boron geochemistry from some typical tibetan hydrothermal systems origin and isotopic fractionation the tibetan plateau is characterized by intense hydrothermal activity and abnormal enrichment of trace elements in geothermal waters hydrochemistry and b isotope samples from geothermal waters in tibet were systematically measured to describe the fractionation mechanisms and provide constraints on potential b reservoirs b concentrations range from 0 35 to 171 90 mg l and isotopic values vary between 16 57 and 0 52 geothermal fields along the indus yarlung zangbo suture zone and n s rifts are observed with high b concentrations and temperatures the similar hydrochemical compositions of high b geothermal waters with magmatic fluid and consistent modeling of b isotopic compositions with present 11b values imply that the b in high b geothermal waters is mainly contributed by magmatic sources probably through magma degassing in contrast geothermal fields in other regions of the lhasa block have relatively low b concentrations and temperatures after considering the small fractionation factor and representative indicators of na ca cl hco3 na k and si the conformity between modeling results and the isotopic compositions of host rocks suggests that the b in low temperature geothermal fields is mainly sourced from host rocks according to simulated results the b in some shallow geothermal waters not only originated from mixing of cold groundwater with deep thermal waters but it was also contributed by equilibration with marine sedimentary rocks with an estimated proportion of 10 it was anticipated that this study would provide useful insight into the sources and fractionation of b as well as further understanding of the relationships between b rich salt lakes and geothermal activities in the tibetan plateau

theory of acoustic propagation in a multi phase stratified liquid flowing within an elastic walled conduit of varying cross sectional area abstract a theoretical solution is derived for the sound field in an arbitrarily layered viscous fluid moving with the non negligible mach number within a duct with elastic walls and varying cross sectional area the solution is applied to the interpretation of infrasonic and seismic signals preceding and accompanying volcanic eruptions and can be used to study the acoustic response of various types of volcanic fluids including magma gas mixtures ash gas mixtures and bubble rich liquids the acoustic field in a magma conduit can be propagated into the atmosphere through an open vent and coupled into the ground through the displacement of the magma conduit walls the theoretical solutions predict that fluids moving with the non negligible mach number will exhibit significant attenuation in the upstream direction thereby reducing the quality factor of the conduit resonance thus acoustic energy generated during an eruption may be preferentially radiated downstream exacerbating the acoustic decoupling between the upper and lower parts of a stratified magma column a source model for a repeated cavitation process is introduced as a possible excitation mechanism for tremor signals

boron isotopic variations in nw usa rhyolites yellowstone snake river plain eastern oregon the geochemistry of nw usa rhyolites correlates strongly with geography and the nature of the underlying basement terranes rhyolites from the snake river plain yellowstone srpy province have higher 87 sr 86 sr 207 pb 206 pb and lower 143 nd 144 nd than those from the oregon high lava plains hlp province reflecting a dominant influence of precambrian cratonic crust east of the western idaho suture zone versus accreted oceanic terranes of phanerozoic age to the west rhyolites from the cratonic domain show significant enrichments of th u and lree hree whereas b concentration and especially b nb and b rb are systematically higher west of the tectonic boundary this decoupling of b from the other incompatible elements is best explained in terms of distinctive magmatic sources east and west of the suture zone b isotopic composition 11 b was measured for natural and synthetic glasses via multiple multiplier laser ablation icp ms 11 b values are systematically lighter in srpy rhyolites 5 6 to 8 9 compared to those from the hlp 0 8 to 3 1 these data are consistent with strongly fluid depleted and or metamorphosed sources for srpy rhyolites whereas hlp sources resemble those of typical oceanic basalts and could reflect melting of juvenile basalt derived protoliths in the crust b isotope ratios of low 18 o rhyolites are indistinct from those with normal 8 o suggesting that 11 b values are not strongly affected by hydrothermal processes that alter source materials with meteoric water considering all data it is likely that b compositions of the rhyolites are inherited from their sources in the crust although low 11 b 0 is also observed in many mantle derived basalts i e oib morb in srpy rhyolites it is associated with enrichments of elements e g u th rb lree typically concentrated in continental crust and thus old high grade metamorphic continental crust is inferred to be b depelted if rhyolite protoliths were originally metasediments it is likely that bulk b and 11 b were selectively removed by metamorphic dehydration reactions and transported to the surface via b enriched fluids

central european vegetation response to abrupt climate change at 8 2 ka oxygen isotope records show a major climatic reversal at 8 2 ka in greenland and europe annually laminated sediments from two lakes in switzerland and germany were sampled contiguously to assess the response of european vegetation to climate change ca 8 2 ka with time resolution and precision comparable to those of the greenland ice cores the pollen assemblages show pronounced and immediate responses 0 20 yr of terrestrial vegetation to the climatic change at 8 2 ka a sudden collapse of corylus avellana hazel was accompanied by the rapid expansion of pinus pine betula birch and tilia linden and by the invasion of fagus silvatica beech and abies alba fir vegetational changes suggest that climatic cooling reduced drought stress allowing more drought sensitive and taller growing species to out compete corylus avellana by forming denser forest canopies climate cooling at 8 2 ka and the immediate reorganization of terrestrial ecosystems has gone unrecognized by previous pollen studies on the basis of our data we conclude that the early holocene high abundance of c avellana in europe was climatically caused and we question the conventional opinion that postglacial expansions of f silvatica and a alba were controlled by low migration rates rather than by climate the close connection between climatic change and vegetational response at a subcontinental scale implies that forecasted global warming may trigger rapid collapses expansions and invasions of tree species

boron and lithium in high grade rocks and minerals from the wawa kapuskasing region ontario there is no preferential partitioning of boron among the principal rock forming minerals in high grade rocks of the kapuskasing structural zone ksz and the wawa domal gneiss region wdg lithium is strongly concentrated in biotite and other ferromagnesian minerals but does not show consistent partitioning between these and the sialic minerals the distribution of b and li within a rock may be studied using an alpha track image which shows that the inconsistencies in partitioning may be largely attributed to disturbance of mineral equilibria by postmetamorphic low grade alteration that deposited b and li boron has similar concentrations in all the rock types studied although it is an incompatible element that elsewhere accumulates in pegmatites lithium concentrations are low in the anorthositic rocks but are otherwise very variable in some but not all rocks higher than usual b and li can be attributed to introduction during alteration boron occurs at low concentrations 2 3 ppm throughout both the k

a cautionary tale of topography and tilt from kīlauea caldera we conduct finite element analysis to investigate the effect of sharp topography on surface ground deformation caused by pressure changes in a magma reservoir tilt data expresses the horizontal gradient of vertical deformation and therefore can emphasise small variations in deformation that go unnoticed using other methods we find that the vertical displacement profile at a surface with a cliff can be thought of as the superposition of the deformation from shallow and deeper sources this combination can create a small peak in vertical displacement that acts as a pseudo source creating a reversal of the deformation gradient and therefore anomalous tilt magnitude and a rotation of up to 180 we apply these models to k lauea caldera and find that surface geometry creates a tilt rotation of 10 partially explaining anomalous tilt that has been observed our analysis highlights the importance of considering topography when assessing tilt measurements at active volcanoes

very long period oscillations of mount erebus volcano as the signal decays vlp scalar moments up to 5 10 11 n m exceed sp moments by an order of magnitude or more suggesting distinct though genetically related sp and vlp source mechanisms we conclude that vlp signals arise from excitation of a quasi linear resonator that is intimately associated with the conduit system and is excited by gravity and inertial forces associated with gas slug ascent eruption and magma recharge vlp signal stability across hundreds of eruptions spanning 5 years the persistence of the lava lake and the rapid posteruptive lava lake recovery indicate a stable near summit magma reservoir and vlp source process index terms 4544 oceanography physical internal and inertial waves 7280 seismology volcano seismology 8419 8414 volcanology eruption mechanisms 8419 volcanology eruption monitoring 7280 keywords strombolian very long period volcano seismology

microlite textures and volatile contents of obsidian from the inyo volcanic chain california 1 we test the hypothesis that microlite textures record progressive degassing during magma ascent we compare microlite number density nv and h2o concentrations in pyroclastic and effusive obsidian obs from the inyo volcanic chain ca comparisons reveal a weak correlation between microlite nv and h2o however most obsidians obss of a given volatile content exhibit a wide range of nv factors other than degassing must also influence final groundmass texture we postulate that obs textures record different ascent rates and residence histories prior to eruption from the conduit we conclude that microlites do not sensitively indicate the extent of magmatic degassing rather they provide qualitative indications of magma ascent and residence time

wind induced internal seiches in lake zurich observed and modeled1 during august and september 1978 3 1 current meters and 120 temperature sensors were deployed to record every 10 or 20 min at various depths at 12 moorings with wind speed and direction at three moorings in lake zurich we explore here the baroclinic internal seiche response to wind impulses observed as fluctuations in isotherm depth and current speeds those fluctuations and their energy spectra are compared with the predictions of two models fitted to basin topography and to the observed average thermal structure a two layered variable depth tvd model developed by d j schwab fitted to basin topography and incorporating a two dimensional horizontal grid and c h mortimer s two layered modification of a simpler procedure originally developed for surface seiche calculations by a defant the dominant responses to wind impulses were internal seiches of the first longitudinal mode average period 44 h weaker signals from the second 24 h and third 17 h modes were also seen in spectra of temperature and current fluctuations the models displayed patterns of thermocline displacement and current which in periodicity and structure were closely similar to those observed predictions of the defant model were less precise particularly for current founded on linear theory and neglecting the effects of rotation the models were unable to reproduce two features occasionally seen in the lake motions clockwise or anticlockwise rotation of current direction and internal surges arising when storms induced large amplitude downstrokes of the thermocline at one basin end or the other the lake s internal response was principally dependent on the timing strength and duration of the wind impulse relative to and interacting with internal seiche motions already in progress

fe isotopes and the contrasting petrogenesis of a i and s type granite abstract we present new fe isotope data of 42 s i and a type ferroan granites from the cambrian delamerian orogen in south australia the palaeozoic lachlan fold belt and western usa interpretation of these data together with modelling suggests that magmatic processes do result in quite complex fe isotopic differentiation trends and can lead to granites with isotopically heavy iron with 57 fe 0 35 by comparison mid ocean ridge basalts morbs have 57 fe 0 15 teng et al 2013 these variations are similar to those previously reported poitrasson and freydier 2005 heimann et al 2008 telus et al 2012 but contrary to some interpretations beard and johnson 2006 heimann et al 2008 heavy values are not necessarily the product of late stage hydrothermal fluid loss though this process is undoubtedly also an important factor in some circumstances a type ferroan granites reach very heavy 57 fe values 0 4 0 5 whereas i types are systematically lighter 57 fe 0 2 s type granites show a range of intermediate values but also tend to be isotopically heavy 57 fe 0 2 0 4 our results show that the iron isotopic values and trends are signatures that reflect granite generation processes a modelling using the rhyolite melts software suggests that contrasting trajectories and end points in fe isotope evolution towards granite depend on oxidation state of the evolving magma and whether or not the system is oxygen buffered iron isotopic evolution supports an origin of ferroan a type granite from protracted closed magma chamber fractionation of moderately reduced mafic magmas in these systems magnetite saturation is delayed and the ferric iron budget is finite i type systems originate with the supply of relatively oxidised hydrous subduction related magmas from the mantle wedge to the upper plate crust these then experience oxygen buffered open system afc processes in lower crustal hot zones s type magmas are crustal melts that crystallise under reduced conditions initially imposed at source by sulphidic or graphitic sedimentary protoliths the composition of the resulting melts reflects the domination of partial melting where conditions are hence buffered open system followed by subsequent late stage closed system fractionation of these extracted reduced magmas

strontium neodymium and lead isotopic compositions of deep crustal xenoliths from the snake river plain evidence for archean basement abstract xenoliths of intermediate to felsic granulites found in evolved lavas from the snake river plain have been analyzed for nd pb and sr isotopic compositions and related trace element contents overall they exhibit wide ranges in present day values of 87 sr 86 sr 0 70235 0 83011 143 nd 144 nd 0 51023 0 51148 and 206 pb 204 pb 13 43 24 65 the rb sr u pb th pb and sm nd decay schemes have been variably affected by granulite facies metamorphism and possibly by transport in the host magmas however pb pb and sm nd isochron systematics seemingly are preserved in many of the xenoliths and indicate essentially concordant metamorphic ages of about 2 8 ga nd model ages are significantly older ca 3 1 3 4 ga for many of the xenoliths precambrian metasediments exposed along the southern margin of the snake river plain have sm nd systematics similar to those of the xenoliths these results suggest that at least two significant thermal events occurred during archean evolution of the crust in this region a early ca 3 1 3 4 ga additions of mantle derived magmas to the crust and b regional metamorphism at 2 8 ga accompanied at least locally by magmatism concordance between the sm nd and pb pb ages suggests that these isotopic systems are little affected by high grade metamorphism in this case the distribution of xenoliths in snake river plain lavas supports the presence of archean crust beneath much of southern idaho although such rocks rarely are exposed at the surface thus nd and pb isotopic studies of crustal xenoliths can provide a useful means of determining the extent of crustal age provinces where surface exposures are lacking

post caldera volcanism in situ measurement of u pb age and oxygen isotope ratio in pleistocene zircons from yellowstone caldera the yellowstone plateau volcanic field the site of some of the largest known silicic volcanic eruptions is the present location of ne migrating hotspot volcanic activity most volcanic rocks in the yellowstone caldera 0 6 ma which formed in response to the climactic eruption of 1000 km 3 of lava creek tuff lct have unusually low oxygen isotope ratios ion microprobe analysis of both u pb age and n 18 o in zircons from these low n 18 o lavas reveals evidence of complex inheritance and remelting a majority of analyzed zircons from low n 18 o lavas erupted inside the yellowstone caldera have cores that range in age from 2 4 to 0 7 ma significantly older than their eruption ages 0 5 0 4 ma these ages and the high n 18 o cores indicate that these lavas are largely derived from nearly total remelting of normal n 18 o huckleberry ridge tuff hrt and other pre lct volcanic rocks a post hrt low n 18 o lava shows similar inheritance of hrt age zircons the recycling of volcanic rocks by shallow remelting can change the water content and eruptive potential of magma this newly proposed mechanism of intracaldera volcanism is best studied by combining in situ analysis of oxygen and u pb isotope ratios of individual crystals fl 2001 elsevier science b v all rights reserved

seismic source mechanism of degassing bursts at kilauea volcano hawaii results from waveform inversion in the 10 50 s band the current march 2008 to february 2009 summit eruptive activity at kilauea volcano is characterized by explosive degassing bursts accompanied by very long period vlp seismic signals we model the source mechanisms of vlp signals in the 10 50 s band using data recorded for 15 bursts with a 10 station broadband network deployed in the summit caldera to determine the source centroid location and source mechanism we minimize the residual error between data and synthetics calculated by the finite difference method for a point source embedded in a homogeneous medium that takes topography into account the vlp signals associated with the bursts originate in a source region 1 km below the eastern perimeter of halemaumau pit crater the observed waveforms are well explained by the combination of a volumetric component and a vertical single force component for the volumetric component several source geometries are obtained which equally explain the observed waveforms these geometries include 1 a pipe dipping 64 to the northeast 2 two intersecting cracks including an east striking crack dike dipping 80 to the north intersecting a north striking crack another dike dipping 65 to the east 3 a pipe dipping 58 to the northeast intersecting a crack dipping 48 to the west southwest and 4 a pipe dipping 57 to the northeast intersecting a pipe dipping 58 to the west southwest using the dual crack model as reference the largest volume change obtained among the 15 bursts is 24 400 m3 and the maximum amplitude peak to peak of the force is 20 gn each burst is marked by a similar sequence of deflation and inflation trailed by decaying oscillations of the volumetric source the vertical force is initially upward synchronous with source deflation then downward synchronous with source reinflation followed by oscillations with polarity opposite to the volumetric oscillations this combination of force and volume change is attributed to pressure and momentum changes induced during a fluid dynamic source mechanism involving the ascent expansion and burst of a large slug of gas within the upper 150 m of the magma conduit as the slug expands upon approach to the surface and more liquid becomes wall supported by viscous shear forces the pressure below the slug decreases inducing conduit deflation and an upward force on the earth the final rapid slug expansion and burst stimulate vlp and lp oscillations of the conduit system which slowly decay due to viscous dissipation and elastic radiation consideration of the fluid dynamic arguments leads us to prefer the dual crack vlp source model as it is the only candidate model capable of producing plausible values of length scales and pressure changes the magnitudes of the vertical forces observed in the 15 bursts appear consistent with slug masses of 104 to 106 kg

trace elements and u pb ages in petrified wood as indicators of paleo hydrologic events abstract subsurface fluid systems are important for chemical weathering ore formation and thermal evolution of the crust changes in the dynamics and distribution of subsurface fluid flow systems are controlled by changes in global and regional terrestrial climate tectonics and elevation this paper concerns the dating of changes in ancient subsurface hydrologic systems however direct dating of water rock interaction is challenging because of the lack of appropriate materials to date and the more open and complex nature of subsurface flow regimes here we explore the prospects of using u pb dating of petrified silicified wood as a means of quantifying continental paleo hydrology oxidizing fluids often of meteoric origin tend to leach and mobilize u from the country rock but when such waters contact organic rich material u can become reduced and immobilized resulting in u rich silicified wood we present in situ laser ablation icpms analyses of u pb isotopes and trace elements in petrified wood from the upper triassic chinle formation 225 208 myr in the petrified forest national park in arizona usa allowing us to establish a generalized workflow for making meaningful paleo hydrologic interpretations of the u pb systematics of silicified wood wood characterized by brownish colors and preservation of cellular structure have low fe contents and positive ce anomalies indicating silicification in reducing environments and isolation in relatively reduced conditions after silicification resulting in closed system behavior of u and pb wood characterized by vivid colors orange red etc and little to no preservation of cellular structure are much higher in fe and exhibit negative ce anomalies indicating influence by more oxidized fluids the brownish samples yield u pb ages clustered between 250 and 200 ma with a peak coinciding with the time of deposition 220 ma which indicates that fossilization largely took place almost immediately after deposition and that u pb in quartz faithfully retains the time of such fossilization in contrast the orangish reddish whitish samples yield younger u pb ages defining distinct errorchron ages which reflect subsequent generations of quartz crystallization scatter associated with errorchrons are likely due to local mm to cm scale u or pb mobility or variable initial pb composition distinct younger age peaks appear to correlate with the timing of regional unconformities associated with tectonic or epeirogenic uplift we suggest that uplift and exhumation may initiate the onset of oxidizing fluid systems resulting in leaching and transport of u from the surroundings followed by subsequent generations of quartz precipitation in summary u pb dating of petrified wood or silicified organic material has high potential for dating paleo hydrologic events however due to complexities in terrestrial hydrologic systems interpretations of u pb systematics must be informed by accompanying geochemical and textural observations

parallel climate and vegetation responses to the early holocene collapse of the laurentide ice sheet parallel changes in lake level and pollen data show that the rapid decline of the laurentide ice sheet lis between 10 000 and 8000 cal yr bp triggered a step like change in north american climates from an ice sheet and insolation dominated climate to a climate primarily controlled by insolation maps of the lake level data from across eastern north america show a reorganization of climate patterns that the pollen data independently match raised lake levels and expanded populations of moist tolerant southern pines pinus document that summer monsoons intensified in the southeastern united states between 9000 and 8000 cal yr bp simultaneously low lake levels and an eastward expansion of the prairie illustrate an increase in mid continental aridity after the hudson bay ice dome collapsed around 8200 cal yr bp lake levels rose in new england as populations of mesic plant taxa such as beech fagus and hemlock tsuga replaced those of dry tolerant northern pines pinus available moisture increased there after a related century scale period of colder than previous conditions around 8200 cal yr bp which is also recorded in the pollen data the comparison between pollen and lake level data confirms that vegetations dynamics reflect climatic patterns on the millennial scale

infrasonic harmonic tremor and degassing bursts from halema uma u crater kilauea volcano hawaii 1 the formation evolution collapse and subsequent resurrection of a vent within halema uma u crater kilauea volcano produced energetic and varied degassing signals recorded by a nearby infrasound array between 2008 and early 2009 after 25 years of quiescence a vent clearing explosive burst on 19 march 2008 produced a clear complex acoustic signal near continuous harmonic infrasonic tremor followed this burst until 4 december 2008 when a period of decreased degassing occurred the tremor spectra suggest volume oscillation and reverberation of a shallow gas filled cavity beneath the vent the dominant tremor peak can be sustained through helmholtz oscillations of the cavity while the secondary tremor peak and overtones are interpreted assuming acoustic resonance the dominant tremor frequency matches the oscillation frequency of the gas emanating from the vent observed by video tremor spectra and power are also correlated with cavity geometry and dynamics with the cavity depth estimated at 219 m and volume 3 106 m3 in november 2008 over 21 varied degassing bursts were observed with extended burst durations and frequency content consistent with a transient release of gas exciting the cavity into resonance correlation of infrasound with seismicity suggests an open system connecting the atmosphere to the seismic excitation process at depth numerous degassing bursts produced very long period 0 03 0 1 hz infrasound the first recorded at kilauea indicative of long duration atmospheric accelerations kilauea infrasound appears controlled by the exsolution of gas from the magma and the interaction of this gas with the conduits and cavities confining it

the landslide tsunami of november 3 1994 skagway harbor alaska we show that the tsunami of november 3 1994 in skagway alaska was generated by an underwater landslide formed during the collapse of a cruise ship wharf undergoing construction at the head of taiya inlet this event occurred at a time of extreme low tide and was not associated with a regional seismic event or incoming oceanic tsunami persistent wave motions with an amplitude of 1 m and a period of 3 min recorded by a tide gauge in skagway harbor following the landslide are linked to the formation of a cross inlet seiche and quarter wave resonance within the harbor the high q factor for the harbor q 20 indicates weak dissipation and strong resonance within the harbor

abrupt cooling repeatedly punctuated early holocene climate in eastern north america climate proxy records and general circulation models suggest that atlantic meridional overturning circulation amoc plays a key role for global climate changes paleoceanographic data document mul

the boron isotope systematics of the yellowstone national park wyoming hydrothermal system a reconnaissance abstract boron concentrations and isotope compositions have been measured in fourteen hot spring waters two drill hole waters an unaltered rhyolite flow and hydrothermally altered rhyolite from the geothermal system in yellowstone national park wyoming the samples are representative of the major thermal areas within the park and span the range of fluid types for the fluids the b concentrations range from 0 043 2 69 mm kg and the 11 b values range from 9 3 to 4 4 there is no relationship between the dissolved b concentrations or isotope compositions with the concentration of any major element other than cl or physical property each basin is characterized by a restricted range in b cl ratios and 11 b values hot spring waters from the morris basin upper geyser basin calcite springs and clearwater have 11 b values close to that of unaltered rhyolite 5 2 and are interpreted to have derived their b from this source waters from mammoth hot springs sheepeater and rainbow springs have lower 11 b values close to 8 these lower values may reflect leaching of b from sedimentary rocks outside the yellowstone caldera but they are similar to the 11 b value of hydrothermally altered rhyolite 9 7 hence the light boron isotope compositions recorded in these hot spring waters may reflect leaching of previously deposited hydrothermal minerals cooler springs along the yellowstone river just outside the park boundary have lower b concentrations and higher 11 b values that may reflect mixing with shallow meteoric water

large volume low δ18o rhyolites of the central snake river plain idaho usa the miocene bruneau jarbidge and adjacent volcanic fields of the central snake river plain southwest idaho are dominated by high temperature rhyolitic tuffs and lavas having an aggregate volume estimated as 7000 km3 samples from units representing at least 50 of this volume are strongly depleted in 18o with magmatic feldspar 18ovsmow vienna standard mean ocean water values between 1 4 and 3 8 the magnitude of the 18o depletion and the complete lack of any rhyolites with normal values 7 10 combine to suggest that assimilation or melting of a caldera block altered by near contemporaneous hydrothermal activity is unlikely instead we envisage generation of the high temperature rhyolites by shallow melting of idaho batholith rocks under the influence of the yellowstone hotspot affected by eocene meteoric hydrothermal events the seeming worldwide scarcity of strongly 18o depleted rhyolites may simply reflect a similar scarcity of suitable crustal protoliths

formation of low δ18o rhyolites after caldera collapse at yellowstone wyoming usa we present a new model for the genesis of low 18o rhyolites of the yellowstone caldera based on analyses of zircons and individual quartz phenocrysts low 18o rhyolites were erupted soon after the massive caldera forming lava creek tuff eruption 602 ka 1000 km3 and contain xenocrysts of quartz and zircon inherited from precaldera rhyolites these zircons are isotopically zoned and out of equilibrium with their host low 18o melts and quartz diffusion modeling predicts that magmatic disequilibria of oxygen isotopes persists for as much as tens of thousands of years following nearly total remelting of the hydrothermally altered igneous roots of the depressed cauldron in which the alteration resistant quartz and zircon initially retained their 18o values these results link melting to caldera collapse rule out rapid or catastrophic magma meteoric water interaction and indicate wholesale melting rather than assimilation or partial melting

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

monitoring very long period seismicity at kilauea volcano hawaii 1 on 19 march 2008 eruptive activity returned to the summit of kilauea volcano hawaii with the formation of a new vent within the halemaumau pit crater the new vent has been gradually increasing in size and exhibiting sustained degassing and the episodic bursting of gas slugs at the surface of a lava pond 200 m below the floor of halemaumau the spectral characteristics source location obtained by radial semblance and hidden markov model pattern recognition of the degassing burst signals are consistent with an increase in gas content in the magma transport system beginning in october 2007 this increase plateaus between march september 2008 and exhibits a fluctuating pattern until 31 january 2010 suggesting that the release of gas is slowly diminishing over time

low δ18o rhyolites from yellowstone magmatic evolution based on analyses of zircons and individual phenocrysts the yellowstone plateau volcanic field is one of the largest centers exchange time to form zoned zircons is between a few hundred and a few thousand years which reflects the residence time of lowo of rhyolitic magmatism on earth major caldera forming eruptions are followed by unusual lowo rhyolites new oxygen isotope magmas after formation and before eruption petrologic and geochemical data from rhyolites belonging to the 2 0 my eruptive history of yellowstone are presented with emphasis on the genesis of lowo magmas erupted after the huckleberry ridge tuff 2 0 ma 2500 km and lava creek tuff 0 6 ma

abrupt climate oscillations during the last deglaciation in central north america evidence from stable isotopes and a variety of proxies from two ontario lakes demonstrate that many of the late glacial to early holocene events that are well known from the north atlantic seaboard such as the gerzensee killarney oscillation also known as the intra allerod cold period younger dryas and preboreal oscillation also occurred in central north america these results thus imply that climatic forcing acted in the same manner in both regions and that atmospheric circulation played an important role in the propagation of these events

lithosphere scale thrusting in the western u s cordillera as constrained by sr and nd isotopic transitions in neogene volcanic rocks the western idaho suture zone juxtaposes continental and oceanic terranes with distinctive sr and nd isotopic signatures across a sharp isotopic transition coincident with the mesozoic sup 87 sr sup 86 sr 0 706 line msl late cretaceous to eocene granitic plutons that define the msl are allochthonous and were transported eastward by approximately 150 km during late mesozoic to tertiary ca 100 55 ma thrusting sr and nd isotopic compositions of neogene rhyolites and basalts from southwestern idaho southeastern oregon and northern nevada define isotopic transitions coincident with the msl there are continental affinities east of long 116 degree 30minutesw and oceanic affinities west of 119w between these longitudes intermediate isotopic compositions imply derivation of magmas from both continental and oceanic mantle basalts and crustal rhyolites sources it is inferred that the basal decollement of the mesozoic and tertiary contractional orogen dips westward below depths of segregation of basaltic magmas and that oceanic lithospheric mantle was thrust eastward over a shelf of old isotopically evolved continental lithospheric mantle that now protrudes approximately 150 km west of the msl

delta15n measurements as a calibration tool for the paleothermometer and gas ice age differences a case study for the 8200 b p event on grip ice isotopic composition measurement on atmospheric nitrogen 15n trapped in ice cores is established as a gravitational enrichment indicator recently it was discovered that thermal diffusion has a significant influence on this parameter during periods of large temperature fluctuations severinghaus et al 1998 here we present results for the 8200 b p event the largest temperature excursion during the holocene which underpin this view and extend it to medium range temperature changes the thermal diffusion component is about one third of the gravitational enrichment for this event the shortness of this cooling event does not significantly affect the gravitational enrichment as documented by rather constant close off depths therefore the 15n residuals can be directly used to estimate temperature changes hence calibrating the paleothermometer since our 15n record can resolve temperature variations as short as a few decades it complements the calibration technique of borehole temperature measurements for which the resolution decreases rapidly with increasing age we obtained a relation 18oice temperature of 0 30 0 11 k which agrees nicely with the temporal dependence for cold periods about 0 30 k and is significantly lower than today s greenland spatial relation 0 67 k this corresponds to a range of the surface temperature shift for the 8200 b p event in central greenland between 5 4 and 11 7 k with a best estimate of 7 4 k by matching the 15n variations with 18oice variations we estimate the mean gas ice age difference to be 209 15 years which is in good agreement with model estimates

the 8k event cause and consequences of a major holocene abrupt climate change abstract a prominent abrupt climate event about 8200 years ago brought generally cold and dry conditions to broad northern hemisphere regions especially in wintertime in response to a very large outburst flood that freshened the north atlantic changes were much larger than typical climate variability before and after the event with anomalies up to many degrees contributing to major displacement of vegetative patterns this 8k event provides a clear case of cause and effect in the paleoclimatic realm and so offers an excellent opportunity for model testing the response to north atlantic freshening has the same general anomaly pattern as observed for older events associated with abrupt climate changes following north atlantic freshening and so greatly strengthens the case that those older events also reflect north atlantic changes the north atlantic involvement in the 8k event helps in estimating limits on climate anomalies that might result in the future if warming caused ice melt and hydrologic cycle intensification at high latitudes lead to major changes in north atlantic circulation few model experiments have directly addressed the 8k event and most studies of proxy records across this event lack the time resolution to fully characterize the anomalies so much work remains to be done

observing calving generated ocean waves with coastal broadband seismometers jakobshavn isbrae greenland we use time lapse photography modis satellite imagery ocean wave measurements and regional broadband seismic data to demonstrate that icebergs that calve from jakobshavn isbrae greenland can generate ocean waves that are detectable over 150 km from their source the waves which are recorded seismically have distinct spectral peaks are not dispersive and persist for several hours on the basis of these observations we suggest that calving events at jakobshavn isbrae can stimulate seiches or basin eigenmodes in both ilulissat icefjord and disko bay our observations furthermore indicate that coastal land based seismometers located near calving termini e g as part of the new greenland ice sheet monitoring network glisn can aid investigations into the largely unexplored oceanographic consequences of iceberg calving

boron sr o and h isotope geochemistry of groundwaters from mt etna sicily hydrologic implications combined b o h and sr isotopic studies of groundwaters from mt etna provide new constraints on their origin and the consequences of fluid rock interaction within this hydrologic system variations in d 18 o 29 7 to 27 2 and d d 262 to 223 mainly lie along the regional meteoric water line and suggest that most waters originated as local precipitation however small shifts in d 18 o and variable 87 sr 86 sr 0 70355 to 0 70879 and d 11 b 25 2 to 125 8 indicate that subsequent interactions occurred between the fluids and local rocks high b cl ratios in all samples seemingly preclude direct involvement of seawater in the hydrologic system despite the proximity to the coast and in some samples elevated 87 sr 86 sr and d 11 b two general end member water types are recognized on the basis of their chemistry these apparently are produced by interactions of local meteoric waters with the dominant reservoir rocks either basaltic lavas of etna or the underlying sediments respectively high d 11 b in the sediment hosted end member points to a significant marine carbonate contribution subsequent mixing between these or similar end members produced a range of intermediate composition groundwaters certain anomalous water compositions require the presence locally of a distinct component with high b and moderate d 11 b ca 110 but relatively low 87 sr 86 sr an anthropogenic source for this component is plausible one unusual sample has b and sr isotopic compositions similar to the other volcanic rock hosted waters but anomalously high cl content that likely reflects local magmatic outgassing near this sampling locality in general this study indicates that groundwater b and sr isotopic compositions are rock dominated these data provide useful constraints on the origin and evolution of groundwaters copyright 2000 elsevier science ltd

very long period conduit oscillations induced by rockfalls at kilauea volcano hawaii 1 eruptive activity at the summit of kilauea volcano hawaii beginning in 2010 and continuing to the present time is characterized by transient outgassing bursts accompanied by very long period vlp seismic signals triggered by rockfalls from the vent walls impacting a lava lake in a pit within the halemaumau pit crater we use raw data recorded with an 11 station broadband network to model the source mechanism of signals accompanying two large rockfalls on 29 august 2012 and two smaller average rockfalls obtained by stacking over all events with similar waveforms to improve the signal to noise ratio to determine the source centroid location and source mechanism we minimize the residual error between data and synthetics calculated by the finite difference method for a point source embedded in a homogeneous medium that takes topography into account we apply a new waveform inversion method that accounts for the contributions from both translation and tilt in horizontal seismograms through the use of green s functions representing the seismometer response to translation and tilt ground motions this method enables a robust description of the source mechanism over the period range 1 1000 s the vlp signals associated with the rockfalls originate in a source region 1 km below the eastern perimeter of the halemaumau pit crater the observed waveforms are well explained by a simple volumetric source with geometry composed of two intersecting cracks including an east striking crack dike dipping 80 to the north intersecting a north striking crack another dike dipping 65 to the east each rockfall is marked by a similar step like inflation trailed by decaying oscillations of the volumetric source attributed to the efficient coupling at the source centroid location of the pressure and momentum changes induced by the rock mass impacting the top of the lava column assuming a simple lumped parameter representation of the shallow magmatic system the observed pressure and volume variations can be modeled with the following attributes rockfall volume 200 4500 m3 length of magma column 120 210 m diameter of pipe connecting the halemaumau pit crater to the subjacent dike system 6 m average thickness of the two underlying dikes 3 6 m and effective magma viscosity 30 210 pa s most rockfalls occur during episodes of sustained deflation of the kilauea summit the mass loss rate in the shallow magmatic system is estimated to be 1400 15 000 kg s 1 based on measurements of the temporal variation of vlp period in the two large rockfalls that occurred on 29 august 2012

quantifying trace element disequilibria in mantle xenoliths and abyssal peridotites we apply a tool based on element distribution between orthopyroxene and clinopyroxene for quantifying rare earth element ree disequilibria in ultramafic rocks in the subsolidus state we present case studies of the ree contents of mineral cores in mantle xenoliths and abyssal peridotites using in situ analytical tools even when only mineral cores are measured to avoid enriched rims equilibrium is not always achieved on the mineral scale mineral cores in mantle xenoliths are closer to equilibrium than those in abyssal peridotites even though mantle xenoliths are known to be light ree contaminated from the host lava in the case of the abyssal peridotites 13 out of 14 are out of equilibrium with the least metasomatized most in disequilibrium and the most metasomatized closest to equilibrium we discuss hypotheses for these observations but regardless of what caused the disequilibria this tool allows one to see through the effects of secondary processes such as infiltration by fluid inclusions via cracks and diffusive exchange between minerals and melts fluids along grain boundaries the ease of making in situ ree measurements makes this tool formidable in identifying different generations of clinopyroxenes in ultramafic lithologies such data will complement the interpretation of isotopic and petrographic studies of continental and oceanic lithospheric mantle

abrupt changes in north american climate during early holocene times recent studies of the greenland ice cores have offered many insights into holocene climatic dynamics at decadal to century timescales1 2 3 despite the abundance of continental records of holocene climate few have sufficient chronological control and sampling resolution to compare with the greenland findings4 butannually laminated sediments varves from lakes can provide high resolution continental palaeoclimate data with secure chronologies here we present analyses of varved sediments from deep lake in minnesota usa trends in the stable oxygen isotope composition of the sedimentary carbonate indicate a pronounced climate cooling from 8 9 to 8 3 kyr before present probably characterized by increased outbreaks of polar air decreased precipitation temperatures and a higher fraction of the annual precipitation falling as snow the abrupt onset of this climate reversal over several decades was probably caused by a reorganization of atmospheric circulation and cooling of the arctic airmass in summer that resulted from the final collapse of the laurentide ice near hudson bay and the discharge of icebergs from the quebec and keewatin centres into the tyrell sea the timing and duration of this climate reversal suggest that it is distinct from the prominent widespread cold snap that occurred 8 200 years ago in greenland and other regions1 5 6 no shifts in the oxygen isotope composition of sediment carbonate occurred at 8 2 kyr before present at deep lake but varve thickness increased dramatically probably as a result of increased deposition of aeolian dust taken together our data suggest that two separate regional scale climate reversals occurred between 9 000 and 8 000 years ago and that they were driven by different mechanisms

terrestrial sensitivity to abrupt cooling recorded by aeolian activity in northwest ohio usa article i nfo article history received 7 may 2010 available online 21 february 2011 optically stimulated luminescence dated sand dunes and pleistocene beach ridges in northwest ohio are used to reconstruct landscape modification more than 5000 yr after deglaciation four of the osl ages 13 3 11 1 ka cluster around the younger dryas cold event five ages 10 8 8 2 ka cluster around the preboreal one young age 0 9 0 7 ka records more recent aeolian activity and one age of 15 1 13 1 ka dates a barrier spit in lake warren in northwest ohio both landscape instability recorded by aeolian activity and a vegetation response recorded by pollen are coeval with the younger dryas however the climate conditions during the preboreal resulting in aeolian activity are not recorded in the available pollen records from this we conclude that aeolian dunes and surfaces susceptible to deflation are sensitive to cooler drier episodes of climate and can complement pollen data younger dryas and preboreal aged aeolian activity in northwestern ohio coincides with aeolian records elsewhere in the great lakes region east of the prairie forest ecotone

lava lake sloshing modes during the 2018 kīlauea volcano eruption probe magma reservoir storativity abstract basaltic volcanoes like k lauea hawai i pose hazards through lava flows and other eruptive activity quantifying hazard requires constraining the volume of magma stored in shallow reservoirs as well as the capacity of those reservoirs to accumulate and discharge magma in response to pressure changes i e storativity shallow reservoirs are often connected through magmatic conduits to lava lakes which are frequently perturbed by rockfalls convection and outgassing here we present a novel method to quantify reservoir storativity at kilauea that exploits the seismically observable oscillatory response of the lake conduit reservoir system to perturbations during the may 2018 eruption seismic events recorded by the summit broadband seismometer network during the eruption feature multiple oscillatory modes in the very long period vlp band the longest period mode 30 40 s here termed the conduit reservoir mode persisted during drainage of the lava lake indicating its primary association with the underlying conduit reservoir system additional modes with periods of 10 20 s vanished during lake drainage and are attributed to lava lake sloshing the surface displacements of the two longest period sloshing modes are explained as the superimposed response to a near surface horizontal force along the axes of the crater from the pressure imbalance during sloshing on the crater walls and a volume change in a reservoir located at the conduit reservoir mode source centroid both sloshing modes are in the deep water surface gravity wave limit where disturbances are largest near the lake surface though pressure changes on the top of the conduit at the lake bottom provide the observed excitation of the underlying conduit reservoir system combining magma sloshing dynamics in the crater and a conduit reservoir oscillation model we bound the storativity of the reservoir to be greater than 0 4 m3 pa this implies a storage volume of a few km3 for an approximately equidimensional e g spherical reservoir a smaller volume is possible but requires the presence of other shapes of magma bodies such as sills or dikes and or significant finite source effect our work demonstrates the signature of lava lake sloshing modes in the seismic data and the potential of these modes in constraining the structure of the shallow magmatic system

paleohydraulics of the last outburst flood from glacial lake agassiz and the 8200 bp cold event abstract during the last deglaciation of north america huge proglacial lakes formed along the southern margin of the laurentide ice sheet the largest of these was glacial lake agassiz which formed about 11 7 14 c kyr and drained into hudson bay about 7 7 14 c kyr 8 45 cal kyr overflow from these lakes was variably directed to the mississippi st lawrence and mackenzie drainage systems and it is thought that switches in routing were accompanied by a response in ocean circulation that produced abrupt climate events when the ice dam across hudson bay finally was breached a massive flood drained lake agassiz which was routed through hudson strait to the labrador sea in terms of stored water volume the largest reservoir was associated with the kinojevis level of lake agassiz for this maximum filling the impounded water volume available to produce floods is estimated as 40 000 151 000 km 3 depending on the location of the ice margin and route used the timing of this rapid release of stored freshwater just precedes the early holocene cooling event at 8 2 cal kyr bp we use the spring hutter theory to simulate flood hydrographs for floods that originate in subglacial drainage conduits and find that flood magnitude and duration are 5 sv and 0 5 yr multiple fillings and floods are possible as are single floods having a complex multipulse structure modelling results suggest that the outburst flood from lake agassiz may have terminated before the lake surface elevation dropped to sea level and that the flood ended when a stable drainage channel was established connecting lake agassiz to the tyrrell sea

detrital metamorphic and metasomatic tourmaline in high pressure metasediments from syros greece intra grain boron isotope patterns determined by secondary ion mass spectrometry the boron isotopic composition of zoned tourmaline in two metasediments from the island of syros determined by secondary ion mass spectrometry sims reflects the sedimentary and metamorphic record of the rocks tourmaline from a silicate bearing marble contains small 20 m detrital cores with highly variable 11b values 10 7 to 3 6 pointing to a heterogeneous protolith derived from multiple sources the sedimentary b isotopic record survived the entire metamorphic cycle with peak temperatures of 500 c prograde to peak metamorphic rims are homogeneous and similar among all analysed grains 11b 0 9 the varying 11b values of detrital cores in the siliceous marble demonstrate that in situ b isotope analysis of tourmaline by sims is a potentially powerful tool for provenance studies not only in sediments but also in metasediments a meta tuffitic blueschist bears abundant tourmaline with dravitic cores of detrital or authigenic origin 11b 3 3 and prograde to peak metamorphic overgrowth zones 1 6 fe rich rims formed during influx of b bearing fluids under retrograde conditions show strongly increasing 11b values up to 7 7 towards the margins of the grains the 11b values of metamorphic tourmaline from syros formed in mixed terrigenous marine sediments reflect the b signal blended from these two different sources and was probably not altered by dehydration during subduction

magma reservoir failure and the onset of caldera collapse at kīlauea volcano in 2018 introduction the 2018 rift zone eruption of k lauea volcano hawai i drained large volumes of magma from the volcano s summit reservoir system causing high rate subsidence of the ground surface and withdrawal of an active lava lake over the span of 1 week the surface of the lava lake fell more than 300 m continued withdrawal of magma caused the rock above the reservoir to fail triggering the onset of episodic caldera collapse surface collapse began near the evacuated lava lake vent but as the eruption continued over 3 months the area of the new caldera expanded to 5 km2 and its volume grew to 0 8 km3 the precursory activity and subsequent growth of the caldera were recorded in far greater detail than was possible at the handful of other caldera collapses observed in the past century these comprehensive observations permit new insights into the conditions that lead to magma reservoir host rock failure and caldera collapse rationale volcanic caldera collapses can be highly destructive and create prominent topographic features but little is known about the architecture of subcaldera magma storage zones or the critical decrease in pressure that triggers collapse withdrawal of k lauea s lava lake in 2018 can be used to gauge pressure change in the underlying magma reservoir we developed a model of time evolving reservoir depressurization to jointly explain lava lake withdrawal rate and the rate and spatial pattern of ground subsidence obtained from radar satellites and a dense local monitoring network results we tracked the evolution of the magmatic system from steady elastic decompression to inelastic failure we were able to estimate the location geometry volume and time evolving pressure within the reservoir as well as conditions required to trigger failure of the overlying crust before the onset of collapse the ground at k lauea s summit was subsiding at nearly 10 cm day and the lava lake surface was retreating at 50 m day we found that these phenomena were caused by drainage of magma at a high rate from a storage reservoir centered 2 km below the surface with a volume of several cubic kilometers drainage rapidly reduced reservoir pressure stressing the surrounding crust two weeks after the rift zone intrusion and eruption began to drain magma from the summit withdrawal of conclusion our results tightly constrain the pressure decrease in the magma reservoir before the onset of collapse together with geodetic data this bounds the magma storage volume and the stress changes needed to cause failure of the host rock above the reservoir our results demonstrate that a magma reservoir s roof may begin to fail after withdrawal of only a small fraction of the stored magma at k lauea this process was likely influenced by a relatively thin and wide reservoir roof and preexisting crustal weaknesses including an established caldera ring fault system and the lava lake vent roof collapses maintained magma pressure sustaining the eruption but they did not as is sometimes assumed completely repressurize the reservoir this indicates residual frictional strength on the collapse bounding faults the eruption was not terminated by complete evacuation of stored magma contrary to assumptions sometimes made when interpreting data from past caldera collapses and indicates that a different process was responsible for the cessation of the eruption joint monitoring of ground deformation and lava lake elevation at other volcanoes when possible may yield rich insights into magmatic processes and conditions

experimental measurement of boron isotope fractionation in seawater abstract the boron isotopic composition of marine carbonates is considered to be a tracer of seawater ph use of this proxy benefits from an intimate understanding of chemical kinetics and thermodynamic isotope exchange reactions between the two dominant boron bearing species in seawater boric acid b oh 3 and borate ion b oh 4 however because of our inability to quantitatively separate these species in solution the degree of boron isotope exchange has only been known through theoretical estimates in this study we present results of a spectrophotometric procedure wherein the boron isotope equilibrium constant 11 10 k b is determined empirically from the difference in the dissociation constants of 11 b oh 3 and 10 b oh 3 in pure water 0 6 mol kg 1 h 2 o kcl and artificial seawater within experimental uncertainty our results show no dependence of 11 10 k b on temperature but 11 10 k b at 25 c in pure water was statistically different than results obtained in solutions at high ionic strength 11 10 k b of the seawater s 35 b t 0 01 mol kg 1 h 2 o at 25 c is 1 0272 0 0006 this result is significantly larger than the theoretical value used in numerous paleo ph studies 11 10 k b 1 0194

the fate of subducted oceanic slabs in the shallow mantle insights from boron isotopes and light element composition of metasomatized blueschists from the mariana forearc abstract serpentine muds from south chamorro seamount scs drilled during odp leg 195 at site 1200 contain metamafic clasts that experienced blueschist facies metamorphism including the critical mineral assemblage pumpellyite na amphibole epidote these schists represent fragments from the actual slab mantle interface at 27 km depth their heterogeneous lithology with a metasomatic character indicates significant mobility of major elements in the mariana forearc a region of melange formation as it can also be observed in onland exposures such as the catalina schist as the mariana forearc blueschists show no late stage alteration they permit the direct study of material transfer during the subduction processes at an active convergent margin this study presents the first data of detailed b isotope 11 b and light element variations in blueschist facies minerals from the mariana arc system the primary foci are b and li concentrations and 11 b values analyzed by sims and tof sims techniques minerals such as na rich amphibole phengite and chlorite are found to be strongly enriched in li up to 70 g g be up to 8 g g and b up to 35 g g and with 11 b values of 6 4 these new data are consistent with isotopically heavy b being released into the mariana forearc mantle wedge serpentinization of dry mantle peridotite after interaction with b rich slab released high ph fluids and confirm models of significant b loss and b isotope fractionation during forearc shallow slab dehydration the elevated li be and b concentrations in minerals that comprise the bulk of the rocks namely amphibole phengite and chlorite bear a strong potential to further transport li and b as well as the isotopically light component of b to greater depths in the mantle where ongoing metamorphism is responsible for further isotope and elemental fractionation and the formation of distinct mantle reservoirs e g volcanic arc and oceanic intra plate oib magmas

the yellowstone hotspot in space and time nd and hf isotopes in silicic magmas abstract over the course of its 16 m y history the yellowstone hotspot has produced silicic magmas exhibiting systematic and often sympathetic variations in isotopic and chemical composition temperature and frequency of eruption nd and hf isotopic ratios vary systematically from initial eruptions at 16 ma contemporaneous with basaltic volcanism in eastern oregon and washington to the present day yellowstone volcanic plateau nd and hf isotopic ratios co vary and span the range of most terrestrial samples reflecting mixing of mantle and crustal sources earliest erupted silicic magmas were hot in excess of 1050 c relatively less evolved and have isotopic ratios within the range of contemporaneous columbia river flood basalts the transit of the hotspot across the lithospheric boundary between the western accreted oceanic terrain and the precambrian craton at 15 ma is marked by shifts in e nd from 4 to 11 and in e hf from 10 to 10 the duration of the transit yields a crustal magma source diameter of 70 km in the interval from 14 to 9 ma e nd systematically increases from 11 to 7 recording a minimum increase in the mantle component from 5 to 30 the mantle component could be twice as great depending upon the isotopic composition of crust and mantle reservoirs in this same interval peak temperatures of 1000 c occurred at 9 ma the last 8 m y are characterized by less frequent eruption of lower temperature 830 900 c and more compositionally evolved magmas

raman spectroscopy for the discrimination of tephras from the hekla eruptions of ad 1510 and 1947 tephrochronology the dating of sedimentary sequences using volcanic ash layers is an important tool for the dating and correlation of sedimentary sequences containing archives and proxies of past environmental change in addition tephra layers provide valuable information on the frequency and nature of ash fallout from volcanic activity successful tephrochronology is usually reliant on the correct geochemical identification of the tephra which has until now been based primarily on the analysis of major element oxide composition of glass shards using electron probe microanalysis epma however it is often impossible to differentiate key tephra layers using epma alone for example the hekla ad 1947 and 1510 tephras which are found as visible layers in iceland and also as crypto tephra microscopic layers in nw europe are currently indistinguishable using epma therefore other stratigraphic or chronological information is needed for their reliable identification raman spectroscopy is commonly used in chemistry since vibrational information is specific to the chemical bonds and symmetry of molecules and can provide a fingerprint by which these can be identified here we demonstrate how raman spectroscopy can be used for the successful discrimination of mineral species in tephra through the analysis of individual glass shards in this study we obtained spectra from minerals within the glass shards we analysed the microlites and intratelluric mineral phases that can definitely be attributed to the tephra shards and the glass itself phenocrysts were not analysed as they could be sourced locally from near site erosion raman spectroscopy can therefore be considered a valuable tool for both proximal and distal tephrochronology because of its non destructive nature and can be used to discriminate hekla 1510 from hekla 1947

geology and 40ar 39ar geochronology of the middle miocene mcdermitt volcanic field oregon and nevada silicic volcanism associated with propagating flood basalt dikes at initiation of the yellowstone hotspot

boron isotope systematics of marine sediments abstract boron contents and boron isotopic compositions were determined for modern and ancient permian to miocene marine sediments including pelagic clay calcareous ooze siliceous ooze and neritic clay sediments 11b values of modern marine sediments range from 6 6 to 4 8 isotopic variation is controlled by the simple mixing of four major constituents detritus of continental origin marine smectite biogenic carbonates and biogenic silica detritus of continental origin with an average 11b value of 13 to 8 is the low 11b end member constituent of marine sediments and its boron is largely controlled by the concentration of illite which originates from wind or fluvial transport marine smectite biogenic carbonate and biogenic silica on the other hand represent the high 11b end members with 11b values of 2 3 to 9 2 8 0 to 26 2 and 2 1 to 4 5 respectively these high 11b values are the result of the equilibrium uptake of boron from seawater spatial variations in boron isotopes in the pacific sediments are essentially due to the distribution of the above four constituents although ancient argillaceous sediments shale and slate have boron contents that are identical with those of modern equivalents boron contents of limestone and chert are distinctly lower than those of modern calcareous and siliceous oozes ancient marine sediments have systematically lower 11b values 17 0 to 5 6 than those of the modern sediments the lower 11b values can be caused by diagenesis which induces 1 preferential removal of high 11b boron in calcium carbonate and silica during recrystallization and 2 boron isotopic exchange in the course of the smectite illite transition the observed boron isotopic compositions of ancient argillaceous sediments are distinctly different from those of fresh and altered morb therefore boron isotope systematics will be useful in identifying components from the descending oceanic slab involved in the formation of island arc magma and in investigating mantle crust recycling through subduction processes

structure of the 8200 year cold event revealed by a speleothem trace element record abrupt first order shifts in strontium and phosphorus concentrations in stalagmite calcite deposited in western ireland during the 8200 year event the major cooling episode 8200 years before the present are interpreted as responses to a drier climate lasting about 37 years both shifts are centered on 8330 80 years before the present coinciding with a large oxygen isotope anomaly and a change in the calcite petrography in this very high resolution monthly record antipathetic second order oscillations in phosphorus and strontium reveal decreased growth rates and increased rainfall seasonality growth rate variations within the event reveal a two pronged structure consistent with recent model simulations

intensity gradients and reversals in late glacial environmental change in east central north america abstract radiocarbon dated pollen sites from the allegheny plateau east and the till plains west document significant vegetational and climatic change between 15 000 and 9000 14 c bp south of the great lakes although limited by the problems of no analog vegetation pollen transfer functions tf and response surfaces rs quantify the climatic changes including a cold oscillation chronologically equivalent to the european younger dryas phase i before ca 13 000 14 c bp conditions across the region were similar january 20 to 16 c july 12 c rs or 19 c tf mean annual precipitation 80 to 90 cm year 1 phase iia between ca 13 000 and 11 000 14 c bp n s and e w climate gradients were initiated till plains temperatures increased by ca 8 c in january and by 8 c rs or 2 3 c tf in july plateau increases for january were 3 6 c and for july were 8 c rs or 1 2 c tf precipitation generally increased somewhat phase iib ca 11 000 to 10 000 14 c bp gradients became less pronounced the western sites show a climate reversal january drop of ca 5 to 2 c july drop to ca 1 2 c becoming more like the plateau sites which show a brief small fluctuation this is followed by an abrupt 10 to 20 cm year 1 reduction in precipitation january warming of ca 3 c and continued cooler julys phase iii after 10 000 14 c bp gradients similar to those of today developed the changes in phases iib and iii are probably linked to the drainage history of the great lakes and via that history to the changes on the european continent

geochronology of age progressive volcanism of the oregon high lava plains implications for the plume interpretation of yellowstone 1 the high lava plains province hlp is a late cenozoic bimodal volcanic field at the northern margin of the basin and range province in southeastern oregon that hosts a westward younging trend of silicic volcanism that crudely mirrors northeastward migration of silicic volcanism along the yellowstone snake river plain ysrp trend we present 40ar 39ar ages for 19 rhyolite domes 5 rhyolite ash flow tuffs and 34 basaltic lavas from the hlp the previously identified trend of westward migration of hlp rhyolites is confirmed the rate of propagation is 33 km m y from 10 to 5 ma slowing to 13 km m y after 5 ma the duration of silicic volcanism at any locus is 2 m y three older hlp dacite domes yielded ages of 15 5 ma basalts are not age progressive we identify several episodes of increased basaltic activity at 7 5 7 8 5 3 5 9 and 2 3 ma with the younger episode likely continuing into the recent the hlp and ysrp trends emerged from the axis of middle miocene basaltic volcanism of the columbia river and steens basalts we propose a model in which 1 miocene flood basalts and widespread silicic rocks are the result of emplacement of a plume head near the craton margin enhanced by flow up a topographic gradient along the base of the lithosphere at the craton margin 2 the hlp trend is the result of westward flow originating at the craton margin and 3 the ysrp trend is the trace of the motion of the north american plate over the tail of the plume

boron isotope insights into the origin of subduction signatures in continent continent collision zone volcanism abstract we present the first boron abundance and 11 b data for young 1 5 0 ma volcanic rocks formed in an active continent continent collision zone the 11 b of post collisional volcanic rocks 5 to 2 from the armenian sector of the arabia eurasia collision zone are heavier than mid ocean ridge basalts morb confirming trace element and isotope evidence for their derivation from a subduction modified mantle source based on the low b nb 0 03 0 25 vs 0 2 90 in arc magmas as well as low ba th and pb ce this source records a subduction signature which is presently fluid mobile element depleted relative to most arc settings the heavier than morb 11 b of post collision volcanic rocks argues against derivation of their subduction signature from a stalled slab which would be expected to produce a component with a lighter than morb 11 b due to previous fluid depletion instead the similarity of 11 b in plio pleistocene post collision to 41 ma alkaline igneous rocks also from armenia and also presented in this study suggests that the subduction signature is inherited from mesozoic paleogene subduction of neotethys oceanic slabs the slab component is then stored in the mantle lithosphere in amphibole which is consistent with the low b in both armenian volcanic rocks and metasomatic amphibole in mantle xenoliths based on trace element and radiogenic isotope systematics this slab component is thought to be dominated by sediment melts or supercritical fluids previously published 11 b of metasediments suggests a sediment derived metasomatic agent could produce the b isotope composition observed in armenian volcanic rocks the lack of evidence for aqueous fluids preserved over the 40 myr since initial collision supports observations that this latter component is transitory while the lifetime of sediment melts supercritical fluids can be extended to 40 myr

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

the sedimentary cycle of the boron isotopes abstract marine sediments contain two isotopically distinct components a non desorbable fraction with 11b between 4 3 and 2 8 per mil n 10 and a desorbable component with 11b between 13 9 and 15 8 per mil n 6 the adsorption coefficient k for the uptake of b from seawater by fluvial suspended material mississippi has an experimentally determined value of 1 54 0 05 the associated isotope fractionation factor is 0 974 0 003 empirical values for k determined from the analysis of marine sediments n 6 were between 3 and 4 the amount of b adsorbed onto fluvial suspended material during estuarine mixing is about 9 109 moles yr based on pore water data adsorption experiments and comparative size fraction analyses suspended sediments from the mississippi river vs bottom deposits from the delta there is no evidence for the incorporation of b into detrital sediments at low temperature however the high b content of bauer deep metalliferous sediments must be due to incorporation of seawater b during formation of authigenic silicates the 11b of these minerals is 2 3 per mil hydrothermally altered sediments from dsdp hole 477 guaymas basin gulf of california have variable b contents from 33 ppm similar to the unaltered detritus to 1 2 ppm in the recrystallized material the latter has 11b as low as 9 0 per mil substantially lower than the unaltered material hydrothermal solutions collected from vents adjacent to the hole have boron contents elevated by about a factor of 4 relative to seawater and 11b between 16 5 and 23 2 per mil the b mobilized from the sediments is isotopically fractionated with the fluids being preferentially enriched in the heavy isotope analysis of an oxisol profile developed over granite in the guyana shield showed that boron is partially mobilized during weathering with an isotopic offset of 2 5 per mil between bedrock and soil the observed enrichment of b in shales relative to igneous rocks does not occur during weathering or during exposure to seawater at low temperature incorporation occurs only during burial diagenesis at temperatures greater than about 60 c however the enrichments cannot be attained during a single cycle of primary weathering and burial but must be cumulative over many cycles

excitation and resonance of acoustic gravity waves in a column of stratified bubbly magma oscillations of magma in volcanic conduits are thought to be the source of certain seismic and infrasonic signals observed near active volcanoes however the multiphase and stratified nature of magma within the conduit complicates the calculation of resonant modes that is required to interpret observations here we present a linearized mathematical framework to describe small amplitude oscillations and waves in a stably stratified column of two phase magma liquid melt and gas bubbles with a traction free upper surface a lava lake we explore the role of time dependent mass exchange between the phases depth varying fluid properties and gravity on the modes of oscillation of inviscid magma within an axisymmetric vertical conduit non equilibrium phase exchange which we refer to as bubble growth and resorption bgr is parameterized by introduction of a kinetic time scale quantifying mass exchange between the liquid and gas phases that evolves the mixture towards a state of thermodynamic equilibrium using a provably stable finite difference method we solve the eigenvalue problem for the resonance frequencies decay rates and spatial structure of the conduit eigenmodes the numerical method is then extended to time domain simulations of waves excited by internal volumetric sources in the conduit or forces applied to the surface of the lava lake we connect time dependent wave propagation simulations to the modal analysis by identifying the primary modes that are excited by representative excitation processes waves propagating through bubbly magma are dispersive and their behaviour is determined by three dimensionless parameters one quantifies the importance of buoyancy and gravitational restoring forces relative to compressibility the second quantifies differences between fluid properties e g mixture compressibility under equilibrium and non equilibrium conditions and the third compares the wave period to the bgr time scale pronounced depth variations in background fluid properties such as the transition from liquid melt with dissolved volatiles at the high pressures at depth to bubbly magma above the gas exsolution depth segment the conduit into distinct regions the longest period modes which are expressed with the largest amplitudes for typical excitation processes are most sensitive to the length of the bubbly region and properties of the bubbly magma within it while the boundary condition at the bottom of the conduit determines whether the fundamental mode is affected by the total conduit length modes localized above the exsolution depth are remarkably insensitive to the overall conduit length our analysis suggests that parameters affecting eruption style such as total volatile content and kinetic time scales of bgr along with excitation source characteristics are imprinted on long period seismic and infrasonic signals at active volcanoes

source composition and distribution of the fluid in the kurile mantle wedge constraints from across arc variations of b nb and b isotopes b and nb concentrations and b isotope composition were determined for lavas covering the entire length of the kurile arc b nb and 11b of these lavas show clear across arc variations in which both are highest at the trench side and continuously decrease as the slab depth increases b nb in the volcanic front lavas 8 25 is significantly higher than those of morb and oib indicating that the mantle wedge is extensively metasomatized by b rich fluid derived from the subducting slab the frontal 11b values are also out of the range of morb and oib and systematic difference exists between northern kurile nk 5 4 0 5 and central and southern kurile csk 4 3 0 3 however these two parameters approach or coincide with mantle values at the most back arc side the 11b and 87sr 86sr linearly correlate with nb b suggesting control by simple mixing of two isotopically homogeneous components that is slab derived fluid and mantle wedge the estimated 11b and 87sr 86sr of the fluid are 7 0 0 6 and 0 70326 0 00005 for nk and 6 3 0 3 and 0 7033 for csk respectively these fluid compositions are consistent with a source constituted by 95 altered oceanic crust and 5 oceanic sediment with the slight difference between nk and csk resulting from the different lithologies of subducting sediments the mantle wedge beneath the kurile arc has b sr and nd isotope compositions identical with morb but shows significantly higher b nb the above trends bear a close resemblance to those observed in the izu arc strongly suggesting their universality in the arc system the across arc decline of b nb observed both in kurile and izu implies that the fluid flux from the slab continuously decreases as the slab depth increases however this relates only to a final stage of slab dehydration since most of the volatile components are lost at the fore arc region in contrast to b k is uniformly enriched across the arc this requires control by a k bearing mineral phase either in the slab phengite or the mantle wedge phlogopite although such a mineral is responsible for only a small part of the whole fluid transport

isotopic and elemental partitioning of boron between hydrous fluid and silicate melt the fractionation of b and its isotopes between aqueous fluid and silicate melt has been studied from 550 to 1100 c and 100 500 mpa fluid melt partition coefficients are 1 for rhyolite melt this shows that b is not always strongly extracted from melts into hydrous fluids boron isotopic fractionation is large compared with the carbon and oxygen stable isotopic systems especially at high t and is most simply explained by differences in coordination trigonal vs tetrahedral among coexisting phases combined with earlier measurements on illite water 300 350 c b isotopic fractionation defines a temperature dependent trend from 300 to 1100 c because of the large magnitude and apparent low sensitivity to bulk composition b isotopic fractionation can be readily applied to studies of diagenesis hydrothermal alteration of planetary bodies subduction zone processing and arc magma generation and magma chamber evolution

constraints on the upper crustal magma reservoir beneath yellowstone caldera inferred from lake seiche induced strain observations 1 seiche waves in yellowstone lake with a 78 minute period and heights 10 cm act as a load on the solid earth observed by borehole strainmeters with subnanostrain sensitivity throughout the yellowstone caldera the far field strain induced by the load of the seiche waves calculated with a homogeneous elastic model representing the upper crust is more than an order of magnitude smaller than the measured strain amplitude 30 km from the lake shore by contrast the observed far field strain amplitudes are consistent with the seiche load on a two layered viscoelastic model representing an elastic upper crust overlying a partially molten body deeper than 3 6 km with maxwell viscosity less than 1011 pa s these strain observations and models provide independent evidence for the presence of partially molten material in the upper crust consistent with seismic tomography studies that inferred 10 30 melt fraction in the upper crust

climatic change recorded by stable isotopes and trace elements in a british holocene tufa combined stable isotope d18o and d13c and trace element mg sr geochemistry from bulk tufa calcite and ostracod shell calcite from an early holocene british tufa reveal clear records of holocene palaeoclimatic change variation in d18o is caused principally by change in the isotopic composition of holocene rainfall recharge itself caused mainly by change in air temperature the d13c variability through much of the deposit reflects increasing influence of soil zone co2 owing to progressive woodland soil development bulk tufa mg ca and sr ca are controlled by their concentrations in the spring water importantly mg ca ratios are not related to d18o values and thus show no temperature dependence first order sympathetic relationships between d13c values and mg ca and sr ca are controlled by aquifer processes residence times co2 degassing and calcite dissolution reprecipitation and probably record intensity of palaeorainfall recharge effects stable isotope records from ostracod shells show evidence of vital effects relative to bulk tufa data the ostracod isotopic records are markedly spiky because the ostracods record snapshots of relatively short duration years whereas the bulk tufa samples record averages of longer time periods probably decades the d18o record appears to show early holocene warming a thermal maximum at ca 8900 cal yr bp and the global 8200 yr bp cold event combined d13c mg ca and sr ca data suggest that early holocene warming was accompanied by decreasing rainfall intensity the mg ca data suggest that the 8200 yr bp cold event was also dry warmer and wetter conditions were re established after the 8200 yr bp cold event until the top of the preserved tufa sequence at ca 7100 cal yr bp

continuous gravity measurements reveal a low density lava lake at kīlauea volcano hawai i abstract on 5 march 2011 the lava lake within the summit eruptive vent at k lauea volcano hawai i began to drain as magma withdrew to feed a dike intrusion and fissure eruption on the volcano s east rift zone the draining was monitored by a variety of continuous geological and geophysical measurements including deformation thermal and visual imagery and gravity over the first 14 hours of the draining the ground near the eruptive vent subsided by about 0 15 m gravity dropped by more than 100 gal and the lava lake retreated by over 120 m we used gps data to correct the gravity signal for the effects of subsurface mass loss and vertical deformation in order to isolate the change in gravity due to draining of the lava lake alone using a model of the eruptive vent geometry based on visual observations and the lava level over time determined from thermal camera data we calculated the best fit lava density to the observed gravity decrease to our knowledge the first geophysical determination of the density of a lava lake anywhere in the world our result 950 300 kg m 3 suggests a lava density less than that of water and indicates that k lauea s lava lake is gas rich which can explain why rockfalls that impact the lake trigger small explosions knowledge of such a fundamental material property as density is also critical to investigations of lava lake convection and degassing and can inform calculations of pressure change in the subsurface magma plumbing system

the 8 2 ka abrupt climate change event in brown s lake northeast ohio many northern hemisphere paleoclimatic records including ice cores speleothems lake sediments ocean cores and glacier chronologies indicate an abrupt cooling event about 8200 cal yr bp a new well dated series of sediment cores taken from brown s lake a kettle in northeast ohio shows two closely spaced intervals of loess deposition during this time period the source of loess is uncertain however it is likely from an abandoned drainage and former glacial lake basin located to the north of the stagnant ice topography that gave rise to the kettle lake strong visual stratigraphy loss on ignition data and sediment grain size analyses dated with 3 ams radiocarbon dates place the two intervals of loess deposition between 8950 and 8005 cal yr bp the possibility of a two phase abrupt climate change at this time is a finding that has been suggested in other research this record adds detail to the spatial extent and timing as well as possible structure of the 8 2 ka abrupt climate change event

crustal reworking at convergent margins traced by fe isotopes in i type intrusions from the gangdese arc tibetan plateau abstract voluminous magmatism at active continental margins and collision zones is marked by i type intrusions paleocene eocene intrusions exposed in the lhasa terrane of the tibetan plateau are part of the gangdese arc that operated during neo tethyan ocean subduction and subsequent india asia collision arc like geochemical trace element signatures and radiogenic isotope systematics are indicative of juvenile i type magmatism with variable silica contents consequent to igneous differentiation here we present the first fe isotope data for this fossil arc terrane which have highly variable 57fe values relative to irmm 014 of 0 05 to 0 57 the data show no obvious correlations with major and trace element systematics except for highly evolved rocks with 70 wt sio2 based on trace element systematics deuteric fluid exsolution is excluded as a cause for the isotope variations in less evolved rocks furthermore there is no apparent relation between fe isotope values and the established tectonic evolution from syn to post collisional magmatism comparison with i type granites of the australian lachlan fold belt and cordilleran snake river plain reveals an on average lighter 57fe in the gangdese suite in primitive lavas yet distinctively heavier than intra oceanic arcs the heavier 57fe values for primitive lachlan fold belt and snake river plain rocks are interpreted here as crustal contribution in the form of s type magmas derived from crustal anatexis which are absent in the gangdese arc gangdese belt data yield an average 57fe of 0 13 0 02 2 which is proposed as the best estimate for juvenile crust at active continental margins rhyolite melts modelling suggests that the gangdese belt data can be reproduced through fractional crystallization along a liquid line of descent at oxygen fugacity between fmq 0 to 2 typical for arc related melts crucially the majority of data is coherent with partial melts of existing mafic crust as the major contributor to the juvenile component in the intrusions with minor mantle derived melts evidenced through heavier primitive fe isotopes this indicates that for the gangdese belt samples the primitive parental melts are derived from lower crustal successions through predominantly crustal reworking with only subordinate crustal growth hence the fe isotope data indicates a two step evolution with melting of underplated mafic material sometime in the geologic past although juvenile in nature these successions are part of the existing crust supporting scenarios in which crustal reworking in convergent margin intrusions is an important process in evolved magma generation

dynamics of magma storage in the summit reservoir of kilauea volcano hawaii an eruption of kilauea volcano hawaii normally results in a decrease in the internal pressure of a summit magma reservoir as it partly drains the interior of the volcano responses to the decrease in pressure 1 by elastic expansion of remaining magma and gas 2 additional exsolution of gas dissolved in the magma and 3 by contraction of the volcanic edifice this process is modeled here using gravity geodetic and observational data for recent events at kilauea during magma removal the ratio of pressure change in the magma reservoir to the volume of associated summit subsidence ranges from less than 0 22 pa m3 to more than 0 43 pa m3 lower ratios occur during large subsidences because of a large effective volume of the reservoir small events may involve source volumes of only 2 km3 in contrast a volume of near 13 km3 is associated with larger events because the boundary between plastic and elastic behavior may migrate outward with increased time and strain the aggregate compressibility of kilauea s reservoir is significantly increased by volumetric changes of the co2 gas phase by bulk compression and solution with pressure this effect is more pronounced for relatively shallow sources because the bulk modulus of gas is proportional to pressure the average reservoir co2 weight fraction may be near 0 0005 to 0 0009 co2 appears to accumulate in the upper portion of the reservoir where the concentration reaches 0 0030 weight fraction gradual long term subsidences are different from the short term deflations associated with specific eruptions during long term subsidence no net change in mass or pressure occurs within the summit reservoir rifting of the summit area which may tend to shorten the reservoir as it widens or slow degassing and contraction of stored magma may cause long term subsidence

variations in loess accumulation rates in the mid continent united states as reflected by magnetic susceptibility detailed magnetic susceptibility records of late wisconsin loess sequences in the southwest indiana region show several distinct changes in magnitude that reflect variations in loess accumulation rate the comparison of the magnetic susceptibility signal and sedimentary features within the loess reveal the following relations 1 low magnetic susceptibility values correspond to incipient paleosols that record periods of low loess accumulation rates 2 highly variable values within intermediate to high magnetic susceptibility zones correspond to stratified loess that represents periods of high loess accumulation rates and 3 moderate to high magnetic susceptibility values correspond to massive loess that may reflect periods of moderate to high loess accumulation rates we suspect that soil moisture controls the loess accumulation rate and if so our work shows that soil moisture alternated about 24 times between 25 and 14 ka in the middle of north america

characterization of very long period seismicity accompanying summit activity at kīlauea volcano hawai i 2007 2013 abstract eruptive activity returned to the summit region of k lauea volcano hawai i with the formation of the overlook crater within the halema uma u crater in march 2008 the new crater continued to grow through episodic collapse of the crater walls and as of late 2013 had grown into an approximately elliptical opening with dimensions of 160 215 m extending to a depth of 200 m occasional weak explosive events and a persistent gas plume continued to occur through 2013 lava was first observed in the new crater in september 2008 and through 2009 the lava level remained deep in the crater and was only occasionally observed since early 2010 a lava lake with fluctuating level within the overlook crater has been nearly continuously present and has reached to within 22 m of the overlook crater rim volcanic activity at k lauea volcano is episodic at all time scales and the characterization of very long period seismicity in the band 2 100 s for the years 2007 2013 illuminates a portion of this broad spectrum of volcanic behavior three types of very long period events have been observed over this time and each is associated with distinct processes type 1 events are associated with vigorous degassing and occurred primarily between 2007 and 2009 type 2 events are associated with rockfalls onto the lava lake and occurred primarily after early 2010 both of these event types are induced by pressure and momentum changes at the top of the magma column that are transmitted downward to a source centroid 1 km below the northeast corner of the halema uma u crater where the energy couples to the solid earth at a geometrical discontinuity in the underlying dike system type 3 events are not related to surficial phenomena but are associated with transients in mass transfer that occur within the dike system very long period tremor has also accompanied the return of eruptive activity with increasing amplitude associated with hours to months long changes in gas emission rates and summit deformation

boron in central andean ignimbrites implications for crustal boron cycles in an active continental margin abstract calc alkaline pumices and lavas from the neogene pleistocene central andean altiplano puna volcanic complex apvc contain quartz phenocrysts with abundant primary melt inclusions melt inclusions represent the melt composition of dacitic to rhyodacitic magmas prior to eruption and they are widely protected from eruptive degassing low temperature vapor phase alteration and post depositional contamination with boron rich dusts and aerosols the average boron isotopic compositions of melt inclusion and matrix glasses are uniform in the units studied overall average 11 b 3 8 2 8 1 sd and overlap with the range of local basement rocks 11 b 11 to 5 b is enriched in glasses 55 14 ppm 1 sd whereas whole rock contents range between 10 and 40 ppm at similar b contents incompatible trace element ratios like b nb are generally higher in the ignimbrites and lavas b nb 2 4 and 4 0 than in crustally derived paleozoic to cretaceous granitoids from nw argentina b nb 1 0 2 7 this suggests a minor contribution of high b nb arc andesites and is consistent with petrogenetic models in which apvc dacites originated from hybridization of dominantly crustally derived melts with andesitic magmas boron rich hydrothermal brines and salt lake water from within the apvc have 11 b 4 1 to 5 7 these values are close to the apvc ignimbrite values and contrast with hydrothermal brines from the eastern puna and eastern cordillera which have lower 11 b 10 to 17 and occur in an area of little volcanic cover this regional pattern suggests that borate enrichments resulted from the leaching of local country rocks ignimbrites in the w altiplano puna and paleozoic basement in the eastern puna and eastern cordillera

shallow degassing events as a trigger for very long period seismicity at kīlauea volcano hawai i the first eruptive activity at k lauea volcano s summit in 25 years began in march 2008 with the opening of a 35 m wide vent in halema uma u crater the new activity has produced prominent very long period vlp signals corresponding with two new behaviors episodic tremor bursts and small explosive events both of which represent degassing events from the top of the lava column previous work has shown that vlp seismicity has long been present at k lauea s summit and is sourced approximately 1 km below halema uma u by integrating video observations infrasound and seismic data we show that the onset of the large vlp signals occurs within several seconds of the onset of the degassing events this timing indicates that the vlp is caused by forces sourced at or very near the lava free surface due to degassing transmitted down the magma column and coupling to the surrounding rock at 1 km depth

magma oscillations in a conduit reservoir system application to very long period vlp seismicity at basaltic volcanoes 2 data inversion and interpretation at kīlauea volcano

remelting of an andesitic crust as a possible origin for rhyolitic magma in oceanic arcs an example from the izu bonin arc

seismically observed seiching in the panama canal 1 a large portion of the seismic noise spectrum is dominated by water wave energy coupled into the solid earth distinct mechanisms of water wave induced ground motions are distinguished by their spectral content for example cultural noise is generally 1 s period microseisms dominate the seismic spectrum from periods of 2 to 20 s and the earth s hum is in the range of 50 to 600 s we show that in a large lake in the panama canal there is an additional source of long period noise generated by standing water waves seiches induced by disturbances such as passing ships and wind pressure we compare seismic waveforms to water level records and relate these observations to changes in local tilt and gravity due to an oscillating seiche the methods and observations discussed in this paper provide a first step toward quantifying the impact of water inundation as recorded by seismometers this type of quantified understanding of water inundation will help in future estimates of similar phenomena such as the seismic observations of tsunami impact

direct evidence for the origin of low 18o silicic magmas quenched samples of a magma chamber s partially fused granitoid walls crater lake oregon abstract partially fused granitoid blocks were ejected in the climactic eruption of mount mazama which was accompanied by collapse of crater lake caldera quartz plagioclase and glass in the granitoids have much lower 18 o values 3 4 to 4 9 than any fresh lavas of mount mazama and the surrounding region 5 8 to 7 0 oxygen isotope fractionation between phases in granitoids is consistent with equilibrium at t 900 c following subsolidus exchange with hydrothermal fluids of meteoric origin assimilation of 10 20 of material similar to these granitoids can account for the o and sr isotopic compositions of lavas and juvenile pyroclasts derived from the climactic magma chamber many of which have 18 o values 0 5 or more lower than comparable lavas of mount mazama the o isotope data provide the only clear evidence for such assimilation because the mineralogy and chemical and radiogenic isotopic compositions of the granitoids dominantly granodiorite are similar to those of erupted juvenile magmas the granitoid blocks from crater lake serve as direct evidence for the origin of 18 o depletion in large shallow silicic magma bodies

magma compressibility and the missing source for some dike intrusions 1 dike intrusions are often accompanied by localized deflation interpreted as depressurizing magma chambers feeding the dike in some cases the inferred volume decrease is a factor of 4 or 5 less than the volume increase of the dike here we explore whether this discrepancy can be explained by compressibility of the magma combined with the fact that cracks are much more compliant than equidimensional magma chambers if pressure changes are small the magma compressibility m is constant and the dike ends up in hydrostatic equilibrium with an ellipsoidal magma chamber at the same depth the ratio rv of the volume of the crack to the volume lost by the chamber is rv 1 4 m 3 1 where is the host rock rigidity for gas poor magmas m 0 6 2 10 10 pa 1 and 3 25 gpa we find 1 2 rv 7 7 large changes in magma compressibility due to gas exsolution increase rv

pressure forced seiches of large amplitude in inlets of the balearic islands large amplitude harbor seiches usually occur in summer in the balearic islands a significant correlation between sea level oscillations and atmospheric pressure disturbances has been found though a proved physical mechanism to account for this atmosphere ocean interaction is still missing using a flat bottom shallow water model we show that a direct coupling between atmospheric pressure and the free mode of an inlet is unlikely but that an oceanic wave of atmospheric origin can act as an intermediate mechanism and adequately force the inlet by resonance the phase relationship derived from this mechanism is in good agreement with observations provided the whole spectrum of oceanic waves is in opposite phase to the generating atmospheric disturbance we also show that the very large oscillations observed at ciutadella an elongated shallow inlet in the west coast of menorca balearic islands can be explained in terms of the particular shape of this inlet

thermal structure beneath the snake river plain implications for the yellowstone hotspot basaltic magmatism associated with the yellowstone hotspot has been widely attributed to upwelling of a mantle plume yet the temporal and spatial distribution of these magmas and their compositional characteristics are distinctive from oceanic hotspot magmatism fundamental questions concern the influence of continental cratonic lithosphere in producing the differences and the extent to which upper plate processes contribute to magma production to better understand scenarios of melt generation p t conditions are estimated for segregation of primitive snake river plain srp basalts from the mantle combined with analysis of trace element and seismic constraints we conclude from this that 1 melt production was concentrated at depths between roughly 70 100 km 2 mantle temperature was only slightly higher than ambient conditions with a maximum potential temperature of 1450 c and 3 the mantle source was relatively fertile mg 90 these results suggest that the seismically imaged plume below yellowstone is significantly cooler than upwellings beneath hawaii iceland and many other oceanic hotspots our findings in combination with other geochemical and geodynamic considerations are permissive of magma generation within the ancient lithospheric mantle keel associated with the wyoming craton plume contributions while not excluded involve physical and geochemical implications that suggest they are subordinate

displacements and tilts from dip slip faults and magma chambers beneath irregular surface topography surface displacements and tilts due to buried deformation sources are influenced by topography the leading order corrections due to topography of arbitrary profile but small slope are determined for dip slip faults edge dislocations and magma bodies lines of inflation in a two dimensional elastic medium the vertical displacement correction is simply the product of the topography and the horizontal normal strain due to the source in a flat half space the correction for a normal fault beneath an idealized basin and range topography is a slight increase in the uplift on the range side the effect of topography for a line of inflation beneath a symmetric volcano is to reduce the central uplift failure to account for topographic influences can bias estimates of source depth and geometry

lava lake level as a gauge of magma reservoir pressure and eruptive hazard forecasting volcanic activity relies fundamentally on tracking magma pressure through the use of proxies such as ground surface deformation and earthquake rates lava lakes at open vent basaltic volcanoes provide a window into the uppermost magma system for gauging reservoir pressure changes more directly at k lauea volcano hawai i usa the surface height of the summit lava lake in halema uma u crater fluctuates with surface deformation over short hours to days and long weeks to months time scales this correlation implies that the lake behaves as a simple piezometer of the subsurface magma reservoir changes in lava level and summit deformation scale with and shortly precede changes in eruption rate from k lauea s east rift zone indicating that summit lava level can be used for short term forecasting of rift zone activity and associated hazards at k lauea

the 8200 year b p event in the slope water system western subpolar north atlantic 1 stable isotope trace metal alkenone paleothermometry and radiocarbon methods have been applied to sediment cores in the western subpolar north atlantic between hudson strait and cape hatteras to reveal the history of climate in that region over the past 11 kyr we focus on cores from the laurentian fan which is known to have rapid and continuous accumulation of hemipelagic sediment although results among our various proxy data are not always in agreement the weight of the evidence alkenone sea surface temperature sst 18o and abundance of globigerinoides ruber indicates a continual cooling of surface waters over laurentian fan from about 18 c in the early holocene to about 8 c today alternatively mg ca data on planktonic foraminifera indicate no systematic change in holocene sst the inferred long term decrease in sst was probably driven by decreasing seasonality of northern hemisphere insolation two series of proxy data show the gradual cooling was interrupted by a two step cold pulse that began 8500 years ago and lasted about 700 years although this event is associated with the final deglaciation of hudson bay there is no 18o minimum anywhere in the labrador sea yet there is some evidence for it as far south as cape hatteras finally although the 8200 year b p event has been implicated in decreasing north atlantic ventilation and hence widespread temperature depression on land and at sea we find inconsistent evidence for a change at that time in deep ocean nutrient content at 4 km water depth