subsurface architecture of the boulder creek critical zone observatory from electrical resistivity tomography the architecture of the critical zone includes the distribution thickness and contacts of various types of slope deposits and weathering products such as saprolite and weathered bedrock resting on solid bedrock a quantitative analysis of architecture is necessary for many model driven approaches used by pedologic geomorphic hydrologic or biologic studies we have used electrical resistivity tomography a well established geophysical technique causing minimum surficial disturbance to portray the subsurface electrical resistivity differences at three study sites green lakes valley gordon gulch betasso at the boulder creek critical zone observatory bcczo possible limitations of the technique are discussed interpretation of the specific resistivity values using natural outcrops pits roadcuts and drilling data as ground truth information allows us to image the critical zone architecture of each site green lakes valley 3700 masl a glacially eroded alpine basin shows a rather simple split configuration with coarse blockfields and sediments partly containing permafrost above bedrock the critical zone in gordon gulch 2650 masl a montane basin with rolling hills and betasso 1925 masl a lower montane basin with v shaped valleys is more variable due to a complex quaternary geomorphic history boundaries between overlying stratified slope deposits and saprolite were identified at mean depths of 3 0 2 2 m and 4 1 3 6 m in the respective sites the boundary between saprolite and weathered bedrock is deeper in betasso at 5 8 3 7 m compared with 4 3 3 0 m in gordon gulch in general the data are consistent with results from seismic studies but electrical resistivity tomography documents a 0 5 1 5 m shallower critical zone above the weathered bedrock on average additionally we document high lateral variability which results from the weathering and sedimentation history and seems to be a consistent aspect of critical zone architecture within the bcczo copyright 2013 john wiley sons ltd

seismic reflection borehole and outcrop geometry of late wisconsin tills at a proposed landfill near toronto ontario the search for new landfill sites in the greater toronto area of southern ontario canada is producing a wealth of data regarding the subsurface stratigraphy and geometry of late wisconsin 25 ka

island wakes in deep and shallow water observations of island wakes from the continental shelf have been used by various authors to suggest that the reynolds number is not an appropriate parameter for wake behaviour in shallow water it is shown here that wake behaviour both in deep and shallow water is well described by the reynolds number if it is derived correctly by taking into account frictional effects in horizontal as well as vertical boundary layers

topographically controlled fronts in the ocean and their biological influence headlands islands and reefs generate complex three dimensional secondary flows that result in physical and biological fronts mixing and diffusion processes near these reefs and headlands are quite different from these processes in the open sea and classical advection diffusion models that were developed for the open sea are not valid near shore topographically generated fronts affect the distribution of sediments and they aggregate waterborne eggs larvae and plankton this aggregation influences the distribution and density of benthic assemblages and of pelagic secondary and tertiary predators

diagnoses of vertical transport in a three dimensional finite element model of the tidal circulation around an island a three dimensional finite element model is used to investigate the formation of shallow water eddies in the wake of rattray island great barrier reef australia field measurements and visual observations show that stable eddies develop in the lee of the island at rising and falling tides the water turbidity downstream of the island suggests the existence of strong upwelling that would be responsible for carrying bed sediments tip to the sea surface we first propose to look at the upwelling velocity and then use the theory of the age to diagnose vertical transport the water age is defined as the time elapsed since particles of water left the sea bottom where the age is prescribed to be zero two versions of this diagnosis are considered although the model predicts upwelling within the eddies it is not sufficiently intense to account for vertical transport throughout the water column during the life span of the eddies as mesh resolution increases this upwelling does not intensify however strong upwelling is then resolved off the island s tips which is confirmed by the results obtained with the age this study also shows that the finite element method together with unstructured meshes performs well for representing three dimensional flow past ail island c 2006 elsevier ltd all rights reserved

island wakes and headland eddies a comparison between remotely sensed data and laboratory experiments island wakes and headland eddies in coastal waters are identified from spaceborne and airborne remotely sensed imagery in the visible wavelengths the imagery were obtained for the bristol and english channels united kingdom which are characterized by high tidal currents and levels of turbidity suspended matter in the surface waters is used as a passive tracer for the flow features scaling parameters e g the reynolds ekman and rossby numbers obtained from the depth averaged equation of motion are presented based upon information on oceanographic conditions at the times of the overpasses the parameters are compared then with data obtained from laboratory model investigations presented by other experimenters in the published literature the remotely sensed data demonstrate that in coastal waters with nonuniform obstacles and bathymetry for a given ekman number the flow regimes occur at a lower rossby number than might be expected from laboratory experiments in the absence of a method for the accurate determination of the horizontal eddy viscosity hence the reynolds number it is concluded that an island wake parameter wolanski et al 1984a should be adopted to describe such features in coastal waters

using a multiple variogram approach to improve the accuracy of subsurface geological models subsurface geological models are often used to visualize and analyze the nature geometry and variability of geologic and hydrogeologic units in the context of groundwater resource studies the de

shallow seismic reflection study of a glaciated valley shallow seismic reflection data were recorded along two long 1 6 km intersecting profiles in the glaciated suhre valley of northern switzerland appropriate choice of source and receiver parameters resulted in a high fold 36 48 data set with common midpoints every 1 25 m as for many shallow seismic reflection data sets upper portions of the shot gathers were contaminated with high amplitude source generated noise e g direct refracted guided surface and airwaves spectral balancing was effective in significantly increasing the strength of the reflected signals relative to the source generated noise and application of carefully selected top mutes ensured guided phases were not misprocessed and misinterpreted as reflections resultant processed sections were characterized by distributions of distinct seismic reflection patterns or facies that were bounded by quasi continuous reflection zones the uppermost reflection zone at 20 to 50 ms 15 to 40 m depth originated from a boundary between

application of seismic stratigraphy and sedimentology to regional hydrogeological investigations an example from oak ridges moraine southern ontario canada hydrogeological models need to be supported by a clear understanding of the subsurface geology to provide effective assessment flow modelling or management of groundwater regimes this paper illustrates how geophysical and sedimentological data can be used to significantly improve watershed scale hydrostratigraphic models by advancing our understanding of the subsurface through regional hydrogeological investigations in the greater toronto area the example of a 3 km shallow seismic reflection survey that traverses a buried channel within bowmanville creek watershed oak ridges moraine ontario illustrates a basis for linking geophysical and sedimentological properties to regional hydrostratigraphic parameters seismic reflection methods plus seismic stratigraphy and a well constrained three dimensional geological framework have helped to i identify regional hydrostratigraphic units ii define properties and trends of these units facies iii improve depositional models that assist hydrogeological

geophysical geological and hydrogeological characterization of a tributary buried bedrock valley in southern ontario buried bedrock valleys infilled with quaternary aged sediment have the potential to become productive aquifers owing to prevalent sand and gravel deposits often associated with these topographic lo

subsurface heterogeneity in the geological and hydraulic properties of the hummocky paris moraine guelph ontario the advance and retreat of ice lobe margins of the laurentide ice sheet formed moraines that are a prevalent feature throughout southwestern ontario in contrast to the well studied stratified moraine complexes recessional and end moraines have largely been ignored in the context of hydrogeological studies recent urban growth has led to development pressures on these moraines and a need to better understand their hydrogeology this study presents data sets from the paris moraine near guelph ontario to examine its geomorphology internal composition and the corresponding hydraulic properties of these ice marginal features the moraine s geomorphic elements were mapped using high resolution global positioning system transects aerial photograph analysis and ground truthing nine continuous sediment cores were recovered to determine the nature and distribution of subsurface sedimentary units and their relation to the regional stratigraphic framework cores were described in detail using standard sedime

a numerical comparison of 2d resistivity imaging with 10 electrode arrays numerical simulations are used to compare the resolution and efficiency of 2d resistivity imaging surveys for 10 electrode arrays the arrays analysed include polepole pp pole dipole pd half wenner hw wenner wn schlumberger sc dipole dipole dd wenner wb array gm multiple or moving gradient array gd and midpoint potential referred measurement mpr arrays five synthetic geological models simulating a buried channel a narrow conductive dike a narrow resistive dike dipping blocks and covered waste ponds were used to examine the surveying efficiency anomaly effects signal to noise ratios and the imaging capabilities of these arrays the responses to variations in the data density and noise sensitivities of these electrode configurations were also investigated using robust l1 norm inversion and smoothness constrained least squares l2 norm inversion for the five synthetic models the results show the following i gm and wn are less contaminated by noise than the other electrode arrays ii the relative anomaly effects for the different arrays vary with the geological models however the relatively high anomaly effects of pp gm and wb surveys do not always give a high resolution image pd dd and gd can yield better resolution images than gm pp wn and wb although they are more susceptible to noise contamination sc is also a strong candidate but is expected to give more edge effects iii the imaging quality of these arrays is relatively robust with respect to reductions in the data density of a multi electrode layout within the tested ranges iv the robust inversion generally gives better imaging results than the l2 norm inversion especially with noisy data except for the dipping block structure presented here v gd and mpr are well suited to multichannel surveying and gd may produce images that are comparable to those obtained with dd and pd accordingly the gd pd dd and sc arrays are strongly recommended for 2d resistivity imaging where the final choice will be determined by the expected geology the purpose of the survey and logistical considerations

nature and origin of sediments infilling poorly defined buried bedrock valleys adjacent to the niagara escarpment southern ontario canada the buried paleozoic bedrock surface of southern ontario is dissected by an interconnected system of valleys these buried valleys are infilled with thick successions of glacial interglacial and fluvial sediments that contain a lengthy record of changing environmental conditions during the late quaternary detailed logging of over 500 m of sediment recovered from 11 continuously cored boreholes provides the basis for this study the boreholes were drilled within two poorly defined bedrock valleys located east of the niagara escarpment in southern ontario as part of a groundwater exploration program six distinct facies types were identified within the cores sand gravel fine grained sediment and sand rich mud rich and clast rich diamict textural characteristics of the cored sediments and vertical changes in facies types were used to identify six stratigraphic units su i through su vi within the valley infill deposits these units are interpreted to record fluvial or colluvial su i lacustrine su ii fluvial glaciofluvial or deltaic su iii subglacial su iv glaciofluvial su v and subglacial or ice marginal su vi conditions sediment characteristics and stratigraphic relationships allow tentative correlation with known surficial deposits analysis of the subsurface characteristics and geometries of this stacked succession of coarse and fine grained stratigraphic units also allows identification of the geometry of potential aquifers

tidal jets nutrient upwelling and their influence on the productivity of the alga halimeda in the ribbon reefs great barrier reef abstract a field experiment was carried out to study water circulation and benthic biological productivity near a passage through the ribbon reefs in the northern great barrier reef of australia the currents through the passage were phase locked with the tide during rising tides strong currents through the passage generated localized upwelling on the upper continental slope enriching the depleted surface waters in nutrients particularly nitrate and phosphate simultaneously on the shelf side of the passage a tidal jet vortex pair system developed which separated from the ribbon reefs so that the coral reefs themselves received little of the upwelled water this was propagated as a bottom trapped layer towards the meadows of the calcareous alga halimeda situated several kilometres inshore of the reefs halimeda can accumulate nutrients particularly nitrate from the relatively low concentrations available from the upwelling events the quantity of nitrogen upwelled was more than sufficient to supply the total nitrogen requirements of the halimeda vegetation a tidal jet also formed offshore from the reef passage during falling tides and the coral covered offshore side of the ribbon reefs may be sustained by the subsequent vertical turbulent entrainment into the jet of deep nutrient rich water immediately offshore from the reef passages these processes require a continuous barrier reef with only narrow passages several kilometers apart numerical models successfully reproduce the observations of jet driven upwelling and of the dynamics of the tidal jet vortex pair system the model predictions are very sensitive to the details of the bathymetry of reef passages as such data are presently unavailable it is not yet possible to use these models to calculate the jet driven nutrient upwelling for the whole great barrier reef

combining multi scale geophysical techniques for robust hydro structural characterisation in catchments underlain by hard rock in post glacial regions summary accurate conceptual models of groundwater systems are essential for correct interpretation of monitoring data in catchment studies in surface water dominated hard rock regions modern ground and surface water monitoring programmes often have very high resolution chemical meteorological and hydrological observations but lack an equivalent emphasis on the subsurface environment the properties of which exert a strong control on flow pathways and interactions with surface waters the reasons for this disparity are the complexity of the system and the difficulty in accurately characterising the subsurface except locally at outcrops or in boreholes this is particularly the case in maritime north western europe where a legacy of glacial activity combined with large areas underlain by heterogeneous igneous and metamorphic bedrock make the structure and weathering of bedrock difficult to map or model traditional approaches which seek to extrapolate information from borehole to field scale are of limited application in these environments due to the high degree of spatial heterogeneity here we apply an integrative and multi scale approach optimising and combining standard geophysical techniques to generate a three dimensional geological conceptual model of the subsurface in a catchment in ne ireland available airborne lidar electromagnetic and magnetic data sets were analysed for the region at field scale surface geophysical methods including electrical resistivity tomography seismic refraction ground penetrating radar and magnetic surveys were used and combined with field mapping of outcrops and borehole testing the study demonstrates how combined interpretation of multiple methods at a range of scales produces robust three dimensional conceptual models and a stronger basis for interpreting groundwater and surface water monitoring data

shallow seismic reflection mapping of the overburden bedrock interface with the engineering seismograph some simple techniques where unconsolidated overburden exceeds 20 m in thickness the reflection method may be efficiently used with a 12 channel engineering seismograph to map topography on the overburden bedrock interface as well as possible structure within the overburden the two techniques we suggest are the simplest forms of reflection profiling which can be applied with a minimum amount of equipment which we suggest is a 12 channel enhancement seismograph a 12 geophone array and a hammer source these techniques require good transmission characteristics of the overburden as well as a sharp velocity discontinuity at the overburden bedrock interface for data processing and display a microcomputer is essential

assessing the flow regime in a contaminated fractured and karstic dolostone aquifer supplying municipal water the silurian dolostone bedrock in ontario canada is a broad 400 km long swath northward from niagara falls through the bruce peninsula that represents an important water source for municipal industrial and agricultural uses where the quaternary overburden is thin or absent karst is common this study concerns an urban area where the dolostone aquifer is 100 m thick beneath up to 50 m thick quaternary deposits and where karst features identified by borehole information are common hydraulic tests show moderate to large bulk rock hydraulic conductivity and rock core tests indicate much smaller matrix hydraulic conductivity than the bulk rock values therefore the aquifer is essentially a dual permeability fully saturated system in which conduits occur within a network of ubiquitous extensive horizontally and vertically interconnected fractures karst features are concentrated in a thin zone at the top of rock likely representing former epikarst and also in a thicker zone in the middle of the aquifer some pumping test results and large yields of some municipal wells are consistent with conduit occurrences however atmospheric tritium distributed source contamination cl view the mathml source and a point source pesticide plume metolachlor show detailed concentration distributions lacking influence of flow in conduits detailed hydraulic head profiles also show no influence of conduit flow this study shows that when designing monitoring networks for groundwater quality and source water protection in similar contexts locating conduits is not necessary because contaminant distributions are governed by the combined influences of the rock matrix fractures and conduits the hydraulic boundary conditions and the interconnected fracture network with only minimal conduit effects prior to glaciations an integrated karstic aquifer could develop with flow controlled by conduits however this original converging flow system became non functional when the quaternary sediments drastically modified the boundary hydrologic conditions and the head distribution

high resolution seismic and resistivity profiling of a buried quaternary subglacial valley northern alberta canada high resolution seismic and resistivity profiles were acquired to assist in the delineation of a buried quaternary subglacial valley the existence of which was first discovered by drilling one aspect of this valley is the glacial sediments that host substantial methane at shallow depths 50 m or less geophysical well logs indicate that the glacial sediments in this area generally have lower compressional wave speeds v p 10 m than adjacent undisturbed cretaceous age rocks which have v p 2200 m s and r 300 m valley the reflection profile reveals a complex series of events consistent with heterogeneous deposition one major reflection dips eastward across the valley the reflection character changes abruptly on either side of this event with dipping clinoform reflections beneath and nearly horizontal reflections above these may be related to changes in deposition processes beneath a retreating ice sheet as has been suggested by earlier workers the buried valley s basal reflections are complex and possibly reflect glaciotectonic deformation or block plucking the near surface methane gas is within but at the edge of the valley the methane gas saturated zone displays anomalously high resistivities both in the well logs and in resistivity tomography

first determination of magma derived gas emissions from bromo volcano eastern java indonesia abstract the composition and fluxes of volcanic gases released by persistent open vent degassing at bromo volcano east java indonesia were characterised in september 2014 from both in situ multi gas analysis and remote spectroscopic dual uv camera measurements of volcanic plume emissions our results demonstrate that bromo volcanic gas is water rich h2o so2 ratios of 56 160 and has co2 so2 4 1 0 7 and co2 stot 3 2 0 7 ratios within the compositional range of other high temperature magma derived gases in indonesia h2 h2o and h2s so2 ratios constrain a magmatic gas source with minimal temperature of 700 c and oxygen fugacity of 10 17 10 18 bars uv camera sensing on september 20 and 21 2014 indicates a steady daily mean so2 output of 166 38 t d 1 which is ten times higher than reported from few previous studies our results indicate that bromo ranks amongst the strongest sources of quiescent volcanic so2 emission measured to date in indonesia being comparable to merapi volcano in central java by combining our results for the gas composition with the so2 plume flux we assess for the first time the fluxes of h2o 4725 2292 t d 1 co2 466 83 t d 1 h2s 25 12 t d 1 and h2 1 1 0 8 from bromo our study thus contributes a new piece of information to the still limited data base for volcanic gas emissions in indonesia and confirms that much remain to be done to fully assess the contribution of this very active arc region to global volcanic gas fluxes

architecture of buried valleys in glaciated canadian prairie regions based on high resolution geophysical data abstract airborne electromagnetic and high resolution seismic geophysical data provide insight into complex buried valley geometry and internal sedimentary architecture of buried valleys in the canadian prairies buried valleys with an extent in excess of 20 000 km beneath the canadian prairie landscape have been previously interpolated using borehole data however they provide only limited insight into the geometry and spatial relationships of these valleys the collected high quality geophysical datasets a three dimensional airborne electromagnetic survey and high resolution seismic profile data provide much greater resolution of buried valley geometry and internal sedimentary architecture of buried valleys several generations of valleys at different scales are identified we interpret multiple erosion surfaces bounding thick diamicton sequences that fill the largest valleys the youngest valleys are filled with variable sediment types three valley morphologies are identified and process origins inferred 1 regional scale extensive subaerial and pre interglacial named type valley 2 regional scale narrow and mainly proglacial type valley and 3 local scale apparently discontinuous subglacial type valley within the glacial sediment stratigraphy filling type valleys are thick diamicton sequences bounded by erosional surfaces the type and type valleys are filled with variable sediment types the proglacial valleys erode bedrock and also occur within the type valley fill conversely the subglacial valleys are observed to crosscut other valleys and may be shallow and wide or deep and narrow the reported geophysical datasets supported by borehole data are able to map buried valleys in three dimensions and hence identify the morphologic and stratigraphic relationships that permit improved constraints on process and erosional origin and fill of buried valleys results provide insight into the relationship between valleys formed as part of tertiary fluvial erosion multiple glaciations and glaciofluvial events these data provide significant insights on the distribution and character of potential groundwater reservoirs in prairie regions

bedrock jointing and geomorphology in southwestern ontario canada an example of tectonic predesign in southwestern ontario canada palaeozoic sedimentary strata are covered by pleistocene glacial sediments the topography of the buried bedrock surface has been mapped over an area of some 45 000 km2 using new computerised depth to bedrock data from more than 200 000 waterwells this information shows that arching of the underlying proterozoic basement canadian shield and differential erosion of carbonate and shale strata are first order regional controls on bedrock geomorphology these data also define a network of buried bedrock channels quantitative analysis of the trends of these channels reveals a statistical correspondence between channel orientation and regional bedrock joint sets formed in response to the mid continent stress field the orientations of bedrock channels and joints correspond regionally with mean trends at 153 and 164 respectively in addition two dominant orientations of postglacial river valleys and bedrock joints correspond with mean trends at 104 vs 104 and 54 vs 52 respectively our findings show that the erosional channelled topography cut on bedrock together with the postglacial drainage pattern cut into younger glacial sediments are related to the trend of bedrock joints and consequently can be described as tectonically predesigned in addition this study yields new insights into the form of the preglacial tertiary drainage system in southern ontario prior to pleistocene glaciation regardless of the precise age of this preglacial system and degree of subsequent glacial modification an important factor in its geomorphic development has been the mid continent stress field

geological and geophysical studies of buried valleys and their fills near elora and rockwood ontario buried bedrock valleys are of economic interest for groundwater and engineering studies and of scientific interest for the sedimentary sequences they may contain two buried valleys about 60 m deep north and northeast of guelph ontario are tributary to the major dundas valley southwest of guelph located initially from water well data their locations and geometry were refined with surface geophysics including very low frequency resistivity terrain conductivity resistivity transient electromagnetic gravity and seismic methods useful data are obtained roughly in proportion to cost cored and rotary holes in the two valleys were followed by geophysical downhole logging with normal electric spontaneous potential single point resistance calliper neutron epithermal neutron gamma gamma and natural gamma methods cores revealed multi till sequences in the upper parts of the holes and together with geophysical logs and their interpreted electrofacies indicate the presence of underlying unifo

landform characterization using geophysics recent advances applications and emerging tools abstract this paper presents an overview of the strengths and limitations of existing and emerging geophysical tools for landform studies the objectives are to discuss recent technical developments and to provide a review of relevant recent literature with a focus on propagating field methods with terrestrial applications for various methods in this category including ground penetrating radar gpr electrical resistivity er seismics and electromagnetic em induction the technical backgrounds are introduced followed by section on novel developments relevant to landform characterization for several decades gpr has been popular for characterization of the shallow subsurface and in particular sedimentary systems novel developments in gpr include the use of multi offset systems to improve signal to noise ratios and data collection efficiency amongst others and the increased use of 3d data multi electrode er systems have become popular in recent years as they allow for relatively fast and detailed mapping novel developments include time lapse monitoring of dynamic processes as well as the use of capacitively coupled systems for fast non invasive surveys em induction methods are especially popular for fast mapping of spatial variation but can also be used to obtain information on the vertical variation in subsurface electrical conductivity in recent years several examples of the use of plane wave em for characterization of landforms have been published seismic methods for landform characterization include seismic reflection and refraction techniques and the use of surface waves a recent development is the use of passive sensing approaches the use of multiple geophysical methods which can benefit from the sensitivity to different subsurface parameters is becoming more common strategies for coupled and joint inversion of complementary datasets will once more widely available benefit the geophysical study of landforms three cases studies are presented on the use of electrical and gpr methods for characterization of landforms in the range of meters to 100 s of meters in dimension in a study of polygonal patterned ground in the saginaw lowlands michigan usa electrical resistivity tomography was used to characterize differences in subsurface texture and water content associated with polygon swale topography also a sand filled thermokarst feature was identified using electrical resistivity data the second example is on the use of constant spread traversing cst for characterization of large scale glaciotectonic deformation in the ludington ridge michigan multiple cst surveys parallel to an 60 m high cliff where broad 100 m synclines and narrow clay rich anticlines are visible illustrated that at least one of the narrow structures extended inland a third case study discusses internal structures of an eolian dune on a coastal spit in new zealand both 35 and 200 mhz gpr data which clearly identified a paleosol and internal sedimentary structures of the dune were used to improve understanding of the development of the dune which may shed light on paleo wind directions

an idealized model of the world ocean part i the global scale water masses abstract a primitive equation three dimensional numerical model of the ocean employing idealized versions of the real topography and surface boundary conditions is used to study the water mass structure of the world ocean in particular the response of the model to three fundamental changes in boundary conditions is investigated in an attempt to identify the mechanisms in the model which are responsible for the establishment of the largest scale features of the global water mass structure with the drake passage closed thermohaline driving alone and a fresh north atlantic surface salinity specified only the coarsest aspects of the observed t and s structure are reproduced and the entire world ocean below the thermocline is dominated by water formed at the southern boundary the salinity configuration in particular lacks much of its observed structure in this case when the drake passage is opened the resulting circumpolar flow serves to isolate the extreme southern ocean this allows waters of no

geological framework of the laurentian trough aquifer system southern ontario the laurentian trough lt a depression 100 km long 3000 km2 in area and 100 m deep at the base of the niagara escarpment extends from within georgian bay to lake ontario it has a complex er

volcanological applications of so2 cameras ground based volcanic gas and ash imaging has the potential to revolutionise the way in which volcanoes are monitored and studied the ability to track and quantify volcanic emissions in space and time with unprecedented fidelity opens the door to integration with geophysical measurements allowing breakthroughs in our understanding of the physical processes driving volcanic activity in may 2013 a european science foundation funded plume imaging workshop was conducted in strombolutaly with the objective of bringing the ground based volcanic plume imaging community together in order to examine the state of the art and move towards a best practice for volcanic ash and gas imaging techniques a particular focus was the development of so2 imaging systems or so2 cameras with six teams deploying and testing various designs of ultraviolet and infrared based imaging systems capable of imagining so2 one conclusion of the workshop was that the term so2 camera should be applied to any so2 imaging system regardless of wavelength of radiation used this special issue on volcanic plume imaging is the direct result of the stromboli workshop and together the papers presented here represent the state of the art of ground based volcano plume imaging science and technology in this work we examine in detail the volcanological applications of the so2 camera reviewing previous works and placing the new research contained in this special issue in context the development of the so2 camera and future developments extending imaging to other volcanic gases is one of the most exciting and novel research frontiers in volcanology today c 2014 published by elsevier b v

combined use of straddle packer testing and flute profiling for hydraulic testing in fractured rock boreholes summary a combination of high resolution hydraulic tests using straddle packers and transmissivity t profiling using the flute flexible liner method liner profiling in densely fractured rock boreholes is shown to be efficient for the determination of the vertical distribution of t along the entire hole the liner t profiling method takes a few hours or less to scan the entire borehole length resulting in a t profile under favorable conditions this method has good reliability for identifying the highest t zones identified by distinct decreases in liner velocity when these zones are covered by the descending liner in contrast for one short test interval e g 1 2 m the multiple test straddle packer method takes a few hours to measure t with good precision and accuracy using a combination of steady state and transient tests e g constant head step tests slug tests and constant rate pumping tests because of the time consuming aspect of this multiple test method it is most efficient in each borehole to conduct straddle packer testing only in priority zones selected after assessment of other borehole data collected prior to packer testing the t profile from the liner method is instrumental in selecting high permeable zones for application of the multiple test method using straddle packers which in turn refines the t estimation from the liner profile results from three boreholes in densely fractured sandstone demonstrate this approach showing the synergistic use of the methods with emphasis on information important for determining hydraulic apertures

buried valley aquifers in the canadian prairies geology hydrogeology and origin11earth science sector ess contribution 20120131 we review over 100 years of literature on prairie buried valleys to provide a platform for future research and policy development prairie buried valley fills commonly function as aquifers that yie

a gravity survey of the dundas buried valley west of copetown ontario a total of 243 bouguer gravity readings have been completed over a 9 km2 area covering the terminus of the dundas buried valley a prominent reentrant in the niagara escarpment a 1 5 mgal 15 m s 2 bouguer anomaly clearly defines an abrupt closure of the bedrock topography west of copetown confirming and extending the results of earlier seismic reflection and refraction surveys an apparent tributary in the contoured gravity entering the terminus from the south is unfortunately poorly resolved it underlies property to which access was denied the bouguer gravity data are transformed to a model of the bedrock depth via a three dimensional model the mean error between data and model gravity after correcting the former for a regional gradient is less than 0 1 mgal 1 m s 2 the estimated error in the observations themselves is 0 11 mgal 1 1 m s 2 the observed bouguer gravity is compared with that which would be produced by the present niagara gorge were it to underlie the survey area the m

buried preglacial fluvial gorges and valleys preserved through quaternary glaciations beneath the eastern laurentide ice sheet the geomorphology geometry and sedimentary infill of buried gorges and v shaped valleys observed at the base of major river valleys in the formerly glaciated southeastern canadian shield region have been revealed from excavation and drilling data acquired during the construction of hydro electric dams and seismic data collected on lakes and offshore compilation of these previously published and unpublished data provided an exceptional opportunity to examine the morphology and spatial distribution of buried bedrock gorges and the mechanical processes responsible for their erosion in some valleys detailed observations of deep gorges have been allowed by their exhumation over large areas archive photographs show deep and large potholes natural pillars furrows flutes and scallops on the well polished bedrock walls of the gorges they also reveal that gorges and valleys have a sharp ending v shape and very narrow base and are superimposed by a u shaped valley forming a buried valley within valley topography the narrow and deep cross profile of these gorges their well polished slopes and the type of bedforms observed within them are typical features of fluvial bedrock channels drilling operations at many sites have also provided data on bedrock topography of these gorges within valleys and on the nature of their sedimentary infill the different lines of evidence presented in this paper indicate that gorges and v shaped valleys of the region were not eroded by the laurentide ice sheet during quaternary glaciations but are relics of a preserved preglacial fluvial system eroded during a lower base level this paleofluvial system is interpreted to be linked to fluvially cut channels observed on the seafloor of the estuary and gulf of st lawrence

flow around islands in rupert bay an investigation of the bottom friction effect aerial photographs of transverse shear flows around islands in rupert bay a shallow and turbid estuary in northern quebec were studied for the effect of bottom friction the island wake depends on the stability of the transverse shear layers developed along the two sides of the island two basic patterns of wake flows were observed a vortex street wake was formed when transverse shear was large as in flows around small islands on the other hand for small transverse shear as in flows around large islands the shear layers were stabilized by bottom friction and in that case a clear water wake of low turbulence and low sediment concentration was observed laboratory demonstration of the bottom friction influence on the turbulent wake in shallow water was made using a shallow water table a similarity solution was obtained for the wake flow in the far field region and numerical calculations were made of the recirculating flow in the wake bubble a wake stability parameter was introduced for wake classification and for correlation of field and laboratory data in rupert bay vortex street wakes were observed in nine out of 27 events when the wake stability parameter was less than a critical value this result is consistent with the laboratory and numerical simulations

tunnel valleys concepts and controversies a review abstract although erosion of valleys by subglacial meltwater was first proposed more than 100 years ago the processes that produced these valleys under past ice sheets have remained a topic of vigorous debate the most commonly hypothesized mechanisms have included gradual formation by sediment deformation into the incipient valleys under steady state conditions and subsequent transport by meltwater to the ice margin time transgressive formation along a retreating ice margin by drainage of surface meltwater to the bed or release of impounded meltwater behind a marginal permafrost wedge probably catastrophically and rapid erosion during widespread catastrophic basal sheetflood events recent application of new and enhanced imaging techniques has led to the identification of many new tunnel valleys both on land and offshore throughout the regions glaciated during former ice ages in addition new advances in understanding of subglacial hydrology both from modelling and field instrumentation have helped to constrain the drainage of meltwater from past ice sheet beds this work elucidates the role of subglacial groundwater flow systems in evacuating meltwater from the bed but also shows that groundwater flow alone was not enough to maintain ice bed meltwater pore pressures below the level of ice flotation both modelling and field observations indicate that subglacial conduits oriented parallel to glacial flow lines reorganize groundwater flow systems into basins containing lateral flow toward conduits cut upward into the ice or downward into the bed because of the inability of groundwater flow to account for all the meltwater produced by basal melting other drainage mechanisms involving both non channelized and channelized meltwater flow have been proposed the notion of catastrophic drainage of impounded basal meltwater is still favored by many and the discovery of hundreds of subglacial lakes beneath the antarctic ice sheet and the likelihood of similar lakes beneath pleistocene ice sheets provides a source of water for those advocating catastrophic formation for tunnel valleys proponents of catastrophic drainage consider the valleys to be channels reflecting the width and perhaps depths of flows that formed them tunnel valleys produced by the scandinavian ice sheet have been described and mapped on land as well as on the sea bed valleys and networks of valleys some of which are totally buried have been linked to 3 or more glaciations tunnel valley networks from the last weichselian glaciation in denmark can be related to specific ice margins developed during ice retreat in north america most research has focused on tunnel valleys associated with ice margins formed by the last wisconsin glaciation along the southern margin of the laurentide ice sheet

a workshop examination of shallow seismic reflection surveying in september 1996 the office of basic energy sciences of the u s department of energy doe sponsored a research workshop in berkeley california where approximately 20 participants analyzed the potential and limitations of near surface seismic reflection methods

buried and open tunnel valleys in denmark erosion beneath multiple ice sheets abstract tunnel valleys are large elongate and irregular depressions cut beneath the margin of former ice sheets they are generally believed to play a substantial role for the entire hydraulic system beneath ice sheets and thus also for ice sheet behaviour their origin however remains poorly understood examination of newly collected danish hydrogeophysical and lithological data has revealed numerous systems of buried valleys 50 350 m deep and 0 5 4 km wide these valleys are similar to the open tunnel valleys found in the present day landscape infills comprise a variety of sediments often with subglacial clay till and meltwater deposits the incised substratum consists of limestone heavy paleogene clay sand and silt the tunnel valleys have preferred orientations and can be divided into several generations each ascribed individual ice advances or ice sheets occurring during multiple glaciations the processes forming the valleys appear to prefer pre existing open and buried valleys for the renewed erosion thus old subglacial erosion pathways have been re used several times and some of the present tunnel valleys may have been established in the middle or early quaternary or even earlier this valley re use effect causes apparently anastomosed valley systems to emerge in the data images the valleys were mainly eroded by meltwater supposed to have drained from subglacially stored reservoirs probably behind a frozen margin the water was most likely released in repeated jokulhlaups and flowed in relatively small channels on the floors of the tunnel valleys which gradually became ice filled with the lowering of the bed selective linear glacial erosion is also believed to have contributed to the erosion this however was most pronounced for the widest valleys and is supposed to have played a secondary role

avoiding pitfalls in shallow seismic reflection surveys acquiring shallow reflection data requires the use of high frequencies preferably accompanied by broad bandwidths problems that sometimes arise with this type of seismic information include spatial aliasing of ground roll erroneous interpretation of processed airwaves and air coupled waves as reflected seismic waves misinterpretation of refractions as reflections on stacked common midpoint cmp sections and emergence of processing artifacts processing and interpreting near surface reflection data correctly often requires more than a simple scaling down of the methods used in oil and gas exploration or crustal studies for example even under favorable conditions separating shallow reflections from shallow refractions during processing may prove difficult if not impossible artifacts emanating from inadequate velocity analysis and inaccurate static corrections during processing are at least as troublesome when they emerge on shallow reflection sections as they are on sections typical of petroleum

flow separation and vertical motions in a tidal flow interacting with a shallow water island this paper reports on the case study of rattray island great barrier reef northeast australia lying perpendicular to tidal flow in shallow waters at ebb and flood attached stable eddies develop in the wake where swirls of turbidity suggest that sediment laden waters are brought to the surface as a result of vertical transport both eddy and tip upwellings are encountered in the tidal flow around rattray island but there is currently no clear cut answer as to which secondary flow generates upwelling with the largest intensity this paper addresses this specific issue through idealized and realistic high resolution numerical experiments the analysis is supported by physical arguments based on the theory of flow separation given rattray s geometry and surrounding bathymetry the mechanism of flow separation in shallow waters helps explain the asymmetry in size of the eddies and their intensity the results of idealized numerical experiments also suggest that eddy and tip upwellings may be of similar intensity at rattray island

quantitative investigations of the hydraulic connection between a large reservoir and a buried valley aquifer in southern alberta quantitative investigations including two aquifer tests and development of a three dimensional 3d ground water flow model were required to determine the hydraulic connection between an irrigation reservoir and a buried valley aquifer in southern alberta evidence of seepage was detected in the buried valley aquifer 10 km east of the pine coulee reservoir at the onset of filling in 1999 when the reservoir level exceeded an elevation of 1035 m above sea level a s l concern for an increase in the local water table and the creation of artesian conditions in the aquifer prompted this study to determine the approximate location of a seepage window that appeared to be connecting the reservoir and aquifer observations of hydraulic head in the aquifer during the pumping tests revealed a barrier bound ary when the reservoir level was at an elevation of 1035 m a s l and a recharge boundary condition when the elevation exceeded 1039 m a s l these data were used to calibrate a 3d groundwater flow model which was needed to deter mine the hydraulic properties and approximate location of the leakage zone the quantitative investigation showed that seepage likely occurred through the sideslopes of the flooded coulee rather than through the low permeability coulee floor sediments or the embankment dam further simulations illustrated the expected seepage rates at various reservoir supply levels and the pumping rates required for relief wells installed in the buried valley aquifer to maintain historic aquifer hydraulic head a brief postanalysis indicated that the forecasted pumping rates were only 15 lower than have been required to maintain preconstruction water levels in the buried valley aquifer

eddy formation in unsteady flows unsteadiness of flow at m2 s2 tidal frequencies is demonstrated to be a dominant factor forming eddies in natural shallow water and continental shelf environments numerical hydrodynamic modelling and field measurements show that during the later stages of the half tidal cycle in a low friction environment currents in the lee of an obstruction accelerate with supporting sea gradients opposite to the adjacent inertial free stream which is still decelerating these opposed currents appear as a phase eddy and ideally can endure for 3 hours in m2 s2 reversing currents case studies are cited and numerical hydrodynamic modeling is applied to examine the formation of these circulation patterns

first estimate of volcanic so2 budget for vanuatu island arc abstract the spatial and temporal coverage of measurements of volcanic gas emissions remains patchy however over the last decade emissions inventories have improved thanks to new measurements of some of the lesser known volcanic areas we report on one such region the vanuatu island arc in the southwest pacific for which we now have sufficient systematic observations to offer a systematic emissions inventory our new estimate is based on so 2 flux measurements made in the period 2004 2009 with ultraviolet spectroscopy techniques for the following volcanoes yasur lopevi ambrym ambae gaua and vanua lava from south to north these are the first ever measurements for lopevi gaua and vanua lava the results reveal the vanuatu arc as one of earth s prominent sources of volcanic degassing with a characteristic annual emission to the atmosphere of 3 tg of so 2 representing about 20 of hitherto published global estimates our new dataset highlights the sustained prodigious degassing of ambrym volcano whose 5 gg day 1 mean flux of so 2 represents nearly two thirds of the total budget for the vanuatu arc this confirms ambrym as one of the largest volcanic sources worldwide comparable to etna often considered as the most vigorous source of volcanic emission on earth we also report a high degassing for ambae of 2 gg day 1 so 2 representing more than 28 of the vanuatu arc budget thus 90 of the so 2 output from vanuatu is focused in the central part of the arc from ambrym and ambae where magmas originate from enriched indian type mantle and where peculiar tectonic conditions could favor high magma production rates

electrical resistivity ground imaging ergi a new tool for mapping the lithology and geometry of channel belts and valley fills efforts to map the lithology and geometry of sand and gravel channel belts and valley fills are limited by an inability to easily obtain information about the shallow subsurface until recently boreholes were the only method available to obtain this information however borehole programmes are costly time consuming and always leave in doubt the stratigraphic connection between and beyond the boreholes although standard shallow geophysical techniques such as ground penetrating radar gpr and shallow seismic can rapidly obtain subsurface data with high horizontal resolution they only function well under select conditions electrical resistivity ground imaging ergi is a recently developed shallow geophysical technique that rapidly produces highresolution profiles of the shallow subsurface under most field conditions ergi uses measurements of the ground s resistance to an electrical current to develop a two dimensional model of the shallow subsurface 200 m called an ergi profile ergi measurements work equally well in resistive sediments

buried bedrock valleys and glacial and subglacial meltwater erosion in southern ontario canada morphometric features from a recently compiled bedrock topography map by the ontario geological survey suggest a glacial erosion origin for the buried large bedrock valleys and troughs in southern ontario the bedrock valleys at milverton wingham and mount forest are tunnel valleys resulting from subglacial meltwater erosion beneath the huron ice lobe probably during or shortly after the late wisconsinan glacial maximum diagnostic features for this interpretation include abrupt valley beginning and termination uneven longitudinal valley profiles and up slope gradients the dundas bedrock valley is the western extension of the lake ontario basin no comparable bedrock valleys were found to connect it to the milverton valley for a joint drainage system as previously suggested the laurentian bedrock trough is the southeastward extension of the georgian bay basin both developed along shale bedrock between the precambrian shield highlands and the niagara escarpment resulting from long term mechanical weathering associated with pleistocene glacial erosion this bedrock low has a floor that exceeds 50 km in width and is 26 m and more below the current water level of georgian bay it could drain georgian bay should the drift cover be removed there is no evidence to suggest that a preglacial river channel if it existed is still preserved in the floor of the laurentian trough as previously suggested the framework for an intensely glacially sculpted bedrock surface differs from the previous view for simple modification of a preglacial landscape and is therefore important in regional subsurface geological mapping and groundwater studies

sequences cycles and basin dynamics in the silurian of the appalachian foreland basin abstract field stratigraphic analysis of the early and medial silurian strata of ontario new york and pennsylvania permits recognition of six major sequences reflecting 3rd order cycles in the niagaran llandoverian ludlovian of new york and adjacent regions these sequences correspond approximately to the medina lower clinton middle clinton upper clinton two sequences and lockport groups each is bounded by widespread unconformities produced by the interplay of eustatic sea level drop and local tectonic uplift in general erosional sequence boundaries and transgressive surfaces are merged with no record of the lowstand wedge each sequence is subdivisible into two to five sub sequences that are marked by sharp though generally non erosional basal discontinuities investigation of the clinton and lockport groups corroborates earlier suggestions that carbonate and siliciclassic tongues extended basinward from opposite margins synchronously in response to sea level drops analysis of the thickness and basinward extent of the progradational tongues reveals the existence of multi scale sedimentary cycles sequences and component sub sequences are correlative basinwide and are synchronous within the resolution of bio and event stratigraphy major drops in relative sea level are represented by the sequence bounding discontinutiies these surfaces are overlain by siliciclastic wedges near terrigenous source areas or winnowed carbonate pack and grainstones on the tectonically passive margin overlying highstand deposits typically shales calcareous mudstones and limestones are separated from lowstand or transgressive deposits by thin condensed intervals commonly marked by phosphatic or glauconitic material and or surfaces of maximum sediment starvation the relative highstand deposits of sequences and sub sequences are developed in relatively deep water facies and are at most slightly progradational hence most sequences and sub sequences are sharply bounded roughly upward deepening to slightly shallowing successions of strata in turn sub sequences are further divisible into widespread minor parasequences and parasequence sets probably corresponding to 6th and 5th order cycles respectively the smaller scale units 0 2 5 mthick commonly display an upward shallowing motif the nested relationship of these cycles supports the hierarchical model of transgressive regressive allocycles proposed by busch and rollins 1984 niagaran cycles discussed herein are equivalent to third fourth and fifth order cycles and are traceable circumbasinally depocenters of successive sequences and sub sequences display a pattern of eastward westward eastward basin axis migration through the silurian during early llandoverian the taconic queenston deltaic complex began to subside and the basin axis depocenter and eastern shoreline shifted eastward approximately 200 km over a 6 million year period as the basin axis migrated eastward the western basin ramp forebulge was repeatedly upwarded and eroded resulting in the generation of regionally angular unconformities at the bases of sequences ii iv and vi the pattern of unconformity greatest to the west suggests rise of the algonquin arch concomitant with eastward basin axis migration during the late llandoverian to early wenlockian the algonquin arch subsided slightly concurrently with a reversal in direction of basin axis migration during deposition of upper clinton and lockport vernon strata sequences v vi the basin axis shifted approximately 300 km back to the west eastward migration of the basin axis corresponds with a time of tectonic quiescence and probable thrust load relaxation the abrupt reversal of migration in the late llandoverian may be a signal of renewed thrusting in the hinterland at the onset of the salinic disturbance

subglacial till formation sedimentary characteristics and classification we review the major subglacial till forming processes as presently understood by glacial researchers and define the parameters within which tills are produced and reconcile them with sedimentary end members processes of deformation flow sliding lodgement and ploughing coexist at the base of temperate glacier ice and act to mobilize and transport sediment and deposit it as various end members ranging from glacitectonically folded and faulted stratified material to texturally homogeneous diamicton the dominance of any one subglacial process varies both spatially and temporally giving rise to the possibility that a till or complex till sequence contains a superimposed signature of former transportation deposition at the ice bed interface we recommend that while glacial geologists and geomorphologists should be able to recognize the sedimentary imprints of various subglacial processes genetic fingerprinting of subglacial tills should be less process specific and till classification must reflect the range of products encompassed by the subglacial till production continuum glacial geologists can presently unequivocally identify a glacitectonite rock or sediment that has been deformed by subglacial shearing deformation but retains some of the structural characteristics of the parent material b subglacial traction till sediment deposited by a glacier sole either sliding over and or deforming its bed the sediment having been released directly from the ice by pressure melting and or liberated from the substrate and then disaggregated and completely or largely homogenised by shearing and support the theoretical case for c melt out till sediment released by the melting of stagnant or slowly moving debris rich glacier ice and directly deposited without subsequent transport or deformation because observations on contemporary glaciers reveal that their beds are most likely to be mosaics of deformation and sliding and warm based and cold based conditions the patterns of which change temporally and spatially it is extremely unlikely that subglacial till end members in the geological record will be anything but hybrids produced by the range of processes operative in the subglacial traction zone

a multi scale model of the hydrodynamics of the whole great barrier reef an unstructured mesh parallel hydrodynamic model of the whole great barrier reef is presented this model simultaneously simulates most scales of motion it allows interactions between small and large scale processes the depth averaged equations of motion are discretized in space by means of a mixed finite element formulation while the time marching procedure is based on a third order explicit adams bashforth scheme the mesh is made up of triangles their size and shape can be modified easily so as to resolve a wide range of scales of motion from those of the regional flows to those of the eddies or tidal jets that develop in the vicinity of reefs and islands the forcings are the surface wind stress the tides and the inflow from the coral sea east australian current coral sea coastal current the latter two forcings being applied along the open boundaries of the computational domain the numerical results compare favourably with observations of both longshore currents and the local perturbations due to narrow reef passages comparisons are also performed with the simulations of a three dimensional model applied to a small domain centered on rattray island showing that both models produce similar horizontal flow fields for a structured mesh model to yield results of the same accuracy there is no doubt that the computational cost would be much higher

island wakes in shallow coastal waters rattray island northeast australia is 1 5 km long 300 m wide and lies in well mixed water approximately 25 m deep its long axis is inclined at about 60 into the direction of the dominant semidiurnal tidal current the length of the wake in the lee of the island as documented by aerial photographs and satellite imagery appears to equal that of the wake behind a flat plate in a two dimensional flow at a reynolds number of about 10 however current metering drogues measurements and temperature mapping indicate internal wake velocities much greater than would be consistent with such a simple low reynolds number model further estimates of the turbulent eddy coefficient suggest an effective reynolds number more in the vicinity of 103 to reconcile these observational differences and to explain the observed upwelling in the core of the wake an ekman pumping model is proposed it is postulated that the ekman benthic boundary layer driven by rotation in the wake allows the vertical vorticity introduced into the water at the tip of the island at the point of separation to be negated by the vorticity of opposite sign introduced at the bottom further it is shown that a large fraction of the kinetic energy of the upstream flow facing the island is used to drive the wake eddies leading to the conclusions that the trapping of water in the lee of islands greatly increases head losses on continental shelves with numerous islands coral reefs and rock outcrops

first synoptic analysis of volcanic degassing in papua new guinea we report the first satellite based survey of volcanic sulphur dioxide so2 degassing in papua new guinea using ozone monitoring instrument omi data omi is sensitive to low level passive degassing these observations are useful for volcano monitoring hazard assessment particularly aviation hazard and assessment of arc geochemical budgets and are of immense value in remote regions with little ground based instrumentation such as papua new guinea we identify bagana manam rabaul ulawun and langila as the active sources of volcanic so2 in papua new guinea with bagana being the largest source we present an omi so2 time series for 2005 2008 and a total detected regional output of 1 8 109 kg so2 about 40 of emissions were released by major eruption events at manam january 2005 bagana june 2006 and rabaul october 2006 over the past century however we estimate that major explosive eruptions contribute 5 of the arc scale so2 emission budget ground based doas measurements of so2 degassing at five of papua new guinea s volcanoes are compared with our omi observations the total omi so2 output is only 20 of the total extrapolated from doas a discrepancy which we demonstrate is consistent with other volcanic arcs therefore the true total regional so2 output may be considerably higher than that detected by omi uncertainties in the omi so2 data include the effects of in plume chemical processing and dilution of so2 prior to the satellite overpass omi s reduced sensitivity to low levels of so2 in the planetary boundary layer and interference by meteorological clouds