characterization of land subsidence induced by groundwater withdrawals in su xi chang area china su xi chang area is one of the typical regions in china which suffers from severe land subsidence various tools of field monitoring were integrated to study the characteristics and mechanisms of land subsidence in this region the occurrence and the development of the land subsidence in this region are strongly related to the groundwater pumping both in time and space the main consolidation layers are the soft mud layers however the compressibility of the confined sandy layers should not be ignored the second and third confined aquifers contributed more than 30 of total subsidence meanwhile irrecoverable deformations were also observed in the sandy layers different sandy layers deform diversely under different stress conditions some have the elastic feature but the soil strata including both sandy layers and clayey layers located in the center of the groundwater level depression cone exhibited obvious viscous mechanical behavior which caused the common lag phenomenon the sand composition mingled with small clay particles or interbeds and sand rheology are the two main reasons for the lag phenomena in sandy layers a series of laboratory tests for modeling the effective stress changes due to groundwater withdrawals were conducted to investigate the mechanism of the lag phenomenon based on the test results the relationship of stress strain time for saturated sands is obtained and it could be expressed as power functions the results also showed that the compression of the sandy layers was time dependent and its deformation could be remarkable when establishing land subsidence model the deformation for the similar soil formation could be elastic visco elastic and even visco elastic plastic because of the different groundwater level fluctuation experienced

birth growth and morphologic evolution of the laghetto cinder cone during the 2001 etna eruption we have undertaken detailed observations of the formation of the laghetto cinder cone a new cone that formed during a 2 week period of intense activity in piano del lago on the upper slopes of mount etna in summer 2001 we describe the events leading to the formation of a small graben the formation of pit craters on the base of the graben the onset of phreatomagmatic activity a transition to intense strombolian activity and a return to phreatomagmatic activity as the eruption came to an end we discuss the reasons for these transitions and describe the morphological development of the cone during these events arcuate cracks on the southern part of the cone were related to withdrawal of magma at the end of the eruption other slope instabilities that developed during the eruption include the formation of small radial grain flows on the outer flanks of the cone and the collapse into the crater of part of the crater rim some of the failure planes we observed were first identified using a flir tm 695 thermal infrared camera this is the first time that infrared thermography has been used to detect instability of volcanic structures results obtained during this test case demonstrate that thermal cameras are a very useful tool for studies of volcanic instability

seismic images of the grenville orogen in ontario in 1990 lithoprobe acquired 240 km of seismic reflection data across parts of the central gneiss belt cgb and the central metasedimentary belt cmb within the western grenville province of southern ontario interpretation of these data in conjunction with geological constraints provided by bedrock mapping supports a model of northwest directed thrusting and crustal shortening for the grenville orogen within the cgb the parry sound shear zone is imaged as a 3 km wide zone of reflections dipping southeastward at 20 25 and soling at depths 7 km in the north and 3 km in the south beneath parry sound domain parry sound domain and the immediately adjacent domains are underlain by a gently southeast dipping reflective zone at 4 5 12 0 km depth interpreted as a detachment surface likely associated with the central britt shear zone this zone may have accommodated northwesterly transport of parry sound southern britt and northwestern rosseau domains over britt domain during grenvillian thrusting wit

static and dynamic angles of repose in loose granular materials under reduced gravity granular materials avalanche when a static angle of repose is exceeded and freeze at a dynamic angle of repose such avalanches occur subaerially on steep hillslopes and wind dunes and subaqueously at the lee side of deltas until now it has been assumed that the angles of repose are independent of gravitational acceleration the objective of this work is to experimentally determine whether the angles of repose depend on gravity in 33 parabolic flights in a well controlled research aircraft we recorded avalanching granular materials in rotating drums at effective gravitational accelerations of 0 1 0 38 and 1 0 times the terrestrial value the granular materials varied in particle size and rounding and had air or water as interstitial fluid materials with angular grains had time averaged angles of about 40 and with rounded grains about 25 for all effective gravitational accelerations except the finest glass beads in air which was explained by static electricity for all materials the static angle of repose increases about 5 with reduced gravity whereas the dynamic angle decreases with about 10 consequently the avalanche size increases with reduced gravity the experimental results suggest that relatively low slopes of granular material on mars may have formed by dry flows without a lubricating fluid on asteroids even lower slopes are expected the dependence on gravity of angle of repose may require reanalysis of models for many phenomena involving sediment also at much lower slope angles

valles marineris tectonic and volcanic history inferred from dikes in eastern coprates chasma magmatic dikes have been proposed to have weakened and fractured the crust allowing the formation of valles marineris hence dikes were studied in the region of eastern coprates chasma in an area that includes a major transition between hesperian aged volcanic deposits in the western walls and pristine noachian crust in the eastern walls over a hundred dikes were identified dike widths are 13 m on average estimation of magma eruption rates are comparable with previous estimates for hesperian lava flows on mars 105 to 106 m3 s 1 dikes dips range from 55 to 90 orientations record two distinct main tectonic stress fields 90 and 70 different from the chasmata dikes striking 90 are only observed at elevations below 1500 m dikes striking 70 are observed at elevation below 0 m and are therefore considered older however linear features are also observed on the late noachian early hesperian surrounding plateaus and could be related to the 70 dike group in the western part of our study area dikes 10 of the total amount of dikes mapped strike 110 sub parallel to valles marineris and suggests a relationship between dike emplacement and graben formation the presence of pre existing faults in the two directions 90 and 70 could explain the shape of eastern valles marineris and chaotic terrains which have a different general orientation than the valles marineris main rift our results suggest a complex relationship between dike emplacement and the formation of valles marineris

the apparent absence of kilometer sized pyroclastic volcanoes on mercury are we looking right spacecraft data reveal that volcanism was active on mercury evidence of large volume effusive and smaller scale explosive eruptions has been detected however only large 15 km volcanic features or vents have been found so far despite abundant high resolution imagery on other volcanic planets the size of volcanoes is anticorrelated with their frequency small volcanoes are much more numerous than large ones here we present results of a numerical model that predicts the shapes of ballistically emplaced volcanic edifices and hence can explain the lack of kilometer sized constructional explosive volcanoes on the surface of mercury we find that due to the absence of the atmosphere particles are spread on this planet over a larger area than is typical for earth or mars erupted volumes are likely insufficient to build edifices with slope angles that enable their easy recognition with currently available data or that could survive destruction by subsequent impact bombardment

small crater modification on meridiani planum and implications for erosion rates and climate change on mars a morphometric and morphologic catalog of 100 small craters imaged by the opportunity rover over the 33 5 km traverse between eagle and endeavour craters on meridiani planum shows craters in six stages of degradation that range from fresh and blocky to eroded and shallow depressions ringed by planed off rim blocks the age of each morphologic class from 50 200 ka to 20 ma has been determined from the size frequency distribution of craters in the catalog the retention age of small craters on meridiani planum and the age of the latest phase of ripple migration the rate of degradation of the craters has been determined from crater depth rim height and ejecta removal over the class age these rates show a rapid decrease from 1 m myr for craters 1 ma to 0 1 m myr for craters 10 20 ma which can be explained by topographic diffusion with modeled diffusivities of 10 6 m2 yr in contrast to these relatively fast short term erosion rates previously estimated average erosion rates on mars over 100 myr and 3 gyr timescales from the amazonian and hesperian are of order 0 01 m myr which is 3 4 orders of magnitude slower than typical terrestrial rates erosion rates during the middle late noachian averaged over 250 myr and 700 myr intervals are around 1 m myr comparable to slow terrestrial erosion rates calculated over similar timescales this argues for a wet climate before 3 ga in which liquid water was the erosional agent followed by a dry environment dominated by slow eolian erosion

morphometry of scoria cones located on a volcano flank a case study from mt etna italy based on high resolution lidar data abstract by using new high resolution 2 m digital elevation model derived from the 2005 lidar survey of mt etna volcano italy our study measured the classical morphometrical parameters for scoria cones i e w co cone width w cr crater diameter h cone height as well as volume inclination of cone slope and substrate and a number of other parameters for 135 scoria cones of mt etna volume and age distribution of cones shows that there is no direct structural control on their emplacement in terms of etna s rift zones the cones are progressively smaller in size toward summit which can be explained by the large volcano s feeding system and progressively frequent lava burial toward top a careful analysis of h w co ratio determined as 0 18 for other volcanic fields worldwide shows that this ratio strongly depends on 1 the calculation method of h and 2 lava burial of cone for etnean cones applying an improved method for calculating h relative to the dipping substrate results in a significantly lowered standard h w co ratio 0 137 which in turn questions the validity of the classical value of 0 18 in the case of large central volcanoes the reduction of the ratio is not only due to methodology but also to the common lava burial this can be expressed even better if h mean is used instead of h max h mean w co 0 098 using this measure at etna well formed cones have higher ratios than structurally deformed e g double or rifted cones furthermore although the sampled scoria cones at etna have formed in a relatively narrow time interval h w co corresponding to erosional changes detected globally h w co 0 143 0 135 and 0 115 for three age classes of etna s scoria cones corresponding to average slopes of 26 6 23 9 and 23 7 because the morphometrical effect of position on a dipping substrate as well as lava burial exceeds the effect of erosion we call attention to use caution in simply using the h w co ratio of scoria cones for detecting age especially on large active volcanoes

detection of aquifer system compaction and land subsidence using interferometric synthetic aperture radar antelope valley mojave desert california interferometric synthetic aperture radar insar has great potential to detect and quantify land subsidence caused by aquifer system compaction insar maps with high spatial detail and resolution of range displacement 10 mm in change of land surface elevation were developed for a groundwater basin 103 km2 in antelope valley california using radar data collected from the ers 1 satellite these data allow comprehensive comparison between recent 1993 1995 subsidence patterns and those detected historically 1926 1992 by more traditional methods the changed subsidence patterns are generally compatible with recent shifts in land and water use the insar detected patterns are generally consistent with predictions based on a coupled model of groundwater flow and aquifer system compaction the minor inconsistencies may reflect our imperfect knowledge of the distribution and properties of compressible sediments when used in conjunction with coincident measurements of groundwater levels and other geologic information insar data may be useful for constraining parameter estimates in simulations of aquifer system compaction

scoria cones on mars detailed investigation of morphometry based on high resolution digital elevation models we analyze the shapes of 28 hypothesized scoria cones in three regions on mars i e ulysses and hydraotes colles and coprates chasma using available high resolution imaging science experiment and context camera ctx digital elevation models we determine the basic morphometric characteristics of the cones and estimate from ballistic modeling the physical parameters of volcanic eruptions that could have formed them when compared to terrestrial scoria cones most of the studied cones show larger volumes up to 4 2 109m3 larger heights up to 573m and smaller average slopes the average slopes of the ulysses hydraotes and coprates cones range between 7 and 25 and the maximum slopes only rarely exceed 30 which suggests only a minor role of scoria redistribution by avalanching ballistic analysis indicates that all cones were formed in a similar way and their shapes are consistent with an ejection velocity about 2 times larger and a particle size about 20 times smaller than on earth our results support the hypothesis that the investigated edifices were formed by low energy strombolian volcanic eruptions and hence are equivalent to terrestrial scoria cones the cones in hydraotes colles and coprates chasma are on average smaller and steeper than the cones in ulysses colles which is likely due to the difference in topographic elevation and the associated difference in atmospheric pressure this study provides the expected morphometric characteristics of martian scoria cones which can be used to identify landforms consistent with this type of activity elsewhere on mars and distinguish them from other conical edifices

a method to estimate groundwater depletion from confining layers 1 although depletion of storage in low permeability confining layers is the source of much of the groundwater produced from many confined aquifer systems it is all too frequently overlooked or ignored this makes effective management of groundwater resources difficult by masking how much water has been derived from storage and in some cases the total amount of water that has been extracted from an aquifer system analyzing confining layer storage is viewed as troublesome because of the additional computational burden and because the hydraulic properties of confining layers are poorly known in this paper we propose a simplified method for computing estimates of confining layer depletion as well as procedures for approximating confining layer hydraulic conductivity k and specific storage ss using geologic information the latter makes the technique useful in developing countries and other settings where minimal data are available or when scoping calculations are needed as such our approach may be helpful for estimating the global transfer of groundwater to surface water a test of the method on a synthetic system suggests that the computational errors will generally be small larger errors will probably result from inaccuracy in confining layer property estimates but these may be no greater than errors in more sophisticated analyses the technique is demonstrated by application to two aquifer systems the dakota artesian aquifer system in south dakota and the coastal plain aquifer system in virginia in both cases depletion from confining layers was substantially larger than depletion from the aquifers

inverse modeling of interbed storage parameters using land subsidence observations antelope valley california 1 we use land subsidence observations from repeatedly surveyed benchmarks and interferometric synthetic aperture radar insar in antelope valley california to estimate spatially varying compaction time constants and inelastic specific skeletal storage coefficients s kv in a previously calibrated regional groundwater flow and subsidence model the observed subsidence patterns reflect both the spatial distribution of head declines and the spatially variable inelastic skeletal storage coefficient using the nonlinear parameter estimation program ucode we estimate compaction time constants between 3 8 and 285 years the s kv values are estimated by linear estimation and range from 0 to almost 0 09 we find that subsidence observations over long time periods are necessary to constrain estimates of the large compaction time constants in antelope valley the insar data used in this study cover only a three year period limiting their usefulness in constraining these time constants this problem will be alleviated as more sar data become available in the future or where time constants are small by incorporating the resulting parameter estimates in the previously calibrated regional model of groundwater flow and land subsidence we can significantly improve the agreement between simulated and observed land subsidence both in terms of magnitude and spatial extent the sum of weighted squared subsidence residuals a common measure of model fit was reduced by 73 with respect to the original model however the ability of the model to adequately reproduce the subsidence observed over only a few years is impaired by the fact that the simulated hydraulic heads over small time periods are often not representative of the actual aquifer hydraulic heads errors in the simulated hydraulic aquifer heads constitute the primary limitation of the approach presented here

martian mud volcanism terrestrial analogs and implications for formational scenarios the geology of mars and the stratigraphic characteristics of its uppermost crust mega regolith suggest that some of the pervasively occurring pitted cones mounds and flows may have formed through processes akin to terrestrial mud volcanism a comparison of terrestrial mud volcanism suggests that equivalent martian processes likely required discrete sedimentary depocenters volatile enriched strata buried rheological instabilities and a mechanism of destabilization to initiate subsurface flow we outline five formational scenarios whereby martian mud volcanism might have occurred a rapid deposition of sediments b volcano induced destabilization c tectonic shortening d long term load induced subsidence and e seismic shaking we describe locations within and around the martian northern plains that broadly fit the geological context of these scenarios and which contain mud volcano like landforms we compare terrestrial and martian satellite images and examine the geological settings of mud volcano provinces on earth in order to describe potential target areas for piercement structures on mars our comparisons help to evaluate not only the role of water as a functional component of geological processes on mars but also how martian mud volcanoes could provide samples of otherwise inaccessible strata some of which could contain astrobiological evidence

geomechanics of subsurface water withdrawal and injection land subsidence and uplift ground ruptures and induced seismicity are the principal geomechanic effects of groundwater withdrawal and injection the major environmental consequence of groundwater pumping is anthropogenic land subsidence the first observation concerning land settlement linked to subsurface processes was made in 1926 by the american geologists pratt and johnson who wrote that the cause of subsidence is to be found in the extensive extraction of fluid from beneath the affected area since then impressive progress has been made in terms of a recognizing the basic hydrologic and geomechanic principles underlying the occurrence b measuring aquifer compaction and ground displacements both vertical and horizontal c modeling and predicting the past and future event and d mitigating environmental impact through aquifer recharge and or surface water injection the first milestone in the theory of pumped aquifer consolidation was reached in 1923 by terzaghi who introduced the principle of effective intergranular stress in the early 1970s the emerging computer technology facilitated development of the first mathematical model of the subsidence of venice made by gambolati and freeze since then the comprehension measuring and simulation of the occurrence have improved dramatically more challenging today are the issues of ground ruptures and induced triggered seismicity which call for a shift from the classical continuum approach to discontinuous mechanics although well known for decades anthropogenic land subsidence is still threatening large urban centers and deltaic areas worldwide such as bangkok jakarta and mexico city at rates in the order of 10 cm yr

shape of scoria cones on mars insights from numerical modeling of ballistic pathways abstract morphological observations of scoria cones on mars show that their cross sectional shapes are different from those on earth due to lower gravity and atmospheric pressure on mars particles are spread over a larger area than on earth hence erupted volumes are typically not large enough for the flank slopes to attain the angle of repose in contrast to earth where this is common the distribution of ejected material forming scoria cones on mars therefore is ruled mainly by ballistic distribution and not by redistribution of flank material by avalanching after the static angle of repose is reached as a consequence the flank slopes of the martian scoria cones do not reach the critical angle of repose in spite of a large volume of ejected material therefore the topography of scoria cones on mars is governed mainly by ballistic distribution of ejected particles and is not influenced by redistribution of flank material by avalanching the growth of a scoria cone can be studied numerically by tracking the ballistic trajectories and tracing the cumulative deposition of repeatedly ejected particles we apply this approach to a specific volcanic field ulysses colles on mars and compare our numerical results with observations the scoria cones in this region are not significantly affected by erosion and their morphological shape still preserves a record of physical conditions at the time of eruption we demonstrate that the topography of these scoria cones can be rather well with accuracy of 10 m reproduced provided that the ejection velocities are a factor of 2 larger and the ejected particles are about ten times finer than typical on earth corresponding to a mean particle velocity of 92 m s and a real particle size of about 4 mm this finding is in agreement with previous theoretical works that argued for larger magma fragmentation and higher ejection velocities on mars than on earth due to lower gravity and different environmental conditions

bright carbonate surfaces on ceres as remnants of salt rich water fountains abstract vinalia and cerealia faculae are bright and salt rich localized areas in occator crater on ceres the predominance of the near infrared signature of sodium carbonate on these surfaces suggests their original material was a brine here we analyze dawn framing camera s images and characterize the surfaces as composed of a central structure either a possible depression vinalia or a central dome cerealia and a discontinuous mantling we consider three materials enabling the ascent and formation of the faculae ice ascent with sublimation and carbonate particle lofting pure gas emission entraining carbonate particles and brine extrusion we find that a mechanism explaining the entire range of morphologies topographies as well as the common composition of the deposits is brine fountaining this process consists of briny liquid extrusion followed by flash freezing of carbonate and ice particles particle fallback and sublimation subsequent increase in briny liquid viscosity leads to doming dawn observations did not detect currently active water plumes indicating the frequency of such extrusions is longer than years

context camera investigation on board the mars reconnaissance orbiter 1 the context camera ctx on the mars reconnaissance orbiter mro is a facility instrument i e government furnished equipment operated by a science team not responsible for design and fabrication designed built and operated by malin space science systems and the mro mars color imager team marci ctx will 1 provide context images for data acquired by other mro instruments 2 observe features of interest to nasa s mars exploration program e g candidate landing sites and 3 conduct a scientific investigation led by the marci team of geologic geomorphic and meteorological processes on mars ctx consists of a digital electronics assembly a 350 mm f 3 25 schmidt type telescope of catadioptric optical design with a 5 7 field of view providing a 30 km wide swath from 290 km altitude and a 5000 element ccd with a band pass of 500 700 nm and 7 m pixels giving 6 m pixel spatial resolution from mro s nearly circular nearly polar mapping orbit raw data are transferred to the mro spacecraft flight computer for processing e g data compression before transmission to earth the ground data system and operations are based on 9 years of mars global surveyor mars orbiter camera on orbit experience ctx has been allocated 12 of the total mro data return or about 3 terabits for the nominal mission this data volume would cover 9 of mars at 6 m pixel but overlapping images for stereo mosaics and observation of changes and meteorological events will reduce this area ctx acquired its first instrument checkout images of mars on 24 march 2006

land subsidence in central mexico detected by alos insar time series abstract massive groundwater extraction is common throughout mexico and is well known to result in land subsidence however most land subsidence surveys focus on one single city mainly mexico city and thus fail to reveal the regional extent of the problem here we use 2007 2011 interferometric synthetic aperture radar insar time series analysis of alos data to resolve land subsidence in the entire central mexico region we identify land subsidence in 21 areas including 17 cities linear vertical rates over 30 cm yr are observed in mexico city while in the other locations rates of 5 10 cm yr are detected we define 3 main categories of subsidence using the averaged velocity maps in conjunction with previously published structural surface geology and land use mapping 1 rapid large scale subsidence 2 rapid local scale subsidence and 3 slow patchy subsidence the correlation between subsidence and land use confirms that groundwater extraction mainly for agricultural and urban activities is the main cause of land subsidence we observe that the boundaries of the subsiding areas are typically characterized by high velocity gradients often coinciding with pre existing faults motion on these faults being driven by water extraction rather than by tectonic activity regional surveys of this type are necessary to understand the spatial and temporal evolution of land subsidence to constrain the distribution and connectivity of water bearing units and ultimately to reach better hazard mitigation plans

numerical simulation and prediction of regional land subsidence caused by groundwater exploitation in the southwest plain of tehran iran abstract this study characterizes land subsidence in southwest plain of tehran using numerical modeling and predicts the trend through 2018 excessive groundwater withdrawal has caused severe land subsidence in tehran in the past 28 years 1984 2012 groundwater level has decreased 11 65 m the multi layered aquifer system in the southwestern plain of tehran contains three aquifers and three aquitard units the present model was developed simulation using pmwin modflow for windows first groundwater level and land subsidence were simulated for the end of 2004 the model was calibrated using hydraulic head measurements and insar data the simulation results were in fairly good agreement with the measurement results the calibrated and evaluated model was then used to assess the future evolution of land subsidence and for prediction of subsidence through the end of 2018 numerical results show that assuming a constant rate of pumping in the future land subsidence in the southwestern plain of tehran will reach 33 cm by 2018 the study confirmed that land subsidence caused by groundwater pumping is a serious threat to southwest tehran

amazonian volcanism inside valles marineris on mars the giant trough system of valles marineris is one of the most spectacular landforms on mars yet its origin is still unclear although often referred to as a rift it also shows some characteristics that are indicative of collapse processes for decades one of the major open questions was whether volcanism was active inside the valles marineris here we present evidence for a volcanic field on the floor of the deepest trough of valles marineris coprates chasma more than 130 individual edifices resemble scoria and tuff cones and are associated with units that are interpreted as lava flows crater counts indicate that the volcanic field was emplaced sometime between 0 4 ga and 0 2 ga the spatial distribution of the cones displays a control by trough parallel subsurface structures suggesting magma ascent in feeder dikes along trough bounding normal faults spectral data reveal an opaline silica rich unit associated with at least one of the cones indicative of hydrothermal processes our results point to magma water interaction an environment of astrobiological interest perhaps associated with late stage activity in the evolution of valles marineris and suggest that the floor of coprates chasma is promising target for the in situ exploration of mars

time dependent land uplift and subsidence in the santa clara valley california from a large interferometric synthetic aperture radar data set 1 we invert 115 differential interferograms derived from 47 synthetic aperture radar sar scenes for a time dependent deformation signal in the santa clara valley california the time dependent deformation is calculated by performing a linear inversion that solves for the incremental range change between sar scene acquisitions a nonlinear range change signal is extracted from the ers insar data without imposing a model of the expected deformation in the santa clara valley cumulative land uplift is observed during the period from 1992 to 2000 with a maximum uplift of 41 18 mm centered north of sunnyvale uplift is also observed east of san jose seasonal uplift and subsidence dominate west of the silver creek fault near san jose with a maximum peak to trough amplitude of 35 mm the pattern of seasonal versus long term uplift provides constraints on the spatial and temporal characteristics of water bearing units within the aquifer the silver creek fault partitions the uplift behavior of the basin suggesting that it acts as a hydrologic barrier to groundwater flow while no tectonic creep is observed along the fault the development of a low permeability barrier that bisects the alluvium suggests that the fault has been active since the deposition of quaternary units

suturing and extensional reactivation in the grenville orogen canada sutures are zones of weakness within orogenic belts that have the potential to become reactivated during orogenic evolution the robertson lake shear zone marks a major tectonic boundary in the southeastern grenville orogen of canada that has been intermittently active for at least 130 m y the shear zone played a major role in the compressional stage of the orogenic cycle as well as during postorogenic collapse the zone separates the elzevir terrane to the west and the frontenac terrane to the east sphene ages u pb indicate that these two terranes have distinct tectonothermal histories and that the shear zone represents a cryptic suture in its current state the shear zone is a low angle 30 ese dip plastic to brittle extensional shear zone that separates the mazinaw footwall and sharbot lake hanging wall domains integration of structural metamorphic and chronologic data leads to a model that describes the complete evolution of this fundamental tectonic boundary that evolved from an early compressional zone ca 1030 ma to a late extensional zone until at least 900 ma

bombs behaving badly unexpected trajectories and cooling of volcanic projectiles we collected thermal infrared video of two explosive eruptions at stromboli in june 2008 and manually traced the trajectories of 95 particles launched during two eruptions we found that 10 15 of the analyzed trajectories deviated from predicted curves due to collisions causing one particle to travel horizontally more than twice as far as expected furthermore we observed an oscillatory cooling behavior for the airborne pyroclasts with a median period of 0 46 s measured cooling was typically much faster than model predicted cooling with discrepancies of up to 40 between measured cooling and theoretical modeling we interpret the measured cooling curves as resulting from the spinning and twisting and tearing of particles during travel the periodic re exposing of the hotter core of the pyroclasts to the atmosphere may cause the observed oscillations and the spinning may accelerate cooling by enhancing convective heat transfer current volcanic trajectory and cooling models do not account for projectile collisions spinning or tearing and can thus severely underestimate the maximum landing distance and cooling rates of large pyroclasts

the effects of pulsed pumping on land subsidence in the santa clara valley california abstract land subsidence caused by pulsed and constant pumping schemes was calculated and the results were compared to determine the possible advantages of pulsed pumping in reducing land subsidence pulsed pumping refers to pumping strategies involving alternation between periods of pumping and recovery in a well subsidence was calculated using a numerical model based on the santa clara valley ca the model accounts for delay in the release of water from storage in compressible interbeds as well as flow within aquifers for these tests the ratio of pumping period length to recovery period length was either 1 1 or 1 3 pulsing interval length length of one pumping period plus one recovery period ranged from 4 to 90 days pumping rates were adjusted so that pulsed pumping and constant pumping removed the same volume of water over the period under consideration pulsed pumping has the potential to concentrate subsidence around the pumping well for all simulations pulsed pumping caused greater subsidence near the test well than constant pumping under some conditions a transition point was reached beyond which pulsed pumping caused less subsidence than steady pumping the distance from the test well to the transition point decreases for a decreasing aquifer transmissivity b decreasing ratio of pumping period to recovery period and c increasing pulsing interval length the concentration of subsidence was reduced considerably when delay in release of water from storage in compressible aquitards was neglected indicating the importance of including delay effects in subsidence studies all pulsed pumping strategies caused a greater total volume of subsidence than steady pumping

an 1161 ma suture in the frontenac terrane ontario segment of the grenville orogen in the central metasedimentary belt of the grenville orogen we recognize two contrasting packages of rocks within what traditionally has been interpreted as a continuous intact stratigraphic sequence metamorphosed under upper amphibolite facies to granulite facies conditions the two packages are separated by a thrust fault the hanging wall of which was transported northwestward relative to rocks of the footwall upper greenschist to lower amphibolite grade marbles make up the footwall whereas the allochthon contains granulites metamorphosed prior to deposition of an unconformably overlying quartzite and intrusion of a compositionally diverse suite of 1179 1162 ma plutons emplacement of the pluton saturated allochthon occurred at 1161 ma and metamorphosed platformal carbonates into the marbles of the footwall we interpret this thrust as part of a fundamental suture within the grenville orogen

geostatistical inverse modeling for the characterization of aquitard heterogeneity using long term multi extensometer data abstract the classical aquitard drainage model compac was used to simulate the deformation of a one dimensional vertically heterogeneous aquitard i e heter compac by coupling heter compac with the quasi linear geostatistical inversion approach the vertical heterogeneities of hydraulic conductivity k v elastic specific storage s ske and inelastic specific storage s skp fields could be characterized with the availability of long term multi extensometer data the methodology was first tested through a group of ten synthetic cases with randomly generated k v s ske and s skp fields results of the synthetic cases revealed that a geostatistical model could characterize the variability of aquitard hydraulic parameter fields and yields improved fits of simulated versus observed zone deformation than a geological model that treats each zone to be homogeneous subsequently the methodology was applied to a research site situated in changzhou city jiangsu province china where long term deformation behaviors of the strata within the aquifer aquitard system have been monitored vertical heterogeneities of k v s ske and s skp fields of the investigated aquitard at the site were characterized using the quasi linear geostatistical approach the correlation length of the three fields that yielded the best quality fit was assessed to be approximately 50 m and the fitting quality was slightly improved in comparison with that produced from calibrating a geological or zonation model through monte carlo analysis of aquitard deformation utilizing the inversed parameters and corresponding uncertainties the investigated aquitard is estimated to have compacted 914 8 42 6 mm before the rise in groundwater levels in adjoining aquifers

post eruptive sediment transport and surface processes on unvegetated volcanic hillslopes a case study of black tank scoria cone cima volcanic field california abstract conical volcanic edifices that are made up from lapilli to block bomb pyroclastic successions such as scoria cones are widespread in terrestrial and extraterrestrial settings eruptive processes responsible for establishing the final facies architecture of a scoria cone are not well linked to numerical simulations of their post eruptive sediment transport using sedimentological geomorphic and 2d fragment morphology data from a 15 ky old scoria cone from the cima volcanic field california this study provides field evidence of the various post eruptive sediment transport and degradation processes of scoria cones located in arid to semi arid environments this study has revealed that pyroclast morphologies vary downslope due to syn eruptive granular flows along with post eruptive modification by rolling bouncing and sliding of individual particles down a slope and overland flow processes the variability of sediment transport rates on hillslopes are not directly controlled by local slope angle variability and the flank length but rather by grain size and morphological characteristics of particles such as shape irregularity of pyroclast fragments and block lapilli ratio due to the abundance of hillslopes degrading in unvegetated regions such as those found in the southwestern usa granulometric influences should be accounted for in the formulation of sediment transport laws for geomorphic modification of volcanic terrains over long geologic time

evidence for ponding and catastrophic floods in central valles marineris mars abstract the valles marineris canyon system of mars is closely related to large flood channels some of which emerge full born from chaotic terrain in canyon floors coprates chasma one of the largest valles marineris canyons is connected at its west end to melas chasma and on its east end to chaotic terrain filled capri and eos chasmata the area from central melas to eos chasmata contains a 1500 km long and about 1 km deep depression in its floor despite the large volumes of groundwater that likely discharged from chaotic terrain in this depression no evidence of related fluvial activity has thus far been reported we present an analysis of the regional topography which together with photogeologic interpretation of available imagery suggests that ponding due to late hesperian discharge of water possibly produced a lake mean depth 842 m spanning parts of the valles marineris depression vmd overflow of this lake at its eastern end resulted in delivery of water to downstream chaos regions and outflow channels our ponding hypothesis is motivated primarily by the identification of scarp and terrace features which despite a lateral spread of about 1500 km have similar elevations furthermore these elevations correspond to the maximum ponding elevation of the region 3560 m simulated ponding in the vmd yields an overflow point at its eastern extremity in eos chasma the neighborhood of this overflow point contains clear indicators of fluvial erosion in a consistent east west orientation

systematic morphometric characterization of volcanic edifices using digital elevation models abstract quantitative characterization of the size and shape of volcanic edifices is an essential step towards the understanding of factors controlling volcano growth and morphology the recent advent of digital elevation models dems with worldwide coverage offers the opportunity to systematically document the morphometry of all types of volcanoes using quantitative well formalized methodologies we present a methodology for the morphometric characterization of volcanic edifices after reviewing previous studies on volcano morphometry and the various existing dem sources we describe an integrated procedure that uses a dem and its derived products slope curvature to extract a coherent set of morphometric parameters for a given volcanic edifice edifice boundaries are manually defined by searching for breaks in slope around the base the parameters describe the overall size basal and summit region area and widths height volume planar shape ellipticity and irregularity index of elevation contours profile shape height width ratios and slope of the edifice similar parameters for relatively large depending on dem spatial resolution summit craters calderas are also computed slope values and ellipticity and irregularity indexes are extracted for successive height intervals providing detailed information of volcano shape as a function of height the number of secondary peaks is also estimated the method is tested on thirteen composite volcanoes in nicaragua using three dem datasets 90 m srtm 30 m aster g dem and an 80 m topographic map derived dem and the resulting parameters are evaluated in terms of boundary delineation and dem source finally the parameters obtained for the nicaraguan volcanoes are discussed as an illustrative example of the type of data and information that can be extracted systematically for volcanoes worldwide

time to reach near steady state in large aquifers 1 a new analytical solution of the flow equation has been developed to estimate the time to reach a near equilibrium state in mixed aquifers i e having unconfined and confined portions following a large hydraulic perturbation near equilibrium is defined as the time for an initial aquifer perturbation to dissipate by an average 95 across the aquifer the new solution has been obtained by solving the flow system of a simplified conceptual model of a mixed aquifer using laplace transforms the conceptual model is based on two assumptions 1 the groundwater flow can be reduced to a horizontal 1 d problem and 2 the transmissivity a function of the saturated thickness is assumed constant on the unconfined portion this new solution depends on the storativity of the unconfined portion the lengths of the unconfined and confined portions and the transmissivity assumed to be constant and equal in both portions of the mixed aquifer this solution was then tested and validated against a numerical flow model where the variations of the saturated thickness and therefore variations of the transmissivity were either ignored or properly modeled the agreement between the results from the new solution and those from the numerical model is good validating the use of this new solution to estimate the time to reach near equilibrium in mixed aquifers this solution for mixed aquifers as well as the solutions for a fully confined or fully unconfined aquifer has been used to estimate the time to reach near equilibrium in 13 large aquifers in the world for those different aquifers the time to reach near equilibrium ranges between 0 7 kyr to 2 4 107 kyr these results suggest that the present hydraulic heads in these aquifers are typically a mixture of responses induced from current and past hydrologic conditions and thus climate conditions for some aquifers the modern hydraulic heads may in fact depend upon hydrologic conditions resulting from several past climate cycles

hydrovolcanic tuff rings and cones as indicators for phreatomagmatic explosive eruptions on mars hydrovolcanism is a common natural phenomenon on earth and should be common on mars too since its surface shows widespread evidence for volcanism and near surface water we investigate fields of pitted cones in the nephentes amenthes region at the southernmargin of the ancient impact basin utopia which were previously interpreted as mud volcanoes the cone fields contain pitted and breached cones with associated outgoing flow like landforms based on stratigraphic relations we determined ahesperian or youngermodel age we test the hypothesis of a hydro volcanic origin based on a detailed morphological and morphometrical analysis and an analysis of the regional context an igneous volcanic origin of these cones as hydrovolcanic edifices produced by phreatomagmatic eruptions is plausible several lines of evidence suggest the existence of subsurface water ice the pitted cones display well developed wide central craters with floor elevations below the preeruptive surface their morphometry and the overall appearance are analogous to terrestrial tuff cones and tuff rings mounds that are also observed in the same region resemble terrestrial lava domes the hydrovolcanic interaction between ascending magma and subsurface water and or water ice may explain the formation of the pitted cones although other scenarios such as mud volcanism cannot be ruled out together with the mounds the cones might represent effusive and explosive edifices of amonogenetic volcanic field composed of lava domes tuff rings tuff cones and possibly maars

rift zone volcanism and associated cinder cone field in utopia planitia mars 1 we analyzed a small cone field in sw utopia planitia that shows striking similarities to volcanic rift zones on earth this is of particular interest as the study area lies off any of the volcanic centers of mars in the northern hemisphere lowlands and is surrounded by material of the amazonian aged vastitas borealis formation vbf we believe that the study area could be the first direct evidence for volcanic activity in utopia planitia prior to the resurfacing by vbf material the most striking characteristics that we observed are 1 a set of broad eruptive fissures showing signs of ongoing extension during cone formation 2 parallel dike swarms 3 magmatic intrusions and 4 a number of lava flows that have erupted from the fissures and pitted cones that surround a larger cone in the center of the study area and that are often associated with or aligned along the fissures and dikes cratering model ages indicate that the study area is of late noachian to early hesperian age and is thus distinctly older than the surrounding vbf falling into the time frame of the main phases of activity in the volcanic centers of syrtis major elysium planitia and the southern highlands

syn eruptive morphometric variability of monogenetic scoria cones according to wood s model morphometric parameters such as slope angle can provide valuable information about the age of conical volcanic edifices such as scoria cones assuming that their initial slopes range from 30 to 33 measured manually on topographic maps and assuming that their inner architectures are homogenous this study examines the morphometric variability of nine young a few thousand years old small volume scoria cones from tenerife canary islands using high resolution digital elevation models in order to assess their slope angle variability because of the young age and minimal development of gullies on the flanks their morphometric variability can be interpreted as the result of syn eruptive processes including 1 pre eruptive surface inclination 2 vent migration and lava outflow with associated crater breaching and 3 diversity of pyroclastic rocks accumulated in the flanks of these volcanic edifices results show that slope angles for flank sectors differ by up to 12 among the studied volcanoes which formed over the same period of time this range greatly exceeds the 2 3 indicated by wood the greater than expected original slope range suggests that use of morphometric data in terms of morphometry based relative dating and detection of erosional processes and settings must be done with great care or detailed knowledge about absolute ages and eruption history especially in field scale morphometric investigation

high resolution imaging science experiment hirise images of volcanic terrains from the first 6 months of the mars reconnaissance orbiter primary science phase 1 in the first 6 months of the mars reconnaissance orbiter s primary science phase the high resolution imaging science experiment hirise camera has returned images sampling the diversity of volcanic terrains on mars while many of these features were noted in earlier imaging they are now seen with unprecedented clarity we find that some volcanic vents produced predominantly effusive products while others generated mostly pyroclastics flood lavas were emplaced in both turbulent and gentle eruptions producing roofed channels and inflation features however many areas on mars are too heavily mantled to allow meter scale volcanic features to be discerned in particular the major volcanic edifices are extensively mantled though it is possible that some of the mantle is pyroclastic material rather than atmospheric dust support imaging by the context imager ctx and topographic information derived from stereo imaging are both invaluable in interpreting the hirise data

explosive volcanic eruptions on mars tephra and accretionary lapilli formation dispersal and recognition in the geologic record explosive volcanic eruptions potentially involving large amounts of magmatic and entrained water are thought to have been very important in the noachian and hesperian periods earlier in mars history and basaltic plinian eruptions are likely to have occurred throughout martian history previous treatments of explosive volcanic plumes on mars have simply extrapolated plume models for the earth s atmosphere to mars taking account of known limitations to the applicability of this approach which suggest that convective plumes may be capable of reaching only 20 km height on mars we introduce the concept of inertial plumes capable of carrying clasts to much greater heights and dropping them into the lower atmosphere over a wide area atmospheric circulation patterns guarantee wide dispersal and thick deposits of tephra resulting from both types of eruption the presence of large amounts of water in convecting explosive eruption plumes can also lead to condensation of water on small particles and the consequent accretion of other particles as the smaller particles fall through the plume producing accretionary lapilli formation of accretionary lapilli significantly alters the spatial distribution and grain sizes of pyroclastic fall deposits from those involving discrete juvenile clasts with negligible clast interactions we model the eruption and dispersal of tephra and the formation of accretionary lapilli on mars under current atmospheric conditions and explore the consequences of this for the geometry and grain size of deposits formed from explosive eruption plumes we show that explosive eruptions can produce thick widespread deposits of ash and lapilli similar to those thought to have produced mantling deposits in several regions of mars we develop a detailed example that shows that local hydrovolcanic explosive eruptions and solely magmatic eruptions originating from the nearby apollinaris patera could have emplaced tephra and accretionary lapilli in the columbia hills region of the mars exploration rover gusev site if the atmospheric pressure was higher early in mars history than now eruptions would have led to somewhat more extensive pyroclast dispersal than under current conditions

modeling compaction of multi layer aquifer system due to groundwater withdrawal abstract excessive groundwater extraction in a sedimentary environment can result in subsidence which not only deteriorates land and agricultural resources but also endangers public infrastructure subsidence can be contributed by compaction in different layers clarifying the causes and estimating the amount of compaction remain a challenge for a multi layer aquifer system with spatially and temporally varying pumping activities a distributed model that comprises an analytical quasi three dimensional groundwater model and a one dimensional deformation model is proposed to model the groundwater flow and deformation for a multi layer aquifer system using the analytical solution the groundwater level variation around a pumping well can be adequately modeled and then the compaction of soil layers can be calculated superposition allows the results to be extended to a system with multi well and or multi layer pumping the integrated model was applied to yuanchang in the center of the yunlin subsidence area taiwan data of groundwater level and compaction at aquifers 2 and 3 in dry season periods were used to explore the pumping effects on compaction the results show that single layer groundwater users are responsible for the large area compaction and that significant local compaction can be attributed to multi layer users constraining multi layer pumping activities and reducing the amount of groundwater exploitation are required to mitigate the subsidence in yunlin

detecting short term evolution of etnean scoria cones a lidar based approach the 2001 and 2002 2003 flank eruptions on mount etna italy were characterized by intense explosive activity which led to the formation of two large monogenetic scoria cones one from each eruption on the upper southern flank of the volcano continuous monitoring of etna especially during flank eruptions has provided detailed information on the growth of these cones they differ in genesis shape and size a set of high resolution 1 m digital elevation models dems derived from light detection and ranging lidar data collected during four different surveys 2004 2005 2006 and 2007 has been used to map morphology and to extract the morphometric parameters of the scoria cones by comparing lidar derived dems with a pre eruption 1998 10 m dem the volume of the two scoria cones was calculated for the first time comparison of the lidar derived dems revealed in unprecedented detail morphological changes during scoria cone degradation in particular the morphologically more exposed and structurally weaker 2002 2003 cone was eroded rapidly during the first few years after its emplacement mainly due to gravitational instability of slopes and wind erosion

evaluation of morphometry based dating of monogenetic volcanoes a case study from bandas del sur tenerife canary islands morphometry based dating provides a first order estimate of the temporal evolution of monogenetic volcanic edifices located within an intraplate monogenetic volcanic field or on the flanks of a polygenetic volcano two widely used morphometric parameters namely cone height width ratio hmax wco and slope angle were applied to extract chronological information and evaluate their accuracy for morphometry based ordering based on these quantitative parameters extracted from contour based digital elevation models dems two event orders for the bandas del sur in tenerife canary islands were constructed and compared with the existing k ar paleomagnetic and stratigraphic data the results obtained suggest that the commonly used hmax wco ratio is not reliable leading to inappropriate temporal order estimates while the slope angle gives slightly better results the overall performance of such descriptive parameters was however generally poor i e there is no strong correlation between morphometry and age the geomorphic morphometric mismatches could be the result of 1 the diversity of syn eruptive processes i e diverse initial morphologies causing geomorphic morphometric variability 2 contrasting edifice specific degradation that depends partly upon the inner facies architecture of the volcanic edifices 3 various external environmental controls e g tephra mantling from pyroclastic density currents unrelated to the edifice evaluated and 4 differences in the scale resolution of input data the observed degradation trend and changes in morphometric parameters over time do not support a simple degradation model for monogenetic scoria cones volcanoes

geodetic evidence for subsidence due to groundwater withdrawal in many parts of the united states of america abstract analysis of repeated levelings conducted by the national geodetic survey indicates many locations of relative subsidence in the u s a specific criteria are used to identify those subsidence features which most likely result from sediment compaction due to lowering of water levels in underground aquifer systems previously reported areas of such subsidence that seem to be confirmed by this study include south central arizona savannah georgia pecos and houston galveston texas denver colorado san joaquin valley santa clara valley saugus basin los angeles basin and bunker hill san timoteo california milford utah raft river valley idaho baton rouge and new orleans louisiana and las vegas nevada in addition our analysis indicates that such subsidence is more widespread than previously reported occurring in a number of locations within the atlantic and gulf of mexico coastal plains and along the mississippi valley as well as in many other unconsolidated sedimentary basins from which groundwater has been extracted and for which repeated leveling measurements are available more than 30 new locations of subsidence possibly due to water withdrawal have been identified the best documented of these include ventura ontario and san pedro santa monica california monroe and alexandria louisiana and jackson mississippi subsidence in newly identified locations ranges from several tens of millimeters to a few hundred millimeters over distances of 10 60 km and times of 2 48 yr subsidence may also have occurred in other groundwater basins where water levels have been drawn down and remained undetected because of a lack of repeated levelings it is important to be aware of and to continue to monitor such effects because of increasing rates of utilization of groundwater resources and the potential for significant engineering problems due to surface movements in addition identifying cases of subsidence due to water withdrawal is essential in order to use effectively releveling observations for investigating tectonic deformation along these lines our analysis suggests that some of the releveling observations used to define a region of tectonic uplift in southern california more likely reflect subsidence due to water level declines within sedimentary basins around the periphery of the presumed zone of uplift

the effects of artificial recharge of groundwater on controlling land subsidence and its influence on groundwater quality and aquifer energy storage in shanghai china long term groundwater overpumping in shanghai has caused serious land subsidence to restore the declined piezometric groundwater levels and to decrease the land subsidence rate artificial recharge ar of groundwater into confined aquifers through injected wells has been proposed as an important measurement since the beginning of the 1960s in the case of shanghai recharge source is tap water whose chemical constituents and temperature are different from groundwater consequently the issues of groundwater quality change and thermal energy are worthy of discussion in this paper we discussed the influences of ar for controlling land subsidence on 1 groundwater level and land subsidence rate 2 groundwater quality 3 aquifer thermal energy storage the results based on the collected long term historical data in the study area show that ar not only is beneficial to groundwater level rising and land rebound but also provides cheap energy sources for industrial production the groundwater quality presented the trend of desalination and a general increase in sulfate iron and manganese contents organic and nitrogenous compounds after the tap water injection however the ar s influence on groundwater quality was limited with the radius 100 m for single well recharge and 1000 m for well groups recharge to control the development of the land subsidence within a safe limit in the study area the injected confined aquifers and the distribution of the ar wells need to be further adjusted due to the limitation of current ar

formation and evolution of the chaotic terrains by subsidence and magmatism hydraotes chaos mars the origin of the martian chaotic terrains is still uncertain and a variety of geologic scenarios have been proposed we provide topographic profiles of different chaos landscapes notably aureum and hydraotes chaos showing that an initial shallow ground subsidence occurred at the first step of the chaos formation we infer that the subsidence was caused by intrusion of a volcanic sill which could have produced consequent melting as well as release of ground water from disrupted aquifer signs of a volcanic activity are observed on the floor of hydraotes chaos a complex and deep depression located at the junction of three channels the volcanic activity is represented by small 0 5 to 1 5 km diameter rounded cones with summit pits the cone s size and morphology as well as the presence of possible surrounding lava flows suggest that they are primary volcanic cones similar to terrestrial cinder cones the identification of volcanic activity on the deepest chaos where the lower crustal thickness and the faults fractures system contributed to the magma rising reveals that magmatic activity proved by the cones and possibly help by structural activity has been a major factor in the formation of chaotic terrains

interbed storage changes and compaction in models of regional groundwater flow water released from permanent compaction of compressible fine grained interbeds within confined aquifers may be a significant source of pumped water permanent or inelastic compaction of the interbeds occurs when head declines from pumping cause the effective stress or grain to grain load to exceed the elastic limits of the interbeds as a result the grains in the interbeds rearrange and excess water is expelled the amount of inelastic compaction generally is proportional to the increase in effective stress and the decrease in head a common approach for the simulation of elastic and inelastic compaction in groundwater flow models is to assume that head changes in the aquifer result in instantaneous storage changes in the compressible interbeds a term is added to the groundwater flow equation to account for the storage changes changes in specific storage may be computed explicitly from the results at the previous time step in the finite difference formulation of the groundwater flow equation a better approach is to implicitly apportion storage changes between elastic and inelastic components within a time step if storage changes cannot be considered to occur instantaneously with change in head in the aquifer another approach is taken equations for horizontal flow in the aquifer are coupled with equations for vertical flow in the compressible interbeds to simulate flow in half a representative doubly draining interbed storage changes and compaction are calculated for the representative half thickness and are extrapolated to the entire thickness of all interbeds within each cell this approach was applied to an existing model of groundwater flow in the central valley of california the simulation demonstrates that solving coupled systems of equations is feasible for a regional flow model

estimating the permanent loss of groundwater storage in the southern san joaquin valley california in the san joaquin valley california recent droughts starting in 2007 have increased the pumping of groundwater leading to widespread subsidence in the southern portion of the san joaquin valley vertical subsidence as high as 85 cm has been observed between june 2007 and december 2010 using interferometric synthetic aperture radar insar this study seeks to map regions where inelastic not recoverable deformation occurred during the study period resulting in permanent compaction and loss of groundwater storage we estimated the amount of permanent compaction by incorporating multiple datasets the total deformation derived from insar estimated skeletal specific storage and hydraulic parameters geologic information and measured water levels during our study period we used two approaches one that we consider to provide an estimate of the lowest possible amount of inelastic deformation and one that provides a more reasonable estimate these two approaches resulted in a spatial distribution of values for the percentage of the total deformation that was inelastic with the former estimating a spatially averaged value of 54 and the latter a spatially averaged value of 98 the former corresponds to the permanent loss of 4 14 108 m3 of groundwater storage or roughly 5 of the volume of groundwater used over the study time period the latter corresponds to the loss of 7 48 108 m3 of groundwater storage or roughly 9 of the volume of groundwater used this study demonstrates that a data driven approach can be used effectively to estimate the permanent loss of groundwater storage this article is protected by copyright all rights reserved

the growth and erosion of cinder cones in guatemala and el salvador models and statistics abstract morphologic data for 147 cinder cones in southern guatemala and western el salvador are compared with data from the san francisco volcanic field arizona usa cima volcanic field california usa michoacan guanajuato volcanic field mexico and the lamongan volcanic field east java the guatemala cones have an average height of 110 50 m an average basal diameter of 660 230 m and an average top diameter of 180 150 m the general morphology of these cones can be described by their average cone angle of slope 24 7 average height to radius ratio 0 33 0 09 and their flatness 0 24 0 18 although the mean values for the guatemalan cones are similar to those for other volcanic fields e g san francisco volcanic field arizona cima volcanic field california michoacan guanajuato volcanic field mexico and lamongan volcanic field east java the range of morphologies encompasses almost all of those observed worldwide for cinder cones three new 40ar 39ar age dates are combined with 19 previously published dates for cones in guatemala and el salvador there is no indication that the morphologies of these cones have changed over the last 500 1000 ka furthermore a re analysis of published data for other volcanic fields suggests that only in the cima volcanic field of those studied is there clear evidence of degradation with age preliminary results of a numerical model of cinder cone growth are used to show that the range of morphologies observed in the guatemalan cinder cones could all be primary that is due to processes occurring at the time of eruption

a numerical model to calculate land subsidence applied at hangu in china abstract the deep unconsolidated sedimentary aquifers of eastern china are heavily over exploited and this causes aquifer compaction 1 which results in land subsidence the geological formation contains significant thicknesses of clay which introduces time delays between the extraction of the groundwater and the resulting subsidence a new computer code called the interbed drainage package has been developed for the popular modflow model to address this behaviour it has been applied in a simulation of the port of hangu and the results are being used to manage the land subsidence problem

groundwater pumping and land subsidence in the emilia romagna coastland italy modeling the past occurrence and the future trend 1 the emilia romagna coastland south of the po river delta italy has experienced a dramatic land settlement mainly due to the large groundwater withdrawal related to the local economic and tourist development started in the early 1950s although the use of surface water has reduced the settlement rate over the last three decades anthropogenic land subsidence still continues in a few kilometer wide coastal strip at a rate larger than the natural one the occurrence is reconstructed since 1946 with the aid of advanced finite element flow and poromechanical models implemented with a realistically detailed geology of the regional shallow multiaquifer system the models have been calibrated against the piezometric leveling and extensometer records observed over the last 50 years and a land subsidence prediction in 2016 is performed the results show that the extensive groundwater pumping that occurred in the past is most likely the main cause of the recent land settlement as well because of the delayed compaction of the clay aquitards comprised between the depleted aquifers however the available pumping data do not allow for a thorough understanding of the current local settlement process along the coastline which is the most vulnerable area of the emilia romagna region from an environmental viewpoint if the planned scenario of groundwater resource management will be implemented anthropogenic land subsidence is bound to become a marginal problem for the central and northern portion of the emilia romagna coastland

visco elasto plastic compaction of aquitards due to groundwater withdrawal in shanghai china long term excessive groundwater withdrawal can cause aquifer systems to compact and land subsidence ensues the compaction of aquitards lags behind the change of groundwater level in adjacent aquifers which is attributed to low hydraulic conductivity and great creep deformation of aquitards under the condition of groundwater withdrawal aquitard clays may compact visco elastically elasto plastically or visco elasto plastically depending on the effective stress history they have experienced laboratory data manifest that aquitard clays have a similar constitutive relationship to aquifer sands therefore the double yielding visco elasto plastic mechanical model proposed for aquifer sands is applicable to aquitard clays a fully coupled one dimensional visco elasto plastic compaction model is constructed for aquitards to predict their compaction by integrating the double yielding mechanical model with the flow governing equation of groundwater the comprehensive compaction model not only makes the groundwater flow and soil deformation coupled but also takes into account the complex deformation characteristics of aquitard units under long term groundwater withdrawal such as creep and plastic deformation under reloading

north polar region craterforms on mars geometric characteristics from the mars orbiter laser altimeter abstract this study focuses on topographic characterization of ice associated north polar region impact craters and several enigmatic polar craterforms using new information from the mars orbiter laser altimeter mola an instrument aboard the mars global surveyor mgs orbiter we find that for ice associated craters the topography reveals several surprising results not previously apparent from orbital images alone first geometric properties for several impact craters associated with ice and frost deposits suggest that cavity infill is as high as 80 of reconstructed preerosion levels second craters associated with ice also demonstrate unique cavity geometries relative to their nonpolar counterparts finally in some cases ice associated impact features are anomalously deep on the basis of depths modeled from the best available scaling laws we suggest that burial of these impact features by either episodic advance of the polar cap margin or by continuous deposition at the highest rates previously estimated for the north polar region of mars has occurred subsequent stripping has exhumed the features leaving behind cavity infill deposits and a few of these display topographic levels above the surrounding preimpact surface in at least one case cavity interior deposits show layering with a typical thickness of 10 m suggesting episodic deposition and ablation of materials as in the polar layered terrain in addition to ice associated craters we investigated the topography of several enigmatic polar craterforms in particular a few craterforms within 150 km of the permanent north polar cap appear to resemble simple effusive lava shield volcanoes found on earth their geometric properties cannot be reconciled with previous suggestions that they were manifestations of martian hydromagmatic processes i e maar volcanism mola s initial measurements of impact craters and other craterforms in the north polar latitudes of mars support the concept of a geologically recent surface with evidence of effusive volcanism and enhanced sedimentation in addition the measured impact crater depths for ice associated craters suggest at least a few cases of enhanced excavation and thus a possibly weaker target relative to the typical northern hemisphere plains

a unique volcanic field in tharsis mars pyroclastic cones as evidence for explosive eruptions based on theoretical grounds explosive basaltic volcanism should be common on mars yet the available morphological evidence is sparse we test this hypothesis by investigating a unique unnamed volcanic field north of the shield volcanoes biblis patera and ulysses patera on mars where we observe several small conical edifices and associated lava flows twenty nine volcanic cones are identified and the morphometry of many of these edifices is determined using established morphometric parameters such as basal width crater width height slope and their respective ratios their morphology morphometry and a comparison to terrestrial analogues suggest that they are martian equivalents of terrestrial pyroclastic cones the most common volcanoes on earth the cones are tentatively interpreted as monogenetic volcanoes according to absolute model age determinations they formed in the amazonian period our results indicate that these pyroclastic cones were formed by explosive activity the cone field is superposed on an old elevated window of fractured crust which survived flooding by younger lava flows it seems possible that a more explosive eruption style was common in the past and that wide spread effusive plain style volcanism in the late amazonian has buried much of its morphological evidence in tharsis

preconsolidation stress of aquifer systems in areas of induced land subsidence aquifer systems in the eloy picacho area arizona the houston galveston area texas and the tulare wasco area and santa clara valley california appear to have been overconsolidated by an amount that ranged approximately from 1 6 to 6 2 bars 16 to 63 m of water before man began to withdraw groundwater from them the relation between land subsidence and water level decline in these areas consists of two linear segments in these areas subsidence per unit water level decline was approximately constant until water levels had declined an amount that ranged from 16 to 63 m when water levels declined past these values subsidence per unit water level decline increased to larger constant values although slow drainage from aquitards may have contributed to this response it is interpreted here to be caused primarily by natural overconsolidation of the compacting part of the aquifer system the water level decline at which the ratio of subsidence to unit water level decline changed indicates approximately the amount by which the preconsolidation stress exceeded the overburden stress on the aquifer system that existed before groundwater withdrawals began

the development and control of the land subsidence in the yangtze delta china land subsidence in china occurs predominantly in 17 provinces cities situated in the eastern and middle regions of the country including shanghai tianjin and jiangsu and hebei provinces it is primarily caused by groundwater overpumping one of the areas most severely affected by land subsidence is the yangtze delta most of which consists of shanghai city the su xi chang area suzhou wuxi and changzhou cities of jiangsu province and the hang jia hu area hangzhou jiaxing and huzhou cities of zhejiang province the excessive exploitation of groundwater forms in a large regional cone of depression and consequently land subsidence is also regional currently centered in the shanghai and su xi chang areas in 2002 the maximum cumulative subsidence of shanghai su xi chang and hang jia hu were 2 63 m 2 00 and 1 06 m respectively the land subsidence area is continuing to expand throughout the yangtze delta to study the characteristics and the pattern of this land subsidence the government has implemented a monitoring system involving the placement of 37 groups of extensometers layers marks and drilling of more than 1000 observation wells these provide an invaluable historical record of deformation and pore water pressure and facilitate studies on the special features of soil deformation when the groundwater level changes due to pumping several measures have been taken in recent years to control the development of the land subsidence in the different areas these include groundwater injection prohibition of pumping deep confined groundwater and an adjustment of the pumping depth and magnitude of the groundwater withdrawn at present although the subsidence area is still increasing slowly the subsidence rate is controlled

the mars observer laser altimeter investigation the primary objective of the mars observer laser altimeter mola investigation is to determine globally the topography of mars at a level suitable for addressing problems in geology and geophysics secondary objectives are to characterize the 1064 nm wavelength surface reflectivity of mars to contribute to analyses of global surface mineralogy and seasonal albedo changes to assist in addressing problems in atmospheric circulation and to provide geodetic control and topographic context for the assessment of possible future mars landing sites the principal components of mola are a diode pumped neodymium doped yttrium aluminum garnet laser transmitter that emits 1064 nm wavelength laser pulses a 0 5 m diameter telescope a silicon avalanche photodiode detector and a time interval unit with 10 ns resolution mola will provide measurements of the topography of mars within approximately 160 m footprints and a center to center along track foot print spacing of 300 m along the mars observer subspacecraft ground track the elevation measurements will be quantized with 1 5 m vertical resolution before correction for orbit and pointing induced errors mola profiles will be assembled into a global 0 2 deg x 0 2 deg grid that will be referenced to mars center of mass with an absolute accuracy of approximately 30 m other data products will include a global grid of topographic gradients corrected individual profiles and a global 0 2 deg x 0 2 deg grid of 1064 nm surface reflectivity

erosion rate and previous extent of interior layered deposits on mars revealed by obstructed landslides we describe interior layered deposits on mars that have obstructed landslides before undergoing retreat by as much as 2 km these landslides differ from typical martian examples in that their toe height increases by as much as 500 m in a distinctive frontal scarp that mimics the shape of the layered deposits by using crater statistics to constrain the formation ages of the individual landslides to between ca 200 and 400 ma we conclude that the retreat of the interior layered deposits was rapid requiring erosion rates of between 1200 and 2300 nm yr 1 we suggest that the interior layered deposits are either extremely friable if eroded strictly by wind or composed of a material whose degradation has been enhanced by ice sublimation these erosion rates also confirm that the interior layered deposits have been in a state of net degradation over the past 400 m y suggesting that the process that caused net deposition in the past has ceased or slowed substantially on mars relative to erosion our results imply that interior layered deposits with a similar morphology across mars including the mound in gale crater have probably undergone similar rapid erosion and retreat suggesting that their total modern volume underrepresents the depositional record and thus sedimentary history of mars

parameter estimation of an overconsolidated aquitard subjected to periodic hydraulic head variations within adjacent aquifers abstract extensometers provide long term records of deformation over a depth interval of interest an overconsolidated aquitard usually undergoes elastic deformation if the hydraulic head within adjacent aquifers remains higher than the preconsolidation head within the aquitard the vertical hydraulic conductivity k v and elastic skeletal specific storage s ske are two critical parameters that control the deformation behavior of an overconsolidated aquitard and they could be interpreted from valuable extensometer data an analytical solution for the elastic aquitard deformation caused by periodic hydraulic head variations phhv within adjacent aquifers is derived using the separation of variables method based on euler s formula the phase difference in phhv between adjacent aquifers is found to reduce the amplitude of periodic aquitard deformation meanwhile the phase difference is found to cause no influence on the growth pattern of the phase shift which is between the periodic aquitard deformation and phhv versus the period a new parameter estimation method is further proposed to interpret aquitard k v and s ske from periodic aquitard deformation data this new method yields robust k v and s ske estimates of a moderately thick aquitard whose deformation history has been recorded by an extensometer located in shanghai china the field study confirms that the phase difference in phhv between the aquifers adjacent to the overconsolidated aquitard of interest cannot be ignored

deformation characteristics of a clayey interbed during fluid injection surface deformation due to fluid withdrawal has long been observed at the surface above aquifers and oil reservoirs uplift associated with fluid injection has also been observed although the processes of subsidence and uplift are reversible in a poroelastic setting the presence of clayey interbeds can result in ground deformation behavior non reversible because of their low permeability and nonlinear behavior in this investigation a cam clay model is used in conjunction with a poroelastic model to simulate the presence of a laterally extensive lens shaped clayey interbed in a sandstone aquifer during fluid injection spatial and temporal changes associated with this interbed during aquifer pressurization are captured and can be clearly differentiated from the deformation of the surrounding poroelastic aquifer formation results for pore pressures and ground surface deformation patterns can be categorized into three distinct time intervals an early time interval where the aquifer is pressurized but not the interbed leading to a lower region above the interbed an intermediate time interval in which the interbed pressures slowly increase approaching the pressure of the adjacent aquifer leading to a potentially large surface uplift above the interbed and a late time interval in which pressure equilibration is achieved between the interbed and aquifer and a highly non symmetrical irregular surface deformation pattern results which may be higher or lower than the background depending on the interbed characteristics reservoir configuration is found to be an important factor influencing ground deformation behavior with more obvious deformation always occurring in a laterally confined aquifer as opposed to a laterally infinite aquifer

phase difference between groundwater storage changes and groundwater level fluctuations due to compaction of an aquifer aquitard system abstract drainage and deformation of intercalated confining layers due to internal stress change discharge recharge cycle in an aquifer aquitard system not only can have great effects on the groundwater storage gws but also can cause unsynchronized water level wl fluctuations the phase relationship between gws and wl is crucial for the accuracy and attribution of gws changes we identify the dominating episodic components of gws and wl through the singular spectrum analysis ssa analysis and harmonic analysis first we analyzed a generic aquifer aquitard system using numerical simulations which showed that the dissipation of overpressure from the aquitard and flow from it is the inherent cause of a phase shift between the gws and wl observations water released from confining layers with compaction time constant of zero no delay to century time scale results in detected phase shift between total gws and wl in the aquifer then we analyzed the complex and varied phase relationship between gws derived using the gravity recovery and climate experiment grace data and measured wl time series in the subsiding north china plain ncp aquifer the spatially varied phase relationship between gws and measured wl is reasonably related to varied land subsidence development features and may be related with the compaction time constant and thickness of the confining layers results of the generic numerical model and the ncp observations suggest that elastic inelastic response need to be considered in the interpretation and correction of gws changes for a compacted aquifer aquitard system

geomorphometric variability of monogenetic volcanic cones evidence from mauna kea lanzarote and experimental cones abstract volcanic cones are the most common volcanic constructs on earth their shape can be quantified using two morphometric ratios the crater cone base ratio wcr wco and the cone height width ratio hco wco the average values for these ratios obtained over entire cone fields have been explained by the repose angle of loose granular material i e scoria controlling cone slopes the observed variability in these ratios between individual cones has been attributed to the effect of erosional processes or contrasting eruptive conditions on cone morphometry using a gis based approach high spatial resolution digital elevation models and airphotos two new geomorphometry datasets for cone fields at mauna kea hawaii usa and lanzarote canary islands spain are extracted and analyzed here the key observation in these datasets is the great variability in morphometric ratios even for simple shape and well preserved cones simple analog experiments are presented to analyze factors influencing the morphometric ratios the formation of a crater is simulated within an analog cone i e a sand pile by opening a drainage conduit at the cone base results from experiments show that variability in the morphometric ratios can be attributed to variations in the width height and horizontal offset of the drainage point relative to the cone symmetry axis to the dip of the underlying slope or to the influence of a small proportion of fine cohesive material gis analysis and analog experiments together with specific examples of cones documented in the field suggest that the morphometric ratios for well preserved volcanic cones are controlled by a combination of 1 the intrinsic cone material properties 2 time dependent eruption conditions 3 the local setting and 4 the method used to estimate the cone height implications for interpreting cone morphometry solely as either an age or as an eruption condition indicator are highlighted

adaptive explicit implicit quasi three dimensional finite element model of flow and subsidence in multiaquifer systems a quasi three dimensional finite element model is presented for the analysis of groundwater flow and land subsidence due to pumpage in multiaquifer systems in the model aquifers are simulated with the aid of two dimensional horizontal finite element grids each aquifer is connected to its neighbors above and below by one dimensional vertical finite element strings which allow leakage to take place across aquitards and aquicludes land subsidence is modeled by varying the void ratio of each vertical element according to a nonlinear version of terzaghi s one dimensional consolidation theory a major feature of the new method is its ability to solve the finite element equations explicitly in one part of the mesh and implicitly in another part depending on the ratio between the stability limit of each node and any given time step size since the hydraulic diffusivity of aquitards is usually very small compared to that of aquifers it is often possible to solve the finite element equations explicitly for most and sometimes all aquitard nodes this leads to a virtual decoupling of the aquifer equations during a given time step which results in a significant saving of computer time and storage

experimental evidence for lava like mud flows under martian surface conditions large outflow channels on ancient terrains of mars have been interpreted as the products of catastrophic flood events the rapid burial of water rich sediments after such flooding could have led to sedimentary volcanism in which mixtures of sediment and water mud erupt to the surface tens of thousands of volcano like landforms populate the northern lowlands and other local sedimentary depocentres on mars however it is difficult to determine whether the edifices are related to igneous or mud extrusions partly because the behaviour of extruded mud under martian surface conditions is poorly constrained here we investigate the mechanisms of mud propagation on mars using experiments performed inside a low pressure chamber at cold temperatures we found that low viscosity mud under martian conditions propagates differently from that on earth because of a rapid freezing and the formation of an icy crust instead the experimental mud flows propagate like terrestrial pahoehoe lava flows with liquid mud spilling from ruptures in the frozen crust and then refreezing to form a new flow lobe we suggest that mud volcanism can explain the formation of some lava like flow morphologies on mars and that similar processes may apply to cryovolcanic extrusions on icy bodies in the solar system

trends in effusive style at the tharsis montes mars and implications for the development of the tharsis province 1 we mapped lava flows on the tharsis montes arsia mons pavonis mons and ascraeus mons using high resolution stereo camera images that centrally transect each shield from north to south covering 20 of each shield s surface these data were co registered to mars orbiter laser altimeter thermal emission imaging system and mars orbiter camera data enabling lava flow structures and vents to be consistently differentiated across each volcano lava flow and vent abundances and relationships are used to provide new insight into the late amazonian eruptive history of the tharsis montes the volcanoes are divided into their main flanks rift aprons and small vent fields where present on the main flanks channel fed flows always embay tube fed flows indicating a change from long lived stable tube forming eruption conditions to shorter lived less stable channel forming eruption conditions superposition relationships suggest that main flank and rift apron development were likely separated by an eruptive hiatus the rift aprons as compared to the main flanks show higher abundances of tube and channel fed flows and embayment of tube fed flows by channel fed flows is less consistent several trends from the arsia mons to ascraeus mons southwest rift aprons and small vent fields were identified including increased tube abundance median slope and number of satellitic eruptive vents and a decrease in channel to tube fed flow ratios apron volumes and maximum apron elevations these trends suggest that the most recent volcanic activity at the tharsis montes might have originated from a single shared magma source possibly marking a change in magma production style from main flank construction

numerical simulation of land subsidence induced by groundwater overexploitation in su xi chang area china su xi chang area is one of the typical regions in china which suffers from severe land subsidence various field monitoring records were integrated to study the characteristics and mechanisms of land subsidence in this region the development of the land subsidence in this region shows a tight spatial and temporal correlation with the groundwater pumping based on the analysis of the field data it is found that the deformation patterns of the hydrogeologic units are greatly related to the hydrogeologic properties and groundwater level variations some have an elastic behavior others may have an elastic plastic rheology hence a 3d finite element numerical model considering the rheological properties of the soil was developed to simulate the groundwater level and land subsidence both hydraulic conductivity and specific storage were expected to vary with the porosity during the process of consolidation multiscale finite element method msfem was applied to solve the model during the period from 1996 to 2004 after calibrating the model with the observed groundwater level and subsidence data the parameters of the multi layers system were estimated the calibrated model outputs fit reasonably well with the observed data consequently the model can be applied to predict groundwater level and land subsidence in future pumping scenarios the model predictive results show that land subsidence rate can be controlled and even rebound may occur after the implementation of the groundwater exploitation prohibition

low palaeopressure of the martian atmosphere estimated from the size distribution of ancient craters the decay of the martian atmosphere which is dominated by carbon dioxide is a component of the long term environmental change on mars from a climate that once allowed rivers to flow to the cold and dry conditions of today the minimum size of craters serves as a proxy for palaeopressure of planetary atmospheres because thinner atmospheres permit smaller objects to reach the surface at high velocities and form craters the aeolis dorsa region near gale crater on mars contains a high density of preserved ancient craters interbedded with river deposits and thus can provide constraints on atmospheric density at the time of fluvial activity here we use high resolution images and digital terrain models from the mars reconnaissance orbiter to identify ancient craters in deposits in aeolis dorsa that date to about 3 6 gyr ago and compare their size distribution with models of atmospheric filtering of impactors we obtain an upper limit of 0 9 0 1 bar for the martian atmospheric palaeopressure rising to 1 9 0 2 bar if rimmed circular mesas interpreted to be erosionally resistant fills or floors of impact craters are excluded we assume target properties appropriate for desert alluvium if sediment had rock mass strength similar to bedrock at the time of impact the paleopressure upper limit increases by a factor of up to two if mars did not have a stable multibar atmosphere at the time that the rivers were flowing as suggested by our results then a warm and wet co 2 h 2o greenhouse is ruled out and long term average temperatures were most likely below freezing

a new type curve method for estimating aquitard hydraulic parameters in a multi layered aquifer system summary we propose a new type curve method for estimating the hydraulic conductivity k and the specific storage s s of an aquitard in a multi layered aquifer system theoretical type curves of rate of aquitard compaction versus time are obtained through drawdown time series in the aquitard under a condition that the drawdown history of the underlying aquifer can be approximated as piecewise linear segments pls in each of which the drawdown shows a linear increase trend with time comparing with previous analytical solutions which are limited by the assumption of a constant head in the overlying unconfined aquifer the superposition principle can be called when water levels fluctuate with time in both upper and lower aquifers adjacent to the aquitard when applying the new pls method to estimate k and s s values of an aquitard the starting point of drawdown history at adjacent aquifers should be determined at first after that the drawdown history is approximated as pls to obtain drawdown rate of change for each linear stage and turning points of drawdown history the new pls method is demonstrated at a field site in changzhou city jiangsu province of china estimated results show that k and s s are respectively 9 80 10 10 m s and 4 46 10 4 m 1 for a thick aquitard and 2 34 3 50 10 10 m s and 2 28 10 4 m 1 for a thin aquitard estimated field k values as well as s s values through the new pls method are generally in accordance with the results obtained from the geologic method by konikow and neuzil 2007 they are also in agreements with the numerically calibrated results of shi et al 2008a at the regional scale and the laboratory experimental values of in situ soil samples collected by geological survey of jiangsu province of china

multi temporal insar evidence of ground subsidence induced by groundwater withdrawal the montellano aquifer sw spain this study uses the insar technique to analyse ground subsidence due to intensive exploitation of an aquifer for agricultural and urban purposes in the montellano town sw spain the detailed deformation maps clearly show that the spatial and temporal extent of subsidence is controlled by piezometric level fluctuations and the thickness of compressible sediments the total vertical displacement measured with multi temporal insar between 1992 and 2010 is 33 mm that corresponds with a decrease of 43 m in the groundwater level this technique allows monitoring the evolution of settlement related to water level fall in an area where subsidence has not yet been reported by population or authorities through infrastructure damages and to discuss the effect of the aquifer recovery this information is therefore valuable for implementing effective groundwater management schemes and land use planning and to propose new building regulations in the most affected areas