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Sample records for hill slope sediment

  1. Hill-slope instability and sediment delivery: discerning geomorphological intensity from a lake sediment sequence.

    NASA Astrophysics Data System (ADS)

    Chiverrell, R. C.; Shen, Zhixiong; Bloemendal, J.

    2009-04-01

    An extensive database of radiocarbon dated alluvial fan and hill-slope gully systems identifies three phases of extensive hill-slope gullying after 2200, between 1250 and 700, and after 500 cal. BP in the uplands of northwest England. Regional pollen records reveal co-incident phases of increased human activity in these uplands, with small scale temporary clearances during the late Bronze Age / early Iron Age and more substantial clearances during the late Iron Age and Romano-British times (2300-1500 cal. BP), and later more substantial woodland clearances from c.1200-900 cal. BP, after which there has been little woodland recovery. This temporal pattern is similar to that in the geomorphology, and suggests that human activity is a critical factor mediating the late Holocene geomorphological record. To assess the linkages between geomorphic activity and adjacent lake basins a record of sediment delivery from a catchment to lake basin is provided by two c. 5.8 m long sediment cores from Crummock Water (NW England). A robust chronology for the sediment record is provided by parallel optical and 14C ages. The lake sediment magnetic and geochemical properties indicate a series of changes in sediment composition during the late Holocene, which correlate well with sediment lithology, water content and weight-loss-on-ignition. A comprehensive grid-based approach characterising the surface soil/sediment magnetic and geochemical properties has enabled a better understanding of source-sink linkages. In the upper 3-2 metres a suite of changes corresponds to the regional onset of human activity after 2000 BC, and particularly to the intensification of human activity at around AD 900. A comparison of the lake sediment magnetic properties and those of the catchment soils shows clear linkages for the period after AD 900. In contrast, detailed magnetic measurements of the early- through mid-Holocene sediments suggest that their magnetic properties are dominated by bacterial

  2. Soil disturbance and hill-slope sediment transport after logging of a severely burned site in northeastern Oregon.

    Treesearch

    James D. McIver; R. McNeil

    2006-01-01

    Despite considerable public debate in recent years on the practice of postfire logging, few studies have directly evaluated its effects. Soil disturbance and hill-slope sediment transport were measured after a postfire logging operation conducted two years after the 1996 Summit Wildfire (Malheur National Forest), in northeastern Oregon. The wildfire was relatively...

  3. 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.

  4. 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

  5. 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

  6. Dynamic behaviour of quartzo-feldspathic loess slopes in the Canterbury Port Hills, Christchurch, New Zealand

    NASA Astrophysics Data System (ADS)

    Carey, Jonathan; McSaveney, Mauri; Massey, Chris; Petley, David

    2014-05-01

    Evidence from New Zealand and elsewhere indicates that thick loess materials are highly susceptible to failure in earthquakes. After the 2010-11 Canterbury Earthquake sequence, 36 large landslides were mapped of which the majority were in fine grained loess deposits in the Canterbury Port Hills. Similar thick loess soil covers 10% of the land surface of the South Island of New Zealand and is also present within the southern part of the North Island. The wind-blown depositional characteristics result in sediments that can mantle steep rock slopes, and can stand in vertical faces. Understanding the mechanisms and triggering conditions under which the loess failures develop, and the relative susceptibility of different loessial soils to failure, is essential in assessing future earthquake-induced landslide risk. In general, investigation of the susceptibility of fine-grained soils to failure in earthquakes has hitherto concentrated on modelling approaches. In most cases, failure potential is determined as a critical ground acceleration threshold above which movement occurs through sliding of a soil block on the slope. Whilst such approaches are widely used, limited empirical data sets are available to assess their suitability. This study provides one of the first empirical datasets on the behaviour of loess soils during seismic events through a series of specialist dynamic back pressured shear-box tests on intact field samples collected from marginally-stable loess slopes in the Canterbury Port Hills. The tests were designed to replicate field conditions under different horizontal shaking characteristics. During each test, the strength reduction and excess pore pressures generated were measured as the sample underwent failure. The dynamic test results were analysed in relation to field mapping and site-monitoring data collected during the latter parts of the earthquake sequence. The study provides new knowledge regarding the mechanisms of shear-surface development in

  7. [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.

  8. 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.

  9. Resuspendable organic matter in nova scotian shelf and slope sediments

    NASA Astrophysics Data System (ADS)

    Grant, Jonathan; Volckaert, Filip; Roberts-Regan, Debra L.

    1987-09-01

    Sediment samples from the continental shelf and slope off Nova Scotia were fractionated with a combination of elutriation and sieving to investigate the most easily resuspended sediment fraction and thus processes of organic deposition. Bulk sediments on the slope were enriched in carbon and nitrogen compared to those on the shelf. Fractionation indicated that<40% of bulk particulate organic carbon (POC) and particulate organic nitrogen (PON) on the shelf (from a sandy bank and a muddy-sand basin) were readily resuspendable, reflecting the large proportion of sand at these stations. On the slope however, about 85% of the bulk POC and PON was resuspendable, due to the high silt-clay content. Resuspendable fractions at all stations did not differ significantly in organic content (i.e. richness). The similarity of these fine fractions, especially at basin and slope stations suggested a related origin (surface production) for these particles. The less resuspendable coarse fraction on the shelf was an organic-poor sand; on the slope the coarse fraction consisted of benthic fecal pellets, similar in richness to the fine fractions. Comparison of predicted and measured sedimentation rates suggested that enrichment of slope sediments could only be explained by horizontal transport of shelf production. This provides further support for the hypothesis that the continental slope is a sink in the global carbon budget.

  10. 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.

  11. An abyssal hill fractionates organic and inorganic matter in deep-sea surface sediments

    NASA Astrophysics Data System (ADS)

    Turnewitsch, Robert; Lahajnar, Niko; Haeckel, Matthias; Christiansen, Bernd

    2015-09-01

    Current estimates suggest that more than 60% of the global seafloor are covered by millions of abyssal hills and mountains. These features introduce spatial fluid-dynamic "granularity" whose influence on deep-ocean sediment biogeochemistry is unknown. Here we compare biogeochemical surface-sediment properties from a fluid-dynamically well-characterized abyssal hill and upstream plain: (1) In hill sediments, organic-carbon and -nitrogen contents are only about half as high as on the plain while proteinaceous material displays less degradation; (2) on the hill, more coarse-grained sediments (reducing particle surface area) and very variable calcite contents (influencing particle surface charge) are proposed to reduce the extent, and influence compound-specificity, of sorptive organic-matter preservation. Further studies are needed to estimate the representativeness of the results in a global context. Given millions of abyssal hills and mountains, their integrative influence on formation and composition of deep-sea sediments warrants more attention.

  12. Natural and man-induced stress evolution of slopes: the Monte Mario hill in Rome

    NASA Astrophysics Data System (ADS)

    Bozzano, F.; Martino, S.; Priori, M.

    2006-07-01

    The paper deals with stress-release effects induced by man-made cuts or excavations into natural stiff clay slopes that experienced erosion in response to valley deepening. The study was focused on the Monte Mario hill in Rome (Italy), which formed part of an area of recent urban expansion. The methodology of the study relied on a reference engineering-geology model, which was developed on the basis of site and laboratory data and stress-strain analyses. The latter analyses were carried out with the finite-difference code FLAC 4.0. Numerical modelling was based on a sequential approach, taking into account the main evolutionary stages of the Tiber river valley in Romeȁ9s urban area and then making cuts at the bottom of the slope located south of the Monte Mario Astronomical Observatory. The simulation revealed the stress-release effects that fluvial erosion and excavation fronts have caused on the investigated slopes and their consequent gravitational instabilities. These processes appear with metre-scale displacements, followed by stress-release cracks (actually observed on the slopes under review). In quantifying stress-release deformations, the simulation took into account the possible role of creep in the observed retardation of stress-release effects.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  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. Seismicity and sedimentation rate effects on submarine slope stability

    NASA Astrophysics Data System (ADS)

    Ten Brink, U. S.; Andrews, B. D.; Miller, N. C.

    2016-12-01

    Large submarine mass-transport scars are commonly observed on continental margins, but are noticeably less abundant on margins that experience frequent earthquakes than on those that seldom experience them. This is a surprising observation, given that horizontal acceleration from earthquakes and associated strength loss from cyclic loading and liquefaction are commonly thought to provide the primary triggers for inducing failures and subsequent mass movements. Mapping submarine failure scars in ten margins worldwide, we find decreasing scar abundance with both increasing frequency of earthquakes and decreasing sedimentation rate. The decrease in scar abundance is interpreted to represent increasing slope stability. The increase in stability is non linear (power law with b<0.5), accelerating with decreasing inter-seismic sediment accumulation, a parameter combining earthquake recurrence with sedimentation rate. The correlation is interpreted as evidence for sediment densification and associated shear strength gain induced by repeated seismic shaking. This conclusion is supported by the correlation of higher mean margin gradient with higher earthquake frequency and with lower scar abundance and by published in-situ measurements showing over consolidation of shallow sediments in areas of frequent earthquakes. Outliers to this correlation likely identify margins where tectonic activity (salt diapirs, seamount subduction, etc.) leads to relatively rapid oversteepening of the slope, implying that the morphology of most margins is in fact, stable over many earthquake cycles. Note that the above correlation averages scar area and sedimentation rate over entire margin areas. Variations in sedimentation rate with time, such as over glacial-interglacial cycles, and intra-margin variations in seismic attenuation, sedimentation rate, composition, and pore pressure, have likely affected the abundance of slope failures in time and space.

  19. [Regulation effects of reverse-slope level terrace on the runoff and sediment yield in sloping farmland].

    PubMed

    Wang, Ping; Wang, Ke-Qin; Li, Tai-Xing; Li, Yun-Jiao

    2011-05-01

    A dynamic monitoring on the rainfall-runoff process and the surface runoff and sediment yield in a sloping farmland was conducted at a natural rainfall runoff plot in the watershed of Jianshan River, the first tributary of Fuxian Lake, Chengjiang, aimed to study the regulation effects of reverse-slope level terrace on the runoff and sediment yield in red soil sloping farmlands of Yunnan. The regulation rates of runoff and sediment yield by the reverse-slope level terrace were 49.5%-87.7% and 56.7%-96.1%, averagely 65.3% and 80.7%, respectively, showing that the regulation effects of reverse-slope level terrace on the runoff and sediment yield, especially the latter in sloping farmland were prominent. The variation coefficients of the test parameters for undisturbed sloping farmland and reverse-slope level terrace were in the order of sediment yield > runoff > rainfall. Comparing with undisturbed sloping farmland, reverse-slope level terrace had smaller surface runoff and smaller relative deviation degree of sediment yield, demonstrating its remarkable effect in controlling runoff and sediment yield in sloping farmland.

  20. 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.

  1. Unraveling bed slope from relative roughness in initial sediment motion

    NASA Astrophysics Data System (ADS)

    Prancevic, Jeff P.; Lamb, Michael P.

    2015-03-01

    Understanding incipient sediment transport is crucial for predicting landscape evolution, mitigating flood hazards, and restoring riverine habitats. Observations show that the critical Shields stress increases with increasing channel bed slope, and proposed explanations for this counterintuitive finding include enhanced form drag from bed forms, particle interlocking across the channel width, and large bed sediment relative to flow depth (relative roughness). Here we use scaled flume experiments with variable channel widths, bed slopes, and particle densities to separate these effects which otherwise covary in natural streams. The critical Shields stress increased with bed slope for both natural gravel (ρs = 2.65 g/cm3) and acrylic particles (ρs = 1.15 g/cm3), and adjusting channel width had no significant effect. However, the lighter acrylic particles required a threefold higher critical Shields stress for mobilization relative to the natural gravel at a fixed slope, which is unexpected because particle density is accounted for directly in the definition of Shields stress. A comparison with model predictions indicates that changes in local velocity and turbulence associated with increasing relative roughness for lighter materials are responsible for increasing the critical Shields stress in our experiments. These changes lead to concurrent changes in the hydraulic resistance and a nearly constant critical stream power value at initial motion. Increased relative roughness can explain much of the observed heightened critical Shields stresses and reduced sediment transport rates in steep channels and also may bias paleohydraulic reconstructions in environments with exotic submerged densities such as iron ore, pumice, or ice clasts on Titan.

  2. 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

  3. Quantifying Slopes with Digital Elevation Models of the Verdugo Hills, California: Effects of Resolution

    NASA Technical Reports Server (NTRS)

    Fielding, E. J.; Burbank, D. W.; Duncan, C. C.

    1996-01-01

    Quantification of surface slope angles is valuable in a wide variety of earth sciences. Slopes measured from digital elevation models (DEMs) or other topographic data sets depend strongly on the length scale or window size used in the slope calculations.

  4. Seed population dynamics on abandoned slopes in the hill and gully Loess Plateau region of China

    NASA Astrophysics Data System (ADS)

    Yu, Weijie; Jiao, Juying

    2017-04-01

    Recovery of natural vegetation is an effective but slow approach to control the soil erosion in the Chinese hill and gully Loess Plateau region. As seed stage is particularly vulnerable to environmental conditions, characteristics of seed population should be needed to study for determining whether the recovery of natural vegetation is limited during this stage on the abandoned slopes in this region. The study was performed on three abandoned slopes in a watershed with an area of 8.27 km2in the Shaanxi province of China. The differences in soil seed banks were investigated in two different points in time, late March2011 and early April 2013. Main factors of seed population dynamics, such as seed yield of dominant species, seed inputs by seed rain as well as seed outputs through seed loss by overland flow and seedling emergence, were monitored from late March 2011 to early April 2013. In this study, seed rain densities of the main later successional species, i.e., Lespedeza davurica, Stipa bungeana and Artemisia gmelinii accounted for 51.5-71.6% of their own seed yields. The soil seed bank density in early April 2013 was larger than that in late March 2011. The density of seed inputs by seed rain was 10186 seeds•m-2, and the total seed bank, including seed rain and seeds present in the soil seed bank in late March 2011, reached a density of 15018 seeds•m-2 during the study period. Seed densities of loss due to overland flow and seedling emergence were 79 seeds•m-2 from 20 species and 938 seedlings•m-2 that belonged to 38 species during a study period, and the seed output through them accounted for 0.5% and 6.3% of the total seed bank, respectively. The study concluded that overland flow could not result in large numbers of seeds loss and seeds were accumulating in the soil seed bank due to seed rain, and vegetation succession might be limited by curbed spatial seed dispersal and seedling establishment.

  5. Carbonate slope morphology revealing bank-to-slope sediment transfer in Little Bahama Bank, Bahamas

    NASA Astrophysics Data System (ADS)

    Mulder, Thierry; Gillet, Hervé; Hanquiez, Vincent; Ducassou, Emmanuelle; Fauquembergue, Kelly; Conesa, Gilles; Principaud, Mélanie; Le Goff, Johan; Ragusa, Jérémy; Bujan, Stephane; Bashah, Sara

    2017-04-01

    New high-quality multibeam data depict the area located between Little Bahama Bank (LBB, Bahamas) and Blake Plateau. The survey details the morphology of a giant 135-km-long canyon, the Great Abaco Canyon (GAC) and its main characteristics. The canyon main axis runs parallel to the margin. The pathway shows several knickpoints and plunge pools. The most important knickpoint is underlined by an abrupt change in slope of the canyon thalweg. The last one leads to the opening towards the Blake Basin. Its morphologic head forms a vast receptacle but does not represent the main source of material at present. The material supplied through the LBB canyon systems does not reach this area which only shows lineaments related to the pathway of the Antilles current and restricted failure scars. Most of the supply comes from the canyon flanks. In the north, tributary canyons drain the contourite deposits forming large flat plateaus above the drowned carbonate platform of the Blake Plateau. In addition, these contourite plateaus are subjected to translational slides moving towards the northern edge of the canyon forming a dissymmetric debris accumulation along the toe of the north canyon edge. Another source of sediment are two large tributaries connecting the GAC directly to the LBB upper slope. Sub bottom profiles suggest the presence of a turbiditic levee on the tributary canyon sides and inferred turbiditic activity. Little Abaco Canyon (LAC) shows morphologic similarities with GAC but at a smaller size. However, the canyon seems more active in terms of sediment transport. Canyons draining the eastern part of LBB show fresh sedimentary structures (sediment waves) suggesting active sedimentary processes. These structures are made of clean sand with shallow water organisms suggesting a direct supply from the carbonate platform edge. In term of size and morphology, the GAC compares to the largest canyons in siliciclastic environments. Its originality comes from the fact it is

  6. 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.

  7. Slope processes in weathered volcaniclastic rocks of the Camaldoli hill (Naples, Italy): Geomorphologic and Engineering-Geological aspects

    NASA Astrophysics Data System (ADS)

    Calcaterra, D.; Coppin, D.; Palma, B.; Parise, M.; Orsi, G.; de Vita, S.; di Vito, M. A.

    2003-04-01

    Following the geological study performed by Orsi et al. (this session), the main results of a geomorphologic and engineering-geological investigation of the stability conditions of the Camaldoli hill (urban area of Naples) are here presented. The Camaldoli hill, the highest peak of the Phlegraean Fields caldera (452 m asl), is characterized by relief energy of a few hundreds of meters, and by high slope gradients, which frequently reach the verticality. Low-order, structurally controlled channels drain the hillslopes; the development of stepped longitudinal profiles in the channels is related to the alternance of rocks and soils. The geological framework of the hill represent a further factor predisposing to mass movements and soil erosion. The Camaldoli hill is in fact characterized, as already highlighted by Orsi et al., by a basal sequence of jointed weak tuffs, overlain by some tens of metres of loose, unconsolidated pyroclastic terrains, ranging in age from about 12.000 and 4.000 yrs. BP. The latter deposits are generally weathered in their upper layers, as a consequence of interaction with decay agents and of past slope instabilities. Present-day morphodynamics of the hill is ruled by the occurrence of a variety of slope processes. Shallow landslides involve the weathered portion of the youngest pyroclastic products, showing features typical of slides or falls. Such events, which usually start in the upper reaches of the slope, may undergo different evolution, essentially controlled by the local slope morphology: (i) low-mobility soil slides-debris flows on open slopes; (ii) slides/falls evolving to hyperconcentrated flows along channels. The first processes have been seldom observed on open slopes, while the transition from slides/falls to hyperconcentrated flows along channels seems much more diffuse in the study area. The flows are generally fed, under intense to extreme rainfall events, by the re-mobilization of pre-existing landslide debris. The upper

  8. 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.

  9. Sediment Transport History on the Northern California Shelf and Slope: Inferences from Acoustic Signatures

    DTIC Science & Technology

    1997-09-30

    the styles of sedimentation and the amount of sediment deposited during the last transgression and still stand of sealevel - the nature and style of...stratigraphic section, and are likely related to the combined results of lower sealevels and higher sediment yields. Shelf Sedimentation Studies of shelf-to-slope...accommodated, although sedimentation remains more-or-less continuous, with only subtle changes associated with shifts in sealevel . Thus, the

  10. 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

  11. 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.

  12. Shelf-slope sedimentation during the late Quaternary on the southwestern Kuril forearc margin, northern Japan

    NASA Astrophysics Data System (ADS)

    Noda, Atsushi; TuZino, Taqumi

    2010-12-01

    We studied an active forearc margin off eastern Hokkaido, northern Japan, to identify the main influences on stratigraphic development from the last glacial to the present highstand. This paper presents new data on the environment, texture, and sedimentation rates of forearc shelf-slope sediments, based on more than 300 samples of seafloor sediments and densely gridded sub-bottom profiling records. Lowstand sedimentary wedges developed upon the shelf margins in areas with a large sediment supply and without incising canyons. The transgressive and highstand deposits formed on the shelf in extensive, low-gradient, and topographically low areas. The narrow shelf is covered by sandy sediments, where winnowed fines are likely to have escaped to the slope via gravity-driven across-shelf transport or ocean-current-induced along-shelf transport. The slope has a mid-slope mud belt at water depths of 700-1600 m. The sedimentation rates on the slope subsequent to 15 ka (the late transgressive to highstand stage) were just 10-70% of the rates prior to this period. These changes in sedimentation rates are ascribed to spatially variable topography. High sedimentation rates were maintained at topographically low and gently sloping areas even during highstand periods, due to concentrations of nepheloid layers or deposition via sediment gravity flows. On the other hand, low sedimentation rates were recognized on topographic highs of interfluves on the upper slope or on axes of anticlines, where main flows or overspills of turbidity currents decreased as sealevel rose. These results suggest that sedimentologic and stratigraphic variations are tied to variations in the physical configuration of the shelf/slope system being influenced by the local topography in addition to the climatic and oceanographic processes.

  13. 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

  14. Terrestrial slopes in northern high latitudes: A paradigm shift regarding sediment origin, composition, and dynamic evolution

    NASA Astrophysics Data System (ADS)

    Lønne, Ida

    2017-01-01

    High-Arctic terrestrial slopes have received limited systematic research interest, but increased vulnerability related to regional warming has driven the call for better knowledge of the dynamics of these systems. Studies of sediment transport from a plateau area in Adventdalen, Svalbard, and associated slopes extending to sea level demonstrate that glacial processes play a more prominent role than earlier anticipated, - especially the impact of glacial meltwater. Traces of drainage at the plateau and the dissection of the plateau edge and upper slope were clearly initiated during various stages of Late Glacial runoff. Further, there is a close association between the sediment distribution and composition at the plateau and the evolution of various types of slopes. The reconstructed sedimentation history shows that the landscape will undergo four stages with contrasting modes of sediment transport: 1) subglacial processes related to active ice, 2) processes related to the margin of active ice, 3) processes related to the melting of inactive ice, and 4) nonglacial processes. These stages form four successions, referred to as supply regimes A-D, which control the supply of water and sediments to a given slope segment. In this landscape, traces of glacial meltwater occur at most altitudes, in "odd" positions and in slope segments "without" catchments. The associated depocenters (isolated, composite or coalescing into aprons), are often outsized compared to the apparent slope catchment. Reworked glacial sediments form a significant part of the slope-debris but are covered partly or entirely by products of physical weathering. Colluvium, senso stricto, thus masks a distinct system shift related to the local termination of glacial meltwater. Consequently, the weathering part of the slope sediment budget in this region is considerably overestimated.

  15. Sediment transport capacity of concentrated flows on steep loessial slope with erodible beds.

    PubMed

    Xiao, Hai; Liu, Gang; Liu, Puling; Zheng, Fenli; Zhang, Jiaqiong; Hu, Feinan

    2017-05-24

    Previous research on sediment transport capacity has been inadequate and incomplete in describing the detachment and transport process of concentrated flows on slope farmlands during rill development. An indoor concentrated flow scouring experiment was carried out on steep loessial soil slope with erodible bed to investigate the sediment transport capacity under different flow rates and slope gradients. The results indicated that the sediment transport capacity increases with increasing flow rate and slope gradient, and these relationships can be described by power functions and exponential functions, respectively. Multivariate, nonlinear regression analysis showed that sediment transport capacity was more sensitive to slope gradient than to flow rate, and it was more sensitive to unit discharge per unit width than to slope gradient for sediment transport capacity in this study. When similar soil was used, the results were similar to those of previous research conducted under both erodible and non-erodible bed conditions. However, the equation derived from previous research under non-erodible bed conditions with for river bed sand tends to overestimate sediment transport capacity in our experiment.

  16. Assessing RUSLE and hill-slope soil movement modeling in the central Appalachians

    Treesearch

    Jingxin Wang; Pam Edwards; Greg W. Hamons; William. Goff

    2010-01-01

    The determination of the topographical attributes responsible for the origination and transfer of sediment were investigated in a central Appalachian mixed hardwood forest from 2002 through 2005. Two study watersheds were chosen on the left fork of Clover Run within the Indian Run watershed in Tucker County, West Virginia. Silt fence was installed around all the stream...

  17. Bottom-slope-induced net sheet-flow sediment transport rate under sinusoidal oscillatory flows

    NASA Astrophysics Data System (ADS)

    Yuan, Jing; Li, Zhiwei; Madsen, O. S.

    2017-01-01

    It is generally believed that the slope of beaches can lead to a net downslope (usually offshore) sediment transport rate under shoaling waves, but very few high-quality measurements have been reported for a quantitative understanding of this phenomenon. In this study, full-scale (1:1) experiments of bottom-slope-induced net sheet-flow sediment transport rate under sinusoidal oscillatory flows are conducted using a tilting oscillatory water tunnel. The tests cover a variety of flow-sediment conditions on bottom slopes up to 2.6°. A laser-based bottom profiler system is developed for measuring net transport rate based on the principle of mass conservation. Experimental results suggest that for a given flow-sediment condition the net transport rate is in the downslope direction and increases linearly with bottom slope. A conceptual model is presented based on the idea that gravity helps bottom shear stress drive bedload transport and consequently enhances (reduces) bedload transport and suspension when the flow is in the downslope (up-slope) direction. The model predicts both the measured net sediment transport rates and the experimental linear relationship between net transport rates and bottom slope with an accuracy generally better than a factor of 2. Some measured net transport rates in this study are comparable to those due to flow skewness obtained in similar sheet-flow studies, despite that our maximum slope could be milder than the actual bottom slope in surf zones, where sheet-flow conditions usually occur. This shows that the slope effect may be as important as wave nonlinearity in producing net cross-shore sheet-flow sediment transport.

  18. [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.

  19. Sediment dynamics and their potential influence on insular-slope mesophotic coral ecosystems

    NASA Astrophysics Data System (ADS)

    Sherman, C.; Schmidt, W.; Appeldoorn, R.; Hutchinson, Y.; Ruiz, H.; Nemeth, M.; Bejarano, I.; Motta, J. J. Cruz; Xu, H.

    2016-10-01

    Although sediment dynamics exert a fundamental control on the character and distribution of reefs, data on sediment dynamics in mesophotic systems are scarce. In this study, sediment traps and benthic photo-transects were used to document spatial and temporal patterns of suspended-sediment and bed-load dynamics at two geomorphically distinct mesophotic coral ecosystems (MCEs) on the upper insular slope of southwest Puerto Rico. Trap accumulation rates of suspended sediment were relatively low and spatiotemporally uniform, averaging <1 mg cm-2 d-1 and never exceeding 3 mg cm-2 d-1 over the sampled period. In contrast, trap accumulation rates of downslope bed-load movement were orders of magnitude higher than suspended-sediment accumulation rates and highly variable, by orders of magnitude, both spatially and temporally. Percent sand cover within photo-transects varied over time from 10% to more than 40% providing further evidence of downslope sediment movement. In general, the more exposed, lower gradient site had higher rates of downslope sediment movement, higher sand cover and lower coral cover than the more sheltered and steep site that exhibited lower rates of downslope sediment movement, lower sand cover and higher coral cover. In most cases, trap accumulation rates of suspended sediment and bed load varied together and peaks in trap accumulation rates correspond to peaks in SWAN-modeled wave-orbital velocities, suggesting that surface waves may influence sediment dynamics even in mesophotic settings. Though variable, off-shelf transport of sediment is a continuous process occurring even during non-storm conditions. Continuous downslope sediment movement in conjunction with degree of exposure to prevailing seas and slope geomorphology are proposed to exert an important influence on the character and distribution of insular-slope MCEs.

  20. Sulfate reduction and iron sulfide mineral formation in the southern East China Sea continental slope sediment

    NASA Astrophysics Data System (ADS)

    Lin, Saulwood; Huang, Kuo-Ming; Chen, Shin-Kuan

    2002-10-01

    Sulfate reduction rate, organic carbon and sulfide burial rate; organic carbon, carbonate carbon, and reactive iron contents; grain size; and sedimentation rate were determined in sediments of the southern East China Sea continental slope. The results show high sulfate reduction and pyrite sulfur burial rates in slope areas with high organic carbon and sedimentation rates. Unusually high rates of organic carbon deposition enhance sulfate reduction and pyrite sulfide burial in the region. Both sulfate reduction rates and pyrite sulfur burial rates increased linearly with increasing organic carbon burial rate, indicating that deposition of organic carbon on the slope is the primary controlling factor for pyrite formation. Abundant reactive iron indicated that iron is not limiting pyrite formation. Pyrite is the predominant sulfide mineral; however, acid volatile sulfide constituted up to 50% of total sulfide at some stations. Up to 240 μmol/g of pyrite sulfur and 5 mmol/m 2/day of sulfate reduction rates were found in the slope sediment. Sulfate reduction rate and pyrite sulfur did not decrease with increasing overlying water depth. High organic carbon burial rates enhanced the sulfate reduction rate and subsequently the rate of pyrite sulfur burial in the slope region. As a result, the southern East China Sea continental slope environment is an efficient pyrite sulfur burial environment.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. The Contribution of Slope and Basin Sediments to Fluid Budgets of the Costa Rica and the Nankai Trough Margins

    NASA Astrophysics Data System (ADS)

    Screaton, E.; James, S. R.; Meridth, L. N.; Villaseñor, T.; Jaeger, J. M.; Kenney, W.

    2016-12-01

    Fluid budgets of subduction zones generally include the fluids entering with sediments at the deformation front but not fluids added to the margin through slope and basin sedimentation. Although the fluids trapped within slope and basin sediments are unlikely to be subducted except in extreme cases, they may still need to be considered in overall fluid budgets. As a first step, we compare the influx of pore fluids contributed by slope and basin sedimentation within 50 km landward of the deformation front to that entering the margin within sediments of the incoming plate. We examine transects offshore of the Osa and Nicoya Peninsulas of Costa Rica and the Kumano Basin transect offshore the Kii Peninsula of Japan. Incoming sediment thicknesses and porosities are determined from Ocean Drilling Program (ODP) and Integrated Ocean Drilling Program (IODP) results. Drilling results also provide estimates of Pleistocene sedimentation rates on slopes and in basins, and seismic reflection profiles are used to roughly estimate basin extent. Slope and basin sediments are assumed to have initial porosities of 70%. Offshore the Nicoya Peninsula the percentage of pore fluids contributed by slope sediment to those carried in sediments on the incoming plate is relatively small, <5%. In contrast, because the Osa Peninsula transect has rapid sedimentation on the upper plate, fluid influx from above can exceed that carried within the thin (<100 m) sediment cover on the incoming plate. The Kumano Basin transect lies between these two extremes. It has thick incoming sediments ( 2 km) but also high sedimentation rates within the Kumano forearc basin. The fluid influx from slope and basin sedimentation is estimated to be 30-40% of the influx at the deformation front. The presentation will further examine the fate of these fluids and the contributions of hydrous minerals in sediments.

  7. 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.

  8. 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.

  9. 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

  10. 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

  11. 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

  12. Large sized non-uniform sediment transport at high capacity on steep slopes

    NASA Astrophysics Data System (ADS)

    Fu, X.; Zhang, L.; Duan, J. G.

    2015-12-01

    Transport of large-sized particles such as cobbles in steep streams still remains poorly understood in spite of its importance in mountain stream morphdynamics. Here we explored the law of cobble transport and the effect of cobble existence on gravel bed material transport, using flume experiments with a steep slope (4.9%) and water and sediment constantly supplying. The experiments were conducted in an 8 m long and 0.6 m wide circulating flume with the maximal size up to 90 mm and cobble concentrations in the sediment bed ranging from 22 percent to 6 percent. The sediment transport rate is on the order of 1000 g/m/s, which could be taken as high rate transport compared with existing researches. Bed load transport rate and flow variables were measured after the flume reached an equilibrium state. Bed surface topography was also measured by applying Kinect range camera before and after each run in order to analyze the fractal characteristics of the bed surface under different flow conditions. Critical shear stress of each size friction was estimated from the reference transport method (RTM) and a new hiding function was recommended. Preliminary results show that the bed was nearly in an equal mobility transport regime. We then plot dimensionless fractional transport rate versus dimensionless shear stress and assess the existing bed load transport formulas of non-uniform sediments for their applicability at high sediment transport capacity. This study contributes to the comprehension of high rate sediment transport on steep slopes.

  13. Shelf-Slope Sedimentation on a Cool-Temperate Glaciated Collisional Margin

    NASA Astrophysics Data System (ADS)

    Powell, R. D.

    2002-12-01

    Collisional margins are unique paleoclimatically because high mountains allow temperate, active glaciation at sea level in mid-latitudes even in interglacial periods, e.g. Alaska and Chile today. Glacial and climatic effects largely impact erosion rates, sediment fluxes, accumulation rates, and sediment architecture on the continental shelf and slope. For example, on the cool-temperate Alaskan shelf each glacial advance alters shelf morphology by erosional foci moving with the glacier during each readvance, cutting new cross-shelf troughs and prograding the slope. The changing foci of erosion and deposition through a glacial cycle force an interplay in uplift and loading between lithostatic and glacial isostasy. Furthermore, rapid tectonic shelf subsidence provides sufficient accommodation space for large sediment volumes produced during advances. High sediment fluxes, also allow episodes of tectonic deformation to be constrained over short time intervals. A strong contrast is apparent between these temperate systems and those of colder glaciated margins. For example, under temperate glacial regimes, subglacial streams dominate sediment fluxes, and where glaciers under convergent flow occupy major cross-shelf troughs, those fluxes form point-source grounding-line fans. At the continental shelf edge that sorted sediment is redeposited as turbidites in submarine fans at the base of the slope and rise. In contrast, under colder regimes, ice in convergent flow within cross-shelf troughs releases deforming-bed till into a grounding- line wedge system where it is redeposited as debrites. At the continental shelf edge, these produce trough-mouth fans at the top of continental slopes. The climatic/glacial regimes control glacial sediment fluxes, both in rates and style, to produce different sedimentary systems on the margins. Grounding lines of glaciers under divergent flow in each glacial regime appear to have lower sediment fluxes of till to be released as debrites at

  14. 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

  15. Seismic displacement of gently-sloping coastal and marine sediment under multidirectional earthquake loading

    USGS Publications Warehouse

    Kayen, Robert

    2017-01-01

    Gentle sediment-laden slopes are typical of the onshore coastal zone and offshore continental shelf and slope. Coastal sediment are commonly young weakly consolidated materials that are well stratified, have low strength, and can mobilize shear displacements at low levels of stress. Seismically-driven plastic displacements of these sediment pose a hazard to coastal cities, buried onshore utilities, and offshore infrastructure like harbor protection and outfalls. One-dimensional rigid downslope-directed Newmark sliding block analyses have been used to predict earthquake deformations generally on steeper slopes that are modeled as frictional materials. This study probes the effect of multidirectional earthquake motions on inertial displacements of gently sloping ground of the coastal and offshore condition where soft-compliant soil is expected. Toward that objective, this investigation seeks to understand the effect on Newmark-type displacements of [1] multidirectional earthquake shaking and [2] soil compliance. In order to model multidirectional effects, the earthquake motions are rotated into the local slope strike- and dip-components. On gently sloping ground, including the strike component of motion always results in a larger and more accurate shear stress vector. Strike motions are found to contribute to downslope deformations on any declivity. Compliant response of the soil mass also influences the plastic displacements. The magnitude of seismic displacements can be estimated with a simplified model using only the estimated soil yield-acceleration (ky) and the peak ground velocity (Vmax) of the earthquake motions. Compliance effects can be effectively mapped using the concept of Plastic Displacement Response Spectra (PDRS).

  16. 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.

  17. 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.

  18. 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.; 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.

  19. Slope, grain size, and roughness controls on dry sediment transport and storage on steep hillslopes

    NASA Astrophysics Data System (ADS)

    DiBiase, Roman A.; Lamb, Michael P.; Ganti, Vamsi; Booth, Adam M.

    2017-04-01

    Existing hillslope sediment transport models developed for low-relief, soil-mantled landscapes are poorly suited to explain the coupling between steep rocky hillslopes and headwater channels. Here we address this knowledge gap using a series of field and numerical experiments to inform a particle-based model of sediment transport by dry ravel—a mechanism of granular transport characteristic of steep hillslopes. We find that particle travel distance increases as a function of the ratio of particle diameter to fine-scale (<1 m) topographic roughness, in agreement with prior laboratory and field experiments. Contrary to models that assume a fixed critical slope, the particle-based model predicts a broad transition as hillslopes steepen from grain-scale to hillslope-scale mean particle travel distances due to the trapping of sediment on slopes more than threefold steeper than the average friction slope. This transition is further broadened by higher macroscale (>1 m) topographic variability associated with rocky landscapes. Applying a 2-D dry-ravel-routing model to lidar-derived surface topography, we show how spatial patterns of local and nonlocal transport control connectivity between hillslopes and steep headwater channels that generate debris flows through failure of ravel-filled channels following wildfire. Our results corroborate field observations of a patchy transition from soil-mantled to bedrock landscapes and suggest that there is a dynamic interplay between sediment storage, roughness, grain sorting, and transport even on hillslopes that well exceed the angle of repose.

  20. 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.

  1. Soil production is faster on south-facing slopes in the Susquehanna/Shale Hills Critical Zone Observatory due to periglacial, vegetative, and climate factors (Invited)

    NASA Astrophysics Data System (ADS)

    Jin, L.; Eissenstat, D.; Lin, H.; Chabaux, F. J.; Ma, L.; Brantley, S. L.

    2010-12-01

    The Susquehanna/Shale Hills Critical Zone Observatory is a V-shaped first-order catchment, developed almost entirely on the Silurian Rose Hill shale. We have focused on this site to investigate the controls, mechanisms and rates of shale weathering and soil formation. The parent rock is comprised primarily of illite, quartz, chlorite and ankerite. Three weathering fronts were observed at different depths identified in the northern ridgetop: ankerite dissolution begins tens of meters below land surface; plagioclase feldspar begins to weather at about 5-6 meters; chlorite and illite dissolve in the soil profiles to form more stable vermiculite and kaolinite. Six soil profiles were characterized: ridge top, mid-slope and valley floor sites on south-facing (9o) and north-facing (12o) planar hillslopes. Particle size analyses revealed that the soil textures were different: silt loam on the S-facing slope and sandy loam on the N-facing slope. All 6 sites show depletion profiles of major elements due to dissolution of clay minerals and feldspar. However, compared to the soils from the N-facing slope, those from S-facing slope were less depleted. Also local variations in element chemistry were observed with depth on S-facing slope to be superimposed on a general depletion trend. U disequilibrium isotopes of the bulk soils as well as parent rock were measured and modeled to estimate the soil production rates. In spite of similar slope, soil was produced, eroded and transported out of the S-facing slope at a faster rate. We argue that periglacial activities broke up bedrock and promoted soil erosion especially on the S-facing slopes, as evidenced by finer soil texture and fractures inferred by zig-zag variations in the depletion profiles. As such, the residence time of soil particles is generally shorter on the S-facing slope, preventing minerals in soils from becoming extensively weathered. Duration for the clay dissolution reactions (kinetically slow) plays a primary role

  2. The granular origin of the relation between slope and sediment flux in soil mantled hillslopes

    NASA Astrophysics Data System (ADS)

    BenDror, Eran; Goren, Liran

    2017-04-01

    Hillslopes occupy most of the Earth's surface area, and are the main source of sediments to the fluvial routing system. Since the slope of soil mantled hillslopes normally lies below the angle of repose, it has been suggested that sediment mobilization across and from hillslopes is facilitated by climatic, biologic, and tectonic environmental disturbances. Previous empirical studies have shown that sediment flux out of hillslopes depends non-linearly on the slope. However, the functional dependency between the slope and the flux that aspires to span a range of processes from slow creep to rapid landsliding generally lacks a mechanistic explanation. The absence of a physical understanding of the slope-flux relation hinders our ability to assess hillslope evolution in different settings and evaluate the effect of changing environmental conditions on the flux. Due to the particulate nature of the material composing the upper layer of soil mantled hillslopes, sediment transport on and from hillslopes has discrete granular characteristics. Entrainment of grains, grain travel distance, velocity and acceleration, all depend on the dynamics of the sediment particles and their interactions. It is therefore likely that the spatial and temporal evolution of the sediment flux in response to a given slope and disturbance characteristics should inherently depend on the inter-particle dynamics. For this reason, the current work investigates the relations between flux, slope, and disturbance characteristics at the granular scale. This has the advantage of using first order mechanical principles without the need to assume a priori empirical relations. We construct a two-dimensional model representing a long hillslope, and we model granular interactions and their response to environmental disturbances using a soft disc granular dynamics algorithm. Environmental disturbances are simulated by applying temporally and spatially variable 'external' forces to individual grains following a

  3. 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.

  4. 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.

  5. Sediment source apportionment in Laurel Hill Creek, PA, using Bayesian chemical mass balance and isotope fingerprinting

    USGS Publications Warehouse

    Stewart, Heather; Massoudieh, Arash; Gellis, Allen C.

    2015-01-01

    A Bayesian chemical mass balance (CMB) approach was used to assess the contribution of potential sources for fluvial samples from Laurel Hill Creek in southwest Pennsylvania. The Bayesian approach provides joint probability density functions of the sources' contributions considering the uncertainties due to source and fluvial sample heterogeneity and measurement error. Both elemental profiles of sources and fluvial samples and 13C and 15N isotopes were used for source apportionment. The sources considered include stream bank erosion, forest, roads and agriculture (pasture and cropland). Agriculture was found to have the largest contribution, followed by stream bank erosion. Also, road erosion was found to have a significant contribution in three of the samples collected during lower-intensity rain events. The source apportionment was performed with and without isotopes. The results were largely consistent; however, the use of isotopes was found to slightly increase the uncertainty in most of the cases. The correlation analysis between the contributions of sources shows strong correlations between stream bank and agriculture, whereas roads and forest seem to be less correlated to other sources. Thus, the method was better able to estimate road and forest contributions independently. The hypothesis that the contributions of sources are not seasonally changing was tested by assuming that all ten fluvial samples had the same source contributions. This hypothesis was rejected, demonstrating a significant seasonal variation in the sources of sediments in the stream.

  6. Coincident sediment slump/clathrate complexes on the U.S. Atlantic continental slope

    USGS Publications Warehouse

    Carpenter, G.

    1981-01-01

    High-resolution seismic reflection data recorded on the continental slope off the east coast of the United States have revealed instances of sediment mass movement (slumps) which appear to occur above clathrate accumulations. The slumping is believed to be related to the liberation of free gas by clathrate decomposition and consequent weakening of unconsolidated sediments above the clathrate. Pleistocene sea-level lowering and/or post-Pleistocene bottom water temperature increases may have had a significant role in this process. ?? 1981 A.M. Dowden, Inc.

  7. 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

  8. Variation in the sediment yield on slopes with different land uses from rainfall simulation

    NASA Astrophysics Data System (ADS)

    Ruiz-Flaño, Purificación; Llorente, José Angel; Arnáez, José; Lasanta, Teodoro

    2010-05-01

    Recent changes in land use of Spanish rural areas (agricultural intensification and/or abandonment) have significantly altered the hydrological behaviour of catchment and erosion rates on hillsides. The rainfall simulation represents a very effective tool to estimate soil losses associated with these changes. This paper gives information about sediment yield with different land uses: intensive crops of vineyards, abandoned terraces and abandoned sloping fields. The vineyards are located in the Ebro basin, on gently sloping hillsides. The abandoned terraces are in the Iberian System (La Rioja), and the abandoned sloping fields are located in the Central Pyrenees. Runoff and sediment yield were studied using rainfall simulation tests. Sixteen simulated rainfall were conducted on vineyards, twelve in terraced fields and sixty in abandoned sloping fields. The median rainfall intensity used in our experiments was 51.1 mm h-1 in vineyards (return period to 20 years), 61.9 mm h-1 (24 years of recurrence) in terraces and 53.4 mm h-1 (recurrence period of 60 years) in sloping fields. In each experiment rainfall was simulated for a period of 30-45 min. A range of parameters was recorded during the experiments: time until runoff began (s), runoff (mm h-1), runoff coefficient (%), mean sediment concentration (g L-1), and erosion rate (g m-2 h-1). The results indicate that the vineyards produce the least runoff (11.2%) but significant sediment production, with average rates of erosion of 15.6 g m-2 h-1. Tillage allows the development of permeable soils with high infiltration capacity, but also with a lot of loose material to be evacuated. The terraces show higher runoff coeficients (26.2%) and moderate erosion rates (11.9 g m-2 h-1), due to the lack of tillage, the trampling by livestock and the high density of vegetation cover. Finally, the sloping fields have the highest runoff coefficients (30%) and sediment yield, with an average erosion rate of 29.8 g m-2 h-1. This is

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Floodplain storage of sediment contaminated by mercury and copper from historic gold mining at Gold Hill, North Carolina, USA

    NASA Astrophysics Data System (ADS)

    Lecce, Scott A.; Pavlowsky, Robert T.

    2014-02-01

    Previous research on the environmental consequences of mining has shown that metal contaminants can have long-lasting impacts on water quality and aquatic ecosystems because of the remobilization of sediment-associated contaminants that have been stored in floodplains. We examined the magnitude and distribution of mercury (Hg) and copper (Cu) contamination of floodplain deposits associated with nineteenth century gold (Au) mining activities in the Gold Hill mining district, North Carolina. A comparison of post-mining metal concentrations in overbank deposits with sediment quality guidelines indicates that overall about 21% are contaminated above the probable effect concentration (PEC; above which adverse effects are expected to occur more often than not) for both Cu and Hg. The highest contamination occurs upstream near the mine source where 51% of the samples exceed the PEC for Hg and 57% exceed the PEC for Cu. Of the three different methods used to estimate metal mass storage, the most reliable estimate suggests that about 6.8 Mg of Hg and 619 Mg of Cu currently reside in floodplain deposits within this watershed. Although overbank sediment storage increases downstream and with valley width, about 75% of the Hg and Cu mass are stored in the upstream portion of the watershed. Hg mass storage displays a strong negative relationship with cross-sectional stream power, but the relationship between Cu mass storage and stream power is insignificant. We used vertical changes in overbank metal concentrations and the mining history to estimate a mean sedimentation rate of 2.7 cm y- 1 during the most intensive period of Au mining at Gold Hill (1842-1856) that is three times the long-term (1842-2007) rate of 0.9 cm y- 1. Long-term average rates at Gold Hill are comparable to those reported elsewhere in the eastern Piedmont. The downstream increase in long-term rates may indicate a spatial and temporal lag effect where the locus of deposition shifts downstream with time.

  14. Lee slope sediment processes leading to avalanche initiation on an aeolian dune

    NASA Astrophysics Data System (ADS)

    Sutton, S. L. F.; McKenna Neuman, C.; Nickling, W.

    2013-09-01

    In order to detail the governing conditions through which a slipface matures to the point of failure, dry sand avalanches were observed in the Dune Simulation Wind Tunnel on a 1:1 replica transverse dune with a crest height of approximately 1.2 m. Areal distributions of grainfall and reptation were measured using traps. Changes in the slipface elevation were observed using 3-D laser scanning with a vertical accuracy of 0.096 mm for approximately every 1 mm2 of surface area. Grainfall decayed exponentially from the brink with a constant rate across all wind velocities. Reptation removed sediment from areas close to the brink and deposited it downslope, creating low amplitude, cross-slope ripples on the slipface. A critical length scale separating grainscale and bulk sediment behavior is identified, and it defines the lower limit to the validity of angle of repose measurements. Avalanche initiation occurred in an area of steep surface slope below a sediment bulge, with distance from the brink independent of wind velocity. The time between avalanches was found to be constant for constant wind velocity.

  15. Influence of diatom microfossils on sediment shear strength and slope stability

    NASA Astrophysics Data System (ADS)

    Wiemer, G.; Kopf, A.

    2017-01-01

    Diatom microfossils have been detected in many natural marine sediment deposits around the globe and are held responsible for the disobedience to well-established geotechnical relationships between index-properties and shear strength. We revisit the static shear strength and present the first cyclic undrained shear strength experiments on diatom microfossil—clayey-silt mixtures to study the role of diatoms on submarine slope stability. It is attested that the angle of internal friction (Φ) increases with diatom content, however, we provide evidence for a significant overestimation of Φ in previous studies. Based on direct shear tests at varying normal stresses ≤ 600 kPa we find Φ = 32° in contrast to 43° in pure diatom. Similarly, to static shear strength, cyclic shear strength increases with diatom content, however, in contrast to static shear strength the most drastic increase does not occur from 0% to 25% diatoms but from 75% to 100%. Interestingly, diatomaceous sediments tend to fail by liquefaction although well-established relations between index properties and liquefaction susceptibility predict the opposite. Liquefaction failure is observed solely in samples containing ≥ 50% diatoms whereas samples with lower diatom content fail by cyclic softening. We conclude diatom microfossils in marine sediments significantly contribute to an increased slope stability under static and cyclic loading conditions since diatoms lead to higher resistance independently of the loading mode. The strength increase is interpreted as a result of particle interlocking and surface roughness, which is very efficient given the highly variable habitus of diatom species.

  16. 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

  17. 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.

  18. Connectivity of runoff and sediments in reclaimed Mediterranean-dry slopes: controlling factors and long-term ecological implications

    NASA Astrophysics Data System (ADS)

    Moreno de las Heras, Mariano; Saco, Patricia M.; Espigares, Tíscar; Nicolau, José M.; Merino Martín, Luis

    2013-04-01

    Hydrological connectivity has emerged in recent years as a critical factor for understanding the transference of runoff, sediments and nutrients across scales. Here we examine its relevance for the successful reclamation of water-limited environments in which vegetation stability largely depends on optimal redistribution of water and soil resources for plant production. We studied the connectivity of runoff and sediments across plot to slope scales in three Mediterranean-dry reclaimed slopes that were restored about 25 years ago and have developed different levels of vegetation cover (24-51%) and rill density (0.5-0.0 m m-2), along a gradient of overland flow (slope-scale runoff coefficient 11.2%-0.5%). Event-based connectivity of runoff and sediments was controlled by the spatial organization of vegetation and rills, and at the same time was modulated by storm intensity. In absence of rill networks, both runoff and sediment yield per unit area decreased from patch to slope scales due to internal redistribution of both water and sediment fluxes. However, the connectivity of the slopes increased with rainfall intensity. Additionally, the presence of rills largely increased the connectivity of runoff and sediments, leading to increases in sediment yield across scales due to active rilling under high intensity storm conditions. Further simulations using an eco-geomorphic modelling approach showed that the development of rill networks structurally enhances the hydrological connectivity in these systems, providing persistent pathways for the routing of water and soil resources out of the slopes that can compromise the development and long-term stability of reclaimed vegetation. Overall, our results confirm the relevance and efficiency of using a surface connectivity analysis for understanding the spatial and temporal dynamics of water-limited eco-geomorphic systems, and call for its application in order to achieve a successful restoration of Mediterranean slopes.

  19. Global prediction of abyssal hill roughness statistics for use in ocean models from digital maps of paleo-spreading rate, paleo-ridge orientation, and sediment thickness

    NASA Astrophysics Data System (ADS)

    Goff, John A.; Arbic, Brian K.

    Abyssal hills are the dominant small-scale roughness fabric over much of the ocean floor. Created at mid-ocean ridges by combined volcanic and tectonic processes, they are rafted away by plate spreading and modified through time by mass wasting and sedimentation. Abyssal hills are morphological indicators of spreading rate and direction: they are lineated parallel to the ridge at the time of formation, and their heights and widths are inversely correlated to spreading rate. Knowledge of abyssal hill roughness statistics is important for high-resolution models, including models of internal wave generation and mixing driven by tidal and low-frequency flows over the rough bottom. In this paper we present a prediction of abyssal hill roughness statistical parameters world-wide via relationships for the average statistical properties of abyssal hills as a function of spreading rate and direction, and for the modification to these roughness parameters as a function of sediment thickness. These relationships are constrained by new publicly-available digital maps of paleo-spreading rate and direction, and sediment thickness. We also develop a new method for generating synthetic topography with variable statistical properties over a grid, and present an example of synthetic abyssal hill roughness generated for the North Atlantic on a 1/2-min grid.

  20. 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

  1. 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

  2. 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.

  3. 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

  4. A Cone Shaped Hill

    NASA Image and Video Library

    2015-10-14

    There are many hills and knobs on Mars that reveal aspects of the local geologic history. Typically, the hills in the relatively-smooth region surrounding this image are flat topped erosional remnants or mesas with irregular or even polyhedral margins. These landforms suggest wide spread erosion of the soft or weakly-cemented sedimentary layers. This hill stands out because of is circular inverted-cone shape and apparent dark streaks along its flanks visible in lower resolution images. Close inspection from HiRISE reveals that the fine soils sloping down from the peak are intersected with radiating lines of rock and eroding rubble. This formation is similar to lava intrusions that form in the core of a volcano. As lava is squeezed up into a central conduit, radiating fractures fill with lava forming rock units called dikes. As the lava cools inside the ground and in the fractures, it forms into a harder rock that is more resistant to erosion. Later, as the surrounding sediments and soils erode, the resistant volcanic rock remains standing to tell a story of what happened underground long ago. http://photojournal.jpl.nasa.gov/catalog/PIA20003

  5. Fine-grained sediment gravity flow deposits induced by flood and lake slope failure events: examples of lacustrine varved sediments in Japan

    NASA Astrophysics Data System (ADS)

    Ishihara, Yoshiro; Sasaki, Yasunori; Sasaki, Hana; Onishi, Yuri

    2016-04-01

    Fine-grained sediment gravity flow deposits induced by flood and lake slope failure events are frequently intercalated in lacustrine successions. When sediment gravity flow deposits are present in varved sediments, it is suggested that they provide valuable information about sediment gravity flows, because they can easily trace laterally and can give the magnitude of erosion and recurrence interval of events. In addition, because large sedimentary bodies of stacked sediment gravity flow deposits in varved sediments of a calm lake are not suggested, a relatively simple depositional environment is expected. In the present study, we analysed sedimentary facies of sediment gravity flow deposits in varved lacustrine diatomites in the Middle Pleistocene Hiruzenbara and Miyajima formations in Japan, and concluded a depositional model of the lacustrine sediment gravity flow deposits. Varved diatomites: The Hiruzenbara Fm., a dammed lake fill as foots of Hiruzen Volcanos, is deposited during an interglacial period during MIS12 to 15. Varves of ca. 8000 yr were measured in a 20 m intercalating flood and lake slope failure-induced sediment gravity flow deposits. The Miyajima Fm., distributed in a paleo-caldera lake in NE Japan, includes many sediment gravity flow deposits possibly originated from fandeltas around the lake. These formations have differences in their depositional setting; the Hiruzebara Fm. was deposited in a large lake basin, whereas the Miyajima Fm. was deposited in a relatively small basin. Because of the depositional setting, intercalation of volcaniclastics is dominant in the Miyajima Fm. Lacustrine sediment gravity flow deposits: Sediment gravity flow deposits in both formations can be classified into flood- and lake slope failure-induced types based on the sedimentary facies. Composites of the both types are also found. Flood-induced types comprise fine-grained silts dominated by carbonaceous fragments, whereas lake slope failure-induced types are

  6. Volcaniclastic Sediments of the Miocene Pickhandle Formation in the Northern Calico Hills: A Sedimentological and Volcanological Perspective

    NASA Astrophysics Data System (ADS)

    Clifford, H.; Garrison, J. M.

    2012-12-01

    The early Miocene Pickhandle Formation in the central Mojave records fluvial and lacustrine sedimentation and significant volcanic deposition related to extensional faulting. Understanding the geologic history and volcanic activity of the Pickhandle Formation is significant because it was deposited coeval with Miocene extensional faulting in the Mojave, and it records recurrent, explosive, rhyolitic volcanism associated with a source that was likely in the region of the Mojave Desert. The Pickhandle Formation was deposited in an extensional basin; it is approximately 1500 meters thick, unconformably overlain by the Barstow Formation, and conformably overlies the Jackhammer Formation near the type section in the Calico Hills north of Barstow, CA. Deposition of the Pickhandle Formation began 23.7 Ma, and occurred synchronously with the development of the Waterman Hills Detachment Fault. Repeated volcanic eruptions, originating from an unknown source near the Calico Mountains, occurred 23.7 to 21.7 Ma ago and all sedimentation ended when extension ceased at 18.9 Ma. Dacite lavas related to the Yermo Dacite Volcanic Field are interbedded with the volcanic sediments in the Pickhandle Formation. The dacite domes and the volcanic ash of the Pickhandle Formation may share the same source. Our preliminary fieldwork identifies a significant ignimbrite deposit, and the 50 cm diameter size of the pumice blocks strongly implies that the source was nearby, possibly near the Calico Mountains. Generally speaking, the Pickhandle Formation can be divided into two units; primary volcanic deposits and reworked volcaniclastic deposits. The goals of this research are to 1) determine the relationship between the Pickhandle Formation volcaniclastic sediments in the Calico Mountains and the Yermo Dacite domes using field observations and geochemical analysis, and 2) to unravel the volcanic history of the Calico Hills region using the volcaniclastic sediments in the Pickhandle Formation. We

  7. 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.

  8. 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

  9. Interaction of along-slope and down-slope sedimentation processes on the Argentina/Uruguayan slope - First seismo-acoustic results from the Meteor cruise M78/3

    NASA Astrophysics Data System (ADS)

    Schwenk, T.; Preu, B.; Krastel, S.; Fekete, N.; Meyer, M.; Lindhorst, K.; Anasetti, A.; Domnina, Y.

    2009-12-01

    Down-slope and along-slope sediment transport processes play a prominent role by shaping of passive continental margins. Mass wasting phenomena at continental margins have become a hot topic in recent time because of their coastal geo-hazard potential. In addition, deposition (and erosion) related to along-slope transport processes documents the impact of bottom currents in time and space. The Argentina/Uruguay margin forms a setting that is well suited to study the interaction of both processes. First, the area is characterized by the huge sediment discharge of the Rio de la Plata draining an extensive hinterland, which leads to a high potential of sedimentary instability and finally favors mass wasting phenomena. Additionally, several canyons deeply incised into the slope contribute to down-slope sediment transport. Second, the area is not only influenced by the Malvinas-Brazil Current confluence, a prominent element in global surface water circulation, but forms also a key location in the intermediate and deep water global conveyor belt, with both the latter having a major impact on lateral sediment transport by strong contour currents. Therefore, the area has been chosen to be one major target of a new project “Slope architecture and evolution of sedimentary regimes” at the MARUM (Center for Marine Environmental Sciences) at the University of Bremen, Germany. During RV Meteor Cruise M78/3 in May-July 2009 (carried out in cooperation between the MARUM, Bremen and the IFM-GEOMAR, Kiel) sediment transport and depositional patterns from the coast to the deep-sea were be investigated offshore Argentina and Uruguay by means of bathymetric swath-sounder, sediment echosounder, high-resolution multichannel seismic as well as coring. On the slope, the work concentrated one two study areas. North of the Rio de la Plata Mouth, slides, scarps and drift features were be imaged and mapped. In front of and south of the Rio de la Plate Mouth, the Mar del Plate canyon was

  10. 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.

  11. 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

  12. Mercury contamination of active channel sediment and floodplain deposits from historic gold mining at Gold Hill, North Carolina, USA

    NASA Astrophysics Data System (ADS)

    Lecce, Scott; Pavlowsky, Robert; Schlomer, Gwenda

    2008-07-01

    A reconnaissance investigation of mercury contamination associated with historic gold mining in North Carolina, USA, revealed high concentrations of mercury in channel and floodplain sediments downstream from the Gold Hill mining district. The most intense period of mining activities in this region occurred in the 1840s and 1850s when mercury amalgamation was used to recover fine gold particles from milled ore. This paper evaluates mercury concentrations measured in active channel sediments and two cores recovered from historic floodplain deposits of the lower portion of Dutch Buffalo Creek. Mercury concentrations in these cores range from 0.01 to 2.2 mg/kg, with maximum concentrations more than 35 times background levels. A later peak in copper concentrations is associated with the operation of a large copper mine between 1899 and 1906. Following the most intense periods of mining, both mercury and copper concentrations decrease upcore to constant levels of about twice pre-mining background concentrations. Results suggest that vertical trends in mercury and other trace metals provide a useful tool for interpreting rates of historic floodplain sedimentation in the Piedmont of North Carolina.

  13. 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.

  14. 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.

  15. Determination of soil erosion in a steep hill slope with different land-use types: a case study in Mertesdorf (Ruwertal/Germany).

    PubMed

    Hacisalihoglu, Sezgin

    2007-04-01

    Inappropriate land use is one of the main reasons for soil erosion and land degradation. Vine growing plays an important role in many semiarid regions all over the world as a permanent plant cover in terms of preventing erosion, sustainable use of land and water resources, defense against desertification and settling population in rural areas. In this paper, in a steep hill slope of the village Mertesdorf (Ruwertal/Germany), Algemeine boden abtrags gleichung (ABAG) have been applied to determine and compare the soil erosion amounts between the different land use types such as vine growing, forest lands, grasslands, shrubs and new forestations. The results show that the soil erosion amounts differs in a high ratio between the land use types. Soil erosion amounts in the vine growing areas are the highest (6.47 t/ha/year), then comes with 1.19 t/ha/year the over grazed grasslands and the lowest erosion amounts have been determined, as expected, in the forest lands (0.66 t/ha/year).

  16. The Role of Microfossils in the Compression of Marine Sediments: Implications for Submarine Slope Failure

    NASA Astrophysics Data System (ADS)

    Reece, J. S.; Shackleton, T.

    2016-12-01

    The influence of microfossils on engineering properties has long been recognized. However, most experimental studies have been conducted on diatomites, which are almost exclusively composed of diatom fossils. Here, instead, we analyze the impact of varying amounts of microfossils in natural marine sediments on the macro-scale mechanical behavior. We use foraminifera as an example for microfossils, which, in contrast to diatoms, have been understudied. We uniformly mix foraminifera with natural mudstone from Site C0011 in the Nankai Trough, offshore Japan, obtained during Integrated Ocean Drilling Program (IODP) Expedition 322, at three different microfossil concentrations: 0 wt%, 5 wt%, and 10 wt%. The foraminifera, extracted by washing and sieving, originated from IODP Site U1338 in the Equatorial Pacific. We use resedimentation to prepare the homogeneous microfossil-rich mudstone samples and uniaxially compress them to 100 kPa. Additionally, we use scanning electron microscopy to investigate microstructural changes during compression as a function of microfossil content. Microfossil-rich sediments are known to initially not consolidate to as low porosities as other marine clays owing to microfossil shells acting as structural components. But they show a delayed compressibility when the yield stress is overcome and microfossil shells collapse resulting in an increase in porosity and compressibility. Here, we investigate the 1) threshold microfossil content at which the microfabric significantly changes during compression and 2) stress at which foraminifera chambers start to break. We anticipate to observe an increase in compressibility and microstructural changes in the vicinity of the yield stress with increasing microfossil content attributed to the crushing of foraminifera and particle rearrangement. But the total axial stress of 100 kPa at the end of the resedimentation experiments may not be large enough to have a significant effect on the macroscopic

  17. 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

  18. 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

  19. 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.

  20. Velocity-porosity relationships for slope apron and accreted sediments in the Nankai Trough Seismogenic Zone Experiment, Integrated Ocean Drilling Program Expedition 315 Site C0001

    NASA Astrophysics Data System (ADS)

    Hashimoto, Y.; Tobin, H. J.; Knuth, M.

    2010-12-01

    In this study, we focused on the porosity and compressional wave velocity of marine sediments to examine the physical properties of the slope apron and the accreted sediments. This approach allows us to identify characteristic variations between sediments being deposited onto the active prism and those deposited on the oceanic plate and then carried into the prism during subduction. For this purpose we conducted ultrasonic compressional wave velocity measurements on the obtained core samples with pore pressure control. Site C0001 in the Nankai Trough Seismogenic Zone Experiment transect of the Integrated Ocean Drilling Program is located in the hanging wall of the midslope megasplay thrust fault in the Nankai subduction zone offshore of the Kii peninsula (SW Japan), penetrating an unconformity at ˜200 m depth between slope apron sediments and the underlying accreted sediments. We used samples from Site C0001. Compressional wave velocity from laboratory measurements ranges from ˜1.6 to ˜2.0 km/s at hydrostatic pore pressure conditions estimated from sample depth. The compressional wave velocity-porosity relationship for the slope apron sediments shows a slope almost parallel to the slope for global empirical relationships. In contrast, the velocity-porosity relationship for the accreted sediments shows a slightly steeper slope than that of the slope apron sediments at 0.55 of porosity. This higher slope in the velocity-porosity relationship is found to be characteristic of the accreted sediments. Textural analysis was also conducted to examine the relationship between microstructural texture and acoustic properties. Images from micro-X-ray CT indicated a homogeneous and well-sorted distribution of small pores both in shallow and in deeper sections. Other mechanisms such as lithology, clay fraction, and abnormal fluid pressure were found to be insufficient to explain the higher velocity for accreted sediments. The higher slope in velocity-porosity relationship for

  1. Fate of Methane Released from Arctic Shelf and Slope Sediments and Implications for Climate Change

    NASA Astrophysics Data System (ADS)

    James, R. H.; Connelly, D.; Graves, C.; Alker, B.; Cole, C.; Wright, I.; Kolomijeca, A.; 253 Shipboard Scientific Party, Jr.

    2011-12-01

    show that the release of methane is significantly moderated by internal biogeochemical processes, including anaerobic oxidation (in sediments) and aerobic oxidation (in the water column). Thus, the significance of methane release from Arctic slope and shelf sediments for climate change depends critically on whether the methane flux is great enough to overcome these oxidative processes. Westbrook, G.K. et al. (2009) Geophys. Res. Lett., 36, L15608, doi:10.1029/2009GL039191.

  2. 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.

  3. Occurrence of submarine canyons, sediment waves and mass movements along the northern continental slope of the South China Sea

    NASA Astrophysics Data System (ADS)

    Chen, Hongjun; Zhan, Wenhuan; Li, Liqing; Wen, Ming-ming

    2017-07-01

    In this study, we reveal a series of newly discovered submarine canyons, sediment waves, and mass movements on a flat and smooth seafloor using high-resolution, multi-beam bathymetry and shallow seismic surveys along the northern slope of the South China Sea. We also describe their geomorphology and seismic stratigraphy characteristics in detail. These canyons display U-shaped cross sections and are roughly elongated in the NNW-SSE direction; they are typically 8-25 km long, 1.2-7 km wide, and form incisions up to 175 m into Pliocene-Quaternary slope deposits at water depths of 400-1000 m. Slide complexes and the sediment wave field are oriented in the NE-SW direction and cover areas of approximately 1790 and 926 km2, respectively. Debris/turbidity flows are present within these canyons and along their lower slopes. Detailed analysis of seismic facies indicates the presence of six seismic facies, in which Cenozoic strata located above the acoustic basement in the study area can be roughly subdivided into three sequences (1-3), which are separated by regional unconformities (Tg, T4, and T3). By combining these data with the regional geological setting and the results of previous studies, we are able to determine the genetic mechanisms used to create these canyons, sediment wave field, and mass movements. For example, frontally confined slide complexes could have been influenced by high sedimentation rates and high pore pressures. A series of very large subaqueous sediment waves, which record wavelengths of 1.4-2 km and wave heights of 30-50 m, were likely produced by interactions between internal solitary waves and along-slope bottom (contour) currents. Canyons were likely initially created by landslides and then widened laterally by the processes of downcutting, headward erosion, and active bottom currents and debris/turbidity flows on canyon floors. We therefore propose a three-dimensional model to describe the development of these mass movements, the sediment

  4. 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

  5. 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

  6. 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.

  7. 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

  8. 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

  9. 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

  10. 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.

  11. Geochemical reanalysis of historical U.S. Geological Survey sediment samples from the Zane Hills, Hughes and Shungnak quadrangles, Alaska

    USGS Publications Warehouse

    Werdon, Melanie B.; Granitto, Matthew; Azain, Jaime S.

    2015-01-01

    The State of Alaska’s Strategic and Critical Minerals (SCM) Assessment project, a State-funded Capital Improvement Project (CIP), is designed to evaluate Alaska’s statewide potential for SCM resources. The SCM Assessment is being implemented by the Alaska Division of Geological & Geophysical Surveys (DGGS), and involves obtaining new airborne-geophysical, geological, and geochemical data. As part of the SCM Assessment, thousands of historical geochemical samples from DGGS, U.S. Geological Survey (USGS), and U.S. Bureau of Mines archives are being reanalyzed by DGGS using modern, quantitative, geochemical-analytical methods. The objective is to update the statewide geochemical database to more clearly identify areas in Alaska with SCM potential.The USGS is also undertaking SCM-related geologic studies in Alaska through the federally funded Alaska Critical Minerals cooperative project. DGGS and USGS share the goal of evaluating Alaska’s strategic and critical minerals potential and together created a Letter of Agreement (signed December 2012) and a supplementary Technical Assistance Agreement (#14CMTAA143458) to facilitate the two agencies’ cooperative work. Under these agreements, DGGS contracted the USGS in Denver to reanalyze historical USGS sediment samples from Alaska.For this report, DGGS funded reanalysis of 105 historical USGS sediment samples from the statewide Alaska Geochemical Database Version 2.0 (AGDB2; Granitto and others, 2013). Samples were chosen from the Zane Hills area in the Hughes and Shungnak quadrangles, Alaska (fig. 1). The USGS was responsible for sample retrieval from the National Geochemical Sample Archive (NGSA) in Denver, Colorado through the final quality assurance/quality control (QA/QC) of the geochemical analyses obtained through the USGS contract lab. The new geochemical data are published in this report as a coauthored DGGS report, and will be incorporated into the statewide geochemical databases of both agencies.

  12. 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.

  13. Estimation of palaeo-slope and sediment volume of a lacustrine rift basin: A semi-quantitative study on the southern steep slope of the Shijiutuo Uplift, Bohai Offshore Basin, China

    NASA Astrophysics Data System (ADS)

    Liu, Hao; Meng, Jun; Banerjee, Santanu

    2017-10-01

    The sequence architecture and depositional systems of the Palaeogene lacustrine rift succession in the southern steep slope of the Shijiutuo Uplift (SU) in Bohai Offshore Basin (BOB) were investigated using combined 3-D seismic, well log and core data. Four second-order/composite sequences and seven third-order sequences were identified. A detailed analysis revealed fan delta, braid delta and lacustrine depositional systems in the third-order sequences 7 (SQ7). Eleven seismic facies were chosen in the SQ7 to calculate the area and sediment budget. We also calculated the palaeo-slope parameters in the southern steep slope of the SU, including the gradient of basin margin fault slope belt, the shape, average width, average height, width/height ratio and cross sectional area of palaeo-valley. The gradient of the fault slope break belt was inversely proportional to the area and volume of sediments. The higher gradient corresponded to the smaller area and volume of sediments. The width and cross sectional area of palaeo-valleys dominated the volume and facies of sediments. A larger cross sectional area of a palaeo-valley involved much more sediments supply and more favorable conditions for the origin of large-scale deltas. Because of favorable sediment transportation path and existence of large-scale braid delta, the eastern part of the SU formed better quality reservoir than that in the west.

  14. [Sediment content and nitrogen and phosphorus load characteristics of surface runoff on bamboo forest slopes: a simulation test].

    PubMed

    Zhang, Li-Ping; Fu, Xing-Tao; Wu, Xi-Yuan

    2012-04-01

    To understand the load characteristics and related mechanisms of surface runoff on two management types of bamboo forests (bamboo timber forest and bamboo shoot forest) slopes (gradient 20 degrees) in Zhejiang Province, this study measured the runoff volume, sediment yield, its total nitrogen (TN) and total phosphorus (TP) concentrations of runoff under six artificial simulated rainfall intensity (31.8-114.0 mm x h(-1)). In bamboo timber forest, the total runoff volume and runoff coefficient were higher, but the runoff sediment content and the total sediment yield were far lower, as compared with those in bamboo shoot forest. The runoff TN concentration in bamboo shoot forest decreased with increasing rainfall intensity. Under the same rainfall intensity, the runoff TN concentration in bamboo shoot forest was 5-6 times of that in bamboo timber forest. The runoff TP concentration was higher in bamboo timber forest than in bamboo shoot forest, but the TP loss from the sediment runoff in bamboo shoot forest was hundreds times of that in bamboo timber forest. During the processes of the TN and TP losses from the sediment runoff, the TN and TP concentrations at the prophase of runoff yield played a cardinal role, while the runoff volume and sediment yield at the anaphase played a decisive role.

  15. Assessment of submarine landslides hazard through geotechnical and rheological analysis of sediments on the French Atlantic continental slope

    NASA Astrophysics Data System (ADS)

    Toucanne, S.; Howlett, S.; Garziglia, S.; Silva Jacinto, R.; Courgeon, S.; Sabine, M.; Riboulot, V.; Marsset, B.

    2016-12-01

    In the aftermath of the devastating tsunami on the Japanese coast in 2011, a French multi-partnership project called TANDEM has been launched to assess the impact of tsunamis generated or propagated in the vicinity of French Channel and Atlantic coastlines. Tsunami are usually generated by earthquakes, but can also be triggered by submarine landslides. This study focuses on submarine landslides along the French Atlantic continental slope using data that were mainly collected in August 2015 during the GITAN cruise (R/V Pourquoi Pas?). Following geomorphological, geophysical and sedimentological analysis of the Bay of Biscay, efforts were oriented towards the determination of the sediment properties controlling landslide dynamics from in situ and laboratory measurements. Preliminary results show over 700 landslide scars on the French Atlantic continental slope, with most of them occurring between 400 and 1000m water depth and in canyon environments. The Plio-Quaternary sediments draping the majority of the Bay of Biscay are generally normally consolidated and composed of high plasticity clays. They show similar geomechanical properties throughout the area studied, with linear evolutions with depth and good reproducibility for rheological parameters such as Storage and Loss modulus. These similarities allow to extend geotechnical and rheological models to a regional scale in the Bay of Biscay. Our multi-disciplinary approach will provide the tools to assess continental slope failures and submarine landslides generation. Finally, we will aim to qualify and quantify the volumes and flow properties of sediment transported obtained through slope-stability modeling on SAMU-3D and rheology modelling on Nixes-SPH. These results will provide the TANDEM actors with the information necessary to simulate tsunami wave generation.

  16. 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.

  17. 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

  18. 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.

  19. Bedrock Control on Slope Gradients in the Luckiamute Watershed, Central Coast Range, Oregon: Implications for Sediment Transport and Storage

    NASA Astrophysics Data System (ADS)

    Taylor, S. B.

    2002-12-01

    -flow hazard models released by the Oregon Department of Forestry, suggesting that hillslopes in the Tyee Domain are most prone to slope failure (percent of domain area in hazard zone: Tyee = 38.1, Siletz = 30.2, Yamhill = 24.6, and Valley Fill = 0.7). Morphometric analysis of valley widths at 500 m increments shows that drainage across the Tyee Domain covers a much wider swath of valley floor (average valley width = 274 m) compared to a similar-sized drainage area in the Yamhill Domain (average valley width = 109 m). These data suggest that bedrock lithology exerts a strong control on hillslope morphology, style of hillslope process, and valley erosion dynamics in headwater portions of the Luckiamute. The interplay between hillslope transport mechanisms, delivery rates, and channel hydraulics control the volume of sediment exported or stored within a mountainous watershed. The comparatively steep, debris-flow-prone slopes and wide valley bottoms in the Tyee Domain indicate a potential for hillslope transport rates to be greater than the ability of the channel system to export sediment. Analytical results presented herein provide a preliminary dataset upon which to build a field-based sediment-storage budget for the Luckiamute watershed. The working hypothesis is that the Tyee Domain has a significantly greater volume of valley-bottom sediment in storage compared to the other upland domains (Siletz, Yamhill). The model implies that spatial variation of bedrock lithology is a primary factor controlling slope gradients, hillslope delivery rates, and the resulting sediment-transport efficiency of the channel system.

  20. Characterization and Timing of Siliciclastic Sediment Fluxes to Continental Slopes of the Coral Sea During the Late Quaternary

    NASA Astrophysics Data System (ADS)

    Francis, J. M.; Dickens, G. R.; Page, M. C.

    2003-12-01

    The continental margins of southern Papua New Guinea and northeastern Australia together form the world's largest extant tropical mixed siliciclastic-carbonate depositional system where both rivers and shallow marine organisms supply large amounts of sediment to the shelf. The flux and composition of sediment shed from these margins to surrounding slopes and basins changes dramatically over the late Quaternary. This is to be expected given mixed sediment sources and large amplitude variations in sea-level and climate during this time. Importantly, though, the observed accumulation of the siliciclastic material on slopes deviates significantly from generic sequence stratigraphic models. Recent studies on the northeast Australian margin clearly show greatly increased fluxes coincident with late transgression ca. 12-7 ka rather than lowstand ca. 25-18 ka (Dunbar and Dickens, Sed. Geology, in press; Page et al., Geology, in press). In this study we examine the mineralogy and grain size of the siliciclastic fraction down a series of well-dated cores along the slope of the northeastern Australian margin to further characterize this phenomenon. Sediment samples were taken at ~10 cm intervals down drill cores (collected on ODP Leg 133) and piston cores. Each sample was reacted with weak acetic acid to digest the carbonate component. The remaining siliciclastic component was analyzed for mineralogy using an XRD and for grain size using a Laser Particle Size Analyzer. Preliminary results from ODP Site 820 show that the siliciclastic component deposited during early transgression is dominated by silt but that, from ca. 10 ka until present, the sand percent of this component increased. These results may support either of two end-member models to explain elevated siliciclastic accumulation during late transgression. In the first model, margin physiography controlled siliciclastic accumulation, whereby sediment was stored behind an exposed barrier reef during lowstand, and

  1. Distribution and generic composition of culturable marine actinomycetes from the sediments of Indian continental slope of Bay of Bengal

    NASA Astrophysics Data System (ADS)

    Das, Surajit; Lyla, P. S.; Ajmal Khan, S.

    2008-05-01

    Actinomycetes population from continental slope sediment of the Bay of Bengal was studied. Samples were collected during two voyages of FORV Sagar Sampada in 2004 (May-June) and 2005 (July) respectively from 11 transects (each transect had ca. 200 m, 500 m, and 1 000 m depth stations). The physicochemical parameters of overlying water, and sediment samples were also recorded. The actinomycete population ranged from 5.17 to 51.94 CFU/g dry sediment weight and 9.38 to 45.22 CFU/g dry sediment weight during the two cruises respectively. No actinomycete colony was isolated from stations in 1 000 m depth. Two-way analysis of variance showed significant variation among stations (ANOVA two-way, P<0.05), but no significance was found between the two cruises (ANOVA two-way, P<0.05). Populations in stations in 500 m depth in both cruises were higher than that of 200 m depth stations with statistically insignificant difference (ANOVA two-way, P>0.05). Three actinomycetes genera were identified. Streptomyces was found to be the dominating one in both the cruises, followed by Micromonospora, and Actinomyces. The spore of Streptomyces isolates showed the abundance in spiral spore chain. Spore surface was smooth. Multiple regression analysis revealed that the influencing physico-chemical factors were sediment pH, sediment temperature, TOC, porosity, salinity, and pressure. The media used in the present study was prepared with seawater. Thus, they may represent an autochthonous marine flora and deny the theory of land runoff carriage into the sea for adaptation to the salinity of the seawater and sediments.

  2. 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

  3. Assessing the performance of a riparian vegetation model in a river with a low slope and fine sediment.

    PubMed

    Sanjaya, Kelum; Asaeda, Takashi

    2017-03-01

    Riparian ecosystems are threatened worldwide, necessitating conservation strategies. Numerical models tailored for specific geographic areas have been developed as management support tools. However, few models are suitable for multiple river conditions, and developing these models or evaluating their suitability has become an emerging topic. The dynamic riparian vegetation model (DRIPVEM) is a numerical model developed for steep and gravelly Japanese rivers, where it has been successfully tested. Our objective was to assess the performance of DRIPVEM in a river with a low slope and fine sediment, similar to the characteristics of continental rivers. A reach of the Hii River was selected for testing the model's ability to predict the distribution of Salix spp. (willow) and herbs, as well as herb biomass and tree age. The model was calibrated based on field investigations of a selected river section. Simulation of the studied reach was carried out for the past five decades, depending on data availability. Non-parametric tests were used to compare the simulated and observed results. The simulated and observed vegetation distribution maps agreed fairly well and the sensitivity of the model for simulation of trees, herbs and bare areas was greater than 0.6. The kappa coefficients of agreement values were 0.48 and 0.49, indicating fair agreement. Moreover, the simulated biomass and tree age agreed well with observation. We conclude that the DRIPVEM simulated the observed conditions in the Hii River well, indicating that the model is applicable to rivers characterized by low slope and fine sediment grain size.

  4. Treatment of a sloping fluid-solid interface and sediment layering with the seismo-acoustic parabolic equation.

    PubMed

    Collins, Michael D; Siegmann, William L

    2015-01-01

    The parabolic equation method is extended to handle problems in seismo-acoustics that have multiple fluid and solid layers, continuous depth dependence within layers, and sloping interfaces between layers. The medium is approximated in terms of a series of range-independent regions, and a single-scattering approximation is used to compute transmitted fields across the vertical interfaces between regions. The approach is implemented in terms of a set of dependent variables that is well suited to piecewise continuous depth dependence in the elastic parameters, but one of the fluid-solid interface conditions in that formulation involves a second derivative that complicates the treatment of sloping interfaces. This issue is resolved by using a non-centered, four-point difference formula for the second derivative. The approach is implemented using a matrix decomposition that is efficient when the parameters of the medium have a general dependence within the upper layers of the sediment but only depend on depth in the water column and deep within the sediment.

  5. Mathematical model of sediment and solute transport along slope land in different rainfall pattern conditions

    NASA Astrophysics Data System (ADS)

    Tao, Wanghai; Wu, Junhu; Wang, Quanjiu

    2017-03-01

    Rainfall erosion is a major cause of inducing soil degradation, and rainfall patterns have a significant influence on the process of sediment yield and nutrient loss. The mathematical models developed in this study were used to simulate the sediment and nutrient loss in surface runoff. Four rainfall patterns, each with a different rainfall intensity variation, were applied during the simulated rainfall experiments. These patterns were designated as: uniform-type, increasing-type, increasing- decreasing -type and decreasing-type. The results revealed that changes in the rainfall intensity can have an appreciable impact on the process of runoff generation, but only a slight effect on the total amount of runoff generated. Variations in the rainfall intensity in a rainfall event not only had a significant effect on the process of sediment yield and nutrient loss, but also the total amount of sediment and nutrient produced, and early high rainfall intensity may lead to the most severe erosion and nutrient loss. In this study, the calculated data concur with the measured values. The model can be used to predict the process of surface runoff, sediment transport and nutrient loss associated with different rainfall patterns.

  6. Mathematical model of sediment and solute transport along slope land in different rainfall pattern conditions

    PubMed Central

    Tao, Wanghai; Wu, Junhu; Wang, Quanjiu

    2017-01-01

    Rainfall erosion is a major cause of inducing soil degradation, and rainfall patterns have a significant influence on the process of sediment yield and nutrient loss. The mathematical models developed in this study were used to simulate the sediment and nutrient loss in surface runoff. Four rainfall patterns, each with a different rainfall intensity variation, were applied during the simulated rainfall experiments. These patterns were designated as: uniform-type, increasing-type, increasing- decreasing -type and decreasing-type. The results revealed that changes in the rainfall intensity can have an appreciable impact on the process of runoff generation, but only a slight effect on the total amount of runoff generated. Variations in the rainfall intensity in a rainfall event not only had a significant effect on the process of sediment yield and nutrient loss, but also the total amount of sediment and nutrient produced, and early high rainfall intensity may lead to the most severe erosion and nutrient loss. In this study, the calculated data concur with the measured values. The model can be used to predict the process of surface runoff, sediment transport and nutrient loss associated with different rainfall patterns. PMID:28272431

  7. 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.

  8. Records of continental slope sediment flow morphodynamic responses to gradient and active faulting from integrated AUV and ROV data, offshore Palos Verdes, southern California Borderland

    USGS Publications Warehouse

    Maier, Katherine L.; Brothers, Daniel; Paull, Charles K.; McGann, Mary; Caress, David W.; Conrad, James E.

    2016-01-01

    Variations in seabed gradient are widely acknowledged to influence deep-water deposition, but are often difficult to measure in sufficient detail from both modern and ancient examples. On the continental slope offshore Los Angeles, California, autonomous underwater vehicle, remotely operated vehicle, and shipboard methods were used to collect a dense grid of high-resolution multibeam bathymetry, chirp sub-bottom profiles, and targeted sediment core samples that demonstrate the influence of seafloor gradient on sediment accumulation, depositional environment, grain size of deposits, and seafloor morphology. In this setting, restraining and releasing bends along the active right-lateral Palos Verdes Fault create and maintain variations in seafloor gradient. Holocene down-slope flows appear to have been generated by slope failure, primarily on the uppermost slope (~ 100–200 m water depth). Turbidity currents created a low relief (< 10 m) channel, up-slope migrating sediment waves (λ = ~ 100 m, h ≤ 2 m), and a series of depocenters that have accumulated up to 4 m of Holocene sediment. Sediment waves increase in wavelength and decrease in wave height with decreasing gradient. Integrated analysis of high-resolution datasets provides quantification of morphodynamic sensitivity to seafloor gradients acting throughout deep-water depositional systems. These results help to bridge gaps in scale between existing deep-sea and experimental datasets and may provide constraints for future numerical modeling studies.

  9. 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.

  10. 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.

  11. 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.

  12. Estimation of Underground Permeability and Porosity of Slope Sediments in the Northern Gulf of Mexico, IODP Expedition 308

    NASA Astrophysics Data System (ADS)

    Aizawa, Y.; Shimamoto, T.; Flemings, P. B.; Behrmann, J. H.; John, C. M.

    2005-12-01

    The Brazos-Trinity Basin #4 and Ursa Basin on the northern continental slope off Texas and Louisiana in the Gulf of Mexico are ideal locations for studying the sedimentation and fluid flow processes leading to the development of overpressure because of their contrasting sedimentation histories. The former is a small basin with a slow sedimentation rate and with no overpressure development. Whereas the sedimentation in the latter is high, resulting in the development of overpressure which is likely to have triggered a large-scale slope failure, slumping and faulting. The purposes of Expedition 308 are to document how pressure, stress and geology are coupled to control fluid migration on passive margins, through drilling at sites U1319 and U1320 in the Brazos-Trinity Basin #4 and at sites U1322 and U1324 in Ursa Basin. Quantitative basin analysis, i.e., analysis of sedimentation, fluid flow and compaction processes at least in two dimensions, is possible based on the measured hydraulic properties of those core samples at elevated effective pressures corresponding to various depths. We have just started systematic measurement of permeability, porosity and specific storage capacity of core samples, using an intravessel deformation and fluid-flow apparatus at Kyoto University. Samples were first dried at temperatures of 90-100°C for more than 3 days to evaporate pore water. Permeability and porosity have been measured with N2 gas flow method and with a picnometer, respectively, at confining pressures up to 200 MPa and pore pressures to 2 MPa. The age of drill cores range from the Pleistocene to the Quarternary, and we plan to evaluate the long-term cementation effect by measuring porosity for samples from all stratigraphic horizons. The complete data set will allow one to estimate permeability and porosity structures at depths even greater than 10 km. Our measurements show that permeability of silt in the shallow part of Brazos-Trinity Basin #4 ranges from 10-15 m2 at

  13. Using remotely-sensed nearshore suspended sediment as an indicator of environmental change on the Alaskan North Slope

    NASA Astrophysics Data System (ADS)

    Hobson, Anne Carrie Hickey

    The effects of climate change are increasing the vulnerability the delicate Arctic system on the North Slope of Alaska. Concurrently, oil and gas development is projected to expand across the region, the wide-scale effects of which are largely unknown in a less-resilient system. This research provides the framework for using satellite data to assess and monitor suspended sediment conditions in the nearshore Alaskan Beaufort Sea, which provide a key indicator of environmental change. Satellite monitoring of suspended sediment levels provides a cost-effective means to obtain nearly real-time, synoptic information about environmental change on the North Slope. This information can be incorporated into cumulative effects analyses and enhance their capability to assess and predict the environmental effects of oil and gas development in a changing climate. Surface reflectance data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Advanced Very High Resolution Radiometer (AVHRR) sensors were calibrated to total suspended sediment (TSS) concentrations in the Alaskan Beaufort Sea and used to construct time series of proxy TSS data for 2000--2005 and 1981--2004, respectively. These time series produced a baseline quantifying the interannual variability and 24-year trends in median annual TSS concentrations at locations in the nearshore Alaskan Beaufort Sea. Increasing trends over the analysis period were identified in the outflow areas of the Ikpikpuk, Colville, Kuparuk and Sagavanirktok Rivers, as well as in Admiralty Bay. Additionally, TSS levels in 1994 and 2000 exceeded the normal range of variability at several of the nearshore locations investigated. Different areas along the nearshore had varying TSS magnitudes and modes of variability, a function of the terrestrial and nearshore processes controlling TSS conditions at each location. An empirical model explained 65 percent of the variability in annual median TSS values using precipitation factors that

  14. Response of geomorphic and geological processes to insufficient and ample sediment supply along the upper continental slope in the north-western South China Sea

    NASA Astrophysics Data System (ADS)

    Chen, Hongjun; Zhan, Wenhuan; Wu, Shiguo

    2016-12-01

    We document upper slope sedimentary process and strata on the passive margin of the north-western South China Sea (SCS) using multibeam bathymetry and high-resolution seismic data. The upper slope can be divided into two segments based on geomorphology, strata, and sediment supply. (1) The east segment is characterised by deep incised canyons and gullies, and slope failure. Submarine canyons with both U- and V-shaped morphology (13-28 km long × 2-4 km wide) are oriented NNE-SSW or NNW-SSE and are approximately perpendicular to the slope. Erosion is dominant, with escarpments, slumps, and several mass transport deposits (MTDs). Shelf-margin clinoforms show strongly upward vertical aggradation with time and are strongly aggradational in style. Since 5.5 Ma, the shelf break line migrated southwards and then retreated to its present position. The segment is classified as erosion-dominated due to insufficient sediment supply. (2) The west segment has a smooth surface, gentle gradient, and a strongly progradational style, with MTDs triggered by high sedimentation rates. Shelf-margin clinoforms display a combination of progradational and aggradational stacking patterns. The shelf break line migrated southwards with time. The segment is classified as deposition-dominated, resulting from plentiful sediment supply. Depositional models have been constructed for each segment: a constant shelf break model with insufficient sediment supply in the east, and a migration shelf break model with plenty sediment supply in the west. This case study contributes to the understanding of the upper slope sedimentary process and stratigraphic style under different sediment supply conditions.

  15. 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 μg/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 μg/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 μg/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.

  16. Observations on Cretaceous abyssal hills in the northeast Pacific

    USGS Publications Warehouse

    Eittreim, S.L.; Piper, D.Z.; Chezar, H.; Jones, D.R.; Kaneps, A.

    1984-01-01

    An abyssal hills area of 50 ?? 60 km in the northeast Pacific was studied using bottom transponder navigation, closely spaced survey lines, and long-traverse oblique photography. The block-faulted north-south hills are bounded by scarps, commonly with 40?? slopes. On these steep scarps sedimentation is inhibited and pillow basalts often crop out. An ash layer of high acoustic reflectivity at about 7 m subbottom depth blankets the area. This ash occurs in multiple beds altered to phillipsite and is highly consolidated. A 24 m.y. age for the ash is based on ichthyolith dates from samples in the overlying sediments. Acoustically transparent Neogene sediments above the ash are thickest in trough bottoms and are absent or thin on steep slopes. These Neogene sediments are composed of pale-brown pelagic clays of illite, quartz, smectite, chlorite and kaolinite. Dark-brown pelagic clays, rich in smectite and amorphous iron oxides, underlie the Neogene surficial sediments. Manganese nodules cover the bottom in varying percentages. The nodules are most abundant near basement outcrops and where the subbottom ash layer is absent. ?? 1984.

  17. Burial and degradation of organic carbon in Louisiana shelf/slope sediments

    NASA Astrophysics Data System (ADS)

    Sampere, Troy P.; Bianchi, Thomas S.; Allison, Mead A.; McKee, Brent A.

    2011-11-01

    The primary focus of this paper is to better understand carbon burial on the Louisiana continental margin using spatial scales that covered various shelf depositional areas far-field and near-field (sediment and organic carbon inputs relative to river mouth proximity) and covering a variety of sedimentation rates. Box-cores samples were collected in July 2003; cores were collected along two depositional transects extending westward and southward from the Southwest Pass (SW Pass). A key difference between the two transects sampled in this study was the greater occurrence of mobile muds derived from spillover from shallower regions along the westward 50 m isobaths. The dominant mechanism for mixing in the surface active zone (SAZ) on the inner Louisiana shelf was due to physical, not biological, forces. Burial efficiencies for organic carbon (57.2-91.5%) and total nitrogen (44.2-86.9%) ranged widely across all shelf stations. Lower burial efficiencies for bulk organic carbon, total nitrogen, and pigment biomarkers were associated with mobile muds west of Southwest Pass. Chlorophyll a concentrations were significantly higher than pheopigments at depth at the Mississippi River and Southwest Pass stations, making up 40.4 and 77.4% of total pigment concentrations in the (SAZ) and 46.2 and 63.2% in the accumulation zone (AZ), respectively. These results are in agreement with earlier plant pigment studies which showed that a large fraction of the phytodetritus delivered to the inner shelf was derived from coastal and river diatoms. The amount of lignin preserved with depth decreased with increasing residence time in the SAZ and diagenetic zone (DZ) along the canyon transect but not along the western transect. Trends for lignin concentration followed previously identified surface sediment trends indicating overall lower burial of refractory terrestrial material at depth with greater distance offshore.

  18. 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.

  19. Calcareous nannofossil biostratigraphy and geochronology of Neogene trench-slope cover sediments in the south Boso Peninsula, central Japan: Implications for the development of a shallow accretionary complex

    NASA Astrophysics Data System (ADS)

    Chiyonobu, Shun; Yamamoto, Yuzuru; Saito, Saneatsu

    2017-07-01

    The geological structure and calcareous nannofossil biostratigraphy of the Middle to Late Miocene trench-slope succession in the southern Boso Peninsula, central Japan, were examined to obtain chronological constraints on the accretion and formation of the trench-slope architecture. As a result, trench-slope cover sediments (Kinone and Amatsu Formations) are clearly distinguishable from the Early Miocene Hota accretionary complex (Hota Group). The Hota accretionary complex was deposited below the carbonate compensation depth (CCD) and was affected by intense shearing, forming an east-west trending and south-verging fold and thrust belt. In contrast, the trench-slope cover sediments basically have a homoclinal dip, except at the northern rim where they are bounded by fault contact. They contain many species of calcareous nannofossils and foraminifers, which are indicative of their depositional environment above the CCD, and they show shallowing-upward sedimentary structures. Biostratigraphy revealed that the depositional age of the trench-slope sediments is ca. 15-5.5 Ma, suggesting that there is an approximately 2 myr hiatus beween the Miura Group and the underlying accretionary prism. Based on these results, the age of accretion of the Hota Group is inferred to be between ca. 17-15 Ma, and the group is covered by trench-slope sediments overlain on it after ca. 15 Ma. The timing of accretion and the age of the trench-slope basin tend to be younger southward of the Boso Peninsula. The accretionary system of the Boso Peninsula apparently developed in two stages, in the Middle Miocene and in the Late Miocene to Pliocene.

  20. Evolution of mud-capped dredge pits following excavation: sediment trapping and slope instability

    NASA Astrophysics Data System (ADS)

    Obelcz, J.; Xu, K.; Bentley, S. J.; Li, C.; Miner, M. D.; O'Connor, M. C.; Wang, J.

    2016-02-01

    Many fluvial channels incised the Northern Gulf of Mexico inner continental shelf during the late Quaternary. Mud-capped dredge pits (MCDPs), which are generally elongate and deep (8-10 m) excavations, target sandy fluvial channel deposits for coastal restoration projects. The morphological evolution of dredge excavations in noncohesive sandy substrate is well studied, but MCDPs have up to a several-meter-thick veneer of Holocene shelf mud overlying sandy channel deposits. This stratigraphy is hypothesized to result in more complex post-dredge morphology than pit walls simply slumping to the angle of repose shortly after excavation. Numerical modeling of MCDP post-dredge response conducted prior to excavation indicates pit walls may retrogressively fail, which is accounted for in pit design by assigning no-dredge setback buffers from pipelines or cultural and environmental resources. To validate model results and test effectiveness of setback buffers, a geophysical survey of the Sandy Point MCDP (20 km west of the Mississippi River Delta in 10m deep water), where 1.7 million m3 of sandy sediment was excavated in 2012, was conducted May 2015. A total of 84 line-km of high-resolution chirp subbottom and a 27 km2 grid of swath bathymetry and sidescan sonar were collected. The data indicate the dredge pit walls are differentially slumping, with the western pit wall in a more active state of failure than the eastern wall. The western failures morphologically resemble features observed along the muddy Mississippi River Delta Front at water depths of 20-100 m, including bowl-shaped collapse failures and retrogressive stair-stepped slumps; these failures may play a key role in evaluating the distance of setback buffer zone to pipelines. These features indicate the cohesive mud overlying the sandy infill has a prominent role in pit wall stability. A 0.5-1 m thick acoustically transparent package overlies the entire pit floor (interpreted as a possible fluid mud layer

  1. 1. Physical properties and age of mid-slope sediments dredged from the Eastern Australian Continental Margin and the implications for continental margin erosion processes

    NASA Astrophysics Data System (ADS)

    Hubble, T.; Yu, P.; Airey, D.; Clarke, S. L.; Boyd, R.; Keene, J.; Exon, N.; Gardner, J. V.

    2010-12-01

    A large number of submarine landslides were identified on the continental slope on the Eastern Australian margin during voyages aboard the RV Southern Surveyor in 2008. Preliminary sedimentological analysis as well as geotechnical and biostratigraphic data determined for mid-slope dredge samples are reported. The dredge samples are normally-consolidated, calcareous sandy-muds of Neogene age and were recovered from submarine scarps located on the mid-continental slope. These scarps probably represent submarine landslide failure surfaces. Slope stability modelling using classical soil mechanics techniques and measured sediment shear-strengths indicates that the slopes should be stable; however, the ubiquity of mid-slope slides on this margin indicates that their occurrence is relatively common and that submarine-sliding should probably be considered to be a normal characteristic of the margin as suggested by Boyd et al (2010). While this presents something of an interpretational paradox, it nevertheless indicates that an, as yet, unidentified mechanism acts to reduce the shear resistance of these sediments to very low values which enables the slope failures to occur. It is suspected that the expansion of the Antarctic Icesheet in Mid-Miocene time and the consequent large-scale production of cold, equator-ward migrating, bottom water has caused significant erosion and removal of material from mid-slope and lower slope of the Australian continental margin in the Tasman Sea since the Mid-Miocene. Such a process would help to explain the exposure of hard Palaeozoic basement rocks along much of the southern part of the Eastern Australian continental margin. It is also suspected that erosion due to equator-ward moving bottom water effectively and progressively removed material from the toe of the continental slope sediment wedge. This rendered the slope sediments that were deposited throughout the Tertiary more susceptible to mass failure than would have otherwise been the

  2. Sediment creep on slopes in pelagic limestones: Upper Jurassic of Northern Calcareous Alps, Austria

    NASA Astrophysics Data System (ADS)

    Ortner, Hugo; Kilian, Sinah

    2016-10-01

    Slump structures in Upper Jurassic pelagic limestones of the Northern Calcareous Alps were studied using methods of ductile structural geology. The early deformation observed cannot be explained by conventional models for slumping, commonly describing slump complexes with an extending upper and contracting lower part. Instead, the structures suggest distributed bedding-parallel surficial stretching, and folding localized by roll-over normal faulting. The initially isoclinal and recumbent folds are pervasively overprinted by stretching, causing reorientation of fold axes into the downslope direction. Transport of folds separates antiformal and synformal hinges, and the resulting isolated hinges resemble intrafolial folds in metamorphic terranes. Only folds formed late in the process of lithification allow insight in the early stages of fold evolution. We suggest that this type of early deformation represents sediment creep that may be characteristic for slump structures in pelagic carbonates.

  3. 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.

  4. 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.

  5. 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

  6. Methane-metabolizing microbial communities in sediments of the Haima cold seep area, northwest slope of the South China Sea.

    PubMed

    Niu, Mingyang; Fan, Xibei; Zhuang, Guangchao; Liang, Qianyong; Wang, Fengping

    2017-09-01

    Cold seeps are widespread chemosynthetic ecosystems in the deep-sea environment, and cold seep microbial communities of the South China Sea are poorly constrained. Here we report on the archaeal communities, particularly those involved in methane metabolization, in sediments of a newly discovered cold seep (named 'Haima') on the northwest slope of the South China Sea. Archaeal diversity, abundance and distribution were investigated in two piston cores collected from a seep area (QDN-14B) and a non-seep control site (QDN-31B). Geochemical investigation of the QDN-14B core identified an estimated sulfate-methane transition zone (Estimated SMTZ) at 300-400 cm below sea floor (cmbsf), where a high abundance of anaerobic methane-oxidizing archaea (ANME) occurred, as revealed by analysis of the 16S rRNA gene and the gene (mcrA) encoding the α-subunit of the key enzyme methyl-coenzyme M reductase. ANME-2a/b was predominant in the upper and middle layers of the estimated SMTZ, whereas ANME-1b outcompeted ANME-2 in the sulfate-depleted bottom layers of the estimated SMTZ and the methanogenic zone. Fine-scale phylogenetic analysis further divided the ANME-1b group into three subgroups with different distribution patterns: ANME-1bI, ANME-1bII and ANME-1bIII. Multivariate analyses indicated that dissolved inorganic carbon and sulfate may be important factors controlling the composition of the methane-metabolizing community. Our study on ANME niche separation and interactions with other archaeal groups improves our understanding of the metabolic diversity and flexibility of ANME, and the findings further suggest that ANME subgroups may have evolved diversified/specified metabolic capabilities other than syntrophic anaerobic oxidation of methane coupled with sulfate reduction in marine sediments. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. Low methane concentrations in sediment along the continental slope north of Siberia: Inference from pore water geochemistry

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    The Eastern Siberian Margin (ESM), a vast region of the Arctic, potentially holds large amounts of methane in sediments as gas hydrate and free gas. Although this CH4 has become a topic of discussion, primarily because of rapid regional climate change, the ESM remains sparingly explored. Here we present pore water chemistry results from 32 cores taken during Leg 2 of the 2014 SWERUS-C3 expedition. The cores come from depth transects across the continental slope of the ESM between Wrangel Island and the New Siberian Islands. Upward CH4 flux towards the seafloor, as inferred from profiles of dissolved sulfate (SO42-), alkalinity, and the δ13C-dissolved inorganic Carbon (DIC), is negligible at all stations east of where the Lomonosov Ridge abuts the ESM at about 143°E. In the upper eight meters of these cores, downward sulfate flux never exceeds 9.2 mol/m2-kyr, the upward alkalinity flux never exceeds 6.8 mol/m2-kyr, and δ13C-DIC only slowly decreases with depth (-3.6‰/m on average). Additionally, dissolved H2S was not detected in these cores, and nutrient and metal profiles reveal that metal oxide reduction by organic carbon dominates the geochemical environment. A single core on Lomonosov Ridge differs, as diffusive fluxes for SO42- and alkalinity were 13.9 and 11.3 mol/m2-kyr, respectively, the δ13C-DIC gradient was 5.6‰/m, and Mn2+ reduction terminated within 1.3 m of the seafloor. These are among the first pore water results generated from this vast climatically sensitive region, and they imply that significant quantities of CH4, including gas hydrates, do not exist in any of our investigated depth transects spread out along much of the ESM continental slope. This contradicts previous assumptions and hypothetical models and discussion, which generally have assumed the presence of substantial CH4.

  13. 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.

  14. 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

  15. 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.

  16. 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

  17. 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

  18. Red Hill

    EPA Pesticide Factsheets

    Information about the Red Hill Bulk Fuel Storage Facility in Hawaii Administrative Order on Consent (AOC), an enforceable agreement of the Hawaii Department of Health, the Environmental Protection Agency, and the U.S. Navy -- Defense Logistics Agency.

  19. 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.

  20. 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

  1. Dark Slope Streaks

    NASA Image and Video Library

    2015-10-20

    Dark streaks are visible on the slopes of hills and crater rims in Amazonis Planitia. It is thought that the removal of dust by downslope movement reveals the darker rocks beneath. Orbit Number: 60745 Latitude: 13.62 Longitude: 191.678 Instrument: VIS Captured: 2015-08-24 11:59 http://photojournal.jpl.nasa.gov/catalog/PIA20072

  2. 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.; hide

    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.

  3. Characterizing landscape-scale erosion using 10Be in detrital fluvial sediment: Slope-based sampling strategy detects the effect of widespread dams

    NASA Astrophysics Data System (ADS)

    Reusser, Lucas J.; Bierman, Paul R.; Rizzo, Donna M.; Portenga, Eric W.; Rood, Dylan H.

    2017-05-01

    Concentrations of in situ 10Be measured in detrital fluvial sediment are frequently used to estimate long-term erosion rates of drainage basins. In many regions, basin-averaged erosion rates are positively correlated with basin average slope. The slope dependence of erosion allows model-based erosion rate estimation for unsampled basins and basins where human disturbance may have biased cosmogenic nuclide concentrations in sediment. Using samples collected from southeastern North America, we demonstrate an approach that explicitly considers the relationship between average basin slope and erosion rate. Because dams and reservoirs are ubiquitous on larger channels in the field area, we selected 36 undammed headwater subbasins (average area 10.6 km2) from which we collected river sand samples and measured 10Be concentrations. We used these data to train a predictive model that relates average basin slope and 10Be-inferred erosion rate. Applying our model to 28 basins in the same region previously studied with 10Be, we find that the model successfully predicts erosion rates for basins of different sizes if they are undammed or if samples were collected >25 km downstream of dams. For samples collected closer to dams, measured erosion rates exceed modeled erosion rates for two-thirds of the samples. In three of four cases where paired samples were collected upstream of reservoirs and downstream of the impounding dam, 10Be concentrations were lower downstream. This finding has implications for detrital cosmogenic studies, whether or not samples were collected directly downstream of dams, because dams obstruct most major rivers around the world, effectively trapping sediment that originated upstream.

  4. 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.

  5. Sediment property changes in response to the glacial activity on the continental slope to the eastern side of Pennell-Iselin Bank in the Ross Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Ha, Sangbeom; Khim, Boo-Keun; Colizza, Ester; Marci, Patrizia; Sagnotti, Leonardo; Caricchi, Chiara; Langone, Leonardo; Giglio, Federico; Kuhn, Gerhard

    2017-04-01

    High latitude marine environments including the Antarctic continental margin have sensitively responded to the climate change, and the Ross Sea is one of these examples. Subglacial marine sedimentary changes have been studied extensively in the continental shelf areas of the Ross Sea to understand the growth and retreat of glaciers in response to the glacial-interglacial changes. However, the continental slope areas of the Ross Sea have not been investigated comparatively less. Thus, in order to comprehend the glaciomarine sedimentation change on the continental slope of the Ross Sea, 3 gravity cores (GC1, GC2, GC3) and 3 box cores (BC1, BC2, BC3) were collected from 3 sites (RS14-C1, C2, C3 by decreasing water depth), respectively, across the continental slope to the eastern side of the Pennell-Iselin Bank during XXIX PNRA (Rosslope II) cruise in 2014. A variety of sedimentological (grain size, magnetic susceptibility, XRF) and geochemical (biogenic opal, total organic carbon, CaCO3, δ13C of organic matter) properties were analyzed along with AMS 14C dating of bulk sediments. All core sediments consist of mostly hemipelagic sandy clay or silty clay with scattered IRD (Ice-Rafted Debris). Sediment color of three cores changes consistently downward from brown to gray with some alternations in core GC1. Based on the basic sediment properties such as sediment color, grain size, and magnetic susceptibility, sediment lithology was decided to divide Unit A and Unit B, both of which were further divided into two subunits. Despite old carbon effect, AMS 14C dates confirm that Unit A belongs to the Holocene and Unit B covers the deglacial to last glacial period at the top of cores. Unit A is characterized by low TOC, low CaCO3, low biogenic opal content and low C/N ratios, whereas Unit B is characterized by high TOC, high CaCO3, moderate to high biogenic opal content and high C/N ratios. Consequently, Unit A represents the modern and interglacial sediments deposited mainly

  6. 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.

  7. [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.

  8. Water Discharge and Sediment Load from the Western Slopes of the Colombian Andes with Focus on Rio San Juan.

    PubMed

    Restrepo; Kjerfve

    2000-01-01

    Small rivers draining high-rainfall basins and mountainous terrain west of the Cordilleras in South America have disproportionately high water discharge and sediment load. Fifteen rivers in western Colombia discharge a combined 254 km3 yr-1 or 8020 m3 s-1 of water into the Pacific. Sediment yield is strongly correlated with basin area (R2=0.97), and sediment load is correlated with water discharge (R2=0.73). Rio San Juan occupies a 16,465-km2 basin with a mean annual rainfall of 7277 mm. It has the highest water discharge (2550 m3 s-1), sediment load (16x106 t yr-1), and basin-wide sediment yield (1150 t km-2 yr-1) on the entire west coast of South America. Rio Patía drains a 23,700-km2 basin with a mean annual rainfall of 2821 mm. Its water discharge, sediment load, and basin-wide sediment yield are 1291 m3 s-1, 14 t yr-1, and 972 t km-2 yr-1, respectively. Rio San Juan and Rio Patía deliver 30x106 t of suspended sediment annually into the Pacific. Analysis of data for an additional 22 rivers in Colombia that drain into the Caribbean Sea indicates that the Pacific rivers have at least twice the sediment yield compared with the larger Rio Magdalena. Our results confirm that the Pacific rivers of Colombia need to be accounted for in global sediment budgets.

  9. 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.

  10. Suspended sediment load and mechanical erosion in the Senegal Basin — Estimation of the surface runoff concentration and relative contributions of channel and slope erosion

    NASA Astrophysics Data System (ADS)

    Kattan, Z.; Gac, J. Y.; Probst, J. L.

    1987-06-01

    The main purpose of this paper is to propose a method to better understand the suspended sediment dynamics in the Senegal Basin, and the behaviour of the river particulate load at Bakel gauging station (218,000 km 2) during the period 1979-1984. The method is based on the estimation of surface discharge using a simple hydrological model which allows separation of the different flow components of the annual hydrograph. Then the suspended sediment loads can be correlated with the surface discharge. During the study period, the mean annual flow (330 m 3s -1) represented only 46% of the mean long-term flow (1903-1984), and the mean yearly particulate load carried by the Senegal River was about 1.9 million tons. Two approaches are used to estimate the different contributions to the river's suspended sediment transport. The main contribution originates from slope erosion, which supplies 50-80% of the total sediment transport and the second originates from channel erosion. The suspended sediment concentration in the surface runoff, primarily calculated by a global annual method, ranges from 0.9 to 1.6 gl -1 and averages 1.3 gl -1. After correction for channel erosion input, this concentration is reduced to 1.1 gl -1.

  11. 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.

  12. 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.; 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

  13. Export of non-point source suspended sediment, nitrogen, and phosphorus from sloping highland agricultural fields in the East Asian monsoon region.

    PubMed

    Reza, Arif; Eum, Jaesung; Jung, Sungmin; Choi, Youngsoon; Owen, Jeffrey S; Kim, Bomchul

    2016-12-01

    Excess sediment and nutrient export from agricultural fields with steep slopes is a major concern linked to surface water quality in Korea. In this study, the export of suspended sediment (SS), total nitrogen (TN), and total phosphorus (TP) and their event mean concentrations (EMCs) in surface runoff from a highland mixed land use (61% forested, 30% cropped, 9% other) watershed were quantified. In 2007, the Korean Ministry of Environment (MoE) declared the study area as a priority region for non-point source (NPS) pollution management and initiated various best management practices (BMPs) in the study watershed. SS, TN, and TP concentrations in Mandae Stream were monitored for 5 years (2009-2013) to evaluate the effectiveness of BMPs. Average EMCs for SS, TN, and TP were as high as 986, 3.4 and 0.8 mg/L, respectively. The agricultural export coefficients of agricultural land in the study watershed for SS, TN, and TP were 5611, 171, and 6.83 kg/ha/year, respectively. A comparison with results from other studies shows that both EMCs and agricultural export coefficients in the study watershed were much higher than most of the results reported for watersheds in other regions. The results show that sediment and nutrient export from intensive agriculture areas with steep slopes continue to be a major concern for the downstream reservoir, Lake Soyang. Remedial strategies should be directed towards controlling sources of SS, TN, and TP to improve downstream water quality in sloping highland agricultural areas in Korea.

  14. 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 ...

  15. 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

  16. Sediment accumulation in the western Gulf of Lions, France: The role of Cap de Creus Canyon in linking shelf and slope sediment dispersal systems

    NASA Astrophysics Data System (ADS)

    DeGeest, A. L.; Mullenbach, B. L.; Puig, P.; Nittrouer, C. A.; Drexler, T. M.; Durrieu de Madron, X.; Orange, D. L.

    2008-08-01

    Previous work in the Gulf of Lions (western Mediterranean Sea) has suggested that significant amounts of sediment escape through the western part of this tectonically passive margin, despite it being far removed from the primary sediment source (the Rhone River, ˜160 km to the NE). The primary mechanism behind this export is hypothesized to be the interaction of a regional, southwestward sediment-transport path with a canyon deeply incising the southwestern part of the shelf, Cap de Creus Canyon. To understand the pattern of off-shelf sediment export from the western Gulf of Lions, and more specifically, the role of Cap de Creus Canyon in this transport, box cores were collected within the canyon and on the adjacent shelf during five cruises from November 2003 to April 2005. Geochronology ( 210Pb-derived accumulation rates), grain-size distributions, and sedimentary structures (X-radiography) were analyzed to assess temporal and spatial sedimentation patterns. Results indicate two mid-shelf depocenters (30-90 m water depth) in the northern and southern portions of the study area, separated by a zone of bypassing due to current acceleration around a headland (Cap Bear). Estimates of a sediment budget indicate that ˜6-8% of the sediment input to the Gulf is sequestered on the shelf region. Within the Cap de Creus Canyon, there is a significant spatial asymmetry in both grain size and accumulation rates. The northern flank is a modern depocenter of fine-grained sediments, while the southern flank is primarily non-depositional for mud and includes locations of apparent erosion. This suggests the influence of multiple oceanographic processes supplying sediment to the canyon: advection of nepheloid layers from the northern rim that provide a relatively continuous sediment supply (over decadal timescales), and episodic strong currents affecting the southern rim, which can scour sediment from the southern flank. The mid-depth thalweg has an ephemeral mud layer, overlying

  17. Soft sediment deformation in the shallow submarine slope off Nice (France) as a result of a variably charged Pliocene aquifer and mass wasting processes

    NASA Astrophysics Data System (ADS)

    Kopf, Achim J.; Stegmann, Sylvia; Garziglia, Sebastien; Henry, Pierre; Dennielou, Bernard; Haas, Simon; Weber, Kai-Christian

    2016-10-01

    Along the Ligurian slope near Nice, southeastern France, a combination of natural and man-made factors govern slope stability, and contributed to a devastating tsunamigenic landslide near Nice airport in 1979. Based on a total of 72 gravity and Kullenberg cores we characterise the architecture and facies of the subbottom sediment. A total of six sedimentary facies types were observed, three of which represent the Pliocene-Holocene background sediment in the wider Nice area while another three are associated with the 1979 landslide and tsunami. The three primary facies types are soft silty clay/clayey silt, somewhat indurated silt/sand interbeds, and Pliocene conglomerates underlying the former. The three other facies are poorly sorted mass wasting deposits up to pebble size, silt representing the finer fraction of the mobilised mass, and a tsunami-related bed into which plant debris and artefacts got amalgamated. Accompanying geotechnical results attest that significant strength variations exist when comparing measurements from the narrow shelf, shelf break and shallow slope as well as the 1979 slide scar. Factors such as groundwater charging in the more permeable horizons further lower the effective stress and, in places, approach lithostatic. Above such permeable silt/sand beds, deformation of soft clay is observed, suggesting that leaching of ions from the clay mineral surfaces and frayed edges also facilitates weakening and creep, micro-slumping and folding. Elevated water supply as well as hydraulic fracturing of the clayey sediment is further attested by pipes of cm-diameter and several decimeters length, which entrained very soupy mud. In the shallowmost deposits in and landward of the slide scar, we also observe remnants from the catastrophic deposition associated with the 2-3 m high tsunami wave triggered in 1979, as attested by amalgamated sea grass and artefacts. Based on our observations and measurements on core-scale and earlier models based on in situ

  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. Landscape Evolution Associated with Recurring Slope Lineae (RSL) on Mars

    NASA Astrophysics Data System (ADS)

    McEwen, A. S.; Dundas, C. M.; Chojnacki, M.; Ojha, L.

    2016-12-01

    RSL are low-albedo features that initiate at bedrock outcrops and extend down steep slopes. Individual slopes may have hundreds of lineae, with widths up to 5 m and lengths up to 1.5 km. RSL appear and lengthen gradually or incrementally, fade when inactive, and recur each year, normally in the warmest season. Small channels (1-20 m wide) are often present and control RSL paths. We have also detected newly-formed topographic land slumps associated with RSL fans in at least 7 locations—4 around a hill in Juventae Chasma, 2 in Garni crater in Melas Chasma, and 1 along wall slopes in Coprates Chasma. This distinctive landform assemblage is seen at several other locations within central and eastern Valles Marineris (VM): Small channels on most slope aspects of isolated hills or crater walls, extending very nearly to the tops of the hills or crater rim, associated with RSL that match the channels in size, and with a set of lobate deposits at the base of RSL fans. RSL activity in VM changes slope aspect with season—N-facing slopes in northern summer and S-facing slopes in southern summer. The slumps form midway down the RSL fans, and have a different seasonality—most active from Ls 0-120, the coldest time of year in VM. Assuming this association between gullies, RSL, and slumps is not coincidental, an integrated landscape evolution model is needed. Perhaps RSL activity carves the small gullies and deposits sediment near the base of angle-of-repose slopes, locally oversteepening the slope, which episodically slumps. RSL activity is seasonal and associated with the transient presence of hydrated salts, which indicates some role for salty water. If the RSL were caused by fluid flow, they should not be precisely confined to angle-of-repose or steeper slopes (>28 deg.), so these seem to be dry granular flows whose activity is triggered by or somehow associated with small amounts of water. There are multiple mysteries, such as how the activity recurs at the same

  20. Concentrations and isotope ratios of mercury in sediments from shelf and continental slope at Campos Basin near Rio de Janeiro, Brazil.

    PubMed

    Araujo, Beatriz Ferreira; Hintelmann, Holger; Dimock, Brian; Almeida, Marcelo Gomes; Rezende, Carlos Eduardo

    2017-07-01

    Mercury (Hg) may originate from both anthropogenic and natural sources. The measurement of spatial and temporal variations of Hg isotope ratios in sediments may enable source identification and tracking of environmental processes. In this study we establish the distribution of mercury concentrations and mercury isotope ratios in surface sediments of three transects along the continental shelf and slope in Campos Basin-RJ-Brazil. The shelf showed on average lower total Hg concentrations (9.2 ± 5.3 ng g(-1)) than the slope (24.6 ± 8.8 ng g(-1)). MMHg average concentrations of shelf 0.15 ± 0.12 ng g(-1) and slope 0.13 ± 0.06 ng g(-1) were not significantly different. Distinct differences in Hg isotope ratio signatures were observed, suggesting that the two regions were impacted by different sources of Hg. The shelf showed more negative δ(202)Hg and Δ(199)Hg values ranging from -0.59 to -2.19‰ and from -0.76 to 0.08‰, respectively. In contrast, the slope exhibited δ(202)Hg values from -0.29 to -1.82‰ and Δ(199)Hg values from -0.23 to 0.09‰. Mercury found on the shelf, especially along the "D" and "I" transects, is depleted in heavy isotopes resulting in more negative δ(202)Hg compared to the slope. Isotope ratios observed in the "D" and "I" shelf region are similar to Hg ratios commonly associated with plants and vegetation and very comparable to those detected in the estuary and adjoining mangrove forest, which suggests that Hg exported from rivers may be the dominating source of Hg in near coastal regions along the northern part of the shelf. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Biozone Characterization of Foraminifera in Upper Pleistocene through Recent Shelf and Slope Sediments, Northern Gulf of Alaska: Integration of SHE-diversity and Polytopic Vector Analyses

    NASA Astrophysics Data System (ADS)

    Zellers, S.; Cowan, E. A.; Davies, M. H.

    2014-12-01

    Gulf of Alaska sediments contain distinct, low-diversity assemblages of benthic and planktic foraminifera, whose distribution is a function of food availability, water mass properties, ice proximity, transport/deposition, predation, and taphonomic processes. Spatial and temporal changes in diversity reflect these processes and provide insight into this margin's history. Two quantitative techniques are integrated to define and characterize benthic foraminferal biozones in Gulf of Alaska sediment core samples collected by the R/V Maurice Ewing in 2004 at shelf site EW0408-79JC (59.53° N, 141.76° W, 158 m depth), and slope site EW0408-85JC (59.56° N, 144.15° W, 682 m depth). Sediments date from the end of the most recent glaciation (diamict in 85JC) to the present (bioturbated, silty clay at both sites). We apply SHE analysis, a graphical, iterative technique, based on diversity trends in a plot of ln E vs. ln N, where E is species evenness and N is cumulative number of specimens. In each step, the plot is examined for the first change in slope between successive samples, representing a change in diversity. At this point a boundary is defined, samples before the break are removed, and the analysis is repeated until all samples are analyzed. Data are further analyzed using an unmixing algorithm known as polytopic vector analyses. This technique defines a small number of orthogonal end members that explain a majority of the variance, thus reducing data complexity and aiding interpretation. SHE-analysis of benthic foraminiferal data defines eighteen informal abundance biozones. Polytopic vector analyses indicate that the faunal assemblages reflect mixtures of up to seven distinct biofacies: outer neritic (2), upper bathyal (2), reduced oxygen (2), and inner neritic. Rapid changes in faunal diversity correspond with increased sedimentation rates, especially during the end of the most recent glaciation (17 to 16 ka). The same relationship occurs over the last 1000

  2. Chemical and isotopic signature of bulk organic matter and hydrocarbon biomarkers within mid-slope accretionary sediments of the northern Cascadia margin gas hydrate system

    USGS Publications Warehouse

    Kaneko, Masanori; Shingai, Hiroshi; Pohlman, John W.; Naraoka, Hiroshi

    2010-01-01

    The chemical and isotopic compositions of sedimentary organic matter (SOM) from two mid-slope sites of the northern Cascadia margin were investigated during Integrated Ocean Drilling Program (IODP) Expedition 311 to elucidate the organic matter origins and identify potential microbial contributions to SOM. Gas hydrate is present at both locations (IODP Sites U1327 and U1328), with distinct patterns of near-seafloor structural accumulations at the cold seep Site U1328 and deeper stratigraphic accumulations at the slope-basin Site U1327. Source characterization and evidence that some components of the organic matter have been diagenetically altered are determined from the concentrations and isotopic compositions of hydrocarbon biomarkers, total organic carbon (TOC), total nitrogen (TN) and total sulfur (TS). The carbon isotopic compositions of TOC (δ13CTOC = −26 to −22‰) and long-chain n-alkanes (C27, C29 and C31, δ13C = −34 to − 29‰) suggest the organic matter at both sites is a mixture of 1) terrestrial plants that employ the C3 photosynthetic pathway and 2) marine algae. In contrast, the δ15NTN values of the bulk sediment (+ 4 to + 8‰) are consistent with a predominantly marine source, but these values most likely have been modified during microbial organic matter degradation. The δ13C values of archaeal biomarker pentamethylicosane (PMI) (− 46.4‰) and bacterial-sourced hopenes, diploptene and hop-21-ene (− 40.9 to − 34.7‰) indicate a partial contribution from methane carbon or a chemoautotrophic pathway. Our multi-isotope and biomarker-based conclusions are consistent with previous studies, based only on the elemental composition of bulk sediments, that suggested a mixed marine-terrestrial organic matter origin for these mid-slope sites of the northern Cascadia margin.

  3. 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.

  4. 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.

  5. Depth Profiles of Stable Nitrogen and Carbon Isotopes and C:N Ratios in Surficial Sediments From the NW Insular Slope of Cuba.

    NASA Astrophysics Data System (ADS)

    Soto, L. A.; de La Lanza, G.; López-Veneroni, D.

    2007-05-01

    The deep sea floor in the studied area remained unexplored for several decades. Recent searching for fossil fuels and gas hydrates in the seabed has renewed interest in studying deep sea processes in the region. Near- surface sediments were recovered with a Reineick box-corer at 3 preselected quadrants located at the channel axis of the Florida Straits and the slope rise off NW Cuba at depths ranging from 1468 to 2094 m. A total of 12- 30 cm long- subcores were sampled for isotopic (15N/14N and 13C/12C) and C:N ratio analyses. Surficial sediment samples exhibited mostly enriched δ15N values ranging from +3.6 to +6.4‰ with an average of +5.4 ± 0.7. δ15N values in the deeper quadrants (I and II) near the channel axis were fairly homogeneous in contrast to the shallower one (III) located at the slope rise, which showed a higher variability and significantly depleted values (+3.6‰). Testing of equality of δ15N values among quadrants was rejected (Friedman's test p<0.368. From the estimated δ15N average value here recorded a significant input of organic matter from a pelagic source is inferred. The δ13C values had a narrow range in all quadrants (-18.5 to -19.13‰) with an average of - 18.71±0.17. A gradient slightly enriched is noted on the seabed from the westernmost quadrants(I and II)towards the slope rise (quadrant III). The average δ13C signal in surficial sediments from the Southern Straits approaches that known for the continental shelf of South Florida (-18.5±0.7). Vertical profiles of TOC and TN are highly heterogeneous among quadrants displaying a diminishing trend with depth (0- 18 cm). TOC values are mostly impoverished ranging from 0.16 to 0.67 mmol/g. Slope rise sites concentrated less TOC than locations near the channel axis. The opposite occurred with TN values. Sites near the slope rise attained 0.90 mmol/g whereas in the channel axis, nitrogen was reduced to 0.46mmol/g. C:N ratios ranged from 1.9 to 10.2. An increasing gradient was noted

  6. Investigation of a hydrological system related to the stability of slope sediments off the Nice Aiport, Ligurian Sea - preliminary data and a sketch for a MSP drilling proposal

    NASA Astrophysics Data System (ADS)

    Henry, P.; Stegmann, S.; Sultan, N.; Sage, F.; Migeon, S.; Kopf, A.

    2009-04-01

    The sedimentary instability of submarine slopes poses a major geohazard and threatens coastal infrastructure both on- and offshore. The Ligurian Margin, Southern France, represents such a potentially unstable slope where factors favouring instability include seismicity, groundwater charging, presence of weak minerals, high sediment accumulation rates, anthropogenic impact by construction, and slope oversteepening. On the 16th of October 1979 a major submarine landslide (~8.7 km2) affected the coastal system offshore Nice and resulted in destruction of an embankment at the Nice airport, a debris flow cutting two submarine cables tens of kilometres away from the sliding area, and a tsunami wave of 2-3 m at the nearby coast. It was proposed several years ago that overpressuring linked to the hydrogeological condition could have been the trigger mechanism of the Nice Airport failure, and seawater composition in this area further suggested that fresh ground water is released offshore by coastal aquifers. The hydrogeological triggering model is also supported by sedimentary and seismic data indicating that gently seaward-dipping permeable layers of sediment may provide aquifer pathways down to a maximum depth of 150 m. An investigation of the superficial sediments (max. 30 mbsf) was recently performed in close collaboration between France (e.g. PRISME cruise with RV L'Atalante, 2007) and Germany (e.g. M73 cruise with RV Meteor, 2007). The study included geophysical acquisition, in situ pore pressure and shear strength measurements (CPTU devices, Penfeld penetrometer) as well as gravity coring. For long- and mid-term measurements, piezometers, which acquire the pore pressure at five different depth levels within the sediment, were installed by IFREMER Brest, France. Short-term measurements were carried out with the marine shallow-water FF-CPTU probe by the MARUM Bremen, Germany, while geochemical analysis was performed on pore water extracted from the cores. The main

  7. 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.

  8. Temporal and Spatial Characterization of Macondo 252 Signatures in Gulf of Mexico Shelf and Slope Sediments: Evidence for Weathering, Biodegradation, and Transport

    NASA Astrophysics Data System (ADS)

    Woodruff, O. P.; Yeager, K. M.; Wade, T.; Louchouarn, P.; Bonner, S.; Rutledge, M. H.

    2014-12-01

    The long-term fate of hydrocarbons in the Gulf of Mexico (GOMx) following the 2010 Deepwater Horizon oil spill has yet to be fully characterized. Elemental (% C and % N), stable isotopes (δ13Corganic), and polycyclic aromatic hydrocarbon (PAH) molecular signatures were investigated in shelf and slope sediments collected in October 2010 and 2011 to gain insight into processes affecting the distribution and fate of spilled Macondo oil. Particulate organic carbon (POC) ranged between 1.55 and 2.22 wt. % in 2010, and between 0.55 and 2.06 % in 2011, while the corresponding δ13Corganic ranges were from -23.37 to -20.77 ‰ (vs. PDB (Pee Dee Belemnite)) in 2010, and -22.68 to -20.75 ‰ (vs. PDB) in 2011. Ranges of total polycyclic aromatic hydrocarbon (TPAH) concentrations were from 72.57 to 7,543.53 ng/g in 2010 and 25.55 to 16,582.77 ng/g in 2011.The significant findings of this study are: a) sediments in 2010 and 2011 both display a deviation from the background signature of GOMx seafloor sediments through elevated POC concentrations, elevated OC:N ratios, depleted δ13Corganic, elevated TPAH concentrations, and a PAH signature dominated by petrogenic source materials, b) sediments collected 19 months after the Deepwater Horizon event display evidence of biodegraded and weathered oil, through decreased POC concentrations and OC:N, enriched δ13Corganic values, decreased TPAH concentrations, and alkyl homologue distributions characteristic of a biodegraded or weathered petrogenic source of PAHs, and c) physical processes that have distributed Macondo oil as indicated by the strong relationship of δ13Corganic (in 2010 and 2011) with longitude, in accordance with previous investigations that have characterized a west, southwest trending subsurface hydrocarbon plume that extended west from the Macondo well.

  9. Platform-margin and marginal slope relationships and sedimentation in Devonian reef complexes of Canning basin, Western Australia

    SciTech Connect

    Playford, P.E.; Kerans, C.; Hurley, N.F.

    1984-04-01

    Devonian limestone platforms in the Canning basin were generally rimmed by reef-margin and reef-flat deposits, constructed by stromatoporoids, algae, and corals in the Givetian and Frasnian, and by algae in the Famennian. However, some platforms were low-relief banks with little or no reef development. The reefs and slowly deposited parts of the marginal-slope facies were subject to pervasive early submarine cementation by fibrous high-magnesium calcite (now radiaxial spar). The strongly cemented reef limestones formed rigid wave-resistant rims to the platforms. Fracturing of these limestones, probably largely associated with earthquake shaking, gave rise to extensive networks of neptunian dikes and sills, and to the collapse of some sections of the margins. Such collapses in turn initiated debris flows and the deposition of allochthonous reef blocks on the adjoining marginal slopes. The reef complexes are being explored extensively for lead-zinc deposits in outcrop and oil in the subsurface. A significant oil discovery was made in a Famennian platform margin (the Blina field) in 1981.

  10. Spatial trends in the chemical composition of sediments on the continental shelf and slope off the Mediterranean coast of Israel

    NASA Astrophysics Data System (ADS)

    Goldsmith, S. L.; Krom, M. D.; Sandler, A.; Herut, B.

    2001-10-01

    In order to determine whether observed trends in total trace metal content were natural or due to anthropogenic inputs, major and trace elements were measured on three size fractions (fine sand (250-63 μm), silt and clay (<63 μm) and clay (<2 μm)) of sediment collected off the Mediterranean coast of Israel. Partitioning of trace metals into carbonate/exchangeable, iron oxide and residual phases for each grain size was also determined. The dominant source of particles was Nile derived material. There was a decrease in Fe/Al, Ti/Al and non-carbonate Mg/Al in the fine sand fraction, interpreted as a decrease in heavy minerals towards the north and an increase in K/Al due to increased feldspars and micas. There was a simultaneous increase in CaCO 3 both towards the north and onshore in all grain size fractions due to a northward increase in local biogenic fragments and river detritus. This is consistent with circulation and sediment transport models for the southeast Levantine basin. The background trend in trace metals corresponds to changes in mineralogy. While the fine sand fraction appeared free of contamination, in the finer fractions there is a significant enrichment of Zn, and Cd towards the north, which is not accounted for by changes in mineralogy. The sediments were also enriched in Cu, Zn and Cd near Tel Aviv and Hadera. The peaks near Tel Aviv may correspond to waste discharged through the Yarqon and an old sewage pipe, whilst near Hadera, the Alexander and Hadera Rivers and the terminal for a coal-fired power station may be the source of contamination. There was also clear evidence for contamination by Pb in the finest sediments. However, there was no enrichment in Pb around the point sources of the other trace metals, therefore it was concluded that the majority of Pb contamination was from the atmosphere. All trace metal contamination may be subject to 'smearing' by sediment transport, particularly in the clay fraction.

  11. 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

  12. Two-phase and three-dimensional simulations of complex fluid-sediment transport down a slope and impacting water bodies

    NASA Astrophysics Data System (ADS)

    Pudasaini, Shiva P.; Kattel, Parameshwari; Kafle, Jeevan; Pokhrel, Puskar R.; Khattri, Khim B.

    2014-05-01

    We present a technique that simulates transport and flow of a real two-phase fluid (a mixture of fluid and sediment particles) down three-dimensional slopes and channels. This technique combines novel mechanics formulations and modeling into a unified high-resolution framework, providing a unique opportunity to simulate two-phase subearial landslides and debris flows with dynamically changing concentrations of solid particles. This mixture then impacts downslope with particle-laden fluid reservoirs, rivers, fjords, lakes, or oceans. This results in a super tsunami wave in the fluid body, while the submarine debris flow moves along the bathymetry. The same modelling technique can be applied to simulate rock-ice avalanches and turbidity currents with changing physical properties and mechanical responses of the phases that enhances the flow mobility. These results fundamentally advance our present knowledge associated with the complex mechanics and dynamics of multi-phase geophysical mass flows, including the subearial and submarine sediment transport and deposition processes. Our findings contribute significantly to our understanding of mixing and separation between phases, generation and propagation of special solid and fluid structures, and phase-transitions during the flow process. Finally, these results provide new insights into the evolution of morphodynamics of steep mountain slopes and channels. References Pudasaini, S. P. A general two-phase debris flow model. Journal of Geophysical Research, 117, F03010, 2012. doi: 10.1029/2011JF002186. Pudasaini, S. P. and Miller, S. A. A real two-phase submarine debris flow and tsunami. American Institute of Physics Proceedings, 1479, 197-200, 2012. doi: 10.1063/1.4756096.

  13. Ultrasonic P-wave velocity measurements with variable effective pressure at the boundary between slope basin sediments and the accretionary prism: IODP Expedition 315 Site C0001

    NASA Astrophysics Data System (ADS)

    Hashimoto, Y.; Knuth, M. W.; Tobin, H. J.; 314/315/316 Scientist, I.

    2008-12-01

    IODP Expedition 315 Site C0001 is located on the hanging wall of the midslope megasplay fault in the Nankai subduction zone off Kii peninsula (SW Japan), and penetrated an unconformity between ~200 m thick slope basin sediments and the accretionary prism. While a down-section porosity increase was clearly observed at the boundary from ~50% to ~60%, logging velocity does not appear to decrease at the boundary, which suggests that different diagenetic processes might exist above and below the boundary. In this study, we conducted ultrasonic P-wave velocity measurements with pore pressure control. We also conducted observations of sediment and chemical analysis. We examined the relationships between the acoustic properties, sediment textures, logging data from IODP Expedition 314 Site C0001 and data from shipboard core analysis. The ultrasonic P-wave velocity measurements were conducted under constant pore pressure (500 kPa) and varying confining pressure to control effective pressure. The confining pressure ranges from 550 kPa to a maximum calculated from the density of overlying sediments (lithostatic pressure - hydrostatic pressure). 8 samples were analyzed, located from ~70 m to ~450 m below the sea floor. P-wave velocity ranges from ~1620 m/s to ~1990 m/s under the hydrostatic pressure condition. These velocities are in good agreement with the logging data. Porosity-velocity relationship in the analyzed data also coincide with that observed in the logging data. Samples shallower than ~300 m fall within previously-defined empirical relationships for normal- and high- consolidation. The deeper samples (at ~370 m and ~450 m below sea floor) show much higher velocity than that predicted by the empirical relationship, suggesting that significant cementation is present in those samples. The textural observations of sediments indicate a decrease in pore space with depth. Quartz and feldspar grains are surrounded by clay mineral matrices. Grain size seems to be almost

  14. Surface water and groundwater interaction on a hill island

    NASA Astrophysics Data System (ADS)

    Rumph Frederiksen, Rasmus; Rømer Rasmussen, Keld; Christensen, Steen

    2014-05-01

    A number of recent studies have indicated that the hydrological system in stream valleys is often complex and exchange of water takes place through semi-permeable contacts and flow paths may be quite diverse. Yet, surface water and groundwater interaction in one of the major Danish landscapes - the hill islands - is relatively unknown. This study aims at providing new information about the rainfall-runoff processes in hill island landscapes where surface water and groundwater interaction is expected to have a dominant role and hill-slope processes not. Through stream flow measurements, field observations, and existing geological and geophysical data, we have investigated the surface water and groundwater interaction in the Abild Stream catchment (<70 km2) on Skovbjerg hill island in the western part of Denmark. Existing discharge data are limited but the hydrographs downstream Abild Stream appear to be strongly influenced by event flow indicating that shallow control by low permeable sediments is important. Nevertheless irrigation is intensive which indicates that the soil and shallow sediments are permeable. Since July 2014 we have measured stream flow during quarterly campaigns at 11 stations along the stream representing different spatial scales and using Acoustic Doppler techniques (ADCP) as well as current-meters. Furthermore we have mapped topography, soil types, geomorphology, ditches, drains and land use through field observations and digital maps. The shallow subsurface geology has been mapped using abundant well described geological data (boreholes) and geophysical data (airborne TEM). Our stream flow measurements show that the tributaries from west and north dry out during the summer period. Significant drained areas in the NW- and SW-part of the catchment have been observed from old topographical maps as well as in the field. The geological data indicate shallow low permeable sediments primarily on the western side of Abild stream, and the geophysical

  15. Slippery Slope?

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This digital elevation map shows the topography of the 'Columbia Hills,' just in front of the Mars Exploration Rover Spirit. Rover planners are currently plotting the safest route for Spirit to climb to the front hill, called 'West Spur.' The direct path from the bottom crosshatch to the top crosshatch may be too steep. Data from the Mars Orbital Camera on the orbiting Mars Global Surveyor were used to create this 3-D map.

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

    PubMed

    Droghei, R; Falcini, F; Casalbore, D; Martorelli, E; Mosetti, R; Sannino, G; Santoleri, R; Chiocci, F L

    2016-11-03

    Subaqueous, asymmetric sand waves are typically observed in marine channel/canyon systems, tidal environments, and continental slopes exposed to strong currents, where they are formed by current shear resulting from a dominant unidirectional flow. However, sand-wave fields may be readily observed in marine environments where no such current exists; the physical processes driving their formation are enigmatic or not well understood. We propose that internal solitary waves (ISWs) induced by tides can produce an effective, unidirectional boundary "current" that forms asymmetric sand waves. We test this idea by examining a sand-wave field off the Messina Strait, where we hypothesize that ISWs formed at the interface between intermediate and surface waters are refracted by topography. Hence, we argue that the deflected pattern (i.e., the depth-dependent orientation) of the sand-wave field is due to refraction of such ISWs. Combining field observations and numerical modelling, we show that ISWs can account for three key features: ISWs produce fluid velocities capable of mobilizing bottom sediments; the predicted refraction pattern resulting from the interaction of ISWs with bottom topography matches the observed deflection of the sand waves; and predicted migration rates of sand waves match empirical estimates. This work shows how ISWs may contribute to sculpting the structure of continental margins and it represents a promising link between the geological and oceanographic communities.

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

    PubMed Central

    Droghei, R.; Falcini, F.; Casalbore, D.; Martorelli, E.; Mosetti, R.; Sannino, G.; Santoleri, R.; Chiocci, F. L.

    2016-01-01

    Subaqueous, asymmetric sand waves are typically observed in marine channel/canyon systems, tidal environments, and continental slopes exposed to strong currents, where they are formed by current shear resulting from a dominant unidirectional flow. However, sand-wave fields may be readily observed in marine environments where no such current exists; the physical processes driving their formation are enigmatic or not well understood. We propose that internal solitary waves (ISWs) induced by tides can produce an effective, unidirectional boundary “current” that forms asymmetric sand waves. We test this idea by examining a sand-wave field off the Messina Strait, where we hypothesize that ISWs formed at the interface between intermediate and surface waters are refracted by topography. Hence, we argue that the deflected pattern (i.e., the depth-dependent orientation) of the sand-wave field is due to refraction of such ISWs. Combining field observations and numerical modelling, we show that ISWs can account for three key features: ISWs produce fluid velocities capable of mobilizing bottom sediments; the predicted refraction pattern resulting from the interaction of ISWs with bottom topography matches the observed deflection of the sand waves; and predicted migration rates of sand waves match empirical estimates. This work shows how ISWs may contribute to sculpting the structure of continental margins and it represents a promising link between the geological and oceanographic communities. PMID:27808239

  18. In situ thermal excursions detected in the Nankai Trough forearc slope sediment at IODP NanTroSEIZE Site C0008

    NASA Astrophysics Data System (ADS)

    Kinoshita, Masataka; Fukase, Hiroaki; Goto, Shusaku; Toki, Tomohiro

    2015-02-01

    At Integrated Ocean Drilling Program (IODP) Site C0008 in the Nankai Trough slope sediment, we discovered in situ temperature anomalies at 80 to 160 m below the seafloor, where pore fluid Cl and δ 18O excursions were identified and interpreted as pore fluid refreshing due to hydrate dissociation. The volume fraction of hydrates is estimated to be approximately 3% and approximately 40% maximum at Holes C0008A and C0008C, respectively. In the vicinity of these anomalies, we discovered negative and positive temperature excursions of up to 1 K measured in situ using the Advanced Piston Corer Temperature (APC-T) tool attached to the shoe of a hydraulic piston corer. They are significantly larger than the uncertainties caused during data acquisition and processing. Frictional heat due to penetration increased the temperature by >10 K, exceeding the gas/hydrate stability temperature at that depth. This heat is partly consumed by hydrate dissociation, which disturbs the thermal decay curve after penetration, but 2D numerical modeling revealed that hydrate dissociation does not significantly change the extrapolated equilibrium temperature. So far, we cannot suggest any acceptable explanation for the observed thermal anomalies, although we strongly suspect that it is related to hydrate dissociation.

  19. 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, R.; Falcini, F.; Casalbore, D.; Martorelli, E.; Mosetti, R.; Sannino, G.; Santoleri, R.; Chiocci, F. L.

    2016-11-01

    Subaqueous, asymmetric sand waves are typically observed in marine channel/canyon systems, tidal environments, and continental slopes exposed to strong currents, where they are formed by current shear resulting from a dominant unidirectional flow. However, sand-wave fields may be readily observed in marine environments where no such current exists; the physical processes driving their formation are enigmatic or not well understood. We propose that internal solitary waves (ISWs) induced by tides can produce an effective, unidirectional boundary “current” that forms asymmetric sand waves. We test this idea by examining a sand-wave field off the Messina Strait, where we hypothesize that ISWs formed at the interface between intermediate and surface waters are refracted by topography. Hence, we argue that the deflected pattern (i.e., the depth-dependent orientation) of the sand-wave field is due to refraction of such ISWs. Combining field observations and numerical modelling, we show that ISWs can account for three key features: ISWs produce fluid velocities capable of mobilizing bottom sediments; the predicted refraction pattern resulting from the interaction of ISWs with bottom topography matches the observed deflection of the sand waves; and predicted migration rates of sand waves match empirical estimates. This work shows how ISWs may contribute to sculpting the structure of continental margins and it represents a promising link between the geological and oceanographic communities.

  20. 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

  1. Lycus Sulci Slope Streaks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    21 May 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark slope streaks coming off of rugged hills in the Lycus Sulci region, north of the Olympus Mons volcano. These slopes are mantled with fine, bright dust. From time to time, the dust will avalanche down a slope, forming a slope streak. The behavior of this dry, granular material can be somewhat fluid-like. New slope streaks can form at any time and, for an area the size of that shown here, may form at a rate of one per Mars year (687 Earth days). Naturally, some scientists have suggested that water plays a role in forming these streaks, but, in general, Mars is drier than the driest deserts on Earth and these streaks are contemporary features that occur in the dustiest regions of the planet. The image is located near 29.8oN, 133.4oW, and covers an area about 3 km (1.9 mi) across. The picture is illuminated by sunlight from the lower left.

  2. 'Columbia Hills' in Stereo

    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

    While en route to higher ground in the 'Columbia Hills,' NASA's Mars Exploration Rover Spirit used its panoramic camera to take the images combined into this 360-degree stereo panorama of its surroundings. Because the rover was parked on a steep slope, it was tilted approximately 22 degrees to the west-northwest. This would be similar to tilting your body sideways like a leaning pole and turning your body and head around to survey your surroundings without bending your neck. At one point, you would be looking slightly down. At another point, you would be looking slightly up. In between those two points, your eyes would be slanted at an angle to the horizon. To compensate for this, image processing experts 'untilted' the images, so to speak, which makes the martian horizon appear flat but also creates a vertical offset between the left and right eyes. This offset can make it difficult to view a scene like this looking through 3-D glasses because the two sides of the stereo image do not line up perfectly. Tilting your head one way or the other may help to view it more easily.

    The highest point visible in this panorama 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 between Spirit's 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

  3. Sedimentation

    Treesearch

    Cliff R. Hupp; Michael R. Schening

    2000-01-01

    Sedimentation is arguably the most important water-quality concern in the United States. Sediment trapping is cited frequently as a major function of riverine-forested wetlands, yet little is known about sedimcntation rates at the landscape scale in relation to site parameters, including woody vegetation type, elevation, velocity, and hydraulic connection to the river...

  4. 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.

  5. 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

  6. 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.

  7. Massive siliciclastic discharge to slopes of the Great Barrier Reef Platform during sea-level transgression: constraints from sediment cores between 15°S and 16°S latitude and possible explanations

    NASA Astrophysics Data System (ADS)

    Dunbar, Gavin B.; Dickens, Gerald R.

    2003-11-01

    The northeast Australian continental margin, including the Great Barrier Reef (GBR) Platform, provides an outstanding modern analogue for understanding sedimentation in tropical mixed siliciclastic/carbonate depositional systems. Previous studies of cores from this margin have suggested that, in contrast to widely accepted models, maximum siliciclastic fluxes to slopes over the last 30 ky occurred when sea level transgressed the shelf ca. 11-7 ka rather than when sea level was at a lowstand before 18 ka. However, climate and bathymetry can affect regional sediment deposition significantly, and the cores examined to date have come from the southern Queensland Trough where the margin has a wet tropical climate and a broad shelf (>50 km) with gradual slopes. In this study, we examine the abundance and accumulation of siliciclastic material in four cores from lower slopes of the northern Queensland Trough where rivers drain a drier region and debouche onto a narrow shelf with steep, incised slopes. Similar to previously examined cores, all cores contain a dark greyish brown horizon within the upper few meters. This horizon represents a low in carbonate content and corresponding high in siliciclastic material, primarily clay, and oxygen isotope stratigraphy shows that it was deposited during late transgression, nominally between 11 and 7 ka. Moreover, mass accumulation rate calculations demonstrate that this horizon reflects a significant rise in siliciclastic fluxes. When combined with the previous work to the south, it appears that slopes all along a large portion of the northeast Australian continental margin received greatly enhanced inputs of siliciclastic material during late transgression, independent of proximal climate and bathymetry. Two general explanations are offered for this observation: (1) climate change induced highly variable riverine discharge over the past 30 ky with a prominent maximum coincident with late transgression, or (2) the shelf stores

  8. Lunar Slope and Distance Estimation

    NASA Astrophysics Data System (ADS)

    Young, Laurence R.; Liu, Andrew M.; Oravetz, Christopher T.

    2008-06-01

    When astronauts return to the moon, they will undertake frequent treks across unknown terrain for geological investigations. Lunar conditions which are expected to affect human terrain perception include: the lack of an atmosphere or haze, the regolith luminance properties, the absence of familiar objects, and reduced gravity. This project examines the perceptual errors in human judgment of slopes and distance on earth using lunar-like terrain. Slope estimation errors of five subjects were measured for five featureless hills in Hanksville, Utah using visual and haptic measurement methods. This experiment was replicated in Virtual Reality (VR) with 7 subjects using stereo photographs. Significant overestimations were found in both experiments. Future work will measure slope and distance judgments on the moon using photographs from Apollo missions. The findings may influence astronaut training and design of navigation aids.

  9. Slope Instability

    NASA Image and Video Library

    2016-07-15

    One small section of this image shows boulders that have rolled down the slope of a crater wall. The boulders vary in size, with the largest one approximately 6 meters across. Unlike the boulder in a previous image, this one is not standing on end. We can tell by using the sun angle and shadow length to figure out the height and then comparing that to its other measurements. We can determine the origin of the boulders by tracing their up-slope tracks. They appear to come from one small part of the crater wall that is less stable than surrounding materials. It is likely that there have been numerous rockfall events from this area, as suggested by the many boulders down-slope of this area, some with clear tracks and others with indistinct or no tracks visible. http://photojournal.jpl.nasa.gov/catalog/PIA20744

  10. Scott on Slope of Hadley Delta

    NASA Technical Reports Server (NTRS)

    1971-01-01

    Astronaut David R. Scott, mission commander, with tongs and gnomon in hand, studies a boulder on the slope of Hadley Delta during the Apollo 15 lunar surface extravehicular activity. The Lunar Roving Vehicle (LRV) or Rover is in right foreground. View is looking slightly south of west. 'Bennett Hill' is at extreme right. Astronaut James B. Irwin, lunar module pilot, took this photograph.

  11. The role of sediment composition and behavior under dynamic loading conditions on slope failure initiation: a study of a subaqueous landslide in earthquake-prone South-Central Chile

    NASA Astrophysics Data System (ADS)

    Wiemer, Gauvain; Moernaut, Jasper; Stark, Nina; Kempf, Philipp; De Batist, Marc; Pino, Mario; Urrutia, Roberto; de Guevara, Bruno Ladrón; Strasser, Michael; Kopf, Achim

    2015-07-01

    Subaqueous slope failure mechanisms are still poorly understood partly because they are difficult to study due to the remote location of submarine landslides. Landslides in lakes are smaller in size and more readily accessible and therefore represent a good alternative to their marine counterparts. Lake Villarrica, located in South-Central Chile, experienced significant slope failure and serves here as an exemplary study area for subaqueous landslide initiation mechanisms in tectonically active settings. Coring and CPTU testing were undertaken with the MARUM free-fall CPTU deployed adjacent to the coring sites where all lithological units involved in the slope failure were sampled. Using geotechnical methods such as pseudo-static factor of safety analysis and cyclic triaxial testing, three types of soils (i.e., diatomaceous ooze, volcanic ash, and quick clay) were analyzed for their role in slope failure, and earthquake shaking was identified as the primary trigger mechanism. The investigated landslide consisted of two distinct phases. During the first phase, slope failure was initiated above a tephra layer. In the second phase, retrogression led to the shoreward extension of the slide scarp along a second failure plane located in a stratigraphically deeper, extremely sensitive lithology (i.e., quick clay). Results show that liquefaction of buried tephra layers was unlikely, but such layers might still have contributed to a reduction in shear strength along the contact area with the neighboring sediment. Furthermore, cyclic shaking-induced pore pressure in diatomaceous ooze may be similar to that in granular soils. We generally infer that failure mechanisms observed in this study are equally important for landslide initiation in submarine settings as diatomaceous ooze intercalated with volcanic ash may be abundantly present along active continental margins.

  12. 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.

  13. Lost Hills Subsidence Animation

    NASA Image and Video Library

    2012-02-06

    This frame from an animation depicts ground subsidence resulting from the extraction of oil. The oil fields are located near the community of Lost Hills, California, approximately 100 km northwest of Bakersfield.

  14. Red Hill Updates

    EPA Pesticide Factsheets

    This and other periodic updates are intended to keep the public informed on major progress being made to protect public health and the environment at the Red Hill Underground Fuel Storage Facility in Hawaii.

  15. Meet Janis Hill.

    ERIC Educational Resources Information Center

    Power, Jane

    1980-01-01

    Janis Hill, an itinerant physical education teacher in Florida, is interviewed about her job, which sometimes involves work with emotionally disturbed or learning disabled students. The importance of teaching children to work together, have fun, and play is stressed. (CJ)

  16. Dunes Streaming through Hills

    NASA Image and Video Library

    2014-02-26

    This dramatic image observed by NASA Mars Reconnaissance Orbiter shows dark rippled bodies of sand, sometimes in the form of dunes, streaming through Ganges Chasma. The floor of the canyon is covered by hills and mesas.

  17. 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.

  18. Slope Morphology of Twin Peaks, Mars Pathfinder Landing Site

    NASA Astrophysics Data System (ADS)

    Hobbs, Steven; Paine, Colin; Clarke, Jon; Caprarelli, Graziella

    2010-05-01

    Development of slope form over time has long been a concern of geomorphologists, although recently this concern has been moved to slope processes rather than form. There are two basic approaches. The first is theoretical, involving modeling of different types and rates of processes, and calculation of results in terms of slope evolution over time. Comparisons with real-life slopes can follow this approach [1], [2]. The second, inductive, approach involves field measurements to test ideas about slope evolution starting from the assumption that observed slopes represent different stages of an essentially similar evolution [3]. Space is substituted for time, and a number of slopes, assumed to be of increasing age, are measured and placed in an evolutionary sequence (e.g. [4], [5], [6]). [5] showed that slope angles are modally distributed, with the modal angles controlled by the materials (regolith) of which the slopes are formed, and by the processes operating on them. Data can be obtained directly from field work or from digital elevation models (DEM) derived from remote sensing investigations [7]. DEMs are particularly useful to study inaccessible planets, such as Mars, where on site observations are restricted to only a few landing sites. Here we present a study of slopes on the Twin Peaks, two small hills located 780 m north and 910 m south of the Mars Pathfinder landing site at the mouth of the Ares and Tiu flood channels. The presence of streamlined hills, jumbled surfaces and conglomerates suggested the region was modified by massive flooding 1.8 - 3.5 billion years ago [8], [9]. The streamlined forms and terraces of the Twin Peaks were taken to indicate catastrophic flood conditions that were believed to be prevalent in the area [8]. It was also suggested that the northernmost peak was topped by floodwater, causing its flatter appearance. Other researchers postulated alternative geomorphological origins for the features observed at the Pathfinder landing site

  19. 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.

  20. 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).

  1. 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

  2. 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).

  3. Layered Slope

    NASA Technical Reports Server (NTRS)

    2005-01-01

    28 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a frost-covered slope in the south polar region of Mars. The layered nature of the terrain in the south polar region is evident in a series of irregular, somewhat stair-stepped bands that run across the image.

    Location near: 84.3oS, 27.2oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  4. 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

  5. Late Pleistocene and Holocene sedimentation, organic-carbon delivery, and paleoclimatic inferences on the continental slope of the northern Pandora Trough, Gulf of Papua

    NASA Astrophysics Data System (ADS)

    Febo, Lawrence A.; Bentley, Samuel J.; Wrenn, John H.; Droxler, André W.; Dickens, Gerald R.; Peterson, Larry C.; Opdyke, Bradley N.

    2008-03-01

    We investigated sediment and organic-carbon accumulation rates in two jumbo piston cores (MV-54, MV-51) retrieved from the midslope of the northeastern Pandora Trough in the Gulf of Papua, Papua New Guinea. Our data provide a first assessment of mass fluxes over the past ˜33,000 14C years B.P. and variations in organic-carbon sources. Core sediments were analyzed using a suite of physical properties, organic geochemistry, and micropaleontological measurements. MV-54 and MV-51 show two periods of rapid sediment accumulation. The first interval is from ˜15,000 to 20,400 Cal. years B.P. (MV-51: ˜1.09 m ka-1 and ˜81.2 g cm-2 ka-1) and the second occurs at >32,000 14C years B.P. (˜2.70 m ka-1 and ˜244 g cm-2 ka-1). Extremely high accumulation rates (˜3.96 m ka-1; ˜428 g cm-2 ka-1) characterize 15,800-17,700 Cal. years B.P. in MV-54 and likely correspond to early transgression when rivers delivered sediments much closer to the shelf edge. A benthic foraminiferal assemblage in MV-51 from ˜18,400 to 20,400 Cal. years B.P. indicates a seasonally variable flux of organic carbon, possibly resulting from enhanced contrast between monsoon seasons. The oldest sediments, >32,000 14C years B.P., contain TOC fluxes >200 g cm2 ka-1, with >50% of it derived from C3 vascular plant matter. Magnetic susceptibility values are 2 to 3 times higher and benthic foraminiferal accumulation rates are 6 times higher during this interval than at any younger time, indicating a greater influence of detrital minerals and labile organic carbon. The MS data suggest more direct dispersal pathways from central and eastern PNG Rivers to the core site.

  6. The optimal downhill slope for acute overspeed running.

    PubMed

    Ebben, William P

    2008-03-01

    This study evaluated a variety of downhill slopes in an effort to determine the optimal slope for overspeed running. Thirteen NCAA Division III college athletes who participated in soccer, track, and football ran 40-yd (36.6-m) sprints, on downhill slopes of 2.1 degrees , 3.3 degrees , 4.7 degrees , 5.8 degrees , and 6.9 degrees in random order. All sprints were timed using the Brower Timing System Speedtrap II. Data were analyzed with SSPS 15.0. A 1-way repeated-measures analysis of variance revealed significant main effects for the test slopes (P = .000). Bonferroni-adjusted pairwise comparisons determined that there were a number of differences between the hill slopes. Analysis reveals that 40-yd sprints performed on hill slopes of approximately 5.8 degrees were optimal compared with flatland running and the other slopes assessed (P < .05). Sprinting on a 5.8 degrees slope increased the subjects' maximal speed by an average of 0.35 s, resulting in a 6.5% +/- 4.0% decrease in 40-yd sprint time compared with flatland running. Compared with the 4.7 degrees slope, the 5.8 degrees slope yielded a 0.10-s faster 40-yd sprint time, resulting in a 1.9% increase in speed. Those who train athletes for speed should use or develop overspeed hills with slopes of approximately 5.8 degrees to maximize acute sprinting speed. The results of this study bring into question previous recommendations to use hills of 3 degrees downhill slope for this form of overspeed training.

  7. Abyssal hills: Influence of topography on benthic foraminiferal assemblages

    NASA Astrophysics Data System (ADS)

    Stefanoudis, Paris V.; Bett, Brian J.; Gooday, Andrew J.

    2016-11-01

    Abyssal plains, often thought of as vast flat areas, encompass a variety of terrains including abyssal hills, features that constitute the single largest landscape type on Earth. The potential influence on deep-sea benthic faunas of mesoscale habitat complexity arising from the presence of abyssal hills is still poorly understood. To address this issue we focus on benthic foraminifera (testate protists) in the >150-μm fraction of Megacorer samples (0-1 cm layer) collected at five different sites in the area of the Porcupine Abyssal Plain Sustained Observatory (NE Atlantic, 4850 m water depth). Three sites are located on the tops of small abyssal hills (200-500 m elevation) and two on the adjacent abyssal plain. We examined benthic foraminiferal assemblage characteristics (standing stock, diversity, composition) in relation to seafloor topography (hills vs. plain). Density and rarefied diversity were not significantly different between the hills and the plain. Nevertheless, hills do support a higher species density (i.e. species per unit area), a distinct fauna, and act to increase the regional species pool. Topographically enhanced bottom-water flows that influence food availability and sediment type are suggested as the most likely mechanisms responsible for these differences. Our findings highlight the potential importance of mesoscale heterogeneity introduced by relatively modest topography in regulating abyssal foraminiferal diversity. Given the predominance of abyssal hill terrain in the global ocean, we suggest the need to include faunal data from abyssal hills in assessments of abyssal ecology.

  8. 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.

  9. 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.; hide

    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.

  10. Compositions of foraminifera-rich turbidite sediments from the Shenhu area on the northern slope of the South China Sea: Implication for the presence of deep water bottom currents

    NASA Astrophysics Data System (ADS)

    Li, Niu; Feng, Dong; Chen, Linying; Wang, Hongbin; Chen, Duofu

    2017-05-01

    The sediments in gravity core DH-1, collected from Shenhu area on the northern slope of the South China Sea, are composed of two dark grey clay silt layers (A1 and A3) and two foraminifera-rich layers (A2 and A4) (A1 is the top layer and A4 is the bottom layer). Major and trace metal contents, along with grain size and mineralogic data suggest that these silt layers represent background hemipelagic sedimentation. Unlike silt layers, the intervening foraminifera-rich layerA4 exhibits a fining-upward trend, is distal turbidite. Grain size CM diagram and the sharp contacts between the foraminifera-rich layer A2 and the upper and lower layers suggest layer A2 is the result of depositional interaction between turbidite and bottom currents. AMS 14C dating of planktonic foraminifera indicate the age of the turbidite in A2 is between15.3 ka and 22.6 ka. We hypothesize that turbidite formation in this period was related to the increase supply of terrigenous matter since the Last Glacial Maximum. The rapid deposition of each turbidite led to reduced rates of oxygen diffusion into the sediment, allowing anoxic conditions develop in sediments and fostering U enrichment (>3.1 μg/g) in foraminifera-rich layer A4b. In contrast, decrease concentration of U and U/Mo ratios in foraminifera-rich layerA2, which is possibly due to U remobilization as a consequence of downward penetration of the oxidation front from the oxygen rich bottom currents. These new data suggest that authigenic U was quite sensitive to the inflow of bottom currents, and U/Mo ratios may indicate the depositional environmental change in relation to the bottom current action on the turbidite.

  11. Landslide susceptibility estimations in the Gerecse hills (Hungary).

    NASA Astrophysics Data System (ADS)

    Dávid, Gerzsenyi; Gáspár, Albert

    2017-04-01

    Surface movement processes are constantly posing threat to property in populated and agricultural areas in the Gerecse hills (Hungary). The affected geological formations are mainly unconsolidated sediments. Pleistocene loess and alluvial terrace sediments are overwhelmingly present, but fluvio-lacustrine sediments of the latest Miocene, and consolidated Eocene and Mesozoic limestones and marls can also be found in the area. Landslides and other surface movement processes are being studied for a long time in the area, but a comprehensive GIS-based geostatistical analysis have not yet been made for the whole area. This was the reason for choosing the Gerecse as the focus area of the study. However, the base data of our study are freely accessible from online servers, so the used method can be applied to other regions in Hungary. Qualitative data was acquired from the landslide-inventory map of the Hungarian Surface Movement Survey and from the Geological Map of Hungary (1 : 100 000). Morphometric parameters derived from the SRMT-1 DEM were used as quantitative variables. Using these parameters the distribution of elevation, slope gradient, aspect and categorized geological features were computed, both for areas affected and not affected by slope movements. Then likelihood values were computed for each parameters by comparing their distribution in the two areas. With combining the likelihood values of the four parameters relative hazard values were computed for each cell. This method is known as the "empirical probability estimation" originally published by Chung (2005). The map created this way shows each cell's place in their ranking based on the relative hazard values as a percentage for the whole study area (787 km2). These values provide information about how similar is a certain area to the areas already affected by landslides based on the four predictor variables. This map can also serve as a base for more complex landslide vulnerability studies involving

  12. Smooth Slopes

    NASA Image and Video Library

    2015-02-13

    The region with fewer impact craters in the bottom-right corner of this image is a small portion of the peak ring of an ancient basin over 200 km in diameter. The peak has fewer superposed impact craters, which could lead to the conclusion that it is younger than the surrounding basin floor. However, the lack of craters is instead due to the steeper slopes of the peak, where impact craters are not preserved as long. This image was acquired as part of the MDIS low-altitude imaging campaign. During MESSENGER's second extended mission, the spacecraft makes a progressively closer approach to Mercury's surface than at any previous point in the mission, enabling the acquisition of high-spatial-resolution data. For spacecraft altitudes below 350 kilometers, NAC images are acquired with pixel scales ranging from 20 meters to as little as 2 meters. http://photojournal.jpl.nasa.gov/catalog/PIA19203

  13. Bacon Hill Substation. Bacon Hill, Cecil Co., MD. Sec. 1201, ...

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

    Bacon Hill Substation. Bacon Hill, Cecil Co., MD. Sec. 1201, MP 48.50. - Northeast Railroad Corridor, Amtrak route between District of Columbia/Maryland state line & Maryland/Delaware state line, Baltimore, Independent City, MD

  14. 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

  15. A Hill Divided

    NASA Image and Video Library

    2015-12-07

    This image captured by NASA 2001 Mars Odyssey spacecraft shows an elevated group of hills east of Phlegra Montes. This highland is divided by a linear channel that is most likely of tectonic origin. Orbit Number: 61195 Latitude: 31.5513 Longitude: 167.142 Instrument: VIS Captured: 2015-09-30 13:26 http://photojournal.jpl.nasa.gov/catalog/PIA20109

  16. Jack Hills, Australia

    NASA Image and Video Library

    2009-06-02

    This image acquired by NASA Terra spacecraft, shows the oldest material on Earth which has yet been dated by man is a zircon mineral of 4.4 billion years old from a sedimentary gneiss in the Jack Hills of the Narre Gneiss Terrane of Australia.

  17. Chocolate Hills Rock

    NASA Image and Video Library

    2010-02-16

    This false-color image, taken by the panoramic camera on NASA rover Opportunity, shows the rock Chocolate Hills, perched on the rim of the 10-meter 33-foot wide Concepcion crater. This rock has a thick, dark-colored coating resembling chocolate.

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. Percent Agricultural Land Cover on Steep Slopes

    EPA Pesticide Factsheets

    Clearing land for agriculture tends to increase soil erosion. The amount of erosion is related to the steepness of the slope, farming methods used and soil type. High amounts of agriculture on steep slopes can increase the amount of soil erosion leading to increased sediment in surface water. Agricultural land cover on steep slopes (AGSL) is the percent of agriculture on slopes greater than or equal to 9%. More information about these resources, including the variables used in this study, may be found here: https://edg.epa.gov/data/Public/ORD/NERL/ReVA/ReVA_Data.zip.

  4. Massive Rock Detachments from the Continental slope of the Balsas River Submarine Delta that occur due to Instability of Sediments which Produce Turbidity Currents and Tsunamis

    NASA Astrophysics Data System (ADS)

    Sandoval-Ochoa, J.; Aguayo-Camargo, J.

    2007-05-01

    During the NOAA oceanographic delivery cruise of the US R/V "Roger Revelle" to the Scripps Institution of Oceanography at the University of California in San Diego, California USA, in July 1996; a well calibrated bathymetric equipment, the SeaBeam* 2012, was tested. Good resolutions in data allowed bathymetric mapping to visualize the sea floor relief. Detailed colorful chartographic images showed a portion of the continental slope between the Balsas River Delta and the Middle America Trench and between the Balsas Canyon and La Necesidad Canyon. The surveyed area covered more than 3 000 square kilometers. After the delivery cruise, one of the goals was to measure and analyze the Morphobathymetry of the uneven lower portion of the Balsas River Submarine Delta. So far some of the findings with the morphometric analyses consist of several isolated slump scars that each comprise more than 12 cubic kilometers in volume and a multiple slump scar with an evident steep hollow about 200 cubic kilometers absent of rock. These volumes of rock apparently underwent a remobilization from the slope during the Late Quaternary. The rock detachments occured in relatively small portions but in instantaneous massive displacements because of their instability as well as other identified factors in the region. Over time more and more authors have accepted that coastal cuts or submarine slump scars have been left by sudden movements of rock and fluids. The phenomena that occur in the region in general, are accompanied on one side by potential and kinetic energies like falling bodies, flows and gravity waves, and on the other side, by mass transfer of rock and fluid mobilization like turbidity currents, accumulations, sea wave surges or tsunamis. In some cases the phenomena is produced by another natural triggering forces or by an earthquake. We propose that events like these, i.e. massive detachments and their products such as accumulations, turbidity currents and depositional debrites

  5. Black Hills hydrology study

    USGS Publications Warehouse

    Driscoll, D.G.

    1994-01-01

    The Black Hills area of western South Dakota is a valuable resource center. The area has attracted numerous residents and industries because of the availability of mineral, timber, agricultural, recreational, and water resources. The water resources of the area have been stressed locally by increasing population, periodic drought, and development of other resources. In response to residents' concerns about these stresses on the water resources, the Black Hills Hydrology Study was initiated in 1990 as a cooperative effort among the U.S. Geological Survey, the South Dakota Department of Environment and Natural Resources, and the West Dakota Water Development District. West Dakota represents the various local and county cooperators. This report describes the purpose, scope, approach, and status of the study and presents highlights from the first project data report produced for the study.

  6. Hill and Depression

    NASA Technical Reports Server (NTRS)

    2004-01-01

    21 November 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows exposures of north polar layered material -- perhaps composed of a mixture of dust and ice--in the form of a hill and an adjacent depression. The depression is in the lower half of the image and forms an oval shape at its lowest elevations. The hill is immediately above the depression (above the center of the image) and forms a similar pattern of arcuate bands. This scene is located near 85.7oN, 21.0oW. The image covers an area approximately 3 km (1.9 mi) wide. Sunlight illuminates the scene from the lower left.

  7. Hill In Deuteronilus

    NASA Technical Reports Server (NTRS)

    2004-01-01

    28 December 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an eroded, rounded hill in the Deuteronilus Colles region of Mars, near 40.3oN, 338.8oW. The plains surrounding the hill have been pitted and modified by erosion. Similar pitting is common throughout the middle latitude regions of Mars. Some Mars science investigators have proposed that the pitted materials were ice-rich, and that sublimation of ice has created these textures. However, no similar landforms are found on Earth, thus there is no clear analog that would help scientists better understand the origin of these features. The picture covers an area about 3 km (1.9 mi) wide and is illuminated by sunlight from the left/lower left.

  8. 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…

  9. Top of the hill.

    PubMed

    Lubell, Jennifer

    2009-08-24

    With healthcare reform the hottest topic in Washington (and at congressional town halls) this summer, it's no surprise President Barack Obama tops our 100 Most Powerful People in Healthcare ranking, joined by plenty of other power players on the Hill. "Clearly, the president is pushing hard on his goals to expand access to care, to reform health insurance and to control costs," says LifePoint's Bill Carpenter.

  10. Notting Hill Carnival 1988.

    PubMed

    Dalton, A M; Sharma, A; Touquet, R

    1989-06-01

    The injuries sustained at the 1988 Notting Hill Carnival were documented in order to suggest ways in which these might be reduced in future years. Sixty-four patients presented to six hospitals participating in the study over a 48-h period, most of whom were victims of accidents (63%) rather than assaults (37%). Many of the accidents were caused by motorized floats or by stepping on broken glass.

  11. Notting Hill Carnival 1988.

    PubMed Central

    Dalton, A M; Sharma, A; Touquet, R

    1989-01-01

    The injuries sustained at the 1988 Notting Hill Carnival were documented in order to suggest ways in which these might be reduced in future years. Sixty-four patients presented to six hospitals participating in the study over a 48-h period, most of whom were victims of accidents (63%) rather than assaults (37%). Many of the accidents were caused by motorized floats or by stepping on broken glass. PMID:2742669

  12. 'Columbia Hills' from Orbit

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This view of the 'Columbia Hills' in Gusev Crater was made by draping an image from the Mars Orbiter Camera on NASA's Mars Global Surveyor orbiter (image E0300012 from that camera) over a digital elevation model that was derived from two Mars Orbiter Camera images (E0300012 and R0200357).

    This unique view is helpful to the rover team members as they plan the journey of NASA's Mars Exploration Rover Spirit to the base of the Columbia Hills and beyond. Spirit successfully completed a three-month primary mission, and so far remains healthy in an extended mission of bonus exploration. As of sol 135 (on May 21, 2004), Spirit sits approximately 680 meters (0.4 miles) away from its first target at the western base of the hills, a spot informally called 'West Spur.' The team estimates that Spirit will reach West Spur by sol 146 (June 1, 2004). Spirit will most likely remain there for about a week to study the outcrops and rocks associated with this location.

    When done there, Spirit will head approximately 620 meters (0.38 miles) to a higher-elevation location informally called 'Lookout Point.' Spirit might reach Lookout Point by around sol 165 (June 20, 2004). On the way, the rover will pass by and study ripple-shaped wind deposits that may reveal more information about wind processes on Mars.

    Lookout Point will provide a great vantage point for scientists to remotely study the inner basin area of the Columbia Hills. This basin contains a broad range of interesting geological targets including the informally named 'Home Plate' and other possible layered outcrops. These features suggest that the hills contain rock layers. Spirit might investigate the layers to determine whether they are water-deposited sedimentary rock.

    Once at Lookout Point, Spirit will acquire 360-degree panoramic images of the entire area to help define the rover's next steps. Assuming the rover stays healthy, Spirit will eventually drive down into the basin to get an up

  13. 'Columbia Hills' from Orbit

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This view of the 'Columbia Hills' in Gusev Crater was made by draping an image from the Mars Orbiter Camera on NASA's Mars Global Surveyor orbiter (image E0300012 from that camera) over a digital elevation model that was derived from two Mars Orbiter Camera images (E0300012 and R0200357).

    This unique view is helpful to the rover team members as they plan the journey of NASA's Mars Exploration Rover Spirit to the base of the Columbia Hills and beyond. Spirit successfully completed a three-month primary mission, and so far remains healthy in an extended mission of bonus exploration. As of sol 135 (on May 21, 2004), Spirit sits approximately 680 meters (0.4 miles) away from its first target at the western base of the hills, a spot informally called 'West Spur.' The team estimates that Spirit will reach West Spur by sol 146 (June 1, 2004). Spirit will most likely remain there for about a week to study the outcrops and rocks associated with this location.

    When done there, Spirit will head approximately 620 meters (0.38 miles) to a higher-elevation location informally called 'Lookout Point.' Spirit might reach Lookout Point by around sol 165 (June 20, 2004). On the way, the rover will pass by and study ripple-shaped wind deposits that may reveal more information about wind processes on Mars.

    Lookout Point will provide a great vantage point for scientists to remotely study the inner basin area of the Columbia Hills. This basin contains a broad range of interesting geological targets including the informally named 'Home Plate' and other possible layered outcrops. These features suggest that the hills contain rock layers. Spirit might investigate the layers to determine whether they are water-deposited sedimentary rock.

    Once at Lookout Point, Spirit will acquire 360-degree panoramic images of the entire area to help define the rover's next steps. Assuming the rover stays healthy, Spirit will eventually drive down into the basin to get an up

  14. 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.

  15. 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.

  16. 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.

  17. Miocene cercopithecoidea from the Tugen Hills, Kenya.

    PubMed

    Gilbert, Christopher C; Goble, Emily D; Hill, Andrew

    2010-11-01

    Miocene to Pleistocene fossiliferous sediments in the Tugen Hills span the time period from at least 15.5 Ma to 0.25 Ma, including time periods unknown or little known elsewhere in Africa. Consequently, the Tugen Hills deposits hold the potential to inform us about crucial phylogenetic events in African faunal evolution and about long-term environmental change. Among the specimens collected from this region are a number of discoveries already important to the understanding of primate evolution. Here, we describe additional cercopithecoid material from the Miocene deposits in the Tugen Hills sequence, including those from securely dated sites in the Muruyur Beds (16-13.4 Ma), the Mpesida Beds (7-6.2 Ma) and the Lukeino Formation (∼ 6.2-5.7 Ma). We also evaluate previously described material from the Ngorora Formation (13-8.8 Ma). Identified taxa include Victoriapithecidae gen. et sp. indet., cf. Parapapio lothagamensis, and at least two colobines. Specimens attributed to cf. Pp. lothagamensis would extend the species' geographic range beyond its type locality. In addition, we describe specimens sharing derived characters with modern African colobines (Tribe: Colobina), a finding that is congruent with previous molecular estimates of colobine divergence dates. These colobine specimens represent some of the earliest known members of the modern African colobine radiation and, in contrast to previous hypotheses, suggest that early African colobines were mainly arboreal and that semi-terrestrial Late Miocene and Plio-Pleistocene colobine taxa were secondarily derived in their locomotor adaptations.

  18. 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

  19. 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

  20. 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.

  1. Recognition of Diagnostic Acoustic Signatures in Shelf and Slope Deposits: The STRATAFORM California Site

    DTIC Science & Technology

    2016-06-07

    gravity deposits, reflector geometry, and inferred sediment processes. Sediment is deposited on shelves and slopes in distinctive packages or sequences...presence and distinctive characteristics of marine sediment- gravity deposits and record the diagnostic geometric patterns of shallow subsurface...is also evident from Huntec DTS lines of the lower slope that sediment gravity flows have occurred on the slope and in the channels fed by gullies

  2. 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.

  3. 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.; hide

    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.

  4. Behavior of fiber reinforced sandy slopes under seepage

    USDA-ARS?s Scientific Manuscript database

    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...

  5. 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.

  6. Hills in Arctic Canada with Impact Origin

    NASA Image and Video Library

    2004-06-02

    While most hills and mountains on Earth originate from tectonic motions or volcanism, Earth also has some examples of hills that originated from impacts of large meteorites, the predominant origin for hills and mountains on the Moon.

  7. 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.

  8. 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.

  9. Toilets in the hills.

    PubMed

    Rosenfield, P; Holcombe, S J

    1990-04-01

    Population and Community Development Association (PDA) in Chieng Rai province in northern Thailand implemented its Environmental Sanitation for the Hill Tribes Project in March 1988 to reduce parasite infection and generate interest in self help development projects. As of early 1990, the hill tribes population growth rate stood at 4.5% compared to 1.5% in lowland Thailand. Other problems included villagers defecating around dwellings, not drinking safe water (since none was available), and not wearing shoes all of which contributed to a high rate of parasite infection. In fact, an analysis of stool samples revealed that parasites infected a mean of almost 70% of the villagers. PDA staff informed villagers about basic environmental health information which influenced them to improve sanitation conditions. They also demonstrated how to build the 1st model latrine. After that, each villager designed and constructed his own latrine. Each villager took out a Baht 150 (US$6) loan to pay for the construction materials (squat casings and cement) provided by PDA. Over the following 10 months, the staff returned to the villages to collect payments and to provide technical assistance. Those villagers that constructed a latrine persuaded others to also construct a latrine. In fact, villagers, not always PDA staff, have even transferred the knowledge to other villages. As of early 1990, villagers and staff have built 1000 squats and 993 latrines. With the health education and latrine use, PDA hoped to see a subsequent reduction in parasite infections. With the help of volunteer contraceptive distributors, PDA has also been able to expand its family planning program to 250 villages. It has also initiated a parasite control pilot project in the area in which infection rates have steadily decreased.

  10. 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

  11. South Polar Layered Slope

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-559, 29 November 2003

    Both the north and south polar regions of Mars exhibit thick deposits of layered sediment. These have been known since the Mariner 9 (1972) and Viking (1976-1980) orbiter missions. The layered deposits are considered to contain a record of climate changes that occurred in the relatively recent martian past, but most of that record will have to wait until some time in the future when a lander or people can go there to study them. Meanwhile, pictures such as this from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) provide opportunities to view the layers where they are exposed on slopes. Here, numerous layers have been exposed by erosion in the south polar region. The picture was obtained in October 2003 and is located near 86.4oS, 112.4oW. The image covers an area 3 km (1.9 mi) wide, and is illuminated by sunlight from the upper left.

  12. 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

  13. Black Hills Region, SD, USA

    NASA Image and Video Library

    1973-06-22

    SL2-81-157 (22 June 1973) --- This view of the Black Hills Region, SD (44.0N, 104.0W) shows the scenic Black Hills where Mt. Rushmore and other monuments are located. Cities and towns in this view include: Rapid City, Deadwood, and Belle Fourche with the nearby Belle Fourche Reservoir. Notable in this scene are the recovering burn scars (seen as irregular shaped light toned patches) from a 1959 forest fire in the Black Hills National Forest near the edge of the photo. Photo credit: NASA

  14. 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

  15. 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

  16. 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

  17. 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

  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. 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

  20. 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

  1. 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

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. Navigating Ski Slopes Safely

    MedlinePlus

    ... medlineplus.gov/news/fullstory_162902.html Navigating Ski Slopes Safely National Ski Areas Association offers advice on ... 2017 (HealthDay News) -- Many people head for the slopes at the first sign of snow, but it's ...

  8. Interrill soil erosion processes on steep slopes

    USDA-ARS?s Scientific Manuscript database

    To date interrill erosion processes and regimes are not fully understood. The objectives are to 1) identify the erosion regimes and limiting processes between detachment and transport on steep slopes, 2) characterize the interactive effects between rainfall intensity and flow depth on sediment trans...

  9. Sediment budget to assess the geomorphic effect of a cyclonic storm, New Zealand

    NASA Astrophysics Data System (ADS)

    Page, M. J.; Trustrum, N. A.; Dymond, J. R.

    1994-05-01

    A short-term sediment budget was constructed to assess the erosion response of a soft-rock hill country watershed to an intense rainstorm event. The watershed is located in a landslide-prone area on the east coast of the North Island, New Zealand. During March 1988, 753 mm of rain was recorded over a four-day period with 320 mm and 329 mm on successive days. Known as Cyclone Bola, this was the largest rainstorm event in the Tutira watershed in the 93-year rainfall record. The budget quantifies the total sediment generated during the storm, the relative contribution of erosion processes involved, the amount of sediment held in storage and the amount discharged into two lakes within the watershed. A landform map of the watershed was constructed and the contribution of each landform type to the total budget was calculated. A total of 1.35 (±0.13) million m 3 of sediment was generated during the storm at an average of 420 m 3/ha. This is equivalent to a denudation value of 42 mm for the total watershed (3208 ha) and 83 mm for the landforms severely affected by landsliding (1427 ha). Of the sediment generated, 21% remained on hillslopes, 22% was deposited on valley floors, 51% was deposited on the lakebeds and the remaining 6% was discharged from the watershed via the lake outlet. Most of the sediment generated during the storm was from primary source areas on hill slopes, with sediment in secondary storage providing only a small contribution. Landslide erosion was the main process, accounting for 89% of the sediment generated. Channel, tunnel gully and sheet erosion were only minor contributors to the budget. Six hillslope landforms, which occupy only 44% of the watershed generated 90% of the sediment. The results of this sediment budget, when put in context with the storm magnitude-frequency history being analysed from lake cores, contribute to the identification of sustainable land use and management of soft-rock hill country.

  10. Drought in the Black Hills

    NASA Image and Video Library

    2005-05-18

    Despite good rainfall and record-setting snowstorms in the spring of 2005, most of northeastern Wyoming, the Black Hills, and western South Dakota remained in the midst of a severe drought. These images are from NASA Terra spacecraft.

  11. Soufriere Hills Volcano

    NASA Image and Video Library

    2002-11-07

    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. http://photojournal.jpl.nasa.gov/catalog/PIA03880

  12. 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.; hide

    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.

  13. 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.

  14. 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

  15. Physical modelling of tsunamis generated by three-dimensional deformable granular landslides on planar and conical island slopes

    NASA Astrophysics Data System (ADS)

    McFall, Brian C.; Fritz, Hermann M.

    2016-04-01

    Tsunamis generated by landslides and volcanic island collapses account for some of the most catastrophic events recorded, yet critically important field data related to the landslide motion and tsunami evolution remain lacking. Landslide-generated tsunami source and propagation scenarios are physically modelled in a three-dimensional tsunami wave basin. A unique pneumatic landslide tsunami generator was deployed to simulate landslides with varying geometry and kinematics. The landslides were generated on a planar hill slope and divergent convex conical hill slope to study lateral hill slope effects on the wave characteristics. The leading wave crest amplitude generated on a planar hill slope is larger on average than the leading wave crest generated on a convex conical hill slope, whereas the leading wave trough and second wave crest amplitudes are smaller. Between 1% and 24% of the landslide kinetic energy is transferred into the wave train. Cobble landslides transfer on average 43% more kinetic energy into the wave train than corresponding gravel landslides. Predictive equations for the offshore propagating wave amplitudes, periods, celerities and lengths generated by landslides on planar and divergent convex conical hill slopes are derived, which allow an initial rapid tsunami hazard assessment.

  16. Physical modelling of tsunamis generated by three-dimensional deformable granular landslides on planar and conical island slopes

    PubMed Central

    2016-01-01

    Tsunamis generated by landslides and volcanic island collapses account for some of the most catastrophic events recorded, yet critically important field data related to the landslide motion and tsunami evolution remain lacking. Landslide-generated tsunami source and propagation scenarios are physically modelled in a three-dimensional tsunami wave basin. A unique pneumatic landslide tsunami generator was deployed to simulate landslides with varying geometry and kinematics. The landslides were generated on a planar hill slope and divergent convex conical hill slope to study lateral hill slope effects on the wave characteristics. The leading wave crest amplitude generated on a planar hill slope is larger on average than the leading wave crest generated on a convex conical hill slope, whereas the leading wave trough and second wave crest amplitudes are smaller. Between 1% and 24% of the landslide kinetic energy is transferred into the wave train. Cobble landslides transfer on average 43% more kinetic energy into the wave train than corresponding gravel landslides. Predictive equations for the offshore propagating wave amplitudes, periods, celerities and lengths generated by landslides on planar and divergent convex conical hill slopes are derived, which allow an initial rapid tsunami hazard assessment. PMID:27274697

  17. Physical modelling of tsunamis generated by three-dimensional deformable granular landslides on planar and conical island slopes.

    PubMed

    McFall, Brian C; Fritz, Hermann M

    2016-04-01

    Tsunamis generated by landslides and volcanic island collapses account for some of the most catastrophic events recorded, yet critically important field data related to the landslide motion and tsunami evolution remain lacking. Landslide-generated tsunami source and propagation scenarios are physically modelled in a three-dimensional tsunami wave basin. A unique pneumatic landslide tsunami generator was deployed to simulate landslides with varying geometry and kinematics. The landslides were generated on a planar hill slope and divergent convex conical hill slope to study lateral hill slope effects on the wave characteristics. The leading wave crest amplitude generated on a planar hill slope is larger on average than the leading wave crest generated on a convex conical hill slope, whereas the leading wave trough and second wave crest amplitudes are smaller. Between 1% and 24% of the landslide kinetic energy is transferred into the wave train. Cobble landslides transfer on average 43% more kinetic energy into the wave train than corresponding gravel landslides. Predictive equations for the offshore propagating wave amplitudes, periods, celerities and lengths generated by landslides on planar and divergent convex conical hill slopes are derived, which allow an initial rapid tsunami hazard assessment.

  18. Transformation of landforms and sediments in the periglacial setting of West Greenland

    NASA Astrophysics Data System (ADS)

    Česnulevičius, Algimantas; Šeirienė, Vaida

    2009-06-01

    The article deals with the cryogenic processes taking place in the terminal zone of the recessing glacier of SW Greenland, which modify the sediment layers and transform the landforms. The sediment horizons were examined in natural outcrops and in trenches. Structural analysis of periglacial sediments in the slopes has shown that subdued evaporation and shallow permafrost favour the development of cryoturbations. In relief declensions, the formation of polygonal surfaces is predetermined by shallow beds of magmatic rocks, permafrost and especially slow evaporation during short warm seasons. Aeolian processes are most active in the valleys sculptured by glaciofluvial flows where cold arid winds blow out or rework inequigranular deposits. Dust is blown out by wind erosion, whereas the coarse-grained material is transported by creeping or saltation. Sand ripple and embryo dune terrains are widespread in glaciofluvial valleys. Wind erosion processes forming pebble-boulder deflation pavements take place in relief declensions. Outcrops sized 10-60 m2 and niches develop in the hill slopes. Diatoms indicate that sedimentation in small closed basins took place under cold, oligotrophic, acidophilous conditions.

  19. 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.

  20. 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

  1. Soil CO2 Emissions on Sloping Lands: Spatial Variations and Slope Sensitivity

    NASA Astrophysics Data System (ADS)

    Hu, Yaxian; Guo, Shengli; Wang, Zhiqi; Wang, Rui

    2017-04-01

    Erosion induced CO2 emissions have been extensively studied across different scales from plots to watersheds. While slope is the essential element to initiate soil erosion and sediment transport, the potential effects of slope gradients and slope positions to soil CO2 emissions have not yet been systematically studied. In this study, six east-facing plots of 100 m2 (20 m × 5 m) with increasing slope gradients of 0.5o (S 0.5), 1o (S1), 3o (S3), 5o (S5), 10o (S10) and 20o (S20), with identical soil preparation and wheat, were established in an eroded gully of the semi-arid Loess Plateau, China. Soil temperature, moisture and CO2 emissions were detected once every week for two years from October 2013 to September 2015. Runoff and sediment yield were collected after detectable natural rainfall events. Surface litter, fine root biomass and aboveground biomass and SOC content of surface soil were also measured once a year. Our results show that: 1) annual soil CO2 emission rates exponentially decreased with slope gradients, on average from 843.7 g C m-2 year-1 at S0.5 to 388.2 g m-2 at S20. This is attributed to increasing C loss through runoff and sediment discharge from slopes of greater gradients (0.075 m3 year-1 from S0.5 vs. 63.8 m3 year-1 from S20), and also in part attributed to limited fine root growth on steeper slopes. 2) On each slope, CO2 emission rates also differed among slope positions, with CO2 emissions 61% greater from upper than lower slopes. This agrees well with the erosion-induced spatial redistribution of SOC and soil moisture along the slope. Overall, slope angle affected soil moisture content and redistribution, and as a consequence, the fine root biomass, crop yields and CO2 emissions within slopes. These impacts must be adequately accounted for to fully understand the environmental impacts of agricultural management on the regional agro-ecosystem.

  2. 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.

  3. Limiting equilibrium and liquefaction potential in infinite submarine slopes

    USGS Publications Warehouse

    Denlinger, R.P.; Iverson, R.M.

    1990-01-01

    Stability evaluation of submarine slopes is hampered by the difficulty of making field measurements. Owing to the scarcity of detailed field data, stability is commonly assessed by assuming homogenous infinite slopes with steady seepage. For these conditions, it is necessary to measure only the slope angle, friction angle, cohesion, and pore pressure at some distance into the sediment to evaluate stability. Examination of available data shows that conditions close to those required for liquefaction are necessary for Coulomb failure in many continental shelf areas. This favors long landslide runouts and flow of sediment subsequent to failure. -from Authors

  4. Slope Streaks or RSL?

    NASA Image and Video Library

    2016-12-14

    The image shows a region we see many slope streaks, typically dark features on slopes in the equatorial regions on Mars. They may extend for tens of meters in length and gradually fade away with time as new ones form. The most common hypothesis is that they are generated by dust avalanches that regularly occur on steep slopes exposing fresh dark materials from underneath the brighter dust. There are many types of slope streaks but one of the most recent and significant findings using HiRISE was the discovery of a new type called "recurring slope lineae," or RSL for short. Recent studies suggest that RSL may form through the flow of briny (extremely salty) liquid water that can be stable on the surface of Mars even under current climatic conditions for a limited time in summer when it is relatively warm. How can we distinguish between conventional slope streaks like the ones we see here and RSL? There are many criteria. For instance, RSL are usually smaller in size than regular slope streaks. However, one of the most important conditions is seasonal behavior, since RSL appear to be active only in summer while regular slope streaks can be active anytime of the year. This site is monitored regularly by HiRISE scientists because of the high density of slope streaks and their different sizes and orientations. If we look at a time-lapse sequence, we will see that a new slope streak has indeed formed in the period since April 2016 (and we can note how dark it is in comparison to the others indicating its freshness). However, this period corresponds mainly to the autumn season in this part of Mars, whereas we do not see any major changes in the summer season. This suggests that the feature that developed is a regular slope streak just like all the others in the area. http://photojournal.jpl.nasa.gov/catalog/PIA21272

  5. Morphology and origins of sedimentary structures on submarine slopes.

    PubMed

    Hulsemann, J

    1968-07-05

    Submarine slopes in deep water, such as continental slopes, are often indented by valleys or channels and made uneven by ridges or levees. The origins of many of these features are unknown or disputed. Morphologically, however, there is often great similarity between forms on deep slopes and forms on shallow slopes or on land. Structurally the slopes in deep water are less well explored, but several observations reveal features, such as lamination and crossbedding, that are known from shallow water also. Measurements of current indicate that periodically the movement of water near the bottom is fast enough to move particles of sediment from time to time. Morphology, fine structure, and currents suggest that internal waves and associated currents, as well as gravity, may control the shape of deep submarine slopes analogously to the shaping by surface waves of slopes in shallow water.

  6. 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.

  7. Spirit's Trip to the Hills

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This overhead view of a portion of Gusev Crater shows the route the Mars Exploration Rover Spirit has traveled since arriving on the red planet over five months ago. On sol 156 (June 11, 2004), Spirit reached the base of the 'Columbia Hills,' where it is currently investigating some unusual rocks. The rover may eventually head to the top of one of the closest hills.

    This image is a composite of images taken by the camera on the orbiting Mars Global Surveyor and the descent image motion estimation system camera located on the bottom of the rover's lander.

  8. 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.

  9. 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.

  10. Interrill soil erosion processes on steep slopes

    NASA Astrophysics Data System (ADS)

    Zhang, X. C. (John); Wang, Z. L.

    2017-05-01

    To date interrill erosion processes are not fully understood under different rainfall and soil conditions. The objectives are to 1) identify the interrill erosion regime and limiting process under the study condition, 2) characterize the interactive effects of rainfall intensity and flow depth on sediment transport competency and mode, and 3) develop a lumped interrill erosion model. A loess loam soil with 39% sand and 45% silt was packed to flumes and exposed to simulated rainfall. A complete factorial design with three factors was used, which included rainfall intensity (48, 62, 102, 149, and 170 mm h-1), slope gradient (17.6, 26.8, 36.4, 46.6, and 57.7%), and slope length (0.4, 0.8, 1.2, 1.6, and 2 m). Rain splash, sediment discharge in runoff, and flow velocity were measured. Results showed that rainfall intensity played a dual role not only in detaching soil materials but also in enhancing sediment transport. Sediment transport was the process limiting interrill erosion rate under the study condition. Two major sediment transport modes were identified: rainfall-driven rolling/creeping and flow-driven rolling/sliding. The relative importance of each mode was largely determined by flow depth. The competence of the flow in transporting sediment decreased downslope as flow depth increased due to increased dissipation of raindrop energy. The optimal mean flow depth for the maximal interrill erosion rates was <0.1 mm, which is much shallower than the widely reported 2 mm. Slope length was negatively related to interrill erosion rate. The negative correlation seemed stronger for heavier rains, indicating the cushioning effects of flow depth. Lumped interrill erosion models, developed from short slopes, are likely to overestimate erosion rates. Given transport as the limiting process, the so called erodibility value, estimated with those models, is indeed sediment transportability under the study condition. The effects of slope length on interrill erosion regimes need

  11. Morphodynamics and slope stability at Mergui Ridge, off western Thailand

    NASA Astrophysics Data System (ADS)

    Schwab, J.; Gross, F.; Krastel, S.; Jintasaeranee, P.; Bunsomboonsakul, S.; Winkelmann, D.; Weinrebe, W.

    2012-04-01

    2D seismic data from the top and the western slope of the Mergui Ridge (200 km off the Thai west coast) have been acquired during MASS cruise III in January 2011 in water depths between 300 and 2200 m. The Mergui Ridge is a part of the outer shelf slope off the Thai-Malay Peninsula and forms the eastern boundary of the East Andaman Basin. Structural features in the working area include faulted older slope sediments at the transition from Mergui Ridge to East Andaman Basin that are onlapping on the (acoustic) basement of Mergui Ridge. At their top these sediments are bordered by a pronounced erosive unconformity. Younger sedimentary units on top include three E-W elongated carbonate platforms. Moreover, drift sediments are deposited on top of the ridge, comprising features such as large scale sediment waves and moats around the platforms indicating transport and reworking of the sediments. These sediments are thinning towards the edge of the ridge where a zone of non-sedimentation prevails. In the East Andaman Basin younger sediments comprise disturbed and partially faulted units that are overlain by plastered drifts with increasing thickness towards south, where pronounced sediment waves within the drifts may indicate slope normal sediment transport by bottom currents. At the basin ridge transition, within the drift sediments on top of Mergui Ridge, and at the edge of the ridge several smaller scale mass transport deposits were identified. These MTDs indicate a general instability of the slope. Instability and general morphology of the slope may result from long-term tectonic processes such as extension due to backarc basin formation in the Andaman Sea basin. Moreover, phases of uplift, erosion and subsidence may have contributed to faulting and deformation of older units in our working area. Ongoing tectonics might still cause deformation and instability. In addition, bottom currents may presently play an important role concerning morphodynamic development by

  12. Clarks Hill Lake Water Quality Study.

    DTIC Science & Technology

    1982-06-01

    MACROINVERTEBRATE TAXONOMIC LIST CLARKS HILL LAKE 1981 Phylum Platyhelminthes Order Diptera Class Turbellaria Ablabesmyia parajanta unidentified Planariidae A...HILL LAKE 1981 Phylum Platyhelminthes Order Diptera (continued) Planaria sp.,’ Bezzia sp. 2 unidentified Planariidae Chaoborus punctipennis unidentified

  13. Percent Agricultural Land Cover on Steep Slopes (Future)

    EPA Pesticide Factsheets

    Clearing land for agriculture tends to increase soil erosion. The amount of erosion is related to the steepness of the slope, farming methods used and soil type. High amounts of agriculture on steep slopes can increase the amount of soil erosion leading to increased sediment in surface water. Agricultural land cover on steep slopes (AGSL) is the percent of agriculture on slopes greater than or equal to 9%. More information about these resources, including the variables used in this study, may be found here: https://edg.epa.gov/data/Public/ORD/NERL/ReVA/ReVA_Data.zip.

  14. Hill & Knowlton's Two Ethical Dilemmas.

    ERIC Educational Resources Information Center

    Pratt, Cornelius B.

    1994-01-01

    Presents arguments for and against the acceptance, in 1990, of two controversial client accounts by the public relations agency Hill & Knowlton. Examines the ethical implications of both accounts and concludes that whatever ethical infractions may have occurred reflect the agency's dominant public relations practices, not necessarily the "greedy…

  15. Seismic sedimentologic interpretation of a carbonate slope, north margin of little Bahama Bank

    SciTech Connect

    Harwood, G.M.; Towers, P.A.

    1988-01-01

    Analysis of seismic profiles plus core descriptions of sediments from ODP Leg 101 have been combined to investigate the evolution of the northern margin of Little Bahama Bank, which has been prograding northward since the early Miocene. Modern depositional systems on the mid-slope and lower slope are found not to be characteristic of interpreted ancient sedimentary environments. Large slump masses converted much of the lower slope during the middle Miocene, possibly triggered by a regional tectonic event. Through the late Miocene and most of the Pilocene, a channel and levee system meandered across the sediment apron of the lower slope. The modern lower slope contains no meandering channels, although gullies incised in the mid-slope funnel sediments to the base of the slope apron, actively promoting sediment bypass on an accretionary margin. These changes in sedimentation pattern on the lower slope indicate increasing strength of ocean-bottom contour-following currents from the Pliocene. Pliocene to Holocene gravitational creep has produced large-scale rotational movement of unlithified sediments, with a major detachment surface along the base of the middle Miocene slump masses. These creep lobes extend far into the lower slope, where sediments are contorted by the propagation of, and movement along, multiple minor detachment surfaces.

  16. 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 maps...

  17. 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 maps...

  18. 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 maps...

  19. 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 maps...

  20. 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 maps...

  1. 27 CFR 9.204 - Tracy Hills.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Tracy Hills. 9.204 Section... Hills. (a) Tracy Hills. The name of the viticultural area described in this section is “Tracy Hills”. For purposes of part 4 of this chapter, “Tracy Hills” is a term of viticultural significance. (b...

  2. Theory of synergistic effects: Hill-type response surfaces as 'null-interaction' models for mixtures.

    PubMed

    Schindler, Michael

    2017-08-02

    The classification of effects caused by mixtures of agents as synergistic, antagonistic or additive depends critically on the reference model of 'null interaction'. Two main approaches are currently in use, the Additive Dose (ADM) or concentration addition (CA) and the Multiplicative Survival (MSM) or independent action (IA) models. We compare several response surface models to a newly developed Hill response surface, obtained by solving a logistic partial differential equation (PDE). Assuming that a mixture of chemicals with individual Hill-type dose-response curves can be described by an n-dimensional logistic function, Hill's differential equation for pure agents is replaced by a PDE for mixtures whose solution provides Hill surfaces as 'null-interaction' models and relies neither on Bliss independence or Loewe additivity nor uses Chou's unified general theory. An n-dimensional logistic PDE decribing the Hill-type response of n-component mixtures is solved. Appropriate boundary conditions ensure the correct asymptotic behaviour. Mathematica 11 (Wolfram, Mathematica Version 11.0, 2016) is used for the mathematics and graphics presented in this article. The Hill response surface ansatz can be applied to mixtures of compounds with arbitrary Hill parameters. Restrictions which are required when deriving analytical expressions for response surfaces from other principles, are unnecessary. Many approaches based on Loewe additivity turn out be special cases of the Hill approach whose increased flexibility permits a better description of 'null-effect' responses. Missing sham-compliance of Bliss IA, known as Colby's model in agrochemistry, leads to incompatibility with the Hill surface ansatz. Examples of binary and ternary mixtures illustrate the differences between the approaches. For Hill-slopes close to one and doses below the half-maximum effect doses MSM (Colby, Bliss, Finney, Abbott) predicts synergistic effects where the Hill model indicates 'null

  3. Influence of debris flow scale on equilibrium bed slope

    NASA Astrophysics Data System (ADS)

    Itoh, T.; Egashira, S.; Papa, M.; Miyamoto, K.

    2003-04-01

    Results obtained from both of flume tests and theory suggest that an equilibrium bed slope in flow over an erodible bed is determined only by sediment discharge rate when the movements of sediment particles are laminar and thus no suspended transportation take place. This means that the static friction force is dominant in debris flow and that sediment concentration is determined by shear stress balance on the bed surface; i.e., the external shear stress must be equal to the resisting static shear stress of sediment particles, as seen in our previous studies. On the other hand, if part of sediment particles in debris flow body is transported in suspension, sediment concentration will be larger in comparison with that in case of laminar motion of sediment particles and the equilibrium bed slope will decrease. These facts are supported Egashira et al.'s experimental data. The present study discusses an influence of flow scales on an equilibrium bed slope and flow structure experimentally and theoretically. Equilibrium bed slopes and velocity profiles are measured for many flow conditions in flume tests. Those results emphasize that the equilibrium bed slope decreases with increasing of flow scale if part of debris flow body is turbulent, and it is predicted corresponding to increase of mass density of fluid phase. Experimental data for velocity profiles are compared to the results predicted by authors' constitutive equations for non-cohesive sediment and water mixture. When no turbulent diffusions take place, flow characteristics such as velocity profiles and flow resistance are predicted very well by our equations. However, the equations will underestimate the flow resistance if a part of the flow body becomes turbulent because of increase of flow scale. These suggest that the changes of equilibrium bed slope and flow structure are caused by phase-shift from solid phase to fluid phase depending on debris flow scale.

  4. Slope-Streaked Knob

    NASA Technical Reports Server (NTRS)

    2005-01-01

    28 May 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark slope streaks coming down the slopes of a knob in western Amazonis Planitia. All of the surfaces in this image are mantled by dust. On the slopes, mass movement of dry dust has created the streaks.

    Location near: 19.6oN, 166.1oW Image width: 3 km (1.9 mi Illumination from: lower left Season: Northern Autumn

  5. Creep behavior of submarine sediments

    USGS Publications Warehouse

    Silva, Armand J.; Booth, J.S.

    1984-01-01

    A series of experiments on drained creep of marine sediment indicates that strength degradation results from the creep process, which implies an associated reduction in slope stability. Furthermore, the highest creep potential of a sediment may be at its preconsolidation stress. Results from the experiments on samples from Georges Bank continental slope were also used in conjunction with a preliminary theoretical model to predict creep displacements. For the case illustrated in this report, steep slopes (>20??) and thick sections (>30 m) give rise to substantial creep and probable creep rupture; as angles or thicknesses decrease, displacements rapidly become negligible. Creep may be a significant geologic process on many marine slopes. Not only can it cause major displacements of surface sediment, but it may also be the precursor to numerous slope failures. ?? 1985 Springer-Verlag New York Inc.

  6. 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.

  7. 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.

  8. Numerical Modelling of Seismic Slope Stability

    NASA Astrophysics Data System (ADS)

    Bourdeau, Céline; Havenith, Hans-Balder; Fleurisson, Jean-Alain; Grandjean, Gilles

    Earthquake ground-motions recorded worldwide have shown that many morphological and geological structures (topography, sedimentary basin) are prone to amplify the seismic shaking (San Fernando, 1971 [Davis and West 1973] Irpinia, 1980 [Del Pezzo et al. 1983]). This phenomenon, called site effects, was again recently observed in El Salvador when, on the 13th of January 2001, the country was struck by a M = 7.6 earthquake. Indeed, while horizontal accelerations on a rock site at Berlin, 80 km from the epicentre, did not exceed 0.23 g, they reached 0.6 g at Armenia, 110 km from the epicentre. Armenia is located on a small hill underlaid by a few meters thick pyroclastic deposits. Both the local topography and the presence of surface layers are likely to have caused the observed amplification effects, which are supposed to have contributed to the triggering of some of the hundreds of landslides related to this seismic event (Murphy et al. 2002). In order to better characterize the way site effects may influence the triggering of landslides along slopes, 2D numerical elastic and elasto-plastic models were developed. Various geometrical, geological and seismic conditions were analysed and the dynamic behaviour of the slope under these con- ditions was studied in terms of creation and location of a sliding surface. Preliminary results suggest that the size of modelled slope failures is dependent on site effects.

  9. Dark Slope Streaks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    13 March 2004 Martian slope streaks occur in the regions most heavily mantled by fine, dry dust, particularly Tharsis, Arabia, and the knobby areas between Amazonis and Cerberus. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some examples of dark slope streaks off of buttes, mesas, and massifs in a dust-mantled crater in central Arabia Terra. New slope streaks form from time to time in the modern martian environment; the streaks in this image probably formed within the past decade. To create them, dust slid or avalanched down the slopes in an almost liquid-like manner. The image is located near 6.8oN, 321.7oW. The picture covers an area 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.

  10. NASA Now: SLOPE

    NASA Image and Video Library

    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...

  11. 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.

  12. Impact cratering on slopes

    NASA Astrophysics Data System (ADS)

    Aschauer, Johannes; Kenkmann, Thomas

    2017-07-01

    The majority of impact craters have circular outlines and axially symmetric morphologies. Deviation from crater circularity is caused by either target heterogeneity, a very oblique impact incidence, post-impact deformation, or by topography. Here, we investigate the effect of topography on crater formation and systematically study impact cratering processes on inclined hillsides up to 25° slope utilizing analogue experiments. A spring-driven air gun mounted in a vertical position shoots into three different types of granular bulk solids (two sorts of glass beads, quartz sand) to emulate impact cratering on slopes. In all, 170 experiments were conducted. The transient crater develops roughly symmetrically perpendicular to the slope plane, resulting in higher ejection angles uphill than downhill when measured with respect to a horizontal plane. Craters become increasingly elliptical with increasing slope angle. At slope angles close to angle of repose of the respective bulk solids, aspect ratios of the craters reach ∼1.7. Uphill-downhill cross sections become increasingly asymmetric, the depth-diameter ratio of the craters decreases, and the deepest point shifts downhill with increasing slope angle. Mass wasting is initiated both in the uphill and downhill sectors of the crater rim. For steep slopes the landslides that emanate from the uphill rim can overshoot the crater cavity and superpose the downhill crater rim in a narrow tongue. Mass wasting initiated at the downhill sector forms broader and shallower tongues and is triggered by the deposition of ejecta on the inclined slope. Our experiments help to explain asymmetric crater morphologies observed on asteroids such as Ceres, Vesta, Lutetia, and also on Mars.

  13. 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

  14. Frosty Slopes in Late Spring

    NASA Image and Video Library

    2014-12-18

    This image from NASA Mars Reconnaissance Orbiter shows frosted gullies on a south-facing slope within a crater. At this time of year only south-facing slopes retain the frost, while the north-facing slopes have melted.

  15. Key Locations Studied at 'Pahrump Hills' on Mars

    NASA Image and Video Library

    2017-06-09

    NASA's Curiosity Mars rover examined a mudstone outcrop area called "Pahrump Hills" on lower Mount Sharp, in 2014 and 2015. This view shows locations of some targets the rover studied there. The blue dots indicate where drilled samples of powdered rock were collected for analysis. The rover drilled a sample of rock powder at "Confidence Hills" in September 2014 and analyzed it with internal laboratory instruments. Then the mission conducted a walkabout survey up the slope, along the route indicated in yellow, stopping for close inspection at the red-dot locations. Observations from the walkabout were used to choose where to take additional drilled samples for analysis during a second pass up the slope. The "Mojave 2" sample was collected in January 2015 and the "Telegraph Peak" one in February 2015. This view of the outcrop and other portions of Mount Sharp beyond is a mosaic of images taken by the rover's Mast Camera (Mastcam) in September 2014. https://photojournal.jpl.nasa.gov/catalog/PIA21709

  16. 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.

  17. 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).

  18. Rolling Mill Hill, Nashville, TN

    EPA Pesticide Factsheets

    Rolling Mill Hill was the home to Nashville General Hospital from 1890 to the 1990s and encompassed several buildings and structures. These existing buildings of historical significance were re-used in the form of apartments. The original Trolley Barns on the site are now artists’ lofts and are home to several companies and non-profit offices. Nance Place, which entails additional buildings built on-site, is a Tax Credit Workforce Housing Development and is Platinum LEED certified.

  19. 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.

  20. Rocks of the Columbia Hills

    NASA Astrophysics Data System (ADS)

    Squyres, Steven W.; Arvidson, Raymond E.; Blaney, Diana L.; Clark, Benton C.; Crumpler, Larry; Farrand, William H.; Gorevan, Stephen; Herkenhoff, Kenneth E.; Hurowitz, Joel; Kusack, Alastair; McSween, Harry Y.; Ming, Douglas W.; Morris, Richard V.; Ruff, Steven W.; Wang, Alian; Yen, Albert

    2006-02-01

    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.

  1. Hydrocarbons in benthic marine algae of the Vestfold Hills, Antarctica

    SciTech Connect

    Dhargalkar, V.K.; Bhosle, N.B.

    1987-02-01

    Recently, Antarctic continent has been the center for diverse research activities. This has resulted in a large number of research and supply vessels visiting Antarctica, which may lead to the contamination of Antarctic environment due to unintentional release of petroleum products. It is, therefore, essential to monitor the concentration of various pollutants in water, sediment, flora and fauna of this region which may also serve as a baseline data for future comparison. With this in view, total hydrocarbon concentration in some marine benthic algae collected from the Vestfold Hills, Antarctica was studied using fluorescence spectroscopy.

  2. 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

  3. Geological evolution of the Coombs Allan Hills area, Ferrar large igneous province, Antarctica: Debris avalanches, mafic pyroclastic density currents, phreatocauldrons

    NASA Astrophysics Data System (ADS)

    Ross, Pierre-Simon; White, James D. L.; McClintock, Murray

    2008-05-01

    The Jurassic Ferrar large igneous province of Antarctica comprises igneous intrusions, flood lavas, and mafic volcaniclastic deposits (now lithified). The latter rocks are particularly diverse and well-exposed in the Coombs-Allan Hills area of South Victoria Land, where they are assigned to the Mawson Formation. In this paper we use these rocks in conjunction with the pre-Ferrar sedimentary rocks (Beacon Supergroup) and the lavas themselves (Kirkpatrick Basalt) to reconstruct the geomorphological and geological evolution of the landscape. In the Early Jurassic, the surface of the region was an alluvial plain, with perhaps 1 km of mostly continental siliciclastic sediments underlying it. After the fall of silicic ash from an unknown but probably distal source, mafic magmatism of the Ferrar province began. The oldest record of this event at Allan Hills is a ≤ 180 m-thick debris-avalanche deposit (member m1 of the Mawson Formation) which contains globular domains of mafic igneous rock. These domains are inferred to represent dismembered Ferrar intrusions emplaced in the source area of the debris avalanche; shallow emplacement of Ferrar magmas caused a slope failure that mobilized the uppermost Beacon Supergroup, and the silicic ash deposits, into a pre-existing valley or basin. The period which followed ('Mawson time') was the main stage for explosive eruptions in the Ferrar province, and several cubic kilometres of both new magma and sedimentary rock were fragmented over many years. Phreatomagmatic explosions were the dominant fragmentation mechanism, with magma-water interaction taking place in both sedimentary aquifers and existing vents filled by volcaniclastic debris. At Coombs Hills, a vent complex or 'phreatocauldron' was formed by coalescence of diatreme-like structures; at Allan Hills, member m2 of the Mawson Formation consists mostly of thick, coarse-grained, poorly sorted layers inferred to represent the lithified deposits of pyroclastic density currents

  4. 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

  5. Dark Slope Streaks

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-412, 5 July 2003

    On the dry, desert planet, Mars, wind is not the only contemporary geologic process that modifies the surface. Gravity also has a role to play. In regions such as Amazonis, Tharsis, and Arabia, most surfaces are covered by mantles of very fine dust. From time to time, an avalanche occurs on a dust-covered slope. This process is happening today, because changes have been observed by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) over the course if its mission, which began in September 1997. This picture shows a variety of dark slope streaks, formed by avalanches of dust, on the walls of a crater in southwest Amazonis near 7.6oN, 171.8oW. The size and shape of each slope streak, including the wide feature near the upper right, is determined by the steepness and texture of the slope on which it occurs. New slope streaks in some regions have been observed to form over periods of less than a few months to a year. This picture was taken in June 2003, and is illuminated from the lower left. The image is 2.3 km (1.4 mi) wide.

  6. 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.

  7. The man and the hill

    USGS Publications Warehouse

    Leopold, Luna Bergere

    1962-01-01

    He was sitting on a large slab of rock. As he looked at the cloud of dust hanging hazily on the horizon, the piece of antler and the block of flint he held in his hand hung as if they were suspended from their previous rapid motion. The man gazed intently across the swaying grass which rose in wave-like billows across the distant hills. What was that dust - a herd of buffalo, a band of hunters, or were coyotes chasing the antelope again? After watching for a while he started again to chip the flint with a rapid twisting motion of the bone in his right hand. The little chips of flint fell in the grass before him. It is the same hill but the scene has changed. Seated on the same rock, holding the reins of a saddle horse, a man dressed in buckskin took the fur cap off his head and wiped his brow. He was looking intently across a brown and desolate landscape at a cloud of dust on the far horizon. Was it the hostile tribe of Indians? It could be buffalo. Nervously he kicked at the ground with the deerhide moccasin, pushing the flint chips out of the way. He wiped the dust from his long rifle. What a terrible place - no water, practically no grass, everything bare and brown. Now at sunset, slanting across the hills green with springtime, a cowman sits on a big rock, pushes his sombrero back on his head, and looks across the valley at a large but quiet herd of stock, moving slowly as each steer walks from one lush patch of grass to another, nibbling. Suddenly he stood up. Far on the horizon some dark objects were moving. Is it the sheepmen? Could it be the stage coach from Baggs to the Sweetwater Crossing?Same hill - a gray truck was grinding slowly toward the summit. It pulled up near a small fenced enclosure where there were some instruments painted a bright silver color. A man stepped out of the truck and turned to his younger companion, "You've never found an arrowhead? Maybe you have never thought about it correctly. If you want to find where an Indian camped long

  8. Arabian Slope Streaks

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-508, 9 October 2003

    Arabia Terra is a vast, heavily cratered region in the martian northern hemisphere. Much of Arabia Terra is thickly blanketed by dust. From time to time, on steep slopes, the dust will avalanche or slide downhill, creating a streak. The majority of slope streaks are darker than their surroundings, but not all of them are dark. In Arabia, it is common to find bright and dark slope streaks, and to find them together. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example, taken from a crater near 10.5oN, 318.4oW. Why some streaks are bright and others are dark is not yet known. This picture covers an area 3 km (1.9 mi) wide and is illuminated by sunlight from the left.

  9. Arabian Slope Streaks

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-508, 9 October 2003

    Arabia Terra is a vast, heavily cratered region in the martian northern hemisphere. Much of Arabia Terra is thickly blanketed by dust. From time to time, on steep slopes, the dust will avalanche or slide downhill, creating a streak. The majority of slope streaks are darker than their surroundings, but not all of them are dark. In Arabia, it is common to find bright and dark slope streaks, and to find them together. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example, taken from a crater near 10.5oN, 318.4oW. Why some streaks are bright and others are dark is not yet known. This picture covers an area 3 km (1.9 mi) wide and is illuminated by sunlight from the left.

  10. 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).

  11. Piecewise Linear Slope Estimation.

    PubMed

    Ingle, A N; Sethares, W A; Varghese, T; Bucklew, J A

    2014-11-01

    This paper presents a method for directly estimating slope values in a noisy piecewise linear function. By imposing a Markov structure on the sequence of slopes, piecewise linear fitting is posed as a maximum a posteriori estimation problem. A dynamic program efficiently solves this by traversing a linearly growing trellis. The alternating maximization algorithm (a kind of pseudo-EM method) is used to estimate the model parameters from data and its convergence behavior is analyzed. Ultrasound shear wave imaging is presented as a primary application. The algorithm is general enough for applicability in other fields, as suggested by an application to the estimation of shifts in financial interest rate data.

  12. Piecewise Linear Slope Estimation

    PubMed Central

    Sethares, W. A.; Bucklew, J. A.

    2015-01-01

    This paper presents a method for directly estimating slope values in a noisy piecewise linear function. By imposing a Markov structure on the sequence of slopes, piecewise linear fitting is posed as a maximum a posteriori estimation problem. A dynamic program efficiently solves this by traversing a linearly growing trellis. The alternating maximization algorithm (a kind of pseudo-EM method) is used to estimate the model parameters from data and its convergence behavior is analyzed. Ultrasound shear wave imaging is presented as a primary application. The algorithm is general enough for applicability in other fields, as suggested by an application to the estimation of shifts in financial interest rate data. PMID:26229417

  13. Lycus Sulci Slope Streaks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    21 March 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark slope streaks on ridges in the Lycus Sulci region, north of the Olympus Mons volcano. Slope streaks form in the dry, dust-mantled regions of Mars. The darker streaks formed more recently than lighter ones, perhaps within the past Mars year or two. These streaks are located near 24.1oN, 146.1oW. This picture covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.

  14. Genetic diversity and structure in hill rice (Oryza sativa L.) landraces from the North-Eastern Himalayas of India.

    PubMed

    Roy, Somnath; Marndi, B C; Mawkhlieng, B; Banerjee, A; Yadav, R M; Misra, A K; Bansal, K C

    2016-07-13

    Hill rices (Oryza sativa L.) are direct seeded rices grown on hill slopes of different gradients. These landraces have evolved under rainfed and harsh environmental conditions and may possess genes governing adaptation traits such as tolerance to cold and moisture stress. In this study, 64 hill rice landraces were collected from the state of Arunachal Pradesh of North-Eastern region of India, and assessed by agro-morphological variability and microsatellite markers polymorphism. Our aim was to use phenotypic and genetic diversity data to understand the basis of farmers' classification of hill rice landraces into two groups: umte and tening. Another goal was to understand the genetic differentiation of hill rices into Indica or japonica subspecies. According to farmers' classification, hill rices were categorized into two groups: umte (large-grained, late maturing) and tening (small-grained, early maturing). We did not find significant difference in days to 50 % flowering between the groups. Principal component analysis revealed that two groups can be distinguished on the basis of kernel length-to-width ration (KLW), kernel length (KL), grain length (GrL), grain length-to-width ration (GrLW) and plant height (Ht). Stepwise canonical discriminant analysis identified KL and Ht as the main discriminatory characters between the cultivar groups. Genetic diversity analysis with 35 SSR markers revealed considerable genetic diversity in the hill rice germplasm (gene diversity: 0.66; polymorphism information content: 0.62). Pair-wise allelic difference between umte and tening groups was not statistically significant. The model-based population structure analysis showed that the hill rices were clustered into two broad groups corresponding to Indica and Japonica. The geographic distribution and cultivars grouping of hill rices were not congruent in genetic clusters. Both distance- and model-based approaches indicated that the hill rices were predominantly japonica or

  15. Astronaut David Scott on slope of Hadley Delta during Apollo 15 EVA

    NASA Technical Reports Server (NTRS)

    1971-01-01

    Astronaut David R. Scott, mission commander, with tongs and gnomon in hand, studies a boulder on the slope of Hadley Delta during the Apollo 15 lunar surface extravehicular activity. The Lunar Roving Vehicle (LRV) or Rover is in right foreground. View is looking slightly south of west. 'Bennett Hill' is at extreme right. Astronaut James B. Irwin, lunar module pilot, took this photograph.

  16. Boron isotopes at the Shale Hills Critical Zone Observatory

    NASA Astrophysics Data System (ADS)

    Gaillardet, J.; Noireaux, J.; Sullivan, P. L.; Steinhoefel, G.; Louvat, P.; Brantley, S. L.

    2015-12-01

    The Shale Hills Critical Zone Observatory is a Northern Appalachian catchment site where a series of geochemical tracers have been applied in order to build a multi-isotope integrative model (referred to as "CZ-tope"). The catchment is small (8ha) and relief is about 30 m. It receives about 107 cm of precipitation per year. Mean annual temperature is 10°C. Shales Hills observatory has a relatively simple lithology consisting of organic-poor shales rich in illite and relatively infrequent interbedded carbonates and sandstones. Vegetation consists mainly of deciduous trees. Soil thickness ranges from 0.3 m at the ridgetop to 3 m in the valley floor. Following the CZ-tope concept, boron isotopes were analysed in the main geochemical reservoirs of the SH catchment (stream, vegetation, soil pore waters, solid phases, groundwaters). Measurements were conducted using MC-ICPMS and a direct injection system after a chemical procedure aiming at isolating boron from geological matrix. Results are expressed as δ11B. Error bars are better than 0.5‰ Boron isotopes in Shale Hills catchment show a large range of variation. While bedrock values are within a narrow range around -5‰, stream waters range between 10‰ and 15‰, and exhibit temporal variations. This very strong 11B enrichment is also observed in the vegetation, groundwater and rainwater reservoirs but with a much larger range of variation. The input of 11B-enriched water by precipitation is contributing to the B budget at the catchment outlet but cannot explain all the 11B enrichment with respect to parent bedrock. The solid phases collected along two different soil profiles and as suspended sediments in the stream are close to the bedrock value or slightly 10B-enriched. The most important conclusion from boron isotope investigation at Shale Hills CZO is that a simple mass budget is not able to reconcile the strong 11B-enrichment measured in the water phases and vegetation with the isotopic signature of the

  17. Sediment and nutrient loading from non-degraded and degraded watershed area in to a tropical water body: a case study using remote sensing

    NASA Astrophysics Data System (ADS)

    Gupta, Mool Chandra

    2006-12-01

    The present study deals with the works relating to integrated watershed management on sustainable basis for evolving tractable operational package so that nutrient, sediment and runoff losses from catchment could be minimized. Study area lies between latitudes 22°5' and 22°12' and longitudes 77°17' and 77°23' covering an area of 6357.5 hectares. Physically it is divided into two different parts, hills and plains. The height of elevation of study area is in between 518 to 630 meters above m.s.l. The thematic maps were generated using satellite data. The present tropical catchment possessing diverse forest ecosystem and agriculture land characterized by weathered black cotton soil derived from basalt with the slope ranging from nearly level to moderately steep to steep sloping and receiving average annual rainfall 1150 mm. The annual return of carbon and nutrient (N, P, K, Ca, Na and Mg) in non degraded and degraded forest and nutrient concentrations in runoff flow and sediment output (sediment loss) during monsoon period from non-degraded forest, degraded forest and agriculture lands were worked out. The sediment and nutrient losses from the catchment to the tropical water body are alarming particularly from agricultural land. The nutrient losses in both the forms (runoff water plus sediment movement) are in the order of agriculture > degraded forest > non-degraded forest. The loss of soil in the form of sediment loss follows the same pattern. The results were alarming when the value of sediment loss of forest was compared to the agriculture land of the catchment. The soil loss as sediment is 33.5 times greater in agriculture land compared to non-degraded forest and 10.2 times greater in agriculture land compared to degraded forest.

  18. Effects of slope gradient on hydro-erosional processes on an aeolian sand-covered loess slope under simulated rainfall

    NASA Astrophysics Data System (ADS)

    Zhang, F. B.; Yang, M. Y.; Li, B. B.; Li, Z. B.; Shi, W. Y.

    2017-10-01

    The aeolian sand-covered loess slope of the Wind-Water Erosion Crisscross Region of the Loess Plateau in China may play a key role in contributing excessive sediment to the Yellow River. Understanding its hydro-erosional processes is crucial to assessing, controlling and predicting soil and water losses in this region and maintaining the ecological sustainability of the Yellow River. Simulated rainfall (intensity 90 mm h-1) was used to investigate the runoff and soil loss from loess slopes with different slope gradients (18%, 27%, 36%, 47%, and 58%) and overlying sand layer thicknesses (0, 5 and 10 cm). As compared with uncovered loess slopes, an overlying sand layer delayed runoff production, reduced cumulative runoff and increased cumulative soil loss, as well as enhancing variations among slope gradients. Cumulative runoff and soil loss from the sand-covered loess slopes increased with increasing slope gradients and then slightly decreased, with a peak at about 47% gradient; they both were greater from the 10-cm sand-covered loess slope than from the 5-cm except for with 18% slope gradient. In general, differences in cumulative runoff between sand layer thicknesses became smaller, while those in cumulative soil loss became larger, with increasing slope gradient. Runoff and soil loss rates on the sand-covered loess slopes exhibited unimodal distributions during the rainstorms. Maximum values tended to occur at the same rain duration, and increased considerably with increasing slope gradient and sand layer thickness on slopes that were less than 47%. Liquefaction process might occur on the lower loess slopes covered with thinner sand layers but failures similar to shallow landslides might occur when the sand layer was thicker on steeper slopes. The presence of an overlying sand layer changed the relationship between runoff and soil loss rates during intense rainstorms and this change varied with different slope gradients. Our results demonstrated that the effects

  19. The Chukchi slope current

    NASA Astrophysics Data System (ADS)

    Corlett, W. Bryce; Pickart, Robert S.

    2017-04-01

    Using a collection of 46 shipboard hydrographic/velocity transects occupied across the shelfbreak and slope of the Chukchi Sea between 2002 and 2014, we have quantified the existence of a current transporting Pacific-origin water westward over the upper continental slope. It has been named the Chukchi slope current, which is believed to emanate from Barrow Canyon. The current is surface-intensified, order 50 km wide, and advects both summer and winter waters. It is not trapped to a particular isobath, but instead is reminiscent of a free jet. There is no significant variation in Pacific water transport with distance from Barrow Canyon. A potential vorticity analysis suggests that the flow is baroclinically unstable, consistent with the notion that it meanders. The current is present during all synoptic wind conditions, but increases in strength from summer to fall presumably due to the seasonal enhancement of the easterly winds in the region. Its transport increased over the 12-year period of data coverage, also likely in response to wind forcing. In the mean, the slope current transports 0.50 ± 0.07 Sv of Pacific water. This estimate allows us to construct a balanced mass budget of the Chukchi shelf inflows and outflows. Our study also confirms the existence of an eastward-flowing Chukchi shelfbreak jet transporting 0.10 ± 0.03 Sv of Pacific water towards Barrow Canyon.

  20. 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.

  1. 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.

  2. Skating down a steeper slope: Fear influences the perception of geographical slant

    PubMed Central

    Stefanucci, Jeanine K.; Proffitt, Dennis R.; Clore, Gerald L.; Parekh, Nazish

    2008-01-01

    Conscious awareness of hill slant is overestimated, but visually guided actions directed at hills are relatively accurate. Also, steep hills are consciously estimated to be steeper from the top as opposed to the bottom, possibly because they are dangerous to walk down. In the present study, participants stood at the top of a hill on either a skateboard or a wooden box of the same height. They gave three estimates of the slant of the hill: a verbal report, a visually matched estimate, and a visually guided action. Fear of descending the hill was also assessed. Those participants that were scared (by standing on the skateboard) consciously judged the hill to be steeper relative to participants who were unafraid. However, the visually guided action measure was accurate across conditions. These results suggest that our explicit awareness of slant is influenced by the fear associated with a potentially dangerous action. “[The phobic] reported that as he drove towards bridges, they appeared to be sloping at a dangerous angle.” (Rachman and Cuk 1992 p. 583). PMID:18414594

  3. Computational tools for fitting the Hill equation to dose-response curves.

    PubMed

    Gadagkar, Sudhindra R; Call, Gerald B

    2015-01-01

    Many biological response curves commonly assume a sigmoidal shape that can be approximated well by means of the 4-parameter nonlinear logistic equation, also called the Hill equation. However, estimation of the Hill equation parameters requires access to commercial software or the ability to write computer code. Here we present two user-friendly and freely available computer programs to fit the Hill equation - a Solver-based Microsoft Excel template and a stand-alone GUI-based "point and click" program, called HEPB. Both computer programs use the iterative method to estimate two of the Hill equation parameters (EC50 and the Hill slope), while constraining the values of the other two parameters (the minimum and maximum asymptotes of the response variable) to fit the Hill equation to the data. In addition, HEPB draws the prediction band at a user-defined confidence level, and determines the EC50 value for each of the limits of this band to give boundary values that help objectively delineate sensitive, normal and resistant responses to the drug being tested. Both programs were tested by analyzing twelve datasets that varied widely in data values, sample size and slope, and were found to yield estimates of the Hill equation parameters that were essentially identical to those provided by commercial software such as GraphPad Prism and nls, the statistical package in the programming language R. The Excel template provides a means to estimate the parameters of the Hill equation and plot the regression line in a familiar Microsoft Office environment. HEPB, in addition to providing the above results, also computes the prediction band for the data at a user-defined level of confidence, and determines objective cut-off values to distinguish among response types (sensitive, normal and resistant). Both programs are found to yield estimated values that are essentially the same as those from standard software such as GraphPad Prism and the R-based nls. Furthermore, HEPB also has

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. Spirit Rover on 'Husband Hill'

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Figure 1: Location of Spirit

    Two Earth years ago, NASA's Mars Exploration Rover Spirit touched down in Gusev Crater. The rover marked its first Mars-year (687 Earth days) anniversary in November 2005. Shortly before Spirit's Martian anniversary, the Mars Orbiter Camera on NASA's Mars Global Surveyor acquired an image covering approximately 3 kilometers by 3 kilometers (1.9 miles by 1.9 miles) centered on the rover's location at that time in the 'Columbia Hills.'

    'Husband Hill,' the tallest in the range, is just below the center of the image. The image has a resolution of about 50 centimeters (1.6 feet) per pixel. North is up; illumination is from the left. The location is near 14.8 degrees south latitude, 184.6 degrees west longitude.

    The image was acquired on Nov. 2, 2005. A white box (see Figure 1) indicates the location of an excerpted portion on which the location of Spirit on that date is marked. Dr. Timothy J. Parker of the Mars Exploration Rover team at the NASA's Jet Propulsion Laboratory, Pasadena, Calif., confirmed the location of the rover in the image. The region toward the bottom of the image shows the area where the rover is currently headed. The large dark patch and other similar dark patches are accumulations of windblown sand and granules.

  10. Spirit Rover on 'Husband Hill'

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Figure 1: Location of Spirit

    Two Earth years ago, NASA's Mars Exploration Rover Spirit touched down in Gusev Crater. The rover marked its first Mars-year (687 Earth days) anniversary in November 2005. Shortly before Spirit's Martian anniversary, the Mars Orbiter Camera on NASA's Mars Global Surveyor acquired an image covering approximately 3 kilometers by 3 kilometers (1.9 miles by 1.9 miles) centered on the rover's location at that time in the 'Columbia Hills.'

    'Husband Hill,' the tallest in the range, is just below the center of the image. The image has a resolution of about 50 centimeters (1.6 feet) per pixel. North is up; illumination is from the left. The location is near 14.8 degrees south latitude, 184.6 degrees west longitude.

    The image was acquired on Nov. 2, 2005. A white box (see Figure 1) indicates the location of an excerpted portion on which the location of Spirit on that date is marked. Dr. Timothy J. Parker of the Mars Exploration Rover team at the NASA's Jet Propulsion Laboratory, Pasadena, Calif., confirmed the location of the rover in the image. The region toward the bottom of the image shows the area where the rover is currently headed. The large dark patch and other similar dark patches are accumulations of windblown sand and granules.

  11. The Black Hills (South Dakota) flood of June 1972: Impacts and implications

    Treesearch

    Howard K. Orr

    1973-01-01

    Rains of 12 inches or more in 6 hours fell on the east slopes of the Black Hills the night of June 9, 1972. Resulting flash floods exacted a disastrous toll in human life and property. Rainfall and discharge so greatly exceeded previous records that recurrence intervals have been presented in terms of multiples of the estimated 50- or 100- year event. Quick runoff was...

  12. Soil and landform interplay in the dry valley of Edson Hills, Ellsworth Mountains, continental Antarctica

    NASA Astrophysics Data System (ADS)

    Delpupo, Caroline; Schaefer, Carlos Ernesto Gonçalves Reynaud; Roque, Mariane Batalha; de Faria, André Luiz Lopes; da Rosa, Katia Kellem; Thomazini, André; de Paula, Mayara Daher

    2017-10-01

    The main relief units from the dry valley of Edson Hills, Ellsworth Mountains, Antarctica (79°49‧12.4″/83°40‧16.1″), were assessed, emphasizing the analysis of soil and landform interplay. Soil morphological, physical, and chemical properties; salinity; surface boulder weathering (frequency and feature); classification; and weathering stages were analyzed. Three distinct landforms summarize the geomorphology of the dry valley of Edson Hills, Ellsworth Mountains: (i) periglacial features like slightly creeping debris-mantled slopes, steep debris-mantled slopes, patterned grounds, and thermokarst; (ii) glacial features like hummocky moraines, lateral moraines (supraglacial), lakes, kettle hole (proglacial), cirques infill (subglacial), horn, and arête (erosional glacial); and (iii) nonglacial features like scree slopes and talus deposits. All these glacial and periglacial features are related to the West Antarctica ice sheet variations. Soils in the dry valley of Edson Hills are pedologically poorly developed. However, the degree of development in soils associated with patterned ground and moraine systems is remarkable. All soils present desert pavement owing to the action of severe aeolian erosion. In addition, soils accumulate salts depending on the local drainage conditions. The most expressive soil classes among the studied soils were Typic Haploturbel and Typic Anhyorthel, especially because of: (i) a general trend of ice-cemented permafrost occurrence in lower portions of the landscape, particularly in the patterned ground area and in the hummocky moraine; and (ii) the presence of dry permafrost in higher positions of the landscape, in relief units such as in debris-mantled slopes and talus deposits. Thus, a close relationship among soil characteristics and landforms were observed in the dry valley of Edson Hills.

  13. 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

  14. Overpressure, Flow Focusing, Compaction and Slope Stability on the continental slope: Insights from IODP Expedition 308

    NASA Astrophysics Data System (ADS)

    Flemings, P. B.

    2010-12-01

    Integrated Ocean Drilling Program Expepedition 308 used direct measurements of pore pressure, analysis of hydromechanical properties, and geological analysis to illuminate how sedimentation, flow focusing, overpressure, and slope stability couple beneath the seafloor on the deepwater continental slope in the Gulf of Mexico. We used pore pressure penetrometers to measure severe overpressures (60% of the difference between lithostatic stress and hydrostatic pressure) that extend from the seafloor for 100’s of meters. We ran uniaxial consolidation experiments on whole core and found that although permeability is relatively high near the seafloor, the sediments are highly compressible. As a result, the coefficient of consolidation (the hydraulic diffusivity) is remarkably constant over a large range of effective stresses. This behavior accounts for the high overpressure that begins near the seafloor and extends to depth. Forward modeling suggests that flow is driven laterally along a permeable unit called the Blue Unit. Calculations suggest that soon after deposition, lateral flow lowered the effective stress and triggered the submarine landslides that we observe. Later in the evolution of this system, overpressure may have pre-conditioned the slope to failure by earthquakes. Results from IODP Expedition 308 illustrate how pore pressure and sedimentation control the large-scale form of continental margins, how submarine landslides form, and provide strategies for designing stable drilling programs.

  15. North Polar Slope

    NASA Technical Reports Server (NTRS)

    2004-01-01

    21 December 2004 Slopes in the north polar region of Mars exhibit outcroppings of layered material. No one knows the composition of the layers, but the uppermost layers of are thought to be a mixture of dust and ice in some proportion. Lower layers in the north polar region are thought to include sand. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a late northern spring view of a slope on which are exposed some of the upper layers in the north polar region. Bright surfaces in this image are covered by frost. The image is located near 81.5oN, 340.6oW. The picture covers an area about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the lower left.

  16. Slope Streaks in Arabia

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-353, 7 May 2003

    Light-, dark-, and intermediate-toned slope streaks are common in the thick, dust-mantled regions of Arabia Terra, parts of Tharsis, Memnonia, and some of the knobby areas west of Amazonis Planitia. They most likely form by avalanching of loose, dry dust, perhaps each triggered by a gust of wind. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, acquired earlier this week (in May 2003), shows a plethora of slope streaks on the walls of an impact crater in east-central Arabia Terra near 13.0oN, 319.8oW. The image is 3 km (1.9 mi) wide; sunlight illuminates the scene from the left/lower left.

  17. 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

  18. Spectral Diversity in the Columbia Hills from Spirit's Mini-TES and PanCam

    NASA Astrophysics Data System (ADS)

    Blaney, D.

    2005-08-01

    Since reaching the Columbia Hills, Spirit has investigated their composition and structure with the Athena payload. Two remote sensing instruments collected spectral information at visible (PanCam) and at thermal infrared (Mini-TES) wavelengths. Observations were coordinated and targeted to determine the mineralogical diversity and identify lithologies for investigation with the rest of the payload. Spirit has measured a wide range of targets including outcrop, rocks, and disturbed soils. While there is variation within classes, materials observed fell into five rock types and two soil types. Class names derive from their general location and a representative example target. Gusev plains rocks (e.g. Adirondack) have an olivine feature in the long wavelength part of the spectrum and are the dominant rocks on the plains. While initially very rare in the Columbia hills, plains basalts have become more common as the rover has climbed into the hills. West Spur rocks (e.g. Palenque) are highly altered. Lower Husband Hill I rocks (e.g. Wishstone) are dominated spectrally by intermediate plagioclase feldspar while Lower Husband Hills II rocks (e.g. Peace) show spectral evidence for bound water. Upon reaching the ``Cumberland Ridge", two types of materials were identified. The ``Watchtower" and ``Jibsheet" outcrops represent the next class, characterized by steep slope from 700 cm-1 to 400 cm-1. Finally, the ``Methuselah" outcrop shares many of the same spectral characteristics as Lower Husband Hill I (e.g. Wishstone). Disturbed soils all have similar characteristics, except for Huron (near Paso Robles), which shows evidence for water at Mini-TES wavelengths and is significantly less ``red" than other materials measured at visible wavelengths. The complex mixture of rock types indicate that multiple processes have been at work in the formation and evolution of the Columbia Hills. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology

  19. 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

  20. Local slope stability analysis

    NASA Astrophysics Data System (ADS)

    Hattendorf, I.; Hergarten, St.; Neugebauer, H. J.

    Mass movements under the influence of gravity occur as result of diverse disturbing and destabilizing processes, for example of climatic or anthropological origin. The stability of slopes is mainly determined by the geometry of the land-surface and designated slip-horizon. Further contributions are supplied by the pore water pressure, cohesion and friction. All relevant factors have to be integrated in a slope stability model, either by measurements and estimations (like phenomenological laws) or derived from physical equations. As result of stability calculations, it's suitable to introduce an expectation value, the factor-of-safety, for the slip-risk. Here, we present a model based on coupled physical equations to simulate hardly measurable phenomenons, like lateral forces and fluid flow. For the displacements of the soil-matrix we use a modified poroelasticity-equation with a Biot-coupling (Biot 1941) for the water pressure. Latter is described by a generalized Boussinesq equation for saturated-unsaturated porous media (Blendinger 1998). One aim of the calculations is to improve the knowledge about stability-distributions and their temporal variations. This requires the introduction of a local factor-of-safety which is the main difference to common stability models with global stability estimations. The reduction of immediate danger is still the emergent task of the most slope and landslide investigations, but this model is also useful with respect to understand the governing processes of landform evolution.

  1. 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

  2. 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

  3. 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

  4. 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

  5. Bluff Hills - Ideal For Hardwood Timber Production

    Treesearch

    Robert L. Johnson

    1958-01-01

    Meandering along the eastern edge of the Mississippi River Valley from Cairo, Illinois, to Baton Rouge, Louisiana, are 4% million acres of forested uplands variously called the Loess Hills, the Thick Loess area, the Brown Loam Bluffs, the Bluff Hills, or just the Bluffs. The area (Fig. 1) is well known to foresters and lumbermen who work in the Lower Mississippi Valley...

  6. 27 CFR 9.193 - Rattlesnake Hills.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Rattlesnake Hills. 9.193... Rattlesnake Hills. (a) Name. The name of the viticultural area described in this section is “Rattlesnake Hills”. For purposes of part 4 of this chapter, “Rattlesnake Hills” is a term of viticultural significance....

  7. 27 CFR 9.193 - Rattlesnake Hills.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Rattlesnake Hills. 9.193... Rattlesnake Hills. (a) Name. The name of the viticultural area described in this section is “Rattlesnake Hills”. For purposes of part 4 of this chapter, “Rattlesnake Hills” is a term of viticultural significance....

  8. 27 CFR 9.193 - Rattlesnake Hills.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Rattlesnake Hills. 9.193... Rattlesnake Hills. (a) Name. The name of the viticultural area described in this section is “Rattlesnake Hills”. For purposes of part 4 of this chapter, “Rattlesnake Hills” is a term of viticultural significance....

  9. 27 CFR 9.193 - Rattlesnake Hills.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Rattlesnake Hills. 9.193... Rattlesnake Hills. (a) Name. The name of the viticultural area described in this section is “Rattlesnake Hills”. For purposes of part 4 of this chapter, “Rattlesnake Hills” is a term of viticultural significance....

  10. 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."…

  11. Management Decisions and the "Dred" Hills

    Treesearch

    Steven W. Anderson

    1992-01-01

    An area of public land called the Red Hills was being so abused by the public that it was often called the "Dred" Hills. Some staff work had been accomplished to protect sensitive areas within the 7,200-acre site, but depreciative behavior continued. Primary destructive activities included off-road vehicle use and indiscriminate shooting and dumping. This...

  12. 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)

  13. 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…

  14. 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…

  15. 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)

  16. 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.

  17. Soufriere Hills Volcano Resumes Activity

    NASA Image and Video Library

    2017-09-27

    A massive eruption of Montserrat’s Soufrière Hills Volcano covered large portions of the island in debris. The eruption was triggered by a collapse of Soufrière Hills’ summit lava dome on February 11, 2010. Pyroclastic flows raced down the northern flank of the volcano, leveling trees and destroying buildings in the village of Harris, which was abandoned after Soufrière Hills became active in 1995. The Montserrat Volcano Observatory reported that some flows, about 15 meters (49 feet) thick, reached the sea at Trant’s Bay. These flows extended the island’s coastline up to 650 meters (2,100 feet). These false-color satellite images show the southern half of Montserrat before and after the dome collapse. The top image shows Montserrat on February 21, 2010, just 10 days after the event. For comparison, the bottom image shows the same area on March 17, 2007. Red areas are vegetated, clouds are white, blue/black areas are ocean water, and gray areas are covered by flow deposits. Fresh deposits tend to be lighter than older deposits. On February 21, the drainages leading down from Soufrière Hills, including the White River Valley, the Tar River Valley, and the Belham River Valley, were filled with fresh debris. According to the Montserrat Volcano Observatory, pyroclastic flows reached the sea through Aymers Ghaut on January 18, 2010, and flows entered the sea near Plymouth on February 5, 2010. NASA Earth Observatory image by Robert Simmon, using data from the NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team. Caption by Robert Simmon. To read more go to: earthobservatory.nasa.gov/IOTD/view.php?id=42792 NASA Goddard Space Flight Center is home to the nation's largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe. Follow us on Twitter Join us on Facebook

  18. Slope basins, headless canyons, and submarine palaeoseismology of the Cascadia accretionary complex

    USGS Publications Warehouse

    McAdoo, B.G.; Orange, D.L.; Screaton, E.; Lee, H.; Kayen, R.

    1997-01-01

    A combination of geomorphological, seismic reflection and geotechnical data constrains this study of sediment erosion and deposition at the toe of the Cascadia accretionary prism. We conducted a series of ALVIN dives in a region south of Astoria Canyon to examine the interrelationship of fluid flow and slope failure in a series of headless submarine canyons. Elevated head gradients at the inflection point of canyons have been inferred to assist in localized failures that feed sediment into a closed slope basin. Measured head gradients are an order of magnitude too low to cause seepage-induced slope failure alone; we therefore propose transient slope failure mechanisms. Intercanyon slopes are uniformly unscarred and smooth, although consolidation tests indicate that up to several metres of material may have been removed. A sheet-like failure would remove sediment uniformly, preserving the observed smooth intercanyon slope. Earthquake-induced liquefaction is a likely trigger for this type of sheet failure as the slope is too steep and short for sediment flow to organize itself into channels. Bathymetric and seismic reflection data suggest sediment in a trench slope basin between the second and third ridges from the prism's deformation is derived locally. A comparison of the amounts of material removed from the slopes and that in the basin shows that the amount of material removed from the slopes may slightly exceed the amount of material in the basin, implying that a small amount of sediment has escaped the basin, perhaps when the second ridge was too low to form a sufficient dam, or through a gap in the second ridge to the south. Regardless, almost 80% of the material shed off the slopes around the basin is deposited locally, whereas the remaining 20% is redeposited on the incoming section and will be re-accreted.

  19. A Simple Method for Estimating the Sediment-Flux Histories of Ancient Shelf-Margin Successions

    NASA Astrophysics Data System (ADS)

    Petter, A. L.; Mohrig, D. C.; Carvajal, C.; Steel, R.; Kim, W.

    2009-12-01

    datasets because it can be used to extrapolate the flux of sediment beyond the area of data coverage. This approach is able to accurately reproduce sediment-flux estimates by previous workers for several ancient shelf margins (the Maastrichtian Fox Hills-Lewis formations of Wyoming, Cenozoic Zambezi margin of East Africa, Cenozoic offshore New Jersey margin, and Albian-Cenomanian North Slope margin of Alaska) using both volumetric and forward-modeling methods. Furthermore, it is seen that the spatial pattern of sediment-flux variability across ancient shelf-margin deposits is similar to the pattern observed on modern margins, specifically rapid decrease in flux just beyond the shelf edge. This pattern suggests that high rates of deposition on the uppermost slope are fundamental to the long-term process of shelf-margin accretion.

  20. 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).

  1. Tiltmeter Indicates Sense of Slope

    NASA Technical Reports Server (NTRS)

    Lonborg, J. O.

    1985-01-01

    Tiltmeter indicates sense and magnitude of slope used in locations where incline not visible to operator. Use of direct rather than alternating current greatly simplifies design of instrument capable of indicating sense of slope.

  2. 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.

  3. Friis Hills glacial history: an international collaboration to examine Miocene climate in Antarctica

    NASA Astrophysics Data System (ADS)

    Halberstadt, A. R. W.; Kowalewski, D. E.

    2016-12-01

    The Friis Hills, Antarctica (western McMurdo Dry Valleys) contain unique, well-preserved records of Miocene climate. These terrestrial deposits hold geomorphic clues for deciphering the glacial history in a region directly adjacent to the East Antarctic Ice Sheet. Stacked till sheets, interbedded with lake sediments and non-glacial deposits, reveal a complex history of ice flow and erosion throughout multiple glacial-interglacial cycles (Lewis and Ashworth, 2015). Fossiliferous beds containing Nothofagus, diatoms, algal cells, pollen, insects, and mosses provide past climatological constraints. The Friis Hills sustained multiple alpine glaciations as well as full ice-sheet development, recording glacial drainage reorganization and evidence of previous ice configurations that possibly overrode the Transantarctic Mountains (Lewis and Ashworth, 2015) exposing only scattered nunataks (i.e. a portion of Friis Hills). Lack of chronological control has previously hindered efforts to link the Friis Hills glacial history with regional context; a tephra deposit at the base of the glacial drifts currently provides a single age constraint within the drift deposits. To build upon previous studies, an international collaboration between the USAP, Antarctic New Zealand, and the Italian Antarctic community proposes to core a paleo-lake in the center of the Friis Hills in November 2016, thereby acquiring one of the oldest continuous sedimentological records within the McMurdo Dry Valleys. Here we report discoveries from this year's fieldwork, and reconstruct paleoenvironment at the periphery of the East Antarctic Ice Sheet for the mid-early Miocene, a critical time when marine isotopic records indicate dramatic ice fluctuations. Ash within the sediment core stratigraphy will provide a more robust chronology for the region, and will also suggest possible outcrop locations of corresponding ash deposits to pursue while in the field. We anticipate that the Friis Hills stratigraphy will

  4. Fracture and slope stability monitoring at Puigcercós landslide (Catalonia, Spain)

    NASA Astrophysics Data System (ADS)

    Khazaradze, Giorgi; Vasquez, Sebastian; López, Robert; Guinau, Guinau; Calvet, Jaume; Vilaplana, Joan Manuel; Blanch, Xabier; Tapia, Mar; Roig, Pere; Suriñach, Emma

    2017-04-01

    The village of Puigcercós ( 50 inhabitants) is located in the region of Pallars Jussà (Lleida) in Catalonia, several km south of the town of Tremp. In 1881 the entire village had to be moved from its historical location on top of the hill to its current location. This was caused by a series of landslides caused by continuing rainfall. The most important landslide occurred on January 13th 1881, which displaced more than 5 million cubic meters of sediments and rocks and created an impressive rock scar of approximately 25 m height and 150 m width. The area where the sediments were accumulated is extensive, reaching 8 hectares. During the last years, our group has chosen the site of Puigcercós to conduct pilot studies of landslides and rockfalls using multidisciplinary approach, involving Terrestrial Laser Scanner, Total Station, DGPS, seismic monitoring and geophysical techniques. The geophysical surveys of the zone of the sediment accumulation, can help determine the internal structure of the displaced sediments. The work presented here mainly concerns the deformation monitoring at the site using geodetic techniques. In July 2015, a network of 11 new geodetic points has been established and measured with GPS. The location of these points was chosen with the purpose of answering two important questions in the studies of the stability and geomorphological activity of the Puigcercós landslide: 1) As a result of combined analysis of the tape-meter, total station and GPS measurements, we hope to obtain absolute values of deformation in the upper part of the escarpment, controlling the stability of the escarpment front and the associated fractures near the coronation. For this purpose, two geodetic control points have been established at the hilltop, some 5 meters away from the escarpment itself. 2) Determine the slope stability of the depositional area, where we established nine geodetic points. As of today, these points have been measured twice, in 2015 and 2016

  5. 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.

  6. 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.

  7. A Different Pitch to Slope

    ERIC Educational Resources Information Center

    Wolbert, William

    2017-01-01

    The query "When are we ever going to use this?" is easily answered when discussing the slope of a line. The pitch of a roof, the grade of a road, and stair stringers are three applications of slope that are used extensively. The concept of slope, which is introduced fairly early in the mathematics curriculum has hands-on applications…

  8. 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.

  9. 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.

  10. Beach slopes of Massachusetts

    USGS Publications Warehouse

    Doran, Kara S.; Long, Joesph W.; Birchler, Justin J.; Weber, Kathryn M.

    2016-01-01

    The National Assessment of Coastal Change Hazards project derives features of beach morphology from lidar elevation data for the purpose of understanding and predicting storm impacts to our nation's coastlines. This dataset defines mean beach slopes along the United States Northeast Atlantic Ocean for Massachusetts for data collected at various times between 2000 and 2013. For further information regarding data collection and/or processing methods refer to USGS Open-File Report 2015–1053 (http://pubs.usgs.gov/of/2015/1053/).

  11. Dark Slope Streaks

    NASA Image and Video Library

    2017-07-21

    This VIS image shows several dark slope streaks on the inner rim of an unnamed crater in Terra Sabaea. These features are thought to be formed by downslope movement of material the removes some of the surface dust, revealing the darker rock beneath. The channel to the north of the crater is Indus Vallis. Orbit Number: 68696 Latitude: 18.7889 Longitude: 40.4151 Instrument: VIS Captured: 2017-06-09 10:50 https://photojournal.jpl.nasa.gov/catalog/PIA21792

  12. Gullied Martian Slope

    NASA Technical Reports Server (NTRS)

    2004-01-01

    25 February 2004 Gullies cut material that mantles the slopes of a deep pit within a crater in Noachis Terra near 50.1oS, 356.4oW in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image. Gully channels seem to originate at layer outcrops in the upper walls of the pit. These may have formed by downslope movement of liquid water mixed with debris in the geologically recent martian past. Similar gullies are found throughout much of the martian middle and high latitudes. Sunlight illuminates the scene from the upper left; the picture covers an area 3 km (1.9 mi) wide.

  13. Terra Sirenum Slope

    NASA Technical Reports Server (NTRS)

    2004-01-01

    16 July 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the layered rocks and boulders exposed on the wall of a trough in the Terra Sirenum region. The layers that erode to produce large boulders are harder and more resistant to weathering and erosion than those that do not. The slope is located near 25.8oS, 139.8oW. The image covers an area 3 km (1.9 mi) wide and is illuminated by sunlight from the upper left.

  14. Dark Slope Streaks

    NASA Image and Video Library

    2016-07-07

    This image captured by NASA 2001 Mars Odyssey spacecraft shows the inner rim of an unnamed crater on the western margin of Daedalia Planum. Numerous dark streaks are visible on the faces of the inner rim. A possible mode of formation of these features is the down slope movement of a block/rock that disturbs the surface dust revealing the darker rock beneath. Orbit Number: 63851 Latitude: -11.9984 Longitude: 213.542 Instrument: VIS Captured: 2016-05-06 07:05 http://photojournal.jpl.nasa.gov/catalog/PIA20775

  15. The investigation of sloping cultivated land on the Loess Plateau with 3S technology

    NASA Astrophysics Data System (ADS)

    Li, Dengke; Liu, Anlin; Deng, Fengdong; Zhang, Jinghong; Zhuo, Jing

    2003-07-01

    The hill and ravine area on the Loess Plateau is the typical region of serious soil erosion, excess reclamation, and deteriorated eco-environment in middle reaches of Yellow River. The main project of eco-environment construction is that recover vegetation, and quit high sloping cultivated land to forest or meadow. The local government in the concerned region poses that sloping cultivated land higher than 15 degree should quit. How many are there qualified and how about their distribution? These are the basis problems of the execution of the eco-environment construction project. In this paper, using TM image and digital relief map, the interpretation of land use classification and the calculation of slope are made for Baota , Yan"an, with the software of ARC/INFO and ERDAS IMAGINE. And also the sloping cultivated land is mapped, basing on the composite analysis of land use map and slope map.

  16. 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

  17. 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.

  18. 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

  19. 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.

  20. 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

  1. 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.'

  2. 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.'

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

    USGS Publications Warehouse

    Piatak, Nadine M.; Argue, Denise M.; Seal, Robert R.; 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

  4. 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.

  5. 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.

  6. Potential role of gas hydrate decomposition in generating submarine slope failures: Chapter 12

    USGS Publications Warehouse

    Pauli, Charles K.; mUssler, William III; Dillon, William P.; Max, Michael D.

    2003-01-01

    Gas hydrate decomposition is hypothesized to be a factor in generating weakness in continental margin sediments that may help explain some of the observed patterns of continental margin sediment instability. The processes associated with formation and decomposition of gas hydrate can cause the strengthening of sediments in which gas hydrate grow and the weakening of sediments in which gas hydrate decomposes. The weakened sediments may form horizons along which the potential for sediment failure is increased. While a causal relationship between slope failures and gas hydrate decomposition has not been proven, a number of empirical observations support their potential connection.

  7. A Symplectic Integrator for Hill's Equations

    NASA Astrophysics Data System (ADS)

    Quinn, Thomas; Perrine, Randall P.; Richardson, Derek C.; Barnes, Rory

    2010-02-01

    Hill's equations are an approximation that is useful in a number of areas of astrophysics including planetary rings and planetesimal disks. We derive a symplectic method for integrating Hill's equations based on a generalized leapfrog. This method is implemented in the parallel N-body code, PKDGRAV, and tested on some simple orbits. The method demonstrates a lack of secular changes in orbital elements, making it a very useful technique for integrating Hill's equations over many dynamical times. Furthermore, the method allows for efficient collision searching using linear extrapolation of particle positions.

  8. A SYMPLECTIC INTEGRATOR FOR HILL'S EQUATIONS

    SciTech Connect

    Quinn, Thomas; Barnes, Rory; Perrine, Randall P.; Richardson, Derek C.

    2010-02-15

    Hill's equations are an approximation that is useful in a number of areas of astrophysics including planetary rings and planetesimal disks. We derive a symplectic method for integrating Hill's equations based on a generalized leapfrog. This method is implemented in the parallel N-body code, PKDGRAV, and tested on some simple orbits. The method demonstrates a lack of secular changes in orbital elements, making it a very useful technique for integrating Hill's equations over many dynamical times. Furthermore, the method allows for efficient collision searching using linear extrapolation of particle positions.

  9. 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.

  10. Stress release, joints, and instability on submarine slopes

    SciTech Connect

    Booth, J.S.; Robb, J.M.

    1984-04-01

    Mass movements related to gradual stress release within a sediment section may be quantitatively important on submarine slopes, particularly when such stress release involves joint sets. The sequence of events that promotes this phenomenon has been established by numerous terrestrial studies. The process involves: mass wasting or erosion to remove vertical stress (overburden) or lateral stress (such as through canyon cutting); consequent elastic rebound of the unloaded section; and opening of existing joints and/or formation of new joint sets. The presence of joints, which constitute planes of weakness within the sediment section, controls and reduces the stability of the affected slope; that is, the stability of the slope may no longer be dependent on the inherent strength of the sediments. The results of this process have been observed on the continental slope off the Mid-Atlantic coast of the United States. There, exposed Tertiary sediments have a well-developed joint pattern that has been observed in sidescan-sonar images, from submersible operations, and in a piston core. The measured preconsolidation stress on an Eocene core sample suggests that more than 100 m (330 ft) of overburden may have been removed from parts of the area. Intact Eocene blocks, which represent apparent failure along joint planes, have fallen from canyon walls on the lower slope and moved onto the upper rise. It is suggested that this process has the potential to operate on most deeply eroded surfaces and that exhumed (overconsolidated) sediments do not necessarily represent stable conditions despite their typical high shear strengths.

  11. 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.

  12. Slope failure experiments triggered by external loads in a laboratory flume - Effects of water content

    NASA Astrophysics Data System (ADS)

    Germer, K.; Braun, J.

    2009-04-01

    Rapid infiltration processes are observed at a hill slope located in the vicinity of the mountain village of Ebnit, Vorarlberg, Austria. These infiltrations generate at upper slope positions a fast increase of soil water saturation in sections of the subsurface several hundred meters down gradient. It is postulated that the seeping soil water leads to a rapid increase in head and hence to buoyancy forces in the lower regions of the slope resulting in slope deformations, observable in the form of slow slope creeping. In order to systematically investigate and quantify the development of slope deformation and slope failure processes, laboratory flume experiments were performed at the Research Facility for Subsurface Remediation (VEGAS) at the Universität Stuttgart. The flume was constructed as a 100 cm high, 200 cm long and 80 cm wide steel container. One long side of this flume is constructed by a glass pane. At the both short sides it is possible to maintain constant head boundary conditions in order to control the flow of groundwater or to adjust a steady state groundwater table. The soil material in the flume is shaped to a slope. On the upper side of the slope a hydraulic cylinder is installed to simulate a load on the slope. Varying either the external load on the slope or the location of the groundwater table provides important information on the factors affecting the stability of the slope and their interdependence. In a first set of experiments, the effect of saturation on the slope stability was investigated. It was shown that in the case where the water along the whole shear band was at negative pressure the slope could sustain 20% more load than in the case where parts of the shear band were underneath the groundwater level.

  13. 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

  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. 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.

  16. The British Geological Survey's 'Slope Dynamics' Project

    NASA Astrophysics Data System (ADS)

    Hobbs, Peter; Foster, Claire; Pearson, Stephen; Jones, Lee; Pennington, Catherine; Jenkins, Gareth; Gibson, Andrew; Cooper, Anthony; Freeborough, Katherine

    2010-05-01

    The aim of the British Geological Survey (BGS)'s ‘Slope Dynamics' project is to provide observational data to slope stability modelling and zoning based on factors of safety obtained from a combination of geotechnical, geomorphological and oceanographic models. The project has been monitoring since 2001 the progress of terrestrial and coastal landslides within 'soft rock' formations in the UK. Recently, field observatories have been set up to allow a variety of methods, some traditional and others novel, to be applied to actively unstable natural slopes in order to achieve a thorough understanding of the substrata, the mass movement processes within them and their relationship to the environment and environmental change. Monitoring has been carried out at six or twelve monthly intervals at test sites on the east coast of England (Holderness and Norfolk) and at Hollin Hill in North Yorkshire. A key part of the project makes use of innovative terrestrial LiDAR methods to produce repeated accurate 3-D models of the ground surface, which then enable ‘change models' of landslide movements to be determined. This work was started in 2001 and is continuing. The BGS currently has two Riegl terrestrial laser scanners: the long-range LPM-i800HA and the very-long-range LPM-2K; the former being equipped with a digital camera. The multiple scans are positioned in the national grid co-ordinate system using high resolution dGPS. Together, these allow accurate observations to be made in remote and exposed locations without the need for potentially dangerous direct access to the steeper more unstable slopes. The coastal test sites, which have exhibited recession rates of between 2m and 9m per year, allow rapid changes to be monitored. Inland active landslides are less common but more suited to instrumentation and long-term monitoring. Results to date have revealed the relationships between landslide style and geology, and also the patterns and time scales of characteristic

  17. 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

  18. 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

  19. Delineation of preventative landslide buffers along steep streamside slopes in northern California

    Treesearch

    Jason S. Woodward; David W. Lamphear; Matthew R. House

    2012-01-01

    Green Diamond Resource Co (GDRCo) applies tree retention buffers to steep slopes along fish bearing (Class I) and non-fish bearing (Class II) streams that are in addition to the standard riparian management zones associated with timber harvest plans. These Steep Streamside Slope (SSS) buffers were designed to reduce the amount of sediment delivering to watercourses as...

  20. Techniques for establishing vegetation for long-term erosion control on disturbed slopes in Alabama

    Treesearch

    M. Dougherty; A. Baharanyi; B. Guertal; J. Grace

    2010-01-01

    One year results from 21 outdoor erosion and sediment control plots constructed in 2008 on a 4:1 slope are presented. The study objectives were to evaluate; 1) the effects of incorporating lime and fertilizer on establishment of bermudagrass on steep slopes, 2) the differences in bermudagrass establishment as a function of temporary covers including wheat straw,...

  1. 27 CFR 9.136 - Texas Hill Country.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 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 Hill...

  2. 27 CFR 9.169 - Red Hills Lake County.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Red Hills Lake County. 9... Red Hills Lake County. (a) Name. The name of the viticultural area described in this section is “Red Hills Lake County”. (b) Approved Map. The appropriate maps for determining the boundary of the Red Hills...

  3. 27 CFR 9.169 - Red Hills Lake County.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Red Hills Lake County. 9... Red Hills Lake County. (a) Name. The name of the viticultural area described in this section is “Red Hills Lake County”. (b) Approved Map. The appropriate maps for determining the boundary of the Red Hills...

  4. 27 CFR 9.169 - Red Hills Lake County.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2013-04-01 2013-04-01 false Red Hills Lake County. 9... Red Hills Lake County. (a) Name. The name of the viticultural area described in this section is “Red Hills Lake County”. (b) Approved Map. The appropriate maps for determining the boundary of the Red Hills...

  5. Frosty Polar Slope

    NASA Technical Reports Server (NTRS)

    2004-01-01

    11 August 2004 Acquired just last week on 3 August 2004, this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dark, layered scarp in the martian north polar region. All of the light-toned surfaces in this image are covered by frost left over from the previous winter. On the scarp, about half of the surfaces once covered by frost are now exposed (as the frost has sublimed away), leaving a large number of bright patches. These patches of frost enhance the appearance of layering on the slopes. This image is located near 81.8oN, 84.4oW. The image covers an area 3 km (1.9 mi) wide, and is illuminated by sunlight from the lower left.

  6. Frosty Polar Slope

    NASA Technical Reports Server (NTRS)

    2004-01-01

    11 August 2004 Acquired just last week on 3 August 2004, this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dark, layered scarp in the martian north polar region. All of the light-toned surfaces in this image are covered by frost left over from the previous winter. On the scarp, about half of the surfaces once covered by frost are now exposed (as the frost has sublimed away), leaving a large number of bright patches. These patches of frost enhance the appearance of layering on the slopes. This image is located near 81.8oN, 84.4oW. The image covers an area 3 km (1.9 mi) wide, and is illuminated by sunlight from the lower left.

  7. Gullied Slopes on Mars

    NASA Astrophysics Data System (ADS)

    Martel, L. M. V.

    2003-08-01

    There are a lot of gullies on certain Martian slopes and just about as many ideas of how they formed. The proposed origins of gullies include seepage of groundwater or brines, outbursts of carbon dioxide, snowmelt, geothermal activity, or dry flows of windblown dust and silt. Research teams have been publishing their hypotheses since the gullies were first announced in 2000, and the discussions are still lively. For example, a quick search of the terms "Martian or Mars or gullies or seepage" on the NASA Astrophysics Data System delivered nearly 20 references to papers or abstracts published just in the past eight months. Gullies are such a hot topic, some researchers would argue, because they could indicate sources of liquid water at shallow depths. PSRD provides a rundown of the leading hypotheses to explain how Martian gullies form and how researchers use chemical data from Martian meteorites and knowledge of the Earth to support their points of view.

  8. Exploring Hill Ciphers with Graphing Calculators.

    ERIC Educational Resources Information Center

    St. John, Dennis

    1998-01-01

    Explains how to code and decode messages using Hill ciphers which combine matrix multiplication and modular arithmetic. Discusses how a graphing calculator can facilitate the matrix and modular arithmetic used in the coding and decoding procedures. (ASK)

  9. Confidence Hills Drill Powder in Scoop

    NASA Image and Video Library

    2014-11-04

    This image from NASA Curiosity rover shows a sample of powdered rock extracted by the rover drill from the Confidence Hills target -- the first rock drilled after Curiosity reached the base of Mount Sharp in September 2014.

  10. Exploring Hill Ciphers with Graphing Calculators.

    ERIC Educational Resources Information Center

    St. John, Dennis

    1998-01-01

    Explains how to code and decode messages using Hill ciphers which combine matrix multiplication and modular arithmetic. Discusses how a graphing calculator can facilitate the matrix and modular arithmetic used in the coding and decoding procedures. (ASK)

  11. Dark Hill on Asteroid Vesta Movie

    NASA Image and Video Library

    2011-12-06

    This still from a movie shows an image taken by NASA Dawn spacecraft layered on a digital terrain model of an unusual hill containing a dark-rayed impact crater and nearby dark deposit on asteroid Vesta.

  12. Factors Influencing Occurrence, Scale, Mobility, Runout, and Morphology of Mass Movements on the Continental Slope

    DTIC Science & Technology

    2016-06-07

    0035 LONG-TERM GOAL Achieve an improved understanding of the relationships between sedimentation, environment , and the morphology of continental slopes...processes. APPROACH Our research focuses on the factors that lead to variations in the sedimentological and environmental conditions determining slope...properties, environmental factors, and slope stability within the framework of a GIS; at Laval: Jacques Locat, Jean-Marie Konrad, Éric Boulanger, Priscilla

  13. Ionospheric Climatology Over Millstone Hill

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Holt, J. M.

    2002-05-01

    26 years of incoherent scatter observations over Millstone Hill since 1976 have been analyzed and modeled in order to study the climatological behavior in the local ionosphere-thermosphere system. A bin-fit technique is applied to process and represent the huge volume of data: measurements are binned according to local time, season, and altitude; sorted data in each bin are fitted into an empirical model where solar activity index F107 and geomagnetical activity index Ap are included as keyed inputs [Holt et al., 2002]. This paper focuses on seasonal, semiannual and annual variations and the long-term trend in electron density, electron temperature and ion temperature measurements over a 200-500 km height range of the F2 layer. A clear semiannual variation of the electron density is seen above the F2 peak during the day, as well as at the F2 peak and below during the later afternoon to evening period (16-20LT) . The semiannual variation of the electron temperature persists with minimum at equinox during the night, while the annual variation prevails by day with maximum in summer.

  14. 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.

  15. 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.

  16. Streamlined Hills of Maja Vallis

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 16 May 2003

    Classic catastrophic flood morphology (streamlined hills and longitudinal grooves) is captured in this image of Lunae Planum. Similar features (although much smaller in size) are seen in terrestrial catastrophic flood regions such as Channeled Scabland of Washington state and in Iceland.

    Image information: VIS instrument. Latitude 14.8, Longitude 301.8East (58.2). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  17. 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.

  18. How do Watershed Characteristics and Precipitation Influence Post-Wildfire Valley Sediment Storage and Delivery Over Time?

    NASA Astrophysics Data System (ADS)

    Brogan, D. J.; Nelson, P. A.; MacDonald, L. H.

    2016-12-01

    Considerable advances have been made in understanding post-wildfire runoff, erosion, and mass wasting at the hillslope and small watershed scale, but the larger-scale effects on flooding, water quality, and sedimentation are often the most significant impacts. The problem is that we have virtually no watershed-specific tools to quantify the proportion of eroded sediment that is stored or delivered from watersheds larger than about 2-5 km2. In this study we are quantifying how channel and valley bottom characteristics affect post-wildfire sediment storage and delivery. Our research is based on intensive monitoring of sediment storage over time in two 15 km2 watersheds (Skin Gulch and Hill Gulch) burned in the 2012 High Park Fire using repeated cross section and longitudinal surveys from fall 2012 through summer 2016, five airborne laser scanning (ALS) datasets from fall 2012 through summer 2015, and both radar and ground-based precipitation measurements. We have computed changes in sediment storage by differencing successive cross sections, and computed spatially explicit changes in successive ALS point clouds using the multiscale model to model cloud comparison (M3C2) algorithm. These channel changes are being related to potential morphometric controls, including valley width, valley slope, confinement, contributing area, valley expansion or contraction, topographic curvature (planform and profile), and estimated sediment inputs. We hypothesize that maximum rainfall intensity and lateral confinement will be the primary independent variables that describe observed patterns of erosion and deposition, and that the results can help predict post-wildfire sediment delivery and identify high priority areas for restoration.

  19. 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.

  20. 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

  1. 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

  2. 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

  3. Colluvial signatures of Pleistocene sediment production in central Pennsylvania

    NASA Astrophysics Data System (ADS)

    Del Vecchio, J.; Denn, A.; DiBiase, R.; Bierman, P. R.

    2016-12-01

    Geomorphologists seek to identify and isolate mechanisms dictating how climate changes impact erosion and sediment transport. South of the Last Glacial Maximum ice extent, central Appalachian headwater valleys contain extensive evidence of relict periglacial surface processes. Garner Run, a 1 km2 sandstone subcatchment of the Susquehanna Shale Hills Critical Zone Observatory, contains relict Pleistocene periglacial features such as solifluction lobes, block fields and thick colluvial valley fill. Such limited landscape modification since glaciation suggests periglacial processes are highly efficient compared to modern temperate processes, but the timing, magnitude, and spatial pattern of hillslope denudation processes in response to Quaternary climate change remain unclear. Here, we pair geomorphic mapping from lidar and field observations with in situ cosmogenic 10Be and 26Al measurements to estimate erosion rates and residence time of sandstone colluvium in Garner Run. Morphology of solifluction lobes and colluvium imply greater sediment discharge from south-facing slopes, suggesting an aspect dependence of periglacial processes consistent with regional morphologic observations. Catchment erosion rates in Garner Run, derived from detrital stream sediment, are slow ( 8 m/My), similar to nearby sandstone catchments and summit erosion rates elsewhere in the Appalachian Mountains. Preliminary analyses of 10Be in boulders mantling north-facing slopes of Garner Run show effective ridgetop exposure ages of 50 ky, and valley bottom ages of 100 ky, suggesting cosmic-ray dosing during downslope transport. We estimate an average valley fill thickness of 10-15 m, representing 2-3 m of bedrock lowering equivalent to 105-106 yrs of sediment production based on erosion rate data. 10Be/26Al burial dating of a valley-bottom drill core recovering 9 m of colluvium will constrain fill age and potential temporal variation in erosion rate due to Pleistocene periglaciations. Our

  4. 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

  5. Exhumed Crater with Slope

    NASA Technical Reports Server (NTRS)

    2004-01-01

    MGS MOC Release No. MOC2-575, 15 December 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a crater in Arabia Terra that has been exhumed. The picture was acquired less than 1 week ago, on 9 December 2003. The crater was buried beneath layered material, but erosion later brought it back to the surface. A thick blanket of dust mantles the scene; dark streaks have formed as some of this dust slid down the crater walls. Old, dust-covered ripples of windblown sediment occur on the floor of the exhumed crater. The image is located near 20.9oN, 320.7oW, and covers an area 3 km (1.9 mi) wide; sunlight illuminates the scene from the lower left.

  6. 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.

  7. Spatial Patterns of Suspended Sediment Yield in the Upper Indus River Basin, Northern Pakistan

    NASA Astrophysics Data System (ADS)

    Ali, K.; de Boer, D. H.; Martz, L. W.

    2004-05-01

    entire annual sediment load is transported. The mean annual sediment yield is greatest in the 28% glaciated Hunza River basin which accounts for more than 2800 t km-2 year-1. Region 2 is characterized by the sediment yields that result from an interaction of monsoon rains and glacier-melt. This region extends from Partab Bridge to Besham Qila. The Astore River produces the highest specific discharges in the basin, which are from southwest flanks of Nanga Parbat. Region 3 includes the area between Besham Qila and Tarbela Dam with the Gorband, Siran and Brandu tributaries. This part of the basin is mainly rain fed with little snow, and experience two types of rainfall: summer monsoon rains, and late winter and early spring rainf