improved m 2 ocean tide from topex poseidon and geosat altimetry topex poseidon t p collinear differences have been used to extract errors in the m2 tide model of cartwright and ray 1991 the fluctuation of the power of these differences clearly shows the need for corrections at a period of about 60 days close to the aliased periods of the m2 and s2 tides the level of the necessary changes at this period is about 4 cm rms further detailed analysis of collinear differences in 4 4 bins allowing for determination of up to 6 luni solar and ocean weather tides annual and semiannual shows that the m2 corrections are well discriminated from the others and have a global power of 3 5 cm rms both in phase and out of phase components of the corrections have similar broad scale characteristics dominated by a few meridionally oriented bands the t p derived m2 model shows rms deviations of 3 1 cm with data at 80 selected ocean island and bottom gauges compared with 3 9 cm for the cartwright and ray 1991 model a weighted combination of geosat and t p derived models achieves residuals of 2 8 cm rms with this global tide gauge data

donnees sur la structure de l arc insulaire des petites antilles entre ste lucie et anguilla abstract geological and geophysical data were collected during a marine geological cruise arcante 1 carried out in 1977 1978 between st lucia and anguilla corresponding to about two thirds of the length of the lesser antilles archipelago they allow of a reconsideration of the structural framework of this island arc considered as a whole the lesser antilles ridge is characterized by a pattern contrasting sharply between its northern and southern halves the major discontinuity axis runs to the south of the guadeloupe archipelago the basement of the northern half is supposed to be mainly mesozoic and is connected with the evolution of the greater antilles whilst the southern half was generated only since the eocene the ne flanks of the lesser antilles ridge are steep and dissected by large submarine valleys such as the desirade sea trough their recent sedimentary cover post lower miocene is lacking or very poor enabling the outcropping of older formations volcanic mesozoic basement around la desirade upper cretaceous eocene and oligocene sediments conversely the nw flanks are gently sloping and are draped by a rather thick overburden of plio pleistocene deposits to the south the steep sw flanks are covered with a moderate thickness of recent sediments and display characteristics contrasting with those of the se flanks facing the barbados accretionary prism from the south up to martinique there is only one volcanic ridge of eocene to present age to the north of martinique this ridge splits into two axes the submarine landmarks of these two arcs have been disclosed during the present survey the eastern one or outer arc shows a row of seamounts and islands often marked by strong magnetic dien bien phu bank marie galante agouti bank or heavy gravimetric marie galante grande terre anomalies this outer arc was superimposed on the pre eocene basement and is expressed in the eocene and oligocene volcanic terrains cropping out in the islands of antigua st bartholomew st martin and anguilla which rise from the wide northern insular shelves a major ca 70 km interruption in the continuity of this axis takes place between dien bien phu bank and marie galante la desirade and barbuda islands although pertaining to the limestone caribbees are not included in the outer arc the western or inner arc made up of upper miocene to present volcanics begins with dominica island and terminates at luymes bank but an interruption of about 50 km is to be noted between basse terre and montserrat the outer and inner arcs are separated by the narrow ca 50 km and elongated ca 250 km kallinago depression this intra arc trough is generally filled by less than 1 km of recent sediments and is subdivided into three smaller basins it was not initiated by extensional rifting related to back arc spreading as was previously assumed it is possible that from martinique to guadeloupe an intermediate arc was in activity during the miocene data from exploratory oil surveys provide some new insights into the geology and the structure of the wide saba bank located to the west of the inner arc and near the northern end of the archipelago its volcanic substratum is of upper cretaceous paleocene age and is part of the pre eocene basement of the northern lesser antilles the general characteristics of the ne flanks of the lesser antilles ridge may indicate some tilting toward the west of the northern part of the island arc this may be ascribed to the arrival of atlantic fracture zone ridges barracuda and tiburon in the subduction zone during the miocene this event could explain the jump of the volcanic line from the outer to the inner arc

tidal corrections in the topex poseidon geophysical data records the aim of this paper is to give an assessment to topex poseidon data users of the two available oceanic tidal corrections which are based on the schwiderski model sch and the cartwright and ray model cr respectively large instantaneous differences are observed between the two corrections and use of either model may sometimes lead to inadequate understanding of the remaining oceanic signals in this paper we give an objective comparison of sch and cr models and point out the major features of both models our methodology is applicable to the validating and testing of future tide models that will soon be appearing

barotropic tides in the global oceans from a nonlinear tidal model assimilating altimetric tides 1 model description and results in this first part of a two part paper we present results from a high resolution data assimilative fully nonlinear barotropic tidal model of the global oceans that excludes the arctic the model assimilates in waters deeper than 1000 m altimetric tides derived from the analysis of 2 years of topex altimetric data it also assimilates tide gage data from coastal tide gages the model domain includes that covered by the altimeter and extends to the antarctic in the first part we present tidal results for the primary semidiurnal m2 s2 n2 and k2 and diurnal k1 o1 p1 and q1 constituents the second part deals with applications kantha et al this issue the model results are compared with observational data from pelagic gages these comparisons show that overall in the open ocean in deep waters away from the margins of the primary basins the model performance is comparable to other tidal models derived using topex data except for m2 and s2 however one advantage of this model compared with those based solely on the analysis of altimetric data is that the altimetry derived tides are subjected to dynamical constraints by the model this results in reduction of subtidal variability often folded into tidal signals by topex data analysis it is also shown that in shallow waters along the margins especially in east asian marginal seas the model differs substantially from these other models in addition to sea surface heights we also present dynamically consistent barotropic currents in the form of tidal ellipses for m2 and k1 constituents since the goal of this research is a global tidal model uniformly valid in both deep and shallow waters we finally present tidal elevations and currents on two well known shallow water areas the northwest european shelf and the northeast american shelf and a semienclosed western pacific marginal sea the bering sea the model results are compared with independent observations and where possible with results from other numerical models the results highlight the importance of bottom topography on the northwest european shelf where accurate bottom topography was included in the model the results are much better than on the northeast american shelf where the digital bathymetric data base 5 dbdb5 topographic database has significant errors results from the bering sea where the topography is more accurate than the dbdb5 compare well with known tides in the region

ocean tide model obtained from topex poseidon altimetry data tidal corrections are very important for oceanographic study of altimetry because tidal signals contaminate the low frequency part of raw altimetric signals accurate tidal predictions are also necessary for geophysical research such as with the superconducting gravimeter scg which needs to distinguish very weak signals from the overwhelming tidal signals the aim of this paper is to derive accurate global ocean tide models from the topex poseidon sea surface height data of 5 cm accuracy more accurate than any other previous altimeter data topex geophysical data records of cycles 9 94 were processed and analyzed we describe response analysis of tidal waves at crossover points and application of hydrodynamical interpolation the tidal solutions with 0 5 grid system are obtained for eight major constituents i e m2 s2 n2 k2 k1 o1 p1 and q1 and compared with the schwiderski 1980a b c model the cartwright and ray 1991 model and the eight constituent version of the egbert et al 1994 model or tpxo 2 the accuracy of the models is checked using island and bottom tide gauge data in open ocean and using scg data in antarctica and japan

diurnal and semidiurnal variations in the earth s rotation rate induced by oceanic tides recent space geodetic observations have revealed daily and subdaily variations in the earth s rotation rate although spectral analysis suggests that the variations are primarily of tidal origin comparisons to previous theoretical predictions based on various ocean models have been less than satisfactory this disagreement is partly caused by deficiencies in physical modeling rotation predictions based on a reliable tidal height model with corresponding tidal currents inferred from a modified form of laplace s momentum equations yield predictions of tidal variations in universal time that agree with very long baseline interferometer observations to 2 microseconds this agreement resolves a major discrepancy between theory and observation and establishes the dominant role of oceanic tides for inducing variation in the earth s rotation at these frequencies

energy budget of the tidal hydrodynamic model fes94 1 this paper presents a detailed energy budget of the m2 tide over the world ocean based on the hydrodynamic solution fes94 1 the global energy input by the astronomical forcing deduced from the 2 2 spherical harmonics of the m2 fes94 1 solution is 2 35 tw a quarter of this input takes place over the south atlantic ocean this energy is dissipated by bottom friction over the main continental shelves among which 40 over the north atlantic ocean the pacific ocean the indian ocean and the south atlantic ocean receive more energy than they dissipate by contrast the atlantic ocean and the arctic ocean show a large deficit compensated by a net influx of energy coming from the other basins one third of the total m2 energy input by astronomical forcing over the world ocean flows northward through the equatorial atlantic detailed energy dissipation estimates are computed over the different areas of dissipation and compared to the previous estimates

intercomparison of recent ocean tide models one of the tremendous achievements of the topex poseidon t p satellite mission is the release of 12 new global ocean tide models during 1994 virtually all of these models are based on the high precision altimetry obtainable from the t p satellite and all of the models are superior to both the cartwright and ray 1990 1991 model as well as to the schwiderski 1980a b model when compared to tide gauges in the present intercomparison only global ocean tide models released during 1994 have been tested as t p continues to operate new ocean tide models will continue to be released and existing ocean models will be updated hence this intercomparison can only present a snapshot of the state of the art within ocean tide modeling however the intercomparison demonstrates the high accuracy and consistency of all these recent ocean tide models from a comparison with a common 104 tide gauge data set compiled by le provost and others unpublished data the general result is that six of the new ocean tide models have rms agreement better than 3 cm the obtainable accuracy with different tide gauge types raises the question about the accuracy of ground truth as ocean tide models become increasingly more accurate the accuracy of the harmonic constants derived from the tide gauge recordings becomes significant generally the rms agreement between models based on 2 years of t p altimetry is significantly better than the agreement between models based on 1 year of t p altimetry for models based on two years of t p altimetry the rms agreement has values around 2 0 1 4 1 0 and 0 7 cm for the m2 s2 k1 and o1 constituents respectively as a preliminary evaluation these values might be taken as a measure of the consistency of ocean tides estimated from the first part of the t p mission which is extremely promising for future ocean tide models derived from t p altimetry using 3 or more years of data this also suggests that further improvement using 3 or more years of data will only be marginal the differences arise when studying the ocean tides on continental shelves surrounding the ocean major differences are seen especially on the patagonian shelf as the continental shelves are critical for tidal dissipation it will be very important to improve tide models on the shelves in future global ocean tide models

energetics of the m2 barotropic ocean tides an estimate of bottom friction dissipation from a hydrodynamic model abstract the aim of this paper is to present a detailed energy budget of the m2 ocean tides over the world ocean based on the hydrodynamic tidal solution fes94 1 which includes not only the characteristics of the sea surface tidal elevations but also of the tidal currents global and regional budgets are given the global energy input by astronomical forcing deduced from the 2 2 spherical harmonic development of the m2 sea surface elevation solution is 2 35 tw lower by 0 1 tw than for the new altimetric solutions produced recently directly from satellite observations one major feature emerging from the present analysis is that a quarter of this energy input takes place over the south atlantic ocean on the other hand ocean tides work against astronomical forcing over three areas eastern indian ocean southwest of the south american continent and around new zealand this energy is dissipated in fes94 1 by bottom friction over the main continental shelves but the outstanding feature is that 40 of the tidal energy is dissipated over the north atlantic ocean energy is thus redistributed from the areas of energy input to feed the areas of dissipation the pacific ocean the indian ocean and the south atlantic ocean receive more energy in total than they dissipate in contrast with the atlantic ocean and the arctic ocean where a large deficit must be compensated by a net influx of energy from the other basins one third of the total m2 energy input by astronomical forcing over the world ocean flows northwards through the equatorial atlantic detailed energy dissipation estimates are computed over the different areas of energy dissipation and compared to the previous estimates published in the literature

sector collapse at kick em jenny submarine volcano lesser antilles numerical simulation and landslide behaviour kick em jenny volcano is the only known active submarine volcano in the lesser antilles it lies within a horseshoe shaped structure open to the west northwest toward the deep grenada basin a detailed bathymetric survey of the basin slope at kick em jenny and resulting high resolution digital elevation model allowed the identification of a major submarine landslide deposit this deposit is thought to result from a single sector collapse event at kick em jenny and to be linked to the formation of the horseshoe shaped structure we estimated the volume and the leading edge runout of the landslide to be ca 4 4 km3 and 14 km respectively we modelled a sector collapse event of a proto kick em jenny volcano using volcflow a finite difference code based on depth integrated mass and momentum equations our models show that the landslide can be simulated by either a coulomb type rheology with low basal friction angles 5 5 6 5 and a significant internal friction angle above 17 5 or with better results by a bingham rheology with low bingham kinematic viscosity 0 b 30 m2 s and high shear strength 130 180 m2 s2 the models and the short runout distance suggest that the landslide travelled as a stiff cohesive flow affected by minimal granular disaggregation and slumping on a non lubricated surface the main submarine landslide deposit can therefore be considered as a submarine mass slide deposit that behaved like a slump

hydrothermal circulation beneath mount pelee inferred by self potential surveying structural and tectonic implications abstract self potential sp surveys were made on mount pelee volcano martinique island french west indies in 1991 and 1992 in order to recognize its hydrothermal system the associated groundwater channeling and the main superficial structures of the massif almost 70 km of profiles were carried out with an average sample spacing of 50 m measurements essentially reveal negative sp anomalies down to 1700 mv with high gradients 1 83 mv m due to the infiltration of meteoric water into the massif rims of summit calderas morne macouba and etang sec present sharp negative sp anomalies on the western northern and eastern flanks negative sp anomalies indicate no upward water flow beneath mount pelee summit on the southwestern volcano flank a 3 5 6 km horseshoe shaped structure corresponding to a southwest flank collapse event older than 25 000 years bp is clearly identified by the sp mapping high gradients border the inner southern rim from morne calebasse to st pierre town and the caribbean sea along the northern rim of the horseshoe shaped structure the negative sp anomalies give place to a positive sp anomaly up to 200 mv of sw ne trend this zone covers the area of two active hot springs sources chaudes and puits chaud 40 65 c marine magnetic surveys and bathymetry show that the horseshoe shaped structure spreads into the caribbean sea up to about 10 km from the coast buried structural discontinuities are evidenced inside the flank collapse structure the upper one deviates the groundwater flow coming from the summit toward the south flank where the flow finds an indentation to expand again downwards this discontinuity is either an old hypothetical caldera rim partly destroyed by the collapse of the south southwestern flank and covered by recent pyroclastic deposits or more probably the trace of a bulge landslide a circulation model of the hydrothermal waters is proposed rainfall 5 6 m year is partly drained inside the summital calderas and the flank collapse zone through pyroclastic flows down to an impermeable basement there the groundwater constitutes perched aquifers at the contact of the bulge landslide or of the hypothetical old caldera rim along the inner northern border of the flank collapse structure the phreatic water is reheated warm groundwater flows along the northern avalanche structure rim and discharges near the coast in ground and marine outcrops of medium temperature finally the main part of the meteoric water is channeled along the old caldera rim or along the bulge landslide towards the south flank of mount pelee where some gaps in the rim exist there the groundwater finds again a subhorizontal gravitational circulation along mount pelee slopes into the caribbean sea

three layer view of transports and hydraulics in the strait of gibraltar a three dimensional model study 1 the ability of a three dimensional sigma coordinate free surface model to reproduce the interfacial layer between the atlantic and mediterranean waters in the strait of gibraltar is verified the model uses a coastal following curvilinear orthogonal grid that includes the gulf of cadiz and the alboran sea with very high resolution in the strait less than 500 m it is forced by imposing the two major semidiurnal tidal components m2 and s2 along the atlantic and the mediterranean open boundaries the main experiment covers an entire spring neap cycle fortnight period results show that the model is able to reproduce a thick interfacial layer that carries a substantial fraction of the total transport the interfacial thickness is strongly modulated by tidal forcing that enhances the vertical exchanges between layers in order to take into account the thick interfacial layer a three layer approximation is used to study the hydraulics results show that the exchange regime is intermittently maximal due to cyclically controlled regions over camarinal sill and within tarifa narrows the analysis has been repeated in a two layer framework to evaluate the impact of the introduction of an interfacial layer on the calculation of hydraulics in the two layer approximation there is not any controlled region extending on the whole cross section so the exchange is always submaximal concluding the two layer approximation underestimates hydraulic controls in the strait respect to the three layer approach

global charts of ocean tide loading effects global ocean tide loading charts of the radial displacement the potential divided by g gravity acceleration and the gravity effect have been computed using the 11 constituents m2 s2 n2 k2 k1 o1 p1 q1 mf mm ssa of schwiderski s tidal model these new charts have a resolution of 1 1 on the continents as well as on the oceanic area a description of farrell s convolution method to compute the loading effects is given and an estimate of the numerical errors leads to the conclusion that these global charts have a precision better than 2 5 independent of the accuracy of schwiderski s maps the current approximation of the loading effects by a proportionality relation with the local oceanic tides is also compared with farrell s convolution method departures of several centimeters systematically appear in particular over the continental shelves we then show that the maps of the oceanic tides deduced from satellite altimetry could be corrected for the loading effect by an iterative computational procedure based on our algorithm of farrell s convolution

synsedimentary volcanic ash derived illite tonsteins in late permian coal bearing formations of southwestern china abstract illite claystones tonsteins of late permian coal bearing formations are well developed and extensively distributed in southwestern china over the past decades it has been recognized that they are synsedimentary volcanic ash falls in origin altered tuff beds based on the data derived from the comprehensive investigations on their stratigraphic and geographic distribution petrographic types chemical composition accessory mineral assemblage as well as on their morphological characteristics recently mineralogical and petrological identifications and x ray diffraction analyses on these peculiar tonsteins further suggest that they can be classified mainly into three categories based on their clay mineral constitution kaolinitic kaolinitic illitic transitional type and illitic as coal partings in most cases these different types of tonsteins show a distinct zonal distribution on a regional scale their mineral constitution is profoundly modified by the combined effects of many factors during deuterogenic diagenesis as indicated by the variation in volatile component percentage vm of the adjacent coal seams vm is calculated on a combustible component basis those tonsteins intercalated in coal with a vm 10 are dominated by kaolinite but they contain increasing amount of illite at the expense of kaolinite when vm of coal decreases from 10 to 8 when vm declines to less than 8 the clay minerals in these tonsteins are almost entirely illite with some sort of accompanying chloritization it is clear that from a regional point of view the variation in clay mineral constitution of these tonsteins is in response to the continual and progressive change in geological processes in addition to the temperature and pressure conditions the existence of a certain amount of alkali metal ions and ferrous ions in solution is one of the controlling factors

on the choice of orbits for an altimetric satellite to study ocean circulation and tides the choice of an orbit for satellite altimetric studies of the ocean s circulation and tides requires an understanding of the orbital characteristics that influence the accuracy of the satellite s measurements of sea level and the temporal and spatial distribution of the measurements three orbital parameters determine the temporal and spatial sampling characteristics of the satellite the orbital altitude the inclination of the orbit and the repetition period the eccentricity of the chosen orbit should be less than 0 001 to minimize altimeter errors caused by uncertainty in determining the time of each altimeter measurement and to maintain the rate of height variation over the oceans within the limits of the altimeter tracker the choice of the satellite s orbital altitude is constrained by the influences of atmospheric drag and errors in models of the gravity field which decrease with height and the required complexity of the altimeter e g the power and or antenna size required and the effect on satellite systems of radiation from earth s radiation belts which increase with height the choice of inclination is constrained by a desire to measure sea level over all the ocean by the requirement that the acute angle between intersections of the subsatellite track be as large as possible and by the time phasing of the repeat of the satellite s ground track as a function of inclination which determines the aliased frequencies of the measurements of the oceanic tides the choice of repetition period is constrained by tradeoffs between temporal and spatial coverage and by the aliasing of tidal constituents combining the above constraints leads to a set of orbits in a narrow range of altitude and inclination called here the topex poseidon window this window extends from 1100 to 1500 km altitude and 62 to 66 inclination for a 10 day repeat period and consists of three subwindows following lines of equal orbit plane precession there are four choices of orbits within these subwindows that overfly the planned calibration sites at bermuda and dakar these are at 64 80 and 1335 km 62 01 and 1252 km 65 84 and 1255 km and 62 69 and 1173 km these choices have a minimum separation between the aliased frequencies of the eight largest diurnal and semidiurnal tides of one cycle per 4 71 years one cycle per 4 86 years one cycle per 4 87 years and one cycle per 4 27 years respectively thus there will be less than one cycle separation over the nominal 3 years mission of these four choices the first at 64 8 and 1335 km is preferable because it is less sensitive to error in estimating the upcoming solar cycle which will be a maximum during the mission and because it is more nearly centered in terms of inclination than the other choices for other calibration sites other choices would have to be made additional work beyond the scope of this paper will also be necessary to determine if the topex poseidon mission requires a frozen orbit i e an orbit for which there are no long term variations in the eccentricity and argument of perigee of the orbit if a frozen orbit is required then the first and third choices listed above have frozen orbits with an eccentricity that is acceptable for topex poseidon

mineralogy of the pennsylvanian coal seam in the datanhao mine daqingshan coalfield inner mongolia china genetic implications for mineral matter in coal deposited in an intermontane basin abstract this paper deals with the mineral matter in the coal and associated strata from the datanhao mine daqingshan coalfield which is closely located to the previously reported adaohai and hailiushu mines of the same coalfield the coal from the datanhao mine is mainly high ash and low sulfur bituminous the mineral assemblage in the coal is dominated by quartz kaolinite with varying proportions of carbonates calcite ankerite and siderite small proportions of muscovite illite pyrite and anatase the associated non coal claystone samples have similar mineral assemblage except that most non coal samples contains less quartz than the adjacent coal plies although deposited in the same intermontane basin of the orogenic belt the yinshan upland the datanhao coal seam shows different mineralogical characteristics from those of the nearby adaohai and hailiushu mines this may reflect the different sediment source regions during the peat accumulation stage the sediment source for the datanhao coal was probably the ordovician quartz rich sandstone or the sinan quartzite in the surrounding sub uplifts high proportions of quartz in the datanhao coal suggest intense terrigenous input into the paleomire and a short distance from the sediment source region different mineralogical characteristics of the coals from the three mines datanhao hailiushu and adaohai of the daqingshan coalfield are probably due to the different source material in their respective surrounding subuplifts within the intermontane basin kaolinite displaying graupen tabular and vermicular textures and the common presence of quartz in the intra seam non coal bands from the datanhao coal seam indicate that most of these bands are tonsteins altered airborne volcanic ash the original magma is probably high level volatile rich silicic in composition

debris avalanche deposits offshore st vincent west indies impact of flank collapse events on the morphological evolution of the island abstract major scarp features have been previously identified on soufriere volcano st vincent lesser antilles and recently interpreted as flank collapse structures although no associated debris avalanche deposits were recognized new offshore high resolution bathymetry and geophysical data have been collected during the caraval cruise n o l atalante february march 2002 offshore of st vincent recent analysis of these data leads us to identify and characterize a debris avalanche deposit on the western flank of soufriere volcano which extends down to the grenada basin the origin of the submarine deposit by submarine slump or flank collapse event is discussed but data analysis tends support the occurrence of a flank collapse event during the evolution of soufriere volcano the collapse volume has been estimated to about 9 km 3 and the age of the event is less than 50 000 years using marine geophysical constraints the origin of the flank collapse can be related to local causes weakening of the flank by intense hydrothermal alteration magmatic injections increase of the load by accumulation of volcanic products and or to regional causes asymmetry of the arc sea level variations induced by climate change that may have an effect on the stability of the volcano taking into account this event we proposed a model for the evolution of soufriere volcano including a new estimation of the magma production rate the estimation indicates that soufriere volcano is one of the most active volcanoes of the arc a future flank collapse event could have catastrophic consequences for the entire area due to the emplacement of voluminous potentially tsunamigenic debris avalanches

caribbean intra plate deformation paleomagnetic evidence from st barthelemy island for post oligocene rotation in the lesser antilles forearc abstract as subduction zones and their related processes are often studied in 2d or cylindrical 3d sections the dynamic effects of trench curvature and its evolution through time remain under explored whereas temporal variations in trench trend may be estimated through restoring upper plate deformation we investigate the forearc deformation history of the strongly curved northern lesser antilles trench connecting the near orthogonal lesser antilles subduction zone with the motagua cayman transform plate boundary our new paleomagnetic dataset consists of 310 cores from eo oligocene magmatic rocks and limestones from st barthelemy island the limestones yielded a post folding magnetization containing a similar magnetic direction to those stored in magmatic rocks that intrude the folded carbonates both indicating a post oligocene 15 and perhaps up to 25 counterclockwise rotation of the island our results highlight that the present day trench curvature formed progressively during the cenozoic allowing us to discuss different tectonic scenarios explaining ne caribbean plate deformation and to identify key targets for future research on tectonic architecture and the potential present day activity of intra plate deformation that may pose seismic hazards

earth s variable rotation recent improvements in geodetic data and practical meteorology have advanced research on fluctuations in the earth9s rotation theinterpretation of these fluctuations is inextricably linked with studies of the dynamics of the earth moon system and dynamical processes in the liquid metallic core of the earth where the geomagnetic field originates other parts of the earth9s interior and the hydrosphere and atmosphere fluctuations in the length of the day occurring on decadal time scales have implications for the topography of the core mantle boundary and the electrical magnetic and other properties of the core and lower mantle investigations of more rapid fluctuations bear on meteorological studies of interannual seasonal and intraseasonal variations in the general circulation of the atmosphere and the response of the oceans to such variations

ocean tides in the asian semienclosed seas from topex poseidon the eight leading ocean tides m2 s2 n2 k2 k1 o1 p1 and q1 have been mapped in asian semienclosed seas by inverting combined sets of tide gauge harmonic constants and a reduced set of topex poseidon satellite altimeter data the tidal maps are given on a 0 5 0 5 grid with their formal error estimates numerical experiments conducted in the south china sea have shown the inverse solutions to be quite insensitive to changes in the parameters of the a priori covariance functions for both the tidal signals and data residual errors once the various parameters of the inversion scheme are fixed the algorithm is applied to the sea of okhotsk the sea of japan the east china sea including the bo hai and yellow seas and the indonesian seas a set of tide gauge constants not used in our solutions is then used for comparison though these accuracy estimates may be biased because of the uneven stations coverage we conclude that the inversion of only 21 cycles of topex poseidon data leads to solutions with an accuracy comparable to the schwiderski 1980b c semiempirical model and the cartwright and ray 1990 model derived from geosat altimetry

two layer tidal modeling of the yellow and east china seas with application to seasonal variability of the m2 tide 1 the baroclinic response of tide and tidal currents in the yellow and east china seas is investigated using a two layer numerical model seasonal variability in the m2 tide especially the smaller summer amplitudes prevailing along the korea tsushima strait kang et al 1995 is investigated by a series of numerical experiments with varying degrees of stratification specific to winter and summer model results show that the summer amplitudes of the m2 tide around the southwestern tip of the korean peninsula and korea tsusima strait decrease with a peak decrease of about 14 cm off the southwestern tip of the korean peninsula while the summer amplitudes in other coastal regions tend to increase this seasonal variability generally coincides with the observations these models results indicate that seasonal stratification has several noticeable effects on the tides including varying degrees of current shear varying frictional dissipation and varying barotropic energy flux in particular it drives complicated seasonal variability in the m2 tide with a peak amplitude modulation of nearly 5 off the southwestern tip of the korean peninsula the seasonal variation of barotropic m2 energy flux through the eastern entrance of the yellow sea is thought to induce the corresponding variability in the m2 amplitude in the korea tsusima strait with smaller amplitudes found in the summer

the patagonian shelf tides the patagonian shelf tides constitute one of the strongest regimes among the biggest in the world where a significant amount of global tidal energy is dissipated by the effect of bottom friction in this paper the tidal response of the patagonian shelf is described by means of information generated by a numerical model and computations of energy fluxes and dissipation rates are presented since measurements of tidal elevations and currents on the patagonian shelf are scarce and mostly limited to coastal locations the information obtained from the model offers valuable insight in a region where a detailed description was not available particularly in the context of global tidal modelling the tidal regime on the patagonian shelf is dominated by the principal lunar semidiurnal tide m2 with contributions from other semidiurnal diurnal and fourth diurnal constituents this regional study shows that dissipation is highly localized and that the integrated value of the dissipation rate over the model domain constitutes a significant fraction of the estimated global dissipation

determination of the ocean circulation using geosat altimetry a spherical harmonic model of the sea surface topography complete to degree and order 10 and a model of the earth s geopotential field complete to degree and order 50 have been obtained in a simultaneous solution using geosat altimeter data and tracking data from 14 different satellites the sea surface topography model compares well with oceanographic models computed using hydrographic data and ship drift data currently errors in the estimated gravity field model limit the determination of the spherical harmonic coefficients of the general ocean circulation to degrees 10 and lower corresponding to a minimum wavelength of 4 000 km error analysis indicates that the correlation between the geoid and the sea surface topography model is less than 0 2 indicating good separation of the geoid and the sea surface topography at wavelengths of 4 000 km or longer estimates of the scale factor for the significant wave height h sub 1 3 which is used to compute the electromagnetic bias correction and the bias for the geosat altimeter are obtained the estimate of the h sub 1 3 correction is 3 6 plus minus 1 5 and the height bias estimate is zero

numerical modeling of the semidiurnal tidal exchange through the strait of gibraltar 1 a three dimensional sigma coordinate free surface model is used to investigate the semidiurnal tidal exchange through the strait of gibraltar the model makes use of a coastal following curvilinear orthogonal grid that includes the gulf of cadiz and the alboran sea with very high resolution in the strait 500 m a lock exchange initial condition is used the western part of the model domain is filled with atlantic water whereas the eastern part is filled with mediterranean water the model is forced at the open boundaries through the specification of the semidiurnal m2 and s2 tidal surface elevation the model is run over a spring neap cycle fortnightly period and the results are compared with available observed data simulated cotidal maps of the m2 and s2 tidal elevation components are in quantitative and qualitative good agreement with observed data as well as with the simulated major and minor axis of tidal ellipse the model reproduces the generation and the subsequent propagation of internal bores both eastward and westward showing that they are always generated during the fortnightly period however the principal aim of this work is to quantify the effects of tidal forcing on mean quantities entrainment and transport of atlantic and mediterranean water along the strait model results reveal that the contribution of the semidiurnal tidal component m2 to the transport is relevant over camarinal sill whereas it is negligible at the eastern end of the strait model results indicate also that the effect of the semidiurnal tide is to increment the mean transport by about 30 both for the inflow and the outflow

tidal evolution of the northwest european shelf seas from the last glacial maximum to the present 1 two dimensional paleotidal simulations have been undertaken to investigate tidal and tide dependent changes tidal amplitudes tidal current velocities seasonal stratification peak bed stress vectors that have occurred in the nw european shelf seas during the last 20 ka the simulations test the effect of shelf wide isostatic changes of sea level by incorporating results from two different crustal rebound models and the effect of the ocean tide variability by setting open boundary values either fixed to the present state or variable according to the results of a global paleotidal model the use of the different crustal rebound models does not affect the overall changes in tidal patterns but the timing of the changes is sensitive to the local isostatic effects that differ between the models the incorporation of ocean tide changes greatly augments the amplitude of tides and tidal currents in the celtic and malin seas before 10 ka bp and has a large impact on the distribution of seasonally stratified conditions magnitude of peak bed stress vectors and tidal dissipation in the shelf seas the predictions on seasonal stratification are supported by well dated evidence on tidal mixing front migration in the celtic sea additional experiments using the global model suggest that the variability of offshore tides has been caused mainly by changes of eustatic sea level and ice sheet extent in particular a large decrease observed at 10 8 ka bp is attributed to the opening of hudson strait accompanied by the retreat of the laurentide ice sheet

la icp ms u pb dating of carboniferous ash layers in the cantabrian zone n spain stratigraphic implications seven centimetre thick volcanic ash fall layers interbedded within the thick carboniferous successions of the cantabrian zone in northern spain were dated by u pb zircon laser ablation inductively coupled plasma mass spectrometry across an interval ranging from visean to kasimovian thus covering most of the carboniferous period all these ash layers occur in fossiliferous successions allowing us to insert the radiometric data within a well constrained biostratigraphic framework considering the analytical uncertainty the obtained ages match the ages inferred from the conodont biostratigraphy established in the mississippian succession which hosts the oldest two ash layers visean in age and the fusuline and mega and microflora data from the strata hosting the moscovian and kasimovian westphalian stephanian tonsteins the age of a langsettian tonstein along with data provided by several papers stating that in the cantabrian zone langsettian floras were contemporaneous with lowermost moscovian fusulines suggest that langsettian floras could have been younger in spain than in other areas our absolute ages provide new constraints not only for the correlation of the carboniferous successions of the cantabrian zone with time equivalent reference successions in other parts of the world but also for calibrating the carboniferous global chronostratigraphic units based on marine fossils with the west european regional units supplementary material stratigraphic position and biostratigraphic information on the studied ash fall layers analytical methods and geochronological results are available at https doi org 10 6084 m9 figshare c 3768701

coalification history of the stephanian cinera matallana pull apart basin nw spain combining anisotropy of vitrinite reflectance and thermal modelling the stephanian cinera matallana basin of nw spain comprises 1 500 m of alluvial to lacustrine coal bearing sediments which were deposited in a late variscan transtensional transpressional pull apart setting the relationship between coalification pattern and rock deformation was evaluated by measurements of the anisotropy of vitrinite reflectance avr the avr ellipsoids reveal both pre tectonic elements related to the bedding fabric and syn tectonic elements related to folding producing biaxial ellipsoid shapes with the maximum reflectance parallel to fold axes the mean coalification gradient for the stephanian succession is about 0 62 rr km calculations of the mean palaeo geothermal gradient are presented on the basis of three different empirical equations a palaeo geothermal gradient of 85 c km is considered the most realistic with an overburden of about 1 000 m 1 d numerical modelling of the burial history results in two possible scenarios the most preferable involving a palaeo heat flow of 150 mw m2 and an overburden of ca 1 050 m these results indicate that maximum coalification was related to a localised but high palaeo heat flow geothermal gradient the anisotropy of vitrinite reflectance highlights the interactive and transitional nature of sedimentary compaction and rock deformation on the maturation of organic material within strike slip fault zones

the pyroclastic tonsteins of the sabero coalfield north western spain and their relationship to the stratigraphy and structural geology abstract the sabero coalfield comprises a succession of strata of over 2000 m of late barruelian to early stephanian b sensu carmaux age proposals have earlier been made to base the boundary stratotype for the top of the barruelian on a section in the lower half of the sabero succession ten different tonstein bands have been located in the principal coal bearing lithostratigraphic units raposa formation sucesiva formation herrera beds and the unica beds material from over 50 sample locations from both surface outcrops and from underground coal workings has been studied by means of microscope thin sections supported by x ray diffraction spectrometry xrd analysis and whole rock chemical analysis on a small number of selected samples all of the 10 bands occur as kaolinite coal tonstein in which the main constituent is kaolinite both as matrix and as abundant fragmentary crystals and phenocrysts the latter predominantly comprising pseudomorphs after biotite and feldspar graupen and irregular kaolinite masses occur in some cases conserving relict structures of volcanic glass feldspars have been identified in the range anorthite albite potassic feldspars are in general absent quartz occurs as acicular splinters and as form and paraform with magmatic re absorption embayments and glass inclusions tridymite has been identified in two bands other accessory primary constituents include idiomorphic apatite and zircon the composition and petrographical features are entirely consistent with a pyroclastic origin locally some apparently secondary alteration of kaolinite to illite is observed and one band shows a lateral progression from kaolinite tonstein through kaolinite illite tonstein to illite tonstein which is apparently coincident with increased intensity of tectonisation a number of the bands have served as the means of resolving structural and stratigraphic problems in the sabero coalfield in particular the identification of level 31 has permitted the reinterpretation of paquete central one of the traditionally principal areas of coal working previously considered to comprise some five or six seams and now recognised as a series of three or more structural repetitions of two workable seams only the overall thickness interpreted for the herrera beds is correspondingly reduced the relatively common presence of ca plagioclase phenocrysts in some bands suggests a rather more dacitic magmatic origin than for the otherwise closely comparable tonsteins of the massif central of france the sabero tonstein bands are closely similar in character and composition with those known in the cinera matallana coalfield and a similar area of origin is surmised although further stratigraphical and petrological work is required before firm correlations can be achieved

aliased tidal errors in topex poseidon sea surface height data alias periods and wavelengths for the m2 s2 n2 k1 o1 and p1 tidal constituents are calculated for topex poseidon alias wavelengths calculated in previous studies are shown to be in error and a correct method is presented with the exception of the k1 constituent all of these tidal aliases for topex poseidon have periods shorter than 90 days and are unlikely to be confounded with long period sea surface height signals associated with real ocean processes in particular the correspondence between the periods and wavelengths of the m2 alias and annual baroclinic rossby waves that plagued geosat sea surface height data is avoided the potential for aliasing residual tidal errors in smoothed estimates of sea surface height is calculated for the six tidal constituents the potential for aliasing the lunar tidal constituents m2 n2 and o1 fluctuates with latitude and is different for estimates made at the crossovers of ascending and descending ground tracks than for estimates at points midway between crossovers the potential for aliasing the solar tidal constituents s2 k1 and p1 varies smoothly with latitude s2 is strongly aliased for latitudes within 50 degrees of the equator while k1 and p1 are only weakly aliased in that range a weighted least squares method for estimating and removing residual tidal errors from topex poseidon sea surface height data is presented a clear understanding of the nature of aliased tidal error in topex poseidon data aids the unambiguous identification of real propagating sea surface height signals unequivocal evidence of annual period westward propagating waves in the north atlantic is presented

tectonic and sedimentary architecture of the karukera spur a record of the lesser antilles fore arc deformations since the neogene the karukera spur is an easternmost submerged rise of the lesser antilles fore arc in the guadeloupe archipelago culminating about 4000 m above the fore arc basin 150 km west of the deformation front the analysis of 3500 km 2d high resolution multichannel seismic reflection and multibeam bathymetric data and the study of 14 core samples allow for the first time to reconstruct its sedimentary anatomy and tectonic evolution seven seismic units us1 to us7 are evidenced organised into four major depositional sequences separated by erosional surfaces units us1 to us4 thicken to the south southeast on the spur the sedimentary deposits rest upon a deeply eroded metamorphic basement of the caribbean plate as in la desirade island sequence 1 units us1 and us2 remains unknown in its lower part because it does not outcrop its upper part comprises early miocene shallow water carbonates sequence s2 unit us3 only comprises an upper miocene transgressive systems tract deposited into basinal environment it is bounded by major erosional surfaces sb2 and sb3 sequence 3 us4 to us6 is zanclean to pleistocene it is dominantly composed of shallow water reefal deposits sequence 4 corresponds to recent deposits the karukera spur experienced three main extensional episodes with alternations between uplift and subsidence periods uplifts are responsible for emersions and erosions subsidence severely drowned shallow water deposits the first extensional episode led to the formation of horsts and grabens in the basement prior to early miocene deposits the second extensional episode occurred during upper miocene in accordance with data in surrounding islands the third tectonic episode developed since calabrian noticeable is the constant reactivation of n130 n150 n150 n180 and n40 trending faults since early miocene and the neoformation of e w trending faults since calabrian our results suggest that at the latitude of guadeloupean archipelago the lesser antilles subduction zone is an erosional margin because of the successive sweepings of the santa lucia then tiburon ridges

seismicity and seismic gap in the lesser antilles arc and earthquake hazard in guadeloupe summary a seismic study of the lesser antilles arc has been carried out first for the period 1950 1978 for which we can use local seismic networks to draw maps of instrumental seismicity then for the period 1530 1950 for which we have catalogues of felt earthquakes the striking feature of the spatial distribution of foci is the cluster of epicentres in the northern half of the arc all large earthquakes m 7 5 are located north of 14 latitude seismicity cross sections through the arc show a variable dipping subduction zone along the arc the deep seismic zone is steeper in the centre of the arc than on the extremity the time space diagram for historical seismicity and the evidence of a seismic gap at the east of guadeloupe lead us to consider the northern half arc as a likely site for a large earthquake in the near future the seismic slip rate calculated from all major earthquakes since 1530 is of much greater value than that obtained from recent plate tectonic models suggesting that the recurrence rate of earthquakes is more than many hundreds of years with a possible aseismic creep

late quaternary explosive silicic volcanism on st lucia west indies many explosive eruptions of dacitic magmas have occurred on st lucia during the late quaternary these have produced widespread aprons and fans of pumice flow and ash flow deposits radiating around the central highlands with co eruptive air fall and surge layers interbedded with palaeosols and epiclastic deposits vents in the highlands have not been located because of the dense tropical jungle but we suspect they are now plugged by lava domes surrounded by aprons of block and ash flow deposits young magmatically related dacitic lava domes have been extruded in the qualibou depression the pumice succession can be divided into older quartz poor deposits forming the choiseul pumice and younger crystal rich deposits with abundant large quartz which are called the belfond pumice the choiseul pumice groups together scattered remnants of the products of many eruptions of different low silica dacitic magma types the belfond pumice is the product of several eruptions of a high silica magma type and 14 c ages have dated these between 20900 to 34200 years b p the pumice flow deposits occur as small volume valley fills a granulometric study of belfond pumice flow deposits shows them to be strongly depleted in finer ash and vitric components it is suggested that the narrow winding and vegetated valleys on the island locally induced turbulence and the flows moved with large highly fluidized and inflated heads resulting in substantial loss of fine vitric ash one ash flow deposit which is extremely rich in crystals and carbonized vegetation is highly depleted in fines and shows enhanced vitric losses this flow may have been a much more violent ash hurricane or blast which surmounted topography ingesting large amounts of lush vegetation ignition of this released the large quantities of gas needed to elutriate most of the fines a model is suggested for the recent volcanic activity on st lucia in which separate batches of silicic magma each having a distinctive petrological and chemical character rose into high level chambers over a large area eruptions of volatile rich magma led to highly explosive pumice forming activity from vents in the central highlands degassed and more crystal rich magma was extruded later from the same vents or in the attenuated flank of the qualibou depression to from lava dome complexes

determination of ocean tides from the first year of topex poseidon altimeter measurements an improved geocentric global ocean tide model has been determined using 1 year of topex poseidon altimeter measurements to provide corrections to the cartwright and ray 1991 model cr91 the corrections were determined on a 3 3 grid using both the harmonic analysis method and the response method the two approaches produce similar solutions the effect on the tide solution of simultaneously adjusting radial orbit correction parameters using altimeter measurements was examined four semidiurnal n2 m2 s2 and k2 four diurnal q1 o1 p1 and k1 and three long period ssa mm and m constituents along with the variation at the annual frequency were included in the harmonic analysis solution the observed annual variation represents the first global measurement describing accurate seasonal changes of the ocean during an el nino year the corrections to the m2 constituent have an rms of 3 6 cm and display a clear banding pattern with regional highs and lows reaching 8 cm the improved tide model reduces the weighted altimeter crossover residual from 9 8 cm rms when the cr91 tide model is used to 8 2 cm rms comparison of the improved model to pelagic tidal constants determined from 80 tide gauges gives rms differences of 2 7 cm for m2 and 1 7 cm for k1 comparable values when the cr91 model is used are 3 9 cm and 2 0 cm respectively examination of topex poseidon sea level anomaly variations using the new tide model further confirms that the tide model has been improved

barotropic tides in the global oceans from a nonlinear tidal model assimilating altimetric tides 2 altimetric and geophysical implications in this second part we explore the implications of the tides derived from the high resolution data assimilative nonlinear barotropic global ocean tidal model described by kantha this issue in altimetric analysis and geophysical applications it is shown that when applied to the task of removing tidal sea surface height from topex altimetric records the model performance is comparable to other global tidal models in the open ocean as measured by the reduction in crossover variances the performance is slightly better than that of the only other high resolution global tidal model from grenoble le provost et al 1994 the results are however mixed in regions shallower than 1000 m and in semienclosed seas such as the bering sea with the model performance slightly worse overall than the grenoble model computations of total power input and hence total tidal dissipation rate are shown to be in excellent agreement with recent analyses of topex data and geophysical observations in addition distributions of the tidal power input tidal dissipation and the power fluxes in the global oceans are shown for the two primary constituents m2 and k1 load tides in solid earth due to ocean tidal loading fluctuations are also computed for the major semidiurnal and diurnal constituents the load tides are shown to be large in the shallow seas adjacent to the coasts with high tides such as the patagonian shelf because of the higher resolution of this global tide model this has potential implications in geophysical applications

petrology and eruption styles of kick em jenny submarine volcano lesser antilles island arc basaltic magmas erupted from the kick em jenny submarine volcano have assimilated amphibole bearing crustal material the mgo content of the basalts ranges from 12 to 4 wt and some of the more evolved members of the suite may have eventually become saturated with amphibole as well as olivine plagioclase clinopyroxene and titanomagnetite major element and trace element compositions are consistent with processes dominated by assimilation fractional crystallization analysis of glassy melt inclusions mgo 2 9 wt in olivine phenocrysts suggests that pre eruption melt water contents may have been as high as 5 wt glass compositions are interpreted to reflect eruption related loss of water submersible observations and dredge sampling of the volcano have revealed two styles of eruption explosive tephra producing eruptions and non explosive dome forming lava eruptions the contrasting styles of eruption are thought to be due principally to the rate and extent of eruption related degassing of 5 wt juvenile h2o although magma interactions with external water may also play a role in explosive eruptions

possible forcing of global temperature by the oceanic tides an approximately decadal periodicity in surface air temperature is discernable in global observations from a d 1855 to 1900 and since a d 1945 but with a periodicity of only about 6 years during the intervening period changes in solar irradiance related to the sunspot cycle have been proposed to account for the former but cannot account for the latter to explain both by a single mechanism we propose that extreme oceanic tides may produce changes in sea surface temperature at repeat periods which alternate between approximately one third and one half of the lunar nodal cycle of 18 6 years these alternations recurring at nearly 90 year intervals reflect varying slight degrees of misalignment and departures from the closest approach of the earth with the moon and sun at times of extreme tide raising forces strong forcing consistent with observed temperature periodicities occurred at 9 year intervals close to perihelion solar perigee for several decades centered on a d 1881 and 1974 but at 6 year intervals for several decades centered on a d 1923 as a physical explanation for tidal forcing of temperature we propose that the dissipation of extreme tides increases vertical mixing of sea water thereby causing episodic cooling near the sea surface if this mechanism correctly explains near decadal temperature periodicities it may also apply to variability in temperature and climate on other times scales even millennial and longer

a new 3d fault model of the bouillante geothermal province combining onshore and offshore structural knowledge french west indies abstract the bouillante area hosts geothermal resources located in a complex structural area guadeloupe island french west indies on one hand faults observed on the field mainly elongate along the e w direction on the other hand offshore structures interpreted from marine seismic lines shows a larger range of directions a coherent 3d interpretation is proposed through a fault model combining onshore and offshore structural knowledge in a zone crossing the island coastline the fault network constructed reveals a hierarchy in the family of structures and highlights the prevalence of the nnw sse direction associated with secondary ne sw trending structures and the e w direction on a geographical point of view the modelled faults are gathered in 3 clusters data available to build the 3d fault model are sometimes sparse especially inland because of intense vegetation cover consequently not only the results and impacts of the 3d fault model are discussed but also its limitations as well as its possible evolution

30 years in the life of an active submarine volcano a time lapse bathymetry study of the kick em jenny volcano lesser antilles effective monitoring is an essential part of identifying and mitigating volcanic hazards in the submarine environment this is more difficult than onshore because observations are typically limited to land based seismic networks and infrequent shipboard surveys since the first recorded eruption in 1939 the kick em jenny kej volcano located 8km off northern grenada has been the source of 13 episodes of t phase signals these distinctive seismic signals often coincident with heightened body wave seismicity are interpreted as extrusive eruptions they have occurred with a recurrence interval of around a decade yet direct confirmation of volcanism has been rare by conducting new bathymetric surveys in 2016 and 2017 and reprocessing 4 legacy datasets spanning 30 years we present a clearer picture of the development of kej through time processed grids with a cell size of 5m and vertical precision on the order of 1 4m allow us to correlate t phase episodes with morphological changes at the volcano s edifice in the time period of observation 7 09x106 m3 of material has been added through constructive volcanism yet 5 times this amount has been lost through landslides limited recent magma production suggests that kej may be susceptible to larger eruptions with longer repeat times than have occurred during the study interval behavior more similar to sub aerial volcanism in the arc than previously thought t phase signals at kej have a varied origin and are unlikely to be solely the result of extrusive submarine eruptions our results confirm the value of repeat swath bathymetry surveys in assessing submarine volcanic hazards

subaqueous intermediate to silicic composition explosive volcanism a review abstract mass flow deposits of pyroclastic debris commonly consist of two parts a lower coarse grained basal section and an upper finer grained bedded section subaqueous pyroclastic flow deposits particularly those derived from a vertically directed eruption appear better sorted than their subaerial counterparts because of the efficient sorting characteristics of water compared to air subaqueous deposits frequently are depleted in bubble wall pumice that floats off and vitric ash that remains in suspension hence the deposits show a relative enrichment of crystals especially at the bases from 1 flotation and suspension of the vitric material and 2 ingestion of water at the head of the flow a subaqueous volcaniclastic flow deposit may contain evidence indicative of both turbulent and non turbulent movement the flow may have had a turbulent head and non turbulent body or flow transformations may have occurred from 1 collapse of the eruption column 2 changes in slope and in the velocity of the flow and or 3 the amount of water mixed into the flow retention of heat in the subaqueous environment may be enhanced by lateral eruptions high eruption rates large eruptive volumes and little or no mixing of pyroclastic debris with water the lack of welded subaqueous deposits in the geologic record may be a result of 1 effusive rather than explosive eruptions in a deep water environment 2 explosive phreatic disintegration of pyroclastic flows in a shallow subaqueous environment and or 3 the inability of subaerial pumiceous pyroclastic flows to penetrate the land water interface characteristics of explosive intermediate to silicic composition subaqueous volcanic eruptions also have been summarized in terms of 1 environment of the eruption 2 orientation of the eruption and 3 composition of the juvenile debris these three aspects of explosive subaqueous volcanism are ideal end members and gradations no doubt occur

a preliminary tidal analysis of topex poseidon altimetry approximately 12 months of data from the topex poseidon satellite altimeter mission are analyzed for the major short period oceanic tides a harmonic analysis is performed on data captured within bins defined on a deep ocean grid which owing to tidal aliasing considerations must have a relatively coarse spatial resolution our analysis is in terms of corrections to the schwiderski and cartwright ray models and it confirms many of the schwiderski differences previously reported by cartwright and ray our differences with respect to the geosat based cartwright and ray model form a sectorial pattern in m2 with high low differences separated roughly 180 in longitude we suggest that these sectorial errors were most likely induced by geosat s relatively large orbit error comparisons to independent data validate the improved topex poseidon solutions in situ ground truth shows m2 rms differences of 4 10cm schwiderski 3 86cm cartwright and ray 2 63cm this paper global rates of energy dissipation confirm earlier estimates for m2 and show improved agreement with satellite tracking studies for k1 and s2 these preliminary exercises confirm that topex poseidon should result in a new generation of improved global tidal models

calderas or gravity slide structures in the lesser antilles island arc abstract large arcuate depressions up to about 10 km in diameter on the back arc side of st lucia dominica and st vincent in the lesser antilles arc are discussed the qualibou depression on st lucia has been previously described as a caldera partly because it was believed to be the source of ignimbrites on the island remapping and stratigraphic studies of these ignimbrites show they were not erupted from the depression but from central vents in the highland rainforests and are much younger dominica is geologically similar and has two scarped depressions at the southern end of the island soufriere volcano st vincent has a prominent arcuate scarp opening to the west the southern half of which has been buried under the youngest volcanic products of the volcano we interpret these structures as the root zones of gravity slides perhaps eruption related and triggered by magmatic inflation post slide activity lava domes and fumaroles has occurred within them due to reduction in lithostatic load and pressure release on the flanks of these island volcanic complexes the presence of these structures only on the western coasts is correlated with the steeper 9 slopes into the grenada basin in contrast to the 1 submarine slopes of the atlantic side

evidence of submarine hydrothermal discharge to the northwest of guadeloupe island lesser antilles island arc abstract during the soviet french survey carried out on board of the r v akademik n strakhov between guadeloupe and montserrat island in the central lesser antilles evidence of submarine hydrothermal activity was discovered on the southeastern tip of the shoe rock escarpment the latter is part of a large 130 km long transverse structure the montserrat marie galante fault which crosses the guadeloupe archipelago another locus of activity probably of subdued importance nowadays is represented by the d entrecasteaux dome a small faulted seamount located about 25 km to the sw of the former area the evidence for hydrothermal activity is a a wide range of values of conductive heat flow q 6 11 mw m 2 and regular vertical variation at some sites with extreme values located close to the two above mentioned features average regional value q 105 mw m 2 s d 32 b occurrence of secondary mineralizations todorokite nontronite etc replacing locally the primary matrix of basal upper pliocene deposits c geochemical anomalies in seawater near the sea bottom showing enrichment in mantle derived 3 he 3 he up to 10 2 correlated with a sharp zn anomaly content up to 523 ppb further investigations along the submerged segments of the montserrat marie galante fault should probably lead to other discoveries of hydrothermal venting and or mineralizations

impact of nonlinear waves on the dissipation of internal tidal energy at a shelf break the vertical and temporal structure of the dissipation of turbulent kinetic energy within the internal tide at a location 5 km shoreward of the shelf break on the malin shelf has been determined using a combination of the free falling light yo yo profiler and acoustic doppler current profilers two distinct internal wave regimes were encountered period i in which large amplitude high frequency nonlinear internal waves niws occurred around neap tides and period ii in which the internal wave spectral continuum was not dominated by any particular frequency band around spring tides empirical orthogonal function analysis shows that for the low frequency waves 76 of the variance was described by mode 1 rising to 95 for the high frequency waves during period i the dissipation and vertical mixing were characterized by the niws and 70 of the dissipation occurred in the bottom boundary layer during period ii the depth integrated dissipation was more evenly distributed throughout the tidal cycle whereas vertical mixing was greatly enhanced during a single hour long episode of elevated thermocline dissipation coincident with weakened stratification during both periods i and ii 30 of the total measured dissipation occurred within the thermocline when averaged over 12 4 hours the remainder occurred within the bottom boundary layer bbl tidal average values for depth integrated dissipation and vertical eddy diffusivity for period i ii were 1 1 10 2 w m 2 4 0 10 2 w m 2 and 5 cm2 s 1 12 cm2 s 1 respectively decay rates and internal damping are discussed and vertical heat fluxes are estimated observed dissipation rates are compared with a simple model for bbl dissipation

energetics and spatio temporal variability of semidiurnal internal tides in the bay of bengal and andaman sea abstract energetics of semidiurnal barotropic and internal tides in the bay of bengal bob and andaman sea as are studied using the simulations from a high resolution ocean general circulation model barotropic m 2 tide which is the largest tidal constituent in this region loses about 65 5 gw of energy in the bob and as most of this barotropic energy 46 5 gw is dissipated by means of bottom friction in the shallow regions such as the head of the bay and the gulf of martaban due to the interaction of barotropic tides with bottom topography about one third of the barotropic m 2 energy 19 1 gw gets converted into internal tides and most of this conversion 84 occurs over the andaman nicobar an ridge on the contrary to the estimates in earlier studies our results show that a large part 59 of this internal tide energy in the bob and as gets dissipated far away from the generation sites compared to the bob energy dissipation rates are found to be large over the entire as and it could result in enhanced vertical mixing in this region further analysis of the temporal variability of conversion within the model domain shows that energy conversion in the semidiurnal band varies between 11 to 27 gw over a spring neap cycle seasonal variability in the stratification due to river runoff significantly changes the conversion of tidal energy at the generation sites in the northern bob and as our study revealed that westward radiating internal tides from an ridge undergo path alteration refraction due to the time varying mesoscale circulation and such path alterations cause large intraseasonal variability in internal tide activity and redistribution of internal tide energy available for mixing in the remote areas such as the continental margins of the western bob

improving ocean tide predictions by using additional semidiurnal constituents from spline interpolation in the frequency domain the improvement in accuracy that can be obtained by increasing the number of constituents in the model at present used for tidal height corrections in the gdrs of satellite altimetric measurements is analysed by referring to the performance of the harmonic method in predicting tides at a selected number of locations in the world where observations of sea level variations are available given the interest in such improvements a way of extending the existing data set is proposed without the need to run a new model of the world s oceans the method relies on the concept of admittance world s oceans maps are derived for five additional constituents and the differences in predicted heights resulting from these improvements are evaluated

m2 ocean tide at cobb seamount from seasat altimeter data seasat altimetry reduced to sea surface heights and harmonically analyzed at the frequencies of the dominant tidal components provides a direct measurement of m2 ocean tide parameters near cobb seamount in the northeast pacific comparison of these altimetric tide parameters with those determined from a bottom pressure gauge located on the summit of cobb seamount shows fair agreement in amplitude 43 cm versus 81 cm and good agreement in greenwich phase angle 243 versus 242 degrees the precision of the altimeter solution is estimated at 8 cm in amplitude and 10 degrees in phase angle

empirical ocean tide models estimated from topex poseidon altimetry three empirical ocean tide models are determined from repeat cycles 10 to 78 of the topex poseidon t p altimeter mission the three models investigate the effects of the satellite orbit ephemeris on the ocean tides determined from t p altimetry and the effect of extracting the free core nutation resonance in the definition of the diurnal ocean tide admittance the altimetric data series use the joint gravity model jgm 2 geopotential orbit ephemeris and the preliminary jgm 3 orbit ephemeris computed at the university of texas center for space research the altimetric data from the t p mission are shown to have the precision necessary to estimate the monthly and fortnightly ocean tides in each bin inclusion of existing models of the ocean tides in the polar latitudes not sampled by the altimeter demonstrates the importance of these latitudes on spherical harmonic representations of the ocean tides the ocean tides are first estimated in bins of size 2 834 in longitude by 1 in latitude and then smoothed to 1 by 1 grids within 66 latitude the orthotide response formalism of groves and reynolds 1975 is used to represent the diurnal and semidiurnal ocean tides while a constant admittance is assumed across narrow bandwidths around each of the monthly mm fortnightly mf and termensual mt tidal components comparisons of the t p ocean tide models to tide gauge observations indicate their accuracies to be of the order of 2 3 cm the t p derived ocean tide models remove approximately 20 cm2 more of the t p measured sea surface variance than the cartwright and ray 1991 tide model and show a 19 cm2 and 15 cm2 improvement over the schwiderski 1980a b and cartwright and ray 1991 tide models respectively when compared to tide gauge estimates of the ocean tides

how can we improve a global ocean tide model at a regional scale a test on the yellow sea and the east china sea a global ocean model has been developed within the context of topex poseidon t p on the basis of a finite element hydrodynamic modeling approach combined with data assimilation based on the representer method the solution produced at global scale represents a spectacular improvement over what was available before the era of t p typically the mean discrepancy between the main tidal components and a hundred in situ tide gauges is 1 7 cm for m2 and 1 cm or less for the other components however the accuracies of this solution and of that produced by different authors within the t p tide working group are all worse near coastlines and over continental shelves this is the case for our finite element solution fes fes94 1 solution over the yellow sea and the east china sea ys ecs where the discrepancy is 33 cm for the m2 tide and 9 cm for the k1 tide when compared to a set of 192 tide gauges distributed along the coastlines this is due largely to the complex geometry of the basin and the limited knowledge of the bathymetry the aim of this paper is to investigate how our fes model can be improved with a dedicated application focused on one of the most energetic coastal basins the ys ecs 180 gigawatts for m2 i e 8 of the global energy dissipated in the whole ocean for this application a finite grid was implemented with a resolution down to 5 km along the coasts and over the continental shelf break particular attention was paid to bathymetry by complementing the etop05 database with regional maps sensitivity tests to the tuning of the bottom friction and the nonlinear interactions between the diurnal and semidiurnal components allow us to investigate the impact of dissipation parameterization and to produce an optimal solution without any data assimilation for nine main components of the tidal spectrum improvement by a factor of 2 m2 distance to the observations is now 17 5 cm global variance of 92 cm and k1 is 4 cm global variance of 21 cm as nonlinear components are significant over these basins the two main quarterdiurnal components are calculated the improvements are explained by five points 1 the choice of a mixed friction 2 a refinement of the mesh 3 a choice of reliable boundary conditions 4 a refined topography and 5 the use of a specific friction coefficient 1 5 10 3 surprisingly the energy budget for the m2 component leads to a dissipation similar to the value estimated by the global fes94 1 this is a major result of this study which leads us to the conclusion that when forcing a regional model with sea level boundary conditions along the open limits the simulated velocity field adjusts to the tuning of friction coefficients in order to dissipate the same amount of energy made available at its open boundaries

contribution of multi method geophysics to the understanding of a high temperature geothermal province the bouillante area guadeloupe lesser antilles the bouillante high temperature geothermal field guadeloupe french lesser antilles is located on the west coast of basse terre island about 15 km from the currently active soufriere volcano we have studied the shallow structure of the geothermal zone using a compilation of all available gravity magnetic and resistivity data both subaerial and marine acquired during the last 30 years geophysical models have been developed based on geological constraints and previous geophysical interpretations the resistivity distribution from electromagnetic surveys is interpreted in terms of water saturation of rocks hydrothermal alteration and presence of hydrated minerals gravity is used to distinguish and characterize the denser formations from the low density areas finally we are able to differentiate structures which pre and post date various recent magnetic inversions using the polarity of the magnetic anomalies by integrating these results the previous conceptual model for the geothermal province has been improved with the layering of the geological formations as defined by geophysical parameters now being taken into account in agreement with the classical scheme of geothermal reservoirs the shallow resistive layer is explained in terms of recent massive formations the conductive intermediate layer marks the low density demagnetized clay cover of the altered geothermal system the deep resistive layer is associated with dense formations increasing in age with depth and corresponds to the deep geothermal reservoir based on our geophysical data the geothermal activity could be more developed towards the east and north compared to the previously proposed area a volcano structural control seems to affect the internal structure of the province and consequently the development of geothermal activity this current work could be used as a basis for future surveys of the bouillante province in order to improve constraints and to increase our knowledge of the island s overall evolution

towed camera investigations of shallow intermediate water depth submarine stratovolcanoes of the southern kermadec arc new zealand southern kermadec arc stratovolcanoes of predominantly basaltic and andesitic composition provide a depth transect of the transition between effusive and explosive submarine volcanism observations along 4 6 km of towed camera track from the crests and upper flanks of the clark and rumble iii volcanoes reveal a consistent pattern of substrate types that are interpreted to record effusive and explosive eruption processes below 700 m water depth substrates are dominated by massive blocky flows pillow lavas pillow and angular block talus localized sheet flows and minor granule sand volcaniclastic detritus the latter typically forms a substrate mode of 5 20 above 450 m sand lapilli that is in part winnowed and rippled have a substrate mode of 50 100 with minor components of massive flows pillow lavas and coarse talus this difference in abundance of sand lapilli between 450 and 700 m is interpreted to record the transition between effusive and explosive both phreatic and phreatomagmatic eruptions between 600 and 700 m a varied distribution of sand lapilli abundance is interpreted as recording a mix of effusive and explosive eruptions consistent with possible differences in the physical interaction of magma water and known compositional magma heterogeneity

preliminary study of tonsteins of the pastora formation stephanian b of the cinera matallana coalfield northwestern spain abstract the correlation of seams of the pastora formation in the cinera matallana basin is affected by facies changes seam discontinuities such as seam splitting and joining and tectonic features exploratory drillings in the matallana syncline and in an underground exposure at the northern flank of the llombera syncline prove for the first time the existence of six tonsteins the investigation provided three kaolin tonsteins one kaolinite illite transition tonstein and two illite tonsteins which are described in detail the determination of coal rank gives evidence that there is no strict co incidence with the degree of diagenesis or metamorphosis of the original volcanic ashes thus further reasons for the alteration have to be considered such as varying compositions of the original volcanic ashes biochemical and chemical processes after deposition local hydrothermal metasomatism caused by the intrusion of basic magma or tectonic stress besides known faunal and facies marker horizons these newly detected tonsteins represent first class markers within the pastora formation the possibility of using these layers for the correlation of strata and for palaeomorphological studies depends on the successful continuation of the search for additional tonsteins as well as on the compilation and evaluation of subsequent investigations

current and tide observations in the southern yellow sea determination of mean currents and tides are particularly difficult in coastal regions flows are often nongeostrophic and short lived bathymetry is frequently not adequately known and can greatly influence coastal dynamics to better quantify tides and currents in the southern yellow sea three pressure gauges and three acoustic doppler current profilers adcps were bottom moored for 4 6 month intervals at depths ranging from 77 to 89 m tidal range is over 2 m and maximum current velocities are between 50 and 80 cm s at the mooring locations the present data are analyzed for 13 significant tidal constituents which are found to account for 85 of the sea surface height variability m2 is the dominant constituent followed by s2 and k1 flow is dominated by the tides mean currents are relatively small ranging from 1 5 cm s at the northern mooring to 4 cm s at the southern mooring delineations of barotropic and depth dependent currents are made from the adcp measurements in terms of mean and eddy kinetic energy currents are found to be most depth dependent in the near surface layers approximately 85 90 of the eddy kinetic energy is depth independent

barotropic tides in the south atlantic bight 1 the characteristics of the principal barotropic diurnal and semidiurnal tides are examined for the south atlantic bight sab of the eastern united states coast we combine recent observations from pressure gauges and adcps on fixed platforms and additional short term deployments off the georgia and south carolina coasts together with national ocean service coastal tidal elevation harmonics these data have shed light on the regional tidal propagation particularly off the georgia south carolina coast which is perforated by a dense estuary tidal inlet complex etic we have computed tidal solutions for the western north atlantic ocean on two model domains one includes a first order representation of the etic in the sab and the other does not include the etic we find that the etic is highly dissipative and affects the regional energy balance of the semidiurnal tides nearshore inner and midshelf model skill at semidiurnal frequencies is sensitive to the inclusion of the etic the numerical solution that includes the etic shows significantly improved skill compared to the solution that does not include the etic for the m2 constituent the largest tidal frequency in the sab overall amplitude and phase error is reduced from 0 25 m to 0 03 m and 13 8 to 2 8 for coastal observation stations similar improvement is shown for midshelf stations diurnal tides are relatively unaffected by the etic

evidence of diurnal shelf waves in satellite tracked drifter trajectories off the kuril islands abstract satellite tracked surface drifters deployed in september 1993 in the vicinity of the kuril kamchatka trench were advected onto the pacific continental shelf of the kuril islands where they encountered strong 40 50 cm s 1 diurnal tidal currents one of the drifters subsequently passed through friz strait into the sea of okhotsk experiencing intense 100 cm s 1 diurnal currents in the strait and strong 35 40 cm s 1 diurnal currents over the okhotsk shelf of the kuril islands the across shelf structure of the diurnal tidal currents is shown to be consistent with that of free topographically trapped subinertial waves propagating along the continental margin of the islands of the three continental shelf wave models considered a barotropic model with zero mean flow a barotropic model with nonzero alongshore mean flow and a baroclinic model based on the observed density structure only the baroclinic model accurately explains the main features of the diurnal currents for the pacific and ok

oceanic tides from geosat altimetry direct tidal analysis of the altimetry from the geosat exact repeat mission s first year is used to derive estimates of the diurnal and semidiurnal oceanic tides the geoid is removed by collinear differences at 34 1 day separation and the orbit error is reduced by subtracting a slowly modulated 1 cycle revolution term a sequence of independent analyses at grid areas of 1 latitude 1 5 longitude using orthotide functions ensures complete definition of the diurnal and semidiurnal species global admittance maps for m2 and s2 within the latitudes 58 n and 59 s compare well with ground truth at 66 open ocean sites maps of differences between geosat and the naval surface weapons center model show important areas of the order of 10 15 cm the integral for the global power input from the moon gives 2 51 tw m2 0 44 tw s2 lower than many previous estimates but in agreement with figures deduced from a recent analysis of satellite orbits

diagenetic quartz and amorphous silica in new zealand coals new zealand coal seams late cretaceous miocene lignite semi anthracite contain numerous and varied occurrences of diagenetic quartz and amorphous silica early diagenetic silicifications include sub horizontal and laterally extensive quartz mineralized bands micro and megascopic euhedral quartz crystals dispersed or concentrated in layers and silicified in situ tree stumps late diagenetic forms include sub horizontal quartz mineralized bands mostly 1 m in length and fracture infillings the origins of the silica remain uncertain but leached basement rocks and coal measure sediments and siliceous phytoliths within the coal forming plants are possible sources the silicification of coal seams may have significant implications for exploration mining and geological studies

reconnaissance de structures tectoniques et volcaniques sous marines de l arc recent des petites antilles kick em jenny qualibou montagne pelee nordouest de la guadeloupe abstract a multibeam bathymetric survey seacarib 1 was carried out in april 1985 on board the r v conrad lamont doherty geological observatory off the western coasts of several islands of the lesser antilles complementing a previous survey of the same type arcante 2 thermosite 1980 devoted to adjoining areas in guadeloupe martinique and st lucia it allowed us to precisely map submarine volcanoes in a marginal setting behind the recent arc the main volcanic axis of the archipelago emplaced during the neogene the kick em jenny volcano south of the grenadines is the only active submarine volcano of the lesser antilles it is a small and very young cone probably only tens or hundreds of years old which was hydrothermally active during the survey the directeur volcano guadeloupe is the largest submerged volcanic centre thus far detected in the lesser antilles having been formed between 3 3 and 2 9 ma during the 1980 survey two other large volcanoes were discovered off southern basse terre guadeloupe vieux fort volcano 2 5 2 0 ma and in front of fort de france bay martinique schoelcher volcano older than 4 2 ma several other much smaller volcanoes have been mapped off the same coasts particularly the bouillante seapeaks guadeloupe moreover large tectonic structures cut the recent arc transversally and obliquely the well known qualibou depression on the island of st lucia was interpreted in various ways neither the hypothesis of a large caldera the western side of which collapsed offshore nor the suggestion of a huge rotational gravity slide are confirmed the depression seems more likely to have been controlled by tectonic factors shaping a complex graben structure the seaward extension appears to be restricted to a northern channel the soufriere channel the st pierre fault in martinique is a large transverse feature extending seaward down to some 2000 m depth to the south it bounds the mount pelee active volcanic system and the escarpment of the fault forms a dam against subaqueous pyroclastic flows running down from the volcano these flows are responsible for the unusually smooth morphology of the submarine flanks the zombi fault of northwest guadeloupe is part of a first order feature extending along at least 130 km from montserrat in the north to marie galante in the east this curved fracture cuts across the northern central part of the lesser antilles passing progressively from a subparallel to a transverse orientation with respect to the axis of the island arc these types of surveys are important because they provide better understanding of the structure and recent geological evolution of the recent volcanic arc they are also a useful complementary tool for geothermal and seismological studies

the qualibou caldera st lucia west indies abstract recent geological geophysical and hydrogeochemical studies conducted in the qualibou area of st lucia west indies provide new data for reevaluation of the geothermal resource and recommendation of sites for renewed drilling activities this work supports the original hypothesis of tomblin that the qualibou depression is a caldera precaldera volcanic activity was concentrated along faults associated with regional ne and nw trending structures basaltic lavas dated at 5 5 ma crop out along the western coast and are overlain by andesitic composite cones dated at 1 2 and 0 9 ma which form the highest ridges of the island superimposed upon the andesitic cones are dacitic domes 0 25 ma the eroded plugs of two of these form the spectacular pitons the major event in this volcanic field was the intermittent eruption of the choiseul pumice concurrent with the formation of the qualibou caldera 32 000 to 39 000 yrs ago about 6 km3 dense rock equivalent of lithic crystal andesitic tephra was erupted mainly as nonwelded to welded pyroclastic flows and surges some of these tuffs have been identified in geothermal drill holes within the 12 km2 caldera postcaldera eruption of dacitic tephra and dome lava 20 000 to 32 000 yrs ago occurred from vents within the caldera and appear to be a result of magmatic resurgence a 5 2 km long dipole dipole dc resistivity survey measured along a north south trending line through the caldera gave apparent resistivity results similar to those obtained in previous studies these results are compatible with a caldera substructure where low apparent resistivities analysis and interpretation of hydrogeochemical data from the qualibou caldera indicate that a geothermal reservoir underlies the sulphur springs area and consists of three layers 1 an upper steam condensate zone 2 an intermediate two phase vapor zone and 3 a lower brine zone measured temperatures at depth of 212 c are complemented by estimated temperatures of 250 c in the brine layer the water chemistry of various thermal springs indicates upwelling primarily near the caldera center at sulphur springs which feeds steam to steamcondensate hot springs along the northern caldera wall

volcano flank instability in the lesser antilles arc diversity of scale processes and temporal recurrence 1 the 1997 boxing day collapse a remarkable feature of the ongoing eruption of soufriere hills on montserrat has prompted new interest in the study of volcano stability in the lesser antilles building on a few cases documented in the literature we have now identified at least 47 flank collapse events on volcanoes of the caribbean arc where this type of behavior is characteristic and repetitive about 15 events occurred on active volcanoes within the last 12 000 years in the northern part of the arc flank collapses are repetitive do not exceed 1 km3 in volume occur in all directions and are promoted by intense hydrothermal alteration and well developed fracturing of the summit part of the edifices in contrast infrequent but large sector collapses with volumes up to tens of km3 are typical of the southern volcanoes they are always directed to the west as a result of the high overall slopes of the islands toward the deep back arc grenada basin because caribbean islands are small a large part of the resulting debris avalanches have flowed into the sea thus contributing voluminous and sudden inputs of volcaniclastic sediments to the grenada basin deposits from such submarine flows have been identified during the recent aguadomar and caraval oceanographic cruises and traced to their source structures on land edifice collapses have a major influence on subsequent volcanic activity but also are of high concern because of their tsunamigenic potential

arc parallel extension and localization of volcanic complexes in guadeloupe lesser antilles 1 subduction of atlantic seafloor under the caribbean plate causes shallow earthquakes within the lesser antilles volcanic arc such earthquakes above the subduction interface show strike slip or normal fault plane solutions the latter with e w striking nodal planes to better assess seismic hazard and the coupling between volcanism and tectonics we investigated faulting related to overriding plate deformation in the guadeloupe archipelago using aerial photographs satellite spot images and topographic maps 1 25000 scale we mapped active and middle to late pleistocene fissures and normal fault systems that cut the uplifted coral platforms grande terre and marie galante and the volcanic rocks of basse terre the available marine geophysical data show that the faults extend offshore to bound submarine rifts the e w striking 1500 m deep v shaped marie galante rift separates the two islands of marie galante and grande terre normal faults in the north of grande terre appear to mark the similarly v shaped western termination of the 5000 m deep n 50e to n130 e striking desirade graben three shallow m 5 5 earthquakes 6 may 1851 29 april 1897 3 august 1992 appear to have ruptured segments of the marie galante rift boundary faults the young la grande decouverte volcanic complex of basse terre including the 1440 a d soufriere dome lies within the western termination of the marie galante rift the ancient volcanic shoulders of the rift buttress the active dome to the north and south which may explain why major prehistoric sector collapses and pyroclastic avalanches have been directed southwestward into the caribbean sea or southeastward into the atlantic ocean the marie galante rift is typical of other troughs transverse to the northeastern edge of the caribbean plate we interpret such troughs which are roughly orthogonal to the arc to result from slip partitioning and extension perpendicular to plate convergence that they disappear southward implies that they result from interaction between the caribbean and north american plates

internal tide radiation from mendocino escarpment abstract strong semidiurnal internal tides are observed near mendocino escarpment in full depth profile time series of velocity temperature and salinity velocity and density profiles are combined to estimate the internal tide energy flux divergence of this flux demonstrates that its source is the barotropic tide interacting with the escarpment a baroclinic energy flux of 7 kw m 1 radiates from the escarpment corresponding to 3 of the 220 kw m 1 fluxing poleward in the surface tide energy and energy flux are concentrated in packets that emanate from the flanks of the ridge surmounting the escarpment and one site 90 km north of the escarpment coherent beamlike structure along semidiurnal ray paths remains identifiable until the first surface reflection beyond the first surface reflection north of the escarpment the energy flux drops by 2 kw m 1 and beams are no longer discernible turbulence as inferred from finescale parameterizations is elevated by over two orders of magnitude relative to th