Science.gov

Sample records for hill slope sediment

  1. Bunker Hill Sediment Characterization Study

    SciTech Connect

    Neal A. Yancey; Debby F. Bruhn

    2009-12-01

    The long history of mineral extraction in the Coeur d’Alene Basin has left a legacy of heavy metal laden mine tailings that have accumulated along the Coeur d’Alene River and its tributaries (U.S. Environmental Protection Agency, 2001; Barton, 2002). Silver, lead and zinc were the primary metals of economic interest in the area, but the ores contained other elements that have become environmental hazards including zinc, cadmium, lead, arsenic, nickel, and copper. The metals have contaminated the water and sediments of Lake Coeur d’Alene, and continue to be transported downstream to Spokane Washington via the Spokane River. In 1983, the EPA listed the Bunker Hill Mining and Metallurgical Complex on the National Priorities List. Since that time, many of the most contaminated areas have been stabilized or isolated, however metal contaminants continue to migrate through the basin. Designation as a Superfund site causes significant problems for the economically depressed communities in the area. Identification of primary sources of contamination can help set priorities for cleanup and cleanup options, which can include source removal, water treatment or no action depending on knowledge about the mobility of contaminants relative to water flow. The mobility of contaminant mobility under natural or engineered conditions depends on multiple factors including the physical and chemical state (or speciation) of metals and the range of processes, some of which can be seasonal, that cause mobilization of metals. As a result, it is particularly important to understand metal speciation (National Research Council, 2005) and the link between speciation and the rates of metal migration and the impact of natural or engineered variations in flow, biological activity or water chemistry.

  2. Rivulets Link the Hydrology of Soils to Hill-Slopes

    NASA Astrophysics Data System (ADS)

    Germann, P. F.

    2007-12-01

    Hydrologists dealing with run-off formation in small catchments often complain about much faster responses to precipitation at the catchment scale than what was predicted with soil hydrological approaches to infiltration and drainage. Constant velocity of the wetting front was observed, for instance, over a depth of 2 m and lasting more than 14 hours during an infiltration-drainage experiment in a tank that was homogeneously filled with sand. Constant velocity means neither acceleration nor deceleration of the moving water. This is only possible if the flow-driving and the flow-impeding forces continuously balance behind the wetting front. Rivulets are the conceptual units that dynamically balance forces during flow. They are considered thin streaks of flow that can be superimposed to rivulet ensembles and to water-content waves. Rivulets keep moving under the impact of gravity unless one of the following processes decelerates them: (i) increase of momentum dissipation due to reduced widths of the flow paths, (ii) capillarity-induced water sorption from the rivulets, and (iii) reduction of the rivulets' momentum due to the cessation of input. The velocities of the rivulets' wetting fronts collected so far in various systems like soils, unconsolidated sediments, fissured granites, and formations of chalk and karst, that extend over distances between 0.1 to 2000 m vary within about a factor of 50, thus offering a way of up-scaling soil hydrological processes to hill-slopes and small catchments that is based on rivulets.

  3. Parameter Calibration of Mini-LEO Hill Slope Model

    NASA Astrophysics Data System (ADS)

    Siegel, H.

    2015-12-01

    The mini-LEO hill slope, located at Biosphere 2, is a small-scale catchment model that is used to study the ways landscapes change in response to biological, chemical, and hydrological processes. Previous experiments have shown that soil heterogeneity can develop as a result of groundwater flow; changing the characteristics of the landscape. To determine whether or not flow has caused heterogeneity within the mini-LEO hill slope, numerical models were used to simulate the observed seepage flow, water table height, and storativity. To begin a numerical model of the hill slope was created using CATchment Hydrology (CATHY). The model was then brought to an initial steady state by applying a rainfall event of 5mm/day for 180 days. Then a specific rainfall experiment of alternating intensities was applied to the model. Next, a parameter calibration was conducted, to fit the model to the observed data, by changing soil parameters individually. The parameters of the best fitting calibration were taken to be the most representative of those present within the mini-LEO hill slope. Our model concluded that heterogeneities had indeed arisen as a result of the rainfall event, resulting in a lower hydraulic conductivity downslope. The lower hydraulic conductivity downslope in turn caused in an increased storage of water and a decrease in seepage flow compared to homogeneous models. This shows that the hydraulic processes acting within a landscape can change the very characteristics of the landscape itself, namely the permeability and conductivity of the soil. In the future results from the excavation of soil in mini-LEO can be compared to the models results to improve the model and validate its findings.

  4. Flow characteristics above a very low and gently sloping hill

    NASA Astrophysics Data System (ADS)

    Smedman, Ann-Sofi; Bergström, Hans

    1984-05-01

    Tower measurements of wind and turbulence in near neutral conditions at the top of a very low and gently sloping hill (height ~ 20 m, with a length scale ~ 1000 m) are analysed in terms of current flow-over-hill theory. Measurements of wind maximum height and the change of the variances of the three wind components from the inner to the outer region are found to be in agreement with predictions from the theory. Spectra of the longitudinal and vertical wind components in the inner region, scaled according to Panofsky et al. (1982), come close to the corresponding Kansas curves in the high frequency range. They have higher energy in the low frequency region, probably a spectral lag effect caused by rougher upwind terrain. In the outer region, the spectra coincide with the corresponding Kansas curves if normalized by their respective variances and plotted against f/f m.

  5. Effect of the degree of hill slope on acute downhill running velocity and acceleration.

    PubMed

    Ebben, William P; Davies, Joseph A; Clewien, Rustin W

    2008-05-01

    This study analyzes the effects of hill slope on acute overspeed running. This study considers both acceleration and supramaximal velocity. Forty-four athletes ran 40-yard sprints, on 5 different hill slopes, ranging from 2.1 degrees to 6.9 degrees . Forty-yard sprint times and 10-yard split times were recorded using the Brower Timing System Speedtrap II. Analysis reveals that 40-yard and 10-yard sprints performed on hill slopes of approximately 5.8 degrees were optimal compared to flatland running and the other slopes assessed. Sprinting on a 5.8 degrees slope increased the subjects' maximal speed by 7.09% +/- 3.66% and increased the subjects' acceleration by 6.54% +/- 1.56%. Strength and conditioning professionals who train athletes for speed should develop and use overspeed hills or platforms with slopes of approximately 5.8 degrees in order to maximize acute sprinting velocity and acceleration.

  6. Spatial heterogeneity in biogeochemical transport on Arctic hill slopes

    NASA Astrophysics Data System (ADS)

    Risser, R.; Harms, T.; Jones, J.

    2013-12-01

    Water tracks, saturated regions of the hill slope in permafrosted Arctic catchments, likely deliver the majority of water entering streams in these regions, and may play a central role in delivery of nutrients. Fate of dissolved nutrients and carbon as they are transported in water tracks has a substantial effect on stream ecosystems, as water tracks may cover up to 35% of the catchment land area. Water tracks are distinguished from adjacent areas of the hillslope by higher rates of hydrologic transport, greater woody biomass, and increased pools of nutrients. Substantial spatial heterogeneity within and between water tracks may influence their role in transfer of materials between the terrestrial and aquatic landscape. We examined spatial variability of hydrologic and chemical characteristics within and between water tracks in the Kuparuk Basin of northern Alaska to increase understanding of the factors influencing nutrient export from arctic catchments. We studied a sedge-dominated water track with perennial surface water flow with shrub-dominated water tracks containing intermittent surface flow. Nominal transit times of water in the perennial site was 5 hours, compared to 15.5 h in an ephemeral track over a 50 meter reach, indicating substantial variation in water residence time and opportunity for biogeochemical reaction across sites. We evaluated spatial heterogeneity in biogeochemical characteristics within 25-m reaches at each site with a grain size of 10 m. Dissolved CH4 concentration was elevated above atmospheric equilibrium only at the perennial water track, where CH4 concentration varied by more than 15-fold within the water track, indicating hot spots of anaerobic microbial activity. Dissolved CO2 concentration was 9 times greater on average at the perennial water track, compared to the ephemeral site, suggesting that continuous water flow supports more rapid microbial activity. CO2 concentration was also more variable in the perennial water track

  7. Hill slope and erosional controls on soil organic geochemistry in intensely managed landscapes

    NASA Astrophysics Data System (ADS)

    Filley, T. R.; Hou, T.; Hughes, M.; Tong, Y.; Papanicolaou, T.; Wacha, K.; Abban, B. K.; Boys, J.; Wilson, C. G.

    2015-12-01

    Like many regions of North America, the last 100 years of agriculture in the glaciated upper Midwest has lead to a major redistribution of soil carbon and nitrogen on the landscape. Through the natural coevolution of geomorphic, pedogenic, and ecological processes in the critical zone or by punctual changes in these processes as a result of intensive management, landscapes established characteristic hierarchies of physicochemical controls on organic matter stability. In the Intensively-Managed Landscapes - Critical Zone Observatory (IML-CZO) in Iowa and Illinois these processes are being studied with a combination of surface soil geochemical surveys and simulated rainfall/erosion experiments to document how the organic geochemistry of hill slopes, under land management ranging from row crop to restored prairie, are currently evolving, and how they evolved during early management and pre settlement. Using a combination of soil analyses including elemental, stable isotope, textural, and soil biopolymers (lignin and cutin/suberin fatty acids (SFA)) we investigated the spatial patterns of static surface soil properties and time course rainfall-erosional experiments along the same slopes to gain insight into soil carbon and biopolymer enrichment patterns in east-central Iowa within the Clear Creek Watershed. Both lignin and substituted fatty acid concentration and their molecular ratios highlighted differences in C3/C4 (soy/corn) management activities in surface soils while over 40 years of prairie restoration dramatically altered surface soil profiles. For example, a general pattern in static baseline samples was an enrichment of 15N in soils down slope and an opposite pattern of accumulation/loss of lignin and SFA in topographic highs and lows. Transport of soil particles, associated biopolymers, and elemental and isotope signatures, exhibited distinct patterns based upon both position of the hill slope and directionality of flow with respect to rill/gully direction

  8. Lidar based morphometric analysis of hoodoos with implications for dryland hill slope process (Invited)

    NASA Astrophysics Data System (ADS)

    Wawrzyniec, T. F.; McFadden, L. D.

    2009-12-01

    A hoodoo is a locally common landform associated with hill slopes in drylands. Some of the better-known examples occur in Bryce National Park of Southwest Utah. Hoodoos form when hill slopes form on rock that have spatially variable resistances to weathering and erosion. Rock that is more resistant effectively shields the softer rock beneath them and as the hill slope retreats the resistant layer or resistant region (e.g., a concretion) breaches through the surface. Local concentration of runoff around the resistant cap presumably causes the development of the typical, capped-spire hoodoo landform. Such unique landforms provide an opportunity to evaluate the processes and rates of change associated with hill slope retreat in drylands. In previous studies we have used lidar data to generate 4D analysis of hill slope change using hoodoos as markers and successfully demonstrated that erosion rates were comparable to erosion rates based on other methods (tree ring studies and radionuclide dating, ~2mm/year). We were also able to indentify discrete areas of change, which seem to be associated with soil removal by water erosion and block fall. The latter may be influenced by both freeze-thaw and thermal isolation. In the current study we are exploring the evolution of hoodoos from breach to pedestal collapse to elucidate rates and processes of hill slope formation in these dryland terrains and to determine how modern changes may be linked to apparent long-term climate trends. Lidar data is being used to complete a detailed morphometric analysis to evaluate the relationships between hoodoo form, rock fabric, slope aspect, and processes related to hill slope retreat and cliff formation. Fracture data collected in the field and directly from lidar-based imagery indicate that taller hoodoo groves, generally found on south or southeast facing slopes, have a form that is strongly influenced by pre-existing tectonic fractures. Hoodoo pedestals found on north or northwest facing

  9. Analysis of Hill slopes predicted by the four-ligand exponential model for a regulatory enzyme.

    PubMed Central

    Ainsworth, S

    1986-01-01

    The four-ligand exponential model for a regulatory enzyme is described as it is applied to kinetic studies of yeast pyruvate kinase in which the concentrations of four ligands are systematically varied. The Hill slopes predicted by this model are calculated for the two situations in which the fourth ligand is either a substrate or an effector. It is shown that the individual terms that make up the expression for the Hill slope assist the interpretation of the observed behaviour in terms of the constants employed by the model. PMID:3718493

  10. [Effects of slope gradient on slope runoff and sediment yield under different single rainfall conditions].

    PubMed

    He, Ji-Jun; Cai, Qiang-Guo; Liu, Song-Bo

    2012-05-01

    Based on the field observation data of runoff and sediment yield produced by single rainfall events in runoff plots, this paper analyzed the variation patterns of runoff and sediment yield on the slopes with different gradients under different single rainfall conditions. The differences in the rainfall conditions had little effects on the variation patterns of slope runoff with the gradient. Under the conditions of six different rainfall events in the study area, the variation patterns of slope runoff with the gradient were basically the same, i. e., the runoff increased with increasing gradient, but the increment of the runoff decreased slightly with increasing gradient, which was mainly determined by the infiltration flux of atmospheric precipitation. Rainfall condition played an important role on the slope sediment yield. Generally, there existed a critical slope gradient for slope erosion, but the critical gradient was not a fixed value, which varied with rainfall condition. The critical slope gradient for slope erosion increased with increasing slope gradient. When the critical slope gradient was greater, the variation of slope sediment yield with slope gradient always became larger.

  11. Sediment Pathways Across Trench Slopes: Results From Numerical Modeling

    NASA Astrophysics Data System (ADS)

    Cormier, M. H.; Seeber, L.; McHugh, C. M.; Fujiwara, T.; Kanamatsu, T.; King, J. W.

    2015-12-01

    Until the 2011 Mw9.0 Tohoku earthquake, the role of earthquakes as agents of sediment dispersal and deposition at erosional trenches was largely under-appreciated. A series of cruises carried out after the 2011 event has revealed a variety of unsuspected sediment transport mechanisms, such as tsunami-triggered sheet turbidites, suggesting that great earthquakes may in fact be important agents for dispersing sediments across trench slopes. To complement these observational data, we have modeled the pathways of sediments across the trench slope based on bathymetric grids. Our approach assumes that transport direction is controlled by slope azimuth only, and ignores obstacles smaller than 0.6-1 km; these constraints are meant to approximate the behavior of turbidites. Results indicate that (1) most pathways issued from the upper slope terminate near the top of the small frontal wedge, and thus do not reach the trench axis; (2) in turn, sediments transported to the trench axis are likely derived from the small frontal wedge or from the subducting Pacific plate. These results are consistent with the stratigraphy imaged in seismic profiles, which reveals that the slope apron does not extend as far as the frontal wedge, and that the thickness of sediments at the trench axis is similar to that of the incoming Pacific plate. We further applied this modeling technique to the Cascadia, Nankai, Middle-America, and Sumatra trenches. Where well-defined canyons carve the trench slopes, sediments from the upper slope may routinely reach the trench axis (e.g., off Costa Rica and Cascadia). In turn, slope basins that are isolated from the canyons drainage systems must mainly accumulate locally-derived sediments. Therefore, their turbiditic infill may be diagnostic of seismic activity only - and not from storm or flood activity. If correct, this would make isolated slope basins ideal targets for paleoseismological investigation.

  12. Sediment distribution about salt domes and ridges on Louisiana slope

    SciTech Connect

    Lowrie, A.

    1984-09-01

    Salt ridges and domes underlie much of the present Louisiana slope. The bathymetric expression of underlying salt could be either a mound or a flattening of the normal rate of descent down the slope. The mounded salt features form barriers to the gravity-driven sediments from the shelf break. Much industrial research has been done in the search for reservoir sands about such an obstruction. Parallel-bedded sediments from foredrifts on the upcurrent side of a seamount. These foredrift sediments were deposited where the prevailing ocean bottom currents were locally decelerated by the obstructing seamount. Moats are found on the sides of the obstruction and are the result of erosion or nondeposition owing to acceleration of deflected waters. Leedrifts are found on the downcurrent side of the obstruction. Current gyres result from deceleration of accelerated currents along the obstruction's flanks, and a complex sedimentation pattern results. Flow over the obstruction's top is determined by size and shape of the obstruction relative to size and velocity of the bottom-following current. A turbulent wave will be set up which may have sufficient amplitude to influence sedimentation on the downcurrent side. If ocean bottoms currents equal gravity-driven terrigenous sediment movement and seamounts equal salt domes and ridges, then the result of deep ocean surveys are directly applicable to sedimentation on slopes with underlying salt basement. The salt-related sedimentation pattern of the present slope should be applicable to similar paleoenvironments.

  13. Tracking snowmelt in the subsurface: time-lapse electrical resistivity imaging on an alpine hill slope.

    NASA Astrophysics Data System (ADS)

    Thayer, D.; Parsekian, A.; Hyde, K.; Beverly, D.; Speckman, H. N.; Ewers, B. E.

    2015-12-01

    In the mountain West region the winter snowpack provides more than 70% of our annual water supply. Modeling and predicting the timing and magnitude of snowmelt-driven water yield is difficult due to the complexities of hydrologic systems that move meltwater from snow to rivers. Particular challenges are understanding the temporal and spatial domain of subsurface hydraulic processes at relevant scales, which range from points to catchments. Subsurface characterization often requires borehole instrumentation, which is expensive and extremely difficult to install in remote, rugged terrain. Advancements in non-invasive geophysical methods allow us to monitor changes in geophysical parameters over time and infer changes in hydraulic processes. In the No-Name experimental catchment in the Medicine Bow National Forest in Wyoming, we are conducting a multi-season, time-lapse electrical resistivity imaging survey on a sub-alpine hill slope. This south-facing, partially forested slope ranges from 5 degrees to 35 degrees in steepness and consists of a soil mantle covering buried glacial talus deposits of unknown depth. A permanent grid of down-slope and cross-slope electrode arrays is monitored up to four times a day. The arrays span the entire vertical distance of the slope, from an exposed bedrock ridge to a seasonal drainage below, and cover treed and non-treed areas. Geophysical measurements are augmented by temperature and moisture time-series instrumented below the surface in a contiguous 3 meter borehole. A time-series of multiple resistivity models each day from May to July shows the changing distribution of subsurface moisture during a seasonal drying sequence punctuated by isolated rain events. Spatial patterns of changing moisture indicate that soil and gravel in the top two meters drain into a saturated layer parallel to the slope which overlies less saturated material. These results suggest that water from snowmelt and rain events tends to move down-slope beneath

  14. Effects of erosion in the fate of soil organic carbon and soil aggregation in a burned Mediterranean hill-slope

    NASA Astrophysics Data System (ADS)

    Campo, Julian; Cammeraat, Erik; Gimeno-García, Eugenia; Andreu, Vicente

    2016-04-01

    The Intergovernmental Panel on Climate Change indicated a higher degree of confidence that meteorological conditions associated to climate change will be propitious to increasing extreme events manifested, among others, in bigger and more frequent wildfires (IPCC, 2014). Wildfires contribute to shaping the landscape, and also the geomorphological and hydrological processes that operate on soil are affected (Bento-Gonçalves et al., 2012). Whereas, it is well documented that wildfires produce significant changes on erosion processes, the associated fate of soil organic carbon (SOC) has received less attention. This research assesses this gap by studying the loss, redistribution, and stabilization of SOC in a Mediterranean forest hill-slope burned the 28-08-2014, with high severity fire, at the Natural Park of Sierra de Espadán, Spain (39°50'45.11"N, 0°22'20.52"W). To this end, soil was sampled (19-9-2014) in the foot's slope (depositional), middle part (transport) and top (eroding) at two depths (<2 cm, 2-5 cm), and in two environments (under canopy soil: UC; bare soil: BS). Sediments were collected from four sediment fences constructed at the foot's slope, and together with soil samples, analysed with regard to SOC content and aggregate stability (AS). The main objective is to increase the understanding on the fate of SOC in Mediterranean burned areas experiencing soil erosion, transport and deposition, with special attention to the role of aggregation and disaggregation in redistribution processes. Immediately after the fire, SOC content was high (≈50 gC kg-1) as well as the AS (water drop test>146 drops). Significant differences (ANOVA, p<0.05) in SOC contents were observed between environments (UC>BS) and soil depths (topsoil>subsoil). However, no significant differences were observed among eroding (58.8+20.8 gC kg-1), transport (67.3+34.4 gC kg-1), and depositional zones (62.0+31.3 gC kg-1), which is not in agreement with other SOC redistribution studies

  15. Recent sedimentation on the new jersey slope and rise.

    PubMed

    Stanley, D J; Nelsen, T A; Stuckenrath, R

    1984-10-12

    Radiocarbon dating and sedimentological studies of closely spaced cores indicate movement during the Holocene of sediments on the New Jersey continental slope and upper rise between Wilmington and Lindenkohl canyons. The uneven time-stratigraphic thickness of the late Quaternary sediment sections between cores and the nonuniform deposition rate at any given core site and among core sites show that the sediment blanket in canyon and intercanyon areas has been affected by downslope, gravity-driven pocesses during the Holocene to the present. The reduced rate of deposition on the slope and upper rise between the late Pleistocene and the present is largely due to decreased off-shelf transport in response to the eustatic rise in sea level. Very old radiocarbon dates at core tops result from emplacement of older reworked materials from upslope or from truncation of sections by mass wasting processes exposing older material at the sea floor. These processes also account for an irregular sequence of dated sections within cores and stratigraphic irregularities of the surficial cover from core to core. Marked variability in deposition rates on the slope and upper rise is largely a function of topographic configuration, proximity and accessibility to sediment source, and transport processes seaward of the shelf break. Moreover, higher accumulation rates on the upper rise are attributed primarily to slope bypassing. Bypassing, prevalent during the late Pleistocene, has continued periodically to the present.

  16. Early and Middle Devonian shelf-slope transition, southern Mahogany Hills, Eureka County, Nevada

    SciTech Connect

    Schalla, R.A. ); Benedetto, K.M. )

    1991-10-01

    In the southern Mahogany Hills the abrupt lateral transition between the lower McColley Canyon Formation (Kobeh Member) and the Beacon Peak (Sevy) Dolomite (Lower Devonian), and the pinch out of the Oxyoke Canyon Sandstone into the upper Sadler Ranch Formation (Middle Devonian), document lithofacies relationships between carbonate shelf and slope deposits. The McColley Canyon/Beacon Peak transition is marked by a change from thin-bedded dolomite and limestone with occasional chert nodules and scattered fossil material, to poorly bedded, largely unfossiliferous, sandy dolomite. This change suggests shallowing and concomitant circulation restriction at the shelf edge during the early stages of platform (ramp) development. Data from measured sections, in the vicinity of Combs Peak, suggest that the location of the shelf edge' was the result of both transgression and paleotopographic relief on the subjacent platform. A thin oxidized zone at the top of the Beacon Peak Dolomite on Combs Peak, interpreted as a paleosol, indicates subaerial exposure of the outer shelf prior to renewed transgression and deposition of the Bartine Member of the McColley Canyon Formation. The location of the carbonate shelf edge is further documented by the westward pinch out of unfossiliferous, arenaceous dolomites of the Oxyoke Canyon Sandstone into fossiliferous, fore-slope dolomites of the Sadler Ranch Formation. This facies change is the result of regression, which caused shoaling along the shelf edge. Lithofacies relationships Mahogany Hills document two transgressive-regressive cycles, and help to establish the location of an Early and Middle Devonian carbonate shelf-slope transition in southern Eureka County.

  17. The geomorphic evolution of slopes and sediment chutes on forereefs

    NASA Astrophysics Data System (ADS)

    Hall, Douglas B.

    1999-03-01

    Frequent slope failures of the forereef dropoff occur in living coral reefs on the island of Bonaire in the southern Caribbean. Topographic profiles of ten sites were taken perpendicular to shore, followed by an estimation of coral ages ( M. annularis) along the topographic profiles. The coral ages were estimated from published rates of growth and sizes of the sampled corals. Comparisons of coral age and adjacent slope angle indicated that the steeper slopes are older and that mass failure of the slope reduces the steepness of the forereef front and destroys the coral community along the disturbed slope. Slopes grow until reaching a critical steepness, after which underwater sliding of the over-steepened forereef front results. In observed slides, the mechanical weakness in the reef structure that facilitates a slide failure was the result of a weak mud and coral rubble layer deposited 2 m below the living coral cover. The remaining slide scarp evolves into a sediment chute that conveys the resulting flow of biogenic sands from the shallow forereef terrace down the forereef edge. Because of the constant flow of sand down these channels, no corals can recolonize the sediment chutes and the chutes become stable topographic features. In addition, these indentations in the forereef front also serve as channels for the vertical density mixing of water of varying salinities and temperatures.

  18. Stratigraphy and paleogeographic significance of a Late Pennsylvanian to Early Permian channeled slope sequence in the Darwin Basin, southern Darwin Hills, east-central California

    USGS Publications Warehouse

    Stevens, Calvin H.; Stone, Paul; Magginetti, Robert T.; Ritter, Scott M.

    2015-01-01

    The complex stratigraphy of late Paleozoic rocks in the southern Darwin Hills consists of regionally extensive Mississippian and Early to Middle Pennsylvanian rocks overlain by latest Pennsylvanian to Early Permian rocks, herein called the Darwin Hills sequence. Deposition of this latter sequence marked the beginning of the Darwin Basin. In Mississippian time, a carbonate platform prograded westward over slightly older slope deposits. In the Late Mississippian this platform was exposed to erosion and siliciclastic sediments were deposited. In Early to Middle Pennsylvanian time the area subsided, forming a west-facing ramp that was subjected to deformation and erosion in Middle or early Late Pennsylvanian time. Later this area was tilted westward and deep-water sediments were deposited on this slope. In latest Pennsylvanian to earliest Permian time, a major channel was cut through the older Pennsylvanian rocks and into the Upper Mississippian strata. This channel was gradually filled with increasingly finer grained, deep-water sediment as the area evolved into a basin floor by Early Permian (Sakmarian) time. Expansion of the Darwin Basin in Artinskian time led to a second phase of deposition represented by strata of the regionally extensive Darwin Canyon Formation. The geology in this small area thus documents tectonic events occurring during the early development of the Darwin Basin.

  19. Early and Middle Devonian shelf-slope transition, southern Mahogany Hills, Eureka County, Nevada

    SciTech Connect

    Schalla, R.A.; Benedetoo, K.M.

    1989-03-01

    In the southern Mahogany Hills of Nevada, the abrupt lateral transition between the lower McColley Canyon Formation (Kobeh Member) and Beacon Peak (Sevy) dolomite (Lower Devonian) and the pinch-out of the Oxyoke Canyon sandstone into the upper Sadler Ranch formation (Middle Devonian) document lithofacies relationships between carbonate shelf and slope deposits. The McColley Canyon-Beacon Peak transition is marked by a change from thin-bedded dolomite and limestone with occasional chert nodules and scattered fossil material to poorly bedded, largely unfossiliferous, sandy dolomite. This change suggests shallowing and concomitant circulation restriction at the shelf edge during the early stages of platform (ramp) development. Measured sections in the vicinity of Combs Peak suggest that the location of the shelf edge is the result of both transgression and paleotopographic relief on the subjacent platform. A thin oxidized zone at the top of the Beacon Peak in section CP II, interpreted as a paleosol, indicates subaerial exposure of the outer shelf prior to renewed transgression and deposition of the Bartine Member. The location of the carbonate shelf edge is further documented by the westward pinch-out of unfossiliferous, arenaceous dolomites of the Oxyoke Canyon sandstone into fossiliferous foreslope dolomites of the Sadler Ranch formation. This facies change is the result of regression, which caused shoaling along the shelf edge. Lithofacies relationships exposed in the southern Mahogany Hills document two transgressive-regressive cycles and help to establish the location of an Early and Middle Devonian carbonate shelf-slope break in southern Eureka County.

  20. ChemCam analyses of the Pahrump Hills sediments in the context of other sediments analysed by the Curiosity rover

    NASA Astrophysics Data System (ADS)

    Mangold, N.; Forni, O.; Blaney, D. L.; Milliken, R.; Nachon, M.; Le Deit, L.; Gasnault, O.; Clegg, S.; Fisk, M.; Grotzinger, J.; Hurowitz, J.; Kah, L. C.; Le Mouélic, S.; McLennan, S.; Maurice, S.; Stack, K.; Sumner, D. Y.; Wiens, R. C.; MSL Team

    2015-10-01

    We report the results of ChemCam observations at the location of Pahrump Hills, analysed by the rover during the end of 2014 and beginning of 2015. Although Pahrump Hills sediment compositions are overall close to that of the coarser conglomerates analysed earlier by the rover, these observations show a strong variability in texture and composition, suggesting variations in source material and a complex aqueous history.

  1. Check dams effects on sediment transport in steep slope flume

    NASA Astrophysics Data System (ADS)

    Piton, Guillaume; Recking, Alain

    2014-05-01

    Depending on many influences (geology, relief, hydrology, land use, etc.) some mountainous watershed are prone to cause casualties and facilities damages. Large amounts of sediments episodically released by torrents are often the biggest problem in torrent related hazard mitigation. Series of transversal structures as check dams and ground sills are often used in the panel of risk mitigation technics. A large literature exits on check dams and it mainly concerns engineering design, e.g. toe scouring, stability stress diagram, changes in upper and lower reaches equilibrium slopes. Check dams in steep slope rivers constitute fixed points in the bed profile and prevent general bed incision. However their influence on sediment transport once they are filled is not yet clear. Two flume test campaigns, synthetize in Table 1, were performed to investigate this question: Table 1 : experiment plan Run (duration) Ref1 (50h)CD1a (30h)CD1b (30h)Ref2 (92h)CD2 (18h) Solid feeding discharge (g.s^-1) 44 44 44 60 60 Number of check dams none 1 3 none 2 A nearly 5-m-long, 10-cm-wide and 12%-steep flume was used. The water discharge was set to 0,55 l/s in all runs. A mixture of poorly sorted natural sediments with diameters between 0.8 and 40 mm was used. An open solid-discharge-feeding circuit kept the inlet sediment flux constant during all experiments. As both feeding rates did not present variation, changes in outlet solid discharge were assumed to be due to bed variations in the bed storage. We observed strong fluctuations of solid flux and slope in each reaches of all runs between: (i) steep aggradating armoured bed and (ii) less steep and finer bed releasing bedload sheets during erosion events and inducing bedload pulses. All experiments showed consistent results: transported volume associated with erosion event decreased with the length between two subsequent check dams. Solid transversal structures shorten the upstream erosion-propagation and avoid downstream change in the

  2. Model for sand hills development: Geometry, sediment supply and deposition, river systems and climatic implications

    SciTech Connect

    Pederson, D.T.; Wayne, W.J. . Geology Dept.); Davis, R.K. . Dept. of Earth Science)

    1992-01-01

    A model of sand hills development was formulated using processes occurring along the Dismal, Middle Loup and Platte rivers. A widespread alluvial fan blanketed by loess and sand dunes with interspersed lacustrine deposits is the product. The great arc of the sediment-supplying river indicates direction of wind transport. The key is a Platte-like river with flows near threshold capacity for transport of sediment from the river's source through the area during wetter climatic periods. During dryer periods stream channels fill with sediment pulses transported from mountain headwaters during snowmelt flood flows. The flood flows cause vertical reworking and sorting of the sediment. With waning flood flows many stream channels dry up leaving sediments vulnerable to wind erosion and transpore. With time stream channels become blocked by aggradation of sediment and dune formation diverting snowmelt floods to new paths in the forming dune field or around the margin of the new dune field. This process continues until increased flows with wetter comates are once again able to transport sediment through the area and erode a new river valley. Rivers rising in sand hills are groundwater fed, uniform in flow, and change only in response to climatic changes. They do not have the energy to rework the extensive gravel deposits of the Platte-like rivers and their net effect is to rework sediment above the coarser alluvium and transport the finer sediment out of the sand hills.

  3. Slope instability in a historical and architectural interest site: the Agrigento hill (Sicily-Italy)

    NASA Astrophysics Data System (ADS)

    Liguori, Vincenzo; Manno, Giorgio

    2014-05-01

    The impact of landslides are an issue for many urban cities and their cultural heritage, especially where both natural factors and human actions are join. Indeed in these cases, both the geological-geomorphological area predisposition and the continuous human actions increase the possibility occurrence of a landslide. In order to study these landslides and their natural hazard, a multi-disciplinary approach is necessary. Agrigento (37°19'18''N; 13°35'22''E), founded around 580 b.C. along the Sicilian southern coast, is an example of a possible impacts of landslides on cultural heritage. This work discusses the geological, geomorphological and hydrological data results, performed in order to study and the monitoring the landslide on the north side of the Agrigento hill (335 m a.s.l.), on which is localized the antique cathedral (sixteenth century) and the old city. The hill geology is a typical regressive Plio-Pleistocene succession and their lithology are clays (Monte Narbone formation) , calcarenites , sands and silts of the Agrigento formation. The landslide phenomena, current since 1315, involves a calcarenitic pack (Pleistocene), weakly cemented, highly porous, fractured and fissured (E-W). This phenomena from 1924, at different times, have produced various types of instability such as: falls, flows and complex movements. From 7 March 2005 have been reactivated fractures of the calcarenitic pack, already highlighted by studies in 1966. These fractures have triggered slope movements damaging the cathedral and the various historic buildings. In order to reduce the risk and thus safeguard the monuments and the activity in this area, carried out the several studies. Since 2005, the landslide is the subject both geological-geomorphological studies and a continuous monitoring, which have used different techniques of different disciplines: interferometric analysis, interpretation of aerial and satellite imagery, geophysical investigations, stratigraphic survey, etc

  4. Slope-stability analysis and creep susceptibility of Quaternary sediments on the northeastern United States continental slope

    USGS Publications Warehouse

    Booth, James S.; Silva, Armand J.; Jordan, Stephen A.

    1984-01-01

    The continental slope off the northeastern United States is a relatively steep, morphologically complex surface which shows abundant evidence of submarine slides and related processes. Because this area may be developed by the petroleum industry, questions arise concerning the potential for further slope failures or unacceptable deformations and the conditions necessary to cause such instabilities. Accordingly, a generalized analysis of slope stability and the stress—strain—time-dependent behavior of the sediments is being conducted.

  5. Linking Slope Sedimentation, Gradient, Morphology, and Active Faulting: An Integrated Example from the Palos Verdes Slope, Southern California Borderland

    NASA Astrophysics Data System (ADS)

    Maier, K. L.; Brothers, D. S.; Paull, C. K.; McGann, M.; Caress, D. W.; Conrad, J. E.

    2015-12-01

    Seafloor gradient variations associated with restraining and releasing bends along the active (1.6-1.9 mm/yr) right-lateral Palos Verdes Fault appear to control Holocene sediment thickness, depositional environment, and morphodynamic processes along a section of the continental slope offshore Los Angeles, California. Autonomous underwater mapping vehicle (AUV), remotely operated vehicle (ROV), and shipboard methods were used to acquire a dense grid of high-resolution chirp profiles (150 m line spacing; 11 cm vertical resolution), multibeam bathymetry (2 m grid), and targeted sediment core samples (<2 m length). Detailed interpretation of Holocene deposits in the chirp profiles combined with radiocarbon dating and laser particle-size analyses allow correlation of Holocene sediment thickness and seafloor gradient with sediment gravity flow deposits. Holocene down-slope flows appear to have been generated by mass wasting processes, primarily on the upper slope (~100-200 m water depth) where shipboard multibeam bathymetry reveals submarine landslide headwall scarps in a region that has been isolated from terrigenous sediment sources throughout the Holocene. Submarine landslides appear to have transformed into sandy and organic-rich turbidity currents that created up-slope migrating sediment waves, a low relief (<5 m) fault-bounded channel, and a series of depocenters. A down-slope gradient profile and a Holocene isopach down-slope profile show that the primary depocenter occurs within a small pull-apart basin associated with a decrease in seafloor gradient of ~1.5°. Holocene sediment-flow deposits vary in number, thickness, and character with subtle changes in seabed gradient (<0.5°) and depositional environment. These results help quantify morphodynamic sensitivity to seafloor gradients and have implications for down-slope flow dynamics, deep-water depositional architecture, Holocene sediment, nutrient, and contaminant transport, and turbidite paleoseismology along

  6. Sediment waves on the tiber prodelta slope: Interaction of deltaic sedimentation and currents along the shelf

    USGS Publications Warehouse

    Trincardi, F.; Normark, W.R.

    1988-01-01

    A regressive depositional sequence has been prograding on the northeastern Tyrrhenian Shelf since the establishment of the present high stand of sea level. Thickness and distribution of this prograding sequence are chiefly controlled by the Tiber Delta sediment source and the oceanographic conditions on the shelf. Wavy bedforms characterize the Tiber prodelta slope between 35 and 100 m water depth. On 3.5 kHz subbottom profiles, these bedforms show the same morphology and internal depositional geometry as most of the deep-water examples of sediment waves. ?? 1988 Springer-Verlag New York Inc.

  7. Climate and topography control the size and flux of sediment produced on steep mountain slopes.

    PubMed

    Riebe, Clifford S; Sklar, Leonard S; Lukens, Claire E; Shuster, David L

    2015-12-22

    Weathering on mountain slopes converts rock to sediment that erodes into channels and thus provides streams with tools for incision into bedrock. Both the size and flux of sediment from slopes can influence channel incision, making sediment production and erosion central to the interplay of climate and tectonics in landscape evolution. Although erosion rates are commonly measured using cosmogenic nuclides, there has been no complementary way to quantify how sediment size varies across slopes where the sediment is produced. Here we show how this limitation can be overcome using a combination of apatite helium ages and cosmogenic nuclides measured in multiple sizes of stream sediment. We applied the approach to a catchment underlain by granodiorite bedrock on the eastern flanks of the High Sierra, in California. Our results show that higher-elevation slopes, which are steeper, colder, and less vegetated, are producing coarser sediment that erodes faster into the channel network. This suggests that both the size and flux of sediment from slopes to channels are governed by altitudinal variations in climate, vegetation, and topography across the catchment. By quantifying spatial variations in the sizes of sediment produced by weathering, this analysis enables new understanding of sediment supply in feedbacks between climate, tectonics, and mountain landscape evolution.

  8. Climate and topography control the size and flux of sediment produced on steep mountain slopes

    PubMed Central

    Riebe, Clifford S.; Sklar, Leonard S.; Lukens, Claire E.; Shuster, David L.

    2015-01-01

    Weathering on mountain slopes converts rock to sediment that erodes into channels and thus provides streams with tools for incision into bedrock. Both the size and flux of sediment from slopes can influence channel incision, making sediment production and erosion central to the interplay of climate and tectonics in landscape evolution. Although erosion rates are commonly measured using cosmogenic nuclides, there has been no complementary way to quantify how sediment size varies across slopes where the sediment is produced. Here we show how this limitation can be overcome using a combination of apatite helium ages and cosmogenic nuclides measured in multiple sizes of stream sediment. We applied the approach to a catchment underlain by granodiorite bedrock on the eastern flanks of the High Sierra, in California. Our results show that higher-elevation slopes, which are steeper, colder, and less vegetated, are producing coarser sediment that erodes faster into the channel network. This suggests that both the size and flux of sediment from slopes to channels are governed by altitudinal variations in climate, vegetation, and topography across the catchment. By quantifying spatial variations in the sizes of sediment produced by weathering, this analysis enables new understanding of sediment supply in feedbacks between climate, tectonics, and mountain landscape evolution. PMID:26630002

  9. Climate and topography control the size and flux of sediment produced on steep mountain slopes.

    PubMed

    Riebe, Clifford S; Sklar, Leonard S; Lukens, Claire E; Shuster, David L

    2015-12-22

    Weathering on mountain slopes converts rock to sediment that erodes into channels and thus provides streams with tools for incision into bedrock. Both the size and flux of sediment from slopes can influence channel incision, making sediment production and erosion central to the interplay of climate and tectonics in landscape evolution. Although erosion rates are commonly measured using cosmogenic nuclides, there has been no complementary way to quantify how sediment size varies across slopes where the sediment is produced. Here we show how this limitation can be overcome using a combination of apatite helium ages and cosmogenic nuclides measured in multiple sizes of stream sediment. We applied the approach to a catchment underlain by granodiorite bedrock on the eastern flanks of the High Sierra, in California. Our results show that higher-elevation slopes, which are steeper, colder, and less vegetated, are producing coarser sediment that erodes faster into the channel network. This suggests that both the size and flux of sediment from slopes to channels are governed by altitudinal variations in climate, vegetation, and topography across the catchment. By quantifying spatial variations in the sizes of sediment produced by weathering, this analysis enables new understanding of sediment supply in feedbacks between climate, tectonics, and mountain landscape evolution. PMID:26630002

  10. Pleistocene slope instability of gas hydrate-laden sediment on the Beaufort Sea margin

    USGS Publications Warehouse

    Kayen, R.E.; Lee, H.J.

    1991-01-01

    In oceanic areas underlain by sediment with gas hydrate, reduction of sea level initiates disassociation along the base of the gas hydrate, which, in turn, causes the release of large volumes of gas into the sediment and creates excess pore-fluid pressures and reduced slope stability. Fluid diffusion properties dominate the disassociation process in fine-grained marine sediment. Slope failure appears likely for this sediment type on moderate slopes unless pressures can be adequately vented away from the gas hydrate base. Pleistocene eustatic-sea level regressions, likely triggered seafloor landslides on the continental slope of the Beaufort Sea and other margins where gas hydrate is present in seafloor sediment. -from Authors

  11. Quantitative estimation of landslide risk from rapid debris slides on natural slopes in the Nilgiri hills, India

    NASA Astrophysics Data System (ADS)

    Jaiswal, P.; van Westen, C. J.; Jetten, V.

    2011-06-01

    A quantitative procedure for estimating landslide risk to life and property is presented and applied in a mountainous area in the Nilgiri hills of southern India. Risk is estimated for elements at risk located in both initiation zones and run-out paths of potential landslides. Loss of life is expressed as individual risk and as societal risk using F-N curves, whereas the direct loss of properties is expressed in monetary terms. An inventory of 1084 landslides was prepared from historical records available for the period between 1987 and 2009. A substantially complete inventory was obtained for landslides on cut slopes (1042 landslides), while for natural slopes information on only 42 landslides was available. Most landslides were shallow translational debris slides and debris flowslides triggered by rainfall. On natural slopes most landslides occurred as first-time failures. For landslide hazard assessment the following information was derived: (1) landslides on natural slopes grouped into three landslide magnitude classes, based on landslide volumes, (2) the number of future landslides on natural slopes, obtained by establishing a relationship between the number of landslides on natural slopes and cut slopes for different return periods using a Gumbel distribution model, (3) landslide susceptible zones, obtained using a logistic regression model, and (4) distribution of landslides in the susceptible zones, obtained from the model fitting performance (success rate curve). The run-out distance of landslides was assessed empirically using landslide volumes, and the vulnerability of elements at risk was subjectively assessed based on limited historic incidents. Direct specific risk was estimated individually for tea/coffee and horticulture plantations, transport infrastructures, buildings, and people both in initiation and run-out areas. Risks were calculated by considering the minimum, average, and maximum landslide volumes in each magnitude class and the

  12. The Effects of Permafrost Thaw on Organic Matter Quality and Availability Along a Hill Slope in Northeastern Siberia

    NASA Astrophysics Data System (ADS)

    Connolly, C. T.; Spawn, S.; Ludwig, S.; Schade, J. D.; Natali, S.

    2014-12-01

    Climate warming and permafrost thaw in northeastern Siberia are expected to change the quantity and quality of organic matter (OM) transported through watersheds, releasing previously frozen carbon (C) to biologically available pool. Hill slopes have shown to influence the distribution of OM, resulting in a downhill accumulation of available C and nutrients relative to uphill. Here we examine how future permafrost thaw will change OM quality and availability along a hill slope in a larch-dominated watershed. We collected soils from the thawed organic and mineral layers, and 1m deep permafrost cores for dissolved organic C (DOC) and total dissolved N (TDN), C composition from measures of colored dissolved organic matter (CDOM), DOC lability from biodegradable DOC (BDOC) incubations, C and nutrient availability from extracellular-enzyme assays (EEA's), and microbial respiration from aerobic soil incubations. Here we show that organic soils (O), in comparison to mineral soils (M) and permafrost (P) are the most abundant source of C (avg O DOC: 51.6mg/L), exhibiting low molecular complexity (avg O SUVA254: 4.05) and high quality. Evidence suggests permafrost OM may be an equally abundant, and more labile source of C than mineral soils (highest P DOC: 16.1 mg/L, lowest P SUVA254: 6.32; median M DOC: 18.5 mg/L, median M SUVA254: 24.0). Furthermore, we demonstrate that there may be a positive relationship in the rate of C mineralization and distance downhill, showing 15-30% greater CO2 production/gC downhill relative to uphill. Evidence also supports a similar relationship in permafrost DOC content and molecular complexity, showing more DOC of a lower complexity further downhill. This indicates DOC transport may have been occurring through the active layer and downhill during ice-rich permafrost formation, and may supply a labile source of carbon to lowland areas and adjacent stream networks upon thaw.

  13. The role of working equines to livelihoods in current day campesino hill-slope communities in central Mexico.

    PubMed

    Velázquez-Beltrán, Leon G; Sánchez-Vera, Ernesto; Nava-Bernal, Eufemio Gabino; Arriaga-Jordán, Carlos M

    2011-12-01

    Small-holder campesino agriculture is based on the diversified use of resources and off-farm work. Working equines have a multifunctional character and sustain the diversification of livelihoods having different values as assets or providing services. The objective was to identify the role of working equines in current diversification strategies in the livelihoods of campesino families in a hill-slope community in central Mexico within livelihoods analysis. Thirty-one variables related to ownership and use of working equines were analysed by cluster analysis and descriptive statistics contrasting the presence of equines in the diversification of livelihoods. Four groups were identified, determined mainly by age of farmer and number of family members who utilise equines. Results show these systems diversify in response to conditions of risk or to take advantage of opportunities, such that a balance is reached by resorting to off-farm activities without the total loss of components of the farming system. Two main situations were found in relation to working equines: the disappearance and change of functions of the large equines (mules), and the adaptation of small equines (donkeys) to the new conditions. It is concluded that there is a process of adaptation in hill-slope campesino farms such that large equines are less present in farms that have moved towards more diversification, but are kept in those farms less diversified. The use of equines for draught force in agricultural production and as pack animals continues, as is the presence of small livestock (sheep and poultry) irrespective of the context of the farm. PMID:21637993

  14. [Optimization of shelterbelt distribution for the gully erosion control of cultivated slope land in rolling hill black soil region of Northeast China].

    PubMed

    Su, Zi-Long; Cui, Ming; Fan, Hao-Ming

    2012-04-01

    Shelterbelt system is one of the main components of cultivated slope land in rolling hill black soil region of Northeast China, which plays an important role in the control of gully erosion. Based on the Quickbird high-resolution remote sensing image and the digital elevation model (DEM), and combining with field survey data, this paper analyzed the effects of shelterbelt system in a small watershed of rolling hill black soil region in Heshan Farm of Heilongjiang Province on the control of gully erosion in the cultivated slope land, and put forward an optimized scheme for gully erosion control based on the features of gully erosion in the cultivated slope land and their relations with the distribution of the shelterbelt system. In the study area, the current distribution of the shelterbelt system promoted the occurrence and development of shallow gully and gully directly and indirectly. The proposed scheme for optimizing the distribution of the present shelterbelts included the adjustment of the direction of the shelterbelt perpendicular to the aspect of slope, the enhancement of the maintenance and regeneration of the shelterbelts to reduce the gaps of the shelterbelts, the increase of the shelterbelt number, and the decrease of the distances between shelterbelts. A method for calculating the shelterbelt number and the distances between the shelterbelts was also given. This study could provide scientific basis for the gully erosion control and the shelterbelts programming in the cultivated slope land of rolling hill black soil region.

  15. Interrill erosion, runoff and sediment size distribution as affected by slope steepness and antecedent moisture content

    NASA Astrophysics Data System (ADS)

    Defersha, M. B.; Quraishi, S.; Melesse, A.

    2010-08-01

    Soil erosion is a two-phase process consisting of the detachment of individual particles and their transport by erosive agents such as flowing water. The rate at which erosion occurs depends upon the individual as well as interactive effects of different parameters responsible for soil erosion. The study discusses results of a laboratory analysis and evaluates the effect of slope steepness and antecedent moisture content on sediment yield (wash) and runoff rate. Interrill sediment yield, splash detachment, runoff, and sediment size distribution were measured in laboratory erosion pans under simulated total duration of 90 min. Rainfall intensity at 120 mm/hr, 70 mm/hr, and 55 mm/hr were applied sequentially at 9, 25, and 45% slope steepness for three soils (Alemaya Black soil, Regosols, and Cambisols) varied from clay to sandy clay loam in texture with wet and dry antecedent water contents. As slope steepness increased from 9 to 25% splash increased for five treatments and decreased for the remaining treatment; washed sediment increased for all treatments. As slope increased from 25 to 45% splash decreased for five treatments but increased for one treatment, and washed sediment increased for three treatments but decreased for the other three treatments. Pre-wetting decreased splash detachment for all soil treatments and rate of reduction was high for the highly aggregated soil, Alemaya Black soil and low for the less aggregated soil Regosols. Splash sediment and sediment yield was not correlated. Change in splash with increase in slope steepness was also not correlated with change in sediment yield. Change in runoff rate with increase in slope steepness was correlated (r=0.66) with change in sediment yield. For Alemaya Black soil and Regosols, splashed sediment size distribution was correlated with washed sediment size distribution. Interrill erosion models that include runoff and rainfall intensity parameters were a better fit for these data than the rainfall

  16. Common vetch (Vicia sativa) for improving the nutrition of working equids in Campesino systems on hill slopes in Central Mexico.

    PubMed

    Velázquez-Beltrán, L G; Felipe-Pérez, Y E; Arriaga-Jordán, C M

    2002-03-01

    Campesino systems on hill slopes in Central Mexico rely on equids for multiple activities and have a problem in adequately feeding them. A participatory trial was conducted to evaluate the inclusion of common vetch in the traditional forage oat crop to improve its feeding value. An agronomic evaluation was undertaken by intersowing common vetch at 40 kg seed/ha with oats at 80-100 kg/ha in small plots, recording the yield and the chemical composition of the fresh forage in ten plots at harvest. The data were analysed as a completely random design, taking each farmer/plot as a treatment. A feeding trial compared the live weight of 7 donkeys fed oats and vetch against 17 donkeys fed traditional forage. There were differences between farmers in forage yields (p < 0.01) that could not be explained as due to soil types or management. The mean yield of 31.0 t/ha of fresh forage of oats-vetch was 20.5% higher than that from monoculture, and had a higher crude protein content. Donkeys fed the oats-vetch were heavier (p < 0.001). The farmers evaluated the oats-vetch association positively, appreciating the higher yields and good condition of their equids. The combination is an appropriate technology for these campesino farming systems.

  17. Common vetch (Vicia sativa) for improving the nutrition of working equids in Campesino systems on hill slopes in Central Mexico.

    PubMed

    Velázquez-Beltrán, L G; Felipe-Pérez, Y E; Arriaga-Jordán, C M

    2002-03-01

    Campesino systems on hill slopes in Central Mexico rely on equids for multiple activities and have a problem in adequately feeding them. A participatory trial was conducted to evaluate the inclusion of common vetch in the traditional forage oat crop to improve its feeding value. An agronomic evaluation was undertaken by intersowing common vetch at 40 kg seed/ha with oats at 80-100 kg/ha in small plots, recording the yield and the chemical composition of the fresh forage in ten plots at harvest. The data were analysed as a completely random design, taking each farmer/plot as a treatment. A feeding trial compared the live weight of 7 donkeys fed oats and vetch against 17 donkeys fed traditional forage. There were differences between farmers in forage yields (p < 0.01) that could not be explained as due to soil types or management. The mean yield of 31.0 t/ha of fresh forage of oats-vetch was 20.5% higher than that from monoculture, and had a higher crude protein content. Donkeys fed the oats-vetch were heavier (p < 0.001). The farmers evaluated the oats-vetch association positively, appreciating the higher yields and good condition of their equids. The combination is an appropriate technology for these campesino farming systems. PMID:11969114

  18. Factors controlling Pliocene-Quaternary sedimentation on the Gulf of Cadiz Continental Slope, Spain

    SciTech Connect

    Baraza, J.; Maldonado, A. ); Nelson, C.H. )

    1990-05-01

    The Pliocene-Quaternary sedimentation on the Gulf of Cadiz continental slope records an interaction between the tectonics responsible for a complex bathymetry, and the Mediterranean outflow undercurrent developed after the opening of the Gibraltar Strait at the end of the Miocene. During periods of low sea level, sedimentation was controlled mainly by changes in the sediment supply from the various rivers that feed the area. During high sea level, periods like the present, deposition is controlled mainly by the Mediterranean undercurrent. The Mediterranean undercurrent flows out from the Strait of Gibraltar toward the northwest and impinges on the Cadiz continental slope at 300- to 500-m depths. Flows are fastest near the Strait of Gibraltar (as much as 200 m/sec) and slow to 10-20 m/sec westward Portugal. The gradual decrease in undercurrent speed from the Strait of Gibraltar to the center of the Gulf of Cadiz results in a westward change from erosional to depositional characteristics on the upper continental slope. Erosion in the southeastern part of the Gulf is characterized by exposed bed rock on the sea floor and by erosional truncation of reflectors on sea-floor slopes. In contrast, several prograding shelf-break types and slope configurations occur in the west, showing the influence of tectonic subsidence, diapir uplift and sediment supply on the Pliocene-Quaternary sedimentation. At middle slope depths, high-energy depositional features, such as cut-and-fill structures, are observed in seismic profiles. Energy decreasing bed-form fields, from east to west, are shown in profiles and sonographic of the most sufficial units on the deep platforms. In addition, sediment drift bodies deposit against basement diapiric ridges near the canyon-ridge central area.

  19. Salt structure and sediment thickness, Texas-Louisiana continental slope, northwestern Gulf of Mexico

    USGS Publications Warehouse

    Martin, Raymond G.

    1973-01-01

    The objectives of this study were to determine the general configuration of the salt surface beneath the Texas-Louisiana continental slope and to isopach the Mesozoic-Cenozoic sedimentary section lying upon it. The structure contour map discloses that the entire slope province between the shelf edge and Sigsbee Escarpment is underlain by salt structures which interconnect at relatively shallow subbottom depths. Salt structures on the slope south of Louisiana and eastern Texas can be grouped according to structural relief and size which define morphological belts of decreasing deformational maturity in a downslope direction. Off northern Mexico and southernmost Texas, salt structures are anticlinal and their trends suggest a structural relationship with the folds of the Mexican Ridge province to the south. Structural trends in the two slope areas meet in the corner of the northwestern gulf where salt structure may have been influenced by a seaward extension of the San Marcos Arch, or an abrupt change in subsalt structural topography. Sediment thickness above the top of salt on the slope averages about 1,400 m (4,620 ft) which is a smaller average than expected from previous estimates. In some synclinal basins between salt structures, sediments may be as thick as 4,000-5,000 m (12,000-17,000 ft). On the average, sedimentary deposits in basins on the upper slope are thicker than on the lower slope. From the isopach map of sediments above salt it is estimated that the U.S. continental slope off Texas and Louisiana contains a sedimentary volume of about 170,000 km3 (41,000 mi3). The bulk of this volume is situated in synclinal basins between domes and principally in those beneath the upper and middle slope regions.

  20. TVA sediment-disturbing activities within the Watts Bar Reservoir and Melton Hill Reservoir areas of the Clinch River

    SciTech Connect

    1993-12-31

    The objectives of Task 5 were to review: (1) the extent of dredging, construction, and other sediment-disturbing activities conducted by the Tennessee Valley Authority (TVA) in potentially contaminated areas of Watts Bar Reservoir; and (2) the disposition of the materials from these activities. This memorandum is the final report for Task 5. This memorandum describes major activities in the Watts Bar Reservoir and Melton Hill Reservoir areas of the Clinch River that possibly resulted in significant disturbance of potentially contaminated sediments. TVA records from the construction of Watts Bar Dam, Kingston Fossil Plant, and Melton Hill Dam were reviewed to facilitate qualitative description of the effect of these activities in disturbing potentially contaminated sediments. The critical period for these activities in disturbing contaminated sediments was during or after 1956 when the peak releases of radioactive contaminants occurred from the Oak Ridge Reservation.

  1. Vertical distribution of benthic infauna in continental slope sediments off Cape Lookout, North Carolina

    NASA Astrophysics Data System (ADS)

    Blake, James A.

    The vertical distribution of 30 species of benthic infauna from continental slope (583-3000 m) sediments off Cape Lookout, North Carolina was closely correlated with feeding types. Carnivores, omnivores, filter feeders, and surface deposit feeders were mostly concentrated in the upper 0-2 cm of the cores. The depth distribution of subsurface deposit feeders was more variable, even among related taxa.

  2. Low Methane Concentrations in Sediment Along the Siberian Slope: Inference From Pore Water Geochemistry

    NASA Astrophysics Data System (ADS)

    Miller, C.; Dickens, G. R.; Jakobsson, M.

    2015-12-01

    The Eastern Siberian Arctic Ocean (ESAO) is experiencing some of the fastest rates of climate warming. Additionally, the ESAO hosts 80% of the world's subsea permafrost, and presumably holds large amounts of methane in sediments as gas hydrate and free gas. Despite these vast stores of vulnerable carbon, the ESAO is sparingly explored. Here, we present pore water geochemistry results from cores taken during the SWERUS-C3 international expedition and along five transects. Four of these are along the slopes of Arlis Spur, Central East Siberia, Henrietta Island-Makarov Basin, and Eastern Lomonosov Ridge; one is along the shelf in Herald Trough.Upward methane flux toward the seafloor, as inferred from dissolved sulfate and alkalinity profiles, is negligible on slopes the Arlis Spur, Central East Siberia, and Eastern Lomonosov Ridge. Methane flux from slopes near Henrietta Island and Makarov Basin ranged from 13.7 (367 m water depth) to 16.2 mmol/m2-kyr (964 m water depth). The highest flux on the slope, located at the intersection with Lomonosov Ridge, is 25.8 mmol/m2-kyr. In contrast to the generally low methane fluxes of the continental slope, the shelf sediments in Herald Trough have high upward methane fluxes, with measured rates up to 156.9 mmol/m2-kyr. These methane results are the first of their kind in this climatically sensitive region, and contradict previous assumptions regarding high methane flux rates along the slope.

  3. Morphobathymetric analysis of the large fine-grained sediment waves over the Gulf of Valencia continental slope (NW Mediterranean)

    NASA Astrophysics Data System (ADS)

    Ribó, Marta; Puig, Pere; Muñoz, Araceli; Lo Iacono, Claudio; Masqué, Pere; Palanques, Albert; Acosta, Juan; Guillén, Jorge; Gómez Ballesteros, María

    2016-01-01

    Detailed analysis of recently acquired swath bathymetry, together with high-resolution seismic profiles and bottom sediment samples, revealed the presence of large-scale fine-grained sediment waves over the Gulf of Valencia continental slope. As many other deep-water sediment waves, these features were previously attributed to gravitational slope failure, related to creep-like deformation, and are here reinterpreted as sediment wave fields extending from 250 m depth to the continental rise, at ~ 850 m depth. Geometric parameters were computed from the high-resolution multibeam dataset. Sediment wave lengths range between 500 and 1000 m, and maximum wave heights of up to 50 m are found on the upper slope, decreasing downslope to minimum values of 2 m high. Sediment waves on the lower part of the slope are quasi-stationary vertically accreting, whereas they show an upslope migrating pattern from the mid-slope to the upper part of the continental slope. High-resolution seismic profiles show continuous internal reflectors, with sediment waves merging down-section and sediment wave packages decreasing in thickness downslope. These sediment packages are thicker on the crest of each individual sediment wave and thinner on the downslope flank. 210Pb analyses conducted on sediment cores collected over the sediment wave fields also indicate slightly higher sediment accumulation rates on the wave crests. Sediment wave formation processes have been inferred from contemporary hydrodynamic observations, which reveal the presence of near-inertial internal waves interacting with the Gulf of Valencia continental slope. Internal wave activity is suggested to be the preferential mechanism for the transport and deposition of sediment, and the maintenance of the observed sediment wave fields.

  4. Causes of two slope-failure types in continental-shelf sediment, northeastern Gulf of Alaska

    USGS Publications Warehouse

    Schwab, William C.; Lee, Homa J.

    1988-01-01

    Slumps and sediment-gravity flows have been identified in Holocene glaciomarine sediment on declivities less than 1.3 degrees on the Gulf of Alaska continental shelf. Geologic and geotechnical investigation suggest that the processes responsible for these slope failures are earthquake and storm-wave loading, coupled with cyclic degradation of the sediment-shear strength. We propose that the failure type is related to the nature of the failure load. For example, a slump that occurs approximately 30 km seaward of Icy Bay in water depth of 70 to 150 m was most likely caused by earthquake loading, whereas sediment-gravity flows on the Alsek prodelta, which occur in water depths of 35 to 80 m, probably were caused primarily by storm-wave loading. Sediment remolding and redistribution and incorporation of water, which occurs more readily during wave loading from a long storm than during the limited number of loading cycles generated by an earthquake, reduces the shear strength and increases the fluidity of the failed sediment mass. Wave-induced slope failures thereby tend to transform into sediment-gravity flows.

  5. Hydrocarbon gas in sediment from the shelf, slope and basin of the Bering Sea.

    USGS Publications Warehouse

    Kvenvolden, K.A.; Redden, G.D.

    1980-01-01

    Methane, ethane, ethene, propane, propene, isobutane and n-butane are present in low concentrations in the top 2m of sediment. Methane is most abundant and its concentration increases with depth in the sediment. Ethane, ethene, propane and propene are present in almost all samples, but the concentrations of these gases are about two orders of magnitude-lower than the concentration of methane. The average ratios of ethane to ethene are usually greater than one in shelf sediment, about one in slope sediment, and usually less than one in basin sediments. These hydrocarbon gases are probably derived from low-temperature chemical and biochemical processes operating at or near the sea-floor. -from Authors

  6. Inorganic geochemistry of surface sediments of the Ebro shelf and slope, northwestern Mediterranean

    USGS Publications Warehouse

    Gardner, J.V.; Dean, W.E.; Alonso, B.

    1990-01-01

    Distributions of major, minor, and trace elements in surface sediment of the continental shelf and upper slope of the northeastern Spanish continental margin reflect the influences of discharge from the Ebro River and changes in eustatic sea levels. Multivariate factor analysis of sediment geochemistry was used to identify five groupings of samples (factors) on the shelf and slope. The first factor is an aluminosilicate factor that represents detrital clastic material. The second factor is a highly variable amount of excess SiO2 and probably represents a quartz residuum originating from winnowing of relict detrital sediments. A carbonate factor (Factor 3) has no positive correlation with other geochemical parameters but is associated with the sand-size fraction. The carbonate in these sediments consists of a mixture of biogenic calcite and angular to subangular detrital grains. Organic carbon is associated with the aluminosilicate factor (Factor 1) but also factors out by itself (Factor 4); this suggests that there may be two sources of organic matter, terrestrial and marine. The fifth factor comprises upper slope sediments that contain high concentrations of manganese. The most likely explanation for these high manganese concentrations is precipitation of Mn oxyhydroxides at the interface between Mn-rich, oxygen-deficient, intermediate waters and oxygenated surface waters. During eustatic low sea levels of the glacial Pleistocene, the Ebro Delta built across the outer continental shelf and deposited sediment with fairly high contents of organic carbon and continental components. The period of marine transgression from eustatic low (glacial) to eustatic high (interglacial) sea levels was characterized by erosion of the outer shelf delta and surficial shelf sediments and the transport of sediment across the slope within numerous canyons. Once eustatic high sea level was reached, delta progradation resumed on the inner shelf. Today, coarse-grained sediment (silt and

  7. Episodic sediment-discharge events in Cascade Springs, southern Black Hills, South Dakota

    USGS Publications Warehouse

    Hayes, Timothy Scott

    1999-01-01

    Cascade Springs is a group of artesian springs in the southern Black Hills, South Dakota, with collective flow of about 19.6 cubic feet per second. Beginning on February 28, 1992, a large discharge of red suspended sediment was observed from two of the six known discharge points. Similar events during 1906-07 and 1969 were documented by local residents and newspaper accounts. Mineralogic and grain-size analyses were performed to identify probable subsurface sources of the sediment. Geochemical modeling was performed to evaluate the geochemical evolution of water discharged from Cascade Springs. Interpretations of results provide a perspective on the role of artesian springs in the regional geohydrologic framework. X-ray diffraction mineralogic analyses of the clay fraction of the suspended sediment were compared to analyses of clay-fraction samples taken from nine geologic units at and stratigraphically below the spring-discharge points. Ongoing development of a subsurface breccia pipe(s) in the upper Minnelusa Formation and/or Opeche Shale was identified as a likely source of the suspended sediment; thus, exposed breccia pipes in lower Hell Canyon were examined. Upper Minnelusa Formation breccia pipes in lower Hell Canyon occur in clusters similar to the discrete discharge points of Cascade Springs. Grain-size analyses showed that breccia masses lack clay fractions and have coarser distributions than the wall rocks, which indicates that the red, fine-grained fractions have been carried out as suspended sediment. These findings support the hypothesis that many breccia pipes were formed as throats of abandoned artesian springs. Geochemical modeling was used to test whether geochemical evolution of ground water is consistent with this hypothesis. The evolution of water at Cascade Springs could not be suitably simulated using only upgradient water from the Minnelusa aquifer. A suitable model involved dissolution of anhydrite accompanied by dedolomitization in the

  8. Dynamic simulations of potential methane release from East Siberian continental slope sediments

    NASA Astrophysics Data System (ADS)

    Stranne, C.; O'Regan, M.; Dickens, G. R.; Crill, P. M.; Miller, C.; Preto, P.; Jakobsson, M.

    2015-12-01

    Sediments deposited along continental margins of the Arctic Ocean presumably host large amounts of CH4 in gas hydrates. Here we apply numerical simulations to assess the potential of gas hydrate dissociation and methane release from the East Siberian slope over the next 100 years. Simulations are based on a hypothesized bottom water warming of 3 °C, and an assumed starting distribution of gas hydrate. The simulation results show that methane hydrate dissociation in these sediments is relatively slow, and that gas fluxes toward the seafloor are limited by low sediment permeability. The latter is true even when sediment fractures are permitted to form through overpressure. With an initial gas hydrate distbution dictated by present-day pressure and temperature conditions, nominally 0.35 gigaton of CH4 are released from the East Siberian slope during the first 100 years of the simulation. However, this methane discharge is reduced significantly (to ~0.05 Gt) if Arctic Ocean history is considered. This is because a lower sea level during the last glacial maximum must result in depleted gas hydrate abundance within the most sensitive region of the modern gas hydrate stability zone. In any case, even if methane reached the atmosphere, amounts coming from East Siberian slopes would be minimal compared to present-day atmospheric methane inputs from other sources.

  9. Dynamic simulations of potential methane release from East Siberian continental slope sediments

    NASA Astrophysics Data System (ADS)

    Stranne, C.; O'Regan, M.; Dickens, G. R.; Crill, P.; Miller, C.; Preto, P.; Jakobsson, M.

    2016-03-01

    Sediments deposited along continental margins of the Arctic Ocean presumably host large amounts of methane (CH4) in gas hydrates. Here we apply numerical simulations to assess the potential of gas hydrate dissociation and methane release from the East Siberian slope over the next 100 years. Simulations are based on a hypothesized bottom water warming of 3°C, and an assumed starting distribution of gas hydrate. The simulation results show that gas hydrate dissociation in these sediments is relatively slow, and that CH4 fluxes toward the seafloor are limited by low sediment permeability. The latter is true even when sediment fractures are permitted to form in response to overpressure in pore space. With an initial gas hydrate distribution dictated by present-day pressure and temperature conditions, nominally 0.35 Gt of CH4 are released from the East Siberian slope during the first 100 years of the simulation. However, this CH4 discharge becomes significantly smaller (˜0.05 Gt) if glacial sea level changes in the Arctic Ocean are considered. This is because a lower sea level during the last glacial maximum (LGM) must result in depleted gas hydrate abundance within the most sensitive region of the modern gas hydrate stability zone. Even if all released CH4 reached the atmosphere, the amount coming from East Siberian slopes would be trivial compared to present-day atmospheric CH4 inputs from other sources.

  10. Geomorphology and sediment stability of a segment of the U.S. continental slope off New Jersey

    USGS Publications Warehouse

    Robb, James M.; Hampson, J.C., Jr.; Twichell, D.C.

    1981-01-01

    The morphology of complex deposits of Pleistocene sediments covering the upper continental slope between Lindenkohl Canyon and South Toms Canyon results from both depositional and erosional processes. Small slump or slide features were detected primarily on the flanks of canyons or valleys and were observed to occur only within Pleistocene-aged sediments. Eocene to Miocene sediments are exposed over much of the mid- and lower slope in this area. Copyright ?? 1981 AAAS.

  11. Geomorphology and Sediment Stability of a Segment of the U.S. Continental Slope off New Jersey.

    PubMed

    Robb, J M; Hampson, J C; Twichell, D C

    1981-02-27

    The morphology of complex deposits of Pleistocene sediments covering the upper continental slope between Lindenkohl Canyon and South Toms Canyon results from both depositional and erosional processes. Small slump or slide features were detected primarily on the flanks of canyons or valleys and were observed to occur only within Pleistocene-aged sediments. Eocene to Miocene sediments are exposed over much of the mid- and lower slope in this area.

  12. Sediment distribution and transport across the continental shelf and slope under idealized wind forcing

    USGS Publications Warehouse

    Condie, S.A.; Sherwood, C.R.

    2006-01-01

    Resuspension, transport, and deposition of sediments over the continental shelf and slope are complex processes and there is still a need to understand the underlying spatial and temporal dynamical scales. As a step towards this goal, a two-dimensional slice model (zero gradients in the alongshore direction) based on the primitive flow equations and a range of sediment classes has been developed. The circulation is forced from rest by upwelling or downwelling winds, which are spatially uniform. Results are presented for a range of wind speeds and sediment settling speeds. Upwelling flows carry fine sediments (low settling speeds) far offshore within the surface Ekman layer, and significant deposition eventually occurs beyond the shelf break. However, coarser sediments quickly settle out of the deeper onshore component of the circulation, which can lead to accumulation of bottom sediments within the coastal zone. Downwelling flows are more effective at transporting coarse sediments off the shelf. However, strong vertical mixing at the shelf break ensures that some material is also carried into the surface Ekman layer and returned onshore. The concentrations and settling fluxes of coarse sediments decrease offshore and increase with depth under both upwelling and downwelling conditions, consistent with trends observed in sediment trap data. However, finer sediments decrease with depth (upwelling) or reach a maximum around the depth of the shelf break (downwelling). It is shown that under uniform wind conditions, suspended sediment concentrations and settling fluxes decay offshore over a length scale of order τs/ρf|ws|, where τs is the wind stress, ρ the water density, f the Coriolis parameter, and ws is the sediment settling velocity. This scaling applies to both upwelling and downwelling conditions, provided offshore transport is dominated by wind-driven advection, rather than horizontal diffusion.

  13. Potential causes for slope instabilities of under-consolidated marine sediments

    SciTech Connect

    Quemeneur, P.; Tisot, J.P.; Cochonat, P.; Bourillet, J.F.; d`Oultremont, V.; Colliat, J.L.; Tofani, R.

    1995-12-31

    Offshore studies have been completed in the Gulf of Guinea, off West Africa. An area has been selected over the Gabon continental slope. A morpho-sedimentological zonation is made regarding acoustic data and geotechnical characteristics of sampled sediments. An old slide has been considered as a criteria for estimating realistic slope failure conditions. Both drained and undrained formulations tend to prove that fluid escape is the most realistic explanation for slides occurrence. Regional hazard charts also allow them to present unstable zones and build up criteria for structures implantation.

  14. Main flow path and chemical alteration in a marly hill prone to slope instability: assessment from petrophysical measurements and borehole image analysis.

    NASA Astrophysics Data System (ADS)

    Lofi, Johanna; Gautier, Stéphanie; Pezard, Philippe; Loggia, Didier; Garel, Emilie

    2010-05-01

    The principal driving force of slope movements is generally considered to be gravity, with the main triggering factor being the increase of pore pressures by the presence of water contained in the geological environment. It is however difficult to anticipate the rupture processes involved in deep seated landslides mainly because of the difficulty in estimating the mechanical behaviors at the scale of the hill slope which is characterized by heterogeneous structures with large and small scale discontinuities. Hydrogeological behaviors are also important parameters and the localization of the main flow paths and saturated zones is a fundamental stage of the slope evolution before and after failure. The processes involved in the rupture is also rock type dependant. Clay shales that have complicated structure at a small scale and are sensible to weathering are very prone to slope instability. In this context, this study focuses a non slided slope made of tectonised clay shales in the Draix Observatory (ORE DRAIX) of the southern Alps (France). The objectives were to characterise at several scales (several m - µm) the internal architecture and main structural and lithological discontinuities of the hill slope in order to locate preferential water flows within the system, and anticipate its possible evolution. This work is based on a mutli-disciplinary approach including petrophysical analyses in the laboratory, well pulse injection tests and downhole geophysical measurements. Optical and acoustical images have been used as an original and efficient tool for internal discontinuities characterization at several scales (several mm - several m) and potential active flow path detection. In all, the integration of measurements leads to propose a simple scenario of fluid circulation and chemical alteration of the hill slope. Owing to the very low permeability of the non altered black marl matrix, the open fractures evidenced from borehole images may be the primary pathways

  15. Changes in Dissolved Carbon and Nitrogen Concentrations Along a Hill Slope Flow Path in Siberian Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Theberge, J.; Schade, J. D.; Fiske, G. J.; Loranty, M. M.; Zimov, N.

    2014-12-01

    Permafrost soils contain a large pool of carbon that has accumulated for thousands of years, and remains frozen in organic form. As climate warms, permafrost thaw will lead to active cycling of old organic materials, possibly leading to release of carbon to the atmosphere or to export of organic carbon to the oceans. Organic matter breakdown may also release reactive forms of nitrogen, which may significantly impact ecosystem processes. We currently have limited understanding of where in Arctic landscapes breakdown of organic materials will occur, or whether this will influence the strength and direction of feedback loops that may occur in response to changes in C and N cycling. In this work, we studied changes in dissolved forms of C and N in water moving down a hillslope linking upland terrestrial environments to lowland floodplains within the Kolyma River watershed in the East Siberian Arctic tundra in July, 2014. The hill slope consisted of a mosaic of dry and saturated soils, generally with drier soils on the periphery and saturated soils in and around pools or short reaches of flowing surface water. We established transects at regular intervals downslope, installing wells in the center of the flow path and 5 meters laterally north and south. We analyzed pore-water from wells and surface water from pools at each transect for dissolved organic carbon (DOC) and total dissolved nitrogen (TDN). We used patterns in water chemistry to develop a conceptual model for biogeochemical changes as water moved downslope through soils, pools and runs. Pore-water analysis showed significantly higher DOC in lateral wells than in surface water and pore water in the center of the flow path, suggesting possible processing of C as water moves laterally towards the valley bottom. In contrast, DOC increased modestly down the center of the flow path, suggesting either higher hydrologic inputs or production of new DOC downslope. TDN concentration decreased downslope, suggesting

  16. Shear-wave velocity of slope sediments near Hudson Canyon from analysis of ambient noise

    NASA Astrophysics Data System (ADS)

    Miller, N. C.; Ten Brink, U. S.; Collins, J. A.; McGuire, J. J.; Flores, C. H.

    2014-12-01

    We present new ambient noise data that help constrain the shear strength of marine sediments on the continental slope north of Hudson Canyon on the U.S. Atlantic margin. Sediment shear strength is a key parameter in models of potentially tsunamigenic, submarine slope failures, but shear strength is difficult to measure in situ and is expected to evolve in time with changes in pore pressure. The ambient noise data were recorded by 11 short-period, ocean-bottom seismometers and hydrophones deployed in a ~1 by 1.5 km array for ~6 months on the continental slope. These high frequency (~0.1 - 50 Hz), narrow-aperture data are expected to record noise propagating as interface waves and/or resonating in the upper ~500 m of sediment. Propagation of interface waves is controlled by the shear-wave velocity of the sediment, which we measure by calculating lag-times in cross-correlations of waveforms recorded by pairs of receivers. These measurements of shear-wave velocity will be used to constrain shear strength. The data also appear to record wind-generated noise resonating in layered sediment. We expect this resonance to also be sensitive to shear-wave velocity, and spectral analysis and modeling of harmonics may provide a second constraint on sediment shear strength. Both the correlogram- and spectral-based measurements can be made using hour- to day-long segments of data, enabling us to constrain temporal evolution of shear-wave velocity and potential forcing mechanisms (e.g., tidal and storm loading and submarine groundwater discharge) through the ~6 month deployment.

  17. Distinguishing sediment waves from slope failure deposits: Field examples, including the 'humboldt slide', and modelling results

    USGS Publications Warehouse

    Lee, H.J.; Syvitski, J.P.M.; Parker, G.; Orange, Daniel L.; Locat, J.; Hutton, E.W.H.; Imran, J.

    2002-01-01

    Migrating sediment waves have been reported in a variety of marine settings, including submarine levee-fan systems, floors of fjords, and other basin or continental slope environments. Examination of such wave fields reveals nine diagnostic characteristics. When these characteristics are applied to several features previously attributed to submarine landslide deformation, they suggest that the features should most likely be reinterpreted as migrating sediment-wave fields. Sites that have been reinterpreted include the 'Humboldt slide' on the Eel River margin in northern California, the continental slope in the Gulf of Cadiz, the continental shelf off the Malaspina Glacier in the Gulf of Alaska, and the Adriatic shelf. A reassessment of all four features strongly suggests that numerous turbidity currents, separated by intervals of ambient hemipelagic sedimentation, deposited the wave fields over thousands of years. A numerical model of hyperpycnal discharge from the Eel River, for example, shows that under certain alongshore-current conditions, such events can produce turbidity currents that flow across the 'Humboldt slide', serving as the mechanism for the development of migrating sediment waves. Numerical experiments also demonstrate that where a series of turbidity currents flows across a rough seafloor (i.e. numerical steps), sediment waves can form and migrate upslope. Hemipelagic sedimentation between turbidity current events further facilitates the upslope migration of the sediment waves. Physical modelling of turbidity currents also confirms the formation and migration of seafloor bedforms. The morphologies of sediment waves generated both numerically and physically in the laboratory bear a strong resemblance to those observed in the field, including those that were previously described as submarine landslides.

  18. Negative priming effect on organic matter mineralisation in NE Atlantic slope sediments.

    PubMed

    Gontikaki, Evangelia; Thornton, Barry; Huvenne, Veerle A I; Witte, Ursula

    2013-01-01

    The priming effect (PE) is a complex phenomenon which describes a modification (acceleration or retardation) in the mineralisation rate of refractory organic matter (OM) following inputs of labile material. PEs are well-studied in terrestrial ecosystems owing to their potential importance in the evolution of soil carbon stocks but have been largely ignored in aquatic systems despite the fact that the prerequisite for their occurrence, i.e. the co-existence of labile and refractory OM, is also true for sediments. We conducted stable isotope tracer experiments in continental margin sediments from the NE Atlantic (550-950 m) to study PE occurrence and intensity in relation to labile OM input. Sediment slurries were treated with increasing quantities of the (13)C-labelled diatom Thalassiosira rotula and PE was quantified after 7, 14 and 21 days. There was a stepwise effect of diatom quantity on its mineralisation although mineralisation efficiency dropped with increasing substrate amounts. The addition of diatomaceous OM yielded a negative PE (i.e. retardation of existing sediment OM mineralisation) at the end of the experiment regardless of diatom quantity. Negative PE is often the result of preferential utilisation of the newly deposited labile material by the microbial community ("preferential substrate utilization", PSU) which is usually observed at excessive substrate additions. The fact that PSU and the associated negative PE occurred even at low substrate levels in this study could be attributed to limited amounts of OM subject to priming in our study area (~0.2% organic carbon [OC]) which seems to be an exception among continental slopes (typically >0.5%OC). We postulate that PEs will normally be positive in continental slope sediments and that their intensity will be a direct function of sediment OC content. More experiments with varying supply of substrate targeting C-poor vs. C-rich sediments are needed to confirm these hypotheses.

  19. Negative priming effect on organic matter mineralisation in NE Atlantic slope sediments.

    PubMed

    Gontikaki, Evangelia; Thornton, Barry; Huvenne, Veerle A I; Witte, Ursula

    2013-01-01

    The priming effect (PE) is a complex phenomenon which describes a modification (acceleration or retardation) in the mineralisation rate of refractory organic matter (OM) following inputs of labile material. PEs are well-studied in terrestrial ecosystems owing to their potential importance in the evolution of soil carbon stocks but have been largely ignored in aquatic systems despite the fact that the prerequisite for their occurrence, i.e. the co-existence of labile and refractory OM, is also true for sediments. We conducted stable isotope tracer experiments in continental margin sediments from the NE Atlantic (550-950 m) to study PE occurrence and intensity in relation to labile OM input. Sediment slurries were treated with increasing quantities of the (13)C-labelled diatom Thalassiosira rotula and PE was quantified after 7, 14 and 21 days. There was a stepwise effect of diatom quantity on its mineralisation although mineralisation efficiency dropped with increasing substrate amounts. The addition of diatomaceous OM yielded a negative PE (i.e. retardation of existing sediment OM mineralisation) at the end of the experiment regardless of diatom quantity. Negative PE is often the result of preferential utilisation of the newly deposited labile material by the microbial community ("preferential substrate utilization", PSU) which is usually observed at excessive substrate additions. The fact that PSU and the associated negative PE occurred even at low substrate levels in this study could be attributed to limited amounts of OM subject to priming in our study area (~0.2% organic carbon [OC]) which seems to be an exception among continental slopes (typically >0.5%OC). We postulate that PEs will normally be positive in continental slope sediments and that their intensity will be a direct function of sediment OC content. More experiments with varying supply of substrate targeting C-poor vs. C-rich sediments are needed to confirm these hypotheses. PMID:23840766

  20. Risk perception, risk management and vulnerability to landslides in the hill slopes in the city of La Paz, Bolivia. A preliminary statement.

    PubMed

    Nathan, Fabien

    2008-09-01

    The article begins by describing the difficult living conditions of many people in the hill slopes (laderas) of La Paz, Bolivia, demonstrating that they are exposed to a combination of natural and social hazards. It shows that residents, community leaders and city planners tend to underestimate or deny risk, with important consequences for risk management, such as a failure to raise risk awareness. The article then proposes some hypotheses to explain risk perceptions in La Paz, discarding the usual single-approach interpretations and suggesting instead more nuanced theoretical explanations to account for why people build their homes in such hazardous environments.

  1. Creep: An underrated type of mass movement on gently dipping hill slopes - examples from the Eastern Alpine foreland

    NASA Astrophysics Data System (ADS)

    Leopold, Philip; Draganits, Erich; Heiss, Gerhard

    2010-05-01

    Creep, as a very slow type of mass movement was first described by Terzahgi (1950) und Haefeli (1954, 1967). Terzaghi (1950) pointed out that creep represents an own type of mass movement cannot be compared with other types, such as slides, as creep occurs without rupture. According to him other mechanical laws than those that typically apply for mass movements, have to be determined for creep. In a more recent classification of mass movements, creep is described as slow earthflow within the flow type of movement (Highland & Bobrowsky, 2008). Aside from different ways of categorization of landslides, a very slow, imperceptible rate of movement is still considered characteristic for creep. Recent geological and geomorphological investigations of all kind of mass movements in the Eastern Alpine foreland in Austria (Eastern part of the Styrian basin, Oberpullendorf basin, Eisenstadt basin) showed that creep is not only widespread, but is in fact the most common type of mass movement in the Neogene sediments of the basins. More than 180 previously unrecognized zones of creep have been classified. Statistical analysis indicates that in some of the investigated areas creep occurs typically on slopes with gradients between only 10-35°. Movement rates are very low, inclinometer and other measurements show displacement rates in the range of a few centimeters per year. Therefore these mass movements have previously remained unnoticed by the population, local authorities and engineers. As a result there have been misjudgments in the land use-, building- and infrastructure planning which have caused a number of damages. Aside from the immediate implications creep has even more severe and longer term consequences. As a landforming process creep acts very constant over a very long period of time. Already Haefeli (1967) realized that creep occurs at a much lower rate of shear stress than the shear strength of the soil material. The rate of shear stress where creep starts to

  2. Report on water quality, sediment and water chemistry data for water and sediment samples collected from source areas to Melton Hill and Watts Bar reservoirs

    SciTech Connect

    Tomaszewski, T.M.; Bruggink, D.J.; Nunn, D.L.

    1995-08-18

    Contamination of surface water and sediments in the Clinch River and Watts Bar Reservoir (CR/WBR) system as a result of past and present activities by the US Department of Energy (DOE) on the Oak Ridge Reservation (ORR) and also activities by non-ORR facilities are being studied by the Clinch River Environmental Restoration Program (CR-ERP). Previous studies have documented the presence of heavy metals, organics, and radionuclides in the sediments of reservoirs in the vicinity. In support of the CR-ERP, during the summer of 1991, TVA collected and evaluated water and sediment samples from swimming areas and municipal water intakes on Watts Bar Reservoir, Melton Hill Reservoir and Norris Reservoir, which was considered a source of less-contaminated reference or background data. Despite the numerous studies, until the current work documented by this report, relatively few sediment or water samples had been collected by the CR-ERP in the immediate vicinity of contaminant point sources. This work focused on water and sediment samples taken from points immediately downstream from suspected effluent point sources both on and off the ORR. In August and September, 1994, TVA sampled surface water and sediment at twelve locations in melton Hill and Watts Bar Reservoirs.

  3. Summary report on water quality, sediment and water chemistry data for water and sediment samples collected from source areas to Melton Hill and Watts Bar reservoirs

    SciTech Connect

    Tomaszewski, T.M.; Bruggink, D.J.; Nunn, D.L.

    1995-08-01

    Contamination of surface water and sediments in the Clinch River and Watts Bar Reservoir (CR/WBR) system as a result of past and present activities by the US Department of Energy (DOE) on the Oak Ridge Reservation (ORR) and also activities by non-ORR facilities are being studied by the Clinch River Environmental Restoration Program (CR-ERP). Previous studies have documented the presence of heavy metals, organics, and radionuclides in the sediments of reservoirs in the vicinity. In support of the CR-ERP, during the summer of 1991, TVA collected and evaluated water and sediment samples from swimming areas and municipal water intakes on Watts Bar Reservoir, Melton Hill Reservoir (which is considered part of the Clinch River and Watts Bar Reservoir System), and Norris Reservoir, which was considered a source of less-contaminated reference or background data. Results of this study indicated that the levels of contamination in the samples from the Watts Bar and Melton Hill Reservoir sites did not pose a threat to human health. Despite the numerous studies, until the current work documented by this report, relatively few sediment or water samples had been collected by the CR-ERP in the immediate vicinity of contaminant point sources. This work focused on water and sediment samples taken from points immediately downstream from suspected effluent point sources both on and off the ORR. In August and September, 1994, TVA sampled surface water and sediment at twelve locations in Melton Hill and Watts Bar Reservoirs. Eleven of the sampling sites were selected based on existence of pollutant discharge permits, known locations of hazardous waste sites, and knowledge of past practices. The twelfth sample site was selected as a relatively less contaminated reference site for comparison purposes.

  4. Microbial Communities in Methane Hydrate-Bearing Sediments from the Alaskan North Slope

    NASA Astrophysics Data System (ADS)

    Schwartz, A.; Briggs, B.; Colwell, F.

    2008-12-01

    High latitude soils and sediments often contain large quantities of methane as well as microbial communities capable of producing and consuming the methane. We studied the microbial communities collected from hydrate-bearing sediments on the Alaskan North Slope to determine how abiotic variables (e.g., grain size, hydrate presence, original depositional environment) may control the type and distribution of microbes in the sediments. The cores were acquired from sub-permafrost, Eocene (35-36 million years ago [MYA]) sediments laid down as a marine transgressive series within which hydrates are believed to have formed 1.5 MYA. Forty samples, eight of which originally contained hydrates, were acquired from depths of ca. 606-666 meters below land surface. Five samples from drilling fluids acquired from the same depth range were included in the analysis as a control for contamination during the drilling and handling of cores. DNA was extracted from the samples (typically <1 ng DNA/g sediment was recovered) and then amplified using polymerase chain reaction with primers specific for bacterial and archaeal 16S rDNA. Only bacterial DNA amplicons were detected. Terminal-restriction fragment length polymorphism (t-RFLP) was used to measure bacterial diversity in the respective samples. Non-metric multidimensional scaling (NMDS) was then used to determine the abiotic variables that may have influenced bacterial diversity. NMDS analysis revealed that sediment samples were distinct from those obtained from drilling fluids suggesting that the samples were not contaminated by the drilling fluids. All samples had evidence of microbial communities and sample depth, temperature, and hydrate presence appeared to have some influence on community diversity. Samples sharing these environmental parameters often shared common t-RFLP profiles. Further examination of selected samples using clone libraries should help to identify the key taxa present in these unique sediments and yield a

  5. Raft tectonics: the effects of basal slope angle and sedimentation rate on progressive extension

    NASA Astrophysics Data System (ADS)

    Mauduit, T.; Guerin, G.; Brun, J.-P.; Lecanu, H.

    1997-09-01

    In the Gulf of Guinea, the Upper Cretaceous-Tertiary sedimentary cover has undergone gravity gliding above an Aptian salt layer for various basal slope angles from 0 ° to 4 °. Gliding started during Albian time and evolved up to the present with variable sedimentation rates. Faulting patterns are seen to vary in particular as a function of the basal slope angle and the syn-kinematic sedimentation rates. A series of laboratory experiments on small-scale models is used to study the effects of the two parameters mentioned above. Models are composed of two-layer slabs, with Newtonian silicone putty at the base to represent a basal salt décollement and dry sand on top to represent the sedimentary overburden. Models are allowed to deform under their own weight for various basal slope angles ranging from 0 ° to 5 ° with two different syn-kinematic sedimentation rates. It is shown that the basal slope angle α controls the location of faulting in the overburden, within a single downslope deformation domain for α values smaller than 2 ° and within two domains lying downslope and upslope for higher values of α. The width of the deformation domains also varies as a function of α. Overburden faulting always starts with syn-kinematic grabens which evolve into symmetric or asymmetric grabens or into tilted blocks bounded by listric normal faults. While synthetic listric normal faults characterize the downslope deformation domains, both synthetic and antithetic listric normal faults can occur in the upslope deformation domain. Ductile deformation within the basal décollement layers results from variable combinations of pure shear and simple shear. Interaction of ductile deformation in the ductile décollement layer with faulting in the overburden locally produces complex and heterogeneous strain patterns, notably within salt rollers. Finally, increasing rates of syn-kinematic sedimentation are seen to increase the rate of downslope displacement and to enhance and favour

  6. Flow Measurements on Steep Slopes and in Sediment-Laden Flows Using the Drop-Box Weir

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Large sediment loads and large particles from unprotected slopes, mined lands, construction areas, and range lands under high intensity rainfalls result from high intensity rainfalls. Flow-measuring devices will become clogged with sediment in a single event, resulting in the loss of runoff and sed...

  7. Off-road vehicular destabilization of hill slopes: the major contributing factor to destructive debris flows in Ogden, Utah, 1979

    USGS Publications Warehouse

    Nakata, John K.; Webb, Robert H.; Wilshire, Howard G.

    1983-01-01

    The Wasatch Mountains in northern Utah are a north-south trending range with steep slopes caused by faulting less than 10,000 years ago. Through the natural processes of rain, frost-wedging, gravity, and earthquakes these slopes are slowly being eroded. A geologic history of instability is recorded at the base of the range in the form of landslide deposits, debris flows, and rock-fall deposits.

  8. Numerical stability analysis of submerged slopes subject to rapid sedimentation processes

    NASA Astrophysics Data System (ADS)

    di Prisco, Claudio; Mancinelli, Luca; Zanelotti, Letizia; Pisanò, Federico

    2015-01-01

    In this paper, the stability of infinitely long submerged slopes subject to rapid sedimentation processes is theoretically/numerically investigated. In particular, rapid deposition is considered as a potential triggering factor for static liquefaction in inclined loose sand layers. The corresponding initial boundary value problem is numerically analysed by employing a one-dimensional finite difference scheme in conjunction with two distinct versions of the same constitutive model—elasto-plastic and elasto-viscoplastic (EV). The EV approach is shown to be the most suitable for describing the onset of liquefaction phenomena, since its mathematical well-posedness and numerical stability are never lost. The results of parametric analyses for both homogeneous and inhomogeneous strata are critically discussed in the light of some case history data concerning natural and anthropic sedimentation processes.

  9. Hydrodynamics over the Gulf of Valencia continental slope and their role in sediment transport

    NASA Astrophysics Data System (ADS)

    Ribó, M.; Puig, P.; van Haren, H.

    2015-01-01

    Circulation patterns and sediment dynamics were studied over the Gulf of Valencia (GoV) continental slope during spring and winter 2011-2012. Two moorings were deployed at two locations; at 450 m depth from February to May 2011, and at 572 m depth from October 2011 to February 2012. At both mooring sites, observations were made of currents, temperature and near-bottom turbidity within the lowermost 80 m above the seafloor. The temperature measurements allowed distinction of the different water masses and their temporal evolution. The fluctuations of the boundary between the Western Mediterranean Deep Water (WMDW) and the Levantine Intermediate Water (LIW) masses were monitored, and several intrusions of Western Mediterranean Intermediate Water (WIW) were observed, generally coinciding with changes in current direction. At both mooring sites, the currents generally maintained low velocities <10 cm s-1, with several pulses of magnitude increases >20 cm s-1, and few reaching up to 35 cm s-1, associated with mesoscale eddies and topographic waves. The current direction was mainly towards the SSE on the first deployment and to the ESE on the second deployment. This second location was affected by a strong bottom offshore veering presumably generated by local topographic effects. Increases in suspended sediment concentrations (SSC) were observed repeatedly throughout the records, reaching values >3 mg l-1. However, these SSC variations were uncorrelated with changes in velocity magnitude and direction and/or with temperature oscillations. Results presented in this paper highlight the complex relation between the hydrodynamics and sediment transport over the GoV continental slope, and suggest that other potential sediment resuspension mechanism not linked with current fluctuations, might play a key role in the present-day sedimentary dynamics. Resuspension due to bottom trawling appears to be the most plausible mechanism.

  10. Benthic remineralisation rates in shelf and slope sediments of the northern Benguela upwelling margin

    NASA Astrophysics Data System (ADS)

    Neumann, Andreas; Lahajnar, Niko; Emeis, Kay-Christian

    2016-02-01

    The Benguela Upwelling System off Namibia is a region of intensive plankton production. Remineralisation of this biomass frequently causes the formation of an oxygen minimum zone. A part of the organic matter is further deposited on the broad shelf in form of an extensive mudbelt with high TOC concentrations. During February 2011 we retrieved sediment samples from shelf and slope sediment along the Namibian coast to establish fluxes of nutrients, oxygen, and N2 on the basis of pore water concentrations. In mudbelt sediment, fluxes were estimated as high as 8 mmol NH4+ m-2 d-1 and 0.9 mmol PO43 - m-2 d-1, which is probably attributable to the activity of large sulphur bacteria. Especially phosphate is mobilised from sediment overlain by oxygen deficient bottom water when and where bottom water oxygen concentrations fall below 50 μmol l-1. In comparison to nutrient transport by Southern Atlantic Central Water flowing onto the Namibian shelf, benthic nutrient fluxes of the mudbelt contribute less than 5% to the nutrient budget of the shelf.

  11. Subsurface hydrologic effects on sediment deposition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Quantification of soil erosion processes has been traditionally focused on soil detachment and sediment transport while efforts in quantifying sediment deposition process are relatively minor. Nevertheless, most sediment generated on the hill slopes are deposited within the field and only a small am...

  12. Hydrological heterogeneity in Mediterranean reclaimed slopes: runoff and sediment yield at the patch and slope scales along a gradient of overland flow

    NASA Astrophysics Data System (ADS)

    Merino-Martín, L.; Moreno-de Las Heras, M.; Pérez-Domingo, S.; Espigares, T.; Nicolau, J. M.

    2011-11-01

    Hydrological heterogeneity is recognized as a fundamental ecosystem attribute in drylands controlling the flux of water and energy through landscapes. Therefore, mosaics of runoff and sediment sinks and source patches are frequently identified in these dry environments. There is a remarkable scarcity of studies about hydrological spatial heterogeneity in restored slopes, where ecological succession and overland flow are interacting. We conducted a field research to study the hydrological role of patches and slopes along an overland flow gradient in three reclaimed slopes coming from mining reclamation in a Mediterranean-continental climate. We found that runoff generation and routing in non-rilled slopes showed a pattern of source and sink areas of runoff. Such hydrological microenvironments were associated to seven vegetation patches (characterized by plant community types and cover). Two types of sink patches were identified: shrub Genista scorpius patches could be considered as a "deep sink", while patches where the graminoids Brachypodium retusum and Lolium perenne dominate were classified as "surface sinks" or "runoff splays". A variety of source patches were also identified spanning from "extreme sources" (Medicago sativa patches; equivalent to bare soil) to "poor sources" (areas scattered by dwarf-shrubs of Thymus vulgaris or herbaceous tussocks of Dactylis glomerata). Finally, we identified the volume of overland flow routing along the slope as a controlling major factor of hydrological diversity: when overland flow increases at the slope scale hydrological diversity diminishes.

  13. Network-scale dynamics of sediment mixtures: how do tectonics affect surface bed texture and channel slope?

    NASA Astrophysics Data System (ADS)

    Gasparini, N. M.; Bras, R. L.; Tucker, G. E.

    2003-04-01

    An alluvial channel's slope and bed texture are intimately linked. Along with fluvial discharge, these variables are the key players in setting alluvial transport rates. We know that both channel slope and mean grain size usually decrease downstream, but how sensitive are these variables to tectonic changes? Are basin concavity and downstream fining drastically disrupted during transitions from one tectonic regime to another? We explore these questions using the CHILD numerical landscape evolution model to generate alluvial networks composed of a sand and gravel mixture. The steady-state and transient patterns of both channel slope and sediment texture are investigated. The steady-state patterns in slope and sediment texture are verified independently by solving the erosion equations under equilibrium conditions, i.e. the case when the erosion rate is equal to the uplift rate across the entire landscape. The inclusion of surface texture as a free parameter (as opposed to just channel slope) leads to some surprising results. In all cases, an increase in uplift rate results in channel beds which are finer at equilibrium (for a given drainage area). Higher uplift rates imply larger equilibrium transport rates; this leads to finer channels that have a smaller critical shear stress to entrain material, and therefore more material can be transported for a given discharge (and channel slope). Changes in equilibrium slopes are less intuitive. An increase in uplift rates can cause channel slopes to increase, remain the same, or decrease, depending on model parameter values. In the surprising case in which equilibrium channel slopes decrease with increasing uplift rates, we suggest that surface texture changes more than compensate for the required increase in transport rates, causing channel slopes to decrease. These results highlight the important role of sediment grain size in determining transport rates and caution us against ignoring this important variable in fluvial

  14. From mass-wasting to slope stabilization - putting constrains on the transition in slope erosion mode: A case study in the Judea Hills, Israel

    NASA Astrophysics Data System (ADS)

    Ryb, U.; Matmon, A.; Porat, N.; Katz, O.

    2012-04-01

    The geomorphic response of a drainage system to the termination of tectonic uplift includes the stabilization of base level followed by a transition in the mode of hillslope erosion from mass wasting to diffusive processes. We test this transition in the Soreq drainage, Judea Hills, Israel. This study area is characterized by Upper Cretaceous marine carbonate rocks and sub-humid Mediterranean climate, and the drainage hillslopes are typically mantled by thick calcrete crusts. Calcretized remnants of landslide debris and alluvial deposits are evident along the presently stable hillslopes. These remnants indicate that a transition from landslides to dissolution-controlled hillslope erosion had occurred, most likely due to the stabilization of the present base-level which probably followed a significant decrease in tectonic uplift during late Cenozoic. Four deposits were dated using thermally transferred OSL of aeolian quartz grains incorporated in the calcrete which cement the ancient deposits. Three deposits are associated with the present streambed and constrain the hillslope stabilization period; one deposit is associated with a ~100 m higher base-level and puts constrains on the rate of stream incision prior to the stabilization of the current streambed. We conclude that incision of ~100 m occurred between 1056±262 ka to 688±86 ka due to ~0.3° westward tilt of the region; such incision invoked high frequency of landslide activity in the drainage. The ages of a younger landslide remnant, alluvial terrace, and alluvial fan, all situated only a few meters above the present level of the active streambed, range between 688±86 ka and 244±25 ka and indicate that since 688±86 the Soreq base level had stabilized and that landslide activity decreased significantly by the middle Pleistocene. This study demonstrates that colluvial deposits may be used as markers for stream incision and base level stabilization, much like alluvial deposits that are commonly used for

  15. Total nitrogen and suspended-sediment loads and identification of suspended-sediment sources in the Laurel Hill Creek watershed, Somerset County, Pennsylvania, water years 2010-11

    USGS Publications Warehouse

    Sloto, Ronald A.; Gellis, Allen C.; Galeone, Daniel G.

    2012-01-01

    Laurel Hill Creek is a watershed of 125 square miles located mostly in Somerset County, Pennsylvania, with small areas extending into Fayette and Westmoreland Counties. The upper part of the watershed is on the Pennsylvania Department of Environmental Protection 303(d) list of impaired streams because of siltation, nutrients, and low dissolved oxygen concentrations. The objectives of this study were to (1) estimate the annual sediment load, (2) estimate the annual nitrogen load, and (3) identify the major sources of fine-grained sediment using the sediment-fingerprinting approach. This study by the U.S. Geological Survey (USGS) was done in cooperation with the Somerset County Conservation District. Discharge, suspended-sediment, and nutrient data were collected at two streamflow-gaging stations—Laurel Hill Creek near Bakersville, Pa., (station 03079600) and Laurel Hill Creek at Ursina, Pa., (station 03080000)—and one ungaged stream site, Laurel Hill Creek below Laurel Hill Creek Lake at Trent (station 03079655). Concentrations of nutrients generally were low. Concentrations of ammonia were less than 0.2 milligrams per liter (mg/L), and concentrations of phosphorus were less than 0.3 mg/L. Most concentrations of phosphorus were less than the detection limit of 0.02 mg/L. Most water samples had concentrations of nitrate plus nitrite less than 1.0 mg/L. At the Bakersville station, concentrations of total nitrogen ranged from 0.63 to 1.3 mg/L in base-flow samples and from 0.57 to 1.5 mg/L in storm composite samples. Median concentrations were 0.88 mg/L in base-flow samples and 1.2 mg/L in storm composite samples. At the Ursina station, concentrations of total nitrogen ranged from 0.25 to 0.92 mg/L in base-flow samples; the median concentration was 0.57 mg/L. The estimated total nitrogen load at the Bakersville station was 262 pounds (lb) for 11 months of the 2010 water year (November 2009 to September 2010) and 266 lb for the 2011 water year. Most of the total

  16. Significant melting of ice-wedges and formation of thermocirques on hill-slopes of thermokarst lakes in Central Yakutia (Siberia)

    NASA Astrophysics Data System (ADS)

    Séjourné, Antoine; Costard, François; Gargani, Julien; Fedorov, Alexander; Skorve, Johnny

    2013-04-01

    On Earth, permafrost containing a high ice volume (referred as ice-rich) are sensible to climate change, they have been regionally degraded (thermokarst) during the early Holocene climatic optimum forming numerous thermokarst lakes in Central Yakutia (eastern Siberia). Recent temperature increases in the Arctic and Subarctic have been significantly greater than global averages. The frequency and magnitude of terrain disturbances associated with thawing permafrost are increasing in these regions and are thought to intensify in the future. Therefore, understand how is the current development of thermokarst is a critical question. Here, we describe the significant melting of ice-wedges on slopes of thermokarst lakes that leads to formation of amphitheatrical hollows referred as thermocirques. The evolution of thermocirques in Central Yakutia has been little studied and analyzing their formation could help to understand the recent thermokarst in relation to climate change in Central Yakutia. We studied the thermocirques at two scales: (i) field surveys of different thermocirques in July 2009-2010 and October 2012 to examine the processes and origin of melting of ice-wedges and; (ii) photo-interpretation of time series of satellite images (KH-9 Hexagon images of 6-9 m/pixel and GeoEye images of 50 cm/pixel) to study the temporal evolution of thermocirques. The melting of ground-ice on the scarp of thermocirque triggers falls and small mud-flows that induce the retreat of the scarp parallel to itself. Based on field studies and on GeoEye image comparison, we show that their rate of retrogressive growth is 1-2 m/year. On the hill-slopes of lakes, the thermokarst could be initiated by different processes that lead to the uncover and then melting of ice-wedges: thermal erosion by the waves of the ice-rich bluff; active-layer detachment (a form of slope failure linked to detachment of the seasonally thawed upper ground); flowing of water on the slope (precipitation) or

  17. Spatial and temporal patterns of aeolian sediment transport on an inland parabolic dune, Bigstick Sand Hills, Saskatchewan, Canada

    NASA Astrophysics Data System (ADS)

    Hugenholtz, C. H.; Wolfe, S. A.; Walker, I. J.; Moorman, B. J.

    2009-04-01

    Topographic changes from erosion pins and on-site meteorological data document the spatial and temporal patterns of aeolian sediment transport at monthly to annual timescales across an active parabolic dune within a vegetation-stabilized inland, prairie dune field. Over two years, the sediment budget, calculated from digital elevation models, shows that the total volume of erosion (9890 m 3) is greater than the amount of deposition (6990 m 3), indicating a net loss of 2900 m 3 of sediment (or ˜ 29% of eroded sediment) from the dune. Sediment erosion occurred mainly on the stoss slope (3600 m 3; ˜ 36% of eroded sediment), but also on the south (2100 m 3; ˜ 21%) and north sides of the dune head (1700 m 3; ˜ 17%), the blowouts along the arms (1740 m 3, ˜ 18%) and the crest (650 m 3; ˜ 7%). Erosion from the deflation basin is limited by surface roughness and armoring effects of a gravel lag deposit (100 m 3; ˜ 1%). Thus, the blowouts currently contribute to maintaining dune mobility because no other sediment input occurs from upwind. Sediment deposition onto the dune occurred primarily beyond the brink on the south and southeast lee slopes (5500 m 3; ˜ 80%), coinciding with the southeasterly resultant transport direction for November 2004-05. The net loss of about 2900 m 3 (˜ 29%) may be attributed to sediment carried in suspension over and beyond the dune. Correlation analysis between sediment transport and meteorological variables suggests that monthly to seasonal changes of surface conditions (e.g., vegetation cover, ground freezing, moisture) buffer the relative importance of temperature and precipitation on rates of sediment transport. Conversely, wind correlates well on a monthly to seasonal basis because it is a driver of transport under all types of surface conditions. Seasonal effects produce a complex interaction between wind, climate and surface conditions. This leads to a dynamic range of threshold velocities, which in turn causes spatial and

  18. Methane sources in arctic thermokarst lake sediments on the North Slope of Alaska.

    PubMed

    Matheus Carnevali, P B; Rohrssen, M; Williams, M R; Michaud, A B; Adams, H; Berisford, D; Love, G D; Priscu, J C; Rassuchine, O; Hand, K P; Murray, A E

    2015-03-01

    The permafrost on the North Slope of Alaska is densely populated by shallow lakes that result from thermokarst erosion. These lakes release methane (CH4 ) derived from a combination of ancient thermogenic pools and contemporary biogenic production. Despite the potential importance of CH4 as a greenhouse gas, the contribution of biogenic CH4 production in arctic thermokarst lakes in Alaska is not currently well understood. To further advance our knowledge of CH4 dynamics in these lakes, we focused our study on (i) the potential for microbial CH4 production in lake sediments, (ii) the role of sediment geochemistry in controlling biogenic CH4 production, and (iii) the temperature dependence of this process. Sediment cores were collected from one site in Siqlukaq Lake and two sites in Sukok Lake in late October to early November. Analyses of pore water geochemistry, sedimentary organic matter and lipid biomarkers, stable carbon isotopes, results from CH4 production experiments, and copy number of a methanogenic pathway-specific gene (mcrA) indicated the existence of different sources of CH4 in each of the lakes chosen for the study. Analysis of this integrated data set revealed that there is biological CH4 production in Siqlukaq at moderate levels, while the very low levels of CH4 detected in Sukok had a mixed origin, with little to no biological CH4 production. Furthermore, methanogenic archaea exhibited temperature-dependent use of in situ substrates for methanogenesis, and the amount of CH4 produced was directly related to the amount of labile organic matter in the sediments. This study constitutes an important first step in better understanding the actual contribution of biogenic CH4 from thermokarst lakes on the coastal plain of Alaska to the current CH4 budgets. PMID:25612141

  19. Hydrological heterogeneity in Mediterranean reclaimed slopes: runoff and sediment yield at the patch and slope scales along a gradient of overland flow

    NASA Astrophysics Data System (ADS)

    Merino-Martín, L.; Moreno-de las Heras, M.; Pérez-Domingo, S.; Espigares, T.; Nicolau, J. M.

    2012-05-01

    Hydrological heterogeneity is recognized as a fundamental ecosystem attribute in drylands controlling the flux of water and energy through landscapes. Therefore, mosaics of runoff and sediment source patches and sinks are frequently identified in these dry environments. There is a remarkable scarcity of studies about hydrological spatial heterogeneity in restored slopes, where ecological succession and overland flow are interacting. We conducted field research to study the hydrological role of patches and slopes along an "overland flow gradient" (gradient of overland flow routing through the slopes caused by different amounts of run-on coming from upslope) in three reclaimed mining slopes of Mediterranean-continental climate. We found that runoff generation and routing in non-rilled slopes showed a pattern of source and sink areas of runoff. Such hydrological microenvironments were associated with seven vegetation patches (characterized by plant community types and cover). Two types of sink patches were identified: shrub Genista scorpius patches could be considered as "deep sinks", while patches where the graminoids Brachypodium retusum and Lolium perenne dominate were classified as "surface sinks" or "runoff splays". A variety of source patches were also identified spanning from "extreme sources" (Medicago sativa patches; equivalent to bare soil) to "poor sources" (areas scattered by dwarf-shrubs of Thymus vulgaris or herbaceous tussocks of Dactylis glomerata). Finally, we identified the volume of overland flow routing along the slope as a major controlling factor of "hydrological diversity" (heterogeneity of hydrological behaviours quantified as Shannon diversity index): when overland flow increases at the slope scale hydrological diversity diminishes.

  20. Benthic Community Structure and Sediment Geochemical Properties at Hydrocarbon Seeps Along the Continental Slope of the Western North Atlantic

    NASA Astrophysics Data System (ADS)

    Demopoulos, A. W.; Bourque, J. R.; Brooke, S.

    2015-12-01

    Hydrocarbon seeps support distinct benthic communities capable of utilizing reduced chemical compounds for nutrition. In recent years, methane seepage has been increasingly documented along the continental slope of the U.S. Atlantic margin. In 2012 and 2013, two seeps were investigated in this region: a shallow site near Baltimore Canyon (410-450 m) and a deep site near Norfolk Canyon (1600 m). Both sites contain extensive mussel beds and microbial mats. Sediment cores and grab samples were collected to quantify the abundance, diversity, and community structure of benthic macrofauna (>300 mm) in relationship to the associated sediment environment (organic carbon and nitrogen, stable isotopes 13C and 15N, grain size, and depth) of mussel beds, mats, and slope habitats. Macrofaunal densities in microbial mats were four times greater than those present in mussel beds and slope sediments. Macrofaunal communities were distinctly different both between depths and among habitat types. Specifically, microbial mat sediments were dominated by the annelid families Dorvilleidae, Capitellidae, and Tubificidae, while mussel habitats had higher proportions of crustaceans. Diversity was lower in Baltimore microbial mat habitats, but higher in mussel and slope sediments compared to Norfolk seep habitats found at deeper depths. Multivariate statistical analysis identified sediment carbon:nitrogen (C:N) ratios and 13C values as important variables for structuring the macrofaunal communities. Higher C:N ratios were present within microbial mat habitats and depleted 13C values occurred in sediments adjacent to mussel beds found in Norfolk Canyon seeps. Differences in the quality and source of organic matter present in the seep habitats are known to be important drivers in macrofaunal community structure and associated food webs. The multivariate analysis provides new insight into the relative importance of the seep sediment quality in supporting dense macrofaunal communities compared

  1. Periglacial features in Patriot Hills, Ellsworth Mountains, Antarctica

    NASA Astrophysics Data System (ADS)

    Vieira, Rosemary; Hinata, Sumirê; da Rosa, Kátia Kellem; Zilberstein, Sérgio; Simoes, Jefferson Cardia

    2012-06-01

    This work describes periglacial features identified at Patriot Hills, at the southernmost part of Ellsworth Mountains, Antarctica, during the 2008/2009 Brazilian Antarctic Expedition, and discusses their morphogenetic environment. Identified periglacial features were classified into: (a) rock glacier-like landform; (b) slightly creeping debris-mantled slopes; (c) steep debris-mantled slopes; and (d) rock falls. Results obtained from sediment sample analysis suggest activity and passive movement of a rock glacier-like landform, albeit minimal. Wind seems to play an important role in Patriot Hills local geomorphology. Periglacial features such as slightly creeping debris-mantled slope appear to have preferred slope orientation. They are commonly found onto slopes where the katabatic wind flows down. Slopewash and groundwater movement processes may be limited or non-existent since most snow disappears through sublimation

  2. [Bacterial and archaeal diversity in surface sediment from the south slope of the South China Sea].

    PubMed

    Li, Tao; Wang, Peng; Wang, Pinxian

    2008-03-01

    Diversity of bacteria and archaea was studied in deep marine sediments by PCR amplification and sequence analysis of 16S rDNA. Sample analysed was from IMAGES (International Marine Past Global Change Study) 147 at site of the south slope of the South China Sea. DNA was amplified from samples at the surface layer of core MD05-2896. Phylogenetic analysis of clone libraries showed a wide variety of uncultured bacteria and archeae. The most abundant bacterial sequences (phylotypes) corresponded to the Proteobacteria, followed by the Planctomycete, Acidobacteria and candidate division OP10. Phylotypes ascribing to Deferrobacteres, Verrucomicrobia, Spirochaetes and candidate division clades of OP3, OP11, OP8 and TM6 were also identified. Archaeal 16S rDNA sequences were within phylums of Crenarchaeota and Euryarchaeota, respectively. The majority of archaeal phylotypes were Marine Benthic Group B (MBGB), Marine Crenarchaeotic Group I (MG I), Marine Benthic Group D (MBGD) and South African Gold Mine Euryarchaeotic Group (SAGMEG). Additional sequences grouped with the C3, Methanobacteriales and Novel Euryarchaeotic Group (NEG). These results indicate that bacteria and archaea are abundant and diversified in surface environment of subseafloor sediments.

  3. Total nitrogen and suspended-sediment loads and identification of suspended-sediment sources in the Laurel Hill Creek watershed, Somerset County, Pennsylvania, water years 2010-11

    USGS Publications Warehouse

    Sloto, Ronald A.; Gellis, Allen C.; Galeone, Daniel G.

    2012-01-01

    Laurel Hill Creek is a watershed of 125 square miles located mostly in Somerset County, Pennsylvania, with small areas extending into Fayette and Westmoreland Counties. The upper part of the watershed is on the Pennsylvania Department of Environmental Protection 303(d) list of impaired streams because of siltation, nutrients, and low dissolved oxygen concentrations. The objectives of this study were to (1) estimate the annual sediment load, (2) estimate the annual nitrogen load, and (3) identify the major sources of fine-grained sediment using the sediment-fingerprinting approach. This study by the U.S. Geological Survey (USGS) was done in cooperation with the Somerset County Conservation District. Discharge, suspended-sediment, and nutrient data were collected at two streamflow-gaging stations—Laurel Hill Creek near Bakersville, Pa., (station 03079600) and Laurel Hill Creek at Ursina, Pa., (station 03080000)—and one ungaged stream site, Laurel Hill Creek below Laurel Hill Creek Lake at Trent (station 03079655). Concentrations of nutrients generally were low. Concentrations of ammonia were less than 0.2 milligrams per liter (mg/L), and concentrations of phosphorus were less than 0.3 mg/L. Most concentrations of phosphorus were less than the detection limit of 0.02 mg/L. Most water samples had concentrations of nitrate plus nitrite less than 1.0 mg/L. At the Bakersville station, concentrations of total nitrogen ranged from 0.63 to 1.3 mg/L in base-flow samples and from 0.57 to 1.5 mg/L in storm composite samples. Median concentrations were 0.88 mg/L in base-flow samples and 1.2 mg/L in storm composite samples. At the Ursina station, concentrations of total nitrogen ranged from 0.25 to 0.92 mg/L in base-flow samples; the median concentration was 0.57 mg/L. The estimated total nitrogen load at the Bakersville station was 262 pounds (lb) for 11 months of the 2010 water year (November 2009 to September 2010) and 266 lb for the 2011 water year. Most of the total

  4. Accumulation of bank-top sediment on the western slope of Great Bahama Bank: rapid progradation of a carbonate megabank

    USGS Publications Warehouse

    Wilber, R. Jude; Milliman, John D.; Halley, Robert B.

    1990-01-01

    High-resolution seismic profiles and submersible observations along the leeward slope of western Great Bahama Bank show large-scale export of bank-top sediment and rapid progradation of the slope during the Holocene. A wedge-shaped sequence, up to 90 m thick, is present along most of the slope and consists of predominantly aragonite mud derived from the bank since flooding of the platform 6-8 ka. Total sediment volume of the slope sequence is 40%-80% that of Holocene sediment currently retained on the bank. Maximum rates of vertical accumulation and lateral progradation are 11-15 m/ka and 80-110 m/ka, respectively: 10 to 100 times greater than previously known for periplatform muds. Slope deposition of exported mud during sea-level highs appears to have been a major mechanism for the westward progradation of Great Bahama Bank throughout the Quaternary; this may provide a critical modern analogue for ancient progradational margins.

  5. Task 5: TVA sediment-disturbing activities within the Watts Bar Reservoir and Melton Hill Reservoir areas of the Clinch River

    SciTech Connect

    1997-06-01

    The objectives of Task 5 of the Interagency Agreement No. DE-AI05-91OR22007 were to review: (1) the extent of dredging, construction, and other sediment-disturbing activities conducted by the Tennessee Valley Authority (TVA) in potentially contaminated areas of Watts Bar Reservoir, and (2) the disposition of the materials from these activities. This memorandum is the final report for Task 5. This memorandum describes major activities in the Watts Bar Reservoir and Melton Hill Reservoir areas of the Clinch River that possibly resulted in significant disturbance of potentially contaminated sediments. TVA records from the construction of Watts Bar Dam, Kingston Fossil Plant, and Melton Hill Dam were reviewed to facilitate qualitative description of the effect of these activities in disturbing potentially contaminated sediments. The critical period for these activities in disturbing contaminated sediments was during or after 1956 when the peak releases of radioactive contaminants occurred from the Oak Ridge Reservation.

  6. Pb-210 fluxes and sedimentation rates on the lower continental slope between Taiwan and the South Okinawa Trough

    NASA Astrophysics Data System (ADS)

    Chung, Y.; Chang, W. C.

    1995-03-01

    Pb-210 and Ra-226 have been measured on 11 cores taken from the continental slope between northern Taiwan and the western South Okinawa Trough. Ra-226 activities generally fall between 0.5 and 2 dpm g -1. Pb-210 activities are widely variable in these cores: negligible excess Pb-210 (or no Pb-210 flux) is observed on the upper and middle slope while large excess Pb-210 values (50-90 dpm g -1) are present on the lower slope. Sedimentation rates estimated from the excess Pb-210 profiles of the cores range from 0.09 to 0.52 cm y -1 (0.08 - 0.42 g cm -2 y -1) for the lower slope and decrease toward the deeper (eastern) slope. Excess Pb-210 inventories and the Pb-210 fluxes calculated from the lower slope are 320-840 dpm cm -2 and 10-26 dpm cm -2 y -1 , respectively, assuming a steady-state input at each site for the past 100 years. Atmospheric input of Pb-210 and local production from Ra-226 do not account for the observed fluxes. Two alternative explanations are proposed: (1) boundary scavenging coupled with the Kuroshio water flowing through the area; or (2) downslope transport of high Pb-210 activity fine-grained particles from the shelf and upper/middle slope to the lower slope where they are deposited.

  7. Seismostratigraphy and sedimentation environment on the shelf and continental slope of Peter the Great Bay (Sea of Japan)

    NASA Astrophysics Data System (ADS)

    Karnaukh, V. N.; Karp, B. Ya.; Tsoy, I. B.

    2007-04-01

    The results of a single channel seismic reflection survey and of a micropaleontological examination of diatom remains in bottom sediment samples on the shelf and continental slope of the Peter the Great Bay area are presented. The composition and age of the sedimentary layer were studied using integrated seismic, micropaleontological and geological data. The continental slope was formed not later than at the beginning of the Early Miocene. The slope is covered with Middle Miocene-Pliocene sediments. The sedimentary thickness on most of the slope is 0.2 0.4 s. The maximum thickness (0.8 1.0 s) is observed within the areas of submarine canyons and valleys. The thickness of the Early Miocene-Pliocene sediments on the shelf is 0.2 0.4 s. On the shelf break and in a southwest-trending trough of the acoustic basement, it increases up to 1.0 s. Two uncomformities were identified in the sediments of the shelf area. The proposed age of the upper uncomformity is 10.0 8.5 My B.P.; it represents the result of a global sea level fall. The age of the lower uncomformity is unknown.

  8. Avalanche Sedimentation in Seas and Oceans, Paper 3: The Second Global Level of Avalanche Sedimentation: The Base of the Continental Slope

    SciTech Connect

    Lisilsyn, A.P.

    1986-03-01

    The paper discusses the sedimentation pattern at the second global hypsometric level - at the base of continental slope, where the bulk of the planet's sedimentary matter is concentrated. Typifying examples are given, and the patterns of quantitative distribution of sedimentary matter at that level are described.

  9. How much does a very active rock slope contribute to the sediment budget of an alpine glacier?

    NASA Astrophysics Data System (ADS)

    Baewert, Henning; Vehling, Lucas; Glira, Philipp; Stocker-Waldhuber, Martin; Morche, David

    2014-05-01

    The ongoing glacier retreat since the mid of the 19th century has significant influence on rock slope stability in alpine high mountain areas. Due to oversteepening by glacial erosion, cold climate weathering processes and debuttressing as a consequence of stress redistribution, rock slopes adjacent to shrinking glaciers generally show an enhanced geotechnical activity. Regarding the glacier sediment budget, the rockfall material deposited on a glacier is particular important, because the debris material can be transported directly and without any intermediate storage. Therefore, gravitational mass movements contribute in a substantial way to the sediment budget of a glacier, especially as rockfall material can easily reach en- or subglacial areas through crevasses and thus affect the subglacial sediment transport and glacial erosion. Here we present the first results regarding the geotechnical rock slope activity of "Schwarze Wand". The "Schwarze Wand" is located at 2400 - 2800 m.a.s.l., right above the tongue of the Gepatschferner, which is one of the largest glaciers in Tyrol (Austria) and contemporarily affected by a high retreat rate. The rock mass consists of strong foliated paragneisses which are dissected by large joint sets. These joint sets provide sliding planes, which favor slope failures. To monitor the rock slope activity at the "Schwarze Wand", multitemporal terrestrial laser scans were carried out in 2012 and 2013 to detect and quantify mass movements. Additional, high resoluted multitemporal airborne laser scan data (10 points/m²) are available to trace larger scale rock slope deformations. The investigations are conducted by the DFG- joint research project PROSA (High-resolution measurements of morphodynamics in rapidly changing PROglacial Systems of the Alps). Our LiDAR data as well as field observations are showing enhanced rock fall activity at the scarp in the last years which is assumed to be the consequence of an activation of a larger deep

  10. Adjustment of Submarine Channel Architecture to Changes in Sediment Supply, Western Niger Delta Slope

    NASA Astrophysics Data System (ADS)

    Jobe, Z. R.; Sylvester, Z.; Parker, A. O.; Pirmez, C.; Slowey, N. C.

    2013-12-01

    Three-dimensional seismic, piston cores, and autonomous underwater vehicle data (chirp sub-bottom profiles, multibeam bathymetry, and sidescan sonar) provide a multi-scale dataset used to examine the evolution of a submarine channel system on the western Niger Delta continental slope. Four phases of channel evolution are documented that are interpreted to relate to changes in the sediment routing system. The first phase is incisional and creates a large valley within which the subsequent phases evolve. The second phase records the development of sinuosity through lateral accretion of the meander bends. Meander cutoffs and channel-bank mass wasting result in terraced and scalloped channel margins. This phase is volumetrically most significant in terms of channel fill. The third phase is characterized by thalweg aggradation with slight channel narrowing; preferential deposition towards the outer banks results in a reduction of sinuosity. This phase likely reflects the updip abandonment of the channel system. The fourth phase is characterized by inner levee deposition that occurs primarily on outer banks, causing a reduction in channel width and sinuosity. These changes are caused by the capture of a small slope channel that is the source for underfit flows that attempt to adjust the channel cross section and thalweg gradient through inner levee deposition. Chirp sub-bottom profiles and piston core data reveal that these sigmoidal inner levees consist of thin-bedded, ripple-laminated turbidites interbedded with mudstones. The channel thalweg consists of amalgamated, sand-rich turbidites with dune-scale bedforms and occasional mass transport deposits. Core transects taken across the channel demonstrate that sand bed thickness decreases with height above the channel thalweg. Laser particle size analyzer data indicate a progressive decrease in grain size with height above the channel thalweg. These vertical trends in grain size and bed thickness distribution are used to

  11. Mercury in sediments from shelf and continental slope at Campos Basin near Rio de Janeiro, Brazil

    NASA Astrophysics Data System (ADS)

    Araujo, Beatriz; Hintelmann, Holger; Dimock, Brian; Gomes de Almeida, Marcelo; Falcão, Ana Paula; de Rezende, Carlos Eduardo

    2016-04-01

    Mercury (Hg) is a global pollutant due to its ability to undergo long-range transport from source regions to remote parts of the world, and its ubiquitous presence in aquatic ecosystems. The Hg isotope ratios could be an effective tool for tracing the sources and process of Hg in the environment. This study aimed to establish the distribution of mercury in surface sediments of three transects (25- 3000m water depth) in continental shelf and slope in Campos Basin-RJ-Brazil, using the Hg isotopes to understand the geochemical processes relating to Hg cycling that occur in a subtropical coastal environment. The study area was divided into three transects: A (located to the south and close to a upwelling area), D (located opposite the mouth of the Paraiba do Sul River) and I (located north near the top of Vitória-ES). Sampling isobaths were 25, 50, 75, 100, 150, 400, 700, 1000, 1300, 1900, 2500 and 3000m. The Total Hg, MMHg and Hg stable isotopes were determined based on EPA Method 1631, EPA method 1630 and Foucher and Hintelmann (2006), respectively. The silt/clay ranged from 0.05 to 95%, and the organic carbon (OC) from 0.07 to 1.43 % for all transects. THg and MMHg concentrations in the shelf were 11.9 ± 7.2 (1.7- 22.2) ng.g‑1 and 0.15 ± 0.12 (0.02 - 0.40) ng.g‑1; in the slope 30.3 ± 9.2 (11.6 - 51.6) ng.g‑1 and 0.13 ± 0.06 (0.03 -0.29) ng.g‑1 , respectively. The δ202Hg and Δ199Hg varied from -0.32 to -1.85 ‰ (-0.79 ± 0.44‰) and -0.41 to 0.09 ‰ (-0.03 ± 0.12 ‰) for all transects, respectively. The delta values between both regions are significantly different, the shelf region showed δ202Hg from -0.59 to -2.19 ‰ (mean: -1.52 ±0.65) and Δ199Hg from - 0.53 to 0.08 ‰ (mean: -0.27 ±0.55) and the slope region were observed δ202Hg values from -0.32 to -1.82 ‰ (mean: -0.73 ±0.39 ‰ n=18) and gΔ199Hg from -0.23 to 0.09‰ (mean: -0.02 ±0.08‰ n=5). The slope appears to be enriched with heavier isotopes compared to the shelf, however

  12. Mercury in sediments from shelf and continental slope at Campos Basin near Rio de Janeiro, Brazil

    NASA Astrophysics Data System (ADS)

    Araujo, Beatriz; Hintelmann, Holger; Dimock, Brian; Gomes de Almeida, Marcelo; Falcão, Ana Paula; de Rezende, Carlos Eduardo

    2016-04-01

    Mercury (Hg) is a global pollutant due to its ability to undergo long-range transport from source regions to remote parts of the world, and its ubiquitous presence in aquatic ecosystems. The Hg isotope ratios could be an effective tool for tracing the sources and process of Hg in the environment. This study aimed to establish the distribution of mercury in surface sediments of three transects (25- 3000m water depth) in continental shelf and slope in Campos Basin-RJ-Brazil, using the Hg isotopes to understand the geochemical processes relating to Hg cycling that occur in a subtropical coastal environment. The study area was divided into three transects: A (located to the south and close to a upwelling area), D (located opposite the mouth of the Paraiba do Sul River) and I (located north near the top of Vitória-ES). Sampling isobaths were 25, 50, 75, 100, 150, 400, 700, 1000, 1300, 1900, 2500 and 3000m. The Total Hg, MMHg and Hg stable isotopes were determined based on EPA Method 1631, EPA method 1630 and Foucher and Hintelmann (2006), respectively. The silt/clay ranged from 0.05 to 95%, and the organic carbon (OC) from 0.07 to 1.43 % for all transects. THg and MMHg concentrations in the shelf were 11.9 ± 7.2 (1.7- 22.2) ng.g-1 and 0.15 ± 0.12 (0.02 - 0.40) ng.g-1; in the slope 30.3 ± 9.2 (11.6 - 51.6) ng.g-1 and 0.13 ± 0.06 (0.03 -0.29) ng.g-1 , respectively. The δ202Hg and Δ199Hg varied from -0.32 to -1.85 ‰ (-0.79 ± 0.44‰) and -0.41 to 0.09 ‰ (-0.03 ± 0.12 ‰) for all transects, respectively. The delta values between both regions are significantly different, the shelf region showed δ202Hg from -0.59 to -2.19 ‰ (mean: -1.52 ±0.65) and Δ199Hg from - 0.53 to 0.08 ‰ (mean: -0.27 ±0.55) and the slope region were observed δ202Hg values from -0.32 to -1.82 ‰ (mean: -0.73 ±0.39 ‰ n=18) and gΔ199Hg from -0.23 to 0.09‰ (mean: -0.02 ±0.08‰ n=5). The slope appears to be enriched with heavier isotopes compared to the shelf, however, in the

  13. Geotechnical properties and preliminary assessment of sediment stability on the continental slope of the northwestern Alboran Sea

    USGS Publications Warehouse

    Baraza, J.; Ercilla, G.; Lee, H.J.

    1992-01-01

    Laboratory analysis of core samples from the western Alboran Sea slope reveal a large variability in texture and geotechnical properties. Stability analysis suggests that the sediment is stable under static gravitational loading but potentially unstable under seismic loading. Slope failures may occur if horizontal ground accelerations greater than 0.16 g are seismically induced. The, Alboran Sea is an active region, on which earthquakes inducing accelerations big enough to exceed the shear strength of the soft soil may occur. Test results contrast with the apparent stability deduced from seismic profiles. ?? 1992 Springer-Verlag New York Inc.

  14. Glaciated appalachian plateau: till shadows on hills.

    PubMed

    Coates, D R

    1966-06-17

    North slopes are twice as steep as south slopes on the hills of central New York. This asymmetry is caused by unequal till thickness-3.6 meters on north slopes and 27.6 meters on south slopes. Previous workers interpreted the hills as being of bedrock sculptured by glacial erosion, with till 0.9 to 3 meters thick.

  15. The interaction of a vortex ring with a sloped sediment layer: Critical criteria for incipient grain motion

    NASA Astrophysics Data System (ADS)

    Munro, R. J.

    2012-02-01

    Experiments were performed to analyse the interaction between a vortex ring and a sloped sediment layer. Attention focussed on interactions under "critical" conditions, in which sediment motion was only just induced by the ring's flow field. Both hydraulically smooth and hydraulically rough bedforms were analysed, using near-spherical monodisperse sediments with relative densities of 1.2 and 2.5 and mean diameters (dp) ranging between 80 and 1087 μm. Measurements of the vortex-ring flow field were obtained, during the interaction, using two-dimensional particle imaging velocimetry. The threshold conditions for incipient sediment motion were analysed in terms of the critical Shields parameter (Nc), defined in terms of the peak tangential velocity measured adjacent to the bed surface. Bed-slope effects were investigated by tilting the sediment layer at various angles between the horizontal and the repose limit for the sediment. In all cases, the propagation axis of the vortex ring was aligned normal to the bed surface. The measured values of Nc were compared with a force-balance model based on the conditions for incipient grain motion on a sloping bed. For hydraulically smooth bedforms, where the bed roughness is small compared to the boundary-layer depth, the model was derived to account for how viscous stresses affect the drag and lift forces acting on the near surface sediment. For hydraulically rough bedforms, where this viscous-damping effect is not present, the model assumes the drag and lift forces scale with the square of the near-bed (inviscid) velocity scale. In both cases, the model predicts that bedforms become more mobile as the bed slope is increased. However, the damping effect of the viscous sublayer acts as a stabilizing influence for hydraulically smooth bedforms, to reduce the rate at which the bed mobility increases with bed slope. The measured values of Nc were in agreement with the trends predicted by this model, and exhibit a transition in

  16. The biogeochemistry of carbon in continental slope sediments: The North Carolina margin

    SciTech Connect

    Blair, N.; Levin, L.; DeMaster, D.; Plaia, G.; Martin, C.; Fornes, W.; Thomas, C.; Pope, R.

    1999-12-01

    The responses of the continental slope benthos to organic detritus deposition were studied with a multiple trace approach. Study sites were offshore of Cape Fear (I) and Cape Hatteras (III), N.C. (both 850 m water depth) and were characterized by different organic C deposition rates, macrofaunal densities (III>I in both cases) and taxa. Natural abundances of {sup 13}C and {sup 12}C in particulate organic carbon (POC), dissolved inorganic carbon (DIC) and macrofauna indicate that the reactive organic detritus is marine in origin. Natural abundance levels of {sup 14}C and uptake of {sup 13}C-labeled diatoms by benthic animals indicate that they incorporate a relatively young component of carbon into their biomass. {sup 13}C-labeled diatoms (Thalassiorsira pseudonana) tagged with {sup 210}Pb, slope sediment tagged with {sup 113}Sn and {sup 228}Th-labeled glass beads were emplaced in plots on the seafloor at both locations and the plots were sampled after 30 min., 1-1.5 d and 14 mo. At Site I, tracer diatom was intercepted at the surface primarily by protozoans and surface-feeding annelids. Little of the diatom C penetrated below 2 cm even after 14 months. Oxidation of organic carbon appeared to be largely aerobic. At Site III, annelids were primarily responsible for the initial uptake of tracer. On the time scale of days, diatom C was transported to a depth of 12 cm and was found in animals collected between 5-10 cm. The hoeing of tracer from the surface by the maldanid Praxillela sp. may have been responsible for some of the rapid nonlocal transport. Oxidation of the diatom organic carbon was evident to at least 10 cm depth. Anaerobic breakdown of organic matter is more important at Site III. Horizontal transport, which was probably biologically mediated, was an order of magnitude more rapid than vertical displacement over a year time scale. If the horizontal transport was associated with biochemical transformations of the organic matter, it may represent an

  17. Physical properties of sediment from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    USGS Publications Warehouse

    Winters, William J.; Walker, Michael; Hunter, Robert; Collett, Timothy S.; Boswell, Ray M.; Rose, Kelly K.; Waite, William F.; Torres, Marta; Patil, Shirish; Dandekar, Abhijit

    2011-01-01

    This study characterizes cored and logged sedimentary strata from the February 2007 BP Exploration Alaska, Department of Energy, U.S. Geological Survey (BPXA-DOE-USGS) Mount Elbert Gas Hydrate Stratigraphic Test Well on the Alaska North Slope (ANS). The physical-properties program analyzed core samples recovered from the well, and in conjunction with downhole geophysical logs, produced an extensive dataset including grain size, water content, porosity, grain density, bulk density, permeability, X-ray diffraction (XRD) mineralogy, nuclear magnetic resonance (NMR), and petrography. This study documents the physical property interrelationships in the well and demonstrates their correlation with the occurrence of gas hydrate. Gas hydrate (GH) occurs in three unconsolidated, coarse silt to fine sand intervals within the Paleocene and Eocene beds of the Sagavanirktok Formation: Unit D-GH (614.4 m-627.9 m); unit C-GH1 (649.8 m-660.8 m); and unit C-GH2 (663.2 m-666.3 m). These intervals are overlain by fine to coarse silt intervals with greater clay content. A deeper interval (unit B) is similar lithologically to the gas-hydrate-bearing strata; however, it is water-saturated and contains no hydrate. In this system it appears that high sediment permeability (k) is critical to the formation of concentrated hydrate deposits. Intervals D-GH and C-GH1 have average "plug" intrinsic permeability to nitrogen values of 1700 mD and 675 mD, respectively. These values are in strong contrast with those of the overlying, gas-hydrate-free sediments, which have k values of 5.7 mD and 49 mD, respectively, and thus would have provided effective seals to trap free gas. The relation between permeability and porosity critically influences the occurrence of GH. For example, an average increase of 4% in porosity increases permeability by an order of magnitude, but the presence of a second fluid (e.g., methane from dissociating gas hydrate) in the reservoir reduces permeability by more than an

  18. Physical properties of sediment from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    USGS Publications Warehouse

    Winters, W.; Walker, M.; Hunter, R.; Collett, T.; Boswell, R.; Rose, K.; Waite, W.; Torres, M.; Patil, S.; Dandekar, A.

    2011-01-01

    This study characterizes cored and logged sedimentary strata from the February 2007 BP Exploration Alaska, Department of Energy, U.S. Geological Survey (BPXA-DOE-USGS) Mount Elbert Gas Hydrate Stratigraphic Test Well on the Alaska North Slope (ANS). The physical-properties program analyzed core samples recovered from the well, and in conjunction with downhole geophysical logs, produced an extensive dataset including grain size, water content, porosity, grain density, bulk density, permeability, X-ray diffraction (XRD) mineralogy, nuclear magnetic resonance (NMR), and petrography.This study documents the physical property interrelationships in the well and demonstrates their correlation with the occurrence of gas hydrate. Gas hydrate (GH) occurs in three unconsolidated, coarse silt to fine sand intervals within the Paleocene and Eocene beds of the Sagavanirktok Formation: Unit D-GH (614.4. m-627.9. m); unit C-GH1 (649.8. m-660.8. m); and unit C-GH2 (663.2. m-666.3. m). These intervals are overlain by fine to coarse silt intervals with greater clay content. A deeper interval (unit B) is similar lithologically to the gas-hydrate-bearing strata; however, it is water-saturated and contains no hydrate.In this system it appears that high sediment permeability (k) is critical to the formation of concentrated hydrate deposits. Intervals D-GH and C-GH1 have average "plug" intrinsic permeability to nitrogen values of 1700 mD and 675 mD, respectively. These values are in strong contrast with those of the overlying, gas-hydrate-free sediments, which have k values of 5.7. mD and 49 mD, respectively, and thus would have provided effective seals to trap free gas. The relation between permeability and porosity critically influences the occurrence of GH. For example, an average increase of 4% in porosity increases permeability by an order of magnitude, but the presence of a second fluid (e.g., methane from dissociating gas hydrate) in the reservoir reduces permeability by more than

  19. Recent seasonal hypoxia on the Western Black Sea shelf recorded in adjacent slope sediments

    NASA Astrophysics Data System (ADS)

    Roepert, Anne; Jilbert, Tom S.; Slomp, Caroline P.

    2015-04-01

    Bottom water hypoxia is a major environmental problem afflicting estuarine and marine environments across the globe (Diaz and Rosenberg, 2008). Hypoxia is often attributed to human-induced increased nutrient discharge from rivers and related eutrophication. The Western Black Sea shelf is a typical example of a system where such anthropogenic impacts are thought to have contributed to the development of seasonal hypoxia in the late 20th century. However, due to the lack of spatially and temporally consistent monitoring in the region, questions remain about the evolution, causes and consequences of the seasonal hypoxia on the Western Black Sea shelf and whether or not the ecological state has recently improved (Capet et al., 2013). In this study a resin-embedded sediment core from a location below the chemocline on the Western Black Sea slope (water depth 377 m) was analyzed for its elemental composition by means of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), recovering a continuous geochemical record at a sub-annual resolution for the last 100 years. Relative enrichments in organic carbon, Pb, Fe, S, and Mo were observed in the depth interval corresponding to the 1970s until the 1990s, suggesting an increased carbon flux to the sediments as well as an anthropogenic pollution signal. We propose that the expansion of eutrophication on the Western Black Sea shelf was responsible for the enhanced carbon flux to our study site, while the associated hypoxia enhanced the shuttling of redox-sensitive elements to locations below the chemocline. The subsequent decrease in organic carbon and metal enrichments at the core top suggests a recent rise in oxygen concentrations and improvement of the ecological state of the Western Black Sea shelf. References: Capet, A., Beckers, J.-M., Grégoire, M. (2013). "Drivers, mechanisms and long-term variability of seasonal hypoxia on the Black Sea northwestern shelf-is there any recovery after eutrophication

  20. Provenance and depositional history of continental slope sediments in the Southwestern Gulf of Mexico unraveled by geochemical analysis

    NASA Astrophysics Data System (ADS)

    Armstrong-Altrin, John S.; Machain-Castillo, María Luisa; Rosales-Hoz, Leticia; Carranza-Edwards, Arturo; Sanchez-Cabeza, Joan-Albert; Ruíz-Fernández, Ana Carolina

    2015-03-01

    The aim of this work is to constrain the provenance and depositional history of continental slope sediments in the Southwestern Gulf of Mexico (~1089-1785 m water depth). To achieve this, 10 piston sediment cores (~5-5.5 m long) were studied for mineralogy, major, trace and rare earth element geochemistry. Samples were analyzed at three core sections, i.e. upper (0-1 cm), middle (30-31 cm) and lower (~300-391 cm). The textural study reveals that the core sediments are characterized by silt and clay fractions. Radiocarbon dating of sediments for the cores at different levels indicated a maximum of ~28,000 year BP. Sediments were classified as shale. The chemical index of alteration (CIA) values for the upper, middle, and lower sections revealed moderate weathering in the source region. The index of chemical maturity (ICV) and SiO2/Al2O3 ratio indicated low compositional maturity for the core sediments. A statistically significant correlation observed between total rare earth elements (∑REE) versus Al2O3 and Zr indicated that REE are mainly housed in detrital minerals. The North American Shale Composite (NASC) normalized REE patterns, trace element concentrations such as Cr, Ni and V, and the comparison of REE concentrations in sediments and source rocks indicated that the study area received sediments from rocks intermediate between felsic and mafic composition. The enrichment factor (EF) results indicated that the Cd and Zn contents of the upper section sediments were influenced by an anthropogenic source. The trace element ratios and authigenic U content of the core sediments indicated the existence of an oxic depositional environment.

  1. Detrital magnetite and chromite in Jack Hills quartzite cobbles: Further evidence for the preservation of primary magnetizations and new insights into sediment provenance

    NASA Astrophysics Data System (ADS)

    Dare, Matthew S.; Tarduno, John A.; Bono, Richard K.; Cottrell, Rory D.; Beard, James S.; Kodama, Kenneth P.

    2016-10-01

    The magnetization of zircons from sedimentary rocks of the Jack Hills (Yilgarn Craton, Western Australia) provide evidence for a Hadean to Paleoarchean geodynamo, 4.0 to 4.2 billion years old. These magnetizations pass a microconglomerate test, attesting to the fidelity of Jack Hills zircons as recorders of these most ancient magnetic signals. The lack of pervasive remagnetization of the Jack Hills is also documented through a positive conglomerate test conducted on cobble-sized clasts. A key element of the latter test is the preservation of a high unblocking temperature magnetization that can survive peak metamorphic temperatures. Rock magnetic studies suggest the mineral carrier is magnetite. Herein, we investigate the magnetic mineral carriers in cobble samples through scanning electron microscope and microprobe analyses, conduct an inter-laboratory paleomagnetic study to evaluate sensitivities required to evaluate the weak magnetizations carried by the Jack Hills sediments, and assess provenance information constrained by the opaque minerals. These data confirm magnetite as a detrital phase and the presence of high unblocking temperature magnetizations, further supporting the posit that the Jack Hills sediments can preserve primary magnetic signatures. We note that some of these magnetizations are near the measurement resolution of standard cryogenic magnetometers and thus exacting laboratory procedures are required to uncover these signals. In addition to magnetite, the cobbles contain an assemblage of Mg poor Cr-Fe chromites, Ni-sulfides and pyrrhotite that suggest a source in a layered intrusion different from the granitoid source of the zircons. Any Hadean rock fragment in these sediments, if present, remains elusive.

  2. Revised Ages for Laminated Sediment and a Holocene-Marker Diatom from the Northern California Continental Slope

    USGS Publications Warehouse

    Hemphill-Haley, E.; Gardner, J.V.

    1994-01-01

    Conventional and accelerator mass spectrometry 14C ages indicate that laminated sediment in three cores from the northern California continental slope near 38??N and 39??N were deposited between 42,000 and 25,000 yr B.P. This revises and refines our previous estimates that laminated sediment accumulated during the late Pleistocene to early Holocene (J. V. Gardner and E. Hemphill-Haley, 1986, Geology 14, 691-694). Preservation of laminated sediment on the upper slope in this area suggests a period of intense coastal upwelling, high primary productivity, and resultant depletion of oxygen in bottomwaters preceding the onset of global glacial conditions. The transition from Pleistocene to Holocene conditions, and the establishment of a modern climatic regime driven by the California Current, included the incursion of the subtropical diatom, Pseudoeunotia doliola. P. doliola is common in sediment younger than about 10,000 yr and thus is a reliable marker species for identifying Holocene deposits off northern California.

  3. C:N:P Molar Ratios, Sources and 14C Dating of Surficial Sediments from the NW Slope of Cuba

    PubMed Central

    de la Lanza Espino, Guadalupe; Soto, Luis A.

    2015-01-01

    The surficial sediments recovered from 12 sites located near the channel axis of the Florida Straits and the lower slope off NW Cuba were analyzed for total organic carbon (TOC), nitrogen (TN), phosphorus (TP), elemental C:N:P ratios, C and N isotopic values, and 14C dating. The depth profiles of TOC, TN, and TP (0-18 cm) displayed a downcore trend and a significant variation. The TOC values were low (0.15 to 0.62%; 66 to 516 µmol g-1). Sites near the island’s lower slope had lower TOC average concentrations (158-333 µmol g-1) than those closer to the channel axis (averaging 341-516 µmol g-1; p <0.05). The TN concentrations near the lower slope attained 0.11% (80 µmol g-1), whereas, towards the channel axis, they decreased to 0.07% (55 µmol g-1; p<0.05). The C:N ratios ranged from 1.9 to 10.2. The mean molar C:N ratio (5.4) indicated a marine hemipelagic deposition. The TP was lower at sites near the lower slope (38.4 to 50.0 µmol g-1; 0.12% to 0.16%) than those near the channel axis (50.0 to 66 µmol g-1; 0.15 to 0.21%). C:P fluctuated from 7.7 to 14.1 in the surficial sediment layer. The bulk organic δ13Corg and δ15N values confirmed pelagic organic sources, and the 14C dating revealed that the sediments were deposited during the Holocene (1000-5000 yr BP). We suggest that the hydrodynamic conditions in the Straits influence vertical and advective fluxes of particulate organic material trapped in the mixed-layer, which reduces the particulate matter flux to the seabed. PMID:26110791

  4. C:N:P Molar Ratios, Sources and 14C Dating of Surficial Sediments from the NW Slope of Cuba.

    PubMed

    de la Lanza Espino, Guadalupe; Soto, Luis A

    2015-01-01

    The surficial sediments recovered from 12 sites located near the channel axis of the Florida Straits and the lower slope off NW Cuba were analyzed for total organic carbon (TOC), nitrogen (TN), phosphorus (TP), elemental C:N:P ratios, C and N isotopic values, and 14C dating. The depth profiles of TOC, TN, and TP (0-18 cm) displayed a downcore trend and a significant variation. The TOC values were low (0.15 to 0.62%; 66 to 516 µmol g(-1)). Sites near the island's lower slope had lower TOC average concentrations (158-333 µmol g(-1)) than those closer to the channel axis (averaging 341-516 µmol g(-1); p <0.05). The TN concentrations near the lower slope attained 0.11% (80 µmol g(-1)), whereas, towards the channel axis, they decreased to 0.07% (55 µmol g(-1); p<0.05). The C:N ratios ranged from 1.9 to 10.2. The mean molar C:N ratio (5.4) indicated a marine hemipelagic deposition. The TP was lower at sites near the lower slope (38.4 to 50.0 µmol gv; 0.12% to 0.16%) than those near the channel axis (50.0 to 66 µmol g(-1); 0.15 to 0.21%). C:P fluctuated from 7.7 to 14.1 in the surficial sediment layer. The bulk organic δ13Corg and δ15N values confirmed pelagic organic sources, and the 14C dating revealed that the sediments were deposited during the Holocene (1000-5000 yr BP). We suggest that the hydrodynamic conditions in the Straits influence vertical and advective fluxes of particulate organic material trapped in the mixed-layer, which reduces the particulate matter flux to the seabed.

  5. Effects of gravel on infiltration, runoff, and sediment yield in landslide deposit slope in Wenchuan earthquake area, China.

    PubMed

    Li, Tianyang; He, Binghui; Chen, Zhanpeng; Zhang, Yi; Liang, Chuan; Wang, Renxin

    2016-06-01

    Amounts of landslide deposits were triggered by the Wenchuan earthquake with magnitude 8.0 on May 12, 2008. The landslide deposits were composed of soil and rock fragments, which play important roles in hydrological and erosion processes in the steep slope of landslide deposits. The mixtures of soil and gravels are common in the top layers of landslide deposits, and its processes are obviously different with the soil without gravels. Based on the data of field investigation, a series of simulated scouring flow experiments with four proportion of gravel (0, 25, 33.3, and 50 %) and three scouring flow rates (4, 8, 12 L/min) under two steep slopes (67.5, 72.7 %) were conducted sequentially to know the effects of proportion of gravel on infiltration capacity, runoff generation, and sediment production in the steep slope of landslide deposit. Results indicated that gravel had promoted or reduced effects on infiltration capacity which could affect further the cumulative runoff volume and cumulative sediment mass increase or decrease. The cumulative infiltration volume in 25 % proportion of gravel was less than those in 0, 33.3, and 50 % proportion of gravel. The cumulative runoff volume was in an order of 25 > 0 > 33.3 > 50 % while cumulative sediment mass ranked as 25 > 33.3 > 0 > 50 % with different proportions of gravel. A significant power relationship was found between scouring time and cumulative runoff volume as well as cumulative sediment mass. The relationship between average soil and water loss rate and proportion of gravel was able to express by quadratic function, with a high degree of reliability. The results have important implications for soil and water conservation and modeling in landslide deposit but also provide useful information for the similar conditions.

  6. Effects of gravel on infiltration, runoff, and sediment yield in landslide deposit slope in Wenchuan earthquake area, China.

    PubMed

    Li, Tianyang; He, Binghui; Chen, Zhanpeng; Zhang, Yi; Liang, Chuan; Wang, Renxin

    2016-06-01

    Amounts of landslide deposits were triggered by the Wenchuan earthquake with magnitude 8.0 on May 12, 2008. The landslide deposits were composed of soil and rock fragments, which play important roles in hydrological and erosion processes in the steep slope of landslide deposits. The mixtures of soil and gravels are common in the top layers of landslide deposits, and its processes are obviously different with the soil without gravels. Based on the data of field investigation, a series of simulated scouring flow experiments with four proportion of gravel (0, 25, 33.3, and 50 %) and three scouring flow rates (4, 8, 12 L/min) under two steep slopes (67.5, 72.7 %) were conducted sequentially to know the effects of proportion of gravel on infiltration capacity, runoff generation, and sediment production in the steep slope of landslide deposit. Results indicated that gravel had promoted or reduced effects on infiltration capacity which could affect further the cumulative runoff volume and cumulative sediment mass increase or decrease. The cumulative infiltration volume in 25 % proportion of gravel was less than those in 0, 33.3, and 50 % proportion of gravel. The cumulative runoff volume was in an order of 25 > 0 > 33.3 > 50 % while cumulative sediment mass ranked as 25 > 33.3 > 0 > 50 % with different proportions of gravel. A significant power relationship was found between scouring time and cumulative runoff volume as well as cumulative sediment mass. The relationship between average soil and water loss rate and proportion of gravel was able to express by quadratic function, with a high degree of reliability. The results have important implications for soil and water conservation and modeling in landslide deposit but also provide useful information for the similar conditions. PMID:26965277

  7. Fluvial Discharge Rates of Martian Gullies: Slope Measurements From Stereo HiRISE Images and Numerical Modeling of Sediment Transport

    NASA Astrophysics Data System (ADS)

    Parsons, R. A.; Nimmo, F.; Kreslavsky, M.

    2008-12-01

    Using a stereo pair of HiRISE images of a crater slope incised by fourteen gullies at -37.86 N, 217.92 E we calculate relative elevation changes between pairs of hand-selected points. Using the method of Kreslavsky [1]. The background slope on which the gullies are located has a slope of 22 degrees. Out of the five gullies we analyzed, all show a steadily decreasing slope from an average of 30 ± 4 degrees at the alcove to 16 ± 2 degrees at the apron. These measurements are in agreement with previous gully slope measurements done at MOLA resolution in a different region [2]. The slope beyond the base of the gully aprons is 4±1 degrees. The depth of alcove incision in nine of the gullies is 17±8.5~m. We take advantage of this slope and incision data to determine the evolution of a one-dimensional gully profile over time with a 1D sediment transport model [3]. The shear stress applied to the channel bed by flowing water is τ = ρ g h sinθ where h is the channel depth, g is gravity, and h is the channel depth. The rate of transport is non-linearly related to τ/τrg where the reference stress for a gravel bed is τrg = 0.035 ( (s-1)ρ g Dg ) where s is the ratio of sediment to water density, ρ is 1000~m3, and Dg is the sediment grainsize. The two significant unknowns in applying the theory to Martian gullies are the sediment grainsize and channel depth. We ran simulations for various channel depths and grainsizes to get a range of water discharges and simulation times that result in alcoves 25~m deep. Erosion is rapid due to the high slopes; incision rates decrease with decreasing channel depth and increasing grainsize. For grains 20~cm in diameter and a conservatively low channel depth of 20~cm, alcove incision occurs over a 5~h period, discharging a volume of 8500 m3 of water. These discharges assume a 1~m wide channel and a constant, bank-full discharge over the duration of the simulation. Gullies are spaced about every 500~m along the slope. If liquid water

  8. Sediment transport to the deep canyons and open-slope of the western Gulf of Lions during the 2006 intense cascading and open-sea convection period

    NASA Astrophysics Data System (ADS)

    Palanques, A.; Puig, P.; Durrieu de Madron, X.; Sanchez-Vidal, A.; Pasqual, C.; Martín, J.; Calafat, A.; Heussner, S.; Canals, M.

    2012-11-01

    An array of mooring lines deployed between 300 and 1900 m depth along the Lacaze-Duthiers and Cap de Creus canyons and in the adjacent southern open slope was used to study the water and sediment transport on the western Gulf of Lions margin during the 2006 intense cascading period. Deep-reaching cascading pulses occurred in early January, in late January and from early March to mid-April. Dense water and sediment transport to the deep environments occurred not only through submarine canyons, but also along the southern open slope. During the deep cascading pulses, temporary upper and mid-canyon and open slope deposits were an important source of sediment to the deep margin. Significant sediment transport events at the canyon head only occurred in early January because of higher sediment availability on the shelf after the stratified and calm season, and in late February because of the interaction of dense shelf water cascading with a strong E-SE storm. During the January deep cascading pulses, increases in suspended sediment concentration within the canyon were greater and earlier at 1000 m depth than at 300 m depth, whereas during the March-April deep cascading pulses sediment concentration only increased below 300 m depth, indicating resuspension and redistribution of sediments previously deposited at upper and mid-canyon depths. Deeper than 1000 m depth, net fluxes show that most of the suspended sediment left the canyon and flowed along the southern open slope towards the Catalan margin, whereas a small part flowed down-canyon and was exported basinward. Additionally, on the mid- and lower-continental slope there was an increase in the near-bottom currents induced by deep open-sea convection processes and the propagation of eddies. This, combined with the arrival of deep cascading pulses, also generated moderate suspended sediment transport events in the deeper slope regions.

  9. Shear strength, cohesion, and overconsolidation in low-stress sediments and their importance for submarine slope failure

    NASA Astrophysics Data System (ADS)

    Ikari, M.; Kopf, A.

    2015-12-01

    Factor-of-safety analyses of submarine slope failure depend critically on the shear strength of the slope material, which has two components: friction and cohesion. While evaluating friction is from laboratory testing is common, cohesion is commonly ignored despite its potential importance in resisting failure. Here, we report on laboratory experiments conducted at effective normal stresses of < 2 MPa where we measure shear strength, but and also directly measure sediment cohesion by measuring its shear strength in a direct-shear apparatus by removing the applied effective normal stress (σn' = 0). We document systematic behavior demonstrating that cohesion depends positively on clay mineral content and consolidation stress. The dependence on clay content suggests that the mechanism of cohesion is hydrogen bonding between charged clay surfaces and water molecules. The stress dependence indicates that estimating cohesion from extrapolating a Coulomb-Mohr failure envelope could lead to inaccurate predictions. Furthermore, the proportion of shear strength attributable to cohesion is higher at lower stresses corresponding to shallow depths where landslide failures are expected. Measuring shear strength and cohesion over a wide range of overconsolidation ratios (OCR) for sediments containing clays show that significantly higher peak strengths are expected to occur for OCR > 4, and the primary source of this strength increase is not friction, but rather increased cohesion which depends log-linearly on the OCR. Our data suggest that in areas which have experienced unroofing due previous mass movements, overconsolidated clays can be stronger than cohesionless sediments such as quartz silt/sand. Overconsolidated clays would exhibit increased peak strength toward the surface, therefore failure would be expected to occur deeper where the OCR is lower. In seismically active areas, this could explain why slope failure recurrence appears to be lower than expected when

  10. An evaluation of along- and down-slope sediment transport processes between Goban Spur and Brenot Spur on the Celtic Margin of the Bay of Biscay

    NASA Astrophysics Data System (ADS)

    Cunningham, M. J.; Hodgson, S.; Masson, D. G.; Parson, L. M.

    2005-08-01

    Multi-beam bathymetry and backscatter, 3.5 kHz pinger profiles, side-scan sonar and seabed samples have been examined to evaluate along- and down-slope sedimentary processes along the Celtic Margin shelf and upper slope in water depths of 200 to 1500 m. The continental shelf and slope are indented and dissected by major canyon systems. The shelf is characterised by major northeast-southwest trending sand banks that are orthogonal to the shelf edge. Along the shelf edge, several fields of asymmetric sandwaves oriented orthogonal to the canyon axes indicate sediment transport into the canyon heads. Less commonly, sandwaves with weak asymmetry suggest sediment transport onto the shelf. These may be reworked and are partly overprinted by more recent sandwaves. Down-slope sediment transport by turbidity currents is the dominant process through the major canyons. Recent faulting has also played a role in canyon development. Turbidity currents are most likely initiated by faulting, and/or slope failure of the walls that bound the canyon head drainage basins and sediment migration from the shelf. This leads to deep incision of sinuous thalwegs in the upper reaches of canyon floors and downcutting and sediment transport on the mid to lower continental slope. The canyons are V-shaped in the upper reaches and become U-shaped progressively down-slope, suggesting they represent either a transition from erosive to depositional processes or sediment bypass conduits carrying sediment between the shelf and abyssal plain. Over-bank spill from canyons leads to deposition of unconfined turbidite deposits (muds) on the intervening canyon spurs.

  11. The effect of DEM resolution on slope estimation and sediment predictions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Moderate resolution (30 m) digital elevation models (DEMs) are normally used to estimate slope for the parameterization of non-point source process-based water quality models. These models, such as the Soil and Water Assessment Tool (SWAT), utilize the Modified Universal Soil Loss Equation (MUSLE) ...

  12. Simulation of long-term debris flow sediment transport based on a slope stability and a debris flow routing model

    NASA Astrophysics Data System (ADS)

    Müller, T.; Hoffmann, T.

    2012-04-01

    Debris flows play a crucial role in the coupling of hillslope-sediment sources and channels in mountain environments. In most landscape evolution models (LEMs), the sediment transport by debris flows is (if at all) often represented by simple empirical rules. This generally results from the mismatch of the coarse resolution of the LEMs and the small scale impacts of debris flow processes. To extend the accuracy and predictive power of LEMs, either a higher resolution of LEMs in combination with process-based debris flow models or a better parametrisation of subpixel scale debris flow processes is necessary. Furthermore, the simulation of sediment transport by debris flows is complicated by their episodic nature and unknown factors controlling the frequency and magnitude of events. Here, we present first results using a slope stability model (SINMAP) and an event-based debris flow routing model (SCIDDICA-S4c) to simulate the effects of debris flows in LEMs. The model was implemented in the XULU modelling platform developed by the Department of Computer Science at the University of Bonn. The combination of the slope stability model and the event-based routing and mass balance model enables us to simulate the triggering and routing of debris flow material through the iteration of single events over several thousand years. Although a detailed calibration and validation remains to be done, the resulting debris flow-affected areas in a test elevation model correspond well with data gained from a geomorphological mapping of the corresponding area, justifying our approach. The increased computation speed allows to run high resolution LEM in convenient short time at relatively low cost. This should encourage the development of more detailed LEMs, in which process-based models should be incorporated.

  13. Late Cretaceous to early Tertiary deltaic to marine sedimentation, North Slope, Alaska

    SciTech Connect

    Phillips, R.L.

    1987-05-01

    Along the lower Colville River near Ocean Point, Alaska, Late Cretaceous to early Tertiary sediments (Colville Group and the Sagavanirktok Formation) record depositional environments from delta plain to prograding delta to shallow marine shelf. The unit hosts the northernmost known dinosaur remains and is less than 100 m thick with numerous tephra deposits in its lower sections. Furthermore, it is characterized by cyclic, relatively fine-grained sediments indicating mostly depositional and few erosional events. The major depositional elements of the delta plain are 3.5 to 5.45-m thick tabular fining-upward cycles that are cut by sand-filled fluvial channels (up to 10 m thick). The cyclic sediments contain abundant roots and grade upward from small-scale cross-beds to laminated and then structureless silt and clay terminating in organic-rich layers. The channel-fill sequences fine upward and change vertically from large to small-scale cross-beds. Over-bank flooding as well as lateral migration of small meandering fluvial channels formed the cyclically interbedded deposits, meandering rivers deposited the thick cross-bedded sands, and soil development or marsh deposits formed the organic-rich horizons that cap each cycle. Plant debris, nonmarine invertebrates, and vertebrate fossils are locally concentrated in the delta plain sediments. Subsidence related to compaction of the deltaic sediments along with possible delta lobe switching resulted in repeated progradation of the delta front over the delta plain. Delta front sediments are 3 to 10-m thick tabular deposits of large and small-scale cross-bedded sands and silt bounded by organic-rich beds. Also, there are abundant roots, rare channels and invertebrate fossils that suggest a transitional environment from sand-flats to estuarine or bay.

  14. Reprint of: Assessment of the use of sediment fences for control of erosion and sediment phosphorus loss after potato harvesting on sloping land.

    PubMed

    Vinten, A J A; Loades, K; Addy, S; Richards, S; Stutter, M; Cook, Y; Watson, H; Taylor, C; Abel, C; Baggaley, N; Ritchie, R; Jeffrey, W

    2014-01-15

    In humid temperate areas, after harvest of potatoes, it is difficult to prevent soil erosion and diffuse pollution. In some autumn weather conditions, in-field mitigation such as cultivation or sowing are not possible, while edge of field measures can be costly and inflexible. We have assessed the potential of modified sediment fences, widely used on building sites, for erosion mitigation post-harvest of potato crops. Field scale assessments were conducted on fields in the Lunan catchment, eastern Scotland. Sediment retention was estimated by two methods: a topographic survey method using a hand held Real Time Kinematic Global Positioning System (RTK-GPS), and direct measurement of sediment depth using a graduated cane. In the 2010/11 trial the main fence comprised 70 m of entrenched fine mesh (0.25 mm) and coarser mesh (4mm) fabric pinned to a contour fence near the base of the field. This retained an estimated 50.9 m(3) (80.2 tonnes) of sediment, with weighted mean total P (TP) content of 0.09 % in the<2mm soil fraction. In the 2011/12 trial, the main 146 m fence was of intermediate mesh size (1.2mm). The fence was partitioned into nine upslope plots, with 3 replicates of each of 3 cultivation methods: T1 (full grubbing--a light, tined cultivator), T2 (partial grubbing) and T3 (no grubbing). Average plot slopes ranged from 9.9 to 11.0 %. The amounts of TP accumulating as sediment at the fences were: 9.3 (sd=7.8), 11.8 (sd=10.2) and 25.7 (sd=5.8)kg P/ha of upslope plot for the T1, T2 and T3 treatments respectively.

  15. Assessment of the use of sediment fences for control of erosion and sediment phosphorus loss after potato harvesting on sloping land.

    PubMed

    Vinten, A J A; Loades, K; Addy, S; Richards, S; Stutter, M; Cook, Y; Watson, H; Taylor, C; Abel, C; Baggaley, N; Ritchie, R; Jeffrey, W

    2014-01-15

    In humid temperate areas, after harvest of potatoes, it is difficult to prevent soil erosion and diffuse pollution. In some autumn weather conditions, in-field mitigation such as cultivation or sowing are not possible, while edge of field measures can be costly and inflexible. We have assessed the potential of modified sediment fences, widely used on building sites, for erosion mitigation post-harvest of potato crops. Field scale assessments were conducted on fields in the Lunan catchment, eastern Scotland. Sediment retention was estimated by two methods: a topographic survey method using a hand held Real Time Kinematic Global Positioning System (RTK-GPS), and direct measurement of sediment depth using a graduated cane. In the 2010/11 trial the main fence comprised 70 m of entrenched fine mesh (0.25 mm) and coarser mesh (4mm) fabric pinned to a contour fence near the base of the field. This retained an estimated 50.9 m(3) (80.2 tonnes) of sediment, with weighted mean total P (TP) content of 0.09 % in the<2mm soil fraction. In the 2011/12 trial, the main 146 m fence was of intermediate mesh size (1.2mm). The fence was partitioned into nine upslope plots, with 3 replicates of each of 3 cultivation methods: T1 (full grubbing--a light, tined cultivator), T2 (partial grubbing) and T3 (no grubbing). Average plot slopes ranged from 9.9 to 11.0 %. The amounts of TP accumulating as sediment at the fences were: 9.3 (sd = 7.8), 11.8 (sd = 10.2) and 25.7 (sd = 5.8)kg P/ha of upslope plot for the T1, T2 and T3 treatments respectively.

  16. Spatial and temporal patterns of off-slope sediment delivery for small catchments subject to shallow landslides within the Waipaoa catchment, New Zealand

    NASA Astrophysics Data System (ADS)

    Jones, Katie E.; Preston, Nicholas J.

    2012-03-01

    The Waipaoa catchment in New Zealand has one of the highest measured specific suspended sediment yields measured in New Zealand compared to basins of comparable size. A significant source of this sediment is from shallow landslides which are often triggered on a regional scale during large magnitude storm events, defined as ~ 200 mm rainfall within 72 h. The first step of this sediment cascade is removal of landslide material from the slope and into the fluvial system when the debris tail is in physical contact and hence considered connected. The difference between the volume of sediment liberated in the event and the volume remaining on the slope immediately following the event is termed the off-slope sediment delivery ratio. This value ranged from 0.12 to 0.28 for small sub-catchments within the Waipaoa catchment depending on catchment morphology, landslide and triggering event characteristics. In the Waipaoa catchment a decrease in the catchment sediment delivery ratio is observed as the sub-catchment size increased. A human induced process which may affect off-slope sediment delivery is regolith exhaustion, as scars move further upslope in response to removal of preferred weathered material during previous events on the lower sections of slope. However, it appears that temporal scar migration away from the channels is not prevalent. Therefore, the hypothesis that hillslope relaxation since deforestation is prevalent in this setting is considered null. Rather the temporal pattern to sediment delivery ratios supports the context of evolving catchment in response to deforestation in the Terrain Event Resistance Model.

  17. Vertical and lateral flux on the continental slope off Pakistan: correlation of sediment core and trap results

    NASA Astrophysics Data System (ADS)

    Schulz, H.; von Rad, U.

    2014-06-01

    Due to the lack of bioturbation, the varve-laminated muds from the oxygen minimum zone (OMZ) off Pakistan provide a unique opportunity to precisely determine the vertical and lateral sediment fluxes in the nearshore part of the northeastern Arabian Sea. West of Karachi (Hab area), the results of two sediment trap stations (EPT and WPT) were correlated with 16 short sediment cores on a depth transect crossing the OMZ. The top of a distinct, either reddish- or light-gray silt layer, 210Pb-dated as AD 1905 ± 10, was used as an isochronous stratigraphic marker bed to calculate sediment accumulation rates. In one core, the red and gray layer were separated by a few (5-10) thin laminae. According to our varve model, this contributes < 10 years to the dating uncertainty, assuming that the different layers are almost synchronous. We directly compared the accumulation rates with the flux rates from the sediment traps that collected the settling material within the water column above. All traps on the steep Makran continental slope show exceptionally high, pulsed winter fluxes of up to 5000 mg m-2 d-1. Based on core results, the flux at the seafloor amounts to 4000 mg m-2 d-1 and agrees remarkably well with the bulk winter flux of material, as well as with the flux of the individual bulk components of organic carbon, calcium carbonate and opal. However, due to the extreme mass of remobilized matter, the high winter flux events exceeded the capacity of the shallow traps. Based on our comparisons, we argue that high-flux events must occur regularly during winter within the upper OMZ off Pakistan to explain the high accumulations rates. These show distribution patterns that are a negative function of water depth and distance from the shelf. Some of the sediment fractions show marked shifts in accumulation rates near the lower boundary of the OMZ. For instance, the flux of benthic foraminifera is lowered but stable below ~1200-1300 m. However, flux and sedimentation in the

  18. Geomorphological features in the southern Canary Island Volcanic Province: The importance of volcanic processes and massive slope instabilities associated with seamounts

    NASA Astrophysics Data System (ADS)

    Palomino, Desirée; Vázquez, Juan-Tomás; Somoza, Luis; León, Ricardo; López-González, Nieves; Medialdea, Teresa; Fernández-Salas, Luis-Miguel; González, Francisco-Javier; Rengel, Juan Antonio

    2016-02-01

    The margin of the continental slope of the Volcanic Province of Canary Islands is characterised by seamounts, submarine hills and large landslides. The seabed morphology including detailed morphology of the seamounts and hills was analysed using multibeam bathymetry and backscatter data, and very high resolution seismic profiles. Some of the elevation data are reported here for the first time. The shape and distribution of characteristics features such as volcanic cones, ridges, slides scars, gullies and channels indicate evolutionary differences. Special attention was paid to recent geological processes that influenced the seamounts. We defined various morpho-sedimentary units, which are mainly due to massive slope instability that disrupt the pelagic sedimentary cover. We also studied other processes such as the role of deep bottom currents in determining sediment distribution. The sediments are interpreted as the result of a complex mixture of material derived from a) slope failures on seamounts and submarine hills; and b) slides and slumps on the continental slope.

  19. Bacterial and archaeal communities in the surface sediment from the northern slope of the South China Sea*

    PubMed Central

    Liao, Li; Xu, Xue-wei; Wang, Chun-sheng; Zhang, Dong-sheng; Wu, Min

    2009-01-01

    Microbial diversity of sediments from the northern slope of the South China Sea was studied by constructing bacterial and archaeal 16S rRNA gene clone libraries. Fourteen bacterial phylogenetic groups were detected, including Gammaproteobacteria, Deltaproteobacteria, Planctomycetes, Alphaproteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, Chloroflexi, Acidobacteria, Betaproteobacteria, Nitrospirae, candidate divisions OP8 and OP11, and an unknown group. Gammaproteobacteria was the predominant group in bacterial libraries with the percentage ranging from 31.8% to 63.2%. However, archaeal libraries had relatively lower diversity, with most clones belonging to marine archaeal group I uncultured Crenarchaeota. In addition, two novel euryarchaeal clones were detected not to match any culture-dependent or -independent isolates. Compared with other gas hydrate-rich ecosystems and different areas of the South China Sea, a distinct microbial community was revealed in this study. PMID:19946953

  20. Bacterial and archaeal communities in the surface sediment from the northern slope of the South China Sea.

    PubMed

    Liao, Li; Xu, Xue-wei; Wang, Chun-sheng; Zhang, Dong-sheng; Wu, Min

    2009-12-01

    Microbial diversity of sediments from the northern slope of the South China Sea was studied by constructing bacterial and archaeal 16S rRNA gene clone libraries. Fourteen bacterial phylogenetic groups were detected, including Gammaproteobacteria, Deltaproteobacteria, Planctomycetes, Alphaproteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, Chloroflexi, Acidobacteria, Betaproteobacteria, Nitrospirae, candidate divisions OP8 and OP11, and an unknown group. Gammaproteobacteria was the predominant group in bacterial libraries with the percentage ranging from 31.8% to 63.2%. However, archaeal libraries had relatively lower diversity, with most clones belonging to marine archaeal group capital I, Ukrainian uncultured Crenarchaeota. In addition, two novel euryarchaeal clones were detected not to match any culture-dependent or -independent isolates. Compared with other gas hydrate-rich ecosystems and different areas of the South China Sea, a distinct microbial community was revealed in this study.

  1. The environmental rule in the shape of soft-sediment deformation structures in the shelf to base of slope settings

    NASA Astrophysics Data System (ADS)

    Monnerat de Oliveira, Carlos M.

    2015-04-01

    Soft-sediment deformation structures (SSDS) can be divided into in situ and detached structures. The latter include slides, slumps, and debrites (mass transport deposits) and dominate the literature compared to processes and products of deformation that takes place in situ. This study addresses in detail the origin and development of in situ SSDS and their stratigraphic and depositional context in well exposed shelf edge and upper to lower slope successions of the Karoo and the Neuquén basins. In the study areas, in situ SSDS occur preferentially in shelf-edge/upper-slope settings, but can also develop in middle and lower slope settings in association with detached structures. Flame and load structures are the most common in situ features and a systematic quantitative study of flame structures shows that they are elongated and have preferential orientation. The relationship between morphometric parameters, such as height, width and spacing, is statistically proven to be independent of the scale of occurrence and depositional environment in the majority of the cases. This indicates that similar physical and rheological conditions occurred during their formation in both shallow and deepwater environments. Divergence in the trends can indicate changes in the boundary conditions. Comparison of statistical results from Karoo and Neuquén datasets indicates a grain size influence on the dimension of structures; the greater the grain size the shorter the flame structures. Morphology of flame structures is independent of outcrop scale, as shown by statistical relationships. This characteristic allows prediction of the dimension/geometry of flame structures at outcrop scale. Extrapolation to scales below or above the range of outcrop limits must be done with care. The methodological basis for the evaluation of these out of outcrop scale situations are initiated here but still need to be effectively evaluated.

  2. Quantification, analysis and modelling of soil erosion on steep slopes using LiDAR and UAV photographs

    NASA Astrophysics Data System (ADS)

    Neugirg, F.; Kaiser, A.; Schmidt, J.; Becht, M.; Haas, F.

    2015-03-01

    Steep hill slopes in the Bavarian Alps and at an artificial waste dump on the Island of Elba are subject to soil erosion through geomorphological processes. Long-term high-resolution terrestrial LiDAR data are available and have been analysed for both areas. The analysis indicated different erosion patterns on the slopes that could be the result of different geomorphological processes. Additionally, both study sites show a good agreement between the annual erosion rates and the size of the hydrological catchment as a proxy for the sediment contributing area. The results presented in this study represent the first analysis of hill slope erosion measured with LiDAR and UAV systems. The hill slope erosion will be subject to measurements using a higher temporal resolution during future years in order to identify different erosion processes throughout the annual time step.

  3. Soft-sediment deformations (convolute lamination and load structures) in turbidites as indicators of flow reflections against bounding slopes

    NASA Astrophysics Data System (ADS)

    Tinterri, Roberto; Muzzi Magalhaes, Pierre; Tagliaferri, Alessio; Cunha, Rogerio S.; Laporta, Michele

    2015-04-01

    turbidites containing these deformative structures show that they are genetically linked to contained-reflected beds in structurally-confined basins, suggesting a trigger mechanism associated with the cyclic-wave loading produced by flow impacts or reflected bores and internal waves related to ponded turbidity currents. The data that can demonstrate this hypothesis come from the foredeep turbidites of the Marnoso-arenacea Formation (northern Italy) and Annot Sandstones (southwestern France), where a basin scale high-resolution stratigraphic framework with bed-by-bed correlations is now available. These data show that the lateral and vertical distribution of convolute laminae and load structures is not random but has an evident depositional logic related to reflection processes against bounding slopes. Therefore, the main objectives of this work are: 1) to show that convolute laminae and load structures are strictly associated with other sedimentary structures that are unequivocally related to reflection and rebound processes of turbidity currents against morphological obstacles; 2) to show that their lateral and vertical distribution increases concomitantly with the number of contained-reflected beds in the proximity of structurally-controlled morphological highs; 3) to show that the increase in contained-reflected beds with convolute laminae is strictly related to the increase in the synsedimentary-structural uplifts producing more pronounced morphologic highs; 4) to discuss the processes that link soft-sediment deformations with cyclic-wave loading related to internal waves and bores produced by reflection processes.

  4. Influence of mining-related activities on concentrations of metals in water and sediment from streams of the Black Hills, South Dakota

    USGS Publications Warehouse

    May, T.W.; Wiedmeyer, Ray H.; Gober, J.; Larson, S.

    2001-01-01

    Water and sediment samples were collected from streams in Spearfish Creek, Whitewood Creek, and Bear Butte Creek watersheds in the Black Hills, SD, an area impacted by gold mining operations. Arsenic concentrations that exceeded the U.S. Environmental Protection Agency's Maximum Concentration Limit of 50 ??g/L for drinking water were found in water from Annie Creek, a tributary of Spearfish Creek, and from Whitewood Creek. Gold Run, a tributary of Whitewood Creek, and Annie Creek contained Se concentrations in water that exceeded the EPA Ecotox threshold of 5 ??g/L and were classified as a high hazard for Se accumulation from water into the planktonic food chain and for resultant toxicity to fish and aquatic birds. Concentrations of As, Cd, Cu, Hg, Ni, Pb, and Zn in sediment exceeded EPA Ecotox thresholds in one or more of the watersheds suggesting potential adverse ecological effects. Sediment from Rubicon Creek, a tributary of Spearfish Creek, contained Se concentrations high enough (4.0 ??g/g) to be a moderate hazard for accumulation from sediments into the benthic food chain, with resultant dietary toxicity to fish and aquatic birds. These results are discussed in light of historical mining activities and recent clean-up and reclamation efforts. Based on the results and comparisons to Ecotox tresholds, further studies of ecological effects are warranted.

  5. Simulation of rainfall effects on sediment transport on steep slopes in an Alpine catchment

    NASA Astrophysics Data System (ADS)

    Kaiser, A.; Neugirg, F.; Schindewolf, M.; Haas, F.; Schmidt, J.

    2015-03-01

    The Alps represent a young, high mountain range which displays strong geomorphological activity. As the major source area in Central Europe, they deliver large quantities of sediment to the lowlands. However, our knowledge on process differentiation is still not sufficient to distinguish between the summer and winter periods of denudation. To increase our understanding of soil detachment, artificial rainfall experiments were carried out to generate data for the physically-based soil erosion model EROSION 2D/3D. Additionally, state-of-the-art, close-range remote sensing methods were applied to validate the results. The first rainfall simulations showed promising results for predicting denudation during the summer period, thus indicating the applicability of this experimental approach. However, further research is required for seasonal dynamics during other times of the year.

  6. Rates of total oxygen uptake of sediments and benthic nutrient fluxes measured using an in situ autonomous benthic chamber in the sediment of the slope off the southwestern part of Ulleung Basin, East Sea

    NASA Astrophysics Data System (ADS)

    Lee, Jae Seong; An, Sung-Uk; Park, Young-Gyu; Kim, Eunsoo; Kim, Dongseon; Kwon, Jung No; Kang, Dong-Jin; Noh, Jae-Hoon

    2015-09-01

    We have developed a new autonomous benthic lander for deep-sea research, the Korea Institute of Ocean Science and Technology (KIOST) Belc II and Belp II. The benthic lander was successfully tested at 950 and 1450 m water depths on the slope off the southwestern part of the Ulleung Basin in the East Sea of Korea. The ex situ measurements of the total oxygen uptake (TOU) rates at all the stations exceeded the in situ measurement values, and may indicate artificial effects from onboard incubation. The TOU rates were estimated to be 5.80 mmol m-2 d-1 and 3.77 mmol m-2 d-1 at water depths of 950 m and 1450 m, respectively. The benthic nutrient fluxes were also higher at water depths of 950 m, which indicates a partitioning of organic degradation with water depth. In addition, the negative phosphate and nitrogen benthic flux ratios and the higher nitrate removal flux via the sediment-water interface at the slope imply that the nitrogen in the bottom water may be preferentially removed via microbial respiration processes in the sediments, and may be coupled with the low nitrogen-to-phosphate ratio found in the deep water. Although our measurements comprised just two experiments in the slope sediment, the robust in situ measurement of the benthic fluxes in the slope sediment is a forerunner for new research into the biogeochemical cycles across the shelf edge-slope-basin system in the East Sea.

  7. Biodiversity of nematode assemblages from deep-sea sediments of the Atacama Slope and Trench (South Pacific Ocean)

    NASA Astrophysics Data System (ADS)

    Gambi, C.; Vanreusel, A.; Danovaro, R.

    2003-01-01

    was more evident at genus than at species level. Epistrate feeders dominated and increased their relevance, determining a reduction of the index of trophic diversity at hadal depths. According to trophic diversity, taxonomic diversity and distinctness also decreased with depth. All diversity indices from the Atacama Slope and Trench were lower than in other equally deep areas world wide (e.g. Puerto Rico Trench). We suggest that such reduction was related to the high nutrient loading observed in this system (up to two orders of magnitude higher than in typical oligotrophic deep-sea sediments).

  8. Shallow structure and stratigraphy of the carbonate West Florida continental slope and their implications to sedimentation and geohazards

    USGS Publications Warehouse

    Doyle, Larry J.

    1983-01-01

    An 1800-joule sparker survey of the West Florida continental slope between about 26?N and 29?15?N showed a top bed of Pleistocene age forming an irregular drape over a surface that is probably Pliocene. The contact between the top two layers is unconformable in the south and, in some places, shows karst collapse and solution features. Karst topography grades into a more hummocky erosional surface to the north, which in turn smoothes out; the contact become conformable still further north. A period of folding, which is widespread over the outer portion of the study area and which may be related to large scale mass wasting, occurred at about the same time represented by the unconformity. Significant subsidence has occurred as late as Pleistocene. The surface layer thins to a minimum (0 in the south) at about 525-meters water depth and then thickens again dramatically to the west, downslope. This thinning is interpreted to be due to the Loop Current, which flows from north to south in the area and which acts to block deposition and scour the bottom. Despite the fact that the margin is dominated by carbonates, usually associated with low sedimentation rates, there is widespread evidence of mass wasting affecting ancient and surficial deposits on the outer part of the upper slope. Three potential groups of geohazards identified are: 1. Potential bottom failure in areas where a thin top layer overlies the karst surface. 2. Potential for sliding and slumping. 3. Scour due to currents which could also affect drilling and engineering activities.

  9. Proterozoic events recorded in quartzite cobbles at Jack Hills, Western Australia: New constraints on sedimentation and source of > 4 Ga zircons

    NASA Astrophysics Data System (ADS)

    Grange, Marion L.; Wilde, Simon A.; Nemchin, Alexander A.; Pidgeon, Robert T.

    2010-03-01

    Rare heavy mineral bands within quartzite cobbles were identified in two conglomerate units within the Jack Hills belt, Western Australia. Seven zircon-bearing cobbles were analysed from one location (site 152) and three from another (site 154), both approximately 1 km west of the site where zircons in excess of 4 Ga are abundant (W74 'discovery' site). Individual pebbles from the 152 site reveal three distinctive features, containing either zircons > 3.0 Ga in age, < 1.9 Ga in age or a range of ages from ˜ 1.2 to ˜ 3.6 Ga. Those from site 154 are more uniform, containing only zircons with ages between 3.1 and 3.9 Ga. Only one grain > 4 Ga was discovered from the entire suite of pebbles, in contrast to the well-studied W74 site. A single detrital zircon with an age of 1220 ± 42 Ma from location 152 is the youngest grain so far reported from sedimentary rocks at Jack Hills. It shows magmatic oscillatory zoning and thus implies at least two sedimentary cycles within the Proterozoic; requiring erosion of an igneous precursor, incorporation into a clastic sediment, induration and subsequent erosion and transport to be hosted in the conglomerate. The nearest source for rocks of this age is the Bangemall Supergroup in the Collier Basin, ˜ 100 km northeast in the Capricorn Orogen. This would imply tectonic interleaving of originally more extensive Bangemall rocks, possibly related to activity along the Cargarah Shear Zone that traverses the Jack Hills belt. The lack of > 4.1 Ga zircons in the pebbles is highly significant, suggesting the immediate source of ancient zircons was no longer present at the Earth's surface. This equates with a general lack of ancient crystals noted in rocks that contain Proterozoic zircons from previous studies and implies that such grains diminish in number as earlier sedimentary rocks were successively recycled.

  10. Cyclicity in Pleistocene upper-slope cool-water carbonates: Unravelling sedimentary dynamics in deep-water sediments, Great Australian Bight, Odp Leg 182, Site 1131A

    NASA Astrophysics Data System (ADS)

    Puga-Bernabéu, Ángel; Betzler, Christian

    2008-03-01

    Ocean Drilling Program Site 1131, located in the central Great Australian Bight, recovered an expanded series of Pleistocene cool-water carbonates. Three distinct facies are arranged in repeating sedimentary cycles. Omission intervals form the base of the cycles and are overlain by laminated deposits. The upper part of the cycles consists of bioturbated sediments. Facies cyclicity parallels glacial-interglacial sea-level changes. Firmground/hardground surfaces formed during latest stages of sea-level falls. Laminated sediments were deposited during later sea-level fall and/or early phases of the sea-level lowstand, and the bioturbated intervals are related to interglacial sea-level highstands. Bottom current activity is interpreted to play an important control on facies and cycle development. During the late stages of sea-level fall, upwelling currents winnowed the slope sediments, leading to hardground formation. During latest sea-level falls and early sea-level lowstands, a relative increase in the ramp sediment supply to the slope leading to the formation of the laminated facies was also a response to the continued action of the near-bottom upwelling currents that reworked previously deposited sediments along the slope. During the early sea-level rises, laminated, upwelling-influenced facies were progressively covered by the bioturbated facies. The adopted approach to decipher sedimentary cyclicity, involving the integrated use of wireline logs, geochemical data, FMS images and sedimentological analysis of the lithofacies has allowed to recognise subtle facies changes in upper-slope settings of a distally-steepened carbonate ramp and their relationship with the sea level, as well as to unravel the importance of the oceanic-current regime in the deposition style on the ramp that otherwise would remain unsolved. This integrated method could be applied to study more precisely apparently homogeneous fine-grained calcareous sediment successions of distal

  11. Sentinel Hill Core Test 1: Facies Descriptions and Stratigraphic Reinterpretations of the Prince Creek and Schrader Bluff Formations, North Slope, Alaska

    USGS Publications Warehouse

    Flores, Romeo M.; Stricker, Gary D.; Decker, Paul L.; Myers, Mark D.

    2007-01-01

    The Sentinel Hill Core Test 1 well penetrated an intertonguing sequence of (1) the marine Schrader Bluff Formation in the depth intervals 950?1,180 ft and 690?751 ft, which consists of shoreface and offshore deposits that accumulated along a storm-dominated, barred shoreline; and (2) the nonmarine Prince Creek Formation in the depth intervals 751?950 ft and surface to 690 ft, which consists of fluvial channel, crevasse splay, backswamp, and ash fall deposits. The strata range in age from early Campanian to early Maastrichtian. An erosional contact at a depth of 690 ft at the base of the upper unit of the Prince Creek Formation is interpreted as a major regional sequence boundary, and the overlying conglomeratic fluvial channel deposits are interpreted to have accumulated in a paleovalley. In its more proximal reaches along the Colville River, channels of this paleovalley cut down 75 ft into the lowermost Prince Creek Formation and the uppermost Schrader Bluff Formation. Farther offshore, the equivalent surface to the aforementioned paleovalley appears to be a subtle discontinuity between middle and lower Schrader Bluff Formation shelfal marine strata. Still farther offshore, the equivalent paleovalley surface is interpreted as a marine mass-wasting surface that locally cuts through the lowermost Schrader Bluff Formation and into the underlying Seabee Formation.

  12. Varying sediment sources (Hudson Strait, Cumberland Sound, Baffin Bay) to the NW Labrador Sea slope between and during Heinrich events 0 to 4

    USGS Publications Warehouse

    Andrews, John T.; Barber, D.C.; Jennings, A.E.; Eberl, D.D.; Maclean, B.; Kirby, M.E.; Stoner, J.S.

    2012-01-01

    Core HU97048-007PC was recovered from the continental Labrador Sea slope at a water depth of 945 m, 250 km seaward from the mouth of Cumberland Sound, and 400 km north of Hudson Strait. Cumberland Sound is a structural trough partly floored by Cretaceous mudstones and Paleozoic carbonates. The record extends from ∼10 to 58 ka. On-board logging revealed a complex series of lithofacies, including buff-colored detrital carbonate-rich sediments [Heinrich (H)-events] frequently bracketed by black facies. We investigate the provenance of these facies using quantitative X-ray diffraction on drill-core samples from Paleozoic and Cretaceous bedrock from the SE Baffin Island Shelf, and on the < 2-mm sediment fraction in a transect of five cores from Cumberland Sound to the NW Labrador Sea. A sediment unmixing program was used to discriminate between sediment sources, which included dolomite-rich sediments from Baffin Bay, calcite-rich sediments from Hudson Strait and discrete sources from Cumberland Sound. Results indicated that the bulk of the sediment was derived from Cumberland Sound, but Baffin Bay contributed to sediments coeval with H-0 (Younger Dryas), whereas Hudson Strait was the source during H-events 1–4. Contributions from the Cretaceous outcrops within Cumberland Sound bracket H-events, thus both leading and lagging Hudson Strait-sourced H-events.

  13. Sediment characterization, stocks and erodible relief quantification in alpine context using sloping local base level, from single watersheds to large-scale source-to-sink systems

    NASA Astrophysics Data System (ADS)

    Rudaz, Benjamin; Gavillet, Lauren; Jaboyedoff, Michel

    2014-05-01

    Erosion rates in alpine context since the last glacial maximum are classically calculated from accumulated sediments in glacial overdeepenings. Such erosion rates omit stored sediments in lateral valleys and secondary glacial troughs that have yet to get transported to the final sink. Their potential availability to the dominant mass wasting processes, such as landslides and debris-flows, is also important to assess, since sediment production and availability is a major driver of those hazardous phenomenon. In this study, a methodology to characterize sediment stocks and estimate their volume is applied to several watersheds, ranging from single torrential systems up to whole lateral valleys, and finally the complete source-to-sink system of the alpine Rhône river. First, areas occupied by colluvium, Holocene processes deposits and slope instabilities are mapped, using geological maps and HR-DEM hillshade. Each area is identified by its dominant formation process, and its situation in regard to glacially shaped valley geometry. For instance, glacial troughs are treated differently from valley walls and glacial cirques. The volume of sediments is given by subtracting a bedrock surface estimated with the SLBL methodology, with rock outcrops as fixed points, from the current topography. Where available, coring and geophysical data are used to constrain the geometry of the bedrock surface. Secondly, erodible relief is identified by considering the upper reaches of hydrologic networks as base levels. The volumes are constrained at the base with a slope angle derived from rock mechanics literature, thus changing with lithology, to emulate future potential slope movements towards the river network. The estimated stocks are then analyzed by process, age, and situation in the sediment cascade. The erodible relief allows localisation of future mass wasting potential, including the remobilization of existing stocks and future input from the still intact rock mass. The

  14. Results of sediment and water sampling and inorganic, organic, and radionuclide analysis at recreation areas and water intakes - Norris, Melton Hill, and Watts Bar Lakes - Data report

    SciTech Connect

    1991-10-01

    Suspected water quality contamination in Watts Bar Reservoir as a result of activities in past decades at the Department of Energy`s (DOE) Oak Ridge facility is of public concern. DOE, the Tennessee Valley Authority (TVA), the State of Tennessee, and other agencies and officials have received many inquiries from the public in recent years concerning this suspected pollution, especially how this potential contamination may affect the health and safety of those persons who use beaches in the area for swimming or other water-body-contact sports. As a result of these concerns, TVA conducted a study in May and June 1991 to obtain data on potential contaminants of concern in the water and sediment of Watts Bar Reservoir. TVA collected water and sediment samples at a total of 29 sites, including 18 recreation areas and 11 water intake locations, located throughout Norris, Melton Hill, and Watts Bar Reservoirs. The samples were analyzed for radionuclides, metals, and organic compounds which could pose a threat to human health.

  15. Results of sediment and water sampling for inorganic, organic, and radionuclide analysis at recreation areas and water intakes -- Norris, Melton Hill, and Watts Bar Lakes. Data report

    SciTech Connect

    1991-10-01

    Suspected water quality contamination in Watts Bar Reservoir as a result of activities in past decades at the Department of Energy`s (DOE) Oak Ridge facility is of public concern. DOE, the Tennessee Valley Authority (TVA), the State of Tennessee, and other agencies and officials have received many inquiries from the public in recent years concerning this suspected pollution, especially how this potential contamination may affect the health and safety of those persons who use beaches in the area for swimming or other water-body-contact sports. As a result of these concerns, TVA conducted a study in May and June 1991 to obtain data on potential contaminants of concern in the water and sediment of Watts Bar Reservoir. TVA collected water and sediment samples at a total of 29 sites, including 18 recreation areas and 11 water intake locations, located throughout Norris, Melton Hill, and Watts Bar Reservoirs. The samples were analyzed for radionuclides, metals, and organic compounds which could pose a threat to human health.

  16. A study of sediment motions and bottom layer dynamics over the Middle Atlantic Bight shelf and upper slope. Final technical report, 1 June 1992--31 May 1995

    SciTech Connect

    Pietrafesa, L.J.

    1995-12-31

    A study of sediment dynamics over the Middle Atlantic Bight (MAB) in the vicinity of the Cape Hatteras Confluence (CHC), including the mouths of estuaries, the shelf and the slope, was carried out by investigators at North Carolina State University as part of the Department of Energy Ocean Margins Program. Studied were processes effecting sediment motion. In particular, the processes which determine rates of vertical transport of dissolved carbon dioxide and organic matter and particulates to and from the bottom by turbulent mixing resuspension and particulate sinking and vertical motions induced by BBL convergences; especially during periods of storm activity when both surface waves and currents are maxima.

  17. Sediment movement and dispersal patterns on the Grand Banks continental shelf and slope were tied to the dynamics of the Laurentide ice-sheet margin

    NASA Astrophysics Data System (ADS)

    Rashid, H.; MacKillop, K.; Piper, D.; Vermooten, M.; Higgins, J.; Marche, B.; Langer, K.; Brockway, B.; Spicer, H. E.; Webb, M. D.; Fournier, E.

    2015-12-01

    The expansion and contraction of the late Pleistocene Laurentide ice-sheet (LIS) was the crucial determining factor for the geomorphic features and shelf and slope sediment mobility on the eastern Canadian continental margin, with abundant mass-transport deposits (MTDs) seaward of ice margins on the upper slope. Here, we report for the first time sediment failure and mass-transport deposits from the central Grand Banks slope in the Salar and Carson petroleum basins. High-resolution seismic profiles and multibeam bathymetry show numerous sediment failure scarps in 500-1600 m water depth. There is no evidence for an ice margin on the upper slope younger than MIS 6. Centimeter-scale X-ray fluorescence analysis (XRF), grain size, and oxygen isotope data from piston cores constrain sediment processes over the past 46 ka. Geotechnical measurements including Atterberg limit tests, vane shear measurements and triaxial and multi-stage isotropic consolidation tests allowed us to assess the instability on the continental margin. Cores with continuous undisturbed stratigraphy in contourite silty muds show normal downcore increase in bulk density and undrained peak shear strength. Heinrich (H) layers are identifiable by a marked increase in the bulk density, high Ca (ppm), increase in iceberg-rafted debris and lighter δ18O in the polar planktonic foram Neogloboquadrina pachyderma (sinistral): with a few C-14 dates they provide a robust chronology. There is no evidence for significant supply of sediment from the Grand Banks at the last-glacial maximum. Mass-transport deposits (MTD) are marked by variability in the bulk density, undrained shear strength and little variation in bulk density or Ca (ppm) values. The MTD are older than 46 ka on the central Grand Banks slope, whereas younger MTDs are present in southern Flemish Pass. Factor of safety calculations suggest the slope is statically stable up to gradients of 10°, but more intervals of silty mud may fail during earthquake

  18. Mineral associations and nutritional quality of organic matter in shelf and upper slope sediments off Cape Hatteras, USA: a case of unusually high loadings

    NASA Astrophysics Data System (ADS)

    Mayer, L.; Benninger, L.; Bock, M.; DeMaster, D.; Roberts, Q.; Martens, C.

    Relationships among organic carbon (OC), enzymatically hydrolyzable amino acid (EHAA) concentrations and mineral surface area (SFA) were assessed for sediments from the shelf and slope region near Cape Hatteras, USA. Grain size, measured here as mineral-specific surface area, explained 55% of the variance in organic matter concentrations. Organic loadings, as ratios of organic carbon to surface area (OC:SFA), decrease with water column and core depth. OC:SFA ratios in this region are comparable to those found in areas with anoxic water columns, and are the highest reported for shelf-slope sediments underlying oxygenated water columns. With increasing water-column depth, organic matter becomes progressively incorporated into low-density (<2.4 g cm -3), organomineral aggregates, reflecting the increase in clay content in sediments with water-column depth. Organic coverage of mineral surfaces was determined by gas sorption methods; throughout the depth range minerals are essentially bare of organic coatings, in spite of high organic loadings. EHAA concentrations increase with water-column depth in a similar fashion as OC concentrations, and help to support intense heterotrophic communities at depth. Rapidly decreasing ratios of EHAA to total organic matter with water-column depth are consistent with previous inferences that largely refractory organic matter is exported from the shelf to the slope. Significant burial of EHAA downcore indicates protection of enzymatically hydrolyzable biopolymers with depth.

  19. Physical and geotechnical properties and assessment of sediment stability on the continental slope and basin of the Bransfield Basin (Antarctica Peninsula)

    USGS Publications Warehouse

    Casas, D.; Ercilla, G.; Estrada, F.; Alonso, B.; Baraza, J.; Lee, H.; Kayen, R.; Chiocci, F.

    2004-01-01

    Our investigation is centred on the continental slope of the Antarctic Peninsula and adjacent basin. Type of sediments, sedimentary stratigraphy, and physical and geotechnical characterization of the sediments have been integrated. Four different types of sediments have been defined: diamictons, silty and muddy turbidites, muddy, silty and muddy matrix embedded clast contourites. There is a close correspondence between the physical properties (density, magnetic susceptibility and p-wave velocity) and the texture and/or fabric as laminations and stratification. From a quantitative point of view, only a few statistical correlations between textural and physical properties have been found. Within the geotechnical properties, only water content is most influenced by texture. This slope, with a maximum gradient observed (20??), is stable, according to the stability under gravitational loading concepts, and the maximum stable slope that would range from 22?? to 29??. Nevertheless, different instability features have been observed. Volcanic activity, bottom currents, glacial loading-unloading or earthquakes can be considered as potential mechanisms to induce instability in this area. Copyright ?? Taylor & Francis Inc.

  20. Bioturbation, geochemistry and geotechnics of sediments affected by the oxygen minimum zone on the Oman continental slope and abyssal plain, Arabian Sea

    NASA Astrophysics Data System (ADS)

    Meadows, Azra; Meadows, Peter S.; West, Fraser J. C.; Murray, John M. H.

    2000-01-01

    We investigate the way the oxygen minimum zone (OMZ) alters interactions between bioturbation and sediment geochemistry, and geotechnical properties. Sediments are compared within and below the OMZ on the Oman continental slope and adjacent abyssal plain during the post monsoonal autumn season. Quantitative measurements were made of Eh and pH, of total organic matter (TOM) and carbonate, of water content and shear strength, and of bioturbation structures in vertical profiles of subcores taken from spade-box core samples. The OMZ stations had distinctively low redox conditions and high carbonate content, and different geotechnical properties and different bioturbation structures than stations below the OMZ on the abyssal plain. These differences are related to the degree of anoxia and to water depth. Within the OMZ, Eh, pH and carbonate increased with water depth, and TOM and water content decreased. We also noted the presence of subsurface sediment heterogeneity on the continental slope within the OMZ. In the OMZ, Eh, water content and bioturbation decreased with increasing sediment depth. There was a slight decrease in pH in the top 5 cm at all stations. Shear strength nearly always increased with increasing sediment depth. At each water depth correlations show down-core trends in these parameters, while across all water depths correlations were significant at deeper sediment depths (20-30 cm). An Eh-pH diagram identified two water-depth groupings: 391-1008 and 1265-3396 m. Cluster analysis showed the upper and lower sediment depths form separate clusters, the break occurring at 4-7.5 cm; while there are also distinct clusters related to water depth. We relate our results to bottom-water oxygen concentrations reported by other investigators, and to regional-scale geochemical processes.

  1. Field observations, experiments, and modeling of sediment production from freeze and thaw action on a bare, weathered granite slope in a temperate region of Japan

    NASA Astrophysics Data System (ADS)

    Tsutsumi, Daizo; Fujita, Masaharu

    2016-08-01

    In the present study, field observations and model simulations were conducted to examine the process of sediment production due to freeze and thaw action in a temperate climate region. Two small areas were designated and observations were conducted to determine the mechanisms of sediment production due to freeze and thaw action on a bare, weathered granite slope in the Tanakami Mountains in the southern part of Shiga Prefecture, Japan. During the cold season from 2004 to 2005, air, surface, and subsurface temperatures were measured at 10-min intervals. The sediment produced on plot 1 was collected and weighed once per week, whereas the sediment produced on plot 2 was left untouched until the end of the cold season. The freeze and thaw cycle occurred repeatedly, with the frozen zone (i.e., temperature < 0 °C) extending to a depth of 10 cm. Sediment was produced as a result of active freeze and thaw processes and, accordingly, there was no longer sediment production at the end of the cold season. Plots 1 and 2 produced 108 and 44 kg m- 2 year- 1 of sediment, respectively. This difference indicates that sediment cover of the saprolite surface mitigated the destructive effects of freezing. During the cold season from 2005 to 2006, a half of plot 1 was covered by broadleaves (Quercus serrata) and the other half was covered by coniferous leaves (Pinus densiflora); plot 2 was covered by no leaves to understand the effects of surface cover on the reduction in sediment production. The results showed that surface leaf cover dramatically decreased sediment production due to freeze and thaw action versus the no-surface cover. A simulation model combining a thermal conductivity analysis and a simple and empirical sediment production model was developed to estimate the amount of sediment produced by the freeze and thaw action. The observation results of temperature change and amount of sediment during the first season, from 2004 to 2005, were simulated with the model. The model

  2. Mechanical Stability of Stratified Sediments along the upper continental Slope off Vesterålen, northern Norway - Insights from in situ CPTU Tests

    NASA Astrophysics Data System (ADS)

    Voelker, D.; Stegmann, S.; Kreiter, S.; L'Heureux, J. S.; Vanneste, M. W. B.; Baeten, N. J.; Knudsen, S.; Rise, L.; Longva, O.; Brendryen, J.; Haflidason, H.; Chand, S.; Mörz, T.; Kopf, A.

    2015-12-01

    High-resolution single channel-seismic data (3.5 kHz) reveal small-scale submarine landslide structures and superficial deformation features (e.g. tension cracks) along the gently dipping (3°) upper continental slope west of the Vesterålen Archipelago off northern Norway. Previous laboratory-based geotechnical studies attest that the slope is per sestable and that seismic events in an order of magnitude M5.7 may have triggered the slope sediments to fail. Here we present geotechnical in situ data (sedimentary strength, pore pressure), which were obtained with RV Poseidon in summer 2014 using the static CPTU system GOST. The CPTU system provided high-resolution geotechnical profiles of the uppermost sediments to a maximum penetration depth of ~ 20 m at six sites within the landslide features and beside them in undisturbed slope sediments as reference. The CPTU data reveal the occurrence of mechanically weaker zones (MWZ) by the drop of sedimentary strength. These zones are interbedded by coarser, more competent layers. The occurrence of sensitive fine-grained material may be responsible for the loss of strength in the deeper portion (appx. 12 to 18 m below seafloor). An 1D infinite pseudo-static stability analysis attests that the mechanically weaker zones (MWZ) correlate well with portions, where the Factor of Safety (FoS) ≤ 1 (meta-stable to unstable) indicates permanent deformation or failure in case additional dynamic load is induced by an earthquake. Thus, the mechanically weak layers can be considered as one important pre-condition for landslide activity. In conclusion, the integration of in situ CPTU data with geophysical data improves soil characterization and hence foster a better understanding of the pre-conditioning factors for slope instability at the upper continental slope off Vesterålen. Risk assessment for the present-day slope off Vesterålen is particularly crucial, because the opening of the region for offshore oil and gas exploration is

  3. Mercury at the Oat Hill Extension Mine and James Creek, Napa County, California: Tailings, Sediment, Water, and Biota, 2003-2004

    USGS Publications Warehouse

    Slowey, Aaron J.; Rytuba, James J.; Hothem, Roger L.; May, Jason T.

    2007-01-01

    Executive Summary The Oat Hill Extension (OHE) Mine is one of several mercury mines located in the James Creek/Pope Creek watershed that produced mercury from the 1870's until 1944 (U.S. Bureau of Mines, 1965). The OHE Mine developed veins and mineralized fault zones hosted in sandstone that extended eastward from the Oat Hill Mine. Waste material from the Oat Hill Mine was reprocessed at the OHE Mine using gravity separation methods to obtain cinnabar concentrates that were processed in a retort. The U.S. Bureau of Land Management requested that the U.S. Geological Survey measure and characterize mercury and other chemical constituents that are potentially relevant to ecological impairment of biota in tailings, sediment, and water at the OHE Mine and in the tributaries of James Creek that drain the mine area (termed Drainage A and B) (Figs. 1 and 2). This report summarizes such data obtained from sampling of tailings and sediments at the OHE on October 17, 2003; water, sediment, and biota from James Creek on May 20, 2004; and biota on October 29, 2004. These data are interpreted to provide a preliminary assessment of the potential ecological impact of the mine on the James Creek watershed. The mine tailings are unusual in that they have not been roasted and contain relatively high concentrations of mercury (400 to 1200 ppm) compared to unroasted waste rock at other mines. These tailings have contaminated a tributary to James Creek with mercury primarily by erosion, on the basis of higher concentration of mercury (780 ng/L) measured in unfiltered (total mercury, HgT) spring water flowing from the OHE to James Creek compared to 5 to 14 ng/L HgT measured in James Creek itself. Tailing piles (presumably from past Oat Hill mine dumping) near the USBLM property boundary and upstream of the main OHE mine drainage channel (Drainage A; Fig. 2) also likely emit mercury, on the basis of their mercury composition (930 to 1200 ppm). The OHE spring water is likely an

  4. Impact of river-tide dynamics on the residual water level slope and residual sediment transport in the Pearl River channel networks

    NASA Astrophysics Data System (ADS)

    Cai, Huayang; Zhang, Zihao; Yang, Qingshu; Ou, Suying

    2016-04-01

    Large-scale delta systems, such as the Rhine-Meuse delta, the Mississippi River delta, the Mekong delta, the Yangtze delta and the Pearl River delta etc., usually feature a typical channel networks, where individual channels are interrelated through a networks system, resulting in both longitudinal and transverse variations of residual water level slope (averaged over a lunar day) caused by the river-tide interplay. Enhancing our insight of river-tide dynamics in these channel networks has vital importance for the protection and management of estuarine environment since river-tide interplay is closely related to sediment transport, water quality, water utilization and estuarine ecosystem. In this study, we investigate the impact of river-tide dynamics on the temporal-spatial changes of flow and suspended sediment load in terms of residual water level slope and residual sediment transport in the Pearl River channel networks, which is one of the complex channel networks in the world. Making use of a nonstationary harmonic analysis (NS_TIDE), the continuous time series observations of velocity covering a spring-neap cycle in 1999 (representing flood season) and 2001 (representing dry season) collected from around 60 stations in the Pearl River channel networks have been used to extract the temporal-spatial changes in residual velocity and tidal properties (including amplitudes and phases) as a function of variable river flow debouching into the delta. On the basis of harmonic analysis, the tidally averaged friction is decomposed into contributions made by riverine forcing alone, river-tide interaction and tidal asymmetry using Chebyshev polynomials approach. It is shown that river flow enhances friction via river-tide interaction, which increases the residual water level slope that influences the distribution of suspended sediment load in the Pearl River channel networks.

  5. [Sediment-yielding process and its mechanisms of slope erosion in wind-water erosion crisscross region of Loess Plateau, Northwest China].

    PubMed

    Tuo, Deng-Feng; Xu, Ming-Xiang; Zheng, Shi-Qing; Li, Qiang

    2012-12-01

    Due to the coupling effects of wind and water erosions in the wind-water erosion crisscross region of Loess Plateau, the slope erosion in the region was quite serious, and the erosion process was quite complicated. By using wind tunnel combined with simulated rainfall, this paper studied the sediment-yielding process and its mechanisms of slope erosion under the effects of wind-water alternate erosion, and quantitatively analyzed the efffects of wind erosion on water erosion and the relationships between wind and water erosions. There was an obvious positive interaction between wind and water erosions. Wind erosion promoted the development of microtopography, and altered the quantitative relationship between the sediment-yielding under water erosion and the variation of rainfall intensity. At the rainfall intensity of 60 and 80 mm x h(-1), the sediment-yielding without wind erosion decreased with the duration of rainfall and tended to be stable, but the sediment-yielding with wind erosion decreased to a certain valley value first, and then showed an increasing trend. At the rainfall intensity of 60, 80, and 100 mm x h(-1), the sediment-yielding with the wind erosion at speeds of 11 and 14 m x s(-1) increased by 7.3%-27.9% and 23.2%-39.0%, respectively, as compared with the sediment-yielding without wind erosion. At the rainfall intensity of 120 and 150 mm x h(-1) and in the rainfall duration of 15 minutes, the sediment-yielding with and without wind erosion presented a decreasing trend, but, with the increase of rainfall duration, the sediment-yielding with wind erosion showed a trend of decreasing first and increasing then, as compared with the sediment-yielding without wind erosion. The mechanisms of wind-water alternate erosion were complicated, reflecting in the mutual relation and mutual promotion of wind erosion and water erosion in the aspects of temporal-spatial distribution, energy supply, and action mode of erosion forces.

  6. KISATCHIE HILLS WILDERNESS, LOUISIANA.

    USGS Publications Warehouse

    Haley, Boyd R.; Ryan, George S.

    1984-01-01

    A mineral-resource survey of the Kisatchie Hills Wilderness, Louisiana indicated little promise for the occurrence of mineral resources. There is insufficient data on oil and gas producing formations that underlie the area to evaluate the oil and gas resource potential. All the oil fields of Wilcox age are less than 40 acres in extent; therefore, closer spaced deeper wells might find additional fields in sediments of Wilcox age. Oil and natural gas have been produced from older reservoirs (Cretaceous age) to the northwest of the wilderness, and deeper wells might find oil and natural gas in sediments of Cretaceous and older age in the vicinity of the wilderness.

  7. Isotopic Composition of Carbon Dioxide Released from Confidence Hills Sediment as Measured by the Sample Analysis at Mars (SAM) Quadrupole Mass Spectrometer

    NASA Technical Reports Server (NTRS)

    Franz, H. B.; Mahaffy, P. R.; Stern, J.; Archer, P., Jr.; Conrad, P.; Eigenbrode, J.; Freissinet, C.; Glavin, D.; Grotzinger, J. P.; Jones, J.; Ming, D.; McAdam, A.; Morris, R.; Navarro-Gozalez, R.; Owen, T.; Steele, A.; Summons, R.; Sutter, B.; Webster, C. R.

    2015-01-01

    In October 2014, the Mars Science Laboratory (MSL) "Curiosity" rover drilled into the sediment at the base of Mount Sharp in a location namsed Cionfidence Hills (CH). CH marked the fifth sample pocessed by the Sample Analysis at Mars (SAM) instrument suite since Curiosity arrived in Gale Crater, with previous analyses performed at Rocknest (RN), John Klein (JK), Cumberland (CB), and Windjana (WJ). Evolved gas analysis (EGA) of all samples has indicated H2O as well as O-, C- and S-bearing phases in the samples, often at abundances that would be below the detection limit of the CheMin instrument. By examining the temperatures at which gases are evolved from samples, SAM EGA data can help provide clues to the mineralogy of volatile-bearing phases when their identities are unclear to CheMin. SAM may also detect gases evolved from amorphous material in solid samples, which is not suitable for analysis by CheMin. Finally, the isotopic composition of these gases may suggest possible formation scenarios and relationships between phases. We will discuss C isotope ratios of CO2 evolved from the CH sample as measured with SAM's quadrupole mass spectrometer (QMS) and draw comparisons to samples previously analyzed by SAM.

  8. Reply to the Comment on "Wave climate, sediment supply and the depth of the sand-mud transition: A global survey" by D.A. George and P.S. Hill [Marine Geology 254 (2008) 121-128

    USGS Publications Warehouse

    George, D.A.; Hill, P.S.

    2009-01-01

    An analysis of concepts presented by George and Hill [George, D.A., Hill, P.S., 2008. Wave climate, sediment supply and the depth of the sand-mud transition: A global survey. Marine Geology, 254, 121-128.] regarding the depth of the sand-mud transition (hSMT) was performed by Guill??n and Jim??nez [Jorge Guill??n and Jos?? A. Jim??nez, Comment on "Wave climate, sediment supply and the depth of the sand-mud transition: A global survey" by D.A. George and P.S. Hill [Marine Geology 254 (2008) 121-128], Marine Geology, in press]. We are pleased that our proposed definition of the hSMT was confirmed to be appropriate. We are encouraged that the authors agree that wave period and wave height should both be used to determine hSMT as we demonstrated in our Eq. (1), which calculates the bed shear stress at hSMT. More in-depth research should focus on characterizing the role of sediment supply in determining hSMT. ?? 2009 Elsevier B.V. All rights reserved.

  9. Provenance of Cretaceous trench slope sediments from the Mesozoic Wandashan Orogen, NE China: Implications for determining ancient drainage systems and tectonics of the Paleo-Pacific

    NASA Astrophysics Data System (ADS)

    Sun, Ming-Dao; Xu, Yi-Gang; Wilde, Simon A.; Chen, Han-Lin

    2015-06-01

    The Wandashan Orogen of NE China is a typical accretionary orogen related to Paleo-Pacific subduction. The Raohe Complex, as a major part of the orogen, consists of mid-Triassic to mid-Jurassic radiolarian chert and intraoceanic igneous rocks in an accretionary prism overlain by weakly sheared terrestrial-sourced clastic trench slope sediments. Sensitive high-resolution ion microprobe U-Pb dating and LA-MC-ICPMS Hf isotopic analysis of detrital zircons from the terrestrial-sourced Yongfuqiao Formation sandstone show that most zircons are Phanerozoic (90%): 140-150 Ma (10%), 180-220 Ma (25%), 240-270 Ma (15%), 300-360 Ma (15%), 391-395 Ma (3%), and 450-540 Ma (20%), whereas 10% are Precambrian in age. About 90% of the zircons have ɛHf(t) values ranging from +11.1 to -12.8. This suggests that the major provenance of the trench slope sediments was from the adjacent eastern segment of the Central Asian Orogenic Belt and the Jiamusi Block. The age of the Yongfuqiao Formation is constrained to the earliest Cretaceous, which represents the accretion time of the mid-Triassic to mid-Jurassic oceanic complexes. When compared with the Mino Complex in Japan and the Tananao Complex in Taiwan, three different provenances are identified suggesting three ancient drainage systems which transported sediments from NE China, North China, and South China to the Paleo-Pacific subduction-accretion system.

  10. Antigravity hills are visual illusions.

    PubMed

    Bressan, Paola; Garlaschelli, Luigi; Barracano, Monica

    2003-09-01

    Antigravity hills, also known as spook hills or magnetic hills, are natural places where cars put into neutral are seen to move uphill on a slightly sloping road, apparently defying the law of gravity. We show that these effects, popularly attributed to gravitational anomalies, are in fact visual illusions. We re-created all the known types of antigravity spots in our laboratory using tabletop models; the number of visible stretches of road, their slant, and the height of the visible horizon were systematically varied in four experiments. We conclude that antigravity-hill effects follow from a misperception of the eye level relative to gravity, caused by the presence of either contextual inclines or a false horizon line.

  11. Recurring Slope Lineae Formation on Changing Slopes.

    NASA Astrophysics Data System (ADS)

    Heydenreich, J.; Mickol, R. L.; Dixon, J. C.; Chevrier, V.

    2015-12-01

    Recurring Slope Lineae (RSLs) and other associated dark streaks appear in the southern mid-latitudes on the martian surface during the spring to summer months. Gullies commonly emerge from bedrock and form from volatile thawing and associated sediment transportation and deposition. All of these forms involve the movement of fluids and associated sediments on variable slopes. The objective of this research is to generate subsurface flows, resembling those of liquid brines, under regolith at slope angle ranges that represent those on which RSLs and gullies occur on Mars. RSLs are generally found on steeper slopes. The higher slopes ranged from 25°-30° and lower slopes 12°-18°. As the slope increased, the total channel and apron length increased. There was a significant increase from the lower to higher slopes. The maximum width of the channel decreased as the slopes increased. Lower slopes produced a more dendritic channel pattern; an alcove, the main channel and an apron with two diverging branches. However, the higher slopes produced channels with more variability in the fluvial features. Lobes diverged from the main channel at varying distances from the water source. Channel walls were more distinct, along with formation of natural levees. Increases in fluid viscosity, produces a more singular channel. From these observations we conclude that lower slopes are more conducive to RSL formations from their basic geomorphology. Higher slopes produce more distinct morphologies associated with fluvial erosion that are more similar to gullies. The effect of viscosity also appears to alter the morphologies of the flow features. Understanding the origin of these fluvial features can lead to greater understanding of fluids on Mars.

  12. Processes controlling very low sedimentation rates on the continental slope of the Gonone-Orosei canyon system, NE Sardinia—terrestrial and oceanic significance

    NASA Astrophysics Data System (ADS)

    Giresse, Pierre; Pascucci, Vincenzo; Lymer, Gaël; Gaullier, Virginie; Thinon, Isabelle

    2014-12-01

    The narrow shelf and upper slope immediately above the Gonone canyon head off NE Sardinia represent areas of very low sedimentation rates. Along the sides of the canyon head (1,600 m water depth), the sediment deposits are homogeneous but show alternating light-grey intervals rich in carbonate and dark-grey ones rich in organic matter, possibly related to distal turbidite processes. Deposits older than 50,000 years are already encountered at core depths of 2.50 m, the sedimentation rates varying from 6-21 cm/103 years in the lower parts of two cores and from 1.5-3 cm/103 years in the upper parts. At about 35,000 years BP, both cores show a simultaneous drop in sedimentation rate by a factor of 3, probably in response to local mechanisms of channel avulsion. Lithological, mineralogical and geochemical properties reveal the environmental factors which are responsible for the extremely slow sediment accumulation. The southernmost sector of the coast, and partly also of the shelf, consists of Jurassic limestones which supply only small amounts of fine-grained material transported in suspension. During the last sea-level highstand, the accumulation of the Cedrino River pro-delta remained restricted to the coast, the low siliciclastic sediment yields resulting in poor shelf sediment trapping. The present morphology of the canyon head prevented the occurrence of gravity processes in the deeper part of the canyon system, including the coring sites. Accordingly, deposition was mainly fed by hemipelagic material of planktonic origin, together with only moderate terrigenous inputs. On a wider late Pleistocene timescale, seismic data indicate the occurrence of a coarse-grained, layered turbidite facies, implying a very different architecture of the canyon drainage system probably prior to 60,000 years BP.

  13. 20,000 years of Nile River dynamics and environmental changes in the Nile catchment area as inferred from Nile upper continental slope sediments

    NASA Astrophysics Data System (ADS)

    Revel, Marie; Ducassou, E.; Skonieczny, C.; Colin, C.; Bastian, L.; Bosch, D.; Migeon, S.; Mascle, J.

    2015-12-01

    Multi-proxy analysis of two marine sediment cores (MS27PT and MD04-2726) from the Nile continental slope provides evidence of changes in Nile sediment discharge related to changes in Ethiopian African Monsoon (EAM) precipitation, and allows us to reconstruct changes in Nile River runoff, vegetation and erosion in the Nile headwaters. Sediment element composition and neodymium isotopic composition reveal significant changes in clastic sediment provenance, with sources oscillating between a Saharan aeolian contribution during the Last Glacial Maximum/deglacial transition and during the Late Holocene, and a Blue/Atbara Nile fluvial contribution during the African Humid Period (AHP). This study provides a new understanding of past environmental changes. Between 14.6 and 14.13 ka there was a major input of sediments from the Ethiopian Highlands, consistent with a stronger EAM at that time. Climate in the Nile basin was wetter between 14.8 and 8.4 ka, with a corresponding increase in Blue Nile water and sediment discharge via the main Nile into the Eastern Mediterranean. The gradual climatic transition from the AHP to the present-day dry climate was reflected in a decrease in Blue Nile sediment deposition and flood discharge between 8.4 and 3.7 ka, with aridity at a maximum between 3.7 and 2.6 ka. The onset of drier conditions in the Blue Nile basin seems to have begun before the 8.2 ka cooling event in the North Atlantic. We speculate that the climatic change from the wet AHP to the dry late Holocene may have been a result of a break in the low latitude dynamic equilibrium between climate, vegetation and erosion, which may in turn have affected the climate in higher latitudes. Reduced Nile flow may also have had an impact on Levantine Intermediate Water originating in the Eastern Mediterranean through an increase in intermediate water formation.

  14. Modes of development of slope canyons and their relation to channel and levee features on the Ebro sediment apron, off-shore northeastern Spain

    USGS Publications Warehouse

    O'Connell, S.; Ryan, William B. F.; Normark, W.R.

    1987-01-01

    Six submarine slope canyons in an area of the northwestern Mediterranean, offshore from the Ebro River and Delta, were surveyed with bathymetric swathmapping (SeaBeam) and mid-range side-looking sonar (SeaMARC I). All of the canyons have slightly winding paths with concave-upwards gradients that are relatively steep shallower than 1,200 m. Two major types of canyons are identified on the basis of their morphologic character at the base of the slope; Type-I canyons lead to an unchannelled base-of-slope deposit and Type-II canyons are continuous with channel-levee systems that cross the rise. Four Type-I canyons were surveyed in the area. Two of these are broad, U-shaped, steep (average gradients of 1:14), do not indent the shelf, and terminate downslope at debris-flow deposits. These two canyons, the most northern in the area, have rounded heads with extensive gullies separated by knife-edge ridges. Relief of the canyon walls is about equal on both sides of the canyons, although the right-hand walls (looking downslope) are generally steeper. The other two Type-I canyons in the area are similar in that they do not indent the shelf, but they are much smaller and shallower and coalesce before terminating in the base-of-slope region. The two Type-II canyons that feed leveed-channels are U-shaped with flatter floors, longer profiles and gentler gradients than Type-I canyons. They are closer to the Valencia Valley and have relatively small cross-sectional areas. We propose a four-stage evolutionary sequence to explain the development of the canyons observed in this section on the prograding Ebro margin. During the initial stage, slumping and erosion on the slope creates a network of small gullies. During the next stage, headward growth of one (or more) gully leads to a major indentation of the shelf. This is the critical factor for developing a channel that will incise the slope and provide a major conduit for moving sediment to the basin. Stage 3 is characterized by the

  15. Geochemical Characterization of Mine Waste, Mine Drainage, and Stream Sediments at the Pike Hill Copper Mine Superfund Site, Orange County, Vermont

    USGS Publications Warehouse

    Piatak, Nadine M.; Seal, Robert R., II; Hammarstrom, Jane M.; Kiah, Richard G.; Deacon, Jeffrey R.; Adams, Monique; Anthony, Michael W.; Briggs, Paul H.; Jackson, John C.

    2006-01-01

    The Pike Hill Copper Mine Superfund Site in the Vermont copper belt consists of the abandoned Smith, Eureka, and Union mines, all of which exploited Besshi-type massive sulfide deposits. The site was listed on the U.S. Environmental Protection Agency (USEPA) National Priorities List in 2004 due to aquatic ecosystem impacts. This study was intended to be a precursor to a formal remedial investigation by the USEPA, and it focused on the characterization of mine waste, mine drainage, and stream sediments. A related study investigated the effects of the mine drainage on downstream surface waters. The potential for mine waste and drainage to have an adverse impact on aquatic ecosystems, on drinking- water supplies, and to human health was assessed on the basis of mineralogy, chemical concentrations, acid generation, and potential for metals to be leached from mine waste and soils. The results were compared to those from analyses of other Vermont copper belt Superfund sites, the Elizabeth Mine and Ely Copper Mine, to evaluate if the waste material at the Pike Hill Copper Mine was sufficiently similar to that of the other mine sites that USEPA can streamline the evaluation of remediation technologies. Mine-waste samples consisted of oxidized and unoxidized sulfidic ore and waste rock, and flotation-mill tailings. These samples contained as much as 16 weight percent sulfides that included chalcopyrite, pyrite, pyrrhotite, and sphalerite. During oxidation, sulfides weather and may release potentially toxic trace elements and may produce acid. In addition, soluble efflorescent sulfate salts were identified at the mines; during rain events, the dissolution of these salts contributes acid and metals to receiving waters. Mine waste contained concentrations of cadmium, copper, and iron that exceeded USEPA Preliminary Remediation Goals. The concentrations of selenium in mine waste were higher than the average composition of eastern United States soils. Most mine waste was

  16. Submarine canyon, slope, and shelf sedimentation in an upper Eocene-Oligocene progradational system (Limnos Island, north Aegean Sea, Greece)

    SciTech Connect

    Roussos, N.

    1988-08-01

    The only well-exposed outcrops of a post-Alpine late Eocene-Oligocene basin in the north Aegean Sea are at Limnos Island. These mostly consist of typical slope deposits overlain by remnants of shallow marine shelf and continental (braided-river) deposits. Three main slope lithofacies are distinguished. Canyon deposits consist of thick-bedded, massive, and pebbly sandstones (facies B), conglomerates (facies A), pebbly mudstone where the matrix shows flow (facies F), rock falls (nummulitic limestones), and zones of slump folds in sandstones (facies F). Channelized facies of massive sandstones, classical turbidites, and thin interbeds of sandstone and mudstone (facies E - probably overbank or levee deposits) are associated with canyon deposits. Pelagic and hemipelagic slope deposits consist of mudstone (facies G) and thin-bedded sandstone (facies D) with occasional small to medium-scale slump folds. These mud-rich slope deposits are incised by several channels filled with conglomerates, thick massive sandstones with well-developed dish structures, and turbidites interbedded with thin layers of mudstone (facies C). This unit composes a typical thinning and fining-upward sequence.

  17. Black Hills

    Atmospheric Science Data Center

    2014-05-15

    article title:  Drought in the Black Hills     View ... and western South Dakota remain in the midst of a severe drought. This set of images and maps from NASA's Multi-angle Imaging ... the 2000 and 2004 dates. As the vegetation faded with the drought, the  albedo  at the surface increased. Albedo measures the ...

  18. Maps showing estimated sediment yield from coastal landslides and active slope distribution along the Big Sur coast, Monterey and San Luis Obispo Counties, California

    USGS Publications Warehouse

    Hapke, Cheryl J.; Green, Krystal R.; Dallas, Kate

    2004-01-01

    The 1982-83 and 1997-98 El Ni?os brought very high precipitation to California?s central coast; this precipitation resulted in raised groundwater levels, coastal flooding, and destabilized slopes throughout the region. Large landslides in the coastal mountains of Big Sur in Monterey and San Luis Obispo Counties blocked sections of California State Route 1, closing the road for months at a time. Large landslides such as these occur frequently in the winter months along the Big Sur coast due to the steep topography and weak bedrock. A large landslide in 1983 resulted in the closure of Highway 1 for over a year to repair the road and stabilize the slope. Resulting work from the 1983 landslide cost over $7 million and generated 30 million cubic yards of debris from landslide removal and excavations to re-establish the highway along the Big Sur coast. Before establishment of the Monterey Bay National Marine Sanctuary (MBNMS) in 1992, typical road opening measures involved disposal of some landslide material and excess material generated from slope stabilization onto the seaward side of the highway. It is likely that some or most of this disposed material, either directly or indirectly through subsequent erosion, was eventually transported downslope into the ocean. In addition to the landslides that initiate above the road, natural slope failures sometimes occur on the steep slopes below the road and thus deliver material to the base of the coastal mountains where it is eroded and dispersed by waves and nearshore currents. Any coastal-slope landslide, generated through natural or anthropogenic processes, can result in sediment entering the nearshore zone. The waters offshore of the Big Sur coast are part of the MBNMS. Since it was established in 1992, landslide-disposal practices came under question for two reasons. The U.S. Code of Federal Regulations, Title 15, Section 922.132 prohibits discharging or depositing, from beyond the boundary of the Sanctuary, any material

  19. The abrupt installation of the euxinic environment as reflected by the unconsolidated sediments of the western slope of the Black Sea off the Romanian shore

    NASA Astrophysics Data System (ADS)

    Duliu, Octavian G.; Oaie, Gheorghe; Bojar, Ana-Voica; Zinicovscaia, Inga; Culicov, Otilia-Ana; Frontasyeva, Marina V.; Gradinaru, Janet

    2016-04-01

    A 4,5 m long core containing unconsolidated sediments collected at a depth of 500 m on the western slope of the Black Sea, off Romanian shore was analyzed by Computed Tomography (CT), X-ray Diffraction (XRD), X-ray Fluorescence (XRF) and Instrumental Neutron Activation Analysis (INAA) in order to investigate the changes in the Black Sea environment during the past 10.5 - 12 ky. The most relevant information regarding unconsolidated sediments was furnished by the CT images, clearly indicating the moment when the euxinic environment settled on this sector of the Black Sea, presumably 2.7 ky ago. This event is represented by the sedimentation of a coccolithic mud consisting of alternation of dark and light thin laminae composed of terigenous and respectively coccoliths rich material. This type of mud is characteristic for the sedimentary unit 1, filling the uppermost 50 cm of the core. The observation was confirmed by subsequent XRF and INAA determinations, which show a high content of calcium carbonate related to accumulation of Emilliania huxley coccoliths as well as of minor elements such as iron, molybdenum and uranium, a typical characteristic of euxinic environment. For instance, the average content of Mo and U is 28 and respectively 4 time higher than the corresponding content of the Upper Continental Core (UCC), while the Fe/Al ratio is around 0.52. Moreover, the average chondrite normalized Ce content of sedimentary unite 1 is 1.37 ± 0.17, slightly higher than 1.22, the characteristic value for the UCC. The Ce data indicate a weak positive anomaly, characteristic also for an euxinic reducing environment. All these investigations confirm the abrupt installation at a depth of 500 m of an euxinic environment on the western slope of the Black Sea, euxinic environment persisting to present time.

  20. Geochemical cycles in sediments deposited on the slopes of the Guaymas and Carmen Basins of the Gulf of California over the last 180 years

    USGS Publications Warehouse

    Dean, W.; Pride, C.; Thunell, R.

    2004-01-01

    Sediments deposited on the slopes of the Guaymas and Carmen Basins in the central Gulf of California were recovered in two box cores. Q-mode factor analyses identified detrital-clastic, carbonate, and redox associations in the elemental composition of these sediments. The detrital-clastic fraction appears to contain two source components, a more mafic component presumably derived from the Sierra Madre Occidental along the west coast of Mexico, and a more felsic component most likely derived from sedimentary rocks (mostly sandstones) of the Colorado Plateau and delivered by the Colorado River. The sediments also contain significant siliceous biogenic components and minor calcareous biogenic components, but those components were not quantified in this study. Redox associations were identified in both cores based on relatively high concentrations of molybdenum, which is indicative of deposition under conditions of sulfate reduction. Decreases in concentrations of molybdenum in younger sediments suggest that the bottom waters of the Gulf have became more oxygenated over the last 100 years. Many geochemical components in both box cores exhibit distinct cyclicity with periodicities of 10-20 years. The most striking are 20-year cycles in the more mafic components (e.g., titanium), particularly in sediments deposited during the 19th century. In that century, the titanium cycles are in very good agreement with warm phases of the Pacific Decadal Oscillation, implying that at times of greater influx of titanium-rich volcanic debris, there were more El Nin??os and higher winter precipitation. The cycles are interpreted as due to greater and lesser riverine influx of volcanic rock debris from the Sierra Madre. There is also spectral evidence for periodicities of 4-8 and 8-16 years, suggesting that the delivery of detrital-clastic material is responding to some multiannual (ENSO?) forcing.

  1. Fore reef upper slope mixed sedimentation response to penultimate glacial interglacial sea level fluctuations: IODP Hole 325-M0058A , Great Barrier Reef, Australia

    NASA Astrophysics Data System (ADS)

    Harper, B.; Bernabéu; Droxler, A. W.; Webster, J. M.; Thomas, A. L.; Tiwari, M.; Gischler, E.; Jovane, L.; Morgan, S.; Lado-Insua, T.

    2012-12-01

    High resolution stratigraphy in IODP Expedition 325 Hole-M0058A(58A) shows that the mixed carbonate siliciclastic sedimentary section, cored on the upper slope of the Great Barrier Reef (GBR) SE of Cairns, corresponds to the last 200 ky or almost two full late Quaternary glacial-interglacial cycles. Contrary to what has been observed in similar settings, strontium (Sr) and silica (Si) X-ray Fluorescence counts-proxies for reef-derived carbonate and terrigenous exports to the upper slope, respectively-appear to be out of phase of well-established models such as highstand shedding for periplatform sediment and lowstand shedding for siliciclastics systems. Hole 58A, drilled at 167 mbsl, is the deepest site along a 7 site transect SE of Cairns offshore the GBR. The recovered 41.4 m-long sedimentary sequence is mainly composed of three unconsolidated green mud sections intercalated with two distinct sandy intervals. The close proximity to the modern GBR and shallow water depth of this hole allows for dramatic changes in sedimentation and energy as a result of the glacial-interglacial high amplitude sea level fluctuations. Planktic foraminifer tests of the species Globigerinoides ruber (white) were picked and analyzed every 10 cm to produce a high resolution oxygen isotope record at Hole 58A. This record clearly exhibits δ18O cyclic variations that are interpreted to correspond with Marine Isotope Stages (MIS) 1-7 or the last 200ky. The disappearance of G. ruber (pink) at 28.5 m, in addition to several uranium/thorium dates, confirm that the interval between 30 and 28 m characterized by a sharp δ18O decrease corresponds to Termination II; moreover three radiocarbon ages (6550 years BP or younger) within the top 6 m of Hole 58A confirm the Holocene. Throughout Hole 58A, Sr and Si count variations appear to be out of phase suggesting periods of alternating neritic and terrigenous input dominance to the upper slope. The pattern, however, does not follow the typical

  2. Depositional environments and processes in Upper Cretaceous nonmarine and marine sediments, Ocean Point dinosaur locality, North Slope, Alaska

    USGS Publications Warehouse

    Phillips, R.L.

    2003-01-01

    A 178-m-thick stratigraphic section exposed along the lower Colville River in northern Alaska, near Ocean Point, represents the uppermost part of a 1500 m Upper Cretaceous stratigraphic section. Strata exposed at Ocean Point are assigned to the Prince Creek and Schrader Bluff formations. Three major depositional environments are identified consisting, in ascending order, of floodplain, interdistributary-bay, and shallow-marine shelf. Nonmarine strata, comprising the lower 140 m of this section, consist of fluvial distributaries, overbank sediments, tephra beds, organic-rich beds, and vertebrate remains. Tephras yield isotopic ages between 68 and 72.9 Ma, generally consistent with paleontologic ages of late Campanian-Maastrichtian determined from dinosaur remains, pollen, foraminifers, and ostracodes. Meandering low-energy rivers on a low-gradient, low-relief floodplain carried a suspended-sediment load. The rivers formed multistoried channel deposits (channels to 10 m deep) as well as solitary channel deposits (channels 2-5 m deep). Extensive overbank deposits resulting from episodic flooding formed fining-upward strata on the floodplain. The fining-upward strata are interbedded with tephra and beds of organic-rich sediment. Vertical-accretion deposits containing abundant roots indicate a sheet flood origin for many beds. Vertebrate and nonmarine invertebrate fossils along with plant debris were locally concentrated in the floodplain sediment. Deciduous conifers as well as abundant wetland plants, such as ferns, horsetails, and mosses, covered the coastal plain. Dinosaur skeletal remains have been found concentrated in floodplain sediments in organic-rich bone beds and as isolated bones in fluvial channel deposits in at least nine separate horizons within a 100-m-thick interval. Arenaceous foraminifers in some organic-rich beds and shallow fluvial distributaries indicate a lower coastal plain environment with marginal marine (bay) influence. Marginal marine strata

  3. Identifying the pollen of an extinct spruce species in the Late Quaternary sediments of the Tunica Hills region, south-eastern United States

    USGS Publications Warehouse

    Luke Mander,; Jacklyn Rodriguez,; Pietra G. Mueller,; Jackson, Stephen T.; Surangi W. Punyasena,

    2014-01-01

    Late Quaternary fluvial deposits in the Tunica Hills region of Louisiana and Mississippi are rich in spruce macrofossils of the extinct species Picea critchfieldii, the one recognized plant extinction of the Late Quaternary. However, the morphology of P. critchfieldii pollen is unknown, presenting a barrier to the interpretation of pollen spectra from the last glacial of North America. To address this issue, we undertook a morphometric study of Picea pollen from Tunica Hills. Morphometric data, together with qualitative observations of pollen morphology using Apotome fluorescence microscopy, indicate that Picea pollen from Tunica Hills is morphologically distinct from the pollen of P. glauca, P. mariana and P. rubens. Measurements of grain length, corpus width and corpus height indicate that Picea pollen from Tunica Hills is larger than the pollen of P. mariana and P. rubens, and is slightly larger than P. glauca pollen. We argue that the morphologically distinctive Tunica Hills Picea pollen was probably produced by the extinct spruce species P. critchfieldii. These morphological differences could be used to identify P. critchfieldii in existing and newly collected pollen records, which would refine its paleoecologic and biogeographic history and clarify the nature and timing of its extinction in the Late Quaternary.

  4. Eruption-controlled epiclastic sedimentation in a Devonian trench-slope basin: Evidence from sandstone petrofacies, Klamath Mountains, California

    SciTech Connect

    Wallin, E.T.; Trabert, D.W. . Dept. of Geoscience)

    1994-04-01

    The Devonian Gazelle Formation comprises sparsely fossiliferous shale, siltstone, siliceous mudstone, volcaniclastic sandstone, and conglomerate whose cumulative thickness is at least 1.25 km. Two end-member sand compositions combined locally to form a third mixed'' petrofacies. The volcaniclastic petrofacies was derived from an undissected magmatic arc, whereas the chert-mudrock petrofacies reflects derivation from melange of the underlying accretionary prism. The stratigraphically restricted mixed petrofacies is compositionally discrete and records thorough mixing of these two compositional end members. Data from sandstone petrography are consistent with independent geologic evidence indicating that the Gazelle Formation represents the fill of a Devonian trench-slope basin that formed above an east-dipping subduction zone. The authors interpretation of the Balaklala Rhyolite as the source of the volcaniclastic petrofacies requires proximity of the Yreka and Eastern Klamath terranes during the Early Devonian, and indicates that the eastern Klamath province has behaved as a single crustal block (sensu lato) ever since. Field study and petrographic analysis indicate that the delivery of coarse terrigenous detritus to the basin was controlled principally by episodic eruptions of rhyolitic tephra in the arc source and also by one discernible episode of change in relative sea level. This study indicates that caution must be used when invoking changes in relative sea level to explain the stratigraphic distribution of epiclastic turbidites in island-arc settings.

  5. Landscape change in eastern Georgia (Transcaucasus) during the Late Holocene - documented by fluvial sediments, slope deposits and archaeology

    NASA Astrophysics Data System (ADS)

    von Suchodoletz, Hans; Sukhishvili, Lasha; Elashvili, Mikheil; Djanelidze, Zurab; Navrozashvili, Levan; Kühn, Peter

    2014-05-01

    The semi-arid Gareja region in the Iori Highland in the eastern part of the Republic of Georgia is characterized by an annual precipitation < 600 mm and shows an open steppic landscape today. As is known from historical sources, the landscape showed the same character already during the 6th century AD when the Gareja monastery located in the center of the region was founded by Assyrian monks. However, archaeological research carried out during the Soviet Period showed the existence of numerous settlements of bronze and iron age in this region almost devoid of water resources today, hinting to some sources of fresh water allowing people to live there during those periods. Furthermore, former archaeobotanical studies assume that the region was covered by forests instead of steppes during the past, although there is no final proof yet. The goal of this study is to shed light on the development of the landscape during the prehistoric period and thus to address some of the issues described above. To do so, our work is based on the spatial pattern of prehistoric settlements derived from archaeologic data of the Soviet period, as well as on the analysis of fluvial and slope deposits from the area using a multi-proxy approach. Altogether, these data indicate a dramatic palaeoenvironmental change in the Gareja region ca. 3 ka ago, leading to the recent steppe and almost unpopulated character of the landscape.

  6. Sediment Budgets the 'Old Fashioned' way for two Subbasins of the Rio Puerco, Central New Mexico

    NASA Astrophysics Data System (ADS)

    Pavich, M. J.; Gellis, A. C.; Clark, I.; Ellwein, A. L.; Aby, S.

    2005-12-01

    A sediment budget was constructed for two subbasins of the Rio Puerco watershed, Volcano Hill Wash (9.30 km2) and Arroyo Chavez (2.28 km2), using data collected from 1995 through 1998. The subbasins were selected based on differences in land use. Arroyo Chavez was considered more degraded than Volcano Hill Wash, the latter of which received a grazing management award. The grazing density in the Arroyo Chavez watershed was higher (7.3 animals per 100 hectares) than in the Volcano Hill Wash watershed (1.0 animals per 100 hectares). A gas pipeline and numerous dirt roads are located within the Arroyo Chavez subbasin; neither are present within the Volcano Hill Wash subbasin. The 'old fashioned' sediment budget refers to the approach that was used--determining the total sediment leaving a basin and accounting for that sediment with a variety of field-based, labor intensive techniques. A sediment station with an automatic suspended-sediment sampler was installed at the mouth of each stream to quantify the amount of sediment leaving the subbasins. Upland erosion was measured using erosion pins and sediment traps. Channel erosion was measured using surveyed channel cross sections, bank pins, and scour chains. Aeolian dust deposition was measured with dust traps. Each subbasin was divided into geomorphic surfaces using aerial photographs and field descriptions of soils, slopes, and vegetation cover. In Volcano Hill Wash subbasin, five geomorphic surfaces were delineated: mesa, steep colluvial slopes, alluvium/ colluvium, eolian/alluvium, and the alluvial valley floor. In the Arroyo Chavez subbasin, seven geomorphic surfaces were delineated: mesa, steep colluvial slopes, moderate sloping hillslopes, gently sloping hillslopes, alluvial fans, well-vegetated alluvial valley floor, and a sparsely vegetated alluvial valley floor. Upland erosion and channel erosion rates were summed for each geomorphic surface using a geographical information system (GIS). Results indicate that

  7. Can control of soil erosion mitigate water pollution by sediments?

    PubMed

    Rickson, R J

    2014-01-15

    The detrimental impact of sediment and associated pollutants on water quality is widely acknowledged, with many watercourses in the UK failing to meet the standard of 'good ecological status'. Catchment sediment budgets show that hill slope erosion processes can be significant sources of waterborne sediment, with rates of erosion likely to increase given predicted future weather patterns. However, linking on-site erosion rates with off-site impacts is complicated because of the limited data on soil erosion rates in the UK and the dynamic nature of the source-pathway-receptor continuum over space and time. Even so, soil erosion control measures are designed to reduce sediment production (source) and mobilisation/transport (pathway) on hill slopes, with consequent mitigation of pollution incidents in watercourses (receptors). The purpose of this paper is to review the scientific evidence of the effectiveness of erosion control measures used in the UK to reduce sediment loads of hill slope origin in watercourses. Although over 73 soil erosion mitigation measures have been identified from the literature, empirical data on erosion control effectiveness are limited. Baseline comparisons for the 18 measures where data do exist reveal erosion control effectiveness is highly variable over time and between study locations. Given the limitations of the evidence base in terms of geographical coverage and duration of monitoring, performance of the different measures cannot be extrapolated to other areas. This uncertainty in effectiveness has implications for implementing erosion/sediment risk reduction policies, where quantified targets are stipulated, as is the case in the EU Freshwater Fish and draft Soil Framework Directives. Also, demonstrating technical effectiveness of erosion control measures alone will not encourage uptake by land managers: quantifying the costs and benefits of adopting erosion mitigation is equally important, but these are uncertain and difficult to

  8. Can control of soil erosion mitigate water pollution by sediments?

    PubMed

    Rickson, R J

    2014-01-15

    The detrimental impact of sediment and associated pollutants on water quality is widely acknowledged, with many watercourses in the UK failing to meet the standard of 'good ecological status'. Catchment sediment budgets show that hill slope erosion processes can be significant sources of waterborne sediment, with rates of erosion likely to increase given predicted future weather patterns. However, linking on-site erosion rates with off-site impacts is complicated because of the limited data on soil erosion rates in the UK and the dynamic nature of the source-pathway-receptor continuum over space and time. Even so, soil erosion control measures are designed to reduce sediment production (source) and mobilisation/transport (pathway) on hill slopes, with consequent mitigation of pollution incidents in watercourses (receptors). The purpose of this paper is to review the scientific evidence of the effectiveness of erosion control measures used in the UK to reduce sediment loads of hill slope origin in watercourses. Although over 73 soil erosion mitigation measures have been identified from the literature, empirical data on erosion control effectiveness are limited. Baseline comparisons for the 18 measures where data do exist reveal erosion control effectiveness is highly variable over time and between study locations. Given the limitations of the evidence base in terms of geographical coverage and duration of monitoring, performance of the different measures cannot be extrapolated to other areas. This uncertainty in effectiveness has implications for implementing erosion/sediment risk reduction policies, where quantified targets are stipulated, as is the case in the EU Freshwater Fish and draft Soil Framework Directives. Also, demonstrating technical effectiveness of erosion control measures alone will not encourage uptake by land managers: quantifying the costs and benefits of adopting erosion mitigation is equally important, but these are uncertain and difficult to

  9. High-resolution well-log derived dielectric properties of gas-hydrate-bearing sediments, Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    USGS Publications Warehouse

    Sun, Y.; Goldberg, D.; Collett, T.; Hunter, R.

    2011-01-01

    A dielectric logging tool, electromagnetic propagation tool (EPT), was deployed in 2007 in the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well (Mount Elbert Well), North Slope, Alaska. The measured dielectric properties in the Mount Elbert well, combined with density log measurements, result in a vertical high-resolution (cm-scale) estimate of gas hydrate saturation. Two hydrate-bearing sand reservoirs about 20 m thick were identified using the EPT log and exhibited gas-hydrate saturation estimates ranging from 45% to 85%. In hydrate-bearing zones where variation of hole size and oil-based mud invasion are minimal, EPT-based gas hydrate saturation estimates on average agree well with lower vertical resolution estimates from the nuclear magnetic resonance logs; however, saturation and porosity estimates based on EPT logs are not reliable in intervals with substantial variations in borehole diameter and oil-based invasion.EPT log interpretation reveals many thin-bedded layers at various depths, both above and below the thick continuous hydrate occurrences, which range from 30-cm to about 1-m thick. Such thin layers are not indicated in other well logs, or from the visual observation of core, with the exception of the image log recorded by the oil-base microimager. We also observe that EPT dielectric measurements can be used to accurately detect fine-scale changes in lithology and pore fluid properties of hydrate-bearing sediments where variation of hole size is minimal. EPT measurements may thus provide high-resolution in-situ hydrate saturation estimates for comparison and calibration with laboratory analysis. ?? 2010 Elsevier Ltd.

  10. Quantifying sediment connectivity in Wadi Al-Arab (NW Jordan) using a sediment budget approach

    NASA Astrophysics Data System (ADS)

    Kraushaar, Sabine; Pöppl, Ronald

    2015-04-01

    Due to data scarcity, sediment connectivity most often only qualitatively describes the potential transfer of sediments through a landscape. However, quantitative information on sediment delivery is of special relevance for modelling approaches as well as for sustainable land and water management, especially in water scarce regions such as Jordan, where valuable water reservoirs suffer from sediment pollution. Measurements are needed to quantify sediment outputs of the different land units and to trace their pathways though the catchments. This study uses the outcomes of a multiple response sediment budget approach conducted in the Wadi al-Arab catchment in northwest Jordan (263.5 km²) to quantify sediment connectivity. The catchment shows a Mediterranean to semi arid climate and consists of carbonatic and marly geology of the Upper Cretaceous. The topography ranges from rolling hills in the East to steeper mountainous areas in the North and West were olive orchards are the main agricultural use. Soil erosion measurements in the main land use units and relevant sediment sources, such as olive orchards, agricultural fields, and natural vegetated slopes uncovered the potential ranges of soil erosion rates in these units. Furthermore, the annual sediment yield in the Wadi Al Arab water reservoir was calculated. With the extrapolation of the erosion rates of the main contributing land use units and the annual sediment amount that reaches the sink, a maximum value of lateral sediment connectivity could be quantified, reaching up to 18%. A multiple sediment fingerprint method was used to delineate the relative contribution of each measured source to the sink based on the lake sediment samples. Supported by additional 137Cs analysis of terrace samples and a survey of the Wadi bed a high longitudinal connectivity could be derived. The applied method mix allowed the quantification of lateral sediment connectivity on catchment scale and gave a comprehensive understanding of

  11. Large-scale deformational systems in the South Polar Layered Deposits (Promethei Lingula, Mars): "Soft-sediment" and Deep-Seated Gravitational Slope Deformations Mechanisms

    NASA Astrophysics Data System (ADS)

    Guallini, Luca; Brozzetti, Francesco; Marinangeli, Lucia

    2012-08-01

    The present study is the first attempt at a detailed structural and kinematic analysis of large-scale deformational systems observed in the South Polar Layered Deposits (SPLDs) in the Promethei Lingula (PL) margins (Mars). By systematically collecting attitude data referable to previously unknown deformational structures and defining the cross-cut relationships of the structures, we reconstructed a deformational history consisting of two superimposed, well-defined stages. The first stage is dominated by large-scale strike-slip and transtensional faults arranged into conjugate systems and delimiting shear zones that show a wide range of subsidiary structures, including normal and reverse faults, drag folds, boudins, S-C tectonites and sub-horizontal interstratal shear planes marked by sygmoidal boudins. Other typical structures referable to this event are ductile folds (locally true convolute folds) and lobes (ball-and-pillow structures) affecting certain marker beds of the succession. We suggest that the structural assemblage might be the expression of a shallow soft-sediment tectonics that possibly occurred during warm periods of the South Pole climate. The second stage seems to affect the weaker and in certain cases pre-deformed stratigraphic levels of the SPLD succession. This stage is mainly characterized by extensional deformations caused by gravity. The consequence of the deformations is the nucleation of Deep-Seated Gravitational Slope Deformations (DSGSDs) marked by typical morphostructures, such as scarps, trenches and bulging basal contractant zones. These phenomena were never observed within an ice cap. According to terrestrial modeling, these slow collapses were caused by (1) the presence of detachment levels (i.e., subhorizontal bedding planes) along which the ice-sheet margins can slide and (2) the development of listric faults within the glacial mass, which merge with sub-horizontal shear planes in the subsurface. The presence of complex

  12. The role of Internal Solitary Waves on deep-water sedimentary processes: the case of up-slope migrating sediment waves off the Messina Strait

    NASA Astrophysics Data System (ADS)

    Droghei, Riccardo; Falcini, Federico; Martorelli, Eleonora; Casalbore, Daniele; Mosetti, Renzo; Salusti, Ettore; Sannino, Gianmaria; Santoleri, Rosalia; Chiocci, Francesco

    2016-04-01

    ., & Reuning, L. (2015). Three-dimensional seismic analysis of sediment waves and related geomorphological features on a carbonate shelf exposed to large amplitude internal waves, Browse Basin region, Australia. Sedimentology, 62(1), 87-109. Alpers, W., & Salusti, E. (1983). Scylla and Charybdis observed from space. Journal of Geophysical Research: Oceans (1978-2012), 88(C3), 1800-1808. Sapia, A., & Salusti, E. (1987). Observation of nonlinear internal solitary wave trains at the northern and southern mouths of the Strait of Messina. Deep Sea Research Part A. Oceanographic Research Papers, 34(7), 1081-1092. Artale, V., Levi, D., Marullo, S., & Santoleri, R. (1990). Analysis of nonlinear internal waves observed by Landsat thematic mapper. Journal of Geophysical Research: Oceans (1978-2012), 95(C9), 16065-16073. Brandt, P., Rubino, A., Quadfasel, D., Alpers, W., Sellschopp, J., & Fiekas, H. V. (1999). Evidence for the influence of Atlantic-Ionian stream fluctuations on the tidally induced internal dynamics in the Strait of Messina. Journal of physical oceanography, 29(5), 1071-1080. Puig, P., Palanques, A., Guillén, J., & El Khatab, M. (2004). Role of internal waves in the generation of nepheloid layers on the northwestern Alboran slope: implications for continental margin shaping. Journal of Geophysical Research: Oceans (1978-2012), 109(C9). Haren, H., Ribó, M., & Puig, P. (2013). (Sub-) inertial wave boundary turbulence in the Gulf of Valencia. Journal of Geophysical Research: Oceans, 118(4), 2067-2073.

  13. Bottom water production variability in the Ross Sea slope during the Late-Pleistocene-Holocene as revealed by benthic foraminifera and sediment geochemistry

    NASA Astrophysics Data System (ADS)

    Asioli, A.; Langone, L.; Tateo, F.; Giannossi, M. L.; Giglio, F.; Summa, V.; Piva, A.; Ridente, D.; Trincardi, F.

    2009-04-01

    The Antarctic area produces bottom waters that ventilate the vast majority of the deep basins in the rest of the world ocean. The rate of formation in the source area and the strength of these cold bottom waters affect their flow toward the equator and are key factors affecting the Global Thermohaline Circulation during modern and past climate conditions. We present the results of a multidisciplinary study carried out on a core collected in 2377m of water depth on the slope off the Drygalski Basin (Ross Sea), along the modern path of the bottom waters. The goal of this research is to detect a qualitative signal of possible changes in the rate of bottom water production during the Late Pleistocene-Holocene by integrating micropaleontological and geochemical proxies. The micropaleontological signal is represented by the quantitative and qualitative variations of the agglutinated benthic foraminifera assemblages, while the amount of TOC, nitrogen, δ13C, δ15N, biogenic silica, CaCO3 in the sediment, along with the bulk rock mineralogy, provide information on the paleoproductivity and allow reconstruction of changes in the paleocirculation. The chronology is supported by 14C AMS datings on organic matter. Although this study is still in progress, the results obtained allow the following observations: 1) the Holocene sequence includes a major turnover around 8-8.5 calib kyr BP, leading to reduced nutrient utilization, probably reflecting an increased nutrient supply induced by an enhanced Upper Circumpolar Deep Water upwelling; 2) within this general context, the total concentration of benthic foraminifera preserved in the fossil component records millennial scale cycles of variable amplitude after 8.5 calib kyr BP and to present time. This oscillatory trend is paralleled by other parameters, such as the magnetic susceptibility, the dry density, the sheet silicates and the δ15N; 3) minima in foraminifera concentration reflect relatively increased dissolution, weaker

  14. A study of sediment motion and bottom boundary layer dynamics over the Middle Atlantic Bight shelf and upper slope. Final report

    SciTech Connect

    Churchill, James H.; Williams, Albert J.

    2001-02-14

    This report summarizes research on circulation and particle dynamics over the Middle Atlantic Bight shelf and upper slope. It includes an overview of the field experiments conducted in the waters off North Carolina, and gives the principal results from these experiments.

  15. Lower Permian sediment-gravity-flow sequence, eastern California

    USGS Publications Warehouse

    Stevens, C.H.; Lico, M.S.; Stone, P.

    1989-01-01

    The Lower Permian (middle Wolfcampian) Zinc Hill sequence, a 65- to 110-m-thick series of beds in the Owens Valley Group in east-central California, comprises sediment-gravity-flow deposits consisting of carbonate sediment that originated on, and siliciclastic sediment that may have been generally ponded behind, a carbonate shelf to the east and northeast. Thickness patterns and paleocurrent indicators show that the sediment forming this sequence was transported primarily southeastward and deposited in a southeast-trending, lobe-shaped body. Evidently, the sediment was carried from the shelf by sediment-gravity flows that travelled westward down the slope and then turned southeastward upon reaching a southeast-trending basin at the base of the slope. Data derived from the study of this basin, which paralleled the shelf edge and is thought to have formed parallel to a southeast-oriented segment of the Early Permian continental margin, constitute one of the most important arguments favoring a Pennsylvanian to Early Permian age of truncation of the western North American continental margin. ?? 1989.

  16. Downward Slope

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This false-color image from NASA's Mars Exploration Rover Opportunity panoramic camera shows a downward view from the rover as it sits at the edge of 'Endurance' crater. The gradual, 'blueberry'-strewn slope before the rover contains an exposed dark layer of rock that wraps around the upper section of the crater. Scientists suspect that this rock layer will provide clues about Mars' distant past. This mosaic image comprises images taken from 10 rover positions using 750, 530 and 430 nanometer filters, acquired on sol 131 (June 6, 2004).

  17. Gullied Slope

    NASA Technical Reports Server (NTRS)

    2005-01-01

    20 May 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows gullies formed on an equator-facing slope among mounds in Acidalia Planitia. Similar gullies occur in a variety of settings at middle and polar latitudes in both martian hemispheres.

    Location near: 49.8oN, 22.7oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Summer

  18. David Keynes Hill.

    PubMed

    Huxley, Andrew

    2003-01-01

    David Hill followed his father, A.V. Hill FRS, into the study of muscular contraction. Using a wide range of experimental techniques, he made several important advances of which the most important was the discovery of the 'short-range elastic component', a phenomenon which implied that even in the resting state there was an interaction between the thick (myosin) and thin (actin) filaments. He also studied physical changes in nerve when stimulated.

  19. Human impact on erosion patterns and sediment transport in the Yangtze River

    NASA Astrophysics Data System (ADS)

    Sun, Xilin; Li, Chang'an; Kuiper, K. F.; Zhang, Zengjie; Gao, Jianhua; Wijbrans, J. R.

    2016-08-01

    Sediment load in rivers is an indicator of erosional processes in the upstream river catchments. Understanding the origin and composition of the sediment load can help to assess the influence of natural processes and human activities on erosion. Tectonic uplift, precipitation and run-off, hill slopes and vegetation can influence erosion in natural systems. Agriculture and deforestation are expected to increase the sediment yield, but dams and reservoirs can trap much of this sediment before it reaches the ocean. Here, we use major element composition and 40Ar/39Ar ages of detrital muscovites to constrain the sediment contribution of various tributaries to sedimentation in the Yangtze delta. The sediment contribution calculated from muscovite data was compared with that estimated from current sediment load data from gauging stations. Muscovite data show that the main contributor to the Yangtze delta sands is the Min River, while the current sediment load suggests that the Jinsha and Jialing rivers are the most important current contributors to delta sediments. We suggest that this difference reflects an "old" and "young" erosion pattern, respectively as medium grained muscovite could be transported much slower than suspended sediment load in the complex river-lake systems of the Yangtze River basin. These two different erosion patterns likely reflect enhanced human activity (deforestation, cultivation, and mining) that increasingly overwhelmed long-time natural factors controls on erosion since ~ 1900 cal years B.P.

  20. Analysis of the seismic signals generated by controlled single-block rockfalls on soft clay shales sediments: the Rioux Bourdoux slope experiment (French Alps).

    NASA Astrophysics Data System (ADS)

    Hibert, Clément; Provost, Floriane; Malet, Jean-Philippe; Bourrier, Franck; Berger, Frédéric; Bornemann, Pierrick; Borgniet, Laurent; Tardif, Pascal; Mermin, Eric

    2016-04-01

    Understanding the dynamics of rockfalls is critical to mitigate the associated hazards but is made very difficult by the nature of these natural disasters that makes them hard to observe directly. Recent advances in seismology allow to determine the dynamics of the largest landslides on Earth from the very low-frequency seismic waves they generate. However, the vast majority of rockfalls that occur worldwide are too small to generate such low-frequency seismic waves and thus these methods cannot be used to reconstruct their dynamics. However, if seismic sensors are close enough, these events will generate high-frequency seismic signals. Unfortunately we cannot yet use these high-frequency seismic records to infer parameters synthetizing the rockfall dynamics as the source of these waves is not well understood. One of the first steps towards understanding the physical processes involved in the generation of high-frequency seismic waves by rockfalls is to study the link between the dynamics of a single block propagating along a well-known path and the features of the seismic signal generated. We conducted controlled releases of single blocks of limestones in a gully of clay-shales (e.g. black marls) in the Rioux Bourdoux torrent (French Alps). 28 blocks, with masses ranging from 76 kg to 472 kg, were released. A monitoring network combining high-velocity cameras, a broadband seismometer and an array of 4 high-frequency seismometers was deployed near the release area and along the travel path. The high-velocity cameras allow to reconstruct the 3D trajectories of the blocks, to estimate their velocities and the position of the different impacts with the slope surface. These data are compared to the seismic signals recorded. As the distance between the block and the seismic sensors at the time of each impact is known, we can determine the associated seismic signal amplitude corrected from propagation and attenuation effects. We can further compare the velocity, the

  1. Confidence Hills Mineralogy and Chemin Results from Base of Mt. Sharp, Pahrump Hills, Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Cavanagh, P. D.; Bish, D. L.; Blake, D. F.; Vaniman, D. T.; Morris, R. V.; Ming, D. W.; Rampe, E. B.; Achilles, C. N.; Chipera, S. J.; Treiman, A. H.; Downs, R. T.; Morrison, S. M.; Fendrich, K. V.; Yen, A. S.; Grotzinger, J.; Crisp, J. A.; Bristow, T. F.; Sarrazin, P. C.; Farmer, J. D.; Des Marais, D. J.; Stolper, E. M.; Morookian, J. M.; Wilson, M. A.; Spanovich, N.; Anderson, R. C.

    2015-01-01

    The Mars Science Laboratory (MSL) rover Curiosity recently completed its fourth drill sampling of sediments on Mars. The Confidence Hills (CH) sample was drilled from a rock located in the Pahrump Hills region at the base of Mt. Sharp in Gale Crater. The CheMin X-ray diffractometer completed five nights of analysis on the sample, more than previously executed for a drill sample, and the data have been analyzed using Rietveld refinement and full-pattern fitting to determine quantitative mineralogy. Confidence Hills mineralogy has several important characteristics: 1) abundant hematite and lesser magnetite; 2) a 10 angstrom phyllosilicate; 3) multiple feldspars including plagioclase and alkali feldspar; 4) mafic silicates including forsterite, orthopyroxene, and two types of clinopyroxene (Ca-rich and Ca-poor), consistent with a basaltic source; and 5) minor contributions from sulfur-bearing species including jarosite.

  2. Western Slope of Andes, Peru

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Along the western flank of the Andes, 400 km SE of Lima Peru, erosion has carved the mountain slopes into long, narrow serpentine ridges. The gently-sloping sediments have been turned into a plate of worms wiggling their way downhill to the ocean.

    The image was acquired September 28, 2004, covers an area of 38 x 31.6 km, and is located near 14.7 degrees south latitude, 74.5 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  3. Sediment and nutrient delivery from thermokarst features in the foothills of the North Slope, Alaska: Potential impacts on headwater stream ecosystems

    USGS Publications Warehouse

    Bowden, W.B.; Gooseff, M.N.; Balser, A.; Green, A.; Peterson, B.J.; Bradford, J.

    2008-01-01

    Permafrost is a defining characteristic of the Arctic environment. However, climate warming is thawing permafrost in many areas leading to failures in soil structure called thermokarst. An extensive survey of a 600 km2 area in and around the Toolik Lake Natural Research Area (TLNRA) revealed at least 34 thermokarst features, two thirds of which were new since ???1980 when a high resolution aerial survey of the area was done. Most of these thermokarst features were associated with headwater streams or lakes. We have measured significantly increased sediment and nutrient loading from thermokarst features to streams in two well-studied locations near the TLNRA. One small thermokarst gully that formed in 2003 on the Toolik River in a 0.9 km2 subcatchment delivered more sediment to the river than is normally delivered in 18 years from 132 km2 in the adjacent upper Kuparuk River basin (a long-term monitoring reference site). Ammonium, nitrate, and phosphate concentrations downstream from a thermokarst feature on Imnavait Creek increased significantly compared to upstream reference concentrations and the increased concentrations persisted over the period of sampling (1999-2005). The downstream concentrations were similar to those we have used in a long-term experimental manipulation of the Kuparuk River and that have significantly altered the structure and function of that river. A subsampling of other thermokarst features from the extensive regional survey showed that concentrations of ammonium, nitrate, and phosphate were always higher downstream of the thermokarst features. Our previous research has shown that even minor increases in nutrient loading stimulate primary and secondary production. However, increased sediment loading could interfere with benthic communities and change the responses to increased nutrient delivery. Although the terrestrial area impacted by thermokarsts is limited, the aquatic habitat altered by these failures can be extensive. If warming in

  4. Change in the Nd isotopic composition of the bottom water and detrital sediments on the Bering Slope over the last 500 kyrs with implications for the formation of the North Pacific Intermediate Water

    NASA Astrophysics Data System (ADS)

    Jang, K.; Huh, Y.; Han, Y.

    2015-12-01

    The Bering Sea is a potential location for the formation of the North Pacific Intermediate/Deep Water (NPIW/NPDW) and may play an important role in the global heat distribution. We reconstructed the neodymium isotopic ratio (ɛNd) of authigenic Fe-Mn oxide coatings and detrital sediments on the Bering Slope (IODP Expedition 323 site U1345; water depth 1008 m) over the last 500 kyrs. The ɛNd is a quasi-conservative water mass tracer. We compared three different leaching techniques to assure that authigenic signals are captured without contamination from terrigenous sources: (1) leaching (3 hours) with 0.02 M hydroxylamine hydrochloride (HH) in 25% buffered acetic acid after decarbonation; sediment/solution (v/v) > 10, (2) leaching (1 hour) with 0.02 M HH in 25% buffered acetic acid without decarbonation; sediment/solution ~ 1, and (3) leaching (1 hour) with 0.005 M HH in 1.5% buffered acetic acid-0.003 M Na-EDTA without decarbonation; sediment/solution > 40. The low Al concentrations and less radiogenic ɛNdvalues indicated that method (2) is the most appropriate leaching process. The average ɛNd of the authigenic fraction over the last 500 kyrs is -3.3 ± 0.9 (1σ, n=38), with large temporal fluctuations. The ɛNd of authigenic and detrital fractions are well correlated (r2 ~ 0.66), suggesting that the bottom water composition in the Bering Sea was governed by terrigenous inflow from surrounding areas. Radiogenic ɛNd peaks (up to -1.9) seem to be influenced by radiogenic water inflow from the the Kamchatka or Aluetian arcs. The high bulk density and low b* values imply higher terrigenous versus biological contribution and enhanced sea ice formation. Subsequent brine formation would have triggered sinking of radiogenic surface water, forming the NPIW. On the other hand, non-radiogenic ɛNd troughs (down to -5.3) are observed at times of low bulk density and high b* values. We presume higher biological productivity which is supported by the high opal content at

  5. Molecular characterisation of five nematode species (Chromadorida, Selachinematidae) from shelf and upper slope sediments off New Zealand, with description of three new species.

    PubMed

    Leduc, Daniel; Zhao, Zeng Qi

    2016-01-01

    Limited molecular sequence data are available for selachinematid nematodes, with little or no data from the Southern Hemisphere or habitats beyond the subtidal zone. Here, we provide molecular sequence data for the small subunit (SSU) 18S rDNA gene and D2-D3 region of large subunit (LSU) 28S rDNA gene of three new (Cheironchus haurakiensis n. sp., Halichoanolaimus anisospermus n. sp., and Bendiella longicauda n. sp.) and two known selachinematid species (Pseudocheironchus ingluviosus Leduc, 2013 and Synonchiella rotundicauda Leduc, 2013) from shelf and upper slope environments off northeastern New Zealand. Cheironchus haurakiensis n. sp. is characterised by having a multispiral amphideal fovea with five turns, lateroventral mandibles with central arm curved distally and bearing 4-5 pointed projections, and each palm bearing 4-5 pointed projections, ten precloacal supplements in a 1 + 9 arrangement, spicules 78 µm long, and blunt conical tail with thickened cuticle. Halichoanolaimus anisospermus n. sp. is characterised by having an amphideal fovea with 5-6 turns, anterior portion of buccal cavity with cuticularised rhabdions terminating in three sets of seven pairs of teeth (denticles), with the central pair of each set positioned above the other six, dimorphism in size of sperm cells between anterior and posterior testes, gubernaculum consisting of two detached lateral pieces (crurae) tapering distally, three small precloacal supplements consisting of slightly thickened and raised cuticle, and a conicocylindrical tail with conical portion 32-38% of total tail length. Bendiella longicauda n. sp. is characterised by having two dorsosublateral rows of pores from midbody to level of cloaca, amphideal fovea with 4.5 turns, posterior rhabdions with numerous small denticles, spicules 2.1 cloacal body diameters long, a conicocylindrical tail 13.3 cloacal body diameters long and with conical portion 8% of tail length. Preliminary phylogenetic analyses for the family

  6. A shallow landslide analysis method consisting of contour line based method and slope stability model with critical slip surface

    NASA Astrophysics Data System (ADS)

    Tsutsumi, D.

    2015-12-01

    To mitigate sediment related disaster triggered by rainfall event, it is necessary to predict a landslide occurrence and subsequent debris flow behavior. Many landslide analysis method have been developed and proposed by numerous researchers for several decades. Among them, distributed slope stability models simulating temporal and spatial instability of local slopes are more essential for early warning or evacuation in area of lower part of hill-slopes. In the present study, a distributed, physically based landslide analysis method consisting of contour line-based method that subdivide a watershed area into stream tubes, and a slope stability analysis in which critical slip surface is searched to identify location and shape of the most instable slip surface in each stream tube, is developed. A target watershed area is divided into stream tubes using GIS technique, grand water flow for each stream tubes during a rainfall event is analyzed by a kinematic wave model, and slope stability for each stream tube is calculated by a simplified Janbu method searching for a critical slip surface using a dynamic programming method. Comparing to previous methods that assume infinite slope for slope stability analysis, the proposed method has advantage simulating landslides more accurately in spatially and temporally, and estimating amount of collapsed slope mass, that can be delivered to a debris flow simulation model as a input data. We applied this method to a small watershed in the Izu Oshima, Tokyo, Japan, where shallow and wide landslides triggered by heavy rainfall and subsequent debris flows attacked Oshima Town, in 2013. Figure shows the temporal and spatial change of simulated grand water level and landslides distribution. The simulated landslides are correspond to the uppermost part of actual landslide area, and the timing of the occurrence of landslides agree well with the actual landslides.

  7. Oblique View of Columbia Hills

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Annotated Version

    This perspective view looking toward the northeast shows part of the Columbia Hills range inside Gusev Crater. At the center is the winter campaign site of NASA's Mars Exploration Rover Spirit.

    On its 805th Martian day, or sol, (April 8, 2006), Spirit was parked on a slope tilting 11 degrees to the north to maximize sunlight on the solar panels during the southern winter season. Science observations were formulated to take advantage of the long time during which the rover was parked. The plan focused on two tasks: tracking atmospheric and surface dynamics by periodically surveying the surface and atmosphere; and extensively examining surrounding terrains, rocks and soils using the panoramic camera and the miniature thermal emission spectrometer, coupled with long duration measurements using the alpha particle X-ray and Moessbauer spectrometers of rock and soil targets. For reference, the feature known as 'Home Plate' is approximately 90 meters (295 feet) wide.

    An image from Mars Global Surveyor's Mars Orbital Camera, catalogued as E03_00012 and courtesy Malin Space Science Systems, was used as the base image for this figure. The perspective was generated using elevation data generated from analyses of the camera's stereo images by the U.S. Geological Survey, Flagstaff, Ariz.

  8. What is the slope of the U.S. continental slope?

    SciTech Connect

    Pratson, L.F.; Haxby, W.F.

    1996-01-01

    Extensive high-resolution, multibeam bathymetry of five U. S. continental margins provides new, detailed information about the angle of continental slopes in different sedimentary and tectonic settings. The steepest continental slope examined is the passive-carbonate west Florida slope (4.4{degree} regional slope and 12.0{degree} mean local slope). The steepest of the four clastic continental slopes is the passive New Jersy-Maryland slope (2.5{degree} and 7.6{degree}). Less steep, at both regional and local scales, are the more rugged, tectonically active and probably unstable salt-tectonized louisiana slope (0.5{degree} and 2.9{degree}), strike-slip California slope (1.8{degree} and 5.2{degree}) and convergent oregon slope (2.0{degree} and 5.2{degree}). Frequency grids of local slope magnitude vs. depth and dip direction for the two passive continental slopes reflect present-day morphology predominantly being shaped by lithology (West Florida), sedimentation (New Jersey-Maryland), and downslope-directed erosion(New Jersey-Maryland, west Florida). The grids for the three tectonically acctive continental slopes reflect morphology partly (California) to predominantly (Louisiana, Oregon) being shaped by tectonics. 15 refs., 2 figs.

  9. Important geological and biological impacts of natural hydrocarbon seeps: Northern Gulf of Mexico continental slope

    SciTech Connect

    Roberts, H.H. )

    1993-11-01

    Large volumes of siliciclastic sediments, input especially during periods of lowered sea level, and compensating salt tectonics have produced a continental slope that is arguably the most complex in today's oceans. Faults associated with deformation of salt and shale provide the primary migration routes for hydrocarbon gases, crude oil, brines, and formation fluids to the modern sea floor. Since the mid 1980s, it has become increasingly clearer that this process has an extremely important impact on the geomorphology, sedimentology, and biology of the modern continental slope. Hydrocarbon source, flux rate, and water depth are important determinants of sea-floor response. Under rapid flux conditions mud volcanoes (to 1 km wide and 50 m high) result, and hydrate hills (rich with authigenic carbonates), carbonate lithoherms, and isolated communities of chemosymbiotic organisms with associated hardgrounds represent much slower flux responses. In numerous moderate- to low-flux cases, cold seep products function to support islands of productivity for communities of chemosymbiotic organisms that contribute both directly (shell material) and through chemical byproducts to the production of massive volumes of calcium-magnesium carbonate in the form of hardgrounds, stacked slabs, and discrete moundlike buildups (commonly >20m). Seep-related carbonates of the Gulf of Mexico continental slope, as well those formed through degassing of accretionary prisms along active margins, are now thought to create hardgrounds and discrete buildups that are excellent analogs for many problematic carbonate buildups in ancient deep-water siliciclastic rocks.

  10. Preventing landslides on terraced slopes: A methodological approach in planning and constructing new terraces

    NASA Astrophysics Data System (ADS)

    Ažman Momirski, Lucija

    2015-04-01

    In everyday practice, the construction of terraces does not follow a premade plan. Consequently, poorly designed and maintained terraces are often significant sediment sources induced by terrace collapse. The purpose of a plan for terrace construction is to arrange terraces according to geological, geomechanical, geodetic, agricultural, and other data. It is possible to anticipate the consequences of these arrangements through carefully considered decisions (about the ratio of the terrace slope, the quantity and direction of soil shifted when constructing terraces, fitting the terrace geometry to the terrain geometry, the width and length of terrace plains, the inclinations of terrace plains, the construction of field roads and turning points, the construction of drainage for removing groundwater, and other factors). Such a methodological approach in planning and constructing new terraces ensures greater stability of terraces, the smallest quantity of earth shifted, and the greatest possible area of usable land. Building terraces is a direct method for preventing landslides. Building terraces according to a plan increases the efficiency of this method. Such an approach is even more important in areas where terraces extend from the top to bottom of slopes. Two case studies from the Mediterranean area are presented: old terraces from Brkini area, where terraces and their slopes have preserved the same form for almost two hundred years, and the planning process for newly constructed terraced vineyards in the Gorizia Hills with post-project monitoring.

  11. Geotechnical characteristics and slope stability in the Gulf of Cadiz

    USGS Publications Warehouse

    Lee, H.; Baraza, J.

    1999-01-01

    Sedimentological and geotechnical analyses of thirty-seven core samples from the Gulf of Cadiz continental margin were used to define the regional variability of sediment properties and to assess slope stability. Considering the sediment property data set as a whole, there is an association between grain size, plasticity and water content. Any one of these properties can be mapped regionally to provide an indication of the dominant surface sediment lithology. Based on static sediment strength, a simplified slope stability analysis showed that only steep slopes (> 16??for even the most vulnerable sediment) can fail under static loading conditions. Accordingly, transient loads, such as earthquakes or storms, are needed to cause failure on more moderate slopes. A regional seismic slope stability analysis of the Cadiz margin was performed based on detailed geotechnical testing of four gravity core samples. The results showed that the stability of these slopes under seismic loading conditions depends upon sediment density, the cyclic loading shear strength, the slope steepness, and the regional seismicity. Sediment density and cyclic loading shear strength are dependent upon water content, which can act as a proxy for plasticity and texture effects. Specifically, Sediment in the water content range of 50-56% is most vulnerable to failure under cyclic loading within the Cadiz margin. As a result, for a uniform seismicity over the region, susceptibility to failure during seismic loading conditions increases with increasing slope steepness and is higher if the sediment water content is in the 50-56% range than if it is not. The only sampled zone of failure on the continental slope contains sediment with water content in this critical range. Storm-wave-induced instability was evaluated for the continental shelf. The evaluation showed that a storm having hundreds of waves with a height in the range of 16 m might be capable of causing failure on the shelf. However, no

  12. Segment lengths influence hill walking strategies.

    PubMed

    Sheehan, Riley C; Gottschall, Jinger S

    2014-08-22

    Segment lengths are known to influence walking kinematics and muscle activity patterns. During level walking at the same speed, taller individuals take longer, slower strides than shorter individuals. Based on this, we sought to determine if segment lengths also influenced hill walking strategies. We hypothesized that individuals with longer segments would display more joint flexion going uphill and more extension going downhill as well as greater lateral gastrocnemius and vastus lateralis activity in both directions. Twenty young adults of varying heights (below 155 cm to above 188 cm) walked at 1.25 m/s on a level treadmill as well as 6° and 12° up and downhill slopes while we collected kinematic and muscle activity data. Subsequently, we ran linear regressions for each of the variables with height, leg, thigh, and shank length. Despite our population having twice the anthropometric variability, the level and hill walking patterns matched closely with previous studies. While there were significant differences between level and hill walking, there were few hill walking variables that were correlated with segment length. In support of our hypothesis, taller individuals had greater knee and ankle flexion during uphill walking. However, the majority of the correlations were between tibialis anterior and lateral gastrocnemius activities and shank length. Contrary to our hypothesis, relative step length and muscle activity decreased with segment length, specifically shank length. In summary, it appears that individuals with shorter segments require greater propulsion and toe clearance during uphill walking as well as greater braking and stability during downhill walking. PMID:24968942

  13. 'Scarecrow' Descends Hill

    NASA Technical Reports Server (NTRS)

    2007-01-01

    An engineering model for NASA's Mars Science Laboratory makes its way up a hill in the Mars Yard testing area at NASA's Jet Propulsion Laboratory. The model, called 'Scarecrow' because it does not include a computer brain, is used for tests of mobility and landing.

    The Mars Science Laboratory rover is in development for launch in 2009. JPL, a division of the California Institute of Technology, Pasadena, manages the mission for the NASA Science Mission Directorate, Washington.

  14. Nose Hill Artifacts

    ERIC Educational Resources Information Center

    Hansen, Vivian

    2008-01-01

    A Blackfoot woman, caught in the act of adultery, was condemned at this site to have her nose cut off as a penalty for her actions. People do not know her story. The tribe cast it on the ground. And so She, Nose Hill, was named. John Laurie Boulevard holds her mound in a circlet of asphalt, defining the map of her "terra incognita." She is a park…

  15. Suspended sediment apportionment in a South-Korean mountain catchment

    NASA Astrophysics Data System (ADS)

    Birkholz, Axel; Meusburger, Katrin; Park, Ji-Hyung; Alewell, Christine

    2016-04-01

    Due to the rapid agricultural expansion and intensification during the last decades in South-Korea, large areas of hill slope forests were transformed to paddies and vegetable fields. The intensive agriculture and the easily erodible soils in our catchment are a major reason for the increased erosion causing suspended sediments to infiltrate into the close drinking water reservoir. The drinking water reservoir Lake Soyang provides water supply for over ten million people in Seoul. Landscape managers need to know the exact origin of these sediments before they can create landscape amelioration schemes. We applied a compound-specific stable isotope (CSSI) approach (Alewell et al., 2015) to apportion the sources of the suspended sediments between forest and agricultural soil contribution to the suspended sediments in a different catchment and applied the same approach to identify and quantify the different sources of the suspended sediments in the river(s) contributing to Lake Soyang. We sampled eight soil sites within the catchment considering the different landuse types forest, rice paddies, maize and vegetables. Suspended sediments were sampled at three outlets of the different sub-catchments. Soils and suspended sediments are analysed for bulk carbon and nitrogen isotopes, compound-specific carbon isotopes of plant-wax derived long-chain fatty acids and long-chain n-alkanes. Fatty acid and alkane isotopes are then used in mixing calculations and the mixing model software IsoSource to find out the contribution of the different source soils to the suspended sediments. We present first data of the source soils and the suspended sediments. C. Alewell, A. Birkholz, K. Meusburger, Y. Schindler-Wildhaber, L. Mabit, 2015. Sediment source attribution from multiple land use systems with CSIA. Biogeosciences Discuss. 12: 14245-14269.

  16. Geologic and paleoecologic studies of the Nebraska Sand Hills

    USGS Publications Warehouse

    Ahlbrandt, Thomas S.; Fryberger, S.G.; Hanley, John H.; Bradbury, J. Platt

    1980-01-01

    PART A: The Nebraska Sand Hills are an inactive, late Quaternary, most probably Holocene, dune field (covering 57,000 km 2 ) that have been eroded along streams and in blowouts, resulting in excellent lateral and vertical exposures of the stratification of dune and interdune sediments. This paper presents new data on the geometry, primary sedimentary structures, modification of sedimentary structures, direction of sand movement, and petrography of these eolian deposits. Eolian deposits of the Sand Hills occur as relatively thin (9-24 m) 'blanket' sands, composed of a complex of dune and discontinuous, diachronous interdune deposits unconformably overlying fluviolacustrine sediments. The internal stratification of large dunes in the Sand Hills (as high as 100 m), is similar to the internal stratification of smaller dunes of the same type in the Sand Hills, differing only in scale. Studies of laminae orientation in the Sand Hills indicate that transverse, barchan, and blowout dunes can be differentiated in rocks of eolian origin using both the mean dip angle of laminae and the mean angular deviation of dip direction. A variety of secondary structures modify or replace primary eolian stratification in the Sand Hills, the more common of which are dissipation structures and bioturbation. Dissipation structures in the Sand Hills may develop when infiltrating water deposits clay adjacent to less permeable layers in the sand, or along the upper margins of frozen layers that form in the sands during winter. Cross-bed measurements from dunes of the Nebraska Sand Hills necessitate a new interpretation of the past sand transport directions. The data from these measurements indicate a general northwest-to-southeast drift of sand, with a more southerly drift in the southeast part of the Sand Hills. A large area of small dunes < 100 m high) described by Smith (1965) as linear or seif in the central part of the Sand Hills was interpreted by him on the basis of morphology only. We

  17. Behavior of fiber reinforced sandy slopes under seepage

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seepage flow is a major contributor to instability of natural hill slopes, river banks and engineered embankments. In order to increase the factor of safety, an emerging technology involves the inclusion of synthetic fibers in the soil. The addition of tension resisting fibers has a favorable effec...

  18. Mineralogy of the Pahrump Hills Region, Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Rampe, E. B.; Ming, D. W.; Vaniman, D. T.; Blake, D. F.; Chipera, S. J.; Morris, R. V.; Bish, D. L.; Cavanagh, P. D.; Achilles, C. N.; Bristow, T. F.; Morrison, S. M.; Treiman, A. H.; Downs, R. T.; Farmer, J. D.; Crisp, J. A.; Fendrich, K.; Morookian, J. M.

    2015-01-01

    The Pahrump Hills region of Gale crater is a approximately 12 millimeter thick section of sedimentary rocks in the Murray formation, interpreted as the basal geological unit of Mount Sharp. The Mars Science Laboratory, Curiosity, arrived at the Pahrump Hills in September, 2014, and performed a detailed six-month investigation of the sedimentary structures, geochemistry, and mineralogy of the area. During the campaign, Curiosity drilled and delivered three rock samples to its internal instruments, including the CheMin XRD/XRF. The three targets, Confidence Hills, Mojave 2, and Telegraph Peak, contain variable amounts of plagioclase, pyroxene, iron oxides, jarosite, phyllosilicates, and X-ray amorphous material. Hematite was predicted at the base of Mount Sharp from orbital visible/near-IR spectroscopy, and CheMin confirmed this detection. The presence of jarosite throughout Pahrump Hills suggests the sediments experienced acid-sulfate alteration, either in-situ or within the source region of the sediments. This acidic leaching environment is in stark contrast to the environment preserved within the Sheepbed mudstone on the plains of Gale crater. The minerals within Sheepbed, including Fe-saponite, indicate these sediments were deposited in a shallow lake with circumneutral pH that may have been habitable.

  19. A Capitol Hill Perspective

    NASA Astrophysics Data System (ADS)

    Sheppard, Christal

    2006-04-01

    Relatively few women receive advanced degrees in the sciences, and relatively few scientists find their way into staff positions on Capitol Hill. Yet in this staffer's experience, I count more female science Ph.D.s in my circle of colleagues than I counted female classmates in physics graduate school. Why, at least anecdotally, does it seem that women with advanced degrees in science are more likely than their male peers to leave the laboratory and join the policy lobby? My observations are based on my own work in energy and environmental policy as a staffer in both the U.S. Senate and the U.S. House of Representatives.

  20. Possible Ni-Rich Mafic-Ultramafic Magmatic Sequence in the Columbia Hills: Evidence from the Spirit Rover

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, David W.; Gellert, R.; McCoy, T.; McSween, H. Y., Jr.; Li, R.

    2006-01-01

    The Spirit rover landed on geologic units of Hesperian age in Gusev Crater. The Columbia Hills rise above the surrounding plains materials, but orbital images show that the Columbia Hills are older [1, 2]. Spirit has recently descended the southeast slope of the Columbia Hills doing detailed measurements of a series of outcrops. The mineralogical and compositional data on these rocks are consistent with an interpretation as a magmatic sequence becoming increasingly olivine-rich down slope. The outcrop sequence is Larry s Bench, Seminole, Algonquin and Comanche. The "teeth" on the Rock Abrasion Tool (RAT) wore away prior to arrival at Larry s Bench; the data discussed are for RAT brushed surfaces.

  1. Water-regolith-energy Interaction in Landscape Evolution and Its Influence on Forming Asymmetric Landscape: An Example from the Shale Hills Critical Zone Observatory of Central Pennsylvania

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Slingerland, R. L.; Shi, Y.; Duffy, C.; West, N.

    2015-12-01

    Shale Hills Critical Zone Observatory (SSHCZO) is a 0.08 km2 first order experimental research catchment with relatively homogeneous bedrock, regolith and tectonic uplift, but with an asymmetric slope and thickness of regolith on the north- and south-facing hillslopes. In this paper, we use a hydrological-morphodynamic model (LE-PIHM), which links bedrock, soil, surface and subsurface water flow, plant, energy, and seasonal climate, to address the influence of water-regolith-energy interaction on soil creep process, the possible factors causing slope asymmetry and the spatial distribution of regolith transport at the SSHCZO. Two non-dimensional parameters were used to explore the competitive relationship between regolith diffusion and advection forming self-organized channel spacing, relief and slope length at steady state. Model simulation under seasonal meteorological forcing shows spatial variations of hillslope sediment fluxes. An experimental study using Beryllium 10 at the SSHCZO (West et al 2013) showed that a south-facing planar slope had a greater diffusion flux rate than a planar on north-facing slope. The model confirms this relationship in general although there are significant local variations. The largest regolith transport rate by overland flow (advection) occurs at the junctions of main channel and swales. The model simulation further suggests that north-south differences in diffusive flux may be a result of asymmetric solar insolation which affects freeze-thaw frequency and sediment transport through the process of soil creep. This study demonstrates the value of physically-based distributed landscape evolution model on estimating spatial distribution of regolith transport and highlights the critical transition zone.

  2. Landslide Monitoring and Cultural Heritage At Risk: The Case Study of San Miniato Hill In Florence

    NASA Astrophysics Data System (ADS)

    Agostini, G.; Casagli, N.; Delmonaco, G.; Fanti, R.; Focardi, P.; Margottini, C.

    San Miniato (known also as Monte alle Croci or Mons Florentinus) is the most fa- mous hill bordering the southern side of the historic center of Florence. Included in the SColli FiorentiniT (Florentine hills) overlooking the monuments and artworks of Flo- & cedil;rence, San Miniato provides a wonderful view of the city. The hillside has always been affected by slope instability phenomena, with periodical reactivations documented in several historic records. Most of the monuments and artworks located on the hill are cracked and fissured and have required restoration works in various circumstances in the centuries after their construction. The first documented studies on the stability of the hill were carried out by Leonardo da Vinci in the XV century and subsequently by various commissions appointed for the restoration works. During the XX century the hill was many times monitored with geotechnical instrumentation and some investiga- tions are still in progress today. This work concerns a review of these historical studies on slope instability and the interpretation of past and present monitoring results. An analytical review of the existing data is a necessary condition for the proposal of a reliable hypothesis concerning the slope instability characterization. This is made dif- ficult by the pluri-centenary urbanization of the entire hill which has led to the almost complete obliteration of the evidence of past movements and by the relevant presence of an invaluable artistic and cultural heritage.

  3. Catchment sediment flux: a lake sediment perspective on the onset of the Anthropocene?

    NASA Astrophysics Data System (ADS)

    Chiverrell, Richard

    2014-05-01

    Definitions of the Anthropocene are varied but from a geomorphological perspective broadly can be described as the interval of recent Earth history during which 'humans have had an 'overwhelming' effect on the Earth system' (Brown et al., 2013). Identifying the switch to a human-dominated geomorphic process regime is actually a challenging process, with in the 'Old World' ramping up of human populations and impacts on earth surface processes since the Neolithic/Mesolithic transition and the onset of agriculture. In the terrestrial realm lakes offer a unique window on changes in human forcing of earth surface processes from a sedimentary flux perspective, because unlike alluvial and hill-slope systems sedimentation is broadly continuous and uninterrupted. Dearing and Jones (2003) showed for a global dataset of lakes a 5-10 fold increase in sediment delivery comparing pre- and post-anthropogenic disturbance. Here sediment records from several lakes in lowland agricultural landscapes are presented to examine the changes in the flux and composition of materials delivered from their catchments. By definition the lakes record the switch to a human dominated system, but not necessary in accelerated sediment accumulation rates with changes in sediment composition equally important. Data from Crose, Hatch and Peckforton Meres, in lowland northwest England are interrogated producing quantitative land-cover reconstructions from pollen spectra calculated using the REVEALS model (Sugita, 2007), geochemical evidence for changes sediment provenance and flux, and 14C and stable Pb pollutant based chronological models detecting changes in sediment accumulation rate. The lake sediment geochemistry points to several phases of heightened human impact within these small agricultural catchments. Following small-in-scale forest cover reductions and limited impacts in terms of sediment flux during the Neolithic, the Bronze to Iron Age saw the first substantial reductions in forest cover

  4. Lost Hills, California Interferogram

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This figure shows a comparison of interferograms from four different years mapping the rapid ground subsidence over the Lost Hills oil field in California. Lost Hills is located about 60 km (40 miles) northwest of Bakersfield in the San Joaquin Valley. The oil field is about 1.5 km (1mile) wide and 6 km (3.5 miles) long.

    Each interferogram was created using pairs of images taken by synthetic aperture radar that have been combined to measure surface deformation or changes that may have occurred in the time between when data for the two images were taken. The images were collected by the European Space Agency's Remote Sensing satellites (ERS-1 and ERS-2) in two months of each year shown (1995, 1996, 1998 and 1999) and were combined to produce these image maps of the apparent surface deformation, or changes.

    The interferometric measurements that show the changes, primarily vertical subsidence of the surface, are rendered in color with purple indicating no motion and the brightest red showing rapid subsidence. The white areas are where the radar measurements could not be obtained, mostly in the agricultural fields around the oil fields where plant growth or plowing altered the radar properties of the surface.

    These radar data show that parts of the oil field were subsiding unusually rapidly, more than 3 centimeters (1.2 inches) a month, in 1995 and 1996. They also reveal that while the ground subsidence rate decreased in the center part of the oil field, it increased in the northern part between 1995 and 1996 and 1998 and 1999.

    Subsidence maps like these combined with records of oil and water extraction and injection will help scientist understand how the rocks within an oil field are behaving, leading to improvements in oil field operations.

  5. Lost Hills, California Interferogram

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This figure shows a comparison of interferograms from four different years mapping the rapid ground subsidence over the Lost Hills oil field in California. Lost Hills is located about 60 km (40 miles) northwest of Bakersfield in the San Joaquin Valley. The oilfield is about 1.5 km (1 mile) wide and 6 km (3.5 miles) long. Each interferogram was created using pairs of images taken by synthetic aperture radar that have been combined to measure surface deformation or changes that may have occurred in the time between when data for the two images were taken. The images were collected by the European Space Agency's Remote Sensing satellites (ERS-1 and ERS-2) in two months of each year shown (1995, 1996, 1998 and 1999) and were combined to produce these image maps of the apparent surface deformation, or changes. The interferometric measurements that show the changes, primarily vertical subsidence of the surface, are rendered in color with purple indicating no motion and the brightest red showing rapid subsidence. The white areas are where the radar measurements could not be obtained, mostly in the agricultural fields around the oilfields where plant growth or plowing altered the radar properties of the surface. These radar data show that parts of the oilfield were subsiding unusually rapidly, more than 3 centimenters (1.2 inches) a month, in 1995 and 1996. They also reveal that while the ground subsidence rate decreased in the center part of the oilfield, it increased in the northern part between 1995 and 1996 and 1998 and 1999. Subsidence maps like these combined with records of oil and water extraction and injection will help scientist understand how the rocks within an oilfield are behaving, leading to improvements in oilfield operations. For more information, read Radar Helps Monitor Oil Fields. Images courtesy Eric Fielding, NASA Jet Propulsion Laboratory

  6. Reconstructed Paleo-topography of the Columbia Hills, Mars

    NASA Astrophysics Data System (ADS)

    Cole, S. B.; Watters, W. A.; Aron, F.; Squyres, S. W.

    2013-12-01

    From June 2004 through March 2010, the Mars Exploration Rover Spirit conducted a detailed campaign examining the Columbia Hills of Gusev Crater. In addition to mineralogical and chemical investigations, Spirit's stereo panoramic (Pancam) and navigation (Navcam) cameras obtained over 7,000 images of geologic targets along the West Spur of the Columbia Hills and Husband Hill, the highest peak. We have analyzed the entirety of this dataset, which includes stereo coverage of several outcrop exposures with apparent bedding. We have measured the bedding plane orientations of hundreds of fine-scale (~1-100cm) features on all of the potentially in-place outcrops using Digital Terrain Models (DTMs) derived from the rover's Pancam stereo image data, and mapped these orientations on a regional HiRISE image and DTM. Assuming that the bedding material was deposited conformably on the topography at the time of emplacement, we reconstruct the paleo-topography of the Columbia Hills. Our reconstructed paleo-topography is similar to the modern shape of Husband Hill, but with steeper slopes, consistent with a substantial amount of erosion since deposition. The Columbia Hills are an irregular, nearly-triangular edifice of uncertain origin, situated near the center of the 160km-diameter crater and hypothesized to be either the remnant of a central peak structure, or overlapping crater rims. They span ~6.6 km in the northerly direction by ~3.6 km in the easterly direction, and rise 90m above the basaltic plains that fill the floor of Gusev Crater and embay the Hills. The topography is as irregular as the perimeter, and is cut by numerous valleys of varying lengths, widths, and directional trends. Along the traverse, Spirit examined several rock classes as defined by elemental abundances from the Alpha Particle X-ray Spectrometer (APXS) and identified remotely by the Miniature Thermal Emission Spectrometer (Mini-TES). Unlike the Gusev Plains, the rocks of the Columbia Hills show

  7. New Insights into the Sedimentary Dynamics along Carbonate Slopes

    NASA Astrophysics Data System (ADS)

    Wunsch, Marco; Betzler, Christian; Lindhorst, Sebastian; Lüdmann, Thomas; Eberli, Gregor

    2016-04-01

    Hydroacoustic, sedimentological and seismic data of the leeward slope of Great Bahama Bank and the windward slope of the adjacent Cay Sal Bank provide new insights into carbonate platform slope sedimentation. Our study focuses on the diversity and complexity of the slope morphologies and sedimentary patterns which characterize the youngest high-frequency sequence, forming since the Last Glacial Maximum. It is shown that both carbonate platform slopes are dissected by furrows, gullies and channels which are genetically not related. Along the windward slope of Cay Sal Bank, toe of slope erosion, in conjunction with the local tectonic regime is responsible for channel incisions. Our data show that these channels were active during the regression after the last interglacial highstand of sea level. During this regression, downwelling transported platform sediment downslope, which was redistributed along the slope by contour currents. It is also shown that large mass transport complexes at the leeward slope of Great Bahama Bank formed during the last sea level lowstand, probably triggered by the release of pore-water pressure. These MTC created a complex slope morphology of gullies and scarps. These gullies act as a point source by confining the exported platform sediments during the present day sea level highstand.

  8. 16. Interior view of Cherry Hill lettuce shed looking up ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    16. Interior view of Cherry Hill lettuce shed looking up at the trusses of the second floor - Richmond Hill Plantation, Cherry Hill Lettuce Shed, East of Richmond Hill on Ford Neck Road, Richmond Hill, Bryan County, GA

  9. 6. Oblique view of Cherry Hill lettuce shed looking northeast, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. Oblique view of Cherry Hill lettuce shed looking northeast, with chute building to the right - Richmond Hill Plantation, Cherry Hill Lettuce Shed, East of Richmond Hill on Ford Neck Road, Richmond Hill, Bryan County, GA

  10. 22. View of second floor of the Cherry Hill lettuce ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    22. View of second floor of the Cherry Hill lettuce shed looking at double doors - Richmond Hill Plantation, Cherry Hill Lettuce Shed, East of Richmond Hill on Ford Neck Road, Richmond Hill, Bryan County, GA

  11. 21. View of second floor of the Cherry Hill lettuce ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    21. View of second floor of the Cherry Hill lettuce shed looking towards window - Richmond Hill Plantation, Cherry Hill Lettuce Shed, East of Richmond Hill on Ford Neck Road, Richmond Hill, Bryan County, GA

  12. 18. View of the second floor of the Cherry Hill ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. View of the second floor of the Cherry Hill lettuce shed looking at door - Richmond Hill Plantation, Cherry Hill Lettuce Shed, East of Richmond Hill on Ford Neck Road, Richmond Hill, Bryan County, GA

  13. 9. View of Cherry Hill lettuce shed looking north, with ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. View of Cherry Hill lettuce shed looking north, with chute building on the left - Richmond Hill Plantation, Cherry Hill Lettuce Shed, East of Richmond Hill on Ford Neck Road, Richmond Hill, Bryan County, GA

  14. 3. View of Cherry Hill lettuce shed looking southeast; parking ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. View of Cherry Hill lettuce shed looking southeast; parking lot in foreground - Richmond Hill Plantation, Cherry Hill Lettuce Shed, East of Richmond Hill on Ford Neck Road, Richmond Hill, Bryan County, GA

  15. 12. Partial view of Cherry Hill lettuce shed looking northwest ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    12. Partial view of Cherry Hill lettuce shed looking northwest showing office - Richmond Hill Plantation, Cherry Hill Lettuce Shed, East of Richmond Hill on Ford Neck Road, Richmond Hill, Bryan County, GA

  16. 20. View of second floor to the Cherry Hill lettuce ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    20. View of second floor to the Cherry Hill lettuce shed looking at floor area - Richmond Hill Plantation, Cherry Hill Lettuce Shed, East of Richmond Hill on Ford Neck Road, Richmond Hill, Bryan County, GA

  17. 15. Interior view of Cherry Hill lettuce shed showing posts ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. Interior view of Cherry Hill lettuce shed showing posts looking towards the chute building - Richmond Hill Plantation, Cherry Hill Lettuce Shed, East of Richmond Hill on Ford Neck Road, Richmond Hill, Bryan County, GA

  18. 14. Interior view of Cherry Hill lettuce shed looking towards ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. Interior view of Cherry Hill lettuce shed looking towards chute building - Richmond Hill Plantation, Cherry Hill Lettuce Shed, East of Richmond Hill on Ford Neck Road, Richmond Hill, Bryan County, GA

  19. 19. View of second floor of the Cherry Hill lettuce ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    19. View of second floor of the Cherry Hill lettuce shed looking at door to stairwell - Richmond Hill Plantation, Cherry Hill Lettuce Shed, East of Richmond Hill on Ford Neck Road, Richmond Hill, Bryan County, GA

  20. 2. Oblique view of Cherry Hill lettuce shed looking south; ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. Oblique view of Cherry Hill lettuce shed looking south; chute building is in background - Richmond Hill Plantation, Cherry Hill Lettuce Shed, East of Richmond Hill on Ford Neck Road, Richmond Hill, Bryan County, GA

  1. Runoff and sediment loss responses to rainfall and land use in two agricultural catchments on the Loess Plateau of China

    NASA Astrophysics Data System (ADS)

    Kang, Shaozhong; Zhang, Lu; Song, Xiaoyu; Zhang, Shuhan; Liu, Xianzhao; Liang, Yinli; Zheng, Shiqing

    2001-04-01

    Soil erosion is a severe problem hindering sustainable agriculture on the Loess Plateau of China. Plot experiments were conducted under the natural rainfall condition during 1995-1997 at Wangdongguo and Aobao catchments in this region to evaluate the effects of various land use, cropping systems, land slopes and rainfall on runoff and sediment losses, as well as the differences in catchment responses. The experiments included various surface conditions ranging from bare soil to vegetated surfaces (maize, wheat residue, Robinia pseudoacacia L., Amorpha fruticosa L., Stipa capillata L., buckwheat and Astragarus adsurgens L.). The measurements were carried out on hill slopes with different gradients (i.e. 0 ° to 36 °). These plots varied from 20 to 60 m in length. Results indicated that runoff and erosion in this region occurred mainly during summer storms. Summer runoff and sediment losses under cropping and other vegetation were significantly less than those from ploughed bare soil (i.e. without crop/plant or crop residue). There were fewer runoff and sediment losses with increasing canopy cover. Land slope had a major effect on runoff and sediment losses and this effect was markedly larger in the tillage plots than that in the natural grass and forest plots, although this effect was very small when the maximum rainfall intensity was larger than 58·8 mm/h or smaller than 2·4 mm/h. Sediment losses per unit area rose with increasing slope length for the same land slope and same land use. The effect of slope length on sediment losses was stronger on a bare soil plot than on a crop/plant plot. The runoff volume and sediment losses were both closely related to rainfall volume and maximum intensity, while runoff coefficient was mainly controlled by maximum rainfall intensity. Hortonian overland flow is the dominant runoff process in the region. The differences in runoff volume, runoff coefficient and sediment losses between the catchments are mainly controlled by the

  2. Quaternary landscape development, alluvial fan chronology and erosion of the Mecca Hills at the southern end of the San Andreas Fault zone

    NASA Astrophysics Data System (ADS)

    Gray, Harrison J.; Owen, Lewis A.; Dietsch, Craig; Beck, Richard A.; Caffee, Marc A.; Finkel, Robert C.; Mahan, Shannon A.

    2014-12-01

    Quantitative geomorphic analysis combined with cosmogenic nuclide 10Be-based geochronology and denudation rates have been used to further the understanding of the Quaternary landscape development of the Mecca Hills, a zone of transpressional uplift along the southern end of the San Andreas Fault, in southern California. The similar timing of convergent uplifts along the San Andreas Fault with the initiation of the sub-parallel San Jacinto Fault suggest a possible link between the two tectonic events. The ages of alluvial fans and the rates of catchment-wide denudation have been integrated to assess the relative influence of climate and tectonic uplift on the development of catchments within the Mecca Hills. Ages for major geomorphic surfaces based on 10Be surface exposure dating of boulders and 10Be depth profiles define the timing of surface stabilization to 2.6 +5.6/-1.3 ka (Qyf1 surface), 67.2 ± 5.3 ka (Qvof2 surface), and 280 ± 24 ka (Qvof1 surface). Comparison of 10Be measurements from active channel deposits (Qac) and fluvial terraces (Qt) illustrate a complex history of erosion, sediment storage, and sediment transport in this environment. Beryllium-10 catchment-wide denudation rates range from 19.9 ± 3.2 to 149 ± 22.5 m/Ma and demonstrate strong correlations with mean catchment slope and with total active fault length normalized by catchment area. The lack of strong correlation with other geomorphic variables suggests that tectonic uplift and rock weakening have the greatest control. The currently measured topography and denudation rates across the Mecca Hills may be most consistent with a model of radial topographic growth in contrast to a model based on the rapid uplift and advection of crust.

  3. Quaternary landscape development, alluvial fan chronology and erosion of the Mecca Hills at the southern end of the San Andreas Fault zone

    USGS Publications Warehouse

    Gray, Harrison J.; Owen, Lewis; Dietsch, Craig; Beck, Richard A.; Caffee, Marc A.; Finkelman, Robert B.; Mahan, Shannon

    2014-01-01

    Quantitative geomorphic analysis combined with cosmogenic nuclide 10Be-based geochronology and denudation rates have been used to further the understanding of the Quaternary landscape development of the Mecca Hills, a zone of transpressional uplift along the southern end of the San Andreas Fault, in southern California. The similar timing of convergent uplifts along the San Andreas Fault with the initiation of the sub-parallel San Jacinto Fault suggest a possible link between the two tectonic events. The ages of alluvial fans and the rates of catchment-wide denudation have been integrated to assess the relative influence of climate and tectonic uplift on the development of catchments within the Mecca Hills. Ages for major geomorphic surfaces based on 10Be surface exposure dating of boulders and 10Be depth profiles define the timing of surface stabilization to 2.6 +5.6/–1.3 ka (Qyf1 surface), 67.2 ± 5.3 ka (Qvof2 surface), and 280 ± 24 ka (Qvof1 surface). Comparison of 10Be measurements from active channel deposits (Qac) and fluvial terraces (Qt) illustrate a complex history of erosion, sediment storage, and sediment transport in this environment. Beryllium-10 catchment-wide denudation rates range from 19.9 ± 3.2 to 149 ± 22.5 m/Ma and demonstrate strong correlations with mean catchment slope and with total active fault length normalized by catchment area. The lack of strong correlation with other geomorphic variables suggests that tectonic uplift and rock weakening have the greatest control. The currently measured topography and denudation rates across the Mecca Hills may be most consistent with a model of radial topographic growth in contrast to a model based on the rapid uplift and advection of crust.

  4. Mars Exploration Rover APXS Results from Matijevic Hill

    NASA Technical Reports Server (NTRS)

    Cohen, B. A.; Clark, B. C.; Gellert, R.; Klingelhoefer, G.; Ming, D. W.; Mittlefehldt, D. W.; Morris, R. V.; Schrader, C. M.; Schroeder, C.; Yen, A. S.; Economou, T.; deSouza, P.; Jolliff, B. L.; Arvidson, R. A.; Squyres, S. W.

    2013-01-01

    Correlation analysis of APXS results on the eastern slope rocks indicate that the Matijevic Hill rocks are overall compositionally distinct from the Shoemaker Formation rocks [6]. Compared to the Shoemaker impactites, Matijevic Hill rocks are higher in Al, Si, and Ni, and lower in Ti, Fe, and Zn. No significant variation is evident in the APXS analyses that indicate the presence of a smectite or other phyllosilicate, as opposed to basaltic rocks. However, APXS data cannot in themselves rule out phyllosilicates. If indeed this material contains smectite, as seen from orbit, it implies that the rock has been isochemically altered to create the phyllosilicate content. The Cl content of the Cape York rocks is relatively high, and whereas the S/Cl ratio in the Burns Formation is 4x higher than in soil, in the Cape York rocks it is lower than in soil. These trends indicate that the alteration processes and types of aqueous salt loads were different between Cape York and Meridiani. In addition, significant deviations from the Martian Mn/Fe ratio are observed in Whitewater Lake coatings and the altered Grasford/Deadwood rocks (Fig. 3). These variations indicate that the redox/pH conditions during alteration of the Shoemaker Formation rocks and the Matijevic Hill rocks were similar, but that the Deadwood/Grasberg unit may have undergone alteration under different conditions, possibly at a later time. The Matijevic Hill outcrops appear to share a common genetic origin. It is not yet clear whether both the Shoemaker impactites and Matijevic Hill rocks are related to the formation of Endeavour Crater, or whether the Matijevic Hill suite represents a prior episode of Martian impact or volcanism. Opportunity continues to investigate both hypotheses.

  5. Multiple slope failures shaped the lower continental slope offshore NW Svalbard in the Fram Strait

    NASA Astrophysics Data System (ADS)

    Osti, Giacomo; Mienert, Jürgen; Forwick, Matthias; Sverre Laberg, Jan

    2016-04-01

    Bathymetry data show that the lower slope (between 1300 m and 3000 m water depth) of the NW-Svalbard passive margin has been affected by multiple slope failure events. The single events differ in terms of extension, volume of mobilized sediments, morphology of the slide scar, run-out distance and age. As for several mega-scale and minor Arctic slides, the trigger mechanism is still speculative and may include high sedimentation rates, dissociation of gas hydrates, excess pore pressure, or earthquakes caused by isostatic rebound. In this study, we discuss the potential trigger mechanisms that have led to the multiple slope failure events within what we suggest to be named the Fram Strait Slide Complex. The slide complex lies in proximity to the tectonically active Spitsbergen Fracture Zone where earthquakes events, occurrences of potential weak layers in the sediment column, low sedimentation rates, and extended gas hydrate-bearing sediments may all have contributed to the causes leading to multiple slope failures. Preliminary results obtained from 14C dating on N. pachyderma sin. from sediment cores from the Spitsbergen Fracture Zone slides (SFZS 1 and 2), coupled with sub-bottom profiler data (frequency 9 to 15 KHz) show that the two shallowest glide planes within one of the observed slide scars failed ~100,000 and ~115,000 yr BP. Whilst SFZS 1 affected an area of 750 km2 mobilizing a total sediment volume of 40 km3, SFZS 2 moved an area of 230 km2 with a sediment volume of 4.5 km3.

  6. The shaping of continental slopes by internal tides

    USGS Publications Warehouse

    Cacchione, D.A.; Pratson, Lincoln F.; Ogston, A.S.

    2002-01-01

    The angles of energy propagation of semidiurnal internal tides may determine the average gradient of continental slopes in ocean basins (???2 to 4 degrees). Intensification of near-bottom water velocities and bottom shear stresses caused by reflection of semi-diurnal internal tides affects sedimentation patterns and bottom gradients, as indicated by recent studies of continental slopes off northern California and New Jersey. Estimates of bottom shear velocities caused by semi-diurnal internal tides are high enough to inhibit deposition of fine-grained sediment onto the slopes.

  7. The shaping of continental slopes by internal tides.

    PubMed

    Cacchione, D A; Pratson, L F; Ogston, A S

    2002-04-26

    The angles of energy propagation of semidiurnal internal tides may determine the average gradient of continental slopes in ocean basins (approximately 2 to 4 degrees). Intensification of near-bottom water velocities and bottom shear stresses caused by reflection of semi-diurnal internal tides affects sedimentation patterns and bottom gradients, as indicated by recent studies of continental slopes off northern California and New Jersey. Estimates of bottom shear velocities caused by semi-diurnal internal tides are high enough to inhibit deposition of fine-grained sediment onto the slopes. PMID:11976451

  8. Sediment transport by streams in the Walla Walla basin, Washington and Oregon, July 1962-June 1965

    USGS Publications Warehouse

    Mapes, B.E.

    1969-01-01

    The Walla Walla River basin covers about 1,760 square miles in southeastern Washington and northeastern Oregon. From the 6,000-foot crest of the Blue Mountains on the east to the 340-foot altitude of Lake Wallula (Columbia River) on the west, the basin is drained by the Touchet River and Dry Creek, entirely within Washington, and by Mill Creek, North and South Forks Walla Walla River, and Pine Creek-Dry Creek, which all head in Oregon. The central lowland of the basin is bordered on the north by Eureka Flat, Touchet slope, and Skyrocket Hills, on the east by the Blue Mountains, and on the south by the Horse Heaven Hills. The basin is underlain by basalt of the Columbia River Group, which .is the only consolidated rock to crop out in the region. Various unconsolidated fluviatile, lacustrine, and eolian sediments cover the basalt. In the western part of the basin the basalt is overlain by lacustrine deposits of silt and sand which in places are mantled by varying thicknesses of loessal deposits. In the northern and central parts of the basin the loess is at least 100 feet thick. The mountainous eastern part of the basin is underlain at shallow depth by basalt which has a residual soil mantle weathered from the rock. The slopes of the mountains are characterized by alluvial fans and deeply cut stream valleys ,filled with alluvium of sand, gravel, and cobbles. Average annual precipitation in the basin ranges from less than 10 inches in the desert-like areas of the west to more than 45 inches in the timbered mountains of the east; 65 percent of the precipitation occurs from October through March. The average runoff from the basin is about 4.8 inches per year. Most of the runoff occurs during late winter and early spring. Exceptionally high runoff generally results from rainfall and rapid melting of snow on partially frozen ground. During the study period, July 1964-June 1965, average annual sediment yields in the basin ranged from 420 tons per square mile in the

  9. Dendrogeomorphic approach to estimating slope retreat, Maxey Flats, Kentucky

    NASA Astrophysics Data System (ADS)

    Hupp, Cliff R.; Carey, William P.

    1990-07-01

    A dendrogeomorphic study of slope retreat was conducted at the Maxey Flats nuclear-waste disposal site in northeastern Kentucky. Tree roots exposed by surface lowering were used as an indicator of ground surface at the time of germination. The amount of lowering was measured and divided by tree-ring-determined tree age. Surface lowering and slope degradation rates were estimated for three slopes below waste-burial trenches and compared with data obtained from sediment troughs and erosion frames at the site. Mean rates of slope retreat ranged from 1.92 to 3.16 mm/yr. Sediment-trough results are two to three orders of magnitude less than dendrogeomorphic and erosion-frame estimates of slope degradation, which suggests that piping and solution-weathering processes may be important in slope degradation. Slope aspect and declivity may be important factors affecting retreat of slopes with a uniform lithology. Dendrogeomorphic techniques provide results comparable to those in the literature and offer a rapid method for estimating slope retreat that integrates slope processes over many years.

  10. Soufriere Hills Volcano

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In this ASTER image of Soufriere Hills Volcano on Montserrat in the Caribbean, continued eruptive activity is evident by the extensive smoke and ash plume streaming towards the west-southwest. Significant eruptive activity began in 1995, forcing the authorities to evacuate more than 7,000 of the island's original population of 11,000. The primary risk now is to the northern part of the island and to the airport. Small rockfalls and pyroclastic flows (ash, rock and hot gases) are common at this time due to continued growth of the dome at the volcano's summit.

    This image was acquired on October 29, 2002 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet.

    ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.

    The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring of dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

    Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Bjorn Eng of JPL is the project manager. The Terra mission is

  11. True 3-D View of 'Columbia Hills' from an Angle

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This mosaic of images from NASA's Mars Exploration Rover Spirit shows a panorama of the 'Columbia Hills' without any adjustment for rover tilt. When viewed through 3-D glasses, depth is much more dramatic and easier to see, compared with a tilt-adjusted version. This is because stereo views are created by producing two images, one corresponding to the view from the panoramic camera's left-eye camera, the other corresponding to the view from the panoramic camera's right-eye camera. The brain processes the visual input more accurately when the two images do not have any vertical offset. In this view, the vertical alignment is nearly perfect, but the horizon appears to curve because of the rover's tilt (because the rover was parked on a steep slope, it was tilted approximately 22 degrees to the west-northwest). Spirit took the images for this 360-degree panorama while en route to higher ground in the 'Columbia Hills.'

    The highest point visible in the hills is 'Husband Hill,' named for space shuttle Columbia Commander Rick Husband. To the right are the rover's tracks through the soil, where it stopped to perform maintenance on its right front wheel in July. In the distance, below the hills, is the floor of Gusev Crater, where Spirit landed Jan. 3, 2004, before traveling more than 3 kilometers (1.8 miles) to reach this point. This vista comprises 188 images taken by Spirit's panoramic camera from its 213th day, or sol, on Mars to its 223rd sol (Aug. 9 to 19, 2004). Team members at NASA's Jet Propulsion Laboratory and Cornell University spent several weeks processing images and producing geometric maps to stitch all the images together in this mosaic. The 360-degree view is presented in a cylindrical-perspective map projection with geometric seam correction.

  12. Design of Rock Slope Reinforcement: An Himalayan Case Study

    NASA Astrophysics Data System (ADS)

    Tiwari, Gaurav; Latha, Gali Madhavi

    2016-06-01

    The stability analysis of the two abutment slopes of a railway bridge proposed at about 359 m above the ground level, crossing a river and connecting two hill faces in the Himalayas, India, is presented. The bridge is located in a zone of high seismic activity. The rock slopes are composed of a heavily jointed rock mass and the spacing, dip and dip direction of joint sets are varying at different locations. Geological mapping was carried out to characterize all discontinuities present along the slopes. Laboratory and field investigations were conducted to assess the geotechnical properties of the intact rock, rock mass and joint infill. Stability analyses of these rock slopes were carried out using numerical programmes. Loads from the foundations resting on the slopes and seismic accelerations estimated from site-specific ground response analysis were considered. The proposed slope profile with several berms between successive foundations was simulated in the numerical model. An equivalent continuum approach with Hoek and Brown failure criterion was initially used in a finite element model to assess the global stability of the slope abutments. In the second stage, finite element analysis of rock slopes with all joint sets with their orientations, spacing and properties explicitly incorporated into the numerical model was taken up using continuum with joints approach. It was observed that the continuum with joints approach was able to capture the local failures in some of the slope sections, which were verified using wedge failure analysis and stereographic projections. Based on the slope deformations and failure patterns observed from the numerical analyses, rock anchors were designed to achieve the target factors of safety against failure while keeping the deformations within the permissible limits. Detailed design of rock anchors and comparison of the stability of slopes with and without reinforcement are presented.

  13. Reef-sourced slope deposits, Holocene, Bahamas

    SciTech Connect

    Ginsburg, R.N.; Eberli, G.P.; Harris, P.M.; Slater, R.; Swart, P.K.

    1987-05-01

    Observations and sampling to 350 m from a two-person submersible off Chub Cay, Berry Island, Bahamas, support the idea that the Holocene deep reef is a principal source of talus, now cemented, that foots the windward margins of Great Bahama Bank. At the Chub Cay dive site, a wall extends from 30 to 170 m subsea; below is a low-relief fore reef slope, ca. 50/sup 0/, of limestone veneered with sediment. The upper wall from 30 to 80 m, the deep reef, has a luxuriant growth of corals and a profusion of the calcareous alga halimeda spp. Below 50 m, living coral decreases, and from 80 to 170 m the wall is highly irregular with discontinuous ledges and blind-end caves. At depths from 150 to 170 m, the wall gives way to the fore reef slope whose relative smooth surface dips at 50/sup 0/ to 60/sup 0/ and extends to 350 m. The fore reef is limestone, but its topography resembles that of alluvial fans; rounded ridges rise a few meters above the intervening valleys that are tens of meters wide. The limestone surface has a discontinuous veneer of fine sediment and algal plates, and locally loose cobble and boulder-sized blocks of limestone. A sample of the limestone slope is of well-cemented coral clasts and skeletal sediment. They infer that the deep reef grows outward so rapidly that it caves periodically. The resulting debris bypasses the wall, but some is perched on the steep fore reef slope below where it is soon incorporated into the slope by submarine cementation.

  14. Stratigraphic Relationships on Husband Hill, Mars

    NASA Astrophysics Data System (ADS)

    Cole, S. B.; Watters, W. A.; Squyres, S. W.

    2011-03-01

    We measure bedding plane orientations of outcrops on Cumberland Ridge in the Columbia Hills. Our measurements are consistent with the hypotheses that the outcrops (1) form a stratigraphic section, and (2) drape the Husband Hill edifice.

  15. NASA Now: SLOPE

    NASA Video Gallery

    Welcome to the SLOPE facility at NASA’s Glenn Research Center in Cleveland, Ohio. In this building, NASA engineers experiment with different wheel designs for lunar rovers. They use a simulated c...

  16. Rock slope stability

    SciTech Connect

    Kliche, C.A.

    1999-07-01

    Whether you're involved in surface mine design, surface mine production, construction, education, or regulation, this is an important new book for your library. It describes the basic rock slope failure modes and methods of analysis--both kinematic and kinetic techniques. Chapters include geotechnical and geomechanical analysis techniques, hydrology, rock slope stabilization techniques, and geotechnical instrumentation and monitoring. Numerous examples, drawings and photos enhance the text.

  17. 'Columbia Hills' Color Elevation Map

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Figure 1: Spirit's Long Journey, Sol 450

    This elevation map shows the region of the 'Columbia Hills' where NASA's Mars Exploration Rover Spirit has been working since mid-2004. Areas colored blue are lower in elevation and areas colored yellow are higher in elevation. The map imagery is from the Mars Orbiter Camera on NASA's Mars Global Surveyor orbiter.

    Spirit's Long Journey, Sol 450 More than 15 months after landing on Mars, NASA's Spirit rover is still going strong, having traveled a total of 4,276 meters (2.66 miles) as of martian day, or sol, 450 (April 8, 2005). This elevation map shows the traverse followed by Spirit since arriving at the 'Columbia Hills' in June, 2004. The areas colored blue are low in elevation and areas colored yellow are high in elevation. The blue area at the foot of the 'Columbia Hills' is approximately 20 meters (66 feet) higher in elevation than the site where Spirit landed in Gusev Crater. The highest peak is on the order of 80 meters (262 feet) higher still. In other words, the hills Spirit is exploring are more than 250 feet high. The map imagery is from the Mars Orbiter Camera on NASA's Mars Global Surveyor.

  18. Coming Down from the Hill

    ERIC Educational Resources Information Center

    Frank, Fiona

    2009-01-01

    Lancaster University's Department of Continuing Education has a long tradition of engagement with older learners. Its latest innovation aims to reach out to older people sometimes suspicious of the "university on the hill". This article discusses how Lancaster University develops a "Senior Learner' Programme", which is continuing as one of the…

  19. 27 CFR 9.52 - Chalk Hill.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Chalk Hill. 9.52 Section 9... TREASURY LIQUORS AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas § 9.52 Chalk Hill. (a) Name. The name of the viticultural area described in this section is “Chalk Hill.” (b) Approved...

  20. 27 CFR 9.52 - Chalk Hill.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Chalk Hill. 9.52 Section 9... TREASURY LIQUORS AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas § 9.52 Chalk Hill. (a) Name. The name of the viticultural area described in this section is “Chalk Hill.” (b) Approved...

  1. 27 CFR 9.52 - Chalk Hill.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Chalk Hill. 9.52 Section 9... TREASURY LIQUORS AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas § 9.52 Chalk Hill. (a) Name. The name of the viticultural area described in this section is “Chalk Hill.” (b) Approved...

  2. 27 CFR 9.52 - Chalk Hill.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Chalk Hill. 9.52 Section 9... TREASURY ALCOHOL AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas § 9.52 Chalk Hill. (a) Name. The name of the viticultural area described in this section is “Chalk Hill.” (b) Approved...

  3. 27 CFR 9.52 - Chalk Hill.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Chalk Hill. 9.52 Section 9... TREASURY ALCOHOL AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas § 9.52 Chalk Hill. (a) Name. The name of the viticultural area described in this section is “Chalk Hill.” (b) Approved...

  4. Recent carbonate slope development on southwest Florida continental margin

    SciTech Connect

    Brooks, G.R.; Holmes, C.W.

    1987-05-01

    The southwest Florida continental slope bordering the Florida Strait contains a thick sequence of seaward-prograding sediments. Sediments consist principally of a mixture of shallow water and pelagic carbonate sands and muds deposited rapidly on the upper slope. Sedimentary patterns are interpreted to be a function of high-frequency sea level fluctuations. Most vigorous off-shelf transport and highest sedimentation rates (exceeding 2.5 m/1000 years) occur during early transgressions and late regressions when water depths on the shelf are shallow. During sea level highstands, off-shelf transport is less vigorous and sedimentation rates decrease. During sea level lowstands, no off-shelf transport takes place and erosion of the previously deposited sequence occurs as a result of an increase in erosional capacity of the Florida Current. The presence of at least nine such sequences, all with similar characteristics, indicates that these processes have been occurring since at least the late Pleistocene in response to high-frequency glacial fluctuations. The location of the southwest Florida slope between the rimmed Bahama platform and the nonrimmed remainder of the west Florida margin, as well as similarities with ancient carbonate slope deposits formed during periods when shelf-edge reef-forming organisms were lacking, suggest that depositional patterns on the southwest Florida slope may be indicative of a transition between rimmed and nonrimmed carbonate platform environments. The southwest Florida slope may provide a valuable modern analog for identifying similar transitional environments in the geologic record.

  5. On the origin of Hill's causal criteria.

    PubMed

    Morabia, A

    1991-09-01

    The rules to assess causation formulated by the eighteenth century Scottish philosopher David Hume are compared to Sir Austin Bradford Hill's causal criteria. The strength of the analogy between Hume's rules and Hill's causal criteria suggests that, irrespective of whether Hume's work was known to Hill or Hill's predecessors, Hume's thinking expresses a point of view still widely shared by contemporary epidemiologists. The lack of systematic experimental proof to causal inferences in epidemiology may explain the analogy of Hume's and Hill's, as opposed to Popper's, logic.

  6. A comparison of soil properties under four vegetation units from six metalliferous hills in Katanga

    NASA Astrophysics Data System (ADS)

    Kaya, Donato; Gregory, Mahy; Michel, Ngongo; Gilles, Colinet

    2013-04-01

    In Katanga (Democratic Republic of Congo), numerous metalliferous hills are distributed along what is called the copperhill belt from Kolwezi to Lubumbashi. Very specific vegetation developed on these hills within the miombo forest in response to very specific soil conditions, among which the copper content. Previous studies have already shown the existence of gradients of copper from the mineralized rocks outcropping at the top of the hills to the foot slopes on colluviums. After a characterization of the vertical variability of soil properties in pits distributed along the main slopes, we investigated the soil-vegetation relationships in six hills located between the towns of Tenke and Fungurume. Observation 1-square meter plots were installed in four vegetation units and sixty of them were selected according to their relative importance on the six hills. The soil from the top 10cm was sampled and analyzed for pH, Total Organic Carbon, available P, K, Mg, Ca, Cu, Co and Mn and soluble Cu and Co. Analysis of variance was performed in order to assess whether the effects of the "Hill" and of the "Vegetation Unit" were significant to explain soil chemical variability. Additionally, short transects were sampled at the boundaries from adjacent vegetation units in order to evaluate the gradual or rough nature of change in soil properties under these units. The results indicate that the six hills can not be considered as different for pH and available nutrients, excepted K, nor for the available Cu and Mn. Only TOC and Co contents were differing, mainly from one hill compared to the other five. The vegetation effect is significant for almost every studied soil characteristics, to the exception of Ca and Mn. Soluble Cu and Co significantly correlate to available Cu and Co, respectively. The pH variations however explain local departures from linear regression. The ANOVA models take into account 30 to 60% of the variations of soil properties. The study of the boundaries

  7. Evolution of the Puente Hills Thrust Fault

    NASA Astrophysics Data System (ADS)

    Bergen, K. J.; Shaw, J. H.; Dolan, J. F.

    2013-12-01

    This study aims to assess the evolution of the blind Puente Hills thrust fault system (PHT) by determining its age of initiation, lateral propagation history, and changes in slip rate over time. The PHT presents one of the largest seismic hazards in the United States, given its location beneath downtown Los Angeles. The PHT is comprised of three fault segments: the Los Angeles (LA), Santa Fe Springs (SFS), and Coyote Hills (CH). The LA and SFS segments are characterized by growth stratigraphy where folds formed by uplift on the fault segments have been continually buried by sediment from the Los Angeles and San Gabriel rivers. The CH segment has developed topography and is characterized by onlapping growth stratigraphy. This depositional setting gives us the unique opportunity to measure uplift on the LA and SFS fault segments, and minimum uplift on the CH fault segment, as the difference in sediment thicknesses across the buried folds. We utilize depth converted oil industry seismic reflection data to image the fold geometries. Identifying time-correlative stratigraphic markers for slip rate determination in the basin has been a problem for researchers in the past, however, as the faunal assemblages observed in wells are time-transgressive by nature. To overcome this, we utilize the sequence stratigraphic model and well picks of Ponti et al. (2007) as a basis for mapping time-correlative sequence boundaries throughout our industry seismic reflection data from the present to the Pleistocene. From the Pleistocene to Miocene we identify additional sequence boundaries in our seismic reflection data from imaged sequence geometries and by correlating industry well formation tops. The sequence and formation top picks are then used to build 3-dimensional surfaces in the modeling program Gocad. From these surfaces we measure the change in thicknesses across the folds to obtain uplift rates between each sequence boundary. Our results show three distinct phases of

  8. Transverse bed slope effects in an annular flume

    NASA Astrophysics Data System (ADS)

    Baar, Anne; Kleinhans, Maarten; de Smit, Jaco; Uijttewaal, Wim

    2016-04-01

    Large scale morphology, in particular bar dimensions and bifurcation dynamics, are greatly affected by the deflection of sediment transport on transverse bed slopes due to gravity and by helical flows. However, existing transverse bed slope predictors are based on a small set of experiments with a minor range of flow conditions and sediment sizes, and do not account for the presence of bedforms. In morphological modelling the deflection angle is therefore often calibrated on measured morphology. Our objective is to experimentally quantify the transverse slope effect for a large range of near-bed flow conditions and sediment sizes (0.17 - 4 mm) to test existing predictors, in order to improve morphological modelling of rivers and estuaries. We have conducted about 400 experiments in an annular flume, which functions as an infinitely long bended flume and therefore avoids boundary effects. Flow is generated by rotating the lid of the flume, while the intensity of the helical flow can be decreased by counterrotating the bottom of the flume. The equilibrium transverse slope that develops during the experiments is a balance between the transverse bed slope effect and the bed shear stress caused by the helical flow. We obtained sediment mobilities from no motion to sheet flow, ranging across bedload and suspended load. Resulting equilibrium transverse slopes show a clear trend with varying sediment mobilities and helical flow intensities that deviate from typical power relations with Shields number. As an end member we found transversely horizontal beds by counterrotation that partially cancelled the helical flow near the bed, which allows us to quantify helical flow. The large range in sediment mobilities caused different bed states from ripples and dunes to sheet flow that affect near-bed flow, which cause novel nonlinear relations between transverse slope and Shields number. In conclusion, our results show for a wide range of conditions and sediments that transverse

  9. Effects of vegetation on runoff generation, sediment yield and soil shear strength on road-side slopes under a simulation rainfall test in the Three Gorges Reservoir Area, China.

    PubMed

    Liu, Yao-Jun; Wang, Tian-Wei; Cai, Chong-Fa; Li, Zhao-Xia; Cheng, Dong-Bing

    2014-07-01

    Vegetation recolonization has often been used to control roadside slope erosion, and in this paper, four restoration models - Natural Restoration, Grass, Grass & Shrub, Sodded Strip - were chosen to recolonize the plants on a newly built unpaved roadside slope in the Three Gorges Reservoir Area. After eight months growth, eight rainfall simulations (intensity of 90 mm h(-1) for 60 min) and in-situ soil shear strength test were then carried out to identify the impacts of vegetation on roadside slope erosion and soil shear strength. The erosion on cutslopes was higher than that on fillslopes. The runoff coefficient and soil detachment rate were significantly lower on the Grass & Shrub model (4.3% and 1.99 g m(-2) min(-1), respectively) compared with the other three, which had the highest surface cover (91.4%), aboveground biomass (1.44 kg m(-2)) and root weight density (3.94 kg m(-3)). The runoff coefficient and soil detachment rate on roadside slopes showed a logarithmic decrease with the root weight density, root length density and aboveground biomass. The soil shear strength measured before and after the rainfall was higher on Grass & Shrub (59.29 and 53.73 kPa) and decreased on Grass (46.93 and 40.48 kPa), Sodded Strip (31.20 and 18.87 kPa) and Natural Restoration (25.31 and 9.36 kPa). Negative linear correlations were found between the soil shear strength reduction and aboveground biomass, root weight density and root length density. The variation of soil shear strength reduction was closely related to the roadside slope erosion, a positive linear correlation was found between runoff coefficient and soil shear strength reduction, and a power function was shown between soil detachment rate and soil shear strength reduction. This study demonstrated that Grass and Grass & Shrub were more suitable and highly cost-effective in controlling initial period erosion of newly built low-volume unpaved road.

  10. Stratigraphy and depositional environments of Fox Hills Formation (Late Cretaceous), Williston basin

    SciTech Connect

    Daly, D.J.

    1986-08-01

    The Fox Hills Formation (Late Cretaceous, Maestrichtian) was investigated where it crops out along the southern flank of the Williston basin and in the subsurface over the central portion of the basin, using 300 well logs. The formation is conformable and gradational with the underlying Pierre formation and can be either conformable or unconformable with the overlying Hell Creek Formation. The Fox Hills Formation is younger, thicker, and stratigraphically more complex to the east and is comprised of marginal marine sediments deposited during the final Cretaceous regression. To the west, the Fox Hills Formation is an upward-coarsening unit generally 30 to 45 m thick and usually contains three members: from the base, Trail City, Timber Lake, and Colgate. The lower Fox Hills (Trail City, Timber Lake) is generally dominated by hummocky bedding and contains a variety of trace fossils, most notably Ophiomorpha. The upper Fox Hills (Colgate), where present, is characterized by cross-bedding. To the east, including the type area, the section is generally 80 to 100 m thick and contains four members: from the base, Trail City, Timber Lake, Iron Lightning (Colgate and Bullhead lithofacies), and Linton. In contrast to the section in the west, this section is as much as three times thicker, contains abundant body fossils, generally lacks hummocky bedding, and contains the Bullhead and Linton strata. In the west, the strata represent lower shoreface deposits, predominantly of storm origin (lower Fox Hills), overlain by upper shoreface and fluvial deposits (upper Fox Hills). In the east, the lower Fox Hills contains deposits of the lower shoreface (Trail City) and a barrier bar complex (Timber Lake), overlain by the deltaic deposits of the upper Fox Hills (Iron Lightning, Linton).

  11. Neuromuscular strategies for the transitions between level and hill surfaces during walking

    PubMed Central

    Gottschall, Jinger S.; Nichols, T. Richard

    2011-01-01

    Despite continual fluctuations in walking surface properties, humans and animals smoothly transition between terrains in their natural surroundings. Walking transitions have the potential to influence dynamic balance in both the anterior–posterior and medial–lateral directions, thereby increasing fall risk and decreasing mobility. The goal of the current manuscript is to provide a review of the literature that pertains to the topic of surface slope transitions between level and hill surfaces, as well as report the recent findings of two experiments that focus on the neuromuscular strategies of surface slope transitions. Our results indicate that in anticipation of a change in surface slope, neuromuscular patterns during level walking prior to a hill are significantly different from the patterns during level walking without the future change in surface. Typically, the changes in muscle activity were due to co-contraction of opposing muscle groups and these changes correspond to modifications in head pitch. In addition, further experiments revealed that the neck proprioceptors may be an initial source of feedback for upcoming surface slope transitions. Together, these results illustrate that in order to safely traverse varying surfaces, transitions strides are functionally distinct from either level walking or hill walking independently. PMID:21502127

  12. Seismic expression of catastrophic slope failure: Lower Cretaceous Torok Formation, North Slope of Alaska

    SciTech Connect

    Kerr, R.S.

    1985-02-01

    Seismic geometries in the deep marine Torok Formation illustrate that catastrophic slope failure involving both slope and basin-plain sediments occurred during Early Cretaceous time on the North Slope of Alaska. The magnitude of the failure emphasizes the importance of slumping and sliding as processes of mass transport of sediment in the deep marine environment. Torok sandstones and shales were deposited on continental slopes, basin plains, and submarine fans. Fluvial-deltaic sands and shales of the Nanushuk Group are the time-equivalent shelf deposits. The nanushuk-Torok relationship is expressed seismically as offlapping reflectors that record shelf-edge progradation. Slumps and slides are common on Torok slopes where gradients of up to 10/sup 0/ are documented. The largest such feature, located near Harrison Bay, is 1500 mi/sup 2/ in area and 2000 ft thick. The disturbed zone is lobate in plan view, wedge shaped in cross section, and thins basinward from a dramatic scarp deeply incised into Torok foreset beds. Seismically, the slide is expressed as a series of remnants of undisturbed or rotated glide blocks that strike parallel with the slump scarp and are encased in chaotically bedded slump debris. Geometric similarities to the Turnagain Heights slide (Anchorage, 1964) suggest block gliding as the mechanism of slope failure. Because the Torok was initially sand-poor, wells drilled through glide blocks and slump debris encountered predominantly shale. Understanding similar seismic geometries in other slope systems will aid in their evaluation as hydrocarbon traps. Favorable reservoir and trap scenarios include turbidite sands in remnant blocks trapped against slump fill and younger turbidite sands ponded behind remnant topography.

  13. GEOCHEMISTRY OF MAJUBA HILL, NEVADA.

    USGS Publications Warehouse

    Wenrich, Karen J.; Mascarenas, Joseph F.; Silberman, Miles L.

    1984-01-01

    Majuba Hill is the erosional remnant of a mineralized volcanic complex of rhyolite porphyry stocks, dikes, sills and irregular masses of breccia intruded into Triassic(? ) argillites. Majuba Hill is best known for its Cu and Sn ore; in addition, it was mineralized with other metals of possible economic significance, most notably, Mo, Ag, and U. Although this is an intrusive complex with no evidence of any extrusive phases, it was intruded sufficiently near the surface to develop a porphyritic texture. Intense sericitic and argillic alteration affected all stages of intrusion. Fresh rocks were not available for K-Ar analyses. Several samples of feldspars and sericite from altered zones yielded K-Ar ages for the alteration of 24. 7 to 25. 5 m. y. The tight clustering of ages suggests that all stages of the complex were altered within less than 1 m. y.

  14. Rocks of the Columbia Hills

    USGS Publications Warehouse

    Squyres, S. W.; Arvidson, R. E.; Blaney, D.L.; Clark, B. C.; Crumpler, L.; Farrand, W. H.; Gorevan, S.; Herkenhoff, K. E.; Hurowitz, J.; Kusack, A.; McSween, H.Y.; Ming, D. W.; Morris, R.V.; Ruff, S.W.; Wang, A.; Yen, A.

    2006-01-01

    The Mars Exploration Rover Spirit has identified five distinct rock types in the Columbia Hills of Gusev crater. Clovis Class rock is a poorly sorted clastic rock that has undergone substantial aqueous alteration. We interpret it to be aqueously altered ejecta deposits formed by impacts into basaltic materials. Wishstone Class rock is also a poorly sorted clastic rock that has a distinctive chemical composition that is high in Ti and P and low in Cr. Wishstone Class rock may be pyroclastic or impact in origin. Peace Class rock is a sedimentary material composed of ultramafic sand grains cemented by significant quantities of Mg- and Ca-sulfates. Peace Class rock may have formed when water briefly saturated the ultramafic sands and evaporated to allow precipitation of the sulfates. Watchtower Class rocks are similar chemically to Wishstone Class rocks and have undergone widely varying degrees of near-isochemical aqueous alteration. They may also be ejecta deposits, formed by impacts into Wishstone-rich materials and altered by small amounts of water. Backstay Class rocks are basalt/trachybasalt lavas that were emplaced in the Columbia Hills after the other rock classes were, either as impact ejecta or by localized volcanic activity. The geologic record preserved in the rocks of the Columbia Hills reveals a period very early in Martian history in which volcanic materials were widespread, impact was a dominant process, and water was commonly present. Copyright 2006 by the American Geophysical Union.

  15. Evidence of slope instability in the Southwestern Adriatic Margin

    NASA Astrophysics Data System (ADS)

    Minisini, D.; Trincardi, F.; Asioli, A.

    2006-01-01

    The Southwestern Adriatic Margin (SAM) shows evidence of widespread failure events that generated slide scars up to 10 km wide and extensive slide deposits with run out distances greater than 50 km. Chirp-sonar profiles, side-scan sonar mosaics, multibeam bathymetry and sediment cores document that the entire slope area underwent repeated failures along a stretch of 150 km and that mass-transport deposits, covering an area of 3320 km2, are highly variable ranging from blocky slides to turbidites, and lay on the lower slope and in the basin. The SAM slope between 300-700 m is impacted by southward bottom currents shaping sediment drifts (partly affected by failure) and areas of dominant erosion of the seafloor. When slide deposits occur in areas swept by bottom currents their fresh appearence and their location at seafloor may give the misleading impression of a very young age. Seismic-stratigraphic correlation of these deposits to the basin floor, however, allow a more reliable age estimate through sediment coring of the post-slide unit. Multiple buried failed masses overlap each other in the lower slope and below the basin floor; the most widespread of these mass-transport deposits occurred during the MIS 2-glacial interval on a combined area of 2670 km2. Displacements affecting Holocene deposits suggest recent failure events during or after the last phases of the last post-glacial eustatic rise. Differences in sediment accumulation rates at the base or within the sediment drifts and presence of downlap surfaces along the slope and further in the basin may provide one or multiple potential weak layers above which widespread collapses take place. Neotectonic activity and seismicity, together with the presence of a steep slope, represent additional elements conducive to sediment instability and failure along the SAM. Evidence of large areas still prone to failure provides elements of tsunamogenic hazard.

  16. Has man altered the cycling of nutrients and organic C on the Washington continental shelf and slope?

    NASA Astrophysics Data System (ADS)

    Carpenter, Roy

    1987-06-01

    Several sets of water column and sediment data from the Washington coastal zone reveal that man has not detectably increased fluxes of planktonic C to continental slow sediments in recent decades by either increasing nutrient fertilization of the waters or by overharvesting higher tropic level organisms. Washington slope sediments are not as important depocenters for storage of anthropogenic CO 2 as the model of WALSHet al. (1985, Deep-Sea Research, 32, 853-883) predicts for slope sediments.

  17. Geologic map of the Bodie Hills, California and Nevada

    USGS Publications Warehouse

    John, David A.; du Bray, Edward A.; Box, Stephen E.; Vikre, Peter G.; Rytuba, James J.; Fleck, Robert J.; Moring, Barry C.

    2015-01-01

    The Bodie Hills covers about 1,200 km2 straddling the California-Nevada state boundary just north of Mono Lake in the western part of the Basin and Range Province, about 20 km east of the central Sierra Nevada. The area is mostly underlain by the partly overlapping, middle to late Miocene Bodie Hills volcanic field and Pliocene to late Pleistocene Aurora volcanic field (John and others, 2012). Upper Miocene to Pliocene sedimentary deposits, mostly basin-filling sediments, gravel deposits, and fanglomerates, lap onto the west, north, and east sides of the Bodie Hills, where they cover older Miocene volcanic rocks. Quaternary surficial deposits, including extensive colluvial, fluvial, glacial, and lacustrine deposits, locally cover all older rocks. Miocene and younger rocks are tilted ≤30° in variable directions. These rocks are cut by several sets of high-angle faults that exhibit a temporal change from conjugate northeast-striking left-lateral and north-striking right-lateral oblique-slip faults in rocks older than about 9 Ma to north- and northwest-striking dip-slip faults in late Miocene rocks. The youngest faults are north-striking normal and northeast-striking left-lateral oblique-slip faults that cut Pliocene-Pleistocene rocks. Numerous hydrothermal systems were active during Miocene magmatism and formed extensive zones of hydrothermally altered rocks and several large mineral deposits, including gold- and silver-rich veins in the Bodie and Aurora mining districts (Vikre and others, in press).

  18. Making Mountains out of Molehills: Sediment Transport by the European Mole (Talpa europaea)

    NASA Astrophysics Data System (ADS)

    Milledge, D.; Loveless, J. C.; Warburton, J.; Densmore, A. L.

    2013-12-01

    Despite its widespread occurrence (across Europe and Eastern North America) the significance of the burrowing activity of the European Mole for sediment transport in the Northern Hemisphere has not been well quantified. In many areas this may have been the dominant mechanism of hillslope sediment transport over the last one to two millenia. The European Mole (Talpa europaea) is prevalent across the UK, particularly in fertile soils. It is highly fossorial, living almost its entire 3-6 year life in a network of tunnels that it maintains to catch prey. Moles can rapidly excavate large amounts of soil (~6 kg in 20 minutes) with waste soil generally pushed to the surface to form molehills. In this study we quantify sediment flux due to mole burrowing based on measured molehill sizes and geometries and estimates of mole hill production rates from time lapse photography. We examine the evolution of the molehills after production through repeat survey of in-situ molehills in the field and rainfall simulation experiments to accelerate degradation in the laboratory. Our initial findings suggest that: 1) molehill masses are generally log-normally distributed with a geometric mean ~1.4 kg; 2) moles move approximately 1.5 times as much soil as earthworms; and 3) the sediment flux due to moles is a non-linear function of the local slope.

  19. Active diapirism and slope steepening, northern Gulf of Mexico continental slope.

    USGS Publications Warehouse

    Martin, R.G.; Bouma, A.H.

    1982-01-01

    Large diapiric and nondiapiric masses of Jurassic salt and Tertiary shale underlie the northern Gulf of Mexico continental slope and adjacent outer continental shelf. Local steepening of the sea floor in response to the vertical growth of these structures is a serious concern to those involved in the site selection and the construction of future oil and gas production and transportation facilities in this frontier petroleum province. The evidence given in this paper supports the conclusion that the present continental slope region of the northern Gulf of Mexico is undergoing active diapirism and consequent slope steepening. Because most of the sediment on the flanks of diapiric structures consists of underconsolidated muds, slumping will take place regularly in response to further diapiric movement.-from Authors

  20. North Atlantic slope and canyon study. Volume 1. Executive summary

    SciTech Connect

    Butman, B.

    1986-12-01

    A field program to investigate the currents and sediment transport along the outershelf and upper slope along the southern flank of Georges Bank was conducted between 1980 and 1984. A major part of the field experiment was conducted in Lydonia Canyon, a large submarine canyon which cuts northward about 20 km into the continental shelf from the shelfbreak. A smaller experiment was conducted in Oceanographer Canyon to compare the currents in these two major canyons. The long-term current observations made in Lydonia and Oceanographer Canyons show that the current regime in these topographic features differs from the adjacent slope, and between canyons. Sediments near the head (depths shallower than about 600 m) in both Lydonia and Oceanographer are frequently resuspended. This frequent resuspension may allow the sediments to strip pollutants from the water column. Currents in Oceanographer Canyon are stronger and the sediments coarser than in Lydonia at comparable depths.

  1. Overpressure and fluid flow in the new jersey continental slope: implications for slope failure and cold seeps

    PubMed

    Dugan; Flemings

    2000-07-14

    Miocene through Pleistocene sediments on the New Jersey continental slope (Ocean Drilling Program Site 1073) are undercompacted (porosity between 40 and 65%) to 640 meters below the sea floor, and this is interpreted to record fluid pressures that reach 95% of the lithostatic stress. A two-dimensional model, where rapid Pleistocene sedimentation loads permeable sandy silt of Miocene age, successfully predicts the observed pressures. The model describes how lateral pressure equilibration in permeable beds produces fluid pressures that approach the lithostatic stress where overburden is thin. This transfer of pressure may cause slope failure and drive cold seeps on passive margins around the world. PMID:10894774

  2. Interfacial liquid water on Mars and its potential role in formation of hill and dune gullies

    NASA Astrophysics Data System (ADS)

    Kossacki, Konrad J.; Markiewicz, Wojciech J.

    2010-11-01

    Gullies are among the most intriguing structures identified on the surface of Mars. Most common are gullies located on the slopes of craters which are probably formed by liquid water transported by shallow aquifers (Heldmann, J.L., Carlsson, E., Johansson, H., Mellon, M.T., Toon, O.B. [2007]. Icarus 188, 324-344). Two particular types of gullies are found on slopes of isolated hills and dunes. The hill-slope gullies are located mostly at 50°S, which is at the high end of latitudes of bulk of the gullies found so far. The dune gullies are found in several locations up to 65°S (Reiss, D., Jaumann, R., Kereszturi, A., Sik, A., Neukum, G. [2007]. Lunar Planet. Sci. XXXVIII. Abstract 1993), but the best known are those in Russel crater at 54°S. The hill and dune gullies are longer than others making the aquifers explanation for their formation unlikely (Balme, M., Mangold, N., Baratoux, D., Costard, F., Gosselin, M., Masson, P., Pnet, P., Neukum, G. [2006]. J. Geophys. Res. 111. doi:10.1029/2005JE002607). Recently it has been noted that thin liquid films of interfacial water can play a role in rheological processes on the surface of Mars (Moehlmann, D. [2008]. Icarus 195, 131-139. Kereszturi, A., Moehlmann, D., Berczi, Sz., Ganti, T., Kuti, A., Sik, A., Horvath, A. [2009]. Icarus 201, 492-503.). Here we try to answer the question whether interfacial liquid water may occur on Mars in quantities large enough to play a role in formation of gullies. To verify this hypothesis we have calculated thermal models for hills and dunes of various steepness, orientation and physical properties. We find that within a range of average expected values of parameters it is not possible to have more than a few monolayers of liquid water at depths greater than a centimeter. To create subsurface interfacial water film significantly thicker and hence to produce conditions for the slope instability, parameters have to be chosen to have their extreme realistic values or an additional source

  3. Modern configuration of the southwest Florida carbonate slope: Development by shelf margin progradation

    USGS Publications Warehouse

    Brooks, G.R.; Holmes, C.W.

    1990-01-01

    Depositional patterns and sedimentary processes influencing modern southwest Florida carbonate slope development have been identified based upon slope morphology, seismic facies and surface sediment characteristics. Three slope-parallel zones have been identified: (1) an upper slope progradational zone (100-500 m) characterized by seaward-trending progradational clinoforms and sediments rich in shelf-derived carbonate material, (2) a lower gullied slope zone (500-800 m) characterized by numerous gullies formed by the downslope transport of gravity flows, and (3) a base-of-slope zone (> 800 m) characterized by thin, lens-shaped gravity flow deposits and irregular topography interpreted to be the result of bottom currents and slope failure along the basal extensions of gullies. Modern slope development is interpreted to have been controlled by the offshelf transport of shallow-water material from the adjacent west Florida shelf, deposition of this material along a seaward advancing sediment front, and intermittent bypassing of the lower slope by sediments transported in the form of gravity flows via gullies. Sediments are transported offshelf by a combination of tides and the Loop Current, augmented by the passage of storm frontal systems. Winter storm fronts produce cold, dense, sediment-laden water that cascades offshelf beneath the strong, eastward flowing Florida Current. Sediments are eventually deposited in a relatively low energy transition zone between the Florida Current on the surface and a deep westward flowing counter current. The influence of the Florida Current is evident in the easternmost part of the study area as eastward prograding sediments form a sediment drift that is progressively burying the Pourtales Terrace. The modern southwest Florida slope has seismic reflection and sedimentological characteristics in common with slopes bordering both the non-rimmed west Florida margin and the rimmed platform of the northern Bahamas, and shows many

  4. Arctic Submarine Slope Stability

    NASA Astrophysics Data System (ADS)

    Winkelmann, D.; Geissler, W.

    2010-12-01

    Submarine landsliding represents aside submarine earthquakes major natural hazard to coastal and sea-floor infrastructure as well as to coastal communities due to their ability to generate large-scale tsunamis with their socio-economic consequences. The investigation of submarine landslides, their conditions and trigger mechanisms, recurrence rates and potential impact remains an important task for the evaluation of risks in coastal management and offshore industrial activities. In the light of a changing globe with warming oceans and rising sea-level accompanied by increasing human population along coasts and enhanced near- and offshore activities, slope stability issues gain more importance than ever before. The Arctic exhibits the most rapid and drastic changes and is predicted to change even faster. Aside rising air temperatures, enhanced inflow of less cooled Atlantic water into the Arctic Ocean reduces sea-ice cover and warms the surroundings. Slope stability is challenged considering large areas of permafrost and hydrates. The Hinlopen/Yermak Megaslide (HYM) north of Svalbard is the first and so far only reported large-scale submarine landslide in the Arctic Ocean. The HYM exhibits the highest headwalls that have been found on siliciclastic margins. With more than 10.000 square kilometer areal extent and app. 2.400 cubic kilometer of involved sedimentary material, it is one of the largest exposed submarine slides worldwide. Geometry and age put this slide in a special position in discussing submarine slope stability on glaciated continental margins. The HYM occurred 30 ka ago, when the global sea-level dropped by app. 50 m within less than one millennium due to rapid onset of global glaciation. It probably caused a tsunami with circum-Arctic impact and wave heights exceeding 130 meters. The HYM affected the slope stability field in its neighbourhood by removal of support. Post-megaslide slope instability as expressed in creeping and smaller-scaled slides are

  5. Geologic characteristics and movement of the Meadow Creek landslide, part of the Coal Hill landslide complex, western Kane County, Utah

    USGS Publications Warehouse

    Ashland, Francis X.; McDonald, Greg N.; Carney, Stephanie M.; Tabet, David E.; Johnson, Cari L.

    2010-01-01

    The Meadow Creek landslide, part of the Coal Hill landslide complex in western Kane County, Utah, is about 1.7 miles (2.7 km) wide and 1.3 miles (2.1 km) long and contains six smaller historical slides. The upper part of the Meadow Creek landslide is gently sloping and consists of displaced and back-rotated blocks of Cretaceous Dakota and Cedar Mountain Formations that form northeast- to locally east-trending ridges that are separated by sediment-filled half-grabens. The lower part of the landslide is gently to moderately sloping, locally incised, and consists of heterogeneous debris that overrides the Jurassic Carmel Formation near Meadow Creek. Monitoring using a survey-grade Global Positioning System (GPS) instrument detected movement of the southern part of the Meadow Creek landslide between October 2005 and October 2008, including movement of two of the historical slides-landslides 1 and 2. The most movement during the measurement period occurred within the limits of persistently moving landslide 1 and ranged from about 24 to 64 inches (61-163 cm). Movement of the abutting southern part of the Meadow Creek landslide ranged from approximately 6 to 10 inches (15-25 cm). State Route 9 crosses over approximately a mile (1.6 km) of the southern part of the Meadow Creek landslide, including landslide 1. The highway and its predecessor (State Route 15) have been periodically displaced and damaged by persistent movement of landslide 1. Most of the landslide characteristics, particularly its size, probable depth, and the inferred weak strength and low permeability of clay-rich gouge derived from the Dakota and Cedar Mountain Formations, are adverse to and pose significant challenges to landslide stabilization. Secondary hazards include piping-induced sinkholes along scarps and ground cracks, and debris flows and rock falls from the main-scarp escarpment.

  6. Keeping pace with Capitol Hill

    USGS Publications Warehouse

    Cooper, C.

    2007-01-01

    At the Capitol Hill, the legislative branch of the United States government, the work is always at pace. Working with Congress is a tough job yet, rewarding. The Congress worked hard together to serve the public interest but many big issues are one small part of what Congress does. However, many US news media do not report what the government does instead, the media report what the government argues about. The media reports the conflicts but story is always incomplete. In order for the people know what is happening to the government, contact the congressional representative to know the complete story.

  7. Impact craters as biospheric microenvironments, Lawn Hill Structure, Northern Australia.

    PubMed

    Lindsay, John; Brasier, Martin

    2006-04-01

    Impact craters on Mars act as traps for eolian sediment and in the past may have provided suitable microenvironments that could have supported and preserved a stressed biosphere. If this is so, terrestrial impact structures such as the 18-km-diameter Lawn Hill Structure, in northern Australia, may prove useful as martian analogs. We sampled outcrop and drill core from the carbonate fill of the Lawn Hill Structure and recorded its gamma-log signature. Facies data along with whole rock geochemistry and stable isotope signatures show that the crater fill is an outlier of the Georgina Basin and was formed by impact at, or shortly before, approximately 509-506 million years ago. Subsequently, it was rapidly engulfed by the Middle Cambrian marine transgression, which filled it with shallow marine carbonates and evaporites. The crater formed a protected but restricted microenvironment in which sediments four times the thickness of the nearby basinal succession accumulated. Similar structures, common on the martian surface, may well have acted as biospheric refuges as the planet's water resources declined. Low-pH aqueous environments on Earth similar to those on Mars, while extreme, support diverse ecologies. The architecture of the eolian crater fill would have been defined by long-term ground water cycles resulting from intermittent precipitation in an extremely arid climate. Nutrient recycling, critical to a closed lacustrine sub-ice biosphere, could be provided by eolian transport onto the frozen water surface.

  8. Impact Craters as Biospheric Microenvironments, Lawn Hill Structure, Northern Australia

    NASA Astrophysics Data System (ADS)

    Lindsay, John; Brasier, Martin

    2006-04-01

    Impact craters on Mars act as traps for eolian sediment and in the past may have provided suitable microenvironments that could have supported and preserved a stressed biosphere. If this is so, terrestrial impact structures such as the 18-km-diameter Lawn Hill Structure, in northern Australia, may prove useful as martian analogs. We sampled outcrop and drill core from the carbonate fill of the Lawn Hill Structure and recorded its gamma-log signature. Facies data along with whole rock geochemistry and stable isotope signatures show that the crater fill is an outlier of the Georgina Basin and was formed by impact at, or shortly before, approximately 509-506 million years ago. Subsequently, it was rapidly engulfed by the Middle Cambrian marine transgression, which filled it with shallow marine carbonates and evaporites. The crater formed a protected but restricted microenvironment in which sediments four times the thickness of the nearby basinal succession accumulated. Similar structures, common on the martian surface, may well have acted as biospheric refuges as the planet's water resources declined. Low-pH aqueous environments on Earth similar to those on Mars, while extreme, support diverse ecologies. The architecture of the eolian crater fill would have been defined by long-term ground water cycles resulting from intermittent precipitation in an extremely arid climate. Nutrient recycling, critical to a closed lacustrine sub-ice biosphere, could be provided by eolian transport onto the frozen water surface.

  9. Impact craters as biospheric microenvironments, Lawn Hill Structure, Northern Australia.

    PubMed

    Lindsay, John; Brasier, Martin

    2006-04-01

    Impact craters on Mars act as traps for eolian sediment and in the past may have provided suitable microenvironments that could have supported and preserved a stressed biosphere. If this is so, terrestrial impact structures such as the 18-km-diameter Lawn Hill Structure, in northern Australia, may prove useful as martian analogs. We sampled outcrop and drill core from the carbonate fill of the Lawn Hill Structure and recorded its gamma-log signature. Facies data along with whole rock geochemistry and stable isotope signatures show that the crater fill is an outlier of the Georgina Basin and was formed by impact at, or shortly before, approximately 509-506 million years ago. Subsequently, it was rapidly engulfed by the Middle Cambrian marine transgression, which filled it with shallow marine carbonates and evaporites. The crater formed a protected but restricted microenvironment in which sediments four times the thickness of the nearby basinal succession accumulated. Similar structures, common on the martian surface, may well have acted as biospheric refuges as the planet's water resources declined. Low-pH aqueous environments on Earth similar to those on Mars, while extreme, support diverse ecologies. The architecture of the eolian crater fill would have been defined by long-term ground water cycles resulting from intermittent precipitation in an extremely arid climate. Nutrient recycling, critical to a closed lacustrine sub-ice biosphere, could be provided by eolian transport onto the frozen water surface. PMID:16689651

  10. The role of climate in balancing soil production and sediment yield in New Zealand

    NASA Astrophysics Data System (ADS)

    Norton, K. P.

    2013-12-01

    New Zealand hosts some of the highest specific sediment yields on the planet reaching up to nearly 30,000 t km-2 yr-1. Sediment yields measure the export of sediment from a basin and give an indication of erosion from hillslopes. In New Zealand high sediment yields correlate with high annual precipitation and high rates of tectonic strain (Hicks et al., 1996). It is, however, unclear how soil production keeps pace with such extreme erosion. Here, this question is investigated by modelling soil production as a function of local climate parameters. Two simple models for building climate into soil production are through effective energy and mass transfer, EEMT, (Rasmussen and Tabor, 2007) and primary chemical weathering. When applied to ~30 year climate data, these models highlight the variability of potential soil production across New Zealand. Due partially to high annual rainfall, some of the fastest erosion rates on the west coast of the South Island are nearly in balance with soil production. In other regions such as the east coast of the North Island, hotspots exist where annual sediment yields exceed reasonable soil production rates such that additional mechanisms must operate to generate sediment and make up this deficit. Globally, precipitation tends to increase and temperature decreases with increasing elevation. In New Zealand, increasing elevations also roughly correlate with an increase in mean basin slope angle and the percent of a basin at >30° slopes. As a result, modelled soil production also tends to increase with increasing mean basin slope angle. This correlation occurs independent of erosion feedbacks on the modelled soil production rates. This relationship presents an intriguing scenario in which the topography of the mountain range may be maintained by climate through variations in soil production. Even with rapid modelled soil production at high precipitation rates and/or high temperatures and/or high temperatures, many basins cannot keep pace

  11. Aquatic assessment of the Pike Hill Copper Mine Superfund site, Corinth, Vermont

    USGS Publications Warehouse

    Piatak, Nadine M.; Argue, Denise M.; Seal, Robert R., II; Kiah, Richard G.; Besser, John M.; Coles, James F.; Hammarstrom, Jane M.; Levitan, Denise M.; Deacon, Jeffrey R.; Ingersoll, Christopher G.

    2013-01-01

    The Pike Hill Copper Mine Superfund site in Corinth, Orange County, Vermont, includes the Eureka, Union, and Smith mines along with areas of downstream aquatic ecosystem impairment. The site was placed on the U.S. Environmental Protection Agency (USEPA) National Priorities List in 2004. The mines, which operated from about 1847 to 1919, contain underground workings, foundations from historical structures, several waste-rock piles, and some flotation tailings. The mine site is drained to the northeast by Pike Hill Brook, which includes several wetland areas, and to the southeast by an unnamed tributary that flows to the south and enters Cookville Brook. Both brooks eventually drain into the Waits River, which flows into the Connecticut River. The aquatic ecosystem at the site was assessed using a variety of approaches that investigated surface-water quality, sediment quality, and various ecological indicators of stream-ecosystem health. The degradation of surface-water quality is caused by elevated concentrations of copper, and to a lesser extent cadmium, with localized effects caused by aluminum, iron, and zinc. Copper concentrations in surface waters reached or exceeded the USEPA national recommended chronic water-quality criteria for the protection of aquatic life in all of the Pike Hill Brook sampling locations except for the location farthest downstream, in half of the locations sampled in the tributary to Cookville Brook, and in about half of the locations in one wetland area located in Pike Hill Brook. Most of these same locations also contained concentrations of cadmium that exceeded the chronic water-quality criteria. In contrast, surface waters at background sampling locations were below these criteria for copper and cadmium. Comparison of hardness-based and Biotic Ligand Model (BLM)-based criteria for copper yields similar results with respect to the extent or number of stations impaired for surface waters in the affected area. However, the BLM

  12. Analysis of pottery from the Palatine Hills of Rome

    SciTech Connect

    Landsberger, S.; Wisseman, S.; Desena, E.; Hostetter, E.; Pena, T.

    1994-12-31

    During the past several summers the Soprintendenza Archeologica di Roma and the American Academy in Rome have carried out collaborative excavations on the late Roman complex located on the northeastern slope of the Palatine Hill. The late Roman complex is situated on the lower slopes of the area commonly known as Vigna Barberini, after its 17th century owners. Because this area, as well as most of the east slope of the Palatine, has never been systematically explored, it remains from an archaeological point of view essentially unknown. The overall aim of the excavations is to investigate layout, function, and occupational history of a mid-to-late imperial building complex located just southwest of the Arch of Constatine. Part of this international project is the chemical characterization of Roman fineware pottery from archaeological excavations on the site of the imperial palaces. Excavation has yielded more than 8 t of Late Roman and Early Medieval pottery (circa 3rd to 10th centuries A.D.). Many classes of pottery have already been classified by their provenance based on distribution patterns, but others require chemical characterization to separate similar clays. To that end routine neutron activation analysis (NAA) methods have been used to analyze {approximately}200 pieces of pottery.

  13. Downslope Eulerian mean flow associated with high-frequency current fluctuations observed on the outer continental shelf and upper slope along the northeastern United States continental margin: implications for sediment transport

    USGS Publications Warehouse

    Butman, B.

    1988-01-01

    Eulerian current measurements made 5-7 m above bottom at six stations along the United States east coast continental margin show a net downslope flow of 1-5 cm s-1. Although the scalar current speed decreases with water depth and toward the bottom, fluctuations in the cross-isobath flow were stronger and increasingly asymmetric near the bottom. Maximum downslope flow exceeded maximum upslope flow by a factor of two to three. The strength of the low-passed downslope flow was proportional to the upslope Reynolds flux of density as well as to the amplitude of the current fluctuations that have periods shorter than 30 h. These flow characteristics may be caused by differential vertical mixing in the bottom boundary layer where a stratified fluid flows upslope (unstable) and downslope (stable). The asymmetry in current strength clearly favors net downslope transport of sediments that move as bedload. ?? 1988.

  14. 7. Detail of balcony rail. August 1936. Joseph Hill, photographer, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. Detail of balcony rail. August 1936. Joseph Hill, photographer, copied from small photo taken by survey member. - Jansonist Colony, Steeple Building, Main & Bishop Hill Streets, Bishop Hill, Henry County, IL

  15. 6. Detail of pilaster cap. Aug. 10, 1936. Joseph Hill, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. Detail of pilaster cap. Aug. 10, 1936. Joseph Hill, photographer, copied from small photo taken by survey member. - Jansonist Colony, Steeple Building, Main & Bishop Hill Streets, Bishop Hill, Henry County, IL

  16. 3. West and south elevations. Joseph Hill, photographer, copied from ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. West and south elevations. Joseph Hill, photographer, copied from photo lent by Evelyn S. Craig. August 1936. - Jansonist Colony, Steeple Building, Main & Bishop Hill Streets, Bishop Hill, Henry County, IL

  17. 1. Historic American Buildings Survey Joseph Hill, Photographer August 1936 ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. Historic American Buildings Survey Joseph Hill, Photographer August 1936 FIRST ORIGINAL STORE AND POSTOFFICE, COPY OF AN EARLY PHOTOGRAPH. LENT BY EVELYN S. CRAIG - Jansonist Colony, Colony Store & Post Office, Main & Bishop Hill Streets, Bishop Hill, Henry County, IL

  18. Erosion in the Mecca Hills: using GIS to investigate potential erosion factors along the southern San Andreas Fault.

    NASA Astrophysics Data System (ADS)

    Maneerat, P.; Reinen, L. A.; Fukutaki, K. G.; Rittiron, S.; Mejias, R.

    2015-12-01

    The Mecca Hills (MH) occur in a region of transpression along the southern San Andreas Fault. These geomorphic features are a result of the interplay between uplift and erosion. The MH are mostly covered by uniform sedimentary rocks with > 70% the Pliocene-Pleistocene Palm Spring Formation, > 20% Quaternary sediments and a minor amount of crystalline rock suggesting similar denudation rate over the region. However, Gray et al. (Quat. Sci. Rev. 2014) found a wide range of denudation rates (20 to 150 m/My) by using 10Be concentrations in active-channel alluvial sediment. We investigate potential causes of erosion to understand the variation of the denudation rate and examine the maturity of watersheds in the MH. We use ArcGIS to find the best geomorphic proxy for the published erosion rates by considering elevation, lithology, mean slope and active faults by using the index value method proposed by Gray et al. We apply the best geomorphic proxy to the overall MH to predict the spatial variation of erosion rate over the region. We use hypsometric integral (HI) and basin elongation ratio (BER) to study the maturity of the overall MH watersheds. We found that active faults are the main factor influencing erosion in the MH. Drainage basins located closer to active faults have higher erosion rates than others. Most watersheds are in a mature stage of the erosion cycle. Overall, the watersheds in the central MH are in a more youthful stage of the erosion cycle than the ones to the north and south. BER values suggest that the watersheds in the central MH formed earlier and have more time to develop their stream networks. Although watersheds in the central MH formed earlier than the others, their stage of erosion cycle is more youthful due to the proximity of active faults enhancing local erosion rates.

  19. The "House" in Half Hollow Hills

    ERIC Educational Resources Information Center

    Karnilow, Sheldon

    2006-01-01

    In this article, the author relates how he initiated a systemic improvement to Half Hollow Hills school district when he became its superintendent. He relates that although he came to Half Hollow Hills with a deep understanding of the models of systemic change, he did not bring with him a specific prescriptive plan for improvement. His plan for…

  20. Counseling Uses of the Hill Interaction Matrix.

    ERIC Educational Resources Information Center

    Boyd, Robert E.

    While the Hill Interaction Matrix was developed as a research instrument to assess interview process, it is also generally useful in any undertaking requiring the evaluation of verbal interaction and, hence, can be used as an aid in modifying communication in order to increase its therapeutic effect. The Hill Interaction Matrix with accompanying…

  1. Leslie Pickney Hill's "Toussaint L'Ouverture."

    ERIC Educational Resources Information Center

    Ako, Edward O.

    1987-01-01

    In his 1928 play, the Harlem Renaissance writer Leslie Pickney Hill portrays Toussaint L'Ouverture, the leader of the Haitian slave rebellion, with historical accuracy. Hill's presentation was aimed at rehabilitating black pride, "A worthy literature reared upon authentic records of achievement is the present spiritual need of the race." (BJV)

  2. Colleges as Shining Cities on a Hill

    ERIC Educational Resources Information Center

    Townsend, Kathleen Kennedy

    2012-01-01

    In this article, the author proposes that the notion of America be reintroduced as the "shining city on a hill," that abiding image from American history. The image of the shining city on a hill captures the imagination because it reflects the abiding truth that people become fully human in society, not outside of it. People need one another to…

  3. Report on the Black Hills Alliance.

    ERIC Educational Resources Information Center

    Ryan, Joe

    1979-01-01

    A rally to save the Black Hills from coal- and uranium-greedy energy companies was held on July 6 and over 2,000 joined in a 15-mile walk on July 7 in Rapid City, South Dakota. The Black Hills Alliance, an Indian coalition concerned about energy development proposals in the Great Plains, sponsored the gathering. (NQ)

  4. Louisiana slope salt-ridge continuity confirmed

    SciTech Connect

    Lowrie, A.; Hoffman, K.S.; Sullivan, N.

    1989-03-01

    The Louisiana offshore is a world-class hydrocarbon province. Abundant reservoirs develop as the result of interaction between salt tectonics and sedimentation. Thus, it is essential to know both regional and local characteristics of the extent and timing of salt tectonics as an aid in hydrocarbon exploration. Exploration mythology mandates that salt domes and ridges are virtually random across the slope area. In sharp contrast, the authors describe a definite pattern to the salt ridges of slightly concave (to the north) arcs, with the southernmost arc located along the Sigsbee Escarpment and the northernmost along the shelf break. Furthermore, salt domes may not be truly randomly located but rather part of ancestral or existent salt ridges. Confirming data are provided by dip bathymatric and seismic profiles. The bathymetric profiles are at 5-mi (8-km) spacings from 1987 published charts of the Gulf of Mexico. Dip seismic lines reveal that bathymetric highs are associated with underlying salt. Buried salt accumulations are surficially expressed by actual ridges and domes, a leveling of sea floor, or a local decrease in the rate of regional slope descent. Salt is the Neogene-age basement of the Louisiana slope. The existence of an overall salt-ridge pattern implies that there is a single dynamic geologic system controlling the evolution of this slope. As salt tectonic rates and timing are deciphered for specific sites along dip, intervening rates may be interpolated to unmapped zones. Confirming an overall salt tectonic pattern is mandatory prior to quantifying regional and specific rates for the whole slope.

  5. Surface area and the seabed area, volume, depth, slope, and topographic variation for the world's seas, oceans, and countries.

    PubMed

    Costello, Mark John; Cheung, Alan; De Hauwere, Nathalie

    2010-12-01

    Depth and topography directly and indirectly influence most ocean environmental conditions, including light penetration and photosynthesis, sedimentation, current movements and stratification, and thus temperature and oxygen gradients. These parameters are thus likely to influence species distribution patterns and productivity in the oceans. They may be considered the foundation for any standardized classification of ocean ecosystems and important correlates of metrics of biodiversity (e.g., species richness and composition, fisheries). While statistics on ocean depth and topography are often quoted, how they were derived is rarely cited, and unless calculated using the same spatial resolution the resulting statistics will not be strictly comparable. We provide such statistics using the best available resolution (1-min) global bathymetry, and open source digital maps of the world's seas and oceans and countries' Exclusive Economic Zones, using a standardized methodology. We created a terrain map and calculated sea surface and seabed area, volume, and mean, standard deviation, maximum, and minimum, of both depth and slope. All the source data and our database are freely available online. We found that although the ocean is flat, and up to 71% of the area has a < 1 degree slope. It had over 1 million approximately circular features that may be seamounts or sea-hills as well as prominent mountain ranges or ridges. However, currently available global data significantly underestimate seabed slopes. The 1-min data set used here predicts there are 68,669 seamounts compared to the 30,314 previously predicted using the same method but lower spatial resolution data. The ocean volume exceeds 1.3 billion km(3) (or 1.3 sextillion liters), and sea surface and seabed areas over 354 million km(2). We propose the coefficient of variation of slope as an index of topographic heterogeneity. Future studies may improve on this database, for example by using a more detailed bathymetry

  6. Surface area and the seabed area, volume, depth, slope, and topographic variation for the world's seas, oceans, and countries.

    PubMed

    Costello, Mark John; Cheung, Alan; De Hauwere, Nathalie

    2010-12-01

    Depth and topography directly and indirectly influence most ocean environmental conditions, including light penetration and photosynthesis, sedimentation, current movements and stratification, and thus temperature and oxygen gradients. These parameters are thus likely to influence species distribution patterns and productivity in the oceans. They may be considered the foundation for any standardized classification of ocean ecosystems and important correlates of metrics of biodiversity (e.g., species richness and composition, fisheries). While statistics on ocean depth and topography are often quoted, how they were derived is rarely cited, and unless calculated using the same spatial resolution the resulting statistics will not be strictly comparable. We provide such statistics using the best available resolution (1-min) global bathymetry, and open source digital maps of the world's seas and oceans and countries' Exclusive Economic Zones, using a standardized methodology. We created a terrain map and calculated sea surface and seabed area, volume, and mean, standard deviation, maximum, and minimum, of both depth and slope. All the source data and our database are freely available online. We found that although the ocean is flat, and up to 71% of the area has a < 1 degree slope. It had over 1 million approximately circular features that may be seamounts or sea-hills as well as prominent mountain ranges or ridges. However, currently available global data significantly underestimate seabed slopes. The 1-min data set used here predicts there are 68,669 seamounts compared to the 30,314 previously predicted using the same method but lower spatial resolution data. The ocean volume exceeds 1.3 billion km(3) (or 1.3 sextillion liters), and sea surface and seabed areas over 354 million km(2). We propose the coefficient of variation of slope as an index of topographic heterogeneity. Future studies may improve on this database, for example by using a more detailed bathymetry

  7. Solar Rossby Wave 'Hills' Identified As Supergranules

    NASA Technical Reports Server (NTRS)

    Williams, P. E.; Hathaway, David H.; Cuntz, M.

    2007-01-01

    We explore the nature of 'hills' observed on the solar surface which had previously been attributed to Rossby waves. We investigate the sol ar hills phenomenon by analyzing the output from a synthetic model ba sed solely on the observed solar photospheric convection spectrum. We show that the characteristics of these hills can be explained by the corrugation of the surface produced by the radial flows of the conve ction. The hills in our simulations are dominated by supergranules, a well-known component of solar convection. Rossby waves have been predicted to exist within the Sun and may play an important role in the d ynamics of the solar interior, including the Sun's differential rotat ion and magnetic dynamo. Our study suggests, however, that the hills observed at the solar limb do not confirm the existence of solar Ross by waves.

  8. A new vision of carbonate slopes: the Little Bahama Bank

    NASA Astrophysics Data System (ADS)

    Mulder, Thierry; Gillet, Hervé; Hanquiez, Vincent; Reijmer, John J.; Tournadour, Elsa; Chabaud, Ludivine; Principaud, Mélanie; Schnyder, Jara; Borgomano, Jean

    2015-04-01

    Recent data collected in November 2014 (RV Walton Smith) on the upper slope of the Little Bahama Bank (LBB) between 30 and 400 m water depth allowed to characterize the uppermost slope (Rankey et al., 2012) over a surface of 170 km2. The new data set includes multibeam bathymetry and acoustic imagery, 3.5 kHz very-high resolution (VHR) seismic reflection lines, 21 gravity cores and 11 Van Veen grabs. The upper slope of the LBB does not show a steep submarine cliff as known from western Great Bahama Bank. The carbonate bank progressively deepens towards the basin through a slighty inclined plateau. The slope value is < 6° down to a water depth of about 70 m. The plateau is incised by decameter-wide gullies that covered with indurated sediment. Some of the gullies like Roberts Cuts show a larger size and may play an important role in sediment transfer from the shallow-water carbonate bank down to the canyon heads at 400-500 m water depth (Mulder et al., 2012). In the gully area, the actual reef rests on paleo-reefs that outcrop at a water depth of about 40 m. These paleo-reef structures could represent reefs that established themselves during past periods of sea-level stagnation. Below this water depth, the slope steepens up to 30° to form the marginal escarpment (Rankey et al., 2012), which is succeeded by the open margin realm (Rankey et al., 2012). The slope inclination value decreases at about 180-200 m water depth. Between 20 and 200 m of water depth, the VHR seismic shows no seafloor sub-bottom reflector. Between 180 and 320 m water depth, the seafloor smoothens. The VHR seismic shows an onlapping sediment wedge, which starts in this water depth and shows a blind or very crudely stratified echo facies. The sediment thickness of this Holocene unit may exceed 20 m. It fills small depressions in the substratum and thickens in front of gullies that cut the carbonate platform edge. Sediment samples show the abundancy of carbonate mud on the present Bahamian

  9. Sedimentation dynamics about salt features

    SciTech Connect

    Lowrie, A.; Blake, D.W.

    1985-02-01

    Detailed side-scan sonar and gridded bathymetric surveys on continental margins reveal the existence of numerous submarine canyons. Recently published compilations of current velocities in submarine canyons indicate that alternating and undirectionaly flows often exceed 20-30 cm/sec with peak velocities ranging from 70 to 100 cm/sec. Current meters attached to the ocean floor have been lost at current velocities of 190 cm/sec. Such velocities are ample to transport sand-size sediments. The results of DSDP Leg 96 show the existence of massive sands and gravels on the Louisiana slope, deposited during the last glacial advance. Thus, present physical oceanographic data may be an analog to conditions during glacially induced lowered sea levels. Salt ridges and domes underlie much of the Louisiana slope, determining morphology. Submarine canyons lace the slope. Given a prograding shelf, the net sediment transport routes will be down the submarine canyons. Sediment deposition patterns around the salt ridges and domes include parallel-bedded foredrifts on the upslope side, lee drifts on the downslope side, and moats along the lateral flanks of the salt features. Major differences exist between the sedimentation patterns around a ridge and a dome. The size and shape of the flow pattern will determine whether there can be a flow over the salt feature with a resulting turbulent wave that may influence sedimentation. Sedimentation patterns about salt features on the present slope should be applicable to similar paleoenvironments.

  10. Glacial History of the Pirrit Hills, West Antarctica

    NASA Astrophysics Data System (ADS)

    Spector, P. E.; Stone, J. O.

    2014-12-01

    We present new ice-thickness constraints from the Pirrit Hills, a small, far-flung group of nunataks located in the Weddell Sector. At the Pirrit Hills, fresh glacial erratics indicate ice levels ~350-450 m above present during the last ice age. The highest erratics have preliminary 10Be exposure ages of ~16 ka, and the ages generally decrease with decreasing elevation, recording the thinning of the ice in the region. Despite the evidence of thicker ice, weathered bedrock extends down to the present ice level, implying prolonged subaerial weathering prior to the last ice age. These features, and the lack of evidence for wet-based glacial erosion, indicate cold-based and non-erosive ice cover. Over the elevation range in which we found glacial erratics, bedrock 10Be, 26Al, and 21Ne concentrations are consistent with modest ice cover, and have exposure ages ranging from ~0.3-1.5 Myr. Around 450 m above the present ice level, bedrock 10Be, 26Al, and 21Ne concentrations increase by a factor of ~4-5 and do not indicate past ice cover. This height coincides with a break in the otherwise steep slopes of the Pirrit Hills, and the bedrock above is more weathered than the bedrock below. This transition marks the height above which ice cover, if it has occurred in the past few million years, has been very rare, brief, and cold-based. This feature may relate to the trimline imprinted on ridges in the Ellsworth Mountains. In both cases, alpine landscapes have been preserved by a polar climate and glacial highstands rising only partway up the mountain flanks.

  11. Geology of Tompkins Hill gas field, Humboldt County, California

    SciTech Connect

    Parker, J.

    1988-03-01

    The Tompkins Hill gas field, located in Humboldt County, California, is the only producing field in the Eel River basin. The field is an anticlinal flexure on the north limb of the Eel River syncline in the central onshore portion of the basin. The Tompkins Hill anticline is doubly plunging and trends east-west. Stratigraphic units present in the field include the Yager, Eel River, and Rio Dell Formations and Scotia Bluffs Sandstone. The Yager occurs below a major unconformity, and forms economic basement. Strata overlying the Eel River, Rio Dell, and Scotia Bluffs represent a progradational basin-fill sequence, including submarine fan, slope, shelf, and littoral deposits. The primary productive interval in the field is within the middle of the Rio Dell and consists of interbedded fine sandstone and mudrock. Portions of the Eel River and upper Rio Dell Formations are also productive. The Tompkins Hill gas field was discovered by the Texas Company in 1937 with the drilling of Eureka 2 in Sec. 22, T3N, R1W. The play was probably based on outcrop mapping and the presence of gas seeps in the area. The primary trapping mechanism in the field is structural, although stratigraphy may have been a factor in constraining gas. To date, 39 producing wells have been drilled and 87.4 bcf of gas, consisting of 98% methane, has been produced. Very minor amounts of condensate are also produced. The source rocks for the gas are uncertain, but both the Yager Formation and strata of the lower Wildcat Group may have contributed.

  12. Very long hillslope transport timescales determined from uranium-series isotopes in river sediments from a large, tectonically stable catchment

    NASA Astrophysics Data System (ADS)

    Suresh, P. O.; Dosseto, A.; Hesse, P. P.; Handley, H. K.

    2014-10-01

    catchment area of the Murrumbidgee River (Suresh et al., 2013), the current results indicate, for the first time, that sediments in the Murrumbidgee catchment are stored in hill slope for long time (∼200 kyr) before carried by the river. The long residence times of sediments indicate a low erosion rate from the catchment. The sediment transport timescales estimated are up to two orders of magnitude higher than those reported for tectonically active catchments in Iceland (Vigier et al., 2006) and in the Himalayas (Granet et al., 2007), indicating the influence of tectonism on catchment erosion.

  13. An Experimental Study of Submarine Canyon Evolution on Continental Slopes

    NASA Astrophysics Data System (ADS)

    Lai, S. Y.; Gerber, T. P.; Amblas, D.

    2013-12-01

    Submarine canyons define the morphology of many continental slopes and are conduits for the transport of sediment from shallow to deep water. Though the origin and evolution of submarine canyons is still debated, there is general agreement that sediment gravity flows play an important role. Here we present results from a simple, reduced-scale sandbox experiment designed to investigate how sediment gravity flows generate submarine canyons. In the experiments, gravity flows were modeled using either sediment-free or turbid saline currents. Unconfined flows were released onto an inclined bed of sand bounded on the downstream end by a movable floor that was incrementally lowered during the course of an experiment to produce an escarpment. This design was developed to represent the growth of relief across the continental slope. To monitor canyon evolution on the slope, we placed an overhead DSLR camera to record vivid time-lapse videos. At the end of each experimental stage we scanned the topography by imaging a series of submerged laser stripes, each projected from a motor-driven transverse laser sheet, onto a calibrated Cartesian coordinate system to produce high resolution bathymetry without draining the ambient water. In areas unaffected by the flows, we observe featureless, angle-of-repose submarine slopes formed by retrogressive breaching processes. In contrast, areas influenced by gravity flows cascading across the shelf break are deeply incised by submarine canyons with well-developed channel networks. Our results show that downslope gravity flows and submarine falling base level are both required to produce realistic canyon morphologies at laboratory scale. Though our mechanism for generating relief may be a rather crude analogue for the processes driving slope evolution, we hope our novel approach can stimulate new questions about the coevolution of canyons and slopes and motivate further experimental work to address them.

  14. Sand-Strewn Summit of 'Husband Hill' on Mars

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Undulating bands of dark and light sand, sloping dunes, and scattered cobbles form an apron around a ridge of light-colored rock that stands in bold relief against distant plains, as viewed by NASA's 'Spirit' rover from the top of 'Husband Hill' on Mars. 'The view of the summit is spectacular where we are right now,' said geologist Larry Crumpler, with the New Mexico Museum of Natural History and Science, Albuquerque.

    From here, Spirit is looking north-northeast en route to examining more of the local geology of the 'Columbia Hills' in Gusev Crater. A few days after taking this picture, Spirit investigated the small, sinuous drifts on the left, located north-northeast of the rover's position in this image. The last previous time Spirit examined a drift was on the rim of 'Bonneville Crater' almost 500 martian days, or sols, ago, in March 2004.

    The largest light-colored rock in the foreground is nicknamed 'Whittaker.' The cliff beyond it and slightly to the left is nicknamed 'Tenzing.' The highest rock on the ridge ahead has been dubbed 'Hillary.' Science team members selected the nicknames in honor of the earliest climbers to scale Mount Everest on Earth. This view covers approximately 50 degrees of the compass from left to right. It is a mosaic assembled from frames Spirit took with the panoramic camera on sol 603 (Sept. 13, 2005). It was taken through a blue (430-nanometer) filter and is presented as a cylindrical projection.

  15. Sediment storage by vegetation in steep bedrock landscapes: Theory, experiments, and implications for postfire sediment yield

    NASA Astrophysics Data System (ADS)

    Lamb, Michael P.; Levina, Mariya; Dibiase, Roman A.; Fuller, Brian M.

    2013-06-01

    models for sediment transport on hillslopes are needed for applications ranging from landscape evolution to debris-flow hazards. Progress has been made for soil-mantled landscapes; however, little is known about sediment production and transport in bedrock landscapes that often maintain a patchy soil mantle, even though slopes exceed the angle of repose. Herein we investigate the hypothesis that patchy soil cover is stable on steep slopes due to local roughness such as vegetation dams that trap sediment upslope. To quantify local sediment storage, we developed a new theory and tested it against tilt-table experiments. Results show that trapped sediment volume scales with the cube of dam width. Where the dam width is less than about fifty grain diameters, particle force chains appear to enhance stability, resulting in greater trapped volumes and sediment-pile slopes that exceed the angle of repose. Trapped volumes are greatest for hillslopes that just exceed the friction slope and are independent of hillslope gradient for gradients greater than about twice the friction slope. For neighboring dams spaced less than about five grain diameters apart, grain bridging results in a single sediment pile that is larger than the sum of individual piles. This work provides a mass-conserving framework for quantifying sediment storage and nonlocal transport in bedrock landscapes. Results may explain the rapid increase in sediment yield following wildfire in steep terrain in the absence of rainfall; as sediment dams are incinerated, particles become gravitationally unstable and move rapidly downslope as dry ravel.

  16. Layered Rocks in 'Columbia Hills'

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This black-and-white image shows the first layered rocks scientists have seen close up in Gusev Crater, where NASA's Mars Exploration Rover Spirit landed Jan. 4, 2004. While Spirit's twin rover, Opportunity, reached the stadium-size Endurance Crater on the other side of Mars and began exploring its many layered outcrops in early May, Spirit traveled more than 3.5 kilometers (2.2 miles) to get to this layered bedrock in the 'Columbia Hills.' Scientists are planning to conduct a study of these rocks to determine if they are volcanic or sedimentary in origin, and if they have been chemically altered. Spirit's panoramic camera took this image on sol 217 (Aug. 13, 2004).

  17. Using cyclic steps on drift wedges to amend established models of carbonate platform slopes

    NASA Astrophysics Data System (ADS)

    Betzler, Christian; Lindhorst, Sebastian; Eberli, Gregor; Reijmer, John; Lüdmann, Thomas

    2015-04-01

    Hydroacoustic and sedimentological data of the western flank of Great Bahama Bank and Cay Sal Bank document how the interplay of offbank sediment export, along-slope transport, and erosion together shape facies and thickness distribution of slope deposits. The integrated data set depicts the combined product of these processes and allows formulating a comprehensive model of a periplatform drift that significantly amends established models of carbonate platform slope facies distribution and geometry. The basinward thinning wedge of the periplatform drift at the foot of the escarpment of Great Bahama Bank displays along- and down-slope variations in sedimentary architecture. Sediments consist of periplatform ooze, i.e. carbonate mud and muddy carbonate sand, coarsening basinward. In zones of lower contour current speed, depth related facies belts develop. In the upper part of the periplatform drift wedge in a water depth of 180 to 300 m and slope angles of 6° - 9° the seafloor displays a smooth surface. Parasound data indicate that this facies is characterized by a parallel layering. Basinward, the slope shows a distinct break at which the seafloor inclination diminishes to 1° to 2°. Downslope of this break, the drift wedge has a 3 - 4 km wide pervasive cover of bedforms down to a water depth of around 500 m. The steep flanks and internal stratification of the wavy bedforms face upslope, indicating upstream migration; the bedforms therefore share all the characteristics of cyclic step sedimentation. This is the first description of cyclic step sedimentation patterns in carbonate slope depositional systems. This new slope sedimentation model aids in understanding the complexity of carbonate slope sedimentation models with facies belts perpendicular and parallel to the platform margin. The new model sharply contrasts with existing slope facies models in which facies belts are solely positioned parallel to the platform margin.

  18. Analysis of slope stability, Wilmington to Lindenkohl Canyons, US mid-Atlantic margin

    SciTech Connect

    Almagor, G.; Bennett, R.H.; Lambert, D.N.; Forde, E.B.; Shephard, L.E.

    1984-01-01

    The continental slope gradient in the study area averages 7 to 8/sup 0/. Many valleys, canyons, and occasionally large sediment slumped masses occur. Moderate to steep slopes (19 to 27/sup 0/) as well as very steep to precipitous slopes (> 27/sup 0/) are abundant and occupy about 7% of the investigated area. The surficial sediments are predominantly terrigenous silty clays of medium to high plasticity (I/sub p/ = 10 to 35% w/sub L/ = 30 to 70%), but contain varying quantities of sands. Angles of internal friction are anti phi/sub d/ = 27 to 32/sup 0/, anti phi/sub cu/ = 30 to 33/sup 0/, and phi/sub cu/ = 14 to 17/sup 0/. The sediments are normally to slightly overconsolidated, but some unconsolidated sediments also were identified. c/sub u//anti p/sub 0/ values range from 0.12 to 0.78. An analysis of force equilibrium within the sediments reveals that (a) the gentle slopes in the study area are mostly stable; (b) that the stability of some steep slopes (19 to 27/sup 0/) is marginal; and (c) that on precipitous slopes (> 27/sup 0/) only a thin veneer of sediments can exist. Observations of these slopes during steep dives support these results. The analysis shows that additional accumulation of sediments and small shocks caused by earthquakes or internal waves can cause the slopes to fail. Collapse resulting from liquefaction in the uppermost slope along the canyons and valley axes, where fine sands and silt accumulate, also is likely. 22 references, 9 figures, 2 tables.

  19. Constraining the Formation of Submarine Gullies on Continental Slopes

    NASA Astrophysics Data System (ADS)

    Shumaker, L.; Jobe, Z. R.; Graham, S. A.

    2015-12-01

    Submarine gullies are ubiquitous on continental slopes and steep areas of seafloor worldwide, but their role in sediment transport remains unresolved. Direct observation of flows in the submarine realm is rare and expensive, but by analyzing basic geometries of gullies in the sedimentary record, it is possible to gain insight into the behavior of the flows that formed them. In shallow 3D seismic reflection data from the Taranaki Basin, New Zealand, we document gullies preserved in a Pliocene-Pleistocene progradational margin sequence. These gullies commonly form aggradational complexes hundreds of meters thick, showing alternating periods of erosion, inactivity, and roughly self-similar aggradation in response to slope sedimentation. Erosional phases speak of modification by energetic turbidity currents, whereas sediment drapes point to extended periods of flow quiescence and hemipelagic deposition. We pair these observations with morphometrics of over 600 gullies in seafloor bathymetry from continental margins worldwide. The slopes of these modern gullies and interfluves are both well described by a power-law decay with along-profile distance. The decay of slopes with distance (concavity) obtained from power-law relationships for interfluves and gullies are well correlated, although gullies attain higher slopes and are slightly more concave than neighboring interfluves. The self-similar growth of gullies in the subsurface and the strong similarity between gully and interfluve profiles in all datasets suggests a link between the evolution of gullies and of the slopes on which they form. We conclude by presenting a conceptual model in which gully and slope morphology are tightly coupled.

  20. Evolution of continental slope gullies on the northern california margin

    USGS Publications Warehouse

    Spinelli, G.A.; Field, M.E.

    2001-01-01

    A series of subparallel, downslope-trending gullies on the northern California continental slope is revealed on high-resolution seismic reflection profiles imaging the uppermost 50 m of sediment. The gullies are typically 100 m wide and have 1 to 3 m of relief. They extend for 10 to 15 km down the slope and merge into larger channels that feed the Trinity Canyon. In the lower half of the 50 m stratigraphic section, the gullies increase in both relief and number up section, to maxima at a surface 5 to 10 m below the last glacial maximum lowstand surface. Gully relief increased as interfluves aggraded more rapidly than thalwegs. Erosion is not evident in the gully bottoms, therefore gully growth was probably due to reduced sediment deposition within the gullies relative to that on interfluves. As the gullies increased in relief, their heads extended upslope toward the shelfbreak. At all times, a minimum of 10 km of non-gullied upper slope and shelf stretched between the heads of the gullies and the paleo-shoreline; the gullies did not connect with a subaerial drainage network at any time. Gully growth occurred when the gully heads were in relatively shallow water (??? 200 m paleo-water depth) and were closest to potential sediment sources. We suggest that prior to the last glacial maximum, the Mad River, then within 10 km of the gully heads, supplied sediment to the upper slope, which fed downslope-eroding sediment flows. These flows removed sediment from nearly parallel gullies at a rate slightly slower than sediment accumulation from the Eel River, 40 km to the south. The process or processes responsible for gully growth and maintenance prior to the last glacial maximum effectively ceased following the lowstand, when sea level rose and gully heads lay in deeper water (??? 300 m water depth), farther from potential sediment sources. During sea-level highstand, the Mad River is separated from the gully heads by a shelf 30 km wide and no longer feeds sediment flows

  1. The hill forts and castle mounds in Lithuania: interaction between geodiversity and human-shaped landscape

    NASA Astrophysics Data System (ADS)

    Skridlaite, Grazina; Guobyte, Rimante; Satkunas, Jonas

    2015-04-01

    Lithuania is famous for its abundant, picturesque hill forts and castle mounds of natural origin. In Lithuania as well as in whole Europe the fortified hills were used as the society dwelling place since the beginning of the Late Bronze Age. Their importance increased when Livonian and Teutonic Orders directed a series of military campaigns against Lithuania with the aim of expansion of Christianity in the region at the end of 1st millennium AD, and they were intensively used till the beginning of the 15th c. when most of them were burned down during fights with the Orders or just abandoned due to the changing political and economical situation. What types of the geodiversity were used for fortified dwellings? The choice in a particular area depended on a variety of geomorphology left behind the retreating ice sheets. High spots dominating their surroundings were of prime interest. In E and SE Lithuania, the Baltic Upland hills marking the eastern margin of the last Weichselian glacier hosted numerous fortified settlements from the end of 2nd millennium BC to the Medieval Ages (Narkunai, Velikuskes etc). In W Lithuania, plateau-like hills of the insular Samogitian Upland had been repeatedly fortified from the beginning of 1st millennium AD to the 14th century (Satrija, Medvegalis etc). Chains of hill forts and castle mounds feature the slopes of glaciofluvial valleys of Nemunas, Neris and other rivers where the slopes were dissected by affluent rivulets and ravines and transformed into isolated, well protected hills (Kernave, Punia, Veliuona etc). Peninsulas and headlands formed by the erosion of fluvial and lacustrine deposits were used in the lowlands, e.g. in central and N Lithuania (Paberze, Mezotne etc). How much the landscape was modified for defense purposes? Long-term erosion and overgrowing vegetation damaged the former fortified sites, however some remains and the archeological excavations allowed their reconstruction. The fortified Bronze Age settlements

  2. Anticipated sediment delivery to the lower Elwha River during and following dam removal: Chapter 2 in Coastal habitats of the Elwha River, Washington--biological and physical patterns and processes prior to dam removal

    USGS Publications Warehouse

    Czuba, Christiana R.; Randle, Timothy J.; Bountry, Jennifer A.; Magirl, Christopher S.; Czuba, Jonathan A.; Curran, Christopher A.; Konrad, Christopher P.; Duda, Jeffrey J.; Warrick, Jonathan A.; Magirl, Christopher S.

    2011-01-01

    During and after the planned incremental removal of two large, century-old concrete dams between 2011 and 2014, the sediment-transport regime in the lower Elwha River of western Washington will initially spike above background levels and then return to pre-dam conditions some years after complete dam removal. Measurements indicate the upper reaches of the steep-gradient Elwha River, draining the northeast section of the Olympic Mountains, carries between an estimated 120,000 and 290,000 cubic meters of sediment annually. This large load has deposited an estimated 19 million cubic meters of sediment within the two reservoirs formed by the Elwha and Glines Canyon Dams. It is anticipated that from 7 to 8 million cubic meters of this trapped sediment will mobilize and transport downstream during and after dam decommissioning, restoring the downstream sections of the sediment-starved river and nearshore marine environments. Downstream transport of sediment from the dam sites will have significant effects on channel morphology, water quality, and aquatic habitat during and after dam removal. Sediment concentrations are expected to be between 200 and 1,000 milligrams per liter during and just after dam removal and could rise to as much as 50,000 milligrams per liter during high flows. Downstream sedimentation in the river channel and flood plain will be potentially large, particularly in the lower Elwha River, an alluvial reach with a wide flood plain. Overall aggradation could be as much as one to several meters. Not all reservoir sediment, however, will be released to the river. Some material will remain on hill slopes and flood plains within the drained reservoirs in quantities that will depend on the hydrology, precipitation, and mechanics of the incising channel. Eventually, vegetation will stabilize this remaining reservoir sediment, and the overall sediment load in the restored river will return to pre-dam levels.

  3. Slope Stability: Factor of Safety along the Seismically Active Continental Slope Offshore Sumatra

    NASA Astrophysics Data System (ADS)

    Patton, J. R.; Goldfinger, C.; Djadjadihardja, Y.; None, U.

    2013-12-01

    Recent papers have documented the probability that turbidites deposited along and downslope of subduction zone accretionary prisms are likely the result of strong ground shaking from great earthquakes. Given the damaging nature of these earthquakes, along with the casualties from the associated tsunamis, the spatial and temporal patterns of these earthquakes can only be evaluated with paleoseismologic coring and seismic reflection methods. We evaluate slope stability for seafloor topography along the Sunda subduction offshore Sumatra, Indonesia. We use sediment material properties, from local (Sumatra) and analogous sites, to constrain our estimates of static slope stability Factor of Safety (FOS) analyses. We then use ground motion prediction equations (GMPE's) to estimate ground motion intensity (Arias Intensity, AI) and acceleration (Peak Ground Acceleration, PGA), as possibly generated by fault rupture, to constrain seismic loads for pseudostatic slope stability FOS analyses. The ground motions taper rapidly with distance from the fault plane, consistent with ground motion - fault distance relations measured during the 2011 Tohoku-Oki subduction zone earthquake. Our FOS analyses include a Morgenstern method of slices probabilistic analysis for 2-D profiles along with Critical Acceleration (Ac) and Newmark Displacement (Dn) analysis of multibeam bathymetry of the seafloor. In addition, we also use estimates of ground motion modeled with a 2004 Sumatra-Andaman subduction zone (SASZ) earthquake fault slip model, to also compare with our static FOS analyses of seafloor topography. All slope and trench sites are statically stable (FOS < 1) and sensitive to ground motions generated by earthquakes of magnitude greater than 7. We conclude that for earthquakes of magnitude 6 to 9, PGA of 0.4-0.6 to 1.4-2.5 g would be expected, respectively, from existing GMPE's. However, saturation of accelerations in the accretionary wedge may limit actual accelerations to less than 1

  4. The Mud Hills, Mojave Desert, California: Structure, stratigraphy and sedimentology of a rapidly extended terrane

    SciTech Connect

    Ingersoll, R.V.; Devaney, K.A.; Geslin, J.K.; Cavazza, W.; Diamond, D.S.; Jagiello, K.J.; Marsaglia, K.M.; Paylor, E.D. II; Short, P.F. . Dept. of Earth and Space Sciences)

    1993-04-01

    The Mud Hills exposes synorogenic breccia (Mud Hills Fm.) deposited during the final stages of crustal extension of the upper plate above the Waterman Hills detachment (20--18 Ma). Previous workers have misinterpreted fault contacts as stratigraphic contacts, and have developed intricate pseudostratigraphy to explain their observations. The authors' detailed mapping, combined with stratigraphic and sedimentologic data, documents that the volcaniclastic Pickhandle Fm. is conformably overlain by the plutoniclastic Mud Hills Fm., with no interfingering. Repetition of these south-dipping lithologic units is due to imbricate, north-dipping listric faults. These relations are demonstrated by the systematic northward v''ing of fault contacts and southward v''ing of stratigraphic contacts. Stratigraphic dip decreases upsection, which is consistent with incremental rotation of basinal strata simultaneously with deposition. Most of the Mud Hills Fm. consists of rock-avalanche breccia and megabreccia derived from granodiorite, which is identical to basement exposed beneath the Pickhandle and Jackhammer Fms. to the north. The Mud Hills Fm. was derived from now-buried granodiorite of a stranded upper-plate block to the south, as demonstrated by northward paleocurrents, facies relations and the presence of fine-grained units close to the presumed master fault (as is typical of half-graben sedimentation). Unconformably overlying the Mud Hills Fm. is the Owl Conglomerate (Barstow Fm.), which has mixed provenance with southward paleocurrents; the Owl Conglomerate was derived from residual highlands after extension ceased. Integration of structural, stratigraphic and sedimentologic information is essential for correct reconstruction of highly extended terranes.

  5. A new vision of carbonate slopes: the Little Bahama Bank

    NASA Astrophysics Data System (ADS)

    Mulder, Thierry; Gillet, Hervé; Hanquiez, Vincent; Reijmer, John J.; Tournadour, Elsa; Chabaud, Ludivine; Principaud, Mélanie; Schnyder, Jara; Borgomano, Jean; Fauquembergue, Kelly; Ducassou, Emmanuelle

    2016-04-01

    Recent high-quality multibeam and seismic data allow to image a large part of the uppermost slope of Northeastern Little Bahama Bank between 30 and 400 m water depth and to characterize the uppermost slope (Rankey and Doolitle, 1992) over a surface of 170 km2. The new data set includes multibeam bathymetry and acoustic imagery, 3.5 kHz very-high resolution (VHR) seismic reflexion lines (1120 km), 21 gravity cores and 11 Van Veen grabs. This dataset completes the recent surveys of the slope adjacent to LBB (Carambar cruise, Mulder et al, 2012). The data provide insight into sediment transfer from the shallow carbonate bank to the adjacent slope. Four major terraces and escarpments dominate the morphology of the slope. The terraces are located at 22 m, 27-33 m, 40-46 and 55-64 m below present water depth (mpwd). They could either be related to periods of stagnating sea-level and therefore increased erosion by waves, or periods of accelerated sea-level rise since the Last Glacial Maximum. Escarpments bound the terraces. The deepest one (64-56 mpwd) is also the steepest 35-50°). It corresponds to the marginal scarp of Rankey and Doolitle (1992). The lower part of the uppermost slope shows a discontinuous Holocene sediment wedge with varying thickness between 0 and 35 m. It forms a blind or very crudely stratified echo facies. This Holocene unit can be thicker than 20 m and consists of mud that forms most of the present sediment export. This unit fills small depressions in the substratum and thickens in front of gullies that cut the carbonate platform edge. It forms by off-bank export initiated when a cold front passes by, resulting in density cascading currents. The associated sediment fall-out and convective sedimentation can generate density currents that flow through linear structures on the upper slope. The survey reveals the presence of recently active channels that extend laterally over the entire uppermost slope and interrupt the density cascading fall

  6. Stability studies of surficial sediments in the Wilmington-Lindenkohl Canyons area, eastern U.S. margin

    USGS Publications Warehouse

    Almagor, G.; Bennett, R.H.; Mc Gregor, B.A.; Shephard, L.E.

    1982-01-01

    Stability analysis, based on infinite slope analysis and geotechnical data from a suite of 34 cores collected from the continental slope between Wilmington and Lindenkohl Canyons, indicates that the Quaternary surficial silty clay sediments on gentle slopes are stable; that sediment stability on steeper slopes (14??-19??) is marginal; and that on precipitous slopes (>50??) only a thin veneer of unconsolidated sediments can exist. Small earthquake-induced accelerations or the effects of internal waves can result in slope sediment instabilities. ?? 1982 A. M. Dowden, Inc.

  7. Using 137Cs to quantify the sediment delivery ratio in a small watershed.

    PubMed

    Li, Mian; Yao, Wenyi; Li, Zhanbin; Liu, Puling; Yang, Er; Shen, Zhenzhou

    2012-01-01

    Understanding the sediment delivery ratio (SDR) is important in controlling sediments for the sustainable development of natural resources and in the design of the construction such as dams and reservoirs. The purpose of this investigation is to determine the SDR by the (137)Cs tracing method in a small watershed in the Sichuan Hilly Basin of China. In the study watershed, different land plots are divided according to the land use type, and 97 sampling sites were selected from these plots. The results show that the average net soil loss rates from the forest land and sloping cultivated land are 1759 and 4468t/km(2)a, respectively. No (137)Cs was detectable on the bare rock surfaces and previous work showed that the erosion rate from the bare rock area was 14,260t/km(2)a. In the depositional zone, the sedimentation rates in the Caoto (a kind of cultivated land located at the foot of hills) and paddy field are 3113 and 3562t/km(2)a, respectively. Combining the area of each land use in the small watershed, the SDR of 0.40 is obtained in the past four decades. The (137)Cs technique was shown to provide an effective and rapid means of estimating the SDR within the small watershed.

  8. Aquatic assessment of the Pike Hill Copper Mine Superfund site, Corinth, Vermont

    USGS Publications Warehouse

    Piatak, Nadine M.; Argue, Denise M.; Seal, Robert R., II; Kiah, Richard G.; Besser, John M.; Coles, James F.; Hammarstrom, Jane M.; Levitan, Denise M.; Deacon, Jeffrey R.; Ingersoll, Christopher G.

    2013-01-01

    The Pike Hill Copper Mine Superfund site in Corinth, Orange County, Vermont, includes the Eureka, Union, and Smith mines along with areas of downstream aquatic ecosystem impairment. The site was placed on the U.S. Environmental Protection Agency (USEPA) National Priorities List in 2004. The mines, which operated from about 1847 to 1919, contain underground workings, foundations from historical structures, several waste-rock piles, and some flotation tailings. The mine site is drained to the northeast by Pike Hill Brook, which includes several wetland areas, and to the southeast by an unnamed tributary that flows to the south and enters Cookville Brook. Both brooks eventually drain into the Waits River, which flows into the Connecticut River. The aquatic ecosystem at the site was assessed using a variety of approaches that investigated surface-water quality, sediment quality, and various ecological indicators of stream-ecosystem health. The degradation of surface-water quality is caused by elevated concentrations of copper, and to a lesser extent cadmium, with localized effects caused by aluminum, iron, and zinc. Copper concentrations in surface waters reached or exceeded the USEPA national recommended chronic water-quality criteria for the protection of aquatic life in all of the Pike Hill Brook sampling locations except for the location farthest downstream, in half of the locations sampled in the tributary to Cookville Brook, and in about half of the locations in one wetland area located in Pike Hill Brook. Most of these same locations also contained concentrations of cadmium that exceeded the chronic water-quality criteria. In contrast, surface waters at background sampling locations were below these criteria for copper and cadmium. Comparison of hardness-based and Biotic Ligand Model (BLM)-based criteria for copper yields similar results with respect to the extent or number of stations impaired for surface waters in the affected area. However, the BLM

  9. Descent from the Summit of 'Husband Hill'

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Click on the image for Descent from the Summit of 'Husband Hill' (QTVR)

    In late November 2005 while descending 'Husband Hill,' NASA's Mars Exploration Rover Spirit took the most detailed panorama so far of the 'Inner Basin,' the rover's next target destination. Spirit acquired the 405 individual images that make up this 360-degree view of the surrounding terrain using five different filters on the panoramic camera. The rover took the images on Martian days, or sols, 672 to 677 (Nov. 23 to 28, 2005 -- the Thanksgiving holiday weekend).

    This image is an approximately true-color rendering using camera's 750-, 530-, and 430-nanometer filters. Seams between individual frames have been eliminated from the sky portion of the mosaic to better simulate the vista a person standing on Mars would see.

    'Home Plate,' a bright, semi-circular feature scientists hope to investigate, is harder to discern in this image than in earlier views taken from higher up the hill. Spirit acquired this more oblique view, known as the 'Seminole panorama,' from about halfway down the south flank of Husband Hill, 50 meters (164 feet) or so below the summit. Near the center of the panorama, on the horizon, are 'McCool Hill' and 'Ramon Hill,' named, like Husband Hill, in honor of the fallen astronauts of the space shuttle Columbia. Husband Hill is visible behind the rover, on the right and left sides of the panorama. An arc of rover tracks made while avoiding obstacles and getting into position to examine rock outcrops can be traced over a long distance by zooming in to explore the panorama in greater detail.

    Spirit is now significantly farther downhill toward the center of this panorama, en route to Home Plate and other enigmatic soils and outcrop rocks in the quest to uncover the history of Gusev Crater and the 'Columbia Hills.'

  10. Co-Variations of Ice Sheet Elevation and Slope with Accumulation, Radar Backscatter, and Temperature in West Antarctica

    NASA Astrophysics Data System (ADS)

    Haran, T.; Scambos, T.

    2004-12-01

    significant correlation with surface structure, in this case elevation. Using 60 clear-sky AVHRR images, we compile a map of mean surface temperature under clear-sky conditions. Locally high areas on the ice sheet show consistently warmer surface temperatures, by 1 to 4 C, under clear-sky conditions. Katabatic winds arise from surface radiative cooling under clear conditions; so the relationship between surface elevation and clear-sky temperature is an indicator of inversion-layer air-flow. We infer that katabatic airflow dominates accumulation via snow re-distribution and may also impact mean annual snow temperature via its interaction with surface morphology at the 2 - 10 km spatial scale. We hypothesize that flow of the inversion layer slows over the upwind face of hills, causing a loss of entrained sediment (snow). Greater concentration of subsurface layering (wind-crust, hoar, or glaze layers per meter depth in the firn) on low-accumulation lee faces leads to higher radar backscatter. Steep, inverted lapse rates in the inversion layer result in persistent temperature-elevation relationships of several degrees C over elevation changes of just a few tens of meters.

  11. Hydrology of two slopes in subarctic Yukon, Canada

    NASA Astrophysics Data System (ADS)

    Carey, Sean K.; Woo, Ming-Ko

    1999-11-01

    Two subarctic forested slopes in central Wolf Creek basin, Yukon, were studied in 1996-1997 to determine the seasonal pattern of the hydrologic processes. A south-facing slope has a dense aspen forest on silty soils with seasonal frost only and a north-facing slope has open stands of black spruce and an organic layer on top of clay sediments with permafrost. Snowmelt is advanced by approximately one month on the south-facing slope due to greater radiation receipt. Meltwater infiltrates its seasonally frozen soil with low ice content, recharging the soil moisture reservoir but yielding no lateral surface or subsurface flow. Summer evaporation depletes this recharged moisture and any additional rainfall input, at the expense of surface or subsurface flow. The north-facing slope with an ice rich substrate hinders deep percolation. Snow meltwater is impounded within the organic layer to produce surface runoff in rills and gullies, and subsurface flow along pipes and within the matrix of the organic soil. During the summer, most subsurface flows are confined to the organic layer which has hydraulic conductivities orders of magnitudes larger than the underlying boulder-clay. Evaporation on the north-facing slope declines as both the frost table and the water table descend in the summer. A water balance of the two slopes demonstrates that vertical processes of infiltration and evaporation dominate moisture exchanges on the south-facing slope, whereas the retardation of deep drainage by frost and by clayey soil on the permafrost slope promotes a strong lateral flow component, principally within the organic layer. These results have the important implication that permafrost slopes and organic horizons are the principal controls on streamflow generation in subarctic catchments.

  12. Slope stability and stabilization methods

    SciTech Connect

    Abramson, L.W.; Lee, T.S.; Boyce, G.M.; Sharma, S.S.

    1995-12-01

    Slope stability can be a major problem during the construction of surface facilities. Cutting into existing ground disturbs the mechanics of the surrounding area, which can result in landslides and rock falls. This practical reference gives you the comprehensive information you need for slope stability analysis, suitable methods of analysis with and without the use of computers, and examples of common stability problems and stabilization methods for cuts and fills. It includes detailed discussions of methods used in slope stability analysis, including the Ordinary Method of Slices, Simplified Janbu Method, Simplified Bishop Method, Spencer`s Method, other limit equilibrium methods, numerical methods, total stress analysis, effective stress analysis, and the use of computer programs to solve problems. Chapters include: General Slope Stability Concepts; Engineering Geology Principles; Groundwater Conditions; Geologic Site Exploration; Laboratory Testing Interpretation; Slope Stability Concepts; Slope Stabilization Methods; and Design, Construction and Maintenance.

  13. Regional variability of slope stability: Application to the Eel margin, California

    USGS Publications Warehouse

    Lee, H.; Locat, J.; Dartnell, P.; Israel, K.; Florence, Wong

    1999-01-01

    Relative values of downslope driving forces and sediment resisting forces determine the locations of submarine slope failures. Both of these vary regionally, and their impact can be addressed when the data are organized in a Geographic Information System (GIS). The study area on the continental margin near the Eel River provides an excellent opportunity to apply GIS spatial analysis techniques for evaluation of slope stability. In this area, swath bathymetric mapping shows seafloor morphology and distribution of slope steepness in fine detail, and sediment analysis of over 70 box cores delineates the variability of sediment density near the seafloor surface. Based on the results of ten geotechnical studies of submarine study areas, we developed an algorithm that relates surface sediment density to the shear strength appropriate to the type of cyclic loading produced by an earthquake. Strength and stress normalization procedures provide results that are conceptually independent of subbottom depth. Results at depth are rigorously applicable if sediment lithology does not vary significantly and consolidation state can be estimated. Otherwise, the method applies only to shallow-seated slope failure. Regional density, slope, and level of anticipated seismic shaking information were combined in a GIS framework to yield a map that illustrates the relative stability of slopes in the face of seismically induced failure. When a measure of predicted relative slope stability is draped on an oblique view of swath bathymetry, a variation in this slope stability is observed on an otherwise smooth slope along the mid-slope region north of a plunging anticline. The section of slope containing diffuse, pockmarked gullies has a lower measure of stability than a separate section containing gullies that have sharper boundaries and somewhat steeper sides. Such an association suggests that our slope-stability analysis relates to the stability of the gully sides. The remainder of the

  14. Hill-Climbing Attacks and Robust Online Signature Verification Algorithm against Hill-Climbing Attacks

    NASA Astrophysics Data System (ADS)

    Muramatsu, Daigo

    Attacks using hill-climbing methods have been reported as a vulnerability of biometric authentication systems. In this paper, we propose a robust online signature verification algorithm against such attacks. Specifically, the attack considered in this paper is a hill-climbing forged data attack. Artificial forgeries are generated offline by using the hill-climbing method, and the forgeries are input to a target system to be attacked. In this paper, we analyze the menace of hill-climbing forged data attacks using six types of hill-climbing forged data and propose a robust algorithm by incorporating the hill-climbing method into an online signature verification algorithm. Experiments to evaluate the proposed system were performed using a public online signature database. The proposed algorithm showed improved performance against this kind of attack.

  15. Sweeping View of the 'Columbia Hills' and Gusev Crater (3-D)

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Left-eye view of a stereo pair for PIA03250

    [figure removed for brevity, see original site] Right-eye view of a stereo pair for PIA03250

    NASA's Mars Exploration Rover Spirit obtained this stereo panorama of the surrounding Martian terrain in Gusev Crater from two positions about 10 meters (33 feet) apart. This is much greater separation than the 30-centimeter (11.8-inch) distance between the left and right 'eyes' of the panoramic camera. The effect of increasing the separation distance of a stereo image is to greatly increase the apparent (visual) depth, allowing scientists and engineers to see details in terrain that are too far away for the standard baseline. Stereo images such as these enable planetary scientists to derive detailed information about slopes and topography, map the terrain, and select routes for the rover. Spirit is now descending from 'Haskin Ridge,' on the left, down the slopes of 'Husband Hill' toward the 'Inner Basin,' a low region between Husband Hill and 'McCool Hill' to the south. Scientists speculate that, on the way, Spirit may drive over successive rock layers or deeper exposures of the bedrock in the 'Columbia Hills.' They hope to reach the conspicuous circular feature (just to the right of the center of the image), nicknamed 'Home Plate,' before the Martian winter, in search of layered rock outcrops that may provide additional information about the geology of the Columbia Hills.

    Current long-range plans are for Spirit to cross the lowest part of the basin and approach Home Plate within 50 to 60 Martian days, or sols. After investigating Home Plate, mission planners will possibly direct Spirit to the sunny, north-facing slopes of McCool Hill, placing the rover in view of the sun as it sinks lower toward the northern horizon. This would put the rover in position to soak up enough rays of solar energy to continue operating through the coming southern-hemisphere winter on

  16. Geotechnical characteristics and slope stability on the Ebro margin, western Mediterranean

    USGS Publications Warehouse

    Baraza, J.; Lee, H.J.; Kayen, R.E.; Hampton, M.A.

    1990-01-01

    Sedimentological and geotechnical analyses of core samples from the Ebro continental slope define two distinct areas on the basis of sediment type, physical properties and geotechnical behavior. The first area is the upper slope area (water depths of 200-500 m), which consists of upper Pleistocene prodeltaic silty clay with a low water content (34% dry weight average), low plasticity, and high overconsolidation near the seafloor. The second area, the middle and lower slope (water depths greater than 500 m), contains clay- and silt-size hemipelagic deposits with a high water content (90% average), high plasticity, and a low to moderate degree of overconsolidation near the sediment surface. Results from geotechnical tests show that the upper slope has a relatively high degree of stability under relatively rapid (undrained) static loading conditions, compared with the middle and lower slopes, which have a higher degree of stability under long-term (drained) static loading conditions. Under cyclic loading, which occurs during earthquakes, the upper slope has a higher degree of stability than the middle and lower slopes. For the surface of the seafloor, calculated critical earthquake accelerations that can trigger slope failures range from 0.73 g on the upper slope to 0.23 g on the lower slope. Sediment buried well below the seafloor may have a critical acceleration as low as 0.09 g on the upper slope and 0.17 g on the lower slope. Seismically induced instability of most of the Ebro slope seems unlikely given that an earthquake shaking of at least intensity VI would be needed, and such strong intensities have never been recorded in the last 70 years. Other cyclic loading events, such as storms or internal waves, do not appear to be direct causes of instability at present. Infrequent, particularly strong earthquakes could cause landslides on the Ebro margin slope. The Columbretes slide on the southwestern Ebro margin may have been caused by intense earthquake shaking

  17. Inside Beacon Hill: Bertrand Russell as Schoolmaster.

    ERIC Educational Resources Information Center

    Jespersen, Shirley

    1987-01-01

    The author describes the life and theories of Bertrand Russell, founder of Beacon Hill School. Russell's educational theories centered on the personal autonomy of the student and democratization of the learning process. (CH)

  18. A perspective on Capitol Hill

    NASA Astrophysics Data System (ADS)

    Hodges, Carroll Ann

    As the AGU Congressional Science Fellow for 1980-1981, I had a unique opportunity to witness the federal engine in action—a remarkable piece of machinery. The American Association for the Advancement of Science organized an excellent orientation program, introducing our class of science fellows (about 30) to the kinds of options available for a year's tenure on Capitol Hill. These include affiliation with a congressman's or senator's staff or with one of the hundred or so standing, select, or joint committees and subcommittees. I arranged to join the personal staff of Congressman Jim Santini (D, Nev.), largely because of his demonstrated interest in Department of Interior affairs in general and the minerals industry in particular. The position of fellow provides no guarantee of work in one's areas of expertise or inclination, however, and I found that my staff assignments included topics ranging from wild horses to peanut subsidies. My principal task involved evaluation of the Air Force proposal to deploy the MX missile in Nevada and the consequent impact of that incredible scheme on the physical and economic environments of the state and the nation, including effects on minerals exploration. I had not expected to become conversant with missile technology, but the exercise provided quite an education.

  19. The Igwisi Hills extrusive 'kimberlites'

    NASA Technical Reports Server (NTRS)

    Reid, A. M.; Donaldson, C. H.; Dawson, J. B.; Brown, R. W.; Ridley, W. I.

    1975-01-01

    The petrography and mineral chemistry of volcanic rocks from the Igwisi Hills in Tanzania are discussed. There is considerable evidence to suggest that the Igwisi rocks are extrusive kimberlites: a two-component nature with high P-T minerals in a low P-T matrix; the presence of chrome pyrope, Al enstatite, chrome diopside, chromite and olivine; a highly oxidized, volatile-rich matrix with serpentine, calcite, magnetite, perovskite; high Sr, Zr, and Nb contents; occurrence in a narrow isolated vent within a stable shield area. The Igwisi rocks differ from kimberlite in the lack of magnesian ilmenite, the scarcity of matrix phlogopite, and the overall low alkali content. They apparently contain material from phlogopite-bearing garnet peridotites with a primary mineral assemblage indicative of equilibrium at upper mantle temperatures and pressures. This primary assemblage was brought rapidly to the surface in a gas-charged, carbonate-rich fluid. Rapid upward transport, extrusion, and rapid cooling have tended to prevent reaction between inclusions and the carbonate-rich matrix that might otherwise have yielded a more typical kimberlite.

  20. Late Holocene eolian activity in the mineralogically mature Nebraska Sand Hills

    USGS Publications Warehouse

    Muhs, D.R.; Stafford, Thomas W.; Swinehart, J.B.; Cowherd, S.D.; Mahan, S.A.; Bush, C.A.; Madole, R.F.; Maat, P.B.

    1997-01-01

    The age of sand dunes in the Nebraska Sand Hills has been controversial, with some investigators suggesting a full-glacial age and others suggesting that they were last active in the late Holocene. New accelerator mass spectrometry radiocarbon ages of unaltered bison bones and organic-rich sediments suggest that eolian sand deposition occurred at least twice in the past 3000 14C yr B.P. in three widely separated localities and as many as three times in the past 800 14C yr at three other localities. These late Holocene episodes of eolian activity are probably the result of droughts more intense than the 1930s "Dust Bowl" period, based on independent Great Plains climate records from lake sediments and tree rings. However, new geochemical data indicate that the Nebraska Sand Hills are mineralogically mature. Eolian sands in Nebraska have lower K-feldspar (and K2O, Rb, and Ba) contents than most possible source sediments and lower K-feldspar contents than dunes of similar age in Colorado. The most likely explanation for mineralogical maturity is reduction of sand-sized K-feldspar to silt-sized particles via ballistic impacts due to strong winds over many cycles of eolian activity. Therefore, dunes of the Nebraska Sand Hills must have had a long history, probably extending over more than one glacial-interglacial cycle, and the potential for reactivation is high, with or without a future greenhouse warming. ?? 1997 University of Washington.

  1. Stability of submerged slopes on the flanks of the Hawaiian Islands, a simplified approach

    SciTech Connect

    Lee, H.J.; Torresan, M.E.; McArthur, W.

    1994-12-31

    Undersea transmission lines and shoreline AC-DC conversion stations and near-shore transmission lines are being considered as part of a system for transporting energy between the Hawaiian Islands. These facilities will need to be designed so that they will not be damaged or destroyed by coastal or undersea landslides. Advanced site surveys and engineering design of these facilities will require detailed site specific analyses, including sediment sampling and laboratory testing of samples, in situ testing of sediment and rock, detailed charting of bathymetry, and two- or three-dimensional numerical analyses of the factors of safety of the slopes against failure from the various possible loading mechanisms. An intermediate approximate approach can be followed that involves gravity and piston cores, laboratory testing and the application of simplified models to determine a seismic angle of repose for actual sediment in the vicinity of the planned facility. An even simpler and more approximate approach involves predictions of angles of repose using classification of the sediment along a proposed route as either a coarse volcaniclastic sand, a calcareous ooze, or a muddy terrigenous sediment. The steepest slope that such a sediment can maintain is the static angle of repose. Sediment may be found on slopes as steep as these, but it must be considered metastable and liable to fail in the event of any disturbance, storm or earthquake. The seismic angle of repose likely governs most slopes on the Hawaiian Ridge. This declivity corresponds to the response of the slope to a continuing seismic environment. As a long history of earthquakes affects the slopes, they gradually flatten to this level. Slopes that exceed or roughly equal this value can be considered at risk to fail during future earthquakes. Seismic and static angles of repose for three sediment types are tabulated in this report.

  2. Is there a distinct continental slope fauna in the Antarctic?

    NASA Astrophysics Data System (ADS)

    Kaiser, Stefanie; Griffiths, Huw J.; Barnes, David K. A.; Brandão, Simone N.; Brandt, Angelika; O'Brien, Philip E.

    2011-02-01

    a unique Antarctic slope fauna, but the paucity of our samples could not demonstrate this in the Scotia Sea. It is very likely that various ecological and evolutionary factors (such as topography, water-mass and sediment characteristics, input of particulate organic carbon (POC) and glaciological history) drive slope distinctness. Isopods showed greatest species richness at slope depths, whereas bryozoans and ostracods were more speciose at shelf depths; however, significance varied across Weddell Sea and Scotia Sea and depending on bathymetric vs. geomorphological definitions. Whilst the slope may harbour some source populations for localised shelf recolonisation, the absence of many shelf species, genera and even families (in a poorly dispersing taxon) from the continental slope indicate that it was not a universal refuge for Antarctic shelf fauna.

  3. Drought in the Black Hills

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Annotated Color-Coded Map

    Despite good rainfall and record-setting snowstorms in the spring of 2005, most of northeastern Wyoming, the Black Hills, and western South Dakota remain in the midst of a severe drought. This set of images and maps from NASA's Multi-angle Imaging SpectroRadiometer (MISR) contrast the appearance of the Black Hills region of northwestern South Dakota on July 12, 2000 (left column), with views acquired four years later, on July 14, 2004 (right column). The natural-color images along the top are from MISR's nadir (downward-looking) camera. The browning that appears in 2004 compared with 2000 indicates that the vigor of green vegetation was significantly diminished in 2004.

    The color-coded maps (along the bottom) provide a quantitative measurement of the sunlight reflected from these surfaces, and the loss of sunlight-absorbing vegetation between the 2000 and 2004 dates. As the vegetation faded with the drought, the albedo at the surface increased. Albedo measures the fraction of incident sunlight that is reflected by a surface, and can vary between zero (if all the incident sunlight is absorbed and none is reflected) and one (if all sunlight is reflected and none is absorbed). Dense forest has a low albedo; bright desert, snow and clouds, have a high albedo. Here, albedo is provided for the wavelengths of sunlight that plants use for photosynthesis (400 - 700 nanometers). This measurement is known as the albedo for Photosynthetically Active Radiation (PAR). Surfaces with greater absorption of PAR appear here in blue hues, whereas surfaces with lower absorption appear as green, yellow, orange or red. Black pixels indicate areas where albedo could not be derived, usually due to the presence of clouds. In July 2004, low albedo areas (blue pixels) are notably reduced in extent, and higher albedo areas (yellow, orange and red pixels) have increased.

    Because incoming sunlight is

  4. The layered subsurface - periglacial slope deposits as crucial elements for soil formation and variability

    NASA Astrophysics Data System (ADS)

    Völkel, Jörg; Huber, Juliane

    2014-05-01

    Still most concepts of soil formation, weathering production rates and weathering front ideas are dealing with a monolayered near-surface underground and subsoil. At best a line is given on so-called moved regolith. In fact the subsurface is often characterized by stratified and multilayered slope deposits with thicknesses exceeding 1 m. These stratified slope sediments play a significant role in the nature of the physical and chemical properties as well as on soil forming processes. Examples are given for sediment sourced chemical elements and common clay minerals, and the significance of slope sediments as both barriers and pathways for interflow that moves through the stratified sediments. The stratified subsurface is often datable by numeric age techniques (OSL) showing up how sediment features contradict weathering effects and meaning e.g. for soil genesis. In the mid latitudes, geomorphic and sedimentologic evidence supports a periglacial origin, involving solifluction, for the origin of these slope deposits. The study areas are situated within the Colorado Front Range, U.S. and the Bavarian Forest, Germany. The projects are currently financed and supported by the German Science Foundation DFG. Literature: Völkel, J., Huber, J. & Leopold, M. (2011): Significance of slope sediments layering on physical characteristics and interflow within the Critical Zone… - Applied Geochemistry 26: 143-145.

  5. Role of submarine canyons in the US Atlantic Continental Slope and upper Continental rise development

    SciTech Connect

    McGregor, B.A.

    1984-04-01

    Three areas of the US Atlantic continental slope and rise (seaward of George Bank, Delaware Bay, and Pamlico Sound north of Cape Hatteras) have been studied using seismic reflection profiles and mid-range sidescan-sonar data. The continental slope in all three areas is dissected by numerous submarine canyons. The general sea floor gradient of the slope and the morphology of the rise, however, vary among the areas. Submarine canyons are dominant morphologic features on the slope and have an important function in sediment transport and distribution on the rise. In the study area north of Cape Hatteras, however, the low relief of the rise topography indicates that ocean currents flowing parallel to the margin may also affect sediment distribution on the rise. Morphology and sedimentation patterns suggest that differences in canyon ages exist both within each area and among the areas. Spatial and temporal variability of canyon activity is important in determining sediment sources for the construction of the rise. Although the US Atlantic slope and rise are relatively sediment-starved at present, mid-range sidescan data and submersible observations and samples suggest that periodic sediment transport events occur within the canyons.

  6. Low-velocity zone and topography as a source of site amplification effect on Tarzana hill, California

    USGS Publications Warehouse

    Graizer, V.

    2009-01-01

    Tarzana station is located in the foothills of the Santa Monica Mountains in California near the crest of a low (<20 m) natural hill with gentle slopes. The hill is about 500 m in length by 130 m in width and is formed of extremely weathered shale at the surface to fresh at depth. Average S-wave is about 250 m/s in the top 17-18 m, and S- and P-wave velocities significantly increase below this depth. According to the NEHRP classification based on VS30???300 m/s it is a site class D. Strong-motion instrumentation at Tarzana consisted of an accelerograph at the top of the hill, a downhole instrument at 60 m depth, and an accelerograph at the base of the hill. More than 20 earthquakes were recorded by at least three instruments at Tarzana from 1998 till 2003. Comparisons of recordings and Fourier spectra indicate strong directional resonance in a direction perpendicular to the strike of the hill. The dominant peaks in ground motion amplification on the top of the hill relative to the base are at frequencies ???3.6 and 8-9 Hz for the horizontal components. Our hypothesis is that the hill acts like a wave trap. This results in an amplification at predominant frequencies f=V/4 h (h is layer's thickness) at f???3.6 Hz for S-waves (using average VS17=246 m/s and h=17 m) and f???7.9 Hz for P-waves (using average VP17=535 m/s and h=17 m). As was shown by Bouchon and Barker [Seismic response of a hill: the example of Tarzana, California. Bull Seism Soc Am 1996;86(1A):66-72], topography of this hill amplifies and polarizes ground motion in the frequency range of 3-5 Hz. Hill acts as a magnifying polarizing glass: It polarizes ground motion in the direction perpendicular to the strike of the hill and also amplifies ground motions that had been also amplified by a low-velocity layer.

  7. Late-glacial and postglacial history of the hill'', Norwich University campus, Northfield, Vermont

    SciTech Connect

    Larsen, F.D. . Dept. of Geology)

    1993-03-01

    The central part of the Norwich University campus at Northfield is built on a kame about 60 ft high on the side of the Dog River valley. Significant excavations made between 1979 and 1991 in the flank of the hill provide details about its glacial origin. Collapsed ice-contact lake deposits on the northwestern flank of the kame are overlain by undisturbed lake sediments formed by turbidity currents that moved southward in glacial Lake Roxbury. Lake Roxbury formed when the retreating ice margin blocked the north-draining Dog River valley and caused melt water to drain south over a 1,010-foot threshold at Roxbury. The lowest deposits exposed on the southeast flank of the kame are highly deformed and include a chaotic slide breccia overlain by progressively less deformed lake-bottom sediments. Northward retreat of the ice margin permitted Lake Roxbury to drop 80 ft to the level of glacial Lake Winooski, which still left 80 ft of lake water over the top of the hill''. Following the lowering of Lake Winooski, stream terraces were cut on the west flank of the hill''. The terraces are underlain by imbricated pebble gravel deposited by the north-flowing Dog River that probably was graded to a lower glacial lake in the Winooski River valley to the north. Downcutting by the Dog River and subsequent lateral migration of its meanders produced the topography the authors see today. The late-glacial and postglacial history can be summarized as follows: (1) deposition of lake sediments in contact with buried ice, (2) collapse and continued deposition of lake sediments during melting of buried ice, (3) deposition of undeformed lake sediments, (4) drainage of glacial lakes, and (5) development of stream terraces and the modern flood plain.

  8. The Black Hills-Rapid City flood of June 9-10, 1972: A description of the storm and flood

    USGS Publications Warehouse

    Schwarz, Francis K.; Hughes, L.A.; Hansen, E.M.; Petersen, M.S.; Kelly, Donovan B.

    1975-01-01

    Almost all the flood peaks occurred between 2230 MDT on June 9 and 0100 MDT on June 10, 1972, in a flood belt about 40 miles long and 20 miles wide along the eastern slopes of the Black Hills. This belt extended from Sturgis, S. Dak., on the north to Hermosa, S. Dak., on the south, with Rapid City near the center. To document the flood, peak discharge determinations were made at 49 sites. Records show that about 13,000 acre-feet of water flowed through Rapid City during the 2 days of flooding. At one point during the night of June 9, the floodwaters rose about 3.5 feet in 15 minutes. Coming off the slopes of the Black Hills, the flood peak traveled the 22 miles between Deer Creek and Rapid City in about 3.5 hours.

  9. The Probable Whole of Slope Submarine Landslides of Southeast Queensland, Australia.

    NASA Astrophysics Data System (ADS)

    Hubble, T.

    2015-12-01

    A research cruise aboard the RV Southern Surveyor (SS2013-V01) conducted in January 2013 offshore east Australia collected regional bathymetric data for the seabed of the continental margin of southern Queensland for the seabed bounded by Noosa Heads in the south and Indian Head, Fraser Island in the north. This newly mapped area presents a particularly steep portion of continental slope (5o to 10 o) that presents numerous submarine landslides, including two 'whole-of-slope' features (The Wide Bay Canyon, and Inskip Slides. The slope is also dissected by three large submarine canyons offshore northern Fraser Island, Wide Bay and Noosa Heads (i.e. the Fraser Canyons, the Wide Bay Canyon and the Noosa Canyon). Dredge and core samples were collected from slide scars in the northern, central and southern areas of the bathymetric survey area. The initial examination of the area's bathymetry, the core and dredge sample sedimentology, and determination of biostratigraphic ages for these sediment samples indicates that the larger, submarine slides present in this study area have probably been shed from the slope since the late Pliocene and that canyon incision is currently active on this portion of the slope. In one case, canyon incision is partly responsible for generating slides due to undercutting and removal of the toe of the slope. Slope sediments are dominantly comprised of hemipelagic muds but the presence of massive coarse sands and graded sands in some cores above erosion surfaces that cut into slope mud units is interpreted to indicate that areas of the southern Queensland continental slope are probably subjected to abrasion by grain-flows and turbidites comprised of shelf-derived sands and upper slope sediment. The results from this voyage confirms and extends previous work on the southeastern Australian continental margin that indicates that sediment transport from the shelf to deep water on this margin is dominated by gravity mass transport and that the margin

  10. Semi-quantitative method for the assessment of debris supply from slopes to river in ungauged catchments.

    PubMed

    Tiranti, Davide; Cavalli, Marco; Crema, Stefano; Zerbato, Marina; Graziadei, Maria; Barbero, Secondo; Cremonini, Roberto; Silvestro, Chiara; Bodrato, Giulia; Tresso, Francesco

    2016-06-01

    This paper presents an integrated empirical methodology for assessing the amount of sediment transported from slopes to the main river in absence of a sediment transport monitoring system. The amount of transported sediment is calculated through the characterization of the sediment source areas including the identification of the slope phenomena responsible for the sediment propagation to the main river: shallow landslides, channelized debris flows and deep-seated rotational slides. On this basis, several scenarios related to the climatic conditions are defined: they indicate the number of possible slope phenomena and potential volumes of mobilized unconsolidated material from sediment source areas to the main river. This methodology was finalized and tested in the Maira River basin (south-western Italian Alps) with quite good results. PMID:26962851

  11. North Atlantic slope and canyon study. Volume 2. Final report

    SciTech Connect

    Butman, B.

    1986-12-01

    A field program to investigate the currents and sediment transport along the outershelf and upper slope along the southern flank of Georges Bank was conducted between 1980 and 1984. A major part of the field experiment was conducted in Lydonia Canyon, a large submarine canyon which cuts northward about 20 km into the continental shelf from the shelfbreak. A smaller experiment was conducted in Oceanographer Canyon to compare the currents in these two major canyons. Long-term current observations were made at 20 locations in or adjacent to Lydonia Canyon, and at 9 stations on the continental slope. Detailed semi-synoptic hydrographic observations were made on 9 cruises. The currents associated with Gulf Stream warm core rings (WCR's) strongly affect the flow along the outer shelf and upper slope; eastward currents in excess of 75cm/s were associated with WCR's.

  12. Erosion and slope instability on Horizon Guyot, Mid-Pacific Mountains

    USGS Publications Warehouse

    Schwab, W.C.; Lee, H.J.; Kayen, R.E.; Quinterno, P.J.; Tate, G.B.

    1988-01-01

    Seismic-reflection profiles, sediment cores, and current velocities were assessed to study the impact of erosion and sediment redistribution on the pelagic sediment cap of Horizon Guyot, a flat-topped submarine volcanic ridge in the Mid-Pacific Mountains. These processes seem to concentrate their effect around the rim of the sediment cap. Sediment slumping occurs on the northwest perimeter of the guyot's sediment cap. Slope stability analysis suggests that if overconsolidation on Horizon Guyot is the result of current reworking or if local undercutting by bottom currents steepens the sea floor declivity, the sediment cap may be unstable during infrequent earthquake loading, transporting sediment from the guyot summit to the abyssal sea floor. ?? 1988 Springer-Verlag New York Inc.

  13. North Slope (Wahluke Slope) expedited response action cleanup plan

    SciTech Connect

    Not Available

    1994-02-01

    The purpose of this action is to mitigate any threat to public health and the environment from hazards on the North Slope and meet the expedited response action (ERA) objective of cleanup to a degree requiring no further action. The ERA may be the final remediation of the 100-I-3 Operable Unit. A No Action record of decision (ROD) may be issued after remediation completion. The US Department of Energy (DOE) currently owns or administers approximately 140 mi{sup 2} (about 90,000 acres) of land north and east of the Columbia River (referred to as the North Slope) that is part of the Hanford Site. The North Slope, also commonly known as the Wahluke Slope, was not used for plutonium production or support facilities; it was used for military air defense of the Hanford Site and vicinity. The North Slope contained seven antiaircraft gun emplacements and three Nike-Ajax missile positions. These military positions were vacated in 1960--1961 as the defense requirements at Hanford changed. They were demolished in 1974. Prior to government control in 1943, the North Slope was homesteaded. Since the initiation of this ERA in the summer of 1992, DOE signed the modified Hanford Federal Agreement and Consent Order (Tri-Party Agreement) with the Washington Department of Ecology (Ecology) and the US Environmental Protection Agency (EPA), in which a milestone was set to complete remediation activities and a draft closeout report by October 1994. Remediation activities will make the North Slope area available for future non-DOE uses. Thirty-nine sites have undergone limited characterization to determine if significant environmental hazards exist. This plan documents the results of that characterization and evaluates the potential remediation alternatives.

  14. Effect of DEM mesh size on AnnAGNPS simulation and slope correction.

    PubMed

    Wang, Xiaoyan; Lin, Q

    2011-08-01

    The objective of this paper is to study the impact of the mesh size of the digital elevation model (DEM) on terrain attributes within an Annualized AGricultural NonPoint Source pollution (AnnAGNPS) Model simulation at watershed scale and provide a correction of slope gradient for low resolution DEMs. The effect of different grid sizes of DEMs on terrain attributes was examined by comparing eight DEMs (30, 40, 50, 60, 70, 80, 90, and 100 m). The accuracy of the AnnAGNPS stimulation on runoff, sediments, and nutrient loads is evaluated. The results are as follows: (1) Rnoff does not vary much with decrease of DEM resolution whereas soil erosion and total nitrogen (TN) load change prominently. There is little effect on runoff simulation of AnnAGNPS modeling by the amended slope using an adjusted 50 m DEM. (2) A decrease of sediment yield and TN load is observed with an increase of DEM mesh size from 30 to 60 m; a slight decrease of sediment and TN load with the DEM mesh size bigger than 60 m. There is similar trend for total phosphorus (TP) variation, but with less range of variation, the simulation of sediment, TN, and TP increase, in which sediment increase up to 1.75 times compared to the model using unadjusted 50 m DEM. In all, the amended simulation still has a large difference relative to the results using 30 m DEM. AnnAGNPS is less reliable for sediment loading prediction in a small hilly watershed. (3) Resolution of DEM has significant impact on slope gradient. The average, minimum, maximum of slope from the various DEMs reduced obviously with the decrease of DEM precision. For the grade of 0∼15°, the slopes at lower resolution DEM are generally bigger than those at higher resolution DEM. But for the grade bigger than 15°, the slopes at lower resolution DEM are generally smaller than those at higher resolution DEM. So it is necessary to adjust the slope with a fitting equation. A cubic model is used for correction of slope gradient from lower resolution to

  15. Controls on the occurrence of large landslides on the continental slope

    NASA Astrophysics Data System (ADS)

    Masson, D. G.; Clayton, C. R. I.; Best, A. I.

    2003-04-01

    Large submarine landslides, incorporating hundreds of km3 of sediment and affecting tens of thousands of km^2 of seafloor, occur widely on continental margins, particularly in areas of fine-grained sediment deposition. Such landslides occur on low slopes (0.5-3^o) and have exceptional runout distances. Various triggers, such as earthquakes, slope loading, and gas hydrate decomposition, have been suggested. In reality, with the exception of a few historical events (e.g. 1929 Grand Banks Slide, triggered by an earthquake) we know very little about large landslide triggers. More importantly, we know almost nothing about the in situ geological pre-conditions which favour landslides and thus we cannot predict which slopes might be prone to instability. The similarity of large landslides on many continental margins suggests a common cause or process. Many landslides have multiple steep headwall scarps and show strong evidence for retrogressive failure. Failure occurs on one of more well-defined, bedding-plane parallel surfaces. Much of the landslide sediment appears to have moved initially as coherent slabs, showing evidence of brittle deformation (faulting and fracturing) in the upper slide region. This gives way to more plastic deformation and flow downslope. Taken together, these observations suggest that failure occurs on discrete ``weak layers", and that most of the sediment involved in the landslide was not inherently unstable. These sediments were initially rafted downslope, only gradually breaking up under mechanical stresses associated with movement. On the Norwegian continental margin, weak layers appear to consist of biogenic ooze and/or contourite sediment with exceptionally high water content. We suggest that such sediments become weakly cemented at shallow sub-seabed depths, building ``structure" into the sediment and slowing sediment dewatering with further burial. Collapse of this structure, (e.g. due to earthquake or slope loading) leads to release of

  16. Matching, maximizing, and hill-climbing

    PubMed Central

    Hinson, John M.; Staddon, J. E. R.

    1983-01-01

    In simple situations, animals consistently choose the better of two alternatives. On concurrent variable-interval variable-interval and variable-interval variable-ratio schedules, they approximately match aggregate choice and reinforcement ratios. The matching law attempts to explain the latter result but does not address the former. Hill-climbing rules such as momentary maximizing can account for both. We show that momentary maximizing constrains molar choice to approximate matching; that molar choice covaries with pigeons' momentary-maximizing estimate; and that the “generalized matching law” follows from almost any hill-climbing rule. PMID:16812350

  17. Photovoltaics - 10 years after Cherry Hill

    NASA Astrophysics Data System (ADS)

    Ralph, E. L.

    The status of R&D programs connected with photovoltaic (PV) systems 10 years after the Cherry Hill workshop on 'Photovoltaic Conversion of Solar Energy for Terrestrial Applications' is assessed. The five categories of research recommended by the Cherry Hill Workshop are listed in a table together with their recommended research budget allocations. The workshop categories include: single-crystal Si cells; poly-Si cells; systems and diagnostics. Categories for thin film CdS/Cu2S and CuInSe2 cells are also included. The roles of government and private utility companies in providing adequate financial support for PV research programs is emphasized.

  18. Elk Hills: still out in front

    SciTech Connect

    Rintoul, B.

    1982-07-01

    The producing history and capacity of the Elk Hills Oil and Gas Fields in California are described. Developments in the field are discussed, including waterflooding. The field presently produces ca. 160,000 bpd of oil and 350 mmcfd of natural gas. Gas liquids production totals ca. 683,000 gal/day. Waterflooding is expected to pay an increasingly important role in the production of crude oil. Steaming techniques also are viewed with favor after analysis of results of pilot projects. Exploratory develoment in Elk Hills also continues.

  19. 3. GENERAL VIEW DOWN EAST HILLS DRIVE, BUILDING 20 (ONE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. GENERAL VIEW DOWN EAST HILLS DRIVE, BUILDING 20 (ONE BEDROOM) AND BUILDING 21 (TWO/THREE BEDROOM); ACTIVITY CENTER IN REAR, FACING NORTHEAST. - Aluminum City Terrace, East Hill Drive, New Kensington, Westmoreland County, PA

  20. OVERVIEW OF GOLD HILL MILL, ROAD, AND WARM SPRINGS CAMP ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    OVERVIEW OF GOLD HILL MILL, ROAD, AND WARM SPRINGS CAMP BUILDINGS, LOOKING SOUTH SOUTHEAST. THE FUNCTION OF THE FLAT AREA AT CENTER RIGHT IS UNKNOWN. - Gold Hill Mill, Warm Spring Canyon Road, Death Valley Junction, Inyo County, CA

  1. Hill-Burton Free and Reduced Cost Health Care

    MedlinePlus

    ... Hill-Burton Spanish Brochure (PDF - 83 KB) HHS Poverty Guidelines HHS Spanish Poverty Guidelines (PDF - 32 KB) Spanish Inquiry Letter (PDF - ... income is at or below the current HHS Poverty Guidelines . You may be eligible for Hill-Burton ...

  2. Slope sensitivities for optical surfaces

    NASA Astrophysics Data System (ADS)

    Rogers, John R.

    2015-09-01

    Setting a tolerance for the slope errors of an optical surface (e.g., surface form errors of the "mid-spatial-frequencies") requires some knowledge of how those surface errors affect the final image of the system. While excellent tools exist for simulating those effects on a surface-by-surface basis, considerable insight may be gained by examining, for each surface, a simple sensitivity parameter that relates the slope error on the surface to the ray displacement at the final image plane. Snell's law gives a relationship between the slope errors of a surface and the angular deviations of the rays emerging from the surface. For a singlet or thin doublet acting by itself, these angular deviations are related to ray deviations at the image plane by the focal length of the lens. However, for optical surfaces inside an optical system having a substantial axial extent, the focal length of the system is not the correct multiplier, as the sensitivity is influenced by the optical surfaces that follow. In this paper, a simple expression is derived that relates the slope errors at an arbitrary optical surface to the ray deviation at the image plane. This expression is experimentally verified by comparison to a real-ray perturbation analysis. The sensitivity parameter relates the RMS slope errors to the RMS spot radius, and also relates the peak slope error to the 100% spot radius, and may be used to create an RSS error budget for slope error. Application to various types of system are shown and discussed.

  3. LOW VELOCITY ZONE AND TOPOGRAPHY AS A SOURCE OF SITE AMPLIFICATION EFFECT ON TARZANA HILL, CALIFORNIA

    NASA Astrophysics Data System (ADS)

    Graizer, V.

    2009-12-01

    Significantly amplified ground accelerations at the Tarzana Hill station were recorded during the 1987 Mw 5.9 Whittier Narrows, the 1994 Mw 6.7 Northridge and the 1999 Mw 7.1 Hector Mine earthquakes. Peak horizontal ground acceleration at the Tarzana station during the Northridge earthquake reached 1.93 g and is considered to be one of the largest ever recorded acceleration. Explanations of the strong-site amplification effect vary significantly from directional topographic effect and unusual Poisson’s ratio to the resonant sliding block. Despite all these efforts none of the above-mentioned studies came up with completely conclusive explanation of the source of the site amplification that produces unusually large motions at Tarzana. Tarzana station is located in the foothills of the Santa Monica Mountains in California near the crest of a low (< 20 m) natural hill with gentle slopes. The hill is about 500 m in length by 130 m in width and is formed of extremely weathered shale at the surface to fresh at depth. Average S-wave velocity is about 250 m/sec in the top 17-18 m, and S- and P-wave velocities significantly increase below this depth. According to the NEHRP classification based on Vs30 ~ 300 m/sec it is a site class D. Strong-motion instrumentation at Tarzana consisted of an accelerograph at the top of the hill, a downhole instrument at 60 m depth, and an accelerograph at the base of the hill. More than twenty earthquakes were recorded by at least three instruments at Tarzana from 1998 till 2003. Comparisons of recordings and Fourier spectra indicate strong directional resonance in a direction perpendicular to the strike of the hill. The dominant peaks in ground motion amplification on the top of the hill relative to the base are at frequencies ~ 3.6 Hz and 8-9 Hz for the horizontal components. Our hypothesis is that the hill acts like a wave trap. This results in an amplification at predominant frequencies f = V/4h (h is layer’s thickness) at f ~ 3.6 Hz

  4. Turbulent behaviour of non-cohesive sediment gravity flows at unexpectedly high flow density

    NASA Astrophysics Data System (ADS)

    Baker, Megan; Baas, Jaco H.; Malarkey, Jonathan; Kane, Ian

    2016-04-01

    affect the flows only at concentrations just below the cubic packing density of spheres of C = 52%. These experimental results also imply that natural flows may be able to transport vast volumes of non-cohesive sediment with relative ease, especially considering that the experimental flows moved on a horizontal slope. References Bagnold, R. A. (1954). Experiments on a Gravity-Free Dispersion of Large Solid Spheres in Newtonian Fluid under Shear. Proceedings of the Royal Society series A: Mathematical, Physical and Engineering Sciences, 225(1160), 49-63. Bagnold, R. A. (1963). Beach and nearshore processes: Part 1. Mechanics of marine sedimentation. In: Hill, M. N. (Ed.) The Earth Beneath the Sea, vol. 3. Wiley-Interscience, London, 507-533.

  5. Altered marine tephra deposits as potential slope failure planes?

    NASA Astrophysics Data System (ADS)

    Wiemer, Gauvain; Kopf, Achim

    2015-08-01

    Weathering of tephra results in increasing proportions of mechanically weak, authigenic clay minerals (smectite). This suggests that altered tephra represent inherent weak layers in slope sediment sequences, and these may facilitate slope failure in submarine and other aquatic environments. In drained direct shear experiments, tephra in different alteration stages were compared to common sand-clay mixtures for geotechnical reference. Attention is drawn to the influence of particle shape on shear strength. The results revealed volcanic ash to have (1) a high strength end-member at low alteration stages due to particle roughness and angularity and (2) a low strength end-member after complete diagenetic alteration, both under static conditions. This would suggest that strongly altered volcanic ash layers could potentially be responsible for slope failures. However, a review of ODP and IODP Expedition reports shows that advanced ash alteration mostly occurs at depths below (>800 mbsf) those commonly observed for slope failure initiation (<400 mbsf). This, in turn, suggests that volcanic ash alteration does not play an important role in the initiation of slope failure.

  6. Sediments of Arabia

    NASA Technical Reports Server (NTRS)

    2005-01-01

    21 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows martian sediment in two basic forms: (1) light-toned, layered, sedimentary rock outcrops and (2) dark, windblown sand dunes. The dark sand of the dunes is most likely composed of grains rich in iron-, magnesium-, aluminum-, and silicon-bearing minerals. The hills and mounds of layered sedimentary rock were once more extensive, covering the entire scene shown here, which occurs on the floor of a crater in western Arabia Terra.

    Location near: 8.9oN, 1.2oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Autumn

  7. Anatomy of gravitationally deformed slopes

    NASA Astrophysics Data System (ADS)

    Chigira, Masahiro; Yamasaki, Shintaro; Hariyama, Takehiro

    2010-05-01

    Deep-seated gravitational slope deformation is the deformation of rocks as well as slope surfaces, but the internal structures have not been well observed and described before. This is mainly due to the difficulty in obtaining undisturbed samples from underground. We analyzed the internal deformational structures of gravitationally deformed slopes by using high quality drilled cores obtained by hybrid drilling technique, which has been recently developed and can recover very fragile materials that could not be taken by the conventional drilling techniques. Investigated slopes were gravitationally deformed out-facing slopes of pelitic schist and shale. The slope surfaces showed deformational features of small steps, depressions, knobs, and linear depressions, but had no major main scarp and landslide body with well-defined outline. This is indicative of slow, deep-seated gravitational deformation. Most of these small deformational features are hidden by vegetations, but they are detected by using airborne laser scanner. Drilled cores showed that the internal deformation is dominated by the slip and tearing off along foliations. Slippage along foliations is conspicuous in pelitic schist: Pelitic schist is sheared, particularly along black layers, which are rich in graphite and pyrite. Graphite is known to be a solid lubricant in material sciences, which seems to be why shearing occurs along the black layers. Rock mass between two slip layers is sheared, rotated, fractured, and pulverized; undulation of bedding or schistosity could be the nucleation points of fracturing. Tearing off along foliations is also the major deformation mode, which forms jagged morphology of rock fragments within shear zones. Rock fragments with jagged surface are commonly observed in "gouge", which is very different from tectonic gouge. This probably reflects the low confining pressures during their formation. Microscopic to mesoscopic openings along fractures are commonly observed with

  8. Linking hydrological, infinite slope stability and land-use change models through GIS for assessing the impact of deforestation on slope stability in high Andean watersheds

    NASA Astrophysics Data System (ADS)

    Vanacker, Veerle; Vanderschaeghe, Michiel; Govers, Gerard; Willems, Edith; Poesen, Jean; Deckers, Jozef; De Bievre, Bert

    2003-06-01

    In the Ecuadorian Andes, episodic slope movements comprising shallow rotational and translational slides and rapid flows of debris and soil material are common. Consequently, not only considerable financial costs are experienced, but also major ecological and environmental problems arise in a larger geographical area. Sediment production by slope movement on hillslopes directly affects sediment transport and deposition in downstream rivers and dams and morphological changes in the stream channels. In developing countries world-wide, slope movement hazards are growing: increasing population pressure and economic development force more people to move to potentially hazardous areas, which are less suitable for agriculture and rangelands. This paper describes the methods used to determine the controlling factors of slope failure and to build upon the results of the statistical analysis a process-based slope stability model, which includes a dynamic soil wetness index using a simple subsurface flow model. The model provides a time-varying estimate of slope movement susceptibility, by linking land-use data with spatially varying hydrologic (soil conductivity, evapotranspiration, soil wetness) and soil strength properties. The slope stability model was applied to a high Andean watershed (Gordeleg Catchment, 250 ha, southern Ecuadorian Andes) and was validated by calculating the association coefficients between the slope movement susceptibility map of 2000 and the spatial pattern of active slope movements, as measured in the field with GPS. The proposed methodology allows assessment of the effects of past and future land-use change on slope stability. A realistic deforestation scenario was presented: past land-use change includes a gradual fragmentation and clear cut of the secondary forests, as observed over the last four decades (1963-2000), future land-use change is simulated based on a binary logistic deforestation model, whereby it was assumed that future land

  9. GLORIA side-scan imagery of Aleutian basin, Bering Sea slope and Abyssal plain

    SciTech Connect

    Carlson, P.R.; Cooper, A.K.; Gardner, J.V.; Karl, H.A.; Marlow, M.S.; Stevenson, A.J.; Huggett, Q.; Kenyon, N.; Parson, L.

    1987-05-01

    During July-September 1986, about 700,000 km/sup 2/ of continental slope and abyssal plain of the Aleutian basin, Bering Sea, were insonified with GLORIA (Geological Long Range Inclined Asdic) side-scane sonar. A sonar mosaic displays prominent geomorphic features including the massive submarine canyons of the Beringian and the northern Aleutian Ridge slopes and shows well-defined sediment patterns including large deep-sea channels and fan systems on the Aleutian basin abyssal plain. Dominant erosional and sediment transport processes on both the Beringian and the Aleutian Ridge slopes include varieties of mass movement that range from small debris flows and slides to massive slides and slumps of blocks measuring kilometers in dimension. Sediment-flow patterns that appear to be formed by sheet flow rather than channelized flow extend basinward from the numerous canyons and gullies that incise the slopes of the Beringian margin and of Bowers Ridge and some places along the Aleutian Ridge. These Beringian and Bowers canyon sediment sources, however, appear to have contributed less modern sediment to the Aleutian basin than the large, well-defined channel systems that emanate from Bering, Umnak, and Amchitka submarine canyons and extend for several hundred kilometers across the abyssal plain. This GLORIA imagery emphasizes the important contribution of the Aleutian Ridge to modern sedimentation in the deep Bering Sea.

  10. General Education at UNC-Chapel Hill

    ERIC Educational Resources Information Center

    Schalin, Jay; Robinson, Jenna Ashley

    2013-01-01

    The general education program at UNC-Chapel Hill has abandoned the concept of a core curriculum. Instead, students choose their "required" classes from lists of thousands of courses that may be as narrow and idiosyncratic as Love, Sex and Marriage in Soviet Culture (RUSS 277) or The Gardens, Shrines and Temples of Japan (ASIA 586).…

  11. 27 CFR 9.193 - Rattlesnake Hills.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... Valley viticultural area (27 CFR 9.69). From the beginning point, the Rattlesnake Hills viticultural area boundary line— (2) Proceeds straight eastward, crossing onto the Elephant Mountain map, to the 2,192-foot...) Yakima East Quadrangle, Washington—Yakima Co., 1953, photorevised 1985; (2) Elephant Mountain...

  12. 27 CFR 9.193 - Rattlesnake Hills.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... Valley viticultural area (27 CFR 9.69). From the beginning point, the Rattlesnake Hills viticultural area boundary line— (2) Proceeds straight eastward, crossing onto the Elephant Mountain map, to the 2,192-foot...) Yakima East Quadrangle, Washington—Yakima Co., 1953, photorevised 1985; (2) Elephant Mountain...

  13. 27 CFR 9.193 - Rattlesnake Hills.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... Valley viticultural area (27 CFR 9.69). From the beginning point, the Rattlesnake Hills viticultural area boundary line— (2) Proceeds straight eastward, crossing onto the Elephant Mountain map, to the 2,192-foot...) Yakima East Quadrangle, Washington—Yakima Co., 1953, photorevised 1985; (2) Elephant Mountain...

  14. 27 CFR 9.193 - Rattlesnake Hills.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... Valley viticultural area (27 CFR 9.69). From the beginning point, the Rattlesnake Hills viticultural area boundary line— (2) Proceeds straight eastward, crossing onto the Elephant Mountain map, to the 2,192-foot...) Yakima East Quadrangle, Washington—Yakima Co., 1953, photorevised 1985; (2) Elephant Mountain...

  15. 27 CFR 9.193 - Rattlesnake Hills.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... Valley viticultural area (27 CFR 9.69). From the beginning point, the Rattlesnake Hills viticultural area boundary line— (2) Proceeds straight eastward, crossing onto the Elephant Mountain map, to the 2,192-foot...) Yakima East Quadrangle, Washington—Yakima Co., 1953, photorevised 1985; (2) Elephant Mountain...

  16. 27 CFR 9.197 - Clements Hills.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... area (27 CFR 9.107). The Clements Hills viticultural areas boundary is as follows— (1) The beginning...., 1968, minor revision 1993; (4) Wallace, Calif., 1962; (5) Valley Springs SW., Calif., 1962... along the San Joaquin-Amador and San Joaquin-Calaveras County lines, crossing over the Wallace map,...

  17. 27 CFR 9.197 - Clements Hills.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... area (27 CFR 9.107). The Clements Hills viticultural areas boundary is as follows— (1) The beginning...., 1968, minor revision 1993; (4) Wallace, Calif., 1962; (5) Valley Springs SW., Calif., 1962... along the San Joaquin-Amador and San Joaquin-Calaveras County lines, crossing over the Wallace map,...

  18. 27 CFR 9.197 - Clements Hills.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... area (27 CFR 9.107). The Clements Hills viticultural areas boundary is as follows— (1) The beginning...., 1968, minor revision 1993; (4) Wallace, Calif., 1962; (5) Valley Springs SW., Calif., 1962... along the San Joaquin-Amador and San Joaquin-Calaveras County lines, crossing over the Wallace map,...

  19. 27 CFR 9.197 - Clements Hills.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... area (27 CFR 9.107). The Clements Hills viticultural areas boundary is as follows— (1) The beginning...., 1968, minor revision 1993; (4) Wallace, Calif., 1962; (5) Valley Springs SW., Calif., 1962... along the San Joaquin-Amador and San Joaquin-Calaveras County lines, crossing over the Wallace map,...

  20. 27 CFR 9.197 - Clements Hills.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... area (27 CFR 9.107). The Clements Hills viticultural areas boundary is as follows— (1) The beginning...., 1968, minor revision 1993; (4) Wallace, Calif., 1962; (5) Valley Springs SW., Calif., 1962... along the San Joaquin-Amador and San Joaquin-Calaveras County lines, crossing over the Wallace map,...

  1. An Unlikely Student Hits Capitol Hill

    ERIC Educational Resources Information Center

    Hoover, Eric

    2009-01-01

    Todd Sollar, a laid-off autoworker from Ohio who is studying for an associate degree in engineering at Sinclair Community College, in Dayton, OH, went to Capitol Hill to help educate lawmakers about the importance of including support for community colleges in the economic-stimulus bill. Mr. Sollar came to Washington with Sinclair's president, and…

  2. Numerical construction of the Hill functions.

    NASA Technical Reports Server (NTRS)

    Segethova, J.

    1972-01-01

    As an aid in the numerical construction of Hill functions and their derivatives, an algorithm using local coordinates and an expansion in Legendre polynomials is proposed. The algorithm is shown to possess sufficient stability, and the orthogonality of the Legendre polynomials simplifies the computation when the Ritz-Galerkin technique is used.

  3. The House on the Hill Challenge

    ERIC Educational Resources Information Center

    Roman, Harry T.

    2011-01-01

    In this article, the author suggests a classroom challenge that will engage students in designing a house on the hill. He suggests teachers ask a local builder to come to the school to discuss the kinds of concerns that must be dealt with when building homes in cold environments. The use of dioramas and cardboard scale models would be very useful…

  4. Ocean Hill-Brownsville, 40 Years Later

    ERIC Educational Resources Information Center

    Kahlenberg, Richard D.

    2008-01-01

    Forty years ago--on May 9, 1968--the local school board in Brooklyn's black ghetto of Ocean Hill-Brownsville sent telegrams to 19 unionized educators, informing them that their employment in the district was terminated. Eighteen were white. One black teacher was mistakenly included on the list, but reinstated almost immediately after the error was…

  5. ENHANCED REMEDIATION DEMONSTRATIONS AT HILL AFB: INTRODUCTION

    EPA Science Inventory

    Nine enhanced aquifer remediation technologies were demonstrated side-by-side at a Hill Air Force Base Chemical Disposal Pit/Fire Training Area site. The demonstrations were performed inside 3 x 5 m cells isolated from the surrounding shallow aquifer by steel piling. The site w...

  6. Plains and Hills Explored by Spirit

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Figure 1: Spirit's Long Journey, Sol 450

    This view from orbit shows the region within Gusev Crater where NASA's Mars Exploration Rover Spirit has been working for the past 15 months. The view is a mosaic of images from the Mars Orbiter Camera on NASA's Mars Global Surveyor orbiter. In the left and central portion, previously released as PIA07192, tracks made by Spirit's wheels are visible from the landing site to the edge of the 'Columbia Hills.'

    Spirit's Long Journey, Sol 450 (Full Traverse) More than 15 months after landing on Mars, NASA's Spirit rover is still going strong, having traveled a total of 4,276 meters (2.66 miles) as of martian day, or sol, 450 (April 8, 2005). This elevation map shows the traverse followed by Spirit since arriving at the 'Columbia Hills' in June, 2004. The areas colored blue are low in elevation and areas colored yellow are high in elevation. The blue area at the foot of the 'Columbia Hills' is approximately 20 meters (66 feet) higher in elevation than the site where Spirit landed in Gusev Crater. The highest peak is on the order of 80 meters (262 feet) higher still. In other words, the hills Spirit is exploring are more than 250 feet high. The map imagery is from the Mars Orbiter Camera on NASA's Mars Global Surveyor.

  7. 27 CFR 9.145 - Dunnigan Hills.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    .... The Dunnigan Hills viticultural area is located in Yolo County, California. The boundary is as follows... and U.S. Route 99W just south of the Colusa-Yolo county line; (2) From the beginning point, the... just north of the town of Yolo, California, on the Woodland, Calif., U.S.G.S. map; (3) The...

  8. 27 CFR 9.145 - Dunnigan Hills.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    .... The Dunnigan Hills viticultural area is located in Yolo County, California. The boundary is as follows... and U.S. Route 99W just south of the Colusa-Yolo county line; (2) From the beginning point, the... just north of the town of Yolo, California, on the Woodland, Calif., U.S.G.S. map; (3) The...

  9. 27 CFR 9.145 - Dunnigan Hills.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    .... The Dunnigan Hills viticultural area is located in Yolo County, California. The boundary is as follows... and U.S. Route 99W just south of the Colusa-Yolo county line; (2) From the beginning point, the... just north of the town of Yolo, California, on the Woodland, Calif., U.S.G.S. map; (3) The...

  10. 27 CFR 9.145 - Dunnigan Hills.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    .... The Dunnigan Hills viticultural area is located in Yolo County, California. The boundary is as follows... and U.S. Route 99W just south of the Colusa-Yolo county line; (2) From the beginning point, the... just north of the town of Yolo, California, on the Woodland, Calif., U.S.G.S. map; (3) The...

  11. Jesse Stuart: Lessons from the Kentucky Hills.

    ERIC Educational Resources Information Center

    Sands, Lu

    1986-01-01

    Highlights events in the life of Jesse Stuart, who began his teaching career at the age of 17 in a remote one-room school in the Kentucky hills and went on to become widely recognized as teacher, lecturer, and significant regional writer. Emphasizes Stuart's love of teaching and his personal values. (JHZ)

  12. 75. Southeast elevation of Forest Hills station looking Northwest ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    75. Southeast elevation of Forest Hills station - looking Northwest from junction of Washington and Walk Hill Streets. At left is the beginning of Section F-7 the exposed steel portion of elevated structure leading to the Forest Hills storage yard (demolished in 1985). - Boston Elevated Railway, Elevated Mainline, Washington Street, Boston, Suffolk County, MA

  13. AERIAL VIEW, LAUREL HILL CEMETERY (LEFT) AND MOUNT PEACE CEMETERY ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    AERIAL VIEW, LAUREL HILL CEMETERY (LEFT) AND MOUNT PEACE CEMETERY (RIGHT). LOCATED ACROSS RIDGE AVENUE FROM LAUREL HILL CEMETERY, MOUNT PEACE CEMETERY WAS FOUNDED BY THE ODD FELLOWS CEMETERY COMPANY IN 1865. - Laurel Hill Cemetery, 3822 Ridge Avenue, Philadelphia, Philadelphia County, PA

  14. 27 CFR 9.136 - Texas Hill Country.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Texas Hill Country. 9.136... Texas Hill Country. (a) Name. The name of the viticultural area described in this section is “Texas Hill Country.” (b) Approved maps. The appropriate maps for determining the boundaries of the “Texas...

  15. 27 CFR 9.136 - Texas Hill Country.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Texas Hill Country. 9.136... Texas Hill Country. (a) Name. The name of the viticultural area described in this section is “Texas Hill Country.” (b) Approved maps. The appropriate maps for determining the boundaries of the “Texas...

  16. 27 CFR 9.136 - Texas Hill Country.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Texas Hill Country. 9.136... Texas Hill Country. (a) Name. The name of the viticultural area described in this section is “Texas Hill Country.” (b) Approved maps. The appropriate maps for determining the boundaries of the “Texas...

  17. 27 CFR 9.136 - Texas Hill Country.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Texas Hill Country. 9.136... Texas Hill Country. (a) Name. The name of the viticultural area described in this section is “Texas Hill Country.” (b) Approved maps. The appropriate maps for determining the boundaries of the “Texas...

  18. View of south boundary of Easter Hill project site, former ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of south boundary of Easter Hill project site, former right of way for Hoffman Boulevard. Note reconstructed Easter Hill Building No. 6 at rear. Looking east - Easter Hill Village, Bordered by South Twenty-sixth Street, South Twenty-eighth Street, Hinkley Avenue, Foothill Avenue & Corto Square, Richmond, Contra Costa County, CA

  19. 27 CFR 9.190 - Red Hill Douglas County, Oregon.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Red Hill Douglas County... Areas § 9.190 Red Hill Douglas County, Oregon. (a) Name. The name of the viticultural area described in this section is “Red Hill Douglas County, Oregon”. For purposes of part 4 of this chapter, “Red...

  20. Sedimentary processes on the Atlantic Continental Slope of the United States

    USGS Publications Warehouse

    Knebel, H. J.

    1984-01-01

    Until recently, the sedimentary processes on the United States Atlantic Continental Slope were inferred mainly from descriptive studies based on the bathymetry and on widely spaced grab samples, bottom photographs, and seismic-reflection profiles. Over the past 6 years, however, much additional information has been collected on the bottom morphology, characteristics of shallow-subbottom strata, velocity of bottom currents, and transport of suspended and bottom sediments. A review of these new data provides a much clearer understanding of the kinds and relative importance of gravitational and hydrodynamic processes that affect the surface sediments. On the rugged slope between Georges Bank and Cape Lookout, N.C., these processes include: (1) small scale mass wasting within submarine canyons and peripheral gullies; (2) density flows within some submarine valleys; (3) sand spillover near the shelf break; (4) sediment creep on the upper slope; and (5) hemipelagic sedimentation on the middle and lower slope. The area between Georges Bank and Hudson Canyon is further distinguished by the relative abundance of large-scale slump scars and deposits on the open slope, the presence of ice-rafted debris, and the transport of sand within the heads of some submarine canyons. Between Cape Lookout and southern Florida, the slope divides into two physiographic units, and the topography is smooth and featureless. On the Florida-Hatteras Slope, offshelf sand spillover and sediment winnowing, related to Gulf Stream flow and possibly to storm-driven currents, are the major processes, whereas hemipelagic sedimentation is dominant over the offshore slope along the seaward edge of the Blake Plateau north of the Blake Spur. Slumping generally is absent south of Cape Lookout, although one large slump scarp (related to uplift over salt diapirs) has been identified east of Cape Romain. Future studies concerning sedimentary processes on the Atlantic slope need to resolve: (1) the ages and

  1. A 5000km2 data set along western Great Bahama Bank illustrates the dynamics of carbonate slope deposition

    NASA Astrophysics Data System (ADS)

    Schnyder, Jara S. D.; Jo, Andrew; Eberli, Gregor P.; Betzler, Christian; Lindhorst, Sebastian; Schiebel, Linda; Hebbeln, Dierk; Wintersteller, Paul; Mulder, Thierry; Principaud, Melanie

    2014-05-01

    An approximately 5000km2 hydroacoustic and seismic data set provides the high-resolution bathymetry map of along the western slope of Great Bahama Bank, the world's largest isolated carbonate platform. This large data set in combination with core and sediment samples, provides and unprecedented insight into the variability of carbonate slope morphology and the processes affecting the platform margin and the slope. This complete dataset documents how the interplay of platform derived sedimentation, distribution by ocean currents, and local slope and margin failure produce a slope-parallel facies distribution that is not governed by downslope gradients. Platform-derived sediments produce a basinward thinning sediment wedge that is modified by currents that change directions and strength depending on water depth and location. As a result, winnowing and deposition change with water depth and distance from the margin. Morphological features like the plunge pool and migrating antidunes are the result of currents flowing from the banktop, while the ocean currents produce contourites and drifts. These continuous processes are punctuated by submarine slope failures of various sizes. The largest of these slope failures produce several hundred of km2 of mass transport complexes and could generate tsunamis. Closer to the Cuban fold and thrust belt, large margin collapses pose an equal threat for tsunami generation. However, the debris from margin and slope failure is the foundation for a teeming community of cold-water corals.

  2. Evidence for Acid-Sulfate Alteration in the Pahrump Hills Region, Gale Crater, Mars

    NASA Astrophysics Data System (ADS)

    Rampe, E. B.; Ming, D. W.; Vaniman, D. T.; Blake, D. F.; Chipera, S.; Morris, R. V.; Bish, D. L.; Cavanagh, P.; Achilles, C.; Bristow, T.; Fairen, A.; Morrison, S. M.; Treiman, A. H.; Crisp, J. A.; Downs, R. T.; Farmer, J. D.; Fendrich, K.; Morookian, J.

    2015-12-01

    The Pahrump Hills region of Gale crater is a ~12 m thick section of sedimentary rock in the Murray formation, interpreted as the basal geological unit of Mount Sharp. The Mars Science Laboratory, Curiosity, arrived at the Pahrump Hills in September 2014 and performed a detailed six-month investigation of the sedimentary structures, geochemistry, and mineralogy of the area. During the campaign, Curiosity drilled and delivered three mudstone samples (targets Confidence Hills, Mojave 2, and Telegraph Peak) to its internal instruments, including the CheMin XRD/XRF. Results from CheMin show that these samples have variable amounts of plagioclase, pyroxene, iron oxides, jarosite, phyllosilicates, cristobalite, and X-ray amorphous material. The presence of jarosite in all samples indicates these rocks were affected by acid-sulfate alteration, and the mineralogical and geochemical trends observed through the section may give more insight into this process. Geochemical data measured by APXS show enrichment in Si and depletion in Mg moving up section. CheMin data show that cristobalite is more abundant up section, whereas pyroxene and phyllosilicates are more abundant at the bottom of the section. Based on mineralogical and geochemical trends and diagenetic features observed in the Pahrump Hills, we hypothesize that the sediments were altered in-situ by acid-sulfate fluids moving down from the top of the section to leach mobile elements, dissolve the minerals most susceptible to acidic alteration, and precipitate secondary silica at the top of the section. Alternative interpretations of the observed mineralogical and geochemical data are possible, including the hypothesis that the redox conditions of the body of water in which the sediments were deposited changed over time.

  3. [Mechanisms of grass in slope erosion control in Loess sandy soil region of Northwest China].

    PubMed

    Zhao, Chun-Hong; Gao, Jian-En; Xu, Zhen

    2013-01-01

    By adopting the method of simulated precipitation and from the viewpoint of slope hydrodynamics, in combining with the analysis of soil resistance to erosion, a quantitative study was made on the mechanisms of grass in controlling the slope erosion in the cross area of wind-water erosion in Loess Plateau of Northwest China under different combinations of rainfall intensity and slope gradient, aimed to provide basis to reveal the mechanisms of vegetation in controlling soil erosion and to select appropriate vegetation for the soil and water conservation in Loess Plateau. The grass Astragalus adsurgens with the coverage about 40% could effectively control the slope erosion. This grass had an efficiency of more than 70% in reducing sediment, and the grass root had a greater effect than grass canopy. On bare slope and on the slopes with the grass plant or only the grass root playing effect, there existed a functional relation between the flow velocity on the slopes and the rainfall intensity and slope gradient (V = DJ(0.33 i 0.5), where V is flow velocity, D is the comprehensive coefficient which varies with different underlying surfaces, i is rainfall intensity, and J is slope gradient). Both the grass root and the grass canopy could markedly decrease the flow velocity on the slopes, and increase the slope resistance, but the effect of grass root in decreasing flow velocity was greater while the effect in increasing resistance was smaller than that of grass canopy. The effect of grass root in increasing slope resistance was mainly achieved by increasing the sediment grain resistance, while the effect of canopy was mainly achieved by increasing the slope form resistance and wave resistance. The evaluation of the soil resistance to erosion by using a conceptual model of sediment generation by overland flow indicated that the critical shear stress value of bare slope and of the slopes with the grass plant or only the grass root playing effect was 0.533, 1.672 and 0

  4. [Mechanisms of grass in slope erosion control in Loess sandy soil region of Northwest China].

    PubMed

    Zhao, Chun-Hong; Gao, Jian-En; Xu, Zhen

    2013-01-01

    By adopting the method of simulated precipitation and from the viewpoint of slope hydrodynamics, in combining with the analysis of soil resistance to erosion, a quantitative study was made on the mechanisms of grass in controlling the slope erosion in the cross area of wind-water erosion in Loess Plateau of Northwest China under different combinations of rainfall intensity and slope gradient, aimed to provide basis to reveal the mechanisms of vegetation in controlling soil erosion and to select appropriate vegetation for the soil and water conservation in Loess Plateau. The grass Astragalus adsurgens with the coverage about 40% could effectively control the slope erosion. This grass had an efficiency of more than 70% in reducing sediment, and the grass root had a greater effect than grass canopy. On bare slope and on the slopes with the grass plant or only the grass root playing effect, there existed a functional relation between the flow velocity on the slopes and the rainfall intensity and slope gradient (V = DJ(0.33 i 0.5), where V is flow velocity, D is the comprehensive coefficient which varies with different underlying surfaces, i is rainfall intensity, and J is slope gradient). Both the grass root and the grass canopy could markedly decrease the flow velocity on the slopes, and increase the slope resistance, but the effect of grass root in decreasing flow velocity was greater while the effect in increasing resistance was smaller than that of grass canopy. The effect of grass root in increasing slope resistance was mainly achieved by increasing the sediment grain resistance, while the effect of canopy was mainly achieved by increasing the slope form resistance and wave resistance. The evaluation of the soil resistance to erosion by using a conceptual model of sediment generation by overland flow indicated that the critical shear stress value of bare slope and of the slopes with the grass plant or only the grass root playing effect was 0.533, 1.672 and 0

  5. Structure, stratigraphy, and origin of Husband Hill, Columbia Hills, Gusev Crater, Mars

    NASA Astrophysics Data System (ADS)

    McCoy, T. J.; Sims, M.; Schmidt, M. E.; Edwards, L.; Tornabene, L. L.; Crumpler, L. S.; Cohen, B. A.; Soderblom, L. A.; Blaney, D. L.; Squyres, S. W.; Arvidson, R. E.; Rice, J. W.; Tréguier, E.; d'Uston, C.; Grant, J. A.; McSween, H. Y.; Golombek, M. P.; Haldemann, A. F. C.; de Souza, P. A.

    2008-06-01

    The strike and dip of lithologic units imaged in stereo by the Spirit rover in the Columbia Hills using three-dimensional imaging software shows that measured dips (15-32°) for bedding on the main edifice of the Columbia Hill are steeper than local topography (~8-10°). Outcrops measured on West Spur are conformable in strike with shallower dips (7-15°) than observed on Husband Hill. Dips are consistent with observed strata draping the Columbia Hills. Initial uplift was likely related either to the formation of the Gusev Crater central peak or ring or through mutual interference of overlapping crater rims. Uplift was followed by subsequent draping by a series of impact and volcaniclastic materials that experienced temporally and spatially variable aqueous infiltration, cementation, and alteration episodically during or after deposition. West Spur likely represents a spatially isolated depositional event. Erosion by a variety of processes, including mass wasting, removed tens of meters of materials and formed the Tennessee Valley primarily after deposition. This was followed by eruption of the Adirondack-class plains basalt lava flows which embayed the Columbia Hills. Minor erosion, impact, and aeolian processes have subsequently modified the Columbia Hills.

  6. Structure, stratigraphy, and origin of Husband Hill, Columbia Hills, Gusev Crater, Mars

    USGS Publications Warehouse

    McCoy, T.J.; Sims, M.; Schmidt, M.E.; Edwards, L.; Tornabene, L.L.; Crumpler, L.S.; Cohen, B. A.; Soderblom, L.A.; Blaney, D.L.; Squyres, S. W.; Arvidson, R. E.; Rica, J.W.; Treguier, E.; d'Uston, C.; Grant, J. A.; McSween, H.Y.; Golombek, M.P.; Haldemann, A.F.C.; de Souza, P.A.

    2008-01-01

    The strike and dip of lithologic units imaged in stereo by the Spirit rover in the Columbia Hills using three-dimensional imaging software shows that measured dips (15-32??) for bedding on the main edifice of the Columbia Hill are steeper than local topography (???8-10??). Outcrops measured on West Spur are conformable in strike with shallower dips (7-15??) than observed on Husband Hill. Dips are consistent with observed strata draping the Columbia Hills. Initial uplift was likely related either to the formation of the Gusev Crater central peak or ring or through mutual interference of overlapping crater rims. Uplift was followed by subsequent draping by a series of impact and volcaniclastic materials that experienced temporally and spatially variable aqueous infiltration, cementation, and alteration episodically during or after deposition. West Spur likely represents a spatially isolated depositional event. Erosion by a variety of processes, including mass wasting, removed tens of meters of materials and formed the Tennessee Valley primarily after deposition. This was followed by eruption of the Adirondack-class plains basalt lava flows which embayed the Columbia Hills. Minor erosion, impact, and aeolian processes have subsequently modified the Columbia Hills. Copyright 2008 by the American Geophysical Union.

  7. Sedimentology and geochemistry of a perennially ice-covered epishelf lake in Bunger Hills Oasis, East Antarctica.

    PubMed

    Doran, P T; Wharton, R A; Lyons, W B; Des Marais, D J; Andersen, D T

    2000-01-01

    A process-oriented study was carried out in White Smoke lake, Bunger Hills, East Antarctica, a perennially ice-covered (1.8 to 2.8 m thick) epishelf (tidally-forced) lake. The lake water has a low conductivity and is relatively well mixed. Sediments are transferred from the adjacent glacier to the lake when glacier ice surrounding the sediment is sublimated at the surface and replaced by accumulating ice from below. The lake bottom at the west end of the lake is mostly rocky with a scant sediment cover. The east end contains a thick sediment profile. Grain size and delta 13C increase with sediment depth, indicating a more proximal glacier in the past. Sedimentary 210Pb and 137Cs signals are exceptionally strong, probably a result of the focusing effect of the large glacial catchment area. The post-bomb and pre-bomb radiocarbon reservoirs are c. 725 14C yr and c. 1950 14C yr, respectively. Radiocarbon dating indicates that the east end of the lake is >3 ka BP, while photographic evidence and the absence of sediment cover indicate that the west end has formed only over the last century. Our results indicate that the southern ice edge of Bunger Hills has been relatively stable with only minor fluctuations (on the scale of hundreds of metres) over the last 3000 years.

  8. Sedimentology and geochemistry of a perennially ice-covered epishelf lake in Bunger Hills Oasis, East Antarctica

    NASA Technical Reports Server (NTRS)

    Doran, P. T.; Wharton, R. A. Jr; Lyons, W. B.; Des Marais, D. J.; Andersen, D. T.; Wharton RA, J. r. (Principal Investigator)

    2000-01-01

    A process-oriented study was carried out in White Smoke lake, Bunger Hills, East Antarctica, a perennially ice-covered (1.8 to 2.8 m thick) epishelf (tidally-forced) lake. The lake water has a low conductivity and is relatively well mixed. Sediments are transferred from the adjacent glacier to the lake when glacier ice surrounding the sediment is sublimated at the surface and replaced by accumulating ice from below. The lake bottom at the west end of the lake is mostly rocky with a scant sediment cover. The east end contains a thick sediment profile. Grain size and delta 13C increase with sediment depth, indicating a more proximal glacier in the past. Sedimentary 210Pb and 137Cs signals are exceptionally strong, probably a result of the focusing effect of the large glacial catchment area. The post-bomb and pre-bomb radiocarbon reservoirs are c. 725 14C yr and c. 1950 14C yr, respectively. Radiocarbon dating indicates that the east end of the lake is >3 ka BP, while photographic evidence and the absence of sediment cover indicate that the west end has formed only over the last century. Our results indicate that the southern ice edge of Bunger Hills has been relatively stable with only minor fluctuations (on the scale of hundreds of metres) over the last 3000 years.

  9. Sedimentology and geochemistry of a perennially ice-covered epishelf lake in Bunger Hills Oasis, East Antarctica.

    PubMed

    Doran, P T; Wharton, R A; Lyons, W B; Des Marais, D J; Andersen, D T

    2000-01-01

    A process-oriented study was carried out in White Smoke lake, Bunger Hills, East Antarctica, a perennially ice-covered (1.8 to 2.8 m thick) epishelf (tidally-forced) lake. The lake water has a low conductivity and is relatively well mixed. Sediments are transferred from the adjacent glacier to the lake when glacier ice surrounding the sediment is sublimated at the surface and replaced by accumulating ice from below. The lake bottom at the west end of the lake is mostly rocky with a scant sediment cover. The east end contains a thick sediment profile. Grain size and delta 13C increase with sediment depth, indicating a more proximal glacier in the past. Sedimentary 210Pb and 137Cs signals are exceptionally strong, probably a result of the focusing effect of the large glacial catchment area. The post-bomb and pre-bomb radiocarbon reservoirs are c. 725 14C yr and c. 1950 14C yr, respectively. Radiocarbon dating indicates that the east end of the lake is >3 ka BP, while photographic evidence and the absence of sediment cover indicate that the west end has formed only over the last century. Our results indicate that the southern ice edge of Bunger Hills has been relatively stable with only minor fluctuations (on the scale of hundreds of metres) over the last 3000 years. PMID:11543521

  10. A temperature and photographic time-series from a seafloor gas hydrate deposit on the Gulf of Mexico Slope

    NASA Astrophysics Data System (ADS)

    MacDonald, I. R.; Vararo, M.; Bender, L.

    2003-04-01

    Under laboratory conditions, gas hydrates are highly sensitive to changes in water temperature. MacDonald et al. (1994) and Roberts et al. (1999) have monitored in-situ deposits and recorded rapid changes in gas flux from vents partially plugged with gas hydrate; the changes appear to correlate with fluctuation in bottom temperature over ranges of <0.2 to 1.0 C. To study this process in a different way, a monitoring array consisting of a time lapse camera and two thermistor probes was deployed at a hydrocarbon seep known as Bush Hill. Every 6 hours for 96 days (until battery power was exhausted), the camera recorded a digital image of a prominent gas hydrate mound consisting of Structure II hydrate with gas vents, chemosynthetic tube worms, and a number of mobile species. The temperature probes comprised two autonomous Antares thermistors, one at each end of a 50-cm PVC wand, which recorded temperatures with precision of better than 0.1 C at 30-min intervals over 327 d. One probe was implanted with a tight seal into a drill hole about 7 cm deep in the top of the gas hydrate mound. The second was inserted about 50 cm deep into the adjacent sediments. For each probe, the top thermistor recorded the ambient water temperature while the bottom thermistor recorded the internal temperature of the hydrate or sediment. Photographic results show no dramatic changes in the size, shape, or gas venting from the mound during the 96 day time-series. There were subtle increases in the amount of hydrate exposed to the water between the end of the photographic time series and the recovery of the monitoring array. Mean temperatures (SDEV) and temperature range recorded by the probes were as follows: In-water: 7.87 ( 0.44) and 6.64-9.73 C In-hydrate: 7.81 ( 0.34) and 6.87-9.18 C In-sediment: 7.81 ( 0.16) and 7.79-9.18 C Spectra of the temperature records showed significant high-frequency peaks for in-water data corresponding to K1, M2 and M3 lunar tides. Of these peaks, only the K1

  11. Syn-eruptive, soft-sediment deformation of deposits from dilute pyroclastic density current: triggers from granular shear, dynamic pore pressure, ballistic impacts and shock waves

    NASA Astrophysics Data System (ADS)

    Douillet, G. A.; Taisne, B.; Tsang-Hin-Sun, E.; Muller, S. K.; Kueppers, U.; Dingwell, D. B.

    2015-05-01

    Soft-sediment deformation structures can provide valuable information about the conditions of parent flows, the sediment state and the surrounding environment. Here, examples of soft-sediment deformation in deposits of dilute pyroclastic density currents are documented and possible syn-eruptive triggers suggested. Outcrops from six different volcanoes have been compiled in order to provide a broad perspective on the variety of structures: Soufriere Hills (Montserrat), Tungurahua (Ecuador), Ubehebe craters (USA), Laacher See (Germany), and Tower Hill and Purrumbete lakes (both Australia). The variety of features can be classified in four groups: (1) tubular features such as pipes; (2) isolated, laterally oriented deformation such as overturned or oversteepened laminations and vortex-shaped laminae; (3) folds-and-faults structures involving thick (>30 cm) units; (4) dominantly vertical inter-penetration of two layers such as potatoids, dishes, or diapiric flame-like structures. The occurrence of degassing pipes together with basal intrusions suggest fluidization during flow stages, and can facilitate the development of other soft-sediment deformation structures. Variations from injection dikes to suction-driven, local uplifts at the base of outcrops indicate the role of dynamic pore pressure. Isolated, centimeter-scale, overturned beds with vortex forms have been interpreted to be the signature of shear instabilities occurring at the boundary of two granular media. They may represent the frozen record of granular, pseudo Kelvin-Helmholtz instabilities. Their recognition can be a diagnostic for flows with a granular basal boundary layer. Vertical inter-penetration and those folds-and-faults features related to slumps are driven by their excess weight and occur after deposition but penecontemporaneous to the eruption. The passage of shock waves emanating from the vent may also produce trains of isolated, fine-grained overturned beds that disturb the surface bedding

  12. Operational slope-limiting circuit

    NASA Technical Reports Server (NTRS)

    Engel, A.

    1973-01-01

    Circuit limits slope of arbitrary waveform to avoid exceeding rate limit of subsequent amplifier, or to form trapezoidal wave with adjustable rise and fall rates from square wave of arbitrary frequency. Integrator provides delay needed to develop output waveform. DC coupling is used to preserve original dc offset.

  13. Exploring Slope with Stairs & Steps

    ERIC Educational Resources Information Center

    Smith, Toni M.; Seshaiyer, Padmanabhan; Peixoto, Nathalia; Suh, Jennifer M.; Bagshaw, Graham; Collins, Laurena K.

    2013-01-01

    As much as ever before, mathematics teachers are searching for ways to connect mathematics to real-life scenarios within STEM contexts. As students develop skill in proportional reasoning, they examine graphical representations of linear functions, learn to associate "slope" with "steepness" and rate of change, and develop…

  14. Columbia Hills, Mars: Aeolian features seen from the ground and orbit

    USGS Publications Warehouse

    Greeley, R.; Whelley, P.L.; Neakrase, L.D.V.; Arvidson, R. E.; Bridges, N.T.; Cabrol, N.A.; Christensen, P.R.; Di, K.; Foley, D.J.; Golombek, M.P.; Herkenhoff, K.; Knudson, A.; Kuzmin, R.O.; Li, R.; Michaels, T.; Squyres, S. W.; Sullivan, R.; Thompson, S.D.

    2008-01-01

    Abundant wind-related features occur along Spirit's traverse into the Columbia Hills over the basaltic plains of Gusev Crater. Most of the windblown sands are probably derived from weathering of rocks within the crater, and possibly from deposits associated with Ma'adim Vallis. Windblown particles act as agents of abrasion, forming ventifacts, and are organized in places, into various bed forms. Wind-related features seen from orbit, results from atmospheric models, and considerations of topography suggest that the general wind patterns and transport pathways involve: (1) winter nighttime winds that carry sediments from the mouth of Ma'adim. Vallis into the landing site area of Spirit, where they are mixed with locally derived sediments, and (2) winter daytime winds that transport the sediments from the landing site southeast toward Husband Hill; similar patterns occur in the summer but with weaker winds. Reversals of daytime flow out of Gusev Crater and nighttime wind flow into the crater can account for the symmetry of the bed forms and bimodal orientations of some ventifacts. Copyright 2008 by the American Geophysical Union.

  15. Columbia Hills, Mars: aeolian features seen from the ground and orbit

    USGS Publications Warehouse

    Greeley, Ronald; Whelley, Patrick L.; Neakrase, Lynn D.V.; Arvidson, Raymond E.; Bridges, Nathan T.; Cabrol, Nathalie A.; Christensen, Philip R.; Di, Kaichang; Foley, Daniel J.; Golombek, Matthew P.; Herkenhoff, Kenneth; Knudson, Amy; Kuzmin, Ruslan O.; Li, Ron; Michaels, Timothy; Squyres, Steven W.; Sullivan, Robert; Thompson, Shane D.

    2008-01-01

    Abundant wind-related features occur along Spirit's traverse into the Columbia Hills over the basaltic plains of Gusev Crater. Most of the windblown sands are probably derived from weathering of rocks within the crater, and possibly from deposits associated with Ma'adim Vallis. Windblown particles act as agents of abrasion, forming ventifacts, and are organized in places into various bed forms. Wind-related features seen from orbit, results from atmospheric models, and considerations of topography suggest that the general wind patterns and transport pathways involve: (1) winter nighttime winds that carry sediments from the mouth of Ma'adim Vallis into the landing site area of Spirit, where they are mixed with locally derived sediments, and (2) winter daytime winds that transport the sediments from the landing site southeast toward Husband Hill; similar patterns occur in the summer but with weaker winds. Reversals of daytime flow out of Gusev Crater and nighttime wind flow into the crater can account for the symmetry of the bed forms and bimodal orientations of some ventifacts.

  16. Timing of deposition and failure of steep carbonate slopes, Tongue of the Ocean, Bahamas

    SciTech Connect

    Grammer, G.M.; Ginsburg, R.N. )

    1991-03-01

    Steep marginal slopes around the Tongue of the Ocean record deposition during the early rise of sea level following the last lowstand some 18,000-21,000 years B.P. Coarse-grained skeletal packstones and grainstones derived from the overlying escarpment were deposited on slopes of 35-45{degree} and rapidly cemented in place. Deposition by rockfall and grainflow processes resulted in a series of elongate lenses oriented parallel to the slope. These lenses are generally less than 0.5 m thick and pinch out downslope within tens of meters. Radiocarbon dating indicates that active deposition on the slopes ceased abruptly about 10,000 years ago as sea level rose above the escarpment and began to flood the top of Great Bahama Bank. Fine-grained, nonskeletal sands and muds derived from the platform are presently by passing these slopes resulting in a 'modern' example of a drowning unconformity. Although these slopes are no longer sites of active deposition, they are still influencing the ultimate record of slope sedimentation. Arcuate, concave-up cracks in the cemented slope indicate zones of weakness and possibly represent areas susceptible to slope failure. These cracks are a few centimeters wide and may extend for tens of meters across the slope. Post-depositional failure of the slope has been observed at several locations. These slide/slump scars are as much as 30 m across and may extend downslope for 70-80 m. Large blocks, some more than 10 m across, derived from failure of the relict slope have been transported for tens or hundreds of meters downslope. The release and transport of such blocks may be one mechanism by which turbidity currents are initiated in deeper slope environments.

  17. Aquatic Sediments.

    ERIC Educational Resources Information Center

    Sanville, W. D.; And Others

    1978-01-01

    Presents a literature review of aquatic sediments and its effect upon water quality, covering publications of 1976-77. This review includes: (1) sediment water interchange; (2) chemical and physical characterization; and (3) heavy water in sediments. A list of 129 references is also presented. (HM)

  18. 10. VIEW OF THE SEDIMENT DAM AND POND, FACING SOUTH. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. VIEW OF THE SEDIMENT DAM AND POND, FACING SOUTH. PHOTO TAKEN FROM WATER PUMP (FEATURE B-25). - Nevada Lucky Tiger Mill & Mine, East slope of Buckskin Mountain, Paradise Valley, Humboldt County, NV

  19. 11. VIEW OF THE ROAD TO SEDIMENT DAM LOOKING FROM ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. VIEW OF THE ROAD TO SEDIMENT DAM LOOKING FROM EDGE OF TAILINGS. WATER PUMP (FEATURE B-25) IS VISIBLE IN CENTER LEFT OF FRAME. - Nevada Lucky Tiger Mill & Mine, East slope of Buckskin Mountain, Paradise Valley, Humboldt County, NV

  20. Uranium series dating of Allan Hills ice

    NASA Astrophysics Data System (ADS)

    Fireman, E. L.

    1986-03-01

    Uranium-238 decay series nuclides dissolved in Antarctic ice samples were measured in areas of both high and low concentrations of volcanic glass shards. Ice from the Allan Hills site (high shard content) had high Ra-226, Th-230 and U-234 activities but similarly low U-238 activities in comparison with Antarctic ice samples without shards. The Ra-226, Th-230 and U-234 excesses were found to be proportional to the shard content, while the U-238 decay series results were consistent with the assumption that alpha decay products recoiled into the ice from the shards. Through this method of uranium series dating, it was learned that the Allen Hills Cul de Sac ice is approximately 325,000 years old.

  1. The planar Hill problem with oblate primary

    NASA Astrophysics Data System (ADS)

    Papadakis, K. E.

    2004-09-01

    The regularized equations of motion of the planar Hill problem which includes the effect of the oblateness of the larger primary body, is presented. Using the Levi-Civita coordinate transformation as well as the corresponding time transformation, we obtain a simple regularized polynomial Hamiltonian of the dynamical system that corresponds to that of two uncoupled harmonic oscillators perturbed by polynomial terms. The relations between the synodic and regularized variables are also given. The convenient numerical computations of the regularized equations of motion, allow derivation of a map of the group of families of simple-periodic orbits, free of collision cases, of both the classical and the Hill problem with oblateness. The horizontal stability of the families is calculated and we determine series of horizontally critical symmetric periodic orbits of the basic families g and g'.

  2. Uranium series dating of Allan Hills ice

    NASA Technical Reports Server (NTRS)

    Fireman, E. L.

    1986-01-01

    Uranium-238 decay series nuclides dissolved in Antarctic ice samples were measured in areas of both high and low concentrations of volcanic glass shards. Ice from the Allan Hills site (high shard content) had high Ra-226, Th-230 and U-234 activities but similarly low U-238 activities in comparison with Antarctic ice samples without shards. The Ra-226, Th-230 and U-234 excesses were found to be proportional to the shard content, while the U-238 decay series results were consistent with the assumption that alpha decay products recoiled into the ice from the shards. Through this method of uranium series dating, it was learned that the Allen Hills Cul de Sac ice is approximately 325,000 years old.

  3. Suspended sediment control and water quality conservation through riparian vegetation:

    NASA Astrophysics Data System (ADS)

    Pavanelli, D.; Cavazza, C.; Correggiari, S.

    2009-04-01

    monitored. The problem of controlling the river suspended sediment concentration can be tackled by increasing the riparian vegetation able to hold back the ground eroded by the slopes, but it is necessary to know where the critical zones are. The aim of the work is to propose a method allow us to detect the risk of soil erosion areas near the river and the functionality of existing riparian vegetation along river as buffers / filters towards the eroded soil from the hill slopes. The proposed methodology is supposed has been designed for water pollution control from suspended solids, pollutants and nutrients coming from hills and an improvement of the quality of the river environment. The methodology was applied on the riparian vegetation of the Gaiana torrent where it was related to soil cover and erosion areas of the hillslope, thus correlating the impact of human activities. The Gaiana catchment area is 8.6 km2 and the mean altitude is 237 a.m.s.l., the average rainfall is of 784 mm.. It is a typical Apennines streams, about 35 km south of Bologna, Italy. The main trunk stream is 6 km long and the whole drainage network is organized in a dendritic pattern, typical of clayey lithology of the basins. The main erosion processes active in the area are caused by precipitation and surface runoff: sheet wash, concentrated water erosion and badlands watersheds (calanchi), which represent about 15% of the basin area. The vegetation of the Gaiana basin is constituted by crops (39%), woods (37%), rock outcrops(i.e. badlands)(15%), bushes (5%) and pastures(3%). The stages of the study are to spot critical areas made up of streambank and the eroded areas on the slopes near the river, with the support of aerial photos and satellite images, survey and a geographic information system. The Gaiana riparian vegetation map has been drawn and, on a strip buffer 200 metres wide along river, the Vegetation cover and the Geomorphology maps (scale 1:5000) has been drawn, after photogrammetric

  4. Suspended sediment control and water quality conservation through riparian vegetation:

    NASA Astrophysics Data System (ADS)

    Pavanelli, D.; Cavazza, C.; Correggiari, S.

    2009-04-01

    monitored. The problem of controlling the river suspended sediment concentration can be tackled by increasing the riparian vegetation able to hold back the ground eroded by the slopes, but it is necessary to know where the critical zones are. The aim of the work is to propose a method allow us to detect the risk of soil erosion areas near the river and the functionality of existing riparian vegetation along river as buffers / filters towards the eroded soil from the hill slopes. The proposed methodology is supposed has been designed for water pollution control from suspended solids, pollutants and nutrients coming from hills and an improvement of the quality of the river environment. The methodology was applied on the riparian vegetation of the Gaiana torrent where it was related to soil cover and erosion areas of the hillslope, thus correlating the impact of human activities. The Gaiana catchment area is 8.6 km2 and the mean altitude is 237 a.m.s.l., the average rainfall is of 784 mm.. It is a typical Apennines streams, about 35 km south of Bologna, Italy. The main trunk stream is 6 km long and the whole drainage network is organized in a dendritic pattern, typical of clayey lithology of the basins. The main erosion processes active in the area are caused by precipitation and surface runoff: sheet wash, concentrated water erosion and badlands watersheds (calanchi), which represent about 15% of the basin area. The vegetation of the Gaiana basin is constituted by crops (39%), woods (37%), rock outcrops(i.e. badlands)(15%), bushes (5%) and pastures(3%). The stages of the study are to spot critical areas made up of streambank and the eroded areas on the slopes near the river, with the support of aerial photos and satellite images, survey and a geographic information system. The Gaiana riparian vegetation map has been drawn and, on a strip buffer 200 metres wide along river, the Vegetation cover and the Geomorphology maps (scale 1:5000) has been drawn, after photogrammetric

  5. Photovoltaics - 10 years after Cherry Hill

    SciTech Connect

    Ralph, E.L.

    1984-05-01

    The question is, could a workshop today be effective in planning the next 10 years of development in the PV industry. Given is some insight into the Cherry Hill workshop, who was there and what was accomplished. Plans were made at workshop sessions, open panels discussed the needs, and invited papers were presented by experts in the field showing what concepts and ideas existed. The need for U.S. Government support of a 10 year PV development program was confirmed.

  6. Possible Meteorites in the Martian Hills

    NASA Technical Reports Server (NTRS)

    2006-01-01

    From its winter outpost at 'Low Ridge' inside Gusev Crater, NASA's Mars Exploration Rover Spirit took this spectacular, color mosaic of hilly, sandy terrain and two potential iron meteorites. The two light-colored, smooth rocks about two-thirds of the way up from the bottom of the frame have been labeled 'Zhong Shan' and 'Allan Hills.'

    The two rocks' informal names are in keeping with the rover science team's campaign to nickname rocks and soils in the area after locations in Antarctica. Zhong Shang is an Antarctic base that the People's Republic of China opened on Feb. 26, 1989, at the Larsemann Hills in Prydz Bay in East Antarctica. Allan Hills is a location where researchers have found many Martian meteorites, including the controversial ALH84001, which achieved fame in 1996 when NASA scientists suggested that it might contain evidence for fossilized extraterrestrial life. Zhong Shan was the given name of Dr. Sun Yat-sen (1866-1925), known as the 'Father of Modern China.' Born to a peasant family in Guangdong, Sun moved to live with his brother in Honolulu at age 13 and later became a medical doctor. He led a series of uprisings against the Qing dynasty that began in 1894 and eventually succeeded in 1911. Sun served as the first provisional president when the Republic of China was founded in 1912.

    The Zhong Shan and Allan Hills rocks, at the left and right, respectively, have unusual morphologies and miniature thermal emission spectrometer signatures that resemble those of a rock known as 'Heat Shield' at the Meridiani site explored by Spirit's twin, Opportunity. Opportunity's analyses revealed Heat Shield to be an iron meteorite.

    Spirit acquired this approximately true-color image on the rover's 872nd Martian day, or sol (June 16, 2006), using exposures taken through three of the panoramic camera's filters, centered on wavelengths of 600 nanometers, 530 nanometers, and 480 nanometers.

  7. Effects of basin bottom slope on jet hydrodynamics and river mouth bar formation

    NASA Astrophysics Data System (ADS)

    Jiménez-Robles, A. M.; Ortega-Sánchez, M.; Losada, M. A.

    2016-06-01

    River mouth bars are strategic morphological units primarily responsible for the development of entire deltaic systems. This paper addresses the role of receiving basin slope in the hydrodynamics of an exiting sediment-laden turbulent jet and in resulting mouth bar morphodynamics. We use Delft3D, a coupled hydrodynamic and morphodynamic numerical model, along with a theoretical formulation to reproduce the physics of the problem, characterized by a fluvially dominated inlet free of waves and tides. We propose an updated theoretical model with a slope-dependent entrainment coefficient, showing that the rate at which ambient fluid is incorporated into a jet increases with higher basin slopes. Transient results reveal that the magnitude of a basin slope can alter the stability of a jet, favoring the formation of an unstable meandering jet. While a stable jet gives rise to "middle-ground" bars accompanied by diverging channels, a "lunate" mouth bar results from unstable jets. Additional morphodynamic simulations demonstrate that the time required for mouth bar stagnation in its final position increases linearly with the basin slope. In contrast, the distance at which the mouth bar eventually forms decreases until reaching an asymptotic value for slopes higher than 2%. Moreover, the basin slope highly influences sedimentary processes responsible for bar formation: for milder slopes, progradation processes prevail, while in steeper basins aggradation is more relevant. Finally, the minimum relative water depth over a bar crest that forces the flow to bifurcate around a fully developed bar decreases with the basin slope.

  8. Flow over periodic hills: an experimental study

    NASA Astrophysics Data System (ADS)

    Rapp, Ch.; Manhart, M.

    2011-07-01

    Two-dimensional flow over periodically arranged hills was investigated experimentally in a water channel. Two-dimensional particle image velocimetry (PIV) and one-dimensional laser Doppler anemometry (LDA) measurements were undertaken at four Reynolds numbers ({5,600} le Re le {37,000}). Two-dimensional PIV field measurements were thoroughly validated by means of point-by-point 1D LDA measurements at certain positions of the flow. A detailed study of the periodicity and the homogeneity was undertaken, which demonstrates that the flow can be regarded as two-dimensional and periodic for Re ge {10,000}. We found a decreasing reattachment length with increasing Reynolds number. This is connected to a higher momentum in the near-wall zone close to flow separation which comes from the velocity speed up above the obstacle. This leads to a velocity overshoot directly above the hill crest which increases with Reynolds number as the inner layer depth decreases. The flow speed up above that layer is independent of the Reynolds number which supports the assumption of inviscid flow disturbance in the outer layer usually made in asymptotic theory for flow over small hills.

  9. The Rocks of the Columbia Hills

    NASA Technical Reports Server (NTRS)

    Squyres, Steven W.; Arvidson, Raymond E.; Blaney, Diana L.; Clark, Benton C.; Crumpler, Larry; Farrand, William H.; Gorevan, Stephen; Herkenhoff, Kenneth; Hurowitz, Joel; Kusack, Alastair; McSween, Harry Y.; Ming, Douglas W.; Morris, Richard V.; Ruff, Steven W.; Wang, Alian; Yen, Albert

    2006-01-01

    The Mars Exploration Rover Spirit has identified five distinct rock types in the Columbia Hills of Gusev crater. Clovis Class rock is a poorly-sorted clastic rock that has undergone substantial aqueous alteration. We interpret it to be aqueously-altered ejecta deposits formed by impacts into basaltic materials. Wishstone Class rock is also a poorly-sorted clastic rock that has a distinctive chemical composition that is high in Ti and P and low in Cr. Wishstone Class rock may be pyroclastic in origin. Peace Class rock is a sedimentary material composed of ultramafic sand grains cemented by significant quantities of Mg- and Ca-sulfates. Peace Class rock may have formed when water briefly saturated the ultramafic sands, and evaporated to allow precipitation of the sulfates. Watchtower Class rocks are similar chemically to Wishstone Class rocks, and have undergone widely varying degrees of near-isochemical aqueous alteration. They may also be ejecta deposits, formed by impacts into Wishstone-rich materials and altered by small amounts of water. Backstay Class rocks are basalt/trachybasalt lavas that were emplaced in the Columbia Hills after the other rock classes were, either as impact ejecta or by localized volcanic activity. The geologic record preserved in the rocks of the Columbia Hills reveals a period very early in martian history in which volcanic materials were widespread, impact was a dominant process, and water was commonly present.

  10. Time-dependent deformations on marine clays on submarine slopes

    SciTech Connect

    Silva, A.J.; Brandes, H.; Sadd, M.H.; Tian, W.M. )

    1990-06-01

    Evidence from geological and geophysical records indicates that time-dependent deformations occur on or within many submarine slopes. Laboratory studies on marine clays from the slope/rise and the ocean's basin have shown that these clays are generally quite viscous and therefore can be expected to deform in the field even under such small stresses as those caused by the downslope component of gravity on relatively gentle slopes. The nature and extent of these deformations has important geologic and engineering applications and depends on a number of factors. A research program at the University of Rhode Island is under way to study these factors, make predictions on rates of displacement, and identify environmental conditions that may lead to catastrophic mass failures. A laboratory testing program on the time-dependent characteristics of marine clays has been under way for a number of years. The data include, among others, long-term drained triaxial, one-dimensional, and direct simple shear creep tests. These results along with practical considerations are used to select a constitutive model for inclusion in the numerical code. Sediment deposits encountered on the continental slope and rise can vary substantially both in composition and behavior over relatively short distances. To analyze the integrated behavior of such a continuum, the authors have selected the finite element method. The code being developed will initially include a numerical model proposed by other investigators. With the aid of the developed methodology, creep deformations can be studied for a number of field cases of interest.

  11. Development of deep-seated gravitational slope deformation on a shale dip-slope: observations from high-quality drillcores

    NASA Astrophysics Data System (ADS)

    Chigira, Masahiro; Hariyama, Takehiro; Yamasaki, Shintaro

    2013-04-01

    The internal structures within a gravitationally deformed slope were observed using high-quality drillcores obtained from a dip slope of a series of shale-dominated sediments. This slope has dimple-like depressions and an overall gentle slope angle, but has no well-defined landslide scarp, suggesting that this area underwent gravitationally deformation but with no separation of the deformed portion from the surrounding area. Three drillcores, to a maximum depth of 96 m, were used during this study, with detailed observations of cut paraffin-impregnated core surfaces used to characterize gravitational deformation in the study area. This logging identified shear zones that consist of disintegrated (brecciated) and pulverized zones that were up to 88 and 19 cm thick, respectively. Disintegrated zone breccias have local jigsaw-fit textures, but other areas contain compositional trails formed by cataclastic flow, and rounded outlines formed by attrition. Pulverized zones underwent increased amounts of shearing, leading to the formation of more rounded fragments and increasing amounts of clayey matrix material, but still containing more than 30% of visible rock fragments. As such, these zones are still classified as breccias in terms of fault rock classification. Planar structures, such as R and Y shears, and P foliations, are not developed in the study area. Shear zones are intermittently located across the slope and have not formed a through-going master sliding zone. Incipient shear zones are present within the slope, including a pair of shear surfaces with a pull apart-like opening, and thin disintegrated or pulverized zones in intact rocks at 3-10 m below the base of the main area of gravitational deformation, suggesting that these shear zones propagate downward in a step-wise manner. This propagation may be related to the redistribution of stress induced by river incision.

  12. Modern Reservoir Sedimentation Management Techniques with Examples

    NASA Astrophysics Data System (ADS)

    Annandale, G. W.

    2014-12-01

    Implementation of reservoir sedimentation management approaches results in a win-win scenario, it assists in enhancing the environment by preserving river function downstream of dams while concurrently providing opportunities to sustainably manage water resource infrastructure. This paper summarizes the most often used reservoir sedimentation management techniques with examples of where they have been implemented. Three categories can be used to classify these technologies, i.e. catchment management, sediment routing and sediment removal. The objective of catchment management techniques is to minimize the amount of sediment that may discharge into a reservoir, thereby reducing the loss of storage space due to sedimentation. Reservoir routing is a set of techniques that aim at minimizing the amount of sediment that may deposit in a reservoir, thereby maximizing the amount of sediment that may be passed downstream. The third group consists of techniques that may be used to remove previously deposited sediment from reservoirs. The selection of reservoir sedimentation management approaches is site specific and depends on various factors, including dam height, reservoir volume, reservoir length, valley shape, valley slope, sediment type and hydrology. Description of the different reservoir sedimentation management techniques that are used in practice will be accompanied by case studies, including video, illustrating criteria that may be used to determine the potential success of implementing the techniques.

  13. Carbonate slope gully system on the Westside Great Bahama Bank

    NASA Astrophysics Data System (ADS)

    Principaud, Mélanie; Mulder, Thierry; Borgomano, Jean; Ducassou, Emmanuelle; Hanquiez, Vincent; Gillet, Hervé; Marieu, Vincent; Sorriaux, Patrick

    2013-04-01

    Gullies are commonly observed on submarine slopes along many continental margins. They are generally small, straight, shallow channels with a depth that does not exceed a few tens of meters. They form on relatively steep slopes. They are important features for downslope sediment transfer from the outer continental shelf to the continental slope and rise. Data collected during the first leg of the Carambar cruise (Nov. 1st - Nov. 15th, 2010) on the RV "Le Suroît" show that the western slope of the Great Bahamas Bank is characterized by the presence of gullies that extend about 100 km from North to South along the carbonate platform. Gullies appear on the upper slope at approximately 410 m water depth in a carbonated mud-dominated environment. Their initiation follows the presence of sediment waves. They extend over a 3° steeped slope down to 610 m water depth. The gully heads are not connected to the platform and to any significant carbonate depositional system. They are relatively linear, sub-parallel, with a symmetric to asymmetric V-shaped cross section and incision does not exceed 30 m. Average gully length and spacing are 4000 and 800 m respectively. A detailed morphometric study based on EM302 multibeam bathymetry and very-high resolution seismic data (Chirp sub bottom profiler) combined with a statistical analysis allowed the gullied slope to be divided into two distinct areas. (1) The northern area characterized by regularly-spaced gullies (spacing varies from 750 to 800 m from North to South). They are generally linear and sub-parallel with an average length of 4 km. Their depth are usually lower than 10 m. Asymmetry is greater in the central region of gullies (northern flank is steeper than southern flank) and seems to be correlated with an increase in gully depth and a decrease in gully spacing. (2) The southern area is characterized by irregularly-shaped gullies that are usually truncated by a large 40 m high N-S deformation escarpment. Gullies have

  14. Horizontal wells improve recovery at the Elk Hills Petroleum Reserve

    SciTech Connect

    Rintoul, B.

    1995-11-01

    In 1988 the US Department of Energy and Bechtel implemented a program to slow production declines in the Elk Hills 26R pool sand of the Naval Petroleum Reserve No. 1. It was also hoped horizontal wells would increase the production rate, decrease gas production and extend economic life of the reservoir. The Stevens sand pool targeted for the project is a high-quality, sand-rich turbidite channel system encapsulated within Miocene Monterey siliceous shales, mudstones and associated sediments. The pool is about 3-miles long by 3/4-mile wide. The paper describes the specifications and drilling of the first four out of the 14 horizontal wells drilled at this facility. Horizontal drilling technology has completely altered the future of the 26R pool. In 1980 estimated ultimate recovery (EUR) from the sand was 211 million bbl. With the latest horizontal well drilling campaign, the pool is expected to pass that estimate in 1997 when oil production is forecasted to be at least 13,000 b/d. EUR form the 26R sand now is more than 250 million bbl, and even that estimate is being revised upward.

  15. Case study of slope failures at Spilmans Island

    SciTech Connect

    Kayyal, M.K.; Hasen, M.

    1998-11-01

    This paper presents a case study for a dredge disposal site called Spilmans Island, located along the Houston-Galveston Ship Channel, east of Houston. Initially classified as a sand bar in the San Jacinto River, Spilmans Island evolved in recent years with the construction of perimeter levees to contain the flow of materials produced from dredging operations. These levees were often constructed on soft dredged sediments, and as the levees were raised, occasionally slope failures occurred. The objectives of this paper are to illustrate the importance of reconstructing the history of a site as a basis for geotechnical analyses, and to demonstrate the significance of keeping accurate records of past investigations, construction activities, slope failures and subsequent remedial measures. The results of the geotechnical investigation described in this paper offer a clear example of how such data can be used to provide reliable predictions on the stability conditions of raised levees.

  16. Compilation of selected hydrologic data, through water year 1992, Black Hills Hydrology Study, western South Dakota

    USGS Publications Warehouse

    Driscoll, Daniel G.; Bradford, Wendell

    1994-01-01

    This report presents water-level, water-quailty, and springflow data that have been collected or compiled, through water year 1992, for the Black Hills Hydrology Study. This study is a long-term cooperative effort between the U.S. Geological Survey, the South Dakota Department of Environmental and Natural Resources, and the West Dakota Water Development District (which represents various local and county cooperators). Water-level data are presented for 32 observation wells and 2 cave sites in the Black Hills area of western South Dakota. The wells are part of a network of observation wells maintained by the South Dakota Department of Environment and Natural Resources and are completed in various bedrock formations that are utilized as aquifers in the Black Hills area. Both cave sites are located within outcrops of the Madison Limestone. Data presented include site descriptions, hydrographs, and tabular data. Water- quality data are presented for 12 surface-water sites and 5 ground-water sites. Data presented include field parameters, bacteria counts, and concentrations of common ions, solids, nutrients, trace elements, radiometrics, cyanide, phenols, dissolved organic carbon, and suspended sediment. Spring data are presented for 83 springs and 21 stream reaches with significant springflow components. Data presented include site information, discharge, and field water-quality parameters including temperature, specific conductance, dissolved oxygen, and pH.

  17. Signals from the ancient geodynamo: A paleomagnetic field test on the Jack Hills metaconglomerate

    NASA Astrophysics Data System (ADS)

    Tarduno, John A.; Cottrell, Rory D.

    2013-04-01

    The oldest history of Earth's magnetic field cannot be directly read from extant bulk rocks because of subsequent metamorphism at temperatures close to or exceeding the Curie temperature of common magnetic minerals. The Jack Hills metasediments of Western Australia, which have seen lower peak metamorphic temperatures, contain zircons as old as ˜4.4 billion-yr-old. To assess whether these sediments can retain an ancient signal of the geodynamo, we present a paleomagnetic conglomerate test on a cobble-bearing Jack Hills unit. Thermal demagnetization reveals a distinct magnetic component with high unblocking temperatures between ˜550 and 580 °C that passes the conglomerate test, indicating magnetization prior to deposition of the conglomerate. This result, together with rock magnetic data, indicates that the high unblocking temperature component is carried by magnetite which records magnetization in an ambient field, and the simplest explanation is that a dynamo was present. Existing geochronological data imply that the clasts could contain mixtures of minerals extending to ages only slightly older than the maximum depositional age at 3.05 billion-yr-ago. However, the positive conglomerate test reported here indicates that the Jack Hills metasediments have the potential to record Paleorchean to Hadean magnetic fields, on a clast or sub-clast mineral scale.

  18. Late Cenozoic sea-level changes and the onset of glaciation: impact on continental slope progradation off eastern Canada

    USGS Publications Warehouse

    Piper, D.J.W.; Normark, W.R.

    1989-01-01

    Late Cenozoic sedimentation from four varied sites on the continental slopes off southeastern Canada has been analysed using high-resolution airgun multichannel seismic profiles, supplemented with some single channel data. Biostratigraphic ties are available to exploratory wells at three of the sites. Uniform, slow accumulation of hemipelagic sediments was locally terminated by the late Miocene sea-level lowering, which is also reflected in changes in foraminiferan faunas on the continental shelf. Data are very limited for the early Pliocene but suggest a return to slow hemipelagic sedimentation. At the beginning of the late Pliocene, there was a change in sedimentation style marked by a several-fold increase in accumulation rates and cutting of slope valleys. This late Pliocene cutting of slope valleys corresponds to the onset of late Cenozoic growth of the Laurentian Fan and the initiation of turbidite sedimentation on the Sohm Abyssal Plain. Although it corresponds to a time of sea-level lowering, the contrast with the late Miocene lowstand indicates that there must also have been a change in sediment delivery to the coastline, perhaps as a result of increased rainfall or development of valley glaciers. High sedimentation rates continued into the early Pleistocene, but the extent of slope dissection by gullies increased. Gully-cutting episodes alternated with sediment-draping episodes. Throughout the southeastern Canadian continental margin, there was a change in sedimentation style in the middle Pleistocene that resulted from extensive ice sheets crossing the continental shelf and delivering coarse sediment directly to the continental slope. ?? 1989.

  19. Age-related differences when walking downhill on different sloped terrains.

    PubMed

    Scaglioni-Solano, Pietro; Aragón-Vargas, Luis Fernando

    2015-01-01

    Despite the common situation of walking on different sloped terrains, previous work on gait has focused on level terrain. This study aims to assess whether any age-related differences exist in spatiotemporal and stability parameters when walking downhill on three different sloped walkways. Two tri-axial accelerometers were used at the levels of head and pelvis to investigate spatiotemporal parameters, magnitude (root mean square, RMS), harmonic content of accelerations (harmonic ratios, HR) and attenuation between body levels (ATT) in 35 older adults (OA, 69 ± 4.5 y.o.) and 22 young adults (YA, 22.1 ± 1.9 y.o.). Older adults walked at the same speed and cadence as young adults in flat terrain (FL, 0%) and moderate hill (MH, 8%). In the highest slope (PH, 20%), older adults reduced speed and step length and both groups increased cadence. Age had no effect on attenuation and RMS profiles. RMS increased with slope in all directions at both head and pelvis, except, for medio-lateral direction (ML), with similar head RMS in all slopes. There is an important shift in ATT from anteroposterior direction (AP) to ML at the highest slope, resulting in smaller antero-posterior attenuation and greater medio-lateral attenuation. Age differences appeared in the smoothness (HR) at the flat terrain, with increased vertical and antero-posterior values for young adults. As slope increased, group differences disappeared and HR decreased for all directions of motion. In general, spatiotemporal adaptations to increased slope seem to be part of a mechanism to improve ML attenuation, in both young and old adults. PMID:25455702

  20. Simulation of River Bluffs and Slip-Off Slopes With a Discrete Particle-Based Model

    NASA Astrophysics Data System (ADS)

    Lancaster, S. T.; Zunka, J. P.; Tucker, G. E.

    2013-12-01

    A discrete particle-based model simulates evolution of two-dimensional valley cross sections similar to those produced by bedrock meandering rivers and thereby suggests that characteristic features such as overhanging cliffs and talus slopes are dependent on specific relationships among process rates. Discrete coordinates on a gridded cross-section define locations of particles of intact bedrock, sediment (loose material with half the bulk density of bedrock), water, or air on that grid, and each particle of rock or sediment has a unique (or zero) concentration of terrestrial cosmogenic nuclides (TCNs). Stochastic processes determine both the possible locations of process actions and the results of those actions. Stochastic discharges generate boundary shear stresses, calculated by an approximation to the ray-isovel model, that determine removal probabilities for candidate particles of bedrock or sediment from the boundary of a self-formed channel. An asymmetric probability distribution governs the selection of candidate particles on the wetted perimeter and drives asymmetric fluvial erosion and transport that can undermine adjacent slopes, so that the channel migrates laterally. Sediment is produced from intact bedrock by weathering and rock fall. The latter acts only on candidate bedrock particles that are undermined and exposed at the surface. Weathering produces two sediment particles from one of bedrock, and thereby inflates the surface, when slope-normal random walks from candidate sites on the surface end at bedrock particles, so that the sediment-bedrock interface is irregular and discontinuous. Diffusive transport moves candidate particles on random walks in random directions along the surface, where transition probabilities depend on local topography. TCNs are produced when the randomly situated and oriented random walks of cosmic rays end at bedrock or sediment, and not water, particles. The model produces asymmetric channels and valley cross sections

  1. How does slope form affect erosion in CATFLOW-SED?

    NASA Astrophysics Data System (ADS)

    Gabelmann, Petra; Wienhöfer, Jan; Zehe, Erwin

    2016-04-01

    Erosion is a severe environmental problem in agro-ecosystems with highly erodible loess soils. It is controlled by various factors, e.g. rainfall intensity, initial wetness conditions, soil type, land use and tillage practice. Furthermore slope form and gradient have been shown to influence erosion amounts to a large extent. Within the last fifty years, various erosion models have been developed to describe the erosion process, estimate erosion amounts and identify erosion-prone areas. These models differ in terms of complexity, the processes which are considered, and the data required for model calibration and they can be categorised into empirical or statistical, conceptual, and physically-based models. CATFLOW-SED is a process-based hydrology and erosion model that can operate on catchment and hillslope scales. Soil water dynamics are described by the Richards equation including effective approaches for preferential flow. Evapotranspiration is simulated using an approach based on the Penman-Monteith equation. The model simulates overland flow using the diffusion wave equation. Soil detachment is related to the attacking forces of rainfall and overland flow, and the erosion resistance of soil. Sediment transport capacity and sediment deposition are related to overland flow velocity using the equation of Engelund and Hansen and the sinking velocity of grain sizes respectively. We performed a study to analyse the erosion process on different virtual hillslopes, with varying slope gradient and slope form, using the CATFLOW-SED model. We explored the role of landform on erosion and sedimentation, particularly we look for forms that either maximise or minimise erosion. Results indicate the importance to performing the process implementation within physically meaningful limits and choose appropriate model parameters respectively.

  2. Slope Streaks in Terra Sabaea

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] Figure 1 Click on image for larger version

    This HiRISE image shows the rim of a crater in the region of Terra Sabaea in the northern hemisphere of Mars.

    The subimage (figure 1) is a close-up view of the crater rim revealing dark and light-toned slope streaks. Slope streak formation is among the few known processes currently active on Mars. While their mechanism of formation and triggering is debated, they are most commonly believed to form by downslope movement of extremely dry sand or very fine-grained dust in an almost fluidlike manner (analogous to a terrestrial snow avalanche) exposing darker underlying material.

    Other ideas include the triggering of slope streak formation by possible concentrations of near-surface ice or scouring of the surface by running water from aquifers intercepting slope faces, spring discharge (perhaps brines), and/or hydrothermal activity.

    Several of the slope streaks in the subimage, particularly the three longest darker streaks, show evidence that downslope movement is being diverted around obstacles such as large boulders. Several streaks also appear to originate at boulders or clumps of rocky material.

    In general, the slope streaks do not have large deposits of displaced material at their downslope ends and do not run out onto the crater floor suggesting that they have little reserve kinetic energy. The darkest slope streaks are youngest and can be seen to cross cut and superpose older and lighter-toned streaks. The lighter-toned streaks are believed to be dark streaks that have lightened with time as new dust is deposited on their surface.

    Observation Geometry Image PSP_001808_1875 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 15-Dec-2006. The complete image is centered at 7.4 degrees latitude, 47.0 degrees East longitude. The range to the target site was 272.1 km

  3. Three-dimensional potential flow over hills and oval mounds

    NASA Technical Reports Server (NTRS)

    Siegel, R.

    1976-01-01

    An analysis was made of the potential flow behavior for an initially uniform flow passing over a single axisymmetric hill, an oval mound, and a combination of two hills. Small perturbation theory was used, and the resulting Laplace equation for the perturbation velocity potential was solved by using either a product solution or a Green's function. The three dimensional solution is of interest in calculating the pressure distribution around obstacles, the flow of pollutants carried by the wind, and the augmentation of wind velocity for windmill siting. The augmentation in velocity at the top of a hill was found to be proportional to the hill height relative to a characteristic width dimension of the hill. An axisymmetric hill produced about 20 percent less velocity increase than a two dimensional ridge having the same cross-sectional profile.

  4. Interplay between down-slope and along-slope sedimentary processes during the late Quaternary along the Capo Vaticano margin (southern Tyrrhenian Sea, Italy)

    NASA Astrophysics Data System (ADS)

    Martorelli, Eleonora; Bosman, Alessandro; Casalbore, Daniele; Falcini, Federico

    2016-04-01

    Late Quaternary along-slope and down-slope sedimentary processes and structures in the upper slope-shelf sector of the Calabro-Tyrrhenian continental margin off Capo Vaticano have been investigated using very high-resolution single-channel seismic profiles and multibeam bathymetric data. The results show that a competition among along-slope bottom currents-vs down-slope mass-wasting mostly contributed in shaping the seafloor and controlling deposition of sedimentary units during the Late Quaternary. Along-slope processes mostly formed elongated drifts located on the upper continental slope and outer shelf, between -90 and -300 m. The contourite deposits and associated erosive elements indicate the presence of a northwestward geostrophic flow that can be related to the modified-LIW issued by the Messina Strait. According to the proposed stratigraphic reconstruction it is likely that the activity of bottom-currents off Capo Vaticano was intensified around the LGM period and during the post-glacial sea-level rise, whereas they were less intense during the Holocene. Gravity-driven down-slope processes formed mass-transport deposits and turbidite systems with erosive channels, locally indenting the present-day shelf. Several slide events affected the upper 10-20 m of the stratigraphic record, dismantling considerable volume of contourite sediment. High-resolution seismic profiles indicate that failure processes appear to be dominated by translational sliding with glide plains mainly developed within contourite deposits. The most striking feature is the Capo Vaticano slide complex, which displays a large spatial coverage (area of about 18 km2) and is composed by several intersecting slide scars and overlapping deposits; these characteristics are peculiar for the Tyrrhenian continental margins, where slide events developed in open-slope areas are usually less complex and smaller in size. The presence of high-amplitude reflectors within contourite deposits (representing

  5. Landscape changes and natural hazards affecting the Pincio hill (Rome, Italy) in historical times

    NASA Astrophysics Data System (ADS)

    Guarino, Paolo Maria; Lucarini, Mauro; Spizzichino, Daniele

    2016-04-01

    This work focuses on preliminary results achieved by means of a research project carried out by ISPRA in collaboration with Soprintendenza Capitolina (the Cultural Heritage Capitoline Superintendence), aimed at defining an interpretative model of natural and anthropic evolution of the Pincio Hill (Rome, Italy) during the last 2,500 years. The study area is located in the NE sector of the city of Rome and includes the Pincio hill Cultural Heritage site and the surrounding area of the Tiber River flood plain. The Pincio Hill is a very interesting case of interplay among: i) natural landscape setting; ii) historical urban transformations; iii) human activity and recurrence of natural hazard events impacting heavily on the territory since ancient times. During the last decades, designs of new areas to be allocated for underground parking jointly with new archaeological excavations surveys have allowed the acquisition of a large amount of new data. The study has been carried out through a new reinterpretation of recently drilled boreholes stratigraphic logs and the conspicuous related archaeological literature. The main outcome of the research activities are summarized as below. Concerning the top of the hill, latest archaeological excavations brought to the light traces of ancient structures and settlements dating from the Archaic period until the fourth century AD, highlighting the facto the character of strong agricultural and landscape appeal that have involved the western sector of the Pincio hill since the ancient times, without evidence of relevant alterations of the original landscape. In the slope sector, the information coming from geotechnical survey allowed the reconstruction of isochronous surfaces inside of landfills, divided according to their age. The profile of the slope below the landfill from the Roman period seems very steep and irregular, in strong contrast to the medieval one and the current one, characterized by multiple succession of terraces. In

  6. Properties of martian slope streak populations

    NASA Astrophysics Data System (ADS)

    Bergonio, Justin R.; Rottas, Kimberly M.; Schorghofer, Norbert

    2013-07-01

    Slope streaks are down-slope mass movements on the surface of Mars that are among the few known examples of contemporary geologic activity on Mars. Here we study slope streak activity over three decades, based on overlapping images in the Lycus Sulci region taken by the Context Camera (CTX) 2007-2010 and the Viking Orbiter Camera in 1977. The number of disappeared slope streaks is nearly equal the number of newly formed slope streaks, suggesting the streak population is balanced. The turnover time of the population is estimated to be four decades. Slope streaks fade gradually over time, with islands of persistence. We also determine the number of observable slope streaks as a function of image resolution based on images by the High Resolution Imaging Science Experiment (HiRISE) camera, and find that the number of discernible slope streaks can increase rapidly with spatial resolution.

  7. Gravity-induced stresses in finite slopes

    USGS Publications Warehouse

    Savage, W.Z.

    1994-01-01

    An exact solution for gravity-induced stresses in finite elastic slopes is presented. This solution, which is applied for gravity-induced stresses in 15, 30, 45 and 90?? finite slopes, has application in pit-slope design, compares favorably with published finite element results for this problem and satisfies the conditions that shear and normal stresses vanish on the ground surface. The solution predicts that horizontal stresses are compressive along the top of the slopes (zero in the case of the 90?? slope) and tensile away from the bottom of the slopes, effects which are caused by downward movement and near-surface horizontal extension in front of the slope in response to gravity loading caused by the additional material associated with the finite slope. ?? 1994.

  8. PLANS AND SECTIONS. WEIR SPILLWAY. TEXAS HILL CANAL STA. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    PLANS AND SECTIONS. WEIR SPILLWAY. TEXAS HILL CANAL - STA. 132+82.15. TEXAS HILL CANAL AND DISTRIBUTION SYSTEM. United States Department of Interior, Bureau of Reclamation; Gila Project, Arizona, Wellton-Mohawk Division. Drawing No. 50-D-3200, dated February 7, 1955, Denver, Colorado - Wellton-Mohawk Irrigation System, Relift Station, Texas Hill Canal 2.5, Northern Terminus of Avenue 51 East, approximately .5 mile south of Union Pacific Railroad, Wellton, Yuma County, AZ

  9. Origin and significance of tourmaline-rich rocks in the Broken Hill district, Australia

    USGS Publications Warehouse

    Slack, J.F.; Palmer, M.R.; Stevens, B.P.J.; Barnes, R.G.

    1993-01-01

    Tourmaline-rich rocks are widespread minor lithologies within the Early Proterozoic Willyama supergroup. Most of the tourmaline-rich rocks are within the Broken Hill Group that hosts the main Pb-Zn-Ag ores. Electron microprobe analyses of tourmalines intergrown with Fe sulfides at the Globe mine show Mg-rich compositions relative to tourmalines in sulfide-free assemblages from the same area, suggesting early (premetamorphic) introduction of boron and Mg enrichment of tourmaline by sulfide-silicate reactions during metamorphism. Combined field and geochemical data indicate that the district tourmalinites represent normal clastic sediments that were metasomatically altered by boron-rich hydrothermal fluids at or below the sediment-water interface. The geochemical data imply relative immobility of Al, Ti, Cr, and heavy REE during hydrothermal alteration and later metamorphism. -from Authors

  10. Changes in deep-water epibenthic megafaunal assemblages in relation to seabed slope on the Nigerian margin

    NASA Astrophysics Data System (ADS)

    Jones, Daniel O. B.; Mrabure, Charles O.; Gates, Andrew R.

    2013-08-01

    Local-scale habitat heterogeneity associated with changes in slope is a ubiquitous feature of bathyal continental margins. The response of deep-sea species to high habitat heterogeneity is poorly known and slope can be used as a proxy for many important ecological variables, such as current flow, sedimentation and substratum type. This study determines how slope angle effects megafaunal species density and diversity at the Usan field, offshore Nigeria, between 740 and 760 m depth. This deep-water area is increasingly exploited for hydrocarbons, yet lacking in baseline biological information. Replicated remotely operated vehicle video transect surveys were carried out using industry infrastructure (through the SERPENT Project) at a representative range of slopes (1°, 3°, 11° and 29°). Twenty-four species of benthic megafaunal invertebrate were found, numerically dominated by the echinoid Phormosoma placenta, and nine species of fish were observed. Megafaunal invertebrate deposit feeder density decreased significantly with increasing slope (density range 0.503-0.081 individuals m-2). Densities of megafaunal suspension feeders were very low except at the highest slope site (mean density 0.17 m-2). Overall species richness was greater on steeper slopes, although the richness of deposit feeders was not affected. Reduced labile organic matter in sediments on steeper slopes likely reduced deposit feeder densities, but increased current flow at higher slopes allowed both increased richness and density of suspension feeders.

  11. Relationship of sediment discharge to streamflow

    USGS Publications Warehouse

    Colby, B.R.

    1956-01-01

    The relationship between rate of sediment discharge and rate of water discharge at a cross section of a stream is frequently expressed by an average curve. This curve is the sediment rating curve. It has been widely used in the computation of average sediment discharge from water discharge for periods when sediment samples were not collected. This report discusses primarily the applications of sediment rating curves for periods during which at least occasional sediment samples were collected. Because sediment rating curves are of many kinds, the selection of the correct kind for each use is important. Each curve should be carefully prepared. In particular, the correct dependent variable must be used or the slope of the sediment rating curve may be incorrect for computing sediment discharges. Sediment rating curves and their applications were studied for the following gaging stations: 1. Niobrara River near Cody, Nebr. 2. Colorado River near Grand Canyon, Ariz. 3. Rio Grande at San Martial, N. Mex. 4. Rio Puerto near Bernardo, N. Mex. 5. White River near Kadoka, S. Dak. 6. Sandusky River near Fremont, Ohio Except for the Sandusky River and the Rio Puerco, which transport mostly fine sediment, one instantaneous sediment rating curve was prepared for the discharge of suspended sands, at each station, and another for the discharge of sediment finer than 0.082 millimeter. Each curve was studied separately, and by trial-end-error multiple correlation some of the factors that cause scatter from the sediment rating curves were determined. Average velocity at the cross section, Water temperature, and erratic fluctuations in concentration seemed to be the three major factors that caused departures from the sediment rating curves for suspended sands. The concentration of suspended sands varied with about the 2.8 power of the mean velocity for the four sediment, rating curves for suspended sands. The effect of water temperature was not so consistent as that of velocity and

  12. 10. Historic American Buildings Survey Joseph Hill, Photographer May, 1936 ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. Historic American Buildings Survey Joseph Hill, Photographer May, 1936 EAST ELEVATION - Rock Island Arsenal, Building No. 346, Davenport Drive, Arsenal Grounds, Rock Island, Rock Island County, IL

  13. 78 FR 73187 - Black Hills National Forest Advisory Board

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-05

    ... entry into the building. FOR FURTHER INFORMATION CONTACT: Scott Jacobson, Committee Coordinator, by... requests for oral comments must be sent to Scott Jacobson, Black Hills National Forest Supervisor's...

  14. Developing Restoration Planting Mixes for Active Ski Slopes: A Multi-Site Reference Community Approach

    NASA Astrophysics Data System (ADS)

    Burt, Jennifer Williamson

    2012-03-01

    Downhill ski areas occupy large expanses of mountainous lands where restoration of ecosystem function is of increasing importance and interest. Establishing diverse native plant communities on ski runs should enhance sediment and water retention, wildlife habitat, biodiversity and aesthetics. Because ski slopes are managed for recreation, ski slope revegetation mixes must consist of low-stature or herbaceous plants that can tolerate typical environmental conditions on ski slopes (high elevation, disturbed soils, open, steep slopes). The most appropriate reference communities for selecting ski slope revegetation species are thus successional, or seral plant communities in similar environments (i.e., other ski slopes). Using results from a broad-scale reference community analysis, I evaluated plant communities naturally occurring on ski slopes from 21 active and abandoned ski areas throughout the northern Sierra Nevada to identify native plant species suitable for use in ski slope restoration. I constructed a baseline planting palette of regionally appropriate plant species (for restoration of either newly created or already existing ski runs) that is functionally diverse and is likely to succeed across a broad range of environments. I also identify a more comprehensive list of species for more specialized planting mixes based on site-specific goals and particular environmental settings. Establishing seral plant communities may be an appropriate restoration goal for many other types of managed lands, including roadsides, firebreaks and utility rights-of-way. This study describes an ecological (and potentially cost-effective) approach to developing restoration planting palettes for such managed lands.

  15. Proposed Schedule for Fenton Hill Experiments

    SciTech Connect

    Albright, James N.; Brown, Donald W.

    1990-10-22

    To help in planning Fenton Hill experimental operations in concert with preparations for the Long-Term Flow Test (LTFT) next summer, the following schedule is proposed. This schedule fits some of the realities of the next few months, including the Laboratory closure during the Holidays, the seismic monitoring tests in Roswell, and the difficulties of operating during the winter months. Whenever possible, cyclic pumping operations during the colder months will be scheduled so that the pump will be on during the late evening and early morning hours to prevent freezeup.

  16. RYAN HILL ROADLESS AREA, NEW MEXICO.

    USGS Publications Warehouse

    Maxwell, C.H.; Ellis, C.E.

    1984-01-01

    On the basis of a geochemical survey, the Ryan Hill Roadless Area, now the Langmuir Research Site in New Mexico has both probable and substantiated resource potential for manganese deposits. The nature of the geologic terrane holds little likelihood for the occurrence of organic fuels. Additional geochemical studies of the manganese vein systems are desirable to better delineate the resource potential; mineralogical and metallurgical studies are needed to determine recoverability of potentially important byproducts, including tungsten and cobalt. Drilling into the vein system at depth would be required to test the continuity of the manganese deposits and evaluate the resource potential of the area for deeply buried base- and precious-metal resources.

  17. Spirit's View of 'Columbia Hills' (3-D)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site] Figure 1

    [figure removed for brevity, see original site] Figure 2

    NASA's Mars Exploration Rover Spirit looked up at the 'Columbia Hills' from its location on the 265th martian day, or sol, of its mission (Sept. 30, 2004) and captured this 3-D view. This cropped mosaic image, presented here in a cylindrical-perspective projection with geometric seam correction, was taken by the rover's navigation camera.

    Figure 1 is the left-eye view of a stereo pair and Figure 2 is the right-eye view of a stereo pair.

  18. Modeling slope failure by the 3D discrete element method: A case study of the dip slope at the Huafan University campus in northern Taiwan

    NASA Astrophysics Data System (ADS)

    Tseng, C. H.; Chan, Y. C.; Jeng, C. J.; Hsieh, Y. C.

    2015-12-01

    Slope failure is a widely observed phenomenon in hill and mountainous areas in Taiwan, which is characterized by high erosion rates (up to 60 mm/yr) due to its climatic and geographical conditions. Slope failure events easily occur after intense rainfall, especially resulting from typhoons and accordingly cause a great loss of human lives and property. At the northern end of the Western Foothill belt in northern Taiwan, Huafan University campus (121.692448˚ E, 24.980724˚ N ) is founded on a dip slope, ~20˚ toward southwest, being composed of early Miocene alternations of sandstone and shale. Data from continuous monitoring over the years by means of inclinometers and groundwater gauges reveal that creep of 6-10 mm of the slope occurred when precipitation exceeded 300 mm during typhoons' striking. In addition, extension cracks on the ground are also found within and on the edge of the campus. Furthermore, potential slip surfaces are detected shown by rock cores to exist 10 and 30 m in depth as well. To understand the kinematic behaviors of the rock slope failure beneath the university campus, a 3D discrete element mothed is applied in this study. Results of the modeling indicate that creeping is the primary behavior pattern when the friction coefficient reduces owing to rise of groundwater during rainstorms. However, rapid slip may take place under influences of earthquake with large magnitude. Suggestions for preventing the slope creep are to construct catchpits to drainage runoff and lower the groundwater table and ground anchors through the slip surfaces to stabilize the slide blocks.

  19. Vertical deformation along the Indio Hills, San Andreas Fault, California

    NASA Astrophysics Data System (ADS)

    Scharer, K. M.; Blisniuk, K.; Sharp, W. D.; Williams, P. L.; Johnson, K.

    2014-12-01

    Halfway between the Salton Sea and San Gorgonio Pass, the southernmost San Andreas Fault (SAF) bifurcates into the Mission Creek and Banning strands. These strands bound the Indio Hills (IH), and mark the first of a series of left-stepping branches that define the transpressional, southern Big Bend of the SAF. Between the fault strands, the Quaternary Ocotillo Formation is deformed with fold axis orientations consistent with dextral shear; structurally the IH are synclinal in the east, transitioning to a complex antiform with increased uplift suggested by exhumation of Tertiary units in the west. We report new long- and short-term erosion rates across the IH and uplift rates on the Banning strand, and we evaluate these measurements in terms of slip rates across the fault system and structural deformation within the IH. Two methods of catchment-averaged erosion rates provide minimum rates yield similar results, (0.08 to 0.34 mm/yr) across 6 catchments. The long-term rates are calculated from eroded volumes estimated from a 10-m DEM surface enveloping the Indio Hills and assume that all folding and uplift initiated ca. 500ka (the 750 ka Bishop ash is uplifted and warped within the IH). The short-term rates, determined from 10Be dating of alluvial sediments, increase gradually to the northwest. Similarity of the rates suggests steady state uplift over the history of the fold; ongoing structural analysis and dating needed to constrain the maximum rates will test this possibility. The new uplift rate for the Banning strand at the east end of the IH is determined from a 60 pts/m^2 DEM produced by structure from motion photogrammetry and U-series ages and cosmogenic dates that provide an age range of 20-76ka for a fan vertically offset by ~2.5 m. The resulting uplift rate on the fault (0.03-0.125 mm/yr) overlaps with the short-term catchment-averaged erosion rate for this location (0.08 mm/yr). Consequently, we interpret that vertical strain is partitioned onto both the

  20. Geometry and significance of stacked gullies on the northern California slope

    USGS Publications Warehouse

    Field, M.E.; Gardner, J.V.; Prior, D.B.

    1999-01-01

    Recent geophysical surveys off northern California reveal patterns of gullies on the sea floor and preserved within continental-slope deposits that represent both erosional and aggradational processes. These surveys, conducted as part of the STRATAFORM project, combined multibeam bathymetry and backscatter with high-resolution seismic profiles. These data provide a new basis for evaluating gully morphology, distribution, and their significance to slope sedimentation and evolution. The continental margin off northern California exhibits an upper slope that has undergone both progradation and aggradation. The slope surface, which dips at <2??to 4.0??, contains a set of straight, evenly spaced, and parallel to sub-parallel gullies that begin at the 380-m isobath and extend onto the Eel and Klamath plateaus and into Trinity Canyon. The surface gullies are typically 100-m wide or more and only 1-2 m deep. The gullied slope is underlain by a sedimentary sequence that contains abundant buried gullies to subsurface depths of over 150 m. Although some of the buried gullies are distinctly erosional, most are part of the aggradational pattern responsible for the overall growth of the slope. The latest phase of gully erosion is marked by a gullied surface lying <20 m below the present-day sea floor. These erosional gullies locally truncate individual reflectors, have small depositional levees, and exhibit greater relief than do overlying gullies exposed on the sea floor. The older subsurface gullies document a period of widespread, but minor, erosion and downslope transport, presumably from a large, proximal sediment source. The cycles of downcutting and gully excavation are a minor part of the stratigraphic section, and are likely related to the combined influence of lower sea levels and higher sediment yields. During aggradation of the slope depositional sequences, sediment was draped over the gully features, producing sediment layers that mimic the underlying gully form

  1. Vegetation and wildfire controls on sediment yield in bedrock landscapes

    NASA Astrophysics Data System (ADS)

    Dibiase, Roman A.; Lamb, Michael P.

    2013-03-01

    rocky landscapes commonly exhibit high sediment yields and are especially sensitive to climate, tectonics, and wildfire. Predicting landscape response to these perturbations demands a quantitative understanding of erosion processes. However, existing models for hillslope sediment production and transport do not apply to landscapes with patchy soil and slopes that exceed the angle for sediment stability. Here we present field measurements in southern California, USA, which indicate that sediment storage on steep slopes is enabled by vegetation that traps sediment upslope. We find that the storage capacity of unburned vegetation dams follows a geometric scaling model with a cubic dependence on effective plant width and an inverse dependence on local slope. Measured sediment volumes behind burned vegetation dams indicate a loss of at least 75% relative to unburned dams, and when expanded to the catchment scale, our measurements match records of postfire sediment yield from nearby retention basins. Contrary to existing models, our observations indicate that wildfire-induced sediment yield is driven by transient storage and release of sediment by vegetation dams, rather than increased bedrock-to-soil conversion rates. Without a feedback between soil production and wildfire, fire may play little role in long-term landscape evolution, and increasing fire frequency in response to climate change may not result in heightened sedimentation hazards due to supply limitations.

  2. Postglacial sedimentary record of the Southern California continental shelf and slope, Point Conception to Dana Point

    USGS Publications Warehouse

    Sommerfield, C.K.; Lee, H.J.; Normark, W.R.

    2009-01-01

    Sedimentary strata on the Southern California shelf and slope (Point Conception to Dana Point) display patterns and rates of sediment accumulation that convey information on sea-level inundation, sediment supply, and oceanic transport processes following the Last Glacial Maximum. In Santa Monica Bay and San Pedro Bay, postglacial transgression is recorded in shelf deposits by wave-ravinement surfaces dated at 13-11 ka and an upsection transition from coastal to shallow-marine sediment facies. Depositional conditions analogous to the modern environment were established in the bays by 8-9 ka. On the continental slope, transgression is evidenced in places by an increase in sediment grain size and accumulation rate ca. 15-10 ka, a consequence of coastal ravinement and downslope resedimentation, perhaps in conjunction with climatic increases in fluvial sediment delivery. Grain sizes and accumulation rates then decreased after 12-10 ka when the shelf flooded and backfilled under rising sea level. The Santa Barbara coastal cell contains the largest mass of postglacial sediment at 32-42 ?? 109 metric tons, most of which occurs between offshore Santa Barbara and Hueneme Canyon. The San Pedro cell contains the second largest quantity of sediment, 8-11 ?? 109 metric tons, much of which is present on the eastern Palos Verdes and outer San Pedro shelves. By comparison, the mass of sediment sequestered within the Santa Monica cell is smaller at ??6-8 ?? 109 metric tons. The postglacial sediment mass distribution among coastal cells reflects the size of local fluvial sediment sources, whereas intracell accumulation patterns reflect antecedent bathymetric features conducive for sediment bypass or trapping. ?? 2009 The Geological Society of America.

  3. Mid-Proterozoic detrital zircons and the depositional history of the Jack Hills (Narryer Gneiss Complex, Western Australia)

    NASA Astrophysics Data System (ADS)

    Bell, E. A.; Harrison, T. M.; Mojzsis, S. J.

    2012-12-01

    Quartz-biotite schists ("metaconglomerates" s.l.) in the Jack Hills outcrops of the Narryer Terrane of Western Australia host detrital >4 Ga zircons. These rocks are presumed to have been deposited at about 3 Ga and subsequently experienced metamorphism and granite intrusion at 2.45-2.6 Ga. Protoliths of the oldest detrital zircon population (>3.8 Ga) have not yet been identified, and the post-2.6 Ga history of the Jack Hills remains murky. Rare metavolcanic units are documented at ca. 1.8-1.9 Ga. Some metasediments near the Hadean zircon "discovery" site that are apparently young enough to have incorporated mid-Proterozoic detrital zircons are evidence of further geologic activity, although it is possible that these rocks were tectonically juxtaposed later. To further resolve the Proterozoic history of the Jack Hills, we report U-Pb age data for 60 detrital zircons extracted from two quartzites from the eastern Jack Hills (~50 km distant from the "discovery" site of Hadean zircons); in this sample suite 26 concordant zircons range in age from 0.168-3.49 Ga, with an age peak at ca. 2.6 Ga and a scattering of ages from 1.06-2.0 Ga. Zircon sources <1.8 Ga have not so far been identified in the Narryer Terrane and may point to far-field sediment transport. Several ca. 1.07 Ga zircons may derive from the Warakurna Large Igneous Province of the same age, which extends through much of central and Western Australia. One concordant zircon with a 206Pb/238U age of 0.166±6 Ga displays a patchy internal texture indicative of alteration; all other concordant grains are >1.06 Ga. Only 2 concordant zircons display ages >3 Ga, unlike the dominant mid-Archean signature from other reported Proterozoic sediments in the Jack Hills. All told, these quartzites display a significantly different provenance than other previously studied units from the terrane, with decreased importance of mid-Archean zircon sources and significantly younger (<1.06 Ga) ages of sedimentation than

  4. A global and regional stochastic analysis of near-ridge Abyssal Hill morphology

    NASA Astrophysics Data System (ADS)

    Goff, John A.

    1991-12-01

    This paper presents the results of a global and regional stochastic analysis of near-ridge abyssal hill morphology. The analysis includes the use of Sea Beam data for the estimation of stochastic parameters up to order 4. These parameters provide important quantitative physical information regarding abyssal hills, including their rms height, azimuthal orientation, characteristic width, aspect ratio, Hausdorff dimension, skewness, tilt, and peakiness. The global data set consists of 64 Sea Beam swaths near the Rivera, Cocos, and Nazca spreading sections of the East Pacific Rise, the Mid-Atlantic Ridge, and the Central Indian Ridge. In one form of analysis, the parameters are averaged among spreading rate bins. Each of the spreading rate subsets can be identified as unique from the others in at least one aspect The slowest spreading rate subset (Mid-Atlantic data) exhibit the largest scales (rms height and characteristic width and length) of abyssal hills. These parameters generally decrease as spreading rate increases up to the fast spreading rate data (Pacific-Cocos) but increase going from fast to very fast (Pacific-Nazca) spreading rate data. This indicates some complexity in the relationship between spreading rate and abyssal hill morphology. The plan view aspect ratio is nearly twice as large for the fast spreading rate data than for any of the other subsets and is smallest for the very fast spreading rate data. The fractal dimension is nearly identical for all spreading rate subsets. The vertical skewness is positive for the slow and medium spreading rate data, indicating larger peaks than troughs, and negative for the fast spreading rate data, indicating larger troughs than peaks. The kurtosis, or peakiness is everywhere larger than the Gaussian value of 3 and tends to be larger in the Atlantic than the Pacific. The tilting parameter provides substantial evidence indicating steeper inward facing slopes in the medium and fast spreading rate data, but only

  5. Inclinometer monitoring system for stability analysis: the western slope of the Bełchatów field case study

    NASA Astrophysics Data System (ADS)

    Cała, Marek; Jakóbczyk, Joanna; Cyran, Katarzyna

    2016-06-01

    The geological structure of the Bełchatów area is very complicated as a result of tectonic and sedimentation processes. The long-term exploitation of the Bełchatów field influenced the development of horizontal displacements. The variety of factors that have impact on the Bełchatów western slope stability conditions, forced the necessity of complex geotechnical monitoring. The geotechnical monitoring of the western slope was carried out with the use of slope inclinometers. From 2005 to 2013 fourteen slope inclinometers were installed, however, currently seven of them are in operation. The present analysis depicts inclinometers situated in the north part of the western slope, for which the largest deformations were registered. The results revealed that the horizontal displacements and formation of slip surfaces are related to complicated geological structure and intensive tectonic deformations in the area. Therefore, the influence of exploitation marked by changes in slope geometry was also noticeable.

  6. Manifestations of hydrothermal discharge from young abyssal hills on the fast-spreading East Pacific Rise flank

    NASA Astrophysics Data System (ADS)

    Haymon, Rachel M.; MacDonald, Ken C.; Benjamin, Sara B.; Ehrhardt, Christopher J.

    2005-02-01

    Spectacular black smokers along the mid-ocean-ridge crest represent a small fraction of total hydrothermal heat loss from ocean lithosphere. Previous models of measured heat flow suggest that 40% 50% of oceanic hydrothermal heat and fluid flux is from young seafloor (0.1 5 Ma) on mid-ocean-ridge flanks. Despite evidence that ridge-flank hydrothermal flux affects crustal properties, ocean chemistry, and the deep-sea biosphere, few ridge-flank vent sites have been discovered. We describe the first known seafloor expressions of hydrothermal discharge from tectonically formed abyssal hills flanking a fast-spreading ridge. Seafloor manifestations of fluid venting from two young East Pacific Rise abyssal hills (0.1 Ma at 10°20‧N, 103°33.2‧W; 0.5 Ma at 9°27‧N, 104°32.3‧W) include fault-scarp hydrothermal mineralization and macrofauna; fault-scarp flocculations containing hyperthermophilic microbes; and hilltop sediment mounds and craters possibly created by fluid expulsion. These visible features can be exploited for hydrothermal exploration of the vast abyssal hill terrain flanking the mid-ocean ridge and for access to the subseafloor biosphere. Petrologic evidence suggests that abyssal hills undergo repeated episodes of transitory fluid discharge, possibly linked to seismic events, and that fluid exit temperatures can be briefly high enough to transport copper (≥250 °C).

  7. Aquatic sediments

    SciTech Connect

    Bonner, J.S.; Autenrieth, R.L.; Schreiber, L. )

    1990-06-01

    The authors present a literature review concerning sediment properties, interactions, and conditions. Topics of discussion include the following: biological activity and toxicity; nutrients; metals; organic compounds; dredging; radionuclides; oxygen demand and organic carbon; mathematical modeling; sediment transport and suspension; and paleolimnology.

  8. Geology and potential hazards of the continental slope between Lindenkohl and South Toms canyons, offshore Mid-Atlantic United States

    USGS Publications Warehouse

    Robb, James M.; Hampson, John C.; Kirby, John R.; Twichell, David C.

    1981-01-01

    Because sediment instability, or slumping, has been identified as a potential hazard to petroleum development of the east-coast Continental Slope, the U.S. Geological Survey, in cooperation with the U.S. Bureau of Land Management, began a detailed study of a segment of the Continental Slope between Lindenkohl and South Toms Canyons off New Jersey. This 40-km x 35-km area was chosen for study because it lies within the area of high interest for petroleum development (Lease sales 49 and 59), and because it includes several wells which provide stratigraphic control. This report discusses the results of geologic mapping, using seismic-reflection data acquired in 1978 and 1979. Some initial results from more recently acquired data are included. The Continental Slope in the study area has a complex surface with ridges, canyons, and valleys. Three slump or slide features were observed in the heads and on the walls of canyons and valleys, and two slides were identified on an intercanyon area. The identified slumps or slides are found in Quaternary sediments and total about 1.3 percent of the Continental Slope area mapped. The slope is generally mantled by less than 2 m of Holocene sediments. Pleistocene sediment (primarily silty clay) is about 450 m thick at the top of the slope and thins to nearly zero or is absent on much of the mid and lower slope, where sediments of Miocene to Eocene age are exposed. Ridges on the midslope (water depths of 800-1,500 m) and parts of the lowr slope (1,500-2,150 m) result primarily from Pleistocene and older deposition. The intervening valleys show evidence of erosion along the deepest parts of their courses. Mid-range sidescan-sonar data show evidence that processes of bottom-current erosion and downcanyon transport of material may be active in the present day. However, major features of the sea floor appear to be unchanged since late-Pleistocene time.

  9. Mycorrhizal aspects in slope stabilisation

    NASA Astrophysics Data System (ADS)

    Graf, Frank

    2016-04-01

    In order to re-colonise and stabilise slopes affected by superficial soil failure with plants essential requirements have to be met: the plants must grow the plants must survive sustainably plant succession must start and continuously develop These requirements, however, are anything but easy given, particularly under the often hostile environmental conditions dominating on bare and steep slopes. Mycorrhizal fungi, the symbiotic partners of almost all plants used in eco-engineering, are said to improve the plants' ability to overcome periods governed by strongly (growth) limiting factors. Subsequently, results of investigations are presented of mycorrhizal effects on different plant and soil functions related to eco-engineering in general and soil and slope stabilisation in particular. Generally, inoculation yielded higher biomass of the host plants above as well as below ground. Furthermore, the survival rate was higher for mycorrhized compared to non-mycorrhized plants, particularly under extreme environmental conditions. However, the scale of the mycorrhizal impact may be species specific of both the plant host as well as the fungal partner(s) and often becomes evident only after a certain time lag. Depending on the plant-fungus combination the root length per soil volume was found to be between 0 and 2.5 times higher for inoculated compared to non-inoculated specimens. On an alpine graded ski slope the survival of inoculated compared to non-treated Salix herbacea cuttings was significant after one vegetation period only for one of the three added mycorrhizal fungus species. However, after three years all of the inoculated plantlets performed significantly better than the non-inoculated controls. The analysis of the potential for producing and stabilising soil aggregates of five different ectomycorrhizal fungi showed high variation and, for the species Inocybe lacera, no significant difference compared to untreated soil. Furthermore, inoculation of Salix

  10. New type of hill-top inflation

    NASA Astrophysics Data System (ADS)

    Barvinsky, A. O.; Kamenshchik, A. Yu.; Nesterov, D. V.

    2016-01-01

    We suggest a new type of hill-top inflation originating from the initial conditions in the form of the microcanonical density matrix for the cosmological model with a large number of quantum fields conformally coupled to gravity. Initial conditions for inflation are set up by cosmological instantons describing underbarrier oscillations in the vicinity of the inflaton potential maximum. These periodic oscillations of the inflaton field and cosmological scale factor are obtained within the approximation of two coupled oscillators subject to the slow roll regime in the Euclidean time. This regime is characterized by rapid oscillations of the scale factor on the background of a slowly varying inflaton, which guarantees smallness of slow roll parameters epsilon and η of the following inflation stage. A hill-like shape of the inflaton potential is shown to be generated by logarithmic loop corrections to the tree-level asymptotically shift-invariant potential in the non-minimal Higgs inflation model and R2-gravity. The solution to the problem of hierarchy between the Planckian scale and the inflation scale is discussed within the concept of conformal higher spin fields, which also suggests the mechanism bringing the model below the gravitational cutoff and, thus, protecting it from large graviton loop corrections.

  11. Spirit's Express Route to 'Columbia Hills'

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This map illustrates the Mars Exploration Rover Spirit's position as of sol 112 (April 26, 2004), near the crater called 'Missoula.' Like a train on a tight schedule, Spirit will make regular stops along the way to its ultimate destination, the 'Columbia Hills.' At each stop, or 'station,' the rover will briefly analyze the area's rocks and soils. Each tick mark on the rover's route represents one sol's worth of travel, or about 60 to 70 meters (200 to 230 feet). Rover planners estimate that Spirit will reach the hills around mid-June. Presently, the rover is stopped at a site called 'Plains Station.'

    The color thermal data show how well different surface features hold onto heat. Red indicates warmth; blue indicates coolness. Areas with higher temperatures are more likely to be rocky, as rocks absorb heat. Lower temperatures denote small particles and fewer rocks. During its traverse, Spirit will document the causes of these temperature variations.

    The map comprises data from the camera on NASA's Mars Global Surveyor orbiter and the thermal emission imaging system on NASA's Mars Odyssey orbiter.

  12. Spirit's Express Route to 'Columbia Hills'

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This map illustrates the Mars Exploration Rover Spirit's position as of sol 112 (April 26, 2004), near the crater called 'Missoula.' Like a train on a tight schedule, Spirit will make regular stops along the way to its ultimate destination, the 'Columbia Hills.' At each stop, or 'station,' the rover will briefly analyze the area's rocks and soils. Each tick mark on the rover's route represents one sol's worth of travel, or about 60 to 70 meters (200 to 230 feet). Rover planners estimate that Spirit will reach the hills around mid-June. Presently, the rover is stopped at a site called 'Plains Station.'

    The color thermal data show how well different surface features hold onto heat. Red indicates a higher thermal inertia associated with rocky terrain (cooler in the day, warmer at night); blue indicates a lower thermal inertia associated with smaller particles and fewer rocks (warmer at night, cooler in the day). During its traverse, Spirit will document the causes of these thermal variations.

    The map comprises data from the camera on NASA's Mars Global Surveyor orbiter and the thermal emission imaging system on NASA's Mars Odyssey orbiter.

  13. Hill crossing during preheating after hilltop inflation

    NASA Astrophysics Data System (ADS)

    Antusch, Stefan; Nolde, David; Orani, Stefano

    2015-06-01

    In ``hilltop inflation'', inflation takes place when the inflaton field slowly rolls from close to a maximum of its potential (i.e. the ``hilltop'') towards its minimum. When the inflaton potential is associated with a phase transition, possible topological defects produced during this phase transition, such as domain walls, are efficiently diluted during inflation. It is typically assumed that they also do not reform after inflation, i.e. that the inflaton field stays on its side of the ``hill'', finally performing damped oscillations around the minimum of the potential. In this paper we study the linear and the non-linear phases of preheating after hilltop inflation. We find that the fluctuations of the inflaton field during the tachyonic oscillation phase grow strong enough to allow the inflaton field to form regions in position space where it crosses ``over the top of the hill'' towards the ``wrong vacuum''. We investigate the formation and behaviour of these overshooting regions using lattice simulations: rather than durable domain walls, these regions form oscillon-like structures (i.e. localized bubbles that oscillate between the two vacua) which should be included in a careful study of preheating in hilltop inflation.

  14. New type of hill-top inflation

    SciTech Connect

    Barvinsky, A.O.; Nesterov, D.V.; Kamenshchik, A.Yu. E-mail: Alexander.Kamenshchik@bo.infn.it

    2016-01-01

    We suggest a new type of hill-top inflation originating from the initial conditions in the form of the microcanonical density matrix for the cosmological model with a large number of quantum fields conformally coupled to gravity. Initial conditions for inflation are set up by cosmological instantons describing underbarrier oscillations in the vicinity of the inflaton potential maximum. These periodic oscillations of the inflaton field and cosmological scale factor are obtained within the approximation of two coupled oscillators subject to the slow roll regime in the Euclidean time. This regime is characterized by rapid oscillations of the scale factor on the background of a slowly varying inflaton, which guarantees smallness of slow roll parameters ε and η of the following inflation stage. A hill-like shape of the inflaton potential is shown to be generated by logarithmic loop corrections to the tree-level asymptotically shift-invariant potential in the non-minimal Higgs inflation model and R{sup 2}-gravity. The solution to the problem of hierarchy between the Planckian scale and the inflation scale is discussed within the concept of conformal higher spin fields, which also suggests the mechanism bringing the model below the gravitational cutoff and, thus, protecting it from large graviton loop corrections.

  15. The Influence of Shales on Slope Instability

    NASA Astrophysics Data System (ADS)

    Stead, Doug

    2016-02-01

    Shales play a major role in the stability of slopes, both natural and engineered. This paper attempts to provide a review of the state-of-the-art in shale slope stability. The complexities of shale terminology and classification are first reviewed followed by a brief discussion of the important physical and mechanical properties of relevance to shale slope stability. The varied mechanisms of shale slope stability are outlined and their importance highlighted by reference to international shale slope failures. Stability analysis and modelling of anisotropic rock slope masses are briefly discussed and the potential role of brittle rock fracture and damage highlighted. A short review of shale slopes in open pits is presented.

  16. Reconstruction of multistage massive rock slope failure: Polymethodical approach in Lake Oeschinen (CH)

    NASA Astrophysics Data System (ADS)

    Knapp, Sibylle; Gilli, Adrian; Anselmetti, Flavio S.; Hajdas, Irka

    2016-04-01

    Lateglacial and Holocene rock-slope failures occur often as multistage failures where paraglacial adjustment and stress adaptation are hypothesised to control stages of detachment. However, we have only limited datasets to reconstruct detailed stages of large multistage rock-slope failures, and still aim at improving our models in terms of geohazard assessment. Here we use lake sediments, well-established for paleoclimate and paleoseismological reconstruction, with a focus on the reconstruction of rock-slope failures. We present a unique inventory from Lake Oeschinen (Bernese Alps, Switzerland) covering about 2.4 kyrs of rock-slope failure history. The lake sediments have been analysed using sediment-core analysis, radiocarbon dating and seismic-to-core and core-to-core correlations, and these were linked to historical and meteorological records. The results imply that the lake is significantly younger than the ~9 kyrs old Kandersteg rock avalanche (Tinner et al., 2005) and shows multiple rock-slope failures, two of which could be C14-dated. Several events detached from the same area potentially initiated by prehistoric earthquakes (Monecke et al., 2006) and later from stress relaxation processes. The data imply unexpected short recurrence rates that can be related to certain detachment scarps and also help to understand the generation of a historical lake-outburst flood. Here we show how polymethodical analysis of lake sediments can help to decipher massive multistage rock-slope failure. References Monecke, K., Anselmetti, F.S., Becker, A., Schnellmann, M., Sturm, M., Giardini, D., 2006. Earthquake-induced deformation structures in lake deposits: A Late Pleistocene to Holocene paleoseismic record for Central Switzerland. Eclogae Geologicae Helvetiae, 99(3), 343-362. Tinner, W., Kaltenrieder, P., Soom, M., Zwahlen, P., Schmidhalter, M., Boschetti, A., Schlüchter, C., 2005. Der nacheiszeitliche Bergsturz im Kandertal (Schweiz): Alter und Auswirkungen auf die

  17. Phreatic flow on sloping soil layers from a finite source: An analytical solution

    SciTech Connect

    Filley, T.H.

    1991-09-01

    Sloping clay layers beneath percolation ponds can cause infiltrating wastewater to pond and move in directions not predicted by vertical infiltration equations. This report presents a method for estimating the potential of wastewater from percolation sumps located over sloping clay layers to interact with nearby groundwater resources. The analytical solution developed is for steady-state conditions and includes a procedure to estimate the time needed to reach steady state. The fundamental assumption used in the mathematical development requires that elevation-head gradients be much larger than pressure-head gradients. A method for testing the validity of this assumption is also included. An example calculation was performed for percolation sumps on the Naval Petroleum Reserve No. 1 in Elk Hills, California. That analysis showed that, under the assumptions used, the sumps may have enabled oil field wastewater to reach groundwater resources within the adjacent San Joaquin Valley. 9 refs., 10 figs.

  18. Rare earth elements tracing the soil erosion processes on slope surface under natural rainfall.

    PubMed

    Zhu, Mingyong; Tan, Shuduan; Dang, Haishan; Zhang, Quanfa

    2011-12-01

    A field experiment using rare earth elements (REEs) as tracers was conducted to investigate soil erosion processes on slope surfaces during rainfall events. A plot of 10m×2m×0.16m with a gradient of 20° (36.4%) was established and the plot was divided into two layers and four segments. Various REE tracers were applied to the different layers and segments to determine sediment dynamics under natural rainfall. Results indicated that sheet erosion accounted for more than 90% of total erosion when the rainfall amount and density was not large enough to generate concentrated flows. Sediment source changed in different sections on the slope surface, and the primary sediment source area tended to move upslope as erosion progressed. In rill erosion, sediment discharge mainly originated from the toe-slope and moved upwards as erosion intensified. The results obtained from this study suggest that multi-REE tracer technique is valuable in understanding the erosion processes and determining sediment sources. PMID:21839555

  19. Rare earth elements tracing the soil erosion processes on slope surface under natural rainfall.

    PubMed

    Zhu, Mingyong; Tan, Shuduan; Dang, Haishan; Zhang, Quanfa

    2011-12-01

    A field experiment using rare earth elements (REEs) as tracers was conducted to investigate soil erosion processes on slope surfaces during rainfall events. A plot of 10m×2m×0.16m with a gradient of 20° (36.4%) was established and the plot was divided into two layers and four segments. Various REE tracers were applied to the different layers and segments to determine sediment dynamics under natural rainfall. Results indicated that sheet erosion accounted for more than 90% of total erosion when the rainfall amount and density was not large enough to generate concentrated flows. Sediment source changed in different sections on the slope surface, and the primary sediment source area tended to move upslope as erosion progressed. In rill erosion, sediment discharge mainly originated from the toe-slope and moved upwards as erosion intensified. The results obtained from this study suggest that multi-REE tracer technique is valuable in understanding the erosion processes and determining sediment sources.

  20. Morphology, origin and evolution of Pleistocene submarine canyons, New Jersey continental slope

    NASA Astrophysics Data System (ADS)

    Bhatnagar, T.; Mountain, G. S.

    2015-12-01

    Submarine canyons serve as important conduits for transport of detrital sediments from nearshore and shelf environments to adjacent deep marine basins. However, the processes controlling the formation, maintenance, and fill of these sediment pathways are complex. This study presents an investigation of these systems at the New Jersey continental margin using a grid of high-resolution, 48-channel seismic reflection data collected in 1995 on the R/V Oceanus cruise Oc270 as a part of the STRATAFORM initiative. The aim is to shed new light on the origin and role of submarine canyons in Pleistocene sedimentation beneath the outer shelf and upper continental slope. Preliminary investigation of the Pleistocene interval reveals prominent unconformities tied to and dated with published studies at 7 sites drilled by ODP Legs 150 and 174A. The profiles of the continental slope unveil a series of abandoned and now buried submarine canyons that have influenced the development of modern canyons. Mapping these systems has revealed a range of canyon geometries, including U, V-shaped and flat-bottomed cross sections, each suggesting different histories. At least three types of seismic facies constitute the canyon fills: parallel onlap, interpreted as infilling by alternating coarser turbidites and finer hemipelagic sediments, chaotic infill, signifying structureless, massive debris flow deposition, and lateral accretion infill by both turbidity and bottom currents. Canyon formation and development appear to be strongly influenced by variations in sediment supply, grain size, and currents on the continental slope. One goal of our research is to establish if the canyons were initiated by failures at the base of the slope followed by upslope erosion, or by erosion at the shelf slope transition, and then downslope extension by erosive events. No single model accounts for all canyons. The history of these canyons may elucidate the extent to which the shelf was exposed during sea

  1. Slope Stability Problems and Back Analysis in Heavily Jointed Rock Mass: A Case Study from Manisa, Turkey

    NASA Astrophysics Data System (ADS)

    Akin, Mutluhan

    2013-03-01

    This paper presents a case study regarding slope stability problems and the remedial slope stabilization work executed during the construction of two reinforced concrete water storage tanks on a steep hill in Manisa, Turkey. Water storage tanks of different capacities were planned to be constructed, one under the other, on closely jointed and deformed shale and sandstone units. The tank on the upper elevation was constructed first and an approximately 20-m cut slope with two benches was excavated in front of this upper tank before the construction of the lower tank. The cut slope failed after a week and the failure threatened the stability of the upper water tank. In addition to re-sloping, a 15.6-m deep contiguous retaining pile wall without anchoring was built to support both the cut slope and the upper tank. Despite the construction of a retaining pile wall, a maximum of 10 mm of displacement was observed by inclinometer measurements due to the re-failure of the slope on the existing slip surface. Permanent stability was achieved after the placement of a granular fill buttress on the slope. Back analysis based on the non-linear (Hoek-Brown) failure criterion indicated that the geological strength index (GSI) value of the slope-forming material is around 21 and is compatible with the in situ-determined GSI value (24). The calculated normal-shear stress plots are also consistent with the Hoek-Brown failure envelope of the rock mass, indicating that the location of the sliding surface, GSI value estimated by back analysis, and the rock mass parameters are well defined. The long-term stability analysis illustrates a safe slope design after the placement of a permanent toe buttress.

  2. Origin and Distribution of the Post KPG Carbonate Debris Flow and Consequent Slope Readjustment in DeSoto Canyon, Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Umbarger, K.; Snedden, J.

    2015-12-01

    The induced seismicity from the Chicxulub impact crater has been postulated as thecatalyst for the dramatic alteration and movement of sediments in the Gulf of Mexico. Previousstudies have proposed the collapse of the continental margin in the Desoto Canyon region of theGulf of Mexico to be associated with the extraterrestrial impact, but provide limited evidence tosupport their claims. Seismic analysis of offshore two-dimensional (2D) seismic data, well logs,and biostratigraphic data provides insight into the Paleogene history of the carbonate marginslope failure and readjustment along the Florida escarpment. A slope's stability is dependent onthe slope material's shear strength, which resists slope failure, and the force of gravity, whichdrives slope failure. However, the slopes of carbonate platforms are seldom homogenous andreceive and lose sediment through the complex interplay of deposition, erosion, and dissolution.It is hypothesized the collapse of the Florida continental margin resulted in a layer of limestoneforming a steep slope due to its hardness producing a higher shear strength and angle of repose.When this is succeeded by the deposition of siliciclastic sediments a period of slope readjustmenttakes place. These finer and softer sediments are unable to assume the high slope angle of theunderlying carbonate sediments. This slope adjustment is continued throughout the Paleogene asthe out-of-grade slope of the Mass Transport Complex adjusts to reach equilibrium. The originand distribution of the post KPg carbonate debris flow in Desoto Canyon, Gulf of Mexico,elucidates the complexity of out-of-grade slopes readjusting to reach its ideal angle ofsedimentation.

  3. Service with Style: Corinne Hill--Denton Public Library, TX

    ERIC Educational Resources Information Center

    Library Journal, 2004

    2004-01-01

    Although a librarian for only eight years, Corinne Hill is already known in Dallas and Denton, TX, for turning dull, little-used branches into vibrant community centers. A stylish woman with a zest for shopping, Hill loves developing new collections and showing them off. She sees no reason why a library should not be as attractive as any good…

  4. Accounting for imperfect detection in Hill numbers for biodiversity studies

    USGS Publications Warehouse

    Broms, Kristin M.; Hooten, Mevin B.; Fitzpatrick, Ryan M.

    2015-01-01

    The occupancy-based Hill number estimators are always at their asymptotic values (i.e. as if an infinite number of samples have been taken for the study region), therefore making it easy to compare biodiversity between different assemblages. In addition, the Hill numbers are computed as derived quantities within a Bayesian hierarchical model, allowing for straightforward inference.

  5. View of sports field and Easter Hill at west side ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of sports field and Easter Hill at west side of project site. Looking west - Easter Hill Village, Bordered by South Twenty-sixth Street, South Twenty-eighth Street, Hinkley Avenue, Foothill Avenue & Corto Square, Richmond, Contra Costa County, CA

  6. View of sports field from Easter Hill looking at intersection ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of sports field from Easter Hill looking at intersection of South Twenty-Sixth Street and Foothill Avenue at left center rear. Buildings No. 36, 35, 25, 27, and 29, from left to right. Looking northeast - Easter Hill Village, Bordered by South Twenty-sixth Street, South Twenty-eighth Street, Hinkley Avenue, Foothill Avenue & Corto Square, Richmond, Contra Costa County, CA

  7. View of sports field and Easter Hill at west side ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of sports field and Easter Hill at west side of project site. Looking southwest - Easter Hill Village, Bordered by South Twenty-sixth Street, South Twenty-eighth Street, Hinkley Avenue, Foothill Avenue & Corto Square, Richmond, Contra Costa County, CA

  8. 78 FR 76100 - Black Hills National Forest Advisory Board

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-12-16

    ...; ] DEPARTMENT OF AGRICULTURE Forest Service Black Hills National Forest Advisory Board AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Black Hills National Forest Advisory Board (Board) will... Committee Act of 1972 (5 U.S.C. App. II), the Forest and Rangeland Renewable Resources Planning Act of...

  9. AmeriFlux US-Blk Black Hills

    SciTech Connect

    Meyers, Tilden

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-Blk Black Hills. Site Description - The Black Hills tower was established by the Institute for Atmospheric Studies of the South Dakota School of Mines and Technology.

  10. Is "Home" Still in the Hills? Staff Paper 153.

    ERIC Educational Resources Information Center

    Smith, Eldon D.

    Although there was expectation that the current recession would bring a new wave of Appalachian Kentuckians back to their homeland hills, as had previous recessions, no great "return to the hills" (or even to other areas of the state) has materialized. Unemployment insurance claims by people formerly employed in other states have not increased in…

  11. OVERVIEW OF GOLD HILL MILL, ROAD, AND WHITE PINE TALC ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    OVERVIEW OF GOLD HILL MILL, ROAD, AND WHITE PINE TALC MINE LOOKING EAST. THE OPENING TO THE TALC MINE IS IN THE DARK AREA AT CENTER LEFT EDGE. WARM SPRINGS CAMP IS OUT OF FRAME TO THE RIGHT. - Gold Hill Mill, Warm Spring Canyon Road, Death Valley Junction, Inyo County, CA

  12. VIEW TO SOUTHEAST TOWARD QUARTERMASTER BUILDINGS GROUP AND RESERVOIR HILL, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW TO SOUTHEAST TOWARD QUARTERMASTER BUILDINGS GROUP AND RESERVOIR HILL, FROM AMMUNITION (IGLOO) HILL. (Part 2 of a 3 view panorama; see also CA-2398-J-1 and CA-2398-16.) - Hamilton Field, East of Nave Drive, Novato, Marin County, CA

  13. "This Delightfull Garden": "Rabbit Hill" and the Pastoral Tradition.

    ERIC Educational Resources Information Center

    Jordan, Anne Devereaux

    1997-01-01

    Contends that Robert Lawson's children's book "Rabbit Hill" (1944) falls within the genre of pastoral literature, in the tradition of Edmund Spenser's "Faerie Queen." Examines the history of the genre and finds reasons for classifying Lawson's book as pastoral. Cites classic elements in "Rabbit Hill." Gives five questions for stimulating student…

  14. 83. GENERAL VIEW FROM NORTH END OF GUN HILL PLATFORM ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    83. GENERAL VIEW FROM NORTH END OF GUN HILL PLATFORM OF 3RD AVENUE EL SHOWING THE SOUTHBOUND TRACK APPROACH INTO GUN HILL STATION. 7TH AVENUE EXPRESS EL ABOVE. - Interborough Rapid Transit Company, Third Avenue Elevated Line, Borough of the Bronx, New York County, NY

  15. 78 FR 64471 - Black Hills National Forest Advisory Board

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-29

    ... Fifth Street, Custer, SD. Please call ahead to Scott Jacobson, ] Committee Management Officer, at 605...: Scott Jacobson, Committee Management Officer, Black Hills National Forest Supervisor's Office, 605-673... comments must be sent to Scott Jacobson, Supervisor's Office, Black Hills National Forest, 1019 North...

  16. 78 FR 59337 - Black Hills National Forest Advisory Board; Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-26

    ... Fifth Street, Custer, SD. Please call ahead to Scott Jacobson, ] Committee Management Officer, at 605...: Scott Jacobson, Committee Management Officer, Black Hills National Forest Supervisor's Office, 605-673... comments must be sent to Scott Jacobson, Supervisor's Office, Black Hills National Forest, 1019 North...

  17. 2. BUNKER HILL LEAD SMELTER. VIEW IS FROM CIA TO ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. BUNKER HILL LEAD SMELTER. VIEW IS FROM CIA TO THE SOUTH. IN FOREGROUND, PLANT DRY, SLAG FUMING PLANT, BLAST FURNACE, SMELTER OFFICE, LEAD AND SILVER REFINERIES ARE VISIBLE, L. TO R. HIGH VELOCITY FLUE LEADS FROM LOWER PLANT TO BAG HOUSE AND STACKS AT TOP OF SMELTING FACILITY. - Bunker Hill Lead Smelter, Bradley Rail Siding, Kellogg, Shoshone County, ID

  18. 3. BUNKER HILL LEAD SMELTER. VIEW IS FROM CIA TO ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. BUNKER HILL LEAD SMELTER. VIEW IS FROM CIA TO THE SOUTHWEST. BUILDINGS NOTED IN ID-29-2 APPEAR, IN ADDITION TO DRY ORE PLANT AND BONNOT COAL PULVERIZING EQUIPMENT BUILDING ON THE RIGHT. - Bunker Hill Lead Smelter, Bradley Rail Siding, Kellogg, Shoshone County, ID

  19. 1. BUNKER HILL LEAD SMELTER. VIEW IS FROM CENTRAL IMPOUNDMENT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. BUNKER HILL LEAD SMELTER. VIEW IS FROM CENTRAL IMPOUNDMENT AREA LOOKING SOUTH. PLANT DRY IS IN CENTER FOREGROUND, SLAG FUMING PLANT IS IN RIGHT FOREGROUND, AND BAG HOUSE IS IN RIGHT BACKGROUND. VARIOUS PLANT STACKS ARE ALSO VISIBLE. - Bunker Hill Lead Smelter, Bradley Rail Siding, Kellogg, Shoshone County, ID

  20. View of south boundary of Easter Hill project site for ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of south boundary of Easter Hill project site for right of way for Hoffman Boulevard. Buildings No. 11 and 14 at right in trees. Looking west - Easter Hill Village, Bordered by South Twenty-sixth Street, South Twenty-eighth Street, Hinkley Avenue, Foothill Avenue & Corto Square, Richmond, Contra Costa County, CA

  1. 77 FR 22755 - Black Hills National Forest Advisory Board

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-17

    ... approval of the Board's re-charter package submitted to the Secretary, U.S. Department of Agriculture...; ] DEPARTMENT OF AGRICULTURE Forest Service Black Hills National Forest Advisory Board AGENCY: USDA Forest Service. ACTION: Notice of cancellation of meetings of the Black Hills National Forest Advisory...

  2. VIEW LOOKING WEST TOWARD RESERVOIR HILL. THE SPRR HOTEL WAS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW LOOKING WEST TOWARD RESERVOIR HILL. THE SPRR HOTEL WAS LOCATED IN THE STRIPED AREA AT THE BOTTOM OF THE IMAGE, AND THE TRACK RAN BETWEEN THE HILL AND THE HOTEL. - Southern Pacific Railroad Water Settling Reservoir, Yuma Crossing, south bank of Colorado River at foot of Madison Avenue, Yuma, Yuma County, AZ

  3. 27 CFR 9.188 - Horse Heaven Hills.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Horse Heaven Hills. 9.188... Horse Heaven Hills. (a) Name. The name of the viticultural area described in this section is “Horse Heaven Hills”. For purposes of part 4 of this chapter, “Horse Heaven Hills” and “Horse Heaven” are...

  4. 27 CFR 9.162 - Sta. Rita Hills.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Sta. Rita Hills. 9.162.... Rita Hills. (a) Name. The name of the viticultural area described in this section is “Sta. Rita Hills”. For purposes of part 4 of this chapter, “Sta. Rita Hills” is a term of viticultural significance....

  5. 27 CFR 9.162 - Sta. Rita Hills.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Sta. Rita Hills. 9.162.... Rita Hills. (a) Name. The name of the viticultural area described in this section is “Sta. Rita Hills”. For purposes of part 4 of this chapter, “Sta. Rita Hills” is a term of viticultural significance....

  6. 27 CFR 9.162 - Sta. Rita Hills.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Sta. Rita Hills. 9.162.... Rita Hills. (a) Name. The name of the viticultural area described in this section is “Sta. Rita Hills”. For purposes of part 4 of this chapter, “Sta. Rita Hills” is a term of viticultural significance....

  7. Framework for North Slope Seminar II

    SciTech Connect

    Tailleur, I.L.

    1985-04-01

    This meeting focuses on a province with enormous potential for fuels and minerals. Oil reserves approach 10% of the total oil already produced in the rest of the country. Estimated coal resources could store a thousand times the 70-80 quads of energy the US uses every year. Potential yields of silver, lead, and zinc range from 10 to 100% of the amounts produced domestically since the middle of the 19th century. Prospects for copper are also large. The province is dominated by the east-trending Brooks Range, whose structures formed during the late Mesozoic Brookian orogeny and are now being shortened longitudinally. Flanking basins succeeded the uplift; the northern one is bounded by a passive continental margin. Early in the orogeny, a relatively thin early Paleozoic through Jurassic megasequence of clastic-wedge, carbonate, and siliceous sediments was telescoped into a fivefold stacking of allochthons and beneath allochthons of volcanic and mafic-ultramafic rocks. The greater than 500-km breadth of sialic crust that had underlain the allochthons disappeared. At about the same time, the Arctic ocean basin replaced the northern provenance. A mid-Paleozoic sialic source area on the opposite margin of the megasequence disappeared by the end of the Carboniferous and near the beginning of siliceous deposition. Basement beneath the North Slope part of the megasequence was created when the Devonian Ellesmerian orogeny added to the crust the late precambrian to early Paleozoic clastic, carbonate, and volcanic rocks of an older megasequence. The northern successor basin accumulated large amounts of coal. Truncation and sealing of potential reservoir rocks on replacement of the northern landmass led to huge pools of hydrocarbons. Late Paleozoic rocks in the lowest allochthon host stratabound base-metal deposits. A narrow belt of reportedly Devonian shallow-seated felsic rocks contain deposits of copper.

  8. Photogrammetric analysis of slope failures feeding the head of the Illgraben debris flow channel

    NASA Astrophysics Data System (ADS)

    Bennett, G. L.; Molnar, P.; Eisenbeiss, H.; McArdell, B. W.

    2012-04-01

    Our understanding of slope failure is restricted by a lack of inventories of sufficient size and directly measured volumes. We used digital photogrammetry to produce a multi-temporal record of erosion of a rock slope in the Illgraben. From this we extracted an inventory of ~2500 slope failures for 3 epochs of 6/7 years between 1986 and 2005 ranging over 6 orders of magnitude in volume. Through analysis of their magnitude-frequency, volume-area and depth-slope gradient relations we aimed to understand the characteristics of slope failure at the head of this active alpine debris-flow catchment. The slope failure volumes follow a characteristic magnitude-frequency distribution with a roll-over at 50m3 and a power-law tail between ~200m3 and 1.6x106m3 with an exponent of 1.65. We compared different methods to estimate the power law scaling exponent and found the maximum likelihood estimator to be the most accurate. Conversely, least squares regression on the probability density function consistently underestimated the exponent. Slope failure volume scales with failure area as a power law with an exponent of 1.1. This exponent is low for the bedrock nature of the slope in comparison with worldwide studies of bedrock and soil landslides and likely results from the highly fractured and incohesive nature of the quartzitic bedrock of the study slope. Comparing the results for different epochs we find that the magnitude-frequency and volume-area relationships are reasonably time-invariant demonstrating their general nature for the setting. We interpret the magnitude-frequency distribution of slope failure volumes as the result of two separate slope failure processes. Type (1) failures are frequent, small slides and slumps within the weathered layer of highly fractured rock and loose sediment. These make up the roll-over of the distribution. Type (2) failures are less frequent rockslides and rockfalls within the internal bedded and fractured slope along pre

  9. Quantification of Gravel Rural Road Sediment Production

    NASA Astrophysics Data System (ADS)

    Silliman, B. A.; Myers Toman, E.

    2014-12-01

    Unbound rural roads are thought to be one of the largest anthropogenic sources of sediment reaching stream channels in small watersheds. This sediment deposition can reduce water quality in the streams negatively impacting aquatic habitat as well as impacting municipal drinking water sources. These roads are thought to see an increase in construction and use in southeast Ohio due to the expansion of shale gas development in the region. This study set out to quantify the amount of sediment these rural roads are able to produce. A controlled rain event of 12.7 millimeters of rain over a half hour period was used to drive sediment production over a 0.03 kilometer section of gravel rural road. These 8 segments varied in many characteristics and produced from 2.0 to 8.4 kilograms of sediment per 0.03 kilometers of road with the average production over the 8 segments being 5.5 kilograms of sediment. Sediment production was not strongly correlated with road segment slope but traffic was found to increase sediment production from 1.1 to 3.9 times as much sediment after traffic use. These results will help inform watershed scale sediment budgeting, and inform best management practices for road maintenance and construction. This study also adds to the understanding of the impacts of rural road use and construction associated with the changing land use from agricultural to natural gas extraction.

  10. Comparisons of calculated and measured helicopter noise near instrument hill

    NASA Technical Reports Server (NTRS)

    Bass, Henry E.; You, Chulsoo

    1993-01-01

    The polar parabolic equation (POPE) method solves for the diffraction of sound by a curved surface including a realistic sound speed profile. POPE is outlined briefly to describe diffraction which propagates the field over a hill. Experimental data are compared with POPE predictions using the measured sound speed profile and ground impedance. Two trial cases are considered for the comparisons: the helicopter located at the base of the hill and far away from the base of the hill, respectively. The physical mechanisms for sound propagation over a hill are examined with and of POPE calculations and experimental data. The shedding of rays from the hillside gives an interference effect with a wave along the flat surface beyond the base of a hill.

  11. Decay of isolated hills and saddles on Si(001)

    NASA Astrophysics Data System (ADS)

    Kirschbaum, Pierre; Brendel, Lothar; Roos, Kelly R.; Horn-von Hoegen, Michael; Heringdorf, Frank-J. Meyer zu

    2016-08-01

    We discuss the high temperature decay of isolated hills and saddle points on Si(001). Using in situ dark-field imaging in low energy electron microscopy, we track the movement of individual steps during high temperature annealing. We find different temperature dependent decay rates for the top of the hill compared to a saddle point with low step density that is present in the vicinity of the hill. The decay rate of the hill is always higher than the decay rate at the saddle. The two rates converge with increasing temperature and become equal at temperatures above 1060 °C. We also report an alternating fast and low decay rate for the layer-by-layer decay of the hills. This surprising finding is independent of temperature and is explained by macroscopic strain in the sample.

  12. Seeing mountains in mole hills: geographical-slant perception

    NASA Technical Reports Server (NTRS)

    Proffitt, D. R.; Creem, S. H.; Zosh, W. D.; Kaiser, M. K. (Principal Investigator)

    2001-01-01

    When observers face directly toward the incline of a hill, their awareness of the slant of the hill is greatly overestimated, but motoric estimates are much more accurate. The present study examined whether similar results would be found when observers were allowed to view the side of a hill. Observers viewed the cross-sections of hills in real (Experiment 1) and virtual (Experiment 2) environments and estimated the inclines with verbal estimates, by adjusting the cross-section of a disk, and by adjusting a board with their unseen hand to match the inclines. We found that the results for cross-section viewing replicated those found when observers directly face the incline. Even though the angles of hills are directly evident when viewed from the side, slant perceptions are still grossly overestimated.

  13. Estimating the failure potential of a partially saturated slope from combined continuum and limit equilibrium modeling (Invited)

    NASA Astrophysics Data System (ADS)

    Borja, R. I.; White, J. A.; Liu, X.; Wu, W.

    2010-12-01

    Rainfall weakens an earth slope and triggers mass movement. Relevant triggering mechanisms are complex and include reduction of capillary pressure due to increased saturation and frictional drag on the sediment induced by fluid flow. Physics-based continuum models utilizing modern computational tools are useful for understanding the mechanisms of deformation in partially saturated slopes; however, they do not provide a scalar indicator called "factor of safety" that measures the potential of a given slope for mass movement. In the present work we employ sequential calculations consisting of a physics-based finite element modeling that couples solid deformation with fluid flow to quantify the stress and deformation fields in a steep hillside slope subjected to rainfall infiltration. This is followed by a limit equilibrium calculation based on the method of slices that evaluates the desired factor of safety. The field condition investigated is similar to the steep experimental catchment CB1 near Coos Bay, Oregon, which failed as a large debris flow from heavy rainfall. We find the pore pressure variation to be a strong link between the continuum and limit-equilibrium solutions: for the same pore pressure variation within the slope, the continuum and limit-equilibrium solutions consistently predicted the same scarp zone for a given slope. Material parameters such as the effective cohesion and friction angle of the sediment tend to influence the timing of failure, but not the failure mechanism itself. Slope topography and rainfall history impact the slope failure mechanism to a great extent.

  14. Carbonate slope and platform accumulations: Lower Florida Keys

    SciTech Connect

    Shinn, E.A.; Lidz, B.H.; Kindinger, J.L. ); Hine, A.C. )

    1990-05-01

    Approximately 500 km of high-resolution seismic-reflection data off the lower Florida Keys reveal (1) a linear reef and trough seaward of the more shallow platform margin reefs and (2) possible late Pleistocene to early Holocene reef and beach-dune deposits 80-100 m below sea level. The linear reef and sand-filled trough are an extension of a reef-and-trough system that extends more than 300 km along the southeast Florida reef tract. In the study area, the outer reef is shallow (-10 m at its top), has relief of up to 30 m, and is separated from the platform margin reef by a 0.5-km-wide, 30-m-deep sediment-filled trough. The outer reef trend is locally broken, and reefs vary in size. Farther north near Miami, the outer reef has lower relief, and the trough separating it from the platform margin is narrower. A 6-m-long rock core recovered from the crest of the outer reef trend in the lower Florida Keys, off Sand Key reef, reveals a Pleistocene massive coral facies that has a thin (< 1 m) Holocene reef veneer. Farther seaward, where the sea floor slopes into the Straits of Florida, thick (5-8 m) fringing-reef and barrier beach-dune deposits are buried beneath thin Holocene slope deposits 80-100 m below sea level. Beach-dune accumulations are distinguished from reef buildups by the presence of seaward and landward seismic reflections. Fringing-reef buildups, in contrast, are massive and lack reflectors. Both beach-dune and reef buildups are overlain by thin Holocene slope sediments. The beach-dune deposits are probably indicative of a paleoshoreline that existed between 9,000 and 15,000 yr ago.

  15. Evidence for Repeated Early Miocene Glaciation and the Cutting of Upper Taylor Valley from the Friis Hills, Antarctica

    NASA Astrophysics Data System (ADS)

    Lewis, A.; Ashworth, A. C.; Marchant, D. R.; Hemming, S. R.

    2009-12-01

    The Friis Hills, located at the head of Taylor Valley in the the McMurdo Dry Valleys, hold a sequence of stacked tills at least Early Miocene in age. Sedimentology, clast lithology and bedrock striations indicate these tills were deposited from wet-based glaciers that flowed southeastward down a shallow paleovalley toward the Ferrar trough. Interbedded paleosols, fluvial, and glaciolacustrine deposits register ice-free periods when the valley held small streams and ponds. Exceptionally well-preserved fossil biota suggests mild conditions during at least two of these interglacial episodes. Proglacial lacustrine deposits that include dropstones and debris flows mark the return of glacial conditions but fossil leaves and wood of Nothofagus suggest conditions during the initial phase of ice advance were also relatively mild. Geomorphic relationships show that major valley incision must have taken place after deposition of these sediments as the Friis Hills is today a flat-topped inselberg, about 5 km across, isolated from nearby topography by the deep glacial troughs of the Taylor Valley drainage. A second suite of tills, directly overlying the first, registers a reorganized glacial system with ice streaming eastward, roughly parallel to Taylor Valley. Like the first, these tills were deposited during repeated ice advances but glaciers never fully inundated the Friis Hills and ice-free periods are marked by onl