postglacial relative sea level histories along the eastern canadian coastline abstract we have assembled a database of relative sea level rsl data points from the eastern coast of canada from hudson bay to the border with the usa in compiling this database we have critically reviewed 1092 radiocarbon dated samples from raised beaches isolation basins intertidal and marine deposits and archaeological indicators to produce 405 sea level index points and 687 sea level limiting points our comprehensive systematic and quality controlled rsl database allowed for the reconstruction of the postglacial evolution of 34 regions of eastern canada providing new basin scale insights into the processes driving rsl changes in the last 16 ka the combination of a database of sea level index points with an innovative empirical bayesian spatio temporal statistical model provided new insights into rates and magnitude of the spatially variable glacial isostatic adjustment gia which dominated the postglacial rsl evolution in this sector of north america a continuous postglacial rsl fall is observed at latitudes 50 n with higher rates up to 35 mm a 1 recorded in southeastern hudson bay at lower latitudes the evolution is non monotonic with rsl that dropped to a spatially variable early holocene lowstand followed by a mid holocene highstand and eventually a gradual drop to present rsl this pattern is particularly evident in the st lawrence corridor along the majority of the newfoundland new brunswick and western nova scotia coasts a late pleistocene early holocene rsl lowstand was followed by a continuous rise through the holocene at the margin of the former ice sheet i e eastern nova scotia our data identify a continuous rsl rise through the holocene these records are characterized by decreasing rates of rsl rise through time commencing with a rapid rise during the early holocene up to 17 mm a 1 a slowdown in the mid holocene average rates 9 mm a 1 and a further reduction in the late holocene average rates

a three dimensional surface velocity field for the mississippi delta implications for coastal restoration and flood potential accurate estimates of the current rate of subsidence in the mississippi delta southern united states provide a context for planning of wetland restoration and predictions of storm surge flooding we present a comprehensive three dimensional surface velocity field for the mississippi delta based on a network of 36 high precision continuous gps stations we show that while the majority of the delta is relatively stable the southern portion continues to experience high rates of subsidence 5 6 mm yr 1 our data are consistent with long term tide gauge records at grand isle louisiana and several stations in florida the current rate of relative sea level rise combined effect of land subsidence and sea level rise along parts of the coastal delta is 8 9 mm yr 1 most tide gauge stations have recorded sea level rise acceleration after a d 1970 these data have implications for land reclamation and wetland restoration in the region parts of the delta may not be viable in the long term

origin of the giant eruption cloud of pinatubo june 15 1991 the series of eruptions of june 15 1991 at mt pinatubo philippines were observed hourly by satellite a giant discshaped cloud covering an area of 60 000 km2 appeared in the satellite images at 14 40 philippine time the cloud expanded radially against wind of 20 m s and spread to an area of more than 120 000 km2 within an hour according to eyewitness accounts there was heavy fine ash fall after 14 00 intermittent lapilli fall started at about 14 20 and heavy and continuous lapilli fall widely started at about 15 00 the occurrence of the giant cloud roughly corresponded to the initiation of the intermittent lapilli fall the air fall deposits of the major eruption are widely distributed including upwind from the vent they are composed of 3 units a silt size fine ash layer layer b a lapilli layer commonly including pumice grains of 1 cm in diameter layer c a lapilli bearing volcanic sand layer layer d judging from its wide distribution and depletion of coarse grains most of the fine ash of layer b is not distal deposits of a small eruption but is originated from a large co ignimbrite cloud it is suggested that the major eruption started with the generation of a pyroclastic flow which was subsequently followed by a plinian eruption resulting in the formation of the giant cloud and the lapilli fall the results of calculations on the dynamics of eruption cloud indicate that the dimension and dynamics of the giant eruption cloud is accounted for by a plinian eruption with a magma discharge rate of the order of 109 kg s

dynamics of magma flow in volcanic conduits with variable fragmentation efficiency and nonequilibrium pumice degassing numerical models of volcanic conduit dynamics assume that the foamy structure of magma is totally destroyed at fragmentation neglecting the presence of vesicular fragments in the above gas particle flow region the abundance of pumice among the volcanic pyroclasts is however the outstanding evidence that such a complete atomization assumption is an oversimplification the present one dimensional multiphase nonequilibrium magma ascent modeling rejects such an assumption taking into account the presence of pumice ash and loose crystals in the turbulent flow region above fragmentation a parametric study is conducted on the role of pumice abundance related to a fragmentation efficiency parameter in affecting the magma ascent dynamics additionally different hypotheses on pumice degassing behavior are evaluated the numerical results show that the presence of even relatively small amounts of pumice translates into a large decrease of continuous gas volume fraction while other flow quantities are mainly affected by the efficiency of pumice degassing a decreased degassing efficiency translates into significant velocity and pressure decrease mixture density increase and further gas volume fraction decrease that overall result in a decrease of the mechanical energy content of the erupted magma by an amount comparable to that due to water content decrease by several weight percent postprocessing of numerical results based on the dynamics of porous flow of gas in pumice allows one to relate the efficiency of pumice degassing to a measurable pumice texture parameter namely the degree of gas bubble coalescence which is therefore identified as a major factor affecting the ascent dynamics of silicic magma

comparative proximal features of the main plinian deposits campanian ignimbrite and pomici di base of campi flegrei and vesuvius abstract the proximal plinian fall deposits of the campanian ignimbrite ci 38 ky fedele et al 2008 and pomici di base pdb 18 ky bertagnini et al 1998 have been investigated in order to understand the contribution of each part of the plume to the proximal sedimentation following houghton et al 2004b we consider three main transport regimes jet phase producing facies fb buoyant region of the plume producing facies fa and direct lateral ejection producing facies fc as well documented in medial locations sparks et al 1992 1997 ernst et al 1996 transport regimes can develop different facies even in proximal locations according to the dynamics of the eruptive column our proximal deposits show stratification and diffuse bedding allowing us to introduce two new facies stratified fa sfa and diffuse bedded fb dbfb these facies retain the transport regime previously proposed for fa buoyant plume and fb jet phase but their lithological features are influenced by near vent depositional conditions lithology and sedimentological data grain size componentry maximum clasts suggest that most of the sedimentation occurred mainly from the buoyant plume with simultaneous contribution from the other two different dynamic regimes coarse clasts falling from the lower margins of the plume strongly affected the sedimentation of the ci proximal fall deposit with a minor contribution from lithic clasts ballistically emplaced and partial collapses of the plume forming pyroclastic density currents in contrast the pdb proximal fall deposit was strongly affected by coarse clasts emplaced directly from the vent through parabolic trajectories with very little contribution of material emplaced from the lower part of the plume these differences can be attributed to different vent conduit processes acting during the eruptions

impact of the lateral blast on the spatial pattern and grain size characteristics of the 18 may 1980 mount st helens fallout deposit the 18 may 1980 eruption of mount st helens started with a lateral blast that fed a pyroclastic surge which then uplifted to form a co blast plume thirty minutes later plinian activity started at the vent and fluctuated in intensity for 9 h the resulting fallout deposit documented to 600 km from vent presents some striking features 1 displacement of the overall deposit to the north of the vent 2 a secondary thickness and mass maximum at 300 km from vent 3 a total grain size distribution dominated by fine ash 62 wt of the deposit 63 m and 4 individual grain size distributions that vary dramatically in the crosswind direction from strongly bimodal in the south to skewed unimodal in the north results from a new deconvolution of the individual grain size distributions show that they are a combination of a coarse subpopulation that decreases in size with distance from vent and a constant fine subpopulation with a mean of 15 m relative proportions of each subpopulation vary asymmetrically in the crosswind directions with the fine subpopulation preponderant toward the north and the coarse one dominating the south of the deposit both reach their absolute maxima in mass on the deposit axis componentry analyses of selected samples show that blast derived material is greatly enriched toward the north of the deposit these results indicate that the co blast plume dispersed fine grained material over great distances and dominated the fine subpopulation comparison with reanalysis data of atmospheric wind fields and satellite images of the spreading ash cloud suggests contrasting ash transport and depositional processes for the early co blast plume and the later vent derived plinian plumes the co blast plume is displaced to the north it had a high overshoot height and eastward dispersion via strong winds low in the stratosphere 10 15 km the plinian plumes were lower and dispersed most of the material to the southeast as the direction of high velocity winds shifted just before the late climactic plinian eruptive phase fine ash fine subpopulation was deposited continuously throughout the deposit with an increase of sedimentation rate 300 km from the vent where there is a secondary maximum in the deposit mass and thickness fine ash probably settled by a combination of enhanced sedimentation mechanisms including not only aggregation but also gravitational convective instabilities of cloud base hydrometeor formation and destruction and entrainment of small particles by larger ones finally we show that half of the deposit by mass in the medial area was deposited by the co blast plume and that a significant proportion of the mount st helens fallout deposit is nonjuvenile which has implications for the magmatic budget of this eruption

space geodetic and water level gauge constraints on continental uplift and tilting over north america regional convergence of the ice 6g_c vm5a vm6 models

the north american late wisconsin ice sheet and mantle viscosity from glacial rebound analyses abstract observations of sea level and crustal response to glacial loading cycles provide constraints on the mantle rheology function e and as well as on the ice load i with the latter being largely free from a priori glaciological or climate assumptions and appropriate therefore for testing any such hypotheses this paper presents new results for both continental mantle e and i for the late wisconsin ice sheet using geological evidence for relative sea level change rsl and tilting of palaeo lake shorelines complemented with loose constraints from observations of present day radial crustal displacement across north america the focus is on evidence from near or within the former maximum ice margins and the resulting earth response is representative of sub continental mantle conditions the inversion of the sea level information has limited resolution for earth rheology and simple three layer models characterized by depth averaged effective lithospheric thickness h and upper and lower mantle viscosities um and um respectively adequately describe the response function yielding parameters earth model e 6 of h 102 85 120 km um 5 1 1020 3 5 7 5 x1020 lm 1 3 1022 0 8 2 8 x1022 where the numbers in parenthesis are 95 confidence limits the details of the ice sheet with one exception are not strongly dependent on the rheological assumptions within this range the exception is the lower mantle viscosity that remains correlated with the magnitude scaling of the ice sheet a link that is largely broken by introducing constraints from glacial loading effects on the earth s rotation and dynamic flattening the difference between the continental um and the comparable estimate of 1 2 5 x1020 for ocean mantle is statistically significant shoreline gradient information from glacial lakes mcconnell agassiz algonquin and ojibway provide strong constraints on the response within the interior of the ice sheet and the resulting ice sheet model lw 6 is characterized by multiple ice domes from at least 17 18 ka onwards the resolution for earlier periods is largely constrained by global ice volume considerations the two principal domes are over southern nunavut the keewatin dome and over quebec labrador both of 3500 m thickness separated by an ice ridge some 1500 m lower than the domes the latter a requirement imposed by the gradient information over western canada ice thickness gradients east of the cordilleras are partly constrained by the shoreline data for former lake mcconnell as is the lateglacial ice thickness of the keewatin dome and indicate that any ice free corridor between the laurentian and cordilleran components is unlikely to have existed before 13ka reconstructions of the glacial lakes are consistent with the locations and timing of the observational evidence for the four major lake systems with the likely drainage routes identified the evolution of the lw 6 ice volume function expressed as equivalent sea level is characterized by a rapid decrease in ice volume from 15 to 14 5 ka corresponding to the bolling allerod period in the main from rapid ice retreat along the southern margin with further contributions from drainage through the st lawrence river valley and from ice retreat from the major northern straits and gulfs but not hudson strait where the rsl data point to late removal of ice after 10 ka the contribution of the drainage of the lakes to global sea level rise is small

itrf2014 a new release of the international terrestrial reference frame modeling nonlinear station motions for the first time in the international terrestrial reference frame itrf history the itrf2014 is generated with an enhanced modeling of nonlinear station motions including seasonal annual and semiannual signals of station positions and postseismic deformation for sites that were subject to major earthquakes using the full observation history of the four space geodetic techniques very long baseline interferometry vlbi satellite laser ranging slr global navigation satellite systems gnss and doppler orbitography and radiopositioning integrated by satellite doris the corresponding international services provided reprocessed time series weekly from slr and doris daily from gnss and 24 h session wise from vlbi of station positions and daily earth orientation parameters itrf2014 is demonstrated to be superior to past itrf releases as it precisely models the actual station trajectories leading to a more robust secular frame and site velocities the itrf2014 long term origin coincides with the earth system center of mass as sensed by slr observations collected on the two lageos satellites over the time span between 1993 0 and 2015 0 the estimated accuracy of the itrf2014 origin as reflected by the level of agreement with the itrf2008 both origins are defined by slr is at the level of less than 3 mm at epoch 2010 0 and less than 0 2 mm yr in time evolution the itrf2014 scale is defined by the arithmetic average of the implicit scales of slr and vlbi solutions as obtained by the stacking of their respective time series the resulting scale and scale rate differences between the two solutions are 1 37 0 10 ppb at epoch 2010 0 and 0 02 0 02 ppb yr while the postseismic deformation models were estimated using gnss gps data the resulting parametric models at earthquake colocation sites were applied to the station position time series of the three other techniques showing a very high level of consistency which enforces more the link between techniques within the itrf2014 frame the users should be aware that the postseismic deformation models are part of the itrf2014 products unlike the annual and semiannual signals which were estimated internally with the only purpose of enhancing the velocity field estimation of the secular frame

present day tilting of the great lakes region based on water level gauges by using monthly mean water levels at 55 sites around the great lakes a regional model of vertical crustal motion was computed for the region in comparison with previous similar studies over the great lakes 15 additional gauge sites data from all seasons instead of the 4 summer months and 8 additional years of data were used all monthly water levels available between 1860 and 2000 as published by the u s national ocean survey and the canadian hydrographic service were used for each lake basin the vertical velocities of the gauge sites relative to each other were simultaneously computed using the least squares adjustment technique our algorithm solves for and removes a monthly bias common to all sites as well as site specific biases it also properly weighs the input water levels resulting in a realistic estimation of the uncertainties in tilting parameters the relative velocities obtained for each lake were then combined to obtain relative velocities over the entire great lakes region finally the gradient of the relative rates for the regional model was found to agree best with the ice 3g global isostatic model of tushingham and peltier whereas the ice 4g gradients were too small around the great lakes

detectability of groundwater storage change within the great lakes water basin using grace groundwater is a primary hydrological reservoir of the great lakes water basin glb which is an important region to both canada and us in terms of culture society and economy due to insufficient observations there is a knowledge gap about groundwater storage variation and its interaction with the great lakes the objective of this study is to examine the detectability of the groundwater storage change within the glb using the monthly models from the gravity recovery and climate experiment grace satellite mission auxiliary soil moisture snow and lake smsl data and predictions from glacial isostatic adjustment gia models a two step filtering method is developed to optimize the extraction of grace signal a two dimensional basin window weight function is also introduced to reduce ringing artifacts caused by the band limited grace models in estimating the water storage change within the glb the groundwater storage gws as deviation from a reference mean storage is estimated for the period of 2002 to 2009 the average gws of the glb clearly show an annual cycle with an amplitude range from 27 to 91 mm in water thickness equivalent wte and a phase range of about two months the estimated phases of gws variations have a half year shift with respect to the phase of smsl water storage variations which show peaks in march and april the least squares estimation gives a gws loss trend of from 2 3 to 9 3 km3 yr within the glb for the period of study this wide range of the grace gws results is caused largely by the differences of soil moisture and snow storage from different land surface models lsms and to a lesser extent by the grace commission and omission errors and the gia model error

dynamics of giant volcanic ash clouds from supervolcanic eruptions 1 the largest explosive volcanic eruptions that have occurred on earth generated giant ash clouds from rising plumes that spread in the stratosphere around a height of neutral buoyancy with estimated supply rates that are in the range 1011 to 1013 m3 s these giant ash clouds are controlled by a balance between gravity and coriolis forces forming spinning bodies of nearly fixed proportions after a few hours and are initially insensitive to stratospheric winds in contrast volcanic plumes from eruptions with small to intermediate magnitude spread as inertial intrusions under the influence of stratospheric winds with the earth s rotation being unimportant in the largest eruptions the giant spinning ash clouds typically develop diameters greater than 600 km and up to 6000 km in the most powerful super eruptions thus explaining why areas of continental size can be covered with volcanic ash the radial expansion and spinning velocities are calculated at tens of metres per second and increase with eruption intensity higher spreading velocities carry larger ash grain sizes to a given radius so that grain size at a given distance from the source increases with eruption intensity consistent with geological observations

a parametric and comparative study of different tephra fallout models abstract we perform a parametric and comparative study on three different tephra dispersal models fall3d hazmap and tephra applied to two different scenarios expected for etna volcano these scenarios are similar to the recent 2002 03 and 1990 etna eruptions and correspond respectively to a weak and to a strong plume eruption for each model and scenario we perform a parametric study on several inputs in order to quantify how a variation on a given input parameter i e an uncertainty on the model input affects the results of the model the study considers topographic effects different description for the eruption column column height influence different fits for terminal velocities of particles the effect of particle shape and finally the variation of the modal grain size model differences are quantified by means of a normalized distance that indicates how close in average the results from two different simulations are we also compare predictions from different models to determine under which circumstances the use of a more elaborated model is justified results from our parametric study show that output of the models can be strongly sensitive to the uncertainties and assumptions on input parameters such as mainly mass eruption rate column height distribution of the mass along the column bulk grain size distribution this highlights that for optimal forecasts is urgent to improve the description of these parameters and of some important physical processes like fragmentation and eruption column dynamics further differences between models are often lower than those due to the uncertainties of input parameters although they become more high in simulating weak plumes thus the choice of the model mainly depends on the kind of application such as the need to simulate the evolution of volcanic clouds in the atmosphere finally the use of both a semi analytical hazmap and a fully computational fall3d model for inverting field data of the 2001 etna eruption showed that the best fit parameters are similar for both models and are consistent with values obtained using independent techniques

crystal settling in a vigorously converting magma chamber there has been much debate concerning the mechanism of fractional crystallization in magma chambers the traditional hypothesis of crystal settling has been widely replaced by the concept of in situ crystallization coupled with compositional convection observations from layered intrusions however are equivocal1 4 doubts have been raised about crystal settling on theoretical grounds because convective velocities in magma chambers are often much greater than the crystal settling velocities predicted by stokes law5 but there has been no experimental study of crystal settling in such vigorous convection here we present physical considerations and laboratory experiments which show that the phenomenon of particle settling in these conditions can be accounted for by a simple theory application of this theory to crystal settling in magma chambers suggests that crystal settling may be an efficient differentiation mechanism at least in basaltic magma chambers despite large convective velocities

oil generation by igneous intrusions in the northern gunnedah basin australia abstract the origin of extensive oil staining recorded over a 120 m interval of the jurassic pilliga sandstone in the fully cored bellata 1 well northern gunnedah basin has been investigated using conventional organic geochemical techniques the borehole intersects 451 m of permian and triassic strata overlain by 640 m of jurassic and cretaceous sediments igneous intrusions occur mainly within the lower part of the triassic napperby formation where the vitrinite reflectance profile shows the effect of significant local heating r v up to 2 43 within the intruded interval lower reflectance values r v 0 57 0 74 occur in the unaffected parts of the permian sequence with even lower values in places due to either marine influence or liptinite rich lacustrine organic facies hydrocarbon biomarkers in the oil stain in the pilliga sandstone indicate its derivation from a higher plant rich shaley source a methylphenanthrene index of 1 48 calculated vitrinite reflectance r c 1 29 for the oil suggests expulsion from a late mature source rock none of the potential source rock samples analysed appear to have attained such a maturation level except those from the lower part of the napperby formation affected by intrusions source specific biomarkers from this formation show several parallels with those of the oil stain but differ from those in the permian goonbri and maules creek formations and the upper parts of the napperby formation a jurassic source can also be excluded based on the immaturity of that part of the section and the absence of jurassic specific biomarkers in the oil stain

reply to comment by w r peltier d f argus and r drummond on an assessment of the ice6g_c vm5a glacial isostatic adjustment model

the use of gps horizontals for loading studies with applications to northern california and southeast greenland received 23 august 2012 revised 15 january 2013 accepted 20 january 2013 published 25 april 2013 1 we describe how gps measurements of horizontal crustal motion can be used to augment vertical crustal motion measurements to improve and extend gps studies of surface loading we show that the ratio of the vertical displacement to the horizontal displacement combined with the direction of the horizontal motion can help determine whether nearby loading is concentrated in a small region for example in a single lake or glacier and where that region is we illustrate this method by applying it to two specific cases an analysis of gps data from northern california to monitor the level of lake shasta and the analysis of data from a single gps site in southeast greenland to determine mass variability of two large nearby outletglaciers helheim glacier and midgaard glacier the californiaexampleserves largely as a proof of concept where the results can be assessed by comparing with independent observations lake shasta tide gauge data in this case our greenland results show that both helheim and midgaard have experienced notable interannual variations in mass loss rate over the last decade helheim sm ass loss accelerated rapidly in mid 2003 decelerated in late 2005 and increased again in 2008 2009 before returning to about its pre 2003 rate in late 2010 midgaard s mass loss accelerated in mid 2004 and remained more or less constant before returning to its pre 2003 rate in late 2008

reconstruction of eruption column dynamics on the basis of grain size of tephra fall deposits 1 methods two inversion methods are developed to reconstruct eruption column dynamics from granulometric data of plinian deposits they are based on the steady tephra dispersal model from umbrella clouds which spread as gravity currents the methods provide 1 expansion rate of an umbrella cloud 2 grain size distribution at the top of the eruption column and 3 total amount of ejecta including very fine particles which are extensively dispersed in the atmosphere the first quantity is correlated to the magma discharge rate the second quantity provides information about sorting processes during column rise and hence about deceleration in the gas thrust region of the eruption column and the timing of column collapse the third quantity together with the estimated magma discharge rate provides the effective duration of the eruption the two methods are based on the same dispersal model but use different averaging combining the two methods can provide additional information about eruption dynamics such as minor flow structures of the umbrella cloud and fluctuations of eruption rate the methods are applicable to large scale eruptions where the radial expansion velocity of the umbrella cloud exceeds wind velocity the applicability of the methods is tested from the viewpoint of comparison with real time observations in the companion paper paper 2

a three dimensional eulerian model for transport and deposition of volcanic ashes abstract volcanic ash fallout represents a serious threat to people living near active volcanoes because it can produce several undesirable effects such as collapse of roofs by ash loading respiratory sickness air traffic disruption or damage to agriculture the assessment of such volcanic risk is therefore an issue of vital importance for public safety and its mitigation often requires to evaluate the temporal evolution of the phenomenon through reliable computational models we develop an eulerian model named fall3d for the transport and deposition of volcanic ashes the model is based on the advection diffusion sedimentation equation with a turbulent diffusion given by the gradient transport theory a wind field obtained from a meteorological limited area model lam and the source term derived from by buoyant plume theory it can be used to forecast either ash concentration in the atmosphere or ash loading on the ground model inputs are topography meteorological data given by a lam mass eruption rate and a particle settling velocity distribution a test application to the july 2001 etna eruption is presented

a review of tephra transport and dispersal models evolution current status and future perspectives abstract tephra transport models try to predict atmospheric dispersion and sedimentation of tephra depending on meteorology particle properties and eruption characteristics defined by eruption column height mass eruption rate and vertical distribution of mass models are used for different purposes from operational forecast of volcanic ash clouds to hazard assessment of tephra dispersion and fallout the size of the erupted particles a key parameter controlling the dynamics of particle sedimentation in the atmosphere varies within a wide range largest centimetric to millimetric particles fallout at proximal to medial distances from the volcano and sediment by gravitational settling on the other extreme smallest micrometric to sub micrometric particles can be transported at continental or even at global scales and are affected by other deposition and aggregation mechanisms different scientific communities had traditionally modeled the dispersion of these two end members volcanologists developed families of models suitable for lapilli and coarse ash and aimed at computing fallout deposits and for hazard assessment in contrast meteorologists and atmospheric scientists have traditionally used other atmospheric transport models dealing with finer particles for tracking motion of volcanic ash clouds and eventually for computing airborne ash concentrations during the last decade the increasing demand for model accuracy and forecast reliability has pushed on two fronts first the original gap between these different families of models has been filled with the emergence of multi scale and multi purpose models second new modeling strategies including for example ensemble and probabilistic forecast or model data assimilation are being investigated for future implementation in models and or modeling strategies this paper reviews the evolution of tephra transport and dispersal models during the last two decades presents the status and limitations of the current modeling strategies and discusses some emergent perspectives expected to be implemented at operational level during the next few years improvements in both real time forecasting and long term hazard assessment are necessary to loss prevention programs on a local regional national and international level

improved methods for observing earth s time variable mass distribution with grace using spherical cap mascons we discuss several classes of improvements to gravity solutions from the gravity recovery and climate experiment grace mission these include both improvements in background geophysical models and orbital parameterization leading to the unconstrained spherical harmonic solution jpl rl05 and an alternate jpl rl05m mass concentration mascon solution benefitting from those same improvements but derived in surface spherical cap mascons the mascon basis functions allow for convenient application of a priori information derived from near global geophysical models to prevent striping in the solutions the resulting mass flux solutions are shown to suffer less from leakage errors than harmonic solutions and do not necessitate empirical filters to remove north south stripes lowering the dependence on using scale factors the global mean scale factor decreases by 0 17 to gain accurate mass estimates ocean bottom pressure obp time series derived from the mascon solutions are shown to have greater correlation with in situ data than do spherical harmonic solutions increase in correlation coefficient of 0 08 globally particularly in low latitude regions with small signal power increase in correlation coefficient of 0 35 regionally in addition to reducing the error rms with respect to the in situ data reduction of 0 37 cm globally and as much as 1 cm regionally greenland and antarctica mass balance estimates derived from the mascon solutions agree within formal uncertainties with previously published results computing basin averages for hydrology applications shows general agreement between harmonic and mascon solutions for large basins however mascon solutions typically have greater resolution for smaller spatial regions in particular when studying secular signals

time variability of the earth s gravity field hydrological and oceanic effects and their possible detection using grace the grace satellite mission scheduled for launch in 2001 is designed to map out the earth s gravity field to high accuracy every 2 4 weeks over a nominal lifetime of 5 years changes in the gravity field are caused by the redistribution of mass within the earth and on or above its surface grace will thus be able to constrain processes that involve mass redistribution in this paper we use output from hydrological oceanographic and atmospheric models to estimate the variability in the gravity field i e in the geoid due to those sources we develop a method for constructing surface mass estimates from the grace gravity coefficients we show the results of simulations where we use synthetic grace gravity data constructed by combining estimated geophysical signals and simulated grace measurement errors to attempt to recover hydrological and oceanographic signals we show that grace may be able to recover changes in continental water storage and in seafloor pressure at scales of a few hundred kilometers and larger and at timescales of a few weeks and longer with accuracies approaching 2 mm in water thickness over land and 0 1 mbar or better in seafloor pressure

petrographic characteristics and methane sorption dynamics of coal and shaly coal samples from ib valley basin odisha india abstract hydrocarbon generation potential methane sorption capacity maturity and petrographic composition of ten borehole 2 shaly coals and 8 coals samples from ib valley india were determined rock eval pyrolysis and total organic carbon toc analysis indicate that all the samples have excellent toc content and hydrocarbon generation potential though tmax values indicate the samples are mostly immature in nature vitrinite reflectance analysis shows that the samples are within the vitrinite reflectance oil window moreover vt60 vitrinite grains having reflectance greater than 0 60 indicates that thermogenic gas generation is occurring to some degree in almost all sample intervals toc content of the samples 25 35 58 15 wt shows good positive relation with langmuir volume vl 0 481 0 551 mmol g rock and methane sorption capacity msc 0 317 0 379 mmol g rock indicating that organic matter abundance is the significant factor in gas sorption capacity of these samples while fourier transform infrared spectrometry ftir spectrum of coal samples shows the presence of aromatic h the same was not observed in the case of shaly coal samples which may be attributed to their lesser organic matter and greater content of clay

the effect of intensity of turbulence in umbrella cloud on tephra dispersion during explosive volcanic eruptions experimental and numerical approaches abstract during an explosive volcanic eruption tephra fall out from the umbrella region of the eruption cloud to the ground surface we investigated the effect of the intensity of turbulence in the umbrella cloud on dispersion and sedimentation of tephra by performing a series of laboratory experiments and three dimensional 3 d numerical simulations in the laboratory experiments spherical glass bead particles are mixed in stirred water with various intensities of turbulence and the spatial distribution and the temporal evolution of the particle concentration are measured the experimental results show that when the root mean square of velocity fluctuation in the fluid w rms is much greater than the particle terminal velocity v t the particles are homogeneously distributed in the fluid and settle at their terminal velocities at the base of the fluid where turbulence diminishes on the other hand when w rms is as small as or smaller than v t the particle concentration increases toward the base of the fluid during settling which substantially increases the rate of particle settling the results of the 3 d simulations of eruption cloud indicate that w rms is up to 40 m s in most of the umbrella cloud even during a large scale plinian eruption with a magma discharge rate of 10 9 kg s these results suggest that relatively coarse pyroclasts more than a few mm in diameter tend to concentrate around the base of the umbrella cloud whereas fine pyroclasts less than 1 8 mm in diameter may be distributed homogeneously throughout the umbrella cloud during tephra dispersion the effect of the gradient of particle concentration in the umbrella cloud explains the granulometric data of the pinatubo 1991 plinian deposits

particle aggregation in volcanic eruption columns we develop a model to describe the formation of aggregates in a volcanic eruption column the model combines a description of the rate of collision and sticking of particles with a model of the vertical transport in the eruption column we thereby determine the evolution of the grain size distribution as a function of height in the eruption column we consider aggregates in which liquid water provides the binding agent for sufficiently large eruption columns we find that this limits the vertical extent of the zone where aggregates may form since near the source all water is in the vapor form while in the upper part of the column the mixture becomes very cold and freezes however in many cases we find that the particles spend sufficient time in the central region where the water is in the liquid form that a substantial amount of aggregation occurs furthermore we predict that owing to the reduction in the binding efficiency of water as particle size increases gilbert and lane 1994 there is a relatively narrow size distribution of aggregates at the plume top we also model the airfall deposits associated with this aggregate rich distribution of particles which is injected to the top of the eruption column we show that the relatively narrow size distribution of particles at the top of the column coupled with the gravitational settling and transport by ambient winds may lead to enhanced deposition close to the source and in some cases secondary thickening of the deposit the relatively near source deposition of fine ash in these deposits is associated with the fallout of aggregates as a simple application we show that the present dynamical aggregation model is consistent with the secondary thickening of the deposit from the may 18 1980 eruption of mount st helens

uncertainty in the velocity between the mass center and surface of earth 1 using spectral analysis and data decimation we estimate the uncertainty in the velocity between the cumulative mass center of earth cm and geodetic sites on earth s surface knowing this velocity is crucial for evaluating space geodetic observations of continental uplift and subsidence in terms of postglacial rebound and sea level rise we find slr observations of satellite lageos to constrain the x and y components of the velocity of cm to 0 4 mm yr and the z component to 0 9 mm yr 95 confidence limits x is in the direction of 0 n0 e y of 0 n9 0 e and z of 90 n the uncertainty in z is high so that the estimate includes the independent inference made jointly using site velocities the rigid plate hypothesis and models of postglacial rebound that the true velocity of cm has a z component of 0 5 1 0 mm yr relative to that in itrf2008 uncertainty in scale rate an intermediate parameter in the determination of an itrf is 0 36 mm yr for vlbi 0 52 mm yr for slr and 0 20 mm yr for gps the scale of gps depends on that of vlbi and slr but the low gps uncertainty indicates that gps results are for the first time unbiased by changing satellite block types evidently due to newly incorporated satellite phase center variations gps constrains the velocity of cm nearly as well as slr representing a technical advance given that a gps satellite is not a sphere and responds strongly to solar radiation pressure citation argus d f 2012 uncertainty in the velocity between the mass center and surface of earth j geophys res 117 b10405 doi 10 1029 2012jb009196

vitrinite reflectance anomalies in the high volatile bituminous coals of the gunnedah basin new south wales australia abstract the rank of the permian coals in the gunnedah basin has been analyzed using both petrographic and chemical methods apart from the effects of local igneous intrusions a number of seams in the sequence have vitrinite reflectance values rv max that deviate significantly from the trend expected with a steady downward increase in coalification correlation of these anomalies with interpreted depositional environments suggests that abnormally low vitrinite reflectance values in the sequence occur in seams either overlain by or intimately associated with marine strata the three dimensional distribution of such low reflectance values in part of the section at least can be related either to the lithofacies pattern or post depositional groundwater flow associated with a major fan delta system coals with anomalously high vitrinite reflectance values appear to contain material described elsewhere as pseudovitrinite a component not previously reported in australian permian bituminous coals both low value and high value anomalies need to be taken into account when interpreting maturation patterns from vitrinite reflectance data in some cases other rank indicators such as air dried moisture may be useful to complement vitrinite reflectance in rank studies of high volatile bituminous coals abnormally low vitrinite reflectance values due to environmental factors such as marine influence on the other hand may be used to identify flooding surface sequence boundaries in the basin for stratigraphic and sedimentological investigations

grain size variation of tephra derived from volcanic umbrella clouds the relationships among the thickness and grain size of tephra fall deposits and the volumetric flow rate of their source umbrella clouds are analytically obtained the logarithm of the ratio of the probability distribution function based on grain size inr f in fall deposits at two localities from the vent r 1 and r 2 respectively has a linear relationship with the particle settling velocity v as in 1n r f frac pi r 2 2 r 1 2 nu q 1n a where q is the volumetric flow rate of the umbrella cloud and a is a constant for a given pair of localities the volumetric flow rate of the umbrella cloud can be estimated from granulometric data using this formula generally the thickness distance relationship of tephra fall deposits depends on the initial grain size distribution and the volumetric flow rate of the umbrella cloud the empirical relationship of the exponential thinning behaviour can be extrapolated towards infinite distance only for a specific initial grain size which is similar to a log normal distribution with 2 5 otherwise it holds only in a limited range of distances in applying these results to the 1991 eruption of mt pinatubo it is shown that the volumetric flow rate of the umbrella cloud during the climactic phase of 15 june was approximately 5x1010 m3 s which is fairly consistent with the expansion rate of the umbrella cloud observed in the satellite images

antarctica greenland and gulf of alaska land ice evolution from an iterated grace global mascon solution we have determined the ice mass evolution of the antarctica and greenland ice sheets ais and gis and gulf of alaska goa glaciers from a new grace global solution of equal area surface mass concentration parcels mascons in equivalent height of water the mascons were estimated directly from the reduction of the inter satellite k band range rate kbrr observations taking into account the full noise covariance and formally iterating the solution the new solution increases signal recovery while reducing the grace kbrr observation residuals the mascons were estimated with 10 day and 1 arc degree equal area sampling applying anisotropic constraints an ensemble empirical mode decomposition adaptive filter was applied to the mascon time series to compute annual mass balances the details and causes of the spatial and temporal variability of the land ice regions studied are discussed the estimated mass trend over the total gis ais and goa glaciers for the time period 1 december 2003 to 1 december 2010 is 380 plus or minus 31 gt a exp 1 equivalent to 1 05 plus or minus 0 09 mma exp 1 sea level rise over the same time period we estimate the mass acceleration to be 41 plus or minus 27 gt a exp 2 equivalent to a 0 11 plus or minus 0 08 mm a exp 2 rate of change in sea level the trends and accelerations are dependent on significant seasonal and annual balance anomalies

review and update of the applications of organic petrology part 1 geological applications abstract organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry coal petrology was then considered a branch of coal science later with the development of specialized nomenclature classification of coal components and the standardization and improvement of analytical microscopical methods this discipline expanded in interests and name becoming organic petrology organic petrology carries a broader context being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources at present organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences throughout the 20th century several important monographs have been published on the discipline of organic petrology including stach s textbook of coal petrology 1st edition 1935 2nd 1975 3rd 1982 updated as the more general organic petrology by taylor et al 1998 more recently the text applied coal petrology the role of petrology in coal utilization was published by suarez ruiz and crelling 2008 this review is the first in a two part review series that describes and updates the role of organic petrology in geosciences a second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow

sequence and eruptive style of the 1783 eruption of asama volcano central japan a case study of an andesitic explosive eruption generating fountain fed lava flow pumice fall scoria flow and forming a cone the 3 month long eruption of asama volcano in 1783 produced andesitic pumice falls pyroclastic flows lava flows and constructed a cone it is divided into six episodes on the basis of waxing and waning inferred from records made during the eruption episodes 1 to 4 were intermittent vulcanian or plinian eruptions which generated several pumice fall deposits the frequency and intensity of the eruption increased dramatically in episode 5 which started on 2 august and culminated in a final phase that began on the night of 4 august lasting for 15 h this climactic phase is further divided into two subphases the first subphase is characterized by generation of a pumice fall whereas the second one is characterized by abundant pyroclastic flows stratigraphic relationships suggest that rapid growth of a cone and the generation of lava flows occurred simultaneously with the generation of both pumice falls and pyroclastic flows the volumes of the ejecta during the first and second subphases are 0 21 km3 dre and 0 27 km3 dre respectively the proportions of the different eruptive products are lava cone pumice fall 84 11 5 in the first subphase and lava cone pyroclastic flow 42 2 56 in the second subphase the lava flows in this eruption consist of three flow units l1 l2 and l3 and they characteristically possess abundant broken phenocrysts and show extensive welding texture these features as well as ghost pyroclastic textures on the surface indicate that the lava was a fountain fed clastogenic lava a high discharge rate for the lava flow up to 106 kg s may also suggest that the lava was initially explosively ejected from the conduit the petrology of the juvenile materials indicates binary mixing of an andesitic magma and a crystal rich dacitic magma the mixing ratio changed with time the dacitic component is dominant in the pyroclasts of the first subphase of the climactic phase while the proportion of the andesitic component increases in the pyroclasts of the second subphase the compositions of the lava flows vary from one flow unit to another l1 and l3 have almost identical compositions to those of pyroclasts of the first and second subphases respectively while l2 has an intermediate composition suggesting that the pyroclasts of the first and second subphases were the source of the lava flows and were partly homogenized during flow the complex features of this eruption can be explained by rapid deposition of coarse pyroclasts near the vent and the subsequent flowage of clastogenic lavas which were accompanied by a high eruption plume generating pumice falls and or pyroclastic flows

numerical simulations of global scale high resolution hydrological crustal deformations 1 high resolution load induced crustal deformations calculated from numerical models are tested for their ability to predict hydrologically induced station height variability as they are known to be large enough to affect epoch wise parameters obtained from the analysis of global geodetic networks loading contributions due to terrestrial water storage as given by global hydrological models are calculated on a 0 5 global regular grid with daily temporal resolution apart from the dominant seasonal variations the hydrological loading signal discloses also rapid changes exceeding 1 mm in several regions that can be associated with major precipitation events and river floods locally strong loading signals with exceptionally high amplitudes in many cases even with nonseasonal nature occur along the major river channels only high resolution loading calculations considering also the water mass anomalies stored in the model river flow can resolve the correct amplitudes in the surrounded area up to 100 km distance the comparison of the modeled hydrological surface deformation with gps station time series shows that high resolution hydrological loading estimates based on global scale models are able to explain a considerable fraction up to 54 of the observed vertical station movements caused by continental water storage variations

rise of great lakes surface water sinking of the upper midwest of the united states and viscous collapse of the forebulge of the former laurentide ice sheet

the antarctica component of postglacial rebound model ice 6g_c vm5a based on gps positioning exposure age dating of ice thicknesses and relative sea level histories

sedimentation from turbulent jets and plumes theoretical models are developed for the sedimentation from the margins of a particle laden axisymmetric turbulent buoyant plume in a still environment and for an axisymmetric turbulent momentum jet the models assume that the mass of each individual size fraction of sediment carried in a parcel of fluid decreases exponentially with time for relatively coarse particles the fallout models predict that the sediment deposition beyond a distance r on the ground expressed in log units should decay linearly with distance away from the vent for the momentum jet and should decrease with r1 3 for the buoyant plume the exponential decay constant j is proportional to the terminal fall velocity vt of the particles in both cases and inversely proportional to the square root of the initial momentum flux m0 for the jet fallout jj vtmo 1 2 and to the third power of the initial buoyancy flux fo for the plume fallout jp vtfo 1 3 smaller particles are affected by reentrainment caused by the turbulent eddies sweeping ambient fluid back into the plume or jet and thus reincorporating some particles that were released from the flow at greater heights this is taken into account by introducing a reentrainment coefficient into the theoretical models with the assumption that the coefficient has a constant value for a plume of given strength in new experiments fallout occurs from the margins of particle laden fresh water buoyant jets and plumes in a tank of salty water and sedimentation is measured on the tank floor two experiments were weakly affected by reentrainment and show excellent agreement with the simple theory for smaller particles and increasingly buoyant plumes and strong jets particle reentrainment is important the experimental data are fitted by the new reentrainment theory confirming that values of the reentrainment coefficient are approximately constant for a given flow a settling number is defined as the ratio of the characteristic velocity of the jet or plume to the particle settling velocity for 1 reentrainment seems to reach an equilibrium state for which the reentrainment coefficient is a constant of value 0 1 for jets and 0 4 for plumes irrespective of flow strength or particle size the plume experiments indicate that the value of the reentrainment coefficient is strongly dependent on plume strength and particle size for slightly less than 1 the general principles of sedimentation from turbulent plumes and jets are applied to the fallout of pumice from volcanic eruption columns and of metalliferous particles from black smokers on the ocean floor for volcanic eruptions the results provide an explanation for the near vent overthickening of tephra fall deposits and imply that lithic and pumice fragments from small lapilli up to at least 1 m diameter blocks are efficiently reentrained into eruption columns the size of particles reentrained in hydrothermal plumes is predicted to vary from less than 100 m in weakly buoyant plumes up to over 1000 m in megaplumes

space geodesy constrains ice age terminal deglaciation the global ice 6g_c vm5a model a new model of the last deglaciation event of the late quaternary ice age is here described and denoted as ice 6g c vm5a it differs from previously published models in this sequence in that it has been explicitly refined by applying all of the available global positioning system gps measurements of vertical motion of the crust that may be brought to bear to constrain the thickness of local ice cover as well as the timing of its removal additional space geodetic constraints have also been applied to specify the reference frame within which the gps data are described the focus of the paper is upon the three main regions of last glacial maximum ice cover namely north america northwestern europe eurasia and antarctica although greenland and the british isles will also be included if peripherally in the discussion in each of the three major regions the model predictions of the time rate of change of the gravitational field are also compared to that being measured by the gravity recovery and climate experiment satellites as an independent means of verifying the improvement of the model achieved by applying the gps constraints several aspects of the global characteristics of this new model are also discussed including the nature of relative sea level history predictions at far field locations in particular the caribbean island of barbados from which especially high quality records of postglacial sea level change are available but which records were not employed in the development of the model although ice 6g c vm5a is a significant improvement insofar as the most recently available gps observations are concerned comparison of model predictions with such far field relative sea level histories enables us to identify a series of additional improvements that should follow from a further stage of model iteration

petrological and chemical characteristics of liptinite rich coals from alberta canada a suite of liptinite rich coals from the lower cretaceous mannville group in the subsurface of alberta canada has been studied with respect to its organic petrology and organic geochemistry the samples are rich in fluorescing vitrinite perhydrous sporinite cutinite exsudatinite and bituminite rock eval analysis shows that the coals are enriched in hydrogen hydrogen index up to 320 mg hc g toc and depleted in oxygen oxygen index up to 11 mg co2 g toc the value of tmax ranges from 445 to 460 c indicating a late catagenic level of thermal maturity equivalent to ro 1 0 1 1 but the vitrinite reflectance is between 0 68 and 0 81 indicating that it is lowered by as much as 0 4 the pyrolysis chromatograms of the coal samples are dominated by substituted benzenes toluene and xylenes naphthalenes phenanthrenes substituted phenols cresols and small amounts of n alkanes in the range c20 gas chromatography mass spectrometry of the steranes and terpanes indicates little or no contribution of allochthonous bitumen to the coals in addition the mz 217 sterane traces are dominated by c29 compounds with little c27 and c28 this along with the high terpane to sterane ratio mz 191 to mz 217 8 8 indicates that the bitumen was generated from terrestrially derived organic matter the bitumen in the coals has most likely been autogenerated by the coals themselves in response to thermal stress the originally sapropelic coals were probably deposited in an anaerobic environment and were much enriched in hydrogen this study shows that terrigenous organic matter when associated with an anomalous liptinite content may have the potential to generate bitumen

structural controls on groundwater flow and groundwater salinity in the spicers creek catchment central west region new south wales saline seepage zone development and hence the onset of dryland salinity is a major environmental problem occurring within the spicers creek catchment the primary objective of this paper was to identify previously unmapped faults and show the correlation between these faults and groundwater salinization as identified from this study there is a close association between geological structural features and the formation of saline seepage zones the most saline groundwaters in the catchment were encountered where two geological structures join and form a fault intersection these saline groundwaters are found at various depths within the fractured aquifers and changes in groundwater chemistry in the aquifers are associated with the presence of fault zones 18o and 2h stable isotopes together with 87sr 86sr isotopic ratios indicate that groundwaters within the fault zones are enriched in 18o and have a strontium signature similar to seawater this study identifies several geological structures in the spicers creek catchment and demonstrates that groundwaters with the highest salinity arise where fault intersections occur the results of this study may be used to interpret further the mechanisms leading to seepage zone formation in dryland salinity affected catchments located throughout the central west region of new south wales australia copyright 2006 john wiley sons ltd

abrupt transitions during sustained explosive eruptions examples from the 1912 eruption of novarupta alaska plinian ignimbrite activity stopped briefly and abruptly 16 and 45 h after commencement of the 1912 novarupta eruption defining three episodes of explosive volcanism before finally giving way after 60 h to effusion of lava domes we focus here on the processes leading to the termination of the second and third of these three episodes early erupted pumice from both episodes show a very similar range in bulk vesicularity but the modal values markedly decrease and the vesicularity range widens toward the end of episode iii clasts erupted at the end of each episode represent textural extremes at the end of episode ii clasts have very thin glass walls and a predominance of large bubbles whereas at the end of episode iii clasts have thick interstices and more small bubbles quantitatively all clasts have very similar vesicle size distributions which show a division in the bubble population at 30 m vesicle diameter and cumulative number densities ranging from 107 109 cm 3 patterns seen in histograms of volume fraction and the trends in the vesicle size data can be explained by coalescence signatures superimposed on an interval of prolonged nucleation and free growth of bubbles compared to experimental data for bubble growth in silicic melts the high 1912 number densities suggest homogeneous nucleation was a significant if not dominant mechanism of bubble nucleation in the dacitic magma the most distinct clast populations occurred toward the end of plinian activity preceding effusive dome growth distributions skewed toward small sizes thick walls and teardrop vesicle shapes are indicative of bubble wall collapse marking maturation of the melt and onset of processes of outgassing the data suggest that the superficially similar pauses in the 1912 eruption which marked the ends of episodes ii and iii had very different causes through episode iii the trend in vesicle size data reflects a progressive shift in the degassing process from rapid magma ascent and coupled gas exsolution to slower ascent with partial open system outgassing as a precursor to effusive dome growth no such trend is visible in the episode ii clast assemblages we suggest that external changes involving failure of the conduit vent walls are more likely to have effected the break in explosive activity at 45 h

changes in geochemistry and mineralogy of thermally altered coal upper hunter valley australia abstract igneous intrusions thermally and geochemically alter coal commonly causing economic and safety problems for many coal mines the effects of two dykes on the inorganic content of the late permian bituminous upper wynn seam were determined from analyses of 44 samples that were collected along transects approaching the intrusions petrographic and xrd data were used to determine sample mineralogy and inaa and xrf spectrometry were utilised to determine the contents of 57 elements the mineralogy of the unaltered coal altered coal and dyke is dominated by carbonates particularly dawsonite which formed by epigenetic precipitation at a late stage after thermal alteration ankerite and siderite are the products of thermal alteration and are restricted to the altered coal and dykes principal component analysis correlations and compositional trends approaching the intrusions were used to subdivide the elements into groups and to identify the mineralogical affinity of each group geochemical data are more sensitive than mineralogy for defining the size of the alteration halo and three zones ranging from unaltered coal through altered coal to highly coked coal are recognised as each intrusion is approached the alteration halos differ in extent 9 5 and 56 m wide but their size is not a multiple of the size of the causative intrusion at the contact between coal and intrusion concentrations of elements with affinities to some aluminosilicates oxides carbonates sulphides and organic components are enriched while other aluminosilicate related elements are depleted in the altered coal towards the edge of the alteration halo some aluminosilicate elements are enriched and oxide elements are depleted

reservoir origin and characterization of gas pools in intrusive rocks of the yingcheng formation songliao basin ne china abstract in 2013 the first discovery of gas pools in well ls 208 in intrusive rocks of the songliao basin sb ne china was made in the 2nd member of the yingcheng formation in the yingtai rift depression proving that intrusive rocks of the sb have the potential for gas exploration however the mechanisms behind the origin of reservoirs in intrusive rocks need to be identified for effective gas exploration the gas pool in intrusive rocks can be characterized as a low abundance high temperature normal pressure methane rich and lithologic pool based on integrated coring logging seismic and oil test methods the intrusive rocks show primary and secondary porosities such as shrinkage fractures sf spongy pores sp secondary sieve pores ssp and tectonic fractures tf the reservoir is of the fracture pore type with low porosity and permeability a capillary pressure curve for mercury intrusion indicates small pore throat size negative skewness medium high displacement pressure and middle low mercury saturation the development of fractures was found to be related to the quenching effects of emplacement and tectonic inversion during the middle late campanian sp and ssp formed during two phases the first phase occurred during emplacement of the intrusive rock in the late albian when the intrusions underwent alteration by organic acids the second phase occurred between the early cenomanian and middle campanian when the intrusions underwent alteration by carbonic acid the sf formed prior to oil charging the ssp sp formed during oil charging and the tf formed during the middle late campanian and promoted the distribution of gas pools throughout the reservoir the intrusive rocks in the sb and the adjacent basins were emplaced in the mudstone and coal units and have great potential for gas exploration

a coupled model for dispersal of tephra during sustained explosive eruptions abstract we present a model for fallout of tephra based on approximate analytical solutions of the advection diffusion transport equation as usual the model requires the distribution of mass throughout the eruptive column as a boundary condition an input which is normally imposed ad hoc by means of analytical expressions we propose an alternative way to assess this input based on coupling the model of fallout with already existing simple models for volcanic plumes flow along the volcanic conduit and magma chamber withdrawal the final outcome is a one way coupled model that involves all the spatial domains simultaneously and has a good compromise between physical accuracy and computational efficiency the coupled model outputs not only maps of isopachs but also several relevant eruptive parameters such as column height mass eruption rate or duration of the eruption time dependency is introduced via a quasi steady approach that is considering a succession of steady states we apply the model to simulate the 2 ka subplinian eruption of montana blanca tenerife island

an experimental study on the effects of phenocrysts on convection in magmas abstract the effect of phenocrysts on convection in magma chambers is investigated experimentally using small heavy particles in convecting fluids the particles are initially uniformly distributed in a fluid which is either heated from below or cooled from above the system is allowed to evolve and temperature and particle concentration profiles are measured as functions of time when the concentration of particles is sufficiently small convection is basically unaffected by their presence when the concentration is above a critical value however the convective motion is considerably altered the effect of particles on the subsequent fluid behaviour is different in the cases of heating from below and cooling from above in the former case there are strong convective motions confined to a sedimentary layer of decreasing thickness beneath a clear layer which displays rather weak convective motions with time the destabilizing increase of temperature in the lower layer overcomes the stabilizing contribution to the bulk density due to the particles and the layer overturns quite suddenly in the situation of cooling from above a critical condition separates a case of continual overturn from a case of no overturn at all with the sedimentary layer falling unimpeded to the bottom theoretical analysis suggests that the critical value is determined primarily by the ratio of the contribution to the bulk density of the suspension due to particles to the change in fluid density due to the thermal effect the size distribution of the particles can also modify the fluid behaviour applying our general results to geological situations we suggest that the presence of relatively small concentrations of phenocrysts can critically influence the mode of convection in magmas

deltaic depositional systems coal distribution and quality and petroleum potential permian gunnedah basin n s w australia abstract upper permian sediments of the lower black jack formation were deposited as a major delta system in the gunnedah basin a foredeep of the rising new england fold belt two principal depositional units are recognized in the lower black jack formation the lower delta plain facies and the shallow marine facies a third but minor depositional unit the western bed load fluvial facies is correlative with the upper part of the shallow marine facies geometry of the framework sandstones indicates that the lower delta plain facies was deposited in a combination of fluvial dominated and wave modified delta systems and that the shallow marine facies was deposited in a tide dominated system sediment source was predominantly from the northeast except for the western bed load fluvial facies which was derived from the lachlan fold belt region to the west the lower delta plain facies was deposited during a major episode of delta construction principal components recognized in drillcore are distributary channel crevasse splay and splay subdelta interdistributary bay lagoon and marsh deposits transgression of the delta possibly initiated by a major eustatic sea level rise led to deposition of the shallow marine facies this facies consists chiefly of beach barrier beach tidal sand ridge and tidal channel fill deposits subsequent lowering of sea level was accompanied by deposition of the western bed load fluvial facies this facies consists predominantly of upward fining fluvial channels which display considerable marine reworking toward the basin centre a vast coal swamp was established rapidly after the marine conditions regressed and is represented by the hoskissons coal member coals of commercial interest are developed within the lower delta plain facies and above the shallow marine facies the lobate geometry of the coal deposits in the lower delta plain facies mirrors the geometry of the framework sandstones and indicates a deltaic origin for coal formation two mechanisms for coal formation are recognized in the lower delta plain facies thick laterally extensive coals such as the melvilles coal member are thought to have originated as blanket peats following delta abandonment thin discontinuous coals formed in interdistributary depressions during active deltaic progradation coal above the shallow marine facies is contained in one major seam the hoskissons coal member this seam probably formed mostly as a back barrier or lagoonal peat depositional setting strongly influenced coal quality isoash trends for the melvilles coal member suggest a marginal marine influence during peat accumulation ash content of the hoskissons coal member has a similar distribution to the percentage of sandstone in the underlying shallow marine facies potential exists for petroleum accumulation in the lower black jack formation suitable reservoir rocks are present in the lower delta plain and shallow marine facies underlying prodelta facies are potential source rocks

thermal maturation pattern in the southern bowen northern gunnedah and surat basins northern new south wales australia abstract comprehensive maximum vitrinite telocollinite reflectance data have been obtained for more than 260 polished sections from 28 petroleum exploration wells in the southern bowen and northern gunnedah basins and the overlying surat basin in an area from north of boggabri to the new south wales queensland border the samples studied were coal and dispersed organic matter dom taken from ditch cuttings and drill cores of the permian triassic and jurassic sedimentary successions vitrinite reflectance profiles show that the coals and dom in the early permian back creek group of the southern bowen basin have anomalously low suppressed reflectance values and a higher reflectance gradient rate of increase in vitrinite reflectance with depth relative to the overlying late permian triassic and jurassic sequences suppression of vitrinite reflectance is recorded in the early permian maules creek and goonbri formations in the northernmost part of the gunnedah basin relative to the overlying triassic and jurassic sequences dispersed organic matter in the marine sediments of the watermark and porcupine formations of the gunnedah basin also shows suppression of vitrinite reflectance the vitrinite in several wells of the study area however displays anomalously high reflectance in parts of the sequence due to the influence of igneous intrusions after allowing for heat effects due to intrusions and anomalies due to marine influence the reflectance gradient over equivalent intervals in the southern bowen basin is higher towards the west where the permian sequence pinches out and the triassic sequence overlies the basement vitrinite reflectance also increases at a higher rate with depth close to the gil gil ridge in the east and close to the moree high in the south this may reflect additional heat flow associated with the basement high features the areas between the gil gil ridge and the goondiwindi thrust in the east and to the west of the gil gil ridge appear to have lower reflectance gradients and equivalent or lower reflectance values despite the greater burial depths

troposphere mapping functions for gps and very long baseline interferometry from european centre for medium range weather forecasts operational analysis data 1 in the analyses of geodetic very long baseline interferometry vlbi and gps data the analytic form used for mapping of the atmosphere delay from zenith to the line of site is most often a three parameter continued fraction in 1 sin elevation using the 40 years reanalysis era 40 data of the european centre for medium range weather forecasts for the year 2001 the b and c coefficients of the continued fraction form for the hydrostatic mapping functions have been redetermined unlike previous mapping functions based on data from numerical weather models isobaric mapping functions niell 2000 and vienna mapping functions vmf boehm and schuh 2004 the new c coefficients are dependent on the day of the year and unlike the niell mapping functions niell 1996 they are no longer symmetric with respect to the equator apart from the opposite phase for the two hemispheres compared to vmf this causes an effect on the vlbi or gps station heights that is constant and as large as 2 mm at the equator and that varies seasonally between 4 mm and 0 mm at the poles the updated vmf based on these new coefficients and called vmf1 hereinafter yields slightly better baseline length repeatabilities for vlbi data the hydrostatic and wet mapping functions are applied in various combinations with different kinds of a priori zenith delays in the analyses of all vlbi international vlbi service for geodesy and astrometry ivs r1 and ivs r4 24 hour sessions of 2002 and 2003 the investigations concentrate on baseline length repeatabilities as well as on absolute changes of station heights

defining the translational velocity of the reference frame of earth summary earth s centre is fundamental to geodesy and geoscience because motions of sites on the surface are estimated relative to it international terrestrial reference frames itrf2000 and itrf2005 are defined by the centre of mass of earth s system cm consisting of solid earth the ice sheets the oceans and the atmosphere satellite lageos rotates about cm satellite laser ranging slr is used to estimate the velocity of cm relative to sites on the surface however itrf2000 and itrf2005 differ by 1 8 mm yr 1 suggesting that the velocity of cm is constrained poorly by slr in this study we define earth s reference frame with the centre of mass of solid earth ce site velocities estimated using slr vlbi gps and doris are corrected for a postglacial rebound model and inverted for the rotational velocities of the plates and the rotational and translational velocities of the four space techniques because the postglacial rebound predictions are relative to ce the velocity of ce relative to sites on the surface is estimated because the input slr site velocities are relative to cm the output slr translational velocity is the velocity of cm relative to ce the estimated velocity of ce does not depend strongly on the postglacial rebound model corrected for equal within uncertainties and having a root mean square of 0 5 mm yr 1 are estimates of the velocity of ce determined assuming that plate interiors are deforming radially as predicted by three postglacial rebound models and an estimate of the velocity of ce determined assuming that parts of plate interiors neither beneath nor along the margins of the late pleistocene ice sheets are not deforming laterally the velocity of ce equals within uncertainties probability greater than 5 per cent the velocity of cm in itrf2000 the velocity of ce differs significantly 0 05 per cent probability from the velocity of cm in itrf2005 earth s reference frame and we believe itrf s should be defined with the tightly constrained velocity of ce not with the poorly constrained velocity of cm because ce is believed to be moving relative to cm no faster than 0 5 mm yr 1 the velocity of ce estimated in this study is likely to be nearer the true velocity of cm than is the velocity of cm estimated using slr

the influence of conduit processes on changes in style of basaltic plinian eruptions tarawera 1886 and etna 122 bc basaltic volcanism is most typically thought to produce effusion of lava with the most explosive manifestations ranging from mild strombolian activity to more energetic fire fountain eruptions however some basaltic eruptions are now recognized as extremely violent i e generating widespread phreatomagmatic subplinian and plinian fall deposits we focus here on the influence of conduit processes especially partial open system degassing in triggering abrupt changes in style and intensity that occurred during two examples of basaltic plinian volcanism we use the 1886 eruption of tarawera new zealand the youngest known basaltic plinian eruption and the only one for which there are detailed written eyewitness accounts and the well documented 122 bc eruption of mount etna italy and present new grain size and vesicularity data from the proximal deposits these data show that even during extremely powerful basaltic eruptions conduit processes play a critical role in modifying the form of the eruptions even with very high discharge and presumably ascent rates partial open system behaviour of basaltic melts becomes a critical factor that leads to development of domains of largely stagnant and outgassed melt that restricts the effective radius of the conduit the exact path taken in the waning stages of the eruptions varied in response to factors which included conduit geometry efficiency and extent of outgassing and availability of ground water but a relatively abrupt cessation to sustained high intensity discharge was an inevitable consequence of the degassing processes

ongoing drought induced uplift in the western united states the western united states has been experiencing severe drought since 2013 the solid earth response to the accompanying loss of surface and near surface water mass should be a broad region of uplift we use seasonally adjusted time series from continuously operating gps stations to measure this uplift which we invert to estimate mass loss the median uplift is 4 mm with values up to 15 mm in california s mountains the associated pattern of mass loss which ranges up to 50 cm of water equivalent is consistent with observed decreases in precipitation and streamflow we estimate the total deficit to be about 240 gt equivalent to a 10 cm layer of water over the entire region or the annual mass loss from the greenland ice sheet

interpretation of vitrinite reflectance depth profiles in the northern denison trough bowen basin australia abstract the denison trough bowen basin australia is a mature hydrocarbon province that contains permian to triassic coal and gas bearing sediments deposited in deltaic to shallow marine shelf conditions the sandstone reservoirs of the permian aldebaran sandstone freitag formation and catherine sandstone of the northern denison trough ndt were evaluated for their co2 storage potential as part of the queensland government s zerogen co2 capture and storage project which found that diagenetic processes acting on the sandstones have resulted in poor permeability and reduced porosity making them unsuitable for large scale injection and storage in this area to better understand the factors acting to degrade these reservoirs the purpose of the current study was to establish a thermal maturity framework for the permian sandstone reservoirs of the northern denison trough based on vitrinite reflectance measurements of coals and rock eval analysis of coals and shales from the aldebaran sandstone through to the catherine sandstone mean maximum vitrinite reflectance of coals rmax ranges from 0 55 to 0 93 and estimated maximum burial temperatures calculated from vitrinite reflectance fall between 83 oc 125 oc calculation of palaeotemperatures from vitrinite reflectance data has been hampered by inversions of depth reflectance profiles at the top of the aldebaran sandstone and scatter in vitrinite reflectance data this has been attributed to depositional effects including the major marine flooding surfaces at the top of the aldebaran sandstone that have affected vitrinite reflectance evolution in the ndt producing low reflecting fluorescing perhydrous vitrinite near marine flooding surfaces and subhydrous vitrinite when oxidising conditions prevailed a vitrinite reflectance difference of up to 0 2 rmax is detected in an isometamorphic coal an equivalent palaeotemperature difference of approximately 19 oc the abundance of perhydrous vitrinite has resulted in largely suppressed vitrinite reflectance throughout the examined permian interval in the northern denison trough and the presence of both perhydrous and subhydrous vitrinite introduces an error in palaeotemperature calculation in high volatile bituminous coals rock eval analysis provides supporting and calibrating maturity data tmax over the studied interval ranges from 421 oc to 447 oc generating a positive broadly linear correlation between rmax and tmax that is applicable specifically to the ndt tmax suppression was also detected in perhydrous coals hydrogen index serves to evaluate the level of vitrinite reflectance suppression through an inverse relationship between the two parameters the rock eval data confirms the oil generation potential of coals in the ndt while shales associated with the same stratigraphic intervals have lower hydrocarbon generation potential this study brings new insights into the thermal maturity framework in the ndt and highlights the importance of reliable vitrinite reflectance data for calculation of maximum burial temperatures particularly in underexplored or frontier areas

complex proximal deposition during the plinian eruptions of 1912 at novarupta alaska proximal 3 km deposits from episodes ii and iii of the 60 h long novarupta 1912 eruption exhibit a very complex stratigraphy the result of at least four transport regimes and diverse depositional mechanisms they contrast with the relatively simple stratigraphy and inferred emplacement mechanisms for the previously documented better known medial distal fall deposits and the valley of ten thousand smokes ignimbrite the proximal products include alternations and mixtures of both locally and regionally dispersed fall ejecta and numerous thin complex deposits of pyroclastic density currents pdcs with no regional analogs the locally dispersed component of the fall deposits forms sector confined wedges of material whose thicknesses halve radially from and concentrically about the vent over distances of 100 300 m cf several kilometers for the medial distal fall deposits this locally dispersed fall material and many of the associated pdc deposits is rich in andesitic and banded pumices and richer in shallow derived wall rock lithics in comparison with the coeval medial fall units of almost entirely dacitic composition there are no marked contrasts in grain size in the near vent deposits however between locally and widely dispersed beds and all samples of the proximal fall deposits plot as a simple continuation of grain size trends for medial distal samples associated pdc deposits form a spectrum of facies from fines poor avalanched beds through thin bedded landscape mantling beds to channelized lobes of pumice block rich ignimbrite the origins of the novarupta near vent deposits are considered within a spectrum of four transport regimes 1 sustained buoyant plume 2 fountaining with co current flow 3 fountaining with counter current flow and 4 direct lateral ejection the novarupta deposits suggest a model where buoyant stable regime 1 plumes characterized most of episodes ii and iii but were accompanied by transient and variable partitioning of clasts into the other three regimes only one short period of vent blockage and cessation of the plinian plume occurred separating episodes ii and iii which was followed by a single pdc interpreted as an overpressured blast involving direct lateral ejection in contrast regimes 2 and 3 were reflected by spasmodic sedimentation from the margins of the jet and perhaps lower plume which were being strongly affected by short lived instabilities these instabilities in turn are inferred to be associated with heterogeneities in the mixture of gas and pyroclasts emerging from the vent of the parameters that control explosive eruptive behavior only such sudden and asymmetrical changes in the particle concentration could operate on time scales sufficiently short to explain the rapid changes in the proximal 1912 products

river basin flood potential inferred using grace gravity observations at several months lead time whether a precipitation event leads to flooding depends on the watershed s wetness a case study of the 2011 missouri river floods demonstrates that the predisposition of a river basin to flooding can be inferred from satellite based gravity data months in advance

complex proximal sedimentation from plinian plumes the example of tarawera 1886 the 1886 eruption of tarawera new zealand was unusual for a plinian eruption because it involved entirely basaltic magma originated in a 17 km long fissure and produced extremely overthickened proximal deposits with a complex geometry this study focuses on an 8 km long segment cutting across mount tarawera where over 50 point source vents were active during the 5 5 h eruption a detailed characterization of the proximal deposits is developed and used to interpret the range of styles and intensities of the vents including changes with time we identify the four vents that contributed most heavily to the plinian fall and evaluate the extent to which current volcanic plume models are compatible with the depositional patterns at tarawera three proximal units are mapped that have phreatomagmatic magmatic and phreatomagmatic characteristics respectively within the magmatic proximal unit beds of like character are grouped into packages and delineated on scaled cross sections package dispersal is quantified by measuring the linear thickness half distance t1 2 in the planes of the fissure walls most packages have localized dispersals low t1 2 indicating that strombolian style activity dominated most vents the more widely dispersed packages high t1 2 reflect contributions from additional transport regimes that were more vigorous but still contributed considerable material to the proximal region we conclude that the geometry of the observed proximal deposits requires three modes of fall transport 1 fallout from the upper portions of the plinian plumes produced principally by vents in four craters 2 sedimentation from the margins of the lower portions of the plinian plumes including the jets and possibly the lower convective regions and 3 ejection by weak strombolian style explosions from vents that did not contribute significant volumes of particles to the high plume we suggest that the curvature of the velocity profile across the jet region of each plume 1 4 km height was important and that the lower velocity at the margins allowed proximal deposition of a large volume of material with a wide grain size range

satellite observations and interpretation of the 1991 mount pinatubo eruption plumes we demonstrate the use of hourly geostationary meteorological satellite gms and noaa polar orbiting advanced very high resolution radiometer avhrr satellite images of the june 1991 mount pinatubo volcanic eruption plumes in providing details of the timing changing eruptive style and umbrella plume movement and dynamics a chronology of explosive events which culminated in a 9 hour long climactic phase on june 15 has been determined from satellite data and favorably compared to ground based and other ancillary information maximum eruption column altitudes of 40 km and column top undercooling in excess of 55 c below the ambient atmosphere occurred during the climactic phase phases dominated by plinian versus coignimbrite eruptive plumes can be distinguished on the images analysis of the spreading umbrella plume during the climactic phase suggests that over the first 4 5 hours the plume spread laterally as a gravitational intrusion before becoming advected in the ambient winds we compare the rate of plume growth to a model of a radially symmetric continuously fed intrusion to describe the motion the rate of plume growth shows good agreement with this simple model for the first 4 5 hours from column top heights we determine eruption rates and obtain an independent estimate of the total volume of magma erupted from june 12 16 of 5 5 km3 dense rock equivalent dre in good agreement with an independent estimate of the total eruptive volume made from deposits on land and submarine ash fall of up to 5 3 km3 dre we also show that secondary explosions in the pinatubo ignimbrite deposits produced ash plumes reaching altitudes as high as 19 km in september 1991 this study indicates that realistic interpretation and monitoring of major eruption plumes can be accomplished by analysis of high temporal resolution satellite data

effects of igneous intrusions on coalbed methane potential gunnedah basin australia abstract the gunnedah basin nsw australia contains more than 500 gt of coal and has been the subject of recent coalbed methane exploration large areas of the basin contain igneous intrusions and large areas of coal have been heat affected as a consequence a detailed study has been undertaken of coal seams intersected in a cored coalbed methane exploration drillhole in which two sill form igneous intrusions are present comparisons are made between coals that are unaltered and coals that have been heat affected using petrographic and chemical data coal seam gas desorption data and gas chemical analysis data results demonstrate that the two igneous intrusions have had a very positive effect on coalbed methane development the gas content in a number of heat affected coal seams within thermal aureoles above and below the sills is substantially higher than in adjacent unaffected coal seams in addition the intrusions have had little effect on gas quality the coals in the heat affected zone were found to contain gas with approximately 95 methane the coals in the thermal aureoles were found under the microscope to contain characteristic micropores and slits which collectively may serve to enhance gas adsorption capacity permeability and gas desorption gas contents below each of the sills is substantially higher than above the sill confirming earlier results that the sills appear to have acted as a reservoir seal during and for some time after intrusion the background coal rank in acm yannergee ddh 1 is in the high volatile bituminous range the igneous intrusions have resulted in an increase in rank such that large areas of coal have moved into the optimal thermogenic gas generation window this rank increase has affected a major part of the coal bearing sequence

reconstruction of eruption column dynamics on the basis of grain size of tephra fall deposits 2 application to the pinatubo 1991 eruption the granulometric methods to reconstruct eruption column dynamics developed in paper 1 are applied to the tephra fall deposits of the climactic plinian phase of the 1991 eruption at pinatubo the tephra fall deposits are composed of two units layer c1 which corresponds to the first half of the climactic phase and layer c2 the second half the granulometric estimates of the expansion rate of the umbrella cloud for layers c1 and c2 are 7 1010 and 3 1010 m3 s respectively which agree with the observations of satellite images these estimates indicate that the magma discharge rate decreased from 9 108 to 3 108 kg s during the eruption the grain size distribution at the top of the eruption column is characterized by depletion of coarse clasts suggesting a distinct deceleration in the gas thrust region down to several tens of meters per second particularly during the second half of the climactic phase the total amount of layers c1 and c2 is estimated to be 3 1012 kg and the very fine particles which did not deposit in the accessible on land area may occupy up to 60 of the total ejecta the effective duration of the eruption estimated by the present methods a few hours or less is substantially shorter than a previous estimate from the real time observation based on infrasonic data 10 hours this discrepancy may be attributed to the overestimation of the magma discharge rate due to the entrainment of the ambient air at the cloud top and or to the underestimation of the total amount of the ejecta due to the effect of the contemporaneous plinian activity and generation of pyroclastic flows it is also suggested that the intensity of eruption was fluctuating with time so that the instantaneous observations such as cloud height in satellite images do not always show a quantitative agreement with the time averaged features predicted by the present methods

the size distribution of pyroclasts and the fragmentation sequence in explosive volcanic eruptions in an explosive eruption the atmospheric column dynamics depend strongly on the mass fraction of gas in the erupting mixture which is fixed by fragmentation in the volcanic conduit at fragmentation gas present in vesicular magmatic liquid gets partitioned between a continuous phase separating magma clasts and a dispersed phase in individual bubbles within the clasts as regards flow behavior it is the former continuous gas phase which matters and we show that its amount is determined by the fragment size analysis of 25 fall deposits and 37 flow deposits demonstrates that ash and pumice populations follow a power law size distribution such that n the number of fragments with radii larger than r is given by n r d d values range from 2 9 to 3 9 and are always larger than 3 0 in fall deposits d values for pyroclastic flow deposits are systematically smaller than those of fall deposits we show that at fragmentation the amount of continuous gas phase is an increasing function of the d value large d values cannot be attributed to a single fragmentation event and are due to secondary fragmentation processes laboratory experiments on bubbly magma and on solid pumice samples demonstrate that primary breakup leads to d values of 2 5 0 1 and that repeated fragment collisions act to increase the d value a model for size dependent refragmentation accounts for the observations we propose that in a volcanic conduit fragmentation proceeds as a sequence of events primary breakup releases a small amount of gas and is followed by fragment collisions due to refragmentation and decompression both the mass and volume fractions of continuous gas increase the final d value and hence the mass fraction of continuous gas at the vent depends on the time spent between primary fragmentation and eruption out of the vent

the angular velocities of the plates and the velocity of earth s centre from space geodesy summary using space geodetic observations from four techniques gps vlbi slr and doris we simultaneously estimate the angular velocities of 11 major plates and the velocity of earth s centre we call this set of relative plate angular velocities geodvel for geodesy velocity plate angular velocities depend on the estimate of the velocity of earth s centre and on the assignment of sites to plates most geodetic estimates of the angular velocities of the plates are determined assuming that earth s centre is fixed in an international terrestrial reference frame itrf and are therefore subject to errors in the estimate of the velocity of earth s centre in itrf2005 and itrf2000 earth s centre is the centre of mass of earth oceans and atmosphere cm the velocity of cm is estimated by slr observation of lageos s orbit herein we define earth s centre to be the centre of mass of solid earth ce we determine the velocity of ce by assuming that the portions of plate interiors not near the late pleistocene ice sheets move laterally as if they were part of a rigid spherical cap the geodvel estimate of the velocity of ce is likely nearer the true velocity of cm than are the itrf2005 and itrf2000 estimates because 1 no phenomena can sustain a significant velocity between cm and ce 2 the plates are indeed nearly rigid aside from vertical motion and 3 the velocity of cm differs between itrf2005 and itrf2000 by an unacceptably large speed of 1 8 mm yr 1 the velocity of earth s centre in geodvel lies between that of itrf2000 and that of itrf2005 with the distance from itrf2005 being about twice that from itrf2000 because the geodvel estimates of uncertainties in plate angular velocities account for uncertainty in the velocity of earth s centre they are more realistic than prior estimates of uncertainties geodvel differs significantly from all prior global sets of relative plate angular velocities determined from space geodesy for example the 95 per cent confidence limits for the angular velocities of geodvel exclude those of revel sella et al for 34 of the 36 plate pairs that can be formed between any two of the nine plates with the best constrained motion the median angular velocity vector difference between geodvel and revel is 0 028 myr 1 which is up to 3 1 mm yr 1 on earth s surface geodvel differs the least from the geodetic angular velocities that altamimi et al determine from itrf2005 geodvel s 95 per cent confidence limits exclude 11 of 36 angular velocities of altamimi et al and the median difference is 0 015 myr 1 geodvel differs significantly from nearly all relative plate angular velocities averaged over the past few million years including those of nuvel 1a the difference of geodvel from updated 3 2 myr angular velocities is statistically significant for all but two of 36 angular velocities with a median difference of 0 063 myr 1 across spreading centres eight have slowed down while only two have sped up we conclude that plate angular velocities over the past few decades differ significantly from the corresponding angular velocity averaged over the past 3 2 myr

sedimentation of tephra by volcanic plumes i theory and its comparison with a study of the fogo a plinian deposit sao miguel azores sedimentation of ejecta from volcanic plumes has been studied as a function of distance from the source in the fogo a plinian deposit sao miguel azores the fogo a trachytic pumice deposit is reversely graded and can be divided into two parts on the basis of pumice colour abundance of syenite accessory lithic clasts and distribution the lower syenite poor part was dispersed to the south and was clearly influenced by wind the upper syenite rich part is coarsegrained and has a nearly symmetrical distribution around the vent elongation of isopachs to the east indicate a weak wind influence the grain size variations of lithic and crystal components in the upper coarse part were studied total accumulation and accumulation per unit area expressed in kg m2 show good fits to a gaussian function at distances greater than 7 km for grain diameters less than 2 cm these results agree with a theoretical model for a radially spreading turbulent current moving over a quiescent fluid the gaussian coefficient is shown to be a function of grain size and the flow rate of material into the umbrella region of the eruption column the coefficient is therefore also a function of column height the column height deduced from these data is 21 km which is in broad agrrement with the column height of 27 km deduced from maximum clast dispersal using the method of carey and sparks 1986 the accumulation of clasts larger than 2 cm agrees with a theory for the fallout of clasts from the margins of the ascending eruption column which treats the plume as a succession of large eddies that decrease their mass of particles as an exponential function of time calculations are also presented for the influence of the radial inflow of surrounding air into the column on the deposition of clasts these calculations constrain the wind speed during the later part of the fogo a eruption to be at most a few metres per second the study has allowed four different dynamic categories of clast behaviour to be recognised in eruption columns

sedimentation from gravity currents generated by turbulent plumes sedimentation from radially spreading gravity currents generated at the top of ascending sediment laden plumes is described by a model which assumes that sediment is dispersed homogeneously by turbulence in the gravity current resulting in an exponential decrease in the concentration of sediment with time as particles settle out of the lower boundary of the current for radial spreading this model predicts a gaussian distribution of sediment accumulation away from the source with an exponential constant b which depends on flow rate q and particle settling velocity v b nv q in the experiments described sedimentation occurs from gravity currents generated by ascent of buoyant particle laden plumes of fresh water in a tank of salty water the sediment accumulation shows close agreement with the theoretical model and the gaussian decay constant b can be determined from a maximum in the accumulated mass of sediment per unit distance and from the slope of the line in s s0 br2 where r is the radial distance s is the sediment mass flux per unit area and s0 is the value of s at r 0 data from the dispersal of volcanic ejecta from a large c 24 km high plinian eruption column in the azores also show good agreement with the theory confirming that it is general and independent of scale and the nature of the fluid the experimental data also show a change in sedimentation behaviour at distances from the source corresponding to the corner of the plume where it diverts into a lateral gravity current and there is an abrupt decrease in vertical velocity sedimentation of coarse grain sizes between the source and the corner occurs from the inclined plume margins and does not behave as predicted by the theoretical model

sustained water loss in california s mountain ranges during severe drought from 2012 to 2015 inferred from gps drought struck california during 7 of the 9 years from 2007 to 2015 reducing the state s available water resources pumping of central valley groundwater has produced spectacular land subsidence uplift of the adjacent sierra nevada mountains has been proposed to be either tectonic uplift or solid earth s elastic response to unloading of central valley groundwater we find that of the 24 mm of uplift of the sierra nevada from october 2011 to october 2015 just 5 mm is produced by central valley groundwater loss less than 2 mm is tectonic uplift and 17 mm is solid earth s elastic response to water loss in the sierra nevada we invert gps vertical displacements recording solid earth s elastic response to infer changes in water storage across the western u s from january 2006 to october 2017 we find water changes to be sustained over periods of drought or heavy precipitation the sierra nevada lost 15 19 km3 of water during drought from october 2006 to october 2009 gained 18 14 km3 of water during heavy precipitation from october 2009 to october 2011 and lost 45 21 km3 of water during severe drought from october 2011 to october 2015 95 confidence limits such large changes are not in hydrology models snow accumulation in october is negligible and long term soil moisture change is small we infer that there must be large loss of either deep soil moisture or groundwater in river alluvium and in crystalline basement in the sierra nevada the results suggest there to be parching of water in the ground during the summer of years of drought and seeping of melting snow into the sierra nevada in the spring of years of heavy precipitation

grain size characteristics of experimental pyroclasts of 1980 mount st helens cryptodome dacite effects of pressure drop and temperature using the fragmentation bomb we analysed the effects of temperature and pressure drop on the grain size characteristics of experimentally produced pyroclasts experiments performed on vesicular samples of grey dacite of the 1980 mount st helens cryptodome at t 20 900 c and initial pressure differential up to 18 5 mpa provide clear evidence of the influence of these physical conditions upon fragment size and character cylindrical dacite samples diameter 17 mm length 50 mm are placed in the high pressure temperature section of the apparatus heated and saturated by argon gas the disruption of a diaphragm located between the high and low pressure sections of the apparatus initiates the rapid depressurisation of the sample the main results may be summarised as follows 1 increasing tempera ture from 20 to 900 c results in a decrease in the fragmentation threshold value from 9 to 3 mpa and an increase in the median diameter of the experimental pyroclasts these observations imply a decrease in the dynamic tensile strength of dacite at higher temperatures which in turn influences the characteristic size of fragments 2 increasing initial pressure differential yields a decrease of the median diameter thus a higher initial elastic potential energy in the magma generates a higher degree of fragmentation 3 fragments of angular shape are observed from experiments at all investigated temperatures 20 900 c including thereby temperatures significantly higher than the classical dilatometrically or calorimetrically determined glass transition temperature determined for this dacite of 810 c thus brittle response of the dacite is observed under rapid decom pression 4 fragment size distributions do not corre spond to log normal distributions and are more closely described by rosin rammler distributions with a de crease of temperature and increase of the initial pressure differential fragment size distributions approach a rosin rammler distribution dependence 5 microscopic and grain size comparison of particle characteristics of ex perimental and natural fragments of the 1980 mount st helens cryptodome dacite demonstrate similar median diameters and shapes

an automatic procedure to forecast tephra fallout tephra fallout constitutes a serious threat to communities around active volcanoes reliable short term forecasts represent a valuable aid for scientists and civil authorities to mitigate the effects of fallout on the surrounding areas during an episode of crisis we present a platform independent automatic procedure with the aim to daily forecast transport and deposition of volcanic particles the procedure builds on a series of programs and interfaces that automate the data flow and the execution and subsequent postprocess of fallout models firstly the procedure downloads regional meteorological forecasts for the area and time interval of interest filters and converts data from its native format and runs the calmet diagnostic model to obtain the wind field and other micro meteorological variables on a finer local scale 3 d grid defined by the user secondly it assesses the distribution of mass along the eruptive column commonly by means of the radial averaged buoyant plume equations depending on the prognostic wind field and on the conditions at the vent granulometry mass eruption rate etc all these data serve as input for the fallout models the initial version of the procedure includes only two eulerian models hazmap and fall3d the latter available as serial and parallel implementations however the procedure is designed to incorporate easily other models in a near future with minor modifications on the model source code the last step is to postprocess the outcomes of models to obtain maps written in standard file formats these maps contain plots of relevant quantities such as predicted ground load expected deposit thickness and for the case of or 3 d models concentration on air or flight safety concentration thresholds