self weight consolidation of soft soils an experimental and theoretical study soil is laid down by sedimentation through water passing through the phases of a fluid supported suspension through a loose structure to a soft soil the stiffness of which then gradually increases under additional load consolidation is caused by the self weight of the soil and while the sediment is soft is accompanied by large strains to predict magnitudes and rates of movement the physical processes must be understood and used as the basis of a theoretical model this paper describes laboratory experiments on the development and consolidation of a soft soil in settling columns with measurement of density using an accurate non destructive x ray technique total stress pore pressure and settlement the results are compared with an earlier theoretical model modifications made to the model in the light of observed experimental features allow it to be used to predict the laboratory consolidation le sol est depose par sedimentation a travers l eau il a d abord la forme d une suspension soutenue

geometry and distribution of regional joint sets in a non homogeneous stress field case study in the ebro basin spain abstract three regional joint sets striking n s e w and wnw ese affect the tertiary rocks of the central ebro basin from analysis of their chronological relationships and spatial distribution it is concluded that they correspond to two different tectonic events the n s set oldest and the e w set younger are present in the southern and central sectors while the wnw ese joint set predominates in the northern one the n s joints propagated in response to joint normal and fluid loads under an intraplate stress field with shmax oriented near n s related to forces caused by the convergence of africa iberia and europe and rifting at the valencia trough during the sedimentary infilling of the basin these joints are only present in the southern part of the area the e w joint set in the southern central sector records the same fracturing event as the wnw ese set does in the northern one its orientation was modified by the presence of the older n s set in the south which perturbed the regional stress field the younger wnw ese and e w joint sets are interpreted as unloading joints these propagated as a consequence of flexural uplift and exhumation related to isostatic rebound at the pyrenees and the ebro foreland basin a numerical approach is used to explain the inhomogeneous distribution of the n s joint set in terms of their absence being controlled by the depth of the water table at the time of their formation

evolution of structural and physical parameters of clays during experimental compaction abstract to provide a better understanding of sedimentary basin geological history it is important to describe correctly the evolution of the various physical mechanical and hydraulic properties of clayey rocks as a function of burial depth as a contribution to this field a programme of experimental studies on reworked clay samples compacted under various load pressures in oedometric conditions has been set up the evolution of samples under compaction was followed with microscopic and macroscopic measurements in a specially designed oedometric cell samples are compacted under different total stresses from 0 1 to 50 mpa in this cell cylindrical cores are submitted to progressive loading from both ends under controlled pore pressure conditions the symmetrical loading allows more even deformation about the midplane of the sample this device allows the evolution of hydraulic pressure radial stress displacement and expelled pore fluid to be followed as a function of time in a first step kaolinite was chosen because it retains a high permeability compared with other clays such as illite or smectite which allows compaction tests to be performed within a few days a complete set of measurements was performed after the tests these measurements are 1 micro structures investigated by means of transmission electron microscopy tem mercury porosimetry water removal under low water vapour pressure granulometry and specific area measured by ethylene glycol adsorption and 2 various physical parameters measured including hydraulic conductivity and thermal conductivity tem gives an understanding of the arrangement of particles it was found that each particle is composed of several crystal units each unit formed by 25 individual kaolinite layers during compaction these particles remain undeformed but are rotated the angular distribution of grain orientation is a function of the applied effective stress this reorientation is in agreement with the observed decrease in porosity and pore size it also explains the occurrence of a strong anisotropy in the thermal conductivity and hydraulic permeability the combination of these experimental results allows a qualitative and quantitative understanding of the behaviour of kaolinite with respect to parameters such as permeability porosity mechanical and thermal properties the knowledge of which are necessary for basin modelling

jupiter s great red spot as a shallow water system most current models of jupiter s great red spot grs are cast in terms of a two layer model where a thin upper weather layer which contains the vortex overlies a much deeper layer which is meant to represent the neutrally stratified deep atmosphere any motions in the deep layer are assumed to be zonal and steady this two layer model is dynamically equivalent to a one layer model with meridionally varying solid bottom topography called the reduced gravity model specifying the motions or lack thereof in the lower layer of the two layer model is equivalent to specifying the bottom topography and hence the far field potential vorticity in the reduced gravity model current models of the grs start by guessing the deep motions and then proceed to study vortices using the implied bottom topography here using the grs cloud top velocity data we derive the bottom topography up to a constant that depends on the unknown radius of deformation or equivalently the product of the reduced gravity and the mean thickness of the upper layer the bottom topography is inferred from three quantities derived from the velocity data bernoulli streamfunction kinetic energy per unit mass and absolute vorticity all of which are functions only of horizontal position in the reference frame of the vortex far from the vortex potential vorticity versus latitude is calculated from the observed cloud top zonal velocity and the derived bottom topography the results show that the deep atmosphere is in differential motion and that the far field potential vorticity gradient changes sign at several latitudes numerical shallow water experiments are performed using both the derived bottom topography and the bottom topographies prescribed by current models the results of three published studies are reproduced in our numerical experiments each of these models is successful in maintaining a long lived isolated vortex but only the present model yields absolute vorticity profiles along streamlines that agree with those observed for the grs by dowling and ingersoll in all the models large vortices form by merging with smaller vortices in the present observationally based model and in one other published model the smaller vortices arise spontaneously because the observed cloud top zonal velocity profile is unstable these two models require an additional momentum source to maintain the upper layer zonal velocity profile in the other two models the bottom topography stabilizes the zonal velocity profile if dissipation is present the latter two models require an additional source of smaller vortices to maintain the larger one a crucial unanswered question for the present model and for jupiter itself is how the cloud top zonal velocity profile is maintained in its present unstable state

analytical and numerical studies of the beta effect in tropical cyclone motion part i zero mean flow abstract the effect on tropical cyclone motion is studied using an analytical as well as a numerical model in a nondivergent barotropic framework the analytical model and the linear version of the numerical model give essentially the same result the linear effect causes a westward stretching of the model vortex but no significant movement of the vortex center an east west asymmetry in the meridional wind field is also created it is the inclusion of the nonlinear term that produces the northwestward movement of the vortex previously found by other investigators e g kitade 1981 this northwestward movement increases with both the maximum wind speed and the radius of maximum wind in a constant shape vortex a wind maximum is also found to the northeast of the vortex which appears to be consistent with the observational findings of shea and gray this asymmetry plays an important role in the vortex motion

evolution of the stress field near the arava basin located along the dead sea fault system as revealed by joint sets abstract to reveal the development of the stress field near the arava basin located along the dead sea fault system we characterized joint sets that were exposed mainly in the santonian and eocene chalk rock outcropping in the study area in total 2600 strike orientations of single layer joints slj and multilayer joints mlj mirrored four main stress fields 1 hnw j1 326 2 hnnw j2 343 3 hnne j3 033 and 4 hn j4 360 the results showed that the relatively lower values of the fracture spacing ratio fsr and their standard deviations in j1 implied that j1 was formed during the burial stage of the eocene chalk formations the inconsistency between the statistical parameters of the log normal distributions of joint spacing and fsr raised doubt about the applicability of the saturation joint density model in our studied area the joint sets characteristics suggest that the regional hnw operated during the eocene during the miocene the regional stress field changed clockwise to hnnw probably in association with the early stage of transform motion along the dead sea fault in the pliocene pleistocene the hnne and hn local stress fields both operated and were accompanied by a tensional stress field that can be identified in the intensive normal faulting evolved along the western arava basin margins

genetic and temporal relations between formation waters and biogenic methane upper devonian antrim shale michigan basin usa abstract controversy remains regarding how well geochemical criteria can distinguish microbial from thermogenic methane natural gas in most conventional deposits has migrated from a source rock to a reservoir rarely remaining associated with the original or cogenetic formation waters we investigated an unusual gas reservoir the late devonian antrim shale in which large volumes of variably saline water are coproduced with gas the antrim shale is organic rich of relatively low thermal maturity extensively fractured and is both source and reservoir for methane that is generated dominantly by microbial activity this hydrogeologic setting permits integration of chemical and isotopic compositions of coproduced water and gas providing a unique opportunity to characterize methane generating mechanisms the well developed fracture network provides a conduit for gas and water mass transport within the antrim shale and allows invasion of meteoric water from overlying aquifers in the glacial drift steep regional concentration gradients in chemical and isotopic data are observed for formation waters and gases dilute waters grade into dense brines 300 000 ppm over lateral distances of less than 30 km radiogenic 14c and 3h and stable isotope 18o and d analyses of shallow antrim shale formation waters and glacial drift groundwaters indicate recharge times from modern to 20 000 yr bp carbon isotope compositions of methane from antrim shale wells are typical of the established range for thermogenic or mixed gas 13c 47 to 56 however the unusually high 13c values of co2 coproduced with methane 22 and dissolved inorganic carbon dic in formation waters 28 require bacterial mediation the d values of methane and coproduced formation water provide the strongest evidence of bacterial methanogenesis methane ethane propane ratios and 13c values for ethane indicate 1 the presence of a thermogenic gas component that increases basinward and 2 progressive bacterial oxidation of ethane as the antrim shale subcrop is approached multiple episodes of pleistocene glaciation over northern michigan appear critical to the development of these gas deposits loading of thick ice sheets may have provided hydraulic head that enhanced dilation of preexisting fractures and influx of meteoric water the physical erosion cycle of repeated glacial advances and retreats exhumed the antrim shale around the northern margin of the michigan basin subjecting it to near surface physiochemical and biochemical processes the chemical and hydrologic relations demonstrated in the antrim shale reservoir suggest a dynamic connection between pleistocene glacial history of the midcontinent region and development of recoverable microbially generated natural gas reserves

cementation of porous materials using calcite a technique of cementing porous materials artificially using calcite is presented the technique depends on flushing a mixture of chemical solutions through a porous medium leading to precipitation of calcite due to reaction of the solution ingredients the experimental procedures adopted to achieve the cementation are described the response of different soils to the cementation process is analysed the bond mechanism created by the calcite is illustrated using optical and electron micrographs the paper discusses the factors that appear to determine the response of geomaterials to calcite treatment it has been found that the strength of a calcite treated material increases with a intrinsic strength of the individual grains b density c decreasing particle size of the host grains d pre coating of grains with calcite and e roundness and non angularity of soil grains the cementation technique described in this paper has proved successful in reproducing the mechanical behaviour of natural

analysis of the experimental compressibility of deep water marine sediments from the gulf of guinea abstract this study strives to analyze the compressibility of deep water marine sediments originating from the gulf of guinea our approach is multi scaled and on the macroscopic level based on two equations which link the overburden effective stress with the liquidity index the biarez favre equation on the one hand and the burland equation on the other hand after calculation of the icl expression as a function of the i l parameter on the local level the evolution of the microstructures is analysed and compared with gog remoulded clay two additional observation techniques have been used the scanning electron microscope and the mercury intrusion porosimetry

is there a genetic relationship between selected regional joints and contemporary stress within the lithosphere of north america on the appalachian plateau of new york ene striking joints parallel the mid continent contemporary stress field and do not correlate with other structures joints within ohio indiana michigan and west virginia also parallel the mid continent maximum horizontal compression as indicated by hydraulic fracture measurements in northern indiana where the contemporary stress field deviates significantly from the orientation of the mid continent stress the attitude of the joints deviates accordingly in addition to joints structures on several scales from subcontinent size fracture systems to microfabrics in shales apparently parallel the mid continent stress field from this i conclude that these joints are mode i cracks whose orientation corresponds to the contemporary tectonic stress field in itself the formation of these structures constitutes a tectonic event that has often been overlooked in favor of tectonic events that produce the more spectacular but less pervasive faults and folds

stratigraphic controls on vertical fracture patterns in silurian dolomite northeastern wisconsin vertical opening mode fractures are mapped on quarry walls to assess the stratigraphic controls on fracture patterns in the relatively undeformed silurian dolomite of northeastern wisconsin our two stage study uses maps of vertical fractures to assess the effectiveness of various types of stratigraphic horizons e g organic partings or cycle bounding mud horizons in terminating opening mode fractures first the mechanical stratigraphy of the exposures is interpreted from the observed fracture pattern both visual inspection and a newly developed quantitative method are employed to identify effective mechanical interfaces the two methods show similar results confirming the validity of qualitative visual inspection the second stage of our study stochastically predicts mechanical stratigraphy and subsequent fracture pattern from empirical relationships between the observed sedimentary stratigraphy and the interpreted mechanical stratigraphy for example 63 of cycle bounding mud horizons within the inner middle and middle shelf facies associations serve as mechanical interfaces these empirical percentages are input to a monte carlo analysis of 50 stochastic realizations of mechanical stratigraphy comparisons of the stochastically predicted and interpreted mechanical stratigraphy yield errors ranging from 13 to 33 this method yields far better results than assuming that all stratigraphic horizons act as mechanical interfaces the methodology presented in this article demonstrates an improved prediction of fracture pattern within relatively undeformed strata from both complete characterization of sedimentary stratigraphy and understanding mechanical controls on fracturing

a case for neotectonic joints along the niagara escarpment in a search for proof that some joints on the appalachian plateau are neotectonic orientation data were collected on more than 1800 fractures in exposures of the lockport dolomite in western new york and southern ontario of greatest interest was a late forming ene joint set present in the central and western portions of the field area these joints increase in abundance with proximity to the niagara escarpment the shape of the east west trending niagara escarpment is defined by a series of asymmetric reentrants with a strong ene linear trend reflecting the bedrock joint pattern the joints appear to have formed near the earth s surface in response to low tensile stresses developed in bedrock adjacent to the retreating escarpment since the current shape and position of the escarpment were controlled by glacial activity during the last 3 m y it is possible that the ene joints and reentrants are neotectonic features

study of the structure of a sensitive champlain clay and of its evolution during consolidation scanning electron microscopy and mercury intrusion porosimetry are used in parallel to identify the structure of a medium sensitivity champlain clay the clay structure is observed firstly on intact remolded and oven dried soils and secondly on soils consolidated at various levels in one dimensional compression both methods of investigation reveal for the intact soil the existence of an aggregated structure characterized by an interaggregate and an intra aggregate porosity remolding affects interaggregate links but does not destroy aggregates the observation of clay structure at various levels of one dimensional compression shows that the collapse of the structure is progressive the largest interaggregate pores being the first affected as the consolidation proceeds smaller and smaller pores are affected for a given pressure increment only the largest existing pores are affected a structure anisotropy has been seen to develop with increasing compression the scanning electron microscope and the me

on the influence of a lower layer on the propagation of nonlinear oceanic eddies abstract the one layer reduced gravity also called equivalent barotropic model has been widely used in countless applications although its validity is based on the assumption that a second lower layer is sufficiently deep to be dynamically inactive the question of how deep that second layer ought to be has not yet received thorough examination when one considers the importance of the two processes excluded from the reduced gravity model namely barotropic motion and baroclinic instability the conventional choice of a second layer much deeper than the first might be too simplistic a scaling analysis aimed at covering all two layer regimes geostrophic as well as ageostrophic leads to a double criterion requiring that the total depth of fluid be much larger than either of two values these values resulting from f plane and plane dynamics apply to the shorter and longer scales respectively a number of numerical experiments on the propagation of eddies on the plane with various eddy radii a

properties and behaviour of hong kong marine deposits with different clay contents large scale marine reclamation has taken place on soft hong kong marine deposits hkmd more and more reclamation is to be undertaken due to the rapid development of infrastructures and housing pr

monitoring sedimentation of a clay slurry electrical impedance measurements are monitored during the sedimentation of a clay slurry and provide an in situ non invasive technique to study the sedimentation process the term normalised resistivity is introduced and data are interpreted in terms of the development of a density profile and the influence of pore fluid concentration on this process particle alignment mechanisms are also inferred from the electrical properties of the slurry

modeling the stability of polygonal patterns of vortices at the poles of jupiter as revealed by the juno spacecraft from its pole to pole orbit the juno spacecraft discovered arrays of cyclonic vortices in polygonal patterns around the poles of jupiter in the north there are eight vortices around a central vortex and in the south there are five the patterns and the individual vortices that define them have been stable since august 2016 the azimuthal velocity profile vs radius has been measured but vertical structure is unknown here we ask what repulsive mechanism prevents the vortices from merging given that cyclones drift poleward in atmospheres of rotating planets like earth what atmospheric properties distinguish jupiter from saturn which has only one cyclone at each pole we model the vortices using the shallow water equations which describe a single layer of fluid that moves horizontally and has a free surface that moves up and down in response to fluid convergence and divergence we find that the stability of the pattern depends mostly on shielding an anticyclonic ring around each cyclone but also on the depth too little shielding and small depth lead to merging and loss of the polygonal pattern too much shielding causes the cyclonic and anticyclonic parts of the vortices to fly apart the stable polygons exist in between why jupiter s vortices occupy this middle range is unknown the budget how the vortices appear and disappear is also unknown since no changes except for an intruder that visited the south pole briefly have occurred at either pole since juno arrived at jupiter in 2016

joint development during fluctuation of the regional stress field in southern israel four trends of joint sets wnw ese nw se nnw sse and ne sw are found in upper turonian carbonate rocks within the neqarot syncline of south central israel the two most predominant sets strike parallel to the trend of maximum compressive stress directions sh associated with the plate related syrian arc stress field sas wnw ese active during the cretaceous to present and the perturbed regional stress field nnw sse related to stress accumulation on the dead sea transform during the miocene to the present eighty two percent of the beds in this study contain joints parallel with the latter trend whereas 42 contain joints parallel to the former trend all beds with layer thickness to spacing ratio fsr 1 5 have nnw sse joint sets compatible with the dead sea transform stress field dss whereas all joints sets that are not compatible with the dss stress field fall beneath this value for fsr considering lithology joints in five of six chalky limestone beds and all marly limestone beds are compatible with the dss whereas joints compatible with the sas do not develop in these marly and chalky limestone beds in the study area the joint sets lack a consistent formation sequence where more than one set is found in a single bed we use these observations to conclude that all studied joints are miocene or younger that the regional stress field from the miocene to the present fluctuated between dss and sas states and that the higher fsrs correspond to a greater amount of joint normal strain in response to the dss q 2001 elsevier science ltd all rights reserved

determining contemporary stress directions from neotectonic joint systems a neotectonic joint is a crack which propagated in a tectonic stress field that has persisted with little or no change of orientation until the present day investigating neotectonic joints is of value because the approximate orientation of the contemporary stress field can be inferred from them although exposed neotectonic joints in the flat lying sedimentary rocks of some cratons are related to regional stress fields their initiation and propagation occurred close to the earth s surface for example neotectonic joints in the centre of the ebro basin n spain preferentially developed in a thin near surface channel sited within a sequence of weak miocene limestones underlying the upper levels of plateaux the ebro basin joints strike uniformly nnw sse throughout an area of at least 10000 km2 and they are parallel or subparallel to the direction of greatest horizontal stress extrapolated from in situ stress measurements and fault plane solutions of earthquakes 1 preamble this paper has three aims firstly to review the general attributes of exposed neotectonic joints secondly to demonstrate that in s england n france and the ebro basin spain the directions of greatest horizontal principal stress that were inferred from neotectonic joints are parallel to those determined later from geophysical observations and thirdly to discuss why neotectonic joints in the ebro basin are better developed in weak limestones cropping out in the upper parts of plateaux in this paper the word neotectonic is used to indicate that a fracture was propagated in a tectonic stress field that has persisted with little or no change of orientation until the present day hancock engelder 1989 a fracture is called a joint if at the scale of observation possible in the field it is barren and there is no measurable offset related to shear dilation or pressure solution because joints are the most abundant of non penetrative geological structures they are of great potential value for tracking the orientations of principal stress axes at the time of failure confidence in the value of joints as stress indicators is greatest where they are uniformly arranged throughout a large area of flat lying rocks

behaviour of a sensitive marine sediment microstructural investigation the aim of this study is to characterise along various stress paths the microstructural evolution of a deep water marine sediment from the gulf of guinea gog results obtained at the macroscopic level have shown that the phenomenological behaviour of the gog sediment is explained by the properties of remoulded samples given by the isotropic and critical state lines and by the properties of the intact samples given by the damage evolution of the inter aggregate bonds microstructural investigations conducted by mercury intrusion porosimetry and scanning electron microscopy demonstrate that the volumetric strains measured at the macroscopic level come from inter aggregate pore variations associated with the degrading of the inter aggregate bonds the mechanism responsible for reorienting the particles appears to apply in the case of the remoulded sediment as for the natural sediment it is first necessary to increase the isotropic consolidation stress towards higher values in order to break the bonds between the aggregates before it becomes possible to activate the particle reorientation mechanism and thus approach the remoulded behaviour

two year observations of the jupiter polar regions by jiram on board juno we observed the evolution of jupiter s polar cyclonic structures over two years between february 2017 and february 2019 using polar observations by the jovian infrared auroral mapper jiram on the juno mission images and spectra were collected by the instrument in the 5 m wavelength range the images were used to monitor the development of the cyclonic and anticyclonic structures at latitudes higher than 80 both in the northern and the southern hemispheres spectroscopic measurements were then used to monitor the abundances of the minor atmospheric constituents water vapor ammonia phosphine and germane in the polar regions where the atmospheric optical depth is less than 1 finally we performed a comparative analysis with oceanic cyclones on earth in an attempt to explain the spectral characteristics of the cyclonic structures we observe in jupiter s polar atmosphere

fractured shale gas systems the first commercial united states natural gas production 1821 came from an organic rich devonian shale in the appalachian basin understanding the geological and geochemical nature of organic shale formations and improving their gas producibility have subsequently been the challenge of millions of dollars worth of research since the 1970s shale gas systems essentially are continuous type biogenic predominant thermogenic or combined biogenic thermogenic gas accumulations characterized by widespread gas saturation subtle trapping mechanisms seals of variable lithology and relatively short hydrocarbon migration distances shale gas may be stored as free gas in natural fractures and intergranular porosity as gas sorbed onto kerogen and clay particle surfaces or as gas dissolved in kerogen and bitumen five united states shale formations that presently produce gas commercially exhibit an unexpectedly wide variation in the values of five key parameters thermal maturity expressed as vitrinite reflectance sorbed gas fraction reservoir thickness total organic carbon content and volume of gas in place the degree of natural fracture development in an otherwise low matrix permeability shale reservoir is a controlling factor in gas producibility to date unstimulated commercial production has been achievable in only a small proportion of shale wells those that intercept natural fracture networks in most other cases a successful shale gas well requires hydraulic stimulation together the devonian antrim shale of the michigan basin and devonian ohio shale of the appalachian basin accounted for about 84 of the total 380 bcf of shale gas produced in 1999 however annual gas production is steadily increasing from three other major organic shale formations that subsequently have been explored and developed the devonian new albany shale in the illinois basin the mississippian barnett shale in the fort worth basin and the cretaceous lewis shale in the san juan basin in the basins for which estimates have been made shale gas resources are substantial with in place volumes of 497 783 tcf the estimated technically recoverable resource exclusive of the lewis shale ranges from 31 to 76 tcf in both cases the ohio shale accounts for the largest share

regional fractures i a mechanism for the formation of regional fractures at depth in flat lying reservoirs 1 regional fractures may form slowly at depth in extension and parallel to regional horizontal tectonic compression such fracture sets can be common in reservoirs despite the absence of flexure of the strata and are commonly important contributors to reservoir permeability such fractures make good targets for deviated wells high formation pore pressure is crucial to creating low effective confining stresses and brittle rock properties in the reservoirs conditions conducive to fracturing despite deep burial but pore pressure does not exceed the least principal stress and does not cause tensile fracturing the mechanism of natural hydraulic fracturing is incompatible with the characteristics of most regional fracture sets rather many regional fractures form duri g far field compression initiate at locally induced tensile stresses caused by flaws in the rock and propagate in the plane of the maximum and intermediate compressive stresses the differential stress required for initiation and propagation of regional fractures is well below that necessary for shear failure in the presence of high pore pressure fractures can be held open at depth by a tectonic basinwide dilatancy of the strata and the open void space commonly becomes mineralized

clusters of cyclones encircling jupiter s poles the familiar axisymmetric zones and belts that characterize jupiter s weather system at lower latitudes give way to pervasive cyclonic activity at higher latitudes two dimensional turbulence in combination with the coriolis effect that is the large meridionally varying coriolis force on the giant planets of the solar system produces alternating zonal flows the zonal flows weaken with rising latitude so that a transition between equatorial jets and polar turbulence on jupiter can occur simulations with shallow water models of giant planets support this transition by producing both alternating flows near the equator and circumpolar cyclones near the poles jovian polar regions are not visible from earth owing to jupiter s low axial tilt and were poorly characterized by previous missions because the trajectories of these missions did not venture far from jupiter s equatorial plane here we report that visible and infrared images obtained from above each pole by the juno spacecraft during its first five orbits reveal persistent polygonal patterns of large cyclones in the north eight circumpolar cyclones are observed about a single polar cyclone in the south one polar cyclone is encircled by five circumpolar cyclones cyclonic circulation is established via time lapse imagery obtained over intervals ranging from 20 minutes to 4 hours although migration of cyclones towards the pole might be expected as a consequence of the coriolis effect by which cyclonic vortices naturally drift towards the rotational pole the configuration of the cyclones is without precedent on other planets including saturn s polar hexagonal features the manner in which the cyclones persist without merging and the process by which they evolve to their current configuration are unknown

joint orientation in devonian rocks in the northern portion of the lower peninsula of michigan the orientations of 4 787 joints were measured at 43 separate locations in the area from charlevoix michigan to alpena michigan and north to the tip of the lower peninsula of michigan the sample localities are all in devonian carbonate rocks and shales of the michigan basin nearly all of the joints are vertical at least one major joint set is identifiable at each location and four major sets are present at more than half of the locations at 40 of the 43 sample localities there is a joint set with a strike of about 54 degrees n54 e at 35 locations there is a set striking about 133 degrees n47 w at 32 locations there is a set with a strike of about 92 degrees n88 w and a set with a strike of about 2 degrees no2 e is present at 31 sample localities mean orientation of any of the four joint sets does vary from location to location but is relatively consistent over the entire area for each of the sets fluctuations in mean orientation of any of the joint sets or the presence or absence of the joint sets is independent of formation lithology and distance between sample stations joint set orientation is independent of the regional strike around the michigan basin which varies from 54 degrees n54 e to 114 degrees n66 w within the study area the joint pattern does not appear to be related to structural trends previously postulated to exist in the precambrian basement of the area two of the joint sets may be related to major low amplitude folds in the paleozoic strata of the michigan basin in situ stress measurements show the orientation of maximum horizontal compressive stress to be compatible with these joint sets and the folds

long term tracking of circumpolar cyclones on jupiter from polar observations with junocam abstract we use observations from the junocam instrument on the juno spacecraft to map the polar regions of jupiter between 2016 and 2018 these polar maps track the long term evolution of the pentagonal and octagonal structures of circumpolar cyclones cpcs the south polar pentagonal and north polar octagonal arrangements of the cpcs have remained largely stable over the last 2 years of observation the morphologies of individual cyclones also remain largely stable for 1 2 years although some changes are observed so that the location of each cpc is uniquely identifiable at both north and south poles individual cyclones move around the center to a limited extent and there is a gap of variable width between one pair of south polar cpcs measurements at consecutive closest approaches perijoves 53 days apart show small movements of individual cyclones both eastward and westward however the south polar cpcs have a long term systematic westward drift rate of 1 5 0 2 per orbit or 0 040 0 005 m s whereas north polar cpcs do not show a consistent drift in longitude around the perimeter of the southern pentagon we detect no rapid jet in short term animations and we provide evidence that anticyclonic white ovals may have a range of longitudinal drifts between 44 and 15 per orbit 1 8 to 0 7 m s measurement of the angular velocities within the cyclones shows increasing angular velocity with decreasing radius except in the inner bright cloud deck of one class of northern cpcs which are inferred to have smaller or even negative angular velocities very near the center tangential wind velocities within the cyclones range up to 100 m s and even 100 m s in the southern polar cyclone and are maximal between radii of 900 1600 km overall we find that the behavior of the polar cyclones constellations compares well to vortex crystal theory even though the theory does not include anticyclonic vorticity

orthogonal fracture systems at the limits of thrusting an example from southwestern wales abstract a well developed orthogonal vein system is located in the autochthonous foreland just beyond the limits of variscan thrusting in southwestern wales the two vein sets trend 200 and 290 perpendicular and parallel respectively to variscan structures the veins contain stretched quartz fibers indicating horizontal extensions of between 0 3 and 2 5 the 200 set has greater extension with a distinctive morphology including shorter more curvilinear fractures that have components of normal offset vein intersections are simple indicating episodic growth by alternating regional propagation of each set during propagation maximum compression was subvertical and the horizontal principal stresses switched direction with the alternation of set growth the system formed during waning variscan compression when the directions of horizontal principal stresses were still controlled by the tectonic compression the differential stress may have been greater during propagation of the 200 set this example indicates that orthogonal fracture systems in forelands beyond thrusting 1 are initiated by fracturing parallel to tectonic compression 2 form in a few stages that are controlled by changes in regional stress and 3 form during waning tectonic compression that controls fracture orientations

fractures in the northern plains stream patterns and the midcontinent stress field fractures in late cretaceous to late pleistocene sediments in saskatchewan eastern montana and western north dakota form two vertical orthogonal sets trending northeast southwest and northwest southeast the pattern is consistent regardless of rock type or age except for concretionary sandstone both sets appear to be extensional in origin and are similar in character to joints in alberta modem stream valleys also trend in the same two dominant directions and may be controlled by the underlying fractures elevation variations on the sub mannville early cretaceous unconformity form a rectilinear pattern also parallel to the fracture sets suggesting that fracturing was initiated at least as early as late jurassic it may have begun earlier but there are insufficient data at present to extend the time of initiation we interpret the fractures as the result of vertical uplift together with plate motion the westward drift of north america the northeast southwest directed maximum principal horizontal

a note on sedimentation and consolidation an extended equation is derived which governs the sedimentation and simultaneous consolidation of pelagic sediments an example of the implementation of this theory is also given in this note trrl

hst imaging of atmospheric phenomena created by the impact of comet shoemaker levy 9 hubble space telescope hst images reveal major atmospheric changes created by the collision of comet shoemaker levy 9 with jupiter plumes rose to 3000 kilometers with ejection velocities on the order of 10 kilometers second 1 some plumes were visible in the shadow of jupiter before rising into sunlight during some impacts the incoming bolide may have been detected impact times were on average about 8 minutes later than predicted atmospheric waves were seen with a wave front speed of 454 20 meters second 1 the hst images reveal impact site evolution and record the overall change in jupiter s appearance as a result of the bombardment