comment on are there internal kelvin waves in lake tanganyika by jaya naithani and eric deleersnijder 1 recent numerical modelling efforts have demonstrated the presence of kelvin waves in lake tanganyika naithani and deleersnijder 2004 however it is claimed that these waves should not appear according to classical scaling arguments based on existing classical scaling arguments supported by laboratory and field investigations i will show why they can and apparently do appear in lake tanganyika

southern kermadec submarine caldera arc volcanoes sw pacific caldera formation by effusive and pyroclastic eruption abstract three newly identified submarine caldera volcanoes brothers healy and rumble ii west of the southern kermadec arc within water depths 80 and low density 0 3 0 5 g cm 3 erupted pumiceous clasts these observations are interpreted as evidence of subaqueously quenched pyroclastic eruption s sheathed by ambient water flashing to steam discharging some 5 km3 of pyroclastic material from healy volcano caldera collapse is inferred to be penecontemporeous with the pyroclastic eruption s although it is possible formation as an explosive crater occurred but we consider the latter unlikely given the volume of erupted material and water depth extrapolation of these observations to other submarine arcs indicates pyroclastic eruption of silicic magmas and syn eruptive caldera collapse is possible within water depths of 500 1000 m

intra oceanic subduction related hydrothermal venting kermadec volcanic arc new zealand intra oceanic volcanic arcs mark the boundaries between converging lithospheric plates where subduction produces volcanic and tectonic activity that ensures a steady supply of magmatic heat and hydrothermal fluids to the seafloor here we report on the first broad and systematic survey of hydrothermal emissions generated along a submarine arc front more than half seven of 13 of the volcanoes surveyed along 260 km of the southern kermadec arc ne of new zealand are hydrothermally active our results indicate that volcanic arcs represent a previously unheeded but potentially extensive source of shallow 2 km water depth vent fields expelling fluids of a unique and heterogeneous composition into the oceans

submarine hydrothermal activity along the mid kermadec arc new zealand large scale effects on venting 1 the 2 500 km kermadec tonga arc is the longest submarine arc on the planet here we report on the second of a series of cruises designed to investigate large scale controls on active hydrothermal venting on this arc the 2002 nzaplume ii cruise surveyed 12 submarine volcanic centers along 580 km of the middle kermadec arc mka extending a 1999 cruise that surveyed 260 km of the southern kermadec arc ska average spacing between volcanic centers increases northward from 30 km on backarc crust along the ska to 45 km on backarc crust along the southern mka to 58 km where the mka joins the kermadec ridge volcanic cones dominate in the backarc and calderas dominate the kermadec ridge the incidence of venting is higher along the mka 83 10 of 12 volcanic centers than the ska 67 8 of 12 but the relative intensity of venting as given by plume thickness areal extent and concentration of dissolved gases and ionic species is generally weaker in the mka this pattern may reflect subduction of the 17 km thick oceanic hikurangi plateau beneath the ska subduction of this basaltic mass should greatly increase fluid loss from the downgoing slab initiating extensive melting in the upper mantle wedge and invigorating the hydrothermal systems of the ska conversely volcanic centers in the southern mka are starved of magma replenishment and so their hydrothermal systems are waning farther north where the mka centers merge with the kermadec ridge fewer but larger magma bodies accumulate in the thicker older crust ensuring more widely separated caldera dominated volcanic centers

collapse and reconstruction of monowai submarine volcano kermadec arc 1998 2004 monowai submarine volcano is one of the three most historically active volcanoes of the kermadec arc repeat multibeam surveys of monowai cone from september 1998 and september 2004 and t wave data recorded by the reseau sismique polynesien network for the same period document the collapse and subsequent regrowth of the cone within this 6 a period grid differencing of the two bathymetric data sets acquired 6 a apart reveals that a landslide 2230 m long occurred between the surveys within which a postcollapse cone and talus ridge 0 023 km3 in volume subsequently formed the volume of this collapse minus postcollapse construction is 0 085 km3 we interpret an unusual strong amplitude t wave event on 24 may 2002 as recording hot landsliding where the 100 to 160 m thick collapse has unroofed the uppermost parts of the vent conduit with the subsequent explosive interaction and cooling of hot magma and volcaniclastic rubble with ambient seawater this interpretation is consistent with the lack of emergent events sharp onset and large amplitude of the 24 may 2002 t waves the subsequent 2500 t wave events between november 2002 and september 2004 occurred in swarms with emerging and waning activity and with typical explosive volcanic acoustic signatures which are interpreted as recording the regrowth of an 90 m high cone back to a near 1998 elevation at an average rate of 47 m a 1 this study provides 1 a lower bound for frequency magnitude relationships of landsliding for submarine arc volcanoes and 2 estimates of 0 013 km3 a 1 of submarine cone growth during eruptive cycles

the physical regime and the respective biogeochemical processes in the lower water mass of lake kinneret physical measurements made in lake kinneret during the stratified period indicate that the lower water mass lwm consists of two layers a turbulent benthic boundary layer bbl and a hypolimnetic layer overlying the bbl the water in the lwm moves in response to vertical mode one seiching of the metalimnion this movement is accentuated near the perimeter of the metalimnion due to shoaling of the seiche and breaking of internal waves the motion associated with this phenomena induce a well mixed benthic boundary layer bbl adjacent to the lake bottom the bbl and hypolimnion were distinguished chemically because transport of solutes between these water bodies was very small compared to the hypolimnion the bbl was characterized by more intensive biomineralisation processes as indicated by the faster depletion of do and no3 by higher levels of nh4 h 2s and soluble reactive phosphorus srp and by lower ph values srp levels in the hypolimnion were particularly low suggesting that phosphorus was either preferentially removed by sedimentation from the hypolimnion or it was not released from particles as a result nh4 over srp ratios in the hypolimnion were significantly higher than in the bbl and diffusional fluxes of both nutrients from the lwm to the trophogenic epipelagic water should therefore be characterized by relatively high n p ratios

cyclic eruptions and sector collapses at monowai submarine volcano kermadec arc 1998 2007 1 repeated multibeam bathymetric surveys at monowai cone a shallow submarine basaltic volcano and part of the monowai volcanic center in the northern kermadec arc were conducted in 1998 2004 and 2007 these surveys document dramatic depth changes at the volcano including negative changes up to 176 m from two sector collapses and positive changes up to 138 m from volcanic reconstruction near the summit and debris avalanche deposits downslope of the slide scars one sector collapse occurred on the se slope between 1998 and 2004 with a volume of 0 09 km3 and another occurred on the sw slope between 2004 and 2007 with a volume of 0 04 km3 the volume of positive depth change due to addition of volcanic material by eruption is of the same order 0 05 km3 between 1998 and 2004 and 0 06 km3 between 2004 and 2007 during these time intervals monitoring by the polynesian seismic network detected frequent t wave swarms at monowai indicative of explosive eruptive activity every few months an unusual t wave swarm on 24 may 2002 was previously interpreted as the collapse event between the 1998 and 2004 surveys but no similarly anomalous t waves were detected between 2004 and 2007 probably because the polynesian seismic network stations were acoustically shadowed from the second slide event we interpret that the sector collapses on monowai are caused by the unstable loading of fragmental erupted material on the summit and steep upper slopes of the volcano 20 moreover there appears to be a cyclic pattern in which recurrent eruptions oversteepen the cone and periodically lead to collapse events that transport volcaniclastic material downslope to the lower apron of the volcano volumetric rate calculations suggest that these two processes may be more or less in equilibrium the repeated collapses at monowai are relatively modest in volume involving only 0 1 0 5 of the edifice volume have occurred much more frequently than is estimated for larger debris avalanches at subaerial volcanoes and may be characteristic of how persistently active shallow submarine arc volcanoes grow

eruption fed particle plumes and volcaniclastic deposits at a submarine volcano nw rota 1 mariana arc 1 nw rota 1 is an active submarine volcano in the mariana arc with a summit depth of 517 m and an explosively erupting volcanic vent southwest of the summit at a depth of 530 560 m during a period of ongoing explosive eruptions particle plumes surrounded the volcano and at least 3 3 107 m3 of volcaniclastic material was deposited on the southern flank particle plumes over the summit were magmatic hydrothermal in origin characterized by 3he enrichment hydrothermal precipitates and low ph values plumes at multiple depths below the summit surrounded the volcano and were composed overwhelmingly of fresh glassy shards of basalt rare anhydrite particles were present but there was a complete absence of other hydrothermal components in the deep plume samples these short lived anhydrite particles indicate the source of the deep plumes is from within or very near the eruptive vent and the mechanism for transport down the flanks of the volcano must be far faster than settling of individual particles the deep plumes most likely originated from sediment gravity flows generated by explosive eruptions or slope failure and landslides of unstable materials that had accumulated near the eruptive vent suspended sediments detach from the volcano slopes at multiple depths and are transported laterally up to tens of kilometers where they contribute to fall out deposits in distal sediments these observations link mechanisms for the transport of volcanic ash in the submarine environment to the types of deposits common in volcaniclastic aprons and fine ash layers in distal sediments

enriched h2 ch4 and 3he concentrations in hydrothermal plumes associated with the 1996 gorda ridge eruptive event abstract the rapid field response in march and april 1996 to diking eruptive events on the northern gorda ridge allowed the first detailed co measurement of 3 he h 2 and ch 4 in plumes associated with a submarine eruption and examination of the chemical transformation of these volatile species during aging of the plumes the diking eruptive event generated extensive event plumes with a low 3 he heat ratio of 0 4 10 12 cm 3 stp gm 1 c 1 while chronic plumes had 3 he heat ratios of 2 1 6 2 10 12 cm 3 stp gm 1 c 1 hydrogen concentrations in the initial event plume ep96a reached a maximum value of 47 nm 235 times that of ocean background concentration 0 2 nm in contrast roughly one month later h 2 concentrations although still elevated had drastically dropped to 40 times background values methane concentrations in both event and chronic plume fluids were also elevated and similar to stable hydrothermal systems in unsedimented ridge environments reaching a maximum value of 7 nm the intense rapid interaction at very high temperatures of hydrothermal fluids with the host rock during dike intrusion or with seawater during extrusion of the basalt likely generated high localized concentrations of h 2 the data indicate however that maximum rates of h 2 production during event plume formation could have lasted a few days at most

pb in the pacmanus sea floor hydrothermal system eastern manus basin numerical modeling of a magmatic versus leached origin mass balance calculations of metal leaching and deposition in the pacmanus submarine hydrothermal vent field in the eastern manus basin in the bismarck sea off the east coast of papua new guinea indicate that simple leaching of the underlying volcanic pile by hydrothermal fluids cannot account for the pb found in associated sulfide deposits and pb enriched altered volcanic rocks with 100 percent leaching transport and precipitation efficiencies 1 69 km3 of volcanic rock would need to be leached to account for pb applying realistic leaching efficiencies of 50 to 60 percent and transport precipitation efficiencies of 10 to 20 percent 14 to 34 km3 of volcanic rock would need to be leached assuming a static reaction zone the estimated available volume of leachable rock is 0 144 km3 much less than required applying a dynamic reaction zone model 98 to 235 volumes of fresh leachable rock 1 volume 0 144 km3 would need to be exposed to hydrothermal fluids this translates into a 588 to 1 410 m migration of the reaction zone a model incorporating such values would not be tenable previously published compositions of melt inclusions in volcanic rocks from pacmanus indicate an aver age of 199 ppm cu 68 ppm zn and 5 2 ppm pb in the melt and 1 3 to 1 7 wt percent of degassed h2o these data suggest that 37 7 million tonnes mt of magmatic fluid containing 7 2 wt percent cu and 2 3 wt percent zn could be released from a 1 km3 body of magma using the same metal transfer efficiency of 80 percent the degassed fluid would have a maximum concentration of 0 17 wt percent pb which translates to 58 000 t of pb from the melt for the highest known fluid discharge rate of 92 000 g s and over a 100 000 year period a concentration of only 12 ppm pb in the original magmatic component could account for all the pb in the pacmanus deposits assuming that 1 percent of the mixed end member fluid is of magmatic origin a wide range of durations of hydrothermal activity and discharge rates assuming a maximum 0 17 wt percent pb concentration in the degassed magmatic fluid can account for the total pb in the deposit

ice flow direction change in interior west antarctica upstream of byrd station west antarctica ice penetrating radar data reveal a distinctive fold structure within the ice in which isochronous layers are unusually deep the fold has an axis more than 50 kilometers long which is aligned up to 45 to the ice flow direction although explanations for the fold s formation under the present flow are problematic it can be explained if flow was parallel to the fold axis 1500 years ago this flow change may be associated with ice stream alterations nearer the margin if this is true central west antarctica may respond to future alterations more than previously thought

sulfur isotopic effects in the disproportionation reaction of sulfur dioxide in hydrothermal fluids implications for the δ 34 s variations of dissolved bisulfate and elemental sulfur from active crater lakes sulfur isotope effects during the so 2 disproportionation reaction to form elemental sulfur 3so 2 3h 2 o 2hso 4 s 2h at 200 330 c and saturated water vapor pressures were experimentally determined initially a large kinetic isotopic fractionation takes place between hso 4 and s followed by a slow approach to equilibrium the equilibrium fractionation factors estimated from the longest run results are expressed by 1000 in hso 4 s 6 21 10 6 t 2 3 62 the rates at which the initial kinetic fractionation factors approach the equilibrium ones were evaluated at the experimental conditions 34 s values of hso 4 and elemental sulfur were examined for active crater lakes including noboribetsu and niseko hokkaido japan khloridnoe bannoe and maly semiachik kamchatka poas costa rica ruapehu new zealand and kawah ijen and keli mutu indonesia hso4 s values are 28 for keli mutu 26 o for kawah ijen 24 c for ruapehu 23 for poas 22 for maly semiachik 21 for yugama 13 for bannoe 9 for niseko 4 o for khloridonoe and 0 for noboribetsu in the decreasing order the so 2 disproportionation reaction in the magmatic hydrothermal system below crater lakes where magmatic gases condense is responsible for high hso4 s values whereas contribution of hso 4 produced through bacterial oxidation of reduced sulfur becomes progressively dominant for lakes with lower hso4 s values currently noboribetsu crater lake contains no hso 4 of magmatic origin a 40 year period observation of 34 s hso4 and 34 s s values at yugama indicated that the isotopic variations reflect changes in the supply rate of so 2 to the magmatic hydrothermal system this implies a possibility of volcano monitoring by continuous observation of 34 s hso4 values the 18 o values of hso 4 and lake water from the studied lakes covary indicating oxygen isotopic equilibration between them the covariance gives strong evidence that lake water circulates through the sublimnic zone at temperatures of 140 30 c

submarine magmatic hydrothermal systems at the monowai volcanic center kermadec arc the monowai volcanic center is located at the midpoint along the 2 530 km long tonga kermadec arc system the monowai volcanic center is comprised of a large elongate caldera monowai caldera area 35 km2 depth to caldera floor 1 590 m which has formed within an older caldera some 84 km2 in area to the south of this nested caldera system is a large composite volcano monowai cone which rises to within 100 m of the sea surface and which has been volcanically active for the past several decades mafic volcanic rocks dominate the monowai volcanic center basalts are the most common rock type recovered from the cone whereas basaltic andesites are common within the caldera hydrothermal plume mapping has shown at least three major hydrothermal systems associated with the caldera and cone 1 the summit of the cone 2 low temperature venting 60 c mussel ridge on the southwestern wall of the caldera and 3 a deeper caldera source with higher temperature venting that has yet to be observed the cone summit plume shows large anomalies in ph a shift of 2 00 ph units and 3he 358 and noticeable h2s up to 32 m and ch4 up to 900 nm the summit plume is also metal rich with elevated total dissolvable fe tdfe up to 4 200 nm tdmn up to 412 nm and tdfe tdmn up to 20 4 particulate samples have elevated fe si al and ti consistent with addition to the hydrothermal fluid from acidic water rock reaction plumes extending from 1 000 to 1 400 m depth provide evidence for a major hydrothermal vent system in the caldera the caldera plume has lower values for tdfe and tdmn although some samples show higher tdmn concentrations than the cone summit plume caldera plume samples are also relatively gas poor i e no h2s detected ph shift of 0 06 ph units ch4 concentrations up to 26 nm the composition of the hydrothermal plumes in the caldera have higher metal contents than the sampled vent fluids along mussel ridge requiring that the source of the caldera plumes is at greater depth and likely of higher temperature minor plumes detected as light scattering anomalies but with no 3he anomalies down the northern flank of the monowai caldera most likely represent remobilization of volcanic debris from the volcano flanks we believe the monowai volcanic center is host to a robust magmatic hydrothermal system with significant differences in the style and composition of venting at the cone and caldera sites at the cone the large shifts in ph very high 3he values elevated tdfe and tdfe tdmn and the h2s and ch4 rich nature of the plume fluids together with elevated ti p v s and al in hydrothermal particulates indicates significant magmatic volatile metal contributions in the hydrothermal system coupled with aggressive acidic water rock interaction by contrast the caldera has low tdfe tdmn in hydrothermal plumes however elevated al and ti contents in caldera particulate samples combined with the presence of alunite pyrophyllite sulfide minerals and native sulfur in samples from mussel ridge suggest past and perhaps recent acid volatile rich venting and active fe sulfide formation in the subsurface

caldera forming processes and the origin of submarine volcanogenic massive sulfide deposits certain volcanogenic massive sulfide vms ore deposits form in submarine calderas this association is well known but the link between caldera formation and the origins of the deposits remains poorly understood here we show that the size and location of a vms deposit within a submarine caldera may be determined by how and when the caldera formed these spatial temporal conditions control development of the hydrothermal system associated with the vms deposit we propose that caldera opening along outward dipping faults promotes magma degassing seawater influx and high temperature leaching resulting in a metal rich hydrothermal fluid these outward dipping faults are considered to provide critical pathways for ore forming fluids responsible for some caldera hosted vms deposits and may also be fundamentally important for the formation of many other caldera hosted ore deposit types

structure and petrology of newly discovered volcanic centers in the northern kermadec southern tofua arc south pacific ocean 1 the nzaplume iii expedition of september october 2004 to the northern kermadec southern tofua nkst arc between 28 52 s and 25 07 s resulted in the discovery of at least seven new submarine volcanic centers and a substantial caldera complex adjacent to the previously known monowai seamount the volcanic centers form a sublinear chain that coincides with the kermadec ridge crest in the south hinetapeka and diverges 45 km westward of the ridge crest in the north v just to the south of where the louisville ridge intersects with the arc all of the centers contain calderas or caldera like structures as well as multiple cones domes fissure ridges and vent fields all show signs of recent eruptive and current hydrothermal activity there are strong structural controls on edifice location with cones and fissure ridges typically associated with faulting parallel to the regional 12 strike of the arc front several of the calderas are ellipsoidal orientated northwest southeast in the general direction of least compressive stress sampled volcanic rocks representing the most recently erupted lavas are all low k tholeiites two of the centers gamble and rakahore yielded only high silica dacite to rhyolite 69 74 wt silica whereas two others monowai and v yielded only basalt to andesite 48 63 wt silica mineral assemblages are plagioclase pyroxene dominated with accessory fe ti oxides apatite olivine and quartz tridymite cristobalite typical of dry volcanic arc systems hornblende occurs only in a felsitic rhyolite from hinepuia volcanic center and zircon is absent glass contents range to 57 in basalts andesites mean 20 and 97 in andesites rhyolites mean 59 and other quench textures including swallow tailed plumose or dendritic crystal forms and crystallites are common most lavas are highly vesicular 63 mean 28 and have low volatile contents mostly 2 wt which together with the occurrence of tridymite or cristobalite indicates explosive eruption and rapid cooling exceptions are rocks from u volcanic center which have low vesicularity and low glass contents across a wide compositional range indicating effusive eruption disequilibrium mineral textures the frequent occurrence of xenoliths and xenocrysts and macroscopic evidence for magma mingling indicate that many of the lavas are hybrids having resided only a short time in upper crustal reservoirs prior to eruption silicic magmas are major components of nkst arc volcanism and caldera formation is the dominant eruptive style the scale of silicic magmatism is in marked contrast to the dominant basaltic andesitic magmatism in the southern kermadec arc with evidence from other arcs silicic magmatism is now recognized as a major feature of intraoceanic arcs globally

geology hydrothermal activity and sea floor massive sulfide mineralization at the rumble ii west mafic caldera abstract sea floor imagery volcanic rock massive sulfide and hydrothermal plume samples 3 he ph dissolved fe and mn and particulate chemistry have been collected from the rumble ii west volcano southern kermadec arc new zealand rumble ii west is a caldera volcano with an 3 km diameter summit depression bounded by ring faults with a resurgent central cone rocks recovered to date are predominantly mafic in composition i e basalt to basaltic andesite with volumetrically lesser intermediate rocks i e andesite on the basis of its size geometry volcanic products and composition rumble ii west can be classified as a mafic caldera volcano rumble ii west has a weak hydrothermal plume signature characterized by a small but detectable 3 he anomaly 25 time series light scattering data though obtained from vertical casts and tow yos do show that hydrothermal activity has increased in intensity between 1999 and 2011 massive sulfides recovered from the eastern caldera wall and eastern flank of the central cone are primarily comprised of barite and chalcopyrite with lesser sphalerite pyrite and traces of galena the weak hydrothermal plume signal indicates that the volcano is in a volcanic hydrothermal quiescent stage compared to other volcanoes along the southern kermadec arc although the preponderance of barite with massive sulfide mineralization indicates higher temperature venting in the past of the volcanoes along the kermadec tonga arc known to host massive sulfides i e clark rumble ii west brothers monowai volcano 19 and volcano 1 the majority five out of six are dominantly mafic in composition and all but one of these mafic volcanoes form moderate size to large calderas to date mafic calderas have been largely ignored as hosts to sea floor massive sulfide deposits that 75 of the presently known massive sulfide bearing calderas along the arc are mafic in composition the dacitic brothers volcano is the exception has important implications for sea floor massive sulfide mineral exploration in the modern oceans and ancient rock record on land

geochemistry of hydrothermal fluids from the pacmanus northeast pual and vienna woods hydrothermal fields manus basin papua new guinea abstract processes controlling the composition of seafloor hydrothermal fluids in silicic back arc or near arc crustal settings remain poorly constrained despite growing evidence for extensive magmatic hydrothermal activity in such environments we conducted a survey of vent fluid compositions from two contrasting sites in the manus back arc basin papua new guinea to examine the influence of variations in host rock composition and magmatic inputs both a function of arc proximity on hydrothermal fluid chemistry fluid samples were collected from felsic hosted hydrothermal vent fields located on pual ridge pacmanus and northeast ne pual near the active new britain arc and a basalt hosted vent field vienna woods located farther from the arc on the manus spreading center vienna woods fluids were characterized by relatively uniform endmember temperatures 273 285 c and major element compositions low dissolved co 2 concentrations 4 4 mmol kg and high measured ph 4 2 4 9 at 25 c temperatures and compositions were highly variable at pacmanus ne pual and a large newly discovered vent area fenway was observed to be vigorously venting boiling 358 c fluid all pacmanus fluids are characterized by negative d h 2 o values in contrast to positive values at vienna woods suggesting substantial magmatic water input to circulating fluids at pual ridge low measured ph 25 c values 2 6 2 7 high endmember co 2 up to 274 mmol kg and negative 34 s h 2 s values down to 2 7 in some vent fluids are also consistent with degassing of acid volatile species from evolved magma dissolved co 2 at pacmanus is more enriched in 13 c 4 1 to 2 3 than vienna woods 5 2 to 5 7 suggesting a contribution of slab derived carbon the mobile elements e g li k rb cs and b are also greatly enriched in pacmanus fluids reflecting increased abundances in the crust there relative to the manus spreading center variations in alkali and dissolved gas abundances with cl at pacmanus and ne pual suggest that phase separation has affected fluid chemistry despite the low temperatures of many vents in further contrast to vienna woods substantial modification of pacmanus ne pual fluids has taken place as a result of seawater ingress into the upflow zone consistently high measured mg concentrations as well as trends of increasingly non conservative so 4 behavior decreasing endmember ca cl and sr cl ratios with increased mg indicate extensive subsurface anhydrite deposition is occurring as a result of subsurface seawater entrainment decreased ph and endmember fe mn ratios in higher mg fluids indicate that the associated mixing cooling gives rise to sulfide deposition and secondary acidity production several low temperature 80 c fluids at pacmanus ne pual also show evidence for anhydrite dissolution and water rock interaction fixation of b subsequent to seawater entrainment hence the evolution of fluid compositions at pual ridge reflects the cumulative effects of water rock interaction admixing and reaction of fluids exsolved from silicic magma phase separation segregation and seawater ingress into upflow zones

the setting style and role of magmatism in the formation of volcanogenic massive sulfide deposits throughout earth s history all volcanogenic massive sulfide vms hosting environments are associated with specific assemblages of mafic and felsic rocks with distinct petrochemistry petrochemical assemblages indicative of formation at anomalously high temperatures within extensional geodynamic environments in mafic dominated juvenile ophiolitic vms environments there is a preferential association with mafic rocks with boninite and low ti tholeiite mid ocean ridge basalt morb and or back arc basin basalt affinities representing forearc rifting or back arc initiation mid ocean ridges or back arc basin spreading or back arc basins respectively felsic rocks in juvenile oceanic arc environments in archean terrains are high field strength element hfse and rare earth element ree enriched in post archean juvenile oceanic arc terrains felsic rocks are commonly hfse and ree depleted and have boninite like to tholeiitic signatures in vms environments that are associated with continental crust i e continental arc and back arc and dominated by felsic volcanic and or sedimentary rocks evolved environments felsic rocks are the dominant hosts to mineralization and are generally hfse and ree enriched with calc alkalic a type and or peralkalic affinities representing continental arc rifts continental back arcs and continental back arcs to continental rifts respectively coeval mafic rocks in evolved environments have alkalic within plate ocean island basalt like and morb signatures that represent arc to back arc rift versus back arc spreading respectively the high temperature magmatic activity in vms environments is directly related to the upwelling of mafic magma beneath rifts in extensional geodynamic environments e g mid ocean ridges back arc basins and intra arc rifts underplated basaltic magma provides the heat required to drive hydrothermal circulation extensional geodynamic activity also provides accommodation space at the base of the lithosphere that allows for the underplated basalt to drive hydrothermal circulation and induce crustal melting the latter leading to the formation of vms associated rhyolites in felsic dominated and bimodal vms environments rifts also provide extensional faults and the permeability and porosity required for recharge and discharge of vms related hydrothermal fluids rifts are also critical in creating environments conducive to preservation of vms mineralization either through shielding massive sulfides from seafloor weathering and mass wasting or by creating environments conducive to the precipitation of subseafloor replacement style mineralization in sedimented rifts subvolcanic intrusions are also products of the elevated heat flow regime common to vms forming environments shallow level intrusive complexes i e within 1 3 km of the seafloor may not be the main drivers of vms related hydrothermal circulation but are likely the manifestation of deeper seated mantle derived heat i e 3 10 km depth that drives hydrothermal circulation these shallower intrusive complexes are commonly long lived i e millions of years and reflect a sustained thermally anomalous geodynamic environment such a thermally anomalous environment has the potential to drive significant hydrothermal circulation and therefore multi phase long lived subvolcanic intrusive complexes are excellent indicators of a potentially fertile vms environment the absence of intrusive complexes however does not indicate an area of low potential as they may have been moved or removed due to post vms tectonic activity in some cases shallow level intrusive systems contribute metals to the vms hydrothermal system

forced resonant oscillations as a response to periodic winds in a stratified reservoir the response of the sau reservoir to a wind field characterized by having marked periodicities of 12 h and 24 h has been studied measurements of temperature with a thermistor string and currents with an acoustic doppler current meter show that the reservoir also responds with the same water periodicities during certain times of the stratified period some of the natural oscillation modes of the reservoir are close to these forcing wind periods in particular in mid july the vertical mode v2 is close to 12 h and in mid to end of september the vertical mode v3 is close to 24 h in these situations these modes are selected out of the spectrum of possible internal waves and the reservoir behaves as a forced oscillator in resonance with the wind the structure and the period of these vertical modes have been elucidated by using the 3d model elcom both modes are affected by the earth s rotation at the widest part of the reservoir

seasonal differences in the evolution of damped basin scale internal waves in a shallow stratified lake the evolution of damped basin scale internal waves was investigated using a modal analysis for layer stratified rotating lakes a simple model for homogeneous oscillatory boundary layers was incorporated into the modal analysis to predict damping rates of individual internal wave modes enabling the prediction of their evolution under wind forcing and bottom friction application of the method to lake kinneret indicated a different dynamic balance in summer and spring despite the continuous presence of large amplitude internal waves in the two seasons in summer strong diurnal winds continuously excited the dominant kelvin waves but the relatively strong damping e folding damping times 3 d suppressed their amplitudes in spring wind forcing was again strong but intermittent and it was weaker damping e folding damping times 10 d that allowed the dominant poincaree waves to persist until the next wind event the significant difference in the damping times was due to the difference in the periods and the structure of the internal waves as well as the bottom boundary layer thickness which limited the ekman transport and energy dissipation within the boundary layer

high frequency internal waves in lake geneva trains of high frequency internal waves have been observed in the thermocline of lake geneva within a few hours after the passing of disturbances which cause a rapid increase or jump in the depth of the thermocline three possible mechanisms for the source of the internal waves are proposed and compared with available data i that the waves are a soliton packet following the jump ii that the waves are generated as the jump passes over or around a local region of rough topography and iii that the jump produces a moving disturbance near the shoreline with internal waves forming a wake behind it the investigation of the last possibility involves the solution of the problem of the form of an internal wave wake in the presence of mean currents which vary in depth both in their strength and direction the wave pattern of the wake in the observed current distribution and stratification of the lake is described and compared with that in the absence of shear an expression for the energy of internal waves propagating in a shear flow is also derived and it is found that the rate of energy loss from the jump to the waves is small the minimum richardson number resulting from the co existence of the mean shear and the internal waves is marginally greater than 1 4 suggesting that the waves may be limited by shear flow instability however none of the mechanisms for their generation and propagation is fully compatible with the available data

near inertial waves in lake erie near inertial poincare waves with a period t p similar to 17 h are the dominant wind induced internal wave motions in central lake erie and consequently have a substantial influence on lake circulation mixing and biogeochemistry however due to the complex three basin bathymetry in lake erie the vertical and horizontal modal structure of these waves remain poorly understood in this study we analyze field data to show wind events energize frequent vertical mode one poincare waves the horizontal modal structure was also investigated in a sensitivity analysis using a calibrated three dimensional hydrodynamic transport model forced with observed and idealized spatially uniform wind events strong horizontal mode one poincare wave cells form in both the central and eastern basins when wind events have a duration of 0 25 t p to 0 5 t p are impulsive and periodic at t p or have anticyclonic rotation with a duration of t p momentum transfer from longer wind events 0 5 tp will oppose the coriolis force rotated currents and damp poincare wave generation in agreement with theory the most efficient wind events are observed and computationally modeled to have a duration of 0 25 t p causing an excitation peak at similar to 0 4 t p and converting similar to 0 8 of the wind energy input to poincare waves the efficiency of wind work in generating poincare wave kinetic energy is given by 1 cos 2 pi f t t 1 where f is the inertial frequency and t is the wind duration therefore the efficiency peaks during each nt p period where n is a non negative integer and decreases significantly for longer wind events

high so2 flux sulfur accumulation and gas fractionation at an erupting submarine volcano strombolian style volcanic activity has persisted for six years at the nw rota 1 submarine volcano in the southern mariana arc allowing direct observation and sampling of gas rich fluids produced by actively degassing lavas and permitting study of the magma hydrothermal transition zone fluids sampled centimeters above erupting lava and percolating through volcaniclastic sediments around an active vent have dissolved sulfite 100 mmol kg total dissolved sulfide 1 mmol kg if nw rota is representative of submarine arc eruptions then volcanic vent fluids from seawater lava interaction on submarine arcs have a significant impact on the global hydrothermal flux of sulfur and al to the oceans but a minimal impact on mg removal gas ratios so 2 co 2 h 2 and he are variable on small spatial and temporal scales indicative of solubility fractionation and gas scrubbing elemental sulfur s e is abundant in solid and molten form produced primarily by disproportionation of magmatic so 2 injected into seawater s e accumulates within the porous rock surrounding the lava conduit connecting the magma source to the seafloor accumulated s e can be heated melted and pushed upward by rising magma to produce molten s e flows and lavas saturated with s e molten s e near the top of the lava conduit may be ejected up into the water column by escaping gases or boiling water this mechanism of s e accumulation and refluxing may underlie the relatively widespread occurrence of s e deposits of many sizes found on submarine arc volcanoes

hydrothermal activity and volcano distribution along the mariana arc 1 submarine volcanic arcs extend for fully a third of the length of the mid ocean ridge system but systematic investigation of hydrothermal venting on those arcs is sparse here we report on the distribution of hydrothermal activity along the intraoceanic mariana arc we identify 76 volcanic edifices along 1370 km of arc grouped into 60 volcanic centers of which at least 26 20 submarine are hydrothermally or volcanically active the overall volcanic center density is 4 4 100 km of arc and that of active centers is 1 9 100 km an equal length of the tonga kermadec arc holds fewer centers 2 9 100 km but a similar density of active centers 1 8 100 km the lower percentage of active centers on the mariana arc results from its having both fewer caldera volcanoes since on both arcs calderas are twice as likely as cones to be active and a lower percentage of active calderas and cones active centers are found from 80 to 230 km above the subducting pacific slab and a quarter lie behind the arc front the frequency distribution of center spacing along the arc front peaks between 20 and 30 km and shows the asymmetric long tail shape typical for many other arcs especially those with volcano populations 20 there is no evidence for a regular spacing of volcanic centers using the new mariana data and recent data from the tonga kermadec arc we estimate that all intraoceanic arcs combined may contribute hydrothermal emissions equal to 10 of that from the global mid ocean ridge

active submarine eruption of boninite in the northeastern lau basin subduction of oceanic crust and the formation of volcanic arcs above the subduction zone are important components in earth s geological and geochemical cycles subduction consumes and recycles material from the oceanic plates releasing fluids and gases that enhance magmatic activity feed hydrothermal systems generate ore deposits and nurture chemosynthetic biological communities among the first lavas to erupt at the surface from a nascent subduction zone are a type classified as boninites these lavas contain information about the early stages of subduction yet because most subduction systems on earth are old and well established boninite lavas have previously only been observed in the ancient geological record here we observe and sample an active boninite eruption occurring at 1 200 m depth at the west mata submarine volcano in the northeast lau basin southwest pacific ocean we find that large volumes of h2o co2 and sulphur are emitted which we suggest are derived from the subducting slab these volatiles drive explosive eruptions that fragment rocks and generate abundant incandescent magma skinned bubbles and pillow lavas the eruption has been ongoing for at least 2 5 years and we conclude that this boninite eruption is a multi year low mass transfer rate eruption thus the lau basin may provide an important site for the long term study of submarine volcanic eruptions related to the early stages of subduction boninite lavas are erupted during the early stages of subduction however they have previously been found only in the ancient geological record discovery of an active boninite eruption shows that abundant volatile gases derived from the subducting slab drive this violent eruptive activity even in the deep sea

the internal wave field in sau reservoir observation and modeling of a third vertical mode water withdrawal from mediterranean reservoirs in summer is usually very high because of this stratification is often continuous and far from the typical two layered structure favoring the excitation of higher vertical modes the analysis of wind temperature and current data from sau reservoir spain shows that the third vertical mode of the internal seiche baroclinic mode dominated the internal wave field at the beginning of september 2003 we used a continuous stratification two dimensional model to calculate the period and velocity distribution of the various modes of the internal seiche and we calculated that the period of the third vertical mode is 24 h which coincides with the period of the dominating winds as a result of the resonance between the third mode and the wind the other oscillation modes were not excited during this period

the seasonal evolution of wind internal wave resonance in lake kinneret data from a thermistor chain and wind sensor collected over an annual stratification cycle in lake kinneret israel during 2000 were used to investigate the seasonal evolution of wind internal wave resonance internal wave periods determined from an analytical model were compared with observations and we show that resonance during 2000 occurred during three distinct times of the year at the onset of stratification march during the heating phase june and during the cooling phase november in all cases resonance was between the wind and the dominant radial azimuthal and vertical mode one cyclonic kelvin wave previously observed in lake kinneret internal waves are a ubiquitous feature of lakes existing because of wind forcing acting on a stratified water column where the stratification is generally due to temperature wind applied to the surface can cause a surface setup of water at the downwind end this pressure force is balanced by a tilting of the metalimnion in the opposite sense that is downward at the downwind end spigel and imberger 1980 when the wind forcing relaxes the water surface oscillates a barotropic wave as does the metalimnion a baroclinic wave the two motions can effectively be considered to be decoupled monismith 1985 because they form orthogonal solutions to the wave equation it is the internal baroclinic waves that are of interest in the present study because they provide much of the energy and motion for biogeochemical processes in lakes in large lakes the picture becomes complicated because the effects of the earth s rotation begin to influence the frequency and structure of the internal waves internal gravity waves in large lakes take the form of cyclonic kelvin and or poincare or anticyclonic poincare waves antenucci et al 2000 antenucci and imberger 2001 where the wave crests rotate around the perimeter of the lake basin antenucci and imberger 2001 showed that the frequency as well as the ratio of potential kinetic energy of internal gravity waves in approximately circular or elliptic lakes was dependent on the aspect ratio radial mode azimuthal mode and burger number the burger number is defined asc lf where c is the phase speed of internal waves in a nonrotating system l is some length scale characterizing the basin width and f is the coriolis parameter for a small burger number rotation dominates over gravity and waves approach the oceanic case known as inertial oscillations in which the motion is dominated by the kinetic energy signal for a large acknowledgments we acknowledge the field support and technical staff from the kinneret limnological laboratory kll for providing assistance particularly tzahi rosenberg for maintaining the lake station and helping in the transfer of data from kll to the centre for water research and peter yeates who provided the time series of the lake number

the seasonal evolution of high vertical mode internal waves in a deep reservoir the causal mechanism and seasonal evolution of the internal wave field in a deep warm monomictic reservoir are examined through the analysis of field observations and numerical techniques the study period extends from the onset of thermal stratification in the spring until midsummer in 2005 during this time wind forcing was periodic with a period of 24 h typical of land sea breezes and the thermal structure in the lake was characterized by the presence of a shallow surface layer overlying a thick metalimnion typical of small to medium sized reservoirs with deep outtakes basin scale internal seiches of high vertical mode ranging from mode v3 to v5 were observed in the metalimnion the structure of the dominant modes of oscillation changed as stratification evolved on seasonal timescales but in all cases their periods were close to that of the local wind forcing i e 24 h suggesting a resonant response nonresonant oscillatory modes of type v1 and v2 became dominant after large frontal events which disrupted the diurnal periodicity of the wind forcing

chemical reaction rates and entrainment within the endeavour ridge hydrothermal plume the aging of the hydrothermal plume over the endeavour segment of the juan de fuca ridge was estimated by measuring the222rn3he ratio in the plume as it dispersed despite uncertainties in the source function of hydrothermal input it wa determined that the relative sequence of removal from the plume ish2 c 222rn ch4 mn where c is a measure of particle concentration and the mean life of222rn is 5 5 days h2 is removed from the plume within hours of input while mn is not removed within the two week timescale of the radon helium clock entrainment of bottom water within the buoyant plume may introduce additional chemical signatures into the spreading effluent layer over that which would be introduced by hydrothermal discharge alone this is particularly significant for those chemical species which are not greatly enriched in the vent fluids relative to bottom water concentration and which display a nutrient like profile in the deep ocean thus we found that significant fractions of the si and226ra anomalies in the plume were not of hydrothermal origin but were derived from entrained bottom water which has a higher concentration of these elements than ambient water at plume height

energetics and damping of basin scale internal waves in a strongly stratified lake energetics and damping of basin scale internal waves and subsequent near bottom transport processes in lake kinneret were investigated using the modal analysis in a layer stratified irregular basin the theory was extended to include small linear damping and energy budgets and damping rates of five dominant internal waves were extracted by fitting numerically calculated internal waves to isotherm displacements measured by six thermistor chains distributed throughout the lake energy contained in the dominant internal waves 3 gj resulted from a balance between energy input from diurnal winds and dissipation within a day both of which were estimated to be 3 4g j d 21 damping was caused primarily by bottom friction and the damping rates e folding time varied from 1 to 3 d depending on the velocity structure currents induced by the internal waves caused considerable spatial variability of the bottom shear stress and near bottom transport processes such as entrainment rate at the top of the benthic boundary layer and mass transfer at the sediment water interface

petrology of philippine geothermal systems and the application of alteration mineralogy to their assessment abstract philippine geothermal systems occur in the vicinity of large holocene calc alkaline volcanic complexes wells drilled in these areas encountered multiple intrusions the latest dikes are the subsurface manifestations of the youngest heat source commonly at least two hydrothermal regimes are juxtaposed in a single area with the latest being in equilibrium with the present temperature and chemical regime alteration by neutral ph water is pervasive and abundant a contact metamorphic aureole also occurs near intrusives alteration due to acid sulfate fluids is generally confined to permeable structures neutral ph alteration is divided into four zones on the basis of key clay minerals and two subzones are defined by calc silicates these are the smectite ambient to 180 c transition 180 230 c illite 230 320 c and biotite 270 340 c zones subzones are defined by epidote 250 340 c and amphibole 280 340 c the four main zones of acid alteration are kaolinite ambient to 120 c dickite kaolinite 120 200 c dickite pyrophyllite 200 250 c and pyrophyllite illite 230 320 c where relict high temperature alteration reaches the surface the area being drilled is usually the outflow zone of the present system these hydrothermal mineral assemblages are used 1 as geothermometers 2 to assist in determining the depth at which the production casing will be set during drilling 3 to estimate fluid ph and other chemical parameters 4 to predict possible corrosion and scaling tendencies of the fluids 5 as a measure of permeability and possible cold water influx into wells 6 as a guide to field hydrology and 7 to estimate roughly the thickness of the eroded overburden

physical controls on the spatial evolution of a dinoflagellate bloom in a large lake a set of satellite images of chlorophyll a concentration for lake kinneret israel from the period february to april 2007 captured the temporal evolution of horizontal patchiness that developed during the typical spring bloom of the dinoflagellate peridinium gatunense narrow bands of high concentration located adjacent to the shoreline at the start of the bloom were followed by progressive propagation of this high concentration region from the shoreline toward the center of the lake as the bloom proceeded a three dimensional 3 d hydrodynamic numerical model and an analytical model for a flat bottomed elliptical basin together explain the observed phenomenon the spatial structure of kelvin waves which were demonstrated to most likely be present in february and april due to resonance produced regions of high velocity gradient contributing to horizontal dispersion close to the shoreline this region of high dispersion was narrow and close to the shoreline at the start of the bloom when the burger number was relatively small but it widened over the course of the season as the burger number increased due to increasing stratification in addition an increase in the dispersion rate with time in the lake interior was inferred from numerical simulation due to increasing wind speeds and a thinner surface layer physical processes in this case horizontal dispersion as a result of both kelvin waves and wind can play an important role in governing the dynamics and spatial evolution of dinoflagellate blooms in lakes spatial heterogeneity of phytoplankton is a ubiquitous occurrence in lakes coastal waters and the open ocean phytoplankton patchiness can be defined by localized abruptly elevated concentrations phytoplankton patches may occur at a broad range of spatial scales and such

geochemistry of hydrothermal fluids from axial seamount hydrothermal emissions study vent field juan de fuca ridge subseafloor boiling and subsequent fluid rock interaction hydrothermal fluids collected from the ashes vent field in 1986 1987 and 1988 exhibit a very wide range of chemical composition over a small area 60 m in diameter compositions range from a 300 c gas enriched 285 mmol kg co2 low chlorinity 33 of seawater fluid to a 328 c relatively gas depleted 50 mmol kg co2 high chlorinity 116 of seawater fluid the entire range of measured compositions at ashes is best explained by a single hydrothermal fluid undergoing phase separation while rising through the ocean crust followed by partial segregation of the vapor and brine phases other mechanisms proposed to produce chlorinity variations in hydrothermal fluids precipitation dissolution of a chloride bearing mineral or crustal hydration cannot produce the covariation of chlorinity and gas content observed at ashes there is good agreement of the measured fluid compositions with compositions generated by a simple model of phase separation in which gases are partitioned according to henry s law and all salt remains in the liquid phase significant enrichments in silica lithium and boron in the low chlorinity fluids over levels predicted by the model are attributed to fluid rock interaction in the upflow zone depletions in iron and calcium suggest that these elements have been removed by iron sulfide and anhydrite precipitation at some time in the history of the low chlorinity fluids the distribution of low and high chlorinity venting is consistent with mechanisms of phase segregation based on differential buoyancy or relative permeability the relatively shallow depth of the seafloor 1540 m and the observed chemistry of ashes fluids are consistent with phase separation in the sub critical or near critical region

submarine hydrothermal activity and gold rich mineralization at brothers volcano kermadec arc new zealand brothers volcano of the kermadec intraoceanic arc is host to a hydrothermal system unique among seafloor hydrothermal systems known anywhere in the world it has two distinct vent fields known as the nw caldera and cone sites whose geology permeability vent fluid compositions mineralogy and ore forming conditions are in stark contrast to each other the nw caldera site strikes for 600 m in a sw ne direction with chimneys occurring over a 145 m depth interval between 1 690 and 1 545 m at least 100 dead and active sulfide chimney spires occur in this field and are typically 2 3 m in height with some reaching 6 7 m their ages at time of sampling fall broadly into three groups 4 23 and 35 years old the chimneys typically occur near the base of individual fault controlled benches on the caldera wall striking in lines orthogonal to the slopes rarer are massive sulfide crusts 2 3 m thick two main types of chimney predominate cu rich up to 28 5 wt cu and more commonly zn rich up to 43 8 wt zn geochemical results show that mo bi co se sn and au up to 91 ppm are correlated with the cu mineralization whereas cd hg sb ag and as are associated with the dominant zn rich mineralization the cone site comprises the upper cone site atop the summit of the recent main dacite cone and the lower cone site that straddles the summit of an older smaller more degraded dacite cone on the ne flank of the main cone huge volumes of diffuse venting are seen at the lower cone site in contrast to venting at both the upper cone and nw caldera sites individual vents are marked by low relief 0 5 m mounds comprising predominately native sulfur with bacterial mats vent fluids of the nw caldera field are focused hot 300 c acidic ph 2 8 metal rich and gas poor calculated end member fluids from nw caldera vents indicate that phase separation has occurred with cl values ranging from 93 to 137 of seawater values by contrast vent fluids at the cone site are diffuse noticeably cooler 122 c more acidic ph 1 9 metal poor and gas rich higher than seawater values of so4 and mg in the cone vent fluids show that these ions are being added to the hydrothermal fluid and are not being depleted via normal water rock interactions iron oxide crusts 3 years in age cover the main cone summit and appear to have formed from fe rich brines evidence for magmatic contributions to the hydrothermal system at brothers includes high concentrations of dissolved co2 e g 206 mm kg at the cone site high co2 3he negative d and 18oh2o for vent fluids negative 34s for sulfides to 4 6 sulfur to 10 2 and 15n2 to 3 5 vent fluid ph values to 1 9 and mineral assemblages common to high sulfidation systems changing physicochemical conditions at the brothers hydrothermal system and especially the cone site occur over periods of months to hundreds of years as shown by interlayered cu au and zn rich zones in chimneys variable fluid and isotopic compositions similar shifts in 3he 4he values for both cone and nw caldera sites and overprinting of magmatic mineral assemblages by water rock dominated assemblages metals especially cu and possibly au may be entering the hydrothermal system via the dissolution of metal rich glasses they are then transported rapidly up into the system via magmatic volatiles utilizing vertical 2 5 km long narrow 300 m diameter pipes consistent with evidence of vent fluids forming at relatively shallow depths the nw caldera and cone sites are considered to represent stages along a continuum between water rock and magmatic hydrothermal dominated end members

seasonal evolution of the basin scale internal wave field in a large stratified lake the response of the water column to varying conditions of stratification and wind forcing was investigated in lake kinneret israel using data collected from thermistor chains and acoustic doppler current profilers during 1997 and 1998 the strong daily sea breeze was found to generate a vertical mode 1 internal kelvin wave and basin scale internal poincarewaves of vertical modes 1 2 and 3 the kelvin wave the dominant component of the internal wave field was responsible for alongshore velocities in the nearshore regions in the upwind nearshore regions velocities were dominated by the forced response to the wind and were cross shore in nature in the lake interior the kelvin wave effect on the horizontal velocity field was minor compared to the higher vertical mode poincarewaves the kelvin wave is shown to exist in resonant and nonforced states with the wind whereas the vertical mode 1 poincarewave energy remained relatively constant despite large variability in the forcing condi tions the energy in the higher mode poincarewaves varied greatly both on daily and seasonal timescales the results demonstrate that the wind energy forces multiple basin scale internal wave modes and that prior motion in the water column must be considered when determining the subsequent internal wave response in periodically forced systems lake kinneret israel has long been an important regional resource providing a substantial supply of drinking water as well as supporting a commercial fishery the monomictic lake is forced daily during the summer by a powerful sea breeze with stratification and wind patterns showing little variation from year to year these factors along with a fa vorable bathymetric pattern combine to make lake kinneret an ideal place for the field investigation of large scale inter nal waves and related phenomena such as the benthic bound ary layer horizontal transport and vertical mixing processes in addition to providing substantial insight into the local pro cesses and hence influencing local management study of the lake also provides fundamental knowledge of the dynam ics of enclosed basins on a geophysical scale during summer the internal rossby radius in lake kin neret is typically one half the basin width hence large scale motion in the lake will be affected by the earth s rotation and basin scale internal waves may be of topographic ross by kelvin or poincareform topographic rossby waves are sub inertial frequency oscillations that exist only in rotating fluids with variable bathymetry mysak et al 1985 stocker and hutter 1987 and these waves result from changes in depth affecting the relative vorticity of fluid elements in the absence of vertical boundaries wavelike solutions to the lin ear inviscid equations of motion for a flat bottomed region of homogeneous fluid with a constant rate of rotation are 1

residual circulation due to internal waves shoaling on a slope we describe the residual circulation induced in a two layer system when internal waves with a wave length equal to or longer than the slope length propagate over a sloping bottom and either reflect or break for the case of no wave breaking scaling is used to derive boussinesq type equations the solution of which leads to an expression for the residual circulation adjacent to the sloping bottom this residual circulation is maintained by a weak slope on the density interface for breaking waves laboratory experiments and numerical modeling were used to ascertain the details of the residual circulation arising from the formation of gravitational intrusions results from these three investigative tools were used to determine as a function of bottom slope and incident wave amplitude the internal wave reflection coefficient and the strength of the residual circulation pattern with and without wave breaking the ocean and most lakes are thermally stratified for at least part of the year in stratified fluids the density anomaly associated with the thermal stratification supports internal waves with a range of vertical modal structures antenucci et al 2000 antenucci and imberger 2001 antenucci and imberger 2003 the gravest or first vertical mode induces a large current over the lake or ocean bottom and when the bottom slopes the waves shoal causing them to break and lose energy to dissipation the associated currents and turbulence can often lead to sediment resuspension and mixing of the water column gloor et al 1994 pierson and weyhenmeyer 1994 steinman et al 1997 the gravitational motions in turn induced by the mixing may combine with secondary internal wave motions to drive a residual circulation that may transport resuspended and dissolved material to the central area of a lake hakanson 1982 ostrovsky et al 1996 inall 2009 also demonstrated mass transport due to intrusion caused by internal wave breaking in the fjord loch etive by using a fluorescent dye tracer such intrusions have been observed but their dynamics do not seem to have received any attention in this paper the processes leading to residual circulation are described when a continuous train of internal waves with an individual wavelength equal to or longer than the slope length supported by a two layer stratification impinges perpendicularly onto a sloping bottom two cases were investigated when the waves break and when they are reflected perfectly without breaking internal waves and their associated mass transport in lakes fjords and coastal oceans are reviewed in ostrovsky and stepanyants 1989 and huthnance 1989 whereas solitary internal waves are reviewed by brown and christie 1998 lamb 2002 and grue et al 2000 regarding mass transport lamb 2002 investigated shoaling of largeamplitude internal waves and demonstrated that trapped

metal leaching and inorganic sulfate reduction in volcanic hosted massive sulfide mineral systems evidence from the paleo archean panorama district western australia comprehensive studies of the well preserved paleo arehean 3 6 3 2 ga panorama volcanic hosted massive sulfide district of western australla provide compelling evidence that metals were leached from the hase of the volcanic pile and redeposited at its top in volcanic hosted massive sulfide deposits this leaching provided more than enough metal to form known deposits implying that direct magmatic input of metal is not required sulfur depletion from the base of the volcanic pile was associated with an increase in fe2o3 feo and hematitic alteration these data combined with sulfur isotope data indicate that seawater sulfate reduction was facilitated by the olddation of rock feo to hematite at high temperature in the h2s stability field this is the first time that seawater sulfate reduction has been demonstrated regionally in an ancient volcanic hosted massive sulfide mineral system the data presented here require pah archean seawater to be sufate bearing

iron ii distribution and oxidation kinetics in hydrothermal plumes at the kairei and edmond vent sites indian ocean deep sea hydrothermal activity cycles the entire volume of the global ocean through deep sea hydrothermal plumes at least every 4 8 103 a a rapid timescale that is comparable to global deep ocean mixing an important process within hydrothermal plumes is the oxidation of dissolved iron discharged with vent fluids leading to the co precipitation of many other vent sourced metals thus modifying gross hydrothermal fluxes to the deep ocean and acting as a net sink in the ocean chemical budgets of certain key tracers here we report direct measurements of dissolved fe ii oxidation rates from two recently discovered indian ocean vent sites that are intermediate between pacific and atlantic values thus demonstrating that the rate of iron oxidation and formation of scavenging fe iii solid phases in hydrothermal plumes varies systematically along the global deep ocean conveyor the average pseudo first order rate constant for the oxidation reaction is 0 303 h 1 and the corresponding half life 2 31 h the rate plots show some curvature however indicating additional processes possibly interactions with organic matter may also influence the net oxidation removal rate different rates of oxidation of iron in hydrothermal plumes in different ocean basins have important implications for the dispersion of produced oxide phases which in turn may impact on uptake of other metals from seawater and deposition into underlying ridge crest and ridge flank sediments

wind forced motions in stratified lakes and their effect on mixed layer shear the solution for the response of a rectangular n layered stratified lake to an arbitrarily varying in time wind stress is presented the case n 3 is considered in detail for a three layered lake the response is made up of the individual responses of one external and two internal modes when the upper layer is shallow relative to the other two layers the mixed layer shear is due almost entirely to the slower second mode response moreover the upper interface can tilt quite severely while the lower interface remains nearly flat calculations based on the three layer model are compared with measurements made in wellington reservoir western australia

spatial structure of the dominant basin scale internal waves in lake kinneret field data and numerical simulations were used to investigate the effects of basin shape continuous stratification and rotation on the three dimensional structure of the dominant natural basin scale internal wave modes in lake kinneret a stratified lake large enough so that the earth s rotation influences the wave motion the structure of the modes was inferred from power spectral density of measured and simulated isotherm vertical displacements and from rotary power spectral density of isopycnal velocities obtained from numerical simulations the shape of the lake at the level of the thermocline in conjunction with the dispersion relationship determines the horizontal configuration of the natural modes the dominant response to wind forcing was an azimuthal and vertical mode 1 kelvin wave with a natural period of 22 6 h that propagated around the entire basin the second most dominant response was a vertical mode 1 wave with a natural period close to 10 5 h and composed of two counter rotating

surface seiche formation on a shallow reservoir in complex terrain this study presents field observations and numerical modeling of surface seiche formations on a shallow reservoir in a complex terrain rules reservoir spain the influence of the surrounding topography on the atmospheric loading barometric pressure and wind speed is investigated with the associated atmospheric hydrodynamic coupling during a 13 day field study maximum free surface oscillations of 4 cm were recorded after the passing of a short duration storm 5 min which included a peak wind gust of 22 m s observations also present evidence of resonant excitation of the free surface caused by high frequency microscale harmonics 10 min in the atmospheric forcing resonant excitation caused by harmonics in the atmospheric forcing is significant for small reservoirs situated in regions of complex terrain where topographical obstacles modify the flow patterns in the near surface boundary layer generating eddies with harmonics in the microscale range of the atmospheric forcing spectrum harmo