tracing mechanisms controlling the release of dissolved silicon in forest soil solutions using si isotopes and ge si ratios the terrestrial biogenic si bsi pool in the soil plant system is ubiquitous and substantial likely impacting the land ocean transfer of dissolved si dsi here we consider the mechanisms controlling dsi in forest soil in a temperate granitic ecosystem that would differ from previous works mostly focused on tropical environments this study aims at tracing the source of dsi in forest floor leachates and in soil solutions under various tree species at homogeneous soil and climate conditions using stable si isotopes and ge si ratios relative to granitic bedrock clays minerals were enriched in si 28 and had high ge si ratios while bsi from phytoliths was also enriched in si 28 but had a low ge si ratio such a contrast is useful to infer the relative contribution of silicate weathering and bsi dissolution in the shallow soil on the release of dsi in forest floor leachate solutions the delta si 30 values in forest floor leachates 1 38 parts per thousand to 2 05 parts per thousand are the lightest ever found in natural waters and ge si ratios are higher in forest floor leachates relative to soil solution these results suggest dissolution of si 28 and ge enriched secondary clay minerals incorporated by bioturbation in organic rich horizons in combination with an isotopic fractionation releasing preferentially light si isotopes during this dissolution process ge si ratios in soil solutions are governed by incongruent weathering of primary minerals and neoformation of secondary clays minerals tree species influence si isotopic compositions and ge si ratios in forest floor leachates through differing incorporation of minerals in organic horizons by bioturbation and to a lesser extent through differing si recycling c 2010 elsevier ltd all rights reserved

finite difference calculation of traveltimes in three dimensions the traveltimes of first arriving seismic rays through most velocity structures can be computed rapidly on a three dimensional numerical grid by finite difference extrapolation head waves are properly treated and shadow zones are filled by the appropriate diffractions differences of less than 0 11 percent are found between the results of this technique and ray tracing for a complex but smooth model this scheme has proven useful for earthquake location and shows promise as an inexpensive well behaved substitute for ray tracing in forward modeling and kirchhoff inversion applications

high resolution velocity structure beneath mount vesuvius from seismic array data 1 a high resolution p wave image of mt vesuvius edifice has been derived from simultaneous inversion of travel times and hypocentral parameters of local earthquakes land based shots and small aperture array data the results give details down to 300 500 m the relocated local seismicity appears to extend down to 5 km below the central crater distributed in a major cluster centered at 3 km below the central crater and in a minor group with diffuse hypocenters inside the volcanic edifice the two clusters are separated by an anomalously high vp region at around 1 km depth a zone with high vp vs in the upper layers is interpreted as produced by the presence of intense fluid circulation the highest energy quakes up to m 3 6 are located in the deeper cluster in a high p wave velocity zone our results favor an interpretation in terms of absence of shallow magma reservoirs

accurate fault mechanism determinations for a 1984 earthquake swarm at campi flegrei caldera italy during an unrest episode implications for volcanological research we have analyzed 42 microearthquakes 1 ml 3 that occurred at campi flegrei volcanic area during an intense swarm like activity more than 500 events in half a day in the last period of strong ground uplift 1982 1984 focal mechanisms of these earthquakes have been computed by a probability method which uses p wave polarity and s wave polarization data composite focal mechanisms for different groups of earthquakes have also been computed by the same technique results show a well defined fault plane in agreement with the elongation of the epicentral pattern the orientation and dip of this fault plane together with other observations about hypocenter locations and focal mechanisms of the whole seismicity accompanying the ground uplift episode suggest the presence of an elliptical fracture system at the caldera center this fracture system dipping toward the center of the caldera should represent the limit of the most recent caldera collapse which is also indicated by a negative bouguer gravity anomaly moreover an important differential feature among various groups of earthquakes has been shown namely a rotation up to about 30 of the strike of the compressive stress axis between the easternmost and the westernmost events the resulting pattern indicates that the axis is always oriented towards the town of pozzuoli which roughly represents the very center of the caldera and also the center of symmetry of the ground deformation these observations strongly suggest that earthquakes are generated by the variation of the stress field associated with the deformation along prefractured zones because of their greater weakeness this study provides then the first direct evidence that both seismicity and ground deformations have a common origin

active stress map of italy we present a new map of the present day stress field in italy obtained from all the available data the map reports 200 horizontal stress directions inferred from 109 borehole breakout data 44 centroid moment tensor solutions 34 other focal mechanisms most of which are from polarity distributions seven stress inversions of microearthquake data two averages of t and p axes of earthquake focal mechanisms in zones of diffuse seismic activity and four fault slip data the integration of breakout data which yield horizontal stress directions with fault plane solutions which reflect the stress regime allows us to obtain an improved map of the present day stress in italy this stress field map can be used for a better comprehension of active tectonic processes for seismic hazard assessment and to foresee the behavior of faults recognized with other methods stress directions obtained from different data although relative to different depth intervals e g 0 7 km for breakouts and 0 20 km for most of the earthquakes and to different tectonic units are consistent since many regions in italy are characterized by an extensional stress regime we report the minimum horizontal stress shmin orientations the map shows that an extensional regime affects most of the apenninic belt conversely a compressional or transpressional regime characterizes the eastern alps the eastern side of the northern apennines and the southern tyrrhenian to northern sicily zone an abrupt change in stress directions marks the transition between northern and southern apennines suggesting that the two arcs are characterized by a different tectonic setting and recent evolution in this paper we report all the data analyzed to date with their geographic coordinates and average stress directions and we describe the main stress provinces in italy in the framework of the tectonic evolution of the region

influences of anthropogenic activities on dissolved silica migration in a granite hosted basin hainan island china abstract the continent ocean transfer of dissolved silica dsi formed as sio2 via rivers constitutes an important part of the global silica cycle the uptake of terrestrial vegetation and riverine phytoplankton are the key process controlling dsi migration within the drainage basin anthropogenic activities including land use change and damming have been altering dsi export by changing biological uptakes in the basin a significant artificial lake effect of damming was exhibited on the spatial variations of chlorophyll a chl a and dsi which caused 15 39 of riverine dsi to be detained in the reservoir region of changhuajiang river basin hainan island china the biological uptake of terrestrial vegetation was behindhand responsible for seasonal fluctuations of dsi the dsi uptake yields ranged from 19 44 t km2 yr to 86 76 t km2 yr during the different terrestrial vegetation types in the basin in turn tropical rainforest crops artificial economic forests grassland the try calculating of the dsi yield released by the silicates weathering was carried out taking biological processes in the basin into account taking into the plants uptake within the basin consideration the corrected dsi yield from the silicates weathering was 18 6 t km2 yr accordingly the silicates weathering rate was up to 41 55 t km2 yr which was 1 36 times higher than that 30 39 t km2 yr without consideration of the biological uptake and close to the fastest weathering rate of the granite basin puerto rico in the earth surface of the dsi released by the silicates weathering 28 56 was absorbed by terrestrial vegetation and 31 43 was consumed by riverine phytoplankton and the rest was drainaged into the south china sea

dem based modelling of surface runoff using diffusion wave equation a digital elevation model dem based overland flow routing model was developed for computation of surface runoff for isolated storm events the model operates on a grid or cell basis and routes the rainfall excess generated over the cells following the dem derived drainage paths to the catchment outlet the rainfall excess for each cell of the catchment was computed using the philip two term infiltration model utilizing the physical properties of the cell the overland flow was described by a finite volume based numerical solution of the diffusion wave approximation of the st venant equations the cell physical properties such as topographic characteristics land use soil etc were extracted from published maps for discretized cells of the catchment using a geographic information system the results of model application indicate that the model satisfactorily predicted the runoff hydrograph the cell based structure of the model allowed for generation of spatially distributed catchment information in terms of the model computed variables such as the depth of flow and discharge

chemical weathering in granitic environments abstract factors controlling chemical weathering in granitic environments are deduced using an extensive database from the literature based on a transition state theory model we evaluated the effects on chemical weathering of runoff temperature and ph the dependence between temperature and runoff and chemical weathering is complicated by other factors such as the presence depth of soil cover soil cover favors chemical weathering when it is thin and rich in weatherable minerals in contrast it reduces chemical weathering when is thick and poor in primary minerals processes that increase the contact time and the surface of the water rock interactions such as physical denudation increase chemical weathering rates in granitic environments the effect of temperature can be quantified assuming an apparent activation energy value of 48 7 kj mol to describe chemical weathering of silica in granitic crystalline environment under high runoff conditions

atmospheric co2 sink silicate weathering or carbonate weathering it is widely accepted that chemical weathering of ca silicate rocks could potentially control long term climate change by providing feedback interaction with atmospheric co2 drawdown by means of precipitation of carbonate and that in contrast weathering of carbonate rocks has not an equivalent impact because all of the co2 consumed in the weathering process is returned to the atmosphere by the comparatively rapid precipitation of carbonates in the oceans here it is shown that the rapid kinetics of carbonate dissolution and the importance of small amounts of carbonate minerals in controlling the dissolved inorganic c dic of silicate watersheds coupled with aquatic photosynthetic uptake of the weatheringrelated dic and burial of some of the resulting organic c suggest that the atmospheric co2 sink from carbonate weathering may previously have been underestimated by a factor of about 3 amounting to 0 477 pg c a this indicates that the contribution of silicate weathering to the atmospheric co2 sink may be only 6 while the other 94 is by carbonate weathering therefore the atmospheric co2 sink by carbonate weathering might be significant in controlling both the short term and long term climate changes this questions the traditional point of view that only chemical weathering of ca silicate rocks potentially controls long term climate change

controls on intense silicate weathering in a tropical river southwestern india the silicate weathering rate swr and associated carbon dioxide consumption rate ccr in tropical silicate terrain is assessed through a study of the major ion chemistry in a small west flowing river of peninsular india the nethravati river the specific features of the river basin are high mean annual rainfall and temperature high runoff and a precambrian basement composed of granitic gneiss charnockite and minor metasediments the water samples n 56 were collected from three locations along the nethravati river and from two of its tributaries over a period of twelve months chemical weathering rate cwr for the entire watershed is calculated by applying rainwater correction using river chloride as a tracer chemical weathering rate in the nethravati watershed is estimated to 44 t km 2 y 1 encompassing a swr of 42 t km 2 y 1 and a maximum carbonate contribution of 2 t km 2 y 1 this swr is among the highest reported for granito gneissic terrains the assessed ccr is 2 9 10 5 mol km 2 y 1 the weathering index re calculated from molecular ratios of dissolved cations and silica in the river suggests an intense silicate weathering leading to kaolinite gibbsite precipitation in the weathering covers the intense swr and ccr could be due to the combination of high runoff and temperature along with the thickness and nature of the weathering cover the comparison of silicate weathering fluxes with other watersheds reveals that under similar morpho climatic settings basalt weathering would be 2 5 times higher than the granite gneissic rocks c 2012 elsevier b v all rights reserved

three dimensional p and s wave velocity structure of redoubt volcano alaska the three dimensional p and s wave structure of redoubt volcano alaska and the underlying crust to depths of 7 8 km is determined from 6219 p wave and 4008 s wave first arrival times recorded by a 30 station seismograph network deployed on and around the volcano first arrival times are calculated using a finite difference technique which allows for flexible parameterization of the slowness model and easy inclusion of topography and source receiver geometry the three dimensional p wave velocity structure and hypocenters are determined simultaneously while the three dimensional s wave velocity model is determined using the relocated seismicity and an initial s wave velocity model derived from the p wave velocity model assuming an average vp vs ratio of 1 78 convergence is steady with approximately 73 and 52 reduction in p and s wave arrival time rms respectively after 10 iterations the most prominent feature observed in the three dimensional velocity models derived for both p and s waves is a relative low velocity near vertical pipelike structure approximately 1 km in diameter that extends from 1 to 6 km beneath sea level this feature aligns axially with the bulk of seismicity and is interpreted as a highly fractured and altered zone encompassing a magma conduit the velocity structure beneath the north flank of the volcano between depths of 1 and 6 km is characterized by large lateral velocity variations high velocities within this region are interpreted as remnant dikes and sills and low velocities as regions along which magma migrates no large low velocity body suggestive of a magma chamber is resolved in the upper 7 8 km of the crust

three dimensional p wave velocity structure of mt etna italy the three dimensional p wave velocity structure of mt etna is determined to depths of 15 km by tomographic inversion of first arrival times from local earthquakes recorded by a network of 29 permanent and temporary seismographs results show a near vertical low velocity zone that extends from beneath the central craters to a depth of 10 km this low velocity region is coincident with a band of steeply dipping seismicity suggesting a magmatic conduit that feeds the summit eruptions the most prominent structure is an approximately 8 km diameter high velocity body located between 2 and 12 km depth below the southeast flank of the volcano this high velocity body is interpreted as a remnant mafic intrusion that is an important structural feature influencing both volcanism and east flank slope stability and faulting

automated river course ridge and basin delineation from digital elevation data starting from a digital elevation model dem formed by a triangular irregular network tin of facets an algorithm that allows for the tracking of the path of steepest slope downstream or upstream from any point on the topographic surface has been developed the analysis shows that when starting such a path in a downstream upstream direction from point p down up to a point m and then from point m in an upstream downstream direction and if the path returns to point p then the segment pm corresponds to a pure streamline otherwise it corresponds to a river course ridge this property allows an easy way to delineate the network of river courses and ridges likewise the repetitive use of this algorithm allows for the definition of basin and sub basins also called contributing areas to any point on a river course finally it is shown how a regular grid dem can be treated as a particular case of the tin dem which gives generality to the presented procedures

a contour based topographic model for hydrological and ecological applications a digital model for discretizing three dimensional terrain into small irregularly shaped polygons or elements based on contour lines and their orthogonals is described from this subdivision the model estimates a number of topographic attributes for each element including the total upslope contributing area element area slope and aspect this form of discretization of a catchment produces natural units for problems involving water flow as either a surface or subsurface flow phenomenon the model therefore has wide potential application for representing the three dimensionality of natural terrain and water flow processes in the fields of hydrology sedimentology and geomorphology three example applications are presented and discussed they are the prediction of zones of surface saturation the prediction of the distribution of potential daily solar radiation and the prediction of zones of erosion and deposition in a catchment

an integrated physically based model for arid region flash flood prediction capable of simulating dynamic transmission loss this paper outlines a physically based model developed for prediction of both arid region flash floods and associated transmission loss it is based on coupling numerical solutions of the st venant equations and the kinematic wave equation for channel and overland flow routing respectively with the richards equation for the determination of infiltration these hydrological components are integrated in one comprehensive model for the above mentioned purposes the robustness of the model and its components have been tested and it has then been applied to a medium size catchment in an arid region the results indicate that reasonable simulations can be achieved with a minimum of calibration but point to problems of representing input rainfall conditions with the necessary time and space resolutions 1998 john wiley sons ltd

riverine hydrochemistry and co2 consumption in the tropic monsoon region a case study in a granite hosted basin hainan island china to evaluate the carbon sink capacity caused by rock chemical weathering processes and its controlling factors in the tropical monsoon region the hydrochemistry of the granite hosted changhuajiang river chjr basin in hainan island china were systematically investigated by collecting water samples from the river mouth to headwater in the dry season and the wet season respectively the results show that na ca2 and hco3 are dominant in the chemical runoff of the chjr the spatial and temporal variations of major ions imply the influence of the multi sources the concentrations of ca2 mg2 hco3 and dsi mainly sourcing from rock silicates and carbonates weathering are lower in the wet season than those in the dry season however the concentrations of k cl so4 2 and no3 mainly sourcing from the atmospheric precipitation and human activities are significantly controlled by the monsoon rainfall and hydrological stage in the chjr basin the contributions of the silicates chemical weathering human activities atmospheric input evaporites dissolution and carbonates chemical weathering to the chemical runoff are 82 62 9 05 5 24 2 05 and 1 05 in the chjr respectively the chemical weathering rates of silicates carbonates and evaporites are 16 25 0 40 and 0 62 t km 2 year 1 respectively chemical weathering rates in global granite hosted basins significantly correlate with temperatures p 10 c on a regional scale we find that the chemical weathering rates in the southern china appear a weak positive correlation with normalized differential vegetation indexes ndvi which need to be confirmed by enough data the flux of atmospheric co2 consumption from rock weathering in the chjr basin is 2 71 105 mol km 2 year 1 by the discharge water of 2014 with being close to that 2 9 105 mol km 2 year 1 in the other tropical basins and far from that 5 06 105 mol km 2 year 1 calculated by the averaged discharge water of over years in the chjr the silicates weathering intensity lies at the moderate phase implying that the weathering processes are still developing in global tropical granite basins hence how the atmospheric co2 consumption from rock weathering will change with increasing the atmospheric co2 level and dam construction altering water cycle in the tropical monsoon area is expected to be deserved

the effects of weathering variability and anthropogenic pressures upon silicon cycling in an intertropical watershed tana river kenya abstract we present the first study of the si isotopic composition of dry season river waters from the tana river kenya data encompasses the entire river basin with samples collected from headwaters to the estuary thereby capturing a salinity gradient in the headwaters the isotopic signature is affected by climate as a result of its control on soil drainage and weathering the 30 si signatures in the basin range from 0 69 up to 2 23 signatures are clearly affected by dams an increase in 30 si ratios of 0 54 and a decrease in the dissolved si dsi concentration by 41 were observed downstream of the masinga dam the largest of a succession of 5 hydroelectric dams this reduction in si load is most likely due to increased diatom productivity as the corresponding change in 30 si signature is consistent with the known fractionation by these organisms the 30 si composition of waters entering the estuary is ca 2 and dsi concentrations are 349 m in the estuary the dsi concentrations decrease linearly following the salinity while the 30 si ratio remains stable indicating the absence of processes affecting the dsi pool for the studied range of salinity

hot dry rock geothermal potential of the xujiaweizi area in songliao basin northeastern china a series of studies was conducted to determine a suitable site for enhanced geothermal systems egss in mainland china first the xujiaweizi xjwz area in the songliao basin in northeastern china was identified to possess several features indicating a huge potential for hot dry rock hdr resource development from the aspects of tectonics geology geophysics and geothermics then a hydraulic fracturing model based on the real geological and logging data of well ys 2 and field fracturing experience in this region was established and the geometric dimension and flow conductivity of the induced fracture were imported into a 3d hydrothermal coupled model established using tough2 eos1 the electricity generation potential of the fractured reservoir using three horizontal well production patterns is evaluated finally three enhanced methods are proposed and discussed based on the simulation results results indicate that hdr resources in the xjwz area demonstrate a significant potential for development from the aspect of geology the yingcheng formation is selected as the potential target formation the gel proppant fracturing method is adopted in consideration of the undeveloped natural fractures in the target formation the generalized egs reservoir region possessed a considerable length of 600 m the maximum production flow rate is determined to be 1 kg s the water flow impedance is relatively high during the heat production process for economic exploitation such an egs reservoir has poor electricity generation capacity a naturally fractured reservoir with a higher temperature should be targeted for electricity generation

the human impact in geomorphology 50 years of change abstract concern with the human impact in geomorphology has a long history what is new is that since 1969 a number of developments have taken place that have led to an increasing realisation of its importance these developments are in four main areas i intellectual and policy related ii technological developments that alter geomorphological processes iii demographic trends and iv the proliferation of techniques for the study of landform and process change there has been a realisation of the role of humans in landscape transformation in ancient times the human impact has developed through time but particularly notable are the potential early effects of fire extinctions and deforestation on geomorphological processes the spread of european agriculture particularly in the nineteenth century transformed erosion and sedimentation rates in many parts of the world notwithstanding the importance of some of these changes in prehistoric and historic times recent researches have demonstrated that humans have become an increasingly important agent of geomorphological change during the period of the great acceleration of the past five or six decades the interest in global warming that has developed since the early 1980s has created considerable interest in its consequences for a range of geomorphological phenomena it is also becoming apparent that anthropogenic geomorphological change is having an impact on the earth system as a whole finally geomorphologists have taken an increasing interest in how they can make an impact in the field of landscape conservation

the bay of naples southern italy constraints on the volcanic structures inferred from a dense seismic survey 1 the bays of naples and pozzuoli host volcanic areas that have been active within recent history in addition the vicinities areas around the vesuvius volcano and the campi flegrei caldera are extremely densely inhabited over the past decade this situation has prompted several active seismic experiments focused on the vesuvius volcano more recently the serapis active seismic survey covered the entire bay of naples with particular attention to pozzuoli bay the processed serapis p wave travel time collection extended with a previously acquired data set has allowed the computation of the most comprehensive three dimensional p wave velocity distribution for the bay of naples which includes a small scale high resolution model of the campi flegrei caldera the joint interpretation of the velocity distribution together with both the available gravity measurements and models and the geothermal drilling information has allowed us to locate and map lithological units at depths we propose a model of the campi flegrei caldera in relation to the underlying mesozoic limestone unit in this model no magma chamber exists in the upper 6 km beneath the bay of naples the feeding system of the campi flegrei caldera is directly controlled by the tectonic structures affecting the limestone unit beneath the bay of naples two ne sw normal faults run beneath the vesuvius volcano and campi flegrei which are related to the pre pleistocene apenninic tectonics

the restless resurgent campi flegrei nested caldera italy constraints on its evolution and configuration abstract we have collected new stratigraphic data in the campi flegrei caldera through surface geological mapping and study of cores drilled to various depths we integrate these data with geological geochronological and geophysical constraints available in the literature to reconstruct the volcanic and deformational history of the caldera the caldera is a resurgent nested structure resulting from two main collapses related to the campanian ignimbrite 37 ka and the neapolitan yellow tuff 12 ka eruptions while the structure is affected by a broad subsidence ongoing local resurgence and unrest occur inside the younger nested caldera structure although most of the caldera floor consists of multiple structural blocks due to long term deformations magmas were able to erupt only in one sector of the resurgent part the caldera has shown signs of unrest during the past 25 years with short term deformations that have generated a net uplift of 3 5 m the short term deformations are related to the neapolitan yellow tuff caldera resurgence and interpreted as the net result of brittle and ductile components the long term deformations likely represent the sum of the permanent brittle component of each short term deformational event

plant impact on the biogeochemical cycle of silicon and related weathering processes abstract the contribution of plants to the biogeochemical cycle of si and related weathering processes was studied in an equatorial rainforest ecosystem congo where the biologic turnover of si is high 58 to 76 kg ha y litterfall leaves a soil profile and groundwaters were analysed phytoliths and organic matter have a similar distribution with depth in the soil profile the model of a bicompartmental distribution of organic matter is applied to phytolith distribution and shows that about 92 of the biogenic silica input is rapidly recycled while about 8 of the biogenic silica input supplies a stable pool of phytoliths with a lower turnover reprecipitation of silica was observed at the base of the soil profile indicating a local geochemical environment that is oversaturated with respect to amorphous silica a balance in biogeochemical cycle of si requires that the vegetation absorb dissolved silicon released from weathering of minerals which otherwise would be available for mineral neoformation or export from the profile towards regional drainages plant uptake of si increases the chemical weathering rate without increasing the denudation rate this study shows that the uptake storage and release of si by the vegetation have to be taken into account when using dissolved si for tracing chemical weathering dynamics

source parameters and three dimensional attenuation structure from the inversion of microearthquake pulse width data qp imaging and inferences on the thermal state of the campi flegrei caldera southern italy the three dimensional p wave attenuation structure of the campi flegrei caldera and the estimate of source parameters for 87 local microearthquakes is obtained by the nonlinear inversion of pulse width and rise time measurements by using the method described by zollo and de lorenzo this issue source radii represent the better resolved parameters with values ranging from 70 m to 230 m the dip and strike angles defining fault orientations are usually affected by larger uncertainties and are well constrained only for 11 events the dip fault is usually confined in the range 30 60 with an average uncertainty of 12 the fault strikes mainly range between 60 and 60 and seem to define preferential directions oriented radially from the symmetry axis of the ground deformation stress drop estimates indicate rather low values 0 01 1 mpa which suggest low strength properties of the incoherent and brittle materials filling the caldera primarily yellow tuffs the three dimensional qp images obtained from the inversion of p pulse durations show two significant low qp anomalies between 0 and 1 km of depth in the north eastern sector and at 2 3 km of depth in the central eastern sector of the caldera the high degree of spatial correlation of the low qp zone and low vs as inferred by aster and meyer 1988 at 0 1 km in depth and other geophysical and geochemical observations suggest that this anomaly can be related to the presence of densely fractured porous and fluid filled rocks in the ne sector of the caldera the deeper low qp anomaly is interpreted as being related to a dominant thermal effect we used the surface and deep borehole temperature measurements available in the area to obtain a local calibration curve to convert qp in temperature at campi flegrei the retrieved t qp map shows a high thermal deep disturbance 450 500 c at depths between 2 and 3 km in the eastern sector of the caldera where the most recent eruptive activity is concentrated the present day temperature field retrieved by qp images has been interpreted by using a three dimensional thermal conduction model assuming an extended heat source initial temperature of 800 c located underneath the attenuation anomalous region the results indicate that the qp inferred temperature field can be related to the heat conduction effect of one or more molten bodies whose top should be at about 4 km depth consistent with recent seismic estimates of the magma chamber top at campi flegrei ferrucci et al 1992 this study suggests that the present thermal state and rock rheology of the inner caldera could be controlled by the cooling of molten bodies that originally intruded at depths of 1 4 1 6 km during one or more recent time of 10 kyr eruptive events

shift a distributed runoff model using irregular triangular facets abstract shift sistema hidrologico de facetas triangulares is a computational system that allows for the 1 creation editing and visualization of a watershed digital elevation model dem based on the triangular irregular network tin concepts 2 input and interpolation of soil river bed and rainfall data and 3 calculation and routing of runoff in all the facets and reaches the tin dem model is constructed from a set of points where the slope changes abruptly afterwards the drainage network is automatically identified and an interactive editor allows the addition or deletion of points to eliminate network discontinuities rainfall data are interpolated by means of a procedure based on the minimization of the bending energy of a thin plate in order to calculate and route the runoff the system determines the routing sequence of river segments and for each one identifies the facets forming the contributing area and determines a cascade of overland flow planes then for each element and time interval the system calculates the infiltration and routes the resultant runoff by a numerical solution of the kinematic wave equations this information is saved and the user can see the hydrograph for any facet or reach

geochemistry of the amazon 1 precipitation chemistry and the marine contribution to the dissolved load at the time of peak discharge analyses of precipitation and surface water are used to estimate the fluxes of marine cyclic salts through that part of the amazon river system draining past obidos 80 of the basin at the time of peak discharge in june amazon precipitation chemistry can be devided into two principal components marine and terrestrial the marine component determined from analyses of marine rain consists of na k mg ca and cl in approximately sea salt proportions with s doubly enriched the excess sulfur is probably derived from gas phase inputs the terrestrial component makes an important contribution of k ca s and n much of which can be related to biological emissions the emission of reduced sulfur in the marine and terrestrial environment and nitrogen in the terrestrial environment is responsible for a natural acid rain in the amazon region with a ph from 4 7 to 5 7 this is about one tenth the acidity of polluted urban rain the chloride content of lowland rivers which drain regions lacking significant geologic sources of chloride shows a systematic decrease in chloride with increasing distance from the ocean this trend is used to define the cyclic salt background for amazonian surface waters cyclic salts in general make only a minor contribution relative to terrestrial inputs to the chemistry of amazon basin rivers even those draining intensely weathered terrains an estimated 17 6 cl 6 9 na 1 3 mg 3 6 s 0 4 k and 0 1 ca of the dissolved load at obidos during peak discharge is cyclic

a geomorphologic kinematic wave gkw model for estimation of floods from small alpine watersheds keywords hydrologie reference hydram article 1999 004 record created on 2005 10 11 modified on 2016 08 08

chemical weathering and co2 consumption in the xijiang river basin south china monthly samples of riverine water were collected and analyzed for the concentrations of major ions ca2 mg2 k na hco3 so42 cl no3 dissolved silicon and total dissolved solids tds at wuzhou hydrological station located between the middle and lower reaches of the xijiang river xjr from march 2005 to april 2006 more frequent sampling and analysis were carried out during the catastrophic flooding in june 2005 stoichiometric analysis was applied for tracing sources of major ions and estimating co2 consumption from the chemical weathering of rocks the results demonstrate that the chemical weathering of carbonate and silicate rocks within the drainage basin is the main source of the dissolved chemical substances in the xjr some 81 20 of the riverine cations originated from the chemical weathering processes induced by carbonic acid 11 32 by sulfuric acid and the other 7 48 from the dissolution of gypsum and precipitates of sea salts within the drainage basin the co2 flux consumed by the rock chemical weathering within the xjr basin is 2 37 x 10 11 mol y 1 of which 0 64 x 10 11 mol y 1 results from silicate rock chemical weathering and 1 73 x 10 11 mol y 1 results from carbonate rock chemical weathering the co2 consumption comprises 0 38 x 10 11 mol during the 9 d catastrophic flooding the co2 consumption from rock chemical weathering in humid subtropical zones regulates atmospheric co2 level and constitutes a significant part of the global carbon budget the carbon sink potential of rock chemical weathering processes in the humid subtropical zones deserves extra attention c 2008 elsevier b v all rights reserved

p sv conversions at a shallow boundary beneath campi flegrei caldera italy evidence for the magma chamber seismograms from an active seismic experiment carried out at campi flegrei caldera near naples italy show a large amplitude 5v polarized shear wave following by less than 1 5 s p waves reflected at wide angle from a deep crustal interface early arriving sv polarized waves with the same delay to direct p waves are also observed in seismograms from a regional 280 km deep magnitude 5 1 earthquake such short delays of s to p waves are consistent with a p sv conversion on transmission occurring at a shallow boundary beneath the receivers the large amplitude of the converted sv phase along with that the p waves are near vertical requires a boundary separating a very low rigidity layer from the upper caldera fill the converted phases are interpreted as a seismic marker of a magma chamber the top of this magma chamber is located slightly deeper than the deepest earthquakes observed during the 1982 1984 unrest of campi flegrei

the present state of the magmatic system of the campi flegrei caldera based on a reconstruction of its behavior in the past 12 ka abstract new geochemical and sr isotope data have been acquired on samples representative of volcanic units erupted inside the resurgent campi flegrei caldera cfc over the past 12 ka these data integrated with previous published petrological and with newly acquired geochronological volcanological and geothermal data shed light on the nature and timing of the processes that controlled the evolution of the phlegraean magmatic system in the past 12 ka three isotopically and geochemically distinct magmatic components were erupted at the cfc as either homogeneous or mixed magma batches one component campanian ignimbrite component cic 87 sr 86 sr 0 70735 0 70740 is similar to the trachytic magma extruded during the first phase of the campanian ignimbrite ci eruption 37 ka a second component neapolitan yellow tuff component nytc 87 sr 86 sr 0 70750 0 70757 is similar to the latitic alkali trachytic magma batches extruded during the course of the neapolitan yellow tuff nyt eruption 12 ka a third component minopoli component mic 87 sr 86 sr 0 7086 is similar to the trachybasaltic magma of the minopoli 2 mi eruption 9 7 ka these components were erupted as either single batches of magma or mixed ci nyt or mi nyt batches of magma through vents located either along the structural boundary of the nyt caldera or inside the nyt caldera mainly on portions of the resurgent block under extensional stress the ci and nyt components represent residual portions of older large volume magma reservoirs which have fed eruptions since about 60 and 15 ka respectively the least evolved mi component was erupted only during the 12 9 5 ka and 8 6 8 2 ka epochs of activity through vents located on a ne sw regional fault system this component could represent a deeper reservoir tapped by the ne sw regional fault system reactivated after the nyt caldera collapse deeper mi and shallower ci and nyt magmatic systems interacted by mixing among batches of magma during their rise to surface overall the data suggest that the cfc magmatic system today is characterized by the presence of two larger independent reservoirs filled by residual portions of the ci and nyt magmas these generated many smaller shallower pockets of evolved magma that fed most of the eruptions that occurred in the cfc over the past 12 ka moreover a deeper reservoir mi tapped by the ne sw regional fault system provided batches of less evolved magma that mixed with magma present in the shallower pockets

quantitative analysis of land surface topography land surface topography significantly affects the processes of runoff and erosion a system which determines slope aspect and curvature in both the down slope and across slope directions is developed for an altitude matrix also the upslope drainage area and maximum drainage distance are determined for every point within the altitude matrix a fortran 66 program performs the analysis

terrestrial ecosystems and the global biogeochemical silica cycle 1 most research on the global si cycle has focused nearly exclusively on weathering or the oceanic si cycle and has not explored the complexity of the terrestrial biogeochemical cycle the global biogeochemical si cycle is of great interest because of its impact on global co2 concentrations through the combined processes of weathering of silicate minerals and transfer of co2 from the atmosphere to the lithosphere a sizable pool of si is contained as accumulations of amorphous silica or biogenic silica bsi in living tissues of growing plants known as phytoliths and after decomposition of organic material as remains in the soil the annual fixation of phytolith silica ranges from 60 200 tmol yr 1 and rivals that fixed in the oceanic biogeochemical cycle 240 tmol yr 1 internal recycling of the phytolith pool is intense with riverine fluxes of dissolved silicate to the oceans buffered by the terrestrial biogeochemical si cycle challenging the ability of weathering models to predict rates of weathering and consequently changes in global climate consideration must be given to the influence of the terrestrial bsi pool on variations in the global biogeochemical si cycle over geologic time and the influence man has had on modifying both the terrestrial and aquatic biogeochemical cycles

silicon and sediment transport of the changjiang river yangtze river could the three gorges reservoir be a filter water samples were collected from the changjiang river yangtze river in may 2005 after the impoundment of the three gorges reservoir tgr to examine the influence of the tgr and large lakes on material delivery to the estuary of the changjiang river the concentrations of suspended particle material spm dissolved silica dsi and biogenic silica bsi in the main stream were analyzed the concentrations of dsi and bsi in the main channel of the changjiang varied between 73 and 100 and 1 1 15 mol l with a distance weighted average of 81 and 8 0 mol l respectively a calculation shows that live diatom comprises only an average value of 5 2 of the bsi in the changjiang river and most of bsi may come from drainage basin the concentrations of bsi and the ratios of bsi spm were relatively low in the changjiang river compared to other rivers throughout the world but the bsi carried in suspension by the changjiang river was an important component of the rivers silicon load i e 13 spm dsi and bsi concentrations as observed in the changjiang river tend to decrease from the upper sections of the river to the three gorges dam tgd reflecting sedimentation associated with bsi trapping and dsi retention in the tgr in the normal water period spm and bsi retention are more strongly influenced by the tgd compared to dsi about 98 of spm 72 of bsi and 16 of dsi were retained within the tgr in may 2005 the fluxes variations of dsi bsi and spm suggested that the large lakes and dams had a coupled effect on the transportation of dsi bsi and spm in the normal water period such a change in silicon dsi and bsi balances of the changjiang river will affect the ecological environment of the changjiang estuary and its adjacent sea to some extent