a multichannel seismic study of lithospheric flexure across the hawaiian emperor seamount chain existing models assume that the thickened crust beneath seamounts is the result of a surface volcanic load flexing an elastic plate new results suggest that flexed oceanic crust beneath the hawaiian emperor seamount chain is underlain by a 4 km thick deep crustal body we intepret the body as a deep crustal sill complex associated with the tholeiitic stage of volcano building along the chain

deformation produced by the subduction of a palaeozoic turbidite sequence in northern chile a deep sea basin plain turbidite succession of ordovician to devonian age is exposed between 25 309 and 27 s in the coastal region of northern chile in the s these turbidites form a large scale tectonic melange alkali basalt pillow lavas and tuffs are interstratified with the sediments to the s of 26 209s the rocks were metamorphosed to the greenschist facies and subjected to two phases of deformation subsequent to the formation of the melange the first phase is characterized by large scale tight chevron folds and an axial planar cleavage the folds of the second phase are smaller and more upright and accompanied by a crenulation cleavage the fold axes of both phases trend between w e and nw se oblique to the n s trending mesozoic and cenozoic andean structures folds are predominantly asymmetric and overturned towards the s and sw suggesting an origin by underthrusting towards the n and ne the deformed succession is interpreted as a subduction complex produced by oblique underthrusting of an oceanic plate towards the n and ne during late devonian to carboniferous times

spatiotemporal model of kīlauea s summit magmatic system inferred from insar time series and geometry free time dependent source inversion k lauea volcano hawai i island has a complex magmatic system including summit reservoirs and rift zones kinematic models of the summit reservoir have so far been limited to first order analytical solutions with pre determined geometry to explore the complex geometry and kinematics of the summit reservoir we apply a multitrack wavelet based insar interferometric synthetic aperture radar algorithm and a novel geometry free time dependent modeling scheme to map spatiotemporally distributed surface deformation signals over k lauea s summit we process sar data sets from two overlapping tracks of the envisat satellite including 100 images during the period 2003 2010 following validation against global positioning system gps data we invert the surface deformation time series to constrain the spatiotemporal evolution of the magmatic system without any prior knowledge of the source geometry the optimum model is characterized by a spheroidal and a tube like zone of volume change beneath the summit and the southwest rift zone at 2 3 km depth respectively to reduce the model dimension we apply a principal component analysis pca scheme which allows for the identification of independent reservoirs the first 3 pcs explaining 99 63 8 28 5 and 6 6 respectively of the model include six independent reservoirs with a complex interaction suggested by temporal analysis the data and model presented here in agreement with earlier studies improve the understanding of k lauea s plumbing system through enhancing the knowledge of temporally variable magma supply storage and transport beneath the summit and verify the link between summit magmatic activity seismicity and rift intrusions

velocity measurements close to rippled beds in oscillatory flow the results are reported of velocity measurements in oscillatory flow over rippled beds velocities were measured with a laser doppler anemometer in both an oscillating tray rig and an oscillatory flow water channel both self formed and artificial ripples were examined in addition some measurements were made with an apparently plane bed with intense sediment motion the experimental results were compared with the predictions of kalkanis 1964 kajiura 1968 bakker 1973 1974 and sleath 1974 the closest agreement between theory and experiment was obtained with the method of sleath measurements of the eulerian drift velocities showed drift towards the adjacent ripple crest in the immediate vicinity of the bed and away from the crest further out

vertical fluxes of sediment in oscillatory sheet flow time series of vertical sediment fluxes are derived from concentration time series in sheet flow under waves while the concentrations c z t vary very little with time for z 10d50 the measured vertical sediment fluxes qzs z t vary strongly with time in this vertical band and their time variation follows to some extent the variation of the grain roughness shields parameter 2 5 t thus sediment distribution models based on the pickup function boundary condition are in some qualitative agreement with the measurements however the pickup function models are only able to model the upward bursts of sediment during the accelerating phases of the flow they are so far unable to model the following strong downward sediment fluxes which are observed during the periods of flow deceleration classical pickup functions which essentially depend on the shields parameter are also incapable of modelling the secondary entrainment fluxes which sometimes occur at free stream velocity reversal the measured vertical fluxes indicate that the effective sediment settling velocity in the high 0 3 c z t 0 4 concentration area is typically only a few percent of the clear water settling velocity while the measurements of richardson and jeronimo chem eng sci 34 1979 1419 from a different physical setting lead to estimates of the order 20 the data does not support gradient diffusion as a model for sediment entrainment from the bed that is detailed modelling of the observed near bed fluxes would require diffusivities that go negative during periods of flow deceleration an observed general trend for concentration variability to increase with elevation close to the bed is also irreconcilable with diffusion models driven by a bottom boundary condition

sediment transport in oscillatory flow over flat beds the motion of sediment in oscillatory flow over a flat bed is investigated both theoretically and experimentally the theory makes use of results for the relationship between stress and strain in steady flow the experiments were performed in two different oscillatory flow water tunnels with two different sediments they were designed to measure the variation of velocity with height in the moving layer of sediment under conditions of intense sediment transport although certainly not perfect the agreement between theory and experiment is reasonable provided the stress ratio is chosen correctly calculated values of the mean sediment transport rate during a half cycle are compared with the predictions of currently available formulas

surface deformation associated with a dipping hydrofracture crustal deformation associated with hydrofracture is modeled by a dipping rectangular dislocation beneath the surface of an elastic half space the burger s vector is taken normal to the rectangular surface analytical expressions for vertical displacements are obtained from integration of volterra s equation by using mindlin s point force solutions for the elastic halfspace in the limits of 0 and 90 dip the results agree with those obtained by maruyama 1964 for poisson s ratio 0 25 expressions for arbitrary poisson s ratio are given for elongate dislocations the displacement field agrees with curves given by pollard and holzhausen 1979 for two dimensional near surface fractures at various dips at dip 0 a deep square dislocation gives displacements indistinguishable from those of sun s 1969 model of a horizontal penny shaped crack beneath the surface of an elastic half space modifying his result for shallow depths shows that they correspond to a dislocation of semi elliptical cross section with the surface displacement field asymptotically approaching a semi elliptical shape as depth decreases to zero similarly the surface displacement field of the square dislocation approaches that of its rectangular cross section nonlinear inversion of surface tilt fields associated with hydrofracture of deep boreholes gives estimates of fracture geometry position and orientation along with their uncertainties two examples are presented one of a near horizontal and one of a near vertical fracture

mechanism of explosive eruptions of kilauea volcano hawaii a small explosive eruption of kilauea volcano hawaii occurred in may 1924 the eruption was preceded by rapid draining of a lava lake and transfer of a large volume of magma from the summit reservoir to the east rift zone this lowered the magma column which reduced hydrostatic pressure beneath halemaumau and allowed groundwater to flow rapidly into areas of hot rock producing a phreatic eruption a comparison with other events at kilauea shows that the transfer of a large volume of magma out of the summit reservoir is not sufficient to produce a phreatic eruption for example the volume transferred at the beginning of explosive activity in may 1924 was less than the volumes transferred in march 1955 and january february 1960 when no explosive activity occurred likewise draining of a lava lake and deepening of the floor of halemaumau which occurred in may 1922 and august 1923 were not sufficient to produce explosive activity a phreatic eruption of kilauea requires both the transfer of a large volume of magma from the summit reservoir and the rapid removal of magma from near the surface where the surrounding rocks have been heated to a sufficient temperature to produce steam explosions when suddenly contacted by groundwater

the concentration of co_ 2 in submarine tholeiitic basalts the concentrations of co 2 and h 2 o in glass separates from submarine tholeiitic basalts have been determined the presence of vesicles in samples precludes accurate determination of the co 2 concentration in glass unless steps are taken to analyze only uncontaminated vesicle free glass special care has been exercised during sample preparation to avoid these problems a new analytical technique for micro determination of h 2 o and co 2 has been applied to five mid ocean ridge and two kilauea submarine east rift zone basalts quenched at pressures as great as 0 5 kb the uncertainty of quenching pressure due to flow of lava subsequent to surface quenching global sea level variations and local deformation of the sea floor are discussed non tectonic uncertainties of quenching pressure have been estimated the concentration of co 2 in glass separates from submarine tholeiitic basalts increases linearly with quenching pressure the apparent solubility of co 2 in tholeiitic basalts

deep volcanic tremor and magma ascent mechanism under kilauea hawaii deep harmonic tremor originating at depths around 40 km under kilauea was studied using records accumulated since 1962 at the hawaii volcano observatory of the u s geological survey the deep source of the tremor was determined by onset times and confirmed by the relative amplitude across the island wide network of seismometers the period of tremor was conclusively shown to be determined by the source effect and not by the path or station site effect because the period would change considerably in time but maintained uniformity across the seismic net during the tremor episode the tremor appeared to be primarily composed of p waves we interpret the observed period and amplitude in terms of the stationary crack model of aki et al 1977 and find that the seismic moment rates for deep tremors are considerably larger than those for shallow tremors suggesting more vigorous transport for the former we propose a kinematic source model which may be more appropriate for deep tremor according to this model a measurable quantity called reduced displacement is directly proportional to the rate of magma flow a systematic search for deep tremor episodes was made for the period from 1962 through 1979 and the amplitude period and duration of the tremor were tabulated we then constructed a cumulative reduced displacement plot over the 18 year period the result shows a generally steady process which does not seem to be significantly affected by major eruptions and large earthquakes near the surface the total magma flow estimated from the reduced displacement is however one order of magnitude smaller than that estimated by swanson 1972 it may be that most channels transport magma aseismically and only those with strong barriers generate tremor

sediment transport in oscillatory sheet flow motivated by an interest in high rates of sediment transport an experimental investigation was conducted to examine sediment motion in conditions of intense sediment transport fluid velocity and sediment concentration were measured simultaneously in a sheet flow regime generated in a u shaped oscillatory water tunnel for two types of noncohesive sediments a probe was developed to measure the instantaneous variations in sediment concentration based on the electrical conductivity of the fluid grain mixture unlike previous concentration devices this probe is nonintrusive and is capable of measuring a wide range of sediment concentrations from extremely dense concentrations within the bed to low concentration suspended load well above the moving layer of sediment horizontal fluid velocities were measured simultaneously using laser doppler anemometry in backscatter mode the sediment concentration measurements provide a comprehensive data set for sediment transport in sheet flow and near sheet flow regimes the temporal variation of sediment transport over the half cycle of oscillation was examined most of the sediment was transported within the moving bed layer with the total transport occurring between the stationary bed height and a distance about twice the thickness of the moving bed layer the temporal variation in sediment transport was found to be proportional to cos t the magnitude of the sediment transport increased with increasing bottom shear stress fluid velocity and sediment concentration measurements were used to calculate instantaneous and mean rates of sediment transport which were compared with predictions from existing models

a sheetflow sediment transport model for skewed asymmetric waves combined with strong opposite currents abstract prototype scale physical model tests were conducted to investigate the sheetflow sediment transport of uniform sand under different skewed asymmetric oscillatory flows with and without the presence of relatively strong currents in the opposite direction against wave propagation experiments show that in most cases with fine sands the cancelling effect which balances the on off shore net transport under pure asymmetric skewed oscillatory flows and results a moderate net transport was developed for combined skewed asymmetric shaped oscillations however under certain conditions t 5 s with coarse sands the onshore sediment transport was enhanced for combined skewed asymmetric flows additionally the new experimental data under collinear oscillatory flows and strong currents show that offshore net transport rates increase with decreasing velocity skewness and acceleration skewness sediment movement behaviors were investigated through analysis of experimental data obtained from the image analysis technique and attempts were made to estimate and formulate the sheetflow layer thickness accordingly sediment transport under oscillatory sheetflow conditions was studied and successfully explained by comparing the bed shear stress and the phase lag parameter at each half cycle consequently these parameters were incorporated in an improved dibajinia and watanabe s type sediment transport model the formula is calibrated against a comprehensive experimental data 331 in total good agreement obtained between predictions and measurements shows that the new formula is fulfilled for practical purposes

a two phase approach to wave induced sediment transport under sheet flow conditions a numerical model for the general description of the sediment transport under oscillatory sheet flow conditions is developed based on a two fluid representation of the two phase turbulent flows the governing equations of the model are the reynolds averaged continuity equations and equations of motion for both the fluid and the sediment phases the two phases are coupled by the interphase forces including the resistance force the inertia force and the lift force turbulence closure of the fluid phase is based on a slightly modified k epsilon model while an algebraic particle turbulence model is applied to the sediment phase the numerical method is based on the modified simple scheme and an improved time stepping technique the model is validated by the published data for the symmetrical oscillatory sheet flows generated in an oscillatory flow tunnel at the university of tokyo and for both the symmetrical and the asymmetrical oscillatory sheet flows generated in an oscillatory flow tunnel at university of aberdeen the numerical results on the temporal and spacial variation of the sediment concentration the horizontal velocities of the two phases the horizontal and vertical fluxes of the sediment phase as well as the thickness of the sheet flow layer all show satisfactory agreement with the laboratory data the model is also shown to predict the net sediment transport rate with a reasonably good accuracy c 2011 elsevier b v all rights reserved

magma supply and storage at kilauea volcano hawaii 1956 1983 abstract shallow crustal magma reservoirs beneath the summit of kilauea volcano and within its rift zones are linked in such a way that the magma supply to each can be estimated from the rate of ground deformation at the volcano s summit our model builds on the well documented pattern of summit inflation as magma accumulates in a shallow summit reservoir followed by deflation as magma is discharged to the surface or into the rift zones magma supply to the summit reservoir is thus proportional to summit uplift and supply to the rift zones is proportional to summit subsidence the average proportionality constant is 0 33 10 6 m 3 rad this model yields minimum supply estimates because it does not account for magma which escapes detection by moving passively through the summit reservoir or directly into the rift zones calculations suggest that magma was supplied to kilauea during july 1956 april 1983 at a minimum average rate of 7 2 10 6 m3 month roughly 35 of the net supply was extruded the rest remains stored within the volcano s east rift zone 55 and southwest rift zone 10 periods of relatively rapid supply were associated with the large kapoho eruption in 1960 and the sustained mauna ulu eruptions in 1969 1971 and 1972 1974 bursts of harmonic tremor from the mantle beneath kilauea were also unusually energetic during 1968 1975 suggesting a close link between kilauea s deep magma supply region and shallow storage reservoirs it remains unclear whether pulses in magma supply from depth give rise to corresponding increases in shallow supply or if instead unloading of a delicately balanced magma transport system during large eruptions or intrusions triggers more rapid ascent from a relatively constant mantle source

effusion rate trends at etna and krafla and their implications for eruptive mechanisms abstract using effusion rates obtained from ground and satellite based data we build a data set of 381 effusion rate measurements during effusive activity at etna and krafla between 1980 and 1999 this allows us to construct detailed effusion rate curves for six fissure fed eruptions at etna and krafla and four summit fed eruptions at etna these define two trends type i and ii type i trends have effusion rates that rise rapidly to an initial peak before declining more slowly resulting in an exponential decrease in eruption rate and declining growth in cumulative volume type ii trends are characterised by steady effusion and eruption rates and hence a linear increase in cumulative volume the former is typical of fissure eruptions and can be explained by tapping of an enclosed pressurised system the latter are typical of persistent etnean summit eruptions plus one persistent effusive eruption at stromboli 1985 1986 examined here and can be explained by overflow of the time averaged magma supply we use our effusion rate data to assess the magma balance at etna 1980 1995 and krafla 1975 1984 between 1980 and 1995 etna was supplied at a time averaged rate of 6 8 2 3 m 3 s 1 of which 13 was erupted at krafla 817 30 10 6 m 3 was erupted and intruded during 1975 1984 and the ratio of erupted to intruded volume was 0 3 at etna there is evidence for intrusion of the unerupted magma within and beneath the edifice as well as storage in the central magma column at krafla unerupted magma was intruded into a rift zone but an increasing proportion of the supply was erupted from 1980 onwards a result of the rift zone capacity being reached magma intruded prior to an eruptive event may also be entrained and or pushed out during eruption to contribute to the initial high effusion rate phases of type i events the detail in our effusion rate curves was only possible using a thermal approach which estimates effusion rates using satellite data we look forward to analysing satellite derived effusion rate trends in real time using data from current and soon to be launched sensors

coupled use of cospec and satellite measurements to define the volumetric balance during effusive eruptions at mt etna italy using etna as a case study location we examine the balance between the volume of magma supplied to the shallow volcanic system using ground based so2 data and the volume erupted using satellite thermal data we do this for three eruptions of mt etna italy during 2002 to 2006 we find that during the three eruptions 2 3 107 m3 or 24 of the degassed volume remained unerupted however variations in the degree of partitioning between supplied vsupply and erupted verupt magma occur within individual eruptions over the time scales of days consequently we define and quantify three types of partitioning in the first case vsupply verupt i e less lava is erupted than is supplied in such a case magma can erupt in an explosive manner as occurred during phase ii of the 2002 2003 eruption or remain within or below the edifice in the third case vsupply verupt i e all supplied magma is erupted during 2002 2006 over a total of 280 days of eruptive activity this balancing case applied to 50 of the time

sand transport by unbroken water waves under sheet flow conditions a model of wave induced onshore sand transport and resulting topographical changes seaward of the break point on a sloping beach is presented for the specific case in which the waves are random normally incident weakly nonlinear and relatively long the bottom boundary layer is fully turbulent and sand transport occurs as sheet flow the model consists of the following components 1 a new empirical expression for sand transport as sheet flow in which the instantaneous transport rate is directly proportional to the instantaneous bottom shear stress 2 an expresssion for the mean bottom shear stress based on a theoretical analysis of the bottom boundary layer 3 a simple representation of the shoaling wave field in which the local properties are described by linear long wave theory the probability density function of the surface displacement is gaussian and the waves conserve energy flux as they shoal and 4 the equation for conservation of sediment mass computations based on the model compare favorably with recently reported field measurements of the onshore motion of a long offshore bar

variations in tilt rate and harmonic tremor amplitude during the january august 1983 east rift eruptions of kilauea volcano hawaii abstract during january august 1983 a network of telemetered tiltmeters and seismometers recorded detailed temporal changes associated with seven major eruptive phases along the east rift of kilauea volcano hawaii each eruptive phase was accompanied by subsidence of the summit region and followed by reinflation of the summit to approximately the same level before renewal of eruptive activity the cyclic summit tilt pattern and the absence of measurable tilt changes near the eruptive site suggest that conditions in the summit region controlled the timing of the last six eruptive phases the rate of summit subsidence progressively increased from one eruptive phase to the next during the last six phases the amplitude of harmonic tremor increased during the last four phases the increases in subsidence rate and in tremor amplitude suggest that frequent periods of magma movement have reduced the flow resistance of the conduit system between the summit and the rift zone

the motion of sediment water mixtures during intense bedload transport computer simulations a new model which couples fluid and particle dynamics has been developed to study the motion of the sediment water mixture during intense bedload transport including the velocity profiles of both sediment and water the roughness length of an upper plane bed and the thickness of moving sediment layers standard mixing length theory is used to model the motion of water above the boundary between the overlying water and the sediment water mixture the turbulent flow within the moving sediment layers is described by a shear stress model in which the effective viscosity of the flowing water is proportional to the velocity difference between the fluid and the sediment the particle dynamics method in which the equations of motion of each of many particles are solved directly is applied to model the movement of sediment particles the particle fluid interaction is expressed by a velocity squared fluid drag force exerted on each sediment particle both computer simulation results and theoretical analysis have shown that the velocities of both sediment and fluid during intense sediment transport decrease exponentially with depth in the top layers of a fast moving sediment water mixture the thickness of the moving sediment layers obtained from the computer simulation results is proportional to the shear stress which agrees with previous experimental observations

the relationship between the height of a volcano and the depth to its magma source zone a critical reexamination it is commonly assumed that hydrostatic pressure balance arguments can be used to establish a relationship between the maximum height to which a volcanic edifice is able to grow and the depth at which the partial melts providing its magma supply are formed such a relationship has been used to infer various aspects of the thermal and stress state of the lithosphere beneath volcanic constructs on earth mars io and venus we examine the assumptions behind this relationship which are that 1 a continuous pressure connection exists between source and summit 2 the pressure around the magma source is the local hydrostatic pressure dictated by the depth below the geoid and 3 the melt erupting at the summit has a net positive buoyancy and show that many of them require geologically unreasonable conditions we then critically assess the evidence cited in the literature for the relationship and find that there are other factors that may explain the observations we conclude that volcano heights on the terrestrial planets cannot be related in any simple way to lithospheric thickness or depth to the magma source zone and we review the range of other factors controlling volcano height

magmatic history of the east rift zone of kilauea volcano hawaii based on drill core from soh 1 abstract deep drilling has allowed for the first time an examination of most of the shield stage of a hawaiian volcano when it is centered over the hotspot and most of its volume is produced we determined the lithologies ages geochemical characteristics and accumulation rates of rocks from the continuously cored 1 7 km deep scientific observation hole soh 1 which was drilled into kilauea s east rift zone the uppermost 750 m of this hole contain relatively unaltered subaerially quenched lavas the lower portion is a mixture of weakly to moderately altered hyaloclastites and massive basalts intruded by dikes unspiked k ar dating was attempted on 14 lavas but only four yielded geologically reasonable ages the oldest age is 351 12 ka for a sample from 1541 m eighty xrf major and trace element analyses of lavas from throughout the section demonstrate that these lavas have the same compositional range as historical kilauea lavas and that there was no systematic geochemical variation for the volcano over the last 350 ka kilauea s average yearly magma supply during this period was probably 0 05 01 km 3 which is identical to its average historical magma supply rate thus kilauea s overall source and melting conditions have remained remarkably constant for the last 350 ka despite its having drifted 42 km over the hawaiian plume these results require that the portion of the plume being melted to produce kilauea magmas be relatively large and well mixed which is inconsistent with models that place this source on the margin of a radially zoned plume

concentrations in oscillatory sheet flow for well sorted and graded sands in wave generated sheet flow conditions oscillatory near bed flow is large ripples are washed out and sand is mainly transported in a thin layer a few centimetres thick close to and below the no flow bed level new experiments in the aberdeen oscillatory flow tunnel have produced a comprehensive dataset of transport processes for well sorted and graded sands in large scale sinusoidal and asymmetric oscillatory sheet flow conditions in this paper detailed time and height varying concentration measurements are analysed the range and level of detail in the measurements make it possible to quantitatively analyse concentration behaviour more rigorously than before a new empirical equation is presented which characterises the time dependent concentration profile in the sheet flow layer the equation involves two time dependent parameters erosion depth and reference concentration the dependence of both parameters on flow and bed conditions is analysed new results are presented which make it possible to estimate time dependent erosion depth reference concentration and therefore concentration profile the effects of grading on sheet flow concentrations are analysed by comparing results from the large range of sand beds tested

variations in magma supply rate at kilauea volcano hawaii when an eruption of kilauea lasts more than 4 months so that a well defined conduit has time to develop magma moves freely through the volcano from a deep source to the eruptive site at a constant rate of 0 09 km3 yr at other times the magma supply rate to kilauea estimated from geodetic measurements of surface displacements may be different for example after a large withdrawal of magma from the summit reservoir such as during a rift zone eruption the magma supply rate is high initially but then lessens and exponentially decays as the reservoir refills different episodes of refilling may have different average rates of magma supply during four year long episodes in the 1960s the annual rate of refilling varied from 0 02 to 0 18 km3 yr bracketing the sustained eruptive rate of 0 09 km3 yr for decade long or longer periods our estimate of magma supply rate is based on long term changes in eruptive rate we use eruptive rate because after a few dozen eruptions the volume of magma that passes through the summit reservoir is much larger than the net change of volume of magma stored within kilauea the low eruptive rate of 0 009 km3 yr between 1840 and 1950 compared to an average eruptive rate of 0 05 km3 yr since 1950 suggests that the magma supply rate was lower between 1840 and 1950 than it has been since 1950 an obvious difference in activity before and since 1950 was the frequency of rift zone eruptions eight rift zone eruptions occurred between 1840 and 1950 but more than 20 rift zone eruptions have occurred since 1950 the frequency of rift zone eruptions influences magma supply rate by suddenly lowering pressure of the summit magma reservoir which feeds magma to rift zone eruptions a temporary drop of reservoir pressure means a larger than normal pressure difference between the reservoir and a deeper source so magma is forced to move upward into kilauea at a faster rate

a stagnation point flow model for melt extraction from a mantle plume we present a two dimensional dynamical model for melt extraction from a mantle plume mantle material rises at constant velocity wo until it reaches a depth at which melting begins the flow in the melt zone above this depth has the form of a stagnation point flow melt migrates through the unmelted matrix in response to the total nonhydrostatic pressure gradient which is the sum of contributions from the deformation of the matrix and the buoyancy of the melt melt extraction is modeled as a melt flux through the upper surface of the melt zone our main conclusions are as follows 1 the nonhydrostatic pressure gradient associated with the deformation of the matrix is small relative to the buoyancy of the melt everywhere within the melt zone and the melt migration within the plume obeys darcy s law the rate of melt extraction from a mantle plume is therefore controlled by the buoyancy and viscosity of the melt itself and not by the viscosity of the matrix 2 melt extraction from a plume occurs over an area comparable to that of the plume itself and about 60 80 of the melt generated within the plume is extracted both the geometry and rate of extraction predicted by the model are consistent with observations in the hawaiian islands 3 layers of segregated melt magma chambers are likely to form at the the base of the lithosphere under intraplate volcanoes

volumetric characteristics of lava flows from interferometric radar and multispectral satellite data the 1995 fernandina and 1998 cerro azul eruptions in the western galapagos we have used a suite of remotely sensed data numerical lava flow modeling and field observations to determine quantitative characteristics of the 1995 fernandina and 1998 cerro azul eruptions in the western galapagos islands flank lava flow areas volumes instantaneous effusion rates and average effusion rates were all determined for these two eruptions for which only limited syn eruptive field observations are available using data from spot topsar ers 1 and ers 2 we determined that the 1995 fernandina flow covers a subaerial area of 6 5 106 m2 and has a subaerial dense rock equivalent dre volume of 42 106 m3 field observations atsr satellite data and the flowgo numerical model allow us to determine that the effusion rate declined exponentially from a high of 60 200 m3 s 1 during the first few hours to 5 m3 s 1 prior to ceasing after 73 days with a mean effusion rate of 4 16 m3 s 1 integrating the atsr derived exponentially declining effusion rate over the eruption duration produces a total subaerial submarine dre volume of between 27 and 100 106 m3 the range in values being due to differing assumptions about heat loss characteristics only values in the higher part of this range are consistent with the independently derived subaerial volume using spot topsar ers 1 and ers 2 data we determine that the 1998 cerro azul flow is 16 km long covers 16 km2 and has a dre volume of 54 106 m3 flowgo produces at vent velocity and effusion rate values of 11 m s 1 and 600 m3 s 1 respectively the velocity value agrees well with the 12 m s 1 estimated in the field the mean effusion rate total dre volume duration was 7 47 m3 s 1 dike dimensions fissure lengths and pressure gradients along the conduit based on magma chamber depth estimates of 3 5 km produce mean effusion rates for the two eruptions that range over nearly four orders of magnitude the range being due to uncertainty in the magma viscosity dike dimensions and pressure gradient between magma chamber and vent although somewhat consistent with mean effusion rates from other techniques their wide range makes them less useful the exponentially declining effusion rates during both eruptions are consistent with release of elastic strain being the driving mechanism of the eruptions our results provide independent input parameters for previously published theoretical relationships between magma chamber pressurization and eruption rates that constrain chamber volumes and increases in volume prior to eruption as well as time constants of exponential decay during the eruption the results and theoretical relationships combine to indicate that at both volcanoes probably 25 30 of the volumetric increase in the magma chamber erupted as lava onto the surface in both eruptions the lava flow volumes are less than 1 of the magma chamber volume

new k ar ages for calculating end of shield extrusion rates at west maui volcano hawaiian island chain thirty seven new k ar ages from west maui volcano hawai i are used to define the waning stages of shield growth and a brief episode of postshield volcanism all but two samples from shield stage strata have reversed polarity magnetization so conceivably the exposed shield is not much older than the olduvai normal polarity subchron or about 1 8 ma the oldest ages obtained are in the range 1 9 2 1 ma but have large analytical error shield volcanism ended about 1 35 ma and postshield volcanism followed soon thereafter persisting until about 1 2 ma exposed shield stage strata were emplaced at a rate of about 0 001 km3 per year a rate smaller than historic hawaiian magmatic rates by a factor of 100 stratigraphic accumulation rates are similar to those measured previously at wai anae volcano o ahu or the upper part of the mauna kea shield sequence hilo drill core hawai i these rates diminish sharply during the final 0 3 0 5 m y of the shield stage hawaiian shield volcanoes begin waning well before their last 0 5 m y of life then end quickly geologically speaking if west maui is representative

measurements of sheet flow transport in acceleration skewed oscillatory flow and comparison with practical formulations near bed oscillatory flows with acceleration skewness are characteristic of steep and breaking waves in shallow water in order to isolate the effects of acceleration skewness on sheet flow sand transport new experiments are carried out in the aberdeen oscillatory flow tunnel the experiments have produced a dataset of net transport rates for full scale oscillatory flows with varying degrees of acceleration skewness and three sand sizes the new data confirm previous research that net transport in acceleration skewed flow is non zero is always in the direction of the largest acceleration and increases with increasing acceleration skewness large transport rates for the fine sand conditions suggest that phase lag effects play an important role in augmenting positive net transport a comparison of the new experimental data with a number of practical sand transport formulations that incorporate acceleration skewness shows that none of the formulations performs well in predicting the measured net transport rates for both the fine and the coarser sands the new experimental data can be used to further develop practical sand transport formulations to better account for acceleration skewness

estimating lava volume by precision combination of multiple baseline spaceborne and airborne interferometric synthetic aperture radar the 1997 eruption of okmok volcano alaska interferometric synthetic aperture radar insar techniques are used to calculate the volume of extrusion at okmok volcano alaska by constructing precise digital elevation models dems that represent volcano topography before and after the 1997 eruption the posteruption dem is generated using airborne topographic synthetic aperture radar topsar data where a three dimensional affine transformation is used to account for the misalignments between different dem patches the preeruption dem is produced using repeat pass european remote sensing satellite data multiple interferograms are combined to reduce errors due to atmospheric variations and deformation rates are estimated independently and removed from the interferograms used for dem generation the extrusive flow volume associated with the 1997 eruption of okmok volcano is 0 154 spl plusmn 0 025 km sup 3 the thickest portion is approximately 50 m although field measurements of the flow margin s height do not exceed 20 m the in situ measurements at lava edges are not representative of the total thickness and precise dem data are absolutely essential to calculate eruption volume based on lava thickness estimations this study is an example that demonstrates how insar will play a significant role in studying volcanoes in remote areas

suspended sediment concentrations under waves abstract a predictive formula is derived for calculation of the magnitude of time averaged suspended sediment concentrations under waves by taking into account the effect of flow contraction near ripple crests the formula applies equally well for rippled beds and sheet flow conditions the formula is in qualitative agreement with the bed load flux formula of madsen and grant 1976

a two dimensional seismic investigation of crustal structure under the hawaiian islands near oahu and kauai two expanding spread profiles esps were analyzed in detail to investigate the deep structure of the volcanoes and the underlying oceanic crust near oahu one esp was located on the southeastern submarine flank of kauai esp 10 and the other was located directly over the ridge axis between oahu and molokai esp 5 two dimensional models of the entire crust were obtained by iterative comparison of both travel times and relative amplitudes of arrivals on the ray theoretical synthetic seismograms with those in the data a 2 4 km vertical offset in the preexisting crust inferred to be a large fault zone was found near the midpoint of esp 10 this fault may form the southern wall of a graben or half graben in which kauai sits the layering and seismic velocities of the preexisting oceanic crust near kauai have remained unmodified by the load of the volcanic pile esp 5 is located over a shallow 4 km thick basin filled with volcaniclastics and possibly volcanic flows bordered by the islands of oahu and molokai penguin bank and two buried rift zones under this basin the main volcanic edifice is 4 to 5 km thick the top of the preexisting oceanic crust is 8 to 9 km below sea level and is 3 to 4 km lower than the crust away from the islands the underlying oceanic crust is 6 to 7 km thick excluding the moho transition zone which is of normal thickness and at a depth from 15 to 16 km the existence of a large subcrustal plutonic body is refuted

laboratory investigations into the threshold of movement of natural sand sized sediments under unidirectional oscillatory and combined flows the threshold of movement of sediment obtained from sandbanks within the bristol channel uk is investigated under unidirectional oscillatory and combined flows the experiments were undertaken in a recirculating unidirectional laboratory flume containing an oscillating plate to simulate wave action with movement along the same axis as the unidirectional flows the sand samples consisted of cohesionless quartz grains with median grain sizes between 0 315 and 0 513 mm the experiments were performed under flow velocities measured at 2 cm above the bed ranging between 0 and 24 cm s 1 and oscillatory currents wave periods of 5 12 and 15 s ranging from 0 to 28 cm s 1 the critical conditions for the initiation of sediment movement were assessed by visual observation using the yalin criterion the results show that under unidirectional flow there is a slight overestimation of the threshold of naturally graded sediments derived on the basis of empirically derived threshold curves for artificially prepared sediments under similar flow conditions in the case of oscillatory flows the threshold for the natural sands is found to be higher than that predicted by previously derived empirical curves under combined flows wave period is shown to control threshold conditions with the unidirectional and oscillatory flow components combining in a linear fashion for long period 12 s and 15 s waves in contrast in the presence of short period 5 s waves the unidirectional and oscillatory components of the flow appear to decouple for high orbital velocities in both cases the effect of the wave period on threshold diminishes

dynamically supported geoid highs over hotspots observation and theory hotspots are associated with long wavelength geoid highs an association that is even stronger when the geoid highs associated with subduction zones are removed we quantify these associations by expanding the hotspot distribution in spherical harmonics and calculating correlation coefficients as a function of harmonic degree the hotspot distribution spectrum is nearly white except for peaks at degrees 2 and 6 it is correlated positively with the slab residual geoid for degrees 2 6 with low seismic velocity in the lower mantle at degree 2 and with low seismic velocity in the upper mantle at degree 6 we test fluid mechanical models for hotspots including lithospheric delamination and hot plumes by calculating their predicted dynamic geoid responses and comparing them to the observations these models include the effects of temperature dependent rheology our preferred hotspot model based on observations of the geoid and seismic tomography has plumes preferentially occurring in regions of large scale background temperature highs in a mantle which has a substantial viscosity increase with depth although other models are possible alternatively strong plumes in the lower mantle may neck down and attenuate in the upper mantle due to changes in plume viscosity the major low density anomalies causing the geoid highs associated with plumes appear to be in the lower mantle we hypothesize that cold lower mantle underlying the complementary geoid lows is due to deeply subducted oceanic lithosphere and that hotspot plumes tend to be excluded from these cold regions of the mantle

monitoring of subsidence and induced seismicity in the lacq gas field france the consequences on gas production and field operation abstract between 1957 when the lacq gas field was first put into production and 1967 2 5 cm of subsidence occurred this corresponded to a period in which the pressure had been depleted by 30 mpa further depletion from 1967 until 1989 of 25 mpa induced an additional subsidence of 3 0 cm which coincided with more than 1000 earthquakes 44 with magnitudes greater than 3 and 4 with magnitudes greater than 4 the strain energy release rate by seismic events increased for the period 1969 1979 and now decreases yearly the method used for processing and interpreting the seismological data takes into account the lithologies and the mechanical properties of the rocks and the source parameters the regional mechanism of the gas field deformation appears to be the lowering of a rigid block located at the top of the structure by a succession of movements along pre existing fractures and faults in the reverse direction to the original from spectrum analysis of seismic recordings the amplitude of the fault slips has been calulated to be of the order of millimetres this may be the reason why there has been no damage to the wells the radii of the sources may give an indication about the size of the blocks to be considered in the reservoir engineering models in spite of the obvious non elastic behaviour of the seismic events the regional response of the rock mass is an elastic one the rock mass can be modeled as a block assembly with localized movements between some blocks being responsible for the induced seismicity the size of the induced events is therefore limited by the pre existing fractures close monitoring of subsidence and seismic events is a new and useful aid to understanding the reservoir response to fluid withdrawal the practical consequences with regard to safety and gas production and a contribution to our knowledge of reservoir behaviour over the course of time

sediment flux based model of instantaneous sediment transport due to pure velocity skewed oscillatory sheet flow with boundary layer stream abstract velocity skewed oscillatory sheet flow transport is studied by an approximate model for instantaneous sediment transport resulting from exponential profiles of sediment concentration and velocity over a mobile bed the phase lag effect and asymmetry in wave friction factor oscillatory flow orbital amplitude roughness height bed shear stress and wave boundary layer thickness are modelled so that the net boundary layer stream of pure velocity skewed oscillatory flow can be obtained the proposed model is found consistent with the previous classical formulas and qualitatively refines a series of exponents of velocity power function for the approximation of instantaneous sediment transport rate under different flow conditions the sediment fluxes can be well predicted with accuracy as that of a two phase numerical model the net boundary layer stream and sediment transport rates are also well predicted especially the negative net stream and rates with large phase residual the phase residual is shown a useful but insufficient factor in the net sediment transport in pure velocity skewed flows in addition the net boundary layer stream resulting from velocity skewed wave boundary layer development difference between onshore and offshore flow durations is an essential factor as well

analysis of surface deformation data kilauea volcano hawaii october 1966 to september 1970 a least squares inversion technique has been applied to surface displacement measurements made at kilauea volcano hawaii in an attempt to locate centers of intrusive activity utilizing analytic expressions for the displacement field arising from dilatational sources in an elastic half space this technique allows for the simultaneous inversion of level tilt and horizontal distance measurements in terms of the location and volume of the intrusive body a variety of simple elastic model geometries representing possible shapes for intrusive bodies in the summit region of kilauea were examined none of the model geometries considered significantly improved the quality of the model fit to the available data over that obtained by a point source model calculations based on elastic models to consecutive level surveys were compared to available tilt data and horizontal distance measurements these comparisons indicate occasional departures from ideal elastic behavior the departure of measured tilt patterns from calculated tilt values may be the result of earthquake activity or episodic block movements superimposed on larger elastic displacements the departure of measured and calculated horizontal measurements reveals a gradual north south extensional strain across the summit caldera of kilauea in addition to the elastic uplift and subsidence patterns determined from level surveys a minimum estimate for the magma supply rate to kilauea is provided by the elastic models to the level data the average rate for the period from october 1966 to september 1970 was 0 07 km3 per year

geomorphological reconstruction and morphometric modelling applied to past volcanism accurate and precise morphometric modelling can be extended to past eruptions after a careful palaeogeomorphological reconstruction of volcanic landforms in an oceanic island this reconstruction was used to derive the pre post eruption and present day digital elevation models dem the correct pixel size interpolation method and quality of these dems are discussed the process in a geographical information system framework of the geological information of cone lava flow and tephra fall deposits together and the aforementioned dems allowed the determination of main morphological features of these volcanic landforms and their derivatives the calibration and validation of morphometric modelling were performed on simulated volcanic landforms and verified by a case study a typical holocene monogenetic basaltic eruption at gran canaria island spain

vertical deformation monitoring at axial seamount since its 1998 eruption using deep sea pressure sensors pressure measurements made on the seafloor at depths between 1500 and 1700 m at axial seamount an active submarine volcano on the juan de fuca ridge in the northeast pacific ocean show evidence that it has been inflating since its 1998 eruption data from continuously recording bottom pressure sensors at the center of axial s caldera suggest that the rate of inflation was highest in the months right after the eruption 20 cm month and has since declined to a steady rate of 15 cm year independent campaign style pressure measurements made each year since 2000 at an array of seafloor benchmarks with a mobile pressure recorder mounted on a remotely operated vehicle also indicate uplift is occurring in the caldera at a rate up to 22f1 3 cm year relative to a point outside the caldera the repeatability of the campaign style pressure measurements progressively improved each year from f15 cm in 2000 to f0 9 cm in 2004 as errors were eliminated and the technique was refined assuming that the uplift has been continuous since the 1998 eruption these observations suggest that the center of the caldera has re inflated about 1 5f0 1 m thus recovering almost 50 of the 3 2 m of subsidence that was measured during the 1998 eruption this rate of inflation can be used to calculate a magma supply rate of 1410 6 m 3 year if this rate of inflation continues it also suggests a recurrence interval of 16 years between eruptions at axial assuming that it will be ready to erupt again when it has re inflated to 1998 levels d 2005 elsevier b v all rights reserved

an increment of volcano collapse kinematics of the 1975 kalapana hawaii earthquake abstract earthquakes on kilauea volcano can be even more hazardous than volcanic eruptions the most recent large earthquake was the 1975 kalapana quake which generated a locally damaging tsunami over 8 m of horizontal surface displacement and 3 m of subsidence at the coast the seismic magnitude estimates for this earthquake range from ms 7 2 to mw 7 7 the complexity of the seismic data is matched by the complex surface deformation that was observed with a combination of leveling tilt and electronic distance measurements edm the geodetic data shows evidence of collapse of the caldera due to magma withdrawal localized subsidence over the rift zone normal faulting associated with shallow slumping along the hilina pali and displacement on the basal detachment fault we model the summit caldera rift zones and basal detachment fault as dislocations in an elastic half space to better quantify the sources of deformation related to this devastating event using inversion techniques that allow us to let the data constrain the geometry and magnitude of these sources we find 0 04 km3 of magma withdrawal at the summit between 3 5 m of opening along the rift zone and 7 1 m of slip along the basal detachment at 8 3 km depth models that allow for finer spatial resolution of slip on the detachment show that the largest slip occurred west of the seismically recorded earthquake hypocenter along the region of the fault below the coast and that the majority of the fault slip occurred south of the region of microseismicity our best fitting model has a geodetic moment of 4 1 1020 nm mw 7 7 which is consistent with tsunami models and recent analysis of long period seismic data the residual displacements of sites located in the hanging wall of the hilina pali slump system which were not used in the inversion of the other sources suggest that triggered shallow slumping contributed several meters of horizontal displacement to the coseismic displacement at these sites

flow tunnel measurements of velocities and sand flux in oscillatory sheet flow for well sorted and graded sands oscillatory flow tunnel measurements of velocities and fluxes for sands in oscillatory sheet flow conditions are presented the experiments involved a range of well sorted and graded sands in two asymmetric flows velocities were measured using an ultrasonic velocity profiler uvp capable of measuring deep within the sheet flow layer velocity profiles are found to be similar for the same flow but different sand beds and display expected features of oscillatory boundary layer flow the near bed velocity leads the main flow velocity by approximately 21 and a small offshore directed current is generated near the bed measures of the boundary layer thickness are in good agreement with those predicted using an equation formulated for the boundary layer thickness over fixed beds velocity data have been combined with concentration data to produce time dependent sand flux profiles covering the sheet flow and suspension regions there are fundamental differences in the transport processes of sands of different size and grading caused by unsteady effects which dominate in the case of fine sand and are largely absent in the case of coarse sand 1 time averaged flux is onshore directed positive in the case of coarse sand and is confined to a region immediately above the bed in contrast time averaged flux in the case of fine sand extends high above the bed is offshore directed negative in the sheet flow layer and becomes onshore directed in the suspension layer 2 net transport in the case of coarse sand is directed onshore as the percentage of fine sand in the bed increases offshore transport becomes increasingly dominant as the percentage of fine sand increases 3 net transport in the suspension layer is onshore while net transport in the sheet flow layer may be onshore or offshore depending on sand size and grading

hawaiian xenolith populations magma supply rates and development of magma chambers hawaiian volcanoes pass through a sequence of four eruptive stages characterized by distinct lava types magma supply rates and xenolith populations magma supply rates are low in the earliest and two latest alkalic stages and high in the tholeiitic second stage magma storage reservoirs develop at shallow and intermediate depths as the magma supply rate increases during the earliest stage magma in these reservoirs solidifies as the supply rate declines during the alkalic third stage these magma storage reservoirs function as hydraulic filters and remove dense xenoliths that the ascending magma has entrained during the earliest and latest stages no magma storage zone exists and mantle xenoliths of lherzolite are carried to the surface in primitive alkalic lava during the tholeiitic second stage magma storage reservoirs develop and persist both at the base of the ocean crust and 3 7 km below the caldera only xenoliths of shallow origin are carried to the surface by differentiated lava during the alkalic third stage magma in the shallow subcaldera reservoir solidifies and crustal xenoliths including oceanic crustal rocks are carried to the surface in lava that fractionates in an intermediate depth reservoir worldwide xenolith populations in tholeiitic and alkalic lava may reflect the presence or absence of subvolcanic magma storage reservoirs

movable bed roughness in unsteady oscillatory flow a model to predict the roughness in unsteady oscillatory flows over movable noncohesive beds is presented the roughness over movable beds is shown to be a function of the boundary shear stress rather than a fixed geometrical scale as is the case for fully rough turbulent boundary shear flows over immobile beds the model partitions the roughness into two distinct contributions these two contributions are due to the form drag around individual bed forms and to the near bed sediment transport the form drag over the bed forms is treated explicitly as a function of the boundary geometry and shear stress the ripples are predicted as a function of the local skin friction and a semiempirical expression is derived using standard law of the wall arguments which gives the ripple or form roughness as a function of the boundary geometry the ripple roughness is found to be proportional to the product of the ripple steepness and height favorable comparison of the form drag model with the results of bagnold s 1946 fixed ripple study is found the value of z0 associated with intense sediment transport in oscillatory flow over a flat bed is determined from carstens et al s 1969 experiments this value is found to be 7 or 8 grain diameters an expression is derived for the roughness associated with the maximum thickness of a near bottom sediment transporting layer consistent with owen s 1964 roughness hypothesis for saltation of uniform grains in air at large values of the boundary shear stress relative to the critical value for initial sediment motion the derived expression is similar to the results of smith and mclean s 1977 unidirectional flow approach modified for oscillatory flow the total roughness model is found to compare favorably with carstens et al s 1969 data in contrast to smith and mclean s 1977 steady flow findings the results here show that when ripples are present they account for a significant portion of the boundary roughness

implications of deflation inflation event models on kīlauea volcano hawaiʻi abstract surface deformation of volcanic areas can reveal information about subsurface magma reservoirs and how magma is transported between them which is an important part of volcano monitoring for hazard mitigation one prominent style of deformation observed at k lauea volcano hawai i is episodic deflation inflation di events which are recorded in surface deformation data and characterized by deflation of the summit region over hours to days followed by rapid re inflation the exact cause of di events is unknown however a commonly proposed explanation is that a temporary blockage occurs in the conduit connecting the south caldera magma reservoir to the shallower halema uma u reservoir thus interrupting the influx of magma this model is investigated by testing the hypothesis that during the deflationary phase of a di event the volume of magma blocked from reaching the halema uma u reservoir is added to the south caldera reservoir using a mass balance approach and deformation modeling the expected deformation tilt pattern was predicted for the reservoirs and compared to tilt observations from 16 large 4 rad magnitude di events between 2010 and 2012 while the predicted tilts due to inflation from the south caldera reservoir are strong enough to be detected this signal is not seen in the tilt observations we also explore the possibility that the blockage occurs below the south caldera reservoir as well as alternative configurations that include a direct connection between the south caldera reservoir and the eruption site none of the simple two reservoir models we test are able to adequately satisfy the observations selected di events show that tilt vectors change in both magnitude and azimuthal direction over the course of deflation we conclude that the portion of the summit storage and plumbing system active during these di events is more complicated than two connected chambers and that it is more likely that these summit reservoirs have their own source conduits connecting in some complex way to the deep magma source

explicit approximation for velocity and sediment flux above mobile sediment bed beneath current and asymmetric wave abstract an explicit approximation is proposed for velocity distribution and sediment flux above mobile sediment bed beneath current and asymmetric wave the predicted velocity is decomposed into an oscillatory part and a current part such that the interaction between current and asymmetric wave can be performed directly the oscillatory part consists of a free stream velocity and a defect function which includes phase lead mobile sediment bed level and wave boundary layer thickness the oscillatory part is influenced by the current due to the changes of both mobile sediment bed level and wave boundary layer thickness the current part is influenced by a wave eddy viscosity in the wave boundary layer and by an apparent wave roughness of the combined wave current flow outside the wave boundary layer eight free variables are required for the approximation and iterative bottom shear stress and roughness height are applied for the wave boundary layer thickness and mobile sediment bed level the mobile sediment bed level takes account of the effects of phase lag phase shift and residual acceleration and flow asymmetry therefore the mobile bed effect instantaneous velocity net velocity and sediment flux in the wave boundary layer can be reasonably presented by the explicit approximation beneath current and asymmetric wave

constructing the upper crust of the mid atlantic ridge a reinterpretation based on the puna ridge kilauea volcano the volcanic morphology of a number of segments of the slow spreading mid atlantic ridge mar have been reinterpreted based on our understanding of dike emplacement dike propagation and eruption at the east rift zone of kilauea volcano hawaii and its submarine extension the puna ridge the styles of volcanic eruption at the submarine puna ridge are remarkably similar to those of the axial volcanic ridges avrs constructed on the median valley floor of the mar we use this observation to relate volcanic processes occurring at kilauea volcano to the mar we now consider that volcanic features e g seamounts and lava terraces built on the flanks of the avrs are secondary features that are fed from lava tubes or channels not primary features fed directly from an underlying dike we examine simple models of pipe flow and conclude that lava tubes can transport lava down the flanks of submarine rifts to build all of the volcanic features observed there in addition deep water lava tubes are strong enough to withstand the pressures of a few megapascals that the building of a volcanic structure 150 m high at the end of the tube would generate the volumes of individual volcanic terraces and seamounts on the puna ridge and at the mar are large 0 1 1 km3 and similar to the volumes of lava flows that are broadly distributed at the subaerial east rift zone of kilauea this striking difference in the volcanic morphology on a scale of 1 2 km producing terraces and seamounts underwater and low relief flows on land must be related to the enhanced cooling and to the greater mechanical stability of tubes in the submarine environment we suggest that at the mar a crustal magma reservoir most likely located beneath shallow flat sections of the segment provides magma to the rift axis through dikes that propagate laterally tens of kilometers the zone of dike intrusion at least in the neighborhood of the magma body is likely narrower than the width resurfaced by flows yielding a crustal structure that has a rapid vertical transition from lavas to sheeted dikes at segment ends the zone of dike intrusion is likely to be wider giving a resulting structure with a more gradual transition from lavas to dikes

monitoring an effusive eruption at piton de la fournaise using radar and thermal infrared remote sensing data insights into the october 2010 eruption and its lava flows