viscous flow features on the surface of mars observations from high resolution mars orbiter camera moc images 10 5 10 7 years of the material our shear stress estimates of 10 1 5 10 2 5 mpa yield strain rates on the order of 10 11 10 16 s 1 which are within the superplastic flow regime of ice mean annual surface temperatures age constraints and strain estimates show that it is possible for a meters thick ice dust mixture to undergo viscous deformation under past or present surface conditions for ice grain sizes 10 mm the meters thick layer in which the viscous flow features formed is morphologically similar to a degraded meters thick ice dust surface deposit dissected mantle terrain locations of the viscous flow features dissected mantle terrain and recent gullies are concentrated in the midlatitude regions and all three show identical distributions as a function of latitude with the maximum frequency of occurrence at 40 n and s the strong association between these small scale flow features and the dissected mantle terrain large scale viscous flow features and recent gullies imply that deposition deformation and removal of ice rich materials has played an important role in the modification of the surface in the midlatitudes of mars during the amazonian and possibly longer index terms 5470 planetology solid surface planets surface materials and properties 5416 planetology solid surface planets glaciation 1863 hydrology snow and ice 1827 1823 hydrology frozen ground 8168 tectonophysics stresses general keywords viscous flow viscous creep dissected mantle terrain ice rich deposits mars climate recent gullies

relict non glacial surfaces in formerly glaciated landscapes abstract relict non glacial surfaces occur within many formerly glaciated landscapes and contain important information on past surface processes and long term landscape evolution relict non glacial surfaces are distinguishable from glacial surfaces by large scale morphologies including rounded summits fluvial valleys and cryoplanation terraces and pediments and the presence of tors blockfields and or saprolites preservation during glaciation occurs either through coverage by non erosive cold based ice or as nunataks although surface morphologies and denudation rates indicate a continuous non glacial surface history since preglacial times relict non glacial surfaces are dynamic features that have evolved during the quaternary depending on spatial variables such as lithology slope regolith depth and the abundance of fine matrix and water some surfaces are denuding very slowly while others display more rapid denudation high spatial variability in denudation rates results in changing surface morphologies over time denudation rates also display high temporal variability with much surface evolution having perhaps occurred soon after the initial onset of glaciation or during paraglacial phases while some parts of non glacial landscapes are currently active others may be largely inactive relicts of past higher energy regimes although non glacial surfaces are dynamic much remains to be determined regarding surface denudation rates and the magnitude of morphological changes over time

formation of patterned ground and fine scale soil development within two late holocene glacial chronosequences jotunheimen norway abstract chronosequences of 250 to 130 years were established on two late holocene glacier forelands in the jotunheimen region of southern norway patterned features occurring within chronologically established time units were studied young patterned features forming 10 20 years after deglaciation are frost active vegetation cover is minimal within the young patterned features consisting of bryophytes organic crusts soil development within patterned ground is also minimal absent because frost action retards horizonization with time and distance from the glaciated ice margin frost activity declines within the patterned features suggesting that a thin active periglacial zone exists near the ice margin initially frost activity decreases at the borders of the features with the centers stabilizing later in time this results in fine scale soil heterogeneity and variations of soil development fine scale pedogenic development is first encountered at the borders of patterned ground that has developed on terrain exposed since the 1930s yet soil development is predominantly absent at the centers of patterned ground with time and distance from the ice margin frost activity declines and allows patterned features to homogenize from border to center positions in regard to soil characteristics across the chronosequences soils within patterned features pedogenically follow previous soil chronosequence studies evolving from usda classifications of entisols into inceptisols frost disturbance within patterned ground however produces a lag effect that results in longer periods of time for pedogenesis to occur and thinner soils than that of the surrounding terrain

landforms indicative of ground ice thaw in the northern high latitudes of mars the confirmation of near surface ground ice and perchlorates at the phoenix landing site suggest that high latitude ground ice thaw may be more easily achieved than previously envisaged providing the potential to drive significant distinctive morphogenesis we describe the results of a survey of 23 high resolution imaging science experiment hirise images covering 337 of longitude between latitudes 59 n and 79 n in which such morphogenesis is apparent confirming that thaw has been a regionally important morphological agent some of the strongest geomorphological indicators of cyclical ground ice thaw described are assemblages of sorted landforms including clastic patterned ground resulting from cryoturbation of ice rich regolith and lobate forms reflecting solifluction also described are braided gully fan systems sourced at thermokarst pits and channels that have evolved from enlarged thermal contraction cracks not only are these landforms indicative of thaw and flowing liquid but the incision of solifluction lobes by thermokarst gullies demonstrates that thaw has been responsible for polycyclic morphogenesis the presence of these landforms across the high northern latitudes of mars indicates that the regional importance of thaw has been underestimated this in turn has important implications for the development of better climate models and the search for life on mars

martian gullies in the southern mid latitudes of mars evidence for climate controlled formation of young fluvial features based upon local and global topography a new survey of mars orbiter camera moc narrow angle images of gullies in the 30 45 s latitude band includes their distribution morphology local topographic setting orientation elevation and slopes these new data show that gully formation is favored over a specific range of conditions elevation 5000 to 3000 m slope 10 and orientation 83 8 on pole facing slopes these data and the frequent occurrence of gullies on isolated topographic highs lead us to support the conclusion that climatic related processes of volatile accumulation and melting driven by orbital variations are the most likely candidate for processes responsible for the geologically recent formation of martian gullies

an analysis of sinuous ridges in the southern argyre planitia mars using hirise and ctx images and mola data 1 a suite of sinuous ridges with branching and braided morphologies forms an anastomosing network in southern argyre planitia mars several modes of origin have been proposed for the argyre ridges imagery from the high resolution imaging science experiment hirise and context camera ctx aboard mars reconnaissance orbiter mro and mars orbiter laser altimeter mola topographic data sets from mars global surveyor mgs are used to constrain processes involved in formation of the argyre ridges we find the characteristics of the ridges and associated layered deposits consistent with glaciofluvial lacustrine processes and conclude that the ridges are most likely eskers in particular variations in ridge height appear to be related to the surrounding surface slope ridge height increases with descending slopes and decreases with ascending slopes this characteristic is observed in terrestrial eskers and is related to subice flow processes the nature of some eroding beds in the ridges suggests induration if the argyre ridges are indeed eskers the southern argyre basin was once covered by the margin of a large thick stagnating or retreating ice deposit that extended for hundreds of kilometers or more during ridge formation water flowed on top within or beneath the ice deposit the continuity and preservation of the ridges suggests that flow was primarily at the base of the ice the dimensions up to hundreds of meters tall and several kilometers wide aspect ratio and extent hundreds of kilometers of the ridges as well as preliminary calculations of discharge suggest that a significant amount of water was available

sorted clastic stripes lobes and associated gullies in high latitude craters on mars landforms indicative of very recent polycyclic ground ice thaw and liquid flows self organised patterns of stone stripes polygons circles and clastic solifluction lobes form by the sorting of clasts from fine grained sediments in freeze thaw cycles we present new high resolution imaging science experiment hirise images of mars which demonstrate that the slopes of high latitude craters including heimdal crater just 25 km east of the phoenix landing site are patterned by all of these landforms the order of magnitude improvement in imaging data resolution afforded by hirise over previous datasets allows not only the reliable identification of these periglacial landforms but also shows that high latitude fluviatile gullies both pre and post date periglacial patterned ground in several high latitude settings on mars because thaw is inherent to the sorting processes that create these periglacial landforms and from the association of this landform assemblage with fluviatile gullies we infer the action of liquid water in a fluvio periglacial context we conclude that these observations are evidence of the protracted widespread action of thaw liquids on and within the martian regolith moreover the size frequency statistics of superposed impact craters demonstrate that this freeze thaw environment is at least in heimdal crater less than a few million years old although the current martian climate does not favour prolonged thaw of water ice observations of possible liquid droplets on the strut of the phoenix lander may imply significant freezing point depression of liquids sourced in the regolith probably driven by the presence of perchlorates in the soil because perchlorates have eutectic temperatures below 240 k and can remain liquid at temperatures far below the freezing point of water we speculate that freeze thaw involving perchlorate brines provides an alternative low temperature hypothesis to the freeze thaw of more pure water ice and might drive significant geomorphological work in some areas of mars considering the proximity of heimdal crater to the phoenix landing site the presence of such hydrated minerals might therefore explain the landforms described here if this is the case then the geographical distribution of martian freeze thaw landforms might reflect relatively high temperatures but still below 273 k and the locally elevated concentration of salts in the regolith c 2010 elsevier inc all rights reserved

morphology and evolution of the ejecta of hale crater in argyre basin mars results from high resolution mapping we use various data sets including images from the high resolution imaging science experiment camera hirise to examine the ejecta of the generally fresh looking hale crater that occurs in the rugged mountain terrain of nereidum montes in the northern rim materials of the argyre impact structure on mars our investigation reveals that the distal parts of the hale crater ejecta and other basin deposits behave like viscous flows which we attribute to the secondary flow of ejecta mixed with water ice rich basin materials consistent with water enrichment of the basin materials our mapping further reveals occasionally deformed surfaces including highly conspicuous features such as mounds and fractured plateaus that we interpret to be a result of periglacial modification subsequent including possibly present day to the transient localized melting and fluvial erosion caused by hale impact generated heating in particular our morphometric analysis of a well defined valley system west of hale crater suggests that it may have been formed through hydrologic glacial activity prior to the hale impact with additional modification resulting from the impact and subsequent geologic and hydrologic phenomena including glacial and periglacial activity

dune morphology sand transport pathways and possible source areas in east thaumasia region mars an aeolian system located in aonia terra eastern thaumasia region consists of six dark dune fields the dune pattern suggests an organized extended sand transport system which is characterized by the presence of long sand corridors the latter connects the different ergs with potential sources the sand stored in the ergs is provided by layered materials exposed in pits and crater walls and by the ergs themselves most of the sand converges from the marginal dune fields into the central erg c the latter develops in an area of convergence of at least three different winds from the southwest the northeast and the northwest the northwesterly flows seem to postdate the other winds as suggested by the development of a complex dune pattern in the western portion of the erg c representing a successive episode of aeolian construction collectively such complex dune patterns show how dune fields could record major changes in the wind regimes of mars

clastic patterned ground in lomonosov crater mars examining fracture controlled formation mechanisms the area surrounding lomonosov crater on mars has a high density of seemingly organised boulder patterns these form seemingly sorted polygons and stripes within kilometre scale blockfields patches of boulder strewn ground which are common across the martian high latitudes several hypotheses have been suggested to explain the formation of clastic patterned ground on mars it has been proposed that these structures could have formed through freeze thaw sorting or conversely by the interaction of boulders with underlying fracture polygons in this investigation a series of sites were examined to evaluate whether boulder patterns appear to be controlled by the distribution of underlying fractures and test the fracture control hypotheses for their formation it was decided to focus on this suite of mechanisms as they are characterised by a clear morphological relationship namely the presence of an underlying fracture network which can easily be evaluated over a large area it was found that in the majority of examples at these sites did not exhibit fracture control although fractures were present at many sites there were very few sites where the fracture network appeared to be controlling the boulder distribution in general these were not the sites with the best examples of organization suggesting that the fracture control mechanisms are not the dominant geomorphic process organising the boulders in this area

sorted clastic polygons in the argyre region mars and possible evidence of pre and post glacial periglaciation in the late amazonian epoch abstract the argyre basin and associated rim materials in the southern highlands of mars are ancient having been formed by the impact of a large body 3 9 gya despite its age the regional landscape exhibits a wide range of geological geomorphological modifications and or features e g fluvial lacustrine aeolian glacial and periglacial collectively this bears witness to the dynamic evolution of the argyre region from the deep past through to perhaps the present day here we present three principal findings that point to at least two distinct episodes of periglaciation separated by a possible glacial interval during the very late amazonian epoch in eastern aonia terra at i e on the western flank of the argyre basin these findings are the product of our circum argyre study of all hirise images 35 65 s and 290 350 e 1 a the first periglacial episode involves the development of small sized 15 25 m in diam and clastically sorted polygons sps the sps are observed at eighteen locations within eastern at hitherto the presence of sps in this region has been reported at one location alone no other observations of sps in the southern hemisphere of mars have been documented morphologically similar landforms develop in cold climate permafrost landscapes on earth by means of periglacial processes i e freeze thaw cycling segregated ice formation cryoturbation and frost heave b we ascribe a periglacial origin to the sps in eastern at on the basis of this similarity of form and no less importantly on the close spatial association of the sps with blockfields whose weathered clastic products are the building blocks of periglacial sorting on earth gelifluction like lobes and possible wet gullies where similar assemblages occur in terrestrial permafrost landscapes the presence of liquid water and of boundary conditions tolerant of freeze thaw cycling are observed or inferred c fifteen of the eighteen sp locations are clustered longitudinally 44 4 57 5 s 289 9 302 4 e this is inconsistent with the latitudinal and obliquity driven dependency of freeze thaw cycling in the late amazonian epoch hypothesised by many workers in the discipline 2 the second periglacial episode is highlighted by the development of small sized and clastically non sorted polygons nsps these polygons could have formed by means of a dry cryotic process i e thermal contraction cracking 3 the nsps incise and thus postdate a light toned mantle thought by numerous workers to comprise an ice dust admixture at some of the locations where the putatively icy mantle has undergone apparent ablation underlying sps are observed this suggests that the sps predate the mantle and derivatively the nsps as well the proposed geochronology of wet based sp icy mantle dry based nsp periods and interval is entirely new to the community moreover it underlines the possibility that periglacial and glacial boundary conditions at least in our study area may have oscillated much more substantially in the very late amazonian epoch than many workers have thought possible

squeezing rock conditions at an igneous contact zone in the taloun tunnels tehran shomal freeway iran a case study squeezing rock conditions at the contact zone of an andesitic basaltic body and tuff country rocks in the taloun tunnels were investigated and analyzed evaluation of the rock mass properties illustrates the fact that they were significantly reduced at the contact zone especially when wet detailed monitoring and measurements of tunnel wall convergence at the contact zone in the taloun service tunnel during the 10 months following excavation and installation of initial support prior to installation of heavy support showed greater than 3 of the normalized tunnel closure this confirms moderate squeezing conditions at the contact zone the measured displacement was even higher than that of the fault zone in which deformation was decreased during the first month and eventually stabilized similarly numerical modeling of the deformation at the contact zone not only confirmed a higher value of the tunnel convergence but also demonstrated the reduction of in situ stress and development of plastic zones across the contact zone these data are also believed to account for the squeezing condition at the contact zone it is expected that this condition will be significantly increased in the main road tunnels due to the fact that these tunnels are twice as wide as the service tunnel therefore proper and timely support must be applied numerical analysis of the support at the contact zone showed that the stress due to bending moment is greater than that of the axial forces on the lining this calls for certain support measures in the form of permanent lining and two layers of steel bars to compensate for the tensile stress exertion on the lining

the nature of the groundmass of surficial suevite from the ries impact structure germany and constraints on its origin surficial suevites from the ries impact structure have been investigated in the field and using optical and analytical scanning electron microscopy the groundmass of these suevites comprises calcite clay minerals impact melt glass crystallites plagioclase garnet and pyroxene francolite and ba phillipsite the latter zeolite is a secondary phase abundant textures have been observed intricate flow textures between the various groundmass phases globules of each phase in the other phases spheroids of pyrrhotite in calcite the budding off of clay globules into silicate glass and or calcite euhedral overgrowths of francolite on apatite clasts and quench textured crystallites in the groundmass groundmass forming calcite displays higher feo mno and sio2 contents than limestone target material the composition of suevite clay minerals is highly variable and not always consistent with montmorillonite three types of glasses are distinguished in the groundmass type 1 glasses are sio2 rich and are clearly derived from sandstones in the sedimentary cover while the protoliths of the other two glass types remains unclear analytical data and micro textures indicate that the calcite silicate glass francolite and clay minerals of the groundmass of the ries suevites represent a series of impact generated melts that were molten at the time of and after deposition on cooling plagioclase pyroxene and garnet crystallized from the groundmass these results are at variance with the current traditional descriptive definition of suevite given that ries is the original type occurrence of suevite some modification to the traditional definition may be in order as the results of this study are most consistent with the groundmass of ries surficial suevites representing a mix of several types of impact generated melts we suggest that a possible origin for these suevites is as some form of impact melt flow s that emanated from different regions of the evolving crater

the distribution of putative periglacial landforms on the martian northern plains in this investigation hirise images were surveyed across three regions of the northern plains of mars acidalia arcadia and utopia planitiae a sample of hirise images within each of these areas was examined the aim of the investigation was to determine the distribution of three varieties of landform clastic patterned ground lobate hill slope features and scalloped depressions these features are of importance as they are morphologically similar to terrestrial periglacial features examples of these landforms were found across the study areas scalloped depressions are common at mid latitudes in each of the three regions sorted patterned ground was not as widespread some examples of sorted patterned ground were found in all three study areas but the main concentration occurs in the north western region of acidalia planitia lobate hill slope features were the least common of the three landform types despite occurring infrequently several possible examples of lobate features were found to occur in proximity to other putative periglacial features it was found that lobate hill slope features and clastic patterns occurred further south than expected beyond the southern extent of many previous studies these features and by extension the processes that form them could thus occur more widely than previously thought it also appears that although putative periglacial features are often found in crater interiors they are not limited to these environments extensive areas of patterned ground were found on the inter crater plains lobate features and sorted stripes were often found on crater walls which would support the hypothesis that they are analogous to hill slope features on earth scalloped depressions were most often found in crater interiors or on crater ejecta although examples on the inter crater plains were not uncommon

weathering indices for rhyolitic tuff and granite in hong kong a series of chemical analyses and dry density tests of rhyolitic tuff and granitic samples have been carried out the test results have been interpreted using a newly developed theoretical weathering model for calculating a mobility index of major elements in rock and soil it is found that this index is useful for describing changes of rock and soil during weathering and classifying the degrees of weathering based on the theoretical model a new parameter called the volume index which combines chemical and physical data is suggested this index appears to be a good indicator for classifying the degree of weathering in hong kong a quantitative classification scheme is suggested

sub horizontal reinforcement of weathered granite before tunneling beneath a spillway abstract sub horizontal jet grouted columns and pipe roof are usually adopted to reinforce weak ground ahead of tunnel excavation face but they bear a low tensile strength and poor waterproof capacity respectively a combination of sub horizontal jet grouted columns and pipe roof was proposed to reinforce weak ground before jiangmen tunnel passed beneath a spillway for drainage of yu long reservoir due to the pipe roof added below the jet grouted columns numerical simulation demonstrates that stress in the jet grouted columns ground surface settlement convergence and stress of primary liner are reduced and the stability of the excavation face is increased substantially the umbrella formed by jet grouted columns works as a shell and the pipes in the pipe roof behave as beams in the longitudinal direction of the tunnel due to their respective features in the working mechanism jiangmen tunnel stayed safe when it passed beneath the spillway the field measurements are comparable to the numerical results although there are some differences in their values due to some influence factors

near surface soil displacement in sorted circles resolute area cornwallis island canadian high arctic lines of dowels originally inserted vertically to depths of 100 and 200 mm in generally fine grained soil across sorted circles were repeatedly surveyed over a 3 year period measurements of dowel

the indication of martian gully formation processes by slope area analysis the formation process of recent gullies on mars is currently under debate this study aims to discriminate between the proposed formation processes pure water flow debris flow and dry mass wasting through the application of geomorphological indices commonly used in terrestrial geomorphology high resolution digital elevation models dems of earth and mars were used to evaluate the drainage characteristics of small slope sections data from earth were used to validate the hillslope debris flow and alluvial process domains previously found for large fluvial catchments on earth and these domains were applied to gullied and ungullied slopes on mars in accordance with other studies our results indicate that debris flow is one of the main processes forming the martian gullies that were being examined the source of the water is predominantly distributed surface melting not an underground aquifer evidence is also presented indicating that other processes may have shaped martian crater slopes such as ice assisted creep and solifluction in agreement with the proposed recent martian glacial and periglacial climate our results suggest that within impact craters different processes are acting on differently oriented slopes but further work is needed to investigate the potential link between these observations and changes in martian climate

periglacial features on the margins of a receding plateau ice cap lyngen north norway some features around the perimeter of the balgesvarri plateau ice cap are described sorted stone circles were found beneath a slowly retreating ice margin the basal ice in this area appears to be below the pressure melting point no absolute dating of features was possible but a relative chronology is suggested resume le retrait glaciaire et les manifestations piriglaciaires sur les marges d un glacier de calotte a lyngen norvege du nord on decrit quelques traits caracteristiques du pourtour du glacier de calotte de balgesvarri des sols polygonaux ont ete decouverts a l aval d un front glaciaire en leger retrait la glace de fond dans cette zone semble ttre en dessous du point de fusion correspondant a la pression il n a pas ete possible d etablir une datation absolue de ces manifestations periglaciaires mais on propose une chronologie relative zusammenfassung gletscherriickgang und periglaziale erscheinungen an den riindern einer plateau eiskappe lyngen nordnorwegen einige erscheinungen an der peripherie der balgesvarri plateaukappe werden beschrieben unter einem langsam zuruckgehenden eisrand wurden steinkreise gefunden das eis am untergrund dieser region durfte si ch unter dem druckschmelzpunkt befinden eine absolute datierung der erscheinungen war nicht moglich doch llisst sich eine relative zeitliche abfolge ermitteln

a new global database of mars impact craters 1 km 1 database creation properties and parameters 1 impact craters have been used as a standard metric for a plethora of planetary applications for many decades including age dating geologic mapping and stratigraphic relationships as tracers for surface processes and as locations for sampling lower crust and upper mantle material utilizing craters for these and other investigations is significantly aided by a uniform catalog of craters across the surface of interest consequently catalogs of craters have been developed for decades for the moon and other planets we present a new global catalog of martian craters statistically complete to diameters d 1 km it contains 384 343 craters and for each crater it lists detailed positional interior morphologic ejecta morphologic and morphometric data and modification state information if it could be determined in this paper we detail how the database was created the different fields assigned and statistical uncertainties and checks in our companion paper robbins and hynek 2012 we discuss the first broad science applications and results of this work

a multiple graph technique for preliminary assessment of ground conditions for tunneling abstract a novel multiple graph technique has been proposed for the preliminary assessment of the ground conditions in the himalayan region this technique has been developed based on the sequential estimation of three quantities viz rock mass strength competency factor and the ground condition rock mass strength is estimated from rock mass quality q moreover two empirical ground classifications have been suggested based on many case histories for separately defining ground condition in soft rocks and hard rocks a graphical work flow chart and practical illustration of this method has been presented using two sets of examples the proposed technique is an efficient tool for quick estimation of the ground condition in the primary phase of design of tunnels and also during the excavation of tunnels

hurricane maximum intensity past and present hurricane intensity forecasting has lagged far behind the forecasting of hurricane track in an effort to improve the understanding of the hurricane intensity dilemma several attempts have been made to compute an upper bound on the intensity of tropical cyclones this paper investigates the strides made into determining the maximum intensity of hurricanes concentrating on the most recent attempts to understand the maximum intensity problem the theories of holland and emanuel are reviewed with the objective of assessing their validity in real tropical cyclones each theory is then tested using both observations and the axisymmetric hurricane numerical models of ooyama and emanuel it is found that ambient convective instability plays a minor role in the determination of the maximum intensity and that the emanuel model is the closest to providing a useful calculation of maximum intensity several shortcomings are revealed in emanuel s theory however showing the need for more basic research on the axisymmetric and asymmetric dynamics of hurricanes as an illustration of the importance of asymmetric vorticity dynamics in the determination of a hurricane s maximum intensity it is shown using ooyama s hurricane model that the maximum intensity of a tropical cyclone may be diminished by convectively generated vorticity anomolies excited outside the primary eyewall the vorticity anomolies are parameterized by adding a concentric ring of vorticity outside the primary eyewall that acts to cut off its supply of angular momentum and moist enthalpy it is suggested that the generation of vorticity rings or bands outside the primary eyewall is a major reason why tropical cyclones fail to attain their maximum intensity even in an otherwise favorable environment the upshot of this work points to the need for obtaining a more complete understanding of asymmetric vorticity processes in hurricanes and their coupling to the boundary layer and convection

mars nature and evolution of young latitude dependent water ice rich mantle 1 high resolution altimetry and imaging have revealed the presence of a meters thick sedimentary layer at middle to high northern and southern latitudes presently covering at least 23 of the planet the layer is interpreted to be water ice rich and to undergone degradation recently its activity very likely coincided with the last major obliquity excursion a few hundred thousand years ago the majority of the layer at higher latitudes however persisted for a much longer time in the late amazonian stratigraphic analysis suggests a complex history of successive episodes of deposition and removal repeated deposition and removal of the mantles are interpreted to be responsible for the unusual statistical properties of kilometer scale topography in the transitional mid latitude zones

hypercanes a possible link in global extinction scenarios bolide impacts and large scale volcanic eruptions have been proposed as possible causes of the massive extinction of life that has occurred episodically in earth s history in spite of the catastrophic disruption of the local environment that accompanies bolide impacts and volcanic eruptions it has been difficult to explain why these events sometimes lead to global extinction of species we propose that in some cases the missing link may be provided by hypercanes runaway hurricanes that are capable of injecting massive amounts of water and aerosols into the middle and upper stratosphere where they may have profound effects on atmospheric chemistry and radiative transfer hypercanes are theorized to occur when the sea surface temperature exceeds a critical threshold which may occur when sea water is locally heated by bolide impact shallow sea volcanism or possibly by overturning of superheated brine pools formed by underwater volcanic activity simulations using a convection resolving nonhydrostatic axisymmetric numerical model show that hypercanes can indeed develop when the sea surface temperature is high and that they inject large amounts of mass into the stratosphere

glacial survival of blockfields on the varanger peninsula northern norway for more than hundred years it has been debated whether blockfields in mountain summit areas can be used to delimit the vertical extent of pleistocene ice sheets in this study the relationship between blockfields developed in quartzites and sandstones on the varanger peninsula northern norway and glacially derived features have been evaluated erratics and circular ablation moraines are superimposed on the blockfields and lateral meltwater channels are eroded into them glacial striations and other signs of glacial sculpturing are restricted to low lying areas with channelled ice flow relative ages of the blockfields and the features in them are inferred and the first measurements of in situ produced cosmogenic nuclides from the varanger peninsula are reported we conclude that the blockfields have survived underneath at least one thick cold based ice sheet thus these blockfields cannot be used as indicators of ice free conditions as previously suggested for southern norway our results have implications for the potential for land surface preservation beneath ice sheets and for glacial reconstructions in northern fennoscandia

investigation of an argyre basin ring structure using mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars 1 the argyre basin a large impact basin in the southern highlands of mars excavates early noachian geologic units and thus is an ideal probe of the compositional layering of ancient highland crust a ring structure defined by circumferential graben is believed to represent the outermost topographic scarp of the basin two distinct layers in the fluvially dissected highland plains unit npld have been exposed by the ring graben in northwest argyre a lower unit enriched in high calcium pyroxene and an upper unit showing laterally extensive occurrences of phyllosilicates including chlorite and iron magnesium smectite these phyllosilicates closely follow the unit contact between unit npld and hpl3 in this region the hesperian aged hpl3 caprock directly covers unit npld two nearby knobs also show phyllosilicate bearing materials over a high ca pyroxene enriched unit although the knobs are located in regions mapped as npl1 and nplh from these observations we suggest that an extensive layer of phyllosilicates underlying a layer of high ca pyroxene bearing rock existed in the region prior to the argyre impact these materials were thrown up by the impact event and deposited as an inverted flap this inverted flap of ejecta was then cut by the circumferential graben that formed as the transient argyre crater collapsed exposing the materials

tunneling in squeezing rock the bolu tunnel anatolian motorway turkey abstract the bolu tunnel is subject to considerable deformation due to stress related failure in the rock mass in thrust zones and strike slip faults that transect the tunnel these deformations resulted in some serious geotechnical problems which were overcome either by flexible or extremely heavy support systems the heavy system was used to prevent or bring under control the large deformations that would take place during excavation whereas the flexible method allows the deformations to develop without restraint the heavy support system was used in thrust fault zones and in flysch zones in the bolu tunnel and produced more successful results in comparison to the flexible support system a brief explanation of the tunnel collapse in the duzce earthquake is also provided

an equatorial periglacial landscape on mars abstract we present evidence drawn from new 25 cm pixel hirise images of mars of landforms indicative of geologically recent thaw degradation of ice rich terrain near the martian equator we have focused our study on the head region of athabasca vallis a catastrophic flood carved outflow channel thought to have been active within the last 2 8 ma the geomorphology of the study area is characterised by a series of polygonally patterned surfaces that are bounded by erosional scarps the scarps are indented with cirque shaped niches that appear to be controlled in scale and form by the pre existing polygonal sculpture shallow basins defined by niche indented scarps are also seen and contain pitted mound and cone structures that are similar in form to terrestrial pingos associated with many of these scarps are dendritic channels and gullies blocky debris and hummocky terminal deposits together these correspond morphologically to terrestrial retrogressive thaw slumps which are landforms typical of thermokarst environments we have also observed an evolutionary sequence of morphologies beginning with subsidence of polygonised surfaces and ending with scarp bounded basins fed by inter polygon channels this is consistent with the former presence of surficial liquid water released by ground ice thaw and is again indicative of thermokarst moreover the observations of epigenetic polygons and channels and of polycyclic retrogressive thaw slumps suggest that thaw and standing water persisted for many seasonal cycles the assemblage of landforms the occurrence of polygons and pingo like forms within erosional basins and observations of fluvial like channels cross cutting pre existing surface features are consistent with a surface that has evolved significantly since it was originally emplaced this precludes this terrain being a volcanic i e primary landscape as has been suggested in the past the formation of this landform assemblage requires that there was thaw of ground ice and persistent liquid water at the surface given the geologically young flood deposits in which this assemblage occurs our observations point to a recent period in which mars climate supported thaw conditions in this region

a model for sorted circles as self organized patterns sorted circles emerge as self organized patterns from a laterally uniform active layer that becomes laterally sorted as frost heave deforms the interface between a stone layer and an underlying soil layer in a three dimensional cellular model of the active layer cyclic freezing and thawing drives transport of stone and soil particles by 1 addition of ice particles representing soil expansion by frost heave 2 removal of ice particles representing soil consolidation during thawing 3 addition of void particles a discrete abstraction of soil compressibility representing soil expansion by water absorption 4 removal of void particles representing compaction and desiccation of underlying soil by frost heave 5 relaxation of surface morphology by soil creep and stone avalanche and 6 vertical sorting of stones and soil by illuviation these transport processes give rise to sorted circles which are characterized by a mean spacing of 3 6 m a 2 4 m wide soil domain surrounded by a 1 0 m wide 0 3 m high annulus of stones and a 750 year period of circulation in the soil domain all consistent with measured characteristics of sorted circles in western spitsbergen in the model instabilities on the stonesoil interface grow upward as soil plugs by drawing in soil from the surrounding subsurface soil layer soil plugs develop into sorted circles as they contact the ground surface simultaneously elevating an encircling annulus of stones sorted circles are dynamically maintained by circulation within the stone and soil domains initiation of soil plugs is driven by a positive feedback in which frost heave near the stone soil interface pushes soil toward more compressible soil regions where the soil layer is thicker the lateral component of these frost heave induced displacements is not reversed during thaw because soil consolidation as ice rich soil melts and drains and soil expansion as desiccated and compacted soil hydrates displace soil vertically further development of soil plugs and sorted circles is determined by an interplay between this positive feedback and amplitude dependent negative feedbacks that result from decoupling of the freezing front from the stone soil interface parameters outside the range in which sorted circles form can result for example in stone islands and labyrinthine patterns the initial wavelength of perturbations on the stone soil interface is accurately predicted using a linear stability analysis but increase in this wavelength through time reflects the nonlinearities that control the spacing of soil plugs and sorted circles namely interactions and mergers between neighboring forms

co2 sublimation in martian gullies laboratory experiments at varied slope angle and regolith grain sizes martian gullies were initially hypothesized to be carved by liquid water due to their resemblance to gullies on earth recent observations have highlighted significant sediment transport events occurring in martian gullies at times and places where co2 ice should be actively sublimating here we explore the role of co2 sublimation in mobilizing sediment through laboratory simulation in our previous experimental work we reported the first observations of sediment slope movement triggered by the sublimation of co2 frost we used a mars regolith simulant near the angle of repose the current study extends our previous work by including two additional substrates fine and coarse sand and by testing slope angles down to 10 we find that the mars regolith simulant is active down to 17 the fine sand is active only near the angle of repose and the coarse sand shows negligible movement using an analytical model we show that under martian gravity motion should be possible at even lower slope angles we conclude that these mass wasting processes could be involved in shaping martian gullies at the present day and intriguingly the newly reported co2 creep process could provide an alternative explanation for putative solifluction lobes on mars

clastic polygonal networks around lyot crater mars possible formation mechanisms from morphometric analysis polygonal networks of patterned ground are a common feature in cold climate environments they can form through the thermal contraction of ice cemented sediment i e formed from fractures or the freezing and thawing of ground ice i e formed by patterns of clasts or ground deformation the characteristics of these landforms provide information about environmental conditions analogous polygonal forms have been observed on mars leading to inferences about environmental conditions we have identified clastic polygonal features located around lyot crater mars 50 n 30 e these polygons are unusually large 100 m diameter compared to terrestrial clastic polygons and contain very large clasts some of which are up to 15 metres in diameter the polygons are distributed in a wide arc around the eastern side of lyot crater at a consistent distance from the crater rim using high resolution imaging data we digi tised these features to extract morphological information these data are compared to existing terrestrial and martian polygon data to look for similarities and differences and to inform hypotheses concerning possible formation mechanisms our results show the clastic polygons do not have any morphometric features that indicate they are similar to terrestrial sorted clastic polygons formed by freeze thaw processes they are too large do not show the expected variation in form with slope and have clasts that do not scale in size with polygon diameter however the clastic networks are similar in network morphology to thermal contraction cracks and there is a potential direct martian analogue in a sub type of thermal contraction polygons located in utopia planitia based upon our observations we reject the hypothesis that polygons located around lyot formed as freeze thaw polygons and instead an alternative mechanism is put forward they result from the infilling of earlier thermal contraction cracks by wind blown material which then became compressed and or cemented resulting in a resistant fill erosion then leads to preservation of these polygons in positive relief while later weathering results in the fracturing of the fill material to form angular clasts these results suggest that there was an extensive area of ice rich terrain the extent of which is linked to ejecta from lyot crater

amazonian northern mid latitude glaciation on mars a proposed climate scenario recent geological observations in the northern mid latitudes of mars show evidence for past glacial activity during the late amazonian similar to the integrated glacial landsystems in the dry valleys of antarctica the large accumulation of ice many hundreds of meters required to create the observed glacial deposits points to significant atmospheric precipitation snow and ice accumulation and glacial flow in order to understand the climate scenario required for these conditions we used the lmd laboratoire de meteorologie dynamique mars gcm general circulation model which is able to reproduce the present day water cycle and to predict past deposition of ice consistent with geological observations in many cases prior to this analysis however significant mid latitude glaciation had not been simulated by the model run under a range of parameters in this analysis we studied the response of the gcm to a wider range of orbital configurations and water ice reservoirs and show that during periods of moderate obliquity 25 35 and high dust opacity sdust 1 5 2 5 broad scale glaciation in the northern mid latitudes occurs if water ice deposited on the flanks of the tharsis volcanoes at higher obliquity is available for sublimation we find that high dust contents of the atmosphere increase its water vapor holding capacity thereby moving the saturation region to the northern mid latitudes precipitation events are then controlled by topographic forcing of stationary planetary waves and transient weather systems producing surface ice distribution and amounts that are consistent with the geological record ice accumulation rates of 10 mm yr

small scale lobate hillslope features on mars a comparative 3d morphological study with terrestrial solifluction lobes and zebra stripe lobes abstract small scale lobes ssl observed at the surface of mars are thought to be the result of solifluction hence their existence has important implications for our understanding of recent climate history the distribution of thaw liquids and its geomorphic effects as water is believed not to have been recently stable at the martian surface these small scale lobes are limited to sloping terrains and often occur alongside polygonal patterned ground attesting to the presence of ice in the environment in this study we perform a comparative 3d morphometric analysis of the lobes on mars with terrestrial analogues we use data from high resolution imaging science experiment hirise camera in order to create digital terrain models dtms on mars at 1 m pix for the terrestrial analogues we use dtms and orthophotos from five periglacial environments with solifluction lobes and from one site with lobate features found in the atacama desert the lobate features in the atacama desert are found within features called zebra stripes which are apparently unique to the atacama and are now generally accepted to be the result of seismic shaking we show that ssl on mars overlap morphometrically with terrestrial solifluction lobes and are less similar to zebra stripe lobes the majority of martian ssl occur below the angle of repose which demonstrates that a dry fall mechanism cannot be responsible for their formation and that lubrication of the subsurface is required we found that martian ssl only occur on slopes greater than 10 a constraint not observed for terrestrial solifluction lobes nor zebra stripe lobes in atacama we hypothesise that this apparent constraint does not result from the lowered gravity on mars but instead from differing soil properties and or thermal regime between mars and earth which affects the slope at which creep can initiate we cannot rule out a role of co2 sublimation in lobe formation based on our terrestrial measurements

geological and hydrological histories of the argyre province mars the geologic history of the multi ringed argyre impact basin and surroundings has been reconstructed on the basis of geologic mapping and relative age dating of rock materials and structures the impact formed a primary basin rim materials and a complex basement structural fabric including faults and valleys that are radial and concentric about the primary basin as well as structurally controlled local basins since its formation the basin has been a regional catchment for volatiles and sedimentary materials as well as a dominant influence on the flow of surface ice debris flows and groundwater through and over its basement structures the basin is interpreted to have been occupied by lakes including a possible mediterranean sized sea that formed in the aftermath of the argyre impact event the hypothesized lakes froze and diminished through time though liquid water may have remained beneath the ice cover and sedimentation may have continued for some time at its deepest the main argyre lake may have taken more than a hundred thousand years to freeze to the bottom even absent any heat source besides the sun but with impact induced hydrothermal heat geothermal heat flow due to long lived radioactivities in early martian history and concentration of solutes in sub ice brine liquid water may have persisted beneath thick ice for many millions of years existence of an ice covered sea perhaps was long enough for life to originate and evolve with gradually colder and more hypersaline conditions the argyre rock materials diverse in origin and emplacement mechanisms have been modified by impact magmatic eolian fluvial lacustrine glacial periglacial alluvial colluvial and tectonic processes post impact adjustment of part of the impact generated basement structural fabric such as concentric faults is apparent distinct basin stratigraphic units are interpreted to be linked to large scale geologic activity far from the basin including growth of the tharsis magmatic tectonic complex and the growth into southern middle latitudes of south polar ice sheets along with the migration of surface and sub surface volatiles towards the central part of the primary basin the substantial difference in elevation with respect to the surrounding highlands and tharsis and the thaumasia highlands result in the trapping of atmospheric volatiles within the basin in the form of fog and regional or local precipitation even today in addition the impact event caused long term millions of years hydrothermal activity as well as deep seated basement structures that have tapped the internal heat of mars as conduits for far greater time possibly even today this possibility is raised by the observation of putative open system pingos and nearby gullies that occur in linear depressions with accompanying systems of faults and fractures long term water and heat energy enrichment complemented by the interaction of the nutrient enriched primordial crustal and mantle materials favorable to life excavated to the surface and near surface environs through the argyre impact event has not only resulted in distinct geomorphology but also makes the argyre basin a potential site of exceptional astrobiological significance

thermal contraction crack polygons on mars classification distribution and climate implications from hirise observations morphology is shown to be consistent with thermal contraction cracking of an ice rich mantling unit consistent with observations of sediment wedge thermal contraction crack polygons forming in ice cemented sediment at the phoenix landing site polygon groups are distributed symmetrically in both northern and southern hemispheres suggesting strong climate controls on polygon morphology northern hemisphere polygonally patterned surfaces are found to decrease in age from low to high latitude spanning surface ages from 1 to 0 1 ma suggesting more recent deposition of ice rich material at high latitudes than at low latitudes six of the seven classes of polygons are interpreted to be capable of forming because of the combined effects of thermal contraction cracking and differential sublimation suggesting that sublimation and sand wedge polygons dominate martian high latitudes gully polygon systems present at midlatitudes suggest that small amounts of liquid water may have been involved in thermal contraction crack polygon processes producing composite wedge polygons no evidence is found for the presence of pervasive small scale ice wedge polygons

self organization of sorted patterned ground striking circular labyrinthine polygonal and striped patterns of stones and soil self organize in many polar and high alpine environments these forms emerge because freeze thaw cycles drive an interplay between two feedback mechanisms first formation of ice lenses in freezing soil sorts stones and soil by displacing soil toward soil rich domains and stones toward stone rich domains second stones are transported along the axis of elongate stone domains which are squeezed and confined as freezing soil domains expand in a numerical model implementing these feedbacks circles labyrinths and islands form when sorting dominates polygonal networks form when stone domain squeezing and confinement dominate and stripes form as hillslope gradient is increased

mars global digital dune database and initial science results 1 a new mars global digital dune database mgd3 constructed using thermal emission imaging system themis infrared ir images provides a comprehensive and quantitative view of the geographic distribution of moderate to large size dune fields area 1 km2 that will help researchers to understand global climatic and sedimentary processes that have shaped the surface of mars mgd3 extends from 65 n to 65 s latitude and includes 550 dune fields covering 70 000 km2 with an estimated total volume of 3 600 km3 this area when combined with polar dune estimates suggests moderate to large size dune field coverage on mars may total 800 000 km2 6 times less than the total areal estimate of 5 000 000 km2 for terrestrial dunes where availability and quality of themis visible vis or mars orbiter camera narrow angle moc na images allow we classify dunes and include dune slipface measurements which are derived from gross dune morphology and represent the prevailing wind direction at the last time of significant dune modification for dunes located within craters the azimuth from crater centroid to dune field centroid referred to as dune centroid azimuth is calculated and can provide an accurate method for tracking dune migration within smooth floored craters these indicators of wind direction are compared to output from a general circulation model gcm dune centroid azimuth values generally correlate to regional wind patterns slipface orientations are less well correlated suggesting that local topographic effects may play a larger role in dune orientation than regional winds

accommodation of late cenozoic oblique shortening in the alborz range northern iran abstract the alborz range northern iran deforms by strain partitioning of oblique shortening onto range parallel left lateral strike slip and thrust faults deformation is due to the north south arabia eurasia convergence and westward motion of the adjacent south caspian relative to iran roughly north south shortening occurs on thrusts that dip inwards from the range margins precambrian basement is not exposed because of detachment along upper proterozoic evaporites and the thickness of overlying strata 10 km other detachments occur within phanerozoic sediments active left lateral strike slip faults trend ene in the east of the range wnw in the west the eastern mosha fault has a left lateral offset of 30 35 km shortening across the range is 30 km 25 30 at the longitude of tehran this is hard to reconcile with the crustal thickness of 35 km which is similar to adjacent basins percentage shortening across the alborz is similar to the adjacent kopet dagh but because the latter is twice as wide finite shortening is roughly half the difference may be accommodated by subduction of the adjacent south caspian basin northwards under the middle caspian south caspian sediments began folding in the pliocene the present kinematics of the alborz may have begun at this time including a reversal from range parallel right lateral to left lateral strike slip faulting but the regional stratigraphy indicates uplift as early as the mid tertiary

high resolution imaging science experiment hirise observations of glacial and periglacial morphologies in the circum argyre planitia highlands mars 1 the landscape of the argyre planitia and adjoining charitum and nereidum montes in the southern hemisphere of mars has been heavily modified since formation of the argyre impact basin this study examines morphologies in the argyre region revealed in images acquired by the high resolution imaging science experiment hirise camera and discusses the implications for glacial and periglacial processes distinctive features such as large grooves semicircular embayments in high topography and streamlined hills are interpreted as glacially eroded grooves cirques and whalebacks or roche moutonnee respectively large boulders scattered across the floor of a valley may be ground moraine deposited by ice ablation glacial interpretations are supported by the association of these features with other landforms typical of glaciated landscapes such as broad valleys with parabolic cross sections and stepped longitudinal profiles lobate debris aprons interpreted as remnant debris covered glaciers or rock glaciers and possible hanging valleys aligned boulders observed on slopes may also indicate glacial processes such as fluting alternatively boulders aligned on slopes and organized in clumps and polygonal patterns on flatter surfaces may indicate periglacial processes perhaps postglaciation that form patterned ground at least portions of the argyre region appear to have been modified by processes of ice accumulation glacial flow erosion sediment deposition ice stagnation and ablation and perhaps subsequent periglacial processes the type of bedrock erosion apparent in images suggests that glaciers were at times wet based the number of superposed craters is consistent with geologically recent glacial activity but may be due to subsequent modification

possible ice wedge polygons and recent landscape modification by wet periglacial processes in and around the argyre impact basin mars abstract the argyre basin and associated rim materials in the southern hemisphere of mars are ancient having been formed by the impact of a large body 4 gya this notwithstanding the regional landscape continues to be altered by a multiplicity of geological and geomorphological processes three landforms whose close spatial association is identified in a new geological map of the argyre region 290 360 e 30 72 s feature prominently in the list of very late amazonian epoch alterations a small sized 20 m in diameter and unsorted polygons that exhibit metre to sub metre elevated margins or shoulders giving them a low centred appearance in wet permafrost environments on earth low centred polygons lcps often are underlain by ice wedges b gullies seemingly formed by wet flow s and incised by the lcps c a putative possibly ice rich latitude dependent mantle ldm that underlies the lcps and spatially convergent wet gullies in all of our observations these landforms occur from the middle to the high near polar latitudes of the region and overlie geological units of all ages hitherto the presence of the lcps has been reported only fleetingly in the literature and only in as much as they have been observed on the walls of a few scalloped depressions in mid utopia planitia by contrast we report the ubiquitous occurrence of the lcps in and around the argyre impact basin on gully margins and adjacent slopes as well as on relatively flat inter crater terrain on the basis of three separate but related lines of reasoning we hypothesise that ice wedges could be present beneath lcp margins in our study region if we are correct then these lcp sites are geomorphological expressions of boundary conditions that were relatively warm and wet in the recent past first substantial ice wedging in permafrost environments on earth requires the availability of meltwater if as some researchers propose the formation of some wet gullies at the martian mid latitudes is induced by the localised slope side and crater wall thaw of the underlying ldm at the gully sites themselves then meltwater also should be available for ice wedging and the formation of lcps at these sites interestingly lcps are observed on gully channel walls as expected if meltwater is associated with gully formation however in some instances the lcps are also observed on the slope side terrain that extends for hundreds of metres beyond the channel walls and even above the gully alcoves this suggests that the distribution of icy terrain affected by thaw could be much more substantial than has been suggested hitherto second lcps that are identical in shape and scale to the slope side lcps are observed on relatively flat inter crater terrain also underlain by the ldm that is distal from the wet gullies by contrast here their distribution extends for kilometres this too could be indicative of meltwater being more extensive in the regional landscape than most workers have thought possible third on earth the dryness or the wetness of a permafrost environment determines whether lcp margins are underlain by sand or by ice when the observed lcps and major deposits of sand in the study region are plotted on our new map of the argyre impact basin we see that these deposits are rarely proximal on the other hand the ldm underlies the lcps in all instances and if modified by thaw seems to be a likelier source of margin fill for the lcps than sand

periglacial mass wasting landforms on mars suggestive of transient liquid water in the recent past insights from solifluction lobes on svalbard abstract on earth periglacial solifluction is a slow mass wasting process related to freeze thaw activity we compare the morphology of small scale lobate features on mars to solifluction lobes in svalbard to constrain their processes of formation the analysis is based on high resolution satellite imagery of mars hirise 25 cm pxl aerial images of svalbard with a similar spatial resolution hrsc ax 20 cm pxl acquired through an air campaign in summer 2008 and ground truth obtained during two summer expeditions in 2009 and 2011 on svalbard we present a detailed study of two crater environments on mars displaying two types of lobate forms characterized as sorted clast banked and non sorted lobes on both svalbard and mars such lobes typically occur as clusters of overlapping risers lobe fronts pointing to differential velocities in the soil the martian small scale lobes have well defined arcuate risers and lobe treads surface lobe widths range between 14 and 127 m and tread lengths between 13 and 105 m riser height is estimated to be approximately 1 5 m the lobes on mars share the plan view morphology of solifluction lobes on svalbard and their morphometry is within the range of values of terrestrial solifluction lobes the lobes are distinct from permafrost creep landforms such as rock glaciers we show the results of a survey of 53 hirise images covering latitudes between 59 n and 81 n similar to svalbard the studied lobate features on mars occur in close spatial proximity to gullies and thermal contraction polygons the widespread distribution of the lobate forms in the northern hemisphere and their close association to ground ice and gullies are best explained by mass wasting processes related to frost creep gelifluction and or plug like flow this suggests a protracted process thousand to several thousands of years of freeze thaw activity at the northern high latitudes on mars age constraints on lobe deposits and superposition relationships with gullies and polygons imply a process involving liquid water within the last few million years

numerical modeling of non deformable support in swelling and squeezing rock abstract choosing the support system in swelling and squeezing rocks is one of the challenges for rock engineers there are many factors that need to be considered such as support type performance of the support the support element rock parameters condition of the rock structure and creating an appropriate support strategy th type steel supports which have long been used in deep underground mine headings have recently started to be used as yield control support system in tunnels however sliding ability of the th steel support allows cross section contractions if the amount of convergence can not be calibrated re shaping studies have to be done at the excavated areas due to the occurrence of time dependent creeps especially in swelling and squeezing rocks also numerical model studies for highly swellable and or squeezable rocks must represent the time dependent creep behavior of the rock simple stiffness parameters such as time dependent creep swelling index and compression index should be addressed into the model it is possible to constitute a high performance support system in this swelling and squeezing types of rocks by choosing appropriate round interval using a non deformable and heavier i profile and using sufficient parameters obtained by analysis the present paper presents in situ measurements and the analysis of time dependent numerical model of non deformable support system at the t 13 tunnel which is applied to one of the 39 tunnels at eskisehir kosekoy high speed railway route

gullies and their relationships to the dust ice mantle in the northwestern argyre basin mars we investigated gullies and their relationships to the atmospherically derived dust ice mantle and aeolian features in the northwestern part of the argyre basin a detailed morphologic map of the argyre study region allowed us to constrain the stratigraphic relationships and relative ages of gullies in addition we investigated the morphologic characteristics and orientations of all gullies in the argyre study region maximum absolute ages for gullies were determined with crater size frequency distribution measurements of the dust ice mantle which is the source material of gullies in the study area gullies only evolve from this mantle probably by melting of its ice content two different morphologies of pristine and degraded gullies were identified mostly occurring on pole and equatorward facing slopes respectively we conclude that the morphologies and orientations were initiated either by a more rapid and extensive erosion of equatorward facing gullies or by at least two generations of gullies with generally older gullies on equatorward facing slopes and younger ones on pole facing slopes different intensities of solar insolation on equator and pole facing slopes might be responsible for the different development of pristine and degraded gullies gullies in the study area generally have ages 20 ma some uncratered and thus very young aeolian dunes are superposed by a few gullies in some locations indicating another even younger generation of gullies with an upper limit absolute model age of about 500 ka

evidence for recent climate change on mars from the identification of youthful near surface ground ice ground ice in the crust and soil may be one of the largest reservoirs of water on mars1 2 3 near surface ground ice is predicted to be stable at latitudes higher than 40 ref 4 where a number of geomorphologic features indicative of viscous creep and hence ground ice have been observed5 mid latitude soils have also been implicated as a water ice reservoir6 the capacity of which is predicted to vary on a 100 000 year timescale owing to orbitally driven variations in climate7 it is uncertain however whether near surface ground ice currently exists at these latitudes and how it is changing with time here we report observational evidence for a mid latitude reservoir of near surface water ice occupying the pore space of soils the thickness of the ice occupied soil reservoir 1 10 m and its distribution in the 30 to 60 latitude bands indicate a reservoir of 1 5 6 0 104 km3 equivalent to a global layer of water 10 40 cm thick we infer that the reservoir was created during the last phase of high orbital obliquity less than 100 000 years ago and is now being diminished

ancient glaciation on mars a large number of anomalous landforms on mars can be attributed to glaciation including the action of ice and meltwater glacial landscapes are concentrated south of lat 33 and in the northern plains suggesting vast austral and boreal ice sheets crater densities on the glaciated terrains indicate that the final glacial epoch occurred late in martian history thus mars may have had a relatively warm moist climate and dense atmosphere much later than previously believed

ice rich periglacial vs icy glacial depressions in the argyre region mars a proposed cold climate dichotomy of landforms on mars so called scalloped depressions are widely observed in utopia planitia up and malea planum mp typically they are rimless metres to decametres deep incised sharply tiered inwardly polygonised and sometimes pitted the depressions seemingly incise terrain that is icy and possibly thermokarstic i e produced by the thermal destabilisation of the icy terrain agewise the depressions are thought to be relatively youthful originating in the late amazonian epoch here we report the presence of similar depressions in the argyre region ar 30 60 s 290 355 e more importantly we separate and differentiate these landforms into two groups ice rich periglacial depressions type 1 and icy glacial depressions type 2a c this differentiation is presented to the mars community for the first time based on a suite of morphological and geological characteristics synonymous with ice complexes in the lena peninsula eastern russia and the tuktoyaktuk coastlands northwest territories canada we propose that the type 1 depressions are ice rich periglacial basins that have undergone volatile depletion largely by sublimation and as the result of thermal destabilisation in keeping with the terms and associated definitions derived of terrestrial periglacial geomorphology ice rich refers to permanently frozen ground in which ice lenses or segregation ice collectively referenced as excess ice have formed we suggest that the depressions are the product of a multi step cold climate geochronology 1 atmospheric precipitation and surface accumulation of an icy mantle during recent high obliquities 2 regional or local triple point conditions and thaw evaporation of the mantle either by exogenic forcing i e obliquity driven rises of aerial and sub aerial temperatures or endogenic forcing i e along argyre impact related basement structures 3 meltwater migration into the regolith at least to the full depth of the depressions 4 freeze thaw cycling and the formation of excess ice 5 sublimation of the excess ice and depression formation as high obliquity dissipates and near surface ice becomes unstable the type 2 depressions exhibit characteristics suggestive of supra glacial dead ice basins and snow ice suncups observed in high alpine landscapes on earth e g the swiss alps and the himalayas like the type 1 depressions the type 2 depressions could be the work of sublimation however the latter differ from the former in that they seem to develop within a glacial like icy mantle that blankets the surface rather than within an ice rich and periglacially revised regolith at near the surface interestingly the type 2 depressions overlie the type 1 depressions at some locations if the periglacial glacial morphological and stratigraphical dichotomy of depressions is valid then this points to recent glaciation at some locations within the ar being precursed by at least one episode of periglaciation this also suggests that periglaciation has a deeper history in the region than has been thought hitherto moreover if the hypothesised differences amongst the argyre based depressions are mirrored in utopia planitia and malea planum then perhaps this periglacial glacial dichotomy and its associated geochronology are as relevant to understanding late period landscape evolution in these two regions as it is in the ar

blockfields old or new evidence and implications from some plateaus in northern norway evidence is presented from investigations on plateau top blockfields in still glaciated regions of north norway pits dug into these blockfields typically show profile depths 0 5 m and sometimes in excess of 1 m analysis of fines shows enrichment in the silt and clay sized fraction suggestive of prolonged chemical weathering chemical alteration of parent material is supported by xrd analysis which identifies a number of clay minerals present in blockfield samples a chemical weathering origin suggests that these plateau top blockfields are features which have considerable longevity in the landscape and have been forming since perhaps tertiary times the original weathering profiles have been destroyed by frost heaving mechanisms protection of the blockfield by cold based ice occurred during periods of glacial coverage

weathering rate of mudstone and tuff on old unlined tunnel walls abstract the mechanisms and rate of weathering of soft sedimentary rocks exposed along unlined tunnel walls were investigated using mineralogical chemical and physical methods tunneling occurred several decades ago within the kakinokidai formation middle pleistocene and the kiwada formation lower pleistocene of the kazusa group of chiba prefecture as well as within the fukuda formation miocene of saitama prefecture in japan since then the walls of the tunnels have been desiccated by ventilation sulfuric acid has been generated by pyrite oxidation calcite and glass have been dissolved by sulfuric acid and gypsum has crystallized on the surface of the tunnel walls the oxidized zone was formed on the surface of the walls by the weathering the formation of this zone and weathering rates determined as rates of movement of the oxidation fronts in the vadose zone are explained by the diffusion of oxygen from the surface of the tunnel walls the relationship between the depth of the oxidation front lcm and the number of years since excavation tyear was expressed by l r oxi t the roxi values from the tunnels ranged among 5 for the middle pleistocene sandy mudstone 2 4 for the middle pleistocene mudstone 0 3 for the lower pleistocene mudstone and 1 3 for the miocene tuff roxi depends on the diffusion coefficients of oxygen and the chemical composition of rocks the diffusion coefficients of oxygen de calculated using the roxi and chemical compositions of the four kinds of rock above were 10 5 cm2 s 10 7 10 5 cm2 s 5 10 8 cm2 s and 4 10 7 3 10 6 cm2 s respectively depending on the air permeabilities of the rocks that correlate closely with the coefficient of water permeabilities k the relationship for the mudstone was log de cm2 s 0 91 log k cm s 0 71 the values of de for the tuff were smaller than for the mudstone due to the smaller air porosities of 0 01 0 04

frost and soils implications for paleosols paleoclimates and stratigraphy abstract frost is a pedogenetic agent this paper describes the use of frost features in soil for paleoclimatic and stratigraphic interpretation it is possible to differentiate periods of frost activity from those of temperate pedogenesis by macroscopic and microscopic criteria and to distinguish between soils with pre syn and epigenetic frost effects an experimental approach is necessary to determine initial frost effects because they are usually difficult to observe at natural active sites work with ecologists also clarifies the evolution of frost affected soils under climatic and vegetational constraints vegetation has important effects on the thermal and hydraulic regimes of soils and on erosion susceptibility the recognition of fossil cryosoils often allows the reconstruction of sequences of paleoclimatic events in periods or environments with little or no micropaleontological evidence the interrelations between frost and other pedogenetic processes allow a better understanding of climatic evolution and deterioration throughout the neogene and especially during the quaternary and the holocene most of the inherited frost features in european soils are younger than 480 ka bp the differentiation between frost and tectonic perturbations is very important for calculation of soil erosional budgets

possible open system hydraulic pingos in and around the argyre impact region of mars abstract we report the observation of possible hydraulic open system pingos osps at the mid latitudes 37 s in and around the argyre impact basin osps are perennial water ice cored mounds they originate and evolve in periglacial and pro glacial landscapes on earth where intra or sub permafrost water under hydraulic artesian pressure uplifts localised sections of surface or near surface permafrost that then freezes in situ we invoke three lines of evidence in support of our analogue based interpretation 1 similarities of shape size and summit traits between terrestrial osps and the martian mounds 2 clustered distribution and the slope side location of the mounds consistent with terrestrial permafrost environments where osps are found and 3 spatially associated landforms putatively indicative of periglacial and glacial processes on mars that characterise osp landscapes on earth this article presents five osp candidate locations and nests these mound locations within a new geological map of the argyre impact basin and margins it also presents three periglacial hypotheses about the possible origin of the water required to develop the mounds alternative non periglacial formation hypotheses also are considered however we show that their robustness is not equal to that of the periglacial ones