long term final void salinity prediction for a post mining landscape in the hunter valley new south wales australia opencast mining alters surface and subsurface hydrology of a landscape both during and post mining at mine closure following opencast mining in mines with low overburden to coal ratios a void is left in the final landform this final void is the location of the active mine pit at closure voids are generally not infilled within the mines lifetime because of the prohibitive cost of earthwork operations and they become post mining water bodies or pit lakes water quality is a significant issue for pit lakes groundwater within coal seams and associated rocks can be saline depending on the nature of the strata and groundwater circulation patterns this groundwater may be preferentially drawn to and collected in the final void surface runoff to the void will not only collect salts from rainfall and atmospheric fallout but also from the ground surface and the weathering of fresh rock as the void water level rises its evaporative surface area increases concentrating salts that are held in solution this paper presents a study of the long term water quality trends in a post mining final void in the hunter valley new south wales australia this process is complex and occurs long term and modelling offers the only method of evaluating water quality using available geochemical climate and hydrogeological data as inputs into a mass balance model water quality in the final void was found to increase rapidly in salinity through time 2452 to 8909 mg l 1 over 500 years as evaporation concentrates the salt in the void and regional groundwater containing high loads of salt continues to flow into the void copyright 2004 john wiley sons ltd

site amplification in the los angeles basin from three dimensional modeling of ground motion it is well established that sedimentary basins can significantly amplify earthquake ground motion however the amplification at any given site can vary with earthquake location to account for basin response in probabilistic seismic hazard analysis therefore we need to know the average amplification and intrinsic variability standard deviation at each site given all earthquakes of concern in the region due to a dearth of empirical ground motion observations theoretical simu lations constitute our best hope of addressing this issue here 0 0 5 hz finite difference finite fault simulations are used to estimate the three dimensional 3d response of the los angeles basin to nine different earthquake scenarios amplifi cation is quantified as the peak velocity obtained from the 3d simulation divided by that predicted using a regional one dimensional 1d crustal model average ampli fication factors are up to a factor of 4 with the values from individual scenarios typically differing by as much as a factor of 2 5 the average amplification correlates with basin depth with values near unity at sites above sediments with thickness less than 2 km and up to factors near 6 above the deepest 9 km and steepest dipping parts of the basin there is also some indication that amplification factors are greater for events located farther from the basin edge if the 3d amplification factors are divided by the 1d vertical sh wave amplification below each site they are lowered by up to a factor of 1 7 the duration of shaking in the 3d model is found to be longer by up to more than 60 seconds relative to the 1d basin response the simu lation of the 1994 northridge earthquake reproduces recorded 0 0 5 hz particle velocities relatively well in particular at near source stations the synthetic and observed peak velocities agree within a factor of two and the log standard deviation of the residuals is 0 36 this is a reduction of 54 and 51 compared to the values obtained for the regional 1d model and a 1d model defined by the velocity and density profile below a site in the middle of the basin dow respectively this result suggests that long period ground motion estimation can be improved consid erably by including the 3d basin structure however there are uncertainties con cerning accuracy of the basin model model resolution the omission of material with shear velocities lower than 1 km s and the fact that only nine scenarios have been considered therefore the amplification factors reported here should be used with caution until they can be further tested against observations however the results do serve as a guide to what should be expected particularly with respect to increased amplification factors at sites located above the deeper parts of the basin

circumferential graben and the structural evolution of alba mons mars abstract alba mons is a unique very extensive but shallow volcanotectonic construct in northern tharsis mars numerous models have been presented to explain the formation of alba mons and its most characteristic feature a wristwatch like pattern of radial and circumferential graben we used a wide selection of topographic datasets to characterize the fault throw variation on nine topographic transects across the circumferential graben in order to provide observational constraints for the different formation models and to gain further insight into the evolution of alba mons in most of the transects summed throws from outwards facing away from the center of the volcano faults are larger than from the inwards facing towards the center ones only the very gently sloping western transects show the opposite emphasizing the east west asymmetry of alba mons 10 40 of the observed topographic relief of alba mons along the nine transects can be accounted for by this throw difference between the inwards and outwards facing faults these results are consistent with predictions of models suggesting an uplift mechanism to explain the formation of the circumferential graben but not with models invoking central subsidence horizontal extensional strain along the transects varies between 0 5 and 2 consistent with strain predictions of the late stage sill complex inflation model of mcgovern et al mcgovern p j solomon s c head j w iii smith d e zuber m t neumann g a 2001 j geophys res 106 e10 23769 23809

three dimensional normal faulting models of the valles marineris mars and geodynamic implications inversion of martian topography using a three dimensional boundary element model permits revised estimates of fault dip angle depth of faulting paleogeothermal gradient and extensional strain in the valles marineris region the major normal faults dip at 40 55 to depths of 60 75 km with comparatively small footwall uplifts 500 m for throws to 10 km implying that paleogeothermal gradients during faulting were 10 k km 1 or less assuming relatively rapid strain rates appropriate to the extending martian crust accumulation of dip slip offsets along the main normal faults likely was associated with anticlinal flexure and deformation of preexisting strata within the troughs the magnitudes of the predicted vertical and horizontal displacements outside the troughs as well as extensional strains are spatially variable depending on both cross and along strike position relative to the troughs the predicted displacements and strains attain maximum values at the troughs and decay to background values at cross strike distances of 250 km corresponding to 3 4 times the depth of faulting with an average province wide strain of 4 15 by implication the aggregate strain field surrounding tharsis is a highly variable spatial and temporal composite of the inhomogeneous strain fields each associated and scaling in size with an individual graben from the smallest structures through the largest valles marineris troughs

quantitative analysis of the extensional tectonics of tharsis bulge mars geodynamic implications about 10 of the tharsis bulge surface is intensely faulted with a fault density up to 1 fault km in these intensely faulted areas 54 impact craters which exhibit faulted walls and floor are now elliptical in shape these ellipticities indicate an average strain value of 10 inside these provinces this strain value is 4 times greater than the strain deduced from normal fault morphometric analysis this high value indicates that the strain is not only due to 60 dip normal faults and that some additional tectonic processes exist such as boudinage this important strain value corresponds to an elongation of about 50 km across thaumasia and tempe mareotis provinces and 20 km across alba patera regio the amount of elongation for the entire tharsis region is 2 orders of magnitude higher than the strains and motions related to standard models of bulge formation these intensely faulted areas are restricted areas where faults are both radial to the bulge and perpendicular to the topographic slope the stretching does not influence the regional topography and there are no topographic shoulders or important level differences between faulted and nonfaulted areas which would indicate that the crust is not thinned under the stretched provinces outside these intensely faulted areas the graben width is remarkably constant all over the tharsis bulge indicating the existence of a brittle ductile transition or an incompetent level at about 1 2 km below the surface a new origin for the tharsis tectonic features is proposed as a preliminary hypothesis the intensely faulted areas correspond to the uphill parts and to denudation zones of gravity slidings which move on a 2km deep incompetent level the gliding of the slab on the very low dipping flanks of tharsis needs three conditions 1 the viscosity of the incompetent layer must be equal to the viscosity of the ice 2 the brittle layer must have been previously faulted by the bulging itself 3 these preexisting radial fault directions must be perpendicular to topographic slope the ridged plain units in lunae palus and coprates provinces thus correspond to a zone of blocking inside the gliding slab due to an interruption of the decollement level

modeling subsurface stormflow on steeply sloping forested watersheds five mathematical models for predicting subsurface flow were compared to discharge measurements made by hewlett and hibbert 1963 on a uniform sloping soil trough at the coweeta hydrologic laboratory the models included one and two dimensional finite element models based on the richards equation a kinematic wave model and two simple storage discharge models based on the kinematic wave and boussinesq assumptions the simple models simulated the subsurface response and water table positions as well as the more complex models based on the richards equation and were much more economical to use from the point of view of computational costs such models have features that would allow them to be incorporated into more complex watershed models thus placing hydrologic prediction on a more physically correct and less empirical footing

stream response to subsidence from underground coal mining in central utah short term geomorphic and hydrologic effects of subsidence induced by longwall mining under burnout creek utah were evaluated during the year after longwall mining 0 3 1 5 m of subsidence was measured near impacted reaches of the mountain stream channel the major channel changes that occurred in a 700 m reach of burnout creek that was subsided from 1992 to 1993 were 1 increase in lengths of cascades and to a lesser extent glides 2 increases in pool length numbers and volumes 3 increase in median particle diameter of bed sediment in pools and 4 some constriction in channel geometry most of the changes appeared short lived with channel recovery approaching pre mining conditions by 1994 in a 300 m reach of the south fork that was subsided from 1993 to 1994 only channel constriction was observed although any impacts on pool morphology may have been confounded by heavy grazing in the riparian reaches during the dry summer of 1994 similar near channel sedimentation and loss of pool volume between 1993 and 1994 were noted throughout burnout creek and in adjacent unmined james creek subsidence during the 3 year period had no effect on baseflows or near channel landslides

grabens basin tectonics and the maximum total expansion of the moon the presence of grabens and wrinkle ridges indicates that stresses sufficient to deform or fault crustal rocks have existed for at least part of lunar history these structures have been explained as due to global expansion and contraction basin subsidence or both even if the extension implied by all lunar grabens were due to global expansion the total radius increase permissible after terminal bombardment would be much less than that predicted by the most conservative models of lunar thermal evolution the obvious areal association of most grabens and wrinkle ridges with impact basins suggests that a genetic relationship exists also but it is necessary to develop either kinematic or dynamic models to determine if basin subsidence alone can account for these structures kinematic models are the most useful because fewer assumptions regarding material properties are needed than for dynamic models for both types the grabens and wrinkle ridges provide the data that must be predicted by the models considerations of geometry kinematics and mechanics suggest that the simple grabens on the moon are reliable indicators of crustal extension two end member kinematic models of postimpact basin modification are derived one assuming that subsidence is accomplished entirely by an increase in radius of curvature of the basin floor the other assuming that subsidence is accomplished without any change in radius of curvature of the basin floor any combination of the two also would be possible both models predict enough extension to account completely for basin related grabens and thus they indicate that virtually all of the extension implied by lunar grabens can be provided by modest amounts of basin subsidence in addition both models also predict total radial and hoop shortening of the basin floor of about the correct magnitude to explain wrinkle ridges if these features are structures resulting from compression consequently almost all extension and shortening of the lunar crust implied by grabens and wrinkle ridges can be explained by basin subsidence alone significant global expansion after 3 9 b y is unlikely and significant global contraction is unnecessary

tectonic history of the tharsis region mars the faults of the tharsis region of mars have been mapped and delineated on the basis of age the orientation of each group of faults was analyzed to determine if they were radial to a point the results indicate that there are at least four discrete centers of faulting within the tharsis area which are of significantly different age the four centers proposed are from oldest to youngest 1 in the thaumasia highlands 2 in northern syria planum and finally 3 and 4 near pavonis mons while episodes 3 and 4 occupy the same geographic position they are separated in time by the development of the tharsis lava plains and shields each episode of tectonism was separated from the next by a period of major basaltic volcanism the tectonic features of the tharsis area are thus viewed as being the cumulative result of the superposition of several discrete episodes of faulting rather than the result of one episode about a single point

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

extension and uplift at alba patera mars insights from mola observations and loading models high resolution mars orbiter laser altimeter mola profiles of the large shield volcano alba patera call for a critical reexamination of models for the growth and evolution of this volcanic edifice an extensive system of graben cuts across alba patera extending from ceraunius fossae to the south to tantalus fossae to the northeast in the vicinity of the edifice the otherwise generally north south orientations of these graben are deflected to circumferential directions mola topography reveals that the circumferential graben are located well up the flanks of alba patera both the type extensional and location midflank of faulting on alba patera are inconsistent with the state of stress predicted for purely surface loaded flexure models to constrain the conditions governing the evolution of alba patera we employ finite element models for the volcano and lithospheric stress field under a combination of loading mechanisms buoyant sublithospheric loads representing underplated magma low density mantle residuum or dynamic support from mantle convection and intralithospheric displacements representing sills trapped by horizontal compressive stresses in the upper lithosphere can generate the observed midflank slope breaks and circumferential extensional fault zones at radial distances comparable to that of the subsurface load s characteristic radial extent both mechanisms moderate stresses in the upper lithosphere in favor of continued magma ascent however bottom loading requires a disk like load geometry and an elastic lithosphere thickness te sufficiently small to allow the load s shape to be apparent in the surface deformation te 32 km such low te is inconsistent with mars global surveyor mgs gravity and topography data in contrast intralithospheric sill complexes can produce the observed topography and faulting at te values consistent with those inferred from gravity and topography 50 te 100 km for these conditions principal stress orientations on the lower flanks are also consistent with the orientations of lower flank graben provided that faulting was induced by dike intrusion or tensile failure rather than shear failure

graben and extension in northern tharsis mars a morphometric analysis of north south trending graben at 35 n in northern tharsis is used to provide the first quantitative measurements of crustal extension in and strain for areas of the martian crust that have undergone both extreme and mild deformation these estimates also demonstrate the viability of the viking data for making such quantitative assessment graben in the region accommodate 8 km of post early amazonian east west extension this extension corresponds to a net regional strain of 0 45 0 61 local strains vary from 1 to 5 extension is nonuniform and localized near 110 south of alba patera and north of ceraunius fossae because of reactivation of preexisting fractures in underlying basement and possibly due to superposition of stress fields from tharsis and alba patera a major mechanical discontinuity in the shallow crust probably representing the base of or a strength contrast within the megaregolith is observed it occurs at a depth of 2 km on the profile flanks and is depressed to about 7 5 km near 110 due to loading of the crust by the volcano a number of more shallow discontinuities occur within the construct and probably represent lithologic contacts

why some alluvial rivers develop an anabranching pattern anabranching rivers have been identified globally but a widely accepted and convincing theoretical explanation for their occurrence has remained elusive using basic flow and sediment transport relations this study analyzes the mechanisms whereby self adjusting alluvial channels can anabranch to alter their flow efficiency sediment transport capacity per unit of stream power it shows that without adjusting channel slope an increase in the number of channels can produce a proportional decrease in flow efficiency a finding particularly relevant to understanding energy consumption in some braided rivers however anabranching efficiency can be significantly increased by a reduction in channel width as occurs when vegetated alluvial islands or between channel ridges form the counteracting effects of width reduction and an increasing number of channels can cause with no adjustment to slope an otherwise unstable system underloaded or overloaded to achieve stability as with other river patterns anabranching can be characterized by stable equilibrium or accreting disequilibrium examples copyright 2007 by the american geophysical union

discontinuities in the shallow martian crust at lunae syria and sinai plana detailed photoclinometric profiles across 125 erosional features and 141 grabens in the western equatorial region of mars indicate the presence of three discontinuities within the shallow crust pits troughs and wall valleys tributary canyons within noctis labyrinthus and valles marineris and escarpments within the fretted terrain of sacra fossae and kasei valles show distinct erosional base levels at depths of 0 3 0 6 km 1 km and 2 3 km the shallowest discontinuity corresponds to thickness estimates for the ridged plains unit in this region and thus the discontinuity probably is the contact between a sequence of layered rock making up this unit and the underlying megaregolith the 1 km discontinuity is reflected in the base levels of erosion of all the features studied and it may correspond to the base of the proposed layer of ground ice model calculations using photoclinometric profiles of simple grabens corrected for the effects of mass wasting and the 60 dip of bounding faults measured from the exposed traces of faults on trough walls show that graben bounding faults consistently intersect at the mechanical discontinuity at about 1 km depth this discontinuity may represent an interface between ice laden and dry regolith ice laden and water laden regolith or pristine and cemented regolith a correlation between wall valley head depth and local thickness of the faulted layer suggests that the 1 km discontinuity also controlled the depth of the heads of sapping canyons there is no apparent relation between the pit and trough depths and the local thickness of the faulted layer which can be explained if pits and troughs developed by subsidence into underlying tension cracks that disrupted the 1 km discontinuity the data do suggest however that erosion of shallow pits and troughs was influenced by the 1 km discontinuity the third discontinuity at a depth of 2 3 km corresponds to the proposed base of the martian megaregolith and is probably the interface between overlying ejected breccia and in situ fractured basement rocks

modeling crater topography and albedo from monoscopic viking orbiter images 1 methodology a new photoclinometric technique for extraction of topographic data from single planetary images is presented that overcomes many previous limitations of photoclinometry the procedure fully compensates for oblique viewing geometry prevalent in spacecraft images albedo variations have been one of the most serious obstacles in the application of photoclinometry to planetary surfaces this problem is overcome in the topographic solution by simultaneously utilizing brightness data from a pair of profiles both segments are assumed to have the same topographic and albedo variations along their lengths profile directions are chosen where the orientation of downslope or upslope is obvious thus resolving a major ambiguity in photoclinometry this requirement is particularly easy to satisfy for craters and not very difficult for many irregular features an additional procedure is presented that eliminates even the requirement of topographic symmetry along the pair of profiles if two profiles have the same relief but their shapes are very different another method can be used in an iterative process to derive topographic profiles however this procedure does require that the albedo not vary along the profiles test results indicate that both procedures have an accuracy and precision of approximately 2 for slopes of typical bowl shaped craters which translates to approximately 5 for depths

topographic analysis of devana chasma venus implications for rift system segmentation and propagation abstract devana chasma is a rift system on venus formed in association with the beta regio and phoebe regio volcanic highlands which are interpreted as mantle plumes we present a new analysis of a 2500 km long segment of devana based on the rift topography the horizontal extension across the rift boundary faults is 3 9 km this is a lower bound on the total rift extension because the altimetry does not resolve the topographic relief across the numerous faults that are visible in radar images of the rift floor the total extension across devana is approximately 20 km similar in magnitude to continental rift systems on earth rift flank elevations are up to 3 1 km in the regions nearest the mantle plumes and decay strongly with increasing distance from the plumes indicating a strong thermal component to the rift flank topography unlike the situation usually reported for terrestrial rifts as on earth there is also a flexural uplift component to the flank topography rift depths are up to 2 5 km below the surrounding plains with considerable along strike variability there is a 600 km lateral offset along devana chasma near the mid point between the two mantle plumes devana most likely formed as two distinct rifts due to the horizontal stresses created by outflow from the upwelling plumes the offset zone formed as a result of the interaction between the two rift tips which requires that upwelling at the two mantle plumes overlapped in time

crustal extension in the ceraunius fossae northern tharsis region mars 1 we investigated the ceraunius fossae area northern tharsis in order to obtain quantitative information on the tectonic extension affecting this area tectonic structures of the ceraunius fossae area have been previously described using viking images and interpreted as extensional structures laser altimetry data mola can be used to quantitatively investigate these structures with a better resolution we developed a method to obtain e w oriented profiles perpendicular to the main tectonic structures with a sufficiently high resolution to analyze tectonic structures in spite of the low data density in this direction we interpreted all the recognizable extensional structures along the profiles and using a simplified structural model we estimated tectonic extension along these transects the extension calculated over the entire profiles is 36 km e24 l1 l0 l0 910 km 874 km 874 km 0 041 and 42 km e26 730 km 688 km 688 km 0 061 along profile 24 and profile 26 respectively in the most deformed area extension reaches the value of 22 km emax l1 l0 l0 186 km 164 km 164 km 0 134 since the extension accounted by the topographic doming is negligible a significant horizontal crustal motion is required to explain the observed extension

tempe fossae mars a planetary analogon to a terrestrial continental rift tempe terra the northeastern part of the tharsis region on mars is characterized by several extensional structures differing in style and age the tempe fossae a particularly well developed system of graben striking n45 e have been studied for the first time in detail on the basis of viking orbiter imagery and mars observer laser altimeter mola topographic data the graben system appears to be unique in the whole region because of its extent the remarkable width and depth of the graben the varying graben pattern and the associated volcanism single graben can be up to 35 km wide and 120 km long while their depth can reach nearly 3000 m they typically show an asymmetric architecture often in halfgraben or step fault style the graben system widens and changes its style along strike from ne to sw from a single very deep and narrow graben to a complex set of several shallower sinuous graben and halfgraben crustal extension was measured in the northeastern part from the observable throw and amounts to 2 5 3 1 km volcanic structures can be found at several locations along the graben in the sw the graben system seems to be connected with the tempe terra volcanic province marked by flood basalts and plains volcanism craters were counted on volcanic units unaffected by extensional tectonics crater statistics indicate an absolute crater model age for the upper end of the extensional deformation of 3 5 ga the dimensions and the characteristics of the mapped graben system resemble those of terrestrial continental rifts and a comparison between them and the kenya rift reveals striking similarities therefore the tempe fossae are interpreted as a martian analog to a continental rift associated with an underlying mantle plume this hypothesis seems to be supported by recent geophysical models based on topography and gravity data from mars global surveyor which indicate regional uplift for tempe terra

polygenic eruptions on alba patera mars a combination of photogeologic mapping analysis of viking orbiter thermal inertia data and numerical modelling of eruption conditions has permitted us to construct a new model for the evolution of the martian volcano alba patera numerous digitate channel networks on the flanks of the volcano are interpreted to be carved by sapping due to the release of non juvenile water from unconsolidated flank deposits using the thermal inertia measurements we estimate the particle size of these deposits to be 3 10 m which together with theoretical modelling of the disperison of explosively derived volcanic materials leads us to conclude that the flank deposits on alba patera are low relief pyroclastic flows the recognition of numerous late stage summit and sub terminal lava flows thus makes alba patera a unique martian volcano that is transitional between the older pyroclastic dominated highland paterae and the more recent effusive central vent volcanoes such as the tharsis montes

domestic water supply impacts by underground coal mining in virginia usa underground coal mining can affect wells and springs used as water supplies in virginia concerns over such impacts are felt by both surface owners and coal mining firms virginia s geologic history has caused faults and fractures to be common in its coalfield region relative to other appalachian coal mining areas the results of 73 investigations of alleged domestic water supply impacts by underground mining were analyzed the investigations were conducted by the virginia division of mined land reclamation vdmlr this analysis was conducted with reference to guidelines that define a primary zone of underground mining influence where dewatering of aquifers is to be expected the vdmlr data set included 27 investigations of alleged water supply impacts by partial extraction room and pillar mines 41 investigations of high extraction room and pillar mines and 4 investigations of longwall mines vdmlr investigators found that 14 of 16 water supplies within the primary zone of influence were likely to have been affected by pillar retreat mining but no water supplies within the primary zone of influence for longwall and room and pillar mines were represented in the data base vdmlr investigators found 42 of 56 water supplies outside of the primary zones were likely to have been affected by mining these cases represented room and pillar pillar retreat and longwall mining geologic circumstances not directly related to subsidence were found to be responsible for 31 of these 42 impacts these geologic circumstances included subsurface fractures and other geologic features acting as aquifers that were drained by underground mining operations vdmlr investigators also found some of the investigated water losses to have been caused by factors other than mining these results demonstrate the inherent difficulties of any attempt to rigidly define a zone of underground mining impact based solely on mine subsidence effects especially in regions where geologic faults and fractures are common such as the southwest virginia coalfield

high resolution topography and albedo of the south polar layered deposits on mars using a new photoclinometric technique with high resolution mariner 9 images maximum slopes of 10 20 are found to occur on an exposure of layered deposits within the south polar residual cap of mars stereophotogrammetry is used to constrain the photoclinometric solutions which resolve layer thicknesses of 100 300 m albedo variations are correlated with slope indicating that frost is present on level areas there is evidence for temporal changes in frost distribution in the 7 days 4 of l s between the two images used in this study the magnitude of the slopes derived here and consideration of the stability of water ice at the surface of the layered deposits strongly suggest the presence of a competent weathering rind the weathered surface may be composed of dark filamentary sublimation residue particles that protect the underlying ice from solar heating this hypothesis is consistent with previous studies of the regional color and albedo of the layered deposits which indicate that the deposits are slightly darker and less red than the bright dust that mantles much of the south polar region furthermore the proposed weathering mechanism provides a plausible source of dark saltating material for the martian polar dune fields

geomorphology and stratigraphy of alba patera mars geomorphic and stratigraphic analysis of alba patera suggests a volcanic construct built by lavas with rheologic properties similar to basalts a series of evolving eruptive styles is suggested by changes in morphology and inferred progressive reductions in flow volume with higher stratigraphic position alba patera s volcanic history has been summarized into four main phases the first is characterized by extensive flood like flows presumably erupted from fissures associated with the initial intrusion of magma into the region the second phase is associated with the emplacement of pyroclastic rock a more speculative interpretation the third phase produced the voluminous tabular crested and undifferentiated flows probably from a more centralized vent source the fourth and last phase is marked the effusion of levee like flows and the collapse of the summit calderas and final graben formation

crustal structure of mauna loa volcano hawaii from seismic refraction and gravity data abstract in october 1978 the u s geological survey established a 100 km long seismic refraction profile normal to the kona coast of hawaii island analysis of these data along with available gravity data suggest that the oceanic crust dips about 3 landward under the submerged flank of the island increasing to 8 5 under the kona coast maximum vertical deflection of the base of crust from beneath the deep ocean to a point beneath the summit of mauna loa is about 9 km high velocity high density rocks vp about 7 1 km sec density about 2 9 gm cm 3 comprise the bulk of the volcanic edifice and reach to within a few kilometers of the surface beneath the north flank of mauna loa the data also suggest that an elongate high velocity high density body lies parallel to the kona coast just below the surface this body probably represents an extinct buried rift zone

thick shell tectonics on one plate planets applications to mars a theory for stress distributions in thick lithospheric shells on one plate planets is developed based on the zero frequency equations of a self gravitating elastic spherical shell overlying a strengthless fluid stress distributions in lithospheres are reviewed for both the compensated and flexural modes in the former case surface stresses only depend on surface topography while for the latter case it is shown for long wavelengths that stress trajectories are mainly dependent on the lithospheric lateral density distribution and not on elastic properties computational analyses are carried out for mars and it is found that isostatically compensated models correctly predict the graben structure in the immediate tharsis region and a flexural loading model is satisfactory in explaining the graben in the regions surrounding tharsis a three stage model is hypothesized for the evolution of tharsis isostasy with north south graben formation on tharsis followed by flexural loading and radial graben formation on the perimeter of tharsis followed by a last stage of loading with little or no regional deformation this model is consistent with the martian lithosphere monotonically thickening over geologic time

mechanics of graben formation in crustal rocks a finite element analysis small 1 10 km wide grabens are ubiquitous tectonic structures that have been observed on the surfaces of all the terrestrial planets and satellites in spite of their frequent occurrence there is no fundamental understanding of how they form other than that they are characteristic of extensional terranes this paper examines the mechanics of the initial stages of graben formation and demonstrates that the configuration of a pair of antithetically dipping normal faults a graben is the energetically most favorable fault configuration in elastic brittle rocks subjected to pure extension a corollary to this hypothesis is that the occurrence of synthetic normal faults is indicative of a stress field other than purely extensional or of nonhomogeneous characteristics of the rock the analysis proceeds by computing the stress field in the vicinity of a single initial normal fault using a two dimensional finite element model it is shown that slip on this fault substantially lowers the proximity to failure of the surrounding rocks except for two small regions one near the surface of the downthrown block and the other near the fault tip the region on the downthrown block is located a horizontal distance from the initial fault slightly less than the fault s depth the proximity to failure actually increases here and a secondary fault develops an antithetic secondary fault would link this region with the other failure zone near the fault tip to demonstrate the preference for antithetic secondary faults more rigorously we show that this fault configuration results in a smaller total strain energy than the synthetic configuration in addition a two layer model is used to show that the graben s width is only weakly dependent upon the presence of mechanically distinct layers in the crust both weak over strong and strong over weak configurations are investigated the depth of the initial fault and the thickness of the top layer are varied and the width of the resulting graben is evaluated by computing the distance between the initial fault and the region of highest proximity to failure near the surface this analysis indicates that the depth of the initial fault is the major factor controlling graben width

volcanic rifting at martian grabens 1 a large fraction of surface extension on mars occurred at segmented grabens having width length ratios akin to oceanic rifts on earth association with volcanic landforms such as pit craters clearly suggests interconnection between tectonic and magmatic processes a martian rift evolution model is proposed on the basis of new geomorphological and structural interpretations of imagery high resolution digital elevation models dems scaled experimental modeling and three dimensional boundary element modeling of magmatic and tectonic processes and a comparison with terrestrial rifts the dems were obtained from mars observer laser altimeter viking orbiter stereo images or a combination of both comparison of terrestrial rifts included afar iceland and the east pacific rise the ambient extensional stress field induced by regional body forces is combined at depth with decompression melting and mantle plume thermal anomaly resulting in emplacement of elongated magma reservoirs along the grabens injection of dikes above the reservoirs and flood basalt eruption result in a reservoir underpressurization of up to hundreds of mpa and induces surface collapse each collapse event is associated with an eruption of volcanic volumes akin to those of individual flow eruptions in large terrestrial igneous provinces the geometry and mechanisms of graben formation and surface collapse are described and used to infer reservoir depth and width we conclude from this study that giant dike swarms akin to typical giant terrestrial dike swarms are unlikely to underlie the volcanic martian grabens on the basis one graben one dike rather every volcanic graben segment appears to own a local dike swarm perhaps analogous to the dike swarms in the icelandic fissure zones index terms 5475 planetology solid surface planets tectonics 8149 5480 planetology solid surface planets volcanism 8450 6225 planetology solar system objects mars 8121 tectonophysics dynamics convection currents and mantle plumes 8010 structural geology fractures and faults keywords rifting graben pit crater magma chamber dyke

tectonic history of the syria planum province of mars we attribute most of the development of extensive fractures in the tharsis region to discrete tectonic provinces within the region rather than to tharsis as a single entity one of these provinces is in syria planum faults and collapse structures in the syria planum tectonic province on mars are grouped into 13 sets based on relative age areal distribution and morphology according to superposition and fault crosscutting relations and crater counts we designate six distinct episodes of tectonic activity in the following chronologic order stage i is an early to late noachian deformation forming mostly east west structures fault set ia some large volcanoes also formed faults were produced possibly by flexural uplift also arcuate north trending grabens set ib indicate that faulting is transitional to the next stage stage ii is late noachian to early hesperian radial faulting centered in syria planum possibly due to isostatic uplift in late noachian set iia to early hesperian set iib time stage iii is early to late hesperian faulting tangential to syria planum that was related to local centers of uplift sets iii1 iii3 on the periphery of syria planum stage iv is a late hesperian graben formation that was circumferential to syria planum set iva caused either by collapse associated with eruption of magma or by flexure of the lithosphere due to volcanic loading in association with volcanism minor faulting occurred producing an oval pattern of faults in southwest syria planum set ivbl and a radial pattern south of the planum set ivb2 that apparently rejuvenated buried stage ii faults stage v is a late hesperian to early amazonian development of grabens and troughs of noctis labyrinthus and western valles marineris set v that was probably instigated by local uplift exposure of groundwater or ground ice zones may have produced further collapse and trough enlargement stage vi is early amazonian northwest trending faulting in noctis fossae set vil perhaps due to tharsis monies centered tectonism and north northwest normal faulting along the eastern side of the claritas rise set vi2 that was due to tectonic subsidence the duration of tectonic activity in the syria planum province was perhaps 2 3 b y photoclinometric topographic profiles across 132 grabens and fault scarps show that syria planum grabens have widths average of 2 5 km and most range from 1 to 6 km similar to lunar grabens but the martian grabens have slightly higher side walls average about 132 m and gentler wall slopes average of 9 and range of 2 25 than lunar grabens 93 m high and 18 slopes scarp degradation on mars has progressed through quakes impact shaking and dry slope processes the lower slopes may be due to mars higher gravity estimates of the amount of extension for individual grabens range from 20 to 350 m most estimates of the thickness of the faulted layer range from 0 5 to 4 5 km average is 1 5 km this thickness range corresponds closely to the 0 8 to 3 6 km range in depth for pits troughs and canyons in noctis labyrinthus and along the walls of valles marineris we propose that the predominant 1 to 1 5 km values obtained for both the thickness of the faulted layer and the depths of the pits troughs and theater heads of the canyons reflect the initial depth to the water table in this region as governed by the depth to the base of ground ice maximum depths for these features may indicate lowered groundwater table depths and the base of ejecta material

wrinkle ridges in lunae planum mars implications for shortening and strain photoclinometric data for lunae planum wrinkle ridges indicate average relief of approximately 130 m and distinct elevation discontinuities across the ridge of 55 m modeling ridges as the result of thrust faulting and associated upper plate folding indicates shortening across individual ridges of approximately 131 m 90 faulting total shortening at 20 degree n across lunae planue is approximately 1 840 m corresponding to a regional compressive strain of 0 29 strain appears uniform across lunae planum although it is accommodated by larger and few structures in the west than in the east

a prediction of mars seismicity from surface faulting the shallow seismicity of mars has been estimated by measurement of the total slip on faults visible on the surface of the planet throughout geologic time seismicity was calibrated with estimates based on surface structures on the moon and measured lunar seismicity that includes the entire seismogenic lithosphere results indicate that mars is seismically active today with a sufficient number of detectable marsquakes to allow seismic investigations of its interior

fault length statistics and implications of graben sets at candor mensa mars abstract the lengths of individual martian grabens from three spatially and temporally distinct regional sets are analyzed by a two dimensional window sampling method length distributions are influenced by fault growth and coalescence processes image resolution window size and the post faulting geologic history of the region cumulative length frequency distributions can be linear for graben lengths between 30 and 100 km with slopes on the area plot of 2 suggesting self similar growth of the graben array post faulting geologic processes contribute to concave cumulative length distributions on the log log plot with curtailment and truncation biases producing strongly non linear distributions for smaller and longer lengths respectively recent evidence for a positive correlation between stratigraphic throw and graben length from analogous terrestrial grabens implies that the magnitudes of throw and extensional strain may also be dependent on relative position along the martian grabens

localization of martian ridges by impact craters mechanical and chronological implications the eastern flank of the tharsis dome mars is affected by compressional ridges two conceptual models exist for these structures 1 the ridges are the expression of a superficial shortening and are rooted on a rheological boundary located in the megaregolith or 2 the ridges result from a global shortening on a lithospheric scale and are rooted on the deep thermal brittle ductile transition inside the lithosphere it is shown that the position of the ridges is strongly influenced by the existence of impact craters the distribution of crater ridge distances has been measured in the coprates area this distribution shows that the intersection of ridges and impact craters with a diameter larger than 4 km is four times as frequent as a homogeneous and random distribution of craters relative to what ridges would produce very detailed geometric studies of relationships between intersecting ridges and craters show that these craters are older than the ridges this localization implies that 1 ridges are superficial structures rooted at shallow depths in the megaregolith and 2 the ridging phase occurred some time after the deposit of the ridged plain unit material probably during the upper hesperian detailed geometrical studies of ridge edges and graben ridge width relationships suggest that ridges are bounded by two reverse faults with different offsets and that the rheological boundary on which ridges and graben are rooted is around 1 5 km deep three ways are possible for an impact crater to localize strain in a regional uniaxial compressional stress field 1 the strength of impacted material is lower than the strength of the surrounding nonaffected rocks 2 the lithostatic pressure underneath the crater is lower than the lithostatic pressure at the same depth in the surroundings due to the existence of the crater cavity and 3 the stress is concentrated on the crater borders if craters can be assimilated to holes in a shortened elastic plate in all three cases the initiation of the ridges occurs in the area where a low strength and or stress concentration envelope around the crater is nearest to the low strength decollement level

modelling potential hydrological impact of abandoned underground mines in the monday creek watershed ohio abandoned underground mines aum have caused dramatic environmental effects that are closely linked to regional sustainability this paper explores the potential hydrological impact of aum in the monday creek watershed a typically mined area in appalachian region using the soil and water assessment tool swat 2005 model and sequential uncertainty fitting sufi 2 calibrated at both the global and local scales the locally calibrated model better incorporates those key parameters relevant to aum for specific sub basins and hydrologic response units data from the years 2003 2004 were used for calibration and 2005 2006 for validation the results were quite satisfactory both the coefficient of determination r2 and the nash sutcliffe efficiency statistic were over 0 80 the potential influences of aum were assessed by modelling an alternative scenario assuming no aum for the period 2003 2009 results show that the hydrological process of lateral subsurface flow plays a dominant role in linking aum to overall watershed hydrology the potential hydrological impact of aum is an increased annual lateral flow of 82 1 and a decrease in annual surface flow by 15 leading to an increase of 16 9 in annual water yield for the monday creek watershed the seasonal fluctuation of water yield has a similar trend to lateral flow decreasing from march to august and increasing from august to january higher volume higher flow peaks and higher recession constants characterized the hydrograph of daily streamflow from aum the results indicate that more emphasis should be put on lateral flow for further study of acid mine drainage and flooding control in those watersheds with aum copyright 2012 john wiley sons ltd

hydrogeological and environmental impact of coal mining jharia coalfield india the jharia coalfield is the most important and active minig region it experiences groundwater inflow and affects groundwater levels in overlying aquifers and it provides the basis for a conceptual model of the hydrogeological impacts of coal mining the several sandstone aquifers of the overburden are separated by aquitards that limit vertical hydraulic connection but the inflow responds to seasonal events and seems to be linked to shallow groundwater behavior the mine drainage behavior suggests a hydraulic connection between the mine and the shallower groundwater system the greatest declines are directly above the panels with an immediate response to coal mining the inflow is localized by natural and induced fracture zones and is mostly into recent workings the groundwater behavior is controlled by hydraulic property changes caused by mine induced fracturing the hydrological and chemical qualities of the shallow groundwater regime in 13 mining collieries in mukunda block have been investigated water samples collected from 30 shallow monitoring dug wells were chosen for the study rainfall runoff and infiltration rates have been calculated in the area the water quality plottings were used to interpret the distribution of individual chemical parameters and in predicting the water quality the underground mine water has been classified as 1 unconfined groundwater in the calcareous siltstone and sandstone its composition is na ca so4 and na mghco3 with moderate total dissolved solids tds 200 1480 ppm 2 the deep groundwater originating from the coal seams and associated sediments in the near surface environments this is a na hco3 water with higher tds and 3 spoil dump waters are essentially na hco3 with high tds this article presents some hydrologic results and conclusions relating to the hydrogeological and environmental impacts of the coal mining in the jharia coalfield

reinterpretation of tractus fossae region as an asymmetric rift system on mars the tractus fossae region of mars is a wide area dominated by grabens normal faults and pit crater chains in this work based on previous studies on the area and the new interpretation of topographic data and morphological units based on images as a geologic framework we present a new insight on the origin of the graben structures as well as on the processes associated with the formation of the volcanic features here we propose a new model for this region on the basis of new measurements of graben extension and geological interpretations together with a reinterpretation of the stratigraphy and the geologic history of the area finally it is postulated that this region underwent a tectonic regime analog to an asymmetric rift system on earth

volcanic flow development at alba patera mars the hesperian amazonian age volcanic shield alba patera has associated with it some of the largest volcanic flows on mars an early hesperian flood lava phase was followed by the extrusion of high volume sheet and tube fed lavas many of which emerged from fissures on the flanks of a rising dome subsequently a plethora of sheet and tube fed lavas were erupted from linear vents located either at or within 200 km of the present summit these built complex flow fields which were erupted at rates several orders of magnitude greater than the maximum hawaiian rates later amazonian volcanism at alba saw extrusions of long narrow flows from two complex summit calderas whose formation is inferred to have been a direct result of magma supply to the volcano s flanks the outflow of thermal energy related to emplacement of some single flows 6 1028 ergs was substantially greater than earth s annual heat loss through volcanism and implies that patera building that have been a significant source of geologically rapid heat loss from mars during the early stages of volcanic centralization on the planet

pseudokinetics arising from the upscaling of geochemical equilibrium 1 multicomponent contaminant transport models in groundwater are typically based on assumptions of local geochemical equilibrium on the grid scale however in heterogenous systems there may be significant coupling between transport processes and geochemical equilibrium at smaller than grid block scale here various pore and field scale examples are considered to illustrate the impact of transport processes on assumptions of geochemical equilibrium in each example the flow length scales required to reach equilibrium are calculated it is shown that these can be as large as many meters at the pore scale and kilometers at field scales the influence of heterogeneity in the distribution of the reactive zones is assessed for the pore scale example and it is shown that patchiness of reactive zones within a pore increases equilibration length with the length and density of reactive zones pore radius and diffusion coefficient all playing a role in the equilibration length when constructing models of field scale problems it may not be reasonable to apply geochemical equilibrium and it may be necessary to explicitly couple pore scale and field scale models in a multiscale simulation a field scale example is also shown to illustrate that the upscaling of geochemical equilibrium poses a significant practical problem because we usually do not know the spatial location and distribution of geochemically active sites and this information is essential input to geochemical transport models