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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

Geomorphic process fingerprints in submarine canyons  

USGS Publications Warehouse

Submarine canyons are common features of continental margins worldwide. They are conduits that funnel vast quantities of sediment from the continents to the deep sea. Though it is known that submarine canyons form primarily from erosion induced by submarine sediment flows, we currently lack quantitative, empirically based expressions that describe the morphology of submarine canyon networks. Multibeam bathymetry data along the entire passive US Atlantic margin (USAM) and along the active central California margin near Monterey Bay provide an opportunity to examine the fine-scale morphology of 171 slope-sourced canyons. Log–log regression analyses of canyon thalweg gradient (S) versus up-canyon catchment area (A) are used to examine linkages between morphological domains and the generation and evolution of submarine sediment flows. For example, canyon reaches of the upper continental slope are characterized by steep, linear and/or convex longitudinal profiles, whereas reaches farther down canyon have distinctly concave longitudinal profiles. The transition between these geomorphic domains is inferred to represent the downslope transformation of debris flows into erosive, canyon-flushing turbidity flows. Over geologic timescales this process appears to leave behind a predictable geomorphic fingerprint that is dependent on the catchment area of the canyon head. Catchment area, in turn, may be a proxy for the volume of sediment released during geomorphically significant failures along the upper continental slope. Focused studies of slope-sourced submarine canyons may provide new insights into the relationships between fine-scale canyon morphology and down-canyon changes in sediment flow dynamics.

Brothers, Daniel S.; ten Brink, Uri S.; Andrews, Brian D.; Chaytor, Jason D.; Twichell, David C.

2013-01-01

3

Seismic expression of Late Quaternary Banda submarine canyon and fan offshore northern Baja California  

SciTech Connect

High-resolution seismic reflection profiles obtained throughout the inner California continental borderland offshore northwestern Baja California, Mexico, show the presence of numerous modern submarine canyons and associated fans. One set of these, the Banda submarine canyon/fan, is of relatively recent origin, as demonstrated by onlap of the basal fan sediments against an acoustically transparent, presumably hemipelagic deposit. Late Quaternary sedimentation rates inferred from isotopically dated piston core samples place the age of the postulated hemipelagic unit at approximately 650,000 years ago. The Banda submarine canyon heads within the Bahia Todos Santo and passes through a narrow gorge between Punta Banda and Islas Todos Santos. It is proposed that this submarine canyon and fan system formed entirely during late Quaternary time, following the breach of the Punta Banda ridge during a late Pleistocene high sea level stand. The presence of an ancient, buried channel exiting to the north out of Bahia Todos Santos probably marks the head of an earlier submarine canyon which acted as the conduit of clastic sediments from Valle Maneadero to the deep borderland basins. The now active Banda submarine canyon pirated the supply of terrigenous clastics from this older canyon. The active Agua Blanca fault zone cuts across the head of Banda submarine canyon, suggesting that tectonic movements may have played a role in the development of the Banda submarine canyon and fan system.

Legg, M.R.

1987-05-01

4

Flow dynamics around downwelling submarine canyons  

NASA Astrophysics Data System (ADS)

Flow dynamics around a downwelling submarine canyon were analysed with the Massachusetts Institute of Technology general circulation model. Blanes Canyon (northwestern Mediterranean) was used for topographic and initial forcing conditions. Fourteen scenarios were modelled with varying forcing conditions. Rossby and Burger numbers were used to determine the significance of Coriolis acceleration and stratification (respectively) and their impacts on flow dynamics. A new non-dimensional parameter (?) was introduced to determine the significance of vertical variations in stratification. Some simulations do see brief periods of upwards displacement of water during the 10-day model period; however, the presence of the submarine canyon is found to enhance downwards advection of density in all model scenarios. High Burger numbers lead to negative vorticity and a trapped anticyclonic eddy within the canyon, as well as an increased density anomaly. Low Burger numbers lead to positive vorticity, cyclonic circulation, and weaker density anomalies. Vertical variations in stratification affect zonal jet placement. Under the same forcing conditions, the zonal jet is pushed offshore in more uniformly stratified domains. The offshore jet location generates upwards density advection away from the canyon, while onshore jets generate downwards density advection everywhere within the model domain. Increasing Rossby values across the canyon axis, as well as decreasing Burger values, increase negative vertical flux at shelf break depth (150 m). Increasing Rossby numbers lead to stronger downwards advection of a passive tracer (nitrate), as well as stronger vorticity within the canyon. Results from previous studies are explained within this new dynamic framework.

Spurgin, J. M.; Allen, S. E.

2014-10-01

5

Contemporary sediment-transport processes in submarine canyons.  

PubMed

Submarine canyons are morphological incisions into continental margins that act as major conduits of sediment from shallow- to deep-sea regions. However, the exact mechanisms involved in sediment transfer within submarine canyons are still a subject of investigation. Several studies have provided direct information about contemporary sedimentary processes in submarine canyons that suggests different modes of transport and various triggering mechanisms. Storm-induced turbidity currents and enhanced off-shelf advection, hyperpycnal flows and failures of recently deposited fluvial sediments, dense shelf-water cascading, canyon-flank failures, and trawling-induced resuspension largely dominate present-day sediment transfer through canyons. Additionally, internal waves periodically resuspend ephemeral deposits within canyons and contribute to dispersing particles or retaining and accumulating them in specific regions. These transport processes commonly deposit sediments in the upper- and middle-canyon reaches for decades or centuries before being completely or partially flushed farther down-canyon by large sediment failures. PMID:23937169

Puig, Pere; Palanques, Albert; Martín, Jacobo

2014-01-01

6

Cascading-driven upwelling in submarine canyons at high latitudes  

Microsoft Academic Search

Numerical simulations and laboratory experiments confirm my initial research hypothesis stating that dense-water cascading down a submarine canyon induces localized upwelling of deeper water onto the shelf. This process, not described before, is associated with internal deformation radii inherent in the cascading process being less the canyon width and geostrophic adjustment of a density front that establishes along the canyon

Jochen Kämpf

2005-01-01

7

Submarine origin for the Neoproterozoic Wonoka canyons, South Australia  

NASA Astrophysics Data System (ADS)

An examination of the deeply incised Ediacaran Wonoka canyons in the Adelaide Geosyncline (most recently interpreted as subaerial valleys) demonstrates their submarine origin, and confirms them as some of the best examples of ancient outcropping submarine canyons in the world. The entire canyon-fill succession is interpreted to be of deep-water (below wave base) origin, consisting of calcareous shale and siltstone together with a variety of mass-flow deposits including turbidites, grain flows and debris flows. The canyon fill lacks definitive shallow-water structures (e.g. mud cracks, fenestral fabrics or wave ripples) at all stratigraphic levels. Canyon-lining carbonate crusts that have previously been interpreted as non-marine calcretes or tufas (and used to suggest a non-marine origin for the canyons) are argued to be of deep-water, marine, microbial origin. Extremely negative carbon isotope values from the canyon-fill and canyon-lining crusts have a primary marine origin. Previously interpreted deepening upward trends in the canyon fill (used as evidence of a subaerial erosion episode followed by drowning) are suggested to be fining upward trends, caused by the transition from canyon cutting to canyon filling, with the majority of the fill being of deep-water slope origin. The basal conglomeratic canyon-fill sediments represent the last vestiges of the high-energy, deep-water, canyon-erosion environment in which the incisions formed. A deep-water origin for the canyons is consistent with all previous stratigraphic observations of the Wonoka canyons, including the conspicuous lack of regional unconformities in the lower Wonoka Formation, and their emanation from the deep-water facies of the Wonoka Formation. A submarine canyon origin also removes the need for extreme (~ 1 km) relative sea level fluctuation and associated problems (i.e. an enclosed basin with Messinian-style evaporative drawdown or thermal uplift above a migrating mantle plume) required by the subaerial valley hypotheses.

Giddings, J. A.; Wallace, M. W.; Haines, P. W.; Mornane, K.

2010-01-01

8

Geologic controls on the morphology of La Aguja submarine canyon  

Microsoft Academic Search

The seascape of the continental shelf and slope offshore Santa Marta is sculpted by the submarine Aguja Canyon, a deep seafloor incision that extends from the inner shelf to the continental rise along some 115km. No major modern rivers flow into this canyon, thus ruling out principal fluvial control on the present geometry of this feature. Recently acquired multibeam sonar

Isabel C. Restrepo-Correa; Germán Y. Ojeda

2010-01-01

9

An Experimental Study of Submarine Canyon Evolution on Continental Slopes  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

10

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

11

Physical modeling of tidal resonance in a submarine canyon  

NASA Astrophysics Data System (ADS)

observations in submarine canyons poleward of 30° are usually dominated by the semidiurnal (M2) tidal frequency, which is superinertial at these latitudes. Observations from a submarine canyon at 44°N (the Gully, Nova Scotia) suggest that canyons can be dominated by the subinertial (K1) tidal frequency if length scales are correct for resonance of the K1 frequency. A model of the Gully was constructed in a tank on a rotating table and tidal currents generated to determine factors that influence resonance. Resonance curves were fit to measurements from the laboratory canyon for a range of stratifications, background rotation rates, and forcing amplitudes. Dense water was observed upwelling onto the continental shelf on either side of the laboratory canyon and traveled at least one canyon width along the shelf. Friction values measured in the laboratory were much higher than expected, probably due to upwelled water surging onto the shelf on each tidal cycle, similar to a tidal bore. By scaling observations from the laboratory to the ocean and assuming friction in the ocean is also affected by water traveling onto the shelf, a resonance curve for the ocean was created. Because of the broad resonance curve, the diurnal tide remains strong year round at the Gully, even as stratification at the shelf break changes. Dense water surging onto the shelf on tidal frequencies may affect friction and mixing at other nonresonant canyons.

Souëf, K. E.; Allen, S. E.

2014-02-01

12

Quantifying submarine landslide processes driven by active tectonic forcing: Cook Strait submarine canyon, New Zealand.  

NASA Astrophysics Data System (ADS)

The Cook Strait submarine canyon system is a multi-branched, deeply incised and highly sinuous feature of New Zealand's active margin, covering some 1500km2 of sea floor between the North and South Islands and spanning water depths of between 50 and 2700m. The canyon occurs at the transition from the westward dipping oblique subduction zone adjacent to the SE North Island and the zone of continental transpression in NE South Island. The recent acquisition of high resolution (5-10m) SIMRAD EM300 bathymetric data allows active tectonic and geomorphic processes to be assessed and quantified at a level of detail previously not possible. While multiple active submarine fault traces have been identified in the Cook Strait by previous studies, quantitative information on their activity has been limited. Cook Strait is structurally characterized by westward dipping thrust faults and E-W trending dextral strike slip faults. The multiple large magnitude high frequency earthquake sources define zones of very high ground shaking expected to contribute to triggering of extensive submarine slope failures. Landslide activity within the canyon system is widespread and represents the dominant mass movement process affecting canyon heads and walls, redistributing material into valley fills. Complexes of large (km3) multi-stepped, deep-seated (100m) translational bedding plane failures represented by gently sloping (<3°) evacuated slide-scar areas with associated blocky valley fill deposits are numerous. Steep catchment heads, channel walls and the leading edges of asymmetric thrust-fault driven anticlines are dominated by gulley and rill systems with associated eroded and/or incipient slump features. Large (107m3+) slide blocks are recognized in discrete failures with quantifiable displacement vectors. Tsunamigenic landslides in this environment are inevitable. This study will provide quantification of landslide models including triggering mechanisms, discrete geometries and displacements that will contribute to the accurate assessment of tsunami hazard levels through the development of frequency magnitude relationships.

Mountjoy, J. J.; Barnes, P. M.; Pettinga, J. R.

2006-12-01

13

Depth Distribution for the Order Cydippid (Phylum Ctenophora, Class Tentaculata) in the Monterey Submarine Canyon  

Microsoft Academic Search

This paper will discuss depth distribution analysis of cydippids in the Monterey Bay Submarine Canyon. Cydippids in the Monterey Canyon have been sighted at many different depths and areas. Since 1989, ten different cydippid species, including two new cydippids this year, were recorded on video using a remotely operated vehicle in ten sites within the Monterey Canyon. Because most of

Laura Dippold; Judith Connor; Nancy Jacobsen

14

Axial Channel Morphology Fill and Movement Within Submarine Canyons off California  

Microsoft Academic Search

Axial channels of seven submarine canyons off California have recently been investigated with ultrahigh resolution multibeam surveys. Vibracores collected from remotely operated vehicles (ROVs) provide ground truth data on the materials within the axis of six of these canyons. Acoustic beacons were used to track movement of the seafloor within the axis of Monterey Canyon. Multibeam bathymetry (0.15 m vertical

C. K. Paull; D. W. Caress; W. Ussler; E. Lundsten; H. Thomas

2008-01-01

15

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

16

Hudson Submarine Canyon Head Offshore New York and New Jersey: A Dynamic Interface  

NASA Astrophysics Data System (ADS)

Hudson Canyon is the largest submarine canyon on the U. S. Atlantic continental margin. Having completed a surface ship multi-beam bathymetric map of the Hudson Canyon region (resolution 100m; http://pubs.usgs.gov/of/2004/1441/index/html), we report preliminary results of mapping portions of the canyon head (75 square km, water depth 200-500 m) using the Eagle Ray autonomous underwater vehicle (Explorer 27- BO1-2200 AUV, ISE Ltd.) of the University of Southern Mississippi. The AUV was equipped with a Simrad EM2000 multi-beam sonar system and flown 50 m above the seafloor for resolution (3 m), and with a CTD to map water column properties. Shipboard CTD casts were also made and water sampled from the shelf break (depth 200 m) to the upper continental rise (3000 m) for detection of methane. The canyon head is of interest as an essential fish habitat (squid, hake, tilefish, and lobster) that may contribute to sustain a regional fishery and that may conduct sediment to the ocean basin. A shallow trough, the Hudson Shelf Valley, extends ~185 km across the continental shelf connecting the mouth of the Hudson River to the canyon head where it indents the seaward edge of the shelf. The canyon head bifurcates with branch 1 (6 km-long) oriented NW-SE aligned with the Shelf Valley, and branch 2 (4 km-long) oriented N-S. The two branches merge into a segment 10 km-long oriented NW-SE aligned with branch 1. Branch 1 has symmetric walls with mean inclinations of 10 degrees and smooth seafloor, suggesting that it is presently inactive and accumulating a cover of hemipelagic sediment. In contrast, the walls of both the N-S branch 2 and of the contiguous NW-SE segment are asymmetric. The walls of the NW-SE segment have a mean inclination of 15 degrees and exhibit semicircular escarpments 800-900 m long and 600-700 m wide, separated by narrow ravines perpendicular to the canyon axis. Slump blocks with sharp rims occur where N-S branch 1 joins the NW- SE segment. Two circular depressions (diameter 100 and 300 m; relief c.15 m; depths 345 m and 390 m) occur at the base of the SW wall of the segment and may be collapse features related to gas discharge evidenced by a high methane anomaly at the shelf edge. The head of Hudson Canyon encompasses diverse habitats and is a dynamic interface between shelf and slope processes. We thank NOAA's National Undersea Research Program for support.

Rona, P.; Guida, V.; Sullivan, M.; Haag, S.; Macelloni, L.; Sweeney, E.; Scranton, M.; Hobbs, J.; Asper, V.

2007-12-01

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 Danube submarine canyon (Black Sea): morphology and sedimentary processes  

Microsoft Academic Search

The Danube Canyon is a large shelf-indenting canyon that has developed seaward of the late Pleistocene paleo-Danube valley. Mechanisms of canyon evolution and factors that controlled it are revealed by analyzing the morphology and the sedimentary structure of the canyon, as well as the main features of the continental margin around the canyon. This is based on investigation by swath

Irina Popescu; Gilles Lericolais; Nicolae Panin; Alain Normand

19

The Danube submarine canyon (Black Sea): morphology and sedimentary processes  

Microsoft Academic Search

The Danube Canyon is a large shelf-indenting canyon that has developed seaward of the late Pleistocene paleo–Danube valley. Mechanisms of canyon evolution and factors that controlled it are revealed by analyzing the morphology and the sedimentary structure of the canyon, as well as the main features of the continental margin around the canyon. This is based on investigation by swath

Irina Popescu; Gilles Lericolais; Nicolae Panin; Alain Normand; Cornel Dinu; Eliane Le Drezen

2004-01-01

20

Hanging canyons of Haida Gwaii, British Columbia, Canada: Fault-control on submarine canyon geomorphology along active continental margins  

NASA Astrophysics Data System (ADS)

Faulting commonly influences the geomorphology of submarine canyons that occur on active continental margins. Here, we examine the geomorphology of canyons located on the continental margin off Haida Gwaii, British Columbia, that are truncated on the mid-slope (1200-1400 m water depth) by the Queen Charlotte Fault Zone (QCFZ). The QCFZ is an oblique strike-slip fault zone that has rates of lateral motion of around 50-60 mm/yr and a small convergent component equal to about 3 mm/yr. Slow subduction along the Cascadia Subduction Zone has accreted a prism of marine sediment against the lower slope (1500-3500 m water depth), forming the Queen Charlotte Terrace, which blocks the mouths of submarine canyons formed on the upper slope (200-1400 m water depth). Consequently, canyons along this margin are short (4-8 km in length), closely spaced (around 800 m), and terminate uniformly along the 1400 m isobath, coinciding with the primary fault trend of the QCFZ. Vertical displacement along the fault has resulted in hanging canyons occurring locally. The Haida Gwaii canyons are compared and contrasted with the Sur Canyon system, located to the south of Monterey Bay, California, on a transform margin, which is not blocked by any accretionary prism, and where canyons thus extend to 4000 m depth, across the full breadth of the slope.

Harris, Peter T.; Barrie, J. Vaughn; Conway, Kim W.; Greene, H. Gary

2014-06-01

21

Tectonically active sediment dispersal system in SW Taiwan margin with emphasis on the Gaoping (Kaoping) Submarine Canyon  

NASA Astrophysics Data System (ADS)

The sediment dispersal system in southwestern Taiwan margin consists of two main parts: the subaerial drainage basin and the offshore receiving marine basin. In plan view, this sediment dispersal system can be further divided into five geomorphic units: (1) the Gaoping (formerly spelled Kaoping) River drainage basin, (2) the Gaoping (Kaoping) Shelf, (3) the Gaoping (Kaoping) Slope, (4) the Gaoping (Kaoping) Submarine Canyon and (5) the Manila Trench in the northernmost South China Sea. The Gaoping River drainage basin is a small (3250 km 2), tectonically active and overfilled foreland basin, receiving sediments derived from the uprising Central Range of Taiwan with a maximum elevation of 3952 m. The Gaoping Submarine Canyon begins at the mouth of the Gaoping River, crosses the narrow Gaoping Shelf (~ 10 km) and the Gaoping Slope, and finally merges into the northern termination of the Manila Trench over a distance of ~ 260 km. The SW Taiwan margin dispersal system is characterized by a direct river-canyon connection with a narrow shelf and frequent episodic sediment discharge events in the canyon head. In a regional source to sink scheme, the Gaoping River drainage basin is the primary source area, the Gaoping Shelf being the sediment bypass zone and the Gaoping Slope being the temporary sink and the Manila Trench being the ultimate sink of the sediment from the Taiwan orogen. It is inferred from seismic data that the outer shelf and upper slope region can be considered as a line source for mass wasting deposits delivered to the lower Gaoping Slope where small depressions between diapiric ridges are partially filled with sediment or are empty. At present, recurrent hyperpycnal flows during the flood seasons are temporarily depositing sediments mainly derived from the Gaoping River in the head of the Gaoping Submarine Canyon. On the decadal and century timescales, sediments temporarily stored in the upper reach are removed over longer timescales probably by downslope-eroding sediment flows within the canyon. Presently, the Gaoping Submarine Canyon serves as the major conduit for transporting terrestrial sediment from the Taiwan orogen to the marine sink of the Manila Trench. Seismic data indicate that the Gaoping Submarine Canyon has been eroding the Gaoping Slope intensely by presumed hyperpycnal flows and transporting sediments from the canyon head to the middle and lower reaches of the canyon. The middle reach is a sediment bypass zone whereas the lower reach serves as either a temporary sediment sink or a sediment conduit, depending on relative prevalence to deposition or erosion during canyon evolution. Contrast differences in channel gradient and travel length between the Gaoping and Amazon sediment dispersal systems suggest that the Gaoping (Kaoping) River-Canyon system is an active sediment dispersal system for transporting terrestrial materials to the deep sea. The fate of the Gaoping River sediment is the northern Manila Trench.

Yu, Ho-Shing; Chiang, Cheng-Shing; Shen, Su-Min

2009-03-01

22

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

23

Holocene sedimentary activity in a non-terrestrially coupled submarine canyon: Cook Strait Canyon system, New Zealand  

NASA Astrophysics Data System (ADS)

The Cook Strait Canyon system, located between the North and South islands of New Zealand, is a large (1800 km2), multi-branching, shelf-indenting canyon on an active subduction margin. The canyon comes within 1 km of the coast, but does not intercept fluvial or littoral sediment systems and is therefore defined as a non-terrestrially coupled system. Sediment transport associated with a strong tidal stream, and seafloor disturbance related to numerous high-activity faults, is known from previous studies. Little is known, however, about the rates of sedimentary activity in the canyon and the processes driving it. A substantial dataset of EM300 multibeam bathymetry, gravity cores, 3.5 kHz seismic reflection profiles, camera and video transects and current meter data have been collected across the region between 2002 and 2011. The canyon system therefore provides an excellent study area for understanding sediment transport in a non-coupled submarine canyon system. Analysis of the data reveals a two-staged sediment transport system where: (1) oceanographic (tidal) processes mobilise sediment from the continental shelf and transport it to depocentres in the upper-central canyons, and (2) tectonic (earthquake) processes remobilise sediment that is transported through the lower canyon to the deep ocean. Tidal boundary-layer currents within the canyon reach velocities up to 0.53 m/s and are capable of mobilising fine sand in the central reach of the upper canyons. The velocity is higher at the canyon rim and capable of mobilising coarse sand. Sediment depocentres resulting from this tidally forced sediment transport have a well formed geomorphology within the mid-upper canyon arms of Cook Strait and Nicholson Canyons. Pseudo-static stability modelling, supported by sediment core analysis, indicates that sediment accumulated in the upper canyons fails during seismic events approximately every 100 years. The 100 year return period ground shaking-level (peak ground acceleration, ignoring the effect of the water column above the seabed) at this site is estimated to be 0.23g. Fresh rock outcrops and bed-scour in the lower canyon floor indicate that remobilised material is transported to the deep ocean. The processes identified here are likely to be analogous to those occurring in many non-coupled shelf-indenting canyons on active margins globally, and provide a framework within which the biological response to geomorphic processes in submarine canyons can be assessed.

Mountjoy, J. J.; Micallef, A.; Stevens, C. L.; Stirling, M. W.

2014-06-01

24

Discovery of two new large submarine canyons in the Bering Sea  

USGS Publications Warehouse

The Beringian continental margin is incised by some of the world's largest submarine canyons. Two newly discovered canyons, St. Matthew and Middle, are hereby added to the roster of Bering Sea canyons. Although these canyons are smaller and not cut back into the Bering shelf like the five very large canyons, they are nonetheless comparable in size to most of the canyons that have been cut into the U.S. eastern continental margin and much larger than the well-known southern California canyons. Both igneous and sedimentary rocks of Eocene to Pliocene age have been dredged from the walls of St. Matthew and Middle Canyons as well as from the walls of several of the other Beringian margin canyons, thus suggesting a late Tertiary to Quaternary genesis of the canyons. We speculate that the ancestral Yukon and possibly Anadyr Rivers were instrumental in initiating the canyon-cutting processes, but that, due to restrictions imposed by island and subsea bedrock barriers, cutting of the two newly discovered canyons may have begun later and been slower than for the other five canyons. ?? 1984.

Carlson, P.R.; Karl, Herman A.

1984-01-01

25

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

26

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. PMID:20444722

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

2010-01-01

27

The eect of a submarine canyon on the river sediment dispersal and inner shelf sediment movements in  

E-print Network

-ping Submarine Canyon; bottom nepheloid layer; mud trap; grain-size distribution; EOF analysis; McLaren Model that coincides with the presence of high suspended sediment concentration (SSC) spots in the bottom nepheloid layer. Outside the submarine canyon on the shelf where the evidence of wave reworking is strong

Lin, Andrew Tien-Shun

28

Quantifying tidal signatures of the benthic nepheloid layer in Gaoping Submarine Canyon in Southern Taiwan  

Microsoft Academic Search

The benthic nepheloid layer (BNL) has been observed in the head region of the Gaoping\\/Kaoping Submarine Canyon (KPSC) throughout a year. The top of the BNL could be as high as 100m above the canyon floor in which the suspended sediment concentration (SSC) could be as high as 30mg\\/l. In the BNL, sand-sized particles comprise the largest size-class in the

James T. Liu; Yu Huai Wang; I-Huan Lee; Ray T. Hsu

2010-01-01

29

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

30

Geomorphic characterization of four shelf-sourced submarine canyons along the U.S. Mid-Atlantic continental margin  

E-print Network

gullies, and the character of the continental shelf surrounding canyon rims. Down-canyon axial profiles continental shelf, slope and rise between Cape Hatteras and Georges Bank (Andrews et al., 2013; Brothers et alGeomorphic characterization of four shelf-sourced submarine canyons along the U.S. Mid

ten Brink, Uri S.

31

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

32

Distribution, composition, and transport of suspended particulate matter in the vicinity of Willapa submarine canyon, Washington  

Microsoft Academic Search

The distribution and composition of suspended particulate matter in the waters over Willapa submarine canyon and the adjacent continental slope off the coast of Wasington describe an apparently continuous botton nepheloid layer ranging in thickness from 160 to 530 m and composed of particles supplied primarily by the nearby Columbia River. Near-bottom particulate concentrations, estimated by continuous vertical profiles of

EDWARD T. BAKER

1976-01-01

33

Particle fluxes dynamics in Blanes submarine canyon (Northwestern Mediterranean)  

NASA Astrophysics Data System (ADS)

Within the framework of the multidisciplinary RECS project and with the aim of describing the particle flux transfer from the continental shelf to the deep basin, an array of five mooring lines equipped with a total of five pairs of PPS3/3 sequential-sampling sediment traps and RCM-7/8 current meters were deployed 30 m above the bottom from March 2003 to March 2004 inside and outside the Blanes Canyon. One mooring line was located in the upper canyon at 600 m depth, one in the canyon axis at 1700 m depth and other two close to the canyon walls at 900 m depth. A fifth mooring line was deployed in the continental open slope at 1500 m water depth. The highest near-bottom downward particle flux (14.50 g m -2 d -1) was recorded at the trap located in the upper canyon (M1), where continental inputs associated with the presence of the Tordera River are most relevant. On the other hand, the downward fluxes (4.35 g m -2 d -1) in the canyon axis (M2) were of the same order as those found in the western flank (M3) of the canyon. Both values were clearly higher than the value (1.95 g m -2 d -1) recorded at the eastern canyon wall (M4). The open slope (M5) mass flux (5.42 mg m -2 d -1) recorded by the sediment trap located outside the canyon system was three orders of magnitude lower than the other values registered by the inner canyon stations. The relevance of our data is that it explains how the transport pathway in the canyon occurs through its western flank, where a more active and persistent current toward the open ocean was recorded over the entire year of the experiment. Off-shelf sediment transport along the canyon axis showed clear differences during the period of the study, with some important events leading to strong intensifications of the current coupled with large transport of particle fluxes to the deepest parts of the canyon. Such events are primarily related to increases in river discharge and the occurrence of strong storms and cascading events during the winter. In summary, in this study it is shown that the dynamics of the water masses and the currents in the study area convert the sharp western flank of the Blanes Canyon in a more active region that favors erosion processes than the eastern flank, which has a smoother topography and where the absence of erosional conditions yields to steadier sedimentary processes.

Zúñiga, Diana; Flexas, M. Mar; Sanchez-Vidal, Anna; Coenjaerts, Johan; Calafat, Antoni; Jordà, Gabriel; García-Orellana, Jordi; Puigdefàbregas, Joan; Canals, Miquel; Espino, Manuel; Sardà, Francesc; Company, Joan B.

2009-09-01

34

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

35

Axial Channel Morphology Fill and Movement Within Submarine Canyons off California  

NASA Astrophysics Data System (ADS)

Axial channels of seven submarine canyons off California have recently been investigated with ultrahigh resolution multibeam surveys. Vibracores collected from remotely operated vehicles (ROVs) provide ground truth data on the materials within the axis of six of these canyons. Acoustic beacons were used to track movement of the seafloor within the axis of Monterey Canyon. Multibeam bathymetry (0.15 m vertical precision and 1.0 m horizontal resolution at 50 m survey altitude) and chirp seismic-reflection profiles (0.11 m vertical resolution) were collected from an autonomous underwater vehicle (AUV). Inertial navigation combined with Doppler velocity sonar allows the AUV to navigate the sinuous canyons at 3 kt on a pre-programmed route ~50 m above the seafloor. Submarine canyons that head near the shoreline (Monterey, Hueneme, Mugu, Redondo and La Jolla) contain similar wave-like bedforms with 20-100 m wavelengths and amplitudes up to 2.5 m oriented roughly perpendicular to the channel axis. These bedforms are asymmetric in profile with a steep down-canyon face and crescent-shaped, concave down-canyon. They are observed throughout the surveys (80-800 m water depth) and appear to form genetically similar packages (0.1 to 3 km long) that terminate upslope at a somewhat higher topographic step. Generally, bedform groups are found within the axial channel, but occasionally extend up the canyon walls. ROV-collected vibracores show that the wave-like bedforms comprise recent, coarse-grained gravity flow deposits, suggesting these canyons are active. In contrast, two submarine canyons with heads on the outer shelf (Soquel and Santa Monica) lack these wave-like bedforms and have relatively smooth axial channel floors. Vibracores show these canyons are filled with generally uniform fine-grained sediments, suggesting they are inactive. Apparently wave-like bedforms are common features of active submarine canyons. To assess whether sediment within a canyon floor is moved by traction currents or mass transport, three acoustic beacons were deployed in Monterey Canyon (~290 m water depth) in February 2007. The beacons were placed in 50-cm-high ~45 kg concrete monuments. These boulder-sized monuments were buried leaving only the top of the beacon extending ~6 cm above the seafloor. The position of these beacons was re-surveyed 8 times between February 2007 and July 2008. While the beacons did not move between most surveys, two down-canyon shifts of ~150 m and >1,200 m were measured. The episodic movement of the buried monuments suggests that the seafloor was remobilized to more than 50-cm- depth during sediment transport events. Four repeat AUV multibeam surveys were also conducted during the first half of 2007. These surveys show that the wave-shaped bedforms occur in the canyon axis down to at least 1,100 m water depth. Because the buried monuments have moved more than two wavelengths down- canyon during an individual event, identification and tracking of individual bedforms between events has proven to be difficult. Apparently, these wave-shaped bedforms are produced during brief, discrete mass transport events.

Paull, C. K.; Caress, D. W.; Ussler, W.; Lundsten, E.; Thomas, H.

2008-12-01

36

Spatial and temporal variability of meiobenthic density in the Blanes submarine canyon (NW Mediterranean)  

NASA Astrophysics Data System (ADS)

Meiofaunal density distribution was studied from 400 m to 1500 m depth inside Blanes submarine canyon (NW Mediterranean), and on the eastern open slope in autumn 2003 and spring 2004. Our multidisciplinary approach allowed to study the hydrodynamics and sedimentary processes in the Blanes Canyon that characterize it as highly heterogeneous environment. Inside the canyon area, particle fluxes were higher than on the slope area, increased from autumn to spring and mostly consisted of lithogenic material. Moreover the canyon’s locations experienced more intense bottoms’ currents and sediment disturbance, being reflected in a greater variability of meiobenthic densities, both between stations and sampling times than on the open slope. No clear trends (e.g. declining densities) associated with increasing depths were observed. Contrary in the open slope, current velocities were relatively lower compared with the canyon area and showed lower temporal variability. At the same time, the nutritional quality of the particle fluxes at deeper grounds were higher, probably allowing the meiofaunal densities not to change over time. In conclusion, the meiobenthos in our system apparently showed a higher temporal variability, inside the canyon area, strongly affected by particle fluxes or erosive and sediment-mixing processes linked to current modifications induced by the canyon topography.

Romano, C.; Coenjaerts, J.; Flexas, M. M.; Zúñiga, D.; Vanreusel, A.; Company, J. B.; Martin, D.

2013-11-01

37

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

38

Composition, export and faunal utilization of drift vegetation in the salt river submarine canyon  

NASA Astrophysics Data System (ADS)

Submarine canyons may be particularly important in the transport process of drift seagrasses and seaweeds from highly productive shallow lagoon areas to deeper water. We studied the composition, export, and faunal utilization of shallow, nearshore benthic vegetation as it was transported to offshore areas via the Salt River submarine canyon on the island of St Croix, U.S. Virgin Islands. The study was conducted using a saturation diving system (NULS-1: Hydrolab) during two missions in April and August, 1980. Using bottom drifters deployed in Salt River Bay and the submarine canyon, we recorded net benthic current flow up to 2 cm s -1 moving out of the lagoon and down the canyon to deeper water. Using bottom nets set up at the canyon head and at the 29 m isobar, and from transect surveys and drift clump samples, we determined drift plant export rates and drift clump biomass and species composition. The dominant drift plants were Thalassia testudinum and Syringodium filiforme and algae in the genera Dictyota, Dictyopterus, and Diloplus. During the second mission, the seagrass Halophila decipiens became more abundant, both in the drift and in large patches along the canyon floor. In both missions, more drift was collected in the nets during high wind conditions than during calmer days. Calculated turnover times ranged from 0·01 to 4·4 days for algae in the order Dictyotales and 4·4 to 18 days for Thalassia blades. Total exported biomass of drift vegetation varied between 1·4 to 65·1 kg wet wt day -1. Samples of drift vegetation contained mostly juvenile forms of both invertebrates and fishes, but in relatively low numbers. Faunal numbers were most strongly related to rate of drift movement.

Josselyn, Michael N.; Cailliet, Gregor M.; Niesen, Thomas M.; Cowen, Robert; Hurley, Ann C.; Connor, Judith; Hawes, Sandra

1983-10-01

39

Focused sound from three-dimensional sound propagation effects over a submarine canyon.  

PubMed

Ship noise data reveal an intensification of the near-surface sound field over a submarine canyon. Numerical modeling of sound propagation is used to study the effect. The noise data were collected during an ocean acoustic and physical oceanography experiment northeast of Taiwan in 2009. In situ measurements of water sound-speed profiles and a database of high-resolution bathymetry are used in the modeling study. The model results suggest that the intensification is caused by three-dimensional sound focusing by the concave canyon seafloor. Uncertainties in the model results from unsampled aspects of the environment are discussed. PMID:21682362

Chiu, Linus Y S; Lin, Ying-Tsong; Chen, Chi-Fang; Duda, Timothy F; Calder, Brian

2011-06-01

40

Sediment dynamics and post-glacial evolution of the continental shelf around the Blanes submarine canyon head (NW Mediterranean)  

NASA Astrophysics Data System (ADS)

The Blanes submarine canyon (BC) deeply incises the Catalan continental shelf in the NW Mediterranean Sea. As a consequence of the closeness (only 4 km) of its head to the coastline and the mouth of the Tordera River, the canyon has a direct influence on the shelf dispersal system as it collects large amounts of sediment, mainly during high-energy events. Multibeam bathymetry, backscatter imagery and very-high resolution seismic reflection profiles have allowed characterizing the morphology of the continental shelf around the canyon head, also identifying sediment sources and transport pathways into the canyon. The morphological data have also been used to reconstruct the evolution of the continental shelf during the last sea-level transgression so that the current understanding of shelf-to-canyon sediment exchanges through time could be improved. The continental shelf surrounding the BC consists of both depositional and erosional or non-depositional areas. Depositional areas display prominent sediment bodies, a generally smooth bathymetry and variable backscatter. These include: (i) an area of modern coarse-grained sediment accumulation that comprises the inner shelf; (ii) a modern fine-grained sedimentation area on the middle shelf offshore Tossa de Mar; and (iii) a modern sediment depleted area that covers most of the middle and outer shelf to the west of the canyon head. Erosional and non-depositional areas display a rough topography and high backscatter, and occur primarily to the east of the canyon head, where the arrival of river-fed inputs is very small. In agreement with this pattern, the continental shelf north and west of the canyon head likely is the main source of shelf sediment into the canyon. To the north, a pattern of very high backscatter extends from the coastline to the canyon head, suggesting the remobilization and off-shelf export of fines. Additionally, relict near-shore sand bodies developed over the Barcelona shelf that extend to the canyon head rim constitute a source of coarse sediment. High-energy processes, namely river floods and coastal storms, are the main controls over the river-shelf-canyon sediment exchange. River floods increase the delivery of terrigenous particles to the coastal system. Storms, mainly from the east, remobilize the sediment temporarily accumulated on the shelf towards the canyon head, so that the finer fractions are preferentially removed and a coarse lag is normally left on the shelf floor. Exceptionally, very strong storms also remove the coarse fractions from the shelf drive them into the canyon. Processes like dense shelf water cascading, which is much more intense in canyons to the north of BC, and the Northern Current also contribute to the transport of suspended sediment from far distant northern sources. During the last post-glacial transgression the BC had a strong influence on the evolution of the inner continental margin, as it interrupted the shelf sediment dispersal system by isolating the shelves to its north and south, named La Planassa and Barcelona shelves, respectively. The detailed study of the geomorphology and uppermost sediment cover of the continental shelf surrounding the Blanes submarine canyon yields insight into the past and present shelf sediment dynamics and the shelf-to-canyon sediment exchanges. The continental shelf near the canyon head consists of mosaic where erosional, or non-depositional, and depositional zones coexist. East of the canyon and offshore Tossa de Mar, the modern sediment deposition is mostly confined to the inner and middle shelf, whilst most of the La Planassa shelf is sediment depleted with numerous relict morphosedimentary features cropping out. Rocky outcrops, narrow ridges and relict coarse sand deposits suggesting erosion or non-deposition of fine sediments in modern times occupy the middle and outer shelf floor east and northeast of the canyon head. In contrast, north and west of the canyon head, the middle and outer shelf comprises several large relict sand bodies that point out to long-term deposition. However

Durán, Ruth; Canals, Miquel; Lastras, Galderic; Micallef, Aaron; Amblas, David; Pedrosa-Pàmies, Rut; Sanz, José Luis

2013-11-01

41

Reconstruction of submarine canyon systems associated with proto-Stockton arch during Late Cretaceous  

SciTech Connect

A hypothetical depositional model of the middle Great Valley gas fields of California includes the area from the Southwest Vernalis gas field in the south (T3S) to the Nicolaus gas field in the north (T12N). The model assumes that (1) the early Campanian Dobbins Shale Member was deposited at or near the shelf/slope break, and (2) the absence of the Dobbins Shale Member indicates scouring processes of active submarine canyon systems. A striking correlation exists between the proposed distribution of the Dobbins Shale Member scour channels and the position of river systems operating today in the valley. The model distinguishes six submarine canyon systems: (1) Feather River/Nicolaus, (2) American River/Florin, (3) Cosumnes River/Poppy Ridge, (4) Mokelumne River/Lodi, (5) Calaveras delta/Mulligan Hill, and (6) Stanislaus River/East Collegeville. The model implies that an extensive delta system was associated with the Calaveras River during deposition of the Dobbins Shale Member, before its erosive exit southwest of the Mulligan Hill gas field, just east of the Los Medanos, Concord, and Willow Pass fields. The presence of possible equivalents of the Dobbins Shale Member of this latter area suggests an early Campanian highland, the proto-Stockton arch. Subsequent Forbes Formation deposition appears to involve apronlike drapes or overlaps of the early Campanian canyons. However, during deposition of the Kione Formation, the canyon systems were reactivated, and canyon scour predominated, matching the scour patterns of the Dobbins Shale Member. From these ancestral canyons, younger canyons could have evolved easily.

Rider, J.

1986-04-01

42

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

43

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

44

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

45

Geomorphic process fingerprints in submarine canyons Daniel S. Brothers , Uri S. ten Brink, Brian D. Andrews, Jason D. Chaytor, David C. Twichell  

E-print Network

Geomorphic process fingerprints in submarine canyons Daniel S. Brothers , Uri S. ten Brink, Brian D fingerprint that is dependent on the catchment area of the canyon head. Catchment area, in turn, may

ten Brink, Uri S.

46

Sedimentary regime of deep submarine canyons around Fylla Banke, northeastern Labrador Sea  

NASA Astrophysics Data System (ADS)

Sedimentary regime of deep submarine canyons around the Fylla Banke, northeastern Labrador Sea Dorthe Paulsen (1), Antoon Kuijpers (2), Marit-Solveig Seidenkrantz (3) and Tove Nielsen (2) 1) Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K 2) Geological Survey of Denmark and Greenland (GEUS), Øster Voldgde 10, DK-1350 Copenhagen K. 3) Centre for Past Climate Studies, Department of Geoscience, Aarhus University. Hoegh-Guldbergs Gade 2, DK-8000 Aarhus C The southern end of the Davis Strait, the comparatively shallow-water area separating the Labrador Sea from the Baffin Bay, is cut by two deep submarine canyons of west Greenland, on the western and eastern side of the Fylla Banke, respectively. The purpose of this study is to investigate Late Pleistocene sedimentary processes governing the area of the two canyons in order to test if gravity flows or ocean currents are the most important factors governing canyon sedimentary processes in this region. Furthermore, an account is given on the formation of the two canyons in order to explain the significant difference between them. The study was carried out based on seismic profiles combined with bathymetric information, and a single sidescan sonar profile from one of the canyons (western canyon). Sedimentary information and an age model are derived from of a 5-m long gravity core (TTR13-AT-479G) collected from the mouth of the western canyon (southern end). The data indicates that the sedimentary regime is today highly affected by northward transport of the ocean currents and that gravity flows (southward from shallower to deep waters) are only of limited significance today. The deep southern end of the canyons are influenced by the upper parts of the deep North Atlantic Deep Water, but the majority of the sediment transport is linked to the strong northward flow of the lower parts of the West Greenland Current. For comparison the sediment transport is held up against earlier studies from the Davis Strait area, where 2D seismic profiles were carried out several places of the west coast of Greenland. These studies are from a contourite drift complex at the Davis Strait and north of Labrador Sea. A further possible process operating in maintaining active sediment transport through the canyon may be the cascading of dense winter water formed on the West Greenland shelf.

Paulsen, Dorthe; Kuijpers, Antoon; Seidenkrantz, Marit-Solveig; Nielsen, Tove

2014-05-01

47

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

48

A comparison of megafaunal communities in five submarine canyons off Southern California, USA  

NASA Astrophysics Data System (ADS)

Remotely operated vehicle surveys were conducted in five submarine canyons off Southern California during research expeditions in 2005 and 2010. Video transects from a range of depths were analysed to produce presence/absence data of megafauna for each site. A comparison of benthic communities at various depths, locales, and canyons was performed. No significant difference was found between canyon communities based on the level of sediment transport activity, however this may be due to the unbalanced sampling of this opportunistic study. There was significant variation in biological community composition and abundance amongst water depths. These depth-related trends are in agreement with the findings of the previous studies and are likely tied to depth-correlated variables such as hydrostatic pressure, temperature, salinity, and oxygen concentration. Species richness was found to initially increase with depth before declining rapidly at the mouths of the studied canyons. Low oxygen levels in the Santa Monica Basin, into which four of the surveyed canyons empty, may explain this.

Duffy, Grant A.; Lundsten, Lonny; Kuhnz, Linda A.; Paull, Charles K.

2014-06-01

49

Geomorphic characterization of four shelf-sourced submarine canyons along the U.S. Mid-Atlantic continental margin  

USGS Publications Warehouse

Shelf-sourced submarine canyons are common features of continental margins and are fundamental to deep-sea sedimentary systems. Despite their geomorphic and geologic significance, relatively few passive margin shelf-breaching canyons worldwide have been mapped using modern geophysical methods. Between 2007 and 2012 a series of geophysical surveys was conducted across four major canyons of the US Mid-Atlantic margin: Wilmington, Baltimore, Washington, and Norfolk canyons. More than 5700 km2 of high-resolution multibeam bathymetry and 890 line-km of sub-bottom CHIRP profiles were collected along the outer shelf and uppermost slope (depths of 80-1200 m). The data allowed us to compare and contrast the fine-scale morphology of each canyon system. The canyons have marked differences in the morphology and orientation of canyon heads, steepness and density of sidewall gullies, and the character of the continental shelf surrounding canyon rims. Down-canyon axial profiles for Washington, Baltimore and Wilmington canyons have linear shapes, and each canyon thalweg exhibits morphological evidence for recent, relatively small-scale sediment transport. For example, Washington Canyon displays extremely steep wall gradients and contains ~100 m wide, 5–10 m deep, v-shaped incisions down the canyon axis, suggesting modern or recent sediment transport. In contrast, the convex axial thalweg profile, the absence of thalweg incision, and evidence for sediment infilling at the canyon head, suggest that depositional processes strongly influence Norfolk Canyon during the current sea-level high-stand. The north walls of Wilmington, Washington and Norfolk canyons are steeper than the south walls due to differential erosion, though the underlying cause for this asymmetry is not clear. Furthermore, we speculate that most of the geomorphic features observed within the canyons (e.g., terraces, tributary canyons, gullies, and hanging valleys) were formed during the Pleistocene, and show only subtle modification by Holocene processes active during the present sea-level high-stand.

Obelcz, Jeffrey; Brothers, Daniel; Chaytor, Jason; ten Brink, Uri S.; Ross, Steve W.; Brooke, Sandra

2013-01-01

50

Lateral advection of organic matter in cascading-dominated submarine canyons  

NASA Astrophysics Data System (ADS)

In the Gulf of Lions (GoL), dense water overflowing off the shelf occurs seasonally and represents the main mechanism affecting the shelf-slope exchange of particulate organic matter (OM). Most of the dense water export takes place in the south-western GoL and in particular through Cap de Creus (CdC) submarine canyon. Here, benthic instruments were deployed to collect down-canyon particulate fluxes whereas surface sediments were taken after the cascading event along the sediment dispersal system on the shelf, in CdC canyon and in the nearby Lacaze-Duthiers (LD) canyon. The chemical composition of the suspended material and surface sediments were investigated using several proxies including organic and inorganic carbon, total nitrogen, biogenic silica, ? 13C, ? 14C, and alkaline CuO oxidation products. Thermohaline anomalies and high current speed events were measured in CdC canyon since December 2004 until mid-April 2005 indicating a marked off-shelf export of dense water trough the canyon. During the cascading, mud and relatively coarse shelf and upper canyon sediments were the major component of the mass flux. Conversely, advection of fine material via nepheloid layers dominated down-slope fluxes during pre- and post-cascading. The resulting change in grain-size affected the flux of mineral-bound terrigenous OC, indicating that the down-canyon transport of land-derived OM did not occur as bulk but rather its composition is driven by sediment sorting associated with different transport mechanisms. Both surface sediments and sediment trap samples indicated that CdC canyon is well connected to the GoL terrigenous dispersal system. Conversely, our results suggest an overall limited influence of land-derived OM in LD canyon. In spite of the reduced fluvial nutrient supply, a significant pulsed input of modern marine OM was observed in April 2005 at the end of the cascading period. Both intense mixing and lack of strong water column stratification likely played a key role allowing for both diffusion of nutrients-rich waters into the euphotic zone and efficient vertical sink of marine OC. On its way toward the seafloor, this fresh pool of OC interacted with the dense plume overflowing off the shelf, becoming part of the material laterally advected to the slope.

Tesi, T.; Puig, P.; Palanques, A.; Goñi, M. A.

2010-03-01

51

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

52

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

53

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

54

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

55

Biogenic Particle Transport in the Gaoping Submarine Canyon off Southwestern Taiwan  

NASA Astrophysics Data System (ADS)

Foraminifera shells have shown to be useful tracers of delivery and transport of biogenic particles in the Gaoping Submarine Canyon (KPSC). Foraminifera collected from sediment trap and sediment cores were analyzed to provide information on biogenic particle transport in the Gaoping River and Gaoping Submarine Canyon system off southwestern Taiwan. A non-sequential sediment trap mooring configured with an acoustic current meter was deployed in the head region of the KPSC, resulting in a 82-cm long "suspended core" in the water column after 70 days of deployment. There exists a positive relationship between the concentration of planktonic foraminiferal shells (tests/g) from the sediment trap samples and wave height recorded on the nearby shelf, albeit with a slight time-lag by 1~2 cm interval. On the other hand, benthic foraminiferal shells do not have any significant correlation with hydrographic parameters, including water temperature, along-canyon component of the current velocity, and the wave height. Furthermore, historical hydrographic conditions off southwestern Taiwan could be reconstructed based on downcore planktonic foraminiferal isotopic records retrieved from continental slope with chronology constrained by Pb-210 and Cs-137 for the last century. Variation of temperature and/or salinity reflected by the del O18 generated from Globigerinoides sacculifer (without sac) could be correlated with the temperature record provided by the Hengchun Weather Station nearby. Nevertheless, some distinctive foraminiferal del O18 signals may be related to the Multivariate ENSO Index (MEI), providing a short but high resolution paleoceanographic record. A common progressive depletion of planktonic foraminiferal del C13 towards present (coretop) found in many cores suggests the influence of anthropogenic activities since the late 1970s. Results of this study indicate that foraminifera provide useful information on the transport and settling of biogenic particle of marine origin in the KPSC. Foraminifera on the slope off southwestern Taiwan also reflect the atmospheric temperature change in the last century.

Lin, H.; Lin, Y.; Huh, C.; Liu, J. T.; Xu, J.

2008-12-01

56

Tales of Two Turbidity Currents Recorded in Monterey Submarine Canyon, USA  

NASA Astrophysics Data System (ADS)

The capacity of turbidity currents to carry sand and coarser sediment from shallow to deep regions in submarine environment has attracted the attention of researchers from different disciplines. Yet not only field measurements of oceanic turbidity currents are a rare achievement but also when such measurements do occur they consist mostly of velocity records with very limited or no data of suspended sediment concentration and grain size distribution. This work focus on two turbidity currents measured in the Monterey Canyon in 2002 with emphasis on suspended sediment from unique samples collected within the body of these currents. It is shown that concentration and grain size of the suspended material, defined by the source of the gravity flows, play a significant role in shaping the characteristics of the currents as they travel downstream the canyon. Before the flows reach their normal state, which is defined by bed slope, bed roughness, and suspended grain size, they might pass through an adjusting preliminary stage where they are subject to capacity-driven deposition releasing heavy material in excess. Flows composed with fine (silt/clay) sediments tend to be thicker than those with sands. The measured velocity and concentration data confirm the different flow patterns between the front and body of turbidity currents and that, even after reaching normal state, the flow regime can be radically disrupted by abrupt changes in canyon morphology.

Xu, J.; Sequeiros, O.; Noble, M. A.

2013-12-01

57

The summer assemblage of large pelagic Crustacea in the Gully submarine canyon: Major patterns  

NASA Astrophysics Data System (ADS)

We describe the trawl-vulnerable crustacean micronekton and macrozooplankton of the Gully, a large, shelf-incising submarine canyon off Nova Scotia, Canada, and a Marine Protected Area. Over 68 species of pelagic crustacea were collected with an International Young Gadoid Pelagic Trawl during three annual summer surveys at one fixed station in the canyon. Depths sampled ranged from the surface to the upper bathypelagic zone, concentrated in the upper 1250 m, with a maximum depth of 1500 m. The crustacean fauna was dominated by cold temperate species typical of mid- to higher-latitudes in the North Atlantic. Meganyctiphanes norvegica and Eusergestes arcticus were particularly dominant in terms of both observed biomass and abundance above 750 m depth. At least 17 species were new records for Canadian waters. The species assemblage of the station varied primarily with depth and diel cycle, the only dominant members of the assemblage showing pronounced inter-annual variations in catch being M. norvegica and Themisto gaudichaudii, both relatively shallow living species.

MacIsaac, K. G.; Kenchington, T. J.; Kenchington, E. L. R.; Best, M.

2014-06-01

58

Modeled alongshore circulation and morphologic evolution onshore of a large submarine canyon  

NASA Astrophysics Data System (ADS)

Alongshore circulation and morphologic evolution observed at an ocean beach during the Nearshore Canyon Experiment, onshore of a large submarine canyon in San Diego, CA (USA), are investigated using a two-dimensional depth-averaged numerical model (Delft3D). The model is forced with waves observed in ~500 m water depth and tidal constituents derived from satellite altimetry. Consistent with field observations, the model indicates that refraction of waves over the canyon results in wave focusing ~500 m upcoast of the canyon and shadowing onshore of the canyon. The spatial variability in the modeled wave field results in a corresponding non-uniform alongshore circulation field. In particular, when waves approach from the northwest the alongshore flow converges near the wave focal zone, while waves that approach from the southwest result in alongshore flow that diverges away from the wave focal zone. The direction and magnitude of alongshore flows are determined by a balance between the (often opposing) radiation stress and alongshore pressure gradients, consistent with observations and previous results. The largest observed morphologic evolution, vertical accretion of about 1.5 m in about 3 m water depth near the wave focal zone, occurred over a one-week period when waves from the northwest reached heights of 1.8 m. The model, with limited tuning, replicates the magnitude and spatial extent of the observed accretion and indicates that net accretion of the cross-shore profile was owing to alongshore transport from converging alongshore flows. The good agreement between the observed and modeled morphology change allows for an in-depth examination of the alongshore force balance that resulted in the sediment convergence. These results indicate that, at least in this case, a depth-averaged hydrodynamic model can replicate observed surfzone morphologic change resulting from forcing that is strongly non-uniform in the alongshore. Funding was provided by the Office of Naval Research, The National Science Foundation, a Woods Hole Oceanographic Institution and United States Geological Survey joint postdoctoral fellowship, and a National Security Science and Engineering Faculty Fellowship.

Hansen, J. E.; Raubenheimer, B.; List, J. H.; Elgar, S.; Guza, R. T.; Lippmann, T. C.

2012-12-01

59

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

60

Geomorphology and sediment processes on the continental shelf and the submarine Akhziv canyon offshore north Galilee, eastern Mediterranean.  

NASA Astrophysics Data System (ADS)

The northern continental shelf of Israel is relatively steep and incised by submarine canyons. The Akhziv canyon is the largest and most developed and the southernmost in a series of canyons that formed off-shore Lebanon up to Beirut. The canyon is incised into the continental shelf 3 km from the northwestern Galilee coast to a depth of 1200 m. This study aims to understand processes responsible for the canyon morphology and the nature of sediment transport and accumulation mechanisms in the continental shelf and down the canyon to the deep sea. Moreover, the geological section in which the canyon is incised to, and the connection to the western Galilee fault system that transverse the continental shelf is explored for the regional perspective. Akhziv canyon consists of two main channels incised in cross-section V-shape at the upper part of the canyon that connect at 700m depth to produce a U-shaped main channel. The canyon's channels orientation implies a possible connection with the region's fault system. The high-resolution bathymetric map (the National Bathymetry Project) was used for the geomorphologic and morphometric analysis to define the connection between the canyon and the north- western Galilee streams that flow in a main east-west direction, parallel to the terrestrial fault system. Gaps in the submarine aeolian calcarenite ridge on the shallow shelf represent the continuation of terrestrial streams westward during low glacial sea level. Alluvial fans, mapped at 40m water depth, testify for sediment transport from land to the continental shelf toward the canyon head. Shallow high-resolution seismic lines (Sparker) were carried out along the continental shelf and canyon head to reveal the sub-surface structure. The seismic interpretation indicates the presence of channel incisions at depths of 10-15 m under the seafloor, with infill of young sediments which represents phases of deposition and erosion along the continental shelf. In addition, Piston cores (2-3 m) and short cores (30-50 cm) were sampled along the main axis of Akhziv canyon and thalweg, from depths of 40 m to 700 m. X-ray reflections of the cores showed the upper section is fine laminated while most of the core is homogenous. The change in sedimentation pattern was also evident from magnetic susceptibility measurements and grain size analysis. The differences in the sedimentation patterns along each core and between different cores represent the transport and accumulation dynamic processes from the terrestrial source along the canyon axis to the deep sea. The geomorphological map, the sub-surface seismic interpretation, and the sedimentary results present the relation between the Akhziv sub-marine canyon and the terrestrial system at the western Galilee. Further efforts on dating the sedimentary record will reveal the connection to the glacial-interglacial cycles and their effects on the eastern Mediterranean continental shelf.

Ashqar, Lana; Bookman, Revital; Almogi-Labin, Ahuva; Ben-Avraham, Zvi

2013-04-01

61

Tidal Signatures of the Benthic Nepheloid Layer (BNL) in the Gaoping/Kaoping Submarine Canyon off Southwestern Taiwan  

NASA Astrophysics Data System (ADS)

Temporal and spatial variations of benthic nepheloid layer (BNL) have been observed in the head region of the Gaoping/Kaoping Submarine Canyon (KPSC) along the canyon thalweg in different seasons between 1999 and 2000. The top of the BNL could be as high as 100 m above the canyon floor whose suspended sediment concentration (SSC) could be as high as 30 mg/l. In the BNL, silt comprises the largest size-class in the suspended sediment population. In 2000, 2002, and 2004 three taut-line moorings were deployed at different locations in the head region of the KPSC for one month. Time series measurements of along- canyon flow velocity, water temperature, and the volume concentration (VC) of clay, very-fine-to-medium silt, coarse silt and sand size-classes were obtained near the canyon floor from each mooring. Results show that the BNL is strongly modulated by the tides in the descending order at semidiurnal, diurnal, and spring-neap frequencies. In the course of a semidiurnal tidal cycle, the flood (up-canyon) current brings colder water from seaward part of the canyon and the SSC and thickness of the BNL increases. The SSC near the canyon floor also increases in response to the peaks of flood and ebb currents of the semidiurnal tide. The tidal-to-total energy ratio (ER) for the along-canon flow is between 70-80%, and between 50-80% among the suspended sediment of clay, very-fine-to-medium silt, coarse silt and sand size-classes. M2 is the most important constituent in the along-canyon flow, water temperature, and the VC of the four size-classes. The local phase difference between the forcing (velocity), and the responses (temperature and VC) at the M2 frequency suggest the a mixture of progressive and standing waves and that topographic effect caused the phase varied along the canyon. The VC tidal amplitude ratio between M4 and M2 constituents of the four size-classes indicates that the temporal fluctuations of the suspended sediment concentration in the BNL are highly nonlinear. The generation of nonlinearity could be through the flow-topography interaction and through the alternate entrainment and deposition of suspended sediment in the course of a semidiurnal tidal cycle. At this point, the relationship among barotropic tides, internal tides, and typhoon events and BNL is not clear. The role of the BNL in the sediment transport and sedimentation in submarine canyons worldwide is also not fully understood. Studies on these subjects in the KPSC are in progress.

Liu, J. T.; Lee, I.; Wang, Y.

2008-12-01

62

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

63

Composition and provenance of terrigenous organic matter transported along submarine canyons in the Gulf of Lion (NW Mediterranean Sea)  

NASA Astrophysics Data System (ADS)

Previous projects in the Gulf of Lion have investigated the path of terrigenous material in the Rhone deltaic system, the continental shelf and the nearby canyon heads. This study focuses on the slope region of the Gulf of Lion to further describe particulate exchanges with ocean’s interior through submarine canyons and atmospheric inputs. Nine sediment traps were deployed from the heads to the mouths of Lacaze-Duthiers and Cap de Creus submarine canyons and on the southern open slope from October 2005 to October 2006. Sediment trap samples were analyzed by CuO oxidation to investigate spatial and temporal variability in the yields and compositional characteristics of terrigenous biomarkers such as lignin-derived phenols and cutin acids. Sediment trap data show that the Dense Shelf Water Cascading event that took place in the months of winter 2006 (January, February and March) had a profound impact on particle fluxes in both canyons. This event was responsible for the majority of lignin phenol (55.4%) and cutin acid (42.8%) inputs to submarine canyons, with lignin compositions similar to those measured along the mid- and outer-continental shelf, which is consistent with the resuspension and lateral transfer of unconsolidated shelf sediment to the canyons. The highest lithogenic-normalized lignin derived phenols contents in sediment trap samples were found during late spring and summer at all stations (i.e., 193.46 ?g VP g-1 lithogenic at deep slope station), when river flow, wave energy and total particle fluxes were relatively low. During this period, lignin compositions were characterized by elevated cinnamyl to vanillyl phenol ratios (>3) at almost all stations, high p-coumaric to ferulic acid ratios (>3) and high yields of cutin acids relative to vanillyl phenols (>1), all trends that are consistent with high pollen inputs. Our results suggest marked differences in the sources and transport processes responsible for terrigenous material export along submarine canyons, mainly consisting of fluvial and shelf sediments during winter and atmospheric dust inputs during spring and summer.

Pasqual, Catalina; Goñi, Miguel A.; Tesi, Tommaso; Sanchez-Vidal, Anna; Calafat, Antoni; Canals, Miquel

2013-11-01

64

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

65

Microbial Communities in Sunken Wood Are Structured by Wood-Boring Bivalves and Location in a Submarine Canyon  

PubMed Central

The cornerstones of sunken wood ecosystems are microorganisms involved in cellulose degradation. These can either be free-living microorganisms in the wood matrix or symbiotic bacteria associated with wood-boring bivalves such as emblematic species of Xylophaga, the most common deep-sea woodborer. Here we use experimentally submerged pine wood, placed in and outside the Mediterranean submarine Blanes Canyon, to compare the microbial communities on the wood, in fecal pellets of Xylophaga spp. and associated with the gills of these animals. Analyses based on tag pyrosequencing of the 16S rRNA bacterial gene showed that sunken wood contained three distinct microbial communities. Wood and pellet communities were different from each other suggesting that Xylophaga spp. create new microbial niches by excreting fecal pellets into their burrows. In turn, gills of Xylophaga spp. contain potential bacterial symbionts, as illustrated by the presence of sequences closely related to symbiotic bacteria found in other wood eating marine invertebrates. Finally, we found that sunken wood communities inside the canyon were different and more diverse than the ones outside the canyon. This finding extends to the microbial world the view that submarine canyons are sites of diverse marine life. PMID:24805961

Fagervold, Sonja K.; Romano, Chiara; Kalenitchenko, Dimitri; Borowski, Christian; Nunes-Jorge, Amandine; Martin, Daniel; Galand, Pierre E.

2014-01-01

66

Scleractinian coral recruitment patterns at Salt River submarine canyon, St. Croix, U.S. Virgin Islands  

NASA Astrophysics Data System (ADS)

Scleractinian coral recruitment patterns were studied at depths of 9, 18, 27 and 37 m on the east and west walls of Salt River submarine canyon, St. Croix, U.S. Virgin Islands, by censusing coral juveniles which settled on experimental settling plates placed on the reef for 3 26 months as well as coral juveniles within quadrats on the reef. The most common species in the juvenile population within quadrats were Agaricia agaricites, Porites astreoides, Madracis decactis, Stephanocoenia michelinii, and A. lamarcki. The only species settling on settling plates were Agaricia spp., Madracis decactis, Porites spp., Stephanocoenia michelinii and Favia fragum. A total of 271 corals settled on 342 plates, with 51% of the juveniles on the east wall and 49% on the west wall. Of these 34% settled on horizontal surfaces and 66% on vertical surfaces. Based on results from quadrats, Agaricia agaricites and Porites astreoides had high recruitment rates relative to their abundance on the reef. In contrast, Agaricia lamarcki, Montastraea annularis, M. cavernosa and Siderastrea siderea had high amounts of cover compared to their abundance as juveniles within quadrats. The mean number of juveniles per m2 within quadrats ranged from 3 to 42. In general, there was a decrease in the mean number of juveniles and the number of species with depth. Total number of juveniles on settling plates was highest at 18 m on both walls. The largest number within quadrats was at 18 m on the east wall, followed by 9 m and 18 m on the west wall. High rates of coral recruitment tended to be associated with low algal biomass and relatively high grazing pressure by urchins and fishes.

Rogers, Caroline S.; Fitz, H. Carl; Gilnack, Marcia; Beets, James; Hardin, John

1984-10-01

67

Habitat associations of deep-water rockfishes in a submarine canyon: an example of  

E-print Network

(genus Se- bastes) and associated habitats in deep water was conducted in Soquel Sub- marine Canyon. There was remarkable concordance between some of the guilds identified in Soquel Canyon and the results of other habi- plified in Soquel Canyon. Rockfishes (Sebastes spp.) are quite speciose, dominate coastal benthic fish

68

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

69

External forcings, oceanographic processes and particle flux dynamics in Cap de Creus submarine canyon, NW Mediterranean Sea  

NASA Astrophysics Data System (ADS)

Particle fluxes (including major components and grain size), and oceanographic parameters (near-bottom water temperature, current speed and suspended sediment concentration) were measured along the Cap de Creus submarine canyon in the Gulf of Lions (GoL; NW Mediterranean Sea) during two consecutive winter-spring periods (2009-2010 and 2010-2011). The comparison of data obtained with the measurements of meteorological and hydrological parameters (wind speed, turbulent heat flux, river discharge) have shown the important role of atmospheric forcings in transporting particulate matter through the submarine canyon and towards the deep sea. Indeed, atmospheric forcing during 2009-2010 and 2010-2011 winter months showed differences in both intensity and persistence that led to distinct oceanographic responses. Persistent dry northern winds caused strong heat losses (14.2 × 103 W m-2) in winter 2009-2010 that triggered a pronounced sea surface cooling compared to winter 2010-2011 (1.6 × 103 W m-2 lower). As a consequence, a large volume of dense shelf water formed in winter 2009-2010, which cascaded at high speed (up to ∼1 m s-1) down Cap de Creus Canyon as measured by a current-meter in the head of the canyon. The lower heat losses recorded in winter 2010-2011, together with an increased river discharge, resulted in lowered density waters over the shelf, thus preventing the formation and downslope transport of dense shelf water. High total mass fluxes (up to 84.9 g m-2 d-1) recorded in winter-spring 2009-2010 indicate that dense shelf water cascading resuspended and transported sediments at least down to the middle canyon. Sediment fluxes were lower (28.9 g m-2 d-1) under the quieter conditions of winter 2010-2011. The dominance of the lithogenic fraction in mass fluxes during the two winter-spring periods points to a resuspension origin for most of the particles transported down canyon. The variability in organic matter and opal contents relates to seasonally controlled inputs associated with the plankton spring bloom during March and April of both years.

Rumín-Caparrós, A.; Sanchez-Vidal, A.; Calafat, A.; Canals, M.; Martín, J.; Puig, P.; Pedrosa-Pàmies, R.

2013-06-01

70

Accumulation of dioxins in deep-sea crustaceans, fish and sediments from a submarine canyon (NW Mediterranean)  

NASA Astrophysics Data System (ADS)

Submarine canyons are efficient pathways transporting sediments and associated pollutants to deep sea. The objective of this work was to provide with the first assessment of polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) levels and accumulation in deep-sea megafauna (crustacean and fish) and sediments in the Blanes submarine canyon (North-Western Mediterranean Sea). The influence of the selected species habitats (pelagic, nektobenthic, and benthic) and the trophic chain level on the accumulation of dioxins was also investigated. Bottom sediment and biota samples were collected at different depths and locations inside the canyon and in the adjacent slope outside the canyon influence. ?2,3,7,8-PCDD/F concentrations in sediments varied from 102 to 680 pg g-1 dry weight (d.w.) (1-6 WHO98-TEQ pg g-1 d.w.). Dioxins are enriched in bottom sediments at higher depths inside the canyon and in particular in the deepest parts of the canyon axis (1700 m depth), whereas no enrichment of dioxins was verified at the deepest sediments from the adjacent open slope outside the canyon influence. The proportion of ?2,3,7,8-PCDF (furans) to ?2,3,7,8-PCDD (dioxins) increased for sediments with higher soot carbon content consistent with the higher affinity of PCDF for sorption onto soot carbon. Higher ?2,3,7,8-PCDD/F levels were found in crustaceans than in fish, ranging from 220 to 795 pg g-1 lipid weight (l.w.) (13-90 WHO98-TEQ pg g-1 l.w.) and 110 to 300 pg g-1 l.w. (22-33 WHO98-TEQ pg g-1 l.w.) in crustaceans and fish, respectively. Dioxin highest concentrations were found in nektobenthic organisms, i.e., benthic organism with swimming capabilities (both fish and crustaceans). These higher levels are consistent with the higher trophic level and predicted biomagnification factors (BMFs) of nektobenthic species. The reduced availability of sediment-bound PCDD/F for benthic species mainly due to soot and organic carbon sorption of these contaminants most probably influenced this result too. While biomagnification exerts a clear influence on the total dioxin concentrations in biota, life habits seem to exert an influence in the differential congener-specific accumulation of dioxins rather than in the total concentration. Thus, pelagic species reflected the estimated congener pattern from the surface water dissolved phase and phytoplankton, whereas the dioxin pattern in benthic and nektobenthic species was more similar to the estimated pattern in the deep-water dissolved phase and the sediment. The three crustacean species considered in this study bioaccumulated higher amounts of other dioxin congeners (non-2,3,7,8-PCDD/Fs) compared to fish. An interplay of several factors, such as biota habitats, differential uptake of water column dioxin (dissolved and particle-bound fractions), and different metabolization capabilities and rates (CYP-mediated metabolism) may explain the differences observed in dioxin patterns among crustacean species and between fish and crustaceans in the Blanes submarine canyon.

Castro-Jiménez, Javier; Rotllant, Guiomar; Ábalos, Manuela; Parera, Jordi; Dachs, Jordi; Company, Joan B.; Calafat, Antoni; Abad, Esteban

2013-11-01

71

Formation of pockmarks and submarine canyons associated with dissociation of gas hydrates on the Joetsu Knoll, eastern margin of the Sea of Japan  

NASA Astrophysics Data System (ADS)

This study, based on 3.5 kHz SBP, 3D seismic data and long piston cores obtained during MD179 cruise, elucidated the timing and causes of pockmark and submarine canyon formation on the Joetsu Knoll in the eastern margin of the Sea of Japan. Gas hydrate mounds and pockmarks aligned parallel to the axis on the top of the Joetsu Knoll are associated with gas chimneys, pull-up structures, faults, and multiple bottom-simulating reflectors (BSRs), suggesting that thermogenic gas migrated upward through gas chimneys and faults from deep hydrocarbon sources and reservoirs. Seismic and core data suggest that submarine canyons on the western slope of the Joetsu Knoll were formed by turbidity currents generated by sand and mud ejection from pockmarks on the knoll. The pockmark and canyon formation probably commenced during the sea-level fall, lasting until transgression stages. Subsequently, hydropressure release during the sea level lowering might have instigated dissociation of the gas hydrate around the base of the gas hydrate, leading to generation and migration of large volumes of methane gas to the seafloor. Accumulation of hydrate caps below mounds eventually caused the collapse of the mounds and the formation of large depressions (pockmarks) along with ejection of sand and mud out of the pockmarks, thereby generating turbidity currents. Prolonged pockmark and submarine canyon activities might have persisted until the transgression stage because of time lags from gas hydrate dissociation around the base of the gas hydrate until upward migration to the seafloor. This study revealed the possibility that submarine canyons were formed by pockmark activities. If that process occurred, it would present important implications for reconstructing the long-term history of shallow gas hydrate activity based on submarine canyon development.

Nakajima, Takeshi; Kakuwa, Yoshitaka; Yasudomi, Yukihito; Itaki, Takuya; Motoyama, Isao; Tomiyama, Takayuki; Machiyama, Hideaki; Katayama, Hajime; Okitsu, Osamu; Morita, Sumito; Tanahashi, Manabu; Matsumoto, Ryo

2014-08-01

72

New High-Resolution Mapping of Submarine Canyons in the Mid-Atlantic Continental Margin  

NASA Astrophysics Data System (ADS)

During June 2011, a BOEMRE/NOAA/USGS -funded multibeam bathymetry survey mapped the upper reaches (<900-m depths) of the Norfolk, Washington, and Baltimore canyons. Combined with existing multibeam bathymetry of the continental slope and rise, the new data provide a detailed view of the sedimentary processes that shaped the mid-Atlantic margin. The shelf-breaching canyon heads are surrounded by two terraces at depths of 95-100 m and 115-125 m in the Norfolk and Washington canyons and at depths of 115-125 m and 135-145 m in the Baltimore canyon. These terraces may represent paleo-shorelines formed during sea level stillstands. The canyon thalwegs within the shelf appear to be filled with sand in accord with old core results. The gradient of their thalweg profile is variable and relatively low across the shelf, slope, and upper rise, in contrast to the concave gradient of most non-shelf breaching canyons in the region. A few of the non-shelf breaching canyons in the mid-Atlantic margin also have relatively low and variable gradients suggesting that they once breached the shelf but are now completely filled. The seaward extensions of the Norfolk, Washington, and Baltimore canyons onto the continental rise are characterized by channels bordered by 100-200 m high levees. In places, these channels meander tightly. The extensions of other canyons onto the rise are either defined by subtle, linear depressions or cannot be traced. Channel-capture by adjacent canyons and channel abandonment originate in the lower slope and were prompted by either landslides or levee breaching. These observations indicate dynamic outer shelf deltas fed by large rivers, which were active at the last glacial maximum (LGM). The river channels on the shelf have been progressively filled during the Holocene. The clear expression of levied channels on the continental rise that extend from shelf-breaching canyons suggests that these canyons were the last ones to deliver turbidity flows to the rise. The terraces, assuming they are former shorelines, indicate that shelf-breaching canyon heads were incised into the shelf during or prior to the LGM. Some of the channels on the rise are partially filled by landslide deposits, suggesting that landslides have continued to shape the rise during the Holocene.

ten Brink, U. S.; Chaytor, J. D.; Brothers, D. S.; Twichell, D. C.; Ross, S. W.; Brooke, S.

2011-12-01

73

Megafauna of vulnerable marine ecosystems in French mediterranean submarine canyons: Spatial distribution and anthropogenic impacts  

NASA Astrophysics Data System (ADS)

Vulnerable Marine Ecosystems (VME) in the deep Mediterranean Sea have been identified by the General Fisheries Commission for the Mediterranean as consisting of communities of Scleractinia (Lophelia pertusa and Madrepora oculata), Pennatulacea (Funiculina quadrangularis) and Alcyonacea (Isidella elongata). This paper deals with video data recorded in the heads of French Mediterranean canyons. Quantitative observations were extracted from 101 video films recorded during the MEDSEACAN cruise in 2009 (Aamp/Comex). Qualitative information was extracted from four other cruises (two Marum/Comex cruises in 2009 and 2011 and two Ifremer cruises in 1995 and 2010) to support the previous observations in the Cassidaigne and Lacaze-Duthiers canyons. All the species, fishing impacts and litter recognized in the video films recorded from 180 to 700 m depth were mapped using GIS. The abundances and distributions of benthic fishing resources (marketable fishes, Aristeidae, Octopodidae), Vulnerable Marine Species, trawling scars and litter of 17 canyons were calculated and compared, as was the open slope between the Stoechades and Toulon canyons. Funiculina quadrangularis was rarely observed, being confined for the most part to the Marti canyon and, I. elongata was abundant in three canyons (Bourcart, Marti, Petit-Rhône). These two cnidarians were encountered in relatively low abundances, and it may be that they have been swept away by repeated trawling. The Lacaze-Duthiers and Cassidaigne canyons comprised the highest densities and largest colony sizes of scleractinian cold-water corals, whose distribution was mapped in detail. These colonies were often seen to be entangled in fishing lines. The alcyonacean Callogorgia verticillata was observed to be highly abundant in the Bourcart canyon and less abundant in several other canyons. This alcyonacean was also severely affected by bottom fishing gears and is proposed as a Vulnerable Marine Species. Our studies on anthropogenic impacts show that seafloor disturbance by benthic fishing is mainly attributable to trawling in the Gulf of Lion and to long lines where rocky substrates are present. The bauxite residue (red mud) expelled in the Cassidaigne canyon was seen to prevent fauna from settling at the bottom of the canyon and it covered much of the flanks. Litter was present in all of the canyons and especially in considerable quantities in the Ligurian Sea, where the heads of the canyons are closer to the coast. Three Marine Protected Areas and one fishing area with restricted access have recently been established and should permit the preservation of these deep ecosystems.

Fabri, M.-C.; Pedel, L.; Beuck, L.; Galgani, F.; Hebbeln, D.; Freiwald, A.

2014-06-01

74

Scavenging rates and particle characteristics in and near the Lacaze-Duthiers submarine canyon, northwest Mediterranean  

Microsoft Academic Search

To better understand the particle exchange processes across the Pyrenean continental margin, sampling was conducted in 1994 and 1995 at stations in and near the Lacaze-Duthiers canyon in the northwestern Mediterranean. Moored current meters provide evidence of water transport along the canyon axis (cross-slope) and along-slope with the prevailing regional circulation. Turbidity measurements show surficial nepheloid layers (SNL) roughly coincident

M. Frignani; T Courp; J. K Cochran; D Hirschberg; L Vitoria i Codina

2002-01-01

75

Resting stages in a submarine canyon: a component of shallow–deep-sea coupling?  

Microsoft Academic Search

The ecological importance of resting stages in shallow waters is well known, but their presence in the deep sea is practically unrecorded. Samples of sinking particles were collected from April 1993 to May 1994 in and around the Foix Canyon (northwest Mediterranean Sea) using PPS3 sediment traps located between -600 m and -1180 m. Dead and viable organisms were collected,

Luigi Della Tommasa; Genuario Belmonte; Alberto Palanques; Pere Puig; Ferdinando Boero

2000-01-01

76

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

77

78 FR 67086 - Safety Zone, Submarine Cable Replacement Operations, Kent Island Narrows; Queen Anne's County, MD  

Federal Register 2010, 2011, 2012, 2013

...establish, and define regulatory safety zones. The purpose of this safety zone is to protect public boaters and their vessels from potential safety hazards associated with the electrical submarine cable replacement...

2013-11-08

78

Impact of bottom trawling on deep-sea sediment properties along the flanks of a submarine canyon.  

PubMed

The offshore displacement of commercial bottom trawling has raised concerns about the impact of this destructive fishing practice on the deep seafloor, which is in general characterized by lower resilience than shallow water regions. This study focuses on the flanks of La Fonera (or Palamós) submarine canyon in the Northwestern Mediterranean, where an intensive bottom trawl fishery has been active during several decades in the 400-800 m depth range. To explore the degree of alteration of surface sediments (0-50 cm depth) caused by this industrial activity, fishing grounds and control (untrawled) sites were sampled along the canyon flanks with an interface multicorer. Sediment cores were analyzed to obtain vertical profiles of sediment grain-size, dry bulk density, organic carbon content and concentration of the radionuclide 210Pb. At control sites, surface sediments presented sedimentological characteristics typical of slope depositional systems, including a topmost unit of unconsolidated and bioturbated material overlying sediments progressively compacted with depth, with consistently high 210Pb inventories and exponential decaying profiles of 210Pb concentrations. Sediment accumulation rates at these untrawled sites ranged from 0.3 to 1.0 cm y-1. Sediment properties at most trawled sites departed from control sites and the sampled cores were characterized by denser sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sediments caused by trawling gears. Other alterations of the physical sediment properties, including thorough mixing or grain-size sorting, as well as organic carbon impoverishment, were also visible at trawled sites. This work contributes to the growing realization of the capacity of bottom trawling to alter the physical properties of surface sediments and affect the seafloor integrity over large spatial scales of the deep-sea. PMID:25111298

Martín, Jacobo; Puig, Pere; Masqué, Pere; Palanques, Albert; Sánchez-Gómez, Anabel

2014-01-01

79

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

NASA Astrophysics Data System (ADS)

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 attributed to spatio-temporal movements by this species associated with submarine canyons in the study area. Despite the economic importance of this species and the decreases in catches in the area in recent years, few studies have provided significant insight into the environmental conditions driving shrimp distribution. We therefore measured daily A. antennatus catches over the course of an entire year and analyzed this time series in terms of daily average temperature, salinity, mean kinetic energy (MKE), and eddy kinetic energy (EKE) values using generalized additive models and decision trees. A. antennatus was captured between 600 and 900 m in the Blanes canyon, depths that include Levantine Intermediate Water (LIW) and the underlying Western Mediterranean Deep Water (WMDW). The greatest catches were associated with relatively salty waters (38.5-38.6), low MKE values (6 and 9 cm 2 s -2) and moderate EKE values (10 and 20 cm 2 s -2). Deep-water rose shrimp occurrence appears to be driven in a non-linear manner by environmental conditions including local temperature. A. antennatus appears to prefer relatively salty (LIW) waters and low currents (MKE) with moderate variability (EKE).

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

2009-09-01

80

Spatial and temporal infaunal dynamics of the Blanes submarine canyon-slope system (NW Mediterranean); changes in nematode standing stocks, feeding types and gender-life stage ratios  

NASA Astrophysics Data System (ADS)

Despite recent advances in the knowledge of submarine canyons ecosystems, our understanding of the faunal patterns and processes in these environments is still marginal. In this study, meiobenthic nematode communities (from 300 m to 1600 m depth) obtained in November 2003 and May 2004 at eight stations inside and outside Blanes submarine canyon were analysed for nematode standing stocks (SSs), feeding types and gender-life stage distributions. Environmental data were obtained by sediment traps and current meters, attached to moorings (April 2003-May 2004), and sediments samples analysed for biogeochemistry and grain size (May 2004). In November 2003, nematode SSs decreased with increasing depth (367.2 individuals and 7.31 ?g C per 10 cm2 at 388 m water depth to 7.7 individuals and 0.18 ?g C per 10 cm2 at 1677 m water depth), showing a significant negative relation (abundance: R2 = 0.620, p = 0.020; biomass: R2 = 0.512, p = 0.046). This was not the case in May 2004 (283.5 individuals and 3.53 ?g C per 10 cm2 at 388 m water depth to 490.8 individuals and 4.93 ?g C per 10 cm2 at 1677 m water depth; abundance: R2 = 0.003, p = 0.902; biomass: R2 = 0.052, p = 0.587), suggesting a temporal effect that overrides the traditional decrease of SSs with increasing water depth. Both water depth and sampling time played a significant role in explaining nematode SSs, but with differences between stations. No overall differences were observed between canyon and open slope stations. Nematode standing stock (SS) patterns can be explained by taking into account the interplay of phytodetrital input and disturbance events, with station differences such as topography playing an important role. Individual nematode size decreased from November 2003 to May 2004 and was explained by a food-induced genera shift and/or a food-induced transition from a ‘latent’ to a ‘reproductive’ nematode community. Our results suggest that size patterns in nematode communities are not solely governed by trophic conditions over longer periods of time in relatively food-rich environments such as canyons. We hypothesize that food pulses in a dynamic and topographical heterogeneous environment such as canyons regulate nematode size distributions, rather than long-term food availability. Feeding type distributions in the Blanes Canyon did not clearly resemble those from other canyon systems, apart from the spring assemblage at one station in the head of the canyon.

Ingels, Jeroen; Vanreusel, Ann; Romano, Chiara; Coenjaerts, Johan; Mar Flexas, M.; Zúñiga, Diana; Martin, Daniel

2013-11-01

81

Large-scale stratigraphic architecture and sequence analysis of an early Pleistocene submarine canyon fill, Monte Ascensione succession (Peri-Adriatic basin, eastern central Italy)  

NASA Astrophysics Data System (ADS)

The Monte Ascensione succession (c. 2.65-2.1 Ma) is a well-exposed example of an exhumed submarine canyon fill embedded within slope hemipelagic mudstones. This gorge represented a long-lasting pathway for sediment transport and deposition and during the Gelasian delivered Apennine-derived clastic sediment to the adjacent Peri-Adriatic basin. A total of six principal lithofacies types, representing both canyon-confining hemipelagic deposits and canyon-filling turbidity current and mass-transport deposits, can be delineated in the studied sedimentary succession. The canyon-fill deposits display a marked cyclic character and the component lithofacies succeed one another to form at least fifteen fining-upward stratal units, which are interpreted to represent high-frequency, unconformity-bounded depositional sequences. Variability in the vertical repetition of constituent lithofacies allows the identification of three basic styles of sequence architecture that can be interpreted in terms of differing positions along a conceptual down-canyon depositional profile. An integrated chronology, based on biostratigraphic data and on palaeomagnetic polarity measurements, strongly supports a one-to-one correlation between the sequence-bounding surfaces and oxygen isotope stages G2-78, suggesting that the most feasible sequence-engendering mechanism is that of orbitally dictated glacio-eustatic changes in sea level, which regulated timing of sediment storage on the shelf and its redistribution beyond the shelf edge. One of the most significant aspects of this study is the demonstration that processes occurring within upper slope canyons can be expected to be strongly influenced by variations in sea level; that is, the erosional and depositional features evident in these deposits can be strongly controlled by allocyclic processes rather than autocyclic or random processes.

Di Celma, Claudio; Teloni, Riccardo; Rustichelli, Andrea

2014-04-01

82

Hazard assessment for a submarine landslide generated local-source tsunami from Kaikoura Canyon  

NASA Astrophysics Data System (ADS)

The Kaikoura Canyon, sediment sink for the Canterbury rivers north of Christchurch, comes to within 500 meters of shore at Goose Bay and accumulates approximately 1.5x106 m3 of sediment each year (Lewis and Barnes, 1999). This sediment, which has accumulated to about seventy meters in thickness (Walters et al., 2006), exhibits tensional fractures, is located in a tectonically active area and could result in catastrophic failure and potentially a local-source tsunami (Lewis and Banes, 1999; Lewis, 1998; Walters et al, 2006). Evidence suggests that this may have happened in the last two hundred years (Lewis, 1998; Lewis and Barnes 1999) and with a return period on the nearby Alpine and Hope faults also in the range of a one to two hundred years (Walters et al, 2006) could happen again relatively soon. A review of the historical record and oral traditions for Kaikoura shows that historically Kaikoura has been affected by 11 events of which 10 are from distant sources and one, though debatable, is possibly from a local source. There are some preserved traditions for the Kaikoura area. These taniwha stories from near Oaro and from the Lyell Creek have been repeated and changed though time though the general essence remains the same. These taniwha legends, though not conclusive, indicate a dangerous shoreline where people have been killed in the past, possibly by flooding or tsunami. Archaeological investigations at Kaikoura found evidence of a Maori occupational layers interrupted by water-worn stones, a "lens of clean gravel between occupation layers" and in other areas of the excavation, the gravels separate discontinuous periods of occupation (Fomison 1963; Foster, 2006). Additionally "pea-gravel" sized greywacke pebbles were found dispersed throughout sections of the South Bay shore platforms, though they were attributesd to slopewash (Duckmanton, 1974) this is less likely since the nearby hills are limestone. A geological investigation along the Kaikoura Coast, at five sites from South Bay to Oara, corroborates this. At four of the sites a similar greywacke pebble bearing layer was found which was not present at test sites to the North and South of the peninsula (Kiwa Rd Campsites and Claverly respectively). These deposits contain diatoms indicating marine provenance. Surveys of Kaikoura peninsula households and businesses showed low levels of preparedness for a local source event. In regards to local-source tsunamis the district council has indicated that they "are unpredictable [and] it is impractical to include rules to mitigate their effects. Instead, the Council is committed to a Civil Defence network which provides an educative role and which sets in place a process for dealing with the results of any tsunami" (Kaikoura District Plan, 2010). Plans and an education strategy need to be formulated and implemented. They need to address considerations such as the fact that about 60% of those surveyed expect some sort of siren warning and the limitations inherent in such a warning system along with signage and public tsunami hazard maps and evacuation zones.

DuBois, J.

2012-04-01

83

Seismic Analysis across the Deformation Front: implications for channel migration in the upper reach of the Penghu Submarine Canyon, Offshore Southwestern Taiwan  

NASA Astrophysics Data System (ADS)

This study analyzes both 2D and 3D seismic images in the upper reach of the Penghu Submarine Canyon to investigate sedimentary and structural processes in this tectonically active zone. The study area lies across the deformation front which separates the rifted South China Sea (SCS) continental slope to the west from the submarine Taiwan accretionary wedge to the east. Using 3D seismic images, several structural and sedimentary features have been identified: in the rifted SCS slope domain, besides the paleo-slope surface, buried submarine channels and mass transport deposits (MTDs), a reverse reactivated normal fault system is recognized, while in the accretionary wedge domain, the fold and thrust structures are dominate. The reverse fault system we interpreted in the rifted SCS slope domain was a normal fault in the past, and then reactivated to become a reverse fault through the arc-continent collision processes. Since the deformation front is defined as the location of the most frontal contractional structures along a convergent plate boundary, no contractional structures should appear west of it. We thus suggest to move the location of the previously mapped deformation front further west to where the reactivated fault lies. High resolution 2D seismic and bathymetry data reveal that the directions of the paleo-submarine channels ran in an across-slope direction, while the present submarine channels head down slope in the study area. The channel migration model we proposed suggests that this might be the result of the fault reactivation. The interactions of down-slope processes and active structural controls affect the channel paths in our study area.

Han, Wei-Chung; Liu, Char-Shine; Chi, Wu-Cheng; Wang, Yun-shuen

2014-05-01

84

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

85

Sedimentology, architecture, and depositional evolution of a coarse-grained submarine canyon fill from the Gelasian (early Pleistocene) of the Peri-Adriatic basin, Offida, central Italy  

NASA Astrophysics Data System (ADS)

The early Pleistocene stratigraphic succession of the Peri-Adriatic basin, eastern central Italy, records the filling of an elongate, N-S oriented piggy-back basin located east of the growing Apennine fold-thrust belt. During the Gelasian (2.588-1.806 Ma), large volumes of gravel, sand and mud derived from the emergent Apennines were redistributed into the basin through a number of slope erosional fairways. These sediment conduits are preserved in the rock record as a series of coarse-grained canyon-fill successions that provide an opportunity for assessing, from an outcrop perspective, how this type of deep-water depositional systems evolves and fills. The present study uses measured stratigraphic sections, photopanels, paleocurrent data, careful lithological mapping, and well-log data from a nearby exploration well to constrain the internal organization of one of these canyon fills, referred to herein as the Offida Canyon. A detailed facies analysis suggests that a variety of gravity-driven subaqueous flows were involved in sediment transport and deposition within the submarine canyon, including slumps, cohesive debris flows, and high- and low-density turbidity currents. Five main lithofacies reflecting both canyon-bounding slope deposits and canyon-filling turbidite and debrite depositional elements have been identified within the exposed succession: (i) clast-supported conglomerates (gravel-rich channel complexes); (ii) medium- to thick-bedded sandstones (overbank lobe); (iii) medium- to very thin-bedded sandstones and mudstones (levee-overbank); (iv) pebbly mudstones and chaotic beds (mudstone-rich mass-transport deposits); and (v) massive mudstones (hemipelagic background deposits). These lithofacies are organized in recurring successions and define fining-upward packages that are regarded as the deep-water expression of high-frequency depositional sequences. Each sequence comprises the sedimentary record of major phases of canyon activity and comprises the following surfaces and systems tracts, in ascending stratigraphic order: (i) a pronounced surface of erosion (sequence boundary) generated by efficient turbidity currents during a period of erosion and complete bypass of sediment to more basinward settings; (ii) a lowstand systems tract composed of a diverse assemblage of genetically related lithofacies (channel-complex conglomerates, levee sandy heterolithics, and overbank lobe sheet-like sandstones) laid down by turbidity currents largely bypassing the area; and (iii) a transgressive to forced regressive systems tract comprising mass-transport deposits produced by instability of shelf-edge staging areas and/or failure of canyon walls when coastal sediment sources were far from the shelf edge. Correlation between sequences and oxygen isotope curve suggests that the recurring fluctuations in sedimentary activity of the submarine canyon are related to the switching on and off of coarse clastic sediments to the slope in response to obliquity-driven (41 ky duration) glacio-eustatic sea-level oscillations, which modulated timing of sediment storage on the shelf and its redistribution beyond the shelf edge.

Di Celma, Claudio

2011-07-01

86

Biophysical Factors Affecting the Distribution of Demersal Fish around the Head of a Submarine Canyon Off the Bonney Coast, South Australia  

PubMed Central

We sampled the demersal fish community of the Bonney Canyon, South Australia at depths (100–1,500 m) and locations that are poorly known. Seventy-eight species of demersal fish were obtained from 12 depth-stratified trawls along, and to either side, of the central canyon axis. Distributional patterns in species richness and biomass were highly correlated. Three fish assemblage groupings, characterised by small suites of species with narrow depth distributions, were identified on the shelf, upper slope and mid slope. The assemblage groupings were largely explained by depth (?w?=?0.78). Compared to the depth gradient, canyon-related effects are weak or occur at spatial or temporal scales not sampled in this study. A conceptual physical model displayed features consistent with the depth zonational patterns in fish, and also indicated that canyon upwelling can occur. The depth zonation of the fish assemblage was associated with the depth distribution of water masses in the area. Notably, the mid-slope community (1,000 m) coincided with a layer of Antarctic Intermediate Water, the upper slope community (500 m) resided within the core of the Flinders Current, and the shelf community was located in a well-mixed layer of surface water (<450 m depth). PMID:22253907

Currie, David R.; McClatchie, Sam; Middleton, John F.; Nayar, Sasi

2012-01-01

87

The controlling factors on the submarine canyon system: a case study of the Central Canyon System in the Qiongdongnan Basin, northern South China Sea  

NASA Astrophysics Data System (ADS)

Based on the integrated analysis of the high-resolution 2D-3D seismic data and the drilling data, this study analyzed the tectonic-sedimentary evolution since Late Miocene, and discussed the controlling factors on the formation and development of the CCS. The sediment failure caused by the relative sea level falling could discharge the deposits from the slope to the canyon. The two suits of the infillings, the turbidite and the mass transport complex, were derived the northwestern source and northern source respectively. The distinct different sediment supplies from the different areas, would lead to the variation of the internal architectures. The tectonic transformation around 11.6 Ma provided the tectonic setting for the CCS and formed an axial sub-basin in the central part of the Changchang Depression, which could be suggested as the rudiment of the CCS. The tectonic activity of the Red River Fault at 5.7 Ma could strengthen the hydrodynamics of the deposits at the junction of the Yinggehai Basin and the Qiongdongnan Basin, and trigger the high energy turbidite current. The mass transport complex from the northern continental slope system would be constrained by the Southern Uplift, which played as the barrier for the infillings of the CCS. Due to the sufficient sediment supply during the Holocene period and the paleo-seafloor morphology, the relief of modern central canyon with the starving shaped in the eastern Changchang Depression may be accentuated by deposition of sediments and vertical growth along the canyon flanks, where the collapse deposits were widely developed. Corresponding to the segmentation of the CCS, the forming mechanisms of the canyon between the three segments would be different. The turbidite channel in the head area was triggered by the abundant sediment supply from northwestern source together with the fault activity at 5.7 Ma of the Red River Fault. The formation and evolution of the canyon in the western segment should be the combined effects of the turbidite channel from northwestern source, the mass transport complex from the northern continental slope, and the paleo-seafloor geomorphology. In the east segment, the canyon should be constrained by the tectonic transformation at about 11.6 Ma and the insufficient sediment supply from the wide-gentle slope.

Su, Ming; Zhang, Cheng; Xie, Xinong; Wang, Zhenfeng; Jiang, Tao; He, Yunlong; Zhang, Cuimei

2013-04-01

88

Mechanisms of vegetation-induced channel narrowing of an unregulated canyon river: Results from a natural field-scale experiment  

NASA Astrophysics Data System (ADS)

The lower Yampa River in Yampa Canyon, western Colorado serves as a natural, field-scale experiment, initiated when the invasive riparian plant, tamarisk (Tamarix spp.), colonized an unregulated river. In response to tamarisk's rapid invasion, the channel narrowed by 6% in the widest reaches since 1961. Taking advantage of this unique setting, we reconstructed the geomorphic and vegetation history in order to identify the key mechanisms for which, in the absence of other environmental perturbations, vegetation alters fluvial processes that result in a narrower channel. From our reconstruction, we identified a distinct similarity in the timing and magnitude of tamarisk encroachment and channel change, albeit with a lag in the channel response, thus suggesting tamarisk as the driving force. Within a decade of establishment, tamarisk effectively trapped sediment and, as a result, increased floodplain construction rates. Increasing tamarisk coverage over time also reduced the occurrence of floodplain stripping. Tamarisk recruitment was driven by both hydrologic and hydraulic variables, and the majority of tamarisk plants (84%) established below the stage of the 2-year flood. Thus, upon establishment nearly all plants regularly interact with the flow and sediment transport field. Our analyses were predicated on the hypothesis that the flow regime of the Yampa River was stationary, and that only the riparian vegetation community had changed. While not heavily impacted by water development, we determined that some aspects of the flow regime have shifted. However, this shift, which involved the clustering in time of extremely wet and dry years, did not influence fluvial processes directly. Instead these changes directly impacted riparian vegetation and changes in vegetation cover, in turn, altered fluvial processes. Today, the rate of channel change and new tamarisk recruitment is small. We believe that the rapid expansion of tamarisk and related floodplain construction that led to a narrower channel pushed the Yampa River into a new stable state, characterized by a relatively static channel.

Manners, Rebecca B.; Schmidt, John C.; Scott, Michael L.

2014-04-01

89

Habitat associations of deep-water rockfishes in a submarine canyon: an example of a natural refuge  

Microsoft Academic Search

Abstract.?A multidisciplinary assess- ment,of benthic ,rockfishes,(genus Se- bastes) and associated,habitats,in deep water,was ,conducted ,in Soquel ,Sub- marine Canyon, Monterey Bay, Califor- nia. Rock habitats,at depths,to 300 m

Mary M. Yoklavich; H. Gary Greene; Gregor M. Cailliet; Deidre E. Sullivan; Robert N. Lea; Milton S. Love

90

High resolution morphobathymetric analysis and short-term evolution of the upper part of the Capbreton submarine canyon (south-east Bay of Biscay - French Atlantic coast)  

NASA Astrophysics Data System (ADS)

The Capbreton Canyon stands out by its deep incision through continental shelf and slope and its present turbidite activity. The head of the canyon is anthropically disconnected from the Adour River since 1310 AD, but is located close enough to the coast to allow a direct supply by longshore drift. Sedimentary processes in upper part of the Capbreton Canyon are poorly documented. Several evidences, including sandy slide scars in the head, suggest that this area plays a major role in triggering downstream gravity currents). However, no modern sedimentary activity in the upper canyon had so far been evidenced. Our study is based on the analysis and comparison of several sets of multibeam bathymetric data acquired in 1998, 2010 and 2012 (up to 1.5 m resolution). The morphobathymetric analysis brought the following key observations: - The upper part of the canyon is characterised by a meandering talweg underlined by two kinds of terraces: (1) small elongated terraces standing only 10 to 15 m above the talweg axis and (2) large terraces standing 45 to 100 m above the talweg axis. - The regular 1° longitudinal slope of the talweg is interrupted by several 10 m high knickpoints. - The floor of the talweg shows some rough areas scattered with transversal bedforms similar to the sediment waves described in the Monterey Canyon upper part (Smith et al, 2005). The morphological evolutions in the upper part of the canyon over the last 14 years especially affect the floor of the talweg: - Between 1998 and 2010, we observe a downstream succession of accretion areas (up to 11m thick) and erosion areas (reaching -25 m). The largest and highest terraces remain stable over this period, whereas the smallest and lowest elongated terraces show active sedimentation (+5 to +8 m). - Difference between 2010 and 2012 DEMs reveals three localized erosion spots corresponding to 200 m backward stepping of the knickpoints. Such observation confirms the active headward erosion in this part of the canyon. - Conversely, the flanks of this part of the canyon do not show significant evolution. We did not observe any large lateral slide such as the canyon flank collapse recently recognised in the upper part of the Monterey or Cap Lopez canyons. (1)Since the lateral sediment supply in the canyon seems to be limited (no significant evolution of the canyon wall), we consider that most of the sediments deposited in this area is supplied from the canyon head. (2)We propose that the lowest elongated terraces are the remnant of sandy slides confined in the upper talweg and later overdeepened by the regressive erosion. This process contrasts with the downstream part of the canyon, where the terraces are constructed by the spilling of turbidity current. (3)These results are consistent with the process evidenced in the head of the canyon and support the assumption that the turbidite processes in modern canyons are related to sandy mass sliding from the head of the canyon.

Gillet, Hervé; Mazières, Alaïs; Mulder, Thierry; Cremer, Michel

2013-04-01

91

Biophysical Factors Affecting the Distribution of Demersal Fish around the Head of a Submarine Canyon Off the Bonney Coast, South Australia  

Microsoft Academic Search

We sampled the demersal fish community of the Bonney Canyon, South Australia at depths (100–1,500 m) and locations that are poorly known. Seventy-eight species of demersal fish were obtained from 12 depth-stratified trawls along, and to either side, of the central canyon axis. Distributional patterns in species richness and biomass were highly correlated. Three fish assemblage groupings, characterised by small

David R. Currie; Sam McClatchie; John F. Middleton; Sasi Nayar

2012-01-01

92

Topographic analysis of submarine cable failures offshore southwestern taiwan  

NASA Astrophysics Data System (ADS)

In 2006, there was large scale of the submarine cable failures offshore southern Taiwan right after the Pingtung Earthquake. Apparently the December 26 Pingtung Earthquake triggered submarine mass movements which generated turbidity currents in the submarine canyons and damaged cables lying across the canyons. In addition, the Typhoon Morakot on August 8-9, 2009 and the Jiashian Earthquake on March 4, 2010 also caused many submarine cable failures offshore southwestern Taiwan. The most of broken cable sites are along the axis of the Gaoping Submarine Canyon (GPSC) and Fangliao Submarine Canyon (FLSC), topography should be an important factor controlling transport processes of submarine mass movement. The cable broken sites indicate that there were submarine mass movement pass through. Therefore, the topographic factor of the cable broken sites can be the threshold to index submarine mass movement. And as, submarine cables are distributed widely offshore southwestern Taiwan, why only a total of 35 sites of submarine cable failures occurred in 2006, 2009 and 2010? We use bathymetry data, CHIRP (compressed high-intensity radar pulse) sonar profile data and the time series of the cable breakage to investigate the characteristics of submarine mass movement and to develop a model for the series of submarine cable failure. Using the Geographic Information System (GIS) software, we analyze the bathymetric data collected before the 35 sites of submarine cable failures offshore southwestern Taiwan. Applying the hydrology in GIS software, the flow movement could be derived from the factors of slope and aspect. We quantify the transport process of submarine mass movement and combine with the time series of the cable breakage to discuss the effect between submarine cable failures. Based on the CHIRP sonar data, we identified the distinct CHIRP echo character patterns after the submarine cable failures and classify the distinct CHIRP echo characters. Using the threshold of topographic factor to expect where will be potential area of submarine mass movement and evidence the result by CHIRP sonar profile data.

Hsia, Pei Cheng; Shine Liu, Char; Hsu, Ho Han

2013-04-01

93

Variation in canyon morphology on the Great Barrier Reef margin, north-eastern Australia: The influence of slope and barrier reefs  

NASA Astrophysics Data System (ADS)

New high-resolution bathymetry, seismic reflection profiles, and existing sidescan data have revealed the presence of a series of submarine canyons in the slope off the Noggin Passage region, north-eastern Australia. The morphology of the Noggin Canyons contrasts with that of the canyons in the Ribbon Reef region, further north along the north-eastern Australia margin. The Noggin Canyons are mostly slope-confined, with canyon heads located at water depths between 200 and 400 m. These narrow and straight canyons show a decrease in canyon relief with depth, and have incision values and canyon gradients lower than the Ribbon Reef Canyons. New findings on the Ribbon Reef Canyons reveal an increase of canyon relief with depth in the shelf-incised canyons, as well as complex relationships between geomorphic parameters, such as canyon gradient, incision, canyon width and canyon wall gradient. The main factors controlling the differences in canyon morphology are the shape of the continental slope and the presence of barrier reefs at the shelf-edge. Steep exponential and linear slope profiles, and the presence of an extensive shelf-edge barrier system in the Ribbon Reef region, are related to large shelf-incised canyons. In contrast, the slope-confined canyons of the Noggin region are linked to sigmoidal slopes, and more open outer-shelf conditions lacking barrier reefs. These conditions allow higher overall sediment supply to the upper slope, and the resulting formation of sigmoidal slope profiles. In the Ribbon Reef region, the physical barriers provided by the shelf-edge barrier reefs reduce the amount of shelf-to-basin sediment transport, thereby forming exponential slopes. Further, sediment gravity flow deposition through the canyons is more prominent in the Ribbon Reef region, as a direct consequence of the more frequent breaching of the shelf by the canyons, otherwise infrequent in the Noggin region. Our results highlight this particular relationship between canyon and slope morphology, and the importance of the variable shelf-edge morphology in controlling the shelf-to-basin sediment transport. This aspect is especially relevant for understanding the margin development in modern and ancient mixed carbonate-siliciclastic continental settings.

Puga-Bernabéu, Ángel; Webster, Jody M.; Beaman, Robin J.; Guilbaud, Vincent

2013-06-01

94

The segmentations and the significances of the Central Canyon System in the Qiongdongnan Basin, northern South China Sea  

NASA Astrophysics Data System (ADS)

The submarine canyons as the important element of the source to sink have attracted the widespread interests in studying their morphologic features, stratigraphic frames, depositional architectures, as well as the related depositional model, hydrodynamic simulation, and hydrocarbon exploration. The Central Canyon System, a large axial submarine canyon, in the Qiongdongnan Basin is developed in Neogene passive continental margin of northern South China Sea, which is paralleled to the shelf break with an "S-shaped" geometry and an NE-NEE orientation. Based on the integrated analysis of high-resolution 2D/3D seismic data and well log data, the whole canyon could be divided into three segments from west to east through its distinct morphological and depositional architecture characteristics, the head area, the western segment and the eastern segment. The canyon shows the classical U-shaped morphology in seismic profiles, and the infillings are composed of a suit of turbidite channel complex in the head area. In the western segment, the canyon demonstrates the sinuous geometry and multiple-shaped morphology in seismic profiles. Four complexes of turbidite channel and mass transport complex (MTC) are observed, which could constitute into two stratigraphic cycles. The canyon in the eastern segment shows V-shaped morphology with steep flanks and a narrow and straight course, which is composed of collapse deposits in the flanks and the sheet sand-MTC complex. The sediment supply, northern continental slope system, paleo-geomorphic characteristics and tectonic setting in the Qiongdongnan Basin are considered as the controlling factors on the development and evolution of the Central Canyon System, each of them have different influences in the three segments. The turbidite channel in the head area was triggered by the abundant sediment supply from western source together with the fault activity at 5.7 Ma of the Red River Fault. The evolution of the canyon in the western segment should be the combined effects of the turbidite channel from western source, the mass transport complex from the northern continental slope, and the paleo-seafloor geomorphology. In the eastern segment, the canyon should be constrained by the semi-closed subbasin in eastern Qiongdongnan Basin corresponding to the tectonic transformation at about 11.6 Ma. This unique submarine canyon in the Qiongdongnan Basin is suggested to be characterized by axial gravity flow, ascribing to different gravity deposits originated from different sediment supplies and the tectonic activities.

Su, Ming; Xie, Xinong; Xie, Yuhong; Wang, Zhenfeng; Zhang, Cheng; Jiang, Tao; He, Yunlong

2014-01-01

95

Linking subaerial erosion wih submarine geomorphology in the northern Ionian Sea, Italy  

NASA Astrophysics Data System (ADS)

The supply of sediment from continental sources is commonly suspected to have exerted a strong influence on the development of canyons and other morphological features on the continental slopes, but rarely is the sediment supply known quantitatively to make this link. Here, we outline an area where offshore morphology, in the northern Ionian Sea, may be linked to supply of sediment from subaerial erosion in NE Sicily and SW Calabria. Shelves in this area are very narrow (< 1 km), and the bathymetry shows that rivers and adjacent submarine channels are almost directly connected. Integrated topographic analyses were performed on a merged digital evelation model (DEM) of ASTER data for subaerial topography and multibeam sonar data for submarine bathymetry. Spatial variations in onshore erosion were assesed using a variety of methods, namely: long-term sediment flux from Pleistocene uplift rates, decadal sediment flux from landslides; published long-term exhumation rates from 10Be cosmogenic nuclide concentrations and published recent sediment yields determined using the Gavrilovic Method. Submarine channels associated with rivers delivering larger sediment fluxes have broad channels, high relief and smooth concave-upward longitudinal profiles. Conversely, submarine channels that lie offshore small-flux rivers have straight longitudinal profiles, low relief and steep gradients. Where river catchments supply a greater sediment flux offshore, shelves tend to be wider (~400 m) and submarine channels have gentler gradients. In contrast, where catchments supply less sediment flux, shelves are narrow (250-300 m) and offshore channel gradients are steeper. How morphology varies with tectonic uplift rate was also studied, but we find that, unlike onshore terrains where tectonics is commonly an important factor influencing channel morphology, in the submarine landscapes, sediment flux appears to dominate.

Goswami, Rajasmita; Mitchell, Neil C.; Argnani, Andrea

2014-05-01

96

Transport of typhoon-induced submarine sediment-laden flows off southwestern Taiwan  

NASA Astrophysics Data System (ADS)

Since 2006, southern Taiwan experienced destructive typhoons and earthquakes which triggered large scale submarine landslides and turbidity currents and devastated many submarine cables off southwestern Taiwan. Most of cable breakages were located in the Gaoping (GPSC) and Fangliao (FLSC) submarine canyons which indicate submarine canyon is an important pathway for underwater gravity flows that induced by natural hazards. A series of investigations were conducted before and after Morakot typhoon, the sub-bottom profiler and core analysis results revealed the GPSC and FLSC may play different roles in transport sediment from coastal seas to the abyssal ocean during the typhoon invaded period. Off southwestern Taiwan, the GPSC and FLSC are incising from continental shelf to deep sea floor and both of them transport considerable amounts of sediment to the South China Sea. GPSC is directly connected to the Gaoping River on land. The hyperpycnal flows, formed during Typhoon Morakot, delivered coarse sands, gravels and branches of trees into GPSC and deposited at the upper reach. On the contrary, the FLSC, which is smaller, younger and confined to the slope, does not associate with any river on land. A series of turbidites and debrites, which composed by coarse slates, fractal shells, wood fragments and fresh leaves, were observed in cores collected from the head of FLSC through Gaoping slope to the lower reach of GPSC. It implies the torrential rains induced landslides at the southernmost Central Mountain Range may directly delivered large amount of slate fragments through narrow Gaoping shelf into the deep sea. Furthermore, according to Water Resources Agency's groundwater level monitoring data, during Typhoon Morakot, the groundwater level raised significantly at the coastal area of Pingtung Plain. The increased groundwater pressure may lead to high flux of submarine groundwater discharge and induced liquefaction on seafloor. From sub-bottom profiles, the liquefaction structures and chaotic deposits were found widely spread off southwestern Taiwan and we suggest it may highly related to the anomalous submarine groundwater discharge incident. Our results reveal the extreme weather induced catastrophic events (e.g. torrential rains, floods, stormy waves… etc.) can generate devastating sediment-laden flows both in the Gaoping and Fangliao Submarine Canyons and provide an efficient way for delivering organic carbon into the deep sea.

Su, C.; Cheng, Y.

2012-12-01

97

Flow Processes and Sedimentation Associated with Erosion and Filling of Sinuous Submarine Channels  

NASA Astrophysics Data System (ADS)

Sinuous submarine channels are common on all of Earth's siliciclastic continental margins. Approaches to studying flow processes and sedimentation of gravity flows in sinuous submarine channels is limited to direct measurements of the modern seafloor, physics-based numerical models, analytical solutions, physical experiments. While these approaches provide insight, no study documents distinctions in flow properties and sedimentation associated with erosion and filling of a natural sinuous submarine channel. Measurements from the modern seafloor cannot be used as their lifespan exceeds that of humans. Therefore, a sinuous submarine channel can not be monitored through its lifespan. However, outcrops of sinuous submarine channels and their fill contain a record of the erosional and depositional stages of the channel's evolution. The Beacon Channel of the Brushy Canyon Formation crops out on multiple cliff faces revealing two complete bends in the sinuous submarine channel. This study uses measurements from a 3D exposure to document how flow properties and sedimentation differ between erosional and filling stages of channels. Two units, recording the sequential evolution of the channel are documented. Unit 1 records gravity flows that deepened and laterally migrated the channel. These gravity flows were mud-rich with a wide grain-size distribution. Flow heights exceeded the depth of the channel resulting in the deposition of levees. Strong secondary flow is evident with a helical pattern reversed to subaerial channels. Point bars have coarsening upward grain-size profiles. Point bars and levees were deposited by tractive processes. Unit 2 records gravity flows that filled the channel. These gravity flows were sand-rich with a relatively narrow grain-size distribution. Flow heights scaled to the depth of the channel, and they contain no evidence for secondary flow. Associated strata are horizontal and deposited primarily from suspension.

Pyles, D. R.; Tomasso, M.; Jennette, D.

2011-12-01

98

Submarine Atmospheres  

Microsoft Academic Search

Atmosphere control in submarines has developed to meet the operational requirements. Until\\u000a the end of WWII submarines were primarily semi-submersibles spending most of their time on the surface\\u000a and submerged for periods of 12 h or less. However, rudimentary control of oxygen and carbon\\u000a dioxide was available in some WWI boats. In the latter years of WWII, the requirement for longer

Waldemar Mazurek

99

Reflection and tunneling of ocean waves observed at a submarine Jim Thomson  

E-print Network

with periods between 20 and 200 s were observed to reflect from a steep-walled submarine canyon. Observations., 1995], and can be used as proxies to detect tsunamis [Rabinovich and Stephenson, 2004]. Much

Kirby, James T.

100

Bioerosion by chemosynthetic biological communities on Holocene submarine slide scars  

Microsoft Academic Search

Geomorphic, stratigraphic, and faunal observations of submarine slide scars that occur along the flanks of Monterey Canyon in 2.0–2.5 km water depths were made to identify the processes that continue to alter the surface of a submarine landslide scar after the initial slope failure. Deep-sea chemosynthetic biological communities and small caves are common on the sediment-free surfaces of the slide scars,

C. K. Paull; W. Ussler; H. G. Greene; J. Barry; R. Keaten

2005-01-01

101

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

102

How Submarines Work  

NSDL National Science Digital Library

In this article, presented by HowStuffWorks.com, shows how a submarine dives and surfaces in the water. It also shows how life support is maintained, how the submarine gets its power, how a submarine finds its way in the deep ocean and how submarines might be rescued. The article addresses many points effectively and is a good survey of the topic.

Brain, Marshall; Freudenrich, Craig

2008-10-09

103

Morphology, seismic characteristics and development of Cap Timiris Canyon, offshore Mauritania: A newly discovered canyon preserved-off a major arid climatic region  

Microsoft Academic Search

We employ a combined interpretation of Hydrosweep swath bathymetry and high resolution multi-channel seismic reflection data to investigate the development of Cap Timiris Canyon, a newly discovered submarine canyon offshore Mauritania. The dominantly V-shaped and deeply entrenched canyon exhibits many fluvial features including dendritic and meander patterns, cut-off loops and terraces, and is presently incising. Distal meander patterns, confined within

Andrew A. Antobreh; Sebastian Krastel

2006-01-01

104

Hot Canyon  

SciTech Connect

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."

None

2012-06-18

105

Hot Canyon  

SciTech Connect

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."

None

2012-01-01

106

Evaluation of Ancient and Future Submarine Landslides Along the Central California Coast and Their Potential to Generate Tsunamis  

Microsoft Academic Search

Submarine landslides have been located along the central California continental margin with the use of multibeam bathymetric and sub-bottom profiling data. These features are primarily concentrated on the lower continental slope and in submarine canyons. Recent evaluation of these landslides indicates that they are of various ages and types and formed in different ways. For example, the extensive slope failure

H. G. Greene; C. K. Paull; S. Ward; W. Ussler; N. M. Maher

2001-01-01

107

Deep Research Submarine  

E-print Network

The Deep Sea Research Submarine (Figure 1) is a modified VIRGINIA Class Submarine that incorporates a permanently installed Deep Sea Operations Compartment (Figure 2). Table 1 summarizes the characteristics of the Deep ...

Woertz, Jeff

2002-02-01

108

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

109

Holocene canyon activity under a combination of tidal and tectonic forcing  

NASA Astrophysics Data System (ADS)

The majority of submarine canyon systems that are active during sea level highstands are coupled to terrestrial or littoral sediment transport systems (e.g. high sediment-yield rivers, wave-base sediment disturbance). However, non-coupled canyon systems can also exhibit sedimentary activity. Characterising the nature, origin, and spatial and temporal influence of the processes responsible for this sedimentary activity is important to understand the extent of sediment and carbon transfer to the deep sea, the impact of sedimentary flows on biological colonisation and diversity, and the control of recent seafloor processes on canyon morphology. The Cook Strait canyon system, between the North and South islands of New Zealand, is a large (1800 km2), multi-branching, shelf-indenting canyon on an active subduction margin. The canyon comes within 1 km of the coast, but does not intercept fluvial or littoral sediment systems and is therefore defined as a non-terrestrially-coupled system. Sediment transport on the continental shelf, associated with a strong tidal stream, and seafloor disturbance related to numerous high-activity faults is known from previous studies. Little is known, however, about the rates of sedimentary activity in the canyon and the processes driving it. The canyon system therefore provides an excellent study area for understanding sediment transport in a non-coupled submarine canyon system. Analysis of EM300 multibeam bathymetry, gravity cores, 3.5 kHz seismic reflection profiles, camera and video transects and current meter data reveals a system where oceanographic (tidal) and tectonic (earthquake) processes are moving sediment from the continental shelf, through the upper canyon, and finally to the deep ocean. Sediment accumulation rates may reach several mm/yr in the upper canyons, with data suggesting minimum rates of 0.5 mm/yr. We demonstrate that tidal currents are sufficient to mobilise fine to medium sand around and within the upper canyon heads, and transported sediment is accumulating in upper canyon depocentres. Based on pseudo-static stability modelling, and supported by sediment core records, we estimate that earthquake triggered failure occurs approximately every 100 years. Lower canyon geomorphology indicates that failed material is being conveyed down the length of the canyon system to the deep ocean. Thus, while flushing rates may be low, the Cook Strait Canyon system can be considered to be an active sedimentary system during the current sea level high stand. The processes identified here are likely to be analogous to those occurring in many non-coupled shelf indenting canyons on tectonically active margins globally, and provide a framework within which the biological response to intermediate disturbance geomorphic processes in submarine canyons can be assessed.

Mountjoy, Joshu; Micallef, Aaron; Stevens, Craig; Stirling, Mark

2013-04-01

110

Microbiological Conditions on Oberon Submarines.  

National Technical Information Service (NTIS)

Microbiological conditions on Oberon submarines were examined to gain an insight into the potential effects on submariners' health. Samples from submarine atmospheres showed that satisfactory standards could be attained. However, samples taken from surfac...

J. F. Upsher, L. E. Fletcher, C. M. Upsher

1994-01-01

111

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

NASA Astrophysics Data System (ADS)

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 and a newly formed submarine canyon have been identified. Seismic reflection parameters of the ancient canyons are characterized by transparent to slightly transparent, continuous to slightly discontinuous, high to moderate amplitude and parallel to sub-parallel reflections. Locally, high amplitude and chaotic reflections were observed. The reflection configurations consist of regular oblique, chaotic oblique, progradational and parallel to sub-parallel types. These seismic reflection characteristics are probably due to variable sedimentation processes within the canyons, which were affected by mass wasting. Canyon morphological features include step-wise and spoon-shaped wall development, deep valley incision, a V-shaped valley, similar orientation in the southeast direction, and simple to complex erosion features in the axial floor. The canyons have a composite origin, caused partly by lowering of the sea level probably associated with the formation of the Antarctic Ice Sheet about 30 Ma ago and partly by complex sedimentary processes. Regional correlation with geological ages using the reflectors show that the canyons cut through the Cretaceous and lower Tertiary sediments while the sedimentary infill of the canyon is predominantly Miocene and younger. Gravity-driven depositional processes, downward excavation by down slope sediment flows, mass wasting from the canyon walls and variation in terrigenous sediment supply have played significant roles in maintaining the canyons. These canyons were probably conduits for sediment transport to deep-waters in the Gulf of Guinea during their period of formation.

Olabode, S. O.; Adekoya, J. A.

2008-03-01

112

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

113

Twenty-nine months of geomorphic change in upper Monterey Canyon (2002–2005)  

Microsoft Academic Search

Time serial multibeam bathymetry is used to evaluate geomorphic trends and submarine processes in the upper 4 km of Monterey Canyon, California. Seven high-resolution bathymetric surveys conducted between September 2002 to February 2005 show that the upper canyon axis and head grew in volume 1000000 m3±700000 m3, at an average annual rate of 400000 m3\\/a±300000 m3\\/a through lateral erosion and vertical incision. This net loss

Douglas P. Smith; Rikk Kvitek; Pat J. Iampietro; Kendra Wong

2007-01-01

114

Submarine neutrino communication  

E-print Network

We discuss the possibility to use a high energy neutrino beam from a muon storage ring to provide one way communication with a submerged submarine. Neutrino interactions produce muons which can be detected either, directly when they pass through the submarine or by their emission of Cerenkov light in sea water, which, in turn, can be exploited with sensitive photo detectors. Due to the very high neutrino flux from a muon storage ring, it is sufficient to mount either detection system directly onto the hull of the submersible. The achievable data transfer rates compare favorable with existing technologies and do allow for a communication at the usual speed and depth of submarines.

Patrick Huber

2009-09-25

115

Submitted to Journal of Hydraulic Research, June, 2004 The Response of Turbidity Currents to a Canyon-Fan Transition: Internal Hydraulic  

E-print Network

Submitted to Journal of Hydraulic Research, June, 2004 The Response of Turbidity Currents, Minneapolis, MN, 55414, USA #12;1 The Response of Turbidity Currents to a Canyon-Fan Transition: Internal Turbidity currents often carve canyons into the continental slope, and then deposit submarine fans on lower

Parker, Gary

116

Topography within the axial channels of Monterey and Soquel Canyons  

NASA Astrophysics Data System (ADS)

Ultrahigh resolution surveys have been conducted that outline the topography and near seafloor structure within the axial channels of Monterey and Soquel Canyons. Multibeam bathymetry (vertical precision of 0.15 m and horizontal resolution of 1.0 m at 50 m survey altitude) were collected using an autonomous underwater vehicle (AUV). An inertial navigation system combined with a doppler velocity sonar allows the AUV to fly through the sinuous canyons at 3 knots on a pre-programmed route while maintaining an altitude of 50 m above the bottom. The AUV has flown down through the sinuous canyons, passed where they join, to 1,900 m water depths, and obtained three or more overlapping swaths covering the axial channel floor and some of its adjacent flanks. One feature revealed in the multibeam bathymetry data are wave-like bedforms with wavelengths of 20 to 100 m and amplitudes up to 2.5 m oriented roughly perpendicular to the channel axis. These bedforms occur throughout the channel of Monterey Canyon. They are asymmetric with a steep face on the down-canyon side while the other face is nearly horizontal or dips up-canyon, and form crescent-shaped ridges oriented down-canyon. Combined with previous mapping of the upper end of Monterey Canyon by CSUMB, we now know that these features extend between 11 m and >1900 m water depths in Monterey Canyon. Repeat mapping shows that these bedforms change position between surveys. Sediment coring and experiments to track seafloor motion show that these changes occur during discrete mass transport events. In contrast the seafloor within the axis of Soquel Canyon is smooth. Chirp profiler data collected simultaneously with the multibeam data failed to resolve sub-bottom structures within the floor of Monterey Canyon, but show that the floor of Soquel Canyon contains up to15 m of horizontally layered fill. These differences are attributed to the processes within an active (e.g., Monterey) versus inactive (e.g., Soquel) submarine canyon and are hypothesized to be associated with the nature of the fill (cohesion-less sand and gravel versus cohesive fine sediments) within these canyons.

Lundsten, E.; Paull, C. K.; Caress, D. W.; Ussler, W.; Thomas, H.

2009-12-01

117

Submarine: Lift Bag Lander  

NSDL National Science Digital Library

In this activity (on page 4), learners create a submarine using a plastic sandwich bag. This is a fun way to learn about buoyancy and how captured gas can cause objects to float. Note: You will also need access to a tank or swimming pool to watch your submarine dive. Safety note: Learners will need an adult's help to drill holes in the film canister.

Cameron, James; Hardy, Kevin

2013-01-01

118

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

119

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

120

Refraction and reflection of infragravity waves near submarine canyons  

Microsoft Academic Search

The propagation of infragravity waves (ocean surface waves with periods from 20 to 200 s) over complex inner shelf (water depths from about 3 to 50 m) bathymetry is investigated with field observations from the southern California coast. A wave-ray-path-based model is used to describe radiation from adjacent beaches, refraction over slopes (smooth changes in bathymetry), and partial reflection from

Jim Thomson; Steve Elgar; T. H. C. Herbers; Britt Raubenheimer; R. T. Guza

2007-01-01

121

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

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

1989-01-01

122

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

123

Satellite to Submarine Laser Communications (SLC): Advanced filter technology  

Microsoft Academic Search

This final report describes results of work to design, fabricate, and test narrow bandwidth, wide field of view (FOV) acousto-optic tunable filters (AOTF's) operating in the green spectral region. Such filters have potential for application in satellite to submarine optical communications (SLC) links. The AOTF tunability has advantages for both downlink and uplink communications. The motivation of the technical approach

John D. Feichtner

1992-01-01

124

Submarine Coaxial Cable Pressure Characteristics  

Microsoft Academic Search

In equalization design of submarine coaxial cable system, the cable attenuation deviation due to pressure in deep sea bottom has significant weight. This paper treats the submarine coaxial cable characteristics pressure dependency. By using an artificial ocean test facility, 1.7 inch submarine coaxial cable attenuation, phase, capacitance and insulator core diameter were studied and their pressure coefficients under a pressure

K. Aida; M. Aiki

1978-01-01

125

Paint-Stirrer Submarine  

NSDL National Science Digital Library

In today's fast-paced, technological world, it is a constant struggle for teachers to find new and exciting ways to challenge and engage our students. The Paint-Stirrer Submarine is a unique and challenging laboratory exercise that keeps the students enthralled. They won't even realize they are learning because they will be having too much fun. This inquiry-based, hands-on experience in building a submarine allows the students to learn about buoyancy, buoyant force, Archimedes' principle, and motion in an engaging manner. It will be an experience neither you nor your students will ever forget.

Young, Jocelyn; Hardy, Kevin

2007-02-01

126

Regional Jurassic Submarine Arc-Apron Complex in the Northern Sierra Nevada, California  

NASA Astrophysics Data System (ADS)

The Tuttle Lake Formation (TLF), a distinctive unit forming part of the wall rocks to the Mesozoic Sierra Nevada batholith in northern California, is interpreted to have developed within a major island arc fringing the western margin of North America during the Jurassic. It extends for 75 km along strike, from mountainous terrain NW of Truckee to the Mt. Tallac pendant SW of Lake Tahoe. Superb glaciated exposures at various locations along strike provide a window into the proximal parts of a submarine Jurassic arc-apron complex. The TLF is >4 km thick and consists mainly of massively bedded, matrix-supported, polymict volcanic breccias containing poorly vesicular, subangular to angular basaltic to andesitic clasts up to 2 m in length. Characteristics of the polymict breccias indicate deposition from submarine debris flows derived from slumping of near-vent accumulations of lithic debris or sector collapse of parts of the volcanic edifice. Interbeds of finer grained andesitic and silicic turbidites and ash-fall tuffs occur sparsely within the debris-flow sequence, as do volumetrically minor pillow-hyaloclastite breccias, recording local extrusion of lavas on the seafloor. Coarse-grained TLF debris-flow deposits abruptly overlie the Early to Middle Jurassic Sailor Canyon Formation, which consists dominantly of andesitic volcanic sandstones and mudstones deposited from distal turbidity currents in a long-lived, deep marine basin. This marked lithologic change records rapid influx of coarse-grained volcanogenic detritus into the Sailor Canyon basin, related to a major shift in position of volcanic centers. Available data show that the TLF accumulated in a narrow time frame in the Middle Jurassic, just prior to regional tilting and batholith emplacement at ~165 Ma. Coeval basaltic to andesitic hypabyssal intrusions typically compose >15% of the exposed area of the TLF. They have identical major- and trace-element compositions and REE patterns to clasts within the host debris-flow sequence, and all analyses plot as a tight group in calc-alkaline, volcanic-arc fields on standard discrimination diagrams. The intrusions range from 3 km in length down to smaller pods and intrusive pillows a few meters across, many of which appear to be tubular feeder conduits in 3D. Marginal peperites indicate that intrusion occurred while the host sediments were still wet and unconsolidated. Abundant, isolated pockets of globular and blocky peperite are inferred to have been supplied by conduits extending from larger intrusions. Magma/sediment interaction was generally non-explosive, but steam explosions locally played a role in generating dispersed peperite. The overall characteristics of the TLF support a model in which coarse-grained volcaniclastic deposits accumulated rapidly in a proximal submarine setting around a major vent complex within the Middle Jurassic arc. Magma/wet-sediment interaction occurred over large areas within proximal parts of the arc apron, where uprising batches of magma were unable to penetrate the thick volcaniclastic sequence to undergo extrusion. Instead, an extensive network of hypabyssal intrusions and peperite formed at shallow levels beneath the sea floor. Complex hypabyssal networks of this type are probably common in submarine arc sequences, but detailed mapping is required to document their full extent and significance.

Templeton, J. H.; Hanson, R. E.; Hargrove, U. S.; Ruff, K. L.

2005-05-01

127

Worldwide Submarine Challenges.  

National Technical Information Service (NTIS)

The Worldwide Submarine Challenges that the United States and its allies face today are more diverse and more complex than at any time during the Cold War. These Challenges now encompass both the open ocean and the littoral. They run the gamut from the hi...

1997-01-01

128

Fiber Optic Submarine Cables  

NASA Astrophysics Data System (ADS)

Submarine communication cables have one of the longest history in the field of technics. During the last 20 years their importance showed a drastic decay in favour of satellites. Presently their future looks bright again as they contain now optical fibers instead of coaxial pairs.

Oestreich, Ulrich H. P.

1990-01-01

129

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

130

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

131

International Submarine Races  

NSDL National Science Digital Library

Engineering design competition in which teams design & build one or two-man submarines. Participants compete for best overall performance, innovation, speed, best use of composite materials, and spirit of the race. Participants include universities, corporations, government agencies, individuals and research labs.

132

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 for the spring of 2009. After validation, a lagrangian transport model was coupled to the hydrodynamic model to study and compare the transport patterns of three different classes of organo-mineral aggregates along the Nazaré canyon. The results show that the transport in the canyon is neither constant, nor unidirectional and that there are preferential areas where deposited matter is resuspended and redistributed. The transport of the larger class size of organo-mineral aggregates (2000 ?m and 4000 ?m) is less pronounced, and a decrease in the phytodetrital carbon flux along the canyon is observed. During the modelled period, the Nazaré canyon acts as a depocentre of sedimentary organic matter rather than a conduit of organo-mineral aggregates to the deep sea, as has been reported by other authors. The results of this study are crucial for the understanding of the oceanic carbon sequestration at the continental margin, and therefore important for evaluating the role of submarine canyons within the global carbon cycle.

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

2013-06-01

133

Distribution and transport of suspended particulate matter in Monterey Canyon, California  

Microsoft Academic Search

From August 1993 to August 1994, six moorings that measure current, temperature, salinity, and water clarity were deployed along the axis of Monterey Canyon to study the circulation and transport of water and suspended particulate matter through the canyon system. The moorings occupied three sites that are morphologically different: a narrow transverse section (axis width 900 m) at 1450 m

J. P Xu; Marlene Noble; Stephen L Eittreim; Leslie K Rosenfeld; Franklin B Schwing; Cynthia H Pilskaln

2002-01-01

134

Newly recognized submarine slide complexes in the southern California Bight  

NASA Astrophysics Data System (ADS)

New high-resolution bathymetric and seismic-reflection surveys have imaged large (<0.5 km3) submarine landslides offshore southern California that have not been previously recognized in the Borderland. The new data show several large slides or slide complexes that include: 1) a slide complex consisting of numerous (>7) individual overlapping slides along the western margin of Santa Cruz Basin (SCB slide); 2) a series of slumps and slide scars on the slope south of San Pedro shelf (SPS slide); and 3) a slope failure along the shelf edge in northern San Diego County, termed the Del Mar slide. The SCB slide complex extends for 30 km along the western slope of Santa Cruz Basin, with debris lobes extending 5-8 km into the basin. Head scarps of some of these slides are 50-75 m high. The SPS slide complex also appears to consist of multiple slides, which roughly parallel the Palos Verdes Fault and the San Gabriel Canyon submarine channel on the shelf edge and slope south of San Pedro shelf. Slide deposits associated with this complex are only partially mapped due to limited high-resolution bathymetric coverage, but extend to the south in the area SW of Lasuen Knoll. Seismic-reflection profiles show that some of these deposits are up to 20 m thick. The Del Mar slide is located about 10 km north of La Jolla Canyon and extends about 6 km along the shelf edge. The head scarp lies along the trend of a branch of the Rose Canyon Fault Zone. Radiocarbon ages of sediment overlying this slide indicate the Del Mar slide is approximately 12-16 ka. These large slide complexes have several characteristics in common. Nearly all occur in areas of tectonic uplift. All of the complexes show evidence of recurrent slide activity, exhibiting multiple headwall scarps and debris lobes, and where available, high-resolution seismic-reflection profiles of these slide areas provide evidence of older, buried mass transport deposits. Assuming typical sedimentation rates, the recurrence interval of major slide events appears to be on the order of tens of thousands of years. Most of the slide complexes do not appear to be located in areas of high sediment input. The SCB and Del Mar slides are in areas receiving relatively small terrestrial sediment input from fluvial sources, as are most other previously recognized submarine slides in the Borderland. Only the SPS slide, which lies adjacent to the San Gabriel Canyon submarine channel, is associated with a significant fluvial sediment source.

Conrad, J. E.; Lee, H. J.; Edwards, B. D.; McGann, M.; Sliter, R. W.

2012-12-01

135

Constraining the timing of turbidity current driven sediment transport down Monterey Canyon, offshore California  

NASA Astrophysics Data System (ADS)

Turbidity currents are responsible for transport of sand down the Monterey Submarine Canyon, offshore California, from the shoreline to Monterey Fan. However the timing of sediment transport events and their frequencies are not fully understood despite recent monitoring of canyon events and AMS 14C dating of foraminifera from hemipelagic sediments bracketing sand deposited during turbidity flows. Quartz optically stimulated luminescence (OSL) dating in sand sequences provides a complementary means of dating sand transport. OSL dates reflect the time interval since the sand grains were last exposed to sunlight. However, the technique has never been applied extensively to canyon sediments before. Here we report both quartz OSL ages of sand deposits and benthic foraminifera ages sampled from the axial channel within Monterey Submarine Canyon and Fan via ROV-collected vibracores. This allows a rare opportunity to directly test the frequency and timing of turbidity current events at different points in the canyon. We use both single-grain and small (~2 mm area) single aliquot regeneration OSL approaches on vibracore samples from various water depths to determine sand transport frequency. Within the upper canyon (<2,000 m water depths) the OSL data require sub-decadal to decadal transit times. Sand bearing fining upward sequences yielding middle Holocene to last few hundred year ages indicate turbidity currents occur at 150 to 250 year event frequencies within the fan channel out to 3,600 m water depth. We suggest that turbidity currents have been active during the current sea-level high stand and that the submarine fan has recorded turbidity currents over the entire Holocene. The increased age spread in single grain OSL dates with water depth provides evidence of sediment mixing and reworking during turbidity flows. Apparently, sand is stored within the canyon for various amounts of time while it is in route to its current location on the fan.

McGann, M.; Stevens, T.; Paull, C. K.; Ussler, W.; Buylaert, J.

2013-12-01

136

Distribution and transport of suspended particulate matter in Monterey Canyon, California  

USGS Publications Warehouse

From August 1993 to August 1994, six moorings that measure current, temperature, salinity, and water clarity were deployed along the axis of Monterey Canyon to study the circulation and transport of water and suspended particulate matter through the canyon system. The moorings occupied three sites that are morphologically different: a narrow transverse section (axis width 900 m) at 1450 m water depth, a wide transverse section at 2837 m, and a third site in the fan valley axis farther offshore at 3223 m that recorded for 3 yr. In addition, CTD/transmissometer casts were conducted within and near the Monterey Canyon during four cruises. Our data show a mainly biogenic, surface turbid layer, a limited intermediate nepheloid layer, and a bottom nepheloid layer. There is a consistent presence of a turbid layer within the canyon at a water depth of about 1500 m. Tidal flow dominates at all sites, but currents above the canyon rim and within the canyon appear to belong to two distinct dynamic systems. Bottom intensification of currents plays an important role in raising the near-bottom shear stress high enough that bottom sediments are often, if not always, resuspended. Mean flow pattern suggests a convergence zone between the narrow and wide site: the near-bed (100 m above bottom where the lowest current meter was located) mean transport is down-canyon at the 1450-m site, while the near-bottom transport at the 2837-m site is up-canyon, at a smaller magnitude. Transport at the 3223-m site is dominantly NNW, cross-canyon, with periods of up-canyon flow over 3 yr. A very high-turbidity event was recorded 100 m above the canyon bottom at the narrow site. The event started very abruptly and lasted more than a week. This event was not detected at either of the deeper sites. A canyon head flushing event is likely the cause. ?? 2002 Elsevier Science B.V. All rights reserved.

Xu, J. P.; Noble, M.; Eittreim, S. L.; Rosenfeld, L. K.; Schwing, F. B.; Pilskaln, C. H.

2002-01-01

137

Unmanned submarine vehicle  

SciTech Connect

An unmanned self-propelled submarine vehicle is provided with a material exchanger-container having a vertical axis of symmetry aligned with both the vehicle's center of gravity and its center of volume. The exchanger-container has a moveable diaphragm which divides the interior into two compartments, a lower ballast compartment equipped with an unloading apparatus and an upper compartment adapted to receive collected material. Ballast is unloaded during material loading to maintain the weight of the vehicle constant during loading.

Hervieu

1984-05-15

138

Flow in bedrock canyons.  

PubMed

Bedrock erosion in rivers sets the pace of landscape evolution, influences the evolution of orogens and determines the size, shape and relief of mountains. A variety of models link fluid flow and sediment transport processes to bedrock incision in canyons. The model components that represent sediment transport processes are increasingly well developed. In contrast, the model components being used to represent fluid flow are largely untested because there are no observations of the flow structure in bedrock canyons. Here we present a 524-kilometre, continuous centreline, acoustic Doppler current profiler survey of the Fraser Canyon in western Canada, which includes 42 individual bedrock canyons. Our observations of three-dimensional flow structure reveal that, as water enters the canyons, a high-velocity core follows the bed surface, causing a velocity inversion (high velocities near the bed and low velocities at the surface). The plunging water then upwells along the canyon walls, resulting in counter-rotating, along-stream coherent flow structures that diverge near the bed. The resulting flow structure promotes deep scour in the bedrock channel floor and undercutting of the canyon walls. This provides a mechanism for channel widening and ensures that the base of the walls is swept clear of the debris that is often deposited there, keeping the walls nearly vertical. These observations reveal that the flow structure in bedrock canyons is more complex than assumed in the models presently used. Fluid flow models that capture the essence of the three-dimensional flow field, using simple phenomenological rules that are computationally tractable, are required to capture the dynamic coupling between flow, bedrock erosion and solid-Earth dynamics. PMID:25254474

Venditti, Jeremy G; Rennie, Colin D; Bomhof, James; Bradley, Ryan W; Little, Malcolm; Church, Michael

2014-09-25

139

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

140

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

141

The turbidity currents records of Kaoping Canyon during past 32000 yrs  

NASA Astrophysics Data System (ADS)

Taiwan is both located in East Asia Monsoon area and plate collision boundary; as the result, frequently episodic rainfall and fractal geologic setting will cause Taiwan become a high potential area that gravity flows happen. When the high density terristrial flows were exported to the sea, it will become the hyperpycnal flow and perhaps can cause submarine geo-hazard happen (i.e. In 2010 Typhoon Morakot, there are numerous terrestrial sediments be delivered to the southwestern offshore Taiwan along the Kaoping Canyon and causing submarine cable be broken). Additionally, turbidite will also be triggered by earthquakes and it will also have the chance to cause submarine geo-hazard. For an example, Pintung earthquake happened in Hengchun, Taiwan in 1996; this earthquake triggered very huge magnitude submarine landslide happened and damaged several hundred kilometers submarine cable along the Kaoping Canyon. Taiwan is a island surrounded by ocean, and there are lots of submarine cables across these seas, especially along the Kaoping Canyon in southwestern offshore Taiwan. In order to avoid too much economic and safety waste, the risk estimation of geo-hazard is very important, and the frequency of turbidity currents happened is a very visible index. Hence, we collected a core located at the downstream of Kaoping Canyon in 2800 meters water depth. Its length is about 39 meters and we can divide this core into two different lithofacies roughly by core description. The upper part is dominated by mud and silt inter-bedded, and the lower part is dominated by massive mud. By the 14C dating, the age of lithofacies change is about 11000 yrs BP. According to the previous studies, We supposed due to Kaoping Canyon is connected with Kaoping river directly and the terrestrial materials of Pintong plain can be delivered from the land to deep ocean directly via the high energy flooding events. In other words, the lithoface change is related to the high energy events happened in land; hence, we propose that from 32000 yrs BP to 11000 yrs BP, the weather in southwestern Taiwan was dryer, and after 11000 yrs BP, it became wetter and frequently turbidity currents happened in Kaoping canyon system.

Yu, S.; Lin, A. T.; Tsai, L.

2013-12-01

142

DEFUELING OF RETIRED NUCLEAR SUBMARINES  

Microsoft Academic Search

The Russian Federation (RF) Decree #518 of May 28, 1998 “On Measures on Supporting Complex Decommissioning of Nuclear Submarines, Withdrawn from Service in the Russian Navy, and Ships of RF Ministry of Transport” entrusted RF Ministry for Atomic Energy (Minatom, presently Rosatom) with the task of drastic increase in the paces of Nuclear Submarine (NS) complex decommissioning, the heaviest burden

A. V. TIMOFEEV; V. I. KOSTIN; N. G. SANDLER; V. N. VAVILKIN; V. V. MOSCALENKO; A. I. KALINKIN

143

18. VIEW OF A CANYON IN THE CLEANUP PHASE. CANYONS ...  

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

18. VIEW OF A CANYON IN THE CLEANUP PHASE. CANYONS WERE PROCESSING ROOMS USED TO HOUSE PLUTONIUM HANDLING OPERATIONS THAT WERE NOT CONTAINED WITHIN GLOVE BOXES. CANYONS WERE DESIGNED TO BECOME CONTAMINATED. (5/10/88) - Rocky Flats Plant, Plutonium Recovery Facility, Northwest portion of Rocky Flats Plant, Golden, Jefferson County, CO

144

Paleogene canyons of Tethyan margin and their hydrocarbon potential, Czechoslovakia  

SciTech Connect

Two Paleogene canyons buried below the Neogene foredeep and the Carpathian thrust belt in Southern Moravia have been outlined by drilling and seismic profiling. The features, as much as 12 km wide and over 1000 m deep, have been traced for 40 km. They are cut into Mesozoic and Paleozoic carbonate and clastic deposits and underlying Precambrian crystalline rocks. The sedimentary fill is made of late Eocene and early oligocene marine deposits, predominantly silty mudstones and siltstones. Sandstones and conglomerates are distributed mainly in the lower axial part of the valleys. Proximal and distal turbidites, grain-flow and debris-flow deposits have been identified in the fill. The common occurrence of slump folds, pebbly mudstones, and chaotic slump deposits indicate that mass movement played a significant role in sediment transport inside the canyons. The canyons are interpreted as being cut by rivers, then submerged and further developed by submarine processes. The organic rich mudstones of the canyon fill are significant source rocks (1-10% TOC). They reached the generative stage only after being tectonically buried below the Carpathian thrust belt in middle Miocene time. Channelized sandstones and proximal turbidities provide reservoirs of limited extent, although more substantial accumulations of sands are possible further downslope at the mouth of these canyons. Several oil fields have been discovered both within the canyon fill and the surrounding rocks. Similar Paleogene valleys may be present elsewhere along the ancient Tethyan margins buried below the Neogene foredeeps and frontal zones of the Alps and Carpathians. Their recognition could prove fruitful in the search for hydrocarbons.

Picha, F.J. (Chevron Overseas Petroleum Inc., San Ramon, CA (United States))

1991-03-01

145

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

146

Hudson River Canyon GRADE LEVEL  

E-print Network

1 FOCUS Hudson River Canyon GRADE LEVEL 7-8 FOCUS QUESTION What are the effects of long activities at the DWD-106 mile site in the Hudson River Canyon. ADAPTATIONS FOR DEAF STUDENTS Teaching time in the Dumps #12;2 Deep East 2001 ­ Grades 7-8 Focus: Hudson River Canyon oceanexplorer.noaa.gov sites

147

Grand Canyon Explorer  

NSDL National Science Digital Library

Maintained by Bob Ribokas, Grand Canyon Explorer is quite extraordinary for a unaffiliated Web site. Updated regularly, it contains everything from stunning photography and geologic descriptions to information about hiking permits and park trials for users planning a trip. A highlight of the site is the guided tour, which provides descriptions and pictures from the park entrance to the Grand Canyon's spectacular formations like Mohave Point on the South Rim. The author has even provided a downloadable version of the Web site for Pocket PC's and PDA's, enabling users to have all the information at their finger tips when visiting the park.

1994-01-01

148

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.

149

Carbohydrate Metabolism in Submariner Personnel.  

National Technical Information Service (NTIS)

Submariners have been shown to have an increased rate of glucose utilization 2 hours after an oral loading test. Relative hypoglycemia due to excess insulin production has been considered a first indication of developing diabetes. However, diabetes can no...

E. Heyder, L. W. Mooney, D. V. Tappan

1983-01-01

150

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

151

Timing of occurrence of large submarine landslides on the Atlantic Ocean margin  

USGS Publications Warehouse

Submarine landslides are distributed unevenly both in space and time. Spatially, they occur most commonly in fjords, active river deltas, submarine canyon-fan systems, the open continental slope and on the flanks of oceanic volcanic islands. Temporally, they are influenced by the size, location, and sedimentology of migrating depocenters, changes in seafloor pressures and temperatures, variations in seismicity and volcanic activity, and changes in groundwater flow conditions. The dominant factor influencing the timing of submarine landslide occurrence is glaciation. A review of known ages of submarine landslides along the margins of the Atlantic Ocean, augmented by a few ages from other submarine locations shows a relatively even distribution of large landslides with time from the last glacial maximum until about five thousand years after the end of glaciation. During the past 5000??yr, the frequency of occurrence is less by a factor of 1.7 to 3.5 than during or shortly after the last glacial/deglaciation period. Such an association likely exists because of the formation of thick deposits of sediment on the upper continental slope during glacial periods and increased seismicity caused by isostatic readjustment during and following deglaciation. Hydrate dissociation may play a role, as suggested previously in the literature, but the connection is unclear.

Lee, H.J.

2009-01-01

152

Geology of a stratigraphically complex natural gas play: Canyon Sandstones, Val Verde Basin, southwest Texas. Topical report, January-October 1993  

SciTech Connect

The report examines the influence of stratigraphy, diagenesis, natural fractures, and in situ stress on low-permeability, gas-bearing sandstone reservoirs of the Paleozoic Ozona and Sonora Canyon Sandstones of the Val Verde Basin, Texas. The main stratigraphic controls on distribution and quality of Canyon Sandstone reservoirs are submarine fan depositional patterns. These patterns are revealed in regional facies and maximum sandstone maps. Siderite cement is key to good within-sandstone reservoir quality. Natural fractures are widespread in both Ozona and Sonora Canyon sandstones. They could be future targets for advanced drilling methods, and they need to be taken into account in hydraulic fracture treatment design and reservoir management.

Laubach, S.E.; Clift, S.J.; Hamlin, H.S.; Dutton, S.P.; Hentz, T.F.

1994-07-01

153

Influence of the Nazaré Canyon, central Portuguese margin, on late winter coccolithophore assemblages  

NASA Astrophysics Data System (ADS)

This paper presents a first attempt to characterize coccolithophore assemblages occurring in the context of an active submarine canyon. Coccolithophores from the upper-middle sections of the Nazaré Canyon (central Portuguese margin) - one of the largest canyons of the European continental margin - were investigated during a late winter period (9-12 March 2010). Species distributions were analyzed in a multiparameter environmental context (temperature, salinity, turbidity, Chl-a and nutrient concentrations). Monthly averaged surface water Chl-a concentrations between 2006 and 2011 assessed from satellite data are also presented, as a framework for interpreting spatial and temporal distribution of phytoplankton in the Nazaré Canyon. The Nazaré Canyon was observed to act as a conduit for advection of relatively nutrient-poor oceanic waters of ENACWst origin into nearshore areas of the continental shelf (less than 10 km off the coast), whilst at the surface a nutrient-rich buoyant plume resulting from intensive coastal runoff prior and during the beginning of the cruise was spreading in oceanward direction. Two distinct coccolithophore assemblages appear representative for the coast to open-ocean gradient: (1) Emiliania huxleyi together with Gephyrocapsa ericsonii and Coronosphaera mediterranea dominated the more productive assemblage present within coastal-neritic surface waters; and (2) Syracosphaera spp. and Ophiaster spp. displayed a higher affinity with open-ocean conditions, and also generally a broader vertical distribution. Local “hotspots” of coccolithophore and phytoplankton biomass potentially associated with perturbations of surface water circulation by the canyon are discussed.

Guerreiro, Catarina; Sá, Carolina; de Stigter, Henko; Oliveira, Anabela; Cachão, Mário; Cros, Llu?sa; Borges, Carlos; Quaresma, Luis; Santos, Ana I.; Fortuño, José-Manuel; Rodrigues, Aurora

2014-06-01

154

Stratigraphy and diagenesis of Sonora Canyon deep-water sandsontes, Val Verde basin, southwest Texas  

SciTech Connect

Several 'Canyon Sands' (Virgilian-Wolfcampian) intervals occur in the Val Verde basin, but the authors' study focuses on the Sonora Canyon, which is centered in western Sutton County. Sonora Canyon sandstones formed in continental-slope and basin-floor depositional systems basinward of a northwest-trending shelf margin. Well-log analysis revealed an overall wedgeshape geometry, thickening southwesterward from 500 ft at the shelf margin to 2000 ft where sandstone grades into basinal shale. The Sonora Canyon comprises coalesced submarine-fan systems forming a slope apron. Deltaic sandstones occur locally along the shelf margin, but mudstone covers most of the outer shelf. On the upper slope, channel-fill sandstones are discontinuous at 0.5- to 1.5-mi well spacing, and are enclosed in thick slope mudstones. Turbidites are the most prominent sedimentary features identified in Sonora Canyon cores. Channel-fill sandstones are massive to normally graded (Bouma divisions A and B) and are associated with slump and debris-flow facies. Sonora Canyon sandstones are mostly fine-grained to very fine-grained sublitharenites and litharenites. Chert, mudstone, sandstone, and low-rank metamorphic rock fragments are the predominant lithic grains. Major diagenetic events were (1) siderite and chlorite cementation, (2) mechanical compaction, (3) quartz cementation, (4) feldspar dissolution and illite and kaolinite precipitation, and (5) ankerite cementation. Intergranular porosity and permeability are higher in samples with abundant siderite cement because early precipitation of siderite inhibited later mechanical compaction and quartz cementation.

Hamlin, H.S.; Clift, S.J.; Dutton, S.P. (Univ. of Austin, TX (United States))

1992-04-01

155

An investigation of the physical factors controlling the sense of secondary flow circulation within submarine meanders  

NASA Astrophysics Data System (ADS)

Motivated by the symposium held at the 2011 AGU on "Submarine Channel Systems: Flow Dynamics and Sedimentary Deposits", we have undertaken a holistic investigation into the factors affecting secondary flow circulation within submarine meander bends. 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 meander bend morphodynamic evolution, the patterns of surface grain size sorting and, ultimately it controls the character of the sedimentary deposits produced. The study we present here uses a simplified analytical model, considering the fundamental interconnectedness of the principle physical forces driving the rotational flow within submarine meanders. This holistic radial flow model, which incorporates centrifugal and Coriolis forces, the radial pressure gradient and the baroclinicity of the flow, is formulated using existing empirical models. The analytical model is validated using experimental data and used to highlight the influence of the principal physical forces acting on the flow. Previous analytical studies have considered a temporally constant, two-dimensional, rotationally invariant, framework that leads to vanishing material flux conditions when applied to flows within bounded channels. However, with reference to experimental studies, we show that a three-dimensional flow framework, with non-zero material fluxes, 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 are presented. These phase-space analyses allow a system wide discussion of secondary flow structure within submarine canyon-fan networks. Our findings highlight the importance of (i) Coriolis, (ii) flow baroclinicity, and (iii) the dimensionality of the space-time continuum in controlling the sense of helical flow in submarine meanders. Specifically, the new model presented here suggests that the propensity for the occurrence of meander 'reversed' flow circulations in canyon-fan networks may be considerably greater than recently advocated.

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

2012-12-01

156

Photomosaics and logs of trenches on the San Andreas Fault at Mill Canyon near Watsonville, California  

USGS Publications Warehouse

We present photomosaics and logs of the walls of trenches excavated for a paleoseismic study at Mill Canyon, one of two sites along the San Andreas fault in the Santa Cruz Mtns. on the Kelley-Thompson Ranch. This site was a part of Rancho Salsipuedes begining in 1834. It was purchased by the present owner’s family in 1851. Remnants of a cabin/mill operations still exist up the canyon dating from 1908 when the area was logged. At this location, faulting has moved a shutter ridge across the mouth of Mill Canyon ponding Holocene sediment. Recent faulting is confined to a narrow zone near the break in slope.

Fumal, Thomas E.; Dawson, Timothy E.; Flowers, Rebecca; Hamilton, John C.; Heingartner, Gordon F.; Kessler, James; Samrad, Laura

2004-01-01

157

Medical Implications of Women On Submarines.  

National Technical Information Service (NTIS)

The review highlights traditionally important medical conditions for submariners along with the unique consequence of women's health care on the submarine. The information covered includes a review of the history of women in the military followed by a dis...

J. L. Kane, W. G. Horn

2001-01-01

158

An ongoing large submarine landslide at the Japan trench  

NASA Astrophysics Data System (ADS)

This paper deals with an active submarine landslide on a landward trench slope in the Japan trench. Studied area is located on the upper terrace ranging from 400 to 1200 m in water depth, off Sendai, northeast Japan. We have surveyed in detail the seabed topography using a multi narrow beam (hereafter MBES) and a subbottom profiler (hereafter SBP) during the cruise MR12-E02 of R/V Mirai. The survey lines were 12 lines in N-S, and 3 lines in E-W, and situated in the region from 141°45'E, 37°40'N to 142°33'E, 38°32'N. Moreover, we used multi-channel seismic profile by the cruise KR04-10 of R/V Kairei in the interpretation of the SBP results. In general, horseshoe-shaped depressions of about 100 km wide along the trench slope are arrayed along the Japan trench. It has thought that they were formed by large submarine landslides, but we could not understand critically the relationship between the depressions and the submarine landslides. Based on the survey results, we found signals of an active submarine landslide in the depression as follows. 1) We observed arcuate-shaped lineaments, which are sub-parallel to a horseshoe-shaped depression. The lineaments concentrate in the south region from 38°N at about 20 km wide. These lineaments are formed by deformation structures as anticlines, synclines and normal fault sense displacements. 2) Most of the synclines and anticlines are not buried to form the lineaments. 3) Normal faults cutting about 1 km deep are observed in a multi-channel seismic profile. The normal faults are located just below the arcuate-shaped lineaments, and are tilted eastward being the downslope direction. It indicates a large submarine landslide. We concluded that the arcuate-shaped lineaments were generated by surface sediment movement with the submarine landsliding. We think that the submarine landslide of about 20 km wide and about 1 km thick move continuously down the landward trench slope. This would be the formation process of the horseshoe-shaped depression along the Japan trench.

Nitta, S.; Kasaya, T.; Miura, S.; Kawamura, K.

2013-12-01

159

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

160

Canyon in DCS Color  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Released July 26, 2004 This image shows two representations of the same infra-red image covering a portion of Ganges Chasma. On the left is a grayscale image showing surface temperature, and on the right is a false-color composite made from 3 individual THEMIS bands. The false-color image is colorized using a technique called decorrelation stretch (DCS), which emphasizes the spectral differences between the bands to highlight compositional variations.

The northern canyon at the top of this image is dominated by a bright red/magenta area consisting primarly basaltic materials on the floor of the canyon and atmospheric dust. Within that area, there are patches of purple, on the walls and in the landslides, that may be due to an olivine rich mineral layer. In the middle of the image, the green on the mesa between the two canyons is from a layer of dust. The patchy blue areas in the southern canyon are likely due to water ice clouds.

Image information: IR instrument. Latitude -6.6, Longitude 316 East (44 West). 100 meter/pixel resolution.

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

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

2004-01-01

161

The Grand Canyon  

NASA Technical Reports Server (NTRS)

Northern Arizona and the Grand Canyon are captured in this pair of MISR images from December 31, 2000 (Terra orbit 5525). The left-hand image is a true color view from the nadir (vertical) camera. The right-hand image is a stereo composite generated using data from MISR's vertical and 46-degree-forward cameras. Viewing the stereo image in 3-D requires the use of red/blue glasses with the red filter placed over your left eye. To facilitate stereo viewing, the images have been oriented with north at the left.

In addition to the Grand Canyon itself, which is visible in the western (lower)half of the images, other landmarks include Lake Powell, on the left, and Humphreys Peak and Sunset Crater National Monument on the right. Meteor Crater appears as a small dark depression with a brighter rim, and is just visible along the upper right-hand edge. Can you find it?

MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

2001-01-01

162

Digital Transmission over Submarine Cables  

Microsoft Academic Search

The problems of transoceanic transmission of large volumes of information have been raised increasingly over the past few years. Lately, the need for transoceanic digital communications has been of interest. This paper discusses the significance of these trends and examines the technical prospects for handling large volumes of digital traffic using submarine cables. Concentrating on transatlantic traffic, an argument is

W. Litchman

1965-01-01

163

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

164

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

165

Hawaiian submarine manganese-iron oxide crusts - A dating tool?  

USGS Publications Warehouse

Black manganese-iron oxide crusts form on most exposed rock on the ocean floor. Such crusts are well developed on the steep lava slopes of the Hawaiian Ridge and have been sampled during dredging and submersible dives. The crusts also occur on fragments detached from bedrock by mass wasting, on submerged coral reefs, and on poorly lithified sedimentary rocks. The thickness of the crusts was measured on samples collected since 1965 on the Hawaiian Ridge from 140 dive or dredge localities. Fifty-nine (42%) of the sites were collected in 2001 by remotely operated vehicles (ROVs). The thinner crusts on many samples apparently result from post-depositional breakage, landsliding, and intermittent burial of outcrops by sediment. The maximum crust thickness was selected from each dredge or dive site to best represent crusts on the original rock surface at that site. The measurements show an irregular progressive thickening of the crusts toward the northwest-i.e., progressive thickening toward the older volcanic features with increasing distance from the Hawaiian hotspot. Comparison of the maximum crust thickness with radiometric ages of related subaerial features supports previous studies that indicate a crust-growth rate of about 2.5 mm/m.y. The thickness information not only allows a comparison of the relative exposure ages of two or more features offshore from different volcanoes, but also provides specific age estimates of volcanic and landslide deposits. The data indicate that some of the landslide blocks within the south Kona landslide are the oldest exposed rock on Mauna Loa, Kilauea, or Loihi volcanoes. Crusts on the floors of submarine canyons off Kohala and East Molokai volcanoes indicate that these canyons are no longer serving as channelways for downslope, sediment-laden currents. Mahukona volcano was approximately synchronous with Hilo Ridge, both being younger than Hana Ridge. The Nuuanu landslide is considerably older than the Wailau landslide. The Waianae landslide southwest of Oahu has yielded samples with the greatest manganese-iron oxide crusts (9.5 mm thick) and therefore apparently represents the oldest submarine material yet found in the study area. The submarine volcanic field 100 km southwest of Oahu is apparently younger than the Waianae landslide. ?? 2004 Geological Society of America.

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

2004-01-01

166

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

167

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

2012-06-21

168

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

169

30. VIEW OF PHOTO CAPTIONED 'SUBMARINE BASE, NEW LONDON, CONNECTICUT. ...  

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

30. VIEW OF PHOTO CAPTIONED 'SUBMARINE BASE, NEW LONDON, CONNECTICUT. 2 JUNE 1930. SUBMARINE TRAINING TANK - STEELWORK 98% COMPLETE; BRICKWORK 95% COMPLETE, PIPING 10% IN PLACE. LOOKING NORTH. CONTRACT NO. Y-1539-ELEVATOR, SUBMARINE ESCAPE TANK.' - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

170

Predicting velocities and turbulent momentum exchange in isolated street canyons  

NASA Astrophysics Data System (ADS)

A simplified way of studying the transport of mass and momentum through dense neighborhoods is to consider the flow field as a combination of a mainly horizontal flow along street canyons and a vertical flow into and out of street canyons. In this paper, we derive a simple, semi-analytical model for calculating the expected wind speeds in narrow, isolated, idealized street canyons of uniform height that are aligned with and at an angle to the wind through the introduction of a non-dimensional parameterization of the vertical turbulent exchange of horizontal momentum between the urban canopy layer (UCL) and the urban boundary layer (UBL). The model is closed and evaluated using computational fluid dynamics (CFD) in a generic way. The RMSE of the normalized bulk velocity in the street canyon in the direction of the freestream flow is 1.8 × 10-4, 2.3 × 10-2 and 9.4 × 10-2 for variations in façade roughness, aspect ratio and canyon orientation, respectively. We argue that there is a need for a fast, simple methodology to assess the impact of urban form on neighborhood microclimate, especially in dense neighborhoods, and specifically for use in the early phases of design. This methodology should be able to predict areas in a neighborhood that are prone to low wind speeds or weak mass and momentum exchange rates with the UBL above because these areas may be particularly susceptible to pollutant retention and the urban heat island (UHI) effect. Current methodologies are often inadequate for this purpose because they use computationally intensive techniques to solve for flow through a neighborhood and often require a strong technical background to support their use. The work in this paper addresses this problem for an idealized, narrow street canyon, and we discuss the need for parameterizations for urban form that are relevant to mass and momentum exchange rates to extend this model beyond a single street canyon. Finally, we discuss how this work could be further developed into generalized planning guidelines and incorporated into a comprehensive urban planning methodology that aims to passively mitigate the UHI effect and pollutant retention through the clever design of urban form.

Hall, Terianne C.; Britter, Rex E.; Norford, Leslie K.

2012-11-01

171

On the pollutant removal, dispersion, and entrainment over two-dimensional idealized street canyons  

NASA Astrophysics Data System (ADS)

Pollutant dispersion over urban areas is not that well understood, in particular at the street canyon scale. This study is therefore conceived to examine how urban morphology modifies the pollutant removal, dispersion, and entrainment over urban areas. An idealized computational domain consisting of 12 two-dimensional (2D) identical street canyons of unity aspect ratio is employed. The large-eddy simulation (LES) is used to calculate the turbulent flows and pollutant transport in the urban boundary layer (UBL). An area source of uniform pollutant concentration is applied on the ground of the first street canyon. A close examination on the roof-level turbulence reveals patches of low-speed air masses in the streamwise flows and narrow high-speed downdrafts in the shear layer. Different from the flows over a smooth surface, the turbulence intensities are peaked near the top of the building roughness. The pollutant is rather uniformly distributed inside a street canyon but disperses quickly in the UBL over the buildings. Partitioning the vertical pollutant flux into its mean and turbulent components demystifies that the pollutant removal is mainly governed by turbulence. Whereas, mean wind carries pollutant into and out of a street canyon simultaneously. In addition to wind speed promotion, turbulent mixing is thus required to dilute the ground-level pollutants, which are then removed from the street canyon to the UBL. Atmospheric flows slow down rapidly after the leeward buildings, leading to updrafts carrying pollutants away from the street canyons (the basic pollutant removal mechanism).

Liu, Chun-Ho; Wong, Colman C. C.

2014-01-01

172

Anatomy of La Jolla Canyon  

Microsoft Academic Search

High-resolution multibeam bathymetry (vertical precision of 0.15 m and horizontal resolution of 1.0 m) and chirp sub-bottom profiler data collected with an autonomous underwater vehicle (AUV) reveal the fine-scale morphology of La Jolla Canyon, offshore southern California. The AUV was pre-programmed to fly three missions within the canyon while maintaining an altitude of 50 m above bottom in water depths

C. K. Paull; D. W. Caress; W. Ussler; E. Lundsten; M. L. McGann; J. E. Conrad; B. D. Edwards; J. A. Covault

2010-01-01

173

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

174

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

175

Transport of persistent organic pollutants by organo-mineral aggregates (OMAs) in the Lisboa-Setúbal Canyon system  

NASA Astrophysics Data System (ADS)

In this work we investigate the role of organo-mineral aggregates (OMAs) in the transport and deposition of persistent organic pollutants in the Lisboa-Setúbal Canyon system. OMAs are more easily remobilized than the underlying sediment surface, and are easily transported in the benthic boundary layer. Since aquatic sediments act as sinks for hydrophobic organic contaminants, OMAs must be a factor in the lateral transport of organic contaminants. Submarine canyons further facilitate the flux of these contaminants from source to deep-sea. Our results show that the difference between the behavior of the OMAs and the underlying superficial sediment is very important in the transport of carbon and persistent organic pollutants to the deep-sea. The Lisboa-Setúbal Canyon system is clearly exporting organic pollutants to the deep-sea through the transport of OMAs.

de Jesus Mendes, Pedro A.; Thomsen, Laurenz; Garcia, Rosa; Gust, Giselher

2011-12-01

176

Plio-Quaternary canyons evolution on South Colombian convergent margin : Tectonic causes and implications  

NASA Astrophysics Data System (ADS)

Investigations of seafloor morphology and sediment deposits associated with the incision of the South Colombia active margin by a major submarine canyon system are used to reveal out-of-sequence fault activity at least since the Middle Pleistocene. The South Colombian convergent margin is located along Northwestern South America, where the Nazca plate underthrusts eastward the South America plate with a 58 mm.yr-1 convergence rate. The morphology and deep multichannel seismic reflection lines obtained across the margin reflect a frontal accretionnary wedge, as well as antiform and faulted internal structural highs that locally extend up to near the continental shelf, suggesting wide-spread Plio-Quaternary tectonic activity. The Amadeus cruise conduced in 2005 brought new seismic and sedimentary data together with 150m and 60m-resolution EM12D multibeam bathymetry. The newly mapped Mira and Patia canyons system incises the South Colombian margin slope over a distance of ~90 and ~150 km respectively, forming an unequivocal Z-shape in map view, breaching the deformation front and feeding a 30-km wide trench fan system. The morphology of the canyon exhibits meanders, steep over-incised walls (~25-30 degrees), alternation between concave-up and convex-up downstream profiles, slope failures scars, and buried channels. These features reflect interactions between tectonics, sedimentation and the canyon evolution. A synthesis of all the data reveals that: A) Uplifting structural highs control canyons path and incision stages. B) Canyons developed asynchronously across the upper, mid and lower margin slopes according to three main stages: a) upper slope incision by downward cutting during Pleistocene, and possibly by retrogressive headward erosion, b) infill of a mid-slope basin bounded by uplifting structural highs, and c) overspill of the slope basin, and breaching its seaward bounding ridge, and the accretionary prism ~150 kyr ago. These processes led to the construction of sedimentary lobes in the trench, and then to a well-developed channel-levees system. C) Occurrences of antecedence, canyon walls over steepening, and convex-up bathymetric profiles of the canyons imply uplift of the fault-controlled structural highs at least during the last ~150 kyr supporting active out-of-sequence tectonic shortening. The long-term causes of the out-of-sequence tectonic could be linked to interplate coupling and basal friction variations. This study strongly reflects the interplay between tectonic deformation and canyon evolution thus providing a good example of the use of canyon morphology and associated deposits as markers of active tectonic deformation

Ratzov, Gueorgui; Sosson, Marc; Collot, Jean-Yves; Migeon, Sebastien

2010-05-01

177

Habitat characterization of deep-water coral reefs in La Gaviera Canyon (Avilés Canyon System, Cantabrian Sea)  

NASA Astrophysics Data System (ADS)

Surveys conducted at the complex Avilés Canyon System (southern Bay of Biscay) in order to identify vulnerable habitats and biological communities revealed the presence of noteworthy deep-water coral reefs in one of the tributaries of the system (La Gaviera Canyon). The aim of the present study is to determine why this deep-sea canyon provides suitable environmental conditions for corals to grow. This hanging canyon is characterized by an irregular U-shaped floor with two narrow differentiated flanks. Sand ripples and rocky outcrops structured in diverse W-E directed steps are observed on the canyon floor, suggesting intense hydrodynamic activity. Accordingly, high-frequency near-bottom current and thermal structure profiles showed that there occur strong shifts in currents/hydrography behaving as front-like features at each tidal cycle. These involve the sudden increase of along-axis velocities to over 50 cm/s and vertical velocities of over 5 cm/s in each tidal cycle associated with the passage of sharp thermal fronts and thermal inversions suggesting overturning. A year-long near-bottom current record showed events with near-bottom velocities well over 1 m/s lasting for several days. Three cold-water coral settings were distinguished: a dense coral reef located on stepped rocky bottoms of the eastern and western flanks, carbonate mounds (20-30 m high) located on the canyon floor, and a cluster of shallower water dead coral framework at the head sector of the canyon. Video and still images from a towed sled and ROV verified the presence of dropstones and rippled sand sheets surrounding the mounds and revealed changes in the coral population (alive or dead; total or patchy coverage) in coral reef and carbonate mound areas. The dominant species of the reef are Lophelia pertusa and Madrepora oculata, which considerably increase the habitat?s complexity and biodiversity in relation to other facies described in the canyon. The presence of living cold-water reefs is directly related to a high-energy environment at depths between 700 and 1200 m in the levels between the lower bound of Eastern North Atlantic Central Water (ENACW) and the core of Mediterranean Water (MW). Such level matches the water density range ??=27.35-27.65 kg m-3 which has been identified as limits for cold-water coral distribution in the North Atlantic.

Sánchez, Francisco; González-Pola, Cesar; Druet, María; García-Alegre, Ana; Acosta, Juan; Cristobo, Javier; Parra, Santiago; Ríos, Pilar; Altuna, Álvaro; Gómez-Ballesteros, María; Muñoz-Recio, Araceli; Rivera, Jesus; del Río, Guillermo Díaz

2014-08-01

178

34. VIEW OF SUBMARINE ESCAPE TRAINING TANK PRIOR TO ADDITION ...  

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

34. VIEW OF SUBMARINE ESCAPE TRAINING TANK PRIOR TO ADDITION OF BLISTERS IN 1959, LOOKING SOUTHEAST - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

179

Submarine landslides in French Polynesia SUBMARINE LANDSLIDES IN SOCIETY AND AUSTRAL ISLANDS,  

E-print Network

Submarine landslides in French Polynesia 1 SUBMARINE LANDSLIDES IN SOCIETY AND AUSTRAL ISLANDS with the age of oceanic islands. Submarine active volcanoes are subject to superficial landslides of fragmental material whereas young islands exhibit marks of mass wasting corresponding to giant lateral collapses due

Clouard, Valerie

180

78 FR 7810 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...Canyon Dam, consistent with the Grand Canyon Protection Act. The AMWG meets...consultation requirements of the Grand Canyon Protection Act (Pub. L. 102-575...technical work group (TWG), a Grand Canyon Monitoring and Research...

2013-02-04

181

The Dangeard and Explorer canyons, South Western Approaches UK: Geology, sedimentology and newly discovered cold-water coral mini-mounds  

NASA Astrophysics Data System (ADS)

The Celtic Margin is a complex area in terms of sedimentary dynamics and evolution, with a number of submarine canyons dissecting the continental slope and outer continental shelf. The complex terrain and diverse range of sea-bed sediments play a part in submarine canyons being described as areas of high habitat heterogeneity. This study has concentrated on the heads of two canyons: Dangeard (also known as Dangaard) and Explorer (first named here) located in UK territorial waters, in water depths between 138 and 1165 m. Multibeam echosounder, 2D reflection seismic and photographic ground-truthing data have been combined to map the sea-bed geomorphology, sedimentary features and canyon megafauna of these canyons. In addition, two previously unknown provinces of cold-water coral (CWC) mini-mounds were discovered on the interfluves of the Dangeard and Explorer canyons. The study area comprises a dendritic network of gullies feeding into the canyon thalwegs. Amphitheatre rims, where slope angles are commonly in excess of 20°, occur along the margins and heads of both canyons and are interpreted as drainage basins indicative of retrogressive mass-wasting in a shelfward direction. The CWC mini-mounds occur in water depths between 250 m and 410 m, with more than 400 mounds identified. They are up to 3 m in height and 50-150 m in diameter with no sub-surface expression, suggesting these mounds are, in geological terms, relatively young and possibly Holocene in age. Biological analyses revealed that the mounds form a habitat for ophiuroids and Munida associated with Lophelia pertusa coral rubble, suggesting these mini-mounds are not present-day living features.

Stewart, Heather A.; Davies, Jaime S.; Guinan, Janine; Howell, Kerry L.

2014-06-01

182

Red Canyon Terrace Project  

NSDL National Science Digital Library

We know that glacial cycles produce changes in stream regimens downstream from the active ice margin, and that successive glacial cycles often result in separate (and usually lower) floodplains that become terraces following each cycle of stream incision. Using a suite of 4-5 glacio-fluvial terraces outside the mouth of Little PopoAgie Canyon on the east flank of Wyoming's Wind River Range, students do the following: (1) produce a map of the major terrace landforms, (2) observe the geomorphic characteristics of each map unit (this includes height above present stream, depth of fine overbank material above coarse bedload, and general weathering characteristics of the units, and whether the unit is a cut or fill terrace), and (3) measure the characteristics of soil profiles dug into each unit (including horizons Id's, depth and thickness of horizons, and carbonate morphology). Students use all this information to place the terrace units into the regional glacio-fluvial chronology by matching the relative age-data with the Pinedale/Bull Lake/Pre-Bull Lake regional sequence. Final project must include a graphic representation of stream heights that fit their interpretations of the regional glacio-fluvial stratigraphy.

Dahms, Dennis

183

DEVIL CANYON-BEAR CANYON PRIMITIVE AREA, CALIFORNIA.  

USGS Publications Warehouse

The Devil Canyon-Bear Canyon Primitive Area, located about 10 mi northeast of Pasadena in the Angeles National Forest, Los Angeles County, California, is an area about 8 mi long by 6 mi wide. To evaluate the mineral-resource potential of the area, geologic examinations were made by foot traverses. Samples of fresh, altered, and mineralized rocks, of sand, gravel, and other sediments, and of some panned concentrates from stream sediments were collected and analyzed. The mineral-resource survey concluded that there is little promise for the occurrence of metallic resources.

Crowder, Dwight F.; Fillo, Paul V.

1984-01-01

184

Prediction of the Dynamic Behaviour and Migration Rates of Sand Waves in the Monterey Canyon System of California  

NASA Astrophysics Data System (ADS)

This research focus on the sand wave field along the canyon axis in the upper 4 km of the Monterey Submarine Canyon revealed by high-resolution multibeam bathymetry collected by MBARI/Mapping Lab of the California State University (http://seafloor.csumb.edu/), spanning six years period (spring 2003 to fall 2008). The goal of the research is to understand how erosion, gravitative processes, sediment liquefaction by storm events, sediment transport by tidal currents, and deposition of the reworked sediment are connected in distal basins with quasi-horizontal floors. Morphometric analysis has been conducted on the sand wave on the canyon head and main axes comparing the waves shape of nearest surveys by means of smoothing filtering and geostatistical techniques. The analysis has allowed to classify the canyon floor in upstream migration zones, downstream migration zones, and completely reworked zones. In the first two zones a sand migration velocity has been inferred, and in the last ones, where the wave field is completely reworked between each surveys, a minimum admissible migration velocity has been deducted. A simple mathematical model has then permitted to reproduce the main features of sand wave inception and growth. In particular the model focus on the prediction of the migration rates that sand waves undergo because of tidal currents. The model output has been compared versus the morphometric analysis results and match and mismatch are discussed. Results of the research show that the sand waves migrate in a predominantly up-canyon direction with tidal and internal tidal currents, despite different behaviour along the canyon. However the research shows that these are not the dominating flows within the canyon. Seismic profiles interpretation, other morphometric analysis results like local channel widening causing lateral erosion of older channel and extension of gully head on canyon walls and rim, point out high velocity transport processes in the canyon main axes. This mechanism can be related to storm events and gravitative processes, possibly triggered by seismic events, as suggested by the slope stability analysis. Moreover, the liquefaction potential analysis of the poorly consolidated sediments characterising the canyon’s head suggests that pore fluid overpressures may develop during earthquake shaking (i.e. earthquakes with peak ground acceleration (PGA) > 0.18 - about 50% of the PGA related to the 1989 M 7.1 Loma Prieta earthquake), further contributing to the destabilization of the canyon slope.

Innocenti, C.; Taramelli, A.; Besio, G.; Pascoletti, F. C.; Disperati, L.; Aiello, I. W.

2009-12-01

185

THE SUBMARINE REVIEW FIXED SONAR SYSTEMS  

E-print Network

in the early 1950's. It was designed using breakthrough discoveries of the propagation paths of sound through to locate submarines that were able to stay below the surface of the ocean for longer periods of time deployed along the ocean floor in strategic areas, designed to detect an enemy submarine as she either left

186

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

187

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

188

Creationism in the Grand Canyon, Texas Textbooks  

Microsoft Academic Search

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

Peter Folger

2004-01-01

189

29. VIEW OF SUBMARINE ESCAPE TRAINING TANK DURING CONSTRUCTION AT ...  

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

29. VIEW OF SUBMARINE ESCAPE TRAINING TANK DURING CONSTRUCTION AT POINT JUST ABOVE THE SUBMARINE SECTION AT THE 110-FOOT LEVEL 1929-1930 - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

190

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

191

Amplification of bedrock canyon incision by wind  

NASA Astrophysics Data System (ADS)

Bedrock canyons etch much of the surface of Earth and Mars, and commonly inform interpretations of long-term hydrologic or tectonic changes within these landscapes. However, many bedrock canyons (particularly on Mars) exist in arid environments where wind abrasion can dramatically alter surface morphology. Although it is hypothesized that wind carves or modifies bedrock canyons on Mars, the interplay of wind and fluvial processes in shaping canyon landscapes is, to our knowledge, unexplored. Consequently, here we exploit a natural experiment along the 4.09 Ma Puripicar ignimbrite, situated on the western slope of the Andes in the Atacama Desert and subject to significant erosion from both wind and rivers. The Puripicar exhibits a series of bedrock gorges nested behind a broad north-south escarpment whose southern half is protected from wind by a large topographic barrier. This shielding provides a natural control to examine the effects of wind abrasion on canyon morphology and in particular knickpoint retreat. Our results show that for a given drainage area, knickpoints in wind-affected canyons have incised an order of magnitude farther upstream than wind-protected canyons. In addition, wind-affected canyons are wider and have more streamlined aspect ratios for a given drainage area than wind-protected canyons. Aeolian abrasion appears to result in knickpoints with average slopes half those of shielded canyons (0.2 and 0.4, respectively). Lastly, although the magnitude of knickpoint retreat is larger in wind-affected canyons, the scaling exponent between knickpoint retreat and drainage area is virtually identical for wind-affected canyons (0.56, R = 0.71) and wind-protected canyons (0.60, R = 0.80). Taken together, our results suggest that fluvial incision and wind abrasion are coupled processes in this landscape: convergent canyons funnel wind towards knickpoints, thereby leading to enhanced aeolian abrasion rates at knickpoints. We speculate that the apparent drainage area dependence of knickpoint retreat in wind-affected canyons reflects the fact that larger rivers create wider canyon mouths. Larger canyons mouths, in turn, increase wind convergence and drive higher aeolian abrasion rates at the heads of larger canyons. This study is the first to demonstrate knickpoint retreat via wind abrasion, and highlights that even in landscapes where large river gorges are present, wind may still exert a dominant control on canyon morphology.

Perkins, J. P.; Finnegan, N. J.; de Silva, S. L.

2013-12-01

192

Jurassic submarine arc-apron deposits and associated magma/wet-sediment interaction, northern Sierra Nevada, California  

NASA Astrophysics Data System (ADS)

Jurassic metavolcanic rocks of the Northern Sierra terrane in northern California are part of an extensive Triassic-Jurassic arc constructed along the western margin of North America. In the English Mountain area, Nevada and Sierra Counties, a well-exposed volcaniclastic sequence 3.6 km thick records Jurassic island-arc activity in a submarine environment. In the lower part of the sequence, thinly bedded andesitic volcanic sandstone turbidites and mudstones of the Lower to Middle Jurassic Sailor Canyon Formation were deposited below storm wave base in a long-lived marine basin. This unit is overlain conformably by the Middle Jurassic Tuttle Lake Formation, which records rapid accumulation of coarse-grained, calc-alkaline volcanic debris in the proximal parts of a submarine apron around a major volcano that developed within the earlier Sailor Canyon basin. The formation consists primarily of massively bedded, matrix-supported, polymict, basaltic to andesitic volcanic breccias deposited from submarine debris flows. Intercalated pillow-hyaloclastite breccias formed during local extrusion of lavas on the seafloor. Numerous intrusions cut the sequence and are petrographically and chemically identical to clasts in the debris-flow deposits. Peperite occurs along intrusion margins and as abundant isolated pockets, indicating intrusion of magma into wet, unconsolidated sediments. Elongate intrusive pods to 13.6 m in length are associated with smaller intrusive pillows and are inferred to represent a network of feeder tubes that extended from larger, coherent intrusions and supplied magma to complex zones of magma/wet-sediment interaction at shallow levels beneath the seafloor. Syndepositional intrusive activity of this type, including formation of abundant peperite, probably is a characteristic feature of submarine volcaniclastic sequences developed in proximal island-arc settings.

Templeton, Jeffrey H.; Hanson, Richard E.

2003-12-01

193

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 (gulf head). 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 in about 60-63 m water depth but is either covered or eroded in the adjacent subbasins. This fossil reef is offset along the offshore Evrona Fault. 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; Ben-Avraham, Zvi; Al-Zoubi, Abdallah; Sade, Ronnie; Hall, John; Hartman, Gal; Akawi, Emad; Abueladas, Abed; Al-Ruzouq, Rami

2010-05-01

194

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

195

Capacity upgrade in WDM submarine cable system  

Microsoft Academic Search

The capacity upgrade from 20 Gbit\\/s to 160 Gbit\\/s in a WDM submarine cable system has been designed based on the experimental study of the dependency of the repeater output power and the number of wavelength

Eiichi Shibano; Hidenori Taga; Toshio Kawazawa; Koji Goto

1999-01-01

196

Comparative naval architecture analysis of diesel submarines  

E-print Network

Many comparative naval architecture analyses of surface ships have been performed, but few published comparative analyses of submarines exist. Of the several design concept papers, reports and studies that have been written ...

Torkelson, Kai Oscar

2005-01-01

197

Addressing submarine geohazards through scientific drilling  

Microsoft Academic Search

Natural submarine geohazards (earthquakes, volcanic eruptions, landslides, volcanic island flank collapses) are geological phenomena originating at or below the seafloor leading to a situation of risk for off-shore and on-shore structures and the coastal population. Addressing submarine geohazards means understanding their spatial and temporal variability, the pre-conditioning factors, their triggers, and the physical processes that control their evolution. Such scientific

A. Camerlenghi

2009-01-01

198

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

199

Variant Narrowing and Extreme Termination  

Microsoft Academic Search

For narrowing with a set of rules modulo a set of axioms B almost nothing is known about terminating narrowing strategies, and basic narrowing is known to be incomplete for B = AC. In this work we ask and answer the question: Is there such a thing as an extremely terminating narrowing strategy modulo B? where we call a narrowing

Santiago Escobar; Jose Meseguer; Ralf Sasse

200

Chirp seismic-reflection data from the Baltimore, Washington, and Norfolk Canyons, U.S. mid-Atlantic margin  

USGS Publications Warehouse

A large number of high-resolution geophysical surveys between Cape Hatteras and Georges Bank have been conducted by federal, state, and academic institutions since the turn of the century. A major goal of these surveys is providing a continuous view of bathymetry and shallow stratigraphy at the shelf edge in order to assess levels of geological activity during the current sea level highstand. In 2012, chirp seismic-reflection data was collected by the U.S. Geologial Survey aboard the motor vessel Tiki XIV near three United States mid-Atlantic margin submarine canyons. These data can be used to further our understanding of passive continental margin processes during the Holocene, as well as providing valuable information regarding potential submarine geohazards.

Obelcz, Jeffrey B.; Brothers, Daniel S.; ten Brink, Uri S.; Chaytor, Jason D.; Worley, Charles R.; Moore, Eric M.

2014-01-01

201

Simulating the 1999 Capbreton canyon turbidity current with a Cellular Automata model  

NASA Astrophysics Data System (ADS)

A numerical model has been developed for the simulation of turbidity currents driven by nonuniform, non cohesive sediment and flowing over a complex three dimensional submarine topography. The model is based on an alternative approach known as Cellular Automata paradigm. The model is validated by comparing a simulation with a reported field-scale event. The chosen case is a turbidity current which occurred in Capbreton Canyon and was initiated by a storm in December 1999. Using data from recent oceanographic cruises, the deposit of the event has been precisely described, which constrain values of model parameters. The model simulates the 1999 turbidity current over the actual canyon topography and related turbidite using three different types of particle. The model successfully simulates areas of erosion and deposition in the canyon. It predicts the vertical and longitudinal grain size evolution, and shows that the fining-up sequence can be deposited by several phases of deposition and erosion related to the current energetic variation during its evolution. This result could explain the presence of intrabed contacts or the frequent lack of facies in Bouma sequences.

Salles, T.; Mulder, T.; Gaudin, M.; Cacas, M. C.; Lopez, S.; Cirac, P.

2008-05-01

202

Distribution of cold-water corals in the Whittard Canyon, NE Atlantic Ocean  

NASA Astrophysics Data System (ADS)

The deep-sea floor occupies about 60% of the surface of the planet and is covered mainly by fine sediments. Most studies of deep-sea benthic fauna therefore have concentrated on soft sediments with little sampling of hard substrata, such as rocky outcrops in submarine canyons. Here we assess the distribution and abundance of cold-water corals within the Whittard Canyon (NE Atlantic) using video footage from the ROV Isis. Abundances per 100 m of video transect were calculated and mapped using ArcGIS. The data were separated into five substratum types, 'Sediment', 'Mixed Sediment and Rock', 'Sediment Slope', 'Lophelia reef' and 'Lophelia and rock'. Abundance and community structure were compared. A maximum abundance of 855 coral colonies per 100 m of ROV transect were observed with 31 coral types identified. Highest taxon richness was observed along a 'Lophelia reef' area, although a larger richness of Octocorallia was observed away from the 'Lophelia reef' areas. 'Lophelia reef' and 'Lophelia and rock' areas were found to have a different coral community structure from the other substratum types. We suggest this is the result of Lophelia outcompeting other coral types because there is increased coral taxon richness in areas without Lophelia. We also hypothesise that the hydrodynamic regime within the Whittard Canyon results in differences in organic matter input including higher quality food, in comparison with other deep-water environments, leading to changes in the coral communities.

Morris, Kirsty J.; Tyler, Paul A.; Masson, Doug G.; Huvenne, Veerle I. A.; Rogers, Alex D.

2013-08-01

203

Hudson Canyon benthic habitats characterization and mapping by integrated analysis of multidisciplinary data  

NASA Astrophysics Data System (ADS)

Hudson Canyon, about 180 km SE of New York City, is the largest eastern U.S. submarine canyon and is under consideration for HAPC (Habitat Area of Particular Concern) status, representing a fisheries and biodiversity hot spot. Interest in the area, within the perspective of ecosystem based management, marine spatial planning, habitat and species conservation, led to a joint project between NOAA Northeast Fisheries, U.S. Geological Survey (USGS), Mississippi Mineral Research Institute (MMRI), National Institute for Undersea Science and Technology (NIUST), Stony Brook and Rutgers Universities for the study of benthic habitats, that includes the assembly of existing data with newly collected ones: acoustic mapping, visual ground-truthing, hydrographic, sedimentological, and trawl data collections. Acoustic mapping, performed using AUV-mounted multibeam sonar, provided ultra-high resolution bathymetric and backscatter imagery (3m and 1m respectively) at all water depths for identification of geomorphological features and for the characterization of surficial sediments along the two thirds of the shelf portion of the canyon. Identification of benthic and demersal communities was accomplished by visual ground thruthing with underwater vehicle video and still cameras, and from trawl catch data. A CTD-rosette sampler provided water column salinity-temperature profiles and water samples for dissolved methane analysis in the vicinity of suspected bottom sources. Analysis of data revealed a complex of topographic structures and hydrological patterns that provide a wide range of physical habitats in a relatively small area. A mosaic of sandy and muddy substrates, gravel beds, rock outcrops, and semilithified clay outcrops host rich and varied faunal assemblages, including deepwater corals and sponge communities. Pockmark fields, occurring below 300 m depth, suggest that methane-based chemosynthetic carbonate deposition contributes to creation of specific hard bottom habitats. Previously described hummocky terrain associated with extensive, long-term burrowing activity by golden tilefish (Lopholatilus chamaeleonticeps) was clearly delineated along the canyon rims. Bedform fields and potential current deposits observed along the upper portion of canyon walls suggest the presence of intense bottom currents flowing parallel to canyon axis. A benthic habitat map of Hudson Canyon head was produced by integration of the different datasets. The distribution of habitats was primarily inferred from geophysical data characteristics. Furthermore habitat characteristics can be related to sedimentary and oceanographic processes acting on the seafloor. Comparison and refinement of bathymetric and backscatter imagery with ground truth data enabled validation of acoustic classification of the seafloor, allowing the definition of morpho-acoustic classes corresponding to as many habitats, and to extend the predictive results over larger areas.

Pierdomenico, Martina; Guida, Vincent G.; Rona, Peter A.; Macelloni, Leonardo; Scranton, Mary I.; Asper, Vernon; Diercks, Arne

2013-04-01

204

Coastal upwelling process on a continental shelf limited by submarine canyons, Concepción, central Chile  

Microsoft Academic Search

The subinertial flow on the continental shelf off Concepción (central Chile) and its relation with the local wind-forcing and the topography are studied. Emphasis is placed on the three-dimensional aspects and the effect of the topography on the classical two-dimensional approach to the coastal upwelling. Time series coming from 18 current meters installed on six moorings during March–April 1994 were

Marcus Sobarzo; Leif Djurfeldt

2004-01-01

205

Reconstruction of submarine canyon systems associated with proto-Stockton arch during Late Cretaceous  

Microsoft Academic Search

A hypothetical depositional model of the middle Great Valley gas fields of California includes the area from the Southwest Vernalis gas field in the south (T3S) to the Nicolaus gas field in the north (T12N). The model assumes that (1) the early Campanian Dobbins Shale Member was deposited at or near the shelf\\/slope break, and (2) the absence of the

Jonathan Rider

1986-01-01

206

Morphotectonics and incision of the Kaoping submarine canyon, SW Taiwan orogenic wedge  

E-print Network

at the juncture of the Ryukyu and Luzon Arcs along the western boundary of the Philippine Sea plate (Fig. 1). The fold-and-thrust belt of Taiwan was formed by an oblique collision between the Luzon Arc and the Chinese

Lin, Andrew Tien-Shun

207

Following the Cantabrian (Ventaniella) fault into the Bay of Biscay: a deeply incised canyon, a change of trend, and 20002 km of unstable continental slope  

NASA Astrophysics Data System (ADS)

The Cantabrian fault, known traditionally with the local name of Ventaniella fault is a long-lived rectilinear feature that runs in a NW-SE direction for more than 200 km across northwest Spain. Its origins are linked to the end of the Variscan orogeny, but its important role took place during the extensional processes of the Mesozoic that led Iberia to become a microplate separated from Europe and Africa. With the initiation of the alpine orogeny Iberia converges with Europe pushed from the south by Africa, and the Ventaniella fault acted as a dextral strike slip fault with an important reverse component. It has a relatively low topographic expression, although its NE block is slightly uplifted with respect to the SW one. Traditionally it has been mapped offshore following the trace of the Aviles canyon, a deeply incised canyon 7 miles from the coast, oblique to the E-W coast trend and which descents from 160 m in the continental shelf , down to 4750 m in the abyssal plain of the Bay of Biscay . All this incision occurs along just 50 km length of the narrow continental shelf in this area, making the Aviles canyon one of the steepest in the Atlantic. Through seismic reflection lines across the continental shelf and slope, a bathymetric model up to date and a 3D geological model the fault has been mapped into the sea integrating the seismicity associated to its SW block and the newest geological mapping on land. At the same time, what is observed in the northwest prolongation and termination of the fault against the oceanic crust of the abyssal plain is a continental slope that is full of mass-wasting processes along more than 80 km length, showing gravitational and submarine slide processes in an area that roughly occupies 2000 km 2 and involves a volume of unstable mass estimated in more than 1000 km3 . One of the biggest displaced masses made the Aviles canyon change its trend to N-S in an almost 90° bend close to the middle slope. Although the displaced masses are big, it does not seem to pose an immediate hazard, as they all show a short run-out distance and, being the actual seismicity of low grade, it is not enough to trigger the fall of the unstable slope. The Ventaniella fault runs in the continental shelf and slope in NW-SE direction, but it also has been deduced with the new data a secondary fault trace slightly more W-E, interpreted as a termination in horsetail of the main strike-slip feature. Both structures seem to be responsible for the seismicity and the mass wasting processes observed along this strip of the Cantabrian margin.

Fernandez Viejo, G.; Lopez-Fernandez, C.; Dominguez-Cuesta, M.

2012-12-01

208

Open architecture framework for improved early stage submarine design  

E-print Network

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? ...

Sewell, Eli A. (Eli Anthony)

2010-01-01

209

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

210

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

211

DESCHUTES CANYON ROADLESS AREA, OREGON.  

USGS Publications Warehouse

An examination of the Deschutes Canyon Roadless Area, Oregon indicated that the area is devoid of mines and active mineral prospects or claims and that there is little likelihood for the occurrence of metallic or nonmetallic mineral resources. There is no evidence to indicate that mineral fuels are present in the roadless area. Nearby parts of central Jefferson County on the Warm Springs Indian Reservation are characterized by higher-than-normal heat flow and by numerous thermal springs, some of which have been partly developed. This may indicate that the region has some as yet undefined potential for the development of geothermal energy.

Walker, George, W.; Winters, Richard, A.

1984-01-01

212

Favorable Street Canyon Aspect Ratios for Pollutant Removal- a Large-Eddy Simulation Approach  

NASA Astrophysics Data System (ADS)

Given the limited land resource, urbanization is one of the solutions to the current rapid economic development and population growth. Narrow streets flanked by high-rise buildings, also known as street canyons, are commonly found in metropolises nowadays. In recent years, this issue has been aroused the public awareness that the air pollutants from domestic sources and vehicular emissions are unable to be removed but trapped inside the street canopy level threatening human health and our living environment. A thorough understanding of the pollutant removal mechanism is the key step to rectify the current poor urban air quality. This study is therefore conceived to examine how the pollutant removal is related to the street width and building height. Large-eddy simulation (LES) with the one-equation subgrid-scale (SGS) turbulence model is employed to investigate the characteristic ventilation and pollutant transport in idealized two-dimensional (2D) street canyons of different building-height-to-street-width (aspect) ratios (ARs) h/b. Model validation is performed by comparing the LES results with those of k-? turbulence model and laboratory experiments. A consistent trend of the pollutant exchange rate (PCH) among the LES, k-? turbulence model, and experimental results is obtained. While its drag is largest, the street canyon of AR = 0.5 is found to be most favorable in the pollutant removal perspective. This finding seems contradict with the presumption that the smaller the AR (wider the street), the more efficient the pollutants removal. In the isolated roughness regime the flows in (wider) street canyons, the entrainment from the prevailing flow aloft down into the ground level purging pollutant away. On the contrary in the skimming flow regime, in (narrower) street canyons, the recirculating flows inside the street canyon are isolated from the prevailing flow in which the (vertical) pollutant removal is governed by roof-level intermittency. Unexpectedly, in the wake interference regime, lying between isolated roughness and skimming flow regimes, the PCH is found to be the least among the three flow regimes. This is likely caused by the shallow purging air stream together with the pollutant re-entrainment from the roof level back into the street canyon. These LES results suggest that the pollutant removal is not simply proportional to the street width. Indeed, the turbulent transport processes should not be overlooked that plays a crucial role in the pollutant removal mechanisms. Hence more ARs should be considered generating a comprehensive picture for the favorable street canyon aspect ratios for better air quality.

Chung, T. N.; Liu, C.

2010-12-01

213

Narrowness and Liberality  

ERIC Educational Resources Information Center

John Agresto, whose task has been to rebuild the war-ravaged infrastructure of a Middle-Eastern university system, is discouraged to see that narrow expertise is the only goal of education there, to the utter exclusion of intellectual breadth. He comments that, although it is not that bad in the U.S., he feels that doctoral programs as currently…

Agresto, John

2003-01-01

214

Broad versus Narrow. Editorial.  

ERIC Educational Resources Information Center

Discusses the different roles played by eclectic versus specialized scholarly journals in education. The narrow focus of specialized journals is useful to scholars with limited time but may exclude authors with controversial viewpoints. Eclectic journals provide a broader picture of educational trends and a forum for scholarly debate, unorthodox…

Buck, George H.

2001-01-01

215

Introduction Fresh or brackish ground water in submarine environ-  

E-print Network

hydrodynamic phenomena (i.e., submarine ground water discharge) along the U.S. Atlantic margin are attractingIntroduction Fresh or brackish ground water in submarine environ- ments has been shown to exist the presence of submarine fresh water as far as 100 km from shore (Manheim 1967). Subsequently, most

Krantz, David

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

36. VIEW OF CUPOLA, SUBMARINE ESCAPE TRAINING TANK, SHOWING ROVING ...  

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

36. VIEW OF CUPOLA, SUBMARINE ESCAPE TRAINING TANK, SHOWING ROVING RESCUE BELL SUSPENDED ABOVE TANK, WITH TWO-LOCK RECOMPRESSION CHAMBER AT REAR, LOOKING WEST. Photo taken after installation of recompression chamber in 1956. - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

218

35. INTERIOR VIEW OF EQUIPMENT HOUSE, SUBMARINE ESCAPE TRAINING TANK, ...  

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

35. INTERIOR VIEW OF EQUIPMENT HOUSE, SUBMARINE ESCAPE TRAINING TANK, PRIOR TO ENLARGEMENT OF ROOM AND INSTALLATION OF TRIPLE-LOCK RECOMPRESSION CHAMBER IN 1957 - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

219

31. VIEW OF SUBMARINE ESCAPE TRAINING TANK DURING CONSTRUCTION OF ...  

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

31. VIEW OF SUBMARINE ESCAPE TRAINING TANK DURING CONSTRUCTION OF THE ELEVATOR AND PASSAGEWAYS TO THE 18- AND 50-FOOT LOCKS AND CUPOLA 1932 - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

220

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

221

A model for the submarine depthkeeping team  

NASA Technical Reports Server (NTRS)

The most difficult task the depthkeeping team must face occurs during periscope-depth operations during which they may be required to maintain a submarine several hundred feet long within a foot of ordered depth and within one-half degree of ordered pitch. The difficulty is compounded by the facts that wave generated forces are extremely high, depth and pitch signals are very noisy and submarine speed is such that overall dynamics are slow. A mathematical simulation of the depthkeeping team based on the optimal control models is described. A solution of the optimal team control problem with an output control restriction (limited display to each controller) is presented.

Ware, J. R.; Best, J. F.; Bozzi, P. J.; Kleinman, D. W.

1981-01-01

222

Physical volcanology of the submarine Mariana and Volcano Arcs  

NASA Astrophysics Data System (ADS)

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 the Mariana Arc tend to be simple cones. Sets of individual cones and volcanic ridges are elongate parallel to the trend of the arc or at 110° counterclockwise from that trend, suggesting a strong fault control on the distribution of arc magmas. Volcanos in the Mariana Arc are generally developed west of the frontal arc ridge, on rifted frontal arc crust or new back-arc basin crust. Volcanos in the central Mariana Arc are usually subaerial, large (> 500 km3), and spaced about 50 70 km apart. Those in the northern and southern Marianas are largely submarine, closer together, and generally less than 500 km3 in volume. There is a shoaling of the arc basement around Iwo Jima, accompanied by the appearance of incompatible-element enriched lavas with alkalic affinities. The larger volcanic edifices must reflect either a higher magma supply rate or a greater age for the larger volcanos. If the magma supply (estimated at 10 20 km3/km of arc per million years at 18° N) has been relatively constant along the Mariana Arc, we can infer a possible evolutionary sequence for arc volcanos from small, irregularly spaced edifices to large (over 1000 km3) edifices spaced at 50 70 km. The volcano distribution and basal depths are consistent with the hypothesis of back-arc propagation into the Volcano Arc.

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

1989-05-01

223

Distribution of submarine landslides along the northern Ligurian Margin (NW Mediterranean) using very high-resolution data: some insights into geohazard assessment  

NASA Astrophysics Data System (ADS)

The northern Ligurian Margin is characterized by a steep and narrow continental-slope, high-sediment supply delivered through small mountain-supplied rivers and a recurrent seismic activity favouring the destabilization of sediments. The recent history of this area is marked by several major earthquakes (M~6) and three historical tsunamis (1564, 1818, and 1887 AD). The morphology of the northern Ligurian Margin and the distribution of submarine failures on the continental slope have been studied using a large dataset including new multibeam bathymetric data (EM300), high resolution Chirp profiles and 24- and 72-channels seismic-reflection profiles collected during the MALISAR1-2 surveys (2006 and 2007) in order to discuss their triggering mechanisms. More than four hundred and fifty submarine failures of various morphology and sizes have been identified along the whole northern margin of the Ligurian Basin. Two zones, East and West, were discriminated along this margin with respect to the continental-slope morphology and the type of sedimentation/erosion processes. The greatest number of large-scale scars incising the quaternary deposits up to 100 to 400 m depth below the seafloor and testifying of large mass-wasting events are preferentially located in the western area (between the cities of Nice, France, and Imperia, Italy), whereas smaller scars are distributed homogeneously on the whole margin. Several types of failures are pointed out along the northern Ligurian Margin: (1) small-scale scars are located at the transition between the shelf and the continental slope where they contribute to the progressive erosion of the shelf which is located, in some areas, only a few hundreds of meters off the coastline or along the walls of canyons. Such type of failures represents about 60 % of the studied scars. This large number of scars affecting quaternary deposits suggests a high frequency of failures that does not allow the preservation of over-consolidated deposits on the continental slope; (2) large-scale amphitheatre-like scarps such as the “Cirque Marcel” are located at the base of the continental slope and possibly related to the seismic activity of a neighbouring fault; (3) the upper part of interfluves is sometimes incised by very vast scars cutting only superficial sediments. This type of instabilities is mainly represented in the eastern part of the basin and could have been triggered by earthquakes as well as by indirect effects of the last sea-level fluctuations. The morphological analysis of the continental slope and the study of the spatial distribution and the main features of the submarine failures help identify the main triggering mechanisms and the factors controlling the failure’s occurrence. Because of the increasing number of inhabitants settled along the Mediterranean Coast, the improvement of geohazard assessment concerning seafloor instabilities is also a relevant societal target.

Hassoun, V.; Migeon, S.; Larroque, C.; Mercier-de-Lepinay, B. F.; Cattaneo, A.

2010-12-01

224

Addressing submarine geohazards through scientific drilling  

NASA Astrophysics Data System (ADS)

Natural submarine geohazards (earthquakes, volcanic eruptions, landslides, volcanic island flank collapses) are geological phenomena originating at or below the seafloor leading to a situation of risk for off-shore and on-shore structures and the coastal population. Addressing submarine geohazards means understanding their spatial and temporal variability, the pre-conditioning factors, their triggers, and the physical processes that control their evolution. Such scientific endeavour is nowadays considered by a large sector of the international scientific community as an obligation in order to contribute to the mitigation of the potentially destructive societal effects of submarine geohazards. The study of submarine geohazards requires a multi-disciplinary scientific approach: geohazards must be studied through their geological record; active processes must be monitored; geohazard evolution must be modelled. Ultimately, the information must be used for the assessment of vulnerability, risk analysis, and development of mitigation strategies. In contrast with the terrestrial environment, the oceanic environment is rather hostile to widespread and fast application of high-resolution remote sensing techniques, accessibility for visual inspection, sampling and installation of monitoring stations. Scientific Drilling through the IODP (including the related pre site-survey investigations, sampling, logging and in situ measurements capability, and as a platform for deployment of long term observatories at the surface and down-hole) can be viewed as the centre of gravity of an international, coordinated, multi-disciplinary scientific approach to address submarine geohazards. The IODP Initial Science Plan expiring in 2013 does not address openly geohazards among the program scientific objectives. Hazards are referred to mainly in relation to earthquakes and initiatives towards the understanding of seismogenesis. Notably, the only drilling initiative presently under way is the multi-platform drilling of the Nankai seismogenic zone. Scientific initiatives are flourishing to drive IODP towards the study of submarine geohazards. In the last three years international workshops, were held to address the topic: ESF-ECORD sponsored a Magellan Workshop focussed on submarine landslides (Barcelona, Spain, 2006); IODP sponsored a world-wide Geohazard Workshop (Portland, Oregon, 2007); ESF-ECORD sponsored another Magellan Workshop focussed on Mediterranean submarine geohazards (Luleå, Sweden, 2008). In addition, following the ECORD-Net Conference on the Deep Sea Frontier (Naples, Italy, 2006), the history, monitoring and prediction of geohazards was identified as one of the 6 major areas for a European science plan to integrate Ocean Drilling, Ocean Margin, and Seabed research. More than 200 scientists and private companies representatives have been mobilized world-wide to attend these meetings, from where it emerged that Ocean Drilling will play a key role in the future to answer the following basic open questions on submarine geohazards: - What is the frequency, magnitude, and distribution of geohazard events? - Do precursory phenomena exist and can they be recognized? - What are the physical and mechanical properties of materials prone to failure? - What are the roles of preconditioning vs. triggering in rapid seafloor deformation? - Can the tsunamigenic potential of past and future events be assessed? Within the global-ocean geohazards, worth of note is the attention given in this preparatory phase to submarine geohazards in the Mediterranean basin, a miniature ocean often called a "natural laboratory" because of the diversity of geological environments it contains. The coastline is very densely-populated, totalling 160 million inhabitants sharing 46,000 km of coastline. The Mediterranean is the World's leading holiday destination, receiving an average of 135 million visitors annually. Submarine landslides, volcanic flank collapses, volcanic island eruptions, earthquakes and the associated tsunamis can lead to destruction of seaf

Camerlenghi, A.

2009-04-01

225

Benthic foraminifera from Capbreton Canyon revisited; faunal evolution after repetitive sediment disturbance  

NASA Astrophysics Data System (ADS)

At a 650 m deep site in the axis of Capbreton Canyon an 18-cm-thick turbidite was deposited in December 1999. During subsequent campaigns, an almost monospecific fauna of the benthic foraminifer Technitella melo, considered as a pioneer species, was found in May 2000. In 2001 this fauna had disappeared and was replaced by an exceptionally rich fauna strongly dominated by the opportunistic species Bolivina subaenariensis. We present sedimentological, radionuclide and foraminiferal data of new cores, sampled in 2005 and 2011, taken with the aim to study the further evolution of the benthic ecosystem. Cores sampled in 2005 show that in the canyon axis a new, ca. 5 cm thick, turbidite has been deposited. The live benthic foraminiferal faunas were much poorer than in 2001, but still had a high dominance and low diversity, although less extreme than in 2001. We conclude that in the canyon axis, benthic foraminiferal faunas remain in an early stage of ecosystem colonization. It appears that the very thick 1999 turbidite marks an exceptional event. The uncommonly rich faunas observed in 2001 could be a response to the concentration of organic-rich material in the fine-grained top of this deposit. In 2011, cores were sampled at a slightly different site, on the lower canyon flank. The sedimentary sequence here is marked by the absence of coarse turbidite layers, although some levels show slightly increased grain size, and lower 210Pbxs activities, indicative of an admixture with advected older sediments. Live foraminiferal faunas are much more equilibrated, as shown by their higher diversity, lower dominance, and deeper penetration into the sediment. All these characteristics are indicative of a much more stable ecosystem. Dead faunas are present throughout the core, indicating that the levels with slightly elevated grain size are not typical turbidites resulting from hyperpycnal currents (which are characterized by levels barren of foraminifera) but denote other, more long-term sedimentary processes leading to the advection of older material, such as bottom nepheloid layers, or repetitive fine-grained turbidite deposits due to small-scale slumping. The comparison of live and dead fauna shows that at both sites, the foraminiferal turnover rates are fairly low. At the lower canyon flank site sampled in 2011, the foraminiferal faunas are renewed every 1.5-2 years. Such a fairly long foraminiferal lifespan corresponds to earlier estimates, but is surprisingly high for the opportunistic taxa that dominate the faunal assemblages in these unstable and food-enriched submarine canyon settings.

Bolliet, T.; Jorissen, F. J.; Schmidt, S.; Howa, H.

2014-06-01

226

Baltimore Canyon Trough, a clastic-carbonate system  

SciTech Connect

Baltimore Canyon Trough is similar in age, architecture, and sedimentary framework to neighboring marginal basins offshore from eastern North America. The other basins are the Scotian and Georges Bank basins and the Carolina Trough. All contain a Jurassic-earliest Cretaceous clastic-carbonate sedimentary section composed of terrigenous basin fill and a shallow-water limestone platform. In Baltimore Canyon Trough, the platform is believed to be over 10 km thick. Upward through the Jurassic System, the platform progrades seaward and narrows. The platform top is earliest Cretaceous (Berriasian) and only about 5-15 km wide. Width of the base is indeterminate but apparently much wider. At the seaward edge of the platform is a limestone buildup and reef complex that consists of bioclastic wackestones, packstones, grainstones, and sponge-stromatoporoid-algal bindstones. Foreslope deposits are thrombolitic stromatactis-pelletal carbonate mudstones. Landward of the buildup, the platform contains numerous siliciclastic interbeds, consisting of mostly calcareous shale and siltstone with inertinite. The calciclastic lime mudstone beds of the platform contain terrigenous siliciclasts and kerogens. All units are oxidized and show considerable sedimentary reworking. Through the Jurassic System and into the Cretaceous, terrigenous clastic sediments became increasingly dominant in the basin and erosional-depositional cycles continually reworked carbonate, as well as siliciclastic, units.

Edson, G.M. (Minerals Management Service, Herndon, VA (USA))

1990-05-01

227

Physical and chemical properties of submarine basaltic rocks from the submarine flanks of the Hawaiian Islands  

USGS Publications Warehouse

To evaluate physical and chemical diversity in submarine basaltic rocks, approximately 280 deep submarine samples recovered by submersibles from the underwater flanks of the Hawaiian Islands were analyzed and compared. Based on observations from the submersibles and hand specimens, these samples were classified into three main occurrence types (lavas, coarse-grained volcaniclastic rocks, and fine-grained sediments), each with several subtypes. The whole-rock sulfur content and porosity in submarine basaltic rocks, recovered from depths greater than 2000 m, range from < 10 ppm and 2 vol.% to 2200 ppm and 47 vol.%, respectively. These wide variations cannot be due just to different ambient pressures at the collection depths, as inferred previously for submarine erupted lavas. The physical and chemical properties of the recovered samples, especially a combination of three whole-rock parameters (Fe-oxidation state, Sulfur content, and Porosity), are closely related to the occurrence type. The FSP triangular diagram is a valuable indicator of the source location of basaltic fragments deposited in deep submarine areas. This diagram can be applied to basaltic rocks such as clasts in debris-flow deposits, submarine-emplaced lava flows that may have crossed the shoreline, and slightly altered geological samples. ?? 2005 Elsevier B.V. All rights reserved.

Yokose, H.; Lipman, P. W.; Kanamatsu, T.

2005-01-01

228

Submarine transmission line: lifeline for Vieques  

Microsoft Academic Search

Lack of an adequate water supply is now a thing of the past for the island of Vieques. On Feb. 10, 1978, a submarine water transmission main from mainland Puerto Rico to Vieques was inaugurated. This facility has dramatically increased the potable water supply for the island, eliminating the need for the operation of twelve low production wells whose waters

Juan J. Mayol; José R. Goitia

1980-01-01

229

Gold plating in submarine telephone cable repeaters  

Microsoft Academic Search

Thousands of miles of submarine telephone cables form an important and growing part of the world pattern of communications.\\u000a Repeaters every few miles along these cables maintain signal strengths, and many of the components in these repeaters are\\u000a gold plated to ensure freedom from deterioration or failure in service.

D. S. Girling

1973-01-01

230

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

231

Submarine Thermal Springs on the Galapagos Rift  

Microsoft Academic Search

The submarine hydrothermal activity on and near the Galapagos Rift has been explored with the aid of the deep submersible Alvin. Analyses of water samples from hydrothermal vents reveal that hydrothermal activity provides significant or dominant sources and sinks for several components of seawater; studies of conductive and convective heat transfer suggest that two-thirds of the heat lost from new

John B. Corliss; Jack Dymond; Louis I. Gordon; John M. Edmond; Richard P. von Herzen; Robert D. Ballard; Kenneth Green; David Williams; Arnold Bainbridge; Kathy Crane; Tjeerd H. van Andel

1979-01-01

232

Researchers Find Japanese Submarine at Pearl Harbor  

NSDL National Science Digital Library

Earlier this week, researchers from the University of Hawaii and the Hawaii Underwater Research Lab located the remains of a Japanese midget submarine. Found in 1200 feet of water, the submarine was sunk by the USS Ward just an hour before the aerial attack on Pearl Harbor on December 7, 1941. Most important, the discovery of the midget submarine offers concrete physical evidence that the United States did fire the first shot against the Japanese. Previous expeditions to locate the sub, including an effort made in 2000 by the National Geographic Society, had been unsuccessful, largely due to the fact that the area is a military "junkyard" with tons of debris on the ocean floor.For more in-depth information on this story, readers may find the first four news links particularly helpful. The fifth link leads to the Hawaii Underwater Research Lab's Web site that features photographs of the midget sub from the expedition earlier this week. The sixth link is to a Web site dealing with the history and missions of the USS Ward. The final link contains detailed information about the 2000 expedition led by Robert Ballard, with support from the National Geographic Society, to find the midget submarine.

Green, Marcia.

2002-01-01

233

Chemical environments of submarine hydrothermal systems  

NASA Technical Reports Server (NTRS)

Perhaps because black-smoker chimneys make tremendous subjects for magazine covers, the proposal that submarine hydrothermal systems were involved in the origin of life has caused many investigators to focus on the eye-catching hydrothermal vents. In much the same way that tourists rush to watch the spectacular eruptions of Old Faithful geyser with little regard for the hydrology of the Yellowstone basin, attention is focused on the spectacular, high-temperature hydrothermal vents to the near exclusion of the enormous underlying hydrothermal systems. Nevertheless, the magnitude and complexity of geologic structures, heat flow, and hydrologic parameters which characterize the geyser basins at Yellowstone also characterize submarine hydrothermal systems. However, in the submarine systems the scale can be considerably more vast. Like Old Faithful, submarine hydrothermal vents have a spectacular quality, but they are only one fascinating aspect of enormous geologic systems operating at seafloor spreading centers throughout all of the ocean basins. A critical study of the possible role of hydrothermal processes in the origin of life should include the full spectrum of probable environments. The goals of this chapter are to synthesize diverse information about the inorganic geochemistry of submarine hydrothermal systems, assemble a description of the fundamental physical and chemical attributes of these systems, and consider the implications of high-temperature, fluid-driven processes for organic synthesis. Information about submarine hydrothermal systems comes from many directions. Measurements made directly on venting fluids provide useful, but remarkably limited, clues about processes operating at depth. The oceanic crust has been drilled to approximately 2.0 km depth providing many other pieces of information, but drilling technology has not allowed the bore holes and core samples to reach the maximum depths to which aqueous fluids circulate in oceanic crust. Such determinations rely on studies of pieces of deep oceanic crust uplifted by tectonic forces such as along the Southwest Indian Ridge, or more complete sections of oceanic crust called ophiolite sequences which are presently exposed on continents owing to tectonic emplacement. Much of what is thought to happen in submarine hydrothermal systems is inferred from studies of ophiolite sequences, and especially from the better-exposed ophiolites in Oman, Cyprus and North America. The focus of much that follows is on a few general features: pressure, temperature, oxidation states, fluid composition and mineral alteration, because these features will control whether organic synthesis can occur in hydrothermal systems.

Shock, Everett L.

1992-01-01

234

Mars Science Laboratory at Canyon  

NASA Technical Reports Server (NTRS)

December 2, 2003

NASA's Mars Science Laboratory travels near a canyon on Mars in this artist's concept. The mission is under development for launch in 2009 and a precision landing on Mars in 2010.

Once on the ground, the Mars Science Laboratory would analyze dozens of samples scooped up from the soil and cored from rocks as it explores with greater range than any previous Mars rover. It would investigate the past or present ability of Mars to support life. NASA is considering nuclear energy for powering the rover to give it a long operating lifespan.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., is managing development of the Mars Smart Laboratory for the NASA Office of Space Science, Washington, D.C.

2003-01-01

235

Structural Features and Gas Hydrate Distribution Across the Boundary of the Submarine Taiwan Accretionary Wedge and Passive China Continental Margin Offshore Southwestern Taiwan  

NASA Astrophysics Data System (ADS)

This study analyzes a 3D seismic data volume in the upper reach of the Penghu Submarine Canyon for gas hydrate investigation. This 3D seismic data set runs across the deformation front which separates the passive China continental slope from the Taiwan accretionary wedge. Bottom-simulating reflectors (BSRs) are widely distributed in the study area which suggests that gas hydrates are present in both the extensional and compressive structure domains. We use 3D seismic images to map the spatial distribution of BSRs, and to identify structural and sedimentary features across the deformation front. Seismic attribute analysis of the 3D seismic volume has been performed which helps to reveal structure details and physical properties of the substrata. Our study identifies detailed structural variations across the deformation front: In the passive continental slope domain, besides normal faults, buried submarine canyons and paleo-topography of the continental slope before the arc-continent collision are recognized, while in the accretionay wedge domain, the fold and thrust structures dominate. BSR distribution in the 3D box correlates well with the seafloor topography, buried channels and fluid migration paths, we suggest that there may be different gas hydrate systems for the passive continental slope and for the accretionary wedge domains. As the Penghu Submarine Canyon is an important conduit offshore southwestern Taiwan for transporting terrestrial and shallow marine sediments, we suggest that the buried channels that filled with coarse-grain sediments could be good reservoirs for gas hydrates and free gases. Accurate substrata velocity models derived from a large-offset 2D seismic profile data in the study area will help us to better estimate the gas hydrate concentration in those reservoirs.

Han, W.; Liu, C.; Lin, C.; Hsu, H.; Ko, C.; Chen, S.; Chung, S.; Wang, Y.

2012-12-01

236

High-Resolution Multibeam, Sidescan, and Subbottom Surveys in and Around Monterey Canyon Using the MBARI Mapping AUV  

NASA Astrophysics Data System (ADS)

During 2004 and 2005, MBARI has conducted several high-resolution bathymetry, sidescan, and subbottom profiler surveys in and around Monterey Canyon, Monterey Bay, California. These surveys were conducted using the new MBARI Mapping Autonomous Underwater Vehicle (AUV). This torpedo-shaped, 6000 m deep rated vehicle is equipped with a 200 kHz multibeam sonar, 110 kHz and 410 kHz chirp sidescan sonar, and a 2-16 kHz sweep subbottom profiler. The sonar package can also be mounted on ROV Ventana, allowing near-bottom bathymetric surveys of sites where extreme topography (e.g. the Monterey Canyon axis) preclude safe autonomous operation. The Mapping AUV is being used to monitor sediment transport through Monterey Canyon by conducting repeated high-resolution bathymetric surveys in the upper canyon. Upper Monterey Canyon is known to have frequent sediment transport events. Four sites have been selected with canyon axis depths of 300 m, 520 m, 1000 m, and 1400 m, respectively. Each survey nominally covers a 600 m by 600 m area with a 35 m line spacing and a 20 m altitude. We are achieving sub-meter lateral resolution and a vertical precision of 0.3 m. The combined bathymetry and backscatter successfully image fine scale channel features, including bedforms, small scarps and plunge pools, and undercutting of the inner canyon walls. All four sites have been surveyed at least once, and we will revisit these sites three times annually for the foreseeable future. We have also collected in excess of 170 km of subbottom profiles around and across the upper canyon. The subbottom profiler successfully images sediment structure to subsurface depths of as much as 50 m. These profiles demonstrate that the upper canyon walls are draped with sediment rather than exposing an erosional surface. Another Mapping AUV survey target is Smooth Ridge, located immediately north of Monterey Canyon and west of Soquel canyon. The upper reaches of Smooth Ridge are connected to the shelf across a narrow ridge, or neck, known from ROV dives to have scattered carbonate outcrops and numerous 1-2 m high scarps. We are scheduled to autonomously survey the upper neck of Smooth Ridge during October 2005, and will present initial results from these data.

Caress, D. W.; Thomas, H.; McEwen, R.; Henthorn, R.; Kirkwood, W. J.; Thompson, D.; Paull, C. K.; McGill, P.

2005-12-01

237

Potential tsunamigenic hazard associated to submarine mass movement along the Ionian continental margin (Mediterranean Sea).  

NASA Astrophysics Data System (ADS)

Submarine mass movements are natural geomorphic processes that transport marine sediment down continental slopes into deep-marine environments. Type of mass wasting include creep, slides, slump, debris flows, each with its own features and taking place over timescale from seconds to years. Submarine landslides can be triggered by a number of different causes, either internal (such as changes in physical chemical sediment properties) or external (e.g. earthquakes, volcanic activity, salt movements, sea level changes etc.). Landslides may mobilize sediments in such a way as to form an impulsive vertical displacement of a body of water, originating a wave or series of waves with long wavelengths and long periods called tsunamis ('harbor waves'). Over 600 km of continental margin has been investigated by OGS in the Ionian sea using geophysical data - morpho-bathymetry (Reson 8111, 8150) and sub-bottom profiles (7-10 KHz) - collected aboard the research vessel OGS Explora in the framework of the MAGIC Project (Marine Geohazard along the Italian Coasts), funded by the Italian Civil Protection. The objective of this project is the definition of elements that may constitute geological risk for coastal areas. Geophysical data allowed the recognition of four main types of mass wasting phenomena along the slopes of the ICM: 1) mass transport complexes (MTCs) within intra-slope basins. Seabed imagery show the slopes of all the seabed ridges to be marked by headwall scarps recording widespread failure, multiple debris flows in several basins indicate one or more past episodes of failure that may be linked to activity on the faults bounding the structural highs. 2) submarine landslide - a multiple failure event have been identified (Assi landslide) at about 6 km away from the coastline nearby Riace Marina. Headwall scars up to 50 m high across water depths of 700 to 1400 m, while sub-bottom profiles indicate stacked slide deposits at and near seabed. 4) canyon headwalls - in the upper parts of all canyons, numerous headwall scarps are consistent with retrogressive activity of the canyons. 3) possible gravity sliding -elongate seabed features oriented subparallel to contours are observed, associated with diapiric structures suggest that the elongate seabed features may record a form of downslope sediment sliding above salt. The aim of this work is to reconstruct the dynamics of different type of submarine mass movements on the tectonically active Ionian Calabrian margin (ICM), calculate the volume of sediment mobilized and assess the potential tsunamigenic hazard associated to different type of mass movements. Assessments of tsunami arrival time in adjacent coastal areas, period and wavelength of the tsunami and implication for coastal geohazards have been formulated for the Calabrian margin (small scale) and extrapolated to adjacent margins of the Mediterranean basin (large scale).

Ceramicola, S.; Tinti, S.; Praeg, D.; Zaniboni, F.; Planinsek, P.

2012-04-01

238

Flow Structure in a Bedrock Canyon (Invited)  

NASA Astrophysics Data System (ADS)

Bedrock canyon incision is widely recognized as setting the pace of landscape evolution. A variety of models link flow and sediment transport processes to the bedrock canyon incision rate. The model components that represent sediment transport processes are quite well developed in some models. In contrast, the model components that represent fluid flow remain rudimentary. Part of the reason is that there have been relatively few observations of flow structure in a bedrock canyon. Here, we present observations of flow obtained using an array of three acoustic Doppler current profilers during a 524 km long continuous centerline traverse of the Fraser River, British Columbia, Canada as it passes through a series of bedrock canyons. Through this portion of the river, the channel alternates between gravel-bedded reaches that are deeply incised into semi-consolidated glacial deposits and solid bedrock-bound reaches. We present observations of flow through 41 bedrock bound reaches of the river, derived from our centerline traverses and more detailed three-dimensional mapping of the flow structure in 2 canyons. Our observations suggest that flow in the most well-defined canyons (deep, laterally constrained, completely bedrock bound) is far more complex than that in a simple prismatic channel. As flow enters the canyon, a high velocity core plunges from the surface to the bed, causing a velocity inversion (high velocities at the bed and low velocities at the surface). This plunging flow then upwells along the canyon wall, resulting in a three-dimensional flow with counter-rotating, along-stream eddies that diverge near the bed. We observe centerline ridges along the canyon floors that result from the divergence and large-scale surface boils caused by the upwelling. This flow structure causes deep scour in the bedrock channel floor, and ensures the base of the canyon walls are swept of debris that otherwise may be deposited due to lower shear stresses abutting the walls. The observations suggest that the modeling approaches currently included in landscape evolution theories may be inadequate to capture the morphodynamics of bedrock canyons.

Venditti, J. G.; Rennie, C. D.; Church, M. A.; Bomhof, J.; Lin, M.

2013-12-01

239

Structure of Flow in a Bedrock Canyon  

NASA Astrophysics Data System (ADS)

Bedrock canyon incision is widely recognized as setting the pace of landscape evolution. A variety of models link flow and sediment transport processes to the bedrock canyon incision rate. The model components that represent sediment transport processes are quite well developed in some models. In contrast, the model components that represent fluid flow remain rudimentary. Part of the reason is that there have been relatively few observations of flow structure in a bedrock canyon. Here, we present observations of flow obtained using an array of three acoustic Doppler current profilers during a 524 km long continuous centerline traverse of the Fraser River, British Columbia, Canada as it passes through a series of bedrock canyons. Through this portion of the river, the channel alternates between gravel-bedded reaches that are deeply incised into semi-consolidated glacial deposits and solid bedrock-bound reaches. We present observations of flow through 41 bedrock bound reaches of the river, derived from our centerline traverses and more detailed three-dimensional mapping of the flow structure in 2 canyons. Our observations suggest that flow in the most well-defined canyons (deep, laterally constrained, completely bedrock bound) is far more complex than that in a simple prismatic channel. As flow enters the canyon, a high velocity core plunges from the surface to the bed, causing a velocity inversion (high velocities at the bed and low velocities at the surface). This plunging flow then upwells along the canyon wall, resulting in a three-dimensional flow with counter-rotating, along-stream eddies that diverge near the bed. We observe centerline ridges along the canyon floors that result from the divergence and large-scale surface boils caused by the upwelling. This flow structure causes deep scour in the bedrock channel floor, and ensures the base of the canyon walls are swept of debris that otherwise may be deposited due to lower shear stresses abutting the walls. The observations suggest that the rudimentary modeling approaches currently included in landscape evolution theories are inadequate to capture the morphodynamics of bedrock canyons.

Venditti, J. G.; Rennie, C. D.; Church, M. A.; Bomhof, J.; Lin, M.

2012-12-01

240

Mission Canyon (Mississippian) reservoir study, Whitney Canyon-Carter Creek Field, southwestern Wyoming thrust belt  

Microsoft Academic Search

Whitney Canyon-Carter Creek field is a giant sour gas and condensate reservoir located in extreme southwestern Wyoming in the Fossil basin area of the Wyoming thrust belt. Discovered in 1977, the field contains 36 wells within an area 13 mi long and 2 mi wide. Porous dolomites of the Mississippian Mission Canyon formation contain over 70% of total proven reserves.

J. L. Sieverding; P. E. Flynn; P. M. Harris

1987-01-01

241

Narrow Angle movie  

NASA Technical Reports Server (NTRS)

This brief three-frame movie of the Moon was made from three Cassini narrow-angle images as the spacecraft passed by the Moon on the way to its closest approach with Earth on August 17, 1999. The purpose of this particular set of images was to calibrate the spectral response of the narrow-angle camera and to test its 'on-chip summing mode' data compression technique in flight. From left to right, they show the Moon in the green, blue and ultraviolet regions of the spectrum in 40, 60 and 80 millisecond exposures, respectively. All three images have been scaled so that the brightness of Crisium basin, the dark circular region in the upper right, is the same in each image. The spatial scale in the blue and ultraviolet images is 1.4 miles per pixel (2.3 kilometers). The original scale in the green image (which was captured in the usual manner and then reduced in size by 2x2 pixel summing within the camera system) was 2.8 miles per pixel (4.6 kilometers). It has been enlarged for display to the same scale as the other two. The imaging data were processed and released by the Cassini Imaging Central Laboratory for Operations (CICLOPS) at the University of Arizona's Lunar and Planetary Laboratory, Tucson, AZ.

Photo Credit: NASA/JPL/Cassini Imaging Team/University of Arizona

Cassini, launched in 1997, is a joint mission of NASA, the European Space Agency and Italian Space Agency. The mission is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Space Science, Washington DC. JPL is a division of the California Institute of Technology, Pasadena, CA.

1999-01-01

242

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

Federal Register 2010, 2011, 2012, 2013

...consultation requirements of the Grand Canyon Protection Act (Pub. L. 102-575...Technical Work Group (TWG), a Grand Canyon Monitoring and Research Center...Canyon Dam consistent with the Grand Canyon Protection Act. The TWG is a...

2010-01-05

243

75 FR 26098 - Safety Zone; Under Water Clean Up of Copper Canyon, Lake Havasu, AZ  

Federal Register 2010, 2011, 2012, 2013

...Safety Zone; Under Water Clean Up of Copper Canyon...sponsoring the Under Water Copper Canyon Clean up, which will involve...zone; Copper Canyon Clean Up, Lake Havasu, AZ...zone will include all waters of Copper Canyon...

2010-05-11

244

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

245

Hypercortisolism as a potential concern for submariners.  

PubMed

Cortisol is a stress-response hormone that is important for survivability in fight or flight situations. Hypercortisolism is a state of chronically elevated cortisol levels due to a failure to return to, or maintain baseline levels. It is a condition that is often undiagnosed and can aid in the development of many physiological and psychological health problems. Some of the health ailments associated with hypercortisolism include metabolic syndrome, decreases in bone mineral density, and depression. Chronic stress and sleep deprivation are two common causes of hypercortisolism, both areas of concern within the submarine community. This review discusses the etiology of hypercortisolism and the likelihood of submariner vulnerability to the condition along with health problems associated with it. Lastly, strategies to prevent chronic elevation of cortisol and mitigate the potential health risks associated with the condition are covered. PMID:21197856

Reini, Seth A

2010-12-01

246

Whale Entanglements With Submarine Telecommunication Cables  

Microsoft Academic Search

Before 1955-1966, 16 instances of whale entanglement with submarine telegraphic cables were reported in the scientific literature. Here we present new information, derived from global cable fault databases, that reveals an absence of whale entanglements since 1959. This cessation coincided with the transition from telegraphic to coaxial telecommunication cables followed by the change to fiber-optic systems in the 1980s. We

Matthew Peter Wood; Lionel Carter

2008-01-01

247

Earth Currents in Short Submarine Cables  

Microsoft Academic Search

PRIOR to 1940, faults on submarine telephone cables between Great Britain and the Continent were normally located by direct-current methods employing a good wire in another cable. Confirmatory tests were usually made by the impedance-frequency method1. When the time came in 1944 to restore telephone communications, no good wires were available. The impedance-frequency method was employed for fault localization with

D. W. Cherry; A. T. Stovold

1946-01-01

248

Submarine Mass Movements and Their Consequences  

Microsoft Academic Search

\\u000a In 1929, an earthquake off the Grand Banks of Newfoundland initiated a submarine mass movement that sheared undersea communication\\u000a cables and generated a tsunami that resulted in deaths of 27 people along the south coast of Newfoundland. This event initiated\\u000a the modern realization that the seafloor is a dynamic environment with potential to do harm. More recent catastrophic examples\\u000a include

D. C. Mosher; L. Moscardelli; R. C. Shipp; J. D. Chaytor; C. D. P. Baxter; H. J. Lee; R. Urgeles

249

Analysis of the operational impacts of alternative propulsion configurations on submarine maneuverability  

E-print Network

In an effort to develop submarine designs that deliver reduced size submarines with equivalent capabilities of the current USS VIRGINIA (SSN-774 Class) submarine, a joint Navy/Defense Advanced Research Projects Agency ...

Heberley, Brian Douglas.

2011-01-01

250

16. INTERIOR VIEW OF SUBMARINE SECTION AT 110FOOT LEVEL, ESCAPE ...  

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

16. INTERIOR VIEW OF SUBMARINE SECTION AT 110-FOOT LEVEL, ESCAPE TRAINING TANK, SHOWING LADDER TO ESCAPE TANK, LOOKING SOUTH - U.S. Naval Submarine Base, New London Submarine Escape Training Tank, Albacore & Darter Roads, Groton, New London County, CT

251

Karst hydrology of Grand Canyon, Arizona, USA  

NASA Astrophysics Data System (ADS)

SummaryCaves in Grand Canyon, Arizona, USA fall into two main categories: those formed under unconfined conditions and those formed under confined conditions. This study focuses on the hydrology and paleohydrology of the confined caves in the Redwall-Muav aquifer, where the aquifer is overlain by rocks of the Supai Group and underlain by the Bright Angel Shale. Unconfined caves are discussed only in their relation to confined caves. Discharge for confined groundwater was, as it is today, primarily from the Redwall Limestone where it has been incised by the main canyon or its tributaries and where it has converged along a structural low or fault. Descent of the potentiometric surface (or water table) over time is recorded by one ore episode and six cave episodes: (1) emplacement of Cu-U ore, (2) precipitation of iron oxide in cavities, (3) dissolution of cave passages, (4) precipitation of calcite-spar linings over cave passage walls, (5) precipitation of cave mammillary coatings, (6) minor replacement of cave wall and ceiling limestone by gypsum, and (7) deposition of subaerial speleothems. The mammillary episode records the approximate position of the water table when the incision of the canyon was at that level. Discharge toward spring points has reorganized and adjusted with respect to ongoing canyon and side-canyon incision. The dissolution of Grand Canyon confined caves was the result of the mixing of epigene waters with hypogene waters so that undersaturation with respect to calcite was achieved. The karst hydrology of Grand Canyon may be unique compared to other hypogene cave areas of the world.

Hill, C. A.; Polyak, V. J.

2010-09-01

252

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

253

Effects of Wall Heating on Flow Characteristics in a Street Canyon  

NASA Astrophysics Data System (ADS)

We develop a large-eddy simulation (LES) model based on a meteorological numerical model for a real scale street-canyon flow with rough building facets heated by a given temperature. The model is applied to a canyon with the aspect ratio of unity for two idealized heating scenarios: (1) the roof and the entire upstream wall are heated, named as `assisting cases', and (2) the roof and the entire downstream wall are heated, named as `opposing cases'. These facets were heated up to 15 K above the air temperature. A wall function for temperature is proposed for a rough facet with an assumption that the thermal roughness length, z 0T, is much smaller than the aerodynamic roughness length, z 0. It is demonstrated that the sensible heat flux and canyon-air temperature are significantly influenced by the near-facet process that is parametrized by z 0T as the primary factor; other processes such as in-canyon mixing and roof-level exchange are secondary. This new finding strongly suggests that it is vital to choose an appropriate value of z 0T in a numerical simulation of street-canyon flows with the facet-air exchange processes of heat or any scalar. The finding also raises an awareness of the demand for carefully designed laboratory or field experiments of quantifying z 0T values for various urban surfaces. For the opposing cases, an unsteady penetrating narrow updraft zone appears occasionally along the heated wall and this feature is consistent field observations. The unique result indicates the superior capability of LES. The results of this study can be used to guide the parametrization of turbulent processes inside the urban canopy layer.

Cai, Xiao-Ming

2012-03-01

254

Mineral resources of the Fish Creek Canyon, Road Canyon, and Mule Canyon Wilderness Study Areas, San Juan County, Utah  

SciTech Connect

This book reports the Fish Creek Canyon (UT-060-204), Road Canyon(UT-060-201), and Mule Canyon (UT-060-205B) Wilderness Study Areas, which comprise 40,160 acres, 52,420 acres, and 5,990 acres, respectively, studied for their mineral endowment. A search of federal, state, and county records showed no current or previous mining-claim activity. No mineral resources were identified during field examination of the study areas. Sandstone and sand and gravel have no unique qualities but could have limited local use for road metal or other construction purposes. However, similar materials are abundant outside the study areas. The three study areas have moderate resource potential for undiscovered oil and gas and low resource potential for undiscovered metals, including uranium and thorium, coal, and geothermal energy.

Bove, D.J.; Shawe, D.R.; Lee, G.K.; Hanna, W.F. (Geological Survey, Reston, VA (USA)); Jeske, R.E. (US Bureau of Mines (US))

1989-01-01

255

Narrow Escape, Part I  

E-print Network

A Brownian particle with diffusion coefficient $D$ is confined to a bounded domain of volume $V$ in $\\rR^3$ by a reflecting boundary, except for a small absorbing window. The mean time to absorption diverges as the window shrinks, thus rendering the calculation of the mean escape time a singular perturbation problem. We construct an asymptotic approximation for the case of an elliptical window of large semi axis $a\\ll V^{1/3}$ and show that the mean escape time is $E\\tau\\sim\\ds{\\frac{V}{2\\pi Da}} K(e)$, where $e$ is the eccentricity of the ellipse; and $K(\\cdot)$ is the complete elliptic integral of the first kind. In the special case of a circular hole the result reduces to Lord Rayleigh's formula $E\\tau\\sim\\ds{\\frac{V}{4aD}}$, which was derived by heuristic considerations. For the special case of a spherical domain, we obtain the asymptotic expansion $E\\tau=\\ds{\\frac{V}{4aD}} [1+\\frac{a}{R} \\log \\frac{R}{a} + O(\\frac{a}{R}) ]$. This problem is important in understanding the flow of ions in and out of narrow valves that control a wide range of biological and technological function.

A. Singer; Z. Schuss; D. Holcman; R. S. Eisenberg

2004-12-15

256

Turbidity currents and submarine morphodynamics River, Coastal and Estuarine Morphodynamics: RCEM 2005 Parker & Garca (eds)  

E-print Network

Turbidity currents and submarine morphodynamics #12;#12;River, Coastal and Estuarine Morphodynamics Submarine channels systems are the conduits that allow turbidity currents to transport and deposit mate

Lajeunesse, Eric

257

Flow and mixing in Juan de Fuca Canyon, Washington  

NASA Astrophysics Data System (ADS)

We report breaking internal lee waves, strong mixing, and hydraulic control associated with wind-driven up-canyon flow in Juan de Fuca Canyon, Washington. Unlike the flow above the canyon rim, which shows a tidal modulation typical on continental shelves, the flow within the canyon is persistently up-canyon during our observations, with isopycnals tilted consistent with a geostrophic cross-canyon momentum balance. As the flow encounters a sill near the canyon entrance at the shelf break, it accelerates significantly and undergoes elevated mixing on the upstream and downstream sides of the sill. On the downstream side, a strong lee wave response is seen, with displacements of O(100 m) and overturns tens of meters high. The resulting diffusivity is O(10-2 m2 s-1), sufficient to substantially modify coastal water masses as they transit the canyon and enter the Salish Sea estuarine system.

Alford, Matthew H.; MacCready, Parker

2014-03-01

258

Diffusion-induced Ramsey narrowing  

E-print Network

A novel form of Ramsey narrowing is identified and characterized. For long-lived coherent atomic states coupled by laser fields, the diffusion of atoms in-and-out of the laser beam induces a spectral narrowing of the atomic resonance lineshape. Illustrative experiments and an intuitive analytical model are presented for this diffusion-induced Ramsey narrowing, which occurs commonly in optically-interrogated systems.

Yanhong Xiao; Irina Novikova; David F. Phillips; Ronald L. Walsworth

2005-07-19

259

Study of Pollutant Dispersion in an Urban Street Canyon.  

National Technical Information Service (NTIS)

Pollutant dispersion from an urban street canyon was studied to determine the process by which pollutants emitted at street level are transported from the canyon and to quantify the net rate of pollutant exchange between the canyon and the upper air. The ...

F. T. DePaul, C. M. Sheih

1984-01-01

260

27 CFR 9.217 - Happy Canyon of Santa Barbara.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 false Happy Canyon of Santa Barbara. 9.217 Section 9.217...Viticultural Areas § 9.217 Happy Canyon of Santa Barbara. (a) Name. The name of...described in this section is “Happy Canyon of Santa Barbara”. For purposes of part 4 of...

2012-04-01

261

27 CFR 9.217 - Happy Canyon of Santa Barbara.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Happy Canyon of Santa Barbara. 9.217 Section 9.217...Viticultural Areas § 9.217 Happy Canyon of Santa Barbara. (a) Name. The name of...described in this section is “Happy Canyon of Santa Barbara”. For purposes of part 4 of...

2010-04-01

262

27 CFR 9.217 - Happy Canyon of Santa Barbara.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Happy Canyon of Santa Barbara. 9.217 Section 9.217...Viticultural Areas § 9.217 Happy Canyon of Santa Barbara. (a) Name. The name of...described in this section is “Happy Canyon of Santa Barbara”. For purposes of part 4 of...

2013-04-01

263

27 CFR 9.217 - Happy Canyon of Santa Barbara.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Happy Canyon of Santa Barbara. 9.217 Section 9.217...Viticultural Areas § 9.217 Happy Canyon of Santa Barbara. (a) Name. The name of...described in this section is “Happy Canyon of Santa Barbara”. For purposes of part 4 of...

2011-04-01

264

27 CFR 9.217 - Happy Canyon of Santa Barbara.  

...2014-04-01 false Happy Canyon of Santa Barbara. 9.217 Section 9.217...Viticultural Areas § 9.217 Happy Canyon of Santa Barbara. (a) Name. The name of...described in this section is “Happy Canyon of Santa Barbara”. For purposes of part 4 of...

2014-04-01

265

27 CFR 9.152 - Malibu-Newton Canyon.  

...2014-04-01 2014-04-01 false Malibu-Newton Canyon. 9.152 Section 9.152...Viticultural Areas § 9.152 Malibu-Newton Canyon. (a) Name. The name of...described in this petition is “Malibu-Newton Canyon.” (b) Approved maps....

2014-04-01

266

27 CFR 9.152 - Malibu-Newton Canyon.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Malibu-Newton Canyon. 9.152 Section 9.152...Viticultural Areas § 9.152 Malibu-Newton Canyon. (a) Name. The name of...described in this petition is “Malibu-Newton Canyon.” (b) Approved maps....

2011-04-01

267

27 CFR 9.152 - Malibu-Newton Canyon.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Malibu-Newton Canyon. 9.152 Section 9.152...Viticultural Areas § 9.152 Malibu-Newton Canyon. (a) Name. The name of...described in this petition is “Malibu-Newton Canyon.” (b) Approved maps....

2010-04-01

268

27 CFR 9.152 - Malibu-Newton Canyon.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Malibu-Newton Canyon. 9.152 Section 9.152...Viticultural Areas § 9.152 Malibu-Newton Canyon. (a) Name. The name of...described in this petition is “Malibu-Newton Canyon.” (b) Approved maps....

2013-04-01

269

27 CFR 9.152 - Malibu-Newton Canyon.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Malibu-Newton Canyon. 9.152 Section 9.152...Viticultural Areas § 9.152 Malibu-Newton Canyon. (a) Name. The name of...described in this petition is “Malibu-Newton Canyon.” (b) Approved maps....

2012-04-01

270

THE SIGNIFICANCE OF ODOR FOR BEES ORIENTING ACROSS A CANYON  

E-print Network

THE SIGNIFICANCE OF ODOR FOR BEES ORIENTING ACROSS A CANYON Franz Josef BOGDANY* Stephen TABER, III* SUMMARY Honey bees (Apis mellifera L.) were step-guided across a 1,200 m wide and 200 m deep canyon. When the food source on the opposite rim of the canyon as opposed to when no scent was presented. No bees were

Boyer, Edmond

271

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

272

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

273

New constraints on oceanographic vs. seismic control on submarine landslide initiation: a geotechnical approach off Uruguay and northern Argentina  

NASA Astrophysics Data System (ADS)

Submarine landslides are common along the Uruguayan and Argentinean continental margin, but size, type and frequency of events differ significantly between distinct settings. Previous studies have proposed sedimentary and oceanographic processes as factors controlling slope instability, but also episodic earthquakes have been postulated as possible triggers. However, quantitative geotechnical slope stability evaluations for this region and, for that matter, elsewhere in the South Atlantic realm are lacking. This study quantitatively assesses continental slope stability for various scenarios including overpressure and earthquake activity, based on sedimentological and geotechnical analyses on three up to 36 m long cores collected on the Uruguayan slope, characterized by muddy contourite deposits and a locus of landslides (up to 2 km3), and in a canyon-dominated area on the northern Argentinean slope characterized by sandy contourite deposits. The results of shear and consolidation tests reveal that these distinct lithologies govern different stability conditions and failure modes. The slope sectors are stable under present-day conditions (factor of safety >5), implying that additional triggers would be required to initiate failure. In the canyon area, current-induced oversteepening of weaker sandy contourite deposits would account for frequent, small-scale slope instabilities. By contrast, static vs. seismic slope stability calculations reveal that a peak ground acceleration of at least 2 m/s2 would be required to cause failure of mechanically stronger muddy contourite deposits. This implies that, also along the western South Atlantic passive margin, submarine landslides on open gentle slopes require episodic large earthquakes as ultimate trigger, as previously postulated for other, northern hemisphere passive margins.

Ai, Fei; Strasser, Michael; Preu, Benedict; Hanebuth, Till J. J.; Krastel, Sebastian; Kopf, Achim

2014-10-01

274

The Place of the Submarine Cable in Aeronautical Communication  

Microsoft Academic Search

Difficulty in satisfying increased requirements for aeronautical communication channels appears to justify investigating the potentialities of various means of submarine cable communication as a means of easing the burden on long radio links. Relief might be found by using submarine cables to connect strategic and widely separated land stations and thus materially reduce the length of radio links required. As

J. J. Gilbert; Cable COW

1956-01-01

275

Technologies required for the future submarine cable networks  

Microsoft Academic Search

The progress of DWDM transoceanic transmission technologies enabled the immense capacity transport of the submarine cable networks and dramatically decreased the unit capacity cost. However, in order to cost-ffectively transport the large capacity traffic using the submarine cable link, the study on the network architecture will be of great importance in terms of the reduction of the system installation cost

Shu Yamamoto

2002-01-01

276

Optical Fiber Submarine Cable System Development at KDD  

Microsoft Academic Search

An optical fiber submarine cable system using longwavelength and single-mode optical fiber is expected to provide economical long-haul digital transmission. This paper describes the recent research and development on an optical fiber submarine cable system for international communication at the KDD Research and Development Laboratories. An experimental model including cable and repeaters has been designed and manufactured. An experimental repeater

YASUHIKO NIIRO

1983-01-01

277

Submarine communications cable for deep-sea application  

Microsoft Academic Search

This paper details the design and qualification of high reliability submarine cables specifically developed for the telecommunications industry. These cables are now readily available to support various offshore applications where multi low loss optical fibers and medium voltage power is required. The paper covers the design requirements specific to submarine application, such as pressure, water and gaseous ingress and installation

Gary Waterworth; I. Watson

2003-01-01

278

A Pareto Frontier for Full Stern Submarines via Genetic Algorithm  

E-print Network

A Pareto Frontier for Full Stern Submarines via Genetic Algorithm by Mark W. Thomas B.S. Electrical of Philosophy in Hydrodynamics at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY June 1998 c flMark W. Thomas, 1998 Submarines via Genetic Algorithm by Mark W. Thomas Submitted to the Department of Ocean Engineering

Coello, Carlos A. Coello

279

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

280

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

281

Introduction Submarine debris-flow deposits are often accompanied  

E-print Network

Introduction Submarine debris-flow deposits are often accompanied by isolated blocks located some landslides. A more general review on the mobility of submarine debris flows is given in this spe- cial issue by De Blasio et al. (2006a). Recently, we have investigated a simple hydrodynamic model of a rigid block

282

Simulation Architecture of Battlefield Damage Integrated Assessment for Some Submarine  

Microsoft Academic Search

A remarkable trait of submarine battle damage is its more uncertainty and association factors. Based on research of battlefield damage analysis technique (BDAT) available and battlefield damage traits of submarine, a distributed battlefield damage assessment architecture based on multi-agent (DBDAABM) had been developed. It consists of three parts including simulation environment architecture (SEA), obtaining technique of simulation data (OTSD) and

Bo Liu; Hongda Fan; Liang Ma; Hao Zuo

2007-01-01

283

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

284

Submarine Landslides along the U.S. Atlantic Margin: Their Distribution, Failure Processes, and Age  

NASA Astrophysics Data System (ADS)

We have investigated the size, distribution, failure mode, and age of submarine landslides on the seafloor along the U.S. Atlantic continental slope and rise, using near-complete multibeam bathymetry coverage, together with new and existing seismic reflection, core, and photographic data sets. These data show that open-slope and canyon-related landslides are ubiquitous features of the continental margin and in places have been a dominant mechanism of downslope sediment transport and slope-rise modification. Retrogressive and translational mechanisms are prevailing modes of failure, although earth-flows, rare in the marine realm, are present along seafloor gradients of less than 1o on the upper rise. Individual and composite open-slope landslides with scar dimensions that exceed 900 km2 in area and 100 km3 in volume and deposit run-out distances greater than 200 km are present off Georges Bank (Munson-Nygren-Retriever complex), southern New England, Cape Hatteras (Currituck and Cape Lookout landslides), and the Blake Plateau (Cape Fear landslide). While dating of several landslides along the margin suggests a link to mechanisms driven by environmental changes at the end of the Last Glacial Maximum, the ages of the majority of the observed landslides are still unknown. In an effort to address the scarcity of age information required to investigate failure process and geohazards, we are utilizing both absolute (radiocarbon and oxygen isotope) and relative dating techniques. Radiocarbon dating of shallow water mollusks from recently collected piston cores in landslide scars and debris deposits offshore of southern New England record multiple landslide events over the last 50,000 years originating from both the continental slope and upper rise. Relative ages of landslide features are obtained from cross-cutting relationships between canyons and landslide scars and related mass-transport deposits.

Chaytor, J. D.; ten Brink, U. S.; Twichell, D. C.; Baxter, C. D.; Hallam, T. D.; Brothers, D. S.

2011-12-01

285

Bioavailable compounds in sinking particulate organic matter, Blanes Canyon, NW Mediterranean Sea: Effects of a large storm and sea surface biological processes  

NASA Astrophysics Data System (ADS)

To ascertain whether the Blanes submarine canyon functions as a conduit of labile organic compounds to the deep margin, we analyzed phytopigment, protein, carbohydrate and lipid contents of sinking particles during a 6-months period comprised between a large storm event and the spring phytoplankton bloom. Four sediment traps were deployed, at 300, 900, 1200, and 1500 m depth along the axis of the canyon from November 2008 to April 2009. Fluxes of all study variables (organic carbon, proteins, carbohydrates and lipids) peaked from mid to late December. Afterwards, organic matter fluxes in the upper canyon decreased to values comparable (BC1200) or much lower (BC900) than those observed at the beginning of the monitoring period. The algal fraction of biopolymeric C (i.e. the percentage contribution of phytopigments to biopolymeric C utilized here as an indicator of particles’ freshness), ranging from 14 to about 100%, was generally low (median value about 32%), and showed the highest values from November to early December 2008 at all stations, except for the station at 1200 m which peaks in April 2009. A severe storm that occurred the 26th of December 2008 determined a strong increase in the downward transport of organic matter along the Blanes Canyon, though associated with a decrease in its nutritional quality. Values of the protein to carbohydrate ratio (utilized here as an indicator of particles’ nutritional quality) ranged from 0.4 to >2.0, increasing from late winter to early spring at 900 and 1200 m depth in association with the spring phytoplankton bloom in superficial waters. The material collected by sediment traps in spring had a higher nutritional value than in autumn-winter at both stations. According to the optimal foraging theory, the results of this study suggest that, following winter episodic events, deep-sea detritus feeders would need to ingest more detritus to fulfill their requirements for labile food than in spring, when fresher material is derived from sinking particles associated with phytoplankton blooms. We conclude that whilst submarine canyons like the Blanes Canyon act as major conduits for material exported from the continental shelf after high-energy episodic events, the supply of labile food to the deep-sea benthic ecosystem is connected to biological processes occurring at the sea surface.

Lopez-Fernandez, Pilar; Bianchelli, Silvia; Pusceddu, Antonio; Calafat, Antoni; Danovaro, Roberto; Canals, Miquel

2013-11-01

286

Geology of the Nine Canyon Map Area.  

National Technical Information Service (NTIS)

The basalt stratigraphy and structure of a 175-square kilometer area (the Nine Canyon Map Area) along the southern margin of the Pasco Basin have been studied to help assess the feasibility of a nuclear waste terminal storage facility. Detailed mapping sh...

M. G. Jones, R. D. Landon

1978-01-01

287

Valles Marineris: The Grand Canyon of Mars  

NSDL National Science Digital Library

This resource provides a general description of this system of canyons located just south of the Martian equator. Included are various images of the terrain: some photographic, some constructed from remotely sensed datasets. One set of images is presented in stereo and must be viewed with 3D glasses.

288

Vision-Based Navigation through Urban Canyons  

E-print Network

27 December 2008 We address the problem of navigating unmanned vehicles safely through urban canyons to the front while remaining centered between obstacles to the side. Through experiments on an unmanned ground, including T-junctions and 90-deg bends. Experiments on a rotorcraft unmanned aerial vehicle, which

Sukhatme, Gaurav S.

289

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

290

Evidence of clastic evaporites in the canyons of the Levant basin (Israel): implications for the Messinian salinity crisis  

NASA Astrophysics Data System (ADS)

The recognition of widespread and thick evaporite deposits below the floor of the Mediterranean Sea has boosted a long standing controversy concerning their depositional setting (shallow versus deep) and their correlation with the onshore sequences. Until a new scientific campaign might be launched to cross those deposits, the discussion is still open to speculation. Many Messinian evaporitic deposits have been interpreted as primary precipitates in very shallow-water or coastal environments, thus favouring the idea of a desiccated Mediterranean basin (Hsu et al., 1973). Recent studies have questioned this interpretation (Hardie and Lowenstein, 2004) and widespread, thick, clastic evaporite facies have been identified in the Mediterranean (Manzi et al., 2005). These clastic deposits are not compatible with a desiccation model as they were clearly emplaced by fully subaqueous, deep-water processes, ranging from submarine slides, to high- and low-density gravity flows. One of the most relevant areas for the understanding of the salinity crisis is the Levant basin where the Messinian evaporites partially fill some of the erosional features (canyons) considered to have formed as a consequence of significant drawdown related to the desiccation of the Mediterranean Sea (up to - 850 m, Druckman et al., 1995). Our complete revisitation of the available cores from onshore Israel cutting through the sedimentary filling of the Messinian canyons (Afiq 1, Ashdod 2, Be'eri Sh1, Be'eri Sh4, Jaffa 1 and Talme-Yaffe 3) revealed exclusively clastic sulfate facies. This is the first direct evidence that the Lower Evaporite Unit offshore Israel may actually consist of deep-water resedimented evaporites that were originally deposited on the margin of the Levant Basin. References Druckman Y., Buchbinder B., Martinotti G.M., Tov R.S., Aharon P., 1995. The buried Afiq Canyon (eastern Mediterranean, Israel): a case study of a Tertiary submarine canyon exposed in Late Messinian times. Marine Geology, 123, 167-185. Hardie L.A. & Lowenstein T.K., 2004. Did the Mediterranean Sea dry out during the Miocene? A reassessment of the evaporite evidence from DSDP Legs 13 and 42A cores. JSR, 74, 453-461. Hsu, K.J., Cita, M.B., and Ryan, W.B.F, 1973. The origin of the Mediterranean evaporites, in Ryan, W.B.F., et al. eds., Initial Reports of the Deep Sea Drilling Project, v. 13, Washington, 1203-1231. Manzi V., Lugli S., Ricci Lucchi F., Roveri M., 2005. Deep-water clastic evaporites deposition in the Messinian Adriatic foredeep (northern Apennines, Italy): did the Mediterranean ever dry out? Sedimentology, 52, 875-902.

Lugli, Stefano; Schreiber, B. Charlotte; Gvirtzman, Zohar; Manzi, Vinicio; Roveri, Marco

2013-04-01

291

Attack submarines: The case for negotiated reductions  

SciTech Connect

In East-West naval arms control, the realistic and genuinely useful options are fairly limited. The United States is likely to resist constraints on the numbers and operations of naval assets that serve national interests beyond East-West security. It is not altogether clear, in a post-Cold War environment, that such constraints on U.S. forces would be in the Soviet interest either. The attack submarine, however, is different - an artifact of the Cold War, with very limited utility in non-Cold War contingencies. Controlling its operations and movements has always been difficult, and is bound to remain so. But operations can be controlled indirectly, and costs can be reduced, by cutting inventories. To bring a substantial benefit, such cuts would need to be large, mutual, and to a more-or-less common ceiling. If something along the lines suggested above were agreed upon and implemented, the United States and the Soviet Union would eliminate from the world's oceans between 200 and 300 attack submarines. That would seem to be quite a respectable start toward building confidence, security, and stability at sea, and toward a more sensible force structure for both navies. 1 tab.

Lacy, J.L.

1990-12-01

292

Argon geochronology of Kilauea's early submarine history  

USGS Publications Warehouse

Submarine alkalic and transitional basalts collected by submersible along Kilauea volcano's south flank represent early eruptive products from Earth's most active volcano. Strongly alkalic basalt fragments sampled from volcaniclastic deposits below the mid-slope Hilina Bench yield 40Ar/39Ar ages from 212 ?? 38 to 280 ?? 20 ka. These ages are similar to high-precision 234 ?? 9 and 239 ?? 10 ka phlogopite ages from nephelinite clasts in the same deposits. Above the mid-slope bench, two intact alkalic to transitional pillow lava sequences protrude through the younger sediment apron. Samples collected from a weakly alkalic basalt section yield 138 ?? 30 to 166 ?? 26 ka ages and others from a transitional basalt section yield 138 ?? 115 and 228 ?? 114 ka ages. The ages are incompatible with previous unspiked K-Ar studies from samples in deep drill holes along the east rift of Kilauea. The submarine birth of Kilauea volcano is estimated at <300 ka. If the weakly alkalic sequence we dated is representative of the volcano as a whole, the transition from alkalic to tholeiitic basalt compositions is dated at ??? 150 ka. ?? 2005 Elsevier B.V. All rights reserved.

Calvert, A.T.; Lanphere, M.A.

2006-01-01

293

Comparison of performance of diesel and fuel cell based submarine power supplies  

Microsoft Academic Search

The use of diesel electric power on submarines can expose the submarine to danger from acoustic and visual detection. With an aim to reduce the amount of time the submarine is required to remain vulnerable in this way, this paper analyses a number of fuel cell diesel hybrid submarine configurations. A generic diesel electric power system model was selected as

Leigh Piper; Sumedha Rajakaruna

2010-01-01

294

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

295

A potential submarine landslide tsunami in South China Sea  

NASA Astrophysics Data System (ADS)

Submarine earthquakes and submarine landslides are two main sources of tsunamis. Tsunami hazard modeling in the South China Sea has been primarily concerned with the potential large submarine earthquakes in the Manila trench. In contrast, evaluating the regional risk posed by tsunamis generated from submarine landslide is a new endeavor. At offshore south central Vietnam, bathymetric and seismic surveys show evidence of potentially tsunamigenic submarine landslides although their ages remain uncertain. We model two hypothetical submarine landslide events at a potential site on the heavily sediment laden, seismically active, steep continental slope offshore southeast Vietnam. Water level rises along the coast of Vietnam are presented for the potential scenarios, which indicate that the southeast coastal areas of Vietnam are at considerable risk of tsunami generated offshore submarine landslides. Key references: Kusnowidjaja Megawati, Felicia Shaw, Kerry Sieh, Zhenhua Huang, Tso-Ren Wu, Y. Lin, Soon Keat Tan and Tso-Chien Pan.(2009). Tsunami hazard from the subduction megathrust of the South China Sea, Part I, Source characterization and the resulting tsunami, Journal of Asian Earth Sciences, Vol. 36(1), pp. 13-20. Enet, F., Grilli, S.T. and Watts, P. (2003). Laboratory experiments for tsunami generated by underwater landslides: comparison with numerical modeling, In: Proceedings of 13th International Conference on Offshore and Polar Engineering, Honolulu, Hawaii, USA, pp. 372-379.

Huang, Z.; Zhang, Y.; Switzer, A. D.

2010-12-01

296

Modelling flow dynamics in an active submarine channel  

NASA Astrophysics Data System (ADS)

A novel 2.5D shallow water model, incorporating vertical stratification of flow density and velocity, has been developed to investigate the hydro- and morphodynamics of submarine meandering systems. Successfully verified against rigorous analytical and numerical test cases, the model has been applied to investigate the flow dynamics within an active submarine channel, formed at the exit of the Strait of Bosphorous in the SW Black Sea. Further, the model has been verified by comparing predicted flow hydrodynamic conditions, including velocity, density and stratification, to equivalent data directly observed within the Black Sea submarine channel. Development of the model has highlighted the importance of stratification as a primary control on submarine flow hydrodynamics. Data obtained from the Black Sea submarine channel system, and the model presented herein, demonstrates that in submarine systems density stratification acts to keep the majority of the flow bounded within the channel system, with a dilute mixing layer forming above the channel boundaries. As stratification diminishes, flow overspill from the channel increases, suggesting a degree of topographic control of flow stratification not accounted for in current empirical models of submarine flow dynamics. We also highlight the fundamental differences in flow dynamics between poorly stratified saline density currents and highly stratified turbidity currents. Specifically, we suggest that flow stratification enables turbidity currents to be contained more readily within their channel systems and therefore to develop over longer distances than equivalent saline density currents.

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

2013-04-01

297

EAARL submarine topography: Biscayne National Park  

USGS Publications Warehouse

This lidar-derived submarine topography map was produced as a collaborative effort between the U.S. Geological Survey (USGS) Coastal and Marine Geology Program, National Park Service (NPS) South Florida/Caribbean Network Inventory and Monitoring Program, and the National Aeronautics and Space Administration (NASA) Wallops Flight Facility. One objective of this research is to create techniques to survey coral reefs for the purposes of habitat mapping, ecological monitoring, change detection, and event assessment (for example: bleaching, hurricanes, disease outbreaks). As part of this project, data from an innovative instrument under development at the NASA Wallops Flight Facility, the NASA Experimental Airborne Advanced Research Lidar (EAARL) are being used. This sensor has the potential to make significant contributions in this realm for measuring water depth and conducting cross-environment surveys. High spectral resolution, water-column correction, and low costs were found to be key factors in providing accurate and affordable imagery to managers of coastal tropical habitats.

Brock, John C.; Wright, C. Wayne; Patterson, Matt; Nayegandhi, Amar; Patterson, Judd; Harris, Melanie S.; Mosher, Lance

2006-01-01

298

Directional VLF antenna for communicating with submarines  

NASA Astrophysics Data System (ADS)

High-power, very low frequency transmitters for communicating with submarines use electrically short, top-loaded, vertical monopoles. These are efficient radiators of the lateral surface wave, but since they are omnidirectional, they expose residents of neighboring urban areas to possibly harmful effects. A possible alternative, the horizontal traveling-wave antenna of the Beverage type, is analyzed, and the design for the frequency range from 10 to 30 kHz is described. The antenna is highly directive in the horizontal plane. Although the field of the unit horizontal dipole over the earth is much smaller than that of the unit vertical dipole, the large effective length of the traveling-wave antenna makes its field comparable to that of the electrically short vertical monopole. Furthermore, since the radiated field in all directions except within a 30° to 60° angle out to sea is small, there is no exposure risk when the electrically long horizontal antenna is located near inhabited areas.

King, Ronold W. P.

1997-01-01

299

Underwater splice for submarine coaxial cable  

SciTech Connect

The invention is a device for splicing submarine coaxial cable underwater on the seafloor with a simple push-on operation to restore and maintain electrical and mechanical strength integrity; the splice device is mateable directly with the severed ends of a coaxial cable to be repaired. Splicing assemblies comprise a dielectric pressure compensating fluid filled guide cavity, a gelled castor oil cap and wiping seals for exclusion of seawater, electrical contacts, a cable strength restoration mechanism, and a pressure compensation system for controlled extrusion of and depletion loss prevention of dielectric seal fluid during cable splicing. A splice is made underwater by directly inserting prepared ends of coaxial cable, having no connector attachments, into splicing assemblies.

Inouye, A.T.; Roe, T. Jr.; Tausing, W.R.; Wilson, J.V.

1984-10-30

300

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

301

Surfacing Rescue Container concept design for trident submarines  

E-print Network

In the wake of the KURSK tragedy, world navies have brought their full attention to the submarine rescue problem. While many rescue systems exist, none have been able to sufficiently address the gamut of scenarios that ...

LaPenna, Joshua J. (Joshua Jonathan)

2009-01-01

302

Ocean circulation promotes methane release from gas hydrate outcrops at the NEPTUNE Canada Barkley Canyon node  

NASA Astrophysics Data System (ADS)

The NEPTUNE Canada cabled observatory network enables non-destructive, controlled experiments and time-series observations with mobile robots on gas hydrates and benthic community structure on a small plateau of about 1 km2 at a water depth of 870 m in Barkley Canyon, about 100 km offshore Vancouver Island, British Columbia. A mobile Internet operated vehicle was used as an instrument platform to monitor and study up to 2000 m2 of sediment surface in real-time. In 2010 the first mission of the robot was to investigate the importance of oscillatory deep ocean currents on methane release at continental margins. Previously, other experimental studies have indicated that methane release from gas hydrate outcrops is diffusion-controlled and should be much higher than seepage from buried hydrate in semipermeable sediments. Our results show that periods of enhanced bottom currents associated with diurnal shelf waves, internal semidiurnal tides, and also wind-generated near-inertial motions can modulate methane seepage. Flow dependent destruction of gas hydrates within the hydrate stability field is possible from enhanced bottom currents when hydrates are not covered by either seafloor biota or sediments. The calculated seepage varied between 40-400 ?mol CH4 m-2 s-1. This is 1-3 orders of magnitude higher than dissolution rates of buried hydrates through permeable sediments and well within the experimentally derived range for exposed gas hydrates under different hydrodynamic boundary conditions. We conclude that submarine canyons which display high hydrodynamic activity can become key areas of enhanced seepage as a result of emerging weather patterns due to climate change.

Thomsen, Laurenz; Barnes, Christopher; Best, Mairi; Chapman, Ross; Pirenne, Benoît; Thomson, Richard; Vogt, Joachim

2012-08-01

303

Numerical estimation of the effective albedo of an urban canyon  

Microsoft Academic Search

Summary  The paper focuses on the absorption of shortwave radiation in an urban street canyon. To test the effective albedo of the\\u000a canyon an analytic solution of the multiple reflection problem is applied. The infinitesimally long canyon is divided into\\u000a slices and a matrix of view factors for the slices is defined. Incoming shortwave radiation includes direct and diffuse parts\\u000a and

K. Fortuniak

2008-01-01

304

Lake Powell, Colorado River, Utah and Grand Canyon, Arizona  

NASA Technical Reports Server (NTRS)

In this stark desert scene, Lake Powell, the Colorado River and the Grand Canyon (36.5N, 111.5W) provide the only relief and source of water. The creation of Lake Powell by the building of the Glen Canyon High Dam led directly to the establishment of a National Recreation Area surrounding the lakes. To the south, following the course of the Colorado River, the NE corner of Grand Canyon can be seen.

1973-01-01

305

Flood Geology and the Grand Canyon: A Critique  

Microsoft Academic Search

Four claims of Flood Geology—as they are related to the Grand Canyon and specifically to the book Grand Canyon: A Different View—are evaluated by directly addressing Young Earth Creationist arguments, by showing rock features that belie these claims, and by presenting the most up-to-date scientific theories on the origin of the Grand Canyon. We conclude that Young Earth Creationism promotes

Carol A. Hill; Stephen O. Moshier

2009-01-01

306

78 FR 25404 - Proposed Establishment of Class E Airspace; Grand Canyon, AZ  

Federal Register 2010, 2011, 2012, 2013

...Establishment of Class E Airspace; Grand Canyon, AZ AGENCY: Federal Aviation...establish Class E airspace at the Grand Canyon VHF Omni-Directional Radio Range...VOR/DME) navigation aid, Grand Canyon, AZ, to facilitate...

2013-05-01

307

78 FR 40381 - Establishment of Class E Airspace; Grand Canyon, AZ  

Federal Register 2010, 2011, 2012, 2013

...Establishment of Class E Airspace; Grand Canyon, AZ AGENCY: Federal Aviation...establishes Class E airspace at the Grand Canyon VHF Omni-Directional Radio Range...VOR/DME) navigation aid, Grand Canyon, AZ, to facilitate...

2013-07-05

308

33 CFR 165.1155 - Security Zone; Diablo Canyon Nuclear Power Plant, Avila Beach, California.  

... Security Zone; Diablo Canyon Nuclear Power Plant, Avila Beach, California... Security Zone; Diablo Canyon Nuclear Power Plant, Avila Beach, California...000 yard radius of Diablo Canyon Nuclear Power Plant centered at position...

2014-07-01

309

78 FR 3879 - Ochoco National Forest, Paulina Ranger District; Oregon; Fox Canyon Cluster Allotment Management...  

Federal Register 2010, 2011, 2012, 2013

...Forest, Paulina Ranger District; Oregon; Fox Canyon Cluster Allotment Management Plan...allotments on the Paulina Ranger District. The Fox Canyon Cluster project area is located approximately...four allotments are Antler, Brush Creek, Fox Canyon, and Gray Prairie. The...

2013-01-17

310

33 CFR 165.1155 - Security Zone; Diablo Canyon Nuclear Power Plant, Avila Beach, California.  

Code of Federal Regulations, 2011 CFR

... Security Zone; Diablo Canyon Nuclear Power Plant, Avila Beach, California... Security Zone; Diablo Canyon Nuclear Power Plant, Avila Beach, California...000 yard radius of Diablo Canyon Nuclear Power Plant centered at position...

2011-07-01

311

33 CFR 165.1155 - Security Zone; Diablo Canyon Nuclear Power Plant, Avila Beach, California.  

Code of Federal Regulations, 2012 CFR

... Security Zone; Diablo Canyon Nuclear Power Plant, Avila Beach, California... Security Zone; Diablo Canyon Nuclear Power Plant, Avila Beach, California...000 yard radius of Diablo Canyon Nuclear Power Plant centered at position...

2012-07-01

312

33 CFR 165.1155 - Security Zone; Diablo Canyon Nuclear Power Plant, Avila Beach, California.  

Code of Federal Regulations, 2010 CFR

... Security Zone; Diablo Canyon Nuclear Power Plant, Avila Beach, California... Security Zone; Diablo Canyon Nuclear Power Plant, Avila Beach, California...000 yard radius of Diablo Canyon Nuclear Power Plant centered at position...

2010-07-01

313

33 CFR 165.1155 - Security Zone; Diablo Canyon Nuclear Power Plant, Avila Beach, California.  

Code of Federal Regulations, 2013 CFR

... Security Zone; Diablo Canyon Nuclear Power Plant, Avila Beach, California... Security Zone; Diablo Canyon Nuclear Power Plant, Avila Beach, California...000 yard radius of Diablo Canyon Nuclear Power Plant centered at position...

2013-07-01

314

DOI Strategic Sciences Working Group Mississippi Canyon 252/Deepwater Horizon Oil Spill  

E-print Network

DOI Strategic Sciences Working Group Mississippi Canyon 252/Deepwater Horizon Oil Spill Strategic Sciences Working Group Mississippi Canyon 252/Deepwater Horizon Oil Spill Progress Report Executive Summary Introduction and Objectives The Mississippi Canyon 252/Deepwater Horizon (MS252) oil spill

Torgersen, Christian

315

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

...2014-07-01 false Copper Canyon, Lake Havasu, Colorado River-Regulated Navigation...District § 165.1171 Copper Canyon, Lake Havasu, Colorado River—Regulated Navigation...1) In the water area of Copper Canyon, Lake Havasu, Colorado River,...

2014-07-01

316

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

Federal Register 2010, 2011, 2012, 2013

...CP12-49-000] Mississippi Canyon Gas Pipeline, LLC; Notice of Request Under...17, 2012, Mississippi Canyon Gas Pipeline, LLC (MCGP), 1100 Louisiana...Compliance, Mississippi Canyon Gas Pipeline, LLC, 1100 Louisiana Suite...

2012-02-06

317

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

318

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

319

Submarine Landslides at Santa Catalina Island, California  

NASA Astrophysics Data System (ADS)

Santa Catalina Island is an active tectonic block of volcanic and metamorphic rocks originally exposed during middle Miocene transtension along the evolving Pacific-North America transform plate boundary. Post-Miocene transpression created the existing large pop-up structure along the major strike-slip restraining bend of the Catalina fault that forms the southwest flank of the uplift. Prominent submerged marine terraces apparent in high-resolution bathymetric maps interrupt the steep submarine slopes in the upper ~400 meters subsea depths. Steep subaerial slopes of the island are covered by Quaternary landslides, especially at the sea cliffs and in the blueschist metamorphic rocks. The submarine slopes also show numerous landslides that range in area from a few hectares to more than three sq-km (300 hectares). Three or more landslides of recent origin exist between the nearshore and first submerged terrace along the north-facing shelf of the island's West End. One of these slides occurred during September 2005 when divers observed a remarkable change in the seafloor configuration after previous dives in the area. Near a sunken yacht at about 45-ft depth where the bottom had sloped gently into deeper water, a "sinkhole" had formed that dropped steeply to 100-ft or greater depths. Some bubbling sand was observed in the shallow water areas that may be related to the landslide process. High-resolution multibeam bathymetry acquired in 2008 by CSU Monterey Bay show this "fresh" slide and at least two other slides of varying age along the West End. The slides are each roughly 2 hectares in area and their debris aprons are spread across the first terrace at about 85-m water depth that is likely associated with the Last Glacial Maximum sealevel lowstand. Larger submarine slides exist along the steep Catalina and Catalina Ridge escarpments along the southwest flank of the island platform. A prominent slide block, exceeding 3 sq-km in area, appears to have slipped more than 5-km down the escarpment, dropping about 550-m and leaving a 1.2-km wide by 30-m deep trench behind in its wake. High-resolution multichannel seismic reflection profiles (MCS) show a finely-layered internal structure of the slide and deformation in the underlying slope sediments. The head scarp area appears to be a bedrock outcrop, possibly exposed metamorphic basement of the Catalina Schist based on island outcrops in this area and the laminated internal structure. The toe of the slide block coincides with a youthful fault that shows west-side up (upward facing) separation, suggesting that an existing seafloor fault scarp may have halted the slide. Possibly a large earthquake that formed the scarp also triggered the slide. Another fault with west-side up displacement exists about 3-km behind (east of) the toe of the slide and deforms the seafloor, which we suggest represents post-slide seafloor fault rupture. A large bedrock slide traveling more than 5-km laterally and dropping more than 500-m likely represents a catastrophic failure and rapid slip capable of producing a locally destructive tsunami. A thin veneer of sediment, less than 15-m, may cover the slide block, but higher resolution data are required to more accurately measure sediment cover and estimate the slide age.

Legg, M. R.; Francis, R. D.

2011-12-01

320

The 3D visualization technology research of submarine pipeline based Horde3D GameEngine  

NASA Astrophysics Data System (ADS)

With the development of 3D display and virtual reality technology, its application gets more and more widespread. This paper applies 3D display technology to the monitoring of submarine pipeline. We reconstruct the submarine pipeline and its surrounding submarine terrain in computer using Horde3D graphics rendering engine on the foundation database "submarine pipeline and relative landforms landscape synthesis database" so as to display the virtual scene of submarine pipeline based virtual reality and show the relevant data collected from the monitoring of submarine pipeline.

Yao, Guanghui; Ma, Xiushui; Chen, Genlang; Ye, Lingjian

2013-10-01

321

Spectral narrowing via quantum coherence  

SciTech Connect

We have studied the transmission through an optically thick {sup 87}Rb vapor that is illuminated by monochromatic and noise-broadened laser fields in {lambda} configuration. The spectral width of the beat signal between the two fields after transmission through the atomic medium is more than 1000 times narrower than the spectral width of this signal before the medium.

Mikhailov, Eugeniy E.; Rostovtsev, Yuri V.; Zhang Aihua; Welch, George R. [Department of Physics and Institute of Quantum Studies, Texas A and M University, College Station, Texas 77843-4242 (United States); Sautenkov, Vladimir A. [Department of Physics and Institute of Quantum Studies, Texas A and M University, College Station, Texas 77843-4242 (United States); P. N. Lebedev Institute of Physics, 119991 Moscow (Russian Federation); Zubairy, M. Suhail [Department of Physics and Institute of Quantum Studies, Texas A and M University, College Station, Texas 77843-4242 (United States); Department of Electronics, Quaid-i-Azam University, Islamabad (Pakistan); Scully, Marlan O. [Department of Physics and Institute of Quantum Studies, Texas A and M University, College Station, Texas 77843-4242 (United States); Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States)

2006-07-15

322

Spectral Narrowing via Quantum Coherence  

E-print Network

We have studied the transmission of an optically thick Rb vapor that is illuminated by monochromatic and noise broaden laser fields in Lambda configuration. The spectral width of the beat signal between the two fields after transmission through the atomic medium is more than 1000 times narrower than the spectral width of this signal before the medium.

Eugeniy E. Mikhailov; Vladimir A. Sautenkov; Yuri V. Rostovtsev; Aihua Zhang; M. Suhail Zubairy; Marlan O. Scully; George R. Welch

2005-03-08

323

Supplement to The Snake Hells Canyon Subbasin Plan Introduction  

E-print Network

1 Supplement to The Snake Hells Canyon Subbasin Plan Introduction This document was written.nwppc.org). Information in this supplement was reviewed and edited by the Hells Canyon Planning Team during the fall of 2004. This supplement is presented in four sections that correspond to information requested

324

The Grand Canyon of the Yellowstone Online Tour  

NSDL National Science Digital Library

This Yellowstone National Park website offers an online tour of the Grand Canyon of the Yellowstone. Prominent viewpoints of the canyon are highlighted with photos and information concerning their history. Other stops include information on giant glacial boulders and waterfalls. Similar tours of the Old Faithful area, the Norris Geyser Basin, the Fountain Paint Pots, and the Mammoth Hot Springs are also available online.

Park, Yellowstone N.

325

The Grand Canyon: The Top Two Rock Layers  

NSDL National Science Digital Library

Watch this short video clip to learn more about the rock layers of the Grand Canyon. This video discusses the two sandstone formations that comprise the uppermost part of the canyon. The video also discusses how the two sandstone layers were formed.

2006-01-01

326

A review of proposed Glen Canyon Dam interim operating criteria  

Microsoft Academic Search

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 criteria set specific limits on dam releases, including maximum and minimum flows, up-ramp and down-ramp rates, and maximum

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

1992-01-01

327

20140430_Green Machine Florida Canyon Hourly Data  

DOE Data Explorer

Employing innovative product developments to demonstrate financial and technical viability of producing electricity from low temperature geothermal fluids, coproduced in a mining operation, by employing ElectraTherm's modular and mobile heat-to-power "micro geothermal" power plant with output capacity expected in the 30-70kWe range. The Green Machine is an Organic Rankine Cycle power plant. The Florida Canyon machine is powered by geothermal brine with air cooled condensing. The data provided is an hourly summary from 01 April to 30 April 2014.

Joe Thibedeau

328

Numerical Methods in Offshore Geotechnics: Applications to Submarine Landslides and Anchor Plates  

E-print Network

communities and the offshore industry can be impacted directly by geohazards, such as submarine slope failures, or by tsunamis generated by the failed mass movements. This study aims at evaluating the triggering mechanisms of submarine landslide under cyclic...

Nouri, Hamid Reza

2013-05-08

329

Intrinsic controls on the range of volumes, morphologies, and dimensions of submarine lobes  

NASA Astrophysics Data System (ADS)

Submarine lobe dimensions from six different systems are compared: 1) the exhumed Permian Fan 3 lobe complex of the Tanqua Karoo, South Africa; 2) the modern Amazon fan channel-mouth lobe complex, offshore Brazil; 3) a portion of the modern distal Zaïre fan, offshore Angola/Congo; 4) a Pleistocene fan of the Kutai basin, subsurface offshore Indonesia; 5) the modern Golo system, offshore east Corsica, France; and 6) a shallow subsurface lobe complex , offshore Nigeria. These six systems have significantly different source-to-sink configurations (shelf dimension and slope topography), sediment supply characteristics (available grain size range and supply rate), tectonic settings, (palaeo) latitude, and delivery systems. Despite these differences, lobe deposits share similar geometric and dimensional characteristics. Lobes are grouped into two distinct populations of geometries that can be related to basin floor topography. The first population corresponds to areally extensive but thin lobes (average width 14 km × length 35 km × thickness 12 m) that were deposited onto low relief basin floor areas. Examples of such systems include the Tanqua Karoo, the Amazon, and the Zaïre systems. The second population corresponds to areally smaller but thicker lobes (average width 5 km × length 8 km × thickness 30 m) that were deposited into settings with higher amplitude of relief, like in the Corsican trough, the Kutai basin, and offshore Nigeria. The two populations of lobe types, however, share similar volumes (a narrow range around 1 or 2 km 3), which suggests that there is a control to the total volume of sediment that individual lobes can reach before they shift to a new locus of deposition. This indicates that the extrinsic processes control the number of lobes deposited per unit time rather than their dimensions. Two alternative hypotheses are presented to explain the similarities in lobe volumes calculated from the six very different systems. The first states that the wide range of starting flow volume and grain size across all systems enters the basin floor as a narrow range due to slope 'filtering' via more overspill and intra-channel deposition in larger systems. The second hypothesis is a result of the gradual decrease in downstream gradient from the distributive channel base to the lobe top during lobe growth. This is not sustainable as the channel will start to aggrade, and when a steeper lateral gradient is present, an avulsion will occur to an adjacent depositional low, which will be used for flows to fill and build a new lobe. This analysis of submarine lobe volumes indicates that the basin floor topography influences lobe geometry, but the fact that lobe volumes have a narrow range indicates a strong influence of intrinsic processes.

Prélat, A.; Covault, J. A.; Hodgson, D. M.; Fildani, A.; Flint, S. S.

2010-12-01

330

Atmospheric Fragmentation of the Canyon Diablo Meteoroid  

NASA Technical Reports Server (NTRS)

About 50 kyr ago the impact of an iron meteoroid excavated Meteor Crater, Arizona, the first terrestrial structure widely recognized as a meteorite impact crater. Recent studies of ballistically dispersed impact melts from Meteor Crater indicate a compositionally unusually heterogeneous impact melt with high SiO2 and exceptionally high (10 to 25% on average) levels of projectile contamination. These are observations that must be explained by any theoretical modeling of the impact event. Simple atmospheric entry models for an iron meteorite similar to Canyon Diablo indicate that the surface impact speed should have been around 12 km/s [Melosh, personal comm.], not the 15-20 km/s generally assumed in previous impact models. This may help explaining the unusual characteristics of the impact melt at Meteor Crater. We present alternative initial estimates of the motion in the atmosphere of an iron projectile similar to Canyon Diablo, to constraint the initial conditions of the impact event that generated Meteor Crater.

Pierazzo, E.; Artemieva, N. A.

2005-01-01

331

Wave effects on submarine groundwater seepage measurement  

NASA Astrophysics Data System (ADS)

Variation of sea-surface and water pressure above the sea bed induces temporal variation of submarine groundwater discharge over time scales ranging from seconds to years. Hydrodynamic theory and measurements suggest that wave-induced exchange between a permeable sediment bed and overlying water column is significant but conventional seepage-meter studies have focussed mainly on tidal dynamics and ignored waves. At Cockburn Sound in Western Australia we measured wave-induced flow reversals through a seepage meter of amplitude 60cmd; however, it was unclear whether the measured flows were real seepage or, partly or wholly, an artifact of wave action on the seepage meter. A numerical model of seepage patterns beneath a vented benthic chamber demonstrated an observer effect introduced by the chamber and not previously identified. Placing a chamber on the sediment bed disturbed the pressure field and changed both the pattern and magnitude of the wave-induced flow. A separate analysis of benthic-chamber movements under the action of shallow surface waves established that micron-scale movements of the chamber at the wave frequency were sufficient to produce apparent seepage amplitudes of O(1-100) cm d -1. We concluded that wave action is a key control on bed seepage and should not be neglected without justification in direct-measurement studies of marine bed discharge. A systematic error during each wave cycle can accumulate to a significant measurement error if the wave cycle error is large or if wave-induced flow is the dominant component of the seepage. In the latter case, the error could potentially be misinterpreted as a steady seepage component.

Smith, Anthony J.; Herne, David E.; Turner, Jeffrey V.

2009-06-01

332

Association of submarine cable reliability and network protection for very high availability transoceanic transmission networks  

Microsoft Academic Search

To match the bandwidth requirements of our fast-growing communication world, submarine networks have to provide ever greater transmission capacity. Thus, almost 2 Tbit\\/s will soon be the capacity available in submarine networks. A high level of availability is achieved owing to a very reliable submarine cable and to powerful network protection mechanisms.

Steven Desbrulais; Vincent Lemaire; Loic Le Gall; Christophe Mathieu

1999-01-01

333

Submarine Communications Cables and Law of the Sea: Problems in Law and Practice  

Microsoft Academic Search

Submarine communications cables laid on the seabed of the ocean are the foundation of the world's international telecommunications network. International law, in particular, the law of the sea, has recognized the freedom to lay submarine cables and perform associated operations and has placed certain obligations on states related to the protection of submarine cables. This article examines the international law

Tara Davenport

2012-01-01

334

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

Code of Federal Regulations, 2012 CFR

...submarine cables and pipelines on nautical charts. 209.310 Section 209.310 Navigation...submarine cables and pipelines on nautical charts. (a) The policy of the Corps of...submarine cables and pipelines on nautical charts published by the Corps of Engineers...

2012-07-01

335

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

Code of Federal Regulations, 2011 CFR

...submarine cables and pipelines on nautical charts. 209.310 Section 209.310 Navigation...submarine cables and pipelines on nautical charts. (a) The policy of the Corps of...submarine cables and pipelines on nautical charts published by the Corps of Engineers...

2011-07-01

336

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

Code of Federal Regulations, 2010 CFR

...submarine cables and pipelines on nautical charts. 209.310 Section 209.310 Navigation...submarine cables and pipelines on nautical charts. (a) The policy of the Corps of...submarine cables and pipelines on nautical charts published by the Corps of Engineers...

2010-07-01

337

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

Code of Federal Regulations, 2013 CFR

...submarine cables and pipelines on nautical charts. 209.310 Section 209.310 Navigation...submarine cables and pipelines on nautical charts. (a) The policy of the Corps of...submarine cables and pipelines on nautical charts published by the Corps of Engineers...

2013-07-01

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

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

340

Ferromagnetic Cylinders in Earth's Magnetic Field-a Two-Dimentional Model of Magnetization of Submarine  

Microsoft Academic Search

For an optimal design of degaussing system of a submarine, a thorough understanding of magnetization of a submarine in the earth's magnetic field is required. As a prelude of three-dimensional modeling of a submarine, in this paper is presented an analysis of magnetization of a two-dimensional magnetizable cylinder placed in the earth's magnetic field. The cylinder is of infinite length

X. B. Xu; L. Zeng

1998-01-01

341

Analysis of 3000 T class submarines equipped with polymer electrolyte fuel cells  

Microsoft Academic Search

The naval submarines have conventionally been equipped with diesel-electric propulsion. The diesel generators charge the batteries when the submarine is at the surface or at snorkelling depth. This is the biggest short-coming of this system as the submarine can be detected due to the infrared signatures from the exhaust of engines. Present study aims in analysing the feasibility of using

P. C. Ghosh; U. Vasudeva

2011-01-01

342

Using Ambient Noise Fields for Submarine Team #525 for the Mathematical Contest in Modeling  

E-print Network

that the measurements of sound are to be made by an array of transducers (piezo-electric crystal microphones) suspen with transducers, submarine, and planar noise waves transducer array Page 3 of 30 #12;#525 Submarine LocationUsing Ambient Noise Fields for Submarine Location Team #525 for the Mathematical Contest

Mitchener, W. Garrett

343

Submarine Ring of Fire 2004 -Mariana Arc R/V Thomas G. Thompson, Cruise TN167  

E-print Network

#12;Submarine Ring of Fire 2004 - Mariana Arc R/V Thomas G. Thompson, Cruise TN167 March 27 - April..............................................................................................................................................3 1.0 SUBMARINE RING OF FIRE 2004 CRUISE SUMMARY (Bob Embley..........................................................................................................25 3.0 SUBMARINE RING OF FIRE (SROF) 2004 DISCIPLINE SUMMARIES

344

28. Fern Canyon (Meier 1979) This established RNA is on the San Dimas  

E-print Network

28. Fern Canyon (Meier 1979) Location This established RNA is on the San Dimas Experimental Forest of bigcone Douglas-fir (BDF) at Fern Canyon have burned recently (1975). Poor reproduction suggestsUSDA Forest Service General Technical Report PSW-GTR-188. 2004. 28. Fern Canyon Figure 58--Fern Canyon

Standiford, Richard B.

345

Parameter study of sound propagation between city canyons with a coupled FDTD-PE model  

Microsoft Academic Search

A parameter study is performed for the case of two-dimensional sound propagation from a (source) city canyon to a nearby, identical (receiver) city canyon. Focus was on sound pressure levels, relative to the free field, in the shielded canyon. An accurate and efficient coupled FDTD-PE model was applied, exploiting symmetry of the source and receiver canyon. With the proposed calculation

Timothy Van Renterghem; E. Salomons; D. Botteldooren

2006-01-01

346

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

347

Spectral narrowing via quantum coherence  

E-print Network

Spectral narrowing via quantum coherence Eugeniy E. Mikhailov,1 Vladimir A. Sautenkov,1,2 Yuri V. Rostovtsev,1 Aihua Zhang,1 M. Suhail Zubairy,1,3 Marlan O. Scully,1,4 and George R. Welch1 1Department of Physics and Institute of Quantum Studies... discussions and grate- fully acknowledge the support from the Office of Naval Re- search, the Air Force Research Laboratory #1;Rome, NY#2;, De- fense Advanced Research Projects Agency, and the Robert A. Welch Foundation #1;Grant No. A1261#2;. #3;1#4; S. E...

Mikhailov, Eugeniy E.; Sautenkov, Vladimir A.; Rostovtsev, Yuri V.; Zhang, Aihua; Zubairy, M. Suhail; Scully, Marlan O.; Welch, George R.

2006-01-01

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

Flushing of a buoyant pollutant from an urban canyon  

NASA Astrophysics Data System (ADS)

We examine the wind driven flushing of a negatively buoyant pollutant from an urban canyon. We examine the rate at which a fluid of buoyancy g' is removed from a two dimensional urban canyon of width W formed by two buildings of height H and square cross section. The flushing is driven by a wind flow, of mean velocity U, normal to the axis of the canyon. A previous study of flushing of a neutrally buoyant fluid by Caton et al. (2003) showed that the mean concentration decayed exponentially with time indicating a steady exchange of fluid between the canyon and the flow above and a uniformly well mixed canyon. However, for the case of a negatively buoyant pollutant, the fluid buoyancy will tend to suppress fluid exchange as additional work is required to lift the dense fluid up and out of the canyon. One would therefore expect that the flushing rate would be a function of the Froude number Fr=U/?g'H as well as the aspect ratio of the canyon H/W. In our experiments the canyon does not remain well mixed, but rather the buoyant fluid is skimmed off the top and the pollutant is etched away over time. We present experimental results for H/W=0.5 and 1 and 0.4canyon, Atmospheric Environment, 2003, 37, 693-702

Kaye, Nigel; Hunt, Gary; Syrios, Konstantinos

2008-11-01

350

Submarine cable OBS using a retired submarine telecommunication cable: GeO-TOC program  

NASA Astrophysics Data System (ADS)

In order to study the Earth's structure and subduction zone tectonics, seismic data from the oceanic region are extremely important. The present seismograph distribution in the oceanic region, however, provides a very poor coverage. To improve this poor seismic coverage, a cable OBS system using a retired submarine telecommunication cable is proposed. The GeO-TOC cable runs from Ninomiya, Japan, to Guam through the Izu-Bonin forearc and the Marina Trough. The total length of the cable is 2659 km. An OBS, IZU, using the GeO-TOC cable, was successfully installed at the landward slope of the Izu-Bonin Trench in January 1997. The IZU OBS is located approximately 400 km south of Tokyo. The installation method is similar to repair work on submarine cables. The IZU OBS is equipped with three accelerometers, a hydrophone, a quartz pressure gauge, and a quartz precision thermometer with a few temperature sensors to monitor overheating of the internal electronics. After installation, the voltage increase is 90 V when the current is maintained at a constant 370 mA. Data from accelerometers are digitized by 24-bit A/D converters and sent to Ninomiya at 9600 bps for each component. Hydrophone data are sent to Ninomiya as analog signals using the AM (Amplitude Modulation) method for safety reasons. Hydrophone data are digitized at the shore station. Other slow-rate data are multiplexed and sent to the shore at 9600 bps. The instrument can be controlled by a shore computer. All data will be transmitted from Ninomiya to Tokyo and combined with other existing seismic data.

Kasahara, Junzo; Utada, Hisashi; Sato, Toshinori; Kinoshita, Hajimu

1998-06-01

351

Gas Metal Arc-Narrow Gap Welding.  

National Technical Information Service (NTIS)

Narrow gap welding techniques have been developed to diminish welding work and to meet the requirements of high fracture toughness in heavy plate structures. Welding in narrow grooves has been found sensitive to weld defects. It requires strict procedural...

J. Koivula, P. Groeger

1984-01-01

352

Depositional environment and reservoir morphology of Canyon sandstones, Central Midland Basin, Texas  

E-print Network

- stone, Lucky Canyon field area. Circled wells indicate cores studied. Countour 1nterval 100 feet. 14 Sedimentary structures in Canyon "B" sandstones, Union Texas Petroleum Farmar 56-2, Rock Pen f1eld, Lucky Canyon area, Irion County, Texas... Munn 1-A. 44 19. Electric log characteristics, texture, composition, and bedding character of Canyon "8" sandstones, Union Texas Petroleum Farmar 56-2 45 20. Electric log characteristics, texture, compostion, and bedding character of Canyon "A...

Jones, James Winston

2012-06-07

353

Compositional range in the Canyon Diablo meteoroid  

NASA Astrophysics Data System (ADS)

The compositional range within the Canyon Diablo (CD) iron meteorites associated with the formation of the Meteor Crater (Arizona) was examined, using the INAA to analyze a set of CD samples consisting of nine irons collected within 7 km of the Meteor Crater, four Arizona IAB irons that were identified by Wasson (1968) as transported CD fragments, and irons from Las Vegas (Nevada) and Moab (Utah) that Buchwald (1975) suggested to be transported CD fragments. Results show that the irons named Helt Township, Idaho, Las Vegas, Mamaroneck, Moab, and Pulaski County are, most likely, mislabeled CD specimens. On the other hand, meteorites named Alexander County, Allan Hills A77283, Ashfork, Fairfield, and Rifle are identified as compositionally distinct independent falls.

Wasson, John T.; Ouyang, Xinwei

1990-11-01

354

The Controlled Flood in Grand Canyon  

NASA Astrophysics Data System (ADS)

The natural flow of almost every river in the United States has been modified to meet various socioeconomic goals—navigation, irrigation, power generation and flood control. The success of the dams and reservoirs built to achieve these goals has been accompanied by changes in the status of riverine resources downstream, a cause of growing environmental and ecological concern. For example, before Glen Canyon Dam was completed, the Colorado River transported large quantities of sediment in floods as large as 8500 m3/s. After the dam was closed in 1963, dam releases typically were less than the powerplant capacity of 890 m3/s and exhibited large daily flow fluctuations. The river carried little sediment. The daily fluctuations in flow eroded sand bars, and the smaller, controlled flow did not redeposit them. The clear, cold water resulted in increased aquatic productivity such that rainbow trout and other nonnative fishes thrived while most native species were lost or endangered.

Webb, Robert H.; Schmidt, John C.; Marzolf, G. Richard; Valdez, Richard A.

355

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

356

Davis Canyon air quality analysis: Revision 2  

SciTech Connect

Detailed supporting calculations, methodology and results of the air quality analysis performed for the Davis Canyon Environmental Assessment are presented in this report. In the absence of onsite meteorological data, data from Salt Wash, Utah, were used in the modeling. The US Environmental Protection Agency Industrial Source Complex (ISC) Model was used to model ground level and fugitive dust sources. The Valley Model was used to model NO/sub 2/ impacts from elevated sources on nearby elevated terrain. Maximum emission rates during site characterization and repository construction and operation are analyzed and reported. Predicted maximum ground level concentrations off site and at Canyonlands National Park are presented. Supporting calculations and computer model runs are presented in appendixes. Salt deposition around the site and impacts to air-quality-related values at Canyonlands, such as visibility, vegetation, and night skyglow are discussed, and results and supporting analyses are presented. 11 refs., 3 figs., 10 tabs.

Not Available

1985-11-01

357

Pollen taphonomy in a canyon stream  

NASA Astrophysics Data System (ADS)

Surface soil samples from the forested Chuska Mountains to the arid steppe of the Chinle Valley, Northeastern Arizona, show close correlation between modern pollen rain and vegetation. In contrast, modern alluvium is dominated by Pinus pollen throughout the canyon; it reflects neither the surrounding floodplain nor plateau vegetation. Pollen in surface soils is deposited by wind; pollen grains in alluvium are deposited by a stream as sedimentary particles. Clay-size particles correlate significantly with Pinus, Quercus, and Populus pollen. These pollen types settle, as clay does, in slack water. Chenopodiaceae- Amaranthus, Artemisia, other Tubuliflorae, and indeterminate pollen types correlate with sand-size particles, and are deposited by more turbulent water. Fluctuating pollen frequencies in alluvial deposits are related to sedimentology and do not reflect the local or regional vegetation where the sediments were deposited. Alluvial pollen is unreliable for reconstruction of paleoenvironments.

Fall, Patricia L.

1987-11-01

358

Compositional range in the Canyon Diablo meteoroid  

SciTech Connect

The Ir distribution in the IAB Canyon Diablo meteorites associated with the formation of Meteor Crater, Arizona, ranges from 2.1 to 2.5 {mu}g/g with peaks at 2.17 and 2.34 {mu}g/g. Only Ir, Ni, and Cu show appreciably more variance in the large set of specimens than observed within a single specimen. The Ir peaks may reflect random sampling of the large (40-100 m), fractionated meteoroid or the presence of two distinct metallic regions differing in composition. None of the other elements they determined show strong correlations with Ir; the Au range is strikingly small (1.5-1.6 {mu}g/g). The presence of chondritic silicates and high contents of planetary-type noble gases in IAB indicates that these solidified rapidly following melting, as expected if they originated as pools of impact-generated melt on a chondritic body. The absence of fractional crystallization trends is consistent with such a model. That 14 of 15 Ir contents fall into two peaks suggests the possibility that the meteoroid included two pools. The alternative that the distribution is continuous can be tested by the study of additional specimens; those from the crater rim are particularly important since these are largely shrapnel spalled from the trailing hemisphere of the meteoroid. Their studies show that the irons named Helt Township, Idaho, Las Vegas, Mamaroneck, Moab, and Pulaski County are probably mislabelled Canyon Diablo specimens; Jenny's Creek and Jenkins are also compositionally indistinguishable. Alexander County, Allan Hills A77283, Ashfork, Fairfield, and Rifle are compositionally distinct, independent falls.

Wasson, J.T.; Ouyang, Xinwei (Univ. of California, Los Angeles (USA))

1990-11-01

359

Aerial Photographic Analysis of Historic Riparian Vegetation Growth and Channel Change at Canyon de Chelly National Monument, Arizona: Preliminary Results  

NASA Astrophysics Data System (ADS)

Aerial photographs over the past 70 years show that a profound alteration in the channels of Canyon de Chelly National Monument has coincided with the establishment and expansion of riparian vegetation, in particular invasive tamarisk ( Tamarix ssp.) and Russian olive ( Elaeagnus angustifolia). Rectification of the air photos, using GIS, enabled detailed mapping of the extent and density of vegetation in the canyon bottom, and analysis of stream channel geometry for each photo set. Photo sets from 1934, 1989, and 2004 were used to track changes in vegetation and channel morphology through time. In 1934, scattered riparian vegetation, including cottonwood ( Populus ssp.) and willow ( Salix ssp.), covered <1% of the canyon bottom. By 2004 the full length of the channel was lined with a riparian vegetation belt, with vegetation covering as much as 40% of the canyon bottom in some 1 km long study reaches . However the width of the riparian belt was spatially discontinuous, with other study reaches having less than 10% coverage of the canyon bottom. Riparian vegetation growth has coincided with an alteration in the hydrology of the streams within the canyon. Air photos from 1934 show a wide sandy wash throughout the extent of the study area. By 1989, some reaches had narrowed, with the channel becoming a single, meandering thread, and with woody riparian vegetation well established on much of the former wash. By 2004, long reaches of the study area were single thread, and dense Russian olive and tamarisk stands filled much of the former wash. While in some reaches the channel changed from a wide braided system to a single thread, other areas remain a sandy wash. Additionally, some reaches of the channel had become deeply incised, as much as 3 meters below the 1934 floodplain, as indicated by persistent cottonwood individuals. Field work indicates that incision was still very active in 2005. However, quantitative analysis of incision through time throughout the study area was not possible using air photos. Instead, incision in discrete reaches was qualitatively described, using historic ground photos to constrain the timing of incision. Vegetation establishment is ubiquitous; however incision is limited to discrete reaches.

Cadol, D. D.; Rathburn, S. L.

2005-12-01

360

Chemical Characteristics of Ground-Water Discharge Along the South Rim of Grand Canyon in Grand Canyon National Park, Arizona, 2000-2001.  

National Technical Information Service (NTIS)

Springs flowing from the south rim of Grand Canyon are an important resource of Grand Canyon National Park, offering refuge to endemic and exotic terrestrial wildlife species and maintaining riparian areas. Population growth on the Coconino Plateau has in...

S. A. Monroe, R. C. Antweiler, R. J. Hart, H. E. Taylor, M. Truini

2004-01-01

361

Preliminary report on the geology and hydrology of Mortandad Canyon near Los Alamos, New Mexico, with reference to disposal of liquid low-level radioactive waste  

USGS Publications Warehouse

The U.S. Geological Survey, in cooperation with the U.S. Atomic Energy Commission and the Los Alamos Scientific Laboratory, selected the upper part of Mortandad Canyon near Los Alamos, New Mexico for a site for disposal of treated liquid low-level radioactive waste. This report summarizes the part of a study of the geology and hydrology that was done from October 1960 through June 1961. Additional work is being continued. Mortandad Canyon is a narrow east-southeast-trending canyon about 9? miles long that heads on the central part of the Pajarito Plateau at an altitude of about 7,340 feet. The canyon is tributary to the Rio Grande. The drainage area of the part of Mortandad Canyon that was investigated is about 2 square miles, and the total drainage area is about 4.9 square miles. The Pajarito Plateau is capped by the Bandelier Tuff of Pleistocene age. Mortandad Canyon is cut in the Bandelier, and alluvium covers the floor of the canyon to depths ranging from less than 1 foot to as much as 100 feet. The Bandelier is underlain by silt, sand, conglomerate, and interbedded basalt of the Santa Fe Group of Miocene, Pliocene, and Pleistocene(?) age. Some ground water is perched in the alluvium in the canyon; however, the top of the main aquifer is in the Santa Fe Group at a depth of about 990 feet below the canyon floor. Joints in the Bandelier Tuff probably were caused by shrinkage of the tuff during cooling. The joints range in width from hairline cracks to fissures several inches wide. Water can infiltrate along the open joints where the Bandelier is at the surface; however, soil, alluvial fill, and autochthonous clay inhibit infiltration on the tops of mesas and probably in the alluvium-floored canyons also. Thirty-three test holes, each less than 100 feet deep, were drilled in 10 lies across Mortandad Canyon from the western margin of the study area to just west of the Los Alamos-Santa Fe County line. Ten of the holes were cased for observation wells to measure water levels and collect water samples from the alluvium. Twenty-three of the holes were cased to seal out water and were used as access tubes to accommodate a neutron-neutron probe for determining the moisture content of the alluvium and tuff. The source of recharge for the perched ground-water body in the alluvium in Mortandad Canyon is the precipitation in the drainage area of the canyon. During the winter of 1960-61, a snowpack 1-2 feet thick accumulated in the narrow shaded upper part of the canyon. The alluvium below the snowpack received some recharge because of diurnal melting during the winter. In March 1961 the snowmelt water saturated most of the thin alluvium in the upper part of the canyon, and a surface stream began to flow on the alluvium. The maximum flow of the stream was about 250 gpm (gallons per minute). Water from the stream infiltrated the alluvium at the front of the stream and in the reach upstream from the front. A ground-water mound was formed beneath the channel by water infiltrating from the stream. The front of the stream and the front of the ground-water mound advanced eastward to about the middle of the area studied. From this point eastward, the alluvium was thick enough to absorb and transmit the amount of flow in 1961. Late in April the front of the stream retreated, and by the first of May the flow stopped. During and after this period the ground-water mound decayed, and ground-water levels declined in the upper part of the canyon as water drained into the channel and downgradient through the alluvium. The amount of recharge was small in the wide lower part of the canyon during the period of study. The rise in ground-water levels and the increase in moisture content of the alluvium in the lower part of the canyon indicate that water moved downgradient by underflow through the alluvium from the recharge area in the upper part of the canyon. Moisture measurements indicate that only a little water moved into the underlyin

Baltz, E. H.; Abrahams, J. H., Jr.; Purtyman, W. D.

1963-01-01

362

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

363

Mass wasting on the submarine Lomonosov Ridge, central Arctic Ocean  

E-print Network

Mass wasting on the submarine Lomonosov Ridge, central Arctic Ocean Yngve Kristoffersen a,, Bernard of the crest of the central part of Lomonosov Ridge, Arctic Ocean. The troughs occur within a restricted ridge over the last c. 600 ka. © 2007 Elsevier B.V. All rights reserved. Keywords: Arctic Ocean; Lomonosov

Kristoffersen, Yngve

364

New power feeding equipment for optical fiber submarine cable  

Microsoft Academic Search

Submarine cable power feeding equipment (PFE) are direct current power supply systems, whose availability has to be very high due to the permanent service they have to fulfil. Tests and maintenance of all PFE devices, redundant power modules or system protections, are possible without any service interruption. The system complies with all EMC requirements. To achieve such purposes, we designed

K. Raoul

1993-01-01

365

Fiber-optic-tethered unmanned submersible for searching submarine cables  

Microsoft Academic Search

A newly developed, fiber-optictethered, unmanned submersible called MARCAS (Marine Cable Search System) has been operating successfully. The mission of MARCAS is to inspect submarine communication cables and the seabed up to 200m in depth. MARCAS has dc and ac magnetometers (proton magnetometers and fluxgate magnetometers) and a metal detector in order to find and trace the cable even if buried

Y. Iwamoto; Y. Shirasaki; K. Asakawa

1982-01-01

366

SCOOP--An Improved Submarine Cable Recovery System  

Microsoft Academic Search

For more than twenty years, acoustically controlled, buoyant subsurface arrays have been utilized by research institutions and industry for mooring, location, and retrieval of oceanographic instruments. Submarine telecommunications cable laying and repair operations typically involve location and retrieval of free cable ends left on the seafloor. In deep water areas, conventional methods for cable-end location and recovery included the use

G. Rich; J. Ewald; C. Jeffcoat; R. Weller

1984-01-01

367

Studies on Loss Aging in Submarine Coaxial Cable During Storage  

Microsoft Academic Search

Attenuation loss change in submarine coaxial cables during 4 years of storage has been measured. Attenuation loss is shown to increase for one year after manufacturing. Then, loss is also shown to increase during summer (May to October) and to stay constant or to decrease during winter (November to April of the next year). This work concentrates on the causes

F. Ashiya; S. Furukawa; Y. Negishi; N. Kojima

1985-01-01

368

Quasi-all-optical network extension for submarine cabled observatories  

Microsoft Academic Search

Submarine cabled networks are designed to collect valuable data in geophysics, geochemistry, biology, or oceanography. Unfortunately, the development of such a network is expensive and needs complex subsea infrastructures. Once in place, a cabled network cannot be easily relocated. The current cost of cables and their installation are one of the major obstacles to these networks deployment. On the one

Frederic Audo; Mikael Guegan; Véronique Quintard; Andre Perennou; Jean Le Bihan; Yves Auffret

2011-01-01

369

Global Deep Ocean Sensor Network on Submarine Cables  

Microsoft Academic Search

This paper describes the implementation and analysis of a deep ocean sensor network that utilizes existing, retired, or new telecommunication submarine cables as hosts to sensor nodes. Due to telecom sub-cable high installation costs, quality of service, and 25-year lifetime requirements, addition of instrumentation nodes must have essentially no impact on system reliability, capacity or availability. A sensor node on

Georgeanne Purvinis; J. Labosky; S. J. Krak; C. M. Baer

2008-01-01

370

The Submarine Optical Cable of the Submarcom S 280 System  

Microsoft Academic Search

Submarine optical telecommunication cables must satisfy a large number of specific items. To comply with specifications, CDL has developed a cable structure based on high-performance optical fibers placed with slack in the grooves of a plastic rod put in the center of a very strong cable. The deep-sea cable is the basic structure for armored cables or land cables. Armor

J. Trezeguet; P. Ollion; P. Franco; J. Thiennot

1984-01-01

371

Analysis of submarine cable and communication satellite systems reliabilities  

Microsoft Academic Search

The performance of AT&T's overseas message telephone circuits for the years 1970-1975 was the basis for ana analysis of the reliability of submarine cables and communication satellite systems. Data presented in 24 tables is devided into three categories: (1) over cable and satellite system outage statistics for each of the six years and the six year average, (2) detailed cable

G. S. Li

1977-01-01

372

Design of Deep-Sea Submarine Optical Fiber Cable  

Microsoft Academic Search

On designing optical fiber cable, it is necessary to deal with optical fiber weakness, such as small breaking elongation compared to metal materials and excess loss under both lateral and hydraulic pressure. This paper presents a structural design method for the submarine optical fiber unit and cable based on the study of both lateral and hydraulic pressure characteristics. This paper

YUKIYASU NEGISHI; KOUSHI ISHIHARA; YASUJI MURAKAMI; NOBUYUKI YOSHIZAWA

1984-01-01

373

Alaskan Submarine Cables: A Struggle with a Harsh Environment  

Microsoft Academic Search

The Alaskan cable system at one time included 86 submarine telegraph cables stretching from Puget Sound northward through the Alaskan Panhandle and thence westward into the Aleutian Island Arc. Cable failures in this system reveal dynamic natural forces affecting the sea floor. The cable failures can primarily be attributed in straits on the continental shelf and upper continental slope to

BRUCE C. HEEZENl; G. LEONARD JOHNSON

374

Mechanical design of submarine power cables for floating platforms  

SciTech Connect

The process of mechanical design of submarine power cables employed by the Simplex Wire and Cable Company is described. The process commences with design criteria and proceeds through preliminary design, load and stress analyses and culminates in extreme value reliability and lifetime predictions. The analytical methods employed are emphasized and some representative numerical results are presented.

Bisplinghoff, R. L.; Libby, D. O.; Costantino, R. W.

1980-01-01

375

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

376

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

377

Tephra layers: A controlling factor on submarine translational sliding?  

Microsoft Academic Search

Submarine slope failures occur at all continental margins, but the processes generating different mass wasting phenomena remain poorly understood. Multibeam bathymetry mapping of the Middle America Trench reveals numerous continental slope failures of different dimensions and origin. For example, large rotational slumps have been interpreted to be caused by slope collapse in the wake of subducting seamounts. In contrast, the

Rieka Harders; Steffen Kutterolf; Christian Hensen; Tobias Moerz; Warner Brueckmann

2010-01-01

378

Deep submarine pyroclastic eruptions: theory and predicted landforms and deposits  

Microsoft Academic Search

Submarine pyroclastic eruptions at depths greater than a few hundred meters are generally considered to be rare or absent because the pressure of the overlying water column is sufficient to suppress juvenile gas exsolution so that magmatic disruption and pyroclastic activity do not occur. Consideration of detailed models of the ascent and eruption of magma in a range of sea

James W. Head; Lionel Wilson

2003-01-01

379

Simulation of Submarine Pipeline Oil Spill Based on Wave Motion  

Microsoft Academic Search

In order to explore the motion law of oil spill to conduct cleaning, simulation for submarine oil spill based on wave motion is carried out by user defined function and volume of fluid in FLUENT, and the dispersion and diffusion of oil spill in deep sea is simulated dynamically. Also the oil spill processes with different wavelength and current velocity

Ming Xiao; Qingjun Gao; Jianguo Lin; Wei Li; Xiao Liang

2010-01-01

380

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

381

The Shape of Trail Canyon Alluvial Fan, Death Valley  

NASA Technical Reports Server (NTRS)

A modified conic equation has been fit to high-resolution digital topographic data for Trail Canyon alluvial fan in Death Valley, California. Fits were accomplished for 3 individual fan units of different age.

Farr, Tom G.; Dohrenwend, John C.

1993-01-01

382

76 FR 24516 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...the AMWG, a technical work group (TWG), a Grand Canyon...Bureau of Reclamation, Upper Colorado Regional Office, 125 South...Chief, Adaptive Management Group, Environmental Resources Division, Upper Colorado Regional Office, Salt...

2011-05-02

383

77 FR 43117 - Glen Canyon Dam Adaptive Management Work Group  

Federal Register 2010, 2011, 2012, 2013

...the AMWG, a technical work group (TWG), a Grand Canyon...Bureau of Reclamation, Upper Colorado Regional Office, 125 South...Chief, Adaptive Management Group, Environmental Resources Division, Upper Colorado Regional Office, Salt...

2012-07-23

384

Valuing wildfire risk mitigation in Kyle Canyon, Nevada.  

E-print Network

??The federal government lists Kyle Canyon, Nevada, as an at-risk wildland-urban interface community. Stakeholders' attitudes and preferences about wildfires and mitigation options were assessed through… (more)

O'Brien, James P.

2005-01-01

385

Flow Focusing as a Control on the Width of Canyons Formed by Outburst Floods  

NASA Astrophysics Data System (ADS)

Spectacular canyons exist on the surfaces of Earth and Mars that were carved by ancient outburst megafloods. These canyons often have steep headwalls and were eroded into jointed rock. This suggests that canyon formation is driven by upstream retreat of waterfalls through toppling failure. Discharge reconstructions remain difficult, however, because we do not understand quantitatively the links between canyon formation and canyon morphology. Here we propose that the width of canyon headwalls is set by the shear stress distribution around the rim of the canyon, which governs the propensity for toppling failure, and that this distribution is controlled by focusing of flood water into the canyon head. To test this hypothesis, we performed a series of numerical simulations of 2-D, depth-averaged, turbulent flow using the hydraulic numerical modeling suite ANUGA Hydro and mapped the shear stresses along the rim of canyons of various geometries. The numerical simulations were designed to explore three dimensionless variables: the aspect ratio of the canyon (length normalized by width), the canyon width relative to the normal flow depth, and the Froude number. Preliminary results show that flow focusing at the head of a canyon can lead to heightened shear stresses there compared to the sides of the canyon. Flow focusing is most efficient for subcritical flows with large canyon aspect ratios, suggesting that canyons grow in all directions until they reach a critical length which depends on the Froude number only. Canyons longer than this critical length maintain a uniform width during canyon formation. Earth-analog canyons, where flood depths were constrained from previous paleo-hydraulic studies, show good agreement with our numerical predictions, suggesting that flow focusing may set the width of canyons during megafloods. Model results allow a link between process and form that will enable us to constrain better flood discharges on Earth and Mars, where other robust paleo-hydraulic tools are not available.

Lapotre, M. G.; Lamb, M. P.; Halliday, C. K.

2012-12-01

386

Tacoma Narrows Bridge: Extreme History  

NSDL National Science Digital Library

Stretching across the southern portion of Puget Sound, the elegant Tacoma Narrows bridge is considered one of the finest suspension bridges in the United States. The current bridge is the second on the site, as it was constructed in 1950 to serve as a replacement to the famous "Galloping Gertie" bridge, which collapsed in a windstorm in the fall of 1940. Currently, the Washington State Department of Transportation is building a bridge to replace the existing structure, and it is anticipated that it will be completed in 2007. This site offers a host of materials on all three structures, including ample information on the construction of the bridges and their aesthetic appeal. Along with these materials, the site also provides a glossary of related terms, Weird Facts, and some information about the dog "Tubby", who perished when "Galloping Gertie" collapsed on that fateful fall day back in 1940.

387

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

388

Submarine Volcanic Cones in the São Miguel Region/Azores  

NASA Astrophysics Data System (ADS)

São Miguel, the main island of the Azores Archipelago, is located in an area ~1500 km west of Portugal where the American, African and Eurasian plates converge. Just as well as the other eight Azorian islands, it is of volcanic origin and therefore volcanic processes also play an important role for the evolution of its submarine domain. Around 300 submarine volcanic cones have been mapped in the vicinity of São Miguel Island with multi-beam data during RV Meteor cruise M79/2 . They are distributed in depth down to 3000 m. They exhibit an average diameter of 600 m, an average slope of 22° and heights mainly between 50 and 200 m, slightly decreasing with increasing water depth. Even if their morphological appearances show no segregation, the volcanic setting can be classified in three different categories. A numerous amount of cones are located on the submarine flank of Sete Cidades Volcano in the west of São Miguel considered as parasitic structures, whereas in the very east they build up an own superstructure possibly reflecting an early submarine stadium of a posterior subaerial stratovolcano like Sete Cidades. The third class is controlled by and orientated along faults, most of them in a graben system southwest of the Island. High-resolution multichannel seismic data depicts that the graben cones extinguished synchronously in the past most likely accompanying with the end of graben formation. Backscatter data reveal a rough surface possibly caused by currents removing the fine grain-size fraction over time. However, a young cone investigated in detail is characterized by a smooth surface, a distal increasing stratification and concave shaped flanks. Other few exhibit craters, all together indicating rather a phreatomagmatic than an effusive evolution of these structures. Very similar in size and shape to cinder cones on-shore São Miguel Island, they appear to be their submarine equivalent.

Weiß, Benedikt; Hübscher, Christian; Wolf, Daniela

2014-05-01

389

The kinematics of debris flow transport down a canyon  

E-print Network

of the scholarly effor is concentrated elsewhere in the canyon system. Much work has been done on the initiation of debris flows (Terzaghi, 1950; Campbell, 1975; Keefer and Johnson, 1983; Pack, 1984; Jeppson, 1985; Ellen and Fleming, 1987; Mathewson and Santi..., 1987), the deposition of material by debris flows at the canyon mouth (Hooke, 1967; Olson, 1985; Keaton and Mathewson, 1987; Lips and Wieczorek, 1987), and on the properties of material while flowing (Johnson, 1970; Rodine, 1974; Johnson This thesis...

Santi, Paul M.

2012-06-07

390

Geology Fieldnotes: Glen Canyon National Recreation Area, Utah and Arizona  

NSDL National Science Digital Library

This Glen Canyon National Recreation Area site contains park geology information, photographs, related links, visitor information, multimedia resources, and teacher features (resources for teaching geology with National Park examples). The park geology section briefly discusses the Park's geologic history, structural geology, Navajo sandstone, and fossil beds. The park maps section contains a link to a features/relief map of Glen Canyon and the surrounding area, from the University of Texas at Austin Perry-Castaneda Library Map Collection.

391

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

392

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

393

Cryogenic Detectors (Narrow Field Instruments)  

NASA Astrophysics Data System (ADS)

Two cryogenic imaging spectrometer arrays are currently considered as focal plane instruments for XEUS. The narrow field imager 1 (NFI 1) will cover the energy range from 0.05 to 3 keV with an energy resolution of 2 eV, or better, at 500 eV. A second narrow field imager (NFI 2) covers the energy range from 1 to 15 keV with an energy resolution of 2 eV (at 1 keV) and 5 eV (at 7 keV), creating some overlap with part of the NFI 1 energy window. Both narrow field imagers have a 0.5 arcmin field of view. Their imaging capabilities are matched to the XEUS optics of 2 to 5 arcsec leading to 1 arcsec pixels. The detector arrays will be cooled by a closed cycle system comprising a mechanical cooler with a base temperature of 2.5 K and either a low temperature 3He sorption pump providing the very low temperature stage and/or an Adiabatic Demagnetization Refrigerator (ADR). The ADR cooler is explicitly needed to cool the NFI 2 array. The narrow field imager 1} Currently a 48 times 48 element array of superconducting tunnel junctions (STJ) is envisaged. Its operating temperature is in the range between 30 and 350 mK. Small, single Ta STJs (20-50 mum on a side) have shown 3.5 eV (FWHM) resolution at E = 525 eV and small arrays have been successfully demonstrated (6 times 6 pixels), or are currently tested (10 times 12 pixels). Alternatively, a prototype Distributed Read-Out Imaging Device (DROID), consisting of a linear superconducting Ta absorber of 20 times 100 mum2, including a 20 times 20 mum STJ for readout at either end, has shown a measured energy resolution of 2.4 eV (FWHM) at E = 500 eV. Simulations involving the diffusion properties as well as loss and tunnel rates have shown that the performance can be further improved by slight modifications in the geometry, and that the size of the DROIDS can be increased to 0.5-1.0 mm without loss in energy resolution. The relatively large areas and good energy resolution compared to single STJs make DROIDS good candidates for the basic elements of the NFI 1 detector array. With a DROID-based array of 48 times 10 elements covering the NFI 1 field of view of 0.5 arcmin, the number of signal wires would already be reduced by a factor 2.4 compared to a 48 times 48 array of single pixels. While the present prototype DROIDS are still covered with a 480 nm thick SiOx insulation layer, this layer could easily be reduced in thickness or omitted. The detection efficiency of such a device with a 500 nm thick Ta absorber would be >80% in the energy range of 100-3000eV, without any disturbing contributions from other layers as in single STJs. Further developments involve devices of lower Tc-superconductors for better energy resolution and faster diffusion (e.g. Mo). The narrow field imager 2 The NFI 2 will consist of an array of 32 times 32 detector pixels. Each detector is a microcalorimeter which consists of a a superconducting to normal phase transition edge thermometer (transition edge sensor, TES) with an operating temperature of 100 mK, and an absorber which allows a detection efficiency of >90% and a filling factor of the focal plane in excess of 90%. Single pixel microcalorimeters with a Ti/Au TES have already shown an energy resolution of 3.9 eV at 5.89 keV in combination with a thermal response time of 100 mus. These results imply that they the high-energy requirement for XEUS can be met, in terms of energy resolution and response time. It has been demonstrated that bismuth can be applied as absorber material without impeding on the detector performance. Bi increases the stopping power in excess of 90 % and allows for a high filling factor since the absorber is can be modeled in the shape of a mushroom, allowing that the wiring to the detector and the thermal support structure are placed under the hat of the mushroom. In order to realize the NFI 2 detector array, there are two major development areas. Firstly, there is the development of micromachined Si and SiN structures that will provide proper cooling for each of the pixels and the production of small membranes to support the

Hoevers, H.; Verhoeve, P.

394

Seismic stratigraphic characteristics of upper Louisiana continental slope: an area east of Green Canyon  

USGS Publications Warehouse

A high-resolution seismic reflection survey was conducted in a small area of the upper Louisiana Continental Slope known as Green Canyon Area. This area includes tracts 427, 428, 471, 472, 515, and 516, that will be offered for sale in March 1982 as part of Lease Sale 67. The sea floor of this region is, slightly hummocky and is underlain by salt diapirs that are mantled by early Tertiary shale. Most of the shale is overlain by younger Tertiary and Quaternary deposits, although locally some of the shale protrudes the sea floor. Because of proximity to older Mississippi River sources, the sediments are thick. The sediment cover shows an abundance of geologic phenomena such as horsts, grabens, growth faults, normal faults, and consolidation faults, zones with distinct and indistinct parallel reflections, semi-transparent zones, distorted zones, and angular unconformities. The major feature of this region is a N-S linear zone of uplifted and intruded sedimentary deposits formed due to diapiric intrusion. Small scale graben development over the crest of the structure can be attributed to extension and collapse. Large scale undulations of reflections well off the flanks of the uplifted structure suggest sediment creep and slumping. Dipping of parallel reflections show block faulting and tilting. Air gun (5 and 40 cubic inch) records reveal at least five major sequences that show masked onlap and slumping in their lower parts grading into more distinct parallel reflections in their upper parts. Such sequences can be related to local uplift and sea level changes. Minisparker records of this area show similar sequences but on a smaller scale. The distinct parallel reflections often onlap the diapir flanks. The highly reflective parts of these sequences may represent turbidite-type deposition, possibly at times of lower sea level. The acoustically more transparent parts of each sequence may represent deposits containing primarily hemipelagic and pelagic sediment. A complex ridge system is present along the west side of the area and distinct parallel reflections onlap onto this structure primarily from the east. Much of this deposition may be ascribed to sedimentation within a submarine canyon whose position is controlled by this ridge.

Bouma, Arnold H.; Feeley, Mary H.; Kindinger, Jack L.; Stelting, Charles E.; Hilde, Thomas W.C.

1981-01-01

395

14 CFR Appendix to Subpart U of... - Special Flight Rules in the Vicinity of the Grand Canyon National Park, AZ  

Code of Federal Regulations, 2011 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...

2011-01-01

396

High-Resolution Chirp and Mini-Sparker Seismic-Reflection Data From the Southern California Continental Shelf - Gaviota to Mugu Canyon  

USGS Publications Warehouse

The U.S. Geological Survey (USGS) collected high-resolution shallow seismic-reflection data in September, 2007, and June-July, 2008, from the continental shelf offshore of southern California between Gaviota and Mugu Canyon, in support of the California's State Waters Mapping Program. Data were acquired using SIG 2mille mini-sparker and Edgetech chirp 512 instruments aboard the R/V Zephyr (Sept. 2007) and R/V Parke Snavely (June-July 2008). The survey area spanned approximately 120 km of coastline, and included shore-perpendicular transects spaced 1.0-1.5 km apart that extended offshore to at least the 3-mile limit of State waters, in water depths ranging from 10 m near shore to 300 m near the offshore extent of Mugu and Hueneme submarine canyons. Subbottom acoustic penetration spanned tens to several hundred meters, variable by location. This report includes maps of the surveyed transects, linked to Google Earth software, as well as digital data files showing images of each transect in SEG-Y, JPEG, and TIFF formats. The images of sediment deposits, tectonic structure, and natural-gas seeps collected during this study provide geologic information that is essential to coastal zone and resource management at Federal, State and local levels, as well as to future research on the sedimentary, tectonic, and climatic record of southern California.

Sliter, Ray W.; Triezenberg, Peter J.; Hart, Patrick E.; Draut, Amy E.; Normark, William R.; Conrad, James E.

2008-01-01

397

Davis Canyon noise analysis: Revision 2  

SciTech Connect

A study was performed as part of the Civilian Radioactive Waste Management Program to quantify the level and effect of noise from the various major phases of development of the proposed potentially acceptable nuclear waste repository site at Davis Canyon, Utah. This report contains the results of a predictive noise level study for the site characterization, repository construction, and repository operational phases. Included herein are graphic representations of energy averaged sound levels, and of audibility levels representing impact zones expected during each phase. Sound levels from onsite and offsite activity including traffic on highways and railroad routes are presented in isopleth maps. A description of the Environmental Noise Prediction Model used for the study, the study basis and methodologies, and actual modeling data are provided. Noise and vibration levels from blasting are also predicted and evaluated. Protective noise criteria containing a margin of safety are used in relation to residences, schools, churches, noise-sensitive recreation areas, and noise-sensitive biological resources. Protective ground motion criteria for ruins and delicate rock formation in Canyonlands National Park and for human annoyance are used in the evaluation of blasting. The evaluations provide the basis for assessing the noise impacts from the related activities at the proposed repository. 45 refs., 21 figs., 15 tabs.

Not Available

1985-11-01

398

Exploration of the 1891 Foerstner submarine vent site (Pantelleria, Italy): insights into the formation of basaltic balloons  

NASA Astrophysics Data System (ADS)

On October 17, 1891, a submarine eruption started at Foerstner volcano located within the Pantelleria Rift of the Strait of Sicily (Italy). Activity occurred for a period of 1 week from an eruptive vent located 4 km northwest of the island of Pantelleria at a water depth of 250 m. The eruption produced lava balloons that discharged gas at the surface and eventually sank to the seafloor. Remotely operated vehicle (ROV) video footage and high-resolution multi-beam mapping of the Foerstner vent site were used to create a geologic map of the AD 1891 deposits and conduct the first detailed study of the source area associated with this unusual type of submarine volcanism. The main Foerstner vent consists of two overlapping circular mounds with a total volume of 6.3 × 105 m3 and relief of 60 m. It is dominantly constructed of clastic scoriaceous deposits with some interbedded pillow lavas. Petrographic and geochemical analyses of Foerstner samples by X-ray fluorescence and inductively coupled plasma mass spectrometry reveal that the majority of the deposits are vesicular, hypocrystalline basanite scoria that display porphyritic, hyaloophitic, and vitrophyric textures. An intact lava balloon recovered from the seafloor consists of a large interior gas cavity surrounded by a thin lava shell comprising two distinct layers: a thin, oxidized, quenched crust surrounding the exterior of the balloon and a dark gray, tachylite layer lying beneath it. Ostwald ripening is proposed to be the dominant bubble growth mechanism of four representative Foerstner scoria samples as inferred by vesicle size distributions. Characterization of the diversity of deposit facies observed at Foerstner in conjunction with quantitative rock texture analysis indicates that submarine Strombolian-like activity is the most likely mechanism for the formation of lava balloons. The deposit facies observed at the main Foerstner vent are very similar to those produced by other known submarine Strombolian eruptions (short pillow flow lobes, large scoriaceous clasts, spatter-like vent facies). Balloons were likely formed from the rapid cooling of extremely vesicular magma fragments as a result of a gas-rich frothy magma source. The exterior of these fragments hyperquenched forming a vesicular glassy shell that acted as an insulating layer preventing magmatic gas in its interior from escaping and thus allowing flotation as densities reached less than 1,000 kg/m3. We believe that lava balloons are a common eruptive product, as the conditions required to generate these products are likely to be present in a variety of submarine volcanic environments. Additionally, the facies relationships observed at Foerstner may be used as a paleoenvironmental indicator for modern and ancient basaltic shallow submarine eruptions because of the relatively narrow depth range over which they likely occur (200-400 m).

Kelly, Joshua T.; Carey, Steven; Pistolesi, Marco; Rosi, Mauro; Croff-Bell, Katherine Lynn; Roman, Chris; Marani, Michael

2014-07-01

399

Narrow gap electronegative capacitive discharges  

NASA Astrophysics Data System (ADS)

Narrow gap electronegative (EN) capacitive discharges are widely used in industry and have unique features not found in conventional discharges. In this paper, plasma parameters are determined over a range of decreasing gap length L from values for which an electropositive (EP) edge exists (2-region case) to smaller L-values for which the EN region connects directly to the sheath (1-region case). Parametric studies are performed at applied voltage Vrf=500 V for pressures of 10, 25, 50, and 100 mTorr, and additionally at 50 mTorr for 1000 and 2000 V. Numerical results are given for a parallel plate oxygen discharge using a planar 1D3v (1 spatial dimension, 3 velocity components) particle-in-cell (PIC) code. New interesting phenomena are found for the case in which an EP edge does not exist. This 1-region case has not previously been investigated in detail, either numerically or analytically. In particular, attachment in the sheaths is important, and the central electron density ne0 is depressed below the density nesh at the sheath edge. The sheath oscillations also extend into the EN core, creating an edge region lying within the sheath and not characterized by the standard diffusion in an EN plasma. An analytical model is developed using minimal inputs from the PIC results, and compared to the PIC results for a base case at Vrf=500 V and 50 mTorr, showing good agreement. Selected comparisons are made at the other voltages and pressures. A self-consistent model is also developed and compared to the PIC results, giving reasonable agreement.

Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J.

2013-10-01

400

Narrow gap electronegative capacitive discharges  

SciTech Connect

Narrow gap electronegative (EN) capacitive discharges are widely used in industry and have unique features not found in conventional discharges. In this paper, plasma parameters are determined over a range of decreasing gap length L from values for which an electropositive (EP) edge exists (2-region case) to smaller L-values for which the EN region connects directly to the sheath (1-region case). Parametric studies are performed at applied voltage V{sub rf}=500 V for pressures of 10, 25, 50, and 100 mTorr, and additionally at 50 mTorr for 1000 and 2000 V. Numerical results are given for a parallel plate oxygen discharge using a planar 1D3v (1 spatial dimension, 3 velocity components) particle-in-cell (PIC) code. New interesting phenomena are found for the case in which an EP edge does not exist. This 1-region case has not previously been investigated in detail, either numerically or analytically. In particular, attachment in the sheaths is important, and the central electron density n{sub e0} is depressed below the density n{sub esh} at the sheath edge. The sheath oscillations also extend into the EN core, creating an edge region lying within the sheath and not characterized by the standard diffusion in an EN plasma. An analytical model is developed using minimal inputs from the PIC results, and compared to the PIC results for a base case at V{sub rf}=500 V and 50 mTorr, showing good agreement. Selected comparisons are made at the other voltages and pressures. A self-consistent model is also developed and compared to the PIC results, giving reasonable agreement.

Kawamura, E.; Lieberman, M. A.; Lichtenberg, A. J. [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720 (United States)] [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720 (United States)

2013-10-15

401

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.

402

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

403

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

404

Submarine Volcanology: 1950 to 2050 and Beyond (Invited)  

Microsoft Academic Search

The vigorous pursuit of submarine volcanism as a major field emerged in the mid 1900's with the post WWII recognition that there is a Mid-Ocean Ridge System that is a 70,000 km long volcanic mountain chain stretching around the world like the strings on a baseball. By the mid 1960's it emerged that rocks from volcanic feature were consistently basaltic

J. R. Delaney; D. S. Kelley

2010-01-01

405

Results of electromagnetic sounding with JASC submarine cable  

Microsoft Academic Search

We present the results of long-term deep geoelectric studies using the JASC (Japan Sea Cable) submarine communication cable\\u000a in the region of the Sea of Japan. In the 2D inversion of the amplitude and phase’s apparent resistivity curves and the frequency\\u000a dependences of the tipper, we invoked the geological and geophysical information about the region and on-shore electromagnetic\\u000a observations to

S. S. Starzhinskii; V. M. Nikiforov

2011-01-01

406