humid to arid to subhumid vegetation shift on pilliga sandstone ulungra springs new south wales abstract the pilliga sandstone region of the northwest slope of new south wales has a natural vegetation cover of sclerophyllous relatively closed to open forests with a largely heathy understorey and a warm subhumid and continental climate pollen analysis of spring fed deposits gives a vegetation history extending from at least 30 000 yr b p to the late holocene tree pollen became scarce after about 25 000 yr b p and an assemblage dominated by chenopodiaceae liguliflorae tubuliflorae and probably poaceae developed no similar assemblage is known from present pollen rain studies carried out in australia however it clearly represents a treeless open shrub steppe formation and therefore an arid or semiarid environment the site thus provides evidence of an eastward late pleistocene extension of the arid zone in australia and is the first full glacial vegetation record between 20 and 35 latitude in australia the present vegetation cover did not become reestablished until the beginning of the holocene which raises questions about the form in which pilliga sandstone vegetation survived full glacial conditions

late pleistocene glaciation of the kosciuszko massif snowy mountains australia abstract late pleistocene glaciation of the australian mainland was restricted to a small area of the southeastern highlands geomorphic mapping of the area and exposure dating using the in situ produced cosmogenic isotope 10be provides evidence for at least two distinct glaciations the early kosciuszko glaciation consisted of a single glacier advance before 59 300 5400 years ago snowy river advance the late kosciuszko glaciation comprised three glacier advances 32 000 2500 headley tarn advance 19 100 1600 blue lake advance and 16 800 1400 years ago mt twynam advance the early kosciuszko glaciation was the most extensive and the late kosciuszko advances were progressively less extensive these periods of glaciation in the highlands correspond to episodes of periglacial activity and peaks in lake levels and river discharge at lower elevations in southeastern australia glacier advances on the kosciuszko massif correlate with advances in tasmania south america and new zealand and are broadly representative of hemispheric climate changes during the last glacial cycle

non newtonian rheology of igneous melts at high stresses and strain rates experimental results for rhyolite andesite basalt and nephelinite the stress strain rate relationships of four silicate melt compositions high silica rhyolite andesite tholeiitic basalt and nephelinite have been studied using the fiber elongation method measurements were conducted in a stress range of 10 400 mpa and a strain rate range of 10 6 to 10 3 s 1 the stress strain rate relationships for all the melts exhibit newtonian behavior at low strain rates but non newtonian nonlinear stress strain rate behavior at higher strain rates with strain rate increasing faster than the applied stress the decrease in calculated shear viscosity with increasing strain rate precedes brittle failure of the fiber as the applied stress approaches the tensile strength of the melt the decrease in viscosity observed at the high strain rates of the present study ranges from 0 25 to 2 54 log10 pa s the shear relaxation times of these melts have been estimated from the low strain rate newtonian shear viscosity using the maxwell relationship s g non newtonian shear viscosity is observed at strain rates time 1 equivalent to time scales that lie 3 log10 units of time above the calculated relaxation time brittle failure of the fibers occurs 2 log10 units of time above the relaxation time this study illustrates that the occurrence of non newtonian viscous flow in geological melts can be predicted to within a log10 unit of strain rate high silica rhyolite melts involved in ash flow eruptions are expected to undergo a non newtonian phase of deformation immediately prior to brittle failure

repeated fracture and healing of silicic magma generate flow banding and earthquakes textures in an exceptionally preserved effusive rhyolite conduit at torfajokull iceland indicate that rising magma repeatedly fractured and healed at shallow levels in the conduit rfh process anastomosing tuffisite veins filled by fine grained juvenile clasts were generated by shear fracture of highly viscous magma in the glass transition interval welding of the particulate material during subsequent deformation led to thorough healing of veins allowing repeated fracture of the same body of magma we propose that the rfh process is a rechargeable trigger mechanism for hybrid seismicity and show that the time scale of the process and the fractures formed by it are consistent with the repeat time and magnitude of hybrid earthquakes during silicic eruptions the rfh process may also form the flow banding that is nearly ubiquitous in obsidian

tectonic plate generation and two phase damage void growth versus grain size reduction 1 the generation of plate tectonics from mantle convection requires shear localization in order to yield narrow weak plate boundaries separating broad strong plates a plausible shear localizing mechanism involves damage e g distributed microcracking one theoretical model of which involves two phase mechanics two phase damage theory employs a nonequilibrium relation between interfacial surface energy pressure and viscous deformation thereby providing a description of void generation and microcracking and hence weakening failure and shear localization here we examine the application of this theory to the problem of generating plate like behavior from convective type divergent convergent poloidal motion through a source sink formulation we extend the previous damage theory to consider two possible damage effects 1 growth and nucleation of voids associated with dilation of the host matrix and 2 increasing fineness i e reducing coarseness of the mixture by for example grain size reduction void generating damage is found to be poor at plate generation because of the predominance of dilational motion that is adverse to the development of plate like flow fineness generating damage is found to be very efficient at generating plate like behavior if we assume that the matrix viscosity is a simple function of grain void size as is typical for diffusion creep the implied grain size reduction mechanism is different from that of dynamic recrystallization and appears to be more capable of generating the requisite shear localization for forming tectonic plates from mantle flow

millennial scale variability in south east australian hydroclimate between 30 000 and 10 000 years ago abstract global climate variability during the late quaternary is commonly investigated within the framework of the bipolar seesaw pattern of asynchronous temperature variations in the northern and southern polar latitudes the terrestrial hydrological response to this pattern in south eastern australia is not fully understood as continuous high resolution well dated proxy records for the hydrological cycle in the region are sparse here we present a well dated highly resolved record of moisture balance spanning 30000 10000 calendar years before present 30 10 ka bp based on x ray fluorescence and organic carbon isotope 13com measurements of a sedimentary sequence from lake surprise in south eastern australia the data provide a locally coherent record of the hydrological cycle elevated si reflecting windblown quartz and clays and relatively high 13com indicate an extended period of relative aridity between 28 and 18 5 ka bp interrupted by millennial scale episodes of decreased si and 13com suggesting increased moisture balance this was followed by a rapid deglacial shift to low si and 13com at 18 5 ka bp indicative of wetter conditions we find that these changes are coeval with other records from south eastern australia and new zealand and use a monte carlo empirical orthogonal function approach to extract a common trend from three high resolution records our analyses suggest that drivers of the regional hydrological cycle have varied on multi millennial time scales in response to major shifts in global atmosphere ocean dynamics during the last glacial interglacial transition southern ocean processes were the dominant control on hydroclimate during glacial times via a strong influence of cold sea surface temperatures on moisture uptake and delivery onshore following the last deglaciation around 18 ka bp the southward migration of cold southern ocean fronts likely resulted in the establishment of conditions more like those of the present day millennial scale variability in records from the region is dominated by a persistent ca 2300 year periodicity consistent with other records across the southern hemisphere mid latitudes however this pervasive periodicity is not obviously linked to the bipolar seesaw and the mechanism remains equivocal

the anatomy of last glacial maximum climate variations in south westland new zealand derived from pollen records abstract we present pollen records from three sites in south westland new zealand that document past vegetation and inferred climate change between approximately 30 000 and 15 000 cal yr bp detailed radiocarbon dating of the enclosing sediments at one of those sites galway tarn provides a more robust chronology for the structure and timing of climate induced vegetation change than has previously been possible in this region the kawakawa oruanui tephra a key isochronous marker affords a precise stratigraphic link across all three pollen records while other tie points are provided by key pollen stratigraphic changes which appear to be synchronous across all three sites collectively the records show three episodes in which grassland interpreted as indicating mostly cold subalpine to alpine conditions was prevalent in lowland south westland separated by phases dominated by subalpine shrubs and montane lowland trees indicating milder interstadial conditions dating expressed as a bayesian estimated single best age followed in parentheses by younger older bounds of the 95 confidence modelled age range indicates that a cold stadial episode whose onset was marked by replacement of woodland by grassland occurred between 28 730 29 390 28 500 and 25 470 26 090 25 270 cal yr bp years before ad 1950 prior to the deposition of the kawakawa oruanui tephra milder interstadial conditions prevailed between 25 470 26 090 25 270 and 24 400 24 840 24 120 cal yr bp and between 22 630 22 930 22 340 and 21 980 22 210 21 580 cal yr bp separated by a return to cold stadial conditions between 24 400 and 22 630 cal yr bp a final episode of grass dominated vegetation indicating cold stadial conditions occurred from 21 980 22 210 21 580 to 18 490 18 670 17 950 cal yr bp the decline in grass pollen indicating progressive climate amelioration was well advanced by 17 370 17 730 17 110 cal yr bp indicating that the onset of the termination in south westland occurred sometime between ca 18 490 and ca 17 370 cal yr bp a similar general pattern of stadials and interstadials is seen to varying degrees of resolution but generally with lesser chronological control in many other paleoclimate proxy records from the new zealand region this highly resolved chronology of vegetation changes from southwestern new zealand contributes to the examination of past climate variations in the southwest pacific region the stadial and interstadial episodes defined by south westland pollen records represent notable climate variability during the latter part of the last glaciation similar climatic patterns recorded farther afield for example from antarctica and the southern ocean imply that climate variations during the latter part of the last glaciation and the transition to the holocene interglacial were inter regionally extensive in the southern hemisphere and thus important to understand in detail and to place into a global context

rheology and rupture of homogeneous silicate liquids at magmatic temperatures homogeneous silicate liquids have a newtonian rheology under conditions of modest stress but under relatively high stress or otherwise imposed high rates of deformation their viscosity may become non newtonian before the onset of rupture this behavior has been discussed semi empirically as well as in terms of the maxwell model liquid here it is shown that the configurational entropy theory for the occurrence of the glass transition can also explain this non newtonian rheology of silicate liquids ranging in composition from silica rich to silica poor the pressure and temperature dependence of the transition from newtonian to non newtonian flow is discussed qualitatively geological applications are indicated fragmentation of silicate liquids takes place when the glass transition is crossed and the liquid has become solid like experimental evidence indicates that the rupture strength is only slightly larger than the stress needed to cause the onset of non newtonian rheology

formation of alunite jarosite and hydrous iron oxides in a hypersaline system lake tyrrell victoria australia abstract alunite kal 3 so 4 2 oh 6 and jarosite kfe 3 so 4 2 oh 6 are common weathering products of aluminosilicates and pyrite long range transport of the constituents forming these minerals and the subsequent deposition of alunite and jarosite in an evaporite setting have not been previously documented such conditions for the occurrence of alunite and jarosite were investigated in a hypersaline system where acid groundwater enriched in k al fe iii and so 4 enter a saltplaya lake sediment cores were studied by thin section xrd and sem eds groundwater and pore water chemistries were also analyzed the results show that alunite and jarosite occur together or as individual layers and cements within the top 20 cm of the sediments where the groundwater is most concentrated due to evaporation hydrous fe oxides also occur as cements or vein fillings with the alunite and jarosite but are distributed throughout the 70 cm sediment column studied the results are consistent with a model in which alunite and jarosite precipitate as a result of the evaporation of water thermodynamic modeling indicates that the pore water in the playa sediments maybe in equilibrium with alunite jarosite and hydrous fe oxides

pulse like crack like and supershear earthquake ruptures with shear strain localization 1 we incorporate shear strain localization into spontaneous elastodynamic rupture simulations using a shear transformation zone stz friction law in the stz model plastic strain in the granular fault gouge occurs in local regions called stzs the number density of stzs is governed by an effective disorder temperature and regions with elevated effective temperature have an increased strain rate stz theory resolves the dynamic evolution of the effective temperature across the width of the fault zone shear bands spontaneously form in the model due to feedbacks amplifying heterogeneities in the initial effective temperature in dynamic earthquake simulations strain localization is a mechanism for dynamic fault weakening a shear band dynamically forms reduces the sliding stress and decreases the frictional energy dissipation on the fault we investigate the effect of the dynamic weakening due to localization in generating pulse like crack like and supershear rupture our results illustrate that the additional weakening and reduction of on fault energy dissipation due to localization have a significant impact on the initial shear stress required for supershear or pulse like rupture to propagate on a fault

role of conduit shear on ascent of the crystal rich magma feeding the 800 year b p plinian eruption of quilotoa volcano ecuador we have characterized pumice products belonging to the climactic phase of the 800 year b p quilotoa eruption bulk rock compositions petrography mineral and glass chemistry and textural investigations were performed on the three end member pumice types namely white gray and mingled pumices all the investigated pumice clasts are dacites characterized by the same bulk rock composition and mineralogical assemblage but glass compositions and bulk textures change according to different pumice types white pumice has higher crystallinity 48 wt abundant euhedral pheno microphenocrysts no groundmass microlites the most evolved glass compositions 74 78 wt sio2 and heterogeneous vesicle populations marked by deformed and highly coalesced vesicles with thin walls gray pumice exhibits lower crystallinity 29 36 wt abundant broken and or resorbed crystals ubiquitous groundmass phenocryst fragments and microlites the widest range of glass compositions 69 78 wt sio2 and quite homogeneous poorly deformed and coalesced vesicles with thicker walls mingled pumices are characterized by the alternation of bands or patches with white and gray pumice compositional and textural characteristics we attribute heterogeneities in glass compositions and crystal and vesicle textures to processes occurring within volcanic conduits as magma is ascending to the surface in particular the above observations and results are consistent with an origin of a gray magma by heating of the original white magma in a strongly sheared region of the conduit because of a mechanism of viscous dissipation and crystal grinding and resorption at the conduit walls the less viscous gray magma therefore would enable the onset and preservation of a high mass flux of the eruption otherwise difficult to explain for highly viscous crystal rich dacitic magmas

bubble deformation in magma under transient flow conditions abstract we investigate the transient behavior of bubble deformation in magma previous studies have used the relationships between capillary number and equilibrium shape for a single bubble under either steady simple shear or steady pure shear to estimate strain rates in pyroclasts and to calculate bubble shapes in a conduit flow we developed a deformation model for a bubble by adjusting the empirical functions used in an existing model for a droplet to fit experimental data for bubble deformation the modified model was used to calculate transient large deformations of a single bubble in arbitrary shear flows in this paper we demonstrate the significance of the modified model through two different applications firstly using this model we are able to simulate the entire history of the evolution of bubble shapes in a time dependent flow using the computational code conflow in this simulation we further include the effect of gas expansion on the bubble shape from this simulation we show that bubble deformation in conduit flow is controlled by the history of both capillary number and strain secondly by using this model to analyze bubble shapes observed in natural magma samples we are able to better estimate the strain rates and deformation durations we apply this model to certain transient features in the relationship between bubble shape and radius in the published data of obsidian clasts from newberry volcano and estimate a deformation duration of 2 7 4 0 min

millennial band climate spectrum resolved and linked to centennial scale solar cycles abstract spectral comparison of the hulu cave grip and gisp2 18o records suggests that the single dominant period centered on 1470 yr in the gisp2 spectrum the so called 1500 yr cycle is an artifact of the age model the 230th dated hulu cave record indicates a millennial band spectrum with a weak spectral peak near this period flanked by two stronger peaks centered on 1667 and 1190 yr similar to the grip 18o record all three millennial band cycles may derive from heterodynes of centennial band solar cycles as observed in the holocene record of atmospheric 14c production this suggests a link between centennial scale solar variability and abrupt climate change at the millennial time scale

the stratigraphy timing and climatic implications of glaciolacustrine deposits in the middle rakaia valley south island new zealand abstract stratigraphic interpretations and infrared stimulated luminescence irsl ages document the glacial history of the middle rakaia gorge section of the rakaia valley canterbury new zealand during the last two glacial cycles sheets of glaciolacustrine sediments several tens of metres in thickness can be traced at least 10 km upstream of the rakaia gorge the stratigraphic package is capped by outwash gravels associated with the last glacial maximum lgm advances the dominant inferred sedimentary environments in the sequence are 1 pro glacial and paraglacial lake beds 2 sub aqueous ice contact fans 3 sub aqueous mass flow deposits 4 supraglacial dump material and 5 outwash gravels syndepositional deformation associated with glacitectonic deformation is common the stratigraphy records glacier margin oscillations including six significant advances these occurred in early mis 6 mid mis 6 mis 5b c100 90 ka mis 5a 4 c 80 ka mid mis 3 c 48 ka and late mis 3 c 40ka all the post mis 6 advances can be corroborated from other sites in new zealand and the timings appear to coincide with both southern hemisphere insolation minima and maxima suggesting variable combinations of climatic forcing in new zealand glaciation

brittleness of fracture in flowing magma 1 understanding the transition to brittle fracture of flowing magma is essential for estimating the explosiveness of a volcanic eruption in order to quantify brittleness of flowing magma a new parameter is introduced which is a function of the ratio of the rate of change of the strain energy due to elastic distortional deformation to the mechanical power due to total distortional deformation rate from the perspective of dependence of brittle fracture of magma on stress decompression rate strain rate and shear thinning effects are reviewed the experimental data of kameda et al 2008 for rapid decompression of simulants of bubbly magma have also been reexamined the results show that exhibits a strong transition that correlates well with the observed transition between ductile expansion to brittle fragmentation moreover is useful in considering the effects of shear thinning and steady creep conditions on brittle fracture statements in the literature that suggest that materials behave in a brittle manner at sufficiently high strain rate are correct however these statements do not precisely quantify the notion of high strain rate so they are easy to misinterpret when considering the effect of shear thinning although shear thinning tends to increase the absolute magnitude of the total strain rate it does not necessarily increase brittleness also in principle it is unlikely for brittle fracture to occur at steady creep cracking observed in steady creep experiments of magma lavallee et al 2007 2008 may be attributed to small fluctuations with sufficiently high frequencies to satisfy the conditions for brittle fracture

brownish discoloration of the summit crater lake of mt shinmoe dake kirishima volcano japan volcanic microbial coupled origin a drastic change in lake water color from blue green to brown was observed in the summit crater lake of mt shinmoe dake kirishima volcano about 8 months after its 2008 eruption the color change lasted for about 2 months april june 2009 the discoloration was attributed to a brownish color suspension that had formed in the lake water x ray fluorescence and fourier transform infrared analyses of a sample of the suspension identified schwertmannite fe8o8 oh 6 so4 a cultivation test of iron oxidizing bacteria for the sampled lake water with lakebed sediment revealed that the crater lake hosts iron oxidizing bacteria which likely participated in schwertmannite formation we suggest that pyrite fes2 provided an energy source for the iron oxidizing bacteria since the mineral was identified in hydrothermally altered tephra ejected by the august 2008 eruption from consideration of these and other factors the brownish discoloration of the summit crater lake of mt shinmoe dake was inferred to have resulted from a combined volcanic microbial process

propagation of acoustic waves in a visco elastic two phase system influences of the liquid viscosity and the internal diffusion abstract the main purpose of the present paper is to present the mathematical expression for the frequency dependent effective acoustic properties of a liquid bubble mixture effects of the bubble resonance the heat and mass transfer between the liquid and bubbles and the viscoelasticity of the liquid are included in the expression several characteristic frequencies associated with these internal processes are represented by simple functions of the material and condition parameters using these expressions the acoustic properties of bubbly magmas are calculated and analyzed it is shown that the dispersion and attenuation of the pressure wave are particularly considerable in the frequency range lower than the characteristic frequency of the mass transfer and in the range near the characteristic frequency of the viscous response of the bubble radius in the frequency range bounded by these two frequencies the bubbly magma can be regarded as an elastic medium with the slow sound speed the significance of such acoustic properties on resonance of a body of bubbly magma is demonstrated in a simple one dimensional system

late quaternary sea ice history in the indian sector of the southern ocean as recorded by diatom assemblages abstract a modern analog technique mat5201 31 has been applied to fossil diatom assemblages to provide down core estimates of february sea surface temperatures ssts and of sea ice duration over the past 220 000 years at 56 40 s 160 14 e at the core location sea ice progression lagged the sst drop by 1 ka at interglacial glacial transitions and sea ice retreat was almost synchronous to the sst increase at glacial interglacial terminations sea ice increased continuously during glacial periods to reach its maximum extent at the end of glacial times although ssts were almost constant during glacials this indicates that ssts are the major parameter determining the advance and retreat of sea ice at transitions but that the sea ice advance during glacial conditions may be related to positive feedbacks of the ice on albedo air temperature and meridional wind stress the strong correlation r 0 75 between sea ice duration at the core location and the vostok co2 record argues for a control of antarctic sea ice extent on atmospheric co2 concentration via the modification of the ocean to atmosphere gas balance

delayed brittle like fragmentation of vesicular magma analogue by decompression abstract a rapid decompression experiment using syrup containing gas bubbles was conducted in order to clarify the fragmentation of vesicular magma which is a key phenomenon in volcanic eruptions we focus on brittle like fragmentation which occurs with a longer time scale than brittle fragmentation the response of the bubbly syrup to the decompression for various viscosities and porosities was tested under various initial pressures pressure differences and decompression times the response observed by high speed photography was classified using the deborah number de dt which is defined as the ratio of the viscoelastic relaxation time of the syrup to the decompression time the maximum differential stress at the bubble surface max and a measure of instantaneous brittleness at the bubble surface c at the time when the differential stress at the surface reaches the critical fracture stress c in a number of the experimental runs in which both de dt and c indicated ductile response of the material brittle like fragmentation occurred when max substantially exceeded c for all of the runs in which brittle like fragmentation was observed the onset of fragmentation was delayed substantially from the relaxation time whereas the onset occurred within the characteristic time for viscous expansion of the bubbles in many cases of brittle like fragmentation fragmentation continued after the onset triggered by a single decompression event detailed analysis indicates that brittle like fragmentation started with a sudden release of the gas in the bubbly syrup through a surface crack which might lead to an increase in local brittleness magma fragmentation may be viewed as sequential brittle like fragmentation this view may provide an explanation for the observed time delay for the onset of an explosive eruption after a triggering decompression event

a multiproxy micro xrf pollen chironomid and stable isotope lake sediment record for the lateglacial to holocene transition from thomastown bog ireland a multiproxy lateglacial environmental record is presented for a ca 3 5 m lacustrine sequence retrieved from a small basin ca 2 km2 at thomastown bog in county meath ireland sediment chemistry pollen chironomid and stable isotope data provide a detailed picture of catchment and lake system changes from the end of the last glacial gs 2a to the early holocene that correspond closely to existing local and regional models of climate change concomitant adjustments in independent proxy records are matched to the ngrip oxygen isotope curve giving 12 event episodes ranging from major climatic shifts to lower amplitude centennial to sub centennial scale adjustments including a previously unreported regressive period of landscape instability during the north west european rammelbeek phase the study emphasizes the potential of palaeoenvironmental reconstruction from sediment chemistry where the sediment mixing system reflects autochthonous versus allochthonous inputs the investigation also indicates problems of interpreting isotope data derived from bulk marl due to possible lag effects controlling the delivery of soil and groundwater and multiple sources of hco3 aq these research findings have implications for core site selection and for studies attempting to use stable isotopes for correlation purposes

climate variability over the last 35 000 years recorded in marine and terrestrial archives in the australian region an oz intimate compilation abstract the australian region spans some 60 of latitude and 50 of longitude and displays considerable regional climate variability both today and during the late quaternary a synthesis of marine and terrestrial climate records combining findings from the southern ocean temperate tropical and arid zones identifies a complex response of climate proxies to a background of changing boundary conditions over the last 35 000 years climate drivers include the seasonal timing of insolation greenhouse gas content of the atmosphere sea level rise and ocean and atmospheric circulation changes our compilation finds few climatic events that could be used to construct a climate event stratigraphy for the entire region limiting the usefulness of this approach instead we have taken a spatial approach looking to discern the patterns of change across the continent the data identify the clearest and most synchronous climatic response at the time of the last glacial maximum lgm 21 3 ka with unambiguous cooling recorded in the ocean and evidence of glaciation in the highlands of tropical new guinea southeast australia and tasmania many terrestrial records suggest drier conditions but with the timing of inferred snowmelt and changes to the rainfall runoff relationships driving higher river discharge at the lgm in contrast the deglaciation is a time of considerable south east to north west variation across the region warming was underway in all regions by 17 ka post glacial sea level rise and its associated regional impacts have played an important role in determining the magnitude and timing of climate response in the north west of the continent in contrast to the southern latitudes no evidence for cooling during the younger dryas chronozone is evident in the region but the antarctic cold reversal clearly occurs south of australia the holocene period is a time of considerable climate variability associated with an intense monsoon in the tropics early in the holocene giving way to a weakened monsoon and an increasingly el nino dominated enso to the present the influence of enso is evident throughout the southeast of australia but not the southwest this climate history provides a template from which to assess the regionality of climate events across australia and make comparisons beyond our region

rheological tests of polyurethane foam undergoing vesiculation deformation solidification as a magma analogue abstract in this study we examined the rheology of polyurethane foam puf as an analogue system of magma undergoing vesiculation deformation and solidification solid puf was formed by mixing two polymeric liquids followed by chemical reactions of foaming and curing the transient rheology during the processes was investigated using an instrument based on a stress controlled rheometer first the oscillatory rheology was measured applying small amplitude oscillations with cyclic frequency sweeps in the foaming stage the frequency dependence of the rheology depends on the dynamic capillary number in a similar way to the existing bubbly flow model in the curing stage the viscoelasticity of the liquid becomes dominant and the rheology of puf shows maxwell type viscoelasticity with relaxation time exponentially increasing with time when the reaction is rapid because of high temperature the viscoelasticity during curing is not scaled by the single relaxation time instead puf passes through a condition called gelation which is characterized by a power law relaxation spectrum next we examined the relationship between the dynamic viscosity measured by the small strain oscillation and the shear viscosity measured with a fixed shear rate at a large strain we found that puf obeys the cox merz rule which states that the two viscosities are equivalent when the shear rate and the angular frequency are equal specifically the shear viscosity tends to be smaller than the dynamic viscosity by a few tens of percent the difference was shown to be in the range expected for bubbly fluid in the foaming stage while it went beyond what can be explained by the bubbly fluid model when the viscoelasticity of the liquid becomes significant x ray computed tomography analyses revealed that samples in these cases contained large bubbles indicating bubble coalescence we infer that the difference is caused by bubble coalescence as well as non newtonian rheology during solidification including gelation all these processes might occur in actual magma during eruptions we show that the ranges of the capillary number comparing the deformation time and the bubble shape relaxation time and deborah number comparing the deformation time and the viscoelastic relaxation time in our experiments are comparable with their ranges expected for magma ascending in an eruptive conduit the characteristic time of viscosity increase of puf was also shown to be realizable for magma in natural volcanoes we conclude that puf is useful for simulating magma processes in eruptive conduits

the record of continental dust from australia in tasman sea sediments abstract the flux of aeolian dust from australia to sediments of the tasman sea has increased during glacial stages of the last four glacial cycles low fluxes of dust from australia before 350 ka were followed by an increase in stage 10 and high fluxes in peak glacial periods thereafter the initiation of higher dust fluxes in stage 10 is consisten with previous estimates of the age of onset of aridity in the source area dust flux to the tasman sea is thought to record the intensity of deflation from the source area in interior southeastern australia which was marked by arid conditions and possibly greater windiness during the last glacial a transect of five cores from the central tasman sea revealed consistently low dust fluxes north of 33 s increasing southward to approximately 40 s glacial to interglacial movement of the northern boundary of the dust plume governed by the position of the subtropical ridge was less than 6 latitude probably closer to 3 350 km the position of the dust plume determined in this study and its response to climate change are significantly different from a previous reconstruction based on the measurement of quartz content of the non biogenic sediment fraction

energetics of glass fragmentation experiments on synthetic and natural glasses 1 natural silicate glasses are an essential component of many volcanic rock types including coherent and pyroclastic rocks they span a wide range of compositions occur in diverse environments and form under a variety of pressure temperature conditions in subsurface volcanic environments e g conduits and feeders melts intersect the thermodynamically defined glass transition temperature to form glasses at elevated confining pressures and under differential stresses we present a series of room temperature experiments designed to explore the fundamental mechanical and fragmentation behavior of natural obsidian and synthetic glasses pyrex under confining pressures of 0 1 100 mpa in each experiment glass cores are driven to brittle failure under compressive triaxial stress analysis of the load displacement response curves is used to quantify the storage of energy in samples prior to failure the brittle release of elastic energy at failure and the residual energy stored in the post failure material we then establish a relationship between the energy density within the sample at failure and the grain size distributions d values of the experimental products the relationship between d values and energy density for compressive fragmentation is significantly different from relationships established by previous workers for decompressive fragmentation compressive fragmentation is found to have lower fragmentation efficiency than fragmentation through decompression i e a smaller change in d value with increasing energy density we further show that the stress storage capacity of natural glasses can be enhanced approaching synthetic glasses through heat treatment

late pleistocene vegetation and climate history of lake selina western tasmania analysis of pollen nrm intensity of sediments and dating of a 397 cm core from lake selina in western tasmania provides a detailed record of vegetation and climate changes for the last interglacial last glacial cycle the vegetation record shows that cool temperate rainforest was present during isotope substage 5e and during the holocene wet montane forest and subalpine shrublands dominated the early last glacial interstades subalpine alpine heathlands and herbfield the stadials stages 4 2 mainly had grassland herbland and heath vegetation there is close correlation between phases of maximum magnetic intensity in the sediments with pollen zones indicating presence of herbaceous vegetation this suggests erosion of the catchment was greater in the absence of forest or woodland climate may have been slightly cooler than present during substage 5e but the evidence is not definitive climate was colder at all times during the last glacial stage until after ca 14 kyr bp maximum temperature depression from present during stage 2 was 3 5 c at lake selina but probably as much as 6 5 c in the west coast range holocene climate was cool and wet comparison of the lake selina record with others in western tasmania and victoria indicate that variations in vegetation during the last interglacial last glacial cycle were primarily responses to temperature changes in western tasmania and to precipitation changes particularly summer drought in western victoria

extreme sulfur cycling in acid brine lake environments of western australia abstract regional scale extreme acid brines in southern western australia are an example of sulfur rich end member continental waters and are amongst the most physically and chemically dynamic settings in the world here aqueous sulfur compounds sulfur minerals and sulfur interacting microorganisms are abundant and diverse and sulfur cycling is intense lake waters and groundwaters of the yilgarn craton are na cl so 4 mg rich with ph as low as 1 7 salinity as high as 32 total dissolved solids and sulfuric acid as the dominant acid measured concentrations of dissolved total s range from 500 to 19 800 ppm and so 4 ranges from 692 to 35 169 ppm the difference between total s and so 4 suggests that other s species are present in these waters particularly in the most acid brines rainwaters which have previously been suggested as a source of sea spray aerosol so 4 to the lake systems yielded 7 to 8 ppm so 4 sulfur isotope analysis shows that 34 s for lake waters is 17 0 to 19 1 for groundwaters is 17 0 to 18 6 for gypsum is 20 2 to 20 4 and for alunite is 18 9 these values are consistent with a combination of s sources and sinks sulfur cycling processes include sulfide oxidation evapoconcentration mineral precipitation mineral dissolution and bacterial reduction and oxidation field petrographic and molecular analyses of microorganisms in these acid saline environments suggest that some are s oxidizing and s reducing bacteria sulfur bearing minerals in the area include both sulfides and sulfates sulfides including pyrite have been observed in veins and disseminated in surface exposures and shallow cores of archean igneous and metamorphic host rocks as well as in overlying sediments sedimentary sulfate minerals include gypsum bassanite anhydrite and rozenite that grow directly from lake waters and gypsum anhydrite jarosite natrojarosite alunite basaluminite hydrobasaluminite langbeinite and rozenite that grow diagenetically from shallow groundwaters these sedimentary minerals are subjected to physical reworking and chemical dissolution and re precipitation sulfur cycling among the lithosphere hydrosphere biosphere and atmosphere in acid saline environments is dynamic driving forces are rock weathering weather and climate which ultimately influence the water chemistry flooding evapoconcentration desiccation cycles accelerate short term local and regional sulfur cycling the combination of low ph highly saline waters and dynamic changes in environment make sulfur arguably the most important element in these environments

last glacial maximum climate in new zealand inferred from a modelled southern alps icefield abstract we present a simulation of the new zealand southern alps icefield at the last glacial maximum lgm c 30 000 20 000 calendar years ago ka in an attempt to constrain the climate of that period we use a 500 m resolution ice sheet model parameterised using empirical glaciological climatological and geological data specific to the model domain to simulate the entire southern alps icefield we find that an lgm cooling of at least 6 6 5 c is necessary to bring about valley glaciers that extend beyond the mountains however climate topography thresholds related to the elevation and hypsometry of individual catchments control the gradient of the rate of glacier expansion in the domain and in order to remain within geologically reconstructed lgm limits we find that the lgm cooling was most likely associated with a precipitation regime up to 25 drier than today wetter than present scenarios give rise to equilibrium line depressions and ice extents that are incompatible with empirical evidence these results perhaps indicate that either the westerly air masses affecting new zealand during the lgm were drier than today or that they were weaker or zonally displaced with respect to present

the smoking gun for atlantic circulation changes the atlantic meridional overturning circulation amoc has long been implicated in rapid climate changes during the most recent ice age however convincing observational evidence from the deep ocean has remained limited on page 470 of this issue henry et al 1 present two independent records from a well dated high resolution sediment core from bermuda rise in the north atlantic see the figure that may be the smoking gun that paleoceanographers have been looking for

vegetation and climate of auckland new zealand since ca 32 000 cal yr ago support for an extended lgm auckland occupies a climatically sensitive position close to a major biogeographic boundary in the southern mid latitudes a new pollen record from kohuora maar crater auckland displays vegetation and climatic changes for the past ca 32 000 years of particular interest are the inferred climatic patterns for the first part of the interval encompassing the last glacial maximum lgm the kohuora record corresponds closely with pollen records from other auckland sites indicating that the patterns observed are at least regional in extent it is also broadly consistent with a variety of palaeoenvironmental evidence from across new zealand including the glacial record from westland other palynological records from north island other palaeoecological records from the south island and aeolian quartz sequences from western north island these records show that glacial conditions prevailed across most if not all of new zealand during the interval ca 29 19 k cal yr bp longer and earlier than the lgm sensu stricto we suggest that the term extended lgm elgm may be more appropriate for the new zealand region within this predominantly cold interval the auckland pollen records indicate a climatic amelioration for the interval ca 26 24 k cal yr bp also consistent with other palaeocological data from canterbury that fall within a period of climate amelioration recognised between the first two elgm glacial advances in westland we refer to this warming interval as the elgm interstadial the ca 27 k cal yr bp kawakawa oruanui tephra is instrumental in most of these inter site comparisons and occurs after the first peak of elgm cooling in a short lived comparatively mild phase a subsequent return to apparently colder climate in the auckland records may indicate a volcanic cooling effect or more likely widespread landscape disturbance following this major eruption event strong correspondence between biotic responses glacial fluctuations and aeolian quartz deposition linked to major shifts in strength and latitudinal extent of the southern westerlies suggest that both the elgm and elgm interstadial may be more widely registered at least across the southern ocean support for this assertion comes from parallel investigations in western and southernmost south america and isotopic and palaeoecological records from southern ocean marine cores recent reconstructions of the globally averaged ice equivalent sea level history are in line with this evidence from the southern hemisphere suggesting that the elgm may have a global registration in light of these observations we suggest a re examination of the defined timing of the lgm along with renewed effort to establish climatic patterns during this period and understand their causes copyright 2007 john wiley sons ltd

viscous heating in rhyolite an in situ experimental determination viscous heating during magmatic flow may play a major role in eruption dynamics in order to document viscous heating during deformation of magma we have conducted a series of rheological experiments where viscous heating is directly monitored via thermocouples in high viscosity magmas we observe experimentally the strain rate dependence of viscous heating viscous heating becomes rheologically significant in the highly viscous lavas investigated at strain rates above ca 10 3 s 1 a simple analysis shows that the temperature increase generated through viscous heating during deformation of melts with viscosities ranging from 108 to 1012 pa s can account for their apparent non newtonian rheology in these experiments this thermal correction transforms apparent non newtonian strain rate dependent rheology of magma to a newtonian behavior over the range of conditions accessed in this work in this manner this study provides an experimental basis for separating the relative roles of structural relaxation and viscous heating in the generation of apparent non newtonian rheology at high strain rates here viscous heating dominates and the observation of the structural onset of non newtonian behavior is precluded by a viscous heating induced lowering of the newtonian viscosity the interplay of viscous heating and structural relaxation in melts in nature is discussed briefly

fragmentation of a porous viscoelastic material implications to magma fragmentation fragmentation of vesicular magma by rapid decompression is one of the most likely triggers for explosive eruptions in this phenomenon the decompression rate and the viscoelastic nature of magma are considered to be key factors in order to obtain a clear idea on the effects of these two factors controlled fragmentation experiments have been conducted these experiments have three advantages first the specimen is made of a viscoelastic material with controlled porosity and geometry second the fragmentation process is directly monitored finally both the magnitude and rate of decompression are controlled brittle fragmentation and ductile expansion were both observed in the same porous material at different timescales the various mechanical responses of the specimen elastic flow and fragmentation were correlated with the pressure profile measured at the base of the specimen fragmentation was noted to occur when the decompression exceeded a critical value within a critical time two relevant timescales are discussed in terms of physical mechanisms of relaxation the first is the measured glass transition time the second is the estimated timescale for the onset of viscous bubble expansion the observed phenomena bear several similarities with natural magma fragmentation it is thus considered that the present results are a useful step toward constructing a model for magma fragmentation

strain induced outgassing of three phase magmas during simple shear a major factor determining the explosivity of silicic eruptions is the removal of volatiles from magma through permeability controlled outgassing we studied the microstructural development of permeability during deformation of highly viscous magma by performing simple shear experiments on bubble 0 12 0 36 volume fraction and crystal bearing 0 0 42 volume fraction silicate melts experiments were performed under torsion at high temperature and pressure 723 873 k and 150 200 mpa in a paterson deformation apparatus at bulk shear strains between 0 and 10 the experimental setup allows for gas escape if bubble connectivity is reached on the sample periphery three dimensional imaging and analysis of deformed bubbles was performed using x ray tomography the development of localized deformation in all samples enhanced by crystal content leads to brittle fracture at bulk strains 2 and sample wide fracturing in samples deformed to strains 5 a decrease in both bubble fraction and dissolved volatile content with increasing strain along with strain hardening rheological behavior suggests significant shear induced outgassing through the fracture networks applicable to shallow conduit degassing in magmas containing crystal fractions of 0 0 42 this study contributes to our understanding of highly viscous magma outgassing and processes governing the effusive explosive transition

the last glacial maximum lgm in western south island new zealand implications for the global lgm and mis 2 abstract the morainic and outwash deposits of the larrikins la and moana mn formations in north westland are correlated with the m5 t5 and m6 t6 deposits in south westland the la m5 deposits resulted from two separate otira glaciation glacial advances la 1 m5 1 la 2 m5 2 of essentially similar extents pollen sequences in peats and coverbeds extending from before to after the kawakawa tephra 26 500 cal yr bp indicate an extensive period of cold with a slight amelioration beginning shortly before tephra deposition this amelioration which is supported by interpretation of coverbed sequences in south westland separates the la 1 m5 1 and la 2 m5 2 advances the three westland glacial advances la 1 m5 1 la 2 m5 2 and mn m6 culminated at ca 28 000 21 500 and 19 000 cal yr bp the last being followed by major rapid glacier retreat pollen and caco 3 records from dsdp 594 east of the south island reflect contemporary glacier fluctuations on the east side of the southern alps they show the last major cold period as lasting from ca 34 000 to ca 16 000 years ago a period starting before the culmination of the la 1 m5 1 advance and ending later than the beginning of glacier retreat from the mn m6 advance the period from the la 1 m5 1 culmination to the mn m6 culmination represents the lgm in new zealand a slightly longer lgm is recorded in chile and a long lgm may also be indicated in australia a long lgm in the southern hemisphere is supported by the global sea level curve and by the regional antarctic temperature criteria of the vostok ice core these different records indicate a southern hemisphere lgm beginning at least as early as 27 000 years ago much earlier than the ocean last isotope maximum lim from 21 500 to 18 000 years ago the beginning of mis 2 defined primarily from deep sea benthic 18 o at 24 000 years is well after the beginning of ice advances leading to the southern hemisphere lgm a review of global land and ocean correlations is desirable

seismological analysis of conduit dynamics in fragmentation experiments we simulate gas burst and volcanic explosions under controlled laboratory conditions inducing fragmentation of volcanic rocks by rapid depressurization a series of experiments were performed in a shock tube apparatus at room temperature and a pressure range of 4 to 20 mpa using argon ar gas and particles or pumice samples of different porosities the instrumentation of this system with high precision piezoelectric sensors enabled us to capture elastic waves and to recognize their characteristic signatures by relating these signals to physical processes in the wave field we have been able to characterize the conduit mechanism and the source dynamics we compare and discuss conspicuous features of the waveforms and frequency spectra of these experimental signals with those of volcanic origin despite the fact that these signals are different in amplitude resulting from different scale conditions our observations indicate that the physical processes that occur during simulated explosions and those that occur during volcanic eruptions yield comparable signatures in their respective records the effects of the source receiver configuration and resonance also have significant implications all this suggests that the physical processes e g pressurization and depressurization of a system involve a system response that causes similar distinctive effects independent of the system size reflecting its intrinsic dynamics these similarities imply that powerful constraints on the source mechanisms of volcanic seismicity can emerge from seismic investigations of experimental simulations of volumetric sources such constraints may yield significant advances in the understanding of volcanic conduit dynamics and in the interpretation of seismic unrest at volcanic centers

non newtonian rheological law for highly crystalline dome lavas volcanic eruption models are hampered by the lack of multiphase magmatic flow laws most rheological models estimate the viscosity of multiphase lavas via the einstein roscoe equation but this simplification cannot be used for high crystallinity and it does not consider the non newtonian strain rate dependence of viscosity we carried out parallel plate experiments on natural samples to simulate multiphase lava deformation under various stresses and strain rates multiphase lavas exhibit an important component of shear thinning and appear to invalidate the adequacy of einstein roscoe based formulations for highly crystalline lava rheology the remarkable singular dependence of viscosity on strain rate yields a novel universal rheology law at eruptive temperatures t i e log 0 993 8974 t 0 543 log our work reveals the importance of considering microcracking and viscous dissipation at very high strain rate 10 3 s 1 explaining the occurrence of seismic swarms along the conduit margins and consequently supporting plug like magma ascent models

the fragmentation threshold of pyroclastic rocks in response to rapid decompression porous magma may fragment explosively this occurs when the melt can no longer withstand forces exerted upon it due to the overpressure in included bubbles this occurs at a critical pressure difference between the bubbles and the surrounding magma in this study we have investigated this pressure threshold necessary for the fragmentation of magma here we present the first comprehensive high temperature experimental quantification of the fragmentation threshold of volcanic rocks varying widely in porosity permeability crystallinity and chemical composition we exposed samples to increasing pressure differentials in a high temperature shock tube apparatus until fragmentation was initiated experimentally we define the fragmentation threshold as the minimum pressure differential that leads to complete fragmentation of the pressurized porous rock sample our results show that the fragmentation threshold is strongly dependent on porosity high porosity samples fragment at lower pressure differentials than low porosity samples the fragmentation threshold is inversely proportional to the porosity of the other factors permeability likely affects the fragmentation threshold at high porosity values whereas chemical composition crystallinity and bubble size distribution appear to have minor effects the relationship for fragmentation threshold presented here can be used to predict the minimum pressure differential necessary for the initiation or cessation of the explosive fragmentation of porous magma

millennial scale dynamics of the east asian winter monsoon during the last 200 000 years the primary productivity dynamics of the last 200 000 years in the sulu sea was reconstructed using the abundance of the coccolithophore florisphaera profunda in the images md97 2141 core we find that primary productivity was enhanced during glacial periods which we suggest is due to a stronger east asian winter monsoon during the last 80 kyr eight significant increases in primary productivity pp in the sulu sea are similar to east asian winter monsoon changes recorded in chinese loess the pp maxima are not linked with heinrich events he in the north atlantic although four pp peaks are synchronous with he the pp oscillations have frequencies near those of the dansgaard oeschger cycles in northern hemisphere ice records and indicate a teleconnection of the east asian winter monsoon with greenland climate in this sulu sea record the east asian winter monsoon oscillates with periodicities of6 4 2 3 4 2 3 and 1 5 kyr in particular the 1 5 kyr cycle exhibits a strong and pervasive signal from stage 6 to the holocene without any ice volume modulation this stationarity suggests that the 1 5 kyr cycle is not driven by some high latitude forcing

temporal evolution of the minoan eruption santorini greece as recorded by its plinian fall deposit and interlayered ash flow beds the plinian fall deposit of the minoan eruption santorini greece and its interlayered ash flow beds show textural componentry and chemical trends indicative of their temporal evolution and conditions that lead to the ash flow emplacement the deposits have been sampled in detail at a selected locality and the following features have been analyzed i maximum clast size ii grain size distribution iii componentry iv lithic types v pumice morphology vi pumice types and vii pumice crystal abundance stratigraphic variations of these features are assumed to record changes that occurred during the eruption including changes in eruptive plume height nature and relative efficiency of the magma fragmentation process conduit stability and magma flow in the conduit based upon the inferred temporal changes we propose the following eruption reconstruction the sustained plinian column activity reached its climax in terms of mass eruption rate and plume altitude soon after the beginning of the eruption and subsequently began to gradually subside as a result of eruption waning the conduit walls began to collapse causing an increase in the shear stress in the flowing vesicular magma and an increase in the efficiency of the magma fragmentation process eventually the conduit closed or became too narrow to support a high standing eruption column leading to ash flow eruption as a result of the collapse of what was left of the eruptive plume and or directly from emission of an overpressured jet subsequent conduit pressure increases led to conduit re opening and a plinian column with associated pumice fallout began anew the eruptive magma fragmentation process is proposed to have been of a brittle nature and linked to the shear stress generated by conduit wall friction fragmentation efficiency is recorded by grain size distributions and free crystal contents of the deposits

from rock to magma and back again the evolution of temperature and deformation mechanism in conduit margin zones abstract explosive silicic volcanism is driven by gas overpressure in systems that are inefficient at outgassing the zone at the margin of a volcanic conduit thought to play an important role in the outgassing of magma and therefore pore pressure changes and explosivity is the boundary through which heat is exchanged from the hot magma to the colder country rock using a simple heat transfer model we first show that the isotherm for the glass transition temperature whereat the glass within the groundmass transitions from a glass to an undercooled liquid moves into the country rock when the magma within the conduit can stay hot or into the conduit when the magma is quasi stagnant and cools on the centimetric scale over days to months we then explore the influence of a migrating viscous boundary on compactive deformation micromechanisms in the conduit margin zone using high pressure effective pressure of 40 mpa high temperature up to 800 c triaxial deformation experiments on porous andesite our experiments show that the micromechanism facilitating compaction in andesite is localised cataclastic pore collapse at all temperatures below the glass transition of the amorphous groundmass glass t g i e rock in this regime porosity is only reduced within the bands of crushed pores the porosity outside the bands remains unchanged further the strength of andesite is a positive function of temperature below the threshold t g due to thermal expansion driven microcrack closure the micromechanism driving compaction above t g i e magma is the distributed viscous flow of the melt phase in this regime porosity loss is distributed and is accommodated by the widespread flattening and closure of pores we find that viscous flow is much more efficient at reducing porosity than cataclastic pore collapse and that it requires stresses much lower than those required to form bands of crushed pores our study therefore highlights that temperature excursions can result in a change in deformation micromechanism that drastically alters the mechanical and hydraulic properties of the material within the conduit margin zone with possible implications for pore pressure augmentation and explosive behaviour

a global perspective on last glacial maximum to holocene climate change while the abrupt climate events of the last deglaciation are well defined in ice core records from the polar regions of both hemispheres their manifestation elsewhere is less well constrained here we compile 104 high resolution paleoclimate records to characterize the timing and spatial pattern of climate change during the last deglaciation this compilation indicates relatively concurrent timing of the last glacial maximum lgm peak glacial conditions and the altithermal peak interglacial conditions in the northern 22 1 4 3 ka and 8 0 3 2 ka and southern 22 3 3 6 ka and 7 4 3 7 ka hemispheres suggesting the hemispheres were synchronized by greenhouse gases local insolation and or northern hemisphere induced ocean circulation changes the magnitude of the glacialeinterglacial temperature change increases with latitude reflecting the polar amplification of climate change with a likely minimum global mean cooling of ww4 9 c during the lgm relative to the altithermal empirical orthogonal function eof analysis of 71 records spanning 19e11 ka indicates that two modes explain 72 of deglacial climate variability eof1 61 of variance shows a globally near uniform pattern with its principal component pc1 strongly correlated with changes in atmospheric co2 e of2 11 of variance exhibits a bipolar seesaw pattern between the hemispheres with its principal component pc2 resembling changes in atlantic meridional overturning circulation strength eof analysis of 90 records from 15 to 11 ka indicates that northern and southern modes of climate variability characterize the younger dryas bolling allerod interval these modes dominate at the higher latitudes of each hemisphere and exhibit a complex interaction in the tropics the magnitude of the younger dryas climate anomaly cooler drier increases with latitude in the northern hemisphere with an opposite pattern warmer wetter in the southern hemisphere reflecting a general bipolar seesaw climate response global mean temperature decreased by w0 6 c during the younger dryas therefore our analysis supports the paradigm that while the younger dryas was a period of global climate change it was not a major global cooling event but rather a manifestation of the bipolar seesaw driven by a reduction in atlantic meridional overturning circulation strength

volcanic dilemma flow or blow volcanic eruptions can be either slow outpourings of lava or explosive ejections of fragmented rock in his perspective dingwell discusses the physical and chemical properties of magma that lead to these two styles of eruption new experiments and computer simulations are pointing to the involvement of solidlike behavior of liquid magma when it makes a transition to a glass

on the feasibility of magma fracture within volcanic conduits constraints from earthquake data and empirical modelling of magma viscosity 1 in the last decade several studies have indicated that magma within volcanic conduits can undergo repeated failure and healing thus providing a realistic source mechanism for the peculiar sequences of low frequency earthquakes that often announce eruptions although geological observations laboratory experiments and numerical modelling support such a hypothesis the links between geophysical observations and the proposed models remain qualitative this study focuses on providing constraints to the relationship between the occurrence of repeating earthquakes and magma fracture at andesite volcanoes empirical modelling of viscosity is incorporated into the fundamental physics of magma fracture in order to assess whether and where the conditions for brittle failure are met within volcanic conduits a case study from the 1995 ongoing eruption of soufriere hills volcano montserrat is presented the locations of earthquakes from a pre eruptive low frequency seismic swarm illuminate a relatively compact source volume at depths of 100 300 meters below sea level viscosity modelling confirms that the soufriere hills magma could rupture at those depths

southern hemisphere synoptic behavior in extreme phases of sam enso sea ice extent and southern australia rainfall abstract the association between southern hemisphere cyclones and anticyclones and the el nino southern oscillation enso southern annular mode sam antarctic sea ice extent sie and rainfall in perth and melbourne is explored those cities are respectively located in the southwestern and southeastern corners of australia where substantial decreasing rainfall trends have been observed over the last decades the need for a more unified understanding of large scale anomalies in storm indicators associated with the climate features itemized above has motivated this study the main aim is to identify cyclone anomalous areas that are potentially important in characterizing continental rainfall anomalies from a hemispheric perspective focusing on midlatitude australia the study covers the satellite era from 1979 to 2003 and was conducted for the southern winter when midlatitude rainfall is predominantly baroclinic the results indicate a well organized hemispheric cyclone pattern associated with en

comparison of organic uk 37 texh86 ldi and faunal proxies foraminiferal assemblages for reconstruction of late quaternary sea surface temperature variability from offshore southeastern australia several proxies have been developed to reconstruct past sea surface temperature sst but different proxies may reflect temperatures of different seasons and each proxy is characterized by certain uncertainties therefore a multiproxy approach is preferred to precisely reconstruct sst here we reconstruct sst of the ocean offshore southeastern australia murray canyons area for the last 135 ka using three independent organic proxies texh86 based on glycerol dialkyl glycerol tetraethers gdgts uk 37 based on alkenones and ldi based on long chain diols in addition to foraminiferal faunal assemblages the organic proxy records show similar trends with the highest temperature 21 c for uk 37 and texh86 and 25 c for ldi during the last interglacial and lowest temperature 8 c for texh86 10 c for uk 37 and 12 c for ldi during the last glacial maximum however the differences in absolute sst estimates obtained by the organic proxies varied over time with differences of up to 9 c between ldi and texh86 the seasonal sst reconstructions based on the modern analogue of foraminiferal assemblages also show similar trends as the organic proxies with highest temperatures during the last interglacial 23 c for the warmest month sst 20 c for mean annual and 18 c for the coolest month and lowest temperature during the last glacial maximum 14 c for the warmest month 11 c for mean annual and 9 c for the coolest month down core comparison between the reconstructed ssts of the organic and inorganic proxies shows that ldi inferred temperatures compare well with the temperature of the warmest month texh86 with the temperature of the coolest month and uk 37 with mean annual temperature an increase in texh86 sst estimates relative to those of other proxies during deglaciations and interglacials suggests that either winter temperatures rapidly warmed possibly due to an invigoration of the leeuwin current over the core site or there was a change in the growth season of the thaumarchaeota the source organism of gdgts our study shows the benefits of a multiproxy approach in the interpretation of sst proxies leading to a more robust knowledge of past ocean temperature changes

late pleistocene glacial stratigraphy of the kumara moana region west coast of south island new zealand abstract on the south island of new zealand large piedmont glaciers descended from an ice cap on the southern alps onto the coastal plain of the west coast during the late pleistocene the series of moraine belts and outwash plains left by the taramakau glacier are used as a type section for interpreting the glacial geology and timing of major climatic events of new zealand and also as a benchmark for comparison with the wider southern hemisphere in this paper we review the chronology of advances by the taramakau glacier during the last or otira glaciation using a combination of exposure dating using the cosmogenic nuclides 10 be and 36 cl and tephrochronology we document three distinct glacial maxima represented by the loopline larrikins and moana formations separated by brief interstadials we find that the loopline formation originally attributed to oxygen isotope chronozone 4 is much younger than previously thought with an advance culminating around 24 900 800 yr the widespread late pleistocene kawakawa oruanui tephra stratigraphically lies immediately above it this formation has the same age previously attributed to the older part of the larrikins formation dating of the larrikins formation demonstrates there is no longer a basis for subdividing it into older and younger phases with an advance lasting about 1000 years between 20 800 500 to 20 000 400 yr the moana formation represents the deposits of the last major advance of ice at 17 300 500 yr and is younger than expected based on limited previous dating the timing of major piedmont glaciation is restricted to between 25 000 and 17 000 yr and this interval corresponds to a time of regionally cold sea surface temperatures expansion of grasslands at the expense of forest on south island and hemisphere wide glaciation