boron lithium relationships in rhyolites and associated thermal waters of young silicic calderas with comments on incompatible element behaviour abstract this study had three goals 1 1 to study b distribution in a rhyolitic volcanic sequence already extensively investigated for other elements 2 2 to interpret the joint behaviour of b and li during the interaction of such rocks with subsurface waters 3 3 to assess the manner in which water affects the behaviour of incompatible elements such as b and gd new b gd and sm analyses have been made on a suite of yellowstone rhyolites including fresh and partially devitrified glassy obsidian from surface exposures of several flows drill core of increasing degrees of alteration in the biscuit basin flow and two drill cores from other flows within the biscuit basin flow the sm and gd concentrations remain rather constant 9 12 and 8 10 ppm respectively and behave conservatively independent of alteration boron decreases from about 10 to 3 ppm with progressive alteration and li increases from about 40 ppm by a factor of 2 3 in the most altered rocks thermal waters reflect leaching from the fresh rocks but contain much less li than b b li 3 compared with 0 8 in fresh obsidian retention of li was favoured by abundant illitic alteration obsidians from the valles and long valley calderas show greater li loss during alteration all the rhyolitic rocks lose b during aqueous alteration the waters acquire both b and li but proportionately much more b natural waters of all kinds including those from the three calderas show six orders of magnitude range in aqueous b and li with a high degree of linear correlation and an average ratio b li essentially constant at 4 0 the linearity mainly expresses processes of dilution and concentration reactions specific to b or li engender waters with deviating b li the patterns of sm gd b li variation in rocks exemplify two kinds of behaviour in petrological processes with no hydrous phase lunar rocks mantle fresh seafloor basalt the lower continental crust these elements are incompatible and behave similarly when an aqueous phase is present b and li behave independently of sm and gd

a new look at the saturn system the voyager 2 images voyager 2 photography has complemented that of voyager i in revealing many additional characteristics of saturn and its satellites and rings saturn s atmosphere contains persistent oval cloud features reminiscent of features on jupiter smaller irregular features track out a pattern of zonal winds that is symmetric about saturn s equator and appears to extend to great depth winds are predominantly eastward and reach 500 meters per second at the equator titan has several haze layers with significantly varying optical properties and a northern polar collar that is dark at short wavelengths several satellites have been photographed at substantially improved resolution enceladus surface ranges from old densely cratered terrain to relatively young uncratered plains crossed by grooves and faults tethys has a crater 400 kilometers in diameter whose floor has domed to match tethys surface curvature and a deep trench that extends at least 270 around tethys circumference hyperion is cratered and irregular in shape iapetus bright trailing hemisphere includes several dark floored craters and phoebe has a very low albedo and rotates in the direction opposite to that of its orbital revolution with a period of 9 hours within saturn s rings the birth of a spoke has been observed and surprising azimuthal and time variability is found in the ringlet structure of the outer b ring these observations lead to speculations about saturn s internal structure and about the collisional and thermal history of the rings and satellites

origins of the ice contact stratified ridges eskers of ireland abstract an extensive system of ridged landforms composed of ice contact stratified sediment was deposited in the central lowland of ireland during the most recent deglaciation 18 000 bp the ridges have been interpreted by others as deposits of an ice sheet drainage system i e eskers and as such have been used with other data to reconstruct the deglacial history the traditional deglaciation model shows systematic retreat of ice from south to north our study which involves an analysis of the ridged landforms using lithofacies sedimentary structures and paleocurrent data in conjunction with the geomorphology indicates that the pattern and nature of the ridges are not compatible with this model and support a new model of deglaciation warren 1991 in which the esker system fo med in an interlobate area during the simultaneous shrinking of two main glacial outflow centers an extensive lake system developed in the lowland between the two outflow centers ridges formed both perpendicular and parallel to ice margins involved both active and stagnating ice are both continuous and segmented beaded and were deposited in subaqueous and subaerial environments almost all of the ridges are associated with lacustrine sediments ice contact ridges are polygenetic and a genetic classification is proposed those that formed perpendicular to the ice margin are termed eskers those that formed parallel are termed moraines distinction between esker types continuous or beaded subglacial tunnel fills fluvial ice channel fills and subaqueous fans and moraine types s baqueous or subaerial is crucial to a reconstruction of the mode and pattern of deglaciation in the central irish lowlands

regression of martian north polar cap 1990 1997 hubble space telescope observations abstract hubble space telescope imaging of mars from december 13 1990 through april 17 1997 has resulted in the synoptic monitoring of parts of four consecutive martian north polar cap regressional cycles spanningls 335 65 tols 144 56 the 1990 1993 observations were obtained with the wide field planetary camera 1 wfpc1 instrument while subsequent observations from 1994 to 1997 were obtained with the improved optics of the wide field planetary camera 2 wfpc2 mars observations were obtained from the ultraviolet 218 nm to the near infrared 1042 nm which has allowed us to constrain the effects of clouds and dust particulates on cap edge measurements hst observations of the polar cap regressions afterls 0 are fairly consistent from year to year with some variations possible beforels 0 the 1991 observations atls 35 25 andls 59 88 in the longitude range 270 280 possibly support a standstill in cap retreat at a latitude 70 n the standstill in cap retreat reported in previous years at a latitude 67 n was not observed in 1992 1997 comparison with previous ground based and spacecraft observations suggests that interannual variations may be significant they may be due to interannual atmospheric changes such as global dust storm activity lambert albedos of the north polar cap in red and violet bandpasses are similar to those reported before

hubble space telescope observations of the martian aphelion cloud belt prior to the pathfinder mission seasonal and interannual variations the presence of a globally extant equatorial belt of water ice clouds on mars is quantitatively investigated using data from three seasons of our hubble space telescope synoptic monitoring program 1993 1997 a subset of the 1996 1997 images covers the landing site of the mars pathfinder including a set of images taken after touchdown using multicolor imaging from the wide field planetary camera and the wide field planetary camera 2 we characterize both water ice cloud and dust optical depths as a function of latitude at several local times for each observing epoch the analysis technique models calibrated data using a multiple scattering radiative transfer code our results support the initial results of clancy et al 1996a regarding changes between the aphelion and perihelion climate of mars and provide a more detailed look at the development and decay of the cloud belt comparing our dust optical depths to those of the viking landers for the same seasons we note a trend toward lower dust loading in late northern winter and in spring our observations of the pathfinder site in july 1997 reveal a dust opacity in good agreement with that reported by pathfinder smith et al 1997b in addition the serendipitous occurrence of a dust storm in valles marineris in late june 1997 allows us to derive a set of dust single scattering albedos for use in more accurately modeling the dust s radiative properties and effects

saturn s zonal winds at cloud level we present an analysis of new cloud motion measurements in saturn s atmosphere from voyager 1 and 2 images and define a nominal zonal wind velocity vs latitude profile for the cloud top level that can be used as reference for the upcoming cassini mission improvements over previous studies include i twice the number of wind vectors used ii independent measurements of cloud tracers iii extended latitudinal coverage iv strict error control and evaluation and v a new zonal averaging methodology mean zonal wind velocities are given for the latitude range 81 to 71 planetographic in steps of 0 5 with a gap between 0 and 10 due to ring shadowing this research also includes the study of the morphology and motions of cloud systems in the equator and in the southern hemisphere which have not been described previously we give an ephemeris motion equation for several long lived features that could be observable if they survive until cassini arrives on saturn the long term behavior of the zonal wind profile is studied by comparing it with a complete set of wind velocities compiled from historical and modern ground based and hst observations significant changes are noted in the equatorial jet between this set and the nominal voyager profile we discuss in detail the possible origin for such differences

the development of polygonal fault systems by syneresis of colloidal sediments abstract polygonal fault systems occur in numerous sedimentary basins worldwide are generally located on passive margins in onlap fill units and tend to comprise the finest grained sediments in this geological setting these fault systems have been most thoroughly described in the central north sea basin and the detailed structure shows a significant correlation with lithological variations both vertically and laterally extension measured in stacked decoupled tiers of polygonal faults correlates positively with both clay fraction and smectite content lateral facies variations are also observed and indicate that time equivalent sequences upslope from the smectite rich polygonally faulted sediments are coarse grained clay poor and undeformed this leads us to believe that the structure and geometry of the fault system are controlled by the colloidal nature of the sediments and that the volumetric contraction measured on seismic sections can be accounted for by syneresis of colloidal smectitic gels during early compaction syneresis results from the spontaneous contraction of a sedimentary gel without evaporation of the constituent pore fluid this process occurs due to the domination of interparticle attractive forces in marine clays dependent on environment and is governed by the change of gel permeability and viscosity with progressive compaction the process of syneresis can account for a number of structural features observed within the fault systems such as tiers of faults the location of maximum fault throw and growth components at upper fault tips as such this paper represents the first attempt to correlate microscale properties of clay rich sediments to their macroscale seismic character

uranus southern circulation revealed by voyager 2 unique characteristics abstract revised calibration and processing of 1600 images of uranus by voyager 2 revealed dozens of discrete features south of 45 latitude where only a single feature was known from voyager images and none has been seen since tracking of these features over five weeks defined the southern rotational profile of uranus with high accuracy and no significant gap the profile has kinks unlike previous profiles and is strongly asymmetric with respect to the northern profile by sromovsky et al sromovsky l a fry p m hammel h b de pater i rages k a 2012 icarus 220 694 712 the asymmetry is larger than that of all previous data on jovian planets a spot that included the south pole off center rotated with a period of 12 24 h 2 h outside the range of all previous observations of uranus the region between 68 and 59 latitude rotated almost like a solid body with a shear that was about 30 times smaller than typical shears on uranus at lower latitudes features were sheared into tightly wound spirals as voyager watched the zone at 84 latitude was exceptionally bland reflectivity variations were only 18 ppm consistent with a signal to noise ratio estimated at 55 000 the low noise was achieved by smoothing over dozens of pixels per image and averaging 1600 images the presented data set in eight filters contains rich information about temporal evolution and spectral characteristics of features on uranus that will be the basis for further analysis

book review sedimentary structures their character and physical basis vols i and ii j r l allen developments in sedimentology 30a 30b elsevier amsterdam 1982 vol i xvii 593 pp us 98 00 dfl 245 00 vol ii xiii 663 pp us 104 00 dfl 260 00 hardcovers

the role of vegetation in the formation of anabranching channels in an ephemeral river northern plains arid central australia as the distribution and abundance of vegetation in drylands is often controlled by the greater availability of water along river channels riparian vegetation has the potential to influence significantly dryland river form process and behaviour this paper demonstrates how a small indigenous shrub the inland teatree melaleuca glomerata influences the formation and maintenance of anabranching channels in a reach of the ephemeral marshall river northern plains arid central australia here the marshall is characterized by ridge form anabranching where water and sediment are routed through subparallel multiple channels of variable size which occur within a typically straight channel train channels are separated by channel train ridges narrow flow aligned vegetated features or by wider islands by providing a substantial element of boundary roughness dense stands of teatrees growing on channel beds or atop the ridges and islands influence flow velocities flow depths and sediment transport resulting in flow diversion bank and floodplain erosion and especially sediment deposition ridges and islands represent a continuum of forms and their formation and development can be divided into a three stage sequence involving teatree growth and alluvial sedimentation 1 teatrees colonize a flat sandy channel bed initiating the formation of ridges by lee side accretion individual ridges grow laterally vertically and longitudinally and maintain a geometrically similar streamlined lemniscate form that presents minimum drag 2 individual ridges grow in size and interact with neighbouring ridges causing the lemniscate forms to become distorted ridges in the lee of other ridges tend to be protected from the erosive effects of floods and survive whereas individual teatrees or small ridges exposed to flow concentrated between larger ridges tend to be removed 3 ridges lengthen and coalesce with downstream ridges eventually subdividing the channel train into well defined anabranches this sequence turns a channel initially obstructed with dense and chaotic stands of teatrees into a well organized system of ridge form anabranches in the moderate to low gradient marshall river which is colonized by an abundance of within channel vegetation and subject to declining downstream discharges this helps to minimize flow resistance thereby maintaining an efficient water and sediment flux copyright 2000 john wiley sons ltd

saturn s cloud structure and temporal evolution from ten years of hubble space telescope images 1994 2003 abstract we present a study of the vertical structure of clouds and hazes in the upper atmosphere of saturn s southern hemisphere during 1994 2003 about one third of a saturn year based on hubble space telescope images the photometrically calibrated wfpc2 images cover the spectral region between the near uv 218 255 nm and the near ir 953 1042 nm including the 890 nm methane band using a radiative transfer code we have reproduced the observed center to limb variations in absolute reflectivity at selected latitudes which allowed us to characterize the vertical structure of the entire hemisphere during this period a model atmosphere with two haze layers has been used to study the variation of hazes with latitude and to characterize their temporal changes both hazes are located above a thick cloud putatively composed of ammonia ice an upper thin haze in the stratosphere between 1 and 10 mbar is found to be persistent and formed by small particles radii 0 2 m the lower thicker haze close to the tropopause level shows a strong latitudinal dependence in its optical thickness typically 20 40 at the equator but 5 at the pole at 814 nm this tropospheric haze is blue absorbent and extends from 50 to 100 mbar to about 400 mbar both hazes show temporal variability but at different time scales first there is a tendency for the optical thickness of the stratospheric haze to increase at all latitudes as insolation increases second the tropospheric haze shows mid term changes over time scales from months to 1 2 years in its optical thickness typically by a factor of 2 such changes always occur within a rather narrow latitude band width 5 10 affecting almost all latitudes but at different times third we detected a long term 10 year decrease in the blue single scattering albedo of the tropospheric haze particles most intense in the equatorial and polar areas long term changes follow seasonal insolation variations smoothly without any apparent delay suggesting photochemical processes that affect the particles optical properties as well as their size in contrast mid term changes are sudden and show various time scales pointing to a dynamical origin

large scale storms in saturn s atmosphere during 1994 large scale storms are rarely observed in saturn s atmosphere but their appearance traces the wind velocity field providing information on the vertical structure of the clouds and on the dynamics of the atmosphere two large scale atmospheric disturbances formed by clouds highly reflective in the visible part of the spectrum were observed on saturn during 1994 an equatorial disturbance with a longitudinal size of 27 000 kilometers drifted in longitude with a velocity of 273 6 meters per second a second disturbance a rapidly evolving convective storm with an initial size 7000 kilometers was observed at 56 degrees south moving with a zonal velocity of 15 5 meters per second

fissure fill and tunnel fill sediments expressions of permafrost and increased hydrostatic pressure a spectacular network of fissure fillings and pipes tunnels cuts quaternary gravelly delta deposits northeast of myvatn precisely on the spreading axis of the north icelandic rift zone the delta was formed in an ice contact lake during deglaciation towards the end of the last glaciation subsequently the lake was drained and permafrost conditions developed in these poorly sorted gravel deposits hydrostatic pressure was transmitted from the adjacent glacier to the non frozen core of the delta beneath the discontinuous permafrost crust and the seasonally frozen active layer owing to increased hydrostatic pressure a network of subhorizontal to vertical fissures was opened along the taliks in these fissures free ground water flow and sediment transport were established tunnel erosion and probably also seepage erosion were associated with these fissures subsequently the fissures and tunnels were filled by laminated fine sediments interbedded with poorly sorted material resulting in the formation of fissure fill sediments and tunnel fill sediments

origin of an esker like ridge erosion or channel fill sedimentology of the monington esker in southwest wales abstract a ridge of stratified gravel and sand near cardigan in southwest wales has previously been interpreted as an esker its sedimentology is exposed in sand pits and consists of cross bedded gravel and sand incised into a complex of climbing ripple cross laminated sand interbedded with silt and clay the succession records the progradation of fluvial channels across a former lake floor there is no clear sedimentological evidence that the sediments were deposited in an ice contact setting and therefore the feature should not be called an esker the interpretation favoured here is that the ridge is an erosional remnant either of a formerly more extensive outwash plain or of a kame terrace deposited when the adjacent valley was filled with dead ice recognition of an esker needs to be based on sedimentology and regional setting as well as on geomorphology

bathymetric and isotopic evidence for a short lived late ordovician glaciation in a greenhouse period the end ordovician glaciation is distinct among phanerozoic glaciations in that co 2 levels were generally high yet major continental ice sheets accumulated on the gondwana supercontinent new oxygen isotopic data indicate substantial changes in sea water temperatures and ice volume coinciding with glacio eustatic changes in sea level reflecting the growth and decay of the gondwana ice cap major glaciation was apparently confined to the hirnantian and was 0 5 1 m y long rather than the 35 m y of earlier estimates carbon isotope values indicate significant changes in carbon cycling as the oceans changed from a state with warm saline bottom waters to a state with cold deep water circulation and then back again we believe that the changes in the carbon cycle effected a reduction in p co 2 levels in the oceans and atmosphere and thus promoted glaciation but were unable to sustain icehouse conditions in a greenhouse world

evidence for rapid sedimentation in a tunnel channel oak ridges moraine southern ontario canada abstract in south central ontario a late wisconsinan regional unconformity consisting of tunnel channels and drumlinized till crops out north of lake ontario the tunnel channels are locally infilled and the unconformity buried by sediment of the oak ridges moraine based on seismic reflection profiling and drillcore the tunnel channels are known to continue beneath the moraine detailed sedimentological analysis of 300 m of continuous core from two drillholes located 7 km apart in subparallel tunnel channels identified three facies the gravel facies is 17 m thick and occurs in only one of the cores it directly overlies the unconformity and may include a number of upward fining units seismic reflection data suggests the gravel forms stacked gravel mesoforms or quasi horizontal gravel layers bed load sheets deposited from fluidal flows along the deep channel axis the graded massive sand facies up to 37 m thick is the most common facies and consists of silty medium sand with minor coarse sand strata are reverse graded normal graded or massive with isolated silt intraclasts and evidence locally for dewatering this facies is interpreted to have been deposited from hyperconcentrated dispersions downflow of a hydraulic jump or major channel confluence the third facies consists of medium scale and small scale cross stratified sand medium scale cross stratification occurs predominantly in the lower 37 m of the core and is interbedded with the graded massive sand facies small scale cross stratified sand is progressively more common upward in core medium and small scale cross stratified sands was deposited respectively by subaqueous dunes and ripples formed in dilute fluid flows the complete succession is interpreted to have been deposited very rapidly within a subglacial tunnel channel before discharge ceased along the channel deposition followed closely and in part coincided with rapid expansion of the channel by erosion in a hydraulic jump or at a major channel confluence along the grounding line of a subglacial lake scour into unconsolidated sediment contributed to the sediment flux and quickly overloaded the flow with suspended sediment which in turn resulted in extremely high rates of sedimentation immediately downflow such depositional conditions support the notion that tunnel channels in the study area formed and or served as conduits for subglacial jokulhlaup discharges and that the laurentide ice sheet most probably did not generally drain by steady state processes but instead by short lived catastrophic events

subglacial water escape structures and till structures slettjokull iceland beyond slettjokull the north part of the ice cap m rdalsjokull south iceland an undulating till plain is dissected by meltwater streams throughout a transect from the ice margin to the 1900 ice marginal moraine a distance of about 1 2 km finely laminated wedge shaped water escape structures wes are present originating in the till and disappearing down ice into the underlying sands and fine gravels a second set of much smaller and deformed black wes occurring within the till has been produced by upward injection into the till as a response to stiffening of the till after dewatering by the downward developing wes at present the toe of the glacier is frozen to its bed and the frozen bed material is more than 2 m thick during the relatively cold period around the turn of the century and until the late 1920s a similar submarginal body of permafrost must have existed the sequence reveals that subglacial meltwater attributed to drainage following the 1918 katla eruption was blocked by a frozen glacier toe causing the formation of water escape structures subsequently glacier flow deformed the substratum and produced the threefold division of the till bed the study has important implications for theories envisaging subglacial floods because it demonstrates that it is very difficult for temperate glaciers with a temporary frozen bed in the toe region to retain subglacial meltwater copyright 1999 john wiley sons ltd

early proterozoic cu au and fe ore deposits associated with regional nacl metasomatism in northern fennoscandia scapolite is widely distributed in 1 9 2 5 ga volcano sedimentary rocks and 1 77 2 2 ga igneous rocks over several hundred square kilometres in northern fennoscandia comprising northern sweden no

temporal behavior of cloud morphologies and motions in saturn s atmosphere saturn s atmosphere displays a variety of temporal changes in its cloud morphology at synoptic and planetary scales hemispheric long term albedo variations which are more pronounced at ultraviolet and blue wavelengths have been well established and are apparently linked to the seasonal insolation cycle short term changes of the order of months have been observed in the spectral reflectivity of the belt zone pattern mainly at mid latitudes some appear to be related to discrete spot activity but for the majority of the changes no such signs of spot activity were detected up to a resolution 2000 km in particular the ribbon structure at 45 n could have been affected by this activity and probably is a transient phenomenon the polar belts at 65 north and south and those at 75 north hexagon and south show a long term stability in their location perhaps for more than a century the most prominent belts located in the equator and the equatorial zone are persistent features of saturn s globe their main changes took place during the development of a rare planetary scale disturbance known as great white spots only five such events have been observed at repetitive regular intervals of about one saturn year since the first report in 1876 and at different latitudes from the equator to 60 n they are probably convective in origin with the seasonal heating of the upper atmosphere acting as a trigger mechanism during its life cycle of 2 3 years the disturbance shows turbulent planetary scale patterns of clouds that might be related to a wave dynamical phenomenon other distinct nonaxisymmetric cloud systems at synoptic scale are very scarce in saturn s atmosphere we observed new isolated features at several latitudes during 1990 and 1991 these spots together with those available from historical records are used as tracers for determining the latitude dependence and time variability of saturn s zonal winds the winds tend to exhibit a long term stability in their latitudinal positions and average wind speed although some significant departures from the zonal mean voyager profile have been detected during the development of the equatorial disturbance in 1990 and 1991

the great white spot and disturbances in saturn s equatorial atmosphere during 1990 a giant storm the great white spot erupted at the end of september 1990 as a localized bright cloud system close to saturn s equator its evolution produced a complex planetary disturbance which affected the whole equatorial region a month later similar spots have appeared approximately once every saturnian year about 30 earth years implying that a seasonal change in solar heating for example may be responsible for their occurrence

shallow water simulations of saturn s giant storms at different latitudes abstract shallow water simulations are used to present a unified study of three major storms on saturn nicknamed as great white spots gws at different latitudes polar 1960 equatorial 1990 and mid latitude 2010 sanchez lavega 2004 sanchez lavega et al 2011 in our model the three gws are initiated by introducing a gaussian function pulse at the latitude of the observed phenomena with controlled horizontal size and amplitude this function represents the convective source that has been observed to trigger the storm a growing disturbance forms when the pulse reacts to ambient winds expanding zonally along the latitude band of the considered domain we then compare the modeled potential vorticity with the cloud field adjusting the model parameters to visually get the closest aspect between simulations and observations simulations of the 2010 gws planetographic latitude 40o zonal velocity of the source 30 m s 1 indicate that the coriolis forces and the wind profile structure shape the disturbance generating as observed a long region to the east of the convective source with a high speed peripheral anticyclonic circulation and a long lived anticyclonic compact vortex accompanied by strong zonal advection on the southern part of the storm forming a turbulent region simulations of the equatorial 1990 gws planetographic latitude 12o 5o zonal velocity of the source 365 400 m s 1 show a different behavior because of the intense eastward jet meridional shear at the equatorial region and low latitude dynamics a round shaped source forms as observed with the rapid growth of a kelvin helmholtz instability on the north side of the source due to advection and to the strong meridional wind shear whereas at the storm latitude the disturbance grows and propagates eastward the storm nucleus is the manifestation of a rossby wave while the eastward propagating planetary scale disturbance is a gravity rossby wave trapped around the equator the simulated 1960 gws disturbance planetographic latitude 56o zonal velocity 4 m s 1 formed a chain of periodic oval spots that mimic the few available observations of the phenomenon for the mid and high latitude storms simulations predict a strong injection of negative relative vorticity due to divergence of the upwelling storm material which may produce large anticyclones on the anticyclonic side of the zonal profile and a quick turbulent expansion on the background cyclonic regions in general simulations indicate that negative relative vorticity injected by storms determines the natural reaction to zonal winds at latitudes where coriolis forces are dominant

vertical cloud structure in saturn s 1990 equatorial storm abstract we present a model study of the evolution of the vertical cloud structure and aerosol optical characteristics of the giant storm that erupted in saturn s atmosphere in september 1990 this analysis is based on the photometric measurements of the reflected intensity of the equatorial region in the optical range 336 890 nm continuum and methane absorption bands that were previously published a sanchez lavegaet al 1994 icarus108 158 168 different stages of the storm evolution are analyzed preoutburst onset and mature october november 1990 and evolved july 1991 good fits between the observations and radiative transfer calculations are found using a three layer model a gas layer a haze layer and a semiinfinite cloud deck two term henyey greenstein and mie phase functions are used for the scattering particles according to the models the main change during the evolution of the disturbance took place in the altitude of the cloud layer cloud tops elevated by 1 2 1 5 scale heights during the onset and mature storm stage relative to the undisturbed atmosphere descending later during the evolved phase by 0 7 scale heights relative to the altitude of the mature clouds the altitude location of the haze layer did not change during the storm development but the single scattering albedo of the haze particles increased significantly during the onset and mature stages in the uv blue wavelengths if the haze particles are modeled as mie spheres their mean radius varied from 0 83 to 0 64 m with real refractive index 1 5 and extreme values of the imaginary index 0 01 370 nm and 0 0005 830 nm

hubble space telescope observations of the 1990 equatorial disturbance on saturn zonal winds and central meridian albedos abstract two sets of hubble space telescope hst data obtained in august 1990 and november 1990 are compared with voyager 1 and 2 data acquired in 1980 and 1981 a rare disturbance developed in the equatorial region of saturn in late september 1990 due to the large equatorial wind shear this disturbance generated inhomogeneous bright cloud structures in the equatorial region that extended to 25 north latitude in november 1990 meridional albedo scans and wind measurements from the voyager northern spring equinox and the hst northern summer observations are compared differences in average zonal winds in the images obtained with the green f547m and the methane f889n filters are interpreted as evidence of vertical shear in the zonal winds longitudinal variations in the equatorial zonal winds are interpreted as evidence of interaction between the storm nucleus generated during the disturbance and the local wind field

hummocky moraine sedimentary record of stagnant laurentide ice sheet lobes resting on soft beds abstract over large areas of the western interior plains of north america hummocky moraine hm formed at the margins of laurentide ice sheet lis lobes that flowed upslope against topographic highs current depositional models argue that hm was deposited supraglacially from stagnant debris rich ice disintegration moraine across southern alberta canada map and outcrop data show that hm is composed of fine grained till as much as 25 m thick containing rafts of soft glaciotectonized bedrock and sediment chaotic non oriented hm commonly passes downslope into weakly oriented hummocks washboard moraine that are transitional to drumlins in topographic lows the same subsurface stratigraphy and till facies is present throughout these landforms and others such as doughnut like rim ridges flat topped moraine plateaux and linear disintegration ridges are identified as belonging to subglacially deposited soft bed terrain this terrain is the record of ice lobes moving over deformation till derived from weakly lithified bentonite rich shale drumlins record continued active ice flow in topographic lows during deglaciation whereas hm was produced below the outer stagnant margins of ice lobes by gravitational loading pressing of remnant dead ice blocks into wet plastic till intervening zones of washboard moraine mark the former boundary of active and stagnant ice and show hybrid drumlins whose streamlined form has been altered by subglacial pressing humdrums below dead ice the presence of hummocky moraine over a very large area of interior north america provides additional support for glaciological models of a soft bedded laurentide ice sheet

ice fracturing during jokulhlaups implications for englacial floodwater routing and outlet development theoretical studies of glacial outburst floods jokulhlaups assume that i intraglacial floodwater is transported efficiently in isolated conduits ii intraglacial conduit enlargement operates proportionally to increasing discharge iii floodwater exits glaciers through pre existing ice marginal outlets and iv the morphology and positioning of outlets remains fixed during flooding direct field observations together with historical jokulhlaup accounts confirm that these theoretical assumptions are not always correct this paper presents new evidence for spatial and temporal changes in intraglacial floodwater routing during jokulhlaups secondly it identifies and explains the mechanisms controlling the position and morphology of supraglacial jokulhlaup outlets and finally it presents a conceptual model of the controls on supraglacial outbursts field observations are presented from two icelandic glaciers skei ararjokull and solheimajokull video footage and aerial photographs taken before during and after the skei ararjokull jokulhlaup and immediately after the solheimajokull jokulhlaup reveal changes in floodwater routing and the positioning and morphology of outlets field observations confirm that glaciers cannot transmit floodwater as efficiently as previously assumed rapid increases in jokulhlaup discharge generate basal hydraulic pressures in excess of ice overburden under these circumstances floodwater can be forced through the surface of glaciers leading to the development of a range of supraglacial outlets the rate of increase in hydraulic pressure strongly influences the type of supraglacial outlet that can develop steady increases in basal hydraulic pressure can retro feed pre existing englacial drainage whereas transient increases in pressure can generate hydraulic fracturing the position and morphology of supraglacial outlets provide important controls on the spatial and temporal impact of flooding the development of supraglacial jokulhlaup outlets provides a new mechanism for rapid englacial debris entrainment

hubble space telescope observations of the 1990 equatorial disturbance on saturn images albedos and limb darkening in september 1990 a major equatorial eruption on saturn produced a disturbance that spread in longitude until it completely girdled the planet we report here on 150 images recorded in six passbands with the wide field planetary camera wf pc aboard the hubble space telescope hst on 17 and 18 november 1990 for comparison we used hst wf pc observations of saturn obtained in three colors on 26 august 1990 before the onset of the disturbance and in six colors on 5 and 6 june 1991 when almost no evidence of the disturbance remained at both of those times the equatorial belt was normal in appearance four of the passbands with mean wavelengths of 336 435 546 and 716 nm were selected for photometric analysis and a patch of the b ring near the central meridian was used for photometric calibration using deconvolved images from all three epochs of observation we measured reflectivities i f of the disk along parallels of latitude as a function of longitudinal distance from the central meridian and also along the central meridian as a function of latitude from 0 to 90 the longitudinal measurements cover essentially the whole visible disk they were made at 1 intervals of planetographic latitude from 0 to 80 and the results are expressed in terms of minnaert coefficients k and minnaert albedos i f 0 we find that the cloud particles associated with the disturbance must differ in character from those that normally make up the visible cloud deck on saturn they were brighter and bluer they had greater limb darkening and their limb darkening was spectrally more neutral the mutual relationship of those properties is such that features which stand out strongly near the meridian fade to invisibility when near the limb

sea floor morphology outside a grounded surging glacier brasvellbreen svalbard abstract acoustical profiling and bottom photography reveal several different sea floor morphological features adjacent to the grounded brasvellbreen glacier on svalbard northwestern barents sea some of the features and their distribution may be closely related to a major glacial surge in 1936 1938 and as such are valuable in identifying former surges in other locations a continuous wide ridge with a characteristic asymmetrical cross section running subparallel to the glacier is the end moraine defining the maximum extent of the surge a large part of the material forming this ridge is most likely rapidly deposited from meltwater during the surge a rhombohedral pattern of smaller mounds inside the ridge is probably an expression of relief in the glacier sole during the surge discontinuous arcuate ridges define local minor oscillations during retreat of the ice at a later stage iceberg plough marks are most frequent seaward of the end moraine their orientation is controlled by the combination of a coastal current offshore katabatic winds and topography superimposed on plough marks are secondary features such as a washboard pattern and striae most likely caused by push up of overconsolidated material during gouging and multi keel icebergs respectively bottom sediments observed in photographs and cores are loose pebbly muds with high variability in clast content resting on overconsolidated material probably basal till mud deposition presently prevails close to the glacier

late ordovician glaciation in southern turkey abstract we present a new survey of several palaeozoic sections in both the taurus range and the border folds that documents typical glacial features including a glacial pavement and striated dropstones halevikdere formation and demonstrates the former presence of an ice sheet in southern and south eastern turkey evidence for the late ashgill hirnantian age of this episode is provided by macro and microfossils found within the glacial formation the extension of ice related deposits into the northernmost part of the arabian platform mardin region implies a much wider distribution of the ordovician ice sheet than was previously believed and strongly suggests that southern turkey lay close to egypt during the lower palaeozoic

early silurian glaciations in brazil abstract the opening of the brazilian paleozoic basins during the late ordovician was followed by a tectonic stabilization in the silurian at the time of the early silurian glaciations deposition of continental sandstones prevailed in the basins offshore environments were present in the amazonas basin and to a smaller extent in the parana basin the ice sheets advanced over fluviatile and littoral sediments except for the south margin of the amazonas basin where the glacial diamictites immediately overlie marine facies the ice produced much meltwater even when advancing and this was probably climatically controlled the ice movements were from the northwest at the northern margin of the amazonas basin and towards the northeast at the southern margin in the parnaiba basin and its outliers the jatoba basin and cariri valley the ice came from southeast and probably also from east further to the south in the parana basin it came from the north and northeast four glaciations have been dated to the early silurian the oldest is dated as latest ashgill and or earliest llandovery in the parana basin as evidenced from tillites in the upper rio ivai and lower vila maria formations including the former iapo formation it is contemporaneous with a glaciation in the cape basin south africa the next glaciation is dated as early middle llandovery gregarius graptolite zone and is present in the amazonas basin and the andean belt and probably also in the parnaiba basin and its outliers the two youngest tillites were widespread in the northern brazilian basins amazonas parnaiba and jatoba basins and cariri valley as well as in the andean belt and are dated as early late llandovery possibly starting already in the late middle llandovery and latest llandovery to earliest wenlock the latter tillite is the most widespread one assuming these glaciations are related to polar positions the apparent migration of the south pole ice cap must have been quite rapid from central north africa in late ashgill towards central brazil in the middle late llandovery the glaciation in the parana basin took place up to 45 from the late ashgillian south pole the cool climate continued during the silurian but no new glaciations are known before latest devonian

temperatures winds and composition in the saturnian system stratospheric temperatures on saturn imply a strong decay of the equatorial winds with altitude if the decrease in winds reported from recent hubble space telescope images is not a temporal change then the features tracked must have been at least 130 kilometers higher than in earlier studies saturn s south polar stratosphere is warmer than predicted from simple radiative models the c h ratio on saturn is seven times solar twice jupiter s saturn s ring temperatures have radial variations down to the smallest scale resolved 100 kilometers diurnal surface temperature variations on phoebe suggest a more porous regolith than on the jovian satellites

saginaw lobe tunnel channels laurentide ice sheet and their significance in south central michigan usa abstract a network of tunnel channels in southern michigan records substantial subglacial meltwater activity beneath the saginaw lobe of the laurentide ice sheet the channels are incompletely filled with outwash contain eskers and in many places crosscut and continue beyond upland ridges previously mapped as recessional moraines the presence of the tunnel channels and drumlins on these upland ridges indicate that the ridges are not recessional moraines instead outwash fans and minor ridges record deglaciation in the area a palimpsest relationship between buried bedrock valleys and tunnel channels records the presence of multiple generations of tunnel channels evidence for a subglacial meltwater sheetflow consists of sheets of boulder gravel in upland 15 km wide with a hummocky upper surface the hummocks transform down flow into erosional remnant drumlins possibly the result of flow acceleration on a negative slope tunnel channels at the distal end of the drumlin swarm suggest collapse of the sheetflow into a channelized flow the tunnel channels then end at the sturgis moraine at the heads of large outwash fans the observed geomorphic relationships between tunnel channels moraines and drumlins in south central michigan are applicable to glacial landform studies elsewhere and indicate the important role of meltwater in landscape evolution

saturn s magnetospheric planetary period oscillations neutral atmosphere circulation and thunderstorm activity implications or otherwise for physical links 1 suggestions that the planetary period oscillations ppos observed in saturn s magnetosphere may be driven or influenced by neutral atmospheric perturbations motivate an exploratory comparison of ppo rotation periods with available tropospheric and stratospheric determinations nonpolar atmospheric rotation periods occupy the range 10 2 10 7 h associated with the latitudinal jet structure are similar north and south and are independent of season while ppo periods lie in a narrower partly overlapping range 10 6 10 8 h are persistently shorter north than south and undergo a seasonal cycle in this cycle widely separated north south ppo periods during southern summer converge across equinox to values lying within the atmospheric west jet band remaining well separated from east jet periods closest convergence occurred 1 year post equinox contemporaneously with the switch in seasonal thunderstorm activity from southern to northern hemispheres since most large scale atmospheric phenomena are related to the west jets rotating with closely similar periods they also rotate with periods close to the ppos under post equinoctial conditions but not otherwise specifically post equinox northern ppos rotate with a period close to the southern thunderstorms as well as the north polar spot and hexagon features while the post equinox southern ppos rotate with a period close to the pre equinox northern string of pearls and the first colocated post equinox northern thunderstorm the great white spot event however even under these conditions no consistent correspondences in period are found at a detailed level which taken together with the lack of correspondence at other times does not suggest a direct physical link exists between these phenomena

periglacial polygonal structures and sand wedges in the late precambrian glacial formations of the taoudeni basin in adrar of mauretania west africa abstract large scale polygonal structures and sand wedges are found over a large area on top of late precambrian continental glacial deposits the exceptionally good preservation of the structures allows comparison with modern periglacial frost wedges filled by wind transported clastic material in a permafrost environment

thermal structure of saturn from voyager infrared measurements implications for atmospheric dynamics abstract saturn atmospheric temperatures at the 150 mbar level retrieved from voyager iris measurements indicate the presence of small scale meridional gradients which are approximately symmetric with respect to the equator but are superposed on a large scale hemispheric thermal asymmetry under the assumption that the retrieved values at this atmospheric level represent kinetic temperatures on a constant pressure surface it is suggested that the small scale structure is produced by a meriodional circulation associated with the dissipative decay of the zonal winds with height while the hemispheric asymmetry represents a thermal response to the seasonally varying insolation the small scale gradients are correlated with zonal winds derived from voyager images at mid and high latitudes through the thermal wind relation the calculated thermal wind shears suggest a decay with height of the jet system toward a state of uniform eatward flow the existence of the approximately symmetric zonal winds and associated temperature gradients in the presence of a large scale seasonal thermal response suggests that the jet system is driven at depths substantially below the levels where seasonally modulated insolation is important p 0 5 bar

the onset and growth of the 1990 equatorial disturbance on saturn abstract the development of cloud structures at low saturnian latitudes in september 1990 can be divided into three phases the onset and expansion of the initial disturbance popularly known as the great white spot the eastward and westward expansion of the bright cloud and the eventual formation of wave like structures encircling the equator the three phases of this storm are consistent with a single convective event this event is evaluated within the historical context of previous occurrences and general seasonal mechanisms are considered

saturn s zonal wind profile in 2004 2009 from cassini iss images and its long term variability abstract five years of cassini imaging science subsystem images from 2004 to 2009 are analyzed in this work to retrieve global zonal wind profiles of saturn s northern and southern hemispheres in the methane absorbing bands at 890 and 727 nm and in their respective adjacent continuum wavelengths of 939 and 752 nm a complete view of saturn s global circulation including the equator at two pressure levels in the tropopause 60 mbar to 250 mbar with the mt filters and in the upper troposphere from 350 mbar to 500 mbar with the cb filter set is presented both zonal wind profiles available at the supplementary material section show the same structure but with significant differences in the peak of the eastward jets and the equatorial region including a region of positive vertical shear symmetrically located around the equator between the 10 c

radiometric performance of the voyager cameras the voyager imaging experiment provided high quality data of jupiter and the galilean satellites with the two flyby trajectories in march and july of 1979 moderately accurate radio metric measurements have been made using these data this paper evaluates the radiometric results and describes the inflight and ground geometric and radiometric correction factors the radiometric quantities of intensity i and geometric albedo i f are derived and scaling factors for each of the filters are tabulated for correcting the calibrated data from the image processing laboratory at jpl in addition the key characteristics of both voyager 1 and voyager 2 cameras are tabulated

motions in saturn s atmosphere observations before voyager encounters abstract a summary is presented of all the telescopic observations of the clouds in saturn s atmosphere made prior to the voyager encounters with the planet saturn displays a pattern of belts and zones like jupiter although they are practically constant in latitude and without significant changes over the last century some dark and white spots with diameters of about 6000 to 10 000 km have been observed allowing us to ascertain the atmospheric rotational period only a strong equatorial jet can be inferred from these measurements the most obvious features of saturn are the great white spots gws with diameters of 20 000 km or more but only five outbursts have been detected since 1876 corrected measurements have been obtained of the zonal velocities at different latitudes u with variations between 430 and 14 msec 1 with respect to the magnetic rotation of the planet m l kaiser m d desch j w warwick and j b pierce science 209 1238 1240 1980 the expansion velocities of some gws have been measured to be u 30 to 100 msec 1 and their lifetimes l from 30 to 150 days a possible subatmospheric origin for the gws is proposed in which it is due to a temporary and local anisotropy in the internal heat source a hot spot in the deeper atmosphere all the multiple features seen in both 1903 and 1933 appear to be linked to a unique system of longitudes rotating with the magnetic period

cassini imaging of saturn southern hemisphere winds and vortices high resolution images of saturn s southern hemisphere acquired by the cassini imaging science subsystem between february and october 2004 are used to create maps of cloud morphology at several wavelengths to derive zonal winds and to characterize the distribution frequency size morphology color behavior and lifetime of vortices nonequatorial wind measurements display only minor differences from those collected since 1981 and reveal a strong prograde flow near the pole the region just southward of the velocity minimum at 40 7 s is especially active containing numerous vortices some generated in the proximity of convective storms the two eastward jets nearest the pole display periodicity in their longitudinal structure but no direct analogs to the northern hemisphere s polar hexagon or ribbon waves were observed characteristics of winds and vortices are compared with those of saturn s northern hemisphere and jupiter s atmosphere

thermal structure and dynamics of saturn s northern springtime disturbance saturn s slow seasonal evolution was disrupted in 2010 2011 by the eruption of a bright storm in its northern spring hemisphere thermal infrared spectroscopy showed that within a month the resulting planetary scale disturbance had generated intense perturbations of atmospheric temperatures winds and composition between 20 and 50 n over an entire hemisphere 140 000 kilometers the tropospheric storm cell produced effects that penetrated hundreds of kilometers into saturn s stratosphere to the 1 millibar region stratospheric subsidence at the edges of the disturbance produced beacons of infrared emission and longitudinal temperature contrasts of 16 kelvin the disturbance substantially altered atmospheric circulation transporting material vertically over great distances modifying stratospheric zonal jets exciting wave activity and turbulence and generating a new cold anticyclonic oval in the center of the disturbance at 41 n

cloud structure of saturn s 2010 storm from ground based visual imaging abstract we present a study of the vertical cloud structure for the initial stage of the great white spot gws a giant storm that developed in saturn in december 2010 using ground based visual images we focus in the characterization of the undisturbed atmosphere preceding the storm and the disturbed region in the wake of the gws the observations were taken at calar alto spain and pic du midi france observatories on 27 december 2010 and 13 january 2011 about 1 month after the detection of the outbreak they cover a spectral range from the ultraviolet at 375 nm to the near infrared at 954 nm including the deep methane absorption band at 890 nm and a number of increasingly weaker methane absorption bands limb to limb scans of the absolute reflectivity of the regions preceding and following the storm at different wavelengths are compared to those produced by a radiative transfer model atmosphere our model assumes three layers of gas and particles stratospheric and tropospheric hazes and a deep cloud we find that the most notorious changes in the wake of the gws occurred in the top level of the semi infinite bottom cloud which ascended from an altitude level p 1 bar in the undisturbed region to p 300 300 100 mbar in the stormy area representing a rise of more than 40 km the density of the tropospheric haze does not change substantially but tropospheric particles are found to be more reflectant at all wavelengths suggesting that they are coated by fresh material putatively coming from deeper levels of the atmosphere

the origin and glaciodynamic significance of sandstone ridge networks from the hirnantian glaciation of the djado basin niger the djado basin niger was located beneath the inner part of the late ordovician ice sheet the felar felar formation consists mainly of glaciomarine deposits associated with the major ice sheet recession within the glaciation and is bounded by two glacial unconformities structures corresponding to sandstone ridges are found within the felar felar formation sandstone ridges are several metres high about 10 m wide and hundreds of metres long these structures are organized in extensive anastomosed to subpolygonal networks the association of sandstone ridge networks with the later glacial unconformity and with other glacial evidence suggests sub glacial conditions for their origin sandstone ridge sedimentological characteristics indicate that sandstone ridges result from the scouring of the felar felar formation by sub glacial turbulent and pressurized meltwater then subglacial cavities were infilled with sand derived from glacial abrasion sandstone ridge networks are comparable with tunnel channels and document unusual drainage structures of the inner part of the palaeo ice sheet

till and moraine emplacement in a deforming bed surge an example from a marine environment the glacier sefstrombreen in spitsbergen surged across an arm of the sea between qsr 1882 and 1886 and rode up onto the island coraholmen marine and terrestrial geological observations and archive records show that the glacier advanced on a deforming carpet of marine mud which was eroded from its original location transported and smeared over the sea bed and coraholmen as a deformation till the glacier emplaced about 210sm 0 2 km 3 of drift in the terminal 2 km of its advance in a maximum of 14 years leaving a thickness of up to 20 m on coraholmen which was doubled in size as a result during the surge subglacial muds were characterised by high water pressures low effective pressures and low frictional resistance to glacier movement original sedimentary inhomogenities permit fold structures to be identified but repeated refolding and progressive remoulding produce mixing and homogenisation of deformation tills the surge was probably shortlived and as the heavily crevassed glacier stagnated underlying water saturated muds were intruded into crevasses and then extruded on the glacier surface reticulate crevasse intrusion ridges on coraholmen and the sea floor reflect the orientation of surge generated crevasses water and sediment was also extruded beyond the glacier at its maximum extent to form extensive flows producing till tongues both on coraholmen and the sea floor extending over 1 3 km from the glacier it is argued that subglacial deformation of pre existing sediment will almost invariably be associated with glaciation of marine areas and that this process will not only produce deformation tills through remoulding of pre existing sediments but will also play a fundamental role in glacier dynamics criteria which perrait glacial tills produced by such events from marine and glaciomarine muds are discussed copyright 1996 elsevier science ltd