north american pacific relative plate motion in southern california from interferometry very long baseline interferometry measurements of baselines crossing the san andreas fault zone in southern california have provided observational constraints on rates of elastic tectonic strain accumulation the single site located near this fault the jet propulsion laboratory site moves in a direction concordant with the pacific plate motion vector but at approximately half the net rate relative to north america this motion agrees approximately in amount with geologically determined displacement rates on the san andreas fault alone but not with the local strike of the fault when considered together with complementary geodetic data these results suggest a complex relation between the short term accumulation of elastic strain and its permanent accommodation on existing faults

coastal dynamics under conditions of rapid sea level rise late pleistocene to early holocene evolution of barrier lagoon systems on the northern adriatic shelf italy this multidisciplinary case study of two preserved barrier systems combined the analysis of radiocarbon datings grain size distributions high resolution seismics and shelf bathymetry with reconstructions of palaeo environmental conditions tides waves sea level change and forward modelling of barrier lagoon systems to provide an integrated view of the coastal transgressive evolution of a large sector of the northern adriatic shelf between 15 and 8 ka bp palaeoenvironmental reconstructions point to increased tidal amplitude low energy wave climate and high rates of sea level rise up to 60 mm a during the formation of the oldest preserved barrier system not vert similar90 m water depth 14 3 cal ka bp a younger barrier system 42 m water depth 10 5 cal ka bp formed under conditions of lower tidal amplitude higher wave energy and a lower rate of sealevel rise 10 mm a forward modelling suggests that the probability of barrier island overstepping during transgression is inversely proportional to tidal amplitude if all other factors are assumed equal the oldest barrier lagoon system developed under conditions of large tidal amplitude which permitted rapid transgression however this system apparently failed to keep up with the anomalously high rate of sea level rise resulting from melt water pulse 1a the youngest barrier system appears to have drowned in place due to antecedent topography as the barrier system transgressed over an ancient pleistocene alluvial plain the rapid increase in backbarrier accommodation caused an abrupt disequilibrium between shoreface and backbarrier sedimentation which led to barrier overstepping although barsim modelling indicates that tidal deposition can reduce the probability of barrier overstepping there are other driving mechanisms in our case extremely rapid sea level rise and antecedent topography which are more determinative in explaining the transgressive coastal evolution of barrier lagoon systems in the northern adriatic sea grain size analysis of shoreface deposits sampled above the transgressive ravinement surface across the northern adriatic shelf indicate a distinct relation between the sediment grain size and the rate of sea level rise during deposition which implies that progressive sorting must have been highly effective

geology of central chryse planitia and the viking 1 landing site implications for the mars pathfinder mission 1 500 000 scale geologic mapping in the central chryse planitia region of mars was correlated with ground truth data gathered by the viking 1 lander materials within the chryse basin can be subdivided into plains and channel units that are typically separated from one another by gradational contacts hesperian ridged plains materials unit 1 hr1 are the oldest materials mapped typically these materials contain numerous fresh impact craters and have sharply defined mare like wrinkle ridges similar to those appearing on the lunar maria these materials grade into hesperian ridged plains materials unit 2 hr2 which are characterized by buried and eroded impact craters and subdued wrinkle ridges from analyses of crater age dates and their associated geologic contacts channel materials appear to have formed at the same time as hr2 materials and it is likely both units represent fluvial sediments measurements of buried craters contained in hr2 materials suggest that in places this unit may be 50 m thick but crater size frequency distribution curves suggest that the areal average may be closer to 170 m based on these observations our interpretation is that hr2 materials were deposited into a standing body of water during channel formation this interpretation implies that many of the rocks visible in the viking 1 lander images were emplaced by fluvial processes possibly finer grained sediments remained in suspension and were subsequently transported out of chryse planitia and into the northern plains during draining of the ponded water east west trending surface undulations visible in lander views toward the south may represent aeolian dunes lava flow fronts or sediment waves formed at the bottom of the standing body of water broad physiographic units seen at the surface are not clearly visible in viking orbiter images however they can be projected at the resolution of the orbiter images these units show that concentrations of drift materials are oriented in a northwesterly direction contrary to the strongest prevailing wind direction which is toward the northeast these materials were probably deposited on ridged plains materials unit 2 during a period of time when aeolian processes were more active in the region both earth based radar and viking thermal data suggest that the mars pathfinder landing site will be similar geologically to the viking 1 site if this is true then the mars pathfinder mission provides the opportunity for building directly on results of the viking program some of the outstanding questions that mars pathfinder may be able to address include determining the aeolian modification history of the chryse planitia region the degree and possibly the relative rate of sediment induration the fraction of rocks and boulders emplaced by impact processes the possibility that some materials are the result of in situ weathering and whether materials were emplaced by fluvial processes and the associated depositional environment

off shelf sedimentary record of recurring global sea level changes during the plio pleistocene evidence from the cyclic fills of exhumed slope systems in central italy the markedly cyclic sedimentary successions of four late pliocene to early pleistocene slope turbidite systems exposed in eastern central italy have been resolved into 31 high frequency sequences chronological constraints from biostratigraphy and magnetostratigraphy indicate that these successions form a composite partially overlapping stratigraphic record and sequence bounding surfaces can be convincingly correlated with glacial oxygen isotope stages g2 60 c 2 65 1 7 ma inclusive the studied successions therefore preserve an extraordinary and legible record of recurring orbitally dictated glacio eustatic sea level fluctuations and provide an unprecedented opportunity to examine the deep water sedimentary response to such high frequency changes from an outcrop perspective supplementary material sedimentological attributes of lithofacies identified in the studied successions are available at www geolsoc org uk sup18549

human impact in the holocene fluvial and coastal evolution of the marche region central italy abstract today the coasts of the marche region are represented by almost continuous rectilinea sand beaches except in the north at the border with the romagna region and in the central part around the conero ridge where there are active rock cliffs the sandy coasts are protected almost everywhere by artificial barriers built up as a protection against the general tendency to retreat along some tracts the coastal erosion started at the beginning of this century but became generalized after 1940 1950 this was mainly due first to the reduction in sediment supply following the improvement in agricultural techniques after the italian unification and later to the widespread extraction of gravels from the thalwegs related to the rapid increase in urban population in the 1950s however in the same period along the rivers there was a widespread creation of artificial levees to prevent lateral erosion or flooding and to extend areas suitable for agriculture following these practices the lower middle tracts of the rivers underwent a strong vertical downcutting which increased as a result of the creation of checkdams downvalley of many bridges which contributed to the store of the sediments in the upper part of the valleys at present most of the rivers have an irregular course and are deeply entrenched in the bedrock or inside their own sediments up to the beginning of the century most of the lower tracts of the valleys were characterized by strong aggradation in a braidplain system this aggradation started as early as the middle ages 1100 ad but increased after the renaissance as a consequence of a generalized deforestation of the periadriatic basin and the following severe soil erosion in the mean time the coast underwent a very fast progradation in some places more than 500 m small deltas were created at the mouths of the rivers and longshore bars and sandy beaches began to occupy the base of the active cliffs which previously extended between one river and another however in the mountain parts of the river basins a meander course existed and in many cases still exists expecially where the human interventions were of limited extent before 1000 1100 ad all the rivers had a meander pattern and at the junction with the sea entered lagoons and swamps in most cases protected by littoral barrier beaches these conditions were established earlier than the third century bc and have been attributed to the first systematic land clearance and the following soil erosion during the bronze and iron ages at that time the regional coastline became almost rectilinear but with many active cliffs between one river and another before being affected by a major human impact earlier than 4000 years bp the natural coastal environment was represented by active rock cliffs which alternated with pocket beaches corresponding to a river mouth in some rivers embayments and beaches were located up to 4 5 km inland from the present day position after the flandrian transgression the evidence presented reveals major changes that can be attributed to human impact

modeling surface deformations at complex strike slip plate boundaries two new versions of the physical base traction model of li and rice 1987 have been developed to study the loading processes and surface deformation near plate boundaries with geometric complexities including a shallow creeping fault segment and two subparallel faults predictions of surface velocity and surface slip rate for the region between the san andreas fault and the pacific coast at the latitude of the parkfield cholame segment using model parameters based on geologic geodetic and seismic considerations were found to be in good agreement with contemporary geodetic field data not used in constraining model parameters also predicted surface velocity for the salton sea coachella valley area were fit to recently derived contemporary geodetic data and very large baseline interferometry data although here the model parameters are not well constrained

morphological changes and human impact in the entella river floodplain northern italy from the 17th century abstract in this article the morphological changes undergone by the entella river northern italy over the last four centuries has been investigated the historical analysis has allowed reconstruction of fluvial evolution and shoreline dynamics and demonstrated their relationship to human disturbance over a very long period compared to most previous studies in italy and europe a set of 12 historical and current maps and aerial photos ranging from the 17th century to the present were entered into a geographic information system gis in order to calculate four morphological parameters i e channel length width sinuosity and centreline shifting and the distance of the shoreline modification of the entella river over the 360 years period 1656 2016 include i a reduction in channel length by 128 m 3 ii a mean narrowing of 56 m 46 iii a decrease in total sinuosity from 1 10 to 1 05 with a variation in river pattern from sinuous to straight iv a total shifting of the centreline of 30 m this evolutionary trend is consistent with most of the previous studies on italian and european rivers conversely the total channel shortening and the recent phase of substantial morphological stability with a slight increase in channel width and length seems to be in contrast with the results of other studies we correlated the channel planform changes and the regression of the shoreline at least until the latter 20th century to the reduction in sediment supply produced by the morphological modifications due to human intervention at the beginning of the 19th century and later from the 1950s to the end of the 20th century channelization channel diversion land use changes and coastal defences accounted for this supply change to the entella river and its floodplain furthermore our findings reveal that human disturbance has contributed to increased flood risk in the plain through the progressive reduction in width of the riverbed and the increasing urbanization along its riverbanks at the same time channelization seems to have a negative effect not only on the morphological evolution of the river but also in terms of prevention and flood risk reduction within the floodplain

detection of a locked zone at depth on the parkfield california segment of the san andreas fault the parkfield california segment of the san andreas fault is transitional in character between the creeping segment of the fault to the northwest and the locked carrizo plain segment to the southeast the rate of shallow fault slip decreases from 25 30 mm yr northwest of the epicenter of the 1966 parkfield earthquake to zero at the southeastern end of the 1966 rupture zone data from a network of trilateration lines spanning the san andreas fault near parkfield and extending to the pacific coast near san luis obispo shed light on the rate of fault slip at depth since the 1966 earthquake in this study average rates of line length change and shallow fault slip were inverted to determine the slip rate at depth on the parkfield fault segment the fault is taken to be a vertical surface with unknown distribution of strike slip displacement in an elastic half space a striking result of the inversions is that all solutions providing acceptable fits to the data exhibit a locked zone essentially coincident with the rupture surface of the 1966 parkfield earthquake the data require that the locked zone extend nearly as far north as the 1966 epicenter however the vertical extent of the locked zone is not well resolved over much of the parkfield segment the fault is slipping faster at the earth s surface than it is at seismogenic depths in order to fit the trilateration measurements it is necessary to include a component of contraction normal to the trend of the san andreas the inversion results suggest a spatially uniform normal strain of 0 06 strain yr the orientation of the contraction is compatible with geologic and seismic evidence of active folding and reverse faulting in the region the magnitude of the contraction is consistent with convergence rates inferred from global plate motion models

mars outflow channels a reappraisal of the estimation of water flow velocities from water depths regional slopes and channel floor properties methods used so far to assess the flow velocities of the water commonly assumed to be responsible for forming the major outflow channel systems on mars have relied widely on various versions of the manning equation this has led to problems in allowing for the difference between the accelerations due to gravity on mars and earth and for the differences of scale between martian floods and most river systems on earth we reanalyze the problem of estimating water flow velocities in martian outflow channels using equations based on the darcy weisbach friction factor instead of the manning n factor we give simplified formulae appropriate to mars for the darcy weisbach friction coefficient as a function of bedrock size distribution for a given channel floor slope and water flood depth similar mean flow velocities are implied for a wide range of values of the ratio of bed roughness to water depth relevant to martian outflow channels using a recent rederivation of manning s equation based on turbulence theory we obtain a new value of 0 0545 s m 1 3 for the manning n coefficient appropriate to martian channels and show that previous analyses have generally overestimated though in some cases underestimated water flow velocities on mars by a factor of order two combining the consequences of this flow velocity overestimate with likely overestimates of flow depth from assuming bank full flow we show that discharges may have been overestimated by a factor of up to 25 leading to corresponding overestimates of subsurface aquifer permeabilities rates of filling of depressions with water and grain sizes of sediments on channel floors despite the availability of an improved value for the manning n coefficient for mars we strongly recommend that modified forms of the original version of the manning equation should be replaced by the modern form or preferably by the darcy weisbach equation in future work

magnitude of a catastrophic flood event at kasei valles mars kasei valles compose an enormous outflow channel system on mars the upper part of the channel system is typically less than 1 km deep and descends from echus chasma about 1 km over a distance of 1000 km it then splits into north and south channels on the basis of a stereomodel of viking images we have measured the geometry of a steep constricted reach of the north channel that drops 900 m in only 100 km a late stage flood is hypothesized to have scoured the channel if we assume that channel striations indicate water levels then the flood had a minimum cross sectional area of 3 12 x 10 7 m 2 the putative flood had a width of 83 km an average depth of 374 m and maximum depth of 1280 m these channel measurements suggest that flood velocities ranged from 32 to 75 m s 1 and that discharge was greater than 1 km 3 s 1 values larger than those calculated for any other flood event on mars or earth the flood maintained supercritical flow and caused intense erosion in this area scouring a 350 m deep megapothole the source of the flood water may have been a temporary lake in echus chasma a deep canyon formed in association with tectonism at valles marineris

the relation of catastrophic flooding of mangala valles mars to faulting of memnonia fossae and tharsis volcanism detailed stratigraphic relations indicate two coeval periods of catastrophic flooding and tharsis centered faulting producing memnonia fossae in the mangala valles region of mars major sequences of lava flows of the tharsis montes formation and local lobate plains flows were erupted during and between these channeling and faulting episodes first late hesperian channel development overlapped in time the tharsis centered faulting that trends north 75 to 90 e next late hesperian early amazonian flooding was coeval with faulting that trends north 55 to 70 e in some reaches resistant lava flows filled the early channels resulting in inverted channel topography after the later flooding swept through both floods likely originated from the same graben which probably was activated during each episode of faulting faulting broke through groundwater barriers and tapped confined aquifers in higher regions west and east of the point of discharge the minimum volume of water required to erode mangala valles about 5 1012 m3 may have been released through two floods that drained a few percent pore volume from a relatively permeable aquifer the peak discharges of the floods may have lasted from days to weeks the perched water discharged from the aquifer may have been produced by hydrothermal groundwater circulation induced by tharsis magmatism tectonic uplift centered at tharsis montes and compaction of saturated crater ejecta due to loading by lava flows

chryse basin channels low gradients and ponded flows gradients on the floors of the martian outflow channels that are derived from radar elevation profiles across lunae planum and the chryse basin have much lower values than those obtained from the u s geological survey s topographic map to arrive at this conclusion 26 radar elevation profiles clustered at four latitudinal channel crossings were analyzed and approximate longitudinal gradients of the channel floors were constructed whereas the gradients of maja and ares valles are similar to those of the catastrophic flood channels in the scablands of washington state and water or ice could have moved through them without difficulty the gradients of simud and tiu valles are essentially level and the movement of fluids to the north poses problems it is proposed that ponding from local runoff occurred before channel formation along the course of simud and tiu valles the ponding may have formed lakes in depressions associated with the valles marineris grabens ancient craters in the chaotic terrain area and possibly even the regional low where most chaotic terrains occur it is envisioned that lakes eventually overflowed drainages became integrated and headward erosion breached interfluves thus forming the present channel configurations when dams broke floods mudflows or mixtures of water sediments and ice were released catastrophically with a final gigantic flood from the valles marineris system of troughs this flood would have had sufficient head to move fluids across nearly level gradients through the simud and tiu channels the ponding and flooding probably occurred during a time when the climate was different from that at present permitting surface runoff of fluids and standing bodies of water

geodetic measurement of horizontal deformation in the northern san francisco bay region california analysis of geodolite observations in the coast ranges of northern california indicates that relative plate motion is spread over a wide zone little or no deformation occurs to the southwest of the san andreas fault itself to the northeast of the san andreas fault a region transected by the parallel rodgers creek and maacama faults 25 6 mm yr of right lateral slip is distributed over about 60 km there is a peak shear strain of 0 6 0 1 rad yr near the san andreas fault elsewhere in the deforming zone shear strain rates are 0 3 0 04 rad yr at the northeastern boundary of the study area the strain rate is less than 0 2 rad yr except for the high strain rate near the san andreas fault there is no evidence of any localization of deformation to the surface traces of the faults nor is there any evidence of creep or aseismic slip on any of the faults in the area the data indicate that the relative motion between the pacific and north american plate occurs primarily to the northeast of the san andreas fault the observations are inconsistent with models that include slip at depth on only the san andreas fault the data can be fit equally well by models with slip at depth on all three of the major faults or with motion distributed across the entire zone from the san andreas fault to the napa valley fault preliminary analysis of observations to the farallon islands about 40 km southwest of the san andreas fault suggests that little or no additional relative motion is accommodated on that side of the san andreas fault in particular it is unlikely that the 20 mm yr difference between the plate motion rate about 55 mm yr and the san andreas fault system rate about 35 mm yr can be explained by deformation between the san andreas fault and the farallon islands

duration and rates of discharge maja valles mars the 1600 km long maja valles outflow system of mars consists of three major divisions including the upper valley on lunae planum the canyon section across xanthe terra and the lower valley across western chryse planitia although water released from the source in juventae chasma could reach the terminus of the present day valley system within 40 hours the original outflow did not traverse the martian surface as an uninterrupted flow nor was the source basin emptied instantaneously the initial flood ponded on northern lunae planum and near the western edge of chryse planitia significantly prolonging the lifetime of surface flow calculation of pond volumes and maximum discharge rates through various parts of the channel system assuming full bank discharge allows an estimate of minimum duration of water flow through the outflow complex about four terrestrial months are required to empty juventae chasma and another 10 months are required to drain the impoundment on lunae planum thus the history of erosion and sedimentation in the lower reaches of the drainage system is potentially much more complex than that of outflow from the source region

natural and anthropogenic influences on depositional architecture of the ural delta kazakhstan northern caspian sea during the past 70 years abstract this paper focuses on the ural delta in the northern zone of the caspian sea an area with particular characteristics where intense influence from anthropogenic and natural factors exists which acts on the fragile delta system we built a database to integrate the data from the published sources bathymetric survey and recent images in the geographical information system gis environment the results were linked to the caspian sea level csl curve which had many variations changing the ural delta system s dynamics and in its architecture in addition the anthropogenic changes contribute to shaping the actual ural delta architecture through the link between the results and csl we reconstructed an evolution model for the ural delta system for the last century and identified three different architectures for the ural delta determined by the energy that acted on the system in the last century and by the anthropogenic changes this work identifies six different delta phases which are shaped by csl changes during the last 70 years and by anthropogenic changes the delta phases recognized are i a lobate delta phase shaped during high csl before 1935 ii natural elongate delta 1935 1950 formed during rapid csl fall iii anthropogenic elongate delta 1950 1966 formed during rapid csl fall and after the ural caspian sea canal construction which modified the sedimentary deposition on the delta iv anthropogenic elongate delta 1966 1982 shaped during low csl phase v anthropogenic elongate delta 1982 1996 formed during a rapid csl rise phase and vi anthropogenic elongate delta 1996 2009 shaped during high csl that represent the last phase and actual ural delta architecture

the holocene transgression into the estuarine central basin of the odiel river mouth cadig gulf sw spain lithology and faunal assemblages abstract six estuarine facies were distinguished recording the holocene history of sea level rise relating according to the start and development of the holocene transgression which flooded the coast of huelva facies 2 gravels facies 3 grey clayey silts facies 5 well sorted sands facies 4 silty sands facies 5 black clayey silts and facies 6 red muds this group overlies neogene sediments facies 1 three faunal assemblages open bay ob central estuary ce and wave domination wd including remains of macrofauna foraminifers and ostracods plus depositional features are identified in a sedimentological log constructed from a borehole with a continuous core sunk in the central basin of the odiel river estuary huela coast sw spain the ob assemblage requires shallow and protected zones controlled by low energy tidal currents the ce assemblage is located within an intertidal zone where reworked marine forms of foraminifers ostracods and scattered macrofauna co exist with small estuarine foraminifers and ostracods the wd assemblage comprises tests of marine macrofauna with fractured shells plus large marine foraminifers and estuarine ostracods during the first stage of continuous sea level rise 8720 260 bp to 5390 155 bp estuarine accretion high energy tidal currents and wave action took place successively allowing the development of the ob ce and wd assemblages the second stage 5390 155 bp to present with a stabilized sea level comprised a vertical decrease of energy with tidal currents favouring deposition in shallow tidal channels and marsh zones leading to less energetic ce assemblages within the estuarine central basin high sediment supply resulted in deposition during this stage which shows a regressive nature

paleodischarge of the late pleistocene bonneville flood snake river idaho computed from new evidence the bonneville flood resulted from catastrophic outflow from pleistocene lake bonneville about 15 000 yr ago when the lake overtopped its rim at red rock pass in southeastern idaho and discharged a vast volume of water down the snake river this paper provides revised estimates of the paleodischarge volume and duration of the bonneville flood based on new evidence of its height and on current understanding of the amount of lowering of lake bonneville evidence for the revised height of the flood is derived from the altitude of erosional features and flood deposits at the head of a constricted reach of the snake river canyon at the mouth of sinker creek and from the altitudes of flood deposits at several places about 53 km upstream using the step backwater method we estimate that peak discharge for the bonneville flood through the constricted reach was from 793 000 to 1 020 000 m 3 s and most likely was 935 000 m 3 s this discharge is 2 2 times the discharge previously reported and is the second largest flood known to have occurred in the world at this rate of discharge the shear stress for the flood would have been 2 500 n m 2 and the unit stream power would have been 75 000 n m s as compared with values of 6 to 10 n m 2 and 12 n m s for recent floods on the mississippi and the amazon other recent studies of the history of lake bonneville show that the volume of water released was 4 700 km 3 or about 3 times greater than the volume previously inferred although this volume indicates a flood duration of 8 weeks at constant peak discharge an accurate estimate of the duration would require dam break modeling at red rock pass from a dam break model flood hydrographs at red rock pass and the hydraulics of the flood wave along the snake river could be computed

hydraulic modeling of a distributary channel of athabasca valles mars using a high resolution digital terrain model 1 estimating magnitudes of flow rates in outflow channels has a central role in developing understanding of the paleohydrology of mars the typical approach to flow estimation is to identify geomorphic features which indicate bankfull levels and then use a hydraulic model to convert these levels into flow rates data constraints have meant that important assumptions about model equations boundary conditions and parameter values have been necessary in this paper we use a high resolution digital terrain model derived from nasa s mars reconnaissance orbiter context camera stereopair imagery to develop a finer resolution step backwater hydraulic model than previously attempted furthermore the data facilitate a more critical more formal and broader assessment of this type of model than has previously been attempted a distributary channel of athabasca valles is used as a case study the median bankfull flow estimate was 39 000 m3 s 1 although estimates range up to 140 000 m3 s 1 depending on the assumptions employed the principal uncertainties stem from assumptions about bankfull levels and downstream boundary conditions and assumptions about the friction coefficient criticality of flow expansion and contraction losses and geometric details of the channel are also important under certain conditions examination of additional dtms further downstream would permit the analysis to be extended to hydraulic control sections that provide better known boundary conditions hence improving flow estimates it is concluded that new generation dtm data provide opportunity for deeper insight into the challenges and opportunities for modeling the paleohydrology of mars although further work is needed to achieve satisfactory levels of confidence

morpho sedimentary characteristics and holocene evolution of the emergent part of the ombrone river delta southern tuscany abstract the holocene evolution of the ombrone river delta has been investigated using morphological and sedimentological evidence the delta had a lagoon like prehistoric evolution while seawards the growth occurred mainly in historical times the data obtained together with the available historical and archeological documentation enable a quantitative evaluation of the volume of the emerged part of the delta to be made moreover for the apical area it has been possible to calculate the annual average increase in the volume of deposition during etruscan and roman times as well as during the middle ages and since the renaissance up to now it has been possible to estimate the periods during which wind exerted a more important role in shaping the delta morphology the volume of sediments deposited during the last 6000 years has been estimated at 1766 10 6 m 3 a combination of climatic conditions littoral dynamics and human action appears to have driven the dynamics of the delta growth which however was not continuous but active especially during the last 3000 years during this period about the 80 of the whole delta volume seems to have deposited high rates of sedimentation occurred between the 16th and the 19th centuries a cold and moist period coinciding with the little ice age when the delta took the typical shape of microtidal wave dominated deltas

anthropogenic influence on recent evolution of shorelines between the conero mt and the tronto r mouth southern marche central italy abstract a study of the shoreline evolution during the last two centuries along the southern portion of the marche region between the promontory of the conero mountain and the tronto river mouth has been carried out on the basis of historical data and taking into account the effects of both natural events and anthropogenic interventions the research started with searching acquiring georeferencing and digitizing all the available maps surveyed from 1835 to the present the above data set has been used to implement a vector geodatabase containing the successive position and shape of shorelines with particular attention to the neighboring river mouths since transitional and beach deposits have been almost completely eroded during the last decades the adoption of traditional techniques of geomorphologic and sedimentological analyses has not been possible the results of the above analyses have been correlated with the main natural events and human interventions occurring during the considered time span the results of this comparison highlights that the evolution of river mouths and neighboring beaches mostly depends on deforestation carried out in their hydrographic basins in the study area the progradation of river mouths continued after the end of the little ice age ended around 1850 namely it has been observed that the retreat coincided with the start of reforestation and agricultural development in the 20 s of the last century during the following decades further interventions such as construction of dams and check dams extraction of sediments from thalwegs fillings modifications of stream paths abandonment of agricultural practices etc contributed to a severe reduction of river solid load with subsequent retreat of both river mouths and beaches thus making it necessary to protect them with artifacts

paleohydrology and flood geomorphology of ares vallis ares vallis is a martian outflow channel which is about 1500 km long and locally exceeds 100 km in width and 1000 m in depth we estimate the channel s paleoflow capacity using paleohydraulic techniques at a constricted and unusually deep reach not affected by tributaries or secondary inflows the estimated possible maximum peak discharges are of the order of 108 109 m3 s these values are 1 to 2 orders of magnitude larger than any known terrestrial floods these high discharge flows were theoretically capable of transporting boulders larger than 10 m in diameter the downstream depositional plain where ares debauches into the chryse planitia displays geomorphological features indicative of high erosional capacity by the flooding in this area site of the proposed pathfinder landing we expect to find a complex sequence of sediments created by varying paleoflood flow hydraulics sediment transport characteristics and probable secondary modification of the primary flood landforms

middle to late holocene glacial variations periglacial processes and alluvial sedimentation on the higher apennine massifs italy the major climatic variations that have affected the summit slopes of the higher apennine massifs in the last 6000 yr are shown in alternating layers of organic matter rich soils and alluvial glacial and periglacial sediments the burial of the soils triggered by environmental climatic variations took place in several phases for the last 3000 yr chronological correlations can be drawn between phases of glacial advance scree and alluvial sedimentation and development of periglacial features during some periods the slopes were covered by vegetation up to 2700 m and beyond while in other phases the same slopes were subject to glacial advances and periglacial processes and alluvial sediments were deposited on the high plateaus around 5740 5590 1560 1370 and 1300 970 cal yr b p organic matter rich soils formed on slopes currently subject to periglacial and glacial processes the mean annual temperature must therefore have been higher than at present furthermore on the basis of the variations in the elevation of the lower limit reached by gelifraction it can be concluded that the oscillations in the minimum winter temperatures could have ranged between 3 0 c lower ca 790 150 cal yr b p and 1 2 c higher ca 5740 5590 cal yr b p than present minimum winter temperatures during the last 3000 yr the cold phases recorded by the calderone glacier advance in the apennines essentially match basically the phases of glacial advance in the alps

shoreline variations and coastal dynamics a space time data analysis of the jonian littoral italy abstract morphological variations of coastlines are caused by several key processes that are influenced by climate conditions sea level variations wave energy tectonics and human induced phenomena these processes affect the dynamics of catchment basins and the coastal environment since the second half of the 20th century the jonian coast of the basilicata region italy has witnessed a widespread retreating phenomenon predominantly due to anthropogenic causes affecting transport processes along the riverbeds and causing reductions in the sediment supply to the coast the disturbance in the balance between sediment transport carried out by the sea and the sediment supply performed by rivers has led to a deficit in the sediment budget to understand the morphological dynamics of the littoral environment and quantify the amount of coastal erosion an analysis of coastline change has been carried out using various data sources historical cartography aerial photographs and gps surveys between 1870 and 1954 the 32 km long jonian littoral under examination showed an accretion trend while the loss in beach surface steadily increased between 1954 and 2005 the average change in beach surface has been calculated as about 55 000 m 2 yr accretion between 1870 and 1954 and 16 500 m 2 yr erosion between 1954 and 2005 overall 640 000 m 2 of sandy beaches were lost along the entire jonian coast of the basilicata region between 1954 and 2005 comparing the shoreline between 1870 and 1954 the average net shoreline movement nsm is 110 m vs 30 m between 1954 and 2005 this analysis approach has proven to be effective in quantifying the erosion phenomenon and its effects despite the lack of homogeneous data series and the variety of spatial and temporal scales over which coastal evolution occurs the study represents an important step in understanding coastal dynamics in this region as coastal areas are being affected by an increasing number of population and socio economic activities identification of shoreline changes and forecasts of coastline evolution represent key information for coastal scientists engineers decision makers and stakeholders for both the management of and development of future plans for coastal environments and for reducing exposure risk to coastal erosion

late pleistocene and holocene fluvial coastal evolution of an uplifting area the tronto river central eastern italy abstract the piedmont area of the river tronto italy is characterised by pleistocene and holocene terraces at progressive elevations a s l after the formation of wide unpaired meander terraces during the early holocene the river created a 20 m deep gorge into bedrock in its inner part in mid valley the thalweg progressively enlarges and the late pleistocene and holocene terraces converge downstream a wide alluvial plain was formed during braid plain aggradation from ca 4 3 bp to the end of the 19th century associated with slope erosion activated by human activities since the end of the 20th century two series of artificial levees were created in order to prevent floods due to the reduced dimensions of the artificial river bed floods still affect large parts of the plain after extreme events in the coastal sector during the early holocene a large bay extended approximately 3 km inland from the present day coastline a barrier beach evolved during the bronze iron age and until the middle ages the river mouth entered a large lagoon progradation occurred from then until the beginning of the 20th century when a delta extended up to 500 m seaward during the 20th century following the creation of the artificial levees and quarrying the beach underwent coastal erosion and had to be protected by breakwater reefs the anthropogenic modifications and their effects are among the main factors in the holocene evolution of the landscape

updrift river mouth migration on cuspate deltas two examples from the coast of tuscany italy the configuration of the arno and ombrone deltas italy is evaluated the terminal courses of the rivers forming these deltas face the dominant wave orthogonal this configuration came about during rapid delta progradation as a consequence of increased river sediment input due to widespread deforestation within the catchment area a prevailing phenomenon from the early middle ages to the xviii century the rivers attained and maintained their directions as the result of the increased accretion rate on the less exposed downdrift side of the delta on the more exposed updrift side delta growth caused the shoreline to gradually rotate so that it directly faced the waves approaching the coast here due to the lower refraction wave energy per shore unit increased whilst accretion rate decreased this rotation of the shoreline induced longshore inversion on the updrift side whereas today cusp erosion is restoring the original drift direction