal spatial change of the sar data is analyzed and used to identify landslides finally through the proposed early landslide detection method the jinpingzi landslide in the wudongde area is investigated to validate the proposed method and the other unknown landslides in this area are also detected which demonstrates the feasibility of the proposed method the outcome of this study provides a workable technique for early detection of landslides in valley reservoir areas

the displacement field of the landers earthquake mapped by radar interferometry geodetic data obtained by ground or space based techniques can be used to infer the distribution of slip on a fault that has ruptured in an earthquake although most geodetic techniques require a surveyed network to be in place before the earthquake1 3 satellite images when collected at regular intervals can capture co seismic displacements without advance knowledge of the earthquake s location synthetic aperture radar sar interferometry first introduced4 in 1974 for topographic mapping5 8 can also be used to detect changes in the ground surface by removing the signal from the topography9 10 here we use sar interferometry to capture the movements produced by the 1992 earthquake in landers california11 we construct an interferogram by combining topographic information with sar images obtained by the ers 1 satellite before and after the earthquake the observed changes in range from the ground surface to the satellite agree well with the slip measured in the field with the displacements measured by surveying and with the results of an elastic dislocation model as a geodetic tool the sar interferogram provides a denser spatial sampling 100 m per pixel than surveying methods1 3 and a better precision 3 cm than previous space imaging techniques12 13

mapping the 2010 merapi pyroclastic deposits using dual polarization synthetic aperture radar sar data l band alos palsar images acquired before during and after the 2010 merapi eruption have been used to classify and map the pyroclastic deposits emplaced during this vei 4 event we characterize the deposits using direct polarized and cross polarized l band sar data and by combining the information of amplitude evolution with temporal decorrelation changes in amplitude of the radar signal enable us to map the pyroclastic density currents pdcs and tephra fall deposits radar amplitudes in direct hh and cross hv polarizations decrease where the valley confined and overbank block and ash flow baf deposits d1 are emplaced rainfall and runoff reworked pdc deposits d2 are characterized by an increase in ground backscattering for hh polarization and a decrease for hv polarization ground backscattering transiently increases in both polarizations after pyroclastic surge d3 and tephra fall d4 deposition we use a supervised classification method based on maximum likelihood to map the deposits d1 d4 the temporal decorrelation of the radar signal and the amplitude evolution improve the quality of classification results classification derived from alos palsar images using the maximum likelihood classification provides a result with 70 classification accuracy for deposits overall the estimated areas of valley confined and overbank pdc deposits either primary or reworked by rainfall and runoff are consistent with the areas measured by other studies while the large discrepancy in area estimated for pyroclastic surge deposits can be partly explained by the strong erosion due to intense rainfall that removed a large part of these thin deposits

two examples of subaqueously welded ash flow tuffs the visean of southern vosges france and the upper cretaceous of northern anatolia turkey abstract pyroclastic deposits interpreted as subaqueous ash flow tuff have been recognized within archean to recent marine and lacustrine sequences several authors proposed a high temperature emplacement for some of these tuffs however the subaqueous welding of pyroclastic deposits remains controversial the visean marine volcaniclastic formations of southern vosges france contain several layers of rhyolitic and rhyodacitic ash flow tuff these deposits include from proximal to distal settings breccia lapilli and fine ash tuff the breccia and lapilli tuff are partly welded as indicated by the presence of fiamme fluidal and axiolitic structures the lapilli tuff form idealized sections with a lower coarse and welded unit and an upper bedded and unwelded fine ash tuff sedimentary structures suggest that the fine ash tuff units were deposited by turbidity currents welded breccias interbedded in a thick submarine volcanic complex indicate the close proximity of the volcanic source the lapilli and fine ash tuff are interbedded in a thick marine sequence composed of alternating sandstones and shales presence of a marine stenohaline fauna and sedimentary structures attest to a marine depositional environment below storm wave base in northern anatolia thick massive sequences of rhyodacitic crystal tuff are interbedded with the upper cretaceous marine turbidites of the mudurnu basin some of these tuffs are welded as in southern vosges partial welding is attested by the presence of fiamme and fluidal structures the latter are frequent in the fresh vitric matrix these tuff units contain a high proportion of vitroclasis and were emplaced by ash flows welded tuff units are associated with non welded crystal tuff and contain abundant bioclasts which indicate mixing with water during flowage at the base basaltic breccia beds are associated with micritic beds containing a marine fauna the welded and non welded tuff sequences are interbedded in an alternation of limestones and marls these limestones are rich in pelagic microfossils the evidence above strongly suggest that in both examples tuff beds are partly welded and were emplaced at high temperature by subaqueous ash flows in a permanent marine environment the sources of the pyroclastic material are unknown in both cases we propose that the ash flows were produced during submarine fissure eruptions such eruptions could produce non turbulent flows which were insulated by a steam carapace before deposition and welding the welded ash flow tuff deposits of southern vosges and northern anatolia give strong evidence for existence of subaqueous welding

grain size distributions of pyroclastic deposits a multivariate statistical technique principal component analysis has been used to investigate the granulometric features of 414 samples of pyroclastic rocks 216 samples were collected from areas of recent and active volcanism in central and southern italy data for the remaining 198 samples were obtained from the literature and relate to products from somma vesuvio mount st helens and the japanese volcanic arc the analysis offers an improved means of discriminating pyroclastic deposits using their grain size characteristics

collection and three dimensional modeling of gps and tilt data at merapi volcano java we study here the deformations associated with the november 1996 to march 1997 eruption period at mount merapi central java one of the most active volcanoes in indonesia this activity period includes a vertical explosion on january 17 and an increase of the lava dome volume by about 3 106 m3 two global positioning system gps campaigns have been carried out on a six benchmark network at the beginning and at the end of the period relative displacements with respect to the reference point show an average subsidence of 6 5 cm a multicomponent tilt station installed on the southeast flank 3 km from the summit recorded a tilt of 11 1 0 7 rad in the tangential direction and 0 9 0 4 rad in the radial direction these data are interpreted using a three dimensional 3 d elastic model based on the mixed boundary element method and a near neighbor monte carlo inversion interpretation of tilt data requires an accurate mesh for discretizing the 3 d topography the final result supports a horizontal elliptic magma source located 8 5 0 4 km below the summit and 2 0 4 km to the east of it in particular the data cannot be consistent with the location of a magma chamber determined from seismic activity analysis i e 2 km below the summit the computed depth depends strongly on the source shape and cannot be constrained properly because of the small amount of data the computed deflation of 11 2 106 m3 is about 3 times larger than the observed increase in the lava dome volume this difference is attributed to rock avalanches and pyroclastic flows on the flanks of the volcano

an 18 m thick volcaniclastic interval in pantelleria trough sicily channel deposited from a large gravitative flow during the green tuff eruption abstract a 30 m long piston core from the floor of pantelleria trough penetrated an 18 m thick volcaniclastic interval under and overlain by hemipelagic sediments the distribution and thickness of the interval is mapped in 3 5 khz profiles across the trough core sediments have been analysed for grain size carbonate content detrital petrology and physical properties such as bulk density and magnetic susceptibility chemical analyses of tephra and included minerals have been made by electron microprobe the volcaniclastic interval is correlated with the youngest large explosive eruption on pantelleria the 50 ka green tuff ignimbrite eruption on the basis of the sedimentation rate of overlying sediment calcareous nannofossil and foraminiferal biostratigraphy a calibrated radiocarbon age of 43 47 2 ka possibly infinite in the underlying marls and many similarities in tephra and mineral chemistry and abundance the lower 8 m of the volcaniclastic interval consists of poorly sorted massive units of lapilli tuff interpreted as resulting from the direct flow of a pyroclastic flow into the sea with the energetic hyperconcentrated flows crossing the length of pantelleria trough and eventually freezing on the low gradients the overlying 10 m thick turbidite probably developed from the dilute turbulent pyroclastic flow of the co ignimbrite cloud and the resulting turbulent subaqueous flow eroded bioclastic material from the shelf and deposited a well graded bed from sand through silt to mud the poorer sorting of the volcaniclastic interval compared with the green tuff ignimbrite on land supports the concept that ignimbrite deposits are sorted by aggrading bed processes

atmospheric effects in interferometric synthetic aperture radar surface deformation and topographic maps interferogram images derived from repeat pass spaceborne synthetic aperture radar systems exhibit artifacts due to the time and space variations of atmospheric water vapor other tropospheric variations such as pressure and temperature also induce distortions but the effects are smaller in magnitude and more evenly distributed throughout the interferogram than the wet troposphere term spatial and temporal changes of 20 in relative humidity lead to 10 cm errors in deformation products and perhaps 100 m of error in derived topographic maps for those pass pairs with unfavorable baseline geometries in wet regions such as hawaii these are by far the dominant errors in the spaceborne imaging radar c and x band synthetic aperature radar sir c x sar interferometric products the unknown time delay from tropospheric distortion is independent of frequency and thus multiwavelength measurements such as those commonly used to correct radar altimeter and global positioning system gps ionospheric biases cannot be used to rectify the error in the topographic case the errors may be mitigated by choosing interferometric pairs with relatively long baselines as the error amplitude is inversely proportional to the perpendicular component of the interferometer baseline for the sir c x sar hawaii data we found that the best longest baseline pair produced a map supporting 100 m contouring whereas the poorest baseline choice yielded an extremely noisy topographic map even at this coarse contour interval in the case of deformation map errors the result is either independent of baseline parameters or else very nearly so here the only solution is averaging of independent interferograms so in order to create accurate deformation products in wet regions many multiple passes may be required rules for designing optimal data acquisition and processing sequences for interferometric analyses in nondesert parts of the world are 1 to use the longest radar wavelengths possible within ionospheric scintillation and faraday rotation limits 2 for topography maximize interferometer baseline within decorrelation limits and 3 for surface deformation use multiple observations and average the derived products following the above recipe yields accuracies of 10 m for digital elevation models and 1 cm for deformation maps even in very wet regions such as hawaii

late quaternary planktonic foraminiferal biostratrigraphy strait of sicily mediterranean sea abstract the development of a detailed planktonic foraminiferal biostratigraphy for the late quaternary latest 180 000 years has allowed the dating and correlation of sediments from the strait of sicily principal component analysis of the assemblages has extracted a climatic history similar to that based upon oxygen isotopic oscillations intercore correlations are supported by tephrochronology and sapropel layer stratigraphy identification of termination ia and ib in several high sedimentation rate cores indicates that the mediterranean sea experienced a two stage warming during the last deglaciation cores collected between water depths of 200 and 600 m contain an erosional hiatus near their tops reflecting an increase in the levantine intermediate water flow sometime since 25 000 years b p and as recently as 7000 years b p during deposition of the youngest sapropel layer a distinct and unusual planktonic foraminiferal succession is associated with sapropel layers this begins in a protosapropel layer immediately beneath a sapropel horizon and continues upwards to the immediately overlying oxidized layer

overview of the 2006 eruption of mt merapi abstract in the last part of the 20th century and the beginning of the 21st century mt merapi in central java indonesia erupted about every 2 5 years most of the eruptions were low in explosivity with vei 3 or less eruptions usually involve the formation of a lava dome either in the beginning or in the end of the eruptive episode for the 2006 eruption the precursory signal was first observed in the middle of the year 2005 with a decrease in edm slope distances to points on the rim an increase of seismicity and a possible increase of so 2 emissions those early events marked the beginning of a more continuous period of inflation which led to the eruption in total the pre eruption displacement of the southern rim reached at least 2 4 m toward the measuring station in kaliurang kal from late april until june 2006 a lava dome grew on the summit with a volume that gradually increased until it reached about 4 1 million m 3 in 38 days the total of erupted magma was about 5 3 million m 3 dense rock equivalent dre the dome subsequently collapsed in three steps from june 4 to june 14 leaving an open scar on its southeast side in this paper we detail the changes of dome morphology that were monitored by taking successive photographs from similar positions the eruption in 2006 marked a significant change in summit morphology from west southwestward opening during the 20th century to the currently southeast orientation also an mw 6 4 earthquake occurred on 26 may midway through the eruption which adds interesting questions about the relationship of the eruption and the earthquake edm data from 2006 and previous eruptions show that the summit remains inflated after each eruption i e no significant deflation occurs following eruptions the lack of post eruption deflation suggests that magma remains in the shallow parts of the edifice after the eruption as a result the complex of summit lava domes and their intrusive roots grow with time and merapi s rim and summit become progressively more unstable and prone to collapse

precursory inflation of shallow magma reservoirs at west sunda volcanoes detected by insar 1 we use 2006 2009 alos interferometric synthetic aperture radar data over the entire west sunda arc indonesia home of 13 of the world s active volcanoes to derive arc wide time dependent ground deformation data we present unambiguous evidence of inflation at six volcanoes three of which erupted after the observation period we show that these volcanoes have shallow magma reservoirs at 1 3 km depth below the average regional elevation a global comparison of reservoir depths at arc volcanoes suggests that volcanoes in extensional and strike slip settings west sunda can develop shallow reservoirs whereas volcanoes in compressional settings may lack them thus magma ascend through the upper crust could be influenced by intra arc tectonic settings

integrated satellite interferometry tropospheric noise gps estimates and implications for interferometric synthetic aperture radar products interferometric synthetic aperture radar insar like other astronomic and space geodetic techniques is limited by the spatially and temporally variable delay of electromagnetic waves propagating through the neutral atmosphere statistical analysis of these variations from a wide variety of instruments reveals a power law dependence on frequency that is characteristic of elementary kolmogorov turbulence a statistical model for a major component of the delay fluctuations the wet component has previously been developed by treuhaft and lanyi 1987 for very long baseline interferometry a continuous global positioning system gps network is now in place in southern california that allows estimation of along with geodetic parameters the total delay due to the atmosphere above each site on a subhourly basis these measurements are shown to conform to the treuhaft and lanyi tl statistical model both temporally and spatially the tl statistical model is applied to the problem of insar and used to produce the covariance between two points separated in time and or space the error due to the atmospheric variations for sar products such as topography and surface deformation is calculated via propagation of errors there are two methods commonly cited to reduce the effect of atmospheric distortion in products from sar interferometry stacking and calibration stacking involves averaging independent interferograms to reduce the noise calibration involves removing part or all of the delay using data from an independent source such as total zenith delay estimates from continuous gps networks despite the relatively poor spatial density of surface measurements calibration can be used to reduce noise if the measurements are sufficiently accurate reduction in tropospheric noise increases with increasing number of measurement points and increasing accuracy up to a maximum of n where n is the number of points stacking and calibration are shown to be complementary and can be used simultaneously to reduce the noise to below that achievable by either method alone

ground deformation at merapi volcano java indonesia distance changes june 1988 october 1995 abstract edifice deformations are reported here for the period 1988 1995 at merapi volcano one of the most active and dangerous volcanoes in indonesia the study period includes a major resumption in lava effusion in january 1992 and a major dome collapse in november 1994 the data comprise electronic distance measurements edm on a summit trilateration network slope distance changes measured to the upper flanks and other data collected from 1988 to 1995 a major consequence of this study is the documentation of a significant 4 year period of deformation precursory to the 1992 eruption cross crater strain rates accelerated from less than 3 10 6 day between 1988 and 1990 to more than 11 10 6 day just prior to the january 1992 activity representing a general asymmetric extension of the summit during high level conduit pressurization after the vent opened and effusion of lava resumed strain occurred at a much reduced rate of less than 2 10 6 day edm measurements between lower flank benchmarks and the upper edifice indicate displacements as great as 1 m per year over the four years before the 1992 eruption the gendol breach a pronounced depression formed by the juxtaposition of old lava coulees on the southeast flank functioned as a major displacement discontinuity since 1993 movements have generally not exceeded the 95 confidence limits of the summit network exceptions to this include 12 cm outward movement for the northwest crater rim in 1992 1993 probably from loading by newly erupted dome lava and movements as much as 7 cm on the south flank between november 1994 and september 1995 no short term precursors were noted before the november 1994 lava dome collapse but long term adjustments of crater geometry accompanied lava dome growth in 1994 short term 2 cm deflation of the edifice occurred following the november 1994 dome collapse

calcareous nannofossils planktonic foraminifera and oxygen isotopes in the late quaternary sapropels of the ionian sea core m 25 4 12 a long piston core 12 20 m recovered in the ionian sea during cruise m25 4 of the r v meteor summer 1993 at a water depth of 2467 m shows an almost complete sequence of sapropels s 1 s 3 to s 10 over the last 330 ka this paper presents the results of an integrated study based on quantitative biostratigraphic analyses performed on both calcareous nannofossils and planktonic foraminifera coupled with the 18o record a decrease in syracosphaera sp 1 and an increase in the abundance of the genus rhabdosphaera and of helicosphaera carteri florisphaera profunda and of the reworked specimens has been found in the calcareous nannofossil assemblage within the sapropels the planktonic foraminiferal assemblage of the sapropels is characterized by a peak in the frequency of globigerinoides ruber var alba and rosea and neogloboquadrina dutertrei the 18o record of globigerinoides ruber and globigerina bulloides allows recognition of isotope stages 1 to 9 and shows a negative fluctuation that corresponds to the sapropel layers these features support the idea of increased productivity coupled to the presence of reduced salinity surface waters that caused the deposition of the sapropels however the need for a good understanding of the ecological requirements of modern assemblages is stressed this is necessary to correctly interpret fossil assemblages this in turn will allow a better understanding of the palaeoceanographic conditions leading to sapropel deposition

palaeoceanographic record of the last deglaciation in the strait of sicily abstract the palaeoceanographic evolution of the levantine waters during the last deglacial time is investigated using the sedimentary record of a deep sea core cs 70 5 from the linosa basin 35 44 4 n 13 11 0 e 1486 m water depth radiocarbon dating and oxygen isotope stratigraphy based on 18 o changes in globigerina bulloides allow us to recognize and to date the different steps of the deglaciation these steps are synchronous with those reported in the north atlantic but correspond to a 18 o decrease of higher amplitude than in the alboran sea or in the north atlantic ocean major faunal events permit the establishment of a local biozonation which differs from those reported either for the alboran sea or the eastern mediterranean basin major breaks in the faunal assemblages occurred during termination i a within the first step of the deglaciation around 14 kyr b p and near 10 6 kyr b p within the younger dryas the onset of the last deglaciation induced important changes in the characteristics of the levantine and atlantic water masses which occupied the strait of sicily the 13 c records of globigerina bulloides and cibicidoides pachyderma indicate that the modifications observed in the assemblages of deep faunas are controlled by the oxygenation of the water column 13 c records of globigerina bulloides are similar throughout the west mediterranean as well as in sediments located below the present mediterranean outflow the distributional pattern as well as its 13 c record suggest that this species could be a good recorder of the upper levantine waters and more precisely of the mixing layer of the overlying atlantic waters with the levantine ones major influxes of atlantic waters during terminations i a and i b could have slowed down the vertical mixing of the different water layers present in the strait of sicily and caused a decrease in the oxygenation of the water column during termination i b the effect of atlantic influxes was reinforced by the occurrence of a low salinity layer in the eastern basin which led to the stagnation of the deep waters the two episodes of decreased oxygenation in the levantine waters also favored the precipitation of inorganic magnesium calcite

the recent explosive volcanism at pantelleria many of the least eighty eruptions of the six silicic eruptive cycles in the last 50 ka at pantelleria started out with explosive phases and ended with lava effusion the pyroclastic rocks are rhyolitic in composition while the later erupted lavas are less evolved up to trachyte probably due to the presence of a shallow and compositionally zoned magma chamber tapped at increasing depth during the eruptions the products of twenty explosive eruptions have been recognized most of them are represented by fallout deposits the only exceptions being the green tuff and the fossa carbonara tuff hydromagmatism is very rare though the magmas interacted with sea water it is supposed that interaction was not efficient because the magmas were not vesiculated and disrupted horizons showing variable degrees of welding up to vitrophyres have often been identified in the air fall tuffs most of the eruptions were characterized by low eruptive columns and were likely to have involved a strombolian type mechanism

ground deformation patterns at mt etna from 1993 to 2000 from joint use of insar and gps techniques abstract combined gps measurements and radar interferometry insar have been applied at mt etna to study the ground deformation affecting the volcano both over the long 1993 2000 and short term 1997 1998 and 1998 2000 the aim was to better understand the dynamics of the volcano during the magma recharging phase following the 1991 93 eruption since 1993 insar and gps data indicate that mt etna has undergone an inflation a deep intrusion was detected by insar on the western flank of the volcano between march and may 1997 in the following months this intrusion rose up leading to a seismic swarm occurring in january 1998 in the western sector this now shallow intrusion is confirmed by gps data from 1998 to 2000 a general deflation affecting the upper part of the volcano was detected over the whole study period a continuous eastward to south eastward motion of the eastern sector of the volcano was also evidenced the analytical inversions of gps data inferred a plane dipping about 12 ese located beneath the eastern flank of the volcano at a depth of 1 4 km b s l the movement along this plane is able to reproduce the observed south eastward motion of a sector bounded northward by the pernicana fault westward by the north east rift and the south rift and southward by the mascalucia tremestieri trecastagni fault system insar data have validated this model

air traffic disturbance due to the 2010 merapi volcano eruption abstract the 2010 merapi eruption was exceptional on several levels intensity of the eruption destructions casualties and for the first time created major air traffic disruptions in yogyakarta leading to the closure of the airport some companies suspended their flights others adapted to the crisis by transferring their flights to other airports and some companies even continued to fly despite the risks involved four major phases emerged first a few days corresponding to the rise of the activity of the eruption a second corresponding to the start of the eruption and first ash emissions then a third peak marked by the eruption which led to the closure of the yogyakarta airport for 15 days and finally a fourth one month long phase where airport activity returned to normal we studied the evolution of disturbances on the field and the correlation between volcanic activity and flight cancelations adaptations between airports were observed adisucipto airport yogyakarta transferred several of its flights to the adi soemarmo of surakarta airport and it transferred its flights to ahmad yani airport in semarang and juanda in surabaya moreover the eruption disrupted the pilgrimage to mecca for thousands of muslims who had waited and saved for years to be able to go nevertheless the organizers coped with the crisis by changing departure airports for the pilgrimage this study allowed us to understand the impacts of a major merapi eruption on air transport from the onset of ash emissions until the late disturbances

nonlinear subsidence rate estimation using permanent scatterers in differential sar interferometry discrete and temporarily stable natural reflectors or permanent scatterers ps can be identified from long temporal series of interferometric sar images even with baselines larger than the so called critical baseline this subset of image pixels can be exploited successfully for high accuracy differential measurements the authors discuss the use of ps in urban areas like pomona ca showing subsidence and absidence effects a new approach to the estimation of the atmospheric phase contributions and the local displacement field is proposed based on simple statistical assumptions new solutions are presented in order to cope with nonlinear motion of the targets

the merapi 2010 eruption an interdisciplinary impact assessment methodology for studying pyroclastic density current dynamics abstract the large explosive eruption of merapi volcano indonesia in 2010 presented a key and rare opportunity to study the impacts of a major explosive eruption in a densely populated area pyroclastic density currents pdcs produced throughout the 2010 eruption were unusually destructive causing near complete devastation across a 22 km 2 swath of the densely populated southern flanks and casualties to the end of their runout at 15 5 km from the volcano the majority 120 of the more than 200 fatalities occurred more than 12 km from the volcano where many people were caught in pdcs as they were evacuating the 2010 eruption vei 4 exhibited a range of pdc behaviour in a complex multi stage event that marked a change in eruption behaviour at merapi being the first eruption of this magnitude and style since 1872 this shift in style may mark a change in regime and so understanding the potential impact of such large explosive eruptions is essential for future risk assessment at merapi we describe a new impact assessment methodology that allowed us to collect important empirical geological damage and casualty information and reconstruct impact dynamics associated with the pdcs in contrast to previous pdc impact studies we combined remote field laboratory and gis assessments and were able to enter the affected areas safely and before their disturbance by rains or human activity by integrating the results of our geological damage and medical studies we could reconstruct the spatial and temporal dynamics of the pdcs and their main hazard characteristics our interdisciplinary methods and preliminary findings are discussed here in the areas damaged by pdcs we used empirical damage data and calculations of material and structural resistance to lateral force to estimate approximate dynamic pressures dynamic pressures associated with the 5 november paroxysm exceeded 15 kpa more than 6 km from source and rapidly attenuated over a distance of less than 1 km at the end of the pdc runouts analysis of thermal indicators such as deformed plastic and correlation with information on burns injuries and fires provided estimates of ambient temperatures associated with the pdcs even at the relatively low temperatures estimated for the pdcs 200 300 c they were lethal to people inside as well as outside buildings in part because of the building design that enabled the pdcs to rapidly infiltrate inside such detailed quantitative data can be used to support numerical pdc and impact modelling and risk assessment at dome forming volcanoes providing an improved understanding of the complexity of pdcs and their associated impacts on exposed populations

historical eruptions of merapi volcano central java indonesia 1768 1998 abstract information on merapi eruptive activity is scattered and much is remotely located a concise and well documented summary of this activity has been long needed to assist researchers and hazard mitigation efforts and the aim of this paper is to synthesize information from the mid 1700s to the present a descriptive chronology is given with an abbreviated chronology in a table that summarizes events by year assigns preliminary volcanic explosivity index vei ratings and hartmann classifications and provides key references the history of volcano monitoring is also outlined the study reveals that a major difference in eruption style exists between the twentieth and nineteenth centuries although the periodicity between larger events seems about the same during the twentieth century activity has comprised mainly the effusive growth of viscous lava domes and lava tongues with occasional gravitational collapses of parts of oversteepened domes to produce the nuees ardentes commonly defined as merapi type in the 1800s however explosive eruptions of relatively large size occurred to vei 4 and some associated fountain collapse nuees ardentes were larger and farther reaching than any produced in the twentieth century these events may also be regarded as typical eruptions for merapi the nineteenth century activity is consistent with the long term pattern of one relatively large event every one or two centuries based on the long term eruptive record deduced by others from volcanic stratigraphy it is uncertain whether or not a recurrence time model continues to apply to merapi but if so merapi could soon be due for another large event and its occurrence with only modest or inadequately appreciated precursors could lead to a disaster unprecedented in merapi s history because the area around the volcano is now much more densely populated

formation of the green tuff pantelleria the strongly peralkaline green tuff pantelleria is an example of a thin densely welded air fall tuff which mantles an area of at least 85 km2 offshore the tuff is correlated with the y 6 ash layer in the central mediterranean sea and the total volume of the eruption is estimated at 7 km3 d r e new petrological data suggests that the tuff was erupted from a zoned magma chamber containing a cooler more fractionated upper zone relative to be bulk of the magma analysis of the distribution of accessory lithic fragments in terms of existing models of eruption dynamics indicates emplacement by a plinian type eruption it is shown that due to the low viscosity of pantelleritic ejecta dense welding can occur at moderate tephra accumulation rates and a rate of the order of 1 cm minute is suggested for the green tuff this yields an estimate for the eruption duration of rather less than one day it is predicted that welded tuff should be formed during large plinian eruptions of pantelleritic magma and therefore that welded airfall tuffs should be common in areas of peralkaline volcanism

merapi 2010 eruption chronology and extrusion rates monitored with satellite radar and used in eruption forecasting abstract despite dense cloud cover satellite borne commercial synthetic aperture radar sar enabled frequent monitoring of merapi volcano s 2010 eruption near real time interpretation of images derived from the amplitude of the sar signals and timely delivery of these interpretations to those responsible for warnings allowed satellite remote sensing for the first time to play an equal role with in situ seismic geodetic and gas monitoring in guiding life saving decisions during a major volcanic crisis our remotely sensed data provide an observational chronology for the main phase of the 2010 eruption which lasted 12 days 26 october 7 november 2010 unlike the prolonged low rate and relatively low explosivity dome forming and collapse eruptions of recent decades at merapi the eruption began with an explosive eruption that produced a new summit crater on 26 october and was accompanied by an ash column and pyroclastic flows that extended 8 km down the flanks this initial explosive event was followed by smaller explosive eruptions on 29 october 1 november then by a period of rapid dome growth on 1 4 november which produced a summit lava dome with a volume of 5 10 6 m 3 a paroxysmal vei 4 magmatic eruption with ash column to 17 km altitude destroyed this dome greatly enlarged the new summit crater and produced extensive pyroclastic flows to 16 km radial distance in the gendol drainage and surges during the night of 4 5 november the paroxysmal eruption was followed by a period of jetting of gas and tephra and by a second short period 12 h of rapid dome growth on 6 november the eruption ended with low level ash and steam emissions that buried the 6 november dome with tephra and continued at low levels until seismicity decreased to background levels by about 23 november our near real time commercial sar documented the explosive events on 26 october and 4 5 november and high rates of dome growth 25 m 3 s 1 an event tree analysis for the previous 2006 merapi eruption indicated that for lava dome extrusion rates 1 2 m 3 s 1 the probability of a large 1872 scale eruption was 10 consequently the order of magnitude greater rates in 2010 along with the explosive start of the eruption on 26 october the large volume of lava accumulating at the summit by 4 november and the rapid and large increases in seismic energy release deformation and gas emissions were the basis for warnings of an unusually large eruption by the indonesian geological agency s center for volcanology and geologic hazard mitigation cvghm and their volcano research and technology development center bpptk in yogyakarta warnings that saved thousands of lives

analysis of the seismic activity associated with the 2010 eruption of merapi volcano java abstract the 2010 eruption of merapi is the first large explosive eruption of the volcano that has been instrumentally observed the main characteristics of the seismic activity during the pre eruptive period and the crisis are presented and interpreted in this paper the first seismic precursors were a series of four shallow swarms during the period between 12 and 4 months before the eruption these swarms are interpreted as the result of perturbations of the hydrothermal system by increasing heat flow shorter term and more continuous precursory seismic activity started about 6 weeks before the initial explosion on 26 october 2010 during this period the rate of seismicity increased almost constantly yielding a cumulative seismic energy release for volcano tectonic vt and multiphase events mp of 7 5 10 10 j this value is 3 times the maximum energy release preceding previous effusive eruptions of merapi the high level reached and the accelerated behavior of both the deformation of the summit and the seismic activity are distinct features of the 2010 eruption the hypocenters of vt events in 2010 occur in two clusters at of 2 5 to 5 km and less than 1 5 km depths below the summit an aseismic zone was detected at 1 5 2 5 km depth consistent with studies of previous eruptions and indicating that this is a robust feature of merapi s subsurface structure our analysis suggests that the aseismic zone is a poorly consolidated layer of altered material within the volcano deep vt events occurred mainly before 17 october 2010 subsequent to that time shallow activity strongly increased the deep seismic activity is interpreted as associated with the enlargement of a narrow conduit by an unusually large volume of rapidly ascending magma the shallow seismicity is interpreted as recording the final magma ascent and the rupture of a summit dome plug which triggered the eruption on 26 october 2010 hindsight forecasting of the occurrence time of the eruption is performed by applying the material failure forecast method ffm using cumulative real time seismic amplitude rsam calculated both from raw records and on signals classified according to their dominant frequency stable estimates of eruption time with errors as small as 4 h are obtained within a 6 day lapse time before the eruption this approach could therefore be useful to support decision making in the case of future large explosive episodes at merapi

a new method for measuring deformation on volcanoes and other natural terrains using insar persistent scatterers 1 we present here a new insar persistent scatterer ps method for analyzing episodic crustal deformation in non urban environments with application to volcanic settings our method for identifying ps pixels in a series of interferograms is based primarily on phase characteristics and finds low amplitude pixels with phase stability that are not identified by the existing amplitude based algorithm our method also uses the spatial correlation of the phases rather than a well defined phase history so that we can observe temporally variable processes e g volcanic deformation the algorithm involves removing the residual topographic component of flattened interferogram phase for each ps then unwrapping the ps phases both spatially and temporally our method finds scatterers with stable phase characteristics independent of amplitudes associated with man made objects and is applicable to areas where conventional insar fails due to complete decorrelation of the majority of scatterers yet a few stable scatterers are present

geologic analyses of shuttle imaging radar sir b data of kilauea volcano hawaii analyses of imaging radar data of volcanic terranes on earth and venus have emphasized the need for a clearer understanding of how these data can be most effectively used to accomplish important volcanological goals including the interpretation of eruptive styles and the characterization of the geologic history of volcanic centers the second shuttle imaging radar experiment sir b obtained two digital images over the summit caldera and the southwest rift zone of kilauea volcano in 1984 our geologic analyses of these images indicate that sir b data are particularly useful for delineating the distribution and surface textural variations of a9a lava flows for mapping large scale topographic features with radar facing slopes and for identifying an areally extensive pyroclastic deposit analyses of the sir b data of kilauea however do not permit unambiguous identification of landforms such as pahoehoe lava flows cinder cones and fissures although separation of low return units such as pahoehoe lava flows and adjacent pyroclastic ash is not greatly improved using standard image enhancement techniques the texture analysis technique applied here did facilitate discrimination of such smooth surfaced volcanic deposits although analyses of the sir b data permit a generally accurate interpretation of the eruptive history of kilauea the inability to distinguish low return pahoehoe flows results in misinterpretation of several aspects of kilauea volcanism suggesting that caution should be exercised in the interpretation of sar data of volcanic terranes

a survey of volcanic deformation on java using alos palsar interferometric time series of the hundreds of volcanic centers throughout the indonesian archipelago few are adequately monitored for pre eruptive activity due to socioeconomic and logistical barriers with the result that volcanic hazards in the region are not well quantified the advent of satellite borne l band synthetic aperture radar provides an opportunity for detection and measurement of volcanic deformation over broad regions in heavily vegetated tropical island arcs we use data from the palsar instrument on the japanese alos satellite to conduct a comprehensive survey of volcanic deformation on the indonesian island of java over a time period of two years 2007 2008 to obtain the most complete temporally continuous record of ground deformation we use a temporally overlapping set of short time interval radar image pairs to produce a deformation time series consistent with previous results from other regions our survey suggests that volcanoes experiencing small eruptions are typically fed by magma bodies too small and or too shallow or deep to produce a recognizable insar signal however we identified a deformation event at lamongan volcano which is likely linked to a magmatic intrusion at several kilometers depth and a second one at slamet volcano at a shallower depth that may have been related to a subsequent eruption this initial test of a broad application of l band data allowed us to better define the satellite imaging criteria required for successful observation as well as developing a useful methodology for monitoring deformation over a wide region

pyroclastic flows and surges over water an example from the 1883 krakatau eruption pyroclastic deposits from the 1883 eruption of krakatau are described from areas northeast of the volcano on the islands of sebesi sebuku and lagoendi and the southeast coast of sumatra massive and poorly stratified units formed predominantly from pyroclastic flows and surges that traveled over the sea for distances up to 80 km granulometric and lithologic characteristics of the deposits indicate that they represent the complement of proximal subaerial and submarine pyroclastic flow deposits laid down on and close to the krakatau islands the distal deposits exhibit a decrease in sorting coefficient median grain size and thickness with increasing distance from krakatau crystal fractionation is consistent with the distal facies being derived from the upper part of gravitationally segregated pyroclastic flows in which the relative amount of crystal enrichment and abundance of dense lithic clasts diminished upwards the deposits are correlated to a major pyroclastic flow phase that occurred on the morning of 27 august at approximately 10 a m energetic flows spread out away from the volcano at speeds in excess of 100 km h and traveled up to 80 km from source the flows retained temperatures high enough to burn victims on the sw coast of sumatra historical accounts from ships in the sunda straits constrain the area affected by the flows to a minimum of 4x103 km2 at the distal edge of this area the flows were relatively dilute and turbulent yet carried enough material to deposit several tens of centimeters of tephra the great mobility of the krakatau flows from the 10 a m activity may be the result of enhanced runout over the sea it is proposed that the generation of steam at the flow seawater interface may have led to a reduction in the sedimentation of particles and consequently a delay in the time before the flows ceased lateral motion and became buoyantly convective the buoyant distal edge of these ash and steam laden clouds lifted off into the atmosphere leading to cooling condensation and mud rain

dome growth and coulee spreading controlled by surface morphology as determined by pixel offsets in photographs of the 2006 merapi eruption abstract at many explosive volcanoes viscous domes extrude which are destroyed by complete or partial collapses although the growth and development of silicic domes and the associated flow and collapse mechanisms are of vital importance for understanding the occurrence and scale of pyroclastic flows quantitative measurements of dome deformations are limited we report on a sequence of photographs taken of a growing and deforming dome a sequence in 2006 featuring the merapi dome taken from similar camera positions allow the application of a digital image correlation algorithm the aim being to detect and explore the temporal evolution of pixel offsets the results suggest that the dome underwent deformation in two regions between september and october 2006 i dome growth and spreading at the volcano summit and ii coulee flow through a narrow canyon the latter is associated with strain localization and flow acceleration which indicates that the displacements and flow velocities at silicic domes are governed by the topographic structure into which the flows develop the downslope motion of the distal parts of the flow and apron slumps continued during episodes of dome extrusion by gravitational spreading an analysis of the 2006 merapi dome and coulee displacement also provides insights into processes that may occur along the newly established southerly eruption direction which also may have influenced pyroclastic flows associated with the 2010 eruption

discrimination of geophysical phenomena in satellite radar interferograms various geophysical phenomena are recorded in the interference patterns formed by differencing two synthetic aperture radar sar images the fringes generated by the topographic relief can be removed using a digital elevation model dem the remaining fringes map the change in satellite to ground range which occurred between the acquisition times of the two images by comparing different pairs of images spanning different intervals of time it is possible to discriminate between geophysical signal and interferometric artifact here we apply this pair wise logic to the area around the 1992 landers california earthquake using sar images acquired by the ers 1 satellite the range varies with time as a constant step impulsive or sloping function examples of each type include a dem error an aftershock two atmospheric perturbations and postseismic afterslip respectively their signatures are identified and separated using the pair wise logic

ground surface deformation patterns magma supply and magma storage at okmok volcano alaska from insar analysis 1 intereruption deformation 1997 2008 eruption magma storage had increased by 3 7 5 2 1 0 7 m 3 or 85 100 of the 1997 eruption volume we propose that the supply rate decreased in response to the diminishing pressure gradient between the shallow storage zone and a deeper magma source region eventuallytheeffectsofcontinuingmagmasupplyandvesiculationofstoredmagmacaused acriticalpressurethresholdtobeexceeded triggeringthe2008eruption asimilarpatternof initially rapid inflation followed by oscillatory but generally slowing inflation was observed prior to the 1997 eruption in both cases withdrawal of magma during the eruptions depressurized the shallow storage zone causing significant volcano wide subsidence and initiating a new intereruption deformation cycle

exploring the limits of identifying sub pixel thermal features using aster tir data abstract understanding the characteristics of volcanic thermal emissions and how they change with time is important for forecasting and monitoring volcanic activity and potential hazards satellite instruments view volcanic thermal features across the globe at various temporal and spatial resolutions thermal features that may be a precursor to a major eruption or indicative of important changes in an on going eruption can be subtle making them challenging to reliably identify with satellite instruments the goal of this study was to explore the limits of the types and magnitudes of thermal anomalies that could be detected using satellite thermal infrared tir data specifically the characterization of sub pixel thermal features with a wide range of temperatures is considered using aster multispectral tir data first theoretical calculations were made to define a thermal mixing detection threshold for aster which quantifies the limits of aster s ability to resolve sub pixel thermal mixing over a range of hot target temperatures and pixel areas then aster tir data were used to model sub pixel thermal features at the yellowstone national park geothermal area hot spring pools with temperatures from 40 to 90 c and at mount erebus volcano antarctica an active lava lake with temperatures from 200 to 800 c finally various sources of uncertainty in sub pixel thermal calculations were quantified for these empirical measurements including pixel resampling atmospheric correction and background temperature and emissivity assumptions

measurements of dielectric constant of volcanic ash erupted from five volcanoes in japan the dielectric properties of volcanic ash from five volcanoes in japan were measured by using the transmission reflection coaxial line method of a network analyzer in a frequency range from 3 to 13 ghz the measured permittivity of powdered ash was then converted to that of solid ash dense rock equivalent with the aid of effective medium theory the values of solid ash relative permittivities for the five volcanoes revealed that they were in a relatively narrow range their real part was generally in a range from five to six in magnitude while their imaginary part was in a range from 0 08 to 0 18

the eruptive history of pantelleria sicily channel in the last 50 ka six silicic eruptive cycles have been recognized in the last 50 ka at pantelleria the products of each cycle exhibit a compositional variation from pantellerite to less peralkaline rhyolite or to trachyte the relationships between the range of chemical variation the erupted volume and the time of eruptions allow us to estimate an average differentiation rate of 5 crystal fractionation per 1000 years and a constant long term rate of magma discharge of 0 1 km3 per 1000 years pressure increase in the magma chamber caused by the addition of new magma accumulation of highly differentiated volatile rich magma in the roof zone and a concomitant build up of a vapour phase is postulated as a possible triggering mechanism for eruptions

deposition of ungraded muds from high density non turbulent turbidity currents turbidity current deposits of mud have recently been found up to 10m in thickness resulting from single depositional events1 2 turbidites 1 5 m thick from the madeira abyssal plain3 4 display long segments with little vertical change of grain size5 6 this suggests that the currents froze in some way making them unable to sort sediment here we suggest that a decline in flow speed of these currents led to a concentration gradient in silt close to the bed that was sufficiently steep to stratify the flow a concentration gradient of 18 kg m 3 over 1 5 m height gives a layer richardson number above the critical value of 0 25 for damping of turbulence we propose that with turbulence severely damped a dense suspension of fine material consolidates like a static suspension while continuing to flow downslope the current changes from a fully turbulent flow to a decelerating flow with suppressed turbulence and increasing density in the latter state interparticle forces prevent differential settling of the coarser grains

a high resolution record of the last deglaciation in the sicily channel based on foraminifera and calcareous nannofossil quantitative distribution abstract relative abundance fluctuations in planktic foraminiferal and calcareous nannofossil assemblages are reported on the basis of a high resolution study of odp leg 160 hole 963d drilled in the sicily strait near capo rossello southern sicily with its 8 m of undisturbed sediments the core covers the interval from 1 5 to 23 kyr allowing a 50 100 yr sampling resolution all the short warm and cold events and sub events recorded in this time interval in the grip greenland ice core and at several mediterranean sites were recognized on this basis a total number of nine ecozones based on planktic foraminifera and seven ecozones based on calcareous nannofossils were identified a short interval of climatic amelioration identified above the base of the holocene precedes the segment contemporaneous with the deposition of sapropel s1 which has no lithological expression in the local sedimentary record this segment has been subdivided into the two warm s1a and s1b phases separated by a cold intermediate event a gradual climatic deterioration is recorded above the top of the interval correlated with sapropel s1 it is interrupted by short cold spells tentatively correlated with similar short duration cold events reported for this interval in the recent literature

sar and gravity change based characterization of the distribution pattern of pyroclastic flow deposits at mt merapi during the past 10 years mt merapi indonesia is one of the most active and dangerous volcanoes in the torrid zone this volcano has erupted frequently and has produced pyroclastic flows following the collapse of the summit lava dome we used synthetic aperture radar sar data acquired by jers 1 and radarsat 1 satellites from april 1996 to july 2006 to clarify the distribution patterns of the pyroclastic flow deposits the extent of the deposits termed p zones was accurately extracted by ratio operation and low level feature extraction from sar intensity images these images highlighted temporal changes of the distribution area perimeter flow distance included angle and collapse direction to validate the image processing results reflectance spectra of the rock samples collected after the eruption in june 2006 were measured in a laboratory the reflectance spectra of all samples showed similar characteristics to the reference spectra which were derived from atmospheric correction of hyperion sensor image data covering the lava dome at the summit therefore p zones were confirmed to be the pyroclastic flow deposits originating from destruction of the lava dome at the summit the image processing results clarified that the extent of the distribution areas perimeter flow distances and included angle of the p zones were variable among the eruptions while the collapse direction had a constant pattern the collapse pattern followed a clockwise change from the south toward the west by comparing the ratio maps of bouguer gravity anomaly data in two periods the change was interpreted to originate from the inclination of the conduit and the formation of shallow and deep magma reservoirs

signs of magma ascent in lp and vlp seismic events and link to degassing an example from the 2010 explosive eruption at merapi volcano indonesia the link between seismicity and degassing is investigated during the vei 4 eruptions of merapi volcano indonesia in october and in early november 2010 seismicity comprised a large number and variety of earthquakes including volcano tectonic events a sustained period of long period seismicity lps i e long period events lp very long period events vlp and tremor lps seismicity is ascribed to the excitation of fluid filled cavity resonance and inertial displacement of fluids and magma we investigate here lps that occurred between 17 october and 4 november 2010 to obtain insights into the volcano eruption processes which preceded the paroxysmal phase of the eruption on 4 5 november we proceed to the moment tensor inversion of a well recorded large vlp event during the intrusion phase on 17 october 2010 i e before the first explosion on 26 october by using two simplified models crack and pipe we find a shallow source for this vlp event at about 1 km to the south of the summit and less than 1 km below the surface we analyze more than 90 lp events that occurred during the multi phase eruption 29 october 4 november we show that most of them have a dominant frequency in the range 0 2 4 hz we could locate 48 of those lp events at least 3 clusters of lp events occurred successively we interpret these observations as generated by different fluid filled containers in the summit area that were excited while magma rose we also observe significant variations of the complex frequency during the course of the eruption we discuss these changes in terms of a variable ratio of fluid to solid densities and or by possible conduit geometry change and or permeability of the conduit or the edifice and or by resonance of different fluid containers during the release of more than 0 4 tg of so2 and large but unknown masses of other volcanic gases finally we also discuss how the major explosions of the eruption were possibly triggered by passing waves resulting from regional tectonic earthquakes on 3 and 4 november

constraints on magma flux from displacements data at merapi volcano java indonesia the displacement field has been monitored in the vicinity of the crater rim at mount merapi indonesia from 1993 to 1997 during this period the volcanic activity has been quasicontinuous with dome growth explosions and pyroclastic flows we measured a nine point network every year with the global positioning system static method interpretation of results is conducted with a three dimensional elastostatic boundary elements code that takes into account topography fractures and complex magma source geometry the inversion technique yields an estimate of the variation with time of the boundary conditions at the magma duct interface together with the probability associated with the best model the young s modulus of the equivalent continuum is found to be very low of the order of 1 gpa a feature which suggests that a viscoelastic behavior may be more appropriate for this rock mass given the observed seismic velocities for the domain of interest a striking compatibility is outlined between observed deformations and the rate of occurrence of multiphase seismic events once the main fractures of the structure have been taken into consideration this suggests that the summit elastic or viscoelastic deformation field is controlled by the magma flux within the duct rather than by magma pressure variations in addition a nonelastic displacement has been identified at the westernmost point of the network this was considered critical for the stability of the summit structure a concern whose validity has been verified a posteriori by the july 1998 explosion

an insar based survey of volcanic deformation in the central andes we extend an earlier interferometric synthetic aperture radar insar survey covering about 900 remote volcanos of the central andes 14 27 s between the years 1992 and 2002 our survey reveals broad 10s of km roughly axisymmetric deformation at 4 volcanic centers two stratovolcanoes are inflating uturuncu bolivia and hualca hualca peru another source of inflation on the border between chile and argentina is not obviously associated with a volcanic edifice here called lazufre and a caldera cerro blanco also called robledo in northwest argentina is subsiding we explore the range of source depths and volumes allowed by our observations using spherical ellipsoidal and crack like source geometries we further examine the effects of local topography upon the deformation field and invert for a spherical point source in both elastic half space and layered space crustal models we use a global search algorithm with gradient search methods used to further constrain best fitting models inferred source depths are model dependent with differences in the assumed source geometry generating a larger range of accepted depths than variations in elastic structure source depths relative to sea level are 8 18 km at hualca hualca 12 25 km for uturuncu 5 13 km for lazufre and 5 10 km at cerro blanco deformation at all four volcanoes seems to be time dependent and only uturuncu and cerro blanco were deforming during the entire time period of observation inflation at hualca hualca stopped in 1997 perhaps related to a large eruption of nearby sabancaya volcano in may 1997 although there is no obvious relation between the rate of deformation and the eruptions of sabancaya we do not observe any deformation associated with eruptions of lascar chile at 16 other volcanoes that had recent small eruptions or fumarolic activity or associated with a short lived thermal anomaly at chiliques volcano we posit a hydrothermal system at cerro blanco to explain the rate of subsidence there for the last decade we calculate the ratio of the volume of magma intruded to extruded is between 1 10 and that the combined rate of intrusion and extrusion is within an order of magnitude of the inferred geologic rate

transient deformation associated with explosive eruption measured at masaya volcano nicaragua using interferometric synthetic aperture radar abstract deformation caused by processes within a volcanic conduit are localised transient and therefore challenging to measure however observations of such deformation are important because they provide insight into conditions preceding explosive activity and are important for hazard assessment here we present measurements of low magnitude transient deformation covering an area of 4 km 2 at masaya volcano spanning a period of explosive eruptions 30th april 17th may 2012 radial uplift of duration 24 days and peak displacements of a few millimeters occurred in the month before the eruption but switched to subsidence 27 days before the onset of the explosive eruption on 30th of april uplift resumed during and continued for 16 days after the end of the explosive eruption period we use a finite element modelling approach to investigate a range of possible source geometries for this deformation and find that the changes in pressurisation of a conduit 450 m below the surface vent radius 160 m and length 700 m surrounded by a halo of brecciated material with a young s modulus of 15 gpa gave a good fit to the insar displacements we propose that the pre eruptive deformation sequence at masaya is likely to have been caused by the movement of magma through a constriction within the shallow conduit system although measuring displacements associated with conduit processes remains challenging new high resolution insar datasets will increasingly allow the measurement of transient and lower magnitude deformation signals improving the method s applicability for observing transitions between volcanic activity characterised by an open and a closed conduit system

the green tuff of pantelleria rheoignimbrite or rheomorphic fall detailed stratigraphic analysis of the green tuff of pantelleria shows that this formation can be divided into several members designateda throughh from base to top these members have a coherent pattern when traced from outcrop to outcrop throughout the island shedding light on their origin only memberg completely mantles the entire island the distribution of the other members is controlled by prevailing wind direction or by topography membera is entirely of fall origin membersc ande are of fall and or surge type membersb d andh have the characteristics of thin welded ash flow tuffs membersf andg are ash flow tuffs with textural characteristics of compound cooling units most of the ash flow tuffs exhibit characteristics of ignimbrites vertical fluidization pipes local concentrations of lithic lapilli imbrication of clasts and valley ponding memberg is unusual in that it is highly welded exhibits large scale rheomorphic structures contains huge lithic clasts and has near vertical foliation where it adheres to cliffs and caldera walls

subaqueous pyroclastic flows and ignimbrites an assessment an assessment of the literature on subaqueous pyroclastic flows and their deposits shows that the term pyroclastic flow is frequently used loosely to describe primary hot gas rich pyroclastic flows mass flows which resulted from the transformation of gassupported flows into water supported ones and secondary mass flows carrying redeposited pyroclastic debris based on subaerial pyroclastic flows the term pyroclastic flow should be restricted to demonstrably hot gas rich mass flows of pyroclastic debris using this definition very few examples of subaqueous pyroclastic deposits with evidence for hot emplacement and of having been wholly submerged have been described in the majority of these cases the evidence for a hot state of emplacement and for the subaqueous nature of the host depositional environment is inadequate the only unequivocal cases of hot pyroclastic flow deposits with adequate supporting evidence are the ordovician nearshore shallow marine ignimbrites of ireland and wales and miocene ignimbrites of southwest japan resulting from the passage of subaerially erupted pyroclastic flows into shallow water other possible examples are near vent dense clast deposits in the donzurobo formation of japan possible submarine intra caldera ponded ignimbrite successions in california and wales and near vent pumiceous deposits of ramsay island wales all other purported cases are either clearly the result of water supported mass flow transportation and deposition debris avalanches debris flows turbidity currents or lack adequate supporting evidence regarding the heat state or the palaeoenvironment only the shallow marine ignimbrites of ireland and wales show adequate evidence of welding but even these could have been nearly wholly exposed above sea level when welding occurred we conclude that when pyroclastic flows enter water they are generally disrupted explosively and or ingest water and transform into water supported mass flows and we suggest the various scenarios in which this occurs there is no evidence to suggest that welding in wholly subaqueous environments is common

recent volcanic history of pantelleria a new interpretation abstract the island of pantelleria is located in the pantelleria rift between sicily and africa this rift is floored by a 20 km thick continental type crust that is characterized by horsts and grabens formed by nw se tensional faults and ne sw shear faults several faults and fractures that intersect the island follow these regional trends prominent volcano tectonic features on the island include two calderas the younger being related to the eruption of the green ignimbrite and the uplifted montagna grande block pantelleria mostly consists of peralkaline silicic rocks with minor trachytes and basalts volcanism on the island is characterized by both explosive and effusive activity reconstruction of the volcanic history of the island since the eruption of the green ignimbrite is based on geological and geochronological data the eruption of the green ignimbrite 50 000 y b p was followed by collapse of the monastero caldera that has been the site of most of the subsequent acid volcanism the montagna grande volcanic complex 35 000 y b p fills the central part while the lower pantelleritic lava flows 16 000 y b p erupted along its rim very probably the young mt gelfiser and khaggiar domes are also located on the caldera rim the montagna grande block rose within the caldera at an estimated average rate between 1 0 and 1 5 cm y for about 20 000 y subsequent pumice cones 9 000 y b p endogenous domes and lava flows also erupted inside this caldera among the main acid volcanic units younger than the green ignimbrite only the mt gelkhamar endogenous dome is not linked to this caldera in the last 50 000 years basaltic activity only occurred in the northern part of the island the basaltic vents are aligned parallel with the main tensional trends of the rift at least two phases have been recognized the older is about 29 000 y b p and the younger is a few thousands of years old a change occurred in the eruptive style after the eruption of the green ignimbrite and collapse of the monastero caldera explosive activity diminished and extrusion of lava became dominant

behaviour of particle laden flows into the ocean experimental simulation and geological implications the behaviour of subaerial particle laden gravity currents e g pyroclastic flows lahars debris flows sediment bearing floods and jokulhlaups flowing into the sea has been simulated with analogue experiments flows of either saline solution simple suspensions of silicon carbide sic in water or complex suspensions of sic and plastic particles in methanol were released down a slope into a tank of water the excess momentum between subaerial and subaqueous flow is dissipated by a surface wave at relatively low density contrasts between the tank water and the saline or simple suspensions the flow mixture enters the water and forms a turbulent cloud involving extensive entrainment of water the cloud then collapses gravitationally to form an underwater gravity current which progresses along the tank floor at higher density contrasts the subaerial flow develops directly into a subaqueous flow the flow slows and thickens in response to the reduced density contrast which is driving motion and then continues in the typical gravity current manner complex suspensions become dense flows along the tank floor or buoyant flows along the water surface if the mixtures are sufficiently denser or lighter than water respectively flows of initially intermediate density are strongly influenced by the internal stratification of the subaerial flow material from the particulate depleted upper sections of the subaerial flow becomes a buoyant gravity current along the water surface whereas material from the particulate enriched lower sections forms a dense flow along the tank floor sedimentation from the dense flow results in a reduction in bulk density until the mixture attains buoyancy lifts off and becomes a secondary buoyant flow along the water surface jokulhlaups lahars and debris flows are typically much denser than seawater and thus will usually form dense flows along the seabed after sufficient sedimentation the freshwater particulate mixture can lift off to form a buoyant flow at the sea surface leading to a decoupling of the fine and coarse particles flood waters with low particulate concentrations 2 may form buoyant flows immediately upon entering the ocean subaerial pyroclastic flows develop a pronounced internal stratification during subaerial run out and thus a flow splitting behaviour is probable which agrees with evidence for sea surface and underwater flows from historic eruptions of krakatau and mont pelee a pyroclastic flow with a bulk density closer to that of sea water may form a turbulent cloud resulting in the deposition of much of the pyroclasts close to the shore dense subaqueous pyroclastic flows will eventually lift off and form secondary buoyant flows either before or after the transformation to a water supported nature

interpretation of ground surface changes prior to the 2010 large eruption of merapi volcano using alos palsar aster tir and gas emission data abstract understanding precursory signals is essential to forecast eruptions hazards and mitigate risks satellite observations have been shown to increasingly contribute to this goal we use differential inteferometric synthetic aperture radar d insar and sar backscattering intensity data from alos palsar to define a time series of ground surface displacements for the 2006 2010 inter eruptive period at merapi volcano we correlate trends in the displacement data to trends for summit temperature determined using data from the aster sensor and to gas emission data we show that processing of the satellite data must be performed carefully before meaningful interpretations can be drawn for example after careful removal of the topographic effect on phase delays we detect only subtle inter eruptive episodes of cyclic deformation in the d insar and sar backscattering data these small mostly sub centimeter displacements contrast with meter scale pre eruptive displacements along an electronic distance measurement edm line on the south flank of the volcano we suggest that this difference is a consequence of localized movement within the summit area a result that has important implications for understanding merapi s structure for monitoring network design and for eruption forecasting although small merapi s inter eruptive deformation cycles are also seen in thermal data from aster and gas emissions accordingly we interpret these cycles as the result of successive movement of individual magma batches migrating upward from deeper to shallower storage systems located along a ne dipping conduit in view of magma migration prior to eruptions these cycles may also serve as a precursory signal for large eruptions at merapi such as the one that took place in early november 2010

pyroclastic flows generated by gravitational instability of the 1996 97 lava dome of soufriere hills volcano montserrat numerous pyroclastic flows were produced during 1996 97 by collapse of the growing andesitic lava dome at soufriere hills volcano montserrat measured deposit volumes from these flows range from 0 2 to 9 106 m flows range from discrete single pulse events to sustained large scale dome collapse events flows entered the sea on the eastern and southern coasts depositing large fans of material at the coast small runout distance 1 km flows had average flow front velocities in the order of 3 10 m s while flow fronts of the larger runout distance flows up to 6 5 km advanced in the order of 15 30 m s many flows were locally highly erosive field relations show that development of the fine grained ash cloud surge component was enhanced during the larger sustained events periods of elevated pyroclastic flow productivity and sustained dome collapse events are linked to pulses of high magma extrusion rates

late quaternary paleoceanography as recorded by benthonic foraminifera in strait of sicily sediment sequences at specific times during the late quaternary a widespread low salinity surface water layer was produced over the eastern mediterranean which created stagnant conditions and associated deposition of sapropelic muds in the deep basins the strait of sicily has been positioned above the anoxic deeper water masses and is therefore devoid of sapropel deposits sediment sequences in the region contain a valuable record of upper bathyal 200 1000 m benthonic foraminiferal change during times of deep basin stagnation quantitative examiniation of benthonic foraminiferal assemblages in strait of sicily quaternary cores generally reveals changes coeval with sapropels s1 s2 s4 s5 and s6 the benthonic foraminiferal expression is seen as increases in frequency ofglobobulimina affinis globobulimina pseudospinescens chilostomella mediterranensis bolivina dilatata and otherbolivina species during intervals corresponding to the episodic abyssal stagnation events some cores also display a decrease incassidulina carinata and an increase inarticulina tubulosa similar assemblage changes have been previously documented to be closely associated with the sapropel layers in the deep basins of the eastern mediterranean the actual sapropel layers usually do not contain benthonic foraminifera however in the strait of sicily area the species exhibit less drastic changes than in the deep eastern basins because of the less severe anoxic conditions in the deep eastern basins benthonic foraminifera almost totally disappeared in sapropel layers at the same time there was a general reduction in foraminiferal numbers in the shallower strait area

stratification and particle segregation in flowing polydisperse suspensions with applications to the transport and sedimentation of pyroclastic density currents abstract pyroclastic density currents pdcs are particle laden gravity driven flows of volcanic origin they typically contain solid particles with a wide range of sizes and densities resulting in complicated segregation effects during transport and sedimentation this paper describes experimental high density aqueous suspension flows scaled approximately to turbulent pyroclastic density currents it provides information on the development of concentration and particle size gradients in such flows and their relationships to vertical and stream wise grading in the resulting deposit the currents were generated by lock exchange release of initially homogeneous suspensions of highly polydispersed particles with concentrations of 13 8 23 0 vol size distributions were chosen to encompass a wide range of rouse pn numbers from particles that were fully supported by turbulence in the currents pn 2 5 to those whose motion was essentially decoupled from turbulent eddies pn 2 5 as in many pyroclastic density currents experimental currents of two different particle populations were studied one containing particles of a single density and another with particles of two different densities in each case the current head was sampled at different locations along the flume in order to study the evolution of vertical gradients in particle size concentration and density distribution in the propagating flow these gradients were then related to grading observed in the resulting deposits differential settling resulted in rapid segregation of particles of different sizes and densities in the currents and the development of both vertical and longitudinal gradients in particle concentrations sizes and proportions longitudinal gradients developed as vertical gradients were pulled out longitudinally by the vertical velocity profile in the fluid gradient development involved principally large particles capable of moving independently of turbulent eddies in the fluid the segregation behaviour of large light particles equivalent to pumice in the natural system in the bidensity currents was strongly influenced by buoyancy forces in the dense initial suspension sedimentation of large light particles was delayed and reverse vertical and longitudinal grading of these particles was generated in the resulting deposit reverse grading in the deposit was not caused by flotation of the large light particles which were normally stratified in the current during transport deposition of large light particles was probably delayed by a thin boundary layer of sufficiently high bulk density at the base of the rapidly evolving density stratified current vertical or longitudinal reverse grading of large pumices in pyroclastic density current deposits does not necessarily imply flotation during transport

2 5 d surface deformation of m6 1 earthquake near mt iwate detected by sar interferometry the two dimensional displacement vector field on the earth s surface associated with a large earthquake near iwate volcano in japan was mapped by combining satellite radar interferometry images from two different track directions the displacement reveals not only large main ruptures but details of many small faults movement of aftershocks and volcanic earthquakes the displacements of the aftershock faults coincide with a stress field reorganized by the main earthquake that accelerated the aftershock fault movements the displacements mimic the topography suggesting that repeated movements of the same faults in the quaternary have led to the presently existing topography

sedimentology of the krakatau 1883 submarine pyroclastic deposits the majority of tephra generated during the paroxysmal 1883 eruption of krakatau volcano indonesia was deposited in the sea within a 15 km radius of the caldera two syneruptive pyroclastic facies have been recovered in scuba cores which sampled the 1883 subaqueous pyroclastic deposit the most commonly recovered facies is a massive textured poorly sorted mixture of pumice and lithic lapilli to block sized fragments set in a silty to sandy ash matrix this facies is indistinguishable from the 1883 subaerial pyroclastic flow deposits preserved on the krakatau islands on the basis of grain size and component abundances a less common facies consists of well sorted planarlaminated to low angle cross bedded vitric enriched silty ash entrance of subaerial pyroclastic flows into the sea resulted in subaqueous deposition of the massive facies primarily by deceleration and sinking of highly concentrated deflated components of pyroclastic flows as they traveled over water the basal component of the deposit suggests no mixing with seawater as inferred from retention of the fine ash fraction high temperature of emplacement and lack of traction structures and no significant hydraulic sorting of components the laminated facies was most likely deposited from low concentration pyroclastic density currents generated by shear along the boundary between the submarine pyroclastic flows and seawater the krakatau deposits are the first well documented example of true submarine pyroclastic flow deposition from a modern eruption and thus constitute an important analog for the interpretation of ancient sequences where subaqueous deposition has been inferred based on the facies characteristics of encapsulating sedimentary sequences

insight into ground deformations at lascar volcano chile from sar interferometry photogrammetry and gps data implications on volcano dynamics and future space monitoring abstract we present a detailed study of lascar volcano chile based on the combination of satellite aerial and ground based data in order i to better characterize the deformation style of andean explosive volcanoes and ii to provide new insights on the potential of space techniques to monitor active volcanic deformations on such edifices lascar is one of the most active volcanoes in central andes characterized by a recent cyclic activity additionally it is located in favourable conditions for radar imaging lascar thus offers very good conditions for studying large to small scale ground deformations associated with volcano dynamics the analysis of insar synthetic aperture radar interferometry time series data from the european and japanese satellites ers jers acquired between 1993 and 2000 encompassing three eruptive events confirmed the absence of broad far field deformation signal thus during the recent activity of lascar we discard significant magmatic input at depth the following approaches were used to improve the insar signal noise ratio in order to detect possible local deformation we carried out a quantitative evaluation of the potential tropospheric contribution in insar interferograms for the salar de atacama lascar area using radar asar envisat and spectrometer modis data we also used an accurate aerial photogrammetric and gps constrained dem in our insar data reprocessing we find a co eruptive ground deformation confined into the summit crater for the 1995 eruption this deformation has spatial dimension of 500 by 400 m and relates to a subsidence of crater floor up to 17 mm we interpret it as pressure or volume decrease at subsurface levels below the active crater our study made it possible to image a new near field volcanic deformation confined within the summit crater of the lascar volcano it also demonstrates that the combination of precise photogrammetry dem and insar data can significantly improve our ability to remotely sense subtle surface deformation on these explosive volcanoes this methodology might contribute to better understand volcano dynamics and to complement their monitoring in remote areas

tephra fall deposits from the 1992 eruption of crater peak alaska implications of clast textures for eruptive processes the 1992 eruption of crater peak mount spurr alaska involved three subplinian tephra producing events of similar volume and duration the tephra consists of two dense juvenile clast types that are identified by color one tan and one gray of similar chemistry mineral assemblage and glass composition in two of the eruptive events the clast types are strongly stratified with tan clasts dominating the basal two thirds of the deposits and gray clasts the upper one third tan clasts have average densities between 1 5 and 1 7 g cc and vesicularities phenocryst free of approximately 42 gray clasts have average densities between 2 1 and 2 3 g cc and vesicularities of approximately 20 both contain abundant microlites average maximum plagioclase microlite lengths 13 15 m in gray clasts in the upper layer are similar regardless of eruptive event and therefore the repose time between them and are larger than average maximum plagioclase microlite lengths 9 11 m in the tan clasts in the lower layer this suggests that microlite growth is a response to eruptive processes and not to magma reservoir heterogeneity or dynamics furthermore we suggest that the low vesicularities of the clasts are due to syneruptive magmatic degassing resulting in microlitic growth prior to fragmentation and not to quenching of clasts by external groundwater

on the emplacement of ignimbrite in shallow marine environments abstract the emplacement of primary pyroclastic flow deposits on the sea floor can occur 1 by nonturbulent dense flows that conserve their heat under water or 2 because the flow either turbulent or nonturbulent temporarily pushes back the shoreline the feasibility of the second mechanism has been investigated theoretically and experimentally using a simple analogue system the experiments involved sustained turbulent saline currents of different densities flowing into a sectorial tank of ambient fluid that was either lighter or denser than the current the currents in all cases displaced the entire layer of ambient fluid up to a distance r irrespective of whether they were denser or lighter r is analogous to the shoreline displacement distance up to which hot ignimbrite can be emplaced by a pyroclastic flow entering the sea by varying flow rate density contrast and depth of the ambient fluid layer a simple equation for r is found that is in good agreement with the experimental data the effect of seawater boiling on shoreline displacement was also investigated by experiments using currents of carbonate solution that produced gas when flowing into a layer of ambient acid the distance r was not reduced in these experiments the equations show that pyroclastic flows of about 10 km 3 or more are capable of pushing back the sea at least a couple of kilometres and possibly more in areas of extensive shallow water enabling hot ignimbrite to be laid down on the seabed at depths corresponding to a few tens of metres shoreline displacement is thus a feasible mechanism for the emplacement of welded ignimbrite in shallow marine settings emplacement of subaerially erupted ignimbrite below storm wave base is not ruled out by the calculations but requires a combination of high discharge rate sustained eruption low density contrast between flow and water steep bathymetric gradient and small island volcano application of the model to the 1883 krakatau eruption suggests that seawater displacement may explain the occurrence of primary ignimbrite on the seabed 10 km northwest of the volcano

paroxysmal dome explosion during the merapi 2010 eruption processes and facies relationships of associated high energy pyroclastic density currents an 11 minute sequence of laterally directed explosions and retrogressive collapses on 5 november 2010 at merapi indonesia destroyed a rapidly growing dome and generated high energy pyroclastic density currents pdcs spreading over 22 km2 with a runout of 8 4 km while contemporaneous co genetic valley confined pdcs reached 15 5 km this event formed stage 4 of the multi stage 2010 eruption the most intense eruptive episode at merapi since 1872 the deposits and the widespread devastating impact of associated high energy pdcs on trees and buildings show striking similarities with those from historical volcanic blasts montagne pelee martinique bezymianny russia mount st helens usa soufriere hills montserrat we provide data from stratigraphic and sedimentologic analyses of 62 sections of the first unequivocal blast like deposits in merapi s recent history we used high resolution satellite imagery to map eruptive units and flow direction from the pattern of extensive tree blowdown the stratigraphy of stage 4 consists of three depositional units u0 u1 u2 that we correlate to the second third and fourth explosions of the seismic record both u1 and u2 show a bi partite layer stratigraphy consisting each of a lower l1 layer and an upper l2 layer the lower l1 layer is typically very coarse grained fines poor poorly sorted and massive and was deposited by the erosive waxing flow head the overlying l2 layer is much finer grained fines rich moderately to well sorted with laminar to wavy stratification l2 was deposited from the waning upper part and wake of the pdc field observations indicate that pdc height reached 330 m with an internal velocity of 100 m s 1 within 3 km from the source the summit s geometry and the terrain morphology formed by a major transversal ridge and a funneling deep canyon strongly focused pdc mass towards a major constriction thereby limiting the loss of kinetic energy this favored elevated pdc velocities and high particle concentration promoted overspilling of pdcs across high ridges into other river valleys and generated significant dynamic pressures to distances of 6 km that caused total destruction of buildings and the forest the merapi 2010 eruption highlights that explosive and gravitational disintegration of a rapidly growing dome can generate devastating high energy high velocity pdcs this constitutes a credible high impact scenario for future multi stage eruptions at merapi and at other volcanoes that pose particular monitoring crisis response and risk reduction challenges

volcano wide fringes in ers synthetic aperture radar interferograms of etna 1992 1998 deformation or tropospheric effect mount etna 3300 m is the volcano that has been first and most studied by differential synthetic aperture radar previous papers gave evidence for a large scale deformation of the entire edifice consistent with unrest episodes but with a poor fit with classical elastic models also atmospheric effects on mountainous areas are known to be very significant accordingly interferograms may reflect both deformation and tropospheric effects we investigate here the possibility of evaluating and correcting tropospheric effects directly from the interferograms from 38 ers synthetic aperture radar ascending scenes taken from 1992 to 1999 we have computed 238 interferograms the amount of data allows us to analyze how the coherence is maintained over long periods of time and thus how it reveals the location of permanent scatters from a simple analysis of phase elevation relation we give evidence for the clear difference in pattern between stratified tropospheric effects and large scale deformation produced by a source in a three dimensional elastic body with topography using combination of inversion processes we analyze both deformation source and tropospheric effects for the complete set of 238 interferograms finally time evolution of the parameters and modeling probability estimation are retrieved for each sar image estimated relative change in tropospheric delay varies in time from 2 7 to 3 0 1 2 fringes they are consistent with other tropospheric estimations at etna based on ground met and global positioning system observations on the same period of time magmatic volume variations remain below error bars and thus cannot be estimated properly finally some of the interferograms may be entirely explained by the difference in tropospheric conditions between the two acquisition periods without the need to invoking a deformation of the volcano

entrance of hot pyroclastic flows into the sea experimental observations the entrance of hot pyroclastic flows into water has been observed in a series of experiments in which shooting granular flows of hot ignimbrite ash 403 c of bulk density near that of water run down a smooth chute and enter a water filled tank at an angle of 26 flows of relatively cool ash 250 c mixing across the water surface over some distance from shore generates steam explosions forming fountains of wet and dry ash and convectively rising fine ash plumes steam explosions increase in strength and lateral extent towards higher ash temperatures and mass fluxes the explosions generate water waves that remain driven by massive fountain fallout across some distance from shore the ash fountains feed pyroclastic surges which advance down tank over water at high speeds underwater plumes of sediment falling from the ash fountains and surges drop coarse load onto the floor whereas the finer load forms a turbidity current high temperature and poor size sorting of pyroclastic flows are key parameters that determine the processes of interaction with water and the associated hazards poor sorting allows for the formation of ash cloud surges moving over water even from cool flows high temperatures cause littoral explosions and facilitate extensive mass transport over water all flows generate tsunami waves by different mechanisms