possible dust devils vortices on mars this paper presents the results of a study of local vortices and dust devils on mars as observed by viking landers 1 and 2 it is found that these vortices are most common during martian spring and summer as occurs on earth seven of the vortices involve wind speeds that may raise dust from the martian surface there is no indication that these possible dust devils contribute to the planet wide spread of major dust storms however it appears that they may help in maintaining the atmospheric dust content the data indicate that there is no preference in rotation direction at least to core diameters of 300 m corresponding to a region of influence of about 3 km diameter

a seismic refraction study of the crustal structure associated with the adamawa plateau and garoua rift cameroon west africa summary recordings of quarry blasts along a 300 km profile across the adamawa plateau at the eastern end of the cameroon volcanic line permitted the determination of the crustal structure of the region to the north of the plateau in the area of the garoua rift an eastern arm of benue trough the crust is about 23 km thick and is underlain by upper mantle with a p wave velocity of 7 8 kms 1 the southern part of the plateau by comparison is associated with a more normal crustal thickness of about 33 km and underlain by upper mantle with a velocity of 8 0 kms 1 between these two areas the seismological experiment was not able to delineate how the crust changes however if the topography and gravity field reflect crustal thickness then there is a rapid change in crustal thickness at the northern edge of the adamawa plateau the study thus provides the first seismic evidence for major crustal thinning beneath the garoua arm of the west african rift system as well as providing evidence for an alternative model for the formation of the cameroon volcanic line

friction wind speeds in dust devils a field study 1 using in situ field measurements we determined surface friction velocities u and aerodynamic roughness heights z0 at the base of 10 dust devils z0 values agree closely with previous studies in this region and range from 0 1 to 1 0 cm the peak u coincide with the largest wind speed measurements within the dust devil and range from 0 9 to 2 4 ms 1 surface friction velocities are sufficient to lift all types of windblown material from dust to pebble sized particles peak u values for dust devils appear to be a linear function of the peak wind speed measured at 2 m height within the dust devil this provides a simple approximation for estimating surface shear stress for dust devils

dust devil track survey at elysium planitia mars implications for the insight landing sites abstract the insight interior exploration using seismic investigations geodesy and heat transport robotic lander is scheduled to land in elysium planitia on mars in september 2016 insight will perform the first comprehensive surface based geophysical investigation including seismic measurements knowledge about encounter rates of dust devils with the insight lander are important for two main reasons 1 dust devils will affect the scientific measurements i e wind induced seismic noise and 2 the power supply of the insight lander and instruments is provided by solar arrays and previous landers and rovers on mars were affected by a steady decline in electrical power output due to atmospheric dust deposition on the solar panels long term science operations were only made possible by dust clearing events of the solar arrays caused by wind gusts and dust devils in this study we analyzed dust devil tracks ddts at the final insight landing site region in elysium planitia formation of ddts is caused by the removal of a layer of dust by passing dust devils hence in principle the same process as clearing of dust from solar panels we mapped the number size width and length and orientation of ddts in repeat observations using high resolution imaging science experiment hirise images covering the exact same surface area acquired within a relatively short time span l s 200 consistent with the seasonal reversal in direction of the hadley circulation ddt formation rates vary between 0 002 and 0 08 ddt km 2 sol 1 ddt area formation rates using the measured ddt widths lengths and formation rates are in the range of 0 0003 0 00006 km 2 km 2 sol 1 implying that a given spot on the surface may be cleared of dust only once between 3000 and 16 000 sols i e every 5 24 mars years measured ddt formation rates were used to find a scaling factor to the seasonal dda index and then integrated over the year to estimate a mean annual ddt formation rate of 0 046 ddt km 2 sol 1 this translates into a solar panel clearing recurrence interval estimate of 11 mars years using the mean annual ddt formation rate and the mean ddt width and length from all measured ddts due to several uncertainties this solar panel clearing recurrence interval for the insight landing should be seen as an upper limit estimate

a regional gravity study of the west african rift system in nigeria and cameroon and its tectonic interpretation abstract this study brings together existing and new gravity data to investigate the nature and cause of the bouguer gravity field associated with the cretaceous west african rift system in nigeria and cameroon the new gravity measurements include data collected over the basement area between the benue trough and the cameroon border and fill an important gap in the gravity coverage after removal of the long wavelength negative anomaly from the observed gravity field the remaining positive gravity anomaly associated with the rift system is interpreted in terms of two and three dimensional crustal models these models are constrained by crustal thicknesses derived from a seismic refraction study carried out across and to the south of the yola rift the results of simple three dimensional gravity modelling indicate the crust beneath the lower and middle benue is approximately 20 km thick while beneath the gongola rift the crust is approximately 25 km thick relative to a normal crustal thickness of 34 km away from the rift assuming the thinned crust associated with the rift system is the result of simple lithospheric stretching then the maximum possible crustal extensions of 95 65 and 55 km have taken place perpendicular to the benue gongola and yola rifts respectively these crustal extensions do not necessarily reflect the total crustal movement affecting these rifts since the benue and yola rifts have been subjected to varying amounts of shear displacement during the cretaceous and early tertiary times crustal extension estimates across the west african rift system could be as much as four times greater than the published extension estimates across the east african rift system these rift systems have the same plate tectonic setting being the failed third arms of successful triple junctions and are the result of extensional and shear tectonics the differences in crustal extension and the resulting isostatic response of the lithosphere beneath these rifts can explain why the west african rift system has been associated with subsidence processes throughout its development whereas the east african rift system in northeast africa has been strongly affected by uplift

convective vortices on mars a reanalysis of viking lander 2 meteorological data sols 1 60 dust devil data from mars is limited by a lack of data relating to diurnal dust devil behaviour previous work looking at the viking lander meteorological data highlighted seasonal changes in temporal occurrence of dust devils and gave an indication of typical dust devil diameter size and internal dynamics the meteorological data from viking lander 2 for sols 1 to 60 have been revisited to provide detailed diurnal dust devil statistics results of our analysis show that the viking lander 2 experienced a possible 38 convective vortices in the first 60 sols of its mission with a higher occurrence in the morning compared to earth possibly as a result of turbulence generated by the lander body dust devil events have been categorised by statistical confidence and intensity some initial analysis and discussion of the results is also presented assuming a similar dust loading to the vortices seen by mars pathfinder it is estimated that the amount of dust lofted in the locality of the lander is approximately 800 10 kgsol 1km 2

natural and anthropogenic factors affecting groundwater quality of an active volcano mt etna italy abstract new geochemical data on dissolved major and minor constituents in 276 groundwater samples from etna aquifers reveal the main processes responsible for their geochemical evolution and mineralisation this topic is of particular interest in the light of the progressive depletion of water resources and groundwater quality in the area multivariate statistical analysis reveal 3 sources of solutes a the leaching of the host basalt driven by the dissolution of magma derived co2 b mixing processes with saline brines rising from the sedimentary basement below etna c contamination from agricultural and urban wastewaters the last process highlighted by increased concentrations of so4 no3 ca f and po4 is more pronounced on the lower slopes of the volcanic edifice associated with areas of high population and intensive agriculture however this study demonstrates that natural processes a and b are also very effective in producing highly mineralised waters which in turn results in many constituents b v mg exceeding maximum admissible concentrations for drinking water

heuristic estimation of dust devil vortex parameters and trajectories from single station meteorological observations application to insight at mars abstract a physically realistic migrating vortex model is developed and applied to generate pressure and wind speed and direction histories for dust devil passage the asymmetric character of wind histories is noted and we examine how these combined data constrain the solution space of dust devil parameters migration velocity diameter and intensity ambient wind and miss distance these histories are compared with a new terrestrial field dataset of high time resolution pressure and wind measurements of over twenty dust devil encounters in new mexico this new dataset is made available electronically and it is found that model fits can be typically achieved with simultaneous root mean square errors of 0 05 hpa 5 10 of the peak pressure signature 20 of wind azimuth and 2 m s windspeed the fits are not unique however and some heuristic aspects of resolving the intrinsic degeneracies of the problem and nonideal features of real encounters are discussed the application of this approach to the insight lander is noted offering the possibility of defining the context for any possible detections of electromagnetic and seismic signatures of dust devils on mars

geochemical and isotope identification of warm groundwaters in coastal basins near tauranga new zealand abstract chemical and isotope analyses of warm waters from wells and springs in the coastal basins extending from katikati to maketu on the bay of plenty coast of the north island new zealand are examined except for a small number influenced by shallow seawater intrusion most of the waters are potable although they have been underground for up to thousands of years there is no evidence that the waters have ever encountered high temperature geothermal conditions rather each sample has acquired a chemical signature characteristic of the igneous rocks it has encountered while circulating underground it is possible to distinguish waters predominantly influenced by andesitic or rhyolitic host rocks on the basis of the molar ratio na k ca mg bicarbonate contents reach relatively high values in some localized areas

active versus passive continental rifting evidence from the west african rift system fitton j g 1983 active versus passive continental rifting evidence from the west african rift system in p morgan and b h baker processes of continental rifting tectonophysics 94 473 481 the west african rift system comprises the cretaceous benue trough and the tertiary to recent volcanic cameroon line the two features are remarkably similar in shape and size and may be superimposed perfectly by rotating one with respect to the other by 7 about a pole in sudan three stages in the geological history of the system are postulated 1 the benue trough was produced by lithosphere stretching as one arm of an rrr triple junction during the early stages of the opening of the south atlantic 2 at about 80 ma santonian a short lived period of clockwise rotation interrupted the otherwise anticlockwise rotation of africa and decoupled the lithosphere from the asthenosphere the hot zone in the asthenosphere beneath the benue trough thus became displaced relative to the lithosphere and moved to a new position beneath cameroon and the gulf of guinea 3 anticlockwise rotation and asthenosphere lithosphere coupling were restored allowing the hot zone to manifest itself as the cameroon line the cameroon line is possibly a unique example of what a rift system produced actively by a thermal anomaly in the asthenosphere would look like it is significant that despite a long history of volcanism and uplift the cameroon line has not developed a graben structure the implication is that rift systems with graben structures are produced passively by lithosphere stretching

convective vortices and dust devils at the msl landing site annual variability two hundred fifty two transient drops in atmospheric pressure likely caused by passing convective vortices were detected by the rover environmental monitoring station instrument during the first martian year of the mars science laboratory msl landed mission these events resembled the vortex signatures detected by the previous mars landers pathfinder and phoenix however the msl observations contained fewer pressure drops greater than 1 5 pa and none greater than 3 0 pa apparently these vortices were generally not lifting dust as only one probable dust devil has been observed visually by msl the obvious explanation for this is the smaller number of strong vortices with large central pressure drops since according to arvidson et al 2014 ample dust seems to be present on the surface the annual variation in the number of detected convective vortices followed approximately the variation in dust devil activity dda predicted by the marswrf numerical climate model this result does not prove however that the amount of dust lifted by dust devils would depend linearly on dda as is assumed in several numerical models of the martian atmosphere since dust devils are only the most intense fraction of all convective vortices on mars and the amount of dust that can be lifted by a dust devil depends on its central pressure drop sol to sol variations in the number of vortices were usually small however on 1 martian solar day a sudden increase in vortex activity related to a dust storm front was detected

mesozoic plate tectonic reconstructions of the central south atlantic ocean the role of the west and central african rift system abstract the mesozoic opening history of the central equatorial and south atlantic oceans is closely linked in time and space to the development of the cretaceous rift system in west and central africa geological and geophysical studies of the west and central african rift system indicate it to be dominated by a set of sinistral and dextral strike slip zones diverging from the gulf of guinea and terminating as extensional rift basins in niger and sudan plate tectonic studies of the opening history of the atlantic basins indicate four stages of development stage 1 the jurassic opening of the central atlantic stage 2 the early cretaceous 130 119 ma opening of the south atlantic with rifting propagating deep into africa via the benue trough stage 3 the opening of the equatorial atlantic 119 105 ma and stage 4 the linkage of these oceanic basins and development of a single opening mid oceanic rift system as seen today the west and central african rift system continued to develop until the end of the cretaceous i e into stage 4 when rifting was terminated by a compressional shear deformation event causing the folding of sediments in the benue trough and reactivation of the central african shear zone and extensional tectonics in the basins of southern sudan this event correlates with an important change in the relative opening of the atlantic basins during tertiary recent times the west african rift system has not been active however during this period domal uplift and volcanism have occurred in central cameroon and western sudan and a very active phase of volcanism has occurred within the last 10 ma along the present day cameroon volcanic line although these uplift and volcanic events indicate thermal processes in the upper mantle there is as yet no clear link between their development and plate tectonic processes

martian dust devil statistics from high resolution large eddy simulations dust devils are one of the key elements in the martian atmospheric circulation in order to examine their statistics we conducted high resolution up to 5 m and wide domain about 20 20 km2 large eddy simulations of the martian daytime convective layer large numbers of dust devils developed spontaneously in the simulations which enabled us to represent a quantitative consideration of martian dust devil frequency distributions we clarify the distributions of size and intensity a topic of debate and conclude that the maximum vertical vorticity of an individual dust devil has an exponential distribution while the radius and circulation have power law distributions a grid refinement experiment shows that the rate parameter of the vorticity distribution and the exponent of the circulation distribution are robust the mode of the size distribution depends on the resolution and it is suggested that the mode is less than 5 m

crustal structure of the mamfe basin west africa based on gravity data abstract the mamfe basin is the smallest and most southerly of three side rifts associated with the benue trough it extends 130 km east from the benue trough into cameroon as far as the cameroon volcanic line and until recently it was the only rift devoid of geophysical studies to indicate its crustal structure and mode of formation between 1984 and 1986 three gravity surveys were made over the basin and adjacent basement areas of nigeria and cameroon to reveal that the western half of the basin is associated with a broad positive bouguer anomaly at least 100 km wide and amplitude in excess of 20 mgal 200 gu superimposed on this gravity high is a negative bouguer anomaly which closely correlates with the area of sedimentary cover using the crustal thickness and density contrasts determined from seismological and gravity studies over the yola side rift located farther north two dimensional modelling of the regional and residual gravity fields have been attempted the regional high has been modelled as a reduction in crustal thickness of about 8 km beneath the basin and the residual low as a sedimentary basin reaching at least 3 km in depth at the nigeria cameroon border the eastern half of the mamfe basin has a gravity expression to indicate no large sedimentary thickness thus the gravity expression of the western end of mamfe basin is similar in character to that found elsewhere within the west african rift system crustal models indicate that extension perpendicular to the mamfe basin could be at most 19 km with geological data indicating only small amounts of compression shear deformation within the basin during the late cretaceous times this lack of deformation probably results from the mamfe basin orientation being more or less perpendicular to the benue trough and foumban or central african shear zone along which most of the shear deformation has occurred during and since cretaceous times

convective vortices and dust devils at the phoenix mars mission landing site 1 the phoenix mars lander detected a larger number of short 20 s pressure drops that probably indicate the passage of convective vortices or dust devils near continuous pressure measurements have allowed for monitoring the frequency of these events and data from other instruments and orbiting spacecraft give information on how these pressure events relate to the seasons and weather phenomena at the phoenix landing site here 502 vortices were identified with a pressure drop larger than 0 3 pa occurring in the 151 sol mission ls 76 to 148 the diurnal distributions show a peak in convective vortices around noon agreeing with current theory and previous observations the few events detected at night might have been mechanically forced by turbulent eddies caused by the nearby heimdal crater a general increase with major peaks in the convective vortex activity occurs during the mission around ls 111 this correlates with changes in midsol surface heat flux increasing wind speeds at the landing site and increases in vortex density comparisons with orbiter imaging show that in contrast to the lower latitudes on mars the dust devil activity at the phoenix landing site is influenced more by active weather events passing by the area than by local forcing

seismometer detection of dust devil vortices by ground tilt we report seismic signals on a desert playa caused by convective vortices and dust devils the long period 10 100 s signatures with tilts of 10 7 radians are correlated with the presence of vortices detected with nearby sensors as sharp temporary pressure drops 0 2 1 mbar and solar obscuration by dust we show that the shape and amplitude of the signals manifesting primarily as horizontal accelerations can be modeled approximately with a simple quasi static point load model of the negative pressure field associated with the vortices acting on the ground as an elastic half space we suggest the load imposed by a dust devil of diameter d and core pressure p o is 2 p o d 2 or for a typical terrestrial dust devil of 5 m diameter and 2 mbar about the weight of a small car the tilt depends on the inverse square of distance and on the elastic properties of the ground and the large signals we observe are in part due to the relatively soft playa sediment and the shallow installation of the instrument ground tilt may be a particularly sensitive means of detecting dust devils the simple point load model fails for large dust devils at short ranges but more elaborate models incorporating the work of sorrells 1971 may explain some of the more complex features in such cases taking the vortex winds and ground velocity into account we discuss some implications for the insight mission to mars online material figure of data and geophysical interpretation of seismic refraction line

weathering of pumice in the sediments as a possible source of major ions for the waters of lake taupo new zealand abstract the mass flows of major ions na k ca mg so 4 cl and hco 3 into lake taupo with the surface waters draining the lake catchment are less than the mass flows of major ions leaving the lake some of these differences are the result of geothermal fluid entering the lake and the mass contributions from this fluid are estimated from the li budget for the lake an accurate hydrological balance for the lake suggests a groundwater inflow of 8 m 3 s 1 by assuming that this groundwater has the same composition as spring waters entering the lake from pumice aquifers the mass contributions from groundwater are included in the majorion budgets combination of all these mass flows in the budgets still leaves unexplained differences between the quantities of major ions entering the lake and the quantities leaving the lake despite the water budget being complete it is shown that the remaining mass flows in the budgets could be due to the dissolution of pumice within the lake na concentrations in the interstitial waters of lake sediments are higher than in the overlying lake water and the calculated flux of na ions from the sediment into the lake water would satisfy the mass budget for na it is concluded that the dissolution of pumice in lake sediments could contribute major ions to the waters of some lakes in volcanic regions

solar panel clearing events dust devil tracks and in situ vortex detections on mars abstract spirit rover solar array data which if publicly archived would provide a useful window on mars meteorology shows dust clearing events coinciding with the onset of dust devil season in three mars years the recurrence interval of 100 700 days is consistent with the extrapolation of pathfinder and phoenix vortex encounters indicated by pressure drops of 6 40 pa similar to laboratory measurements of dust lifting threshold and with observed areas and rates of generation of dust devil tracks on mars

dust devils in thin air vortex observations at a high elevation mars analog site in the argentinian puna we report in situ measurements and field observations of dust devils at 3800 4200 m elevation in the argentine desert plateau puna these first quantitative data at elevations where the ambient atmospheric pressure is only 600 700 mbar support the notion that large and strong dust devils may be systematically more common in low pressure conditions although regional meteorology and or surface thermophysical properties may also contribute

dust devils on earth and mars 1 dust devils particle loaded vertical convective vortices found on both earth and mars are characterized by high rotating wind speeds significant electrostatic fields and reduced pressure and enhanced temperature at their centers on earth they are subordinate to boundary layer winds in the dust cycle and except possibly in arid regions are only nuisance level phenomena on mars though they seem to support the persistent background atmospheric haze to influence the surface albedo through the formation of tracks on the surface and to possibly endanger future exploration because of their high dust load and large potential gradients high resolution numerical simulations and thermophysical scaling models successfully describe dust devil like vortices on mars but fitting dust devil action into the martian global dust cycle is still problematic reliable parameterizations of their erosional abilities and solid temporal and spatial distribution data are still required to build and test a complete model of dust devil action

occurrence and mobility of major and trace elements in groundwater from pristine volcanic aquifers in jeju island korea abstract major and trace elements in groundwater from basaltic aquifers in pristine conditions were investigated in a volcanic island to evaluate sources sinks and mobility of elements over a wide range of mineralization conditions with total dissolved solids from 50 mg l to 3400 mg l groundwater was highly undersaturated with respect to primary silicate minerals indicating that dissolution of basaltic rocks may continue under conditions with precipitation of calcite and secondary silicates evolution of b cl ratio in groundwater from marine aerosols to basaltic rocks showed that the ratio could be used as a conservative tracer for interactions between water and basaltic rocks relative mobility rm of elements calculated using the concentrations of elements in the local basaltic rocks and those in groundwater showed that mobility decreased in the order of b rb na k mg ca mo v si sr sc p u zn pb cr cu ba ni ti mn al fe co th indicating that oxyanion forming elements and alkali metals had the highest mobility compared to average rm v had decreased mobility and fe and mn had increased mobility in anoxic groundwater while v mo and u had higher mobility in oxic alkaline water the sources of v cr cu and zn in rocks were estimated using the partition coefficients between minerals and basaltic melt and the disparity between sources and mobility indicated that sinks are more important for controlling the concentrations of these elements in groundwater than the contents in the rocks principal component analysis pca of hydrogeochemical parameters in groundwater produced three principal components pc which represent dissolution of basaltic rocks without significant attenuation of released solutes higher degree of water rock interactions resulting in oxic alkaline conditions and attenuation of zn and cu in higher ph respectively spatial distribution of pcs revealed that groundwater with elevated concentrations of mobile elements was concentrated in the southwestern area and that concentrations of v and cr were more scattered which is likely to be controlled by ph and redox states of groundwater as well as degree of water rock interactions

depositional and structural styles in chad basin of northeastern nigeria seismic reflection data in the maiduguri area of the chad basin reveal a significant juxtaposition of faults and folds the primary structural orientation of which is northeast southwest and parallel to the surface structural pattern in the contiguous benue trough the faults in the basin consist of both basement involved faults and detached faults the folds are simple symmetrical structures restricted to the deeper parts of the basin concomitant compressive structures are notably scarce the structural pattern is complicated further by the presence of intrusions that are presumed to be the subsurface extension of volcanic outcrops that rim the southeastern part of the maiduguri subbasin seismic reflection data also reveal distinguishable seismic sequences that correl te with the established stratigraphic sequence of the basin the apparent structure and the seismically derived stratigraphy suggest a rift origin for the basin furthermore the seismic stratigraphy sedimentologic implications and seismically determined structural features suggest that the maiduguri area of the chad basin has good prospects for hydrocarbon plays in cretaceous rocks with high potentials for both structural and stratigraphic traps

on the age and origin of lake ejagham cameroon and its endemic fishes lake ejagham is a small shallow lake in cameroon west africa which supports five endemic species of cichlid fishes in two distinct lineages genetic evidence suggests a relatively young age for the species flocks but supporting geologic evidence has thus far been unavailable here we present diatom geochemical mineralogical and radiocarbon data from two sediment cores that provide new insights into the age and origin of lake ejagham and its endemic fishes radiocarbon ages at the base of the longer core indicate that the lake formed approximately 9 ka ago and the diatom record of the shorter core suggests that hydroclimate variability during the last 3 millennia was similar to that of other lakes in cameroon and ghana these findings establish a maximum age of ca 9 cal ka bp for the lake and its endemic species and suggest that repeated cichlid speciation in two distinct lineages occurred rapidly within the lake local geology and west african paleoclimate records argue against a volcanic chemical or climatic origin for lake ejagham although not conclusive the morphometry of the lake and possible signs of impact induced effects on quartz grains are instead more suggestive of a bolide impact

crustal structure of nigeria and southern ghana west africa from p wave receiver functions abstract we report new estimates of crustal thickness moho depth poisson s ratio and shear wave velocities for eleven broadband seismological stations in nigeria and ghana data used for this study came from teleseismic earthquakes recorded at epicentral distances between 30 and 95 and with moment magnitudes greater than or equal to 5 5 p wave receiver functions were modeled using the moho ps arrival times h k stacking and joint inversion of receiver functions and rayleigh wave group velocities the average crustal thickness of the stations in the neoproterozoic basement complex of nigeria is 36 km and 23 km for the stations in the cretaceous benue trough the crustal structure of the paleoproterozoic birimian terrain and neoproterozoic dahomeyan terrain and togo structural unit in southern ghana is similar with an average moho depth of 44 km poisson s ratios for all the stations range from 0 24 to 0 26 indicating a bulk felsic to intermediate crustal composition the crustal structure of the basement complex in nigeria is similar to the average crustal structure of neoproterozoic terrains in other parts of africa but the two neoproterozoic terrains in southern ghana have a thicker crust with a thick mafic lower crust ranging in thickness from 12 to 17 km both the thicker crust and thick mafic lower crustal section are consistent with many precambrian suture zones and thus we suggest that both features are relict from the collisional event during the formation of gondwana

stratigraphy petrochemistry and quaternary depositional record of the songaksan tuff ring jeju island korea abstract the songaksan tuff ring str is one of several recent hydrovolcanic centers on jeju island korea which provides an excellent example of proximal to distal facies changes in wet pyroclastic surge deposits a multidisciplinary study has been carried out on the str and adjacent lithostratigraphic units to constrain absolute age geochemical characteristics and quaternary depositional history a number of rock units were identified inside the crater of the str including scoria deposit i trachybasalt lava scoria deposit ii and a late stage basaltic tuff indicative of a rather complex sequence of magmatic and phreatomagmatic eruptions after the construction of the tuff ring petrochemical analysis shows that the str was generated from different magma batches that fractionated from a homogenous magma chamber and the early erupted magma was more evolved and volatile rich reworking of the str commenced shortly after the hydromagmatic eruption in a high energy nearshore environment resulting in deposition of the hamori formation the formation is composed of planar stratified and low to high angle cross stratified tuffaceous pebbly sandstones and occurs up to an altitude of about 4 m above present sea level 14c dating of molluscan shells beneath the formation indicates that it began to be deposited after about 4000 yr bp detailed sedimentary logging reveals that the formation consists of several stratal packages bounded by laterally persistent and distinct lithologic boundaries probably formed by millennial scale sea level fluctuations occurrence of another hydrovolcanic sequence the sinyangri formation on the opposite side of jeju island having similar sedimentary characteristics and ages suggests that the sea level fluctuations as seen in the hamori formation have affected a wide area of jeju island probably related to the high frequency sea level oscillations during the post 6 ka bp regression period in the east asian region it can be concluded that the formation of the str was possible because of the holocene transgression which made the present coastal areas water saturated and adequate for hydrovolcanic eruptions the str in turn contributed to record high frequency sea level fluctuations during the holocene via acting as a local and short lived but affluent source of loose sediment

phosphorus in spring waters of the taupo volcanic zone north island new zealand abstract cold spring waters of the taupo volcanic zone new zealand contain phosphorus at concentrations up to 0 3 g m 3 and for some lakes of the region the phosphorus loading from these spring waters is substantial several spring waters derived from a rhyolitic pumice aquifer were examined together with the aquifer recharge water collected from below the forest root zone an accurate water balance was obtained for the aquifer catchment and the mass recharge to the aquifer shows that 95 of the phosphorus and some of the sodium calcium and magnesium in the spring waters are derived from within the aquifer presumably by reaction of the rhyolitic substrate with recharge water acidic due to dissolved carbon dioxide although the chemistry of the spring waters from both pumice and ignimbrite aquifers suggests hydroxyapatite as the solid phase which could limit the phosphorus concentrations in these waters thermodynamic considerations show that phosphorus can reach the high concentrations found without exceeding the solubility of this mineral because of the low less than 4 g m 3 concentrations of calcium present in these waters

evolution of alkalic lavas at haleakala volcano east maui hawaii the postshield and posterosional stages of haleakala volcano contain intercalated alkalic basalt and evolved alkalic lavas isotopic and incompatible element abundance ratios in the haleakala postshield basalts changed systematically with time providing evidence for significant temporal changes in the mantle components contributing to the magmatic sources specifically a depleted i e low87sr 86sr and high143nd 144nd mantle component is more abundant in younger lavas however as magma production rates decreased during the postshield and posterosional stages basaltic melts in magma reservoirs cooled and fractionated leading to evolved residual melts such as hawaiite because primary basalt compositions changed with time the evolved haleakala lavas formed from a range of parental compositions however basalts and evolved lavas of similar age and isotopic ratios sr and nd have major and trace element contents that are consistent with a crystal fractionation model although alkalic basalt and hawaiite are the dominant lavas of the postshield stages of both haleakala and mauna kea volcanoes there are important differences between their lavas for example compositional differences between the hawaiite suites at haleakala and mauna kea indicate that on average the evolved lavas at haleakala formed at lower pressures also at haleakala basalts are intercalated with hawaiites whereas at mauna kea basalts and hawaiites are separated by a sharp boundary these differences probably reflect a higher magma supply rate to the haleakala volcano

a gravity interpretation of the benue trough nigeria abstract reconnaissance gravity surveys carried out in the benue trough from 1975 to 1977 have revealed a broad positive regional anomaly over the whole trough attributable to moho uplift superimposed on this regional gravity high in the lower benue trough is an axial positive anomaly this positive anomaly with a maximum width of 100 km and an amplitude of 20 mgal seems to disappear around latitude 9 n and is associated with a basic body of density 2 90 gcm 3 that decreases in width and thickness from the south to the north an axial negative anomaly observed in the upper benue is attributed to sedimentary fill 6000 m thick in the middle and lower benue flanking negative anomalies are attributable to the accumulation in the marginal basins of post deformational sediments up to 5000 m thick

geomagnetic field intensity determination from pleistocene trachytic lava flows in jeju geopark 1 a composite of 28 trachytic lava flows were recovered from the jeju geopark drilling project jgdp in jeju geopark one of the new seven wonders of nature declared by unesco in 2011 each trachytic lava flow has a tendency to increase in magnetic grain size from the rapidly cooled brecciated margin and vesicle streaked zone downward into the massive crystalline flow interiors the brecciated margin and vesicle streaked zone of individual trachytic lava flow contains exclusively fine grained magnetite as inclusions in plagioclase high fidelity paleointensity determinations were obtained from 26 out of 224 examined samples from jgdp cores temporal variation of virtual axial dipole moments vadms calculated from the absolute paleointensity estimates follows the trend of sint 800 data for the interval from 80 to 360 ka high vadm from flow 21 possibly represents real intensity peak as previously recognized high vadm in japan at 336 ka in trans mexican volcanism 339 and in hawaii 340 350 ka perhaps such a strong magnetic intensity near 325 350 ka might be smoothed out in relative paleointensity records

vortex encounter rates with fixed barometer stations comparison with visual dust devil counts and large eddy simulations abstracta phenomenological model is developed wherein vortices are introduced at random into a virtual arena with specified distributions of diameter core pressure drop longevity and translation speed and the pressure history at a fixed station is generated using an analytic model of vortex structure only a subset of the vortices present are detected as temporary pressure drops and the observed peak pressure drop distribution has a shallower slope than the vortex core pressure drops field studies indicate a detection rate of about two vortex events per day under favorable conditions for a threshold of 0 2 mb 1 mb 1 hpa this encounter rate and the observed falloff of events with increasing pressure drop can be reproduced in the model with approximately 300 vortices per square kilometer per day rather more than the highest visual dust devil counts of approximately 100 devils per square kilometer per day this difference can be reconciled if dust lifting typically only occurs in the field above a