recent climate cycles on mars stratigraphic relationships between multiple generations of gullies and the latitude dependent mantle reconstructions of the orbital parameters of mars spanning the last 20 myr combined with global circulation models predict multiple cycles of accumulation and degradation of an ice rich mantle in the mid latitudes driven primarily by insolation at the poles during periods when obliquity was more than ten degrees greater than it is today i e 35 while evidence of an ice rich latitude dependent mantle ldm consistent with these predictions is abundant features indicative of cycles of emplacement and degradation of this unit are isolated and rare in addition fundamental physical properties of the ldm such as paleo thickness maxima have not been determined gullies which are sinuous channels found on steep slopes in mid and high latitudes interact with the ldm and provide a stratigraphic feature useful for documenting both cyclical emplacement removal and thickness estimates in past climate regimes in the southern hemisphere where gullies are most common we present extensive evidence of 1 cyclical degradation and removal of gullies in the lower mid latitudes 30 40 s and 2 burial and exhumation of inverted gully channels in the transitional latitude band between dissected and preserved ldm 40 50 s which can only be accounted for if an additional tens of meters of ldm were present at these locations during channel formation these relationships support a model in which end to end gully evolution is controlled by the behavior of the ldm at lower latitudes gullies incise an ice rich substrate and are removed when that ice becomes unstable and at higher latitudes gullies are buried by successive emplacement of ldm where ice remains stable near the surface further the presence of dormant buried gullies implies that present day activity within gullies likely to be controlled by the behavior of co 2 frost is insufficient to explain the entire gully population and that conditions conducive to increased gully activity preceded the most recent phase of ldm emplacement

the comparison of topographic long profiles of gullies on earth to gullies on mars a signal of water on mars the topographic signature of a landform can give important clues as to its formation process here we have used topographic long profiles to study the process of gully formation on mars we studied topographic long profiles of gullies on earth to 1 confirm that previously published generalisations of how long profile shape varies with process also applies at the kilometre scale of martian gullies and 2 use as a direct comparison with the martian data we have compared 24 fluvial and 22 debris flow long profiles of terrestrial gullies derived from laser altimeter and gps measurements to 78 long profiles of a range of gullies on mars derived from a stereo photogrammetry point matching technique we have confirmed that this manual point matching technique is reliable for the martian data by comparison with full digital elevation models we used nine different characteristics of the long profiles including slope and curvature parameters to perform a canonical discriminant analysis which allowed us to identify the variables most important for differentiating between fluvial and debris flow gullies on earth in agreement with published literature for larger scale features we found that terrestrial debris flow gullies tend to be steeper and less concave than fluvial gullies we have found that gully long profiles on mars can resemble long profiles of terrestrial gullies formed by either fluvial or debris flow processes with slightly more affinity to fluvial systems gullies on mars can only be weakly separated from those on earth they can be separated from terrestrial fluvial gullies on curvature parameters and from terrestrial debris flow gullies by slope parameters in addition we have found that different alcove types identified from planview morphology are also distinctive in terms of their long profile morphology gullies which incise back into the bedrock are more similar to terrestrial debris flows whereas polar pit gullies are most similar to terrestrial fluvial gullies our findings suggest that the presence of a bedrock alcove promotes debris flow behaviour in gullies on mars

numerical modeling of martian gully sediment transport testing the fluvial hypothesis 1 using a stereo pair of hirise images of a pole facing crater slope at 38 s 218 e we measure topographic profiles along nine gullies typical slopes of the interior channel region above the depositional apron are 20 we test the hypothesis that sediment transport on gully slopes occurs via fluvial transport processes by developing a numerical sediment transport model based on steep flume experiments performed by smart 1984 at 20 slopes channels 1 m deep by 8 m wide and 0 1 m deep by 3 m wide transport a sediment volume equal to the alcove volume of 6 105 m3 in 10 h and 40 days respectively under constant flow conditions snowpack melting cannot produce the water discharge rates necessary for fluvial sediment transport unless long term kyr storage of the resulting meltwater occurs if these volumes of water are discharged as groundwater the required aquifer thicknesses and aquifer drawdown lengths would be unrealistically large for a single discharge event more plausibly the water volume required by the fluvial transport model could be discharged in 10 episodes for an aquifer 30 m thick with a recurrence interval similar to that of martian obliquity cycles 0 1 myr

co2 gas fluidization in the initiation and formation of martian polar gullies 1 martian gully landforms indicative of rapid flow of sediment down steep slopes have been cited as evidence of the action of near surface liquid water in mars recent past gullies in polar regions cannot involve pure liquid water because ambient temperatures are too low here we show that polar gullies could be initiated by fluidization of sediment over a subliming seasonal deposit of co2 frost as has been proposed previously for gullies in sand the gas speed and co2 sublimation rate required for fluidization is calculated with the semi empirical ergun relation as validated in industrial applications for gullies in dust the gas speed and sublimation rate required for fluidization are estimated from laboratory experiments with comparable materials to determine if those rates can be achieved we compute diurnal and seasonal surface and subsurface temperatures through a martian year including co2 condensation and sublimation using the marstherm one dimensional finite difference thermal model models were run without sediment and with layers of sand or dust 10 4 10 1 m thick deposited over a seasonal layer of co2 frost the simulations show that in the spring sufficient heat reaches the co2 frost underlying the surface sediment layer to fluidize them this result confirms that martian gullies may have diverse origins and that polar and mid latitude gullies can be initiated on steep slopes by the fluidization of loose sediment on a sublimating seasonal deposit of co2 gas

identification of gully debris flow deposits in protonilus mensae mars characterization of a water bearing energetic gully forming process gullies are a class of geologically recent landform on mars that show evidence of downslope transport of sedimentary material from recessed alcoves through incised channels to distributary fans or aprons the mechanisms invoked to account for the formation of gullies on mars range from completely dry granular flows or landslides to debris flows that incorporate some component of liquid water to fluvial erosion and alluvial fan like deposition each of these processes requires different amounts of liquid water and produces different characteristic morphologies we report on the identification of unusual lobate structures present in proximity to gullies in protonilus mensae the lobes are up to 3 m thick and terminate in rounded snouts these lobate structures are present mostly downslope of gullies and can be traced upslope through channels to gully fan termini and in places onto gully fan surfaces crater dating indicates that the deposits formed recently potentially within the past 500 ka we use hrsc digital elevation models to constrain mechanical properties of the lobate deposits and to compare their formation environment to that of typical martian gullies the protonilus mensae lobate deposits are interpreted to indicate local dominance of wet debris flows in the formation of the observed gullies and lobes these observations are consistent with 1 top down melting of the ice component of the latitude dependent mantle terrain in which the gullies form and 2 initiation of debris flows by mobilization of the dusty lithic component of the mantle the suite of morphological observations diagnostic of wet debris flow processes suggests the identification of an unusual environment in which the wet debris flow formational end member is locally the dominant gully forming process elsewhere on mars gully morphology may be more consistent with a range of other water related sediment transport mechanisms including fluvial erosion hyperconcentrated flow and low strength mudflows that deposit as fans rather than lobes these results suggest that 1 gully forming processes involve liquid water 2 that the water source is associated with the martian latitude dependent mantle and 3 that a range of water related sediment transport processes is involved in gully formation

a new chronostratigraphical and evolutionary model for la gomera implications for the overall evolution of the canarian archipelago a review of the general volcano stratigraphy and geochronology of la gomera one of the lesser known canary islands has led to the establishment of a new evolutionary model the oldest edifice corresponds to the submarine stage built up between 20 and 15 ma the construction of the submarine edifice was followed by an important break in the activity about 4 ma and deep erosion of the edifice about 10 5 ma ago the main present day edifice the old edifice 10 5 6 4 ma emerged which was also submarine in its initial phases two different main stages are distinguishable the first stage was represented by a large some 22 km wide basaltic shield volcano the lower old edifice several lateral collapse events tazo and san marcos avalanches occurred during this time and were responsible for the removal of an important part of its northern flank in the second growth stage the upper old edifice the activity migrated southwards a 25 km wide composite volcano arose covering part of the remaining earlier shield volcano the felsic trachytic to phonolitic activity occurring in two separate episodes formed a significant component of this composite volcano finally one more recent large edifice the young edifice built up from 5 7 to 4 ma the lava flows of this younger edifice covered completely the centre and the south of the island and filled deep ravines in the north more evolved magmas including significant felsic magmas the third and last felsic episode occurred in this phase of activity the growth of la gomera was long lasting separated by an important gap in the activity in the middle miocene with no quaternary activity at all at the same time on tenerife the nearest island east of la gomera three large edifices grew separately roque del conde anaga and teno initially three separated islands from the available data it is inferred that the subaerial activity started earlier in the roque del conde edifice then on la gomera and later in teno in the nw and anaga in ne of tenerife which is the youngest of all these edifices these facts together with the irregular general progress of the volcanic activity support more complex views of the genesis for the canary islands than the simple hotspot model

distribution and orientation of northern hemisphere gullies on mars from the evaluation of hrsc and moc na data abstract martian gullies show morphologic characteristics that indicate the presence of a flowing liquid during their formation process however the current climate in the northern hemisphere of mars does not allow the existence of substantial amounts of liquid water and therefore an assessment of the regional distribution and characteristics of gullies is required in order to understand the most recent climatic development of mars we examined high resolution stereo camera hrsc and mars orbiter camera narrow angle moc na data covering the northern hemisphere in order to determine the distribution geological setting and orientation of gullied slopes we used these results to test the consistency of formation models proposed in earlier works and to define the climate dependence gully orientations were analyzed only at impact crater walls because craters have an azimuthally uniform distribution of slopes this is ideal when investigating the influence of insolation on the distribution and development of landforms we examined 230 hrsc and 21 000 moc na images and identified more than 2200 gullies on hrsc and more than 3100 gullies in moc na data both surveys show the highest densities of gullies between 35 n and 55 n and a shift of gully orientation at 40 n from pole facing slopes to slopes facing the equator orientation trends as well as the latitudinal distribution of identified gullies strongly support the view of gully formation caused by insolation climatic conditions this result suggests that formation mechanisms based on the assumption of atmospheric water ice deposition proposed in earlier work are more likely than processes related to groundwater flow further support for a theory related to deposition is gained through observation of the high occurrence of gullies at isolated knobs and hills which cannot be associated with formation models based upon groundwater flow

avalanche slope angles in low gravity environments from active martian sand dunes 1 the properties of granular material have an important effect on surface landforms and processes recently it has been suggested that material properties called dynamic and static angle of repose vary with gravitational acceleration which would have a significant effect on many planetary surface processes such as crater collapse and gully formation in order to test that hypothesis we measured lee slopes of active aeolian sand dunes on mars using the high resolution imaging experiment hirise dtms digital terrain model we examined dune fields in nili patera herschel crater and gale crater our measurements showed that the dynamic angles of repose for the sands in these areas are 33 34 in the first region and 30 31 in the other two these results fall within the 30 to 35 window for the dynamic angles of repose for terrestrial dunes with similar flow depths and grain properties and thus show that this angle does not significantly vary with decreasing gravity

formation of recent martian gullies through melting of extensive water rich snow deposits the observation of gullies on mars indicates the presence of liquid water near the surface in recent times1 2 which is difficult to reconcile with the current cold climate gullies have been proposed to form through surface runoff from subsurface aquifers1 3 or through melting of near surface ice under warmer conditions4 but these gullies are observed to occur preferentially in cold mid latitudes2 where the presence of liquid water is less likely and on isolated surfaces where groundwater seepage would not be expected making both potential explanations unsatisfactory here i show that gullies can form by the melting of water rich snow that has been transported from the poles to mid latitudes during periods of high obliquity within the past 105 to 106 years refs 5 6 melting within this snow7 can generate sufficient water to erode gullies in about 5 000 years my proposed model for gully formation is consistent with the age and location of the gullies and it explains the occurrence of liquid water in the cold mid latitudes as well as on isolated surfaces remnants of the snowpacks are still present on mid latitude pole facing slopes and the recent or current occurrence of liquid water within them provides a potential abode for life

global documentation of gullies with the mars reconnaissance orbiter context camera and implications for their formation abstract hypotheses ranging from fluvial processes and debris flows to co 2 frost lubricated or entirely dry flows have been proposed for the formation of martian gullies in order to constrain these potential formation mechanisms we mapped the global distribution of gullies on mars using 54 000 images from the mars reconnaissance orbiter mro context camera ctx covering 85 of the martian surface at a resolution of 6 m pixel the results of this mapping effort confirm the results of studies using lower resolution and or less areally extensive datasets that gullies are confined to the martian mid to high latitudes 30 80 in both hemispheres we also find a clear transition in gully orientation with increasing latitude going from poleward facing to equator facing preference in general gullies are more developed on poleward facing walls and mid latitude gullies are more developed than those at higher latitudes gullies are also found to be strongly correlated with regions of distinct thermophysical properties of sand to pebble sized grains low albedo and higher thermal inertia these observations all point to climate insolation and thermal properties of the substrate playing key factors in gully formation on mars supporting either a melting ground ice or snowpack hypothesis as the source for water involved in gully formation

integrated magnetostratigraphy and biostratigraphy of the upper pliocene lower pleistocene from the monte singa and crotone areas in calabria italy the results of a detailed magnetostratigraphic and biostratigraphic study of late pliocene to early pleistocene marine marl sequences from the monte singa and crotone areas in calabria italy are presented the magnetostratigraphy from the monte singa sequence ranges from below the gauss matuyama boundary up to and including the lower olduvai boundary normal polarities at a level corresponding to isotope stage 81 most probably represent the r union subchron from the lower olduvai boundary upward a reliable magnetostratigraphy could not be established due to increased weathering of the marls resulting in mainly secondary magnetizations the magnetostratigraphy from the composite sequence of the crotone area belongs to a large part of the matuyama chron and includes the olduvai subchron the position of the lower and upper boundaries of the olduvai subzone could be established more precisely than from earlier results moreover the upper boundary of the olduvai subzone poses an ambiguity a relatively long normal polarity interval representing the main olduvai subchron and corresponding to a duration of 115 ka is followed by a short 30 ka reversed subchron and the short 15 ka normal vrica subchron another option and more in accordance with the duration of the olduvai subchron in literature would be to consider the complete n r n polarity succession with a total duration of 160 ka as representing the olduvai subchron implying that this olduvai subchron has a short reversed interval in its upper part linear interpolation and extrapolation yield ages for the most important late pliocene early pleistocene biostratigraphic datum levels an age of 1 69 ma is found for the pliocene pleistocene boundary using the conventional polarity time scale dated with radiometric results however hilgen 1 in correlating the sapropel groups and patterns to the precession curve of the earth s orbit obtained significantly different ages for the polarity transitions of the present study according to this astronomically calibrated polarity time scale the age of the pliocene pleistocene boundary is 1 81 ma

present day seasonal gully activity in a south polar pit sisyphi cavi on mars abstract the large amount of multi temporal high resolution images acquired in the last few years offers the opportunity to identify morphological changes associated with recent geologic activity on the surface of mars in this study we focus on a single gully in sisyphi cavi located in the south polar region at 1 44 e and 68 54 s the gully incises the gullied equator facing slope of an isolated polar pit within an infilled impact crater it is important to notice that the following investigations describe the activity and modifications of an existing gully and not the formation of the gully itself high resolution image data analyses show new deposits at the terminus of the gully channel and on the gully apron within spring after solar longitudes of 236 of martian years my 29 and 31 our morphological investigations show that the identified new deposits were formed by dark flows through the entire gully deposited on top of the apron between solar longitudes l s 218 and 226 thermal data show a temperature increase between l s 218 and 226 near infrared spectral data show relatively constant band strengths of co 2 ice and h 2 o ice in this time range after the formation of the dark flows after l s 226 temperatures increase rapidly from 180 k to 270 k at l s 250 at this time spectral data indicate that all volatiles on the surface sublimated however an earlier beginning of sublimation when the dark flows were observed between l s 218 and 226 is likely due to the fact that the instruments can only show the last phase of sublimation decrease of volatile band strengths spectral modeling shows that from winter to mid spring the surface of the studied area is covered by translucent co 2 slab ice contaminated by minor amounts of h 2 o ice and dust furthermore our spectral modeling indicates that the dark material most likely flows on top of the co 2 slab ice cover three different scenarios were proposed to explain the identified dark flows including 1 flows supported by liquid h 2 o 2 flows supported by co 2 gas and 3 dry flows on the basis of our study we find that scenario 1 is unlikely because of the very low temperatures while scenario 2 is consistent with the observed beginning of co 2 ice sublimation in the study area it is unlikely because of the limitation of the activity to only one gully compared to surrounding gullies that share the same morphologies slope angles and volatile contents also with scenario 3 dry flows the activity of only one gully is difficult to explain thus we propose a mixture of scenario 2 and 3 dry flows supported by the ongoing sublimation of co 2 ice within the gully to be the most plausible scenario when the observed active gully comprises different source material than the surrounding gullies i e a higher content of probably sand sized material from outcrops located in the alcove

evidence of gully formation by regional groundwater flow in the gorgonum newton region mars abstract the discovery of gullies on mars suggests liquid water activity near the surface of the planet in recent times since liquid water is unstable under the present day p t martian conditions the formation mechanisms of the gullies and the source of the putative water have been a matter of debate for the last years to provide new insights into these matters we have approached the problem studying the gullies in relation to their regional setting a major point in our study relates to the geographic orientation of gullies an aspect that has been previously regarded as a crucial matter in different models and has profound implications regarding their origin we present a comprehensive and detailed survey of the gorgonum newton region and a study of the dao and nirgal vallis regions the survey was carried out with the aid of 965 high resolution moc images 752 for gorgonum newton 102 for nirgal vallis and 111 for dao vallis regions and mola derived dems we found that gullies display a clear regional pattern geographically and topographically consistent with a decreasing regional slope we interpret the results in terms of the existence of several groundwater flow systems operating at different scales which ultimately may have led to gully formation by seepage at the slopes of craters and canyons we suggest that aquifers discharging at gully systems may have recharged from the surface in response to the melting of young partially eroded ice rich deposits

upper triassic lower cretaceous seismic sequence stratigraphy and basin tectonics at bornholm denmark tornquist zone nw europe abstract an integrated analysis of seismic sequence stratigraphy and structural evolution of a dynamic intraplate fault basin was conducted along a segment of the tornquist zone at the boundary between the northwest european craton and the baltic shield east european platform high quality regional seismic reflection lines document the late triassic through early late cretaceous tectonic history and depositional sequence architecture the stratigraphic package was divided into three major transgressive regressive cycles 1st order sub cycles the upper upper triassic through lower cretaceous siliciclastic cycles i and ii are divided into 2nd order transgressive regressive facies cycles composed of higher frequency 3rd order sequences the lowstand basin fill comprises stacked successions of lowstand systems tracts produced by relative sea level rises and falls during the 3rd order regressive intervals highstand dominated depositional conditions prevailed to the northwest while lowstand dominated conditions occurred to the southeast cycle iii records an upper cretaceous major siliciclastic chalk cycle the magnitude of the relative sea level highs and lows increased up through the studied interval a two dimensional structural evolution analysis is based on the variation of the sediment thickness across the fault blocks up through the sedimentary column basin subsidence can be divided into successive structural tectonic regimes fault block rotation and structural inversion characterized the early subsidence of the basin floor during the second interval inversion ceased while fault block rotation continued in the third interval the rotation also stopped and no deformation of the basin is recognized the three major transgressive regressive facies cycles and associated relative sea level cycles are linked with the structural regimes contemporaneous deposition of 3rd order highstand and lowstand dominated complexes related to differential subsidence and uplift is also evidence of basin tectonics as the controlling factor on relative sea level changes comparison of the relative sea level curve developed for the study area with eustatic sea level curves shows that they follow different trends the deviations between these curves and the correlation of sequence boundaries with changes of the tectonic regime support the conclusion that tectonics was a major control on relative sea level fluctuations in the study area the 2nd order cycles linked with deformation episodes along the tornqist zone correlate with lower middle jurassic 2nd order cycles in england deformation along the tornquist zone may thus have influenced the sequence stratigraphy across the entire northwest european craton

geologically recent gully polygon relationships on mars insights from the antarctic dry valleys on the roles of permafrost microclimates and water sources for surface flow we describe the morphology and spatial relationships between composite wedge polygons and mars like gullies consisting of alcoves channels and fans in the hyper arid antarctic dry valleys adv as a basis for understanding possible origins for martian gullies that also occur in association with polygonally patterned ground gullies in the adv arise in part from the melting of atmospherically derived wind blown snow trapped in polygon troughs snowmelt that yields surface flow can occur during peak southern hemisphere summer daytime insolation conditions ice cemented permafrost provides an impermeable substrate over which meltwater flows but does not significantly contribute to meltwater generation relationships between contraction crack polygons and sedimentary fans at the distal ends of gullies show deposition of fan material in polygon troughs and dissection of fans by expanding polygon troughs these observations suggest the continuous presence of meters thick ice cemented permafrost beneath adv gullies we document strong morphological similarities between gullies and polygons on mars and those observed in the adv inland mixed microclimate zone on the basis of this morphological comparison we propose an analogous top down melting model for the initiation and evolution of martian gullies that occur on polygonally patterned mantled surfaces

frosted granular flow a new hypothesis for mass wasting in martian gullies abstract recent gully deposits on mars have been attributed to both wet and dry mass wasting processes in this paper frosted granular flow fgf is presented as a new hypothesis for recent mass wasting activity in martian gullies fgf is a rare type of granular flow observed on a talus slope in the province of quebec canada hetu b van steijn h vandelac p 1994 geogr phys quat 48 3 22 frost reduces dynamic inter particle friction enabling flows to mobilize onto relatively low slope gradients 25 30 compared to those involving dry granular flow of the same material 35 41 resulting erosional and depositional features include straight to sinuous channels levees and digitate to branching arrangements of terminal deposits similar features are commonly found in association with geologically young gully systems on mars based on terrestrial observations of fgf processes the minimum criteria required for their occurrence on mars include i readily mobilized unconsolidated sediment at the surface ii an upper slope gradient at or near the angle of repose iii frost accumulation at the surface and iv triggering by rock fall all four conditions appear to be met in many areas on present day mars though triggering mechanisms may vary compared to terrestrial fgfs which are lubricated by thin liquid films at inter particle contacts those occurring on mars are more likely lubricated by vaporization of co 2 and small amounts of h 2 o frost that becomes incorporated in the translating mass some recent mass wasting activity in martian gullies therefore could be interpreted as the product of fgf

absolute dune ages and implications for the time of formation of gullies in nirgal vallis mars 1 transverse dunes cover the valley floor of nirgal vallis a 670 km long valley network at 318 e and 29 s the dunes are superposed by small undeformed impact craters which implies that the dunes are inactive under present atmospheric conditions the last active phase of dune movement absolute age can be determined by crater size frequency distributions the derived absolute ages from high resolution mars global surveyor mars orbiter camera imagery range from approximately 300 000 years to 1 4 myr b p error of factor of 2 the dunes are also superposed by gully deposits aprons which implies a younger age of the gullies these superposition relationships show that the gullies in this midlatitude region are at the most 3 myr old but might be even younger than 300 000 years

formation of recent martian debris flows by melting of near surface ground ice at high obliquity the observation of small gullies associated with recent surface runoff on mars has renewed the question of liquid water stability at the surface of mars the gullies could be formed by groundwater seepage from underground aquifers however observations of gullies originating from isolated peaks and dune crests question this scenario we show that these landforms may result from the melting of water ice in the top few meters of the martian subsurface at high obliquity our conclusions are based on the analogy between the martian gullies and terrestrial debris flows observed in greenland and numerical simulations that show that above freezing temperatures can occur at high obliquities in the near surface of mars and that such temperatures are only predicted at latitudes and for slope orientations corresponding to where the gullies have been observed on mars

glacial erosion evolution of river long profiles and the organization of process domains in mountain drainage basins of coastal british columbia 1 in glaciated british columbia canada quaternary climate changes are responsible for profound spatial reorganization of earth surface processes these changes have left a landscape characterized by topographic anisotropy associated with a hierarchy of glacial troughs the evolution of glaciated landscapes is examined by analyzing the structure of geomorphic process domains and channel long profiles to identify process domains we use channel surveys and gis analysis to construct slope area transects of the channel network this analysis reveals generalized process form disequilibrium with a mismatch between topographic signatures and currently active geomorphic process domains at the landscape scale of source colluvial channels contributing area 1 km2 the glacial paraglacial signature commonly overrides that produced by contemporary debris flows along the axis of former ice flows relict glacial cirques introduce a hanging fluvial domain at contributing areas as small as 8 10 2 km2 and produce complex channel long profiles similar to those observed for rivers responding to tectonic forcing slope area relations typical of unglaciated equilibrium environments do not apply here the concept of process domains appears to hold however some major glacially forced modifications in the alluvial colluvial transition are observed and the definition of a depositional colluvial subdomain is proposed comparison between field and gis measured slopes reveals that gis associated error is not uniform between process domains and that gis based plots do not successfully discriminate field based process domains the combination of glacial and post glacial fingerprints and the effects of ongoing earth surface processes generate a complex landscape whose glacial signatures may persist until the onset of the next ice age

geologic history of the polar regions of mars based on mars global surveyor data i noachian and hesperian periods during the noachian period the south polar region of mars underwent intense cratering construction of three groups of volcanoes widespread contractional deformation resurfacing of low areas and local dissection of valley networks no evidence for polar deposits ice sheets or glaciation is recognized south polar hesperian geology is broadly characterized by waning impacts volcanism and tectonism emplacement of the polar dorsa argentea formation daf occurred during the hesperian period mars orbiter laser altimeter topographic data and mars orbiter camera images elucidate stratigraphic morphologic and topographic relations permitting the dividing of the daf into eight members which surround and underlie about half of the amazonian south polar layered deposits the lobate fronts and lack of typical volcanic flow morphology of the six plains units indicate that they may be made up of debris flows we think that these flows tens of meters to 200 m thick may have originated by the discharge of huge volumes of slurry fluidized by ground water or liquid co2 perhaps triggered by local impacts igneous activity or basal melting beneath polar deposits the cavi and rugged members include irregular depressions that penetrate the subsurface some of the pits have raised rims the depressions may have formed by collapse due to expulsion of subsurface material in which local explosive activity built up the raised rims further smaller eruptions of volatile rich material may have resulted in narrow sinuous channel deposits within aggrading fine grained unconsolidated material perhaps produced by gaseous discharge of subsurface volatiles preferential erosion of the latter material could have produced the dorsa argentea type sinuous ridges associated mainly with the daf alternatively the ridges may be eskers but the lack of associated glacial and fluvial morphologies casts doubt on this interpretation the knobby degraded materials forming scandia colles may represent the only noachian geologic record exposed in the north polar region most of the north polar region was buried by water or debris ocean sediments during the hesperian period originating from uplands areas and perhaps knobby terrains in the northern plains the sediments either mantle or were deformed by wrinkle ridges radial and concentric to utopia basin and concentric to northern tharsis sources of stress probably included sediment loading in the northern plains and regional magmatic and loading activity at tharsis polar layered deposits began piling up during the early amazonian or later

an inventory and population scale analysis of martian glacier like forms abstract martian glacier like forms glfs indicate that water ice has undergone deformation on the planet within its recent geological past but the driving mechanisms behind the origin evolution and dynamics of these landforms remain poorly understood here we present the results of a comprehensive inventory of glfs derived from a database of 8058 context camera ctx images to describe the physical controls on glf concentration and morphometry the inventory identifies 1309 glfs 727 glfs in the northern hemisphere and 582 in the southern hemisphere clustered in the mid latitudes centred on a mean latitude of 39 3 in the north and 40 7 in the south and in areas of rough topography morphometric data show inter hemispheric similarity in glf length mean 4 66 km and width mean 1 27 km suggesting a common evolutionary history and a poleward orientation of glfs in both hemispheres indicating a sensitivity to climate and insolation on a local scale elevation is shown to be the most important control on glf location with most glfs occurring above an altitude threshold of 3000 m aod and in areas of moderate but not high relief we propose therefore that martian glfs may not exhibit accumulation or ablation areas as is the norm for terrestrial glacial systems but reflect ice motion in response to local relief within a widely distributed reservoir of ice deposited within prescribed latitudinal and elevational ranges

testing the tectonic significance of some parameters of longitudinal river profiles the case of the ardenne belgium nw europe the longitudinal profiles of 24 rivers of 3rd to 5th order have been analyzed in order to recognize the regional tectonic differentiation pattern of the ardenne a paleozoic massif of nw europe data collected exclusively from 1 25 000 topographic maps were used to define a set of parameters related to the geometry of the profile and proxies for river bedload and drainage area validation of the proxy defined for the bedload discharge ratio demonstrates its potential use for inter river comparison based on its value at the river mouth it is however inadequate to estimate the ratio changes along a given stream course this proxy has been computed to estimate the portion accounted for by hydrodynamic factors in the river bed profiling thus outliers to the correlation function linking it to the river bed gradient have been considered as undergoing other influences principally of lithologic or tectonic origin most indicative of the computed profile parameters are those related to the concavity of the profile four more or less regional longitudinal profile types are recognized which are partly determined by differential tectonic movement the combined analysis of all the parameters confirms the current uplift of the ne ardenne and points to a subsidence of the namur area with respect to its sw and se surroundings whether periglacial or tectonic in origin the upper pleistocene lowering of a local base level has also been identified in the famenne another conclusion of this study is that in order to evidence tectonic influences and to avoid any misinterpretation in a region of complex geologic and geomorphic history and moderate tectonic activity it is essential to consider a number of parameters and to consider their significance within the framework of detailed geologic setting and morphogenetic history

orientation and distribution of recent gullies in the southern hemisphere of mars observations from high resolution stereo camera mars express hrsc mex and mars orbiter camera mars global surveyor moc mgs data 1 geologically recent small gullies on mars display morphologies consistent with erosion by water or by debris flows suggested formation models are divided into two main categories 1 groundwater or 2 melting of near surface ice snow sourced from the atmosphere we have measured location and orientation and recorded the local contexts of gullies to constrain the likely models of gully formation more than 22 000 mars orbiter camera narrow angle moc na and 120 mars express high resolution stereo camera hrsc images in the southern hemisphere were searched for gullies discrete gullied slope sections with consistent orientation were recorded rather than individual gullies slope setting impact crater valley wall etc location and orientation were recorded for each slope section more than 750 moc images with gullies 900 distinct gullied slope sections and more than 40 hrsc images 380 distinct gullied slope sections were identified from both moc and hrsc gullies were found to be most common between 30 and 50 degrees latitude and to have an overall pole facing preference the preferred gully orientation for hrsc is southeast rather than south in moc owing to illumination effects that make gullies difficult to detect on south to southwest facing slopes in hrsc in both moc and hrsc surveys higher latitude gullies show less preference for pole facing than those at mid latitudes both data sets produced similar results demonstrating that our data are reliable we suggest that the observed latitudinal and orientation distributions of gullies show that insolation and atmospheric conditions play a key role in gully formation

geological evolution of the volcanic island la gomera canary islands from analysis of its geomorphology abstract erosion and landslide processes played an important role in shaping the geomorphology of the canary islands but for the heavily eroded la gomera island those processes have been unclear we conducted an integrated study of its offshore extension onshore geology and links between them in order to determine the geomorphological evolution of the island relative to the rest of the archipelago the characteristics of the island s barrancos and its interfluves have led us to differentiate four types of morphological areas whose fluvial networks are in different stages of evolution those barrancos offshore are interrupted by la gomera s shelf and its erosion has been much greater than for the rest of the canary islands such erosion is both a function of time and varied swell action la gomera s insular slope is carved by a system of submarine canyons and channels that have morphology indicative of turbidity current erosion many of the barrancos onshore and the canyons offshore have steps or knickpoints some are the result of varied resistance to erosion and others are explained by other mechanisms a ridge whose crest is covered by cone like shape structures is interpreted as of volcanic origin with the particularity that it lacks onshore continuation the opposite of what has been observed elsewhere in the canary islands also in contrast with the other islands of the archipelago la gomera s margin does not seem to have resulted from destructive mass wasting and the only offshore sign of catastrophic events are the presence of two embayments along la gomera s northern shelf edge and a lobe structure on the insular apron at 3000 m depth these features may be the remains of the catastrophic failures that took place on the island 9 4 8 7 ma ago alternatively they could be due to recent catastrophic failures on the upper slope due to sediment steeping since the conclusion of the main volcanic activity 4 0 ma ago la gomera has been intensively eroded by gradual fluvial denudation and secondary failures la gomera s insular margin reveals much regarding its evolution but more comprehensive studies including seismic and coring are needed to understand its whole geological history

local late amazonian boulder breakdown and denudation rate on mars inactive fan surfaces become smoother and develop desert pavement over time by weathering and erosion we use this mechanism to estimate late amazonian boulder breakdown and surface denudation rates on a young 1 25 ma schon et al 2009 fan on mars this is done by comparing boulder size and surface relief between lobes of different ages the boulder breakdown rate is 3 5 m myr surface smoothing denudation rate is approximated as 0 89 m myr these rates exceed previous estimates for the amazonian by orders of magnitude we attribute this to locality high initial smoothing rates after morphological activity and obliquity and eccentricity driven variation in the availability of metastable liquid water which acts as a catalyst for weathering during these periods the results have major implications for process interpretation of martian landforms as they imply that typical small scale morphology may be subdued within 1 myr

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

metastability of liquid water on mars abstract a simple model of local heat transport on mars demonstrates that transient melting of ice may occur in depressions and gullies nearly anywhere on the planet where thin ice is illuminated by normal incidence insolation an experiment has been performed to confirm the model of evaporation rate at low pressure reduction of radiative cooling due to gully geometry is shown to be important since appropriate meteorological topographic and optical conditions may occur on slopes nearly anywhere on the planet hydrological features such as gullies would likely form only where such ice might accumulate notably in sheltered locations at high latitudes it is suggested that cold trapping of winter condensation could concentrate a sufficient amount of ice to allow seasonal melting in gullies

geologic settings of martian gullies implications for their origins 1 martian gullies are found on steep slopes of all origins on all sorts of terrains of all ages scattered across nearly all of mars gullies are observed on all manner of substrates layered massive shattered rubble with or without nearby mantling deposits gullies are most common in the southern midlatitudes but also occur in the northern hemisphere in near polar terrain on equatorial volcanoes and on northern plains most gullies in the southern hemisphere are on south facing slopes but they occur on slopes of all orientations gullies are among the youngest features on mars but locally are overlain by eolian deposits and cut by faults old or eroded gullies are rare and those found have been partially stripped from slopes leaving no rock debris behind most gully deposits contain no detectable rocks these data are inconsistent with published hypotheses of gully formation including seeps and breakouts of water or brine hydrothermal activity cryovolcanism and breakouts from liquid carbon dioxide the data are consistent with gullies being dry flows of eolian material dust and silt comparable to climax snow avalanches on earth eolian sedimentation should be correlated little with underlying geology cause of slope age of terrain type of terrain or the nature of the rocks eolian sedimentation should be correlated with wind deceleration which will cause suspended sediment to drop and areas with common gullies are those with strong wind deceleration predicted by global circulation model in such areas sediment will be deposited preferentially in the lee of obstacles for the gully rich areas of the southern midlatitudes winds blow from the nnw so that sediment is deposited on sse facing slopes i e poleward these predictions are in accord with observations