earth s magnetic field in the early 19th century from french sources 1 we present both a description of a new magnetic data set covering predominantly the 18th and 19th centuries and the results derived from it for the small window 1820 1850 from which the bulk of the data originate the data set comprises measurements of declination taken overwhelmingly on french naval and hydrographic vessels a list of the vessels is given for one of the data sets when augmented by extant inclination measurements the data are capable of resolving the magnetic field at the core mantle boundary to a high degree of fidelity and thus are a valuable addition to the data set of historical geomagnetic measurements

aspects of climate variability in the north atlantic sector discussion and relation to the greenland ice sheet project 2 high resolution isotopic signal this paper reviews aspects of climate variability in the north atlantic sector that may influence the seasonal to decadal scale isotopic signal in the greenland ice sheet project 2 gisp2 ice core interpretation of the isotopic signal and its spatial applicability at the seasonal level requires investigation into synoptic scale climatology we discuss possible climatic influences of 1 likely source regions of precipitation reaching the gisp2 site 2 the characteristics of cyclone activity over the north atlantic sector and 3 changes in major atmospheric features such as the mean sea level icelandic low and azores high pressure systems the north atlantic oscillation and the baffin trough next we evaluate correlations between the gisp2 deuterium isotopic signal and coastal temperatures with atmospheric pressure patterns thereby deriving climatic interpretations of the high resolution isotopic record the gisp2 site is influenced by both the icelandic low to the southeast and davis strait baffin bay storms to the southwest and west the north atlantic oscillation influences the gisp2 isotopic signal through the seesaw in winter temperatures between west greenland and northern europe agreement in excursion directions of gisp2 isotopes and east greenland and iceland temperature records is associated with different positions of the baffin trough in winter and also with anomalous 500 mbar net geostrophic flow linkages between isotopic excursion direction and atmospheric variability need to be explored further by comparison with additional seasonal data sets from other greenland ice cores

rates of soil erosion in his report decreased rates of alluvial sediment storage in the coon creek basin wisconsin 1975 93 20 aug p 1244 1 stanley w trimble presents the significant findings that there is a relatively constant supply of sediments released to the mississippi river from coon creek and

remote sensing of the albedo and detection of the slush line on the greenland ice sheet advanced very high resolution radiometer images of a section of the greenland ice sheet western part between 64 5 and 70 5 n with a size of 667 n s by 700 w e km were processed in order to retrieve the surface albedo the images were for the summer seasons of 1990 1997 inclusive and results were compared to simultaneous mass balance measurements carried out along the transect 67 n the main findings are as follows first many images show a distinct transition from low spatial variability of the albedo at higher elevations to higher spatial variability of the albedo at lower elevations it is argued that these transitions most likely correspond to transitions at the surface slush line in short from the area that is uniformly covered by snow to a mosaic of snow patches slush and ice second 70 of the interannual variations in the mean specific mass balance can be explained by interannual variations in the maximum elevation of the slush line i e the slush limit however a higher percentage 82 can be explained by interannual variations in the sum of positive degree days third in 3 years with a relatively large amount of melt the inland migration of the slush line stopped or slowed considerably down at a fixed distance from the ice sheet margin we believe that this so called maximum slush line coincides with an abrupt change in the density profile the maximum slush line forms an important limitation for the use of satellite data to monitor interannual variations in the mass balance its position is a climate indicator and was determined for the entire section of the greenland ice sheet investigated

secular variation in north america during historical times summary the secular variation of the declination inclination and total force of the geomagnetic field has been plotted for 74 locations in north america a comparison of the occurrences of maxima and minima in the sv clirves from different stations shows little evidence of drift in north america although a declination maximum exhibits westward drift up to 1915 all other extrema in declination inclination and total intensity occur almost simultaneously over a wide area the major feature of sv in north america appears to be a 4000 nt decrease in the total field since 1850 which may be due to a decrease in the dipole moment coupled with the decay of a large non dipole anomaly situated under the continent short period changes in the rate of decrease are possibly jerks of the magnetic field maximum entropy spectral analysis of all three components of the field indicates periods of 102 and 53 yr

linking landslide susceptibility to sediment yield at regional scale application to romania abstract it is generally accepted that catchment sediment yield sy t km 2 y 1 can be strongly influenced by landsliding nevertheless due to data requirements only few studies investigated this effect at a regional scale the objective of this study is therefore to explore the potential of a landslide susceptibility map for explaining the spatial variation of sy in romania we selected 133 catchments in romania for which sy was measured during a period of at least 10 years for each catchment we derived a variety of proxies that potentially explain sy including several indicators of landslide occurrence the latter were derived from a published landslide susceptibility map results show that sy is significantly correlated with mean landslide susceptibility r 2 0 30 estimates of average sheet and rill erosion rates showed a much weaker correlation with sy r 2 0 06 further analyses showed that the strong correlation between sy and landslide susceptibility is mainly attributed to regional variations in lithology and seismicity especially the latter may play a crucial role in understanding denudation rates at regional scales e g by facilitating the occurrence of landslides using landslide proxies that also account for sediment connectivity did not result in stronger correlations overall our results show that landslide susceptibility maps can be a highly useful tool to predict sy at regional scales provided that they incorporate all relevant factors

surface mass balance observations and automatic weather station data along a transect near kangerlussuaq west greenland surface mass balance data from the kangerlussuaq transect k transect located on the western part of the greenland ice sheet near 678n are presented the series covers the period 1990 2003 and is the longest series of surface mass balance measurements in greenland the surface mass balance measurements cover an altitude range of 390 1850m and show a linear increase of the specific mass balance with a mass balance gradient of 3 7 10 3 mm 1 and a mean equilibrium line altitude of 1535ma s l interannual variability shows a weak 4yearly periodicity in addition to the surface mass balance data automatic weather station data at an elevation of approximately 1010m are available for the period 1997 2002 these data are used to explain observed surface mass balance anomalies over the same 5years it is shown that variations in shortwave radiation dominate interannual variability the mean annual cycle of temperature is characterized by a maximum in summer around the melting point leading to a mean summer outgoing longwave radiation of approximately 314wm 2 the mean annual cycle in wind speed shows a maximum in winter on average around 8ms 1 and a minimum in summer on average around 5ms 1 which is characteristic for a katabatic forcing during summer the net radiation is on average about 61wm 2 which is used for ice melting at a rate of typically 2cmw e d 1 net radiation contributes 84 of the total energy used for summer melting averaged over the 5years

mass balance of the greenland ice sheet at high elevations comparison of ice discharge from higher elevation areas of the entire greenland ice sheet with total snow accumulation gives estimates of ice thickening rates over the past few decades on average the region has been in balance but with thickening of 21 centimeters per year in the southwest and thinning of 30 centimeters per year in the southeast the north of the ice sheet shows less variability with average thickening of 2 centimeters per year in the northeast and thinning of about 5 centimeters per year in the northwest these results agree well with those from repeated altimeter surveys except in the extreme south where we find substantially higher rates of both thickening and thinning

humans as geologic agents a deep time perspective humans move increasingly large amounts of rock and sediment during various construction activities and mean rates of cropland soil loss may exceed rates of formation by up to an order of magnitude but appreciating the actual importance of humans as agents of global erosion necessitates knowledge of prehistoric denudation rates imposed on land surfaces solely by natural processes amounts of weathering debris that compose continental and oceanic sedimentary rocks provide one such source of information and indicate that mean denudation over the past half billion years of earth history has lowered continental surfaces by a few tens of meters per million years in comparison construction and agricultural activities currently result in the transport of enough sediment and rock to lower all ice free continental surfaces by a few hundred meters per million years humans are now an order of magnitude more important at moving sediment than the sum of all other natural processes operating on the surface of the planet relationships between temporal trends in land use and global population indicate that humans became the prime agents of erosion sometime during the latter part of the first millennium a d

on the history of humans as geomorphic agents the human population has been increasing exponentially simultaneously as digging sticks and antlers have given way to wooden plows iron spades steam shovels and today s huge excavators our ability and motivation to modify the landscape by moving earth in construction and mining activities have also increased dramatically as a consequence we have now become arguably the premier geomorphic agent sculpting the landscape and the rate at which we are moving earth is increasing exponentially as hunter gatherer cultures were replaced by agrarian societies to feed this expanding population erosion from agricultural fields also until recently increased steadily this constitutes an unintended additional human impact on the landscape

gully catchments as a sediment sink not just a source results from a long term 12 500 year sediment budget sediment delivery from hillslopes to trunk streams represents a significant pathway of mass transfer in the landscape with a large fraction facilitated by gully systems the internal gully geomorphic dynamics represent a considerable gap in many landscape and empirical erosion models therefore a better understanding of these processes over longer timescales 10 10 years is needed this study analyses the sediment mass balance and storage dynamics within a headwater gully catchment in central europe over the last 12 500 years human induced erosion resulted in hillslope erosion rates 2 3 times higher than under naturally de vegetated conditions during the younger dryas however the total sediment inputs to the gully system and therefore gully aggradation were similar net gully storage has consistently increased to become the second largest term in the sediment budget after hillslope erosion storage is 45 and 73 of inputs during two separate erosion and aggradation cycles in terms of the depletion of gully sediment storage the sediment mass balance shows that export beyond the gully fan was not significant until the last 500 years due to reduced gully fan accommodation space the significance of storage effects on the gully sediment mass balance particularly the export terms means that it would be difficult to determine the influences of human impact and or climatic changes from floodplain or lake sedimentary archives alone and that the sediment budgets of the headwater catchments from which they drain are more likely to provide these mechanistic links

historic and paleomagnetic secular variation and the earth s core dynamo process this paper attempts to summarize briefly the recent and ongoing efforts of the geomagnetism and paleomagnetism community to understand both the earth s magnetic field secular variation and its implications for the core dynamo process secular variation is defined in this paper as the general spatio temporal variation of the field secular change will refer to the first time derivative of the spatial field strict geomagnetic definition of secular variation we will emphasize here the long term 10 year or longer behavior of the historic secular variation hsv for this is the variation that is comparable with the paleomagnetic secular variation psv two important related topics the 1969 1970 geomagnetic jerk in secular acceleration and the spatial geomagnetic field components due to crustal or mantle sources are treated more fully in other reviews

continental erosion and large scale relief a worldwide investigation of continental erosion is carried out by the study of large drainage basins on the basis of hydrological data environmental factors and basin relief distribution inside each basin mean geochemical and mechanical denudation rates are defined a multicorrelation analysis shows that the mechanical denudation rates ds are uncorrelated with environmental factors and correlated with mean basin elevation h while chemical denudation rates dd are insensitive to relief but correlated with mean annual precipitation furthermore two linear relationships between h and ds are detected 1 ds m 10 yr 419 10 6 h m 0 245 with v explained variance 95 1 this law concerns basins related to orogenies younger than 250 ma the negative intercept is interpreted as a continental sedimentation rate of 245 m m y an alternative model in which one invokes a critical elevation separating erosion from sedimentation is equally successful and leads to lower sedimentation rates 60 110 m m y for both models one derives from the slope of the adjustments erosion time constants on the order of 2 5 m y 2 ds m 10 yr 61 10 6 h m with v 86 5 this law concerns basins related to older orogenies the null intercept suggests the lack of continental storage because of the more important dispersion of the data the erosion time constant is calculated separately for each basin it ranges from 15 to 360 m y the tectonic implications of these results are discussed in particular the short time constant 2 5 m y agrees with orogenic uplift rates on the order of 1 mm yr observed in active mountain chains

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

visual stratigraphic dating of the gisp2 ice core basis reproducibility and application annual layers are visible in the greenland ice sheet project 2 ice core from central greenland allowing rapid dating of the core changes in bubble and grain structure caused by near surface primarily summertime formation of hoar complexes provide the main visible annual marker in the holocene and changes in cloudiness of the ice correlated with dustiness mark wisconsinan annual cycles both markers are evident and have been intercalibrated in early holocene ice layer counts are reproducible between different workers and for one worker at different times with 1 error over century length times in the holocene reproducibility is typically 5 in wisconsinan ice age ice and decreases with increasing age and depth cumulative ages from visible stratigraphy are not significantly different from independent ages of prominent events for ice older than the historical record and younger than approximately 50 000 years visible observations are not greatly degraded by brittle ice or many other core quality problems allowing construction of long consistently sampled time series high accuracy requires careful study of the core by dedicated observers

what factors control mechanical erosion rates mechanical erosion rates are important factors in understanding how continents evolve mechanical erosion is much faster than chemical erosion especially for highly elevated regions of the earth s surface it is a principal way in which mountain ranges are removed exposing deep metamorphic roots which comprise much of the older portions of the continental masses in addition there has to be a long term balance between erosion and mountain building a new data set allows us to explore in greater detail some of the many factors which control mechanical erosion rates the most important factors are some expression of the average slope of a drainage basin some measurement of the amount of water available for erosion some environmental measurements and also a measurement of basin length for which we have no good explanation the estimate of global mechanical erosion rate obtained here is considerably lower than those obtained by some other workers some of whom have concentrated on the fact that smaller river basins tend to get eroded faster than larger basins and it is mainly smaller basins which have not been measured and which are therefore not allowed for by simple arithmetic averaging of observed erosion rates it is shown here that although smaller basins are eroded faster this is mainly because they are steeper than larger basins we also show that extrapolation of current data to smaller basins does not work because the observed continental area which is draining to the ocean cannot be attained by the simplest extrapolation scheme

signal and noise in four ice core records from the agassiz ice cap ellesmere island canada details of the last millennium for stable isotopes melt and solid conductivity four ice cores and two deep pit auger sequences from the top of the agassiz ice cap have been variously analysed for o18 ecm solid conductivity and ice melt layer stratigraphy the high resolution data are presented on time scales covering about the last 1000 years the 8 time series are compared and the noise examined in terms of snow drifting and wind scouring of winter snow from the higher exposed parts of flow lines the highly scoured 8 records reflect a mixture of summer biased conditions and the amount of winter scoured snow sites away from the ridges and domes are not scoured the signal part of the scoured and unscoured sites is obtained by stacking averaging normalized series the stacked unscoured series of 8 and accumulation are compared to similar stacked series from central greenland for the last century of annual averages the comparison is surprisingly good suggesting that at these resolutions low noise 8 series have some coherence over fairly large distances the percentage melt

assessment of the surface mass balance along the k transect greenland ice sheet from satellite derived albedos this paper explores the potential of using satellite derived albedos to estimate the surface mass balance of the kangerlussuaq transect k transect greenland ice sheet we first retrieved surface albedos from advanced very high resolution radar data by using among other techniques a new cloud detection algorithm based on the relation between brightness temperature and surface elevation we then computed the satellite derived mass balance bsat from the mean albedo for the transect by taking fixed values for atmospheric transmissivity and the longwave and turbulent fluxes we found that bsat explains 71 of the variance in 13 years of stake mass balance measurements bm our method also provides good estimates of the magnitude of the interannual variability in bm the performance of the method degrades considerably without correction for anisotropic reflection at the surface and recalibration of the satellite sensors with dry snow at the top of the ice sheet sensitivity tests indicate that the method s performance is hardly sensitive to uncertainties in parameters therefore we expect that the method could be successfully applied on other glaciers and parts of ice sheets and ice caps especially where accumulation rates are relatively small we show that the investigated method performs best just below the mean equilibrium line altitude

altitudinal gradient of mass balance sensitivity to climatic change from 18 years of observations on glacier d argentiere france assessment of the contribution of small glaciers to sea level rise or the reconstruction of past glacial mass balance requires knowledge of mass balance sensitivity to climatic variations the aim of this paper is to clarify this relation the mass balance fluctuations analyzed from measurements on glacier d argentiere mont blanc massif france between 1850 and 2700 m a s l were compared with climatic variations at a nearby meteorological station statistical study of the data shows that 1 the annual mass balance fluctuations are dependent on elevation and 2 the mass balance sensitivity to temperature decreases with altitude and diverges from current model results consequences of a temperature variation of 1 c for global volume variations are significant a simple calculation on glacier des bossons mont blanc massif france shows that the sensitivity from the model can lead to volume variations twice as high as results compatible with our observations

toward a uniform theory of clastic sediment yield in fluvial systems sediment is delivered to streams by creep slope wash rill and gully erosion and collapse of oversteepened banks the first three of these operate on all transportlimited slopes their efficacy varies directly with precipitation or runoff and inversely with vegetation cover sediment yield from these processes is also likely to increase with slope angle and in the case of slope wash and rill erosion with rainfall intensity and slope length sloughing from oversteepened banks however occurs where rivers are actively cutting into valley sides the frequency of occurrence of such locations increases with the mean slope angle and the frequency of collapse increases with runoff thus this process is likely to be dominant in mountainous areas with high runoff expressing these effects analytically leads to a tentative general relation for specific sediment yield if we had sufficient knowledge of the various parameters involved this relation could be integrated over a basin to obtain the total yield at present however its main value is to draw attention to the numerous assumptions implicit in many much simpler equations in common use

hillslopes rivers plows and trucks mass transport on earth s surface by natural and technological processes the surface of the earth is being transformed by a new force in the form of technological systems and processes that move significant quantities of mass large distances because movement of mass is perhaps the most basic geomorphic process and because the continuing rise of technology appears to characterize a new epoch in earth evolution the anthropocene it is of interest to compare technological and natural mass transport mechanisms a purely dynamical mass action metric representing the product of mass displaced distance moved and mean speed of displacement is used to compare the transport effectiveness of selected systems systems with large mass action tend to be advective and systems with small mass action diffusive local environments are conditioned by mass action through the introduction of transport corridors such as roads and rivers which put constraints on mass transport by embedded diffusive systems advection also subjects local environments to externally determined time scales such as the times for delivery of unit mass of water or sediment to a river mouth and supports the emergence of associated dynamical processes there for example those of human activity or delta construction that are too rapid to be sustained by diffusion most of the world s mass action is generated by the motion of fluids of global or continental extent as in atmospheric circulation or river flow technological mass action exceeds that of all land based geomorphic systems except rivers technological systems with large mass action tend to be comprised of discrete self powered units e g trucks discretization of transported mass reflects the different locomotion strategy required for transport of solids on land compared with the transport requirements of spatially extensive fluids in nature the principle of maximum entropy production may provide a framework for understanding the emergence of advective technological mass transport systems copyright 2010 john wiley sons ltd

lithosphere asthenosphere interaction beneath the western united states from the joint inversion of body wave traveltimes and surface wave phase velocities summary the relation between the complex geological history of the western margin of the north american plate and the processes in the mantle is still not fully documented and understood several pre usarray local seismic studies showed how the characteristics of key geological features such as the colorado plateau and the yellowstone snake river plains are linked to their deep mantle structure recent body wave models based on the deployment of the high density large aperture usarray have provided far more details on the mantle structure while surface wave tomography ballistic waves and noise correlations informs us on the shallow structure here we combine constraints from these two data sets to image and study the link between the geology of the western united states the shallow structure of the earth and the convective processes in mantle our multiphase dna10 s model provides new constraints on the extent of the archean lithosphere imaged as a large deeply rooted fast body that encompasses the stable great plains and a large portion of the northern and central rocky mountains widespread slow anomalies are found in the lower crust and upper mantle suggesting that low density rocks isostatically sustain part of the high topography of the western united states the yellowstone anomaly is imaged as a large slow body rising from the lower mantle intruding the overlying lithosphere and controlling locally the seismicity and the topography the large e w extent of the usarray used in this study allows imaging the slab graveyard a sequence of farallon fragments aligned with the currently subducting juan de fuca slab north of the mendocino triple junction the lithospheric root of the colorado plateau has apparently been weakened and partly removed through dripping the distribution of the slower regions around the colorado plateau and other rigid blocks follows closely the trend of cenozoic volcanic fields and ancient lithospheric sutures suggesting that the later exert a control on the locus of magmato tectonic activity today the dna velocity models are available for download and slicing at http dna berkeley edu

denudation rates on cratonic landscapes comparison between suspended and dissolved fluxes and 10be analysis in the nyong and sanaga river basins south cameroon south cameroon is located in a tropical and tectonically quiescent region with landscapes characterized by thick highly weathered regolith indicative of the long term predominance of chemical weathering over erosion currently this region undergoes huge changes due to accelerated mutations related to a growing population and economical developments with associated needs and increasing pressures on land and natural resources we analysed two of the main south cameroon rivers the nyong river and sanaga river the sanaga catchment undergoes a contrasted tropical climate from sub humid mountainous and humid climate and is impacted by deforestation agriculture damming mining and urbanization especially in the mbam sub basin draining the highly populated volcanic highlands by contrast the nyong catchment only under humid tropical climate is preserved from anthropogenic disturbance with low population except in the region of yaounde mefou sub basin moreover the nyong basin is dam free and less impacted by agriculture and logging we explore both denudation temporal variability and the ratio between chemical and physical denudation through two catchment averaged erosion and denudation datasets the first one consists of an 11 year long gauging dataset while the second one comes from cosmogenic radionuclides crns here beryllium 10 be 10 from sand sampled in the river mainstreams timescale of tens to hundreds of thousands of years modern fluxes estimated from gauging data range from 5 to 100m ma 10 to 200t km 2 yr our calculations indicate that the usual relative contribution of chemical versus physical denudation is 60 and 40 respectively of the total denudation beryllium 10 denudation rates and sediment fluxes range from 4 8 to 40 3m ma or 13 to 109t km 2 yr respectively after correction for quartz enrichment these fluxes are slightly less than the modern fluxes observed in cameroon and other stable tropical areas the highest be 10 derived fluxes and the highest physical versus chemical denudation ratios are attributed to anthropogenic impact copyright c 2016 john wiley sons ltd

reconstructing early permian tropical climates from chemical weathering indices this study was financially supported by the national natural science foundation of china grants 41302083 41572078 the national basic research program of china grant 2011cb808800 and the fundamental research funds for the central universities grant cugl140402 china university of geosciences wuhan p a cawood acknowledges support from nerc grant ne j021822 1

6700 yr sedimentary record of climatic and anthropogenic signals in lake aydat french massif central a 19 meters long sedimentary record that was retrieved in lake aydat french massif central covers the last 6700 yrs at a high resolution a multi proxy approach density magnetic susceptibility xrf rock eval analyses pollen and non pollen palynomorphs analyses and historical archives study was used to characterise and tentatively propose a model of the sedimentation the important deposition rate results from the narrow and incised fluvial valley dammed by a lava flow ca 8550 years ago two contrasted periods of sedimentation 6700 200 3180 90 cal bp and 1770 60 cal bp now are characterized the lower unit mid holocene displays a fine and regular lamination and holds a single major flood deposit this unit is capped by an erosive mass wasting deposit triggered ca 1770 60 cal bp the upper unit late holocene is made of organic rich and fine grained faintly laminated sediment with numerous interbedded flood deposits 56 events and layers resulting from blooms of diatoms the sedimentation was principally controlled by climatic forcings solar activity until ca 1100 cal bp accompanied by detritic events linked to human activities around the lake then a more detrital input attested by numerous and recurrent flood deposits can be linked to the intensification of a persistent anthropogenic impact on the catchment two phases of lake eutrophication are highlighted a first phase between 1200 1130 cal bp as a result of increased anthropogenic pressure and the current phase that could have started ca 150 cal bp

glaciological investigations in the crete area central greenland a search for a new deep drilling site the results of the 1984 85 post gisp campaigns in central greenland are presented eight ice cores were obtained some spanning up to 360 years we present i geographical positions and elevations at the drill sites

historical soil erosion and land use change during the last two millennia recorded in lake sediments of frickenhauser see northern bavaria central germany based on palaeolimnological investigations on a 1275 cm long lacustrine sediment record sediment yields sy and denudation rates dr for the last 2000 years were reconstructed from frickenhauser

historical soil erosion by water in germany scales and archives chronology research perspectives abstract the published record of historical soil erosion by water in germany as deduced from dated slope deposits n 306 alluvial sediments n 120 and lake sediments is summarized in this paper the number of sediments investigated reflects the state of knowledge chronology of historical soil erosion and to a certain degree the intensity of the human impact on german landscapes during the holocene even though few data of calculated historical soil erosion intensities exist an estimation of historical soil erosion in germany combining the available data has been calculated soil erosion in germany occurred first locally during the early holocene probably triggered by climatic variability from the neolithic onward the record reflects the human impact according to agricultural land use the observed variability indicates phases of weaker and regained intensity of agricultural land use in germany few records characterise the early and middle bronze age ca 2000 1600 bc and the migration period and the early medieval times ca 400 1000 ad surprisingly for the roman emperor times ca 1 400 ad a decreasing number of soil sediments is recorded even when the data from southern germany is examined separately phases characterised by an increase in soil erosion were the late bronze age and pre roman iron age ca 1600 bc 1 ad the high and late medieval times ca 1000 1350 ad and the modern times ca 1500 ad until today some extraordinary heavy precipitation events late 18th early 19th first half of 14th century pre roman iron age topped the even high soil erosion intensities research gaps as well as potential for future research as derived from the available data are outlined

greenland ice sheet mass balance distribution a variance analysis of existing field data a large number of mass balance measurements have been carried out on the greenland ice sheet but few of the series obtained are well suited for statistical studies rather than looking at the global mass balance value this paper deals with the spatial and temporal mass balance variability on the ice sheet two sorts of analysis are possible direct comparisons of the series measured at a given site or a broader approach involving comparisons between different sites using variance analysis for glaciers in the southwest ablation area a significant interannual variability around 1 0 m w e is found this variability is spatially consistent in the accumulation area the results are more complex for example there is consistent evidence of year to year variations on the west east expeditions glaciologiques internationales au groenland egig profile but other closer sites are weakly correlated these results emphasize the need for a better coverage of measurements over the entire ice sheet as well as longer and more continuous measurement series

an evolving research agenda for human coastal systems within the broad discourses of environmental change sustainability science and anthropogenic earth surface systems a focused body of work involves the coupled economic and physical dynamics of developed shorelines rapid rates of change in coastal environments from wetlands and deltas to inlets and dune systems help researchers recognize observe and investigate coupling in natural non human morphodynamics and biomorphodynamics this same intrinsic quality of fast paced change also makes developed coastal zones exemplars of observable coupling between physical processes and human activities in many coastal communities beach erosion is a natural hazard with economic costs that coastal management counters through a variety of mitigation strategies including beach replenishment groynes revetments and seawalls as cycles of erosion and mitigation iterate coastline change and economically driven interventions become mutually linked emergent dynamics of two way economic physical coupling is a recent research discovery having established a strong theoretical basis research into coupled human coastal systems has passed its early proof of concept phase this paper frames three major challenges that need resolving in order to advance theoretical and empirical treatments of human coastal systems 1 codifying salient individual and social behaviors of decision making in ways that capture societal actions across a range of scales thus engaging economics social science and policy disciplines 2 quantifying anthropogenic effects on alongshore and cross shore sediment pathways and long term landscape evolution in coastal zones through time including direct measurement of cumulative changes to sediment cells resulting from coastal development and management practices e g construction of buildings and artificial dunes bulldozer removal of overwash after major storms and 3 reciprocal knowledge and data exchange between researchers in coastal morphodynamics and practitioners of coastal management future research into human coastal systems can benefit from decades of interdisciplinary work on the complex dynamics of common pool resources from computational efficiency and new techniques in numerical modeling and from the growing catalog of high resolution geospatial data for natural and developed coastlines around the world

greenland ice sheet high elevation balance and peripheral thinning aircraft laser altimeter surveys over northern greenland in 1994 and 1999 have been coupled with previously reported data from southern greenland to analyze the recent mass balance of the greenland ice sheet above 2000 meters elevation the ice sheet is in balance on average but has some regions of local thickening or thinning thinning predominates at lower elevations with rates exceeding 1 meter per year close to the coast interpolation of our results between flight lines indicates a net loss of about 51 cubic kilometers of ice per year from the entire ice sheet sufficient to raise sea level by 0 13 millimeter per year approximately 7 of the observed rise

records of geomagnetic secular variation since 1200 ad and the potential for chronological control of lake sediments in northern alberta we assess whether absolutely aged declination changes can be used to date recent massive lake sediments at the sub century scale three issues limiting such studies are addressed recovery of undisturbed recent lake sediments assessment of the reliability of the geomagnetic record and the comparison of lake sediment records with historic re cords a 793 year long geomagnetic chronology was obtained from the annually laminated sediment of rainbow lake a sediment disturbance was minimized by freezing the sediment in situ and maintaining this state for geomagnetic analyses geomagnetic chronologies ca 600 years long from the massive sediments of fariya lake and ninisith lake were collected in removable plastic tubes using a piston corer sediment disturbance was minimized by ex situ draining of water from the plastic tubes the reliability of the geomagnetic record was assessed using a measure of internal co herence with an absolute cutoff of 15 by further separating the samples at coherence values of 5 and 7 5 it was possible to identify zones of disturbance and reduced compaction the most reliable samples had a high magnetic in tensity due to high inputs of magnetic minerals sediment compression and inputs of stable magnetic minerals neither freezing nor dewatering of the sediments appeared to decrease reliability of the geomagnetic record the declination chronology from the annually laminated sediments was significantly correlated with a 230 year long historical record from churchill manitoba and with the massive lake sediment chronology from fariya lake geomagnetic dating was not possible however because of the large amplitude in the annually laminated sediment declination record the large number of years of sediment in many specimens and the lack of reliability for samples that contain few years of sedi ment per specimen

analysis of fluvial suspended sediment load contribution through anthropocene history to the south atlantic bight coastal zone u s a abstract discerning the effects of anthropogenic activities i e reservoir construction land use change as opposed to those of natural processes i e climate variability on suspended sediment flux has become an increasingly difficult challenge this contribution presents water and suspended sediment flux from five major watersheds that discharge into the southeastern u s atlantic a region that is currently considered sediment starved three periods of anthropocene time were defined and evaluated 1 pre european conditions 1680 1700 2 pre dam conditions 1905 1925 and 3 post dam conditions 1985 2005 physical and hydrologic watershed data were used to run a climate driven hydrological transport numerical model hydrotrend to estimate suspended sediment flux for each period results indicate that the suspended sediment contribution to the south atlantic bight coastal zone increased by up to 145 as a result of accelerated soil erosion conditions caused by the arrival of europe

mass balance of glaciers other than the ice sheets small glaciers appear to have been at equilibrium or shrinking very slightly during 1961 90 according to analysis of an essentially compl ete set of published measurements simple calculations give an average annual mass balance of 195 59 mm a 1 water equivalent but this is too low because of systema tic errors eglect of internal accumulation is respon sible for some tens of millime ters of under esti mate uneven spatial coverage with fewer measurements where mass balances are less negative accounts for about 50 mm a 1 of underestimate this figure derives from spatial interpolati on based on global data on ice extent and on an analysis of correlations between balance time series the eorrelogram shows exponential decay the scale length being about 600 km the largest bias is due to a newly detec ted dependence of mass balance on glacier size among the 231 measured glaciers many arc small and belong to a restricted size range in which balance is negativ e but much of the small glacier extent is accounted for by larger glac iers in a size range where balance is indisti ngui shable from zero correct ing for this size bias increases the average balance to 35 89 mm a i inspection of time series for 1940 95 251 glaciers shows that mass balance was least negative during the 1960s and has varied in broad agreementvith northern hemisphere temperature anomalies smaller small glaciers a 16 km2 appear to be more sensitive than larger small glaciers to changes in thermal forci ng the small glaci er contribution to sea level rise implied by this asse ssment is only 0 06 0 32 mm a i consistent with glaciers in general mak i ng little or no contri bution to sea level change during 1961 90

new precipitation and accumulation maps for greenland annual total precipitation and the annual accumulation on the greenland ice sheet are evaluated and presented in two maps the maps are based on accumulation measurements of 25 1 pits and cores obtained from the upper accumulation zone and precipitation measurements made at 35 meteorological stations in the coastal region to construct the accumulation map the annual precipitation was split into solid and liquid precipitation components annual total precipitation exceeding 2500 mm w e occurs on the southeastern tip of greenland while the minimum precipitation is estimated to occur on the northeastern slope of the ice sheet the mean annual precipitation for all of greenland is 340 mm w e the largest annual accumulation of about 1500 mm w e is found on the glaciers in the southeastern corner of greenland while the smallest accumulation is found on the northeastern slope of the ice sheet west of danmarkshavn the mean accumulation on the greenland ice sheet is estimated at 310 mm w e the regional difference in accumulation is examined with respect to the 850 hpa m bar level circulation the present surface topography is found to play an important role in determining regional accumulation on the ice sheet

annual accumulation at two sites in northwest greenland during recent centuries during summer 1995 150 m firn and ice cores were drilled to determine annual accumulation rates at two greenland sites 73 84 n 49 49 w nasa u site and 78 53 n 56 83 w humboldt glacier site annual layers were identified in the cores using multiple parameters 18 o and concentrations of dust h 2 o 2 nh 4 ca 2 and no 3 using all parameters together to define annual layers resulted in a 350 year record for the nasa u core with no dating uncertainty for the lower accumulation humboldt core the dating uncertainty is about 5 years over the 852 year period of record with no uncertainty over the past 200 years annual accumulation over the periods of record at the two sites averaged about 0 34 and 0 14 m water equivalent respectively a set of 20 m firn cores drilled near the main 150 m cores showed that interannual variability of accumulation exceeded spatial variability at nasa u the humboldt cores showed equal spatial and interannual variability the accumulation rates at both sites showed a low frequency variation of about 100 years and both sites showed 200 year cumulative fluctuations of about 2 m from mean accumulation rates compared to central greenland and to nasa u the humboldt core showed higher annual accumulation rates around 1760 1810 possibly indicating a changed circulation pattern for the more northern part of greenland in that period

ten conceptual models of large scale legacy sedimentation a review abstract considerable interest has been directed toward the recognition and documentation of legacy sediment i e anthropogenic sediment in fluvial systems little has been written however to identify implicit or explicit theories about how these deposits form and evolve over decennial to centennial time scales this review attempts to redress this void by examining conceptual models of the physical behavior and characteristics of catchment scale anthropic fluvial sedimentation events these concepts which are not unique to anthropogenic sediment include cascades sediment delivery ratios waves aggradation degradation episodes residence times budgets connectivity stream power nonlinear dynamical systems and geohistorical geoarchaeological and chronostratigraphic principles a broad definition of legacy sediment as episodically produced anthropogenic sediment is adopted that includes early episodes of large scale human induced sedimentation throughout the world the models apply to a variety of environments so the examples from north america following the introduction of european settlement can be related to other post settlement sedimentation episodes elsewhere during aggradation episodes rates of erosion and sedimentation often increased an order of magnitude in response to land clearance for agriculture timbering or mining these sediments may remain as a lasting geomorphic legacy that provides evidence of anthropogenic change and governs modern rates of sediment production and nonpoint source pollution

mountain erosion over 10 yr 10 k y and 10 m y time scales we used cosmogenic 10 be to measure erosion rates over 10 k y time scales at 32 idaho mountain catchments ranging from small experimental watersheds 0 2 km 2 t o large river basins 35 000 km 2 these long term sediment yields are on average 17 times higher than stream sediment fluxes measured over 10 84 yr but are consistent with 10 m y erosion rates measured by apatite fission tracks our results imply that conventional sediment yield measurements even those made over decades can greatly underestimate long term average rates of sediment delivery and thus overestimate the life spans of engineered reservoirs our observations also suggest that sediment delivery from mountainous terrain is extremely episodic sporadically subjecting mountain stream ecosystems to extensive disturbance

human topographic signatures and derived geomorphic processes across landscapes abstract the earth s surface morphology in an abiotic context is a consequence of major forcings such as tectonic uplift erosion sediment transport and climate recently however it has become essential for the geomorphological community to also take into account biota as a geomorphological agent that has a role in shaping the landscape even if at a different scale and magnitude from that of geology although the modern literature is flourishing on the impacts of vegetation on geomorphic processes the study of anthropogenic pressures on geomorphology is still in its early stages topography emerges as a result of natural driving forces but some human activities such as mining agricultural practices and the construction of road networks directly or indirectly move large quantities of soil which leave clear topographic signatures embedded on the earth s morphology these signatures can cause drastic changes to the geomorphological organization of the landscape with direct consequences on earth surface processes this review provides an overview of the recent literature on the role of humans as a geological agent in shaping the morphology of the landscape we explore different contexts that are significantly characterized by anthropogenic topographic signatures landscapes affected by mining activities road networks and agricultural practices we underline the main characteristics of those landscapes and the implications of human impacts on earth surface processes the final section considers future challenges wherein we explore recent novelties and trials in the concept of anthropogenic geomorphology herein we focus on the role of high resolution topographic and remote sensing technologies the reconstruction or identification of artificial or anthropogenic topographies provides a mechanism for quantifying anthropogenic changes to landscape systems this study may allow an improved understanding and targeted mitigation of the processes driving geomorphic changes during anthropogenic development and help guide future research directions for development based watershed studies human society is deeply affecting the environment with consequences on the landscape therefore establishing improved management measures that consider the earth s rapidly changing systems is fundamental

long period geomagnetic secular variations since 12 000 yr bp a comparison of secular variation records of the geomagnetic field inclination obtained from palaeomagnetic studies of european and north american post glacial and late glacial sediments suggests that geomagnetic westward drift has persisted through the past 12 000 yr between 12 000 and 2 500 yr bp the overall average drift rate was between 0 14 and 0 16 deg yr 1 at 2 500 yr bp it is tentatively suggested that the drift rate increased and rose to a maximum of nearly 0 5 deg yr 1 before decreasing to historically observed values of 0 25 deg yr 1

restoring dense vegetation can slow mountain erosion to near natural benchmark levels tropical mountain areas may undergo rapid land degradation as demographic growth and intensified agriculture cause more people to migrate to fragile ecosystems to assess the extent of the resulting damage an erosion rate benchmark against which changes in erosion can be evaluated is required benchmarks reflecting natural erosion rates are usually not provided by conventional sediment fluxes which are often biased due to modern land use change and also miss large episodic events within the measuring period to overcome this we combined three independent assessment tools in the southern ecuadorian andes an area that is severely affected by soil erosion first denudation rates from cosmogenic nuclides in river sediment average over time periods of 1 100 k y and establish a natural benchmark of only 150 100 t km 2 yr 1 second we find that land use practices have increased modern sediment yields as derived from reservoir sedimentation rates which average over periods of 10 100 yr to as much as 15 10 3 t km 2 yr 1 third our land cover analysis has shown us that vegetation cover exerts first order control over present day erosion rates at the catchment scale areas with high vegetation density erode at rates that are characteristically similar to those of the natural benchmark regardless of whether the type of vegetation is native or anthropogenic therefore our data suggest that even in steep mountain environments sediment fluxes can slow to near their natural benchmark levels with suitable revegetation programs a set of techniques is now in place to evaluate the effectiveness of erosion mitigation strategies

the irrawaddy river sediment flux to the indian ocean the original nineteenth century data revisited the irrawaddy ayeyarwady river of myanmar is ranked as having the fifth largest suspended load and the fourthhighest total dissolved load of the world s rivers and the combined irrawaddy and salween thanlwin system is regarded as contributing 20 of the total flux of material from the himalayan tibetan orogen the estimates for the irrawaddy are taken from published quotations of a nineteenth century data set and there are no available published data for the myanmar reaches of the salween apart from our own field studies in 2005 and 2006 no recent research documenting the sediment load of these important large rivers has been conducted although their contribution to biogeochemical cycles and ocean geochemistry is clearly significant we present a reanalysis of the irrawaddy data from the original 550 page report of gordon covering 10 yr of discharge 1869 1879 and 1 yr of sediment concentration measurements 1877 1878 we describe gordon s methodologies evaluate his measurements and calculations and the adjustments he made to his data set and present our revised interpretation of nineteenth century discharge and sediment load with an estimate of uncertainty the 10 yr average of annual suspended sediment load currently cited in the literature is assessed as being underestimated by 27 on the basis of our sediment rating curve of the nineteenthcentury data on the basis of our sampling of suspended load the nineteenth century concentrations are interpreted to be missing about 18 of their total mass which is the proportion of sediment recovered by a 0 45 mm filter the new annual irrawaddy suspended sediment load is mt our revised estimate of the annual sediment load 364 60 from the irrawaddy salween system for the nineteenth century 600 mt represents more than half the present day ganges brahmaputra flux to the indian ocean since major chinese rivers have reduced their load due to damming the irrawaddy is likely the third largest contributor of sediment load in the world

calculated variations of annual ice ablation at the margin of the greenland ice sheet west greenland 1961 90 annual ice ablation has been measured at three locations at the margin of the greenland ice sheet nordbogletscher for 6 years 1977 78 to 1982 83 qaman rssup sermia 8 years 1979 80 to 1986 87 and at paakitsup akuliarusersua 7 years 1982 83 to the present as the data sets cover different periods it is difficult to compare ablation directly between the three sites however measured series at each site can be extended over the last 30 years 1961 90 by simulations using climatic data and the extended data series can be compared

natural controls of fluvial denudation rates in major world drainage basins we present a new compilation of estimates of modern rates of mechanical and chemical denudation for externally drained basins exceeding 5 105 km2 in area these estimates are based on sediment and solute load data selected in order to represent natural rates as far as possible chemical denudation rates have been calculated by deducting the nondenudational component of solute load mechanical denudation rates range from 1 mm kyr 1 for the st lawrence and dnepr basins to 670 mm kyr 1 for the brahmaputra basin chemical denudation rates vary from 1 mm kyr 1 kolyma niger nile and rio grande basins to 27 mm kyr 1 chiang jiang basin the kolyma basin has the lowest 4 mm kyr 1 and the brahmaputra basin the highest overall rate of denudation 688 mm kyr 1 relationships between denudation rates and a range of morphometric hydrologic and climatic variables are investigated through correlation and regression analysis morphometric variables such as mean local relief are accurately calculated for large basins for the first time by using the national geophysical data center 10 minute topographic database variables expressing basin relief characteristics and runoff are found to be most strongly associated with both mechanical and chemical denudation rates with more than 60 of the variance in total denudation being accounted for by basin relief ratio and runoff basin area runoff variability and mean temperature however are only weakly associated with rates of denudation although direct comparisons cannot be made it appears that rates of basin denudation derived from present day mass flux estimates are not overall significantly different from estimates of long term rates based on sediment volume and thermochronologic data it therefore appears that the key factors identified as controlling denudation rates here are also applicable to the geological time spans relevant to the interaction between tectonic and denudational processes

erosion rates of alpine bedrock summit surfaces deduced from in situ 10be and 26al we have measured the concentration of in situ produced cosmogenic 10be and 26al from bare bedrock surfaces on summit flats in four western u s mountain ranges the maximum mean bare bedrock erosion rate from these alpine environments is 7 6 3 9 m my 1 individual measurements vary between 2 and 19 m my 1 these erosion rates are similar to previous cosmogenic radionuclide crn erosion rates measured in other environments except for those from extremely arid regions this indicates that bare bedrock is not weathered into transportable material more rapidly in alpine environments than in other environments even though frost weathering should be intense in these areas our crn deduced point measurements of bedrock erosion are slower than typical basin averaged denudation rates 50 m my 1 if our measured crn erosion rates are accurate indicators of the rate at which summit flats are lowered by erosion then relief in the mountain ranges examined here is probably increasing we develop a model of outcrop erosion to investigate the magnitude of errors associated with applying the steady state erosion model to episodically eroding outcrops our simulations show that interpreting measurements with the steady state erosion model can yield erosion rates which are either greater or less than the actual long term mean erosion rate while errors resulting from episodic erosion are potentially greater than both measurement and production rate errors for single samples the mean value of many steady state erosion rate measurements provides a much better estimate of the long term erosion rate

time series analysis of the 10 000 yr geomagnetic secular variation record from se australia summary a 10 000 yr continuous secular variation record from intensively dated lake sediments in se australia has been subjected to periodogram and maximum entropy method analysis tests on synthetic data reveal some of the limitations of the latter method particularly when applied to complex number series anticlockwise precession of the magnetic vector at a period of 5000 1000 yr is tentatively ascribed to dipole precession and clockwise precession at a period of about 2800 yr is probably due to westward drift of features of the non dipole field the effect of calibrating the radiocarbon time scale is important and results in periodicity shifts of up to 25 per cent even for well dated lacustrine sequences power spectra are poorly constrained it is thus possible that the geomagnetic secular variation on a time scale of thousands of years is more uniform than often supposed mismatches between declination and inclination spectra can arise as a natural consequence of certain types of source mechanism and should not be simply attributed to figments of the analysis employed

rates of continental erosion and mountain building the first objective of this work was to obtain values for the rates at which continental erosion can smooth out or remove the topographic expression produced by orogeny the dominant part is played by mechanical erosion which acts most strongly in regions of large topographic expression chemical erosion depends strongly on precipitation or runoff in individual river drainage basins but because most continents have very similar average rainfall chemical erosion is fairly uniform for continental sized areas and will succeed in planing down all continents to a level peneplain if given enough time the exception to this rule is australia which has a very low chemical erosion rate because of its dryness the time constants for mechanical and chemical erosion so obtained vary between about 30 and 300 my depending on the continent and the assumptions made mountain building occurs throughout the geological time scale but at a non uniform rate although there will not be a balance between erosion and mountain building over a short time scale due to the non uniform rate of mountain building the long term situation must be that the two phenomena should balance out it is shown that the freeboard of continents will respond to the long term balance between mountain building and erosion an expression has been derived for the average continental elevation in which the rate of mountain building depends on the rate of radiogenic heat production within the earth it is shown that relatively small changes in average elevation above sea level of a few hundred metres are predicted to have occurred since the beginning of the proterozoic as mountain building is predicted to decrease on average with time because of the reduction in internal heat generation and as erosion is dependent on the average elevation this average elevation will decrease slowly through time the opposite of what some workers have predicted a more complicated model of mountain building is then investigated in which one component of mountain building has a sinusoidal signal the oscillations in average elevation depend on the period of the sinusoid being smaller for shorter periods finally an average continental elevation is derived using a list of real orogenic events although this list of orogenies is incomplete there is some indication that the actual continental elevation as seen in the flooding history of the continents is similar to that derived in this paper

combining geomorphometry feature extraction techniques and earth surface processes research the way forward abstract in recent years the wealth of technological development revolutionised our ability to collect data in geosciences due to the unprecedented level of detail of these datasets geomorphologists are facing new challenges giving more in depth answers to a broad er range of fundamental questions across the full spectrum of the earth s and planetary processes this contribution builds on the existing literature of geomorphometry the science of quantitative land surface analysis and feature extraction translate land surface parameters into extents of geomorphological elements it provides evidence of critical themes as well as emerging fields of future research in the digital realm supporting the likely effectiveness of geomorphometry and feature extractions as they are advancing the theoretical empirical and applied dimension of geomorphology the review further discusses the role of geomorphometric legacies and scientific reproducibility and how they can be implemented in the hope that this will facilitate action towards improving the transparency and efficiency of scientific research and accelerate discoveries in geomorphology in the current landscape substantial changes in landforms ecosystems land use hydrological routing and direct anthropogenic modifications impact systems across the full spectrum of geomorphological processes although uncertainties in the precise nature and likelihood of changes exist geomorphometry and feature extraction can aid exploring process regimes and landscape responses taken together they can revolutionise geomorphology by opening the doors to improved investigations crossing space and time scales blurring the boundaries between traditional approaches and computer modelling and facilitating cross disciplinary research ultimately the exploitation of the available wealth of digital information can help to translate our understanding of geomorphic processes which is often based on observations of past or current conditions into the rapidly changing future

rare earth and trace elements of microbialites in upper jurassic coral and sponge microbialite reefs major trace y zr pb th and u rare earth element ree and sm nd isotope analyses were carried out on microbialites and detrital carbonate sediments collected in upper jurassic coral and sponge microbialite reef settings selected bioconstructions developed in various palaeogeographic settings and depositional environments on northwestern tethys and eastern atlantic margins pure carbonate lagoon carbonate dominated deep shelf to epicontinental basin and mixed carbonate siliciclastic shallow ramp and lagoon the proximity to terrigenous sources directly controlled ree patterns of carbonate samples lateral and intrareef sediments and to a lesser degree stromatolitic microbial crusts are more susceptible to contamination by terrigenous material than are microbialites of thrombolitic fabric in mixed carbonate siliciclastic settings microbialites display a flat shale normalized ree pattern in pure carbonate lagoonal settings microbialites have shale normalized ree patterns similar to those of modern seawaters with a negative ce anomaly ce ce up to 0 14 positive la and gd anomalies and light ree depletion relative to heavy ree these data imply that similar ree chemistry than modern seawater already occurred on the northwestern tethys margin at the upper jurassic strong negative ce anomalies b0 4 imply microbialite formation in well oxygenated seawaters both in coral reefs of pure carbonate lagoonal environments pagny sur meuse and sponge bioherms of deep shelf settings plettenberg absence of positive ce anomalies rules out an influence of alkaline and high ph seawaters thus ree patterns and nd isotopic signatures which are in perfect agreement with existing results for tethysian seawater confirm that microbialites can be used as proxies of palaeoenvironmental seawater chemical characteristics

the worldwide character of the 1969 1970 impulse of the secular acceleration rate abstract this paper continues earlier studies to ascertain whether the distribution of the 1969 1970 jump of the secular variation rate has a worldwide character the geometry of the jump presents some similarities with the geometry of the secular variation itself we give a new estimation of the westward drift rate and information about spatial and temporal variations of the secular variation field

rates and spatial variations of soil erosion in europe a study based on erosion plot data an extensive database of short to medium term erosion rates as measured on erosion plots in europe under natural rainfall was compiled from the literature statistical analysis confirmed the dominant influence of land use and cover on soil erosion rates sheet and rill erosion rates are highest on bare soil vineyards show the second highest soil losses followed by other arable lands spring crops orchards and winter crops a land with a permanent vegetation cover shrubs grassland and forest is characterised by soil losses which are generally more than an order of magnitude lower than those on arable land disturbance of permanent vegetation by fire leads to momentarily higher erosion rates but rates are still lower than those measured on arable land we also noticed important regional differences in erosion rates erosion rates are generally much lower in the mediterranean as compared to other areas in europe this is mainly attributed to the high soil stoniness in the mediterranean measured erosion rates on arable and bare land were related to topography slope steepness and length and soil texture while this was not the case for plots with a permanent land cover we attribute this to a fundamental difference in runoff generation and sediment transfer according to land cover types on the basis of these results we calculated mean sheet and rill erosion rates for the european area covered by the corine database estimated rill and interrill erosion rates are ca 1 2 t ha 1 year for the whole corine area and ca 3 6 t ha 1 year 1 for arable land these estimates are much lower than some earlier estimates which were based on the erroneous extrapolation of small datasets high erosion rates occur in areas dominated by vineyards the hilly loess areas in west and central europe and the agricultural areas located in the piedmont areas of the major european mountain ranges c 2010 elsevier b v all rights reserved