the shape and internal structure of the moon from the clementine mission global topographic and gravitational field models derived from data collected by the clementine spacecraft reveal a new picture of the shape and internal structure of the moon the moon exhibits a 16 kilometer range of elevation with the greatest topographic excursions occurring on the far side lunar highlands are in a state of near isostatic compensation whereas impact basins display a wide range of compensation states that do not correlate simply with basin size or age a global crustal thickness map reveals crustal thinning under all resolvable lunar basins the results indicate that the structure and thermal history of the moon are more complex than was previously believed

venus topography a harmonic analysis a model of venusian global topography has been obtained by fitting an eighteenth degree harmonic series to pioneer venus orbiter radar altimeter data the mean radius is 6051 45 0 04 km the corresponding mean density is 5244 8 0 5 kg m 3 the center of figure is displaced from the center of mass by 0 339 0 088 km towards 6 6 10 1 n 148 8 7 7 e the figure of venus is distinctly triaxial but the orientation and magnitudes of the principal topographic axes correlate rather poorly with the gravitational principal axes however the higher degree harmonics of topography and gravity are significantly correlated the topographic variance spectrum of venus is very similar in form to those of the moon mars and especially earth we suggest that this spectral similarity simply reflects a statistical balance between constructional and degradational geomorphic processes venus and earth are particularly similar and differ from the moon and mars in that the larger bodies both exhibit a significant low degree deficit relative to the extrapolated trend of the higher harmonics

origin of late archean granite geochemical evidence from the vermilion granitic complex of northern minnesota the 2 700 ma vermilion granitic complex of northern minnesota is a granite migmatite terrane composed of supracrustal metasedimentary rocks mafic rocks tonalitic and granodioritic plutonic rocks and granite the metasedimentary rocks are predominantly graywacke which has been regionally metamorphosed to garnet sillimanite muscovite bearing biotite schist and has locally undergone anatexis the mafic rocks form early phases within the complex and are of two types 1 basaltic amphibolite and 2 monzodiorite and essexite rich in large ion lithophile elements lile the members of the early plutonic suite form small bodies that intrude the metasedimentary rocks and mafic rocks producing an early migmatite the granite is of two distinct varieties 1 white garnet muscovite biotite leucogranite s type chappell and white 1974 and 2 grayish pink biotite magnetite lac la croix granite i type the leucogranite occurs in the early migmatite and in paragneissic portions of the complex whereas the lac la croix granite is a late stage intrusive phase that invades the early migmatite and metasediment producing a late migmatite and forms a batholith this study focuses specifically on the origin of granite in the vermilion granitic complex chemical mass balance calculations suggest that the s type two mica leucogranite had a metagraywacke source and that the i type lac la croix granite formed via partial fusion of calc alkaline tonalitic material which may have been similar to rocks of the early plutonic suite this model is satisfactory for petrogenesis of similar late archean post kinematic granites throughout the canadian shield

gravity field determination and characteristics retrospective and prospective gravimetry has had a long history using pendulums torsion balances and static spring gravimeters relative accuracy adequate for many geophysical problems was already attained by 1900 but it took another half century to build readily portable gravimeters calibration and datum definition remained problems until the 1970s when free fall absolute gravimeters were developed that now have a precision of 10 3 mgal the problems of geographic inaccessibility and field party costs notably in areas of greatest tectonic interest are now being overcome by airborne gravimetry that has already achieved accuracies of 1 3 mgal with resolutions of 10 to 20 km satellite techniques are the best way to determine the long wavelength variations of the gravity field the resolution of the models has steadily improved with the number of satellites and the precision of the observations the best current model includes tracking data from more than 30 satellites satellite altimetry and surface gravimetry and has a resolution of about 290 km harmonic degree 70 with the most recent improvements coming from doppler orbitography and radiopositioning integrated by satellite doris tracking of the spot 2 satellite and satellite laser ranging slr doris and global positioning system gps tracking of the topex poseidon satellite meanwhile radar altimetry has become the dominant technique to infer the marine geoid with a resolution of tens of kilometers or shorter similarly the gravity fields of the moon venus and mars have been determined to harmonic degrees 70 75 and 50 respectively although tracking limitations result in variations of spatial resolution modeling earth s gravity field from the abundance of precise data has become an increasingly complex task with which the development of computer capacity has kept pace contemporary solutions now entail about 10 000 parameters half of them for effects other than the fixed gravity field of earth temporal variations arising from tides have long been well modeled and nontidal changes are now being identified the improvement in gravitational models engendered corresponding advances in geophysical interpretation isostatic models were refined and expanded to account for regional thermal and tectonic histories interpretation of the long wavelength gravity field determined by satellite techniques has been mainly in terms of plate tectonics as a manifestation of mantle convection gravity has been significant in inferring that there must be a large increase in viscosity with depth most strongly from the apparent slow sinking of subducted slabs the prospects for increasing accuracy and resolution in the determination of earth s gravity field rest primarily with the development of new measurement systems airborne gravimetry is taking promising new steps using gps but significant global model improvement awaits a dedicated satellite gravimetry system and future satellite altimeter missions will do more for ocean dynamics studies than geoid improvement advances in interpretation will occur through the development of other data such as seismic tomography and larger scale computer modeling of tectonics and convection

high resolution gravity model of venus the anomalous gravity field of venus shows high correlation with surface features revealed by radar we extract gravity models from the doppler tracking data from the pioneer venus orbiter pvo by means of a two step process in the first step we solve the nonlinear spacecraft state estimation problem using a kalman filter smoother the kalman filter has been evaluated through simulations this evaluation and some unusual features of the filter are discussed in the second step we perform a geophysical inversion using a linear bayesian estimator to allow an unbiased comparison between gravity and topography we use a simulation technique to smooth and distort the radar topographic data so as to yield maps having the same characteristics as our gravity maps the maps presented cover 2 3 of the surface of venus and display the strong topography gravity correlation previously reported the topography gravity scatter plots show two distinct trends

geochronology of orthogneiss adjacent to the archean lake of the woods greenstone belt northwestern ontario a possible basement complex deformed and recrystallized amphibolite facies trondhjemitic to granodioritic orthogneiss along the north margin of the archean lake of the woods greenstone belt has an rb sr isochron age of 2950 150 ma and an initial 87sr 86sr ratio of 0 7028 0 0014 preserved primary textures and complex internal intrusive relationships document the original plutonic nature of the orthogneiss based on isotopic age and degree of deformation and recrystallization the orthogneiss is interpreted to be basement to the adjacent metavolcanic sequence of the greenstone belt the contact between the orthogneiss and greenstone belt is the locus of deformation but may be an unconformity it is also the boundary between the english river subprovince on the north and the wabigoon subprovince on the south similar orthogneiss ranging in age from 2800 to 3800 ma is widespread in the canadian shield it is basement to the 2650 2750 ma archean volcanism at least in some areas but is not necessarily basement to the older 2800

the structural geometry and geological history of archean rocks at kenora north western ontario a proposed type area for the kenoran orogeny the kenora area at the south margin of the english river subprovince consists of polydeformed gneisses intruded by granitoid plutons some of which are also deformed the gneisses are mainly tona

venus gravity a harmonic analysis an improved model of venusian global gravity has been obtained by fitting an eighteenth degree and eighteenth order spherical harmonic series to 78 orbital arcs of high altitude 950 1350 km at periapsis tracking data and 351 orbital arcs of lower altitude 150 200 km at periapsis data from the pioneer venus orbiter pvo compared to a recently published tenth degree model mottinger et al 1985 which is based on the 78 high altitude arcs only the current model provides a significant improvement in resolution and fidelity as a measure of this improvement we note that for the low altitude arcs alone the variance of the residuals for the present model is reduced to 19 of the data variance compared to 51 for the tenth degree model venus differs significantly from the earth in that it exhibits a significant correlation between long wavelength topography and gravity the gravity topography spectral admittances are inconsistent with either airy or pratt isostasy but they are consistent with dynamic support by mantle convection

analyzing the variability of sediment yield a case study from paired watersheds in the upper blue nile basin ethiopia abstract improved knowledge of watershed scale spatial and temporal variability of sediment yields sy is needed to design erosion control strategies particularly in the most severely eroded areas the present study was conducted to provide this knowledge for the humid tropical highlands of ethiopia using the akusity and kasiry paired watersheds in the guder portion of the upper blue nile basin discharge and suspended sediment concentration data were monitored during the rainy season of 2014 and 2015 using automatic flow stage sensors manual staff gauges and a depth integrated sediment sampler the sy was calculated using empirical discharge sediment curves for different parts of each rainy season the measured mean daily sediment concentration differed greatly between years and watersheds 0 51 g l 1 in 2014 and 0 92 g l 1 in 2015 for kasiry and 1 04 g l 1 in 2014 and 2 20 g l 1 in 2015 for akusity sediment concentrations at both sites decreased as the rainy season progressed regardless of the rainfall pattern owing to depletion of the sediment supply and limited transport capacity of the flows caused by increased vegetation cover rainy season sys for kasiry were 7 6 t ha 1 in 2014 and 27 2 t ha 1 in 2015 while in akusity sys were 25 7 t ha 1 in 2014 and 71 2 t ha 1 in 2015 the much larger values in 2015 can be partly explained by increased rainfall and larger peak flow events the magnitude and timing of peak flow events are major determinants of the amount and variability of sys thus site specific assessment of such events is crucial to reveal sy dynamics of small watersheds in tropical highland environments

the late antiquity environmental crisis in emilia region po river plain northern italy geoarchaeological evidence and paleoclimatic considerations abstract for about four decades in italy local scientific literature has occasionally dealt with fluvial avulsions suggesting they should be considered as genetically linked to a peculiar climatic worsening that occurred in the late 6th century ad the so called paul the deacon deluge research performed by the soprintendenza per i beni archeologici dell emilia romagna over the last few years has allowed better definition of the timing of a more articulated alluvial history mainly concerning the roman imperial age and late antiquity 1st 6th century ad the main stratigraphic details of fourteen selected archaeological excavation sites eleven recently surveyed and three reviewed from the literature performed in the cities of modena bologna and related surroundings have been summarized eleven 14 c dates ranging between the years 130 ad and 810 ad allowed us to chronologically delimit a first framework for the riverbed network behaviour during ancient times in the central part of the region the alluvial process appeared to be continuous throughout the time span examined the fan trench was the most sensitive reach of the river system it started to aggrade during the 4th century ad during the 5th century ad and probably after the end of the 6th century ad a number of avulsions occurred this indicates that the fluvial system was in a metastable equilibrium whose behavioural threshold was finally overcome hence the importance of the supposed year 589 ad crisis the deluge appears to be less than previously supposed the riverbed aggradation became evident immediately after the roman empire s economic and demographic crisis of the 3rd century ad and it was probably due to the loss of the land preservation systems in the mountain catchment areas the long duration of the aggradation phase suggests that more than one human settlement phase in the minor catchment areas and or a minor climatic worsening pulse probably occurred during the 5th century ad the starting of the aggradation also coincided with the end of the petit maclu 1 high level phase of the european lakes notwithstanding this the climate s role as a forcing co factor can still be hard to evaluate positively due to the lack of local proxy data

venus gravity anomalies and their correlations with topography this report provides a summary of the high resolution gravity data obtained from the pioneer venus orbiter radio tracking data gravity maps covering a 70 latitude band through 360 of longitude are displayed as line of sight and vertical gravity topography converted to gravity and bouguer gravity maps are also shown in both systems topography to gravity ratios are made over several regions of the planet there are markedly different ratios for the aphrodite area as compared to the beta and atla areas

geomorphic connectivity within abandoned small catchments stolowe mts sw poland abstract studying 5 small catchments 0 6 2 7 km2 located in the central part of the stolowe mountains sw poland which are partly or totally abandoned has revealed the substantial changes of connectivity within the catchments field investigation geomorphic mapping morphometric analyses and gis based analyses of historical data show that slope channel coupling is much less efficient than in the past mainly due to the decrease of unpaved road network especially roads linked directly with streams also land use change with considerable loss of arable land does not support erosion from slopes the general direction of geomorphic change due to depopulation and lack of maintenance of anthropogenic features tends towards higher stability and lower efficiency of morphological processes connected with a sustained decrease in slope channel coupling this tendency is evidenced by relict landscape features e g road gullies abandoned roads formed in the period of more intensive land use for which higher dynamics of the morphogenetic system may be inferred the evidence of contemporary erosion and mineral material transport is very local and spatially limited to a few roads which are still in use sediment transfer is additionally slowed down by the presence of numerous anthropogenic barriers within slope and valley floor domains even though their total impact may seem only local and negligible at the catchment scale their contribution to increase the diversity of morphological processes is significant especially the neglect of hydrotechnical constructions enhances trapping of material within the catchments

an improved gravity model for mars goddard mars model 1 doppler tracking data of three orbiting spacecraft have been reanalyzed to develop a new gravitational field model for the planet mars goddard mars model 1 gmm 1 this model employs nearly all available data consisting of approximately 1100 days of s band tracking data collected by nasa s deep space network from the mariner 9 and viking 1 and viking 2 spacecraft in seven different orbits between 1971 and 1979 gmm 1 is complete to spherical harmonic degree and order 50 which corresponds to a half wavelength spatial resolution of 200 300 km where the data permit gmm 1 represents satellite orbits with considerably better accuracy than previous mars gravity models and shows greater resolution of identifiable geological structures the notable improvement in gmm 1 over previous models is a consequence of several factors improved computational capabilities the use of optimum weighting and least squares collocation solution techniques which stabilized the behavior of the solution at high degree and order and the use of longer satellite arcs than employed in previous solutions that were made possible by improved force and measurement models the inclusion of x band tracking data from the 379 km altitude near polar orbiting mars observer spacecraft should provide a significant improvement over gmm 1 particularly at high latitudes where current data poorly resolve the gravitational signature of the planet

quantitative analysis of factors controlling sediment yield in mountainous watersheds abstract sediment and turbidity are primary causes of impaired river ecosystems remedial action for these impairments requires the identification of their sources and controlling factors this paper examines the combined effects of watershed complexity in terms of land use and physiography on the specific sediment yield of the upper du river watershed 8973 km2 in china the land use composition land use pattern morphometric variables and soil properties of the watershed were calculated at the subwatershed scale and considered to be potentially influential factors because these watershed characteristics are highly codependent a partial least squares regression plsr was used to elucidate the linkages between the specific sediment yield and metrics composed of 19 selected watershed characteristics the first order factors were identified by calculating the variable importance for the projection vip the results revealed that the land use composition and land use pattern exerted the largest effects on the specific sediment yield and explained 65 2 of the variation in the specific sediment yield a set of physiographic indices was also found to have a large effect on the specific sediment yield and explained 17 7 of the observed variation in the specific sediment yield the following are the dominant first order factors of the specific sediment yield at the subwatershed scale the areal percentages of agriculture and forest patch density value of the shannon s diversity index contagion value of the hypsometric integral and saturated soil hydraulic conductivity the watershed size exerted a substantial effect on the sediment delivery ratio sdr the vip values also suggested that the shannon s diversity index contagion and hypsometric integral are important factors in the sdr with a readily available digital spatial database and rapid developments in geographic information system gis technology this practical and simple plsr approach could be applied to a variety of watersheds

venus global gravity and topography a new gravity field determination that has been produced combines both the pioneer venus orbiter pvo and the magellan doppler radio data comparisons between this estimate a spherical harmonic model of degree and order 21 and previous models show that significant improvements have been made results are displayed as gravity contours overlaying a topographic map we also calculate a new spherical harmonic model of topography based on magellan altimetry with pvo altimetry included where gaps exist in the magellan data this model is also of degree and order 21 so in conjunction with the gravity model bouguer and isostatic anomaly maps can be produced these results are very consistent with previous results but reveal more spatial resolution in the higher latitudes

long term rotation and mantle dynamics of the earth mars and venus in response to internal and surface tectonic processes the terrestrial planets have the ability to displace the axis of rotation with respect to the mantle this behavior is quantified by means of a nondimensional number defined here as the rotational number ro that allows classification of the planets into two categories the first containing mars and the earth where true polar wander is a feasible mechanism and the second to which venus belongs where rotation equilibrium is attained by means of mega wobbles driven by internal mass anomalies the number ro is related to the timescale characterizing the readjustment of the equatorial bulge during long term polar motion and to the length of the sidereal day if these two timescales are well separated the planet experiences true polar wander nonlinear liouville equations for stratified viscoelastic bodies with linear maxwell rheology are solved in order to assess the relevance of surface and mantle processes in driving long term rotation instabilities in the terrestrial planets the amount of true polar wander estimated for the earth and mars is reproduced correctly by our modeling with mantle viscosities and lithospheric thickness consistent with other studies the major difference between the earth and mars is the driving mechanism subduction for the earth and lithospheric loading for mars when mantle viscosities similar to those of the earth are considered for venus the most updated estimate for the offset of about 0 5 between the rotation axis and the axis of maximum inertia is well reproduced during the mega wobbles induced by internal mass redistribution we show that the degree 2 topography of these three planets can be affected by their rotation which is responsible for the dominance of the sectorial component on the earth and mars and for the zonal component on venus

building reliable local models of the venus gravity field from the cycles 5 and 6 of the magellan los gravity data we present a new way to build reliable local models of the venus gravity field from the cycles 5 and 6 of the magellan probe by directly considering the doppler residual profiles instead of the derived residual acceleration profiles we give an example over a test area

internal differentiation of rare element pegmatites effects of boron phosphorus and fluorine lithium rich rare element pegmatites are characterized by high concentrations of b p and f the interactions of these components with h2o and rare alkalis lower liquidas and solidus temperatures enhance silicate liquid h2o miscibility and control partitioning and concentration of group i elements and higher field strength cations boron f and perhaps p may form peralkaline na and li species that promote early saturation in mica quartz activities of f p and especially b are largely unbuffered throughout crystallization concentration of these components through fractional crystallization involving muscovite generates a peralkaline na aluminosilicate rich melt or vapor from which albitites rich in tourmaline phosphates f rich micas beryl zircon and nb ta sn oxides crystallize phase equilibrium experiments with peraluminous b p f rich rhyolite obsidian macusanite simulate many features of rare element pegmatites especially at h2o undersaturated conditions

are strongly peraluminous magmas derived from pelitic sedimentary sources igneous compositions that require the presence of a phase more aluminous than biotite are here designated as strongly peraluminous ps such compositions are common but subordinate in felsic rocks and exceedingly rare in more mafic rocks the term s type has been applied to many igneous rocks based largely or even solely upon their ps compositions neglecting or placing less emphasis on other criteria for sedimentary parentage in chappell and white s i and s type classification system the s type designation was in fact initially restricted to granites which were thought to have been derived from a chemically mature strongly weathered pelitic shaly source application of chappell s and white s criteria together with others based upon isotopic and phase equilibria considerations leads to the following conclusions about ps igneous rocks worldwide 1 very few ps rocks are derived entirely from pelitic sources 2 a majority are derived largely from intermediate to felsic crustal sources including

erosion in mediterranean mountain landscapes during the last millennium a quantitative approach based on lake sediment sequences iberian range spain abstract land degradation and soil erosion are key environmental problems in mediterranean mountains characterized by both a long history of human occupation and strong seasonality of hydrological regimes experimental monitored catchments have identified main controlling factors on erosion dynamics but because of the short time span of the instrumental measurements they do not integrate the complete temporal and spatial variability of these environments to obtain some long term series of mediterranean landscape evolution we propose a novel strategy based on multi proxy analyses of lake sediments aimed to quantify sediment delivery and erosion dynamics karstic lakes in the iberian range central spain provide an opportunity to reconstruct the depositional evolution of the watersheds and to evaluate the response to both the variable anthropogenic impacts and climate forcings during the last 1000 years the most significant periods of increased sediment delivery 26 483 t km yr 1 in the iberian range sites took place during the 15th 16th and 18th 19th centuries as a result of large land use changes and land clearing positive synergies between increasing human population and more humid periods led to peaks in sediment deliver during some phases of the little ice age recent changes associated with the rural exodus and land abandonment during mid 20th century are more clearly shown in larger watersheds by decreased sediment delivery to the lakes due to the re vegetation of the landscape 6 200 t km yr 1 this new integrated approach based on long term lake sequences provides a longer perspective of erosion processes in mediterranean watersheds and validates the main factors identified in monitoring surveys land cover and surface formations erodibility in both settings lakes and experimental catchments most sediment delivery occurs during flooding events measured and reconstructed values show comparable large ranges underlying the punctuated nature of sediment dynamics in mediterranean landscapes at decadal and centennial scales

sensitivity of west and central european river systems to environmental changes during the holocene a review abstract sediment deposition in floodplains is an essential part of the sediment dynamics of a catchment these sediment dynamics can vary largely on a holocene time scale under the influence of driving forces such as land use and climatic variations in this paper we review the holocene floodplain sediment deposition history of rivers in west and central europe with special attention to the influence of climate and land use variability during the early holocene preboreal to atlantic period most floodplains were rather stable with limited floodplain aggradation after this initial phase of relative stability sedimentation rates increase during the middle and late holocene with often the most important deposition phase during the last 1000 to 2000 a the start of the increase in sedimentation varies spatially with an earlier start in the west france germany then in the east poland belarus ukraine while there are also local differences between regions which are settled early e g loess regions compared to later settled regions the sedimentation history of most floodplains can be linked to the local land use history while influence of climatic variations on floodplain aggradation is often reported to be of minor importance processes related to bedload are often reported to be more influenced by climatic events relationships between the driving forces and the sediment history are mainly based on synchronicity and there is seldom proof for a direct causal relationship future research should focus on a system based approach integrating the floodplain deposition in the entire sediment dynamics which includes also erosion colluvial deposition and export main research questions that need further attention include integration of system based concepts like landscape connectivity and buffering effects and also the assessment of the individual contribution of land use changes and climatologic variations on the sediment dynamics detailed sediment budget studies combined with modeling studies can make an important contribution to the understanding of floodplain sediment dynamics

gravitational and topographic isotropy of the earth moon mars and venus the internal structures and surface shapes of the terrestrial planets are expected to be dominantiy isotropic we attempt to test this hypothesis by developing a criterion for recognizing statistical isotropy of spherical scalar fields and applying that test to the nonhydrostatic components of the gravitational and topographic fields of the earth moon mars and venus the criterion for topographic or geoidal surfaces is that the directional variance should be independent of azimuth that is the mean square east west slopes should be equal to the mean square north south slopes all four planets generally pass the criteria with a few minor exceptions most of the exceptions are likely to be artifacts of the current generation of planetary gravity and topography models rather than real features of the planets of the several broad band departures from isotropy which we found the only one likely to be real is the tendency for the earth s gravity and topography to have only 80 as much variance in a north south direction as in an east west direction

the response of soil erosion and sediment export to land use change in four areas of europe the importance of landscape pattern the response of erosion and sediment export to past land use change has been studied in four agricultural areas of europe three of these areas were subject to land abandonment or de intensification and one to intensification of land use practices erosion and sediment yield were modeled using the watem sedem model which combines the rusle equation with a sediment routing algorithm spatial relationships between the rusle c factor i e land use and other erosion and sediment export determining factors slope soil erodibility and distance to rivers were investigated as these account for non linearity in the response of erosion and sediment export to land use change erosion and sediment export have decreased enormously in the de intensified areas but slightly increased in the intensively cultivated area the spatial pattern of land use change in relation to other erosion and sediment export determining factors appears to have a large impact on the response of soil erosion and sediment export to land use change that the drivers of abandonment of arable land and erosion coincide indicates that de intensification leads to a more favourable landscape pattern with respect to reduction of erosion and sediment export this mechanism applies not only within the study areas but also among the european study areas where the process of intensification of some areas and de intensification of others might result in an overall decrease of erosion and sediment yield through time c 2007 elsevier b v all rights reserved

a high resolution gravity model for venus gvm 1 a spherical harmonic model of the gravitational field of venus complete to degree and order 50 has been developed using the s band doppler tracking data of the pioneer venus orbiter pvo collected between 1979 and 1982 the short wavelengths of this model could only be resolved near the pvo periapse location 14 n latitude therefore a priori constraints were applied to the model to bias poorly observed coefficients towards zero the resulting model has a half wavelength resolution of 400 km near the pvo periapse location but the resolution degrades to greater than 1000 km near the poles this gravity model correlates well with a degree 50 spherical harmonic expansion of the venus topography derived from a combination of magellan and pvo data new tracking data from magellan s gravity mission should provide some improvement to this model although a complete model of the venusian gravity field will depend on tracking of magellan after the circularization of it s orbit using aerobraking

sediment variability in a small catchment of the polish western carpathians during transition from centrally planned to free market economics abstract the purpose of this study was to analyse suspended sediment ss transport in a small catchment 13 km2 located in the polish carpathians affected by various forms of human activity in the period 1970 2017 this period covers two stages of socioeconomic development with contrasting forms of human activity the centrally planned economy related to the communist system up to 1989 and the period of a free market economy following analysis indicates increases in grassland and forest areas of the analysed catchment of 90 and 10 respectively and a decrease in cultivated land of 82 changes in land use and land cover lulc have reduced soil erosion by 74 as calculated using the revised universal soil loss equation at the same time population number of buildings and construction works along the stream increased and number of cart roads decreased hydrometeorological data as well as suspended sediment load ssl have not shown a statistically significant trend despite changes in forms of human activity in 1970 2017 in the first three decades of the analysed period 1970 1979 1980 1989 and 1990 1999 ssl gradually decreased in 2010 2017 suspended sediment load was the highest in the whole investigated period principal component analysis pca confirmed that it was a result of the appearance of new sediment sources associated with intensification of landslides and new forms of human activity such as construction works the imposition on these factors resulted in an increase in ssl and masked the effects of rainfall lulc change in the catchment analysis shows that proper recognition of changes in sediment sources in the catchment is fundamental for correct interpretation of long term sediment transport in the streams

venus gravity a high resolution map the doppler data from the radio tracking of the pioneer venus orbiter pv0 have been used in a two stage analysis to develop a high resolution map of the gravitational potential of venus represented by a central mass and a surface mass density the two stage procedure invokes a kalman filter smoother to determine the orbit of the spacecraft and a stabilized linear inverter to estimate the surface mass density the resultant gravity map is highly correlated with the topographic map derived from the pv0 radar altimeter data however the magnitudes of the gravity variations are smaller than would be expected if the topography were uncompensated indicating that at least partial compensation has taken place

river channel response to short term human induced change in landscape connectivity in andean ecosystems the drainage basin of the deleg river 88 km 2 located in the southern ecuadorian andes was studied to assess the geomorphic and hydrologic response of a fluvial system to human induced environmental change in its contributing area historical data on land use channel morphology and sedimentology were collected based on a spatial analysis of aerial photographs 1963 1995 and a field survey 2002 analysis of channel cross sectional profiles and sedimentological data revealed a major change in morphology and sedimentology of the deleg river during the past four decades i the active river channel narrowed by over 45 ii the riverbed incised on average by over 1 0 m and iii the median grain size of the bed surface decreased from 13 2 cm to 4 7 cm the spatial pattern of land cover within the deleg catchment also changed considerably highly degraded agricultural land in the low lying areas was abandoned and partially afforested for timber and wood production whereas secondary upland forest was increasingly cleared for expansion of cropland and pastures notwithstanding large changes in the spatial organization of land use within the catchment the overall land use did not change significantly during the past four decades this suggests that the response of the deleg river to land use change not only depends on the overall land use change but also on the spatial pattern of land use cover change within the catchment although forestation and regeneration of bare gully slopes and floors throughout the catchment only represented a minor part of the total land use change these land use cover changes had a major impact on the hydrological and sediment connectivity in the landscape c 2005 elsevier b v all rights reserved

contrasting geochemistry of two pegmatite fields in manitoba products of juvenile aphebian crust and polycyclic archean evolution abstract the geochemistry of the proterozoic wekusko lake pegmatite field in the flin flon snow lake greenstone belt of the churchill province is remarkably primitive compared with the kenoran cat lake winnipeg river pegmatite field in the superior province and its analogs elsewhere in archean cratons comparable pegmatite types at wekusko lake are slightly depleted in li considerably impoverished in rb cs be p and f and poor in sn nb and ta relative to those in the cat lake winnipeg river terrane eliminating differences in plutonic evolution level of erosion and to a degree in the effectiveness of volatile components the principal reason for the difference in the geochemical signature of the pegmatite fields is the nature of the crust and its evolution in the two regions the proterozoic greenstone belt resulted from a single cycle metamorphism and melting of juvenile volcanic sedimentary sequences derived from depleted mantle nd 5 with minimal if any contribution from pre existing crust consequently the source rocks of the granite pegmatite evolution were highly primitive in contrast the host terrane of the kenoran pegmatite field contains pre 2800 ma crustal components of several generations and a 2780 ma tonalitic basement the greenstone belt lithologies and associated batholithic granitoids are derived in part from a heterogeneous near chondritic to ree and lile enriched mantle nd 2 in part from the pre existing crust this polycyclic crustal evolution generated highly enriched protoliths from which the fertile granites and their pegmatite aureoles evolved the low level of geochemical evolution in the wekusko lake field is not necessarily characteristic of other proterozoic rare element pegmatites in the svecofennian terrane of sweden and finland developed in part over archean basement and with considerable archean components in its lithologies the fertile granites and their pegmatite aureoles reached the same fractionation levels as in the kenoran provinces

mass anomaly structure of the earth gravitational interaction is the weakest among the four known forces in the universe the particular gravity equipotential field that coincides with sea level is called the geoid and satellite data have revealed anomalies in its pattern that are puzzling to explain dynamic topography solutions have offered the preferred explanation for the past 15 years but problems remain an alternative explanation presented here contends that very large mass anomalies lie deep in the earth presumably produced by topography at the coremantle boundary cmb and only much smaller mass anomalies occur at shallower depths the principal distinction is whether one is willing to accept the possibility that processes within the earth s core may generate the cmb topography an analysis of the south american regional geoid high spherical harmonic degrees 2 10 indicates that only mass anomalies shallower than 1200 km are its cause this single positive source is contrary to dynamic topography solutions that would generate negative deflections of both the surface and the cmb in response to the positive subducted mass for the earth s fourth greatest geoid high our alternate explanation is tested utilizing a set of 9274 subduction 5 cube slab bloblet center points developed from reconstructed plate history that provide estimates of the locations of material subducted into the earth s mantle two global mass solutions are offered utilizing 1 only those bloblets in the outer 800 km and 2 only those bloblets in the outer 1400 km four point masses at 3000 km depth to simulate cmb topography produced by processes within the core unrelated to mantle dynamic topography complete the two mass models both models show reasonable agreement with patterns and magnitudes of the regional geoid and its component degree parts the model cmb mass anomalies are only a factor of 3 greater than those initially estimated by gravity to geoid ratios from observed values at geoid anomaly center locations difficulties with the dynamic topography solutions matters of the density of the subducted material the proper hydrostatic flattening value to use for analyses and possible causes for the cmb topography are discussed the subduction mass models are also used to estimate the magnitude of the driving force for plate tectonics 2 78 1020 to 3 23 1021 n approximately equivalent to 7 0 1012 to 8 1 1013 n m 1 these force values are comparable to published slab force estimates based on thermal considerations

venus topography and kilometer scale slopes during the first 8 months of the magellan mission the radar altimeter has made some three million measurements of the surface of venus covering the latitude range from 85 n to 80 s methods involving range correlation doppler filtering multi burst summation and range migration are used to focus the observations and to achieve high surface resolution results are presented as maps of the global distribution of topography meter scale roughness and power reflection coefficient the results are similar to those reported in previous experiments surface heights exhibit a unimodal distribution with more than 80 of the surface lying within 1 km of the 6051 84 km mean radius but the higher resolution of the magellan altimeter has disclosed several surprisingly steep features e g the southwest face of the maxwell montes the southern face of the danu montes and the chasmata to the east of thetis regio where average kilometer scale slopes of greater than 30 are not uncommon this conclusion is corroborated by close inspection of synthetic aperture radar imagery

terrestrial and planetary gravity fields the determination of the gravity field together with knowledge of the surface topography provides one of the primary means of inferring the density structure and dynamics of planetary interiors phillips and lambeck 1980 hager 1985 after removing the topographic gravity signal the distribution of internal density anomalies caused by thermal or compositional differences can be studied gravity field models can also be used to study the compensation of surface topography which can provide information on the mechanical properties and state of stress of the lithosphere the determination of these models has been accomplished using a wide variety of different measurement types and solution techniques the near earth measurement types can be divided into satellite tracking measurements surface gravity measurements and satellite altimeter measurements in both near earth and interplanetary contexts tracking data are used to measure gravitational perturbations affecting satellites with the accuracy and spatial temporal distribution of the data being the most important factors in the resulting field accuracy and resolution surface gravity data provide a more direct measurement of the gravity field but acquiring data uniformly over the earth has always been difficult satellite altimetry provides precise measurements of the marine gravity field provided that satellite orbit errors and non geoidal sea surface height variations can be adequately modeled comprehensive gravity field solutions must incorporate these disparate data types in order to estimate mathematical parameters describing the gravity field such as spherical harmonic coefficients the proper combination of these data along with the desire to acquire an accurate representation of the model errors require that complex procedures be developed for computing these solutions

a 70th degree lunar gravity model glgm 2 from clementine and other tracking data a spherical harmonic model of the lunar gravity field complete to degree and order 70 has been developed from s band doppler tracking data from the clementine mission as well as historical tracking data from lunar orbiters 1 5 and the apollo 15 and 16 subsatellites the model combines 361 000 doppler observations from clementine with 347 000 historical observations the historical data consist of mostly 60 s doppler with a noise of 0 25 to several mm s the clementine data consist of mostly 10 s doppler data with a data noise of 0 25 mm s for the observations from the deep space network and 2 5 mm s for the data from a naval tracking station at pomonkey maryland observations provided clementine provide the strongest satellite constraint on the moon s low degree field in contrast the historical data collected by spacecraft that had lower periapsis altitudes provide distributed regions of high resolution coverage within 29 of the nearside lunar equator to obtain the solution for a high degree field in the absence of a uniform distribution of observations we applied an a priori power law constraint of the form 15 10 5 l2 which had the effect of limiting the gravitational power and noise at short wavelengths coefficients through degree and order 18 are not significantly affected by the constraint and so the model permits geophysical analysis of effects of the major basins at degrees 10 12 the glgm 2 model confirms major features of the lunar gravity field shown in previous gravitational field models but also reveals significantly more detail particularly at intermediate wavelengths 103 km free air gravity anomaly maps derived from the new model show the nearside and farside highlands to be gravitationally smooth reflecting a state of isostatic compensation mascon basins including imbrium serenitatis crisium smythii and humorum are denoted by gravity highs first recognized from lunar orbiter tracking all of the major mascons are bounded by annuli of negative anomalies representing significant subsurface mass deficiencies mare orientale appears as a minor mascon surrounded by a horseshoe shaped gravity low centered on the inner and outer rook rings that is evidence of significant subsurface structural heterogeneity although direct tracking is not available over a significant part of the lunar farside glgm 2 resolves negative anomalies that correlate with many farside basins including south pole aitken hertzsprung korolev moscoviense tsiolkovsky and freundlich sharonov

rainfall runoff and suspended sediment delivery relationships in a small agricultural watershed of the three gorges area china abstract following construction of the three gorges dam many farmers resettled in surrounding mountain areas and cultivated marginal lands which are mostly on steep slopes with soil of poor structure in general high soil loss rates occur during intense storms therefore soil erosion is a major environmental problem in the three gorges area tga of china understanding and quantifying sediment load is important for sustainable agriculture and the environment in this region this paper analyzes the relationships between rainfall runoff and sediment transport in the wangjiaqiao watershed strong seasonal and monthly variability in sediment load was found sediment was strongly transported during summer months a period when frequent flood events of high magnitude and intensity occurred analysis of the relationships between precipitation discharge and sediment transport at an individual event scale showed significant correlations between total precipitation peak discharge total water yield maximum 30 min rainfall intensity and sediment related variables stepwise multiple regression analysis revealed that rainfall amount is the major cause of runoff while events producing a large discharge in a short time play an important role in inducing severe soil erosion during 40 flood events three different types of hysteretic loops were observed clockwise 28 events 70 figure eight 5 events 12 5 and complex 7 events 17 5 the results of this study confirm the complex and heterogeneous nature of sediment response in the wangjiaqiao watershed

the impact of land use and climate change on late holocene and future suspended sediment yield of the meuse catchment abstract in this study we investigate the relative importance of changes in land use and climate on suspended sediment yield sy on millennial timescales in the meuse basin we use a spatially distributed soil erosion and sediment delivery model watem sedem to simulate sy in three time periods 4000 3000 bp minimal anthropogenic influence 1000 2000 ad includes land use and climate change and the 21st century changes in climate are based on climate model output ecbilt clio vecode for the 21st century the model is forced according to two emission scenarios of the intergovernmental panel on climate change ipcc namely the sres scenarios a2 and b1 these scenarios lie towards the higher and lower end of the full ipcc scenario range respectively for 4000 3000 bp the basin is assumed to be almost fully forested for 1000 2000 ad land use is reconstructed using corine data historical sources and land use modelling and for the 21st century land use is based on the european land use change project eururalis whilst rainfall erosivity increases by only 3 between 4000 3000 bp and 1000 2000 ad sy increases from ca 92 000 mg a 1 to ca 306 000 mg a 1 this model prediction is in agreement with the limited regional multi proxy data available our simulations show that almost all of this increase is due to the conversion of forest to agricultural land over the period 1000 1900 ad sy shows a significant increasing trend with a peak of ca 388 000 mg a 1 in the 19th century due to continuing deforestation in the 20th century reforestation and rapid urbanisation result in a decrease to ca 281 000 mg a 1 sensitivity analyses show that although land use change acts as the primary control on long term changes in sy the sensitivity of sy to changes in climate increases as the percentage of deforested land increases for the 21st century the results are highly sensitive to the scenarios used due to relatively large increases in rainfall erosivity sy increases by 12 compared to the 20th century according to scenario a2 or by 8 according to b1 however the associated land use change scenarios cause decreases in sy by 26 a2 and 46 b1 the net effect is thus a decrease of sy this study highlights the potentially significant efficacy of land use planning as a tool to mitigate the negative effects of soil erosion and sediment delivery to rivers

temporal changes in suspended sediment transport in an atlantic catchment nw spain catchment scale suspended sediment ss transport studies in northwest spain are of special interest as little research at this scale has been done in this region however the role of sediments in the transfer of nutrients and contaminants to coastal areas in this region has been highlighted data were collected from the corbeira catchment during a 3 year period and the variability in ss load at different temporal scales within events variability monthly seasonal and annual was analyzed the statistical relationship between discharge and suspended sediment concentration ssc from samples obtained every 15 days as well as during runoff events in october 2004 to september 2007 showed a marked scatter of points hence the rating curve method does not seem appropriate to estimate ssc in this catchment the results also demonstrated that at the within events scale most of the ss peaks preceded the discharge peaks 70 of runoff events implying that zones nearby or well connected to the stream are the dominant sediment source areas in some cases rills and ephemeral gullies developed in cropland were the main source of sediment delivered to the stream furthermore a reduction in ssc was observed in sequences of events which can be mainly linked to a phenomenon of sediment exhaustion at the seasonal scale most of the total annual ss load was transported during the autumn months the period in which generally the largest number of events occurred while in the summer total annual ss load was very low 1 at the annual scale specific ss yield ssy ranged from 5 4 to 11 2 mg km 2 y 1 the variability in ssy was correlated with the number and magnitude of runoff events recorded yearly since runoff events dominated ss transport and yield for instance in the last hydrological year 2006 07 more than 80 of the ss load was exported in runoff events involving 10 of the time

the spin and inertia of venus one of the most remarkable rotational features of venus is the presence of a relatively large offset between spin and maximum inertia axis according to the most recent gravity field models this offset may amount to 0 5 considerably larger than the one which characterizes the earth s chandler wobble 0 3 at present it is not clear whether the offset of venus is the result of the limited resolution of the gravity models or alternatively it may be regarded as an evidence in support to the existence of a wobble purpose of this note is to demonstrate on quantitative grounds that an offset between spin axis and maximum inertia axis is to be expected on the time scales of mantle convection due to the peculiar rotational characteristics of venus we also show that the inertia perturbation associated to the rising of hot thermal plumes from the core mantle boundary to the surface is large enough to maintain offsets ranging between 0 1 and 1 of course this does not preclude that other processes such as venusquakes or periodic atmospheric variabilities may contribute significantly to the observed offset on shorter time scales

quantifying the dominant sources of sediment in a drained lowland agricultural catchment the application of a thorium based particle size correction in sediment fingerprinting soil erosion is one of the main factors influencing land degradation and water quality at the global scale identifying the main sediment sources is therefore essential for the implementation of appropriate soil erosion mitigation measures accordingly caesium 137 137cs concentrations were used to determine the relative contribution of surface and subsurface erosion sources in a lowland drained catchment in france as 137cs concentrations are often dependent on particle size specific surface area ssa and novel thorium th based particle size corrections were applied surface and subsurface samples were collected to characterize the radionuclide properties of potential sources sediment samples were collected during one hydrological year and a sediment core was sampled to represent sediment accumulated over a longer temporal period additionally sediment from tile drains was sampled to determine the radionuclide properties of sediment exported from the drainage network a distribution modelling approach was used to quantify the relative sediment contributions from surface and subsurface sources the results highlight a substantial enrichment in fine particles and associated 137cs concentrations between the sources and the sediment the application of both correction factors reduced this difference with the th correction providing a more accurate comparison of source and sediment samples than the ssa correction modelling results clearly indicate the dominance of surface sources during the flood events and in the sediment core sediment exported from the drainage network was modelled to originate predominantly from surface sources this study demonstrates the potential of th to correct for 137cs particle size enrichment more importantly this research indicates that drainage networks may significantly increase the connectivity of surface sources to stream networks managing sediment transferred through drainage networks may reduce the deleterious effects of suspended sediment loads on riverine systems in similar lowland drained agricultural catchments

relationship of runoff erosion and sediment yield to weather types in the iberian peninsula precipitation has been recognized as one of the main factors driving soil erosion and sediment yield sy and its spatial and temporal variability is recognized as one of the main reasons for spatial and temporal analyses of soil erosion variability the weather types wts approach classifies the continuum of atmospheric circulation into a small number of categories or types and has been proven a good indicator of the spatial and temporal variability of precipitation thus the main objective of this study is to analyze the relationship between wts runoff soil erosion measured in plots and sediment yield measured in catchments in different areas of the iberian peninsula ip with the aim of detecting spatial variations in these relationships to this end hydrological and sediment information covering the ip from several spanish research teams has been combined and related with daily wts estimated by using the nmc ncar 40 year reanalysis project the results show that in general a few wts particularly westerly southwesterly and cyclonic provide the largest amounts of precipitation and southwesterly northwesterly and westerly wts play an important role in runoff generation erosion and sediment yield as they coincide with the wettest wts however this study highlights the spatial variability of erosion and sediment yield in the ip according to wt differentiating 1 areas under the influence of north and or north westerly flows the north coast of cantabria and inland central areas 2 areas under the influence of westerly southwesterly and cyclonic wts western and southwestern ip 3 areas in which erosion and sediment yield are controlled by easterly flows mediterranean coastland and 4 lastly a transitional zone in the inland northeast ebro catchment where we detected a high variability in the effects of wts on erosion overall results suggest that the use of wts derived from observed atmospheric pressure patterns could be a useful tool for inclusion in future projections of the spatial variability of erosion and sediment yield as models capture pressure fields reliably

the depositional evolution of the svecofennian supracrustal sequence in finland and sweden abstract on the basis of six new zircon ages from metavolcanic rocks together with other isotopic geophysical and geological data the chronological and tectono stratigraphic evolution of the early proterozoic svecofennian supracrustal rocks in finland and sweden are discussed these data suggest that a nw se displacement from the bothnian bay to lake ladoga and a sinking of the southwestern block was initiated 1950 2000 ma ago accumulation of pelitic sediments and greywackes on the subsiding archaean basement continued until about 1860 ma in south central and northern sweden shallow submarine and subaerial volcanics were extruded 1880 1890 ma ago the thick sedimentary piles and volcanic rocks were subsequently intruded by plutonic rocks forming large batholiths 1860 1890 ma ago

coldspots and hotspots global tectonics and mantle dynamics of venus magellan radar images and altimetry data and pioneer venus gravity data of major highlands and lowlands on venus are examined with the objective of relating these tectonic and volcanic landforms to convection within venus mantle two roughly circular lowlands atalanta and lavinia planitiae are bowl shaped depressions which contain compressional tectonic features and lack hotspot related features such as coronae and shield volcanoes they are identified as surface expressions of young mantle coldspots or regions of mantle downwelling highlands can be divided into two distinct groups volcanic rises and plateau shaped highlands volcanic rises are domical circular to elongate regions characterized by volcanic construction extensional tectonism large positive gravity and geoid anomalies centered on the highlands and large apparent depths of compensation volcanic rises include beta bell atla and western eistla regiones and are identified as surface expressions of large mantle hotspots or plumes plateau shaped highlands are steep sided elevated regions that range from circular alpha regio to elongate or irregular ovda regio tellus regio in shape their surfaces are dominated by complex ridged terrain rather than the shield volcanoes and flows that dominate volcanic rises most plateau shaped highlands contain compressional structures some of which commonly lie along their margins and have small gravity and geoid anomalies and small apparent depths of compensation compared to volcanic rises plateau shaped highlands which include those mentioned above and western ishtar terra thetis regio and phoebe regio are identified as surface expressions of mantle coldspots or regions of downwelling the highland coldspot features are elevated as a consequence of crustal thickening crustal thickening is absent or minor at lowland coldspots the importance of mantle downwelling in the tectonic deformation of venus suggests that its mantle like the mantle of earth is strongly heated from within the major venusian hotspots attest to the existence of large mantle plumes carrying heat upward from the planet s core