subsurface flow in a soil mantled subtropical dolomite karst slope a field rainfall simulation study abstract soil and epikarst co evolve resulting in complex structures but their coupled structural effects on hydrological processes are poorly understood in karst regions this study examined the plot scale subsurface flow characteristics from an integrated soil epikarst system perspective in a humid subtropical cockpit karst region of southwest china a trench was excavated to the epikarst lower boundary for collecting individual subsurface flows in five sections with different soil thicknesses four field rainfall simulation experiments were carried out under different initial moisture conditions dry and wet and rainfall intensities 114 mm h 1 high and 46 mm h 1 low on average the soil epikarst system was characterized by shallow soil overlaying a highly irregular epikarst surface with a near steady infiltration rate of about 35 mm h 1 the subsurface flows occurred mainly along the soil epikarst interface and were dominated by preferential flow the subsurface flow hydrographs showed strong spatial variability and had high steady state coefficients 0 52 and 0 36 for high and low rainfall intensity events irregular epikarst surface combining with high vertical drainage capacity resulted in high threshold rainfall depths for subsurface flows 67 mm and 263 mm for initial wet and dry conditions respectively the above results evidenced that the irregular and permeable soil epikarst interface was a crucial component of soil epikarst architecture and consequently should be taken into account in the hydrological modeling for karst regions

undrained stress path of loose sand predicted from dry tests the constitutive properties of the soil skeleton of loose sand most relevant for predicting liquefaction flow slides are contraction and elastic compressibility they can be determined with dry triaxial tests a mathematical description of these idryi properties is presented and used to predict the specific stress path found in undrained triaxial tests a comparison between predicted and measured stress paths is discussed resume les propriotos de comportement du squelette de sable meuble les plus pertinentes pour prodire les couloes par liquofaction sont la contraction et la compessibilito olastique elles peuvent tre doterminoes par des essais triaxiaux secs une description mathomatique de ces propriotos sches est prosentoe et utilisoe pour prodire le cheminement de contraintes spocifique trouvo dans les essais triaxiaux une comparaison entre les cheminements mesuros et prodits est discutoe mots clos sable meuble liquofaction cheminement de contraintes non drainoes porosito mouilloe critique otat permanent traduit par la rodaction

predicting ground water movement in large mine spoil areas in the appalachian plateau abstract spoil created by surface mining can accumulate large quantities of ground water which can create geotechnical or regulatory problems as well as flood active mine pits a current study at a large 4 1 km2 thick up to 90 m spoil body in eastern kentucky reveals important factors that control the storage and movement of water ground water recharge occurs along the periphery of the spoil body where surface water drainage is blocked as well as from infiltration along the spoil bedrock contact recharge from adjacent bedrock and to a minor extent through macropores at the spoil s surface based on an average saturated thickness of 6 4 m for all spoil wells and assuming an estimated porosity of 20 approximately 5 2 106 m3 of water is stored within the existing 4 1 km2 of reclaimed spoil a conceptual model of ground water flow based on data from monitoring wells dye tracing data discharge from springs and ponds hydraulic gradients chemical data field reconnaissance and aerial photographs indicate that three distinct but interconnected saturated zones have been established one in the spoil s interior and others in the valley fills that surround the main spoil body at lower elevations ground water movement is sluggish in the spoil s interior but moves quickly through the valley fills the conceptual model shows that a prediction of ground water occurrence movement and quality can be made for active or abandoned spoil areas if all or some of the following data are available structural contour of the base of the lowest coal seam being mined pre mining topography documentation of mining methods employed throughout the mine overburden characteristics and aerial photographs of mine progression

macropore flow on a reclaimed surface mine infiltration and hillslope hydrology abstract surface coal mining in central pennsylvania alters the physical and hydrological properties of soil from its undisturbed state and changes the surface hydrologic response to precipitation newly reclaimed minesoils exhibit low steady state rates of infiltration 1 2 cm h and produce runoff dominated by infiltration excess overland flow within 4 years after reclamation rates of infiltration on some minesoil surfaces approach pre mined rates 8 cm h as a greater percentage of rainfall infiltrates these reclaimed minesoils little change occurs in the total volume of surface storm runoff on an event basis this indicates that infiltrated water contributes to storm runoff by the processes of throughflow and return flow as the rate of infiltration increases with time the hydrologic response of the minesoil is controlled by rapid macropore throughflow within the unsaturated minesoil application of fluorescent dyes on the reclaimed surface reveals preferred flowpaths through macropores surrounding the numerous large rock fragments in the minesoil development and integration of a macropore network on a reclaimed surface mined watershed has a significant direct effect on the contributions to surface storm runoff from infiltration excess overland flow throughflow and return flow as rates of infiltration increase through time and slightly delayed macropore return flow increases the peak rate of surface storm runoff is reduced therefore reducing the potential for severe gully erosion on the reclaimed site in addition throughflow moves predominantly within the minesoil horizon and has limited contact with potentially acid producing backfill better understanding of the process of macropore flow in reclaimed minesoils will help investigators evaluate past strategies and develop new reclamation techniques that will optimize the long term effluent and ground water quality while minimizing the short term surface erosional effects of mining and reclamation

large scale crustal conductivity pattern in central europe and its correlation to deep tectonic structures the results of magnetovariational mv soundings are usually presented in the form of induction arrows however many examples show that the horizontal magnetic tensor hmt is more informative the distribution of some hmt invariants directly traces the location of well conducting rocks in the crust and upper mantle the hmt determination requires simultaneous observations in an entire region which is a substantial disadvantage yet it is possible to apply techniques capable of restoring all the magnetic field components necessary for hmt estimation from tipper data arrays alone these techniques exploit the spatial relationships between electromagnetic field components in a non conducting atmosphere for central europe a large data set of induction arrows has been collected by the effort of many groups during the last 50 years based on these data hmt values were calculated and the results are very significant the spatial behavior of certain hmt invariants demonstrates the presence of deeply seated well conducting rocks in the crust anomaly maximums display an arc shaped trend that may be genetically linked with the caledonian and or variscan margin thrust belts which developed following the collision between baltica and avalonia and or gondwana derived terranes respectively this is an important finding because the position of these deformation fronts in relation to the edge of the east european platform is still controversial

magnetovariational study over a seismically active area in the deccan trap province of western india this paper presents the results of a magnetovariational study undertaken over a basalt covered region of western india which has been experiencing a swarm of seismic activity since early 1986 the most striking feature of the transient variations is the anomalous enhancement of the east west y component at stations bounding the seismically active belt from the nature of the horizontal transfer functions and the anomalous induction arrows it is inferred that this behaviour is related to the presence of a resistive body embedded in a north south oriented conductive belt consistent with an evolutionary model of deccan volcanism and other geophysical data it is suggested that the central resistive block coincident with the concentrated belt of earthquake epicentres represents either a dormant volcanic plug or a plutonic body rooted in upwarped conducting mantle to account for the phase relationship between the anomalous y variations and the normal north south x variations it is proposed that the upwarped asthenosphere with its associated high geothermal anomaly acts as a conducting path to channel induced current from the region of the cambay triple junction located towards the northwest of the array the existence of the strong induced currents in the region of the triple junction conforms with the induction arrow pattern observed at the array stations

distortion of magnetotelluric sounding curves by three dimensional structures distortions of magnetotelluric fields caused by three dimensional 3 d structures can be severe and are not predictable using one dimensional or two dimensional modeling i used a 3 d modeling algorithm based upon an extension of a generalized thin sheet analysis due to ranganayaki and madden 1980 to examine field distortions in crustal environments three major physical mechanisms cause these distortions these mechanisms are resistive coupling between the electrical mantle and upper crust resistive coupling between conductive features within the upper crust and local induction of current loops within good conductors each mechanism produces different spatial and frequency effects upon the background field so identification of the dominant mechanism can be used as an interpretational aid i finally use this analysis to identify distortion mechanisms seen in magnetotelluric data from beowawe nevada to aid in an interpretation of that area

assessment of preferential flow processes in a forest reclaimed lignitic mine soil by multicell sampling of drainage water and three tracers abstract predictions of the long term development of newly established forest reclaimed ecosystems are required for land use planning of post mining landscapes the geological and mineralogical composition the small distance heterogeneity and inclined structures of the mine spoil s overburden sediment mixtures as well as the physical and chemical properties of acidic and lignitic mine soil components have raised questions about the water flow and solute transport processes in these soils the objective of this study was to quantify preferential flow processes and spatially resolved solute transport in order to better distinguish between dominating processes for such soils the experimental study was carried out by determining spatially resolved rates of throughfall drainage and tracer leaching from underneath a 110 cm deep mine soil block drainage water was collected using 45 contiguous suction cells of 27 cm edge length a tracer cocktail consisting of bromide terbuthylazine and deuterium was applied at the soil surface and subjected to natural infiltration tracer concentrations in drainage waters were analysed for a period of about 10 months then the mine soil block was sampled completely in the form of 225 cubes of about 27 cm edge length to determine the residual bromide content tracer labelled drainage in 110 cm depth occurred in spring 2001 over about 71 and in autumn 2001 over 35 of the total cross sectional drainage area respectively local drainage maxima shifted from spring to autumn but also within drainage periods by 1 2 cell lengths bromide concentrations of drainage effluents varied by a factor of 4 between individual cells bypass type preferential flow seems not to be a dominating transport mechanism since terbuthylazine in drainage waters occurred only singularly in spring with concentrations just above the detection limit perhaps the dilution in relatively large cells was too effective to detect modest contributions of tracer through preferential flow paths relative concentrations of deuterium and of bromide were akin during both drainage periods indicating similar transport behaviour of both tracers in the mine soil the spatial distribution of residual bromide concentrations in the subsoil seemed to correspond with the inclined spoil ripple structures the spatial patterns of leached bromide suggest a funnelling type flow concentration in this lignitic mine soil preferential flow is presumably caused by the temporarily varying effects of multiple determinants such as inclined dumping structures spatial variability of hydraulic properties water repellence and the properties of lignitic dust and fragments with some immobile porosity

the importance of breaching as a mechanism of subaqueous slope failure in fine sand large bank failures comprising up to 10 6 m 3 of sediment are common features along steep channel banks in estuaries and large rivers that consist of clean fine sands and are mostly assumed to be generated by sudden liquefaction of large masses of very loosely packed sand another less commonly recognized type of failure is manifested by the gradual retrogression of a very steep wall steeper than the angle of repose instead of the voluminous surging plastic sediment water flow or hyperconcentrated density flow sensu mulder alexander 2001 generated by liquefaction this type of failure known as breaching by dredging companies and hydraulic engineers produces a sustained quasi steady turbidity current to date sedimentologists have not recognized the process of breaching as such in this paper it is suggested that breaching may be the origin of many thick massive sand layers known from ancient deposits from various environments notably in some turbidite successions possible differences in the sedimentary structure of the deposits produced by breach failures vs liquefaction slope failures liquefaction flow slides can be deduced from a knowledge of the sediment transport processes initiated by the failure a field study is presented on some poorly structured beds in the eocene vlierzele sands in belgium which are supposed to have originated from liquefaction failures but are reinterpreted to be the products of breaching it is postulated that the local steep slope disturbance required to initiate an active breach can be produced by a small liquefaction slope failure liquefaction flow slide failure or local erosion by river or tidal channel flow at the initial stage of the failure event

state boundary surface for very loose sand and its practical implications a state boundary surface defines a boundary in stress void ratio space above which no stress state can exist the applicability of the state boundary surface for sand has not gained widespread attention primarily because sand is not generally considered to be a difficult soil from a design point of view apart from liquefaction liquefaction is a phenomenon usually encountered in very loose cohesionless materials an experimental study relating the drained and undrained behavior of very loose saturated sand is presented it is shown that the post peak portion of undrained stress paths travels along the state boundary and that the state boundary can be approximated by a straight line the slope of this straight line appears to stay constant for very loose sand there are potentially an infinite number of these lines which form a three dimensional surface in deviator stress effective mean normal stress void ratio space previously published results by various researchers are used to confirm the existe

flow slide prediction method influence of slope geometry a quasi two dimensional method is presented for predicting liquefaction flow slides in a slope with saturated loose sand the initial stresses at the start of the actual flow slide process are predicted assuming completely drained conditions during the gradual change in slope geometry caused by erosion or sedimentation the condition for a flow slide is considered to be the presence of at least one sand element in a metastable stress state i e a state in which the undrained response to any quick change in load however small it may be consists of a sudden large increase in pore pressure the metastability of any sand element is predicted as a function of its constitutive properties its location in the slope and the slope geometry the constitutive properties are derived from dry triaxial tests and basically describe the liquefiability brittleness of the sand the metastability criterion for a soil element in a slope is different from that under triaxial loading flow slides observed in large scale

a geomorphic classification of ephemeral channels in a mountainous arid region southwestern arizona usa article i nfo despite the global abundance of arid region ephemeral streams hydrologic and geomorphic data for these systems are limited compared to their perennial counterparts high spatial and temporal variability in flow makes hydrologic and geomorphic aspects of dryland ephemeral channels difficult to characterize perennial stream classifications have been extended to dryland ephemeral streams but do not adequately describe ob served differences in channel geometry and characteristics of ephemeral channels in desert environments we present a geomorphic classification for ephemeral streams in mountainous regions based on planform degree of confinement and composition of confining material five stream types were identified in the sonoran desert ofsouthwestern arizona 1 piedmontheadwater 2 bedrock 3 bedrockwith alluvium 4 incisedalluvium and 5 braided channels nonparametric permutational multivariate analysis of variance for 101 surveyed reaches indicated differences p b 0 001 in channel geometry and hydraulics among the five stream types nonmetric multidimensional scaling ordination identified the strongest channel geometry and hydraulic vari ables capable of distinguishing the five channel types and a classification tree determined relative importance of these variables in the following order width to depth ratio w d stream gradient s stream power and shear stress a classification tree and discriminant analysis used w d s and for 86 study reaches on the u s army yuma proving ground 77 and 77 internal validation hit rate respectively to predict stream type of 15 separate study reaches on barry goldwater air force range with 67 and 73 external validation hit rates respectively differences in channel geometry among the five stream types reflect likely differences in hydrology hydraulics and sediment transport with implications for disturbance regime channel adjustment to disturbance and ecological sensitivity

impacts of surface mine valley fills on headwater floods in eastern kentucky the potential impacts of valley fills associated with mountaintop removal valley fill mtr vf coal mining on downstream flooding in the coalfields of eastern kentucky and adjacent states are a subject of public debate and scientific uncertainty this study explored two aspects of this issue first hydrologic indices of relative runoff production and surface and subsurface flow detention were applied to conditions typical of headwater and low order drainage basins in eastern kentucky results show that there is a clear risk of increased flooding greater runoff production and less surface flow detention following mtr vf operations and suggest that on balance valley fills are more likely to increase rather than decrease flood potential however there is a wide range of outcomes qualitatively and quantitatively flood risks can be increased or decreased and the degree of either may vary markedly the effects of mtr vf mining on downstream peak flows are highly contingent on local pre and post mining conditions and it would be unwise to apply generalizations to specific sites second the occurrence of flash floods downstream of mtr vf operations when nearby unmined areas did not flood or had less severe floods has frequently been explained without supporting data in terms of locally greater precipitation the likelihood of such short range variability of storm precipitation is evaluated by applying the state probability function to nexrad radar estimates of precipitation for two 2001 storms which produced flash floods in eastern kentucky the spatial structure of the storm precipitation indicates that at the scale of the analysis pixel size of approximately 2 km large local variations in storm precipitation are unlikely that is the probability of nearby hollows or low order drainage basins receiving substantially different storm precipitation totals is low

soil thickness effect on hydrological and erosion characteristics under sloping lands a hydropedological perspective abstract soil thickness exerts a first order control on the hydrological processes of the hillslopes however from a hydropedological perspective the knowledge of soil thickness effect on hydrological and erosion characteristics under sloping lands is limited based on a comprehensive survey of an experimental watershed in the three gorges area of china five typical sloping land plots 2 m 1 m with different soil thickness were selected along a hillslope to investigate their hydrological processes and erosion response under three rainfall intensities 60 90 and 120 mm h 1 using a portable rainfall simulator the results can be summarized as follows 1 the surface flow coefficient was increased with increasing soil thickness especially under the event of 60 mm h 1 2 the subsurface flow of the 23 31 and 45 cm plots mainly took the form of preferential flow conversely the 59 and 76 cm plots mainly took the form of matrix flow 3 a prolonged low intensity rainfall is much more likely to facilitate deep percolation and subsurface flow than a short high intensity rainfall regardless of soil thickness 4 soil thickness and rock fragment cover were the most important factors than other soil properties in determining the hydrological and erosion behaviors thin soils showed higher infiltration capacity than thick soils due to their more distinct hydrological processes of subsurface flow and deep percolation rock fragment cover enhanced infiltration and served as a shield to protect the soil surface from detaching due to the synergies between thin soil thickness and high rock fragment cover thin soils displayed significantly lower erosion rates than thick soils in all rainfall events which increased from 211 g m 2 h 1 for the 23 cm plot with rainfall of 60 mm h 1 to 4220 g m 2 h 1 for the 76 cm plot with rainfall of 120 mm h 1 our study suggested that the emerging interdisciplinary field of hydropedology promotes synergistic integration of pedology e g watershed scale soil thickness investigation and soil profile description and hydrology e g rainfall simulation subsurface flow and deep percolation to enhance the holistic study of soil water interactions in the sloping lands with different soil thickness

effects of crust and shrub patches on runoff sedimentation and related nutrient c n redistribution in the desertified steppe zone of the tengger desert northern china runoff and erosion are critical geomorphic processes in arid ecosystems and they are strongly affected by vegetation patterns little is known about the influence of spot structured vegetation on runoff and erosion in temperate deserts especially the effects of vegetation patterns and human induced disturbances on runoff triggered nutrients redistribution are poorly understood a series of simulated rainfall experiments were conducted in the tengger desert northern china to examine 1 the effects of shrub patches on runoff and erosion and related nutrients redistribution on hillslopes 2 whether different amounts of water and nutrients are stored in the shrub patches compared to open inter patch areas and 3 how the runoff and erosion and related nutrients redistribution processes respond to human induced disturbances the results indicate that in undisturbed plots 53 of the applied water became runoff from crust patches and 55 of this was redistributed to the shrub patches water penetration was significantly deeper in shrub patches than in crust patches and more than 75 of the sediments 63 soil carbon 74 nitrogen and 45 73 dissolved nutrients triggered by runoff from crust patches were delivered to shrub patches the disturbance of crust patches tended to result in the uniform distribution of water over the whole slope and the reduction of flow of vital resources from the crust patches to the shrub patches disturbance of macrophytic patches significantly degraded the capacity for resource capture and retention and thereby decreased resources all of which are crucial for the maintenance of plant productivity and vegetation cover the understanding of the function of patterned vegetation in the study area suggests that it represents an aspect of the ecosystem that requires careful management

the liquefaction of sands a collapse surface approach recent large scale slides occurring during the hydraulic placement of an artificial island berm in the beaufort sea resulted from the liquefaction of the berm sand subsequent laboratory tests and

the simulation of magnetic variation anomalies using single station data abstract hypothetical event maps of the vertical field derived from single station magnetic variation transfer functions are biased by the anomalous horizontal fields an iterative scheme proposed earlier is used to estimate and correct for the anomalous fields the scheme here is applied to single station transfer functions from 90 sites in southern scotland and northern england it converges to a stable solution in four iterations and the results compare favourably with those predicted in the southern part of the area using measured inter station transfer functions the resultant hypothetical event maps of the anomalous horizontal fields show that the northumberland trough and southern uplands conductivity anomalies are both strikingly linear features which correlate more closely than previously supposed with other geological and geophysical observations

the deep structure of northern england and the iapetus suture zone from birps deep seismic reflection profiles the nec deep seismic reflection profile images structures in the lower crust which represent the iapetus suture zone beneath southern scotland and northern england on the basis of reflectivity characteristics of the lower crust and reflection moho we recognize four different crustal zones which correspond to four crustal terrane types midland valley zone a a sub continental subduction complex zone b lake district zone c and midland platform zone d the junctions between each of these zones are interpreted as being tectonic a and b originate from the northern continental margin of the iapetus ocean and are separated from c and d which are derived from a southern continent by strong northerly dipping reflections between approximately 15 and 30 km deep in the crust the structure responsible for these reflections does not displace the reflection moho north of the ab cd junction the base of zone b and base of the reflective crust is marked by a pair of parallel reflectors persistent for a horizontal length of about 55 km these reflectors are interpreted as the top and bottom of a slice of remnant oceanic crust at their northerly limit the deepest of the two parallel reflectors transects the moho to a depth of 6 7 km into the uppermost mantle we suggest that their termination delimits the northerly extent of a decollement or shear zone at the present continental moho the shear zone was active during the late stages of caledonian collision when mantle originally from beneath the southern continent underthrust old and newly created crust of the collision zone

a two dimensional interpretation of the geomagnetic coast effect of southeast australia observed on land and seafloor abstract data from detailed investigations of the geomagnetic coast effect across the southeast australian continental margin are interpreted in terms of a two dimensional numerical model there is both land and seafloor control on this model and both e pol and b pol mode responses are incorporated the good fit to the data of a model comprising ocean water and marine sediments is improved when the sub ocean electrical conductivity profile is allowed to differ from the continental conductivity profile a final model is determined by an inversion procedure based on systematic search the main characteristic of this model is that an increase in conductivity occurs at a shallower depth beneath the ocean than beneath the land some 100 km beneath ocean 200 km beneath land the southeast continental margin of australia is considered to have formed by passive rifting at the time of the opening of the tasman sea a depth of 100 km for the base of the oceanic lithosphere corresponds well to the age of rifting some 80 ma ago the contrast with the continental profile suggests an electrical asthenosphere relatively deeper beneath southeast australia

deep crustal geoelectric structure beneath the northumberland basin in terms of lateral variations in conductivity structure the southern southern uplands and northumberland basin are characterized by a region of attenuated vertical magnetic fields with small spatial gradients reflecting the presence of a substantial conducting zone five magnetotelluric data sets from the region have been analysed to provide accurate and unbiased estimates of the impedance tensor the response data are used to investigate the deep geoelectric crustal structure of the region three appropriate sets of response data have been subjected to two construction algorithms for 1 d inversion the geoelectric profiles recovered identify a deep crustal conducting zone underlying the northumberland basin the zone modelled as a layered structure dips steeply from mid crustal depths underneath the northumberland basin to lower crustal depths to the nw the structure thus correlates in location and geometry with a deep crustal reflecting wedge detected offshore by a deep seismic reflection profile

a thin sheet model of electromagnetic induction in northern england and southern scotland electric currents induced in the seas surrounding the british isles influence the electromagnetic fields observed on land observational data suggest that at certain periods anomalous currents concentrate in a thin sheet comprising the shallow seas and onshore sedimentary sequences the block and basin structure of northern england and southern scotland provides a physical basis for the implementation of a thin sheet approximation in quantitative electromagnetic modelling studies of the region the model comprises a non uniform thin sheet at the surface of a layered half space the solution to this problem as formulated by vasseur weidelt has been applied to a regional thin sheet model of northern england and southern scotland a regional observational data set comprising the anomalous vertical field at a period of 750s is used to constrain possible models geological and geophysical observations are used to provide a realistic model for the major sedimentary basin of the region and the results obtained are compared with observations the results suggest that such a basin is capable of establishing a substantial onshore perturbation in the anomalous vertical field of similar geometry to that observed although the present study is necessarily limited in its depth resolution it is suggested that other models presented go some way to defining the lateral extent of the conductive configuration for the region

electrical resistivity imaging of hydrologic flow through surface coal mine valley fills with comparison to other landforms surface coal mining has altered land cover near surface geologic structure and hydrologic processes of large areas in central appalachia usa these alterations are associated with changes in water quality such as elevated total dissolved solids which is usually measured via its surrogate specific conductance sc the sc of valley fill effluent streams is a function of fill construction methods materials and age yet hydrologic studies that relate these variables to water quality are sparse due to the difficulty of conducting traditional hydrologic studies in mined landscapes we used electrical resistivity imaging eri to visualize the subsurface geologic structure and hydrologic flow paths within a valley fill eri is a noninvasive geophysical technique that maps spatiotemporal changes in resistivity of the subsurface we paired eri with artificial rainfall experiments to track infiltrated water as it moved through the valley fill results indicate that eri can be used to identify subsurface geologic structure and track advancing wetting fronts or preferential flow paths our results suggest that the upper portion of the fill contains significant fines whereas the deeper profile is primarily large rocks and void spaces water tended to pond on the surface of compacted areas until it reached preferential flow paths where it appeared to infiltrate quickly down to 15 m depth in 75 min eri applications can improve understanding of how fill construction techniques influence subsurface water movement and in turn may aid in the development of valley fill construction methods to reduce water quality effects

causes of high crustal conductivity beneath the iapetus suture zone in great britain summary two magnetic variation anomalies in southern scotland and northern england have been linked to the position of the iapetus suture previous magnetotelluric measurements along a 140 km profile that crosses both anomalies have been supplemented by new high quality broad band observations groom bailey decomposition of the impedance and hypothetical event analysis of the magnetic variation data agree in defining different strike directions for the two halves of the mt profile n50 e for the northern part over the southern uplands and n90 e for the southern part over the northumberland trough te and tm mode apparent resistivity and phase data at representative frequencies have been inverted for the two sub profiles separately using the smooth inverse of smith booker 1990 the uppermost layer has a low resistivity is variable in thickness and correlates well with the known position and thickness of carboniferous sedimentary rocks the second layer has a very high resistivity thousands of m and reaches the surface where the lower palaeozoic metamorphic rocks of the southern uplands crop out a relatively rapid transition to low resistivities occurs at depths of between 8 and 16 km the conducting layer appears to be quasi continuous but where the profile crosses the anomalies identified by magnetic variation measurements the conductance increases and the upper surface is shallower the spatial coverage of the magnetic variation data has enabled us to extrapolate conductive features away from the line of section and project the electrical image onto the nec vertical incidence seismic reflection profile in the north sea there is excellent agreement between a number of features in the acoustical and electrical images the shallowing of the low resistivity layer to form a narrow wedge like feature corresponds to the offshore position of the stublick fault while to the north of the fault the top of the layer coincides with a south dipping reflector thought to be a thrust however the zones of high conductance and high lower crustal reflectivity do not in general correlate the good conductor beneath he northumberland trough spans two zones which were differentiated on ihe nec profile in terms of their reflectivity the shape of the conductor s upper surface in the vicinity of the stublick fault agrees well with the model of chadwick holliday 1991 who proposed that the iapetus suture was a whole crustal shear with a gently dipping central ramp the coincidence between the present day low resistivity layer and a surface of weakness that was active 300 400 myr ago is much more readily explained in terms of mineralogy the presence of graphite than the presence of fluids there is also strong support for interpreting the northern conductor in the same way its upper surface is relatively flat and occupies the position predicted as the horizontal detachment surface over which wedges of the southern uplands rocks were thrust its northeastward extension is sampled by a group of carboniferous vents from which xenolith suites of crust and upper mantle origin have been obtained the middle to upper crust is believed to be represented by quartzo feldspathic gneisses that contain abundant graphite

separation of local and regional information in distorted gds response functions by hypothetical event analysis summary electromagnetic investigations are usually intended to examine regional structures where induction takes place at a given period range however the regional information is often distorted by galvanic eiects at local conductivity boundaries bahr 1985 and groom bailey 1989 developed a physical distortion model for decomposing the mt impedance tensor based upon local galvanic distortion of a regional 2 d electromagnetic eld we have extended their method to predict the magnetic variation elds created at an array of sites the magnetic response functions at periods around 1000 s may be distorted by large scale inhomogeneities in the upper or middle crust in this period range the data measured by a magnetometer array contain common information that can be extracted if the data set is treated as a unit for example by using hypothetical event analysis with this technique it is always possible to recover the regional strike direction from distorted data even if a strong spatially varying regional vertical eld component is present in the data set the determination of the regional impedance phases on the other hand is far more sensitive to deviations from the physical distortion model the approach has been used to investigate the iapetus data set for the array which covers an area of 200 km 300 km in northern england southern scotland the technique revealed a common regional strike azimuth of ca n125 0 e in the period range 500 2000 s this direction diiers from the strike indicated by the induction arrows which seem in uenced mainly by local current concentrations along the east weststriking northumberland trough and a ne sw striking mid crustal conductor both impedance phases are positive and diier by ca 1 0 0 which supports the assumptions of distortion elds in the data set and that the regional structure is 2 d

magnetometer array studies earth structure and tectonic processes this review presents results from magnetovariation fields recorded by two dimensional arrays of magnetometers the emphasis is on the conductive structures mapped and studied and their tectonic implications eleven arrays were operated in north america between 1967 and 1985 a region of highly conductive uppermost mantle and or lower crust extending at least from 33 n to 54 n has been shown to extend beneath much of the continent west of the rocky mountains two recent investigations are discussed in more detail those of conductive structures under the canadian rockies and emslab electromagnetic sounding of the lithosphere and beyond array results for washington and oregon including a conductive strip beneath the cascades volcanoes correlations with high heat flow and seismic parameters make it reasonable to attribute these regional conductors to partial melting and or hot saline water within the craton the north american central plains conductor is discussed this narrow crustal feature is associated with a major fracture zone and age boundary which may be a plate boundary of proterozoic time an array beneath the auroral electrojet for study of the external currents is noted results from four array studies in southern africa are considered two of these relate to the southern cape conductive belt which correlates not with high heat flow but with a large static magnetic anomaly the magnetovariation magnetic and gravity anomalies and geological data can be accounted for if an accumulation of ophiolitic rocks including serpentine is present in the lower crust such an accumulation may have formed at a subduction in proterozoic time two other arrays delineated a conductive belt associated with the southwestern end of the african rift system in namibia subsequent resistivity soundings located a conductor of resistivity 10 ohm m at less than 4 km depth two array studies in india follow one in the north and one in the south the array in the himalayan foothills and indo gangetic plain mapped a conductor transverse to the regional strike this may be a fracture zone produced in the interplate collision with a rise of asthenospheric material such as fluids into the fractures the southern indian array reveals crustal conductors under the indo sri lankan graben and another under the comorin ridge southwest of the tip of the subcontinent array studies in central and southeastern australia and in fennoscandia in regions without large local conductivity anomalies have been used to study conductivity variation with depth a note on the carpathian crustal anomaly is included as an example of combination of response parameters secured at different times to form a virtual array

hydrologic evolution of drainage basins disturbed by surface mining central pennsylvania the hydrologic evolution of drainage basins disturbed by surface mining in central pennsylvania is regulated by infiltration capacity of minesoils and its control on hillslope runoff processes steady state infiltration capacity of newly reclaimed minesoils is uniformly low less than 1 cm hr and it generally increases up to 6 cm hr with time the magnitude of increase being dependent on soil characteristics and vegetation in drainage basins where steady state infiltration capacity recovers to less than 3 cm hr the dominant runoff process is infiltration excess overland flow increased peak runoff rates associated with infiltration excess overland flow are sufficient to initiate drainage network evolution in these basins with phases of expansion and abstraction storm hydrographs are characterized by 1 increasing peak and total runoff and decreasing time to peak runoff during periods of network extension and 2 decreasing peak and total runoff and increasing time to peak runoff during network abstraction trends in hydrograph evolution are due to the relative efficiency of channeled versus overland flow processes for removing excess rainfall from the basin in contrast in drainage basins where steady state infiltration capacity recovers to greater than 3 cm hr runoff is initially dominated by infiltration excess overland flow but saturation overland flow is increasingly dominant with time drainage network evolution is limited to skeletal network initiation and elongation which occur while the basin is dominated by infiltration excess overland flow changes in storm hydrographs include decreasing peak runoff and increasing time to peak runoff the result of the increasing dominance and lagged response of saturation overland flow although steady state infiltration capacity increases in these basins total runoff remains essentially constant due to the extended and less steep recession limb of storm hydrographs which is a characteristic of hydrographs from basins dominated by saturation overland flow the hydrologic response of drainage basins to changes in the dominant runoff process has important implications for models of long term drainage basin evolution particularly those used to evaluate climate change and associated changes in vegetation and soil chemical and physical properties each of which may affect infiltration capacity

vegetation influences near surface hydrological characteristics on a surface coal mine in eastern usa abstract mining processes alter natural landscapes worldwide and methods for restoration of mined areas are widely studied establishment of vegetation is essential to mined land restoration prior research has addressed vegetative influence on erosion and runoff but effects of vegetation type on surface hydrologic processes are less studied we measured infiltration rates and observed subsurface flow paths in mine soils on a reforested area and a grassed area on a former surface coal mine in the eastern united states the two areas were constructed and reclaimed fourteen years prior to our study using processes similar in all aspects except vegetation minidisk tension infiltrometers and brilliant blue fcf dye staining analyses were utilized to evaluate near surface flow processes in the vegetated mine soils mean infiltration rates were 16 5 10 7 cm h 1 and 10 4 7 7 cm h 1 for the reforested and grassed areas respectively infiltration rates hydraulic conductivities dye coverage and dye stained areas were significantly higher in the reforested area the grassed area had constant dye coverage with depth but more flow paths than the reforested area a transition from vegetation controlled subsurface flow to abiotic control at greater depths was evident in the stained soil profiles results highlight the heterogeneous nature of mine soils and the influence of vegetation type in development of mine soil hydrologic processes

lifespan of mountain ranges scaled by feedbacks between landsliding and erosion by rivers an important challenge in geomorphology is the reconciliation of the high fluvial incision rates observed in tectonically active mountain ranges with the long term preservation of significant mountain range relief in ancient tectonically inactive orogenic belts river bedrock erosion and sediment transport are widely recognized to be the principal controls on the lifespan of mountain ranges but the factors controlling the rate of erosion and the reasons why they seem to vary significantly as a function of tectonic activity remain controversial here we use computational simulations to show that the key to understanding variations in the rate of erosion between tectonically active and inactive mountain ranges may relate to a bidirectional coupling between bedrock river incision and landslides whereas fluvial incision steepens surrounding hillslopes and increases landslide frequency landsliding affects fluvial erosion rates in two fundamentally distinct ways on the one hand large landslides overwhelm the river transport capacity and cause upstream build up of sediment that protects the river bed from further erosion on the other hand in delivering abrasive agents to the streams landslides help accelerate fluvial erosion our models illustrate how this coupling has fundamentally different implications for rates of fluvial incision in active and inactive mountain ranges the coupling therefore provides a plausible physical explanation for the preservation of significant mountain range relief in old orogenic belts up to several hundred million years after tectonic activity has effectively ceased

resistance to overland flow on desert hillslopes abstract this study examines the relation between the darcy weisbach friction factor f and the reynolds number re for overland flow on six runoff plots in semiarid southern arizona the surfaces of these plots are irregular and covered with stones as overland flow increases the stones and microtopographic protuberances which constitute the major roughness elements are progressively inundated thereby altering the flow resistance analyses of 14 cross sections reveal that the resulting f re relations have two basic shapes convex upward and negatively sloping these shapes bear little resemblance to the conventional f re relation for shallow flow over a plane bed whose shape is a function of the state of flow rather they are explained in terms of the simultaneous operation of two processes the first is the progressive inundation of roughness elements and increase in their wetted upstream projected area as discharge increases this process causes f to increase the second is the progressive increase in the depth of flow over already inundated parts of the bed as discharge increases this process causes f to decline whether the f re relation has a positive or a negative slope depends on whether the first or second process dominates and this depends on the configuration of the bed and level of discharge these findings have profound implications for the mathematical modeling of overland flow on desert hillslopes whether a model is based on the saint venant equations or makes use of the kinematic wave approximation it requires the specification of a relation between f and re or surrogates thereof and the computed hydrograph is very sensitive to the form of this relation hitherto the most widely used relation has been the conventional one for shallow flow over a plane bed however the present study suggests that this relation does not apply to desert hillslopes additional field and laboratory studies are needed to learn more of the behavior and controls of f re relations on such hillslopes so that models of overland flow can employ more realistic relations and better simulate runoff hydrographs

flow path visualization in a lignitic mine soil using iodine starch staining abstract a dye tracer visualization experiment was carried out in order to study the importance of preferential flow at forest reclaimed mine soils the objective was to evaluate iodine starch staining for the identification of flow paths in such soils for the commonly used dye tracer brilliant blue showed a poor contrast to the relatively dark lignitic mine soil the experimental site was located in the lusatian mining district northeast germany and afforested with pinus nigra at the experimental plot area of 250 130 cm 60 mm of iodide solution was applied at a rate of 7 5 mm h flow path visualization was conducted at 10 cm increments down to 150 cm soil depth the soil surface was powdered with starch and sprayed with a bleaching agent iodine starch staining indicated the tracer conducting soil regions stained soil sections were documented by photography as well as by manual tracing on transparent window films at each depth increment 25 core samples were taken at a regular grid of 25 25 cm for each core sample the amount of residual iodide was determined according to the visualized flow paths the iodide solution infiltrated into the mine soil at distinct points beneath a redistribution zone at 10 cm flow paths occurred as fingers which constricted the hydraulically active soil volume to about 15 and persisted down to a depth of 60 cm at one point to 150 cm only a part of the iodine starch stainings spatially coincided with the vertical iodide concentration for a closer relationship the analysis of the complete soil volume seems to be necessary iodine starch staining proved to be suitable for flow path visualization at dark lignitic mine soils under field conditions and seems to be feasible also for other dark soils at lignitic forest reclaimed mine soils fingered flow has to be considered in water and solute budgets

initial hydro geomorphic development and rill network evolution in an artificial catchment the formation of erosion rills and gullies is a critical step in land surface development but possibilities to study initial unaffected surface development under natural conditions and with well defined initial and boundary conditions are rare the objective of this study was to characterize rill network development from point zero in the artificially created catchment huhnerwasser to ensure unaffected development the study was largely restricted to the analysis of remotely sensed data we analyzed a series of photogrammetry based digital elevation models dems for 10 points in time over a period of five years and beginning with the initial state the evolving erosion rill network was quantitatively described based on mapping from aerial photographs dems and rill network maps were combined to specifically analyze the development of morphometry for different parts of the network and to characterize energy dissipation and connectivity the restriction to remote sensing data did not allow for analyzing specific processes governing rill network development nevertheless two major development phases could be characterized we observed a phase of growth of the rill network along with variations in drainage patterns during the first two years of development and a subsequent phase of reduction of its area along with comparably stable patterns region specific analysis of morphometry indicates that besides effects of changing sediment characteristics and vegetation cover development locally evolving hydro geomorphic feedback cycles influenced this development results show an increasing similarity of overall statistical characteristics e g drainage density for two parts of the catchment but a persistent influence of initial conditions on specific rill geometry the observed development towards higher orderliness and increased connectivity is consistent with experiments and concepts on drainage network evolution across scales however we did not observe major influences of rill piracy and cross grading or a reduction of energy dissipation with network development copyright 2013 john wiley sons ltd

critical density of sand although hardly used in theoretical soil mechanics nowadays critical density still is an important parameter in cases where the flow slide susceptibility of sand deposits has to be investigated in this paper two types of triaxial tests in which the critical porosity of sand is measured are described during the first type of test on dry sand the volume change is measured in the second type of test undrained and stress controlled on saturated sand the sudden collapse and liquefaction of the loose samples is observed the results of the two tests are related to each other by means of calculations and a more safe criterion is derived in the wet critical porosity the unsafe influences of membrane penetration and of insufficient saturation are removed with this method the sudden failure and liquefaction of saturated samples under stress controlled but completely drained conditions could be explained quoique rarement utilisee a l heure actuelle dans les travaux theoriques relatifs a la mecanique du

hydrologic characteristics of appalachian loose dumped spoil in the cumberland plateau of eastern kentucky heavily compacted lands typical of traditional surface mine reclamation techniques have been shown to hinder tree growth increase levels of flooding and produce suboptimal water quality utilizing loose dumped spoil in accordance with the forestry reclamation approach fra has demonstrated success with regards to promoting tree growth and survival however additional information is needed to assess the potential of fra to ameliorate other environmental concerns related to water quantity to better understand the hydrologic characteristics of loose dumped spoil key hydrograph parameters discharge volume peak discharge discharge duration lag time and response time were monitored for three common spoil types 1 predominately brown weathered sandstone 2 predominately gray weathered sandstone and 3 a mixture of both sandstones and shale although spoil types were found to differ hydrologically these differences were relatively minor measured discharge volumes were low averaging 12 of rainfall for all events and treatments peak discharge rates were small between 2 5 10 5 and 3 10 3 m3 s and the duration of discharge was long 6 days on average from a hydrologic perspective the results of this study indicate that mine spoils need not be segregated for reclamation as long as the spoil is placed in accordance with the loose dumped techniques as outlined in the fra copyright 2009 john wiley sons ltd

geomagnetic variation anomalies in northern england processing and presentation of data from a non simultaneous array summary the block and basin structure of northern england has been investigated by an array of 35 magnetometer stations over a grid with a spacing of 1okm recordings at these sites were made simultaneously with those at a reference site using the common reference data transfer function analysis enables the three anomalous field components to be estimated at each site for the period range 10 104s using the transfer functions obtained maps of the anomalous field components may be generated across the array and used for interpretation of electrical conductivity structure maps thus obtained from the non simultaneous array data in northern england are used to illustrate the advantages of the method and provide evidence of an east west current flow concentrated along the southern margin of the northumberland trough the limitations of the procedure although slight are considered the errors which arise in the method are deduced and techniques for their removal are suggested

flow resistance in concentrated overland flow on rough slope surfaces field experiments have been done on simulated flows over different rough pre rill and rill bed surfaces the purpose of the experiments was to evaluate the hydraulic roughness properties of these bed surfaces conventional equations describing the relation of the resistance coefficient to the reynolds number for flow in closed conduits or open channels can also be applied to shallow flows provided the boundary values of the reynolds number which discriminate between the various flow regimes are adapted when the reynolds number is less than 100 the flow regime is laminar above this figure the flow is either transitional or turbulent depending on the roughness of the bed surface the degree of turbulence can be deduced from a morphological description of the pre rill and rill bed surface roughness

crustal structure south of the iapetus suture beneath northern england the crustal structure just south of the iapetus suture1 along a line extending from the mid north sea high across northern england to the solway basin has been investigated as part of the caledonian suture seismic experiment of 1982 this unique sea to land wide angle explosion seismology project has produced data of unprecedented quantity and quality the main innovation was the use of both closely spaced shots mainly at sea and closely spaced stations mainly on land yielding a data set which can eventually be arranged in a variety of new ways for phase correlation and modelling such as constant offset and common mid point the line was extended by irish and german groups across ireland to the shannon estuary having a total length of over 600 km but here we present only preliminary results for northern england and adjacent marine regions the results for this region differ radically from those of the earlier lispb experiment2 in that we have recognized a well defined 6 15 km s 1 basement interpreted as pre caledonian metamorphic basement beneath most of the line at relatively shallow depth and there is a well defined mid crustal refractor starting at approximately 16 km depth beneath the north sea and northern england which is not recognized beneath the irish sea

geophysical images of the deep crust the iapetus suture the iapetus suture arguably the most fundamental lineament of british and irish structure has been previously identified on the birps winch deep seismic reflection profiles offshore as a nw dipping feature new depth migrated interpretations of these and other reflection data show good correlation of structure for 100 km along strike in the northern irish sea towards magnetotelluric stations onshore in the north of england and southern uplands of scotland three different methods of inverting data from these sites all reveal a thin nw dipping slab of high conductivity a contour map of the suture trace dipping at 15 25 nw can be constructed down to and through the moho at 28 km depth this map suggests crustal stretching below the solway basin the mylonitic suture zone is characterized by good seismic reflection layering high conductivity presumably fluid produced and a steep increase of p wave velocity over the few kilometres of its width crustal refraction experiments lispb and cssp provide useful velocities but locally misleading structure so that the combination of the seismic reflection and geoelectric methods may be the most powerful means of determining deep crustal structure with a good degree of both vertical and lateral resolution

magnetic variation anomalies in northern england and southern scotland single station transfer functions linking the time variations of the vertical and horizontal components of the magnetic field at stations in northern england and southern scotland have been compiled into a uniform data set from hypothetical event analysis we show here that there are two distinct anomalies in the borders region one runs south west to north east immediately to the south east of the southern uplands fault the second follows the northumberland basin and seems to exist because the conductive sedimentary rocks filling the basin create a link between the irish and north seas if the lapetus suture is marked by a conductivity anomaly as has been suggested1 2 these results place it beneath the southern uplands unless it is masked by the surface conductor in the northumberland basin

flow slides in the netherlands experience and engineering practice this paper deals with flow slide experience in the netherlands it gives an extensive survey of empirical field data concerning the geological characteristics of the region the profiles just before the flow slides and the damage that flow slides can cause the traditional dutch procedure for analyzing the flow slide potential of underwater sand slopes is described this is an engineering approach that is mainly based on the empirical field data together with geological surveys and soil investigations performed at the relevant site key words sand collapse flow slides liquefaction slope stability

the interpretation of the northumberland trough geomagnetic variation anomaly using two dimensional current models summary the electromagnetic fields at the surface are non linear functionals of the electrical conductivity of the earth however the anomalous magnetic fields which are created by lateral variations in the conductivity are linear functionals of the internal current density the inverse problem analysed in this paper is that of using the spatial structure of the vertical field defined along a profile perpendicular to the strike of a 2 d structure to infer the lateral and vertical distribution of current parallel to the strike in the northumberland trough survey magnetometers at some sites are operated simultaneously with a reference instrument at durham and interstation vertical field transfer functions were fitted to the data they are subsequently used to predict the vertical field at each site which is associated with a specific horizontal field at the reference other magnetometers were run separately and only single station transfer functions could be computed these yield predictions of the vertical field which are biased by anomalous horizontal fields when the spatial structure of the anomaly is known the horizontal component of the field can be predicted from the vertical by using the constraint that the field derives from a potential which satisfies the laplace equation the corrections that are required to convert from singlestation to inter station transfer functions can be estimated from the maps of the horizontal field this approach is used to generate vertical field values at sites spaced at 10 km intervals along a 100 km profile traversing the alston block and northumberland trough in northern england the map of the horizontal component anomalies relates more simply to the structure than the vertical component map the surface magnetic fields do not define a unique distribution of current density withm the earth the non uniqueness is removed by fixing the direction and bounding the magnitude of the current density the inversion of the set of constraints is solved by linear programming methods the current density in the carboniferous sedimentary rocks filling the northumberland trough is calculated by combining estimates of their conductivity based on archie s law with measurements of the electric field at a magneto

local and regional induction in the british isles electric currents induced in the shallow seas and deep ocean around the british isles have a profound effect upon the electromagnetic fields observed at stations on the land the configuration of anomalous currents changes with frequency and causes corresponding changes in the geomagnetic transfer functions magnetic variations have been recorded at a dense network of sites in southern scotland and northern england single station transfer functions have been used to generate hypothetical event maps of the anomalous vertical field and hence to infer the configuration of the anomalous internal currents at periods exceeding 2000 s the vertical field is dominated by the effects of electric currents to the west presumably in the atlantic ocean in the period range 400 2000 s anomalous currents are concentrated in a thin sheet comprising the shallow seas the t hick sequences of post caledonian sedimentary rock which underlie them and the extensions of the sedimentary basins into the land the response of the individual basin is determined not only by its local conductivity structure but also by the extent of its connection to the shallow seas i e its regional importance within the conductive sheet at periods less than 200 s on the other hand the anomalous fields at inland sites are principally determined by the local geological structure these results confirm conclusions reached from theoretical studies of electromagnetic induction in a heterogeneous surface layer park orange madden that electromagnetic response data measured in a 3 d environment such as the northumberland basin must be interpreted using 3 d models if one or 2 d models are used the data must be corrected on the basis of regional measurements

undrained shear behaviour of sands subjected to large shear displacement and estimation of excess pore pressure generation from drained ring shear tests undrained shear behaviour of fine silica and weathered granitic sand subjected to large shear displacement is examined parallel experiments using ring shear and the triaxial compression tests on soil specimens through a wide range of initial void ratios were conducted to investigate undrained shear strength as the key factor in the flow like motion of landslides the steady state undrained shear strengths achieved in ring shear tests were in general smaller than those in the triaxial compression tests probably because of the excess pore pressure generation by grain crushing within the shear zone that occurred in ring shear very low steady state shear strengths were achieved however in triaxial compression tests on the dense silica sand in which well defined shear surfaces developed in the cylindrical specimens in these triaxial compression tests shear deformation must have been concentrated on these surfaces to generate excess pore pressure similar to that found in ring shear tests an attempt wa

pleistocene geomorphology and geochronology of eastern grand canyon linkages of landscape components during climate changes we report new mapping soils survey and geochronologic luminescence u series and cosmogenic nuclide data from pleistocene deposits in the arid setting of eastern grand canyon the result is a stratigraphic framework of inset fill gravels and associated terraces that provide a record of the responses of hillslopes tributary streams and the colorado river to the last 400 kyr of glacial interglacial climate change the best preserved last 80 kyr of this record indicates a stratigraphic chronologic disconnect between both deposition and incision along the colorado river versus along the trunks of local tributaries for example the colorado river finished aggrading and had already begun incising before the main pulse of aggradation in the trunks of local catchments during marine isotope stage 3 and then tributary incision followed during the millennial scale fluctuations of the last glacial epoch potentially concurrent with mainstem aggradation the mainstem record appears to broadly correlate with regional paleoclimate and upstream geomorphic records and thus may be responding to climatic hydrologic changes in its mountain headwaters with aggradation beginning during full glacial times and continuing into subsequent interglacials the contrasting lag time in responses of the dryland catchments within grand canyon may be largely a function of the weathering limited nature of hillslope sediment supply r 2005 elsevier ltd all rights reserved

environmental controls on the evolution of alluvial fans in buena vista valley north central nevada during late quaternary time abstract alluvial fans in buena vista valley north central nevada formed during at least four time periods during the late quaternary as evidenced by four temporally and spatially constrained fan deposits qf1 qf2 qf3 and qf4 from oldest to youngest the stratigraphic relation between qf3 and remnant beach ridge deposits of pluvial lake lahontan the latter of which forms a paleoclimatic proxy for this region indicate that climate and climatic change are primary controls on the evolution of fans qf3 deposition commenced during or immediately following the highstand of lake lahontan between 13 5 and 12 5 ka and continued as lake levels plummeted to levels below the sill elevation of the buena vista subbasin we interpret qf3 to be the result of a dynamic interplay between hillslope vegetation soils and hydrology as they are conditioned by climate and climatic change accelerated pedogenesis because of aerosolic silts and clays from exposed lake sediments coupled with decreased density of vegetation reduced infiltration capacity of the hillslope soils in interscrub areas in contrast to fans in more arid climates the increased runoff was not associated with increased coarse grained sediment yield and major fan aggradation discharge from sediment deficient basins entrenched older proximal fan deposits and transported the sediment downfan to form secondary fans the process response of qf3 to climatic change in north central nevada is especially illustrative of the impact of climate on landscapes in that 1 it results from changes in basin sediment and or water yield that occur in less than 500 years and 2 it differs from responses in arid climates to the south and more semiarid climates to the north the magnitude of vegetation change including type and density of vegetation and the relative proportion of interscrub area is particularly critical to water and sediment yield unit qf2 an early late pleistocene deposit may also have been deposited during a transition from a wetter to drier climate the synchronism of aggradation stability and entrenchment on all fans along the perimeter of buena vista valley in the late quaternary is further support for the dominance of climatic control on fan process on the other hand the impact of other extrinsic variables on fan process including tectonism base level and basin lithology all of which vary along the perimeter is negligible

2 d inversion of geomagnetic deep sounding data near ujjain guna india summary the inductive response of a hypothesized conductor located between ujjain and guna india has been modelled in the absence of a satisfactory fit from forward numerical modelling 2 d inversion of the anomaly profile of z h ratio has revealed the main conductor to be situated below ujjain guna with an offset and another secondary conductor in the form of a jointed body the main conductor is at a depth of 23 km from the surface thickness being 20 km and the resistivity 3 m the jointed secondary conductors are at depths of 31 km and 28 km with thicknesses of 14 km and 21 km and resistivities 3 m and 5 m respectively the resistivity contrast with the background is a factor of 1600 or even slightly more the possibility of mineralization on the flanks of the subsurface granitic intrusion cannot be ruled out however partial melting of the subsurface granites seems to be another plausible explanation for the high conductivity contrast

threshold response of small streams to surface coal mining bituminous coal fields central pennsylvania stream response to surface coal mining and reclamation was studied in 29 small 0 13 to 5 72 km2 watersheds located in the bituminous coal fields of central pennsylvania these basins up to 82 per cent mined were selected from 176 first order tributaries of beech creek with similar vegetation soil lithology and basin characteristics measurements were made at 262 cross sections an average of nine cross sections per stream of channel cross section area bankfull width mean bankfull depth dimensions of the largest moving blocks stream slope valley side slope basin area and mined area observed differences in channel morphology were related to differences in extent of mining by means of scatter plots correlation cluster analysis and bivariate regression stream response to increased peak discharge and channel shear stress produced by increased surface runoff from regraded mine spoil takes the form of enlarged channels and increases in the size of moving blocks large basin areas appear to dampen the effect of mining resulting in limited channel enlargement with greater extent of mining in contrast where peak discharges and associated shear stresses exceed the combined erosional resistance of floodplain vegetation colluvial blocks and channel banks streams adjust extensively to higher levels of mining causing an abrupt increase in the size of transported blocks and eroded channels in the first order basins studied this stepped response occurs at approximately 0 45 km2 mined area and 50 per cent of the total basin area mined for streams that have exceeded both threshold levels disequilibrium is demonstrated by a strong positive correlation between local stream slope and basin area where both threshold levels of mining are exceeded steep channel slopes reinforce the tendency of stream cross sections to increase with greater disturbance by mining necessitating that these streams rapidly adjust their morphology in order to attain a new equilibrium which is compatible with the conditions imposed by mining and reclamation

on the variation of infiltration into a homogeneous soil matrix containing a population of macropores a population of channels penetrates a soil matrix that is otherwise homogeneous the channels are assumed to be vertical and of circular cross section with constant diameter but channel depths and radii are allowed to vary over the population this paper uses a model based on the green ampt assumptions to predict infiltration rates through the walls and bases of channels resulting in a mathematical description of the way in which infiltration develops in the soil and in which channels fill with water until eventually overland flow is initiated this model takes account of the fact that there may be a random distribution of channels in space expressions for the expected mean and variance of infiltration volumes are derived some example results are given and show that below the matrix wetting front the variance of the change in water content with 30 and 50 channels per square meter may be of the same order as the mean change in water content the presence of channels can lead to significant increases in predicted channel volumes

experimental evidence for fluvial bedrock incision by suspended and bedload sediment fluvial bedrock incision sets the pace of landscape evolution and can be dominated by abrasion from impacting particles existing bedrock incision models diverge on the ability of sediment to erode within the suspension regime leading to competing predictions of lowland river erosion rates knickpoint formation and evolution and the transient response of orogens to external forcing we present controlled abrasion mill experiments designed to test fluvial incision models in the bedload and suspension regimes by varying sediment size while holding fixed hydraulics sediment load and substrate strength measurable erosion occurred within the suspension regime and erosion rates agree with a mechanistic incision theory for erosion by mixed suspended and bedload sediment our experimental results indicate that suspension regime erosion can dominate channel incision during large floods and in steep channels with significant implications for the pace of landscape evolution

inversion of electromagnetic induction data for the iapetus suture zone in the uk abstract the iapetus suture zone isz corresponding to the join between the european crust of northern england and the north american derived crust of scotland has been examined by numerous seismic and induction experiments over a 20 year period the university of edinburgh electromagnetic em induction group is in the process of building a database comprising magnetotelluric and magnetic variation stations from this region in this paper we present 2d inversions of selected induction sites along roughly north south traverses across the isz in northern england and southern scotland the first inversion involves both the transverse electric te and transverse magnetic tm modes for 10 audio magnetotelluric approximately 100 0 1 hz sites care has been taken to remove the effects of static shifts this inversion resolves a conductive feature beginning under the southern northumberland trough at depths of 10 km dipping to the south below the alston block in the second inversion 12 longer period magnetic variation sites were added to the original data set improving the resolution of this feature which correlates well with a dipping bright reflector detected by the north east coast nec seismic reflection experiment in addition the southern uplands anomaly is imaged no north dipping mid to deep crustal conductor is observed which would correlate to north dipping palaeozoic subduction under laurentia

reach scale geomorphic differences between headwater streams draining mountaintop mined and unmined catchments article i nfo mountaintop surface mining mtm isa controversial coal extraction method commonly practiced in the central andsouthernappalachianmountains usa thatdrasticallyreengineerspreviouslysteep forestedlandscapesand alters sediment and water delivery processes to and along headwater channels draining mined areas although sediment delivery and hydrologic response from mtm operations remain highly variable and poorly resolved the inherent close coupling between hillslopes and headwater channels is expected to result in geomorphic dif ferences in stream channels draining mtm landscapes relative to unmined landscapes dedicated geomorphic studies are severely lacking in comparison to extensive research on water quality impacts of mtm this study re ports moderate geomorphic differences between headwater catchment area b 6 km 2 stream channels draining mtm and unmined catchments in tributaries of the mud river in southern west virginia univariate and multivariate analyses indicate that mtm streams are characterized by deeper maximum channel depths smaller width to depth ratios increased bedrock exposure along the streambed and increased frequency of very fine silt and sand deposition relative to channels draining unmined catchments geomorphic differences