calculated volumes of individual shield volcanoes at the young end of the hawaiian ridge abstract high resolution multibeam bathymetry and a digital elevation model of the hawaiian islands are used to calculate the volumes of individual shield volcanoes and island complexes niihau kauai oahu the maui nui complex and hawaii taking into account subsidence of the pacific plate under the load of the hawaiian ridge our calculated volume for the island of hawaii and its submarine extent 213 103 km3 is nearly twice the previous estimate 113 103 km3 due primarily to crustal subsidence that had not been accounted for in the earlier work the volcanoes that make up the island of hawaii mahukona kohala mauna kea hualalai mauna loa kilauea and loihi are generally considered to have been formed within the past million years and our revised volume for the island indicates that magma supply rates are greater than previously estimated 0 21 km3 yr as opposed to 0 1 km3 yr this result also shows that compared with rates calculated for the hawaiian islands 0 6 ma 0 095 km3 yr the hawaiian ridge 0 45 ma 0 017 km3 yr and the emperor seamounts 45 80 ma 0 010 km3 yr magma supply rates have increased dramatically to build the island of hawaii

magmatic evolution of a volcano studied by 230th 238u disequilibrium and trace elements systematics the etna case age determinations of several lava flows from etna through 230th 238u disequilibrium internal isochrons yield a precise chronology of the volcano s history for the last 200 000 years and emphasize the main episodes in the formation of this huge complex strato volcano study of 230th232th 0 initial ratios of lavas together with their trace element compositions yields a consistent model of magmatic evolution implying the existence for 200 000 years of a deep reservoir of alkalic magma periodically mixed with magmas of tholeiitic affinity these short periods of mixing appear to be related to the formation of the large calderas of etna in addition to these processes affecting the deep reservoir fractional crystallization also occurred in more superficial levels of the volcanic edifice thereby yielding several series of differentiation of relatively short duration as for its geochemistry etna s volcanism is of oceanic type but with its own characteristics and in a peculiar geodynamic context at the edge of the african plate

exploring links between arctic amplification and mid latitude weather 1 this study examines observed changes 1979 2011 in atmospheric planetary wave amplitude over northern mid latitudes which have been proposed as a possible mechanism linking arctic amplification and mid latitude weather extremes we use two distinct but equally valid definitions of planetary wave amplitude termed meridional amplitude a measure of north south meandering and zonal amplitude a measure of the intensity of atmospheric ridges and troughs at 45 n statistically significant changes in either metric are limited to few seasons wavelengths and longitudinal sectors however in summer we identify significant increases in meridional amplitude over europe but significant decreases in zonal amplitude hemispherically and also individually over europe and asia therefore we argue that possible connections between arctic amplification and planetary waves and implications of these are sensitive to how waves are conceptualized the contrasting meridional and zonal amplitude trends have different and complex possible implications for midlatitude weather and we encourage further work to better understand these

postshield volcanism and catastrophic mass wasting of the waianae volcano oahu hawaii the 3 9 to 2 9 ma waianae volcano is the older of two volcanoes making up the island of oahu hawaii exposed on the volcanic edifice are tholeiitic shield lavas overlain by transitional and alkalic postshield lavas the postshield alkalic cap consists of aphyric hawaiite of the palehua member of the waianae volcanics overlain unconformably by a small volume of alkalic basalt of the kolekole volcanics kolekole volcanics mantle erosional topography including the uppermost slopes of the great lualualei valley on the lee side of the waianae range twenty new k ar dates combined with magnetic polarity data and geologic relationships constrain the ages of lavas of the palehua member to 3 06 2 98 ma and lavas of the kolekole volcanics to 2 97 2 90 ma the geochemical data and the nearly contemporaneous ages suggest that the kolekole volcanics do not represent a completely independent or separate volcanic event from earlier postshield activity thus the kolekole volcanics are reduced in rank becoming the kolekole member of the waianae volcanics magmas of the palehua and kolekole members have similar incompatible element ratios and both suites show evidence for early crystallization of clinopyroxene consistent with evolution at high pressures below the edifice however lavas of the kolekole member are less fractionated and appear to have evolved at greater depths than the earlier palehua hawaiites postshield primary magma compositions of the palehua and kolekole members are consistent with formation by partial melting of mantle material of less than 5 10 relative to waianae shield lavas within the section of palehua member lavas an increase with respect to time of highly incompatible to moderately incompatible element ratios is consistent with a further decrease in partial melting by approximately 1 2 this trend is reversed with the onset of eruption of kolekole member lavas where an increase in extent of partial melting is indicated the relatively short time interval between the eruption of palehua and kolekole member lavas appears to date the initial formation of lualualei valley which was accompanied by a marked change in magmatic conditions we speculate that the mass wasting event separating lavas of the palehua and kolekole members may be related to the formation of a large submarine landslide west and southwest of waianae volcano enhanced decompression melting associated with removal of the equivalent volume of this landslide deposit from the edifice is more than sufficient to produce the modeled increase of 1 2 in extent of melting between the youngest palehua magmas and the posterosional magmas of the kolekole member the association between magmatic change and a giant landsliding event suggests that there may be a general relationship between large mass wasting events and subsequent magmatism in hawaiian volcano evolution

new data from hadar ethiopia support orbitally tuned time scale to 3 3 ma support for the astronomically calibrated geomagnetic polarity time scale is provided by new 40ar 39ar dating and magnetostratigraphic data from the hadar formation ethiopia three tuffs and a basalt flow at hadar span the mammoth subchron of the gauss chron and range in age from 3 18 0 01 to 3 40 0 03 ma interpolation of sediment accumulation rates in two magnetostratigraphic sections yields an estimated age range of 3 30 0 02 to 3 21 0 01 ma for the mammoth subchron closely coinciding with orbitally based predictions of 3 33 to 3 22 ma rather than with previous estimates of 3 15 to 3 05 ma

the role of rossby wave breaking in shaping the equilibrium atmospheric circulation response to north atlantic boundary forcing abstract the role of rossby wave breaking rwb is explored in the transient response of an atmospheric general circulation model to boundary forcing by sea ice anomalies related to the north atlantic oscillation nao when the ncar community climate model version 3 was forced by an exaggerated sea ice extent anomaly corresponding to one arising from a positive nao a localized baroclinic response developed and evolved into a larger scale equivalent barotropic pattern resembling the negative polarity of the nao the initial baroclinic response shifted the phase speeds of the dominant eddies away from a critical value equal to the background zonal flow speed resulting in significant changes in the spatial distribution of rwb the forcing of the background zonal flow by the changes in rwb accounts for 88 of the temporal pattern of the response and 80 of the spatial pattern of the zonally averaged response although results here focus on one experiment this rwb critical line mechanism appears to be

maintenance of the sea ice edge abstract a coupled global climate model is used to evaluate processes that determine the equilibrium location of the sea ice edge and its climatological annual cycle the extent to which the wintertime ice edge departs from a symmetric ring around either pole depends primarily on coastlines ice motion and the melt rate at the ice ocean interface at any location the principal drivers of the oceanic heat flux that melts sea ice are absorbed solar radiation and the convergence of heat transported by ocean currents the distance between the ice edge and the pole and the magnitude of the ocean heat flux convergence at the ice edge are inversely related the chief exception to this rule is in the east greenland current where the ocean heat flux convergence just east of the ice edge is relatively high but ice survives due to its swift southward motion and the protection of the cold southward flowing surface water in regions where the ice edge extends relatively far equatorward absorbed solar radiation is t

absolute paleointensity and reversal records from the waianae sequence oahu hawaii usa abstract paleointensity experiments were performed on samples from four parallel sections of the waianae volcanics of oahu hawaii that document 0 4 myr of geomagnetic field variations the records of the three successive gilbert gauss lower and upper mammoth reversals confirm that large oscillations of directions precede or follow the reversals which are similar to waveforms generated by paleosecular variation with their amplitude being considerably amplified by the decrease of the dipole determinations of absolute paleointensity were attempted on 546 samples we only selected data which were obtained from segments covering a large part of the remanent magnetization more than 70 on the average and without concave up arai diagrams this procedure limited the success rate to 14 but provided consistent and reliable paleointensities in addition to other time intervals the results document the field variations surrounding the lower mammoth transition a weak field period dominated before the reversal then the transition was initiated by a transit from normal to reverse polarity followed by a short restoration of the field intensity in reverse polarity a second episode of a very weak field was accompanied by a return to positive inclinations before definitely reaching the reverse polarity a strong and apparent rapid recovery of the dipole following the completion of the reversal culminated at a value of 16 1022 am2 similar to field intensities reported for the other detailed volcanic records of reversals studied so far the asymmetry between the pre and the post reversal phases indicates the importance of field regeneration to initiate a new stable polarity interval

the role of ocean atmosphere coupling in the zonal mean atmospheric response to arctic sea ice loss abstractthe role of ocean atmosphere coupling in the zonal mean climate response to projected late twenty first century arctic sea ice loss is investigated using community climate system model version 4 ccsm4 at 1 spatial resolution parallel experiments with different ocean model configurations full depth slab and no interactive ocean allow the roles of dynamical and thermodynamic ocean feedbacks to be isolated in the absence of ocean coupling the atmospheric response to arctic sea ice loss is confined to north of 30 n consisting of a weakening and equatorward shift of the westerlies accompanied by lower tropospheric warming and enhanced precipitation at high latitudes with ocean feedbacks the response expands to cover the whole globe and exhibits a high degree of equatorial symmetry the entire troposphere warms the global hydrological cycle strengthens and the intertropical convergence zones shift equatorward ocean dynamics are fundamental to producing this equatorially symmetric pattern

atmospheric impact of arctic sea ice loss in a coupled ocean atmosphere simulation the atmospheric response to an idealized decline in arctic sea ice is investigated in a novel fully coupled climatemodel experiment in this experimenttwo ensembles of single year model integrations are performed starting on 1 april the approximate start of the ice melt season by perturbing the initial conditions of sea ice thickness sit declines in both sea ice concentration and sit which result in sea ice distributions that are similar to the recent sea ice minima of 2007 and 2012 are induced in the ice loss regions there are strong 3k local increasesin sea surface temperature sst additionally there are remoteincreases in sst in the central north pacific and subpolar gyre in the north atlantic over the central arctic there are increases in surface air temperature sat of 8k due to increases in ocean atmosphere heatfluxes there are increases in sat over continental north america that are in good agreement with recent changes as seen by reanalysis data it is estimated that up to two thirds of the observed increase in sat in this region could be related to arctic sea ice loss in early summer there is a significant but weak atmospheric circulation response that projects onto the summer north atlantic oscillation nao in early summer and early autumn there is an equatorward shift of the eddy driven jet over the north atlantic as a result of a reduction in the meridional temperature gradients in winter there is no projection onto a particular phase of the nao

saddle shaped 40ar39ar age spectra from young microstructurally complex potassium feldspars abstract a suite of young potassium feldspars show markedly saddle shaped 40 ar 39 ar age spectra as a result of incorporating 10 10 to 10 9 mol g of excess 40ar the minima of these age spectra record reasonable cooling ages based on the known thermal history and geology of the samples acid etching of one sample indicates that excess 40ar is concentrated near grain margins the release of a substantial portion of this excess ar at high temperatures in the laboratory requires that this component be situated in a more retentive site than radiogenic 40ar anion vacancies have been proposed to act in this role in plagioclase and we speculate that this is so in k feldspar as well such a mechanism would explain the observation that relative to radiogenic 40ar excess 40ar is incorporated at low temperatures in nature but is released at high temperatures in the laboratory oxygen diffusion provides an appropriate analogy for this phenomenon being relatively fast under natural hydrothermal conditions but extremely slow in anhydrous environments such as an ar extraction system tem observations made on two of the samples confirm that their effective grain sizes for diffusion are likely to be on the order of ten microns due to the presence of such microstructures as incoherent exsolution lamellae dislocations and stepped twins tem observations also reveal the presence in one sample of orthoclase enclaves in a microcline host

the effects of north atlantic sst and sea ice anomalies on the winter circulation in ccm3 part i main features and storm track characteristics of the response observed multidecadal trends in extratropical atmospheric flow such as the positive trend in the north atlantic oscillation nao index may be attributable to a number of causes this study addresses the question of whether the atmospheric trends may be caused by observed trends in oceanic boundary forcing experiments were carried out using the ncar atmospheric general circulation model with specified sea surface temperature sst and sea ice anomalies confined to the north atlantic sector the spatial pattern of the anomalous forcing was chosen to be realistic in that it corresponds to the recent 40 yr trend in sst and sea ice but the anomaly amplitude was exaggerated in order to make the response statistically more robust the wintertime response to both types of forcing resembles the nao to first order even for an exaggerated amplitude the atmospheric response to the sst anomaly is quite weak compared to the observed positive trend in the nao but has the same sign indicative of a weak positive feedback the anomalies in sea ice extent are more efficient than sst anomalies at exciting an atmospheric response comparable in amplitude to the observed nao trend however this atmospheric response has the opposite sign to the observed trend indicative of a significant negative feedback associated with the sea ice forcing additional experiments using sst anomalies with opposite sign to the observed trend indicate that there are significant nonlinearities associated with the atmospheric response the transient eddy response to the observed sst trend is consistent with the positive nao response with the north atlantic storm track amplifying downstream and developing a more pronounced meridional tilt in contrast the storm track response to the observed sea ice trend corresponds to a weaker southward shifted more zonal storm track which is consistent with the negative nao response

geomagnetic paleosecular variation at hawaii around 3 ma from a sequence of 107 lava flows at kaena point oahu abstract we have sampled a sequence of 107 lava flows in the waianae series on oahu hawaii in two separate stretches the first 51 flows at kaena point extends from sea level to an altitude of 190 m and the second 56 flows follows the satellite tracking station road from 218 m to 360 m above sea level thermal and af demagnetization yield very similar results and reveal only normal polarities k ar dating at five different horizons combined with the paleomagnetic results indicate that the sequence was emplaced entirely in the normal polarity interval between the upper mammoth and the lower kaena polarity transitions 3 22 3 11 ma some of the flows are serially correlated filtering does not however drastically affect the final results inclinations are shallower than those expected from a centered dipole field although large 13 the inclination anomaly is consistent with results from other sites at the same latitude the scatter of the vgps about the geographic pole is consistent with available data from other regions at similar latitudes the scatter of the directions is also consistent with the predictions of recent statistical models of paleosecular variation therefore these results do not support the hypothesis of a pacific dipole window

fluorine geochemistry of basaltic rocks from continental and oceanic regions and petrogenetic application fluorine contents in about 300 samples of various types of basalts and related rocks from continental southwestern u s a zaire deccan and south africa and oceanic regions hawaii and mid atlantic ridge between 23 n and 40 n were determined by a selective ion electrode method

the effects of north atlantic sst and sea ice anomalies on the winter circulation in ccm3 part ii direct and indirect components of the response the wintertime atmospheric circulation responses to observed patterns of north atlantic sea surface temperature and sea ice cover trends in recent decades are studied by means of experiments with an atmospheric general circulation model here the relationship between the forced responses and the dominant pattern of internally generated atmospheric variability is focused on the total response is partioned into a portion that projects onto the leading mode of internal variability the indirect response and a portion that is the residual from that projection the direct response this empirical decomposition yields physically meaningful patterns whose distinctive horizontal and vertical structures imply different governing mechanisms the indirect response which dominates the total geopotential height response is hemispheric in scale with resemblance to the north atlantic oscillation or northern hemisphere annular mode and equivalent barotropic in the vertical from the surface to the tropopause in contrast the direct response is localized to the vicinity of the surface thermal anomaly sst or sea ice and exhibits a baroclinic structure in the vertical with a surface trough and upper level ridge in the case of a positive heating anomaly consistent with theoretical models of the linear baroclinic response to extratropical thermal forcing both components of the response scale linearly with respect to the amplitude of the forcing but nonlinearly with respect to the polarity of the forcing the deeper vertical penetration of anomalous heating compared to cooling is suggested to play a role in the nonlinearity of the response to sst forcing

palaeointensity record through the lower mammoth reversal from the waianae volcano hawaii the normal to reverse lower mammoth reversal 3 33 ma has been recorded in several sequences of lava from the waianae volcano the island of oahu hawaii 137 samples from 29 flows from the pu u paheehee section have been the subject of a palaeointensity study using the microwave technique duplicate sister samples from the directional study of herrero bervera and valet earth planet sci lett 171 1999 139 148 were used microwave demagnetisation was carried out on all samples and the directions compared to the published flow mean directions microwave palaeointensity experiments were carried out on all accepted samples using the 8 2 ghz and 14 ghz microwave systems the perpendicular applied field palaeointensity method and a coe analogue method were used eighty four samples from 24 flows gave acceptable palaeointensity results the results indicate that the geomagnetic field was low mean 5 9 1 3 t n 7 prior to the transitional directions during the first stage of the reversal the field remains low results however could only be obtained from three transitional flows the field then strongly recovers with very high intensity 70 t and reversed direction after this the intensity decreases before the field becomes transitional again for a cluster of four flows the field does not reduce as much as previously rather it is about twice the pre reversal intensity for the final section of reversed flows the intensity is more than twice the pre reversal mean value 15 1 5 9 t n 7 whilst some similarities are seen between this reversal and other reversals of different ages and locations there is not enough data at present to say whether there is any systematic behaviour

a new geomagnetic polarity time scale for the late cretaceous and cenozoic we have constructed a magnetic polarity time scale for the late cretaceous and cenozoic based on an analysis of marine magnetic profiles from the world s ocean basins this is the first time since heirtzler et al 1968 published their time scale that the relative widths of the magnetic polarity intervals for the entire late cretaceous and cenozoic have been systematically determined from magnetic profiles a composite geomagnetic polarity sequence was derived based primarily on data from the south atlantic anomaly spacings in the south atlantic were constrained by a combination of finite rotation poles and averages of stacked profiles fine scale information was derived from magnetic profiles on faster spreading ridges in the pacific and indian oceans and inserted into the south ariantic sequence based on the assumption that spreading rates in the south atlantic were smoothly varying but not necessarily constant a time scale was generated by using a spline function to fit a set of nine age calibration points

a role for barotropic eddy mean flow feedbacks in the zonal wind response to sea ice loss and arctic amplification abstractprevious studies have suggested that in the zonal mean the climatological northern hemisphere wintertime eddy driven jet streams will weaken and shift equatorward in response to arctic am

k ar 40ar 39ar ages and magnetostratigraphy of brunhes and matuyama lava sequences from la palma island abstract we have applied geological mapping magnetostratigraphy and unspiked k ar and 40 ar 39 ar datings to reconstruct the main volcanic stages of the northern part of la palma an oceanic volcanic island of the canaries archipelago based on 57 new k ar and 40 ar 39 ar ages mostly concordant with the astronomic polarity time scale three main volcanic units are distinguished the garafia volcano and the lower and upper taburiente volcanoes this entirely subaerial activity took place between 1722 25 and 440 8 ka the oldest stage corresponding to the garafia volcano encompasses the post olduvai cobb mountain period with isotopic age determinations ranging from 1722 25 to 1208 8 ka the oldest lava flows of the taburiente volcano which was active between 1 08 0 04 and 833 11 ka recorded the jaramillo normal polarity subchron and younger reversed flows were erupted during the upper part of the post jaramillo matuyama period all the upper taburiente lava flows were erupted during the brunhes chron and have ages ranging from 770 11 to 440 8 ka the age of the garafia collapse lies between 1 20 0 05 and 1 08 0 04 ma while the cumbre nueva collapse occurred at about 550 ka

geomagnetic paleointensities at hawaii between 3 9 and 2 1 ma preliminary results abstract thellier thellier experiments have been conducted on 454 samples from different sequences of the waianae and koolau volcanoes in oahu hawaii the sampled interval as determined by k ar dating spans from 3 9 to 2 1 ma results from 89 samples from 41 flows meet restrictive reliability criteria and provide the first paleointensity estimates from hawaii for the sampled period with good temporal resolution on this time interval the vadm shows ample fluctuations from a minimum of 2 3 1022 am2 to a maximum of 11 5 1022 am2 about an average value of 7 0 2 3 1022 am2 suggesting that fluctuations of the geomagnetic field strength comparable in amplitude to the time averaged value may be a characteristic of the field during both the reverse mammoth chron and the normal chron between the mammoth and the kaena the field strength appears to increase with time

volatiles in basalts and andesites from the galapagos spreading center 85 to 86 w abstract glasses from submarine lavas recovered by the alvin submersible from the galapagos spreading center gsc near 86 w have been analyzed by electron microprobe for major elements and by high temperature mass spectrometry for volatiles the samples studied range in composition from basalt to andesite and are more evolved than typical morbs previous studies indicate that they are related to normal morb by extensive crystal fractionation in small isolated magma chambers the h 2 o cl and f contents of these lavas are substantially higher than any previously reported for morbs h 2 o cl and f abundances increase linearly with p 2 o 5 content which is used as an indicator of the extent of crystal fractionation the fe 2 o 3 feo fe 2 o 3 ratios measured in the andesite glasses progressively decrease with increasing p 2 o 5 content and are probably related to fractionation of fe tioxides reduced carbon gas species principally ch 4 and co were discovered in these glasses the presence of reduced carbon species in gsc glasses may be indicative of a more reduced oxidation state of the upper mantle than is commonly assumed

the 40ar 39ar and k ar dating of lavas from the hilo 1 km core hole hawaii scientific drilling project mauna kea lava flows cored in the hilo hole range in age from 200 ka to about 400 ka based on 40ar 39ar incremental heating and k ar analyses of 16 groundmass samples and one coexisting plagioclase the lavas all subaerially deposited include a lower section consisting only of tholeiitic basalts and an upper section of interbedded alkalic transitional tholeiitic and tholeiitic basalts the lower section has yielded predominantly complex discordant 40ar 39ar age spectra that result from mobility of 40ar and perhaps k the presence of excess 40ar and redistribution of 39ar by recoil comparison of k ar ages with 40ar 39ar integrated ages indicates that some of these samples have also lost 39ar nevertheless two plateau ages of 391 40 and 400 26 ka from deep in the hole combined with data from the upper section show that the tholeiitic section accumulated at an average rate of about 7 to 8 m kyr and has a mean recurrence interval of 0 5 kyr flow unit samples from the upper section yield relatively precise 40ar 39ar plateau and isotope correlation ages of 326 23 241 5 232 4 and 199 9 ka for depths of 415 7 m to 299 2 m within their uncertainty these ages define a linear relationship with depth with an average accumulation rate of 0 9 m kyr and an average recurrence interval of 4 8 kyr flow unit the top of the mauna kea sequence at 280 m must be older than the plateau age of 132 32 ka obtained for the basal mauna loa flow in the corehole the upward decrease in lava accumulation rate is a consequence of the decreasing magma supply available to mauna kea as it rode the pacific plate away from its magma source the hawaiian mantle plume the age depth relation in the core hole may be used to test and refine models that relate the growth of mauna kea to the thermal and compositional structure of the mantle plume

warm season subseasonal variability and climate extremes in the northern hemisphere the role of stationary rossby waves abstractthis study examines the nature of boreal summer subseasonal atmospheric variability based on the new nasa modern era retrospective analysis for research and applications merra for the period 1979 2010 an analysis of the june july and august subseasonal 250 hpa meridional wind anomalies shows distinct rossby wave like structures that appear to be guided by the mean jets on monthly subseasonal time scales the leading waves the first 10 rotated empirical orthogonal functions reofs of the 250 hpa wind explain about 50 of the northern hemisphere wind variability and account for more than 30 60 of the precipitation surface temperature variability over a number of regions of the northern middle and high latitudes including the u s northern great plains parts of canada europe and russia the first reof in particular consists of a rossby wave that extends across northern eurasia where it is a dominant contributor to monthly surface temperature and precipitation variability and

high resolution 40ar 39ar geochronology of the louisville seamounts iodp expedition 330 drill sites implications for the duration of hot spot related volcanism and age progressions

fluorine in basalts from iceland the fluorine content of icelandic tholeiitic and alkaline basalts matches values found in similar rocks from other areas covariation between fluorine and incompatible minor elements such as potassium or phosphorus is found in evolved tholeiites and alkali basalts lack of such covariation in primitive olivine tholeiites indicates that fluorine and other incompatible minor and trace elements are not controlled by minerals such as amphibole mica or apatite in the mantle residue and that the covariation between these elements in the evolved basalts cannot be inherited from the mantle model calculations on rocks from the langjokull area show that olivine tholeiite suites are if derived by simple fractional crystallization enriched in incompatible elements much in excess of the increase due to crystal removal these observations are taken to indicate that the well documented covariation between fluorine and other incompatible elements is not established until evolution of the basaltic magma has started in crustal holding chambers the constancy of element ratios and enrichment in excess of what can be accounted for by crystal fractionation or incremental addition of new batches of primitive magmas does indicate 1 mineral control involving amphibole mica or apatite and 2 addition of fluorine potassium and phosphorous from an external source it is argued that this source is the crustal envelope of the holding chamber

melt inclusion investigation of the volatile behaviour in historic alkali basaltic magmas of etna crystallization paths of basaltic 1763 eruption and hawaiitic 1865 and 1329 eruptions scoria from etna were deduced from mineralogy and melt inclusion chemistry the volatile behaviour was investigated through the study of melt inclusions trapped in the phenocrysts and those of the whole rocks and the matrix glasses the results from the 1763 eruption point to the early crystallization of olivine fo 81 7 from a water rich alkaline basalt with high cl 1750 2000 ppm and s 2100 2400 ppm concentrations the hawaiitic melt inclusions trapped in olivine fo 74 salite and plagioclase are characterized by a decrease in cl k2o and s k2o ratios in each investigated system there is good correlation between k2o and p2o5 in the whole rocks cl ranges from 980 to 1680 ppm from basaltic to hawaiitic lavas whereas s 110 136 ppm remains low cl and s behaviour in the 1763 magma suggests an early degassing stage of cl and s with co2 and a water rich gaseous phase for a pressure close to 100 mpa consistent with a permanent outgassing at the summit craters of etna during the eruption the sulphur remaining in the hawaiitic liquid is lost and the degassing of chlorine is limited such a degassing model can be extended to the 1865 and 1329a d eruptions

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

forced annular mode patterns in a simple atmospheric general circulation model abstract previous studies using simplified general circulation models have shown that annular modes arise as the dominant mode of variability a simple gcm is used here to explore to what extent these modes are also the preferred response of the system to generic forcing a number of trials are conducted under which the model is subjected to an artificial zonally symmetric angular momentum forcing and the climatologies of these trials are compared to that of the control the forcing location is varied among the several trials it is found that the changes in the model s climatology are generally annular mode like as long as the imposed forcing projects strongly upon the annular modes of the unforced model the role of changes to the eddy zonal flow feedback versus the action of direct forcing is also considered through the use of a zonally symmetric version of the model it is found that the direct responses to forcing are insufficient to capture either the strength or the structure of the annular mo

new k ar ages of shield lavas from waianae volcano oahu hawaiian archipelago abstract a geochronological study utilized the unspiked potassium argon k ar technique to obtain ages from the two main volcanic members of the shield stage of the waianae volcano hi these new dates are further constrained using a combination of stratigraphic relationships magnetostratigraphy and major element geochemistry exposed shield lavas encompass 0 85 ma with reliably dated tholeiitic lavas from the main shield ranging from 3 93 0 08 to 3 54 0 04 ma and a later shield stage ranging in age from 3 57 0 04 to 3 08 0 04 ma these data suggest that the total extent of waianae shield activity was significantly more than 1 ma the age of faulting in two flank zones is constrained to be about 3 4 ma preliminary estimates of lava accumulation rates vary from about 0 3 to 2 0 mm a calculated rates show no systematic variation with location in the volcano or with time

chlorine and fluorine in tholeiitic and alkaline lavas of etna sicily abstract chlorine and fluorine were measured from whole rock samples from tholeiites 150 000 years old to present day hawaiites the overall range of f content is from 240 to 985 ppm with a slight decrease of f th and f cl ratios from tholeiites to hawaiites chlorine is positively correlated with th cl th 100 as well as k2o and p2o5 as the differentiation progresses and increases from 220 ppm in tholeiites to 2410 ppm in mugearites data obtained from present day hawaiites indicate that cl lost by degassing during eruption is limited however cl contents of some whole rock samples are inconsistent with previous results published for melt inclusions of phenocrysts from the same historic hawaiite samples and suggesting outgassing of cl prior to the eruption this implies that apparent correlation between cl and th can be considered as the result of superimposition of several petrogenetic processes results point out the richness of etnean tholeiites in chlorine compared to m a r basalts such a character could have been inherited from the mantle source or during the mantle source melting

volcanic tremors and shocks associated with eruptions at etna sicily september 1980 abstract three strong ash eruptions superimposed on an otherwise rather quiet state of volcanic activity took place from the northeast crater of etna during september 1980 the eruptions lasted only a few hours and were associated with an increase in the amplitudes of volcanic tremors by a factor of 10 compared with the mean value of the preceding months special emphasis in the tremor analysis was given to the eruption of september 26 1980 the time function of the amplitude envelope of the tremors follows a mathematical function which resembles the behaviour of a mechanical oscillator with a resonant period of about 300 s a detailed spectral analysis of the tremors before during and after the eruption reveals factors which seem to be associated with the ascent and descent of the tremor sources in the magma columns the turbulent eruptive magma flow apparently is concentrated in a few dykes and pipes their eigenvibrations during an eruption are observed as spectral peaks of small bandwidth superimposed on the smoother spectrum without a volcanic eruption an analysis of seismicity shows a maximum in august with epicenters clustering along a nw se direction

models of hawaiian volcano growth and plume structure implications of results from the hawaii scientific drilling project the shapes of typical hawaiian volcanoes are simply parameterized and a relationship is derived for the dependence of lava accumulation rates on volcano volume and volumetric growth rate the dependence of lava accumulation rate on time is derived by estimating the eruption rate of a volcano as it traverses the hawaiian plume with the eruption rate determined from a specified radial dependence of magma generation in the plume and assuming that a volcano captures melt from a circular area centered on the volcano summit the timescale of volcano growth is t 2 r plate where r is the radius of the melting zone of the circular plume and plate is the velocity of the pacific plate the growth progress of a volcano can be described by a dimensionless time t t plate 2r where t 0 is chosen to be the start of volcano growth and t 1 approximates the end of shield growth using a melt generation rate for the whole plume of 0 2 km 3 yr a plume diameter of 50 km and a plate velocity of 10 cm yr we calculate that the lifetime of a typical volcano is 1000 kyr for a volcano that traverses the axis of the plume the standard dimensions are a volume of 57 000 km 3 a summit thickness of 18 km a summit elevation of 3 6 km and a basal radius of 60 km the volcano first breaches the sea surface at t 0 22 when it has attained only 5 of its eventual volume 80 of the volume accumulates between t 0 3 and t 0 7 typical lava accumulation rates start out over 50 m kyr in the earliest stages of growth from the seafloor and level out at 35 m kyr from t 0 05 until t 0 4 from t 0 4 to t 0 9 the submarine lava accumulation rates decrease almost linearly from 35 m kyr to 0 subaerial accumulation rates are about 30 lower the lava accumulation rate is a good indicator of volcano age a volcano that passes over the plume at a distance 0 4r off to the side of the plume axis is predicted to have a volume of about 60 of the standard volcano a lifetime about 8 shorter and lava accumulation rates about 15 20 smaller the depth age data for mauna kea lavas cored by the hawaii scientific drilling project are a good fit to the model parameters used given that mauna kea appears to have crossed the plume about 15 20 km off axis the lifetime of mauna kea is estimated to be 920 kyr mauna loa is predicted to be at a stage corresponding to t 0 8 kilauea is at t 0 6 and loihi is at t 0 16 the model also allows the subsurface structure of the volcanoes the interfaces between lavas from different volcanoes to be modeled radial geochemical structure in the plume may be blurred in the lavas because the volcanoes capture magma from a sizeable cross sectional area of the plume this inference is qualitatively born out by available isotopic data the model predicts that new hawaiian volcanoes are typically initiated on the seafloor near the base of the next older volcano but generally off the older volcano s flank

dikes and the petrology of waianae volcano oahu we summarize the distribution orientation and composition of the dikes of waianae volcano and attempt to relate this summary to the evolution of the volcano dikes are located in the caldera in a well defined northwest rift zone and in less well defined south and northeast rift zones the active axis of the south rift zone may have shifted with time the dikes generally are parallel to their rift zones and are oriented in many directions in the caldera area they commonly dip about 70 to 80 and are generally less than a meter thick most are virtually identical in texture mineralogy and composition to nearby extrusive rocks a few have unusual low magnesium silicic compositions not yet observed in flows these may be classified as icelandites trends defined by the compositions of tholeiitic dikes are similar to but extend further than crystal fractionation trends of tholeiitic flows of waianae and other hawaiian volcanoes the basalts can be divided into a more silica saturated strongly tholeiitic subgroup and a less saturated mildly tholeiitic subgroup the icelandites lie on trend with the second group most of the analyzed rift zone dikes are strongly tholeiitic most of the analyzed caldera dikes are mildly tholeiitic all of the differentiated high silica low magnesium dikes found are inside the caldera near the eruptive center

on the existence of storm tracks abstract given that middle latitude weather systems transport heat in a manner such as to weaken the baroclinicity that is thought to be crucial to their growth it is perhaps surprising that concentrated regions of such eddy activity i e storm tracks are found in the northern hemisphere winter the existence and possible self maintenance of storm tracks is investigated using a linear stationary wave model with storm track region forcings taken from data averaged over a number of winters it is found that the direct thermal effect of the eddies does indeed act against the existence of the storm track their vorticity fluxes lead to some reduction of this effect it is argued that the mean diabatic heating in the storm track region is an indirect eddy effect this heating is found to maintain the mean maximum in baroclinicity in the region further the mean low level flow induced by the eddy effects is such as to enhance the warm western oceanic boundary currents that are crucial to the existence of t

dating of quaternary basalts using the cosmogenic 3he and 14c methods with implications for excess 40ar concordant radiocarbon and cosmogenic sup 3 he dates of 3 and 11 ka on basalt flows and associated scoria deposits from the zuni bandera volcanic field in new mexico further substantiate published production rates and latitudinal and altitudinal corrections for sup 3 he identical sup 3 he concentrations in coexisting olivine and clinopyroxene confirm that these two minerals have very similar production rates a cosmogenic sup 3 he date of 57 ka on another flow is concordant with a u series date and is younger than two k ar dates suggesting that this flow contains excess sup 40 ar this excess sup 40 ar is also evident in gases released by vacuum crushing of olivine clinopyroxene fractions from all three flows 27 refs 3 figs 3 tabs

unspiked k ar dating of koolau lavas hawaii evaluation of the influence of weathering alteration on age determinations abstract in order to evaluate the influence of weathering alteration on k ar dating for hawaiian tholeiites unspiked k ar ages were determined for 21 samples from four lava flows with varying degrees of weathering or alteration collected from the makapuu head section of koolau volcano hawaii the samples were classified based on freshness of olivine phenocrysts and the groundmass olivine and the presence of secondary minerals in vesicles the results indicate that the ages for samples with fresh groundmass olivine are reliable even though olivine phenocrysts may be slightly altered thin reaction rims or secondary minerals may have crystallized in the vesicles the ages for the lowermost lava flow in the makapuu head section and the lava flow approximately 120 m above it are 2 58 0 13 and 2 36 0 09 ma respectively the accumulation rate of this section is calculated to be 0 04 0 11 cm year we also report k ar ages for lava samples collected from the submarine flank of the koolau volcano and the nuuanu landslide blocks the age for an early makapuu stage lava collected from the submarine flank of koolau volcano is 2 5 ma similar to the age from the lower part of the subaerial makapuu head section another lava sample collected from the submarine flank of the koolau volcano has an age of 3 3 ma older than any subaerial part of koolau volcano these results suggest that the onset of koolau s shield stage volcanism was no later than 3 3 ma and the duration of the shield stage was at least 1 2 m y

a mechanism and simple dynamical model of the north atlantic oscillation and annular modes a simple dynamical model is presented for the basic spatial and temporal structure of the large scale modes of intraseasonal variability and associated variations in the zonal index such variability in the extratropical atmosphere is known to be represented by fairly well defined patterns and among the most prominent are the north atlantic oscillation nao and a more zonally symmetric pattern known as an annular mode which is most pronounced in the southern hemisphere these patterns may be produced by the momentum fluxes associated with large scale midlatitude stirring such as that provided by baroclinic eddies it is shown how such stirring as represented by a simple stochastic forcing in a barotropic model leads to a variability in the zonal flow via a variability in the eddy momentum flux convergence and to patterns similar to those observed typically the leading modes of variability may be characterized as a mixture of wobbles in the zonal jet position and pulses in the zonal jet strength if the stochastic forcing is statistically zonally uniform then the resulting patterns of variability as represented by empirical orthogonal functions are almost zonally uniform and the pressure pattern is dipolar in the meridional direction resembling an annular mode if the forcing is enhanced in a zonally localized region thus mimicking the effects of a storm track over the ocean then the resulting variability pattern is zonally localized resembling the north atlantic oscillation this suggests that the north atlantic oscillation and annular modes are produced by the same mechanism and are manifestations of the same phenomenon the time scale of variability of the patterns is longer than the decorrelation time scale of the stochastic forcing because of the temporal integration of the forcing by the equations of motion limited by the effects of nonlinear dynamics and friction for reasonable parameters these produce a decorrelation time of the order of 5 10 days the model also produces some long term 100 days or longer variability without imposing such variability via the external parameters except insofar as it is contained in the nearly white stochastic forcing

determining palaeointensity from the gilbert gauss reversal recorded in the pu u heleakala lava section wai anae volcano oahu hawaii abstract the ability of the earth s magnetic field to reverse is one of its most intriguing characteristics a full vector directions and intensity description during reversals is necessary to fully understand the magnetic field generation process in the earth s liquid outer core the reverse to normal gilbert gauss reversal 3 58 ma is recorded in a 470 m high sequence of lava flows at pu u heleakala waianae volcano oahu hawaii 133 samples from 34 flows sister samples from the directional study of herrero bervera and coe j geophys res 104 1999 29157 29173 were subjected to microwave demagnetisation experiments unfortunately many samples have been overprinted with a lightning induced remanence so that only 65 samples 49 were deemed suitable for microwave palaeointensity analysis both the 8 2 and 14 ghz systems were used with the perpendicular applied field and coe analogue methods individually acceptable results were obtained for 63 of the studied samples however not all flows gave internally consistent results in total 10 flows yielded microwave palaeointensity results from 2 or more samples that met the 25 self consistency criteria with flow mean palaeointensities ranging from 16 to 39 t it is pertinent to ascertain if there is any systematic behaviour seen between different reversals from the sparse data set obtained in this study the behaviour of the field appears to be different to that of the nearby pu u paheehee section that records the lower mammoth 3 33 ma transition however the two sections have different temporal resolution and the uncertainties in the palaeointensity estimates found in this study may account for some of the discrepancies

the maximum warmings of the pleistocene world climate recorded in the canary islands abstract evidence of the warmest pleistocene climatic changes is preserved in the eastern canary islands although the existence of raised fossiliferous marine deposits in northern gran canaria has been known since the 19th century their chronology and significance with regard to past sea levels and temperatures have remained uncertain here we show three marine transgressions recorded by raised marine deposits the highest 85 m above sea level masl and oldest marine deposit is interbedded in basaltic lava flows and has been dated using both palaeomagnetic and radiometric methods the age of these deposits located on the northwest coast of gran canaria near the town of agaete places the marine transgression in a first pleistocene interglacial into the plio pleistocene limit the marine deposit at an intermediate altitude 35 masl has been dated using the unspiked k ar method on a pillowed basaltic lava flow the age of these deposits in arucas places the transgression in the penultimate european mindel riss sense interglacial the deposits at 12 masl in las palmas are attributed to the last pleistocene interglacial on the basis of their fossil content which is similar to that of the matagorda deposits in lanzarote and matas blancas in fuerteventura radiometric dating of a lava flow overlying similar deposits at el cotillo in fuerteventura has been carried out the molluscan fauna associated with the deposits permits an estimation of the sea temperatures by reference to their present biogeographical distributions the plio pleistocene boundary coincides at agaete end of olduvai event with a high sea level between 1 8 and 1 75 ma oxygen isotopic stage ois 63 the dated marine deposits at arucas 0 42 ma place an interglacial in ois 11 3 and finally we confirm that in the canaries with only one high sea level with a senegalese fauna ois 5 5 they are not an outpost for the mediterranean tyrrhenian deposits with strombus oscillations

ka ena volcano a precursor volcano of the island of o ahu hawai i ka ena and wai alu ridges form prominent submarine ridges nw of the island of o ahu hawai i we evaluate whether or not either one of these ridges represents a submarine extension of wai anae volcano on o ahu using new bottom observations geophysical surveys and geochemical data acquired on new samples from the region wai alu ridge has the morphology of a submarine rift zone but is too shallow for its distance from the o ahu shoreline ka ena ridge also is unusually shallow and is surmounted by two topographic shields ka ena and wai alu ridges have similar magmatic and volcanic evolutionary histories beginning ca 5 ma with a submarine shield phase of volcanism that produced high sio 2 low feo tholeiites with higher 208 pb 204 pb than in the adjacent wai anae volcano late shield volcanism included transitional and alkalic rock types with lower sio 2 and enrichment in incompatible elements especially p 2 o 5 nb zr ti and light rare earth elements the transition from shield to late shield stage occurred as the edifice was beginning to emerge from the sea geological observations and k ar ages indicate that ka ena emerged above sea level ca 3 5 ma reaching a maximum height of 4000 m above the abyssal ocean floor and 1000 m above sea level relatively weak gravity anomalies topographic lineaments and the orientation of dike complexes indicate a volcanic structure that is independent of wai anae volcano thus volcanic structure geochemistry and age all indicate a precursor volcano to the island of o ahu which we call ka ena volcano after emergence ka ena volcano tilted 2 to the south we estimate a total volume of 20 27 10 3 km 3 for ka ena volcano taking into account overlapping geometry of concurrently active volcanoes sample compositions from the ka ena landslide deposit are entirely consistent with derivation from ka ena whereas most samples from the wai anae slump are likely derived from wai anae volcano uniformly oriented dikes in the wai anae nw rift zone likely reflect buttressing by a preexisting ka ena volcano unusual isotopic compositions of some wai anae samples including unique hydrous silicic lavas probably reflect interaction with underlying ka ena crust a newly recognized lava flow field on the southern flank of ka ena ridge extends the previously known distribution of secondary volcanism in the kaua i channel putative submarine volcanic activity in the region in 1956 cannot have built a large edifice and is unlikely to have produced pumice that was found on o ahu shores this eruptive activity therefore remains unconfirmed

evolution of the etna volcano information from the southern wall of the valle del bove caldera abstract the greater part of etna can be regarded as a complex strato shield volcano constructed from the overlapping products of several centres of trachy basaltic activity the valle del bove is a horse shoe shaped caldera 8 km long and 5 km wide cut into the eastern flanks of etna the caldera is one of the few areas on the volcano where historic eruptions have not obscured the products of pre historic centres of activity and these are well exposed in the cliff walls surrounding the caldera examination of these older volcanics provides important information on the eruptive style and internal plumbing of the etna volcano during pre historic times and suggests that both were significantly different from the present day much of the southern wall of the valle del bove represents a surviving portion of the trifoglietto ii volcano the largest pre historic centre of activity a stratigraphy is constructed for the southern wall the trifoglietto ii lavas and pyroclastics rest unconformably upon the eroded remnants of an older centre and are themselves overlain by the products of younger centres all the lavas exposed in the southern wall are of alkalic affinity and comprise a trachybasaltic suite ranging from hawaiite to benmoreite variation in the chemistry of the lavas can be explained by their differentiation at high levels in the crust from a more basic magma of alkali olivine basalt hawaiite composition an anomalous trend in the tio 2 content of the trifoglietto ii lavas may be explained by the fractionation of kaersutite ti rich amphibole a study has been made of the numerous dykes exposed in the walls of the valle del bove the alignments of which parallel trends which are important on etna at the present time it is proposed that the initial opening of the valle del bove occurred sometime between 20 000 and 10 000 y b p as a result of a phreatic or phreato magmatic explosion near the base of the eastern flank of trifoglietto ii this is visualised as triggering a slope failure and resulting in the destruction of much of the centre by a catastrophic landslide this mechanism has much in common with the explosive eruptions which produced both the bandai san japan caldera in 1888 and the mount st helens caldera in may 1980