effects of soil heterogeneity on martian ground ice stability and orbital estimates of ice table depth abstract data from the mars odyssey gamma ray spectrometer grs instrument suite and results from numerical simulations of subsurface ground ice stability have been used to estimate the depth of martian ground ice geographic correlation between these estimates is remarkable the relative ice table depth distributions also agree well however grs based estimates of ice table depth are generally deeper than predictions based on ground ice stability simulations this discrepancy may be related to heterogeneities in the martian surface such as rocks dust and albedo variations we develop a multi dimensional numerical model of ground ice stability in a heterogeneous martian subsurface and use it to place the first quantitative constraints on the response of the ice table to meter scale heterogeneities we find that heterogeneities produce significant undulations topography in the ice table at horizontal length scales of a few meters decimeter scale rocks create localized areas of deep ice producing a vertical depression of 10 60 cm in the ice table over a horizontal range of 1 2 rock radii decimeter scale dust lenses produce locally shallow ice however the magnitude of the vertical deflection of the ice table is small 1 4 cm the effects of decimeter scale albedo variations on the ice table are nearly negligible although albedo very weakly enhances the effects of dark rocks and bright dust on the ice table additionally we investigate the role played by rocks in estimates of ice table depth based on orbital data surface rocks can account for more than half of the discrepancy between ice table depths inferred from grs data and those predicted by theoretical ice stability simulations that utilize thermophysical observations our results have considerable relevance to the up coming mars scout mission phoenix because they indicate that the uncertainty in the ice table depth of a given region is greater than differences between current depth estimates likewise small scale depth variability due to heterogeneities at the eventual landing site is potentially greater than differences between current depth estimates

transport processes induced by metastable boiling water under martian surface conditions liquid water on the martian surface is expected to be metastable owing to low atmospheric pressure experiments at martian conditions reveal that water and briny flows induce grain saltation and slope destabilization with geomorphic consequences

water tracks and permafrost in taylor valley antarctica extensive and shallow groundwater connectivity in a cold desert ecosystem water tracks are zones of high soil moisture that route water downslope over the ice table in polar environments we present physical hydrological and geochemical evidence collected in taylor valley mcmurdo dry valleys antarctica which suggests that previously unexplored water tracks are a significant component of this cold desert land system and constitute the major flow path in a cryptic hydrological system geological geochemical and hydrological analyses show that the water tracks are generated by a combination of infiltration from melting snowpacks melting of pore ice at the ice table beneath the water tracks and melting of buried segregation ice formed during winter freezing the water tracks are enriched in solutes derived from chemical weathering of sediments as well as from dissolution of soil salts the water tracks empty into ice covered lakes such as lake hoare resulting in the interfingering of shallow groundwater solutions and glacier derived stream water adding complexity to the geochemical profile approximately four orders of magnitude less water is delivered to lake hoare by any given water track than is delivered by surface runoff from stream flow however the solute delivery to lake hoare by water tracks equals or may exceed the mass of solutes delivered from stream flow making water tracks significant geochemical pathways additionally solute transport is two orders of magnitude faster in water tracks than in adjacent dry or damp soil making water tracks salt superhighways in the antarctic cold desert accordingly water tracks represent a new geological pathway that distributes water energy and nutrients in antarctic dry valley cold desert soil ecosystems providing hydrological and geochemical connectivity at the hillslope scale

brine formation via deliquescence by salts found near don juan pond antarctica laboratory experiments and field observational results abstract the observed darkening of water tracks near don juan pond djp as well as the formation of wet patches elsewhere in the mcmurdo dry valleys is attributed at least partially to deliquescence a process by which salts absorb atmospheric water vapor and form brine coupled with liquid phase growth when the atmospheric relative humidity exceeds the water activity here we perform laboratory experiments to investigate the temperature and relative humidity conditions necessary for deliquescence to occur in calcium chloride rich sediments collected from the djp watershed we use a raman microscope equipped with an environmental cell to study both deliquescence and efflorescence recrystallization of the soluble salt component of djp soils between 30 and 15 c in this temperature range we find that the soluble salt component of the djp sediments begins to deliquesce between 19 and 46 rh slightly higher than the deliquescence relative humidity of the primary pure component calcium chloride we find a limited hysteresis between deliquescence and efflorescence but much greater supersaturation of the salt brine can occur at temperatures above 0 c the relative humidity conditions were varied either slowly over 8 h to observe near equilibrium phases or rapidly over

post eruptive morphological evolution of island volcanoes surtsey as a modern case study abstract surtsey is a small volcanic island in the vestmannaeyjar archipelago off the south coast of iceland the eruption leading to the island s emersion lasted for 3 5 yr 1963 1967 while destructive forces have been active for over 50 yr 1963 present day during which surtsey has suffered rapid subaerial and submarine erosion and undergone major morphological changes surtsey is a well documented modern example of the post eruptive degradational stage of island volcanoes and has provided the unique opportunity to continuously observe and quantify the effects of intense geomorphic processes in this paper we focus on coastal and marine processes re shaping the shoreline and shallow water portions of the surtsey complex since its formation and on the related geomorphological record analogies with the post eruptive morphological evolution of recently active island volcanoes at the emerging stage encompassing different climatic conditions wave regimes and geological contexts are discussed

a model of thermal conductivity for planetary soils 2 theory for cemented soils 1 a numerical model of heat conduction through particulate media made of spherical grains cemented by various bonding agents is presented the pore filling gas conductivity volume fraction and thermal conductivity of the cementing phase are tunable parameters cement fractions 0 001 0 01 in volume have small effects on the soil bulk thermal conductivity a significant conductivity increase factor 3 8 is observed for bond fractions of 0 01 to 1 in volume in the 1 to 15 bond fraction domain the conductivity increases continuously but less intensely 25 100 conductivity increase compared to a 1 bond system beyond 15 of cements the conductivity increases vigorously and the bulk conductivity rapidly approaches that of bedrock the composition of the cements i e conductivity has little influence on the bulk thermal inertia of the soil especially if the volume of bond 10 these results indicate that temperature measurements are sufficient to detect cemented soils and quantify the amount of cementing phase but the mineralogical nature of the bonds and the typical grain size are unlikely to be determined from orbit on mars a widespread surface unit characterized by a medium albedo 0 19 0 26 and medium high thermal inertia 200 600 j s 0 5 m 2 k 1 has long been hypothesized to be associated with a duricrust the fraction of cement required to fit the thermal data is less than 1 5 by volume this small amount of material is consistent with orbital observations confirming that soil cementation is an important factor controlling the thermal inertia of the martian surface

laboratory studies of perchlorate phase transitions support for metastable aqueous perchlorate solutions on mars abstract perchlorate salts recently discovered on mars are known to readily absorb water vapor from the atmosphere and deliquesce into the aqueous phase at room temperature here we study the deliquescence crystalline solid to liquid transition and efflorescence liquid to crystalline solid transition of perchlorate salts at low temperatures relevant to mars a raman microscope and environmental cell were used to determine the deliquescence relative humidity drh and efflorescence relative humidity erh of naclo 4 and mg clo 4 2 as a function of temperature and hydration state we find that the deliquescence of anhydrous naclo 4 is only slightly dependent on temperature and occurs at 38 rh the drh of naclo 4 h 2 o increases with decreasing temperature from 51 at 273 k to 64 at 228 k the drh of mg clo 4 2 6h 2 o also increases with decreasing temperature from 42 at 273 k to 64 at 223 k the efflorescence of both naclo 4 and mg clo 4 2 salt solutions occurs at a lower rh than deliquescence due to the kinetic inhibition of crystallization for all temperatures studied the erh values of naclo 4 and mg clo 4 2 are 13 and 19 respectively these results indicate perchlorate salts can exist as metastable supersaturated solutions over a wide range of rh and temperature conditions summer diurnal temperature and relative humidity cycles at low latitudes on mars could allow the surface salts to be aqueous for several hours per day

context camera investigation on board the mars reconnaissance orbiter 1 the context camera ctx on the mars reconnaissance orbiter mro is a facility instrument i e government furnished equipment operated by a science team not responsible for design and fabrication designed built and operated by malin space science systems and the mro mars color imager team marci ctx will 1 provide context images for data acquired by other mro instruments 2 observe features of interest to nasa s mars exploration program e g candidate landing sites and 3 conduct a scientific investigation led by the marci team of geologic geomorphic and meteorological processes on mars ctx consists of a digital electronics assembly a 350 mm f 3 25 schmidt type telescope of catadioptric optical design with a 5 7 field of view providing a 30 km wide swath from 290 km altitude and a 5000 element ccd with a band pass of 500 700 nm and 7 m pixels giving 6 m pixel spatial resolution from mro s nearly circular nearly polar mapping orbit raw data are transferred to the mro spacecraft flight computer for processing e g data compression before transmission to earth the ground data system and operations are based on 9 years of mars global surveyor mars orbiter camera on orbit experience ctx has been allocated 12 of the total mro data return or about 3 terabits for the nominal mission this data volume would cover 9 of mars at 6 m pixel but overlapping images for stereo mosaics and observation of changes and meteorological events will reduce this area ctx acquired its first instrument checkout images of mars on 24 march 2006

on the secular retention of ground water and ice on mars tropical ground ice on mars undergoes long term sublimation and likely exospheric escape without restriction of sublimation the cryosphere would eventually breach leading to massive loss of any underlying groundwater we seek to understand the conditions under which the ground ice seal groundwater and subsurface habitability are preserved using multi reservoir models for the evolution of deuterium to hydrogen ratios d h we derive a median estimate of the hesperian amazonian h2o loss of 60 m interquartile range 30 120 m global equivalent layer gel neglecting magmatic degassing most of the loss may have been early with consequent low loss in the modern cold and dry climate we modeled global h2o transport within mars following an assumed abrupt transition to modern conditions at 3 ga sublimation is retarded in order of decreasing priority by higher obliquity smaller porosity higher tortuosity lower heat flow and smaller pore radius higher obliquity reduces h2o loss by decreasing tropical surface temperatures and raising global atmospheric water vapor time variable obliquities do not overly influence outcomes as long as the total duration 30 obliquity is 1 gyr with no interval longer than a few hundred myr decreased solar luminosity or a thicker co2 atmosphere can also retard loss of subsurface h2o whereas lower atmospheric water vapor accelerates sublimation if mars post noachian crustal h2o inventory was a few hundred meters gel or more then the modest loss since then implies that the cryospheric seal has been maintained following top down freezing and that groundwater likely exists globally on mars today

the graham bank sicily channel central mediterranean sea seafloor signatures of volcanic and tectonic controls abstract graham bank is a dominant physiographic element of the nw sicily channel central mediterranean sea affected in the last 100 years by numerous well documented volcanic eruptions we present the first results of a geomorphological study where the graham bank region in the depth interval 7 350 m was mapped for the first time with multi beam echosounder and high resolution seismic and multi channel seismic reflection profiles we describe in high resolution the detailed geomorphological features of graham bank and how the superficial expression of different process and dynamics occurring in the sub seafloor evidence volcanic and tectonic controls on seafloor morphology across a relatively small area the north eastern part of the study area is dominated by seamounts with heights ranging from 97 to 152 m and auxiliary small cones reaching heights of 2 10 m on the whole forming a hummocky surface in this region fluid seepages are an important expression of the volcanic processes affecting the study area the western region comprises a flat seafloor covered by upper pleistocene holocene outer shelf sedimentary deposits here aligned mounds and pockmarks are predominantly oriented nw se or nnw sse running parallel to the main structural trend of the sicily channel the pockmarks have sub circular planform shapes and u shaped cross section and different depths and mean axis lengths numerous mass transport deposits mtds are distributed across the study area graham bank is 45 km from the coast of sicily and is intersected by submarine cables consequently the mapped volcanic seamounts pockmarks and mtds could pose a significant economic risk to the submarine cables

teresa scolamacchia and jose luis macias eds active volcanoes of chiapas mexico el chichon and tacana springer verlag berlin heidelberg 2015 in active volcanoes of the world xi 180 pages hardcover isbn 978 3 642 25889 3 usd 129 00 hardcover ebook isbn 978 3 642 25890 9 usd 99 00 ebook doi 10 1007 978 3 642 25890 9

evaluation of wet and dry recurring slope lineae rsl formation mechanisms based on quantitative mapping of rsl in garni crater valles marineris mars abstract recurring slope lineae rsl are narrow 0 5 5 m low albedo features that incrementally lengthen down steep slopes during warm seasons fade in colder seasons and recur each mars year to reduce the effort involved in manually mapping and analyzing each rsl in garni crater we developed mapping and automated analysis of rsl maarsl to analyze a set of orthorectified high resolution imaging science experiment hirise images and a digital elevation map maarsl along with manual mapping allowed us to detect rsl compute descriptive statistics and characterize changes over time we mapped 2910 rsl in 22 orthoimages from mars year my 31 solar longitude ls 133 0 to my32 ls 323 7 the maarsl results confirmed that rsl lengthening and fading occur concurrently on slopes with the same orientation and many times within some individual rsl slope angles of rsl and a slope slump show that some rsl start stop and have mean slope angles that are below the angle of repose our analysis shows that rsl are actively lengthening on at least one slope facing direction in all hirise observations of the crater we also found that ne n and nw facing rsl in garni crater lengthened during times of increasing shortwave insolation while s and sw facing rsl lengthened during increasing and decreasing shortwave insolation a non orthorectified hirise image acquired shortly after the my34 dust storm and shows rsl on every slope facing direction which is anomalous with respect to observations prior to the dust storm we find that dust removal and deposition could explain the darkening and fading respectively of rsl and could also explain the apparent lack of material being transported observations of rsl lengthening and fading occur concurrently on slopes could suggest overprinting of dry granular flows dry flows could also explain the significant lengthening activity of every slope facing direction after a fresh layer of dust was deposited via the my34 dust storm alternatively briny shallow subsurface flows are consistent with observations of rsl on slopes below the angle of repose and those that exhibit concurrent lengthening and fading however the most significant problem with briny rsl flows is accessing a source of briny water and removing excess salt from the regolith

offshore evidence of large scale lateral collapses on the eastern flank of stromboli italy due to structurally controlled bilateral flank instability abstract new detailed swath bathymetry and long range side scan sonar data on the submerged flanks of stromboli integrated with seismic data and seabed sampling indicate that repeated lateral instability processes occurred on the eastern flank of the volcano although no debris avalanche deposits were known before the high resolution exploration of the seabed this flank of the island is opposite to the northwestern side more evidently affected by repeated flank collapses and this setting is evidence for a structurally controlled bilateral flank instability of the volcanic edifice evidence of at least two large scale lateral collapses is represented by a superficial hummocky megablock field partially outcropping on the middle lower eastern submerged slope and by a chaotic unit estimated volume is 1 2 km3 actually embedded within the volcaniclastic sequence at the foot of the submerged flank a main submarine scar open towards the se is carved in the upper slope on the eastern flank of the island being partially filled with gravity flow deposits owing to the present day depositional setting of the volcano s submerged flank a morphological continuity can be envisaged between this submerged scar and an inferred subaerial one likely encompassing the rina grande depression and several minor nested landslide scars recognized on the eastern stromboli flank a spatial and temporal reconstruction of possible events is proposed the chaotic debris avalanche unit buried within the volcaniclastic apron at the slope base and partially reworked in its distal part within the stromboli canyon floor is thought to be the result of a lateral collapse event called paleostromboli lateral collapse plc as it likely occurred in the earlier stages of the subaerial development of the island affecting a wide sector of the eastern stromboli flank the megablock field might instead result from a more superficial debris avalanche deposit partially eroded by gravity flows currently acting on the seabed it is tentatively related to the recent subaerial scar morphologies affecting the vancori units and for this reason named vancori lateral collapse vlc displaced materials have lower volume and mobility than the plc

transition from circular to stellate forms of submarine volcanoes large volcanic islands and guyots have stellate forms that reflect the relief of radiating volcanic rift zones multiple volcanic centers and embayments due to giant flank failures small mid ocean ridge volcanoes in contrast are commonly subcircular in plan view and show only embryonic rift zones in order to characterize the transition between these two end members the morphology of 141 seamounts and guyots was studied using the shape of the depth contour at half the height of each edifice irregularity was characterized by measuring perimeter distance elongation and moment of inertia of the contours assuming an ideal edifice is circular the analysis reveals a general transition over 2 4 km edifice height best transition estimate 3 km while some large edifices 4 5 km high show no major embayments or ridges suggesting considerable variation in the effectiveness of mechanisms that cause flank instability and growth of rift zones the various origins of the transition are discussed and the upper limit of magma chambers many of which lie above the basement of the larger edifices is proposed to affect the morphologic complexity via a number of mechanisms and is an important factor affecting the mode of growth the origins of the truncated cone shape of mid ocean ridge volcanoes are also discussed of the eruption mechanisms that have been proposed to explain their flat summits the most likely mechanisms involve eruption from small ephemeral magma bodies lying within the low density upper oceanic crust the discussion includes speculations on factors affecting the depths of magma chambers beneath oceanic volcanoes supporting table is available via web browser or via anonymous ftp from ftp kosmos agu org directory append username anonymous password guest subdirectories in the ftp site are arranged by paper number information on searching and submitting electronic supplements is found at http www agu org pubs csupp about html

development of volcanic insular shelves insights from observations and modelling of faial island in the azores archipelago a variety of geological processes contribute to the development of volcanic island shelves although their relative importance remains unclear we have mapped the morphology of faial island s shelf in the azores from geophysical multibeam sonar chirp and boomer seismic reflection and geological data sediment sampling a wave erosional model and a eustatic record of glacially induced oscillations of sea level which modulated the elevation at which the waves operated through time was used to determine the contribution of mechanical wave erosion to shelf development wave regimes varied according to the orientation of the coast the model was run for 10 to 800 ka depending on the age of the various coastal sectors based on published radiometric data the modelling replicated the shape of the island s shelf reasonably well supporting the contention that it developed primarily through mechanical wave erosion operating in an intertidal zone that migrated landwards and seawards with changes in the level of the sea disparities between modelled and actual shelf morphologies may reflect varied geological resistance to erosion errors in the radiometric dates more recent unrecognised volcanic deposits sediment deposition and tectonic vertical movements there were some variation in rates of shelf development over different time scales but over the long term the relationship between shelf age and width was essentially linear the depth of the shelf break in some areas suggests that there have been differential vertical movements of the land around the island probably related to local faults the poor development or absence of terraces on the shelf may be attributed either to recent volcanic progradation or to sediment infilling of the space created by earlier erosion however poorly developed terraces on the southern shelf of faial are similar to those predicted by the model given appropriate adjustments for vertical movements of the land

volcanic geomorphological classification of the cinder cones of tenerife canary islands spain this paper proposes a method to establish a morphological classification of tenerife s cinder cones on the basis of a dual analysis of qualitative existence geometry and disposition of craters and quantitative morphometric parameters major and minor diameters and cone elongation major and minor diameters and crater elongation the result obtained is a morphological classification of the cinder cones of tenerife which can be sub divided into four types ring shaped cones horseshoe shaped volcanoes multiple volcanoes and volcanoes without crater in tenerife there is a clear dominance of horseshoe shaped volcanoes 69 0 over ring shaped cones 13 1 volcanoes without craters 11 4 and multiple volcanoes 6 4 the classification presented in this paper is characterized by its simplicity which makes it possible to include all morphological types of volcanoes found in tenerife this fact also renders our classification a useful tool to apply in other both insular and continental volcanic areas to eventually analyze and systematize the study of eruptive edifices with similar traits

lidar observations of dust layers transience in the stratosphere following the el chichon volcanic eruption intense stratospheric dust layers have been observed with a lidar at l aquila 42 n 13 e during the months of july and august 1982 these features were located at 22 26km with a maximum scattering ratio of 13 in one occasion a layer was also observed at 32km maximum integrated scattering is of the order of 0 001 sr 1 the almost daily frequency of the observations has revealed an unusually fast decrease of the altitude of the layers with an apparent velocity of 0 2 0 3km day this pattern is repeated in both the high altitude layers observed it is speculated that this effect could be attributed to the zonal distribution of the dust which in turn could depends on dust formation process

formation of recurring slope lineae by liquid brines on present day mars 1 recurring slope lineae rsl are small scale seasonal flow features identified by mars reconnaissance orbiter that present several interesting characteristics such as an albedo contrast seasonal dependence and a strong preference for equator facing slopes all of these characteristics strongly suggest a thermally driven mechanism such as a liquid triggered or dominated flow here we investigate the possibility that these features are formed by melting of brines of various compositions via a combination of thermodynamic and kinetic numerical models results suggest that a solution with a freezing temperature of 223 k can best reproduce the observed seasonality relatively high surface evaporation rates at the rsl locations make the flows quickly disappear over a single season our model reproduces well the seasonality of rsl and can explain the preference for equator facing slopes suggesting that brine flows and therefore liquids are possible on a small time and space scale today on mars however if the rsl are indeed formed by brines it may indicate that a recharge mechanism is active in order to maintain a source of brine over even short geological timescales which would have important implications for the martian water cycle

formation of submarine flat topped volcanic cones in hawai i high resolution bathymetric mapping has shown that submarine flat topped volcanic cones morphologically similar to ones on the deep sea floor and near mid ocean ridges are common on or near submarine rift zones of kilauea kohala or mauna kea mahukona and haleakala volcanoes four flat topped cones on kohala were explored and sampled with the pisces v submersible in october 1998 samples show that flat topped cones on rift zones are constructed of tholeiitic basalt erupted during the shield stage similarly shaped flat topped cones on the northwest submarine flank of ni ihau are apparently formed of alkalic basalt erupted during the rejuvenated stage submarine postshield stage eruptions on hilo ridge mahukona hana ridge and offshore ni ihau form pointed cones of alkalic basalt and hawaiite the shield stage flat topped cones have steep 25 sides remarkably flat horizontal tops basal diameters of 1 3 km and heights 300 m the flat tops commonly have either a low mound or a deep crater in the center the rejuvenated stage flat topped cones have the same shape with steep sides and flat horizontal tops but are much larger with basal diameters up to 5 5 km and heights commonly greater than 200 m the flat tops have a central low mound shallow crater or levees that surrounded lava ponds as large as 1 km across most of the rejuvenated stage flat topped cones formed on slopes 10 and formed adjacent semicircular steps down the flank of ni ihau rather than circular structures all the flat topped cones appear to be monogenetic and formed during steady effusive eruptions lasting years to decades these and other submarine volcanic cones of similar size and shape apparently form as continuously overflowing submarine lava ponds a lava pond surrounded by a levee forms above a sea floor vent as lava continues to flow into the pond the lava flow surface rises and overflows the lowest point on the levee forming elongate pillow lava flows that simultaneously build the rim outward and upward but also dam and fill in the low point on the rim the process repeats at the new lowest point forming a circular structure with a flat horizontal top and steep pillowed margins there is a delicate balance between lava heat supply to the pond and cooling and thickening of the floating crust factors that facilitate construction of such landforms include effusive eruption of lava with low volatile contents moderate to high confining pressure at moderate to great ocean depth long lived steady eruption years to decades moderate effusion rates probably ca 0 1 km3 year and low but not necessarily flat slopes with higher effusion rates sheet flows flood the slope with lower effusion rates pillow mounds form hawaiian shield stage eruptions begin as fissure eruptions if the eruption is too brief it will not consolidate activity at a point and fissure fed flows will form a pond with irregular levees the pond will solidify between eruptive pulses if the eruption is not steady lava that is too volatile rich or that is erupted in too shallow water will produce fragmental and highly vesicular lava that will accumulate to form steep pointed cones as occurs during the post shield stage the steady effusion of lava on land constructs lava shields which are probably the subaerial analogs to submarine flat topped cones but formed under different cooling conditions

topographic measurements of slope streaks on mars abstract slope streaks are enigmatic actively forming albedo features occurring on slopes in high albedo low thermal inertia dust rich equatorial regions on mars they are a specifically martian phenomenon with no direct analogs on the earth their morphology suggests that the streaks are initiated at their upslope tips and propagate down to their termini however the physical mechanism of their formation is uncertain we performed a large series of measurements of slopes associated with slope streaks using stereo pairs of high resolution orbital images obtained by hirise camera and generated several digital elevation models for selected streaks we found that 1 slopes at the upslope streak tips range widely however there is a strong indication that streaks can be initiated only on slopes steeper than 20 2 slopes of the streak termini show an even wider range with some streaks terminating at slopes as steep as their tips while others propagate all the way down to horizontal surfaces 3 the streaks can propagate stably for long many hundreds of meters distances and can turn following the topographic gradient on 10 15 slopes 4 no uphill propagation of streaks is detected over baselines of tens of meters 5 the slope streaks often propagate over 1 2 m high obstacles and can climb 1 2 m uphill over short meters distances we used these findings to assess the viability of two classes of hypotheses about slope streak formation mechanisms proposed earlier 1 dry some kind of run away avalanche like dry granular flow and 2 wet some kind of run away propagation of a front of percolating brines in the shallow subsurface no specific observation unambiguously proves or rejects either of the two mechanisms several of our findings are readily explained by the dry mechanism and cannot be easily explained with any kind of wet mechanism while other findings are closely consistent with the wet mechanism and are difficult to reconcile with the dry mechanism this situation might be explained by equifinality meaning that the streaks despite their similarity are formed by different physical processes alternatively some modifications to either the dry or wet mechanisms may be able to provide a coherent explanation it is also possible that new ideas are needed to understand the processes involved

slope activity in gale crater mars abstract high resolution repeat imaging of aeolis mons the central mound in gale crater reveals active slope processes within tens of kilometers of the curiosity rover at one location near the base of northeastern aeolis mons dozens of transient narrow lineae were observed resembling features recurring slope lineae that are potentially due to liquid water however the lineae faded and have not recurred in subsequent mars years other small scale slope activity is common but has different spatial and temporal characteristics we have not identified confirmed rsl which rummel et al rummel j d et al 2014 astrobiology 14 887 968 recommended be treated as potential special regions for planetary protection repeat images acquired as curiosity approaches the base of aeolis mons could detect changes due to active slope processes which could enable the rover to examine recently exposed material

submarine volcanism surrounding tenerife canary islands implications for tectonic controls and oceanic shield forming processes abstract using high resolution bathymetric data 97 seamounts within two large submarine areas n and se of tenerife have been identified and studied in detail main dimensions and associated parameters of these seamounts have been measured allowing a morphometric and morphologic classification on a shape basis in order to be certain of their volcanic origin several restrictive criteria were applied conical shape with maximum height 150 m basal ratio 1 aspect ratio 0 1 to the initial tally obtaining finally 31 regular shapes that can be identified without any reasonable doubt as volcanic seamounts these are very similar to submarine volcanoes described elsewhere on the sea floor most of these volcanic seamounts are aligned along two lines that follow the main volcano tectonic trends of the canary archipelago the nw se line crosses the island while the ne sw line coincides with a seismically active reverse fault that separates the tenerife and gran canaria insular blocks the distribution of the submarine volcanism to the north of tenerife permits a better knowledge of the island from its base on the sea floor and defines the tectonic control of the growth of the shield between 4 and 2 ma therefore the evolution of the submarine edifice of tenerife shows that the widespread parasite or satellite eruption centres are also very important in the overall growth of large shield edifices of volcanic islands

seasonal activity and morphological changes in martian gullies abstract recent studies of martian dune and non dune gullies have suggested a seasonal control on present day gully activity the timing of current gully activity especially activity involving the formation or modification of channels which commonly have been taken as evidence of fluvial processes has important implications regarding likely gully formation processes and necessary environmental conditions in this study we describe the results of frequent meter scale monitoring of several active gully sites by the high resolution imaging science experiment hirise on the mars reconnaissance orbiter mro the aim is to better assess the scope and nature of current morphological changes and to provide improved constraints on timing of gully activity on both dune and non dune slopes our observations indicate that 1 gully formation on mars is ongoing today and 2 the most significant morphological changes are strongly associated with seasonal frost and defrosting activity observed changes include formation of all major components of typical gully landforms although we have not observed alcove formation in coherent bedrock these results reduce the need to invoke recent climate change or present day groundwater seepage to explain the many martian gullies with pristine appearance

slope elevation and thermal inertia trends of martian recurring slope lineae initiation and termination points multiple possible processes occurring on coarse sandy slopes abstract recurring slope lineae rsl are dark linear features on the surface of mars that advance incrementally downslope fading and re growing annually numerous hypotheses have been proposed to explain rsl formation including wet models that involve liquid water or brines and dry mechanisms involving liquid free mass wasting or solid vapor phase changes that trigger granular flow in part hypotheses to explain rsl formation rely on observations of the physical characteristics of the slopes on which rsl are present to determine if rsl exhibit physical characteristics typical of one particular formation mechanism we examined the initiation and termination points of over 10 000 rsl across 16 confirmed rsl sites to determine their slope elevation orientation and thermal inertia rsl typically form within an envelope of high elevations at each mapping site are oriented equatorward and west and have hillslope thermal inertia values consistent with sand and gravel notably the rsl begin and end at slopes above within and below the angle of repose required to trigger and sustain dry granular flows sensitivity testing indicates that these slope values are not a result of pixel scale noise discontinuous rsl are observed at several study sites the slope and thermal inertia values of the rsl as well as these additional geomorphic observations of discontinuous dark features are not consistent with the characteristics of dry flows in which continuous dust avalanches begin within the dynamic angle of repose and terminate within the static angle of repose although rsl are found to be common on coarse sandy and rocky slopes not all sandy slopes in rsl regions that are close to the angle of repose contain rsl we conclude that mechanisms other than dry mass wasting are needed to explain all of the observed geomorphic characteristics of rsl source and termination points

lidar detection of volcanic aerosols in the atmosphere following the mount st helen eruption we report lidar measurements of the aerosol content of the atmosphere for the first two months following the volcanic eruption of mt st helen the measurements were taken near l aquila italy with a lidar system utilizing a 50cm diameter telescope the measurements are compared to similar data for the previous quiescent period and show a large increase of the backscattering ratio in the stratosphere and upper troposphere layers have been observed at various altitudes a strong layer at 10 14km has been observed only initially layers between 14 25km have been observed continually these features show a considerable day to day variability

modelled atmospheric temperatures and global sea levels over the past million years the climate has passed through a series of glacials and interglacials over the past million years but the nature of this cyclicity in terms of temperature ice volume and sea level and the underlying causes are not well known bintanja et al use a new method to deduce a one million year time series of these variables the reconstructed records are much longer than other methods have provided for any of these variables individually the most intense glacial stages were 17 c colder than today and most of the continental ice was present in north america strong cooling in the beginning of glacials was found to precede ice sheet build up these findings may shed light on the causes of ice age cycles marine records of sediment oxygen isotope compositions show that the earth s climate has gone through a succession of glacial and interglacial periods during the past million years but the interpretation of the oxygen isotope records is complicated because both isotope storage in ice sheets and deep water temperature affect the recorded isotopic composition1 2 3 4 5 separating these two effects would require long records of either sea level or deep ocean temperature which are currently not available here we use a coupled model of the northern hemisphere ice sheets6 and ocean temperatures forced to match an oxygen isotope record for the past million years compiled from 57 globally distributed sediment cores to quantify both contributions simultaneously we find that the ice sheet contribution to the variability in oxygen isotope composition varied from ten per cent in the beginning of glacial periods to sixty per cent at glacial maxima suggesting that strong ocean cooling preceded slow ice sheet build up the model yields mutually consistent time series of continental mean surface temperatures between 40 and 80 n ice volume and global sea level we find that during extreme glacial stages air temperatures were 17 1 8 c lower than present with a 120 10 m sea level equivalent of continental ice present

morphometry of scoria cones located on a volcano flank a case study from mt etna italy based on high resolution lidar data abstract by using new high resolution 2 m digital elevation model derived from the 2005 lidar survey of mt etna volcano italy our study measured the classical morphometrical parameters for scoria cones i e w co cone width w cr crater diameter h cone height as well as volume inclination of cone slope and substrate and a number of other parameters for 135 scoria cones of mt etna volume and age distribution of cones shows that there is no direct structural control on their emplacement in terms of etna s rift zones the cones are progressively smaller in size toward summit which can be explained by the large volcano s feeding system and progressively frequent lava burial toward top a careful analysis of h w co ratio determined as 0 18 for other volcanic fields worldwide shows that this ratio strongly depends on 1 the calculation method of h and 2 lava burial of cone for etnean cones applying an improved method for calculating h relative to the dipping substrate results in a significantly lowered standard h w co ratio 0 137 which in turn questions the validity of the classical value of 0 18 in the case of large central volcanoes the reduction of the ratio is not only due to methodology but also to the common lava burial this can be expressed even better if h mean is used instead of h max h mean w co 0 098 using this measure at etna well formed cones have higher ratios than structurally deformed e g double or rifted cones furthermore although the sampled scoria cones at etna have formed in a relatively narrow time interval h w co corresponding to erosional changes detected globally h w co 0 143 0 135 and 0 115 for three age classes of etna s scoria cones corresponding to average slopes of 26 6 23 9 and 23 7 because the morphometrical effect of position on a dipping substrate as well as lava burial exceeds the effect of erosion we call attention to use caution in simply using the h w co ratio of scoria cones for detecting age especially on large active volcanoes

submarine depositional terraces in the tyrrhenian sea as a proxy for paleo sea level reconstruction problems and perspective abstract in the last decade great effort was put in the study of relative sea level changes on mediterranean coastlines through the integration of geophysical modelling and proxy data of paleo shorelines in this paper we show potential and limitations of using additional marine geomorphic sedimentary markers for earlier and lower sea levels these markers are submarine depositional terraces sdts i e deposits formed by a set of small prograding sedimentary wedges having a terraced shape and found at variable shallow water depths mainly the first 150 m on continental and insular shelves in the tyrrhenian sea the shallowest terraces near shore have their edges at depths between 10 m and 30 m approximating the modern local storm wave base level their formation is thought to be associated with the modern sea level highstand and thus can be used as the modern analogue for deeper terraces formed in the past when the sea level was on the middle and outer shelf mid shelf terraces have their edges at variable depths between 40 m and 90 m and probably formed during the last sea level rise they show a patchy spatial distribution and a large variability in their internal structure so that they are not suitable for correlation on a regional scale shelf edge terraces have their edges at depths between 120 m and 170 m which is close or deeper than the last glacial maximum lgm sea level stand they show a remarkable lateral continuity and a prograding internal structure similar to those at shallower depth and thus represent a proxy for the sea level position at around 20 ka however the position of sdts edges is not a direct measure of paleo sea level positions because their depth depends on a complex interplay of several factors such as the base of the storm wave and its variation in response to coastal physiography as well as the occurrence of subsequent erosional or depositional processes depending on the geophysical and mapping methods used to determine their depth the associated error range can also differ based on the analysis of these complexities and a wide range of physiographic settings of the tyrrhenian sea we discuss these error ranges in order to assess potential and limitation of the sdt for analyses of vertical mobility of an area

morphological and statistical characterisation of recent mafic volcanism on tenerife canary islands spain abstract tenerife is the largest island of the canarian archipelago and presents a complex volcanic history the construction of a mafic shield and a phonolitic composite volcano represent the main features of the volcanic evolution of the island both volcanic complexes are still active the first through two main rift zones and the second through the teide pico viejo central complex up to 297 mafic monogenetic volcanoes can be recognised on tenerife most of them corresponding to scoria cones that can been grouped into five geographical volcanic fields characterised by similar volcanological features the large number of these edifices compared to the other existing morphological volcano types indicates that they represent the most common eruptive events occurring during tenerife s recent geological past and therefore the type with the shortest recurrence period and the most likely to occur in the near future in this paper the most frequent mafic monogenetic volcano is defined by means of the statistical analysis of its main volcano morphological features cone height cone width ratio crater width crater depth etc we have applied a simple methodology of our own design based on statistical correlations and modal intervals of the morphological and morphometric parameters best defining the volcanoes morphology the most frequently identified mafic monogenetic volcano corresponds to a scoria cone with strombolian to violent strombolian dynamics 100 high and 3 in volume covering an area of 2 by defining this most common mafic volcano or volcano type we may provide key information on the nature of a potential volcanic event on tenerife in the future

recurring slope lineae and chlorides on the surface of mars recurring slope lineae rsl are dark streaks that appear on steep slopes on the martian surface while their apparent movement suggests liquid flow remote sensing studies have not found evidence of fresh water some rsl have been observed at temperatures below the freezing point of water if liquid water is present therefore it is likely in the form of a brine in contrast to studies of other dissolved species such as perchlorates this study explores the possibility of chloride as a dissolved component in rsl using thermal emission imaging system themis decorrelation stretch dcs products and hirise images the presence of chloride lag deposits at rsl sites was assessed on a global scale though faint potential chloride signatures were detected at two rsl sites emissivity spectra showed no significant variation from surrounding geology no other rsl showed indications of chlorides using a simple model the upper limit of chloride required for positive detection is estimated to be 30 15 g m2 the total brine required to produce a detectable lag deposit is 80 35 ml m2 at a eutectic concentration of calcium chloride over the last climate cycle brine production could be up to 8 3 x 10 4 ml m2 yr without producing a detectable lag deposit based on these results we conclude that chloride abundance is not the limiting factor for rsl generation rsl could be produced by capillary wicking of chloride rich brines to the surface where small amounts of brine produce lag deposits below the detection limits of currently orbiting instruments

martian gullies a comprehensive review of observations mechanisms and insights from earth analogues upon their discovery in 2000 martian gullies were hailed as the first proof of recent i e less than a few million years flowing liquid water on the surface of a dry desert planet many processes have been proposed to have formed martian gullies ranging from liquid water seepage from aquifers melting of snow ice and frost to dry granular flows potentially lubricated by co2 terrestrial analogues have played a pivotal role in the conception and validation of gully formation mechanisms comparison with the terrestrial landscape argues for gully formation by liquid water debris flows originating from surface melting however limited knowledge of sediment transport by sublimation is a critical factor in impeding progress on the co2 sublimation hypothesis we propose avenues towards resolving the debate a laboratory simulations targeting variables that can be measured from orbit b applications of landscape evolution models c incorporation of the concept of sediment connectivity d using 3d fluid dynamic models to link deposit morphology and flow rheology and e a more intense exchange of techniques between terrestrial and planetary geomorphology including quantitative and temporal approaches finally we emphasize that the present may not accurately represent the past and that martian gullies likely formed by a combination of processes

cone morphologies associated with shallow marine eruptions east pico island azores eruptions in shallow water typically produce cones of volcaniclastic material in order to identify any systematic effects of water depth and other environmental parameters on cone morphology we have measured the heights and widths of cones in multibeam echo sounder data from a submarine ridge extending southeast from pico island azores xrf analyses of dredged samples show that lavas here vary compositionally from alkali basalt to trachybasalt and trachyandesite cones in deeper water are generally steep sided with upper flanks close to 30 the dip of talus at the angle of repose however height width ratios of cones vary more in shallow water 200 400 m summit depth with extreme values below 0 1 while some shallow water cones are steep sided as in deep water others are much flatter three such cones lie on a bench at 300 m depth immediately east of pico island and have flank slopes of only 10 20 we speculate that exceptionally shallow cone slopes here were produced by forced spreading of the erupting columns on reaching the water air density barrier

atmospheric imaging results from the mars exploration rovers spirit and opportunity a visible atmospheric optical depth of 0 9 was measured by the spirit rover at gusev crater and by the opportunity rover at meridiani planum optical depth decreased by about 0 6 to 0 7 per sol through both 90 sol primary missions the vertical distribution of atmospheric dust at gusev crater was consistent with uniform mixing with a measured scale height of 11 56 0 62 kilometers the dust s cross section weighted mean radius was 1 47 0 21 micrometers mm at gusev and 1 52 0 18 mm at meridiani comparison of visible optical depths with 9 mm optical depths shows a visible to infrared optical depth ratio of 2 0 0 2 for comparison with previous monitoring of infrared optical depths

imprints of volcanic erosional depositional tectonic and mass wasting processes in the morphology of santa maria insular shelf azores abstract the present day morphology of volcanic island shelves is the result of several factors namely the original shape and structure of the volcanic edifice the nature and age of the materials that compose its flanks and the erosional volcanic tectonic and sedimentary processes that acted to form these shelves by combining detailed seafloor mapping with onshore studies it is possible to gain a unique insight onto the evolution of volcanic island edifices and the processes that helped to shape their shelves here we look at santa maria island in the azores archipelago which is a 6 ma old ocean island volcano surrounded by a 135 km2 shelf characterized by an history of subsidence since its formation c 6 ma ago followed by uplift from 3 5 ma onwards by analyzing the geomorphic parameters of the insular shelf such as the shelf width and the erosive edge depth the island s history of vertical movements and by relating the morphology of the outcrops found on the shelf with those onshore we contribute to a better knowledge of the evolutionary history of santa maria with particular focus on its earlier stages of growth we infer that the outer part of the northern shelf is carved on units older than the oldest volcanic sequences exposed on land the western and southern shelves are almost entirely carved in the products of the oldest shield volcano anjos volcanic complex whilst the eastern shelf is the youngest in formation being related to units of the pico alto volcanic complex we also discuss the distribution of sediments on the shelf high wave energy concomitant with sea level drops contributed to the erosion and transport of older sequences offshore which were ultimately lost to the slopes of the island resulting in a shelf that is sediment stripped for the most part presently wide shelves further contribute to wave energy dissipation resulting in a significantly diminished sediment production the shelf edges around santa maria exhibit several erosive scars interpreted as the head of a submarine drainage network carved on the slopes of the island on the western southern and eastern shelves these mass wasting features are mostly controlled by tectonics since the extension of faults can be followed from onshore to the shelf edge on the northern shelf mass wasting appears to be mostly correlated with presence of unstable sediments on the shelf edge that triggered landsliding overall this work shows how detailed mapping of the shelves surrounding old volcanic islands can still provide important complementary information about the evolution of these islands which could not be acquired solely by the study of their subaerial and deeper submarine parts

evolution of submarine eruptive activity during the 2011 2012 el hierro event as documented by hydroacoustic images and remotely operated vehicle observations submarine volcanic eruptions are frequent and important events yet they are rarely observed here we relate bathymetric and hydroacoustic images from the 2011 to 2012 el hierro eruption with surface observations and deposits imaged and sampled by rov as a result of the shallow submarine eruption a new volcano named tagoro grew from 375 to 89 m depth the eruption consisted of two main phases of edifice construction intercalated with collapse events hydroacoustic images show that the eruptions ranged from explosive to effusive with variable plume types and resulting deposits even over short time intervals at the base of the edifice rov observations show large accumulations of lava balloons changing in size and type downslope coinciding with the area where floating lava balloon fallout was observed peaks in eruption intensity during explosive phases generated vigorous bubbling at the surface extensive ash vesicular lapilli and formed high density currents which together with periods of edifice gravitational collapse produced extensive deep volcaniclastic aprons secondary cones developed in the last stages and show evidence for effusive activity with lava ponds and lava flows that cover deposits of stacked lava balloons chaotic masses of heterometric boulders around the summit of the principal cone are related to progressive sealing of the vent with decreasing or variable magma supply hornitos represent the final eruptive activity with hydrothermal alteration and bacterial mats at the summit our study documents the distinct evolution of a submarine volcano and highlights the range of deposit types that may form and be rapidly destroyed in such eruptions

lateral collapses and active sedimentary processes on the northwestern flank of stromboli volcano italy abstract the marine volcaniclastic system extending to 3 km water depth on the northwest flank of stromboli volcano has been surveyed using seismo acoustic profiling multibeam bathymetry deep towed long range side scan sonar imaging and box core sampling deposits and sea floor topography record repeated flank collapses that have occurred during the last 13 ka and created the present sciara del fuoco scar an extensive 170 km2 debris avalanche deposit characterized by subdued hummocks megablocks is buried by turbidites formed from gravity currents that originated in sciara del fuoco the currents were mainly deflected along the margin of the avalanche deposit but also spilt over onto it the turbidites reflect topographic flow stripping and their thinning towards slightly steeper slopes indicates that some material that settled there drained further downslope as secondary higher concentration flows the estimated volume of the entire fan shaped bulge amounts to 12 2 5 km3 about 3 5 km3 of which is attributed to the post collapse sedimentation the remaining 8 5 2 5 km3 is in the order of the volume computed for the material removed by the multiple sector collapses that affected the nw stromboli flank two units are identified in the distal part of the bulge through the recognition of their fronts and these indicate a layered structure for successive debris avalanche deposits granulometric and particle type characterization of seabed samples shows clast population evolution with sedimentary transport distance from the main entrance point of debris in sciara del fuoco to the confluence with the stromboli canyon and into the marsili basin some 45 km from the island changes in particle populations are due to selective sedimentation and also mixing with a wide range of terrigenous detritus brought by currents that descended the main stromboli canyon from the continental shelf abundant fine sand and silt is produced at the volcano and occurrence of mainly coarse grained material along the channel to the marsili basin indicates that a considerable volume of volcaniclastic material from stromboli lies in the sedimentary succession accumulating on the distal basin floor where a deep sea fan is growing

an aeolian grainflow model for martian recurring slope lineae abstract recurring slope lineae rsl on mars have been enigmatic since their discovery their behavior resembles a seeping liquid but sources of water remain puzzling this work demonstrates that the properties of rsl are consistent with observed behaviors of martian and terrestrial aeolian processes specifically rsl are well explained as flows of sand that remove a thin coating of dust observed rsl properties are supportive of or consistent with this model which requires no liquid water or other exotic processes but rather indicates seasonal aeolian behavior these settings and behaviors resemble features observed by rovers and also explain the occurrence of many slope lineae on mars that do not meet the strict definition of rsl this indicates that rsl can be explained simply as aeolian features other processes may add complexities just as they could modify the behavior of any sand dune

the mars regional atmospheric modeling system model description and selected simulations the mars regional atmospheric modeling system mrams is introduced and selected model results are presented and compared with landed meteorological data when possible mrams is descended from a nonhydrostatic earth mesoscale and cloud scale model that is widely used for forecasting weather and simulating atmospheric systems over complex terrain mesoscale models such as mrams are ideal tools for making use of the high resolution data sets arriving from mars global surveyor experiments simulation of the mars pathfinder mpf landing site at lsd 142 using 1 2 degree mars orbiter laser altimeter mola derived topography and thermal emission spectrometer thermal inertia is shown to be in good agreement with observed near surface temperature pressure and wind direction simulations of topographically induced thermal circulations and mountain induced gravity waves are shown to be consistent with theory and earlier studies that tie large amplitude mountain waves to strong winds capable of producing dust streaks and local dust lifting events a large eddy simulation of the convective boundary layer provides estimates of vertical profiles of heat flux momentum flux turbulent kinetic energy and vertical velocity variance the model results suggest that the martian atmosphere is roughly two to three times more turbulent than the terrestrial atmosphere during the afternoon but fluxes are roughly an order of magnitude smaller due to the lower density dust devillike circulations are also predicted in the large eddy simulation finally a simulation that examines atmosphere surface interactions near big crater is discussed predicted surface wind stress patterns are consistent with aeolian processes inferred through mars orbiter camera imagery of big crater located near the mpf landing site c 2001 academic press

hydrological characteristics of recurrent slope lineae on mars evidence for liquid flow through regolith and comparisons with antarctic terrestrial analogs abstract on the basis of their morphology and seasonal thermal characteristics recurrent slope lineae rsl on mars have been inferred to be a possible result of the flow of a liquid likely a saline brine through the upper portions of the martian regolith in this note we analyze repeat hirise imaging of rsl to show that the downslope growth rate of recurrent slope lineae is well fit by an elementary groundwater flow model that also describes the downslope propagation of antarctic water tracks terrestrial analogs to rsl and that the apparent permeability of rsl bearing slopes is consistent with the observed sandy regolith substrate

volcanic tectonic and mass wasting processes offshore terceira island azores revealed by high resolution seafloor mapping terceira island in the azores archipelago lies at the intersection of four submarine volcanic ridges new high resolution bathymetric and seismic reflection data have been used to analyze the main volcanic tectonic and mass wasting features of the island offshore volcanic features such as linear volcanic centers and pointy and flat topped cones are mainly concentrated on the narrow western and north western ridges characterized by an overall rugged morphology fault scarps dominate mainly the broad eastern and south eastern ridges which are characterized by an overall smooth and terrace like morphology on the eastern ridge faults form a series of horsts and grabens related to the onshore lajes graben the strikes of the fault scarps linear volcanic centers and alignment of volcanic cones on the ridges reveal two main structural trends wnw ese and nnw sse consistent with the main tectonic structures observed on the azores plateau in contrast a large variability of strike was observed in inter ridge areas reflecting the relative importance of regional and local stresses in producing these structures mass wasting features are subordinate and mostly represented by hundred meter wide scars that indent the edge of the insular shelf surrounding the island apart from two large deeper scars identified on the southern steep flank of the western ridge finally the remarkable morpho structural differences between the western and eastern ridges are discussed in the framework of the evolution of the terceira volcanic edifice and hypothesized to reflect successive stages of ridge evolution

the strait of sicily continental rift systems physiography and petrochemistry of the submarine volcanic centres abstract new morphological geophysical mineralogical and petrochemical data on the submarine volcanic centres of the strait of sicily continental rift systems lead to the following conclusions magma types both in the rift valleys pantelleria and linosa and plateau areas adventure bank suggest mantle sources and fractionation processes comparable to those of the ethiopian afar section of the east african rift despite their different tectonic regimes however the volume of the erupted magmas less than 2000 3000 km 3 indicates the similarity with low volcanicity dry rifts this is probably related to the peculiar tectonic setting of the pelagian block african foreland dominated by extensional transcurrent motions connected with a strong neogene compressive dextral e w megashear along the sicilian collisional front in the plateau regions the most evolved rocks are hawaiites graham bank which formed by fractionation in the uppermost mantle probably at the base of the crust magma types vary from quartz tholeiites to basanites in the rift valleys the range of magma types is more restricted transitional to alkali basalts and a considerable volume of highly evolved magmas particularly in the axial volcanic complex of the pantelleria rift was produced in crustal magma chambers isotopic trace element evidence suggests the involvement of transitional to enriched morb and oib type mantle sources in the genesis of the quartz tholeiites alkali basalts and basanites throughout the strait of sicily continental rift system including the iblean plateau

direct sediment transfer from land to deep sea insights into shallow multibeam bathymetry at la reunion island abstract submarine canyon heads are key areas for understanding the triggering factors of gravity currents responsible for the transfer of detrital sediment to the deep basins this contribution offers a detailed picture of canyon heads off la reunion island with high resolution multibeam bathymetry in the water depth range of 4 220 m the present feeding of the cilaos turbidite system one of the largest modern volcaniclastic systems in the world is deduced from morphological and sedimentological interpretations of newly acquired data the study highlights small scale sedimentary features indicating hydrodynamic and sedimentary processes a direct connexion between the saint etienne river mouth and submarine canyons is evidenced by the complete incision of the shelf and the presence of canyon heads connected to the modern deltaic bar this direct connection supplied by river torrential floods cyclonic floods every two or three years suggests the continuity of high density fluvial flows to submarine gravity flows forming hyperpycnal flows in the canyon the initiation of secondary submarine gravity flows by storm waves large austral waves and cyclonic waves is also proposed for submarine canyons with large canyon heads developed in the surf zone from a sandy coastal bar bedforms in active canyon axis are considered as an indicator of the frequent activity of high density turbidity currents moreover a morphological record of last glacial and deglacial sea level variations is preserved and particularly the last glacial maximum sea level with the presence of small vertical cliffs observed in this bathymetric data which likely corresponds to a paleo shoreline or paleo reefs

physical models and predictions for recurring slope lineae formed by wet and dry processes abstract the observation of low albedo elongated and transient features lengthening downhill on mars has attracted wide interest because of the possible role of aqueous fluids in their formation these recurring gravity driven processes called recurring slope lineae rsl remain mysterious in that although the influence of local climate conditions has been established their nature dry versus wet and the mechanisms that govern their growth and fading are debated we present three different physical models for the growth of rsl the first two are wet based models with different aqueous fluid evaporation models and the last is based on dry granular theory we discuss the prediction of each model with regards to the growth and fading of rsl and their morphology we finally discuss the strengths and weaknesses of these models in light of what we currently observe on mars we find that both wet and dry rsl scenario face challenges mostly regarding aspects of mass balance however water based scenarios provide a consistent framework to reconcile the different sets of morphological observations made on rsl

kilometer scale roughness of mars results from mola data analysis the mars orbiter laser altimeter mola data are used to characterize the kilometer scale surface roughness of mars the median absolute value of the differential slope at a given baseline is proposed as a data derived measure of the surface roughness at this scale study of the scale dependence of roughness for the smoothest terrains gives an independent estimate of 20 cm for mola ranging accuracy the baseline lengths from 0 6 to 20 km are used and kilometer scale roughness is mapped for the entire surface the maps show that different geological units have distinctive roughness characteristics scale dependence of roughness for a number of geological units is presented and discussed the southern polar cap is rougher than the northern at kilometer and subkilometer scale which suggests differences in the sublimation condensation balance the vastitas borealis formation has a distinctive 3 km scale background surface topography which suggests a nonvolcanic origin for its upper layer young volcanic plains in amazonis planitia and the eastern part of elysium planitia are very similar to each other in their roughness characteristics and differ from other volcanic plains on mars which suggests a distinctive eruption style there are systematic latitudinal variations of roughness in both the southern highlands and the northern lowlands terrains at high latitude are smoother at short baselines the characteristic vertical scale related to this difference is several meters processes that could be responsible for formation of this trend include creep of ice rich near surface material at high latitudes treatment of the surface with repetitive deposition and sublimation of seasonal frost climate controlled deposition and or cementation of dust at high latitudes and repetitive sublimation and accumulation of subsurface ice at low latitudes with climate variations all mechanisms of origin could operate more effectively under different climate conditions relevant morphological observations favor mechanisms involving deposition of smooth blankets at high latitudes

origin of spectacular fields of submarine sediment waves around volcanic islands understanding how large eruptions and landslides are recorded by seafloor morphology and deposits on volcanic island flanks is important for reconstruction of volcanic island history and geohazard assessment spectacular fields of bedforms have been recognised recently on submerged flanks of volcanic islands at multiple locations worldwide these fields of bedforms can extend over 50 km and individual bedforms can be 3 km in length and 150 m in height the origin of these bedform fields however is poorly understood here we show that bedforms result from eruption fed supercritical density flows turbidity currents in some locations but most likely rotational landslides at other locations general criteria are provided for distinguishing between submarine bedforms formed by eruptions and landslides and emphasise a need for high resolution seismic datasets to prevent ambiguity bedforms associated with rotational landslides have a narrower source with a distinct headscarp they are more laterally confined and internal bedform structure does not suggest upslope migration of each bedform eruption fed density currents produce wide fields of bedforms which extend radially from the caldera internal layers imaged by detailed seismic data show that these bedforms migrated up slope indicating that the flows that produced them were froude supercritical due to the low density contrast between interstitial fluid and sediment the extent and dimensions of submarine eruption fed bedforms is much greater than those produced by pyroclastic density currents on land

the insular shelves of the faial pico ridge azores archipelago a morphological record of its evolution shelves surrounding reefless volcanic ocean islands are formed by surf erosion of their slopes during changing sea levels posterosional lava flows if abundant can cross the coastal cliffs and fill partially or completely the accommodation space left by erosion in this study multibeam bathymetry high resolution seismic reflection profiles and sediment samples are used to characterize the morphology of the insular shelves adjacent to pico island the data show offshore fresh lava flow morphologies as well as an irregular basement beneath shelf sedimentary bodies and reduced shelf width adjacent to older volcanic edifices in pico these observations suggest that these shelves have been significantly filled by volcanic progradation and can thus be classified as rejuvenated despite the general volcanic infilling of the shelves around pico most of their edges are below the depth of the last glacial maximum revealing that at least parts of the island have subsided after the shelves formed by surf erosion prograding lava deltas reached the shelf edge in some areas triggering small slope failures locally decreasing the shelf width and depth of their edges these areas can represent a significant risk for the local population hence their identification can be useful for hazard assessment and contribute to wiser land use planning shelf and subaerial geomorphology magnetic anomalies and crustal structure data of the two islands were also interpreted to reconstruct the long term combined onshore and offshore evolution of the faial pico ridge the subaerial emergence of this ridge is apparently older than previously thought i e before 850 ka

a case study of recurring slope lineae rsl at tivat crater implications for rsl origins abstract the origin or origins of recurring slope lineae rsl on mars are enigmatic these seasonally dark linear features correlate with temperatures appropriate for liquid water or brine they also progress slowly downslope and fade disappear when inactive similar to shallow subsurface groundwater flows that wick moisture to the surface if liquid water or brine does indeed flow so near the surface and is sufficiently dilute it could have profound implications for the modern habitability of mars we present the results of a case study at tivat crater in the southern midlatitudes that provide new insights into rsl including their potential origins at tivat these results include comprehensive maps of rsl extents in four mars years detailed rsl evolution across one growth season rockfall markings and dust devil tracks in two well constrained years rsl and rockfall markings which are more widely distributed than rsl fade at the same time suggesting a fading mechanism that acts across tivat based on relative albedo analyses rsl and rockfall markings at tivat fade because their host slopes darken which is most easily explained by the widespread removal of dust such a dry fading mechanism would favor a dry origin for rsl we also present a wide range of other rsl observations including highly variable growth pooling like behavior where slopes shallow to roughly 30 and total areal extents that decrease each year across a span of five years we discuss the implications of these observations for various rsl formation models including a new conceptual model that primarily mobilizes dust taken together our observations seem to favor a dry mass movement origin for rsl at tivat but significant challenges remain for each examined model

seasonal slumps in juventae chasma mars dark topographic slumps several meters wide tens of meters in length and up to a meter in depth are observed on the slopes of juventae chasma jc valles marineris vm mars these slumps usually originate near the terminal points of recurring slope lineae rsl near their initiation points the slumps have topographic depressions due to the removal of materials near their lowermost reaches new materials are deposited in lobes over the course of three mars years ten active slumps have been observed in jc all of which formed in or near the same season areocentric longitude ls 0 120 mars color imager marci observations show low altitude atmospheric obscurations confined within the topography of the vm and jc in the seasons when the slumps form in one instance data from the compact reconnaissance imaging spectrometer for mars crism and marci show evidence of h2o ice in the atmospheric obscuration likely due to the formation of a low level afternoon cloud above a dust storm or mixing of condensate clouds with a diffuse dust cloud the presence of atmospheric obscurations with h2o ice near times when the slumps form is intriguing but no direct evidence currently exists to support that they aid in slump formation further monitoring of this site will help establish if rsl and or atmospheric events play a role in the creation of contemporary slumps

relationships among crustal structure volcanism and strike slip tectonics in the lipari vulcano volcanic complex aeolian islands southern tyrrhenian sea italy abstract the lipari vulcano volcanic complex lvvc aeolian arc southern tyrrhenian sea italy develops along a strike slip fault system that bisects the aeolian arc the lvvc crustal structure is investigated by applying seismic methods to two data sets p wavefronts generated by local and distant events constrain the shallow velocity structure dss data provide shape and depth of the main crustal discontinuities the obtained velocity model shows that the lvvc shallow structure is characterized by the presence of two sharp lateral discontinuities the northern discontinuity bounds a low velocity basin like structure including the la fossa caldera and mt guardia caldera depressions the southern discontinuity coincides with the southern boundary of a high velocity diffractor located beneath the la fossa cone direct modeling of dss data define three crustal discontinuities showing a complex geometry the intra crustal interfaces and the moho discontinuity show an upheaval beneath the lvvc central sector the estimated crustal velocities are lower than those generally reported for the continental crust this feature is due to the high heat flux and fluid circulation affecting the lvvc area the ratio between the thickness of the upper and lower crust and the presence of the moho upheaval are consistent with that reported for continental areas affected by extensional strain the collected geophysical data combined with volcanological and structural information indicate that a the mt guardia and la fossa caldera depressions represent the surface expression of a single structure whose formation is mainly due to tectonic processes b the lvvc crustal structure and the evolution of the volcanism are consistent with those recognized in zones of transition from arc related to rift volcanism in addition results of a preliminary mechanical analysis based on the available structural data indicate low values of the ratio between magmatic overpressure and tectonic stress this suggests a passive mechanism of mantle upwelling the mantle upwelling is due the post collisional normal strike slip tectonics affecting the aeolian arc

experimental investigation of the stability and evaporation of sulfate and chloride brines on mars abstract we have investigated the evaporation of concentrated magnesium and ferrous sulfate and magnesium and ferric chloride brines as possible sources for liquid water on the surface of mars with special emphasis on the effect of freezing and crystallization of solutions experimental evaporation rates range from 0 04 mm h 1 for 25 wt mgso4 at 271 9 k to 0 19 mm h 1 for 18 wt feso4 at 270 5 k for chloride solutions evaporation rates range from 0 09 mm h 1 for 40 wt fecl3 at 261 34 k to 0 43 mm h 1 for 20 wt mgcl2 at 267 2 k these evaporation rates are significantly lower than for pure water i e 1 35 mm h 1 at 273 k using the pitzer ion interaction model we show that the decrease in evaporation rate is due to lower water activity in concentrated solutions down to 0 91 for saturated mgso4 and 0 97 for saturated feso4 at their eutectic temperatures for saturated mgcl2 and fecl3 the calculated water activities are 0 57 and 0 60 at their respective eutectic temperatures in addition we show that the water activity drops significantly when salts are crystallizing down to 0 17 and 0 21 for mgso4 and feso4 respectively our experiments and calculations show that the water activity and evaporation rate are dependent on the hydration state of the precipitating salt which is in turn controlled by the temperature and the relative humidity low hydration state salts precipitate at lower humidity with lower evaporation rates our study suggests that martian brines could remain stable for longer periods of time at low temperatures and low humidity than previously thought brines formed from these salts would be a more stable source of water on mars thus beneficial for any putative martian life past and or present

a series of volcanic edifices discovered a few kilometers off the coast of sw sicily abstract the graham and terrible banks located about 35 km from the south western coast of sicily host a large number of volcanic constructs the most famous being the ephemeral ferdinandea island these volcanoes occur along two n s trending strike slip lineaments that constitute the lithospheric scale capo granitola sciacca fault zone here we present recently acquired swath bathymetric data and magnetic measurements in conjunction with high resolution seismic profiles which reveal the presence of another six volcanic edifices located very close to the sicilian coasts one of which is only 7 km away three of these volcanic constructs have been previously identified only on the basis of available seismic profiles but their morphology and their volcanic nature had so far not been documented two edifices to the north show a possible tuff cone ring like morphology modified by crater breaching while the three southernmost volcanoes have a truncated conical shape the northwestern most volcano here called actea shows a more complex morphology probably representing the remnants of a previous crater rim seismic data analysis suggests that the six volcanic edifices were generated during a pre last glacial maximum lgm ca 20 ka b p magmatic phase associated with a tectonic event only the actea volcano shows indications of magmatic reactivation possibly between the lgm and the initial post lgm transgressive phase this reactivation is evident by the emplacement of a prominent young lava flow the discovery of submerged volcanoes so close to the populated coast of sicily demonstrates that there are large submerged areas near the littoral that are still little known and studied and underlines how crucial it is to analyze the issue of volcanic risk for densely inhabited coastal areas like sicily

morphometry of scoria cones and their relation to geodynamic setting a dem based analysis abstract the morphometry of a great number of scoria cones belonging to volcanic fields of various geodynamic settings has been measured and analyzed addressing the question whether there is a relation between the prevalent cone shape in a given field and the geodynamic setting of the field itself morphometric analysis was carried out on freely downloadable digital elevation models dems the accuracy of the used dems and the associated error in scoria cone morphometry were determined by cross comparing high resolution lidar derived dems usgs ned tinitaly dem and aster gdem the 10 m tinitaly 01 and usgs ned dems are proven to be suitable for scoria cone morphometry whereas aster gdem can be used reliably for cones with volume greater than 30 10 6 m 3 according to a detailed morphometry of all scoria cones we propose that the cones related to subductional setting show relatively higher values of h c o w co and lower values of w cr w co than the cones related to extensional setting the detected differences can be imputable to peculiar eruption dynamics resulting in slight but systematic changes in shape and differences in lithological and sedimentological characteristics that govern post eruptive erosion to constrain the pathway of scoria cone erosion the detected morphometric changes were also interpreted using a simple linear degradation model utilizing the obtained simulation results the inferred initial cone base and the age of scoria cones we calculated a diffusion coefficient k for several dated cones which are related to the prevalent climate our results despite the high error associated allow to assess the median k for all volcanic fields due to the complexity of the factors behind it is not easy to understand if the prevalent shape characterizing a certain volcanic field is due mainly to sin eruptive or post eruptive mechanisms however our distinction between the two main geodynamic settings may be the first step to decipher these factors

fracture control on type morphology and distribution of parasitic volcanic cones an example from mt etna italy abstract this paper uses a coupled morphometric and stratigraphic analysis of several tens of parasitic pyroclastic cones of the se flank of mt etna volcano italy to explain the structure of a poorly understood actively deforming zone of the volcano moreover we present a new general classification of pyroclastic cones based on the parameterisation of coeval eruption points along the same magma feeding fracture each cone has been studied in detail in order to define its stratigraphic position morphometric characteristics growth evolution in relation to fracture distribution and orientation stress field and morphology of the substratum end members of this classification are at one side a simple circular or elongated edifice that grew around a single eruption point and can be related to a magma feeding fracture constrained by a relatively high confining stress in the substratum or a low magma pressure the other end member is a multiple rifted strongly elongated cone formed along multiple eruption points of a magma feeding fracture constrained by a relatively low confining stress or a high magma pressure lithostratigraphic and historical analyses demonstrate that the cones in this area developed between 15 ka bp and historical times the most recent one in 1669 ad testifying to a high rate of lateral eruption occurrence in the area these cones show n s elongated maximum crater axes n s trending axis of the depressed points of the crater rim and southward and southeastward breaching directions while coeval cones are n s aligned these morphometric characteristics reflect the geometry of n s magma feeding fractures the area can be regarded as a transitional weakness zone between the n s rift and the releasing system represented by the transtensional trecastagni and mascalucia faults indicating an e w oriented local component of extension possibly related to the interplay between the regional timpe fault system and the eastward gravitational spreading of the volcano the azimuth of breaching is controlled by magma feeding fracture orientation and substrate morphology especially in the eastern part of the area where it is influenced by the scarps related to the timpe regional fault system but it is also sensitive to cone development

the morphology of insular shelves as a key for understanding the geological evolution of volcanic islands insights from terceira island azores shelves from volcanic ocean islands result from the competition between two main processes wave erosion that forms and enlarges them and volcanic progradation that reduces their dimension in places where erosion dominates over volcanism shelf width can be used as a proxy for the relative age of the subaerial volcanic edifices and reconstruction of their extents prior to erosion can be achieved in this study new multibeam bathymetry and high resolution seismic reflection profiles are exploited to characterize the morphology of the insular shelves adjacent to each volcanic edifice of terceira island in order to improve the understanding of its evolution subaerial morphological and geological stratigraphic data were also used to establish the connection between the onshore and offshore evolution shelf width contiguous to each main volcanic edifice is consistent with the known subaerial geological history of the island most of the older edifices have wider shelves than younger ones the shelf edge proved to be a very useful indicator in revealing the original extent of each volcanic edifice in plan view its depth was also used to reconstruct vertical movements showing that older edifices like serra do cume ribeirinha guilherme moniz and pico alto have subsided while more recent ones have not the morphology of the shelf namely the absence presence of fresh lava flow morphologies and several types of erosional depositional and tectonic features integrated with the analysis of the coastline morphology allowed us to better constrain previous geological interpretations of the island evolution

fluvial geomorphology on earth like planetary surfaces a review morphological evidence for ancient channelized flows fluvial and fluvial like landforms exists on the surfaces of all of the inner planets and on some of the satellites of the solar system in some cases the relevant fluid flows are related to a planetary evolution that involves the global cycling of a volatile component water for earth and mars methane for saturn s moon titan in other cases as on mercury venus earth s moon and jupiter s moon io the flows were of highly fluid lava the discovery in 1972 of what are now known to be fluvial channels and valleys on mars sparked a major controversy over the role of water in shaping the surface of that planet the recognition of the fluvial character of these features has opened unresolved fundamental questions about the geological history of water on mars including the presence of an ancient ocean and the operation of a hydrological cycle during the earliest phases of planetary history other fundamental questions posed by fluvial and fluvial like features on planetary bodies include the possible erosive action of large scale outpourings of very fluid lavas such as those that may have produced the remarkable canali forms on venus the ability of exotic fluids such as methane to create fluvial like landforms as observed on saturn s moon titan and the nature of sedimentation and erosion under different conditions of planetary surface gravity planetary fluvial geomorphology also illustrates fundamental epistemological and methodological issues including the role of analogy in geomorphological geological inquiry

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

a deep groundwater origin for recurring slope lineae on mars the recurring slope lineae on mars have been hypothesized to originate from snow melting deliquescence dry flow or shallow groundwater except for the dry flow origin these hypotheses imply the presence of surficial or near surface volatiles placing the exploration and characterization of potential habitable environments within the reach of existing technology here we present observations from the high resolution imaging science experiment heat flow modelling and terrestrial analogues which indicate that the source of recurring slope lineae could be natural discharge along geological structures from briny aquifers within the cryosphere at depths of approximately 750 m spatial correlation between recurring slope lineae source regions and multi scale fractures such as joints and faults in the southern mid latitudes and in valles marineris suggests that recurring slope lineae preferably emanate from tectonic and impact related fractures we suggest that deep groundwater occasionally surfaces on mars in present day conditions observations and heat flow modelling suggest that briny groundwater surfacing from fractures forms recurring slope lineae on mars

the pantelleria graben sicily channel central mediterranean an example of intraplate passive rift abstract we present new high resolution swath bathymetric data and multichannel seismic profiles acquired in the pantelleria graben one of the three main tectonic depressions forming the sicily channel rift zone this region experienced a late miocene early pliocene continental extension with the development of nw trending fault bounded troughs later accompanied by widespread volcanic manifestations data support the interpretation that the pantelleria graben evolution was dominated by two tectonic phases a lithospheric scale continental rifting early pliocene in which the whole graben was formed and a successive phase late pliocene pleistocene characterized by a magma assisted extensional mechanism ascending magmas within the graben floor seem to migrate from the s e sector of the depression toward the n w sector which is almost entirely floored by igneous material and where the volcanic edifice of the pantelleria island is emerged the volcanic activity is presently concentrated north of the pantelleria island the tectonic evolution of the pantelleria graben characterized by the chronological sequence of events rifting doming volcanism can be referred to as a passive rifting model crustal stretching and subsequent fault development and rifting within the pelagian block may have been controlled by slab pull forces of the northward subducting african slab

sulfate deposition in subsurface regolith in gusev crater mars excavating into the shallow martian subsurface has the potential to expose stratigraphic layers and mature regolith which may hold a record of more ancient aqueous interactions than those expected under current martian surface conditions during the spirit rover s exploration of gusev crater rover wheels were used to dig three trenches into the subsurface regolith down to 6 11 cm depth road cut the big hole and the boroughs a high oxidation state of fe and high concentrations of mg s cl and br were found in the subsurface regolith within the two trenches on the plains between the bonneville crater and the foot of columbia hills data analyses on the basis of geochemistry and mineralogy observations suggest the deposition of sulfate minerals within the subsurface regolith mainly mg sulfates accompanied by minor ca sulfates and perhaps fe sulfates an increase of fe2o3 an excess of sio2 and a minor decrease in the olivine proportion relative to surface materials are also inferred three hypotheses are proposed to explain the geochemical trends observed in trenches 1 multiple episodes of acidic fluid infiltration accompanied by in situ interaction with igneous minerals and salt deposition 2 an open hydrologic system characterized by ion transportation in the fluid subsequent evaporation of the fluid and salt deposition and 3 emplacement and mixing of impact ejecta of variable composition while all three may have plausibly contributed to the current state of the subsurface regolith the geochemical data are most consistent with ion transportation by fluids and salt deposition as a result of open system hydrologic behavior although sulfates make up 20 wt of the regolith in the wall of the boroughs trench a higher hydrated sulfate than kieserite within the boroughs or a greater abundance of sulfates elsewhere than is seen in the boroughs wall regolith would be needed to hold the structural water indicated by the water equivalent hydrogen concentration observed by the gamma ray spectrometer on odyssey in the gusev region copyright 2006 by the american geophysical union

morpho bathymetric and seismo stratigraphic analysis of the insular shelf of salina aeolian archipelago to unveil its late quaternary geological evolution abstract the distribution and morphological characteristics of the shelves around salina island have been analyzed and integrated with observations from onshore geological field studies in order to improve knowledge about its evolution and to demonstrate how shelf width depth can be used as proxies for reconstructing the development of the volcanic edifice insular shelves form essentially through marine erosion of volcanic centres during stages of reduced or inactive volcanism and are representative of their original extension shelves having larger widths commonly 1000 m and deeper edges over 125 m depth experienced wave erosion during successive cycles of sea level fluctuations and subsidence after their formation thus being indicative of a relatively older age of the eroded volcanic centres accordingly we document offshore salina the occurrence of presently submerged and largely dismantled volcanic centres namely pizzo capo north and fossa delle felci south predating the oldest subaerial products exposed on the adjacent coastal sectors these offshore centres have subsided after their erosion and are no more documented on land furthermore the finding of the largest and deepest shelf around the subaerial remnants of pizzo di corvo volcanic edifice allows relating it to an earlier stage of evolution of salina shedding light on contradictory radiometric ages on land narrower shelves commonly on the whole our results show the importance of integrated field and marine studies to unravel the geological evolution of insular volcanoes and to obtain inferences on their vertical mobility

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

two pulses of seasonal activity in martian southern mid latitude recurring slope lineae rsl abstract recurring slope lineae rsl are narrow dark features that incrementally lengthen down steep low albedo slopes when temperatures are warm subsequently fade and reoccur annually rsl could be caused by wet wet triggered debris or dry granular flow mechanisms we have classified 190 candidate and confirmed southern mid latitude sml rsl sites using six mars years of high resolution imagery to provide new constraints on rsl flow mechanisms we demonstrate that at least three confirmed sml rsl sites have at least two pulses of active lengthening we have also confirmed that rsl start much earlier than previously thought the first sml rsl pulse occurs from solar longitude ls 187 6 to 226 14 or 62 32 sols while the second pulse occurs from ls 260 26 to 329 29 or 113 89 sols even with the newly observed early pulse the total sml rsl active duration is still shorter than rsl found elsewhere on the planet no significant seasonal variations exist between the dominant n nw w slope face orientations the central peak of hale crater appears to be anomalous in that it has a third pulse that rejuvenates rsl late in the southern summer ls 330 1 to 348 19 or 48 26 sols these additional rsl pulses of activity add increased complexity to rsl behavior follow up missions may be needed to unambiguously discriminate between rsl mechanisms

newly discovered submarine flank eruption at stromboli volcano aeolian islands italy 1 the nw submarine portion of stromboli volcano has been investigated by deep towed sidescan sonar bathymetric surveys video camera runs and dredging during two research cruises in 2002 and 2004 the surveys resulted in the identification of an extensive pillow lava field 106 107m3 at about 2300 m of water depth and 9 km from the shoreline of stromboli island the pillow lavas have a unique composition that does not match any known subaerial product although a limited affinity exists with those erupted during the neostromboli eruptive cycle of the island 13 6 ka this is the first finding of a submarine eruption on the northern side of stromboli and improves the knowledge of its flank activity and volcanic hazards this eruption is interpreted as marking the onset of a new volcanic cycle from the edifice periphery fed by a new distinct magma mixed with traces of the previous magma that survived the emptying of the neostromboli magma chamber

the 1891 submarine eruption offshore pantelleria island sicily channel italy identification of the vent and characterization of products and eruptive style high resolution bathymetry and seafloor sampling have been used to characterize the 1891 submarine eruption of the pantelleria volcanic complex this submarine eruption has been documented mainly by historical reports describing basaltic scoria bombs floating on the sea surface i e lava balloons in this study the 1891 eruptive vent has been identified as a small cone volume of 700 000 m3 rising 90 m from 350 m w d and located within a newly discovered submarine volcanic field covering a wide area offshore from the nw coast of pantelleria recently kelly et al 2012 confirmed this location by a multibeam and rov survey pyroclasts from the 1891 eruption crop out directly on the seafloor and are fresh scoria clasts i e small bombs bomb fragments and lapilli and glass ash sized grains both have been characterized in their morphology textures and geochemistry the distinctive vesicularity and crystallization characteristics displayed by the scoriaceous pyroclasts reflect modes of degassing in both syn and posteruptive regimes these characteristics along with the distribution of deposits suggest for the strongest eruptive phase of the 1891 eruption a style analogous to hawaiian fountaining glass grains from a buoyant plume were dispersed northward from the vent up to distances of 1 5 km redirected by the levantine intermediate water the identification of the 1891 submarine eruptive vent offshore pantelleria as well as the features of erupted pyroclasts improve our knowledge of submarine explosive eruptions that occur at shallow intermediate depths and among these of the rare eruptions producing lava balloons

morpho structural setting of stromboli volcano revealed by high resolution bathymetry and backscatter data of its submarine portions the first high resolution bathymetric and backscatter maps of offshore stromboli island are presented together with an interpretation of its volcanic structural and sedimentary features the volcanic edifice is characterized by a sub conical shape with a quasi bilateral symmetry with respect to a ne sw axis the dimensions of the strombolicchio volcanic centre to the ne of stromboli have been restored by redrawing its morphology before wave action that eroded it in late quaternary time on the ne submarine flank of strombolicchio a n64 e structural trend controls the shape of strombolicchio canyon on the southern side of stromboli the submarine flank has a radial structural trend possibly reflecting a volcanic stress regime landslide scars at various scales are ubiquitous on the submarine slopes of stromboli repeated large scale lateral collapses have affected both the northwestern and southeastern unbuttressed flanks of the volcano producing large debris avalanche deposits

insular erosion isostasy and subsidence organic reefs and shore erosion record the intersection of sea level with islands from this record it is possible to reconstruct the history of vertical movement of the islands and the adjacent deep sea floor including midplate swells as judged by coral thickness islands with barrier reefs sink as though they were on thermally youthful crust regardless of the actual age reefless islands do not sink until truncated by erosion apparently thermal subsidence is balanced by isostatic uplift in response to erosion barrier reefs prevent wave erosion of encircled volcanoes and capture products of stream erosion so that isostatic uplift is eliminated insular shelves widen initially at rates of 0 6 to 1 7 kilometers per million years the rates decrease with time thus the subsidence of islands depends on the size of the is land and the presence of reefs and it may not always be the same as that of the surrounding oceanic crust

equatorial locations of water on mars improved resolution maps based on mars odyssey neutron spectrometer data abstract we present a map of the near subsurface hydrogen distribution on mars based on epithermal neutron data from the mars odyssey neutron spectrometer the map s spatial resolution is approximately improved two fold via a new form of the pixon image reconstruction technique we discover hydrogen rich mineralogy far from the poles including 10 wt water equivalent hydrogen weh on the flanks of the tharsis montes and 40 wt weh at the medusae fossae formation mff the high weh abundance at the mff implies the presence of bulk water ice this supports the hypothesis of recent periods of high orbital obliquity during which water ice was stable on the surface we find the young undivided channel system material in southern elysium planitia to be distinct from its surroundings and exceptionally dry there is no evidence of hydration at the location in elysium planitia suggested to contain a buried water ice sea finally we find that the sites of recurring slope lineae rsl do not correlate with subsurface hydration this implies that rsl are not fed by large near subsurface aquifers but are instead the result of either small

a giant landslide on the north flank of tenerife canary islands the extent of mass wasting along the north flank of tenerife has been mapped using swath bathymetry gloria side scan sonar and 3 5 khz echo sounder data the marine surveys show that north of tenerife a giant landslide is exposed over an area of 5500 km2 of the seafloor more than twice the surface area of the island the landslide truncates an older ridge and valley topography that is associated with the shield building basalts on tenerife we interpret the ridge and valley topography as the result of subaerial erosion the landslide is estimated to have a length of 100 km a width of up to 80 km and a volume of about 1000 km3 it extends onshore into the orotava and icod valleys which have been interpreted as of landslide origin k ar dating of basaltic flows in the steep headwall of orotava suggests an age of formation for the valley is younger than 0 78 ma and may even be younger than 0 27 ma the icod valley is located immediately to the north of the most recent volcano on tenerife las canadas and has been associated with the collapse of its caldera between 1 2 and 0 2 ma a young age for the landslide is supported by the 3 5 khz echo sounder data which show that the landslide is draped by a thin 10 m layer of younger sediment the landslide did not form however during a single catastrophic event but represents the amalgamation of a number of separate landslides the occurrence of the ridge and valley topography in water depths of up to 2 5 km suggests that the shield building basalts have subsided by at least this amount since they formed 3 3 8 0 ma we speculate that this subsidence is caused by some form of stress relaxation that occurs in the underlying lithosphere the giant landslide imaged in our sonar data is associated with the late stages in the development of the most recent volcano on tenerife las canadas which only began at about 1 8 ma thus landsliding may be a particular feature of the time soon after emplacement when because of incomplete isostatic adjustment oceanic volcanoes have their greatest elevations above sea level and therefore are most susceptible to slope failure

characteristics of the numerous and widespread recurring slope lineae rsl in valles marineris mars abstract recurring slope lineae rsl are narrow 0 5 5 m dark features on mars that incrementally lengthen down steep slopes fade in colder seasons and recur annually these traits suggest that liquid water is flowing in the shallow subsurface of mars today here we describe high resolution imaging science experiment hirise observations of rsl within valles marineris vm we have identified 239 candidate and confirmed rsl sites within all the major canyons of vm with the exception of echus chasma about half of all the globally known rsl locations occur within vm and the areal density of rsl on coprates montes appears to be the greatest on the planet vm rsl are heterogeneously distributed as they are primarily clustered in certain areas while being conspicuously absent in other locations that appear otherwise favorable rsl have been found on many of the interior layered deposits ilds within vm such ild rsl appear to traverse bedrock instead of regolith like all other rsl forty six of the vm rsl sites show incremental lengthening and exhibit similar behavior in most of the canyons of vm but the rsl duration at one site in juventae chasma is significantly reduced furthermore the lengthening seasonality depends solely on slope orientation with typical vm rsl on a given slope lengthening for 42 74 of a mars year there are always rsl lengthening within vm regardless of the season if rsl are caused by water such a long active season at hundreds of vm rsl sites suggests that an appreciable source of water must be recharging these rsl thermophysical modeling indicates that a melting temperature range of 246 264 k is needed to reproduce the seasonal phenomenology of the vm rsl suggesting the involvement of a brine consisting of tens of wt salt the mechanism s by which rsl are recharged annually remain uncertain overall gaining a better understanding of how rsl form and recur can benefit the search for extant life on mars and could provide details about an in situ water resource

downslope sediment transport by boiling liquid water under mars like conditions experiments and potential implications for martian gullies gullies are widespread morphological features on mars for which current changes have been observed liquid water has been one of the potential mechanisms to explain their formation and activity however under present day martian conditions liquid water is unstable and should only be transiently present in small amounts at the surface yet little attention has been paid to the mechanisms by which unstable water transports sediment under low atmospheric pressure here we present the results of laboratory experiments studying the interaction between liquid water owing over a sand bed under mars like atmospheric pressure c 9 mbar the experiments were performed in a mars simulation chamber at the open university uk in which we placed a test bed of ne sand at a 25 slope we chose to investigate the in uence of two parameters the temperature of the water and the temperature of the sand we performed 27 experiments with nine different combinations of water and sand temperatures ranging from 278 to 297 k under all experimental conditions the water was boiling we investigated and compared the types and timing of sediment transport events and the shapes characteristics and volumes of the resulting morphologies in agreement with previous laboratory studies we found that more intense boiling increased the volume of sediment transported for a given volume of water we found four main types of sediment transport entrainment by overland ow grain ejection grain avalanches and levitation of saturated sand pellets our results showed that increasing sand temperature was the main driving parameter in increasing the sand transport and in modifying the dominant sediment transport mechanism the temperature of the water played a negligible or minor role apart from the duration of sand ejection and avalanches which lasted longer at low water temperature at low sand temperature the majority of the sand was transported by overland ow of the liquid water at higher sand temperatures the transport was dominated by processes triggered by the boiling behaviour of the water at the highest temperatures sediment transport was dominated by the formation of levitating pellets dry avalanches and ejection of the sand grains this resulted in a transport volume about nine times greater at a sand temperature of 297 k compared with 278 k our heat transfer scaling shows that the boiling behaviour will be enhanced under martian low gravity resulting in more ef cient transport of sediment by levitating sand pellets even at temperatures close to the triple point our results showed that the boiling intensity played an important role in the physics of sediment transport by liquid water this implied that the amount of water required to produce morphological changes at the surface of mars could be lower than previously estimated by assuming stable liquid water boiling is a critical process to be considered when assessing gully formation and modi cation mechanisms mobilized by liquid water our work could have similar implications for any water formed landform on mars which could include recurring slope lineae dark dune ows and slope streaks

new insights on the evolution of the linosa volcano sicily channel from the study of its submarine portions abstract linosa island represents the emergent tip of a mostly submarine much wider volcanic edifice with at least 96 of its areal extent lying below sea level marine geological surveys carried out in 2016 and 2017 allowed to reconstruct the submarine portions of linosa and to characterize the main volcanic features providing new unexpected insights on the evolution of this little explored volcanic complex in particular the submarine setting of the nw offshore is represented by a 10 km long volcanic belt punctuated by a number of small eruptive cones appearing more recent with respect to the assumed mid late quaternary age of volcanism on the island this evidence suggests that the growth of the volcanic edifice has likely been more complex than that claimed on the base of subaerial volcanism only and supports a north westward migration of the activity over time the submarine southern flank of the volcanic edifice is also characterized by eccentric eruptive cones but mostly without evidences of recent activity the main processes responsible for the growth and evolution of linosa volcano and their possible relative chronology are discussed in the framework of what previously known on the base of the limited subaerial portions with implications on the potential hazard of the volcanic edifice considered as not active in recent times similarity with the pantelleria volcano located in the nw sicily channel are also evidenced especially for what regards the distribution and morphometric characteristics of eruptive cones occurring in the submarine portions of both islands

a model for calculating eruptive volumes for monogenetic volcanoes implication for the quaternary auckland volcanic field new zealand abstract monogenetic basaltic volcanism is characterised by a complex array of behaviours in the spatial distribution of magma output and also temporal variability in magma flux and eruptive frequency investigating this in detail is hindered by the difficulty in evaluating ages of volcanic events as well as volumes erupted in each volcano eruptive volumes are an important input parameter for volcanic hazard assessment and may control eruptive scenarios especially transitions between explosive and effusive behaviour and the length of eruptions erosion superposition and lack of exposure limit the accuracy of volume determination even for very young volcanoes in this study a systematic volume estimation model is developed and applied to the auckland volcanic field in new zealand in this model a basaltic monogenetic volcano is categorised in six parts subsurface portions of volcanoes such as diatremes beneath phreatomagmatic volcanoes or crater infills are approximated by geometrical considerations based on exposed analogue volcanoes positive volcanic landforms such as scoria spatter cones tephras rings and lava flow were defined by using a light detection and ranging lidar survey based digital surface model dsm finally the distal tephra associated with explosive eruptions was approximated using published relationships that relate original crater size to ejecta volumes considering only those parts with high reliability the overall magma output converted to dense rock equivalent for the post 250 ka active auckland volcanic field in new zealand is a minimum of 1 704 km3 this is made up of 1 329 km3 in lava flows 0 067 km3 in phreatomagmatic crater lava infills 0 090 km3 within tephra tuff rings 0 112 km3 inside crater lava infills and 0 104 km3 within scoria cones using the minimum eruptive volumes the spatial and temporal magma fluxes are estimated at 0 005 km3 km2 and 0 007 km3 ka the temporal volumetric evolution of auckland is characterised by an increasing magma flux in the last 40 ky which is inferred to be triggered by plate tectonics processes e g increased asthenospheric shearing and backarc spreading of underneath the auckland region

geologic context of recurring slope lineae in melas and coprates chasmata mars one of the major mars discoveries of recent years is the existence of recurring slope lineae rsl which suggests that liquid water occurs on or near the surface of mars today these dark and narrow features emerge from steep rocky exposures and incrementally grow fade and reform on a seasonal basis and are detected in images from the high resolution imaging science experiment camera rsl are known to occur at scattered midlatitude and equatorial sites with little spatial connection to one another one major exception is the steep low albedo slopes of melas and coprates chasmata in valles marineris where rsl are detected among diverse geologic surfaces e g bedrock and talus and landforms e g inselbergs and landslides new images show topographic changes including sediment deposition on active rsl slopes midwall locations in coprates and melas appear to have more areally extensively abundant rsl and related fans as compared with other rsl sites found on mars water budget estimates for regional rsl are on the order of 105 to 106 m3 of fluid for depths of 10 to 100 mm and suggest that a significant amount of near surface water might be present many rsl are concentrated near local topographic highs such as ridge crests or peaks which is challenging to explain via groundwater or ice without a recharge mechanism collectively results provide additional support for the notion that significant amounts of near surface water can be found on mars today and suggest that a widespread mechanism possibly related to the atmosphere is recharging rsl sources

new observations of martian southern mid latitude recurring slope lineae rsl imply formation by freshwater subsurface flows abstract southern mid latitude sml recurring slope lineae rsl are narrow 0 5 5 m dark albedo features that emanate from bedrock and incrementally lengthen down steep slopes that preferentially face the equator we observe that sml rsl begin lengthening prior to southern summer at a solar longitude ls of 245 11 when mars global surveyor thermal emission spectrometer tes derived near maximum surface temperatures are 296 5 k and mars reconnaissance orbiter mars climate sounder mcs and mars odyssey thermal emission imaging system themis derived mid afternoon surface temperatures are 273 k sml rsl continue to lengthen for 104 38 sols with an average near maximum surface temperature of 298 5 k the sml rsl then stop lengthening at ls 314 12 when mid afternoon surface temperatures drop below 273 k they remain dark for another 116 41 sols until ls 16 14 as surface temperatures continue to fall although the rsl recharge mechanism remains unknown our observation that the vast majority of rsl lengthen only when mid afternoon surface temperatures are 273 k supports the hypothesis that they are formed by shallow subsurface liquid water flows without significant freezing point depression the number and length of rsl at multiple sites increased dramatically following the mars year 28 globe encircling dust storm we interpret this increase to be due to warmer subsurface temperatures created by a dust laden greenhouse effect that may be unique to the southern mid latitudes near ls 270 therefore sml rsl flow is quite sensitive to ground temperature and may only occur under favorable orbital parameters when mean insolation during the rsl lengthening season is above that of the current southern mid latitude mean insolation value this value is currently at a peak that has not been attained for the last 100 ka meanwhile the rsl poor northern mid latitude mean insolation is near a minimum and has a value 27 lower than the southern value if sml rsl are indeed formed by shallow subsurface freshwater flows then they may be some of the best locations on mars to explore for extant life

sublimation rate of ice under simulated mars conditions and the effect of layers of mock regolith jsc mars 1 1 we have studied the sublimation of ice buried beneath 200 mm of jsc mars 1 model regolith under simulated mars conditions as expected even thin layers of regolith cause large decreases in sublimation rate up to one order of magnitude at 50 mm when the depth of the regolith was 50 to 200 mm we detected water desorbing from the overlying layers for which we were able to determine a desorption coefficient of 1 45 0 5 10 3 h 1 after allowing for the effect of desorption we found that the diffusion coefficient for water vapor through our regolith is 1 74 0 70 10 4 m2 s 1 in excellent agreement with theoretical values we thus find that a 1 m thick layer of ice buried below a meter of regolith resembling jsc mars 1 on mars at 235 k would last 800 years

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

present day formation and seasonal evolution of linear dune gullies on mars linear dune gullies are a sub type of martian gullies as their name suggests they only occur on sandy substrates and comprise very long compared to their width straight or sinuous channels with relatively small source areas and almost non existent visible deposits linear dune gullies have never been observed on terrestrial dunes and their formation process on mars is unclear here we present the results of the first systematic survey of these features in mars southern hemisphere and an in depth study of six dunefields where repeat imaging allows us to monitor the changes in these gullies over time this study was undertaken with hirise images at 25 30 cm pix and 1 m pix elevation data derived from hirise stereo images we find the latitudinal distribution and orientation of linear dune gullies broadly consistent with the general population of martian gullies they occur predominantly between 36 3 s and 54 3 s and occasionally between 64 6 s and 70 4 s they are generally oriented toward ssw at bearings between 150 and 260 we find that these gullies are extremely active over the most recent 5 martian years of images activity comprises 1 appearance of new channels 2 lengthening of existing channels 3 complete or partial reactivation and 4 disappearance of gullies we find that gully channels lengthen by 100 m per year the intense activity and the progressive disappearance of linear dune gullies argues against the hypothesis that these are remnant morphologies left over from previous periods of high obliquity millions of years ago the activity of linear dune gullies reoccurs every year between the end of winter and the beginning of spring ls 167 4 216 6 and coincides with the final stages of the sublimation of annual co ice deposit this activity often coincides spatially and temporally with the appearance of recurrent diffusing flows rdfs digitate shaped dark patches with low relative albedo up to 48 lower than the adjacent dune that encompass the active site south and ssw facing dune slopes are those which preferentially host co2 frost deposits however it is only those with angles of 20 just below the crest which possess linear dune gullies suggesting a slope limited formation process these observations provide a wealth of temporal and morphometric data that can be used to undertake numerical modeling to direct future image monitoring and guide laboratory experiments that can be used to better constrain the formation process of these features