recently growing subaqueous flowstones occurrence petrography and growth conditions abstract subaqueous flowstones have been studied in two resurgence caves in slovak karst southern slovakia namely krasnohorska and drienovska caves the flowstones litter streambeds within the distance of several hundred meters upstream from resurgences they form laminated crusts within channels of the underground streams flowing through the caves layers composed of columnar sparry calcite alternate with those composed of microcrystalline calcite the latter are enriched in fine detrital non carbonate components which resulted in crystallization of microcrystalline calcite instead of sparry calcite the growth rate of the studied flowstones reaches 0 96 mg cm 2 day which corresponds to ca 0 3 mm per year seasonal observations conducted between november 2010 and september 2012 reveal that deposition of subaqueous flowstones in the studied caves significantly depends on the local hydrological conditions during the periods of low flow si calc values of underground stream increase and columnar sparry calcite grows conversely during peak flow periods si calc values decrease and subaqueous flowstones are subjected to destruction both by mechanical erosion and corrosion the decreasing discharge just after peak flows causes deposition of fine grained particles which results in precipitation of microcrystalline layers subaqueous flowstones grow in complete darkness and in atmosphere with elevated co 2 content similarly to typical speleothems but they are fed with turbulent stream water similarly to calcareous tufas their growth rate is higher than those of normal flowstones fed with a film of water seeping down it falls within a range of growth rate of calcareous tufas though near the lower limit of this range therefore subaqueous flowstones represent an intermediate link between other speleothems and tufas deposited outside the cave environment

gnss r nonlocal sea state dependencies model and empirical verification global navigation satellite system reflectometry gnss r is an active bistatic remote sensing technique operating at l band frequencies gnss r signals scattered from a rough ocean surface are known to interact with longer surface waves than traditional scatterometery and altimetry signals a revised forward model for gnss r measurements is presented which assumes an ocean surface wave spectrum that is forced by other sources than just the local near surface winds the model is motivated by recent spaceborne gnss r observations that indicate a strong scattering dependence on significant wave height even after controlling for local wind speed this behavior is not well represented by the most commonly used gnss r scattering model which features a one to one relationship between wind speed and the mean square slope of the ocean surface the revised forward model incorporates a third generation wave model that is skillful at representing long waves an anchored spectral tail model and a gnss r electromagnetic scattering model in comparisons with the spaceborne measurements the new model is much better able to reproduce the empirical behavior

friction and dynamics of rock avalanches travelling on glaciers rock avalanches travelling on glaciers often exhibit effective friction coefficient lower than those on a rocky terrain after briefly considering some data of rock avalanches on glaciers the physics of sliding of solid objects on icy surfaces is reviewed and a model is put forward for the mechanics of rock avalanche sliding on ice accounting for the formation of a natural lubricating layer it is suggested that at the beginning of the flow of a rock avalanche friction results from rocky blocks ploughing on ice as the erosion continues a gouge of ice particles results which clogs the interstices between blocks and may partially melt as a consequence of the production of frictional heat this conceptual model is numerically investigated for a slab travelling on ice the results show an increase in mobility as a function of slab thickness travelled length and the gravity field in agreement with case studies the results are useful to interpret the peculiar features of rock avalanches travelling on icy surfaces such as digitations out runner blocks and longitudinal furrows the lubrication theory for landslides on ice proposed here may provide a framework for understanding landslides on earth and for future modelling in addition it may help elucidate the presence of similar landslide deposits on the surface of mars

petrography and microanalysis of pennsylvanian coal ball concretions herrin coal illinois basin usa bearing on fossil plant preservation and coal ball origins abstract petrographic analyses of 25 coal balls from well studied paleobotanical profiles in the middle pennsylvanian herrin coal westphalian d illinois basin and five select coal balls from university collections indicate that herrin coal ball peats were permineralized by fibrous and non fibrous carbonates fibrous carbonates occur in fan like to spherulitic arrays in many intracellular within tissue pores and are best developed in relatively open extracellular between plant pore spaces acid etched fibrous carbonates appear white under reflected light and possess a microcrystalline texture attributable to abundant microdolomite scanning electron microscopy x ray diffraction and electron microprobe analysis demonstrate that individual fibers have a distinct trigonal prism morphology and are notable for their magnesium content 9 15 mol mgco 3 non fibrous carbonates fill intercrystalline spaces among fibers and pores within the peat as primary precipitates and neomorphic replacements in the immediate vicinity of plant cell walls non fibrous carbonates cut across fibrous carbonates as a secondary neomorphic phase attributed to coalification of plant cell walls dolomite occurs as diagenetic microdolomite associated with the fibrous carbonate phase as sparite replacements and as void filling cement maximum dolomite 50 59 wt is in the top of seam coal ball zone at the sahara mine which is overlain by the marine anna shale coal ball formation in the herrin coal began with the precipitation of fibrous high magnesium calcite the trigonal prism morphology of the carbonate fibers suggests rapid precipitation from super saturated meteoric pore waters carbonate precipitation from marine waters is discounted on the basis of stratigraphic paleobotanical and stable isotopic evidence most non fibrous carbonate is attributable to later diagenetic events including void fill replacements recrystallization and post depositional fracture fills evidence suggests that co 2 degassing was important in coal ball formation in the herrin coal which mainly occurred sequentially upward with peat accumulation in the sites studied

biogenic structures and micrite in stalactites from grand cayman island british west indies stalactites from modern and old caves developed in the bluff formation of grand cayman island contain laminae and bulbous masses of micrite intercalated with sparry calcite the micrite as well as some of the sparry calcite around it contains small up to 25 m long ovate to spherical bodies that have a high concentration of either manganese or iron such bodies may be of bacterial origin the micrite contains numerous calcified filaments that are probably of algal origin calcification of the filaments occurred either during life or shortly after death of the algae the algae played an important role in trapping and binding the micrite furthermore the algae may be directly or indirectly responsible for the formation of much of the micrite

the alteration of sparry calcite crystals in a vadose setting grand cayman island calcite crystals that cement the dolostone clasts in a karst breccia from grand cayman island have been substantially altered as a result of infestation by algae and or fungi as well as etching that may or may not be related to organic activity the features produced include 1 borings 2 constructive micrite envelopes 3 spiky calcite 4 almond shaped etch pits 5 crystal surfaces with a blocky topography and 6 etched crystal surfaces that suggest some of the crystals may have grown by spiral growth spar calcite crystals in a vadose setting can be subjected to complex chemical and physical processes that are commonly mediated by algae and or fungi these microorganisms are capable of removing caco3 from substrates via dissolution transporting that caco3 elsewhere and then directly or indirectly causing its reprecipitation during the calcification of their filaments and or the formation of the constructive micrite envelopes the extensive alteration of calcite cements in the karst brecci

friction of ice the frictional strength of ice seems to be well below that for all other rocks triaxial testing of cylinders of pure water ice containing a 45 inclined sawcut at temperatures of 77 t 115 k and confining pressures 0 1 p 250 mpa reveals the frictional laws 0 20 n 8 3 mpa for p 10 mpa and 0 55 n 1 0 mpa for p 5 mpa where and n are the shear and normal stresses on the sawcut surface friction is independent of t and over the one order of magnitude tested of average sliding velocity the sliding behavior is invariably stick slip examination of sliding surfaces shows only minor gouge development a curious arrangement of densely packed short vertical fractures occurs primarily in samples with anomalously low strength these results apply to models of near surface tectonic activity on jupiter s three large icy moons europa callisto and ganymede they indicate for example that a global expansion on ganymede of 3 linear percent will cause extensional movement on preexisting faults at depths to 7 3 km

calcite from the quaternary spring waters at tylicz krynica polish carpathians at tylicz near krynica spa polish carpathians spelean deposits fill fissures and caverns in eocene flysch rocks they occur as 1 clastic cave sediments transformed into hard crusts due to cementation by finely crystalline low mg calcite 2 drusy calcite that covers crust surfaces and fills voids in the crust and 3 colloform calcite two varieties of drusy calcite are distinguished acicular and columnar the acicular calcite is built up of crystallites forming spherulitic fans or cones in places it is syntaxially covered with colloform calcite the drusy calcite is low mg ferroan calcite with non ferroan subzones whereas the colloform calcite is a low mg non ferroan variety the columnar calcite crystals form fan like bundles cross sections cut perpendicular to the c axes of columnar crystals are equilateral triangular in shape although some have slightly curved edges the columnar crystals have steep rhombic terminations and most have curved triangular faces i e gothic arch calcite saddle crystals have also been observed the columnar crystals are composed of radially orientated crystallites whose long dimension is parallel to the c axis the curved crystal faces of such polycrystals are interpreted as a result of differential growth rates of the crystallites the spelean calcites precipitated from co2 saturated water the high rate of caco3 precipitation is thought to be responsible for the formation of radial structures finely crystalline calcite formed within pore spaces of clastic sediments close to the water air interface drusy calcite crystallized beneath the water air interface and colloform calcite precipitated from thin films of water

seasonal pattern in the high elevation fluvial travertine from the jiuzhaigou national nature reserve sichuan southwestern china abstract the jiuzhaigou national nature reserve on the tibetan plateau sichuan southwestern china is characterized by the deposition of fluvial travertine in a spectacular array of shoals waterfalls pool dams and multicolored lakes this is possibly the highest vegetated travertine setting of the world from 2200 to 2900 m above sea level an environment sensitive to minimal changes in temperature and precipitation regime the evolution of the system is driven by two seasonal monsoon climate patterns with a wet spring summer travertine deposition and then a dry fall winter characterized by no precipitation or erosion spring and phreatic vadose deposits transition from laminated columnar calcite to clotted micrite encrustation possibly correlated with a mid holocene peak in precipitation and high lake levels in the northeastern tibetan area connected to glacial advance the most peculiar features are the fluvial shoals a rather uncommon travertine surface consisting of two main superimposed facies of alternating weak and strong turbulence water flow the low turbulence facies consists of clotted micrite encrustation of mosses and cyanobacteria filaments and platy calcite crystals covering algal filaments the high water turbulence facies show seasonal alternation of diatom rich bundles of phormidium sp late spring with algal oocardium stratum levels summer fall upslope and downslope of the shoals the precipitation of calcium carbonate results in the formation of prograding waterfalls and dam pool systems that encrust macrophytes with microspar and clotted micrite encrusted chironomids larvae tubes are present in the waterfall walls up to an elevation of 2860 m possibly the highest ever recorded early diagenetic processes such as dissolution of diatom frustules take place over the span of several years a slower phenomenon compared to other travertine occurrences in this high elevation extreme setting travertine sand and gravel bar deposits are produced by the exposure to severe weathering of a section of the valley that is bypassed through an underground karst system during the winter dry season high elevation travertine probably has a low preservation potential but it appears to be more sensitive to climate changes than other depositional settings especially in the himalayan tibetan area where the extent of the quaternary glacial advances and retreats is still a matter of debate

relationship between gps signals reflected from sea surfaces and surface winds modeling results and comparisons with aircraft measurements theoretical calculations of global positioning system gps signals reflected from rough sea surfaces are discussed and compared with the aircraft measurements the theoretical model is based on the assumption that rough sea surfaces are composed of facets and the reflection of gps signals from the facets can be calculated on the basis of geometric optics in order to determine the slopes of the sea surface facets the statistical model of cox and munk 1954 for ocean surface slopes is used since much of the sea surface roughness observed is at scales much less than the gps wavelength the dependence of the mean square slopes on frequency is taken into consideration model results agree well with aircraft measurements the differences between model results and observations are within the level of experimental errors for calm sea surfaces near sea surface wind speeds 7 m s 1 the correlation powers decrease their peak values to 4 8 db significantly widen time delay responses and shift toward the delays corresponding to path lengths longer than those of specular points sensitivity tests show that there is considerable potential for current or advanced gps receiving systems to estimate near sea surface wind speeds the errors in the wind speed estimates could be smaller than 2 m s 1 for near sea surface wind directions the maximum changes in the correlation powers of the gps signals as a function of azimuth appear to be 0 5 db for current gps receiving systems which may be too small for wind direction estimation new designs of the gps receivers or a higher signal to noise ratio than that of current aircraft receivers may be needed

the dependence of ocean backscatter at k sub u band on oceanic and atmospheric parameters the jet propulsion laboratory nuscat k sub u band scatterometer successfully acquired ocean backscatter data over a wide variety of oceanic and atmospheric conditions during the surface wave dynamics experiment swade ten flights resulted in 30 h of data collection were conducted on the nasa ames c130 aircraft the swade experimental area was deployed with several buoys providing appropriate in situ measurements to correlate with the radar backscatter for incidence angles from 10 to 60 spl deg at both horizontal and vertical polarizations the nuscat swade backscatter data base was utilized in conjunction with buoy measurements to investigate ocean backscatter signatures over the range of conditions encountered during swade to account for modulations and fluctuations in incidence angles a backscatter analysis independent of a priori geophysical model functions was developed tested and implemented results for backscatter azimuth modulations in terms of upwind downwind and crosswind radar returns are compared to airborne radscat results and to sass i and ii geophysical model functions versus neutral wind speed u sub n nuscat swade results are closest overall to sass ii values fit best with sass i at 10 spl deg incidence angle and are significantly higher than radscat effects of friction velocity u wave age c sub o u and significant wave height h sub 1 3 on ocean backscatter are studied the backscatter shows a good positive sensitivity to u an inverse dependence on c sub o u and no systematic trend with h sub 1 3 excluding cases of large swells coefficients of empirical relations between backscatter and neutral wind speed friction velocity and wave age are derived for 10 40 spl deg incidence angles at both horizontal and vertical polarizations covariance studies of backscatter with the derived relations to winds show an overall deviation factor in the order of 1 db for ocean signatures including uncertainties in surface conditions

generalized linear observables for ocean wind retrieval from calibrated gnss r delay doppler maps the cyclone global navigation satellite system cygnss mission will use global navigation satellite system reflectometry to measure ocean surface winds in and near the hurricane inner core including regions beneath the eye wall which could not previously be measured from space due to intense precipitation the cygnss constellation will consist of eight small satellite observatories in 500 km circular orbits at an inclination of 35 cygnss observatories will receive both direct and reflected signals from global positioning system satellites direct signals will be used both for conventional navigation of the observatory positions and for calibration of the incident signal power reflected signals respond to ocean surface roughness from which wind speed is retrieved this is observed as changes in a delay doppler map ddm a generalized observable which is defined as a linear combination of the ddm samples is optimized using three different methods maximum signal to noise ratio minimum variance of the wind speed and principal component analysis pca performance of each of these three approaches is compared with each other and with that of the baseline level 2 retrievals defined for cygnss ddm average leading edge slope and the minimum variance combination of both pca is found to have the best performance

thermal stability of ice on ceres with rough topography the dwarf planet ceres may have an ice rich crust and subsurface ice exposed by impacts or endogenic activity would be subject to sublimation we model surface and subsurface temperatures on ceres to assess lifetimes of water ice and other volatiles topographic shadowing allows a small but non negligible fraction 0 4 of ceres surface to be perennially below the 110 k criterion for 1 gyr of stability these areas are found above 60 latitude other molecules ch3oh nh3 so2 co2 may be cold trapped in smaller abundances a model for the transport gravitational escape and photoionization of h2o molecules suggests net accumulation in the cold traps buried ice is stable within a meter for 1 gyr at latitudes higher than 50 an illuminated polar cap of water ice would be stable within a few degrees of the poles only if it maintained a high albedo 0 5 at present obliquity if the obliquity exceeded 5 in the geologically recent past then a putative polar cap would have been erased at latitudes 0 30 ice is stable under solar illumination only briefly 10 100 yr unless it has high albedo and thermal inertia in which case lifetimes of 104 yr are possible finally a small hemispheric asymmetry exists due to the timing of ceres perihelion passage which would lead to a detectable enhancement of ice in the northern hemisphere if the orbital elements vary slowly relative to the ice accumulation rate our model results are potentially testable during the dawn science mission

effect of sea roughness on bistatically scattered range coded signals from the global positioning system a series of aircraft experiments was performed using a specialized gps receiver and a nadir oriented left hand circularly polarized antenna this apparatus received reflections of the gps signals from water surfaces under a variety of sea states the cross correlation between the reflected signal and a reference pseudo random noise code was recorded as a function of the relative time delay the shape of this function showed a dependence on the roughness of the reflecting surface this dependence generally followed that predicted by theory for bistatic scattering of range coded signals use of this information as a remote sensing technique for the determination of sea state is discussed

brucite and carbonate assemblages from altered olivine rich materials on ceres the mineralogy of the dwarf planet ceres has long remained uncertain the infrared spectral features of this planetary body are indicative of minerals derived from the aqueous alteration of olivine rich materials suggesting that ceres is not represented by any known meteorite the dwarf planet ceres is the largest object in the asteroid belt and is generally thought to be a differentiated body composed primarily of silicate materials and water ice1 2 some remotely observed features however indicate that ceres may instead have a composition more similar to that of the most common types of carbonaceous meteorite3 4 5 6 7 in particular ceres has been shown to have a distinct infrared absorption feature centred at a wavelength of 3 06 m that is superimposed on a broader absorption from 2 8 to 3 7 m refs 5 8 which suggests the presence of oh or h2o bearing phases the specific mineral composition of ceres and its relationship to known meteorite mineral assemblages however remains uncertain here we show that the spectral features of ceres can be attributed to the presence of the hydroxide brucite magnesium carbonates and serpentines a mineralogy consistent with the aqueous alteration of olivine rich materials we therefore suggest that the thermal and aqueous alteration history of ceres is different from that recorded by carbonaceous meteorites and that samples from ceres are not represented in existing meteorite collections

the application of reflected gps signals to ocean remote sensing abstract the l band broadcast signal from the global positioning system gps reflected off of the sea surface is under study for use as a ocean coastal and wetlands remote sensing tool the reflected signal from a given gps satellite is cross correlated with the pseudorandom noise code uniquely identifying that satellite the shape of this cross correlation ordinarily a very sharp triangle when tracking a direct line of sight signal becomes wider and smoother as the mean square slope of the reflecting surface increases it is proposed that the surface wind speed can be determined by matching the recorded shape of this cross correlation to that predicted by theoretical models as a function of wind speed and direction the significance of these effects increases with altitude of the receiver experimental data have been collected using a specially modified gps receiver on aircraft and on a balloon at altitudes of up to 25 km these data compare favorably with predictions of analytical models and demonstrate the dependence of the waveform shape on surface wind speed and receiver altitude the advantages that this measurement technique has over conventional scatterometers is the small size low cost and simplicity of the receiver hardware no requirement for a transmitter and the ability to simultaneously collect data from usually 10 or more points from a low earth orbiting satellite this number could be larger if the russian global navigation satellite system satellites are also considered as additional sources of radiation furthermore the bistatic scattering geometry is complementary to the backscatter used by conventional scatterometers

the effect of mineralogy and effective normal stress on frictional strength of sheet silicates abstract phyllosilicates are common constituents of upper crustal faults and subduction forearcs we studied the effect of mineralogy and controlled effective normal stress between 5 mpa and 100 mpa on frictional strength although the effect of mineralogy on frictional strength of single phase phyllosilicate gouges has been previously studied the influence of effective normal stress has not we conducted water saturated and vacuum dry frictional tests on single phase phyllosilicate gouges using a triaxial apparatus minerals included talc pyrophyllite kaolinite lizardite illite montmorillonite chlorite muscovite phlogopite and biotite particle size 20 mpa dry friction coefficients are constant and wet friction coefficients show a small increase this is attributed to loss of water and increased contact area the results indicate that frictional strength of clay rich faults increases at depths less than 1 km under hydrostatic pore fluid pressures

large mass movements on callisto galileo images reveal the presence of mass movement deposits within impact craters on callisto eleven such deposits were found in 830 candidate craters imaged at sufficient resolutions 86 280 m pixel for their identification all of the deposits are located within impact craters and their sources appear to be crater wall material the morphologies of the callistan deposits are similar to terrestrial mass movements and rock glaciers rock glaciers involve ductile flow of ice and rock but in the callistan environment water ice is likely to undergo brittle deformation consequently rock glaciers are unlikely analogs for the features on callisto three morphologies are observed one blocky one slump like and nine lobate deposits blocky deposits are characterized by massive blocks on the crater floor while slump like deposits appear as debris piles along the base of the crater wall lobate deposits are 1 7 9 9 km long average 90 m in thickness and have tapered or semicircular terminations callistan lobate deposits are morphologically similar to rapidly emplaced dry rock avalanches on earth their significant thickness and steep frontal margins suggest that they may have behaved similarly to bingham plastic material with a critical yield strength the callistan deposits have yield strengths similar to those estimated for terrestrial dry rock avalanches the blocky deposit appears similar to terrestrial block glide deposits in which large blocks detach and slide downslope individual blocks within the blocky deposits may be up to 1 km across and stand 30 60 m high callistan slump like deposits are similar to terrestrial slumps which fail along rotational planes mass movements on callisto are not confined to craters they have also been observed along the base of scarps knobs and ridges three of the callistan deposits may have been impact triggered because of the proximity of an impact crater near the source first order analyses of the ground force generated by impacts show that two of the candidate deposits are capable of being impact triggered the callistan mass movements are probably set into motion by a combination of sublimation of ice which undermines a near surface layer of lag material and seismic triggering associated with nearby impact events

sensitivity analysis of wind vector measurements from ocean reflected gps signals the power received by a gps receiver located on an airplane flying over the ocean and collecting the gps signal reflected off the surface is estimated for varying wind speed and wind direction platform altitude satellite elevation angle and receiver integration time by accounting for the wind induced anisotropy on the surface it is shown that the trailing edges of computed waveforms change with both wind speed and direction when the receiver integration time is properly chosen substantial differences in the waveforms at different wind directions are exhibited even at the beginning of the trailing edge particularly for reflections from high elevation satellites these differences are associated with the extent and directional properties of the scattered fields as a function of reflection angle an analysis of the interdependence of the observational geometric parameters the coherence time and the receiver integration time is presented to suggest a suitable arrangement for enhanced measurement sensitivity to the wind direction

stable isotope composition of spelean calcites and gaseous co2 from tylicz polish carpathians abstract spelean calcites discovered in fissures and caverns within flysch deposits at tylicz polish carpathians have been examined isotopically together with co 2 rich water from several springs occurring in this area 13 c values of tdc and spelean calcites indicate that caco 3 has precipitated under conditions close to carbon isotope equilibrium with participation of co 2 of deep origin analyses of 18 o suggest the existence of oxygen isotope disequilibrium between water and gaseous co 2 which can be explained by the short time of contact between the co 2 flux and the shallow groundwaters of meteoric origin

mobility of large rock avalanches evidence from valles marineris mars measurements of h l height of drop length of runout vs volume for landslides in valles marineris on mars show a trend of decreasing h l with increasing volume this trend which is linear on a log log plot is parallel to but lies above the trend for terrestrial dry rock avalanches this result and estimates of 10 4 to 10 5 pa yield strength suggest that the landslides were not water saturated as suggested by previous workers the offset between the h l vs volume trends shows that a typical martian avalanche must be nearly two orders of magnitude more voluminous than a typical terrestrial avalanche in order to achieve the same mobility this offset might be explained by the effects of gravity on flows with high yield strengths these results should prove useful to future efforts to resolve the controversy over the mechan ics of long runout avalanches

deposition and diagenesis of mammoth hot springs travertine yellowstone national park wyoming u s a strata forming a 113 m long core through mammoth hot springs record the holocene evolution of this travertine accumulation from deposition as part of a lacustrine to a terraced mound environment the deposit is readily divided into four intervals 113 67 m carbonate cemented volcaniclastic with intercalated layers of travertine 67 60 m moderately pure travertine with some volcaniclastics 60 50 m carbonate cemented volcaniclastic rich interval and 50 0 m essentially pure travertine lithologic composition sedimentary structures and the rare ostracode fossils indicate that the lower 67 m predominantly accumulated in a lacustrine environment whereas the upper 40 m are terraced mound deposits all of the travertine is calcite some after aragonite layers of shrubs oncoids and peloids all bacterial in origin form the dominant allochems within the travertine stable isotopic carbon and oxygen values n 128 are strongly positively correlated and decrease up core 4 and 8 respectively reflec

landslide mobility and hazards implications of the 2014 oso disaster abstract landslides reflect landscape instability that evolves over meteorological and geological timescales and they also pose threats to people property and the environment the severity of these threats depends largely on landslide speed and travel distance which are collectively described as landslide mobility to investigate causes and effects of mobility we focus on a disastrous landslide that occurred on 22 march 2014 near oso washington usa following a long period of abnormally wet weather the landslide s impacts were severe because its mobility exceeded that of prior historical landslides at the site and also exceeded that of comparable landslides elsewhere the 8 10 6 m 3 landslide originated on a gently sloping