origin of magnetic anomalies in the large ebersbrunn diatreme w saxony germany the ebersbrunn diatreme is a deeply eroded 1 km diatreme structure in western saxony germany at current erosion levels this ultramafic to carbonatitic diatreme is about 2 1 5 km in map view which makes it a large one based on shallow drill cores the diatreme contains coarse unbedded volcaniclastic rocks with up to 80 country rock fragments the diatreme is characterised by positive and negative magnetic anomalies which are controlled mostly by the changing proportions of magnetic minerals in the rocks the magnetic minerals are themselves contained in the juvenile fraction rock magnetic studies on three drill cores one from the magnetic low and two from magnetic highs including bulk susceptibility and its anisotropy temperature dependent susceptibility various remanence measurements natural remanent magnetisation anhysteretic remanence and isothermal remanent magnetisation and alternating field demagnetisation have been performed additionally scanning electron microscope imaging and energy dispersive x ray spectroscopy were performed to better characterise the magnetic minerals magnetisation is caused by titanomagnetite with slightly varying ti contents within all cores samples from the positive magnetic anomalies have a relatively high degree of anisotropy but no preferred orientation of one of the principal axes can be seen the magnetic highs are caused by non bedded volcaniclastic rocks comparatively rich in juvenile particles the negative magnetic anomaly is associated with a compaction like magnetic fabric but without macroscopically visible bedding hence the magnetic low is caused by rocks with a lower content of juvenile material to the authors knowledge this is the first time rock magnetic methods have been applied to diatreme rocks

response of southern ocean ventilation to changes in midlatitude westerly winds abstractchanges in ventilation of the southern hemisphere oceans in response to changes in midlatitude westerly winds are examined by analyzing the ideal age tracer from global eddy permitting ocea

electrical resistivity tomography revealing the internal structure of monogenetic volcanoes 1 eruptive activity of individual monogenetic volcanoes usually lasts a few days or weeks however their short lifetime does not always mean that their dynamics and structure are simple monogenetic cones construction is rarely witnessed from the beginning to the end and conditions for observing their internal structure are hardly reached we provide high resolution electrical resistivity sections 10 m electrode spacing of three monogenetic cones from northeastern spain comparing our results to geological observations to interpret their underground continuation the 100 m maximum depth of exploration provides information on almost the entire edifices highlighting the relationships between strombolian and hydromagmatic deposits in two multiphase edifices a main observation is a column of distinct resistivity centered on the puig d adri volcano which we interpret as the eruptive conduit this method can provide valuable information on the past volcanic dynamics of monogenetic volcanic fields which has real implications for the forecast of future activity

a multidisciplinary effort to assign realistic source parameters to models of volcanic ash cloud transport and dispersion during eruptions during volcanic eruptions volcanic ash transport and dispersion models vatds are used to forecast the location and movement of ash clouds over hours to days in order to define hazards to aircraft and to communities downwind those models use input parameters called eruption source parameters such as plume height h mass eruption rate duration d and the mass fraction m63 of erupted debris finer than about 4 or 63 m which can remain in the cloud for many hours or days observational constraints on the value of such parameters are frequently unavailable in the first minutes or hours after an eruption is detected moreover observed plume height may change during an eruption requiring rapid assignment of new parameters this paper reports on a group effort to improve the accuracy of source parameters used by vatds in the early hours of an eruption we do so by first compiling a list of eruptions for which these parameters are well constrained and then using these data to review and update previously studied parameter relationships we find that the existing scatter in plots of h versus yields an uncertainty within the 50 confidence interval of plus or minus a factor of four in eruption rate for a given plume height this scatter is not clearly attributable to biases in measurement techniques or to well recognized processes such as elutriation from pyroclastic flows sparse data on total grain size distribution suggest that the mass fraction of fine debris m63 could vary by nearly two orders of magnitude between small basaltic eruptions 0 01 and large silicic ones 0 5 we classify eleven eruption types four types each for different sizes of silicic and mafic eruptions submarine eruptions brief or vulcanian eruptions and eruptions that generate co ignimbrite or co pyroclastic flow plumes for each eruption type we assign source parameters we then assign a characteristic eruption type to each of the world s 1500 holocene volcanoes these eruption types and associated parameters can be used for ash cloud modeling in the event of an eruption when no observational constraints on these parameters are available

discovery of the first quaternary maar in the bohemian massif central europe based on combined geophysical and geological surveys abstract based on results of previous investigations of tephra tuff volcaniclastic deposits and a geophysical survey in the surroundings of the elezna h rka quaternary volcano west bohemia we performed detailed geophysical surveys using gravimetry magnetometry and electrical conductivity techniques striking anomalies were revealed in a morphological depression near m tina west bohemia as a strong evidence of the assumed maar diatreme structure the sharp isometric gravity low of 2 30 mgal as well as the corresponding positive magnetic anomaly of 200 nt with a negative rim on its northern side indicate a steeply dipping geological body of low density and containing magnetic rocks minerals magnetic survey also showed pronounced local anomalies outside the depression that can reflect relicts of the tephra rim of the maar this geophysical evidence was then proven by an exploratory drilling near the centre of the gravity anomaly macroscopic on site evaluation of the core and more detailed sedimentological petrochemical palynological and microbiological laboratory analyses further confirmed the existence of a maar structure filled by 84 m of lake sediments reflecting a succession of several warm and cold climatic periods results of palynological analyses confirm the presence of a continuous palaeoclimate archive with at least three successive warmer periods of most probably interstadial character from the upper quaternary saalian complex therefore the recovered sediment sequence holds strong potential for in depth paleoclimate reconstruction and deep biosphere studies at the bottom of the m tina 1 my 1 borehole 84 85 5 m country rock debris was found containing also volcanic bombs and lapilli the discovered volcanic structure is considered to be the first known quaternary maar diatreme volcano on the territory of the bohemian massif because of hidden active magmatic processes in combination with earthquake swarm seismicity ca 20 30 km north of the m tina maar reconstruction of the palaeovolcanological evolution is important for evaluation of hazard potential of the ne and e part of the cheb basin

numerical modelling of the destructive meteotsunami of 15 june 2006 on the coast of the balearic islands a destructive tsunami like event locally known as rissaga waves occurring on 15 june 2006 in ciutadella harbour menorca balearic islands is reproduced by a numerical model forced by a travelling atmospheric disturbance the disturbance is reconstructed from microbarograph measurements being the only available instrumental data at the time of the event the model is verified based on two weaker 1997 events which were recorded by a number of bottom pressure recorders operating at that time on the menorca shelf in ciutadella inlet and adjacent platja gran inlet both 1997 events are numerically simulated and good agreement is achieved with observations in time frequency including eigenfrequencies of the affected inlets and wave heights subsequently the same model is applied to simulate the 2006 event the vigorous currents with speeds up to 400 cm s are found to occur specifically at those areas of the harbour where the most severe damage and sinking of boats had been reported maximum simulated sea level heights of 2 5 m were about one half of those reported by eyewitnesses this difference is apparently caused by quality and spatial resolution of bathymetry data however in general the model is capable of reproducing the event fairly well and can probably be used for future assessment and mitigation activities on the coasts of the balearic islands

subsurface structure of a large basaltic maar volcano examined using geologically constrained potential field modelling lake purrumbete maar newer volcanics province southeastern australia abstract lake purrumbete maar lpm is situated in the late cenozoic intraplate basaltic newer volcanics province southeastern australia it is one of the largest maar volcanoes in the world with a near circular crater that is up to 2800 m in diameter containing a 45 m deep lake gellibrand marl accidental lithics which occurs to a maximum depth of 250 m below lpm represent the deepest excavated host rock unit present in the volcanic succession irregular clast shapes and peperitic textures observed in marl lithics suggest the host rock was poorly consolidated during the eruption high resolution lake and land based gravity and magnetic data were collected to conduct forward and inverse modelling of the subsurface architecture of the maar this is done to test the assumption based on lithics that the diatreme is limited to 250 m depth and identify the reasons behind lpm s large size the collection of gravity data presented a unique challenge due to the nature of measuring small changes in gravitational forces

three dimensional resistivity tomography in extreme coastal terrain amidst dense cultural signals application to cliff stability assessment at the historic d day site summary pointe du hoc overlooking the english channel in normandy france was host to one of the most important military engagements of world war ii but is vulnerable to cliff collapses that threaten important german fortifications including the forward observation post op and rudder s command post the objective of this study is to apply advanced 3 d resistivity tomography towards a detailed site stability assessment with special attention to the two at risk buildings 3 d resistivity tomography data sets at pointe du hoc in the presence of extreme topography and dense cultural clutter have been successfully acquired inverted and interpreted a cliff stability hazard assessment scheme has been designed in which regions of high resistivity are interpreted as zones of open dry fractures with a moderate mass movement potential regions of low resistivity are zones of wet clay filled fractures with a high mass movement potential the op tomography results indicate that the highest mass movement hazard appears to be associated with the marine caverns at the base of the cliff that are positioned at the point of strongest wave attack these caverns likely occupy the future site of development of a sea arch that will threaten the op building the mass movement potential at the rudder s command post area is low to moderate the greatest risk there is associated with soil wedge failures at the top of the cliffs

statistical characteristics of seiches in longkou harbour abstract amplitudes of seiches are generally very small in chinese coastal waters with the exception of longkou harbour where some extraordinary seiches have occurred tide gauge records over a period of twenty three years including 137 seiches with a maximum fluctuation greater than 40 cm were examined preliminary results given here include variabilities of occurrences distributions of mean periods maximum fluctuations and occurrence durations along with a list of large seiches in addition an illustration of the seiche on 1 september 1980 with a maximum fluctuation of 293 cm is given

zonal jet structure and the leading mode of variability an observational analysis of the northern hemisphere circulation during winter reveals that the leading mode of variability depends on longitude in particular the first eof of the zonal mean circulation differs over the atlantic and pacific sectors these results provide motivation for a series of model runs where a simple gcm is used to investigate the effects of the zonal jet structure on the leading mode of variability in the northern hemisphere model results indicate that the leading mode of variability depends on the distance between the eddy driven and subtropical jets when the jets are well separated the leading mode of variability describes latitudinal shifting of the eddy driven jet however when the two jets are nearly collocated pulsing of the combined jet dominates the variability this change coincides with a weakening of the positive feedback between the eddies and zonal flow anomalies these results provide a possible explanation for the reduced amplitude of the northern annular mode in the pacific sector relative to that in the atlantic sector during northern hemisphere winter

a numerical comparison of 2d resistivity imaging with 10 electrode arrays numerical simulations are used to compare the resolution and efficiency of 2d resistivity imaging surveys for 10 electrode arrays the arrays analysed include polepole pp pole dipole pd half wenner hw wenner wn schlumberger sc dipole dipole dd wenner wb array gm multiple or moving gradient array gd and midpoint potential referred measurement mpr arrays five synthetic geological models simulating a buried channel a narrow conductive dike a narrow resistive dike dipping blocks and covered waste ponds were used to examine the surveying efficiency anomaly effects signal to noise ratios and the imaging capabilities of these arrays the responses to variations in the data density and noise sensitivities of these electrode configurations were also investigated using robust l1 norm inversion and smoothness constrained least squares l2 norm inversion for the five synthetic models the results show the following i gm and wn are less contaminated by noise than the other electrode arrays ii the relative anomaly effects for the different arrays vary with the geological models however the relatively high anomaly effects of pp gm and wb surveys do not always give a high resolution image pd dd and gd can yield better resolution images than gm pp wn and wb although they are more susceptible to noise contamination sc is also a strong candidate but is expected to give more edge effects iii the imaging quality of these arrays is relatively robust with respect to reductions in the data density of a multi electrode layout within the tested ranges iv the robust inversion generally gives better imaging results than the l2 norm inversion especially with noisy data except for the dipping block structure presented here v gd and mpr are well suited to multichannel surveying and gd may produce images that are comparable to those obtained with dd and pd accordingly the gd pd dd and sc arrays are strongly recommended for 2d resistivity imaging where the final choice will be determined by the expected geology the purpose of the survey and logistical considerations

revised conceptual model for maar diatremes subsurface processes energetics and eruptive products diatremes are debris filled structures beneath maars that result from many magma water phreatomagmatic explosions during a monogenetic volcano s lifetime a long standing model requires deepening explosions due to water table drawdown that eject progressively deeper seated country rock from the explosion sites while the overlying diatreme and its surface crater widen due to subsidence a revised model is proposed wherein explosions can take place at any level within a diatreme at a given time most effectively venting material from near surface explosions deep seated country rock lithics in tephra deposits record stepwise vertical mixing of material by upward directed debris jets and downward subsidence rather than direct ejection from deep explosions juvenile and lithic clasts erupted during a given explosion may have had a complex history within the diatreme and need not directly reflect fragmentation or brecciation during the explosion that ejects them

monthly monitoring of gas and isotope compositions in the free gas phase at degassing locations close to the nový kostel focal zone in the western eger rift czech republic abstract we report new data on gas and isotope compositions of mantle derived exhalations from five locations in the vogtland germany nw bohemia czech republic area close to the nov kostel focal zone recorded by monthly sampling of gases over a three year period this region is the locus typicus for the term earthquake swarm since 1985 86 the largest numbers of earthquake swarms in the vogtland nw bohemia have occurred in the nov kostel focal zone mantle derived degassing has been studied at four locations within the cheb basin degassing centre and at the wettinquelle spring to the north on the edge of the cheb basin the bublak and u mostku locations are on the pocatky plesna fault zone ppz while the kopanina and dolni castkov locations are on the marianske lazn fault mlf the mantle derived helium content at locations along the ppz covers the range of the sub continental lithospheric mantle sclm along the mlf the 3 he 4 he ratios are with up to 5 4 ra a little bit lower as at the ppz locations the co 2 3 he ratios point to a predominantly magmatic source depending on the magnitude of gas flux the monthly sampling results indicated various major influences on the fluid signatures at the monitored locations due to seasonal cycles based on the different strong influence of co 2 water interaction micro seismicity occurred repeatedly during the monitoring period and seismically triggered geochemical anomalies were repeatedly observed at the locations close to the focal zone the 3 he 4 he ratios drop from 5 9 ra mean up to 5 6 ra at bublak and from 5 6 ra up to 5 3 ra at u mostku a decrease in 3 he 4 he ratios was observed prior to seismic events due to stress accumulation before rupturing and also after the events due to the release of crustal derived components within the area of the focal zone due to the higher helium baseline content of the kopanina gas the 3 he 4 he ratios decreased there only from 4 6 to 4 5 ra at the wettinquelle the most distant from the focal zone the 3 he 4 he ratios ranged between 2 3 and 2 5 ra altogether superimposed to the seismically induced anomalies a clear three month lasting increase of mantle derived helium was observed at the locations on the ppz the 3 he 4 he ratios increased to 6 3 ra at bublak and to 6 0 ra at u mostku an increase in the 3 he 4 he ratios was also noted at kopanina to 4 7 ra and dolni castkov to 5 4 ra interpreted as indicating an ascent of less degassed magma dyke intrusions from the deeper lithospheric mantle reservoir superimposed geochemical effects initiated by the temporal and spatial evolution of a hidden magmatic driven geodynamic process have therefore been observed in a continental rift system for the first time

comparing trends in the southern annular mode and surface westerly jet abstractthis paper examines trends in the southern annular mode sam and the strength position and width of the southern hemisphere surface westerly wind jet in observations reanalyses and models from phase 5 of the coupled model intercomparison project cmip5 first the period over 1951 2011 is considered and it is shown that there are differences in the sam and jet trends between the cmip5 models the hadley centre gridded slp hadslp2r dataset and the twentieth century reanalysis the relationships between these trends demonstrate that the sam index cannot be used to directly infer changes in any one kinematic property of the jet the spatial structure of the observed trends in slp and zonal winds is shown to be largest but also most uncertain in the southeastern pacific to constrain this uncertainty six reanalyses are included and compared with station based observations of slp the cmip5 mean slp trends generally agree well with the direct observations despite some climatological biases

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

possible atmospheric origin of the 7 may 2007 western black sea shelf tsunami event 1 the paper examines the possibility that tsunami event recorded in the western black sea on 7 may 2007 was triggered by a traveling atmospheric disturbance as meteotsunamis are favored by specific synoptic conditions we inspected available ground and sounding observations european centre for medium range weather forecasts reanalysis fields and satellite based products and compared them to the documented mediterranean meteotsunamis we found an atmospheric disturbance traveling toward 30 nne with amplitude of 2 3 hpa and propagation speed of about 16 m s passing through few tens of kilometers wide pathway over the region affected by the tsunami this disturbance occurred in the lower troposphere but it was capped by instable convective cell that preserved gravity disturbance s coherence over a region at least 150 km long an ocean modeling study showed that such a disturbance is capable of generating large tsunami waves and strong currents over the shallow regions following the observations over the region where maximum sea level oscillations have been documented therefore this event has a potential to be classified as a meteotsunami the first of such kind in the black sea

electrical tomography of la soufriere of guadeloupe volcano field experiments 1d inversion and qualitative interpretation the soufriere of guadeloupe lava dome consists of several 3d domains of relatively unaltered massive andesite separated by major radial fractures that reach at least up to about half of the dome s height more than 20 000 geo electrical measurements made on the top and the flanks of the lava dome are used to construct the first geophysical image of the internal structure of this active volcano the main features of the apparent conductivity structure of the lava dome are high conductivity regions associated with the strongly altered material of present and fossil hydrothermal zones local 1d inversions of data subsets belonging to regions where the geological structure is supposed laterally invariant confirm the structures observed in the pseudo sections the relatively stable units lie above a basal inclined layer of highly conductive geological materials interpreted to be more altered and thus characterised by reduced internal friction and probably increased pore pressure past and current hydrothermal fluid circulation through these fractures has promoted rock alteration and particularly along the base of the dome that likely contributes to the instability of parts of the edifice

heat distribution in the southeast pacific is only weakly sensitive to high latitude heat flux and wind stress the southern ocean features regionally varying ventilation pathways that transport heat and carbon from the surface ocean to the interior thermocline on timescales of decades to centuries but the factors that control the distribution of heat along these pathways are not well understood in this study we use a global ocean state estimate eccov4 to 1 define the recently ventilated interior pacific rvp using numerical passive tracer experiments over a 10 year period and 2 use an adjoint approach to calculate the sensitivities of the rvp heat content rvph to changes in net heat flux and wind stress we find that rvph is most sensitive to local heat flux and wind stress anomalies north of the sea surface height contours that delineate the antarctic circumpolar current with especially high sensitivities over the south pacific gyre surprisingly rvph is not especially sensitive to changes at higher latitudes we perform a set of step response experiments over the south pacific gyre the subduction region and the high latitude so in consistency with the adjoint sensitivity fields rvph is most sensitive to wind stress curl over the subtropical gyre which alter isopycnal heave and it is only weakly sensitive to changes at higher latitudes our results suggest that despite the localized nature of mode water subduction hotspots changes in basin scale pressure gradients are an important controlling factor on rvph because basin scale wind stress is expected to change in the coming decades to centuries our results may have implications for climate via the atmosphere ocean partitioning of heat

role of tropical variability in driving decadal shifts in the southern hemisphere summertime eddy driven jet abstractthe southern hemisphere summertime eddy driven jet and storm tracks have shifted poleward over the recent few decades in previous studies explanations have mainly stressed the influence o

interpreting subsurface volcanic structures using geologically constrained 3 d gravity inversions examples of maar diatremes newer volcanics province southeastern australia we present results and a method to geophysically image the subsurface structures of maar volcanoes to better understand eruption mechanisms and risks associated with maar forming eruptions high resolution ground gravity and magnetic data were acquired across several maar volcanoes within the newer volcanics province of southeastern australia including the ecklin maar red rock volcanic complex and mount leura volcanic complex the depth and geometry of subsurface volcanic structures were determined by interpretation of gridded geophysical data and constrained 2 5 d forward and 3 d inverse modeling techniques bouguer gravity lows identified across the volcanic craters reflect lower density lake sediments and pyroclastic debris infilling the underlying maar diatremes these anomalies were reproduced during modeling by shallow coalesced diatremes short wavelength positive gravity and magnetic anomalies identified within the center of the craters suggest complex internal structures modeling identified feeder vents consisting of higher proportions of volcanic debris intrusive dikes and ponded magma because potential field models are nonunique sensitivity analyses were undertaken to understand where uncertainty lies in the interpretations and how the models may vary between the bounds of the constraints rather than producing a single ideal model multiple models consistent with available geologic information are created using different inversion techniques the modeling technique we present focuses on maar volcanoes but there are wider implications for imaging the subsurface of other volcanic systems such as kimberlite pipes scoria cones tuff rings and calderas

the mad sea phenomenon in the strait of sicily sea level observations at cape bon tunisia and mazara del vallo sicily show that large coherent oscillations exist across the strait of sicily with significant energy bands centered at periods of 35 3 41 6 50 6 75 8 and 134 5 min whose possible structure is confirmed by a numerical approximation to the gravitational barotropic normal modes with realistic topography it is observed that these oscillations are related to the passage of synoptic weather systems over the region an investigation on the configuration phase velocity and direction of approach of atmospheric disturbances over the region suggests that the oscillations in the strait of sicily could be forced by instabilities that develop in large scale low pressure fronts that propagate as pressure gravity waves with an approximate phase speed between 24 and 30 m s21

are meteotsunamis an underrated hazard meteotsunamis are generated by meteorological events particularly moving pressure disturbances due to squalls thunderstorms frontal passages and atmospheric gravity waves relatively small initial sea level perturbations of the order of a few centimetres can increase significantly through multi resonant phenomena to create destructive events through the superposition of different factors the global occurrence of meteotsunamis and the different resonance phenomena leading to amplification of meteotsunamis are reviewed results from idealized numerical modelling and field measurements from southwest australia are presented to highlight the relative importance of the different processes it is shown that the main influence that leads to amplification of the initial disturbance is due to wave shoaling and topographic resonance although meteotsunamis are not catastrophic to the extent of major seismically induced basin scale events the temporal and spatial occurrence of meteotsunamis are higher than those of seismic tsunamis as the atmospheric disturbances responsible for the generation of meteotsunamis are more common high energy events occur only for very specific combinations of resonant effects the rareness of such combinations is perhaps the main reason why destructive meteotsunamis are exceptional and observed only at a limited number of sites globally

kuril islands tsunami of november 2006 1 impact at crescent city by distant scattering 1 a numerical model for the global tsunami computation constructed by kowalik et al 2005 2007a is applied to the tsunami of november 15 2006 in the northern pacific with spatial resolution of one minute numerical results are compared to sea level data collected by pacific dart buoys the tide gauge at crescent city cc recorded an initial tsunami wave of about 20 cm amplitude and a second larger energy packet arriving 2 hours later the first energy input into the cc harbor was the primary direct wave traveling over the deep waters of the north pacific interactions with submarine ridges and numerous seamounts located in the tsunami path were a larger source of tsunami energy than the direct wave travel time for these amplified energy fluxes is longer than for the direct wave prime sources for the larger fluxes at cc are interactions with koko guyot and hess rise tsunami waves travel next over the mendocino escarpment where the tsunami energy flux is concentrated owing to refraction and directed toward cc local tsunami amplification over the shelf break and shelf are important as well in many locations along the north pacific coast the first arriving signal or forerunner has lower amplitude than the main signal which often is delayed understanding this temporal distribution is important for an application to tsunami warning and prediction as a tsunami hazard mitigation tool we propose that along with the sea level records which are often quite noisy an energy flux for prediction of the delayed tsunami signals be used

large amplitude pressure oscillations in the western mediterranean pressure oscillations with unusually large amplitude of some 3 mb and periods of about 50 min have been registered in the balearic islands western mediterranean sea during summer 1989 these large pressure oscillations are maintained over several hours and have been recorded on several occasions the synoptic pattern and vertical structure of the atmosphere simultaneous with these oscillations is described the large amplitude waves described here do not appear to be directly related to convective activity some of the characteristics of these waves are described however their source mechanism remains unclear

integrated geophysical and geological methods to investigate the inner and outer structures of the quaternary mýtina maar w bohemia czech republic the m tina maar is the first known quaternary maar in the bohemian massif based on the results of mrlina et al j volcanol geother res 182 97 112 2009 a multiparametric geophysical electrical resistivity tomography gravimetry magnetometry seismics and geological petrochemical research study had been carried out the interpretation of the data has provided new information about the inner structure of the volcanic complex 1 specification of the depth of post volcanic sedimentary fill up to 100 m and 2 magnetic and resistivity signs of one or two hidden volcanic structures interpreted as intrusions or remains of a scoria cone the findings at the outer structure of the maar incorporate the 1 evidence of circular fracture zones outside the maar 2 detection and distribution of volcanic ejecta and tephra fall deposits at the surface and 3 indications from electrical resistivity tomography and gravity data in the area between the m tina maar and elezna h rka scoria cone interpreted as a palaeovalley filled by volcaniclastic rocks and aligned along the strike line nw se of the tachov fault zone these findings are valuable contributions to extend the knowledge about structure of maar volcanoes in general because of ongoing active magmatic processes in the north east part of the cheb basin ca 15 30 km north of the investigation area the m tina maar diatreme volcano and surroundings is a suitable key area for research directed to reconstruction of the palaeovolcanic evolution and assessment of possible future hazard potential in the bohemian massif

examination of generation mechanisms for an english channel meteotsunami combining observations and modeling abstracton the morning of 23 june 2016 a 0 70 m meteotsunami was observed in the english channel between the united kingdom and france this wave was measured by several tide gauges and coincided

coupling between two inlets observation and modeling 1 the resonance coupling between two adjacent inlets is investigated field evidence of this natural phenomenon is found for two elongated inlets in the region of ciutadella menorca island in the western mediterranean ciutadella and platja gran to illustrate the fundamental features of the problem analytical solutions for two rectangular inlets with constant depth are constructed and analyzed the theoretical results mimic well the field data and demonstrate the resonance coupling characteristics of the inlet responses the phenomenon is also examined with a numeric model so that the effects of real bathymetry can be considered numerical computations show the specific resonant features of local topography and the agreement between field data and numerical results is very good

coupled ocean atmosphere ice response to variations in the southern annular mode abstract the coupled ocean atmosphere ice response to variations in the southern annular mode sam is examined in the national center for atmospheric research ncar community coupled climate model version 2 the model shows considerable skill in capturing the predominantly zonally symmetric sam while regional deviations between model and observation sam winds go a long way in explaining the generally small differences between simulated and observed sam responses in the ocean and sea ice systems vacillations in the position and strength of the circumpolar winds and the ensuing variations in advection of heat and moisture result in a dynamic and thermodynamic forcing of the ocean and sea ice both meridional and zonal components of ocean circulation are modified through ekman transport which in turn leads to anomalous surface convergences and divergences that strongly affect the meridional overturning circulation and potentially the pathways of intermediate water ventilation a heat budget analysis de

active magmatic underplating in western eger rift central europe the eger rift is an active element of the european cenozoic rift system associated with intense cenozoic intraplate alkaline volcanism and system of sedimentary basins the intracontinental cheb basin at its western part displays geodynamic activity with fluid emanations persistent seismicity cenozoic volcanism and neotectonic crustal movements at the intersections of major intraplate faults in this paper we study detailed geometry of the crust mantle boundary and its possible origin in the western eger rift we review existing seismic and seismological studies provide new interpretation of the reflection profile 9hr and supplement it by new results from local seismicity we identify significant lateral variations of the high velocity lower crust and relate them to the distribution and chemical status of mantle derived fluids and to xenolith studies from corresponding depths new interpretation based on combined seismic and isotope study points to a local scale magmatic emplacement at the base of the continental crust within a new rift environment this concept of magmatic underplating is supported by detecting two types of the lower crust a high velocity lower crust with pronounced reflectivity and a high velocity reflection free lower crust the character of the underplated material enables to differentiate timing and tectonic setting of two episodes with different times of origin of underplating events the lower crust with high reflectivity evidences magmatic underplating west of the eger rift of the late variscan age the reflection free lower crust together with a strong reflector at its top at depths of 28 30 km forms a magma body indicating magmatic underplating of the late cenozoic middle and upper miocene to recent spatial and temporal relations to recent geodynamic processes suggest active magmatic underplating in the intracontinental setting

diffuse gas emissions at the ukinrek maars alaska implications for magmatic degassing and volcanic monitoring abstract diffuse co 2 efflux near the ukinrek maars two small volcanic craters that formed in 1977 in a remote part of the alaska peninsula was investigated using accumulation chamber measurements high co 2 efflux in many places exceeding 1000 g m 2 d 1 was found in conspicuous zones of plant damage or kill that cover 30 000 50 000 m 2 in area total diffuse co 2 emission was estimated at 21 44 t d 1 gas vents 3 km away at the gas rocks produce 0 5 t d 1 of co 2 that probably derives from the ukinrek maars basalt based on similar 13 c values 6 3 he 4 he ratios 5 9 7 2 r a and co 2 3 he ratios 1 2 10 9 in the two areas a lower 3 he 4 he ratio 2 7 r a and much higher co 2 3 he ratio 9 10 10 in gas from the nearest arc front volcanic center mount peulik ugashik provide a useful comparison the large diffuse co 2 emission at ukinrek has important implications for magmatic degassing subsurface gas transport and local toxicity hazards gas water rock interactions play a major role in the location magnitude and chemistry of the emissions

cooling rates of pyroclastic deposits inferred from mineral magnetic investigations a case study from the pleistocene mýtina maar czech republic tephra layers of the m tina maar czech republic contain ferrimagnetic mg al rich titanomagnetite which is suggested to originate from a fractionated alkaline co 2 rich lithospheric mantle melt we investigated the magnetic mineralogy and curie temperature t c from tephra deposits of two drill cores 9 m depth t c calculated 208 14 c from chemical composition fe 2 0 8 mg 0 5 fe 3 1 1 al 0 3 ti 0 3 o 4 is in accordance with tc retrieved from cooling curves of temperature dependent magnetic susceptibility measurements 195 232 c however thermomagnetic curves are irreversible either with lower type i or higher type ii tc in the heating curve all curves show transition temperatures above ca 390 c indicating maghemitization we interpret the irreversibility of tc t c in terms of different degrees of cation ordering overprinted or masked by different degrees of maghemitization which is a low temperature phenomenon negative t c indicates that original deposited titanomagnetite has cooled faster and therefore has stored a lower degree of cation ordering compared to heating cooling rate of 11 c min in the kappabridge type ii with positive t c indicates higher degree of cation ordering and therefore slower cooling rate the central part of this deposit shows most severe maghemitization indicating rather wet emplacement we therefore suggest different eruption styles for deposition of type i pyroclastics with more phreatomagmatic and type ii pyroclastics with more phreato strombolian eruption styles our study is a new approach to discriminate different cooling histories in maar deposits using the curie temperature of titanomagnetite we suggest that this method has the potential to discriminate different emplacement modes resulting from different eruption styles

reconnaissance study of an inferred quaternary maar structure in the western part of the bohemian massif near neualbenreuth ne bavaria germany after a comprehensive geophysical prospecting the quaternary m tina maar located on a line between the two quaternary scoria cones komorni h rka kammerbuhl and elezna h rka eisenbuhl could be revealed by a scientific drilling at the german czech border in 2007 further geophysical field investigations led to the discovery of another geological structure about 2 5 km ese of the small town neualbenreuth ne bavaria germany inferred to be also a maar structure being the fourth volcanic feature aligned along the nw se trending tachov fault zone it is only faintly indicated as a partial circular rim in the digital elevation model though not expressed by a clear magnetic anomaly geoelectric and refraction seismic tomography strongly indicates a bowl shaped depression filled with low resistivity and low velocity material correlating well with the well defined negative gravity anomaly of 2 5 mgal below ca 15 m thick debris layer successions of mostly laminated sediments were recovered in a 100 m long sediment core in 2015 sections of finely laminated layers likely varves rich in organic matter and tree pollen were recognized in the upper 22 30 m and lower 70 86 m part of the core respectively interpreted as interglacials whereas mostly minerogenic laminated deposits poor in organic matter and almost barren of tree pollen are interpreted as clastic glacial deposits according to a preliminary age model based on magnetostratigraphy palynology radiocarbon dating and cyclostratigraphy the recovered sediments span the time window from about 85 ka back to about 270 ka covering marine isotope stages 5 8 sedimentation rates are in the range of 10 cm ka 1 in interglacials and up to 100 cm ka 1 in glacial phases the stratigraphic record resembles the one from m tina maar with its eruption date being derived from a nearby tephra deposit at 288 17 ka thus supporting the age model of the inferred neualbenreuth maar

contrasting recent trends in southern hemisphere westerlies across different ocean basins many studies have documented the trends in the latitudinal position and strength of the midlatitude westerly jet in the southern hemisphere however very little attention has been paid to the long

synchronous variability in the southern hemisphere atmosphere sea ice and ocean resulting from the annular mode zonally symmetric fluctuations of the midlatitude westerly winds characterize the primary mode of atmospheric variability in the southern hemisphere during all seasons this is true not only in observations but also in an unforced 15 000 yr integration of a coarse resolution r15 coupled ocean atmosphere model here it is documented how this mode of atmospheric variability known as the southern annular mode sam generates ocean circulation and sea ice variations in the model integration on interannual to centennial timescales that are tightly in phase with the sam the positive phase of the sam is associated with an intensification of the surface westerlies over the circumpolar ocean around 608s and a weakening of the surface westerlies farther north this induces ekman drift to the north at all longitudes of the circumpolar ocean and ekman drift to the south at around 308s through mass continuity the ekman drift generates anomalous upwelling along the margins of the antarctic continent and downwelling around 458s the anomalous flow diverging from the antarctic continent also increases the vertical tilt of the isopycnals in the southern ocean so that a more intense circumpolar current is also closely associated with positive sam in addition the anomalous divergent flow advects sea ice farther north resulting in an increase in sea ice coverage finally positive sam drives increases in poleward heat transport at about 308s while decreases occur in the circumpolar region ocean and sea ice anomalies of the opposite sign occur when the sam is negative the ocean and sea ice fluctuations associated with the sam constitute a significant fraction of simulated ocean variability poleward of 308s year round the robustness of the mechanisms relating the sam to oceanic variability suggests that the sam is likely an important source of large scale variability in the real southern hemisphere ocean

co2 discharge in an active non volcanic continental rift area czech republic characterisation δ13c 3he 4he and quantification of diffuse and vent co2 emissions abstract in the western eger rift er area along the pocatky plesna fault zone ppz co 2 degassing occurs predominantly within two mofette fields bublak and hartousov we studied 27 wet mofettes belonging to these mofette fields for gas emission rates repeatedly between 2007 and 2009 and selected mofettes for gas composition and isotope ratios 13 c 3 he 4 he detailed ground mapping along the ppz provided further two separated diffuse degassing structures dds within the mofette fields hartousov and bublak the dds hartousov was studied in detail by measurements of 682 co 2 soil gas concentrations 762 co 2 soil gas fluxes max 10 grid spacing and partly by analyses of isotope ratios 13 c 12 c 3 he 4 he of soil gas at the dds hartousov the total co 2 soil flux yielded 1 559 t m 2 d 1 in spring 2009 and the co 2 emission rate at the wet mofettes of hartousov mofette field yielded 0 62 t d 1 the total co 2 discharge of the 27 wet mofettes was 3 75 t d 1 at sites with high co 2 soil flux the portion of mantle derived helium is in the same range as the releasing at wet mofettes both cover the signature of the subcontinental mantle also the 13 c values analysed in the gas releasing from wet mofettes and those analysed in soil gas are nearly the same taking in account a biogenic soil co 2 flux of 25 g m 2 d 1 as background the mantle derived co 2 flux yielded approximately 1566 t m 2 d 1 as a result of the co 2 flux mapping of the dds hartousov it could be proved that 97 4 of the released soil co 2 1 518 t m 2 d 1 stems from sites with co 2 fluxes higher than 500 g m 2 d 1 pointing to dominantly fault related co 2 release at the central mofette bublak b2 the gas emission rate was determined for the first time in 1993 measurements repeated between 2007 and 2009 showed a clear increase in the gas emission rate of more than 40 correlating well with the increase of the 3 he 4 he ratios from 5 ra to approximately 6 ra between 1993 and 2008 at this location brauer et al 2009 the bublak mofette field is characterised by the highest co 2 emission rate along the ppz and in combination with the helium isotope signature of the european subcontinental mantle this area was identified as a deep reaching fluid injection zone

investigation of the inner structure of la crosa de sant dalmai maar catalan volcanic zone spain abstract la crosa de sant dalmai volcano is the largest volcanic edifice of the catalan volcanic zone ne spain it is a very well preserved maar type structure 1 5 km in diameter excavated at the contact between a hard substrate and a soft substrate formed by palaeozoic granites and pliocene and quaternary gravels respectively in order to infer the uppermost inner structure of la crosa de sant dalmai maar and to characterise its main geological and tectonic constraints we have performed a multiparametric geophysical study including gravimetry magnetometry self potential and electrical resistivity tomography the results obtained together with a field geology revision and additional geological data from two drill cores provide a detailed picture of the post eruptive maar infill sequence as well as of the uppermost part of the maar diatreme structure this information helps in understanding the origin and subsequent evolution of the volcano which included an alternation of phreatomagmatic and strombolian phases geophysical data show that the last strombolian phase which culminated with the formation of a scoria cone inside the maar was associated with a nw se trending regional fault the little erosion and degradation of the original tephra ring suggest a much younger age of la crosa de sant dalmai maar than was previously stated

resonant coupling of a traveling air pressure disturbance with the east adriatic coastal waters 1 exceptional sea level oscillations and strong current reversals observed in the east adriatic on 27 june 2003 are analyzed using available meteorological and tide gauge measurements and numerical model results it is shown that the variability in the atmosphere sea system was characterized by high frequencies 0 01 0 1 min 1 and sea level and current amplitudes surpassing 1 m and 1 m s 1 respectively the event was related to the occurrence of a gravity disturbance in the atmosphere above the adriatic the disturbance traveled toward the east southeast at a speed of 22 m s 1 and was resonantly coupled with a wave in the sea 50 m deep the resulting forced wave was further amplified when entering funnel shaped bays opened to it there are indications that the forcing disturbance and its counterpart in the sea excited normal modes of the bays and harbors in the area moreover nonlinear steepening of the forced wave seemingly occurred resulting in the formation of high frequency wave trains this process along with the generation of coastal seiches could explain the observed and modeled differences between the spectra of coastal variability and the spectrum of forcing wave

root zone processes in the phreatomagmatic pipe emplacement model and consequences for the evolution of maar diatreme volcanoes abstract the understanding of processes within the root zone of maar diatreme volcanoes is important for the interpretation of the geology volcanology and even hazard assessment of these volcanoes in the phreatomagmatic model of pipe formation the irregularly shaped root zone is the site of the phreatomagmatic explosions and thus functions as the engine for pipe formation in this model the root zone grows over a period of time in a series of many single thermohydraulic i e phreatomagmatic explosions the explosions initially occur close to the surface and with ongoing explosive activity penetrate towards deeper levels the ejection of country rock clasts from the root zone results in a mass deficiency in the root zone that causes the overlying tephra and the adjacent country rocks to subside passively in a sinkhole like fashion into the root zone many phreatomagmatic eruptions consequently result in the formation of a cone shaped diatreme thus with ongoing eruptions the cone shaped diatreme has to grow systematically both in depth and diameter during its growth processes in the lower diatreme levels successively destroy the upper levels of the evolving root zone at the surface the maar crater in turn reacts to the underlying subsidence processes and also grows both in depth and diameter thermohydraulic explosions which fragment both magma and the surrounding country rocks mostly occur within the bottom part of the root zone violent explosions in small pipes may clear the overlying diatreme for a short period of time before tephra fall and collapse of the walls of the new crater refill the small initial diatreme in larger pipes via expansion of the mixture of highly pressurized water vapor juvenile gas phases and explosively produced tephra the confined and expanding eruption cloud has to pierce through the diatreme fill in a feeder conduit in order to erupt diatreme clearing events in large pipes are difficult or impossible to maintain since the explosive force in the root zone is only in exceptional instances strong enough to lift or entrain the entire diatreme tephra knowledge of the genetic relationships between root zones and diatremes is critical to understand pipe growth processes the combination of such processes can lead to substantial variation in volcanic behavior and thus produce fundamentally different volcano and rock types it is the purpose of this paper to outline important features of root zones and suggest their significance for the genesis and evolution of maar diatreme and related volcanoes

geophysical surveys of the joya honda maar mexico and surroundings volcanic implications abstract joya honda jh is a quaternary maar excavated in mesozoic limestone it is located in central mexico and belongs to the ventura volcanic field vvf which is composed by cinder cones and maars made of intraplate type mafic alkalic rocks volcanoes in the region form n20w lineaments roughly parallel to a regional set of normal faults but there is no obvious relation between these faults and vent distribution in the exposed geology around the maar the volcanic rock volume is small in the vvf and most volcanoes and their products are scattered in a region where outcrops are dominated by limestone the near vent tephra associated to the jh maar lies north of the crater this relation suggests that the crater was formed by directed hydromagmatic explosions and may indicate an inclined volcanic conduit near the surface the tephra stratigraphy suggests that the initial explosions were relatively dry and the amount of water increased during the maar forming eruption therefore the existing model of the maar diatreme formation may not be applicable to joya honda as it requires the formation of a cone of depression in the aquifer and deepening of the focii of the explosions as the crater and underlying diatreme grew thus it is unlikely that there is a diatreme below joya honda aeromagnetic data shows a boundary between two regional magnetic domains near the elongated volcanic cluster of the vvf the boundary is straight with a distinct kink from ne to nw trend near jh the limit between the domains is interpreted as fault contacts between mid tertiary volcanic rocks and marine mesozoic sedimentary rocks hence magma ascent in the area may have been facilitated by fractures near the surface magnetic and gravimetric ground surveys show that the anomalies associated with the maar are not centered in the crater which could be consistent with an inclined volcanic conduit a magnetic profile measured on exposed limestone across the volcanic lineament failed to show an anomaly such as that caused by a connecting dike between the volcanoes therefore either the dike does not exist or it is so deep or so thin that it is beyond the limit of detection of the method and or equipment used thus the volcanic conduit immediately below joya honda can be reasonably modeled in the shape of a plug a 2 d model of the crater anomaly is consistent with a roughly tabular deposit formed by fall back pyroclasts and slump deposits near the surface based on this result we propose an alternative model for the formation of maar type volcanoes excavated in hard rock where there is no evidence of a gradual decrease of the water magma ratio as the eruption advanced

decadal spinup of the south pacific subtropical gyre abstract an increase in the circulation of the south pacific ocean subtropical gyre extending from the sea surface to middepth is observed over 12 years datasets used to quantify the decadal gyre spinup include satellite altimetric height the world ocean circulation experiment woce hydrographic and float survey of the south pacific a repeated hydrographic transect along 170 w and profiling float data from the global argo array the signal in sea surface height is a 12 cm increase between 1993 and 2004 on large spatial scale centered at about 40 s 170 w the subsurface datasets show that this signal is predominantly due to density variations in the water column that is to deepening of isopycnal surfaces extending to depths of at least 1800 m the maximum increase in dynamic height is collocated with the deep center of the subtropical gyre and the signal represents an increase in the total counterclockwise geostrophic circulation of the gyre by at least 20 at 1000 m a comparison of woce and

maar diatreme volcanoes a review maar diatreme volcanoes are produced by explosive eruptions that cut deeply into the country rock a maar is the crater cut into the ground and surrounded by an ejecta ring while the diatreme structure continues downward and encloses diatreme and root zone deposits here we attempt an evenhanded review of maar diatreme volcanology that extends from mafic to kimberlitic varieties and from historical maar eruptions to deeply eroded or mined diatreme structures we conclude that maar diatreme eruptions are episodic ejecta rings provide invaluable insight into eruption processes and sequence but are incomplete records of diatreme formation deposits within the diatreme structure include in varying proportions lower unbedded deposits sometimes typified by subvertical contacts among domains of debris emplaced sequentially and upper bedded deposits formed by sedimentation on surfaces open to the atmosphere a basal root zone comprises the transition from coherent magmatic feeder dike to clastic deposits formed by fragmentation of magma and enclosing country rock root zones are irregular in form and the clastic deposits are typically intruded by contorted dikes irregular root zone like chaotic breccias cut by contorted dikes are also present within diatreme deposits where they represent intra diatreme fragmentation zones and record changes in the location of the explosion locus during eruption

syn and posteruptive hazards of maar diatreme volcanoes abstract maar diatreme volcanoes represent the second most common volcano type on continents and islands this study presents a first review of syn and posteruptive volcanic and related hazards and intends to stimulate future research in this field maar diatreme volcanoes are phreatomagmatic monogenetic volcanoes they may erupt explosively for days to 15 years above the preeruptive surface a relatively flat tephra ring forms below the preeruptive surface the maar crater is incised because of formation and downward penetration of a cone shaped diatreme and its root zone during activity both the maar crater and the diatreme grow in depth and diameter inside the diatreme which may penetrate downwards for up to 2 5 km fragmented country rocks and juvenile pyroclasts accumulate in primary pyroclastic deposits but to a large extent also as reworked deposits ejection of large volumes of country rocks results in a mass deficiency in the root zone of the diatreme and causes the diatreme fill to subside thus the diatreme represents a kind of growing sinkhole due to the subsidence of the diatreme underneath the maar crater is a subsidence crater and also grows in depth and diameter with ongoing activity as long as phreatomagmatic eruptions continue the tephra ring grows in thickness and outer slope angle syneruptive hazards of maar diatreme volcanoes are earthquakes eruption clouds tephra fall base surges ballistic blocks and bombs lahars volcanic gases cutting of the growing maar crater into the preeruptive ground formation of a tephra ring fragmentation of country rocks thus destruction of area and ground changes in groundwater table and potential renewal of eruptions the main hazards mostly affect an area 3 to possibly 5 km in radius distal effects are comparable to those of small eruption clouds from polygenetic volcanoes syneruptive effects on infrastructure people animals vegetation agricultural land and drainage are pointed out posteruptive hazards concern erosion and formation of lahars inside the crater a lake usually forms and diverse types of sediments accumulate in the crater volcanic gases may be released in the crater compaction and other diagenetic processes within the diatreme fill result in its subsidence this posteruptive subsidence of the diatreme fill and thus crater floor is relatively large initially but will decrease with time it may last millions of years various studies and monitoring are suggested for syn and posteruptive activities of maar diatreme volcanoes erupting in the future the recently formed maar diatreme volcanoes should be investigated repeatedly to understand more about their syneruptive behaviour and hazards and also their posteruptive topographic limnic and biologic evolution and potential posteruptive hazards for future maar diatreme eruptions a hazard map with four principal hazard zones is suggested with the two innermost ones having a joint radius of up to 5 km areas that are potentially endangered by maar diatreme eruptions in the future are pointed out

detailed investigation of preserved maar structures by combined geophysical surveys the detection of completely preserved maar structures is important not only for underground mapping but also for paleoclimate research because laminated maar lake sediments may contain a very detailed archive of climate history objective evidence for the existence of such structures can only be provided by geophysics and boreholes the combination of gravity and magnetic ground surveys appears to be an excellent tool to detect and identify buried maar structures their prominent properties are an almost circular gravity minimum corresponding to a crater filled with limnic sediments of low density and a magnetic anomaly caused by a pyroclastic or basaltic body in the diatreme which indicates the volcanic character seismic measurements provide the most detailed information about the internal structure of the maar sediments zones of low seismic reflectivity and very low density represent sediments of the late maar lake period the early lake period is indicated by debris flow deposits and turbidites represented by seismic reflectors the seismic sections clearly reveal the bowl like structure of the maar outside this bowl like structure there are only a few reflections which represent the basement taking into account the shape of the gravity anomaly seismic information allows geometrical modelling of the maar structure optimal drilling sites can be selected based on the results of geophysical surveying comparing the results of combined geophysical surveys above two maar structures of different ages yields a marked similarity in their geophysical pattern

three dimensional potential field modelling of a multi vent maar diatreme the lake coragulac maar newer volcanics province south eastern australia abstract high resolution gravity and magnetic data have been acquired across lake coragulac a quaternary maar volcano located in the newer volcanics province of south eastern australia a gravity low is observed across the maar crater with several local gravity highs identified in the centre of the crater often with corresponding magnetic anomalies geophysical data has been integrated with geologic observations and subjected to 2d forward and 3d inverse potential field modelling modelling has revealed a complex subsurface maar structure with four coalesced diatremes and several intrusive dykes identified the modelled diatremes are shallow maximum of 290 m deep with the margins having a similar density to the host rock while the diatreme centre is often denser indicating that higher volumes of volcanic debris are present deposits of the maar rim sequence show frequent transitions between phreatomagmatic and magmatic fragmentation styles a result of fluctuations in magma rise rate and interactions with external water the complex nature of the underlying maar diatreme suggests that the maar formed from at least four vents which migrated laterally during the eruption

investigation of a tertiary maar structure using three dimensional resistivity imaging this paper presents the application of the electrical resistivity tomography ert method to the investigation of the tertiary maar structure of baruth germany known from previous gravimetric surveys ert was applied to support the optimum location for a palaeoclimatological drill hole special modifications of data acquisition signal processing and inversion are introduced to adapt the method of ert to the special requirements for the 3 d investigation of structures with horizontal extensions of 1 km or more more than 5000 dipole dipole combinations were recorded at three concentric circular electrode arrangements using stand alone transient data acquisition systems reftek we present a fast approximate imaging technique based on the simultaneous iterative reconstruction technique sirt as the complete calculation of the inverse frechet matrix is avoided the algorithm is especially suitable for large data and model spaces where complete inversion is beyond the limits of available computing hardware the single step method is applicable to arbitrary irregular electrode layouts synthetic tests show that the imaging procedure reconstructs the main features of the subsurface a low resistivity body could be interpreted as limnic sediments filling the interior of the tertiary maar crater considering the horizontal resistivity gradient estimates for the lateral and depth extents of the structure were made an optimum position for a palaeoclimatological borehole was found and was in good agreement with the gravimetric minimum

growth of phreatomagmatic explosion craters a model inferred from suoana crater in miyakejima volcano japan abstract a subvertical cross section of a maar diatreme volcano is exposed in the wall of the a d 2000 caldera on miyakejima volcano the maar suoana is one of the lateral vents of this volcano and it was inferred to be formed in the 7th century the subvertical wall of the a d 2000 caldera truncated the suoana maar crater at its center revealing the near comlete cross section of this small maar diatreme volcano exposed in the cross section are a 400 m wide maar crater an associated tuff ring with a maximum thickness of 20 m a diatreme extending vertically to a depth of about 220 m from the floor of the maar crater and a feeder dike connected to the base of the diatreme the depth of the diatreme structure is about 260 m from the original ground surface the outline of the diatreme resembles an upward opening funnel with an almost vertical wall below 560 m asl and an upward flaring wall above 560 m asl coarse grained volcanic breccia fills the diatreme the deposits of which can be divided into 6 units based on lithological and structural characteristics the upper half of the diatreme is filled with landslide deposits mainly derived from the surrounding crater wall the bottom of the diatreme is occupied by massive explosion breccia some coherent blocks were detached from the wall of the diatreme and preserved in the diatreme fill the y shaped cross sectional geometry of the suoana diatreme is the result of a combination of an underground subsidence in the lower part of the diatreme and the surface landslide in its upper part the inwardly inclined stratification of pyroclastic rock units and development of many small faults in the diatreme filling breccia indicate successive collapse and deformation of these materials within the diatreme during the eruption the upper part of the diatreme was formed by the landslides of the crater wall induced by the subsidence of the crater floor discharge of tephra from the bottom of the diatreme caused infill subsidence which induced sliding of the inner wall of the crater as a result the topographic diameter of the crater became much larger than that of the diatreme itself the tephra ring surrounding the crater consists mainly of pyroclastic fall deposits

post eruptive development of the ukinrek east maar since its eruption in 1977 a d in the periglacial area of south west alaska maar eruptions form small initially steep walled basins that contain important archives for the climatic and palaeoenvironmental history in continental areas the two ukinrek maars in south western alaska erupted between 30 march and 9 april 1977 and are the best documented maars that have erupted in historical time this study presents a preliminary analysis of geomorphology hydrology magnetic susceptibility geochemistry and sedimentology data of a field study in august 2004 these results photographs and topographic surveys are combined for reconstructing the post eruptive evolution of ukinrek east maar within less than 30 years the initially polygonal shape of the crater with nearly vertical crater walls has developed into an almost elliptic form with slopes of 35 inclination on debris fans between a few escarpments the water table and the crater floor have risen significantly and the crater diameter depth ratio increased from 3 4 to 5 7 whereas the average height of the crater rim remained almost constant the main sub aerial resedimentation process is formation of rock falls rock slumps and scree resulting in debris flows and turbidites within the lake that is ice covered throughout about half of the year distal lake sediments consist of laminated minerogenic clayey sandy silts that document frequent turbidity currents from the linear sedimentation rate of only ca 5 mm year 1 in 17 cm long cores it may be concluded that the largest portion of the crater sediments formed within the first few months of the maar history however this has to be confirmed by future studies

meteotsunami tide interactions and high frequency sea level oscillations in the eastern yellow sea while an air pressure jump was moving southeastward over the shallow water region of the eastern yellow sea in march 2007 a long ocean wave meteotsunami was generated and amplified due to the proudman resonance the long wave arrived at the coast during high tide with wave amplitude of 1 4 m and seawater overflew seawalls and inundated the land high frequency sea level oscillations continued for 8 9 h after the long wave hit a local coast the moon s age was 12 days and the tidal range was about 4 m between neap and spring tides two dimensional numerical simulations were performed to reproduce amplification of the long ocean wave in offshore and oscillations of sea level at the coast both tidal elevation and tidal currents were found to affect the growth of the long wave amplitude by the interactions between tides and the long wave long wave tides interactions are important processes for the accurate prediction of long wave arrival time and maximum height and for the reduction of coastal hazards in the macrotidal region after the long wave hit the coast of remote regions reflected waves propagated radially from remote regions to a local coast the high frequency sea level oscillations at a local observation station continued until all of the reflected waves from remote regions had passed by it was concluded that high frequency oscillations of sea level are generated not only by local reflection of the long wave but also by propagation of the reflected waves from remote regions

a contribution towards the palynostratigraphical classification of the middle pleistocene in central europe the pollen record of the neualbenreuth maar northeastern bavaria germany abstract palaeoecological evidence of intra saalian warm stages in central europe which was strongly affected by glacial and periglacial processes during the major middle and late pleistocene cold periods is ambiguous so far recently the first continuous sedimentary sequence of central europe containing the saalian complex mis 8 6 with the eemian interglacial in stratigraphic superposition was recovered from the newly discovered neualbenreuth maar ne bavaria here we present palynological results from this record allowing us to critically discuss the available biostratigraphical evidence of alternating intra saalian warm cold intervals from central europe the new pollen record from the neualbenreuth maar comprises a continuous record of vegetation and climate changes encompassing four warm stages and five cold periods the dominance of cold and dry tolerant herbs and the sparse representation of pioneer trees and shrubs during most parts of the sequence indicate open landscapes of steppe to woody steppe character typical of late middle and late pleistocene glacial periods in central europe the pollen assemblages of the warm stage in the upper part of the core clearly support its correlation with the eemian interglacial the three pre eemian warm stages represent terrestrial analogues of the marine isotope stages mis 7e 7c and 7a during each of these intervals forests were established but the reduced abundances and lower diversity of thermophilous and sub oceanic elements in comparison to the eemian attest to a weak interglacial character each of these interglacials shows a similar vegetation succession and only minor differences in the vegetation composition the intervening stadial periods represent a strong mis 7d and a moderate mis 7b climate deterioration respectively the vegetation and climate succession during the saalian glacial interglacial complex of neualbenreuth is broadly in line with the respective palynological signature from the velay record french massif central and the hoogeveen interstadial the netherlands in contrast there is only limited correspondence with most pollen records from northern and southern central europe which were hitherto classified as mis 7