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1

Currents in Monterey Submarine Canyon  

Microsoft Academic Search

Flow fields of mean, subtidal, and tidal frequencies between 250 and 3300 m water depths in Monterey Submarine Canyon are examined using current measurements obtained in three yearlong field experiments. Spatial variations in flow fields are mainly controlled by the topography (shape and width) of the canyon. The mean currents flow upcanyon in the offshore reaches (>1000 m) and downcanyon

J. P. Xu; Marlene A. Noble

2009-01-01

2

Plunge Pools in Submarine Canyons  

NASA Astrophysics Data System (ADS)

Many submarine canyon systems include well-defined intra-canyon depressions. Often, these depressions are found at the base of scarps along the canyon thalweg, with morphologic characteristics similar to subarial plunge pools formed at waterfalls. One plausible mechanism for the origin of these features is scouring during submarine debris flows. Other processes which can plausibly contribute to the formation of re-entrants and depressions in submarine canyons include erosion by spring sapping, slumping, collapse following gas expulsion or subsurface dissolution, and channel damming by mass wasting of canyon walls. We have examined multibeam bathymetry surveys of a number of submarine canyons, and identified more than fifteen apparent plunge pools within submarine canyon systems offshore of Australia, Hawaii, and North America. These features range in scale from 2 km long, 6 km across, and 300 m deep (the largest plunge pool in Perth Canyon, offshore Australia) down to as small as 10 m deep and 150 m across (the smallest plunge pool identified offshore Kohala, Hawaii). Although these features vary considerably in scale, they share common characteristics. Each basin is located at the base of a headwall scarp within the canyon, and is bounded on the down-canyon side by a sill. Measurements of the characteristic dimensions of the plunge pools show that the basin depth (defined relative to the down-canyon sill) increases with the headwall scarp height,. However, the across and down canyon basin widths do not strongly correlate with the scarp height, and seem to be more closely related to the width of the overall canyon channel. The Monterey Bay Aquarium Research Institute investigated three apparent plunge pools using ROV Tiburon during a spring 2001 expedition to the Hawaiian Islands. These basins are located in submarine canyons on the north side of Molokai and the Kohala coast of Hawaii. Our ROV observations support the hypothesis that these intra-canyon depressions are formed through scouring during submarine debris flows. In all cases the down-canyon depression sills are dams composed of debris piles, with angular rubble exposed on the depression side and sand covering the down-canyon side. The Molokai plunge pool is draped with mud and silt, suggesting no recent activity. However, the Kohala plunge pools show clear signs of recent scour and no sediment cover. The headwalls above the plunge pools expose layered volcanoclastic and lava flow units, with more resistant layers frequently forming vertical or overhanging walls. We interpret these canyons as being largely formed through retrogressive (headward) erosion and slope failure. Periodic rockfalls and debris flows following undercutting of the headwalls scours the depressions, builds the pool dams, and both lengthens and deepens the canyons. Modern bathymetric surveys indicate that plunge pools occur in many, but not most submarine canyons. Our ROV observations suggest that stratigraphic variability is a key prerequisite for plunge pool formation. Headwall scarps can persist within active canyons when the existence of more and less resistive layers allows for differential erosion. In turn, plunge pools form when headwall scarps are persistent features.

Caress, D. W.; Greene, H. G.; Paull, C. K.

2002-12-01

3

Plunge Pools in Hawaiian Submarine Canyons  

NASA Astrophysics Data System (ADS)

Many submarine canyon systems include well-defined intra-canyon depressions. Often, these depressions are found at the base of scarps along the canyon thalweg, with morphologic characteristics similar to subarial plunge pools formed at waterfalls. One plausible mechanism for the origin of these features is scouring during submarine debris flows. Other processes which can plausibly contribute to the formation of re-entrants and depressions in submarine canyons include erosion by spring sapping, slumping, collapse following gas expulsion or subsurface dissolution, and channel damming by mass wasting of canyon walls. The Monterey Bay Aquarium Research Institution conducted ROV dives around the Hawaiian Islands during a spring 2001 expedition of the R/V Western Flyer and ROV Tiburon. Three ROV dives investigated submarine canyons on the north (windward) sides of Molokai and Hawaii that exhibit well-developed intra-canyon depressions. These depressions ranged from 10 m deep and 150 m across to 90 m deep and 750 m across. The headwall scarps ranged from 20 m to 350 m. ROV video observations combined with rock and sediment sampling allowed us to characterize the depressions' detailed morphology, relate the morphology to the underlying geology, and view the genesis of these features in the context of the origin and evolution of the canyon systems as a whole. Our observations support the hypothesis that these intra-canyon depressions, or plunge pools, are formed through scouring during submarine debris flows. In all cases the down-canyon depression sills are dams composed of debris piles, with angular rubble exposed on the depression side and sand covering the down-canyon side. The Molokai plunge pool is draped with mud and silt, suggesting no recent activity. However, the Kohala plunge pools show clear signs of recent scour and no sediment cover. The headwalls above the plunge pools expose layered volcanoclastic and lava flow units, with more resistant layers frequently forming vertical or overhanging walls. We interpret these canyons as being largely formed through retrogressive (headward) erosion and slope failure. Periodic rockfalls and debris flows following undercutting of the headwalls scours the depressions, builds the pool dams, and both lengthens and deepens the canyons. >http://www.mbari.org/education/cruises/Hawaii/

Caress, D. W.; Greene, H. G.; Greene, H. G.; Paull, C. K.; Ussler, W.; Clague, D.; Moore, J. G.; Maher, N. H.

2001-12-01

4

Submarine canyon and fan systems of the California Continental Borderland  

USGS Publications Warehouse

Late Quaternary turbidite and related gravity-flow deposits have accumulated in basins of the California Borderland under a variety of conditions of sediment supply and sea-level stand. The northern basins (Santa Barbara, Santa Monica, and San Pedro) are closed and thus trap virtually all sediment supplied through submarine canyons and smaller gulley systems along the basin margins. The southern basins (Gulf of Santa Catalina and San Diego Trough) are open, and, under some conditions, turbidity currents flow from one basin to another. Seismic-reflection profiles at a variety of resolutions are used to determine the distribution of late Quaternary turbidites. Patterns of turbidite-dominated deposition during lowstand conditions of oxygen isotope stages 2 and 6 are similar within each of the basins. Chronology is provided by radiocarbon dating of sediment from two Ocean Drilling Program sites, the Mohole test-drill site, and large numbers of piston cores. High-resolution, seismic-stratigraphic frameworks developed for Santa Monica Basin and the open southern basins show rapid lateral shifts in sediment accumulation on scales that range from individual lobe elements to entire fan complexes. More than half of the submarine fans in the Borderland remain active at any given position of relative sea level. Where the continental shelf is narrow, canyons are able to cut headward during sea-level transgression and maintain sediment supply to the basins from rivers and longshore currents during highstands. Rivers with high bedload discharge transfer sediment to submarine fans during both highstand and lowstand conditions. ?? 2009 The Geological Society of America.

Normark, W. R.; Piper, D. J. W.; Romans, B. W.; Covault, J. A.; Dartnell, P.; Sliter, R. W.

2009-01-01

5

Resonant amplification of subinertial tides in a submarine canyon  

NASA Astrophysics Data System (ADS)

Tidal oscillations dominate the flow field in many submarine canyons. Observations have shown that semidiurnal tidal energy in submarine canyons is significantly amplified with respect to adjacent shelves. This amplification is thought to be caused by focusing of propagating internal tides incident from the open ocean, or local in-canyon generation on critical canyon floor slopes. These mechanisms require freely propagating internal tides, with superinertial frequencies. We present results from a moored array in a canyon at 44°N, where the observed velocities reached over 0.8 m s-1. The canyon flow field was highly unusual because it was dominated by the subinertial diurnal tide. This occurred despite the fact that the barotropic tide was predominantly semidiurnal. The diurnal tide was dramatically amplified in the canyon, its velocities increasing toward the seafloor and canyon head. The diurnal oscillations also exhibited marked modulation in time by the background barotropic forcing. Length scales suggest that the diurnal tide should be resonant in the canyon. An analytical framework is used to explain the mechanisms behind the strong diurnal currents observed by the moored array. In the model, along-shelf barotropic flow sets up a double Kelvin wave response in the canyon, generating along-canyon velocities which are subsequently amplified by resonance. The pattern of the model predictions is in excellent agreement with the observed velocity pattern.

Swart, N. C.; Allen, S. E.; Greenan, B. J. W.

2011-09-01

6

Dense shelf water cascades in two northwestern Mediterranean submarine canyon heads during winters 2007 and 2008  

Microsoft Academic Search

Submarine canyons incised in continental margins are considered to be preferential pathways for the exchange of water and particles between the coastal area and the open sea. Hydrodynamics and sediment transport processes in submarine canyons depend upon several forcing conditions in the region such as general circulation, seafloor morphology and atmospheric regime. The off-shelf sediment transport trough submarine canyons, due

Marta Ribo; Pere Puig; Albert Palanques; Claudio Lo Iacono

2010-01-01

7

Sand Wave Migrations Within Monterey Submarine Canyon, California  

NASA Astrophysics Data System (ADS)

Repeated high-resolution multi-beam surveys revealed the existence of a sand wave field along the axis of the Monterey submarine canyon between 20 and 300 m water depth. These sand waves range in wave length from 20 to 70 m and 2 to 5 m in height. Comparison of sequential multi-beam grid data (months apart) indicates that the sand waves apparently migrate upcanyon at some places while the same data clearly show that the sand waves migrate downcanyon at other locations. One hypothesis is that strong internal tidal flows, whose upcanyon component is intensified by the narrow canyon, are responsible for forming the sand wave field and for migrating the sand waves upcanyon. Another hypothesis is that the sand wave field is formed by creeping (analogous to the movement within glaciers), and in general they move in the downcanyon direction. A field experiment was conducted in 2005-06 to measure the driving forces (in hypothesis #1) that form and move the sand waves, and to collect the internal sedimentological structure within the sand waves that could reveal information on hypothesis #2. A mooring designed to measure near-floor velocity profiles, temperature, salinity, and sediment concentration in the water column was deployed for one year (June 2005 -July 2006) at 250 m water depth, slightly downcanyon of the sand wave field. In addition, a mapping survey was conducted in February, 2006 for collecting multi-beam and chirp profiles in the canyon head area of the sand wave field. Preliminary examination of the ADCP (downward looking) showed some very interesting features - the near- floor current dramatically changes with the spring-neap cycle of the surface tide. The time variation of the along-canyon current during neap tides - a sudden jump of upcanyon velocity before gradually tapering down, is typical of internal tides (internal bores). The time variation during spring tides when along canyon velocities reverse directions from upcanyon to downcanyon and gradually ramp up the speed before suddenly shutting down, is almost the mirror opposite of the neap tide pattern. Strong flow asymmetries exist during both spring and neap tides, with much stronger semi-diurnal currents directed upcanyon during neap and larger pulses of current at diurnal frequency pointing downcanyon during spring tides. In this presentation, we will attempt to explain the sand wave migration with the hydrodynamic data from the mooring.

Xu, J.; Wong, F. L.

2006-12-01

8

Wave Propagation over a Submarine Canyon: Field Observations  

NASA Astrophysics Data System (ADS)

Although abrupt bottom features such as submarine canyons, reefs, banks and shoals are present on many continental shelves, field measurements of their effects on ocean surface waves are scarce. During September-December 2003 an extensive array of wave-measuring instruments was deployed near La Jolla, California, as part of the Nearshore Canyon Experiment (NCEX). The field site is characterized by two submarine canyons, La Jolla Canyon and Scripps Canyon, that strongly affect the propagation of long period Pacific swell. An array of 7 Datawell Directional Waverider Buoys, 17 bottom pressure recorders and 12 Nortek Vector pressure-velocity sensors was deployed in depths ranging from about 10-100 m. The three-month-long observations include numerous long-period swell arrivals from both southern and northern hemisphere storms. Preliminary analysis indicates extreme spatial variations in wave energy in the vicinity of Scripps Canyon. In particular, swell arriving from the west is effectively blocked by the canyon. The observed amplification of swell energy on the north side of the canyon and extremely low energy levels on the south side are consistent with refraction predictions. This research is supported by the Office of Naval Research and the National Science Foundation.

Peak, S.; Herbers, T.; Jessen, P.; O'Reilly, W.; Kirk, M.; Elgar, S.

2004-12-01

9

Geology and biology of Oceanographer submarine canyon.  

USGS Publications Warehouse

Santonian beds more than 100 m thick are the oldest rocks collected from the canyon. Quaternary silty clay veneers the canyon walls in many places and is commonly burrowed by benthic organisms that cause extensive erosion of the canyon walls, especially in the depth zone (100-1300 m) inhabited by the crabs Geryon and Cancer. Bioerosion is minimal on high, near-vertical cliffs of sedimentary rock, in areas of continual sediment movement, and where the sea floor is paved by gravel. A thin layer of rippled, unconsolidated silt and sand is commonly present on the canyon walls and in the axis. Shelf sediments are transported from Georges Bank over the E rim and in the Canyon by the SW drift and storm currents; tidal currents and internal waves move the sediment downcanyon along the walls and axis.- from Authors

Valentine, P. C.; Uzmann, J. R.; Cooper, R. A.

1980-01-01

10

Global distribution of large submarine canyons: Geomorphic differences between active and passive continental margins  

Microsoft Academic Search

The aim of this study is to assess the global occurrence of large submarine canyons to provide context and guidance for discussions regarding canyon occurrence, distribution, geological and oceanographic significance and conservation. Based on an analysis of the ETOPO1 data set, this study has compiled the first inventory of 5849 separate large submarine canyons in the world ocean. Active continental

Peter T. Harris; Tanya Whiteway

2011-01-01

11

Cyclone-induced hyperpycnal turbidity currents in a submarine canyon  

NASA Astrophysics Data System (ADS)

Density currents such as turbidity currents are major transport agents in various terrestrial, lacustrine, and marine environments worldwide. However, a gap exists between those who study the deposits by turbidity currents (turbidite) on a field scale, and those who study turbidity currents using small-scale laboratory experiments and theoretical/numerical models. We report two typhoon-triggered hyperpycnal turbidity current events observed in a submarine canyon. Our findings verify turbidite sequences with the characteristics of suspended sediment carried by passing turbidity currents that displayed distinct waxing and waning phases. Our study also confirms the direct link between typhoon-triggered hyperpycnal flows in a small mountainous river and turbidity currents in a nearby submarine canyon that transport sediment to the deep-sea efficiently.

Liu, James T.; Wang, Yu-Huai; Yang, Rick J.; Hsu, Ray T.; Kao, Shuh-Ji; Lin, Hui-Ling; Kuo, Fang Hsu

2012-04-01

12

Submarine canyons: multiple causes and long-time persistence  

SciTech Connect

Submarine canyons are of composite origin and that many of the hypotheses suggested in the past were partly correct but did not appreciate that coordination of other processes was required. Thus there is growing evidence that, in the history of many canyons, there was a period in which subaerial erosion was an important precursor, but that present features are predominantly the result of marine erosion. Those advocating turbidity currents as the unique cause of canyons failed to appreciate that debris flows down the incipient valleys, as well as other types of landslides, could be an almost equally important factor in marine erosion. The great effect of biologic activity on the rock walls of incipient canyons has been almost completely neglected in explanations, and various types of currents such as those of the tides have been left largely out of the picture. Perhaps the most important feature absent in these various hypotheses has been the realization that canyons may well be the result of a long period of formation, much longer than the short episodes of Pleistocene glacial sea-level lowering usually considered explanation enough of these giant features which commonly cut into hard crystalline rock. New information is showing that the canyons may date back to at least the Cretaceous. (JMT)

Shepard, F.P.

1981-06-01

13

Transient wind-driven upwelling in a submarine canyon: A process-oriented modeling study  

Microsoft Academic Search

A hydrodynamic model is employed to study flow near a submarine canyon during conditions of upwelling-favorable coastal winds. Findings reveal that up-canyon flow is the rapid geostrophic adjustment to barotropic pressure gradients establishing across the canyon. Stratification leads to the formation of a cyclonic eddy within the canyon, trapping neutrally buoyant matter, and limits the upwelling depth only when a

Jochen Kämpf

2006-01-01

14

Hydrodynamics and particle transport associated with a submarine canyon off Blanes (Spain), NW Mediterranean Sea  

Microsoft Academic Search

Particle transport rates were observed to be higher in a submarine canyon in the NW Mediterranean Sea than in areas surrounding the canyon. Velocity and particle profiles were used to reconstruct a three-dimensional (2-layer) grid of the flow field and resulting particle transport. Canyon topography enhanced both horizontal and downward transport of particles in an anticyclonic flow region over the

Timothy C. Granata; Beatriz Vidondo; Carlos M. Duarte; Maria Paola Satta; Marc Garcia

1999-01-01

15

Deep-sea scavenging amphipod assemblages from the submarine canyons of the Western Iberian Peninsula  

NASA Astrophysics Data System (ADS)

Submarine canyons have often been identified as hotspots of secondary production with the potential to house distinct faunal assemblages and idiosyncratic ecosystems. Within these deep-sea habitats, assemblages of scavenging fauna play a vital role in reintroducing organic matter from large food falls into the wider deep-sea food chain. Free-fall baited traps were set at different depths within three submarine canyons on the Iberian Margin. Amphipods from the traps were identified to species level and counted. Scavenging amphipod assemblages were compared at different depths within each canyon and between individual canyon systems. Using data from literature, abyssal plain assemblages were compared to submarine canyon assemblages. Samples from canyons were found to contain common abyssal plain species but in greater than expected abundances. It is proposed that this is a result of the high organic carbon input into canyon systems owing to their interception of sediment from the continental shelf and input from associated estuarine systems. Community composition differed significantly between the submarine canyons and abyssal plains. The cause of this difference cannot be attributed to one environmental variable due to the numerous inherent differences between canyons and abyssal plains.

Duffy, G. A.; Horton, T.; Billett, D. S. M.

2012-11-01

16

Deep-sea scavenging amphipod assemblages from the submarine canyons of the Iberian Peninsula  

NASA Astrophysics Data System (ADS)

Submarine canyons have often been identified as hotspots of secondary production with the potential to house distinct faunal assemblages and idiosyncratic ecosystems. Within these deep-sea habitats, assemblages of scavenging fauna play a vital role in reintroducing organic matter from large food falls into the wider deep-sea food chain. Free-fall baited traps were set at different depths within three submarine canyons on the Iberian Margin. Amphipods from the traps were identified to species level and counted. Scavenging amphipod assemblages were compared at different depths within each canyon, between individual canyon systems, and between the abyssal plain and submarine canyon sites. Samples from canyons were found to contain common abyssal plain species but in greater than expected abundances. Community composition differed significantly between the submarine canyons and abyssal plains. It is proposed that this is a result of the high organic carbon input into canyon systems owing to their interception of sediment from the continental shelf and input from associated estuarine systems.

Duffy, G. A.; Horton, T.; Billett, D. S. M.

2012-06-01

17

Dispersal of natural and anthropogenic lead through submarine canyons at the Portuguese margin  

Microsoft Academic Search

Submarine canyons represent natural conduits for preferential transport of particulate material, including anthropogenic contaminants, from coastal zones directly to the deep sea. To assess related dispersal of natural and anthropogenic lead (Pb), we analyzed Pb concentrations and stable isotope ratios in surface sediments and sediment trap particulate material from the Portuguese margin Nazaré and Setúbal\\/Lisbon canyons. Geochemical data are integrated

T. O. Richter; H. C. de Stigter; W. Boer; C. C. Jesus; T. C. E. van Weering

2009-01-01

18

The Influence of Sediment Supply & Caliber on Submarine Canyon Morphology and Turbidity-Flow Character  

NASA Astrophysics Data System (ADS)

Coastal areas of high coarse-grained sediment supply generally produce submarine canyons that indent the shelf edge and contain highly erosive morphologies due to the erosive power of sand-rich turbidity flows. Typically, this volume of coarse sediment is transferred through the canyons onto large submarine fans. However, canyons formed in areas of low and/or very muddy sediment supply do not indent the shelf edge, have aggradational morphologies, and lack downslope fans. More dilute, mud-rich turbidity flows and hemipelagic deposition cause canyon aggradation rather than erosion. Temporal changes in the supply and caliber of sediment can significantly alter the types of flows available to a continental margin, thereby influencing the morphology of submarine canyons and the presence of submarine fans. This study uses an example from the continental margin of Equatorial Guinea, West Africa to illustrate this point. During the late Cretaceous, the continental margin of Equatorial Guinea was dominated by an erosional, sand-rich, submarine canyon system. This system was abandoned during the Paleogene, but the relict topography was re-activated in the Miocene during submarine erosion associated with tectonic uplift. Subsequently, a decrease in sediment supply resulted in a drastic transformation in canyon morphology. The result is a modern, muddy, aggradational canyon system that does not indent the shelf edge and has no downslope sediment apron. Draping reflections indicate that hemipelagic deposition aggrades the canyons. Intra-canyon lateral accretion deposits indicate that canyon concavity is maintained by thick (> 150 m), dilute, sluggish, mud-rich turbidity currents of a much different character than those in erosive canyons. Spatial and temporal changes in sediment supply and caliber to the Equatorial Guinean margin have been caused by tectonic uplift, climatic forcing, and shelf morphology. In particular, longshore drift provides high sediment supply to shelfal recesses, creating shelf-indenting, erosional canyons and associated submarine fans. Leeward of these shelfal recesses, the margin is starved of coarse sediment and canyons do not indent the shelf edge and are muddy and aggradational.

Jobe, Z.

2010-12-01

19

General patterns of circulation, sediment fluxes and ecology of the Palamós (La Fonera) submarine canyon, northwestern Mediterranean  

Microsoft Academic Search

Currents, particle fluxes and ecology were studied in the Palamós submarine canyon (also known as the Fonera canyon), located in the northwestern Mediterranean. Seven mooring arrays equipped with current meters and sediment traps were deployed along the main canyon axis, on the canyon walls and on the adjacent slope. Additionally, local and regional hydrographic cruises were carried out. Current data

Albert Palanques; Emilio García-Ladona; Damià Gomis; Jacobo Martín; Marta Marcos; Ananda Pascual; Pere Puig; Josep-Maria Gili; Mikhail Emelianov; Sebastià Monserrat; Jorge Guillén; Joaquín Tintoré; Mariona Segura; Antoni Jordi; Simón Ruiz; Gotzon Basterretxea; Dolors Blasco; Francesc Pagès

2005-01-01

20

Dense shelf water cascades in two northwestern Mediterranean submarine canyon heads during winters 2007 and 2008  

NASA Astrophysics Data System (ADS)

Submarine canyons incised in continental margins are considered to be preferential pathways for the exchange of water and particles between the coastal area and the open sea. Hydrodynamics and sediment transport processes in submarine canyons depend upon several forcing conditions in the region such as general circulation, seafloor morphology and atmospheric regime. The off-shelf sediment transport trough submarine canyons, due to storms and river floods, can be significant and recently dense shelf-water cascading (DSWC) has been also identified as an important transport mechanism able to generate high sediment fluxes in submarine canyons. DSWC is seasonal, resulting from the formation of dense water by cooling and/or evaporation over the shelf, and occurs on both high- and low latitude continental margins. The Palamós and the Cap de Creus submarine canyon heads were instrumented during two consecutive winters to study their respective role in the dynamics of the sediment transport on the northwestern Mediterranean Sea. The Cap de Creus submarine canyon has been intensively studied during the past years as it acts as a major transport conduit during storms and DSWC events. On the contrary, little information exists about the sediment transport processes operating within the Palamós submarine canyon during winter conditions. Observational work during this study consisted of a series of field measurements carried out with instrument moorings during winters 2007 and 2008 at the heads of both submarine canyons, at around 300 m depth. These moorings were equipped with a current meter with temperature, conductivity, pressure and turbidity sensors, placed at 5 m above the seafloor. Multibeam bathymetry from both canyon heads was also acquired and used to determine the canyon axis morphology, which was considered to compute down-canyon fluxes. Forcing conditions were obtained from oceanographic buoys and gaps in the wave height and peak period time series were filled with models outputs. Daily river discharges from nearby rivers were also analyzed. Sediment transport events during winters 2007 and 2008 were quite similar, and several DSWC events were identified and compared among them. Down-canyon current velocities of > 60 cm/s were detected in the Cap de Creus Canyon, and velocities of > 40 cm/s in the Palamós Canyon. Increases in current speed were associated with subtle drops in temperature (~ 1 °C) related to DSWC, and peaks of suspended sediment concentration. Values up to 170 mg/l were recorded during both studied winters at the Cap de Creus canyon head coinciding with the first DSWC event concurrent with an eastern storm. During both study periods no relation was found between sediment transport events and nearby river discharges. The amount of sediment transported during DSWC events at the Cap de Creus Canyon was one order of magnitude greater than the one observed at the Palamós Canyon. This corroborates the fact that most of the off-shelf sediment transport in the northwestern Mediterranean during DSWC events occurs at the southwestern end of the Gulf of Lions, through the Cap de Creus submarine canyon.

Ribo, Marta; Puig, Pere; Palanques, Albert; Lo Iacono, Claudio

2010-05-01

21

Numerical study of sources of baroclinic tides in Gaoping Submarine Canyon, southwestern Taiwan  

NASA Astrophysics Data System (ADS)

The Gaoping Submarine Canyon (GPSC) is a narrow (maximum width of 8 km) and steep (~0.03) canyon locates off southwestern Taiwan. Previous observations indicate depth integrated baroclinic tide energy (~14 kW/m) was strong with complicated generating mechanisms in the GPSC. A hydrostatic, three-dimensional model with two different domains, with or without the Luzon Strait (LS), and two corresponding horizontal resolutions is adopted to investigate sources of baroclinic tides in the GPSC. The initial temperature and salinity fields of the two domains are vertically stratified but horizontal homogeneous. The model is driven by tidal sea level variations calculated from TWTIDE08 at open boundaries. The analyses of large-domain/coarse-grid and small-domain/fine-grid simulations suggest that most of the baroclinic tide energy in GPSC originates remotely from the two meridional ridges in the LS. The semidiurnal M2 tide is the dominant source of the baroclinic tide energy. When the baroclinic tides from LS hit the steep shelf slope in the northern South China Sea, part of the reflected baroclinic energy could propagate into the GPSC. The local baroclinic tide generation becomes effective when the remote baroclinic tides propagate from deep region (>1000 m) towards the head of the GPSC.

Chiou, M.; Jan, S.

2010-12-01

22

Submarine canyons: hotspots of benthic biomass and productivity in the deep sea  

PubMed Central

Submarine canyons are dramatic and widespread topographic features crossing continental and island margins in all oceans. Canyons can be sites of enhanced organic-matter flux and deposition through entrainment of coastal detrital export, dense shelf-water cascade, channelling of resuspended particulate material and focusing of sediment deposition. Despite their unusual ecological characteristics and global distribution along oceanic continental margins, only scattered information is available about the influence of submarine canyons on deep-sea ecosystem structure and productivity. Here, we show that deep-sea canyons such as the Kaikoura Canyon on the eastern New Zealand margin (42°01? S, 173°03? E) can sustain enormous biomasses of infaunal megabenthic invertebrates over large areas. Our reported biomass values are 100-fold higher than those previously reported for deep-sea (non-chemosynthetic) habitats below 500 m in the ocean. We also present evidence from deep-sea-towed camera images that areas in the canyon that have the extraordinary benthic biomass also harbour high abundances of macrourid (rattail) fishes likely to be feeding on the macro- and megabenthos. Bottom-trawl catch data also indicate that the Kaikoura Canyon has dramatically higher abundances of benthic-feeding fishes than adjacent slopes. Our results demonstrate that the Kaikoura Canyon is one of the most productive habitats described so far in the deep sea. A new global inventory suggests there are at least 660 submarine canyons worldwide, approximately 100 of which could be biomass hotspots similar to the Kaikoura Canyon. The importance of such deep-sea canyons as potential hotspots of production and commercial fisheries yields merits substantial further study.

De Leo, Fabio C.; Smith, Craig R.; Rowden, Ashley A.; Bowden, David A.; Clark, Malcolm R.

2010-01-01

23

Tectonic controls on nearshore sediment accumulation and submarine canyon morphology offshore La Jolla, Southern California  

Microsoft Academic Search

CHIRP seismic and swath bathymetry data acquired offshore La Jolla, California provide an unprecedented three-dimensional view of the La Jolla and Scripps submarine canyons. Shore-parallel patterns of tectonic deformation appear to control nearshore sediment thickness and distribution around the canyons. These shore-parallel patterns allow the impact of local tectonic deformation to be separated from the influence of eustatic sea-level fluctuations.

Nicolas Le Dantec; Leah J. Hogarth; Neal W. Driscoll; Jeffrey M. Babcock; Walter A. Barnhardt; William C. Schwab

2010-01-01

24

Space-for-time substitution and the evolution of submarine canyons in a passive, progradational margin.  

NASA Astrophysics Data System (ADS)

40% of submarine canyons worldwide are located in passive margins, where they constitute preferential conduits of sediment and biodiversity hotspots. Recent studies have presented evidence that submarine canyons incising passive, progradational margins can co-evolve with the adjacent continental slope during long-term margin construction. The stages of submarine canyon initiation and their development into a mature canyon-channel system are still poorly constrained, however, which is problematic when attempting to reconstruct the development of passive continental margins. In this study we analyse multibeam echosounder and seismic reflection data from the southern Ebro margin (western Mediterranean Sea) to document the stages through which a first-order gully develops into a mature, shelf-breaching canyon and, finally, into a canyon-channel system. This morphological evolution allows the application of a space-for-time substitution approach. Initial gully growth on the continental slope takes place via incision and downslope elongation, with limited upslope head retreat. Gravity flows are the main driver of canyon evolution, whereas slope failures are the main agent of erosion; they control the extent of valley widening, promote tributary development, and their influence becomes more significant with time. Breaching of the continental shelf by a canyon results in higher water/sediment loads that enhance canyon development, particularly in the upper reaches. Connection of the canyon head with a paleo-river changes evolution dynamics significantly, promoting development of a channel and formation of depositional landforms. Morphometric analyses demonstrate that canyons develop into geometrically self-similar systems that approach steady-state and higher drainage efficiency. Canyon activity in the southern Ebro margin is pulsating and enhanced during sea level lowstands. Rapid sedimentation by extension of the palaeo-Millars River into the outermost shelf and upper slope is inferred as the source of gravity flows driving canyon evolution. Canyon morphology is shown to be maintained over the course of more than one fall and rise in sea-level. Our model of canyon evolution is applicable to other passive margins (e.g. Argentine continental margin).

Micallef, Aaron; Ribó, Marta; Canals, Miquel; Puig, Pere; Lastras, Galderic; Tubau, Xavier

2013-04-01

25

From suspended particles to strata: The fate of terrestrial substances in the Gaoping (Kaoping) submarine canyon  

Microsoft Academic Search

The river–sea system consisting of the Gaoping (new spelling according to the latest government's directive, formerly spelled Kaoping) River (KPR), shelf, and Submarine Canyon (KPRSC) located off southern Taiwan is an ideal natural laboratory to study the source, pathway, transport, and fate of terrestrial substances. In 2004 during the flood season of the KPR, a system-wide comprehensive field experiment was

James T. Liu; Jia-Jang Hung; Hui-Ling Lin; Chih-An Huh; Chon-Lin Lee; Ray T. Hsu; Ya-Wen Huang; Joel C. Chu

2009-01-01

26

Transient wind-driven upwelling in a submarine canyon: A process-oriented modeling study  

NASA Astrophysics Data System (ADS)

A hydrodynamic model is employed to study flow near a submarine canyon during conditions of upwelling-favorable coastal winds. Findings reveal that up-canyon flow is the rapid geostrophic adjustment to barotropic pressure gradients establishing across the canyon. Stratification leads to the formation of a cyclonic eddy within the canyon, trapping neutrally buoyant matter, and limits the upwelling depth only when a strong seasonal pycnocline is located below shelf-break depth. Typical speeds of up-canyon flow are 10-30 cm/s. Constrained by the timescale of synoptic weather patterns (˜5 days), only stronger events (high upwelling index) can move slope water from a depth >300 m onto the continental shelf and close toward the coast, where it can be lifted into surface layers during a subsequent upwelling event.

KäMpf, Jochen

2006-11-01

27

Headless submarine canyons and fluid flow on the toe of the Cascadia accretionary complex  

USGS Publications Warehouse

Headless submarine canyons with steep headwalls and shallowly sloping floors occur on both the second and third landward vergent anticlines on the toe of the Cascadia accretionary complex off central Oregon (45 ??N, 125?? 30??W). In September 1993, we carried out a series of nine deep tow camera sled runs and nine ALVIN dives to examine the relationship between fluid venting, structure and canyon formation. We studied four canyons on the second and third landward vergent anticlines, as well as the apparently unfailed intercanyon regions along strike. All evidence of fluid expulsion is associated with the canyons; we found no evidence of fluid flow between canyons. Even though all fluid seeps are related to canyons, we did not find seeps in all canyons, and the location of the seeps within the canyons differed. On the landward facing limb of the second landward vergent anticline a robust cold seep community occurs at the canyon's inflection point. This seep is characterized by chemosynthetic vent clams, tube worms and extensive authigenic carbonate. Fluids for this seep may utilize high-permeability flow paths either parallel to bedding within the second thrust ridge or along the underlying thrust fault before leaking into the overriding section. Two seaward facing canyons on the third anticlinal ridge have vent clam communities near the canyon mouths at approximately the intersection between the anticlinal ridge and the adjacent forearc basin. No seeps were found along strike at the intersection of the slope basin and anticlinal ridge. We infer that the lack of seepage along strike and the presence of seeps in canyons may be related to fluid flow below the forearc basin/slope unconformity (overpressured by the impinging thrust fault to the west?) directed toward canyons at the surface.

Orange, D. L.; McAdoo, B. G.; Moore, J. C.; Tobin, H.; Screaton, E.; Chezar, H.; Lee, H.; Reid, M.; Vail, R.

1997-01-01

28

Export of terrigenous organic carbon along submarine canyons driven by dense shelf water cascading  

NASA Astrophysics Data System (ADS)

At current highstand in sea level, shelves are considered major sites of terrigenous organic carbon (OCterr) accumulation with relatively little connectivity to the ocean interior. In recent years, the process of dense water cascading from the continental shelf, which occurs in numerous places around the world, has been suggested as carrier for OCterr to the deep ocean. The land-locked Mediterranean Sea is characterized by intense and recurrent cascades of dense shelf water. In winter, cold and dry winds cause the formation of dense water over the shelf that may overflow it and travel down to the outer margin and basin. Moored instruments were deployed in the canyons of the Gulf of Lion (France-Spain) and the Adriatic Sea (Italy) to intercept particulate material escaping the shelf and to investigate hydrodynamic and physical properties of the water column. Surface sediments along the shelves were also sampled to evaluate their contribution to the particle fluxes. The relative fractions of autochthonous and advected OC in sediment trap samples were investigated using biogeochemical proxies including alkaline CuO oxidation products (lignin phenols, dicarboxylic acids, and fatty acids), radiocarbon measurements (Ä14C), and elemental and carbon stable isotope (ä13C) compositions. Lignin-derived CuO products were a powerful biogeochemical tool that allowed us to identify the provenance of the material from the continental margin and to assess the amount of OCterr transferred across the slope in both Mediterranean regions. The results indicate that the composition of OC escaping the shelf through submarine canyons depends on the geomorphological setting. At the present sea level stage, cascading on a broad shelf limits the transport of OCterr, promoting instead the down-slope export of material accumulated in the mid- and outer-shelf. In contrast, cascade events on narrow shelves lead to the efficient export of OCterr from shallower regions of the margin along with the dense water formed on the inner-shelf.

Tesi, T.; Puig, P.; Goni, M.; Canals, M.; Langone, L.; Palanques, A.; Miserocchi, S.; Heussner, S.; Trincardi, F.; Calafat, A.; Turchetto, M.; Fabres, J.; Durrieu de Madron, X.; Boldrin, A.

2008-12-01

29

Geomorphic Thresholds of Submarine Canyons Along the U.S. Atlantic Continental Margin  

NASA Astrophysics Data System (ADS)

Vast networks of submarine canyons and associated channels are incised into the U.S. Atlantic continental slope and rise. Submarine canyons form by differential erosion and deposition, primarily from sedimentary turbidity flows. Theoretical and laboratory studies have investigated the initiation of turbidity flows and their capacity to erode and entrain sedimentary material at distances far from the shelf edge. The results have helped understand the nature of turbidite deposits on the continental slope and rise. Nevertheless, few studies have examined the linkages between down-canyon sediment transport and the morphology of canyon/channel networks using mesoscale analyses of swath bathymetry data. We present quantitative analysis of 100-m resolution multibeam bathymetry data spanning ~616,000 km2 of the slope and rise between Georges Banks and the Blake Plateau (New England to North Carolina). Canyons are categorized as shelf-indenting or slope-confined based on spatial scale, vertical relief and connection with terrestrial river systems during sea level low stands. Shelf-indenting canyons usually represent the trunk-canyon of submerged channel networks. On the rise, shelf-indenting canyons have relatively well-developed channel-levees and sharp inner-thalwag incision suggesting much higher frequency and volume of turbidity flows. Because of the similarities between submarine canyon networks and terrestrial river systems, we apply methods originally developed to study fluvial morphology. Along-canyon profiles are extracted from the bathymetry data and the power-law relationship between thalwag gradient and drainage area is examined for more than 180 canyons along an ~1200 km stretch of the US Atlantic margin. We observe distinct thresholds in the power-law relationship between drainage area and gradient. Almost all canyons with heads on the upper slope contain at least two linear segments when plotted in log-log form. The first segment along the upper slope is flat (constant gradient, low area). The second segment dips (exponentially decreasing gradient with increasing area). We interpret the transition between the two segments to be either diffusive creep/landslide processes that evolve into turbidity flows or the boundary that separates up-canyon infilling from relic, lower-canyon incision. Furthermore, the threshold occurs at a nearly constant drainage area regardless of location and morphology of the drainage network. This suggests that time-averaged erosion rate in submarine canyons depends on frequency of turbidity flows, which in turn depends on the volume of unstable sediments deposited near canyon heads and along canyon walls. We find that the gradient-area relationship does not follow a power-law in shelf-indenting canyons, most likely due to allogenic processes of the continental shelf and linkage to terrestrial river discharge.

Brothers, D. S.; ten Brink, U. S.; Andrews, B. D.; Chaytor, J. D.

2011-12-01

30

Geotechnical and sedimentological properties of Nice slope and submarine Var canyon deposits  

SciTech Connect

The submarine topography of the Baie des Anges consists of a narrow shelf and a steep slope where about 1,000 m-thick Pliocene-Quaternary deposits overlie the Messinian erosion surface. After a stage of rapid development, this large sedimentary body was submitted during the Quaternary to degradation through active mass-wasting processes. Thirteen piston cores were taken in several parts along the flanks and the floor of the Var canyon. Logging of these cores included gamma-density measurements, sedimentary structure descriptions, and microfacies observations (nannofossils). The cores were also sampled for a first geotechnical analysis. Geotechnical parameters such as water content, bulk density, vane shear strength, and Atterberg limits allowed us to study the response of surficial sediments to the vertical effective pressure and to discriminate several geotechnical groups related to different genetic types of sediment. Particularly the consolidation state was evaluated with the calculated ratio between undrained cohesion and vertical effective pressure (C/sub u//P). The sediment stability was assessed using the infinite slope stability analysis method under undrained conditions. Results of this preliminary analysis show that sedimentary instabilities could occur on important slopes.

Cochonat, P.; Schieb, T.; Guillaume, J.; Kerbrat, R.; Tisot, J.P.; Auffret, G.A.; Mueller, C.

1988-08-01

31

Submarine canyon development in the Izu-Bonin forearc: A SeaMARC II and seismic survey of Aoga Shima Canyon  

Microsoft Academic Search

SeaMARC II sidescan (imagery and bathymetry) and seismic data reveal the morphology, sedimentary processes, and structural controls on submarine canyon development in the central Izu-Bonin forearc, south of Japan. Canyons extend up to 150 km across the forearc from the trench-slope break to the active volcanic arc. The canyons are most deeply incised (1200–1700 m) into the gentle gradients (1–2°)

Adam Klaus; Brian Taylor

1991-01-01

32

Organic geochemistry of submarine canyons: The Portuguese Margin  

NASA Astrophysics Data System (ADS)

The organic geochemistry of the Portuguese Margin of the North-Eastern Atlantic Ocean reveals a highly heterogeneous environment that is strongly influenced by canyons that incise the continental margin. Suspended particulate organic matter (sPOM) is funnelled through the canyons to the deep sea, particularly in the Nazaré Canyon where there are high concentrations of sPOM even at >2000 m water depth. The nature of the sPOM through the water column varies, with that transported through the canyons having higher contributions of terrestrial organic matter (higher C/N and larger contribution of land plant-derived lipids) than sPOM in overlying waters and close to the seafloor on the adjacent slope. Zooplankton-derived lipids dominate sPOM associated with the upper and lower boundaries of the Mediterranean Overflow Water (MOW˜600 and 1500 m, respectively). Canyon sediments are enriched in organic carbon when compared to slope sediments, but sedimentary organic matter also appears to derive from multiple sources and undergoes significant alteration prior to deposition. On the open slope, low sedimentation rates and long oxygen exposure times lead to intensive oxidation of organic matter.

Kiriakoulakis, Kostas; Blackbird, Sabena; Ingels, Jeroen; Vanreusel, Ann; Wolff, George A.

2011-12-01

33

Organic enrichment of submarine-canyon and continental-shelf benthic communities by macroalgal drift imported from nearshore kelp forests  

Microsoft Academic Search

Remotely operated vehicle (ROV) surveys were conducted over a 3-year period to evaluate the importance of macroalgal drift exported from nearshore forests of giant kelp (Macrocystis pyrifera) to adjacent submarine-canyon and continental-shelf benthic habitats. Abundant macroalgal drift was found in the Carmel Submarine Canyon (153- 454-m depth) but was rare at Pt. Joe, a continental shelf habitat 9 km away

Christopher Harrold; Karen Light; Susan Lisin

1998-01-01

34

Litter in submarine canyons off the west coast of Portugal  

Microsoft Academic Search

Marine litter is of global concern and is present in all the world's oceans, including deep benthic habitats where the extent of the problem is still largely unknown. Litter abundance and composition were investigated using video footage and still images from 16 Remotely Operated Vehicle (ROV) dives in Lisbon, Setúbal, Cascais and Nazaré Canyons located west of Portugal. Litter was

Gideon Mordecai; Paul A. Tyler; Douglas G. Masson; Veerle A. I. Huvenne

2011-01-01

35

Sedimentary Filling of the Submarine Canyon "Swatch of No Ground", Bengal Shelf  

NASA Astrophysics Data System (ADS)

The submarine canyon "Swatch of No Ground" (SoNG), deeply incised into the Bengal Shelf, plays an important role in the source to sink system Himalaya-Bengal Fan by connecting the Ganges and Brahmaputra rivers, which drain the Himalayas, with the largest submarine fan on Earth. It is believed that around one third of the delivered sediments of at least 1 billion ton per year are transported through this canyon to the deep sea fan. In general the SoNG acts as a temporary trap and releases the sediments episodically by turbidity currents to the fan. Transportation of the sediments to the head of the canyon under quite weather conditions is done by tidal currents during high discharge periods. More effective, passages of cyclones remobilize shelf sediments and transport them to the canyon, and trigger also failures in the canyon flanks with consequent mass wasting downward. Finally all processes lead to high sedimentation rates of 50 cm per year in the head of the canyon. To understand the filling architecture and depositional processes, high-resolution multichannel seismic data were collected in summer 2006 in the upper canyon with the German research vessel "Sonne". Additionally, multibeam and sediment echosounder data were gathered, together with gravity cores. Hydroacoustic data and cores were also already collected on cruises in 1994 and 1997 and consequently, some lines and stations were revisited to study the deposition within the last years. The seismic data, shot on a dense grid of lines along and across the axis including flanks and shoulders, reveal a thick (1.5 sec TWT) sedimentary fill. Well stratified layer alternate with transparent to chaotic units intercalated by filled channels. Two main unconformities could be identified in the seismic data. Faulting is also found in the study area, probably caused by sediment compaction. The data set should be used to develop an IODP proposal to drill into this unique high resolution archive.

Palamenghi, L.; Schwenk, T.; Kudrass, H. R.; Spiess, V.

2008-12-01

36

Tidal and flood signatures of settling particles in the Gaoping submarine canyon (SW Taiwan) revealed from radionuclide and flow measurements  

Microsoft Academic Search

Sediment transport and sedimentation processes in the Gaoping submarine canyon were studied using sediment trap and current meter moorings deployed at a location during the winter (January–March) and the summer (July–September) months in 2008. At the end of each deployment, sediment cores were also collected from the canyon floor at the mooring site. Samples from sediment traps and sediment cores

Chih-An Huh; James T. Liu; Hui-Ling Lin; J. P. Xu

2009-01-01

37

Near-bottom particulate matter dynamics in the Nazaré submarine canyon under calm and stormy conditions  

Microsoft Academic Search

Two mooring lines equipped with near-bottom sediment traps were deployed in the axis of the Nazaré submarine canyon at ?1600 and ?3300m depth, respectively. We studied time-series of particle flux, composition (biogenic silica, carbonates, organic matter and lithogenic fractions), granulometry, mineralogy and 210Pb concentration of particulate matter over five sediment trap deployments between October 2002 and December 2004. Current meters

Jacobo Martín; Albert Palanques; João Vitorino; Anabela Oliveira; Henko C. de Stigter

2011-01-01

38

Form of submarine erosion from confluences in Atlantic USA continental slope Canyons  

Microsoft Academic Search

Submarine canyons of the Atlantic continental slope are found to have some remarkably analogous morphological properties to river networks, such as inverse power-law relations between channel gradient S and contributing area A (S A). Such relationships for bedrock-incising rivers have been interpreted using models in which bed erosion rates (E?) depend on A and S according to EAmSn, where the

NEIL C. MITCHELL

2004-01-01

39

Morphology of Submarine Canyons in the Palomares Margin (East of Alboran Sea, western Mediterranean)  

NASA Astrophysics Data System (ADS)

Morphological analysis on the Palomares Margin has been done using high-resolution swath bathymetry data collected during the MARSIBAL-06 (2006) cruise on board of the R/V BIO Hespérides. Complemented with data from GEBCO 2000 and Ifremer (Medimap Group, 2007) the data-set provides the first complete bathymetric mosaic of the Palomares Margin. The bathymetric mosaic allows to study the physiographic provinces of the Palomares Margin and to conduct, for the first time, a detailed morphological analysis of the two main sediment-transfer conduits: the Gata and the Alias-Almanzora Canyons. The Gata Canyon extends for 64km from the outer shelf to the base of the slope with a general W-E direction. A tributary system of canyons originates at the shelf break and continues on the slope until they merge at 1230m water depth. The walls of the canyons are characterized by repeated slides. Perpendicular profiles to the Canyon pathway reveal gentle transversal "V" asymmetrical shapes with a marked axial incision on the canyon floor (highs between 65 to 103m in the southern flank, and between 30-90m in the northern flank ). The transition from an erosional canyon to a deposition channel is located at 2100m water depth, and is characterized by trapezoidal shapes on transversal profiles accompanied of lower relieves (40-65m). At the mouth of the canyon-channel system no sedimentary lobes are observed. The Alias-Almanzora canyon (73km long and preferential direction W-E) is located North of the Gata Canyon and extends from the continental shelf to the base of the slope. A tributary system to the Alias- Almanzora canyon-head locates less than 150m from the coast, facing a fluvial drainage system onland. Proximal tributary canyons and gullies feed the main canyon until it merges in the continental slope at 1516m water depth. The tributary system exhibits a marked "V" shape in transverse profiles and marked axial incisions. Down slope, transversal profiles have trapezoidal shapes. Longitudinal profiles show convex-up sections along the tributary system and concave-up sections from the merge in the main canyon down slope. The transition from an erosional canyon to a depositional channel is located at 2100m water depth. The mouth of the Alias-Almanzora Canyon-channel system is characterized by distributaries channels and lobated features. Morphological analyses from these Canyons indicate they have different origin and evolution. The connection of the Alias-Almanzora Canyon to a fluvial drainage system offshore suggests the canyon formed by erosion of the continental shelf edge during sea-level low stand periods, when entrapment of sediment on deltas and reduced sediment transport through submarine canyons occurred. The Gata Canyon has instead developed by head wards erosion and gravitational instabilities. Both canyon systems are highly influenced by recent tectonics, and structural trends influence their location and changes in pathways. Contribution from Projects SAGAS CTM2005-08071-03-01 and TOPO-IBERIA CSD2006-00041 (R & D National Plan of the Ministry of Science and Technology and FEDER funding, Spain).

Perez-Hernandez, S.; Comas, M. C.; Escutia, C.

2009-04-01

40

Anthropogenic trace metals in the sedimentary record of the Llobregat continental shelf and adjacent Foix Submarine Canyon (northwestern Mediterranean)  

Microsoft Academic Search

Anthropogenic trace-metal concentrations and inventories were studied on the Llobregat continental margin, from the Llobregat river mouth to the Foix submarine canyon. A prodelta sedimentary depocentre was identified along with a previously known canyon depocentre. Significant upward increases in trace-metal contents were detected in sediment cores of the prodelta and upper part of the canyon (down to 860 m depth). Metal

Albert Palanques; Pere Masqué; Pere Puig; Joan Albert Sanchez-Cabeza; Mauro Frignani; Francesca Alvisi

2008-01-01

41

Litter in submarine canyons off the west coast of Portugal  

NASA Astrophysics Data System (ADS)

Marine litter is of global concern and is present in all the world's oceans, including deep benthic habitats where the extent of the problem is still largely unknown. Litter abundance and composition were investigated using video footage and still images from 16 Remotely Operated Vehicle (ROV) dives in Lisbon, Setúbal, Cascais and Nazaré Canyons located west of Portugal. Litter was most abundant at sites closest to the coastline and population centres, suggesting the majority of the litter was land sourced. Plastic was the dominant type of debris, followed by fishing gear. Standardised mean abundance was 1100 litter items km -2, but was as high as 6600 litter items km -2 in canyons close to Lisbon. Although all anthropogenic material may be harmful to biota, debris was also used as a habitat by some macro-invertebrates. Litter composition and abundance observed in the canyons of the Portuguese margin were comparable to those seen in other deep sea areas around the world. Accumulation of litter in the deep sea is a consequence of human activities both on land and at sea. This needs to be taken into account in future policy decisions regarding marine pollution.

Mordecai, Gideon; Tyler, Paul A.; Masson, Douglas G.; Huvenne, Veerle A. I.

2011-12-01

42

Dispersal of natural and anthropogenic lead through submarine canyons at the Portuguese margin  

NASA Astrophysics Data System (ADS)

Submarine canyons represent natural conduits for preferential transport of particulate material, including anthropogenic contaminants, from coastal zones directly to the deep sea. To assess related dispersal of natural and anthropogenic lead (Pb), we analyzed Pb concentrations and stable isotope ratios in surface sediments and sediment trap particulate material from the Portuguese margin Nazaré and Setúbal/Lisbon canyons. Geochemical data are integrated with previously obtained data on near-bottom hydrodynamics and processes and pathways of sediment transport. The two canyon systems are located in close geographic proximity to each other, but represent contrasting settings in terms of sediment input and down-canyon sediment transport processes. Concentration-isotope diagrams and three-isotope plots ( 206Pb/ 207Pb vs. 208Pb/ 206Pb) suggest binary mixing between natural and anthropogenic end members. The inferred isotopic signature of pollutant Pb ( 206Pb/ 207Pb=1.143 [1.134-1.149, 95% confidence interval]) is most consistent with industrial Pb; ongoing influence from gasoline Pb additives is at most of minor importance. Two proposed natural end members most likely bracket the isotopic signature of natural Pb. Accordingly, binary mixing calculations indicate that on average 20-45% vs. 35-55% of total Pb is derived from anthropogenic sources in the Nazaré and Setúbal-Lisbon canyon systems, respectively. Enhanced anthropogenic influence in the latter area is consistent with its proximity to heavily populated and industrialized areas and with sediment input from the Tagus and Sado rivers, potential major carriers of pollutant particles. In both canyon systems, the anthropogenic component generally decreases with increasing water depth. Isotopic signatures of sediment trap particulate material are generally consistent with surface sediment data at similar water depth, but show large variability in the upper Nazaré canyon and major deviations from surface sediments in the lower canyon. In the lower canyon, Pb isotopic ratios of sediment trap particulate material mostly reflect low pelagic fluxes from the overlying water column, whereas surface sediment signatures are dominated by episodic down-canyon mass transport events. Such gravity flows appear to incorporate older (pre-industrial) material masking the isotopic signature of pollutant Pb. Large variability in the upper canyon reflects continuous sediment resuspension by bottom currents. Stronger average bottom currents are associated with higher 206Pb/ 207Pb ratios of sediment trap particulate material and hence decreased influence of pollutant Pb. This may reflect preferential resuspension of natural Pb at the canyon floor and/or additional remobilization of older, less-polluted sediment in adjacent areas such as the canyon walls.

Richter, T. O.; de Stigter, H. C.; Boer, W.; Jesus, C. C.; van Weering, T. C. E.

2009-02-01

43

Late Quaternary evolution of the San Antonio Submarine Canyon in the central Chile forearc ( ??? 33??S)  

USGS Publications Warehouse

Hydrosweep swath-bathymetry and seismic-reflection data reveal the morphology, sedimentary processes, and structural controls on the submarine San Antonio Canyon. The canyon crosses the forearc slope of the central Chile margin for more than 150 km before it empties into the Chile Trench near 33??S latitude. In its upper reaches, the nearly orthogonal segments of the San Antonio Canyon incise ??? 1 km into thick sediment following underlying margin-perpendicular basement faults and along the landward side of a prominent margin-parallel thrust ridge on the outer mid-slope. At a breach in the outer ridge, the canyon makes a sharp turn into the San Antonio Reentrant. Resistance to erosion of outcropping basement at the head of the reentrant has prevented the development of a uniformly sloping thalweg, leaving gentle gradients ( 6??) across the lower slope. Emergence of an obstruction across the head of the San Antonio Reentrant has trapped sediment in the midslope segments of the canyon. Presently, little sediment appears to reach the Chile Trench through the San Antonio Canyon. The development of the San Antonio Canyon was controlled by the impact of a subducted seamount, which formed the San Antonio Reentrant and warped the middle slope along its landward advancing path. Incision of the canyon landward of the outer mid-slope ridge may be ascribed to a combination of headward erosion and entrenchment by captured unconfined turbidity currents. Flushing of the canyon was likely enhanced during the lowered sea level of the last glaciation. Where the canyon occupies the triangular embayment of the reentrant at the base of the slope, sediment has ponded behind a small accretionary ridge. On the trench floor opposite the San Antonio Canyon mouth, a 200-m-thick levee-overbank complex formed on the left side of a distributary channel emanating from a breach in the accretionary ridge. Axial transfer of sediment was inhibited to the north of the San Antonio Canyon mouth, which left the trench to the north sediment starved. Between ??? 32??40???S and 33??40???S, the Chile Trench axial turbidite channel deeply incises the San Antonio distributary complex. This entrenchment may have been initiated when the barrier to northward transport was eliminated. ?? 2002 Elsevier Science B.V. All rights reserved.

Laursen, J.; Normark, W. R.

2002-01-01

44

Tectonic controls on nearshore sediment accumulation and submarine canyon morphology offshore La Jolla, Southern California  

USGS Publications Warehouse

CHIRP seismic and swath bathymetry data acquired offshore La Jolla, California provide an unprecedented three-dimensional view of the La Jolla and Scripps submarine canyons. Shore-parallel patterns of tectonic deformation appear to control nearshore sediment thickness and distribution around the canyons. These shore-parallel patterns allow the impact of local tectonic deformation to be separated from the influence of eustatic sea-level fluctuations. Based on stratal geometry and acoustic character, we identify a prominent angular unconformity inferred to be the transgressive surface and three sedimentary sequences: an acoustically laminated estuarine unit deposited during early transgression, an infilling or "healing-phase" unit formed during the transgression, and an upper transparent unit. Beneath the transgressive surface, steeply dipping reflectors with several dip reversals record faulting and folding along the La Jolla margin. Scripps Canyon is located at the crest of an antiform, where the rocks are fractured and more susceptible to erosion. La Jolla Canyon is located along the northern strand of the Rose Canyon Fault Zone, which separates Cretaceous lithified rocks to the south from poorly cemented Eocene sands and gravels to the north. Isopach and structure contour maps of the three sedimentary units reveal how their thicknesses and spatial distributions relate to regional tectonic deformation. For example, the estuarine unit is predominantly deposited along the edges of the canyons in paleotopographic lows that may have been inlets along barrier beaches during the Holocene sea-level rise. The distribution of the infilling unit is controlled by pre-existing relief that records tectonic deformation and erosional processes. The thickness and distribution of the upper transparent unit are controlled by long-wavelength, tectonically induced relief on the transgressive surface and hydrodynamics. ?? 2009 Elsevier B.V.

Le, Dantec, N.; Hogarth, L. J.; Driscoll, N. W.; Babcock, J. M.; Barnhardt, W. A.; Schwab, W. C.

2010-01-01

45

Food quality determines sediment community responses to marine vs. terrigenous organic matter in a submarine canyon  

NASA Astrophysics Data System (ADS)

The Whittard canyon is a branching submarine canyon on the Celtic continental margin, which may act as a conduit for sediment and organic matter (OM) transport from the European continental slope to the abyssal sea floor. In situ stable-isotope labelling experiments were conducted in the eastern and western branches of the Whittard canyon testing short term (3-7 day) responses of sediment communities to deposition of nitrogen-rich marine (Thallassiosira weissflogii) and nitrogen-poor terrigenous (Triticum aestivum) phytodetritus. 13C and 15N labels were traced into faunal biomass and bulk sediments, and the 13C label traced into bacterial polar lipid fatty acids (PLFAs). Isotopic labels penetrated to 5 cm sediment depth, with no differences between stations or experimental treatments (substrate or time). Macrofaunal assemblage structure differed between the eastern and western canyon branches. Following deposition of marine phytodetritus, no changes in macrofaunal feeding activity were observed between the eastern and western branches, with little change between 3 and 7 days. Macrofaunal C and N uptake was substantially lower following deposition of terrigenous phytodetritus with feeding activity governed by a strong N demand. Bacterial C uptake was greatest, in the western branch of the Whittard canyon, but feeding activity decreased between 3 and 7 days. Bacterial processing of marine and terrigenous OM were similar to the macrofauna in surficial (0-1 cm) sediments. However, in deeper sediments bacteria utilised greater proportions of terrigenous OM. Bacterial biomass decreased following phytodetritus deposition and was negatively correlated to macrofaunal feeding activity. Consequently, this study suggests that macrofaunal-bacterial interactions influence benthic C cycling in the Whittard canyon, resulting in differential fates for marine and terrigenous OM.

Hunter, W. R.; Jamieson, A.; Huvenne, V. A. I.; Witte, U.

2012-08-01

46

Sediment community responses to marine vs. terrigenous organic matter in a submarine canyon  

NASA Astrophysics Data System (ADS)

The Whittard Canyon is a branching submarine canyon on the Celtic continental margin, which may act as a conduit for sediment and organic matter (OM) transport from the European continental slope to the abyssal sea floor. In situ stable-isotope labelling experiments were conducted in the eastern and western branches of the Whittard Canyon, testing short-term (3-7 days) responses of sediment communities to deposition of nitrogen-rich marine (Thalassiosira weissflogii) and nitrogen-poor terrigenous (Triticum aestivum) phytodetritus. 13C and 15N labels were traced into faunal biomass and bulk sediments, and the 13C label traced into bacterial polar lipid fatty acids (PLFAs). Isotopic labels penetrated to 5 cm sediment depth, with no differences between stations or experimental treatments (substrate or time). Macrofaunal assemblage structure differed between the eastern and western canyon branches. Following deposition of marine phytodetritus, no changes in macrofaunal feeding activity were observed between the eastern and western branches, with little change between 3 and 7 days. Macrofaunal C and N uptake was substantially lower following deposition of terrigenous phytodetritus with feeding activity governed by a strong N demand. Bacterial C uptake was greatest in the western branch of the Whittard Canyon, but feeding activity decreased between 3 and 7 days. Bacterial processing of marine and terrigenous OM were similar to the macrofauna in surficial (0-1 cm) sediments. However, in deeper sediments bacteria utilised greater proportions of terrigenous OM. Bacterial biomass decreased following phytodetritus deposition and was negatively correlated to macrofaunal feeding activity. Consequently, this study suggests that macrofaunal-bacterial interactions influence benthic C cycling in the Whittard Canyon, resulting in differential fates for marine and terrigenous OM.

Hunter, W. R.; Jamieson, A.; Huvenne, V. A. I.; Witte, U.

2013-01-01

47

Biodiversity of macrofaunal assemblages from three Portuguese submarine canyons (NE Atlantic)  

NASA Astrophysics Data System (ADS)

The macrofaunal assemblages from three Portuguese submarine canyons, Nazaré, Cascais and Setúbal were studied from samples collected at their upper (900-1000 m), middle (3200-3500 m) and lower sections (4200-4500 m) and at the adjacent open slopes (˜1000 m), during the HERMES cruises D297 (R.R.S. Discovery, 2005) CD179 (R.R.S. Charles Darwin, 2006) and 64PE252 (R.V. Pelagia, 2006). The taxonomic composition and patterns in biodiversity, abundance and community structure of the benthic macrofauna were described. Annelida (42.1% of total abundance; 137 species) and Arthropoda (20.6%; 162 species) were, respectively, the most abundant and the most species-rich Phyla among the 342 taxa identified during this study. Multivariate analyses showed significant differences between and within canyons and between canyons and open slope assemblages. At their upper section, canyons supported higher macrofauna abundance but slightly lower biodiversity than the adjacent slopes at similar depth. In all canyons abundance reached the highest value in the middle section and the lowest in the upper section, with marked fluctuations in Nazaré (474-4599 ind. m -2) and lower variability in Cascais (583-1125 ind. m -2). The high abundance and dominance of the assemblages in the middle section of Nazaré and Setúbal was accompanied by depressed biodiversity, while in Cascais, Hurlbert's expected species richness showed increasing values from the upper to the middle canyon, and maintained the high values at the lower section. Overall, the Nazaré Canyon showed the lowest expected species richness (ES (100): 16-39) and the Cascais Canyon the highest (39-54). There was a significant negative Kendall's correlation between total organic carbon concentrations in the superficial sediments and ES (100) and a significant positive correlation between total nitrogen and macrofauna density. The influences of organic enrichment, sediment heterogeneity and hydrodynamic regime on the abundance, diversity and community structure of the macrofauna are discussed. It is suggested that altered and localised environmental conditions in the Portuguese canyons play an important role in modifying more common abundance and diversity bathymetric patterns evident in many continental slope environments.

Cunha, Marina R.; Paterson, Gordon L. J.; Amaro, Teresa; Blackbird, Sabena; de Stigter, Henko C.; Ferreira, Clarisse; Glover, Adrian; Hilário, Ana; Kiriakoulakis, Konstadinos; Neal, Lenka; Ravara, Ascensão; Rodrigues, Clara F.; Tiago, Áurea; Billett, David S. M.

2011-12-01

48

Near-bottom particulate matter dynamics in the Nazaré submarine canyon under calm and stormy conditions  

NASA Astrophysics Data System (ADS)

Two mooring lines equipped with near-bottom sediment traps were deployed in the axis of the Nazaré submarine canyon at ˜1600 and ˜3300 m depth, respectively. We studied time-series of particle flux, composition (biogenic silica, carbonates, organic matter and lithogenic fractions), granulometry, mineralogy and 210Pb concentration of particulate matter over five sediment trap deployments between October 2002 and December 2004. Current meters equipped with turbidimeters were also deployed at trap depths to monitor the water flow, temperature, salinity and suspended particle concentration. The composition of the collected particles was fairly constant year-round, dominated by the lithogenic fraction and with OC/N ratios in the range 11-21, suggesting an important terrigenous influence inside the canyon. The results show contrasting dynamic environments in the upper (1600 m depth) and middle (3300 m depth) canyon. High current speeds (spring tides up to 80 cm s-1) and high apparent mass fluxes of particulate matter (mean 65 g m-2 d-1; maximum 265 g m-2 d-1) are permanent at the shallowest station. At the deepest site, fluxes were below 10 g m-2 d-1 most of the time and the annual flux was governed by events of sharp flux increase. Storms affecting the continental shelf during autumn and winter are a major driver of down-canyon dispersal of sediments to the middle canyon and beyond. Important nepheloid activity developed inside the canyon in response to storms with significant wave heights between 4 and 6 m, as testified by turbidimeters deployed in midwater and near the seabed at 1600 m water depth. On three occasions during the study period, significant wave heights of incident storms surpassed 7 m, leading to notable episodes of down-canyon transport that were clearly observed in the middle canyon. During one of these stormy periods (January 2003) a sediment gravity flow transporting unusual quantities of sand and coastal plant debris was observed at 3200 m. However, a storm with significant wave heights as low as 5 m was apparently able to trigger a sediment gravity flow reaching beyond the middle canyon. The role of storms in the offshore dispersal of sediments is clearly relevant but seems to be modulated by synergic factors such as river flooding.

Martín, Jacobo; Palanques, Albert; Vitorino, João; Oliveira, Anabela; de Stigter, Henko C.

2011-12-01

49

Biodiversity of macrofaunal assemblages from three Portuguese submarine canyons (NE Atlantic)  

NASA Astrophysics Data System (ADS)

The macrofaunal assemblages from three Portuguese submarine canyons, Nazaré, Cascais and Setúbal were studied from samples collected at their upper (900-1000 m), middle (3200-3500 m) and lower sections (4200-4500 m) and at the adjacent open slopes (˜1000 m), during the HERMES cruises D297 (R.R.S. Discovery, 2005) CD179 (R.R.S. Charles Darwin, 2006) and 64PE252 (R.V. Pelagia, 2006). The taxonomic composition and patterns in biodiversity, abundance and community structure of the benthic macrofauna were described. Annelida (42.1% of total abundance; 137 species) and Arthropoda (20.6%; 162 species) were, respectively, the most abundant and the most species-rich Phyla among the 342 taxa identified during this study. Multivariate analyses showed significant differences between and within canyons and between canyons and open slope assemblages. At their upper section, canyons supported higher macrofauna abundance but slightly lower biodiversity than the adjacent slopes at similar depth. In all canyons abundance reached the highest value in the middle section and the lowest in the upper section, with marked fluctuations in Nazaré (474-4599 ind. m-2) and lower variability in Cascais (583-1125 ind. m-2). The high abundance and dominance of the assemblages in the middle section of Nazaré and Setúbal was accompanied by depressed biodiversity, while in Cascais, Hurlbert's expected species richness showed increasing values from the upper to the middle canyon, and maintained the high values at the lower section. Overall, the Nazaré Canyon showed the lowest expected species richness (ES(100): 16-39) and the Cascais Canyon the highest (39-54). There was a significant negative Kendall's correlation between total organic carbon concentrations in the superficial sediments and ES(100) and a significant positive correlation between total nitrogen and macrofauna density. The influences of organic enrichment, sediment heterogeneity and hydrodynamic regime on the abundance, diversity and community structure of the macrofauna are discussed. It is suggested that altered and localised environmental conditions in the Portuguese canyons play an important role in modifying more common abundance and diversity bathymetric patterns evident in many continental slope environments.

Cunha, Marina R.; Paterson, Gordon L. J.; Amaro, Teresa; Blackbird, Sabena; de Stigter, Henko C.; Ferreira, Clarisse; Glover, Adrian; Hilário, Ana; Kiriakoulakis, Konstadinos; Neal, Lenka; Ravara, Ascensão; Rodrigues, Clara F.; Tiago, Áurea; Billett, David S. M.

2011-12-01

50

Plankton dynamics controlled by hydrodynamic processes near a submarine canyon off NW corsican coast: A numerical modelling study  

Microsoft Academic Search

A three-dimensional (3D) non-linear high-resolution hydrodynamic model coupled to a coastal plankton ecosystem model is used to estimate the impact of hydrodynamic processes on the evolution of the spring phytoplankton bloom in the vicinity of a submarine canyon. Model results for the plankton distribution showed a clear 3D character around and in the canyon, with large horizontal and vertical gradients,

N. Skliris; S. Djenidi

2006-01-01

51

3D seismic interpretation of Plio-Pleistocene headless submarine canyons on the Ebro margin: implications for deepwater sand transport  

Microsoft Academic Search

Recently acquired 3D seismic data from the Ebro continental margin (Eastern Spain) have been used to study a series of spectacular buried post-Messinian submarine canyons that are restricted to the slope i.e. they do not link to incised valleys on the shelf. Understanding the origin of this type of `headless' canyon is important for overall considerations of shelf by-pass and

C. Bertoni; J. Cartwright; J. Fernandez

2003-01-01

52

The Nankai OOST zone exposed along the Shionomisaki Submarine Canyon - Dive results of YK05-08 Leg 2  

Microsoft Academic Search

The Shionomisaki submarine canyon cuts EW-trending five major ridges developed in the Plio-Pleistocene Nankai accretionary prism. The fifth ridge (numbered from the accretion toe in the south) is an extension of the Omine ridge where the out-of-sequence thrust (Nankai OOST zone) were detected through CDEX seismic profiles. We observed structures developed around the Nankai OOST zone along the canyon slope

R. Anma; Y. Ogawa; G. Moore; K. Kawamura

2005-01-01

53

The propagation of sound in narrow street canyons  

NASA Astrophysics Data System (ADS)

This paper addresses an important problem of predicting sound propagation in narrow street canyons with width less than 10 m, which are commonly found in a built-up urban district. Major noise sources are, for example, air conditioners installed on building facades and powered mechanical equipment for repair and construction work. Interference effects due to multiple reflections from building facades and ground surfaces are important contributions in these complex environments. Although the studies of sound transmission in urban areas can be traced back to as early as the 1960s, the resulting mathematical and numerical models are still unable to predict sound fields accurately in city streets. This is understandable because sound propagation in city streets involves many intriguing phenomena such as reflections and scattering at the building facades, diffusion effects due to recessions and protrusions of building surfaces, geometric spreading, and atmospheric absorption. This paper describes the development of a numerical model for the prediction of sound fields in city streets. To simplify the problem, a typical city street is represented by two parallel reflecting walls and a flat impedance ground. The numerical model is based on a simple ray theory that takes account of multiple reflections from the building facades. The sound fields due to the point source and its images are summed coherently such that mutual interference effects between contributing rays can be included in the analysis. Indoor experiments are conducted in an anechoic chamber. Experimental data are compared with theoretical predictions to establish the validity and usefulness of this simple model. Outdoor experimental measurements have also been conducted to further validate the model. copyright 2002 Acoustical Society of America.

Iu, K. K.; Li, K. M.

2002-08-01

54

Spatial and Temporal Scales of Recent Turbidity Currents in Monterey Submarine Canyon, California  

NASA Astrophysics Data System (ADS)

Turbidity currents are responsible for transporting and depositing most of the sand and other coarse clastic sediment to deep-sea fans and deltas, and for creating and maintaining the omnipresent submarine channels on the continental slope. The temporal and spatial scales (duration, speed, and run-out distance) of turbidity currents have always been of keen interest to geologists because of their importance in determining the size and distribution of turbidites - deposits formed by turbidity currents. Here we present in-situ velocity and turbidity data of modern-day turbidity currents measured in Monterey Submarine Canyon during 2002 - 2011. The experiments co-conducted by the U.S. Geological Survey and the Monterey Bay Aquarium Research Institute were among the first studies specifically designed to measure field scale turbidity currents, which have provided by far the most complete picture of any marine turbidity current. Concurrent measurements from downward-looking ADCPs at multiple locations along the canyon provided high-resolution velocity profiles of the turbidity currents. Temperature and turbidity sensors above the ADCPs recorded the time of arrival and the duration of the turbidity currents. These high-resolution, high-frequency data allowed us to quantitatively characterize the bulk properties (maximum speed, thickness, density, etc) and their along-canyon evolution. The measured properties of field turbidity currents are used to examine the validity of empirical relationships obtained from theoretical analysis and laboratory experiments. The correlations between these properties and the lateral size (run-out distance) and the autosuspension criteria are also discussed.

Xu, J.; Paull, C. K.; Barry, J. P.; Noble, M. A.

2011-12-01

55

A multidisciplinary study of the role of submarine canyons off western Portugal  

NASA Astrophysics Data System (ADS)

A multidisciplinary research aimed to characterise the dominant aspects of the Portuguese canyon systems and their role on the shelf-deep ocean sediment exchanges is being conducted in the framework of EU project Eurostrataform. Three contrasting systems are studied: (1) the Nazaré Canyon is a narrow and deep canyon which extends from the deep ocean and completely cuts the NW Portuguese shelf, with no local riverine sources; (2) the Setubal-Lisbon canyon system affects an area marked by complex topography and coastline configuration and with riverine contributions provided by the Tagus and Sado rivers; (3) the Oporto canyon is restricted to the outer shelf, with a major local riverine source (Douro river). We present preliminary results from the ongoing program of observations, which includes multidisciplinary surveys (CTD, suspended particle matter measurments, shallow seismic) and both long- and short-term moorings. Process studies are extended with the use of system MOCASSIM, an operational system for the forecast of oceanographic conditions off the Portuguese coast, which is presently being developped at Instituto Hidrografico. The system integrates wave and circulation models and makes use of data assimilation methods to provide numerical results which are consistent with the observed conditions.

Vitorino, J.; Oliveira, A.; Rodrigues, A.

2003-04-01

56

A million miles from rivers: secondary flow in submarine canyon-fan systems.  

NASA Astrophysics Data System (ADS)

In both subaerial and submarine meander bends, fluid flow travels in a helical spiral, as centrifugal and hydrostatic forces balance the turbulent shear stress within the flow. Understanding the sense of the secondary flow circulation is important because the near bed orientation of the fluid flow vector strongly affects sediment transport and hence meander bend morphodynamic evolution, the patterns of surface grain size sorting and therefore the character of the sedimentary deposits produced. To evaluate the conditions favouring the onset of distinctive secondary flow circulations (and in particular, to discriminate cases when the near-bed radial flow is directed towards the inner bank ('river like') or outer bank ('river reversed'), we develop a holistic analytical model incorporating centrifugal and Coriolis forces, the radial pressure gradient and the baroclinicity of the flow. This new model is validated using experimental data and used to highlight the influence on the secondary flow of the principle physical forces acting on the flow. Previous analytical studies have considered a temporally constant, two-dimensional, rotationally invariant, framework that leads to vanishing radial material flux conditions when applied to flows within bounded channels. However, we show that a three-dimensional flow framework, with non-zero radial material fluxes resultant of flow super-elevation and overspill, is required to capture the rotational structure of flow within submarine meanders. Given this three-dimensional model, we present phase-space diagrams indicating the variation of the generic vertical structure of rotational flow within submarine meanders. Our findings highlight the importance of the radial flux boundary conditions as the primary control of secondary flow dynamics of submarine meanders. Further, the new model presented here suggests that the propensity for the occurrence of "river-reversed" secondary flow in canyon-fan networks is greater than recently advocated.

Dorrell, Robert; Darby, Steve; Peakall, Jeff; Parsons, Dan; Sumner, Esther; Wynn, Russell

2013-04-01

57

General patterns of circulation, sediment fluxes and ecology of the Palamós (La Fonera) submarine canyon, northwestern Mediterranean  

NASA Astrophysics Data System (ADS)

Currents, particle fluxes and ecology were studied in the Palamós submarine canyon (also known as the Fonera canyon), located in the northwestern Mediterranean. Seven mooring arrays equipped with current meters and sediment traps were deployed along the main canyon axis, on the canyon walls and on the adjacent slope. Additionally, local and regional hydrographic cruises were carried out. Current data showed that mean near surface and mid-depth currents were oriented along the mean flow direction (NE SW), although at 400 and 1200 m depth within the canyon current reversals were significant, indicating a more closed circulation inside the canyon. Mean near-bottom currents were constrained by the local bathymetry, especially at the canyon head. The most significant frequency at all levels was the inertial frequency. A second frequency of about three days, attributed to a topographic wave, was observed at all depths, suggesting that this wave was probably not trapped near the bottom. The current field observed during the most complete survey revealed a meandering pattern with cyclonic vorticity just upstream from and within the canyon. The associated vertical velocity ranged between 10 and 20 m/day and was constrained to the upper 300 m. This latter feature, together with other computations, suggests that during this survey the meander was not induced by the canyon but by some kind of instability of the mean flow. In the canyon, suspended sediment concentration, downward particle fluxes, chlorophyll and particulate C and N were significantly higher up-canyon from about 1200 m depth than offshore, defining, along with the different hydrodynamics, two canyon domains: one from the canyon head to about 1200 m depth more affected by the canyon confinement and the other deeper than 1200 m depth more controlled by the mean flow and the shelf-slope front. The higher near-bottom downward total mass fluxes were recorded in the canyon axis at 1200 m depth along with sharp turbidity increases and are related to sediment gravity flows. During the deployment period, the increase in downward particle fluxes occurred by mid-November, when a severe storm took place. On the canyon walls at 1200 m depth, suspended sediment concentrations, downward particle fluxes, chlorophyll and particulate C and N were higher on the southern wall than on the northern wall inversely to the current’s energy. This could be caused by an upward water supply on the southern canyon wall and/or the mean flow interacting with the canyon bathymetry. In the swimmers collected by the sediment traps, the dominant species was an elasipod holothurian, which has not been recorded in other canyons or elsewhere in the Mediterranean, indicating particular speciation.

Palanques, Albert; García-Ladona, Emilio; Gomis, Damià; Martín, Jacobo; Marcos, Marta; Pascual, Ananda; Puig, Pere; Gili, Josep-Maria; Emelianov, Mikhail; Monserrat, Sebastià; Guillén, Jorge; Tintoré, Joaquín; Segura, Mariona; Jordi, Antoni; Ruiz, Simón; Basterretxea, Gotzon; Font, Jordi; Blasco, Dolors; Pagès, Francesc

2005-08-01

58

Large wave-shaped bedforms in the axial channel of Monterey Submarine Canyon: Monterey Bay, California  

NASA Astrophysics Data System (ADS)

Multibeam bathymetric data show that large wave-shaped bedforms exist on the seafloor within the axial channel of Monterey Submarine Canyon offshore northern California (Smith et al., 2006). These features have wavelengths up to 70 m, amplitudes up to 2 m, and distinct asymmetrical crests that are roughly perpendicular to the channel. Comparisons of repetitive multibeam surveys since 2004 shows that the bedforms are active features because their positions change between surveys. Three complementary studies are underway to understand the origin of these features: (1) Vibracoring - In June 2007, the ROV Ventana collected 18 vibracores up to 2 m in length along a 130-m transect in ~285 m water depth that spanned the crests of two and the flanks of three waves. Sediment in these cores is composed of one or more sequences of coarse gravel or multicolored clay-clasts that fine upward into sand. Sometimes individual gravel-clasts or clay-chips occur within sand. The internal stratigraphy of these waves shows they resemble classic gravity-flow deposits. (2) Sediment Movement - A pilot study was conducted to assess whether sediment within the canyon floor moves by traction from currents or mass transport. On February 8, 2007, three acoustic beacons were deployed in ~290 m water depth within the canyon axis using Ventana. The beacons were placed within recesses in 50-cm-high ~45 kg poured-concrete monuments. These boulder-sized monuments were buried leaving only the top of the beacon standing ~6 cm above the sediment surface. Thus, the monuments were largely entombed within the seafloor. We also placed 3 acoustic beacons mounted on trapezoidal frames at the edge of a terrace on the canyon's lower flank. On February 12th, we returned to the area and determined that all three monuments had moved ~150 m down canyon. Two trapezoidal frames were found on their sides entwined with each other 50 and 75 m down canyon from their deployment site. The third frame was never located. A sediment trap mooring downstream at 1,300 m water depth independently showed that there was a gravity flow event on February 9th. The locations of the acoustic beacons have been re-determined on 4 subsequent occasions and they have not changed as of June 28, 2007. Because the monuments moved more than one wavelength down-canyon during the February 2007 event, aliasing problems may occur when trying to track the movement of individual wave crests in the repeat mapping surveys. The movement of the buried monuments suggests that the seafloor was remobilized to more than 50-cm-depth during this sediment transport event. (3) Repeat Mapping - Repeat surveys, including AUV multibeam mapping and chirp sub-bottom profiling, are being conducted 3-4 times per year. These surveys show that the wave-shaped bedforms occur in the canyon axis down to at least 1,100 m water depth. No internal structures are seen in the chirp data. Tracking the movement of these waves is proving difficult because it depends on identifying individual waves in successive surveys. Given that initially buried boulder-sized monuments moved more than two wavelengths down-canyon during an individual event limits our confidence in the identification and tracking of individual waves. Apparently, these wave-shaped bedforms are produced during brief, discrete mass transport and/or gravity flow events.

Paull, C. K.; Normark, W. R.; Ussler, W.; Caress, D. W.; Keaten, R.; Barry, J.; Xu, J.; Smith, D.; Covault, J. A.; Maier, K. L.

2007-12-01

59

The effects of submarine canyons and the oxygen minimum zone on deep-sea fish assemblages off Hawai'i  

NASA Astrophysics Data System (ADS)

Submarine canyons are reported to be sites of enhanced fish biomass and productivity on continental margins. However, little is known about the effects of canyons on fish biodiversity, in particular on oceanic islands, which are imbedded in regions of low productivity. Using submersibles and high-definition video surveys, we investigated demersal fish assemblages in two submarine canyons and slope areas off the island of Moloka'i, Hawai'i, at depths ranging from 314 to 1100 m. We addressed the interactions between the abundance, species richness and composition of the fish assemblage, and organic matter input and habitat heterogeneity, testing the hypotheses that heterogeneous bottom habitats and higher organic matter input in canyons enhance demersal fish abundance, and species density, richness and diversity, thereby driving differences in assemblage structure between canyons and slopes. Sediment type, substrate inclination, water-mass properties (temperature and dissolved oxygen) and organic matter input (modeled POC flux and percent detritus occurrence) were put into multivariate multiple regression models to identify potential drivers of fish assemblage structure. A total of 824 fish were recorded during ˜13 h of video yielding 55 putative species. Macrouridae was the most diverse family with 13 species, followed by Congridae (5), Ophidiidae (4) and Halosauridae (3). Assemblage structure changed markedly with depth, with the most abrupt change in species composition occurring between the shallowest stratum (314-480 m) and intermediate and deep strata (571-719 m, 946-1100 m). Chlorophthalmus sp. dominated the shallow stratum, macrourids and synaphobranchid eels at intermediate depths, and halosaurs in the deepest stratum. Assemblages only differed significantly between canyon and slope habitats for the shallow stratum, and the deep stratum at one site. Dissolved oxygen explained the greatest proportion of variance in the multivariate data, followed by POC flux and percent organic-detritus occurrence. Fish abundances were generally higher in canyons but only statistically significant for the deepest stratum. Reduced fish abundances both in canyon and slope transects occurred at intermediate depths within the core of the oxygen minimum zone (OMZ). Species density, diversity and richness and abundance were usually higher in the canyons, but only statistically higher in the deepest stratum. Possible causes for increased abundance and species densities and richness in the deepest stratum in canyons include reduced disturbance at deeper depths. We conclude that submarine canyons on oceanic islands are likely to be sites of enhanced fish abundance and species richness, but that these enhancing effects are offset when oxygen concentrations fall below ˜0.7 ml l-1 in OMZs.

De Leo, Fabio C.; Drazen, Jeffrey C.; Vetter, Eric W.; Rowden, Ashley A.; Smith, Craig R.

2012-06-01

60

The Role of Submarine Canyons in the Development of Large-scale Shoreline Features  

NASA Astrophysics Data System (ADS)

Carchuna, located in the Spanish Mediterranean Coast, is a 5 km long beach characterized by the presence of large scale shoreline features (horns) which do not appear to be periodically spaced. A leading hypothesis for their formation is the generation of circulation patterns associated with highly oblique wave propagation over submarine canyons present in the bathymetry (Ortega-Sánchez et al, Marine Geology, 2003). The dynamics of such a circulatory system are explored over the idealized case of linear contours down to 6 m, superimposed over the deeper true bathymetry. A time-dependent 2DH circulation model (Özkan-Haller and Kirby, JGR, 1999) forced using radiation stress gradients derived from a spectral wave model is used. The coupled wave- circulation model can predict the spatial location of large offshore directed flows (rip currents), showing their influence on the development of Carchuna beach features. As well, the model provides spatial and temporal variations in the circulation system due to possible instabilities of the cross-shore and longshore currents. Low-frequency gravity motions, such as edge waves, are also observed. Three different energy sea state contents are considered, each arriving from the most probable wave incoming wave direction. These results will provide insight regarding the possible role of wave propagation and wave-induced circulation patterns along canyon walls in the development of large-scaled shoreline morphology.

Ortega-Sanchez, M.; Ozkan-Haller, T.; Losada, M. A.

2006-12-01

61

Morphology of submarine canyon system and geotechnical properties of surficial sediments across the Peru-Chile forearc  

SciTech Connect

During August 1987, a SeaMARC II side-scan and sampling survey was conducted across the Peru-Chile forearc from 17/degrees/30'S to 19/degrees/30'S. Side-scan images reveal a complex submarine canyon system. Incised canyons meander across the Arequipa basin; their sinuosity results from erosion and cutbank slumping of the basin sediments. Lenticular packets of strata visible in reprocessed digital single-channel seismic profiles are interpreted to be buried channels. Tributary canyons coalesce into a single canyon at the structural high that deviates from its north-south course to a northeast-southwest course as a result of stream piracy. A dendritic drainage basin forming on the midslope may be the rejuvenation of an abandoned channel. Sediment properties were measured on 42 free-fall cores and 7 piston cores recovered both in and around the submarine canyon. Olive-gray (5Y 3/2) hemipelagic mud is the predominant sediment across the forearc. Most cores exhibit a small degree of bioturbation and thin laminae of sand; the number of sand laminae increases as the distance away from the canyon decreases. Shear strengths, averaged over a 1-m core length, decrease slightly with water depth. Carbonate content in all samples from this area is negligible with the exception of one piston core recovered from the upper reaches of the canyon, the bottom of which is composed of gravel- and sand-size shell fragments. Bulk mineralogy, determined from semiquantitative analysis of x-ray diffraction patterns, shows a decrease in relative feldspar percent and an increase in total clay content with increasing water depth. Preliminary analysis of core tops shows a mean grain size in the medium to very fine silt class, with increasing grain size toward the canyon. Smear slide counts generally show a surprisingly low abundance of volcanic glass and biogenic material, particularly diatoms.

Bergersen, D.D.; Coulbourn, W.T.; Moberly, R.

1989-03-01

62

Submarine canyons of the north-western Sicilian offshore (Southern Tyrrhenian Sea): variability in morphologies, sedimentary processes and tectonic settings  

NASA Astrophysics Data System (ADS)

Swath-bathymetry and high-resolution seismic reflection records acquired during the last two decades in the northern Sicilian offshore has unveiled a dense network of submarine canyons within the depth range of 80-2100 m, displaying a relevant variability in their geometry, morphologies and sedimentary processes. The studied margin shows a young, tectonically active shelf to slope setting linking the Sicilian-Maghrebian Thrust Belt to the Tyrrhenian oceanic realm, developed during the Neogene-Quaternary time span. The aim of this study is to highlight the main governing factors that contributed to the evolution and differentiation of the northern Sicilian canyons, mainly focusing on the Gulf of Castellamare and on the Gulf of Palermo areas. Canyons range 10-62 km in length and 1-5 km in amplitude, the slope gradient along their axis ranges between 1.8° and 9° and their sinuosity index ranges between 1 and 1.7. Generally, canyons, tributaries and gullies mapped in the Gulf of Castellamare indent the shelf-edge and display sinuous to meandriform paths on a upward concave gently sloping margin, showing a relevant role of coastal/shelf sedimentary inputs in their evolution. Otherwise, canyons along the upward convex slope in the Palermo Gulf are steep and almost linear, with retrograding submarine landslides controlling their evolution and only one canyon (the Oreto Canyon) showing a proved connection with fluvial sedimentary inputs. Results suggest that the different structural settings of the Castellammare and Palermo basins, together with an inferred difference in fluvial sedimentary inputs, are responsible for the variability of the north-western Sicilian submarine canyon systems, which originated and evolved contemporary with the upper Pliocene(?)-Quaternary sedimentary succession and have probably been more active during the Quaternary glacial maxima. On a local scale, neo-tectonic features, mass-movements and fluid seeps processes are significant controlling factors on the distribution of the canyons. The present day morphology of the margin shows that the most incised canyons are those facing the prominent capes along the coast, suggesting how the interaction of bottom currents with the shelf geometry likely has controlled their recent evolution.

Lo Iacono, Claudio; Sulli, Attilio; Agate, Mauro; Pennino, Valentina

2013-04-01

63

Tidal and flood signatures of settling particles in the Gaoping submarine canyon (SW Taiwan) revealed from radionuclide and flow measurements  

USGS Publications Warehouse

Sediment transport and sedimentation processes in the Gaoping submarine canyon were studied using sediment trap and current meter moorings deployed at a location during the winter (January-March) and the summer (July-September) months in 2008. At the end of each deployment, sediment cores were also collected from the canyon floor at the mooring site. Samples from sediment traps and sediment cores were analyzed for 210Pb and 234Th by gamma spectrometry. In conjunction with particle size and flow measurements, the datasets suggest that sediment transport in the canyon is tidally-modulated in the drier winter season and flood (river)-dominated in the wetter summer season. From the magnitude and temporal variation of sediment flux in the canyon with respect to the burial flux and sediment budget on the open shelf and slope region, we reaffirm that, on annual or longer timescales, the Gaoping submarine canyon is an effective conduit transporting sediments from the Gaoping River's drainage basin (the source) to the deep South China Sea (the ultimate sink). ?? 2009 Elsevier B.V.

Huh, C. -A.; Liu, J. T.; Lin, H. -L.; Xu, J. P.

2009-01-01

64

Plankton dynamics controlled by hydrodynamic processes near a submarine canyon off NW corsican coast: A numerical modelling study  

NASA Astrophysics Data System (ADS)

A three-dimensional (3D) non-linear high-resolution hydrodynamic model coupled to a coastal plankton ecosystem model is used to estimate the impact of hydrodynamic processes on the evolution of the spring phytoplankton bloom in the vicinity of a submarine canyon. Model results for the plankton distribution showed a clear 3D character around and in the canyon, with large horizontal and vertical gradients, induced by the hydrodynamic constraints. Phytoplankton concentrations were significantly larger all along the slope domain with maximum values obtained over the canyon. Upwelling of deep water rich in nitrate takes place both upstream (with respect to the current direction normal to the central axis of the canyon) and downstream of the canyon enhancing primary production. As phytoplankton-rich water enters into the western part of the canyon it is downwelled and trapped by the cyclonic circulation leading to accumulation of phytoplankton biomass there. The effect of wind events was to induce an upward nitrate flux into the upper layer through vertical turbulent diffusion, allowing the start of a short-live phytoplankton bloom. Maximum surface nitrate concentrations were found along the slope and particularly upstream and downstream of the canyon just after the wind stopped. Enhanced turbulent diffusion combined with upwelling motion in these areas resulted in larger upward nitrate transports, further enhancing primary production.

Skliris, N.; Djenidi, S.

2006-08-01

65

Suspended sediment fluxes and transport processes in the Gulf of Lions submarine canyons. The role of storms and dense water cascading  

Microsoft Academic Search

Contemporary suspended sediment transport was studied in seven submarine canyons of the Gulf of Lions (GoL). Current meters equipped with turbidity sensors were moored 4 m above bottom at 300 m depth in the canyon axis from November 2003 to May 2004. Sediment transport events were monitored and studied in relation to forcing conditions. There was a large flood in early December,

Albert Palanques; Xavier Durrieu de Madron; Pere Puig; Joan Fabres; Jorge Guillén; Antoni Calafat; Miquel Canals; Serge Heussner; Jerôme Bonnin

2006-01-01

66

Relationship between environment and the occurrence of the deep-water rose shrimp Aristeus antennatus (Risso, 1816) in the Blanes submarine canyon (NW Mediterranean)  

Microsoft Academic Search

We performed a multidisciplinary study characterizing the relationships between hydrodynamic conditions (currents and water masses) and the presence and abundance of the deep-water rose shrimp Aristeus antennatus in a submarine canyon (Blanes canyon in the NW Mediterranean Sea). This species is heavily commercially exploited and is the main target species of a bottom trawl fishery. Seasonal fluctuations in landings are

F. Sardà; N. Bahamón; G. Rotllant; M. M. Flexas; J. D. Sánchez; D. Zúñiga; J. Coenjaerts; D. Orellana; G. Jordà; J. Puigdefábregas; A. Sánchez-Vidal; A. Calafat; D. Martín; M. Espino

2009-01-01

67

Submarine canyon morphologies in the Gulf of Palermo (Southern Tyrrhenian Sea) and possible implications for geo-hazard  

Microsoft Academic Search

The continental shelf and the upper slope of the Gulf of Palermo (Southern Tyrrhenian Sea) in the depth interval ranging from\\u000a 50 to 1,500 m were mapped for the first time with Multi Beam echosounder and high resolution seismic. Seven submarine canyons\\u000a are confined to the upper slope or indent the shelf-edge and enter the Palermo intraslope basin at a depth

Claudio Lo Iacono; Attilio Sulli; Mauro Agate; Valeria Lo Presti; Fabrizio Pepe; Raimondo Catalano

2011-01-01

68

Submarine canyons associated with alternating sediment starvation and shelf-edge wedge development: Northern KwaZulu-Natal continental margin, South Africa  

Microsoft Academic Search

Multibeam bathymetry and high resolution boomer data reveal a shelf-edge wedge embayed by numerous canyons on the currently sediment starved northern KwaZulu-Natal continental margin. Submarine canyons in the southern portions of the study area may be differentiated from those in the north by the presence of an underlying erosive surface marked by palaeo-depressions and a thinner shelf edge-wedge. Canyons exhibit

Andrew Green

2011-01-01

69

Sources of baroclinic tidal energy in the Gaoping Submarine Canyon off southwestern Taiwan  

NASA Astrophysics Data System (ADS)

A three-dimensional model driven by tidal constituents O1, K1, M2 and S2 was adopted to evaluate the sources of baroclinic tidal energy in the Gaoping Submarine Canyon (GPSC) off southwestern Taiwan. The model domain covered the probable primary generation sites, including the Luzon Strait (LS) and the southeastern Taiwan Strait (TS). The simulated baroclinic tides agreed with the observations of tidal current velocity, isotherm vertical displacement, and baroclinic tidal energy flux (Fbc) in the GPSC. The depth-integrated, seven-day-averaged Fbc computed from the model result was 2.2 kW m-1 in the GPSC, and the corresponding area-integrated Fbc reached 189.4 MW. The results obtained from the model suggest that the baroclinic tides lead to strong turbulent mixing near the canyon head with a vertical diffusivity of 3.5 × 10-3 m2 s-1. Baroclinic tidal energy in the GPSC is mainly generated on the western ridge in the LS and on the steep topography in the southeastern TS. The local generation of baroclinic energy only accounts for 4.4% of the total value. The other 95.6% of the baroclinic tidal energy is remotely generated at the LS and the southeastern TS of which 31.9% and 8.8% are directly emanated, respectively, into the GPSC. The northwestward and southeastward baroclinic energy beams radiating from the LS and the southeastern TS, respectively, meet each other and form internal partial standing tides outside the GPSC. The transverse baroclinic energy from the internal partial standing tides accounts for the remaining 54.9% of the baroclinic tidal energy in the GPSC.

Chiou, Ming-Da; Jan, Sen; Wang, Joe; Lien, Ren-Chieh; Chien, Hwa

2011-12-01

70

Submarine canyon morphologies and evolution on a modern carbonate system: the Northern Slope of Little Bahama Bank (Bahamas).  

NASA Astrophysics Data System (ADS)

The recent CARAMBAR cruise (Nov. 2010) on the northern slope of Little Bahama Bank (LBB, Bahamas) provided new seafloor and subsurface data, that improve our knowledge on carbonate slope systems. The new high-resolution multibeam bathymetry data (Kongsberg EM302 echosounder) and very high resolution (3.5 kHz/Chirp subbotom profiler) seismic data show that the upper LBB slope is dissected by 18 canyons. These canyons evolve sharply into short channels opening to depositional fan-shaped lobes. These architectural elements form a narrow carbonate gravity system extending over 40 km along the LBB slope. The features previously described as small linear canyons have a more complex morphology than originally supposed. The several architectural elements that can be distinguished share similar characteristics with siliciclastic canyons. The average morphological features of the canyons are: minimum and maximum water depths of 460 and 970 m resp., mean length = 16.3 km and sinuosity = 1.14. Canyons are floored with flat elongated morphologies interpreted as terraces. Some of these terraces are located at the toe of slide scars on canyon heads and canyon sides which suggest that they result from sediment failures. On the Chirp seismic data, wedge-shape aggrading terraces interpreted as "internal levees" can be observed. These terraces would then be formed by overbanking of the upper part of turbidity currents. Between 530 and 630 m water depth, some canyons exhibit an amphitheater-shaped head with a head wall height ranging from 80 to 100 m. The wall edges of these canyon heads consist of coalescing arcuate slump scars, which suggests that the canyons formed by retrogressive erosion. Other canyons show an amphitheater-shaped head that evolves upslope into linear valleys incising the upper slope between 460 m and 530 m water depth. The onset and the spatial distribution of these linear valleys seem to be influenced by sediments transported from oolitic shoals of Walker Cay located 5 km upstream toward the upper slope. Indeed, upslope the canyon heads, the reflectivity map shows low backscatters characteristic of fine grained sediments within small elongated depressions (3-5 km long, 1-5 m deep) that are probably-formed by the flow of sediments coming the platform. These initial results allow a preliminary model of the canyon evolution to be proposed with two stages: (1) a first stage controlled by retrogressive erosion, generating several slides and collapses finally forming the amphitheater-shaped canyon heads, (2) a second stage of retrogressive erosion influenced on the upper slope by the sediment input from the platform along small erosional depressions located seaward of the carbonate bank. These small depressions can locally merge with the canyon heads.

Tournadour, Elsa; Mulder, Thierry; Borgomano, Jean; Hanquiez, Vincent; Ducassou, Emmanuelle; Gillet, Hervé; Sorriaux, Patrick

2013-04-01

71

Submarine canyon morphologies in the Gulf of Palermo (Southern Tyrrhenian Sea) and possible implications for geo-hazard  

NASA Astrophysics Data System (ADS)

The continental shelf and the upper slope of the Gulf of Palermo (Southern Tyrrhenian Sea) in the depth interval ranging from 50 to 1,500 m were mapped for the first time with Multi Beam echosounder and high resolution seismic. Seven submarine canyons are confined to the upper slope or indent the shelf-edge and enter the Palermo intraslope basin at a depth of around 1,300 m. The canyons evolved through concurrent top-down turbiditic processes and bottom-up retrogressive mass failures. Most of the mass failure features of the area are related to canyon-shaping processes and only few of them are not confined to the upper slope. In general, these features probably do not represent a significant tsunami hazard along the coast. The geological element that controls the evolution of the canyons and induces sediment instability corresponds to the steep slope gradient, especially in the western sector of the Gulf, where the steepest canyons are located. The structural features mapped in the Palermo offshore contributed to the regulation of mass failure processes in the area, with direct faults and antiform structures coinciding with some of the canyon heads. Furthermore, the occurrence of pockmarks and highs that probably consist of authigenic carbonates above faulted and folded strata suggests a local relationship between structural control, fluid escape processes and mass failure. This paper presents a valuable high-resolution morphologic dataset of the Gulf of Palermo, which constitutes a reliable base for evaluating the geo-hazard potential related to slope failure in the area.

Lo Iacono, Claudio; Sulli, Attilio; Agate, Mauro; Lo Presti, Valeria; Pepe, Fabrizio; Catalano, Raimondo

2011-03-01

72

Biological and physical processes in and around Astoria submarine Canyon, Oregon, USA  

Microsoft Academic Search

Astoria Canyon represents the westernmost portion of the Columbia River drainage system, with the head of the canyon beginning just 16 km west of the mouth of the Columbia River along the northern Oregon and southern Washington coasts. During the summer of 2001, physical, chemical, and biological measurements in the canyon were taken to better understand the hydrodynamic setting of,

Keith L. Bosley; J. William Lavelle; Richard D. Brodeur; W. Waldo Wakefield; Robert L. Emmett; Edward T. Baker; Kara M. Rehmke

2004-01-01

73

Sedimentary features and processes in the Nazaré and Setúbal submarine canyons, west Iberian margin  

Microsoft Academic Search

Here we present part of the first complete sidescan sonar dataset of the Nazaré and Setúbal Canyons, west Iberian margin, which, in combination with multibeam bathymetry, shallow seismic profiles and precise piston coring of intra-canyon targets, are used to characterise the sedimentary dynamics of these deep-sea settings. The results show that Nazaré and Setúbal Canyons are highly complex environments. They

Raquel G. Arzola; Russell B. Wynn; Galderic Lastras; Douglas G. Masson; Philip P. E. Weaver

2008-01-01

74

Recent transfer of coastal sediments to the Laurentian Channel, Lower St. Lawrence Estuary (Eastern Canada), through submarine canyon and fan systems  

Microsoft Academic Search

Multibeam sonar data, acoustic sub-bottom profiles and box cores were used to study the activity of submarine canyons and\\u000a fans near the city of Les Escoumins, on the North Shore of the Lower St. Lawrence Estuary (Eastern Canada). The multibeam\\u000a data were used to generate a high-resolution digital terrain model that reveals the presence of a large number of canyons

Hubert Gagné; Patrick Lajeunesse; Guillaume St-Onge; Andrée Bolduc

2009-01-01

75

Shelf erosion and submarine river canyons: implications for deep-sea oxygenation and ocean productivity during glaciation  

NASA Astrophysics Data System (ADS)

The areal exposure of continental shelves during glacial sea level lowering enhanced the transfer of erodible reactive organic matter to the open ocean. Sea level fall also activated submarine canyons thereby allowing large rivers to deposit their particulate load, via gravity flows, directly in the deep-sea. Here, we analyze the effects of shelf erosion and particulate matter re-routing to the open ocean during interglacial to glacial transitions, using a coupled model of the marine phosphorus, organic carbon and oxygen cycles. The results indicate that shelf erosion and submarine canyon formation may significantly lower deep sea oxygen levels, by up to 25%, during sea level low stands, mainly due to the supply of new material from the shelves, and to a lesser extent due to particulate organic matter bypassing the coastal zone. Our simulations imply that deep-sea oxygen levels can drop significantly if eroded shelf material is deposited to the seafloor. Thus the glacial ocean's oxygen content could have been significantly lower than during interglacial stages. Primary production, organic carbon burial and dissolved phosphorus inventories are all affected by the erosion and rerouting mechanisms. However, re-routing of the continental and eroded shelf material to the deep sea-sea has the effect of decoupling deep-sea oxygen demand from primary productivity in the open ocean. P burial is also not affected showing a disconnection between the biogeochemical cycles in the water column and the P burial record.

Tsandev, I.; Rabouille, C.; Slomp, C. P.; van Cappellen, P.

2010-02-01

76

Shelf erosion and submarine river canyons: implications for deep-sea oxygenation and ocean productivity during glaciation  

NASA Astrophysics Data System (ADS)

The areal exposure of continental shelves during glacial sea level lowering enhanced the transfer of erodible reactive organic matter to the open ocean. Sea level fall also activated submarine canyons thereby allowing large rivers to deposit their particulate load, via gravity flows, directly in the deep-sea. Here, we analyze the effects of shelf erosion and particulate matter re-routing to the open ocean during interglacial to glacial transitions, using a coupled model of the marine phosphorus, organic carbon and oxygen cycles. The results indicate that shelf erosion and submarine canyon formation may significantly lower deep-sea oxygen levels, by up to 25%, during sea level low stands, mainly due to the supply of new material from the shelves, and to a lesser extent due to particulate organic matter bypassing the coastal zone. Our simulations imply that deep-sea oxygen levels can drop significantly if eroded shelf material is deposited to the seafloor. Thus the glacial ocean's oxygen content could have been significantly lower than during interglacial stages. Primary production, organic carbon burial and dissolved phosphorus inventories are all affected by the erosion and rerouting mechanisms. However, re-routing of the continental and eroded shelf material to the deep-sea has the effect of decoupling deep-sea oxygen demand from primary productivity in the open ocean. P burial is also not affected showing a disconnection between the biogeochemical cycles in the water column and the P burial record.

Tsandev, I.; Rabouille, C.; Slomp, C. P.; van Cappellen, P.

2010-06-01

77

The Nankai OOST zone exposed along the Shionomisaki Submarine Canyon - Dive results of YK05-08 Leg 2  

NASA Astrophysics Data System (ADS)

The Shionomisaki submarine canyon cuts EW-trending five major ridges developed in the Plio-Pleistocene Nankai accretionary prism. The fifth ridge (numbered from the accretion toe in the south) is an extension of the Omine ridge where the out-of-sequence thrust (Nankai OOST zone) were detected through CDEX seismic profiles. We observed structures developed around the Nankai OOST zone along the canyon slope using submersible Shinkai 6500 during JAMSTEC cruise YK05-08 Leg 2. Three dives in addition to two previous dives (one include transect along the third ridge) verified that Shionomisaki Canyon exposes typical accretionary prism features in sandstone dominant thick turbidite sequences, including regular repetition of offscraping and underplating structure. Only near the Nankai OOST zone, extensive activities of fluid seepages were observed demarcated by the presence of chemosynthetic biocommunities, such as Calyptogena and Vesicomyid clams and Vestimentiferan tube worm. Each dive was designed to start from the canyon bottom, climbing up the canyon slope and end in EW-trending gully developed in the fifth ridge, to obtain a 3D images of the Nankai OOST ridge. Distributions of the chemosynthetic biocommunities were observed in the north of the Nankai OOST ridge suggesting a development of antithetic fault system. The ridge itself was disrupted by numerous EW-trending gullies where Calyptogena colonies were widely distributed. These gullies must correspond to spray faults that were bifurcated form the main OOST fault. Detailed observations on collected specimens revealed developments of web and vein structures together with black seams. Needle test indicated that the rocks in the middle part of the OOST ridge is more consolidated compared to those of the north and south exposures.

Anma, R.; Ogawa, Y.; Moore, G.; Kawamura, K.

2005-12-01

78

On vertical advection truncation errors in terrain-following numerical models: Comparison to a laboratory model for upwelling over submarine canyons  

NASA Astrophysics Data System (ADS)

Submarine canyons which indent the continental shelf are frequently regions of steep (up to 45°), three-dimensional topography. Recent observations have delineated the flow over several submarine canyons during 2-4 day long upwelling episodes. Thus upwelling episodes over submarine canyons provide an excellent flow regime for evaluating numerical and physical models. Here we compare a physical and numerical model simulation of an upwelling event over a simplified submarine canyon. The numerical model being evaluated is a version of the S-Coordinate Rutgers University Model (SCRUM). Careful matching between the models is necessary for a stringent comparison. Results show a poor comparison for the homogeneous case due to nonhydrostatic effects in the laboratory model. Results for the stratified case are better but show a systematic difference between the numerical results and laboratory results. This difference is shown not to be due to nonhydrostatic effects. Rather, the difference is due to truncation errors in the calculation of the vertical advection of density in the numerical model. The calculation is inaccurate due to the terrain-following coordinates combined with a strong vertical gradient in density, vertical shear in the horizontal velocity and topography with strong curvature.

Allen, S. E.; Dinniman, M. S.; Klinck, J. M.; Gorby, D. D.; Hewett, A. J.; Hickey, B. M.

2003-01-01

79

Effects of extreme meteorological conditions on coastal dynamics near a submarine canyon  

Microsoft Academic Search

A 3-D hydrodynamic model is applied to assess shelf\\/slope exchanges in the Calvi Canyon region (Corsica, NW Mediterranean) during the violent storm that affected the Western Europe in December 1999. Simulations are carried out using high-frequency sampling meteorological data to take into account the short-term variability of the atmospheric conditions. It is shown that the combined effects of canyon topography

N. Skliris; G. Lacroix; S. Djenidi

2004-01-01

80

Recent transfer of coastal sediments to the Laurentian Channel, Lower St. Lawrence Estuary (Eastern Canada), through submarine canyon and fan systems  

NASA Astrophysics Data System (ADS)

Multibeam sonar data, acoustic sub-bottom profiles and box cores were used to study the activity of submarine canyons and fans near the city of Les Escoumins, on the North Shore of the Lower St. Lawrence Estuary (Eastern Canada). The multibeam data were used to generate a high-resolution digital terrain model that reveals the presence of a large number of canyons and fans along the northern slopes of the Laurentian Channel. This paper focuses on two of the larger canyons, and their associated submarine fans. The sub-bottom profiles on the fans reveal high-amplitude reflections at the sediment/water interface and near the seafloor surface, indicating the occurrence of layers of coarse material. A turbidite was observed in a box core sampled in one of the fans, confirming the nature of the coarse layer. Geophysical and sedimentological data indicate that the canyons and fans play an important role in transferring coastal sandy sediments to the deeper marine environments by longshore drift-initiated turbidity flows, and thereby contribute to the negative sediment budget along the coast. The morphology of the canyons indicates that they were produced by a combination of erosive turbidity flows and retrogressive failures. The two box cores sampled on the fans reveal a recent (~last 60 years) quasi-exponential increase in sand content near the surface of the cores, possibly reflecting recent deforestation and/or increased coastal erosion.

Gagné, Hubert; Lajeunesse, Patrick; St-Onge, Guillaume; Bolduc, Andrée

2009-06-01

81

Sedimentary processes at submarine canyons in the Palomares Margin: Approach from swath bathymetry and high resolution side-scan sonar images.  

NASA Astrophysics Data System (ADS)

The continental slope of the Palomares Margin (South Iberian Margin, Western Mediterranean) is dissected by submarine canyons. Previous works on the Palomares Margin have been focused mainly on structural studies related to the Gibraltar Arc geodynamics, but the understanding of sedimentary and erosive processes shaping the margin and their control factors have received few attention till now. We present here morphologic features of the two mayor canyons in the Palomares Margin: the Gata and the Alías-Almanzora canyons, and interpret these characteristics in terms of sedimentary processes. Our study is built on swath bathymetry (Simrad EM-120), and deep-towed side-scan sonar (MAK-1M) data. Both canyons incise from the continental shelf of the Palomares Margin conducting sediment transfer by down-canyon gravity flows to the continental rise. The Gata Canyon is 64 km long, and headed by three tributary canyons. The Alías-Almanzora Canyon, which locates about 50 km to the north of the Gata Canyon, is 73 km long and headed by four tributary canyons facing rivers. The side-scan sonar images reveal erosion, transport and sedimentation processes along both canyon-valleys. Erosive bedforms are reliable evidence for the persistence of bottom currents (speed > 1 m s-1) along the thalwegs. The V-shaped of the Gata Canyon, confined by basement seamounts, suggests that turbidity currents have been the most important erosive mechanism and mass-wasting could be the dominant process to favour retrogressive sediment failures. Gullies with a herringbone pattern have been observed at the Alías-Almanzora valley; these forms are interpreted as derived from river-flooding events and/or from water-currents development at the continental shelf. Sediment waves observed at the Alías-Almanzora canyon-mouth can be related to events of contour bottom currents at the base of slope. Relative sea-level variations induced either by tectonic processes (Palomares margin uplift) or Mediterranean eustatic sea-level changes, or both, are considered significant control factors on the evolution of these canyons. Considering the tectonic setting of the studied region, we favour that the Pliocene-to-Present tectonic uplift recognized in the Palomares Margin is the major cause driving the development of these canyons. Acknowledgments: This study was supported by projects CTM2009-07715, TOPOMED-CGL2008-03474-E/BTE and CONSOLIDER-INGENIO2010-CSD2006-00041Projects (MICINN and FEDER funding, Spain) and RNM3713, RNM215 (PAI, Junta de Andalucía funding, Spain.

Perez-Hernandez, Silvia; Comas, Menchu; Escutia, Carlota

2010-05-01

82

Analytical Solutions for Tsunami Waves Generated by Submarine Landslides in Narrow Bays and Channels  

NASA Astrophysics Data System (ADS)

Analytical theory of tsunami wave generation by submarine landslides is extended to the case of narrow bays and channels of different geometry, in the shallow-water theory framework. New analytical solutions are obtained. For a number of bottom configurations, the wave field can be found explicitly in the form of the Duhamel integral. It is described by three waves: one forced wave propagating together with the landslide and two free waves propagating in opposite directions. The cases for bays with triangular (V-shaped bay), parabolic (U-shaped bay), and rectangular cross-sections are discussed in detail. The dynamics of the offshore-propagating wave in linearly inclined bays of different cross-section are also studied asymptotically for the resonant moving landslide. Different cases of landslides of increasing and decreasing volume are considered. It is shown that even if the landslide is moving under fully resonant conditions, the amplitude of the propagating tsunami wave may still be bounded, depending on the type of the landslide.

Didenkulova, Ira; Pelinovsky, Efim

2013-09-01

83

Bioluminescence in the Monterey Submarine Canyon: image analysis of video recordings from a midwater submersible  

Microsoft Academic Search

Video images of bioluminescence were recorded in situ during a 1985 study of the midwater environment of the Monterey Canyon, using a single-person, untethered submersible. Gelatinous organisms were responsible for the most brilliant bioluminescent displays, often exhibiting elaborate kinetics in response to mechanical stimulation. Images of bioluminescent displays recorded from identified organisms are shown and display patterns are described. All

E. A. Widder; S. A. Bernstein; D. F. Bracher; J. F. Case; K. R. Reisenbichler; J. J. Torres; B. H. Robison

1989-01-01

84

Deposition rates, mixing intensity and organic content in two contrasting submarine canyons  

Microsoft Academic Search

The hydrographically different conditions characterising the Western Iberian Margin (NE Atlantic) and the Gulf of Lions (Mediterranean) may play an important role in determining the biogeochemical characteristics of the sediments. To investigate this, we compared the Nazaré and Cap de Creus canyons, and their respective adjacent open slopes in terms of the organic carbon (Corg) contents, chlorophyll-a (chl-a) concentrations, C:N

R. García; D. van Oevelen; K. E. R. Soetaert; L. Thomsen; H. C. De Stigter; E. Epping

2008-01-01

85

A Picture on the Wall: Innovative Mapping Reveals Cold-Water Coral Refuge in Submarine Canyon  

PubMed Central

Cold-water corals are azooxanthellate species found throughout the ocean at water depths down to 5000 m. They occur in patches, reefs or large mound structures up to 380 m high, and as ecosystem engineers create important habitats for a diverse fauna. However, the majority of these habitats are now within reach of deep-sea bottom trawling. Many have been severely damaged or are under threat, despite recent protection initiatives. Here we present a cold-water coral habitat type that so far has been overlooked – quite literally – and that has received minimal impact from human activities. Vertical and overhanging cliffs in deep-sea canyons, revealed using an innovative approach to marine habitat mapping, are shown to provide the perfect substratum for extensive cold-water coral-based communities. Typical canyon-related processes, including locally enhanced internal tides and focussed downslope organic carbon transport, provide favourable environmental conditions (current regime, food input) to sustain the communities, even outside the optimal depth and density envelopes reported elsewhere in the NE Atlantic. Our findings show that deep-sea canyons can form natural refuges for faunal communities sensitive to anthropogenic disturbance, and have the potential to fulfil the crucial role of larval sources for the recolonisation of damaged sites elsewhere on the margin.

Huvenne, Veerle A. I.; Tyler, Paul A.; Masson, Doug G.; Fisher, Elizabeth H.; Hauton, Chris; Huhnerbach, Veit; Le Bas, Timothy P.; Wolff, George A.

2011-01-01

86

Examining sediment transport processes within two submarine canyons off coastal southern California using sediment trap arrays and naturally-occurring radionuclides  

NASA Astrophysics Data System (ADS)

The transport of sediment was examined in two submarine canyons (Mugu and Hueneme) located in southern California, just south of Ventura. Two vertically-separated sediment traps were deployed in each canyon for approximately 6 months. The mooring in Mugu Canyon, which presumably receives most of its sediment load from the Calleguas Creek, was deployed in 180m of water and the two sediment traps were positioned 30m and 60m above the sea floor. Huemene Canyon lies just south of the Santa Clara River and in this system the sediment traps were also located at 30m and 60m above the sea floor on a mooring deployed in 190m of water. As has been shown previously, the offshore transport of sediment from land in this region occurs mostly during episodic winter storm events that can deliver sediment as distinct pulses that are usually correlated to heightened precipitation events. Naturally-occurring radionuclides were measured in discrete time-stamped intervals of the four extruded sediment trap columns to obtain time-series flux estimates that can provide insight into particle scavenging and removal processes. In general, 226Ra fluxes (1-31 dpm g-1 d-1) are highly correlated (R2 up to 95) to total mass fluxes (1-13 g m-2 d-1), while excess xs210Pb:total mass fluxes reveal substantial additional input/removal processes. An xs234Th-based geochronology (0.4cm d-1) of the Mugu Canyon upper sediment trap is consistent with the observed (80cm in 190 d) sedimentation rate. Our results suggest that in these two submarine canyon systems, the supply of sediment consists of two components (allochthonous and reworked/resuspended) that can be tracked using naturally-occurring radionuclides.

Swarzenski, P. W.; Xu, J.

2008-12-01

87

Sediment transport off Bangladesh: the power of tropical cyclones recorded in a submarine canyon  

NASA Astrophysics Data System (ADS)

Marine sediments offshore Bangladesh are mainly supplied by the Ganges-Brahmaputra river system and are accumulated on the shelf of Bangladesh. The average sediment discharge of the world's biggest river system is estimated to be 0.8-1 billion tons per year. The shallow shelf is cut by a steep and up to 1000 m deep anaerobic canyon, called the "Swatch of No Ground", which acts as a sediment trap. An extremely high annual sedimentation flux of 20-45 cm was determined for the last 50 years by 137Cs and 210Pb measurements. In order to investigate the sediment transport in the Bay of Bengal a marine sediment core was taken from the mid-part of the Swatch of No Ground (21°18N/89°34E) and analyzed for element composition and grain-size distributions. Results show a sequence of graded fine-sand-silt-clay layers. These sequences can be directly related to the historical record of tropical storms, which move across the northern Bay of Bengal during pre- and post-monsoon flood peak and mobilize huge amounts of the shallow marine and coastal sediments into turbid hyperpycnal water masses. Due to the anti-clockwise rotation of the cyclones and their northward path the main transport direction is westward. The coarse grained sediment, remobilized by storm waves, is supported by cyclone-induced currents toward the canyon while the fine grained fraction follows afterward supported by the storm swell plus the semi-diurnal tidal component. Despite the high riverine input the amount of sediment mobilized during normal weather conditions is minimal compared to the sediment mobilized by the cyclonic high-energy input. Similar cyclone-induced sediment transport probably also governs erosion and deposition in most tropical shelf areas affected by the monsoon regime.

Meyer, I.; Kudrass, H.; Palamenghi, L.

2011-12-01

88

Paleocene Sepultura Formation: submarine canyon at La Mesa, Baja California, Mexico  

SciTech Connect

The Paleocene Sepultura Formation has been interpreted as the result of both deposition in a basin that varied in depth from strandline to at least 30-40 fathoms, and to widely distributed fluvial deposition. At La Mesa, east of Puerto Santa Catarina, Baja California, an excellent exposure exhibits canyon-fed sediments not reported in other places for this formation. The sediments at La Mesa consist of a sequence of alternating clastics and resedimented carbonate materials. The sequence begins with fine sandstone cut by channels, which indicates gravity-induced catastrophic sedimentation, such as debris flows. The channels are filled with massive nodular algal limestone with rip-up clasts of sandstone, some of them 1 m wide, with abundant Turritella pachecoensis and Venericardia sp. The massive limestone is overlain by clastic sediments that, in places, exhibit slumping and laminar bedding with limestone rip-ups. Apparently this unit is an upper-fan deposit. The nodular limestone grades laterally into thin-bedded calcarenites. These allodapic limestones exhibit A and B divisions of the Bouma sequence, similar to overbank levee deposits.

Tellez-Duarte, M.A.; Navarro-Fuentes, J.C.; Valdez-Noriega, M.A.

1988-03-01

89

Particulate Scavenging and Lateral Transport Processes in the Gaoping Submarine Canyon Deduced From Pb-210 and Po-210 Observations  

NASA Astrophysics Data System (ADS)

Pb-210 and Po-210 were measured on the suspended particulate matter(SPM) and filtered water samples collected in profile from five stations in the Gaoping Submarine Canyon (GPSC) during a cruise aboard R/V Ocean Researcher III in late November, 2006. These stations were selected along the axis of the GPSC, and denoted as CW1 through CW5 sequentially from the shallow part near the mouth of the Gaoping River to the deep-water region of the canyon. Except for CW4, the SPM profiles generally show a rapid increase to a maximum near bottom, the value of which is an order of magnitude higher than that observed above, suggesting a significant particulate resuspension or lateral input in the bottom layer. The SPM concentrations obtained at canyon head stations(CW1 to CW3) vary between 0.36 and 19.17 mg/kg. These values are generally higher than those obtained farther outward(CW4 and CW5), which range from 0.01 to 2.13 mg/kg, indicating a decrease away from the shore. The dissolved Pb-210 and Po-210 profiles observed from CW1 and CW2 are fairly uniform for the entire water column, with a mean of about 14 and 12 dpm/100kg, respectively. The other stations show a large variation in dissolved Pb-210 and Po-210 with a mean of about 23 and 14 dpm/100kg, respectively. At stations CW1, CW2 and CW3, the particulate Pb-210 and Po-210 profiles generally display a maximum around 28-38 and 27-48 dpm/100kg, respectively, in the bottom layer, suggesting significant particulate resuspension and scavenging. Variable Pb-210 and Po-210 activities in the particulates at CW4 and CW5 are observed in the surface layer. Both the dissolved and the total (dissolved + particulate) Po-210 to Pb-210 activity ratios vary between 0.1 and 1.7, mostly less than 1.0, with a mean of 0.7 and 0.8, indicating a variable deficiency of Po-210 relative to Pb- 210 in this study area. Total activities of Pb-210 are generally higher than those of Po-210. The Ra-226 profiles show much lower activities than those of the corresponding Pb-210 and Po-210, indicating large excesses of both Pb-210 and Po-210 over its parent , Ra-226. Assuming at steady-state, the mean residence times for the dissolved and particulate Pb-210 in the surface mixed layer are 0.6-1.3 and 0.8-3.9 years, respectively. The residence times of dissolved and particulate Po-210 are 0.4-2.6 and 0.1-0.4 years, respectively. The mean residence times are estimated to be on the order of days if advection terms are taken into account.

Hung, G.; Wang, P.; Shen, Y.

2009-05-01

90

Terrigenous organic matter signals in submarine canyons along the southwestern Gulf of Lion margin during Dense Shelf Water Cascading and quiescent conditions  

NASA Astrophysics Data System (ADS)

Previous projects in the Gulf of Lion have analyzed the path of terrigenous compounds in the Rhone deltaic system, the continental shelf and the canyon heads. In this study we present results from the HERMES project, focused on the GoL slope to further assess the particulate exchange with the interior ocean. Experimental design consisted in nine sediment traps deployed along the Lacaze-Duthiers and Cap de Creus submarine canyons (from the canyon heads to the canyon mouth) and the southern open slope during 1 year. Sediment trap materials were analyzed by CuO oxidation to investigate spatial and temporal variability in the yields and compositional characteristics of lignin-derived phenols. These organic biomarkers are uniquely synthesized by vascular plants, most of which inhabit the aerial ecosystems, and have been used extensively to trace the contribution and source of terrigenous organic matter in many environments. Sediment trap data indicate that the Dense Shelf Water Cascading event that took place in winter 2006 dominates overall particle fluxes in both canyons. During the deployment, fluxes of biogeochemical parameters were positively correlated with the total mass flux. Lignin fluxes were also highly correlated with mass fluxes, but the ratio of lignin to lithogenic material and lignin composition varied significantly indicating significant changes in the composition and nature of land-derived materials mobilized along both canyons. For example, during the DSWC period land-derived material is not significantly enriched in lignins and main changes in lignin composition are the enrichment in vanillyn phenols respect to syringyl and cinamyl phenols in the middle Cap de Creus canyon and upper open slope samples. Lithogenic-normalized lignin contents were higher during late spring and summer at all stations, when overall particle fluxes are relatively low. During these periods, lignin compositions were characterized by elevated cinnamyl to vanillyl phenol ratios, a trend that is consistent with elevated inputs of pollen. Our results suggest large differences in the sources and transport processes responsible for terrigenous material transport along canyons, ranging from export of fluvial and shelf sediments during winter to atmospheric dust inputs during spring and summer.

Pasqual, Catalina; Tesi, Tomasso; Sanchez-Vidal, Anna; Goñi, Miguel; Calafat, Antoni; Lee, Cindy; Canals, Miquel

2010-05-01

91

Modern accumulation rates and a budget of sediment off the Gaoping (Kaoping) River, SW Taiwan: A tidal and flood dominated depositional environment around a submarine canyon  

Microsoft Academic Search

Ninety-two box cores collected during 2004–2006 from an area of ~3000 km2 off the Gaoping (formerly spelled Kaoping) River, SW Taiwan, were analyzed for fallout radionuclides (210Pb, 137Cs and 7Be) to elucidate sedimentation rates and processes, and for the calculation of a sediment budget. The study area is located at an active collision margin with a narrow shelf and a submarine

Chih-An Huh; Hui-Ling Lin; Saulwood Lin; Ya-Wen Huang

2009-01-01

92

Structure-Forming Corals and Sponges and Their Use as Fish Habitat in Bering Sea Submarine Canyons  

PubMed Central

Continental margins are dynamic, heterogeneous settings that can include canyons, seamounts, and banks. Two of the largest canyons in the world, Zhemchug and Pribilof, cut into the edge of the continental shelf in the southeastern Bering Sea. Here currents and upwelling interact to produce a highly productive area, termed the Green Belt, that supports an abundance of fishes and squids as well as birds and marine mammals. We show that in some areas the floor of these canyons harbors high densities of gorgonian and pennatulacean corals and sponges, likely due to enhanced surface productivity, benthic currents and seafloor topography. Rockfishes, including the commercially important Pacific ocean perch, Sebastes alutus, were associated with corals and sponges as well as with isolated boulders. Sculpins, poachers and pleuronectid flounders were also associated with corals in Pribilof Canyon, where corals were most abundant. Fishes likely use corals and sponges as sources of vertical relief, which may harbor prey as well as provide shelter from predators. Boulders may be equivalent habitat in this regard, but are sparse in the canyons, strongly suggesting that biogenic structure is important fish habitat. Evidence of disturbance to the benthos from fishing activities was observed in these remote canyons. Bottom trawling and other benthic fishing gear has been shown to damage corals and sponges that may be very slow to recover from such disturbance. Regulation of these destructive practices is key to conservation of benthic habitats in these canyons and the ecosystem services they provide.

Miller, Robert J.; Hocevar, John; Stone, Robert P.; Fedorov, Dmitry V.

2012-01-01

93

Structure-forming corals and sponges and their use as fish habitat in Bering Sea submarine canyons.  

PubMed

Continental margins are dynamic, heterogeneous settings that can include canyons, seamounts, and banks. Two of the largest canyons in the world, Zhemchug and Pribilof, cut into the edge of the continental shelf in the southeastern Bering Sea. Here currents and upwelling interact to produce a highly productive area, termed the Green Belt, that supports an abundance of fishes and squids as well as birds and marine mammals. We show that in some areas the floor of these canyons harbors high densities of gorgonian and pennatulacean corals and sponges, likely due to enhanced surface productivity, benthic currents and seafloor topography. Rockfishes, including the commercially important Pacific ocean perch, Sebastes alutus, were associated with corals and sponges as well as with isolated boulders. Sculpins, poachers and pleuronectid flounders were also associated with corals in Pribilof Canyon, where corals were most abundant. Fishes likely use corals and sponges as sources of vertical relief, which may harbor prey as well as provide shelter from predators. Boulders may be equivalent habitat in this regard, but are sparse in the canyons, strongly suggesting that biogenic structure is important fish habitat. Evidence of disturbance to the benthos from fishing activities was observed in these remote canyons. Bottom trawling and other benthic fishing gear has been shown to damage corals and sponges that may be very slow to recover from such disturbance. Regulation of these destructive practices is key to conservation of benthic habitats in these canyons and the ecosystem services they provide. PMID:22470486

Miller, Robert J; Hocevar, John; Stone, Robert P; Fedorov, Dmitry V

2012-03-21

94

Structural Architecture of the Nankai Accretionary Prism along the Tenryu Submarine Canyon as Revealed in Submersible Studies  

NASA Astrophysics Data System (ADS)

Previous geologic structures of the Nankai accretionary prism have consisted mainly of seismic data analysis of 3D macrostructures and structural analysis of 1D vertical microstructures in drilled core samples. In this study, we have examined the structural architecture of the prism using the manned submersible _gShinkai 6500_h and the unmanned submersible _gKaiko_h operated by JAMSTEC. The accretionary prism strata exposed in the NNE-running Tenryu Canyon are deeply incised, providing excellent exposures in 3D along the canyon walls, locally up to 1000 meters in height. We collected structural data and rock samples successively from the shallower fore-arc basin deposits down to 1000 m deeper into the prism proper during the course of our studies. A total of eleven dive surveys were performed during four consecutive cruises, R/V Kairei-Kaiko (KR97-05 and 97-06) and R/V Yokosuka-Shinkai 6500 cruises (K03-03 and YK05-08). The unmanned Kaiko dived three times at the mouth of the Tenryu Canyon, and the manned Shinkai dived eight times at the sidewalls of the canyon. The strata in the Nankai prism are composed mainly of gently folded turbiditic beds, approximately several cm to several 10s of cm in thickness. Muddy layers in these turbidites commonly display vein structures and fracture cleavages, oriented approximately N-S and E-W near the large thrust faults. We observed five ENE-WSW-running large thrust faults associated with fault propagation folds (anticlines), collectively forming asymmetric topographic ridges. Observed thrust faults are mostly gently dipping (low-angle), although high-angle thrust faults with high asymmetric ridges also occur as an artifact of late-stage deformation caused by the subduction-collision of the Paleo-Zenisu ridge of the Izu Island Arc. The structural architecture of the Nankai accretionary prism along the Tenryu Canyon is a result of the combined effects of tectonic accretionary processes, including offscraping and underplating, and an arc-arc collision.

Kawamura, K.; Ogawa, Y.; Anma, R.; Dilek, Y.; Yokoyama, S.; Kawakami, S.

2005-12-01

95

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

SciTech Connect

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

Roussos, N. (Public Petroleum Corp. of Greece, Athens)

1988-08-01

96

Initiation and evolution processes of submarine instabilities and canyons: insights from the Northern margin of the Gulf of Aden.  

NASA Astrophysics Data System (ADS)

The study of turbiditic systems and their interactions (sea-level falls, floods, earthquakes) are not well known and require the comparison of observations in various geological contexts. On young continental margins, it provides informations on sedimentological processes during early phases of rifting, for which vertical movements (subsidence, uplift) can be more important. The understanding of facies and depositional sequences is a major challenge for the knowledge of the post-rift tectono-sedimentological evolution of the Gulf of Aden, rare current example of young passive margin. The data were acquired during oceanographic cruises (ENCENS-SHEBA (Leroy et al 2004; and ENCENS; Leroy et al 2006). The Northern margin has been studied by both a stratigraphic (seismic reflection data) and a semi-quantitative geomorphologic approach (acoustic imagery, bathymetry and ground DEM) leading firstly to a morphologies classification. This "seismic geomorphology" study let us to distinguish three sedimentological domains, which match to the structural segmentation inherited from the formation of margin in oblique rifting context. All the incision/erosion stages of continental slope (from slope instabilities set up to the formation of mature canyon) observed on the eastern part of the margin lead to an incision shaping model on a steep continental slope. The sedimentary record is strongly controlled by a recent tectonic phase. Vertical movements lead to the formation of numerous instabilities on the continental slope and Mass-Transport Deposits (MTDs) on the lower slope and deep basin. The drainage network extraction shows the sporadic connexion between some of rivers and noticed deep sea fans (which extending canyons with axial incision). Links with the continental drainage network are probably interfered with the recent vertical movements. The quaternary uplift rate increase eastward, toward the Socotra-Hadbeen transform fault zone. The recurrence of the gravitational events shows that the margin history can be divided into active and passive periods since the beginning of the post-rifting evolution of the Northeastern Aden margin (about 17.6 Ma; d'Acremont et al 2006). There is a main sedimentological switch in the studied zone around 7-10 Ma. This major change of sedimentation rate and facies types (slope-wash detritus, Mass-transport deposits MTDs, first occurrence of deep sea fans) is probably due to the uplift of the margin and climatic change (first occurrence of the Monsoon in this region).

Baurion, Céline; Gorini, Christian; Leroy, Sylvie; Lucazeau, Francis; Bache, François; Al-Toubi, Khalfan

2010-05-01

97

Exploration models for submarine slope sandstones  

Microsoft Academic Search

Recent published studies have demonstrated a far greater potential than previously recognized for submarine slope sandstones to contain significant oil and gas reserves in the Gulf Coast and elsewhere. Comparison of modern slopes with outcrop and subsurface analogs from several areas provided the framework for developing the following submarine slope sandstone exploration models: submarine canyon fill, slope gully\\/channel fill, slope

Slatt

1986-01-01

98

Initiation and evolution processes of submarine instabilities and canyons: Insights from the Northern margin of the Gulf of Aden  

NASA Astrophysics Data System (ADS)

The study of turbiditic systems and their interactions (climate, tectonic) are not well known in monsoon-influenced areas and on young margins. The Gulf of Aden is a good example of young stretched margin (35-18 Ma), where post-rift sediments are recording the intensification of the Asian monsoon (~7-8 Ma). Therefore the understanding of facies and depositional sequences on this margin is a major challenge for the knowledge of the interactions between sedimentological processes and the dynamic of a young stretched margin. In this paper, the Northern margin of the Gulf of Aden (South Sultanate of Oman; Dhofar) has been studied by both a stratigraphic (seismic reflection data) and a semi-quantitative geomorphologic approach (acoustic imagery, bathymetry and ground DEM) leading firstly to a morphology classification. Three morphological domains have been defined, which match to the structural segmentation inherited from the Oligocene-Miocene margin formation in an oblique rifting context. On the eastern part of the margin, the quaternary to current sedimentary record is strongly controlled by a late uplift. Vertical movements lead to the formation of numerous gravitational instabilities on the continental slope and Mass-Transport Complexes (MTCs) on the lower slope and deep basin. All the incision/erosion stages of the continental slope, from slope instabilities to the formation of mature canyon, are observed on the eastern part of the margin and lead to an incision shaping model on a tectonically controlled steep slope. A main sedimentological switch at least 10 Ma affects the eastern basin of the Gulf of Aden and is characterized by the first occurrence and evolution of deep sea fans and associated MTCs. This supersequence can be divided in two sequences: the first occurrences of MTCs and deep sea fans on the whole margin in the sedimentological record, and only on the eastern part of the margin, the second MTCs event linked to the rising mean slope value. Two hypothesis can be proposed to explain this switch: (i) a 2nd and 3rd order of the relative sea-level fall which explain the first occurrence of MTCs (Serravalian/Tortonian transition). This variation of relative sea level combined to a climatic switch (Asian monsoon intensification around 7-8 Ma) control the sediment flux and the setting up and evolution of deep sea fans; (ii) a very late uplift on the Eastern part of the study area generates the gravity-driven transport structures and the evolution from erosive-depositional to erosional systems.

Céline, B.; Christian, G.; Leroy, S.; Francis, L.; François, B.; Al-Toubi, K. I.

2010-12-01

99

Geomorphology and evolution of the gigantic Murray canyons on the Australian southern margin  

Microsoft Academic Search

The Murray canyons are a group of deeply incised submarine canyons on a steep 400?km section of the continental slope off Kangaroo Island, South Australia. Some of the canyons are amongst the largest on Earth. The canyons, some 80?km long, descend from the shelf edge to the abyssal plain 5200?m deep. Sprigg Canyon, the deepest and one of the largest,

Hill Pj; P. De Deckker; Exon Nf

2005-01-01

100

Canyon dynamics and related sedimentary impacts off western Portugal  

NASA Astrophysics Data System (ADS)

Submarine canyons are areas of increased exchanges between the continental shelf and the deep ocean. We present preliminary results from a multidisciplinary research focussing the dynamics of several canyon systems that occur along the Portuguese continental margin. The research is being conducted in the framework of EU project Eurostrataform and aims to understand the dominant aspects of the interaction between shelf/slope flows and canyons and to relate those aspects with the exportation of sediments from the shelf. The present work is intended to complement results from previous projects that were focussed on the quasi-inertial dynamics of the Portuguese canyon systems. Three contrasting systems are studied: (1) the Nazaré Canyon, a narrow and deep canyon which completely cuts the shelf, with no local riverine sources; (2) the Setubal-Lisbon canyon system, located in an area of complex topography and coastline configuration, with local riverine sources (Tagus and Sado rivers) and (3) the Oporto canyon, which is restricted to the outer shelf and affected by a major riverine source (Douro river). The ongoing program of observations includes multidisciplinary surveys (CTD, ADCP, suspended particle matter measurements, shallow seismic) and both long-term and short-term currentmeter moorings. The observations will cover both the summer upwelling regime as well as the highly energetic winter conditions. Process studies will combine observations and numerical modeling tools through the use of MOCASSIM system, which is presently being developed at Instituto Hidrografico. The system integrates several numerical models and is intended to characterise the wave and current conditions over the study areas.

Vitorino, J.; Oliveira, A.; Silva, R.; Quaresma, L.; Marreiros, R.

2003-04-01

101

Let's Bet on Sediments! Hudson Canyon Cruise--Grades 9-12. Focus: Sediments of Hudson Canyon.  

ERIC Educational Resources Information Center

|These activities are designed to teach about the sediments of Hudson Canyon. Students investigate and analyze the patterns of sedimentation in the Hudson Canyon, observe how heavier particles sink faster than finer particles, and learn that submarine landslides are avalanches of sediment in deep ocean canyons. The activity provides learning…

National Oceanic and Atmospheric Administration (DOC), Rockville, MD.

102

The trophic biology of the holothurian Molpadia musculus: implications for organic matter cycling and ecosystem functioning in a deep submarine canyon  

NASA Astrophysics Data System (ADS)

Megafaunal organisms play a key role in ecosystem functioning in the deep-sea through bioturbation, bioirrigation and organic matter cycling. At 3500 m water depth in the Nazaré Canyon, NE Atlantic, very high abundances of the infaunal holothurian Molpadia musculus were observed. To quantify the role of M. musculus in sediment cycling, sediment samples and holothurians were collected using an ROV and in situ experiments were conducted with incubation chambers. The biochemical composition of the sediment (in terms of proteins, carbohydrates and lipids), the holothurians' gut contents and holothurians' faecal material were analysed. In the sediments, proteins were the dominant organic compound, followed by carbohydrates and lipids. In the holothurian's gut contents, protein concentrations were higher than the other compounds, decreasing significantly as the material passed through the digestive tract. Approximately 33±1% of the proteins were digested by the time sediment reached the mid gut, with a total digestion rate equal to 67±1%. Carbohydrates and lipids were ingested in smaller amounts and digested with lower efficiencies (23±11% and 50±11%, respectively). As a result, the biopolymeric C digestion rate was on average 62±3%. We estimated that the population of M. musculus could remove approximately 0.49±0.13 g biopolymeric C and 0.13±0.03 g N m-2 d-1 from the sediments. These results suggest that M. musculus plays a key role in the benthic tropho-dynamics and biogeochemical processes in the Nazaré Canyon.

Amaro, T.; Bianchelli, S.; Billett, D. S. M.; Cunha, M. R.; Pusceddu, A.; Danovaro, R.

2010-08-01

103

Sedimentology and regional correlation of a basinally restricted deepwater siliciclastic wedge: Brushy Canyon Formation-Cherry Canyon Tongue (Lower Guadalupian), Delaware basin  

Microsoft Academic Search

Sedimentologic data and a new regional correlation based on seismic and field data constrain depositional models for basinally restricted siliciclastics of the Brushy Canyon Formation and sandstones of the immediately overlying Cherry Canyon Tongue. In the Guadalupe Mountains, the Brushy Canyon thins at the basin margin, from 300 m to pinch-out, by onlap onto a basinward-sloping submarine unconformity. The onlapping

C. Rossen; J. F. Sarg

1987-01-01

104

Seismic stratigraphy and development of Avon canyon in Benin (Dahomey) basin, southwestern Nigeria  

Microsoft Academic Search

Interpretation of a grid of high resolution seismic profiles from the offshore eastern part of the Benin (Dahomey) basin in southwestern Nigeria area permitted the identification of cyclic events of cut and fill associated with the Avon canyon. Seismic stratigraphic analysis was carried out to evaluate the canyon morphology, origin and evolution. At least three generations of ancient submarine canyons

S. O. Olabode; J. A. Adekoya

2008-01-01

105

The effect of canyon aspect ratio on flushing of dense pollutants from an isolated street canyon.  

PubMed

This study presents an experimental investigation of the effect of canyon aspect ratio on the dense pollutant removal from a street canyon by a turbulent overflow. Four series of experiments for different aspect ratios (?=0.45, 0.75, 1, 2) were conducted for a range of Richardson numbers. The qualitative and quantitative results are discussed and compared. Increasing the Richardson number and decreasing the canyon aspect ratio resulted in an increasingly strong stratification within the canyon and longer trapping times for the pollutant. The aspect ratio strongly affects the initial flushing mechanics and subsequent flow regime within the canyon. Narrower street canyons limit the width of large-scale vortices in the canyon and hence reduce vertical mixing. Based on the initial Richardson number, for all geometric configurations, three different flow regimes were observed in the canyon. The Richardson number at which there is a transition between these regimes is a function of the canyon geometry. PMID:23183223

Baratian-Ghorghi, Z; Kaye, Nigel B

2012-11-23

106

White submarine  

NASA Astrophysics Data System (ADS)

While not everyone gets to live in a yellow submarine, the scientific community may get to have a decommissioned U.S. Navy nuclear submarine dedicated to it. The Sturgeon class of submarines, which scientists say are the ideal choice for the project, will be coming up for decommissioning in this next decade. So the time is ripe, scientists say. Two weeks ago, oceanographers, submarine specialists, marine biologists, and geophysicists, among others met at AGU headquarters in Washington to discuss how to get the project in the water. If all goes well, the project would be the "biggest thing that ever happened in ocean and Earth science," according to Lloyd Keigwin of the Woods Hole Oceanographic Institution, who convened the meeting. For example, the submarine could make many types of "compelling" research possible that can not be done now by other means, such as studies in the Arctic that may have significant bearing on global change research, Keigwin says. However, the imposing hurdles that the project must overcome are as big as the opportunities it offers. Foremost, there is a question as to who will pick up the tab for such an endeavor.

107

Distribution and Tsunamigenic Potential of Submarine Landslides in the Gulf of Mexico  

Microsoft Academic Search

\\u000a The Gulf of Mexico (GOM) is a geologically diverse ocean basin that includes three distinct geologic provinces: a carbonate\\u000a province, a salt province, and canyon to deep-sea fan province, all of which contain evidence of submarine mass movements.\\u000a The threat of submarine landslides in the GOM as a generator of near-field damaging tsunamis has not been widely addressed.\\u000a Submarine landslides

J. D. Chaytor; D. C. Twichell; P. Lynett; E. L. Geist

108

Submarine fans  

NASA Astrophysics Data System (ADS)

Seisimic evidence from a study of 35-m.y.-old sediment contradicts the prevailing theory that bottom currents are the main cause of sediment distribution patterns and the shape of the continental rise.In the research area 200 miles offshore from New Jersey to Cape Hatteras, N.C., Stanley D. Locker of the University of South Florida, St. Petersburg, has found that submarine fans and deep-sea sediment drifts may develop simultaneously as companion systems. He presented his work at the Geological Society of America meeting in St. Louis, Mo., November 6-9.

Bush, Susan M.

109

Geomorphology of continental slope canyons  

NASA Astrophysics Data System (ADS)

Work on the US Atlantic slope reveals some remarkably analogous geomorphological properties to subaerial surfaces. Although the processes creating and modifying submarine slopes are different to those affecting landscapes above sea level, these geometrical similarities suggest that it may become possible to model slope evolution by analogous methods to those in subaerial geomorphology. Canyons in continental slopes, for example, can have similar "concavity" to bedrock eroding rivers (upwards-curved longitudinal profiles), tributaries can join main channels at confluences with smoothly converging elevations (obeying Playfair's Law), and tributaries with smaller contributing area tend to be steeper than their associated principal channels. Knickpoints in channels of tectonically active slopes also show fluvial-like tendencies, for example, there is evidence that they can advect up-stream or smooth out like in alluvial channels. Based on these observations, work has concentrated on assessing whether the "flow power" erosion models of fluvial geomorphology can be adapted to model submarine canyons. Other features of the Atlantic slope canyons can also be analogous to subaerial systems, for example, inter-canyon ridges can be sharp where bounded by steep, linear hillslopes analogous to threshold slopes on land. Many weakly incised areas of the uppermost continental slope in the USA Atlantic are smooth and upwards-convex between channels, much like in diffusive lowland landscapes. While some of this correspondence is fortuitous, the gravity effect on saltating sand may produce a down- slope movement proportional to local bed gradient that leads to a diffusive-like evolution of the surface topography in some circumstances.

Mitchell, N. C.

2006-12-01

110

Hot Canyon  

ScienceCinema

This historical film footage, originally produced in the early 1950s as part of a series by WOI-TV, shows atomic research at Ames Laboratory. The work was conducted in a special area of the Laboratory known as the "Hot Canyon."

111

SUBMARINE AUTOMATION: DEMONSTRATION #5  

Microsoft Academic Search

This paper describes the results obtained in the final performing period of the ARPA sponsored submarine automation project1. Efforts on the mapping between the submarine operational environment and the RCS software architecture lead to the result of three watch station graphic user interface panels. The submarine automation model has been expanded to include some engineering systems control capability. On the

Hui-Min Huang; Richard Quintero

112

On the magnitude of upwelling fluxes in shelf-break canyons  

NASA Astrophysics Data System (ADS)

A hydrodynamic model is employed to derive the magnitude of on-shelf fluxes through a shelf-break canyon for a wide range of canyon sizes and ambient oceanic conditions. Predicted canyon-upwelling fluxes are of the order of 0.05 0.1 Sv (1 Sv=1 million m3/s), being several orders of magnitude greater than upslope fluxes in the bottom Ekman layer on the ambient continental slope. On the basis of ˜150 simulations conducted, a bulk formula of upwelling flux in a submarine canyon is derived. For typical conditions, the upwelling flux varies quadratically with forcing strength (speed of incident flow), linearly with canyon depth, and is inversely proportional to the buoyancy frequency of the density stratification inside the canyon. Other parameters such as density stratification above shelf-break depth and bottom friction are found to have minor influences on the resultant canyon-upwelling flux.

Kämpf, Jochen

2007-10-01

113

Sediment-laden flow induced submarine cable failures off southwestern Taiwan  

NASA Astrophysics Data System (ADS)

Taiwan is located on the convergent boundary between the Eurasian and Philippine Sea plates, where has a highly frequency of earthquakes. Furthermore, the interaction between the largest continent (Eurasia Continent) and ocean (Pacific Ocean) leads to torrential-rain-induced flooding in the plume rain (May-June) and typhoon seasons (July-October). According to statistics from Water Resources Agency, in the last few decades, the mean annual sediment load was 384 million tons from the island of Taiwan into the sea. Off southwestern Taiwan, two major submarine canyons, the Gaoping submarine canyon (GPSC) and Fangliao submarine canyon (FLSC), are incising from continental shelf to deep sea floor and both of them transport considerable amounts of sediment to the South China Sea. In contrast to the GPSC which is directly connected to the Gaoping River, the FLSC which is smaller, younger and confined to the slope, does not associate with any river on land. Since 2006, southern Taiwan has been through several big typhoons and earthquakes which triggered submarine landslides and turbidity currents and damaged many submarine cables. The analytical results from sediment cores which taken from the GPSC and FLSC during 2005 to 2010 show these submarine cable break events may caused by different processes. In the upper GPSC, hyperpycnal flow might be the major process which caused the cable damages. On the contrary, cable failures in FLSC are due to sediment liquefaction.

Cheng, Y.; Su, C. C.

2012-04-01

114

Submarine Barrier Detection Model.  

National Technical Information Service (NTIS)

The paper presents a model for calculating the maximum probability of detection of a submarine using a detection barrier of fixed length. It is assumed in this calculation that location and heading of the submarine are known to some degree of certainty. T...

A. W. Starr W. T. McCormick

1971-01-01

115

Application of a Lagrangian transport model to organo-mineral aggregates within the Nazaré canyon  

NASA Astrophysics Data System (ADS)

In this study, a hydrodynamic model was applied to the Nazaré submarine canyon with boundary forcing provided by an operational forecast model for the West Iberian coast. After validation, a Lagrangian transport model was coupled to the hydrodynamic model to study the transport patterns of the organo-mineral aggregates along the Nazaré canyon comparing three different classes of organo-mineral aggregates. The results showed that the transport in the canyon is neither constant, nor unidirectional and that there are preferential areas where suspended matter is resuspended, transported and deposited. The results showed that the transport of the larger size classes of organo-mineral aggregates is less pronounced, and that there is a decrease in the phytodetrital carbon flux along the canyon. The Nazaré canyon acts as depocenter of sedimentary organic matter and the canyon is not a conduit of organo-mineral aggregates to the deep sea.

Pando, S.; Juliano, M.; Garcia, R.; Mendes, P. A. de Jesus; Thomsen, L.

2013-01-01

116

Prodigious submarine landslides on the Hawaiian Ridge  

NASA Astrophysics Data System (ADS)

The extensive area covered by major submarine mass wasting deposits on or near the Hawaiian Ridge has been delimited by systematic mapping of the Hawaiian exclusive economic zone using the side-looking sonar system GLORIA. These surveys show that slumps and debris avalanche deposits are exposed over about 100,000 km2 of the ridge and adjacent seafloor from Kauai to Hawaii, covering an area more than 5 times the land area of the islands. Some of the individual debris avalanches are more than 200 km long and about 5000 km3 in volume, ranking them among the largest on Earth. The slope failures that produce these deposits begin early in the history of individual volcanoes when they are small submarine seamounts, culminate near the end of subaerial shield building, and apparently continue long after dormancy. Consequently, landslide debris is an important element in the internal structure of the volcanoes. The dynamic behavior of the volcanoes can be modulated by slope failure, and the structural features of the landslides are related to elements of the volcanoes including rift zones and fault systems. The landslides are of two general types, slumps and debris avalanches. The slumps are slow moving, wide (up to 110 km), and thick (about 10 km) with transverse blocky ridges and steep toes. The debris avalanches are fast moving, long (up to 230 km) compared to width, and thinner (0.05-2 km); they commonly have a well-defined amphitheater at their head and hummocky terrain in the lower part. Oceanic disturbance caused by rapid emplacement of debris avalanches may have produced high-level wave deposits (such as the 365-m elevation Hulopoe Gravel on Lanai) that are found on several islands. Most present-day submarine canyons were originally carved subaerially in the upper parts of debris avalanches. Subaerial canyon cutting was apparently promoted by the recently steepened and stripped slopes of the landslide amphitheaters.

Moore, J. G.; Clague, D. A.; Holcomb, R. T.; Lipman, P. W.; Normark, W. R.; Torresan, M. E.

1989-12-01

117

Sedimentary architecture of a canyon-style fairway feeding a deep-water clastic system, the Miocene Cingöz Formation, southern Turkey: significance for reservoir characterisation and modelling  

Microsoft Academic Search

The sedimentary architecture of a submarine canyon-fill supplying sediment to a deep-water fan system in the Adana Basin, southern Turkey is described and quantified. The canyon is at least 9-km long, 3–4-km wide, asymmetric in cross-section and has an exposed fill, 360-m thick consisting of sands and gravels deposited in sheets across the entire width of the canyon. Normal graded

N. Satur; G. Kelling; B. T. Cronin; A. Hurst; K. Gürbüz

2005-01-01

118

Hearing Conservation for Submariners.  

National Technical Information Service (NTIS)

The report advises the U.S. Navy concerning hearing conservation aboard future submarines. Included are criteria for hazard, as well as suggested techniques for hearing protection, involving personal protection, environmental damping, and noise control at...

W. D. Ward

1971-01-01

119

Morphology, paleogeographic setting, and origin of the middle Wilcox Yoakum Canyon, Texas coastal plain  

SciTech Connect

The Yoakum canyon is the largest of the Gulf Coast Eocene erosional gorges and is interpreted as a buried submarine channel. The canyon can be traced for 67 mi (108 km) from the Wilcox fault zone, which defines the position of the early Eocene shelf edge, nearly to present outcrop. In this paper, the authors expand on previously published descriptions of the canyon and use a more extensive subsurface database. Decompaction of the canyon shale-fill reveals that original depths of the canyon exceeded 3,500 ft (1,067 m). Apparent canyon-wall slump scarps and a peripheral chaotic zone, interpreted as an incipient slump feature, are comparable to similar features of the late Quaternary Mississippi submarine canyon. The Yoakum canyon formed within the Garwood subembayment to the west of and adjacent to the middle Wilcox Rockdale delta system. Quantitative mapping of facies adjacent to the Yoakum shale indicate the following sequence of events. (1) Muddy, distal deltaic and shelf facies of the lower middle Wilcox subgroup were deposited during a retrogradation. (2) A resurgence of progradation deposited upper middle Wilcox deltaic facies atop the unconsolidated, lower middle Wilcox continental margin muds, loading the shelf edge and initiating slump failure of the continental margin. (3) Headward erosion of the canyon across the shelf occurred contemporaneously with a subsidence-induced transgression that coincided with a disruption in sediment supply. The Yoakum canyon was excavated by a combination of slumping and current scour. (4) The canyon was filled by hemipelagic and prodelta muds of the upper Wilcox subgroup. 19 figs.

Dingus, W.F. (Exxon Co., Midland, TX (USA)); Galloway, W.E. (Univ. of Texas, Austin (USA))

1990-07-01

120

Movements and Swimming Behavior of Three Species of Sharks in La Jolla Canyon, California  

Microsoft Academic Search

We tracked six individuals of three shark species, the shortfin mako, Isurus oxyrinchus, great white, Carcharodon carcharias, and blue, Prionace glauca, near the submarine canyon off La Jolla, southern California during the summers of 1995 and 1997. The duration of tracking ranged from 2 to 38 h per shark. The mode of travel differed in one respect among species. The

A. Peter Klimley; Sallie C. Beavers; Tobey H. Curtis; Salvador J. Jorgensen

2002-01-01

121

Canyon conditions impact carbon flows in food webs of three sections of the Nazaré canyon  

NASA Astrophysics Data System (ADS)

Submarine canyons transport large amounts of sediment and organic matter (OM) from the continental shelf to the abyssal plain. Three carbon-based food web models were constructed for the upper (300-750 m water depth), middle (2700-3500 m) and lower section (4000-5000 m) of the Nazaré canyon (eastern Atlantic Ocean) using linear inverse modeling to examine how the food web is influenced by the characteristics of the respective canyon section. The models were based on an empirical dataset consisting of biomass and carbon processing data, and general physiological data constraints from the literature. Environmental conditions, most notably organic matter (OM) input and hydrodynamic activity, differed between the canyon sections and strongly affected the benthic food web structure. Despite the large difference in depth, the OM inputs into the food webs of the upper and middle sections were of similar magnitude (7.98±0.84 and 9.30±0.71 mmol C m -2 d -1, respectively). OM input to the lower section was however almost 6-7 times lower (1.26±0.03 mmol C m -2 d -1). Carbon processing in the upper section was dominated by prokaryotes (70% of total respiration), though there was a significant meiofaunal (21%) and smaller macrofaunal (9%) contribution. The high total faunal contribution to carbon processing resembles that found in shallower continental shelves and upper slopes, although the meiofaunal contribution is surprisingly high and suggest that high current speeds and sediment resuspension in the upper canyon favor the role of the meiofauna. The high OM input and conditions in the accreting sediments of the middle canyon section were more beneficial for megafauna (holothurians), than for the other food web compartments. The high megafaunal biomass (516 mmol C m -2), their large contribution to respiration (56% of total respiration) and secondary production (0.08 mmol C m -2 d -1) shows that these accreting sediments in canyons are megafaunal hotspots in the deep-sea. Conversely, carbon cycling in the lower canyon section was strongly dominated by prokaryotes (86% of respiration) and the food web structure therefore resembled that of lower slope and abyssal plain sediments. This study shows that elevated OM input in canyons may favor the faunal contribution to carbon processing and create hotspots of faunal biomass and carbon processing along the continental shelf.

van Oevelen, Dick; Soetaert, Karline; Garcia, R.; de Stigter, Henko C.; Cunha, Marina R.; Pusceddu, Antonio; Danovaro, Roberto

2011-12-01

122

Submarine Automation: Demonstration No. 5.  

National Technical Information Service (NTIS)

The major objectives of this project are to: Demonstrate the application of the NIST RCS to submarine automation; and Refine and document the RCS methodology. This cycle of the submarine automation project emphasizes: Continuing investigating and developi...

H. M. Huang R. Quintero K. Young

1995-01-01

123

Physical volcanology of the submarine Mariana and Volcano Arcs  

Microsoft Academic Search

Narrow-beam maps, selected dredge samplings, and surveys of the Mariana and Volcano Arcs identify 42 submarine volcanos. Observed activity and sample characteristics indicate 22 of these to be active or dormant. Edifices in the Volcano Arc are larger than most of the Mariana Arc edifices, more irregularly shaped with numerous subsidiary cones, and regularly spaced at 50–70 km. Volcanos in

Sherman H. Bloomer; Robert J. Stern; N. Christian Smoot

1989-01-01

124

Superelevation and overspill control secondary flow dynamics in submarine channels  

NASA Astrophysics Data System (ADS)

In subaerial and submarine meander bends, fluid flow travels downstream in a helical spiral, the structure of which is determined by centrifugal, hydrostatic, baroclinic, and Coriolis forces that together balance frictional stresses generated by the flow. The sense of rotation of this helical flow, and in particular, whether the near bed flow is directed toward the inner bank, e.g., "river-normal," or outer bank, e.g., "river-reversed," is crucial to the morphodynamic evolution of the channel. However, in recent years, there has been a debate over the river-normal or river-reversed nature of submarine flows. Herein, we develop a novel three-dimensional closure of secondary flow dynamics, incorporating downstream convective material transport, to cast new light on this debate. Specifically, we show that the presence of net radial material transport, arising from flow superelevation and overspill, exerts a key control on the near bed orientation of secondary flow in submarine meanders. Our analysis implies that river-reversed flows are likely to be much more prevalent throughout submarine-canyon fan systems than prior studies have indicated.

Dorrell, R. M.; Darby, S. E.; Peakall, J.; Sumner, E. J.; Parsons, D. R.; Wynn, R. B.

2013-08-01

125

Making a Submarine.  

ERIC Educational Resources Information Center

Describes Archimedes principle and why a ship sinks when it gets a hole in it. Suggests an activity for teaching the concept of density and water displacement through the construction of a simple submarine. Includes materials and procedures for this activity. (KHR)

Cornacchia, Deborah J.

2002-01-01

126

The Stability of Submarines  

Microsoft Academic Search

SIR WILLIAM WHITE, in his paper in the Roy. Soc. Proceedings (vol. lxxvii. A., p. 528), discusses the hydrostatic forces tending to stability or instability of a submarine at the surface of the water. When the vessel is in motion, hydrodynamical forces come into play from the stream-line action of the water, and these also will affect the stability of

J. H. Jeans

1906-01-01

127

Submarine Dynamic Modeling  

Microsoft Academic Search

This paper discusses the development of a dynamic model for a torpedo shaped sub- marine. Expressions for hydrostatic, added mass, hydrodynamic, control surface and pro- peller forces and moments are derived from first principles. Experimental data obtained from flume tests of the submarine are inserted into the model in order to provide computer simulations of the open loop behavior of

Peter Ridley; Julien Fontan; Peter Corke

128

Yellow, Yellow submarin  

NASA Astrophysics Data System (ADS)

The recollections reports on a trip by author to Severodvinsk on the White Sea border (in the Russian Federation), where one of the Buroes and the Soviet atomic submarins Factory was placed. The factory and the buroe is placed there till present. A biography of one of the constructors is given.

Gaina, Alex

2009-12-01

129

The Grand Canyon  

NSDL National Science Digital Library

The first site from PBS.org, called Lost in the Canyon (1), offers an excellent online learning experience. Visitors learn about John Wesley Powell's expedition down the Colorado River, covered in transcripts from the companion television show and a timeline of Powell's life. Other features include an interactive lesson on running rapids and a look at the unique geologic history of the area. Next, from StudyWorks! Online comes the lesson entitled Sleuthing at the Grand Canyon: Using Rocks to Tell Us About the Past (2). Through basic descriptions, photographs, and illustrations, students learn how rocks form, how scientists use them to find out about past environments, and much more. The third site is provided by the Grand Canyon Monitoring and Research Center called The Grand Canyon Monitoring and Research Center Fiscal Year 2000-2004 Monitoring and Research Strategic Plan (3). Readers will discover the mission of the center, history of monitoring in the area, management strategies, research activities, and much more. Next is a site offered by Richard S. Naylor of Northeastern University's Department of Geology called Unconformities in the Grand Canyon (4). Visitors will find descriptions and photographs of several sites in the Grand Canyon that exhibit geologic unconformities or surfaces that represent a break in the geologic record. The fifth site is maintained by kaibob.org called the Geology of Grand Canyon (5). This site contains basic information on how the canyon was formed, where all the rock came from, why it looks like it does, and when it all happened. From NASA's Visible Earth Web site comes the 3-D View of Grand Canyon (6) page. The canyon can be viewed in a low or high resolution JPEG format, which shows the surrounding area, part of the Colorado river, and the canyon itself in dynamic colors. Part of Northern Arizona University, the seventh site is entitled Canyons, Culture, and Environmental Change: An Introduction to the Land Use History of the Colorado Plateau (7). The site provides an introduction to the environmental history of the Colorado Plateau and summarizes a vast body of research from multiple disciplines in an easily accessible format. The last site from NOAA's Colorado River Basin Forecast Center is the River Forecasts and Data page (8). Provided are data from various sites along the river that offer a wide range of relevant information such as simulated hydrographs.

Brieske, Joel A.

2002-01-01

130

Sedimentology and regional correlation of a basinally restricted deepwater siliciclastic wedge: Brushy Canyon Formation-Cherry Canyon Tongue (Lower Guadalupian), Delaware basin  

SciTech Connect

Sedimentologic data and a new regional correlation based on seismic and field data constrain depositional models for basinally restricted siliciclastics of the Brushy Canyon Formation and sandstones of the immediately overlying Cherry Canyon Tongue. In the Guadalupe Mountains, the Brushy Canyon thins at the basin margin, from 300 m to pinch-out, by onlap onto a basinward-sloping submarine unconformity. The onlapping wedge contains numerous basinward-trending channels (up to 50 m deep and 1 km wide). Laminated siltstones comprise interchannel areas and occur in channels as draping units of constant thickness. Sandstones (rippled, parallel laminated, and massive beds) are restricted to channels and onlap channel walls. Density-driven currents flowing into a density-stratified basin as interflows and underflows best explain these geometries. Concentration of sandstones in vertically stacked, 20 to 50-m deep channels suggests sands were point-sourced into the basin. Increasing proportions of high-energy deposits in successive sandstone channel fills indicate progradation of the Brushy Canyon wedge. Correlation of the Brushy Canyon unconformity shelfward to an interpreted disconformity within the San Andres Formation suggests that the shelf was subaerially exposed. Allochthonous fossils in Brushy Canyon sandstones indicate existing submerged shallow, upper slope areas were normal marine. Updip portions of the lower Cherry Canyon Sandstone Tongue are confined within paleocanyons and are deltaic in origin, suggesting fluvial delivery of sand across the shelf. These regional constraints suggest that density-driven currents were turbidity currents rather than saline density currents sourced by hypersaline shelf waters.

Rossen, C.; Sarg, J.F.

1987-05-01

131

Comparison of horizontal and downward particle fluxes across canyons of the Gulf of Lions (NW Mediterranean): Meteorological and hydrodynamical forcing  

Microsoft Academic Search

In the framework of the European project Eurostrataform, an array of six near-bottom mooring lines was deployed in the heads of the major submarine canyons incising the continental slope of the Gulf of Lions (NW Mediterranean). All moorings were equipped with sediment traps, current meters and turbidity Optical Backscatters Sensors (OBS) situated at few meters above the bottom. Particulate mass

J. Bonnin; S. Heussner; A. Calafat; J. Fabres; A. Palanques; X. Durrieu de Madron; M. Canals; P. Puig; J. Avril; N. Delsaut

2008-01-01

132

Deep Canyon and Slope Suspended Sediment Transport in the Western Gulf of Lions During the 2006 Intense Cascading Period  

Microsoft Academic Search

Recent studies have demonstrated that most of the off-shelf suspended sediment transport in the Gulf of Lions occurs in its westernmost sector, preferentially through the Cap de Creus submarine canyon. Based on this previous knowledge, a focussed monitoring strategy was designed within the HERMES project, to better constrain the contemporary sediment transport processes in this region. A network of mooring

A. Palanques; P. Puig; X. Durrieu de Madron; A. Calafat; M. Canals; S. Heussner

2008-01-01

133

Canyon and channel networks of Peru-Chile fore arc at Arica Bight  

SciTech Connect

Canyons and channels of the Peru-Chile fore arc between 17{degree}30'S to 19{degree}30'S form a complex, integrated network revealed in SeaMARC II side-scan mosaics. The largest canyon, incised 200-600 m, is bordered by a series of sidewall slumps, producing a sinuosity that mimics subaerial meanders. The canyon courses across the Arequipa fore-arc basin floor, across a structural high and onto the middle trench slope to about 4,000 m where it disappears into a background of complex small-scale structures, From 500-2,500 m depth the canyon strikes north-south oblique to the regional slope. At 2,500 m, it abruptly turns to the southwest toward the trench axis. At this elbow, a second canyon heads on the midslope and also trends north-south until 3,500 m, where it too abruptly changes to a southwest course. A history of stream piracy analogous to subaerial systems is implied in this geometry. Tributaries join this main canyon from the landward side, forming a dendritic pattern. These channels have levees which are linked by submarine crevasse splays to sediment waves on the Arequipa basin floor. The orientation of the waves is reminiscent of bow waves from a passing ship, oblique to channel and pointing downslope, and may provide an indication of the vertical extent of passing turbidity currents. Sediments are dominantly olive gray, hemipelagic silts with sands present only immediately adjacent to the canyons. Boulders of mudstone line portions of the canyon floor. Sands are absent from the lowermost slope and trench axis, as are any indications of submarine fans. Sands may be rare in this system, with those that are present kneaded into the active margin system along the lower trench slope.

Coulbourn, W.T. (Hawaii Institute of Geophysics, Honolulu (USA))

1990-05-01

134

CBO Testimony: Attack Submarine Programs.  

National Technical Information Service (NTIS)

Attack submarine programs are a significant portion of the Navy's overall acquisition plan: in its 1996 request, the Administration has allocated $2.8 billion for them. That sum includes $1,507 million to complete the funding for a third Seawolf submarine...

C. Williams

1995-01-01

135

Current submarine atmosphere control technology.  

PubMed

Air purification in submarines was introduced towards the end of World War II and was limited to the use of soda lime for the removal of carbon dioxide and oxygen candles for the regeneration of oxygen. The next major advances came with the advent of nuclear-powered submarines. These included the development of regenerative and, sometimes, energy-intensive processes for comprehensive atmosphere revitalization. With the present development of conventional submarines using air-independent propulsion there is a requirement for air purification similar to that of the nuclear-powered submarines but it is constrained by limited power and space. Some progress has been made in the development of new technology and the adoption of air purification equipment used in the nuclear-powered submarines for this application. PMID:11876194

Mazurek, W

1998-01-01

136

Anomalous topography on the continental shelf around Hudson Canyon  

USGS Publications Warehouse

Recent seismic-reflection data show that the topography on the Continental Shelf around Hudson Canyon is composed of a series of depressions having variable spacings (< 100 m to 2 km), depths (1-10 m), outlines, and bottom configurations that give the sea floor an anomalous "jagged" appearance in profile. The acoustic and sedimentary characteristics, the proximity to relict shores, and the areal distribution indicate that this rough topography is an erosional surface formed on Upper Pleistocene silty sands about 13,000 to 15,000 years ago by processes related to Hudson Canyon. The pronounced southward extension of the surface, in particular, may reflect a former increase in the longshore-current erosion capacity caused by the loss of sediments over the canyon. Modern erosion or nondeposition of sediments has prevented the ubiquitous sand sheet on the Middle Atlantic shelf from covering the surface. The "anomalous" topography may, in fact, be characteristic of areas near other submarine canyons that interrupt or have interrupted the longshore drift of sediments. ?? 1979.

Knebel, H. J.

1979-01-01

137

Bathymetrical distribution and size structure of cold-water coral populations in the Cap de Creus and Lacaze-Duthiers canyons (northwestern Mediterranean)  

NASA Astrophysics Data System (ADS)

Submarine canyons are known as one of the seafloor morphological features where living cold-water coral (CWC) communities develop in the Mediterranean Sea. We investigated the CWC community of the two westernmost submarine canyons of the Gulf of Lions canyon system: the Cap de Creus Canyon (CCC) and Lacaze-Duthiers Canyon (LDC). Coral associations have been studied through video material recorded by means of a manned submersible and a remotely operated vehicle. Video transects have been conducted and analyzed in order to obtain information on (1) coral bathymetric distribution and density patterns, (2) size structure of coral populations, and (3) coral colony position with respect to the substrate. Madrepora oculata was the most abundant CWC in both canyons, while Lophelia pertusa and Dendrophyllia cornigera mostly occurred as isolated colonies or in small patches. An important exception was detected in a vertical cliff in LDC where a large L. pertusa framework was documented. This is the first record of such an extended L. pertusa framework in the Mediterranean Sea. In both canyons coral populations were dominated by medium and large colonies, but the frequent presence of small-sized colonies also indicate active recruitment. The predominant coral orientation (90° and 135°) is probably driven by the current regime as well as by the sediment load transported by the current flows. In general, no clear differences were observed in the abundance and in the size structure of the CWC populations between CCC and LDC, despite large differences in particulate matter between canyons.

Gori, A.; Orejas, C.; Madurell, T.; Bramanti, L.; Martins, M.; Quintanilla, E.; Marti-Puig, P.; Lo Iacono, C.; Puig, P.; Requena, S.; Greenacre, M.; Gili, J. M.

2013-03-01

138

Bathymetrical distribution and size structure of cold-water coral populations in the Cap de Creus and Lacaze-Duthiers canyons (northwestern Mediterranean)  

NASA Astrophysics Data System (ADS)

Submarine canyons are known as one of the seafloor morphological features where living cold-water coral (CWC) communities develop in the Mediterranean Sea. We investigated the CWC community of the two westernmost submarine canyons of the Gulf of Lions canyon system: the Cap de Creus Canyon (CCC) and Lacaze Duthiers Canyon (LDC). Coral associations have been studied through video material recorded by means of a manned submersible and a remotely operated vehicle. Video transects have been conducted and analyzed in order to obtain information on (1) coral bathymetric distribution and density patterns, (2) size structure of coral populations, and (3) coral colony orientation with respect to the substrate. Madrepora oculata was the most abundant CWC in both canyons, while Lophelia pertusa and Dendrophyllia cornigera mostly occurred as isolated colonies or in small patches. An important exception was detected in a vertical cliff in LDC where a large Lophelia pertusa framework was documented. This is the first record of such an extended L. pertusa framework in the Mediterranean Sea. In both canyons coral populations were dominated by medium and large colonies, but the frequent presence of small-sized colonies also indicate active recruitment. The predominant coral orientation with respect to the substrate (90° and 135°) is probably driven by the current regime as well as by the sediment load transported by the current flows. In general no clear differences were observed between the CWC populations from CCC and LDC, despite large differences in particulate matter between canyons.

Gori, A.; Orejas, C.; Madurell, T.; Bramanti, L.; Martins, M.; Quintanilla, E.; Marti-Puig, P.; Lo Iacono, C.; Puig, P.; Requena, S.; Greenacre, M.; Gili, J.

2012-12-01

139

Flow structure in submarine meandering channels, a continuous discussion on secondary flow  

NASA Astrophysics Data System (ADS)

The understanding of the flow structure in deep-sea turbidity currents is important for the formation of submarine meandering channels. Similarly to the case of subaerial channels, several types of secondary flows include turbulence-, curvature- and bed morphodynamic-driven flow structures that modulate sediment transport and channel bed morphodynamics. This study focuses on [1] a review of long-time research effort (Abad et al., 2011) that tackles the description of the secondary flow associated with a subaqueous bottom current (saline) in a high-curvature meandering channel and [2] ongoing numerical simulations of similar settings as the experiments to describe the entire flow structure. In the case of subaerial channels, the classical Rozovskiian paradigm is often invoked which indicates that the near-bottom secondary flow in a bend is directed inward. It has recently been suggested based on experimental and theoretical considerations, however, that this pattern is reversed (near-bottom secondary flow is directed outward) in the case of submarine meandering channels. Experimental results presented here, on the other hand, indicate near-bottom secondary flows that have the same direction as observed in a river (normal secondary flow). The implication is an apparent contradiction between experimental results. This study combines theory, experiments, reconstructions of field flows and ongoing simulations to resolve this apparent contradiction based on the flow densimetric Froude number. Three ranges of densimetric Froude number are found, such that a) in an upper regime, secondary flow is reversed, b) in a middle regime, it is normal and c) in a lower regime, it is reversed. These results are applied to field scale channel-forming turbidity currents in the Amazon submarine canyon-fan system (Amazon Channel) and the Monterey canyon and a saline underflow in the Black Sea flowing from the Bosphorus. Our analysis indicates that secondary flow should be normal throughout most of the Amazon submarine fan reach, lower-regime reversed in the case of the Black Sea underflow, and upper-regime reversed in the case of the Monterey canyon. The analysis predicts both normal and reversed regimes in the Amazon submarine canyon reach. This research presents insights on the importance of flow structure not only to describe subaqueous bed morphodynamics, but also to understand evolution of submarine meandering channels, therefore its importance for developing accurate morphodynamic models. Reference: Abad, J. D., Sequeiros, O. E., Spinewine, B., Pirmez, C., Garcia, M. H., Parker, G. (2011). SECONDARY CURRENT OF SALINE UNDERFLOW IN A HIGHLY MEANDERING CHANNEL: EXPERIMENTS AND THEORY. In press, Journal of Sedimentary Research

Abad, J. D.; Parker, G.; Sequeiros, O.; Spinewine, B.; Garcia, M. H.; Pirmez, C.

2011-12-01

140

Black Canyon Outreach Education  

NSDL National Science Digital Library

This portal features links to K-12 outreach education units on the Black Canyon of the Gunnison National Park and Curecanti National Recreation Area. They focus on topics such as trees, habitats, fossils, animal adaptations, seasons, weather, the water cycle, mapping and geology. There are also downloadable activities for sutdents to perform either before or after their visits to the area.

141

Adventures in Glen Canyon.  

National Technical Information Service (NTIS)

Depicts the beauty of Lake Powell and the magnitude of Glen Canyon dam located on the Colorado River in southern Utah and northern Arizona; the geology and early history of the region, construction of the dam, and available recreational activities. Primar...

1994-01-01

142

Ancient Observatories: Chaco Canyon  

NSDL National Science Digital Library

This Exploratorium site offers an online "tour" of the sites and structures within Chaco Canyon, thought to have once been an ancient solar observatory. The different pages on the tour detail several of the most famous sites where significant solar alignments occur each year. A section called "seasons and solstices" provides further information.

2009-03-12

143

Next Generation Strategic Submarine Navigator.  

National Technical Information Service (NTIS)

For the last forty-five years, Strategic Systems Programs (SSP) has been entrusted with total life cycle responsibility for the United States and the Royal (United Kingdom) Navy's Strategic Submarine (SSBN) launched ballistic missile weapons systems. SSP'...

M. J. Ringlein N. J. Barnett M. B. May

2000-01-01

144

Submarine Periscope Eyeguard Housing Assembly.  

National Technical Information Service (NTIS)

A submarine periscope eyeguard housing assembly includes a viewing lens housing having a viewing lens aperture and viewing lens therein, first and second arm members fixed to the viewing lens housing and extending therefrom, a first blinder mounted on the...

W. C. Maciejewski R. Sayegh

2001-01-01

145

Sedimentary processes in the middle Nazaré Canyon  

NASA Astrophysics Data System (ADS)

Nazaré Canyon extends from a water depth of 50 m near the Portuguese coast to 5000 m at the edge of the Iberian Abyssal Plain. The system is not connected to a modern river and instead obtains its present day sediment input by capture of along-shelf sediment transport. Much of this sediment is deposited in the middle canyon between about 2700 and 3800 m. However, the middle canyon is a highly heterogeneous environment, with areas of both high and low sedimentation rates, exposed rock outcrop, erosion and stable and unstable slopes in close juxtaposition. This paper explores how the various sedimentary processes interact to create the observed heterogeneous canyon environment, which will influence benthic biodiversity in the canyon. Seafloor heterogeneity is investigated using a nested approach to data interpretation, using local high-resolution data to calibrate regional lower resolution data. Six different data types, ship and ROV-mounted swath bathymetry, 30 kHz sidescan sonar images, sediment cores, seafloor video/photographs and current metre/acoustic backscatter data, were incorporated into the analysis. The main morphological characteristic of the middle canyon is a narrow, steep-sided, axial channel flanked by gently sloping terraces. Small-scale landsliding, active at the present day, is the main process that exposes a variety of substrates, ranging from semi-consolidated Holocene sediments to rock of probable Mesozoic age, on the steep axial channel walls. The axial channel floor is characterised in part by large-scale sediment bedforms and in part by landslide debris, suggesting some reworking of landslide debris by currents within the channel. The terraces are interpreted as inner levees with high sedimentation rates. Cores show a dominantly muddy sequence interrupted by thin turbidite sands emplaced on decadal to centennial timescales. The fine-grained sedimentation is the product of continuous settling from fine-grained flows that range from gravity currents to lateral advection of nepheloid layers. The close proximity of areas of high sedimentation and erosion creates a highly heterogeneous seafloor, with the highest heterogeneity on the steepest slopes.

Masson, D. G.; Huvenne, V. A. I.; de Stigter, H. C.; Arzola, R. G.; Lebas, T. P.

2011-12-01

146

Exo-enzymatic activities and organic matter properties in deep-sea canyon and slope systems off the southern Cretan margin  

NASA Astrophysics Data System (ADS)

Enzymatic activities of aminopeptidase and ?- D-glucosidase were investigated in sediments collected from deep-sea canyon (Samaria) and slope systems of the unexplored southern Cretan margin (Eastern Mediterranean Sea). Stations were grouped in defined regions, inside the canyon, in nearby slopes and in open slope systems. Redox potential values, organic carbon concentrations, C/N ratios, chlorophyll- a, phaeopigments, prokaryotic abundances and carbon (C) mineralization rates were also estimated. The main aim of this investigation was to examine the links among prokaryotic abundance and activities and organic matter parameters along the axis of a submarine canyon (Samaria), and laterally along the slopes of the deep southern Cretan margin (Eastern Mediterranean Sea). The recorded aminopeptidase activities exhibited elevated values near the mouth of the canyon and the nearby slope systems and were found to be comparable to those reported for mesotrophic ecosystems. Statistical comparisons revealed that chloroplastic pigment equivalents, C/N ratios and carbon mineralization rates did not differ significantly between the deep stations in and outside the canyon (of either 2000 or 3500 m water depth). On the other hand, organic carbon and nitrogen content, prokaryotic abundances, and enzymatic activities differ substantially between the canyon and slope stations. It is suggested that the deep basins at the outlet of the submarine canyon of Samaria and the nearby slope systems are promising targets for the identification of microbial hotspots.

Polymenakou, Paraskevi N.; Lampadariou, Nikolaos; Tselepides, Anastasios

2008-10-01

147

Stratigraphy and depositional environment of unnamed (lower Miocene) submarine-fan sandstone unit in Sierra Madre and San Rafael Mountains, northeastern Santa Barbara County, California  

SciTech Connect

A relatively thick and extensive, previously unnamed, lower Miocene sandstone unit occurs in the central Sierra Madre and in the Hurricane Deck area of the San Rafael Mountains of northeastern Santa Barbara County, California. It is underlain conformably and interfingers with a dark mudstone that correlates with the Soda Lake Shale Member of the Vaqueros Formation; it is overlain conformably and interfingers with a brown shale that correlates with the Saltos Member of the Monterey Shale. Northeastern exposures along the north flank of the Sierra Madre are almost exclusively medium to coarse-grained, structureless sandstone with scattered pebbly conglomerate beds. Thickness ranges from zero in the southeastern part of the Sierra Madre to 70 m in the northeast, 75 m in the northwest, and 600 m in the central part of the range. Toward the southwest in the Hurricane Deck area of the San Rafael Mountains, the unit becomes thicker and more extensively interbedded with mudstone. Lithology of the unit consists of 0.3-3.5 m thick beds of medium to coarse-grained, structureless to vaguely graded sandstone with scoured contacts at the base. Sandstone beds 0.3-3.0 m thick, which are more distinctly graded from coarse to very fine are also present. The interbedded mudstone commonly is bioturbated, so bedding is indistinct. Thickness ranges from 1020 m in the central part of the area to 750 m toward the southwest and 92 m toward the northwest. The unit most likely represents deposition in a submarine-canyon and fan complex that had its channel head in the northeast and spread southwestward into a thick sequence of submarine-fan sandstone lobes, which were confined in a narrow west-trending trough.

Thomas, G.D.; Fritsche, A.E.; Condon, M.W.

1988-03-01

148

Experiments on Submarine Knickpoints  

NASA Astrophysics Data System (ADS)

The results of a laboratory study on the upstream migration of submarine knickpoints are presented. The main goal of this research was to obtain the formation of these features at laboratory scale. In order to achieve the objective, eight experiments using different materials were conducted in a flume at the Saint Anthony Falls Laboratory, University of Minnesota. The sediment used in these experiments was: kaolin clay, silica flour and fine sand. Silica flour and fine sand were used as single sediment in four experiments. The other four experiments consisted of a combination of the previous materials. The total sediment concentration in the experiments was 5% (one experiment) and 10% (seven experiments) by volume. The discharge ranged from 0.011 to 0.055 l/s. The experiment started with an initial slope in the channel bed of 15%. The bed deposit inside the flume was built up as the experiment progressed. Knickpoints were observed in six of the eight experiments. They were formed when one material or a combination of them was used in the tests. Initial calculations on the upstream migration velocity indicate values in the vicinity of 0.5 mm/s.

Toniolo, H.; Cantelli, A.

2004-12-01

149

Optical fiber submarine cable  

SciTech Connect

An optical fiber submarine cable, which is provided with at least one coated optical fiber, a power supplying, pressure resisting layer of a pipe-like configuration, a tension resisting wire layer formed of a conductive material of relatively low conductivity and disposed in close contact with the power supplying, pressure resisting layer of the pipe-like configuration, and an insulator layer disposed around the tension resisting wire layer. The power supplying, pressure resisting layer is formed as at least one inner layer and an outer layer. The inner layer is formed as a single layer or composite layers by forming a tape-like good conductor material into a pipe-like configuration with its joint made a mere butt, or by assembling together a plurality of pressure resisting material segments equally divided in the circumference direction for at least one layer of the inner layer and having housed the above-mentioned at least one coated optical fiber in an optical fiber housing space defined centrally of the inner layer. The outer layer is formed by winding a metal tape on the inner layer.

Nakai, T.; Ejiri, Y.; Furusawa, K.; Niiro, Y.; Nunokawa, M.; Sato, M.

1984-12-25

150

Morpho-structural setting of Stromboli volcano revealed by high-resolution bathymetry and backscatter data of its submarine portions  

NASA Astrophysics Data System (ADS)

The first high-resolution bathymetric and backscatter maps of offshore Stromboli Island are presented, together with an interpretation of its volcanic, structural and sedimentary features. The volcanic edifice is characterized by a sub-conical shape with a quasi-bilateral symmetry with respect to a NE-SW axis. The dimensions of the Strombolicchio volcanic centre, to the NE of Stromboli, have been restored by redrawing its morphology before wave action that eroded it in Late Quaternary time. On the NE submarine flank of Strombolicchio, a N64°E structural trend controls the shape of Strombolicchio Canyon. On the southern side of Stromboli, the submarine flank has a radial structural trend, possibly reflecting a volcanic stress regime. Landslide scars at various scales are ubiquitous on the submarine slopes of Stromboli. Repeated large-scale lateral collapses have affected both the northwestern and southeastern unbuttressed flanks of the volcano, producing large debris avalanche deposits.

Bosman, Alessandro; Chiocci, Francesco L.; Romagnoli, Claudia

2009-11-01

151

The bathypelagic community of Monterey Canyon  

NASA Astrophysics Data System (ADS)

We used a quiet, deep-diving remotely operated vehicle (ROV) to conduct oblique, quantitative video transects of the bathypelagic fauna at depths between 1000 and 3500 m at a site over the Monterey Submarine Canyon, in the eastern North Pacific off central California. Fifteen such dives were made over a two-year period. Analyses of the video data revealed a rich and diverse fauna dominated by gelatinous animals. In particular, the holopelagic polychaete Poeobius meseres was an important detritivore in the upper half of this depth range. As Poeobius abundance eventually declined with increasing depth, larvacean abundance increased. In contrast, the relative numbers of crustacean grazers, principally copepods and mysids, remained relatively constant with depth. Medusae were most abundant and most diverse among the gelatinous predators, which also included ctenophores, and siphonophores. Chaetognaths occurred chiefly in the upper half of the depth range. While there is considerable overlap, the bathypelagic fauna can be separated into upper (1000 to 2300 m) and lower (2400 to 3300 m) zones, as well as a distinct and populous benthic boundary layer. Within the overall bathypelagic community is a complex web of trophic links involving gelatinous predators that feed on both gelatinous and hard-bodied particle feeders, as well as on each other. The amount of organic carbon contained in this jelly web is substantial but its ecological fate is uncertain. The assessment of bathypelagic communities will be important for establishing baselines to conserve deep pelagic biodiversity within high-seas protected areas.

Robison, Bruce H.; Sherlock, Rob E.; Reisenbichler, Kim R.

2010-08-01

152

California State Waters Map Series--Hueneme Canyon and vicinity, California  

USGS Publications Warehouse

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California's State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow (to about 100 m) subsurface geology. The Hueneme Canyon and vicinity map area lies within the eastern Santa Barbara Channel region of the Southern California Bight. The area is part of the Western Transverse Ranges geologic province, which is north of the California Continental Borderland. Significant clockwise rotation - at least 90° - since the early Miocene has been proposed for the Western Transverse Ranges, and the region is presently undergoing north-south shortening. This geologically complex region forms a major biogeographic transition zone, separating the cold-temperate Oregonian province north of Point Conception from the warm-temperate California province to the south. The map area, which is offshore of the Oxnard plain and west of and along the trend of the south flank of the Santa Monica Mountains, lies at the east end of the Santa Barbara littoral cell, characterized by west-to-east littoral transport of sediment derived mainly from coastal watersheds. The Hueneme Canyon and vicinity map area in California's State Waters is characterized by two major physiographic features: (1) the nearshore continental shelf, and (2) the Hueneme and Mugu Submarine Canyon system, which, in the map area, includes Hueneme Canyon and parts of three smaller, unnamed headless canyons incised into the shelf southeast of Hueneme Canyon. The shelf is underlain by tens of meters of interbedded upper Quaternary shelf, estuarine, and fluvial deposits that formed as sea level fluctuated in the last several hundred thousand years. Hueneme Canyon extends about 15 km offshore from its canyon head near the dredged navigation channel of the Port of Hueneme. The canyon is relatively deep (about 150 m at the California's State Waters limit) and steep (canyon flanks as steep as 25° to 30°). Historically, Hueneme Canyon functioned as the eastern termination of the Santa Barbara littoral cell by trapping all eastward littoral drift, not only feeding the large Hueneme submarine fan but acting as the major conduit of sediment to the deep Santa Monica Basin; however, recent dredging programs needed to maintain Channel Islands Harbor and the Port of Hueneme have moved the nearshore sediment trapped by jetties and breakwaters to an area southeast of the Hueneme Canyon head. Seafloor habitats in the broad Santa Barbara Channel region consist of significant amounts of soft sediment and isolated areas of rocky habitat that support kelp-forest communities nearshore and rocky-reef communities in deep water. The potential marine benthic habitat types mapped in the Hueneme Canyon and vicinity map area are related directly to the geomorphology and sedimentary processes that are the result of its Quaternary geologic history. The two basic megahabitats in the map area are Shelf (continental shelf) and Flank (continental slope). The flat seafloor of the continental shelf in the Hueneme Canyon and vicinity map area is dynamic, as indicated by mobile sand sheets and coarser grained scour depressions. The active Hueneme Canyon provides considerable relief to the continental shelf in the map area, and its irregular morphology of eroded walls, landslide scarps, and deposits and gullies provide promising habitat for groundfish, crabs, shrimp, and other marine benthic organisms. Most invertebrates observed in the map area durin

Johnson, Samuel Y.; Dartnell, Peter; Cochrane, Guy R.; Golden, Nadine E.; Phillips, Eleyne L.; Ritchie, Andrew C.; Kvitek, Rikk G.; Greene, H. Gary; Krigsman, Lisa M.; Endris, Charles A.; Clahan, Kevin B.; Sliter, Ray W.; Wong, Florence L.; Yoklavich, Mary M.; Normark, William R.; edited by Johnson, Samuel Y.

2012-01-01

153

Initial waves from submarine landslides  

Microsoft Academic Search

Modeling tsunamis generated by submarine mass failure is not as well understood as waves generated by seismic displacements. Co-seismic deformation occurs very rapidly even in comparison with the shallow-water wave speed, allowing for a specification of the displacement of the sea surface to be set as identical to the deformation of the ocean floor, as initial conditions for computer modeling.

R. Weiss; C. Synolakis

2009-01-01

154

Initial waves from submarine landslides  

Microsoft Academic Search

Modeling tsunamis generated by submarine mass failure is not as well understood as waves generated by seismic displacements. Co-seismic deformation occurs very rapidly even in comparison with the shallow-water wave speed, allowing for a specification of the displacement of the sea surface to be set as identical to the deformation of the ocean floor, as initial conditions for computer modeling.

R. Weiss; C. E. Synolakis; J. A. O'Shay

2010-01-01

155

Submarine Tanker Concepts and Problems.  

National Technical Information Service (NTIS)

The National energy crisis of the U.S. can be responded to and diminished by the use of the large deposits of oil in the Arctic. This study discusses the use of nuclear powered submarine tankers for the transportation of oil from the Arctic regions. The a...

P. Moloney

1974-01-01

156

Human powered submarine propeller design  

Microsoft Academic Search

While all parts of a submarine contribute to its overall performance, the propeller blade design is often neglected due to the difficulties in analyzing the impact in design changes combined with a lack of previous research in blade designs for the power and speed requirements as dictated by a human powered vehicle. To aid us in the design of our

B. Ellis; D. Wacholder

2003-01-01

157

Wind and topographic effects on the Labrador Current at Carson Canyon  

NASA Astrophysics Data System (ADS)

We present results from an experimental investigation of the interaction between a shelf break jet and a submarine canyon and of the response of this system to a single upwelling favorable wind event. The field site was Carson Canyon, located at the edge of the Grand Bank of Newfoundland. The shelf break jet is the Labrador Current. The time-averaged current measurements indicate that the interaction between the Labrador Current and the canyon topography is nonlinear and that the mean current crosses isobaths to flow into the canyon on the upstream side but is steered off shelf on the downstream side. The mean flow vorticity balance in the near field and far field is examined, using a two-layer model with the lower layer at rest. In the far field we obtain an interesting result which suggests that the cross-stream shear in combination with bottom friction can drive a significant on-shelf flow. This flow is equivalent to a volume transport of about 60 m3 s-1 per 100 m of along-shelf distance, which is comparable to typical wind-driven Ekman transports on and off continental shelves and which appears to have important implications for the on-off-shelf transport of icebergs in the Grand Banks region. In the near field the Rossby number is of order unity and bottom friction is less important. Many of the observed flow properties can be explained qualitatively in terms of an upstream inertial boundary layer and potential vorticity conservation. The time-dependent response to upwelling favorable winds was registered by current meters in the canyon and at the shelf break at the canyon perimeter. These observations indicate an amplified upwelling response at the shelf break and vertical ascent rates within the canyon of about 0.7 cm s-1.

Kinsella, E. Douglas; Hay, Alex E.; Denner, Warren W.

1987-09-01

158

Calcareous nannoplankton and benthic foraminiferal assemblages from the Nazaré Canyon (Portuguese continental margin): Preliminary results  

NASA Astrophysics Data System (ADS)

Submarine canyons are assumed to play an important role in oceanic/neritic circulation, marine productivity and sedimentary processes, acting as preferential conduits between the littoral and deep oceanic domain. Here we present first results of a comparative micropalaeontological study on calcareous nannoplankton and benthic foraminifera from surface sediments from the surroundings of the upper Nazaré Canyon (Portuguese continental margin) and from the shelf north of the canyon. Regardless of the difficulty to distinguish taphonomical from (palaeo)ecological effects in such a complex and still poorly known marine system, the first results suggest that the canyon's hydro-sedimentary dynamic regime act as a prolongation of the shore/inner shelf hydrodynamic conditions towards west, preventing deposition and/or preservation of the smaller and fragile species of calcareous nannoplankton (e.g. E. huxleyi and G. ericsonii) and enhancing the record of the larger and more opportunistic ones (e.g. G. oceanica); and disturbing benthic foraminiferal productivity and/or diversity, or their preservation in the fossil record. Both calcareous nannoplankton and benthic foraminifera are more abundant off the canyon's domain, suggesting that its highly energetic thalweg conditions are probably filtering the fossil record in the sediment. Still, preliminary results suggest that the occurrence of persistent physical phenomena related with the canyon's morphology and proximity to the coast (e.g. solitary internal waves) may be locally promoting favourable conditions for calcareous nannoplankton, as shown by high values of nannoliths, chlorophyll a and 19' hexanoyloxyfucoxantine (unpublished data) north of the canyon's head. It is our goal to test this hypothesis in the near future by (a) studying multicore and surficial sediments from more recent surveys, and (b) calibrating the sediment results with water column data presently in process at the Institute of Oceanography (IO).

Guerreiro, C.; Rosa, F.; Oliveira, A.; Cachão, M.; Fatela, F.; Rodrigues, A.

2009-01-01

159

Simulation of submarine hovering based on PID control  

Microsoft Academic Search

The underwater hovering of submarine is a nonlinear process, which changes with the submarine state and navigation condition. Analysis is made on motion characters, realizing conditions and disturbing factors for submarine. The submarine hovering mathematic model is established, as well as the disturbing force. PID control is used to simulate submarine hovering, which provides the technical support.

Xiong Ying; Xu Jian

2010-01-01

160

Submarine structure of Reunion Island (Indian Ocean) inferred from gravity  

NASA Astrophysics Data System (ADS)

La Reunion is a large (diameter: 220 km; height: 7 km), mostly immerged (97%) oceanic volcanic system. New land and marine gravity data are used to study the structure of its submarine part. The gravity models are interpreted jointly with the published geology interpretations and compared with magnetic models. This allows us to derive a new model of the shallow and internal structure of the submarine flanks. Recent cruises have collected high quality gravity, magnetic and multi-beam swath bathymetry data over the submarine flanks of La Réunion and the surrounding oceanic plate. A new Bouguer anomaly map has been computed for a reduction density of 2.67.103 kg m-3. A magnetic anomalies map covering the same area has been also built. Studies based on bathymetric and acoustic data have previously shown the presence of different types of submarine features: a coastal shelf, huge bulges built by debris avalanches and sediment deposits, erosion canyons, volcanic constructions near the coast, isolated seamounts offshore, and elongate volcanic ridges on the Mascarene plate. On the new Bouguer anomaly map, all these features are associated with negative anomalies. They have been modeled using 2 3/4 D modeling techniques. The short wavelength anomalies over the coastal shelf area can be explained by piles of low density layers. This suggests that they are mostly built by hyaloclastites which are generally characterized by lower densities than lava flows. The voluminous debris avalanche deposits which formed the huge Submarine Bulges to the east, north, west, and south of the island have also been modeled as low density formations. Each bulge is modeled with an overall density less than 2.67.103 kg m-3, in order to account for its long wavelength anomaly. Some shorter wavelength features are superimposed on these long wavelength negative anomalies. They probably represent heterogeneities within the bulges. Some shallow ones can be associated with observed surface geological features such as secondary landslide deposits or sedimentary areas. The interpretation of the negative short wavelength gravity anomalies associated with the seamounts and the volcanic ridges is less simple. Available data indicate that they are more likely built by lava flows than by low density pyroclastites or breccias. The observed negative anomalies can be accounted for if we consider an isostatic compensation of the surface constructions. Finally, a joint analysis of the gravity and magnetic anomalies allows us to refine the structural models of particular areas. Reversely magnetized formations near the seashore can be associated with volcanic constructions. Conversely, the deeper submarine flanks are poorly magnetized. This is coherent with the interpretation of the bulges as piles of mass-wasting deposits. 3D models have been then calculated in order to provide a first insight of the internal structure of the Reunion complex submarine part.

Gailler, L.; Lénat, J.

2008-12-01

161

Grand Canyon Explorer: The Geology of the Grand Canyon  

NSDL National Science Digital Library

This site provides an overview of how the Grand Canyon was formed. Concepts discussed include erosion by water, ice and wind, continental drift, and deposition. A photo gallery and stratigraphic figures support the text.

Ribokas, Bob

162

New York Canyon Stimulation  

SciTech Connect

The New York Canyon Stimulation Project was to demonstrate the commercial application of Enhanced Geothermal System techniques in Buena Vista Valley area of Pershing County, Nevada. From October 2009 to early 2012, TGP Development Company aggressively implemented Phase I of Pre-Stimulation and Site/Wellbore readiness. This included: geological studies; water studies and analyses and procurement of initial permits for drilling. Oversubscription of water rights and lack of water needed for implementation of EGS were identified and remained primary obstacles. Despite extended efforts to find alternative solutions, the water supply circumstances could not be overcome and led TGP to determine a "����No Go"��� decision and initiate project termination in April 2012.

Raemy, B. Principal Investigator, TGP Development Company, LLC Kulikowski Tan, A Subcontractor, AKT Consulting Inc. LLC

2012-06-21

163

John Wesley Powell, Canyon Geologist.  

National Technical Information Service (NTIS)

Relives parts of John Wesley Powell's pioneering exploration through the Grand Canyon in 1869. Visits scenes of Powell's early exploits. Explains the geologic features he encountered. Tells, with excerpts from his diary, of the ordeals sustained during th...

1994-01-01

164

Submarines, spacecraft and exhaled breath.  

PubMed

Foreword The International Association of Breath Research (IABR) meetings are an eclectic gathering of researchers in the medical, environmental and instrumentation fields; our focus is on human health as assessed by the measurement and interpretation of trace chemicals in human exhaled breath. What may have escaped our notice is a complementary field of research that explores the creation and maintenance of artificial atmospheres practised by the submarine air monitoring and air purification (SAMAP) community. SAMAP is comprised of manufacturers, researchers and medical professionals dealing with the engineering and instrumentation to support human life in submarines and spacecraft (including shuttlecraft and manned rockets, high-altitude aircraft, and the International Space Station (ISS)). Here, the immediate concerns are short-term survival and long-term health in fairly confined environments where one cannot simply 'open the window' for fresh air. As such, one of the main concerns is air monitoring and the main sources of contamination are CO(2) and other constituents of human exhaled breath. Since the inaugural meeting in 1994 in Adelaide, Australia, SAMAP meetings have been held every two or three years alternating between the North American and European continents. The meetings are organized by Dr Wally Mazurek (a member of IABR) of the Defense Systems Technology Organization (DSTO) of Australia, and individual meetings are co-hosted by the navies of the countries in which they are held. An overriding focus at SAMAP is life support (oxygen availability and carbon dioxide removal). Certainly, other air constituents are also important; for example, the closed environment of a submarine or the ISS can build up contaminants from consumer products, cooking, refrigeration, accidental fires, propulsion and atmosphere maintenance. However, the most immediate concern is sustaining human metabolism: removing exhaled CO(2) and replacing metabolized O(2). Another important concern is a suite of products from chemical reactions among oxidizing compounds with biological chemicals such as amines, thiols and carbonyls. SAMAP Meeting We (Armin and Joachim) attended the 2011 SAMAP conference in Taranto, Italy (10-14 October), which occurred just a few weeks after the IABR meeting in Parma, Italy (11-15 September 2011). It was held at the Officers' Club of the Taranto Naval Base under the patronage of the Italian navy; the local host was Lucio Ricciardi of the University of Insubria, Varese, Italy. At the 2011 SAMAP meeting, the theme was air-independent propulsion (AIP), meaning the capability of recharging the main batteries of the submarine without the need to surface. Only a few navies (e.g. US, UK, France, Russia, China) have historically had this capability using nuclear-powered submarines that can function underwater for extended periods of time (months). Most navies operate submarines with conventional diesel-electric propulsion, wherein diesel-powered generators charge battery banks which then drive an electric motor connected to the propeller. The batteries are charged while the boat is on the surface or during snorkelling, when the boat is submerged a few meters below the surface and a snorkel tube is extended to the surface. The period between battery charges can vary from several hours to one or two days depending on the power requirements and the nature of the mission. The process is necessary for breathing air revitalization (flushing out accumulated contaminants) and for the operation of the diesel engines. However, during this period the submarine is vulnerable to detection. Since the 1940s there have been various attempts to develop a power generation system that is independent of external air (AIP). To this end hydrogen peroxide was initially used and later liquid oxygen (LOX). Currently, most AIP submarines use fuel cell technology (LOX and hydrogen) to supplement the conventional diesel-electric system in order to extend the underwater endurance to 2-3 weeks. These propulsion engineering changes also reduce per

Pleil, Joachim D; Hansel, Armin

2012-02-27

165

32 CFR 707.7 - Submarine identification light.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Submarine identification light. 707.7 Section 707.7 National Defense...WITH RESPECT TO ADDITIONAL STATION AND SIGNAL LIGHTS § 707.7 Submarine identification light. Submarines may display, as a...

2013-07-01

166

Initial waves from submarine landslides  

NASA Astrophysics Data System (ADS)

Modeling tsunamis generated by submarine mass failure is not as well understood as waves generated by seismic displacements. Co-seismic deformation occurs very rapidly even in comparison with the shallow-water wave speed, allowing for a specification of the displacement of the sea surface to be set as identical to the deformation of the ocean floor, as initial conditions for computer modeling. Submarine mass failure exhibits slower speeds and water gravitationally adjusts to a new potential field while the submarine mass is failing. Empirical formulae and computer models exist to calculate the one or two-dimensional surface waveform generated by underwater mass movements. For different empirical formulae, estimates vary over orders of magnitude for the same slide. We present the scatter from ten different empirical formulations for the leading wave amplitude for 19 different underwater landslides. Some of these formulations are based on modeling, some on analytical solutions, and some are based on experimental data. The scatter highlights that it is important to use higher order approximations of the Navier-Stokes equations to reliably and robustly compute the interaction between water surface and the deforming mass. We carry out modeling with iSALE, a hydrocode that numerically solves the compressible Navier-Stokes equations in a multi-material and multi-rheology framework, and present preliminary results for the leading wave height with varying rheologies to account for different slide materials. It appears that multi-material modeling is important in for understanding the hydrodynamics of tsunamis generated by submarine mass failures under geophysically realistic conditions.

Weiss, R.; Synolakis, C.

2009-12-01

167

Initial waves from submarine landslides  

NASA Astrophysics Data System (ADS)

Modeling tsunamis generated by submarine mass failure is not as well understood as waves generated by seismic displacements. Co-seismic deformation occurs very rapidly even in comparison with the shallow-water wave speed, allowing for a specification of the displacement of the sea surface to be set as identical to the deformation of the ocean floor, as initial conditions for computer modeling. Submarine mass failure exhibits slower speeds and water gravitationally adjusts to a new potential field while the submarine mass is failing. Empirical formulae and computer models exist to calculate the one or two-dimensional surface waveform generated by underwater mass movements. For different empirical formulae, estimates vary over orders of magnitude for the same slide. We present the scatter from ten different empirical formulations for the leading wave amplitude for 19 different underwater landslides. Some of these formulations are based on modeling, some on analytical solutions, and some are based on experimental data. The scatter highlights that it is important to use higher order approximations of the Navier-Stokes equations to reliably and robustly compute the interaction between water surface and the deforming mass. We carry out modeling with iSALE, a hydrocode that numerically solves the compressible Navier-Stokes equations in a multi-material and multi-rheology framework, and present preliminary results for the leading wave height with varying rheologies to account for different slide materials. It appears that multi-material modeling is important in for understanding the hydrodynamics of tsunamis generated by submarine mass failures under geophysically realistic conditions.

Weiss, R.; Synolakis, C. E.; O'Shay, J. A.

2010-12-01

168

Canyon Effects on Nearshore Infragravity Waves During NCEX  

NASA Astrophysics Data System (ADS)

Infragravity waves become increasingly important as the water depth gets shallower and wind generated waves become saturated due to wave breaking. Infragravity wave energy is composed of wave-group forced long waves and reflected leaky waves and trapped edge waves. Typically conditions on a approximately alongshore uniform beach are consisdered (e.g. Herbers et al., 1994, van Dongeren et al., 2003). Here we examine the alongshore variability in the infragravity conditions induced by nearby canyons utilizing a 2D-surfbeat model (Reniers et al., 2004). The model simulates the propagation of both leaky and trapped infragravity waves that are generated by directionally spread wave groups. Model computations are used to examine the potential reflection (Inman et al., 1976, Huntley et al., 1981) of shore-trapped edge waves from the canyon walls by considering various model-scenarios with and without the canyons. Computational results will be compared with observations of infragravity conditons obtained from an alongshore array of pressure and velocity meters situated just north of the canyon (MacMahan et al., 2004, this conference). References Herbers, T.H.C., Steve Elgar and R.T. Guza, 1994: Infragravity-frequency (0.005 0.05 Hz) motions on the shelf. Part 1: Forced waves. J. Phys. Oc., 25, 1063-1079. Huntley, D. A., R. T. Guza and E. B. Thornton, 1981, "Field Observations of Surf Beat: Part I, Progressive Edge Waves", J. Geophys. Res., 86, 6451-6466. Inman, D.L., C.E. Nordstrom and R.E. Flick, 1976: Currents in sub-marine canyons: An air-sea-land interaction, Ann. Rev. Fluid Mech., 8, 275-310. MacMahan, J., E.B. Thornton, A. Reniers and T.P. Stanton, 2004, The Torrey Pines Rip-currents, this conference. Reniers, A.J.H.M., E.B. Thornton and J.A. Roelvink, 2004: Morphodynamic modeling of an embayed beach under wave-group forcing, J. Geophys. Res., 109, C01030, doi:10.1029/2002JC001586. Van Dongeren, A.R., A.J.H.M. Reniers, J.A. Battjes and I.A. Svendsen, 2003, "Numerical modeling of infragravity wave response during Delilah." J. Geoph. Res, 108 (C9), 4-1-19

Reniers, A.; Macmahan, J.; Thornton, E.; Stanton, T.

2004-12-01

169

Evidence of bioturbation in the Cap-Ferret Canyon in the deep northeastern Atlantic  

NASA Astrophysics Data System (ADS)

In the sedimentary column, a combined quantification of burrows and macrobenthic community provides evidence of bioturbation features in the submarine canyon of Cap-Ferret between 2000 and 3000 m depth. An image-processing technique allows accurate quantification of burrow volumes with depth in the sedimentary column. The major bioturbation mode seems to be different in the channel compared to the interfluve. Macrobenthic activity is more inclined to mix the sediment in the channel in response to increased organic matter supplies. Sediment mixing leads to burrow destruction in the upper mixed layer of sediment in the canyon. Burrows are better preserved on the interfluve where mixing is slower. Under the mixed zone, the volume of recorded burrows is higher when sedimentation rate increases, as in the upper canyon. In this transition layer, the burrow volume is estimated to be between 3 and 64% of the total sediment volume depending on the sediment depth. The fill-down of numerous burrows with surface sediment by bioregeneration suggests that anaerobic degradation of fresh organic matter is dominant in this canyon. In the sedimentary column, the negative relationship between carbonate content and macrobenthic abundance confirms that carbonate dissolution is largely influenced by bioturbation.

Gerino, Magali; Stora, Georges; Weber, Olivier

1999-10-01

170

How Was the Grand Canyon Formed?  

NSDL National Science Digital Library

In this lesson students will learn about how the Grand Canyon was formed, focusing on the process of erosion. They will examine the canyon's rock layers to infer what the area looked like when the layers were created. Students will conclude by creating posters illustrating and describing what the Grand Canyon looks like today and what it looked in the past. Students will locate Arizona on a United States map and find the Grand Canyon. They will locate the Colorado River and trace its route from east to west through the canyon. Students will study a photograph of the Grand Canyon, brainstorm how the canyon was formed, and discuss their ideas. They will also view and discuss drawings of the Grand Canyon region as its various rock layers were deposited.

171

Submarine Maneuvers Prediction using Recursive Neural Networks  

Microsoft Academic Search

Recursive neural networks (RNNs) are a technique for developing time-dependent, nonlinear equation systems. In this paper, we applied RNN to simulate the maneuvers of submarine. The forces and moments acting on the body of submarine are functions of the motion state variables. Component force modules is developed to calculate five component forces as inputs to the recursive neural networks. These

Hassan Fahmy Hashem; Alexandria HighInstitute

2006-01-01

172

Research on Submarine Maneuverability of Flooded Compartment  

Microsoft Academic Search

The paper establishes the emergency recovery maneuver motion model. According to the characteristic of hydrodynamics coefficients on flooded submarine, attaining hydrodynamics coefficients of different angle of attack by limited ship model hydrodynamics experiment of large angle of attack. A sensitivity index is introduced to evaluate submarine's controllability. The experiment results are regressed to two kinds of hydrodynamic coefficients for big

Liu Hui; Pu Jinyun; Jin Tao

2009-01-01

173

Submarine landslides around the Canary Islands  

Microsoft Academic Search

The morphology and structure of the submarine flanks of the Canary Islands were mapped using the GLORIA long-range side-scan sonar system, bathymetric multibeam systems, and sediment echosounders. Twelve young (<2 Ma) giant landslides have been identified on the submarine flanks of the Canary Islands up to now. Older landslide events are long buried under a thick sediment cover due to

Sebastian Krastel; Hans-Ulrich Schmincke; Colin L. Jacobs; Roland Rihm; Timothy P. Le Bas; Bárbara Alibés

2001-01-01

174

Third World Submarine Threat - Another Great Equalizer.  

National Technical Information Service (NTIS)

This paper examines the growing submarine capability in the third world and the possible impact on the U.S. Navy's ability to execute its deterrence, sea control, and power projection missions in the near future. The effect of submarines on a naval force ...

F. C. Lawton

1991-01-01

175

Geology Fieldnotes: Grand Canyon National Park, Arizona  

NSDL National Science Digital Library

Visitors can access park geology information, photographs, related links, visitor information, multimedia resources, and resources for teaching geology with National Park examples. The park geology section discusses the Grand Canyon's geologic history, structural geology, and features a question-and-answer section about the canyon. The history of the canyon as a park and environmental issues surrounding it are also discussed. A geologic cross section of the canyon showing the various rock layers is included.

176

Submarine mass failures as tsunami sources: their climate control.  

PubMed

Recent research on submarine mass failures (SMFs) shows that they are a source of hazardous tsunamis, with the tsunami magnitude mainly dependent on water depth of failure, SMF volume and failure mechanism, cohesive slump or fragmental landslide. A major control on the mechanism of SMFs is the sediment type, together with its post-depositional alteration. The type of sediment, fine- or coarse-grained, its rate of deposition together with post-depositional processes may all be influenced by climate. Post-depositional processes, termed sediment 'preconditioning', are known to promote instability and failure. Climate may also control the triggering of SMFs, for example through earthquake loading or cyclic loading from storm waves or tides. Instantaneous triggering by other mechanisms such as fluid overpressuring and hydrate instability is controversial, but is here considered unlikely. However, these mechanisms are known to promote sediment instability. SMFs occur in numerous environments, including the open continental shelf, submarine canyon/fan systems, fjords, active river deltas and convergent margins. In all these environments there is a latitudinal variation in the scale of SMFs. The database is limited, but the greatest climate influence appears to be in high latitudes where glacial/interglacial cyclicity has considerable control on sedimentation, preconditioning and triggering. Consideration of the different types of SMFs in the context of their climate controls provides additional insight into their potential hazard in sourcing tsunamis. For example, in the Atlantic, where SMFs are common, the tsunami hazard under the present-day climate may not be as great as their common occurrence suggests. PMID:20403835

Tappin, D R

2010-05-28

177

Seven years of geomorphic change in the head of Monterey Canyon, CA: Steady state equilibrium or monotonic change?  

NASA Astrophysics Data System (ADS)

The head of Monterey submarine canyon has been surveyed with high-precision multibeam sonar at least once each year since September 2002. This poster provides a summary of changes between September 2002 and September 2008. Data were collected with a variety of Reson mulitbeam sonar heads, and logged with an ISIS data acquisition system. Vessel attitude was corrected using an Applanix POS MV equipped with an auxillary C-Nav 2050 GPS receiver. Data were processed and filtered and cleaned in Caris HIPS. Depth changes for various time spans were determined through raster subtraction of pairs of 3-m resolution bathymetric grids in ArcMap. The depth change analyses focused on the canyon floor, except where a landslide occurred on a wall, and where obvious gullying near the headwall had occurred during the time of our study. Canyon walls were generally excluded from analysis. The analysis area was 1,414,240 sq meters. The gross changes between 2002 and 2008 include net erosion of 2,300,000 m^3 +/- 800,000 m^3 of material from the canyon. The annualized rate of net sediment loss from this time frame agrees within an order of magnitude with our previously published estimates from earlier (shorter) time frames, so the erosion events seem to be moderate magnitude and frequent, rather than infrequent and catastrophic. The greatest sediment loss appears to be from lateral erosion of channel-bounding terraces rather than deepening or scouring of the existing channel axis. A single landslide event that occurred in summer 2003 had an initial slide scar (void) volume of 71,000 m^3. The scar was observed to increase annually, and had grown to approximately 96,000 m^3 by 2008. The initial slide was too small to be tsunamigenic. In contrast to the monotonic canyon axis widening, the shoreward terminus of the canyon (canyon lip) appears to be in steady state equilibrium with sediment supply entering the canyon from the littoral zone. The lip position, indicated by the clearly defined shelf/slope break, typically oscillates offshore and onshore about 20 m to 30 m annually, but a 50 m change was measured. This oscillation likely represents cycles of sediment wedge progradation followed by slope failure and shoreward lip retreat. At this time, it appears that buildings along Moss Landing strand are not at risk from net shoreward canyon growth. The canyon appears to be excavating material that was previously stored in the canyon during an era when sediment supply outcompeted submarine transport processes. Published ages and pollen analyses from the canyon walls indicate that an enormous volume of sediment entered the canyon in post-European settlement time, with up to 1.6 m of sediment drape occurring after 1945 (presence of trace DDT). Likewise, 1930’s-era bathymetric charts indicate that major depositional features now located in the canyon were not present in the 1930’s, again suggesting a very young age for the deposits now being excavated from the canyon. One possible source of the young deposits is the construction of nearby Moss Landing Harbor in 1946, which has led to very high erosion rates in adjacent Elkhorn Slough.

Smith, D. P.; Kvitek, R. G.; Ross, E.; Iampietro, P.; Paull, C. K.; Sandersfeld, M.

2010-12-01

178

Academy of the Canyons Report, Fall 2002.  

ERIC Educational Resources Information Center

This report analyzes the Academy of the Canyons (AOC) program at College of the Canyons (COC), California. AOC, a middle college high school, is a collaboration between the William S. Hart High School District and College of the Canyons. The program is designed to provide a supportive, flexible, and academically enriched environment for students…

Meuschke, Daylene M.; Gribbons, Barry C.

179

Sustaining U.S. Nuclear Submarine Design Capabilities. Executive Summary.  

National Technical Information Service (NTIS)

The U.S. submarine eet currently numbers more than 50 fast attack submarines (SSNs) and 18 submarines built to launch ballistic missiles (SSBNs). All are nuclear powered to maximize the duration and speed of underwater operations. While the submarine eet ...

J. Riposo J. F. Schank K. Curry M. V. Arena P. DeLuca

2007-01-01

180

Thomas Moran: "The Grand Canyon."  

ERIC Educational Resources Information Center

Presents a lesson plan for introducing students in grades four through six to Thomas Moran's painting, "The Grand Canyon." The goal of the lesson is to illustrate the importance of the American West as a subject for artists in the nineteenth century. (JDH)

Brubaker, Ann

1986-01-01

181

Active tectonic morphology and submarine deformation of the northern Gulf of Eilat/Aqaba from analyses of multibeam data  

NASA Astrophysics Data System (ADS)

A high-resolution marine geophysical study was conducted during October-November 2006 in the northern Gulf of Aqaba/Eilat, providing the first multibeam imaging of the seafloor across the entire gulf head spanning both Israeli and Jordanian territorial waters. Analyses of the seafloor morphology show that the gulf head can be subdivided into the Eilat and Aqaba subbasins separated by the north-south-trending Ayla high. The Aqaba submarine basin appears starved of sediment supply, apparently causing erosion and a landward retreat of the shelf edge. Along the eastern border of this subbasin, the shelf is largely absent and its margin is influenced by the Aqaba Fault zone that forms a steep slope partially covered by sedimentary fan deltas from the adjacent ephemeral drainages. The Eilat subbasin, west of the Ayla high, receives a large amount of sediment derived from the extensive drainage basins of the Arava Valley (Wadi ’Arabah) and Yutim River to the north-northeast. These sediments and those entering from canyons on the south-western border of this subbasin are transported to the deep basin by turbidity currents and gravity slides, forming the Arava submarine fan. Large detached blocks and collapsed walls of submarine canyons and the western gulf margin indicate that mass wasting may be triggered by seismic activity. Seafloor lineaments defined by slope gradient analyses suggest that the Eilat Canyon and the boundaries of the Ayla high align along north- to northwest-striking fault systems—the Evrona Fault zone to the west and the Ayla Fault zone to the east. The shelf-slope break that lies along the 100 m isobath in the Eilat subbasin, and shallower (70-80 m isobaths) in the Aqaba subbasin, is offset by approx. 150 m along the eastern edge of the Ayla high. This offset might be the result of horizontal and vertical movements along what we call the Ayla Fault on the east side of the structure. Remnants of two marine terraces at 100 m and approx. 150 m water depths line the southwest margin of the gulf. These terraces are truncated by faulting along their northern end. Fossil coral reefs, which have a similar morphological appearance to the present-day, basin margin reefs, crop out along these deeper submarine terraces and along the shelf-slope break. One fossil reef is exposed on the shelf across the Ayla high at about 60-63 m water depth but is either covered or eroded in the adjacent subbasins. The offshore extension of the Evrona Fault offsets a fossil reef along the shelf and extends south of the canyon to linear fractures on the deep basin floor.

Tibor, Gideon; Niemi, Tina M.; Ben-Avraham, Zvi; Al-Zoubi, Abdallah; Sade, Ronnie A.; Hall, John K.; Hartman, Gal; Akawi, Emad; Abueladas, Abdelrahmem; Al-Ruzouq, Rami

2010-12-01

182

Numerical simulation of tsunami waves generated by deformable submarine landslides  

NASA Astrophysics Data System (ADS)

This paper presents a new submarine landslide model based on the non-hydrostatic wave model NHWAVE of Ma et al. (2012). The landslide is modeled as a water-sediment mixture. The dense plume is driven by baroclinic pressure forcing introduced by spatial density variations. The model is validated using laboratory measurements of turbidity currents and of water wave generation by a granular landslide. The model is then utilized to study the dependence of landslide motion and associated tsunami wave generation on parameters including sediment settling velocity, initial depth of the landslide and slide density. Model results show that the slide motion and water waves which it generates are both sensitive to these parameters. The relative tsunamigenic response to rigid and deformable landslides of equal initial geometry and density is also examined. It is found that the wave energy is mostly concentrated on a narrow band of the dominant slide direction for the waves generated by rigid landslides, while directional spreading is more significant for waves generated by deformable landslides. The deformable landslide has larger speed and acceleration at the early stage of landslide, resulting in larger surface waves. The numerical results indicate that the model is capable of reasonably simulating tsunami wave generation by submarine landslides.

Ma, Gangfeng; Kirby, James T.; Shi, Fengyan

2013-09-01

183

Is submarine groundwater discharge predictable?  

NASA Astrophysics Data System (ADS)

The contribution of submarine groundwater discharge (SGD) to the total hydrological discharges to the sea may be large but has been difficult to quantify. We have tested the applicability and generality of a suggested linear relationship between annual average total SGD and its fresh groundwater component against various SGD simulation results and field data. This relationship is found to constitute a general attractor for hydrologically simulated and directly measured SGD values across a wide range of conditions and world regions. But these consistent SGD quantifications differ systematically and largely from indirect SGD interpretations of tracers in seawater. This is an essential gap between inland- and sea-based methods of SGD estimation that needs to be bridged.

Prieto, Carmen; Destouni, Georgia

2011-01-01

184

Submarine landslides in Spitsbergen fjords  

NASA Astrophysics Data System (ADS)

Fjords are areas that can be exposed to repeated submarine mass wasting, and more than 50% of the depositional sequences can be reworked occasionally. The largest and most frequent slope failures occur typically in relation to the advance and retreat of grounded ice. However, also areas not directly affected by ice can be exposed to slope failure. We provide an overview of mass-transport deposits (MTDs) from the Isfjorden fjord system, the largest fjord system on Spitsbergen. We discuss pre-conditioning factors, trigger mechanisms and the potential of MTDs as indicators for the activity of tidewater and terrestrial glaciers. Slides, slumps, debris-flow deposits and turbidites have been observed. We distinguish three 'types' of MTDs: 1) 'Glacigenic MTDs', including muddy debris-flow lobes, as well as thin sandy MTDs deposited in front of or beneath glaciers; 2) 'Fluvial MTDs', including sandy turbidites and other MTDs originating from slope failures beyond river mouths; 3) 'Other MTDs', i.e. deposits related to failures on slopes that are neither supplied with sediments from glaciers nor from rivers. Such deposits include sediment lobes (debris flows or slumps) and slides. The available data indicate that mass wasting in the Isfjorden area commenced shortly after the deglaciation of the mouth of the trunk fjord around 14,100 cal. years BP. The most frequent pre-conditioning factors and trigger mechanisms are probably high sediment supply and earthquakes related to isostatic adjustments. However, marked changes in the slope gradient (related to bedrock or moraine ridges) also affect the stability of the fronts of tidewater glaciers and the positions of grounding lines, thus influencing the locations of sediment sources and, in consequence, the distribution of glacigenic MTDs. In addition to providing information about the dynamics of marine-terminating glaciers, submarine MTDs occasionally also provide information about the dynamics of terrestrial glaciers during the Holocene.

Forwick, M.; Vorren, T. O.

2012-04-01

185

CHALLENGES POSED BY RETIRED RUSSIAN NUCLEAR SUBMARINES  

SciTech Connect

The purpose of this paper is to provide an overview of the challenges posed by retired Russian nuclear submarines, review current U.S. and International efforts and provide an assessment of the success of these efforts.

Rudolph, Dieter; Kroken, Ingjerd; Latyshev, Eduard; Griffith, Andrew

2003-02-27

186

Improved Submarine Deployed Sea-State Sensor.  

National Technical Information Service (NTIS)

The invention relates generally to the field of electronic sensing devices, and more particularly to sensors for sensing selected conditions on an ocean surface. The invention specifically provides a sensor which may be deployed by a submarine or other su...

D. Shonting J. R. Knox

1996-01-01

187

Submarine Deployed Sea-State Sensor.  

National Technical Information Service (NTIS)

A submarine deployed sea state sensor comprises an elongated housing having a nose cone and an aft end, the housing having a forward buoyant chamber for receiving an accelerometer. Aft of the buoyant chamber, a damping assembly communication link deployme...

D. H. Shonting

1996-01-01

188

Crisis stability of a submarine deterrent.  

National Technical Information Service (NTIS)

Without defenses, stability indices fall monotonically as the number of submarine-launched ballistic missiles (SLBMs) is reduced. For few SLBMs, the favorable stability properties of the survivable SLBMs are masked by the unfavorable stability properties ...

G. H. Canavan

1992-01-01

189

Seismic reflections associated with submarine gas hydrates.  

National Technical Information Service (NTIS)

Gas hydrates are often suggested as a future energy resource. This doctoral thesis improves the understanding of the concentration and distribution of natural submarine gas hydrates. The presence of these hydrates are commonly inferred from strong bottom ...

K. Andreassen

1995-01-01

190

Eyecup Assembly for a Submarine Periscope.  

National Technical Information Service (NTIS)

An eyecup assembly for a submarine periscope blinder assembly includes an annularly-shaped ring having a multiplicity of holes, which are unthreaded, extending therethrough and adapted to receive screws for securing the eyecup assembly to a like multiplic...

W. C. Macieiewski R. Sayegh

2000-01-01

191

Personality characteristics of successful Navy submarine personnel.  

PubMed

This study evaluated the personality characteristics of senior enlisted and occupationally successful Navy submarine personnel. One hundred subjects completed the Schedule for Nonadaptive and Adaptive Personality (SNAP). Results indicated that the traits of detachment, propriety, and workaholism were most descriptive of the sample. Thirty-seven percent met SNAP criteria for a personality disorder, typically antisocial, obsessive-compulsive, or avoidant. The results are discussed in terms of adaptation to environmental demands aboard submarines. Suggestions for further research are offered. PMID:8935516

Moes, G S; Lall, R; Johnson, W B

1996-04-01

192

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

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 development of a continuous channel accompanied by levee growth across the lobe. In the final stage, the channel-levee system becomes inactive either through destruction by mass wasting, infilling of the channel, or loss of the major sediment source. ?? 1987.

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

1987-01-01

193

Restoration of Bighorn Sheep to Hells Canyon: The Hells Canyon Initiative.  

National Technical Information Service (NTIS)

The Hells Canyon Initiative is a state, federal, and private partnership to restore Rocky Mountain bighorn sheep (Ovis canadensis canadensis) in the Hells Canyon area of Oregon, Idaho, and Washington. This plan describes project goals and objectives, the ...

F. Cassirer J. Beecham V. Coggins D. Whittaker P. Fowler R. Johnson K. Martin T. Schommer E. Taylor A. Thomas

1997-01-01

194

Hydraulic Jumps, Cyclic Steps and Scour Formation in an Active Submarine Channel  

NASA Astrophysics Data System (ADS)

Field scale submarine channel gravity currents are notoriously difficult to measure and thus directly investigate due to their inaccessible location and infrequent nature, which is compounded by present sea-level high-stand. An exception to this is the almost continuous density-driven current that results from the inflow of saline Mediterranean water, via the Bosporus strait, into the Black Sea. This flow has carved a sinuous channel system in water depths of 70 to 120 m containing a series of prominent scours at the upstream end. Despite being driven by the salinity contrast, the flow is sufficiently energetic to transport and rework coarse sand within the channel network. The relatively shallow depths of the channel and the continuous nature of this current provide a unique opportunity to study three-dimensional flow dynamics and the interaction of the flow with a seafloor channel network. Thus, it provides a rare analogue for channelized dilute sediment-laden turbidity currents. There has been speculation for nearly half a century that hydraulic jumps are an important process in submarine density currents. Hydraulic jumps have been implicated in causing the development of submarine fans, large scale (km-scale) scouring, the formation of cyclic steps and channel genesis. However, until now this has been inferred from a combination of small scale laboratory experiments and making inferences about flow processes from the geological record and modern bathymetry. Here we provide the first direct field evidence of hydraulic jumps and cyclic step formation in a density-driven current. The decrease in density due to entrainment of fluid across the jump is negligible compared to entrainment into the supercritical flow prior to the jump. The largest hydraulic jump imaged corresponds to a 100 m scour in the seafloor, with which it is in-phase. The decrease in velocity and thus bed shear stress across the jump is not as extreme as present models predict, and this suggests that hydraulic jumps need not lead to instantaneous deposition of submarine fans as density currents exit canyons as presently envisaged. Instead there is likely to be an area of erosion at the base of the canyon followed by fan deposition more distally.

Sumner, E. J.; Peakall, J.; Parsons, D. R.; Darby, S. E.; Dorrell, R. M.; Wynn, R.

2011-12-01

195

36 CFR 7.70 - Glen Canyon National Recreation Area.  

Code of Federal Regulations, 2010 CFR

...downstream to the eastern boundary of Grand Canyon National Park: (1) No...issued by the Superintendent of Grand Canyon National Park. The National... (i) The Superintendent of Grand Canyon National Park shall...

2010-07-01

196

36 CFR 7.70 - Glen Canyon National Recreation Area.  

Code of Federal Regulations, 2010 CFR

...downstream to the eastern boundary of Grand Canyon National Park: (1) No...issued by the Superintendent of Grand Canyon National Park. The National... (i) The Superintendent of Grand Canyon National Park shall...

2009-07-01

197

77 FR 9265 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Work Group AGENCY...SUMMARY: The Glen Canyon Dam Adaptive Management Work Group (AMWG...Secretary of the Interior concerning Glen Canyon Dam operations and other management...

2012-02-16

198

78 FR 7810 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Work Group AGENCY...SUMMARY: The Glen Canyon Dam Adaptive Management Work Group (AMWG...Secretary of the Interior concerning Glen Canyon Dam operations and other management...

2013-02-04

199

76 FR 24516 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Work Group AGENCY...SUMMARY: The Glen Canyon Dam Adaptive Management Work Group (AMWG...Secretary of the Interior concerning Glen Canyon Dam operations and other management...

2011-05-02

200

78 FR 21415 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Work Group AGENCY...SUMMARY: The Glen Canyon Dam Adaptive Management Work Group (AMWG...Secretary of the Interior concerning Glen Canyon Dam operations and other management...

2013-04-10

201

77 FR 22801 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Work Group AGENCY...SUMMARY: The Glen Canyon Dam Adaptive Management Work Group (AMWG...Secretary of the Interior concerning Glen Canyon Dam operations and other management...

2012-04-17

202

77 FR 43117 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Work Group AGENCY...SUMMARY: The Glen Canyon Dam Adaptive Management Work Group (AMWG...Secretary of the Interior concerning Glen Canyon Dam operations and other management...

2012-07-23

203

Survey of Interest, Canyon Country College of the Canyons Site, January 2001.  

ERIC Educational Resources Information Center

In the process of planning a new site to serve students in Canyon Country (California), the College of the Canyons (COC) in Santa Clarita surveyed students to assess their needs. Anonymous questionnaires were mailed to the homes of 1,000 randomly selected students who lived in Canyon Country and had attended COC in fall 2000 or spring 2001. Of the…

Dixon, P. Scott; Gribbons, Barry C.

204

Modeling and Understanding Remotely Forced Rip Current Systems at the Nearshore Canyon Experiment (NCEX)  

NASA Astrophysics Data System (ADS)

Evaluation of data collected during the Nearshore Canyon Experiment, has shown that our time-dependent circulation model (OK-Model; Özkan-Haller and Kirby, JGR, 1999), forced using radiation stress gradients derived from spectral wave models, can predict the spatial location of large offshore directed flows (rip currents). The locations of these transient rip currents, which are not controlled by the local nearshore bathymetry, are visible in remote sensing time exposure and variance images due to the advection of foam on the water surface (Eos Trans. AGU, 84(46), Ocean Sci. Meet. Suppl., Abstract OS21I-04, 2003). Further investigation has indicated that optical measurements of circulation patterns coincide with the numerical predictions. With this validation, the numerical models are being used to evaluate the sensitivity of the dynamic rip current system at the NCEX site to changes in wave conditions and nearshore bathymetry. Additionally, the walls of the offshore submarine canyon contain an undulating pattern that may be important in generating small-scale variations in waveheight, thereby driving rip currents where the water surface is at a local minimum, even in regions where the wave height is generally high. Theoretical tests using bottom boundaries with anomalies in intermediate and deep water are being performed to determine the effect these offshore contours can have in dictating nearshore circulation patterns. These results will provide insight regarding the role of patterns along canyon walls in prescribing the spatial location of the rip currents.

Long, J. W.; Özkan-Haller, H. T.; Holman, R. A.

2004-12-01

205

Narrow complex (supraventricular) tachycardias  

Microsoft Academic Search

Patients experiencing a narrow complex tachycardia are usually at a lower risk than those in whom a broad complex tachycardia occurs. Therefore, in the UK cardiologists are frequently involved in broad complex dysrhythmias at an early stage, while general physicians and general practitioners will often have greater involvement in the management of patients with narrow complex arrhythmias. We describe the

N W F Linton; S W Dubrey

2009-01-01

206

Export of terrigenous organic carbon along submarine canyons driven by dense shelf water cascading  

Microsoft Academic Search

At current highstand in sea level, shelves are considered major sites of terrigenous organic carbon (OCterr) accumulation with relatively little connectivity to the ocean interior. In recent years, the process of dense water cascading from the continental shelf, which occurs in numerous places around the world, has been suggested as carrier for OCterr to the deep ocean. The land-locked Mediterranean

T. Tesi; P. Puig; M. Goni; M. Canals; L. Langone; A. Palanques; S. Miserocchi; S. Heussner; F. Trincardi; A. Calafat; M. Turchetto; J. Fabres; X. Durrieu de Madron; A. Boldrin

2008-01-01

207

Submarine groundwater discharge into the near-shore zone of the Great Barrier Reef, Australia.  

PubMed

Along the tropical coastline of the Great Barrier Reef (GBR) region, little is known to date about submarine groundwater discharge (SGD) into the near-shore ocean. In an oceanographic sense, SGD consists of freshwater flow from land as well as seawater circulated through sediments. Recent radiochemical and geophysical studies, using the tracer (222)Rn and apparent ground conductivity respectively, provide evidence for SGD to occur in a variety of hydrogeological settings. In this paper, a non-quantitative overview of different settings of SGD in the region is presented: (1) recirculation of seawater through animal burrows in mangrove forests, (2) freshwater SGD from unconfined aquifers as a narrow coastal fringe of freshwater along Wet Tropics beaches, (3) SGD from coastal dune systems in form of localised freshwater springs in the intertidal zone, (4) inner-shelf SGD from confined submarine aquifer systems comprised of riverine paleochannels incised into the shelf. PMID:15757707

Stieglitz, Thomas

2004-12-09

208

Open Architecture Framework for Improved Early Stage Submarine Design.  

National Technical Information Service (NTIS)

Could transparency between current disparate methods improve efficiency in early stage submarine design. Does the lack of transparency between current design methods hinder the effectiveness of early stage submarine design. This thesis proposes that coord...

E. A. Sewell

2010-01-01

209

Exercise Aboard Attack Submarines: Rationale and New Options.  

National Technical Information Service (NTIS)

Substantial scientific evidence supports the potential benefits of exercise for submariners: regular exercise improves many human functions that directly apply to submarine operations. These benefits include improved alertness, cognitive function, immune ...

D. E. Watenpaugh A. J. Quatroche J. Bertoline D. M. Fothergill

2004-01-01

210

Mathematical modelling of submarine landslide motion  

NASA Astrophysics Data System (ADS)

Mathematical modelling of submarine landslide motion The paper presents a mathematical model to calculate dynamic parameters of a submarine landslide. The problem of estimation possible submarine landslides dynamic parameters and run-out distances as well as their effect on submarine structures becomes more and more actual because they can have significant impacts on infrastructure such as the rupture of submarine cables and pipelines, damage to offshore drilling platforms, cause a tsunami. In this paper a landslide is considered as a viscoplastic flow and is described by continuum mechanics equations, averaged over the flow depth. The model takes into account friction at the bottom and at the landslide-water boundary, as well as the involvement of bottom material in motion. A software was created and series of test calculations were performed. Calculations permitted to estimate the contribution of various model coefficients and initial conditions. Motion down inclined bottom was studied both for constant and variable slope angle. Examples of typical distributions of the flow velocity, thickness and density along the landslide body at different stages of motion are given.

Burminskij, A.

2012-04-01

211

Turbidity events observed in situ along the Congo submarine channel  

NASA Astrophysics Data System (ADS)

As part of the multidisciplinary programme BIOZAIRE devoted to studying deep-sea benthic ecosystems in the Gulf of Guinea, particulate input and its relationship with near-bottom hydrodynamics were monitored using long-term moorings from 2000 to early 2005. Particular attention was given to material input through the Congo (ex-Zaïre) submarine channel that extends 760 km from the Congo River mouth to the abyssal plain (>5100 m) near 6°S. Due to its direct connection to the Congo River, the Congo canyon and channel system are characterised by particularly active recent sediment transport. During this first in situ long-term monitoring along the channel, an energetic turbidity event was observed in January 2004 at three locations along the channel from 3420 to 4790 m in depth. This event tilted and displaced the moorings installed at 3420 m (site ZR') and 4070 m (site ZD'), and resulted in high sediment deposition at all three mooring sites. The event moved at an average velocity of 3.5 m s -1 along the numerous channel meanders between 3420 and 4070 m, then at 0.7 m s -1 between 4070 m and the end of the channel at 4790 m. The particle cloud rose above the top of the valley at 4070 m (site ZD'), but not at 3420 m (site ZR') where the channel was too deep. Lastly, the mooring line broke at site ZD' in October 2004 probably due to a strong event like that of 2001 previously described by Khripounoff et al. [Khripounoff, A., Vangriesheim, A., Babonneau, N., Crassous, P., Denniellou, B., Savoye, B., 2003. Direct observation of intense turbidity activity in the Zaire submarine valley at 4000 m water depth. Marine Geology (194), 151-158]. Between these strong events, several peaks of high turbidity and particle flux occurred, but without noticeable current increases. These events were probably due to local sliding of sediment accumulated on the walls or terraces on the side of the channel. The area near 4000 m depth and the lobe appear to be the main depocentres of particulate input rich in organic matter derived from the Congo River.

Vangriesheim, Annick; Khripounoff, Alexis; Crassous, Philippe

2009-12-01

212

Satellites See Smoke from Fourmile Canyon Fire  

NASA Video Gallery

On the morning of September 6, 2010, a wildfire known as the Fourmile Canyon Fire broke out just west of Boulder, Colorado. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra and Aqua satellites captured these images of the Fourmile Canyon Fire and its resulting smoke plume on September 7th and 8th.

gsfcvideo

2010-09-08

213

ACCELERATED PILOT PROJECT FOR U CANYON DEMOLITION  

SciTech Connect

At the U.S. Department of Energy's Hanford Site in southeast Washington State, CH2M HILL Plateau Remediation Company (CH2M HILL) is underway on a first-of-a-kind project with the decommissioning and demolition of the U Canyon. Following the U.S. Environmental Protection Agency's Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) Record of Decision for the final remediation of the canyon, CH2M HILL is combining old and new technology and techniques to prepare U Canyon for demolition. The selected remedial action called first for consolidating and grouting equipment currently in the canyon into lower levels of the plant (openings called cells), after which the cell galleries, hot pipe trench, ventilation tunnel, drains and other voids below the operating deck and crane-way deck levels will be filled with approximately 20,000 cubic yards of grout and the canyon roof and walls demolished down to the approximate level of the canyon deck. The remaining canyon structure will then be buried beneath an engineered barrier designed to control potential contaminant migration for a 500-year life. Methods and lessons learned from this project will set the stage for the future demolition of Hanford's four other canyon-type processing facilities.

KEHLER KL

2011-01-13

214

Upper Los Alamos canyon fact sheet  

Microsoft Academic Search

Los Alamos National Laboratory is planning to make environmental assessments in portions of Upper Los Alamos Canyon. Upper Los Alamos Canyon is one of the areas included in the 2005 Consent Order agreed to by Los Alamos National Laboratory, the National Nuclear Security Administration, and the New Mexico Environment Department. As such, it must be evaluated for potential contamination. The

Jeffrey H

2007-01-01

215

Urban street canyons: Coupling dynamics, chemistry and within-canyon chemical processing of emissions  

NASA Astrophysics Data System (ADS)

Street canyons, formed by rows of buildings in urban environments, are associated with high levels of atmospheric pollutants emitted primarily from vehicles, and substantial human exposure. The street canyon forms a semi-enclosed environment, within which emissions may be entrained in a re-circulatory system; chemical processing of emitted compounds alters the composition of the air vented to the overlying boundary layer, compared with the primary emissions. As the prevailing atmospheric chemistry is highly non-linear, and the canyon mixing and predominant chemical reaction timescales are comparable, the combined impacts of dynamics and chemistry must be considered to quantify these effects. Here we report a model study of the coupled impacts of dynamical and chemical processing upon the atmospheric composition in a street canyon environment, to assess the impacts upon air pollutant levels within the canyon, and to quantify the extent to which within-canyon chemical processing alters the composition of canyon outflow, in comparison to the primary emissions within the canyon. A new model for the simulation of street canyon atmospheric chemical processing has been developed, by integrating an existing Large-Eddy Simulation (LES) dynamical model of canyon atmospheric motion with a detailed chemical reaction mechanism, a Reduced Chemical Scheme (RCS) comprising 51 chemical species and 136 reactions, based upon a subset of the Master Chemical Mechanism (MCM). The combined LES-RCS model is used to investigate the combined effects of mixing and chemical processing upon air quality within an idealised street canyon. The effect of the combination of dynamical (segregation) and chemical effects is determined by comparing the outputs of the full LES-RCS canyon model with those obtained when representing the canyon as a zero-dimensional box model (i.e. assuming mixing is complete and instantaneous). The LES-RCS approach predicts lower (canyon-averaged) levels of NOx, OH and HO2, but higher levels of O3, compared with the box model run under identical chemical and emissions conditions. When considering the level of chemical detail implemented, segregation effects were found to reduce the error introduced by simplifying the reaction mechanism. Chemical processing of emissions within the canyon leads to a significant increase in the Ox flux from the canyon into the overlying boundary layer, relative to primary emissions, for the idealised case considered here. These results demonstrate that within-canyon atmospheric chemical processing can substantially alter the concentrations of pollutants injected into the urban canopy layer, compared with the raw emission rates within the street canyon. The extent to which these effects occur is likely to be dependent upon the nature of the domain (canyon aspect ratio), prevailing meteorology and emission/pollution scenario considered.

Bright, Vivien Bianca; Bloss, William James; Cai, Xiaoming

2013-04-01

216

Theory of NURBS and its application in submarine hull modeling  

Microsoft Academic Search

Submarine hull consists of complicated spatial freeform surface. During the development of submarine design, the design of its body is the important factor which will decide whether this design is successful or not. But the design of complex curve and curve surface is the core in the CAD of submarine body. It is the key skill to speed up the

Zhang Jing; He Qiwei; Feng Shaowei

2010-01-01

217

47 CFR 32.2424 - Submarine & deep sea cable.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false Submarine & deep sea cable. 32.2424...Balance Sheet Accounts § 32.2424 Submarine & deep sea cable. (a) This...shall include the original cost of submarine cable and deep sea cable...

2009-10-01

218

32 CFR 700.1058 - Command of a submarine.  

Code of Federal Regulations, 2013 CFR

... 2013-07-01 false Command of a submarine. 700.1058 Section 700.1058 National...Detail to Duty § 700.1058 Command of a submarine. The officer detailed to command a submarine shall be an officer of the line in...

2013-07-01

219

47 CFR 32.2424 - Submarine & deep sea cable.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Submarine & deep sea cable. 32.2424...Balance Sheet Accounts § 32.2424 Submarine & deep sea cable. (a) This...shall include the original cost of submarine cable and deep sea cable...

2010-10-01

220

The mortality of Royal Naval submariners 1960-89  

Microsoft Academic Search

OBJECTIVES: To examine the mortality pattern of submariners in the Royal Navy to assess the long term effects on health of serving in submarines. Any specific cause of death which was increased was considered in advance to be of interest, but attention focused particularly on cancer mortality. METHOD: A mortality follow up study: 15 138 submariners who had conducted their

H Inskip; M Snee; L Styles

1997-01-01

221

A 250-Year Sediment Record of Anthropogenic Contaminants in the Lisbon Canyon, Portuguese Margin  

NASA Astrophysics Data System (ADS)

The Lisbon Canyon on the continental margin of Portugal is located in the immediate vicinity of a densely populated and industrialized metropolitan area, and receives terrigenous sediments from the Tagus River draining a large part of the Iberian Peninsula. Radionuclide records (210Pb, 137Cs) for piston cores retrieved from the canyon indicate rapid and almost continuous accumulation over the last 250 years, with sedimentation rates of up to 1 cm per year. The devastating 1755AD Lisbon Earthquake is represented in some cores by a sandy turbidite layer with erosive base, but subsequently disturbance of the sedimentary record by mass sedimentation events has been very limited. In one core at 1710 m water depth, Pb concentrations increased gradually over the last 250 years, and more abruptly after ~1960AD. Subsequently, anthropogenic lead contributed more than half of total lead deposition. Stable Pb isotope ratios indicate concurrent shifts in sources of Pb and increasing influence of anthropogenic pollutants. A slight reversal in both long-term trends after ~1990AD presumably reflects the phase-out of leaded gasoline. Organic contaminant analyses of a core collected from 1112 m water depth demonstrate enrichment of the canyon sediments with a variety of polychlorinated biphenyls (PCBs) and polyaromatic hydrocarbons (PAHs) over the last century. PCBs increased abruptly during the second half of the 20th century but show a slight decrease over the most recent decade. PAHs appear to have had their maximum in the late 19th century, possibly reflecting fallout of coal dust from one of the busiest shipping routes of the eastern Atlantic. The present study illustrates the potential of submarine canyon sediments as high-resolution archives of human impacts on the continental margin.

de Stigter, H. C.; Richter, T. O.; Booij, K.; Boer, W.; Jesus, C. C.; van Weering, T. C.

2008-12-01

222

What Controls Submarine Groundwater Discharge?  

NASA Astrophysics Data System (ADS)

Numerous processes have been implicated in controlling submarine groundwater discharge (SGD) to coastal zones since Ghyben, Herzberg and Dupuit developed models of fresh water discharge from coastal aquifers at the turn of the 19th century. Multiple empirical and modeling techniques have also been applied to these environments to measure the flow. By the mid-1950's, Cooper had demonstrated that dispersion across the fresh water-salt water boundary required salt water entrained into fresh water flow be balanced by recharge of salt water across the sediment-water interface seaward of the outflow face. Percolation of water into the beach face from wind and tidal wave run up and changes in pressure at the sediment-water interface with fluctuating tides have now been recognized, and observed, as processes driving seawater into the sediments. Within the past few years, variations in water table levels and the 1:40 amplification from density difference in fresh water and seawater have been implicated to pump salt water seasonally across the sediment- water interface. Salt water driven by waves, tides and seasonal water table fluctuations is now recognized as a component of SGD when it flows back to overlying surface waters. None of these processes are sufficiently large to provide measured volumes of SGD in Indian River Lagoon, Florida, however, because minimal tides and waves exist, flat topography and transmissive aquifers minimize fluctuations of the water table, and little water is entrained across the salt water-fresh water boundary. Nonetheless, the saline fraction of SGD represents more than 99% of the volume of total SGD in the Indian River Lagoon. This volume of saline SGD can be driven by the abundance of burrowing organisms in the lagoon, which pump sufficient amounts of water through the sediment- water interface. These bioirrigating organisms are ubiquitous at all water depths in sandy sediment and thus may provide one of the major sources of SGD world wide. Because bioirrigated water is well oxygenated and passes through sedimentary pore spaces, its influence may be quite large on fluxes of diagenetic reactive components, including organic matter, nutrients, and redox sensitive metals. While fresh meteoric groundwater may be confined to the shoreline in most cases and delivers new material from continents to the ocean, seawater circulating through sediments as part of SGD is apparently a much greater fraction of the total water flux and hence has the potential to significantly impact sediment diagenetic processes and subsequent export of nutrients and other solutes from the sediment to the water column.

Martin, J. B.; Cable, J. E.; Cherrier, J.; Roy, M.; Smith, C. G.; Dorsett, A.

2008-05-01

223

Nitrogen Dioxide Levels Aboard Nuclear Submarines.  

National Technical Information Service (NTIS)

The NO2 levels permitted aboard submarines are 0.5 ppm for 90 days, 1 ppm for 24 hours and 10 ppm for 1-hour. The 90 day limit 'represents an average value for continuous exposure which may be temporarily exceeded so long as there are corresponding period...

K. R. Bondi M. L. Shea R. M. DeBell

1983-01-01

224

Vitamin D Status of Submariners During Patrol.  

National Technical Information Service (NTIS)

The circulating vitamin D (25-OH-D) levels were measured in 22 submariners before, during and after a three month patrol. Eleven subjects received a multivitamin-mineral supplement that contained 10.0 mg of ergocalciferol while the other 11 received a pla...

C. L. Schlichting D. J. Styer

1989-01-01

225

Sliding of outrunner blocks from submarine landslides  

Microsoft Academic Search

Outrunner blocks are nearly intact pieces of debris that detach from a slowing-down submarine landslide and flow ahead of the front. Data gathered from different sliding areas highlight some properties of outrunner blocks and in particular their inordinate mobility reflected in runouts of up to 25 kilometres, even on very gentle slopes. Blocks may produce an erosion glide track on

Fabio Vittorio De Blasio; Lars Enok Engvik; Anders Elverhøi

2006-01-01

226

Monitoring corrosion in submarine sonar domes  

Microsoft Academic Search

The Applied Physics Laboratory at the University of Washington (APL-UW) and the Naval Sea Systems Command (NAVSEA) are involved in a long-term study to reduce corrosion in submarine sonar domes. Besides periodically inspecting the structures in tile domes and recommending improvements in their design, materials, and maintenance, APLUW has recently developed an instrument package to monitor selected parameters of the

C. J. Sandwith; R. L. Ruedisueli; K. G. Booth; J. P. Papageorge; B. A. Eng

1993-01-01

227

Submarine launched ballistic missile - Improved accuracy  

Microsoft Academic Search

The Improved Accuracy Program, a U.S. Navy advanced technology development program which is to provide the capability for predicting with confidence the costs and schedules associated with achieving quantified accuracy improvements in future submarine launched ballistic missile (SLBM) systems, is presented. The stellar inertial Trident I system, which is the baseline upon which improvements are being considered, is summarized. The

R. L. Topping

1981-01-01

228

Arctic Ocean warming: submarine and acoustic measurements  

Microsoft Academic Search

In 1993 the USS Pargo made the first Submarine Science Expedition (SCICEX) to the Arctic Ocean. In April 1994 the first Transarctic Acoustic Propagation (TAP) experiment designed to measure Arctic Ocean temperature was conducted. SCICEX cruises to the Arctic followed annually from 1995 to 2000. Expendable CTDs and on some cruises standard CTDs were deployed along or close to the

P. Mikhalevsky; A. Gavrilov; M. S. Moustafa; B. Sperry

2001-01-01

229

The Grand Canyon: How It Formed  

NSDL National Science Digital Library

Today, in the deepest part of the Grand Canyon, the Colorado River flows past rocks that are 1.7 billion years old. This video describes how the river cut vertically through layers of pre-existing rock as the plateau beneath it was uplifted by tectonic forces. It also explains that other forces worked to widen the canyon, particluarly the activity of tributary streams and debris flows caused by flash flooding from intense rainfall or rapid snowmelt moving loose rock and boulders down canyon walls and side channels. A background essay and list of discussion questions are also provided.

2011-02-23

230

The Grand Canyon: How It Formed  

NSDL National Science Digital Library

Today, in the deepest part of the Grand Canyon, the Colorado River flows past rocks that are 1.7 billion years old. This video describes how the river cut vertically through layers of pre-existing rock as the plateau beneath it was uplifted by tectonic forces. It also explains that other forces worked to widen the canyon, particluarly the activity of tributary streams and debris flows caused by flash flooding from intense rainfall or rapid snowmelt moving loose rock and boulders down canyon walls and side channels. A background essay and list of discussion questions are also provided.

231

Modelling Aerosol Dispersion in Urban Street Canyons  

NASA Astrophysics Data System (ADS)

Flow patterns within an urban street canyon are influenced by various micrometeorological factors. It also represents an environment where pollutants such as aerosols accumulate to high levels due to high volumes of traffic. As adverse health effects are being attributed to exposure to aerosols, an investigation of the dispersion of aerosols within such environments is of growing importance. In particular, one is concerned with the vertical structure of the aerosol concentration, the ventilation characteristics of the street canyon and the influence of aerosol microphysical processes. Due to the inherent heterogeneity of the aerosol concentrations within the street canyon and the lack of spatial resolution of measurement campaigns, these issues are an on-going debate. Therefore, a modelling tool is required to represent aerosol dispersion patterns to provide insights to results of past measurement campaigns. Computational Fluid Dynamics (CFD) models are able to predict detailed airflow patterns within urban geometries. This capability may be further extended to include aerosol dispersion, by an Euler-Euler multiphase approach. To facilitate the investigation, a two-dimensional, multiphase CFD tool coupled with the k-epsilon turbulence model and with the capability of modelling mixed convection flow regimes arising from both wind driven flows and buoyancy effects from heated walls was developed. Assuming wind blowing perpendicularly to the canyon axis and treating aerosols as a passive scalar, an attempt will be made to assess the sensitivities of aerosol vertical structure and ventilation characteristics to the various flow conditions. Numerical studies were performed using an idealized 10m by 10m canyon to represent a regular canyon and 10m by 5m to represent a deep one. An aerosol emission source was assigned on the centerline of the canyon to represent exhaust emissions. The vertical structure of the aerosols would inform future directives regarding the recommended height for pollutant measurements to represent pedestrian exposure. The vertical structure of aerosols within a street canyon is a topic of constant debate, due to the inability of measurement campaigns to have sufficient spatial resolution to adequately represent the entire vertical structure. Several vertical profiles have been proposed: one where the concentration is the highest at the bottom, decreasing exponentially with increasing height; a homogenous profile across the canyon depth or one with a maximum observed near the road surface. Consistent with previous measurement results, modelling studies found that at the leeward side of the canyon, there was an increase in aerosol concentration up to approximately 2 m in height, followed by a decrease along the height of the canyon. It was also found that the vertical structure of the aerosols would be influenced by the relative contributions of convection and turbulent diffusivities and therefore vary at different locations of the canyon. Using a first-order eddy viscosity turbulence closure, knowledge of the vertical structure of the aerosol concentration would provide insights into the emission velocity structure within the canyon and account for its observed heterogeneity. Investigation of the different factors which influence the ventilation characteristics of the canyon are presented and we show how these facilitate parameterizations into other modelling platforms. Both vertical turbulent flux and flux due to mean flow contribute to the overall ventilation characteristics of a street canyon and these are described. The influence of micro-meteorological factors on the vertical flux of aerosols at the roof level of the street canyon and the relative contributions of flux due to mean flow and turbulent flux at different flow conditions are also investigated. Turbulent flux was found to be of an order of magnitude higher than mean flow flux in isothermal conditions. Therefore, whilst the net effect of turbulent flux is the loss of aerosols to the urban canopy and the net effect of mean flow flux is to re

Tay, B. K.; Jones, D. P.; Gallagher, M. W.; McFiggans, G. B.; Watkins, A. P.

2009-04-01

232

Walnut Canyon National Monument: An Archeological Overview.  

National Technical Information Service (NTIS)

Walnut Canyon National Monument is viewed here in the environmental context of the region surrounding Flagstaff, Arizona, and in the archeological context of the Sinagua culture area, with emphasis on the effective environment and on the importance of the...

P. A. Gilman

1976-01-01

233

Solar Filament Eruption Creates 'Canyon of Fire'  

NASA Website

filament of solar material erupted on the sun in late September, breaking the quiet conditions in a spectacular fashion. The 200,000 mile long filament ripped through the sun's atmosphere, the corona, leaving behind what looks like a canyon ...

234

Flow dynamics of a wide Arctic canyon  

NASA Astrophysics Data System (ADS)

We extend and interpret acoustic Doppler current profiler and conductivity-temperature-depth data collected in the summer of 1993 over Barrow Canyon in order to implement a high resolution (1.5 to 5 km) model of the Beaufort and Chukchi Seas. This paper addresses physical processes relevant to the Barrow Canyon region using common dynamical analyses of both field data and numerical results. The field data reveal the dominant physical processes that guide the design of our numerical experiments. The observed velocity field shows an intense and variable down canyon flow with transports ranging from 0.5 to 1.4 Sv. A momentum analysis reveals that the cross-canyon dynamic balance for the barotropic component is primarily geostrophic. Conversely, the baroclinic cross-canyon momentum balance is ageostrophic and secondary flow results from a local imbalance between the vertically varying Coriolis acceleration and the cross-canyon pressure gradient. In addition to the moderate influence of stratification (Froude number of 0.4 and Burger number of 0.06), the barotropic pressure gradient component across the canyon (inferred from the large magnitude and little vertical variability of the residuals) is dynamically important for both upcanyon and downcanyon flows that occur at different locations concurrently. The along-canyon dynamic balance is ageostrophic since the time derivative and the Coriolis term are of the same order of magnitude (temporal Rossby number is approximately 1). An analysis of the longitudinal density and velocity fields from the model reveals that the main driving mechanism for generating the observed upcanyon flow is the nonlinear interaction of the variable barotropic flow with the steep topography. Stratification is maintained by the downcanyon advection of fresh and warm water from the Bering and Chukchi Seas and the upcanyon advection of saltier and colder water from the Arctic.

Signorini, S. R.; Münchow, A.; Haidvogel, D.

1997-08-01

235

Different Views of the Grand Canyon  

NASA Astrophysics Data System (ADS)

Each year the spectacular scenery of the Grand Canyon of Arizona awes its more than 4,000,000 visitors. Just as its enormous scale dwarfs our human sense of space, its geology also dwarfs our human sense of time. Perhaps here, more than anywhere else on the planet, we can experience a sense of ``Deep Time.'' The colorful rocks exposed in the vertical walls of the canyon display a span of 1.8 billion years of Earth's history [Beus and Morales, 2003]. But wait! There is a different view! According to Vail [2003], this time span is only 6,000 years and the Grand Canyon and its rocks are a record of the Biblical 6 days of creation and Noah's flood. During a visit to Grand Canyon, in August 2003, I learned that Vail's book, Grand Canyon: A Different View, is being sold within the National Park. The author and compiler of Grand Canyon: A Different View is a Colorado River guide who is well acquainted with the Grand Canyon at river level. He has produced a book with an attractive layout and beautiful photographs. The book is remarkable because it has 23 co-authors, all male, who comprise a veritable ``Who's Who'' in creationism. For example, Henry Morris and John Whitcomb, the authors of the seminal young Earth creationist text, The Genesis Flood [Whitcomb and Morris, 1961], each contribute a brief introduction. Each chapter of Grand Canyon: A Different View begins with an overview by Vail, followed by brief comments by several contributors that ``have been peer reviewed to ensure a consistent and Biblical perspective.'' This perspective is strict Biblical literalism.

Elders, Wilfred A.

236

Hudson Canyon Offshore New York and New Jersey: Active Circular Depressions, Fans, Ravines, Methane Discharge and Water Masses  

NASA Astrophysics Data System (ADS)

We investigated Hudson Canyon from where it begins at the seaward edge of the continental shelf (water depth 100 m) to ~30 km seaward (100-700 m) using high-resolution bathymetry (AUV Eagle Ray; ISE Explorer; EM2000 sonar) and standard oceanographic methods. We find features and processes that create varied distinctive habitats in submarine canyons on passive continental margins, as follows: 1)Sediment conduit: The initial 10 km- long section of the canyon head connects with cross-shelf sediment transport and is smoothed by sediment accumulation indicating that it is presently inactive as a sediment conduit, in contrast to its active role during prior intervals of lowered sea level. 2)Circular depressions: A population of circular depressions with diameters from 50 to 400 m, rim-to-floor relief up to 20 m increasing directly with diameter, flat rough floors and steep walls (15-25 degrees) occur in sediment near the base of both walls of the canyon. The number of circular depressions increases with water depth with one at 325 m in the initial 10 km-long NW-SE section of the canyon, two at 350 m in the next 10 km N-S section, and nineteen at 300 to 500 m at the SW wall of the next 10 km NW-SE section. The sharp shape of the depressions suggests that they are actively forming. Larger circular depressions (diameter <800 m) exhibit different characteristics. 3)Methane chemistry: A methane anomaly (50 nmol) ten times background was measured in August 2008 in the near-bottom water column adjacent to one of the two circular depressions in the middle canyon section. In August 2009 water samples were recovered at other circular depressions and are being analyzed to test for methane discharge. We suggest that the circular depressions are gas release-collapse features possibly produced by dissociation of underlying gas hydrates. 4)Fans and ravines: Sediment fans with intervening ravines about 1 km apart extend orthogonal to the canyon axis down the two walls of the canyon in the second and third sections. 5)Hydrography: A dynamic system of multiple layers of inter-leaved shelf (cold, fresh) and slope (warm, salty) water masses was observed in the canyon head in summers 2007, 2008 and 2009 and found to produce shifting fronts and strong currents. Dynamic interactions between the hydrography and different terrains create a wide range of habitat conditions in the canyon critical for biodiversity. Enhanced shelf-slope exchange of water masses facilitated by the complex canyon topography may influence adjacent shelf circulation, and impact ecosystems including commercial fish stocks well beyond the canyon. We thank NOAA National Marine Fisheries Service(NMFS), National Institute of Science and Technology (NIUST), and National Undersea Research Program (NURP) for support.

Rona, P. A.; Guida, V.; Scranton, M. I.; Gong, D.; Haag, S.; Macelloni, L.; Simonetti, A.; James, J.; Diercks, A.; Asper, V. L.

2009-12-01

237

Submarine Paleoseismology Based on Turbidite Records  

NASA Astrophysics Data System (ADS)

Many of the largest earthquakes are generated at subduction zones or other plate boundary fault systems near enough to the coast that marine environments may record evidence of them. During and shortly after large earthquakes in the coastal and marine environments, a spectrum of evidence may be left behind, mirroring onshore paleoseismic evidence. Shaking or displacement of the seafloor can trigger processes such as turbidity currents, submarine landslides, tsunami (which may be recorded both onshore and offshore), and soft-sediment deformation. Marine sites may also share evidence of fault scarps, colluvial wedges, offset features, and liquefaction or fluid expulsion with their onshore counterparts. This article reviews the use of submarine turbidite deposits for paleoseismology, focuses on the dating and correlation techniques used to establish stratigraphic continuity of marine deposits, and outlines criteria for distinguishing earthquake deposits and the strategies used to acquire suitable samples and data for marine paleoseismology.

Goldfinger, Chris

2011-01-01

238

Submarine Volcanoes in Arctic Ocean Surprise Scientists  

NSDL National Science Digital Library

Until now, geoscientists believed that spreading ridges under the Arctic Ocean were too slow-spreading and cool to vent molten rock. An article published this month in Nature details sonar data revealing two young volcanoes under Arctic waters. Dr. Marago H. Edwards of the University of Hawaii led the exploration team in which civilian scientists worked in cooperation with the Navy, using a nuclear submarine to take sonar readings of the ocean floor. A submarine was employed because the ice cover makes the Arctic seafloor unviewable by satellites and difficult for ships bearing seismic instruments to navigate. The two volcanoes were found at the Gakkel Ridge, the Earth's slowest spreading mid-ocean ridge. During August and September of 2001, Russian icebreakers and Mir submersibles will be employed to investigate the volcanoes, taking rock samples and looking for organisms living at the volcanic vents. This week's In the News takes a closer look at this discovery.

Sanders, Hilary C.

2001-01-01

239

Submarine paleoseismology based on turbidite records.  

PubMed

Many of the largest earthquakes are generated at subduction zones or other plate boundary fault systems near enough to the coast that marine environments may record evidence of them. During and shortly after large earthquakes in the coastal and marine environments, a spectrum of evidence may be left behind, mirroring onshore paleoseismic evidence. Shaking or displacement of the seafloor can trigger processes such as turbidity currents, submarine landslides, tsunami (which may be recorded both onshore and offshore), and soft-sediment deformation. Marine sites may also share evidence of fault scarps, colluvial wedges, offset features, and liquefaction or fluid expulsion with their onshore counterparts. This article reviews the use of submarine turbidite deposits for paleoseismology, focuses on the dating and correlation techniques used to establish stratigraphic continuity of marine deposits, and outlines criteria for distinguishing earthquake deposits and the strategies used to acquire suitable samples and data for marine paleoseismology. PMID:21329198

Goldfinger, Chris

2011-01-01

240

33 CFR 334.75 - Thames River, Naval Submarine Base New London, restricted area.  

Code of Federal Regulations, 2010 CFR

...Thames River, Naval Submarine Base New London, restricted area. 334.75 ...Thames River, Naval Submarine Base New London, restricted area. (a) The area...area when notified by personnel of the New London Submarine Base that such...

2010-07-01

241

33 CFR 334.75 - Thames River, Naval Submarine Base New London, restricted area.  

Code of Federal Regulations, 2010 CFR

...Thames River, Naval Submarine Base New London, restricted area. 334.75 ...Thames River, Naval Submarine Base New London, restricted area. (a) The area...area when notified by personnel of the New London Submarine Base that such...

2009-07-01

242

Narrow-complex tachycardia.  

PubMed

The term "narrow-complex tachycardia" is applied to a number of common and rare arrhythmias. Atrial fibrillation is the narrow-complex tachycardia most frequently seen in clinical practice. Sinus tachycardia is associated with underlying metabolic abnormalities, and paroxysmal atrial tachycardia most often results from digitalis toxicity. Multifocal atrial tachycardia usually occurs in older adults with chronic obstructive pulmonary disease. Atrioventricular nodal reentrant tachycardia is commonly found in otherwise healthy children and adolescents. The initial diagnosis should be reconsidered if drug therapy is unsuccessful, because differences in rhythm disturbances are often subtle. Radiofrequency catheter ablation is an effective treatment for atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia (Wolff-Parkinson-White syndrome) and the permanent form of junctional reentrant tachycardia. Catheter ablation should also be considered in difficult cases of atrial flutter, intra-atrial reentry and automatic atrial tachycardia. PMID:8116517

Giudici, M C; Gumpert, T J; Heathman, L L

1994-03-01

243

Submarine seawater reverse osmosis desalination system  

Microsoft Academic Search

The project presented addresses the strategic topic of providing drinking and irrigation water through seawater desalination via a very energy-efficient and cost-competitive submarine technology. In conventional surface based industrial desalination plants applying the reverse osmosis (RO) technology, the freshwater flow behind the membranes is approximately 20–45% of the inlet seawater flow, depending on membrane type and characteristics. The resulting brine

Paolo Pacenti; Mario de Gerloni; Mario Reali; David Chiaramonti; Sven O. Gärtner; Peter Helm; Michael Stöhr

1999-01-01

244

Tracking of Constrained Submarine Robot Arms  

Microsoft Academic Search

Despite the appearance of impressive submarine robot arms (SRA), simple posture (position\\/orientation) regulators are implemented\\u000a nowadays and tracking still remains an open issue, let alone the force\\/posture tracking goal. The main challenge to achieve\\u000a simultaneous tracking of posture and force seems the complex dynamical structure, the difficulty to measure precisely the\\u000a inertial parameters of SRA and the access to the

Ernesto Olguín-Díaz; Vicente Parra-Vega

245

Mineralized microbes from Giggenbach submarine volcano  

Microsoft Academic Search

The Giggenbach submarine volcano, which forms part of the Kermadec active arc front, is located ?780 km NNE of the North Island of New Zealand. Samples collected from chimneys associated with seafloor hydrothermal vents on this volcano, at a depth of 160–180 m, contain silicified microbes and microbes entombed in reticular Fe-rich precipitates. The mineralized biota includes filamentous, rod-shaped, and

Brian Jones; C. E. J. de Ronde; Robin W. Renaut

2008-01-01

246

Storm-triggered mass failure and sediment liquefaction in the Swatch of No Ground canyon, offshore Bangladesh  

NASA Astrophysics Data System (ADS)

In November 2007 the eye of a major tropical storm, Cyclone Sidr, tracked over the offshore canyon associated with the Ganges-Brahmaputra river delta. Known as the Swatch of No Ground (SoNG), this large canyon incises within 30 km of the deltaic coast and is accreting rapidly (10 to >50 cm/yr) with fluvially derived sediments. Historically numerous tropical storms have affected the northern Bay of Bengal each year, but more recently cyclogenesis has been weak and Sidr is the first major cyclone to impact the Bengal shelf since 1991. As part of an ongoing study, our research team had just completed a high-resolution sub- bottom sonar (chirp) survey of the SoNG canyon head six months prior to Cyclone Sidr. Following the storm, we organized a second sub-bottom survey to assess the storm's impact on canyon morphology and sedimentation patterns. A comparison of our pre- and post-storm surveys reveal dramatic mass failures around the canyon wall, but also vast areas that were largely unaffected. Among the failures, many had dimensions 10s of meters thick and >1 km wide. These large-scale failures appear to have been preferentially located where there is pre-storm evidence for fluid escape, perhaps via submarine groundwater discharge through onshore sandy delta complex. Fluid chimneys, apparently gas charged, are also associated with many of the large failures. However, many locations with prominent shallow gas show no disruption after the storm, suggesting that zones prone to major failure are associated fluid flow. Other areas of the canyon show storm-induced liquefaction of surface sediments (<5 m below seabed) and resulting mudflows. Runout distances are only a few hundred meters, though, suggesting rapid consolidation of the flows even on sloping surfaces (1-3°). As interesting as these storm-related failures are the actively accreting, steep-walled (>5°) gullies that show no apparent effect of the storm. Overall it appears that areas of the canyon most susceptible to failure are not necessarily the steepest or most rapidly accreting, but rather those associated with subsurface fluid flow and planes of weakness along escape structures.

Goodbred, S. L.; Rogers, K. G.; Khan, S. R.; Ullah, M. S.; Mondal, D. R.

2008-12-01

247

The submarine service of the future?  

PubMed

Space missions, although now routine, are unique in terms of their environment and logistical requirements. The number of missions (man-hours) remains relatively small and planning still relies on comparisons with analogous missions, including submarine operations. Antarctic missions, which tend not to be classified, have provided more information about isolated communities because of the number of personnel per base. Space medicine has traditionally been an extension of aviation medicine with high g-forces involved in the transition from Earth to orbit and astronauts such as Neil Armstrong recruited from the test pilot fraternity. As the length of a mission increases and the space habitation relies more on regenerative systems, the environment becomes more analogous with today's nuclear submarines. As well as the air purification implications, radiation still is a significant hazard with even greater impact on future Mars missions requiring the provision of health physics monitoring, advice and countermeasures well established in the submarine flotilla. Nevertheless, the specialty space medicine will progress as a specialty in its own right, pooling expertise from other specialties such as aviation, radiation, emergency and occupational medicine taking human exploration beyond the confines of land and sea. PMID:11346925

Bland, S A

2000-01-01

248

Influence of near-bottom environmental conditions on the structure of bathyal macrobenthic crustacean assemblages from the Capbreton canyon (Bay of Biscay, NE Atlantic)  

NASA Astrophysics Data System (ADS)

Sled and box-corer samplings were performed at two sites in the Capbreton canyon in order to appreciate the influence of near-bottom environmental conditions on the structure of their macrobenthic communities (crustaceans). Although located at similar depths (ca. 1?000 m), these two sites were characterised by different physicochemical conditions at the sediment-water interface, probably related with the morphology of the submarine valley (reduced environment, oxygen depletion and stagnation of bottom water at site A; normal oceanic conditions on the near-bottom environment of site B). The analysis of the collected fauna revealed a low similarity between the two sites, mainly due to the unusual dominance of three epibenthic species in sled samples from site A: the amphipod Bonnierella abyssorum, the tanaid Apseudes spinosus and the isopod Arcturopsis giardi. Due to their apparent rarity or absence in adjacent non-canyon communities, such epibenthic crustaceans may be considered as `canyon indicator species' able to exhibit abundant populations within the peculiar confinement area of this canyon.

Marquiegui, Mikel A.; Sorbe, Jean Claude

1999-07-01

249

A Submarine Perspective on Hawaiian Volcanoes  

NASA Astrophysics Data System (ADS)

Postwar improvements in navigation, sonar-based mapping, and submarine photography enabled the development of bathymetric maps, which revealed submarine morphologic features that could be dredged or explored and sampled with a new generation of manned and unmanned submersibles. The maps revealed debris fields from giant landslides, the great extent of rift zones radiating from volcanic centers, and two previously unknown submarine volcanoes named Mahukona and Loihi, the youngest Hawaiian volcano. About 70 major landslides cover half the flanks of the Hawaiian Ridge out to Midway Island. Some of the landslides attain lengths of 200 km and have volumes exceeding 5,000 km3. More recent higher resolution bathymetry and sidescan data reveal that many submarine eruptions construct circular, flat-topped, monogenetic cones; that large fields of young strongly alkalic lava flows, such as the North Arch and South Arch lava fields, erupt on the seafloor within several hundred km of the islands; and that alkalic lavas erupt during the shield stage on Kilauea and Mauna Loa. The North Arch flow field covers about 24,000 km2, has an estimated volume between about 1000 and 1250 km3, has flows as long as 108 km, and erupted from over 100 vents. The source and melting mechanisms for their production is still debated. The maps also displayed stair-step terraces, mostly constructed of drowned coral reefs, which form during early rapid subsidence of the volcanoes during periods of oscillating sea level. The combination of scuba and underwater photography facilitated the first motion pictures of the mechanism of formation of pillow lava in shallow water offshore Kilauea. The age progression known from the main islands was extended westward along the Hawaiian Ridge past Midway Island, around a bend in the chain and northward along the Emperor Seamounts. Radiometric dating of dredged samples from these submarine volcanoes show that the magma source that built the chain has been active for over 80 Ma and established the remarkable linearity of the age-progression along the chain. Glass rinds on submarine lava quenched at depth contain initial magmatic volatiles and yield data on the juvenile water, sulfur, CO2, and rare gas contents of basaltic magmas, and continue to reveal nuances of the volatile contents of lava. Rock sampling at Loihi Seamount led to the discovery of the pre-shield alkalic phase of Hawaiian volcanism, which mirrors the well-known post-shield alkalic phase. Lava compositions from the Hawaiian Ridge and Emperor Seamounts have clear affinities to present-day Hawaiian lavas, but subtle source differences as well. The progression from small to large and back to small degrees of melting at individual volcanoes and the compositional changes along the chain constrain the melting processes and source compositions of Hawaiian volcanism. Coupling the age of lavas with that of submerged coral reefs has provided data on the growth and subsidence of volcanic centers. This information has meshed nicely with the age, composition, and morphology of lavas from the 3.2-km-deep Hawaiian Scientific Drill Hole. Submarine studies have taught us much about the workings of Hawaiian Volcanoes, and in the process have stimulated new work and concepts on marine volcanism worldwide.

Clague, D. A.; Moore, J. G.

2011-12-01

250

Grand Canyon Humpback Chub Population Improving  

USGS Publications Warehouse

The humpback chub (Gila cypha) is a long-lived, freshwater fish found only in the Colorado River Basin. Physical adaptations-large adult body size, large predorsal hump, and small eyes-appear to have helped humpback chub evolve in the historically turbulent Colorado River. A variety of factors, including habitat alterations and the introduction of nonnative fishes, likely prompted the decline of native Colorado River fishes. Declining numbers propelled the humpback chub onto the Federal list of endangered species in 1967, and the species is today protected under the Endangered Species Act of 1973. Only six populations of humpback chub are currently known to exist, five in the Colorado River Basin above Lees Ferry, Ariz., and one in Grand Canyon, Ariz. The U.S. Geological Survey's Grand Canyon Monitoring and Research Center oversees monitoring and research activities for the Grand Canyon population under the auspices of the Glen Canyon Dam Adaptive Management Program (GCDAMP). Analysis of data collected through 2006 suggests that the number of adult (age 4+ years) humpback chub in Grand Canyon increased to approximately 6,000 fish in 2006, following an approximate 40-50 percent decline between 1989 and 2001. Increasing numbers of adult fish appear to be the result of steadily increasing numbers of juvenile fish reaching adulthood beginning in the mid- to late-1990s and continuing through at least 2002.

Andersen, Matthew E.

2007-01-01

251

43. and Design, Grand Canyon National Park, dated August 23, ...  

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

43. and Design, Grand Canyon National Park, dated August 23, 1934, and September 17, 1934 (original located at Federal Records Center, Denver, Colorado, #113/3084-set of 2) SEWAGE PLANT ADDITION. - Water Reclamation Plant, Grand Canyon, Coconino County, AZ

252

Overview of the Colorado River Canyon from the helicopter pad. ...  

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

Overview of the Colorado River Canyon from the helicopter pad. View of the Nevada side where new bridge will cross canyon, view northwest - Hoover Dam, Spanning Colorado River at Route 93, Boulder City, Clark County, NV

253

36 CFR 7.92 - Bighorn Canyon National Recreation Area.  

Code of Federal Regulations, 2013 CFR

...AREAS OF THE NATIONAL PARK SYSTEM § 7.92 Bighorn Canyon National Recreation Area. (a) Aircraft-designated...Bighorn Canyon National Recreation Area, except in the...boundary delineated by park installed buoys. ...protection, and other management activities and...

2013-07-01

254

10. August, 1971. GV W FROM PROVO CANYON. AT PRESSURE ...  

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

10. August, 1971. GV W FROM PROVO CANYON. AT PRESSURE HOUSE SHOWING POWER STATION AT BOTTOM OF PHOTO. - Telluride Power Company, Olmsted Hydroelectric Plant, mouth of Provo River Canyon West of U.S. Route 189, Orem, Utah County, UT

255

The narrow pentaquark  

SciTech Connect

The experimental status of the pentaquark searches is briefly reviewed. Recent null results by the CLAS collaboration are commented, and new strong evidence of a very narrow {theta}+ resonance by the DIANA collaboration is presented. On the theory side, I revisit the argument against the existence of the pentaquark - that of Callan and Klebanov - and show that actually a strong resonance is predicted in that approach, however its width is grossly overestimated. A recent calculation gives 2 MeV for the pentaquark width, and this number is probably still an upper bound.

Diakonov, Dmitri [Petersburg Nuclear Physics Institute, Gatchina, 188 300, St. Petersburg (Russian Federation)

2007-02-27

256

Stromboli Island (Italy): Scenarios of Tsunamis Generated by Submarine Landslides  

NASA Astrophysics Data System (ADS)

Stromboli is an Italian volcanic island known for its persistent state of activity, which leads to frequent mass failures and consequently to frequent tsunamis ranging from large (and rare) catastrophic events involving the entire southern Tyrrhenian Sea to smaller events with, however, extremely strong local impact. Most of tsunamigenic landslides occur in the Sciara del Fuoco (SdF) zone, which is a deep scar in the NW flank of the volcano, that was produced by a Holocene massive flank collapse and that is the accumulation area of all the eruptive ejecta from the craters. Shallow-water bathymetric surveys around the island help one to identify submarine canyons and detachment scars giving evidence of mass instabilities and failures that may have produced and might produce tsunamis. The main purpose of this paper is to call attention to tsunami sources in Stromboli that are located outside the SdF area. Further, we do not touch on tsunami scenarios associated with gigantic sector collapses that have repeat times in the order of several thousands of years, but rather concentrate on intermediate size tsunamis, such as the ones that occurred in December 2002. Though we cannot omit tsunamis from the zone of the SdF, the main emphasis is on the elaboration of preliminary scenarios for three more possible source areas around Stromboli, namely Punta Lena Sud, Forgia Vecchia and Strombolicchio, with the aim of purposeful contributing to the evaluation of the hazard associated with such events and to increase the knowledge of potential threats affecting Stromboli and the nearby islands of the Aeolian archipelago. The simulations show that tsunami sources outside of the SdF can produce disastrous effects. As a consequence, we recommend that the monitoring system that is presently operating in Stromboli and that is focussed on the SdF source area be extended in order to cover even the other sources. Moreover, a synoptic analysis of the results from all the considered tsunami scenarios leads to a very interesting relation between the tsunami total energy and the landslide potential energy, that could be used as a very effective tool to evaluate the expected tsunami size from estimates of the landslide size.

Tinti, Stefano; Zaniboni, Filippo; Pagnoni, Gianluca; Manucci, Anna

2008-12-01

257

Dispersion Mechanisms In A Street Canyon.  

NASA Astrophysics Data System (ADS)

In this article, we investigate experimentally and analytically the dispersion mecha- nisms of a passive tracer in a two-dimensional street canyon model. The central point concerns the concentration transfer between the street and the external flow. In con- trast to previous studies, the mass fluxes are not only inferred from mean concentration measurements but also directly measured thanks to a Particle Tracking Velocimetry technique. Visualizations of the evolution of the concentration field evidence the role of the shear layer at the top of the street canyon. Analytical transfer and dispersion models are derived, exhibiting the importance of external turbulence properties on the transfer. Those models are in excellent agreement with the measurements. The results presented in this article strongly suggest that the transfer in a street canyon does depend on the structure of the incoming turbulence, i.e. on the local stability conditions and on the upwind build-up.

Caton, F.; Britter, R. E.; Dalziel, S.

258

Recreational impacts on Colorado River beaches in Glen Canyon, Arizona  

Microsoft Academic Search

Recreational impact was measured on eight beaches in Glen Canyon National Recreation Area and 15 beaches in Grand Canyon National Park using permanently located transects and plots. Recreational impact indices included densities of human trash and charcoal and a measure of sand discoloration due to charcoal. Significant increases in the indices occurred on several Glen Canyon beaches over a seven-month

Steven W. Carothers; Robert A. Johnson; Robert Dolan

1984-01-01

259

36 CFR 7.4 - Grand Canyon National Park.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Grand Canyon National Park. 7.4 Section...NATIONAL PARK SYSTEM § 7.4 Grand Canyon National Park. (a) Commercial...passengers by motor vehicles to Grand Canyon National Park contained...

2010-07-01

260

36 CFR 7.4 - Grand Canyon National Park.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Grand Canyon National Park. 7.4 Section...NATIONAL PARK SYSTEM § 7.4 Grand Canyon National Park. (a) Commercial...passengers by motor vehicles to Grand Canyon National Park contained...

2009-07-01

261

5. DARK CANYON SIPHON Photographic copy of historic photo, ...  

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

5. DARK CANYON SIPHON - Photographic copy of historic photo, November 11, 1906 (original print located at the Carlsbad Irrigation District offices, Carlsbad, New Mexico) photographer unknown 'LOWER END OF DARK CANYON SIPHON CONSTRUCTION' - Carlsbad Irrigation District, Dark Canyon Siphon, On Main Canal, 1 mile South of Carlsbad, Carlsbad, Eddy County, NM

262

Air Pollution Optimal Traffic Control in Integrated Street Canyons  

Microsoft Academic Search

This paper presents a system analysis integrated approach to pro-ecological urban traffic management and control problems. In this context optimal (in the sense of air pollution) traffic road control problems in street canyons are formulated and solved. A general traffic control idea for street canyons is proposed with emphasis on the development of advanced hydrodynamic control models of street canyon

A. Adamski; M. M. Duras

263

75 FR 34476 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Work Group AGENCY...renewing the charter for the Glen Canyon Dam Adaptive Management Work Group. The purpose...respect to the operation of Glen Canyon Dam and the exercise of other authorities...

2010-06-17

264

Australia's Submarine Design Capabilities and Capacities: Challenges and Options for the Future Submarine.  

National Technical Information Service (NTIS)

Australia has committed itself to acquiring 12 new submarines to replace the Collins vessels, all of which face retirement by the mid- to late 2030s unless they undergo life extension programs. As detailed by the Australian Government in its Defence White...

J. Birkler J. Riposo J. F. Schank M. V. Arena R. W. Button

2011-01-01

265

The origin of Messinian canyons in the Mediterranean: the role of brine-related dense shelf water cascading currents  

NASA Astrophysics Data System (ADS)

Recent studies on modern deep-sea environments have documented the role of submarine processes, such as turbidity currents, fluvial flood-related hyperpycnal flows and dense shelf water cascading (DSWC), in the genesis and evolution of canyons and gullies. These processes are largely independent from sea-level fluctuations and significant erosion has been shown to occur even at present-day sea-level highstand conditions. The study of ancient deep-marine environments and processes may take great advantage from the knowledge produced during the last decade in this field of research. The study of some exceptional events of the past is an exciting issue for a common effort of specialists from different disciplines (geomorphology, geology, physical oceanography) in the understanding of modern and ancient deep seascape. An example is provided by the genesis of the widespread Messinian erosional surface (MES) and the associated gullies and canyons, which have been recognized through seismic data along the Mediterranean shelves and slopes. These features are commonly related to subaerial fluvial processes that imply a 1500 m drawdown and the desiccation of the Mediterranean Sea during what has been called the "Messinian salinity crisis" (MSC). Such an interpretation is one of the main arguments for the shallow-water deep-basin model (Hsü et al., 1973), which is the current paradigm for the MSC. However, no unquestionable evidence for subaerial deposits associated with the MES has been ever documented. We suggest that fully submarine erosional processes played a significant role in shaping the Mediterranean slopes also during the MSC; thus, no desiccation is needed to explain canyon formation and/or rejuvenation. We want to stress here the importance of the processes, driven by evaporative fluxes in shallow areas, that lead to the formation of seasonal high-density contrasts and cause the development of cascading along the continental slopes (Shapiro et al., 2003). These processes are active today in the Mediterranean margins where they produce large-scale erosional features within canyons (Canals et al., 2006; Palanques et al., 2012). On the basis of modelling of cascading events that recently occurred in the Gulf of Lions, we performed numerical simulations of Messinian brine-related cascading currents at different water density contrasts. Our results show that the activation of downslope flow of hypersaline dense waters may well account for both significant slope erosion and progressive salinity rise leading to the accumulation of deep-seated supersaturated brines. These findings support a "deep-water deep-basin" model thus implying that the evaporite deposition occurred in a non-desiccated basin with strongly reduced connections with the global ocean. References Canals M. et al., 2006. Flushing submarine canyons, Nature, 444, 354-357. Hsü K.J., Ryan W.B.F. and Cita M.B., 1973 Late Miocene desiccation of the Mediterranean. Nature, 242, 240-244. Palanques A. et al., 2012. Sediment transport to the deep canyons and open-slope of the western Gulf of Lyon during 2006 intense cascading and open-sea convection period, Progress in Oceanography, 106, 1-15. Shapiro G.I., Huthnance J.M. and Ivanov V.V., 2003 Dense water cascading off the continental shelf, J. Geophys. Res., 108, 3390.

Roveri, Marco; Bergamasco, Andrea; Marcello Falcieri, Francesco; Gennari, Rocco; Lugli, Stefano; Manzi, Vinicio; Schreiber, B. Charlotte

2013-04-01

266

Physical Activity Aboard Nuclear Submarines as Measured by Pedometry.  

National Technical Information Service (NTIS)

Activity levels of 44 submarines were monitored before and during a fleet ballistic missile submarine patrol. These levels were determined by use of a pedometer worn on the hip. Readings were obtained daily and recorded in a log as miles walked. Through e...

K. R. Bondi J. H. Dougherty

1985-01-01

267

The universal gravity module for enhanced submarine navigation  

Microsoft Academic Search

With a view toward current and future submarine missions requiring operations in the littoral and accurate navigation under covert conditions, Navigation and Gravity Systems (NGS) of Lockheed Martin Federal Systems has developed the Universal Gravity Module (UGM). The UGM is a low cost modular add-on to an existing submarine navigator which, through gravity measurements, infuses new capabilities into undersea warfare,

John Moryl; Hugh Rice; Stanley Shinners

1998-01-01

268

Tethered submarine pressure transfer storage facility for liquified energy gases  

Microsoft Academic Search

An improved offshore submarine storage facility in the ocean and like water bodies for storing liquified energy gases and similar liquid materials under pressure and at cryogenic temperatures is disclosed. The facility includes a two-part insulated submarine storage tank positioned at a selected depth in the water for storing said materials, wherein the two parts thereof move in a slidably

1984-01-01

269

Inertia dominated forces on submarine pipelines near seabed  

Microsoft Academic Search

An experimental investigation on regular wave induced forces on a smooth submarine pipeline fixed horizontally near a simulated seabed is carried out in the inertia dominated regime. A simple potential flow around the cylinder is assumed in analysing the hydrodynamic forces on submarine pipelines considering the size of the pipe' and wave conditions employed in this study. The inline hydrodynamic

Hin-Fatt Cheong; N. Jothi Shankar; K. Subbiah

1989-01-01

270

Flow processes and sedimentation in submarine channel bends  

Microsoft Academic Search

Turbidity currents in sinuous submarine channels are an important mechanism for transporting terrestrial sediments to deep water, and their deposits are of increasing importance as hydrocarbon exploration targets. Despite this, the architecture and dynamics of submarine channel systems are not well understood. Analogies are often drawn with fluvial systems due to similarities between their planform shapes even though differences in

Jeff Peakall; Kathryn J. Amos; Gareth M. Keevil; P. William Bradbury; Sanjeev Gupta

2007-01-01

271

Simulated Deep Submarine Escape from 459 Feet of Sea Water.  

National Technical Information Service (NTIS)

A series of deep simulated submarine escapes were conducted utilizing the British Mark VII Submarine Escape Immersion Equipment (SEIE). Two escapee subjects were exposed in a step-wise fashion to 2, 4, 8 and 16 ATA and brought directly to the surface. A r...

D. A. Hall J. K. Summitt

1970-01-01

272

Sustaining U.S. Nuclear Submarine Design Capabilities.  

National Technical Information Service (NTIS)

For the first time, the U.S. Navy faces a period that could last a number of years in which there will be no design program under way for a new class of nuclear-powered submarines. The resulting lack of demand for the services of submarine designers and e...

J. Riposo J. F. Schank K. Curry M. V. Arena P. DeLuca

2007-01-01

273

Enemy Below the Global Diffusion of Submarines and Related Technology.  

National Technical Information Service (NTIS)

Submarines are ideal for a case study in technology diffusion. The submarine was largely an American invention, although the development of the technology can trace its origins back to Alexander the Great. In 1900, the US Navy bought the first successful ...

K. G. Weiss

2002-01-01

274

The Grand Canyon: Its Youngest Rocks  

NSDL National Science Digital Library

This video segment adapted from NOVA shows a dramatic landscape created by relatively recent rock-forming activity in the Grand Canyon. Volcanic eruptions only a million years ago created the canyon's youngest rocks. In contrast with the much older Vishnu Schist formation, this younger rock has been much more susceptible to physical change. When three-hundred-meter (thousand-foot) lava dams periodically blocked the river, they were quickly eroded away and river flow restored. A background essay and list of discussion questions are included.

2011-03-14

275

Geology Fieldnotes: Bryce Canyon National Park, Utah  

NSDL National Science Digital Library

Located on the Colorado Plateau in Utah, this canyon is comprised mostly of sedimentary rocks, and continues to be eroded and shaped by the Paria River. Its geologic and human history are outlined on this site, including the formation of the canyon, from the Cretaceous period (144 million years ago) to the present, and geologic features, such as fins, columns, pinnacles, and hoodoos. Visitor information, links to other resources, maps, and a teacher feature (resources for teaching geology with National Park examples) are also available.

Foos, Annabelle

276

Submarine tsunamigenic landslides at Stromboli Volcano: characterization and estimation of recurrence time  

NASA Astrophysics Data System (ADS)

Seafloor mapping and morphometric analysis of landslide scars can provide useful insights for marine geo-hazard assessment, as demonstrated by several studies performed on different geological settings. The availability of high-resolution multibeam bathymetry and long-range side scan sonar data on the submarine portions of Stromboli Volcano allow us to map and characterize the main mass-wasting features that affect, on the whole, about the 90% of its submarine extension. In particular, two main kinds of tsunamigenic landslides have been recognized and analyzed. Large-scale sector collapses (Fig. 1) are catastrophic events that mobilize 1-2 cubic kilometers of material, generating huge tsunami waves that may affect Stromboli and propagate in surrounding areas; related hazard is not very high, as they show recurrence periods of some (or more) thousand years. Conversely, medium-scale landslides are more hazardous, as they occur at higher frequency with respect to the previous events, i.e. from some hundreds up to few tens of years. These events are, however, able to generate local but severe tsunamis when occurring in shallow water, as demonstrated by the recent 2002 tsunamigenic landslides that struck the Stromboli coasts with waves up to 10 m-high. The aim of this contribution is thus to evidence the main predisposing factors, the possible recurrence time and the size of potentially induced tsunami for the different recognized landslides according to the available geologic constraints and historical tsunami report. Fig. 1 3D images of Eastern (a) and Northwestern (b) flank of Stromboli Volcano (vertical exaggeration 2x). Note the presence of scars in the upper part of the flank and debris avalanche deposits (i.e., megablocks) in the lower part. SdF: Sciara del Fuoco, Stromboli Cy: Stromboli Canyon

Casalbore, D.; Chiocci, F. L.; Romagnoli, C.; Bosman, A.

2010-12-01

277

Geohydrology of White Rock Canyon of the Rio Grande from Otowi to Frijoles Canyon  

SciTech Connect

Twenty-seven springs discharge from the Totavi Lentil and Tesuque Formation in White Rock Canyon. Water generally acquires its chemical characteristics from rock units that comprise the spring aquifer. Twenty-two of the springs are separated into three groups of similar aquifer-related chemical quality. The five remaining springs make up a fourth group with a chemical quality that differs due to localized conditions in the aquifer. Localized conditions may be related to recharge or discharge in or near basalt intrusion or through faults. Streams from Pajarito, Ancho, and Frijoles Canyons discharge into the Rio Grande in White Rock Canyon. The base flow in the streams is from springs. Sanitary effluent in Mortandad Canyon from the treatment plant at White Rock also reaches the Rio Grande.

Purtymun, W.D.; Peters, R.J.; Owens, J.W.

1980-12-01

278

Recreational impacts on Colorado River beaches in Glen Canyon, Arizona  

NASA Astrophysics Data System (ADS)

Recreational impact was measured on eight beaches in Glen Canyon National Recreation Area and 15 beaches in Grand Canyon National Park using permanently located transects and plots. Recreational impact indices included densities of human trash and charcoal and a measure of sand discoloration due to charcoal. Significant increases in the indices occurred on several Glen Canyon beaches over a seven-month period. Sand discoloration became significantly higher over all Glen Canyon beaches during the same time period. All indices were significantly higher in Glen Canyon than on similar Grand Canyon beaches. These differences are probably due to differences in: (a) level of impacts tolerated by the respective management regimes and, (b) in the number of user days among the two National Park Service administrative units. Management alternatives are presented for reversing the present trends of recreational impact on Glen Canyon beaches.

Carothers, Steven W.; Johnson, Robert A.; Dolan, Robert

1984-07-01

279

The Colorado River in the Grand Canyon.  

ERIC Educational Resources Information Center

|An assessment of the water quality of the Colorado River in the Grand Canyon was made, using the following parameters: dissolved oxygen, water temperature, hydrogen ion concentration, total dissolved solids, turbidity, and ammonium/nitrogen levels. These parameters were used to provide some clue as to the "wellness" and stability of the aquatic…

Speece, Susan

1991-01-01

280

Bowen Canyon Bald Eagle Sanctuary: An Overview.  

National Technical Information Service (NTIS)

Bowen Canyon ACEC is located 10 miles south of American Falls, Idaho on the northern end of the Deep Creek Mountains. Its purpose is to protect the winter roost of a significant portion of Idaho's wintering bald eagles. The ACEC sits at an elevation of ab...

C. Ketchum

1985-01-01

281

77 FR 48151 - Boulder Canyon Project  

Federal Register 2010, 2011, 2012, 2013

...DEPARTMENT OF ENERGY Western Area Power...Deputy Secretary of Energy (Deputy Secretary...Charge and Rates for Boulder Canyon...INFORMATION: Hoover Dam, authorized by...border. Hoover Dam power plant has...generating units (two for plant use) and...Base Charge by energy sales in the...

2012-08-13

282

78 FR 48670 - Boulder Canyon Project  

Federal Register 2010, 2011, 2012, 2013

...Secretary of Energy (Deputy Secretary...Charge and Rates for Boulder Canyon...INFORMATION: Hoover Dam, authorized...Department of Energy, Western Area...Base Charge for BCP electric...Other factors for the decrease...from the Hoover Dam Visitor Center...The FY 2014 energy rate of...

2013-08-09

283

Mt. Vernon Canyon Runaway Truck Escape Ramp.  

National Technical Information Service (NTIS)

A gravel arrester bed type Runaway Truck Escape Ramp was built on a 5.2% downgrade along I-70 in Mt. Vernon Canyon, Colorado. The ramp was completed in July 1979 and to date it has stopped fifty-three runaway or potentially runaway trucks. Only two trucks...

R. L. Hayden

1982-01-01

284

Different Views of the Grand Canyon  

Microsoft Academic Search

Each year the spectacular scenery of the Grand Canyon of Arizona awes its more than 4,000,000 visitors. Just as its enormous scale dwarfs our human sense of space, its geology also dwarfs our human sense of time. Perhaps here, more than anywhere else on the planet, we can experience a sense of ``Deep Time.'' The colorful rocks exposed in the

Wilfred A. Elders

2003-01-01

285

Sliding of outrunner blocks from submarine landslides  

NASA Astrophysics Data System (ADS)

Outrunner blocks are nearly intact pieces of debris that detach from a slowing-down submarine landslide and flow ahead of the front. Data gathered from different sliding areas highlight some properties of outrunner blocks and in particular their inordinate mobility reflected in runouts of up to 25 kilometres, even on very gentle slopes. Blocks may produce an erosion glide track on the sea floor few centimetres to several metres deep, which in some cases exhibits regularly spaced grooves along the flow direction. Understanding the dynamics of outrunner blocks may shed light on the flow and lubrication of submarine landslides. We develop a simple hydrodynamic model of a rigid block interacting with ambient water and subject to lubrication with the sea floor, and calculate numerically the equation of motion for the block. We find that as a consequence of lift forces and water lubrication, the block may reach long runouts, in agreement with data. When the block is moving at high speed, we find an oscillating solution to the equations of motion which could explain the creation of dashed grooves.

De Blasio, Fabio Vittorio; Engvik, Lars Enok; Elverhøi, Anders

2006-03-01

286

Morphology of Submarine Landslides in Puget Sound  

NASA Astrophysics Data System (ADS)

Submarine landslides, probably triggered by large earthquakes, disturb Holocene sediments in Puget Sound. High-resolution seismic reflection profiling and sidescan swath surveys were conducted over large submarine landslides and debris flows. These large slides are in close proximity to the South Whidbey Island fault zone at Possession Point, Mukilteo, and Edgewater; near the Seattle fault off Alki Point; and near the Tacoma fault at Maury Island. The boundaries of the slides were mapped using sidescan swath surveys. Preliminary slide morphologies were determined from the seismic cross-sections. Three large slide complexes with multiple block slides and debris flows are found off Possession Point; the largest of which is 1.5 km x 1.0 km with a maximum thickness of approximately 50 meters. Large sand flows with maximum thicknesses of 30 to 40 meters occur off Mukilteo and Edgewater. An approximately 3.3 km x 2.2 km, 30 meter thick flow off Alki Point was deposited on top of folded sediments within the deformation zone of the Seattle Fault zone. Three large block slides are present off Maury Island; the largest of which is 2.75 km x 1.0 km, with a maximum thickness of approximately 100 meters. The volumes of these landslides are more than an order of magnitude larger than subaerial landslides in the region. Tsunamis generated by landsliding potentially constitute a major seismic hazard in coastal areas of the Puget Lowland.

Smith, S. B.; Karlin, R.

2003-12-01

287

Creationism in the Grand Canyon, Texas Textbooks  

NASA Astrophysics Data System (ADS)

AGU President Bob Dickinson, together with presidents of six other scientific societies, have written to Joseph Alston, Superintendent of Grand Canyon National Park, pointing out that a creationist book, The Grand Canyon: A Different View, is being sold in bookstores within the borders of the park as a scientific explanation about Grand Canyon geologic history. President Dickinson's 16 December letter urges that Alston clearly separate The Grand Canyon: A Different View from books and materials that discuss the legitimate scientific understanding of the origin of the Grand Canyon. The letter warns the Park Service against giving the impression that it approves of the anti-science movement known as young-Earth creationism, or that it endorses the advancement of religious tenets disguised as science. The text of the letter is on AGU's Web site http://www.agu.org/sci_soc/policy/sci_pol.html. Also, this fall, AGU sent an alert to Texas members about efforts by intelligent design creationists aimed at weakening the teaching of biological evolution in textbooks used in Texas schools. The alert pointed scientists to a letter, drafted by AGU, together with the American Institute of Physics, the American Physical Society, the Optical Society of America, and the American Astronomical Society, that urged the Texas State Board of Education to adopt textbooks that presented only accepted, peer-reviewed science and pedagogical expertise. Over 550 scientists in Texas added their names to the letter (http://www.agu.org/sci_soc/policy/texas_textbooks.pdf ), sent to the Board of Education on 1 November prior to their vote to adopt a slate of new science textbooks. The Board voted 11-5 in favor of keeping the textbooks free of changes advocated by groups supporting intelligent design creationism.

Folger, Peter

2004-01-01

288

Morphology, structure, and tectonic evolution of the Mona canyon (northern Mona passage) from multibeam bathymetry, side-scan sonar, and seismic reflection profiles  

NASA Astrophysics Data System (ADS)

The submarine Mona Canyon is a rift between Puerto Rico and Hispaniola of the Greater Antilles. An integrated marine geophysical data set, including multibeam bathymetry, side-scan sonar imagery, single channel and multichannel seismic reflection profiles is used to evaluate the morphology, structure, and tectonic evolution of the Mona Canyon. A structural restoration of the central Mona canyon indicates that extension in the rift initiated in the Middle Oligocene, approximately 30 Ma. A minimum total extension of 6.1 km and a minimum longitudinal strain of 11.4% across the central Mona canyon are calculated. The overall extension is proposed to have occurred over two phases. Phase I occurred from the Middle Oligocene to Late Miocene, and was a slow (0.09 mm/yr) stage of at least 1.7 km of opening. Phase II was most likely controlled by the impact of the subducted southeast portion of the Bahamas platform beneath the northeastern Caribbean plate margin. Phase II was a more rapid (0.4 mm/yr) stage of extension of at least 4.4 km that occurred from the Late Pliocene to the Recent as the SE Bahamas collision warped the middle and upper slope of the northern Puerto Rico margin along its advancing path and slowed the eastward movement of Hispaniola relative to Puerto Rico. The upper reaches of the Mona canyon form the trailing edge of the Puerto Rico-Virgin Islands block as it pulls away from a pinned Hispaniola. The Mona reentrant marks the trailing edge of a northern Hispaniola forearc sliver that forms due to increased coupling between the subducting North America plate and the overriding plate.

Mondziel, Steven; Grindlay, Nancy; Mann, Paul; Escalona, Alejandro; Abrams, Lewis

2010-04-01

289

Big Canyon Creek Ecological Restoration Strategy.  

SciTech Connect

He-yey, Nez Perce for steelhead or rainbow trout (Oncorhynchus mykiss), are a culturally and ecologically significant resource within the Big Canyon Creek watershed; they are also part of the federally listed Snake River Basin Steelhead DPS. The majority of the Big Canyon Creek drainage is considered critical habitat for that DPS as well as for the federally listed Snake River fall chinook (Oncorhynchus tshawytscha) ESU. The Nez Perce Soil and Water Conservation District (District) and the Nez Perce Tribe Department of Fisheries Resources Management-Watershed (Tribe), in an effort to support the continued existence of these and other aquatic species, have developed this document to direct funding toward priority restoration projects in priority areas for the Big Canyon Creek watershed. In order to achieve this, the District and the Tribe: (1) Developed a working group and technical team composed of managers from a variety of stakeholders within the basin; (2) Established geographically distinct sub-watershed areas called Assessment Units (AUs); (3) Created a prioritization framework for the AUs and prioritized them; and (4) Developed treatment strategies to utilize within the prioritized AUs. Assessment Units were delineated by significant shifts in sampled juvenile O. mykiss (steelhead/rainbow trout) densities, which were found to fall at fish passage barriers. The prioritization framework considered four aspects critical to determining the relative importance of performing restoration in a certain area: density of critical fish species, physical condition of the AU, water quantity, and water quality. It was established, through vigorous data analysis within these four areas, that the geographic priority areas for restoration within the Big Canyon Creek watershed are Big Canyon Creek from stream km 45.5 to the headwaters, Little Canyon from km 15 to 30, the mainstem corridors of Big Canyon (mouth to 7km) and Little Canyon (mouth to 7km). The District and the Tribe then used data collected from the District's stream assessment and inventory, utilizing the Stream Visual Assessment Protocol (SVAP), to determine treatment necessary to bring 90% of reaches ranked Poor or Fair through the SVAP up to good or excellent. In 10 year's time, all reaches that were previously evaluated with SVAP will be reevaluated to determine progress and to adapt methods for continued success. Over 400 miles of stream need treatment in order to meet identified restoration goals. Treatments include practices which result in riparian habitat improvements, nutrient reductions, channel condition improvements, fish habitat improvements, invasive species control, water withdrawal reductions, improved hydrologic alterations, upland sediment reductions, and passage barrier removal. The Nez Perce Soil and Water Conservation District (District) and the Nez Perce Tribe Department of Fisheries Resource Management Watershed Division (Tribe) developed this document to guide restoration activities within the Big Canyon Creek watershed for the period of 2008-2018. This plan was created to demonstrate the ongoing need and potential for anadromous fish habitat restoration within the watershed and to ensure continued implementation of restoration actions and activities. It was developed not only to guide the District and the Tribe, but also to encourage cooperation among all stakeholders, including landowners, government agencies, private organizations, tribal governments, and elected officials. Through sharing information, skills, and resources in an active, cooperative relationships, all concerned parties will have the opportunity to join together to strengthen and maintain a sustainable natural resource base for present and future generations within the watershed. The primary goal of the strategy is to address aquatic habitat restoration needs on a watershed level for resident and anadromous fish species, promoting quality habitat within a self-sustaining watershed. Seven objectives have been developed to support this goal: (1) Identify factors limiting quality

Rasmussen, Lynn; Richardson, Shannon

2007-10-01

290

On the (mis-) Behavior of Thunderstorms at the Grand Canyon, Arizona  

Microsoft Academic Search

The area density of cloud-to-ground (CG) lightning strokes reported by the NLDN near the Grand Canyon, Arizona, show strong variations near the canyon rim. The average area density of strokes outside the canyon is about 8-times larger than within the canyon, and there is a clear increase in the frequency of lightning attachments near the top edge of the canyon

K. L. Cummins; M. M. Saba; W. Schulz; C. Noggle; M. G. Quick; A. C. Saraiva; E. P. Krider

2009-01-01

291

Basin configuration and depositional trends in the Mission Canyon and Ratcliffe beds, U.S. portion of the Williston basin  

SciTech Connect

Construction of Mission Canyon and Ratcliffe depositional trends utilizing shoreline models and anhydrite edge maps shows a significant change in basin configuration associated with regional sea level changes. Sea level highstand, which began during deposition of the Scallion member of the Lodgepole Formation, was punctuated by two lowstand events. The first occurred during deposition of the MC-2 anhydrite (Tilston). During this lowstand event, the width of the carbonate basin decreased significantly. With sea level rise, a broad basin formed with carbonate and evaporate ramp deposition (Lands, Wayne, Glenburn and Mohall members). The top of the Mohall contains evidence of the second lowstand event. This event introduced quartz sand detritus into the basin (Kisbey Sandstone). Because of sea level lowstand, Sherwood and younger Mission Canyon beds were deposited during highstand in a narrower carbonate basin. Funneling of marine currents and tides in this basin created higher energy shoreline and shoal deposits than those commonly found in older Mission Canyon sediments. The top of the Mission Canyon (Rival) was capped by a deepening event or transgression which enlarged the basin and created broad Ratcliffe ramp systems similar to those that existed during Glenburn and Mohall deposition. By utilizing sequence stratigraphy and mapping shoreline trends and basin configuration, reservoir and trap geometries are identified, and exploration success is improved.

Hendricks, M.L. [Hendricks and Associates, Inc., Englewood, CO (United States)

1996-06-01

292

On the origin of the Andoya Canyon of Norway  

NASA Astrophysics Data System (ADS)

The Andøya Canyon is located on the northern, steepest part of the continental slope of Norway (68o - 70o N) where the slope gradient is more than 4 o. On the upper slope the canyon is characterised by a V-shaped cross-section and width between canyon shoulders is about 8 km. Canyon incision into the slope and outer shelf is about 1100 m and 6 km, respectively. Further downslope the canyon has a U-shaped cross-section, is up to 25 km wide and the canyon floor is located about 900 m below the shoulders. In this area the canyon walls and floor are dominated by an irregular relief. From the above observations we suggest a combination of processes responsible for the canyon formation. The upper, V-shaped cross-section is indicative of erosion from fluid flow processes. We speculate that the erosion may be caused by downslope flowing turbidity currents generated by mass wasting in the headwall area, piracy of winnowed shelf sediments or bottom currents and/or internal waves within the canyon. Deposits from these currents are found as a thick levée on the northern flank of the deep-sea channel at the canyon mouth. In the lower part of the canyon, retrogressive sidewall collapse due to sliding/slumping seems to have been active as indicated by the U-shaped cross-section and irregular relief. Thus the Andøya Canyon may exemplify canyon formation both by downslope erosion by turbidity currents and upslope erosion from retrogressive sliding and slumping.

Laberg, J. S.; Vorren, T. O.

2003-04-01

293

Nitrogen biogeochemistry of submarine groundwater discharge  

USGS Publications Warehouse

To investigate the role of the seepage zone in transport, chemical speciation, and attenuation of nitrogen loads carried by submarine groundwater discharge, we collected nearshore groundwater samples (n = 328) and examined the distribution and isotopic signature (??15N) of nitrate and ammonium. In addition, we estimated nutrient fluxes from terrestrial and marine groundwater sources. We discuss our results in the context of three aquifer zones: a fresh groundwater zone, a shallow salinity transition zone (STZ), and a deep STZ. Groundwater plumes containing nitrate and ammonium occurred in the freshwater zone, whereas the deep STZ carried almost exclusively ammonium. The distributions of redox-cycled elements were consistent with theoretical thermodynamic stability of chemical species, with sharp interfaces between water masses of distinct oxidation : reduction potential, suggesting that microbial transformations of nitrogen were rapid relative to dispersive mixing. In limited locations in which overlap occurs between distribution of nitrate with that of ammonium and dissolved Fe2+, changes in concentration and in ??15N suggest loss of all species. Concurrent removal of NO 3- and NH4+, both in freshwater and the deep STZ, might occur through a range of mechanisms, including heterotrophic or autotrophic denitrification, coupled nitrfication : denitrification, anammox, or Mn oxidation of NH4+. Loss of nitrogen was not apparent in the shallow STZ, perhaps because of short water residence time. Despite organic C-poor conditions, the nearshore aquifer and subterranean estuary are biogeochemically active zones, where attenuation of N loads can occur. Extent of attenuation is controlled by the degree of mixing of biogeochemically dissimilar water masses, highlighting the critical role of hydrogeology in N biogeochemistry. Mixing is related in part to thinning of the freshwater lens before discharge and to dispersion at the fresh : saline groundwater interface, features common to all submarine groundwater discharge zones. ?? 2008, by the American Society of Limnology and Oceanography, Inc.

Kroeger, K. D.; Charette, M. A.

2008-01-01

294

Stabilization of Monoethanolamine Solutions for Submarine Carbon Dioxide Scrubbers.  

National Technical Information Service (NTIS)

Monoethanolamine (MEA), the regenerative absorbent used in all CO(2) scrubbers aboard nuclear submarines, is at present stabilized with a chelating agent, the monosodium salt of N, N-diethanolglycine (VFS). In dynamic tests at 131F the additive, although ...

C. H. Blachly H. Ravner

1964-01-01

295

New Approach to Satisfy Dynamic Similarity for Model Submarine Maneuvers.  

National Technical Information Service (NTIS)

Dimensional analysis and dynamic similarity requirements show that Reynolds, Froude, and Strouhal scales are important parameters to be satisfied for free-running submarine model maneuvering tests in order that they correctly represent full scale behavior...

D. E. Hess Y. T. Shen

2007-01-01

296

Analysis of Kidney Stones in the Submarine Force.  

National Technical Information Service (NTIS)

This report presents the results of a retrospective review of nephrolithiasis waiver and disqualification packages submitted to Atlantic and Pacific Force Medical Officers over the past three years. General characteristics of stone-formers in the submarin...

P. L. Perrotta J. L. Hyashi D. J. Dlugos

1992-01-01

297

View west of reserve basin of submarine trout and frigate ...  

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

View west of reserve basin of submarine trout and frigate Edward E. McDonnell - Naval Base Philadelphia-Philadelphia Naval Shipyard, Reserve Basin & Marine Railway, League Island, Philadelphia, Philadelphia County, PA

298

Employment of Fast Attack Submarines by the Operational Commander.  

National Technical Information Service (NTIS)

For operational commanders, the use of military force today requires flexibility, efficiency, and careful risk management among joint forces. In light of these requirements, this paper examines the influence of the fast attack nuclear submarine (SSN) and ...

G. C. Williams

1998-01-01

299

Biochemical Profiles of Submariners: A Longitudinal Health Study.  

National Technical Information Service (NTIS)

As part of this Laboratory's Longitudinal Health Study, the sera of 466 submariners were analyzed for 12 biochemical parameters using standardized automated procedures. In addition, a two hour glucose tolerance test was performed on each participant. Mean...

D. V. Tappan M. J. Jacey E. Heyder W. A. Tansey

1975-01-01

300

Grand Canyon Monitoring and Research Center  

NSDL National Science Digital Library

Created in 1995, the Grand Canyon Monitoring and Research Center (GCMRC) was created in order to measure the effects of Glen Canyon Dam operations on natural and physical resources along the Colorado River. As such, the GCMRC's projects also monitor and examine the biological, cultural, and physical resources of the entire Colorado River ecosystem. The materials on their site are divided into five primary sections, including "News & Info", "Research", and "Products". In the "News & Info" area visitors can learn about the endangered species that reside in the area covered by the GCMRC and also take a look at their outreach materials, which include fact sheets, posters, and transcripts from recent symposia. The "Research" area is a bit more technical in nature, containing papers on water flow simulations and elevation data. The site is rounded out by the "Products" area, where visitors can look over new publications and evaluate simulation models.

301

Holocene vegetation in chaco canyon, new Mexico.  

PubMed

Well-preserved plant remains in packrat middens chronicle vegetation change in Chaco Canyon over the past 11,000 years. Early Holocene evidence of communities dominated by Douglas fir, Rocky Mountain juniper, and limber pine in the San Juan Basin calls for revision of traditional constructs based on fossil pollen. Middle and late Holocene vegetation in the canyon was pinyon-juniper woodland up until Anasazi occupation between 1000 and 800 years ago. Instead of climate, Anasazi fuel needs may explain the drastic reduction of pinyon and juniper after 1230 years ago. The lack of pinyon-juniper recovery over the past millennium has implications for contemporary forest and range ecology. PMID:17839658

Betancourt, J L; VAN Devender, T R

1981-11-01

302

Flat-panel technology impact on submarine tactical system designs  

NASA Astrophysics Data System (ADS)

Flat panel display products could have an important effect on submarine design decisions. Beyond the obvious volume savings, flat panel displays offer improved flexibility during system design, and thus, create new opportunities for useful and innovative compartment and equipment arrangements. While suitable MIL-SPEC flat panel displays are still a number of years away, advanced flat panel-based submarine control room concepts, anticipating the technology, are already being explored.

Chaum, Erik

1992-07-01

303

4. View to northwest from within Castro Creek Canyon, looking ...  

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

4. View to northwest from within Castro Creek Canyon, looking up at 'Antique' Building (HABS-CA-2611-C) at left and center, 'Champagne' Building (HABS-CA-2611-D) at right behind redwood trees. View gives indication of steepness of canyon, siting of these two buildings at canyon's edge. - Deetjen's Big Sur Inn, East Side of State Highway 1, Big Sur, Monterey County, CA

304

Wind fields and turbulence statistics in an urban street canyon  

Microsoft Academic Search

This is the first paper of a long-term measurement campaign to explore wind, temperature, radiation and energy fields within an urban canyon. A canyon and a rooftop mast were installed in a canyon with an aspect ratio (Height\\/Width) of ?2.1 in Göteborg, Sweden. A number of instruments including sonic anemometers, radiometers and thermocouples were mounted in vertical profiles and across

I. Eliasson; B. Offerle; C. S. B. Grimmond; S. Lindqvist

2006-01-01

305

77 FR 5790 - Mississippi Canyon Gas Pipeline, LLC; Notice of Request Under Blanket Authorization  

Federal Register 2010, 2011, 2012, 2013

...Commission [Docket No. CP12-49-000] Mississippi Canyon Gas Pipeline, LLC; Notice of Request...notice that on January 17, 2012, Mississippi Canyon Gas Pipeline, LLC (MCGP), 1100...Manager, Regulatory Compliance, Mississippi Canyon Gas Pipeline, LLC, 1100...

2012-02-06

306

33 CFR 165.1171 - Copper Canyon, Lake Havasu, Colorado River-Regulated Navigation Area.  

Code of Federal Regulations, 2013 CFR

...false Copper Canyon, Lake Havasu, Colorado River-Regulated Navigation Area...1171 Copper Canyon, Lake Havasu, Colorado RiverâRegulated Navigation Area...area of Copper Canyon, Lake Havasu, Colorado River, beginning at the...

2013-07-01

307

33 CFR 165.1171 - Copper Canyon, Lake Havasu, Colorado River-Regulated Navigation Area.  

Code of Federal Regulations, 2010 CFR

... Copper Canyon, Lake Havasu, Colorado River-Regulated Navigation Area... Copper Canyon, Lake Havasu, Colorado RiverâRegulated Navigation Area...Copper Canyon, Lake Havasu, Colorado River, beginning at the...

2010-07-01

308

33 CFR 165.1171 - Copper Canyon, Lake Havasu, Colorado River-Regulated Navigation Area.  

Code of Federal Regulations, 2010 CFR

... Copper Canyon, Lake Havasu, Colorado River-Regulated Navigation Area... Copper Canyon, Lake Havasu, Colorado RiverâRegulated Navigation Area...Copper Canyon, Lake Havasu, Colorado River, beginning at the...

2009-07-01

309

75 FR 20381 - Glen Canyon Dam Adaptive Management Work Group (AMWG)  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Work Group (AMWG...SUMMARY: The Glen Canyon Dam Adaptive Management Program (AMP) was...Decision on the Operation of Glen Canyon Dam Final Environmental Impact Statement...

2010-04-19

310

78 FR 54482 - Charter Renewal, Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...4073000] Charter Renewal, Glen Canyon Dam Adaptive Management Work Group AGENCY...renewing the charter for the Glen Canyon Dam Adaptive Management Work Group. The purpose...concerning the operation of Glen Canyon Dam and the exercise of other authorities...

2013-09-04

311

76 FR 584 - Glen Canyon Dam Adaptive Management Program Work Group (AMWG)  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Program Work Group...SUMMARY: The Glen Canyon Dam Adaptive Management Program (AMP) was...Decision on the Operation of Glen Canyon Dam Final Environmental Impact Statement...

2011-01-05

312

75 FR 439 - Glen Canyon Dam Adaptive Management Work Group (AMWG)  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Work Group (AMWG...SUMMARY: The Glen Canyon Dam Adaptive Management Program (AMP) was...Decision on the Operation of Glen Canyon Dam Final Environmental Impact Statement...

2010-01-05

313

75 FR 44809 - Glen Canyon Dam Adaptive Management Work Group (AMWG)  

Federal Register 2010, 2011, 2012, 2013

...INTERIOR Bureau of Reclamation Glen Canyon Dam Adaptive Management Work Group (AMWG...SUMMARY: The Glen Canyon Dam Adaptive Management Program (AMP) was...Decision on the Operation of Glen Canyon Dam Final Environmental Impact Statement...

2010-07-29

314

Ancient impact structures on modern continental shelves: The Chesapeake Bay, Montagnais, and Toms Canyon craters, Atlantic margin of North America  

USGS Publications Warehouse

Three ancient impact craters (Chesapeake Bay - 35.7 Ma; Toms Canyon - 35.7 Ma; Montagnais - 51 Ma) and one multiring impact basin (Chicxulub - 65 Ma) are currently known to be buried beneath modern continental shelves. All occur on the passive Atlantic margin of North America in regions extensively explored by seismic reflection surveys in the search for oil and gas reserves. We limit our discussion herein to the three youngest structures. These craters were created by submarine impacts, which produced many structural and morphological features similar in construction, composition, and variability to those documented in well-preserved subaerial and planetary impact craters. The subcircular Chesapeake Bay (diameter 85 km) and ovate Montagnais (diameter 45-50 km) structures display outer-rim scarps, annular troughs, peak rings, inner basins, and central peaks similar to those incorporated in the widely cited conceptual model of complex impact craters. These craters differ in several respects from the model, however. For example, the Montagnais crater lacks a raised lip on the outer rim, the Chesapeake Bay crater displays only small remnants of a raised lip, and both craters contain an unusually thick body of impact breccia. The subtriangular Toms Canyon crater (diameter 20-22 km), on the other hand, contains none of the internal features of a complex crater, nor is it typical of a simple crater. It displays a prominent raised lip on the outer rim, but the lip is present only on the western side of the crater. In addition, each of these craters contains some distinct features, which are not present in one or both of the others. For example, the central peak at Montagnais rises well above the elevation of the outer rim, whereas at Chesapeake Bay, the outer rim is higher than the central peak. The floor of the Toms Canyon crater is marked by parallel deep troughs and linear ridges formed of sedimentary rocks, whereas at Chesapeake Bay, the crater floor contains concentric faults and compression ridges formed in rocks of the crystalline basement. The Chesapeake Bay crater is distinguished further by its cluster of at least 23 adjacent secondary craters. The North American tektite strewn field, a widespread deposit of distal ejecta, is thought to be derived from the Chesapeake Bay impact, perhaps with a small contribution from the Toms Canyon impact. No ejecta field is known to be associated with the Montagnais impact. No immediate major extinction event is directly linked to any of these three impacts. There is evidence, however, that the Chesapeake Bay and Toms Canyon impacts helped initiate a long-term pulse of warm global climate, whose eventual dissipation coincided with an early Oligocene mass extinction event, 2 Ma after the impacts.

Poag, C. Wylie; Plescia, J. B.; Molzer, P. C.

2002-01-01

315

Transfer processes in a simulated urban street canyon  

NASA Astrophysics Data System (ADS)

The transfer processes within and above a simulated urban street canyon were investigated in a generic manner. Computational fluid dynamics (CFD) was used to aid understanding and to produce some simple operational parameterisations. In this study we addressed specifically the commonly met situation where buoyancy effects arising from elevated surface temperatures are not important, i.e. when mechanical forces outweigh buoyancy forces. In a geophysical context this requires that some suitably defined Richardson number is small. From an engineering perspective this is interpreted as the important case when heat transfer within and above urban street canyons is by forced convection. Surprisingly, this particular scenario (for which the heat transfer coefficient between buildings and the flow is largest), has been less well studied than the situation where buoyancy effects are important. The CFD technique was compared against wind-tunnel experiments to provide model evaluation. The height-to-width ratio of the canyon was varied through the range 0.5 5 and the flow was normal to the canyon axis. By setting the canyon’s facets to have the same or different temperatures or to have a partial temperature distribution, simulations were carried out to investigate: (a) the influence of geometry on the flow and mixing within the canyon and (b) the exchange processes within the canyon and across the canyon top interface. Results showed that the vortex-type circulation and turbulence developed within the canyon produced a temperature distribution that was, essentially, spatially uniform (apart from a relatively thin near-wall thermal boundary layer) This allowed the temperatures within the street canyon to be specified by just one value T can , the canyon temperature. The variation of T can with wind speed, surface temperatures and geometry was extensively studied. Finally, the exchange velocity u E across the interface between the canyon and the flow above was calculated based on a heat flux balance within the canyon and between the canyon and the flow above. Results showed that u E was approximately 1% of a characteristic wind velocity above the street canyon. The problem of radiative exchange is not addressed but it can, of course, be introduced analytically, or computationally, when necessary.

Solazzo, E.; Britter, R. E.

2007-07-01

316

The Role of Late-Cenozoic Lava Flows in the Evolution of the Owyhee River Canyon, Oregon  

NASA Astrophysics Data System (ADS)

Over the last 2 Ma, at least six lava flows entered the canyon of the Owyhee River in southeastern Oregon, dramatically and repeatedly altering the river's course and profile. A combination of geochronologic, geochemical, and paleomagnetic analyses accompanied by extensive field mapping shows that these lava flows erupted from upland vents 10s of km from the river, entered the canyon via tributary or rim, and formed blockages sufficient to create lakes. Thick deltas of pillow lavas and rising passage zones in the head of the dams and subaerial lavas downstream of the dam indicate effective damming. The presence of fine grained laminated sediments deposited in the lakes suggests the dams were fairly long lived. Pending OSL dates and ongoing field study of these sediments will shed light on the nature and duration of dam construction and removal. Lava-water interaction during dam construction was extensive, and thick pillow lava deltas are common. In contrast to rivers in other locations, we did not find evidence of pyroclastics such as cinders associated with the dams. The three oldest intracanyon lava flows: the lower undivided Bogus lavas (>1.92 ± 0.22 Ma), the Bogus Rim (1.92 ± 0.22 Ma), and the Greeley Bar lavas (>780 ka), all record the filling of a wide, deep canyon, damming of the Owyhee River, and creation of extensive lakes at elevations 230 to 310 m above the modern river. The three younger lava flows, the Clarks Butte (248 ± 45 ka), the Saddle Butte (~125 ka), and the West Crater (60-90 ka), record the occurrence of similar events but in a narrower, deeper canyon similar to the modern one. Overall, this array of late Cenozoic intracanyon lava flows provides key insights into the long-term incision history of the canyon, possibly including the effect of integration with the Snake River, and supports a model of long-term, regional landscape evolution that is strongly linked to lava-water interactions.

Brossy, C. C.; House, P. K.; Ely, L. L.; O'Connor, J. E.; Safran, E. B.; Bondre, N.; Champion, D. E.; Grant, G.

2008-12-01

317

Submarine Volcanic Morphology of Santorini Caldera, Greece  

NASA Astrophysics Data System (ADS)

Santorini volcanic group form the central part of the modern Aegean volcanic arc, developed within the Hellenic arc and trench system, because of the ongoing subduction of the African plate beneath the European margin throughout Cenozoic. It comprises three distinct volcanic structures occurring along a NE-SW direction: Christianna form the southwestern part of the group, Santorini occupies the middle part and Koloumbo volcanic rift zone extends towards the northeastern part. The geology of the Santorini volcano has been described by a large number of researchers with petrological as well as geochronological data. The offshore area of the Santorini volcanic field has only recently been investigated with emphasis mainly inside the Santorini caldera and the submarine volcano of Kolumbo. In September 2011, cruise NA-014 on the E/V Nautilus carried out new surveys on the submarine volcanism of the study area, investigating the seafloor morphology with high-definition video imaging. Submarine hydrothermal vents were found on the seafloor of the northern basin of the Santorini caldera with no evidence of high temperature fluid discharges or massive sulphide formations, but only low temperature seeps characterized by meter-high mounds of bacteria-rich sediment. This vent field is located in line with the normal fault system of the Kolumbo rift, and also near the margin of a shallow intrusion that occurs within the sediments of the North Basin. Push cores have been collected and they will provide insights for their geochemical characteristics and their relationship to the active vents of the Kolumbo underwater volcano. Similar vent mounds occur in the South Basin, at shallow depths around the islets of Nea and Palaia Kameni. ROV exploration at the northern slopes of Nea Kameni revealed a fascinating underwater landscape of lava flows, lava spines and fractured lava blocks that have been formed as a result of 1707-1711 and 1925-1928 AD eruptions. A hummocky topography at the area that lies between the town of Fira on the main island of Santorini and Nea Kammeni has been revealed. The lower slopes were covered with landslide debris which consisted of lava blocks mostly mantled with soft sediment. At the upper slopes an abrupt cliff face was exposed that was highly indurated by biologic material. At the top of a volcanic dome, a crater with its deepest part at 43m, its rim at about 34m with an approximately 8m diameter was also found. Shimmery water with temperatures as much as 25°C above ambient was observed there but the source of venting has not yet been found. The combination of ROV video footage and multibeam data provide new information about the main morphological characteristics of Santorini Caldera which demonstrates the intense geodynamic processes occurring at the central part of the active Hellenic volcanic arc. These results will be useful for the interpretation of understanding the offshore volcanic area and its linkage with the onshore structures.

Nomikou, P.; Croff Bell, K.; Carey, S.; Bejelou, K.; Parks, M.; Antoniou, V.

2012-04-01

318

Narrow tetraquarks at large N  

NASA Astrophysics Data System (ADS)

Following a recent suggestion by Weinberg, we use the large-N expansion in QCD to discuss the decay amplitudes of tetraquarks into ordinary mesons as well as their mixing properties. We find that the flavor structure of the tetraquark is a crucial ingredient to determine both this mixing as well as the decays. Although in some cases tetraquarks should be expected to be as narrow as ordinary mesons, they may get to be even narrower, depending on this flavor structure.

Knecht, Marc; Peris, Santiago

2013-08-01

319

Sedimentation in Rio La Venta Canyon in Netzahualcoyotl Reservoir, Chiapas, Mexico  

NASA Astrophysics Data System (ADS)

Sedimentation of Rio La Venta as it enters the Netzahualcoyotl Reservoir in Chiapas, Mexico, threatens a unique part of the aquatic ecosystem. Rio La Venta enters the reservoir via a narrow canyon about 16 km long with spectacular, near-vertical limestone bluffs up to 320 m high and inhabited by the flora and fauna of a pristine tropical forest. Karst terrain underlies most of the Rio La Venta basin in the vicinity of the reservoir, while deeply weathered granitic terrain underlies the Rio Negro basin, and the headwaters of the Rio La Venta to the south. The Rio Negro joins Rio La Venta 3 km downstream of the upper limit of the reservoir and delivers the bulk of the total clastic sediment (mostly sand and finer material). The canyon and much of the contributing basin lie within the Reserva de la Biosfera, Selva El Ocote, administered by the Comision Nacional de Areas Naturales Protegidas, part of the Secretaria de Medioambiente y Recursos Naturales. The Klamath National Forest Forest has cooperated with its Mexican counterparts since 1993 in natural resource management, neo-tropical bird inventories, wildfire management, and more recently in watershed analyses. Rates of sedimentation are estimated from bathymetric surveys conducted in March, 2002. A longitudinal profile down the inundated canyon during a high reservoir level shows an inflection from a slope of 0.0017 to one of 0.0075 at 7.2 km downstream of the mouth of Rio Negro. The bed elevation at this point corresponds to the lowest reservoir level, suggesting that the gentler sloping bed upstream is formed by fluvial processes during drawdown and that downstream by pluvial processes. Using accounts that boats could access Rio Negro during low water levels in 1984, we estimate an annual sedimentation rate of roughly 3 million cubic meters per year. This suggests that boats might no longer be able to access the most spectacular section of canyon upstream of Rio Negro within a decade, depending on how the depositional profile develops. Additionally, canyon filling will change the aquatic ecology of the river and the reservoir, and result in loss of fish habitat. A monitoring program is in place to answer this critical question.

de La Fuente, J. A.; Lisle, T.; Velasquez, J.; Allison, B. L.; Miller, A.

2002-12-01

320

How long are submarine landslides coupled to the water column?  

NASA Astrophysics Data System (ADS)

Waves generated from submarine mass failure, come in second only to earthquakes as the most frequent causes of tsunami waves. The gap however between the understanding of earthquake generated waves and the generation of tsunami waves from submarine mass failure (hereafter called submarine landslides) is quite large. A critical component of shortening this gap is to understand the efficiency that submarine landslides have in generating tsunamis. Unlike earthquake-induced tsunamis, where the deformation at the free surface can be derived directly from the deformation of the seafloor, submarine landslides exhibit a complex and nonlinear energy transfer from the moving slide to the water column. Therefore the application of several empirical formulae and equations derived from theory do not lead consistent results. For example inverting the amplitude of the leading wave with such equations can result in a scatter of the wave height up to six orders of magnitude. To derive more robust and reliable estimates of leading-wave characteristics, the coupling between the slide body and the water surface need to be investigated further to shed light on the energy transfer. We present results from parameters studies, carried out with the hydrocode iSALE. iSALE has proven to be a reliable simulation tool for generation of large waves from subaerial and submarine landslides. In order to shed more light on energy transfer from the slide body to the water column, we focus, in here, on the duration of the energy transfer. In our modeling the slide motion generates a trough with depth, s, which increases after the slide is in motion, ds/dt > 0. Decoupling, tau, is then defined when ds/dt ? 0, and the decoupling time, ?d, as being reached when ds/dt = 0. A parameter study relating the decoupling to mass, depth of submergence, and viscosity is conducted as an initial step in elucidating the generation processes of submarine landslide-generated tsunamis.

O'Shay, J.; Weiss, R.; Synolakis, C. E.

2012-04-01

321

Initiation and evolution processes of submarine instabilities and canyons: Insights from the Northern margin of the Gulf of Aden  

Microsoft Academic Search

The study of turbiditic systems and their interactions (climate, tectonic) are not well known in monsoon-influenced areas and on young margins. The Gulf of Aden is a good example of young stretched margin (35-18 Ma), where post-rift sediments are recording the intensification of the Asian monsoon (~7-8 Ma). Therefore the understanding of facies and depositional sequences on this margin is

B. Céline; G. Christian; S. Leroy; L. Francis; B. François; K. I. Al-Toubi

2010-01-01

322

Martian Canyons and African Rifts: Structural Comparisons and Implications.  

National Technical Information Service (NTIS)

The resistant parts of the canyon walls of the Martian rift complex Valled Marineris were used to infer an earlier, less eroded reconstruction of the major roughs. The individual canyons were then compared with individual rifts of East Africa. When measur...

H. Frey

1978-01-01

323

Adobe unlocks Cherry Canyon, other zones in prolific Barstow unit  

Microsoft Academic Search

Recent discoveries by Adobe Oil and Gas Corp. in the Barstow unit skirting the Pecos River near Pecos, Texas have extended the Cherry Canyon play approx. 10 miles west in Ward County. In February, Adobe reported an oil discovery, 10 Barstow, drilled between No. 9 and No. 11 (gas wells) in section 34. The well reestablished Cherry Canyon oil production

1979-01-01

324

4. VISTA POINT AND INTERPRETIVE PLAQUE AT LEE VINING CANYON. ...  

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

4. VISTA POINT AND INTERPRETIVE PLAQUE AT LEE VINING CANYON. NOTE ROAD CUT ON CANYON WALL. LOOKING NNE. GIS: N-37 56 30.3 / 119 13 44.8 - Tioga Road, Between Crane Flat & Tioga Pass, Yosemite Village, Mariposa County, CA

325

Radionuclide content of an exhumed canyon tank and neighboring soil  

Microsoft Academic Search

To assess the long-term hazard potential associated with the burial of partially decontaminated process equipment, burial emplacements of equipment from an irradiated-fuel separations building (canyon) are being exhumed and examined. One piece of equipment, a Purex feed adjustment tank that was retired in 1957 from service in a hot canyon at the Savannah River Plant, has been exhumed and studied.

1977-01-01

326

Review of proposed Glen Canyon Dam interim operating criteria.  

National Technical Information Service (NTIS)

Three sets of interim operating criteria for Glen Canyon Dam on the Colorado River have been proposed for the period of November 1991, to the completion of the record of decision for the Glen Canyon Dam environmental impact statement (about 1993). These c...

K. LaGory I. Hlohowskyj D. Tomasko J. Hayse L. Durham

1992-01-01

327

Warm water interactions in the Barrow Canyon in winter  

NASA Astrophysics Data System (ADS)

An extensive set of salinity-temperature measurements was taken in the ice-covered Barrow Canyon in early April 1976. An intrusion of relatively warm water into the mid-depth of the canyon is believed due to a surge-driven mixing of the Atlantic Layer with Arctic Ocean surface water on the upper continental slope.

Garrison, G. R.; Paquette, R. G.

1982-07-01

328

Adaptation of a Computer-Assisted Diagnosis Program for Use by Hospital Corpsmen Aboard Nuclear Submarines.  

National Technical Information Service (NTIS)

Acute illness occurring aboard a patrolling nuclear submarine is costly in terms of risk to the patient, the expense of evacuation, and compromise of national defense (if the submarine's mission must be terminated). There are currently no physicians assig...

J. V. Henderson G. M. Moeller B. M. Ryack G. M. Shumaik

1978-01-01

329

Development of a Six Degree of Freedom Motion Simulation Model for Use in Submarine Design Analysis.  

National Technical Information Service (NTIS)

A computer mathematical model that will simulate the six degree of freedom motion of a submarine has been developed. Hydrodynamic coefficients obtained from the testing of physical models enable the user to accurately simulate specific submarine designs. ...

J. T. Hammond

1978-01-01

330

Addressing the Challenges of a Smoke-Free U.S. Navy Submarine Force.  

National Technical Information Service (NTIS)

Traditionally submarines have had a smoking space. A study conducted 2007-9 concluded nonsmokers are exposed to significant levels of environmental tobacco smoke, regardless of location on the submarine. In 2009, a working group was established to create ...

F. Yeo J. McQuade L. Williams M. Long

2011-01-01

331

Future of the Ballistic Missile Submarine Force in the Russian Nuclear Triad.  

National Technical Information Service (NTIS)

This thesis analyzes the current status of the Russian Federation's ballistic missile submarine force. It reviews the history of the ballistic missile submarine force, its current status, and the implementation of plans currently in progress and as well a...

R. T. Lesiw

2008-01-01

332

The Navy Mod I Submarine Deck Exposure Suit (Physiological, Buoyancy and Field Evaluation Studies).  

National Technical Information Service (NTIS)

The Navy Clothing and Textile Research Facility (NCTRF) conducted physiological studies which established that the experimental Type B Submarine Deck Exposure Suit (SDES) prototype was a possible replacement for the Interim SDES currently worn on submarin...

J. Silvia N. F. Audet D. A. Reins

1978-01-01

333

Results of Inspections of MK-10 Submarine Escape and Immersion Equipment Life Rafts Following Leeway Testing.  

National Technical Information Service (NTIS)

NSMRL funded the United States Coast Guard Research and Development Center in Groton, Connecticut to conduct testing to determine the leeway coefficients for the Submarine Emergency Position Indicating Radio Beacons (SEPIRB) and the Mark-10 Submarine Esca...

A. J. Quatroche P. S. Turnbull W. G. Horn

2007-01-01

334

Long-Term Submarine Groundwater Discharge: Model Constraints on Magnitudes and Driving Forces for Passive Margins  

NASA Astrophysics Data System (ADS)

Numerical models of continental shelf hydrogeology document that submarine groundwater discharge (SGD) to the ocean varies significantly in space and time due to sea level fluctuations, aquifer distribution, and, at high latitudes, glaciation. Our high-resolution, 3D, variable-density groundwater model that includes sea level variation and ice sheet loading (GW_ICE) shows SGD up to 100 km offshore from Miocene sands off New England at rates near 1 cm/yr. The highest discharge occurs in Baltimore and Hudson canyons during sea level lowstands when shore normal gradients are highest and where shallow Miocene sands outcrop. Coincident with elevated SGD, recharge rates are up to four times of modern rates beneath the Laurentide ice sheet. As sea level rises, flow fields reverse and seawater recharges sediments at rates approaching 0.75 cm/yr. Today seawater is still invading shelf aquifers, as the aquifers are not in equilibrium with modern sea level. Key driving forces to offshore freshwater and SGD on long-time scales are: onshore meteoric infiltration for large flow systems, local flow cells aided by sea level lowstands and local topography, and sub-ice-sheet recharge. In non-glaciated regions, SGD occurs farthest offshore, primarily driven by enhanced hydraulic gradients from lower sea level. Glaciated regions have near-shore changes in SGD and freshwater distribution controlled by ice sheet extent and thickness. Additionally our continental shelf modeling predicts that up to 10,000 km3 of freshwater may exist along New England’s continental shelf. Our results suggest that chemical and nutrient supply to oceans from SGD varies significantly through time, which could have important implications for local/regional seafloor life and ocean chemistry. The models provide new insights into long-term variations of submarine groundwater discharge and new constraints on time-integrated fluxes along continental margins which will help us better understand SGD and its implications for nutrient fluxes to the ocean, marine ecology, and biogeochemistry especially during large-scale, episodic flushing of continental shelf sediments.

Dugan, B.; Person, M. A.; Cohen, D. O.

2009-12-01

335

Active geologic processes in Barrow Canyon, northeast Chukchi Sea  

USGS Publications Warehouse

Circulation patterns on the shelf and at the shelf break appear to dominate the Barrow Canyon system. The canyon's shelf portion underlies and is maintained by the Alaska Coastal Current (A.C.C.), which flows northeastward along the coast toward the northeast corner of the broad Chukchi Sea. Offshelf and onshelf advective processes are indicated by oceanographic measurements of other workers. These advective processes may play an important role in the production of bedforms that are found near the canyon head as well as in processes of erosion or non-deposition in the deeper canyon itself. Coarse sediments recovered from the canyon axis at 400 to 570 m indicate that there is presently significant flow along the canyon. The canyon hooks left at a point north of Point Barrow where the A.C.C. loses its coastal constriction. The left hook, as well as preferential west-wall erosion, continues down to the abyssal plain of the Canada Basin at 3800 m. A possible explanation for the preferential west-wall erosion along the canyon, at least for the upper few hundred meters, is that the occasional upwelling events, which cause nutrient-rich water to flow along the west wall would in turn cause larger populations of burrowing organisms to live there than on the east wall, and that these organisms cause high rates of bioerosion. This hypothesis assumes that the dominant factor in the canyon's erosion is biological activity, not current velocity. Sedimentary bedforms consisting of waves and furrows are formed in soft mud in a region on the shelf west of the canyon head; their presence there perhaps reflects: (a) the supply of fine suspended sediments delivered by the A.C.C. from sources to the south, probably the Yukon and other rivers draining northwestern Alaska; and (b) the westward transport of these suspended sediments by the prevailing Beaufort Gyre which flows along the outer shelf. ?? 1982.

Eittreim, S.; Grantz, A.; Greenberg, J.

1982-01-01

336

Test Excavations at Box Canyon and Three Other Side Canyon Sites in the McNary Reservoir.  

National Technical Information Service (NTIS)

The Columbia River Side Canyon Sites superficially appear as lithic, shell and bone scatters exposed in four north to south running breaks through basalt cliff terraces and adjacent to McNary Reservoir. All of the canyons are characterized to some extent ...

G. C. Burtchard K. Simmons E. Adams-Rasmussen B. D. Cochran

1981-01-01

337

Numerical Simulation on the Horseshoe Vortex Formation Around the Hull-Sail Junction of Submarine  

Microsoft Academic Search

The horseshoe vortex is typical flow characteristic around the appendage-body junction. The horseshoe vortex formation around the hull-said junction has important influence on the submarine hydrodynamics performance. The origination process of the submarine horseshoe vertex and its influence on submarine flow is analyzed. The numerical simulation on the horseshoe vortex is carried out using DES method (Detached Eddies Simulation); the

Liu Zhihua; Xiong Ying

2010-01-01

338

Structural and acoustic responses of a submarine hull due to propeller forces  

Microsoft Academic Search

The low frequency structural and acoustic responses of a simplified axisymmetric submarine model to fluctuating propeller forces along the submarine axis are investigated. The forces arise from a hydrodynamic mechanism and are transmitted from the propeller to the submarine hull through both the shaft and the fluid. Numerical models have been developed to simulate the strongly coupled structure–fluid interaction of

Sascha Merz; Roger Kinns; Nicole Kessissoglou

2009-01-01

339

33 CFR 165.1302 - Bangor Naval Submarine Base, Bangor, WA.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Bangor Naval Submarine Base, Bangor, WA. 165.1302 Section...District § 165.1302 Bangor Naval Submarine Base, Bangor, WA. (a) Location...Vessels that are performing work at Naval Submarine Base Bangor pursuant to a...

2010-07-01

340

33 CFR 165.1328 - Regulated Navigation Area; U.S. Navy submarines, Hood Canal, WA.  

Code of Federal Regulations, 2013 CFR

...Regulated Navigation Area; U.S. Navy submarines, Hood Canal, WA. 165.1328 Section...Regulated Navigation Area; U.S. Navy submarines, Hood Canal, WA. (a) Location...Washington whenever any U.S. Navy submarine is operating in the Hood Canal and is being...

2013-07-01

341

33 CFR 209.310 - Representation of submarine cables and pipelines on nautical charts.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false Representation of submarine cables and pipelines on nautical charts...PROCEDURE § 209.310 Representation of submarine cables and pipelines on nautical charts...with respect to showing the locations of submarine cables and pipelines on nautical...

2009-07-01

342

33 CFR 165.1302 - Bangor Naval Submarine Base, Bangor, WA.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false Bangor Naval Submarine Base, Bangor, WA. 165.1302 Section...District § 165.1302 Bangor Naval Submarine Base, Bangor, WA. (a) Location...Vessels that are performing work at Naval Submarine Base Bangor pursuant to a...

2009-07-01

343

33 CFR 209.310 - Representation of submarine cables and pipelines on nautical charts.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Representation of submarine cables and pipelines on nautical charts...PROCEDURE § 209.310 Representation of submarine cables and pipelines on nautical charts...with respect to showing the locations of submarine cables and pipelines on nautical...

2010-07-01

344

33 CFR 165.1302 - Bangor Naval Submarine Base, Bangor, WA.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Bangor Naval Submarine Base, Bangor, WA. 165.1302 Section...District § 165.1302 Bangor Naval Submarine Base, Bangor, WA. (a) Location...Vessels that are performing work at Naval Submarine Base Bangor pursuant to a...

2013-07-01

345

Sequence architecture and lithofacies assemblages of submarine fan deposits in Los Molles Formation (Jurassic), Neuquen Basin, Argentina  

SciTech Connect

The Neuquen basin is a remnant of the Mesozoic back-arc basin trend that developed along the western margin of South America. It contains a thick, diverse sequence of Jurassic sedimentary strata, whose facies distribution was strongly influenced by syndepositional tectonism. The predominantly dark, laminated shales and siltstones of the Los Molles Formation range from Pliensbachian to Callovian in age and record the progradation of the outer shelf, slope, and basin-plain sediments deposited during the shoaling phase of the lowermost, or Cuyan, Jurassic cycle. Based on outcrop, well, and seismic data, several thick packages of sandstone and conglomerate within the Los Molles are interpreted to represent submarine fan deposits that developed during periods of relative sea level lowstand. Sea level falls were probably related to local synchronous tectonic pulses rather than true eustatic fluctuations. The distribution of coarse-grained fan deposits was apparently strongly controlled by the location of major Jurassic fault trends that stabilized the position of the shelf-slope break through time. Based on the geometry and sequence architecture, two distinct styles of fan development are recognized in the Los Molles sandstones. The most common style (type A) is characterized by sequences that have poorly defined, sand-poor lobes with well-developed channel-levee complexes. Some channels exhibit large-scale accretion surfaces, probably resulting from lateral migration. Thick-bedded arenite facies are limited to amalgamated channel fills, whereas thin-bedded classical turbidites are present as overbank deposits. Type A fans were built by turbidity and fluxoturbidity currents from submarine canyon point sources. The less common fan sequences (type B) lack channeling; they are dominated by thick, massive beds of internally featureless sandstone that are bounded by chaotic slump deposits.

Dean, J.S.

1986-05-01

346

Preliminary Velocity Measurements in the Wake of a Submarine Model  

NASA Astrophysics Data System (ADS)

Preliminary Particle Image Velocimetry (PIV) over a submarine shape has been conducted in a low speed wind tunnel at Princeton University. The model is a 1/67 replica of the USS Albacore, an experimental submarine designed to achieve maximum underwater performance, and based on "bodies of revolution." The model is tested with a sail, and different tail appendages. Velocity vector fields and flow visualizations in the wake region are presented for Reynolds numbers based on model length up to 10^5. The experiments establish the groundwork for future investigations of submarine models in the new High Reynolds Number Test Facility (http://www.princeton.edu/ gasdyn/HRTF.html). Supported by ONR Grants N00014-97-1-0325, N00014-97-1-0340 and N00014-97-1-0618.

Jimenez, J. M.; Reynolds, R.; Smits, A. J.

2000-11-01

347

Hawaiian Shield Stage Submarine Volcaniclastics: Insights From HSDP Core  

NASA Astrophysics Data System (ADS)

Ocean island volcanoes are traditionally associated with the non-explosive eruption of fluid lavas, but volcaniclastic rocks comprise a significant portion of many submarine shield volcanoes. Deep drilling (3,098 m) by the Hawaiian Scientific Drilling Project (HSDP) into the flank of Mauna Kea volcano has exposed the volcaniclastics within the pedestals of a Hawaiian volcano that were previously poorly known. The HSDP continuously cored 2,019 m of submarine Mauna Kea deposits with ˜95% recovery and revealed that volcaniclastics comprise ˜55% of this section. The shallow submarine section consists of ˜80% volcaniclastics interbedded with thin ( ˜3 m) massive lava flows and the deep section is ˜35% volcaniclastics interbedded with packages of pillow lavas up to 180 m thick. Throughout the submarine section, the volcaniclastics can occur in thick packages up to ˜100 m. The emplacement of submarine volcaniclastics is not well understood. Possible origins include primary fragmentation of lava via magmatic explosivity and magma-water interactions, and secondary fragmentation via erosion. Secondary transport of material down the steep submarine flanks by gravity flows is expected to be common, as is reworking by currents. Emplacement processes are predicted to evolve as the volcano shoals. In this study major element analyses of glassy clasts in the volcaniclastics are used to distinguish monomict and polymict assemblages, which can indicate primary versus secondary fragmentation. Clast shapes reflect fragmentation mechanisms and secondary processes and this study attempts to improve on this approach with quantitative analysis of clast shapes for the HSDP volcaniclastics and for samples of known origin. The first documentation of the textures of the Mauna Kea volcaniclastics, integrated with geochemistry, petrography, and quantitative clast shape analysis and inferences about their origins and modes of transport and deposition will be presented to better understand the shoaling of Hawaiian volcanoes.

Bridges, K. P.; Garcia, M.; Houghton, B.; Thordarson, T.

2003-12-01

348

Fine-scale predictive mapping of Cold Water Coral species in the Cap de Creus Canyon (NW Mediterranean): first insights  

NASA Astrophysics Data System (ADS)

Cold-water corals (CWC) are azooxanthellate species which develop in a complex environment ruled out by a delicate interplay between geological, biological and oceanographic conditions.High impact deep-sea bottom trawling activities are seriously compromising the health and state of conservation of CWC habitats. It has been recently discovered that submarine canyons can act as hosting areas for benthic communities dominated by CWCs. Favorable environmental conditions along the canyons coupled with the rough seafloor morphology can foster their development and facilitate their preservation from the trawling threat. The aim of this study is to statistically predict the distribution of three CWC species (Madrepora oculata, Lophelia pertusa, Dendrophyllia cornigera) in the Cap de Creus Canyon (NW Mediterranean) based on high-resolution swath-bathymetry data (pixel resolution: 5m) and video observations from the submersible JAGO (IFM-GEOMAR). Species distribution models have been constructed with a Maximum Entropy approach (MaxEnt model) using the presence data from video imagery and layers derived from multibeam bathymetry such as slope, geomorphologic category, rugosity, aspect (orientation of the pixel respect to the North) and backscatter. For the three species the predictive model performance is outstanding, with the area under the curve (AUC) from the sensitivity-specificity approach of 0.98 for M. oculata and D. cornigera and of 0.99 for L. pertusa. The most relevant variables responsible for the CWC distribution are the slope and aspect for M. oculata and L. pertusa, and rugosity and aspect for D. cornigera. According to the models, CWC species are most likely to be found on the medium to steep rough walls of the southern flank of the Cap de Creus Canyon and almost exclusively along the regions facing the North and the North-West, from where strong organic sediment-rich currents flow. Results are coherent with previous observations and quantitative studies performed in the area. Insights coming out from the application of geo-spatial statistical models could represent the basis for the development of a scientifically-based approach in the planning and management of Marine Protected Areas.

Lo Iacono, Claudio; Gonzalez-Villanueva, Rita; Gori, Andrea; Orejas, Covadonga; Gili, Josep Maria

2013-04-01

349

A Karst Connection model for Grand Canyon, Arizona, USA  

NASA Astrophysics Data System (ADS)

A new model for the connection of the eastern and western Grand Canyon is proposed that involves westward flow of Redwall karst aquifer water under the Kaibab arch along the steepest hydraulic gradient to discharge at a structural low in a headward-eroding protowestern Grand Canyon. A karst-aquifer hydrological connection was first established between the eastern and western Grand Canyon, then collapse, incision, and headward erosion of the canyon followed this subterranean route. This proposed model is based on what is happening today on the northern Marble Platform where the Redwall-Muav aquifer is still intact. The three sinkhole/caves Ah Hol Sah, Indian Pit, and Black Abyss provide vertical flow routes down to the Redwall karst aquifer, joining water discharging from the Kaiparowits hydrologic basin to the Colorado River along the Fence Springs system. Projecting this process back in time and spatially southward, we propose that at around 6 Ma a sinkhole or sinkholes existed at the confluence of the Colorado River with the Little Colorado River. Little Colorado River water, then flowing northward to an interior lake basin ("Glen Lake") in southern Utah, became pirated down this sinkhole(s), thus causing a reversal of drainage (barbed tributaries) in Marble Canyon. Headward erosion then proceeded up Marble and Little Colorado Canyons from the collapsing sinkhole, with Marble Canyon incision breaching Glen Lake at around 5.5 Ma. This effected the "final connection" and total integration of the Colorado River from Colorado to the Gulf of California.

Hill, C. A.; Eberz, N.; Buecher, R. H.

2008-03-01

350

Pleistocene Submarine Groundwater Discharge Along the Atlantic Continental Shelf, New England: The Role of Ice Sheets  

NASA Astrophysics Data System (ADS)

Well bores have long shown that relatively fresh groundwater exists far offshore beneath the Atlantic continental shelves of North and South America. This freshwater was emplaced during Pleistocene sea-level low stands when the shelf was exposed to meteoric recharge and parts were over-run by the Laurentide Ice Sheet. Details of the emplacement mechanism of the fresh water remain poorly understood. At issue is whether the recharge occurred locally through meteoric seepage or was a more regional process driven by ice sheets. These two mechanisms predict very different distributions of water beneath the shelf, and identifying which dominated would help predict whether freshwater is widespread beneath the shelf or isolated in discrete pockets. Here we present results from high-resolution paleohydrologic models of groundwater flow and solute transport beneath the continental shelf from New Jersey to Maine over the last 2 million years. Our analyses show that freshwater emplacement beneath New England's continental shelf was dominated by the presence of the Laurentide Ice Sheet, which the models show increased recharge rates by four times relative to modern levels. Our analyses further suggest that the presence of fresh to brackish water more than 100 km offshore New Jersey was facilitated by discharge from submarine springs along the Baltimore and Hudson Canyons, with outflow rates close to 1 cm/yr during the last glacial maximum (LGM). We estimate that the volume of emplaced Pleistocene continental shelf freshwater (< 1 ppt) to be 1200 km3 in New England, 4300 km3 along the North and South American shelf, and 106,000 km3 along passive margins globally. This water represents a potentially valuable, albeit non-renewable resource for coastal megacities.

Cohen, D.; Person, M.; Peng, W.; Gable, C.; Hutchinson, D.; Marksammer, A.; Brandon, D.; Kooi, H.; Koos, G.; Evans, R.; Lizarralde, D.

2008-12-01

351

Reef to back-reef microfacies and diagenesis of Permian (Guadalupian) Tansill-Capitan transition, Dark Canyon, Guadalupe mountains, New Mexico  

SciTech Connect

In Dark Canyon, the transition from Capitan reef facies to Tansill back-reef facies occur across a distance of 150 m (500 ft). Detailed 3-dimensional sampling of the transition reveals facies based on biota content and textural changes. Also revealed are postdepositional modifications owing to diagenesis. Three microfacies (A, B, and C), defined by the presence of a few diagnostic biota, occur between the Capitan reef and Tansill back-reef deposits. Submarine cements that have been modified diagenetically are dominant. The majority of the biota has been micritized. Large voids are filled by fibrousaragonite which has been replaced by botryoidal radial fibrous calcite. Many reef and near-reef limestones are extremely recrystallized. Back-reef areas have undergone several stages of dolomitization, whereas the actual reef is limestone. Some anhydrite moldic porosity is occluded by sparry calcite. More recent episodes of cementation have left some gravitational voids.

Biggers, B.

1984-04-01

352

Lynch Canyon combination thermal drive project. [Termination  

SciTech Connect

The following report provides a summary of the Lynch Canyon Thermal Drive Project. This demonstration project was begun in 1978 and terminated in 1980. The project originally was divided into four phases; Geologic Evaluation, Injectivity Test, Field Development Combined with Air-Water Injection, and a Project Review. Following the First Phase operations, which included drilling of four wells for geologic evaluation, a joint decision to cancel the project was made. The conditions which were thought to exist at the initiation of the project, would have provided an excellent opportunity to conduct a Pilot Combination Thermal Drive. However, potential problems which were discovered in the Phase One Operations significantly altered the economics of the project and removed the favorable conditions under which the project was begun.

Stair, J. R.

1980-11-01

353

Report Summary, Final Hells Canyon Environmental Investigation.  

SciTech Connect

The Northwest Electric Power Planning and Conservation Act of 1980 provided for the establishment of a Regional Power Planning Council (Regional Council) and mandated the development of a Columbia River Basin Fish and Wildlife Program (F&W Program). The F&W Program was adopted by the Regional Council in November 1982. and is intended to mitigate fish and wildlife losses resulting from the development of hydroelectric dams on the Columbia and Snake Rivers. One element of the FLW Program is the Water Budget. It calls for additional flows in the Columbia and Snake Rivers between April 15 and June 15 to improve the survival of juvenile salmon and steelhead migrating downstream. The Snake River's contribution to the Water Budget is 20,000 cubic feet per second-months (A volume of water equal to a flow of 20.000 cubic feet per second, 24 hours per day, for a period of a month) over and above water that would normally flow for power production. The water for the Water Budget would come out of Idaho Power Company's (IPCo) Hells Canyon Complex and the Corps of Engineers' (Corps) Dvorshak Reservoir. IPCo's Hells Canyon Complex consists of three dams, Brownlee, Oxbow, and Hells Canyon. Brownlee, at the upstream end, contains a large reservoir and controls flow to the lower dams. IPCo's participation in the Water Budget could affect the level of the Brownlee Reservoir and flows downstream of the Hells Canyon Complex on the Snake River. In light of this, Bonneville Power Administration (BPA) and IPCo contracted with the consulting firm of CH2!4 Hill to study the potential changes that could occur to the environment. The Environmental Investigation (EI) takes into account concerns that were expressed by the public at a series of public meetings held in the Snake River area during June 1983 and again during September 1984. Existing information and consultations with agencies which have management responsibilities in the project area formed the basis for the data used in the EI. This document summarizes the findings of the final EI in the following areas: (1) natural features, water use, and air and water quality; (2) fish, wildlife, and vegetation; (3) land use, recreation, and aesthetics; and (4) historical and archaeological resources. The EI provides information to be used by IPCo as they assess the effect on the system operations (power and nonpower) resulting from Water Budget participation. BPA and IPCo are continuing to discuss the prospects for IPCo's involvement in implementation of the Water Budget on the Snake River. When IPCo reaches a decision on whether and to what extent it wishes to participate in a Water Budget agreement with BPA, the proposed agreement will be subject to analysis under the National Environmental Policy Act (NEPA). That analysis will consider alternatives, significance of impacts to the environment, and mitigative measures.

United States. Bonneville Power Administration.

1985-01-01

354

OTEC submarine cable environmental characteristics and hazards analysis  

Microsoft Academic Search

This analysis focuses on submarine cable protection criteria and technology as applied to four potential OTEC plants and cable routes at Hawaii, Puerto Rico, Guam and Florida. The environmental characteristics are presented for each site as follows: (a) natural factors, such as location, tides, currents, wind, waves, bottom soil type, seafloor movement, and (b) man-made factors, such as ship traffic,

C. Chern; W. Tudor

1982-01-01

355

Submarine Biofouling Control- Chlorination DATS Study at Pearl Harbor.  

National Technical Information Service (NTIS)

The intent of this document is to sumarize the chlorination studies performed at Naval Station, Pearl Harbor in support of biofouling control initiatives for the submarine community, as requested by NAVSEA 92T. The document is a compilation of the status ...

J. Wegand K. Lucas T. Jackovic P. Slebodnick J. Bergh

2001-01-01

356

Size distributions and failure initiation of submarine and subaerial landslides  

Microsoft Academic Search

Landslides are often viewed together with other natural hazards, such as earthquakes and fires, as phenomena whose size distribution obeys an inverse power law. Inverse power law distributions are the result of additive avalanche processes, in which the final size cannot be predicted at the onset of the disturbance. Volume and area distributions of submarine landslides along the U.S. Atlantic

R. Barkan; B. D. Andrews; J. D. Chaytor

2009-01-01

357

Passive sonar fusion for submarine C2 systems  

Microsoft Academic Search

The most important sensors for gathering target information onboard a submarine are passive sonars. Problems concerning fusion of these passive sonars are discussed. Three typical passive sonars-passive noise sonar, passive ranging sonar and acoustic pulse surveillance sonar-constitute a passive sonar system for data fusion. This paper is concerned mainly with problems of significance in system development, such as tactical application

Pailon Shar; X. Rong Li

2000-01-01

358

Preliminary Study of Cardiovascular Risks in Retired Submariners.  

National Technical Information Service (NTIS)

Two sets of studies seem to agree that both retired and active duty submariners have increased levels of a personality component strongly related to cardiovascular risks and have lowered levels at least two factors associated with reduced risk. One of the...

D. V. Tappan D. R. Knight E. Heyder K. R. Bondi

1983-01-01

359

Present Thoughts on Exercise, Weight, and Performance Aboard Nuclear Submarines.  

National Technical Information Service (NTIS)

Because nuclear submariners undergo long periods of long confinement and demanding mental tasks, these topics are of interest to both them and those concerned with their short and long term health. This report provides a brief survey of data concerning we...

K. R. Bondi

1983-01-01

360

Debris Avalanche Formation at Kick'em Jenny Submarine Volcano  

Microsoft Academic Search

Kick'em Jenny submarine volcano near Grenada is the most active volcanic center in the Lesser Antilles arc. Multibeam surveys of the volcano by NOAA in 2002 revealed an arcuate fault scarp east of the active cone, suggesting flank collapse. More extensive NOAA surveys in 2003 demonstrated the presence of an associated debris avalanche deposit, judging from their surface morphologic expression

H. Sigurdsson; S. N. Carey; D. Wilson

2005-01-01

361

Probabilistic analysis for wave?induced submarine landslides  

Microsoft Academic Search

When waves propagate over the ocean floor, they induce a change of hydrodynamic pressure, positive under the crest and negative under the trough. These pressure changes may cause shear failure in soft sediments and lead to submarine landslides. This paper presents a general analytical procedure for evaluating the probability of wave?induced failure in offshore clay sediments. Both the wave and

M. S. Rahman; F. M. Layas

1985-01-01

362

Radar imaging of submarine sand waves in tidal channels  

Microsoft Academic Search

The simple theoretical model of Alpers and Hennings describing the radar imaging of submarine bottom topography in coastal waters with strong unidirectional tidal currents is analytically extended to show the influence of advection. The theory applies for L band radar, where second-order terms in the hydrodynamic interaction can be neglected as a first approximation. If future imaging radars from satellites

Ingo Hennings

1990-01-01

363

Does calving matter? Evidence for significant submarine melt  

USGS Publications Warehouse

During the summer in the northeast Pacific Ocean, the Alaska Coastal Current sweeps water with temperatures in excess of 12?°C past the mouths of glacierized fjords and bays. The extent to which these warm waters affect the mass balance of Alaskan tidewater glaciers is uncertain. Here we report hydrographic measurements made within Icy Bay, Alaska, and calculate rates of submarine melt at Yahtse Glacier, a tidewater glacier terminating in Icy Bay. We find strongly stratified water properties consistent with estuarine circulation and evidence that warm Gulf of Alaska water reaches the head of 40 km-long Icy Bay, largely unaltered. A 10–20 m layer of cold, fresh, glacially-modified water overlies warm, saline water. The saline water is observed to reach up to 10.4?°C within 1.5 km of the terminus of Yahtse Glacier. By quantifying the heat and salt deficit within the glacially-modified water, we place bounds on the rate of submarine melt. The submarine melt rate is estimated at >9 m?d?1, at least half the rate at which ice flows into the terminus region, and can plausibly account for all of the submarine terminus mass loss. Our measurements suggest that summer and fall subaerial calving is a direct response to thermal undercutting of the terminus, further demonstrating the critical role of the ocean in modulating tidewater glacier dynamics.

Bartholomaus, Timothy C.; Larsen, Christopher F.; O’Neel, Shad

2013-01-01

364

Attitude changes during and after long submarine missions.  

PubMed

To assess the kind and degree of attitude changes occurring during a 2-month submerged mission, two enlisted crews of one fleet ballistic missile submarine (FBM) (n = 101 each) were administered the Submarine Attitude Questionnaire before and after two 55-day submerged missions interspersed with a rehabilitation period of the same duration. Results showed that time-in-service and pay grade bore a U-shaped relationship to positive attitudes toward the service. During submergence, most attitudes became negative and then reversed polarity during rehabilitation. However, there were no cumulative effects upon attitudes during successive missions. Attitudes pertaining to the realities of the mission (for example, boredom, hazardous aspects) became more negative but recovered faster. On the other hand, attitude changes related to long-range expectancies in terms of goal achievement of the crew members were less likely to recover. Several possible explanations for these attitude changes are discussed in the context of the mission of the FBM submarine. Suggestions for preventing or alleviating untoward attitude changes during long submarine missions are also presented. PMID:505625

Weybrew, B B; Molish, H B

1979-01-01

365

Air contaminants in a submarine equipped with air independent propulsion.  

PubMed

The Swedish Navy has operated submarines equipped with air independent propulsion for two decades. This type of submarine can stay submerged for periods far longer than other non-nuclear submarines are capable of. The air quality during longer periods of submersion has so far not been thoroughly investigated. This study presents results for a number of air quality parameters obtained during more than one week of continuous submerged operation. The measured parameters are pressure, temperature, relative humidity, oxygen, carbon dioxide, hydrogen, formaldehyde and other volatile organic compounds, ozone, nitrogen dioxide, particulate matter and microbiological contaminants. The measurements of airborne particles demonstrate that air pollutants typically occur at a low baseline level due to high air exchange rates and efficient air-cleaning devices. However, short-lived peaks with comparatively high concentrations occur, several of the sources for these have been identified. The concentrations of the pollutants measured in this study do not indicate a build-up of hazardous compounds during eight days of submersion. It is reasonable to assume that a substantial build-up of the investigated contaminants is not likely if the submersion period is prolonged several times, which is the case for modern submarines equipped with air independent propulsion. PMID:17075617

Persson, Ola; Ostberg, Christina; Pagels, Joakim; Sebastian, Aleksandra

2006-09-26

366

SLCSAT (Submarine Laser Communication Satellite) communication system design study  

Microsoft Academic Search

This report summarizes the results of a Lincoln Laboratory study of issues affecting Submarine Laser Communication Satellite (SLCSAT) implementation. The study compares alternative SLCSAT downlink implementations using semiconductor and solid-state lasers in terms of the satellite transmitter power required to provide a given level of communication service. Signal coding is applied to increase transmitter design flexibility by accommodating a wider

S. L. Bernstein; R. S. Bondurant; E. A. Bucher; V. W. Chan; F. G. Walther

1989-01-01

367

Mk 14 Submarine-Launched Torpedo: Four Decades of Service.  

National Technical Information Service (NTIS)

In the early years of World War II, few would have predicted that Mk 14 submarine-launched torpedo would play a major role in defeating the Japanese naval and merchant fleets. Initially a problem-plagued and unreliable weapon, the Mk 14 torpedo was the so...

1994-01-01

368

Evaluation of Welding Consumables and Procedures for Submarine Construction.  

National Technical Information Service (NTIS)

This report provides a summary of three developments in the welding of BIS 812 EMA and HY 590 high strength steels for the new RAN Collins Class submarine. Firstly, the established benchmark properties for Charpy energy, dynamic tear energy and elongation...

B. F. Dixon

1994-01-01

369

Does calving matter? Evidence for significant submarine melt  

NASA Astrophysics Data System (ADS)

During the summer in the northeast Pacific Ocean, the Alaska Coastal Current sweeps water with temperatures in excess of 12 °C past the mouths of glacierized fjords and bays. The extent to which these warm waters affect the mass balance of Alaskan tidewater glaciers is uncertain. Here we report hydrographic measurements made within Icy Bay, Alaska, and calculate rates of submarine melt at Yahtse Glacier, a tidewater glacier terminating in Icy Bay. We find strongly stratified water properties consistent with estuarine circulation and evidence that warm Gulf of Alaska water reaches the head of 40 km-long Icy Bay, largely unaltered. A 10-20 m layer of cold, fresh, glacially-modified water overlies warm, saline water. The saline water is observed to reach up to 10.4 °C within 1.5 km of the terminus of Yahtse Glacier. By quantifying the heat and salt deficit within the glacially-modified water, we place bounds on the rate of submarine melt. The submarine melt rate is estimated at >9 m d-1, at least half the rate at which ice flows into the terminus region, and can plausibly account for all of the submarine terminus mass loss. Our measurements suggest that summer and fall subaerial calving is a direct response to thermal undercutting of the terminus, further demonstrating the critical role of the ocean in modulating tidewater glacier dynamics.

Bartholomaus, Timothy C.; Larsen, Christopher F.; O'Neel, Shad

2013-10-01

370

Physiological and Manikin Evaluations of Submarine-Deck Exposure Suits.  

National Technical Information Service (NTIS)

Navy Clothing and Textile Research Facility (NCTRF) compared the standard (STD) submarine-deck exposure suit (SDES) with a more watertight, modified (MOD) version. The suits were compared on the thermal manikin, in both a static and a dynamic mode, and on...

B. A. Avellini J. W. Giblo

1988-01-01

371

Review of advanced composite structures for naval ships and submarines  

Microsoft Academic Search

The recent applications of fibre-reinforced polymer composites to naval ships and submarines are reviewed. Since the mid-1980s the use of composites has increased considerably as the military strive to reduce the acquisition and maintenance costs and improve the structural and operational performance of naval craft. A wide range of new applications of composites to naval vessels are described, including their

A. P Mouritz; E Gellert; P Burchill; K Challis

2001-01-01

372

Coastal submarine hydrothermal activity off northern Baja California  

Microsoft Academic Search

In situ observations of submarine hydrothermal activity have been conducted in Punta Banda. Baja Califronia, Mexico, approximately 400 m from the coast and at a seawater depth of 30 m. The hydrothermal activity occurs within the Agua Blanca Fault, a major transverse structure of Northern Baja California. Hot springwater samples have been collected and analyzed. Marked differences exist between the

Victor M. V. Vidal; Francisco V. Vidal; John D. Isaacs; David R. Young

1978-01-01

373

Elucidating the Mechanisms of Microbial Weathering of Submarine Basalts  

Microsoft Academic Search

In recent years there has been as increasing interest in microbe-mineral interactions, specifically the molecular mechanisms of mineral formation and dissolution. While not a true mineral, submarine basaltic glass represents an important rock surface and one of the most reactive components of the ocean crust. The high solubility of reduced glasses and the large disequilibrium with oxygenated seawater leads to

B. M. Tebo; A. Templeton; L. Haucke; B. Bailey; H. Staudigel

2005-01-01

374

Concept of Operations for a New Deep-Diving Submarine.  

National Technical Information Service (NTIS)

The nation has one deep-diving nuclear research submarine-the NR-1. The NR-1 was built in 1969. Its design for prolonged (30-day) operation on or near the sea bottom at a speed of up to 4 knots separated it from the majority of other deep submersibles. Th...

F. W. Lacroix R. W. Button S. E. Johnson J. R. Wise

2001-01-01

375

60. SUPPORT CARRIAGE ASSEMBLY AT ISLIP CANYON SHOWING CURVED RAILS ...  

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

60. SUPPORT CARRIAGE ASSEMBLY AT ISLIP CANYON SHOWING CURVED RAILS AND FLOATING BARGE IN BACKGROUND, February 16, 1948. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

376

View of Nevada side of Colorado River Canyon showing US ...  

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

View of Nevada side of Colorado River Canyon showing US 93, Visitor Center parking lot, transmission lines, and static towers in background, view west - Hoover Dam, Spanning Colorado River at Route 93, Boulder City, Clark County, NV

377

View of the Colorado River Canyon showing lower portal road ...  

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

View of the Colorado River Canyon showing lower portal road in background taken from the rim of Hoover Dam, view south - Hoover Dam, Spanning Colorado River at Route 93, Boulder City, Clark County, NV

378

View of the Colorado River Canyon form the Nevada side ...  

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

View of the Colorado River Canyon form the Nevada side showing the Nevada rim towers and portions of US 93, view south - Hoover Dam, Spanning Colorado River at Route 93, Boulder City, Clark County, NV

379

36 CFR 7.4 - Grand Canyon National Park.  

Code of Federal Regulations, 2013 CFR

...National Park Service, along the Colorado River within Grand Canyon National Park...permitted on beach areas along the Colorado River. (8) Swimming and bathing...also authorizes camping along the Colorado River by persons in the river...

2013-07-01

380

View of Nevada side of Colorado River Canyon taken from ...  

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

View of Nevada side of Colorado River Canyon taken from Lower Portal Road looking up towards area where new bridge will be located, view northwest - Hoover Dam, Spanning Colorado River at Route 93, Boulder City, Clark County, NV

381

36 CFR 7.70 - Glen Canyon National Recreation Area.  

Code of Federal Regulations, 2013 CFR

...by the Superintendent. (c) Colorado River white-water boat trips...National Park Service along the Colorado River within Glen Canyon National...No camping is allowed along the Colorado River bank between the Lees Ferry...

2013-07-01

382

View of Nevada side of Colorado River Canyon showing US ...  

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

View of Nevada side of Colorado River Canyon showing US 93 in foreground, transmission towers and static towers in background, view west - Hoover Dam, Spanning Colorado River at Route 93, Boulder City, Clark County, NV

383

View of Arizona side of Colorado River Canyon taken from ...  

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

View of Arizona side of Colorado River Canyon taken from Lower Portal Road looking up towards area where new bridge will be located, view northeast - Hoover Dam, Spanning Colorado River at Route 93, Boulder City, Clark County, NV

384

27 CFR 9.217 - Happy Canyon of Santa Barbara.  

Code of Federal Regulations, 2013 CFR

...BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL AMERICAN VITICULTURAL AREAS Approved American Viticultural Areas § 9.217 Happy Canyon...River to the west of Lake Cachuma and Bradbury Dam, T6N, R30W; then (6) Proceed...

2013-04-01

385

Radionuclide Content of an Exhumed Canyon Tank and Neighboring Soil.  

National Technical Information Service (NTIS)

To assess the long-term hazard potential associated with the burial of partially decontaminated process equipment, burial emplacements of equipment from an irradiated-fuel separations building (canyon) are being exhumed and examined. One piece of equipmen...

H. P. Holcomb

1977-01-01

386

24. Mormon Flat reservoir, or Canyon Lake. Photographer Mark Durben, ...  

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

24. Mormon Flat reservoir, or Canyon Lake. Photographer Mark Durben, 1988. Source: Salt River Project. - Mormon Flat Dam, On Salt River, Eastern Maricopa County, east of Phoenix, Phoenix, Maricopa County, AZ

387

1. GENERAL VIEW OF SHOSHONE HYDROELECTRIC PLANT IN GLENWOOD CANYON, ...  

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

1. GENERAL VIEW OF SHOSHONE HYDROELECTRIC PLANT IN GLENWOOD CANYON, VIEW TO THE NORTHEAST ALONG U.S. 6 AND THE COLORADO RIVER. - Shoshone Hydroelectric Plant Complex, 60111 U.S. Highway 6, Glenwood Springs, Garfield County, CO

388

H CANYON PROCESSING IN CORRELATION WITH FH ANALYTICAL LABS  

SciTech Connect

Management of radioactive chemical waste can be a complicated business. H Canyon and F/H Analytical Labs are two facilities present at the Savannah River Site in Aiken, SC that are at the forefront. In fact H Canyon is the only large-scale radiochemical processing facility in the United States and this processing is only enhanced by the aid given from F/H Analytical Labs. As H Canyon processes incoming materials, F/H Labs provide support through a variety of chemical analyses. Necessary checks of the chemical makeup, processing, and accountability of the samples taken from H Canyon process tanks are performed at the labs along with further checks on waste leaving the canyon after processing. Used nuclear material taken in by the canyon is actually not waste. Only a small portion of the radioactive material itself is actually consumed in nuclear reactors. As a result various radioactive elements such as Uranium, Plutonium and Neptunium are commonly found in waste and may be useful to recover. Specific processing is needed to allow for separation of these products from the waste. This is H Canyon's specialty. Furthermore, H Canyon has the capacity to initiate the process for weapons-grade nuclear material to be converted into nuclear fuel. This is one of the main campaigns being set up for the fall of 2012. Once usable material is separated and purified of impurities such as fission products, it can be converted to an oxide and ultimately turned into commercial fuel. The processing of weapons-grade material for commercial fuel is important in the necessary disposition of plutonium. Another processing campaign to start in the fall in H Canyon involves the reprocessing of used nuclear fuel for disposal in improved containment units. The importance of this campaign involves the proper disposal of nuclear waste in order to ensure the safety and well-being of future generations and the environment. As processing proceeds in the fall, H Canyon will have a substantial number of samples being sent to F/H Labs. All analyses of these samples are imperative to safe and efficient processing. The important campaigns to occur would be impossible without feedback from analyses such as chemical makeup of solutions, concentrations of dissolution acids and nuclear material, as well as nuclear isotopic data. The necessity of analysis for radiochemical processing is evident. Processing devoid of F/H Lab's feedback would go against the ideals of a safety-conscious and highly accomplished processing facility such as H Canyon.

Weinheimer, E.

2012-08-06

389

Grand Canyon Glass Skywalk creates excitement and controversy  

NSDL National Science Digital Library

Skywalk at Grand Canyon making its debuthttp://www.azcentral.com/news/articles/0320grandcanyonskywalk20-ON.htmlGrand Canyon National Park [pdf]http://www.nps.gov/grca/Hualapai Tribehttp://www.itcaonline.com/tribes_hualapai.htmlASU Libraries: Native Americans Onlinehttp://www.asu.edu/lib/archives/links.htmGrand Canyon Skywalk [Macromedia Flash Player]http://www.grandcanyonskywalk.com/Over the millennia, the Grand Canyon has been the source of wonder and amazement as it was traversed first by indigenous people and a host of other individuals, including John Wesley Powell, who surveyed the area in 1869. This Tuesday saw the formal opening of a recent man-made addition to the rim of the Canyon that generated plenty of commentary and controversy months before it opened. The Grand Canyon Skywalk, which resembles a massive horseshoe, extends 70 feet beyond the canyon's edge. The Las Vegas developer, David Jin, created this project. Visitors to the Skywalk who pay $25 will get to look down through glass panels to the canyon floor some 4000 feet below, which could be both exhilarating and frightening, depending one one's temperament and tolerance for heights. The Hualapai Indians, who have aggressively defended the Skywalk as a form of effective economic development, approved the Skywalk and Sheri Yellowhawk who has been overseeing the project commented, "When we have so much poverty and so much unemployment, we have to do something." Other individuals and organizations have voiced strong concerns about the Skywalk, and Kieran Suckling, policy director for the Center for Biological Diversity is one of their number. In a recent interview, he commented "The tribe has repeatedly brought tacky, gross commercial ventures into the canyon, and it's inappropriate."The first link will take users to a well-written piece from Devika Bhat of the Times which comments on the opening of the Skywalk. The second link takes users to another piece on the Skywalk, offered courtesy of the Arizona Republic. Moving along, the third link leads to the very authoritative and informative National Park Service site dedicated to the natural history and geography of the Grand Canyon. The fourth link whisks users away to the Inter Tribal Council of Arizona's site on the Hualapai Tribe. The fifth link will take users to the Arizona State University Libraries' Native Americans Online site. Here, visitors can look over an extensive set of links that lead to a variety of online resources, such as digital collections and such. The final link leads to the official homepage of the Grand Canyon Skywalk, which is available in Korean, Japanese, Chinese, and English.

Grinnell, Max

390

Southeastern slope of the Bohemian Massif: Paleogene submarine fill of the Nesvacilka depression and its importance for petroleum exploration  

SciTech Connect

The Nesvacilka depression is a trough-like paleovalley, about 2000 m deep, that was cut at the transition from the Cretaceous to the Paleocene by fluvial erosion into Jurassic and Carboniferous strata. This morphological feature, which is superimposed on an ancient tectonic zone, trends to the present southeast boundary of the Bohemian massif and is, from a hydrocarbon exploration point of view, the most important structure in the Czech Republic. During the Paleogene, marine transgressions gradually flooded this paleovalley. In the resulting relatively closed water body, more than 1500 m of thick deeper water clastics accumulated. These clastics display features similar to those described from submarine fan lobes in other hydrocarbon-producing basins. Following the discovery of two oil and gas accumulations contained in Jurassic and Paleogene clastic rocks, exploration was focused on the central parts of the Nesvacilka depression. The depositional pattern of its Paleogene fill was worked out on the basis of well data and the results of two-dimensional and three-dimensional seismic surveys. From this, it was concluded that accumulation of the Paleogene clastic series was significantly influenced by sea level changes. The depositional concepts developed may be applied to the deeper parts of the Nesvacilka Canyon, where exploration for hydrocarbons is still at an early stage. Results obtained so far indicate that the Nesvacilka depression can be ranked as the most prospective oil play in the Czech Republic. Play concepts developed may be extrapolated to similar morphological features occurring elsewhere in the Carpathian foreland.

Benada, S.; Berka, J.; Brzobohaty, J.; Rehanek, J. (Moravske Naftove Doly, Hodanin (Czech Republic))

1993-09-01

391

[Effect of greenbelt on pollutant dispersion in street canyon].  

PubMed

The effect feature of greenbelt on flow field and pollutant dispersion in urban street canyon was researched. The greenbelt was assumed as uniform porous media and its aerodynamics property defined by the pressure loss coefficient. Subsequently, the pollutant dispersion in the street canyon of which there was greenbelt in the middle was simulated with the steady-state standard kappa-epsilon turbulence model and species transport equation. The simulated results agreed well with the wind-tunnel data. Compared with the treeless case, it finds that the street canyon contain a clockwise vortex, the pollutant concentration of the leeward was several times than the windward and the growth rate of pollutant concentration was 46.0%. The further simulation for the impact of tree crown position on the airflow and pollutant dispersion finds that the height of major vortex center in the street canyon increases with the height of tree crown and gradually closes the top of windward building This causes that the average wind speed in the street canyon decreases. Especially when the top of tree crown over the roof and hinder the air flow above the street canyon, the average pollutant concentration increases with the height of tree crown rapidly. PMID:22509593

Xu, Wei-Jia; Xing, Hong; Yu, Zhi

2012-02-01

392

Character of submarine groundwater discharge around islands  

NASA Astrophysics Data System (ADS)

Submarine groundwater discharge (SGD) from oceanic islands has been estimated to contribute over a third of the global SGD due to the high shoreline-to-land area ratio, orographic precipitation, short aquifer pathways and poorly developed surface drainage. Relatively few islands have been studied, but SGD is typically found to be an important, and often the only, source of nutrients to coastal waters, enhanced by the short distances between the areas of recharge inland and discharge at the shoreline. An inverse correlation between salinity and the concentrations of nitrate plus nitrite ([NOx]) found in northern Guam, Barbados and the Balearic Islands demonstrate the freshwater source of NOx. Inputs can be strongly modulated seasonally; in Barbados, the low-salinity end-member [NOx] was 1.8 times greater in the dry season than the wet season. Observations on islands can be challenging not only because of extremes seasonal precipitation but also because of the inhomogeneous nature of aquifers, and strong, oceanic influences. On islands with fractured rock (Mauritius) or karstic (Barbados, Guam, or the Balearic Islands) aquifers, discharge is often into shallow coastal lagoons where a thin veneer of sand often covers the highly permeable aquifer rock; the rapid, but heterogeneous, pathway makes the distribution of SGD variable both in time and space. In Mauritius, SGD exceeded 4.9 m/d near a known spring, but large variations in SGD rates were seen over distances of a few meters. In Guam, SGD was four times greater around the northern, permeable limestone aquifer, than it was along the southern, semi-impermeable volcanic terrain; [NOx] was sevenfold greater along the coast of northern Guam while, in the south, silicate concentrations were two times greater, phosphate concentrations were four times greater and ammonia concentrations were 1.3 times greater than those in the north. Oceanic influences, such as the recirculation of ocean water through fringing reefs, also can exert a strong influence on an island’s SGD. SGD in Mallorca showed little or no dilution from the ambient, open-water salinity being dominated by the recirculation of sea water through the aquifer, driven by oceanic processes. SGD at one site in Barbados had a 33% freshwater component of SGD, while an adjacent watershed’s SGD was composed entirely of recirculated seawater. ([NOx] was an order of magnitude greater with the freshwater component of SGD). Even tiny Mauritius could be supplying almost 80 million cubic meters per day to carry the composition of the subterranean estuary into the adjacent, deep ocean. Other investigators have found the geochemical signature of SGD widespread offshore of Puerto Rico at depths up to 3.5 km. High population densities and limited freshwater resources also make islands especially sensitive to the impacts of climate change. SGD provides not only a link between development and water quality in the coastal zone but can be expected to be one bellwether of climatic changes. Forecast changes in precipitation, temperature, growing season and the intensity of wet and dry periods should all alter SGD.

Bokuniewicz, H.; Coffey, R.; Charette, M. A.

2009-12-01

393

2008 High-Flow Experiment at Glen Canyon Dam Benefits Colorado River Resources in Grand Canyon National Park  

USGS Publications Warehouse

On March 5, 2008, the Department of the Interior began a 60-hour high-flow experiment at Glen Canyon Dam, Arizona, to determine if water releases designed to mimic natural seasonal flooding could be used to improve downstream resources in Glen Canyon National Recreation Area and Grand Canyon National Park. U.S. Geological Survey (USGS) scientists and their cooperators undertook a wide range of physical and biological resource monitoring and research activities before, during, and after the release. Scientists sought to determine whether or not high flows could be used to rebuild Grand Canyon sandbars, create nearshore habitat for the endangered humpback chub, and benefit other resources such as archaeological sites, rainbow trout, aquatic food availability, and riverside vegetation. This fact sheet summarizes research completed by January 2010.

Melis, Theodore S.; Topping, David J.; Grams, Paul E.; Rubin, David M.; Wright, Scott A.; Draut, Amy E.; Hazel, Joseph E., Jr.,; Ralston, Barbara E.; Kennedy, Theodore A.; Rosi-Marshall, Emma; Korman, Josh; Hilwig, Kara D.; Schmit, Lara M.

2010-01-01

394

Archaeological Investigations at Historic Sites in the Choke Canyon Reservoir, Southern Texas. Choke Canyon Series: Volume 12.  

National Technical Information Service (NTIS)

Between July 7 and August 13, 1981, archaeologists from the Center for Archaeological Research (CAR), The University of Texas at San Antonio (UTSA), conducted Archaeological investigations were conducted at eight historic sites at Choke Canyon Reservoir i...

A. A. Fox P. Ward

1986-01-01

395

Petrology of Westwater Canyon member, Morrison Formation, East Chaco Canyon drilling project, New Mexico-comparison with Grants mineral belt  

Microsoft Academic Search

The results of this report are based on 47 samples of Westwater Canyon Sandstone, Morrison Formation (Upper Jurassic). The 250 to 350 ft (75 to 100-m) thick Westwater Canyon Member is 80 percent fine- to medium-grained arkosic sandstone and 20 percent interbedded red and green mudstones. Nine zones of low-grade uranium mineralization were intercepted by five drill holes. The alteration

R. T. Hicks; R. M. Lowry; R. S. Della Valle; D. G. Brookins

1980-01-01

396

New Strategy to Address Loss of Submarine Qualifications in Submariners Who are Helicobacter Pylori Positive and Diagnosed with Peptic Ulcer Disease: Background to the Change in Policy.  

National Technical Information Service (NTIS)

PROBLEM: It was USN policy to disqualify submariners from returning to submarine duty for two years following a peptic ulcer. This resulted in a loss of experienced personnel which was considered to be unnecessary given the current medical advances in pep...

R. P. Jackson J. J. Costello C. C. Steevens R. Sylvestor J. Clark

1998-01-01

397

14 CFR Special Federal Aviation... - 2-Special Flight Rules in the Vicinity of the Grand Canyon National Park, AZ  

Code of Federal Regulations, 2010 CFR

...Flight Rules in the Vicinity of the Grand Canyon National Park, AZ Federal ...Flight Rules in the Vicinity of the Grand Canyon National Park, AZ Section 1...following airspace, designated as the Grand Canyon National Park Special Flight...

2010-01-01

398

14 CFR Special Federal Aviation... - 2-Special Flight Rules in the Vicinity of the Grand Canyon National Park, AZ  

Code of Federal Regulations, 2010 CFR

...Flight Rules in the Vicinity of the Grand Canyon National Park, AZ Federal ...Flight Rules in the Vicinity of the Grand Canyon National Park, AZ Section 1...following airspace, designated as the Grand Canyon National Park Special Flight...

2009-01-01

399

14 CFR Appendix to Subpart U of... - Special Flight Rules in the Vicinity of the Grand Canyon National Park, AZ  

Code of Federal Regulations, 2010 CFR

...Flight Rules in the Vicinity of the Grand Canyon National Park, AZ Appendix to...Flight Rules in the Vicinity of Grand Canyon National Park, AZ Pt. 93...Flight Rules in the Vicinity of the Grand Canyon National Park, AZ...

2009-01-01

400

14 CFR Appendix to Subpart U of... - Special Flight Rules in the Vicinity of the Grand Canyon National Park, AZ  

Code of Federal Regulations, 2010 CFR

...Flight Rules in the Vicinity of the Grand Canyon National Park, AZ Appendix to...Flight Rules in the Vicinity of Grand Canyon National Park, AZ Pt. 93...Flight Rules in the Vicinity of the Grand Canyon National Park, AZ...

2010-01-01

401

76 FR 47237 - Notice of Public Meeting for the Glen Canyon Dam Adaptive Management Work Group Federal Advisory...  

Federal Register 2010, 2011, 2012, 2013

...Notice of Public Meeting for the Glen Canyon Dam Adaptive Management Work Group Federal Advisory...SUMMARY: The Glen Canyon Dam Adaptive Management Work Group (AMWG...Secretary of the Interior concerning Glen Canyon Dam operations and other management...

2011-08-04

402

Contrasting pyroclast density spectra from subaerial and submarine silicic eruptions in the Kermadec arc: implications for eruption processes and dredge sampling  

NASA Astrophysics Data System (ADS)

Pyroclastic deposits from four caldera volcanoes in the Kermadec arc have been sampled from subaerial sections (Raoul and Macauley) and by dredging from the submerged volcano flanks (Macauley, Healy, and the newly discovered Raoul SW). Suites of 16-32 mm sized clasts have been analyzed for density and shape, and larger clasts have been analyzed for major element compositions. Density spectra for subaerial dry-type eruptions on Raoul Island have narrow unimodal distributions peaking at vesicularities of 80-85%, whereas ingress of external water (wet-type eruption) or extended timescales for degassing generate broader distributions, including denser clasts. Submarine-erupted pyroclasts show two different patterns. Healy and Raoul SW dredge samples and Macauley Island subaerial-emplaced samples are dominated by modes at ~80-85%, implying that submarine explosive volcanism at high eruption rates can generate clasts with similar vesicularities to their subaerial counterparts. A minor proportion of Healy and Raoul SW clasts also show a pink oxidation color, suggesting that hot clasts met air despite 0.5 to >1 km of intervening water. In contrast, Macauley dredged samples have a bimodal density spectrum dominated by clasts formed in a submarine-eruptive style that is not highly explosive. Macauley dredged pyroclasts are also the mixed products of multiple eruptions, as shown by pumice major-element chemistry, and the sea-floor deposits reflect complex volcanic and sedimentation histories. The Kermadec calderas are composite features, and wide dispersal of pumice does not require large single eruptions. When coupled with chemical constraints and textural observations, density spectra are useful for interpreting both eruptive style and the diversity of samples collected from the submarine environment.

Barker, Simon J.; Rotella, Melissa D.; Wilson, Colin J. N.; Wright, Ian C.; Wysoczanski, Richard J.

2012-08-01

403

Metamorphic signature of the Gneiss Canyon Shear Zone, Lower Granite Gorge, Grand Canyon, Arizona  

SciTech Connect

The Proterozoic orogen in Arizona consists of structural blocks separated by NE trending shear zones. The Gneiss Canyon Shear Zone (GCSZ) is important because it appears to define in part the boundary between the amphibolite facies Yavapai Province and the granulite facies Mojave Province. An early NW striking foliation is clearly visible in many samples from the Lower Granite Gorge (LGG). In Travertine Canyon, east of the GCSZ, pelitic schists contain And-Sil-Crd-Bi and Gar-Sil-Sta-Bi. Mafic rocks exhibit complex phase relations between cummingtonite, anthophyllite, gedrite, garnet, and cordierite. The coexistence of cordierite-cummingtonite is indicative of low pressure metamorphism. Microprobe analyses of garnets reveal prograde growth zoning profiles. Temperature and pressure estimates of peak metamorphism are 550--600 C and 3 kb. Just east of the GCSZ, pelitic assemblages contain Gar-Bi [+-] Sil [+-] Mus, and garnet zoning profiles are flat in the cores. In Spencer Canyon, west of the GCSZ, samples commonly contain Gar-Bi-Sil-Crd, and in many samples cordierite is being replaced by sillimanite. Thermobarometric calculations yield temperature and pressure estimates of 650 C and 3.5 kb. Mineral assemblages and quantitative thermobarometry suggest higher peak metamorphic temperature west of the GCSZ but relatively constant pressures across the LGG. On the east side of the GCSZ, temperatures increase toward the Shear Zone, probably due to the presence of extensive dikes, pods, and veins of variably deformed granite. Peak mineral assemblages are syntectonic with respect to the NE-striking GCSZ fabric. If a suture exists in the LGG, the GCSZ fabrics apparently reflect post-accretionary tectonism, with accretion occurring prior to the peak of metamorphism.

Robinson, K.; Williams, M.L. (Univ. of Massachusetts, Amherst, MA (United States). Dept. of Geology and Geography)

1992-01-01

404

Regional depositional history of the Miocene-Pleistocene Louisiana Slope, Green Canyon and Mississippi Canyon  

SciTech Connect

A regional sequence-stratigraphic analysis was recently completed for the Tertiary slope sediments in Green Canyon, Ewing Bank, and Mississippi Canyon to provide a chronostratigraphic framework for basin reconstructions and predict lithofacies distributions of reservoir and seal rocks. Sixteen third-order sequences of lowstand deep-water deposits were interpreted for the middle Miocene-Pleistocene section. Thirty regional lithofacies maps were made of predominantly lowstand deposits showing the distribution of shale and sand-prone sediments, slumping, channel levee systems, and fan lobes based on distinctive seismic reflection and well log patterns. These maps were combined with isochrons of selected sequences to identify depositional fairways, depocenters, and paleosalt positions that constantly changed through time. Depositional trends were principally north to south but were also observed to be east-west as salt modified the gradient on the gently dipping slope. In some cases, the structural and stratigraphic trends could be projected under allochthonous tabular salt. Miocene channel and fan lobe sands were found concentrated on the middle-lower paleoslope across the study area. The sedimentation rate doubled (0.7 m/1000 yr) in the early-middle Pliocene, which caused large-scale salt movements and trapped sand-prone turbidites along the upper-middle slope. A four-fold decrease in sediment influx during the late Pliocene-early Pleistocene produced a stacked condensed section of four sequences over the eastern Louisiana slope. A return to rapid sedimentation (up to 2.1 m/1000 yr.) during the Pleistocene reactivated salt movements and depocenters in the Green Canyon, Ewing Bank, and Mississippi Trough areas.

Risch, D.L.; Chowdhury, A.N.; Hannan, A.E. [Geco-Prakla, Houston, TX (United States)

1994-09-01

405

Submarine UXO Detection Using Resonance Scattering Sonar  

NASA Astrophysics Data System (ADS)

Resonance scattered waves from a dataset collected in a pond setting were utilized to detect and characterize unexploded ordnance (UXO) located proud off the bottom sediments. Furthermore, it was investigated whether UXO can be characterized by their size and filler velocities and whether medium velocities can be derived from the field data. Analysis of the field data was supported by numerical modeling. It was found that resonance scattered waves were present in all numerical data and in the field cases of a proud sphere and a buried cylinder. In all other cases of proud UXO the field data revealed frequency dependent scattered waves that were part of the direct reflected waves. Imaging UXO with monochromatic data produces surprisingly good results considering that in most investigated cases a small fraction of the data with very low amplitudes were used in comparison to data typically used for Kirchhoff migration or SAS imaging. The images derived from resonance scattered waves were generated by data obtained from narrow passbands throughout the whole frequency spectrum such that different parts of the UXO can be illumination separately. Range resolution is reduced when imaging is done with monochromatic signals. However, the image resolution can be dramatically improved by adding data from different azimuth as was demonstrated for the cases of a proud sphere and bomb. A suite of results ranging from numerical calculations to field data will be presented to show how the properties of resonance scattering can be utilized to detect, locate and characterize an UXO in littoral environments.

Gritto, R.; Korneev, V. A.; Johnson, L. R.

2010-12-01

406

Debris in the deep: Using a 22-year video annotation database to survey marine litter in Monterey Canyon, central California, USA  

NASA Astrophysics Data System (ADS)

Anthropogenic marine debris is an increasing concern because of its potential negative impacts on marine ecosystems. This is a global problem that will have lasting effects for many reasons, including: (1) the input of debris into marine environments is likely to continue (commensurate with population increase and globalization), (2) accumulation, and possibly retention, of debris will occur in specific areas due to hydrography and geomorphology, and (3) the most common types of debris observed to date will likely persist for centuries. Due to the technical challenges and prohibitive costs of conducting research in the deep sea, little is known about the abundance, types, sources, and impacts of human refuse on this vast habitat, and the extreme depths to which this debris is penetrating has only recently been exposed. We reviewed 1149 video records of marine debris from 22 years of remotely operated vehicle deployments in Monterey Bay, covering depths from 25 m to 3971 m. We characterize debris by type, examine patterns of distribution, and discuss potential sources and dispersal mechanisms. Debris was most abundant within Monterey Canyon where aggregation and downslope transport of debris from the continental shelf are enhanced by natural canyon dynamics. The majority of debris was plastic (33%) and metal (23%). The highest relative frequencies of plastic and metal observations occurred below 2000 m, indicating that previous studies may greatly underestimate the extent of anthropogenic marine debris on the seafloor due to limitations in observing deeper regions. Our findings provide evidence that submarine canyons function to collect debris and act as conduits for debris transport from coastal to deep-sea habitats.

Schlining, Kyra; von Thun, Susan; Kuhnz, Linda; Schlining, Brian; Lundsten, Lonny; Jacobsen Stout, Nancy; Chaney, Lori; Connor, Judith

2013-09-01

407

Swept Narrow Band Random on Random.  

National Technical Information Service (NTIS)

The implementation of swept narrow band random on random on the HP5451C Fourier Analyzer System and the HP5427A Vibration Control System is discussed. Up to five narrow bands of a dynamically changing narrow band random spectrum can be super-imposed on a ...

F. T. Mercer

1980-01-01

408

Narrow band gap amorphous silicon semiconductors  

Microsoft Academic Search

Disclosed is a narrow band gap amorphous silicon semiconductor comprising an alloy of amorphous silicon and a band gap narrowing element selected from the group consisting of Sn, Ge, and Pb, with an electron donor dopant selected from the group consisting of P, As, Sb, Bi and N. The process for producing the narrow band gap amorphous silicon semiconductor comprises

A. Madan; A. H. Mahan

1985-01-01

409

The clinical implications of a smoking ban on submarines in the U.S. Navy.  

PubMed

By the end of calendar year 2010, a total smoking ban on submarines is expected to be implemented throughout the submarine force because of the negative health effects of environmental tobacco smoke and the recently demonstrated exposure of nonsmoking submariners to measurable levels of nicotine during submarine deployments. Historically, smoking has been highly prevalent in the military, but new data on the negative health effects of tobacco have led the military to change its policies, restricting its use in certain environments. A number of research studies have examined the effect of smoking on the military, cessation and prevention interventions, effect of environmental tobacco smoke onboard the submarine, and treatment modalities aimed at smokers attempting to quit. With the potential for considerable physical and psychological effects, a mass tobacco cessation program is being implemented to support the prohibition onboard the submarine. Recommendations for a successful implementation program are included. PMID:21366089

Shah, Anil N; Arnold, Michael J

2011-02-01

410

Reverse-engineering a submarine pyroclastic flow from its deposit  

NASA Astrophysics Data System (ADS)

Pyroclastic density currents occur in many ocean island and other ocean-proximal settings, in which there is potential for flows to propagate from the land in to the sea. There are several well observed examples of this, both recently (e.g. Tar River valley, Montserrat), and in the geological record (e.g. Grande Savanne, Dominica). The transition between subaerial and submarine flow requires a switch between gas fluidisation to water fluidisation. This in turn will lead to changes in the transport dynamics of the flow, as properties including viscosity, particle buoyancy, and compressibility change. By constraining the initial parameters for the submarine portion of the flow, a better understanding of the transition conditions can be gained. We present an approach using the Move turbidity current modelling software to reconstruct the parameter ranges required to form a known Tar valley offshore deposit East of Montserrat.

Rowley, P.; Waltham, D.; McLean, S.

2012-04-01

411

Ocean bottom tiltmeter developed for submarine volcano monitoring  

NASA Astrophysics Data System (ADS)

Most of the oceanic crust is formed by intrusive processes, yet these processes at mid-ocean ridges are poorly understood when compared to on-land volcanos that are well monitored with respect to their surface deformation and seismic activity. This limited knowledge of tectonic processes at mid-ocean ridges stems from an absence of direct observations and inhibits our understanding of their magmatic segmentation, and many first-order magmatic processes, including fractionation and mixing. As a means to improve this situation, we have installed tiltmeters in the Scripps Ocean Bottom Seismographs (OBS) and begun initial performance testing in sediment and hard rock environments. These tests indicate that the TILT-OBS is now ready for realistic, designated testing on submarine volcanos. Such tests may be in the form of a rapid response monitoring of recently discovered submarine volcanic activity, or as the first trial measurements of strain in more stable, mid-ocean ridge volcanos.

Staudigel, H.; Wyatt, F. K.; Orcutt, J. O.

412

Characterisation of submarine groundwater discharge offshore south-eastern Sicily  

Microsoft Academic Search

A complex approach in characterisation of submarine groundwater discharge (SGD) off south-eastern Sicily comprising applications of radioactive and non-radioactive tracers, direct seepage measurements, geophysical surveys and a numerical modelling is presented. SGD fluxes in the Donnalucata boat basin were estimated by direct seepage measurements to be from 4 to 12Ls?1, which are comparable with the total SGD flux in the

P. P. Povinec; P. K. Aggarwal; A. Aureli; W. C. Burnett; E. A. Kontar; K. M. Kulkarni; R. Rajar; M. Taniguchi; J.-F. Comanducci; G. Cusimano; H. Dulaiova; L. Gatto; M. Groening; S. Hauser; I. Levy-Palomo; B. Oregioni; Y. R. Ozorovich; A. M. G. Privitera; M. A. Schiavo

2006-01-01

413

A Database on Submarine Landslides of the Mediterranean Sea  

Microsoft Academic Search

\\u000a Submarine landslides are ubiquitous along the continental margins of the Mediterranean basin and occur on tectonically-dominated\\u000a margins as well as on passive margins and volcanic island flanks. Tectonically quiet zones seem to have the highest density\\u000a of known events. Most landslides occur as long run-out distance debris flows, but slumps and deep-seated failures are also\\u000a relatively common. In abyssal plains

A. Camerlenghi; R. Urgeles; L. Fantoni

414

On the crisis stability of a submarine deterrent  

SciTech Connect

Without defenses, stability indices fall monotonically as the number of submarine-launched ballistic missiles (SLBMs) is reduced. For few SLBMs, the favorable stability properties of the survivable SLBMs are masked by the unfavorable stability properties of the non-survivable land missiles. With ground-based interceptor (GBI) defenses, stability initially falls faster. The number of GBIs could be increased gradually to minimize their impact on stability.

Canavan, G.H.

1992-05-01

415

On the crisis stability of a submarine deterrent  

Microsoft Academic Search

Without defenses, stability indices fall monotonically as the number of submarine-launched ballistic missiles (SLBMs) is reduced. For few SLBMs, the favorable stability properties of the survivable SLBMs are masked by the unfavorable stability properties of the non-survivable land missiles. With ground-based interceptor (GBI) defenses, stability initially falls faster. The number of GBIs could be increased gradually to minimize their impact

Canavan

1992-01-01

416

Interior of rail mill, now an iron foundry; The submarine ...  

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

Interior of rail mill, now an iron foundry; The submarine car in the distance is filled with molten iron that will be poured into a ladle which will, in turn, be poured into the molds lining the center of the building - Bethlehem Steel Corporation, South Bethlehem Works, Iron Foundry, Along Lehigh River, North of Fourth Street, West of Minsi Trail Bridge, Bethlehem, Northampton County, PA

417

Submarine landforms characteristic of glacier surges in two Spitsbergen fjords  

Microsoft Academic Search

Well-preserved submarine landforms, all less than 100 years old, are imaged on high-resolution swath bathymetry obtained from Van Keulenfjorden and Rindersbukta (inner Van Mijenfjorden), Spitsbergen, Svalbard. Several tidewater glaciers in these fjords have surged in the last few hundred years. Streamlined landforms, found within the limits of known surges, are interpreted as mega-scale glacial lineations (MSGL) formed subglacially beneath actively

D. Ottesen; J. A. Dowdeswell; D. I. Benn; L. Kristensen; H. H. Christiansen; O. Christensen; L. Hansen; E. Lebesbye; M. Forwick; T. O. Vorren

2008-01-01

418

Submarine Hydrogeological Data from Cape Cod National Seashore  

USGS Publications Warehouse

In order to test hypotheses about ground water flow under and into estuaries and the Atlantic Ocean, geophysical surveys, geophysical probing, submarine ground-water sampling, and sediment coring were conducted by U.S. Geological Survey (USGS) scientists at Cape Cod National Seashore (CCNS) in Massachusetts from 2004 through 2006. This USGS Open-File Report presents the data collected as a result of these field efforts.

Cross, VeeAnn A.; Bratton, John F.; Crusius, John; Colman, John A.; McCobb, Timothy D.

2008-01-01

419

Cold-water coral banks and submarine landslides: a review  

Microsoft Academic Search

This paper aims to review the relation between cold-water coral bank development and submarine landslides. Both are common\\u000a features on continental margins, but so far it has not been reviewed which effect—if at all—they may have upon each other.\\u000a Indirect and direct relations between coral banks and landslides are evaluated here, based on four case studies: the Magellan\\u000a Mound Province

Ben De Mol; Veerle Huvenne; Miquel Canals

2009-01-01

420

A giant three-stage submarine slide off Norway  

Microsoft Academic Search

One of the largest submarine slides known, The Storegga Slide, is located on the Norwegian continental margin. The slide is up to 450 m thick and has a total volume of about 5,600 km3. The headwall of the slide scar is 290 km long and the total run-out distance is about 800 km. The slide involved sediments of Quaternary to

Tom Bugge; Stein Befring; Robert H. Belderson; Tor Eidvin; Eystein Jansen; Neil H. Kenyon; Hans Holtedahl; Hans Petter Sejrup

1987-01-01

421

Non-nuclear submarine tankers could cost-effectively move Arctic oil and gas  

Microsoft Academic Search

Before the advent of nuclear propulsion for U.S. Navy submarines, fuel cells were considered to be the next logical step forward from battery powered submarines which required recharging. But with the launching of the USS Nautilus (SSN-571) in 1954, the development of fuel-cell propulsion was sidelined by the naval community. Nearly 30 years later fuel-cell propulsion on board submarines is

Kumm

1984-01-01

422

Downstream effects of Glen Canyon Dam on the Colorado River in Grand Canyon: A review  

NASA Astrophysics Data System (ADS)

Glen Canyon Dam, completed in 1963, has altered geomorphic and ecological processes and resources of the Colorado River in Grand Canyon. Before the dam was completed, the river transported large quantities of sediment during spring floods as large as 8500 m3/s. After 1963, dam releases typically were less than 900 m3/s with large diurnal fluctuations and little sediment. The 2-yr peak discharge decreased by a factor of 2.5, resulting in aggraded rapids and a large increase in riparian vegetation. The clearwater releases from the dam eroded sand deposited on the bed and banks. Although pre-dam water temperatures varied seasonally, dam releases typically are about 8°C year round. Because of the clear, cold water and reduced flooding, post-dam aquatic productivity is considerably higher in the tailwater. Rainbow trout and other non-native fishes are now common, 3 native species have been extirpated, and the remaining species, including the endangered humpback chub, cannot successfully reproduce in the river.

Webb, R. H.; Wegner, D. L.; Andrews, E. D.; Valdez, R. A.; Patten, D. T.

423

Sequence stratigraphy of the Plio-Pleistocene sediments, northeastern Green Canyon and eastern Ewing Bank Areas, northern Gulf of Mexico  

SciTech Connect

A sequence stratigraphic study of the Plio-Pleistocene sediments in the northeastern Green Canyon and Ewing Bank areas has defined seven deposition sequences (5.5, 4.2, 3.8, 3.0, 1.4, 1.1, 0.8, 0.7, and 0.5 Ma). These sequences were correlated, and detailed seismic and geologic facies were constructed for each sequence. Data base for the study comprises 1,436 line miles of forty-fold, migrated, 2-D seismic data, as well as logs from 25 wells, and biostratigraphic data from 17 wells. The area consists of seven mini-basins separated by salt features with differing geometries, and faults. Paleoecology indicates that the area rested primarily in bathyal settings. The early Pliocene sequences (5.5 to 3.0 Ma) consist of sand-rich, areally widespread turbidite systems comprising basin-floor fans (amalgamated sheet sands), surrounded and overlain by overbank shales. Petroleum discoveries in the area occur primarily in reservoirs in this interval. Structural restorations indicate that most of the mini-basins in the study area began to develop during this period of time associated with loading of shallow salt sheets. The interval between 3.0 - 1.4 Ma represents a major condensed zone, including three stacked condensed sections. Lithologies are dominantly shales with some thin sands. This interval varies from 50 to 200 feet in thickness. During the Pleistocene (1.4 Ma to present), mud-rich turbidite systems were deposited extensively in the area, including channel-levee systems and related settings. Sands tend to be concentrated near sequence boundaries and primarily in channel-fill facies. Extensive overbank settings are interpreted for the mud-rich portion of these sequences, based on both siesmich facies and regional distribution. Extensive slides are present also in this interval. By 0.5 Ma, submarine canyons also began to develop in this area; these canyons are interpereted to have fed sediments in the Mississippi Fan in the deep Gulf of Mexico.

Budhijanto, F.M.; Weimer, P. [Univ. of Colorado, Boulder, CO (United States)

1995-10-01

424

Subjective symptoms and postural control during a disabled submarine simulation.  

PubMed

To simulate conditions aboard a disabled submarine, 7 submariners were confined for 5 d to a normobaric environment of 16.75% O2, 2.5% CO2, 4 degrees C, and 85% relative humidity (RH). After 2 control days and 1 d o