a new model for the emplacement of columbia river basalts as large inflated pahoehoe lava flow fields extensive flows of the columbia river basalt crb group in washington oregon and idaho are dominantly inflated compound pahoehoe sheet lavas early studies recognized that crb lavas are compound pahoehoe flows with textures suggesting low flow velocities but it was thought that the great thickness and extent of the major flows required very rapid emplacement as turbulent floods of lava over a period of days or weeks however small volume 1 km compound pahoehoe flows on kilauea hawai i demonstrate that such flows can thicken by at least an order of magnitude through gradual inflation and the same mechanism has been proposed for larger 10 20 km3 pahoehoe flows in iceland the vertical distribution of vesicles and other morphologic features within crb lava flows indicate that they grew similarly by inflation small pahoehoe lobes at the base and top of many crb pahoehoe lava flows indicate emplacement in a gradual piecemeal manner rather than as a single flood we propose that each thick crb sheet flow was active for months to years and that each group of flows produced by a single eruption a flow field was emplaced slowly over many years

plagioclase rich chondrules in the reduced cv chondrites evidence for complex formation history and genetic links between calcium aluminum rich inclusions and ferromagnesian chondrules plagioclase rich chondrules prcs in the reduced cv chondrites efremovka leoville vigarano and grosvenor mountains gro 94329 consist of magnesian low ca pyroxene al ti cr rich pigeonite and augite forsterite anorthitic plagioclase feni metal sulfide nodules and crystalline mesostasis composed of silica anorthitic plagioclase and al ti cr rich augite the silica grains in the mesostases of the cv prcs are typically replaced by hedenbergitic pyroxenes whereas anorthitic plagioclase is replaced by feldspathoids nepheline and minor sodalite some of the prcs contain regions that are texturally and mineralogically similar to type i chondrules and consist of forsterite low ca pyroxene and abundant feni metal nodules several prcs are surrounded by igneous rims or form independent compound objects twelve prcs contain relic calcium aluminum rich inclusions cais composed of anorthite spinel high ca pyroxene forsterite and al rich low ca pyroxene anorthite of these cais is generally more heavily replaced by feldspathoids than anorthitic plagioclase of the host chondrules this suggests that either the alteration predated formation of the prcs or that anorthite of the relic cais was more susceptible to the alteration than anorthitic plagioclase of the host chondrules these observations and the presence of igneous rims around prcs and independent compound prcs suggest that the cv prcs may have had a complex multistage formation history compared to a more simple formation history of the cr prcs relatively high abundances of moderately volatile elements such as cr mn and si in the prcs suggests that these chondrules could not have been produced by volatilization of ferromagnesian chondrule precursors or by melting of refractory materials only we infer instead that prcs in carbonaceous chondrites formed by melting of the reduced chondrule precursors magnesian olivine and pyroxene feni metal mixed with refractory materials relic cais composed of anorthite spinel high ca pyroxene and forsterite the mineralogical chemical and textural similarities of the prcs in several carbonaceous chondrite groups cv co ch cr and common presence of relic cais in these chondrules suggest that prcs may have formed in the region s intermediate between the regions where cais and ferromagnesian chondrules originated

holocene climate changes over the desert loess transition of north central china a 2 m trench section at the desert loess transition of north central china was analyzed at 2 cm intervals for grain size distribution md m and total organic carbon toc ams 14c time series of the md and toc records provides direct information on variations of the east asian monsoon climate during the last 10 000 yr md is considered to represent the wind strength and high md reflects strong winter monsoon winds toc denotes the degree of vegetation cover a function of the intensity of summer monsoon circulations from ca 10 000 to 7000 cal yr bp the climate was dominated by a strong winter monsoon and a very weak summer monsoon as indicated by high md and low toc values subsequently climatic conditions became warmer gradually from ca 7000 to 5500 cal yr bp the period between ca 5500 and 2700 cal yr bp displayed the highest toc and lowest md values over the last 10 000 yr marking a stable state of a warm humid climate i e the holocene climatic optimum of china during the interval of ca 2700 1500 cal yr bp the expansion and intensification of agrarian activities could have led to desertification and acceleration of deposition of coarse grained particles resulting in a decreased organic carbon accumulation rate however the toc during this interval still has values as high as during the episode of ca 7000 5500 cal yr bp reflecting a relatively stronger summer monsoon circulation since ca 1500 cal yr ago high amplitude fluctuations of toc that fluctuate in phase with the clay size fraction imply that the climate experienced three major oscillations with a prominent peak of enhanced summer monsoon circulation at ca 1300 cal yr ago and with two intervals of increased winter monsoon strength occurring around ca 1000 and 300 cal yr ago the md and toc records over the past 5000 yr demonstrate a good correlation with the archaeological phenological and historical records of china climate changes in the east asian monsoon region were not only related to the changing seasonality of solar insolation resulting from progressive changes in the earth s orbital parameters but were also controlled by the pattern and intensity of the atmospheric circulation

strontium calcium ratios in modern porites corals from the great barrier reef as a proxy for sea surface temperature calibration of the thermometer and monitoring of enso high precision sr ca ratios are reported for porites corals from davies reef at 19 s on the midshelf of the great barrier reef australia skeletal growth parameters were also determined from coral slabs using x ray photographs and densitometry measurements a calibration of the sr ca thermometer has been obtained using in situ measured sea surface temperatures which gives sr ca 10 10 48 0 01 0 0615 0 0004 t wheret is in c this calibration applies to different species of porites and a large range of annual extension and calcification rates provided sampling follows a major growth axis biases of 1 2 c have been observed in the low density margins where growth is hampered by interfering fans of corallites the analytical and the long term reproducibility of sr ca derived temperatures are both better than 0 3 c 2 coral growth parameters such as the extension rate or density generally appear to respond to environmental changes such as rainfall but do not affect the sr ca partitioning between coralline aragonite and seawater no correlation has been found between calcification rate and sr ca variations consistent with sr ca being mainly controlled by temperature in the great barrier reef the interannual variability in sst is primarily related to the el nino southern oscillation phenomenon and is typically marked by a cold anomaly during the winter preceding the mature warm phase instrumental records show that the surface waters of the coral sea around 19 s have experienced a significant cooling associated with the el ninos of 1965 1972 and 1982 1983 which the porites corals record faithfully the coral derived temperatures for the period from 1965 to 1993 show an increase of 1 3 c which has occurred mainly since 1979 this warming is larger in magnitude but consistent with the trend for the southern hemisphere land and marine temperature records which shows an increase of around 0 4 c

deglacial sea level record from tahiti corals and the timing of global meltwater discharge the timing of the last deglaciation is important to our understanding of the dynamics of large ice sheets1 and their effects on the earth s surface2 3 moreover the disappearance of the glacial ice sheets was responsible for dramatic increases in freshwater fluxes to the oceans which probably disturbed the ocean s thermohaline circulation and hence global climate4 7 sea level increases bear witness to the melting of continental ice sheets but only two such records from barbados8 9 and new guinea10 11 corals have been accurately dated but these corals overlie active subduction zones where tectonic movements are large and often discontinuous especially in new guinea so the apparent sea level records may be contaminated by a complex tectonic component here we date fossil corals from tahiti which is far from plate boundaries and thus is likely to be tectonically relatively stable and remote from the locations of large former ice sheets the resulting record indicates a large sea level jump shortly before 13 800 calendar years bp which corresponds to meltwater pulse 1a in the barbados coral records8 9 the timing of this event is more accurately constrained in the tahiti record revealing that the meltwater pulse coincides with a short and intense climate cooling event12 15 that followed the initiation of the bolling allerod warm period12 16 but preceded the younger dryas cold event by about 1 000 years

a field investigation of the basaltic ring structures of the channeled scabland and the relevance to mars abstract the basaltic ring structure brs is a class of peculiar features only reported in the channeled scabland of eastern washington state they have been suggested to be good analogs however for some circular features on mars brss are found where pleistocene floods scoured the columbia river basin stripping off the uppermost part of the miocene columbia river basalt group and exposing structures that were previously embedded in the lava the odessa craters near odessa wa are 50 500 m wide brss that are comprised of discontinuous concentric outcrops of subvertically jointed basalt and autointrusive dikes detailed field investigation of the odessa craters in planform and a cross sectional exposure of a similar structure above banks lake wa lead us to propose that brss formed by concurrent phreatovolcanism and lava flow inflation in this model phreatovolcanic a k a rootless cones formed on a relatively thin active lava flow the lava flow inflated around the cones locally inverting topography tensile stresses caused concentric fracturing of the lava crust lava from within the molten interior of the flow exploited the fractures and buried the phreatovolcanic cones and subsequent erosive floods excavated the structures another population of brss near tokio station wa consists of single ringed raised rimmed structures that are smaller and more randomly distributed than the odessa craters we find evidence for a phreatovolcanic component to the origin as well and hypothesize that they are either flood eroded phreatovolcanic cones or odessa crater like brss this work indicates that brss are not good analogs to the features on mars because the martian features are found on the uneroded surfaces despite this the now superseded concepts for brs formation are useful for understanding the formation of the martian features

rapid analysis of high precision sr ca ratios in corals and other marine carbonates a method for rapid determination of high precision sr ca ratios in scleractinian corals is presented using an inductively coupled plasma atomic emission spectrophotometer samples are corrected for instrument drift using a reference solution similar to the approach used for analysis of stable isotopes using gas source mass spectrometry further correction for variation of the sr ca ratio with ca concentration is accomplished using internal standards the precision once all corrections have been made is better than 0 1 relative standard deviation 1 for samples of similar ca concentration and better than 0 2 for samples with variable ca concentrations this method increases the sample throughput by approximately a factor of 20 relative to thermal ionization mass spectrometry and significantly reduces instrument and per sample costs comparison of sr ca data for a coral from the galapagos islands with an instrumental temperature record shows excellent agreement and demonstrates the potential for application of this technique to samples of modern and fossil scleractinian corals and other marine carbonates including foraminifera

column on column structures as indicators of lava ice interaction ruapehu andesite volcano new zealand abstract lava flows of the mangawhero formation ca 15 60 ka on ruapehu volcano erupted during the last glaciation in a distal flow lobe at tukino on the east side of the mountain small secondary columns 10 20 cm thick have formed on the sides of large rectangular primary 0 5 3 m thick cooling columns thick 10 m zones of such small columns form a lateral and basal outer rind of the lobe as they do not mark glassy zones of quenching these secondary columns are interpreted as being formed by a second cooling event at temperatures below the boundary between the low creep and elastic regimes 600 c by rapid influx of copious amounts of water temperature drops deduced from extensional strains of the two sets of columns were used to gauge the viability of such a two stage process absence of reliable data on andesite contraction coefficients was overcome by using a sliding scale to assess a large range of values the estimates indicate that two stage chilling is feasible after flowing across relatively ice poor terrain the lava flow must have interacted with a valley glacier that provided water for further chilling the already formed primary columns and formation of the outer rind small columns given this evidence for lava ice interaction it is likely that prominent thick flows elsewhere in the mangawhero formation may have been constrained to their ridge top locations by ice conditions similar to those described by lescinsky and sisson lescinsky d t sisson t w 1998 ridge forming ice bounded lava flows at mount rainier washington geology 26 351 354

the gisp2 δ18o climate record of the past 16 500 years and the role of the sun ocean and volcanoes measured 18o 16o ratios from the greenland ice sheet project 2 gisp2 ice core extending back to 16 500 cal yr b p provide a continuous record of climate change since the last glaciation high resolution annual 18o 16o results were obtained for most of the current millennium a d 818 1985 and record the medieval warm period the little ice age and a distinct 11 yr 18o 16o cycle volcanic aerosols depress central greenland annual temperature 1 5 c maximally and annual 18o 16o for about 4 yr after each major eruptive event on a bidecadal to millennial time scale the contribution of solar variability to holocene greenlandic temperature change is 0 4 c the role of thermohaline circulation change on climate problematic during the holocene is more distinct for the 16 500 10 000 cal yr b p interval analogous to 14c age calibration terminology we express time in calibrated cal yr b p a d 1950 0 cal yr b p the oldest dryas bolling older dryas allerod younger dryas sequence appears in great detail bidecadal variance in 18o 16o but not necessarily in temperature is enhanced during the last phase of lateglacial time and the younger dryas interval suggesting switches of air mass transport between jet stream branches the branched system is nearly instantaneously replaced at the beginning of the bolling and holocene at 14 670 and 11 650 cal yr b p respectively by an atmospheric circulation system in which 18o 16o and annual accumulation initially track each other closely thermodynamic considerations of the accumulation rate temperature relationship can be used to evaluate the 18 o 16o temperature relationship the gisp2 ice layer count years of major gisp2 climate transitions also support the use of coral 14c ages for age calibration

abrupt changes in early holocene tropical sea surface temperature derived from coral records for many high latitude regions of the globe it is now clear that the transition to modern climate following the last glacial maximum was punctuated by a number of rapid and substantial climate oscillations1 2 in contrast relatively little is known about how the tropics responded to the deglaciation because few high resolution records are available from lower latitudes corals have recently been shown to provide an important source of tropical climate records because they can be easily and accurately dated using either 14c or 230th and because past sea surface temperatures can be recovered from the sr ca ratios in coral skeletons here we use this technique to derive several early holocene sea surface temperature records from a coral drill core recovered from espiritu santo vanuatu in the tropical southwest pacific ocean these records indicate that sea surface temperatures in this region were depressed by as much as 6 5 c below modern values at 10 350 calendar years bp but rose very abruptly during the following 1 500 years this temperature increase lags the post younger dryas increase observed in a coral record from the tropical atlantic ocean3by about 3 000 years an unexpected phase shift that may ultimately shed light on the mechanisms of deglacial climate change

fayalite in the vigarano cv3 carbonaceous chondrite occurrences formation age and conditions abstract we have performed petrographic characterization 53mn 53cr age determination and thermodynamic stability evaluations of fayalite in vigarano meteorite that belongs to the reduced subgroup of cv3 chondrites vigarano is a breccia consisting of clasts which are separate chondrules surrounded by olivine rich fine grained materials four out of twenty three explored clasts contain fayalites that represent materials of the bali like oxidized subgroup of cv3 chondrites the fayalites fa 80 with grain sizes typically

mini columns and ghost columns in columbia river lava abstract the master joints bounding the columns that make up the basal colonnade of large lava flows of the columbia plateau are in places flanked by sub horizontal mini columns that have grown normal to the master joints the secondary mini columns grow into the main columns and are clearly younger than them they are small adjacent to the master joint but merge together and thicken away from the fracture toward the master column interior commonly the mini columns are one half meter in length and 2 12 cm in diameter where the horizontal mini columns grow longer they intersect toward the middle of the master joints this plexus of joints changes the aspect of the original master columns making them almost unrecognizable producing ghost columns the basalt flow may acquire an entablature like appearance where the ghost column outlines disappear due to extensive secondary fracturing at the time that the hot flow center had cooled sufficiently below the brittle plastic transformation the primary vertical basal colonnade joints growing up from the bottom connected with those in the upper colonnade growing down this allowed steam trapped beneath the flow to be released to the surface and ushered in a change from a conduction cooling regime to a convection cooling regime the steam beneath the flow was formed and sustained by heat from the lava that boiled the groundwater in the underlying substrate large volumes of the rising steam was on average much cooler than the hot fractures in the flow interior through which it passed causing contraction of the master column walls to produce the secondary horizontal mini columns the presence of mini columns indicates emplacement of lava over moist ground and are absent where the lavas advanced across arid areas or flowed over recently erupted lava the extreme shattering that forms ghost columns by late stage convective cooling can produce a flow layer of considerable thickness a layer that can later serve as an aquifer with high porosity and permeability

snow contact volcanic facies and their use in determining past eruptive environments at nevados de chillan volcano chile studies of the eruptive products from volcanoes with variable ice and snow cover and a long history of activity enable reconstruction of erupted palaeoenvironments as well as highlighting the hazards associated with meltwater production such as jokulhlaups and magma water interaction existing difficulties include estimation of ice snow thicknesses and discrimination between ice and snow contact lithofacies we present field evidence from the cerro blanco subcomplex of nevados de chillan stratovolcano central chile which has erupted numerous times in glacial and non glacial periods and most recently produced andesitic lava flows in the 1861 1865 eruption from the santa gertrudis cone on the northwest flank of the volcano the main period of lava effusion occurred during the winter of 1861 when the upper flanks of the volcano were reportedly covered in snow and ice the bases and margins of the first lava flows produced are cut by arcuate fractures which are interpreted as snow contact features formed when steam generated from the melting of snow entered tensional fractures at the flow base in contrast the interiors and upper parts of these flows as well as the overlying flow units have autobrecciated and blocky textures typical of subaerial conditions due to insulation by the underlying lava similar textures found in a lava flow dated at 90 0 0 6 ka that was emplaced on the northwest flank of cerro blanco are also inferred to be ice and snow contact features these textures have been used to infer that a small valley glacier overlain by snow existed in the santa gertrudis valley at the time of the eruption such reconstructions are important for determining the long term evolution of the volcano as well as assessing future hazards at seasonally snow covered volcanoes

high frequency winter cooling and reef coral mortality during the holocene climatic optimum a detailed ecological micro structural and skeletal sr ca study of a 3 42 m thick goniopora reef profile from an emerged holocene reef terrace at the northern south china sea reveals at least nine abrupt massive goniopora stress and mortality events occurred in winter during the 7 0 7 5 thousand calendar years before present cal ka bp within the holocene climatic optimum whilst calculated sr ca sst sea surface temperature maxima during this period are comparable to those in the 1990s sr ca sst minima are significantly lower probably due to stronger winter monsoons such generally cooler winters superimposed by further exceptional winter cooling on inter annual to decadal scales may have caused stress and mortality of the corals about every 50 years sea level rose by similar to 3 42 m during this period with present sea level reached at similar to 7 3 ka bp and a sea level highstand of at least similar to 1 8 m occurred at similar to 7 0 ka the results show that it took about 20 25 years for a killed goniopora coral reef to recover c 2004 elsevier b v all rights reserved

columnar jointed bentonite below a doleritic sill tideswell dale derbyshire uk formation during prograde contact metamorphism columnar jointed tuffs bentonites are located below the lower carboniferous tideswell dale sill derbyshire in an abandoned quarry there are three zones of prismatic joints columnar joints 60 cm thick and mean column width of 4 1 cm and massive conchoidally fractured rock sequentially from the dolerite contact downwards the rocks are very fine grained 1 10 m and consist mainly of sanidine interlayered illite smectite and hematite with minor quartz apatite montmorillonite anatase and detrital minerals high k2o and fe2o3 low na2o and low mgo are interpreted as due to alteration of felsic volcanic ash the bentonite was contact metamorphosed by the sill to temperatures of c 300 c the progression of fracture geometries thermal considerations and application of theories of column formation indicate that columns formed downwards away from the sill due to prograde contact metamorphism of the originally clay rich bentonite the formation of columnar fracture networks by shrinkage due to igneous heating may have implications for the effectiveness of bentonite as a barrier for disposal of high level radioactive waste regional dimensions include documenting widespread felsic explosive volcanism and inferring a triassic oxidation event from palaeomagnetic data

temperature constraints on the ginkgo flow of the columbia river basalt group this study provides the first quantitative estimate of heat loss for a columbia river basalt group flow a glass composition based geothermometer was experimentally calibrated for a composition representative of the 500 km long ginkgo flow of the columbia river basalt group to measure temperature change during transport melting experiments were conducted on a bulk sample at 1 atm between 1200 and 1050 c natural glass was sampled from the margin of a feeder dike near kahlotus washington and from pillow basalt at distances of 120 km vantage washington 350 km molalla oregon and 370 km portland oregon ginkgo basalt was also sampled at its distal end at yaquina head oregon 500 km comparison of the glass mgo content k 2 o in plagioclase and measured crystallinities in the experimental charges and natural samples tightly constrains the minimum flow temperature to 1085 5 c glass and plagioclase compositions indicate an upper temperature of 1095 5 c thus the maximum temperature decrease along the flow axis of the ginkgo is 20 c suggesting cooling rates of 0 02 0 04 c km these cooling rates substantially lower than rates observed in active and historic flows are inconsistent with turbulent flow models calculated melt temperatures and viscosities of 240 750 pa s allow emplacement either as a fast laminar flow under an insulating crust or as a slower inflated flow

the formation of columnar joints produced by cooling in basalt at staffa scotland columnar jointing in basaltic lava flows on the island of staffa nw scotland was studied using a combination of field mapping and measurement of column dimensions sample petrology and measurements of plagioclase crystal size distributions csds interpreted using theoretical models of cooling four different lava flow units were measured and column ordering was assessed using the hexagonality index and relative standard deviations of column side length top area and internal angle upper and lower colonnades consist of dominantly 5 6 and 7 sided columns with a hexagonality index value very similar to that of giant s causeway and other basaltic columnar jointed localities csds from samples at different heights within one colonnade were used to infer the propagation of the solidus isotherm which was consistent with a convective cooling mechanism within the colonnade interior sample petrology and csd measurements suggest that entablature can form both by the interaction of propagating joint sets and flooding of the flow surface by water and the most widely exposed unit on staffa shows evidence of both mechanisms operating on the same flow crystal size distribution measurements can provide a useful tool for field interpretation of lava flow cooling mechanisms

timing and duration of the last interglacial evidence for a restricted interval of widespread coral reef growth abstract we report new mass spectrometric u series ages for eight last interglacial fossil reefs along the continental margin of western australia corals were selected in growth position from localities that are characterized by apparently low levels of diagenesis and relative tectonic stability so that the fossil reefs provide critical information on last interglacial sea levels without requiring corrections for tectonic movements in addition we have improved the constraint on the timing of onset of reef growth by recovering drill core coral from the base of the reefs uranium and thorium isotopes were measured with high levels of precision leading to improvements in age resolution and allowing samples which have undergone diagenetic exchange of uranium and thorium to be more easily identified and discarded these data supplement our previous results for rottnest island and leander point leading to more than seventy mass spectrometric u series ages from which constraints can be placed on the timing duration and character of the last interglacial sea level highstand reliable ages show that reef growth started contemporaneously at 128 1 ka along the entire western australian coastline while relative sea levels were at least 3 m above the present level because western australia is located far from the former penultimate glacial maximum ice sheets and are not significantly effected by glacial unloading these data constrain the timing of onset of the last interglacial period to 128 1 ka assuming reef growth started soon after sea level approached interglacial levels a unique regressive reef sequence at mangrove bay constrains the timing of termination of the last interglacial period to 116 1 ka the major episode of reef building however both globally and locally along the western australian coast is restricted to a very narrow interval occurring from 128 ka and 121 ka suggesting that global ocean surface temperatures were warm and or sea levels were stable enough to allow prolific reef growth only during the earlier part of the last interglacial

does the trigger for abrupt climate change reside in the ocean or in the atmosphere two hypotheses have been put forward to explain the large and abrupt climate changes that punctuated glacial time one attributes such changes to reorganizations of the ocean s thermohaline circulation and the other to changes in tropical atmosphere ocean dynamics in an attempt to distinguish between these hypotheses two lines of evidence are examined the first involves the timing of the freshwater injections to the northern atlantic that have been suggested as triggers for the global impacts associated with the younger dryas and heinrich events the second has to do with evidence for precursory events associated with the heinrich ice rafted debris layers in the northern atlantic and with the abrupt dansgaard oeschger warmings recorded in the santa barbara basin

late cenozoic columnar jointed basaltic lavas in eastern and southeastern china morphologies structures and formation mechanisms late cenozoic basaltic lavas in eastern and southeastern china commonly display spectacular columnar joints in four volcanic fields in this region we have observed and classified five types of colonnade vertical inclined horizontal fanning upwards and fanning downwards that provide information on the cooling regime and emplacement mechanism of the lava flows in total we analyzed the geometry and morphology of joints across ten different lava flow areas in the changle volcanic field cvf luhe volcanic field lvf eastern zhejiang volcanic field ezvf and niutoushan linjin island nanding island volcanic field nlnvf field observations show that columnar jointed alkaline basalts commonly exhibit narrow and irregular shapes indicating fast cooling tholeiites with columnar joints in contrast show wide and regular polygons indicating slower cooling vertical columnar joints and other types horizontal and fanning shaped have different mature patterns with the implication that lavas flowed on relatively flat land and in paleo valleys respectively this study suggests a simple qualitative description of different types of colonnade can be made based on their alignment patterns which represents a direct and easy way to derive solidification processes after lava eruption from colonnaded lavas in outcrop

structures textures and cooling histories of columbia river basalt flows flood basalt flows of the columbia river basalt group commonly exhibit well developed colonnade and entablature structures formed during cooling of individual flows the colonnade refers to the well defined columnar structure of many flows which appears in the lowermost 10 to 30 and in places the uppermost 10 to 20 entablature refers to those parts of a flow that have smaller column diameters and more irregular pattern fractures than those of colonnade entablature commonly occupies the central 60 to 70 of a flow in some cases however the entablature is interrupted by colonnade in such cases the entablature and colonnade may be repeated once or twice within a single flow in other cases flows may lack an entablature entirely petrographic examination reveals a pronounced correlation between structural and textural features thin sections of colonnade basalt have relatively coarse cruciform or octahedral fe ti oxide crystals and 20 glassy mesostasis the central entablature basalt in contrast has much more mesostasis as much as 60 and has textural features such as feathery fe ti oxide crystals indicative of more rapid cooling these features are the reverse of what might be expected for normal conductive cooling because cooling rates at the flow margins should be greater than those in the flow interior we reconciled the observed basalt textures with thermal models by taking into account rainfall and deranged drainage during crystallization of the flow downward migration of water through cracks would cause convective cooling of underlying unsolidified lava this effect and its consequences have been modeled numerically in order to clarify the physical constraints on the mechanism by which the central part of the lava can be quenched we have found that a water infiltration front can explain the presence of a thick quenched flow interior provided that the infiltration front moves downward just behind the lava solidification front despite heavy rainfall on hawaii for example 250 cm yr at kilauea iki exposed prehistoric lava flows on that island exhibit only colonnades we deduce from this that heavy rainfall alone is inadequate to quench flow interiors extensive flooding by deranged drainage or perhaps extremely heavy rainfall 250 cm yr is apparently required to produce entablatures the model also can be used to explain the occurrence of repeated entablature and colonnade by considering the effects of intermittent inundation the imposition of boundary conditions that mimic the removal and reoccurrence of flooding yields cooling histories that are consistent with the development of multiple colonnades and entablatures

emplacement and inflation of pahoehoe sheet flows observations and measurements of active lava flows on kilauea volcano hawaii inflated pahoehoe sheet flows have a distinctive horizontal upper surface which can be several hundred meters across and are bounded by steep monoclinal uplifts the inflated sheet flows we studied ranged from 1 to 5 m in thickness but initially propagated as thin sheets of fluid pahoehoe lava generally 20 30 cm thick individual lobes originated at outbreaks from the inflated front of a prior sheet flow lobe and initially moved rapidly away from their source velocities slowed greatly within hours due to radial spreading and to depletion of lava stored within the source flow as the outward flow velocity decreases cooling promotes rapid crustal growth at first the crust behaves plastically as pahoehoe toes form after the crust attains a thickness of 2 5 cm it behaves more rigidly and develops enough strength to retain incoming lava thus increasing the hydrostatic head at the flow front the increased hydrostatic pressure is distributed evenly through the liquid lava core of the flow resulting in uniform uplift of the entire sheet flow lobe initial uplift rates are rapid flows thicken to 1 m in 1 2 hours but rates decline sharply as crustal thickness increases and as outbreaks occur from the margins of the inflating lobe one flow reached a final thickness of nearly 4 m after 350 hr inflation data define power law curves whereas crustal cooling follows square root of time relationships the combination of data can be used to construct simple models of inflated sheet flows as the flow advances preferred pathways develop in the older portions of the liquid cored flow these pathways can evolve into lavatube systems within a few weeks formation of lava tubes results in highly efficient delivery of lava at velocities of several kilometers per hour to a flow front that may be moving 1 2 orders of magnitude slower if advance of the sheet flow is terminated the tube remains filled with lava that crystallizes in situ rather than draining to form the cave like lava tubes commonly associated with pahoehoe flows inflated sheet flows from kilauea and mauna loa are morphologically similar to some thick icelandic and submarine sheet flows suggesting a similar mechanism of emplacement the planar sheet like geometry of flood basalt flows may also result from inflation of sequentially emplaced flow lobes rather than nearly instantaneous emplacement as literal floods of lava

refining the eustatic sea level curve since the last glacial maximum using far and intermediate field sites the eustatic component of relative sea level change provides a measure of the amount of ice transferred between the continents and oceans during glacial cycles this has been quantified for the period since the last glacial maximum by correcting observed sea level change for the glacio hydro isostatic contributions using realistic ice distribution and earth models during the last glacial maximum lgm the eustatic sea level was 125 5 m lower than the present day equivalent to a land based ice volume of 4 6 4 9 107 km3 evidence for a non uniform rise in eustatic sea level from the lgm to the end of the deglaciation is examined the initial rate of rise from ca 21 to 17 ka was relatively slow with an average rate of ca 6 m ka 1 followed by an average rate of ca 10 m ka 1 for the next 10 ka significant departures from these average rates may have occurred at the time of the younger dryas and possibly also around 14 ka most of the decay of the large ice sheets was completed by 7 ka but 3 5 m of water has been added to the oceans since that time

the temperature relationship in coralline aragonite influence of variability in and skeletal growth parameters this paper provides an evaluation of two of the most likely pitfalls of sr ca thermometry i e the effect of biogenic cycling of sr vs ca in the surface ocean and the effect of variable extension rate on sr incorporation in coralline aragonite the authors also report calibration of the sr ca temperature relationship for three coral species porites lobata pocillopora eydouxi and pavona clavus collected for the hawaiian and galapagos islands analyses of seawater samples show significant spatial and depth variability in the sr ca ratio the uncertainty introduced by this effect is estimated to be 0 2 degrees c for corals located in tropical oligotrophic waters and potentially larger for corals located in upwelling areas sr ca along two different growth axes of a galapagos pavona clavus with annual extension rates of approximately 6 and 12 mm y respectively indicate an offset of 1 2 degrees c with higher sr ca values associated with slower extension rates the offset observed between the two growth axes may be the result of variations in extension and or calcification rate these results are important in determining past sea surface temperatures for reconstruction of paleoclimates

a high resolution sr ca and δ18o coral record from the great barrier reef australia and the 1982 1983 el nino abstract a high resolution near weekly sr ca and oxygen isotopic record is presented for a coral from the pandora reef in the great barrier reef gbr of australia during the period 1978 to 1984 the records are well correlated except for periods of high rainfall when river runoff has significantly modified the 18o value of seawater using the sr ca temperature calibration of de villiers et al 1994 the sr ca records exhibit seasonally controlled cyclical sst sea surface temperature variations of from 21 to 28 c during the very strong el nino of 1982 1983 the sr ca systematics indicate a sharp drop in the winter sst to 18 5 c this represents a temperature anomaly of 3 c which is approximately twice that given by the 18o variations suggesting an 2 amplification of the anomaly by the sr ca system possibly due to the increasing dominance of inorganically controlled aragoniteseawater fractionation the oxygen isotopic systematics show the combined effects of both temperature and changing seawater 18o values the latter reflecting the influx of 18o depleted runoff during periods of high rainfall due to the extremely low 10 3 sr and ca contents of river run off relative to seawater it is possible to use the sr ca thermometer to calculate temperatures independent of major floods and hence deconvolve the combined effects in the oxygen isotopic record of variable temperature and the 18o value of seawater using this approach it is possible to quantitatively reproduce the volume of runoff from the burdekin river during the periods of major flooding that occurred in early 1979 and 1981 the results of this study demonstrate that the combined use of high resolution sr ca and 18o systematics in scleractinian corals is a powerful tool for providing quantitative constraints on past climate

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

holocene and late pleistocene relative sea level fluctuations along the east coast of india abstract hermatypic coral colonies and intertidal fossil bearing grainstone packstone and sandstone beds of holocene and of a late pleistocene highstand are exposed above the present high tide level htl at a number of locations along the east coast of india from cape comorin to rameswaram being a passive margin boundary free from indications of late quaternary seismogenic movements this sector provides a benchmark for defining minor relative sea level perturbations during the late pleistocene and holocene highstands along a tropical coast lying between latitudes 5 n and 10 n a series of marine terraces carved on and locally blanketted by late pleistocene biotic and terrigenous accumulations occur at different elevations up to 4 4 m above ltl at manappad point possibly signifying discrete stillstand episodes followed by abrupt intervals of rising falling sea level sea level indicators of the holocene highstand occur in this sector as well as along the fringes of the godavari delta further north the holocene highstand reached nearly 3 m above ltl at 7 3 ka remained stable for approximately 1 7 kyr and was followed by a relative sea level fall between 5 2 and 4 2 ka there was a second pulse of relative sea level rise of a few metres leading to a fresh spurt in coral growth along the northern coast of mandapam and rameswaram this was nearly contemporaneous with fresh melting of ice sheets of antarctica the little ice age lia witnessed a minor 1 m relative sea level fall along this coast resulting in rapid diagenetic hardening and infiltration of goethite into the emerged foreshore sand at karikovil and its neighbourhood this was followed by a rise of the sea level during the last few centuries

corals at their latitudinal limits laser ablation trace element systematics in porites from shirigai bay japan the rapid analytical technique of laser ablation inductively coupled plasma mass spectrometry la icp ms was used to measure the trace elements b mg sr ba and u in a high latitude coral colony porites lobata taken from shirigai bay japan 32 n a wide range of sea surface temperatures ssts 14 5 28 c and upwelling events influenced this coral cold winter ssts caused a decrease and or cessation of skeletal extension measurements of u ca and sr ca indicate an approximately linear response to ssts above 18 c and a non linear response below 18 c mg ca and b ca measurements both showed annual cycles broadly consistent with sst variations but also exhibited intra annual fluctuations not associated with temperature suggesting that the incorporation of mg and b into the coral skeleton was not simply regulated by temperature it is shown that ba ca ratios provide a proxy for wind induced seasonal upwelling this is inferred from the strong correlations between the strength of zonal winds 1 month prior to the sst minimum and the ba ca maximum secondary upwelling events occurred during the summers of 1982 1987 1991 and 1992 these summers were cooler than average and were associated with el nino southern oscillation events

surface morphology of columnar joints and its significance to mechanics and direction of joint growth columnar joints in basaltic lava flows display conspicuous bands oriented normal to column axes new observations show that each band contains a single plumose structure and thus represents an individual crack or joint segment formed during a discrete growth event analysis of plumose structure and intersections of cracks leads to a new kinematic model of columnar jointing and provides the first direct proof that columnar joints grow incrementally from exterior to interior regions of solidifying magma bodies columnar joints form by nucleation and growth of new cracks on the edges of older cracks each new crack begins at a point and propagates mostly normal to column axes and along the leading edge of a developing column face where thermal stress is concentrated inward propagation of cracks toward hotter regions is limited by a decrease of thermal stress and by the brittle ductile transition of lava outward and lateral propagation is limited by mechanical interaction with previous cracks and by low thermal stress in already fractured lava cracks often diverge slightly from the planes of previous cracks probably because of spatial and temporal changes in directions of local principal stresses mechanical interaction causes a diverging crack to overlap curve toward and usually intersect the previous crack behind its edge leaving a blind tip that points in the overall growth direction of the columnar joints this and other directional criteria are applied to determine joint growth patterns in several lava flows of the western united states in two tiered and multi tiered flows downward growing columnar joints usually meet upward growing joints well below the middle of the flows which indicates very rapid cooling of upper portions relative to lower portions this supports the idea that convection of water in columnar joints connected to the surface may be an important mechanism for cooling the upper portions of these flows whereas conduction is probably the dominant cooling mechanism at the bases

speleothem u series dating of semi synchronous climate oscillations during the last deglaciation evidence for nearly synchronous climate oscillations during the last deglaciation has been found throughout the northern hemisphere but few records are based on independent time scales of calendar years we present a rare uranium series dated oxygen carbon isotope record for a speleothem from tangshan cave china which demonstrates that abrupt deglacial climatic oscillations from 16 800 to 10 500 yr bp are semi synchronous with those found in greenland ice core records relatively rapid shifts in speleothem oxygen isotope ratios demonstrate that the intensity of the east asian monsoon switched in parallel with the abrupt transitions separating the bolling allerod younger dryas and pre boreal climatic reversals however the dated isotopic transitions appear to have lasted longer our results demonstrate the dominant role of atmospheric teleconnections in the rapid propagation of deglacial climatic signals on a hemispheric scale and highlight the importance of u series dated speleothems in the timing and characterization of abrupt climate change c 2003 elsevier b v all rights reserved

viscoelastic thermal stress in cooling basalt flows polygonal fractures commonly form in basaltic lava flows during cooling of the molten lava a transient thermomechanical model is constructed to apply the temperature history in a cooling basalt flow as a boundary condition in a mechanical model of viscoelastic stress in cooling basalt nearly all past modeling of stress in cooling basalt has treated the material as purely elastic below a well defined glass transition temperature an important distinction of this model is that the viscosity of the material is allowed to be temperature dependent and the effects of viscoelastic relaxation are included on the basis of this research faster cooling and higher strain rates lead to markedly higher effective glass transition temperatures consistent with previous observations by researchers the total thermal strain in the system is constant yet the percentage of strain that is not relaxed by viscous flow varies with position relative to the cooling surface this elastic strain partition is the portion of the total strain that creates stress in the material and it is directly dependent on cooling rate thus a genetic link between cooling rate and magnitude of stress is identified

a lithic clast of oxidized cv3 material in the reduced cv3 chondrite breccia vigarano reference epfl conf 177129view record in web of science record created on 2012 05 15 modified on 2016 08 09

a deterministic methodology for prediction of fracture distribution in basaltic multiflows the fracture distribution in basalt flows is a direct result of thermal processes thus basalt flows present a unique opportunity to characterize a nearly perfect deterministic system with its fundamental physical parameters fracture distribution data collected on cliff exposures of basalt flows near the idaho national engineering and environmental laboratory ineel are combined with calculations of cooling rate and temperature distribution from a finite element model to construct a predictive methodology for fracture spacing the methodology is based on an empirical power law relationship between inverse cooling rate and fracture spacing the methodology may be applied to unexposed basalt flows of approximately elliptical cross section whose thickness and width are constrained only by geophysical or borehole data if sufficient fracture data on nearby exposed flows are available the methodology aids waste remediation efforts at sites involving contaminant transport through fractured basalt such as the ineel and the hanford site in washington as well as involving transport and fluid flow through volcanic or intrusive rocks where thermal processes are responsible for fracturing

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds